• 대한핵의학회지
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• 제21권2호
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• pp.191-197
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• 1987

39 patients with focal hepatic lesions were evaluated by $^{99m}Tc-RBC$ liver scan. The diagnosis of focal hepatic lesions were made by percutaneous needle biopsy, angiography, surgery, or clinical courses. Thses diagnoses included 24 cases of hemangioma, 7 hepatomas, 6 metastatic disease, 1 abscess, and 1 cyst. 19 hemangiomas showed focal hot activity on delayed static planar images. 3 small deep seated hemangiomas were diagnosed by SPECT that would have been missed by planar images alone. 2 large hemangiomas had no radioisotope uptake within the lesions on delayed images and at surgery cavernous hemangioma with thrombosis, calcification, and fibrosis were found. For hepatic hemangiomas in our series, the sensitivity was 91.7% and the specificity was 100%. The remaining 15 patients including hepatomas, metastatic lesions, cyst and abscess showed cold defect on delayed blood pool images. It is concluded that $^{99m}Tc-RBC$ liver scan should be the choice of primary diagnostic procecure for clinically suspected hepatic hemangioma since it's inexpensive, non-invasive, and readly available.

• Archives of Plastic Surgery
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• 제48권2호
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• pp.224-230
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• 2021

Background Little is known about the sensate recovery of skin grafts over free non-neurotized muscle flaps. The aim of this study was to evaluate the sensitivity of free gracilis muscle flaps and meshed skin grafts without nerve coaptation. Methods Thirteen consecutive patients with a median age of 55 years (range, 21-70 years) who underwent lower extremity reconstruction between September 2014 and October 2016 were included. Complications, flap contour, skin perception, and sensate recovery were assessed. Results All flaps survived completely. In one patient, wound dehiscence and infection occurred 1 month after surgery. After a median follow-up of 14 months (range, 10-51 months), a satisfactory contour and skin perception were achieved. The Semmes-Weinstein (SW) monofilament test (154.8±22 g) and static two-point discrimination (2-PD) (12.6±0.7 mm) showed intermediate recovery compared to the surrounding site (41% and 76%, respectively). There was an intermediate correlation between flap size and sensate recovery (2-PD: r=0.27, P=0.36; SW test: r=0.45, P=0.12). Vibration sensation recovered to 60%, whereas thermal sensation remained poor (19% at 5℃ and 25% at 25℃). Conclusions Finer sensation could be partially restored. However, thermal sensation remained poor.

• 대기
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• 제31권1호
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• pp.85-100
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• 2021

The necessity of accurate high-resolution meteorological forecasts becomes increasing in socio-economical applications and disaster risk management. The Korea Meteorological Administration Post-Processing (KMAPP) system has been operated to provide high-resolution meteorological forecasts of 100 m over the South Korea region. This study evaluates and improves the KMAPP performance in simulating wind speeds over complex terrain areas using the ICE-POP 2018 field campaign measurements. The mountainous measurements give a unique opportunity to evaluate the operational wind speed forecasts over the complex terrain area. The one-month wintertime forecasts revealed that the operational Local Data Assimilation and Prediction System (LDAPS) has systematic errors over the complex mountainous area, especially in deep valley areas, due to the orographic smoothing effect. The KMAPP reproduced the orographic height variation over the complex terrain area but failed to reduce the wind speed forecast errors of the LDAPS model. It even showed unreasonable values (~0.1 m s-1) for deep valley sites due to topographic overcorrection. The model's static parameters have been revised and applied to the KMAPP-Wind system, developed newly in this study, to represent the local topographic characteristics better over the region. Besides, sensitivity tests were conducted to investigate the effects of the model's physical correction methods. The KMAPP-Wind system showed better performance in predicting near-surface wind speed during the ICE-POP period than the original KMAPP version, reducing the forecast error by 21.2%. It suggests that a realistic representation of the topographic parameters is a prerequisite for the physical downscaling of near-ground wind speed over complex terrain areas.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1382-1399
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• 2023

Pressure relief valve (PRV) is one of the important control valves used in nuclear power plants, and its sealing performance is crucial to ensure the safety and function of the entire pressure system. For the sealing performance improving purpose, an explicit function that accounts for all design parameters and can accurately describe the relationship between the multi-design parameters and the seal performance is essential, which is also the challenge of the valve seal design and/or optimization work. On this basis, a surrogate model-based design optimization is carried out in this paper. To obtain the basic data required by the surrogate model, both the Finite Element Model (FEM) and the Computational Fluid Dynamics (CFD) based numerical models were successively established, and thereby both the contact stresses of valve static sealing and dynamic impact (between valve disk and nozzle) could be predicted. With these basic data, the polynomial chaos expansion (PCE) surrogate model which can not only be used for inputs-outputs relationship construction, but also produce the sensitivity of different design parameters were developed. Based on the PCE surrogate model, a new design scheme was obtained after optimization, in which the valve sealing stress is increased by 24.42% while keeping the maximum impact stress lower than 90% of the material allowable stress. The result confirms the ability and feasibility of the method proposed in this paper, and should also be suitable for performance design optimizations of control valves with similar structures.

• 문화기술의 융합
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• 제9권2호
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• pp.189-197
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• 2023

본 연구는 대학생의 창업환경, 기업가가정신 요인이 창업의도에 미치는 영향을 살펴보고자 하였다. 연구의 결과는 다음과 같다. 대학생의 창업의도에 미치는 창업환경요인들간의 상관관계는 교육환경, 법제도 및 정부지원, 사회적가치관 값들이 정적인 상관계수의 값을 가지는 것을 확인할 수 있었다. 6개의 세부 가설이 타당할 것이고 영향을 미칠 것이라고 예측하였지만 예상과 다르게 나타난 결과도 도출되었다. 첫째, 대학생의 창업환경은 창업의도에 영향을 미칠 것이라는 가설은 부분 채택됐다. 고용환경, 교육환경은 기각되었고, 법제도 및 정부지원. 사회적가치관이 창업의도에 정(+)의 영향을 미치는 것으로 확인됐다. 둘째, 대학생의 기업가정신이 창업의도에 영향을 미칠 것이라는 가설도 부분 채택됐다. 위험감수성은 기각되었으며, 혁신성, 진취성은 정(+)의 영향을 미치는 것으로 확인되었다.

• Advances in concrete construction
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• 제14권3호
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• pp.195-204
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• 2022

As a brittle failure mode, punching-shear failure can be widely found in traditional RC slab-column connections, which may lead to the entire collapse of a flat plate structure. In this paper, a novel RC slab-column connection with inner steel truss was proposed to enhance the punching strength. In the proposed connection, steel trusses, each of which was composed of four steel angles and a series of steel strips, were pre-assembled at the periphery of the column capital and behaved as transverse reinforcements. With the aim of exploring the punching behavior of this novel RC slab-column connection, a static punching test was conducted on two full-scaled RC slab specimens, and the crack patterns, failure modes, load-deflection and load-strain responses were thoroughly analyzed to explore the contribution of the applied inner steel trusses to the overall punching behavior. The test results indicated that all the test specimens suffered the typical punching-shear failure, and the higher punching strength and initial stiffness could be found in the specimen with inner steel trusses. The numerical models of tested specimens were analyzed in ABAQUS. These models were verified by comparing the results of the tests with the results of the analyzes, and subsequently the sensitivity of the punching capacity to different parameters was studied. Based on the test results, a modified critical shear crack theory, which could take the contribution of the steel trusses into account, was put forward to predict the punching strength of this novel RC slab-column connection, and the calculated results agreed well with the test results.

• Steel and Composite Structures
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• 제51권1호
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• pp.25-41
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• 2024

The measurement of pile bearing capacity is crucial for the design of pile foundations, where in-situ tests could be costly and time needed. The primary objective of this research was to investigate the potential use of fuzzy-based techniques to anticipate the maximum weight that concrete driven piles might bear. Despite the existence of several suggested designs, there is a scarcity of specialized studies on the exploration of adaptive neuro-fuzzy inference systems (ANFIS) for the estimation of pile bearing capacity. This paper presents the introduction and validation of a novel technique that integrates the fire hawk optimizer (FHO) and equilibrium optimizer (EO) with the ANFIS, referred to as ANFIS_FHO and ANFIS_EO, respectively. A comprehensive compilation of 472 static load test results for driven piles was located within the database. The recommended framework was built, validated, and tested using the training set (70%), validation set (15%), and testing set (15%) of the dataset, accordingly. Moreover, the sensitivity analysis is performed in order to determine the impact of each input on the output. The results show that ANFIS_FHO and ANFIS_EO both have amazing potential for precisely calculating pile bearing capacity. The R² values obtained for ANFIS_FHO were 0.9817, 0.9753, and 0.9823 for the training, validating, and testing phases. The findings of the examination of uncertainty showed that the ANFIS_FHO system had less uncertainty than the ANFIS_EO model. The research found that the ANFIS_FHO model provides a more satisfactory estimation of the bearing capacity of concrete driven piles when considering various performance evaluations and comparing it with existing literature.

• Coupled systems mechanics
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• 제13권4호
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• pp.293-310
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• 2024

This paper investigates the dynamic response of structures during earthquakes and provides a clear understanding of soil-structure interaction phenomena. It analyses various parameters, comprising ground shear wave velocity and structure properties. The effect of soil impedance function form on the structural response of the system through the use of springs and dashpots with two frequency cases: independent and dependent frequencies. The superstructure and the ground were modeled linearly. Using the substructure method, two different approaches are used in this study. The first is an analytical formulation based on the dynamic equilibrium of the soil-structure system modeled by an analog model with three degrees of freedom. The second is a numerical analysis generated with 2D finite element modeling using ABAQUS software. The superstructure is represented as a SDOF system in all the SSI models assessed. This analysis establishes the key parameters affecting the soil-structure interaction and their effects. The different results obtained from the analysis are compared for each studied case (frequency-independent and frequency-dependent impedance functions). The achieved results confirm the sensitivity of buildings to soil-structure interaction and highlight the various factors and effects, such as soil and structure properties, specifically the shear wave velocity, the height and mass of the structure. Excitation frequency, and the foundation anchoring height, also has a significant impact on the fundamental parameters and the response of the coupled system at the same time. On the other hand, it have been demonstrated that the impedance function forms play a critical role in the accurate evaluation of structural behavior during seismic excitation. As a result, the evaluation of SSI effects on structural response must take into account the dynamic properties of the structure and soil accordingly.

• 한국광학회지
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• 제17권1호
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• pp.94-98
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• 2006

본 논문에서는 듀얼 코어 광섬유 콜리메이터(dual-core fiber collimator)와 멤브레인형 마이크로미러를 이용한 광마이크로폰을 제안하고 구현하였다. 콜리메이터와 미러는 각각 광헤드(optical head)와 반사형 진동판으로서 사용된다. 특히, 미러 진동판은 얇은 실리콘 바(bar)에 의해 프레임에 연결되어 있어서 인가된 음압에 따라 자유롭게 움직인다. 두 개의 콜리메이터가 집적된 광헤드는 음압을 감지하고 변조하는데 사용되는 광을 공급하고 받는 역할을 한다. 이 콜리메이터 광헤드를 사용함으로써 진동판과의 초기 정렬시 기존의 광섬유를 이용한 경우에 비해 허용 오차가 클 뿐만 아니라 전체적으로 광마이크로폰의 구조도 간단해졌다. 본 논문에서는 광헤드와 진동판 사이의 거 리를 변화시켜 가면서 응답 특성을 측정하여 선형성과 민감도가 최대인 지점을 동작점으로 결정하였다. 음성신호의 주파수를 변화시켜 가면서 광마이크로폰의 출력을 측정하여 얻은 주파수 대역폭은 약 $\pm$5 dB 이하 출력 변화에 대해 약 3 kHz였다.

• Steel and Composite Structures
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• 제22권5호
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• pp.1001-1018
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• 2016

The purpose of this paper is to compare the structural responses obtained from the stochastic analysis of a suspension bridge subjected to uniform and partially correlated seismic ground motions, using different spatial correlation functions commonly used in the earthquake engineering. The spatial correlation function employed in this study consists of a term that characterizes the loss of coherency. To account for the spatial variability of ground motions, the widely used four loss of coherency models in the literature has been taken into account in this study. Because each of these models has its own characteristics, it is intended to determine the sensitivity of a suspension bridge due to these losses of coherency models which represent the spatial variability of ground motions. Bosporus Suspension Bridge connects Europe to Asia in Istanbul is selected as a numerical example. The bridge has steel towers that are flexible, inclined hangers and a steel box-deck of 1074 m main span, with side spans of 231 and 255 m on the European and Asian sides, respectively. For the ground motion the filtered white noise model is considered and applied in the vertical direction, the intensity parameter of this model is obtained by using the S16E component of Pacoima Dam record of 1971 San Fernando earthquake. An analytically simple model called as filtered white noise ground motion model is chosen to represent the earthquake ground motion. When compared with the uniform ground motion case, the results obtained from the spatial variability models with partial correlation outline the necessity to include the spatial variability of ground motions in the stochastic dynamic analysis of suspension bridges. It is observed that while the largest response values are obtained for the model proposed by Harichandran and Vanmarcke, the model proposed by Uscinski produces the smallest responses among the considered partially correlated ground motion models. The response values obtained from the uniform ground motion case are usually smaller than those of the responses obtained from the partially correlated ground motion cases. While the response values at the flexible parts of the bridge are totally dominated by the dynamic component, the pseudo-static component also has significant contributions for the response values at the rigid parts of the bridge. The results also show the consistency of the spatial variability models, which have different characteristics, considered in this study.