13,351 research outputs found
Lim Keun-Woo
No full text학위논문(박사)--아주대학교 일반대학원 :컴퓨터공학과,2014. 2본 논문에서는 WLAN 기반 멀티 홉 네트워크에서 데이터를 보급할 때 서비스 품질 (QoS) 을 향상시키기 위한 효율적인 기술에 대해 연구한다. 스마트폰 및 이동 네트워킹 기술이 큰 발전을 이룸에 따라, 새로운 무선 네트워킹 서비스 및 어플리케이션이 대두될 것으로 기대되고 있다. 이 트랜드를 따라 WLAN 기반의 네트워킹 제품 및 디바이스가 미래 서비스를 지원하기 위한 가장 핵심 기술로 떠오르고 있다. 하지만, 기존 WLAN 환경에서의 QoS 를 지원하기 위한 연구는 미래의 다양한 서비스 및 어플리케이션이 요구하는 요구사항을 만족할 수 없다. 그렇기 때문에, WLAN 기반의 통신 기술은 미래의 다양한 서비스 지원을 위해 이러한 요구사항을 충족하고 효율적인 QoS 를 지원할 수 있는 방법을 제시하여야 한다.
본 논문에서는 WLAN 기반 멀티 홉 네트워킹 환경의 다양한 미래 시나리오 및 사용 예시를 분석하고 이러한 환경에서 발생할 수 있는 문제점을 분석한다. 또한, 이러한 문제점을 해결하기 위하여 새로운 기술을 제시하고, 성능 분석을 통해 해당 기술들이 미래 다양한 WLAN 기반 서비스의 효율성을 높일 수 있다는 것을 증명한다. 특히 QoS 향상을 위한 다음 3가지 기술에 초점을 맞춘다: 1) 차량 통신 시스템에서의 QoS 향상 기술, 2) 실시간 멀티미디어 감시 시스템 기술, 3) 에너지 효율적인 QoS 향상 기술. 각각의 QoS 향상 기술은 WLAN 기반 멀티 홉 네트워킹 환경에서 요구하는 다양한 요구 사항에 맞춰 서비스 품질을 향상시킬 수 있을 것이라 기대된다.CHAPTER I INTRODUCTION
I.A Contributions of this Thesis
I.B Overview of the Thesis
CHAPTER II BACKGROUND AND RELATED WORK
II.A IEEE 802.11 WLAN standard
III.A.1 Service Differentiation
III.A.2 Multi-hop routing
III.A.3 Mobility Management
III.A.4 Wi-Fi Direct for mobile D2D communication
II.B Taxonomy of QoS in WLAN based networks
II.C Work on Ensuring Mobile Reliability
II.C.1 Related Work on Fast Handover
II.C.2 Related Work on Mobile Data Provisioning
II.D Work on WLAN Access Control
II.D.1 Related Work on Rate Control
II.D.2 Related Work on Multi-hop Flow Control
II.D.3 Related Work on Admission Control
II.E Work on Service Differentiation
II.E.1 Related Work on Queue-based Service Differentiation
II.E.2 Related Work on Station-based Service Differentiation
II.F Design Considerations for enhancing QoS in future services
CHAPTER III QOS-ENHANCED DATA HARVESTING IN VEHICULAR NETWORKS
III.A Background
III.B Proposed Scheme
III.B.1 Scheme 1: Multi-hop Data Harvesting with Replicas (MDH-R)
III.B.2 Scheme 2: Multi-hop Data Harvesting with Replicas and Aggregation (MDH-RA)
III.C Performance Evaluation
III.C.1 Simulation Environments
III.C.2 Simulation Results of MDH-R
III.C.3 Simulation Results of MDH-RA
III.D Chapter Summary
CHAPTER IV REAL-TIME DATA DISSEMINATION IN WLAN MESH NETWORKS
IV.A Background
IV.B Proposed Scheme
IV.B.1 Adaptive Mesh Network Architecture
IV.B.2 Multi-Gateway Route Selection
IV.B.3 Congestion Prediction
IV.B.4 Congestion Avoidance
IV.B.5 Routing Loop Prevention
IV.B.6 Example of MGR-CA Operation
IV.C Performance Evaluation
IV.C.1 Testbed Implementation
IV.C.2 Simulation Results
IV.D Chapter Summary
CHAPTER V POWER-EFFICIENT QOS IN WLAN BASED D2D ENVIRONMENTS
V.A Background
V.B Proposed Scheme
V.B.1 Problem Statement
V.B.2 Dynamically Synchronized Power Management
V.B.3 Adaptive CTWindow Control (AC)
V.B.4 Adaptive Temporary CTWindow Control (AT)
V.C Performance Evaluation
V.C.1 Formulation of Duty Cycle and End-to-End delay
V.C.2 Performance Evaluation
V.C.3 Formulation and Evaluation of AC and AT control
V.D Chapter Summary
CHAPTER VI CONCLUSIONDoctoralThis thesis focuses on methods of enhancing Quality-of-Service (QoS) in WLAN based multi-hop networks for more efficient data dissemination. With great advancements in the technology of smartphones and mobile networking, the global society is beginning to embrace another boom of various wireless networking services and applications. Following this trend, WLAN based networking devices and products have become the most popular means of data communication for supporting these future services. However, contrary to existing QoS researches conducted in WLAN environments, these future applications have unique demands and requirements depending on the type of service they provide. Therefore, as being the primary means of communication in the present and future alike, WLAN based communication technology must account for these difference in services and provide efficient means of supporting QoS for them.
This thesis views various scenarios and use cases of WLAN based multi-hop networking environments and analyzes the problems that current WLAN systems may pose. To account for these problems, novel solutions are proposed and analyzed to show that the contributions in this thesis can greatly improve the efficiency of future WLAN based services. Especially, three technologies of supporting QoS are discussed: 1) Enhancing QoS for data dissemination in vehicular speed communications systems, 2) Streaming multimedia surveillance systems, and 3) Power efficient QoS for battery-limited systems. It is expected that each technology can improve the performance of QoS in WLAN based multi-hop networking applications depending on the various requirements that they demand
STSAT-2C mission achievements with on orbit verifications
No full textThe STSAT-2C is a small satellite with 100kg mass and was launched on 30 January 2013, on the third fight of the KSLV-1, Korean rocket. Lift of occurred from the Naro Space Centre in Korea, and the launch vehicle successfully deployed the satellite into at 297km by 1,512km Low Earth Orbit inclined at 80.3 degrees. The objectives of STSAT-2C consist of three missions. The first is to demonstrate the capability of the KSLV-I as a launch vehicle for LEO missions. The Second is observation of space environment. And the third is to perform new space technology demonstration in orbit. The STSAT-2C was developed very shortly in a year for the KSLV-1, which had previously failed to launch STSAT-2A in 2009 and STSAT-2B in 2010. The STSAT-2C is operated by Satellite Technology Research Center of KAIST and was achieved mission requirement successfully in orbit. It has new developed space technology include IR Sensor, Femto-Second Laser, Reaction Wheel and Li-Ion battery system using COTS devices and etc
Yong Cheol Lim
No full text학위논문(석사)--아주대학교 일반대학원 :의학과,2006. 8목적: 고프로락틴혈증은 다양한 원인에 의하여 성선 기능의 저하와 유즙분비를 유발하는 비교적 흔한 질환으로, 가장 중용한 원인인 프로락틴분비선종(Prolactin-secreting adenomas, prolactinomas)은 뇌하수체선종의 약 30%, 기능성 뇌하수체 종양의 50 - 60%를 차지하는 흔한 뇌하수체 종양이다. 일반적인 치료원칙은 호르몬 분비를 억제시킴으로써 고프로락틴혈증에 의해 유발된 성선기능의 저하나 유루증 등의 증상을 완화시키고, 원인이 되는 종양을 제거하거나, 뇌하수체기능을 보존하면서 종양의 재발이나 진행을 억제하는데 있다. 그 외 치료방법으로 수술적으로 절제하거나 통상적인 방사선치료 혹은 방사선수술 등이 있다. 본 연구에서는 본원에서 시행한 호르몬 검사상 고프로락틴혈증의 소견을 보였던 환자를 대상으로 고프로락틴혈증의 원인을 분류하고 수술치료를 시행한 뇌하수체 프로락틴선종 환자를 대상으로 수술치료후 결과를 비교하여 적절한 치료방향의 설정을 위하여 연구를 계획하였다.
대상 및 방법: 1998년 1월부터 2005년 3월까지 7년동안 아주대학교병원에서 내분비 검사 및 터키안 자기공명촬영(Sellar MRI)을 시행하여 고프로락틴혈증으로 진단된 198명의 환자를 대상으로 원인을 분류하고, 뇌하수체선종으로 진단을 받고 수술을 시행받은 62명중 면역조직화학염색상 프로락틴선종으로 확진된 34명의 환자를 대상으로 추적검사 결과를 분석하였다.
결과: 고프로락틴혈증을 보였던 198명의 환자중 남자가 35명(17.7%), 여자가 163명(82.3%)이었고 연령은 평균 38.97세(7～81)였다. 터키안 자기공명촬영상 뇌하수체선종으로 진단된 환자가 121명(61.1%), 정상소견 44명(22.2%), empty sellae 17명(8.6%), 뇌하수체hyperplasia 7명(3.5%), RCC 3명(1.5%)였고, 지방종(lipoma), 수막종(meningioma), stalk mass가 각각 1명이었다. 프로락틴선종으로 수술을 시행한 환자의 61.8%에서 혈중 프로락틴치의 정상화를 보였으며, 수술치료만으로 혈중 프로락틴치의 정상화를 보였던 환자는 모두 15명으로 미세선종에서 11명(73.3%), 거대선종에서 4명(21%)이었다. 특히 혈중 프로락틴치가 100𝜇g/L이하인 미세선종에서는 모든 례에서 수술치료만으로 완전 조절되었고, 일과성 중추성 요붕증 이외의 합병증은 나타나지 않았다.
결론: 미세 프로락틴선종, 특히 혈중 프로락틴치가 100𝜇g/L이하인 환자에서 모든 례에서 수술치료만으로 일과성 중추성 요붕증 이외의 합병증이 없이 혈중 프로락틴치의 완전 조절을 보여 미세 프로락틴선종의 치료에서 종양의 위치나 침습성 여부, 혈중 프로락틴치, 약물치료의 반응정도, 수술자의 경험을 기준으로, 젊은 환자 특히 임신을 원하는 미세선종의 여자 환자에서 경험이 많은 수술자의 경우 미세선종의 치료로 수술치료를 고려할 수 있는 적응이 될 수 있을 것으로 사료된다.국문요약 ---------------------------------- 1
차례 ---------------------------------- 3
그림 차례 ---------------------------------- 5
표 차례 ---------------------------------- 6
I. 서론 -------------------------------- 8
II. 연구대상 및 방법 ---------------------- 10
A. 연구 대상 ---------------------- 10
B. 연구 방법 ---------------------- 10
III. 결과 --------------------------------- 12
A. 연령분포 및 성별 -----------------------12
B. 자기공명촬영 결과 및 혈중 프로락틴 수치 -- 14
C. 뇌하수체선종의 수술치료---------------- 18
1. 성별 및 연령분포---------------------- 18
2. 조직학적 진단 결과-------------------- 19
D. 프로락틴분비 선종의 수술치료 결과------- 20
1. 임상증상 및 종양의 크기에 따른 혈중 프로락틴 수치-- 21
2. 수술치료의 선택 ---------------------------------23
3. 수술치료의 결과 ---------------------------------23
IV. 고찰 --------------------------------------------25
V. 결론 --------------------------------------------39
참고문헌 --------------------------------------------40
영문요약 --------------------------------------------44Maste
Sai Woo
No full textMenu from Sai Woo restaurant in Vancouver, BC. Soups, chop suey, chow mein, pork spare ribs, meat and vegetables, sea foods, egg foo-young, chicken, fried rice, noodles, cold dishes.From the Imogene Lim restaurant menu collectio
Detection of fatigue crack on a rotating steel shaft using air-coupled nonlinear ultrasonic modulation
No full textRotating shafts in drop lifts of manufacturing facilities are susceptible to fatigue cracks as they are under repetitive heavy loading and high speed spins. However, it is challenging to use conventional contact transducers to monitor these shafts as they are continuously spinning with a high speed. In this study, a noncontact crack detection technique for a rotating shaft is proposed using air-coupled transducers (ACTs). (1) Low frequency (LF) and high frequency (HF) sinusoidal inputs are simultaneously applied to a shaft using two ACTs, respectively. A fatigue crack can provide a mechanism for nonlinear ultrasonic modulation and create spectral sidebands at the modulation frequencies, which are the sum and difference of the two input frequencies Then LF and HF inputs are independently applied to the shaft using each ACT. These three ultrasonic responses are measured using another ACT. (2) The damage index (DI) is defined as the energy of the first sideband components, which corresponding to the frequency sum and difference between HF and LF inputs. (3) Steps 1 and 2 are repeated with various combinations of HF and LF inputs. Crack existence is detected through an outlier analysis of the DIs. The effectiveness of the proposed technique is investigated using a steel shaft with a real fatigue crack
High Efficiency and High Power Density Weinberg Converter Reducing Conduction Loss and Output Current Ripple for Space Applications
No full textWeinberg converter is widely used to battery discharge regulator of satellite system because it guarantees soft-switching of all devices and has low output current ripple. However, due to leakage inductance of the coupled inductor and transformer, the voltage stress of powering diode and the output current spike are increased. To overcome these problems, weinberg converter with auxiliary switch and capacitor is presented in this paper. The proposed converter significantly reduces the voltage stress of powering diode. In additions, the output current spike is decreased by adopting auxiliary circuit. Thus, the conduction loss of the powering diode and output current ripple are reduced. As a results the proposed converter achieves high efficiency and high power density with the reduced output filter. The verification is performed with 400 W/50 V prototype
비접촉 내구 진단 장치 및 방법
No full textA non-contact durability diagnosis apparatus includes: (a) applying non-contactly and sequentially at least two excitation ultrasonic waves to an object and storing frequency signals generated from the object; (b) applying non-contactly and simultaneously the at least two excitation ultrasonic waves to the object and storing frequency signals generated from the object; (c) storing derived frequency signals remaining after removing an overlapping portion of the frequency signals of step (a) and the frequency signals of step (b); and (d) determining that the object is damaged when at least one of the generated frequency signals of step (c) is larger than a predetermined value
불포화 기공 매체내에서 지하수흐름과 방사성 핵종 이동의 질량보존 수치해에 관한 연구
No full text학위논문(박사) - 한국과학기술원 : 원자력공학과, 1993.8, [ xi, 102 p. ]A theoretical model for soil water characteristic curves based on the effective pore radius distribution of the soil medium and capillarity law, was derived. Using this new curve and Mualem``s model, the evolution of unsaturated hydraulic conductivity and soil water diffusivity functions was explored. The equations for these three parameters are not expressed in analytic forms but as integrals. However, it was found that they reveal realistically the characteristics of unsaturated soils. Results of the new soil water characteristic and relative hydraulic conductivity relationship were compared with observed data of four soils with a wide range of soil physical properties. A fairly good agreement between the calculated curves and observed data was obtained irrespective of the scale of effective pore radius. The Galerkin finite element formulation is used to solve the problem of one-dimensional, vertical flow of water and mass transport of conservative-nonconservative solute in unsaturated porous media. Numerical approximations based on different forms of governing equation, although they are equivalent in continuous forms, can result in remarkably different solutions in unsaturated flow problem. Solutions given by simple Picard iteration method based on the h-based Richards equation yields large mass balance error and underestimation of infiltration depth. Usually the -based form of Richards equation has not been used for unsaturated flow analysis because of the restriction in convergence. With the employment of ROMV (Restoration of Main Variable) concept in the discretization step, the mass conservative numerical solution algorithm for water flow has been derived. When the ROMV concept is used, the discretized equations based on the standard h-based and -based Richards equation can also be used for flow analysis in unsaturated soil media. The resulting computational schemes for water flow and mass transport are applied to sandy soil. The ROMV me...한국과학기술원 : 원자력공학과
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