• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.373-384
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• 1989

The motions of a spinning rotor and a fluid enclosed in its cavity are known to have mutual interactions, which change the frequencies of forced vibrations and cause instabilities. These phenomena are of technical importance for fluid-cooled turbines as well as spin-stabilized satellites or rockets containing liquid fuels. In this paper the characteristics of unstable whirling of a rotor containing a partitioned cavity filled with two kinds of liquids are investigated experimentally. It studies the influence of rotational speed and filling ratio of two kinds of liquids on unstable whiring. As a result, it is found that the whirl velocity is approximately equal to, or slightly lower for large masses of trapped fluid than rotor critical speed. In case of a spinning rotor partially filled with two kinds of liquids the boundary surface plays a similar role to the free surface, and cases unstable forward whirl.

• Economic and Environmental Geology
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• v.21 no.3
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• pp.209-221
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• 1988

The ore deposit of the Ohtani mine is one of repesentatives of plutonic tungsten-tin veins related genetically to acidic magmatism of Late Cretaceous in the Inner zone of Southwest Japan. Based on macrostructures of vein filling on the order of ore body, three major mineralization stages, called stage I, stage II, and stage ill from earliest to latest, are distinguished by major tectonic breaks. The alteration zories are characterized by specific mineral associations in pseudomorphs after biotite. The alteration zones can be divided into two parts, i. e. a chlorite zone and a muscovite zone, each repesenting mineralogical and chemical changes produced by the hydrothermal alteration. The chloritic alteration took place at the beginning of mineralization, and muscovite alteration in additions to chloritic alteration took place at stage II and ill. The alteration zones are considered to be formed by either of two alteration mechanism. 1) The zones are formed by reaction of the rock with successive flows of solution of different composition and different stage. 2) The zones are formed contemporaneously as the solution move outward. Reaction between the solution and the wall-rock results in a continuous change in solution chemistry. The migration of the successive replacement of the fresh zone$\rightarrow$the chlorite zone$\rightarrow$the muscovite zone may have transgressed slowly veinward, leaving metasomatic borders between the different zones.

• Journal of the Korean Institute of Gas
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• v.11 no.2 s.35
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• pp.37-42
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• 2007

This paper presents the leakage safety of two O-rings, which are located at the rectangular groove between a valve body and a valve stem. The leakage safety analysis of 0-ring seals has been computed as functions of a compression set and a liquefied petroleum gas pressure of a LPG cylinder using a FEM program, MARC. The FEM computed results indicate that the loads from the filling pressure of $8kg/cm^2$ to the upper limit of the safety valve, $24.8kg/cm^2$ work safely according to the pressure vessel code. But two O-rings should consider the aging effects for an increased safety of the o-ring.

• Structural Engineering and Mechanics
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• v.81 no.6
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• pp.769-780
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• 2022

This paper studies the dynamic behavior of laminated composite circular cylindrical shells interacting with a fluid. The mathematical formulation of the dynamic problem for an elastic body is developed based on the variational principle of virtual displacements and the relations of linear elasticity theory. The behavior of an ideal compressible fluid is described by the potential theory, the equations of which together with boundary conditions are transformed to a weak form. The hydrodynamic pressure exerted by the fluid on the internal surface of the shell is calculated according to the linearized Bernoulli equation. The numerical implementation of the mathematical formulation has been done using the semi-analytical finite element method. The influence of the ply angle and lay-up configurations of laminated composites on the natural vibration frequencies and the hydroelastic stability boundary have been analyzed for shells with different geometrical dimensions and under different kinematic boundary conditions set at their edges. It has been found that the optimal value of the ply angle depends on the level of filling of the shell with a fluid. The obtained results support the view that by choosing the optimal configuration of the layered composite material it is possible to change upwards or downwards the frequency and mode shape, as well as the critical velocity for stability loss over a wide range.

• Advances in nano research
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• v.16 no.1
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• pp.71-79
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• 2024

Nanotechnology is the latest technology developed by humanity, trying to use the molecular properties of materials found in nature to create devices that solve the problems plaguing humanity and their efficiency. Man is also trying to change the meaning of molecules to nano so that a body made up of these particles has all the properties of these particles. Nanotechnology is not a new field but a new approach in all areas. A new perspective in concrete technology has been created by the use of nanoparticles in recent years. Adding silica nanoparticles to concrete mixes improves its properties and increases its strength. However, different results and reported mechanisms explain the behavior of nanoparticles in the mixture; Therefore, it took much work to generalize the results and predict the behavior of nano concretes. This article is about the construction simulation technology of civil engineering based on artificial intelligence, which deals with the effect of nanoparticles on improving concrete properties. This was demonstrated by analyzing laboratory samples in various mixture configurations and observing how silica nanoparticles affected their microstructure with scanning electron microscopy (SEM). Based on SEM measurements, silica nanoparticles have a powerful effect because of their specific surface area. Their increase and decrease must be sought in interacting with the filling and nucleation mechanism and the pozzolanic activity. Each of these mechanisms dominates at different ages of hydration and affects the microstructure and mechanical properties of concrete.

• The Journal of the Korea Contents Association
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• v.18 no.3
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• pp.196-204
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• 2018

The purpose of this study is to provide basic data for the oral health and obesity management of adults by grasping the relationship between obesity and oral health. Among the patients who visited the dental clinic, 229 patients who agreed to fill out questionnaires were analyzed by self - filling questionnaire. Body mass index and waist circumference were used for the study of obesity. Body mass index and poor periodontal health status were significantly higher(33.3%) and abdominal obesity and poor periodontal health status were 10.9%.Abdominal obesity was significantly higher(28.6%) in the group with less than 20 teeth. Body mass index and abdominal obesity were higher in body pain, psychological discomfort, physical abilities, psychological abilities, social disadvantage, and oral health than in normal subjects. As a result of correlation analysis with obesity index, it was found that the more period of obesity, the more periodontal disease and mucosal state related symptoms appeared(p<0.05). Therefore, in order to solve health problems such as obesity, it is necessary to recognize the importance of oral health and to make efforts to induce positive oral health behavior.

• Journal of the Korean Society of Clothing and Textiles
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• v.26 no.5
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• pp.630-641
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• 2002

The purpose of this study is to suggest the standard of bodytype which offers various data with regard to three-dimensional characteristics of body, and which offers the criterion for the sizes and shapes to interpret various bodytypes, to estimate filling, and to construct ready-made clothing. In this study, standard bodytype was defined as a typical type with beautiful proportion and shape which a large number of people have, too. In order to continue this study, there were two ways of analyzing bodytypes of subjects in the view of statistics and beauty. We primarily carried on statistical analysis in this report. Taken as a sample, the subjects were ninety-seven females who were between the ages of 18 and 24 years o1d. They were measured on November 1999. The data of seven hundred and few females, 18∼24 year-old, from the National Somatometry Survey of 1997 were used for analysis, too. Three kinds of classification methods were used for statistical analysis. The first method was based on the lateral view of the body, the second was based on the Factor and Cluster analysis of the photographic measurements of each of the anterior and lateral body, and the third was based on the Factor and Cluster analysis of the anthropometric measurements of the whole body. From the analysis on the distribution of R hrer Index the difference of width, the difference of depth, the proportion of height and head height, the High-frequency Proportion(H.P.)range were selected. The straight type from the lateral view, High-frequency type from each method, and subjects in H.P. range were compared with each other. As the result, it was confirmed that it is proper to base on the size and shape of subjects in H.P. range to analyze the standard bodytype.

• Geomechanics and Engineering
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• v.21 no.1
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• pp.23-33
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• 2020

An advancing cutting roof for gob-side entry retaining with no-pillar mining under specific geological conditions is more conducive to the safe and efficient production in a coalmine. This method is being promoted for use in a large number of coalmines because it has many advantages compared to the retaining method with an artificial filling wall as the gateway side filling body. In order to observe the inner structure of the gateway cutting roof and understand its stability mechanism, an equivalent material simulation experiment for a coalmine with complex geological conditions was carried out in this study. The results show that a "self-stabilization bearing structure" equilibrium model was found after the cutting roof caving when the cut line deviation angle was unequal to zero and the cut height was greater than the mining height, and the caving roof rock was hard without damage. The model showed that its stability was mainly controlled by two key blocks. Furthermore, in order to determine the optimal parameters of the cut height and the cut line deviation angle for the cutting roof of the retaining gateway, an in-depth analysis with theoretical mechanics and mine rock mechanics of the model was performed, and the relationship between the roof balance control force and the cut height and cut line deviation angle was solved. It was found that the selection of the values of the cut height and the cut line deviation angle had to conform to a certain principle that it should not only utilize the support force provided by the coal wall and the contact surface of the two key blocks but also prevent the failure of the coal wall and the contact surface.

• Journal of the Korea Concrete Institute
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• v.19 no.5
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• pp.623-630
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• 2007

Grouting materials are used for the unification of superstructural and substructural body like bridge seat (shoe) or machinery pedestal and e.t.c by filling their intercalary voids. Accordingly, grouting materials have been developed and used mainly with products of high strength because those materials are constructed specially in a part receiving large or impact load. In this situation, the structural body constructed by grouting materials with high stiffness-centered (caused by high strength) products is apt to cause brittle failure when receiving over a limit stress and to cause cracks according to cumulative fatigue by continuous and cyclic load. In addition, grouting materials are apt to cause cracks by using too much rapid hardening agents that give rise to high heat of hydration to maintain high strength at early age. In this study, to overcome these problems, cement type grouting materials including powder of waste tire and resin as elastic materials which aim to be more stable construction and to be improvement of mother-body's unification are developed and endowed with properties of high toughness and high durability add to existing properties of high flowability, non-shrinkage and high strength. Besides, this study contribute to of for green construction materials for being possible recycling industrial waste like waste tire and flyash. On the whole, seven type mixing conditions are tested and investigated to choose the best mixing condition.

• Proceedings of the KOR-BRONCHOESO Conference
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• 1981.05a
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• pp.11.2-11
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• 1981

Compared with other medical parts, there are relatively rare cases of the calculi in the Otolaryngologic field. The authors have recently experienced cases of the tonsillolith and huge rhinolith. They were removed successfully under the local anesthesia. Small quantities of calcareous or gritty particles are often found in the center of the caseous plugs filling the crypts of the tonsil in chronic follicular tonsillitis. The patients usually give a history of repeated tonsillitis in the earlier years. The patient may be aware of a constant sensation as of a foreign body in the throat. The breath is often fetid. The tonsillar calculi was found to be the accumulated keratohyalin masses in the crypts. The rhinoliths are rare in nasal cavity. They usualy have a foreign body nucleus of bacteria, blood, pus cells, mucus, crusts, or some foreign material from outside the body. They are largely composed of calcium and magnesium salts, principally carbonate with traces of sodium chloride. The condition is commonly found in adults and in female. They are usualy unilateral and are located, in the majority of instances, in the lower portion of the nasal cavity. The first well documented cases of rhinolithiasis, however, were reported by Bartholin in 1654. Since then over 400 cases have been reported.