수중 무선 센서 네트워크를 위한 클러스터 헤드 오류 복구 기법

허준영,민홍 한국인터넷방송통신학회 2011 한국인터넷방송통신학회 논문지 Vol.11 No.4

수중 환경은 육상 환경과 많은 차이를 보이며 무선 통신에 사용되는 자원과 제약 조건들도 다르다. 일반적으로 수중 통신 환경은 육상 통신 환경보다 열악하고, 파도, 조류와 같은 해수의 흐름으로 인한 노드의 이동성 때문에 오류 발생 가능성이 기존의 지상 무선 센서 네트워크 보다 높다. 따라서 수중 무선 센서 네트워크의 통신 환경을 고려하여 노드 간 데이터 전송률을 향상시키기 위한 기법들에 대한 요구가 높아지고 있다. 본 논문에서는 수중 무선 센서 네트워크의 통신 환경을 고려하여 클러스터 헤드 노드의 오류 발생 시 이를 빠른 시간 내에 복구하기 위한 체크포인팅 기법을 제안한다. 또한 실험을 통해 제안 기법이 네트워크 운영의 신뢰도를 향상 시킬 수 있을 뿐만 아니라, 에너지 소모량과 오류 복구 지연 시간 측면에서 제안 기법을 적용하지 않았을 때보다 좋은 성능을 보인다는 것을 검증한다. The underwater environments are quite different from the terrestrial ones in terms of the communication channel and constrains. In underwater wireless sensor network, the probability of node failure is high because sensor nodes are deployed in more harsh environments than the ground based networks and moved by waves and currents. There are researches considering the communication environments of underwater to improve the data transmission throughput. In this paper, we present a checkpointing scheme of the cluster heads that recoveries from a cluster head failure quickly. Experimental results show that the proposed scheme enhances the reliability of the networks and more efficient in terms of the energy consumption and the recovery latency than without checkpointing.

고속전자밸브를 사용한 유압장치의 PWM 제어에 관한 연구

허준영,Wennmacher,G. 대한기계학회 1995 대한기계학회논문집 Vol.19 No.3

This study deals with a position control of an electro-hydraulic servo system which consist of cylinder and high speed on-off valves operated by microcomputer. The merits of PWM control of hydraulic equipment are the robustness of the high spee on-off valve, its low price and the direct control without D/A converter. In the PWM control of high speed on-off valve, the time lag and switching time existing between the input and output signals of valve are considered as demerit points. To get analytical results, the effects of these demerits have to be clarified in detail. The object of this study is to propose a mathematical model for the behavior of high speed on-off valve and to get analytical results of this system. The dynamic characteristics of this system is examined by digital computer simulation analytically and compared with experimental results to varify the proposed mathematical model.

불안정한 환경에서의 안정성? - 통독전 동독이탈주민에 대한 서독의 통합정책

허준영 한독사회과학회 2011 한독사회과학논총 Vol.21 No.1

본 연구의 목적은 독일 분단기인 제 2차 세계대전후 부터 통독 시기까지 동독 이탈주민에 대한 서독의 통합정책을 살펴보고 한국에 주는 시사점을 도출하는데 있다. 동독 이탈주민의 서독사회로의 통합은 서독의 전 사회적인 노력에 의해 가능했던바 동 기간 전후재건 및 통일까지 서독사회 내외 다양한 환경변화를 감안할 때 통합정책과 환경과의 관계에 대해 보다 역동적인 이해를 할 필요성이 제기된다. 이러한 문제의식을 가지고 본 연구는 서독의 통합정책과 정치, 경제 그리고 사회적 환경과의 상호관계에 주목하여 논의를 이끌어 간다. 연구결과에 따르면 탈동독 이주민의 특성은 시대에 따라 계속 변화하였고 환경 변수의 불안정한 변화 즉, 정치, 경제, 사회적 환경의 제약조건 하에서 서독의 통합정책은 안정적으로 유지되었다. 이렇듯 정책의 일관성이 가능했던 내·외적 원인을 찾아보고 이와 관련하여 한국적인 시사점과 적용가능성을 살펴본다. Thema dieses Aufsatzes ist die westdeutschen Integrationspolitik ostdeutscher Flüchtlinge zwischen dem Ende des zweiten Weltkriegs und der deutschen Wiedervereinigung. Die Integration ostdeutscher Flüchtlinge in die westdeutsche Gesellschaft wurde durch die Anteilnahme der ganzen Gesellschaft möglich. Vor diesem Hintergrund verfolgt die vorliegende Untersuchung zwei Ziele: Zum einen sollen westdeutsche Integrationsbemühungen für ostdeutsche Flüchtlinge dynamisch aufgefasst werden, wobei die Einflüsse der Umwelt wie die politische, wirtschaftliche und soziale Lage mit bedacht werden. Zum anderen werden der Standpunkt der vorliegenden Arbeit und die daraus gewonnenen Untersuchungsergebnisse auf die Frage hin geprüft, inwieweit die deutschen Erfahrungen auf die Integrationspolitik Südkoreas für nordkoreanische Flüchtlinge übertragen werden könnten. Nach den Forschungsergebnissen werden die Charakterzüge der deutschen Integrationspolitik wie folgende zusammengefasst: Trotz wachsender Unterschiede der Charakteristika der Zielgruppe und des instabilen Umfelds behielt die Integrationspolitik ihre Kontinuität in Bezug auf die Grundkonzepte sowie -maßnahmen bei. Abschließend wird eine Übertragbarkeit der deutschen Erfahrungen mit der Integrationspolitik auf Korea angedacht.

확장칼만필터를 사용한 유압식 사판기구의 파라메타 추정

허준영 한국기술교육대학교 2003 論文集 Vol.10 No.1

An estimation technique called the Extended Kalman Filter is used to estimate viscous friction, coulomb friction, and the spring constant on the swash plate of a variable displacement pump. The feasibility of the approach was established using a simulation study. It showed that these parameters could be estimated very accurately in a reliable and independent fashion. A special experimental system was set up to facilitate the measurement of certain states to enhance the Kalman Filtering approach. The aforementioned parameters were estimated and found to be reasonably repeatable for a common operating point. It was very evident that as the operating conditions changed (i.e. temperature) so did the estimated values of certain parameters such as viscous friction. This was believed to be a good verification test for the approach.

흰쥐 적출 소장의 수축성에 미치는 GABA의 영향

허준영,권오철,하정희,이광윤,김원준 영남대학교 기초/임상의학연구소 1991 Yeungnam University Journal of Medicine Vol.8 No.2

제1종 LiBr-H₂O 흡수식 열펌프의 시뮬레이션

허준영,최영돈,Huh, J.Y.,Choi, Y.D. 대한설비공학회 1990 설비공학 논문집 Vol.2 No.1

The first kind LiBr -$H_2O$ absorption heat pump system was simulated and the performances of it were predicted. The elements of heat pump system, evaporator, absorber and generator were analysed by solving the energy balance equations and concentration equations which describe the reactions between working fluids. The results show that the temperature gain of absorber and condenser and the COP of the system are affected considerably by the operating conditions of heat pump system.

PWM 제어되는 유압장치의 안정성 해석

허준영,Wennmacher, G. 대한기계학회 1995 대한기계학회논문집 Vol.19 No.6

PWM control is a kind of nonlinear control. The merits of PWM control of hydraulic equipment are the robustness of the high speed on-off valve and its low price. And it is easily implemented to hydraulic equipments with microcomputer. The high speed on-off valve is directly digitally controlled without any D/A converter. The objectives of this study is to analyze the limit cycle which regularly appear in the position control system using high speed on-off valve, and to give a criterion for the stability of this system. To do this, the nonlinear characteristics of PWM and cylinder friction of this system are described by harmonic linearization and the effects of parameter variations to the system stability are examined theoretically and experimentally. Consequently, the availability of the proposed method is confirmed well.

Topology optimization based on spline-based meshfree method using topological derivatives

허준영,강필성,윤성기 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.5

Spline-based meshfree method (SBMFM) is originated from the Isogeometric analysis (IGA) which integrates design and analysis through Non-uniform rational B-spline (NURBS) basis functions. SBMFM utilizes trimming technique of CAD system by representing the domain using NURBS curves. In this work, an explicit boundary topology optimization using SBMFM is presented with an effective boundary update scheme. There have been similar works in this subject. However unlike the previous works where semi-analytic method for calculating design sensitivities is employed, the design update is done by using topological derivatives. In this research, the topological derivative is used to derive the sensitivity of boundary curves and for the creation of new holes. Based on the values of topological derivatives, the shape of boundary curves is updated. Also, the topological change is achieved by insertion and removal of the inner holes. The presented approach is validated through several compliance minimization problems.

2방향형 고속전자밸브를 사용한 유압장치의 압력서보제어

허준영 한국기술교육대학교 1997 論文集 Vol.4 No.1

This study deals with a pressure control of an electro-hydraulic servo system using 2-way high speed on-off valves operated in PWM mode. The merits of PWM control of the hydraulic equipment are the robustness of the high speed on-off valve, its low price and the direct control without D/A converter. In the PWM control of high speed on-off valve, the time lag and switching time existing between the input and output signals of valve are considered as demerit points. To get analytical results, the effects of these demerits have to be clarified in detail. The object of this study is to propose a mathematical model for the behavior of high speed on-off valve and to get analytical results of this system. The dynamic characteristics of this system is examined by digital computer simulation analytically and compared with experimental results to varify the proposed mathematical model.

고속온오프밸브를 사용한 서보인텍싱시스템의 슬라이딩모드제어에 관한 연구

허준영 韓國技術敎育大學校 1994 論文集 Vol.1 No.1

This study deals with an electrohydraulic servo indexing system of a flexible forging center, which is operated by four 2-way high speed solenoid valves in the PWM digital mode. A flexible forging center consists of a forging machine and a indexing system. The role of the indexing system is to rotate a workpiece fast and accurately to a desired position. There are practical problems to be solved in this system, such as variations of system parameters during each forging step and serious nonlinearities in the valve characteristics. In order to overcome such problems, a sliding mode control is proposed. The salient feature of the sliding mode control is that the sliding mode occures on a switching surface. While in sliding mode, the system remains insensitive to parameter variations and disturbances. So robust performance can be achieved. In addition, this controller has a strategy to use an integrator to eliminate significant nonlinearities, such as the dead zone, which regularly appear with an PWM operated servo system. The dynamic characteristics of the system driven by the proposed method are investigated by digital simulation. Consequently, the availability of the proposed method is confirmed well.