• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.367-369
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• 2002

We have designed ramp profile excitation pulse based on the Shinnar-Le Roux (SLR) algorithm. The algorithm provides many advantages to pulse designers. The first advantage is the freedom of deciding the amplitudes, frequencies, and ripple sizes of stopband, passband, and transition band of pulse profile. The second advantage is the freedom of deciding the pulse phase, more specifically, minimum phase, linear phase, maximum phase, and any phase between them. The minimum phase pulse is the best choice in the case of 3D TOF, because it minimizes the echo time, which implies the best image quality in the same MR examination condition. In addition, the half echo technique is slightly modified in our case. In general, using the half echo technique means that the acquired data size is half and the rest part can be filled with complex conjugate of acquired data. But in our case, the echo center is just shifted to left, which implies the reduction of echo time, and the acquired data size is the same as the one without using the half echo technique. In this case, the increase of right part of data leads to improvement of the resolution and the decrease of left part of data leads to decrease of signal to noise ratio. Since in the case of 3D TOF, the signal to noise ratio is sufficiently high and the resolution is more important than signal to noise ratio, the proposed method appears to be significantly affective and gives rise to the improved high resolution angiograms.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.6
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• pp.572-581
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• 2014

A design and control method of DC/DC converter, which can control variable DC-link voltage to drive a fuel cell electric vehicle (FCEV), is proposed in this study. Given that a fuel cell has low-voltage and high-current characteristics, the required voltage for operating motor must be output through the DC/DC boost converter in the system to drive an FCEV. The proposed converter can choose the output voltage of battery or fuel cell in consideration of the driving mode, as well as control DC-link voltage in accordance with the back electromotive force. The switching lag-time to prevent shortage of pulse-width modulation inverter arms makes distorted current waveform caused by voltage distortion. Through this control method, the proposed converter can reduce the output voltage distortion and current ripple of the inverter, thereby reducing the distorted torque. Simulations and experimental results are presented to verify the reliability of the proposed DC/DC converter.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2C
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• pp.213-221
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• 2004

A new method for design of two-channel finite-impulse response(FIR) quadrature mirror-image filter(QMF) banks with low reconstruction delay using weighting function is proposed. The weighting function used in this paper is calculated from the previous updated filter coefficients vector which is adjusted from iteration to iteration in the design of QMF banks. In this paper, passband and stopband edge frequency are used in design of QMF banks with low delay characteristic in time domain instead of specific frequency interval where the artifacts occur in conventional design method. The investigation of specific frequency interval where artifacts occur can not be required by using passband and stopband edge frequency. Some comparisons of performance are made with other existing design method to demonstrate the proposed method for QMF bank design. and it was observed that the proposed method using the weighted function and passband and stopband edge frequency improves the peak reconstruction error by 0.001 [dB], the peak-to-peak passband ripple by 0.003[dB], SNR with a white noise by 7[dB] and SNR with a step input by 32[dB], but with a reduction of the computational efficiency because of updating the weighting function over the conventional method in Ref [11].

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.277-283
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• 2020

In a concentric magnetic gear, which replaces the teeth of a mechanical gear with a permanent magnet, the polar ratio of the magnet that determines the reduction ratio affects the behavior of the magnetic gear dramatically. This study analyzed the density of transmission torque, the efficiency of torque considering the solid loss, and the torque quality, including the cogging characteristics using finite element analysis. When the pole number on the driving side was changed from two to five, it was confirmed that there was an optimal pole ratio, in which the transmission torque was maximized. Because eddy current generation density is proportional to the magnetic field, the transmission efficiency also shows a similar tendency to the transmission torque density, and the efficiency is more than 95% at a low gear ratio. The cogging characteristics due to the interaction of the permanent magnets with the limited number of poles are inversely proportional to the least common multiple between the number of magnets on the drive side and the number of modulator teeth. A test model was built for the transmission torque evaluation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.10
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• pp.73-82
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• 2015

This paper proposes an ripple reduction algorithm and analyzes the effects of offset and scale errors generated by voltage sensor while measuring grid voltage in grid-tied single-phase inverters. Generally, the grid-connected inverter needs to detect the phase angle information by measuring grid voltage for synchronization, so that the single-phase inverter can be accurately driven based on estimated phase angle information. However, offset and scale errors are inevitably generated owing to the non-linear characteristics of voltage sensor and these errors affect that the phase angle includes 1st harmonic component under using SRF-PLL(Synchronous Reference Frame - Phase Locked Loop) system for detecting grid phase angle. Also, the performance of the overall system is degraded from the distorted phase angle including the specific harmonic component. As a result, in this paper, offset and scale error due to the voltage sensor in single-phase grid connected inverter under SRF-PLL is analyzed in detail and proportional resonant controller is used to reduce the ripples caused by the offset error. Especially, the integrator output of PI(Proportional Integral) controller in SRF-PLL is selected as an input signal of the proportional resonant controller. Simulation and experiment are performed to verify the effectiveness of the proposed algorithm.

• Land and Housing Review
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• v.2 no.4
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• pp.491-501
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• 2011

This study estimated economic value and benefits of Yongsan National Park, which will be constructed by financial investment of the government and objectively estimated the real value of it by understanding the value of the park from a user's view of the park. For this, the value of Yongsan National Park is divided into using value such as carbon reduction and the function of relieving urban heat island as an environmental material and non-using value based on willingness to pay of the public according to the construction of the park. As a result of the analysis, it was found out that the using value of Yongsan National Park would reach 130 million won up to maximum level of 450 million won per year, and the non-using value was analyzed to be worthy of 2,344 won per capita every month. Besides, economic ripple effect that can be expected in the process of the park construction project was analyzed to be a national policy that creates effect on production inducement of 2.6 trillion won and value added of 809.6 billion won and new jobs for 25,620 persons. Considering the value of Yongsan National Park and the effect of the project based on the result of this study, it was found that it could sufficiently secure the validity of implementing the project compared to the financial investment by the government. Therefore, it must be emphasized that diffusion strategy is necessary for national understanding and for a nation to make it understood its appropriateness widely in respect to the construction of Yongsan National Park for the successful construction of Yongsan National Park and to raise its using value in the future.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.3
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• pp.31-39
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• 2022

The Army, Navy, and Air Force are currently making various efforts to apply defense IoT technology by reflecting the characteristics of each military. However, there are concerns that comprehensive collection, management, and analysis may be limited because each military has no overlapping system or guaranteed interoperability of data, and there are inefficient aspects in terms of using and investing a limited defense budget. In this study, evaluation items and priorities for pilot projects were selected by applying Delphi technique and AHP method to determine which projects are preferentially effective when commonly applied in terms of Army, Navy, and Air force. As a result of the analysis, the project basis and driving force, project feasibility, performance and ripple effect, redundancy and connection were identified in the order of IoT-based small detachment units and unmanned base construction, intelligent smart unit, smart ground ammunition depot, and smart training management system. According to the comprehensive results reflecting the weights of each evaluation item, the fact that small detachment units and unmanned base construction project are recognized as the first project to be applied to the Army, Navy, and Air Force is a valid approach to be effective while each military is burdened with personnel management because of the reduction of manpower. Through the research results, it is expected that the direction of application to the policy of the defense IoT project can be confirmed in terms of efficient use of limited budgets.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.5
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• pp.993-999
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• 2001

The purpose of the study was to develop a nutritional counseling program using expert system to assist obese people to lose weight through behavior modification in the internet. The counseling internet program for weight loss was developed by the accumulation of knowledge for dealing with eating habits and exercising behaviors into expert system tool, Knowledge Engineering Agent (KEA) by a dietitian without any help of computer expert. KEA was built based on the theory of Multiple Classification Ripple Down Rules. To accumulate knowledge into KEA, survey was performed in 150 obese people, the dietitian reviewed and consulted each survey case, and the consulted contents were learned and accumulated into KEA. Survey questionnaires were the same as those of the internet consulting program, and they included general characteristics, dietary habits, lifestyle, and exercise patterns related to obesity. KEA was used for nutritional counseling of obese people after KEA had enough knowledge for weight loss based on behavior modification by the dietitian. To accumulate knowledge to KEA, the dietitian selected proper factors inferred from the survey questionnaire of each case, and added the conclusions for them. Conclusions were made for helping clients to correct bad eating behaviors and accumulate good behaviors for losing weight. When clients answered survey questionnaires in a counseling internet program, KEA gave the recommendation how to eat, to exercise and the deal with stress in a real time for each case. If KEA did not have enough knowledge for a specific case, the conclusion window wrote no conclusion and the dietitian needed to add conclusions for the case. The conclusions for the new case added to the KEA knowledge base. In conclusions, a counseling internet program for weight reduction can be used for give advices how to deal with obesity in a man-to-man way in a real time using KEA where nutritional knowledge based on behavior modification for weight loss was accumulated.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.1
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• pp.9-18
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• 2012

Annual power consumption of our country is positioned in the upper percentile in the world, and because the proportion of fossil power generation is high, which ranks the 10th $CO_2$ emission country. In this regard, government has established and is implementing the National Energy Basic Plan to realize to get out of fossilization in energy supply while focusing on securing the technology for renewable energy as well as its commercialization in order to reduce greenhouse gas. Resource recovery technology for deep seawater thermal energy which is one of renewable energies is newly getting attention domestically as well as in overseas for securing resources and environmental improvement as a core technology for multilateral use of marine resources for low carbon and green growth. Economic feasibility analysis was conducted for the research and development as follows on the use of ocean thermal energy conversion and seawater air conditioning. First, in the case of power generation using deep seawater and warm discharge water from ocean thermal energy conversion plant of 1MW level, it is judged that the economic feasibility is insufficient but the feasibility will be significantly improved if we consider not only power generation but also drinking water and certified emission reduction by developing the power plant to the size for commercialization. Second, the economic feasibility for the use of deep seawater as air conditioning for the power plant of 1,000RT level turned out to be very good. Especially, when we consider certified emission reduction, it will be possible to secure sufficient economic feasibility. When we use it in connection with ocean thermal energy conversion, water conversion and agricultural and fishery use, it is judged that economic ripple effect will be significant and therefore it will be necessary to conduct research and development for early commercialization, distribution and diffusion of deep seawater energy.

• Journal of Environmental Impact Assessment
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• v.33 no.1
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• pp.30-41
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• 2024

The way we work is changing significantly with the rapid development of digitaltechnology, and paper documents are being replaced by electronic documents. However, in accordance with the Enforcement Decree and Enforcement Regulation of the Environmental Impact Assessment Act, the environmental impact assessment report must submit a set number of paper reports to organizations related to the project, and about 42 years have passed since it was submitted as a paperreport. In 2022, the National Institute of Ecology introduced a system to review paperreports as electronic documents in line with the trend of digital transformation. The cost reduction and carbon emission reduction effects of electronic document review were analyzed for 1,398 environmental impact assessments submitted and reviewed in 2022. In addition, a satisfaction survey was conducted targeting type 1 environmental impact assessment companies that were directly affected, and a total of 134 people responded. As a result of analyzing the effect of reviewing electronic documents, costs are reduced by a total of 101,424,900 won per year and carbon emissions are reduced by about 59.7 tons. As a result of the satisfaction survey, 94.8% of the respondents said electronic documentreview was very helpful, and 4.5% said it was helpful. The effectiveness of electronic documentreview was high, with 94.8% of respondents saying it was helpful in economic terms and 91.8% saying it was helpful in reducing work hours. If electronic documents are reviewed through the revisions to the Enforcement Decree and Enforcement Regulation of the Environmental Impact Assessment Act, the implementation of electronic document review is expected to have a ripple effect across the country, not only reducing costs and carbon emissions, but also reducing administrative time and saving storage space. Rapid changes in law and administration are needed to adapt to the digital transformation era.