• Carbon letters
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• v.10 no.3
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• pp.202-207
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• 2009

Pitch-based carbon fiber tows were prepared from naphtha cracking bottom oil by reforming and carbonization. The relationship between exothermic heat and carbon contents of the fiber was investigated by changing the carbonization conditions. The carbon contents and the crystallinities of isotropic pitch-based carbon fibers were 86.8~93.8 wt% and 33.7~40.1%, respectively, which were linearly proportional to the increase of carbonization temperature from 700 to $1000^{\circ}C$. The exothermic heat (temperature increase) of fiber tows was measured in a short time, which was also linearly proportional to the increase of carbon contents due to the increase of crystallinity, even though the crystallinity was low. Therefore, the carbon contents or carbonization degree of fibers can rapidly and indirectly be estimated by measuring the surface temperature increase of fibers.

• Carbon letters
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• v.10 no.4
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• pp.339-344
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• 2009

Henequen fiber was air-stabilized, carbonized, and steam-activated to obtain high surface area activated henequen fiber (AHF). Thermal behavior of henequen fibers has been studied by TGA. The structural morphology and characteristics were observed by SEM and BET surface area measurement. The yield of AHF from natural henequen was in the range of 20~25 wt%. Mesopores (2~2.5 nm) were developed on the AHF as the activation temperature was raised up to $700^{\circ}C$, and the band of mesopore size distribution moved to 15~30 nm when the activation were carried out at $900^{\circ}C$ for 30 min. The specific surface area and the total pore volume were about $1394\;m^2/g$ and $1.30\;cm^3/g$, respectively at this activation conditions.

• Carbon letters
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• v.11 no.2
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• pp.131-136
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• 2010

Propellant waste was impregnated on the surface of activated carbon fiber and heat-treated at different temperature to introduce newly developed functional groups on the ACF surface. Functional groups of nitrogen and oxygen such as pyridine, pyridone, pyrrol, lacton and carboxyl were newly introduced on the surface of modified activated carbon fiber. The porosity, specific surface area, and morphology of those modified ACFs were changed as increasing the heat-treated temperature from 200 to $500^{\circ}C$. The optimum heat-treatment temperature was suggested to $500^{\circ}C$, because lower temperature given rise to the decrease of specific surface area and higher temperature resulted in the decrease of weight loss. Propellant waste can be used as an useful surface modifier to porous carbons.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.33.5-33
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• 2001

We consider here the problem of spectral estimation of multidimensional wide sense stationary (WSS) random process. A method, employing a special difference equation of correlation function, is proposed to solve the problem of multidimensional spectral estimation. In this approach, the special difference equation of correlation function is derived by modal decomposition method. Maximum likelihood estimator and Kalman filter are used to estimate the model parameters of the difference equation and the decomposed spectral residues. An algorithm is presented to estimate the multidimensional spectral density. According to the result of the simulation, these methods are feasible to estimate the spectral density of WSS process, which is realized by finite dimensional multivariable lineal system driven by white noise.

• Spatial Information Research
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• v.2 no.2
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• pp.219-224
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• 1994

The construction of digital map which is the basis of GIS becomes more important. The digital map is made up of image, numeric, and character data. The development of mapping system which makes the data inputted easily is important. In this paper interactive map¬ping system is introduced, which is currently developed. Also, map data structure is seriously discussed. The points of improvement on this system are considered.

• Journal of applied mathematics & informatics
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• v.20 no.1_2
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• pp.327-343
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• 2006

A general methodology is suggested to solve shelf-space allocation problem of retailers. A multi-item inventory model of breakable items is developed, where items are either complementary or substitute. Demands of the items depend on the amount of stock on the showroom and unit price of the respective items. Also demand of one item decreases (increases) due to the presence of others in case of substitute (complementary) product. For such a model, a Contractive Mapping Genetic Algorithm (CMGA) has been developed and implemented to find the values of different decision variables. These are evaluated to have maximum possible profit out of the proposed system. The system has been illustrated numerically and results for some particular cases are derived. The results are compared with some other heuristic approaches- Simulated Annealing (SA), simple Genetic Algorithm (GA) and Greedy Search Approach (GSA) developed for the present model.

• Research in Mathematical Education
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• v.13 no.1
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• pp.31-48
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• 2009

Utilizing the path analysis method, the study explores the relationships among the influential factors in mathematics modeling academic achievement. The following conclusions are drawn: 1. Achievement motivation, creative inclination, cognitive style, the mathematical cognitive structure and mathematics modeling self-monitoring ability, those have significant correlation with mathematics modeling academic achievement; 2. Mathematical cognitive structure and mathematics modeling self-monitoring ability have significant and regressive effect on mathematics modeling academic achievement, and two factors can explain 55.8% variations of mathematics modeling academic achievement; 3. Achievement motivation, creative inclination, cognitive style, mathematical cognitive structure have significant and regressive effect on mathematics modeling self-monitoring ability, and four factors can explain 70.1% variations of mathematics modeling self-monitoring ability; 4. Achievement motivation, creative inclination, and cognitive style have significant and regressive effect on mathematical cognitive structure, and three factors can explain 40.9% variations of mathematical cognitive structure.

• Research in Mathematical Education
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• v.17 no.3
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• pp.153-167
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• 2013

Mathematics has been stereotyped as a male-dominated subject, and there is considerable evidence to support this belief. There has been much research in the past three decades on gender-related differences in elementrny and secondrny school mathematics. The research found that teachers possess different beliefs about male and female students that influence their teaching behaviour, which then directly or indirectly impact their students' behaviours, beliefs, and achievements in mathematics. Based on data collected from teacher questionnaire surveys in the Chinese Mainland and Hong Kong, this study examines teachers' beliefs about the achievements of boys and girls in mathematics. The study also compares the findings in the two regions surveyed. Results showed that teachers gave more attention to boys than girls, regardless of the teacher's gender. Not only are teachers more likely to recall more boys than girls, but also more boys than girls with average academic standards.

• Journal of the Korean Society of Costume
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• v.25
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• pp.41-62
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• 1995

This research was intended to investigate how risk perception and risk reduction behavior by consumers differ according to different product characteristics of clothing. The responses of 318 female college students living in Seoul and surrounding vicinities were collected and analyzed. Inner wear, blue-jean pants, coat were selected as representing each clothing product characteristics. Frequencies distribution, regression and correlation coefficient were utilized for statistical analysis. Results are as follows. 1. The type of perceived risk and risk reduction behavior differed according to product characteristics of clothing. Physical and performance risk were more highly perceived for the purchase of innerwear. However, for the purchase of jean pants and coat, socio-psycho-logical and economic risk were also perceived highly because the rate of fashion change, social symbolism, and coordination with other clothing items become more important characteristics. To reduce perceived risk, dependency on past purchase experiences and shop-ping were mostly preferred method regardless of product characteristics of clothing. 2. Risk type as determinant variables for predicting overall risk differed according to product characteristics of clothing. But fashionability and usefulness were common determinant risk variables, which identifies typical characteristics of clothing product.

• Research in Mathematical Education
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• v.14 no.1
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• pp.79-98
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• 2010

To analyze the relationships between self-control, thinking quality and mathematical academic achievement, 197 senior school students were asked to complete questionnaires called "self-control ability on mathematics for middle school students" and "thinking quality for senior school students." The results were as follows: (1) There was strongly positive relevance between self-control ability, thinking quality and mathematical academic achievement. (2) A model was presented in which self-control ability had a direct impact on mathematical academic achievement, meanwhile had indirectly influenced mathematical academic achievement by thinking quality which acted as the intermediate variable. Thinking quality had a direct impact on mathematical academic achievement, too. (3) There's no significant difference between the two groups of boys and girls on the structural weights.