• Journal of Advanced Marine Engineering and Technology
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• v.38 no.1
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• pp.31-38
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• 2014

Ejector is a simple device which can transport a low-pressure secondary flow by using a high-pressure primary flow. The efficiency of the ejector system is relatively very low, compared to other fluid transport devices driven mainly by the forces acting on the normal direction. However, its major advantage is a simple structure with no moving parts, and it transports a large amount of fluid with a small driving energy. In this study, the performance of side-type liquid ejector commonly used in ships; is analyzed by using experimental and CFD methods under steady and incompressible flow condition by varying the length of the throat and diffuser, the flow pattern and suction phenomenon were studied in detail.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.565-572
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• 2007

This paper addresses the kinematic study for the structural analysis of the S60ME-C multi-cylinder vessel engine. The load conditions such as the lateral force and the reaction force by the crank-shaft are required for the FEM analysis. The driving parts in vessel engine are assumed to be in frictionless rigid plane motion. We analytically derive dynamic forces for a single cylinder by using the dynamic force equilibrium. But, for the structural analysis for a single cylinder block, we use the loading conditions of two neighboring cylinders. Meanwhile, we use the single cylinder's loading condition to calculate the multi-cylinder's loading conditions, because each cylinder shows a cyclic loading pattern with respect to the crank arm's rotation angle.

• Journal of Advanced Navigation Technology
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• v.14 no.1
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• pp.93-101
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• 2010

In this study, the performance characteristics of turbocharged engine is analyzed. The methods of engine performance improvements are suggested not only for full load characteristics of the engine but also for partial load characteristics of the engine, which is more frequently used in actual driving conditions. The compression ratio of the compressor is increased rapidly in a straight line pattern until 1260 engine rpm, and after that it is increased slowly to 2.5 ratio. Also the brake mean effective pressure increased until 1260 engine rpm and decreased rapidly after 1600 engine rpm. The higher the pressure ratio, the better the fuel consumption, air excess ratio and brake mean effective pressure. But those are higher in the rated revolution range than in the mid-low revolution range. The turbocharger is operated in a stable condition from 1260 rpm and its efficiency is low in the low speed range for the reason of its characteristics. The results of this study can be applied in the fundamental control methods of turbocharged engine for stable load and speed.

• Journal of Korean Physical Therapy Science
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• v.16 no.3
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• pp.55-66
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• 2009

Background: The purpose of this research was to investigate the factors affecting the low back pain of workers in hospital. 214 subjects waking at two general hospitals in Yosu city participated in this survey. Subjects consisted of doctors, nurses, medical engineers, officers and general laborers. The survey data were collected by a written questionnaire which made out by themselves for 25 days, from fourth August to 29th August, 2008. Methods: The questionnaire consisted of four categories, general, occupational, working habitual and the daily living characteristics. The collected data were analyzed by Chi-square test based on the present or absent of low back pain. Results: 1. In the general characteristics, low back pain had no significant relationship to all factors, sex, ago, body mass index, weight and height. 2. In the occupational characteristics, the phase of distribution of low back pain had statistical significant differences in the working hours a week, satisfaction of pay, satisfaction of occupation(p<0.05). However low back pain did not significantly related to the kind of occupation, period of work and degree of stress. 3. In the habitual characteristics, low back pain was significantly influenced by working posture, frequency of using lumbar and heavy material lifting, monotonous repetition of working operation and noise(p<0.05). No significant difference was shown in the factor of convenience of chair. 4. In the daily living characteristics, low back pain shown the significant differences in walking time a day, status of health and smoking pattern(p<0.05). there were, however, no significant differences in the aspect of the kind of house and bed, sleeping attitude, driving, riding time on the vehicle, exercising, frequency of cultural life and drinking alcohol. Conclusion: when I see above resultants totally, it appears a higher incidence caused by working environment rather than living habit and then consequently compared to hospital workers, they also have high incidence like others. In order to reduce incidence of low back pain and enjoy the our life we need to educate ourselves preventing program for low back pain and try to effort for preventing of low back pain on each department and individual.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.632-639
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• 2018

Recently, a policy has been enforced to supply Plug-in Electric Vehicles (PEVs) but this may require reinforcement of the power system depending on its clustering because PEVs are charged directly from power systems. On the other hand, as the reinforcement of power system is limited by time and budget, it is important to supply the charging demand of PEVs efficiently using the existing power systems to increase the diffusion of PEVs. This paper establishes a charging schedule for Plug-in Electric Vehicles (PEVs) considering the power system constraints. For this, the required amount and time of the charging demand for an individual PEV was modeled to integrate into power systems based on the driving pattern and charging tariff of PEV. Furthermore, the charging schedule of PEVs was established to meet the power system constraints by calculating the operating conditions of the power systems with PEVs.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.4
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• pp.539-553
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• 2004

Up to the present time, many methods to estimate emissions from a particular diesel engines have wholly depended on the quantity of diesel fuel consumed. Then, the recommended emission factors were normalized by fuel consumption, and further total activity was estimated by the total fuel consumed. One of main purposes in the study is newly to develop emission factors for the railroad diesel rolling stock (RDRS) and to estimate a total amount of major gaseous pollutants from the RDRS in Korea. Prior to develop a Korean mode emission factor. the emission factor from the USEPA was simply applied for comparative studies. When applying the USEPA emission factors, total exhaust emissions from the RDRS in Korea were estimated by 28,117tons of NOx, 2,832.3tons of CO, and 1,237.5tons of HC, etc in 2001. In this study, a emission factor for the RDRS, so called the KoRail mode (the Korean Railroad mode) has been developed on the basis of analyzing the driving pattern of the Gyeongbu-Line especially for the line-haul mode. Explicitly to make the site specific emission factors, many uncertainty problems concerning weighting factors for each power mode, limited emission test, incomplete data for RDRS, and other important input parameters were extensively examined. Total exhaust emissions by KoRail mode in Korea were estimated by 10,960tons of NOx, and 4,622tons of CO, and so on in the year of 2001. The emissions estimated by the USEPA mode were 2.6 times higher for NOx, and 1.6 times lower for CO than those by the KoRail mode. As a conclusion, based on the emission calculated from both the USEPA mode and the KoRail mode, the RDRS is considered as one of the significant mobile sources for major gaseous pollutants and thus management plans an(1 control strategies for the RDRS must be established to improve air quality near future in Korea.

• Journal of Astronomy and Space Sciences
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• v.25 no.4
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• pp.415-424
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• 2008

Kwak et al. (2008) found that the mean neutral wind pattern in the high-latitude lower thermosphere is dominated by rotational flow than by divergent flow. As an extension of the our previous work (Kwak et al. 2008), we performed a term analysis of vorticity equation that describes the driving forces for the rotational component of the horizontal wind in order to determine key processes that causes strong rotational flow in the high-latitude lower thermospheric winds. For this study the National Center for Atmospheric Research Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR-TIEGCM) is used. The primary forces that determine variations of the vorticity are the ion drag term and the horizontal advection term. Significant contributions, however, can be made by the stretching term. The effects of IMF on the vorticity forces are seen down to around 105-110km.

• The Korean Journal of Physiology and Pharmacology
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• v.7 no.2
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• pp.97-101
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• 2003

The salivary glands produce 1.5L of fluid per day. As in other exocrine organs, the general mechanism in the salivary glands is that water movement occurs secondary to osmotic driving forces created by active salt transport. Therefore, high water permeability in the salivary glands is expected to have a variety of aquaporin (AQP), a water channel. Although some AQPs have been known to be present in the salivary glands, roles of parasympathetic nerve in AQP expression have not yet been examined. This study was designed to examine the changes of AQPs and extracellular signal-regulated kinase (ERK) in the submandibular glands after parasympathetic denervation. Right chorda-lingual nerve was cut, and each right (experiment) and left (control) submandibular gland was excised at 1, 3, 7, 14, 30 days after denervation. The denervated right submandibular glands were resulted in weight loss and morphologic changes, including cell loss and atrophy, as the time elapsed after parasympathetic denervation increased, whereas there were no histologic alteration in control side. AQP5 which is known to reside in apical membrane and secretory caraliculi of the submandibular acini were gradually underexpressed according, as the time after denervation increased. Expression of AQP4 in submandibular ductal epithelium was down-regulated after denervation. Besides, AQP3 and 8, which is known to be present in basolateral membrane of the glandular acini, were gradually underexpressed after denervation, similar to the pattern of other types. Expression of ERK, a mitogen-activated protein kinase, was downregulated after parasympathetic denervation in the submandibular gland. These results suggest that parasympathetic nervous system regulates the expression of AQPs in salivary glands, and is in part mediated by ERK pathway.

• Journal of Digital Convergence
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• v.16 no.3
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• pp.157-167
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• 2018

The shortage of research in Vietnam port evolvement is uncontroversial although a huge amount of investment is observed to upgrade both quantity and quality. This study examines the port system performance, in the context of spatially concentration ratio, in Southern Vietnam for the period 2007-2016, by using prevailing indicators for spatially concentration assessment including concentration ratios (CR), the Herfindahl-Hirschman index (HHI), the Gini coefficient, the Lorenz curve and shift-share analysis (SSA), a trend of deconcentration is described in Southern Vietnam port system, since the traditional ports to new deep-water ports. Also, driving forces of this shifting would be discussed in detail. Implications from this study would enable not only port administrators, port operators but also shipping lines, cargo owners, logistics service providers to comprehensively understand the growth of the port system in Southern Vietnam.

• International Journal of Fluid Machinery and Systems
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• v.5 no.3
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• pp.134-142
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• 2012

The competition to deliver ultra-low emitting vehicles at a reasonable cost is driving the automotive industry to invest significant manpower and test laboratory resources in the design optimization of increasingly complex exhaust after-treatment systems. Optimization can no longer be based on traditional approaches, which are intensive in hardware use and laboratory testing. The CFD is in high demand for the analysis and design in order to reduce developing cost and time consuming in experiments. This paper describes the development of a comprehensive practical model based on experiments for simulating the performance of automotive three-way catalytic converters, which are employed to reduce engine exhaust emissions. An experiment is conducted to measure species concentrations before and after catalytic converter for different loads on engine. The model simulates the emission system behavior by using an exhaust system heat conservation and catalyst chemical kinetic sub-model. CFD simulation is used to study the performance of automotive catalytic converter. The substrate is modeled as a porous media in FLUENT and the standard k-e model is used for turbulence. The flow pattern is changed from axial to radial by changing the substrate model inside the catalytic converter and the flow distribution and the conversion efficiency of CO, HC and NOx are achieved first, and the predictions are in good agreement with the experimental measurements. It is found that the conversion from axial to radial flow makes the catalytic converter more efficient. These studies help to understand better the performance of the catalytic converter in order to optimize the converter design.