• 한국해양학회지
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• v.25 no.2
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• pp.62-73
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• 1990

An experimental study is performed in order to catch the characteristics of the flow field at arrested salt wedge, using a rectangular open channel. Arrested salt wedge is generally so stable that the observations are easy, but velocities and interfacial waves are measured with the aid of visualization method, by injection of fluorescent dyes. The density interface, which is defined as the zone of maximum density variation with depth, exists in about 0.5 cm below the visual interface, and vertical density profile is quite well satisfied with Homeborn model. Interfacial layer has high turbulent intensity and its thickness decreases as the overall Richardson number increases and has magnitude of roughly 17% of upper layer. Cross-sectional velocity distribution just shows the influence of a side-wall friction and in the upper layer vertical velocity profile also becomes uniformly as Reynolds number increases, but in the lower layer it shows nearly parabolic type. Supposes that we divide salt wedge into three domains, that is, river mouth, intermediate and tip zone, entertainment coefficient is small at the intermediate zone and large at the river mouth and the tip zone. River mouth or intermediate zone has comparatively stable interface and capillary wave therefore s produced and propagated downstream. On the other hand, tip zone is very unstable, cusping ripple or bursting ripple is then produced incessantly. Arrested salt wedge form is nearly linear and has no relation to densimetric Froude number and Reynolds number.

• The Journal of Sustainable Design and Educational Environment Research
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• v.17 no.3
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• pp.26-34
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• 2018

This research is a pre-research to find out profit module of 20 students in a classroom. I researched the widths of passages in the 30 classrooms of 5 elementary schools in Nothern Kyeonggi-do. I found the conclusions as follows. 1st, the area of 1 student's unit is $650(W){\times}950(D)$ 2nd, most of classrooms' students table placements are one-way types(77%). U-types are 13%. group study-types are 7% 3rd, The width between blackboard and front student's table is 2.08m. The width of passage between back seat and backboard is 1.12m. The width of passage between side wall and near student's table is 0.89m. The width of passage between window and near student's table is 0.74m. The width of vertical passage(A) between student's tables is 0.68m. The width of vertical passage(B) between student's tables is 0.7m. 4th, The area of teachers' is $2.1m{\sim}2.25m{\times}2.1m=4.41{\sim}4.73m^2$

• Journal of the Korean Geotechnical Society
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• v.18 no.6
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• pp.33-42
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• 2002

Ground reaction curve is a very important information for evaluating the side wall displacements and installation time of the tunnle support. The ground reaction curve can be estimated by analytical closed form solutions derived on the supposition of circular section and isotropic stress condition. The conditions of stress field and tunnel configurations, however, are quite different in practice. Therefore, it is necessary to investigate the effects of stress anisotropy and tunnel configurations in order to use simply in practical design. This paper describes a study of influence factors in the ground reaction curve. In order to evaluate the applicability of analytical closed form solution in practical design, two sets of parametric studies were carried out by numerical analysis in elastic tunnel behaviour: one set of studies investigated the influence of the K and the other set investigated the influence of the tunnel configurations such as circular and horse-shoe shape. In the studies, K value varies between 0.5 and 3.0, initial ground vertical stress varies between 5～30MPa far each K values. The results indicated that the self-supportability of ground is larger in the ground having lower K value. However, it is suggested that the applicability of closed form solution may not be adequate to determine directly the installation time of the support and self-supportability of ground. It is necessary to consider stress anisotropy and tunnel configurations.

• Korean Journal of Agricultural Science
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• v.4 no.2
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• pp.126-140
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• 1977

Present studies were carried out for breeding cold resistant clones of Citrus, improving overwintering techniques of Citrus in Jeju island as well as other southern region, Result obtained were as follows 1. In the vinyl house covered with two sheets of straw mat, 12 indivuals were found as non-injury and 15 were slightly injured by leaf freeging test at $-9^{\circ}C$ for 2 hours treatment. 2. In the condition of vinyl house covered with straw mat and viny film mulching and heat-in by sun-light, the inside temperature of vinyl house were not lowered below $-3^{\circ}C$ and the ground temperatura in vinyl house keeps above $0^{\circ}C$ during winter though outdoor temperature were lower by $-15^{\circ}C$(Daejeon area). 3. The vinyl tunnel inside the vinyl house and vinyl film mulching on ground position showed greater effectiveness for preventing heat loss from house but there were no significant difference between the color of vinyl film covered the tunnel. 4. In the vertical distribution of maximum temperature in vinyl house, the upper space was slightly higher than the lower position at high temperature condition, while minimum temperature was distributed as higher as the middle position, ground surface and upper position in order at low temperature condition 5. In the horizontal distribution of temperature in vinyl house, ground and surface-temperature of north side was lower than the other sides, and citrus planted within 30cm from north side wall died by cold injury and in the other side near wall appeared slight symptom of cold injury. 6. The insulating trench ($30{\times}30{\times}30cm$) packed with straw bundle installed under north wall might be effective to prevent heat loss of ground temperature. 7. In cloudy and snowy day, the temperature difference between indoor and outdoor were less, and the indoor temperature were maintained highly during night due to the effect of prevention of heat loss. 8. The highest temperature in a day was observed at about P.M. 3 both inside and outside of vinyl house and the lowest temperature was observed at about A.M. 6. The difference between the highest and lowest temperature of indoor in a sunny day was $19^{\circ}C$, compared with $9^{\circ}C$ on a cloudy or snowy day in late November. Especially, lowering of temperature in a snowy day was so less that the curve of temperature change was comparatively constant, 9. If the effective methods of citrus cultivation in vinyl house with improved clone such as hardiness. semi-dwarf and spur type are applied, it might be possible to cultivate the citrus tree safely in Jeju island as well as other southern rejion and to magnity the cultivation of citrus tree.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.1
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• pp.70-75
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• 2012

Purpose: It is important to acquire accurate data because the SPECT scan affected by various physical factors. The aim of this study was to compare the uniformity when both centers were matched or mismatched differed from position of heart in COR. Materials and methods: The images were acquired with cylindrical uniform phantom (6.7 cm diameter, 9 cm length) and heart insert phantom using Cardio MD SPECT system (Philips, USA). The phantoms were positioned on COR as well as four different points which were 10 cm above, below, left and right side from the COR. The counts from the both edge of cylindrical uniform phantom and those from the both wall of heart insert phantom were compared by using vertical and horizontal line profile. In addition, the qualitative evaluation was performed with heart insert phantom images and volunteer test. Results: In heart insert phantom study, the differences of counts between COR and 10 cm above, below, left and right point of COR were 1.1, 4.1, 4.9, 2.2 and 0.9% using T-A curve for horizontal view. In case of vertical view of COR 3.9, 21.9, 3.5, 23.9, 14.0% were shown. In cylindrical phantom study, the differences of counts between COR and 10 cm above, below, left and right point of COR were 4.3, 0.3, 3.3, 2.6 and 0.7% using T-A curve for horizontal view. In case of vertical view of COR 2.7, 3.0, 1.0, 0.3, 3.4% were shown. For qualitative evaluation, the images at COR were the most uniform for both of heart insert phantom and volunteer test, whereas other four positions showed somewhat distorted images. Conclusion: It showed the most uniform images when COR is matched with the heart. Therefore, we can expect that distortion which increased or decreased of myocardial perfusion will be prevented by matching the heart and COR when positioning. Furthermore, the accuracy of diagnosis will be improved as well.

• Journal of Korean Society of Forest Science
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• v.9 no.1
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• pp.1-44
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• 1969

The important results which have been obtained in the investigation can be recapitulated as follows. 1. As demostrated by the experimental results and analyses concerning their effects in the on-ground type mushroom house, the constructions in relation to the side wall and ceiling of the experimental houses showed a sufficient heat insulation on effect to protect insides of the houses from outside climatic conditions. 2. As the effect on the solar type experimental mushroom house which was constructed in a half basement has been shown by the experimental results and analyses, it has been proved to be effective for making use of solar heat. However there were found two problems to be improved for putting solar houses to practical use in the farm mushroom growing: (1) the construction of the roof and ceiling should be the same as for the on-ground type house, and (2) the solar heat generating system should be reconstructed properly. A trial solar heat generating system is shown in Fig. 40. 3. Among several ventilation systems which have been studied in the experiments, the underground earthen pipe and ceiling ventilation, and vertical side wall and ceiling ventilation systems have been proved to be most effective for natural ventilation. 4. The experimental results have shown that ventilation systems such as the vertical side wall and underground ventilation systems are suitable to put to practical use as natural ventilation systems for farm mushroom houses. These ventilation systems can remarkably improve the temperature of fresh air which is introduced into the house by heat transfers within the ventilation passages, so as to approach to the desired temperature of the house without any cooling or heating operation. For example, if it is assuming that x is the outside temperature and y is the amount of temperature adjustment made by the influence of the ventilation system, the relationships that exist between x and y can be expressed by the following regression lines. Underground iron pipe ventilation system ${\cdots}{\cdots}$ y=0.9x-12.8 Underground earthen pipe ventilation system ${\cdots}{\cdots}$y=0.96x-15.11 Vertical side wall ventilation system${\cdots}{\cdots}$ y=0.94x-17.57 5. The experimental results have shown that the relationships existing between the admitted and expelled air and the $Co_2$ concentration can be described with experimental regression lines or an exponent equation as follows: 1) If it is assumed that x is an air speed cm/sec. and y is an expelled air speed in cm/sec. in a natural ventilation system, since the y is a function of the x, the relationships that exist between x and y can be expressed by the regression lines shown below: 2) If it is assumed that x is an admitted volume of air in $m^3/hr$ and y is an expelled volume of air in $m^3/hr$ in a natural ventilation system, since the y is a function of the x, the relationships that exist between x and y can be expressed by the regression lines shown below. 3) If it is assumed that the expelled air speed in cm/sec and replacement air speed in cm/sec. at the bed surface in a natural ventilation system are shown as x and y, respectively, since the y is a function of the x, the relationships that exist between x and y can be expressed by the following regression line: G.E. (100%)- C.V. (50%) ventilation system${\cdots}$ y=0.54X+0.84 4) If it is assumed that the replacement air speed in cm/sec. at the bed surface is shown as x, and $CO_2$ concentration which is expressed by multiplying 1000 times the actual value of $CO_2$ % is shown as y, in a natural ventilation system, since the y is a function of the x the relationships that exist between x and y can be expressed by the following regression line: G.E. (100%)- C.V. (50%) ventilation system${\cdots}{\cdots}$ y=114.53-6.42x 5) If it is assumed that the expelled volume of air is shown as x and the $CO_2$ concentration which is expressed by multiplying 1000 times the actual of $CO_2$ % is shown as y in a natural ventilation system, since the y is a function of of the x, the relationships that exist between x and y can be expressed by the following exponent equation: G.E. (100%)-C.V. (50%) ventilation system${\cdots}{\cdots}$ $$y=127.18{\times}1.0093^{-X}$$ 6. The experimental results have shown that the ratios of the crass sectional area of the G.E. and C.V. vent to the total cubic capacity of the house, required for providing an adequate amount of air in a natural ventilation system, can be estimated as follows: G.E. (admitting vent of the underground ventilation)${\cdots}{\cdots}$ 0.30-0.5% (controllable) C.V. (expelling vent of the ceiling ventilation)${\cdots}{\cdots}$ 0.8-1.0% (controllable) 7. Among several heating devices which were studied in the experiments, the hot-water boilor which was modified to be fitted both as hot-water toiler and as a pressureless steam-water was found most suitable for farm mushroom growing.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.3
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• pp.175-184
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• 2002

Ground reaction curve is very useful information for estimating the installation time of the tunnel support. The ground reaction curve can be estimated by analytical closed form solutions derived in case of circular section and isotropic stress condition. The nature of the ground reaction, however, depends significantly on tunnel configurations. Nevertheless, few purely analytical and experimental studies of this problem due to tunnel configurations appear to have been carried out. Therefore, it is necessary to investigate the influence of tunnel configurations in order to use simply in practical design. This paper describes a numerical study for the intial elastic displacement in the ground reaction curve due to configuration of tunnel excavation. In order to evaluate the applicability of analytical closed form solution in practical design, the parametric studies were carried out by numerical analysis in elastic tunnel behaviour. In the studies, S value, namely configuration factor, defined as the ratio between tunnel height (b) and width (a), varies between 0.5 and 3.0, initial ground vertical stress varies between 5~30 MPa for each S values. The results indicated that the self-supportability of ground is larger in the ground having low S value. It, however, is suggested that the applicability of closed form solution may not be adequate to determine directly the installation time of the support and self-supportability of ground. It should be necessary to perform the additional numerical analysis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.4
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• pp.337-346
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• 2014

This study aimed to understand the mode characteristics of a droplet subject to periodic forced vibration and the detachment of a droplet placed on a plate surface. An surface was coated with Teflon to clearly observe the behavior of a droplet. The contact angle between the droplet and surface and the hysteresis were found to be approximately $115^{\circ}C$ and within $25^{\circ}C$, respectively. The coating process was performed in a clean room that had an environment with a low level of contaminants and impurities such as air dust, detergents, and particles. To predict the resonance frequency of a droplet, theoretical and experimental approaches were applied. Two high-speed cameras were configured to acquire side and top views and thus capture different characteristics of a droplet: the mode shape, the detachment, the separated secondary droplet, and the waggling motion. A comparison of the theoretical and experimental results shows no more than 18 discrepancies when predicting the resonance frequency. These differences seem to be caused by contact line friction, nonlinear wall adhesion, and the uncertainty of the experiment. For lower energy inputs, the contact line of the droplet was pinned and the oscillation pattern was axisymmetric. However, the contact line of the droplet was de-pinned as the oscillation became more vigorous with increased energy input. The size of each lobe at the resonance frequency is somewhat larger than that at the neighboring frequency. A droplet in mode 2, one of the primary mode frequencies, exhibits vertical periodic movement as well as detachment and secondary ejection from the main droplet.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.899-915
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• 2018

In this study, in order to construct an eco-friendly advanced road transportation network, the multi-layer tunnel, which is a small-sized car road, is designed to have a height of less than 60 cm. However, the shape of the tunnel is low and the height of the traffic sign is small. In order to solve these problems, traffic sign characters were designed in three dimensions, and the possibility of applying the design of the three - dimensional sign that can obtain greater visibility than the existing signs at the same distance and the possibility verification through virtual simulation were performed. The three-dimensional sign is horizontally installed on the ceiling of the multi-layer tunnel. To be seen vertically, it is enlarged by a certain ratio by the perspective, and the width and height are enlarged. Respectively. In addition, 3D simulation was performed to verify the visibility of the stereoscopic signs when the driver ran through the stereoscopic sign design specifications. As a result of the design and experimental study, it was confirmed that the stereoscopic sign could be designed through the theoretical formula and that it could provide the driver with a larger traffic sign character because there is no limitation of the facility limit compared to the existing vertical traffic sign. Also, we confirmed that it can be implemented in the side wall by using the stereoscopic sign design principle installed on the ceiling part. It was confirmed that the design of the stereoscopic sign can be designed to be smaller as the distance that the driver visually recognizes the sperm is shorter, the height of the protrusion vertically at the lower part of the stereoscopic sign becomes higher. As a result of 3D simulation running experiment based on the design information of the stereoscopic sign, it was confirmed that the stereoscopic sign is visually the same as the vertical sign at the planned distance. Although the detailed research and institutional improvement of stereoscopic signs have not been made in Korea and abroad, it is evolved into a core technology of new road traffic facilities through various studies through the possibility of designing and applying stereoscopic signs developed through this study Expect.

• Conservation Science in Museum
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• v.26
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• pp.161-182
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• 2021

A jungwangu, a type of medium-sized mortar, is a firearm with a barrel and a bowl-shaped projectileloading component. A bigyeokjincheonroe (bombshell) or a danseok (stone ball) could be used as a projectile. According to the Hwaposik eonhae (Korean Translation of the Method of Production and Use of Artillery, 1635) by Yi Seo, mortars were classified into four types according to its size: large, medium, small, or extra-small. A total of three mortars from the Joseon period have survived, including one large mortar (Treasure No. 857) and two medium versions (Treasure Nos. 858 and 859). In this study, the production method for medium mortars was investigated based on scientific analysis of the two extant medium mortars, respectively housed in the Jinju National Museum (Treasure No. 858) and the Korea Naval Academy Museum (Treasure No. 859). Since only two medium mortars remain in Korea, detailed specifications were compared between them based on precise 3D scanning information of the items, and the measurements were compared with the figures in relevant records from the period. According to the investigation, the two mortars showed only a minute difference in overall size but their weight differed by 5,507 grams. In particular, the location of the wick hole and the length of the handle were distinct. The extant medium mortars are highly similar to the specifications listed in the Hwaposik eonhae. The composition of the medium mortars was analyzed and compared with other bronze gunpowder weapons. The surface composition analysis showed that the medium mortars were made of a ternary alloy of Cu-Sn-Pb with average respective proportions of (wt%) 85.24, 10.16, and 2.98. The material composition of the medium mortars was very similar to the average composition of the small gun from the Joseon period analyzed in previous research. It also showed a similarity with that of bronze gun-metal from medieval Europe. The casting technique was investigated based on a casting defect on the surface and the CT image. Judging by the mold line on the side, it appears that they were made in a piece-mold wherein the mold was halved and using a vertical design with molten metal poured through the end of the chamber and the muzzle was at the bottom. Chaplets, an auxiliary device that fixed the mold and the core to the barrel wall, were identified, which may have been applied to maintain the uniformity of the barrel wall. While the two medium mortars (Treasure Nos. 858 and 859) are highly similar to each other in appearance, considering the difference in the arrangement of the chaplets between the two items it is likely that a different mold design was used for each item.