Journal of the korean academy of Pediatric Dentistry
/
v.33
no.3
/
pp.365-376
/
2006
The purpose of this study was to evaluate the efficacy of blocking the oxygen in the air during the polymerization of sealant. All curing were performed with various light curing units under the application of oxygen gel barrier, stream of nitrogen and carbon dioxide gas for inhibition of oxygen diffusion into sealant surface. The results of present study can be summarized as follows : 1. The amount of eluted TEGDMA form the specimens cured with all the three different light units in the stream of $N_2$ and $CO_2$ gas and application of Oxygen gel barrier($DeOx^{(R)}$) were significantly lower than in the room-air atmosphere (Control) (p<0.05). 2. In the $DeOx^{(R)}$ application, the amount of eluted TEGDMA the specimen cured with PAC light for 10seconds was less than that cured in the stream of $N_2$ and $CO_2$ atmospheric conditions (p<0.05) 3. In the LED using 10 or 20sec irradiation times under the stream of $N_2$ and $CO_2$, the eluted TEGDMA showed to be no statistically significant difference (p>0.05). 4. The microhardness from the specimens cured with all the three different light units under each treated conditions were significantly higher than in the room-air atmosphere (p<0.05). 5. The surface treatment by $DeOx^{(R)}$, $N_2$ and $CO_2$ reduces the thickness of oxygen inhibited layer by sp proximately 49% of the untreated control value.
Kim, Choonsig;Kim, Weon-Seok;An, Hyun-Chul;Cho, Hyun-Seo;Choo, Gab-Chul;Lim, Jong-Taek
Journal of Korean Society of Forest Science
/
v.101
no.3
/
pp.405-411
/
2012
This study was conducted to evaluate short-term effects on soil properties and leaf characteristics after various treatments of soil amendments (organic fertilizer: 20 kg tree-1; compound fertilizer+wood-char: compound fertilizer 4 kg tree-1+wood-char 2 kg tree-1; lime fertilizer: 3 kg tree-1; mixed fertilizer: compound fertilizer 1 kg tree-1+organic fertilizer 10 kg tree-1+wood-char 1 kg tree-1; control) in chestnut (Castanea crenata S. et Z.) orchards of Jinju and Sancheong, Gyeongsangnam-do. Soil bulk density, soil pH, soil organic carbon, total nitrogen, exchangeable Ca2+ and Mg2+ in chestnut orchards were not significantly affected by soil amendment treatments. However, leaf weight was significantly higher in the lime fertilizer ($0.65\;g\;leaf^{-1}$) in Jinju and the organic fertilizer ($0.68\;g\;leaf^{-1}$) in Sancheong than in the control treatments (Jinju: $0.46\;g\;leaf^{-1}$; Sancheong: $0.53\;g\;leaf^{-1}$). Leaf area was also significantly higher in the lime fertilizer ($79.1\;cm^2\;leaf^{-1}$) in Jinju and the soil amendments ($70.4\;cm^2\;leaf^{-1}{\sim}78.2\;cm^2\;leaf^{-1}$) in Sancheong than in the control treatments (Jinju: $56.2\;cm^2\;leaf^{-1}$; Sancheong: $60.5\;cm^2\;leaf^{-1}$). Nitrogen concentration of leaf increased significantly in the mixed fertilizer (2.51%) and the compound fertilizer+wood-char (2.50%) compared with the control (1.98%) treatments. The results suggest that soil properties were not affected by soil amendment treatments during short-term period, but leaf characteristics and nitrogen concentration can be an indicator of soil nutrient improvements in chestnut orchards.
KSCE Journal of Civil and Environmental Engineering Research
/
v.35
no.5
/
pp.1135-1146
/
2015
This thesis aims to improve the safety of bicycle traffic for activating the use of bicycle, main means of non-powered and non-carbon transportation in order to cope with worldwide crisis such as climate change and energy depletion and to implement sustainable traffic system. In this regard, I analyzed the problem of bicycle roads currently installed and operated, and developed the bicycle accident forecasting model. Following are the processes for this. First, this study presented the current status of bicycle road in Korea as well as accident data, collect the data on bicycle traffic accidents generated throughout the country for recent 3 years (2009~2011) and analyzed the features of bicycle traffic accidents based on the data. Second, this study selected the variable affecting the number of bicycle accidents through accident feature analysis of bicycle accidents at Jeollanam-do, and developed accident forecast model using the multiple regression analysis of 'SPSS Statistics 21'. At this time, the number of accidents due to extension per road types (crossing, crosswalk, other single road) was used. To verify the accident forecast model deduced, this study used the data on bicycle accident generated in Gwangju, 2011, and compared the prediction value with actual number of accidents. As a result, it was found out that reliability of accident forecast model was secured through reconciling with actual number of cases except certain data. Third, this study carried out field survey on the bicycle road as well as questionnaire on satisfaction of bicycle road and use of bicycle for analysis of bicycle road problems, and presented safety improvement measures for the problems deduced as well as bicycle activation plans. This study is considered to serve as the fundamental data for planning and reorganizing of bicycle road in the future, and expected to improve safety of bicycle users and to promote activation of bicycle use as the means of transportation.
Journal of the Korean Applied Science and Technology
/
v.32
no.1
/
pp.148-156
/
2015
In this study the differences in the sample size and sample input changes as characteristics of bio-oil oak(Quercus variabilis), the oak 0.5~2.0 mm of the oak weighing 300~900g was processed into bio-oil via fast pyrolysis for 1.64 seconds. In this study, the physico-chemical properties of biooil using oak were investigated. Fast pyrolysis was adopted to increase the bio-oil yield from raw material. Although the differences in sample size and sample input changes in the yield of pyrolysis products were not significantly noticeable, increases in the yield of bio-oil accounted for approximately 60.3 to 62.1%, in the order of non-condensed gas, and biochar. When the primary bio-oil obtained by the condensation of the cooling tube and the seconary bio-oil obtained from the electric dust collector were measured separately, the yield of primary bio-oil was twice as higher than that of the secondary bio-oil. However, HHV (Higher Heating Value) of the secondary bio-oil was approximately twice as higher than that of the primary bio-oil by up to 5,602 kcal/kg. The water content of the primary bio-oil was more than 20% of the moisture content of the secondary bio-oil, which was 10% or less. In addition, the result of the elemental analysis regarding the secondary bio-oil, its primary carbon content was higher than that of the primary bio-oil, and since the oxygen content is low, the water content as well as elemental composition are believed to have an effect on the calorific value. The higher the storage temperature or the longer the storage period, the degree of the viscosity of the secondary bio-oil was higher than that of the primary bio-oil. This can be the attributed to the chemical bond between the polymeric bio-oil that forms during the storage period.
Journal of the Korean Applied Science and Technology
/
v.37
no.5
/
pp.1323-1329
/
2020
To characterize the molecular structure of PhE-gal synthesized using Escherichia coli 𝛽-gal, NMR (1H- and 13C-) spectroscopy and mass spectrometry of PhE-gal were conducted. 1H NMR spectrum of PhE-gal showed multiple peaks corresponding to the galactosyl group, which is an evidence of galactosylation on 2-phenylethanol (PhE). Downfield proton peaks at 𝛿H 7.30~7.21 ppm showed the presence of aromatic protons of PhE as well as benzyl CH2 protons at 𝛿H 2.88 ppm. Up field proton peaks at 𝛿H 4.31 ppm, 4.07 ppm and multiple peaks from 𝛿H 3.86~3.38 ppm are indicative of galactocylation on PhE. 13C NMR spectrum revealed the presence of 12 carbons suggestive of PhE-gal. Among 12 carbon peaks from PhE-gal, the four peaks at 138.7, 129.0, 128.6 and 126.5 were assigned aromatic carbons in the phenyl ring. Three peaks at 129.0, 128.6 and 126.5 showed high intensities, indicating CH aromatic carbons. 13C NMR data of PhE-gal showed 6 monosaccharide peaks from galactose and 2 peaks from aliphatic chain of PhE, indicating that PhE-gal was galactosyl PhE. The mass value (sodium adduct ion of PhE-gal, m/z = 307.1181) from mass spectrometry analysis of PhE-gal, and 1H and 13C NMR spectral data were in good agreement with the expecting structure of PhE-gal. We are expecting that through future study it will eventually be able to develop a new additive with low cytotoxicity.
During the two-years(1979 to 1980) fertilization trial on 4-year-old chestnut tree plantations, total insolation was diminished in 1980 because of unseasonable weather. In every fertilization treatment plot, especially in the NPK-fertilized plot with magnesium, growth of trees and yield of chestnuts have been increased significantly. The results obtained are as follows: 1) The growth in the NPK-fertilized plot with boron and magnesium was 20 percent higher than in plots fertilized with NPK alone. 2) Although there was some frost damage to trees on November 14, 1979, the 1979 weather was otherwise normal and daily insolation averaged 7 hours from June through september, The 1979 fertilization indices for chesnut yield were 167 for NPK with boron and 207 for NPK with magnesium, as compared with the base index of 100 for NPK alone. 3) In 1980, the second year of the fertilization trial, unseasonable weather decreased the average daily insolation from June through September to 3.8 hours. Under such conditions, the fertilization indices for chestnut yield were 620 for NPK with boron and 741 for NPK with magnesium, and Boron, as compared to the base index of 100 for NPK alone; i.e. the yields of plots treated with NPK and magnesium were 21 percent higher than for plots with NPK and boron and 7 times the yields for plots with NPK alone, But in the trial plot of NPK, yield of chestnut in 1980 decreased compared with 1979, 4) All test plots had natural magnesium levels lower than 0.8me/100gr., and the treatments with NPK and magnesium would have been less apparent on soils with higher magnesium level. The spectacular effects of treatment with NPK and magnesium during periods of low insolation may result from increased chlorophyll production and corresponding increases in active carbon assimilation, which should play an important role in carbohydrate formation.
To offer the basic information for sustainable production of forest resources and conservation of the global environment, change in potential natural vegetation (PNV) associated with climate change due to doubling atmospheric carbon dioxide ($2{\times}CO_2$) was estimated with the global natural vegetation mapping system based an K${\ddot{o}}$ppen scheme. The system interpolates climate data spherically to each grid cell, determines the vegetation types onto the grid cell, and produces potential vegetation map and area on the globe and continents. The climate data consist of the current, ($1{\times}CO_2$) climate prior to AD 1958 observed at some 2,000 stations and the doubling ($2{\times}CO_2$) climate estimated from Meteorological Research Institute of Japan. The vegetation zone under the $2{\times}CO_2$ climate scenario expanded mainly toward the poles due to the rise in temperature. The changed PNV area on the globe amounts to 1/3 (4.91 billion (G) ha) of the total land area (15.04 Gha). Kappa statistic for judging agreement between the patterns of vegetation distribution under $1{\times}CO_2$ climate and $2{\times}CO_2$ climates shows good agreement (0.63) for the globe as a whole. The most stable areas are desert and ice. The potential forest area (PFA) was estimated at 6.82 Gha of the land area in $2{\times}CO_2$ climate scenario. In terms of continental changes in PFA, North America and Asis are increased under the $2{\times}CO_2$ climate. However, the potential forest arms of the other continents are decreased by the climate. Europe has no change in the PFA. Especially, the expansion of desert area in Oceania would be accelerated by the $2{\times}CO_2$ climate.
Journal of the Korean Society of Food Science and Nutrition
/
v.41
no.8
/
pp.1094-1099
/
2012
This study investigated the effect of a long-term high-fat diet on energy metabolic substrate utilization in resting rats in order to revalue source fat energy efficiency during a high-fat diet and its effect on energy expenditure and body fat accumulation. Sprague-Dawley male rats at 4 weeks of age were bought from Orient Bio Con. The rats were divided into a control (CON) group and a high-fat diet (HF) group. Rats ate a high-fat diet (w/w 40%, kcal/kcal 64.9%) ad libitum for 5 weeks. Food intake and body weight were measured every day at 09:00 throughout the experimental period. Energy expenditure was measured using an animal energy metabolism chamber after 4 weeks. The final body weight did not change between the CON and HF groups, but caloric intake was significantly higher in the HF group than in the CON group (p<0.05). There was no difference between the groups in oxygen uptake, however carbon dioxide production was significantly higher in the HF group. Also, the respiratory exchange ratio was higher in the HF group. Carbohydrate oxidation was lower in the HF group than in the CON group, but fat oxidation in the HF group was greater. These results mean that energy substrate oxidation at rest is affected by diet composition, especially dietary fat content. Abdominal fat fad weights were significantly higher by 33% in the HF group than in the CON group even though the calorie intake in the HF group was higher by 6%. These results suggested that the dietary fat calorie value might have a higher Atwater value of 9 kcal/g, which mean that dietary fat calorie values could be reconsidered in body weight control scenarios such as which the obese or weight class athletes.
Journal of the Korean Institute of Landscape Architecture
/
v.38
no.4
/
pp.64-74
/
2010
The study is based on an urban park design that is designed in consideration of the characteristics of Uijeongbu City, applied with adequate functions for the environment and showcasing the unique scenery in relation to the relocation of the US Air Force Camp Falling Water. The bases of the design are: the reasonable convergence of the square and park in consideration of the site characteristics; the application of an urban context as the park is located near a station; and the realization of an eco-friendly space. This study is based on foundation research regarding a review of urban square patterns, particular items in planning in relation to modern urban parks and the adaptability of the park in the future. Regarding space usage, the design is applied with notable ideas that allow the space to make its own characteristics through voluntary user activity in conjunction with the environment that will allow the park to cope with changes in the future, as opposed to a space that users experience through pre-determined programs. Below are the focal points of the design. First, the park is designed as an empty space which may accommodate the urban structural context of and usage patterns for being a field of the city ecology that changes and develops, beyond a passively-created square pattern. Such open spaces have a continuity which allows it to adapt to the development of the city. In addition, the design facilitates spontaneous processes through changes in usage pattern and time. Second, the design includes the message that the park and the city, natural things and artificial things, must communicate and network with each other. Hence the park shall not be an isolated green island within the city, but is an open space accommodating the demands for open area from nearby commercial, public and residential facilities; the park shall include a field that can accommodate a variety of programs. Third, the park is designed to encourage the effect of direct and indirect practical education by reflecting a physical plan as well as interesting experience design methods to lower carbon emissions and to create and maintain an eco-friendly space, the basis of a zero-emissions city.
Ha, Tai-Moon;Yoon, Seon-Mee;Ju, Young-Cheuol;Sung, Jae-Mo
The Korean Journal of Mycology
/
v.36
no.2
/
pp.163-171
/
2008
We have surveyed the variation of physical and chemical characteristics of aerobic and anaerobic outdoor fermentation of cotton wastes using for oyster mushroom cultivation. The inner temperature of cotton wastes fermented aerobically covered with thin cloth and setting pallet at bottom was higher than that of anaerobic fermented cotton wastes covered with P.E vinyl and the maximum temperature was $75^{\circ}C$ at 5th day after fermentation. pH of cotton wastes fermented aerobically was increased up to 8.9 after fermentation of $9{\sim}12$ days, but that of anaerobically fermented was decreased up to 5.0. Total carbon content was decreased but total nitrogen content was increased when fermentation was in progress. Oxygen concentration of cotton wastes fermented aerobically was decreased until 6 days after fermentation but increased after 9 days of fermentation. Ammonia concentration of cotton wastes fermented aerobically and anaerobically was below 10 ppm and $20{\sim}85\;ppm$ respectively. In anaerobic condition the cotton wastes was contaminated with mold ($15{\sim}50%$), where no contamination was found in aerobic condition during spawn running stage. Yields of mushroom grown on cotton wastes aerobically fermented for $6{\sim}9$ days was $23.0{\sim}23.6\;kg$ per $3.3\;m^2$ area.
본 웹사이트에 게시된 이메일 주소가 전자우편 수집 프로그램이나
그 밖의 기술적 장치를 이용하여 무단으로 수집되는 것을 거부하며,
이를 위반시 정보통신망법에 의해 형사 처벌됨을 유념하시기 바랍니다.
[게시일 2004년 10월 1일]
이용약관
제 1 장 총칙
제 1 조 (목적)
이 이용약관은 KoreaScience 홈페이지(이하 “당 사이트”)에서 제공하는 인터넷 서비스(이하 '서비스')의 가입조건 및 이용에 관한 제반 사항과 기타 필요한 사항을 구체적으로 규정함을 목적으로 합니다.
제 2 조 (용어의 정의)
① "이용자"라 함은 당 사이트에 접속하여 이 약관에 따라 당 사이트가 제공하는 서비스를 받는 회원 및 비회원을
말합니다.
② "회원"이라 함은 서비스를 이용하기 위하여 당 사이트에 개인정보를 제공하여 아이디(ID)와 비밀번호를 부여
받은 자를 말합니다.
③ "회원 아이디(ID)"라 함은 회원의 식별 및 서비스 이용을 위하여 자신이 선정한 문자 및 숫자의 조합을
말합니다.
④ "비밀번호(패스워드)"라 함은 회원이 자신의 비밀보호를 위하여 선정한 문자 및 숫자의 조합을 말합니다.
제 3 조 (이용약관의 효력 및 변경)
① 이 약관은 당 사이트에 게시하거나 기타의 방법으로 회원에게 공지함으로써 효력이 발생합니다.
② 당 사이트는 이 약관을 개정할 경우에 적용일자 및 개정사유를 명시하여 현행 약관과 함께 당 사이트의
초기화면에 그 적용일자 7일 이전부터 적용일자 전일까지 공지합니다. 다만, 회원에게 불리하게 약관내용을
변경하는 경우에는 최소한 30일 이상의 사전 유예기간을 두고 공지합니다. 이 경우 당 사이트는 개정 전
내용과 개정 후 내용을 명확하게 비교하여 이용자가 알기 쉽도록 표시합니다.
제 4 조(약관 외 준칙)
① 이 약관은 당 사이트가 제공하는 서비스에 관한 이용안내와 함께 적용됩니다.
② 이 약관에 명시되지 아니한 사항은 관계법령의 규정이 적용됩니다.
제 2 장 이용계약의 체결
제 5 조 (이용계약의 성립 등)
① 이용계약은 이용고객이 당 사이트가 정한 약관에 「동의합니다」를 선택하고, 당 사이트가 정한
온라인신청양식을 작성하여 서비스 이용을 신청한 후, 당 사이트가 이를 승낙함으로써 성립합니다.
② 제1항의 승낙은 당 사이트가 제공하는 과학기술정보검색, 맞춤정보, 서지정보 등 다른 서비스의 이용승낙을
포함합니다.
제 6 조 (회원가입)
서비스를 이용하고자 하는 고객은 당 사이트에서 정한 회원가입양식에 개인정보를 기재하여 가입을 하여야 합니다.
제 7 조 (개인정보의 보호 및 사용)
당 사이트는 관계법령이 정하는 바에 따라 회원 등록정보를 포함한 회원의 개인정보를 보호하기 위해 노력합니다. 회원 개인정보의 보호 및 사용에 대해서는 관련법령 및 당 사이트의 개인정보 보호정책이 적용됩니다.
제 8 조 (이용 신청의 승낙과 제한)
① 당 사이트는 제6조의 규정에 의한 이용신청고객에 대하여 서비스 이용을 승낙합니다.
② 당 사이트는 아래사항에 해당하는 경우에 대해서 승낙하지 아니 합니다.
- 이용계약 신청서의 내용을 허위로 기재한 경우
- 기타 규정한 제반사항을 위반하며 신청하는 경우
제 9 조 (회원 ID 부여 및 변경 등)
① 당 사이트는 이용고객에 대하여 약관에 정하는 바에 따라 자신이 선정한 회원 ID를 부여합니다.
② 회원 ID는 원칙적으로 변경이 불가하며 부득이한 사유로 인하여 변경 하고자 하는 경우에는 해당 ID를
해지하고 재가입해야 합니다.
③ 기타 회원 개인정보 관리 및 변경 등에 관한 사항은 서비스별 안내에 정하는 바에 의합니다.
제 3 장 계약 당사자의 의무
제 10 조 (KISTI의 의무)
① 당 사이트는 이용고객이 희망한 서비스 제공 개시일에 특별한 사정이 없는 한 서비스를 이용할 수 있도록
하여야 합니다.
② 당 사이트는 개인정보 보호를 위해 보안시스템을 구축하며 개인정보 보호정책을 공시하고 준수합니다.
③ 당 사이트는 회원으로부터 제기되는 의견이나 불만이 정당하다고 객관적으로 인정될 경우에는 적절한 절차를
거쳐 즉시 처리하여야 합니다. 다만, 즉시 처리가 곤란한 경우는 회원에게 그 사유와 처리일정을 통보하여야
합니다.
제 11 조 (회원의 의무)
① 이용자는 회원가입 신청 또는 회원정보 변경 시 실명으로 모든 사항을 사실에 근거하여 작성하여야 하며,
허위 또는 타인의 정보를 등록할 경우 일체의 권리를 주장할 수 없습니다.
② 당 사이트가 관계법령 및 개인정보 보호정책에 의거하여 그 책임을 지는 경우를 제외하고 회원에게 부여된
ID의 비밀번호 관리소홀, 부정사용에 의하여 발생하는 모든 결과에 대한 책임은 회원에게 있습니다.
③ 회원은 당 사이트 및 제 3자의 지적 재산권을 침해해서는 안 됩니다.
제 4 장 서비스의 이용
제 12 조 (서비스 이용 시간)
① 서비스 이용은 당 사이트의 업무상 또는 기술상 특별한 지장이 없는 한 연중무휴, 1일 24시간 운영을
원칙으로 합니다. 단, 당 사이트는 시스템 정기점검, 증설 및 교체를 위해 당 사이트가 정한 날이나 시간에
서비스를 일시 중단할 수 있으며, 예정되어 있는 작업으로 인한 서비스 일시중단은 당 사이트 홈페이지를
통해 사전에 공지합니다.
② 당 사이트는 서비스를 특정범위로 분할하여 각 범위별로 이용가능시간을 별도로 지정할 수 있습니다. 다만
이 경우 그 내용을 공지합니다.
제 13 조 (홈페이지 저작권)
① NDSL에서 제공하는 모든 저작물의 저작권은 원저작자에게 있으며, KISTI는 복제/배포/전송권을 확보하고
있습니다.
② NDSL에서 제공하는 콘텐츠를 상업적 및 기타 영리목적으로 복제/배포/전송할 경우 사전에 KISTI의 허락을
받아야 합니다.
③ NDSL에서 제공하는 콘텐츠를 보도, 비평, 교육, 연구 등을 위하여 정당한 범위 안에서 공정한 관행에
합치되게 인용할 수 있습니다.
④ NDSL에서 제공하는 콘텐츠를 무단 복제, 전송, 배포 기타 저작권법에 위반되는 방법으로 이용할 경우
저작권법 제136조에 따라 5년 이하의 징역 또는 5천만 원 이하의 벌금에 처해질 수 있습니다.
제 14 조 (유료서비스)
① 당 사이트 및 협력기관이 정한 유료서비스(원문복사 등)는 별도로 정해진 바에 따르며, 변경사항은 시행 전에
당 사이트 홈페이지를 통하여 회원에게 공지합니다.
② 유료서비스를 이용하려는 회원은 정해진 요금체계에 따라 요금을 납부해야 합니다.
제 5 장 계약 해지 및 이용 제한
제 15 조 (계약 해지)
회원이 이용계약을 해지하고자 하는 때에는 [가입해지] 메뉴를 이용해 직접 해지해야 합니다.
제 16 조 (서비스 이용제한)
① 당 사이트는 회원이 서비스 이용내용에 있어서 본 약관 제 11조 내용을 위반하거나, 다음 각 호에 해당하는
경우 서비스 이용을 제한할 수 있습니다.
- 2년 이상 서비스를 이용한 적이 없는 경우
- 기타 정상적인 서비스 운영에 방해가 될 경우
② 상기 이용제한 규정에 따라 서비스를 이용하는 회원에게 서비스 이용에 대하여 별도 공지 없이 서비스 이용의
일시정지, 이용계약 해지 할 수 있습니다.
제 17 조 (전자우편주소 수집 금지)
회원은 전자우편주소 추출기 등을 이용하여 전자우편주소를 수집 또는 제3자에게 제공할 수 없습니다.
제 6 장 손해배상 및 기타사항
제 18 조 (손해배상)
당 사이트는 무료로 제공되는 서비스와 관련하여 회원에게 어떠한 손해가 발생하더라도 당 사이트가 고의 또는 과실로 인한 손해발생을 제외하고는 이에 대하여 책임을 부담하지 아니합니다.
제 19 조 (관할 법원)
서비스 이용으로 발생한 분쟁에 대해 소송이 제기되는 경우 민사 소송법상의 관할 법원에 제기합니다.
[부 칙]
1. (시행일) 이 약관은 2016년 9월 5일부터 적용되며, 종전 약관은 본 약관으로 대체되며, 개정된 약관의 적용일 이전 가입자도 개정된 약관의 적용을 받습니다.