• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.142-154
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• 1998

A stirling engine is a mechanism used to convert heat to power and operates on a closed regenerative thermodynamic cycle with compression and expansion of the working fluid at different temperature. The performance of a stilting cycle machine is a function of six independent parameters, namely; (1) speed N(r.p.m), (2) pressure of the working fluid p(Pa), (3) ratio of the temperature in the compression and expansion space ${\tau}(=T_C/T_E)$ , (4) ratio of the swept volumes in these two spaces K, (5) phase angle $\alpha$ and (6) dead volume ratio X. This paper describes the procedure and presents the results of computations carried out to establish the optimum combinations of these six parameters for maximum engine output for the machine acting as a prime mover, over a combined temperature range from $300^{\circ}K$ to $1000^{\circ}K$ and dead volume ratio X ranging from 0.1 to 2.0. The output of a stilting cycle machine can be expressed in terms of nondimensional power in several different ways. Four methods were studied in detail, the parameters optimized and design charts and engine power charts prepared. The results of this paper may be useful as a guide to the likely effects on the performance of some of the important design parameters and regenerator design.

• Korean Management Science Review
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• v.12 no.2
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• pp.129-146
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• 1995

As society's relience on computerized information systems to support a wide range of activities proliferates, the long recognized importance for adequate data quality becomes imperative. Furthermore, current trends in information systems such as dispersal of the data resource together with its management have increased the difficulty of maintaining suitable levels of data integrity. Especially, the importance of adequate accounting (transaction) data quality has been long recognized and many procedures (extensive and often elaborate checks and controls) to prevent errors in accounting systems have been introduced and developed. Nevertheless, over time, even in the best maintained systems, deficiencies in stored data will develop. In order to maintain the accuracy and reliability of accounting data at certain level, periodic internal checks and error corrections (internal audits) are required as a part of internal control system. In this paper we develop a general data quality degradation (error accumulation ) and cost model for an account in which we have both error occurrences and error amounts and provide a closed form of optimal audit timing in terms of the number of transactions that should occur before an internal audit should be initiated. This paper also considers the cost- effectiveness of various audit types and different error prevention efforts and suggests how to select the most economical audit type and error prevention method.

• Computers and Concrete
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• v.18 no.5
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• pp.983-998
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• 2016

Structural optimization is one of the most important topics in structural engineering and has a wide range of applicability. Therefore, the main objective of the present study is to apply the Lagrange Multiplier Method (LMM) for minimum cost design of singly and doubly reinforced rectangular concrete beams. Concrete and steel material costs are used as objective cost function to be minimized in this study, and ultimate flexural strength of the beam is considered to be as the main constraint. The ultimate limit state method with partial material strength factors and equivalent concrete stress block is used to derive general relations for flexural strength of RC beam and empirical coefficients are taken from topic 9 of the Iranian National Building Regulation (INBR9). Optimum designs are obtained by using the LMM and are presented in closed form solutions. Graphical representation of solutions are presented and it is shown that proposed design curves can be used for minimum cost design of the beams without prior knowledge of optimization and without the need for iterative trials. The applicability of the proposed relations and curves are demonstrated through two real life examples of SRB and DRB design situations and it is shown that the minimum cost design is actually reached using proposed method.

• Structural Engineering and Mechanics
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• v.24 no.5
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• pp.543-560
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• 2006

In this paper, first, the equations of motion for a rectangular isotropic plate have been derived. This derivation is based on the Von Karmann theory and the effects of shear deformation have been considered. Introducing an Airy stress function, the equations of motion have been transformed to a nonlinear coupled equation. Using Galerkin method, this equation has been separated into position and time functions. By means of the dimensional analysis, it is shown that the orders of magnitude for nonlinear terms are small with respect to linear terms. The Multiple Scales Method has been applied to the equation of motion in the forced vibration and free vibration cases and closed-form relations for the nonlinear natural frequencies, displacement and frequency response of the plate have been derived. The obtained results in comparison with numerical methods are in good agreements. Using the obtained relation, the effects of initial displacement, thickness and dimensions of the plate on the nonlinear natural frequencies and displacements have been investigated. These results are valid for a special range of the ratio of thickness to dimensions of the plate, which is a characteristic of the Multiple Scales Method. In the forced vibration case, the frequency response equation for the primary resonance condition is calculated and the effects of various parameters on the frequency response of system have been studied.

• Structural Engineering and Mechanics
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• v.34 no.4
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• pp.507-523
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• 2010

Parametric and forced non-linear vibrations of an axially moving rotor both in non-resonance and near-resonance cases have been investigated analytically in this paper. The axial speed is assumed to involve a mean value along with small harmonic fluctuations. Hamilton's principle is employed for this gyroscopic system to derive three coupled non-linear equations of motion. Longitudinal inertia is neglected under the quasi-static stretch assumption and two integro-partial-differential equations are obtained. With introducing a complex variable, the equations of motion is presented in the form of a single, complex equation. The method of multiple scales is applied directly to the resulting equation and the approximate closed-form solution is obtained. Stability boundaries for the steady-state response are formulated and the frequency-response curves are drawn. A number of case studies are considered and the numerical simulations are presented to highlight the effects of system parameters on the linear and nonlinear natural frequencies, mode shapes, limit cycles and the frequency-response curves of the system.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2481-2485
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• 2007

Spatially resolved, quantitative, non-destructive analysis using synchrotron x-ray reflectivity (XR) with subnano-scale resolution was successfully performed on the nanoporous organosilicate thin films for low dielectric applications. The structural information of porous thin films, which were prepared with polymethylsilsesquioxane and thermally labile 4-armed, star-shaped poly(ε-caprolactone) (PCL) composites, were characterized in terms of the laterally averaged electron density profile along with a film thickness as well as a total thickness. The thermal process used in this work caused to efficiently undergo sacrificial thermal degradation, generating closed nanopores in the film. The resultant nanoporous films became homogeneous, well-defined structure with a thin skin layer and low surface roughness. The average electron density of the calcined film reduced with increase of the initial porogen loading, and finally leaded to corresponding porosity ranged from 0 to 22.8% over the porogen loading range of 0-30 wt%. In addition to XR analysis, the surface and the inner structures of films are investigated and discussed with atomic force and scanning electron microscopy images.

• Structural Engineering and Mechanics
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• v.20 no.5
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• pp.589-608
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• 2005

There is a growing need for the development and implementation of new methods for the rapid and cost-effective rehabilitation of deteriorating steel structural components to offset the drawbacks related to welding and/or bolting in the field. Carbon fiber reinforced polymer (CFRP) composites provide a potential alternative as externally bonded patches for strengthening and repair of metallic structural members for building and bridge systems. This paper describes results of an investigation of tensile and fatigue response of steel/CFRP joints simulating scenarios of strengthening and crack-patching. It is shown that appropriately designed schemes, even when fabricated with levels of inaccuracy as could be expected in the field, can provide significant strain relief and load transfer capability. A simplified elasto-plastic closed form solution for stress analysis is presented, and validated experimentally. It is shown that the bond development length remains constant in the linear range, whereas it increases as the adhesive is deformed plastically. Fatigue resistance is shown to be at least comparable with the requirements for welded cover plates without attendant decreases in stiffness and strength.

• The Korean Journal of Ecology
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• v.25 no.1
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• pp.45-49
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• 2002

Pollen analyses and $^{14}$ C dating of the sediments of the Akindonuma moor, which is situated in a closed depression of an old landslide, were peformed in order to study the vegetation history of the montane zone of the Miyagi Prefecture, Northeast Japan. The main results are as follows: Two forest zones have been distinguished: 1) the A-I zone, or the Fagus-Quercus-Betula forest (R I stage, before about 11,700 yrs B.P.), and 2) the A-II zone, or the Fagus-Quercus forest (R II stage, after about 11,700 yrs B.P.). By comparing the geological section with the pollen diagram of the moor, it is assumed that the deposit environment of the Middle Part, which mostly consists of peat layers, is very stable. During the period, the Ulmus/Zelfkova pollen ratio was very low and small peak was not recognized. According to the preceding research, theme is a close relationship between the fluctuation of the Ulmus/Zelkova pollen ratio and the general trend of hillslope instability in the changing balance of temporature and precipitation Actually, Zelkova serrata tends to cover the footslope and the lower sideslope. Ulmus davidiana covers the footslope and the alluvial cone. Therefore, the fact that the Ulmus/Zeikova pollen ratio was very low and small peak was not recognized, is believed to reflect the stability of the earth's surface environment, which was estimated from the geological section.

• Physical Therapy Korea
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• v.24 no.4
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• pp.20-28
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• 2017

Background: Rasch analysis has the advantage of placing both the items and the person along a single ratio scale and calibrates person ability and item difficulty onto an interval scale by logits. Therefore, Rasch analysis has been recommended as a better method for evaluating functional outcome questionnaires than traditional analyses. Objects: The aim of current study was to investigate item fit, item difficulty, rating scale, and separation index of the Korean version of the Fullerton Advanced Balance (KFAB) scale using Rasch analysis. Methods: In total, 93 patients with stroke (male=58, female=35) participated in this study. To investigate the item fit, difficulty, rating scale, and separation index of the KFAB scale, Rasch analysis was completed by the Winsteps software program. Results: In this study, all items of the KFAB scale were included in the Rasch model. The most difficult item was 'standing with feet together and eyes closed', and the easiest item was 'two-footed jump'. The rating scale was a 4-point scale instead of the original 5-point scale. Person and item separation indices showed high values that can identify a person with a wide range of balance ability. Conclusion: The KFAB scale appears to be a reliable and valid tool to assess balance function in patients with stroke. Furthermore, the scale was found to discriminate among stroke patients of varying balance abilities.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.234-238
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• 1999

In order to radiate X-ray, the low ripple stabilized high voltage DC over the range of 40KV to 150KV is directly inflicted to X-ray tube. The energy characteristics of the radiated X-ray depend on the pulsating waveforms of the DC voltage supplied X-ray tube. In general, the low ripple voltage waveforms with fast rising times are required to increase with the dosage per unit time lest the exposure time should be longer in orde that the motion artifacts of an object may be eliminated in actual. The conventional types of X-ray generators were bulky in physical size and heavy in weight, and the control accuracies of the output voltages were not always satisfactory. The high frequency switching inverter and converter technology on power conversion and control systems have been greatly closed up introducing new power semiconductor devices. To decreasing the volume and the weight of high voltage transformer, and to stabilize ripple, a high frequency PWM inverter is connected between DC source and high voltage transformer. This paper describes the output characteristics according to stabilize ripple of X-ray tube voltage and compared the reproducibility, direcibility and doesage.