• Journal of Korean Society of Forest Science
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• 제85권1호
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• pp.66-75
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• 1996

This study was carried out to examine the forest fire effect on water storage characteristics in the forests. Water storage capacity of the burned area was analyzed by several major factors, such as soil pore, maximum water content, effective water storage, and percolation rate. The results obtained from the analysis of major factors are as follows; The deeper soil depth, the less total pore, coarse pore, effective water storage, and percolation rate. However, fine pore increased slightly in both burned area and control plot. As compared with control plot, burned area showed lower percolation rate, coarse pore, and effective water storage, but higher values of fine pore. Directly after forest fire, the soil pore is little affected. But as the time passes, top soil structure changes and soil pore also is affected even in a deep soil. Estimated effective water storage was lower at top soil of Namcheon and at deep soil of Namha in all the burned areas, but slowly decreased in deep soil compared to control plots. Therefore it was concluded that forest water storage capacity was greatly affected by the forest fire.

• Journal of Korean Society of Steel Construction
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• 제9권2호통권31호
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• pp.171-179
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• 1997

The high-tension bolted joints are clamped by the axial force which approaches the yielding strength. The introduced axial force is transmitted to the connection members pass through washer. The transferred load in connections is balanced to the compressive stress of plates, axial force in bolts and the external loads. In this mechanism, the compressive stress and slip load we dominated by the effective stiffness of bolted joints and plates. In general the effective stiffness is specified to product to the effective area and elasticity modulus in connections. In this reason, the conic projection formular which is assumed that the axial force in bolts is distributed to the cone shape and that region is related to the elastic deformation mechanism in connections, was proposed. But it conclude what kind of formula is justified. Therefore in this paper, the fatigue tests are performed to the high tension bolted joints and inspected to the phase on the friction face. And using the FEM and numerical method, it is analyzed and approximated to the compressive stress distribution and its region. Moreover, it is estimated to the effective area and to the relation the friction area to the effective compressive distribution region.

• Spatial Information Research
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• 제8권1호
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• pp.171-182
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• 2000

Random sampling or systematic sampling method is commonly used to assess the accuracy of classification results. In remote sensing, with these sampling method, much time and tedious works are required to acquire sufficient ground truth data. So , a more effective sampling method that can retain the characteristics of the population is required. In this study, fractal analysis is adopted as an index for reference sampling . The fractal dimensions of the whole study area and the sub-regions are calculated to choose sub-regions that have the most similar dimensionality to that of whole-area. Then the whole -area s classification accuracy is compared to those of sub-regions, respectively, and it is verified that the accuracies of selected sub regions are similar to that of full-area . Using the above procedure, a new kind of reference sampling method is proposed. The result shows that it is possible to reduced sampling area and sample size keeping up the same results as existing methods in accuracy tests. Thus, the proposed method is proved cost-effective for reference data sampling.

• Korean Journal of Fisheries and Aquatic Sciences
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• 제34권6호
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• pp.705-712
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• 2001

It is of great importance to represent the directional ocean waves in a laboratory basin for hydraulic model tests. The directional ocean waves can be expressed as a linear superposition of a large number of component waves with different frequencies and propagating directions. The aim of the study is to check the wave generating characteristics by serpent-type wave generating system in PKNU (Pukyong National University) which is composed of 10 piston-type wave generators. In the experiment, spatial variation of irregular wave heights and propagating angles are measured in the multi-directional wave maker basin. Target wave directional spectrum is reproduced in the area of multi-directional wave maker basin. The directional spreading of the generated waves varied spacially in the basin. They differed from target spectrum as the measurement point becomes far from the center line normal to the generator face, The effective generation area where that target can be reproduced is limited to the triangular area attached the generator face. According to the results, it is emphasized that the effective experiment area in the basin considered wave generator characteristics should be determined in consideration of experimental conditions including structural shapes, water depth, wave directionality etc.

• Proceedings of the KSME Conference
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.421-425
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• 2007

In the fabrication of dry adhesive structure, increasing contact-points or contact-area is the primary goal because the adhesive force grows in proportion to the contact-area. The simplest way to extend the contact surface is the fabrication by using soft materials. However, the column-array structure could confront the matting phenomenon which columns are stuck together. Therefore, we need a novel design to reduce the effective stiffness with adequate stiff materials like a gecko's setae. In this study, we propose a novel design for the dry adhesive structure. Moreover, we analyzed whether the adhesive structure conforms the rough surface sufficiently through finite element method adopted the non-bonding interaction as the body force. Also, we fabricated the novel structures via UV lithography and some techniques. In addition, we examined the adhesive force of the novel structures.

• Transactions of The Korea Fluid Power Systems Society
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• 제8권2호
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• pp.17-22
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• 2011

The analysis of an air spring characteristics is necessary to design and control automotive air suspension system properly. A mathematical model of an air spring was derived in light of energy conservation first. Then static and dynamic experiments of the air spring have been fulfilled. The static stiffness with various initial pressures and effective areas were obtained from the static experimental results. Theoretical static stiffness obtained by using the mathematical model and effective area data is in close accordance with the experimental estimation. The dynamic experimental results show that the hysteresis in displacement-force cycle decreases when the frequency of the harmonic displacement excitation signal increases, but it does not change too much as the frequency is higher than 1Hz. And the dynamic stiffness goes up with increasing of the initial pressure and the excitation frequency.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제21권3호
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• pp.197-202
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• 2008

In this paper, we proposed an analytical model for TFT which has series of the polycrystalline structures. An average speed is defined as carrier speed by the electric field. The effective square is suggested as the area of grain without depletion for the changed grain size. First, physical parameters such as grain size, channel lenght and trap density, have been changed to prove the validity of the average speed model and the value of the effective square has been estimated through drain-source current.

• Journal of the Korea Safety Management & Science
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• 제9권2호
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• pp.19-31
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• 2007

If you examine the Industrial Disaster Analysis Content that occurs every year in the small and medium enterprise, industrial disaster occurs because of manager's lack of safety and worker's unprepared safety education. Therefore effective safety education systems are needed to offer adequate knowledge and technology to the workers. On this research, to give an effective education way to decrease industrial disaster we administered to the workers who are in charge of 300 workplace in Incheon area to search actual condition of industrial disaster and to disclose a link between industrial disaster and industrial safety education. We put in effect on frequency study and examined x2 using SPSSWIN 10.0. On the research, the results shows that the industrial safety education and training are in effect regularly and the satisfaction are low. But the manager's satisfactions are high through safety education. So it shows that we need to find a way to put in effect safety education to satisfy the workers.

• Journal of IKEEE
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• 제20권1호
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• pp.1-8
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• 2016

In this paper, we propose an effective time-of-arrival (TOA)-based localization method with adaptive bias computation in indoor environments. The goal of the localization is to estimate an accurate target's location in wireless localization system. However, in indoor environments, non-line-of-sight (NLOS) errors block the signal propagation between target device and base station. The NLOS errors have significant effects on ranging between two devices for wireless localization. In TOA-based localization, finding the target's location inside the overlapped area in the TOA-circles is difficult. We present an effective localization method using compensated distance with adaptive bias computation. The proposed method is possible for the target's location to estimate an accurate location in the overlapped area using the measured distances with subtracted adaptive bias. Through localization experiments in indoor environments, estimation error is reduced comparing to the conventional localization methods.

• Journal of the Optical Society of Korea
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• 제9권4호
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• pp.140-144
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• 2005

In this paper we have investigated the guiding properties of photonic crystal fibers (PCFs) with a square-lattice of air-holes in the cladding. We have shown numerical results of PCFs with various air hole sizes and hole-to-hole spacings over a wide wavelength range. The group velocity dispersion, effective area and effective refractive index of PCF have been calculated numerically. The waveguide dispersion has greatly affected the group velocity dispersion when hole-to-hole spacing is about $1{\mu}m$. The effective area is quite flat over the wide spectral range whether the hole-to-hole spacing is large or ratio of diameter to pitch is large. From the field distribution, we found that the field is tightly confined within the core region of PCF when the pitch is $3{\mu}m$ and the air-filling fraction is 0.9.