• Journal of the Korean Institute of Gas
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• v.16 no.6
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• pp.128-135
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• 2012

In this paper, we proposed a system and a scenario to raise efficiency of gas safety management by developing wireless ZigBee communication modules, smart-home gas safety appliances and the system suitable for gas safety. Our designed system consists of a micom gas meter, an automatic extinguisher, sensors, and a wall-pad. A micom-gas-meter monitors gas flow, gas pressure, and earthquake. An automatic fire extinguisher checks combustible gas leaks and temperature of $100^{\circ}C$(cut off) and $130^{\circ}C$(fire). Sensors measure smoke and CO gas. In our novel system, a micom-gas meter cut off inner valve with warnings, an automatic fire extinguisher cut off middle valve and spray extinguishing materials, and sensors generate signals when detecting smoke and CO and then take a next action. Gas safety appliances and sensors automatically takes measures, and transmit those information to a wall-pad. The wall-pad again transmits real time information to server. Users can check and manage gas safety situations by connecting BcN server through web or mobile application. We hereby devised scenarios for gas safety and risk management based on the smart, and demonstrated their efficiency through test applied to filed.

• Journal of Chest Surgery
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• v.46 no.2
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• pp.104-110
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• 2013

Background: We reviewed the long-term outcomes of aortic root replacement at Asan Medical Center and investigated the predictors affecting mortality. Materials and Methods: A retrospective analysis was performed on 225 consecutive adult patients undergoing aortic root replacement with mechanical conduits (n=169), porcine aortic root prosthesis (n=23), or aortic homografts (n=33) from January 1992 to September 2009. The median follow-up duration was 6.1 years (range, 0 to 18.0 years). Results: The porcine root group was older than the other groups (freestyle $55.9{\pm}14.3$ years vs. mechanical $46.3{\pm}14.6$ years, homograft $48.1{\pm}14.7$ years; p=0.02). The mechanical group had the highest incidence of the Marfan syndrome (mechanical 22%, freestyle 4%, homograft 3%; p=0.01). Surgery performed for infective endocarditis was more frequent in the homograft group (mechanical 10%, freestyle 10%, homograft 40%; p<0.001). The overall 30-day mortality was 5.3% (12/225). Actuarial survival rates in the mechanical, porcine root, and homograft groups were 79.4%, 81.5%, and 83.5% at 5 years and 67%, 61.9%, and 61.1% at 10 years, respectively (p=0.73). By multivariate analysis, preoperative diabetes mellitus, older age, and longer cardiopulmonary bypass time were independent predictors of mortality. Incidence of postoperative complications, including infective endocarditis and thromboembolism were comparable in all of the groups. Conclusion: Aortic root replacement can be safely performed with different types of prostheses as the outcome was not affected by the choice of prosthesis. Further studies are required to assess the long-term durability of biological prostheses.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.3
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• pp.13-20
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• 2011

In this paper, we proposed a system to raise gas safety management by using the wireless communication module and intelligent gas safety appliances. Our designed systems configure a micom-gas meter, an automatic extinguisher, sensors, and a wallpad. A micom-gas-meter monitors gas flow, gas pressure, and earthquake. An automatic fire extinguisher checks gas(combustible) leaks and temperature of $100^{\circ}C$ and $130^{\circ}C$. Sensors measure smoke and CO gas. In our novel system, a micom-gas meter cut off inner valve with warnings, an automatic fire extinguisher cut off middle valve and spray extinguishing materials, and sensors generate signals for smoke and CO when occurring gas risk. Gas safety appliances and sensors takes safety measures, and transmit those signal to a wallpad. The wallpad again transmit signal like events to a control server. Users can connect web pages for gas safety through B-ISDN and control and manage them. We hereby devised scenarios for gas safety and risk management, and demonstrated their effectiveness through experiments.

• Journal of the Korean GEO-environmental Society
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• v.22 no.12
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• pp.41-50
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• 2021

This study investigated the changes in engineering characteristics of sand-tire chip mixtures during repetitive loading. To quantify the changes in the maximum shear modulus according to the tire chip content in the mixtures and the particle size ratio between sand particle and tire chip, the samples were prepared with tire chip content of TC = 0, 10, 20, 40, 60, and 100%, and the particle size ratios SR were also set to be SR = 0.44, 1.27, 1.87, and 4.00. The stress of the prepared sample was applied through a pneumatic cylinder. The experiment was conducted in the order of static loading (= 50 kPa), cyclic loading (= 50-150 kPa), static loading (= 400 kPa) and unloading. The stress applied to tested mixtures was controlled by a pressure panel and a pneumatic valve by using an air compressor. The shear wave velocity was measured during static and cyclic loadings by installing bender elements at the upper and lower caps of the mold. The results demonstrated that the change in maximum shear modulus of all tested materials with varying SR during repetitive loading is the most significant when TC ~ 40%. In addition, the mixture with smaller SR at a given TC shows greater increase in maximum shear modulus during repetitive loading.

• Korean Journal of Radiology
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• v.22 no.10
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• pp.1609-1618
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• 2021

Objective: Arrhythmogenic mitral valve prolapse (MVP) is an important cause of sudden cardiac death characterized by fibrosis of the papillary muscles or left ventricle (LV) wall, and an association between late gadolinium enhancement (LGE) of the LV papillary muscles and ventricular arrhythmia in MVP has been reported. However, LGE of the papillary muscles may be observed in other causes of mitral regurgitation, and it is not limited to patients with MVP. This study was to evaluate the association of LGE of the LV papillary muscles or ventricular wall on cardiac magnetic resonance imaging (CMR) and ventricular arrhythmia in patients with mitral regurgitation. Materials and Methods: This study included 88 patients (mean age ± standard deviation, 58.3 ± 12.0 years; male, 42%) with mitral regurgitation who underwent CMR. They were allocated to the MVP (n = 43) and non-MVP (n = 45) groups, and their LGE images on CMR, clinical characteristics, echocardiographic findings, and presence of arrhythmia were compared. Results: LV myocardial wall enhancement was more frequent in the MVP group than in the non-MVP group (28% vs. 11%, p = 0.046). Papillary muscle enhancement was observed in 7 (7.9%) patients. Of the 43 patients with MVP, 15 (34.8%) showed LGE in the papillary muscles or LV myocardium, including 12 (27.9%) with LV myocardial wall enhancement and 4 (9.3%) with papillary muscle enhancement. One patient with bilateral diffuse papillary muscle enhancement experienced sudden cardiac arrest due to ventricular fibrillation. Univariable logistic regression analysis showed that high systolic blood pressure (BP; odds ratio [OR], 1.05; 95% confidence interval [CI], 1.01-1.09; p = 0.027) and ventricular arrhythmia (OR, 6.84; 95% CI, 1.29-36.19; p = 0.024) were significantly associated with LGE of the papillary muscles. Conclusion: LGE of the papillary muscles was present not only in patients with MVP, but also in patients with other etiologies of mitral regurgitation, and it was associated with high systolic BP and ventricular arrhythmia. Papillary muscle enhancement on CMR should not be overlooked.

• Korean Journal of Radiology
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• v.20 no.6
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• pp.956-966
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• 2019

Objective: To characterize the changes in right ventricular (RV) volume, volume load, and function measured with cardiac computed tomography (CT) over the entire time course of tetralogy of Fallot (TOF). Materials and Methods: In 374 patients with TOF, the ventricular volume, ventricular function, and RV volume load were measured with cardiac CT preoperatively (stage 1), after palliative operation (stage 2), after total surgical repair (stage 3), or after pulmonary valve replacement (PVR) (stage 4). The CT-measured variables were compared among the four stages. After total surgical repair, the postoperative duration (POD) and the CT-measured variables were correlated with each other. In addition, the demographic and CT-measured variables in the early postoperative groups were compared with those in the late postoperative and the preoperative group. Results: Significantly different CT-based measures were found between stages 1 and 3 (indexed RV end-diastolic volume [EDV], 63.6 ± 15.2 mL/m² vs. 147.0 ± 38.5 mL/m² and indexed stroke volume (SV) difference, 7.7 ± 10.3 mL/m² vs. 32.2 ± 16.4 mL/m²; p < 0.001), and between stages 2 and 3 (indexed RV EDV, 72.4 ± 19.7 mL/m² vs. 147.0 ± 38.5 mL/m² and indexed SV difference, 5.7 ± 13.1 mL/m² vs. 32.2 ± 16.4 mL/m²; p < 0.001). After PVR, the effect of RV volume load (i.e., indexed SV difference) was reduced from 32.2 mL/m² to 1.7 mL/m². Positive (0.2 to 0.8) or negative (-0.2 to -0.4) correlations were found among the CT-based measures except between the RV ejection fraction (EF) and the RV volume load parameters. With increasing POD, an early rapid increase was followed by a slow increase and a plateau in the indexed ventricular volumes and the RV volume load parameters. Compared with the preoperative data, larger ventricular volumes and lower EFs were observed in the early postoperative period. Conclusion: Cardiac CT can be used to characterize RV volume, volume load, and function over the entire time course of TOF.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.11
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• pp.1349-1354
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• 2013

Sealing structure to prevent flowing hot gas into the driving device, located between the driving shaft and the liner of On-Off valve for controlling the hot gas flow path was studied. Wear occurs due to the constant movement of the driving shaft controlled by actuator on graphite as the sealing material. In this paper, the dynamic wear behavior in high temperature of graphite(HK-6) to be used as sealing material was evaluated. Reciprocating wear test was carried out for the graphite(HK-6) to the relative motion between shaft materials(W-25Re). The results of friction coefficient and specific wear rate according to contact load, sliding speed at room temperature and $485^{\circ}C$ considering the actual operating environment were evaluated. Through the SEM analysis of the worn surface, third body as lubricant films were observed and lubricant effect of third body was considered.

• Journal of Chest Surgery
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• v.31 no.10
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• pp.939-944
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• 1998

Background: The sugical results of the Cox-Maze procedure (CMP) for lone atrial fibrillation(AF) have proven to be exellent. However, those for AF associated with mitral valve(MV) disease have been reported to be a little inferior. Materials and methods: To assess the efficacy and safety of the CMP as a combined procedure with MV operation, we studied retrospectively our experiences. Between April 1994 and October 1997, we experienced 70 (23 males, 47 females) cases of CMP concomitantly with MV operation. Results: The etiologies of MV disease were rheumatic in 67 and degenerative in 3 cases. The mean duration of AF before sugery was 66$\pm$70 months. Fifteen patients had the past medical history of thromboembolic complications, and left atrial thrombi were identified at operation in 24 patients. Twelve cases were reoperations. Aortic cross clamp (ACC) time was mean 151$\pm$44 minutes, and cardiopulmonary bypass (CPB) time was mean 246$\pm$65 minutes. Concomitant procedures were mitral valve replacement (MVR) in 19, MVR and aortic valve replacement (AVR) in 14, MVR and tricupid annuloplasty (TAP) in 8, MVR with AV repair in 3, MV repair in 11, MVR and coronary artery bypass grafting (CABG) in 2, MVR and AVR and CABG in 1, redo-MVR in 10, redo-MVR and redo-AVR in 2 patients. The rate of hospital mortality was 1.4%(1/70). Perioperative recurrence of AF was seen in 44(62.9%), and atrial tachyarrhythmias in 10(14.3%), low cardiac output syndrome in 4(5.7%), postoperative bleeding that required mediastinal exploration in 4(5.7%) patients. Other complications were acute renal failure in 2, aggravation of preoperative hemiplegia in 1, and transient delirium in 1 patient. We followed up all the survivors for 16.4 months(3-44months) on an average. Sinus rhythm has been restored in 65(94.2%) patients. AF has been controlled by operation alone in 73.9% and operation plus medication in 20.3%. Two patients needed permanent pacemaker implantation; one with sick sinus syndrome, and the other with tachycardia- bradycardia syndrome. Only two patients remained in AF. We followed up our patients with transthoracic echocardiography to assess the atrial contractilities and other cardiac functions. Right atrial contractility could be demonstrated in 92% and left atrial contractility in 53%.We compared our non-redo cases with redo cases. Although the duration of AF was significantly longer in redo cases, there was no differences in ACC time, CPB time, postoperative bleeding amount and sinus conversion rate. Conclusions: In conclusion, the CMP concomitant with MV operation demonstrated a high sinus conversion rate under the acceptable operative risk even in case of reoperation.

• Journal of Biosystems Engineering
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• v.33 no.6
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• pp.371-378
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• 2008

Bio-diesel applications seem to be extended due to bio-diesel policies and changes of agricultural environment. This study was conducted to develop a rapeseed reaping equipment attachable to the conventional combine. This paper was intended to report concept design, process and manufacturing of the prototype rapeseed reaping equipment. For concept design, physical properties of "SUNMANG", which is a typical rapeseed as bio-diesel materials, were considered. The designed prototype rapeseed reaping equipment consisted of wide-width plates, finger type knifes, side cutter knifes and drive equipments. The wide-width plate is 2.1 m wide, 0.7 m long, and 0.002 m thick. The finger type cutter knifes have 14.5 fingers, 30 knifes, and the specification was 7.6 cm of pitch, 8.3 cm of length and $21^{\circ}$ of cutting angle. The side cutter knifes consisted of a hydraulic pump, a hydraulic motor, a flow control and a relief valve, a hydraulic hose, a driving equipment and a reciprocating cutter knife. The 18 reciprocating cutter knifes were 137 cm long and knife pitch, knife length and cutting angle were 7.7 cm, 10.5 cm, and $18^{\circ}$. Prototype weight of the rapeseed reaping equipment was heavier by 272 kg when compared with the manual reaping equipments. Load distributions of left and right side showed 50% and 49%, and those of front and rear side showed 64% and 36%. Static turn-over angles in left and right of the prototype were $38.1^{\circ}$ and $38.7^{\circ}$, respectively. The designed prototype rapeseed reaping equipment was properly mounted at the front of a conventional combine.

• Journal of Welding and Joining
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• v.13 no.2
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• pp.42-52
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• 1995

In the evaluation of aging degradation on the structural materials based on the fracture mechanics, the detection and size prediction of defect are very important. Aiming at nondestructive detection and size prediction ol defect with high accuracy and resolution, therefore, an lnduced Current Focusing Potential Drop(ICFPD) technique has been developed. The principle of this technique is to induce a focusing current at an exploratory region by an induction wire flowing an alternating current(AC) that is a constant ampere and frequency. Defects are assessed with the potential drops that are measured the induced current on the surface of metallic material by the potential pick-up pins. In this study, the lCFPD technique was applied for evaluating the location and size of the surface crack and blind crack made in plate specimens, and also for detecting the defects existing in valve, a field component, that were developed by SCC etc. during the service. The results of this present study show that surface crack and blind crack are able to defect with potential drop. these cracks are distinguished with the distribution of potential drop, and the crack depths can be estimated with each normalized potential drop that are parameters estimating the depth of each type crack. In the field component, the defects estimated by experiment result correspond with those in the cutting face of the measuring point within a higher sensitivity.