• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.2
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• pp.120-132
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• 1993

A continuous hollow fiber membrane reactor(CHFMR) was developed and optimized for the production of yellowfin sole(Limanda aspera) skin gelatin hydrolysates using trypsin. The results were summerized as follows: The $K_m$ value of the CHFMR was 2.4 times higher than that of the batch reactor, indicating reduced enzyme affinity for the substrate. The $K_2$ value of the CHFMR was 8.5 times lower than that of the batch process, showing a significant reduction in trypsin activity in the CHFMR. The optimum operating conditions for the CHFMR process were $55^{\circ}C$, pH 9.0, flux 7.79 ml/min, residence time 77min, and trypsin to substrate ratio, 0.01(w/w) After operating for 60min under the above conditions, $79\%$ of the total amount of initial gelatin was hydrolysed. Enzyme leakage was observed through the 10,000 MWCO membrane after the 20min of reactor operation, while none occurred after 5hr. Total enzyme leakage was about $12.95\%$ at $55^{\circ}C$ for 5hrs. However, there was no apparent correlation between enzyme leakage and substrate hydrolysis. The membrane has a significant effect on trypsin activity loss for 60min of the CHFMR operation. The CHFMR operating with the membrane lost $34\%$ of the initial activity versus a $23\%$ loss of activity after 3hr in the continuous reactor lacking the hollow fiber membrane. The measurement of fouling property showed that relative flux reduction was $91\%$ and flux recover rate was $92\%$ at $10\%$ substrate solution. The productivity(378.85mg product/mg enzyme) of the CHFMR was more than 4 times higher than that of the batch reactor at $55^{\circ}C$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.10
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• pp.829-841
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• 1990

On assuming that the transmission speed of the original information is the fifth-order transmission speed of the Korea digital multiplex hierarchy (564.992Mb/s), this paper proposes a new structure of the transmission line frame at the terminal repeater system, in order to not only maintain and conserve 565Mb/s optical fiber transmission system but also make the B.S.I. of digital communication network for the optical transmission. And the structure uses the mBIZ transmission line code, which is considered the optimal transmission line code of conventional transmission line codes. System hardware of the transmission line frame structure proposed in this paper is consisted by a method of pulse stuffing after converting the speed of the original information signal sequence at the terminal repeater system for 565Mb/s optical transmission. As a result of this, we can prevent the optical transmission system from a domino phenomenon, the phenomenon of the continuous error multiplication of systems by the transmission error, and suppress timing jitter and the identical consecutive digit number. And also we can improve SNR of the optical transmission system about 2dB because of raising total BER at the optical terminal system up to 10.

• Composites Research
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• v.26 no.4
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• pp.245-253
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• 2013

In this paper, we developed a theoretical model which is able to predict the tensile strength and elastic modulus of hybrid composites reinforced by two types of randomly distributed discontinuous reinforcements. For this, we considered two known models; One is a prediction model based on the assumption that the composite is reinforced by two types of well aligned continuous reinforcements. The other is a statistical model for the composite which is reinforced by only one type of randomly distributed discontinuous reinforcements. In order to evaluate the validity of accuracy of our prediction model, we measured the strength and elastic modulus of polypropylene hybrid composite reinforced by talc and short glass fiber. We found that the present model drastically enhances the accuracy of strength prediction compared to an existing model, and predicts the elastic modulus within the same order with experimentally measured values.

• Journal of the Korean Wood Science and Technology
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• v.40 no.3
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• pp.156-163
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• 2012

This research has been carried out to investigate the characteristics of cellulose nanofibers manufactured from domestic lignocellulosic materials by mechanical grinding method. The continuous grinding process was effective for loosening cell wall structure, with increasing grinding time, much smaller nanofibers were observed. Filtration time was linearly increased with increasing grinding time for all experimental materials. Relative crystallinity of cellulose was not changed by grinding process, but increased by delignification treatment. Tensile property of fiber sheets was drastically improved with increasing grinding time. Fibers sheets obtained from delignified cone stalks showed an excellent tensile strength. Consequently, it is considered that this study presented some effective information for manufacturing cellulose nanofibers with domestic plantation resources.

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.4
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• pp.278-291
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• 1998

Fracture process of continuous fiber reinforced composites is very complex because various fracture mechanisms such as matrix cracking, debonding, delamination and fiber breaking occur simultaneously during crack growth. If fibers cause crack bridging during crack growth, the stable crack growth and unstable crack growth appear repeatedly. Therefore, it is very difficult to exactly determine tile starting point of crack growth and the fracture toughness at the critical crack length in composites. In this research, fracture toughness test for CFRP was accomplished by using acoustic emission(AE) and recording of tile fracture process in real time by video-microscope. The starting point of crack growth, pop-in point and the point of unstable crack growth can be exactly determined. Each fracture mechanism can be classified by analyzing the fracture process through AE and video-microscope. The more reliable method ior the fracture toughness measurement of composite materials was proposed by using the combination of R-curve method, AE and video microscope.

• Journal of the Korean Society of Clothing and Textiles
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• v.25 no.1
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• pp.173-182
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• 2001

The physical properties and biodegradability of cellulose fabrics, such as cotton and rayon, are expected to vary with textile care. In this study cotton and rayon fabrics were washed repeatedly with detergents, bleaches, or softeners. The changes of physical properties were investigated by measuring retention of breaking strength, shrinkage, handle, and the fiber surface was observed by SEM. The biodegradability of fabrics was also estimated by soil burial test. The results were as follows. Cotton fabrics laundered repeatedly by detergents and bleaches lost virtually no strength. The breaking strength of the rayon fabrics decreased by about 17%∼25% after repeated launderings. Shrinkage in weft direction was much larger than that in warp direction. Bending rigidities of both fabrics decreased remarkably within 10 wash cycles. Shear rigidity in cotton fabrics increased continuously with repeated washing cycles, however, that in rayon fabrics did not show any change as washing went on. Friction coefficient increased in both fabrics after 10 wash cycles, and this is thought to be attributed to the wrinkle, interlocking of hairs, surface damage resulted from repeated washings. In cotton fabrics made of staple yarns, short hairs on the yarn surface entangled together with repeated launderings. This resulted in the continuous increase in % shrinkage, shear rigidity, friction coefficient. Rayon fabrics made of filament yarns, however, did not show this phenomenon. Softener treated fabrics showed the lowest values in bending rigidity, shear rigidity and friction coefficient because the cationic surfactants adsorbed on the fiber surface behaved like lubricants. The biodegradability of fabrics was noticeably affected by the composition of washing solutions. The fabrics washed with detergents and bleaches were decomposed faster than those washed with the others were and the cotton fabrics washed with detergents and softeners hardly degraded. The fabrics soiled with milk were decomposed almost completely and those soiled with Palmitic acid did not degrade greatly.

• Composites Research
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• v.14 no.2
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• pp.8-12
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• 2001

Filament Winding Process is a comparatively simple operation in which continuous reinforcements in the form of roving are wound over a rotating mandrel. It is well established and versatile method for storage tanks and pipes for the chemical and other industries. In this study, tensile strength of a filament wound ring specimens were evaluated by a split disk test fixture and a dress disk test fixture. The results obtained from experiments were compared with the theoretical values from the rule of mixtures. The purpose of this paper is the suggestion of an appropriate test method for the evaluation of tensile properties of filament wound structures. The tensile strength of a ring specimen tested by the dress disk test showed better agreement with the theoretical values than those tested by the split disk test because of higher stress concentration in edges of a split disk test fixture. The results showed that the tensile strength of a ring specimen was influenced by the geometry of test fixture, the continuity of fibers, fiber-tension, fiber-end and stress concentration in specimen.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.5
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• pp.73-81
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• 2017

The improved movable weir supplements the advantages and disadvantages of the rubber weir and the conduction gate. It consists of a stainless steel gate, air bags, and a steel clamping plate. The stainless steel gate is the main body of the weir, and the inflatable rubber sheet serves to support the steel gate. The steel clamping plate is typically in direct continuous contact with water, but this leads to corrosion issues that can reduce the life of the entire movable weir. In this study, a panel-type glass-fiber-reinforced polymer (GFRP) clamping plate was designed and fabricated. The test results showed that the flexural load of the panel-type GFRP composite clamping plate was over twice that of the wings type GFRP clamping plate. The lowest moisture absorption value was obtained upon exposure to tap water, and exposure to other solutions showed similar values. Additionally, flexural load testing after exposure to an accelerated environment found the lowest residual loads of 80.51 % and 78.50 % at 50 and 100 days, respectively, for exposure to a $CaCl_2$ solution, while exposure to other environments showed residual failure loads of over 80 % at both 50 and 100 days.

• The korean journal of orthodontics
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• v.21 no.3
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• pp.635-656
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• 1991

It was the aim of this investigation to evaluate some histologic aspect of rat pulp tissue after it had been compromised by an experimental orthodontic force. Experimental animals of thirty five Spraque-Dawley rats were employed. The first upper molars had been successively mesial moved (initial load 100 gr.) with a closed coil spring during 21 days. The experimental periods were set on immediate, 1 day, 1 week, 2 weeks, 3 weeks, 4 weeks following retention time. On each experimental period, the rats were killed and prepared for the light microscopy. After prepared with H/E stain and Gomori's one-step trichrome stain, the specimens were analyzed with evaluation criteria which were adopted in this study. The result may be summarized as follows; 1. The main pulp changes due to experimental orthodontic force included vacuolization of odontoblastic layer, circulation disturbance, root resorption, reduced pulp collagenous fiber density and mean cell count of pulp fibroblast in the immediate group. 2. The pulp tissue changes were revealed reversible because the relieved pulp tissues from experimental orthodontic force were recovered rapidly in each evaluation criteria during retention periods. 3. Compared with normal control group, pulp collagenous fiber density were decreased in immediated group (p < 0.01), but increased in each retention groups. These seem to suggest that the pulp tissues were aged after experimental orthodontic force conditions. 4. Compared with normal control group, mean cell counts of pulp fibroblasts were decreased in immediate group (p < 0.05), but increased continuous in each retention groups. These seem to indicate that the pulp tissues were highly regenerative after experimental orthodontic force conditions. 5. Compared with normal control group, root resorptions occurred in all immediate specimens (p < 0.01) and they were healed in each retention periods, but often observed in 4 weeks retention group. These seem to indicate that root resorptions were recovered slowly after experimental orthodontic force conditions.

• Polymer(Korea)
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• v.27 no.1
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• pp.61-68
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• 2003

In this study, we have investigated the preparation of mixed bead and fiber type hybrid ion-exchanger for recovering nickel ion from plating rinse water. There was little dependence of adsorption capacity for nickel ion on the mixing ratio of resin type and fiber type of ion exchangers. However, it increased with increasing the resin content in the mixed bed. It was shown that the data Langmuir and Freundlich's adsorption isotherm model were well fitted to the linear. Affinity between the functional groups in the ion exchanger and nickel ion in the process was confirmed. The pressure drop decreased with increasing the number of stage in the multistage bed, but it increased with increasing the resin content in the mixing bed. The initial breakthrough time in the multistage bed was short due to the increase of number of stage in the continuous process. It was found that the final breakthrough time of the multistage bed was little changed. The breakthrough time decreased with increasing the amount of fibrous ion exchanger in the mixed bed. The maximum adsorption capacities of the mixed and multistage beds were 2.51 meq/g and 2.69 meq/g, respectively. The desorption time for the nickel ion with $1N H_2SO_4$ solution was lower than 10 minutes and the yield of desorption was greater than 98 percent.