• Geomechanics and Engineering
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• v.8 no.4
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• pp.495-510
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• 2015

The applications of water jet cutting (WJC) in coal mine have progressed slowly. In this paper, we analyzed the possibility and reasonableness of WJC application to pressure relief in hard coal seam, simulated the distributive characteristics of stress and energy fields suffered by hard coal roadway wallrock and the internal relationships of the fields to the instability due to WJC (including horizontal radial slot and vertical annular slot) on roadway wallrock. The results showed that: (1) WJC can unload hard coal seam effectively by inducing stress release and energy dissipation in coal mass near its slots; its annular slots also can block or weaken stress and energy transfer in coal mass; (2) the two slots may cause "the beam structure" and "the small pillar skeleton", and "the layered energy reservoir structure", respectively, which lead to the increase in stress concentration and energy accumulation in coal element mass near the slots; (3) the reasonable design and optimization of slots' positions and their combination not only can significantly reduce the scope of stress concentration and energy accumulation, but also destroy coal mass structure on a larger scale to force stress to transfer deeper coal mass.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.507-510
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• 2005

Brake judder, which occurs when brakes are suddenly applied to a vehicle driving at high speed, affects the driver's safety to a great extent. It also has a low frequency that drivers can easily feel. Among theses presented, none offered studies using modeling of actual brakes in computer simulation in order to recreate the brake judder phenomenon, and most of them directly applied the frequency generated by the judder. To resolve this issue, this study hopes to develop a computer model that can recreate the phenomenon of brake judder. In this paper, in order to examine the vibration problem occurring when brake is applied on the test car, the multibody dynamic analysis program ADAMS was used to develop a computer model that can recreate the actual braking mechanism while breaking away from the existing understanding of brakes. Thus the existence of the brake judder phenomenon due to DTV(Dist Thickness Variation) and wheel rotating speed was examined through the developed model.

• Korean Journal of Veterinary Research
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• v.41 no.4
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• pp.505-510
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• 2001

A total of 701 swine sera from 55 swine farms (Mar, 1998 through Feb, 2001) were nation-widely collected for the presence of antibody to porcine parvovirus (PPV) in sows and 30-, 60-, 90-day-old pigs. Sero-prevalence by haemagglutination inhibition assay with guinea pig red blood cells was investigated on the basis of year, region and season, respectively. In general, there was no significant difference with gradual decrease of passive immunity for the sero-prevalence to PPV in sows and 30-, 60-, 90-day-old pigs for the period of 1999 and 2000. However, regional variation was observed in the provinces of Kyonggi, Choongnam and Kyungnam, Natural infection of the virus in 90-day-old pigs was increased during the fall and the winter. Thus, it seems that the natural infection of PPV in growing pigs may be attributed to the increased outbreak of postweaning multisystemic wasting syndorme in co-infection with porcine circoviruses.

• Macromolecular Research
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• v.11 no.6
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• pp.471-475
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• 2003

A new poly[2-(2',5'-dimethylphenyl)-1,4-phenylenevinylene] (PDMPPV) that features a bulky 2',5'-dimethylphenyl substituent, which can induce steric hindrance between the PPV backbone and the methyl groups, was designed and synthesized. The polymer structure having no TBB defects was confirmed by $^1$H-NMR and $\^$13/CNMR spectroscopy. The polymer showed good thermal stability with high T$\_$g/. The polymer film showed a maximum absorption at 415 nm with an absorption onset at 480 nm. The maximum emission peak showed at ca. 515 nm, with a shoulder at 530 nm. The turn-on voltages of ITO/PEDOT/PDMPPV/Al and ITO/PDMPPV/Al devices were 8 and 10 V, respectively. The electroluminescence spectrum from the device showed a maximum peak at 510 nm with a shoulder at ca. 535 nm.

• Korean Journal of Pharmacognosy
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• v.48 no.3
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• pp.255-259
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• 2017

This study was conducted to provide basic information on ginseng saponin of dried ginseng radices. In order to achieve the proposed objective ginsenoside compositions of dried ginseng radices extract with 70% ethyl alcohol were examined by HPLC. The total saponin content, the sum of all ginsenosides, showed that Wild simulated ginseng (WSG), White fine ginseng (WFG), Skin White ginseng (SWG), and White ginseng (WG) stood at 2.510%, 1.643%, 0.587, and 0.429%, respectively. WSG in PPD/PPT ratio was highest at 3.190, WFG (1.934), WG (1.600), SWG (1.386) in order. In the content of ginsenoside Rb1, one of the marker compounds of ginseng, WSG (1.095%) showed the highest content, and WFG (0.527%), SWG (0.246%), WG (0.133%) in this order. The content of ginsenoside Rb1 of WSG (1.095%) was 4.5 times higher than SWG (0.246%). WSG (0.230%) showed the highest content in ginsenoside Rg1, a marker compounds of ginseng, followed by WFG (0.180%), SWG (0.141%) and WG (0.086%). The content of ginsenoside Rg1 of WSG (0.230%) was 1.6 times higher than SWG (0.141%).

• Journal of Power Electronics
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• v.18 no.2
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• pp.502-510
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• 2018

A circulating current is a major problem caused by directly connecting voltage-source inverters (VSIs) in parallel. This circulating current occurs as a zero-sequence current between the inverters by specific switch states. Several studies have presented alternatives using hardware and software methods. When coupled inductors (CIs) are employed for the high-frequency circulating current, a controller is required to prevent the low-frequency circulating current from saturating the CIs. In this study, the zero-sequence circulating current and its alternatives are investigated using hardware and mathematical description. A high-performance circulating current controller is proposed by applying a repetitive controller to the zero-sequence current control loop. The proposed controller can effectively minimize the low-frequency circulating current without any data sharing between the inverters in unfavorable conditions. It can also be applicable to the modular configuration of parallel three-phase VSIs. Experimental results verify the performance of the proposed controller.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.4
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• pp.493-501
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• 2013

Taking into account the increasingly stringent legislation on emissions from marine engines, this work aims to analyze several internal engine modifications to reduce $NO_x$ (nitrogen oxides) and other pollutants. To this end, a numerical model was employed to simulate the operation cycle and characterize the exhaust gas composition. After a preliminary validation process was carried out using experimental data from a four-stroke, medium-speed marine engine, the numerical model was employed to study the influence of several internal modifications, such as water addition from 0 to 100% water to fuel ratios, exhaust gas recirculation from 0 to 100% EGR rates, modification of the overlap timing from 60 to $120^{\circ}$, modification of the intake valve closing from 510 to $570^{\circ}$, and modification of the cooling water temperature from 70 to $90^{\circ}C$. $NO_x$ was reduced by nearly 100%. As expected, it was found that, by lowering the combustion temperature, there is a notable reduction in $NO_x$, but an increase in CO (carbon monoxide), HC (hydrocarbons) and consumption.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.900-903
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• 2003

Using $DV-X{\alpha}$ method, it is calculated that nickel reduces the energy band gap of manganese oxide in 3 additives of titanium, nickel and tin. Therefore, it is estimated that the electrical conductivity of manganese-nickel oxide has the lowest value in 3 kinds of manganese oxide. The manganese oxide and manganese-nickel oxide which were produced by anodic deposition under $30mA/cm^2$ at room temperature in manganese sulfate and manganese-nickel sulfate solution were thermal-analyzed by DTA and TGA. The weight change of manganese oxide continuously decreased below $508^{\circ}C$ and kept constant at $518{\sim}600^{\circ}C$. However, the manganeses-nickel oxide transformed at the temperature range of $510{\sim}537^{\circ}C$. It is observed that the nickel addition to manganese oxide increases transformation temperature and its range.

• Asian-Australasian Journal of Animal Sciences
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• v.13 no.4
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• pp.506-510
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• 2000

This experiment was to determine the usefulness of gum safflower phospholipid as a feed ingredient. Forty female broiler chicks were divided into four groups and fed experimental diets containing following fats and oils; beef tallow (Tallow), the blend of safflower oil and palm oil (SP-oil), gum rapeseed phospholipid (Rap-PL), or gum safflower phospholipid (Saf-PL) for 21days. There were no differences in growth performances among the treatments. Abdominal fat weight tended to be reduced in the chicks fed. phospholipids. The activity of hepatic acetyl-CoA carboxylase was significantly reduced in the Rap-PL and Saf-PL as compared to that of Tallow. Feeding dietary phospholipids resulted in a slight reduction in total fat and triglyceride contents in the breast and thigh muscles. In addition, total fat and triglyceride contents in the thigh muscle were significantly decreased by dietary Saf-PL as compared to those of Tallow. These results suggested that dietary gum phospholipids, either from rapeseed or safflower, had desirable effects of lowing abdominal and muscle fats, and could be used as a feed ingredient for broiler diets.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.5
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• pp.496-510
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• 2016

Simulation technology is a type of shipbuilding product lifecycle management solution used to support production planning or decision-making. Normally, most shipbuilding processes are consisted of job shop production, and the modeling and simulation require professional skills and experience on shipbuilding. For these reasons, many shipbuilding companies have difficulties adapting simulation systems, regardless of the necessity for the technology. In this paper, the data model for shipyard production simulation model generation was defined by analyzing the iterative simulation modeling procedure. The shipyard production simulation data model defined in this study contains the information necessary for the conventional simulation modeling procedure and can serve as a basis for simulation model generation. The efficacy of the developed system was validated by applying it to the simulation model generation of the panel block production line. By implementing the initial simulation model generation process, which was performed in the past with a simulation modeler, the proposed system substantially reduced the modeling time. In addition, by reducing the difficulties posed by different modeler-dependent generation methods, the proposed system makes the standardization of the simulation model quality possible.