• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.38-39
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• 2014

In order to reduce fatal accidents, a systematic safety management should be performed at a construction site. A lot of researches on direct causes of fatal accidents and indirect causes which affect the direct causes have been conducted for effective safety management. In the previous studies, these causes are considered separately because of the difficulty of recognition of indirect causes. It is also hard to measure the negative impact of these causes and notice their occurrence the perception of its problem. However, a study on identification of complicated relationship between these two types of causes is necessary since an accident occurs due to the chain reaction that indirect causes trigger the direct causes which lead to the fatal accidents. Therefore, this study proposes a safety management plan that considers indirect and direct causes of fatal accidents cases in the Korean construction industry. Then this paper suggests a plan of safety management by identifying major causes of the accidents.

• Food Science and Biotechnology
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• v.15 no.6
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• pp.866-870
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• 2006

The maintenance of physiological activity during dilution is very critical for the accurate enumeration of Vibrio spp. in marine samples. We investigated the effect of various diluents on the recovery of Vibrio parahaemolyticus using the direct plate counting and most probable number (MPN) methods. The effects of NaCl (0.85 and 3%) and pH (from 6.6 to 7.4) in diluents based on distilled water or phosphate buffered saline (PBS) were evaluated with three V. parahaemolyticus strains. PBS-3% NaCl (pH 6.6), as opposed to PBS, was the most effective diluent at maintaining viable cell numbers up to 2 log CFU/g during dilution for direct plate counting using on thiosulfate citrate bile salts sucrose (TCBS) selective agar, as well as minimizing the difference in cell numbers between TCBS and non-selective nutrient agar. It also increased counts of V parahaemolyticus inoculated into oysters relative to PBS (p<0.01), suggesting that PBS-3% NaCl (PH 6.6) can reduce the problem of underestimating V. parhaemolyticus counts using PBS alone.

• Journal of the Korean institute of surface engineering
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• v.50 no.1
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• pp.17-23
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• 2017

This work demonstrates arc generation and anodic film formation behaviors on Al1050 alloy during PEO (plasma electrolytic oxidation) treatment under a constant direct current in an alkaline electrolyte containing silicate, carbonate and borate ions. Only one big arc more than 2 mm diameter was generated first at the edges and it was moving on the fresh surface or staying occasionally at the edges, resulting in the local burning due to generation of an extremely big orange colored arc at the edges. Central region of the flat surface was not fully covered with PEO films even after sufficiently long treatment time because of the local burning problem. The anodic oxides formed on the flat surface by arcing once were found to consist of a number of small oxide nodules with spherical shape of $3{\sim}6{\mu}m$ size and irregular shapes of about $5{\sim}10{\mu}m$ width and $10{\sim}20{\mu}m$ length. The anodic oxide nodules showed uniform thickness of about $3{\mu}m$ and rounded edges. These experimental results suggest that one big arc observed on the specimen surface under the application of a constant direct current is composed of a number of small micro-arcs less than $20{\mu}m$ size.

• Journal of Power System Engineering
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• v.22 no.1
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• pp.56-63
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• 2018

After the recent fabrication of diesel vehicle exhaust gas by Volkswagen, nitrogen oxides ($NO_x$) and particulate matter (PM) are drawing attention as representative pollutants included in exhaust gas. When gasoline and diesel fuels are combusted through direct injection into a combustion chamber at high pressure, PM emission is actually increased. To find a solution to this problem, a basic study was conducted to derive an optimized variable for combustion of compressed natural gas (CNG) by applying CNG, acknowledged as a clean fuel, to direct injection system. The essence of this study is in the introduction of a radical ignition technology for compressed natural gas (RI-CNG) in a sub-chamber type engine. The direct injection system was applied to a sub-chamber to remove residual gas from previous combustion cycle. In addition, optimal mixer distribution was achieved by precisely setting ignition timing based on fuel injection timing and excess air ratio.

• Restorative Dentistry and Endodontics
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• v.27 no.3
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• pp.284-289
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• 2002

Background : The purpose of the present study was to evaluate the direct and indirect composite restorations which had been placed for 1 year Methods : The composite restorations which had been placed between 1999. Mar and 1999, Dec was evaluated after 1 year For direct restorations. Spectrum (Dentsply, USA) and Z100 (3M, USA) were used in the anterior teeth and Surefil (Dentsply, USA) were used. For class V restorations of anterior and posterior teeth. Spectrum was used. For indirect restorations, Targis/Vectris system (Vivadent/Ivoclar, Liechtenstein) was used 2 examiners evaluated marginal quality, proximal contact. discoloration, presence of 2$^{nd}$ caries, loss of filling and hypersensitivity of restorations. The restorations was clinically evaluated by modified methods based on USPHS. Results : 60 teeth were evaluated. 59 were clinically acceptable and 1 restoration which was placed in class v cavity in the posterior tooth was fallen out. In most cases, the restorations were clinically accept-able. For restorations which had been directly placed in the class II cavities, loose proximal contact was indicated as the main complaints. Conclusions : Most of Anterior and posterior restorations which bad been directly or indirectly placed for 1 year were clinically acceptable. For posterior teeth, loose proximal contact was indicated as the main problem in the directly placed Class II restorations. Long term clinical study is needed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.10
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• pp.1157-1163
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• 1992

The development of adaptive control algorithms for possibly nonminimum phase systems has been hampered by singularities that may arise in the control law. To solve this problem, one securing convergence of the estimates to their true values by inducing persistency of excitation in the plant signals using direct adaptive control method and indirect adaptive control method, and another in which the estimates are adequately modified to meet the controllability requirements using indirect adaptive control method, without persistency of excitation. This paper presents an adaptive scheme that achieves regulation without persistent excitation condition using direct adaptive control method and reduces estimation algorithms with direct estimation of controller parameters without estimation of plant parameters.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.5
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• pp.413-419
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• 2004

In the induction motor direct vector control system using the Gopinath model flux observer, the deterioration of the dynamic response due to the detuned rotor time constant is investigated. To solve this problem, the on line estimation algorithm of the rotor time constant using model reference adaptive control is proposed. The effect of the motor parameter variation on the rotor time constant estimation is analyzed through experiment. The estimation error due to the parameter variation converges within 5%. Thus applying the proposed algorithm to the Gopinath model flux observer, the robust direct vector control system of the induction motor to the parameter variation can be implemented.

• Journal of Power Electronics
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• v.17 no.3
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• pp.674-685
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• 2017

The conventional model predictive direct torque control (MPDTC) method uses all of the voltage vectors available from a two level voltage source inverter for the prediction of the stator flux and stator current, which leads to a heavy computational burden. This paper proposes an improved model predictive direct torque control method. The stator flux predictive controller is obtained from an analysis of the relationship between the stator flux and the torque, which can be used to calculate the desired voltage vector based on the stator flux and torque reference. Then this method only needs to evaluate three voltage vectors in the sector of the desired voltage vector. As a result, the computational burden of the conventional MPDTC is effectively reduced. The time delay introduced by the computational time causes the stator current to oscillate around its reference. It also increases the current and torque ripples. To address this problem, a delay compensation method is adopted in this paper. Furthermore, the switching frequency of the inverter is significantly reduced by introducing the constraint of the power semiconductor switching number to the cost function of the MPDTC. Both simulation and experimental results are presented to verify the validity and feasibility of the proposed method.

• Journal of the Korean Mathematical Society
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• v.47 no.2
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• pp.331-350
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• 2010

We consider the variational problem consisting of minimizing a polyconvex integrand for maps between manifolds. We offer a simple and direct proof of the existence of a minimizing map. The proof is based on Young measures.

• Journal of Practical Agriculture & Fisheries Research
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• v.7 no.1
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• pp.35-46
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• 2005

This research was conducted to improve and establish Bokto direct seeding technology use of silicate in rice. Bokto direct seeding technology has recently released to alternative new method for transplanting method of the rice plant. In recent rice production has serious problem due to higher cost and labor shortage in Korea. In particular rice has been faced on open market to internationally due to WTO, FTA agreement etc. Thus rice growers in Korea have been more concentrated on cost reduction using by direct seeding technology such as dry seeding and water seeding while those methods have severe constraints like poor seedling, more weed occurrence, lodging and poor grain quality. In recent a new technology for improvement of these problem has released to farmer's field and proven to alternative rice growing technology of transplanting. In this technology there was additional application of silicate which has known as soil improvement and this research was obtained in the following results. At the application of silicate, sand, and soil there was high in seedling establishment by 90~100% in pot experiment but there was 55.0% seedling stand of the untreated control. Under dry condition seedling stand was 0% at the untreated control while 65~100% high in application of silicate, sand, and soil. Meanwhile, under rainy condition untreated control there was 85% of seedling stand but soil application was 20% of seedling establishment due to blocking of oxygen and physical soil blockage.