• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.5
• /
• pp.1176-1181
• /
• 1995

Microdrilling is one of the most difficult operations because of the poor chip discharge and the weakness of tool. This study is concerned about the development of a microdrilling monitoring system that is useful for minimizing the tool breakage and enhancing the machinability in the air spindle based microdrilling. The system is composed of a drilling state detection unit and an adaptive step-feed control unit that controls the micro-stepping motor driven spindle axis. Drilling states such as overload, tood breakage are recognized by the change of the air spindle speed which is measured via the reflective photo sensor. Based on the monitoring results, the adaptive step-feed control algorithm adjusts the step increment to keep the decrease of spindle speed within a specified range. The results of evaluation tests have shown that the developed system is very effective to prevent the breakage of microdrill and improves the productivity in comparison with the conventional microdrilling.

• Journal of Korean Society on Water Environment
• /
• v.22 no.1
• /
• pp.110-115
• /
• 2006

Flooding situation of Sutak basin was simulated and simulation seemed to be consistent with the real flooding situation in terms of high water levels and timings of flooding. The flood simulation model was used to evaluate alternatives to mitigate flooding problems in Sutak basin. From the evaluation of flood mitigation plans, it was found that combined operation of Sutak and Inchang pumping stations through partial diversion of inflow of Sutak pumping station to Inchang pumping station was the most effective one among the suggested mitigation plans. About 500 meter diversion channel will be needed to send 30% of Sutak pumping station inflow to Inchang pumping station. This will reduce overload of Sutak pumping station and the storage capacity of Inchang pumping station will be more efficiently utilized.

• Journal of the Ergonomics Society of Korea
• /
• v.18 no.1
• /
• pp.133-147
• /
• 1999

Traffic signs without a cognitive consideration in their design may cause information-processing problem that could result in a mental confusion among drivers often lead to a serious traffic accident. Therefore, in this study, several traffic signs currently used in Seoul Metropolitan area have been sampled and analyzed to identify design problems that usually caused by neglecting drivers cognitive ability. To classify the practical design problems, five major information-processing problems have been suggested: indistinguishable information, information conflict, missing information, sign-load mismatch, and information overload. In order to solve these cognitive problems, new traffic signs have been suggested in this study. An experiment was also performed to validate the new traffic sign. Twenty-four healthy subjects participated in the experiment. They were asked to answer the Question after observing the traffic signs continuously displayed on computer screen. The result indicated that subjects improved the accuracy in understanding the signs by 1.4 times when they used the suggested traffic sign compared to the old one. Based upon the results, a cognitive guideline was suggested for correct and speedy reading of traffic signs by improving information processing and reducing of human error. In conclusion, the traffic sign may well be applied to design an intelligent traffic sign system to increase the safety and comfort of drivers, especially in complex load condition.

• Journal of Information Processing Systems
• /
• v.8 no.4
• /
• pp.721-738
• /
• 2012

The Internet has become an increasingly important source for finding the right employees, so more and more companies post their job openings on the Web. The large amount and dynamic nature of career recruiting information causes information overload problems for job seekers. To assist Internet users in searching for the right job, a range of research and commercial systems were developed over the past 10 years. Surprisingly, the majority of existing job search systems support just one, rarely two ways of information access. In contrast, our work focused on exploring a value of comprehensive access to job information in a single system (i.e., a system which supports multiple ways). We designed Proactive, a recommendation system providing comprehensive and personalized information access. To assist the varied needs of users, Proactive has four information retrieval methods - a navigable list of jobs, keyword-based search, implicit preference-based recommendations, and explicit preference-based recommendations. This paper introduces the Proactive and reports the results of a study focusing on the experimental evaluation of these methods. The goal of the study was to assess whether all of the methods are necessary for users to find relevant jobs and to what extent different methods can meet different users' information requirements.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.3 no.3
• /
• pp.129-137
• /
• 1999

Reinforced concrete structures using early age concrete were result in the degradation of structural performance due to crack, overload, unexpected vibration and impact load. It demands urgently that reinforced concrete structure using early age concrete should be improved the serviceability and structural performance with the application of new fiber materials. Therefore specimens, designed by the test varibles, such as with or without stirrup and percent of steel fiber incorporated, were constructed and tested to evaluate and develop the structural performance of reinforced steel fiber concrete beam. Based on the test results reported in this study, the following conclusions are made. Specimens, designed by the over 0.75% of steel fiber incorporated, were showed the ductile behavior and failed slowly with flexure and flexure-shear. Comparing with the load-displacement relationship of specimen BSS, designed by the recommendations of the Ministry of Construction and Transportation, reinforced steel fiber concrete beam using early age concrete, over 0.75% of steel fiber incorporated, gets enough load carrying capacity and ductility. Increasing the percent of steel fiber incorporated(0.25~2.0%), the ultimate shear stress of each specimen were increased 12~40% than that of control specimen SSS.

• Journal of the Korean Society for Precision Engineering
• /
• v.12 no.5
• /
• pp.98-107
• /
• 1995

The in-process detection of drill wear and breakage is one of the most importnat technical problems in unmaned machining system. In this paper, the monitoring system is developed to monitor abnormal drilling states such as drill breakage, drill wear and unstable cutting using motor current. Drill breakage is detected by level monitoring. Tool wear is classified by fuzzy pattern recognition. The key feature for classification of tool wear is the estimated flank wear which is calculated by the proposed flank wear model. The characteristic of the model is not sensitive to the variation of cutting conditions but is sensitive to drill wear state. Unstable cutting states due to the unsmooth chip disposal and the overload are monitored by the variance/mean ratio of spindle motor current. Variance/mean ratio also includes the information about the prediction of drill wear and drill breakage. The evaluation experiments have shown that the developed system works very well.

• Journal of Wind Energy
• /
• v.10 no.4
• /
• pp.20-27
• /
• 2019

High-speed shaft coupling in a wind power system transmits power and absorbs variations in length and spindle dislocation between the gearbox and generator. Furthermore, the coupling has an insulation function that prevents electrical corrosion caused by the flow of the generator's current into the gearbox and prevents overload resulting from sudden power failure from being transferred to the gearbox. Its design, functions, and part verification are described in the IEC61400 and GL Guidelines, which specify that the part must have a durability life of 20 years or longer under distance variation and axial misalignment between the gearbox and the generator. This study presents the design of a high-speed coupling through composite stiffness calculation, structural analysis, and comparative analysis of test and theory to identify the characteristics of high-speed coupling for a large-capacity 6 MW wind power generator. A prototype was fabricated by optimizing the manufacturing process for each part based on the design, and the reliability of the fabricated prototype was verified by evaluating the performance of the target quantitative evaluation items.

• Journal of Venture Innovation
• /
• v.1 no.2
• /
• pp.75-87
• /
• 2018

We designed this study for verifying the differences of causes and individual results of job stress between Koreans in Korea and Chinese in China of a same company. The results in the study are as follow. Significant differences between two groups were identified in job stressors: Koreans showed higher levels than Chinese for factors like inter-group conflicts, supervision/evaluation, job overload, task characteristics, socio-demographic factors, and Chinese showed higher levels than Koreans for factors like job conflicts, job ambiguity, family-related factors. We also identified that levels of stress perceived by individuals as anxiety, depression, and physical symptoms of Koreans are higher than those of Chinese. As to the influence of job stressors on stress level, Koreans show significant results for supervision/evaluation, decision making/responsibility, family-related factors, and Chinese show significant results for family-related factors, social support, socio-demographic factors. Based on the results of this study, implications, limitations, and future research topics were discussed.

• Journal of the Korea Society for Simulation
• /
• v.17 no.3
• /
• pp.1-8
• /
• 2008

It is essential to maintain constant QoS despite of cell overload or erroneous wireless link during transmission because QoS of a multimedia service may be severely degraded by small delay or packet loss. This paper deals with a cell selection method for supporting the QoS of multimedia services over heterogeneous networks. The proposed scheme is based on Fuzzy Multi-Criteria Decision Making (FMCDM), in which uncertain parameters such as user system preference, the communication cost and cell load, and the transmission delay are used in the decision process using the aggregation function in fuzzy set theory. In this scheme, errors in the evaluation parameters impose milder changes on the total evaluation value than in binary logics. Simulation is focused on the average delay and packet loss rate, and the simulation results show that our proposed method provides mobile terminals the optimal performance.

• The Journal of the Korea Contents Association
• /
• v.21 no.12
• /
• pp.662-675
• /
• 2021

In order to evaluate the effectiveness of the Jeollabuk-do social welfare errand center, this study focused on identifying the effects of users' personal characteristics and workers' job environment characteristics on user satisfaction. The data analyzed are survey data collected from users and workers at 11 social welfare errand centers in each city and county in Jeollabuk-do. In the detailed analysis, the first-level independent variable for the users' personal characteristics, the second-level independent variable for the worker's job environment characteristics, and the user satisfaction were set as the dependent variables, and then a hierarchical linear model analysis model was applied. As a result of the analysis, it was confirmed that households with disabilities, sense of job value, job stress, role overload, and salary satisfaction had a significant effect on the service satisfaction of users. The results of this analysis show that the characteristics of the job environment of the workers have a major effect on the satisfaction of service users. This suggests that there is a strong need for improvement in the fields.