• 호남수학학술지
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• 제26권4호
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• pp.423-439
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• 2004

We are concerned with the robust control problem for the Keller-Segel equations with the distributed control and disturbance. We consider the present problem as a differential game finding the best control which takes into account the worst disturbance. We prove the existence of solutions and the optimality conditions to a corresponding problem.

• 한국주거학회논문집
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• 제2권1호
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• pp.77-92
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• 1991

This study is to investigate urban housing conditions in Seoul since 1945. The purposes of this study is to analyze the changes of housing conditions and the gap of average housing conditions and the housing norms longitudinally.For those purposes, the indicators that present the housing conditions are introduced, and the changes of average housing conditions are analyzed by social class, using Population and Housing Census and relateddata. Korean urban housing conditions has been better since 1970s in the aspect of quality. It is, however, relatively much worse than that of developed countries. The gap of housing conditions among social classes is large, especially in qualitative indicators, density and housing facilities. Comparing it with housing norm(as an ideal measurement), it is much worse.

• Kyungpook Mathematical Journal
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• 제46권1호
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• pp.131-137
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• 2006

The object of the present paper is to obtain new conditions for analytic function to be strongly starlike and strongly convex function defined in the open unit disk.

• Geomechanics and Engineering
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• 제24권6호
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• pp.505-518
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• 2021

The present paper has been carried out to understand the effects of impact loading on the rock tunnels, constructed in different region corresponding to varying unconfined compressive strength (UCS), through finite element method. The UCS of rockmass has substantial role in the stability of rock tunnels under impact loading condition due to falling rocks or other objects. In the present study, Dolomite, Shale, Sandstone, Granite, Basalt, and Quartzite rocks have been taken into consideration for understanding of the effect of UCS that vary from 2.85 MPa to 207.03 MPa. The Mohr-Coulomb constitutive model has been considered in the present study for the nonlinear elastoplastic analysis for all the rocks surrounding the tunnel opening. The geometry and boundary conditions of the model remains constant throughout the analysis and missile has 100 kg of weight. The general hard contact has been assigned to incorporate the interaction between different parts of the model. The present study focuses on studying the deformations in the rock tunnel caused by impacting load due to missile for tunnels having different concrete grade, and steel grade. The broader range of rock strength depicts the strong relationship between the UCS of rock and the extent of damage produced under different impact loading conditions. The energy released during an impact loading simulation shows the variation of safety and serviceability of the rock tunnel.

• Steel and Composite Structures
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• 제38권1호
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• pp.1-15
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• 2021

In this paper, a higher order shear deformation theory for bending analysis of functionally graded plates resting on Pasternak foundation and under various boundary conditions is exposed. The proposed theory is based on the assumption that porosities can be produced within functionally graded plate which may lead to decline in strength of materials. In this research a novel distribution of porosity according to the thickness of FG plate are supposing. Governing equations of the present theory are derived by employing the virtual work principle, and the closed-form solutions of functionally graded plates have been obtained using Navier solution. Numerical results for deflections and stresses of several types of boundary conditions are presented. The exactitude of the present study is confirmed by comparing the obtained results with those available in the literature. The effects of porosity parameter, slenderness ratio, foundation parameters, power law index and boundary condition types on the deflections and stresses are presented.

• Journal of Mechanical Science and Technology
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• 제15권12호
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• pp.1882-1891
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• 2001

The present paper investigated the effect of ultrasonic vibrations on the melting process of a phase-change material (PCM). Furthermore, the present study considered constant heat flux boundary conditions unlike many of the previous researches adopted constant wall temperature conditions. Therefore, in the present study, modified dimensionless parameters such as Ste* and Ra* were used. Also, general relationships between melting with ultrasonic vibrations and melting without ultrasonic vibrations were established during the melting of PCM. Experimental observations show that the effect of ultrasonic vibrations on heat transfer is very important throughout the melting process. The results of the present study reveal that ultrasonic vibrations accompany the effects like agitation, acoustic streaming, cavitation, and oscillating fluid motion. Such effects are a prime mechanism in the overall melting process when ultrasonic vibrations are applied. They enhance the melting process as much as 2.5 tildes, compared with the result of natural melting. Also, energy can be saved by applying ultrasonic vibrations to the natural melting. In addition, various time-wise dimensionless numbers provide conclusive evidence of the important role of ultrasonic vibrations on the melting phenomena.

• 한국응용과학기술학회지
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• 제28권3호
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• pp.284-289
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• 2011

All spectroscopic methods used in this work indicate the instability of tungstophosphates in aqueous solutions and considerable dependence on pH with regard to the dominant species present in the solution. UV spectroscopy indicates that some changes occur in the system but they cannot be specified. IR spectroscopy gives more information on the identification of the dominant species as a function the pH of the solution. NMR spectroscopy provides unique data, which can be used for more accurate interpretation of changes in the solution of various pH values. In the case of aqueous solutions of tungstophosphates, the parent anion was present only in a very acidic solution of ca. pH 1. Some differences in interpretation of the molecular species present under various experimental conditions can be ascribed to some extent to the diversity of chemical shifts of NMR. Under physiological conditions attained with the addition of NaOH, tungstophosphates was dominantly present in the form of the lacunary monovacant anion.

• 한국주거학회논문집
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• 제18권6호
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• pp.103-113
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• 2007

In Korea, open spaces of urban housing do not serve residents as "regular living areas". We carried out research on the "streets" of urban housings in that the meaning of traditional "streets", playing roles which are not only means of passage but also boundary of life, cannot include present meaning of "streets" of the urban housing. This research is to propose the direction of planning Community Streets for the recovery of the public- and communal urban housing's streets, researching the present employment condition of Community Streets that were prepared recently. Working with 3 complexes which have been completed since 2000, We studied the present employment condition and planned signification, according to the conditions of their surroundings, the physical conditions of Community Streets, and the relationship among main apartment buildings, open spaces, and facilities. From this study, We came up with several suggestions that can present the planning line of Community Streets. Therefore this research is to create the Community Streets for the activity of the streets, the recovery of the community, and improvement of ambulatory environment.

• Nuclear Engineering and Technology
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• 제28권3호
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• pp.299-310
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• 1996

A two-step approach has been used to obtain a new criterion for the onset of slug formation : (1) In the first step, a more general expression than the existing models for the onset of slug flow criterion has been derived from the analysis of singular points and neutral stability conditions of the transient one-dimensional two-phase flow equations of two-fluid model. (2) In the second step, introducing simplifications and incorporating a parameter into the general expression obtained in the first step to satisfy a number of physical conditions a priori specified, a new simple criterion for the onset of slug flow has been derived. Comparisons of the present model with existing models and experimental data show that the present model agrees very closely with Taitel & Dukler's model and experimental data in horizontal pipes. In an inclined pipe ($\theta$ =50$^{\circ}$), however, the difference between the predictions of the present model and those of existing models is appreciably large and the present model gives the best agreement with Ohnuki et al.'s data.

• 한국실내디자인학회:학술대회논문집
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• 한국실내디자인학회 2004년도 추계학술발표대회 논문집
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• pp.157-158
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• 2004

In this study, we try to understand the present condition of elderly housing facilities in Contra Costa County, California, USA. We got the basic information of 92 facilities through the interview with the chief of elderly housing department in Contra Costa County, California. In practical way of research, this study bears various components of the elderly housing facilities, which are type of facility, financial aids, type of apartment, and provided living services. The short summerising of researches are; The present conditions of elderly housing facilities can be classified as Independent Living(53), Congregate Housing(23), Assisted Living(33), Dementia Care(12). The financial aid conditions are shown like SSI, HA, HUD. The types of apartment are studio type, 1 bedroom type, 2 bedroom type. These facilities provides meals, housekeeping, transportation, small pets. As a result of studying the present condition of elderly housing facilities in Contra Costa County, we propose the basic statistical report on the most general type of housing, financial aids, type of services that people of the states want to get.