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Newman, David, Steve Begg, and Matthew Welsh. "Front end loading: misunderstood or misapplied?" APPEA Journal 56, no. 1 (2016): 247. http://dx.doi.org/10.1071/aj15019.
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Historically, oil and gas projects have struggled to achieve promised outcomes. Research has demonstrated that a good predictor of project outcomes is the level of front end loading (FEL) achieved at the final investment decision (FID). Specifically, projects with high levels of FEL have more predictable costs, shorter schedules and better production attainment. Anecdotally, however, the application of FEL within the industry is patchy, with many companies advocating its use but allowing projects to pass decision gates with incomplete levels of FEL. To understand why this occurs, the authors have interviewed more than 30 senior personnel from a range of oil and gas companies, asking them a series of questions about their understanding and acceptance of FEL. Those interviewed had significant experience, averaging more than 25 years in oil and gas, and more than 20 years’ experience on opportunities and projects. Results suggest that, while FEL is highly regarded and the concept is well understood, it is not always applied appropriately. It is used as a final hurdle—checking the level of FEL just prior to the FID—rather than as a guide from the early stages to determine what work needs to be focused on to achieve a good FEL score. Furthermore, lower FEL benchmark scores are often overridden by expert judgment, justified by a project’s unique characteristics, allowing it to proceed. This approach, focusing on the specific attributes of a project and ignoring general effects or predictive models such as FEL benchmarking, is referred to as taking an inside view and is known to produce inferior results, such as cost and time overruns. The authors argue that a stricter application of FEL and benchmarking predictions, integrating it from the early stages of projects and allowing overrides only in truly exceptional cases, will produce superior outcomes.
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Beare, John B. "Uncertainty and front-end loading of labor agreements." Journal of Labor Research 6, no. 1 (March 1985): 113–17. http://dx.doi.org/10.1007/bf02685156.
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Denney, Dennis. "Front-End Loading for Change Management and Capability Delivery." Journal of Petroleum Technology 62, no. 10 (October 1, 2010): 61–62. http://dx.doi.org/10.2118/1010-0061-jpt.
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Miao, Chun-He, Liang-Zhu Yuan, Jian-Hua Lu, Peng-Fei Wang, and Song-Lin Xu. "Deformation evolution and diffusion characteristics of PMMA under impact loading." Acta Physica Sinica 71, no. 21 (2022): 216201. http://dx.doi.org/10.7498/aps.71.20220740.
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Dynamic compression experiments on cubic polymethyl methacrylate (PMMA) specimens and two kinds of trapezoid PMMA specimens are carried by changing the transmission bars into steel bar and aluminum bar on the experimental device of split Hopkinson pressure bar (SHPB). The compression processes of PMMA specimens are recorded by high-speed photography, and the breakage processes of PMMA specimens are analyzed based on the force displacement curves and high-speed images. The evolutions of deformation and diffusion resistances of PMMA specimens under impact loading are discussed. The results show that the failure of the sample is caused mainly by the partial failure front at the contact end, and then the failure front propagates to the inside of the sample, s leading the sample to break. The failure front of cubic sample is generated preferentially at the transmission end under low speed impact and at the incident end under the higher speed impact. After changing the shape of the specimen and the material of the transmission bar, the relaxation phenomenon is prominent, and the failure front occurs only at the incident end. The compressive deformation of the trapezoid sample before breakage is non-uniform, and the stress and strain in the sample gradually decrease with the increase of the cross section, and show a linear diffusion distribution. The strain distribution and shear activation diffusion equation are used to obtain the generalized diffusion resistance distribution of the failure front. The generalized diffusion resistance increases first in front of the failure front and decreases after the failure front, and the amplitude of the generalized diffusion resistance is related to the release of local strain energy.
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Yusuf F, Akhmad, Ilyas Nuryasin, and Zamah Sari. "Optimasi Kecepatan Loading Time Web Template Dengan Implementasi Teknik Front-End." Jurnal Repositor 2, no. 11 (December 4, 2020): 1456. http://dx.doi.org/10.22219/repositor.v2i11.746.
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AbstrakSitus web merupakan sekumpulan dokumen Hypertext Markup Language (HTML) statis yang dibangun untuk memudahkan setiap orang berbagi informasi, selama terhubung ke dalam jaringan internet. Salah satu bagian dari sistem sebuah situs web adalah web template. Web template adalah komponen dasar dari sistem web template berguna untuk memudahkan pengembang web merancang ulang sebuah halaman web. Salah satu yang mempengaruhi kinerja halaman web yaitu loading time, dimana loading time adalah waktu yang dibutuhkan oleh browser agar dapat menampilkan halaman web secara menyeluruh oleh pengguna ketika pengguna melakukan request, selain itu loading time merupakan salah satu bagian penting dari optimasi situs web. Optimasi merupakan suatu proses dimana memodifikasi atau merubah sesuatu yang telah ada agar efektifitasnya meningkat. Dalam sebuah situs web, terdapat beberapa konsep dalam optimasi, yaitu First Paint, Time To Interactivity (TTI), First Meaningful Paint (FMP) dan Long Task. Berdasarkan penelitian-penelitian yang sudah ada, diketahui bahwa optimasi loading time web dapat dilakukan dari sisi front-end. Oleh karena itu pada penelitian ini melakukan teknik optimasi dengan menggunakan critical rendering path, above the fold, priority resource, bundle and minify, gzip, dan splitting code. Hasil dari peforma web berdasarkan metriks first meaningful paint (FMP), first contetful paint (FCP), dan time to interactivity (TTI) mengalami peningkatan rata-rata kecepatan (perosentase) yaitu FMP sebesar 73%, FCP sebesar 60%, TTI sebesar 50%, dan loading time sebesar 29%. Selanjutnya, pada resource file rata-rata ukuran file menurun sebesar 59% dan jumlah request file menurun sebesar 21%.AbstractWebsite is a collection of HTML documents that are built to make it easy for everyone to share information, as long as they are connected to the internet. One part of a website system is a web template. Web templates are the basic components of a web template system useful for making it easy for web developers to redesign a web page. One that affects the performance of web pages is loading time, where loading time is the time needed by the browser to be able to display the web page as a whole by the user when the user makes a request, besides that loading time is one important part of website optimization. Optimization is a process where modifying or changing something that already exists in order to increase its effectiveness. In a website, there are several concepts in optimization, namely First Paint, Time To Interactivity, and First Meaningful Paint Based on existing research, it is known that web loading time optimization can be done from the front-end side. Therefore, in this study, optimization techniques using critical rendering path, above the fold, priority resources, bundle and minify, gzip, and splitting code. The implementation of matrics first meaningful paint (FMP), first contetful paint (FCP), dan time to interactivity (TTI) make increase average of speed FMP as 73%, FCP as 60%, TTI as 50%, and loading time as 29%. And then average of resource file decrease as 59% and total file of request decrease as 21%.
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Allen, Jeanne Maree, and Mark Richard Sinclair. "The Limitations of Front-end Loading in Undergraduate University Programs." Journal of the World Universities Forum 4, no. 2 (2011): 9–24. http://dx.doi.org/10.18848/1835-2030/cgp/v04i02/56740.
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Hansen, Seng, Eric Too, and Tiendung Le. "Retrospective look on front-end planning in the construction industry: Aliterature review of 30 years of research." International Journal of Construction Supply Chain Management 8, no. 1 (July 31, 2018): 19–42. http://dx.doi.org/10.14424/ijcscm801018-19-42.
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Academics and practitioners have paid close attention to front-end planning research, especially in the construction industry. It is known with many acronyms including pre-project planning and front-end loading. Since 1994, Construction Industry Institute (CII) has set front-end planning as one of themain research topicareas in their knowledge structure. A lot of research related to front-end planning and project scope definition has been conductedsince then. However, there lacks a comprehensive review of the currentstudies on the topic. Thus, the objective of this research was to undertake a comprehensive literature review of papers related to front-end planning. Reviewing 83 selected papers, this research raises several important issues regarding front-end planning such as the position of front-end planning in project life cycle, the differentiation between front-end planning and project planning, the significance of front-end planning, the front-end planning organization management, the front-end planning phases, the challenges in front-end planning implementation, and the identification of research gaps in front-end planning. The findings of this research contribute to furtherunderstanding of front-end planning andwould be useful for practitioners and academics to conduct further empirical studies on the subject matter.
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Jergeas, George. "Analysis of the Front-End Loading of Alberta Mega Oil Sands Projects." Project Management Journal 39, no. 4 (December 2008): 95–104. http://dx.doi.org/10.1002/pmj.20080.
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Malon, H., A. Ayuda, F. J. Garcia-Ramos, M. Vidal, and J. Cuartero. "Application of Low-Cost Sensors for the Development of a Methodology to Design Front-End Loaders for Tractors." Journal of Sensors 2020 (February 28, 2020): 1–13. http://dx.doi.org/10.1155/2020/3504389.
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Tractor front-end loaders are an essential part of the equipment used on farms. At present, there are an important number of small- and medium-sized companies involved in the manufacturing of this equipment. These companies rely heavily on experience for innovative designs, as in the vast majority of cases they lack access to adequate methodology for the optimal design of new front-end loaders. The study conducted has developed a methodology to design tractor front-end loaders with a view of obtaining their accurate design during the bucket loading process. The methodology comprises two phases: the first phase involves a numerical analysis of the structural behaviour of the front-end loader components by means of the Finite Element Method; the second phase, the experimental phase, makes use of low-cost sensors, in particular, strain gauges, to analyse existing strains at selected points in the front-end loader structure. The experimental results obtained by means of low-cost sensors fitted onto the front-end loader allow analysing the existing strains at the points measured, as well as validate the numerical model developed. This methodology is validated by applying it to a commercial front-end loader, more specifically to model 430E2 of the company Maquinaria Agrícola El León S.A (Spain).
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Madau, Riccardo, Daniele Colombara, Addison Alexander, Andrea Vacca, and Luigi Mazza. "An online estimation algorithm to predict external forces acting on a front-end loader." Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering 235, no. 9 (March 27, 2021): 1678–97. http://dx.doi.org/10.1177/09596518211005583.
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One of the most significant goals of earthmoving equipment is to maximize productivity during loading cycles. A real-time knowledge of the forces exchanged between the machine implement and the surrounding, that is, while digging, can be used in different ways to increase productivity. It can be used to determine the amount of material moved by the machine; or to find the optimal bucket trajectory; moreover, as input to traction control systems. This article presents an online force estimation algorithm able to predict vertical and horizontal forces exchanged between the front-loader and the surrounding environment, as well as the reaction forces through the implement itself. Taking the case of a 14-ton wheel loader as reference, this article illustrates the development of a simulation model for the analysis of the machine digging system, along with the instrumentation and testing of the proposed estimation algorithm. The model is divided into two sections describing, respectively, system kinematic and system dynamics. The kinematic model of the front-loader is compared against measurements, and results show an average error lower than 1%. The dynamic model predicts both hydraulic and dynamic features of the machine implement, achieving an accuracy on the payload mass within 2%–3%, even during dynamic conditions. The estimated pushing force reflects the expected behavior when tested for various pushing efforts and in different ground conditions. Eventually, the algorithm was tested on a complete loading cycle and the results show good consistency considering the measured front-loader trajectory and vehicle speed. The proposed model overcomes some drawbacks of the currently used technologies. For example, it allows for an online estimation of the bucket forces for any position of the implement. Although the results discussed in this article pertain to a specific reference machine, the proposed method can be extended to most wheel loaders equipped with standard digging equipment.
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Szudarek, Maciej, Konrad Kamieniecki, Sylwester Tudruj, and Janusz Piechna. "Towards Balanced Aerodynamic Axle Loading of a Car with Covered Wheels—Inflatable Splitter." Energies 15, no. 15 (July 30, 2022): 5543. http://dx.doi.org/10.3390/en15155543.
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Generating aerodynamic downforce for the wheels on the front axle of a car is a much more difficult task than for the rear axle. This paper, submitted to the special issue of Energies “Future of Road Vehicle Aerodynamics”, presents an unusual solution to increase the aerodynamic downforce of the front axle for cars with covered wheels, with the use of an elastic splitter. The effect of the inflatable splitter on the aerodynamic forces and moments was studied in a DrivAer passenger car and a fast sports car, Arrinera Hussarya. Providing that the ground clearance was low enough, the proposed solution was successful in increasing the front axle downforce without a significant increase in drag force. The possibility of emergency application of such a splitter in the configuration of the body rotated by up to 2 degrees with the front end raised was also analyzed. An elastic, deformed splitter remained effective for the nonzero pitch case. The results of the calculations are presented in the form of numerical data of aerodynamic forces, pressure and velocity distributions, and their comparisons. The benefits of the elastic splitter are documented, and the noted disadvantages are discussed.
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Liang, Jiahui, Qiuyan Fan, Menghan Liu, and Tianyu Li. "Physical Model Test on the Influence of Karst Cave under and in front of Pile on the Stability of Embedded End of Antislide Pile." Mathematical Problems in Engineering 2022 (May 28, 2022): 1–13. http://dx.doi.org/10.1155/2022/6963982.
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With the extensive use of antislide piles in engineering, the stability of the embedded end of antislide piles in karst areas has become increasingly prominent. When there is a cave in front of the antislide pile, the cave may be deformed under horizontal load, causing the stability of the embedded end of the antislide pile to lose its stability. Based on the similarity model theory, this study establishes two different shapes of caves (horizontal in the longitudinal direction and vertical in the longitudinal direction) beneath and in front of the rock-socketed section of the antislide pile. Using horizontal loading tests, the influence of the karst cave beneath and in front of the elliptical pile on the stability of the antisliding pile embedded end was studied, and the following relevant conclusions were obtained. (1) Compared with the model without cavities, the presence of cavities in front of and under the pile significantly reduces the horizontal bearing capacity of the antislip pile. The fracture trace initially develops from the bottom of the pile against the side of the active zone, roughly at 90° to the horizontal direction through the top plate of the cave and continues to develop under the cave until the boundary. (2) The horizontal bearing capacity of horizontal bearing pile is greatly reduced by karst cave. The karst cave under the pile has a greater influence on this property than that in front of pile and the influence of the two karst caves has a common effect. (3) Both sides of the bottom for pile and the roof of karst cave are prone to damage. Besides, the roof of the karst cave under the pile is more prone to damage for more obvious stress concentration. (4) The loading failure processes of all model can be roughly divided into three stages: gentle deformation, stable expansion of deformation, and accelerated expansion of deformation. (5) Compared with the case where there is no karst cave in front of pile, the karst cave in front of pile will increase the deformation of pile under horizontal load and the same level of load. (6) Based on the limit equilibrium method, a check calculation method for the bearing capacity of the anchored end when a cave existing in front of the pile is proposed. The verification method was verified.
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Allen, Jeanne Maree. "How front-end loading contributes to creating and sustaining the theory-practice gap in higher education programs." Asia Pacific Education Review 12, no. 2 (December 19, 2010): 289–99. http://dx.doi.org/10.1007/s12564-010-9141-x.
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Cho, Yoonkyung, Changsang Yun, and Chung Hee Park. "The effect of fabric movement on washing performance in a front-loading washer IV: under 3.25-kg laundry load condition." Textile Research Journal 87, no. 9 (May 13, 2016): 1071–80. http://dx.doi.org/10.1177/0040517516648508.
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This study investigated the effects of fabric movement on detergency in a front-loading washer. To this end, various fabric movements of 3.25-kg loads were induced by controlling wash spin speeds at 34, 46, 50, and 54 r/min and detergency was measured, after which the correlation between the fabric movement and detergency at each wash speed was analyzed. The observed fabric movement characteristics were represented by 10 Fabric Movement Indexes (FMIs), with numerical values defined to describe fabric movements in a front-loading washer. It was revealed that detergency was highest at the wash spin speed of 46 r/min. It was also found that each speed resulted in distinguishing characteristics of fabric movements and two FMIs, “Distance from the center of the drum to the tracer fabric” and “Number of appearances of the tracer fabric”, had the greatest influence on detergency. These results show that not only falling movement, which provides high mechanical force to fabric, but also fabric interactions, such as abrasion and mixing, also affected detergency just as significantly.
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Burchill, Madeleine, Simon A. Barter, and Michael Jones. "The Effect of Crack Growth Retardation when Comparing Constant Amplitude to Variable Amplitude Loading in an Aluminium Alloy." Advanced Materials Research 891-892 (March 2014): 948–54. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.948.
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It has often been observed that the growth of short fatigue cracks under variable amplitude (VA) cyclic loading is not well predicted when utilising standard constant amplitude (CA) crack growth rate/stress intensity data (da/dN v DK). This paper outlines a coupon fatigue test program and analyses, investigating a possible cause of crack growth retardation from CA-only testing. Various test loading spectra were developed with sub-blocks of VA and CA cycles, then using quantitative fractography (QF) the sub-block crack growth increments were measured. Comparison of these results found that, after establishing a consistent uniform crack front using a VA load sequence, the average crack growth rate then progressively slowed down with the number of subsequent CA load cycles applied. Further fractographic investigation of the fracture surface at the end of each CA and VA sub-block crack growth, identified significant crack front morphology differences. Thus it is postulated that a variation or deviation from an efficient crack path is a driver of local retardation in short crack growth during CA loading. This may be a source of error in analytical predictions of crack growth under VA spectra loading that may need to be considered in addition to other potential effects such asless closure whilst cracks are small. For aircraft designers, using solely CA data for fatigue life predictions this may result in non-conservative estimates of total crack fatigue life, producing unexpected failures or an increased maintenance burden.
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Adebayo, B., and A. E. Aladejare. "Effect of Rock Properties on Excavation-Loading Operation in Selected Quarries." Advanced Materials Research 824 (September 2013): 86–90. http://dx.doi.org/10.4028/www.scientific.net/amr.824.86.
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The effect of rock properties on excavation-loading operation in quarries was investigated by conducting test on the mechanical properties of selected rocks. These rock samples were tested in the laboratory for specific gravity, point load strength, uniaxial compressive strength and mineral composition using weigh balance, point load tester, 1100kN compression machine and petrological microscope respectively. The filling rates of the front end loaders bucket were determined. The result obtained show that value of uniaxial compressive strength varied from 29.22 MPa-30.87 MPa. The bucket filling rate varied from 0.180-0.250 m3/s and 0.145-0.170 m3/s for porphyritic biotite granite and coarse biotite granite respectively. There is strong relationship between bucket filling rate and strength properties with values of R2 ranging from 0.9737 to 0.9981.Therefore strength parameters of the rock have effect on excavation loading operation in quarries.
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Xia, Ning, Mao Sen Cao, and Qing Wen Ren. "Experimental Study on Bonding Mechanism between Corroded Bolts and Grout." Key Engineering Materials 345-346 (August 2007): 1063–66. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.1063.
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In this study, an experiment program is presented to study the bonding mechanism between corroded bolts and grout and in particular the influence on bonding behavior in terms of different corrosion sections along anchor. With respect to four groups of manufactured bolt specimens, the noncorroded and the corroded, respectively, on the front, middle and rear section along anchor, a pullout test is conducted to reveal the relationship between load and loading-end slip and to investigate the bond-stress distribution characterization along full anchor. Experimental results show that corrosion product, acting as lubricating effect at the interface between bolts and grout, can result in the degradation of bonding mechanical behavior. Meanwhile, corrosion on different sections along anchor has a different effect on the anchorage capacity of bolts. Especially, corrosion on the front section induces the greatest decrease of anchorage capacity of bolts. Thus, it is concluded that the front section along anchor is the key region affecting the bonding mechanical behavior between bolts and grout.
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Chichekin, Ilya V., Filipp A. Nyrkov, and Vladimir S. Grigoruev. "Development of a dynamic model of a front loader for the analysis of operational properties and determination of loads acting on its elements." Izvestiya MGTU MAMI 16, no. 1 (November 2, 2022): 71–80. http://dx.doi.org/10.17816/2074-0530-108869.
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BACKGROUND: For front-end loaders, it is important to minimize energy consumption when performing loading and unloading operations. To ensure competitive properties at a given time of folding links, lifting and with sufficient power of the steering and boom and bucket control drives. This requirement significantly affects the autonomy, versatility and, ultimately, the economic efficiency of loading and unloading operations.
AIMS: Development of a dynamic model of a front loader to determine various operational properties and loads in the joints when working in specified load conditions.
METHODS: A dynamic model has been developed and its operation has been simulated in a system for calculating the dynamics of coupled bodies. The mathematical model includes all the main elements of a front loader drive axles, internal combustion engine, generator, steering hydraulic cylinders, cargo, bucket, rear axle, cab, wheels, bucket lifting and tipping mechanism, load-bearing system, support surface, TED drive of the driving wheels. The elements are modeled using graphical primitives, hinges and power ones from the standard library of the application for calculating the dynamics of connected bodies.
RESULTS: The article presents a description of a mathematical model of a front loader made in the application for the calculation of connected bodies. A typical list of load modes is presented and examples and simulation results are shown. Possible areas of use of the described mathematical model are shown.
CONCLUSIONS: The developed dynamic model of the front loader makes it possible to analyze various design solutions at the early stages of design, such as the model and number of electric motors, kinematics of the bucket lifting and tilting mechanism, steering kinematics, etc. for energy costs during typical operations. In addition, the developed dynamic model allows you to determine the loads in the hinges and power connections, which can be used when performing strength calculations or when selecting loader components.
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Guo, Benqing, Hongpeng Chen, Xuebing Wang, Lei Li, and Wanting Zhou. "A wideband receiver front-end with low noise and high linearity by exploiting reconfigurable dual paths in 180 nm CMOS." Modern Physics Letters B 35, no. 12 (February 9, 2021): 2150210. http://dx.doi.org/10.1142/s0217984921502109.
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In this paper, a wideband receiver front-end including the flexible reconfigurable main and auxiliary paths is proposed. Therein, the main path has the low-noise advantage thanks to the low-noise transconductance amplifier (LNTA) preceding the mixer and baseband. Meanwhile, by utilizing a mixer-first structure, the auxiliary path renders a high in-band and out-of-band linearity. Furthermore, an inductor resonance structure is also designed to mitigate the baseband noise crosstalk issue which is disclosed by a charging/discharging mechanism via the tail capacitance of passive mixers. Both of the receiving paths have shared a common baseband circuit while loading a commonly-shared 25% duty-cycle LO source generator. Simulation results by a 180 nm CMOS have demonstrated that the main path provides a low noise figure (NF) of 2.7 dB, while the auxiliary path obtains the in-band and out-of-band IIP3 of 9.2 and 21 dBm under typical LO excitation frequency of [Formula: see text] GHz. The power consumption of the main path of the dual-path front-end is 57 mW and that of the auxiliary path is 26 mW under a supply voltage of 1.8 V.
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Toribio, Jesús, Beatriz González, and Juan-Carlos Matos. "Hydrogen-Assisted Fatigue Propagation in Corner Cracks at Holes Located in Plates under Tensile Loading." Metals 11, no. 4 (March 29, 2021): 552. http://dx.doi.org/10.3390/met11040552.
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In this study, hydrogen-assisted fatigue propagation (a kind of corrosion fatigue phenomenon) in corner cracks at holes located in plates under tensile loading was studied, the results compared with those obtained for propagation by fatigue in air. To this end, numerical modeling was carried out for the case studied to evaluate the advance of the crack front based on the Paris equation and the stress intensity factors (SIFs) obtained by Raju and Newman. The results showed that the cracks tended toward a preferential propagation path in their growth, the effect of the presence of the stress concentrator on the preferential fatigue propagation path being more pronounced in the crack growth by fatigue in air than in the crack growth by corrosion fatigue.
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Oliveira, Geiza Lima de, Asher Kiperstok, Ricardo de Araújo Kalid, Karla Patrícia Santos Oliveira Rodríguez Esquerre, and Emerson Andrade Sales. "Metodologia TECLIM para uso racional de água na indústria: o banco de ideias no contexto da metodologia front-end loading." Engenharia Sanitaria e Ambiental 21, no. 4 (December 2016): 753–64. http://dx.doi.org/10.1590/s1413-41522016109240.
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RESUMO O banco de ideias (BI) é uma ferramenta da metodologia TECLIM para otimização ambiental de processos industriais. Está conceitualmente associado com a metodologia front-end loading (FEL), a qual considera que forte atenção nas etapas iniciais de identificação e seleção de alternativas aumenta as chances de sucesso de um projeto, evitando que recursos sejam desperdiçados ou mal alocados. O BI abrange a etapa FEL 1, na qual é feito o levantamento de ideias, e segue até parte da etapa FEL 2, na qual as oportunidades selecionadas são desenvolvidas a projetos conceituais. O método para priorização de oportunidades no BI é apresentado demonstrando-se a sinergia com a FEL. A aplicação do BI permitiu o cadastro e processamento de 500 ideias com potencial de redução do consumo de água em 1,4 x 103 t.h-1 e de efluentes em pelo menos 0,5 x 103 t.h-1. O BI direciona recursos para projetos conceituais mais atrativos e sustentáveis.
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Bi, Kexin, Mengke Yang, Latif Zahid, and Xiaoguang Zhou. "A New Solution for City Distribution to Achieve Environmental Benefits within the Trend of Green Logistics: A Case Study in China." Sustainability 12, no. 20 (October 9, 2020): 8312. http://dx.doi.org/10.3390/su12208312.
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Green logistics has become a consensus and an important method to achieve sustainable development in industrial activities. However, the traditional direct distribution mode has high carbon emissions, an uncertain delivery time, and a low delivery efficiency. Uncoordinated resource allocations and unreasonable network layouts of terminal distributions have shackled green development within the express delivery industry. Considering the trend of green logistics, this study innovatively proposes a comprehensive and environmentally friendly mode for city distribution based on end crowdsourcing service stations (ECSSs). This study also adopts node centrality indices of complex network theory to evaluate the node importance of existing terminal distribution outlets. The comprehensive weights of the indices are obtained via the three-scale AHP (Analytic Hierarchy Process) and TOPSIS (Technology for Order Preference by Similarity to an Ideal Solution) methods to identify the candidate nodes for ECSSs. Finally, a location model is built to determine the optimal location to establish the ECSSs. A real-world case study was conducted to provide the location scheme of ECSSs in Beijing, China. Environmental benefits as well as economic and social benefits can be substantially achieved through the implementation of the new mode. The results show that carbon emissions can be reduced by 23.79–28.49% for the end of the distribution, 16.27–16.35% for the front-end, and approximately 17% for the entire distribution. Additionally, the loading rate of vans for the front-end of the distribution can be improved by 15.77%.
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Qian, X., Robert H. Dodds, and Y. S. Choo. "Mode Mixity for Circular Hollow Section X Joints With Weld Toe Cracks." Journal of Offshore Mechanics and Arctic Engineering 127, no. 3 (January 26, 2005): 269–79. http://dx.doi.org/10.1115/1.1951771.
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This paper describes the mode mixity of stress-intensity factors for surface cracks at weld toes located at the saddle point in circular hollow section X joints. The remote loading applies a uniform tensile stress at the end of the brace along its axis. The three-dimensional finite element models employ mesh tieing between a topologically continuous, global mesh and a separate, local crack-front mesh. Analyses of a simple plate model that approximates key features of toe cracks at the brace-chord intersection verify the negligible effects of the recommended mesh-tieing scheme on stress intensity factors. The linear-elastic analyses compute the mixed-mode stress intensity factors along the crack front using an interaction-integral approach. The mixed-mode stress intensity factors indicate that the crack front experiences predominantly mode I loading, with KIII→0 near the deepest point on the front (ϕ=π∕2). The total crack driving force, described by the J integral, reaches a maximum value at the deepest point of the crack for the crack aspect ratio a∕c=0.25 considered here. The mode-mixity angle, ψ=tan−1(KII∕KI), at ϕ=π∕2 is compared for a range of practical X-joint configurations and crack-depth ratios. The present study demonstrates that the mode-mixity angle ψ increases with increasing brace-to-chord diameter ratio (β) and decreasing chord radius to wall thickness ratio (γ). Values of the nondimensional stress intensity factors (FI=KI∕σ¯brπa and FII=KII∕σ¯brπa), however, show an opposite trend, with higher crack driving forces for small β and large γ ratios. The variations in the brace-to-chord wall thickness ratio (τ) and the crack depth ratio (a∕t0) do not generate significant effects on the mode mixity.
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Ben-Ami, Y., I. Koren, O. Altaratz, A. B. Kostinski, and Y. Lehahn. "Discernible rhythm in the spatio/temporal distributions of transatlantic dust." Atmospheric Chemistry and Physics Discussions 11, no. 8 (August 19, 2011): 23513–39. http://dx.doi.org/10.5194/acpd-11-23513-2011.
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Abstract. The differences in North African dust emission regions and transport routes, between the boreal winter and summer are thoroughly documented. Here we re-examine the spatial and temporal characteristics of dust transport over the tropical and subtropical North Atlantic Ocean, using 10 years of satellite data, in order to determine better the different dust transport periods and their characteristics. We see a robust annual triplet: a discernible rhythm of "transatlantic dust weather". The proposed annual partition is composed of two heavy loading periods, associated here with a northern-route period and southern-route period, and one clean, light-loading period, accompanied by unusually low average optical depth of dust. The two dusty periods are quite different in character: their duration, transport routes, characteristic aerosol loading and frequency of pronounced dust episodes. The southern route period lasts about ~4 months, from the end of November to end of March. It is characterized by a relatively steady southern positioning, low frequency of dust events, low background values and high variance in dust loading. The northern-route period lasts ~6.5 months, from the end of March to mid October, and is associated with a steady drift northward of ~0.1 latitude day−1, reaching ~1500 km north of the southern route. The northern period is characterized by higher frequency of dust events, higher (and variable) background and smaller variance in dust loading. It is less episodic than the southern period. Transitions between the periods are brief. Separation between the southern and northern periods is marked by northward latitudinal shift in dust transport and by moderate reduction in the overall dust loading. The second transition between the northern and southern periods commences with an abrupt reduction in dust loading (thereby initiating the clean period) and rapid shift southward of ~0.2 latitude day−1, and 1300 km in total. These rates of northward advance and southern retreat of the dust transport route are in accordance with the simultaneous shift of the Inter Tropical Front. Based on cross-correlation analyses, we attribute the observed rhythm to the contrast between the northwestern and southern Saharan dust source spatial distributions. Despite the vast difference in areas, the Bodélé Depression, located in Chad, appears to modulate transatlantic dust patterns about half the time. The proposed partition captures the essence of transatlantic dust climatology and may, therefore, supply a natural temporal framework for dust analysis via models and observations.
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Abdullah, Muhammad A'imullah, Mohammad Reza Arjmandi, Seyed Saeid Rahimian Koloor, King Jye Wong, and Mohd Nasir Tamin. "Interlaminar Damage Behavior of CFRP Composite Laminates under Cyclic Shear Loading Conditions." Advanced Materials Research 1125 (October 2015): 121–25. http://dx.doi.org/10.4028/www.scientific.net/amr.1125.121.
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This paper provides quantitative description of interlaminar damage process in CFRP composite laminates under cyclic shear loading. Quasi-static end-notched flexural (ENF) test on 16-ply CFRP composite laminate beam, [0]16 and its complementary validated FE model provide the reference “no-interlaminar damage” condition. Two identical ENF samples were fatigue to 50000 cycles, but at different load amplitude of 90 and 180 N, respectively (Load ratio, R = 0.1) to induce selectively property degradation at the interface crack front region. Subsequent quasi-static ENF tests establish the characteristic of the interlaminar damage degradation. The residual peak load for the fatigued ENF samples is measured at 1048 and 914 N for the load amplitude of 90 and 180 N, respectively. Cyclic interlaminar shear damage is represented by a linear degradation of the residual critical energy release rate, GIIC with the accumulated damage. Reasonably close comparisons of the predicted residual load-displacement responses with measured curves serve to verify the suitability of the assumed bilinear traction-separation law for the cyclic cohesive zone model (CCZM) used.
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Yilbas, B. S., and S. J. Hyder. "Analysis of a flexural wave due to a laser heating pulse: The two-layer assembly case." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 216, no. 12 (December 1, 2002): 1165–74. http://dx.doi.org/10.1243/095440602321029409.
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In the present study laser ablation of a two-layer assembly with a cantilever arrangement is considered. The recoil pressure generated at the vapour front-workpiece interface is formulated and the resulting pressure force (loading force) is computed. The flexural motion of the workpiece due to the loading force is formulated. The first layer of the workpiece is Inconel 625 with a thickness on the order of 200 μm, which may resemble the HVOF (high-velocity oxygen fuel) coating, while the second layer is 1 mm thick stainless steel plate. The simulations are repeated for four values of the first layer thickness and the relation between the magnitude of the displacement and the first layer thickness is discussed. It is found that the displacement of the workpiece reaches as high as 2 μm in the region close to the free end, while the equivalent stress level is high in the region close to the fixed end. The temporal behaviour of the equivalent stress almost follows the displacement behaviour of the workpiece. As the first layer thickness increases, the displacement reduces. The variation of displacement with the first layer thickness is almost linear and the slope of this variation attains high values for certain time periods in the flexural motion.
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Yang, Q. D., A. Rosakis, and B. N. Cox. "Dynamic fibre sliding along debonded, frictional interfaces." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 462, no. 2068 (January 17, 2006): 1081–106. http://dx.doi.org/10.1098/rspa.2005.1602.
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The problem is considered of a fibre that is driven dynamically, by compression at one end, into a matrix. The fibre is not initially bonded to the matrix, so that its motion is resisted solely by friction. Prior work based on simplified models has shown that the combination of inertial effects and friction acting over long domains of the fibre–matrix interface gives rise to behaviour that is far more complex than in the well-known static loading problem. The front velocity may depart significantly from the bar wave speed and regimes of slip, slip/stick and reverse slip can exist for different material choices and loading rates. Here more realistic numerical simulations and detailed observations of dynamic displacement fields in a model push-in experiment are used to seek more complete understanding of the problem. The prior results are at least partly confirmed, especially the ability of simple shear-lag theory to predict front velocities and gross features of the deformation. Some other fundamental aspects are newly revealed, including oscillations in the interface stresses during loading; and suggestions of unstable, possibly chaotic interface conditions during unloading. Consideration of the experiments and two different orders of model suggest that the tentatively characterized chaotic phenomena may arise because of the essential nonlinearity of friction, that the shear traction changes discontinuously with the sense of the motion, rather than being associated with the details of the constitutive law that is assumed for the friction. This contrasts with recent understanding of instability and ill-posedness at interfaces loaded uniformly in time, where the nature of the assumed friction law dominates the outcome.
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Nor, Fethma M., Joong Yeon Lim, Mohd Nasir Tamin, Ho Yong Lee, and D. Kurniawan. "Effects of Starter Defect on Energy Release Rate of Three-Point End-Notch Flexure Tested Unidirectional Carbon Fiber Reinforced Polymer Composite." Polymers 12, no. 4 (April 14, 2020): 904. http://dx.doi.org/10.3390/polym12040904.
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The mechanics of damage and fracture process in unidirectional carbon fiber reinforced polymer (CFRP) composites subjected to shear loading (Mode II) were examined using the experimental method of the three-point end-notch flexure (3ENF) test. The CFRP composite consists of [0o]16 with an insert film in the middle plane for a starter defect. A 3ENF test sample with a span of 50 mm and interface delamination crack length of 12.5 mm was tested to yield the load vs. deformation response. A sudden load drop observed at maximum force value indicates the onset of delamination crack propagation. The results are used to extract the energy release rate, GIIC, of the laminates with an insert film starter defect. The effect of the starter defect on the magnitude of GIIC was examined using the CFRP composite sample with a Mode II delamination pre-crack. The higher magnitude of GIIC for the sample with insert film starter defect was attributed to the initial straight geometry of the notch/interface crack and the toughness of the resin at the notch front of the fabricated film insert. The fractured sample was examined using a micro-computerized tomography scanner to establish the shape of the internal delamination crack front. Results revealed that the interface delamination propagated in a non-uniform manner, leaving a curved-shaped crack profile.
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Sethi, Munish, and Kishan Chand Gupta. "Propagation of longitudinal waves in non-homogeneous four-parameter viscoelastic rods." Journal of the Mechanical Behaviour of Materials 20, no. 4-6 (June 1, 2012): 67–71. http://dx.doi.org/10.1515/jmbm.2011.012.
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AbstractThe purpose of this paper was to study the propagation of longitudinal waves in non-homogeneous four-parameter viscoelastic rods of arbitrary thickness. The rods were initially supposed to be unstressed and at rest. Apart from a sudden rising traction uniformly applied over the boundary of the opening and parallel to the faces of the plates, which is steadily maintained thereafter, the rods are otherwise free from loading. Methods for treating reflection at the free end of the finite rod and reflection and transmission at an interface between two media in the semi-infinite bi-viscoelastic rod are also presented. Asymptotic techniques are used throughout, and formal asymptotic wave-front expansions of the solution functions are obtained.
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Alhyari, Omar, and Golam Newaz. "Energy Absorption in Carbon Fiber Composites with Holes under Quasi-Static Loading." C 7, no. 1 (February 1, 2021): 16. http://dx.doi.org/10.3390/c7010016.
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Composite tubular structures have shown promise as energy absorbers in the automobile industry. This paper investigates the energy absorption characteristics of carbon fiber reinforced plastic (CFRP) tubes with pre-existing holes. Holes may represent an extreme case of impact damage that perforates the tube, e.g., stones from road surface impacting the tubes. Tubes with holes represent more conservative performance characteristics, since impact damage of the same size will have residual material, which may carry some load. Tubes with holes can provide the lower limit of CFRP tube performance under axial crushing relative to impact damaged tubes with perforation diameter close to the hole diameter. In this study, tubes with lay-up of [05/902/04] with one and two holes in defined locations and different diameters are experimentally studied under quasi-static loading. It was found that specific energy absorption (SEA) reduces by 50% with one or two holes of 15 mm size, 100 mm from top of the tube. The SEA reduction is about 60% lower than the regular tube when the diameter of the hole is 20 mm located at 100 mm from top. The most severe reduction occurs if the location of single or double holes are 75 mm from the top. In this case, a SEA reduction of 75% can be expected. Results indicate that holes can significantly alter the energy absorption capability of the tubes. It is also clear that in axial crushing of composite tubes, the location of the hole (100 to 75 mm) appears to create more pronounced effect than the size of the hole itself (15 vs. 20 mm) for the cases investigated. The failure modes for tubes with holes seem to preserve similar damage modes with delamination, frond creation, and brittle fracture, which is typically observed in regular composite tubes under axial crushing load. This is due to primarily front end crushing, which dominates the failure modes, while hole induced damage occurs later.
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Malakahmad, Amirhossein, Noor Ezlin Ahmad Basri, and Sharom Md Zain. "Study on Performance and Characteristic of Microorganisms in a Waste-to-Energy System." Advanced Materials Research 626 (December 2012): 625–30. http://dx.doi.org/10.4028/www.scientific.net/amr.626.625.
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Performance and characterization of microorganisms in a laboratory-scale anaerobic baffled reactor (ABR) was studied. The ABR was fed continuously at organic loading rate (OLR) of 15.2 g COD/l.d with a substrate containing pre-tested combination of kitchen waste and activated sludge. The HRT (hydraulic retention time), C/N (carbon/nitrogen) and F/M (food/microorganisms) ratios were maintained at 3 d, 31.4 and 0.35 gCOD/gVSS.d, respectively. The amounts of fat, protein, cellulose, hemi-cellulose and lignin which are significant polymers for anaerobic digestion start-up were found to be in appropriate ranges. Results show reduction of pH in front compartments and its boost in successive compartments. This indicates proper placement of acidogens and methanogens in the ABR. Also, significant growth in height of ABR granule bed was observed in the system based on formation and retention of granules. Microorganism characterization reveals large population ofMethanosarcinain front part of the reactor although toward the end the amount forMethanosaetaincreased. WhileMethanobacterium,Methanosprilium,MethanococcusandMethanobrevibacterwere observed in the ABR, higher percentage ofMethanosarcinaandMethanotrixindicates production of methane from acetate conversion.
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Chen, Jiehao, Xifeng Liang, Ping Xu, and Shuguang Yao. "Crashworthiness Analysis and Multi-Objective Optimisation of Multi-Cell Windowed Structures under Dynamic Impact Loading." Shock and Vibration 2022 (January 31, 2022): 1–17. http://dx.doi.org/10.1155/2022/2263308.
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Applying a windowed design in a thin-walled structure is a method to further enhance the crashworthiness of the structure. In this study, two kinds of windowed designs were introduced into different regions of a multi-cell energy absorption structure to form a multi-cell windowed structure, and its crashworthiness under dynamic impact was studied. Dynamic impact testing and LS-DYNA finite element modelling were combined to calculate the crashworthiness response of the structure. The simulation results show that the use of the windowed multi-cell structure can improve the crashworthiness response of the multi-cell structure. The influence of the windowed design on the structural deformation mode was analysed in detail. In addition, the multi-objective optimization design of different windowed structures was carried out to obtain a comprehensive crashworthiness evaluation, and the results show that the windowed design at the front end of the structure yields good results regarding the initial peak force (PCF), while the windowed design in the middle of the structure can effectively improve the specific energy absorption (SEA) and energy absorption (EA).
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Feng, Jian Xiang, Si Feng Zhang, and Jin Sheng Du. "PFC2D Numerical Simulation Study of Interfaces Characteristics for Prestressed Anchor Cable under Cyclic Loading." Key Engineering Materials 629-630 (October 2014): 579–83. http://dx.doi.org/10.4028/www.scientific.net/kem.629-630.579.
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Abstract: Affected by various external factors, the tensile force of prestressed anchorage structures presents loop and fluctuation characteristics in practical engineerings, which will cause severe impact on the inner anchoring section of the prestressed anchorage structures. On this base, PFC2D discrete element program was established for numerical simulation analysis of microscopic physical and mechanical changing characteristics of stress, porosity, angle, etc. of different interfaces locations for prestressed anchor cable under cyclic loading. The results showed that: at locations of the front-middle, the grouting body near interfaces were divided into tensile stress area of the inside part and compressive stress area of the outside part, and two locations of y-direction stress concentration were located at the two end of inner anchoring section; The interfaces had the feature of progressive failure and the characteristic of shear stress peak shifting; While loading finish, particles at different locations of interfaces basically generated clockwise rotation angle, but at two locations of y-direction stress concentration, the particles rotation angle, which was very small at the other locations, was very large; At y-direction tension and compression stress boundary, the particles spinning direction showed instability characteristic and the ultimate rotation angle was small.
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Kotasek, D., J. L. Canon, J. San Miguel, M. Hedenus, L. Hendricks, G. Rossi, and K. Taylor. "Correction/Maintenance Dosing (Front Loading) of Darbepoetin alfa: Final Results from a Randomized Phase 3 Active Controlled Trial." Blood 104, no. 11 (November 16, 2004): 1636. http://dx.doi.org/10.1182/blood.v104.11.1636.1636.
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Abstract Prior research with darbepoetin alfa (DA; Aranesp®) in patients with chemotherapy-induced anemia (CIA) has indicated the possibility of decreasing the time to response through the use of higher initial doses (4.5 mcg/kg once weekly [QW]) compared with standard dosing regimens (either of DA or epoetin alfa [Procrit®]). Research has also shown that an every 3 week (Q3W) dosing schedule of DA is effective in alleviating the symptoms of CIA. Pilot studies using a correction/maintenance approach (‘front loading’) have combined these two potentially attractive clinical attributes. This active-controlled trial examined the efficacy of DA using a correction/maintenance dosing regimen in patients with nonmyeloid malignancies receiving chemotherapy. In this study, 727 anemic patients (hemoglobin [Hb] <11g/dL) were randomized 1:1 to receive a DA dose of either 2.25 mcg/kg QW for 16 weeks or 4.5 mcg/kg QW for weeks 1–4, followed by a Q3W maintenance regimen using the same dose (4.5 mcg/kg) for weeks 5–16. The primary endpoint was to demonstrate the non-inferiority of correction/maintenance dosing versus standard weekly dosing, with respect to the proportion of patients either requiring a transfusion or withdrawing from the study during the 16-week treatment period. The pre-specified, non-inferiority margin, based on the effect size observed in DA placebo-controlled trials, was 12.5%. The two treatment groups were well balanced for baseline characteristics: 32% had hematologic malignancies, 15% breast cancer and 13% lung cancer. Both groups had a mean (SD) baseline Hb of 9.6 (1.0) g/dL. Non-inferiority was demonstrated with respect to the primary endpoint with a mean (95% CL) difference between groups of 1% (−7, 9). No difference was observed for the proportion of patients receiving a RBC transfusion from week 5 to end of treatment [24% (19, 28) for the 2.25 mcg/kg QW group vs 25% (20, 30) for the correction/maintenance group]. Over the entire study period, 87% (83, 91) of patients in the DA 2.25 mcg/kg group achieved a hematopoietic response at the end of treatment compared with 68% (62, 73) in the correction/maintenance group, suggesting no additional benefit for correction/maintenance dosing compared with standard dosing. During the initial 7 weeks of study, no differences were observed between patients receiving 2.25 mcg/kg QW or 4.5 mcg/kg QW for any endpoint (eg, Hb change of 1.4 g/dL after 6 weeks in both groups); Q3W dosing at 4.5 mcg/kg was shown to be effective in maintaining Hb through the remainder of the treatment period. No difference in adverse events between the two groups was observed. DA 2.25 mcg/kg QW is highly effective with respect to the reduction of transfusion requirements and management of anemia symptoms in patients with CIA. In this study of anemic patients with nonmyeloid malignancies receiving chemotherapy, almost all patients in the 2.25 mcg/kg QW dose group achieved a hematopoietic response, offering little room for additional clinical benefit that may have been expected in the 4.5 mcg/kg QW group as a result of the increased dose. Q3W dosing with DA 4.5 mcg/kg was shown to effectively maintain Hb levels. The effectiveness of lower/less frequent doses cannot be determined from this trial.
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Son, Jaeho, Martin Mack, and Kris G. Mattila. "Nonlinear cash flow optimization model." Canadian Journal of Civil Engineering 33, no. 11 (November 1, 2006): 1450–54. http://dx.doi.org/10.1139/l06-086.
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During construction, progress payments (cash inflow) are made periodically to contractors based on work performed. Contractors are required to pay the direct costs (cash outflow) during construction. The net difference between the cash inflow and outflow is the overdraft, which contractors must finance either from the bank or from their own resources. To increase profit margin, contractors consider methods to improve their cash flow, which will increase profit. These methods include front end loading (Stark 1974) and shifting of activities (Easa 1992). These two linear procedures could be done sequentially. However, this sequential linear formulation may not produce an optimized solution because of the nonlinear characteristics of the model. This note examines the combination of the two linear procedures into a single nonlinear formulation such that better profit margin can be achieved.Key words: cost analysis, optimization, linear programming, nonlinear programming.
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Yang, Heli, and Xinqian Zheng. "Investigation of endwall treatment and shock control in a five-stage axial compressor." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 234, no. 5 (October 11, 2017): 1035–49. http://dx.doi.org/10.1177/0954410017734884.
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Multistage axial compressor is one of the key components in aero engines and gas turbines. In this paper, a five-stage axial compressor was studied to improve the efficiency. First, the loss analyses of the datum compressor were performed. The results showed that front rotors and rear stators have higher loss. Based on the loss analyses, the corresponding flow controls were introduced. The endwall treatment was performed with the rear stators, S3, S4, and S5, by end-bow, which changed the blade loading and reduced the loss due to endwall boundary layer. The efficiency of the datum compressor was increased by 0.5%. Based on the improved redesign of rear stators, shock control was introduced to front rotors, R1 and R2, characterized by sweep, which changed the shock structure and decreased the shock-induced loss and shock-tip leakage interaction. Coupled between endwall treatment and shock control, compared to the datum compressor, the efficiency, peak pressure ratio, and choked mass flow were increased by 1.1%, 1.1%, and 1.2%, respectively. At off-design speeds, the performances were also improved, which implies the flow controls for design speed remain effective in a range of off-design speeds. The reliability of the redesigned compressor was validated by stress and mode analyses.
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Dyke, Chris. "Characteristics of Pre-Proceedings and Care Proceedings Cases in an English Local Authority, 2013–2017: An Exploratory Data Analysis." British Journal of Social Work 50, no. 7 (October 26, 2019): 2040–62. http://dx.doi.org/10.1093/bjsw/bcz123.
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Abstract Since reforms in 2014, care proceedings—where a local authority seeks to intervene legally to protect a child—have become shorter, with greater emphasis on ‘front-loading’ preventative and analytical work before, rather than during, proceedings. National findings on case outcomes are emerging, but in-depth local analyses are still rare. This exploratory data analysis of 937 children in 522 families in one London local authority sought to identify trends in the length, outcome and nature of pre-proceedings and proceedings cases, including outcomes six, twelve and twenty-four months after the end of these processes. Consistent with national-level findings on care proceedings, from 2013 to 2017 both the pre-proceedings and care proceedings processes became shorter, and more likely to end with the child at home. The data do not suggest that this increased ‘decisiveness’ leads to rushed decisions. Only 1.4 per cent of the children stepped-down from pre-proceedings, and 6.6 per cent of the children who remained at home after care proceedings came into care within two years of that decision. This research offers a model for similar analyses by practitioner researchers within their own local authorities.
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Paimushin, V. N., V. A. Firsov, and V. M. Shishkin. "MATHEMATICAL MODELING OF THE VIBRATIONS PROPAGATION IN THIN-WALL FRAMEWORK STRUCTURES. 2. FINITE ELEMENT MODELS AND NUMERICAL EXPERIMENTS." Problems of Strength and Plasticity 84, no. 3 (2022): 311–30. http://dx.doi.org/10.32326/1814-9146-2022-84-3-311-330.
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Based on the refined S.P. Timoshenko shear model, one-dimensional finite elements for modeling the dynamic response of flat rods with clamped section of finite length on one of the front faces have been constructed. To analyze their stationary dynamic response under harmonic external action, a system of resolving equations in a complex form is formed. Three models of kinematic conjugation of clamped and free sections of rods are developed using the equation of connection between the rotation angle of the cross section and axial displacement at the boundary between the marked parts of the rod, the transitional finite element, and the concept of a single finite element with nodes located on one of its front faces. It is noted that for practical implementation, the most convenient model is one that uses a single finite element to represent fixed and free sections of the rod. On the basis of the noted model, a finite element solution of the problem of transverse bending vibrations of a cantilevered flat rod under vibration loading conditions by a periodic axial force applied to the end section of a clamped section of finite length, as well as the problem of transverse bending vibrations of a flat rod with two free ends and clamped length section between them under vibration loading by a transverse force on one of the free ends of the rod was found. The results of the finite element solution of the noted two problems are in good agreement with the previously obtained exact analytical solutions found on the basis of the S.P. Timoshenko shear model. The presence of a significant transformation of the parameters of the stress-strain state of the considered rods during the transition through the boundary from free to the clamped length areas on one of the face surfaces is noted.
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Thorat, Mahesh, Shiba Sahu, Viren Menezes, Amol Gokhale, and Hamid Hosano. "Shock Loading of Closed Cell Aluminum Foams in the Presence of an Air Cavity." Applied Sciences 10, no. 12 (June 16, 2020): 4128. http://dx.doi.org/10.3390/app10124128.
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It is important to protect assets located within cavities vulnerable to incident shock waves generated by explosions. The aim of the present work is to explore if closed cell aluminum foams can mediate and attenuate incident shocks experienced by cavities. A small cavity of 9 mm diameter and 2 mm length was created within the steel end-wall of a shock tube and exposed to shocks, directly or after isolating by aluminum foam liners. Shock waves with incident pressure of 9–10 bar travelling at a velocity of 1000–1050 m/s were generated in the shock tube. Compared to the no-foam condition, the pressure induced in the cavity was either equal or lower, depending on whether the foam density was low (0.28 g/cc) or high (0.31 to 0.49 g/cc), respectively. Moreover, the rate of pressure rise, which was very high without and with the low density foam barrier, reduced substantially with increasing foam density. Foams deformed plastically under shock loading, with the extent of deformation decreasing with increasing foam density. Some interesting responses such as perforation of cell walls in the front side and densification in the far side of the foam were observed by a combination of scanning electron microscopy and X-ray microscopy. The present work conclusively shows that shocks in cavities within rigid walls can be attenuated by using foam liners of sufficiently high densities, which resist densification and extrusion into the cavities. Even such relatively high-density foams would be much lighter than fully dense materials capable of protecting cavities from shocks.
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Zhao, Yang, Guoming Xia, Qin Shi, and Anping Qiu. "Expanding Bias-instability of MEMS Silicon Oscillating Accelerometer Utilizing AC Polarization and Self-Compensation." Sensors 20, no. 5 (March 6, 2020): 1455. http://dx.doi.org/10.3390/s20051455.
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This paper presents a MEMS (Micro-Electro-Mechanical System) Silicon Oscillating Accelerometer (SOA) with AC (alternating current) polarization to expand its bias-instability limited by the up-converted 1/f noise from front-end transimpedance amplifier (TIA). In contrast to the conventional DC (direct current) scheme, AC polarization breaks the trade-off between input transistor gate size and white noise floor of TIA, a relative low input loading capacitance can be implemented for low noise consideration. Besides, a self-compensation technique combining polarization source and reference in automatic-gain-control (AGC) is put forward. It cancels the 1/f noise and drift introduced by the polarization source itself, which applies to both DC and AC polarization cases. The experimental result indicates the proposed AC polarization and self-compensation strategy expand the bias-instability of studied SOA from 2.58 μg to 0.51 μg with a full scale of ± 30 g, a 155.6 dB dynamic range is realized in this work.
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Leishear, Robert A. "Stresses in a Cylinder Subjected to an Internal Shock." Journal of Pressure Vessel Technology 129, no. 3 (January 21, 2007): 372–82. http://dx.doi.org/10.1115/1.2748820.
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Hoop stresses due to a moving shock front in either a gas or liquid filled cylinder can be approximated using vibration theory. The equation of motion can be combined with hoop stress equations to describe the dynamic changes in hoop stress to provide insight into the phenomenon of flexural resonance, which creates pipe stresses significantly in excess of the stresses expected from a slowly applied, or static, pressure loading. To investigate flexural resonance, vibration equations were successfully compared to available experimental results. At shock velocities, the maximum hoop stress is related to a vibration equation for a suddenly applied load. Consideration of structural and fluid damping, as well as pipe constraints at the end of the pipe, were considered in the derivation of the vibration equations. In short, vibration equations are presented in this paper and are compared to available experimental work. The equations describe hoop stresses in a pipe when a step increase in pressure travels the bore of a pipe at sonic or supersonic velocities.
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Kwon, Yi Sug. "Dynamic Analysis Step-by-Step." Mechanical Engineering 120, no. 08 (August 1, 1998): 61–62. http://dx.doi.org/10.1115/1.1998-aug-3.
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This article discusses about engineers who are relying on mechanical simulations to improve their understanding of loading and operating conditions with high-rise escalators gain in popularity. To model an escalator design’s steps for dynamic analysis, LG engineers simplified the mechanical system by applying the drive directly to the upper terminal gear and the driving pulley without the motor. To model an escalator’s continuous elastic handrail, LG engineers divided it into 127 discrete rigid bodies, resulting in a total of 381 independent degrees of freedom. Two friction contact elements for each handrail body are applied to prevent rotational motion of the handrail. LG Industrial Systems managers decided to expand the number of engineers at the company with access to the simulation model. They assigned LG engineers to work with Computer Aided Design Software, Inc. (CADSI), of Coralville, Iowa analysts to develop a front end to DADS that simplifies the process of developing a custom escalator model.
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Zamma, Abdellah, Salah Eddine Jalal, and Brahim Boubeker. "Elastic and Elasto-Plastic Study for Bucket Tooth - Contribution to the Increase for Resistance of Collapse -." Advanced Materials Research 682 (April 2013): 113–18. http://dx.doi.org/10.4028/www.scientific.net/amr.682.113.
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The bucket is a metal entity, linked to a machine called DRAGLINE, used for loading the different sizes of granular materials in large quantities. Each bucket is provided with six teeth which in contact with materials to be discharged, in order to extract the mineral. These teeth are connected to the bucket via a semi-rigid connection. In operation, except for the wear phenomenon "normal", some teeth break after a few hours of operation at the fixed portion in the singularity region (radius of curvature equal to zero). We observed via elastic numerical simulation in quasi-static regime, performed using PATRAN and NASTRAN software, that hot spots are located at the singularity region. We also used this numerical calculation for analyzing the effect of the variation radius of curvature on the stress concentration factor by plotting the variation of this factor vs of said radius. To deepen, we repeated the same study but this time considering the material of the tooth as elastic perfectly plastic for seeking the limit load. For each value of the radius of curvature, was plotted the variation of the elasto-plastic external force according to the displacement of the front end of the tooth, knowing that the other end is fixed.
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Kim, Myung-Hun, Eul-Bum Lee, and Han-Suk Choi. "Detail Engineering Completion Rating Index System (DECRIS) for Optimal Initiation of Construction Works to Improve Contractors’ Schedule-Cost Performance for Offshore Oil and Gas EPC Projects." Sustainability 10, no. 7 (July 14, 2018): 2469. http://dx.doi.org/10.3390/su10072469.
Full textAbstract:
Engineering, Procurement, and Construction (EPC) contractors with lump-sum turnkey contracts have recently been suffering massive profit losses due to re-works and schedule delays in offshore oil and gas EPC megaprojects. The main objective of this research is to develop and implement a detail engineering completion rating index system (DECRIS) to assist EPC contractors to optimize fabrication and construction works schedules while minimizing potential re-work/re-order. This is achieved through adequate detail design development and results in minimizing schedule delays and potential liquidated damages (i.e., delay penalties). The developed DECRIS was based on findings from an extensive review of existing literature, industry-led studies, expert surveys, and expert workshops. The DECRIS model is an evolution, and improvement of existing tools such as the project definition raking index (PDRI) and front-end loading (FEL) developed specifically for the early stage of engineering maturity assessment (i.e., planning, basic design, and front-end engineering design (FEED)), prior to EPC projects. The DECRIS was evaluated and validated with thirteen sample as-built offshore megaprojects completed recently. When the DECRIS was applied to the completed projects post-hoc, a correlation (R-squared 0.71) was found between DECRIS scores and schedule/cost performances. This is much superior to the PDRI-Industrial model’s correlation (R-squared 0.04), which was primarily devised for owners’ basic engineering or FEED completion assessment. Finally, as a means of further validation, project schedule and cost performance of an ongoing project was predicted based on the correlations found on the thirteen completed projects. The resultant predicted schedule and cost performance was well matched with the current project performance status. Based on the accuracy of the DECRIS model found in the validation, said model is an effective prospective tool for EPC contractors to manage their engineering and procurement/construction risks during the initial detail design stages.
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Gorelov, V. A., B. B. Kositsyn, A. A. Stadukhin, and O. I. Chudakov. "Method for determining the parameters of the front loader electromechanical transmission." Traktory i sel hozmashiny 88, no. 5 (October 15, 2021): 38–45. http://dx.doi.org/10.31992/0321-4443-2021-5-38-45.
Full textAbstract:
A method for calculating the traction motor of a hybrid transmission of a front-end loader is proposed. It is indicated that these vehicles are characterized by a mode of operation with multiple accelerations and decelerations, as well as alternating operations with high and low required traction force. An electromechanical transmission scheme is proposed. This scheme can be effectively used in such conditions.
The proposed method uses the concept of the magnitude of the range of an electric motor, which can be used to select a specific electric motor that provides the required mobility of the vehicle. For a front loader with a lifting capacity of 3500 kg, a maximum speed of 40 km / h and a maximum specific thrust of 1, the main parameters of the traction motor were determined. However, for the transmission with one fixed gear ratio (EMT1), an electric motor with an excessively high power was obtained. Therefore, the determination of the characteristics of the electric motor for an electromechanical transmission with two fixed gear ratios (EMT2) was carried out. In the process of calculating this transmission, a significantly lower required engine power was obtained.
The article provides an approximate assessment of the energy efficiency of EMT1 and EMT2 transmissions. A method to determine the efficiency of an electric motor depending on its operating mode (on the current angular speed of the shaft and torque) was used. It was determined that the EMT2 transmission has the best efficiency of the electric motor both during bulldozing operation and when driving at maximum speed.
The general conclusion is that it is most rational to use a transmission with two fixed gear ratios. As a further direction of research, the use of computer simulation for evaluating the energy efficiency of a loader in a loading-unloading cycle is highlighted.
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Martínez, Fernando, E. Tynan, M. Arregui, G. Obieta, and J. Aurrekoetxea. "Electroactive Pressure Sensors for Smart Structures." Advances in Science and Technology 56 (September 2008): 122–26. http://dx.doi.org/10.4028/www.scientific.net/ast.56.122.
Full textAbstract:
A hardware-software interface for smart electroactive pressure sensors has been designed with the objective of providing a low power consumption and high performance impact monitoring system, integrated in new smart structures. The interface is specifically designed for its use with distributed pressure sensors based on conductive polymers. Their low cost and flexibility make them suitable for placing on large surfaces. The smart sensor integrates a microprocessor, a radio chip and a complete analog front end based on a period-modulated oscillator. The software developed implements new interface applications for this hardware in TinyOS. The response of the sensor, both loading and unloading, to different impact energies first, and then to different probe stiffness is presented. The behaviour of the sensor to impact is also compared to the response in static, and the different factors affecting the sensor response in both conditions are described. Comparing and contrasting the sensor signal with that of an impact pendulum shows that the sensor is suitable for measuring impact in both flexible and rigid structures.
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Shim, Euijin, Jeong-Phil Jang, Jai-Joung Moon, and Yeonsang Kim. "Improvement of Polytetrafluoroethylene Membrane High-Efficiency Particulate Air Filter Performance with Melt-Blown Media." Polymers 13, no. 23 (November 23, 2021): 4067. http://dx.doi.org/10.3390/polym13234067.
Full textAbstract:
Polytetrafluoroethylene (PTFE) membrane filters are widely used in low-load application areas, such as industrial cleanrooms, due to their low initial pressure drop. In this study, melt-blown (MB) nonwoven was introduced as a pre-filtration layer at the front end of a high-efficiency particulate air (HEPA) filter to improve the filter performance of the PTFE membrane. Pre-filtration reduces the average particle size, which reaches the PTFE membrane and reduces the dust load on the HEPA filters. A comparative analysis of the HEPA filters by composite MB and PTFE was conducted. Regarding the MB composite on the PTFE, low-weight and high-weight MB composites were effective in increasing dust filtration efficiency, and the dust loading capacity of the PTFE composite with high-weight MB increased by approximately three times that of the PTFE membrane. In addition, the filter was installed on an external air conditioner in an actual use environment and showed a high efficiency of 99.984% without a change in differential pressure after 120 days.
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Kuyuk, Ali, Seyed Ghoreishi-Madiseh, Agus Sasmito, and Ferri Hassani. "Designing a Large-Scale Lake Cooling System for an Ultra-Deep Mine: A Canadian Case Study." Energies 12, no. 5 (March 1, 2019): 811. http://dx.doi.org/10.3390/en12050811.
Full textAbstract:
Subsurface mining operations are continuously getting deeper and more complex due to depletion of shallow deposits. This fact inevitably brings more expensive, high-tech oriented and most importantly energy intensive subsurface mining operations to come alive. Accordingly, while big mining companies are developing sensible extraction methods to exploit orebodies located at great depths, they are also seeking to cut down their costs and carbon footprint. A large percentage of the energy needed by a subsurface mine is due to the mine ventilation and air conditioning reasons. In fact, for mines deeper than 2 km, mine air conditioning becomes a must. Yet, as there are not many alternatives developed, most of the modern mines are subjected to deploy tens of megawatts worth of cooling plants using massive refrigeration units. This does not only create a large financial burden during the project stage but also results in heavy energy demands during the operation. This paper aims to investigate a natural, alternative deep-mine lake cooling system by providing a detailed ‘front-end-loading’ design conducted for a real-life, Canadian example.
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Wanjala, Sylvester Timona. "A Framework for Implementing Micro Frontend Architecture." International Journal of Computer Applications Technology and Research 10, no. 12 (December 2021): 267–75. http://dx.doi.org/10.7753/ijcatr1012.1002.
Full textAbstract:
Web applications are an indispensable part of any enterprise information system. In the recent past, we have seen maturity in technologies that enable the separation of frontend and backend, with the backend adopting microservices architecture style. The front end has maintained the traditional monolithic architecture. Micro frontends have come up as a solution to the conventional monolithic frontend, which has received much attention. Still, so far, there is no straightforward approach to implementation that satisfies different practical requirements of a modern web application. This paper proposes an architectural pattern for implementing micro frontends to address challenges experienced in earlier implementations, such as inconsistent user experience, managing security, and complexity. We developed two simple web applications, one using the proposed architectural pattern, and another using the monolithic architecture and compared the performance. We used Google lighthouse to measure the performance of two applications. The landing page for the application developed using micro frontend architecture showed a higher performance score of 99 against 86 for a similar page in an application developed using the monolithic architecture. The proposed framework showed outstanding performance in handling the issues of consistent layout with a Cumulative Layout shift of 0. Breaking down the frontend with lazy loading of micro frontends improved the web application's performance, while the proposed framework reduced development complexity. However, more research is needed to provide seamless integration of micro frontends into the main application with the support of loading shared libraries in the main application; this will significantly reduce the payload size.
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Mishani, Siamak, Brian Evans, Vamegh Rasouli, Reem Roufail, Soren Soe, and Peter Jaensch. "Interlaminar modelling to predict composite coiled tube failure." APPEA Journal 55, no. 1 (2015): 361. http://dx.doi.org/10.1071/aj14029.
Full textAbstract:
In a field operation that uses coiled tubing in its applications, fibre-reinforced polymer matrix composite tubing is seldom used. Fibre-composite coiled tubes offer advantages, compared to steel material, through a reduction in weight and improvement in fatigue life. The stiffness of composite material degrades progressively when increasing the number of cyclic loading. The fatigue damage and failure criteria of fibre-reinforced composite coiled tubes are more complex than that of steel; hence, failure predictions are somewhat unreliable. Among the defects in composite materials, interlaminar delamination is the foremost problem in fibre-reinforced composite material, and it leads to a reduction in strength and stiffness especially in cyclic-load conditions. Delamination causes a redistribution of the load path along the composite structure, which is unpredictable; therefore, delamination in a composite coiled tube in an oil and gas field eventually leads to final failure, which could be catastrophic. A-ply-by-ply mathematical modelling and numerical simulation method was developed to predict interlaminar delamination of filament-wound composite coiled tubes under a combination of different loading scenarios with consideration to low-cycle fatigue. The objective of this paper is to explain interlaminar delamination as an initial crack and source of stress concentration in composite coiled tubes in the framework of meso-cracking progression of matrix damage modelling of composite laminates. The paper focuses on delamination failure because the largest span of the composite lifecycle is at the crack propagation phase, which manifests itself in the form of delamination. The analysis shows that the crack front tip is not uniform, and also shows that carbon fibre possesses higher stiffness values compared to glass fibre. The paper confirms that 2D modelling cannot express the real release strain energy rate at the crack front tip. Mode-I testing, however, showed that the double cantilever beam (DCB) only represents the normal stress from the release strain energy rate. The results also indicated that there were other sources contributing to the strain energy release rate, such as inter-layer frictions and normal stress in the end notched flexure (ENF) testing mode.