• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.33-38
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• 2008

A ground-loop heat exchanger in a ground source heat pump system is an important unit that determines the thermal performance of a system and its initial cost. The Size and performance of this heat exchanger is highly dependent on ground thermal properties. A proper design requires certain site-specific parameters, most importantly the ground effective thermal conductivity, the borehole thermal resistance and the undisturbed ground temperature. This study was performed to investigate the effect of some parameters such as borehole lengths, various grouting materials and U-tube configurations on ground effective thermal conductivity. In this study, thermal response tests were conducted using a testing device with 9-different ground-loop heat exchangers. From the experimental results, the length of ground-loop heat exchanger affects to the effective thermal conductivity. Among the various grouting materials, the bentonite-based grout with silica sand shows the largest thermal conductivity value.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.5
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• pp.381-389
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• 2011

In this study, we are focusing our attention on lift characteristics of the low aspect wings for Wing-In Ground effect crafts (WIG). Experimental measurements at an open-type wind tunnel are carried out and results are comparatively presented. In order to simulate the realistic ground condition in where the WIG craft is flying, moving ground is implemented by a conveyor belt rotating with the same velocity of the inflow. We consider two different wings (NACA0012 and DHMTU section) which have four different aspect ratios (0.5, 1.0, 1.5 and 2.0). Forces acting on the wings are measured and lift characteristics are elaborately investigated for various different conditions. In addition, end-plate effects are estimated. Results are validated by comparing with theoretic solutions of the symmetric airfoil. Present results show that ground effects are differently generated in moving or fixed ground conditions, and hence left characteristics are affected by the ground condition. Consequently, accurate aerodynamic forces acting on the WIG craft are guaranteed in a realistic moving ground condition.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.12
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• pp.2243-2250
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• 2006

When a patient is positioned at insulated bed and practitioner is positioned at insulated floor, that condition could be a cause of lessening effect in acupuncture practice. We investigated how Ground connection and Insulation could influence on the electrical meridian potential between practitioner and patient during acupuncture practice. We treated 30 normal healthy subjects with acupuncture and measured changes in the electrical potential between the stomach meridian points ST-39 and ST-37 in response to light touch after insertion of a needle at ST-36. At first, we stimulated non-insulated needle and measured electrical potentials for non ground, patient ground only, practitioner ground only, all ground respectively. Then we used insulated needles and measured same as above. Non-insulated all ground subject elicited positive mean potential $44.6{\pm}19.2{\mu}V$ and showed $181.4{\pm}59.7{\mu}V$ peak to peak potential. Practitioner ground only showed negative mean potential of $51.5{\pm}9.3{\mu}V$ and $367.4{\pm}27.8{\mu}V$ of peak to peak potential. Patient ground only revealed no mean potential of $2.9{\pm}1.3{\mu}V$, $16.4{\pm}11.9{\mu}V$ of peak to peak potential. All ground showed no mean potential of $1.6{\pm}0.7{\mu}V$, $3.3{\pm}1.9{\mu}V$ of peak to peak potential. In case of Insulated condition, there elicited no mean potential. Non ground and Practitioner only showed weak value of peak to peak potential as $7.8{\pm}2.6{\mu}V$ and $8.4{\pm}2.5{\mu}V$ each. But patient only and all ground showed no potential as $4.7{\pm}2.2{\mu}V$, $3.4{\pm}2.2{\mu}V$, respectively. Therefore, Ground connection modulate the energy transfer course between practitioner and patient. Insulation block energy transfer but static electrical impulse between practitioner and patient.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.1
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• pp.39-49
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• 2018

In the satellite operation phase, a ground station should continuously monitor the status of the satellite and sends out a tasking order, and a satellite should transmit data acquired in the space to the Earth. Therefore, the communication between the satellites and the ground stations is essential. However, a satellite and a ground station located in a specific region on Earth can be connected for a limited time because the satellite is continuously orbiting the Earth, and the communication between satellites and ground stations is only possible on a one-to-one basis. That is, one satellite can not communicate with plural ground stations, and one ground station can communicate with plural satellites concurrently. For such reasons, the efficiency of the communication schedule directly affects the utilization of the satellites. Thus, in this research, considering aforementioned unique situations of spacial communication, the mixed integer programming (MIP) model for the optimal communication planning between multiple satellites and multiple ground stations (MS-MG) is proposed. Furthermore, some numerical experiments are performed to verify and validate the mathematical model. The practical example for them is constructed based on the information of existing satellites and ground stations. The communicable time slots between them were obtained by STK (System Tool Kit), which is a well known professional software for space flight simulation. In the MIP model for the MS-MG problems, the objective function is also considered the minimization of communication cost, and ILOG CPLEX software searches the optimal schedule. Furthermore, it is confirmed that this study can be applied to the location selection of the ground stations.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.6
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• pp.851-858
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• 2002

This study was conducted to determine effects of whole (intact), coarsely-ground (4 mm), finely-ground (1 mm), steam-flaked and steam-flaked-ground (1 mm) corns on in vitro and in situ DM digestibilities and also in vitro fermentation characteristics. After 48 h incubation, in vitro dry matter digestibilities of whole, steam-flaked, coarsely-ground, steam-flaked-ground, and finely-ground corns were 6.79, 61.68, 76.48, 85.72 and 90.31%, respectively. Steam-flaked-ground corn showed the highest digestibility until 24 h incubation (p<0.01). After 48 h incubation, pH of whole corn decreased with a small range. However the values of pH of other media significantly decreased (p<0.01). The gas productions of finely-ground and steam-flaked-ground corns were higher than those of the other corns (p<0.01). After 24 h incubation, $NH_3$-N concentration of finely-ground and steam-flaked-ground corns increased rapidly. Total VFA was the highest in finely-ground corn, followed by steam-flaked-ground, steam-flaked, coarsely-ground and whole corns. Incorporating steam-flaked corn resulted in the highest propionate concentration (p<0.01) and the lowest acetate : propionate value (p<0.05). Finely-ground corn showed the highest in situ DM digestibility throughout the incubation period (p<0.01), followed by coarsely-ground, steam-flaked and whole corns, respectively. Overall, DM of whole corn was merely digested in vitro as well as in situ.

• Journal of Astronomy and Space Sciences
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• v.37 no.4
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• pp.237-247
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• 2020

The ground tracking support is a critical factor for the navigation performance of spacecraft orbiting around the Moon. Because of the tracking limit of antennas, only a small number of facilities can support lunar missions. Therefore, case studies for various ground tracking support conditions are needed for lunar missions on the stage of preliminary mission analysis. This study analyzes the ground supporting condition effect on orbit determination (OD) of Korea Pathfinder Lunar Orbiter (KPLO) in the lunar orbit. For the assumption of ground support conditions, daily tracking frequency, cut-off angle for low elevation, tracking measurement accuracy, and tracking failure situations were considered. Two antennas of deep space network (DSN) and Korea Deep Space Antenna (KDSA) are utilized for various tracking conditions configuration. For the investigation of the daily tracking frequency effect, three cases (full support, DSN 4 pass/day and KDSA 4 pass/day, and DSN 2 pass/day and KDSA 2 pass/day) are prepared. For the elevation cut-off angle effect, two situations, which are 5 deg and 10 deg, are assumed. Three cases (0%, 30%, and 50% of degradation) were considered for the tracking measurement accuracy effect. Three cases such as no missing, 1-day KDSA missing, and 2-day KDSA missing are assumed for tracking failure effect. For OD, a sequential estimation algorithm was used, and for the OD performance evaluation, position uncertainty, position differences between true and estimated orbits, and orbit overlap precision according to various ground supporting conditions were investigated. Orbit prediction accuracy variations due to ground tracking conditions were also demonstrated. This study provides a guideline for selecting ground tracking support levels and preparing a backup plan for the KPLO lunar mission phase.

• International Journal of Automotive Technology
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• v.7 no.7
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• pp.833-839
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• 2006

In this paper, roll behavior of three planar half car models are compared. The first model is a simple model whose contact point between a wheel and the ground is assumed to be fixed with a revolute joint. The second model is a modified model of the fIrst model, whose wheel tread width can vary. In this model, the instant center of a wheel with respect to the ground, which is crucial to find the roll center, is assumed to be at the contact point of a wheel and the ground. The last model uses the pole of a wheel with respect to the ground for small displacement as the instant center of a wheel with respect to the ground. Loci of the center of gravity point, the fixed and the moving centrodes which are traces of roll center position in the ground and the body frame respectively, wheel contact points, and instant centers of a wheel with respect to the ground are calculated.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.537-544
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• 2005

We find out many soft ground deep excavation cases where results of careless overexcavation accelerate the advance of loosening zone of adjacent ground, bucklings of struts and bottom heaves happen due to delayed supporting time. This article introduces a soft ground deep excavation case where steel pipe sheet piles were used with struts as an earth retaining system. There were 2 times of buckling in the supporting system and heaving of bottom ground due to overexcavation and insufficient penetration depth of the steel pipe sheet piles. The effort of this article aims to improve and develop the technique of design and construction in the coming projects having similar ground condition and supporting method.

• Journal of Information Processing Systems
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• v.13 no.3
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• pp.491-499
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• 2017

In this study, we proposed a new approach to segment ground and nonground points gained from a 3D laser range sensor. The primary aim of this research was to provide a fast and effective method for ground segmentation. In each frame, we divide the point cloud into small groups. All threshold points and start-ground points in each group are then analyzed. To determine threshold points we depend on three features: gradient, lost threshold points, and abnormalities in the distance between the sensor and a particular threshold point. After a threshold point is determined, a start-ground point is then identified by considering the height difference between two consecutive points. All points from a start-ground point to the next threshold point are ground points. Other points are nonground. This process is then repeated until all points are labelled.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.25 no.3
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• pp.63-82
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• 2022

The purpose of this study is to compare growth condition of landscape woody plants growing on the different ground structures in apartment complex. I chose Manseok Beach Town Complex 2, in Manseok-dong, Seo-gu, Incheon which has both natural and artificial ground as a subject site. Analysis of three phases of soil showed that artificial ground had average liquid phase of 30.89%, artificial ground mounding 33.88% and natural ground 24.40%. It means that artificial ground has higher water content than natural ground despite having same earthiness. It is believed that artificial ground is not as well drained as natural ground even though it is connected to the natural ground and has a deep soil depth because of mounding. Comparative study between woody plants on natural ground and those on artificial ground demonstrated that trees on natural ground grew 40.4% compared to those on artificial ground(0.875mm more) in terms of diameter growth. Average diameter growth of trees on natural ground was 3.040mm against 2.165mm for those on artificial ground. All 19 tree species which were measured for root diameter growth showed similar or higher growth on natural ground than on artificial ground. When it comes to growth of height, arborvitae showed highest growth on natural ground, followed by Thuja occidentalis, Pinus strobus, Magnolia denudata, Diospyros kaki and Aesculus turbinata. I measured branch growth and rate of leaf adherence of Pinus strobus. Average annual rate of branch growth of woody plants on natural ground was twice as high as those on artificial ground. I could conclude that ground structure influences branch growth of Pinus strobus. Statistics analysis of tree damage demonstrated significant result, meaning that there is a difference in the average damage rate depending on structure of ground. In order to validate growth difference by planting ground, I conducted T-Test of growth of diameter, root diameter, branch and height on woody plants growing on natural and artificial ground. As a result, it is believed that there is a difference in the growth of trees depending on the ground structure. Putting all these results together demonstrates that woody plants on natural ground generally grow better than those on artificial ground, which means ground structure does have an influence on the environment of growth of trees.