• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.4
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• pp.100-106
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• 2008

Typical household load have nonlinear loads including a personal computer, video, refrigerator, microwave oven, TV, and audio set. These nonlinear loads generate harmonic currents and create distortions on the sinusoidal voltage of the power system. Harmonic field measurements have shown that the harmonic contents of a waveform varies with time. A cumulative probablistic approach is the most commonly used method to solve time varying harmonics. This paper provides in depth analysis on harmonics field measurement of the typical household loads and harmonics simulation using EDSA program for the case study.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.2
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• pp.68-74
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• 2004

This paper presents a novel hybrid multilevel inverter using DC-Link voltage combination in order to improve the waveshape of output voltage and reduce harmonics. The proposed multilevel inverter can generate an 11-level output voltage. It employs three H-bridge cell, which consists of single phase full-bridge inverter module. Among them, two modules are used for level generation, and one module performs PWM switching. Nine levels are synthesised by the level inverter, and two levels are added to output by the PWM inverter. As a result, it generates an 11-level. The operational principles are explained in depth, and the validity of the proposed system is verified through the PSpice simulation and experimental results based on a prototype.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.2
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• pp.29-37
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• 2006

Heavy chemical industries have nonlinear loads including elecrolyzers. AC-DC converters are the most widely used in an elecrolysis in a chemical plant. The electrolysis consists of AC-DC converter groups connected in parallel at the DC side. The converter operations cause harmonic currents and create distortions on the sinusoidal voltage of the AC power system. This paper provides an in depth analysis on harmonics field measurement for the electrolyzer loads and harmonics assessment by the international harmonic standards IEC 61000-3-6 and IEEE 519-1992.

• Magazine of the Korean Society of Agricultural Engineers
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• v.21 no.1
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• pp.53-62
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• 1979

Since the first installation of irrigation Systems in Korea , a large number of small and medium sized reservoirs have been constructed as the main water sources Some 412, 000 ha are at present irrigated from these sources of supply. Many of the reservoirs were designed in accordance with old low standards and have in addition suffered a loss in capacity through sedimentation. At the same time, water demand has increased with the in troduction of high yielding varieties of rice. The combination has resulted in severe water deficits. To study the problem, 16 sample reservoirs have been surveyed and analysed. The results of the study are summarized be low: 1. Average decrease in reservoir capacity from the installation to present-8% 2. Average soil erosion loss (m$^3$/km$^2$/year) is 536 m$^3$/km$^2$/year and average erosion depth of soil is 0. 5mm per year. 3. No relationship, between reservoir capacity per unit of watershed (m$^3$/km$^2$) and soil erosion loss was found. 4. Increases are required in reservoir capacity: 15.8% due to the introduction of HYV's; 16.6% due to the change of system losses from 10%to 25% The conclusion to be drawn from the above results is that existing reservoir capacity should be increased by an average of 32%. The unit storage capacity to be adopted should be 661 mm

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.9
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• pp.73-79
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• 2012

In this paper, we study on how to determine the number of hidden layer neurons in neural network for predicting defect size of steam generator tube. It was reported in the literature that the number of hidden layer neurons can be efficiently determined with the help of cross-validation. Although the cross-validation provides decent estimation performance in most cases, the performance depends on the selection of validation set and rather poor performance may be led to in some cases. In order to avoid such a problem, we propose to use multifold cross-validation. Through the simulation study, it is shown that the estimation performance of defect width (defect depth, respectively) attains 94% (99.4%, respectively) of the best performance achievable among the considered neuron numbers.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.5
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• pp.103-110
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• 2003

The grounding system is necessary to provide means to dissipate electric currents into the earth without exceeding any operating and equipment limits. The ground is composed of various soils and the resistivity of the soil depends on many parameters. It depends on the type of soil and varies with distance as well as with depth. Especially, soil resistivity of volcanic area such as Jeju is ve교 high and it is difficult to acquire necessary grounding resistivity. This paper introduces the efficient grounding construction using coring technique for proper grounding resistance in high resistivity area. Because it is difficult to measure the accurate resistivity of soils, their resistivities are estimated using measured value of ground resistance and equivalent radius method. Estimated resistivities are used for grounding resistance in scheduled construction region.

• Journal of the Korean Society of Safety
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• v.12 no.4
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• pp.114-121
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• 1997

Helical anchors are foundation structure that designed to resist uplift loads are installed by applying in load to shaft while rotating it into the ground. These can be a cost effective means of proving tension anchorage for foundation where soil conditions permit their installation because of ease of installation. At present time, tapered helical anchors are commonly used to carry uplift loads. The uplift capacity includes the following factors : the height of overburden above the top helix, the resistant along a cylinder, the weight of the soil in the cylinder and suction force. In order to make clear behavior characteristics of helical anchors with pullout, model tests were conducted with respect to various embedment depth, space of helix, shape of helix. Based on the experimental study, the following conclusions are drawn. 1) The uplift capacity of multi helical anchors increase with embedment ratio of anchors The increase is smooth after critical uplift capacity. 2) Critical breakout factors and critical embedment ratio of multi helical anchor exist 7∼8, 4∼6 respectively. 3) Variation of uplift capacity with helix spaces show down after S/D=5. 4) Critical breakout factors of helical anchor in the laboratory test are similar to Das's theory.

• Journal of the Korean Society of Safety
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• v.31 no.1
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• pp.54-60
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• 2016

The bottom of dikes must be kept impermeable to control hazardous chemicals spilled from storage tanks. Currently, insufficient related chemical control laws lead to a possibility to spread through the bottom. Generally, due to the high cost of installation and periodical maintenance, many businesses prefer to install the bottom with general concrete. But, since the impermeability of concrete is dependent on the kind of materials and chemical reaction, all concrete cannot be considered as impermeable material. Thus, it is necessary to make the installation standards of the dike bottom clear in order to avoid the argument over the impermeability and prevent the chemical accident. This study has suggested the standards of impermeable concrete by conducting 7-day exposure test to crude oil with the pilot dikes. The results have showed that the standards have the better impermeable performance compared with the germany standard, which have been penetrated at the maximum penetration depth of 1.9 cm. This study is expected to contribute to both the risk reduction of penetrating into the bottom and the cost reduction of spending to make the bottom of dikes impermeable.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.8 no.2
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• pp.33-40
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• 1994

This study investigates the relationship between size, illumination, and display of show window. The average width, height, and depth of show windows in Taegu area were 341.3, 233.4, and 125.8cm, respectively. As light source, halogen lamp was most frequently used, followed by fluorescent lamp and incandescence lamp. In the actual illumination, however, a combined use of more than 2 light sources was common Further, a local illumination method, e. g., spot light, was generally adopted. The thought of employers and employees in fashion shops on display and illumination was examined as well. On the whole, the necessity and importance of display were well recognized but the fact that the illumination should be harmonized with other factors such as color and arrangement of goods was underestimated.

• Geomechanics and Engineering
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• v.21 no.6
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• pp.551-564
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• 2020

High-stress and complex geological conditions impose great challenges to maintain excavation stability during deep underground mining. In this research, large anisotropic deformation and its management by support system at a deep underground mine in Western Australia were simulated through three-dimensional finite-difference model. The ubiquitous-joint model was used and calibrated in FLAC3D to reproduce the deformation and failure characteristics of the excavation based on the field monitoring results. After modeling verification, the roles of mining depth also the intercept angle between excavation axis and foliation orientation on the deformation and damage were studied. Based on the results, quantitative relationships between key factors and damage classifications were presented, which can be used as an engineering tool. Subsequently, the performance of support system installation sequences was simulated and compared at four different scenarios. The results show that, first surface support and then reinforcement installation can obtain a better controlling effect. Finally, the influence of bolt spacing and ring spacing were also discussed. The outcomes obtained in this research may play a meaningful reference for facing the challenges in thin-bedded or foliated ground conditions.