리프팅에서의 근력 보조와 자세 가이드를 위한 유연한 착용형 장치 개발

학위논문 (석사)-- 서울대학교 대학원 : 공과대학 기계항공공학부, 2018. 2. 조규진.There is a saying: comfortable posture is usually bad posture. A human feels comfortable and consumes less energy when holding the object on the floor by flexing his back than bending leg, because of characteristics of human body design. However, from a spinal point of view, lifting a heavy load in a back bent posture is a dangerous act that may increase the risk of a disc injury by 2 to 4 times. We have developed a soft wearable device that can reconfigure these contradictory human body systems to make to feel the correct posture comfortable and bad posture uncomfortable. A representative posture correction functions of this device is to correct the wearers habit to use a lifting technique called squat instead of the stoop and to induce wearer to keep his knee behind the toes in the process of bending the legs. Experiments with varying lift posture showed that this device interfered with the stoop motion but assisted the squat motion. Also, we proved that the muscular force assistive effect of the device increased in knee backed posture. Another experiment was conducted in which the 15kg box was repeatedly lifted at a rate of 10lifts/min for 6minutes. In case of taking squat posture, EMG values of spinal erector, biceps femoris, and rectus femoris decreased by 14.0%, 17.0%, and 14.3% respectively when wearing the device. Also, in this case, the metabolic energy cost decreased by 29.5% and the heart rate decreased by 13.6%, proving that the device is effective in reducing fatigue of the worker. Compared to stooping without a device, the result was a 24.7% reduction in metabolic energy cost and a 7.3% reduction in heart rate when the subject takes squat posture with wearing the device. Therefore, the device is expected to help stuff transportation workers to lift objects in correct posture with small fatigue.Chapter 1. Introduction 1 1.1. Study Background 1 1.2. Purpose of Research 2 Chapter 2. Design 3 2.1. Design Strategy 4 2.1.1. Posture Correction Principle 6 2.1.2. Muscular Force Support Principle 11 2.2. Anchor Design 12 2.2.1. Anchoring Issue#1: Force & Torque Setting 14 2.2.2. Anchoring Issue#2: Fixing 15 2.3. Cable Routing 17 2.3.1. Routing Issue#1: Enabling Leg Motions 18 2.3.2. Routing Issue#2: Maintaining the Cable Path 20 Chapter 3. Experiment 22 3.1. Effect of Lifting Technique 22 3.2. Effect of Knee posture in the Squat 25 3.3. Evaluation of Fatigue Reduction 29 Chapter 4. Conclusion 32 Bibliography 34 Abstract in Korean 38Maste

의사 3차원 수치모델을 이용한 수압파쇄균열의 전파예측에 관한 연구

Thesis (master`s)--서울대학교 대학원 :자원공학과,1995.Maste

공공부문의 현금관리와 적정현금보유량에 대한 연구

우리의 상식과는 달리 현금액수는 우리가 영원히 파악할 수 없는 현상의 하나이다. 아무도 조직의 정확한 현금액수를 파악할 수는 없으며 오로지 진정한 현금액수를 추정할 뿐이다. 현금의 이러한 특성 때문에 현금관리정보시스템이 필요하며 현금관리정보시스템에 근거하여 현금예산이 편성되어야 한다. 바람직한 현금관리정보시스템과 현금예산이 존재한다면 적정현금보유량을 유지함으로써 순현금수입의 극대화를 달성할 수 있지만 적정현금보유량은 현금관리정보시스템과 현금예산이 존재한다고 해서 자동적으로 결정될 수 있는 것은 아니다. 적정현금 보유량결정은 현금관리의 부분적인 개념이 아니라 현금관리의 또 다른 측면이라고 볼 수 있다. 현금관리정보시스템과 현금예산이 적정현금보유량을 결정하기 위한 것이라고 해도 지나치지 않을 정도로 적정현금보유량의 결정은 현금관리의 모든 내용과 연계되어 있다. 민간부문에서는 적정현금보유량을 결정하는 수리모델이 사용되지만 공공부문에 적합하지 않기 때문에 본 연구에서는 공공부문의 적정현금보유량결정을 위한 모델을 제시하고자 한다. 공공부문의 현금흐름은 종적인 변화와 횡적인 변화가 민간부문과는 다른 특성이 있기 때문에 공공부문의 적정현금보유량을 결정할 때 이를 감안하여야 한다

Effect of maternal stress on circadian rhythm and metabolism

학위논문 (석사)-- 서울대학교 대학원 : 생명과학부, 2013. 2. 김경진.It is well established that maternal stress causes defective functions in several important brain regions such as hypothalamus, hippocampus and amygdala. However, the effect of maternal stress on the suprachiasmatic nucleus (SCN) which acts as a central pacemaker driving circadian rhythm remains largely unknown. In the present study, I focused on the question whether stress in pregnant mice could influence the circadian clockwork in the SCN of their offspring and its physiological relevance. SCN slices from 1 week-old transgenic mice maintained rhythmic PER1::LUC expression for more than a week, and maternal stress caused shortened periodicity and reduced amplitude, and even loss of rhythm in some cases. However, in SCN slices from 5 week-old mice, altered period and arrhythmicity were recovered as similar to those of adult mice while the amplitude of PER1::LUC was still lower than the control group. In addition, mRNA profiles of several molecular clock genes in liver of prenatally stressed adult mice were affected. In accordance with the liver clock, rhythmic profiles of metabolic genes involved in glucose metabolism were altered in maternally stressed mice. However, although liver glycogen contents were slightly decreased, plasma glucose levels were not changed, suggesting that maternal stress cannot disrupt glucose homeostasis in normal feeding condition. Taken together, these findings suggest that maternally stressed mice can adjust to their environment after birth, likely for overcoming the effect of prenatal stress on circadian timing systemABSTRACT………………………………………………………………………… 1 INTRODUCTION………………………………………………………………….… 3 MATERIALS AND METHODS…………………………………………………..… 8 Animal care and handling Maternal stress procedure. Preparation of plasma and tissues RNA isolation and RT-PCR Measurement of metabolic parameters Ex vivo tissue explant culture Quantitative real-time bioluminescence monitoring on the SCN Statistical analysis RESULTS……………………………………………………………………………15 Altered cyclic PER1::LUC expression in SCN from 1 week-old mice Cyclic PER1::LUC expression in SCN from 5 week-old mice Expression of clock genes in the local clock Effect of maternal stress on carbohydrate metabolism DISCUSSION………………………………………………………………………. 33 REFERENCES……………………………………………………………………... 37 ABSTRACT IN KOREAN…………………………………………………………. 44Maste

A study on the effectiveness of the privatization policy of the public enterprise

최근 선진국의 정부개혁에서 민영화는 항상 중요한 문제였다. 그러나 민영화의 당위성에 대한 주장은 상당부분 공감을 얻어왔지만 민영화정책의 효과성에 대한 학문적 논의는 아직도 진행 중이다. 공기업의 비효율성은 소유구조 문제, 경쟁부재 및 정부의 과잉간섭 등 여러 가지 문제들로 인하여 계속 지적되어 왔다. 민영화는 이러한 공기업 비효율의 문제가 처음부터 발생하지 않는 환경으로 전환하는 것이다. 공기업 민영화정책은 소유권이전을 통한 기업체질 개선을 통해, 공공부문의 여러 문제점을 해결하고 비효율을 개선하려는 정책이다. 이러한 문제의식을 가지고, 본 연구는 실증분석을 통해 공기업 민영화정책의 효과를 분석하였다. 구체적으로 과거 공기업에서 민영화된 기업사례분석을 통해 민영화가 실제 기업의 효율성 향상에 어떠한 영향을 미쳤는지를 실증분석하였다. 분석결과 민영화된 기업은 원가, 인건비 등 비용요소보다는 매출액, 가격 등 산출요소에 집착하는 양상을 보였고, 분석대상기업 대부분이 민영화 이전보다 재무성과가 나빠졌다. 즉 민영화기업이 효율성향상을 위해 노력하도록 하는 어떠한 유인도 존재하지 않는 것으로 나타났다. 이러한 결과는 민영화가 자동적으로 기업의 효율성을 증가시키지는 못한다는 것을 보여주는 결과이다. Recently the privatization always was the point of issue in governmental reform of developed nations. Although the justification of privatization gets considerable agreement, the efficiency of privatization is upon the debates. The inefficiency of public enterprises was caused by their ownership structure, competition absence and government's interference. Privatization has long been believed to be very effective making the structural environment in which public enterprise become more efficient. The privatization policy of the public enterprise is the policy that solves a lot of problems and inefficiency of public sector by transferring of ownership. Based on this perception, this study finds how the privatization affects the efficiency improvement of enterprises which became privatized. The results of this study prove that many enterprises prefer to improve their output factors such as sales, price rather than their input factors such as unit cost, labor costs and their financial conditions become worse after privatization. In other words, there does not exist any incentive scheme that improves their efficiency. This result shows that the privatization in itself does not automatically guarantee the efficient public enterprise