• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2873-2878
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• 2007

The mixing vanes attached to the spacer grid of rod bundles are used to improve the heat transfer in heat exchanger devices by controlling the characteristics of the flow structures and turbulence. In this study, velocity patterns induced by two types of mixing vane(split and swirl vane) are measured by the PIV technique to better understand how to effect on the cross and secondary vortex flow patterns in $5{\times}$ rod bundle simulating the fuel assembly of the nuclear reactor. A successful measurement of the lateral velocity patterns was conducted using a specially designed beam sheet generator and experimental loop at KAERI. As the result, we found that for the cross flow between subchannels, the split vane is more effective than the swirl vane, while for the secondary vortex flow in each subchannel, the swirl vane's one is larger and longer than split vane's one.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.934-939
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• 2001

In computational study of the flow in piston engines and the flow through moving valves, the use of moving vertices is essential for modelling flows with moving boundaries. The positions of cell vertices in such cases must be allowed to vary with time. To simulate 3-dimensional port-valve and piston-cylinder of HIMSEN 6H21/32 engine, a commercially available code, STAR-CD, was used. Changes in mesh geometry was specified by PROSTAR commands.(i.e. the Change Grid operation in the EVENTS command module.) Control of the intake flow is expected to play an important role as designers seek to obtain better fuel spray characteristics, fuel mixing and mixture preparation, combustion performance, and emissions reductions to meet national standards. As a result of analysis, velocity fields indicate the presence of a structured flow comprised of one pair of counter-rotating vortices under the intake valve during the early induction process. These flow structures remain visible for most of the intake process. As the piston moves towards BDC, these vortices develops into a larger tumbling motion that dominates the flow structure.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.7
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• pp.963-970
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• 2010

This study makes an estimate of the laser-assisted machining (LAM) of an economically viable process for manufacturing precision silicon nitride ceramic parts using a high-power diode laser (HPDL). The surface is locally heated by an intense laser source prior to material removal, and the resulting softening and damage of the workpiece surface simplify the machining of the ceramics. The most important advantage of LAM is its ability to produce much better workpiece surface quality compared to conventional machining. Also important are its larger material removal rates and longer tool life. The cutting force and surface temperature were measured on-line using a pyrometer and a dynamometer, respectively. Tool wear, chips and the surface of the workpiece were measured using optical microscopy, and the surface and fractured cross-section of $Si_3N_4$ were measured by SEM. During the LAM process, the cutting force and tool wear were reduced and oxidation of the machined surface was increased according to the increase in the laser power. Moreover, the more the feed rate increased, the more the cutting force and tool wear increased.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.3
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• pp.1507-1512
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• 2016

Background: Risk of developing breast cancer increases with short breastfeeding and the use of hormones. The prognosis of breast cancer is better if the tumours are hormone receptor positive. Since breast feeding affects estrogen and progesterone receptors, we wanted to investigate how such reproductive factors as breastfeeding and the use of hormones interact with known prognostic markers and specific tumour characteristics in women with breast cancer. Materials and Methods: A total of 250 women treated for breast cancer from a larger cohort completed a questionnaire on breastfeeding, number and age at births and use of hormones. A logistic regression analysis was made to search for connections between known prognostic markers on the one hand (type of cancer, grade, tumor size, estrogen receptor and progesterone receptor, lymphovascular invasion and DNA-ploidy) and reproductive data, breastfeeding, and hormone use on the other. Results and Conclusions: Hormone use, but not breastfeeding, was significantly associated, also on multivariate analysis, with the prognostic variable lymphovascular invasion, connected to a worse prognosis. No other hormone use or breast feeding correlations with prognostic variables were found.

• Wind and Structures
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• v.24 no.4
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• pp.351-365
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• 2017

The minimization method is widely used to predict the dynamic characteristics of a system. Generally, data recorded by experiment (for example displacement) tends to contain noise, and the error in the properties of the system is proportional to the noise level (NL). In addition, the accuracy of the results depends on various factors such as the signal character, filtering method or cut off frequency. In particular, coupled terms in multimode systems show larger differences compared to the true value when measured in an environment with a high NL. The iterative least square (ILS) method was proposed to reduce these errors that occur under a high NL, and has been verified in previous research. However, the ILS method might be sensitive to the signal processing, including the determination of cutoff frequency. This paper focused on improving the accuracy of the ILS method, and proposed the modified ILS (MILS) method, which differs from the ILS method by the addition of a new calculation process based on correlation coefficients for each degree of freedom. Comparing the results of these systems with those of a numerical simulation revealed that both ILS and the proposed MILS method provided good prediction of the dynamic properties of the system under investigation (in this case, the damping ratio and damped frequency). Moreover, the proposed MILS method provided even better prediction results for the coupling terms of stiffness and damping coefficient matrix.

• Steel and Composite Structures
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• v.22 no.6
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• pp.1217-1238
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• 2016

Mega composite structure systems have been widely used in high rise buildings in China. Compared to other structures, this type of composite structure systems has a larger cross-section with less weight. Concrete filled steel tubular (CFST) laced column to box-beam connections are gaining popularity, in particular for the mega composite structure system in high rise buildings. To enable a better understanding of the destruction characteristics and aseismic performance of these connections, three different connection types of specimens including single-limb bracing, cross bracing and diaphragms for core area of connections were tested under low cyclic and reciprocating loading. Hysteresis curves and skeleton curves were obtained from cyclic loading tests under axial loading. Based on these tested curves, a new trilinear hysteretic restoring force model considering rigidity degradation is proposed for CFST laced column to box-beam connections in a mega composite structure system, including a trilinear skeleton model based on calculation, law of stiffness degradation and hysteresis rules. The trilinear hysteretic restoring force model is compared with the experimental results. The experimental data shows that the new hysteretic restoring force model tallies with the test curves well and can be referenced for elastic-plastic seismic analysis of CFST laced column to composite box-beam connection in a mega composite structure system.

• Journal of Power System Engineering
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• v.9 no.3
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• pp.50-57
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• 2005

A cross-flow fan is strongly influenced by the various design factors of a rear-guider and a stabilizer. The purpose of this paper is to investigate the effects of a rear-guider and a stabilizer on the surface pressure of a rear-guider in an indoor room air-conditioner using a cross-flow fan. The design factors considered in this paper are a rear-guider clearance, a stabilizer clearance, and a stabilizer setup angle, respectively. The operating condition of a cross-flow fan was controlled by changing the static pressure and flowrate using a fan tester. All surface pressures of a rear-guider are differently distributed according to the stabilizer setup angle, and show a zero value in the flow coefficient, ${\Phi}{\fallingdotseq}0.5$ only of a stabilizer setup angle, $45^{\circ}$. Especially, they show a big negative value in the expansion angle larger than $34^{\circ}$ regardless of a rear-guider clearance, a stabilizer clearance, and a stabilizer setup angle. On the other hand, surface pressures for various stabilizer cutoff clearances are better than those for various rear-guider clearances.

• The Journal of the Acoustical Society of Korea
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• v.9 no.3
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• pp.11-23
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• 1990

In order to investigate the acoustical characteristics of the Hae-keum (Korean traditional musical instrument) tone quality, the spectrum and wave form of Hae-keum sounds were analyzed by the FFT Analyzer. The analysis was carried out by the varying of the tension of Hae-keum strings, the positions of bridge and the top plate's thickness of Hae-keum respectively. According to the experiment, the following results are obtained ; the over tone's amplitude nearby the top plate resonance frequency is greater than the fundamental tone's amplitude because the top plate resonance frequency is higher than the fundamental tone's frequency. Tone qualities are better when the bridge is situated in the middle of top plate and the tension of strings is larger. The inharmonicity coefficient of the Hae-keum's second string is 0.049 cents/$n^2$. The brilliance and richness is poor, because we seldom found the over tone over 5kHz and the inharmonicity of the Hae-keum is greater than that of a violin. Also we confirmed that we are able to get the best tone quality in 4.5mm thickness of the Hae-keum's top plate.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.35 no.3
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• pp.3-12
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• 2019

Since offline contact becomes a strong differentiator as online market expands, the shopping mall calls for more complex and diverse tenant combinations and deployment plan strategies. There is, however, few practical research and causal verification of Tenant Mix, i.e., the combination and placement of tenant and users' behavior, has been conducted which is a key factor in spatial configuration. In practice, Tenant Mix is limited in prediction of consumption behavior of customers by the MD planners's experience and depends only on qualitative arbitrary plan. The purpose of this study is to find out the interrelationship between the spatial configuration and the users' behavior of Tenant Mix in shopping mall, and to present an objective basis in MD planning. According to the analysis, it was possible to know that there are differences in the relationship between the spatial configuration and the users' behavior dependent on the Tenant Mix, which is the space planning of shopping mall. It was also possible to find out the characteristics and differences in the users' behavior which is dependent on the spatial configuration for each tenant. Through this study, it was possible to know the impact of space organization on the users' behavior and the interrelationship between the use's behavior and spatial configuration by tenant together with their characteristics. We prove that the current MD planning has limitation due to lack of objective research on the combination and arrangement of space in the commercial space and only done empirically. This analysis can show the practical plan of combination and placement of tenant which is emphasized in complex and larger shopping malls, and contribute to the revitalization of shopping mall by better use of tenant.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.5 s.120
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• pp.471-477
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• 2007

This paper presents the characteristics of electromagnetic field uniformity in a reverberation chamber with flat diffusers composed of multiple dielectric materials that can be used as an alternative facility for the analysis, test and evaluation of electromagnetic interference and immunity. The field characteristics and the size of the test volume inside the reverberation chamber with the new diffuser of multiple dielectric materials are simulated and analyzed at $2.5{\sim}3$ GHz band. The FDTD method is used to analyze the field characteristics. The field uniformity, polarization characteristics and tolerance are improved by the new diffuser with smaller physical size. The reverberation chamber with flat diffusers composed of multiple dielectric materials shows better electromagnetic performance and larger test volume than normal chamber.