• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.713-716
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• 2007

This paper suggests One-time Password key exchange authentication technique for a strong authentication based on Ad-hoc Networks and through identify wireless environment security vulnerabilities, analyzes current authentication techniques. The suggested authentication technique consists of 3 steps: Routing, Registration, and Running. The Routing step sets a safe route using AODV protocol. The Registration and Running step apply the One-time password S/key and the DH-EKE based on the password, for source node authentication. In setting the Session key for safe packet transmission and data encryption, the suggested authentication technique encrypts message as H(pwd) verifiers, performs key exchange and utilizes One time password for the password possession verification and the efficiency enhancement. EKE sets end to end session key using the DH-EKE in which it expounds the identifier to hash function with the modula exponent. A safe session key exchange is possible through encryption of the H(pwd) verifier.

• Korean Journal of Environmental Biology
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• v.36 no.4
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• pp.626-637
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• 2018

In this study, a series of survey were conducted to identify the distribution patterns of macrobenthos at the Bongam sand tidal flat in Masan Bay. We collected macrobenthos at 9 sampling sites twice in June and September of every year from 2012 to 2017 using a box core sampler (collecting area, $0.025m^2$). There was a total of 50 species with a community density of $6,388ind.m^{-2}$ and a biomass of $313.9g\;wet\;m^{-2}$ during the study period. Polychaetes had the highest number of species and density among the macrofauna, but the mollusks had the largest biomass. The number of species ranged from 10 to 25 during study period but increased to over 20 species in 2014. The density which ranged from $1,508ind.m^{-2}$ to $12,008ind.m^{-2}$ rapidly increased in 2015. The dominant species were all polychaetes such as Heteromastus filiformis, Prionospio japonicus, Hediste diadroma, and Neanthes succinea. The mean diversity index ranged from 1.2 to 1.9, richness index from 1.2 to 2.4, and evenness index from 0.5 to 0.9. From the cluster analysis results, there was a spatial difference in the similarity of faunal composition of macrobenthos and this pattern was maintained throughout the study period, that is, the temporal similarities were higher than the spatial similarities. There was a change in community composition from June 2014 to June 2015 in most of the sampling sites. During this time, the dominant species also changed from H. filiformis and N. succinea to H. filiformis and H. diadroma. The density of opportunistic species such as Capitella capitata and Polydora ligni decreased compared to the early 2000s while the population of H. diadroma increased from 2015. There was little ecological information on H. diadroma such as when and where this species occurred.

• Tribology and Lubricants
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• v.36 no.3
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• pp.139-146
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• 2020

Global warming has led to an increase in demand of eco-friendly vehicles, such as electric cars, for reducing greenhouse gas emissions, and especially, regulating carbon dioxide generation. In addition, electric vehicles are equipped with an electric drive-type hermetic scroll compressor and a refrigerant, which exhibit current and future trends of using environmentally friendly refrigerants, including R-1234yf. In this study, polyol ester-based refrigeration oils are prepared via condensation esterification of polyol and fatty acids. The oils can be combined with R-1234yf refrigerant for applications in air conditioning and cooling systems of electric vehicles. The structure of synthetic polyol esters is confirmed via ¹H-NMR and FT-IR spectrum analysis, and the composition of the polyol ester is analyzed via gas chromatogram analysis. Furthermore, kinematic viscosity, viscosity index, total acid value, pour point, and color are analyzed as fundamental physical properties of the synthetic polyol esters. The compatibility and chemical stability of the synthetic polyol ester combined with the R-1234yf refrigerant are obtained via high temperature and high pressure oil-resistant refrigerant tests. The changes in the oil color and catalyst activity are observed before and after the experiment to determine whether it is suitable as a refrigerator oil.

• Phonetics and Speech Sciences
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• v.6 no.3
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• pp.41-48
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• 2014

This study investigated the differences between emotional parameters BDI, VHI, STAI-X-I and STAI-X-II according to the menstrual cycles of the female and the relation between changes of the depression index and voice characteristics (jitter, shimmer, CPP, HNR, $pF0{\cdot}F1{\cdot}F2{\cdot}F3$, sF0, sF4, sB1, $H1_{c/u}$, $A1_u$, $A3_c$, $H1A3_{c/u}$, $H1A1_u$). Twenty three females ($30{\pm}4.4$ years old) living in Seoul and Gyeonggi Province were participated in this study to answer the questionnaires and record their voice. The participants prolonged /a/ vowel for 5 seconds in a natural condition for their voice recording. Voice data were analyzed using the Matlab and Praat program. A t-test and a correlation analysis were conducted by using SPSS for the statistical analysis. The results are as follows. First, the BDI is significantly higher in group I (lurear phase contrast the menstrual period) and group II (follicular phase against the menstrual period) than group III (luteal phase for follicular phase) (p<.05). Second, shimmer, CPP, pF0 showed a statistically high correlation regarding the BDI in group I (lurear phase contrast the menstrual period). Voice parameters may be useful as supplement in evaluating the emotional change in the phase of menstrual cycle.

• Journal of Korean Medicine for Obesity Research
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• v.21 no.1
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• pp.32-41
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• 2021

Objectives: We aim to observe the relation of body mass index (BMI) and the indicators of oral health. Methods: 400 subjects participated in the study. The BMI values are calculated from the height and weight. For the tongue diagnosis, we used the tongue imaging device to analyze the color, tongue coating, and tooth marks. We measured the concentration of hydrogen sulfide (H₂S) and methyl mercaptan (CH₃SH) to evaluate the halitosis. The dry mouth was evaluated through the measurement of saliva secretion and with the questionnaire asking the frequency of dry mouth. Results: The BMI values were significantly higher in the group with light-white and blue-purple colored tongue, and significantly lower for lightly-coated tongue. However, the correlation of BMI and the amounts of saliva secretion was not significant as well as in the correlation of BMI and the concentration of H₂S, CH₃SH. In tongue diagnosis, the subjects who had blue-purple colored tongue also had significantly higher H₂S and CH₃SH, but tendency of lower saliva secretion. Conclusion: We obtain data showing that BMI value and the indicators of oral health including tongue diagnosis have meaningful correlation.

• Korean Journal of Weed Science
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• v.4 no.1
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• pp.4-10
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• 1984

This experiment was conducted to determine the change in weed flora with season and cultivated crop and land. There are 44 species in 38 genera and 18 families, consisting of 22 annual, 11 biennial and 9 perennial weeds in uplands in Jeonbug Province. Digitaria sanguinalis Scopol. occurred with the highest frequency of 67.2% and in decreasing order Portulaca oleracea L., Chenopodium album L. and Erigeron canadensis L. followed. About 60% of total sites studied indicated Simpson`s index ranging from 0.20 to 0.50. The Simpson`s index decreased from 0.65 on June 8 to 0.15 on November 10. Dominant weed species were Alopecurus aequalis Sosbol, and Polygonum hydropiper Spach in double cropping paddy field, but D. sanguinalis and P. oleracea were the dominant species in uplands. In reclaimed uplands various weed species including, 4rtemisia asiatica Nakai occurred almost equally. Average Simpson`s index for six crops studied was 0.40 and irrespective of the crops being cultivated P. oleracea and D. sanguinalis were dominant weed species and Y. hydropiper, C. album, Exolus blitum Grenier and E. canadensis were sub-dominant.

• Economic and Environmental Geology
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• v.43 no.1
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• pp.21-31
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• 2010

Mine and leachate waters were collected from the Okdong mine for study on reaction with oxidizing agents such as NaOCl and $H_2O_2$. The pH and EC of the mine and leachate waters are 5.77, 831 uS/cm, and 6.38, 1920 uS/cm, respectively. The concentrations of Mg, Mn, and Zn are 23.25 mg/l, 14.90 mg/l, and 22.99 mg/l for the mine water and 98.75 mg/l, 3.38 mg/l, and 6.16 mg/l for the leachate water. The concentrations of Mg, Mn and Zn decreased after the reaction with the oxidizing agents and mine water. The concentrations of Mg, Mn and Zn rapidly decreased when oxidizing agents increased. The saturation indices that were computed by visual MINTEQ for initial mine and leachate water were undersaturated with Mg, Zn and Mn compounds. The precipitates after the reaction with the oxidizing agents are composed mainly of mangano-calcite[(Mn, Ca)$CO_3$] with small amount of calcite-magnesian and calcite.

• Journal of the Korean Chemical Society
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• v.50 no.3
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• pp.237-242
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• 2006

Nowadays, LEDs has been applied to the luminescent devices of various fields because of the invention of high efficient blue chip. Recently, especially, the white LEDs composed of InGaN blue chips and a yellow phosphor (YAG:Ce3+) have been investigated extensively. With the exception of YAG:Ce3+ phosphor, however, there are no reports on yellow phosphor that has significant emission in the 450~470 nm excitation range and this LED system is the rather low color rendering index due to their using two wavelength. Hence, we have attempted to synthesize thiogallate phosphors that efficiently under the long wavelength excitation range in the present case. Among those phosphors, we have synthesized Sr2Ga2S5:Eu2+ phosphor by change the host material of SrGa2S4:Eu2+ which is well known phosphor and we investigated the luminescent properties. In order to obtain the harmlessness and simplification of the synthesis process, sulfide materials and mixture gas of 5 % H2/95 % N2 were used instead of the CS2 or H2S gas. The prepared phosphor shows the yellow color peaking at the 550 nm wavelength and it possible to emit efficiently under the broad excitation band in the range of 300~500 nm. And this phosphor shows high luminescent intensity more than 110 % in comparison with commercial YAG:Ce3+ phosphor and it can be applied for UV LED due to excitation property in UV region.

• Journal of Environmental Science International
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• v.30 no.2
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• pp.161-172
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• 2021

This study was initiated to isolate the microorganisms removing phosphorus (P) from domestic sewage and to investigate the effects of environmental factors on the growth and P removal of the isolated bacteria. Microorganisms isolated from the sewage were identified as Chryseobacterium sp., Stenotrophomonas maltophilia, and Bacillus licheniformis. Among them, Bacillus licheniformis was selected as the P removal microorganism. The environmental factors considered in this study included initial phosphorus concentration, temperature, pH, and carbon source. At initial P concentrations of 10, 20, and 30 mg/L, the P removal efficiencies were 100.0%, 84.0%, and 16.5%, respectively. At 20℃, 30℃, and 40℃, the P removal efficiencies were 0%, 75.8%, and 60.6%, respectively. The removal efficiencies of phosphorus according to pH were 1.6%, 91.7%, and 51.1% at pH 5, pH 7, and pH 9, respectively. Using glucose, acetate, and glucose + acetate as carbon sources yielded P removal efficiencies of 80.9%, 33.6%, and 54.1%, respectively. Therefore, the results from the study demonstrated that the P removal efficiencies of Bacillus licheniformis were the highest when the initial P concentration, temperature, pH, and carbon source were 10 mg/L, 30℃, 7, and glucose, respectively.

• Journal of Bio-Environment Control
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• v.5 no.2
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• pp.236-247
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• 1996

The main objective of this study was to evaluate the effectiveness of nutrient solutions, substrates, and nutrient solution concentrations in substrate culture of radish(Raphanus sativus L. var. sativus). Cooper's, Hoagland ＆ Arnon' 5, and Yamazaki's solution were used to determine the most suitable nutrient solution in deep flow culture(DFC). In result, Yamazaki's solution treatment showed better results than Hoagland's and Cooper's solution treatments in leaf length, leaf number, shoot and root fresh weights. Cooper's solution was much worse than others. Root shape index were low as 0.6 in all treatments. The selection of suitable was conducted among 14 kinds of substrates which were used commercially, such as sand, perlite and peatmoss, in substrates culture. Sand was the most proper in radish growth and shortened the growth periods. Sand also showed better results then others in leaf length, leaf number, shoot and root fresh weight. On the contrary, radish growth in peatmoss was the worst. Generally, root shape index was higher in substrate than in DFC. In order to investigate the suitable ionic strength in radish, Yamazaki's solution was treated with EC of 0.5, 1.0, 1.5, and 2.0 mS/cm. Generally radish growth above 1.0 mS/cm concentration was good, and the best result was shown in 1.5 mS/cm. Vitamin C contents were not significantly different in the roots of radish grown under 1.0 mS/cm or more. The highest vitamin C content was shown in 0.5 mS/cm, and so was thiocyanate content. Anthocyanin contents increased with the increase of the ionic strength in nutrient solution. Mineral nutrient contents had no significant statistical differences between the treatments, but potassium content was remarkably high in 1.5 mS/cm.