• Proceedings of the Materials Research Society of Korea Conference
• /
• 2011.05a
• /
• pp.33.1-33.1
• /
• 2011

최근 산업에서는 산업의 고도화로 인한 환경오염이 큰 문제로 대두되고 있다. 이러한 문제점을 해결하기 위한 방안 중, 친환경소재에 대해 연구가 활발히 진행하고 있다. 연잎의 자기세정효과(self-cleaning effect)에 관한 연구는 이러한 친환경소재에 대한 연구 중 하나이다. 연잎의 표면은 마이크로 크기의 돌기와 나노 크기의 왁스의 dual-scale의 구조로 이루어져 있으며, 왁스의 경우 소수성을 가진다. 이러한 dual-scale 구조와 소수성의 왁스에 의해 초소수성이 발현되고, 결과적으로 연잎의 자기세정효과가 발현된다. 본 연구에서는 나노임프린트 리소그래피와 수열합성법을 이용한 나노로드 성장을 이용하여, 연잎의 dual-scale의 표면구조를 형성하는 실험을 진행하였다. 나노임프린트 리소그래피와 수열합성법은 다른 공정에 비하여 상대적으로 적은 비용을 필요로 하고, 대면적에 적용이 가능한 기술이다. 실험 진행은 먼저 silicon 마스터 스탬프를 역상으로 복제한 PDMS (Polydimethylsiloxane) 스탬프와 $TiO_2$ sol을 이용하여 기판 위에 $TiO_2$ gel 패턴을 형성한 후, 열처리 과정을 통해 $TiO_2$ gel 패턴을 결정화한다. 다음으로 결정화된 $TiO_2$ 패턴 기판을 수열합성 방법을 이용하여 $TiO_2$ 나노로드를 무작위적으로 형성하였다. 마지막으로 소수성을 갖는 자기 조립 단분자막 용액을 이용하여 소수성 표면처리를 한 후 접촉각을 측정하였다. 본 연구에서 개발한 기술을 이용하여 다양한 형태의 기판에 초소수성 표면을 형성할 수 있고, 자기세정효과를 갖는 표면을 구현할 수 있다.

• Transactions of the Korean hydrogen and new energy society
• /
• v.25 no.2
• /
• pp.145-150
• /
• 2014

This study investigates the preparation of anti-reflective (AR) coating film to improve the efficiency of solar cell. The AR coating film was successfully obtained by dip-coating with AR coatings prepared by sol-gel method. Fluoroalkylsilane was additionally introduced into the coatings to give the self-cleaning effect of AR coating film. We performed the abrasion test, pencil scratch hardness test and cross-cut test to identify the mechanical strength of AR coating film. As the results, the transmittance of AR coating films with 9.07, 18.13 and 27.20 of IPA/MTMS molar ratios were 93.1, 93.6 and 95.3%, respectively. The water contact angle and transmittance of AR coating film increased by the introduction of hydrophobicity. The prepared AR coating film shows the high level of abrasion, hardness and adhesion. The IPA/MTMS molar ratio of 27.20 and the withdrawing speed range of 0.20 ~ 0.28cm/sec are the optimal coating condition in terms of the transmittance and mechanical strength of AR coating film.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.7
• /
• pp.1002-1009
• /
• 2000

Among the various types of diesel after-treatment device, the corona discharge reactor may be considered as a powerful process for trapping submicron particles. But after precipitation on the electrodes occurs, the reentrainment of particles is severe and often causes low or negative precipitation efficiency. Experiments were performed to investigate the effect of an applied voltage on the reentrainment of soot particles from the electrodes. A co-annular laminar diffusion flame burner was used as the soot generator. When a highly negative voltage was applied, exfoliation of the deposited soot particles and an increase in concentration of particles smaller than approximately 150 nm were observed. Turbulence induced from the negative tuft corona and sputtering caused particle reentrainment from the corona wire and from plates as well. Under soot laden combustion gas, a streamer corona often occurred in the wire-cylinder reactor. Because of its transient nature, streamer corona violently increased the concentration of reentrained particles and CO gas.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.41 no.3
• /
• pp.205-209
• /
• 2017

Unlike spherical drop impact, ellipsoidal drop impact can control the bouncing height on a heated surface by significantly altering impact behavior. To scrutinize the effect of the aspect ratio (AR) of the drop on the bounce suppression, in this study, non-axisymmetric spreading behaviors are observed from two side views and characterized based on the spreading width of the drop for horizontal principal axes. In addition, the maximum spreading width is investigated for various ARs. The results show that as the AR increases, the maximum spreading width of the minor axis increases, whereas that of the major axis shows no significant variation. In the regime of high AR and high impact velocity, liquid fragmentations by three parts are observed during bouncing. These fragmentations are discussed in this work. The hydrodynamic features of ellipsoidal drop impact will help understand bouncing control on non-wetting surfaces for several applications, such as self-cleaning and spray cooling.

• The Journal of the Korean dental association
• /
• v.54 no.12
• /
• pp.1035-1044
• /
• 2016

Purpose : The purpose of this study was to compare the plaque removal effects of vacuum oral cleaner developed for the patients with limited mobility with those of manual toothbrushes and high pressure injection oral cleaner (dental water jet). Meterials and methods : Thirty human subjects were measured with Patient Hygiene Performance index (PHP index) and O'Leary index before and after the use of toothbrush, high pressure injection oral cleaner and vacuum oral cleaner. These three different oral hygiene methods were conducted with seven-day intermittence. Then the statistical analysis was carried out to define plaque removal rate of three different oral hygiene methods (${\alpha}=.05$). Results : According to the efficacy analysis of plaque removal before and after the oral cleaning using each of three methods, significant reduction in plaque after the treatment compared to the previous state when using toothbrush, high pressure injection oral cleaner, and vacuum oral cleaner was observed (P < 0.001). PHP index of tooth brushing was higher than that of the high pressure injection oral cleaner, while PHP index of vacuum oral cleaner did not show significant difference from either of the other two methods. There was no significance difference in O'Leary index among the three methods. Conclusion : Effect of plaque removal using the vacuum oral cleaner is comparable to that of manual tooth brush or high pressure injection oral cleaner, so it will be helpful for self-oral hygiene care of the patients with limited mobility.

• Korean Journal of Community Nutrition
• /
• v.15 no.4
• /
• pp.475-484
• /
• 2010

The purpose of this study was to evaluate the effect of the nutrition education on preschool children's nutrition knowledge and behaviors. The study subjects were preschool children attending J kindergarten located in Wonju. Each of the control group and the education group consisted of 49 children and the education group was exposed to nutrition education while the control group did not. The nutrition education intervention lasted 9 weeks weekly basis. The t-test for the homogeneity of each group showed no meaningful difference at the beginning point of nutrition education. After nutrition education a test of nutrition knowledge using picture-questionnaire was carried out by the researcher for the subjects of education group and control group and the caretakers of the education group were offered self-administered questionnaire on the changes in children's dietary behaviors. The results of the study were as follows: 1. Nutrition education intervention showed a meaningful difference in children's understanding nutrition; the kinds and function of food, the relationship between food and body, the function of nutrients and enhanced their idea on hygiene compared to the control group (p < p.005). 2. However, nutrition education intervention made no statistically meaningful difference in children's dietary behaviors such as having breakfast, keeping balanced diet, washing hands before meals, saying "thanks" before and after meals, cleaning the table after meals, brushing teeth after meals and so on. Therefore, we found that it is hard to expect children to correct their dietary behaviors in such a short period of 9 weeks and nutrition education for preschool children should be offered to caretakers at the same time.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.86-86
• /
• 2010

Micro- and nanoscale texturing and control of surface energy have been considered for superhydrophobicity on polymer and silicon. However these surfaces have been reported to be difficult to meet the robustness and transparency requirements for further applications, from self cleaning windows to biochip technology. Here we provided a novel method to fabricate a nearly superhydrophobic soda-lime glass using two-step method. The first step involved wet etching process to fabricate micro-sale patterns on soda-lime glass. The second step involved application of $SiO_x$-incorporated DLC to generate high intrinsic contact angle on the surface using chemical vapor deposition (CVD) process. To investigate the effect of surface roughness, we used both positive and negative micro-scale patterns on soda-limeglass, which is relatively hard for surface texturing in comparison to quartz or Pyrex glasses due to the presence of impurities, but cheaper. For all samples we tested the static wetting angle and transparency before and after 100 cycles of wear test using woolen steel. The surface morphology is observed using optical and scanning electron microscope (SEM). The results shows that negative patterns had a greater wear resistance while the hydrophobicity was best achieved using positive patterns having static contact angle up to 140 deg. with about 80% transparency. The overall experiment shows that positive patterns at etching time of 1 min shows the optimum transparency and hydrophobicity. The optimization of micro-scale pattern to achieve a robust, transparent, superhydrophobic soda-lime glass will be further investigated in the future works.

• Textile Coloration and Finishing
• /
• v.30 no.4
• /
• pp.245-255
• /
• 2018

In this study, cotton fabrics were coated with $TiO_2$ nanoparticles using 3-mercaptopropyltrimethoxysilane(3-MPTMS), which is highly reactive to cotton fabrics, as a medium, and the characteristics, antimicrobial properties, and photodegradation properties of the fibers were measured. The manufacturing process is as follows. (1) 3-MPTMS was added to isopropanol, and $TiO_2$ colloid was added to the mixture to prepare a solution. (2) Cellulose fibers were immersed in the prepared $3-MPTMS/TiO_2$ solution, stirred for 90 minutes at $45^{\circ}C$ in a constant temperature water bath, and dried thereafter. In order to identify the morphology of the cellulose fibers coated with $TiO_2$ nanoparticles, the surface was observed with a scanning electron microscope(SEM), and SEM-EDS was measured to identify the adhesion of $TiO_2$ nanoparticles. The SEM images showed $TiO_2$ nanoparticle and 3-MPTMS coated layers on the fibers and it was identified that $TiO_2$ nanoparticles were attached to the cellulose fibers. The antimicrobial activity of $3-MPTMS/TiO_2$-treated cotton fabrics was measured using a bacterial reduction method. $3-MPTMS/TiO_2$ cellulose fibers which was irradiated by ultra violet light, showed antimicrobial activity against Escherichia coli(ATCC 43895) and Staphylococcus aureus(ATCCBAA-1707) unlike unirradiated fibers. The cellulose fibers were stained with methylene blue and the photodegradation performance of the stained fabrics was analyzed. The stained fabrics showed high degradation performance with photolytic reactions of $TiO_2$ nanoparticles.

• Membrane and Water Treatment
• /
• v.10 no.4
• /
• pp.287-298
• /
• 2019

Lotus leaf has a special dual micro and nano surface structure which gives its highly hydrophobic surface characteristics and so-called self cleaning effect. In order to endow PVDF hollow fiber membrane with this special structure and improve the hydrophobicity of membrane surface, PVDF hollow fiber composite membranes was obtained through the immersion coating of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) dilute solution on the outside surface of PVDF support membrane. The prepared PVDF composite membranes were used in the vacuum membrane distillation (VMD) for the desalination. The effects of PVDF-HFP dilute solution concentration in the dope solution and coating time on VMD separation performance was studied. Membranes were characterized by SEM, WCA measurement, porosity, and liquid entry pressure of water. VMD test was carried out using $35g{\cdot}L^{-1}$ NaCl aqueous solution as the feed solution at feed temperature of $30^{\circ}C$ and the permeate pressure of 31.3 kPa. The vapour flux reached a maximum when PVDF-HFP concentration in the dilute solution was 5 wt% and the coating time was kept in the range of 10-60 s. This was attributed to the well configuration of micro-nano rods which was similar with the dual micro-nano structure on the lotus leaf. Compared with the original PVDF membrane, the salt rejection can be well maintained which was greater than 99.99 % meanwhile permeation water conductivity was kept at a low value of $7-9{\mu}S{\cdot}cm^{-1}$ during the continuous testing for 360 h.

• Journal of Convergence for Information Technology
• /
• v.12 no.5
• /
• pp.298-304
• /
• 2022

In this study, it is intended to provide basic research data on hair loss and problematic scalp that is expanding to lower age groups and women. When using Company B's hair ampoule containing L-Menthol, Salicylic acid, and Dexpanthenol daily for women in their 20s with problematic scalp, the effect on the scalp and hair after 4 weeks was investigated. As a result of this study, when using Company B's ampoule containing L-Menthol, Salicylic acid, and Dexpanthenol, the subjects showed improvement effects such as relieving inflammation, reducing scalp fever and erythema, reducing itching and hair loss, and increasing hair thickness. In addition, it was confirmed that the scalp self-diagnosis of the subjects showed improvement effects on scalp satisfaction, scalp vitality and elasticity, heat generation, scalp pulling after cleaning, and itching. Through these research results, it is believed that products containing L-Menthol, Salicylic acid, and Dexpanthenol will help improve problematic scalp and hair.