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Splitting of reinforced concrete panels under concentrated loads
Foster, Stephen J.,Rogowsky, David M. Techno-Press 1997 Structural Engineering and Mechanics, An Int'l Jou Vol.5 No.6
It is well understood that concentrated forces applied in the plane of a beam or panel (such as a wall or slab) lead to splitting forces developing within a disturbed region forming beyond the bearing zone. In a linearly elastic material the length of the disturbed region is approximately equal to the depth of the member. In concrete structures, however, the length of the disturbed region is a function of the orthotropic properties of the concrete-steel composite. In the detailing of steel reinforcement within the disturbed regions two limit states must be satisfied; strength and serviceability (in this case the serviceability requirement being acceptable crack widths). If the design requires large redistribution of stresses, the member may perform poorly at service and/or overload. In this paper the results of a plane stress finite element investigation of concentrated loads on reinforced concrete panels are presented. Two cases are examined (i) panels loaded concentrically, and (ii) panels loaded eccentrically. The numerical investigation suggests that the bursting force distribution is substantially different from that calculated using elastic design methods currently used in some codes of practice. The optimum solution for a uniformly reinforced bursting region was found to be with the reinforcement distributed from approximately 0.2 times the effective depth of the member ($0.2D_e$) to between $1.2D_e$ and $1.6D_e$. Strut and tie models based on the finite element analyses are proposed herein.
Foster Kwame Kholi,Albert Mucci,Mimbo Shim(심민보),J. K. Min(민준기),M. Y Ha(하만영) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
Heat pipes, HP, are phase change devices with high conductivities compared to existing technologies of the same dimensions. However, for HP with multi-layer wicks, the layers and location of the dense wicks significantly affect the thermo-fluidics of the device. The influence of these factors on the overall performance of HP is presented for a standard mesh-screen wick HP with different layers - uniform and non-uniform wick layers. An in-house code assisted in predicting the limit of HP, which show increased heat transfer limit as the number of layers increase, especially for a mixture of layers of uniform and non-uniform wicks. The heat transfer improves in different inclinations when the dense wicks located in the core of the HP, in contact with the vapour flow. This arrangement restricts the entrainment of liquid from the wick surface. The results have shown that the performance of HP can easily be improved through proper wick arrangement.
Foster Kwame Kholi,Alberto Mucci,Hariharan Kallath,하만영,Jason Chetwynd-Chatwin,민준기 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.6
Previous correlations that have been used to predict the heat transfer performance of pulsating heat pipes (PHPs) offer limited thermal predictions within a narrow range of fluid-filling ratios and PHP inclinations. In this paper, a novel semi-empirical correlation with improved scope is proposed, with an increased range of fluid-filling ratios and PHP inclinations. The proposed correlation employs the dimensionless numbers governing the thermohydrodynamic operation of PHPs, and achieved ±30 % accuracy when predicting selected experimental data, showing reasonably good agreement. Unlike previous correlations, the new correlation can be used for different working fluids, geometrical aspect ratios, and heat loads. A comprehensive assessment of the relative significance of the correlation parameters on the total heat transfer performance is discussed. The new correlation with its flexible application range is expected to assist in faster and more enhanced thermal predictions as interest in PHPs grows.
Foster Kwame Kholi,Jaehyun Park(박재현),Hyo Je Son(손효제),Hariharan Kallath,Michael Klingsporn,Jason Chetwynd-Chatwin,June Kee Min(민준기) 한국전산유체공학회 2020 한국전산유체공학회지 Vol.25 No.4
This study examined the cooling performance of a fuel-cooled oil cooler (FCOC) under typical operating conditions. The oil cooler can fail due to the congealing of oil in the FCOC core at low-temperature conditions, which could be recovered by de-congealing the oil flow. The de-congealing time can be affected by changes in oil pressure and temperature conditions, flow re-routing, and malfunctioning of the oil bypass valve (OBV). In this study, we proposed a prediction model for the transient oil de-congealing phenomenon in the FCOC. The numerical procedure was based on the one-dimensional (1D) flow and thermal network analysis and the effectiveness (ε)-NTU method. The commercial code was customized to implement the de-congealing phenomena. Pre-defined empirical correlations and property corrections aided the modeling of the detailed de-congealing process. Moreover, the 3D CFD temperature contours provided a visual insight into the internal flow inside the FCOC core during the de-congealing process. An experimental study was conducted in parallel to validate the prediction result. Both experimental and numerical methods showed a loss of cooling when the OBV fails. The oil temperature and pressure, and flow directions affect the de-congealing process. The present model proved useful for various oil cooler configurations that are difficult to investigate experimentally and could quickly provide oil de-congealing results.
TRANSFORMATION OF LOCAL BIFURCATIONS UNDER COLLOCATION METHODS
Foster, Andrew,Khumalo, Melusi Korean Mathematical Society 2011 대한수학회지 Vol.48 No.6
Numerical schemes are routinely used to predict the behavior of continuous dynamical systems. All such schemes transform flows into maps, which can possess dynamical behavior deviating from their continuous counterparts. Here the common bifurcations of scalar dynamical systems are transformed under a class of algorithms known as linearized one-point collocation methods. Through the use of normal forms, we prove that each such bifurcation in an originating flow gives rise to an exactly corresponding one in its discretization. The conditions for spurious period doubling behavior under this class of algorithm are derived. We discuss the global behavioral consequences of a singular set induced by the discretizing methods, including loss of monotonicity of solutions, intermittency, and distortion of attractor basins.
OCCUPATIONAL SAFETY AND HEALTH TRENDS IN THE FOUR "EAST ASIAN TIGERS"
Foster C Rinefort,Joseph A Petrick People&Global Business Association 2006 Global Business and Finance Review Vol.11 No.1
This empirical short-note paper provides information on occupational safety and health trends in the Four "East Asian Tigers," discusses their economic impacts on the Tigers and China, and recommends widespread use of global resources and strengthened national infrastructures to improve human and economic sustainability.
Foster, Julian 영상영어교육학회 2017 영상영어교육 (STEM journal) Vol.18 No.4
A vast resource of materials to use in teaching English as a Second Language (ESL) or English as a Foreign Language (EFL) can be found in movies as well as TV and social media. One area of education that is slow to adopt the use of videos and movies in ESL and EFL is Elementary Schools in Japan. At the same time, English education at this level is characterized by low contact hours and English proficiency. Researchers have identified weak phonetic awareness in English ESL reading as a major impediment to developing reading skills. It is government policy to avoid teaching English reading and writing at this level and perhaps not surprisingly students have weak confidence levels of reading English as well as confusion resulting from the use of Roman letters in the writing of Japanese words. In order to remedy this situation, It is suggested that using movies and TV can introduce a variety of phonemes to young students in stages. This approach incorporates vocabulary presented in existing textbooks while highlighting key phonetic features. It is hoped that this approach can build a phonetic and word base young students can take with them into the future.
Foster, Richard Ian,Sung, Hyun-Hee,Kim, Kwang-Wook,Lee, Keunyoung Korean Radioactive Waste Society 2020 방사성폐기물학회지 Vol.18 No.3
Thermal decomposition of the uranyl phosphate mineral phase meta-ankoleite (KUO<sub>2</sub>PO<sub>4</sub>·3H<sub>2</sub>O) has been considered in relation to high temperature thermal sintering for the immobilisation of a uranyl phosphate containing waste. Meta-ankoleite thermal decomposition was studied across the temperature range 25 - 1200℃ under an inert N<sub>2</sub> atmosphere at 1 atm. It is shown that the meta-ankoleite mineral phase undergoes a double de-hydration event at 56.90 and 125.85℃. Subsequently, synthetically produced pure meta-ankoleite remains stable until at least 1150℃ exhibiting no apparent phase changes. In contrast, when present in a mixed waste the meta-ankoleite phase is not identifiable after thermal treatment indicating incorporation within the bulk waste either as an amorphous phase and/or as uranium oxide. Visual inspection of the waste post thermal treatment showed evidence of self-sintering owing to the presence of glass former materials, namely, silica (SiO<sub>2</sub>) and antimony(V) oxide (Sb<sub>2</sub>O<sub>5</sub>). Therefore, incorporation of the uranium phase into the waste as part of waste sentencing and immobilisation via high temperature sintering for the purpose of long-term disposal is deemed feasible.