• Magazine of the Korean Society of Agricultural Engineers
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• v.31 no.3
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• pp.70-80
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• 1989

In this research program special triaxial compression tests and dehydration-swelling tests under the condition of freeze-thaw process were conducted to show the effects of freezethaw process on the physical properties of weathered granite soil, and their results as follows; 1.Consolidation settlement of weathered granite soil mass was increased due to freeze-thaw process, and the initial tangent coefficient of dense state was higher than that of loose state. 2.Compression behaviour of soil was increased according to the decrease of freezing temperature, and when the freezing temperature was reached under - 10$^{\circ}$C, the compression rate was not influenced by change of freezing temperature. 3.The experiments showed that the void ratio and permeability of soil were converged into their values of shrinkage limit, and the permeability was higher due to the freeze-thaw process and as the lower the freezing temperature. 4.The decrease of liquid limit was indicated as the lower the freezing temperature, and as more the freeze4haw cycles, the moisture content was shown the lower side. 5.It was shown that the shrinkage was decreased by freeze-thaw process and not influenced by way of freezing temperature, but dehydration rate was higher.

• Magazine of the Korean Society of Agricultural Engineers
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• v.27 no.4
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• pp.53-60
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• 1985

The plaster mixed to loam and sandy soil from 4 to 12 percent by dry soil weight, and the compaction, permeability, CBR, unconfined compressive strength and freezingthawing test were performed The results obtained are summarized as follows; 1.The coefficient of permeability reduced sharply at the plaster content of 4 percent, and in the CBR test, the swelling ratio reduced by the increment of plaster content. 2.The addition of plaster increased the unconfined compressive strength by the cementing effect, and it was found that the optimum plaster content, existed with the soil type, which showed the maximum strength 3.It was possible to enhance the unconfined compressive strength of the gypsum-lime-soil mixtures when the optimum content of plaster was mixed to the hydrated lime. 4.In case of sandy soil, the relative frost heave decreased with the mixture of plaster, however in loam soil, the relative frost heave began to increase at the plaster content of 12 percent than non-treated soil. Therefore the optimum plaster content existed for protecting frost heave by the different soil type. 5.The above summarized results make it possible to expect the effects such as improvement of soil properties, decrement of permeability, increment of unconfined compressive strength, and protection of frost heave, etc, therefore, it is considered that it is possible to it is plaster as sub-base materials of road.

• Journal of the Korean Wood Science and Technology
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• v.44 no.2
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• pp.191-203
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• 2016

To investigate the dynamic sorptive and hygroexpansive behaviors of wood by different cyclic hygrothermal changing effects, poplar (populus euramericana Cv.) specimens, were exposed to dynamic sorption processes where relative humidity (RH) and temperature changed simultaneously in sinusoidal waves at 75-45% and $5-35^{\circ}C$ (condition A) and where RH changed sinusoidally at 75-45% but temperature was controlled at $20^{\circ}C$ (condition B), both for three cyclic periods of 1, 6, and 24 h. Moisture and dimensional changes measured during the cycling gave the following results: Moisture and transverse dimensional changes were generally sinusoidal. Moisture and dimensional amplitude increased with increasing cyclic period but all were lower for thicker specimens. The amplitude ratio of condition A to condition B ranged from 1.0 to 1.6 with the maximum value of 1.57 occurring at the shortest cyclic period, not as much as expected. T/R increased as cyclic period increased or specimen thickness decreased. T/R from condition B was weaker than that from condition A. Sorption and swelling hysteresis existed in both conditions. Sorption hysteresis was negatively related to cyclic period but in positive correlation with specimen thickness. Sorption hysteresis was found more obvious in condition B, while moisture sorption coefficient and humidity expansion coefficient showed the opposite results.

• Imaging Science in Dentistry
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• v.30 no.3
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• pp.199-205
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• 2000

Purpose: To determine whether the significant relationship exists between radiographic appearance, whether it is unilocular or multilocular, and its corresponding clinical and histologic features by examining the odontogenic keratocyst clinically, radiologically and histologically. Materials and Methods: This study was conducted on 48 cases of odontogenic keratocyst from the files of Dental Hospital, Yonsei University for the years 1982 through 1995. Results and Conclusions : The mean age of patients was 30.5 years in the unilocular group and 35.5 years in the multilocular group. The male to female ratio was 1 : 1.06 in the unilocular group and 1 : 1.75 in the multilocular group. The chief complaint was swelling in both groups(unilocular 35.1 %, multilocular 54.5%). In the occurrence site, the border of the lesion, the displacement and external root resorption of the adjacent teeth, there were no statistically significant difference between the unilocular group and multilocular group, but in the border type, there was statistically significant difference (x²-test, p<0.05)wo recurred cases were observed among 11 cases of odontogenic keratocyst. One was unilocular case and the other was multilocular case.

• Fashion & Textile Research Journal
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• v.5 no.5
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• pp.529-538
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• 2003

Chitosan should be satisfied a certain Mw range for the final application, Low molecular weight chitosan(LMWC) can be acquired by depolymerizing high molecular weight starting chitosan. Using $H_2O_2$ in depolymerizing chitosan is very effective and reproducible in controlling Mw of resulting LMWC. However, $H_2O_2$ can break glycoside linkage of chitosan and oxidize some $-NH_2$ groups in chitosan. It has been reported that decrease in DA(degree of deacetylation) of LMWC prepared by $H_2O_2$. However, any quantitative data of decrease in DA has not been reported yet. In this study, DA of initial chitosan and DA of $H_2O_2$ treated chitosan were measured and the change in DA of chitosan upon $H_2O_2$ treatment were investigated. Change in DA was very different upon $H_2O_2$ treatment condition. LMWC also showed DA change upon time passage. Pre-swelling treatment of initial chitosan and low ratio of $H_2O_2$/chitosan prevented a decrease in DA significantly. Yellowing of LMWC was detected upon time passage, however, decrease in DA was minimal (around 1%).

• Archives of Pharmacal Research
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• v.24 no.1
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• pp.69-73
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• 2001

Biodegradable hydrogels based on glycidyl methacrylate dextran (CMD) and dimethacrylate poly(ethylene glycol) (DMP) were proposed for colon-specific drug delivery. GMD was synthesized by coupling of glycidyl methacylate with dextran in the presence of 4-(N, N-dimethylamino)pyridine (DMAP) using dimethylsulfoxide as a solvent. Methacrylate-terminated poly (ethylene glycol) (PEG) macromer was prepared by the reaction of PEG with methacryloyl chloride. CMD/DMP hydrogels were prepared by radical polymerization of phosphate buffer solution (0.1 M, pH 7.4) of GMD and DMP using ammonium peroxydisulfate (APS) and UV as initiating system. The synthetic GMD, DMP and GMD/DMP hydrogels were characterized by fourier transform infrared (FT-lR) spectroscopy. The FITC-albumin loaded hydrogels were prepared by adding FITC-albumin solution before UV irradiation. Swelling capacity of GMD/DMP hydrogels was controlled not only by molecular weight of dextran, but also by incorporation ratio of DMP Degradation of the hydrogels has been studied in vitro with dextranase. FITC-albumin release from the GMD/DMP hydrogels was affected by molecular weight of nextran and the presence of dextranase in the release medium.

• Journal of the Korean Wood Science and Technology
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• v.43 no.5
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• pp.539-547
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• 2015

To investigate dimensional responses of wood under dynamic temperature condition, poplar (populous euramericana Cv.) specimens, 20 mm in radial (R) and tangential (T) directions with two thicknesses of 4 and 10 mm along the grain, were exposed to cyclic temperature changes in square wave between $25^{\circ}C$ and $40^{\circ}C$ at 60% relative humidity (RH) for three different cycling periods of 6 h, 12 h and 24 h. R and T dimensional changes measured during the cycling gave the following results: 1) Transverse dimensional changes of the specimens were generally square but at an opposite phase and lagged behind the imposed temperature changes. The phase lag was inversely correlated with cycling period, but positively related to specimen thickness, while the response amplitude was directly proportional to cycling period, but in a negative correlation with specimen thickness. 2) The specimens showed swelling hysteresis behavior. The heat shrinkage coefficient (HSC) became greater as cycling period increased or specimen thickness decreased. 3) Dimensional changes of the specimens produced deformation accumulation during repeated adsorption and desorption. The deformation accumulating ratio decreased with an increase in cycling period and specimen thickness. 4) Wood suffered 1.5 times as many dimensional changes per unit temperature variation as per unit humidity variation, and this deformation behaved even more seriously under static condition.

• Biomaterials and Biomechanics in Bioengineering
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• v.1 no.3
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• pp.163-174
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• 2014

The objective of this study is to prepare an artificial extracellular matrix (ECM) for cell culture by using polymer hydrogels. The polymer used is a cytocompatible water-soluble phospholipid polymer: poly[2-methacryloyloxyethyl phosphorylcholine (MPC)-n-butyl methacrylate-p-nitrophenyloxycarbonyl poly(ethylene oxide) methacrylate (MEONP)] (PMBN). The hydrogels are prepared using a cross-linking reaction between PMBN and diamine compounds, which can easily react to the MEONP moiety under mild conditions. The most favorable diamine is the bis(3-aminopropyl) poly(ethylene oxide) (APEO). The effects of cross-linking density and the chemical structure of cross-linking molecules on the mechanical properties of the hydrogel are evaluated. The storage modulus of the hydrogel is tailored by tuning the PMBN concentration and the MEONP/amino group ratio. The porous structure of the hydrogel networks depends not only on these parameters but also on the reaction temperature. We prepare a hydrogel with $40-50{\mu}m$ diameter pores and more than 90 wt% swelling. The permeation of proteins through the hydrogel increases dramatically with an increase in pore size. To induce cell adhesion, the cell-attaching oligopeptide, RGDS, is immobilized onto the hydrogel using MEONP residue. Bovine pulmonary artery endothelial cells (BPAECs) are cultured on the hydrogel matrix and are able to migrate into the artificial matrix. Hence, the RGDS-modified PMBN hydrogel matrix with cross-linked APEO functions as an artificial ECM for growing cells for applications in tissue engineering.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.40.2-40.2
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• 2010

In this study, oxidized alginate/gelatin/biphase calcium phosphate (BCP)- based hydrogel composites were fabricated. Alginate sodium was oxidized by periodate. The oxidized product was confirmed by using $^1H$ and $^{13}C$ NMR spectra. The number average molecular weight ($M_n$), the average molecular weight ($M_w$) of the oxidized alginate were determined by Gel Permeation Chromatography (GPC). The hydrogel was formed from the oxidized alginate and gelatin solution via Schift-base reaction. The hydrogel showed a highly porosity by a Scanning Electron Microscope (SEM) and Mercury Intrusion Porosimetry (MIP). Crosslinked density of the gel matrix were assessd by trinitrobenzene sulfonic acid (TNBS) assay that shows a high effect on swelling ratio. Increment of the crosslinked desity resulted in enhancing compressive strength of the hydrogel composite. The cytotoxity of hydrogel was assessed with osteoblast MG-63. The hydrogel composites show a high compatibility. The obtained results showed a potential application for bone regeneration in future.

• Journal of the Korean Wood Science and Technology
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• v.24 no.3
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• pp.101-109
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• 1996

Effects of process variables were evaluated in physical properties of the wood fiber-thermoplastic fiber composites using nonwoven web method. Turbulent air mixer using compressed air was employed to mix wood fiber with two types of thermoplastic polypropylene and nylon 6 fibers. The optimal hot press temperature and time were found to be $190^{\circ}C$ and 9 minutes in wood fiber-polypropylene fiber composite and to be $220^{\circ}C$ and 9 minutes in wood fiber-nylon 6 fiber composite. As the density of wood fiber-polypropylene fiber composite and wood fiber-nylon 6 fiber composite increased, the physical properties were improved The density appeared to be the most significant factor on physical properties in the statistical analysis. The composition ratio of polypropylene or nylon 6 fiber to wood fiber was considered not to be statistically significant factor. The thickness swelling decreased somewhat in wood fiber-polypropylene fiber composite and wood fiber-nylon 6 fiber composite as the content of synthetic fiber increased. As the increase of mat moisture content, dimensional stability was improved in wood fiber-polypropylene fiber composite but not in wood fiber-nylon 6 fiber composite.