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Search Results: 1 - 10 of 193165 matches for " D. Woo "
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Reliability Design of Ice-Maker System Subjected to Repetitive Loading  [PDF]
Seong-Woo Woo
Engineering (ENG) , 2016, DOI: 10.4236/eng.2016.89056
Abstract: Parametric Accelerated Life Testing (ALT) was used to improve the reliability of ice-maker system with a fractured helix upper dispenser in field. By using bond graphs and state equations, a variety of mechanical loads in the assembly were analyzed. The acceleration factor was derived from a generalized life-stress failure model with a new load concept. To reproduce the failure modes and mechanisms causing the fracture, new sample size equation was derived. The sample size equation with the acceleration factor also enabled the parametric accelerated life testing to quickly reproduce early failure in field. Consequently, the failure modes and mechanisms found were identical with those of the failed sample. The design of this testing should help an engineer uncover the design parameters affecting the reliability of fractured helix upper dispenser in field. By eliminating the design flaws, gaps and weldline, the B1 life of the redesign of helix upper dispenser is now guaranteed to be over 10 years with a yearly failure rate of 0.1% that is the reliability quantitative test specifications (RQ).
Torsion as a dynamic degree of freedom of quantum gravity
Sang-Woo Kim,D. G. Pak
Physics , 2006, DOI: 10.1088/0264-9381/25/6/065011
Abstract: The gauge approach to gravity based on the local Lorentz group with a general independent affine connection A_{\mu cd} is developed. We consider SO(1,3) gauge theory with a Lagrangian quadratic in curvature as a simple model of quantum gravity. The torsion is proposed to represent a dynamic degree of freedom of quantum gravity at scales above the Planckian energy. The Einstein-Hilbert theory is induced as an effective theory due to quantum corrections of torsion via generating a stable gravito-magnetic condensate. We conjecture that torsion possesses an intrinsic quantum nature and can be confined. A minimal Abelian projection for the Lorentz gauge model has been constructed, and an effective theory of the cosmic knot at the Planckian scale is proposed.
Determining Adaptability Performance of Artificial Neural Network-Based Thermal Control Logics for Envelope Conditions in Residential Buildings
Jin Woo Moon,Jae D. Chang,Sooyoung Kim
Energies , 2013, DOI: 10.3390/en6073548
Abstract: This study examines the performance and adaptability of Artificial Neural Network (ANN)-based thermal control strategies for diverse thermal properties of building envelope conditions applied to residential buildings. The thermal performance using two non-ANN-based control logics and two predictive ANN-based control logics was numerically tested using simulation software after validation. The performance tests were conducted for a two-story single-family house for various envelope insulation levels and window-to-wall ratios on the envelopes. The percentages of the period within the targeted ranges for air temperature, humidity and PMV, and the magnitudes of the overshoots and undershoots outside of the targeted comfort range were analyzed for each control logic scheme. The results revealed that the two predictive control logics that employed thermal predictions of the ANN models achieved longer periods of thermal comfort than the non-ANN-based models in terms of the comfort periods and the reductions of the magnitudes of the overshoots and undershoots. The ANN-based models proved their adaptability through accurate control of the thermal conditions in buildings with various architectural variables. The ANN-based predictive control methods demonstrated their potential to create more comfortable thermal conditions in single-family homes compared to non-ANN based control logics.
Large voltage-induced modification of spin-orbit torques in Pt/Co/GdOx
Satoru Emori,Uwe Bauer,Seonghoon Woo,Geoffrey S. D. Beach
Physics , 2014, DOI: 10.1063/1.4903041
Abstract: We report on large modifications of current-induced spin-orbit torques in a gated Pt/Co/Gd-oxide microstrip due to voltage-driven O$^{2-}$ migration. The Slonczewski-like and field-like torques are quantified using a low-frequency harmonic technique based on the polar magneto-optical Kerr effect. Voltage-induced oxidation of Co enhances the Slonczewski-like torque by as much as an order of magnitude, and simultaneously reduces the anisotropy energy barrier by a factor of ~5. Such magneto-ionic tuning of interfacial spin-orbit effects may significantly enhance the efficiency of magnetization switching and provide additional degrees of freedom in spintronic devices.
Redundancy of Exchangeable Estimators
Narayana P. Santhanam,Anand D. Sarwate,Jae Oh Woo
Mathematics , 2014, DOI: 10.3390/e16105339
Abstract: Exchangeable random partition processes are the basis for Bayesian approaches to statistical inference in large alphabet settings. On the other hand, the notion of the pattern of a sequence provides an information-theoretic framework for data compression in large alphabet scenarios. Because data compression and parameter estimation are intimately related, we study the redundancy of Bayes estimators coming from Poisson-Dirichlet priors (or "Chinese restaurant processes") and the Pitman-Yor prior. This provides an understanding of these estimators in the setting of unknown discrete alphabets from the perspective of universal compression. In particular, we identify relations between alphabet sizes and sample sizes where the redundancy is small, thereby characterizing useful regimes for these estimators.
Effect of On-Line Hemodiafiltration on Dry Weight Adjustment in Intradialytic Hypotension-Prone Patients: Comparative Study of Conventional Hemodialysis and On-Line Hemodiafiltration  [PDF]
Sun Woo Kang
Open Journal of Nephrology (OJNeph) , 2014, DOI: 10.4236/ojneph.2014.41001
Abstract:

Introduction: Correct adjustment of dry weight after hemodialysis (HD) with no signs of hypervolemia is important. Intradialytic hypotension (IDH) is the most common complication during HD. IDH occurs in 15% to 30% and possibly in up to 50% of dialysis sessions. IDH augments mortality essentially due to chronic overhydration and the inability to reach the proper dry weight. On-line hemodiafiltration (ol-HDF) has been reported to reduce the frequency of IDH. The aim of this study was to assess the effect of ol-HDF on hemodynamic stability and dry weight adjustment compared with low-flux HD. Methods: IDH-prone HD patients at our center were enrolled. This study was designed as a crossover trial with two phases (A arm: low-flux HD for 8 weeks followed by ol-HDF for 8 weeks vs. B arm: ol-HDF for 8 weeks followed by low-flux HD for 8 weeks) and two treatment arms (ol-HDF vs. low-flux HD), each phase lasting 8 weeks. We measured the proportion of body water using a body composition monitor (BCM). Results: In a comparison of the systolic blood pressure (SBP) and diastolic blood pressure (DBP) reductions from the baseline blood pressure between the HD and ol-HDF groups, statistically significant differences were observed only in the SBP of the B arm (SBP: HD vs. HDF, -9.83 ± 6.64 vs. -4.62 ± 1.61 mmHg, p = 0.036; DBP: HD vs. HDF, -3.29 ± 4.05 vs. -1.86 ± 1.49 mmHg, p = 0.261). Neither the mean of the interdialytic body weight gains nor the frequency of IDH was different between the A and B arms (p = 0.817 and p = 0.562, respectively). In terms of dialysis modality, there were no significant differences in the amount of overhydration between the conventional

Improving the Reliability of a Domestic Refrigerator Compressor Subjected to Repetitive Loading  [PDF]
Seong-Woo Woo, Dennis L. O’Neal
Engineering (ENG) , 2016, DOI: 10.4236/eng.2016.83012
Abstract: As a reliability quantitative specification, parametric accelerated life testing was used to assess the reliability of a newly designed compressor of a commercial refrigerator subjected to repetitive stresses. A generalized life-stress failure model and new sample size equation with a new load concept were derived starting with the basic refrigeration cycle. The sample size equation with the acceleration factor also enabled the parametric accelerated life testing to quickly evaluate the expected lifetime. The design of this testing should help an engineer uncover the design parameters affecting reliability during the design process of the compressor system. Consequently, it should help companies improve product reliability and avoid recalls due to the product failures in the field. A newly designed compressor in a commercial refrigerator was used as a test case.
Forest decline of the world: A linkage with air pollution and global warming
SY Woo
African Journal of Biotechnology , 2009,
Abstract: Various forest declines and forest health conditions have been described for forest ecosystems throughout the world. The connection to global warming and air pollution is clear in some area, but not in others. In this study, some evidences that support or contradict air pollution and global warming being causal factors in reported cases of decline in Eastern North America, Central Europe and Republic of Korea. Many studies suggested that forest decline phenomenon seems to be strongly associated to air pollution and global warming.
Epidermal leaf characteristics and seasonal changes of net photosynthesis of five Populus
SY Woo
African Journal of Biotechnology , 2010,
Abstract: Net photosynthesis (PN) and leaf epidermal characteristics of five poplars; 72-31 (Populus alba x Populus glandulosa), Eco28 (Populus euramericana), Suwon (Populus koreana x Populus nigra var. italica), Dorskamp (Populus deltoides x P. nigra), and 62-2 (P. nigra x Populus maximowiczii) were investigated to come up with parameters for comparison. The poplars, 72-31, Suwon and Dorskamp had a significant PN decreasing from May through September. A wide significant variation in the stomata size and density of the genotypes were observed. Especially, Dorskamp and 62-2 had significantly lower number of stomata than Eco-28, 72-31 and Suwon had, but significantly larger stomata length than Suwon and 72-31 had. In addition, 72-31 had trichomes in the abaxial surface, which may be one of the phytoremediation characteristics of this clone compared to other clones.
Letter: Surmounting the Roadblocks
Patricia Woo
Opticon1826 , 2008, DOI: 10.5334/opt.040817
Abstract: Dr Banerjee is quite right in highlighting the roadblocks to success for women in academia. The reality for academic success depends on papers and grants and everyone, mother or not, works long hours on the way, and now that I am 60 I still put in the hours. ...
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