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1
Senetakis, Kostas, and Anastasios Anastasiadis. "Material Damping of Crushed Rock in Free-Decay Mode." Applied Mechanics and Materials 775 (July 2015): 283–86. http://dx.doi.org/10.4028/www.scientific.net/amm.775.283.
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Damping of geo-materials in resonant column test is commonly evaluated with two alternative experimental methods; during a steady-state vibration (SSV) and during free-vibration decay (FVD). Damping is an important dynamic property necessary to capture the complete behavior of soils. In the study, representative test results on crushed rock are discussed with a focus on material damping derivations along with stiffness degradation test results derived from torsional resonant column tests. A comparison between material damping derived from the SSV and FVD methods and from small to medium shear strains is presented and discussed. In the first part of the paper, the definition of material damping by means of a closed loop in the shear stress - shear strain plane is presented along with a report on literature data associated with damping of coarse-grained soils and the important factors that control material damping of sands and gravels. In the second part, the materials and experimental techniques of the study are described briefly and the background of determining material damping in a resonant column test is also presented along with the analytical formulae. Finally, in the third part representative test results are given including both stiffness and damping, and a comparison of damping derivations using different methods is also highlighted.
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Kim, Dong-Soo, Gi-Chul Kweon, and Kwang-Ho Lee. "Alternative Method of Determining Resilient Modulus of Compacted Subgrade Soils Using Free-Free Resonant Column Test." Transportation Research Record: Journal of the Transportation Research Board 1577, no. 1 (January 1997): 62–69. http://dx.doi.org/10.3141/1577-08.
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An alternative procedure of determining the resilient modulus ( MR) of compacted subgrade soils using a free-free resonant column (FF-RC) test is proposed. The FF-RC test was used to determine a small-strain Young’s modulus ( Emax) and Poisson’s ratio on the basis of the elastic wave propagation theory. Resonant column (RC) and torsional shear (TS) tests were performed to investigate the effects of loading frequency and strain amplitude on the resilient modulus of subgrade soils. By performing FF-RC, RC/TS, and MR tests on the synthetic specimens of known stiffnesses, the feasibility of using the FF-RC test to measure the MR was evaluated and the MR testing equipment was calibrated. Moduli of subgrade soils determined by FF-RC tests match well with values obtained from RC and TS tests at small strains, indicating that the FF-RC test can provide a reliable estimation of Emax, if the effects of loading frequency are considered. In the proposed method, Emax obtained from the FF-RC test can be combined with the effect of loading frequency and the modulus reduction curve determined by the data base of the RC and TS tests for the compacted subgrade soils of various plasticity indexes. Moduli obtained from the proposed method overlapped nicely with MR values determined by standard MR testing, showing the capability of the proposed method being used in determining MR values, provided that the effects of loading frequency and modulus reduction curve are considered.
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Facciorusso, Johann, and Claudia Madiai. "On Cohesive Soil Damping Estimation by Free Vibration Method in Resonant Column Test." Geotechnical Testing Journal 43, no. 6 (April 1, 2020): 20180241. http://dx.doi.org/10.1520/gtj20180241.
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Gabryś, Katarzyna, Emil Soból, Wojciech Sas, and Alojzy Szymański. "Material damping ratio from free-vibration method." Annals of Warsaw University of Life Sciences – SGGW. Land Reclamation 50, no. 2 (June 1, 2018): 83–97. http://dx.doi.org/10.2478/sggw-2018-0007.
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Abstract One important aspect of soil dynamics is attenuation or energy loses. This inherent dynamic property is essential in the analysis of soil behavior subjected to a dynamic load. Energy absorption in soils leads to the definition of an equivalent viscous damping ratio (D). In resonant column testing there are commonly two different approaches in measuring material damping: during a steady-state vibration (SSV), when the specimen is vibrated at its first mode; and during free-vibration decay (FVD). The study reports results associated with the small to medium strain range material damping from FVD method, i.e. there is a cut off the constant vibration of the specimen at resonance and the specimen is allowed to free-vibration mode while the decay strain amplitude during free-vibration is calculated. The experiments were conducted on cohesive soils (sasiCl, Cl, clSa) from various test sites located in Warsaw, Poland. All the specimens were subjected to torsional mode of vibration at their first natural frequency, at different mean effective stress. The authors paid particular attention to the number of successive cycles after the free-vibration of the material is initiated. They examined various propositions from the literature and compare the received damping values using different number of cycles of vibration. The results showed that the most stable values of material damping ratio can be obtained by selecting each time a line of best fit on the authors’ choice of number of free-vibration cycles. However, the number of these cycles should not exceed 10.
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Schaeffer, Kevin, Richard Bearce, and Judith Wang. "Dynamic Modulus and Damping Ratio Measurements from Free-Free Resonance and Fixed-Free Resonant Column Procedures." Journal of Geotechnical and Geoenvironmental Engineering 139, no. 12 (December 2013): 2145–55. http://dx.doi.org/10.1061/(asce)gt.1943-5606.0000945.
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David Suits, L., TC Sheahan, ME Kalinski, and MSR Thummaluru. "A New Free-Free Resonant Column Device for Measurement of Gmax and Dmin at Higher Confining Stresses." Geotechnical Testing Journal 28, no. 2 (2005): 12187. http://dx.doi.org/10.1520/gtj12187.
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Prokhorov, V. E. "COLLISION OF THE DROPLET WITH THE FREE SURFACE: ACOUSTIC EMISSION IN THE WATER COLUMN." DEDICATED TO THE 90TH ANNIVERSARY OF PROF. K.N. FEDOROV OCEAN PHYSICS 47, no. 3 (November 6, 2019): 114–21. http://dx.doi.org/10.29006/1564-2291.jor-2019.47(3).10.
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An experimental study of the emission of sound by droplets falling into an unperturbed liquid was performed using wideband hydrophones and a high-speed video camera. Collision of a drop with a water surface is accompanied by air entrainment and the formation of underwater gas cavities, which leads to the appearance of surface forces and fast flows, generating extreme accelerations, which are sufficient for resonant acoustic excitation of cavities and emission of sound packets. The sequence of emitted signals contains a shock pulse, as well as one or more sound packets generated by resonant bubbles detached from underwater cavities. The number of resonating bubbles varies from experience to experience, depending on the collision scenario and further behavior, including, in particular, the process of fragmentation of the primary cavities. The dimensions of the bubbles, measured on video frames, correspond to the values calculated in accordance with the Minnaert resonance frequency.
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Tallavo, Fernando, Giovanni Cascante, Ayan Sadhu, and Mahesh D. Pandey. "New Analysis Methodology for Dynamic Soil Characterization Using Free-Decay Response in Resonant-Column Testing." Journal of Geotechnical and Geoenvironmental Engineering 140, no. 1 (January 2014): 121–32. http://dx.doi.org/10.1061/(asce)gt.1943-5606.0000984.
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Cascante, Giovanni, John Vanderkooy, and Wilson Chung. "A new mathematical model for resonant-column measurements including eddy-current effects." Canadian Geotechnical Journal 42, no. 1 (February 1, 2005): 121–35. http://dx.doi.org/10.1139/t04-073.
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Wave velocity and attenuation are commonly studied in the laboratory with the resonant-column device (American Society for Testing and Materials standard), which is driven by a set of coils and magnets. This paper presents a new and robust mathematical model of the electromechanical resonant-column system. The model is used to compute various transfer functions. Eddy currents, a new source of damping identified in the resonant-column device, introduce damping proportional to the velocity of the magnets. Eddy-current damping is considered in the mathematical model. A testing program is devised to calibrate the resonant column with three aluminum probes. Experimental and theoretical results show an excellent agreement (4% maximum error). Exploratory results are presented for a dry-sand specimen. A resonant-column device is modified to demonstrate the significant effect of the induced voltage (electromotive force (EMF)) on damping ratio if tests are not based on current measurements. Free-vibration tests on aluminum specimens and a dry-sand specimen show a significant effect of the induced EMF (up to 400% increase in damping for the sand specimen). The induced voltage depends on the resonant frequency and damping of the specimen. In the case of aluminum probes, eddy-current damping represents 20150 times the material damping of the specimen. Preliminary results on dry sand show that eddy-current damping represents up to a 15% increase in damping ratio. However, the magnitude of eddy-current damping depends on the configuration and materials used in the resonant-column device. The smaller the damping ratio of the specimen is, the more important the eddy-current damping becomes.Key words: damping, eddy currents, mechanical waves, resonant-column device, shear modulus, wave velocity.
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Xiao, Ding Jun, Bin Li, Chuan Jin Pu, and Hui Qi Zhou. "Model Test and Numerical Simulation for Directional Pressure Relief Blasting." Advanced Materials Research 779-780 (September 2013): 848–56. http://dx.doi.org/10.4028/www.scientific.net/amr.779-780.848.
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To study directional pressure relief blasting, cement mortar model tests are carried out. Protecting borehole wall, free-face wall and bottom wall are tested of the dynamic strain. Three-dimensional numerical simulation and numerical calculation of the tests are conducted by using LS-DYNA3D. The pressure values and test results of the protecting borehole wall, free-face wall and bottom wall with the same distance from the explosives are compared. Development and distribution of pressure regularity are analyzed; blast hole pressure relief effect of protecting borehole wall materials and bottom interval air column are explicated. The present results indicate that there is an obvious stress concentration phenomenon on the free-face wall, with an average pressure decrease rate of 26% from the free-face wall to the protecting borehole wall with the same distance to the explosive center, while the isolation materialPVCU plays a good directional protection. The pressure effect of the blast hole bottom air column on the blast hole is apparent. The simulation results are consistent with the experimental dates.
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Senetakis, Kostas, Anastasios Anastasiadis, and Kyriazis Pitilakis. "A comparison of material damping measurements in resonant column using the steady-state and free-vibration decay methods." Soil Dynamics and Earthquake Engineering 74 (July 2015): 10–13. http://dx.doi.org/10.1016/j.soildyn.2015.03.009.
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Cha, Min Su, Young Jong Sim, Gye Chun Cho, and Sung Won Lee. "The Effect of Joint Conditions on the Longitudinal and Flexural Wave Velocities of a Rock Mass." Key Engineering Materials 321-323 (October 2006): 306–9. http://dx.doi.org/10.4028/www.scientific.net/kem.321-323.306.
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The behavior of a jointed rock is different from that of an intact rock, and the characteristics of elastic wave propagation in a jointed rock are different from those of an intact rock. In this study, a rock resonant column testing device is designed to measure the longitudinal and flexural wave velocities of jointed rocks under different states of stress. A column of more than 12 rock discs is stacked on a steel base, which acts as a free-fixed system. This configuration ensures that waves propagate under an equivalent continuum condition, thereby rendering a constant and unique velocity. The effect of joint conditions on the wave velocities is investigated through rock resonant column testings. The results show that velocities are sensitive to the state of stress and increase nonlinearly with stress. The velocities are also affected by joint conditions such as roughness, spacing, and filling. The results are useful for rock mass classification based on near-surface geophysical characterization.
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Wang, Haishen, Francesca Barbagallo, and Peng Pan. "Test of precast pre-stressed beam-to-column joint with damage-free reinforced concrete slab." Engineering Structures 210 (May 2020): 110368. http://dx.doi.org/10.1016/j.engstruct.2020.110368.
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Jin, Dandan, Xianwen Huang, Binghui Wang, Aizhao Zhou, and Shunqing Liu. "Method Improvements of Testing Modulus of Soil Based on Free-Vibration Column." Advances in Civil Engineering 2019 (October 31, 2019): 1–9. http://dx.doi.org/10.1155/2019/9743295.
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It is difficult to directly measure the dynamic elastic modulus of soils when the strain is less than 10−4, though the dynamic shear modulus can be easily obtained by the free-vibration testing method. Some improvements were adapted to the traditional free-vibration column for measuring dynamic elastic modulus of soil precisely with lateral vibration in small strain (10−4∼10−6). Differing from the traditional lateral vibration theory, a new dynamic elastic modulus testing method based on bending vibration equation of cantilever beam was put forward based on the improved free-vibration column of GZZ-50. Firstly, some descriptions about calibration process of needed testing parameter (moment of inertia of drive board) were made, and then, Poisson’s ratio of standardized column was used to confirm the measured results. Four main improvements were applied, including the shape of drive board which made the bending vibration equation solved, laser displacement sensors for correcting specimen’s height parameter with uncontacted manner which can reduce the influence of specimen, a hoop with plug used to make the split mould be removed, and air duct used when installing drive board to increase the success rate of installing specimen. Finally, standard process of installing specimen was described, which can be used as reference of similar test.
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Park, Jae-Hyuk, and Jun Akedo. "Metal-based Optical MEMS Scanning Devices Using Lead-Free Piezoelectric Sheets Prepared by Aerosol Deposition." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2012, CICMT (September 1, 2012): 000246–50. http://dx.doi.org/10.4071/cicmt-2012-tp62.
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We demonstrate metal-based lamb-wave resonant optical MEMS scanning devices actuated by aerosol deposition (AD) piezoelectric film and report their temperature properties and durability. Metal-based structure was introduced to reduce the production cost and to improve the optical scanning performance, simultaneously. The optical scanning devices with large mirror size as well as high scanning angle were fabricated. A high optical scanning angle (more than 60 °) and a high resonant frequency (more than 25 kHz) were achieved in ambient air without vacuum packaging. The resonant frequency and the scanning angle do not have any changes during life test of approximately 50,000 hours. In this report, BaTiO3 (BTO) thick film as a lead free piezoelectric material was prepared by AD process for a piezoelectric exaltation source of scanning devices. Piezoelectric d31 of BTO-AD film was approximately −138 pm/V. The performance of optical scanner driven by AD-BTO thick film was comparable with that of BTO bulk material and AD-PZT thick film. From these results, AD-BTO film might be used to practical applications on the MEMS devices.
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Schwab, Harry. "Vibration Testing a Large Guided Missile on Air-Spring Supports." Journal of the IEST 42, no. 4 (July 14, 1999): 35–40. http://dx.doi.org/10.17764/jiet.42.4.p56174w22v3rnu15.
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When performing a vibration test on a guided missile, it is necessary to simulate the free-free condition of the missile in flight. This procedure presents technical difficulties because the missile must be supported for the test in the laboratory, and the supports can affect the mode shapes and resonant frequencies. To avoid the problems that occurred when using slings or bungee cords, an air-spring support system was developed. The performance of the air-spring support system exceeded expectations. The missile could be raised quickly and consistently on the saddles, and the supports had minimal effects on the vibration responses.
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Liu, Tingjin, Siyuan Zheng, Xinwei Tang, and Weixing Xu. "Experimental Study on Seismic Response of a Large-Span and Column-Free Subway Station in Composite Strata." Shock and Vibration 2019 (October 13, 2019): 1–15. http://dx.doi.org/10.1155/2019/8412390.
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In this paper, a shaking table test was conducted to investigate the seismic response of the large-span and column-free subway station in the upper-soft and lower-hard strata. The acceleration of the structure and the soil, the dynamic soil pressure, and the strain response of the subway station were obtained and analyzed. The results demonstrate the reasonable test design as the boundary effect was eliminated. The seismic response of the structure and soil became more severe as the acceleration amplitude of the input motion increased. It is indicated that possible shear damage of the soil and irreversible plastic deformation of the structure might have occurred as the test proceeded. The soft clay had a greater effect on the structure than that of the artificial rock. For the model structure, the tensile strain amplitude in the support region was larger than that in the midspan region. The support regions of the roof slab, lateral wall, and middle slab were the vulnerable components of the model structure during earthquakes.
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Jing, Yan Qiu, Jian Jun Liu, Guang Liang Li, Yang Hong, Xin Hua Zhang, Li Xin Xue, Xiao Hui Xie, and Jin Le. "Effect of Different Ratio of Cake Fertilizer and Inorganic Fertilizer on Free-Amino Acids in Burley Leaves." Applied Mechanics and Materials 79 (July 2011): 43–47. http://dx.doi.org/10.4028/www.scientific.net/amm.79.43.
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A Reversed-Phase High Performance Liquid Chromatographic method was developed for determining free Amino Acids in Burley Tobacco. The test was done by OPA/3-mercaptopropionic Acid as the pre-column derivatising reagent. Chromatographic column was Elitte C18 column (4.6mm×250mm i.d., 5um). Mobile phase A was 18mmol/L NaAc (PH=7.2) including 0.002% (v/v) triethylamine and 0.3% (v/v) furanidine. Mobile phase B was 100 mmol/L NaAc (PH=7.2) -Acetonitrile- methanol (v/v=1:2:2). The column temperature was 40°C and the flow rate was 1.0ml/min. The fluorescence detector was used with 350nm excitation wave length and 450nm emission wave length. The average recoveries of the method ranged 95.3% to 100.7% with the relative standard deviation of 2.32%~9.24%. The method is simple, accurate and has good repeatability. The results of the determination of seventeen kinds of free amino acids in burley leaves which were produced by way of different ratio of cake fertilizer and inorganic fertilizer. The results show that aspartic acid has the highest content however ratio of cake fertilizer and inorganic fertilizer. The most contents of free amino acids are increased and then gradually decreased with the increase of organic manure. The most contents of free amino acids are very close at the ratio of 15%:85% ratio and 30%:70% between cake fertilizer and inorganic fertilizer. The total content of free amino acids is the highest at the ratio of 30%: 70% between cake fertilizer and inorganic fertilizer. Considering comprehensively, the quality of burley leaves is the best at the ratio of 30%:70% between cake fertilizer and inorganic fertilizer.
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Bai, Yang, Carl Meggs, and Tim W. Button. "Investigation of Using Free-Standing Thick-Film Piezoelectric Energy Harvesters to Develop Wideband Devices." International Journal of Structural Stability and Dynamics 14, no. 08 (November 25, 2014): 1440016. http://dx.doi.org/10.1142/s0219455414400161.
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This paper is concerned with the wideband behavior of single-frequency and multi-frequency free-standing thick-film piezoelectric energy harvesters. The energy harvesting devices have been fabricated and brief fabrication information is provided. The individual harvesters have been combined with either symmetric or asymmetric tip masses, with some being connected together to form a harvester array. Testing has been undertaken using harmonic vibrations with a wide range of frequencies and accelerations, and also using a random machinery vibration, and data have been recorded in terms of un-rectified and rectified open-circuit voltage, output power with matched resistive loads, peak-to-peak tip displacement, and even charging rates of capacitors. As a general result, the individual harvesters with asymmetric tip masses have vibrated nonlinearly below and in the vicinity of the resonant frequencies. An individual harvester vibrating at the resonant frequency with 0.5 g acceleration has been able to charge a 1000 μF capacitor to 1 V within 12 min and to 1.5 V within 30 min. Also, the harvester array has exhibited a wideband response, where an open-circuit voltage of above 0.8 V has been provided within a certain range of frequencies. Finally, the harvester array has successfully charged a capacitor on a vibrating test sieve shaker, proving the feasibility of the proposed device in real applications.
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Santamarina, J. C., and G. Cascante. "Stress anisotropy and wave propagation: a micromechanical view." Canadian Geotechnical Journal 33, no. 5 (November 6, 1996): 770–82. http://dx.doi.org/10.1139/t96-102-323.
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Wave propagation is a constant-fabric macrophenomenon, suitable to microinterpretation. Both velocity and attenuation characterize state, including inherent and stress-induced anisotropy. The purpose of this research is to study the effect of isotropic and deviatoric stresses on wave propagation in particulate materials at low strains and to interpret results at the microlevel. A resonant-column device was midified to allow for the application of axial extension and axial compression deviatoric loading. The fixed-free boundary condition of the sample was maintained. Data for round, hard-grained sand show that shear wave velocity and attenuation are primarily dependent on the mean stress on the polarization plane, with minimal effect of the deviatoric component, in agreement with prior observations at stress ratios less than 23. Attenuation is strongly correlated with the mean stress in the polarization plane and the level of shear strain. Damping does not vanish at low strains, contrary to predictions based on hysteretic behaviour; hence, other loss mechanisms must take place at low strains. Low-strain wave parameters are adequately corrected for mid-strain using modified hyperbolic models. Measured velocity and damping trends during isotropic and anisotropic loading qualitatively agree with predictions based on regular arrays. Key words: mechanical waves, resonant column, damping, shear modulus, stress anisotropy, random vibration.
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Novianti, Yuniar Siska, Muhammad Reza, Evi Fatmawati, and Rully Ramanda. "UJI FREE DRAINING COLUMN LEACH MENGGUNAKAN VARIASI PERSENTASI MATERIAL PAF DAN NAF: STUDI KASUS OVERBURDEN TAMBANG BATUBARA." Jurnal GEOSAPTA 7, no. 1 (March 1, 2021): 43. http://dx.doi.org/10.20527/jg.v7i1.10115.
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Karakterisasi batuan penutup/overburden diperlukan untuk mengetahui penggolongan batuan berpotensi membentuk asam atau tidak sehingga dapat memperediksi potensi pembentukan air asam tambang pada kegiatan penaambangan. Salah satu bentuk karakterisasi batuan tersebut adalah dengan melakukan uji kinetik ynag berupa free draining column leach test (FDCL), tujuan pengujian FDCL ini adalah untuk mengetahui reaktivitas mineral sulfida, oksidasi dan kualitas air lindian. Dalam pengujian FDCL ini sampel diberikan berdasarkan persentasi material PAF dan NAF yaitu, kombinasi pertama adalah 40:60, kombinasi pertama adalah 50:50 dan kombinasi ketiga adalah 60:40. Pengujian ini mengguanakan siklus basah-kering dan dilakukan selama 22 hari dalam siklus harian, dan melakukan pengujian air hasil lindian dengan parameter pH, TDS dan EC. Dari hasil pengujian didapatkan bahwa ketiga kombinasi untuk nilai TDS dan EC sudah menunjukkan korelasi yang positif karena berada didalam range nilai kualitas air normal sebesar 0.5, pH awal hasil uji statik untuk batuan PAF pada pengujian ini sebesar 2.31 dan pH untruk batuan NAFnya sebesar 6.49 sehingga untuk hasil lindian pada parameter pH hari pertama berada pada kisaran 3 - 3.5 kondisi ini pada ketiga kombinasi mengalami perubahan nilai pH menuju pH netral setiap waktunya, namun pada hari ke 22 kombinasi pertama dan ketiga mengalami penurunan hal ini besar kemungkinan reaktivitas mineral sulfida masih berlangsung dan laju pelapukan batuan juga masih berproses. Sehingga harapannya jika siklus penyiraman dilanjutkan untuk siklus mingguan dan bulanan proses reaktivitas minerl sulfida dan oksidasi dapat menunjukkan nilai yang konstan. Dan untuk kombinasi yang memiliki peningkatan nilai pH yang baik ditunjukkan pada kombinasi 2 dengan pH hari pertama air lindian sebesar 3.5 dan menjadi 4.7 pada hari keduapuluh dua pengujian. Keywords: PAF; NAF; Free draining column leach test
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Sugeng, Dhani Avianto, Ahmad Muhsin Ithnin, Wira Jazair Yahya, and Hasannuddin Abd Kadir. "Emulsifier-Free Water-in-Biodiesel Emulsion Fuel via Steam Emulsification: Its Physical Properties, Combustion Performance, and Exhaust Emission." Energies 13, no. 20 (October 16, 2020): 5406. http://dx.doi.org/10.3390/en13205406.
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The focus of this work is to investigate the effect of emulsifier-free emulsion fuel via steam emulsification (SD) to the diesel engine through physical properties, combustion performance, and exhaust analysis, and compare with conventional emulsion fuel with water percentages of 5% and 10% (E5 and E10) and biodiesel blend (B5). The SD was prepared using a custom 200 mL glass mixing column. The B5 fuel quantitatively was filled in the column, and then the steam was injected from the bottom of the mixing column through the porous frit glass with the pores ranging from 40 to 100 µm. The average water droplet size of SD is 0.375 µm with the average water percentage of 6.18%. The brake specific fuel consumption (BSFC) and brake thermal efficiency (BTE) of SD improved 4.19% and 3.92%, respectively, as compared to B5. The in-cylinder pressure (ICP) was lower than B5, however, yielding close to the B5 at 4 kW engine load. As for the exhaust emission test, NOx and PM for SD were reduced significantly with a percentage reduction of 25.22% and 10.68%, respectively, as compared to neat B5. The steam emulsification method offers a huge potential to be explored further as the concept offers the alternative method of making emulsion fuel without the use of conventional mechanical mixers.
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Digilov, Rafael M., and Haim Abramovich. "Flexural Vibration Test of a Beam Elastically Restrained at One End: A New Approach for Young’s Modulus Determination." Advances in Materials Science and Engineering 2013 (2013): 1–6. http://dx.doi.org/10.1155/2013/329530.
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A new vibration beam technique for the fast determination of the dynamic Young modulus is developed. The method is based on measuring the resonant frequency of flexural vibrations of a partially restrained rectangular beam. The strip-shaped specimen fixed at one end to a force sensor and free at the other forms the Euler Bernoulli cantilever beam with linear and torsion spring on the fixed end. The beam is subjected to free bending vibrations by simply releasing it from a flexural position and its dynamic response detected by the force sensor is processed by FFT analysis. Identified natural frequencies are initially used in the frequency equation to find the corresponding modal numbers and then to calculate the Young modulus. The validity of the procedure was tested on a number of industrial materials by comparing the measured modulus with known values from the literature and good agreement was found.
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Püttmann, M., H. Krug, E. von Ochsenstein, and R. Kattermann. "Fast HPLC determination of serum free fatty acids in the picomole range." Clinical Chemistry 39, no. 5 (May 1, 1993): 825–32. http://dx.doi.org/10.1093/clinchem/39.5.825.
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Abstract We developed a method for determining individual free fatty acids in serum by using a modified one-step Dole extraction, derivatization, and a new high-performance liquid chromatographic (HPLC) separation. Sample handling is minimized to a single transfer of the fatty acids (upper layer of the Dole extract), which are readily derivatized at 85 degrees C with p-bromophenacyl bromide without significant hydrolysis of esterified fatty acids. The derivatization mixture is directly injected into the HPLC apparatus. The new method, which uses C6 (3-microns particle) column material and an isocratic acetonitrile-water eluent, separates nearly to baseline 12 of the physiologically most abundant long-chain fatty acids (C12-C22) in < 20 min with a detection limit of approximately 2 pmol. It is therefore suitable for routine analysis even with basic HPLC equipment and can easily analyze a series of 10-20 samples in about 2 h including extraction until first results are available. The method is also applicable to other matrices than serum, e.g., for determination of precursor fatty acids such as arachidonic acid in platelets or of fatty acid patterns liberated by lipases or phospholipases A1/A2 in test systems.
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D'Antimo, Marina, Mariana Zimbru, Mario D'Aniello, Jean François Demonceau, Jean Pierre Jaspart, and Raffaele Landolfo. "Preliminary Finite Element Analyses on Seismic Resistant FREE from DAMage Beam to Column Joints under Impact Loading." Key Engineering Materials 763 (February 2018): 592–99. http://dx.doi.org/10.4028/www.scientific.net/kem.763.592.
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Nowadays, the interest on structural robustness is increasing because of the recent terroristic attacks. Although a large number of research projects have been carried out in this field, limited design guidelines as well as code recommendations are nowadays available. Leading to the fact that the design for robustness is far from being current practice. Conversely, the design for natural hazards as the earthquake is a well-consolidated practice and modern codes implement effective and well-recognized design rules. Even though seismic design philosophy based on the concept of hierarchy of resistance enables structural robustness for conventional structural systems, this is not demonstrated for structures equipped with anti-seismic devices as well as innovative dissipative systems. Recently, the use of friction based dissipative joints has been proved to be a promising solution for seismically design steel moment resisting frames. However, the robustness and the resistance against impact loading of this type of joints is not yet investigated. With the aim to develop an experimental campaign based on impact tests, preliminary finite element analyses have been carried out to identify the main criticisms and to drive the rational design of the joint specimens. With this regard, in the present paper, the results of a numerical parametric study on the preliminary push-down test are presented and discussed.
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Sellars, Frank. "Seakeeping Characteristics of a Drifting Vessel." Journal of Ship Research 30, no. 01 (March 1, 1986): 26–34. http://dx.doi.org/10.5957/jsr.1986.30.1.26.
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This paper describes investigation of the roll response of a ship drifting broadside to the waves. Results of experiments with a modified Mariner-type cargo ship model free to roll, sway, heave, and pitch showed broadside drift caused a 20 percent increase in resonant roll amplitude. Calculation results for roll in beam seas with broadside drift confirmed that an increase in resonant roll amplitude is expected. These results are different from previous model tests which showed a reduction in roll when drift occurred. These previous tests had sway restrained and the effect of model test sway restraint on roll has been considered herein. It is concluded that sway restraint has a significant effect on roll.
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Nazarian, S., D. Yuan, and A. Medichetti. "Optimizing Opening of Portland Cement Concrete Pavements Using Integrated Maturity and Nondestructive Tests." Transportation Research Record: Journal of the Transportation Research Board 1861, no. 1 (January 2003): 3–9. http://dx.doi.org/10.3141/1861-01.
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The seismic testing technique was combined with the maturity concept to monitor and predict the strength gain of portland cement concrete. In this process, the dynamic modulus of elasticity of a given mixture, obtained from its stress wave velocity, can be related to the strength parameters and static modulus of the mixture by using the same specimens used in the calibration process commonly carried out for maturity tests. When these relationships are combined with the maturity parameters, the predictive power is significantly improved. In this investigation, laboratory tests with molded specimens and cores were carried out by the simplified free–free resonant column method, and field tests of concrete slabs were performed with a handheld device called the portable seismic pavement analyzer. On the basis of the results of these experiments, relationships between the dynamic modulus and the strength parameters as well as the maturity are proposed. The technique was shown to be a rapid, simple, and economical means for optimization of concrete mix design, quality control–quality assurance of concrete construction, and determination of the time required before a repaired or newly constructed structure is ready for use.
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Wang, Dong Fang, Qian Jin Liu, and Bao You Xu. "The Active Power Filter Research Based on ANN Harmonic Detection and PR Control." Advanced Materials Research 403-408 (November 2011): 1668–71. http://dx.doi.org/10.4028/www.scientific.net/amr.403-408.1668.
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This article proposed the adaptive harmonic detection based on artificial neural network，and which can test the amplitude and phase of all the harmonics. This paper also proposed the quasi-resonant control ratio strategy of active power filter. This strategy can compensate a specific harmonic of power system in real time, can achieve Static error-free control and with a strong ability of anti-grid frequency fluctuations. The results show that the method is feasible and effective.
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Zancan, Matelda, Francesca Galdi, Fulvio Di Tonno, Chiara Mazzariol, Claudio Orlando, Francesca Malentacchi, Marco Agostini, et al. "Evaluation of Cell-free DNA in Urine as a Marker for Bladder Cancer Diagnosis." International Journal of Biological Markers 24, no. 3 (July 2009): 147–55. http://dx.doi.org/10.1177/172460080902400304.
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The diagnosis and follow-up of bladder cancer are mainly based on cystoscopy, an invasive method which could be negative in case of flat malignancies such as carcinoma in situ. Other noninvasive diagnostic methods have not yet given satisfactory results. There is a need for a reliable yet noninvasive method for the detection of bladder cancer. Our aim was to investigate whether cell-free DNA quantified in urine (ucf-DNA) could be a useful marker for the diagnosis of bladder cancer. A standard urine test was performed in 150 naturally voided morning urine samples that were processed to obtain a quantitative evaluation of ucf-DNA. Leukocyturia and/or bacteriuria were found in 18 subjects, who were excluded from the study. Statistical analysis was performed on 45 bladder cancer patients and 87 healthy subjects. Ucf-DNA was extracted from urine samples by a spin column-based method and quantified using four different methods: GeneQuant Pro (Amersham Biosciences, Pittsburg, PA, USA), Quant-iT™ DNA high-sensitivity assay kit (Invitrogen, Carlsbad, CA, USA), Real-Time PCR (Applied Biosystems, Foster City, CA, USA), and NanoDrop 1000 (NanoDrop Technologies, Houston, TX, USA). Median free DNA quantification did not differ statistically between bladder cancer patients and healthy subjects. A receiver-operating characteristic (ROC) curve was developed to evaluate the diagnostic performance of ucf-DNA quantification for each method. The area under the ROC curve was 0.578 for GeneQuant Pro, 0.573 for the Quant-iT™ DNA high-sensitivity assay kit, 0.507 for Real-Time PCR, and 0.551 for NanoDrop 1000, which indicated that ucf-DNA quantification by these methods is not able to discriminate between the presence and absence of bladder cancer. No association was found between ucf-DNA quantification and tumor size or tumor focality. In conclusion, ucf-DNA isolated by a spin column-based method and quantified by GeneQuant Pro, Quant-iT™ DNA high-sensitivity assay kit, Real-Time PCR or NanoDrop 1000 does not seem to be a reliable marker for the diagnosis of bladder cancer.
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Lau, John, and Walter Dauksher. "Reliability of an 1657CCGA (Ceramic Column Grid Array) Package With 95.5SN3.9AG0.6CU Lead-Free Solder Paste on PCBS (Printed Circuit Boards)." Journal of Electronic Packaging 127, no. 2 (June 1, 2005): 96–105. http://dx.doi.org/10.1115/1.1846069.
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In many applications such as computers and telecommunications, the IC chip sizes are very big, the on-chip frequency and power dissipation are very high, and the number of chip I/Os is very large. The CCGA (ceramic column grid array) package developed by IBM is one of the best candidates for housing these kinds of chips. There are two parts in this study. One is to show that the two-parameter Weibull life distribution is adequate for modeling the thermal-fatigue life of lead-free solder joints. This is demonstrated by comparing the two-parameter and three-parameter Weibull distributions with life test data of an 1657-pin CCGA package with the 95.5 wt %Sn3.9 wt %Ag0.6 wt %Cu lead-free solder paste on lead-free printed circuit boards under thermal cycling conditions. The other part of this study is to determine the time-history creep strain energy density of the 1657-pin CCGA solder column with two different solder paste materials, namely, 95.5 wt %Sn3.9 wt %Ag0.6 wt %Cu and 63 wt %Sn37 wt %Pb and under three different thermal cycling profiles, namely, 25↔75°C, 0↔100°C, and −25↔125°C. The effects of these solder pastes and temperature conditions on the thermal-fatigue life of the high-lead (10 wt %Sn90 wt %Pb) solder columns of the CCGA package are provided and discussed.
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Yao, Zeliang, and Eric M. Lui. "Experimental and numerical investigation of the seismic performance of an A-frame–truss–column hybrid supporting structure." Advances in Structural Engineering 20, no. 9 (November 11, 2016): 1277–98. http://dx.doi.org/10.1177/1369433216674951.
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A hybrid structural system designed for use in large thermal power plants in China to house air-cooled condenser systems is investigated. The hybrid structure consists of a series of metal A-frames resting on a steel space truss supported by an array of reinforced concrete columns. To gain a better understanding of this structural system, a one-eighth (1:8) scale test structure modeled after a prototype structure was constructed and tested. The test structure was subjected to both free vibration and forced excitation tests with the following objectives: (1) determining its modal properties and seismic response characteristics, (2) gaining insight into its response and most probable failure modes under dynamic excitations, (3) obtaining some useful experimental data for future research, and (4) providing important data to complement the Chinese seismic design code as well as to guide the design of this type of structure in practical engineering applications. The free vibration tests were carried out by inducing an initial displacement to the structure and measuring its natural frequencies and mode shapes. The forced excitation tests consist of a series of quasi-static and pseudo-dynamic tests. For the quasi-static tests, 10 reciprocating displacement excitations with peaks ranging from 6 to 100 mm were used, and for the pseudo-dynamic tests, six ground motions with scaled maximum accelerations ranging from 50 to 800 cm/s2 were employed. Based on the results of these tests, modal properties of the hybrid structure such as natural frequencies, mode shapes, and equivalent damping ratios, as well as some seismic response characteristics such as seismic shears, accelerations, deformations, interstory drifts, roof drifts, and hold-down forces were determined and presented. In addition, nonlinear analysis of the test and prototype structures was conducted using the finite element software ANSYS and compared with the test results. Detailed damage inspection was performed, and important findings were summarized.
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Farhan, Muhammad, and Candra Nugraha. "Pengaruh Penggunaan Fly Ash dan Bottom Ash sebagai Cover dalam Pencegahan Pembentukan Air Asam Tambang Menggunakan Metode Free Draining Column Leach Test." Jurnal Rekayasa Hijau 5, no. 2 (July 29, 2021): 136–49. http://dx.doi.org/10.26760/jrh.v5i2.136-149.
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ABSTRAKUpaya pencegahan pembentukan air asam tambang dapat dilakukan dengan metode dry cover yang dilakukan dengan menutup batuan yang berpotensi membentuk asam (PAF) dengan batuan yang tidak berpotensi membentuk asam (NAF). Penelitian ini bertujuan untuk mengetahui pengaruh penggunaan fly ash dan bottom ash sebagai NAF dalam mencegah pembentukan AAT dengan cara mengurangi kontak antara mineral sulfida dengan air dan oksigen. Metode Free Draining Column Leach Test digunakan untuk memprediksi pembentukan AAT yang terbentuk. Simulasi perbedaan perlakuan sampel digunakan dengan 2 variasi pelapisan sampel NAF dan 3 variasi pencampuran sampel NAF. Hasilsimulasi menunjukkan bahwa dengan variasi pelapisan sampel NAF didapatkan kualitas air yang lebih baik. Penggunaan variasi pelapisanmeningkatkan nilai pH, menurunkan nilai TDS serta DHL sebagai hasil oksidasi pirit didalam batuan. Untuk menunjang hasil analisis kualitas air, pengujian statistika juga digunakan untuk mengetahui perbedaan dari variasi penggunaan fly ash dan bottom ash terhadap perubahan nilai pH, TDS dan DHL yang dihasilkan. Kata kunci : Fly ash, Bottom ash, pH, TDS, DHL ABSTRACTAcid mine drainage prevention efforts can be carried out by the method of the dry cover which is done by closing the rock that is potentially acid forming (PAF) with the non-potentially acid forming rock (NAF). This study aims to determine the effect of the fly ash and bottom ash as NAF in preventing the formation of AMD by reduce contact between the sulfide minerals with water and oxygen. The method of Free Draining Column Leach Test is used to predict the formation of AMD formed. Simulated difference in sample treatment is used with 2 variations in the coating samples of NAF and 3 variations of the mixing a sample of NAF. The simulation results show that with the variation of the coating sample of NAF obtained better water quality. The use of variations of the coating increases pH value, lower the value of TDS as well as DHL as a result of oxidation of pyrite. To support the results of water quality analysis, the statistics test is also used to determine the difference from the variation of the use of fly ash and bottom ash to change the pH value, TDS and DHL that is produced.Keywords: Fly ash, Bottom ash, pH, TDS, DHL
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Cho, Bong-Ho, Jae-Sub Lee, Hongjin Kim, and Dae-Jin Kim. "Structural Performance of a New Blind-Bolted Frame Modular Beam-Column Connection under Lateral Loading." Applied Sciences 9, no. 9 (May 10, 2019): 1929. http://dx.doi.org/10.3390/app9091929.
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This study proposes an effective steel frame modular system and evaluates the structural performance of its beam-column connection through experimental and analytical work. The new steel frame modular system utilizes the blind bolts, which allow free access to the structural members of the closed cross-section. In addition, the new modular system is designed such that the strength of its beam members is considerably lower than that of its column members to implement the strong column-weak beam concept. In order to investigate the effectiveness of the proposed modular beam-column connection, two types of specimens were designed and tested. One of the two specimens has four knee brace members to increase the bending stiffness of the connection, while the other does not have these components. The applied load versus displacement curves are plotted for the two specimens, and their failure modes are identified. Finally, a simplified analytical model for the modular beam-column connection is proposed, and its effectiveness is validated by performing its push-over analysis and comparing its results with the test results.
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Phillips, Tom, Adrian Burns, J. Adams, O. Bennett, M. Curry, S. El-Zemity, T. Esselburn, et al. "Determination of Phenols and Phenates in Disinfectant Formulations by Liquid Chromatography with UV Detection: Collaborative Study." Journal of AOAC INTERNATIONAL 95, no. 2 (March 1, 2012): 411–18. http://dx.doi.org/10.5740/jaoacint.cs2011_26.
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Abstract Fourteen collaborating laboratories assayed o-phenylphenol (OPP), p-t-amylphenol (PTAP), and o-benzyl-p-chlorophenol (OBPCP) in formulated products, both ready-to-use and concentrates, by RP-HPLC. The actives in the samples ranged from 0.03 to 11% OPP, 0.06 to 4% PTAP, and 0.07 to 10% OBPCP either in free forms or as salts. Seven blind duplicates were analyzed. The samples were diluted/extracted with acidified methanol, filtered, and analyzed by LC on a C18 column using gradient elution and UV detection at 285 nm. The concentration of the active ingredients was calculated from a standard curve. Each laboratory weighed each test sample twice within a single analytical run. The data were analyzed using all 14 laboratory results, with appropriate statistical tests to detect outliers. The repeatability RSDs ranged from 0.98 to 3.40% for the free phenols, and 1.26 to 2.51% for the salts. The reproducibility RSDs ranged from 5.31 to 7.80% for the free phenols, and 5.50 to 8.67% for the salts. The HorRat ranged from 0.86 to 2.17 for the free phenols, and 1.54 to 2.72 for the salts.
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Romo, M. P., A. Jaime, and D. Reséndiz. "The Mexico Earthquake of September 19, 1985—General Soil Conditions and Clay Properties in the Valley of Mexico." Earthquake Spectra 4, no. 4 (November 1988): 731–52. http://dx.doi.org/10.1193/1.1585499.
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We present and discuss the results of resonant column and cyclic triaxial tests on clay samples obtained from different sites within the Lake zone in the Valley of Mexico. Of particular interest are the nearly elastic behavior and low damping ratio even for shear strain amplitudes as high as 0.3 (%). A hyperbolic model reproduces adequately well the resulting shear modulus vs strain curves. Degradation of shear modulus caused by load repetition is negligible for strains lower than about 1 (%) but increases significantly for higher strains. A power-type expression fits well the modulus degradation vs number of cycles curves. Results from static triaxial tests indicate that for compression stress paths the induced pore water pressure is uniquely related to axial strains. Analyses of ground motions show that one dimensional wave propagation models may be used to predict free field seismic motions in most parts of the Lake zone.
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Sarwar, Ghulam, and Herbert G. Botting. "Rapid Analysis of Nutritionally Important Free Amino Acids in Serum and Organs (Liver, Brain, and Heart) by Liquid Chromatography of Precolumn Phenylisothiocyanate Derivatives." Journal of AOAC INTERNATIONAL 73, no. 3 (May 1, 1990): 470–75. http://dx.doi.org/10.1093/jaoac/73.3.470.
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Abstract An amino acid analysis method for protein hydrolysates, using precolumn phenylisothiocyanate (PITC) derivatlzatlon and liquid chromatography, was modified for its application In rapid analysis of commonly occurring free amino acids in serum and other physiological samples. The modifications Included changes In column temperature (47.5°C compared to 25-35°C used In analyzing protein hydrolysates), method of preparing standard and test samples, and gradient conditions. By using a Waters Pico-Tag amino acid analysis 15 cm long column (which Is also used for analyzing protein hydrolysates), separation of 27 PTC-amino acids in human serum and rat liver, brain, or heart was completed in 20 mln by the modified method. The total time for analysis and equilibration was 30 mln. The modified method was much faster than the traditional ion-exchange methods (2-3 h) or the existing liquid chromatographic methods using PITC derivatlzatlon (66-80 mln) for determining nutritionally Important free amino acids In physiological fluids and tissues. Variability of the method (expressed as coefficients of variation) for the determination (Including deprotelnizatlon, derivatlzatlon, and liquid chromatography) of all amino acids was less than 5%, which compared favorably with the reproducibility of Ion-exchange methods
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Bai, Yang, Hana Hughes, Pavel Tofel, Carl Meggs, and Tim W. Button. "Fabrication and Characterization of Vibration and Wind Energy Harvesters Using Multilayer Free-Standing Piezoelectric Thick Films." Journal of Microelectronics and Electronic Packaging 12, no. 4 (October 1, 2015): 181–88. http://dx.doi.org/10.4071/imaps.483.
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This article demonstrates the feasibility of fabricating energy harvesters based on piezoelectric cantilevers with a free-standing thick-film structure. Demonstrator devices have been designed, built, and evaluated in a range of mechanical coupling configurations to harvest energy from machinery vibrations and weak air flow. In terms of wideband vibration energy harvesters, arrays of the individual harvesters were assembled onto plastic test circuit boards integrated with diode bridge rectifiers. The harvesters were designed with different dimensions, and various tip masses were attached on the tip of the cantilevers to individually tune the resonant frequencies. The assembled harvesters were tested under harmonic vibration conditions. Great potential of harvesting vibration energy and broadening working bandwidth has been exhibited. In terms of the harvester for weak air flow, two individual cantilever devices were assembled on the chassis of a free-spinning fan. Permanent magnets were fixed on the blades of the fan as well as on the cantilevers. The device was tested in an open fluidic environment. The air flow was successfully transferred to axial oscillations, thus driving the cantilevers bending up and down. Possibilities of such devices being optimized to meet the requirements of real applications of self-powered wireless sensor networks can be foreseen.
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Du, Jie, Hui Ling Du, and Qun Li An. "Study on Methane Adsorption Capacity of Sensor Probe Based on Lead-Free Piezoelectric Resonance Modified by Zeolite X." Key Engineering Materials 748 (August 2017): 363–68. http://dx.doi.org/10.4028/www.scientific.net/kem.748.363.
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The preparation and adsorption capacity of a methane based sensor probe based on lead-free piezoelectric resonance ceramics were investigated in this paper. The zeolite X which synthesized via hydro-thermal process was used to modify the sensor probe surface. The phase structure and microstructure of the zeolite membranes was examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM).Due to the special crystal structure, the zeolite X molecular contain a regular form, uniform pore, larger surface area and a strong surface polarity. In order to test the sensor probe sensitivity, the impedance spectrum of methane adsorption sensitivity was measured at a methane concentration range from 0 to 5%. The results indicate that the sensor probe exhibits enhanced sensitivity with an offset resonant frequency of 590Hz especially at the lower methane concentration found in coal mining. The sensitivity can reach 165 Hz/1% CH4 at the concentration of methanol below 3%. With further increase of methane concentration from 3% to 5%, the sensitivity of sensor probe dropped slightly to 120Hz/1% CH4.
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Karsli, Ozlem, Avni Aksoy, Caglar Kaya, Burak Koc, Mustafa Dogan, O. Faruk Elcim, and Mehmet Bozdogan. "High power RF operations studies at TARLA facility." Canadian Journal of Physics 97, no. 11 (November 2019): 1171–76. http://dx.doi.org/10.1139/cjp-2018-0778.
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Turkish Accelerator and Radiation Laboratory (TARLA) is a facility capable of accelerating an electron beam up to 40 MeV. Two beamlines were proposed to generate free-electron laser radiation and bremsstrahlung. The accelerator employs two normal conducting cavities, so-called buncher cavities: subharmonic buncher (SHB) and fundamental buncher (FB), and two cryomodules that house two TESLA cavities each. SHB operates in 260 MHz and FB in 1.3 GHz, and is powered by 1.5 kW and 500 W radio frequency (RF) amplifiers, respectively. Each TESLA cavity is driven by 18 kW saturated high-power solid-state amplifiers (SSA). In addition, a L band pulse compressor system is designed and implemented at the facility to actively promote high-power RF research. Currently, setup of a resonant ring test bench is approved to test the RF components under high power RF conditions. This paper describes the TARLA high power RF, RF controller, and network structures. High power tests and measurements of the RF components of the TARLA beamline are given. Outcomes from the operation of the L band pulse compressor are explained, and the resonant ring test stand is stated as a summary.
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Bai, Yang, Hana Hughes, Pavel Tofel, Carl Meggs, and Tim W. Button. "Fabrication and Characterisation of Vibration and Wind Energy Harvesters Using Multi-layer Free-standing Piezoelectric Thick-films." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2015, CICMT (September 1, 2015): 000195–202. http://dx.doi.org/10.4071/cicmt-wa34.
Full textAbstract:
This paper demonstrates the feasibility of fabricating energy harvesters based on piezoelectric cantilevers with a free-standing thick-film structure. Demonstrator devices have been designed, built and evaluated in a range of mechanical coupling configurations, in order to harvest energy from machinery vibrations and weak air flow. In terms of wideband vibration energy harvesters, arrays of the individual harvesters were assembled onto plastic test circuit boards integrated with diode bridge rectifiers. The harvesters were designed with different dimensions and various tip masses were attached on the tip of the cantilevers in order to individually tune the resonant frequencies. The assembled harvesters were tested under harmonic vibration conditions. Great potential of harvesting vibration energy and broadening working bandwidth has been exhibited. In terms of the harvester for weak air flow, two individual cantilever devices were assembled on the chassis of a free-spinning fan. Permanent magnets were fixed on the blades of the fan as well as the cantilevers. The device was tested in an open fluidic environments. The air flow has been successfully transferred to axial oscillations thus driving the cantilevers bending up and down. Possibilities of such devices being optimised to meet the requirements of real applications of self-powered wireless sensor networks can be foreseen.
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Pokhotelov, O. A., R. Z. Sagdeev, M. A. Balikhin, V. N. Fedun, and G. I. Dudnikova. "Nonlinear Mirror and Weibel modes: peculiarities of quasi-linear dynamics." Annales Geophysicae 28, no. 12 (December 1, 2010): 2161–67. http://dx.doi.org/10.5194/angeo-28-2161-2010.
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Abstract. A theory for nonlinear evolution of the mirror modes near the instability threshold is developed. It is shown that during initial stage the major instability saturation is provided by the flattening of the velocity distribution function in the vicinity of small parallel ion velocities. The relaxation scenario in this case is accompanied by rapid attenuation of resonant particle interaction which is replaced by a weaker adiabatic interaction with mirror modes. The saturated plasma state can be considered as a magnetic counterpart to electrostatic BGK modes. After quasi-linear saturation a further nonlinear scenario is controlled by the mode coupling effects and nonlinear variation of the ion Larmor radius. Our analytical model is verified by relevant numerical simulations. Test particle and PIC simulations indeed show that it is a modification of distribution function at small parallel velocities that results in fading away of free energy driving the mirror mode. The similarity with resonant Weibel instability is discussed.
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Prodolleet, Jacques, Emmanuel Bugner, and Max Feevberg. "Determination of Carbohydrates in Soluble Coffee by Anion-Exchange Chromatography with Pulsed Amperometric Detection: Interlaboratory Study." Journal of AOAC INTERNATIONAL 78, no. 3 (May 1, 1995): 768–82. http://dx.doi.org/10.1093/jaoac/78.3.768.
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Abstract A collaborative study was conducted to validate a liquid chromatographic (LC) method to determine the free and total (after acid hydrolysis) carbohydrate profile of soluble coffee. Carbohydrates were separated on a pellicular anion-exchange column using pure water as mobile phase, and were detected by pulsed amperometry. Eleven collaborators were sent 6 test samples of commercial soluble coffee for duplicate analysis. They were also sent a practice sample with known levels of free and total carbohydrates and material for preparation of all standard solutions. The reproducibility relative standard deviations (RSDR) were 9.9–59.5% for mannitol, 35.6–72.6% for fucose, 4.9–21.1% for arabinose, 4.1–13.0% for galactose, 6.1–24.3% for glucose, 10.0–41.6% for sucrose, 20.2–37.7% for xylose, 10.6–40.0% for mannose, 15.5–71.7% for fructose, and 17.8–97.9% for ribose. Precision in the determination of free and total carbohydrates was very similar. The average repeatability RSDr and RSDR values were 4.5 and 14.3%, respectively, for carbohydrate levels above 0.3%. The precision of the technique was considered good, regardless of the usual peak integration problems always encountered in LC, the low levels of free carbohydrates, the hydrolysis step, and the relative lack of experience of most participating laboratories. The method allows good and reproducible separation of all major carbohydrates found in soluble coffee and is, therefore, suitable for routine analysis.
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Pols, Alana, Eric Gubesch, Nagi Abdussamie, Irene Penesis, and Christopher Chin. "Mooring Analysis of a Floating OWC Wave Energy Converter." Journal of Marine Science and Engineering 9, no. 2 (February 20, 2021): 228. http://dx.doi.org/10.3390/jmse9020228.
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This investigation focuses on the modelling of a floating oscillating water column (FOWC) wave energy converter with a numerical code (ANSYS AQWA) based on potential flow theory. Free-floating motions predicted by the numerical model were validated against experimental data extrapolated from a 1:36 scale model device in regular and irregular sea states. Upon validation, an assessment of the device’s motions when dynamically coupled with a four-line catenary mooring arrangement was conducted at different incident wave angles and sea states ranging from operational to survivable conditions, including the simulation of the failure of a single mooring line. The lack of viscosity in the numerical modelling led to overpredicted motions in the vicinity of the resonant frequencies; however, the addition of an external linear damping coefficient was shown to be an acceptable method of mitigating these discrepancies. The incident wave angle was found to have a limited influence on the magnitudes of heave, pitch, and surge motions. Furthermore, the obtained results indicated that the mooring restoring force is controlled by the forward mooring lines under the tested conditions.
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Swamy, L. Radha, Chinnasamy Senthamaraikannan, and R. Ramesh. "Investigation of the Elastic Modulus Effect on Free Vibration Characteristics of Fiber Reinforced Polymer Composite Beams Made of Various Fundamental Shapes." Advanced Materials Research 1088 (February 2015): 401–6. http://dx.doi.org/10.4028/www.scientific.net/amr.1088.401.
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Woven fiber reinforced polymer composites plays major role in structural applications. Structures subjected to dynamic situations, this leads to increased attention in finding characteristic behaviour/performance of FRP composites beams under vibrating conditions. The objective of this work is to understand and investigate the influence of cross sectional shapes of beams on successive vibration resonance frequencies and its damping performance under cantilever end conditions. The beams were fabricated by hand lay-up method in two different modulus material and cross sections like I and channel; maintaining uniform cross sectional area and moment of inertia apart from length of the beams using woven carbon fibre. The investigation was performed by impulse frequency response method using standard test procedure on low modulus Glass/epoxy composite beams and compared with high modulus Carbon/epoxy beams. Frequency response curve of I and channel shaped beams were compared for their damping performance. The modal frequencies of all fabricated beams were obtained using MEScopeVES® software and modal resonant frequencies, loss factor were compared against shapes.
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Kim, Dong-Jun, and Kyuho Sim. "Linear Dynamic Analysis of Free-Piston Stirling Engines on Operable Charge Pressure and Working Frequency along with Experimental Verifications." Applied Sciences 11, no. 11 (June 3, 2021): 5205. http://dx.doi.org/10.3390/app11115205.
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This paper presents a linear dynamic analysis on operable charge pressure and working frequency of free-piston Stirling engines (FPSE) along with experimental verifications. The equations of motion of the FPSE are formulated as a 2-degree-of-freedom (DOF) vibration system of the power piston (PP) and displacer piston (DP), based on the state equation of ideal gas and the isothermal Stirling cycle model. The dynamic models of FPSE we considered are the 1-DOF simple vibration model of each piston and the 2-DOF root locus model of coupled pistons. We developed a test FPSE for verification of the dynamic models and conducted a series of experiments to measure the dynamic behaviors of PP and DP under varying charge pressures for various masses and stiffnesses of the PP. As a result, both prediction models showed good agreements with experimental results. The 1-DOF vibration model was found to be simple and effective for predicting the operating frequency and charge pressure of FPSE. The root locus method showed reasonable predictions with an operation criterion of the PP–DP phase angle of 90°. In addition, the FPSE was confirmed to operate in resonant oscillations when the DP–PP phase angle is 90°, based on analysis of the force vector diagram of the two pistons.
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Saha, Debasish, Jayagopal Vithya, Ramalingam Kumar, and Mathew Joseph. "Studies on purification of 89Sr from irradiated yttria target by multi-column extraction chromatography using DtBuCH18-C-6/XAD-7 resin." Radiochimica Acta 107, no. 6 (June 26, 2019): 479–87. http://dx.doi.org/10.1515/ract-2018-2997.
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Abstract89Sr is being produced using yttria target via the nuclear reaction89Y(n,p)89Sr in Fast Breeder Test Reactor (FBTR), Kalpakkam. The isotope89Sr is a pure beta emitter with a half-life of 50.53 days which is useful mainly for bone pain palliation in patients with bone metastases. The existing method for processing the irradiated yttria target to obtain the pure89Sr source involves separation of the bulk yttrium target by solvent extraction using TBP-HNO3followed by purification of89Sr source by cation exchange chromatography technique using Dowex resin. The study described here involves the selective extraction and purification of89Sr by multi-column extraction chromatography technique using the Sr-specific crown ether, DtBuCH18C6 (CE) coated onto an XAD-7 resin matrix for superior separation and increased yield compared to single column technique. The89Sr source thus purified from the irradiated yttria target is free from other radionuclidic impurities produced during the target irradiation i.e.88Y,65Zn,139,141Ce,154Eu and160Tb.
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BEAUMONT, NICHOLAS. "FITTING A TABLE TO A PAGE USING NONLINEAR OPTIMIZATION." Asia-Pacific Journal of Operational Research 21, no. 02 (June 2004): 259–70. http://dx.doi.org/10.1142/s0217595904000230.
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It is sometimes difficult to fit a large table comprising several rows and columns onto a page. The usual tactic is to manually adjust column widths, abbreviate some text, and/or change some cells' font sizes until the table fits onto a page. We show that it is possible to express the problem of adjusting column widths so as to minimize the height of a table as an optimization problem with nonlinear constraints. Five test problems were routinely solved using a free software package. We stress that the solutions are approximate because the model imperfectly simulates how many lines of a cell of a table will be required to contain a segment of text, but they appear to provide good approximations in difficult cases. The scant literature is summarized; the formulation and solution techniques outlined; examples are described; and differences between theoretical and actual answers explained. It would be possible to incorporate the calculations in word processing and typesetting packages such as Word and TeX.
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Lawrence, J. P., J. S. Anand, J. D. Vande Hey, J. White, R. R. Leigh, P. S. Monks, and R. J. Leigh. "High-resolution measurements from the airborne Atmospheric Nitrogen Dioxide Imager (ANDI)." Atmospheric Measurement Techniques 8, no. 11 (November 10, 2015): 4735–54. http://dx.doi.org/10.5194/amt-8-4735-2015.
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Abstract. Nitrogen dioxide is both a primary pollutant with direct health effects and a key precursor of the secondary pollutant ozone. This paper reports on the development, characterisation and test flight of the Atmospheric Nitrogen Dioxide Imager (ANDI) remote sensing system. The ANDI system includes an imaging UV/Vis grating spectrometer able to capture scattered sunlight spectra for the determination of tropospheric nitrogen dioxide (NO2) concentrations by way of DOAS slant column density and vertical column density measurements. Results are shown for an ANDI test flight over Leicester City in the UK on a cloud-free winter day in February 2013. Retrieved NO2 columns gridded to a surface resolution of 80 m × 20 m revealed hotspots in a series of locations around Leicester City, including road junctions, the train station, major car parks, areas of heavy industry, a nearby airport (East Midlands) and a power station (Ratcliffe-on-Soar). In the city centre the dominant source of NO2 emissions was identified as road traffic, contributing to a background concentration as well as producing localised hotspots. Quantitative analysis revealed a significant urban increment over the city centre which increased throughout the flight.
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Urbański, Marek. "Compressive Strength of Modified FRP Hybrid Bars." Materials 13, no. 8 (April 17, 2020): 1898. http://dx.doi.org/10.3390/ma13081898.
Full textAbstract:
A new type of HFRP hybrid bars (hybrid fiber reinforced polymer) was introduced to increase the rigidity of FRP reinforcement, which was a basic drawback of the FRP bars used so far. Compared to the BFRP (basalt fiber reinforced polymer) bars, modification has been introduced in HFRP bars consisting of swapping basalt fibers with carbon fibers. One of the most important mechanical properties of FRP bars is compressive strength, which determines the scope of reinforcement in compressed reinforced concrete elements (e.g., column). The compression properties of FRP bars are currently ignored in the standards (ACI, CSA). The article presents compression properties for HFRP bars based on the developed compression test method. Thirty HFRP bars were tested for comparison with previously tested BFRP bars. All bars had a nominal diameter of 8 mm and their nonanchored (free) length varied from 50 to 220 mm. Test results showed that the ultimate compressive strength of nonbuckled HFRP bars as a result of axial compression is about 46% of the ultimate strength. In addition, the modulus of elasticity under compression does not change significantly compared to the modulus of elasticity under tension. A linear correlation of buckling load strength was proposed depending on the free length of HFRP bars.
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Shrestha, Avishek, Apiniti Jotisankasa, Susit Chaiprakaikeow, Sony Pramusandi, Suttisak Soralump, and Satoshi Nishimura. "Determining Shrinkage Cracks Based on the Small-Strain Shear Modulus–Suction Relationship." Geosciences 9, no. 9 (August 22, 2019): 362. http://dx.doi.org/10.3390/geosciences9090362.
Full textAbstract:
This research aims to propose the use of spectral analysis of surface wave (SASW) tests along with in-situ suction measurements for non-destructive determination of shrinkage cracks. The underlying principle behind this proposed method is that, while suction and the small-strain shear modulus are positively correlated for intact samples, this is not the case for cracked ground. A series of SASW tests were performed on a clay embankment at different periods, during which the suction, modulus, and shrinkage crack depth varied seasonally. The soil water retention curve (SWRC) of the undisturbed sample collected from the cracked zone was determined, which related the suction-to-moisture content and void ratio of the soil. A free-free resonant frequency (FFR) test in the lab was conducted to determine the small-strain shear modulus (G0) at various moisture contents. The small-strain moduli from the SASW tests on the intact ground were generally higher than those from the FFR tests due to the effect of confining stress. A drop in the small-strain modulus determined using the SASW test was observed as an increase in suction-induced cracks and it relieved the horizontal stress. The crack depth measured in the field was then modelled using a semi-empirical procedure that can be used to predict crack depth relative to suction.