16,452 research outputs found
KIM MIN TAE
No full text학위논문(석사)--아주대학교 ITS대학원 :교통공학과,2009. 2인체와 노면간의 마찰계수에 대한 실험적 연구
차 대 보행자 교통사고는 다른 유형의 사고에 비해 피해가 매우 크고 사고의 비중도 높으나 사고의 특성 상 교통사고의 과학적 접근이 쉽지 않다. 기존 보행자 사고에 관한 연구의 대부분은 차 대 보행자의 충돌 실험에 대한 실험식 도출에 집중되어 있고, 실험식에서 중요한 변수로 작용되는 인체 활주 마찰 계수에 대한 연구가 부족한 실정이다. 본 연구에서는 인체와 노면간의 마찰계수에 대한 현장실험을 실시하여 이에 대한 실험값을 측정하여 제시하였다.
본 연구에서 조사된 건조한 아스팔트 도로에서의 인체노면 마찰계수의 값은 0.59~0.62, 건조한 콘크리트 도로에서는 0.59~0.61로 측정되었다. 또한, 젖은 아스팔트 도로에서의 인체 마찰계수는 0.56~0.59, 젖은 콘크리트 도로에서에서는 0.51~0.54로 파악되어 건조한 노면 상태와 비교하여 각각 5.0%와 8.3% 감소하는 것으로 파악되었다.
도출된 인체 마찰계수는 컴퓨터 시뮬레이션 프로그램을 이용한 사고 상황과 보행자 전도거리 공식을 이용하여 검증하였는데, 실험 수치와 시뮬레이션 결과가 유사함을 확인하였다.
이러한 실험결과를 바탕으로 현재 국내에서 교통사고 조사 시 사용되고 있는 인체 마찰계수의 적용 값의 범위를 축소하였고 이는 실제 교통사고 분석업무에 활용되어 사고 조사의 정확성 향상에 도움을 줄 수 있을 것으로 기대한다.- 목 차 -
제 1장 서 론 1
제 1절 연구의 배경 및 목적 1
제 2절 연구의 범위 및 방법 2
제 3절 연구의 흐름도 3
제 2장 이론적 고찰 4
제 1절 인체 노면 마찰 계수에 관한 기존 연구 고찰 4
1. 마찰계수의 일반적인 특성 4
제 2절 보행자 사고와 관련된 기존 이론 고찰 8
1. 보행자 사고 발생 시의 쟁점사항 8
2. 차 대 보행자 사고에서의 보행자의 움직임 10
3. 차 대 보행자 사고의 유형 14
4. 차 대 보행자 사고 재현 및 분석 방법 15
5. 보행자 충돌속도 계산식 16
제 3장 실험 결과 및 분석 18
제 1절 실험 방법 및 도구 18
1. 실험 방법 18
2. 실험 과정 18
제 2절 인체 마찰계수에 대한 실험적 연구 20
1. 건조한 아스팔트 도로 20
2. 건조한 콘크리트 도로 22
3. 젖은 아스팔트 도로 24
4. 젖은 콘크리트 도로 27
제 3절 컴퓨터 시뮬레이션(by PC-CRASH)에 의한 연구 결과 검증 28
1. 건조한 노면에서의 인체 마찰계수에 관한 실험적 검증 28
2. 젖은 노면에서의 인체 마찰계수에 관한 실험적 검증 30
제 4장 결론 및 향후과제 33
참 고 문 헌 34
ABSTRACT 35
감 사 의 글 37Maste
Mesenchymal Stem Cell-derived Extracellular Vesicles for Skin Wound Healing
No full textSkin is vulnerable to various external insults such as burn, severe injury, or inflammation, which necessitates a better strategy for wound repair. Mesenchymal stem cells (MSCs) can self-renew and differentiate into various supporting tissues including cartilage, bone, muscle, and adipose tissue. Along with their unique multipotent capacity, they secrete various paracrine mediators such as growth factors, cytokines, and membrane-enclosed particles called extracellular vesicles (EVs). Herein, we discussed the general traits of EVs such as cell-to-cell communicator, and highlighted the recent preclinical outcomes, with a focus on the application of MSC-derived EVs in wound repair. This chapter provides insights into developing novel strategies for skin wound healing in a cell-free manner.N
“The Power of Ethical Leadership”: The Influence of Corporate Social Responsibility on Creativity, the Mediating Function of Psychological Safety, and the Moderating Role of Ethical Leadership
No full textA body of existing literature delves into how corporate social responsibility (CSR) affects employees’ cognition, emotion, and behavior within an organization. These previous studies, however, pay relatively little attention to the influence of CSR on levels of creativity in employees. Considering that creativity is closely related to innovative capability, which is critical for a firm to survive, the relationship between CSR and employees’ creativity and its elaborate underlying processes need further investigation. Based on a group creativity model, we argue that CSR may increase levels of creativity in employees through mediation of enhanced levels of psychological safety in employees. In addition, existing works on CSR have relatively underexplored the contextual role of leadership in translating CSR practices into employees’ attitudes, perceptions, and behaviors. Using three-wave time-lagged survey data from 311 employees in South Korea, we found that CSR enhances employees’ creativity via mediation of psychological safety. Additionally, ethical leadership positively moderates the relationship between CSR and psychological safety. Our findings suggest that psychological safety in employees functions as an important underlying mechanism to describe the CSR–employee creativity link. Furthermore, this paper emphasizes the importance of the moderating role of ethical leadership in the process of CSR activities
Percutaneous transthoracic localization of pulmonary nodules under C-arm cone-beam CT virtual navigation guidance
No full textPURPOSEWe aimed to describe our initial experience with percutaneous transthoracic localization (PTL) of pulmonary nodules using a C-arm cone-beam CT (CBCT) virtual navigation guidance system.METHODSFrom February 2013 to March 2014, 79 consecutive patients (mean age, 61±10 years) with 81 solid or ground-glass nodules (mean size, 12.36±7.21 mm; range, 4.8–25 mm) underwent PTLs prior to video-assisted thoracoscopic surgery (VATS) excision under CBCT virtual navigation guidance using lipiodol (mean volume, 0.18±0.04 mL). Their procedural details, radiation dose, and complication rates were described.RESULTSAll 81 target nodules were successfully localized within 10 mm (mean distance, 2.54±3.24 mm) from the lipiodol markings. Mean number of CT acquisitions was 3.2±0.7, total procedure time was 14.6±5.14 min, and estimated radiation exposure during the localization was 5.21±2.51 mSv. Postprocedural complications occurred in 14 cases (17.3%); complications were minimal pneumothorax (n=10, 12.3%), parenchymal hemorrhage (n=3, 3.7%), and a small amount of hemoptysis (n=1, 1.2%). All target nodules were completely resected; pathologic diagnosis included invasive adenocarcinoma (n=53), adenocarcinoma-in-situ (n=10), atypical adenomatous hyperplasia (n=4), metastasis (n=7), and benign lesions (n=7).CONCLUSIONPTL procedures can be performed safely and accurately under the guidance of a CBCT virtual navigation system
ISAR imaging and cross-range scaling of high-speed manoeuvring target with complex motion via compressive sensing
No full textFor targets with extreme manoeuvres, inverse synthetic aperture radar (ISAR) imaging suffers from translational motion (TM), which is modelled as a one-dimensional (1D) phase error, and non-uniform rotational motion (RM), which is a multidimensional (MD) phase error that causes severe blurring in ISAR images. Full-aperture data collection is often unachievable because of interference with other radar activities, resulting in sparse-aperture (SA) data. In this study, the authors present a new framework for SA-ISAR imaging and cross-range scaling for manoeuvring targets based on compressive sensing. Instead of solving conventional optimisation problems constrained by a sparsity of signals, the proposed method utilises the sensing-matrix estimation technique for ISAR image reconstruction using parametric signal-model reconstruction. To do this, it looks for basis functions that best represent the behaviour of a sensing-dictionary matrix comprising the observed SA data. The sensing-matrix reconstruction is based on a modified orthogonal matching pursuit-type basis function-searching scheme. Finally, they generate a well-focused and scaled ISAR image from the recovered complete ISAR signal using the conventional Fourier transform after the removal of signals corresponding to 1D TM and MD RM phase errors. They utilise both simulated and real measured datasets to confirm the effectiveness of proposed method.113sciescopu
An Energy-Aware Hierarchical Event Detection in Battery-Operated Wireless Video Surveillance Systems
No full textEngineered bioclogging in sands: comparison of microbially induced and enzyme-induced biopolymer formation
No full textThis study presents two methods of producing an insoluble biopolymer, the microbially induced biopolymer formation (MIBF) and enzyme-induced biopolymer formation (EIBF) and explores their ability to reduce hydraulic conductivity and cause bioclogging in soil from pore to column scales. The batch experiments confirm that insoluble polysaccharidic biopolymers, dextran, are successfully produced either by the model bacteria or by the extracted cell-free enzyme. The results show that the EIBF method is more efficient in producing biopolymer and reducing hydraulic conductivity compared to the MIBF method. This study also uses microfluidic chips, which reveals the pore-filling behavior of biopolymers produced by both methods. EIBF produces larger dextran flocs than MIBF, and hence EIBF lowers the hydraulic conductivity more than MIBF for a given pore occupancy of dextran. Column experiments demonstrate that both MIBF and EIBF can significantly lower the hydraulic conductivity of coarse sands by two orders of magnitude with only 3% biopolymer pore saturation. The presented results suggest that both methods have the potential to induce well-controlled, engineered bioclogging in coarse-grained soils, and have applications in various geotechnical practices, such as sealing leakage in water-front structures, installing hydraulic barriers, and mitigating soil erosion.
Compressive Sensing Approach for High-Resolution ISAR Image Reconstruction and Autofocus
No full text1
- …
