• Journal of Energy Engineering
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• v.28 no.4
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• pp.1-7
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• 2019

In response to the recent increase in demand for hydrogen stations, the Ministry of Trade and Industry has enacted and promulgated special notifications to enable the installation of hydrogen stations in the form of the combined complex in existing automotive fuel supply facilities such as LPG, CNG, and gas stations. Hydrogen multi energy filling stations haven't been operated yet in Korea till the establishment of special standards, so it is necessary create special standards by considering all Korean environmental characteristics such as four seasons and daily crossings. In this study, we collected and analyzed the charging data of Ulsan LPG-Hydrogen Multi Fueling Station installed for the first time in Korea. The data are hourly temperature and pressure data from compressors, storage vessels and dispensers. We used the data collected for a year, including the highest temperature and the lowest temperature in Ulsan to compare seasonal characteristics. As a result, it was found that the change of the outside temperature affects the initial temperature of the vehicle's container of the hydrogen car, which finally affects the charging time and the charging speed of the vehicle. There was no effect on vehicle containers because the limit temperature suggested by the Korean Hydrogen Station Standard(KGS FP217) and the US Filling Protocol(SAE J2601) was not exceeded.

• Journal of KIISE:Computing Practices and Letters
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• v.7 no.5
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• pp.402-415
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• 2001

Advantages of flash memories are their shock resistance and fast read speed, which is much faster than that of a HDD. Because of these characteristics, they are increasingly used in the traditional household electric appliance and portable handset and therefore, development of file systems which use them as storage medium is increasingly needed. But they have two problems as storage medium. First, data stored in them cannot be overwritten: it must be erased before new data can be stored. Unfortunately, this erase operation usually takes about one second. Consequently, updating data in flash memories takes long time. In this paper, their problem is solved by using a data update mechanism like LFS(Log-structured File System). Second, their erase operations are restricted. We propose novel cleaning policy in order to increase the life cycle. We implemented FAT file system, which is suitable to small storage medium and solved problems, which usually happen in implementing FAT. We evaluated the performance of sequential writes and random writes on our implemented flash file system.

• Korean Chemical Engineering Research
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• v.53 no.2
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• pp.236-242
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• 2015

We present two data-driven modeling methods, partial least square (PLS) and artificial neural network (ANN), to predict the major operating and performance variables of a polymer electrolyte membrane (PEM) fuel cell stack. PLS and ANN models were constructed using the experimental data obtained from the testing of a 30 kW-class PEM fuel cell stack, and then were compared with each other in terms of their prediction and computational performances. To reduce the complexity of the models, we combined a variables importance on PLS projection (VIP) as a variable selection method into the modeling procedure in which the predictor variables are selected from a set of input operation variables. The modeling results showed that the ANN models outperformed the PLS models in predicting the average cell voltage and cathode outlet temperature of the fuel cell stack. However, the PLS models also offered satisfactory prediction performances although they can only capture linear correlations between the predictor and output variables. Depending on the degree of modeling accuracy and speed, both ANN and PLS models can be employed for performance predictions, offline and online optimizations, controls, and fault diagnoses in the field of PEM fuel cell designs and operations.

• The Journal of the Korea Contents Association
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• v.20 no.3
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• pp.298-308
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• 2020

This study was designed to verify reliability and feasibility by analyzing elderly drivers' ability test tools for older drivers aged 65 or older, which were improved in 2018 and are currently being conducted by the Korea Highway Traffic Authority. Only those aged 65 or older who voluntarily applied to the elderly driving ability evaluation system implemented by the Seoul branch of the Korea Highway Traffic Authority. The research was conducted for about 50 days until Aug. 31, 2018, starting with the registration and inspection of the first study subjects. The analysis performed a correlation analysis with existing tools and cognitive testing tools (MMSE_K) to determine their feasibility and reliability as an improved tool in 2018. As a result, the first, the speed distance, time-space memory, and dispersionism of each sub-component of the old version showed statistically significant static correlation with the sub-factor of the current version. Persistence, on the other hand, was not statistically significant to the current version. The limitations of this study were as follows. Most of the people in the study were highly educated and residents in the metropolitan area. Therefore, it is likely that the results of MSE_K, which checks cognitive and judgment skills, have been upgraded. Also, cognitive tools that are measured by computers are likely to have real measurement errors for generations who are not familiar with computers. Therefore, it is expected that improvement and development of tools for improving the limit points at the site and assessing actual operation capability will be required.

• Journal of the Korean Society for Railway
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• v.20 no.2
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• pp.234-240
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• 2017

In this study, the influences of rail surface roughness on dynamic wheel-rail forces currently employed in conventional lines were assessed by performing field measurements according to grinding of rail surface roughness. The influence of the grinding effect was evaluated using a previous empirical prediction model for dynamic wheel-rail forces; model includes first-order derivatives of QI (Quality Index) and vehicle velocity. The theoretical dynamic wheel-rail force determined using the previous prediction equation was analyzed using the QI, which decreased due to rail grinding as determined through field measurements. At a constant track support stiffness, an increase in the QI caused an increase in dynamic wheel-rail forces. Further, it can be inferred that the results of dynamic wheel-rail analysis obtained using the measured data, such as the variation of QI due to rail grinding, can be used to predict the peak dynamic forces. Therefore, it is obvious that the optimum amount of rail grinding can be determined by considering the QI, that was regarding an operation characteristics of the target track (vehicle velocity and wheel load).

• Korean Journal of Agricultural Science
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• v.39 no.2
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• pp.271-277
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• 2012

Dimensions, operation conditions and improvement items for round roof windows were investigated in arch shape single-span plastic greenhouse with roof vents, and natural ventilation performance was analyzed based on the ventilation theory. Diameter of round roof windows was mostly 60 cm, and chimney height projected on roof was average 30 cm. Installation space was mostly 5 to 6 m but farmhouse of 10 m and over was 16.7% also. A round roof window which has 60 cm diameter was installed to 6 m space generally and 80 cm diameter was installed to 10 m space, but correct standards did not exist. There were a lot of opinions that ventilation effect of round roof windows is fairly good and user satisfaction is generally excellent. It is problem that there is few effects in summer and that vinyl around each vent tears well and rainwater leaks, and improvement hope item required development of automatic control system. In the wind speed of 0.3 m/s, it was estimated that natural ventilation rates were 0.69, 0.55, 0.50 and 0.48 volumes per minute in case of 2, 4, 6 and 8 m installation space for round roof windows, respectively. It was analyzed that the ratio of ventilation due to buoyancy out of total ventilation were 65.2, 41.9, 29.9 and 22.8% in case of 2, 4, 6 and 8m installation space, respectively. By the round roof windows installed at space of 6 m, ventilation rate was estimated to 0.5 volumes per minute, and we can expect the increase in ventilation rate of 30%. In order to meet the recommended ventilation rate for summer season, we have to install the round roof windows at space of 1 to 2 m. However, it is difficult to apply those installation space because of falling productivity due to lower light transmittance as well as rising costs. It is estimated that the installation space of 6m is appropriate for spring or fall season. Therefore it is necessary to encourage installing the roof windows in single-span plastic greenhouses.

• Journal of the Korea Society of Computer and Information
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• v.5 no.2
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• pp.30-36
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• 2000

The hidden node plays a role of the functional units that classifies the features of input pattern in the given question. Therefore, a neural network that consists of the number of a suitable optimum hidden node has be on the rise as a factor that has an important effect upon a result. However there is a problem that decides the number of hidden nodes based on back-propagation learning algorithm. If the number of hidden nodes is designated very small perfect learning is not done because the input pattern given cannot be classified enough. On the other hand, if designated a lot, overfitting occurs due to the unnecessary execution of operation and extravagance of memory point. So, the recognition rate is been law and the generality is fallen. Therefore, this paper suggests a method that decides the number of neural network node with feature information consisted of the parameter of learning algorithm. It excludes a node in the Pruning target, that has a maximum value among the feature value obtained and compares the average of the rest of hidden node feature value with the feature value of each hidden node, and then would like to improve the learning speed of neural network deciding the optimum structure of the multi-layer neural network as pruning the hidden node that has the feature value smaller than the average.

• Journal of Wetlands Research
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• v.22 no.4
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• pp.312-320
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• 2020

Various LIDs with natural water circulation function are applied to reduce urban environmental problems and environmental impact of development projects. However, excessive Infiltration and evaporation of LID facilities dry the LID internal soil, thus reducing plant and microbial activity and reducing environmental re duction ability. The purpose of this study was to develop a real-time measurement system with complex sensors to derive the management plan of LID facilities. The test of measurable sensors and Internet of Things (IoT) application was conducted in artificial wetlands shaped in acrylic boxes. The applied sensors were intended to be built at a low cost considering the distributed LID and were based on Arduino and Raspberry Pi, which are relatively inexpensive and commercialized. In addition, the goal was to develop complex sensor measurements to analyze the current state o f LID facilities and the effects of maintenance and abnormal weather conditions. Sensors are required to measure wind direction, wind speed, rainfall, carbon dioxide, Micro-dust, temperature and humidity, acidity, and location information in real time. Data collection devices, storage server programs, and operation programs for PC and mobile devices were developed to collect, transmit and check the results of measured data from applied sensors. The measurements obtained through each sensor are passed through the Wifi module to the management server and stored on the database server in real time. Analysis of the four-month measurement result values conducted in this study confirmed the stability and applicability of ICT technology application to LID facilities. Real-time measured values are found to be able to utilize big data to evaluate the functions of LID facilities and derive maintenance measures.

• Korean Journal of Medicinal Crop Science
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• v.5 no.4
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• pp.284-288
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• 1997

In order to study on suitable harvest time of adlay utilizing self-feeding combine harvester with four rows, which is originally designed for rice harvest, harvesting were carried out at four different times (40, 50, 60 and 70 days after anthesis) . For efficient operation, appropriate working rows were 2 rows at 50 days after anthesis and working speed was 0.26m/sec at 60 days after anthesis. Theoretical working capability was 11.23a/hr at 60 days after anthesis. As the harvesting was delayed, water content of adlay decreased. Water content of culm+leaf was $69.7{\sim}55.3%$ and water content of grain was 34.2% at 60 days after anthesis. The later adlay was harvested. the higher the percent of ripened grain was. But the immature grain was decreased. Remnants was less than 1.8% at 60 days after anthesis. The later adlay was harvested, the heavier volume weight was. Yield was the highest at 60 days after anthesis. When utilizing self-feeding combine harvester with four rows, which was originally designed for rice harvest, suitable harvesting time was 60 days after anthesis. Therefore, theoretically suitable harvest time was 68 days after anthesis.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.7
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• pp.726-731
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• 2005

Sedimentation is treated as the most important unit process in waterworks, and plays great role on turbidity removal efficiency. Rectangle sedimentation basin is the most widely accepted sedimentation process. But it has some problems with short-circuit flow and density flow caused by temperature and influent turbidity variation. To solve these problems, installation of rectification wall was suggested, but not generally fully accepted in field. Because hole of rectification wall cause jet flow. In this research, use of moving baffle was investigated. Moving baffle was designed to induce uniform velocity at every section of water flow. The baffle walls was made from soft fiber materials. The baffle walls with flow of sedimentation basin moves at same speed. It is like that it controls density flow and short-circuit flow and induce uniform velocity at every section of water flow in sedimentation basin. When moving baffle was operated retention time of sedimentation basin was extended to 1 hours. When it talked again and the effluent time of highest concentration of the chlorine ion from 100 minutes was extended to 160 minutes. Turbidity removal efficiency was tested with different operation modes(continuous and batch) with influent turbidity and retention time. It was revealed that turbidity removal efficiency carl be improved up to 36%(continuous mode) and 58%(batch mode) respectively. Consequently if moving baffle introduces in Rectangle sedimentation basin, it forecasts that the turbidity improvement above 30% will be possible.