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동계 난방시 구조체 축열 공조시스템의 축·방열 특성에 관한 연구
임지훈,이시환,차영호,정광섭,이정재 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.1
It is the plan that storage gets energy done by in structure with what thermal storage of structure changes only supply air duct among the existing HVAC system, and a basic principle coordinates the damper that it was installed makeup air in supply air duct like former HVAC system to an inside at supply and a night by day, and do makeup air supply with in ceiling space of thermal storage of structure HVAC system. This thermal storage of structure HVAC system uses the existing utility system, and energy saving can get structure of building done with energy storage, before air conditioning and peak load cut getting day heat load done.
류지구,최혁환,차영호,김정헌,조경연 釜慶大學校 1997 釜慶大學校 論文集 Vol.2 No.2
The wide spread of multimedia sysrem deands a large viewing display device which can inform a message to many peoples in open area. This paper is about the design and simulating of a large viewing digital multi-wision control ASIC(Application Specific Integrated Circuit). In this paper. the digital multi-vision ASIC has one channel of imput cideo signal wihich is compliance with CCIR-656 specification and four channels of output video signal which are compliance with CCIR-601 specificarion. It has 2 operating mode. The one is the pass-thro;ugh mode. input vido signal goes to output video signal without any change, and the another one is the expension mode, input video signal is expended by from 2 to 16 times into output video signal. In expension mode. awindow could be programmed and only the input video signal in the window is expended. The 0.6 micron CMOS sEA OF Gate is used to design the ASIC in amount of about 23,000 gates, and it is simulated at 48MHz.
서울의 Penicillinase Producing Neisseria Gonorrhoeae 발생빈도(1996)
김재홍,황동규,전재홍,김윤석,김중환,김용준,이창균,임동진,김현수,조창근,김경문,박상훈,전우형,김희성,이호정,차명수,김갑형,김형석,김석우,황지환,박병순,권오상,이민수,송기훈,성소영,이인섭,부태성 대한화학요법학회 1999 대한화학요법학회지 Vol.17 No.2
Background : In recent years, gonorrhea has been panedemic and remains one of the most commom STDs in the world, especially in developing countries. Objective & Methods: For the detection of a more effective therapeutic regimen and assessing the prevalence of PPNG, we have been trying to study the patients who have visited the VD Clinic of Choong-Ku Public Health Center in Seoul since 1980 by means of the chromogenic cephalosporin method. Results: In 1996, 139 strains of N. gonorrhoeae were isolated, among which 53(39.0%) were PPNG. Conclusion: Our results suggests that after a peak of 74.3% in 1993, the prevalence of PPNG in Seoul is gradually declining.
On Multipurpose Replacement Policies for the General Failure Model
Cha, Ji-Hwan The Korean Data and Information Science Society 2003 한국데이터정보과학회지 Vol.14 No.2
In this paper, various replacement policies for the general failure model are considered. There are two types of failure in the general failure model. One is Type I failure (minor failure) which can be removed by a minimal repair and the other is Type II failure (catastrophic failure) which can be removed only by a complete repair. In this model, when the unit fails at its age t, Type I failure occurs with probability 1-p(t) and Type II failure occurs with probability p(t), $0{\leq}p(t){\leq}1$. Under the model, optimal replacement policies for the long-run average cost rate and the limiting efficiency are considered. Also taking the cost and the efficiency into consideration at the same time, the properties of the optimal policies under the Cost-Priority-Criterion and the Efficiency-Priority-Criterion are obtained.
On a class of multivariate counting processes
Cha, Ji Hwan,Giorgio, Massimiliano Cambridge University Press 2016 Advances in applied probability Vol.48 No.2
<B>Abstract</B><P> In this paper we define and study a new class of multivariate counting processes, named `multivariate generalized Pólya process'. Initially, we define and study the bivariate generalized Pólya process and briefly discuss its reliability application. In order to derive the main properties of the process, we suggest some key properties and an important characterization of the process. Due to these properties and the characterization, the main properties of the bivariate generalized Pólya process are obtained efficiently. The marginal processes of the multivariate generalized Pólya process are shown to be the univariate generalized Pólya processes studied in Cha (2014). Given the history of a marginal process, the conditional property of the other process is also discussed. The bivariate generalized Pólya process is extended to the multivariate case. We define a new dependence concept for multivariate point processes and, based on it, we analyze the dependence structure of the multivariate generalized Pólya process. </P>
Maximizing Mean Time to the Catastrophic Failure through Burn-In
Cha, Ji-Hwan Korean Data and Information Science Society 2003 한국데이터정보과학회지 Vol.14 No.4
In this paper, the problem of determining optimal burn-in time is considered under a general failure model. There are two types of failure in the general failure model. One is Type I failure (minor failure) which can be removed by a minimal repair and the other is Type II failure (catastrophic failure) which can be removed only by a complete repair. In this model, when the unit fails at its age t, Type I failure occurs with probability 1 - p(t) and Type II failure occurs with probability p(t), $0{\leq}p(t)\leq1$. Under the model, the properties of optimal burn-in time maximizing mean time to the catastrophic failure during field operation are obtained. The obtained results are also applied to some illustrative examples.
Optimal mission abort policy for partially repairable heterogeneous systems
Cha, Ji Hwan,Finkelstein, Maxim,Levitin, Gregory Elsevier 2018 european journal of operational research - Vol.271 No.3
<P><B>Abstract</B></P> <P>To enhance survivability of many real-world critical systems (e.g., aircrafts, human space flight systems and dangerous technological processes), mission abort procedures are often utilized in practice. In such cases, in order to improve survivability, a rescue or recovery procedure is initiated. In this paper, we first develop a methodology for obtaining the mission success probability (MSP) and the system survival probability (SSP) for heterogeneous systems with major and minor failures. A major failure is non-repairable and results in a failure of a mission, whereas a minor failure is minimally repaired. We consider a policy where a mission is aborted and a rescue procedure is activated if the <I>m</I>th minimal repair occurs before time <I>ξ</I> since the start of a mission. We demonstrate the tradeoff between the SSP and the MSP that should be balanced by the proper choice of the decision variables <I>m</I> and <I>ξ</I>. A detailed illustrative example is presented.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mission abort for heterogeneous systems is considered based on updated information. </LI> <LI> A random shock model is used to represent the random environment. </LI> <LI> Mission success probability and system survivability are suggested. </LI> <LI> Tradeoff between mission success probability and system survivability is demonstrated. </LI> <LI> Optimal mission abort policy is analyzed based on the model. </LI> </UL> </P>
Optimal Long-Run Imperfect Maintenance With Asymptotic Virtual Age
Ji Hwan Cha,Finkelstein, Maxim IEEE 2016 IEEE transactions on reliability Vol.65 No.1
<P>We consider imperfect, periodic preventive maintenance of items with increasing failure rates, and minimal repairs in-between. The imperfect maintenance is performed in accordance with a Kijima II virtual age model. The obtained deterministic asymptotic value of virtual age defines the starting age of an item at the beginning of each cycle in the formulated and analyzed long-run optimization problem. A similar approach is used for the corresponding age-based preventive maintenance, where the starting age of the renewal-type cycle is already a random variable. Some meaningful examples are considered.</P>