• 한국유체기계학회 논문집
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• 제19권4호
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• pp.5-12
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• 2016

In this study, a parametric study on a cavity as casing treatment of a centrifugal compressor has been conducted using three-dimensional Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model. Two kinds of cavity were applied at choke and surge conditions, respectively, in this work. Inlet and outlet port widths, angle of outlet port, and length of cavity were chosen as the geometric parameters and investigated to find their effects on the aerodynamic performances such as adiabatic efficiency at design mass flow rate and stall margin of the centrifugal compressor. It was found that the aerodynamic performances of the centrifugal compressor were affected considerably by the four geometric parameters. The adiabatic efficiency was hardly changed by the geometric parameters, excepts for the angle of outlet port. With an increase in the angle of outlet port, the adiabatic efficiency and the stall margin decreased. The stall margin was more sensitive to the outlet port width than to the other geometric parameters. And, with a decrease in the outlet port width, the stall margin increased by 2% compared to that of the reference.

• 시스템엔지니어링학술지
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• 제17권2호
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• pp.49-60
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• 2021

The Core Protection Calculator System (CPCS) is vital for plant safety as it ensures the required Specified Acceptance Fuel Design Limit (SAFDL) are not exceeded. The CPCS generates trip signals when Departure from Nucleate Boiling Ratio (DNBR) and Local Power Density (LPD) exceeds their predetermined setpoints. These setpoints are established based on the operating margin from the analysis that produces the SAFDL values. The goal of this research is to create a simplified CPCS that optimizes operating margin for I-SMRs. Because the I-SMR is compact in design, instrumentation placement is a challenge, as it is with Ex-core detectors and RCP instrumentation. The proposed CPCS addresses the issue of power flux measurement with In-Core Instrumentation (ICI), while flow measurement is handled with differential pressure transmitters between Steam Generators (SG). Simplification of CPCS is based on a Look-Up-Table (LUT) for determining the CEA groups' position. However, simplification brings approximations that result in a loss of operational margin, which necessitates compensation. Appropriate compensation is performed based on the result of analysis. FPGAs (Field Programmable Gate Arrays) are presented as a way to compensate for the inadequacies of current systems by providing faster execution speeds and a lower Common Cause Failure rate (CCF).

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2006년도 ISMP 2006
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• pp.293-316
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• 2006

[ $\blacksquare$ ] I/O Signal $\square$ We see adequate margin for the RC B design $\square$ Minimum ODW value is 328ps using Ac to DC measurement for the read case. $\square$ Minimum ODW value is 350ps using AC to DC mesurement method for the write case. $\blacksquare$ CLK Signal $\square$ The slew-rate decreases when the Cterm value increases $\square$ Lower slew-rate could effect delay and jitter. $\square$ There are some ldge issues during transitions with lower Cterm and without Cterm. $\square$ Our recommendation for the Cterm value range is between 1.5pF to 2.4pF. $\blacksquare$ ADD/CMD/Ctrl Signal $\square$ High output slew-rate at low VDD causes ring back that reduces voltage margin because of x-talk. $\square$ 30ohm Rterm for the CTRL signal shows a better signal integrity result compared to 36ohm.

• 한국병원경영학회지
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• 제9권1호
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• pp.22-45
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• 2004

This study was performed to identify factors affecting the profitability of private hospitals in Korea different and to make informations that could be very helpful to hospitals in improving profitability. Data used in this study were collected from 112 hospitals with complete general data of present conditions as well as financial statements(balance sheets, income statements). They were chosen from hospitals that passed the standardization audit undertaken by the Korean Hospital Association from 1998 to 2001 for the purpose of accrediting training hospitals. The dependent variables were used operating margin to total assets and operating margin to gross revenues as proxy indicators for profitability. The independent variables were ownership type, location, bed size, period of establishment, debt to total assets, current ratio, fixed ratio, total asset turnover, average length of stay, bed occupancy rate, admission ratio of outpatients, personnel costs per adjusted inpatient, and fiscal years. The factors had significantly positive effect on operating margin to total assets and operating margin to gross revenues were bed size, total asset turnover. And the factors had significantly negative effect on operating margin to total assets and operating margin to gross revenues were period of establishment, debt to total assets, average length of stay, personnel costs per adjusted inpatient. The adjusted $R^2$ of multiple regression equation was 25.2%, 21.4% respectively. It is very important for private hospitals to improve profitability by raising total asset turnover, and reducing debt to total assets, average length of stay, and personnel costs per adjusted inpatient using the rational and efficient business strategy.

• Korean Journal of Radiology
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• 제19권6호
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• pp.1053-1065
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• 2018

Objective: To evaluate the clinical impact of using registration software for ablative margin assessment on pre-radiofrequency ablation (RFA) magnetic resonance imaging (MRI) and post-RFA computed tomography (CT) compared with the conventional side-by-side MR-CT visual comparison. Materials and Methods: In this Institutional Review Board-approved prospective study, 68 patients with 88 hepatocellulcar carcinomas (HCCs) who had undergone pre-RFA MRI were enrolled. Informed consent was obtained from all patients. Pre-RFA MRI and post-RFA CT images were analyzed to evaluate the presence of a sufficient safety margin (${\geq}3mm$) in two separate sessions using either side-by-side visual comparison or non-rigid registration software. Patients with an insufficient ablative margin on either one or both methods underwent additional treatment depending on the technical feasibility and patient's condition. Then, ablative margins were re-assessed using both methods. Local tumor progression (LTP) rates were compared between the sufficient and insufficient margin groups in each method. Results: The two methods showed 14.8% (13/88) discordance in estimating sufficient ablative margins. On registration software-assisted inspection, patients with insufficient ablative margins showed a significantly higher 5-year LTP rate than those with sufficient ablative margins (66.7% vs. 27.0%, p = 0.004). However, classification by visual inspection alone did not reveal a significant difference in 5-year LTP between the two groups (28.6% vs. 30.5%, p = 0.79). Conclusion: Registration software provided better ablative margin assessment than did visual inspection in patients with HCCs who had undergone pre-RFA MRI and post-RFA CT for prediction of LTP after RFA and may provide more precise risk stratification of those who are treated with RFA.

• Journal of Communications and Networks
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• 제9권2호
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• pp.112-117
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• 2007

In this paper, we focus on the total transmission power minimization problem for downlink beamforming multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems while ensuring each user's QoS requirement. Although the linear integer programming (LIP) solution we formulate provides the performance upper bound of the margin adaptive (MA) optimization problem, it is hard to be implemented in practice due to its high computational complexity. By regarding each user's equivalent channel gain as approximate independent values and using iterative descent method, we present a heuristic MA resource allocation algorithm. Simulation results show that the proposed algorithm efficiently converges to the local optimum, which is very close to the performance of the optimal LIP solution. Compared with existing space division multiple access (SDMA) OFDM systems with or without adaptive resource allocation, the proposed algorithm achieves significant performance improvement by exploiting the frequency diversity and multi-user diversity in downlink multiple-input single-output (MISO) OFDM systems.

• 대한골관절종양학회지
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• 제16권2호
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• pp.62-68
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• 2010

목적: 사지에 발생한 지방육종의 치료 결과와 임상적 예후 인자에 대해 알아보고자 하였다. 대상 및 방법: 1994년 4월부터 2005년 12월까지 본원에서 사지에서 발생한 원발성 지방육종으로 진단받고 치료받은 44명 중 5년 이상 추시 관찰이 가능하였던 40명을 대상으로 후향적 분석을 시행하였다. 이 중 13명은 수술 후 방사선 치료를 함께 시행 받았다. 국소 재발과 원격 전이 및 5년 무병생존율을 조사하였고, 나이, 성별, 종양의 크기, 비계획적 절제술 여부, 조직학적 유형, 수술적 절제연, 방사선 치료 병행 유무 등이 5년 무병생존율에 미치는 영향을 분석하였다. 결과: 국소 재발 3예, 원격 전이는 4예가 있었고, 5년 무병생존율은 85.0%였다. 조직학적 유형은 점액성 지방육종이 26예, 고분화 지방육종이 8예, 원형 세포형 지방육종이 4예였으며, 비분화 지방육종, 다형성 지방육종이 각각 한 예였다. 고분화 지방육종, 점액성 지방육종, 원형 세포형 지방육종 세 군의 5년 무병 생존율은 각각 100.0%, 84.6%, 75.0%였다(p=0.419). 수술 절제연에서 종양 세포가 관찰되지 않았던 환자(n=32)에서는 5년 무병 생존율이 90.6%였고, 절제연에서 종양 세포가 관찰된 환자(n=8)에서는 62.5%였다(p=0.003). 결론: 수술적 절제연에서 종양 세포의 관찰 여부가 5년 무병생존율에 유의한 인자였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.18-21
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• 2002

As the mask design rules get smaller, the probability of the process failure becomes higher due to the narrow overlay margin between the contact and metal interconnect layers. To obtain the minimum process margin, a tabbing and cutting method is applied with the rule based optical proximity correction to the metal layer, so that the protection to bridge problems caused by the insufficient space margin between the metal layers can be accomplished. The side-lobe phenomenon from the attenuated phase shift mask with the tight design nile is analyzed through the aerial image simulation for test patterns with variation of the process parameters such as numerical aperture, transmission rate, and partial coherence. The corrected patterns are finally generated by the rules extracted from the side-lobe simulation.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(2)
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• pp.209-212
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• 2002

As the mask design rules get smaller, the probability of the process failure becomes higher doc to the narrow overlay margin between the contact and metal interconnect layers. To obtain the minimum process margin, a tabbing and cutting method Is applied with the rule based optical\ulcorner proximity correction to the metal layer, so that the protection to bridge problems caused by the insufficient space margin between the metal layers can be accomplished. The side-lobe phenomenon from the attenuated phase shift mask with the tight design rule is analyzed through the aerial image simulation for test patterns with variation of the process parameters such as numerical aperture, transmission rate, and partial coherence. The corrected patterns are finally generated by the rules extracted from the side-lobe simulation.

• 제어로봇시스템학회논문지
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• 제19권11호
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• pp.991-997
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• 2013

In this paper, we propose a CFWC (CCD and fuzzy PID based width control) scheme to obtain the desired delivery width margin of a vertical rolling mill in hot strip process. A WMS(width measurement system) is composed of two line scan cameras, an edge detection algorithm, a glitch filter, and so on. A dynamic model of the mill is derived from a gauge meter equation in order to design the fuzzy PID controller. The controller is a self-learning structure to select the PID gains from the error and error rate of the width margin. The effectiveness of the proposed CFWC is verified from simulation results under a width disturbance of the entry in the mill. Using a field test, we show that the performance of the width control is improved by the proposed control scheme.