• The KSFM Journal of Fluid Machinery
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• v.18 no.4
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• pp.30-35
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• 2015

This study analyzed the variations in the performance and operation of a 200 kW class micro gas turbine according to performance degradation of compressor and turbine. An in-house code, developed by the present authors and presented in the first part of these series of papers, were used for the analysis. The degradation of compressor and turbine were simulated by modifications in the their performance maps: mass flow rate, pressure ratio and efficiency were decreased from the reference values. Firstly, the variations in the operating conditions (air flow rate, pressure ratio) were predicted for the full load condition. Then, the same analysis were performed for a wide partial load operating range. The change in engine's performance (power output and efficiency) due to the component degradation was predicted. In addition, the change in the compressor surge margin, which is an important indicator for safe engine operation, was evaluated.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.6
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• pp.485-490
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• 2016

This study focused on developing an electro-discharge truing method for the ELID grinding process using a metal-bonded grinding wheel. The truing process in grinding plays important roles in enhancing the quality of the ground surface. In this study, a reference current in the electro-discharge truing process was confirmed to be a viable solution for efficient truing through performance experiments. Current and voltage variation experiments were carried out and the variation output data were collected with a monitoring program to understand the electrodischarge phenomenon that occurs between metal-bonded grinding wheels and copper electrodes. The experimental results showed that as the reference current decreased, the average electro-discharge energy decreased. Therefore, the reference current can be used as an indicator to estimate the size of the gap between the truer and grinding wheel.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2003.10a
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• pp.335-338
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• 2003

최근의 통계에 따르면 국내의 인터넷 인용율은 2000년도에 44.7%, 2001년도에 56.6%, 2002년도에는 55.2%로 아이슬랜드(60.8%), 스웨덴(57.3%)에 이어 세계에서 세번째로 높은 것으로 나타났다. 또한 인구 100명당 PC보급율 또한 미국(62.5대), 덴마크(57.68대)에 이어 한국(55.58대)이 세계3위를 기록해 명실상부한 정보화 선진국임이 입증되고 있다. 따라서 잘 발달된 infrastructure을 이용하는 기술개발은 초고속정보이용을 가능케하고 있다. 근래에 들어 인터넷을 기반으로 기본적인 활용인 문자, 음성 및 영상 전송 등의 데이터 전송뿐만 아니라, 근래에는 인터넷을 통한 remote control 및 monitoring system에 대한 연구가 활발히 진행되고 있다. 기존의 증류공정은 DCS(Dispersion Control System)로써 공정상태(온도, 압력, 유량, 레벨, 순도등)를 Control room까지 선로를 통하여 신호전달이 이루어지고 있다. 따라서, 제한된 지역에서만 I/O(Input/output)이 이루어지고 있다. 이로 인해 안전감시시스템의 효율성이 떨어지고 있는 게 사실이다. 본 연구에서는 PC기반의 프로그램을 바탕으로 인터넷을 이용한 remote control 및 monitoring system을 개발함으로써 close Network에서 Open Network으로 발전시켰다. 여기서 local plant의 안전시스템 알고리즘은 그대로 Server system에 도입하였으며 사용자의 실정에 맞게 손쉽게 설정을 할 수 있도록 확장성을 높였다. 이는 PC기반의 시스템을 구축함으로써 가능하게 된 것이다. 또한, 웹 상에서의 무차별적 접근으로부터 보호하기 위하여 감시 대상의 성질에 따라 프로그램상에서 차별적 접근형식을 택할 수 있으며, control room의 indicator들과 controller를 프로그램상에 그대로 이식시킴으로써 감시자에게 충분한 정보제공 및 원격제어가 가능하도록 하고있다.

• Smart Structures and Systems
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• v.10 no.4_5
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• pp.353-373
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• 2012

The instrumented Canton Tower is a 610 m high-rise structure, which has been considered as a benchmark problem for structural health monitoring (SHM) research. In this paper, an improved automatic modal identification method is presented based on a natural excitation technique in conjunction with the eigensystem realization algorithm (NExT/ERA). In the proposed modal identification method, damping ratio, consistent mode indicator from observability matrices (CMI_O) and modal amplitude coherence (MAC) are used as criteria to distinguish the physically true modes from spurious modes. Enhanced frequency domain decomposition (EFDD), the data-driven stochastic subspace identification method (SSI-DATA) and the proposed method are respectively applied to extract the modal parameters of the Canton Tower under different environmental conditions. Results of modal parameter identification based on output-only measurements are presented and discussed. User-selected parameters used in those methods are suggested and discussed. Furthermore, the effect of environmental conditions on the dynamic characteristics of Canton tower is investigated.

• KIEAE Journal
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• v.13 no.6
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• pp.83-91
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• 2013

Cool roofs are currently being emerged as one of important mechanism to save energy in relation to the building. It is specifically proposed that the changing trends of rooftop surface temperature in the flat roof building model could be used effectively as an indicator to reduced cooling load reduced by cool roof since it can present stable temperature record, that is not influenced according to the nearby physical as well as human variables. The temperature of cool roof in summer was lower around $20^{\circ}C$, compared to the general roofs. Such a seasonal or daily comparative study for rooftop temperature in the building model will highlight that the cool roof efficiency could be calculated in much area-wide context according to rooftop color distribution in urban residential area. It is anticipated that this research output could be used as a valuable reference in identifying energy saving by cool roof since an objective monitoring has been proposed based on the rooftop temperature in the building model, fully quantitative performance of thermal infrared image.

• ETRI Journal
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• v.38 no.2
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• pp.280-290
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• 2016

To implement high-order multiuser multiple input and multiple output (MU-MIMO) for massive MIMO systems, there must be a feedback scheme that can warrant its performance with a limited signaling overhead. The interference-to-noise ratio can be a basis for a novel form of Codebook (CB)-based MU-MIMO feedback scheme. The objective of this paper is to verify such a scheme's performance under a practical system configuration with a 3D channel model in various radio environments. We evaluate the performance of various CB-based feedback schemes with different types of overhead reduction approaches, providing an experimental ground with which to optimize a CB-based MU-MIMO feedback scheme while identifying the design constraints for a massive MIMO system.

• Journal of Agricultural Extension & Community Development
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• v.4 no.1
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• pp.201-209
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• 1997

The objective of this study were 1) to review concepts of user information satisfaction (UIS), 2) to analyze tools for measuring user information satisfaction, 3) to identify factors affecting information satisfaction. The study was carried out by the analysis of literatures related to information system. The construct of UIS has been operationalized in many different ways. Several studies employed single-item rating scales; such scales have been criticized as unreliable. Single-item scales also provide little information as to what the user finds dissatisfying(satisfying) and are thus of limited utility outside a research setting. Multiple-item UIS measures have become increasingly common. Generally, they are of two types. The first focuses on the information system product. With such diverse names as "system acceptance", "output quality", and "appreciation", these scales focus on the content of the information system and the manner in which the information is presented. The second type of multiple-item scale includes the organizational support for developing and maintaining the system as well as the system product itself. This type of instrument contains items concerned with training, documentation, development procedures, systems maintenance, etc., as well as items related to system content. Thus it provides an indicator of the overall quality of information services provided by an information service function. Generally, UIS measures have not been carefully validated. Recently, however, several rigorous attempts have been made to develop valid and reliable UIS measure.

• KSBB Journal
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• v.5 no.3
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• pp.307-313
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• 1990

A microcomputer-aided fermentation system was constructed for high density fed-batch culture using dissolved oxygen(DO) as a substrate feeding indicator. DO signal was processed prior to aquisition to computer. Agitation speed and oxygen flow rate was changed stepwisely to maintain DO value at a constant level. Agitation speed was controlled by the output signal of D/A converter. Oxygen flow rate was controlled by a flow rate control valve connected to a stepping motor. Substrate was fed with a feeding pump operated by the abrupt increase of DO signal. Methylobacillus sp. SK1 was cultivated to test the system and 16.53g/l of cell density was obtained after 10 hr.

• Journal of Environmental Impact Assessment
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• v.20 no.2
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• pp.175-185
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• 2011

It is usual for energy consumption in accordance with facing and sitting direction of tower-type apartments to be calculated by the official statistics or computer simulation. Previous studies for energy consumption appear to be very limited due to the dependence on flat type of apartment. Acknowledging these constraints, an empirical study for a tower type apartment was conducted to demonstrate how a on-site indoor temperature measurement in spring can be used to assist in estimating the total energy consumption in terms of facing and sitting orientation specific settings. The results indicate that maximum temperature difference in spring was identified as $1.16^{\circ}C$ between south and eastern direction. It is known that raising $1^{\circ}C$ indoor temperature require 7% more energy consumption than normal. The $1.16^{\circ}C$ difference means that sitting direction of tower type apartment is a crucial explanatory variable as unit of analysis for energy consumption. It was demonstrated that the indoor temperature could be used effectively as an indicator to estimate energy consumption among various sitting direction of tower type apartments. It is anticipated that this research output could be used as a valuable reference to support more scientific and objective decision-making for facing and sitting orientation of tower type apartments.

• Health Policy and Management
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• v.9 no.4
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• pp.87-119
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• 1999

The main purpose of this research is to measure and analyze how productive the health centers are and how much inputs(or outputs) in the inefficient health centers should be decreased(or increased) for efficiency. The evaluation of the performance of health centers gives a strong incentive to improve resource allocation in regional health planning. It has been, however, implemented very rarely until now. In this regard, this paper measures the performance of the health centers with a single indicator for multiple-outputs in terms of productivity(technical efficiency), based on Data Envelopment method. The 20 Kyungnam health centers which provide clinic services and specific primary health care services were analyzed. The results show that 50.0% of 20 health centers were productive with respective to overall technical efficiency, 65.0% were productive for pure technical efficiency, and 50.0% for scale efficiency. The inefficient group includes Geoje, Mahsan, Miryang, Sahchun, Tongyoung, Gosung, Nahmhae, Euryang, Hahmahn, Hahbchun health centers. The worst case was identified as Tongyoung health center which represented a 47.5% efficiency, compared with productive health centers. The empirical results for input-output analysis indicates that the low-productive health centers have excessive manpower in administration department, producing low outputs in clinical services and vaccination program. These findings imply that a systemic evaluation of the performance of the Korean health centers and the subsequent structural reform are strongly required.