• Proceedings of the KIEE Conference
• /
• 1996.11a
• /
• pp.49-51
• /
• 1996

The z-transform method is a basic mathematical tool in analyzing and designing sampled-data control systems. However, since the z-transform method relates only the sampling-instants signals, another mathematical tool is necessary to describe the continous signals between the sampling instants. For this purpose the delayed and the modi fled z-transform methods were developed. The definition of the modi fled z-transform includes a sample in the interval [-T,0] of the original signal in its series expression, where the signal value is always zero for any physical system. From this reason one step skew of the time index always appears in its application formulas. This introduces an unnecessary operation and a gap in linking the mathematical formula and its physical interpretation. Considering the conceptual difficulty and application inconvenience, a method of using the advanced z-transform in analysis of sampled-data control systems is developed as a replacement of the modi fled z-transform. With one formulation of the advanced z-transform, now it is possible to relate both the signals of the sampling instants and those in between without any complication and conceptual difficulty.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2022.04a
• /
• pp.27-28
• /
• 2022

There is a limit to preventing various types of safety accidents in advance at construction sites. Even for buildings of the same total floor area, it is expected that the more complex the building shape or the higher the number of floors, the higher the probability of a safety accident. Therefore, it is necessary to analyze the effect of the shape of a building on safety accidents using safety accident data generated during actual construction. The purpose of this study is to analyze the impact of building shape on safety accidents. As a result, the R2 value of shape factor and safety accident was 0.901, and the R2 value of construction difficulty and safety accident was 0.944. In the future, the results of this study will be used as basic data for improving safety management related systems.

• Design & Manufacturing
• /
• v.6 no.1
• /
• pp.12-17
• /
• 2012

In order to produce high-quality optical components, aspheric lenses have been widely applied in recent years. An aspheric lens consists of aspheric surfaces instead of spherical ones, which causes difficulty in the design process as well as the manufacturing procedure. Although injection molding is widely used to fabricate optical lenses owing to its high productivity, there remains lots of difficulty to determine appropriate mold design factors and injection molding parameters. In the injection molding fields, computer simulation has been effectively applied to analyze processes based on the shell analysis so far. Considering the geometry of optical lenses, a full-3d simulation based on solid elements has been reported as a reliable approach. The present work covers three-dimensional injection molding simulation and relevant deformation analysis of an injection molded plastic lens based on 3d solid elements. Numerical analyses have been applied to the injection molding processes of three aspheric lenses for an image sensing module of a mobile phone. The reliability of the proposed approach has been verified in comparison with the experimental results.

• Journal of the Korea Convergence Society
• /
• v.8 no.7
• /
• pp.93-99
• /
• 2017

Necessity of adjustment in level of difficulty of national examination for radiological technologists is being brought up. However, objective reasons are required to make those arguments more valid. Therefore in this research, result of national examination for radiological technologists under present system was analyzed in more convergence perspective via statistical analysis. This will provide basic data which is applicable when system of national examination for radiological technologists undergo improvements. For this, statistical analysis such as descriptive statistics and correlation analysis was conducted using SPSS program. Results are as follow. First, ratio of successful applicants for radiological technologists was highly fluctuant relative to other national examinations like doctor, nurse, physical therapist, etc. Second, level of difficulty and discernment of national examination for radiological technologists were differentiated from other examinations like doctor, nurse, physical therapist. Third, the 43th examination for radiological technologists conducted in 2015 had the highest discernment as 0.41, despite of lowest level of difficulty as 89.2, for radiologic applications. The results of this research is expected to be used as basic data when system of national examination for radiological technologists undergo improvements, in accordance with increased supplying plan of work-forces in medical radiological technologists.

• The korean journal of orthodontics
• /
• v.35 no.1 s.108
• /
• pp.69-81
• /
• 2005

As one of the variations in growth and development of the craniofacial complex. malocclusion shows lack of concordance In the recognition and severity of malocclusion for dentists as well as the acceptance and need of orthodontic treatment for the patient The purposes of this study were 1) to examine the relationships between objective malocclusion severity aid subjective treatment difficulty. 2) to evaluate the effect of malocclusion components to the subjective perceived difficulty of treatment. 3) to establish the weighted values of malocclusion components to reflect the treatment difficulty 100 pairs of dental casts with the general characteristics of malocclusion. were selected from the orthodontic departments of Kyunghee University and Samsuug Medical Center. The severity of malocclusion was evaluated by the author with the PAR index The perceived treatment difficulty and the estimated treatment duration on these dental models were evaluated by 8 experienced orthodontists. The relationships between the objective malocclusion severity and the subjective treatment difficulty were statistically evaluated. and the weighted values of malocclusion components to reflect treatment difficulty were statistically formulated. There were significant relationships between objective malocclusion severity and subjective treatment difficulty The malocclusion components which significantly affected the treatment difficulty and their weighted values in parentheses were as follows upper anterior alignment(1). overbite (2). buccal occlusion (3) middline (4), and overjet (5). This study Provides the fundamental principle to evaluate the objective malocclusion severity which is reflected by the subjective treatment difficulty of Korean orthodontists.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.15 no.2
• /
• pp.67-80
• /
• 2020

This study has been conducted at a time when Korean government continues to extend support for youth startups as part of its policy to create jobs and the focus moves from career and employment to youth startups with a growing interest in the field of youth startups. Against this background, this study aims to identify difficulty factors of youth startups in areas besides the Seoul Metropolitan Area, seek ways to overcome difficulty factors, and propose policy implications. To this end, this study set five criteria and 25 sub-criteria to evaluate the difficulties of youth startups by reviewing previous studies and conducting literature review, and performing brainstorming method. The empirical analysis of the evaluation criteria was performed, using the analytic hierarchy process (AHP) method, on youths aged 19 to 39 in Gunsan area. The analysis results showed that the largest difficulty factors facing local youths include business model establishment, business administration and management, and startup funding in the criteria. As for sub-criteria, the largest difficulty factors are market information acquisition, technology commercialization, project feasibility, technology development, and new market pioneering in descending order. Local youths have much difficulty about the process of turning a business item into a product and commercializing it. According to a comparative analysis by gender, men were a relatively high difficulty in commercializing business models than women. men were a relatively high difficulty in commercializing business models than women. On the other hand, women were higher than men in all factors (management management, entrepreneurship, improvement of entrepreneurship system, and improvement of entrepreneurship awareness) except for factors affecting business model. In addition, the factors of entrepreneurship were found to be relatively different among young people (college students, prospective entrepreneurs, entrepreneurs). In conclusion, it was suggested that in order to revitalize youth entrepreneurship in the region, it is necessary to actively resolve the difficulties of business model commercialization rather than entrepreneurship funds. In addition, it is necessary to strategically support customized entrepreneurship support and situational administrative services because gender and hierarchical difficulties are different than general solutions. This study presented practical priorities and derivation methods for the entrepreneurship difficulties faced by local youth, and suggested measures and improvements for vitalizing local youth entrepreneurship in the future.

• Journal of The Korean Association For Science Education
• /
• v.34 no.3
• /
• pp.295-301
• /
• 2014

The purpose of this study is to investigate the difficulties of teachers and students on the unit about 'measuring weight.' In this research, we have acquired data about teachers through survey, interview, and self-reflection journals, at the same time we have collected information on the students through survey, assessment test, and interview. We have extracted the difficulties from analysis with constant comparison method. In addition, we have analysed the curriculum of science and mathematics to know the leaning sequence. The analysis had been checked up by experts in science education. The result of the study is as follows: The difficulties of teachers are from the lack of teachers' descriptive knowledge, disorder of conceptual hierarchy in the curriculum, poor experimental instruments, and low psychomotor skill of students. The difficulties of students are from common misconceptions, opaque concepts, lack of manipulation skill, insufficiency of mathematical ability, difficulty of application of principles to the real situation, and lack of problem-solving ability. In addition, teachers have recognized that students face more difficulties in experiment class, while students think that they face more difficulties in conceptual understanding class.

• The Korean Journal of Rehabilitation Nursing
• /
• v.12 no.1
• /
• pp.16-29
• /
• 2009

Purpose: The aim of this study was to develop and to analyze the duty and the task of rehabilitation nurse in Korea. Method: The definition of rehabilitation nurse and job description was developed based on developing curriculum(DACUM) by panels who have experienced in DACUM analysis and rehabilitation nursing. 228 nurses who were working at rehabilitation centers and rehabilitation unit in general hospitals were participated. The questionnaire included frequency, importance, and difficulty of duties and tasks. The data were collected in March and April 2009, analyzed by descriptive statistics. Results: The job description of rehabilitation nurse in Korea revealed 11 duties, and 61 tasks. On the all 11 duties, the highest duty in frequency and importance was direct nursing care ($2.47{\pm}.31$, $2.77{\pm}2.8$) and the highest duty in difficulty was self-development ($2.39{\pm}.48$). Among the tasks of duties 'direct nursing care' in 'manage medication' ($2.87{\pm}.35$) in frequency, the task 'prevent and manage bedsore' ($2.91{\pm}.31$) of duty 'direct nursing care' in importance, and 'cope emergency situations' ($2.72{\pm}.49$) of duty direct nursing care in difficulty showed the highest degree. Conclusion: The political efforts for the legislation of role and task of rehabilitation nurse were needed.

• Journal of Korean Society of Archives and Records Management
• /
• v.16 no.3
• /
• pp.131-156
• /
• 2016

The purpose of this study is to prepare a plan for the improvement of the tasks of record managers in offices of education by understanding the details of their work; analyzing the importance, difficulty, and performance frequency of their tasks; and investigating their working environment and the problems of record management in offices of education. For this purpose, through a literature review and an analysis of related conditions, this study drew out 5 task domains and 24 detailed record management tasks in offices of education. To investigate the level of importance, difficulty, and performance frequency of the drawn-out task domains and task factors, this study conducted a questionnaire survey on record managers working in offices of education and analyzed the survey results using the IPA technique by crossing the level of importance, difficulty, and performance frequency. Based on the survey results, to improve the tasks of record managers in offices of education, and strengthen their task competency, a plan for improvement was suggested.

• Journal of Korean Biological Nursing Science
• /
• v.20 no.1
• /
• pp.11-19
• /
• 2018

Purpose: The purposes of this study were to perform items analysis using the classical test theory (CTT) and the item response theory (IRT), and to establish the validity and reliability of the Korean version of pressure ulcer prevention knowledge. Methods: The 26-item pressure ulcer prevention knowledge instrument was translated into Korean, and the item analysis of the 22 items having an adequate content validity index (CVI), was conducted. A total of 240 registered nurses in 2 university hospitals completed the questionnaire. Each item was analyzed applying CTT and IRT according to 2-parameter logistic model. Response alternatives quality, item difficulty and item discrimination were evaluated. For testing validity and reliability, Pearson correlation coefficient and Kuder Richardson-20 (KR-20) were used. Results: Scale CVI was .90 (Item-CVI range= .75-1.00). The total correct answer rate for this study population was relatively low as 52.5%. The quality of response alternatives was found to be relatively good (range= .02-.83). The item difficulty of the questions ranged form .10 to .86 according to CTT and -12.19 to 29.92 according to the IRT. This instrument had 12-low, 2-medium and 8-high item difficulty applying IRT. The values for the item discrimination ranged .04-.57 applying CTT and .00-1.47 applying IRT. And overall internal consistency (KR-20) was .62 and stability (test-retest) was .82. Conclusion: The instrument had relatively weak construct validity, item discrimination according to the IRT. Therefore, the cautious usage of a Korean version of this instrument would be recommended for discrimination because there are so many attractive response alternatives and low internal consistency.