• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.7211-7218
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• 2015

Tens of thousands of malicious codes are generated on average in a day. New types of malicious codes are surging each year. Diverse methods are used to detect such codes including those based on signature, API flow, strings, etc. But most of them are limited in detecting new malicious codes due to bypass techniques. Therefore, a lot of researches have been performed for more efficient detection of malicious codes. Of them, visualization technique is one of the most actively researched areas these days. Since the method enables more intuitive recognition of malicious codes, it is useful in detecting and examining a large number of malicious codes efficiently. In this paper, we analyze the relationships between malicious codes and Native API functions. Also, by applying the word cloud with text mining technique, major Native APIs of malicious codes are visualized to assess their maliciousness. The proposed malicious code analysis method would be helpful in intuitively probing behaviors of malware.

• Journal of the Korea Society for Simulation
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• v.23 no.2
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• pp.17-24
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• 2014

This study attempts to show an example of developing and applying thermal hydraulic simulation model for Aircraft-EHA. The overview of research procedure is as in the following. First, The unit hydraulic simulation model, which reflects physical quantity answering engineer's purpose is developed. Second, The unit hydraulic simulation model is combined, and then branched out to EHA hydraulic model. Third, a simulation model including flow thermal is developed, and then oil temperature rise time according to 'initial temperature and load' is examined. Finally, the master graph that can be used for designing EHA combined with thermal hydraulic analysis results in several cases is compiled, and suggested. AMESim, commercial software, is used through whole procedure.

• Nuclear Engineering and Technology
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• v.27 no.3
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• pp.317-326
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• 1995

The oater level control system of the steam generator in a pressurized water reactor and its control Problems are analysed. In this work a stable control strategy Particularly during low Power operation based on the fuzzy control method is studied. The control strategy employs substitutional information using the bypass valve opening instead of incorrectly measured signal at the low How rate as the fuzzy variable of the flow rate during low power operation, and includes the flexible scale adjusting method for fast response at a large transient. A self-tuning algorithm based on the control performance and the descent method is also suggested for tuning the membership function scale. It gives a practical way to tune the controller under real operation. Simulation was carried out on the Compact Nuclear Simulator set up at Korea Atomic Energy Research Institute and its result showed the good performance of the controller and effectiveness of its tuning.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.833-837
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• 2010

This study aims at finding an optimal exhaust diffuser design of a high altitude testing chamber for a low bypass turbofan engine (F404-402) with thrust pound force of 17,700 and air mass flow rate of 66kg/s ejecting at a speed of Mach 1.66. The final proposed ejector size has better pressure recovery characteristics and targets to reduce operational cost at engine performance testing. Conventional high altitude test chamber layout was adopted and first drawn in two dimensions using Autocad software so as to determine the gas path, the ejector frontal size was then determined from gas dynamics equations considering traditional gas ejection method where both the engine exhaust and cell cooling air are exhausted via the ejector. Modification to a smaller ejector with an alternative secondary cell cooling exhaust port was then performed and modelled in 3D using Solid Works software.

• Journal of architectural history
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• v.23 no.1
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• pp.7-19
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• 2014

This study considers the proper repair techniques by examining the most representative repair cases of the Korean arch bridges and proposes the constructional manual which can apply similar occasions. The cases are Seonamsa Seungseongyo and Songgwangsa Geukrockgyo where this researcher had taken part in the repair works. This Study proposes the maintenance construction manual about the performance degradation drew by performance degradation of the both Korean arch bridges in the maintenance process. First, arch bridge maintenance should be carried out in the dry season, when water is impermeable in the bottom surface of the bridge. Moreover, risk factors of the maintenance should be excluded to secure the water vally flow, the bypass and the temporary bridge. Second, prior to repair, it has to precede (1)3D shooting (2)formal examination (3)structure safety test (4)geological and lithic surveys (5)arch curvature establishment and makeshift frame settlement before transformation (6)relationship expert comments. Third, if the baduk and the foundation stones are inevitable to replace due to performance degradation on the foundation, it should use the high quality stones and secure greater stress by extending the standard range. The foundation on irregular rock needs to be flattened and underside on the replaced materials require Grengyijil to deliver the equal loads. Fourth, In the process of dismantling the stones of the arched bridge, it could make heavy weathering degree and not reuse the materials. Charge should converge the expert advices to choose the reuseable, the conservate and the alternative materials, and increase the reutilization of the raw materials by preservation and reinforcement treatments. Fifth, the side wall should be repaired by the rubble work technique which is not able to pile compost satiety, so it must use long depth of masonary stones for reinforcement. It is considered to reinforce the stone wall in shore as much as possible and protect the abutment and the side wall on the upstream for the arch bridge maintenance works.

• Journal of Chest Surgery
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• v.29 no.11
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• pp.1270-1275
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• 1996

Pulmonary artery aneurysms are extremely rare conditions usually associated with congenital cardiac defects that cause increased pulmonary blood flow and pulmonary hypertension. The prognosis of pulmonary artery aneurysms is fatal due to the potential for rupture of the aneurysm and the underlying severe pulmonary hypertension. A 40-year old woman was admitted to our hospital with headache following traffic accident. On admission a continuous murmur was heard over the 2nd to 3rd intercostal space along left sternal border and a calcified cystic mass at left hilar portion was incidentally discoverd on chest reontgenogram. Cardiac catherization was diagnostic of a left to right shunt at main pulmoanry artery level and pulmonary hypertension. Pulmonary angiogram demonstrated a large aneurysm of main pulmonary artery extending into proximal left pulmonary artery. The pulmonary artery aneurysm associated with patent ductus arteriosus was diagnosed definitively and the patient was underwent resection of pulmonary artery aneurysm, closure of PDA and Dacron prosthetic graft replacement under cardiopulmonary bypass. The postoperative course was uneventful and the patient was discharged without any problem.

• Journal of Chest Surgery
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• v.44 no.5
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• pp.338-342
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• 2011

Background: The axillary artery is frequently used for cardiopulmonary bypass, especially in acute aortic dissection. We have cannulated the axillary artery using a side graft or by directly using Seldinger's technique. The purpose of this study was to assess the technical problems and complications of both cannulation techniques. Materials and Methods: From January 2003 to December 2009, 53 patients underwent operations using the axillary artery for arterial cannulation. The axillary artery was cannulated with a side graft in 35 patients (side graft group) and directly using Seldinger's technique in 18 patients (direct group). Results: The results were compared between two groups, focusing on cannulation-related morbidities including neurologic morbidity. Arterial damage or dissection of the axillary artery occurred in 1 (2.9%) patient in the side graft group and in 1 (5.6%) patient in the direct group. Malperfusion and insufficient flow did not occur in either group. There were no postoperative complications related to axillary cannulation, such as brachial plexus injury, compartment syndrome, or local wound infection, in either group. Conclusion: Technical problems and complications of the axillary arterial cannulation in both techniques were rare. Direct arterial cannulation using Seldinger's technique was done safely and more simply than the previous technique. It was concluded that both axillary arterial cannulation techniques are acceptable and it remains the surgeon's preference which technique should be used.

• Journal of Chest Surgery
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• v.42 no.6
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• pp.774-776
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• 2009

A 57-year-old man with dyspnea was transferred to our institution. Echocardiography demonstrated grade III aortic valve regurgitation with a bicuspid aortic valve. The preoperative coronary angiography showed a left single nary artery. Replacement of the aortic valve was performed. Ventricular fibrillation developed during weaning patient of cardiopulmonary bypass after aortotomy repair. An anomalous origin of the coronary arteries is an incidental finding. However, in patients who are undergoing aortic valve replacement, a can significantly complicate the procedure. If this is present, then it is imperative that the clearly identified and the required procedure should be modified to avoid injury to these.

• Journal of Chest Surgery
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• v.54 no.5
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• pp.383-388
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• 2021

Background: Achieving external access to and manual occlusion of the left atrial appendage (LAA) during minimally invasive mitral valve surgery (MIMVS) through a small right thoracotomy is difficult. Occlusion of the LAA using an epicardial closure device seems quite useful compared to other surgical techniques. Methods: Fourteen patients with atrial fibrillation underwent MIMVS with concomitant surgical occlusion of the LAA using double-layered endocardial closure stitches (n=6, endocardial suture group) or the AtriClip Pro closure device (n=8, AtriClip group) at our institution. The primary safety endpoint was any device-related adverse event, and the primary efficacy endpoint was successful complete occlusion of blood flow into the LAA as assessed by transthoracic echocardiography at hospital discharge. The primary efficacy endpoint for stroke reduction was the occurrence of ischemic or hemorrhagic neurologic events. Results: All patients underwent LAA occlusion as scheduled. The cardiopulmonary bypass and aortic cross-clamp times in the endocardial suture group and the AtriClip group were 202±39 and 128±41 minutes, and 213±53 and 136±44 minutes, respectively (p=0.68, p=0.73). No patients in either group experienced any device-related serious adverse events, incomplete LAA occlusion, early postoperative stroke, or neurologic complication. Conclusion: Epicardial LAA occlusion using the AtriClip Pro during MIMVS in patients with mitral valve disease and atrial fibrillation is a simple, safe, and effective adjunctive procedure.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.1
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• pp.105-115
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• 2019

Recently, intelligent Android malicious codes have become difficult to detect malicious behavior by static analysis alone. Malicious code with SO file, dynamic loading, and string obfuscation are difficult to extract information about original code even with various tools for static analysis. There are many dynamic analysis methods to solve this problem, but dynamic analysis requires rooting or emulator environment. However, in the case of dynamic analysis, malicious code performs the rooting and the emulator detection to bypass the analysis environment. To solve this problem, this paper investigates a variety of root detection schemes and builds an environment for bypassing the rooting detection in real devices. In addition, SDK code hooking module for Android malicious code analysis is designed using Xposed, and intent tracking for code flow, dynamic loading file information, and various API information extraction are implemented. This work will contribute to the analysis of obfuscated information and behavior of Android Malware.