• Carbon letters
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• v.12 no.3
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• pp.131-137
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• 2011

Kenaf fibers, cellulose-based natural fibers, were used as precursor for preparing kenafbased carbon fibers. The effects of carbonization temperature ($700^{\circ}C$ to $1100^{\circ}C$) and chemical pre-treatment (NaOH and $NH_4Cl$) at various concentrations on the thermal change, chemical composition and fiber morphology of kenaf-based carbon fibers were investigated. Remarkable weight loss and longitudinal shrinkage were found to occur during the thermal conversion from kenaf precursor to kenaf-based carbon fiber, depending on the carbonization temperature. It was noted that the alkali pre-treatment of kenaf with NaOH played a role in reducing the weight loss and the longitudinal shrinkage and also in increasing the carbon content of kenaf-based carbon fibers. The number and size of the cells and the fiber diameter were reduced with increasing carbonization temperature. Morphological observations implied that the micrometer-sized cells were combined or fused and then re-organized with the neighboring cells during the carbonization process. By the pre-treatment of kenaf with 10 and 15 wt% NaOH solutions and the subsequent carbonization process, the inner cells completely disappeared through the transverse direction of the kenaf fiber, resulting in the fiber densification. It was noticeable that the alkali pre-treatment of the kenaf fibers prior to carbonization contributed to the forming of kenaf-based carbon fibers.

• Applied Chemistry for Engineering
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• v.8 no.5
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• pp.853-859
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• 1997

For asymmetric polyetherimide membranes having a dense layer gradient structure on the skin layer, the morphology change and pervaporation behaviors of water/isopropanol mixture through chemical modification of dense skin layer were investigated. The extent of the density was controlled by the evaporation, time, and when the evaporation time was increased from 0 min to 4 min, the permeation flux was decreased, the separation factor was increased. Also, the pervaporation behaviors of the polyetherimide membranes modified with sodium hydroxide solution, as the modification time of dense skin layer increased, the selectivity increased, and the permeation flux decreased. The morphology change identified by SEM shows that the density of dense skin layer tends to increase with increasing modification time, this result is consistent with above observations.

• Journal of Dairy Science and Biotechnology
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• v.24 no.2
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• pp.55-60
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• 2006

The common recognition which the organic baby foods is compared as safe to baby does not mean there is especially plentiful nutrition in organic product. Because the mineral content of agricultural products is partly influenced by the soil quality, chemical fertilizer may change the mineral contents of the products. In that case, it may result in the possibility of the change of the contents of the agricultural vegetable products. However, the contents and the compositions of vitamin, carbohydrate, protein and fatty acids does not change largely from their original nutrition facts of the organic foods. The most advantage of organic baby foods seems to protect the agricultural products from the possibility of chemical contamination. It must be the most strong desire of all the consumers to provide and to nurse their babies with the high quality of baby foods made from organic food materials which are safe, reliable and healthier. That would also be a sincerely good way for the environment and ecosystem of the world.

• Carbon letters
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• v.5 no.1
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• pp.18-22
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• 2004

The failure behaviours of unidirectional pultruded carbon fiber reinforced polymer (CFRP) composites were monitored by the electrical resistance measurement during tensile loading, three-point-bending, interlaminar shear loading. The tensile failure behaviour of carbon fiber tows was also investigated by the electrical resistance measurement. Infrared thermography non-destructive evaluation was performed in real time during tensile test of CFRP composites to validate the change of microdamage in the materials. Experiment results demonstrated that the CFRP composites and carbon fiber tows were damaged by different damage mechinsms during tensile loading, for the CFRP composites, mainly being in the forms of matrix damage and the debonding between matrix and fibers, while for the carbon fiber tows, mainly being in the forms of fiber fracture. The correlation between the infrared thermographs and the change in the electrical resistance could be regarded as an evidence of the damage mechanisms of the CFRP composites. During three-point-bending loading, the main damage forms were the simultaneity fracture of matrix and fibers firstly, then matrix cracking and the debonding between matrix and fiber were carried out. This results can be shown in Fig. 9(a) and (b). During interlaminar shear loading, the change in the electrical resistance was related to the damage degree of interlaminar structure. Electrical resistance measurement was more sensitive to the damage behaviour of the CFRP composites than the stress/time curve.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.33 no.5
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• pp.1-11
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• 2001

In the past, abundant and clean water was available for paper mills'use. However, the growth of population and industry made water less available nowadays. Also, environmental regulation limits wastewater discharge, which affects mill operation cost. Therefore, paper mills are under pressure to use more recycled water and mill system closure. As a result, chemical and physical parameters of water are changing and new environment if being created for microorganisms in paper mill system as well. The more soluble or suspended organic materials are increased as more water is recycled and less or scarce dissolved oxygen is available, depending on the degree of recycled water usage. Microorganism flora ill paper mill system will be a1so shifted according to the environmental change of mill system. Anaerobic bacteria, including sulfate reducing bacteria (SRB), will be dominant in the system as very low or almost no oxygen available in the system. Nevertheless, it is common in domestic paper mills that employ the same and old biocides as a means of microbial control, and microbiological control is often less recognized or even neglected. The right biocide selection for increased reductive environment of mills is critical for operation and estimated loss from paper quality defects such as sheet break, holes due to microbiological cause is tremendous compared to the microbiological control cost. It is imperative to investigate and diagnosis the environmental change of mills for right control of cumbersome microorganisms. Several useful diagnosis tools, including new technology employing OFM(Optical Fouling Monitor) in situ, are illustrated.

• Korean Chemical Engineering Research
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• v.43 no.5
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• pp.571-578
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• 2005

We propose a new optimization framework for the reactive scheduling. The proposed rescheduling scheme is specially focused on how to generate rescheduling results when equipment failure occurs. The approach is based on a continuous-time problem representation that takes into account the schedule in progress, the updated information on the batches still to be processed, the present plant state, the deviations in plant parameters and the time data. To update the predictive scheduling, we used right shift rescheduling and total regeneration when equipment failure occurs. And, a practical solution to the rescheduling problem requires satisfaction of two often confliction measures: the efficiency measure that evaluates the satisfaction of a desired objective function value and the stability measure that evaluates the amount of change between the schedules before and after the disruption. In this paper, the efficiency is measured by the makespan of all jobs in the system. And, the stability is measured by the percentage change in makespan and the modified sequence deviation in the predictive scheduling and rescheduling.

• Journal of Plant Biotechnology
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• v.48 no.4
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• pp.207-222
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• 2021

Coffee is the most frequently consumed functional beverage world wide. The average daily coffee consumption is increasing. This crop, which plays an important role in the global economy is under great threat from climate change. To with stand the current climate change, farmers have to learn crop cultivation techniques, strategies to protect crops from diseases, and understand which type of seed varieties to use to avoid crop loss. The present review briefly discusses the coffee cultivation techniques, impact of climate changes on coffee production, processing techniques of coffee, and the importance of coffee in our society, including its chemical composition and prevention against, major diseases. Furthermore, the importance and role of advanced nanotechnology along with molecular approaches for coffee crop improvement and facing challenges are explained.

• Tribology and Lubricants
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• v.33 no.5
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• pp.228-233
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• 2017

Chemical Mechanical Polishing of chemically stable sapphire substrates is dominantly affected by the mechanical processing of abrasives, in terms of the material removal rate. In this study, we investigated the effect of electrostatic force between the abrasives and substrate, on the polishing. If potassium chloride (KCl) is added to slurry, water molecules are decomposed into $H^+$ and $OH^-$ ions, and the amount of ions in the slurry changes. The zeta potential of the abrasives decreases with an increase in the amount of $H^+$ ions in the stern layer; consequently, the electrostatic force between the abrasives and substrate decreases. The change in zeta potential of abrasives in the slurry is affected by the slurry pH. In acidic zones, the amount of ions bound to the abrasives increases if the amount of $H^+$ ions is increased by adding KCl. However, in basic zones, there is no change in the corresponding amount. In acidic zones, zeta potential decreases as molar concentration of potassium increases; however, it does not change significantly in basic zones. The removal rate tends to decrease with increase in molar amount of potassium in acidic zones, where zeta potential changes significantly. However, in basic zones, the removal rate does not change with zeta potential. The tendencies of zeta potential and that of the frictional force generated during polishing show strong correlation. Through experiments, it is confirmed that the contact probability of abrasives changes according to the electrostatic force generated between the abrasives and substrate, and variation in removal rate.

• Journal of Fashion Business
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• v.12 no.6
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• pp.11-22
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• 2008

The goal of this study is to provide beauticians with the fundamental material to use effectively heat permanent wave in beauty industry as well as their customer's satisfaction. It carried out an experiment with damaged hair of a woman in her late twenties to investigate the change of physical and morphological characteristics by its water content when performing heat permanent wave. After spreading 0g, 1g, 2g, 3g, and 4g of water on damaged hair respectively, heat permanent wave was treated and the change of hair was observed. The change of physical characteristic was compared through permanent wave form of hair, tensile strength and elongation. The change of morphological characteristic was observed through Scanning Electron Microscope(SEM) and Transmission Electron Microscope(TEM). The result of experiment on the physical specificity revealed that permanent wave form was the most ideal when the water content was 2g, also 3g. Though the materials with much moisture content formed the results were not satisfied. The material with 0g of water content didn't make the wave. In terms of tensile strength and elongation, tensile strength was generally reduced as per the damaged degree of hair. On the contrary, elongation was increased. It observed the changes of morphological characteristic that the damage on hair cuticle was deepen, as its moisture content was decreased, and cuticle's surface was worn away. The observation of fine structure on hair section by transmission electronic microscope also certainly showed the result that damaged hair having experience with chemical treatment had got much damaged to hair cuticle as well as hair cortex. Generally chemical treatment makes hair damaged. Under consideration of this aspect, the ultimate goal of this thesis is to minimize the damage of hair caused by chemical treatment and get the satisfaction on the hair style. According to the result of experiment, the damaged hair whose moisture content was 3g showed the best permanent wave form.

• Journal of the Korean GEO-environmental Society
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• v.13 no.3
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• pp.71-76
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• 2012

Since sediment in a stable state is disturbed during the process from sediment in a natural state to dredged soil, the turbidity of water is not good. When the dredged soil settles again, the volume change in the sediment occurs. Coagulant and flocculant are added for turbidity mitigation of the water and faster settling process of suspended solid, and the amount of the substances affects the characteristics of the dredged soil. This study is to investigate the characteristics of the dredged soil depending on the amount of three chemical products added to the wet dredged soil and the dry dredged soil through measuring the suspended solids (SS), volume change and sedimentation velocity. The experimental measurements show that the SS decreased, the volume change rate increased, and the sedimentation velocity increased, as the chemical amount increased. In addition, it was found that the dry dredged soil reacted even with little quantity of the chemicals because derelict and microorganism are removed due to the drying process at $100{\pm}5^{\circ}C$.