• 한국항공우주학회지
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• 제46권12호
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• pp.1004-1011
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• 2018

최근 우수한 충격 저감 효과로 인해 파이로테크닉 분리 장치의 한 종류인 저충격 파이로 테크닉 분리 너트에 많은 관심이 주어지고 있다. 하지만 파이로테크닉 분리 너트의 경우 일반 너트 대신 분할 너트가 사용되기 때문에 볼트 풀림 거동에 대한 연구가 충분히 이루어지지 않은 측면이 있다. 이에 본 연구에서는 Junker 진동시험을 준거삼아 볼트 풀림 해석을 수행하였다. 해석은 크게 두 단계로 이루어져 있다. 첫 번째 단계는 체결토크를 이용하여 볼트를 분리너트에 체결하는 과정이고, 두 번째 단계는 횡 방향 가진을 통해 볼트가 풀리는 과정이다. 이러한 과정을 통해 볼트 풀림 거동을 얻을 수 있었다. 또한 신뢰성 있는 파이로테크닉 분리 너트의 설계를 위해 체결부 틈새가 볼트 풀림 거동에 미치는 영향을 고찰하였다.

• Korean Circulation Journal
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• 제54권3호
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• pp.113-123
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• 2024

Background and Objectives: Previous studies have reported an association between impaired renal function and poor outcomes after radiofrequency catheter ablation in patients with atrial fibrillation (AF). However, outcomes of cryoballoon ablation (CBA) in patients with renal insufficiency are not fully elucidated. This study aimed to compare outcomes of CBA in AF patients with chronic kidney disease (CKD) versus those without CKD and to assess changes in renal function over 12 months following CBA. Methods: A total of 839 patients (65.1% with non-paroxysmal AF [PAF]) who underwent de novo CBA were prospectively enrolled. We divided patients into two groups based on creatinine clearance rate (CCr) and performed intracardiac echocardiography (ICE)-guided contrast agent-free CBA. Results: In comparison with patients without CKD (CCr >50, n=722), those with CKD (CCr ≤50, n=117) were older and predominantly female, had a lower body mass index, and showed a higher prevalence of heart failure and hypertension. Mean CHA₂DS₂-VAS score was significantly higher in CKD group than in non-CKD group. Procedure-related complications were not significantly different between two groups. During a mean follow-up period of 25.4±11.9 months, clinical recurrence occurred in 182 patients (21.7%) and not significantly different between two groups. In multivariate analysis, non-PAF and left atrial size were independent predictors of AF recurrence. CCr levels significantly improved over 12 months after CBA in CKD group. Conclusions: ICE-guided contrast-agent-free CBA showed comparable long-term clinical outcomes without increasing procedure-related complications and improvement of renal function over 12 months following CBA in AF patients with CKD.

• Journal of Mechanical Science and Technology
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• 제17권6호
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• pp.844-853
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• 2003

In this paper, a dynamic analysis of the reciprocating compression mechanism of a small refrigeration compressor is performed. In the problem formulation of the mechanism dynamics, the viscous frictional force between the piston and the cylinder wall is considered in order to determine the coupled dynamic behaviors of the piston and the crankshaft. Simultaneous solutions are obtained for the equations of motion of the reciprocating mechanism and the time-dependent Reynolds equations for the lubricating film between the piston and the cylinder wall and for the oil films on the journal bearings. The hydrodynamic forces of the journal bearings are calculated by using a finite bearing model along with the Gumbel boundary condition. A Newton-Raphson procedure is employed in solving the nonlinear equations for the piston and crankshaft. The developed computer program can be used to calculate the complete trajectories of the piston and the crankshaft as functions of the crank angle under compressor-running conditions. The results explored the effects of the radial clearance of the piston, oil viscosity, and mass and mass moment of inertia of the piston and connecting rod on the stability of the compression mechanism.

• 대한치과보철학회지
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• 제31권1호
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• pp.151-162
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• 1993

The author installed $3.75mm\times10mm$ $Br{\aa}nrmark$ osseointegrated implants and $3.5mm\times8mm$ I.T.I. hollow screw implants(Benefit) as a free standing abutment to replace lower left and right molars of 44-year-old female patient. Form the foregoing procedure, the author obtained the following results. 1. Free-standing $Br{\aa}nrmark$ and I.T.I. Hollow screw implants(Benefit) could be used to replace molars effectively without reduction of adjacent natural teeth, 2. Rotation of occlusal gold screw of $Br{\aa}nrmark$ implants was observed under occlusal force. 3. Adjustment of height of I.T.I. abutments was necessary in the mandibular second molar because of the limited occlusal clearance. 4. Form the oral examination, patient comments, panoramic and periapical radiographs, there were no pain, gingival imflammation and mobility, but slight reduction of alveolar bone level was shown around both implant systems. 5. Patient comments were comfortable on both systems. but the patient complained about economic problem of $Br{\aa}nrmark$ system and long treatment treatment time of both systems.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 정보 및 제어부문
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• pp.261-263
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• 2005

In this paper, we implement an identification system using the vein image of the hand. The vein pattern is obtained in the grey-scale 2D image through the infrared-red imaging from back of the hand. Since the frame has lack of clearance, we use some enhancing methods such as the complement, addition, and multiplication to the image to increase the contrast. After Wiener filtering for smoothness of the vein pattern, we transform the image into the binary image with mean function. The binarized image is session thinned and the cross-points in the vein tree are obtained by calculating the number of pixels connected because the image is shaped as a tree. We choose the point and find the nearest to the center if it has majority, where we find the two end points of the selected line. We can get the angle between the two lines joined at the cross-point and store its coordinates, angle, and label the values. The values are used as the feature vector of the vein pattern. This procedure is similar to the human cognition sequences. It is shown that the proposed method is simple for the vein recognition.

• IEIE Transactions on Smart Processing and Computing
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• 제5권2호
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• pp.107-116
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• 2016

Premature babies of less than 37 weeks gestation might require oxygen therapy as an integral part of treatment and respiratory support. Because of their under-developed lungs, these so-called "preemies" might contract respiratory distress syndrome (RDS). To treat RDS, neonatal oxygen therapy is administered, where controlled oxygen gas is measured as a fraction of inspired oxygen ($FiO_2$). However, exposure to high oxygen content during long treatment could cause oxygen intoxication, which might cause permanent blindness due to retinopathy of prematurity (ROP), whereas insufficient oxygen exposure could cause severe hypoxia. A doctor would use oxygen saturation ($SpO_2$) data and prescribe a dose of $FiO_2$ to maintain $SpO_2$ within a suitable range. One objective is to maintain $SpO_2$ within the acceptable range using $FiO_2$ that is as low as possible. Adjustment of $FiO_2$ would normally be done by nurses every 15 to 30 minutes, which might not be safe in many situations. An error in $FiO_2$ adjustment during a manual procedure could be as large as +/- 2.5%. This paper presents a system that can determine an $FiO_2$ value suitable to the current $SpO_2$ and that automatically adjusts $FiO_2$ with an error clearance of +/- 0.25%.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.277-280
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• 2000

Reverse Engineering is a procedure where the results of engineering decisions in manufacturing is feedback to the design phase and the knowledge-base is generated from the process know-how to reduce the errors. Since it used to take lots of time and efforts to finalize the machining of dies out of the original CAD design especially for die spotting and try-outs, reverse engineering is important to improve the productivity and quality of the die manufacturing process. In this regard, we developed system to support reverse engineering in machining of stamping dies for auto-body production. They automatically generate the relevant MC programs for a CMM simply with the input of measuring points in CAD environments, and show the CAD model and the results of inspection simultaneously for the ease of comparison. They also help reduce the overall clearance between the lower and upper dies. Applying these systems to the machining process of stamping dies, we could improve the reliability of measuring and get the optimal compensation distance between the two dies. We also analyzed the expected benefits of the system in terms of savings in time and costs.

• 무역상무연구
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• 제13권
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• pp.735-765
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• 2000

The paper aims to introduce and to discuss seafood import systems in terms of tariff and Non-Tariff Measurements which have been changed by the establishment of WTO. The paper can be used as materials for seafood trade policy making. The Non-Tariff Measurements for seafood import control in Japan are explored as follows; Import Quota, Import License, Pre-identification, Standard system, Customs Clearance Procedure, Import Port Nomination, Import Channel, Unification. The paper is composed of six chapters. Chapter 1 shows the current situation of seafood trade of major countries and background of the research. Chapter 2 deals with fisheries negotiations in the Uruguay Round, their impacts and major issues of tariffs and Non-Tariff Measurements in seafood trade. Chapter 3 analyzes seafood import of Japan, which is the core nation in the seafood trade of Northeast Asian Region, by item and the structure and characteristics of Japanese seafood import tariff including Non-Tariff Measurements. Chapter 4 and chapter 5 tackle seafood import management system of EU and USA respectively. Chapter 6 summarizes the issues of seafood import by focusing on Japan which is the biggest import market of Korean seafood.

• 한국자동차공학회논문집
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• 제5권2호
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• pp.136-148
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• 1997

The present study has been carried out to develop a computational procedure for the analysis of the off-design performance in centrifugal compressors with vaneless diffusers by integrating empirical loss models and analytical equations. Losses in centrifugal compressors stem from a number of sources and their exact calculation is not yet possible. This study investigates several modeling schemes and shows that a fairly good prediction can be achieved by a proper selection of the most important flow parameters resulting form a meanline one-dimensional analysis. The performance maps for compressors are calculated and compared with measured performance maps. The off-design performance characteristics in terms of the pressure ratio vs. mass flow produced have generally correct forms. However, no universal means have been found to predict accurately the onset of surge. The prediction method developed through this study can serve as a tool to ensure good matching between parts and it can assist the understanding of the operational characteristics of general purpose centrifugal compressors.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.264-270
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• 2011

The goal of this study is a stability evaluation through eigenvalue and rotor dynamics analysis of the vacuum pump. The vacuum pump used is a roots type pump, one of the dry middle vacuum pumps, is necessary at the procedure to produce semiconductor and display. The eigenvalue evaluation is solved by numerical analysis through using Modal test and 2D 3D models. Both the experiment and the analysis result are similar, the analysis result using 2D is more oculate the 3D model comparing with test result. So rotor dynamic evaluation is performed through using 2D model. Rotor dynamic evaluation used the campbell diagram and root locus map which were acquired by complex eigenvalue analysis. And we checked minimum clearance of vacuum pump composition between two rotors through unbalance response analysis. Thus, vacuum pump, the target object of this study, was evaluated to be operated stably.