• Journal of Electrical Engineering and Technology
• /
• v.13 no.4
• /
• pp.1604-1613
• /
• 2018

The paper presents the equivalent circuit of an induction machine (IM) model which includes fundamental stray load and iron losses. The corresponding equivalent resistances are introduced and modeled as variable with respect to the stator frequency and flux. Their computation does not require any tests apart from those imposed by international standards, nor does it involve IM constructional details. In addition, by the convenient positioning of these resistances within the proposed equivalent circuit, the order of the conventional IM model is preserved, thus restraining the inevitable increase of the computational complexity. In this way, a compromise is achieved between the complexity of the analyzed phenomena on the one hand and the model's practicability on the other. The proposed model has been experimentally verified using four IMs of different efficiency class and rotor cage material, all rated 1.5 kW. Besides enabling a quantitative insight into the impact of the stray load and iron losses on the operation of mains-supplied and vector-controlled IMs, the proposed model offers an opportunity to develop advanced vector control algorithms since vector control is based on the fundamental harmonic component of IM variables.

• Structural Engineering and Mechanics
• /
• v.57 no.5
• /
• pp.877-895
• /
• 2016

This paper is concerned with the analytical derivation of natural sloshing frequencies of liquid in annular cylindrical tank and its verification by experiment. The whole liquid domain is divided into three simple sub-regions, and the region-wise linearized velocity potentials are derived by the separation of variables. Two sets of matrix equations for solving the natural sloshing frequencies are derived by enforcing the boundary conditions and the continuity conditions at the interfaces between sub-regions. In addition, the natural sloshing frequencies are measured by experiment and the numerical accuracy of the proposed analytical method is verified through the comparison between the analytical and experimental results. It is confirmed that the present analytical method provides the fundamental sloshing frequencies which are in an excellent agreement with the experiment. As well, the effects of the tank radial gap, the bottom flow gap and the liquid fill height on the fundamental sloshing frequency are parametrically investigated.

• Journal of Digital Convergence
• /
• v.18 no.6
• /
• pp.389-399
• /
• 2020

This study was conducted to identify the effects of fundamental nursing practice education using flipped learning on self confidence performance, academic achievement and critical thinking. The subjects of this study were 38 experimental groups and 36 control groups, who were in the second year of the department of nursing at D university, and Flip learning was applied to the experimental group for four weeks, while the existing teaching methods were applied to the control group. As a result, the academic achievement of vital signs in the experimental group after the experiment with flip learning was significantly higher than the control group (t=2.921, p=.005), but other variables were not significant. In addition, the critical thinking of the experimental group was significantly increased after the experiment than before (t=2.277 p=.029). However, it was not significant in the control group. In the future, various studies using flip learning in nursing are needed.

• International Journal of Highway Engineering
• /
• v.17 no.2
• /
• pp.1-11
• /
• 2015

PURPOSES : This study set out to investigate the fundamental properties of alkali-activated concrete (AAC) using modified slag as the pavement maintenance material. METHODS: The material properties of modified slag based alkali-activated concrete (MSAAC) were analyzed and evaluated against those of alkali-activated slag concrete (AASC). Several mix formulations were considered, including one MSACC and four AASCs. The main variables considered in the study were slump, air content, compressive strength, rapid chloride permeability test, scaling resistance, freeze-thaw test, XRD, SEM, and EDS. RESULTS: MSAAC exhibits a compressive strength in excess of 21 MPa six hours after curing. Also, the charge passed of the MSACC was found to be less than 2000 coulombs after seven days and about 1000 coulombs after 28 days. The weight loss determined from a scaling test did not exceed $1kg/cm^2$ in the case of the MSACC, but that of the AASCs had already exceeded $1kg/cm^2$ at the 10th cycle. Based on the results of the freeze-thaw test, the relative dynamic modulus of every mix was found to be in excess of 90%. An energy dispersive spectroscopy(EDS) analysis found that the weight rate percentage of the calcium and aluminum in the MSAAC mix is twice that of the AASC mixes. CONCLUSIONS : It was found that the MSAAC mix exhibits significantly better performance than AASC mixes, based on various fundamental properties.

• Economic and Environmental Geology
• /
• v.41 no.1
• /
• pp.133-144
• /
• 2008

The outputs from the fundamental research program of the Korea Institute of Geoscience and Mineral Resources (KIGAM) were analyzed using the research budget and manpower as input variables. The analysis was performed based on the research outputs of the past 3 years (FY2004 to 2006). More articles and patents came out in applied and development research areas among the geosciences fields. The statistical analysis indicates that each sub-field has different characteristics in research outputs. Research articles, patents, and research budget increase as the manpower increase. But research articles and patents do not always show positive relations to research budget.

• Journal of Digital Convergence
• /
• v.18 no.4
• /
• pp.251-262
• /
• 2020

The study was conducted to investigate factors influencing satisfaction in major on nursing students. A convenience sample 159 nursing student was selected from G do and C do, between 17 June and 24 June 2019. Data were analyzed t-test, one-way ANOVA, Pearson's correlation, and multiple regression analysis. Factors that influenced satisfaction in major included gender, age, religion, perceived academic achievement, acquisition of fundamental nursing skills(FNS), perceived health state. Satisfaction in major showed a positive correlation with learning self-efficacy(LSE), confidence in performance of FNS and satisfaction with practicum. These variables revealed regression analysis that significant factor and explained 63.0% of the variance. It is necessary to develop and test programs to ensure an improvement in LSE, confidence in performance of FNS and satisfaction with practicum among nursing students to increase their satisfaction in major.

• Korean Parent-Child Health Journal
• /
• v.11 no.1
• /
• pp.61-72
• /
• 2008

This study is a descriptive research attempted to examine the exercise practice of junior high school students and figure out their changing process, decision-making balance, and self-efficacy according to the exercise practice so that they can be utilized as fundamental data for developing exercise intervention programs for junior high school students. The study subjects were students from five junior high schools in B City. Total 600 questionnaires were distributed, and 554 responded ones were analyzed. The collected data were analyzed using SPSS/Win 10.0. According to the results of analyzing the subjects with the exercise changing stage tool, exercise non-practice group including the precontemplation stage, contemplation stage, and preparation stage occupies 57.6% while the exercise practice group including the action stage and maintenance stage consists of 42.4%. And according to the results of discriminating analysis setting total 10 factors of transtheoretical model variables as predictive factors to predict each group based on whether they practice exercise or not, it was found out that the subordinate factors of the changing process, consciousness-raising (F=33.98, p=.000), self-cognitive decision (F=21.55, p=.000), contrary condition provision (F=84.67, p=.000), helping relationship (F=28.52, p=.000), reinforced thinking (F=14.15, p=.000), and stimulus control (F=54.64, p=.000), and the subordinate factors of the decision-making balance, beneficial factors (F=15.65, p= .000) and hindering factors (F=8.58, p=.004), and self-efficacy (F=78.60. p=.000) were significant predictive factors and discriminating variables. Based on the research findings above, it will be necessary to develop exercise intervention programs sufficiently reflecting the changing process, decision-making balance, and self-efficacy suitably for the subjects and make strategies to encourage their active participation and exercise maintenance, through verifying transtheoretical model variables according to whether the junior high school students practice exercise or not.

• The Mathematical Education
• /
• v.59 no.1
• /
• pp.47-62
• /
• 2020

Understanding the concept of probability distribution becomes more important. We considered probabilities defined in the sample space, the definition of discrete random variables, the probability of defined discrete probability distribution, and the relationship between them as knowledge of discrete probability distribution, and investigated the understanding degree of the mathematics preservice teachers. The results are as follows. Firstly, about 70% of preservice teachers who participated in this study expressed discrete probability distribution graphs in ordered pairs or continuous distribution. Secondly, with regard to the two factors for obtaining discrete probability distributions: probability for each element in the sample space and the concept of random variables that convert each element in the sample space into a real value, only 13% of the preservice teachers understood and addressed both factors. Thirdly, 39% of the preservice teachers correctly responded to whether different probability distributions can be defined for one sample space. Fourthly, when the probability of each fundamental event was determined to obtain the probability distribution of the discrete random variables defined in the undefined sample space, approximately 70% habitually calculated by the uniform probability. Finally, about 20% of preservice teachers understood the meaning and relationship of binomial distribution, discrete random variables, and sample space. In relation, clear definitions and full explanations of concept need to be provided from textbooks and a program to improve the understanding of preservice teachers need to be developed.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.2
• /
• pp.185-192
• /
• 2014

Planetary gear design is complex because it involves a combination of discrete variables such as module, integer variables such as the number of teeth, and continuous variables such as face width and aspect ratio. Thus, an optimum design technique is needed. In this study, we applied a genetic algorithm to the design optimization of a planetary gear. In this algorithm, tooth root strength and surface durability are assessed with fundamental variables such as the number of teeth, module, pressure angle, and face width. With the help of this technique, gear designers could reduce trial and error in the initial design stages, thus cutting the time required for planetary gear design.

• Journal of Korean Biological Nursing Science
• /
• v.2 no.2
• /
• pp.53-66
• /
• 2000

Objectives: The studies in biological, behavioral and psychosocial perspectives in nursing research are fundamental in the balanced development of nursing knowledge. Many nursing researchers have placed a strong emphasis on developing psychological and behavioral aspects of nursing knowledge as is evidenced by the large body of research in these areas. However, the paucity of nursing research using the principles of biological science for measurements and techniques have often invited open criticism by many nursing researchers. This study attempts to characterize the researches performed in master and doctoral thesis which used physiological variables. Methods: We analyzed masters' thesis from 1962 to 1996 and doctoral thesis from 1982 to 1996 listed in CD from Korean Nurses Association. Results: Out of 3060 masters' thesis from 1962 to 1996, 342 (11.2%) thesis used physiological variables whereas 43 (10.1%) doctoral thesis used physiological ones. Number of thesis with physiological variables was the highest in Seoul National University for masters' thesis whereas for the doctoral thesis the number was the highest in Yonsei University. The research subjects in these thesis with physiological variables were mostly patients (53.5% in masters' and 69.8% in doctoral). Master's thesis often conducted either nonexperimental or survey research (69.9%) whereas experimental research design prevailed vital signs(181 thesis), blood tests(133), body composition(124), microorganisms(74), gastrointestinal functions(36), lab test(33), drug(21), urinary functions(20), movement(17), Apgar Score(15), reproductive functions(9), skin related functions(6), body fluid and electrolytes(4), parasite(4), metabolism(3), and sensory(1), Among the 338 master' thesis which studied the common nursing concepts such as anxiety, pain, stress, and depression, 48(14.2%) thesis utilized physiological variables while 15 out of 35 doctoral thesis addressed these concepts using physiological variables. Conclusion: In summary, our results indicate that despite the large amount of nursing research performed over the last decades, there are a few nursing researches done with physiological variables either in masters' or doctoral thesis. To enrich nursing knowledge with different perspectives of nursing including especially biological ones, the efforts have to be made to conduct bionursing science research.