The Transactions of The Korean Institute of Electrical Engineers
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v.65
no.5
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pp.878-882
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2016
These days, SFCLs are being developed in order to limit fault current. However, the superconducting elements that limit the fault current have such problems as capacity increase and require auxiliary devices including cooling device. If devices that comprise the current power network can withstand fault current for at least one cycle, it is possible to limit the fault current with current limiting elements by bypassing it on the fault line. In this study, the fault current limiter was configured with current transformer, vacuum interrupter, and current limiting element. Through the experience, it was confirmed that the fault current was limited within one cycle. The superconducting element, as a current limiting element, limited the fault current by 80 % within one cycle from fault occurrence, and the passive element limited it more than 95 %. Also, through the comparison between resistance curve and power consumption curve, it was confirmed that the current limiting element using a passive element was more stable than the superconducting element that required capacity increase and other auxiliary devices. It was considered that the FCL proposed in this study could limit fault current stably within one cycle from fault occurrence by using the existing power technologies such as fault current detection and solenoid valve operating circuit.
Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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2004.11a
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pp.962-966
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2004
Ball screw feed drive systems have been broadly used in machine tools or precision automatic feed systems. Recently, modern machine tools require high speed and high precision and drive system to achieve high productivity. Unfortunately, a feed drive system, even though it was optimum designed, may experience severe transient vibrations during high-speed operation if its feed rate control is unsuitable. A rough feed rate curve having discontinuity in its acceleration profile causes a serious vibration problem in the feed slide system. This paper presents a feed rate optimization of a machine tool feed slide system, which is driven by a ball screw, for its minimum vibrations. Firstly, a 6-degree-of-freedom lumped parameter model was proposed for the vibration analysis of a ball screw driven machine tool feed drive system. Next, a feed rate optimization of the feed slide was carried out for minimum vibrations. The feed rate curve optimization strategy is to find out the most appropriate acceleration profile having finite jerk. Of course, the optimized feed rate should approximate to the desired one as possible. A genetic algorithm with variable penalty function was used in this feed rate optimization.
Bilgi, Zeynep;Batirel, Hasan Fevzi;Yildizeli, Bedrettin;Bostanci, Korkut;Lacin, Tunc;Yuksel, Mustafa
Journal of Chest Surgery
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v.50
no.4
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pp.275-280
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2017
Background: Video-assisted thoracoscopic surgery (VATS) anatomic lung resections are gradually becoming the standard surgical approach in early-stage non-small cell lung cancer (NSCLC). The technique is being applied in cases of larger tumors depending on the experience of the surgical team. The objective of this study was to compare early surgical and survival outcomes in patients undergoing anatomic pulmonary resections using VATS and thoracotomy techniques for clinical T2 NSCLC during the adaptation period of the surgical team to the VATS approach. Methods: The data of all patients who underwent anatomic pulmonary resection for NSCLC using VATS and open techniques since April 2012 were recorded to create a prospective lung cancer database. Clinical T2 NSCLC patients who underwent VATS anatomic lung resection were identified and compared with cT2 patients who underwent open resection. Results: Between April 2012 and August 2014, 269 anatomical resections for NSCLC were performed (80 VATS and 189 thoracotomy). Thirty-four VATS patients who had clinical T2 disease were identified and stage-matched to thoracotomy patients. The average tumor diameter was comparable ($34.2{\pm}11.1{\times}29.8{\pm}10.1mm$ vs. $32.3{\pm}9.8{\times}32.5{\pm}12.2mm$, p=0.4). Major complications were higher in the thoracotomy group (n=0 vs. n=5, p=0.053). There was no 30-day mortality, and the 2-year survival rate was 91% for VATS and 82% for thoracotomy patients (p=0.4). Conclusion: VATS anatomic resections in clinical T2 NSCLC tumors are safe and have perioperative and pathologic outcomes similar to those of thoracotomy, while remaining within the learning curve.
Purpose: Most stomach surgeons have been educated sufficiently in conventional open distal gastrectomy (ODG) but insufficiently in laparoscopy-assisted distal gastrectomy (LADG). We compared learning curves and clinical outcomes between ODG and LADG by a single surgeon who had sufficient education of ODG and insufficient education of LADG. Materials and Methods: ODG (90 patients, January through September, 2004) and LADG groups (90 patients, June 2006 to June 2007) were compared. The learning curve was assessed with the mean number of retrieved lymph nodes, operation time, and postoperative morbidity/mortality. Results: Mean operation time was 168.3 minutes for ODG and 183.6 minutes for LADG. The mean number of retrieved lymph nodes was 37.9. Up to about the 20th to 25th cases, the slope decrease in the learning curve for LADG was more apparent than for ODG, although they both reached plateaus after the 50th cases. The mean number of retrieved lymph nodes reached the overall mean after the 30th and 40th cases for ODG and LADG, respectively. For ODG, complications were evenly distributed throughout the subgroups, whereas for LADG, complications occurred in 10 (33.3%) of the first 30 cases. Conclusions: Compared with conventional ODG, LADG is feasible, in particular for a surgeon who has had much experience with conventional ODG, although LADG required more operative time, slightly more time to get adequately retrieved lymph nodes and more complications. However, there were more minor problems in the first 30 LADG than ODG cases. The unfavorable results for LADG can be overcome easily through an adequate training program for LADG.
Purpose : The purpose of this study was to investigate subjective symptoms according to the wearing, purchase and fitting status of soft contact lens wearers, and consumer perception of base curve. Methods : A survey was conducted for those who visited optical shops and lens shops in Seoul from June to August 2018. A total of 98 answer sheets they submitted were used for the analysis. The chi-square test and Fisher's exact test were used to compare subjective symptoms (dryness, glare, uncomfortable fitting, and decreased vision) according to whether fitting condition is screened (case history and push-up test, ect relevant to wearing sensation), and the odds ratio (OR) was obtained by the logistic regression analysis. Results : When the contact lenses were purchased, the rate of which the visual acuity test was performed was 86.6% at optical shop and 64.7% at lens shop. When purchasing contact lens and the contact lens was not tested for fitting, they more experienced dryness (OR 4.41, 95% CI 1.25-15.62) and uncomfortable fitting (OR 2.68, 95% CI 1.08-6.64) than testing for fitting. In addition, it was investigated that 87.8% of contact lens wearers did not know about the term base curve, 92.9% did not listen to an explanation related to the base curve when purchasing contact lenses, and 96.9% did not experience with base curve test. Conclusion : It would be thought that satisfaction of the contact lens fitting of existing consumers should be improved by changing a proper base curve by confirming the fitting condition when prescribing soft contact lens.
Yu, Woo Sik;Lee, Chang Young;Lee, Seokkee;Kim, Do Jung;Chung, Kyung Young
Journal of Chest Surgery
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v.48
no.2
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pp.105-111
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2015
Background: The aim of this study was to establish whether pulmonary lobectomy using video-assisted thoracic surgery (VATS) can be safely performed by trainees with limited experience with open lobectomy. Methods: Data were retrospectively collected from 251 patients who underwent VATS lobectomy at a single institution between October 2007 and April 2011. The surgical outcomes of the procedures that were performed by three trainee surgeons were compared to the outcomes of procedures performed by a surgeon who had performed more than 150 VATS lobectomies. The cumulative failure graph of each trainee was used for quality assessment and learning curve analysis. Results: The surgery time, estimated blood loss, final pathologic stage, thoracotomy conversion rate, chest tube duration, duration of hospital stay, complication rate, and mortality rate were comparable between the expert surgeon and each trainee. Cumulative failure graphs showed that the performance of each trainee was acceptable and that all trainees reached proficiency in performing VATS lobectomy after 40 cases. Conclusion: This study shows that trainees with limited experience with open lobectomy can safely learn to perform VATS lobectomy for the treatment of lung cancer under expert supervision without compromising outcomes.
The Commercial space are changed gradually large scalized and complexed to introduce different culture exchanges and experience. However, the mass-complex commercial space are limited as of their complexed space composition or degree of space depth, which may become factors causing people to get tired easily. Thus, having a design strategy is important to create economical effectiveness in order to overcome these limitations and for the people to stay longer and do their consumption activities through more experiences and social interchanges. Recently, Jerde Partnership's who designed many complex commercial spaces made a commercial success by their unique design strategy to setup a new space and lead the interaction between space and people. The purpose of this study is based on Jerd's design concept to analyze Jerd Partnership's design strategy and space related structure to propose their space construction and design method for mass-complex commercial spaces. The results are as follows. (1)Jerde Partnership's causes the abundant space experience of the user through mass and space constitution to have a theme and a story. (2)They builds an excursion type line of flow system with an organic curve, and a non-daily experience by the change of the space scale and the application of various programs is enabled and guides the stay for the long time. (3)They builds the doorway of various courses and a circulation system through the open space and controls depth of the space. In addition, various events are performed in the center of such a circulation system, and this event makes a unique place.
Kim, Tae-Young;Choi, Jin-Woo;Lee, Sam-Sun;Huh, Kyung-Hoe;Yi, Won-Jin;Heo, Min-Suk;Choi, Soon-Chul
Imaging Science in Dentistry
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v.41
no.1
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pp.11-16
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2011
Purpose : The aim of this study was to evaluate the effect of liquid crystal display (LCD) monitor type and observer experience on the diagnostic performance in soft-copy interpretations of maxillary sinus inflammatory lesions on panoramic radiographs. Materials and Methods : Ninety maxillary sinuses on panoramic images were grouped into negative and positive groups according to the presence of inflammatory lesions, using CT for confirmation. Monochrome and color LCDs were used. Six observers participated and ROC analysis was performed to evaluate the diagnostic performance. The reading time, fatigue score, and inter-/intra-observer agreements were assessed. Results : The interpretation of maxillary sinus inflammatory lesions was affected by the LCD monitor type used and by the experience of the observer. The reading time was not significantly different, however the fatigue score was significantly different between two LCD monitors. Inter-observer agreement was relatively good in experienced observers, while the intra-observer agreement for all observers was good with monochrome LCD but not with color LCD. Conclusion : The less experienced observers showed lowered diagnostic ability with a general color LCD.
The purpose of this study was to analyze the financial status of Korean elderly households to make a financial plan for retirement preparation. The sample obtained from 1997 KHPS, consisted of 326 households of 55-64 aged and 210 households of 65 and over aged. Statistics employed for the analysis were frequencies, percentile, univariate analysis and logistic analysis. And Lorenz curve and Gini coefficient were used to compare the financial status. The results could be summarized as follows. First, total income, total expenditure, total debt and net worth of 55-64 aged group were higher than those of 65 and over group, while total asset of 55-64 aged group was similar to 65 and over group's Second, total expediture to total imcome ratio(R1) and total asset to total debt ratio(R4) of 55-64 aged group were higher than 65 and over group's, but net worth to minimum cost of living ratio(R2) and financial asset to monthly expenditure ratio(R3) of 65 and over group were higher than 55-64 aged group's . Third, R4's Gini coefficient was the highest and R1's Gini coefficient was the lowest among all Gini coefficients. Also, R1's and R4's Gini coefficients of 55-64 aged group were greater than 65 and over group's. ourth, variables affecting R1's stability of 55-64 aged group were household head's age, educatonal attainment and family type, while those of 65 and over group were household head's age, past economic experience and the number of children. There was no significant variable affecting R2's stability of 55-64 aged group, but there was only household head's pst economic experience affecting those of 65 and over group. The variable contributing to R3's stability of 55-64 aged group was residence while the variables of 65 and over group were household head's educational attainment, past economic experience and the number of children. The variables contributing to R4's stability of 55-64 aged group were the number of children and residence, and the number of children was one variable of contributing to R4's stability of 65 and over aged group.
Hyoung Suk Park;Kiwan Jeon;Yeon Jin Cho;Se Woo Kim;Seul Bi Lee;Gayoung Choi;Seunghyun Lee;Young Hun Choi;Jung-Eun Cheon;Woo Sun Kim;Young Jin Ryu;Jae-Yeon Hwang
Korean Journal of Radiology
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v.22
no.4
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pp.612-623
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2021
Objective: To evaluate the diagnostic performance of a deep learning algorithm for the automated detection of developmental dysplasia of the hip (DDH) on anteroposterior (AP) radiographs. Materials and Methods: Of 2601 hip AP radiographs, 5076 cropped unilateral hip joint images were used to construct a dataset that was further divided into training (80%), validation (10%), or test sets (10%). Three radiologists were asked to label the hip images as normal or DDH. To investigate the diagnostic performance of the deep learning algorithm, we calculated the receiver operating characteristics (ROC), precision-recall curve (PRC) plots, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) and compared them with the performance of radiologists with different levels of experience. Results: The area under the ROC plot generated by the deep learning algorithm and radiologists was 0.988 and 0.988-0.919, respectively. The area under the PRC plot generated by the deep learning algorithm and radiologists was 0.973 and 0.618-0.958, respectively. The sensitivity, specificity, PPV, and NPV of the proposed deep learning algorithm were 98.0, 98.1, 84.5, and 99.8%, respectively. There was no significant difference in the diagnosis of DDH by the algorithm and the radiologist with experience in pediatric radiology (p = 0.180). However, the proposed model showed higher sensitivity, specificity, and PPV, compared to the radiologist without experience in pediatric radiology (p < 0.001). Conclusion: The proposed deep learning algorithm provided an accurate diagnosis of DDH on hip radiographs, which was comparable to the diagnosis by an experienced radiologist.
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