• 설비공학논문집
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• 제15권7호
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• pp.551-556
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• 2003

The present study concerns an experiment on the heating characteristics of a system air-conditioner (A/C) using PWM method or inverter method at low temperature con-ditions. The compressors used are digital scroll type and BLDC inverter type. Under the low outside temperature condition, -5$^{\circ}C$, -1$0^{\circ}C$, -15$^{\circ}C$, heating capacities and COPs are mea-sured by the psychometric calorimeter using air enthalpy method. Also, outlet air temperatures at heating operation mode are measured at -5$^{\circ}C$, -1$0^{\circ}C$ and -15$^{\circ}C$. Experimental results show that COPs of the system A/C using a PWM method are more effective than those of the inverter method at heating operation mode. Although the heater is on, COPs of PWM method are similar to those of BLDC inverter method. Moreover, the heating capacities of PWM method at -5$^{\circ}C$, -1$0^{\circ}C$ and -15$^{\circ}C$ are larger about 10~20% and outlet air tempe-rature at -15$^{\circ}C$ is larger about 10%, compared to the inverter method.

• 제어로봇시스템학회논문지
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• 제16권2호
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• pp.188-193
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• 2010

With GPS being the primary navigation system, Loran use is in steep decline. However, according to the final report of vulnerability assessment of the transportation infrastructure relying on the global positioning system prepared by the John A. Volpe National Transportation Systems Center, there are current attempts to enhance and re-popularize Loran as a GPS backup system through the characteristic of the ground based low frequency navigation system. To advance the Loran system such as Loran-C modernization and eLoran development, research is definitely needed in the field of Loran-C receiver signal processing as well as Loran-C signal design and the technology of a receiver. We have developed a set of Matlab tools, which implement a software Loran-C receiver that performs the receiver's position determination through the following procedure. The procedure consists of receiving the Loran-C signal, cycle selection, calculation of the TDOA and range, and receiver's position determination through the Least Square Method. We experiences the effect of an incorrect cycle selection and various error factors (ECD, ASF, sky wave, CRI, etc.) from the result of the Loran-C signal processing. It is apparent that researches which focus on the elimination and mitigation of various error factors need to be investigated on a software Loran-C receiver. These aspects will be explored in further work through the method such as PLL and Kalman filtering.

• 대한산업공학회지
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• 제39권1호
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• pp.20-29
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• 2013

Medical errors such as adverse drug event, improper transfusion, wrong-site surgery, mistaken patient identity and so on commonly occur at health care practice. Information technology, like Drug Utilization Review(DUR) system which reviews, analyzes, and interprets medication data when prescribing, can play a key role in reducing such medical errors and improving patient safety. Korean Government has guided all hospitals to implement concurrent DUR(cDUR) system, which is the first case worldwide in that all healthcare providers have to use cDUR system when prescribing. This paper introduced a case study that a tertiary hospital has integrated the cDUR system into its comprehensive Hospital Information System(HIS) and analyzed the whole prescription data during a week right after adoption of cDUR system. Considering technical strength and weakness, the cDUR system was integrated into the HIS, using Broker Servers for minimizing doctors' anxiety. As the quantitative analysis of the whole prescription data, DUR conflict events, which mainly included duplicate medications and contra-indicated drug interactions for outpatients, were 2.77%. Although only 0.7% is for the contra-indicated drug interactions, it will be greatly devoted to achieve the purpose of DUR such as improving patient safety.

• 지능정보연구
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• 제4권1호
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• pp.115-131
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• 1998

Customer service process is one of the most important processes in today's competitive business environment. Among the various activities of customer service process, equipment malfunction diagnosis activity should be performed fast and accurately. When a customer calls the service center and reports the observed symptoms, he/she describes them in layman's terms. Therefore, the customer-reported symptoms have not been considered helpful information for service representatives. However, in order to perform diagnosis activity fast and accurately, we need to make use of the customer-reported symptoms actively. In this research, we developed three systems called R-EMD (Rule-based Equipment Malfunction Diagnostic system), C-EMD (Case-based Equipment Malfunction Diagnostic system) and R&C-EMD (Rule & Case-based Equipment Malfunction Diagnostic system), each of which diagnoses equipment malfunctions using the customer-reported symptoms. R&C-EMD is a hybrid system that utilizes both rule-based and case-based technologies. The diagnosis rules used in R&C-EMD and R-EMD were not acquired from service manuals or interviews with service representatives. Rater, we extracted them directly from the past diagnosis cases based on symptoms' frequencies. By this way, we were able to overcome the knowledge acquisition bottleneck. Using the real 100 malfunction diagnosis cases, we evaluated the performances of R&C-EMC, R-EMD and C-EMD in terms of speed and accuracy. In diagnosis time, R&C-EMD took longer than R-EMD and shorter than C-EMD. However, R&C-EMC was the best in accuracy.

• 한국자동차공학회논문집
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• 제9권6호
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• pp.103-111
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• 2001

During cold-start period, the reduction of exhaust emissions is a challenging task. To decrease harmful gaseous substances such as HC, it is necessary to realize a fast catalyst warm-up. In this study, the performance of dual pipe exhaust system have been carried out through different test mode. From measurement of gas temperature and HC concentration, the following conclusions were derived ; 1) Compared with single pipe, dual pipe exhaust system remarkably increase temperature of exhaust gas going through M.C.C(Main Catalytic Converter). 2) W.C.C.(Warm-up Catalytic Converter) also decreases HC emission. To reduce HC emission, it is helpful to use W.C.C. as well as dual pipe exhaust system. 3) Using finite element method, it is shown that inner parts have much higher distribution of temperature than outer parts.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1536-1541
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• 2003

In order to investigate the cooling and heating characteristics of a variable-capacity system A/C using a digital scroll compressor, the cooling and heating capacities and EER are measured by the psychrometric calorimeter. The capacity of the system is controlled by the digital scroll compressor, which is operated by controling PWM valve and the loading vs. unloading time. When the system A/C is operated under the cooling and heating standard conditions, EER is nearly uniform but cooling capacity and heating capacity increase at minimum, rated and maximum modes. When the auxiliary heater is on, at the cold region, the system A/C produces the excellent heating capacity.

• 한국표면공학회지
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• 제36권2호
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• pp.141-147
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• 2003

Silicon carbide thin film was deposited in APCVD and LPCVD system with 1,3-DSB precursor 1,3-DSB is the single precursor to deposit SiC on Si at low temperature. SiC film was deposited at $850^{\circ}C$ lower than ordinary temperature ($1000~1200^{\circ}C$) in CVD process. SiC thin film glowed to high oriented (111) plane in APCVD system. In LPCVD system, SiC film groved to preferred (220) plane at same temperature. This discrepancy between preferred planes can be described by the difference of deposition mechanism. Amorphous phase and crystal defect were observed in APCVD system with the main growth mechanism of mass transport limited region. But in LPCVD system, we got the SIC film of uniform, faceted structure and high quality.

• 한국결정성장학회지
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• 제9권1호
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• pp.14-19
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• 1999

Hexamethyldisilane$(Si_{2}(CH_{3})_{6})$의 single precursor를 사용하여 화학기상증착법으로 $1100^{\circ}C$에서 Si 기판의에 $\beta$-SiC 막을 증착시켰다. 증착과정 중 hexamethyldisilane/$H_{2}$ gas system에 HCI gas를 도입하여 mask 재료에 의해 부분적으로 덮여져 있는 Si 기판에서 SiC 증착의 선택성을 조사하였다. Si 기판과 mask 재료에서 SiC 증착의 선택성을 증진시키기 위해 출발물질과 HCI gas의 공급 방법을 변화시켰다. 결국, HCI gas를 도입함으로서 SiC 증착의 선택성은 증진되었고 펄스 형태로의 gas 공급 방법은 선택성을 향상시키는데 효율적이었다.

• 한국분말재료학회지
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• 제6권1호
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• pp.18-35
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• 1999

Phase equilibria in the system Si3N4-TiC-TiCxN1-x-C-N were determined by thermodynamic calculations (CALPHAD-method). The reaction peaction paths for Si3N4-TiC and SiC-TiC composites in the Ti-Si-C-n system were simulated at I bar N2-pressure and varying terpreatures. At a temperature of 1923 K two tie-triangles (TiC0.34N0.66+SiC+C and TiC0.13N0.87+SiC+Si3N4) and two 2-phase fieds (TiCxN1-x+SiC; 0.13

• Journal of Information Technology Applications and Management
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• 제16권4호
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• pp.205-222
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• 2009

Considering time-lag in the performance evaluation of information system (IS) investment is important because its effect reveals after certain period of time passed. Particularly it is more in the systems of e-government informatization projects which the amount of investment and the scale of business are huge. Many methods to solve this issue have been proposed such as system dynamics methods, simulations, structural equations etc. However, it is still difficult and unsolved problem because collecting practical data for time-lag analysis is very hard. In this paper, we analyze IS time-lag effect through factor analysis using the accumulated practical operational DB data. For the performance evaluation of the G4C system, the representative e-government web portal, we selected eleven factors reflecting time passing in G4C DB data. With these factors this paper conduct time-lag analysis in four view points. First, we conducted 'Stabilizing of G4C system' and got a result that IS is needed about three years for the stabilization. Second, we conducted 'Utilization of G4C system' and got a result that the utilization reaches appropriate level after in three years later after the introduction of G4C system. Third, we conducted 'Cost reduction effect' and got a result that cost reduction is stable in the third year after the introduction of G4C system. Lastly, we conducted 'System maturity effect' and got a result that the system reaches to the quality level that users expect after third to fourth years. According to the results of this research, we found that performance of IS improv continuously not immediately, and it needs three or four years of time-lag.