• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1997년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Fall 1997
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• pp.173-181
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• 1997

To investigate the effects of haunch repair on the system seismic performance of steel moment-resisting frames (steel MRFs), a case study was conducted for a 13-story frame damaged during the 1994 Northridge earthquake. It was assumed that only those locations with reported damage would be repaired with haunches. A new analytical modeling technique for the dual panel zone developed by the author was incorporated in the analysis. Both the inelastic static and dynamic analyses did not indicate detrimental side effects resulting from the repair. As a result of the increased strength in dual panel zones, yielding in these locations were eliminated and larger plastic rotation demand occurred in the beams next to the shallow end of the haunches. Nevertheless, the beam plastic rotation demand produced by the Sylmar record of 1994 Northridge earthquake was still limited to 1.7% radians. The repair resulted in a minor increase in earthquake energy input. In the original structure, the panel zones should dissipate about 80%(for the Oxnard record) and 70%(for the Sylmar record) of the absorbed energy, assuming no brittle failure of moment connections. After repair, the energy dissipated in the panel zones and beams were about equal.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권11호
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• pp.4595-4610
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• 2020

In the practical communication environment, the accurate channel state information (CSI) is difficult to obtain, which will cause the mismatch of resource and degrade the system performance. In this paper, to account for the channel uncertainties, a robust power allocation scheme for a downlink Non-orthogonal multiple access (NOMA) heterogeneous network (HetNet) is designed to maximize energy efficiency (EE), which can ensure the quality of service (QoS) of users. We conduct the robust optimization model based on worse-case method, in which the channel gains belong to certain ellipsoid sets. To solve the non-convex non-liner optimization, we transform the optimization problem via Dinkelbach method and sequential convex programming, and the power allocation of small cell users (SCUs) is achieved by Lagrange dual approach. Finally, we analysis the convergence performance of proposed scheme. The simulation results demonstrate that the proposed algorithm can improve total EE of SCUs, and has a fast convergence performance.

• 대한방사선기술학회지:방사선기술과학
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• 제41권1호
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• pp.47-51
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• 2018

To evaluate the applicability of osteoporosis management by statistical analysis of the correlation between bone mineral density (BMD) changes after menopause by dividing the T-score of bone mineral density measured by dual energy X-ray absorptiometry do. Between January 1, 2016 and July 31, 2017, women who visited the medical center of W Medical Center were enrolled in this study. The postmenopausal period was divided into 5 groups, There were 18 patients within 5 years, 44 patients in 6~10 years, 134 patients in 11~15 years, 109 patients in 16~20 years and 21 patients in 21 years or older. And postmenopausal women. Bone mineral density (BMD) of the lumbar spine and femur was measured using a dual energy X-ray absorptiometry. The lowest value among lumbar spine 1, 2, 3 and 4 and the lowest value among the femoral neck, greater trochanter, total femur, and ward Values were measured. The statistical significance was analyzed by using bivariate correlation coefficient method and one - way ANOVA. In 326 patients who underwent BMD, the correlation between bone mineral density and postmenopausal BMD showed a negative correlation (-.159, p<.01) with BMD of femur and BMD of lumbar spine The correlation between the menopausal period and negative (-.208, p<.01) was shown. There was a significant difference (p<.012) between the postmenopausal femur bone density and the mean value of the lumbar spine BMD (p<.000). The relationship between bone mineral density (BMD) and postmenopausal women's postmenopausal status can be estimated by estimating the bone mineral density and using it as a basic data for osteoporosis management.

• 방사선산업학회지
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• 제12권4호
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• pp.317-324
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• 2018

The results of bone mineral density analysis using DXA were compared between automatic and manual methods. The purpose of this paper is to verify the range of errors of each analysis method in the same patient and select a proper method to minimize errors. Comparisons between automatic and manual analysis methods were made using BMD, BMC and AREA. Basal and follow up examinations were performed with the patients of normal, osteopenia and osteoporosis. In the basal examinations, the precision errors between automatic and manual method showed 1.9% in normal, 3.1% in osteopenia and 3.8% in osteoporosis. In case of follow up studies, the precision errors between automatic and manual method showed 2.3% in normal, 3.2% in osteopenia and 3.5% in osteoporosis. BMC and AREA also showed a tendency to increase precision errors on osteopenia and osteoporosis. Therefore, a manual method would be a better option to minimize errors in patients with osteopenia and osteoporosis.

• Structural Engineering and Mechanics
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• 제92권1호
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• pp.99-110
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• 2024

The crack propagation path can be considered as a boundary problem in which the crack advances towards the interior of the domain. Consequently, this poses an optimization problem wherein the local crack-growth direction angle can be treated as a design variable. The advantage of this approach is that the continuous minimization of strain energy naturally leads to the mode I propagation path. Furthermore, this procedure does not rely on the precise characterization of the stress field at the crack tip and is independent of stress intensity factors. This paper proposes an algorithm based on internal point exploration as well as shape sensitivity optimization and strain energy minimization to determine the crack propagation direction. To implement this methodology, the algorithm utilizes a modeling GUI associated with an academic analysis program based on the Dual Boundary Elements Method and determines the propagation path by exploiting the elastic strain energy at points in the domain that are candidates to be included in the boundary. The sensitivity of the optimal solution is also assessed in the vicinity of the optimum point, ensuring the stability and robustness of the solution. The results obtained demonstrate that the proposed methodology accurately predicts the crack propagation direction in Mode I opening for a single crack (lateral and central). Furthermore, robust optimal solutions were achieved in all cases, indicating that the optimal solution was not highly sensitive to changes in the design variable in the vicinity of the optimal point.

• 에너지공학
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• 제19권4호
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• pp.246-250
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• 2010

12 리터급 경유엔진을 개조한 LNG 혼소엔진에 대해 출력, 연비 및 배출가스등의 성능을 평가하였으며 이를 바탕으로 LNG혼소 화물 자동차의 경제성을 분석하였다. 출력은 경유엔진에 비해 5% 정도 낮은 수준으로 평가되었으며 엔진효율은 경유의 경우 37.4%, LNG혼소의 경우 35.9%로 경유엔진의 경우가 다소 높게 나타났다. 배출가스는 탄화수소를 제외하고 PM, NOx, CO 및 $CO_2$는 LNG 혼소의 경우가 낮은 특성을 보였다. 경제성 비교를 위해 연료비용과 환경비용 관점에서 각각 분석하였으며 유가보조금 및 할인을고려할 경우에도 LNG 혼소 화물차의 경제성이 있는 것으로 분석되었다.

• Journal of Power Electronics
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• 제17권6호
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• pp.1433-1444
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• 2017

A family of non-isolated DC-DC three-port converters (TPCs) that allows for a more flexible power flow among a renewable energy source, an energy storage device and a current-reversible DC bus is introduced. Most of the reported non-isolated topologies in this area consider only a power consuming load. However, for applications such as hybrid-electric vehicle braking systems and DC microgrids, the load power generating capability should also be considered. The proposed three-port family consists of one unidirectional port and two bi-directional ports. Hence, they are well-suited for photovoltaic (PV)-battery-DC bus systems from the power flow viewpoint. Three-port converters are derived by combining different commonly known power converters in an integrated manner while considering the voltage polarity, voltage levels among the ports and the overall voltage conversion ratio. The derived converter topologies are able to allow for seven different modes of operation among the sources and load. A three-port converter which integrates a boost converter with a buck converter is used as a design example. Extensions of these topologies by combining the soft-switching technique with the proposed design example are also presented. Experiment results are given to verify the proposed three-port converter family and its analysis.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.539-542
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• 2006

Many researches about next generation vehicles are trending toward HEV which has better fuel economy than an internal-combustion engine. But existing HEV has some defects at specific running states(eg. highway running It is possible that dual-mode hybrid system overcomes that defects. Mode change parameter, ${\gamma}$ helps to analyse the mode changing of dual mode hybrid and is applied at a numerical analysis on testing the performance. There is an additional constraint when vehicles drive on engine mode. No power assistance of battery applies on engine mode. Because vehicles must be sustained by only engine power while vehicle drives on constant speed mode. At the conclusion of this paper, graphs show the ability of motors that satisfy the equilibrium of the lever system. Designers can roughly determine capacities of the motors, parameters of the lever system by this analysing method.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권1호
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• pp.60-73
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• 2014

The seaward reverse wave, occurring on the submerged dual porous horizontal plate, can contribute to the reduction of the transmitted wave as it reflects the propagating wave. However, the collision between the propagating and seaward reverse waves increases the water level and acts as a weight on the horizontal plate. This study investigated the characteristics of the wave pressure created by the seaward reverse wave through the analysis of experimental data. The analysis confirmed the following results: 1) the time series of the wave pressure showed reverse phase phenomena due to the collision, and the wave pressures acted simultaneously on both upper and lower surfaces of the horizontal plate; 2) the horizontal plate became repeatedly compressed and tensile before and after the occurrence of the seaward reverse wave; and 3) the seaward reverse wave created the total wave pressure to the maximum towards the direction of gravity, primarily on the upper plate. It was also confirmed that the wave distributions showed a similar trend to the wave steepness. Such outcome of the analysis will provide basic information to the structural analysis of the horizontal plate as a wave dissipater of the steel-type breakwater (STB).

• Korean Journal of Radiology
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• 제21권9호
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• pp.1095-1103
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• 2020

Objective: The present study aimed to investigate whether quantitative dual-energy computed tomography (DECT) parameters offer an incremental risk stratification benefit over the CT ventricular diameter ratio in patients with acute pulmonary embolism (PE) by using propensity score analysis. Materials and Methods: This study was conducted on 480 patients with acute PE who underwent CT pulmonary angiography (CTPA) or DECT pulmonary angiography (DE CT-PA). This propensity-matched study population included 240 patients with acute PE each in the CTPA and DECT groups. Altogether, 260 (54.1%) patients were men, and the mean age was 64.9 years (64.9 ± 13.5 years). The primary endpoint was all-cause death within 30 days. The Cox proportional hazards regression model was used to identify associations between CT parameters and outcomes and to identify potential predictors. Concordance (C) statistics were used to compare the prognoses between the two groups. Results: In both CTPA and DECT groups, right to left ventricle diameter ratio ≥ 1 was associated with an increased risk of all-cause death within 30 days (hazard ratio: 3.707, p < 0.001 and 5.573, p < 0.001, respectively). However, C-statistics showed no statistically significant difference between the CTPA and DECT groups for predicting death within 30 days (C-statistics: 0.759 vs. 0.819, p = 0.117). Conclusion: Quantitative measurement of lung perfusion defect volume by DECT had no added benefit over CT ventricular diameter ratio for predicting all-cause death within 30 days.