• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.7
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• pp.1006-1013
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• 2004

Operating experience of steam generators shows that the tubes are degraded by stress corrosion cracking, fretting wear and so on. These defected tubes could stay in service if it is proved that the tubes have sufficient structural margin to preclude the risk of tube bursting. This paper provides detailed plastic limit pressure solutions for through-wall cracks in the steam generator tubes. These are developed based on three dimensional(3D) finite element analyses assuming elastic-perfectly plastic material behavior. Both axial and circumferential through-wall cracks in free span and in u-bend regions are considered. The resulting limit pressure solutions are given in a polynomial form, and thus can be simply used in practical integrity assessment of the steam generator tubes.

• The Journal of the Korea institute of electronic communication sciences
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• v.3 no.4
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• pp.228-232
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• 2008

For the past several years, many countries have passed or have recommended legislation making it illegal to use in-hand mobile phones while driving and several manufacturers have released car kit solutions enabling hands-free operation of the mobile phone. But an automobile environment can pose extremely harsh physical conditions impacting audio quality, safety, and reliability. This article introduced a Car Kits that provided a total entertainment and telematics solution, which support all current features within the constraints of low power consumption, form factor, price, ease-of-use, manufacture ability, testability and high total quality.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.302-307
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• 1998

In the production of semiconductor wafer, optical and electron microscopes, ion-beam, laser device must maintain their alignments within a sub-micrometer. This equipment requires a vibration free environment to provide its proper function. Especially, lithography and inspection devices, which have sub-nanometer class high accuracy and resolution, have come to necessity for producing more improved giga and tera class semiconductor wafers. This high technology equipments require very strict environmental vibration standard, vibration criteria, in proportion to the accuracy of the manufacturing, inspecting devices. The vibration criteria of high sensitive equipment should be represented in the form of exactness and accuracy, because this is used as basic data for the design of building structure and structural dynamics of equipment. The study on the evaluation of the factors affecting the permissible vibration criteria is required to design the efficient isolation system of the semiconductor manufacturing of equipment. This paper deals with the properties of the effected factor for vibration criteria of high sensitive equipment.

• Wind and Structures
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• v.29 no.6
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• pp.371-387
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• 2019

In the present paper, a simple refined nth-higher-order shear deformation theory is applied for the free vibration analysis of laminated composite plates. The proposed displacement field is based on a novel kinematic in which include the undetermined integral terms and contains only four unknowns, as against five or more in case of other higher-order theories. The present theory accounts for adequate distribution of the transverse shear strains through the plate thickness and satisfies the shear stress-free boundary conditions on the top and bottom surfaces of the plate, therefore, it does not require problem dependent shear correction factor. The governing equations of motion are derived from Hamilton's principle and solved via Navier-type to obtain closed form solutions. The numerical results of non-dimensional natural frequencies obtained by using the present theory are presented and compared with those of other theories available in the literature to verify the validity of present solutions. It can be concluded that the present refined theory is accurate and efficient in predicting the natural frequencies of isotropic, orthotropic and laminated composite plates.

• Bulletin of the Society of Naval Architects of Korea
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• v.11 no.1
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• pp.9-16
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• 1974

To contribute towards more accurate estimation of the virtual inertia coefficient for the horizontal vibration of ships, three dimensional correction factor $J_H$ for the added mass of finitely long elliptic prismatic bars in horizontal vibration in a free surface of an ideal fluid are calculated. In the problem formulation Dr. T. Kumai's quasi-finite length concept[1,11,12] is employed. Now that, in Dr. Kumai's work[1] for the horizontal vibration the mathematical model was a circular cylinder, the principal aim of the authors' work is to investigate the influence of the beam-draft ratio B/T on $J_H$. The numerical results of this work are shown in Fig.3 graphically, from which we may recognize that the influence of B/T on $J_H$ is remarkable as much as that of the length-draft ratio L/T(refer to Fig.1 also). In Fig.3 the curves for B/T=2.00 are of those based on Dr. Kumai's result[1]. On the other hand, the experimental data obtained by Burril et al.[9] for the horizontal vibration of finitely long prismatic bars of various cross-section shapes are compared with the theoretical added mass coefficients defined by combination of the authors' $J_H$ from Fig.3 and two dimensional coefficients $C_H$ obtained by Lewis form approximation for the corresponding sections. They are in reasonable correspondence with each other as shown in Fig.2. Finally, considering that the longitudinal profile of full-form ship's hull is well resembled to that of an elliptic cylinder and that the influences of other factors such as the sectional area coefficient and the shape of section contour itself can be well merged in the two dimensional added mass coefficient, the authors recommend that the data given in Fig.3 may be successfully adopted for the three dimensional correction factor the added mass in the horizontal vibration of hull-form ships.

• Steel and Composite Structures
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• v.24 no.2
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• pp.151-176
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• 2017

This paper deals with general equations of motion for free vibration analysis response of thick three-layer doubly curved sandwich panels (DCSP) under simply supported boundary conditions (BCs) using higher order shear deformation theory. In this model, the face sheets are orthotropic laminated composite that follow the first order shear deformation theory (FSDT) based on Rissners-Mindlin (RM) kinematics field. The core is made of orthotropic material and its in-plane transverse displacements are modeled using the third order of the Taylor's series extension. It provides the potentiality for considering both compressible and incompressible cores. To find these equations and boundary conditions, Hamilton's principle is used. Also, the effect of trapezoidal shape factor for cross-section of curved panel element ($1{\pm}z/R$) is considered. The natural frequency parameters of DCSP are obtained using Galerkin Method. Convergence studies are performed with the appropriate formulas in general form for three-layer sandwich plate, cylindrical and spherical shells (both deep and shallow). The influences of core stiffness, ratio of core to face sheets thickness and radii of curvatures are investigated. Finally, for the first time, an optimum range for the core to face sheet stiffness ratio by considering the existence of in-plane stress which significantly affects the natural frequencies of DCSP are presented.

• Smart Structures and Systems
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• v.22 no.1
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• pp.121-132
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• 2018

This research investigates the free vibration analysis of advanced composite plates such as functionally graded plates (FGPs) resting on a two-parameter elastic foundations using a hybrid quasi-3D (trigonometric as well as polynomial) higher-order shear deformation theory (HSDT). This present theory, which does not require shear correction factor, accounts for shear deformation and thickness stretching effects by a sinusoidal and parabolic variation of all displacements across the thickness. Governing equations of motion for FGM plates are derived from Hamilton's principle. The closed form solutions are obtained by using Navier technique, and natural frequencies are found, for simply supported plates, by solving the results of eigenvalue problems. The accuracy of the present method is verified by comparing the obtained results with First-order shear deformation theory, and other predicted by quasi-3D higher-order shear deformation theories. It can be concluded that the proposed theory is efficient and simple in predicting the natural frequencies of functionally graded plates on elastic foundations.

• Korean Journal of Bronchoesophagology
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• v.9 no.1
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• pp.30-38
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• 2003

Cancers of the cervical esophagus occur uncommonly, but treatment is remaining a challenging problem and surgery demands special knowledge of abdominal, thoracic, and neck surgery. The primary risk factor is chronic heartburn, leading to a sequence of esophagitis, Barrett's esophagus, reflux esophagitis and etc. Among the various treatment modalities, Surgery is still a mainstay of treatment. The main aim of surgery is not only oncologically adequate resection but also preservation or restoration of physiologic functions, such as deglutition and phonation. Surgical treatment of cervical esophageal cancer is influenced by special problems arising from tumor factors, patient factors and surgeon factors. Complete clearance of loco-regional disease and prevention of postoperative complications are of particular importance for the improvement of long-term survival in patients with these cancers. So the cervical and thoracic extension of these tumors usually required an extensive lymphadenectomy with primary resection. Radical resection of the primary site almostly include sacrifice of the larynx, but the voice could be rehabilitated with various methods, such as tracheoesophageal prosthesis or tracheoesophageal shunts, etc. Restoration of the esophageal conduit can be performed using gastric or colon interposition, radial forearm free flap or jejunum free flap, etc. Recently, the advances of radiation therapy and chemotherapy will enable less extended resections with greater rates of laryngeal preservation. At initial presentation, up to 50％ to 70％ of patients will have advanced locoregional or distant disease with virtually no chance for cure. Patients with advanced but potentially resectable esophageal cancer are generally treated by surgery with some form of neoadjuvant chemotherapy, radiotherapy, or both, with 5-year survivals in the 20％ to 30％ range. So the significant adverse factors affecting survival should be taken into account to select the candidates for surgery.

• Korean journal of food and cookery science
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• v.28 no.6
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• pp.665-673
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• 2012

The purpose of this study was to propose optimal mixing proportion by adding stevia in powder form, which are low caloric and high intensity sweetener to cookies, and to determine the characteristic of product. It reduced the average sugar content of cookies to 50%, processed stevia powder, add them in 2, 4, 6, and 8% to make cookies and measured various product characteristics, including anti-oxidant activity. The antioxidant activity was highly correlated with the total phenolic composition of stevia cookies (r=0.967). Total phenolic contents and DPPH free radical scavenging activity of cookies significantly increased with increasing stevia powder. The bulk density of the dough, spread factor and the hardness, total polyphenol contents and DPPH free radical scavenging activity of cookies significantly increased with increasing stevia powder, while the pH of the dough, and L values of the cookies decreased with increasing stevia powder content (p<0.001). Additionally, the consumer acceptability scores for the 4% stevia cookie groups ranked significantly (p<0.001) higher than those of the other groups in color, taste, flavor, sweetness and overall preference. All the take together, the results of this study suggest that stevia powder is a good ingredient for increasing the consumer acceptability and the functionality of cookies.

• Bulletin of the Korean Chemical Society
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• v.12 no.1
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• pp.61-67
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• 1991

Conformational free energy calculations using an empirical potential function and the hydration shell model (a program CONBIO) were carried out on the neutral L-ascorbic acid (AA) in the unhydrated and hydrated states. The conformational energy was minimized from starting conformations which included possible conformations of six torsion angles in the molecule. The conformational entropy of each low energy conformation in both states was computed using a harmonic approximation. From the analysis of conformational free energies for AA in both states, intramolecular hydrogen bonds (HBs) are proved to be an essential factor in stabilizing the overall conformations, and cause the conformations in both states to be quite different from those in crystal. In the case of hydrated AA, there is a competition between HBs and hydration, and the hydration around the two hydroxyl groups attached to the acyclic side chain forces the molecule to form less stable HBs. The hydration affects strongly the conformational energy surfaces of AA. Several feasible conformations obtained in this work indicate that there exists an ensemble of several conformations in aqueous solution. The calculated probable conformations for the rotation about the C5-C6 bond of the acyclic side chain are trans and gauche +, which are in good agreement with results of NMR experiment.