• Journal of the Society of Disaster Information
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• v.20 no.1
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• pp.169-176
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• 2024

Purpose: In this paper, an experimental study was conducted to analyze the difference in shear strength caused by the problem of excluding coarse particles due to the size of the test specimen in the direct shear test. Method: A large-scale direct shear test was conducted on three weathered soils containing coarse aggregates with a maximum diameter of 50mm. In addition, a small-scale direct shear test was performed using a sample with a maximum diameter of 5 mm, excluding coarse aggregates. Result: In the case of the small-scale direct shear test, compared to the results of the large-scale direct shear test containing large particles, the internal friction angle was about 2.3% smaller, and there was no significant difference. In terms of cohesion, compared to the large-scale direct shear test, the small-scale direct shear test derived about 80.3% smaller value, showing a relatively large difference. Conclusion: In the large-scale direct shear test, it was analyzed that the coarse particles had a greater impact on the cohesion than the internal friction angle. Therefore, granite weathered clay containing coarse particles is judged to have the same shear strength as the cohesive force that is not affected by vertical stress. In this study, it was analyzed that the small-scale direct shear test, which excludes the coarse particles that are commonly used, provides results on the safety side by excluding the effect of coarse particles.

• Journal of Families and Better Life
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• v.10 no.1 s.19
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• pp.139-156
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• 1992

The purpose of this study is to provide basic data for the solution of occupant problems related to the house purchasing. For the purpose, the content of problems and actual conditions of house purchasing are examined. Also the structural analysis of occupant's evaluation of housing purchasing is executed. For these purposes, a survey was conducted using questionnaires. Data analysis was conducted from 263 house owners in Seoul. Major findings of this study can be summarized as follows ; 1) The frequency and the contend of occupation's problems with house purchasing are studied. The rate of housing problem occurrence is 71.2%, so the majority of respondents experience problems. The most common problems are the difference from supplier's description(53.2%). The rate of housing problems occurrence is qenerally high with the houses of mult-housedhold houses and mult-family houses type. 2) There is a significant difference in housing satisfaction extend according to the existence of an housing problem experience. Therefore, it can be inferred that experience of housing problem has an important effects upon the housing satasfaction extent. 3) Occupants' countermoves to the housing problems are examined. Occupants make active regotiation with house suppliers only on the direct damages such as an economical loss or a living difficulty. However, they usually make no countermove at all on the other indirect troubles. House suppliers make correction only when occupants' countermove actively, but refuse to do when occupant's reactions are not active. 4) As a means of countermove, most occupants depend on direct personal regotiation with house suppliers. The rate of using a specialist or public and private consultant is extremely low. 5) Problems with house purchasing and the countermove process of both occupant and house supplier are displayed in the figure(Fig. 4-4).

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1527-1539
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• 2015

In this paper the hardware implementation of the direct torque control based on the fuzzy logic technique of induction motor on the Field-Programmable Gate Array (FPGA) is presented. Due to its complexity, the fuzzy logic technique implemented on a digital system like the DSP (Digital Signal Processor) and microcontroller is characterized by a calculating delay. This delay is due to the processing speed which depends on the system complexity. The limitation of these solutions is inevitable. To solve this problem, an alternative digital solution is used, based on the FPGA, which is characterized by a fast processing speed, to take the advantage of the performances of the fuzzy logic technique in spite of its complex computation. The Conventional Direct Torque Control (CDTC) of the induction machine faces problems, like the high stator flux, electromagnetic torque ripples, and stator current distortions. To overcome the CDTC problems many methods are used such as the space vector modulation which is sensitive to the parameters variations of the machine, the increase in the switches inverter number which increases the cost of the inverter, and the artificial intelligence. In this paper an intelligent technique based on the fuzzy logic is used because it is allows controlling the systems without knowing the mathematical model. Also, we use a new method based on the Xilinx system generator for the hardware implementation of Direct Torque Fuzzy Control (DTFC) on the FPGA. The simulation results of the DTFC are compared to those of the CDTC. The comparison results illustrate the reduction in the torque and stator flux ripples of the DTFC and show the Xilinx Virtex V FPGA performances in terms of execution time.

• The Journal of the Korea Contents Association
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• v.17 no.1
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• pp.496-506
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• 2017

This study tried to examine the validity of the technical and institutional method to perform the purpose of public interest in terrestrial broadcasting. For this purpose, this study concentrated to the rate of direct reception of the terrestrial broadcasting that government and broadcasting company have offered since the digital transition. Results of analysis, it appeared that have not possibility of realization to set the direct receiving antenna and built-in Antenna for enhanced reception of the signal of the terrestrial broadcasting. Second, the MMS, if not enhanced the direct reception, was expected that repeated the retransmission through the pay broadcasting as the time of digital transition. Finally, the disaster broadcast was revealed that reduce the effectiveness of the UHD TV policy because of the mutual interference between frequencies and the incomplete solution of shadow area. According to these results, it is expected to be difficult for a while to perform the purpose of public interest in UHD TV.

• Journal of Environmental Health Sciences
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• v.33 no.5
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• pp.470-477
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• 2007

This research was conducted to evaluate the effect of moisture content on direct landfilling prohibition of organic sludge. Organic sludges with moisture content (Me) of 75 and 85% were filled in two lysimeters. The lysimeters were named as Exp.75 and Exp.85, respectively. LFG of 2,064 l was generated greatly for Exp.85, compared to 1,500 l for Exp.75. LFG generations in Exp.75 and Exp.85 were 64.1 l/kg and 157.1 l/kg as dry TS basis, and 113.6 l/kg and 266.2 l/kg as dry VS basis. Total $CH_4$ generation in LFG for Exp.85 was 1,238 l, while 1,050 l for Exp.75. $H_2S$ of $3{\sim}150$ ppmv was generated from Exp.85, which was 5 times higher than $2{\sim}30$ppmv from Exp.75. Leachate was not generated from Exp.75 during operation time. However, 420 ml of leachate was generated from Exp.85. From the results of gas generation, composition, odorous compounds, and leachate generation, landfilling of organic sludge with high MC was more harmful to the environment in spite of great LFG generation. However, direct landfilling of organic sludges without great difference of MC made a severe odor problem. Therefore, it was thought that current direct landfilling prohibition law for all organic sludge was appropriate.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.5
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• pp.869-876
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• 2001

In modern wireless communication, it has been regarded as a important problem for the spectrum efficiency to utilize the limited frequency-resource efficiently. In addition, the system architecture has been designed for low cost, low power consumption and ultra-lightweight. In this paper, we directly modulated the BCPFSK with a superior spectrum efficiency using the DDS and applied the direct conversion to the system architecture. Finally, we designed a transceiver which has the 433 MHz BCPFSK output and evaluated the system performance. In the measured result, we know that as for spectrum and the power efficiency, BCPFSK method is better than conventional one. Also, the results of the designed system is 433.92 MHz in center frequency and about 33 dBc in carrier suppression ratio. And we get the better results in local oscillator leakage and the spurious of the ISM out-band the same as -69dBc and under 60dBc.

• Journal of the Korean School Mathematics Society
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• v.17 no.4
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• pp.717-746
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• 2014

The study aimed to explore how to improve mathematical thinking through metacognitive learning by stressing metacognitive abilities as a core strategy to increase mathematical creativity and problem-solving abilities. Theoretical exploration was followed by an analysis of correlations between metacognitive abilities and various ways of mathematical thinking. Various metacognitive teaching and learning methods used by many teachers at school were integrated for sharing. Also, the methods of learning application and assessment of metacognitive thinking were explored. The results are as follows: First, metacognitive abilities were positively related to 'reasoning, communication, creative problem solving and commitment' with direct and indirect effects on mathematical thinking. Second, various megacognitive ability-applied teaching and learning methods had positive impacts on definitive areas such as 'anxiety over Mathematics, self-efficacy, learning habit, interest, confidence and trust' as well as cognitive areas such as 'learning performance, reasoning, problem solving, metacognitive ability, communication and expression', which is a result applicable to top, middle and low-performance students at primary and secondary education facilities. Third, 'metacognitive activities, metaproblem-solving process, personal strength and weakness management project, metacognitive notes, observation tables and metacognitive checklists' for metacognitive learning were suggested as alternatives to performance assessment covering problem-solving and thinking processes. Various metacognitive learning methods helped to improve creative and systemic problem solving and increase mathematical thinking. They did not only imitate uniform problem-solving methods suggested by a teacher but also induced direct experiences of mathematical thinking as well as adjustment and control of the thinking process. The study will help teachers recognize the importance of metacognition, devise and apply teaching or learning models for their teaching environments, improving students' metacognitive ability as well as mathematical and creative thinking.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.7
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• pp.627-631
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• 2012

Observable mathematical model of DDM (Direct Dirve Motor) was suggested. The motor that operates the object system directly is called DDM. DDM has many strong points, however, it has a significant disadvantage, that it is more sensitive to the external force than the motor with reduction gear. In other word, if the force is applied, air gap of the motor can be perturbed. This causes not only difficulty in motor control but also even more serious problem, such as the breakdown of motor. However, if the air gap variation can be estimated, it can help prevent these problems. DDM should be modeled to estimate the air gap variation. The type of researched DDM is PMSM (Permanent Magnet Synchronous Motor) and precedent model of PMSM includes only characteristics of electro-magnetic system and rotational motion. However, suggested model should also include characteristics of translational motion of rotor to estimate the air gap variation. Also, this model should satisfy observability condition, because state observer is designed based on this model.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.7
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• pp.657-664
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• 2011

This study proposes an inverse method for estimating the boundary temperature in a gas-filled, onedimensional parallel domain enclosed by parallel plates. The distance between the plates is considered submicron to one mm. In the current method, it is assumed that the conditions of both heat flux and temperature are simultaneously applicable to one boundary, while no conditions are applicable to the other boundary The temperature on one of the boundaries should be inversely determined from the known temperature and heat flux on the other boundary. This study proposes a procedure for estimating the unknown boundary temperature through Monte Carlo simulation. Both the forward and inverse problems employ the Monte Carlo approach. The forward (direct) problem is solved by using the direct simulation Monte Carlo while the inverse solution is obtained by the simulated annealing.

• Journal of the Korean Society of Safety
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• v.24 no.5
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• pp.34-42
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• 2009

There are many accident causes related to even an accident. As well four(4) stepped causes of one accident at construction sites are analyzed in the study. First, eleven(11) cause factors are set up at each step such as policy level, management, indirect, direct level which are discussed and determined by field experts with 15year experience or more. Therefore, one direct cause occurred in construction site can be connected to the previous cause than in direct and management, and policy problem of previous management. These questionnaires results are analyzed with three different methods such as weighing level by Delphi technique, correlation analysis, critical pass method. Three different methods show their characteristic to see which subcontract work is more dangerous or not. Subcontract or at a construction site can be use the above three different cases as they need at their site in order to make more effective countermeasures.