• The Journal of the Korea Contents Association
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• v.21 no.12
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• pp.190-201
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• 2021

The variable message sign (VMS) is equipment to improve the efficiency of traffic flow and safety of travel by providing real-time information to road users on traffic, road, weather situation, and traffic control due to construction. The information messages of the letter-based VMS taking up most of the VMS on the general national highways consist of section, travel time in sections, and road control situation. This study devised an improvement plan centered on road users, not road managers-centered existing message-based VMS through an analysis of road users' preference targeting the letter-based VMS operated in the general national highways in the Seoul Metropolitan Area. By presenting the measure for system improvement through which information on unexpected situations that road users prefer the most can be quickly and efficiently provided, this study aims to improve the efficiency of road user-centered VMS traffic information.

• The Journal of the Acoustical Society of Korea
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• v.42 no.3
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• pp.233-242
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• 2023

In this paper, the effect of mass injection on the control of tip vortex cavitation was studied experimentally. A mass injection system for a 3D hydrofoil was designed to control the location of injection as well as the injection rate. A series of cavitation tests were carried out in a cavitation tunnel for different injection locations and rates. The cavitation behaviour was observed using a high-speed camera and the corresponding noise was measured using a hydrophone installed in the observation window. The results showed that the tip vortex cavitation was suppressed under certain conditions and the noise was reduced in some frequency bands. It was also found that there is a location where the effect of mass injection could be maximized and hence the noise reduction.

• Transactions of the Korean hydrogen and new energy society
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• v.35 no.3
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• pp.280-289
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• 2024

In this study, a cryogenic vessel was constructed to maintain and control the safe pressure of liquid hydrogen boil-off gas (BOG), and the numerical analysis was conducted on the development of computational fluid dynamics model inside the high-pressure vessel. An evaluation system was constructed using cryogenic inner and outer containers, pre-cooler, upper flange, and internal high-pressure container. We attempted to analyze the performance of the safety valve by injecting relatively high temperature hydrogen gas to generate BOG gas and quickly control the pressure of the high-pressure vessel up to 10 bar. As a results, the liquid volume fraction decreased with a rapid evaporation, and the pressure distribution increased monotonically inside a high pressure vessel. Additionally, it was found that the time to reach 10 bar was greatly affected by the filling rate of liquid hydrogen.

• Journal of Bio-Environment Control
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• v.20 no.3
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• pp.189-196
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• 2011

The objective of this study was to investigate the effects of light intensity and electrical conductivity (EC) of nutrient solution during short day treatment in an ebb and flow systems on the growth and nutrient uptake of potted Kalanchoe blossfeldiana 'Rako' and the nutrient accumulation of growing medium. Nutrient concentrations in the growing medium were also analyzed to investigate the accumulation rates of macro-nutrients such as T-N, P, K, Ca, and Mg, respectively. To achieve the objectives, plants were fed with a nutrient solution with 1.2, 1.8, or $2.4dS{\cdot}m^{-1}$ under three daily photosynthetic photon flux (PPF) of 4.26, 5.51, or $9.75mol{\cdot}m^{-2}{\cdot}d^{-1}$. Both light intensity and EC of nutrient solution significantly influenced the crop growth. The elevation of PPFs resulted in the increase of plant growth. For each light condition, plant growth, such as dry and fresh weight and leaf area, was the highest when the electrical conductivity of nutrient solution was controlled to $2.4dS{\cdot}m^{-1}$. However, growth was acceptable in the EC ranges from 1.8 to $2.4dS{\cdot}m^{-1}$. Both light intensity and EC of nutrient solution significantly influenced the uptake of nutrients in the solution tanks and the accumulation of nutrients in the growing medium. As the EC of nutrient solution was elevated, the absorption rates of $NO_3^-$, $PO_4^{-3}$, $K^+$, and $Mg^{2+}$ by crops and accumulation of those in growing medium increased, but the light intensity did not significantly influence the absorption rates. Based on the above results, the regression models were suggested for anticipating the macro-nutrient accumulations in growing medium.

• Journal of Korean Society of Transportation
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• v.27 no.2
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• pp.199-206
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• 2009

In relation with economical efficiency analysis on investment evaluation of transportation system, among vehicle operating cost saving benefit that is applied to general preliminary assessment guidelines and investment evaluation guidelines, oil expense calculated data which concentrated and analyze on the relationship between oil consumption amount on running state and running speed. For uninterrupted flow which does not have stopped delay due to traffic signal, consideration for reduction benefit is possible due to the changes of running speed and travel time however, for interrupted flow which the stopping occurs due to signal control on actual signal intersection has no consideration for stopping delay time reduction and stopping rate improvement thus reflection of reality on improved effect analysis is difficult. Therefore, this research makes a framework to analyze benefits that reflects the features of signalized intersections by benefits associated with decrease of stopping delay time with existing research and developing vehicle operating cost calculation model formula. Vehicle operating cost has been redefined considering the stopping delay time by applying the oil consumption amount at idling and the economical benefit between conventional model and newly developed model when applied for the optimization of traffic signal system on the two roads in Seosan city has been analyzed comparative. While the importance of traffic system maintenance is being emphasized due to the increase of congested areas on roads, it is expected to assist in more realistic economical analysis which reflect the delay improvement through the presentation of an economic analysis model that considers the features of signalized intersections in signal optimization system improvements and effect analysis of congestion improvement projects`.

• Nuclear Engineering and Technology
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• v.14 no.4
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• pp.186-195
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• 1982

The steam line break accident for Kori Unit 1 is analyzed by a code SYSRAN which calculates nuclear power and heat flux using the point kinetics equation and the lumped-parameter model and calculates system transient using the mass and energy balance equation with the assumption of uniform reactor coolant system pressure. The 1.4 f $t^2$ steam line break accident is analyzed at EOL (End of Life), hot shutdown condition in which case the accident would be most severe. The steam discharge rate is assumed to follow the Moody critical flow model. The results reveal the peak heat flux of 38% of nominal full power value at 60 second after the accident initiates, which is higher than the FSAR result of 26%. Trends for the transient are in good agreement with FSAR results. A sensitivity study shows that this accident is most sensitive to the moderator density coefficient and the lower plenum mixing factor. The DNBR calculation under the assumption of $F_{{\Delta}H}$=3.66, which is used in the FSAR with all the control and the shutdown assemblies inserted except one B bank assembly and of Fz=1.55 shows that minimum DNBR reaches 1.62 at 60 second, indicating that the fuel failure is not anticipated to occur. The point kinetics equation, the lumped-parameter model and the system transient model which uses the mass and energy balance equation are verified to be effective to follow the system transient phenomena of the nuclear power plants.lear power plants.

• Korean Journal of Remote Sensing
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• v.37 no.3
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• pp.395-408
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• 2021

In this study, we investigated the effects of wind speed and direction on building fires using GIS and a CFD model. We conducted numerical simulations for a fire event that occurred at an apartment in Ulsan on October 8, 2020. For realistic simulations, we used the profiles of wind speeds and directions and temperatures predicted by the local data assimilation and prediction system (LDAPS). First, using the realistic boundary conditions, we conducted two numerical simulations (a control run, CNTL, considered the building fire and the other assumed the same conditions as CNTL except for the building fire). Then, we conducted the additional four simulations with the same conditions as CNTL except for the inflow wind speeds and direction. When the ignition point was located on the windward of the building, strong updraft induced by the fire had a wide impact on the building roof and downwind region. The evacuation floor (15th floor) played a role to spread fire to the downwind wall of the building. The weaker the wind speed, the narrower fire spread around the ignition point, but the higher the flame above the building reaches. When the ignition point was located on the downwind wall of the building, the flame didn't spread to the upwind wall of the building. The results showed that wind speed and direction were important for the flow and temperature (or flame) distribution around a firing building.

• Journal of Bio-Environment Control
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• v.20 no.1
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• pp.1-7
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• 2011

The objective of the present study is to identify the applicability of a low pressure fogging system for cooling commercial tomato greenhouse. In particular, the cooling system in this experiment utilizes low pressure spray nozzles which were developed in Korea recently. The experimental result that the temperature in fog-cooled greenhouse was lower than the non-cooled greenhouse showed the cooling effect by the low pressure fogging system. But because the relative humidity in fog-cooled greenhouse was comparatively low, the satisfactory cooling effect could be acquired by narrowing the space of fog nozzles and extending fogging time to supply more fog spray quantity. The variation of temperature distribution in fog-cooled greenhouse along timelag was insignificant during short time, but that was great during long period of day. This result showed the variation of temperature along timelag was slight by fog cooling but great by other factors like radiation, ventilation, air flow, etc. The advanced operation technology of fog system was required to reduce the variation of temperature along time lag. We plan to suggest the advanced installation and operation technology of low pressure fogging system for cooling commercial tomato greenhouse by further experiments in near future.

• Journal of the Korean Society for Library and Information Science
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• v.23
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• pp.207-261
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• 1992

The purpose of this study is (1) to design and test a database which can be automatically classified, and (2) to generate automatic classification number by processing the keywords in titles using the code combination method of Colon Classification(CC) as well as an automatic recognition of subjects in order to develop an automatic classification system (Auto BC System) based on CC which can be applied to any research library. To conduct this study, 1,510 words in the fields of agricultrue and medicine were selected, analized in terms of [P], [M], [E], [S], [T] employed in CC, and included in a database for classification. For the above-mentioned subject fields, the principle of an automatic classification was specified in order to generate automatic classification codes as well as to perform an automatic subject recognition of the titles included. Whenever necessary, editing, deleting, appending and reindexing of a database can be made in this automatic classification system. Appendix 1 shows the result of the automatic classification of books in the fields of agriculture and medicine. The results of the study are summarized below. 1. The classification number for the title of a book can be automatically generated by using the facet principles of Colon Classification. 2. The automatic subject recognition of a book is achieved by designing a database making use of a globe-principle, and by specifying the subject field for each word. 3. The automatic subject-recognition of input data is achieved by measuring the number of searched words by each subject field. 4. The combination of classification numbers is achieved by flowcharting of classification formular of each subject field. 5. The efficient control of classification numbers is achieved by designing control codes on the database for classification. 6. The automatic classification by means of Auto BC has been proved to be successful in the research library concentrating on a Single field. The general library may have some problem in employing this system. The automatic classification through Auto BC has the following advantages: 1. Speed of the classification process can be improve. 2. The revision or updating of classification schemes can be facilitated. 3. Multiple concepts can be expressed in a single classification code. 4. The consistency of classification can be achieved with the classification formular rather than the classifier's subjective judgement. 5. A user's retrieving process can be made after combining the classification numbers through keywords relating to the material to be searched. 6. The materials can be classified by a librarian without subject backgrounds. 7. The large body of materials can be quickly classified by means of a machine processing. 8. This automatic classification is expected to make a good contribution to design of the total system for library operations. 9. The information flow among libraries can be promoted owing to the use of the same program for the automatic classification.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.12
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• pp.844-861
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• 2008

The papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during the year of 2007 have been reviewed. Focus has been put on current status of research in the aspect of heating, cooling, ventilation, sanitation and building environments. The conclusions are as follows. (1) The research trends of fluid engineering have been surveyed as groups of general fluid flow, fluid machinery and piping, etc. New research topics include micro nano fluid, micropump and fuel cell. Traditional CFD was still popular and widely used in research and development. Studies about fans and pumps were performed in the field of fluid machinery. Characteristics of flow and fin shape optimization are studied in the field of piping system. (2) The research works on heat transfer have been reviewed in the field of heat transfer characteristics, heat exchangers, and desiccant cooling systems. The research on heat transfer characteristics includes thermal transport in pulse tubes, high temperature superconductors, ground heat exchangers, fuel cell stacks and ice slurry systems. For the heat 'exchangers, the research on pin-tube heat exchanger, plate heat exchanger, condensers and gas coolers has been cordially implemented. The research works on heat transfer augmenting tubes have been also reported. For the desiccant cooling systems, the studies on the design and operating conditions for desiccant rotors as well as performance index are noticeable. (3) In the field of refrigeration, many papers were presented on the air conditioning system using CO2 as a refrigerant. The issues on the two-stage compression, the oil selection, and the appropriate oil charge were treated. The subjects of alternative refrigerants were also studied steadily. Hydrocarbons, DME and their mixtures were considered and various heat transfer correlations were proposed. (4) Research papers have been reviewed in the field of building facilities by grouping into the researches on heat and cold sources, air conditioning and air cleaning, ventilation and fire research including tunnel ventilation, flow control of piping system, and sound research with drain system. Main focuses have been addressed to the promotion of efficient or effective use of energy, which helps to save energy and results in reduced environmental pollution and operating cost. (5) Studies were mostly focused on analyzing the indoor environment in various spaces like cars, old tombs, machine rooms, and etc. in an architectural environmental field. Moreover, subjects of various fields such as the evaluation of noise, thermal environment, indoor air quality and development of energy analysis program were researched by various methods of survey, simulation, and field experiment.