• Journal of Korean Elementary Science Education
• /
• v.24 no.5
• /
• pp.531-538
• /
• 2005

The primary purpose of the study was to investigate the degree of difficulty and the causes of the difficulties in science instruction reported by elementary teachers and students. The secondary purpose was to suggest the effective methods to both of them to improve the efficiency of science instruction. For this study, the survey was carried out on 322 students and 156 teachers in the 3rd, 4th, and 5th grades. The questionnaires consisted of interest, difficulty and its factors. The results of this investigation are summarized as follows; 1. Teachers had relatively higher interest than students in science instruction content(textbook). Furthermore, the units that teachers showed interest differed from those that students had. This means that there is a significant difference of interest in instruction process between teachers and students. 2. Teachers felt much higher difficulty than students in the content of science instruction. This shows that the degree of interest might have little relation with that of difficulty, and that teaching of science seemed more difficult than teaming. Moreover, there was a difference of difficulty in the units between the teachers and students. The result shows a distinctive difference of difficulty in 8 units of the 3rd grade, 9 units n the 4th grade, and 12 units in the 5th grade (p<.05, p<.001, p<.005, respectively). It means that the difficulty depended on the units. 3. Students responded that they are responsible for difficulty factors of teaming, otherwise teachers thought that students are responsible for it, when the factors were divided into student factor, teacher factor, and curriculum factor. 4. Students demanded many experiments in the lab as well as easy and interesting instructions in order to reduce the degree of difficulty and to improve the condition of science instructions. However, teachers demanded the expansion of experimental equipments and materials as well as the improvement of the lab condition.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.57 no.4
• /
• pp.85-99
• /
• 2015

It is urgent to redevelop the superannuated reservoir levee through the levee raising for countermeasure to climate change and improvement of storage capacity of reservoir. However, low compaction degree of the raised reservoir levee owing to poor construction condition leads to degradation of the stability of the reservoir levee on seepage and earthquake. In this study, seepage and seismic behavior of raised reservoir levee with low compaction degree was evaluated through numerical simulation. From the simulated results, water level raising possibly induces crack and/or sinkhole on the surface of the poorly-compacted raised reservoir levee owing to the increase of the subsidences at the crown and the front side of that. In addition, relatively larger displacement and acceleration response at the front side of raised reservoir levee in seismic condition may degrade overall stability of reservoir levee. Therefore, reasonable construction management for the compaction of the raised reservoir levee is required for ensuring long-term stability on seepage and earthquake.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.18 no.5
• /
• pp.615-621
• /
• 1994

This study was carried out to investigate the effect of clothing habit on physiological adaptation to the change of season. The survey of clothing weight in fall '||'&'||' winter for 2 years, the frequency of cold infection in winter and degree of fatigue was performed with 110 female high school students. The actual condition of clothing and the correlations between clothing weight and cold infection, and between the clothing weight and degree of fatigue were suveyed. The results are followed as; 1. The clothing insulation was nearly same to indoor standard clothing insulation in H hun wearing normal clothing, but was higher 2 clo in S hun clothed uniform. Especially in spite of similar enviromental condition the clothing weight, minimum '||'&'||' maximum and variation of clothing weight for 2 years were showed to be heavier in S hun than H hun. Also indoor thermal sensation felt by the subjects indicated "cold", and the difference between clothing insulation and standard clothing insulation showed increase gradually. 2. L group was indicated to be lower in cold infaction ratio than M '||'&'||' H group, and the correlation between clothing group and cold infection ratio was recognized to be significant (p<0.05). And H hun and L-H group showed to be lower in cold infection ratio than S hun, H-L group. 3. The coefficience between clothing weight and degree of fatigue was recognized to be significant (p<0.05).

• Computers and Concrete
• /
• v.19 no.1
• /
• pp.69-78
• /
• 2017

This study aimed at exploring the effect of presoaking degree of lightweight aggregate (LWA) on the fresh and hardened properties of concrete. Two series (i.e., Series A and Series B) of concrete mixes that were made of LWA with different moisture states were prepared. The presoaking degree of LWA was divided into three types: oven dry state, 1 hour prewetted and 24 hours prewetted. For the Series A, the water content of the lightweight aggregate concrete (LWAC) mixes was adjusted in accordance with the moisture condition of the LWA. Whereas the amount of water added in the Series B mixes was deliberately not adjusted for the moisture condition of the LWA. Slump test, mechanical tests, interfacial transition zone microscopical tests and thermal conductivity test were carried out on the specimens of different concretes and compared with control normal-weight aggregate concretes. The test results showed that the effect of mixing water absorption by LWA with different moisture states was reflected in the fresh concrete as the loss of mixture workability, while in the hardened concrete as the increase of its strength. With the use of oven-dried LWA, the effect of reduction of water-cement ratio was more significant, and thus the microstructure of the ITZ was more compact.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 1993.10a
• /
• pp.1254-1263
• /
• 1993

Representing knowledge uncertainty , aggregating evidence confidences , and propagation uncertainties are three key elements that effect the ability of a rule-based expert system to represent domains with uncertainty . Fuzzy set theory provide a good mathematical tool for representing the vagueness associated with a variable when , as the condition of a rule , it only partially corresponds to the input data. However, the aggregation of ANDed and Ored confidences is not as simple as the intersection and union operators defined for fuzzy set membership. There is, in fact, a certain degree of compensation that occurs when an expert aggregates confidences associated with compound evidence . Further, expert often consider individual evidences to be varying importance , or weight , in their support for a conclusion. This paper presents a flexible approach for evaluating evidence and conclusion confidences. Evidences may be represented as fuzzy or nonfuzzy variables with as associat d degree of certainty . different weight can also be associated degree of certainty. Different weights can also be assigned to the individual condition in determining the confidence of compound evidence . Conclusion confidence is calculated using a modified approach combining the evidence confidence and a rule strength. The techniques developed offer a flexible framework for representing knowledge and propagating uncertainties. This framework has the potention to reflect human aggregation of uncertain information more accurately than simple minimum and maximum operator do.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.3
• /
• pp.582-589
• /
• 1988

A rapid expansion of moist air or steam in a supersonic nozzle gives rise to condensation, and the total pressure of the flow is decreased due to this irreversibility of condensation phenomenon. In the present paper, the loss in total pressure during the condensation process has been studied, by numerical analysis and pressure measurement, in the case of moist air expanding in a supersonic nozzle. The effects of the degree of supersaturation at the stagnation condition and expansion rate of the nozzle on the total pressure loss have been studied. The length of the region where the total pressure decreases during the condensation process is longer than that of the nonequilibrium condensation region, and of difference between the length of these two increases with the increase of the degree of supersaturation at the stagnation condition. Furthermore, the larger the expansion rate of the nozzle and the higher the temperature and the degree of supersaturation at the reservoir are, the larger the total pressure loss of the flow becomes. And, it is turned out that the total pressure loss be about 2 to 8 percent in the present study.

• Journal of KSNVE
• /
• v.10 no.5
• /
• pp.775-782
• /
• 2000

Being carried out a number of studies for the resilient mounting system of automobile engine than that of the studies for marine engines, many research results for the case of the resilient mounting system of the automobile engine have applied in the analysis for the case of marine engine. However, the size and the power of automobile engines are not only relatively small but also their operating conditions are quite different form those of marine engines. For the analysis of the automobile engine Wavelet shrinkage, misfire condition and unload condition have not been considered. Accordingly , it is not desirable to apply the results obtained form the case of automobile engines to the case of marine engines. In this study , exciting and damping forces working on the marine engine are formulated mathematically in order to apply to the design of a resilient mounting system of engine effectively. futhermore, some mathematical formulation for the analysis of the transmissibility of multi-body system are proposed. A new computer program which is able to calculate the free vibration, the transmissibility and the forced vibration of a resilient mounting system has been developed, As an application of this developed computer program, the dynamic behavior of resilient system with an actual rubber spring for the case of 6-degree-of-freedom system and 36-degree-of-freedom system are evaluated quantitatively.

• Journal of the Korea Society of Computer and Information
• /
• v.22 no.7
• /
• pp.109-115
• /
• 2017

This study was performed to investigate the changes in turnover intention according to the level of occupational stress and to find the mediating factor that reducing the turnover intention among fire officer. To compare change of turnover intention according to the degree of occupational stress, statistical analyses were done by using the logistic regression model. In logistic regression analysis, the possibility of high turnover intention in a group with high occupational stress was hjgher by 4.11 times than a group with low occupational stress. The results of analyzing the degree of change in turnover intention after applying the mediating parameters(physical condition, emotional labor, burn out), turnover intention decreased by about 50.6%(from 4.11 times to 2.03 times) at the high level of occupational stress. As a result, it was found that the occupational stress experienced by the fire-officers had a positive effect on the turnover intention. In order to reduce the turnover intention due to the occupational stress of the fire-officers, it is necessary to manage factors such as work environmental factors(emotional labor, burn out) and individual factor(physical condition).

• Fashion & Textile Research Journal
• /
• v.22 no.4
• /
• pp.523-533
• /
• 2020

Previous studies are used to examine cellulose content, degumming period, fiber quality, production yield, production cost, development limit of fiber according to physical, chemical, and microbial degumming methods. Three types of degumming methods are used to measure surface condition after degumming, necessity of additional degumming and degree of impurity removal. First, previous studies confirmed that the microbial degumming method is superior in terms of cellulose content, fiber quality, production yield, production cost, and fiber development possibility. Second, surface condition and the necessity of additional degumming were analyzed by SEM. The black skin binding material was removed in the case of the Sangnangyi and chemical degumming; however, it was insufficient and further degumming was required. Skin fiber binding material was removed in the case of microbial degumming and the surface was cleanest after degumming; in addition, most showed the form of yarn decomposition. The FT-IR spectrum determined the degree of removal of impurities and showed that it can utilize inherent physical properties as the best degumming method. The degree of removal of pectin and lignin by microbial degumming was cleanest with hemicellulose also reduced by microbial degumming.

• Proceedings of the KIEE Conference
• /
• 1994.11a
• /
• pp.261-263
• /
• 1994

This paper deals with the on off arc characteristics of electromagnetic relay contacts contaminated by NaCl and $H_2SO_4$. In this paper, I have studied the characteristics of on-off voltage waveform. the contact errosion, contact surface analysis by SEM and EDAX under changed R-L parameter of testing circuit. After considers these result, I have tried to promote the diagnosis method and developed the contacts. As a results, (1) The arc duration and the numbers of arc occurrence characteristics are depended on contamination degree. The contamination degree is high when the arc characteristics is high. (2) Under clean condition, arc occurrence voltage, surge peak voltage, arc duration and the rate of contact errosion is lower than wet condition. (3) Surge peak voltage and arc duration is depended on L parameter. When L is High, the arc characteristics is high.