• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.3
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• pp.89-94
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• 2009

The stack effect in high-rise buildings is expected more significant at nights in winter due to the large temperature difference between the inside and outside of the buildings. However, the existence of large openings such as natural ventilators on the floor may effect the position of neutral plane, smoke spread at fire and thus obstruct the door openings for rescue. In this paper, the vertical and horizontal pressure distribution with different openings of natural smoke ventilators was experimentally analyzed by investigating pressure differentials.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.3
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• pp.127-133
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• 2017

Performance analysis has been carried out on a high side scroll compressor that had a fixed scroll equipped with a circular oil groove on its thrust surface. Oil was supplied to the oil groove through an intermittent opening from a high pressure oil reservoir formed inside the orbiting scroll hub. Oil in the groove was then delivered to both suction and back pressure chambers by pressure differentials and viscous pumping action of the orbiting scroll base plate. Mathematical modeling of this oil groove system was incorporated into a main compressor performance simulation program for an optimum oil groove design. The study findings were as follows. Pressure in the oil groove can be controlled by changing its configuration and the oil passage area. With an enlarged oil passage, the pressure in the oil groove heightens due to an increased flow rate, but the pressure elevation in the back pressure chamber is small, resulting in reduced friction loss at the thrust surface between the two scrolls. On the other hand, by increasing the oil passage area, the oil content in the refrigerant flow increases. Considering all these factors, the energy efficiency ratio could be improved by about 3.6% under the ARI condition by an optimal oil groove design.

• The Research Journal of the Costume Culture
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• v.14 no.1
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• pp.40-47
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• 2006

Three-dimensional body scanners were used for years in the clothing manufacturing fields. The 3D body surface provide essential data to draft patterns for mass customization, virtual fit model, and computerized patternmaking systems. This research proposed the methods of drafting patterns for men's jacket by using three dimensional body scan data. Eight male subjects were scanned, the surface data was flattened. The differentials of the flattened body surface and the jacket draft were measured, and analyzed the regressions. To verify the fit of the patterns, the jacket was constructed by the regression formulae and tested by experts. The fit of the jacket were significantly improved rather than a ready-made suit especially the shoulder areas. This means that the methods that we proposed were good to improve the fit of the garments and could be used effectively to implement mass customization strategies in the apparel retail industry.

• Korean Journal of Health Education and Promotion
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• v.30 no.1
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• pp.41-52
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• 2013

Objectives: Rural-urban differences in suicide have been observed in many settings. However, there has been little research addressing what factors can explain these differences. The purpose of this study was to analyze which compositional factors and contextual factors in local areas might be related to local suicide. Methods: The study design was cross-sectional. The data for 251 primary local governments on their age-standardized suicide mortality and their predefined indicators of compositional factors and contextual factors were obtained from Korean Statistical Information Service as of year 2010. Bivariate analysis including one-way ANOVA and chi-square test were used to identify the differences in local features by area type. Seven poisson regression models for each of total, males, and females were used to analyze which compositional and contextual factors were related to suicide. Results: There were differences in suicide between gu and goon in total, male, and female groups. For total, compositional factors including divorce and smoking rate, and contextual factors including financial independency, water and waterwaste coverage, and number of wastewater discharge factories were found to explain the urban-rural differences. Conclusions: This study provided some evidence that contextual factors at the local level as well as compositional factors are useful for predicting local suicide mortality.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.4
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• pp.803-807
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• 2018

The Fantomas and the Robin are the block ciphers included in the LS-designs, the family of block ciphers. They are designed to efficiently apply the masking technique, which is a side-channel analysis countermeasure technique, using L-boxes and S-boxes capable of bit slice implementation. In this paper, we show that the key recovery attacks of Fantomas and Robin through the related-key differential analysis are possible with $2^{56}$ and $2^{72}$ time complexity, $2^{56}$ and $2^{69}$ chosen plaintext respectively.

• Journal of Energy Engineering
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• v.26 no.1
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• pp.9-22
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• 2017

A combined thermal and flow analysis was carried out to study the behavior and performance of a small, commercial LTD (Low-Temperature-Differential) heat engine. Laminar-flow solutions for annulus and channel flows were employed to estimate the viscous drags on the piston and the displacer and the pressure difference across the displacer. Temperature correction factors were introduced to account for the departure from the ideal heat transfer processes. The analysis results indicate that the work required to overcome the viscous drags on engine moving parts and to move the displacer is much smaller than the moving-boundary work produced by the power piston for temperature differentials in the neighborhood of $20^{\circ}C$ and engine speeds below 10 RPS. A comparison with experimental data reveals large degradations from the ideal heat transfer processes. Thus, heat-transfer devices inside the displacer cylinder are recommended.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.950-953
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• 2005

Floor impact sounds from two different floor systems were measured. One of the two floor systems is a dry floor system (with 150mm concrete slab) and the other is a standard floor system (210mm concrete slab). Real impact sources such as jumping and running of children were used as well as standard impact sources (bang machine, impact ball and tapping machine) to evaluate sound Isolation of the two floor systems. Subjective evaluations of the floor impact sound isolation performance for the two systems were also conducted by the methods of 3 scales & 9 categories, paired comparison and semantic differentials. Measurement results indicate that floor impact sound isolation performance of the dry floor was better than that of standard floor in both cases of real and standard impact sources. The subjects in auditory experiments also evaluated the dry floor as a better sound isolation system.

• Journal of agriculture & life science
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• v.44 no.6
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• pp.201-211
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• 2010

This paper estimates the degree of market power of marketers in the Korean beef market, especially focusing on wholesale and retail marketing levels. Prices in various marketing levels show that there is a possibility of more price differentials than marketing costs in the Korean beef market. Annual price and quantity data are used to estimate the degree of market power in the wholesale and retail levels. The empirical results show that the domestic beef retail market is far from perfect competition and the wholesale market is relatively near to perfect competition.

• Phonetics and Speech Sciences
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• v.10 no.4
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• pp.39-44
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• 2018

This study aimed to examine whether preconsonantal vowel shortening, which occurs in many languages, exists in Chinese. To this end, we compared 15 pairs of Chinese bi-syllabic words with intervocalic unaspirated/aspirated stops. The results revealed that (1) the effect of the feature aspiration of the following stop on the preceding vowel (V1) was neither significant nor consistent though V1 tends to be a little longer before an unaspirated stop; (2) the following unaspirated stop closure (C) was similar to or longer than its aspirated cognate; (3) the durational sum of V1 and C was longer when the stop is unaspirated, and V1 and C had no compensatory relationship; (4) Voice Onset Time (VOT) was significantly longer when the stop is aspirated than unaspirated; (5) the vowel (V2) following VOT was significantly longer when the stop is unaspirated, so the differentials in VOT were partially compensated; (6) despite the partial compensation, the sum of VOT and V2 was longer when the stop is aspirated; (7) words with an intervocalic aspirated stop were longer than those with its unaspirated cognate. It is concluded that while VOT is the most important factor for deciding the timing structure of Chinese words with intervocalic stops, closure duration is crucial for Korean and many other languages.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.1
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• pp.435-451
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• 2019

Impossible differential cryptanalysis is an essential cryptanalytic technique and its key point is whether there is an impossible differential path. The main factor of influencing impossible differential cryptanalysis is the length of the rounds of the impossible differential trail because the attack will be more close to the real encryption algorithm with the number becoming longer. We provide the upper bound of the longest impossible differential trails of several important block ciphers. We first analyse the national standard of the Russian Federation in 2015, Kuznyechik, which utilizes the 16-byte LFSR to achieve the linear transformation. We conclude that there is no any 3-round impossible differential trail of the Kuznyechik without the consideration of the specific S-boxes. Then we ascertain the longest impossible differential paths of several other important block ciphers by using the matrix method which can be extended to many other block ciphers. As a result, we show that, unless considering the details of the S-boxes, there is no any more than or equal to 5-round, 7-round and 9-round impossible differential paths for KLEIN, Midori64 and MIBS respectively.