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1
Bair, Scott. "The Variation of Viscosity With Temperature and Pressure for Various Real Lubricants." Journal of Tribology 123, no. 2 (June 27, 2000): 433–36. http://dx.doi.org/10.1115/1.1308024.
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To date, nearly all analyses of lubricant traction behavior in the Hertzian zone of concentrated contact have been performed with viscosity correlations which understate the effect of pressure and temperature at high pressures. We present viscometer measurements of lubricant viscosity for pressures to 1.4 GPa and temperatures to 165°C for various lubricants including automotive transmission fluids, aerospace lubricants, a turbine oil, and a metal working oil. Parameters of a free-volume correlation are provided for use in numerical modeling of traction, film thickness, and roughness interactions in concentrated contact.
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Kolmanovsky, Ilya, Michael P. Polis, and Irina F. Sivergina. "Identification of the Heat Flux in a Quasi-Static Thermoelastic System." Journal of Dynamic Systems, Measurement, and Control 128, no. 3 (November 28, 2005): 608–16. http://dx.doi.org/10.1115/1.2232685.
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This paper treats the problem of estimating the heat flux through the free end of a thermoelastic rod, which is allowed to come into contact with a rigid obstacle. This problem is motivated by the need to develop techniques for indirect measurement of heating in applications, such as, brake systems and machine tools. Under a quasi-static approximation, the problem becomes that of characterizing thermal processes in the rod. Assuming that direct and exact measurements at the contacting end of the rod cannot be taken, the problem is to determine if there is contact with the obstacle; and if there is contact, to characterize the conductivity processes at the contacting end. We study the case of weighted-average temperature measurements throughout the rod. Identifiability results and on-line recursive estimation procedures are developed.
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Bair, S. "Measurements of real non-Newtonian response for liquid lubricants under moderate pressures." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 215, no. 3 (March 1, 2001): 223–33. http://dx.doi.org/10.1243/1350650011543493.
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A thorough characterization of all viscous flow properties relevant to steady simple shear was carried out for five liquid lubricants of current interest to tribology. Shear stresses were generated to values significant to concentrated contact lubrication. Two types of non-Newtonian response were observed: shear-thinning as a power-law fluid and near rate-independence. Functions and parameters were obtained for the temperature and pressure dependence of the viscosity and of the time constant for the Carreau-Yasuda equation. Results are consistent with free volume and kinetic theory, but directly contradict many assumptions currently utilized for numerical simulation and for extracting rheological properties from contact measurements.
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Poongothai, N., R. Athira, and P. K. Neena. "A Green Approach to Preparing Bio-Inhibitor for Mild Steel Corrosion in Different Acid Mediums." International Journal of Engineering & Technology 7, no. 3.6 (July 4, 2018): 322. http://dx.doi.org/10.14419/ijet.v7i3.6.15124.
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Inhibition efficiency (I. E) of various concentrations of Carica Papaya (C. P)extracts on the corrosion of mild steel (MS) in 1M HCl and 0.5M H2SO4medium was investigated by weight loss and electrochemical methods at room temperature and elevated temperature. Acid extract of C. P was characterized by using FTIR and XRD spectral studies to identify the major constituents present in it. Zeta potential and EDAX analysis were carried out for the extract to identify electrochemical aspect of a particle’s surface, and information about a particle’s dispersibility, aggregability, and adhesion ability can be obtained from this measurement. Surface analysis studies such as FESEM and contact angle measurement were carried out for the C. P extracts to locate the surface coverage of the inhibitor and confirm the hydrophilic nature on the metal surface. Langmuir and Temkin adsorption isotherm confirm the mono layer adsorption and heterogeneity of the MS surface. Thermodynamic data’s such as activation energy, Gibbs free energy, enthalpy and entropy changes were calculated using weight loss measurements data at room as well as elevated temperatures and identified free energy of adsorption and exothermic reaction taking place during corrosion process. Phytochemical studies confirm the presence of chemical constituents with hetero atom that provide more I.E due to its adsorption of inhibitor on metal surface.
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Stephenson, D. A. "Assessment of Steady-State Metal Cutting Temperature Models Based on Simultaneous Infrared and Thermocouple Data." Journal of Engineering for Industry 113, no. 2 (May 1, 1991): 121–28. http://dx.doi.org/10.1115/1.2899668.
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Several models for metal cutting temperatures which could be applied in simulation programs have been reported in the literature. Since the temperature predicted by the models are difficult to measure, however, there is not sufficient experimental data to determine which available model is most accurate and whether further theoretical refinement is needed. In this paper calculations from four steady-state cutting temperature models are compared with simultaneous infrared and tool-chip thermocouple temperature measurements from end turning tests on 1018 steel, 2024 aluminum, free machining brass, and gray cast iron tubes. Deformation zone temperatures calculated using the models are compared to source temperatures determined from infrared measurements using a new inverse method. Calculated tool-chip contact temperatures are compared to rake face temperatures measured by the widely used tool-work thermocouple method. The data indicates most models, though quantitatively accurate, overestimate cutting temperatures. Models based on Jaeger’s friction slider solution which include workpiece thermal property variations, however, generally give results accurate to within the reliability of experimentai methods for the materials tested. Loewen and Shaw’s model, recently generalized to three-dimensional cutting by Venuvinod and Lau, seems most accurate over a broad range of workpiece and cutting conditions. No model accurately predicts tool-chip temperatures for cast iron or 2024 aluminum, indicating that further theoretical refinement for discontinuous chip formation is needed.
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Jiang, Guojun, and Sheng Xie. "Comparison of AFM Nanoindentation and Gold Nanoparticle Embedding Techniques for Measuring the Properties of Polymer Thin Films." Polymers 11, no. 4 (April 3, 2019): 617. http://dx.doi.org/10.3390/polym11040617.
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The surfaces of polymer and interfaces between polymer and inorganic particles are of particular importance for the properties of polymers and composites. However, the determination of the properties of surfaces and interfaces poses many challenges due to their extremely small dimensions. Herein, polystyrene and polymethyl methacrylate thin film on silicon wafer was used as a model system for the measurement of the properties of the polymer near free surface and at the polymer-solid interface. Two different methods, i.e., nanoindentation using atomic force microscopy (AFM) and the gold nanoparticle embedding technique, were used for these measurements. The results showed the elastic modulus of PS near the free surface determined by nanoindentation was lower than the bulk value. Based on contact mechanics analysis, nanoparticle embedding also revealed the existence of a lower-modulus, non-glassy layer near the free surface at temperatures below the bulk glass transition temperature (Tg). However, near the polymer-solid interface, the AFM nanoindentation method is not applicable due to the geometry confinement effect. On the other hand, the nanoparticle embedding technique can still correctly reflect the interactions between the polymer and the substrate when compared to the ellipsometry results.
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Kim, Jae Kwan, and Kahp Y. Suh. "Room Temperature Detachment Nanolithography Using a Rigiflex Polymeric Mold." Journal of Nanoscience and Nanotechnology 8, no. 7 (July 1, 2008): 3621–25. http://dx.doi.org/10.1166/jnn.2008.162.
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We report on detachment nanolithography of an organic thin film at room temperature mediated by ultraviolet (UV) exposure. A nanopatterned, UV curable polyurethane acrylate (PUA) mold was placed on a spin-coated organic film made of 4,4′-bis[N-1-napthyl-N-phenyl-amino]biphenyl (NPB) under a low pressure (1–2 bar). A higher work of adhesion at the organic/mold interface induced detachment of the contacting layer on silicon or gold substrate, resulting in well-defined nanopatterns without a residual layer. The detachment was highly improved by a short-term UV exposure, rendering the film surface free from contaminant hydrocarbons with a lower cohesive force, as confirmed by Fourier transform infrared (FTIR) spectroscopy and measurements of contact angle of water.
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Kakar, Muhammad Rafiq, Meor Othman Hamzah, Mohammad Nishat Akhtar, and Junita Mohamad Saleh. "Evaluating the Surface Free Energy and Moisture Sensitivity of Warm Mix Asphalt Binders Using Dynamic Contact Angle." Advances in Civil Engineering 2019 (March 3, 2019): 1–15. http://dx.doi.org/10.1155/2019/9153603.
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From the environmental conservation perspective, warm mix asphalt is more preferable compared to hot mix asphalt. This is because warm mix asphalt can be produced and paved in the temperature range 20–40°C lower than its equivalent hot mix asphalt. In terms of cost-effectiveness, warm mix asphalt can significantly improve the mixture workability at a lower temperature and thus reduce greenhouse gas emissions, to be environment friendly. However, the concern, which is challenging to warm mix asphalt, is its susceptibility to moisture damage due to its reduced production temperature. This may cause adhesive failure, which could eventually result in stripping of the asphalt binder from the aggregates. This research highlights the significance of Cecabase warm mix additive to lower the production temperature of warm mix asphalt and improvise the asphalt binder adhesion properties with aggregate. The binders used in the preparation of the test specimen were PG-64 and PG-76. The contact angle values were measured by using the dynamic Wilhelmy plate device. The surface free energy of Cecabase-modified binders was then computed by developing a dedicated algorithm using the C++ program. The analytical measurements such as the spreadability coefficient, work of adhesion, and compatibility ratio were used to analyze the results. The results inferred that the Cecabase improved the spreadability of the asphalt binder over limestone compared to the granite aggregate substrate. Nevertheless, the Cecabase-modified binders improved the work of adhesion. In terms of moisture sensitivity, it is also evident from the compatibility ratio indicator that, unlike granite aggregates, the limestone aggregates were less susceptible to moisture damage.
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Diehl, K., M. Debertshäuser, O. Eppers, H. Schmithüsen, S. K. Mitra, and S. Borrmann. "Particle surface area dependence of mineral dust in immersion freezing mode: investigations with freely suspended drops in an acoustic levitator and a vertical wind tunnel." Atmospheric Chemistry and Physics 14, no. 22 (November 25, 2014): 12343–55. http://dx.doi.org/10.5194/acp-14-12343-2014.
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Abstract. The heterogeneous freezing temperatures of supercooled drops were measured using an acoustic levitator. This technique allows one to freely suspend single drops in the air without any wall contact. Heterogeneous nucleation by two types of illite (illite IMt1 and illite NX) and a montmorillonite sample was investigated in the immersion mode. Drops of 1 mm in radius were monitored by a video camera while cooled down to −28 °C to simulate freezing within the tropospheric temperature range. The surface temperature of the drops was contact-free, determined with an infrared thermometer; the onset of freezing was indicated by a sudden increase of the drop surface temperature. For comparison, measurements with one particle type (illite NX) were additionally performed in the Mainz vertical wind tunnel with drops of 340 μm radius freely suspended. Immersion freezing was observed in a temperature range between −13 and −26 °C as a function of particle type and particle surface area immersed in the drops. Isothermal experiments in the wind tunnel indicated that after the cooling stage freezing still proceeds, at least during the investigated time period of 30 s. The results were evaluated by applying two descriptions of heterogeneous freezing, the stochastic and the singular model. Although the wind tunnel results do not support the time-independence of the freezing process both models are applicable for comparing the results from the two experimental techniques.
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Lindemann, Joerg, Kerstin Wiesmiller, Tilman Keck, and Konrad Kastl. "Dynamic Nasal Infrared Thermography in Patients with Nasal Septal Perforations." American Journal of Rhinology & Allergy 23, no. 5 (September 2009): 471–74. http://dx.doi.org/10.2500/ajra.2009.23.3351.
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Background Nasal obstruction is a typical symptom in patients with nasal septal perforations. Rhinomanometry and acoustic rhinometry are not reliable in these cases because the perforations generate incorrect results. Infrared thermography camera (ITC) systems allow contact-free intranasal recordings of the nasal surface temperature and the semiquantification of nasal airflow. The aim of this study was to perform contact-free temperature measurements of the nasal vestibular surface by application of ITC systems in patients with septal perforations to investigate the disturbed intranasal heat exchange and nasal airflow. Methods The surface temperature profiles within the nasal vestibules of healthy volunteers (n = 10) and patients with septal perforations (n = 3) were recorded with an ITC during several breathing cycles. Thermal images were taken (60/s) displaying the surface temperature in degrees centigrade corresponding to a color scale. Results The temperature recordings showed a disturbed intranasal heat exchange during inspiration and expiration in patients with septal perforations in comparison with healthy subjects. A reduced and irregular inspiratory cooling of the entire surface within the nasal vestibules visualizes a reduced and disturbed airflow volume. Conclusion The study was able to prove the feasibility of intranasal temperature recordings of the surface with an ITC system in patients with septal perforations. Contrary to rhinomanometry and acoustic rhinometry, thermography cameras can be applied to examine airflow in patients with septal perforations. The detected reduced cooling of the surface during inspiration might be a possible explanation for the patients' feelings of nasal obstruction.
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Yang, Xiangyu, Wenping Geng, Kaixi Bi, Linyu Mei, Yaqing Li, Jian He, Jiliang Mu, Xiaojuan Hou, and Xiujian Chou. "The Wafer-Level Integration of Single-Crystal LiNbO3 on Silicon via Polyimide Material." Micromachines 12, no. 1 (January 9, 2021): 70. http://dx.doi.org/10.3390/mi12010070.
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In situ measurements of sensing signals in space platforms requires that the micro-electro-mechanical system (MEMS) sensors be located directly at the point to be measured and in contact with the subject to be measured. Traditional radiation-tolerant silicon-based MEMS sensors cannot acquire spatial signals directly. Compared to silicon-based structures, LiNbO3 single crystalline has wide application prospects in the aerospace field owing to its excellent corrosion resistance, low-temperature resistance and radiation resistance. In our work, 4-inch LiNbO3 and LiNbO3/Cr/Au wafers are fabricated to silicon substrate by means of a polyimide bonding method, respectively. The low-temperature bonding process (≤100 ℃) is also useful for heterostructure to avoid wafer fragmentation results from a coefficient of thermal expansion (CTE) mismatch. The hydrophilic polyimide surfaces result from the increasing of -OH groups were acquired based on contact angle and X-ray photoelectron spectroscopy characterizations. A tight and defect-free bonding interface was confirmed by scanning electron microscopy. More importantly, benefiting from low-temperature tolerance and radiation-hardened properties of polyimide material, the bonding strength of the heterostructure based on oxygen plasma activation achieved 6.582 MPa and 3.339 MPa corresponding to room temperature and ultra-low temperature (≈ -263.15 °C), which meets the bonding strength requirements of aerospace applications.
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Yang, Xiangyu, Wenping Geng, Kaixi Bi, Linyu Mei, Yaqing Li, Jian He, Jiliang Mu, Xiaojuan Hou, and Xiujian Chou. "The Wafer-Level Integration of Single-Crystal LiNbO3 on Silicon via Polyimide Material." Micromachines 12, no. 1 (January 9, 2021): 70. http://dx.doi.org/10.3390/mi12010070.
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In situ measurements of sensing signals in space platforms requires that the micro-electro-mechanical system (MEMS) sensors be located directly at the point to be measured and in contact with the subject to be measured. Traditional radiation-tolerant silicon-based MEMS sensors cannot acquire spatial signals directly. Compared to silicon-based structures, LiNbO3 single crystalline has wide application prospects in the aerospace field owing to its excellent corrosion resistance, low-temperature resistance and radiation resistance. In our work, 4-inch LiNbO3 and LiNbO3/Cr/Au wafers are fabricated to silicon substrate by means of a polyimide bonding method, respectively. The low-temperature bonding process (≤100 °C) is also useful for heterostructure to avoid wafer fragmentation results from a coefficient of thermal expansion (CTE) mismatch. The hydrophilic polyimide surfaces result from the increasing of -OH groups were acquired based on contact angle and X-ray photoelectron spectroscopy characterizations. A tight and defect-free bonding interface was confirmed by scanning electron microscopy. More importantly, benefiting from low-temperature tolerance and radiation-hardened properties of polyimide material, the bonding strength of the heterostructure based on oxygen plasma activation achieved 6.582 MPa and 3.339 MPa corresponding to room temperature and ultra-low temperature (≈ −263.15 °C), which meets the bonding strength requirements of aerospace applications.
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Paganelli, Mariano, and Daniele Paganelli. "New Development in the Non Contact Optical Measurement of Thermo-Mechanical Properties of Materials." Advances in Science and Technology 68 (October 2010): 23–30. http://dx.doi.org/10.4028/www.scientific.net/ast.68.23.
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The optical measurement of thermo-mechanical properties allows the sample to be completely free from constraints. This enables the possibility to measure the true change in size or volume of a material during a sintering process. Thanks to the fact that the measure is carried out with no contact in becomes possible to carry out other measurements during the test, like the change in mass. Joining a double beam optical dilatometer and an electronic scale we can measure simultaneously the change in size with a resolution of one part over 100.000 and the change in weight of the specimen, with a resolution of 1 part over 10.000. Moreover, thanks to a innovative temperature controller design, the heat treatment can be designed with complete freedom, even from a mathematical formula (i.e. sinusoidal or exponential) and it can be controlled by the change in size of the specimen during the test. This makes it possible to perform the controlled rate sintering (shrinkage) even if the driving force of the sintering process is the viscous flow of glassy phases, like in traditional ceramics.
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Hidayat, Niko Azhari, Prisma Megantoro, Abdufattah Yurianta, Amila Sofiah, Shofa Aulia Aldhama, and Yutika Amelia Effendi. "The application of instrumentation system on a contactless robotic triage assistant to detect early transmission on a COVID-19 suspect." Indonesian Journal of Electrical Engineering and Computer Science 22, no. 3 (June 1, 2021): 1334. http://dx.doi.org/10.11591/ijeecs.v22.i3.pp1334-1344.
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<p>This article discusses the instrumentation system of airlangga robotic triage assistant version 1 (ARTA-1), a robot used as a contact-free triage assistant for Coronavirus disease (COVID-19) suspects. The triage process consists of automatic vital signs check-up as well as the suspect’s anamnesis that in turns will determine whether the suspect will get a specific care or not. Measurements of a suspect’s vital conditions, i.e. temperature, height, and weight, are carried out with sensors integrated with the Arduino boards, while a touch-free, hand gesture questions and answers is carried out to complete anamnesis process. A portable document format (PDF) format of the triage report, which recommends what to do to the suspect, will then be automatically generated and emailed to a designated medical staff.</p>
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Fan, Aoran, Qinyi Li, Weigang Ma, and Xing Zhang. "Laser Flash Raman Spectroscopy Method for Characterizing the Specific Heat of a Single Nanoparticle." Journal of Nanoscience and Nanotechnology 19, no. 11 (November 1, 2019): 7004–13. http://dx.doi.org/10.1166/jnn.2019.16626.
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Nanoparticles are widely used in composite materials, nanoscale devices, biological detectors and medical treatment. The thermophysical properties of a single nanoparticle are, therefore, important for both nanotechnology and nanoscience applications. However, property measurements are limited by the spatial resolution of conventional measurement methods, so there are not yet any effective measurement methods to characterize the thermophysical properties of a single nanoparticle. This paper describes a laser flash Raman spectroscopy method for measuring the specific heat of a single nanoparticle supported on a free-standing substrate based on a lumped parameter model for the nanoparticle coupled with a transient 2D thermal conduction model for the suspended substrate. A series of square laser pulses are assumed to be used to heat the supported single nanoparticle in a vacuum. The temperature increases in the single nanoparticle and the suspended substrate are then measured based on their Raman band shifts. The laser absorption coefficients of the nanoparticle and the substrate are then eliminated by comparing the temperature increases measured using different laser pulse widths. The specific heat of the nanoparticle and the thermal contact conductance between the nanoparticle and the substrate can then be extracted by fitting the temperatures of both the nanoparticle and the substrate. Case studies show that the method can accurately measure the specific heat of a single nanoparticle about 100 nm in diameter using ~1 ns pulse widths. The influence of the nanoparticle geometry and the thermophysical properties of the substrate are also discussed.
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Jiang, Yuanping, Jiaxun Li, Fangming Liu, Zongcai Zhang, Zhengjun Li, Mingbo Yang, and Lixin Li. "The effects of surface modification using O2 low temperature plasma on chrome tanning properties of natural leather." Journal of Industrial Textiles 49, no. 4 (September 30, 2018): 534–47. http://dx.doi.org/10.1177/1528083718804205.
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Low temperature plasma technology has the characteristics of economy, pollution-free and high efficiency. The pioneering works were carried out by applying low temperature plasma to surface modification of natural leather and chrome tanning process, to reduce water pollution. The effects of oxygen low temperature plasma treatment on the micro-structure, chemical compositions and active groups of leather fiber were studied in this paper. The optimal low temperature plasma treatment time was 10 min, which had the maximal chrome exhausting value. The SEM results showed that the leather surface was etched rougher with time increasing. The contact angle measurements showed that the hydrophilic property of leather surface increased after low temperature plasma process. The XPS data showed that the O1s area ratios increased from 19.49% to 26.45%, the content of COOH roughly tripled after O2 low temperature plasma treatment for 10 min, and the surface chrome content increased from 1.09% to 1.31% after chrome tanning. Based on the above results, low temperature plasma technology may provide a new exploring method for high-exhaustion chrome tanning technology.
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Shilin, Alexandr, Alexey Shilin, Sergey Dementyev, and Nadezhda Kuznetsova. "Device for contactless ice buildup monitoring of overhead power line wires." Energy Safety and Energy Economy 3 (June 2021): 5–11. http://dx.doi.org/10.18635/2071-2219-2021-3-5-11.
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Ice buildup monitoring is essential to prevent wire breakage on overhead power lines. Conventional telemetry systems which are based on load cell sensors have some drawbacks as reflected in this paper. We suggest an innovative device for contactless ice buildup monitoring of overhead power line wires video recording the power line clearance. A specific algorithm for detecting the lowest point of wire sag has been provided. Also, we analyze a possibility of indirect contact sensor-free measurements of a wire temperature when the wire is being covered by icy deposits. A specific buildup type can be determined comparing a dew point and desublimation point as shown in this paper.
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Buffel, Bart, Marijke Amerijckx, Martijn Hamblok, Bart van Mieghem, Frederik Desplentere, and Albert van Bael. "Experimental and Computational Analysis of the Heating Step during Thermoforming of Thermoplastics." Key Engineering Materials 651-653 (July 2015): 1003–8. http://dx.doi.org/10.4028/www.scientific.net/kem.651-653.1003.
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The present study addresses the difficulties in heating thermoplastic sheets for ther-moforming applications. In industrial environments, the sheets are heated in a contact free method by means of convective hot air ovens and infrared radiation. In this study the temperature evolution at the outer surface as well as the core of thermoplastic sheets as a function of time is measured by means of thermocouples. These measurements reveal significant through thickness temperature dif-ferences which need to be resolved before high quality products can be made. The temperature dif-ferences can be decreased by decreasing the radiative power. This is however not acceptable in in-dustry since it lowers the number of produced parts per unit of time.In order to gain insight in the time-temperature relationship during the heating phase, a finite differ-ence model is developed. The model clearly shows the constantly changing through thickness tem-perature distribution and can be used as a tool by the thermoforming industry to optimize the pro-duction process.
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Abdel–Fattah, Essam. "Surface Activation of Poly(Methyl Methacrylate) with Atmospheric Pressure Ar + H2O Plasma." Coatings 9, no. 4 (March 30, 2019): 228. http://dx.doi.org/10.3390/coatings9040228.
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The atmospheric pressure of Ar + H 2 O plasma jet has been analyzed and its effects on the poly(methyl methacrylate) (PMMA) surface has been investigated. The PMMA surface treatment was performed at a fixed gas flow-rate discharge voltage, while varying the plasma treatment time. The Ar + H 2 O plasma was studied with optical emission spectroscopy (OES). Optimum plasma conditions for PMMA surface treatment were determined from relative intensities of Argon, hydroxyl radical (OH), oxygen (O) I emission spectra. The rotational temperature T rot of Ar + H 2 O plasma was determined from OH emission band. The PMMA surfaces before and after plasma treatment were characterized by contact angle and surface free energy measurements, X-ray photoelectrons spectroscopy (XPS), atomic force microscope (AFM) and UV-spectroscopy. The contact angle decreased and surface free energy increased with plasma treatment time. XPS results revealed the oxygen to carbon ratio (O/C) on plasma-treated PMMA surfaces remarkably increased for short treatment time ≤60 s, beyond which it has weakly dependent on treatment time. The carbon C1s peak deconvoluted into four components: C–C, C–C=O, C–O–C and O–C=O bonds and their percentage ratio vary in accordance with plasma treatment time. AFM showed the PMMA surface roughness increases with plasma treatment time. UV-visible measurements revealed that plasma treatment has no considerable effect on the transparency of PMMA samples.
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Journal, Baghdad Science. "Adsorption of Congo, Red Rhodamine B and Disperse Blue Dyes From Aqueous Solution onto Raw Flint Clay." Baghdad Science Journal 9, no. 4 (December 2, 2012): 680–88. http://dx.doi.org/10.21123/bsj.9.4.680-688.
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Removal of Congo red, Rhodamine B, and Dispers Blue dyes from water solution have been achieved using Flint Clay as an adsorbent. The adsorption was studied as a function of contact time, adsorbent dose, pH, and temperature under batch adsorption technique. The equilibrium data fit with Langmuir, Freundlich and Toth models of adsorption and the linear regression coefficient R2 was used to elucidate the best fitting isotherm model. Different thermodynamic parameters, namely Gibb’s free energy, enthalpy and entropy of the on-going adsorption process have also been evaluated. Batch technique has been employed for the kinetic measurements and the adsorption of the three dyes follows a second order rate kinetics. The kinetic investigations also reveal that intraparticle diffusion mechanism was operative
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Haas, Charles N., Josh Joffe, Mark Heath, Joseph Jacangelo, and Uma Anmangandla. "Predicting disinfection performance in continuous flow systems from batch disinfection kinetics." Water Science and Technology 38, no. 6 (September 1, 1998): 171–79. http://dx.doi.org/10.2166/wst.1998.0250.
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Disinfection processes have often been characterized by the “CT” concept i.e., the product of disinfectant residual and contact time (perhaps as a function of pH, temperature, and other water quality variations) produces a given level of disinfection. The objective of this work was to develop and validate the use of reaction kinetic models for disinfection process design. Using bench scale (batch) kinetic information, and hydraulic characterization of pilot scale continuous disinfection processes, predictions of continuous process performance were made using a segregated flow model. These predictions were compared to independent experimental measurements of actual inactivation in pilot scale processes. Preammoniation, free residual chlorination, and ozonation were used on two waters from Portland, Oregon (US). Organisms used were Giardia muris, bacteriophage MS2, and Escherichia coli.
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Chong, William Woei Fong, Siti Hartini Hamdan, King Jye Wong, and Suzana Yusup. "Modelling Transitions in Regimes of Lubrication for Rough Surface Contact." Lubricants 7, no. 9 (September 2, 2019): 77. http://dx.doi.org/10.3390/lubricants7090077.
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Accurately predicting frictional performance of lubrication systems requires mathematical predictive tools with reliable lubricant shear-related input parameters, which might not be easily accessible. Therefore, the study proposes a semi-empirical framework to predict accurately the friction performance of lubricant systems operating across a wide range of lubricant regimes. The semi-analytical framework integrates laboratory-scale experimental measurements from a pin-on-disk tribometer with a unified numerical iterative scheme. The numerical scheme couples the effect of hydrodynamic pressure generated from the lubricant and interacting asperity pressure, essential along the mixed lubrication regime. The lubricant viscosity-pressure coefficient is determined using a free-volume approach, requiring only the lubricant viscosity-temperature relation as the input. The simulated rough surface contact shows transition in lubricant regimes, from the boundary to the elastohydrodynamic lubrication regime with increasing sliding velocity. Through correlation with pin-on-disk frictional measurements, the slope of the limiting shear stress-pressure relation γ and the pressure coefficient of boundary shear strength m for the studied engine lubricants are determined. Thus, the proposed approach presents an effective and robust semi-empirical framework to determine shear properties of fully-formulated engine lubricants. These parameters are essential for application in mathematical tools to predict more accurately the frictional performance of lubrication systems operating across a wide range of lubrication regimes.
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Shipps, Catharine, H. Ray Kelly, Peter J. Dahl, Sophia M. Yi, Dennis Vu, David Boyer, Calina Glynn, et al. "Intrinsic electronic conductivity of individual atomically resolved amyloid crystals reveals micrometer-long hole hopping via tyrosines." Proceedings of the National Academy of Sciences 118, no. 2 (December 28, 2020): e2014139118. http://dx.doi.org/10.1073/pnas.2014139118.
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Proteins are commonly known to transfer electrons over distances limited to a few nanometers. However, many biological processes require electron transport over far longer distances. For example, soil and sediment bacteria transport electrons, over hundreds of micrometers to even centimeters, via putative filamentous proteins rich in aromatic residues. However, measurements of true protein conductivity have been hampered by artifacts due to large contact resistances between proteins and electrodes. Using individual amyloid protein crystals with atomic-resolution structures as a model system, we perform contact-free measurements of intrinsic electronic conductivity using a four-electrode approach. We find hole transport through micrometer-long stacked tyrosines at physiologically relevant potentials. Notably, the transport rate through tyrosines (105 s−1) is comparable to cytochromes. Our studies therefore show that amyloid proteins can efficiently transport charges, under ordinary thermal conditions, without any need for redox-active metal cofactors, large driving force, or photosensitizers to generate a high oxidation state for charge injection. By measuring conductivity as a function of molecular length, voltage, and temperature, while eliminating the dominant contribution of contact resistances, we show that a multistep hopping mechanism (composed of multiple tunneling steps), not single-step tunneling, explains the measured conductivity. Combined experimental and computational studies reveal that proton-coupled electron transfer confers conductivity; both the energetics of the proton acceptor, a neighboring glutamine, and its proximity to tyrosine influence the hole transport rate through a proton rocking mechanism. Surprisingly, conductivity increases 200-fold upon cooling due to higher availability of the proton acceptor by increased hydrogen bonding.
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Carmeli, Enrico, Bao Wang, Paolo Moretti, Davide Tranchida, and Dario Cavallo. "Estimating the Nucleation Ability of Various Surfaces Towards Isotactic Polypropylene via Light Intensity Induction Time Measurements." Entropy 21, no. 11 (October 31, 2019): 1068. http://dx.doi.org/10.3390/e21111068.
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Crystallization of isotactic polypropylene (iPP) at the interface with crystalline films of two commercially employed nucleating agents (sodium benzoate (NaBz) and sodium 2,2’-methylene bis-(4,6-di-tert-butylphenyl)phosphate (NA-11)) and with a glass fiber (GF) was investigated using a polarized optical microscope. The analysis of the light intensity evolution during the crystallization process enabled the successful estimation of the time at which the crystal growth began, i.e., the induction time (ti), at various crystallization temperatures. Meaningful differences in the ti values were observed between the investigated systems. Moreover, the ti data have been analyzed according to different nucleation models proposed in the literature, which consider either the time to form the first crystalline layer in contact with the substrate or the time required to grow a cluster of critical size. It has been found that the two models are applicable in different temperature ranges depending on the efficiency of the given substrate. Therefore, in order to obtain the value of the surface free energy difference function, Δσ, which is directly related to the nucleation energy barrier and useful for the definition of a universal nucleating efficiency scale, a model that considers both the above-mentioned times was fitted to the overall data. The values of Δσ for the nucleation of iPP on the surface of the different substrates are thus obtained and discussed in the framework of the literature results.
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Wiese, Klaus, Thiemo M. Kessel, Reinhard Mundl, and Burkhard Wies. "An Analytical Thermodynamic Approach to Friction of Rubber on Ice." Tire Science and Technology 40, no. 2 (April 1, 2012): 124–50. http://dx.doi.org/10.2346/1945-5852-40.2.124.
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ABSTRACT The presented investigation is motivated by the need for performance improvement in winter tires, based on the idea of innovative “functional” surfaces. Current tread design features focus on macroscopic length scales. The potential of microscopic surface effects for friction on wintery roads has not been considered extensively yet. We limit our considerations to length scales for which rubber is rough, in contrast to a perfectly smooth ice surface. Therefore we assume that the only source of frictional forces is the viscosity of a sheared intermediate thin liquid layer of melted ice. Rubber hysteresis and adhesion effects are considered to be negligible. The height of the liquid layer is driven by an equilibrium between the heat built up by viscous friction, energy consumption for phase transition between ice and water, and heat flow into the cold underlying ice. In addition, the microscopic “squeeze-out” phenomena of melted water resulting from rubber asperities are also taken into consideration. The size and microscopic real contact area of these asperities are derived from roughness parameters of the free rubber surface using Greenwood-Williamson contact theory and compared with the measured real contact area. The derived one-dimensional differential equation for the height of an averaged liquid layer is solved for stationary sliding by a piecewise analytical approximation. The frictional shear forces are deduced and integrated over the whole macroscopic contact area to result in a global coefficient of friction. The boundary condition at the leading edge of the contact area is prescribed by the height of a “quasi-liquid layer,” which already exists on the “free” ice surface. It turns out that this approach meets the measured coefficient of friction in the laboratory. More precisely, the calculated dependencies of the friction coefficient on ice temperature, sliding speed, and contact pressure are confirmed by measurements of a simple rubber block sample on artificial ice in the laboratory.
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McConnochie, Craig D., and Ross C. Kerr. "Dissolution of a sloping solid surface by turbulent compositional convection." Journal of Fluid Mechanics 846 (May 8, 2018): 563–77. http://dx.doi.org/10.1017/jfm.2018.282.
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We examine the dissolution of a sloping solid surface driven by turbulent compositional convection. The scaling analysis presented by Kerr & McConnochie (J. Fluid Mech., vol. 765, 2015, pp. 211–228) for the dissolution of a vertical wall is extended to the case of a sloping wall. The model has no free parameters and no dependence on height. It predicts that while the interfacial temperature and interfacial composition are independent of the slope, the dissolution velocity is proportional to $\cos ^{2/3}\unicode[STIX]{x1D703}$, where $\unicode[STIX]{x1D703}$ is the angle of the sloping surface to the vertical. The analysis is tested by comparing it with laboratory measurements of the ablation of a sloping ice wall in contact with salty water. We apply the model to make predictions of the turbulent convective dissolution of a sloping ice shelf in the polar oceans.
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Zatko, Bohumir, Andrea Sagatova, Katarina Sedlackova, Vladimir Necas, Frantisek Dubecky, Michael Solar, and Carlos Granja. "Detection of fast neutrons from D–T nuclear reaction using a 4H–SiC radiation detector." International Journal of Modern Physics: Conference Series 44 (January 2016): 1660235. http://dx.doi.org/10.1142/s2010194516602350.
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The particle detector based on a high purity epitaxial layer of 4H–SiC exhibits promising properties in detection of various types of ionizing radiation. Due to the wide band gap of 4H–SiC semiconductor material, the detector can reliably operate at room and also elevated temperatures. In this work we focused on detection of fast neutrons generated the by D–T (deuterium–tritium) nuclear reaction. The epitaxial layer with a thickness of 105 [Formula: see text]m was used as a detection part. A circular Schottky contact of a Au/Ni double layer was evaporated on both sides of the detector material. The detector structure was characterized by current-voltage and capacitance-voltage measurements, at first. The results show very low current density (<0.1 nA/cm[Formula: see text] at room temperature and good homogeneity of free carrier concentration in the investigated depth. The fabricated detectors were tested for detection of fast neutrons generated by the D–T reaction. The energies of detected fast neutrons varied from 16.0 MeV to 18.3 MeV according to the acceleration potential of deuterons, which increased from 600 kV up to 2 MV. Detection of fast neutrons in the SiC detector is caused by the elastic and inelastic scattering on the silicon or carbide component of the detector material. Another possibility that increases the detection efficiency is the use of a conversion layer. In our measurements, we glued a HDPE (high density polyethylene) conversion layer on the detector Schottky contact to transform fast neutrons to protons. Hydrogen atoms contained in the conversion layer have a high probability of interaction with neutrons through elastic scattering. Secondary generated protons flying to the detector can be easily detected. The detection properties of detectors with and without the HDPE conversion layer were compared.
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Leinss, S., H. Löwe, M. Proksch, J. Lemmetyinen, A. Wiesmann, and I. Hajnsek. "Anisotropy of seasonal snow measured by polarimetric phase differences in radar time series." Cryosphere Discussions 9, no. 6 (November 5, 2015): 6061–123. http://dx.doi.org/10.5194/tcd-9-6061-2015.
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Abstract. Snow settles under the force of gravity and recrystallizes by vertical temperature gradients. Both effects are assumed to form oriented ice crystals which induce an anisotropy in mechanical, thermal, and dielectric properties of the snow pack. On microscopic scales, the anisotropy could be hitherto determined only from stereology or computer tomography of samples taken from snow pits. In this paper we present an alternative method and show how the anisotropy of a natural snow pack can be observed contact- and destruction-free with polarimetric radar measurements. The copolar phase differences (CPD) of polarized microwaves transmitted through dry snow were analyzed for four winter seasons (2009–2013) from the SnowScat Instrument, installed at a test site near the town of Sodankylä, Finnland. An electrodynamic model was established based on anisotropic optics and on Maxwell–Garnett-type mixing formulas to provide a link between the structural anisotropy and the measured CPD. The anisotropy values derived from the CPD were compared with in-situ anisotropy measurements obtained by computer tomography. In addition, we show that the CPD measurements obtained from SnowScat show the same temporal evolution as space-borne CPD measurements from the satellite TerraSAR-X. The presented dataset provides a valuable basis for the future development of snow models capable of including the anisotropic structure of snow.
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Tiwari, Rupali, Vlastimil Boháč, Peter Dieška, and Gregor Götzl. "Thermophysical Parameters of Carbonate Rock estimated by Slab Model Developed for Pulse Transient Technique." Measurement Science Review 20, no. 5 (October 1, 2020): 218–23. http://dx.doi.org/10.2478/msr-2020-0027.
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AbstractThe slab model has been used for parameter estimation from the measurement performed by the Pulse Transient Technique. The estimation of thermophysical parameters was done on carbonate rock sample. In addition to basic thermal parameter for example thermal diffusivity, thermal conductivity and specific heat capacity, the slab model takes into account the heat capacity of the heat source, as well as the heat transfer coefficient between the heat source and the sample. The thermophysical parameters were estimated for the case when thermal conductive paste as a heat contact agent was not used for the measurements. The paste contains silicone oil that penetrates into the porous stone material and thus causes irreversible changes of properties during the measurement so we decided not to use it. The experiment was done with dry contacts at the interfaces that causes the disturbances in the measurement that have been introduced and resolved using the slab model. Uncertainty analysis of the estimation of the parameters by the slab model was done for real measurements conducted on the carbonate rock. In this paper we analyzed the quality of the temperature response fit in dependency on the originally free fitted parameters of the heat transfer coefficient and the heat capacity of the heat source that was replaced by constant values in two steps. The heat capacity of the heat source was calculated from the material properties, e.g., the nickel and Kapton. The fit results obtained by the slab model were compared with the data obtained by the ideal and cuboid model. The analysis of the sensitivity coefficients and calculated uncertainties of estimated parameters with the slab model help to improve the accuracy of parameter estimation.
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Ananyin, V. M., P. V. Morokhov, B. A. Kalin, R. S. Kuzmin, and O. N. Sevryukov. "Study of melting and crystallization of Cu – P alloy using a universal vacuum viscometer and thermal analysis." Industrial laboratory. Diagnostics of materials 84, no. 7 (August 8, 2018): 34–37. http://dx.doi.org/10.26896/1028-6861-2018-84-7-34-37.
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Methods of differential thermal analysis (DTA) and measurement of the melt viscosity are widely used in studying the properties of alloys at high temperatures. We have made an attempt to combine those two complementary methods of research. In contrast to the single-stranded Shvidkovskii viscometer, a bifilar suspension on two thermocouple wires is used in the proposed construction of the installation. The system based on the bifilar suspension provides using thermocouple in contact with the crucible with a sample, thus ensuring measurements of the crucible temperature like the measuring cell in DTA. The adjusting thermocouple located near the coil of a bifilar heater is used as a reference thermocouple. Since thermal analysis requires linear heating at a constant rate, and the viscosity is usually measured in a steady-state (steady-state) regime with long exposures at each measurement temperature, a series of dynamic viscosity determinations with a heating rate of 1, 2, 3 and 5 °C/min is carried out, the heating rates of 1 and 2 °C/min being approximately equal to the average heating rate under steady-state conditions. It is shown that when measuring in a dynamic mode at a heating rate up to 3 °C/min, the viscosity curves coincide with the measurement data in a steady-state mode, and the results of the thermal analysis (experimental setup) are consistent with the data of DTA (STA 409 setup). Results of measuring the logarithmic decrement of vibrations for Cu – 7.3% P alloy and data of thermal analysis are presented. Data of thermal analysis obtained on our experimental setup coincide completely with the DTA results obtained on a STA 409 unit. A model experiment carried out to explain the delay of growth of the logarithmic damping decrement at the beginning of melting and sharp decrease at the beginning of crystallization indicates to the effect of blocking free flow of the liquid melt component by the solid skeleton having a higher melting point.
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Baniya, Hom Bahadur, Rajesh Prakash Guragain, and Deepak Prasad Subedi. "Cold Atmospheric Pressure Plasma Technology for Modifying Polymers to Enhance Adhesion: A Critical Review." Reviews of Adhesion and Adhesives 9, no. 2 (June 2, 2021): 269–307. http://dx.doi.org/10.7569/raa.2021.097306.
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This review summarizes the results of cold atmospheric pressure plasma technology application in polymers surface treatment. Attention is given to results of changes in the hydrophilic property of polymer surfaces by incorporation of polar functional groups when exposed to atmospheric pressure plasma, depending on the time of treatment, applied voltage, gas flow rate, and distance from the surface. We have successfully developed a plasma device that is able to generate cold atmospheric pressure argon plasma of low temperature (20 – 26) ° C downstream using a high-voltage power source which can be widely used in materials processing. Therefore, a cost-effective system of generating a plasma jet at atmospheric pressure with potential applications has been developed. Cold atmospheric pressure plasma jet (CAPPJ) has shown a lot of applications in recent years such as in materials processing, surface modification, and biomedical materials processing. CAPPJ has been generated by a high voltage (0-20 kV) and high frequency (20-30 kHz) power supply.<br/> The discharge has been characterized by optical and electrical methods. In order to characterize cold atmospheric pressure argon plasma jet, its electron density, electron temperature, rotational temperature, and vibration temperature have been determined using the power balance method, intensity ratio method, Stark broadening method, and Boltzmann plot method, respectively. The improvement in hydrophilicity of the cold plasma-treated polymer samples was characterized by contact angle measurements, surface free energy analysis, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). Contact angle analysis showed that the discharge was effective in improving the wettability of polymers after the treatment. Furthermore, atmospheric plasma can be effectively used to remove surface contamination and to chemically modify different polymer surfaces. The chemical changes, especially oxidation and cross-linking, enhance the surface properties of the polymers.
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Winnik, Françoise M., Alexander Adronov, and Hiromi Kitano. "Pyrene-labeled amphiphilic poly-(N-isopropylacrylamides) prepared by using a lipophilic radical initiator: synthesis, solution properties in water, and interactions with liposomes." Canadian Journal of Chemistry 73, no. 11 (November 1, 1995): 2030–40. http://dx.doi.org/10.1139/v95-251.
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Fluorescently labeled amphiphilic poly-(N-isopropylacrylamides) (PNIPAM) substituted with a N-[4-(1-pyrenyl)butyl]-N-n-octadecyl group at the chain end were prepared by free-radical polymerization in dioxane of N-isopropylacrylamide (NIPAM) using 4,4′-azobis{4-cyano-N,N-[4-(1-pyrenyl)butyl]-n-octadecyl}pentanamide as the initiator. The solution properties of the polymers in water were studied as a function of polymer concentration and temperature. Quasi-elastic light-scattering measurements and fluorescence experiments monitoring the pyrene excimer and pyrene monomer emissions revealed the presence of multimolecular polymeric micelles below the lower critical solution temperature (LCST) of PNIPAM. These underwent partial, reversible reorganization as they were heated above the LCST. The interactions of the pyrene-labeled amphiphilic PNIPAM with dimyristoylphosphatidylcholine (DMPC) liposomes have been examined in water at 25 °C. From fluorescence experiments it was established that the polymeric micelles are disrupted irreversibly upon contact with the liposomes. The anchoring of the polymer chains occurs by insertion of their hydrophobic tail within the phospholipidic bilayer, as evidenced from a large decrease of the pyrene excimer emission relative to pyrene monomer emission. The copolymers remained anchored within the bilayer as the temperature of the copolymer–liposome suspension was raised above the LCST of PNIPAM. Keywords: liposome, poly-(N-isopropylacrylamide), fluorescence, micelles.
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Vasconcellos, F. C., R. A. Bataglioli, E. B. Flores, and Marisa Masumi Beppu. "Thermal Treatment Effects on Biopolymer Multilayered Thin Films." Advanced Materials Research 409 (November 2011): 181–86. http://dx.doi.org/10.4028/www.scientific.net/amr.409.181.
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Sterilization is very important for the use of biomaterials in the medical field. This work describes the preparation of chitosan/carboxymethylcellulose thin films with the layer-by-layer deposition technique, and the investigation on the effects that thermal treatments have on them during sterilization. The influence of different heating and sterilization methods on the chemical and physical structure of biopolymer thin films composed of chitosan and carboxymethylcellulose was evaluated. Films were heated in an oven at specified temperatures or autoclaved and their characteristics analyzed with contact angle, profilometry, FTIR, anionic dye uptake and UV-Vis measurements. Results show that, depending on the heating conditions, these thin films may undergo the Maillard reaction that turns the films from being transparent to brownish in color. This reaction may lead to a decrease in the free hydroxyl groups of both carboxymethylcellulose and chitosan and free ammonium groups of chitosan - consequently leading to changes in hydrophilicity and wettability of the film. Temperature effects on the characteristics of the synthetic pre-layer coating composed of poly (diallyldimethylammonium chloride) and poly (sodium 4-styrene-sulfonate) - used to provide a high cationic surface for the deposition of the biopolymer films - were also observed. These findings are of practical interest because biopolymer thin films find a great number of applications where sterilization is a must, such as clinical and medical applications and in the areas of materials science and biotechnology.
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Guo, Yudi, Dongyan Tang, and Fan Yang. "Transparent fluorinate acrylic polyurethane with hydrophobicity obtained by crosslinking of hydroxyl-containing fluoroacrylate copolymer with HDI trimer." Materials Science-Poland 33, no. 3 (September 1, 2015): 451–59. http://dx.doi.org/10.1515/msp-2015-0076.
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Abstract Hydroxyl-containing fluoroacrylate copolymers with different fluorine and hydroxyl concentrations were synthesized via free-radical solution polymerization. Transparent fluorinated polyurethane (FPU) films were prepared by curing the copolymers with HDI (hexamethylene diisocyanate) trimer. The Fourier transform infrared spectroscopy (FT-IR) results revealed introduction of fluorine both into the copolymer and polyurethane. X-ray photoelectron spectroscopy (XPS) analyses indicated that a gradient concentration of fluorine existed in the depth profile of the fluorinated polyurethane films. The highest contact angle (CA) was obtained for the FPU film with fluoroacrylate monomer concentration of 22 wt.% because of fluorine present on the film surface. The surface topographies detected by SEM and AFM indicated that surface roughness contributed little to the film hydrophobicity. By increasing the fluoroacrylate monomer concentration, the decreasing of crosslinking degree of hard segment resulted in lowering the first degradation temperature, while more C-F groups in soft segment led to higher second degradation temperature. UV-Vis spectrophotometer measurements indicated that the FPU film with the fluoroacrylate monomer concentration of 16 wt.% still had a high transmittance of more than 90 % in the whole visible wavelength range.
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Nadler, J. H., T. H. Sanders, J. K. Cochran, and S. S. Kim. "Oxide reduction and diffusion in Fe-Cr alloy honeycombs." Journal de Physique IV 120 (December 2004): 47–54. http://dx.doi.org/10.1051/jp4:2004120004.
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The goal of this study is to develop practices for evaluating and predicting the microstructural evolution of directly reduced iron-chromium alloys. This fundamental knowledge is being applied to a process developed at the Georgia Institute of Technology to fabricate metal honeycomb extrusions. A paste composed of oxide powders, binders and lubricants is extruded through a die of the desired cross-section and subsequently reduced to metal with hydrogen. The effects of time, temperature and composition on the extent of reduction and diffusion in reducing Fe2O3-Cr2O3 powder mixtures is investigated. The thermodynamics and kinetics of Fe2O3-Cr2O3 reduction are evaluated in terms of the free energy of formation as well as reducing species. The kinetics of the microstructural changes are evaluated through diffusion measurements. A thermodynamic model for Fe2O3-Cr2O3 was developed and used to determine the maximum amount of Cr2O3 that would reduce when in contact with iron as a function of the $\frac{P_{H_{2}}}{P_{H_{2}O}}$ ratio . Diffusion studies consisted of Fe-Cr2O3 couples held at temperature in a reducing atmosphere. Cr diffusion in Fe showed a concentration dependence for the geometries investigated.
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Liu, Gang, Chunlin Liu, Yuyuan Chen, Shuai Qin, Suyuan Yang, Dun Wu, Haitao Xi, and Zheng Cao. "Formation of the Self-assembled Multilayers Containing the Temperature/ pH Dual-responsive Microgels." Nanoscience &Nanotechnology-Asia 9, no. 2 (June 25, 2019): 267–77. http://dx.doi.org/10.2174/2210681208666180416154332.
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<P>Background: Stimuli-responsive microgels have attracted extensive investigations due to their potential applications in drug delivery, catalysis, and sensor technology. The self-assembled mcirogel films can contain different functional groups (e.g., -COOH, -NH2, -C=ONH2) to interact with specific molecules and ions in water, and their study is becoming increasingly important for developing both absorbent materials and sensor coatings. This paper is aimed to obtain a better understanding of the LbL multilayer formation of microgels and the branched PEI using the mass sensitive QCM. Additionally the influence of the temperature and pH on the formation of the microgel films can be achieved. </P><P> Methods: The temperature and pH sensitive P(NIPAM-co-AA-co-TMSPMA) microgels were prepared by surfactant-free emulsion polymerization and confirmed by FT-IR, laser particle size analysis, and SEM. The obtained microgel and PEI were further used to prepare multilayer thin films by the LbL self-assembly technique monitored by QCM, and their morphology and hydrophilic properties were determined by AFM and water contact angle measurements. </P><P> Results: The thermosensitive and pH sensitive P(NIPAM-co-AA-co-TMSPMA) microgels were prepared by surfactant-free emulsion polymerization. The size and swelling properties of the microgels prepared are highly dependent on the preparation conditions such as the AA and crosslinker content, and microgels showed good temperature and pH responsive properties. SEM images showed that microgels dispersed evenly on the substrate and had a uniform particle size distribution, which was consistent with the light particle size analysis results. Furthermore, multilayer films composed of the negatively charged microgels and the positively charged PEI have been built up by a facile LbL assembly method and the influence of the deposition conditions on their formation was monitored in real time by QCM. Compared to the temperature of 25 °C, the high temperature of 35°C above the phase transition temperature leads to the more adsorbed mass of microgels on the gold surface of QCM sensors. The absorbed mass values at the deposition pH 7 and 10 are 9.82 and 7.28 µg cm-2, respectively, which are much higher than 1.51 µg cm-2 of the layers deposited at pH 4. The water contact angle and AFM both confirmed the wettability properties and morphology of multilayers on the gold surface of QCM sensors. </P><P> Conclusion: The formation of the multilayer films on the gold surface by the layer-by-layer deposition technique of the negatively charged microgels and the oppositely charged PEI can be achieved. The controllable multilayer formation can be attributed to the size difference, changes in the hydrophilic property and surface charge density of microgels responsive to the external temperature and pH.</P>
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Mohammed, Maha J., Kadhum M. Shabeeb, and Bassam I. Khalil. "Effect of Polyvinyl Pyrrolidone on Polyvinyl Chloride-Graft-Acrylamide Membranes." Engineering and Technology Journal 38, no. 9A (September 25, 2020): 1305–15. http://dx.doi.org/10.30684/etj.v38i9a.1319.
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Polyvinyl-chloride (PVC) was dehydrochlorinated by alkaline-solution (NaOH) in determining molarity (3.0 M) followed by grafting with acrylamide (AM) monomer onto dehydrochlorinated PVC (DHPVC) backbone by free-radical graft copolymerization to produce new grafted polymer referred as graft 3M. Then investigated the effect of polyvinyl pyrrolidone (PVP) addition on the grafted polymer. Membranes from pure PVC, graft 3M, and graft 3M/ PVP were synthesis via a phase inversion method. The successful AM grafting onto PVC was confirmed by characterization of the membranes by Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscope (FESEM) analysis, porosity, pore size, and contact angle measurements. The new synthesis (graft 3M) and (graft 3M/ PVP) membranes show excellent hydrophilicity in compared to pure PVC membranes, confirmed by higher pure water flux (PWF). The graft 3M/ 3wt.% PVP membrane exhibited the highest pure water permeate flux was about 540 L/m2 h at 28 °C of feed temperature and 1bar of pressure, i.e. was improved by about 270 times compared to the unmodified PVC membrane and 2.35 times compared to the graft 3M membrane.
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Dohle, Rainer, Stefan Härter, Andreas Wirth, Jörg Goßler, Marek Gorywoda, Andreas Reinhardt, and Jörg Franke. "Electromigration Performance of Flip-Chips with Lead-Free Solder Bumps between 30 μm and 60 μm Diameter." International Symposium on Microelectronics 2012, no. 1 (January 1, 2012): 000891–905. http://dx.doi.org/10.4071/isom-2012-wp41.
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As the solder bump sizes continuously decrease with scaling of the geometries, current densities within individual solder bumps will increase along with higher operation temperatures of the dies. Since electromigration of flip-chip interconnects is highly affected by these factors and therefore an increasing reliability concern, long-term characterization of new interconnect developments needs to be done regarding the electromigration performance using accelerated life tests. Furthermore, a large temperature gradient exists across the solder interconnects, leading to thermomigration. In this study, a comprehensive overlook of the long-term reliability and analysis of the achieved electromigration performance of flip-chip test specimen will be given, supplemented by an in-depth material science analysis. In addition, the challenges to a better understanding of electromigration and thermomigration in ultra fine-pitch flip-chip solder joints are discussed. For all experiments, specially designed flip-chips with a pitch of 100 μm and solder bump diameters of 30–60 μm have been used [1]. Solder spheres can be made of every lead-free alloy (in our case SAC305) and are placed on a UBM which has been realized for our test chips in an electroless nickel process [2]. For the electromigration tests within this study, multiple combinations of individual current densities and temperatures were adapted to the respective solder sphere diameters. Online measurements over a time period up to 10,000 hours with separate daisy chain connections of each test coupon provide exact lifetime data during the electromigration tests. As failure modes have been identified: UBM consumption at the chip side or depletion of the Nickel layer at the substrate side, interfacial void formation at the cathode contact interface, and - to a much lesser degree - Kirkendall-like void formation at the anode side. A comparison between calculated life time data using Weibull distribution and lognormal distribution will be given.
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Mansoor, M. M., I. U. Vakarelski, J. O. Marston, T. T. Truscott, and S. T. Thoroddsen. "Stable–streamlined and helical cavities following the impact of Leidenfrost spheres." Journal of Fluid Mechanics 823 (June 23, 2017): 716–54. http://dx.doi.org/10.1017/jfm.2017.337.
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We report results from an experimental study on the formation of stable–streamlined and helical cavity wakes following the free-surface impact of Leidenfrost spheres. Similar to the observations of Mansoor et al. (J. Fluid Mech., vol. 743, 2014, pp. 295–326), we show that acoustic ripples form along the interface of elongated cavities entrained in the presence of wall effects as soon as the primary cavity pinch-off takes place. The crests of these ripples can act as favourable points for closure, producing multiple acoustic pinch-offs, which are found to occur in an acoustic pinch-off cascade. We show that these ripples pacify with time in the absence of physical contact between the sphere and the liquid, leading to extremely smooth cavity wake profiles. More importantly, the downward-facing jet at the apex of the cavity is continually suppressed due to a skin-friction drag effect at the colliding cavity-wall junction, which ultimately produces a stable–streamlined cavity wake. This streamlined configuration is found to experience drag coefficients an order of a magnitude lower than those acting on room-temperature spheres. A striking observation is the formation of helical cavities which occur for impact Reynolds numbers $Re_{0}\gtrsim 1.4\times 10^{5}$ and are characterized by multiple interfacial ridges, stemming from and rotating synchronously about an evident contact line around the sphere equator. The contact line is shown to result from the degeneration of Kelvin–Helmholtz billows into turbulence which are observed forming along the liquid–vapour interface around the bottom hemisphere of the sphere. Using sphere trajectory measurements, we show that this helical cavity wake configuration has 40 %–55 % smaller force coefficients than those obtained in the formation of stable cavity wakes.
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Drygała, Aleksandra, Marek Szindler, Magdalena Szindler, and Ewa Jonda. "Atomic layer deposition of TiO2 blocking layers for dye-sensitized solar cells." Microelectronics International 37, no. 2 (May 4, 2020): 87–93. http://dx.doi.org/10.1108/mi-01-2020-0007.
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Purpose The purpose of this paper is to improve the efficiency of dye-sensitized solar cells (DSSCs) which present promising low-cost alternative to the conventional silicon solar cells mainly due to comparatively low manufacturing cost, ease of fabrication and relatively good efficiency. One of the undesirable factor in DSSCs is the electron recombination process that takes place at the transparent conductive oxide/electrolyte interface, on the side of photoelectrode. To reduce this effect in the structure of the solar cell, a TiO2 blocking layer (BL) by atomic layer deposition (ALD) was deposited. Design/methodology/approach Scanning electron microscope, Raman and UV-Vis spectroscopy were used to evaluate the influence of BL on the photovoltaic properties. Electrical parameters of manufactured DSSCs with and without BL were characterized by measurements of current-voltage characteristics under standard AM 1.5 radiation. Findings The TiO2 BL prevents the physical contact of fluorine-doped tin oxide (FTO) and the electrolyte and leads to increase in the cell’s overall efficiency, from 5.15 to 6.18%. Higher density of the BL, together with larger contact area and improved adherence between the TiO2 layer and FTO surface provide more electron pathways from TiO2 to FTO which facilitates electron transfer. Originality/value This paper demonstrates that the introduction of a BL into the photovoltaic device structure is an important step in technology of DSSCs to improve its efficiency. Moreover, the ALD is a powerful technique which allows for the highly reproducible growth of pinhole-free thin films with excellent thickness accuracy and conformality at low temperature.
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Yugova, T. G., A. G. Belov, V. E. Kanevskii, E. I. Kladova, and S. N. Knyazev. "Comparison of the results of optical and electrophysical measurements of free electron density in n-GaAs samples doped with tellurium." Izvestiya Vysshikh Uchebnykh Zavedenii. Materialy Elektronnoi Tekhniki = Materials of Electronics Engineering 24, no. 1 (April 20, 2021): 27–33. http://dx.doi.org/10.17073/1609-3577-2021-1-27-33.
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A theoretical model has been developed that allows one to determine free electron density in n-GaAs from the characteristic points on far-infrared reflection spectra. It was shown that, in this case, it is necessary to take into account the plasmon-phonon coupling (otherwise, the electron density is overestimated). The calculated dependence of electron density, Nopt, on the characteristic wave number, ν+, which is described by a second degree polynomial, has been obtained.Twenty-five tellurium-doped gallium arsenide samples were used to measure the electron density in two ways: according to traditional four-contact Hall method (Van der Pauw method) and using the optical method we developed (measurements were carried out at room temperature). Based on the experimental results, the dependence was constructed of the electron density values obtained from the Hall data, NHall, on the electron density obtained by the optical method, Nopt. It is shown that this dependence is described by linear function. It is established that the data of optical and electrophysical measurements coincide if the electron density is Neq = 1.07 ⋅ 1018 cm-3, for lower values of the Hall density NHall < Nopt, and for large values NHall > Nopt. A qualitative model is proposed to explain the results. It has been suggested that tellurium atoms bind to vacancies of arsenic into complexes, as a result of which the electron density decreases. On the surface of the crystal, the concentration of arsenic vacancies is lower and, therefore, the condition Nopt > NHall should be satisfied. As the doping level increases, more and more tellurium atoms remain electrically active, so electron density in the volume begins to prevail over the surface one. However, with a further increase in the doping level, the ratio NHall/Nopt again decreases, tending to unity. This, probably, is due to the fact that the rate of decomposition of the complexes “tellurium atom + arsenic vacancy” decreases with increasing doping level.
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Han, Yu Mei, and Masoud Farzaneh. "Synthesis and Characterization of CeO2-Al2O3 Nanocomposite Coating on the AA6061 Alloy." Advanced Materials Research 1120-1121 (July 2015): 750–62. http://dx.doi.org/10.4028/www.scientific.net/amr.1120-1121.750.
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In the present study, a thick, uniform and crack-free sol-gel coating embedded with Al2O3-CeO2 nanoparticles was successfully synthesized and deposited on aluminum alloy AA6061 by spin coating method. The coating morphology was characterized by using a scanning electron microscopy coupled with electron diffraction x-ray spectrometer (SEM-EDX), an atomic force microscopy (AFM) and water contact angle measurements. FT-IR spectra were obtained using a Fourier transformation infrared spectrometer. The corrosion resistance of this coating in 3.5 wt.% NaCl solution was evaluated with electrochemical methods including potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). The stability of the corrosion resistance of this coating was evaluated by immersion in 3.5 wt.% NaCl solution and by exposure to the UV radiation condition. In addition, the adhesion resistance of the coating was also assessed. SEM and AFM results showed that Al2O3-CeO2 nanoparticles dispersed uniformly in the room temperature vulcanized (RTV) silicon rubber matrix and formed a thick and crack-free coating. Both polarization and impedance results reveal that CeO2-Al2O3 nanoparticles embedded silicon rubber coating can improve the corrosion resistance of the AA6061 alloy by more than three orders of magnitude. Meanwhile, the corrosion resistance of this coating was found to be stable under immersion in 3.5 wt.% NaCl solution and UV exposure conditions. However, excessive content of CeO2 nanoparticles in the coating made the coating morphology porous and decreased the thickness of the coating, which resulted in the decrease in the corrosion resistance of the coating.
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Mei, Henny C. Van der, Marjorie M. Cowan, Michel J. Genet, Paul G. Rouxhet, and Henk J. Busscher. "Structural and physicochemical surface properties of Serratia marcescens strains." Canadian Journal of Microbiology 38, no. 10 (October 1, 1992): 1033–41. http://dx.doi.org/10.1139/m92-170.
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Serratia marcescens is an important pathogen with noteworthy hydrophobicity characteristics as assessed by microbial adhesion to hydrocarbons. However, the present knowledge on the surface characteristics of S. marcescens strains does not include physicochemical properties relevant for adhesion such as surface free energy and zeta potential. Also, little attention has been paid hitherto to the structural features and chemical composition of the cell surface. Therefore, as a primary aim of this paper, we characterized S. marcescens strains by means of contact angle and zeta potential measurements, X-ray photoelectron spectroscopy, and infrared spectroscopy. In addition, transmission electron microscopy on negatively stained (methylamine tungstate) and ruthenium red stained cells was employed to study structural features on the cell surface. Furthermore, as a secondary aim of this paper, the power of the various techniques to discriminate between strains was evaluated. Negative staining showed that S. marcescens RZ almost completely lost its surface fibrils upon increasing the growth temperature from 30 to 37 °C. This loss of surface fibrils was accompanied by a decrease in hydrophobicity, as measured by water contact angles on bacterial lawns. No significant differences in hexadecane contact angles were observed. Zeta potentials were only different for S. marcescens 3164, showing a considerably higher isoelectric point (IEP = 3.9) than the other strains involved (IEP about 2.5). X-ray photoelectron spectroscopy yielded differences in O/C, N/C, and P/C surface concentration ratios, which related with the IEPs of the strains, despite the fact that X-ray photoelectron spectroscopy is done on fully dehydrated cells, whereas zeta potentials are measured on cells in their physiological state. Infrared spectroscopy was not sufficiently surface sensitive to discriminate between these strains. N/C surface concentration ratios by X-ray photoelectron spectroscopy, which probes approximately 5 nm deep from the surface, were slightly higher for the pigmented, prodigiosin-containing strains RZ30 and 3164, although the presence of prodigiosin did not influence the cell surface hydrophobicity. Thus the prodigiosin is probably confined in deeper layers than probed by contact angles (approximately 0.3–0.5 nm). Key words: Serratia marcescens, fibrils, surface properties, hydrophobicity, zeta potential.
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Fan, Xiaoguang, Shiya Gu, Liyan Wu, and Lei Yang. "Preparation and characterization of thermoresponsive poly(N-isopropylacrylamide) copolymers with enhanced hydrophilicity." e-Polymers 20, no. 1 (October 30, 2020): 561–70. http://dx.doi.org/10.1515/epoly-2020-0061.
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AbstractThe poly(N-isopropylacrylamide) copolymers with the enhanced hydrophilicity were synthesized by free radical polymerization from a mixture of the monomers N-isopropylacrylamide (NIPAAm), N-vinyl pyrrolidone (NVP), hydroxypropyl methacrylate (HPM) and 3-trimethoxysilypropyl methacrylate (TMSPM) at different feeding ratios. The attenuated total reflectance-Fourier transform infrared spectrometry (ATR-FTIR), nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC) were applied to characterize the resultant copolymers. The lower critical solution temperature (LCST) of the copolymers was determined via dynamic light scattering (DLS). By alternating the molar ratios of NIPAAm and NVP, the copolymers were synthesized to have their own distinctive LCST from 25°C to 40°C. Regardless of the starting feed ratio used, the final copolymers had the similar monomeric ratio as planned. The copolymer films were then formed on platinum wafers by drop coating and thermal annealing owing to 3-trimethoxysilyl crosslinking and reacting with hydroxyl groups. The surface wettability and morphology of the specimens were observed using contact angle measurements and scanning electron microscopy (SEM), respectively. The results demonstrated that with the increase of the NVP content, the film surface became more hydrophilic. The surface microstructure of the thermoresponsive films varied depending on the copolymer composition and ambient temperature. The experimental results indicated that the addition of NVP not only increased the LCST of copolymers but also improved the hydrophilicity of the products derived from the copolymers. This ability to elevate the LCST of the polymers provides excellent flexibility in tailoring transitions for specific uses, like controlled drug release and nondestructive cell harvest.
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Ramkumar, S. Manian, and Krishnaswami Srihari. "A Novel Anisotropic Conductive Adhesive for Lead-Free Surface Mount Electronics Packaging." Journal of Electronic Packaging 129, no. 2 (August 14, 2006): 149–56. http://dx.doi.org/10.1115/1.2721086.
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The electronics industry, in recent years, has been focusing primarily on product miniaturization and lead-free assembly. The need for product miniaturization is due to the continuous demand for portable electronic products that are multifunctional, yet smaller, faster, cheaper, and lighter. This is forcing the industry to design and assemble products with miniature passive and active devices. These devices typically have fine pitch footprints that provide a very small surface area for attachment. The solder attach technique relies primarily on the formation of intermetallics between the mating metallic surfaces. With a reduction in the surface area of the pads, the ratio of intermetallic to solder is very high once the solder joint is formed. This could result in unreliable solder joints, due to the brittle nature of intermetallics. In addition, the need to eliminate lead-based materials as a means of interconnection has renewed the industry’s interest in exploring other means of assembling surface mount devices reliably. The use of a novel anisotropic conductive adhesive (ACA) as a means for assembling surface mount devices, the ACA’s performance characteristics, and preliminary research findings are discussed in this paper. Typically, ACAs require the application of pressure during the curing process to establish the electrical connection. The novel ACA uses a magnetic field to align the particles in the Z-axis direction and eliminates the need for pressure during curing. The formation of conductive columns within the polymer matrix provides a very high insulation resistance between adjacent conductors. The novel ACA also enables mass curing of the adhesive, eliminating the need for sequential assembly. The novel ACA was found to be very effective in providing the interconnection for surface mount technology (SMT) passives and leaded, bumped, or bumpless integrated circuit packages. The requirement for precise stencil printing was eliminated, as the application of magnetic field aligned the conductive columns in the Z-axis direction eliminating any lateral conductivity. The ability to mass cure the adhesive while applying the magnetic field reduced the assembly time considerably. Placement accuracy was still found to be very critical. Shear testing of adhesive joints after thermal aging showed significance past 500 h and after temperature–humidity aging showed significance within the first 100 h. I–V characteristics of the daisy chained ball grid array devices assembled with and without bumps revealed considerable difference in the breakdown current. The correlation between initial contact resistance of the daisy chain and the final breakdown current was also determined. Preliminary experiments and findings, discussed in this paper, show the viability of the ACA for mixed SMT assembly. Further experimentations will include in situ contact resistance measurements during thermal aging, temperature–humidity aging, drop testing and thermal shock.
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Nejad, Jalil Ghassemi, Bae-Hun Lee, Ji-Yung Kim, Befekadu Chemere, Si-Chul Kim, Byong-Wan Kim, Kyu-Hyun Park, and Kyung-Il Sung. "Body Temperature Responses and Hair Cortisol Levels in Dairy Holstein Cows Fed High- and Low-Forage Diet and Under Water Deprivation During Thermal-Humidity Exposure." Annals of Animal Science 19, no. 1 (January 1, 2019): 113–25. http://dx.doi.org/10.2478/aoas-2018-0042.
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AbstractBody temperature responses and hair cortisol levels in dairy Holstein cows fed high- and low-forage diet and under water deprivation during thermal-humidity exposure (THE) were evaluated. Two experiments (Exps.) were conducted between July and September 2012 and 2013 for 64 d and 74 d, respectively. First, twenty dairy Holstein cows (90±30 DIM; 37.2±1.7 l milk/d, 620±75 kg BW) were used. The practical forage:concentrate (F:C) ratios in the low forage (LF) and high forage (HF) group were 44:56 and 56:44, respectively, while they were designed to be 40:60 and 60:40. Second, thirty dairy cows (53.5±30.4 DIM; 41.7±1.5 l milk/d,650±53 kg BW) were allotted into two groups of free access to water (FAW) and 2 h water deprivation (2hWD) following feeding. The animals were subjected to having the hair cut (1 to 2 g) from their foreheads at the same time (12:00 h) twice at the beginning (prior to the beginning of heat stress) and the end of the experiment when the cows were under THE. Hair cortisol levels (initial hair cut as the baseline and re-grown hair) were measured using ELISA method. Body temperature (BT) was measured twice daily at 7 body points of cows including rectum, vagina, hip, udder, rumen-side (flank), ear, and forehead using non-contact forehead infrared thermometer (infrared gun having two modes: inner and skin) on the 7 d of the beginning and the last 7 d of the experiment at 1000 and 1400 h. Statistical analyses were carried out using the MIXED model of SAS as repeated measurements. The intra-assay and inter-assay coefficients of variations for hair cortisol measurements were 3.15 and 10.05, respectively. Hair cortisol (HC) levels were not different within the two groups in both Exps. (P>0.05); however, HC level was lower (P<0.0001) prior to temperature-humidity exposure (THE). Results of Exp. 1 showed that vagina inner temperature was higher (P=0.041) and rectal temperature tended to be higher (P=0.083) in the HF compared to the LF group. The inner ear temperature was lower and ear skin temperature was higher (P=0.032) in the HF compared to the LF group. Forehead inner temperature was higher (P=0.048) in the LF group than in the HF group while forehead skin temperature was lower in the HF group (P=0.041). No differences were observed in the hip, udder and rumen-side (flank) temperature (both in body and skin) between the HF and LF group (P=0.012). In Exp. 2, no temperature differences were observed at all of the body points, inner and skin, between the two groups (P>0.05). However, the skin temperature in the 2hWD groups tended to be higher than in the FAW group (P=0.093). Conclusions drawn indicate the beneficial use of measuring BT at different body points of the cow in addition to RT under THE.
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Seal, Sayan, Brandon Passmore, and Brice McPherson. "Evaluation of Low Cost, High Temperature Die and Substrate Attach Materials for Silicon Carbide (SiC) Power Modules." International Symposium on Microelectronics 2018, no. 1 (October 1, 2018): 000317–25. http://dx.doi.org/10.4071/2380-4505-2018.1.000317.
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Abstract The performance of SiC power devices has demonstrated superior characteristics as compared to conventional Silicon (Si) devices. Some of the advantages of SiC power devices over Si include higher voltage blocking capability, low specific on-resistance, high switching frequency, high temperature operation, and high power density. Thus, SiC modules are capable of processing significant levels of power within much smaller volumes compared with its Si counterparts. These high thermal loads present a formidable challenge in integrating SiC devices in power modules. For example, known-good materials and processes for silicon power modules are not rated at the aggressive operating conditions associated with SiC devices. Two of the most critical interfaces in a power electronics module are the die-attach and substrate- attach. A degradation in these interfaces often results in potentially catastrophic electrical and thermal failure. Therefore, it is very important to thoroughly evaluate die-attach materials before implementing them in SiC power modules. This paper presents the methodology for the evaluation of die attach materials for SiC power modules. Preforms of a lead-free high-temperature attach material were used to perform a die and substrate attach process on a conventional power module platform. The initial attach quality was inspected using non- destructive methods consisting of acoustic microscopy and x-ray scanning. Die attach and substrate attach voiding of < 5% was obtained indicating a very good attach quality. Cross-sectioning techniques were used to validate the inspection methods. The initial attach strength was measured using pull tests and shear tests. The measurements were repeated at the rated temperature of the module to ensure that the properties did not degrade excessively at the service temperature. At the rated module temperature of 175 °C, the die bonding strength was found to be ~ 75 kg. This was only 25% lower than the strength at room temperature. In addition, the contact pull strength was measured to be > 90 kg at 175 °C, which was 25% lower than the value measured at room temperature. The effect of power cycling and thermal cycling on the quality and strength of the die and substrate attach layers was also investigated.
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Baniya, Hom Bahadur, Rajesh Prakash Guragain, Binod Baniya, and Deepak Prasad Subedi. "Experimental Study of Cold Atmospheric Pressure Plasma Jet and Its Application in the Surface Modification of Polypropylene." Reviews of Adhesion and Adhesives 8, no. 2 (June 30, 2020): S1—S14. http://dx.doi.org/10.7569/raa.2020.097304.
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The cold plasma technology is gaining popularity as one of the most effective tools for a wide range of applications. Cold atmospheric pressure plasma jet (CAPPJ) has attracted considerable attention in recent times for materials processing such as surface modification and biomedical applications. The cold atmospheric pressure plasma jet sustained in pure argon has been used here to modify the surface properties of polypropylene. CAPPJ has been generated by a high voltage power supply 5 kV at an operating frequency of 20 kHz. This paper reports the diagnostics of CAPPJ in argon environment by electrical and optical methods and its application in the surface modification of polypropylene (PP). The surface properties of the untreated and plasma-treated PP samples were characterized by contact angle measurements, surface free energy determination, scanning electron microscopy and Fourier transform infrared spectroscopy analysis. Most of the previous work has used RF power supply which is more expensive compared to the power supply used in the present study. The plasma jet is designed with locally available materials and can be used for continuous treatment for long time. We have successfully developed a plasma device that is able to generate a non-equilibrium atmospheric pressure argon plasma jet of low temperature. Therefore, a cost-effective system of generating a plasma jet at atmospheric pressure with potential applications in materials processing and biomedical research has been developed.
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Košelová, Zuzana, Jozef Ráheľ, and Oleksandr Galmiz. "Plasma Treatment of Thermally Modified and Unmodified Norway Spruce Wood by Diffuse Coplanar Surface Barrier Discharge." Coatings 11, no. 1 (January 1, 2021): 40. http://dx.doi.org/10.3390/coatings11010040.
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This work deals with the treatment of wood surfaces by diffuse coplanar surface barrier discharge (DCSBD) generated at atmospheric pressure. The effect of the distance of the sample from the electrode surface and the composition of the working gas in the chamber was studied. Norway spruce (Picea abies) wood, both unmodified and thermally modified, was chosen as the investigated material. The change in the surface free energy (SFE) of the wood surface was investigated by contact angles measurements. Chemical and structural changes were studied using infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Activation at a 0.15 mm gap from the electrode led in all cases to an increase in the SFE. The largest change in SFE components was recorded for wood thermally modified to 200 °C. At a 1 mm gap from the electrode increase of SFE occurred only when oxygen (O2) and argon (Ar) were used as working gas. Treatment in air and nitrogen (N2) resulted in an anomalous reduction of SFE. With the growing temperature of thermal modification, this hydrophobization effect became less pronounced. The results point out the importance of precise position control during the DCSBD mediated plasma treatment. A slight reduction of SFE on thermally modified spruce was achieved also by short term ultra-violet (UV) light exposure, generated by DCSBD.
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Negrila, Constantin-Catalin, Mihail Florin Lazarescu, Constantin Logofatu, Costel Cotirlan, Rodica V. Ghita, Florica Frumosu, and Lucian Trupina. "XPS Analysis of AuGeNi/Cleaved GaAs(110) Interface." Journal of Nanomaterials 2016 (2016): 1–6. http://dx.doi.org/10.1155/2016/7574526.
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The depth composition of the thin layer alloy, AuGeNi, devoted to acting as an ohmic contact on n-GaAs(110) has been investigated by in situ XPS combined with Argon ion sputtering techniques. The fresh cleaved surfaces, supposed to be free of oxygen, were usually deposited with a 200 nm metallic layer in high vacuum conditions (better than 10−7 torr), by thermal evaporation, and annealed at a 430–450° Celsius temperature for 5 minutes. About 18 sessions of ion Ar surfaces etching and intermediate XPS measurements were performed in order to reveal the border of the metal/semiconductor interface. The atomic concentrations of the chemical elements have been approximated. Au4f, Ga3d, Ga2p, As3d, As2p, Ni2p3/2, Ge3d, O1s, and C1s spectral lines were recorded. The Au, Ge, and Ni have a homogenous distribution while Ga and As tend to diffuse to the surface. Oxygen is present in the first layers of the surface while carbon completely disappears after the second etching step. The existence of an Au-Ga alloy was detected and XPS spectra show only metal Ni and Ge within the layer and at the interface. We tried to perform a study about the depth chemical composition profile analysis of AuGeNi layer on cleaved n-GaAs(110) by X-Ray Photoelectron Spectroscopy (XPS) technique.