• 설비공학논문집
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• 제22권6호
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• pp.337-344
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• 2010

Good plant-growth conditions can be achieved by means of using greenhouses. One of the main issues in greenhouse cultivation is energy savings through the development of high efficient heating and cooling system. GSHPs are one of the recommended systems to cope with this pending need. The aim of this study is to investigate the heating performance of ground source multi-heat pump system installed in a greenhouse under part load conditions. Daily average heating COP of the heat pump unit was very high by at least 7.4, because of relatively large condenser, evaporator, and mass flow rate through ground loop heat exchanger. However, the system COP, overall heating coefficient of the performance of the system with heat pump unit and GLHX, decreased drastically due to relatively large power consumption of circulating pump under part load condition. It is suggested that the technology to enhance the performance of the ground source multi-heat pump system for a greenhouse under part load conditions should be developed.

• 로봇학회논문지
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• 제18권4호
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• pp.427-435
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• 2023

This paper proposes a method of estimating the pose of a mobile robot by using a learning model. When estimating the pose of a mobile robot, wheel encoder and inertial measurement unit (IMU) data are generally utilized. However, depending on the condition of the ground surface, slip occurs due to interaction between the wheel and the floor. In this case, it is hard to predict pose accurately by using only encoder and IMU. Thus, in order to reduce pose error even in such conditions, this paper introduces a pose estimation method based on a learning model using data of the wheel encoder and IMU. As the learning model, long short-term memory (LSTM) network is adopted. The inputs to LSTM are velocity and acceleration data from the wheel encoder and IMU. Outputs from network are corrected linear and angular velocity. Estimated pose is calculated through numerically integrating output velocities. Dataset used as ground truth of learning model is collected in various ground conditions. Experimental results demonstrate that proposed learning model has higher accuracy of pose estimation than extended Kalman filter (EKF) and other learning models using the same data under various ground conditions.

• 대한토목학회논문집
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• 제33권4호
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• pp.1541-1549
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• 2013

본 연구는 모래지반에서 터널의 굴착조건(터널깊이 및 터널직경)과 시공조건(지반손실량), 지반조건(조밀한 모래, 느슨한 모래)을 변화시키면서 터널상부에 위치한 구조물의 거동변화를 조사 및 분석한 것이다. 분석에 사용된 구조물은 4층 블록식구조물로서 변형 등에 의한 균열발생과 균열폭의 차이로 인해 구조물의 손상정도를 쉽게 파악할 수 있는 특징이 있다. 다양한 터널 굴착조건 및 시공조건, 지반조건에 대해서 발생할 수 있는 터널상부 블록구조물의 거동상태를 파악하기 위해 수치해석적 매개변수 해석을 수행하였으며, 수치해석은 구조물의 실제크랙 발생을 묘사할 수 있도록 개별요소법(DEM)에 근거하여 수행하였다. 다양한 매개변수 해석으로부터 얻어진 구조물의 거동상태에 대한 결과는 터널 굴착조건 및 시공조건, 지반조건과 상호연관하여 함께 반영될 수 있도록 도표화 하였으며, 이를 이용하여 향후 모래지반에서 다양한 터널굴착 및 시공조건, 지반조건으로 인해 유발되는 터널 상부구조물의 손상정도를 보다 용이하게 파악할 수 있을 것으로 기대된다.

• KIEAE Journal
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• 제10권4호
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• pp.75-80
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• 2010

Generally, ground-source heat pump (GSHP) systems have a higher performance than conventional air-source systems. However, the major fault of GSHP systems is their expensive boring costs. Therefore, it is important issue that to reduce initial cost and ensure stability of system through accurate prediction of the heat extraction and injection rates of the ground heat exchanger. Conventional analysis methods employed by line source theory are used to predict heat transfer rate between ground heat exchanger and soil. Shape of ground heat exchanger was simplified by equivalent diameter model, but these methods do not accurately reflect the heat transfer characteristics according to the heat exchanger geometry. In this study, a numerical model that combines a user subroutine module that calculates circulation water conditions in the ground heat exchanger and FEFLOW program which can simulate heat/moisture transfer in the soil, is developed. Heat transfer performance was evaluated for 3 different types ground heat exchanger(U-tube, Double U-tube, Coaxial).

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.1065-1070
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• 2004

Recenlty, there are many cases that structures are constructed on soft ground in domestic. Generally in those cases, appropriate geotechnical techniques for the ground are needed. In this study, an example for ground improvement of OO railroad station construction site is introduced and analyzed. The ground conditions of this site which is soft ground are that N value is under 6, average depth and ground water table is 24.4m, GL-1.7. So, as a countermeasure technique for bearing reinforcement, Compaction Grouting System (CGS) method was applied on construction site. To estimate the application of CGS method, piezo cone penetration test and static pile loading test were carried out during the construction. Results of analysis show that CGS method for improving the bearing capacity of soft ground is applicable for the ground well.

• 지질공학
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• 제27권1호
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• pp.41-49
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• 2017

본 연구는 수치해석을 통해 구근체, 보강재 변화와 지반 조건 변화에 따른 지반 내 영향범위를 확인하고자 하였다. 구근체의 증가에 따른 보강효과 증가 폭을 확인하고 지반조건 변화에 따른 경향을 파악하게 되면 쏘일네일링의 보강재 및 구근체를 결정할 수 있게 되어, 경제적인 시공이 되도록 기초자료로 활용할 수 있을 것으로 판단된다. 본 논문에서는 범용 수치해석 프로그램인 MIDAS GTS NX를 활용하여 보강재 위치 별 하중에 따른 변위를 분석 하였다. 또한 쏘일네일의 인발하중에 따른 사질토, 화강풍화토 지반에서 보강재의 구근체 이완영역이 지반 내 어떠한 특성을 나타내는지 비교 분석 하여 구근체 크기와 보강재의 직경 별 경제성을 확보할 수 있는 기준을 선정하기 위한 수치해석을 수행하였다.

• 한국운동역학회지
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• 제25권3호
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• pp.241-248
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• 2015

Objective : The purpose of this study was to investigate the theta on the components of ground reaction force according to the ground conditions during gait. Method : Six healthy women(mean age: 22 yrs, mean height: $166.14{\pm}2.51cm$, mean body weights: $56.61{\pm}4.58kg$) participated in this study. The medial-lateral GRF(Fx 1), anterior-posterior GRF(Fy 1, Fy 2), vertical GRF(Fz 1, Fz 2, Fz 3), and impact loading rate were determined from time function and frequency domain. Also, GRF theta were time function and forces. Results : Fx 1, Fy 1 and Fy 2 of stair descending showed significant statistically higher forces than that of level walking, and ascending. Fz 1 of stairs descending showed significant statistically higher forces than that of level walking and stairs ascending(theta $88.62^{\circ}$). Also, Fz 2 of level walking showed significant statistically higher forces than that of stairs ascending and descending(theta $65.78^{\circ}$). Fz 3 of stairs ascending showed significant statistically higher forces than that of level walking and stairs descending($65.26^{\circ}$). Impact loading rate of stairs descending showed significant statistically higher forces than that of level and ascending walking. The GRF showed similar correlation with GRF theta(r=.603) according to the ground conditions during gait. Conclusion : These results suggest that the GRF theta can be used in conjunction with a gait characteristics, prediction of loading rate and dynamic stability.

• 한국산학기술학회논문지
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• 제16권4호
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• pp.2899-2905
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• 2015

본 논문은 지반 조건에 따른 족저압의 압력분포에 대한 연구이다. 실내화, 실외화, 걷기화, 운동화의 네 가지 카테고리의 신발이 본 연구에 사용되었으며, 260mm(유럽 코드 EU40)를 착용하는 45명의 20대 남성을 대상으로 콘크리트, 모래 지반에서의 실험을 실시하였다. 보행 시 응력과 압력의 측정은 Techstorm사의 Insole System을 사용하여 측정하였으며 발의 발가락, 전족, 중족, 후족 네 가지 영역에서 족저압을 측정하였다. 연구 결과 신발과 지반 조건에 따라 다른 응력 및 압력의 분포를 나타냈으며 본 연구 결과는 모래 지반에서 착용 가능한 신발의 개발에 유용하게 사용될 것으로 기대된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.750-758
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• 2009

This study, as basic research which was intended to develope the surface reinforcement method using reinforcement material which is applicable to very soft ground in Korea, was aimed at proposing the design parameter for the surface ground improvement method. To that end, a wide width tensile test using geotextile, geogrid and steel bar (substitute for bamboo) and 25 kinds of the laboratory model tests with the end restraint conditions of the reinforcement that comprises the constrained and partially constrained (3 types) conditions were conducted. And the result indicated that the modulus of subgrade reaction or $N_c$ value (5.3) apparently overestimated the bearing capacity of very soft ground such as dredged ground. Moreover, as a result of model test by partially constraining the preload of 23.0kgf using geotextile, the effect of bearing capacity($q_1$) appeared to be the largest till the loading stress was $0.4tf/m^2$ due to cohesion, while it reached 75% of the maximum bearing force after $0.4tf/m^2$ due to increase in the effect of bearing capacity($q_2$) caused by the tensile force of the reinforcement. Such results tended to have appeared constantly or very similarly with each other, irrespective of the type of reinforcement (geogrid, steel bar) and constraint conditions.

• 한국농공학회논문집
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• 제53권3호
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• pp.53-58
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• 2011

This study is analyzed the characteristics of the soil erosion with the geotechnical conditions and rainfall conditions, such as the ground slope, the compaction ratio, rainfall intensity and duration of rainfall etc. To this ends, a series of model test are conducted on clayey sands. From the results, the variation of soil loss is analyzed with the geotechnical and the rainfall conditions. The amount of soil loss is decreased as the increase of compaction ratio and is increased as the ground slope, rainfall intensity and the duration of rainfall.