• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.201-208
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• 2004

In this study a general Galerkin FE lubrication analysis method was utilized to analyze the complex lubrication performance of a spiral groove seal having an additional inner circular groove, which was designed for a chemical process mixer operating at a low speed of the maximum 500 rpm. Equilibrium seal clearance analyses under varying outer pressure revealed that the seal maintains a certain levitation seal clearance under the outer pressure of more than about 1.5 bar, regardless of a rotating speed. Also, under the normal outer pressure of 11 bar, the axial stiffness of the seal was predicted to have a high value of more than 7.0e+07 N/m, regardless of a rotating speed and thereby, the seal is expected to maintain a stable thickness of lubrication film under a certain external excitation acting.

• Tribology and Lubricants
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• v.5 no.2
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• pp.94-100
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• 1989

Friction and Wear behavior of continuous graphite fiber composites was studied for different fiber orientations against the sliding direction. The effect of fiber orientation on friction and wear of the composite and on the deformation of the counterface was investigated experimentally. Pin on disk type testing machine was built and employed to generate the friction and wear data. A graphite fiber composite plate was produced by the bleeder ply molding in an autoclave and machined into rectangular pin specimens with specific fiber orientations, i.e., normal, transverse, and longitudinal directions. Three different wear conditions were employed for two different periods of time, 24 and 48 hours. The wear track of the worn specimens and the metal counterface was examined with a scanning electron microscope (SEM) to observe the damaged fibers on the surface and wear film generation on the counterface. Wear mechanism of the composite during sliding wear is proposed based on the experimental results.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.13 no.4
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• pp.29-42
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• 2005

The passenger security screening is a mandatory procedure for boarding the aircraft according to ICAO standard as well as national law of each country. The enhanced threat of terrorism have had the security procedure strengthened since 9/11 events. However the effectiveness of passenger screening is not satisfactory and the service level for passenger is getting worse because of tightened security measurements. This research studied the responsibility issue for the enhancement of the effectiveness and service quality in passenger security screening. The study concluded that a desirable responsibility assignment for passenger screening is to the airport authority at normal time and to the government authority at the time of high threat.

• The Journal of Korean Society for Radiation Therapy
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• v.2 no.1
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• pp.75-80
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• 1987

Intraoperative Radiation therapy (IORT) is a cancer treatment modality in which resectable masses or organs are removed surgically and residual cancer calls are sterilized by irradiation with a single massive dose during while patient is still anesthetized. Because it is possible that the turner mass can be visualized directly at the time of surgical exploration, tumor volume can be determined more precisely and at the same tin e sensitive adjacent structures can be pulled aside from the irradiation. With these theoretical advantages as compare to conventional external irradiation, IORT can improve the therapeutic ratio of tumor control to normal tissue injury. Yonsei cancer center initiated a pilot study of multidisciplinary IORT program in february of 1986 for the fist attempt in Korea. IORT Was performed in 7 patients with stomach cancer by using existing NELAC-1018 Linear Accelerator treatment room as a surgical suite. IOTR team included department of surgery, Department of Anethesiology, Department of Clinical pathology, operating room nursing personal and Department of radiation oncology.

• Journal of the Korean Professional Engineers Association
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• v.30 no.3
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• pp.104-114
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• 1997

Throughout the practical process engineering design and commissioning 8E startup experiences focused on chemical process safety, the review of design and installation of the thermal relief valve with its surrounding facility in a chemical plant piping system is made to help the better understanding of the piping system of characteristics of thermal relief valve which Is consisting of theoretical approach, correlation in terms of temperature and pressure increase caused by external heat supply in a piping system, consideration of thermal relief valve design, pressure relieving system of serial thermal relief valves and exception of their installation. It is earnestly recommended that following topic should be implemented during thermal relief valve design, installation and normal operation as well.

• Journal of the Korean Mathematical Society
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• v.54 no.2
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• pp.517-543
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• 2017

Let H be a cocommutative faithfully flat Hopf quasigroup in a strict symmetric monoidal category with equalizers. In this paper we introduce the notion of (strong) Galois H-object and we prove that the set of isomorphism classes of (strong) Galois H-objects is a (group) monoid which coincides, in the Hopf algebra setting, with the Galois group of H-Galois objects introduced by Chase and Sweedler.

• Structural Engineering and Mechanics
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• v.53 no.3
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• pp.411-427
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• 2015

Based on linear elastic theory of quasicrystals, various equations and solutions for quasicrystal beams are deduced systematically and directly from plane problem of two-dimensional quasicrystals. Without employing ad hoc stress or deformation assumptions, the refined theory of beams is explicitly established from the general solution of quasicrystals and the Lur'e symbolic method. In the case of homogeneous boundary conditions, the exact equations and exact solutions for beams are derived, which consist of the fourth-order part and transcendental part. In the case of non-homogeneous boundary conditions, the exact governing differential equations and solutions under normal loadings only and shear loadings only are derived directly from the refined beam theory, respectively. In two illustrative examples of quasicrystal beams, it is shown that the exact or accurate analytical solutions can be obtained in use of the refined theory.

• Geomechanics and Engineering
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• v.10 no.1
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• pp.1-19
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• 2016

This paper presents the results of an intensive experimental investigation on cyclic behavior of various sands and structural materials interface. Comprehensive measurements of the horizontal displacement and shear stresses developed during testing were performed using an automated constant normal load (CNL) cyclic direct shear test apparatus. Two different particle sizes (0.5 mm-0.25 mm and, 2.0 mm-1.0 mm) of sands having distinct shapes (rounded and angular) were tested in a cyclic direct shear testing apparatus at two vertical stress levels (${\sigma}=50kPa$, and 100 kPa) and two rates of displacement ($R_D=2.0mm/min$, and 0.025 mm/min) against various structural materials (i.e., steel, concrete, and wood). The cyclic direct shear tests performed during this investigation indicate that (i) the shear stresses developed during shearing highly depend on both the shape and size of sand grains; (ii) characteristics of the structural materials are closely related to interface response; and (iii) the rate of displacement is slightly effective on the results.

• Proceedings of the KOSOMBE Conference
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• v.1995 no.11
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• pp.177-182
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• 1995

Since one property(i.e. coarseness, orientation, regularity, granularity etc.) of ultrasound liver images was not sufficiently enough to classify the characteristics of livers, we used the multi-feature vectors from ultrasound images to diagnose the liver disease. The proposed classifier, which uses the multi-feature vectors and Bayes decision rule, performed well for the classification of normal, fat and cirrhosis liver. In our simulation, we used the Battacharyya distance and Hotelling Trace Criterion to select the best multi-feature vectors for the classifier and obtained less classification errors than other methods using single feature vector.

• Bulletin of the Korean Mathematical Society
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• v.46 no.4
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• pp.645-656
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• 2009

J. Wang [21] proposed a problem: whether the Hyers-Ulam-Rassias stability of Jensen's equation for the case p, q, r, s $\in$ ($\beta$, $\frac{1}{\beta}$) \ {1} holds or not under the assumption that G and E are $\beta$-homogeneous Fspace (0 < $\beta\;\leq$ 1). The main purpose of this paper is to give an answer to Wang's problem. Furthermore, we proved that the stability property of Jensen's equation is not true as long as p or q is equal to $\beta$, $\frac{1}{\beta}$, or $\frac{\beta_2}{\beta_1}$ (0 < $\beta_1,\beta_2\leq$ 1).