• Transactions of the Korean Society of Automotive Engineers
• /
• v.15 no.5
• /
• pp.86-96
• /
• 2007

A direct-injection stratified-charge(DISC) engine has been considered as a promising alternative in spite of high unburned hydrocarbon emission levels during light load operation. In this paper investigation is made to characterize formation and combustion processes of stratified mixture charge in a simple constant volume combustion chamber. Both experimental and numerical analyses are performed for fluid and combustion characteristics with 3 different induction types for rich, homogeneous and lean mixture conditions. The commercial code FIRE is applied to the turbulent combustion process in terms of measured and calculated pressure traces and calculated distributions of mean temperature, OH radical and reaction rate. It turns out that the highest combustion rate occurs for the rich state condition at the spark ignition location due to existence of stoichiometric mixture and timing.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.58 no.4
• /
• pp.563-567
• /
• 2009

The polymer electrolyte membrane fuel cell(PEMFC) with the advantages of low-operating temperature, high current density, low cost and volume, fast start-up ability, and suitability for discontinuous operation becomes the most reasonable and attractive power system for transportation vehicle and micro-grid power plant in a household. 200W PEM-type FCs system was integrated by this study, then the electrical characteristics and diagnosis of the fuel cell were analyzed with variations on mass flow rate and stack temperature. The ranges of the variations are 1~8L/min on $H_2$ volume and $20{\sim}70^{\circ}C$ on stack temperature.

• Proceedings of KOSOMES biannual meeting
• /
• 2001.05a
• /
• pp.105-133
• /
• 2001

World trade has been increasing continuously in total volume, on the other hand, environmental protection on sea and conservation of fishery resources has been rising up the major issue. All of the world are pushing their efforts two major purposes to the full, one is taking competitive place in marine transportation throughout the world and another Is environment protection. Pusan Port as world leading Port put its all effort in bring more ocean going vessels and securing their traffic route by providing them more information related marine traffics through PTMS in port. During two years of operation, statistics of marine traffic accidents showed that many dynamic casualties such as collisions, groundings, and rammings has been decreased. However, due to increasing cargo volume, limited water area and unpredictable weather condition, potential risks still exist high. In this paper, in order to maximize the efficiency of PTMS and reduce various risks in the future, we examine risk factors over operational results and experience, and propose reasonable operational methods of PTMS.

• Nuclear Engineering and Technology
• /
• v.29 no.1
• /
• pp.58-67
• /
• 1997

A numerical study has been peformed to investigate the flow and mixing characteristics of a chemical injection tank in the chemical and volume control system (CVCS) of Yonggwang 5&6 (YGN 5&6). This study was undertaken to provide a basis for modification of the previous design (YGN 3&4) which gave a lot of difficulties in installation and operation of the chemical injection system during the start-up test because it needs a special reciprocating pump with a high actual head. For the tank of length-to-diameter ratios (L/D) of 1,2 and 3, each with and without a baffle inside, calculation results were obtained by solving the unsteady laminar two-dimensional elliptic forms of governing equations for the mass, momentum and species concentration. Finite-difference method was used to obtain discretized equations, and the SIMPLER solution algorithm, which was developed based on the staggered grid control volume, was employed for the calculation procedure. Results showed that the baffle is very effective in enhancing the mixing in the tank and that a baffle should be installed near the tank entrance in order to 110 chemicals into the reactor coolant system (RCS) within the operating time required.

• Journal of Korean Society on Water Environment
• /
• v.18 no.4
• /
• pp.435-440
• /
• 2002

A pilot scale SBR (effective volume, $20m^3$) for the treatment of piggery wastewater treatment was performed with three different kinds of wastewater; fermenter effluent, scraper type and slurry type. The react phase in SBR was performed by sub-cycle operation consisting of repeated short cycle of anoxic-aerobic step. The fermenter effluent was characterized by the rapid nitrification and $NO_X-N$ accumulation due to depletion of organic matter in wastewater. The scraper type wastewater showed appropriate nitrogen removal efficiency, however, a poor response capacity for high loading rate often resulted in increased nitrogen concentration in effluent. Moreover, severe P release was the most serious problem in scraper type wastewater. SBR treated slurry type wastewater with high nitrogen removal efficiency to satisfy effluent quality requirement. It was thought that high concentration of organic matter in slurry made it possible to uptake P during SBR operation, where P concentration of 140mgP/l was decreased to 8mgP/l. As results, SBR was suitable to treat slurry type wastewater which has been discharged to the ocean till now.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.13 no.4
• /
• pp.138-147
• /
• 2010

As inaccurate traffic volume prediction may result in inadequate transportation planning and design, traffic volume prediction based on traffic volume data is very important in spatial decision making processes such as transportation planning and operation. In order to improve the accuracy of traffic volume prediction, recent studies are using the geostatistical approach called kriging and according to their reports, the method shows high predictability compared to conventional methods. Thus, this study estimated traffic volume data for St. Louis in the State of Missouri, USA using the kriging method, and tested its accuracy by comparing the estimates with actual measurements. In addition, we suggested a new method for enhancing the accuracy of prediction by the kriging method. In the new method, we estimated traffic volume data: first, by applying anisotropy, which is a characteristic of traffic volume data appearing in determining variogram factors; and second, by performing co-kriging analysis using interstate highway, which is in a high spatial correlation with traffic volume data, as a secondary variable. According to the results of the analysis, the analysis applying anisotropy showed higher accuracy than the kriging method, and co-kriging performed on the application of anisotropy produced the most accurate estimates.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.22 no.2
• /
• pp.155-163
• /
• 2000

Osteoporosis is the consequence of an imbalance between osteoclastic and osteoblastic activity, coupled with an increased rate of bone turnover observed with menopause. Estrogen is generally considered to maintain bone mass through suppression of bone resorption. The purpose of this study was to evaluate the rat femoral trabecular change not only in the deficiency of estrogen but also in the administration of estrogen following ovariectomy(OVX). 30 female Sprague-Dawley rats were subjected to bilateral OVX or sham surgery(control). Groups of OVX were divided into 4 groups. The first group was injected daily with vehicle alone for 20 days after 20 weeks following OVX. The additional groups of OVX was injected daily with low, medium, or high doses of $17{\beta}-estradiol$(10, 25 or $50{\mu}g/kg$ BW, respectively). All rats were sacrified 23 weeks after OVX, and their femur were processed for H&E, MT stain and histomorphometry. The results were as follows; 1. In the histomorphometric analysis, the trabecular bone volume/tissue volume, trabecular thickness and trabecular seperation were respectively $31.2{\pm}8.3%$, $54.3{\pm}4.8{\mu}m$ and $280.7{\pm}16.4{\mu}m$ in vehicle treated OVX group and $48.6{\pm}7.3%$, $90.4{\pm}4.5{\mu}m$ and $126.3{\pm}5{\mu}m$ in sham operation group, and they showed statistical significance compare to control group. 2. The trabecular bone volume/tissue volume, trabecular thickness and trabecular separation were respectively $44.4{\pm}4.3%$, $109.5{\pm}12.3{\mu}m$ and $94.9{\pm}8.5{\mu}m$ in low doses of $17{\beta}-estradiol$ injected group and they showed statistical significance compare to OVX group. 3. The trabecular bone volume/tissue volume, trabecular thickness and trabecular separation were respectively $44.4{\pm}4.3%$, $109.5{\pm}12.3{\mu}m$ and $94.9{\pm}8.5{\mu}m$ in medium doses of $17{\beta}-estradiol$ injected group and they showed statistical significance compare to OVX group, but they didn't show statistical significance compare to low doses of $17{\beta}-estradiol$ injected group. 4. The trabecular bone volume/tissue volume, trabecular thickness and trabecular separation were respectively $46.4{\pm}4.5%$, $154.4{\pm}13.2{\mu}m$ and $113.7{\pm}12.8{\mu}m$ in high doses of $17{\beta}-estradiol$ injected group and they also showed statistical significance compare to OVX group, but they didn't show statistical significance compare to other experimental groups. From the above results, metaphyseal bone formation was markedly reduced in OVX rate but treatment of OVX rats with $17{\beta}-estradiol$ resulted in normalization of femur trabecular bone volume. But they didn't show statistical significance the effect of bone formation according to the dose dependency.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.7 no.3
• /
• pp.163-170
• /
• 2002

This report describes the use of a transtubular bioreactor to study the relative effects of diffusion versus perfusion of medium on antibody production by a hybridoma cell line. The study was performed with a high-density cell culture maintained in a serum-free, low-protein medium for 77 days. It was determined that the reactor possessed a macro-mixing pattern residence time distribution similar to a continuous stirred tank reactor (CSTR), However, due to the arrangement of the medium lines in the reactor, the flow patterns for nutrient distribution consist of largely independent medium path lengths ranging from short to long. When operated with cyclic, reversing, transtubular medium flow, some regions of the reactor (with short residence times) are more accessible to medium than others (with long residence times). From this standpoint, the reactor can be divided into three regions: a captive volume, which consists of medium primarily delivered via diffusion; a lapped volume, which provides nutrients through unilateral convection; and a swept volume, which operates through bilateral convection. The relative sizes of these three volumes were modified experimentally by changing the period over which the direction of medium flow was reversed from 15 min (larger captive volume) to 9 h (larger swept volume). The results suggest that antibody concentration increases as the size of the diffusion-limited (captive) volume is increased to a maximum at around 30 min with a sharp decrease thereafter. As reflected by changes in measured consumption of glucose and production of lactate, no significant difference in cellular metabolism occurred as the reactor was moved between these different states. These results indicate that the mode of operation of the transtubular bioreactor may influence antibody productivity under serum-free, low-protein conditions with minimal effects on cellular metabolism.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.9 no.9
• /
• pp.3635-3654
• /
• 2015

With the rapid development of smart devices and mobile Internet, the video application plays an increasingly important role on mobile devices. Understanding user behavior patterns is critical for optimized operation of mobile live streaming systems. On the other hand, volume based billing models on cloud services make it easier for video service providers to scale their services as well as to reduce the waste from oversized service capacities. In this paper, the watching behaviors of a commercial mobile live streaming system are studied in a content-centric manner. Our analysis captures the intrinsic correlation existing between popularity and watching intensity of programs due to the synchronized watching behaviors with program schedule. The watching pattern is further used to estimate traffic volume generated by the program, which is useful on data volume capacity reservation and billing strategy selection in cloud services. The traffic range of programs is estimated based on a naive popularity prediction. In cross validation, the traffic ranges of around 94% of programs are successfully estimated. In high popularity programs (>20000 viewers), the overestimated traffic is less than 15% of real happened traffic when using upper bound to estimate program traffic.

• Journal of Korean Society of Water and Wastewater
• /
• v.14 no.2
• /
• pp.147-156
• /
• 2000

In this study, the optimal operation parameters of MLE(Modified Ludzack-Ettinger) process treating the liquid supernatant separated from the slurry excreta of swine feedlot was studied as a promising biological treatment process. The nitrogen removal characteristics with different volume ratio between nitrification and denitrification reactor and the operational effect with different nitrogen loading rate, and different C/N($COD_{Cr}/TKN$) ratio were investigated. Based on the laboratory results, pilot MLE plant was operated to examine the effect of ambient temperature for five months including winter. The denitrification reactor which is 20% of total volume was proposed as the most optimal volume fraction for nitrification and denitrification. The optimum ratios of F/M and $F_N/M$ were increased with increase of the C/N ratio. However, optimum F/M ratio was changed more rapidly than $F_N/M$ ratio with increase of the C/N ratio. Therefore, MLE process is desirable to be controlled by F/M ratio in the range of high C/N ratio and by $F_N/M$ ratio in the range of low C/N ratio. Pilot MLE plant showed the higher removal efficiencies of COD and TKN in winter than in summer and was operated most stably at the temperature of $20{\sim}25^{\circ}C$ for mixed liqour.