• Journal of Korean Society of Environmental Engineers
• /
• v.28 no.8
• /
• pp.878-883
• /
• 2006

Removal efficiency of As(III) was investigated with a pilot-scale filtration system packed with an equal amount(each 21.5 kg) of manganese-coated sand(MCS) in the bottom and iron-coated sand(ICS) in the top. Height and diameter of the used column was 200 cm and 15 cm, respectively. The As(III) solution was introduced into the bottom of the filtration system with a peristaltic pump at a speed of $5{\times}10^{-3}$ cm/s over 148 days. Breakthrough of total arsenic in the mid-sampling position(end of the MCS bed) and final-sampling position(end of the ICS bed) was started after 18 and 44 days, respectively, and then showed a complete breakthrough after 148 days. Although the breakthrough of total arsenic in the mid-sampling position was started after 18 days, the concentration of As(III) in this effluent was below 50 ppb up to 61 days. This result indicates that MCS has a sufficient oxidizing capacity to As(III) and can oxidize 92 mg of As(III) with 1 kg of MCS up to 61 days. When a complete breakthrough of total arsenic occurred, the removed total arsenic by MCS was calculated as 79.0 mg with 1 kg MCS. As variation of head loss is small at each sampling position over the entire reaction time, it was possible to operate the filtration system with ICS and MCS for a long time without a significant head loss.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.3
• /
• pp.405-415
• /
• 2000

Experiments for autotrophic denitrification were performed using an upf10w reac1.or packed with sulfur particles as an electron donor. The influent $NO_3{^-}$-N concentration was kept almost constant, but the hydraulic retention time(HRT) and temperature varied. Results of the research showed that the denitrification efficiency and gas generation rate decreased as the HRT and temperature were reduced. During the HRT effect experiment, alkalinities of 3.44~5.71g, with an average of 4.67 g which is close to the theoretical value of 4.57g were consumed for each gram of $NO_3{^-}$-N removed. During the temperature effect experiment, however, the values were 6.58~13.41 g with an average of 9.12 g which is almost twice the theoretical value Denitrification along the length of the reactor appeared to be a first-order reaction with a reaction rate constant of 0.1648/hr. On the other hand, the sulfate generation showed a zero-order reaction with a reaction rate constant of 241/hr. There was some discrepancy in the nitrogen mass balance between the theoretical and measured values, requiring further researches.

• Journal of Korean Society of Environmental Engineers
• /
• v.28 no.7
• /
• pp.752-756
• /
• 2006

The independent anoxic reactor was introduced in biological aerated filters as the regulation of water quality requirement, especially total nitrogen, had been strengthened. The process studied in this work was upflow $Biobead^{(R)}$ process which was used commercial invented for removal of organic materials and nitrification. For the purpose of evaluating the independent anoxic reactor, PCR-DGGE, of the molecular biological methods, was performed. Two types of nitrite reductase genes were selected. One is nirS represented cytocrome $cd_1$ nitrite reductase gene and the other is nirK represented Cu-containing nitrite reductase gene. Denitrifier community in the independent anoxic reactor was analyzed with PCR-DGGE using these two denitrifying functional genes. As the result of the PCR, only nirS gene was detected between nirS and nirK. With the result of the DGGE, specific bands became strong, as the operating days were longer, nitrate loading rate was increased. otherwise those of the initial activated sludge showed various bands. In the consequence of the sequence of DGGE bands, various denitrifiers were sequenced in the initial activated sludge, while specific denitrifiers like alcaligenes faecalis were predominant in the anoxic reactor. Consequently, introduction of the independent anoxic reactor made it possible to achieve 96% denitrification efficiency, and was proper for the modification of BAF process.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.19 no.5
• /
• pp.40-51
• /
• 2020

Much time has passed since Korea's expressway congestion-threshold speed was revised in 2011. In the meantime, various expressway environments have changed owing to improved performance of vehicles, expanded operations of transport competition (i.e., the KTX), and increased speed limits along some expressway sections. In addition, the speed that expressway users expect to travel at is also increasing. Therefore, through a survey, this study investigates expressway users' perceptions of congestion, and reviews the adjustment of the expressway speed congestion threshold by analyzing expressway traffic flow. One result of the survey confirms that the threshold speed expressway users consider to be congestion has slightly increased. Analyzing traffic and speed data through a K-means algorithm found that the threshold speed for congestion is 60 km/h. In addition, assuming the congestion threshold speed increase from 40 km/h to 50 km/h and 60 km/h, frequently congested expressway sections are identified, determining that 50 km/h is appropriate as a congestion threshold for proper expressway mobility management.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.9
• /
• pp.200-207
• /
• 2014

Arrhythmia electrocardiogram signal contains a specific unusual heartbeat with abnormal morphology. Because unusual heartbeat is useful for diagnosis and classification of various diseases, such as arrhythmia, detection of unusual heartbeat from the arrhythmic ECG signal is very important. Amplitude and kurtosis at R-peak point and RR interval are characteristics of ECG signal on R-wave. In this paper, we provide a method for detecting unusual heartbeat based on these. Through the value of the attribute deviates more from the average value if unusual heartbeat is more certainly, the proposed method detects unusual heartbeat in order using the mean and standard deviation. From 15 ECG signals of MIT-BIH arrhythmia database which has R-wave distortion, we compare the result of conventional method which uses the fixed threshold value and the result of proposed method. Throughout the experiment, the sensitivity is significantly increased to 97% from 50% using the proposed method.

• Fire Science and Engineering
• /
• v.24 no.5
• /
• pp.79-86
• /
• 2010

In this study, we confirmed the fact that air egress velocity of pressure differential system which is installed in vestibule of smokeproof stairway in domestic high-rise building becomes back-flow into the vestibule not into the livingroom when the doors open to escape in case of fire by actual measurement. It concerned that fire smoke inflow into the vestibule of smokeproof stairway. so, reflux symptoms were developing the condition does not occur by creating an area of $2m^2$ and a model. if it‘s area is less, airflow in upper area was severely reflux. in the case upward 45 gradient of supply damper’s angle of blade, The results that reflux symptoms include upper door but bottom has some reflux. also vestibule of smokeproof stairway‘s area of $4m^2$ in the living room door in the direction of the flow distributon was normal. if a vestibule of smokeproof stairway is smaller, it designed to be performance-based design should be.

• Journal of Korean Society of Transportation
• /
• v.25 no.1 s.94
• /
• pp.73-79
• /
• 2007

This study deals with traffic accidents at the ramps of trumpet interchanges. The purpose of the study is to analyze the relations between tke turning direction of ramps (and combinations with other factors) and traffic accidents. In Pursuing this analysis, this study gives particular attention to the combination of turning direction and grade and the combination of turning direction and radius of curvature in the case of the trumpet interchange ramps. The null hypothesis tests show that the average accident number and average accident rate ate rejected at the 90% and 95% significance level respectively Also. the null hypothesis tests show that the combinations or turning direction and Evade as well as turning direction and radius are all rejected at the 95% significance level. In summary, right turn movements ate more dangerous than left turns on the trumpet interchange vamps. Also, ramps with a right turn and up grade or with a left turn and radius more than 200m have more traffic accident Potential than other types of ramps.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.38 no.11
• /
• pp.1123-1129
• /
• 2010

Angular Deviation(AD) on transparency applied to TA-50 Aircraft deteriorates armament system's accuracy because it makes a difference in between actual and theoretical targets. In order to increase accuracy, therefore, TA-50 Aircraft measures AD on transparency and provide the measured values for the integrated mission display computer as a type of AD coefficients. This makes AD revised so that pilots can accurately see the actual target on their head-up display. In order to implement such mechanism into a real field, we develop a new device and system automatically measuring AD for the first time. We also deal with basic concept including AD induction formula as well as operating systems. As a consequence of testing the accuracy and precision for verifying reliability of the system, we got satisfactory results. In specific, the accuracy was within the resultant criterion of 1%. The precision was also satisfied with respect to the whole criteria. The system developed through this research is qualified as a military standard equipment for transparency of the canopy.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.42 no.4
• /
• pp.703-715
• /
• 2017

In this paper, we analyze the channel characteristics of the long distance air-ground wideband common data link and we propose a mathematical method to analyze the effect of narrowband and wideband interference of air-ground channel on the received signal of wideband data link. In this paper, we analyze the reception performance according to the communication distance using the proposed performance analysis method, and found out that the communication distance is limited by the narrowband and wideband interference of ground reflection wave. As a result of the performance analysis of the method of controlling the receiving antenna upward, not only the narrow band but also the wideband interference is effectively reduced, so that the communication distance is increased even in the existing wideband data link not including the equalizer.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.40 no.7
• /
• pp.457-470
• /
• 2016

Most CFD codes, that mainly adopt the heat partitioning model as the wall boiling model, have shown low accuracies in predicting the two-phase flow parameters of subcooled boiling phenomena under low pressure conditions. In this study, a number of subcooled boiling experiments in vertical channels were analyzed using a thermal-hydraulic component code, CUPID. The prediction of the void fraction distribution using the CUPID code agreed well with experimental data at high-pressure conditions; whereas at low-pressure conditions, the predicted void fraction deviated considerably from measured ones. Sensitivity tests were performed on the submodels for major parameters in the heat partitioning model to find the optimized sets of empirical correlations suitable for low-pressure subcooled flow boiling. The effect of the K-factor on the void fraction distribution was also evaluated.