• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2435-2443
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• 2022

The once-through steam generator used in the small modular reactor needs to consider the stability of the outlet steam pressure and steam superheat of the secondary circuit to achieve better operating efficiency. For this reason, this paper designs a controllable operation scheme for the steam pressure and superheat of the small reactor once-through steam generator. On this basis, designs a variable universe fuzzy controller, first, design the fuzzy control rules to make the controller adjust the PI controller parameters according to the change of the error; secondly, use the domain adjustment factor to further subdivide the input and output domain of the fuzzy controller according to the change of the error, to improve the system control performance. The simulation results show that the operation scheme proposed in this paper have better system performance than the original scheme of the small reactor system, and controller proposed in this paper have better control performance than traditional PI controller and fuzzy PI controller, what's more, the designed control system also showed better anti-disturbance performance in lifting experiment between 100% and 80% working conditions. Finally, the experimental platform formed by connecting the digital small reactor with Matlab/Simulink through OPC(OLE for Process Control) communication technology also verified the feasibility of the proposed scheme.

• ETRI Journal
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• v.46 no.2
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• pp.184-193
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• 2024

This paper presents the performance evaluation of an amplify-and-forward (AF) relay-assisted multiuser multiple input-multiple output (MU-MIMO) downlink transmission system for correlated fading channels. The overall system performance was improved by incorporating a double-quadrature spatial modulation (DQSM) scheme. The bit error rate (BER) performance and detection complexity of the AF-MU-MIMO-DQSM system were analyzed and compared with those of a conventional AF-MU-MIMO system under the same conditions and parameters. The results showed that the correlated fading channel severely affected the performance of systems with higher spectral efficiency (SE). Considering an SE of 12 bpcu/user, the AF-MU-MIMO-DQSM system yielded a gain of up to 3 dB in BER performance compared with that of its conventional counterpart for the analyzed cases. In terms of detection complexity, the AF-MU-MIMO-DQSM system showed a reduction of up to 56 % compared with that of the conventional system for the optimal maximum likelihood detection criterion.

• The Journal of the Acoustical Society of Korea
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• v.26 no.5
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• pp.188-193
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• 2007

In general, analog amplifiers for 5.1 or more channels have been used to configure home theater systems. In order to make high-performance systems, it is desirable to process audio signals in digital techniques in consideration of output and efficiency of speakers. Especially we need 7.1-channel system to separate audio signals efficiently. In this paper we implemented the architecture of S/PDIF 7.1-channel digital amplifier for home theater systems. The amplifier shows good performance with less loss of original sounds because of both strong characteristics against noises and direct processing of input data.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.32 no.1
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• pp.61-70
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• 2024

In response to the continuously increasing demand for air travel, various studies are being conducted. This research focuses on the design of a simulation model for improving airport slot allocation in the strategic phase. It addresses three aspects of model design, introducing considerations such as the objective function. Additionally, it explains the conceptual procedures for the overall simulation operation and detailed processes within the model including input and output data. Emphasizing the SAL, this study excludes policy and qualitative judgments from its scope. The target airport for application will be confirmed in future research. This study marks a crucial first step toward optimizing air traffic flow, with expectations of contributing to the enhancement of operational efficiency at airports.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.2
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• pp.103-110
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• 2010

In this paper, a new mode changeable asymmetric full bridge dc/dc converter is proposed to solve the freewheeling current problem of the conventional zero voltage switching(ZVS) phase shift full bridge(PSFB) dc/dc converter of low output voltage and high output current applications. The proposed converter is operated as an asymmetric full bridge converter when the duty cycle is less than 50% and active clamp full bridge converter when the duty cycle is greater than 50%. As a result, since its freewheeling current is eliminated, the conduction loss is lower than that of the conventional ZVS PSFB dc/dc converter. Moreover, ZVS of all power switches can be ensured along a wide load ranges and output current ripple is very small. Therefore, high efficiency of the proposed converter can be achieved. Especially since its operation mode is changed to the active clamp full bridge converter during hold up time and can be operated with 50~100% duty ratio, it can produce the stable output voltage along wide input voltage range. The operational principles, theoretical analysis and design considerations are presented. To confirm the operation, validity and features of the proposed converter, experimental results from a 1.2kW($400V_{dc}/12V_{dc}$) prototype are presented.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.565-568
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• 2014

This paper presents a 0.2V DC/DC boost converter with regulated output for thermoelectric energy harvesting. To use low voltages from a thermoelectric device, a start-up circuit consisting of native NMOS transistors and resistors boosts an internal VDD, and the boosted VDD is used to operate the internal control block. When the VDD reaches a predefined value, a detector circuit makes the start-up block turn off to minimize current consumption. The final boosted VSTO is achieved by alternately operating the sub-boost converter for VDD and the main boost converter for VSTO according to the comparator outputs. When the VSTO reaches 2.4V, a buck converter starts to operate to generate a stabilized output VOUT. Simulation results shows that the designed converter generates a regulated 1.8V output from an input voltage of 0.2V, and its maximum power efficiency is 60%. The chip designed using a $0.35{\mu}m$ CMOS process occupies $1.1mm{\times}1.0mm$ including pads.

• Journal of Digital Convergence
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• v.17 no.5
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• pp.117-125
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• 2019

This study measured inefficiencies of Korean banks with weighted Russell directional distance function, WRDDM, for the years of 2004-2013. Checking contributions of inputs and outputs to these inefficiencies, we found that non-performing loan as undesirable output was the most influential factor. The annual average of inefficiencies of Korean banks was 0.3912, and it consisted of non-performing loan 0.1883, output factors 0.098 except non-performing loan, input factors 0.098. The annual average inefficiency went sharply up from 0.2995 to 0.4829 mainly due to the sharp increase of inefficiency of non-performing loan from 0.1088 to 0.2678 before and after 2007-2008 Global financial crisis. We empirically showed the non-performing loan needed to be considered since it was the most important factor among the influential factors of technical inefficiency such as manpower, total deposit, securities, and non-performing loan. This study had some limitation since we did not control financial environment factor in WRDDM.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2455-2464
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• 2013

This study is focused on the effect of reformation of public transportation system on the efficiency of bus route system as a result of change of government subsidy scheme. Two types of government subsidy scheme has been considered and before and after analysis by Data Envelopment Analysis technique has been carried out for bus routes in Ulsan Metropolitan City. The analysis output has shown that there is no clear evidence to clarify the relationship between the change of government subsidy scheme and the efficiency of bus route system. There are two types of backgrounds may be suggested for this situation such as more longer period necessary to identify the policy effect and limitation to increase the number of passenger in a provincial city. Tobit regression analysis has also been conducted to discover the most effective variables for maximum efficiency and three variables including route length, frequency per vehicle per day, and headway are found to be influential. It is also seen that strategy to minimising input factors and service upgrade plan such as shortened route length and headway, increasing frequency per vehicle are necessary to develop the efficiency of bus routes operated in Ulsan city.

• Journal of Biomedical Engineering Research
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• v.22 no.5
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• pp.449-458
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• 2001

This is a test report of system efficiency for the moving-actuator type Bi-ventricular assist device (AnyHear $t^{MT}$ ) Seoul National University). $AnyHeart^{TM}$), as an energy converter. utilities a brushless DC motor(S/M 566-26A. Sierracin/ Magnedyne, Carlsbad, CA. U.S.A.) generating their pendulous motion in the epicyclic gear train. It is necessary to know about the overall efficiency of the system. The system is subdivided into three parts: motor part, actuator part and blood sac part (including valves, etc.) according to system mechanism. The motor was operated with a variable range of torque. angular speed and width of voltage Pulse In this report. $AnyHeart^{TM}$ is focused on the efficiency of the motor and actuator parts. 4 $\ell/min$ pump output. which is normal condition of $AnyHeart^{TM}$ system, the total system efficiency is 8%, which is composed of 50%, 85% and 17% efficiency (motor Part, actuator Part and blood sac Part) respectively. In the analyzed result. applied input voltage on normal condition of $AnyHeart^{TM}$ is determined. Also speed Profile with considering filling state of blood sac is Provided. In the test of the in vitro mock circulation. some experimental results are Provided to demonstrate the effectiveness of the Presented approach.

• Journal of Korea Technology Innovation Society
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• v.19 no.4
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• pp.711-735
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• 2016

Drug Development is very important for promoting public health and pharmaceutical industry. There has been many studies on the efficiency of drug development, but there are few studies on the drug development R&D performed by government. Since CCR model assumes unidirectional influence of input and output, it is not appropriate to analyze the efficiency of R&D due to the time-lag and spill-over effect. Also, BBC model which assumes variable returns to scale has difficulty in deriving priorities between decision making units. Recently, Range Adjusted Measure (RAM) model has been suggested in R&D efficiency analysis. RAM model measures the efficincy by eliminating inefficiencies under variable returns to scale assumption, and its strong monotonicity enables to provide clear priorities between decision making units. In this study, we analyzed the efficiency of national R&D programs for drug development using the two-step approach, including RAM model and Tobit regression analysis, and discussed major policy implications.