• Progress in Superconductivity and Cryogenics
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• v.24 no.3
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• pp.62-67
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• 2022

Liquid hydrogen (LH₂) has a higher density than gaseous hydrogen, so it has high transport efficiency and can be stored at relatively low pressure. In order to use efficient bulk hydrogen in the industry, research for the LH₂ supply system is needed. In the high-pressure hydrogen station based on LH₂ currently being developed in Korea, a heat exchanger is used to heat up supercritical hydrogen at 700 bar and 60 K, which is pressurized by a cryogenic high-pressure pump, to gas hydrogen at 700 bar and 300 K. Accordingly, the heat exchanger used in the hydrogen station should consider the design of high-pressure tubes, miniaturization, and freezing prevention. A helical heat exchanger generates secondary flow due to the curvature characteristics of a curved tube and can be miniaturized compared to a straight one on the same heat transfer length. This paper evaluates the heat transfer performance through parametric study on the distance between coils, guide effect, and anti-icing design of helical heat exchanger. The helical heat exchanger has better heat transfer performance than the straight tube exchanger due to the influence of the secondary flow. When the distance between the coils is uniform, the heat transfer is enhanced. The guide between coils increases the heat transfer performance by increasing the heat transfer length of the shell side fluid. The freezing is observed around the inlet of distribution tube wall, and to solve this problem, an anti-icing structure and a modified operating condition are suggested.

• Science of Emotion and Sensibility
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• v.12 no.4
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• pp.411-424
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• 2009

Morality is one of the references when people judge the world. In two studies we addressed the impact of social distance and mood on moral judgment. Participants judged the people who kill one person to save the many by moral and action appropriateness. In study 1 Social distance was induced in best friends and strangers condition. We hypothesized that judgments rely on deontology depends on social distance. Study 1 showed that same actions in moral dilemmas are judged more severely when the people are more socially distant(strangers). But this effect of social distant was found only judgment of moral appropriateness. Study 2 examined how mood can affect moral judgment. There have been many work investigated the role of mood in determining the kind of cognitive processing. Results from study 2 showed participants in positive mood condition are judged more severely. This difference between positive and negative mood was found only judgment of action appropriateness in contrast with study 1. These results suggested that moral judgment can be affected by social distance and mood. We also found that these factors have selected impact on moral and action appropriateness.

• Phonetics and Speech Sciences
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• v.12 no.3
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• pp.25-32
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• 2020

An analysis of emotional English utterances with 7 emotions (calm, happy, sad, angry, fearful, disgust, surprised) was conducted using the measurement of prosodic distance between 672 emotional and 48 neutral utterances. Applying the technique proposed in the automatic evaluation model of English pronunciation to the present study on emotional utterances, Euclidean distance measurement of 3 prosodic elements such as F0, intensity and duration extracted from emotional and neutral utterances was utilized. This paper, furthermore, extended the analytical methods to include Euclidean distance normalization, z-score and z-score normalization resulting in 4 groups of measurement schemes (sqrF0, sqrINT, sqrDUR; norsqrF0, norsqrINT, norsqrDUR; sqrzF0, sqrzINT, sqrzDUR; norsqrzF0, norsqrzINT, norsqrzDUR). All of the results from perceptual analysis and acoustical analysis of emotional utteances consistently indicated the greater effectiveness of norsqrF0, norsqrINT and norsqrDUR, among 4 groups of measurement schemes, which normalized the Euclidean measurement. The greatest acoustical change of prosodic information influenced by emotion was shown in the values of F0 followed by duration and intensity in descending order according to the effect size based on the estimation of distance between emotional utterances and neutral counterparts. Tukey Post Hoc test revealed 4 homogeneous subsets (calm

• Journal of the Korean Society of Radiology
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• v.18 no.5
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• pp.523-529
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• 2024

The purpose of this study is to investigate the effect of differences in grid focal distance used in general radiography on the exposure index and image quality, and to provide useful information for the application of grids in clinical radiography. With AEC applied and SID set to 110 cm, 30 images were obtained for each focus distance of the grid at 110 cm, 140 cm, and 180 cm under the same exposure conditions. The dose was measured using the DAP and ESD, while image quality was evaluated using the SNR and CNR. The exposure index (EI) was determined based on the values shown in the image. EI was derived from the values indicated in the images. The mean DAP values at focus distances of 180, 140, and 110 cm were 10.944±0.613, 10.687±0.516, and 9.74±0.588 cGy·cm², respectively. The ESD values were 1041.75±57.92, 1019.99±49.61, and 930.86±55.77 μGy, while the EI values were 205.97±11.77, 210.59±10.37, and 193.8±11.86. The SNR values were 28.48±0.62, 28.41±0.64, and 27.13±0.72 dB, and the CNR values were 0.09859±0.004276, 0.09864±0.004378, and 0.09026±0.004783 dB. The differences in the mean values were statistically significant (p < 0.01). The values were significantly higher at focal distances of 140 cm and 180 cm compared to 110 cm, but there was no significant difference between the focal distances of 140 cm and 180 cm. The correlation analysis results revealed significant negative correlations between FD and DAP (r = -0.642, p < 0.01), ESD (r = -0.629, p < 0.01), EI (r = -0.376, p < 0.01), SNR (r = -0.615, p < 0.01), and CNR (r = -0.575, p < 0.01) for all variables. The results of this study showed a moderate negative correlation between the focus distance of the grid and the SNR, CNR, DAP, and ESD, and a weak negative correlation with the EI. Therefore, radiological technologists should be aware that even when the same exposure conditions are applied using an AEC system, variations in focus distance of the grid can affect the exposure index, dose, and image quality. Careful consideration is needed when setting the target exposure index.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.2
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• pp.119-131
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• 2005

The two dimensional behaviors of the existing upper tunnel and the ground at crossed area due to the excavation of a lower tunnel were studied experimentally, The model tests were conducted by changing the relative location of the existing upper tunnel and the lower tunnel. The results of the study show that a vertical earth pressure outside the loosened area was increased due to longitudinal arching effect same as a single tunnel. In case vertical distance between the upper and lower tunnel is 0.7 H and 1.0 H respectively (H is a height of the lower tunnel), vertical earth pressure increased in the loosened area behind the tunnel face. But when a vertical distance is 1, 3 H, ground behaviors appeared similarly to a single tunnel.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.5
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• pp.48-56
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• 2009

Regulation of Visible Light Transmission Percentage (VLT%) has been argued because it was known that the degree of darkness of tinted vehicle can affect to driving maneuver. Previously, it was proven that low level of VLT affects capacity reduction. But, due to lack of field data they could not analyze the effect of Car-Following model parameters. This study focuses on the effect of a tinted vehicle on following traffic flow. RTK GPS receiving data through field experiment analyzed based on headway distance, acceleration noise, sensitivity, and reaction time. As a result of analysis through GM 1st Model and 3rd Model, influence of following vehicle vary inversely with VLT and risk according as tinting of lead vehicle is third vehicle bigger than second vehicle. Also the results patterns of GM 3rd model include distance-headway are same with GM 1st Model. In the further need to research for influence analysis of traffic flow stability by the level of VLT.

• Explosives and Blasting
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• v.33 no.4
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• pp.14-24
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• 2015

We conducted test blasting in 3 sites to identify the effect on safety of the earth retaining wall by near blasting vibration. As a test result, we confirm that underground structures(earth anchor et al.) are relatively safer than surface structures as the underground vibration is 10~52% of surface vibration at a same distance. We derived surface and underground vibration prediction equations by regression analysis of measured 3 sites' surface and underground vibration PPV. Also we calculated minimum separation distance by blasting pattern about underground and surface curing concrete. Unless any discontinuity which are unsafe on the earth retaining wall appear, blasting work using under 2.4kg per delay is not meaningful to the earth retaining wall's safety as the result of measuring near blasting vibration, confirming change the earth retaining wall's instrument, and observation of structural deformation.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.9 no.3
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• pp.215-221
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• 1976

In this study, noise arresting effect of the noise control room from the transmission of surrounding noise was tested when the packing noise control rooms were set up in the test room in which the prerecorded noise from an engine room was reradiated at the same level as the original pressure. The inner space of control room A is $3.389m^3(1.19\times1.19\times2.14m)$ having walls furnished with plywood board 9mm in thickness and noise control room door$(60\times45cm) $ and illumination lamp are placed. In case of the control room B, noise absorption board(10mm fiber board which holds the corntype concavity with diameter of 5mm, depth 5mm, space 15mm) is adhered to the internal ceiling and styrol foam boards(20mm) to the walls. The other struction is same as the control room A. Type C is the same as B except wool board(Glass Fiber, 33mm) on the walls. Type D is same as type A except that the thickness of wall is 12mm and wood pyramid type cone$(5\times5\times13cm)$ is adhered to the ceiling ana walls(Fig. 1). When the recorded noise and vibrated noise were controlled in various levels. The noise pressure which passed through the control rooms was measured by sound level meter(Bruel & Kjar 2205, measuring range 37-140dB). In order to calculate the absorption rate in the control rooms the noise pressure was measured at different distances when the recorded noise pressure was radiated. The followings are the results obtained from the experiment. 1. When the noise pressure of the test room was 60dB, transmission rate of type A was $69.7\%$ and increased $3.3\%$ per 10dB. At the same condition, the rate was $53.9\%$ and increased $4.5\%$ per 10dB in type D. Type D was the most effective in noise arresting of the four and the effect was D,C,B and A in order(Fig.2). 2. When the oscillator sound and vessels noise were radiated in 1,000Hz, at one meter distance to the type A and D, the oscillator sound pressure were 77dB and 73dB, while the vessels noise pressure were 73.3dB and 66.2dB respectivley(Fig.3). 3. Refering to the influence of the frequency to the lower oscillator sound(1,000Hz) pressure, both type C and D were almost same at 140cm but type C was 0.3dB lower than type D at 20cm distance(Fig.4).

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.3
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• pp.640-655
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• 2018

Recently, the construction of the urban area has been rapidly increasing, and the excavation work of the ground has been frequently performed at the upper part of the existing underground structures. Especially, when the structure is constructed after the excavation of the ground, the loading and unloading process in the ground under the excavation basement can affect the existing underground structures. Therefore, in order to maintain the stability of the existing underground structure due to the excavation of the ground, it is necessary to accurately grasp the influence of the excavation and the structure load in the adjoining part. In this study, the effect of the excavation of the ground and the new structure load on the existing tunnel was experimentally implemented and the influence of the adjacent construction on the existing tunnel was investigated. For this purpose a large testing model with 1/5 scale of the actual size was manufactured. The influence of ground excavation, width of the load due to new structure, and distance between centers of tunnel and of excavation on the existing tunnel was investigated. In this study, it was confirmed that the influence on the existing tunnel gets larger, as the excavation depth get deeper. At the same distance, it was confirmed that the tunnel displacement increased up to three times according to the increase of the building load width. That is, the load width influences the existing tunnel larger than the excavation depth. As the impact of the distance between centers of tunnel and of excavation, it was confirmed that tunnel crown displacement decreased by 48%. The result showed that a tunnel is located in the range of 1D (D: tunnel diameter) from the center of excavation, the effect of excavation is the largest.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1996.11a
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• pp.72-75
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• 1996

The objectives of this paper investigate the effect of installed spacing on the activation of spot type heat detection devices. The flow of hot gases under a ceiling resulting from the impingement of a fire plume activates heat detectors and sprinklers. Local temperature and velocity in this ceiling jet are usually expressed with the function of a ceiling height, the distance from a fire location and the heat release rate of fire. And detectors having different. RTI respond in different ways to the same temperature and velocity of ceiling jet. Thus great care should be taken to decide installed spacing of heat detection devices by considering above effects.