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Search Results: 1 - 10 of 7296 matches for " Won Suk Choi "
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Rolling Fatigue Test of Large-Sized UHPC Member for Cable Stayed Bridge  [PDF]
Jeong-Rae Cho, Young Jin Kim, Jong Sup Park, Eun Suk Choi, Won Jong Chin
Engineering (ENG) , 2012, DOI: 10.4236/eng.2012.410082
Abstract: Recently, research strives to apply Ultra High Performance Concrete (UHPC) to large-sized structures owing to its remarkable mechanical performance and durability compared to normal concrete. The Korea Institute of Construction Technology proposed SuperBridge800, an edge girder type UHPC cable stayed bridge with central span of 800 m, through its detailed design. The bridge is designed to be erected through the connection of precast UHPC segments. The precast UHPC segment is monolithically composed of one ribbed deck slab and edge girders at each side. The connection between the precast segments is achieved by steel bars at the edge girders and by UHPC cast-in-place wet joint at the slab. Despite of the outstanding mechanical performance of UHPC, the fabrication of large-sized members is a difficult task since UHPC hardens faster than normal concrete and requires a special curing process. Therefore, the constructability of large-sized UHPC segment should be secured to achieve SuperBridge800. Besides, the performance of the connection between segments should also be guaranteed, especially in terms of the fatigue performance of the UHPC cast-in-place joint, which constitutes a weak point. To that goal, two half-scaled UHPC segments are manufactured and the constructability is examined by fabricating a large-sized UHPC member connected with respect to the design conditions. This study conducts rolling fatigue test on the so-fabricated large-sized UHPC member. Rolling fatigue test is carried out up to 2 million cycles considering actual vehicle load at each center and quarter points of the member. The test results confirm that the service limit state is satisfied.
A Study on the Bond Strength between High Performance Concrete and Reinforcing Bar  [PDF]
Eun Suk Choi, Jung Woo Lee, Seong Jun Kim, Jong Won Kwark
Engineering (ENG) , 2015, DOI: 10.4236/eng.2015.77033
Abstract: As a preliminary study for the erection of floating structures using high performance concrete, this paper examines the bond characteristics between concrete and the reinforcing bar. Since the floating structure is constructed in aquatic environment, corrosion of the reinforcing steel is likely to develop more prematurely than in onshore structure in case of concrete cracking. A solution to this corrosion problem could use FRP rebar instead of steel reinforcement. To that goal, an experimental study is conducted on the concrete-FRP bond strength to verify if such FRP rebar develops performance comparable to the conventional steel rebar. A series of tests are performed considering the bond length of ordinary steel rebar and G-FRP rebar as test variable with respect to the strength of concrete, and the results are presented.
Noise Reduction in Brainwaves by Using Both EEG Signals and Frontal Viewing Camera Images
Jae Won Bang,Jong-Suk Choi,Kang Ryoung Park
Sensors , 2013, DOI: 10.3390/s130506272
Abstract: Electroencephalogram (EEG)-based brain-computer interfaces (BCIs) have been used in various applications, including human–computer interfaces, diagnosis of brain diseases, and measurement of cognitive status. However, EEG signals can be contaminated with noise caused by user’s head movements. Therefore, we propose a new method that combines an EEG acquisition device and a frontal viewing camera to isolate and exclude the sections of EEG data containing these noises. This method is novel in the following three ways. First, we compare the accuracies of detecting head movements based on the features of EEG signals in the frequency and time domains and on the motion features of images captured by the frontal viewing camera. Second, the features of EEG signals in the frequency domain and the motion features captured by the frontal viewing camera are selected as optimal ones. The dimension reduction of the features and feature selection are performed using linear discriminant analysis. Third, the combined features are used as inputs to support vector machine (SVM), which improves the accuracy in detecting head movements. The experimental results show that the proposed method can detect head movements with an average error rate of approximately 3.22%, which is smaller than that of other methods.
Determination of Correction Factors for Small Field Based on Measurement and Numerical Calculation using Cylindrical Ionization Chambers
Kwangwoo Park,Wonhoon Choi,Sungho Park,Jin Hwa Choi,Suk Won Park,Jino Bak
Physics , 2015,
Abstract: We studied the investigation of volume averaging effect for air-filled cylindrical ionization chambers to determine correction factors in small photon field for the given chamber. As a method, we measured output factors using several cylindrical ionization chambers and calculated with mathematical method similar to deconvolution in which we modeled non-constant and inhomogeneous exposure function in the cavity of chamber. The parameters in exposure function and correction factors were determined by solving a system of equations we developed with measurement data and geometry of the given chamber. Correction factors (CFs) we had found are very similar to that from Monte Carlo (MC) simulation. For example, CFs in this study were computed as 1.116 for PTW31010, and 1.0225 for PTW31016, while CFs from MC were reported as approximately between 1.17 and 1.20 for PTW31010, and between 1.02 and 1.06 for PTW31016 in of 6MV photon beam . Furthermore, the result from the method of deconvolution combined with MC for chamber response function, also showed similar CF for PTW 30013, which was reported as 2.29 and 1.54 in and filed size respectively. The CFs from our method provided similarly as 2.42 and 1.54. In addition, we reported CFs for PTW30013, PTW31010, PTW31016, IBA FC23-C, and IBA CC13. As a consequence, we suggested a newly developed method to measure correct output factor using the fact that inhomogeneous exposure, force a volume averaging effect in a cavity of air filled cylindrical ionization chamber. The result from this method is very similar to that from MC simulation. The method we developed can easily be applied to clinic.
Fault Diagnosis System of Induction Motors Based on Neural Network and Genetic Algorithm Using Stator Current Signals
Tian Han,Bo-Suk Yang,Won-Ho Choi,Jae-Sik Kim
International Journal of Rotating Machinery , 2006, DOI: 10.1155/ijrm/2006/61690
Abstract: This paper proposes an online fault diagnosis system for induction motors through the combination of discrete wavelet transform (DWT), feature extraction, genetic algorithm (GA), and neural network (ANN) techniques. The wavelet transform improves the signal-to-noise ratio during a preprocessing. Features are extracted from motor stator current, while reducing data transfers and making online application available. GA is used to select the most significant features from the whole feature database and optimize the ANN structure parameter. Optimized ANN is trained and tested by the selected features of the measurement data of stator current. The combination of advanced techniques reduces the learning time and increases the diagnosis accuracy. The efficiency of the proposed system is demonstrated through motor faults of electrical and mechanical origins on the induction motors. The results of the test indicate that the proposed system is promising for the real-time application.
Enhanced Perception of User Intention by Combining EEG and Gaze-Tracking for Brain-Computer Interfaces (BCIs)
Jong-Suk Choi,Jae Won Bang,Kang Ryoung Park,Mincheol Whang
Sensors , 2013, DOI: 10.3390/s130303454
Abstract: Speller UI systems tend to be less accurate because of individual variation and the noise of EEG signals. Therefore, we propose a new method to combine the EEG signals and gaze-tracking. This research is novel in the following four aspects. First, two wearable devices are combined to simultaneously measure both the EEG signal and the gaze position. Second, the speller UI system usually has a 6 × 6 matrix of alphanumeric characters, which has disadvantage in that the number of characters is limited to 36. Thus, a 12 × 12 matrix that includes 144 characters is used. Third, in order to reduce the highlighting time of each of the 12 × 12 rows and columns, only the three rows and three columns (which are determined on the basis of the 3 × 3 area centered on the user’s gaze position) are highlighted. Fourth, by analyzing the P300 EEG signal that is obtained only when each of the 3 × 3 rows and columns is highlighted, the accuracy of selecting the correct character is enhanced. The experimental results showed that the accuracy of proposed method was higher than the other methods.
A Pathogenic Potential of Acinetobacter baumannii-Derived Membrane Vesicles
Jong Suk Jin,Dong Chan Moon,Chi-Won Choi,Seung-Il Kim
Journal of Analytical Science & Technology , 2011,
Abstract: Acinetobacter baumannii secretes outer membrane vesicles (OMVs). A. baumannii OMVs deliver many virulence factors to host cells and then induce cytotoxicity and innate immune response. OMVs secreted from bacteria contribute directly to host pathology during A. baumannii infection.
Study on the Demodulation Structure of Reader Receiver in a Passive RFID Environment
Ji-Hoon Bae;Won-Kyu Choi;Jeong-seok Kim;Gil-Young Choi;Jong-Suk Chae
PIER , 2009, DOI: 10.2528/PIER09021103
Abstract: In this paper, we present a demodulation structure suitable for a reader receiver in a passive Radio Frequency IDentification (RFID) environment. In a passive RFID configuration, undesirable DC-offset phenomenon may appear in the baseband of the reader receiver. As a result, this DC-offset phenomenon can severely degrade the performance of the extraction of valid information from a received signal in the reader receiver. To mitigate the DC-offset phenomenon, we propose a demodulation structure to reconstruct a corrupted signal with the DC-offset phenomenon, by extracting useful transition information from the corrupted signal. It is shown that the proposed method can successfully detect valid data from a received signal, even when the received baseband signal is distorted with the DC-offset phenomenon.
Real-Time Imaging of the Epithelial-Mesenchymal Transition Using microRNA-200a Sequence-Based Molecular Beacon-Conjugated Magnetic Nanoparticles
YoonSeok Choi, Hoe Suk Kim, Jisu Woo, Eun Hye Hwang, Kyoung-Won Cho, Soonhag Kim, Woo Kyung Moon
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0102164
Abstract: The epithelial-mesenchymal transition (EMT) plays important roles in tumor progression to metastasis. Thus, the development of an imaging probe that can monitor transient periods of the EMT process in live cells is required for a better understanding of metastatic process. Inspired by the fact that the mRNA expression levels of zinc finger E-box-binding homeobox 1 (ZEB1) increase when cells adopt mesenchyme characteristics and that microRNA-200a (miR-200a) can bind to ZEB1 mRNA, we conjugated molecular beacon (MB) mimicking mature miR-200a to magnetic nanoparticles (miR-200a-MB-MNPs) and devised an imaging method to observe transitional changes in the cells during EMT. Transforming growth factor-β1 treated epithelial cells and breast cancer cell lines representing both epithelial and mesenchymal phenotypes were used for the validation of miR-200a-MB-MNPs as an EMT imaging probe. The real-time imaging of live cells acquired with the induction of EMT revealed an increase in fluorescence signals by miR-200a-MB-MNPs, cell morphology alterations, and the loss of cell-cell adhesion. Our results suggest that miR-200a-MB-MNPs can be used as an imaging probe for the real-time monitoring of the EMT process in live cells.
A Surgeon’s Perspective of Abdominal Wall Endometriosis at a Caesarean Section Incision: Nine Cases in a Single Institution
Eun Mee Oh,Won-Suk Lee,Jin Mo Kang,Sang Tae Choi,Keon Kuk Kim,Woon Kee Lee
Surgery Research and Practice , 2014, DOI: 10.1155/2014/765372
Abstract: Abdominal wall endometriosis in a Caesarean section scar (AEC) is an infrequent type of extrapelvic endometriosis which rarely transforms into a malignant lesion. A painful mass located in the scar of a Caesarean section is a typical sign of AEC. This condition is diagnosed preoperatively using imaging modalities such as computed tomography and ultrasonography, as well as fine-needle aspiration. Although AEC has typical signs, general surgeons often misdiagnose it due to its rarity. Herein, we report our experience of AEC in a single institution. 1. Introduction Extrapelvic endometriosis, an uncommon form of the disease, can affect unusual sites including the urinary tract, gastrointestinal tract, and thorax. The incidence of abdominal wall endometriosis in a previous Caesarean section (C/S) scar has been reported at ~1-2% in patients undergoing lower abdominal surgery [1]. Despite its rarity, several reports on abdominal wall endometriosis in a Caesarean section scar (AEC) have been published. A tender and painful abdominal wall mass is considered suggestive of AEC in females of reproductive age with a previous history of C/S [1, 2]. Imaging studies including ultrasonography (USG) and computed tomography (CT) can aid the diagnosis of AEC; however, the condition is often misdiagnosed and referred to general surgeons [3]. Herein, we report nine cases of AEC from the perspective of a general surgeon. 2. Case Report The study data were gathered from the electronic medical records from the period 2002 to 2013, during which a total of nine cases of AEC were confirmed histologically. Among them, six female patients presented to general surgeons and the remaining three visited a gynaecology clinic due to their chief complaint. Nine clinicians, including three gynaecologists and six general surgeons, evaluated and treated these nine patients. All patients were premenopausal and between 29 and 40 years of age. Five patients had undergone C/S twice and the remaining four patients had had one C/S. One of the patients had a history of preeclampsia and the other eight had no notable obstetric or gynaecologic history. Pfannenstiel skin incisions and tender masses were found in the previous C/S scars of all patients. In four of the patients, menstruation was associated with tenderness in the C/S scar. The duration of clinical symptoms varied from 3 months to 3 years. Computed tomography (CT) was used in five patients and ultrasonography (USG) was used in three patients to evaluate the lesions. No imaging was used in the remaining patient, but the first impression of
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