• 한국의류학회지
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• 제47권3호
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• pp.577-592
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• 2023

In this study, nanofiber-based textile sensors were developed for motion detection and monitoring. Poly(vinylidene fluoride) (PVDF) nanofibers containing zinc oxide (ZnO) nanoparticles and silver nanowires (AgNW) were fabricated using electrospinning. PVDF was chosen as a piezoelectric polymer, zinc oxide as a piezoelectric ceramic, and AgNW as a metal to improve electric conductivity. The PVDF/ZnO/AgNW nanocomposite fibers were used to develop a textile sensor, which was then incorporated into an elbow band to develop a wearable smart band. Changes in the output voltage and peak-to-peak voltage (V_p-p) generated by the joint's flexion and extension were investigated using a dummy elbow. The β-phase crystallinity of pure PVDF nanofibers was 58% when analyzed using Fourier transform infrared spectroscopy; however, the β-phase crystallinity increased to 70% in PVDF nanofibers containing ZnO and to 78% in PVDF nanocomposite fibers containing both ZnO and AgNW. The textile sensor's output voltage values varied with joint-bending angle; upon increasing the joint angle from 45° to 90° to 150°, the V_p-p value increased from 0.321 V_p-p to 0.542 V_p-p to 0.660 V_p-p respectively. This suggests that the textile sensor can be used to detect and monitor body movements.

• 대한소아치과학회지
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• 제10권1호
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• pp.35-45
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• 1983

This study was undertaken to evaluate the pulpal responses to the intermediate restorative materials such as Zinc phosphate cement, Polycarboxylate cement, IRM (zinc oxide eugenol cement), Dycal, Life, Cresatin, and Fluoride in caivties which were cut with high speed instrument. 5 dogs were used as experimental animals and devided into 8 groups. The intervals of observaobservation ranged 3 days, 1, 3, 4, 8 weeks after experiment respectively. The specimens were fixed with 10% formalin and decalcified in 5% nitric acid. All slides were stained with hemtoxylin-eosin and examined histopathologically. The results were as follows: 1. In control group, severe vacuolar degeneration and atrophy of odontoblasts were seen in 3 days, hemorrhage and congestion continued until 8 weeks. Necrosis of odontoblastic layer was seen in zinc phosphate cement group and polycarboxylate cement group. 2. In dycal group, vacuolar degeneration and atrophy of odontoblast were not seen. but in Life group, these were seen in 3 days and partially continued until 3 weeks. In 4 weeks, regeneration of odontoblast was occured. 3. In Crcsatin group, there was no pathosis except odontoblastic displacement. In Fluoride group, vacuolar degeneration of odontoblast was seen and soon disappeared. As compared with control group, pathological change of the pulp tissue in experimental group were decreased after amalgam restoration.

• 지질공학
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• 제33권1호
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• pp.39-49
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• 2023

국내에서 관리되고 있는 토양오염물질 중 지질 기원의 영향이 큰 물질로는 비소, 카드뮴, 구리, 납, 아연, 니켈, 수은, 불소 등이 있다. 본 연구에서는 국내 토양오염 조사 자료를 바탕으로 GIS 모델링을 통해 오염물질의 분포 현황을 파악하고 오염원과의 공간적 개연성을 확인하였다. 그 결과, 카드뮴, 구리, 납, 니켈, 수은의 경우 1% 미만의 낮은 기준초과 빈도를 나타내고 있다. 비소와 아연의 경우 각각 광산 영향범위와 산업단지 부지 내에서 높은 초과 빈도를 나타내며, 주변 오염인자에 의한 영향이 매우 높은 것으로 확인되었다. 그러나 불소의 경우 조사지점 수가 가장 적고, 기준초과 빈도가 가장 높음에도 불구하고 뚜렷한 인위적 오염원이 확인되지 않았고, 분포 특성 또한 광역적인 연속성을 보임에 따라 지질 분포와의 개연성이 매우 높을 것으로 추정된다. 불소 항목의 기준초과 지점에 대한 지질 분포 현황을 확인한 결과, 쥐라기 화강암(40.00%)과 선캄브리아기 호상편마암(34.12%)에서 집중적인 초과 빈도를 나타내고 있다. 이는 화강암과 편마암에 존재하는 높은 불소 함량이 암석의 풍화에 따른 토양의 생성 과정에서 토양의 구성 성분으로 존재함에 따라 이들 암석이 분포하는 지역의 토양 중 불소 농도가 높게 나타난 것으로 판단된다.

• 한국식품위생안전성학회지
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• 제9권4호
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• pp.229-235
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• 1994

It is very important to investigate the sanitary chemical conditions of farmwaters used for cattle breeding in the dairy farms. For this purpose we examined pH, KMnO4 consumption, total hardness, chloride, sulfate, NH3-N, NO3-N, fluoride, lead, iron, manganese, cadmium, copper, zinc and chrome in the farmwaters sampled 2 times(spring and summer)in Choongcheongnam and Kangwon Province. The pH of farmwaters in Choongcheongnam and Kangwon Province was 6.49$\pm$0.09, 6.70$\pm$0.06, total hardness 90.21$\pm$7.07, 64.53$\pm$6.38 mg/ι, consumption of KMnO4 4.13$\pm$0.62, 4.34$\pm$0.26mg/ι, NO3-N 6.51$\pm$0.55, 3.61$\pm$0.58 mg/ι, chloride ion 20.51$\pm$1.99, 5.41$\pm$1.36 mg/ι and sulfate ion 6.61$\pm$1.02, 7.28$\pm$1.30 mg/ι, respectively. But NH3-N was scarcely detected. Fluoride, iron, lead, cadmium, zinc, manganese and chrome were not detected from the tested farmwaters. There was high significance between each other in total hardness, NO3-N, chloride ion and sulfate ion. There was regional and seasonal significance in only NO3-N but only regional significance in total hardness and chloride ion.

• 대한심미치과학회지
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• 제8권1호
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• pp.76-82
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• 1999

Zinc phosphate cement has long been the material of choice for permanent luting of cast restorations, and through many years of use has been considered effective to retain castings. However, cast restorations cemented with this material have been susceptible to secondary caries. Glass ionomer luting agents become available in the late 1970s. These material s, through release of fluoride, show considerable promise as a means of reducing secondary caries. Other favorable traits include significantly less disintegration in vivo than zinc phosphate cements, a film thickness comparable to that of zinc phosphate cement, and adhesion to tooth structure. Compomer materials were created in 1993 as a filling material for deciduous teeth, cervical lesions, and class III cavities. In the meantime, compomer have been developed as chemical hardening cements for cast gold restorations. The aim of this paper is to review the articles on luting cements to help the choice of dental cements.

• Smart Structures and Systems
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• 제12권1호
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• pp.55-71
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• 2013

Structural health monitoring (SHM) is vital for detecting the onset of damage and for preventing catastrophic failure of civil infrastructure systems. In particular, piezoelectric transducers have the ability to excite and actively interrogate structures (e.g., using surface waves) while measuring their response for sensing and damage detection. In fact, piezoelectric transducers such as lead zirconate titanate (PZT) and poly(vinylidene fluoride) (PVDF) have been used for various laboratory/field tests and possess significant advantages as compared to visual inspection and vibration-based methods, to name a few. However, PZTs are inherently brittle, and PVDF films do not possess high piezoelectricity, thereby limiting each of these devices to certain specific applications. The objective of this study is to design, characterize, and validate piezoelectric nanocomposites consisting of zinc oxide (ZnO) nanoparticles assembled in a PVDF copolymer matrix for sensing and SHM applications. These films provide greater mechanical flexibility as compared to PZTs, yet possess enhanced piezoelectricity as compared to pristine PVDF copolymers. This study started with spin coating dispersed ZnO- and PVDF-TrFE-based solutions to fabricate the piezoelectric nanocomposites. The concentration of ZnO nanoparticles was varied from 0 to 20 wt.% (in 5 % increments) to determine their influence on bulk film piezoelectricity. Second, their electric polarization responses were obtained for quantifying thin film remnant polarization, which is directly correlated to piezoelectricity. Based on these results, the films were poled (at 50 $MV-m^{-1}$) to permanently align their electrical domains and to enhance their bulk film piezoelectricity. Then, a series of hammer impact tests were conducted, and the voltage generated by poled ZnO-based thin films was compared to commercially poled PVDF copolymer thin films. The hammer impact tests showed comparable results between the prototype and commercial samples, and increasing ZnO content provided enhanced piezoelectric performance. Lastly, the films were further validated for sensing using different energy levels of hammer impact, different distances between the impact locations and the film electrodes, and cantilever free vibration testing for dynamic strain sensing.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.1504-1507
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• 2009

In this paper, the etching behavior of ZnO in $CF_4$ plasma mixed Ar was investigated. Previously, the etch rate in $CF_4$/Ar plasma was reported that it is slower than that in Cl containing plasma. But, plasma included Cl atom can produce the by-product such as $ZnCl_2$. In order to solve this film contamination, no Cl containing etching gas is required. We controlled the etching parameter such as source power, substrate bias power, and $CF_4$/Ar gas ratio to acquire the fast etch rate using a ICP etcher. We accomplished the etching rate of 144.85 nm/min with the substrate bias power of 200W. As the energetic fluorine atoms were bonded with Zinc atoms, the fluoride zinc crystal ($ZnF_2$) was observed by X-ray photoelectron spectroscopy (XPS).

• 대한화학회지
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• 제62권1호
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• pp.7-13
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• 2018

The potential of zinc fluorides with different molar ratios of Zn/F was applied as a solid catalyst in the simultaneous reaction of transesterification and esterification of crude palm oil (CPO) for biodiesel production. These materials were prepared by the fluorolytic sol-gel technique with different fluorine contents. The resulting samples were investigated using elemental analysis, XRD, FT-IR, TG/DTG, $N_2$ physisorption measurements and SEM. The results exhibited that the presence of fluorine strongly affected the catalytic activity in the biodiesel production. The catalysts with smaller fluorine contents (${\leq}1$) showed the best performance in all of the observed samples, yields from 92.94 to 89.95, 87.38 and 85.21% with increasing fluorine contents, respectively. The yield toward the formation of biodiesel depended on the phase and particle sizes of catalysts, but it was not influenced by surface area, pore size, and volume of the samples. The recovered catalyst showed a gradual decrease in activity over three cycles of same reactions.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 춘계학술발표회 논문집
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• pp.322-323
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• 2012

This study discussed the formation of phosphate conversion coatings on AZ31 Mg alloy (AZ31) from the zinc phosphating bath with various concentrations of sodium fluoride (NaF). The effects of NaF on the formation, structure, composition and electrochemical behavior of the phosphate coatings were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD) weight balances, open circuit potential (OCP) transients, potentiodynamic polarization curves and immersion test. The coatings were composed of two layers: an outer $Zn_2(PO_4)_3.4H_2O$ (hopeite) crystal layer and an inner amorphous of $MgZn_2(PO_4)_2$. NaF concentration is emphasized to be highly effective in the formation of the hopeite crystal and etching and coating rates. Potentiodynamic polarization and immersion test showed that the coatings formed in the zinc phosphating bath with addition of NaF have much higher corrosion resistance than bare AZ31.

• Journal of the Korean Wood Science and Technology
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• 제31권6호
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• pp.55-59
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• 2003

The fixation and leaching characteristics of chromated copper arsenate (CCA Type C) and chromium- copper-fluoride-zinc (CCFZ) in domestic softwood (Japanese red pine, Korean pine, and Japanese larch) sapwood were investigated using the expressate method to follow chromium fixation and the American Wood-Preservers' Association (AWPA) leaching procedure to determine leaching properties after fixation. The rates of fixation were affected by preservative types; CCA was fixed much faster than CCFZ for all species evaluated. There were definite differences in the fixation rates of different species, with Korean pine requiring shorter to fix than the other species evaluated. Chromium fixation was greatly enhanced by elevated temperatures, and fixation time can be estimated according to fixation temperatures applied. The percentage of arsenic and zinc leached from domestic softwoods was relatively high compared to chromium and copper, indicating that there is still a relatively high unfixed arsenic and zinc components after complete chromium fixation in CCA-and CCFZ-treated samples, respectively.