• Structural Engineering and Mechanics
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• 제12권5호
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• pp.507-526
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• 2001

In standard finite element algorithms, the local stability conditions are not accounted for in the formulation of the tangent stiffness matrix. As a result, the loss of the local stability is not adequately related to the onset of the global instability. The phenomenon typically arises with material-type localizations, such as shear bands and plastic hinges. This paper addresses the problem in the context of the planar, finite-strain, rate-independent, materially non-linear beam theory, although the proposed technology is in principle not limited to beam structures. A weak formulation of Reissner's finite-strain beam theory is first presented, where the pseudocurvature of the deformed axis is the only unknown function. We further derive the local stability conditions for the large deformation case, and suggest various possible combinations of the interpolation and numerical integration schemes that trigger the simultaneous loss of the local and global instabilities of a statically determined beam. For practical applications, we advice on a procedure that uses a special numerical integration rule, where interpolation nodes and integration points are equal in number, but not in locations, except for the point of the local instability, where the interpolation node and the integration point coalesce. Provided that the point of instability is an end-point of the beam-a condition often met in engineering practice-the procedure simplifies substantially; one of such algorithms uses the combination of the Lagrangian interpolation and Lobatto's integration. The present paper uses the Galerkin finite element discretization, but a conceptually similar technology could be extended to other discretization methods.

• Advances in nano research
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• 제15권4호
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• pp.339-353
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• 2023

This work aims to present a solution for the buckling behavior of perforated nano/microbeams with deformable boundary conditions using nonlocal strain gradient theory (NLSGT). For the first time, a solution that can provide buckling loads based on the non-local and strain gradient effects of perforated nanostructures on an elastic foundation, while taking into account both deformable and rigid boundary conditions. Stokes' transformation and Fourier series are used to realize this aim and determine the buckling loads under various boundary conditions. We employ the NLSGT to account for size-dependent effects and utilize the Winkler model to formulate the elastic foundation. The buckling behavior of the perforated nano/microbeams restrained with lateral springs at both ends is studied for various parameters such as the number of holes, the length and filling ratio of the perforated beam, the internal length, the nonlocal parameter and the dimensionless foundation parameter. Our results indicate that the number of holes and filling ratio significantly affect the buckling response of perforated nano/microbeams. Increasing the filling ratio increases buckling loads, while increasing the number of holes decreases buckling loads. The effects of the non-local and internal length parameters on the buckling behavior of the perforated nano/microbeams are also discussed. These material length parameters have opposite effects on the variation of buckling loads. This study presents an effective eigenvalue solution based on Stokes' transformation and Fourier series of the restrained nano/microbeams under the effects of elastic medium, perforation parameters, deformable boundaries and nonlocal strain gradient elasticity for the first time.

• Journal of Advanced Marine Engineering and Technology
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• 제20권3호
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• pp.91-100
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• 1996

Experimental results for forced convection condensation of non-azeotropic refrigerant mixtures inside a horizontal smooth tube are presented. The mixtures of R-22+R-134a and pure refrigerants R-22 and R-134a are used as the test fluids and a double pipe heat exchanger of 7.5mm ID and 4800mm long inside tube is used. The range of parameters are 100-300kg/h of mass flow rate, 0-1.0 of quality, and 0, 33, 50, 67, and 100 weight percent of R-22 mass fraction in the mixtures. The heat flux, vapor pressure, vapor temperature and tube wall temperature were measured. Using the data, the local and average heat transfer coefficients for the condensation have been obtained. In the same given experimental conditions, the liquid heat transfer coefficients for NARMs were considerally lower than that of the pure refrigerant of R-22 and R-134a. Local heat transfer characteristics for NARMs were different from pure refrigerant R-22 and R-134a. In some regions, local heat transfer coefficients for NARMs were increased in the following order ; Bottom$\rightarrow$Top$\rightarrow$Side. The condensation heat transfer coefficients for NARMs increased with mass velocity, heat flux, and quality, but were considerably lower than that of pure refigerant R-22 and R-134a.

• Journal of Mechanical Science and Technology
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• 제17권8호
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• pp.1171-1184
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• 2003

An experimental study on critical heat flux (CHF) has been performed in an internally heated vertical annulus with non-uniform heating. The CHF data for the chopped cosine heat flux have been compared with those for uniform heat flux obtained from the previous study of the authors, in order to investigate the effect of axial heat flux distribution on CHF. The local CHF with the parameters such as mass flux and critical quality shows an irregular behavior. However, the total critical power with mass flux and the average CHF with critical quality are represented by a unique curve without the irregularity. The effect of the heat flux distribution on CHF is large at low pressure conditions but becomes rapidly smaller as the pressure increases. The relationship between the critical quality and the boiling length is represented by a single curve, independent of the axial heat flux distribution. For non-uniform axial heat flux distribution, the prediction results from Doerffer et al.'s and Bowling's CHF correlations have considerably large errors, compared to the prediction for uniform heat flux distribution.

• 수완나부미
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• 제13권1호
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• pp.135-159
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• 2021

Thơ mới (Vietnamese New Poetry, 1932-1945) is a literary movement in colonial Vietnam that is broadly considered to have marked the modernization of Vietnamese literature. This paper examines depictions about natural disasters, ecological wounds, and about relationships between humans and nature in New Poetry, asking how those descriptions reflect social and political issues in colonial Vietnam. The paper argues that ecocriticism, developed in Western academy, brought to the New Poetry Movement new meanings, associated with a material world. That is the specific reality of colonial Vietnam in the early twentieth century, when the colonial modernization resulted in natural and social collapses in the area. This approach is especially significant, given that New Poetry is largely seen as the embodiment of the expansion of Western romanticism by Vietnamese scholars. Moreover, in examining Thơ mới (Vietnam) from perspective of ecocriticism, this paper extends the ecocritical approach to non-Western literatures. Specifically, although ecocriticism developed in the West, particularly in United States and England, it has become an effective approach to non-Western literatures, particularly since the early twentieth first century. In this context, Asian literatures, particularly Southeast Asian literatures, potentially offer ecocriticism new meanings, many of which are associated with local social and political conditions and histories.

• 한국환경과학회지
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• 제6권6호
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• pp.645-658
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• 1997

A study on ventilation design using the spreadsheet model is carried out to propose means of available design. A sample of complex ventilation system In the non-standard condition Is used to illustrate thins spreadsheet model. In developing the spreadsheet model, this study has attempted to it general by using computional equations and design parameters that can be readily applied to any spreadsheet software. Also, most design data is contained in the spreadsheet template. This template provides the same design information as the ACGIH worksheet, and operates Quickly and emclenuy, and is fiexible enough to use under different conditions. This spreadsheet model allows the ventilation engineer to design quickly and accurately the ventilation system, without spending too much effort In the design process. By storing on computer and diskette, the design data computed finally can be used as a permanent record of specific ventilation system, and because of finally to be able to design over and over again while making only slight changes to the Input data, the spreadsheet model is used availably to accomplish the design optimazation by redesign and troubleshooting by review from field measurements. Also, the spreadsheet model is available for designing ventilation system under different condition or evaluating existing system or design drawing, because changes In the layout or formulae can be readily made to fit the needs of the designer.

• 한국연소학회지
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• 제17권1호
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• pp.22-29
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• 2012

The detachment stability characteristics of syngas $H_2$/CO jet attached flames were studied. The flame stability was observed while varying the syngas fuel composition, coaxial nozzle diameter and fuel nozzle rim thickness. The detachment stability limit of the syngas single jet flame was found to decrease with increasing mole fraction of carbon monoxide in the fuel. In hydrogen jet flames with coaxial air, the flame detachment stability was found to be independent of the coaxial nozzle diameter. However, velocities of appearance of liftoff and blowout velocities of lifted flames have dependence. At lower fuel velocity range, the critical coaxial air velocity leading to flame detachment increases with increasing fuel jet velocity, whereas at higher fuel velocity range, it decreases. This increasing-decreasing non-monotonic trend appears for all $H_2$/CO syngas compositions (50/50~100/0% $H_2$/CO). To qualitatively understand the flame behavior near the nozzle rim, $OH^*$ chemiluminescence imaging was performed near the detachment limit conditions. For all fuel compositions, local extinction on the rim is observed at lower fuel velocities(increasing stability region), while local flame extinction downstream of the rim is observed at higher fuel velocities(decreasing stability region). Maximum values of the non-monotonic trends appear to be identical when the fuel jet velocity is normalized by the critical fuel velocity obtained in the single jet cases.

• 한국응급구조학회지
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• 제10권1호
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• pp.13-21
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• 2006

Purpose: This study aims to examine characteristics and actual conditions of patients using emergency room at farming and fishing villages, solve overcrowding of emergency room at the tertiary hospital and activate local emergency clinics. Methods: It examines department of diagnosis and treatment, vehicles used, sex, age, residential area, visit hour, length of stay, presence or absence of trauma, measures after first aid and degree of severity based on medical records of 6,740 patients using emergency room at farming and fishing villages from Jan. 1 to Dec. 31, 2005. Conclusion : 1. Sex distribution of patients of emergency room was male 54.9% and female 45.1% and age distribution between over 40 and below 50 was most as 15.9%. 2. Transport means to emergency room were 91.4 of private car and others (public transport and going on foot), 7.5 of 119, 129 and police car and 1.0% of ambulance. 3. According to distribution of residential areas of emergency patients, 38.9% were Eup area, 42.1% Myeon area, 11.4% distant area and 7.5% adjacent area. 4. According to distribution of emergency patients by department of diagnosis and treatment, internal medicine was most as 35.8% and 55% of patients visited emergency room from 3:31 p.m. to 11:30 p.m.. 5. According to total hours of diagnosis and treatment of subjects, 51.2% were within 30min. and cases of non-trauma disease were 68.2%. 6. According to degree of emergency of emergency patients, non-emergency cases were 65.3%, urgent cases 27.7% and emergency cases 7.0% and 74.2% of patients returned home after first aid and 20.6% of them hospitalized. In conclusion, characteristics and diversification of patients should be examined and efforts by government and local medical institutions which must organize emergency system and facility and personnel levels suitable to regional conditions are needed in order to prevent overcrowding of emergency center of the tertiary hospital and activate local emergency center.

• 대한영양사협회학술지
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• 제26권3호
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• pp.196-207
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• 2020

This study was undertaken to provide basic data for revitalizing the school meal support centers and improving school meals, by analyzing the purchase conditions and satisfaction of food according to an adoption of a school meal service support center. Comparing the purchasing efficiency, convenience to purchase, and higher overall satisfaction was achieved when a school meal service support center was adopted by the local government, as compared to non-adopted school meal service support centers. Therefore, it is considered that the adaption of a school meal service support center is urgently required by non-adoption local governments. Moreover, the stability of food material supplies was also higher in the adopted rather than the non-adopted centers. Satisfaction with the quality of food ingredients was also found to be significantly higher in the adopted centers. These results indicate that if the local government adopts and introduces the school meal support center, inconsistencies observed in the return and exchange processes experienced by the non-adopted centers can be resolved, and food quality satisfaction can be improved. We, therefore, propose the necessity to implement a system for determining reasonable pricing by establishing systematic cooperation among schools, manufacturing entities (suppliers), and the School Meal Service Support Center.

• Journal of applied mathematics & informatics
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• 제29권5_6호
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• pp.1167-1178
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• 2011

In this paper, we further investigate the local Hermitian and skew-Hermitian splitting (LHSS) iteration method and the modified LHSS (MLHSS) iteration method for solving generalized nonsymmetric saddle point problems with nonzero (2,2) blocks. When A is non-symmetric positive definite, the convergence conditions are obtained, which generalize some results of Jiang and Cao [M.-Q. Jiang and Y. Cao, On local Hermitian and Skew-Hermitian splitting iteration methods for generalized saddle point problems, J. Comput. Appl. Math., 2009(231): 973-982] for the generalized saddle point problems to generalized nonsymmetric saddle point problems with nonzero (2,2) blocks. Numerical experiments show the effectiveness of the iterative methods.