• Polymer(Korea)
• /
• v.30 no.1
• /
• pp.85-89
• /
• 2006

The effect of vapor grown carbon fiber (VGCF) contents on electrical and rheological properties of VGCF filled polyphenylene sulfide (PPS) composites prepared through melt mixing using a twin screw exruder was studied. This method was proved to be quite effective to produce good dispersion of VGCF in the matrix even for highly filled PPS. From the dependence of the electrical conductivity on VGCF content, the percolation phenomena began to occur above $10\;wt\%$. While there is only a marginal increase of viscosity for 1 and $5\;wt\%$ VGCF filled PPS, the composites containing $10\;wt\%$. While VGCF showed abrupt increase in viscosity as well as flattening of frequency vs modulus curve, indicating a transition from a liquid-like to a solid-like behavior due to the creation of VGCF network. This result agrees well to the fact that the network formation in the composite can be composite by rheological property dependence on filler content as well as by electrical conductivity measurement.

• Korean Journal of Food Science and Technology
• /
• v.32 no.3
• /
• pp.646-653
• /
• 2000

Using agar and waxy com starch as the wall material, we could encapsulate the purified fish oil. Firstly, we have developed a simple and sensitive method for the quantitative analysis of the microencapsulation yield using 5% cupric acetate pyridine solution. Then, the optimum conditions such as the ratio of [core material] to [wall material]$(X_1)$, the temperature of dispersion fluid$(X_2)$, and the emulsifier concentration$(X_3)$ for the microencapsulation process were determined by using response surface methodology(RSM). The regression model equation for the yield of microencapsulation(Y, %) of purified fish oil upon three kinds of independent variables could be predicted as follows; Y = 100.138621-0.735000$(X_1)$+0.840000$(X_1)(X_2)$+0.817500$(X_1)(X_3)$-0.852500$(X_2)(X_3)$. And the optimum conditions for the microencapsulation of the purified fish oil were the ratio of [core material] to [wall material] of 4.9 : 5.1(w/w), the emulsifier concentration of 0.48%, and dispersion fluid temperature of $19.4^{\circ}C$. The microcapsules containing the purified fish oil showed the highest storage stability at pH 7.0 and $20{\sim}25^{\circ}C$.

• Journal of the Korea Institute of Building Construction
• /
• v.11 no.6
• /
• pp.530-537
• /
• 2011

The purpose of this study is to examine material performance of fiber reinforced cement composite for mass production. It is necessary to manufacture SHCC(Strain Hardening Cement Composite) by batch plant for field application and mass production. For the study, a mock-up test of SHCC manufactured in the batch plant was conducted, and the performance was compared with SHCC manufactured in the laboratory. Assessment items were freshness and hardening properties. Specifically, direct tensile test machine was used for performance verification of SHCC. As a result, there was a tendency of less satisfactory fiber dispersion and performance of strain hardening compared with the performance of SHCC manufactured in the laboratory. To address this, dry mixing and mortar mixing time should be increased compared to laboratory mixing, and injection time of an agent such as a water reducing agent should be properly controlled according to mixing combination, or the capacity to secure dispersion and homogeneity of material.

• The Journal of Korean Academy of Prosthodontics
• /
• v.43 no.1
• /
• pp.61-77
• /
• 2005

Statement of problem. The implant prosthesis has been utilized in various clinical cases thanks to its increase in scientific effective application. The relevant implant therapy should have the high success rate in osseointegration, and the implant prosthesis should last for a long period of time without failure. Resorption of the peri-implant alveolar bone is the most frequent and serious problem in implant prosthesis. Excessive concentration of stress from the occlusal force and biopressure around the implant has been known to be the main cause of the bone destruction. Therefore, to decide the location and angulation of the implant is one of the major considering factors for the stress around the implant fixture to be dispersed in the limit of bio-capacity of load support for the successful and long-lasting clinical result. Yet, the detailed mechanism of this phenomenon is not well understood. To some extent, this is related to the paucity of basic science research. Purpose. The purpose of this study is to perform the stress analysis of the implant prosthesis in the partially edentulous mandible according to the different nature locations and angulations using three dimensional finite element method. Material and methods, Three 3.75mm standard implants were placed in the area of first and second bicuspids, and first molar in the mandible Thereafter, implant prostheses were fabricated using UCLA abutments. Five experimental groups were designed as follows : 1) straight placement of three implants, 2) 5$^{\circ}$ buccal and lingual angulation of straightly aligned three implants, 3) 10$^{\circ}$ buccal and lingual angulation of straightly aligned three implants. 4) lingual offset placement of three implants, and 5) buccal offset placement of three implants. Average occlusal force with a variation of perpendicular and 30$^{\circ}$ angulation was applied on the buccal cusp of each implant prosthesis, followed by the measurement of alteration and amount of stress on each configurational implant part and peri-implant bio-structures. The results of this study are extracted from the comparison between the distribution of Von mises stress and the maximum Von mises stress using three dimensional finite element stress analysis for each experimental group. Conclusion. The conclusions were as follows : 1. Providing angulations of the fixture did not help in stress dispersion in the restoration of partially edentulous mandible. 2. It is beneficial to place the fixture in a straight vertical direction, since bio-pressure in the peri-implant bone increases when the fixture is implanted in an angle. 3. It is important to select an appropriate prosthodontic material that prevents fractures, since the bio-pressure is concentrated on the prosthodontic structures when the fixture is implanted in an angle. 4. Offset placement of the fixtures is effective in stress dispersion in the restoration of partially edentulous mandible.

• Archives of Pharmacal Research
• /
• v.28 no.5
• /
• pp.604-611
• /
• 2005

Polyethylene glycol (PEG) 6000-based solid dispersions (SDs), by incorporating various pharmaceutical excipients or microemulsion systems, were prepared using a fusion method, t o compare the dissolution rates and bioavailabilities in rats. The amorphous structure of the drug in SDs was also characterized by powder X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). The ketoconazole (KT), as an antifungal agent, was selected as a model drug. The dissolution rate of KT increased when solubilizing excipients were incorporated into the PEG-based SDs. When hydrophilic and lipophilic excipients were combined and incorporated into PEG-based SDs, a remarkable enhancement of the dissolution rate was observed. The PEG-based SDs, incorporating a self microemulsifying drug delivery system (SMEDDS) or microemulsion (ME), were also useful at improving the dissolution rate by forming a microemulsion or dispersible particles within the aqueous medium. However, due to the limited solubilization capacity, these PEG-based SDs showed dissolution rates, below 50% in this study, under sink conditions. The PEG-based SD, with no pharmaceutical excipients incorporated, increased the maximum plasma concentration (C$_{max}$) and area under the plasma concentration curve (AUC$_{0-6h}$) two-fold compared to the drug only. The bioavailability was more pronounced in the cases of solubilizing and microemulsifying PEG-based SDs. The thermograms of the PEG-based SDs showed the characteristic peak of the carrier matrix around 60$^{\circ}C$, without a drug peak, indicating that the drug had changed into an amorphous structure. The diffraction pattern of the pure drug showed the drug to be highly crystalline in nature, as indicated by numerous distinctive peaks. The lack of the numerous distinctive peaks of the drug in the PEG-based SDs demonstrated that a high concentration of the drug molecules was dissolved in the solid-state carrier matrix of the amorphous structure. The utilization of oils, fatty acid and surfactant, or their mixtures, in PEG-based SD could be a useful tool to enhance the dissolution and bioavailability of poorly water-soluble drugs by forming solubilizing and microemulsifying systems when exposed to gastrointestinal fluid.

• Journal of Adhesion and Interface
• /
• v.9 no.3
• /
• pp.7-13
• /
• 2008

The particulate type silicon carbide (SiC) and fiber type carbon fiber (CF) filler, of similar thermal conductivities, were mixed with polyetheretherketone (PEEK) to investigate the filler effects on the thermal diffusivity. The SiC and CF fillers had a good and uniform dispersion in PEEK matrix. Thermal diffusivities of PEEK composites were measured from ambient temperature up to $200^{\circ}C$ by laser flash method. The diffusivities were decreased as increasing temperature due to the phonon scattering between PEEK-filler and filler-filler interfaces. Thermal diffusivity of PEEK composites was increased with increasing filler content and the thermal conductivities of two-phase system were compared to the experimental results and it gave ideas on the filler dispersion, orientation, aspect ratio, and filler-filler interactions. Nielson equation gave a good prediction to the experimental results of PEEK/SiC. The easy network formation by CF was found to be substantially more effective than SiC and it gave a higher thermal diffusivities of PEEK/CF than PEEK/SiC.

• Journal of Adhesion and Interface
• /
• v.19 no.3
• /
• pp.106-112
• /
• 2018

Recently, the hyperthermia treatment of malignant tissues has gained great attention as a biocompatible and benign method that facilitates successful cancer therapy compared to radiation and chemotherapy. In this study, superparamagnetic ($Fe_3O_4$) iron oxide nanoparticles (IONP) coated with biocompatible polymer (IONP@P(MPC/FOM)) for the purpose of hyperthermia treatment were prepared and related characterization were performed. IONPs with having 15 nm diameter were first prepared by coprecipitation and followed by surface modification with 4-cyanopentanoic acid dithiobenzoate (CTP) for reversible addition-fragmentation chain transfer (RAFT) copolymerization by using 2-methacryloyloxyethyl phosphorylcholine (MPC) and fluorescein O-methacrylate (FOM) to form corona layer of P(MPC/FOM) on the surface of the IONP. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) confirmed the morphology and hydrodynamic size of the IONP@P(MPC/FOM) and thermogravimetric analysis (TGA) confirmed the formation of P(MPC/FOM) corona layer, respectively. Exposing IONP dispersion to alternating magnetic field suggests that the IONP@P(MPC/FOM) aqueous dispersion with 0.2 wt.% can be used for hyperthermia treatment.

• Membrane Journal
• /
• v.21 no.4
• /
• pp.389-397
• /
• 2011

In this study, polymer composite membranes based on sulfonated poly(arylene ether sulfone) (SPAES) were prepared using a solution casting method with different amount of vermiculite (VMT) content. The dispersion of VMT particles in the SPAES matrix was confirmed by means of a scanning electron microscopy observation. The composite membrane containing less than 1 wt% of VMT has a smooth skin on the top and bottom, which means there is a good dispersion of VMT in the matrix. The water uptake of the composite membranes gradually increases as the temperature increases, and the results confirm that all the adsorbed water is bound water because VMT has a strong water affinity on account of its high cation exchange value. A composite membrane with a VMT content of less than 1 wt% increases the proton conductivity and reduces the methanol permeability. Of all the composite membranes, the membrane SPAES/VMT 1.0 has the best fuel cell performance in terms of membrane selectivity. The performance value of SPAES/VMT 1.0 is double that of Nafion 112, which suggests that SPAES/VMT1.0 could be an excellent candidate for direct methanol fuel cells.

• The Journal of Korean Medical History
• /
• v.30 no.1
• /
• pp.23-31
• /
• 2017

Euibangyoochui (醫方類聚), the largest medical book in Korea, has medical and historical significance in that it had classified almost all East Asian medical accomplishments before Joseon Dynasty (1392-1910). Focusing on these values, this research investigates Yi'an (醫案), an East Asian tradition of describing clinical encounters and the therapies employed, in Euibangyoochui. By this investigation, this study expected to not only establish how the genre of Yi'an is employed for what purpose in Euibangyoochui, but also to shed a light on the appearance of Yi'an before Joseon Dynasty. At first, this study extracted Yi'an from Euibangyoochui (醫方類聚), as Yi'an does not have a standardized format. In total, the number of extracted Yi'ans is 1,025 with handwork results. Extracted Yi'ans are analyzed statically, in order to find dispersion of Yi'ans for each chapter and its references. Overall, there are 73 chapters of Euibangyoochui, which has a total of 93 chapters, containing Yi'an, while the chapter on gynecology contains the highest number of Yi'ans, 86. Judged from these result, the genre of Yi'an was used diversely and frequently, indicating various messages in Euibangyoochui. To categorize the usage and purpose of writing of Yi'ans in Euibangyoochui, this study considers some examples of Yi'ans and concludes that 3 types of Yi'ans are employed in Euibangyoochui in order to deliver the adequate medical message. One is result-centered Yi'an delivering a broader medical lesson, such as a taboo in treatment or a doctrine in medicine. The second is the concise-styled Yi'an presenting a short effective medical method. The third is multiple-information Yi'an that describes complex information of patients and medical theories, transmitting diverse lessons. Yi'ans in Euibangyoochui refer to 58 medical books. Books written by JangJaHwa (張子和; 1156-1228) are the most cited books, offering almost a quarter of total amount of Yi'ans in Euibangyoochui. This study is meaningful in that it provides basic information, such as numbers, applications, purpose of writing and references of Yi'an in Euibangyoochui. Moreover considering the historic values of Euibangyoochui, this information reflects, on the other hands, overall figures of Yi'an written before publication of Euibangyoochui.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.7B
• /
• pp.795-805
• /
• 2011

The research on the immersive media technology is actively being done with the emergence of immersive services using immersive media, especially in the broadcasting industry and with the increased market demand for it. The industry which produces, transmits, processes and services the immersive contents is commonly called Immersive Media Industry. Immersive Media Industry has recently received attention as next-generation strategic industry with its high marketability and its high possibility of market expansion through convergence with other industry such as education, health, advertisement, travel and public service industry. As other advanccd country such as the U.S., Japan and Europe buckle down to take the innitiative in the immersive media industry, Korea government also begins to make plan to promote the immersive media industry. As above, immersive media industry is a cutting-edge convergence industry which embraces broadcasting, telecommunication and contents industry and it is rising as core growth engine industry. This article analyses the economic effects of immersive media industry through quantatitive method and evaluates the relations between the immersive media industry and the other related industries. As a result, the effect on production inducement of immersive media industry is 610.9 billion Korean Won; the effect on value-added inducement is 468.7 billion Korean Won; and it is measured that 3,258 job will be created by the immersive media industry.