Numerical model of journal bearing lubrication considering a bending stiffness effect

An analysis for operating characteristics of journal bearing lubrication system is performed based on the numerical model. Dynamic bearing lubrication characteristics such as oil film pressure and thickness distribution can be analyzed through a numerical model with an integration of elastohydrodynamics and multi-flexible-body dynamics (MFBD). In particular, the oil film thickness variation by elastic deformation is considered in the elastohydrodynamic analysis by applying the bending stiffness effect of journal. And the oil film thickness variation by the bending stiffness effect is applied to the fluid governing equations to calculate the oil film pressure in the elastohydrodynamic lubrication region. A series of process proposed in this study is available for the analysis of realistic elastohydrodynamic lubrication phenomenon. Also, a numerical example for the journal bearing lubrication system is demonstrated and compared with the experimental results. The numerical results considering the bending stiffness effect show a good agreement with the experimental results

Two-Year Changes in Diabetic Kidney Disease Phenotype and the Risk of Heart Failure: A Nationwide Population-Based Study in Korea

Background Diabetic kidney disease (DKD) is a risk factor for hospitalization for heart failure (HHF). DKD could be classified into four phenotypes by estimated glomerular filtration rate (eGFR, normal vs. low) and proteinuria (PU, negative vs. positive). Also, the phenotype often changes dynamically. This study examined HHF risk according to the DKD phenotype changes across 2-year assessments. Methods The study included 1,343,116 patients with type 2 diabetes mellitus (T2DM) from the Korean National Health Insurance Service database after excluding a very high-risk phenotype (eGFR <30 mL/min/1.73 m2) at baseline, who underwent two cycles of medical checkups between 2009 and 2014. From the baseline and 2-year eGFR and PU results, participants were divided into 10 DKD phenotypic change categories. Results During an average of 6.5 years of follow-up, 7,874 subjects developed HHF. The cumulative incidence of HHF from index date was highest in the eGFRlowPU– phenotype, followed by eGFRnorPU+ and eGFRnorPU–. Changes in DKD phenotype differently affect HHF risk. When the persistent eGFRnorPU– category was the reference, hazard ratios for HHF were 3.10 (95% confidence interval [CI], 2.73 to 3.52) in persistent eGFRnorPU+ and 1.86 (95% CI, 1.73 to 1.99) in persistent eGFRlowPU–. Among altered phenotypes, the category converted to eGFRlowPU+ showed the highest risk. In the normal eGFR category at the second examination, those who converted from PU– to PU+ showed a higher risk of HHF than those who converted from PU+ to PU–. Conclusion Changes in DKD phenotype, particularly with the presence of PU, are more likely to reflect the risk of HHF, compared with DKD phenotype based on a single time point in patients with T2DM

An efficient Generalized Geometry Contact algorithm including modal reduction flexible bodies

In the MFBD (Multi-Flexible-Body Dynamics) (RecurDyn, 2017), the contact analysis is very important. To develop the general purpose contact algorithm for rigid and flexible bodies, the Generalized Geometry Contact algorithm, which is called ‘Geo Contact&apos;, has been developed by Choi&apos;s (Choi et al., 2013), (Choi and Choi, 2012), (Choi, 2009) for the contact problems between the rigid and flexible bodies with the general shaped geometries. In the previous researches, the nodal approach for flexible body was considered. But, the flexible body is classified as two types. The one is a nodal flexible body based on the Finite Element Method and the other is a modal reduction flexible body. The modal reduction flexible body is widely used in the MFBD system for the efficient analysis for small deformation problems. In order to get a flexible body of modal reduction, the CMS (Component Mode Synthesis) analysis of Craig-Bampton&apos;s (Craig and Bampton, 1965) is widely used. Therefore, in this study, we will expand the existing contact algorithm to the modal reduction flexible body. The node of the modal reduction flexible body can be deformed like as the nodal flexible body. Therefore, the contact algorithm is similar to the nodal flexible body. We made two interface functions in pre and post processing in the previous Generalized Geometry Contact (Geo Contact) algorithm in order to support the contact for the modal reduction flexible body. Consequentially, this method can be applied for various contact cases with three types of bodies. There are total six cases using three types of bodies such as (1) rigid-rigid body, (2) rigid-nodal flexible body, (3) rigid-modal reduction flexible body, (4) nodal flexible-modal reduction flexible body, (5) nodal flexible-nodal flexible body, and (6) modal reduction flexible-modal reduction flexible body. We will show that whole contact cases work well with Generalized Geometry Contact algorithm with some examples

Iterative Coordinate Reduction Algorithm of Flexible Multibody Dynamics Using a Posteriori Eigenvalue Error Estimation

Coordinate reduction has been widely used for efficient simulation of flexible multibody dynamics. To achieve the reduction of flexible bodies with reasonable accuracy, the appropriate number of dominant modes used for the reduction process must be selected. To handle this issue, an iterative coordinate reduction strategy is introduced. In the iteration step, more dominant modes of flexible bodies are selected than the ones in the previous step. Among the various methods, the conventional frequency cut-off rule is here considered. As a stop criterion, a novel a posteriori error estimator that can evaluate the relative eigenvalue error between full and reduced flexible bodies is proposed. Through the estimated relative eigenvalue error obtained, the number of dominant modes is automatically selected to satisfy the error tolerance up to the desired mode range. The applicability to the automation process is verified through numerical examples. It is also evaluated that efficient and accurate flexible multibody dynamics simulation is available with the reduced flexible body, generated by the proposed algorithm

Physicochemical Stabilization of Pt against Sintering for a Dehydrogenation Catalyst with High Activity, Selectivity, and Durability

Suppressing irreversible catalyst deactivation is critical in heterogeneous catalysis. In particular, deactivation via sintering of active sites is a significant issue for reactions involving harsh reaction/regeneration conditions. In this work, we developed a PtGa/γ-Al₂O₃ alkane dehydrogenation catalyst with exceptionally high activity, selectivity, and long-term stability by markedly suppressing Pt sintering under harsh conditions (reaction/regeneration at >823 K). To stabilize Pt, physical and chemical stabilization strategies were synergistically combined. For the former, Pt was introduced during the synthesis of γ-Al₂O₃ via sol–gel chemistry, which can increase the interfacial contact between Pt and γ-Al₂O₃ due to the partial entrapment of Pt in γ-Al₂O₃. For the latter, atomically dispersed Ce was doped on γ-Al₂O₃, which can stabilize Pt via strong Pt–O–Ce interactions. Because of effective Pt stabilization, the catalyst showed remarkably steady activity and selectivity behaviors over the repeated reaction cycles, although the catalyst is regenerated via simple oxidation rather than industrially used oxychlorination. The Pt stabilization strategies reported in this work can be applied to other metal-catalyzed reactions that involve severe reaction/regeneration conditions

Service Quality beyond Access: A Multilevel Analysis of Neonatal, Infant, and Under-Five Child Mortality Using the Indian Demographic and Health Survey 2015~2016

Purpose: The purpose of this study was to derive contextual indicators of medical provider quality and assess their relative importance along with the individual utilization of antenatal care (ANC) and institutional births with a skilled birth attendant (SBA) in India using a multilevel framework. Methods: The 2015~2016 Demographic and Health Survey (DHS) from India was used to assess the outcomes of neonatal, infant, and under-five child mortality. The final analytic sample included 182,980 children across 28,283 communities, 640 districts, and 36 states and union territories. The contextual indicators of medical provider quality for districts and states were derived from the individual-level number of ANC visits (<4 or≥4) and institutional delivery with SBA. A series of random effects logistic regression models were estimated with a stepwise addition of predictor variables. Results: About half of the mothers (47.3%) had attended≥4 ANC visits and 75.8% delivered in institutional settings with SBAs. Based on ANC visits, 276~281 districts (43.1~43.9%) and 13~16 states (36.5~44.4%) were classified as low quality areas, whereas 268~285 districts (41.9~44.5%) and 8~9 states (22.2~25.0%) were classified as low quality areas based on institutional delivery with SBAs. Conditional on a comprehensive set of covariates, the individual use of both ANC and SBA were significantly associated with all mortality outcomes (OR: 1.17, 95% CI: 1.08, 1.26, and OR: 1.10, 95% CI: 1.02, 1.19, respectively, for under-five child mortality) and remained robust even after adjusting for contextual indicators of medical provider quality. Districts and states with low quality were associated with 57~61% and 27~43% higher odds of under-five child mortality, respectively. Conclusion: When simultaneously considered, district- and state-level provider quality mattered more than individual access to care for all mortality outcomes in India. Further investigations are needed to assess the importance of improving the quality of health service delivery at higher levels to prevent unnecessary child deaths in developing countries

Energy Cost Optimization for Water Distribution Networks Using Demand Pattern and Storage Facilities

Energy consumption in water supply systems is closely connected with the demand for water, since energy is mostly consumed in the process of water transport and distribution, in addition to the energy that might be needed to pump the water from its sources. Existing studies have been carried out on optimizing the pump operations to attain appropriate pressure and on controlling the water level of storage facilities to transfer the required demand and to reduce the energy cost. The idea is to reduce the amount of the water being supplied when the unit price of energy is high and to increase the supply when the unit price is low. To realize this scheme, the energy consumption of water supply systems, the amount of water transfer, the organization of energy cost structure, the utilization of water tanks, and so forth are investigated and analyzed to establish a model of optimized water demand management based on the application of water tanks in supplied areas. In this study, with the assumption that energy cost can be reduced by the redistribution of a demand pattern, a numerical analysis is conducted on transferring water demand at storage facilities from the peak energy cost hours to the lower energy cost hours. This study was applied at the Bupyeong 2 reservoir catchment, Incheon, Korea