• Korean Journal of Agricultural Science
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• v.38 no.4
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• pp.747-752
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• 2011

Wireless technology has enabled farmers monitor and control protected production environment more efficiently. Utilization of USN (Ubiquitous Sensor Network) devices also brought benefits due to reduced wiring and central data handling requirements. However, wireless communication loses signal under unfavorable conditions (e.g., blocked signal path, low signal intensity). In this paper, performance of commercial wireless communication devices were evaluated for application to protected crop production. Two different models of wireless communication devices were tested. Sensors used in the study were weather units installed outside and top of a greenhouse (wind velocity and direction, precipitation, temperature and humidity), inside ambient condition units (temperature, humidity, $CO_2$, and light intensity), and irrigation status units (irrigation flow and pressure, and soil water content). Performance of wireless communication was evaluated with and without crop. For a 2.4 GHz device, communication distance was decreased by about 10% when crops were present between the transmitting and receiving antennas installed on the ground, and the best performance was obtained when the antennas were installed 2 m above the crop canopy. When tested in a greenhouse, center of a greenhouse was chosen as the location of receiving antenna. The results would provide information useful for implementation of wireless environment monitoring system for protected crop production using USN devices.

• Journal of Semiconductor Engineering
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• v.1 no.1
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• pp.1-12
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• 2020

Handling precise timing in high-speed transceivers has always been a primary design target to achieve better performance. Many different approaches have been tried, and one of those is utilizing the beneficial nature of injection locking. Though the phenomenon was not intended for building integrated circuits at first, its coupling effect between neighboring oscillators has been utilized deliberately. Consequently, the dynamics of the injection-locked oscillator (ILO) have been explored, starting from R. Adler. As many aspects of the ILO were revealed, further studies followed to utilize the technique in practice, suggesting alternatives to the conventional frequency syntheses, which tend to be complicated and expensive. In this review, the historical analysis techniques from R. Adler are studied for better comprehension with proper notation of the variables, resulting in numerical results. In addition, how the timing jitter or phase noise in the ILO is attenuated from noise sources is presented in contrast to the clock generators based on the phase-locked loop (PLL). Although the ILO is very promising with higher cost effectiveness and better noise immunity than other schemes, unless correctly controlled or tuned, the promises above might not be realized. In order to present the favorable conditions, several strategies have been explored in diverse applications like frequency multiplication, data recovery, frequency division, clock distribution, etc. This paper reviews those research results for clock multiplication and data recovery in detail with their advantages and disadvantages they are referring to. Through this review, the readers will hopefully grasp the overall insight of the ILO, as well as its practical issues, in order to incorporate it on silicon successfully.

• Journal of radiological science and technology
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• v.46 no.2
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• pp.131-139
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• 2023

High-dose I-131 used for the treatment of thyroid cancer causes localized exposure among radiology technologists handling it. There is a delay between the calibration date and when the dose of I-131 is administered to a patient. Therefore, it is necessary to directly measure the radioactivity of the administered dose using a dose calibrator. In this study, we attempted to apply machine learning modeling to measured external dose rates from shielded I-131 in order to predict their radioactivity. External dose rates were measured at 1 m, 0.3 m, and 0.1 m distances from a shielded container with the I-131, with a total of 868 sets of measurements taken. For the modeling process, we utilized the hold-out method to partition the data with a 7:3 ratio (609 for the training set:259 for the test set). For the machine learning algorithms, we chose linear regression, decision tree, random forest and XGBoost. To evaluate the models, we calculated root mean square error (RMSE), mean square error (MSE), and mean absolute error (MAE) to evaluate accuracy and R² to evaluate explanatory power. Evaluation results are as follows. Linear regression (RMSE 268.15, MSE 71901.87, MAE 231.68, R² 0.92), decision tree (RMSE 108.89, MSE 11856.92, MAE 19.24, R² 0.99), random forest (RMSE 8.89, MSE 79.10, MAE 6.55, R² 0.99), XGBoost (RMSE 10.21, MSE 104.22, MAE 7.68, R² 0.99). The random forest model achieved the highest predictive ability. Improving the model's performance in the future is expected to contribute to lowering exposure among radiology technologists.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.3
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• pp.148-156
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• 2013

Since the demand for new military vehicle to fulfill the necessary conditions such as multi-purpose, high-mobility, and survivability has raised continuously from the army, the prototype of a Korean light tactical vehicle was developed to meet these requirements using our own technology. In particular, the new tactical vehicle was equipped with a double wishbone independent suspension to improve ride and handling and maximize off-road driving performance. In this paper, a comprehensive virtual durability process to evaluate the service life of the prototype is presented. A reliability of the trimmed body model based on CATIA data was verified by comparison result between mode analysis and modal test. The dynamic model was constructed using ADAMS/Car, and then the weight distribution and lateral slope driving performance of it were compared with the results of static weight and lateral slope tests. The validity of the VTL(Virtual Test Lab) was checked with test results from the 3-inch spaced impact road. The durability performances of trimmed body and suspension components were evaluated through MSM(Modal Superposition Method) fatigue analysis. It is shown that the virtual durability process could be a helpful tool to find out the weak areas and improve their structures in developing new military vehicle.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.1
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• pp.85-95
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• 2013

As the conventional hydraulic power steering system in the passenger vehicles is being rapidly replaced by EPS (Electric Power Steering) system, performance evaluation of the EPS system has become an important issue in the automotive industries. But the evaluation process takes significant expertise since steering conditions in the test protocols must be implemented with high accuracy. EPS HILS (Hardware-In the-Loop Simulation) system is developed together with robot steering system in this study. Main components of EPS HILS system include: C-EPS hardware, CarSim vehicle model, and road reaction force generation system powered by servo motor. The robot steering system, operated by another servo motor, was combined with EPS HILS system to substitute for steering efforts of human driver. The road reaction force generation system and the robot steering system were carefully validated by using the data obtained from vehicle tests. An on-center handling test was conducted by using EPS HILS system combined with the robot steering system. In the result of this study, robot-steered EPS HILS system developed with its high reliability and no need of skilled driver's, can be widely adopted to evaluate any performance of EPS system.

• Journal of Korean Public Health Nursing
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• v.2 no.2
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• pp.62-80
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• 1988

The main purpose of this study was to find out the actual status of safety and heal th education activities in the manufacturing industries through survey of 136 plants in Seoul City and Gyunggi- Province Area which employ nurses being charged in the safety and health care services to the employees. A questionaire was mailed to the employees on the Mar. 2, 1987. Total 634 responds from 87 industries were collected by Apr. 20, 1987. Among the total, 618 responds from 80 industries were included in the analysis. The major findings obtainded from this study are summarized as follows; 1. Safety and health education activities in each industry: 1) The $67.6\%$ of safety directors surveyed were performing the education to the employees. And in case of medical directors, it was $18.8\%$ of them. 2) Periodically, annual safety' and health education programs were being drawn up in the $65.0\%$ of the industries (52 companies). And the $60.6\%$ of the planners were safety directors of safety staffs in charge. 3) It was only $27.5\%$ of the companies surveyed in which the safety and health education were performed more than an hour every month. In the $22.5\%$ of the companies, neither safety programs nor health education activities were performed. 4) In the $47.5\%$ of them, safety and health educations were performed in cooperation with related agencies such as health center. 2. The rate of employees participated in safety and health educations; 1) The received rates by subjects of the educations when labors were newly employed to their companies were as follows; education regarding danger and profer handling method of machinery and appliances: $64.2\%$, education regarding noxiousness and handling method of raw materials: $42.2\%$, etc. 2) The $63.6\%$ of the labors received educations on safety and health when they changed their work places. 3) The $74.8\%$ of the labors received specific safety and health educations. 4) The general safety and health educations were received by the $47.2\%$ of management and clerical personnel and $50.0\%$ of labors pre and post physical examination. 3. The main reasons of inactive performance of the educations were as follows; lack of knowledge and inexperience of the occupational safety and health staffs, lack of cooperations between themselves and low need of workers for safety and health education, etc. 4. The preferable subjects of educations for workers; (1) pre and post education of physical examination, (2) education regarding the prevention of accidents. (3) general health care, sex education and family planning, etc. As a result of this study, we can conclude that the safety and health education work in industries as the subject of this study is on the incipient stage. Appropriate measures are to be taken for the activation of safety and health education work such as; continuous public relations, financial and technical supports of the government, training of professional/occupational safety and health staffs, efforts of workers to receive the education and collaborations of the employers.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.2
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• pp.274-282
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• 2011

The purpose of this study was to investigate factory workers' knowledge of sanitation management of school foodstuffs and sanitation practices. A questionnaire that identified employees' food safety sanitation management knowledge and practices was developed based on a review of literature. Subjects consisted of 221 factory workers employed at 34 factories in the Daegu and Gyeongbuk areas. Almost half of the factory workers were 40~49 years of age (45.7%), 34.8% had 1~3 years of work experience, 62.4% of the respondents received food safety education 1~2 times a month and 75.1% of the respondents were satisfied with sanitation education. However, the total score for factory worker sanitation knowledge was low: 4.63/9. Sanitation performance was self-evaluated using a Likert 5-point scale. The total mean score for the factory workers' sanitation performance was 4.63/5. Satisfaction level and the amount of sanitation education, application of sanitation knowledge, attitude regarding sanitation management, and sanitation management performance level were significantly high among workers employed in a HACCP certification facility (p<0.05). The difficulties were found to be sanitation management and the time to deliver food to schools. To instill a sense of duty and pride among workers and to ensure that the food suppliers provide best-quality school foodstuffs safely, school dietitians and factory managers must actively educate workers in safe food handling and sanitation.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.12
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• pp.1388-1396
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• 2011

This paper is focused on the procedure of the development of a micro air vehicle which has vertical take-off and landing capability for indoor reconnaissance mission. Trade studies on mission feasibility led to the proposal of a coaxial rotorcraft configuration as the platform. The survey to provide a guide for preliminary design were conducted based on commercial off-the-shelf platform, and the rotor performance was estimated by the simple momentum theory. To determine the initial size of the micro air vehicle, the modified conventional fuel balance method was applied to adopt for electric powered vehicle, and the sizing problem was optimized with the sequential quadratic programming method using MATLAB. The designed rotor blades were fabricated with high strength carbon composite material and integrated with the platform. The developed coaxial rotorcraft micro air vehicle shows stable handling quality with manual flight test in indoor situation.

• Korean Journal of Agricultural and Forest Meteorology
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• v.19 no.3
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• pp.153-163
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• 2017

The objective of this study is to enhance the model's speed of estimating weather variables (e.g., minimum/maximum temperature, sunshine hour, PRISM (Parameter-elevation Regression on Independent Slopes Model) based precipitation), which are applied to the Agrometeorological Early Warning System (http://www.agmet.kr). The current process of weather estimation is operated on high-performance multi-core CPUs that have 8 physical cores and 16 logical threads. Nonetheless, the server is not even dedicated to the handling of a single county, indicating that very high overhead is involved in calculating the 10 counties of the Seomjin River Basin. In order to reduce such overhead, several cache and parallelization techniques were used to measure the performance and to check the applicability. Results are as follows: (1) for simple calculations such as Growing Degree Days accumulation, the time required for Input and Output (I/O) is significantly greater than that for calculation, suggesting the need of a technique which reduces disk I/O bottlenecks; (2) when there are many I/O, it is advantageous to distribute them on several servers. However, each server must have a cache for input data so that it does not compete for the same resource; and (3) GPU-based parallel processing method is most suitable for models such as PRISM with large computation loads.

• International Journal of Control, Automation, and Systems
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• v.5 no.2
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• pp.147-154
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• 2007

This paper describes a 'gyro-mouse', which provides a new human-computer interface (HCI) for persons who are disabled in their upper extremities, for handling the mouse-click and mouse-move function. We adopted the artificial neural network to recognize a quick-nodding pattern of the disabled person as the gyro-mouse click. The performance of our gyro-mouse was evaluated by three indices that include 'click recognition rate', 'error in cursor position control', and 'click rate per minute' on a target box appearing at random positions. Although it turned out that the average error in cursor positioning control was 1.4-1.5 times larger than that of optical mouse control, and the average click rate per minute was 40% of the optical mouse, the overall click recognition rate was 93%. Moreover, the click rate per minute increased from 35.2% to 44% with repetitive trials. Hence, our suggested gyro-mouse system can be used to provide a new user interface tool especially for those persons who do not have full use of their upper extremities.