• Nuclear Engineering and Technology
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• v.54 no.12
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• pp.4776-4797
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• 2022

In the one-dimensional thermal-hydraulic (TH) codes, a subcooled boiling model to predict the void fraction profiles in a vertical channel consists of wall heat flux partitioning, the vapor condensation rate, the bubbly-to-slug flow transition criterion, and drift-flux models. Model performance has been investigated in detail, and necessary refinements have been incorporated into the Safety and Performance Analysis Code (SPACE) developed by the Korean nuclear industry for the safety analysis of pressurized water reactors (PWRs). The necessary refinements to models related to pumping factor, net vapor generation (NVG), vapor condensation, and drift-flux velocity were investigated in this study. In particular, a new NVG empirical correlation was also developed using artificial neural network (ANN) techniques. Simulations of a series of subcooled flow boiling experiments at pressures ranging from 1 to 149.9 bar were performed with the refined SPACE code, and reasonable agreement with the experimental data for the void fraction in the vertical channel was obtained. From the root-mean-square (RMS) error analysis for the predicted void fraction in the subcooled boiling region, the results with the refined SPACE code produce the best predictions for the entire pressure range compared to those using the original SPACE and RELAP5 codes.

• Journal of Plant Biology
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• v.35 no.3
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• pp.211-217
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• 1992

In order to elucidate the formation of reaction tissues during the transition from primary to secondary growth, the developmental anatomy was conducted in the first internode of Acer sacchan'num seedling in horizontal position. During the transition from primary to secondary growth, tension wood(gelatinous fiber) was gradually developed on the upper side only, And the tension wood formation in the upper side of the horizontal first internode proceeds acropetally from base to apical portion. Some of the anatomical features of tension wood start to be in the primary vascular tissue and a typical tension wood show during the secondary growth, Therefore, the procambium seems to respond to the gravity as well as vascular cambium. For this reason, both procambium and vascular cambium has to regard as the same meristem, On the other hand, the upper side vessels were longer than those of the lower side in the horizontal first internode. The lateral-wall pitting of vessel elements, however, showed no differences between upper and lower sides which have alternate type. The width and height of rayon the upper side of horizontal first internode was larger as compared with the lower side.r side.

• Journal of architectural history
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• v.23 no.4
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• pp.7-17
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• 2014

This paper aims at researching the cave concept of the Japanese architect Terunobu Fujimori and the result could be summarised as follows. First, a cave is Fujimori's only theme related to the interior space. He set some design guidelines for practice concerning openings of the wall and finishing materials of the interior, following the two major characteristics of a cave: 'comfortability' and 'homogeneity in material'. And 'fire' was also the premise in the cave as a 'spirit' of the space. Second, Fujimori applied the concrete guidelines to Tanpopo House (1994~95), which had in fact borne the ideas. Yakisugi House (2005~07) that took the cave as its design theme showed the transition of his cave concept, from closedness to openness. Third, though his cave concept might deserve the criticism that it is inclined to 'image' rather than 'essence', it illustrates that he seeks after an archetype of human dwelling before the purity of the original space was tarnished with rationality and abstraction. And the cave idea allows the seemingly contradictory 'sachlich' and 'surrealistic' features to coexist. Summing up, Fujimori's cave concept proves that his architecture is a rejection of the Cartesian modernist ideal and the contemporary architects' desire for dematerialisation. In a fundamental level, however, it is a result of his strategic choice induced by his own primary principle that his building must not be similar to any styles in history or any other architects' works in the world.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1566-1574
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• 1992

Local heat transfer characteristics for a round air jet impinging normally on a heated flat plate were experimentally investigated. The problem parameters investigated were jet Reynolds number, Re=4000,10000, and 20000, and nozzle-to-plate spacing(L/D) of 2,6, and 10. The temperature variations on the flat uniform heat flux surface were mapped using a thermo-sensitive liquid crytal sheet. The isochromatic images corresponding to the characteristic temperature of liquid crystal were analyzed with the help of a digital image processing system. The local Nusselt number, Nu decreased rapidly in the impingement region and exhibited a similar profiles in the wall jet region independent of the nozzle-to-plate spacing L/D. In the case of large Reynolds number, heat transfer rate (Nu) was proportional to 0.5 power of the Reynolds number. For L/D=2, a secondary peak in the heat transfer rate was seen in the region of X/D=1.5~3 due to the transition from laminar to turbulent boundary layer.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.1
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• pp.80-84
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• 2014

The discharge characteristics of Surface Dielectric Barrier Discharge (SDBD) reactor are investigated to find optimal driving condition with adjusting various parameter. When the high voltage with sine wave form is applied to SDBD source, successive pulsed current waveforms are observed owing to multiple ignitions through the long discharge channel and wall charge accumulation on the dielectric surface. The discharge voltage, total charge between dielectrics, mean energy and power are calculated from measured current and voltage according to electrode gap and dielectric thickness. Discharge mode transition from filamentary to diffusive glow is observed for narrow gap and high applied voltage case. However, when the diffusive discharge is occurred with high applied voltage, the actual firing voltage is always lower than that with low driving voltage. The $Si_3N_4$, $MgF_2$, $Al_2O_3$ and $TiO_2$ are considered for dielectric protection and high secondary electron emission coefficient. SDBD with $MgF_2$ shows the lowest breakdown voltage. $MgF_2$ thin film is proposed as a protection layer for low voltage atmospheric dielectric barrier discharge devices.

• Culinary science and hospitality research
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• v.17 no.5
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• pp.139-153
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• 2011

The study is a hotel firm's brand evidence on the switching and relational performance by identifying a causal relationship to the differentiated and competitive was to provide useful information. Units of samples for evidence of brand switching hotels in Seoul participated in surveys customers in 2011, from June 10 to 20 July 2011 for a total of 500 copies for distribution and the Department of dual 408 with SPSS 18.0 and AMOS 18.0 Using factor analysis and reliability verification carried out, and presented research in order to test the hypothesis covariance structure analysis was performed. Analysis, employee services switching barriers and switching costs showed no significant affect. Switching barriers and switching costs, brand name, image congruence transition castle wall and switching costs, alternative attractiveness showed no significant visible results. And perceived price on switching barriers to conversion rates showed was significant affect. Second, switching barriers, switching costs, alternative attractiveness and that the relationship, to help conversion of non-financial performance showed no significant affect. Third, the practitioner services, brand names, images, match the castle there, and non-financial performance of the transition showing a statistically significant result was found.

• International Journal of Automotive Technology
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• v.1 no.1
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• pp.17-25
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• 2000

The electromechanical valve train (EMV) technology allows for a reduction in fuel consumption while operating under a stoichiometric air-fuel-ratio and preserves the ability to use conventional exhaust gas aftertreatment technology with a 3-way-catalyst. Compared with an engine with a camshaft-driven valve train, the variable valve timing concept makes possible an additional optimization of cold start, warm-up and transient operation. In contrast with the conventionally throttled engine, optimized control of load and in-cylinder gas movement can be used for each individual cylinder and engine cycle. A load control strategy using a "Late Intake Valve Open" (LIO) provides a reduction in start-up HC emissions of approximately 60%. Due to reduced wall-wetting, the LIO control strategy improves the transition from start to idle. "Late Exhaust Valve Open" (LEO) timing during the exhaust stroke leads to exhaust gas afterburning and, thereby, results in high exhaust gas temperatures and low HC emissions. Vehicle investigations have demonstrated an improved accuracy of the air-fuel-ratio during transient operation. Results in the New European Driving Cycle have confirmed a reduction in fuel consumption of more than 15％ while meeting EURO IV emission limits.

• Journal of the Korean Society of Visualization
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• v.12 no.3
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• pp.9-14
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• 2014

Two-photon microscopy (TPM) has been used in plant research as a high-resolution high-depth 3D imaging modality. However, TPM is known to induce photo-damage to the plant in case of long time exposure, and optimal excitation wavelength for plant imaging has not been investigated. Longer excitation wavelength may be appropriate for in vivo two-photon imaging of Arabidopsis thaliana leaves, and effects of longer excitation wavelength were investigated in terms of imaging depth, emission spectrum. Changes of emission spectrum as a function of exposure time at longer excitation wavelength were measured for in vivo longitudinal imaging. Imaging depth was not changed much probably because photon scattering at the cell wall was a limiting factor. Chloroplast emission spectrum showed its intensity peak shift by 20 nm with transition of excitation wavelength from 849 nm or below to 850 nm or higher. Emission spectrum showed different change patterns with excitation wavelengths in longitudinal imaging. Longer excitation wavelengths appeared to interact with chloroplasts differently in comparison with 780 nm excitation wavelength, and may be good for in vivo imaging.

• Journal of Energy Engineering
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• v.12 no.2
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• pp.131-138
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• 2003

This paper considered the structural mechanism of transitional boundary layer by the experimental approach. In order to measure the turbulence quantity in the boundary layer, we made a wind tunnel with 400${\times}$190${\times}$2500 mm test section and a flat plate with well fabricated leading edge. Hot wire anemometer was used for acquiring the continuous turbulence signal which is processed by special software. The results of experiment show that the region where turbulence spot is dominant moves from near wall to overall layer and thus the anisotropy of velocity fluctuation shows so large value. Also the turbulence energy originally contained in low frequency band comes up to the high frequency band. Finally the turbulence model needs minimum two length scales to consider the pre-transition region.

• Journal of the Korean Society of Visualization
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• v.9 no.2
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• pp.61-65
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• 2011

Several previous works on rocket nozzle flows have revealed the existence of the transition from FSS to RSS and the occurrence of asymmetric flow associated with the boundary layer separation, which can cause excessive side-loads of the propulsion system. Thus, it is of practical importance to investigate the asymmetric flow behaviors of the propulsion nozzle and to develop its control method. In the present study, the asymmetric flow control method using a cavity system was applied to supersonic nozzle flow. Time-dependent asymmetric flow was experimentally investigated with the rate of change of the nozzle pressure ratio. The results obtained showed that the cavity system installed on nozzle wall would be helpful in fixing the unsteady motions of the boundary layer separation, consequently reducing the possibility of the occurrence of the asymmetric flow.