• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.9
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• pp.854-864
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• 2016

The use of small drone platform has become a popular topic in these days but its application for SAR operation has been little known due to the burden of the payload implementation. Drone platforms are distinguished from the conventional UAV system by the increased vulnerability to the turbulences, control-errors and poor motion stability. Consequently, sophisticated motion compensation may be required to guarantee the successful acquisition of high quality SAR imagery. Extremely limited power and mass budgets may prevent the use of additional hardwares for motion compensation and the difficulty of SAR focusing is further aggravated. In this paper, we have carried out a feasibility study of mico-SAR drone operation. We present the image acquisition results from the preliminary flight tests and a quality assessment is followed on the experimental SAR images. The in-flight motion errors derived from the unique drone movements are investigated and attempts have been made to compensate for the geometrical and phase errors caused by motions against the nominal trajectory. Finally, the successful operation of drone SAR system is validated through the focussed SAR images taken over test sites.

• 한국노년학
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• v.37 no.1
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• pp.201-219
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• 2017

This study was performed to test the socioemotional selectivity theory (SST) with Korean adults. According to SST, perceiving their life as limited, people are motivated to enhance their mood by regulating their mood in such a way to maximize the positive emotions and weaken the negative ones. Being founded on the dialectical constructs which assume the positive and negative sides of emotional experience coexist, Korean adults were supposed to be less motivated to maximize positive emotions and weaken negative emotions. Thus the elderly koreans might regulate emotions not in the direction of maximizing the positive emotions and weakening the negative ones, but in the direction of not being highly aroused. 166 youth, middle-aged, and elderly were asked to rate the frequencies of 31 positive and negative emotions they had experienced during the last month. In addition, they were asked to judge whether they weaken / adapt / maximize their emotions after experiencing positive and negative events. The elderly experienced less positive emotions as well as negative emotions than youth. Youth experienced emotions of high arousal more often than those of low arousal, but the elderly experienced emotions of high arousal less often. The responses of weakening their negative emotions and their positive emotions were largest in the elderly group. On the other hand, the response of maximizing their positive emotions were largest in the youth group. These results show that the elderly maintains emotional stability by weakening both positive and negative emotions of high arousal.

• Science of Emotion and Sensibility
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• v.24 no.2
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• pp.13-24
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• 2021

In level 5 (mind-off) of autonomous driving, the autonomous vehicle passengers are expected to have various activities such as face-to-face meetings, working, relaxing, and watching movies. In particular, various changes in the interior space of the vehicle are expected. Moreover, according to the survey conducted by the American Automobile Association, 73% of the respondents reported that they were afraid to board autonomous vehicles. In level 5 of autonomous driving, the subject of safety was expected to be transferred to autonomous vehicles; thus, research should be conducted from the user's perspective. Recently, various studies have been conducted to secure the safety of fully autonomous vehicles. However, there are limited studies addressing the psychological safety of actual passengers. Therefore, this study conducted a questionnaire based on the AHP technique. Consequently, the automobile safety system's priority for securing passengers' psychological safety according to each type of indoor behavior was derived, and the interior space for securing the psychological stability of passengers was suggested based on the obtained results. This study offers a new direction for interior space design, satisfying the psychological safety of passengers. This study is important because it advocates that the interior environment of fully autonomous driving cars is expected to be designed to secure the user's psychological safety.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.3
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• pp.122-130
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• 2021

A wind-speed estimation at the arbitrary elevations is key component for the design of the offshore wind energy structures and the computation of the wind-wave generation. However, the wind-speed estimation of the target elevation has been carried out by using the typical functions and their typical parameters, e.g., power and logarithmic functions because the available wind speed data is limited to the specific elevation, such as 2~3m, 10 m, and so on. In this study, the parameters of the vertical profile functions are estimated with optimal and analyzed the parameter ranges using the HeMOSU-1 platform wind data monitored at the eight different locations. The results show that the mean value of the exponent of the power function is 0.1, which is significantly lower than the typically recommended value, 0.14. The values of the exponent, the friction velocity, and the roughness parameters are in the ranges 0.0~0.3, 0~10 (m/s), and 0.0~1.0 (m), respectively. The parameter ranges differ from the typical ranges because the atmospheric stability condition is assumed as the neutral condition. To improve the estimation accuracy, the atmospheric condition should be considered, and a more general (non-linear) vertical profile functions should be introduced to fit the diverse profile patterns and parameters.

• Plant Journal
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• v.18 no.3
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• pp.41-51
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• 2022

Recently, LNG power plants are increasing drastically and the desire of an improvement in the quality of life is growing. The delay of power plant construction can hinder the stability of power supply and increase the cost. So this study was conducted to help power plant construction progressing from now on by studying on the social acceptance of a LNG power plant. On this study I limited the scope of the study to the stage of Site Selection which is the most conflict stage and can interrupt the project. To conduct this study I researched the recently constructed power plants which have been delayed, in particular Eumseong Natural Power Plant and Daegu LNG Power Plant which are under bitter conflicts with local residents and have difficulty in construction progressing. So I found out that it is very important to collect the opinions of the residents in the stage of Site Selection and it is necessary to change ACT ON ASSISTANCE TO ELECTRIC POWER PLANTS- NEIGHBORING AREAS. Lastly it is very important to adapt the state-of-the-art facilities to increase the social acceptance of a LNG power plant.

• Environmental and Resource Economics Review
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• v.33 no.2
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• pp.113-133
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• 2024

Variable renewable energy (VRE) such as solar and wind power is the main sources of achieving carbon net zero, but it undermines the stability of power supply due to high variability and uncertainty. Energy storage system (ESS) can not only reduce the curtailment of VRE by load shifting but also contribute to stable power system operation by providing ancillary services. This study analyzes how the allocation of ESS resources between load shifting and ancillary service can contribute to maximizing the efficiency of power supply in a situation where the problems caused by VRE are becoming more and more serious. A stochastic power system optimization model that can realistically simulate the variability and uncertainty of VRE was applied. The analysis time point was set to 2023 and 2036, and the optimal resource allocation strategy and benefits of ESS by varying VRE penetration levels were analyzed. The analysis results can be largely summarized into the following three. First, ESS provides excellent functions for both load shifting and ancillary service, and it was confirmed that the higher the reserve price, the more limited the load shifting and focused on providing reserve. Second, the curtailment of VRE can be a effective substitute for the required reserve, and the higher the reserve price level, the higher the curtailment of VRE and the lower the required amount of reserve. Third, if a reasonable reserve offer price reflecting the opportunity cost is applied, ESS can secure economic feasibility in the near future, and the higher the proportion of VRE, the greater the economic feasibility of ESS. This study suggests that cost-effective low-carbon transition in the power system is possible when the price signal is correctly designed so that power supply resources can be efficiently utilized.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.11
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• pp.730-742
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• 2014

In the case of On-demand routing protocol in cognitive radio ad-hoc networks, broadcasting of control packets may occur common control channel overload and packet collisions during the routing procedure. This situation is to increase the overhead of path finding and also limited to find the accurate and reliable path. Since reliable channel and path finding is restricted, path life time is shorten and path reliability is reduced. In this paper, we propose a new routing algorithm that reduces control channel overhead and increases path life time by considering the probability of appearance of primary user and channel status of neighbor nodes. Each node performs periodic local sensing to detect primary user signal and to derive primary user activity patterns. The probability of primary appearance on the current channel and the channel status can be obtained based on the periodic sensing. In addition, each node identifies the quality of the channel by message exchange through a common channel with neighbor nodes, then determines Link_Levels with neighbor nodes. In the proposed method, the Link Level condition reduces the number of control messages that are generated during the route discovery process. The proposed method can improve path life time by choosing a path through Path_Reliability in which stability and quality are weighted depending on the location. Through simulation, we show that our proposed algorithm reduces packet collisions and increases path life time in comparison with the traditional algorithm.

• Advances in aircraft and spacecraft science
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• v.5 no.2
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• pp.225-237
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• 2018

The difficulties of satellite vibration testing are due to the commonly expressed qualification requirements being incompatible with the limited performance of the entire controlled system (satellite + interface + shaker + controller). Two features cause the problem: firstly, the main satellite modes (i.e., the first structural mode and the high and low tank modes) are very weakly damped; secondly, the controller is just too basic to achieve the expected performance in such cases. The combination of these two issues results in oscillations around the notching levels and high amplitude beating immediately after the mode. The beating overshoots are a major risk source because they can result in the test being aborted if the qualification upper limit is exceeded. Although the abort is, in itself, a safety measure protecting the tested satellite, it increases the risk of structural fatigue, firstly because the abort threshold has been already reached, and secondly, because the test must restart at the same close-resonance frequency and remain there until the qualification level is reached and the sweep frequency can continue. The beat minimum relates only to small successive frequency ranges in which the qualification level is not reached. Although they are less problematic because they do not cause an inadvertent test shutdown, such situations inevitably result in waiver requests from the client. A controlled-system analysis indicates an operating principle that cannot provide sufficient stability: the drive calculation (which controls the process) simply multiplies the frequency reference (usually called cola) and a function of the following setpoint, the ratio between the amplitude already reached and the previous setpoint, and the compression factor. This function value changes at each cola interval, but it never takes into account the sensor signal phase. Because of these limitations, we firstly examined whether it was possible to empirically determine, using a series of tests with a very simple dummy, a controller setting process that significantly improves the results. As the attempt failed, we have performed simulations seeking an optimum adjustment by finding the Least Mean Square of the difference between the reference and response signal. The simulations showed a significant improvement during the notch beat and a small reduction in the beat amplitude. However, the small improvement in this process was not useful because it highlighted the need to change the reference at each cola interval, sometimes with instructions almost twice the qualification level. Another uncertainty regarding the consequences of such an approach involves the impact of differences between the estimated model (used in the simulation) and the actual system. As limitations in the current controller were identified in different approaches, we considered the feasibility of a new controller that takes into account an estimated single-input multi-output (SIMO) model. Its parameters were estimated from a very low-level throughput. Against this backdrop, we analyzed the feasibility of an LQG control in cancelling beating, and this article highlights the relevance of such an approach.

• The Journal of Engineering Geology
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• v.20 no.3
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• pp.243-255
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• 2010

The slope design of an open-pit mine must consider economical efficiency and stability. Thus, the overall slope angle is the principal factor because of limited support or reinforcement options available in such a setting. In this study, slope displacement, as monitored by a GPS system, was analyzed for a coal mine at Pasir, Indonesia. Predictions of failure time by inverse velocity analysis showed good agreement with field observations. Therefore, the failure time of an unstable slope can be roughly estimated prior to failure. A GIS model that combines fuzzy theory and the analytical hierarchy process (AHP) was developed to assess slope instability in open-pit coal mines. This model simultaneously considers seven factors that influence the instability of open-pit slopes (i.e., overall slope gradient, slope height, surface flows, excavation plan, tension cracks, faults, and water body). Application of the proposed method to an open-pit coal mine revealed an enhanced prediction accuracy of failure time and failure site compared with existing methods.

• Clinics in Shoulder and Elbow
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• v.16 no.2
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• pp.170-177
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• 2013

Total elbow arthroplasty is still in its infancy compared with other arthroplasties, such as knee or hip arthroplasties. Implant design has been evolving with clinical experiences; however, there are only limited data on the long-term clinical outcome of elbow arthroplasty in the literature. The design of total elbow prostheses can be divided into three categories: linked (constrained or semi-constrained), unlinked (unconstrained), and convertible types. The choice between an unlinked (unconstrained) implant and a linked (semi-constrained) implant depends on joint stability and adequacy of the bone stock. Linked elbow arthroplasty has provided high patient satisfaction, and pain relief thanks to proper patient selection, advancement of implant design, improvement in cement techniques, meticulous surgical technique, and appropriate postoperative rehabilitation. Concerns remain about the use of this implant in young or high-demand patients. This article focuses on the linked (semi-constrained) prostheses, which provides an overview of the current state of linked total elbow arthroplasty.