• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1844-1846
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• 2005

The characteristic of negative differential resistance(NDR) is decreased current when the applied voltage is increased. The NDR is potentially very useful in molecular electronics device schemes. Here, we investigated the NDR property of self-assembled 4,4- Di(ethynylphenyl)-2'-nitro-1-(thioacetyl)benzene, which has been well known as a conducting molecule. Self-assembly monolayers(SAMs) were prepared on Au(111), which had been thermally deposited onto pre-treatment$(H_2SO_4:H_2O_2=3:1)$ Si. The Au substrate was exposed to a 1mM/l solution of 1-dodecanethiol in ethanol for 24 hours to form a monolayer. After thorough rinsing the sample, it was exposed to a $0.1{\mu}M/l$ solution of 4,4-Di(ethynylphenyl)-2'-nitro-1-(thioacetyl)benzene in dimethylformamide(DMF) for 30 min and kept in the dark during immersion to avoid photo-oxidation. After the assembly, the samples were removed from the solutions, rinsed thoroughly with methanol, acetone, and $CH_2Cl_2$, and finally blown dry with $N_2$. Under these conditions, we measured electrical properties of self-assembly monolayers(SAMs) using ultra high vacuum scanning tunneling microscopy(UHV-STM). The applied voltages were from -2V to +2V with 299K temperature. The vacuum condition is $6{\times}10^{-8}$ Torr. As a result, we found the NDR voltage of the nitro-benzene is $-1.61{\pm}0.26$ V(negative region) and $1.84{\pm}0.33$ (positive region), respectively.

• Magazine of the Korean Society of Agricultural Engineers
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• v.26 no.2
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• pp.85-96
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• 1984

石膏(改良劑)處理 및 用水管理方法에 依한 鹽害土壤의 除鹽效果를 分析하기 爲하여 浸出法(leaching method), 水洗法(rinsing method), 湛水法(ponding method ; 石膏混合處理 및 石膏非混合處理)에 依해서 3處理 3反復 4回連續抽出實驗이 遂行되었다. 나트륨減少量과 總鹽分減少率은 浸出法이 水洗法이나 湛水法에 比하여 더욱 效果的이었다. 石膏處理區의 除鹽率이 石膏無處理區의 除鹽率보다 比較的 높았으며 石膏處理區(에이커當 2톤 石膏處理區 및 4톤 石膏處理區) 사이에는 別差異가 없었다. 除鹽實驗後 나트륨吸着度(SAR)는 浸出法과 水洗法을 使用한 石膏處理區에서 $10(meq/l)^{1/2}$以下로 減少되었다. 連續抽出의 境遇 SAR은 水洗法을 使用한 石膏處理法에서 單位土壤깊이當 供給用水깊이의 比率($D_w/D_s$)이 3.0以上으로 될때 $10(meq/l)^{1/2}$以下로 減少되었고 浸出法을 使用한 石膏處理區에서는 $D_w/D_s$가 1.5以上일때 $10(meq/l)^{1/2}$以下로 減少되었다. 除鹽實驗後 飽和抽出液의 電氣傳導度(EC)는 全實驗區에서 4mmhos/cm以下로 減少되었다. 連續抽出의 境遇 EC는 水洗法을 使用한 石膏處理區에서 $D_w/D_s$가 3.0以上일때 4mmhos/cm以下로 減少되었고浸出法을 使用한 石膏處理區에서는 $D_w/D_s$가 1.5以上으로 될때 4mmhos/cm以下로 減少되었다. 排水가 比較的 良好한 土壤의 置換性나트륨百分率(ESP)은 除鹽實驗後 浸出法과 水洗法을 使用한 石膏處理區에서 15%以下로 減少되었고 排水가 不良한 土壤의 ESP는 水洗法을 使用한 石膏處理區에서 15%以下로 減少되었다. 나트륨吸着度, 電氣傳導度, 置換性나트륨百分率 等을 勘案하여 볼때 本鹽害土壤은 石膏處理浸出法 또는 石膏處理水洗法에 依하여 比較的 쉽게 改良될 수 있다고 判斷된다. 除鹽效果 및 改良劑費用等을 考慮하여 보면 排水가 比較적 良好한 鹽害土壤의 境遇 에이커當 2톤 石膏處理 浸出法이 效果的인 方法으로 보이며 排水가 不良한 鹽害土壤의 境遇에는 에이커當 2톤 石膏處理 水洗法이 比較的 效率的인 除鹽 方法이라고 思科된다. 排水가 不良한 鹽害土壤의 浸透率을 增加시키고 除鹽을 促進시키기 爲해서는 石膏等과 같은 改良劑의 供給이 必要한 것으로 看做되며 現場條件下에서도 表土層土壤의 除鹽을 爲해서는 石膏處理浸出法과 石膏處理水洗法이 效率的인 方法으로 期待된다.

• Journal of dental hygiene science
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• v.20 no.4
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• pp.187-199
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• 2020

Background: Korean dental hygienists perform various tasks under the supervision of dentists in addition to the tasks listed in the law. Many meaningful studies have been conducted to determine the actual tasks of dental hygienists, but these studies did not show common results due to the differences in research methods or designs. Hence, this study aimed to review the reported data on the tasks of dental hygienists in Korea and to clarify them based on a systematic literature review. Methods: For the literature search, the COre, Standard, and Ideal model presented by the National Library of Medicine was referenced. Seven databases were searched for literatures published in Korea, including PubMed, and Google Scholar. Of the 352 studies found using key words, titles, and abstracts, 46 were finally extracted based on the first and second exclusion criteria. After confirming the tasks of Korean dental hygienists in 46 literatures, 136 tasks were listed and calculated as appearance rate in the literature. Results: The most common tasks in 46 studies were fluoride application (67.2%), radiography (65.4%), scaling (65.4%), sealant (60.7%), patient management and counseling (56.7%), tooth-brushing education (52.2%), impression taking with alginate (50.1%), and making temporary crowns (47.9%). The most mentioned tasks of dental hygienists in public health centers were fluoride application (100%), sealant (100%), oral health education (71.4%), public oral health program evaluation (71.4%), school fluoride mouth-rinsing program (71.4%), water fluoridation (57.1%), tooth-brushing education (57.1%), school oral health programs (57.1%), and public elderly oral health programs (57.1%). Conclusion: This study showed that Korean dental hygienists had 136 tasks by reviewing 46 related studies and that the main job of Korean dental hygienists was oral disease prevention including scaling, sealant, and fluoride application.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.1
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• pp.22-27
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• 2022

In accordance with the growing trend of decommissioning nuclear facilities, research on the cutting process is actively proceeding worldwide. In general, a thermal cutting process, such as plasma cutting is applied to decommissioning a nuclear reactor pressure vessel (RPV). Plasma cutting has the advantage of removing the radioactive materials and being able to cut thick materials. However, when operating under water, the molten metal remains in the cut plane and re-solidifies. Hence, cutting is not entirely accomplished. For these environmental reasons, it is difficult to cut thick metal. The contact arc metal cutting (CAMC) process can be used to cut thick metal under water. CAMC is a process that cuts metal using a plate-shaped electrode based on a high-current arc plasma heat source. During the cutting process, high-pressure water is sprayed from the electrode to remove the molten metal, known as rinsing. As the CAMC is conducted without using a shielding gas, such as Argon, the electrode is consumed during the process. In this study, CAMC is introduced as a method for dismantling nuclear vessels and the relationship between the metal removal and electrode consumption is investigated according to the cutting conditions.

• Journal of the Korean Society of Food Culture
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• v.22 no.4
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• pp.441-448
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• 2007

The purpose of this study was to identify HACCP-based CCP and CP from the microbial quality assessment on the process of side dish (stir-fried dried-shrimp with garlic stems) production in the meal service operation for the elderly. Total plate counts (TPC) of fresh garlic stalks were $7.80{\times}10^{3}$ CFU/g and they were above the standard value of microbial growth potential. The TPC, Coliform and E.coli were not detected in the dried shrimps. The TPCs after rinsing and slicing the garlic stems were $2.5{\times}10^{2}$ CFU/g and $5.5{\times}10^{2}$ CFU/g, respectively. The TPC number of cook’s hand and cutting board were also exceeded the standard limit with values of $2.2{\times}10^{2}$ CFU/g and $10.0{\times}10$ CFU/g, respectively. However, the TPC, Coliform and E.coli were not detected in the other cooking instruments. The identified CCP in inspection step was fresh garlic stems and that of prepreparation step was slicing the stems after blanching. Cook’s hand and cutting board were also verified as CCP and the other steps in cooking process and utensils tested were identified as CP’s. These result’s suggest that it is important to control the microbial contamination of raw materials at purchasing step and the sanitary education program should be developed for the employees for continuous supplement of safe and sound meal service for the elderly.

• Journal of the korean academy of Pediatric Dentistry
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• v.44 no.1
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• pp.72-81
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• 2017

The aim of this study was to evaluate the effectiveness of artificial saliva contamination and decontamination procedures at different stages of a bonding procedure on the microtensile bond strength (MTBS) of two one-step self-etch adhesives and a two-step total-etch adhesive to dentin of primary teeth. Forty-two extracted sound primary molars were randomly divided into three groups depending on three adhesives, Scotchbond Universal Adhesive (SBU), All-Bond Universal (ABU) and Prime & Bond NT (PNT). For each adhesive, the teeth were allocated into seven groups. Except for control group, group 1, the groups were contaminated with artificial saliva at three different stages: the groups 2 and 3 - before adhesive application; the groups 4 and 5 - before adhesive polymerization; the groups 6 and 7 - after adhesive polymerization. Decontaminating procedures were rinsing, air-drying (group 2, 4, 6) and air-drying (group 3, 5, 7). The specimens were restored with composite resin (Filtek, Z350) and microtensile bond strength was measured. The data was analyzed with one-way ANOVA and Tukey HSD test (p < 0.05). In the control group, using PNT resulted in significantly higher bond strength than when ABU and SBU were used (p < 0.001). For three adhesives, the groups 2, 4 and 6 had greater bond strength than the groups 3, 5 and 7. Also, when the artificial saliva was contaminated before adhesive polymerization (group 4, 5), it showed a significantly lower bond strength. Generally the two-step total-etch adhesive generated a higher bond strength than the one-step self-etch adhesive. Artificial saliva contamination before adhesive polymerization led to a drastic decrease in bond strength, and rinsing with water followed by air-drying could not recover the bond strength.

• Journal of dental hygiene science
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• v.3 no.1
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• pp.45-50
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• 2003

In order to develop the program of oral hygiene education for elementary school senior-students, a questionnaire survey of elementary fourth, fifth and sixth students who are under continual control program of oral hygiene. (1) For tooth brushing time, after dinner is more than before. 73.7% of respondents brushed the teeth twice or more a day. (2) 62.1% of respondents took the cariogenic food twice or more a day. (3) 90.1% of respondents had visited a dental clinic. (4) Concerning fear for dental treatment, only 14.4% had a feeling of fear. (5) Regarding the experience with a preventive treatment, 39.7% had an experience with pit and fissure sealing, and 24.2% had an experience with the application of fluorides. (6) 46.2% of respondents had a preference for the fluoride mouth rinsing program, and 38.4% wanted that program to keep going on. As to the reason to favor the fluoride mouth rinsing program, 38.2% preferred it because of prevention of dental caries, and 43.0%, the largest percentage, didn't favor it because they found it too much trouble to do. (7) Comparing with the research result in 2000, we proved positively the educational effect of brushing frequency, positive understanding and preference to water school fluoridation program, and got the negative data of experience of visiting to oral clinic and preventive treatment.

• Journal of Food Hygiene and Safety
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• v.26 no.4
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• pp.403-409
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• 2011

The removal amount of pesticide residue which were remained in baechu (Chinese cabbage) and perilla leaf were measured during the preparation process of kimchi. The amounts of diazinon, procymidone and endosulfan applied to chinese cabbage were $9.18{\pm}0.03$mg/kg, $22.27{\pm}0.22$ and $10.46{\pm}0.02$ mg/kg respectively. When chinese cabbage was brined with 10% salt solution for 12 hours, the removal rates of three pesticides were 22.5%, 25.3% and 0.6% for diazinon, procymidone and endosulfan, respectively. When chinese cabbage was brined and rinsed 3 times with water, the removal rates of three pesticides were 69.9%, 85.6% and 11.2% for diazinon, procymidone and endosulfan, respectively. When kimchi was prepared and fermented for 28 days at $4^{\circ}C$, the removal rates of three pesticides were 79.4%, 94.4% and 21.0% for diazinon, procymidone and endosulfan, respectively. The relative percentages of removal dose of pesticides during brining were 28.4%, 26.9% and 3.2% for diazinon, procymidone and endosulfan, respectively and which were 59.7%, 63.8% and 50.4% during rinsing and which were 11.9%, 9.3% and 46.4% during fermentation, respectively. The amounts of diazinon, procymidone and endosulfan applied to perilla leaf were $18.11{\pm}0.62$ mg/kg, $31.80{\pm}0.33$ and $12.01{\pm}0.01$ mg/kg, respectively. When perilla leaf was rinsed 3 times with water, the removal rates of three pesticides were 60.5%, 52.0% and 23.7% for diazinon, procymidone and endosulfan, respectively. When perilla leaf was rinsed and brined with 10% salt solution for 14 days, the removal rates of three pesticides were 93.9%, 92.4% and 49.6% for diazinon, procymidone and endosulfan, respectively. The relative percentages of removal dose of pesticides during rinsing were 64.5%, 56.3% and 47.8% for diazinon, procymidone and endosulfan, respectively, and which during brining were 35.5%, 43.7% and 52.2% for diazinon, procymidone and endosulfan, respectively.

• Clean Technology
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• v.10 no.2
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• pp.73-87
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• 2004

In most of industrial fields, cleaning is employed for removing soils on their products or parts. Halogenated cleaning agents such as CFC-113, 1,1,1-TCE(1,1,1-trichloroethane), MC(methylene chloride) and TCE (trichloroethylene) have been used as cleaning ones in most of companies in the world since their excellent performance of cleaning ability and good material compatibility. However, CFC-113 and 1,1,1-TCE which are ozone destruction substances are not used any more in the advanced countries because of the which are ozone destruction substances are not used any more in the advanced countries because of the Montreal protocol. MC and TCE are now used restrictively at small part of industrial fields in most of countries since they are known to be hazardous or carcinogenic materials. Thus, it is indispensible that the alternative cleaning agents which are environmental-friendly and safe, and show good cleaning ability should be developed or utilized for replacement of the halogenated cleaning agents. Aqueous/semi-aqueous cleaning agents are evaluated to be promising alternative ones among various alternatives in environmental and economical view point. In this study, commercially available 12 aqueous and 6 semi-aqueous cleaning agents were selected and their physical properties, cleaning abilities, rinsing abilities and recycling of contaminated rinse water were measured and analyzed. Aqueous cleaning agents with higher wetting index showed better cleaning ability compared with those with lower wetting index. However wetting index did not have any correlation with cleaning ability in semi-aqueous cleaning agents. It was observed that soil concentration in aqueous and semi-aqueous cleaning agents should be maintained below the certain concentrations which depend on types of clearing agents. More than 70% soils in contaminated rinse water by some of aqueous and semi-aqueous clearing agents could be separated by simple settling method. This means that some cleaning agents with high oil-water separation efficiency will be effiective for recycling oil-contaminated rinse water. It was found that contaminated rinse water with aqueous agents was purified easiy by ultrafiltration method with PAN membrane of 30 kDa.

• Restorative Dentistry and Endodontics
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• v.25 no.1
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• pp.46-55
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• 2000

During bonding procedure of composite resin, the prepared cavity can be contaminated by saliva. In this study, marginal microleakage and shear bond strength of a composite resin to primed enamel and dentin treated with artificial saliva(Taliva$^{(R)}$) were evaluated. For the marginal microleakage test, Class V cavities were prepared in the buccal surfaces of fifty molars. The samples were randomly assigned into 5 groups with 10 samples in each group. Control group was applied with a bonding system (Scotchbond$^{TM}$ Multi-Purpose plus) according to manufacture's directions without saliva contamination. Experimental groups were divided into 4 groups and contaminated with artificial saliva for 30 seconds after priming: Experimental 1 group ; artificial saliva was dried with compressed air only, Experimental 2 group ; artificial saliva was rinsed and dried. Experimental 3 group ; cavities were etched with 35% phosphoric acid for 15 seconds after rinsing and drying artificial saliva. Experimental 4 group ; cavities were etched with 35% phosphoric acid for 15 seconds and primer was reapplied after rinsing and drying artificial saliva. All the cavities were applied a bonding agent and filled with a composite resin (Z-100$^{TM}$). Specimens were immersed in 0.5% basic fuschin dye for 24 hours and embedded in transparent acrylic resin and sectioned buccolingually with diamond wheel saw. Four sections were obtained from one specimen. Degree of marginal leakage was scored under stereomicroscope and their scores were averaged from four sections. The data were analyzed by Kruscal-Wallis test and Fisher's LSD. For the shear bond strength test, the buccal or occlusal surfaces of one hundred molar teeth were ground to expose enamel(n=50) or dentin(n=50) using diamond wheel saw and its surface was smoothed with Lapping and Polishing Machine(South Bay Technology Co., U.S.A.). Samples were divided into 5 groups. Treatment of saliva-contaminated enamel and dentin surfaces was same as the marginal microleakage test and composite resin was bonded via a gelatin capsule. All specimens were stored in distilled water for 48 hours. The shear bond strengths were measured by universal testing machine (AGS-1000 4D, Shimaduzu Co., Japan) with a crosshead speed of 5 mm/minute. Failure mode of fracture sites was examined under stereomicroscope. The data were analyzed by ANOVA and Tukey's studentized range test. The results of this study were as follows : 1. Enamel marginal microleakage showed no significant difference among groups. 2. Dentinal marginal microleakages of control, experimental 2 and 4 groups were lower than those of experimental 1 and 3 groups (p<0.05). 3. The shear bond strength to enamel was the highest value in control group (20.03${\pm}$4.47MPa) and the lowest value in experimental 1 group (13.28${\pm}$6.52MPa). There were significant differences between experimental 1 group and other groups (p<0.05). 4. The shear bond strength to dentin was higher in control group (17.87${\pm}$4.02MPa) and experimental 4 group (16.38${\pm}$3.23MPa) than in other groups, its value was low in experimental 1 group (3.95${\pm}$2.51 MPa) and experimental 2 group (6.72${\pm}$2.26MPa)(p<0.05). 5. Failure mode of fractured site on the enamel showed mostly adhesive failures in experimental 1 and 3 groups. 6. Failure mode of fractured site on the dentin did not show adhesive failures in control group, but showed mostly adhesive failure in experimental groups. As a summary of above results, if the primed tooth surface was contaminated with artificial saliva, primer should be reapplied after re-etching it.