• Journal of Korea Port Economic Association
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• v.26 no.4
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• pp.63-87
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• 2010

The purpose of this paper is to measure the efficiency of Korean container terminals by using SFA(Stochastic Frontier Analysis). Inputs[Number of Employee, Quay Length, Container Terminal Area, Number of Gantry Crane], and output[TEU] are used for 3 years(2002,2003, and 2004) for 8 Korean container terminals by applying both SFA and DEA models. Empirical main results are as follows: First, Null hypothesis that technical inefficiency is not existed is rejected and in the trasnslog model, the estimate is significant. Second, time-series models show the significant results. Third, average technical efficiency of Korean container terminals are 73.49% in Cobb-Douglas model, and 79.04% in translog model. Fourth, to enhance the technical efficiency, Korean container terminals should increase the handling amount of TEUs. Fifth, both SFA and DEA models have the high Spearman ranking of correlation coefficients(84.45%). The main policy implication based on the findings of this study is that the manager of port investment and management of Ministry of Land, Transport and Maritime Affairs in Korea should introduce the SFA with DEA models for measuring the efficiency of Korean ports and terminals.

• Journal of Satellite, Information and Communications
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• v.2 no.2
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• pp.80-84
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• 2007

In this paper, the introductory study of the multi input multi output (MIMO) techniques for satellite communication systems is presented. Because of the advantage of wide coverage of satellite, it has been considered for broadcasting services and fill-in services. On the other hand, state of the art multi input multi output (MIMO) techniques such as space time code (STC) and spatial multiplexing (SM) makes the terrestrial system increase link performance and their coverage, and also increase the link throughput. For these regard, in order to satisfy the requirements of the next generation communications and coexists with terrestrial systems harmoniously, the studying about satellite MIMO techniques is necessary. In this paper, we introduce some system model and scenarios to apply MIMO technique to intermediate module repeater (IMR). The possibility of these techniques and technical requirements are also considered. Especially, Space time code is used to enhance IMRs coverage and increase the link performance, and space time multiplexing is utilized to multiplex satellite broadcasting signals with local broadcasting signal in IMR cell.

• Annals of Hepato-Biliary-Pancreatic Surgery
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• v.26 no.4
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• pp.347-354
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• 2022

Backgrounds/Aims: Endoscopic retrograde cholangiopancreatography (ERCP) remains the primary treatment for a subset of patients with pancreatic fistulae. The objective of this study was reporting outcomes of ERCP and predictors of resolution in patients with pancreatic fistulae refractory to conservative therapy. Methods: Retrospective review of patients who underwent ERCP and pancreatic stent placement for pancreatic fistula not responding to medical therapy was performed. Clinical features, laboratory parameters, radiological features and pancreatogram findings were noted. Clinical resolution of fistula was the primary outcome measure. Results: Sixty-eight patients underwent ERCP for high-output pancreatic fistula (Mean age 34.1 years, 91.1% males, 35/68 chronic pancreatitis, 52.9% alcohol etiology). Internal fistulae (pancreatic ascites, pleural effusion, or pericardial effusion) were seen in 55 (80.9%) patients and external fistula in 13 (19.1%) patients. Technical success for ERCP was 92.6% (63/68). Leak was seen in 98.4% (62/63). The most common leak site was body (69.8%). Multiple leak sites were seen in 23.1%. Pancreatic stricture was found in 36.5%. In 44 (69.4%) patients, stent was placed beyond the site of the leak. Resolution at six weeks was achieved in 76.4% (52/68). On univariate and multivariate analyses, placement of stent beyond site of leak was significantly associated with resolution of high-output fistulae (3/41 [7.3%] vs. 5/19 [26.3%], p = 0.03; odds ratio: 6.5, 95% confidence interval: 1.211-34.94). Conclusions: In our experience, ERCP was successful in 76% of patients with pancreatic fistulae refractory to conservative therapy. Stent placement beyond the site of leak was associated with higher resolution of fistulae.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.11
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• pp.1550-1559
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• 2013

Light emitting diode(LED) lighting has been applied various industry fields because of its high efficiency, low power consumption, long life time, and environment friendly characteristics. Generally, LED lighting needs a driver to maintain constant current. Most popular driver is the switching converter. In the converter, there are several electrolytic capacitors. However the lifespan of the electrolytic capacitor is much shorter than LED. Therefore the lifespan of LED lighting with electrolytic capacitor is decreased. Also, LED lighting needs dimming control because of various needs and energy saving. This paper presents the dimmable single-stage PFC DCM flyback converter without electrolytic capacitor and parallel LC resonant filter for reducing 120[Hz] ripple on the output. The type 2 controller is used to maintain constant current and the analog dimming control is used. The proposed converter is verified through simulation and experimental works.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.2
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• pp.790-794
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• 2012

A output strength is limited according to the frequency used in order to protect other wireless stations from interference caused by radio waves emitted from the low power wireless installations. For receivers, unwanted spurious emission is regulated, and regulations in Korea define that additional spurious emission for receivers in the low power wireless installations under 1GHz should be -54dBm, but no regulations have been established yet for low power wireless installations over 1GHz. It is presently required to set domestic standards for devices over 1GHz on account of the expansion of the communication market and its service.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1115-1120
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• 2003

The present paper shows the possible development of particle swarm optimization (PSO) based fuzzy-neural networks (FNN) which can be employed as an important building block in real life robot systems, controlled by voice-based commands. The PSO is employed to train the FNNs which can accurately output the crisp control signals for the robot systems, based on fuzzy linguistic spoken language commands, issued by an user. The FNN is also trained to capture the user spoken directive in the context of the present performance of the robot system. Hidden Markov Model (HMM) based automatic speech recognizers are developed, as part of the entire system, so that the system can identify important user directives from the running utterances. The system is successfully employed in a real life situation for motion control of a redundant manipulator.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.520-523
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• 2004

A phase-locked loop control system designed by using the linear quadratic regulator approach is presented in this paper. The system thus designed is optimal system when system is in locked state and the parameter value of loop filter which is an active PI filter can be obtained easily. By considering the structure of loop filter of phase-locked loop is included in the process to be controlled, a type 1 servo system can be constructed when voltage control oscillator is considered as an integrator. The integral gain of the proposed system obtained by linear quadratic regulator approach can be used as an optimal value to design the parameter of loop filter. The implemented result in controlling the second-order lag pressure process by using the proposed scheme show that the system response is fast with no overshoot and no steady-state error. Furthermore, the experimental results are also shown in term of output disturbance effect rejection, tracking and process parameter changed.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.450-453
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• 2002

In this paper a Phase-based virtual image encryption and decryption techniques based on a joint transform correlator (JTC) are proposed. In this method, an encrypted image is obtained by multiplying a phase-encoded virtual image that contains no information from the decrypted image with a random phase. Even if this encryption process converts a virtual image into a white-noise-like image, the unauthorized users can permit a counterfeiting of the encrypted image by analyzing the random phase mask using some phase-contrast technique. However, they cannot reconstruct the required image because the virtual image protects the original image from counterfeiting and unauthorized access. The proposed encryption technique does not suffer from strong auto-correlation terms appearing in the output plane. In addition, the reconstructed data can be directly transmitted to a digital system for real-time processing. Based on computer simulations, the proposed encryption technique and decoding system were demonstrated as adequate for optical security applications.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.3
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• pp.415-419
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• 2016

As the need for clean coal technology has grown, so has the global research and development efforts into integrated gasification combined cycle (IGCC) plants. An IGCC plant couples a gas turbine to a gasification block. Various technical and economic problems exist in designing such a system. One such problem is the difficulty in realizing economies of scale because the single-train flow capacity of commercial IGCC synthetic gas turbine plants is limited; the capacity does not exceed a net power rating of 300 MW. To address this problem, this study modeled and simulated a synthetic gas turbine with the goal of evaluating the feasibility of a 500 MW or larger IGCC plant. First, a gas turbine with the best output and efficiency was chosen for use with natural gas. The turbine was modeled using GateCycle (a simulation tool), and the integrity of the model validated by comparing the result to the design value. Next, off-design modeling was carried out for a gas turbine with synthetic gas based on its on-design model, and the result was compared with the study result of the gas turbine manufacturer. The simulation confirmed that it is possible to create a large capacity IGCC plant by undertaking the remodeling of a gas turbine designed to use natural gas into one suitable for synthetic gas.

• The Korean Journal of Health Service Management
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• v.9 no.1
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• pp.17-29
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• 2015

This study, an examination of the plan for effective resource management for national university hospitals, was performed to determine the relationship between the effectiveness of patient output by considering input personnel using the DEA model and Management Performance, in which 4 years of data from 12 national university hospitals were analyzed. Among the components of the effectiveness, utilizing properly imput components from the application of VRS(Variable Returns to Scale), the Management Performance of national university hospitals was found to be affirmatively influenced by PTE(Pure Technical Efficiency). Regarding the Management Performance of national university hospitals in their attempts to establish a plan for effective human resource management, the management of patient numbers on the basis of calculation level with input is more recommendable than the controlling of personnel input using patient numbers. Thus, the establishment of a strategy plan for the proper allocation of administrative staff and sickbeds, considering the variation of patient numbers, is suggested.