• KSBB Journal
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• v.18 no.5
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• pp.412-417
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• 2003

We first investigated basic characteristics of reticulated polyurethane (PU) foams as microbial carriers. In general, the specific surface area of PU foams increases with respect to decreasing pore sizes. However, the number of microbes adhered on the unit surface of reticulated PU foams decreases with respect to decreasing pore sizes. Thus, as a result of totally considering all effects such as apparent density, hydrolysis rate, and adhesion, we can know that PU foams with 45 PPI is the most appropriate microbial carrier. In this study, we can also investigate the effect of various physico-chemical surface treatments on the adhesion of microbes on the surface of PU foams. We used a chitosan treatment, a PEI (Polyethylene Imine) treatment, a xanthane treatment and a plasma treatment. As a result of comparing all surface treatments, the plasma surface treatment was the best.

• Science of Emotion and Sensibility
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• v.25 no.4
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• pp.45-52
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• 2022

Recently, interest in and demand for sensors that recognize physical activity and their products are increasing. In particular, the development of wearable materials that are flexible, stretchable, and able to detect the user's biological signals is drawing attention. In this study, an experiment was conducted to improve the dip-coating efficiency of a single-walled carbon nanotube dispersion solution after fine holes were made in a hydrophobic material with a micro needle. In this study, dip-coating was performed with a material that was not penetrated, and comparative analysis was performed. The electrical conductivity of the sensor was measured when the sensor was stretched using a strain universal testing machine (Dacell Co. Ltd., Seoul, Korea) and a multimeter (Keysight Technologies, Santa Rosa, CA, USA) was used to measure resistance. It was found that the electrical conductivity of a sensor that was subjected to needling was at least 16 times better than that of a sensor that was not. In addition, the gauge factor was excellent, relative to the initial resistance of the sensor, so good performance as a sensor could be confirmed. Here, the dip-coating efficiency of hydrophobic materials, which have superior physical properties to hydrophilic materials but are not suitable due to their high surface tension, can be adopted to more effectively detect body movements and manufacture sensors with excellent durability and usability.

• Membrane Journal
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• v.16 no.4
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• pp.303-312
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• 2006

The asymmetric hybrid membranes of polyethersulfone (PES) and $ZrO_2$ nanoparticles were prepared via new one-step procedure combining simultaneously the phase-inversion method and the sol-gel technique. The optimum contents of $Zr(PrO)_4\;and\;HNO_3$ catalyst were determined by the adsorption experiments of phosphate anion onto the resulting hybrid membranes. The maximum adsorption of phosphate anion is obtained at the conditions of 0.15 mL $Zr(PrO)_4$ addition per 1 mL PES and 30 mL $HNO_3$ addition per 1 mL $Zr(PrO)_4$. Variation of morphology, performance and incorporated $ZrO_2$ amount of the resulting hybrid membranes were discussed and determined using SEM, pure water flux, TGA, ICP, XRD and contact angle measurements. Increasing $Zr(PrO)_4$ addition into casting solution, pure water flux is increased and $ZrO_2$ amount in the hybrid membrane is maximized at the conditions 0.15 mL $Zr(PrO)_4$ addition per 1 mL PES. The prephosphatation of PES-$ZrO_2$ hybrid membrane was studied to modify the surface characteristics of membrane. Ultrafiltration of bovine serum albumin (BSA) solution was performed in a dead-end cell using both a bare (non-phosphated) and a phosphated hybrid membrane. It is revealed that both the permeate flux and BSA rejection were increased as about 40% by prephosphatation of hybrid membrane. These results may be explained on the basis of the increase of membrane hydrophilicity, which was determined from contact angle measurements.

• Polymer(Korea)
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• v.29 no.4
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• pp.408-412
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• 2005

Structure and characteristic of the films blended chitosan matrix with silk fibroin, extracted from Bombyx mori, were studied by X-ray diffraction, differential scanning calorimetry, FT-IR spectra analysis, SEM photographs, contact angle measurement and water absorbency in order to use as biomaterials. The blend films of $0\~30 wt\%$ fibroin content were prepared in acetic solution with $Li^+$ ion. It was found that the crystallinity of chitosan/fibroin blend films was decreased by the presence of intermolecular interactions such as hydrogen bonding between animo groups of chitosan and carbonyl groups of fibroin. As the proportion of fibroin in the blend increased, anhydrous crystalline phase of chitosan disappeared, and hydrated crystalline phase decreased, and $\beta$-structure crystalline phase of fibroin was formed. Therefore the blend films were crystallized into two different crystalline region of chitosan and fibroin. Surface hydrophilicity and water absorbency increased with blending fibroin. Above 20 $wt\%$ fibroin content, hydrogel film was formed. The surface and section of the film showed uniform microstructure on SEM photographs.

• Science of Emotion and Sensibility
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• v.20 no.2
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• pp.117-126
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• 2017

In this study, moisture transport characteristics for the woven and knitted fabrics made of 8 kinds of fiber materials using MMT (moisture management tester) were measured and discussed with the Bireck bt MMT and water evaporating rate (WER) measuring methods, which are vertical moisture transport methods. In addition, the drying property by MMT of the eight kinds of specimens was compared and discussed with the results measured by the vertical drying measurement. MMT experimental result which is horizental moisture transport appeared to be similar to the result of the Bireck method, which is the vertical moisture transport experiment. Absortion time measured from drip method of the fabrics made of the bamboo, linen, and cotton/nylon composite fabrics was short and thus they showed best wicking property, which was attributed to the low contact angle on the fabric surface and high porosity of the fabrics due to the staple yarn structure composed of the hydrophilic staple fibers. In drying property of the fabric specimens by MMT, maximum absorption radius of the dry-zone knit and bamboo woven fabrics were the highest and they showed the best drying property, which was a little different result compared with vertical drying measurement method. Half time of the drying rate in the MMT method was highly correlated with the fabric thickness and saturated moisture absortion rate and their regression coefficients were 0.9 and 0.88, respectively. This means that the knitted and woven fabric design technology for retaining good wicking and drying properties of the fabrics with thin fabric thickness is very important for obtaining high functional wear comfort fabrics. In addition, wicking and drying properties of the fabrics made of different fiber materials and with different yarns and fabric structures showed different results according to the measuring methods.

• The Korean Journal of Financial Management
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• v.12 no.1
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• pp.33-56
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• 1995

본(本) 연구(硏究)는 자본구조이론과 전통적 연구에서 제시된 변수를 통합하고 횡단면(橫斷面) 요인(要因)과 시계열(時系列) 요인(要因)을 결합하여 우리나라의 자본구조결정 요인을 식별할 수 있는 이론적(理論的) 모형(模型)을 제시하여, 또한 제시된 모형을 한국증권시장(韓國證券市場)의 자료(資料)를 이용하여 실증적(實證的)으로 분석(分析)하였다. 그리고 실증적 분석에는 횡단면(橫斷面) 자료(資料)와 시계열(時系列) 자료(資料)를 결합하는 패널자료추정법(資料推定法)을 사용하였다. 본(本) 연구(硏究)에서 제시된 자본구조이론(資本構造理論)과 관련된 결정 요인으로는 기업(企業)의 성장기(成長機)을, 내부주주(內部株主)의 지분율(持分率) 그리고 내부주주수(內部株主數)의 비율 등을, 전통적 횡단면 요인으로는 경영위험(經營危險), 자산구성(資産構成), 수익성(收益性), 기업규모(企業規模) 등을, 그리고 전통적 시계열 요인으로는 법인세율(法人稅率)과 물가수준(物價水準) 등을 제시하였다. 본(本) 연구(硏究)에서 다루는 실증분석기간은 1981년 1월부터 1990년 12월까지의 10년간이었으며, 추출된 표본기업(標本企業)의 수(數)는 104개사이다. 실증적 분석결과, 본(本) 연구(硏究)에서 제시된 설명변수들이 자본구조(資本構造)의 변동(變動)을 49.91%정도 설명하고 있으며 설명변수 중 기업(企業)의 성장기회(成長機會), 내부주주(內部株主)의 지분을, 경영위험(經營危險), 수익성(收益性), 기업규모(企業規模), 물가수준(物價水準) 등은 자본구조의 결정 요인으로 통계적인 의미를 갖는 변수로 밝혀졌으며 회귀계수(回歸係數)의 부호도 기대하였던 바와 일치하고 있다. 질산으로 처리된 것이 컸고 0.75 M과 1.0 M의 질산을 사용했을 때는 작음이 확인되었다. 이상의 실험결과들로부터 친수성인 $NH_4Y$형 제올라이트를 소수성의 것으로 변환시키기 위한 수증기의 온도는 $500^{\circ}C$와 $600^{\circ}C$가, 그리고 질산의 농도는 0.5 M이 적합한 것으로 결론지을 수 있고, 이와 같은 결론은 BET비표면적과 TPV값과 같은 경향을 보인 벤젠과 톨루엔의 흡착용량측정결과로 입증되었다. 탈알루미늄된 제올라이트들의 수분에 대한 Si/Al비와 흡착용량은 각각 높은 농도의 질산으로 처리된 것일수록 증가하고 감소하여 소수성이 증가함을 나타내었다.(不適合性)이 나타났다. 본 연구는 기존의 기대수익률(期待收益率) 위주의 요일효과(曜日效果) 분석에서 주식수익률(株式收益率)의 분산(分散) 즉, 변동성(變動性)에 촛점을 두어 분석하였으며, 이는 투자자의 정확한 위험측정(危險測定)수단의 제공이라는 면에서 의의(意義)가 있을 것으로 생각된다.據金) 운용(運用)에 관한 정책수립시(政策樹立時) 금융선진국(金融先進國)의 증거금(證據金) 정책운용(政策運用)을 통한 시장관리(市場管理) 경험(經驗)을 어느 정도 참고할 수 있음을 시사한다고 할 것이다. 한다. 실증분석결과는 본문의 <표 1>에 제시되어 있으며 그 내용을 간략하게 요약하면 다음과 같다. (A) 실증분석모형 : 본 연구에서는 다기간 자산가격결정모형중에서 대표적인 Lucas (1978)모형을 직접 사용한다. $$1={\beta}\;E_t[\frac{U'(C_{t+1})\;P_t\;s_{t+1}}{U'(C_t)

• Membrane Journal
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• v.22 no.4
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• pp.272-279
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• 2012

The neutral polymer, poly (vinyl alcohol) (PVA), was coated onto polyamide (PA) thin film composite reverse osmosis (RO) membranes. And then these membranes were investigated for the model foulants, bovine serum albumin (BSA), humic acid (HA), and sodium alginate (SA) whether there are aome improvement. As the operating pressure increased with 2, 4, 8 atm for BSA, HA and SA 100 ppm in feed solution, the fouling phenomena was worse for both none and PSSA coated membranes. The fouling occurred in the sequence of BSA > HA > SA due to the interactions between PVA snd functional groups of foulants, and on the other hand the fouling reduction was observed in the order of HA > BSA > SA. The observation of scanning electron microscopy photographs showed the same trend. As a result, there should be the improvement of fouling phenomena for the PVA coated RO membranes and the case of HA was shown distinct.

• Polymer(Korea)
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• v.35 no.2
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• pp.157-160
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• 2011

In this paper, poly (dimethyl siloxane) (PDMS) was modified using electron beam irradiation and its property was investigated. PDMS sheets prepared using a conventional thermal curing method were irradiated by electron beams at absorbed doses between 20 and 200 kGy and their properties were characterized using swelling degree and contact angle measurements, universal testing machine (UTM), thermogravimetric analyzer (TGA), and X -ray photoelectron spectrometer (XPS). The results of the swelling degree measurements, UTM, and TGA revealed that the swelling degree of the irradiated PDMS sheets was reduced down to 24% in comparison to the control sheet, and their compression strength and thermal decomposition temperature increased up to maximum 2.5 MFa and $10^{\circ}C$, respectively, due to the increase in crosslinking density by irradiation. In addition, on the basis of the results of contact angle measurements and XPS, the wettability of the PDMS sheets was enhanced up to 24% owing to the generation of hydrophilic functional groups on the PDMS surface by oxidation during electron beam irradiation.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.4
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• pp.328-334
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• 2019

Purpose: The aim of this study was to confirm if Laser-treated implants were soaked in 0.9% NaCl solution for 2 weeks could increase the surface hydrophilicity, and the Remoal Torque of each implant that inserted in rabbit tibia for initial healing period of 10 days. Materials and methods: Twenty machined titanium surface screws were produced with a diameter 3 mm, length 8 mm. Ten screws had their surface treated with a laser only (laser treated group), and the other 10 were soaked in saline for 2 weeks after surface treatment with a laser (laser treated + saline soaked group). Implants were inserted in rabbit tibia (ten adult New Zealand white rabbits), and the RTQ of each implant was measured after 10 days. The wettability among implants was compared by measuring the contact angle. Surface composition and surface topography were analyzed. Results: After 10 days, the laser treat + soaking group implants had a significantly higher mean RTQ than the laser treated implants (P = .002, < .05). There were no significant morphological differences between groups, and no remarkable differences were found between the two groups in the SEM analysis. Conclusion: Saline soaking implants is expected to produce excellent RTQ and surface analysis results.

• Membrane Journal
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• v.29 no.1
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• pp.51-60
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• 2019

In order to improve gas separation properties of polymeric membranes which have been widely applied in the industry field, aluminosilicate hollow nanoparticles named as allophanes were synthesized by sol-gel method and formulated in Poly(dimethylsiloxane) (PDMS) matrix to investigate the gas separation properties of PDMS membrane. Transmission electron microscope (TEM), Energy dispersive X-ray analysis (EDX), X-ray diffractometer (XRD), Surface area and pore size analyzer (BET) and Fourier transform infrared spectrophotometer (FTIR) were carried out to characterize the synthetic allophanes. Then the PDMS mixed matrix membranes were prepared by adding different volume fraction of allophanes. To examine the effect of allophanes addition in PDMS matrix using unmodified allophane and modified ones, the gas permeation experiments were performed using oxygen, nitrogen, methane and carbon dioxide. As the volume fraction of modified allophane increased up to 4.05 Vol% the permeability of four test gases through PDMS mixed matrix membranes increased. Also, the selectivity of $O_2/N_2$ and $CO_2/CH_4$ increased with the contents of the modified allophane. Further improvement of gas separation properties of PDMS mixed matrix membranes containing higher volume percent of allophanes can be expected as long as well dispersion of allophanes in PDMS matrix can be achieved for better PDMS membranes.