• Journal of Korean Society for Atmospheric Environment
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• v.9 no.E
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• pp.364-372
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• 1993

The purpose of this study is to analyze traffic patterns by use of TRANSYT-7F Model, and to choose the optimum traffic-light cycle length and cycle splite to improve traffic flow and air quality at Samsung Intersection in Seoul. Emission rates of air pollutants are calculated for three time segments 0700-0900, 0900-1800 and 1800-2000. The traffic volume correlated reasonably well with air pollutants emitted ; however, the phasing and timing of traffic signals was found to equally be important. The results of performance with optimal setting indicate that the best cycle length were 80sec(0700-0900), 95sec(0900-1800) and 90sec(1800-2000), res-pectively. As expected the highest emissions of air pollutants were observed during the evening rush hours (1800-2000). A properly designed signalized intersection can help reduce traffic delay, driver discomfort, fuel consumption, and air pollution by efficiently the capacity of existing intersection.

• Tribology and Lubricants
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• v.31 no.3
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• pp.79-85
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• 2015

RC delay is a critical issue for achieving high performance of ULSI devices. In order to minimize the RC delay time, we uses the CMP process to introduce high-conductivity Cu and low-k materials on the damascene. The low-k materials are generally soft and fragile, resulting in structure collapse during the conventional high-pressure CMP process. One troubleshooting method is electrochemical mechanical polishing (ECMP) which has the advantages of high removal rate, and low polishing pressure, resulting in a well-polished surface because of high removal rate, low polishing pressure, and well-polished surface, due to the electrochemical acceleration of the copper dissolution. This study analyzes an electrochemical state (active, passive, transpassive state) on a potentiodynamic curve using a three-electrode cell consisting of a working electrode (WE), counter electrode (CE), and reference electrode (RE) in a potentiostat to verify an electrochemical removal mechanism. This study also tries to find optimum conditions for ECMP through experimentation. Furthermore, during the low-pressure ECMP process, we investigate the effect of current density on surface roughness and removal rate through anodic oxidation, dissolution, and reaction with a chelating agent. In addition, according to the Faraday’s law, as the current density increases, the amount of oxidized and dissolved copper increases. Finally, we confirm that the surface roughness improves with polishing time, and the current decreases in this process.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.11 s.114
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• pp.1058-1064
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• 2006

In this paper, the channel capacity of a specified wireless indoor multiple-input multiple-output(MIMO) channel is estimated by analyzing spatial characteristics of this channel using the three-dimensional ray tracing method, and a technique for deriving an optimized separation of multi-antenna elements is proposed. At first, the ray paths, the path losses, and the time-delay profile are computed using the three-dimensional ray tracing method in an indoor corridor environment, which has the line of sight(LOS) and non-line of sight(NLOS) regions. The ray tracing method is verified by a comparison between the computation results and the measurements which are obtained with dipole antennas, an amplifier and a network analyzer. Then, an MIMO system is positioned in the indoor channel environment and the ray paths and path losses are computed for four antenna-position combinations and various values of the antenna separation to obtain the channel capacity for the MIMO system. An optimum antenna-separation is derived by averaging the channel capacities of 100 receiver positions with four different antenna combinations.

• Journal of Korean Society for Geospatial Information Science
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• v.5 no.2 s.10
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• pp.131-144
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• 1997

Traffic jam densified day by day is phenomenon to occur lack of the road capacity in comparison with traffic density, but lack of the road cannot be concluded by main cause of traffic ism. Because the central function of a city would be concentrated upon the downtown and traffic demand would not be evenly distributed by the classification of an hour. Therefore, this study based on the fact that each driver will select the route generating traffic delay very low when path choice from origin to destination in travel plan estimating the quality of passage could be maintained the speed he want will approach to a characteristic grasp of a road, traffic, driver changing every moment by traffic-demand of road increased as a geometrical series with analysis a classification of a street, a intersection along the path on traffic density and highway capacity analysis the path using GIS techniques about complex street network, also will get the path of actual optimum for traffic delay trend creating under various condition the classification per a hour, a day of week and an incident through network such as analysis for traffic generation zone adjacent about street, intersection, afterward will expect the result increasing efficiency of the road-use through a good distribution of traffic by optimum-path choice, accordingly will prepare the scientific, objective, appropriate basis to decide the reasonable time of a road-widen and expansion through section analysis along a rate of traffic volume vs. road capacity.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.1 no.1
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• pp.37-44
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• 1978

The purpose of this study is to search for an efficient application method in solving delay-phenomenon problems which influence upon total production cost through case study. The method of this study is an experimental study based on cutting time data in lead cutting operations from "Lead Cutting Machine (Stripper)" and its service rate data from a large electronic products company which utilizes conveyor line system for the products "Car Stereo" The procedure of this experimental study is as follows; 1) Using loading(Man-Hour) analysis technique j,1 order to analyse and evaluate Production capacity, efficiency, operation and idle rate assembly charge, waiting and service cost -when its are controlled by stripper operator(server) 2) Establishing adequate waiting time model of finite population caused by the interference of 4 stripper machine which is drawn from mathematical statistics testing, that is, goodness of fit test in the waiting and service rate and to search for optimal solution by utilizing the above mentioned model The experimental result was that amount to 8,546,618won Per year was brought down, that is, by optimum point, it shows a decrease as compared with Present point. The major limitation of this experimental study is that the Queue in the Finite Population, so to speak. it comes from the interference of 4 stripper machine dealt with this case were limited only on the Car Stereo conveyor line. Further study of application of this application method to the areas such as material handling, personnel management marketing and transportation management is strong1y recommended.trong1y recommended.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.83-87
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• 2009

The MAC protocol of HiperLAN/2 is based on TDMA/TDD. Mobile terminal acquires a data transmission opportunity as successfulness in channel competition through RCH (Random CHannel) phase. Therefore, AP (Access Point) be able to dynamically assign optimum RCH at next frame according to the number of success and collision. In this paper, we suggest scheme that fluctuate RCH (Random CHannel) number as fixed value considering success and collision for improvement of performance in HiperLAN/2. To prove efficiency of proposed scheme, a lots of simulations are conducted and analyzed in view of throughput and access delay.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.261-261
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• 2017

This study was carried out to provide basic data for spreading rice direct seeding by inducing stabilization of seedlings, yield and quality according to sowing times in rice direct seeding cultivation. In 2016, 'Sukwang' was seeded 3 times by 10 days interval on May. 10, 20, 30 and 6kg/10ha of seeding rate respectively in Iksan. In summary, the number of rice seedling establishment was higher than the optimum seedling establishment level at all sowing periods and the seeding rate was better as the sowing period was delayed. Weed development by sowing was the highest at early sowing, May 10, and decreased at late sowing. Heading dates were delayed by 3days for sowing on May 10, 7days for sowing on May 20, and 11 days on sowing on May 30. Rice yield increased with the delay sowing time and compared to the transplanting. It was 84% in sowing on May 10, 94% in sowing on May 20, and 99% in sowing on May 30. In addition, head rice ratio and head rice yield increased according to delayed of seedling.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.2
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• pp.101-107
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• 2016

Generally, the shipbuilding industry has finite resources and limited workspace. Due to finite resources, limited workspace and state of block preparation, erection process in shipbuilding industry is frequently delayed than erection process scheduling which is planned at long-term plan stage. In this study, considering variability of block reserve ratio, the degree of delay in real erection process is measured and compared to scheduling which is planned at long-term plan stage in shipbuilding industry including finite capacity and variative lead time. Also, the erection process scheduling which has minimum lead time can be checked through simulation. The results of this study could be improved the accuracy of erection process scheduling by checking the main event compliance ratio by block reserve ratio and calculating the optimum erection pitch for the main event compliance.

• Advances in concrete construction
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• v.11 no.3
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• pp.219-229
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• 2021

In recent years, geopolymer cements, have gained significant attention as an environmental-friendly type of cement. In this experimental research, effects of different alkaline activator solutions and variations of associated parameters, including time of addition, concentration, and weight ratio, on the mechanical strengths of Granulated Ground Blast Furnace Slag (GGBFS)-based Geopolymer Concrete (GPC) were investigated. Investigation of the effects of simultaneous usage of KOH and NaOH solutions on the tensile and flexural strengths of GGBFS-based GPC, and the influence of NaOH solution addition time delay on the mechanical strengths is among the novel aspects investigated in this research. four series of mix designs and corresponding specimen testing is conducted to study different parameters of the active alkali solutions on GPC mechanical strengths. The results showed that addition of NaOH to the mix after 3 min of mixing KOH and Na2SiO3 with dry components (1/3 of the total mixing duration) resulted in the highest compressive, tensile and flexural strengths amongst other cases. Moreover, increasing the KOH concentration up to 12 M resulted in the highest compressive strength, while weight ratio of 1.5 for Na2SiO3/KOH was the optimum value to achieve highest compressive strengths.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.25 no.4
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• pp.1-9
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• 1980

To determine the optimum harvest time of recent rice varieties from Indica/Japonica remote crosses, leading varieties Suweon 264 and Milyang 23 were tested for the changes in dry matter weight and moisture content of grain, shattering, shelling ratio, milling ratio, and apparant physical quality during grain development at 5 day-intervals from 20 days to 55 days after heading. The results are summarized as follows: 1. Grain weight (dry matter) reached its maximum (physiological maturity) at 30 days after flowering (DAF) in Suweon 264, and at 35 days in Milyang 23, and thereafter it did not change significantly until 55 DAF. 2. Time course of decrease in grain moisture content (Y, %) during maturation (X, DAF) consisted of two linear phases, i.e. a fast and a slow period: Y=68.245-1.33X until 34DAF, and Y=23.025-0.470X until 55DAF after 34DAF in Suweon 264; Y=73.62-1.634X until 24.5DAF, and Y=33.59-0.570X until 55DAF after 24.5DAF in Milyang 23. Two varieties showed the same grain moisture content of 28% (wet basis) at physiological maturity in spite of the distinct differences in the heading date, time of physiological maturity and thereby ripening climate. 3. Force to shatter a grain ranged about 90 to 100g in Milyang 23, and about 200 to 250g in Suweon 264 and in a Japonica variety, Jinheung. The force, however, did not change significantly with harvest time from 35DAF to 50DAF. 4. The changes in the ratios of shelling, milling, broken rice and tinted rice with harvest time were insignificant during a period from 35DAF to 55DAF. However, ratios of green rice and white belly rice decreased significantly with delay in harvest time during 10 days after physiological maturity. 5. The best time of harvest for maximum yield and good quality is thought to be 10 days after physiological maturity, and grain moisture content at this time was about 20% on wet basis.