MMOG의 확장성을 위한 클라우드 컴퓨팅 기반의 P2P 시스템

김진환,Kim, Jin-Hwan 한국인터넷방송통신학회 2021 한국인터넷방송통신학회 논문지 Vol.21 No.4

In this paper, we propose an approach that combines the technological advantages of P2P and cloud computing to support MMOGs that allowing a huge amount of users worldwide to share a real-time virtual environment. The proposed P2P system based on cloud computing can provide a greater level of scalability because their more resources are added to the infrastructure even when the amount of users grows rapidly. This system also relieves a lot of computational power and network traffic, the load on the servers in the cloud by exploiting the capacity of the peers. In this paper, we describe the concept and basic architecture of cloud computing-based P2P Systems for scalability of MMOGs. An efficient and effective provisioning of resources and mapping of load are mandatory to realize this architecture that scales in economical cost and quality of service to large communities of users. Simulation results show that by controlling the amount of cloud and user-provided resource, the proposed P2P system can reduce the bandwidth at the server while utilizing their enough bandwidth when the number of simultaneous users keeps growing.

분산 모바일 멀티미디어 시스템에서 재생 버퍼 수준에 기반한 동적 대역폭 할당 기법

김진환,Kim, Jin-Hwan 한국정보처리학회 2010 정보처리학회논문지B Vol.17 No.6

In this paper, we propose a scheme for dynamic allocating network bandwidth based on the playback buffer levels of the clients in a distributed mobile multimedia system. In this scheme, the amount of bandwidth allocated to serve a video request depends on the buffer level of the requesting client. If the buffer level of a client is low or high temporarily, more or less bandwidth will be allocated to serve it with an objective to make it more adaptive to the playback situation of this client. By employing the playback buffer level based bandwidth allocation policy, fair services can also be provided to the clients. In order to support high quality video playbacks, video frames must be transported to the client prior to their playback times. The main objectives in this bandwidth allocation scheme are to enhance the quality of service and performance of individual video playback such as to minimize the number of dropped video frames and at the same time to provide fair services to all the concurrent video requests. The performance of the proposed scheme is compared with that of other static bandwidth allocation scheme through extensive simulation experiments, resulting in the 4-9% lower ratio of frames dropped according to the buffer level. 분산 모바일 멀티미디어 시스템에서 클라이언트의 재생 버퍼 수준에 기반하여 통신망 대역폭을 동적으로 할당하는 기법이 본 논문에서 제시된다. 이 기법에서 비디오 요청을 서비스하기 위해 할당된 대역폭의 양은 요구한 클라이언트의 버퍼 수준에 따라 결정된다. 즉 클라이언트의 버퍼 수준이 일시적으로 낮아지거나 높아지면 재생 상황을 개선하기 위한 목적으로 더 많은 대역폭 또는 더 적은 대역폭이 할당되는 것이다. 또한 재생 버퍼 수준 기반 대역폭 할당 기법을 사용함으로써 클라이언트들에게 공평한 서비스가 제공될 수 있다. 고품질의 비디오 재생을 지원하기 위해서 비디오 프레임들은 반드시 재생 시간 전까지 클라이언트에 전송되어야 한다. 이 대역폭 할당 기법의 주목적은 전송이 중단되는 프레임의 수를 최소화하여 비디오 재생 성능과 서비스 품질을 향상시키며 동시에 진행되는 모든 비디오 요청 작업을 공평하게 서비스하는 것이다. 제시된 기법의 성능은 시뮬레이션을 통하여 다른 정적 대역폭 할당 기법과 비교 분석되었으며 프레임의 전송중단율은 버퍼수준에 따라 약 4%에서 9% 정도 감소된 것으로 나타났다.

A Distributed Method for Bottleneck Node Detection in Wireless Sensor Network

김진환,유영환,Gou, Haosong,Kim, Jin-Hwan,Yoo, Young-Hwan 한국정보처리학회 2009 정보처리학회논문지 C : 정보통신,정보보안 Vol.16 No.5

무선 센서망은 위험이 존재하는 환경에서 공공 기관이나 군사적 목적의 신뢰성 있는 모니터링을 위한 수단으로 사용되어 왔다. 위험 상황이나 위험 물질이 존재하는 환경에서 사용된다는 특성 때문에, 망의 수명이 기존 무선망에서보다 더욱 중요한 성능 요소로 간주된다. 망 전체의 수명을 결정짓는 주요 요소 중 하나는 수명을 다하는 최초의 노드가 얼마나 이른 시간에 나타나느냐 하는 것이고, 이 최초의 노드는 망에 존재하는 병목 노드일 확률이 높다. 무선망의 병목 노드를 찾아내기 위한 방법으로 MINCUT 알고리즘이 대표적이나, 이는 중앙 집중형 방법이어서 많은 수의 노드로 이루어진 무선 센서망에는 적합하지 않다. 본 논문에서는 알고리즘의 계산 복잡도를 낮추어 매우 짧은 시간 내에 병목 노드를 탐지해 내는 분산형 방법을 제안한다. 수학적 분석과 실험을 통해 제안된 알고리즘이 기존 방법보다 훨신 향상된 성능을 보임을 확인할 수 있다. Wireless sensor networks (WSNs) have been considered as a promising method for reliably monitoring both civil and military environments under hazardous or dangerous conditions. Due to the special property and difference from the traditional wireless network, the lifetime of the whole network is the most important aspect. The bottleneck nodes widely exist in WSNs and lead to decrease the lifetime of the whole network. In order to find out the bottleneck nodes, the traditional centralized bottleneck detection method MINCUT has been proposed as a solution for WSNs. However they are impractical for the networks that have a huge number of nodes. This paper first proposes a distributed algorithm called DBND (Distributed Bottleneck Node detection) that can reduce the time for location information collection, lower the algorithm complexity and find out the bottleneck nodes quickly. We also give two simple suggestions of how to solve the bottleneck problem. The simulation results and analysis show that our algorithm achieves much better performance and our solutions can relax the bottleneck problem, resulting in the prolonging of the network lifetime.

태그 경로 및 텍스트 출현 빈도를 이용한 HTML 본문 추출

김진환,김은경,Kim, Jin-Hwan,Kim, Eun-Gyung 한국정보통신학회 2021 한국정보통신학회논문지 Vol.25 No.12

In order to accurately extract the necessary text from the web page, the method of specifying the tag and style attributes where the main contents exist to the web crawler has a problem in that the logic for extracting the main contents. This method needs to be modified whenever the web page configuration is changed. In order to solve this problem, the method of extracting the text by analyzing the frequency of appearance of the text proposed in the previous study had a limitation in that the performance deviation was large depending on the collection channel of the web page. Therefore, in this paper, we proposed a method of extracting texts with high accuracy from various collection channels by analyzing not only the frequency of appearance of text but also parent tag paths of text nodes extracted from the DOM tree of web pages.

PEMFC용 캐소드를 위한 Pt/C, PtCo/C 촉매제조 및 전기화학평가

김진환,류호진,Kim, Jin-Hwan,Ryu, Ho-Jin 한국반도체디스플레이기술학회 2008 반도체디스플레이기술학회지 Vol.7 No.4

For the commercialization of polymer electrolyte membrane fuel cell (PEMFC), some serious problems such as the decrease of platinum use as catalysts and a larger overpotential of oxygen reduction reaction (ORR) at cathode must be solved. In this study, 20%Pt/C and 20%PtCo/C catalysts for the cathode of PEMFC were synthesized from the chemical reduction method and evaluated using an electrochemical measurement. The ORR activity of synthesized 20%Pt/C and 20%PtCo/C had higher than that of the 20%Pt/C on the market. The synthesized 20%PtCo/C with the cobalt concentration (Pt:Co atomic ratio) from 5 to 20% showed the highest ORR activity.

화학환원법(化學還元法)을 이용(利用)해 제조(製造)한 20% Pt/C 캐소드 촉매(觸媒)의 열처리(熱處理)에 따른 산소환원반응(酸素還元反應) 평가(評價)

김진환,강석민,류호진,Kim, Jin-Hwan,Kang, Suk-Min,Thube, Dilip.R.,Ryu, Ho-Jin 한국자원리싸이클링학회 2009 자원리싸이클링 Vol.18 No.5

The 20% Pt/C catalysts were synthesized using the chemical reduction method for polymer electrolyte fuel cell cathode and were heat-treated in the temperature range from 300 to $600^{\circ}C$. The oxygen reduction reaction of the catalysts was evaluated using the electrochemical measurement. The oxygen reduction reaction of the heat-treated Pt/C at $300^{\circ}C$ had high catalytic activity and the oxygen reduction reaction current of that was 2 times than that of non-heat treatment catalyst. It is considered that the change of the crystallinity and particle size by heat treatment could increase the catalytic activity.

Calcium Aluminate Phosphor Supported $TiO_2$ Nanoparticles

김진환,강석민,류호진,Thube, Dilip R.,Kim, Jin-Hwan,Kang, Suk-Min,Ryu, Ho-Jin 한국자원리싸이클링학회 2009 資源 리싸이클링 Vol.18 No.4

희토류 원소를 기반으로한 알루미늄산 형광체에 담지된 산화티탄은 졸겔방법 으로 제조되었다. 이렇게 제조된 산화티탄 나노입자의 재료물성을 분석하기 위해 XRD, FT-IR, DRS UV-Vis, TEM 측정을 실시하였다. 형광체에 담지된 산화티탄 입자의 소결 전후의 XRD분석결과는 600도 이상의 온도에서 아나타제에서 루틸로 상변화가 일어나지 않았다. 600도 이상의 온도에서 지속적인(장시간) 열처리 후에도 형광체에 담지된 산화티탄이 결정화도가 높은 아나타제로 존재 하는 것은 형광체 지지체와 담지된 산화티탄의 서로 다른 결정입계에 의하여 결정성장과 상변화에 필요한 치밀화가 억제되기 때문으로 판단된다. DRS측정결과 형광체에 담지된 산화티탄은 산화티탄이 없는 형광체에 비하여 보다 긴 장파로 쉬프트한 것은 밴드갭 에너지의 환원을 나타낸다. 이러한 형광체에 담지된 산화티탄의 FT-IR 스펙트럼은 피크의 위치가 더 높은 파수로 이동하였다. 이것은 산화티탄 입자와 지지체 사이의 공유결합이 관계하기 때문 이라 판단된다. TEM 이미지는 형광체 지지체에 다른 입자 크기로 담지되어 있는 산화티탄의 분산, 결정화 및 입자 형상을 나타낸다. Rare earth based calcium aluminate phosphor ($CaAl_2O_4:Eu^{2+}$, $Nd^{3+}$) supported $TiO_2$ nanoparticles are synthesized by using sol-gel method, which are further characterized using powder X-ray diffraction (XRD), fourier transform infrared (FT-IR), diffuse reflectance UV-Visible spectroscopy (DRS UV-Vis) and transmission electron microscopy (TEM). The XRD pattern of as-prepared and sintered phosphor supported $TiO_2$ does not show the tendency to change the crystal structure from anatase to rutile phase up to $600^{\circ}C$. This indicates that the phosphor support might inhibit the densification and crystallite growth by providing dissimilar boundaries. The diffuse reflectance spectral (DRS) measurements showed shift towards longer wavelength indicating reduction in the band-gap energy as compared to free $TiO_2$. The FT-IR spectra of phosphor supported $TiO_2$ nanoparticles show shift in the peak positions to lower wavelengths. This indicates that the $TiO_2$ nanoparticles are not free, but covalently bonded to the phosphor support. TEM micrographs show presence of crystalline and spherical $TiO_2$ nanoparticles (8 - 15 nm diameter) dispersed uniformly on the surface of phosphor.

빈도 분석을 이용한 HTML 텍스트 추출

김진환,김은경,Kim, Jin-Hwan,Kim, Eun-Gyung 한국정보통신학회 2021 한국정보통신학회논문지 Vol.25 No.9

Recently, text collection using a web crawler for big data analysis has been frequently performed. However, in order to collect only the necessary text from a web page that is complexly composed of numerous tags and texts, there is a cumbersome requirement to specify HTML tags and style attributes that contain the text required for big data analysis in the web crawler. In this paper, we proposed a method of extracting text using the frequency of text appearing in web pages without specifying HTML tags and style attributes. In the proposed method, the text was extracted from the DOM tree of all collected web pages, the frequency of appearance of the text was analyzed, and the main text was extracted by excluding the text with high frequency of appearance. Through this study, the superiority of the proposed method was verified.

한국 농구선수들의 SCAT 규준 개발

김진환,정지혜,정우식 ( Jin Hwan Kim,Ji Hye Chung,Woo Shik Chung ) 한국스포츠심리학회 1993 한국스포츠심리학회지 Vol.4 No.2

절토사면 현황자료를 이용한 충청도 관내 위험지구 결정

김진환,구호본,이종현,윤천주,Kim. Jin-Hwan,Koo. Ho-Bon,Rhee. Jong-Hyun,Yoon. Chun-Joo 한국방재학회 2008 한국방재학회 학술발표대회논문집 Vol.2008 No.1

KICT has been carried out inventory research on the cut slopes of national roads. Inventory research results are basic data using cut slope management system. Inventory data are classified by general status, cut slope characteristics and inspector opinion. Inventory data are utilized to figure out dangerous slopes and decide survey ranking of detailed safety diagnostication. This paper drew the distribution area of dangerous cut slopes using inventory data in Chungcheongdo, and verified efficiency on distribution area of dangerous cut slopes by comparing occurrence frequency of real collapsed cut slopes.