• Journal of the Society of Disaster Information
• /
• v.4 no.2
• /
• pp.138-154
• /
• 2008

The conventional non-dig underground structure building method which made an appearance to reduce the social and environmental costs and maximize the efficiency of the social overhead capital facilities could not help being uneconomical because of many problems such as unnecessary excessive excavation, water leakage, obstacle interference, difficulty of curvilinear application and connection complexity between propelled and injected bodies due to indiscriminate application of small and large circular steel pipes without consideration of the site conditions. The T.S.T.M, in which a protruded square tube is applied as a propulsion and injection body in a design that considered site conditions such as ground condition, depth of soil and live load, was able to be economical as it solved the problems of water resistance, minimization of obstacle interference and curvilinearity, and we can see that it can be applied to all grounds by utilizing or complementing the target ground in terms of engineering. Also in configuring the transverse section, it is possible to not only secure excellent structural safety but also implement all of the above engineering characteristics not only in the square cross section but also in the arch cross section, so it was possible to build structures on any section or ground, and we could confirm the LCC reduction effect and the VE effect.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.25 no.6
• /
• pp.35-41
• /
• 2011

In order to design effectively the grounding system, it is very important to determine the optimum soil resistivity at the desired location of the connection to earth. This paper deals with the reasonable methods of measuring the soil resistivity where grounding electrodes are buried. The soil resistivity at three test sites with different resistivity of soil were measured as functions of the spacing between the test probes in the Wenner's four-point method and the length of test ground rod in the three-point method. In the case of the three-point method, the length of test ground rod of 2-10[m] in length was appropriate in two-layered soil structure. In the length range of 2-10[m], the results measured by the three-point method using the test ground rod with the length corresponding to the spacing between the test probes of the Wenner's four-point method are in good agreement with the data obtained from the Wenner's four-point method.

• Journal of Korean Society of Rural Planning
• /
• v.26 no.2
• /
• pp.51-59
• /
• 2020

In this study, we analyzed the characteristics of 511 agricultural districts through statistical data, and classify these districts as the vulnerable area to drought through correlation and cluster analysis. The criteria for classification was related to ground-water recharge, irrigation water demand, and water supply. As a result, 8 types of agricultural districts were extracted. For example, the type 1 indicated the high priority area for ground-water development, thus the districts which were classified as type 1 showed ground-water use was less than 80 % of maximum capacity, and irrigation water supply was only 37.5 % and 76.5 % of irrigation water demand in upland and paddy field, respectively. As a result, 44 of 511 districts were classified as type 1.36 districts (types 5-8) were areas where groundwater development is limited. The results of this study are expected to provide useful information for establishing the direction of the rural area development project in connection with the revitalization of policy of people return to rural area.

• Journal of Korean Elementary Science Education
• /
• v.33 no.2
• /
• pp.335-351
• /
• 2014

The 96 elementary school teachers' the degrees of understandings about the characteristics of the currents according to the connection methods of batteries in simple electric circuits were investigated. In this study, the concepts on the characteristics of currents according to the connection methods of batteries were divided 'the learned concepts' and 'the differentiated concepts'. The characteristics of the currents in the region of the larger resistance of load than the internal resistance of a battery were called the learned concepts, they are taught in the science curriculum. While the characteristics of the currents in the region of the smaller resistance of load than the internal resistance of a battery were called the differentiated concepts, they are not exposed clearly in the science curriculum. The results obtained in this study are as follows: The average score related to the learned concepts was relatively high, while the degree of the teachers' cognitions of the internal resistance of a battery and the resistance of wires were low. Also the average score related to the differentiated concepts was very low because it seems so new to the elementary school teachers. It strongly suggests that the elementary school teachers did not understand meaningfully the characteristics of the currents related to the connections of batteries on the ground of the cognitions of the internal resistances of batteries and the resistances of loads in simple electric circuits. Hence, they might experience difficulties due to the problems occurred in relation to the connections of batteries in the elementary school science lessons.

• Steel and Composite Structures
• /
• v.23 no.2
• /
• pp.143-152
• /
• 2017

This paper focuses on the seismic performance of pallet-type steel storage rack structures in their down aisle direction. As evidenced by experimental research, the seismic response of storage racks in the down-aisle direction is strongly affected by the nonlinear moment-rotation response of the beam-to-column connections. In their down-aisle direction, rack structures are designed to resist lateral seismic loads with typical moment frames utilizing proprietary beam-to-column moment-resisting connections. These connections are mostly boltless hooked type connections and they exhibit significantly large rotations resulting in large lateral frame displacements when subjected to strong ground motions. In this paper, typical hooked boltless beam-to-column connections are studied experimentally to obtain their non-linear reversed cyclic moment-rotation response. Additionally, a compound type connection involving the standard hooks and additional bolts were also tested under similar conditions. The simple introduction of the additional bolts within the hooked connection is considered to be a practical way of structural upgrade in the connection. The experimentally evaluated characteristics of the connections are compared in terms of some important performance indicators such as maximum moment and rotation capacity, change in stiffness and accumulated energy levels within the cyclic loading protocol. Finally, the obtained characteristics were used to carry out seismic performance assessment of rack frames incorporating the tested beam-to-column connections. The assessment involves a displacement based approach that utilizes a simple analytical model that captures the seismic behavior of racks in their down-aisle direction. The results of the study indicate that the proposed method of upgrading appears to be a very practical and effective way of increasing the seismic performance of hooked connections and hence the rack frames in their down-aisle direction.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.28 no.2
• /
• pp.85-92
• /
• 2024

This study presents code-compliant seismic details by addressing dry mechanical splices for precast concrete (PC) beam-column connections in the ACI 318-19 code. To this end, critical observations of previous test results on precast beam-column connection specimens with the proposed seismic detail are briefly reported in this study, along with a typical reinforced concrete (RC) monolithic connection. On this basis, nonlinear dynamic models were developed to verify seismic responses of the PC emulative moment-resisting frame systems. As the current design code allows only the emulative design approach, this study aims at identifying the seismic performances of PC moment frame systems depending on their emulative levels, for which two extreme cases were intentionally chosen as the non-emulative (unbonded self-centering with marginal energy dissipation) and fully-emulative connection details. Their corresponding hysteresis models were set by using commercial finite element analysis software. According to the current seismic design provisions, a typical five-story building was designed as a target PC building. Subsequently, nonlinear dynamic time history analyses were performed with seven ground motions to investigate the impact of emulation level or hysteresis models (i.e., energy dissipation performance) on system responses between the emulative and non-emulative PC moment frames. The analytical results showed that both the base shear and story drift ratio were substantially reduced in the emulative system compared to that of the non-emulative one, and it indicates the importance of the code-compliant (i.e., emulative) connection details on the seismic performance of the precast building.

• Nuclear Engineering and Technology
• /
• v.10 no.3
• /
• pp.153-163
• /
• 1978

The problems of solid waste disposal into the ground in connection with environmental aspects in the vicinity of a site would be very significant, though ground disposal for solid waste is safe and economical method. Studies of the waste-movement and migration of radionuclides (Sr-90 and Cs-137) for the disposal into the ground were performed under laboratory and field conditions. Affinity of the soils for radionuclide solution was higher than that in the acid solution. The sorption of radionuclides by the soils showed a time-dependent reation. The migration rates of radiostrontium and radiocesium were a range of 3.73$\times$10$^{-3}$ to 10.9$\times$10$^{-3}$ cm/day. The nuclides in the soil migrate much more slowly than the water, probably due to its high exchange capacity. The observed distribution of tritium was compared with that calculated by a mathematical model based on diffusivity. This study suggests that the tritiated water can be used to trace the movement of ground water.

• Geophysics and Geophysical Exploration
• /
• v.25 no.4
• /
• pp.189-200
• /
• 2022

Ground subsidence on urban roads is a social issue that can lead to human and property damages. Therefore, it is crucial to detect underground cavities in advance and repair them. Underground cavity detection is mainly performed using ground penetrating radar (GPR) surveys. This process is time-consuming, as a massive amount of GPR data needs to be interpreted, and the results vary depending on the skills and subjectivity of experts. To address these problems, researchers have studied automation and quantification techniques for GPR data interpretation, and recent studies have focused on deep learning-based interpretation techniques. In this study, we described a hyperbolic event detection process based on deep learning for GPR data interpretation. To demonstrate this process, we implemented a series of algorithms introduced in the preexisting research step by step. First, a deep learning-based YOLOv3 object detection model was applied to automatically detect hyperbolic signals. Subsequently, only hyperbolic signals were extracted using the column-connection clustering (C3) algorithm. Finally, the horizontal locations of the underground cavities were determined using regression analysis. The hyperbolic event detection using the YOLOv3 object detection technique achieved 84% precision and a recall score of 92% based on AP50. The predicted horizontal locations of the four underground cavities were approximately 0.12 ~ 0.36 m away from their actual locations. Thus, we confirmed that the existing deep learning-based interpretation technique is reliable with regard to detecting the hyperbolic patterns indicating underground cavities.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.12
• /
• pp.8927-8932
• /
• 2015

A directional feeding method at the railway transformer is applied for supplying the power to the electric railway substations, and the pre-installed facilities with common feeder are utilized in preparation for the failure of feeding system and in finding a fault location in case that the catenary failure occurs. However, it is some difficulty in finding the fault location since there is an interface problem with the facilities when the supplying power system operates. In this paper, Auto Fault Locator Transfer Drive System (ALTDS) is designed to search for the fault location efficiently, and the measuring data are obtained and compared with the KORAIL standards. Further, the ground connection test is accomplished 24 times as the verification method, and it is shown that the methodology provides better performance than the existing traditional one.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.18 no.7
• /
• pp.689-697
• /
• 2007

This thesis suggests ways on how to enhance handset radiation power under head phantom condition. Generally, peak EIRP(Effective Isotropic Radiated Power) is used to measure the radiation performance. TRP is more effective to represent indication of mobile radiation performance in the field than EIRP. In this case, we measure the TRP as an index of radiation power. The factors which effect TRP are antenna length, antenna position, folder angle and ground connection method. More detailed analysis is performed over these items. Significant item is ground connection method between main PCB and folder GND. Using the FPCB we connect main GND to folder GND through the hinge near the antenna. The result is that TRP attenuation is decreased about 5 dB under head phantom condition.