다중 컴퓨터를 이용한 고속 시뮬레이션 기법에 관한 연구

양희재 慶星大學校 1992 論文集 Vol.13 No.2

A fast simulation method, called the parallel batch means method, is presented and analyzed in this paper. Contrary to the conventional parallel simulation methods, it assumes a large grain-size parallelism and thus it is less dependent on the speed of communications between the computers. The method is based on the theory of batch means, which is a well-known simulation output analysis technique. The method achieves a linear speedup characteristic and an experimental simulation using the method shows that it produces even accurate simulation results with great saving in simulation time. As inexpensive computers are increasingly available nowadays, the method will be indispensable for fast and accurate computer simulation.

에너지 관점에서 임베디드 자바가상기계의 메모리 접근 형태

양희재,Yang Heejae 한국정보처리학회 2005 정보처리학회논문지 A Vol.12 No.3

임베디드 시스템에서 일반적으로 메모리가 가장 많은 에너지를 소비하는 것으로 알려지고 있다. 임베디드 자바가상기계의 경우도 마찬가지이며, 따라서 보다 에너지 효율이 높은 자바가상기계의 개발을 위해서는 자바 메모리의 에너지 사용을 최적화 하는 것이 무엇보다 중요하다. 본 논문에서는 자바 프로그램 실행 시 수많은 바이트코드들이 어떻게 논리적 메모리를 접근하는지 분석하였다. 이런 접근 형태 분석은 자바 메모리의 설계 및 구현 기술을 선택하는데 큰 통찰력을 제공해 준다 힙, 오퍼랜드 스택, 지역변수배열 등 세 가지 논리적 데이터 공간에 대해 각각 메모리 접근을 분석하였으며, 분석 결과 오퍼랜드 스택이 가장 빈번하게, 또한 균일하게 사용되었으며 힙이 가장 드물게, 그리고 불균일하게 사용되었음을 알 수 있었다. 힙과 지역변수배열은 읽기 위주로 사용되었으며, 오퍼랜드 스택은 읽기와 쓰기 비율이 크게 다르지 않았다. Several researchers have pointed out that the energy consumption in memory takes a dominant fraction on the energy budget of a whole embedded system. This applies to the embedded Java virtual machine tn, and to develop a more energy-efficient JVM it is absolutely necessary to optimize the energy usage in Jana memory. In this paper we have analyzed the logical memory access pattern in JVM as it executes numerous number of bytecode instructions while running a Java program. The access pattern gives us an insight how to design and select a suitable memory technology for Java memory. We present the memory access pattern for the three logical data spaces of JVM: heap, operand stack, and local variable array. The result saws that operand stack is accessed most frequently and uniformly, whereas heap used least frequently and non-uniformly among the three. Both heap and local variable array are accessed mostly in read-only fashion, but no remarkable difference is found between read and write operations for operand stack usage.

내장형 시스템을 위한 자바 클래스 파일에서 상수풀 항목에 대한 통계

양희재,권중장 경성대학교 공학기술연구소 2002 공학기술연구지 Vol.9 No.-

Constant pool is known to occupy the biggest part in size in a typical Java class file. It is very important for any embedded system to restrict the usage of memory since memory is one of the most vital resource of the system. Because constant pool holds the majority of Java class file in size, we are interested in knowing how to reduce its effect. In this paper we have analyzed all entries in constant pool and gathered the statistics in detail. Specifically, we have investigated a hundred of Java class files for embedded system, one from the J2ME/CLDC classes of Sun Microsystems, and others from the simpleRTJ classes of RTJ Computing. The statistics said that there are forty four constants on the average in the pool and only six percents of them are actually used to execute the bytecode instructions. Another seventy eight percents of the constant are used merely for type-checking and linking classes. It suggests the possibility of reducing memory usage by restricting runtime type-checking and dynamic class loading, which is not an extraordinary condition for embedded system. The result would be applied to build a more memory-efficient embedded Java system.

WebCheck: 효율적인 WWW 로그 분석기

양희재 慶星大學校 1998 論文集 Vol.19 No.2

WebCheck, a WWW log analyzer, was developed to understand user surfing behavior by exploring the Web sever log files efficiently. As the popularity of the Web has exploded, there is a strong desire to analyze the usage of one's own Web server. Although many log analyzers have been already developed and used in real world, little is known about the internal structure of a log analyzer and few research parers on it have been published yet. Furthermore, as the size of Web server log files increases rapidly, efficiency is becoming the most important issue for which a log analyzer must have. In this paper, we describe the design of WebCheck and point out what is important to build an efficient log analyzer. Specifically we propose some hash functions to be applied to efficiently analyze the domain names of client hosts as well as the path names the clients requested. WebCheck is implemented on a Windows 95 system and the experiment says that it outperforms than many other commercial analyzers because of its proprietary efficient hash functions.

내장형 자바 시스템을 위한 클래스 라이브러리의 특성

양희재 한국정보통신학회 2003 한국정보통신학회논문지 Vol.7 No.4

Class library is one of the most crucial element of Java runtime environment in addition to Java virtual machine. In particular, embedded Java system depends heavily on the class library due to having a low bandwidth communication link and a small amount of memory which are a common restriction of embedded system. It is therefore quite necessary to find the characteristic of the class library for embedded Java system to build an efficient Java runtime environment. In this paper we have analyzed the characteristic of the class library for embedded system. The analysis includes sorts of classes in the library, typical size of the file which contains the class, and the composition of constant pool which is a major part of the file. We also have found typical number of field and method a class contains, the sizes of stack and local variable array each method requires, and the length of bytecode in the method. The result of this study can be used to estimate the startup time for class loading and the size of memory to create an instance of class which are a mandatory information to design an efficient embedded Java virtual machine. 클래스 라이브러리는 자바가상기계와 더불어 자바실행환경을 이루는 가장 중요한 요소들 중 한가지다. 통신속도나 메모리의 용량 면에서 제한을 받게 되는 내장형 시스템의 특징상 내장형 자바 시스템은 클래스 라이브러리에 대한 의존도가 매우 높다. 따라서 효율적인 내장형 자바 시스템의 구축을 위해서는 클래스 라이브러리에 대한 면밀한 분석이 필수적이다. 본 논문에서는 내장형 자바 시스템을 위한 클래스 라이브러리의 특성에 대해 분석하였다. 즉 라이브러리를 이루는 클래스 구성과, 그 클래스들을 담은 파일의 크기 및 파일 내 주요 요소인 상수풀에 대한 분석을 하였다. 또한 클래스들이 갖고 있는 필드 및 메소드의 개수, 각 메소드들이 필요로 하는 스택과 지역변수배열의 크기, 그리고 각 메소드의 바이트코드 길이 등에 대해 조사하였다. 이 연구의 결과는 내장형 자바 시스템의 클래스 적재에 따른 지연시간 해석, 인스턴스를 만들 때 소요되는 메모리의 크기 예측 등 효율적 내장형 자바가상기계의 설계에 사용될 것이다.

가상 도메인명의 지원을 위한 URL 전달 서버

양희재 경성대학교 공학기술연구소 2002 공학기술연구지 Vol.9 No.-

A lot many WWW sites are come into the world more and more as Web is considered as the unified Internet information tool. The location of each site or resource is usually specified by a physical URL, which is often too long to remember and tends to raise difficulty to show the aim of the site intuitively by seeing it. Since any person or organization can get his/her own domain name easily, it is more desirable to use a logical URL with the domain name which can be chosen more compact to remember and meaningful to represent the ultimate intension of the site. This paper presents an implementation of a URL forwarding server which forwards a URL to another, so that a WWW site can use a logical URL instead of a physical one. The server consists of a domain mapper which uses the redirection transaction of the HTTP protocol, and a name server based on the BIND. The paper shows how the interaction between the domain mapper and the name server can make forwarding possible and describes its implmentation in detail. Experimental results shows that the overhead incurred by URL forwarding is negligible compared to the typical delay of current Internet traffic condition.

진도영등축제 프로그램 차별화 방안 : 관광객의 참여동기와 축제이미지를 중심으로

양희재,이장주 한국문화관광학회 2003 문화관광연구 Vol.5 No.1

Giant congenital melanocytic nevus of the upper extremity: Coverage with a pre-expanded pedicled thoracodorsal artery perforator flap and re-expanded transferred flap

양희재,강상윤 대한미용성형외과학회 2020 Archives of Aesthetic Plastic Surgery Vol.26 No.1

Giant congenital melanocytic nevi are rare, and it is recommended to excise due to the possibility of malignancy. Although tissue expansion for nevus removal involves multiple stages, the advantages of tissue expansion are known well. We report a case of a giant congenital melanocytic nevus of the upper extremity that extended from the elbow to the shoulder. This case was challenging due to the circumferential nature of the lesion, the lack of healthy skin, the need to ensure minimal scarring, and the desire to impact the patient’s daily life as little as possible. The use of a pre-expanded thoracodorsal artery perforator (TDAP) flap and re-expansion of the transferred flap were considered most appropriate. A pre-expanded pedicled TDAP flap can be transferred to any anatomical region with its versatility. The re-expansion of the transferred flap ensures the health of the skin and minimizes donor site scarring. Here, we achieved the optimal outcome through the combined use of a pre-expanded pedicled TDAP flap and sequential re-expansion of the transferred flap in the treatment of a giant nevus of the upper extremity.

simpleRTJ 임베디드 자바가상기계의 ROMizer 분석 연구

양희재 한국정보처리학회 2003 정보처리학회논문지. 컴퓨터 및 통신시스템 Vol.10 No.5

논리적 URL 사용을 위한 포워딩 서버의 설계 및 구현

양희재 한국정보통신학회 2003 한국정보통신학회논문지 Vol.7 No.2

웹이 인터넷 정보도구의 표준으로 자리잡게 됨에 따라 점점 더 많은 웹 사이트들이 만들어졌고, 동시에 더 많은 웹 주소 공간이 필요하게 되었다. 그러나 웹 주소를 나타내는 물리적 URL은 기억하기에 너무 길뿐 아니라 웹 사이트 내용을 직관적으로 나타내기 어려운 점이 많았다. 본 논문에서는 물리적 URL 대신 논리적 URL을 사용하여 이런 어려움을 개선할 수 있도록 하는 URL 전달 서버의 구현에 대해 고찰하였다. URL 전달서버는 HTTP 재방향 트랜잭션을 이용하는 도메인 매퍼와 BIND에 기반한 네임서버로 구성되어지며, 본 논문에서는 이들 상호간의 작용 및 동작에 대해 상세히 연구하였다. 실험 결과 URL 전달에 따른 시간은 현재의 인터넷 트래픽 조건에 비해 무시할 만한 수준인 것으로 나타났다. A lot many WWW sites are come into the world more and more as Web is considered as the unified Internet information tool. The location of each site or resource is usually specified by a physical URL, which is often too long to remember and tends to raise difficulty to show the aim of the site intuitively by seeing it. Since any person or organization can get his/her own domain name easily, it is more desirable to use a logical URL with the domain name which can be chosen more compact to remember and meaningful to represent the ultimate intention of the site. This paper presents an implementation of a URL forwarding server which forwards a URL to another, so that a WWW site can use a logical URL instead of a physical one. The server consists of a domain mapper which uses the redirection transaction of the HTTP protocol, and a name server based on the HIND. The paper shows how the interaction between the domain mapper and the name sever can make forwarding possible and describes its implementation in detail. Experimental results shows that the overhead incurred by URL forwarding is negligible compared to the typical delay of current Internet traffic condition.