• Journal of Yeungnam Medical Science
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• v.41 no.3
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• pp.213-219
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• 2024

Background: Aortic valve replacement (AVR) has recently been performed at many centers using a minimally invasive approach to reduce postoperative mortality, morbidity, and pain. Most previous reports on minimally invasive AVR (MiAVR) have mainly focused on aortic stenosis, and those exclusively dealing with aortic regurgitation (AR) are few. The purpose of this study was to investigate early surgical results and review our experience with patients with chronic severe AR who underwent AVR via right anterior mini-thoracotomy (RAT). Methods: Data were retrospectively collected in this single-center study. Eight patients who underwent RAT AVR between January 2020 and January 2024 were enrolled. Short-term outcomes, including the length of hospital stay, in-hospital mortality, postoperative complications, and echocardiographic data, were analyzed. Results: No in-hospital mortalities were observed. Postoperative atrial fibrillation occurred temporarily in three patients (37.5%). However, none required permanent pacemaker implantation or renal replacement therapy. The median values of ventilator time, length of intensive care unit stay, and hospital stay were 17 hours, 34.5 hours, and 9 days, respectively. Preoperative and postoperative measurements of left ventricular ejection fraction were similar. However, the left ventricular end systolic and diastolic diameters significantly decreased postoperatively from 42 mm to 35.5 mm (p=0.018) and 63 mm to 51 mm (p=0.012), respectively. Conclusion: MiAVR via RAT is a safe and reproducible procedure with acceptable morbidity and complication rates in patients with chronic severe AR. Despite some limitations such as a narrow surgical field and demanding learning curve, MiAVR is a competent method for AR.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.4
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• pp.379-384
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• 1999

In this paper, we present a new time-varying sliding surface to achieve fast and robust tracking of higher-order uncertain systems. The surface passes through an initial error, and afterwards, it moves towards a predetermined target surface by means of a variable named by sliding surface gain and its intercept. Specifically, the sliding surface gain is determined so that its initial value can minimize a shifting distance of the surface and that the system roots in sliding mode can follow certain stable trajectories. The designed sliding mode control forces the system errors to stay always on the proposed surface from the beginning. By this means, the system remains insensitive to system uncertainties and disturbances for the whole time. To illustrate the effectiveness of the proposed method, the comparative study with conventional time-invariant sliding mode control is performed.

• Journal of Korean Institute of Industrial Engineers
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• v.34 no.3
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• pp.296-307
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• 2008

A semiconductor production system has sophisticated manufacturing operations and needs high capital investment for its expensive equipment, which warrants efficient real-time flow control for wafers. In the bay, we consider material handling equipment that can handle multiple carriers of wafers. The dispatching logic first determines the transportation time of each carrier to its destination by each unit of transportation equipment and uses this information to determine the destination machine and target carrier. When there is no available buffer space at the machine tool, the logic allows carriers to stay at the buffer of a machine tool and determine the delay time, which is used to determine the destination of carriers in URL. A simulation study shows this dispatching logic performs better than the procedure currently in use to reduce the mean flow time and average WIP of wafers and increase efficiency of material handling equipment.

• Journal of Digital Convergence
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• v.12 no.8
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• pp.377-387
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• 2014

The purpose of this study is to suggest improvement ways of outpatient process via a simulation model and to improve operational efficiency. Three experimentation scenarios were implemented into the simulation model to determine which proposed scenario provides better improvement in terms of the following performance measures: LOS(Length of Stay), patient waiting time, patient travel time, and staff utilization. The hospital medical data collection and statistical tools used to analyze the process mining tools. And the PIOS simulation tool was used and the validity of the model was verified by using t-test. The simulation results demonstrated that oupatient process of center type is most efficient. Simulation approach is a powerful technique that supports efficient decision-making compared to traditional healthcare management approach based on past experience, feelings, and intuition. Therefore, the proposed experimentation model has wide applicability in healthcare systems.

• Korean Institute of Interior Design Journal
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• v.22 no.6
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• pp.212-219
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• 2013

This study uses a fashion shop facade design to track human gaze, find gaze frequency for gaze time for the gaze points along the path of sight, and expose the importance of facade design and figure out the value through theoretical systematization. Thus, this study employed the measurement method in physiological psychology which is sight-tracking device with eye-tracking to perform effective data evaluation. To find gaze frequency and study the contents to reflect on the facade, precedent study review, and case study of facade design to collect stimulants to be used in eye-tracking experiment were executed. And the eye-tracking experiment which traces the movement of eye[pupil] was performed. As the result of analyzing gaze frequency, The characteristics of such gaze path formation made the characteristics for gaze frequency even clearer. What was characteristic in the analysis result according to 'average value for gaze time' was that only 8 out of 2000 areas showed over 1 second of frequency and, and all other shoed less than 1 second of gaze time. This indicates that human sight endlessly jumps around, and that it 'Stay' where it has interest. This study found the average of the frequency of this 'Stay' in facade design. This study well presents the major points to add value to the design of the space of facade based on scientific measurement/analysis data obtained through visual understanding. Through such, this study is thought to be able to have a positive interaction with marketing by forming a theoretical background bringing utility to purchase environment and assisting in sales increase.

• Journal of Gastric Cancer
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• v.15 no.3
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• pp.151-158
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• 2015

Purpose: Obesity is associated with morbidity following gastric cancer surgery, but whether obesity influences morbidity after laparoscopic gastrectomy (LG) remains controversial. The present study evaluated whether body mass index (BMI) and visceral fat area (VFA) predict postoperative complications. Materials and Methods: A total of 217 consecutive patients who had undergone LG for gastric cancer between May 2003 and December 2005 were included in the present study. We divided the patients into two groups ('before learning curve' and 'after learning curve') based on the learning curve effect of the surgeon. Each of these groups was sub-classified according to BMI (<$25kg/m^2$ and ${\geq}25kg/m^2$) and VFA (<$100cm^2$ and ${\geq}100cm^2$). Surgical outcomes, including operative time, quantity of blood loss, and postoperative complications, were compared between BMI and VFA subgroups. Results: The mean operative time, length of hospital stay, and complication rate were significantly higher in the before learning curve group than in the after learning curve group. In the subgroup analysis, complication rate and length of hospital stay did not differ according to BMI or VFA; however, for the before learning curve group, mean operative time and blood loss were significantly higher in the high VFA subgroup than in the low VFA subgroup (P=0.047 and P=0.028, respectively). Conclusions: VFA may be a better predictive marker than BMI for selecting candidates for LG, which may help to get a better surgical outcome for inexperienced surgeons.

• Journal of Gastric Cancer
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• v.13 no.4
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• pp.255-262
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• 2013

Purpose: Robotic surgery for gastric cancer is a promising alternative to laparoscopic surgery, but the data are limited. We aimed to evaluate whether gaining experience in robotic gastrectomy could improve surgical outcomes in the treatment of gastric cancer. Materials and Methods: Two hundred and seven consecutive cases of patients with clinical stage I gastric cancer who underwent robotic surgery at the National Cancer Center of Korea between February 2009 and February 2012 were retrospectively reviewed. Surgical outcomes were analyzed and compared between the initial 100 and later 100 cases. Results: Seven patients required conversion to open surgery and were excluded from further analysis. The mean operating time for all patients was 248.8 minutes, and mean length of hospitalization was 8.0 days. Twenty patients developed postoperative complications. Thirteen were managed conservatively, while 6 had major complications requiring invasive procedures. One mortality occurred owing to myocardial infarction. Operating time was significantly shorter in the latter 100 cases than in the initial 100 cases (269.9 versus 233.5 minutes, P<0.001). The number of retrieved lymph nodes was significantly greater in the latter cases (35.9 versus 39.9, P=0.032). The hospital stay of patients with complications was significantly longer in the initial cases than in the latter cases (16 versus 7 days, P=0.005). Conclusions: Increased experience with the robotic procedure for gastric cancer was associated with improved outcomes, especially in operating time, lymph node retrieval, and shortened hospital stay of complicated patients. Further development of surgical techniques and technology might enhance the role of robotic surgery for gastric cancer.

• Quality Improvement in Health Care
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• v.8 no.1
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• pp.74-83
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• 2001

Background : Since a Gamma Knife had been installed on December 1997, 405 patients have been treated until December 1999 at department of neurosurgery of Seoul National University hospital. The authors analyzed results of a work to improve satisfaction of Gamma Knife surgery patients and to reduce hospital length of stay. Methods : To understand main discontent of patients, a pre-survey was performed from October 1998 to December 1999 using a questionnaire. By Analyzing 93 questionnaire received from 234 patients, pain on frame application, explanation before surgery, waiting time before surgery, waiting time before medical procedure were main discontent factor and overall satisfaction ratio was 71.0%. To improve satisfaction ratio, several quality improvement activity works were designed and applied to 123 patients during the period between January 2000 and September 2000. The same questionnaire were analyzed. Works to reduce the patient hospital LOS were devised and applied during the same period. Results : The overall satisfaction ratio of Gamma Knife radiosurgery patients was increased to 83.7%(P=0.10). The main factor to improve satisfaction ratio was to reduce waiting time(P=0.05) and improvement of discomfort during the surgery(P=0.06). The average LOS was reduced from 3.1 to 2.7 days(P=0.003). Conclusion : As a result of quality assurance activities, the overall satisfaction ratio of patients was improved and LOS was reduced. The pain during frame application was remained as a main discontent factor and a further study is required to reduce this pain.

• Advances in pediatric surgery
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• v.13 no.1
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• pp.52-60
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• 2007

Pediatric laparoscopic appendectomy is controversial particularly in complicated appendicitis. We evaluated the outcomes of laparoscopic appendectomy (LA) and open appendectomy (OA) in simple appendicitis and complicated appendicitis respectively. Since June 2004, initial LA has been our policy in all appendicitis including complicated ones. A total of 160 patients were included in this study, consisting of 80 OA (August 2001 - August 2003) and 80 LA (June 2004 - June 2006). We compared the operating time, the length of hospital stay, the length of antibiotics use, and the postoperative complications between LA and OA. In simple appendicitis (73), there were no differences between LA and OA. However in the 87 patients with complicated appendicitis, the operating time was longer in LA (64.8 min vs. 50.2 min) but the length of hospital stay was shorter in LA than OA (8.5 days vs. 9.6 days). There was one complication in simple appendicitis group and six in complicated appendicitis group (3 cases in LA, 3 cases in OA). There was no difference in the results of LA versus OA in simple appendicitis. Therefore for simple appendicitis, LA is recommended in consideration of the cosmetic effect (fewer scar). In complicated appendicitis, early discharge was an advantage and there were no differences in complications in LA despite a longer operative time. So we conclude LA can be considered as the first choice of treatment for all pediatric appendicitis including complicated appendicitis. To confirm our impressions, more well controlled randomized prospective studied need to be done.

• Journal of Families and Better Life
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• v.29 no.2
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• pp.73-87
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• 2011

The purpose of this study is to investigate the influence of children's socia-demographic variables(i.e., gender, birth order, and the amount of time staying in kindergarten) on, leadership, self-regulation and children's peer play behaviors. The participants of this study are 336 children aged between five and seven in four classes in a private kindergarten and eight classes in a private preschool located in the capital region. The results revealed that, girls showed more leadership, self-regulation, and play interaction section than boys: whereas, boys showed higher response in play disruption and the lack of play disconnection. However, birth order, did not have a significant effect on the sub-domain of leadership, self-regulation competence, and peer play behaviors. As for the duration children stay in preschool or in preschool or kindergarten, children who spend half-day showed higher reaction in behavioral self-control and emotional taking abilities than children who stay in the preschool or kindergarten full day. On the other hand, self-esteem of full-time children was higher than half-time children. Children who were emotionally sensitive, knew how to lead their peer group, and those who were sociable and self-regulated presented to be more active in peer-interaction than others. Second, as the result of the correlation analysis reveals, children's leadership, self-regulation competence, peer play behaviors, and play interaction had a meaningful effect on the sub-variations of children's leadership and self-regulation and they showed significant influence upon play disruption and play disconnection. In addition, girls who were not able to manage or to inspect their behavior and had insensitive emotion demonstrated higher tendency to play disconnected. Children, who participated in full-day program with having difficulties in self-regulation or inspecting their behavior properly but had a strong leadership and insensitive showed play disruption highly.