• Journal of Power Electronics
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• v.11 no.4
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• pp.456-463
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• 2011

Grid-connected converters have widely adopted LCL filters to acquire high harmonic suppression. However, the LCL filter increases the system order so that the design of the system stability would be complicated. Recently, sole-loop control strategies have been used for grid-connected converters with L or LC filters. But if the sole-loop control is directly transplanted to grid-connected converters with LCL filters, the systems may be unstable. This paper presents a novel dual-loop power control strategy composed of a power outer loop and a current inner loop. The outer loop regulates the grid-connected power. The inner loop improves the system stability margin and suppresses the resonant peak caused by the LCL filter. To obtain the control variables, a single-phase current detection is proposed based on PQ theory. The system transfer function is derived in detail and the influence of control gains on the system stability is analyzed with the root locus. Simulation and experimental results demonstrate the feasibility of the proposed control.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.8
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• pp.101-107
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• 1997

In general, grinding is one of the final machining processes which determines the surface quality of machined products. Since the ground surface is affected by the states of grains and voids on the grinding wheel surface, the wheel should be dressed before the machined surface deteriorates over a quality limit This paper describes a systematic approach to decide a proper dressing chance and an optimal dressing depth for the working grinding wheel. An eddy current sensor and a laser displacement sensor are used to measure the loading on the working wheel surface and the topography of the dressed wheel surface respec- tively. The dressing chance can be properly decided through the relational locus between the amount of handing and the machined surface roughness. An optimal dressing depth to guarantee the less wheel loss and the higher wheel surface quality is decided through the analysis of the variance of topography for the dressed wheel surface, which decreases at three different rates according to the accumulated dressing depth.

• Molecules and Cells
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• v.39 no.10
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• pp.715-721
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• 2016

Plants have become physiologically adapted to a seasonally shifting environment by evolving many sensory mechanisms. Seasonal flowering is a good example of adaptation to local environmental demands and is crucial for maximizing reproductive fitness. Photoperiod and temperature are major environmental stimuli that control flowering through expression of a floral inducer, FLOWERING LOCUS T (FT) protein. Recent discoveries made using the model plant Arabidopsis thaliana have shown that the functions of photoreceptors are essential for the timing of FT gene induction, via modulation of the transcriptional activator CONSTANS (CO) at transcriptional and post-translational levels in response to seasonal variations. The activation of FT transcription by the fine-tuned CO protein enables plants to switch from vegetative growth to flowering under inductive environmental conditions. The present review briefly summarizes our current understanding of the molecular mechanisms by which the information of environmental stimuli is sensed and transduced to trigger FT induction in leaves.

• Research in Plant Disease
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• v.28 no.2
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• pp.57-60
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• 2022

Leaves of Chionanthus retusus were found to be damaged by leaf spot disease associated with a fungus in Iksan, Korea. Leaf spots were angular to irregular, vein-limited, scattered, 1-8 mm diameter, brownish-gray to dark brown when dry, with heavy fructification. The pathogen causes premature defoliation of C. retusus plant and was identified as Pseudocercospora chionanthi-retusi based on morphological and molecular-phylogenetic analyses. The phylogenetic tree was constructed using multi-locus DNA sequence data of partial actin (actA), partial translation elongation factor 1-alfa (tef1), partial DNA-directed RNA polymerase II second largest subunit (rpb2) genes, and internal transcribed spacer regions. Current study provides detail morphological description of P. chionanthi-retusi on C. retusus in Korea, with supports of phylogenetic analysis and pathogenicity test.

• Journal of Engineering Education Research
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• v.22 no.3
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• pp.3-10
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• 2019

The purpose of this study is to analyze the educational needs of the industry for engineering education using the engineering competency scale. For needs assessment, t-test, Borich Needs Assessment and the Locus for Focus(LFF) were conducted using 400 employees' answers of industry. The results of this analysis are as follows. First, there was a significant difference between the level of importance and actual level. Second, all items were ranked using the Borich's needs assessment formula. Third, as a result of LFF model, 19 items were placed in the highest priority HH section. Fourth, 17 items with the highest priority in engineering education were selected. Finally, the highest educational needs were 6 items related with interpersonal skills, 2 items related with leadership, and 9 items related with professional attitude and ability. Based on the results of this paper, it is necessary to develop and operate an education program to reduce the gap between the industry requirement and the current level of engineering students.

• Journal of Information Processing Systems
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• v.17 no.5
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• pp.960-971
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• 2021

As the era of the 4th Industrial Revolution enters, the importance of software safety is increasing, but related systematic educational curriculum and trained professional engineers are insufficient. The purpose of this research is to propose the high priority elements for the software safety education program through needs analysis. For this purpose, 74 candidate elements of software safety education program were derived through contents analysis of literature and nominal group technique (NGT) process with five software safety professionals from various industries in South Korea. Targeting potential education participants including industrial workers and students, an on-line survey was conducted to measure the current and required level of each element. Using descriptive statistics, t-test, Borich needs assessment and Locus for focus model, 16 high priority elements were derived for software safety education program. Based on the results, suggestions were made to develop a more effective education program for software safety education.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.66-69
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• 2008

In this paper, The author present a load current feed-forward compensator by method that improve voltage controller of Step-down Chopper to get stable output voltage to sudden change of load current. To confirm the characteristicsof a presented load current feed -forward compensator compared each transfer function of whole system that load current feed-forward compensator is added with transfer function of whole system that existent voltage controller is included using Mason gains formula in Root locus and Bode diagram. As a result the pole of system is improved, extreme point of the wave and system improves, and size of peak value and phase margin of break frequency in resonance frequency confirmed that is good. Therefore, presented control technique could confirm that reduce influence by perturbation and improves stationary state and dynamic characteristics in output of Step-down Chopper.

• Journal of Korean Academy of Nursing
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• v.20 no.3
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• pp.399-413
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• 1990

This descriptive study was under taken to explore relationships among the quality of life, health locus of control and perceived state of health persons with cancer to contribute theoretical understanding about these phenomenon of interest to the quality of nursing care. The subjects of this were 200 persons with cancer (100- in patients and 100- out patients), both male and female, between 30 and 59 years of age. Data were obtained using a convenience sample technique from two university hospitals in seoul from August, 1989, to June, 1990. The instruments used for this study were the Quality of life scale developed by Ro, You - Ja and the Health Locus of Control scale developed by Wallston & Wallston. Data were analyzed using a SAS program for ANOVA, t-test, Schefffe test, Pearson Correlation Coefficients and Stepwise multiple regression. The results were as follows : 1. The scores on the quality of life scale ranged from 95 to 191 with as mean of 147.85(range 47 to 235). The Mean scores(range 1-5) on the different dimensions were family relationships 3.50, relationships with neighbours 3.48, self - esteem 3.17, physical state and function 2.99, economic life 2.93 and emotional life 2.91. 2. Significantly higher scores on the quality of life and demographic characteristics were as follows : the quality of life for women(t＝2.80, p＝ .006), for those without complications(t＝2.54, p＝ .013), and for those who perceived their illness as mild(F＝4.85, p＝ .009). Higher scores on quality of life were correlated with the following : 1) emotional state and the age group 50-59(F＝3.43, p＝ .34). 2) economic life and higher income(F＝6.72, p＝ .002), those without complications(t＝2.68, p＝ .00), and those who perceived their illness as mild(F＝3.11, p＝ .05). 3) self-esteem and marriage(F＝3.64, p＝.028), those without complications(t＝2.18, p＝.03), and those who perceived their illness as mild(F＝7.72, p＝.000). 4) physical state and funciton and the age group 30-39(F＝4.65, p＝.010), those without complications (t＝2.00, p＝.05), and those who perceived their illness as mild(F＝3.38, p＝.04). 5) family relationship and those who live with their spouse(t＝2.82, p＝.005). 3. There was a significant positive correlation between the subjects perceptions of their current state of health and the quality of life score(r＝.4364, p＝.0001). 4. There was no relationship between Locus of control and quality of life in this sample. 5. Stepwise multiple regression analysis showed that: 1) the perception of current health status was the main predictor and accounted for 20.11% of the total variance. 2) sex and educational level accounted for an additional 21.71% of the total variance. 6. The quality of life and the perception of their current health status of these patients with cancer were generally lower than those of healthy adults as noted in previous studies. In conclusion, the quality of life for these cancer patients was generally low especially in regard to their emotional state. The current perceived state of health, sex, complications and perceived degree of illness were important variables relatiog to quality of life.

• 대한공업교육학회지
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• v.40 no.1
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• pp.142-162
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• 2015

The purpose of this study are to provide the basic data materials and implementations for successful performance of electric-work field representatives of South Korean firms by identifying their roles and competency and examining their educational need. For this research purposes, three phased analysis was followed on: (1) the roles of electric-work field representatives, (2) competency of electric-work field representatives and (3) educational need for their competency. This research method was to conduct a focus group interview for 10 expert field representatives along with survey. The collected data materials were processed by MS Excel and SPSS 21.0 for statistical analysis including average, standard deviation and other basic statistics; the gap in awareness of field representatives; and need values. For the needs analysis, the difference between significance of field representatives' competency and current status was examined by t test. And the awareness gap between competency importance and current status was identified based on the Borich equation. The Locus for Focus model was employed herein to identify the kinds of competency with high importance and high inconsistency to prioritize. As a result, this research has found as follows: first, the roles of field representatives were found to be in 13 different kinds of roles. Second, electric-work field representatives were found to need to have 16 different skills. Third, regarding the 16 abilities, the gap between current status and significance was analyzed herein. The results showed statistically significant differences in all cases. The Borich needs analysis found the first required ability was communication ability followed by power of execution, conflict management ability, analytical thinking and time management ability. Also, the results of Locus for Focus model analysis displayed that the first quadrant(HH) included 7 highly-demanded abilities of communication ability, analytical thinking, decision making ability, specialty, time management ability, power of execution and drive for work implementation. The top-priority group was found to have 5 items of communication ability, analytical thinking, time management ability, power of execution and drive for work implementation which were commonly seen in the Locus for Focus model outcomes. Based on these findings, this research could identify the roles and competency of electric-work field representatives and provide the basic data materials applicable to future personal management of electricity companies including recruitment, division of work, job description, evaluation, etc. Also this research offered guidelines on demanded abilities in the field and where to place priority. The kinds of abilities with high educational demand as found in this research must be considered in designing educational programs for the competency building of field representatives. This research is expected to provide useful information in developing such educational programs for field representatives.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.1
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• pp.32-41
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• 1992

This paper presents a comprehensive study on the stability of several control schemes for the induction motor driven by current source inverters. A stator voltage controlled current source inverter drive system without a speed sensor is investigated in order to find appropriate control schemes, which are primarily based on direct or, alternatively, indirect frequency control scheme. It can be seen, especially that an introduction of the indirect frequency control method improves the inherent instability of the current source inverter drive system for the induction motor. The overall control systems with either voltage control loop or current and voltage control loops in addition to each frequency control scheme, are analyzed by utilizing the root locus method and simulated by computer to show the validity of this analysis.