나노 스케일에서 Modified Berkovich 압입자를 활용한 2축 잔류응력 평가

학위논문 (석사)-- 서울대학교 대학원 : 재료공학부, 2017. 2. 권동일.Residual stress is generated by manufacturing processes and thermochemical treatments. These residual stresses combines with external loads to influence deformation and fracture properties. At nanoscale, thin films which have already undergone roll-to-roll processing, have non-equal biaxial residual stress, and this will reduce the reliability of materials. Conventional methods of measuring residual stress, like the x-ray diffraction and curvature methods, have stringent requirements on specimen microstructure or can evaluate only the surface mean residual stress. However, instrumented indentation testing is a non-destructive, simple method that can evaluate local residual stress quantitatively. On macroscale, the Vickers indenter is used to measure the magnitude of residual stress and the Knoop indenter to evaluate stress directionality. At nanoscale, the Berkovich indenter is widely used to measure the residual stress magnitude. But no research has been done on evaluating the stress ratio of residual stress using instrumented indentation testing. In this research, in order to measure biaxial residual stress, a Modified Berkovich indenter was designed that is based on the Berkovich indenter but is extended along one direction to yield different load sensitivity. Before manufacture, we used FEA to verify the validity of this new indenter. Since the Modified Berkovich indenter had geometrical self-similarity, conversion factor ratios were measured for the unstressed and stressed states at a given indentation depth. Moreover, by applying various biaxial stresses to cruciform specimens, the non-equal biaxial residual stress was evaluated by analyzing the load-depth curves. The model was verified by comparing the measured stress with applied stress.Chapter 1. Introduction 1 1.1 Objective of the Thesis 1 1.2 Outline of the Thesis 4 Chapter 2. Research Background 7 2.1 About Residual Stress 7 2.1.1 Definition of Residual Stress 7 2.1.2 Origins of Residual Stress on Nanoscale 8 2.2 Measuring Methods of Nano Residual Stress 9 2.2.1 X-ray Diffraction Method 10 2.2.2 Curvature Method 11 2.2.3 Instrumented Indentation Testing 12 2.3 Stress Assessment using Indentation Test 15 2.3.1 Vickers Indentation Model 15 2.3.2. Knoop Indentation Model 17 Chapter 3. Modified Berkovich Indenter 25 3.1 Limitations of Conventional Indenters 25 3.2 Knoop Indenter on Nanoscales 27 3.3 New Indenter Modified Berkovich Indenter 29 3.3.1 Design of a New Indenter 29 3.3.2 Verification of Modified Berkovich Indenter by FEA 31 3.3.3 Checking the Shape of Modified Berkovich Indenter 32 Chapter 4. Evaluation of Biaxial Residual Stress using Modified Berkovich Indenter 41 4.1 Determination of Conversion Factor Ratio 41 4.2 Experimental Details Conversion Factor Ratio 42 4.2.1 Testing Equipment, Specimens and Jig 42 4.2.2 Applying Stress 43 4.2.3 Experimental Process 44 4.3 Evaluation of Biaxial Residual Stress 45 4.4 Experimental Details Biaxial Residual Stress 46 4.4.1 Testing Equipment, Specimens and Jig 46 4.4.2 Experimental Process 47 Chapter 5. Results and Discussion 56 5.1 Determination of Conversion Factor Ratio 56 5.2 Comparison of Measured Stress Ratio with Applied Stress Ratio 57 5.3 Evaluation of Biaxial Residual Stress using Modified Berkovich Indenter and Berkovich Indenter 58 Chapter 6. Conclusion 68 References 69 초 록 71Maste

Does Health Information Exchange Improve Long-Term Care Service Quality? Evidence from the Panel Data Analysis of the U.S. Long-term Care Facilities

This paper examines the impact of health information exchange (HIE) on the service quality of long-term care (LTC) facilities based on a five-year period (2013-2017) panel data of the U.S. LTC facilities. Our results show a reverse impact of the HIE adoption on the readmission rate of LTC facilities. The readmission rate of an LTC facility with an operational HIE is reduced by 2% on average as compared to the rate of a facility without operational HIE. We also estimate the heterogeneous effect of HIE by two innovative healthcare ITs (EHR and Telemedicine). We find that the applications of EHR and Telemedicine in LTC facilities are still at a very early stage. Our findings empirically demonstrate the importance of promoting effective data exchange in LTC facilities as well as improving the use of EHR and Telemedicine to increase the value that HIE can create

Association of MTHFR polymorphisms with nsCL/P in Chinese Uyghur population

AbstractBackgroundnsCL/P (nonsyndromic cleft lip with or without cleft palate) is a complex disorder with a multifactorial etiology that involves both genetic and environmental factors. A number of studies identified that MTHFR (methylenetetrahydrofolate reductase) was associated with nsCL/P in different populations.AimIn this study, we aim to investigate the association between the polymorphism in MTHFR gene (rs1801131, rs1801133) and nsCL/P in Chinese Uyghur population.Subjects and methodsWe conducted a case–control study comparing 120 nsCL/P patients to 100 controls. The distribution of MTHFR genotypes and frequency of alleles were compared between patients and controls by chi-square test. The odds ratios (OR) and corresponding 95% confidence intervals (95% CIs) were calculated to estimate the strength of association of MTHFR gene (C677T and A1298C).ResultsFor rs1801131, allele C frequency was higher in cases than in controls (30.4%>19.0%), and the difference was statistically significant (χ2=7.538, P=0.006). The genotype distribution at rs1801131 was different between cases (AC>AA>CC, 49.2%>45.0%>5.8%) and controls (AA>AC>CC, 65.0%>32.0%>3.0%), and the difference was statistically significant (χ2=8.883, P=0.012). AC genotype was found to increase the susceptibility of nsCL/P (OR=2.219, 95% CI=1.266–3.892, P=0.005). No association was found between rs1801133 and nsCL/P.ConclusionThis study indicated that rs1801131 polymorphism in MTHFR was associated with nsCL/P in Chinese Uyghur population. Given the unique genetic and environmental characters of the Uyghur population, these findings may be helpful for exploring the pathogenesis of this complex disease

A generic user interface for energy management in smart homes

Abstract Building operating systems play an important role in monitoring energy consumption of devices and improving energy efficiency in household buildings. From this arises a need for a preferably flexible and full-featured user interface to visualize the energy data in the building and allow residents to collect and realize various needs and preferences to the system. This article introduces a generic user interface for building operating systems which is presented from aspects of design, implementation and evaluation. To ensure the user interface can be flexibly adapted to various types of buildings, we design a series of generic data models which are independent of any building operating system. Besides, three roles with different permissions and a number of functional components of the user interface are also introduced in the article. Based on the design, a prototype of such a generic user interface named Building Operating System User Interface (BOS UI) has been implemented to operate the Energy Smart Home Lab (ESHL) at the Karlsruhe Institute of Technology (KIT). We evaluate the design, functionality and usability of the BOS UI qualitatively and quantitatively. The evaluation results show that the BOS UI meets a set of desired requirements (except for system configuration) for a generic user interface of building operating systems. Besides this, the evaluation experiments yielded very positive feedback in many aspects including improvement of energy efficiency and user experience. More than 90% of the test users agreed that the BOS UI provided them with enough information and functionalities that they would need in their daily lives and it can help them to save money. Furthermore, the mean score of the System Usability Scale (SUS) is 79.0, which indicates a good usability. The experiments prove that the user interface is still easy to use, despite abundant features are integrated into the system

Influence of Exercise on the Human Gut Microbiota of Healthy Adults: A Systematic Review

SUPPLEMENTARY MATERIAL accompanies this paper at http://links.lww.com/CTG/A166OBJECTIVES: To summarize the literature on the influence of exercise on the gut microbiota of healthy adults. METHODS: A systematic and comprehensive search in electronic database, including SciELO, Scopus, PubMed, and Web of Science up to July 5, 2019. Eligibility criterion was original studies conducted on healthy humans including exercise interventions or interventions involving any type of physical activity. RESULTS: The initial search retrieved 619 articles of which 18 met the inclusion criteria, 9 were observational, 4 reported very short-term exercise interventions, and 5 reported medium/long-term exercise interventions. Higher levels of physical activity or cardiorespiratory fitness were positively associated with fecal bacterial alpha diversity. Contrasting associations were detected between both the level of physical activity and cardiorespiratory fitness and fecal counts for the phyla Firmicutes, Bacteroidetes, and Proteobacteria. Higher levels of physical activity and cardiorespiratory fitness were positively associated with the fecal concentration of short-chain fatty acids. Reports on the effects of very shortterm and medium/long-term exercise interventions on the composition of the gut microbiota were inconsistent. DISCUSSION: Higher levels of physical activity and cardiorespiratory fitness are associated with higher fecal bacterial alpha diversity and with the increased representation of some phyla and certain short-chain fatty acids in the feces of healthy adults. Very short-term and medium/long-term exercise interventions seem to influence the fecal counts of some phyla. However, the heterogeneity between studies hampers any strong conclusions from being drawn. Better-designed studies are needed to unravel the possible mechanisms through which exercise might influence the composition and activity of the human gut microbiota.The study was funded by the Spanish Ministry of Economy and Competitiveness via the Fondo de Investigación Sanitaria del Instituto de Salud Carlos III (PI13/01393), Retos de la Sociedad (DEP2016-79512-R), and European Regional Development Funds (ERDF), by the Spanish Ministry of Education (FPU 16/05159 and FPU17/01523), the Fundación Iberoamericana de Nutrición (FINUT), the Redes Temáticas De Investigación Cooperativa RETIC (Red SAMID RD16/0022), AstraZeneca HealthCare Foundation, the University of Granada Plan Propio de Investigación 2016 (Excellence actions: Unit of Excellence on Exercise and Health [UCEES]), and by the Junta de Andalucía, Consejería de Conocimiento, Investigación y Universidades (ERDF, SOMM17/ 6107/UGR). B.M.-T. is supported by individual postdoctoral grants from the Fundación Alfonso Martin Escudero

Gold substrate-induced single-mode lasing of GaN nanowires

We demonstrate a method for mode-selection by coupling a GaN nanowire laser to an underlying gold substrate. Multimode lasing of GaN nanowires is converted to single-mode behavior following placement onto a gold film. A mode-dependent loss is generated by the absorbing substrate to suppress multiple transverse-mode operation with a concomitant increase in lasing threshold of only ∼13%. This method provides greater flexibility in realizing practical single-mode nanowire lasers and offers insight into the design of metal-contacted nanoscale optoelectronics