• Title/Summary/Keyword: Content management

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An Analysis of the Practices of Dental Hygienists in Offering Oral Health Education -In Case of Adult Patients Visiting Dental Clinics- (치과위생사의 구강보건지도 실천분석 -진료실내의 성인환자를 중심으로-)

  • Lee, Sung-Sook;Cho, Myung-Sook;Kim, Seol-Ag
    • Journal of the Korean Society of School Health
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    • v.12 no.1
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    • pp.131-141
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    • 1999
  • The purpose of this study was to serve as a basis for the planning of oral health education and the development of an oral health-promotion program for patients who visited dental clinics by examining how much dental hygienists offered oral health education to adult patients at dental clinics. A parent group was selected, being made up of 1,600 dental hygienists who registered with the Dental Hygienist Association and worked in Seoul. The questionnaire survey was carried out and an ${\chi}^2-test$ was made using the data collected from 218 subjects to determine how their practice of oral health education was different according to certain general characteristics(the sort of organization for which they worked, age, the term of their service, and the mean number of patients per day). As a result, the following findings were obtained: 1. Thees general characteristics made the following differences to the content of oral health, education: The sort of organization for which the subjects worked made a significant difference in the following tooth brushing instruction (p<0.05), the effect of oral prophylaxis or education about aftereffects (p<0.05), the regular examination of prosthesis (p<0.05), smoking-prohibition education (p<0.05), and the prevention poor-quality fillings (p<0.01). The mean number of patients per day made significant differences to the regular examination of prosthesis (p<0.05) and the prevention poor-quality fillings (p<0.01). But no significant disparity was generated by age or the term of service. 2. The general characteristics made the following differences to education about nutrition and diet counseling: The sort of organization for which the subjects worked had a significant effect just on the importance of a balanced menu (p<0.05). Age made significant differences in advice for vitamin, mineral, protein or other nutrients (p<0.01), and the importance of balanced menu (p<0.001). The term of service made significant differences in the importance of balanced menu (p<0.01), and advice for nutrients including vitamin, mineral or protein (p<0.01). 3. The general characteristics made the following differences to the recommendation and use of oral hygiene aids: The sort of oragnization for which they worked made significant differences only to a gingival massager and water pick (p<0.05). No significant difference was produced by age, the term of service or the mean number of patients per day. 4. The use of educational media for oral health was different according to the general characteristics: The use of pamphlets or booklets significantly varied depending on the organization for which they worked and with the mean number of patients per day (p<0.05). The use of slides or slide projectors was significantly affected by age (p<0.05). But no significant disparity was yielded by the term of service. 5. The general characteristics made the following difference as to whether a continued oral management system was carried out or not: The sort of organization for which they worked had very a significant effect on this result (p<0.001), and no significant disparity was made by age, the term of service or the mean number of patients per day. 6. The place where oral health education was giver differed according to the following general characteristics: The sort of organization for which they worked made very a significant difference as to the use of an examination room's dental unit chair or waiting room (p<0.01), and to the use of an oral health education room or reception counter (p<0.001). The term of service had a significant effect on the use of a counseling room (p<0.01). And the mean number of patients per day made significant differences in the use of a dental unit chair or reception counter (p<0.05), and to the use of an oral health education room or waiting room (p<0.01).

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Evaluation of No-tillage Rice Cover Crop Cropping Systems for Organic Farming (벼 유기농업을 위한 무경운 피복작물 작부체계 평가)

  • Lee, Young-Han
    • Korean Journal of Soil Science and Fertilizer
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    • v.43 no.2
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    • pp.200-208
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    • 2010
  • The objectives of this study were to evaluate no-tillage cover crop cropping systems for organic farming in paddy. The experiment was performed at Ihyeon series (silt loam: 9.1% sand, 73.0% silt and 17.9% clay) which affected by different management practices. Planthopper population per 20 plant was significantly higher 65.3 for conventional tillage with chemical compounds (control) compared with 3.4~9.6 for no-tillage treatments (without rice straw or green manure, amended with rice straw, hairy vetch, rape, rye, and Chinese milk vetch). Also, disease severity of sheath blight was significantly higher 10.5% for control compared to 0.7~2.9% for no-tillage treatments. Four weed species, namely Monochoria vaginalis, Ludwigia prostrata, Rotala indica, and Aneilema keisak occurred in no-tillage paddy, whereas Monochoria vaginalis occurred in control only. The pH, available phosphate, and microbial biomass C in paddy were steeply decreased in response to submerging, but increased at first heading stage. Soil $NH_4$-N content at first heading stage was significantly higher in no-tillage treatments compared with control. The grain yield was significantly higher in 4.30 Mg $ha^{-1}$ for control than other treatments. Meanwhile, rice productivity was significantly higher in 2.69 Mg $ha^{-1}$ for no-tillage amended with Chinese milk vetch compared to other no-tillage treatments. The number of panicle per plant, grain number perpanicle, and percent ripened grain were highly related for increasing the yield of rice. These results show that Chinese milk vetch was optimum cover crop for organic farming in no-tillage paddy.

Effects of Application Method of Dairy Liquid Manure on Productivity of Silage Corn and Sorghum × Sudangrass Hybrid and Soil Characteristics (젖소액비 시용방법이 담근먹이 옥수수와 수수 × 수단그라스 잡종의 생산성 및 토양특성에 미치는 영향)

  • Shin, J.S.;Lee, H.H.;Shin, D.E.;Jo, Y.M.;Jung, E.S.;Lee, J.K.;Yoon, S.H.
    • Journal of The Korean Society of Grassland and Forage Science
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    • v.19 no.4
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    • pp.333-338
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    • 1999
  • The experiment was carried out to find the effects of the application method of dairy liquid manure on productivity of silage corn(P3352) and sorghum $\times$ sudangrass hybrid(P988) and physical and chemical properties of soil during 2 years at Suwon. Crude protein content of T1(Chemical fertilizer) was highest by 6.5%, 8.9% in both forage, respectively, but total digestible nutrient(TDN) percent of T3(dairy liquid manure, basal + chemical fertilizer, topdressing) was highest by 73.8%, 59.0% in both forage, respectively. In TND yield, it was little different between T1(9.5 MT/ha) and others(8.4~9.3 MT/ha) at silage corn, but T4(chemical fertilizer at basal + dairy liquid manure at topdressing) was highest as 13.3 MT/ha at sorghum $\times$ sudangrass hybrid(p<0.05). pH of the soil after experiment was lower than that of the soil before experiment in the both forages, but soil organic matter was high at after trial than before trial. Available phosphorous and exchangeable cation were not shown the regular trend in this experiment. Based on the results of this experiment, it was not shown among different application method for silage corn (P3352), but application of chemical fertilizer at basal and liquid manure at topdressing was good for sorghum $\times$ sudangrass hybrid(P988).

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Drainage Performance of Various Subsurface Drain Materials- (배수개선공법개발에 관한 연구(I) -각종 지하배수용 암거재료의 배수성능-)

  • 김철회;이근후;유시조;서원명
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.21 no.3
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    • pp.104-120
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    • 1979
  • I. Title of the Study Studies on the Development of Improved Subsurface Drainage Methods. -Drainage Performance of Various Subsurface Drain Materials- II. Object of the Study Studies were carried out to select the drain material having the highest performance of drainage; And to develop the water budget model which is necessary for the planning of the drainage project and the establishment of water management standards in the water-logged paddy field. III. Content and Scope of the Study 1. The experiment was carried out in the laboratory by using a sand tank model. The drainage performance of various drain materials was compared evaluated. 2. A water budget model was established. Various parameters necessary for the model were investigated by analyzing existing data and measured data from the experimental field. The adaptability of the model was evaluated by comparing the estimated values to the field data. IV. Results and Recommendations 1. A corrugated tube enveloped with gravel or mat showed the highest drainage performance among the eight materials submmitted for the experiment. 2. The drainage performance of the long cement tile(50 cm long) was higher than that of the short cement tile(25 cm long). 3. Rice bran was superior to gravel in its' drain performance. 4. No difference was shown between a grave envelope and a P.V.C. wool mat in their performance of drainage. Continues investigation is needed to clarify the envelope performance. 5. All the results described above were obtained from the laboratory tests. A field test is recommended to confirm the results obtained. 6. As a water balance model of a given soil profile, the soil moisture depletion D, could be represented as follows; $$D=\Sigma\limit_{t=1}^{n}(Et-R_{\ell}-I+W_d)..........(17)$$ 7. Among the various empirical formulae for potential evapotranspiration, Penman's formular was best fit to the data observed with the evaporation pans in Jinju area. High degree of positive correlation between Penman;s predicted data and observed data was confirmed. The regression equation was Y=1.4X-22.86, where Y represents evaporation rate from small pan, in mm/100 days, and X represents potential evapotranspiration rate estimated by Penman's formular. The coefficient of correlation was r=0.94.** 8. To estimate evapotranspiration in the field, the consumptive use coefficient, Kc, was introduced. Kc was defined by the function of the characteristics of the crop soil as follows; $Kc=Kco{\cdot}Ka+Ks..........(20)$ where, Kco, Ka ans Ks represents the crop coefficient, the soil moisture coefficient, and the correction coefficient, respectively. The value of Kco and Ka was obtained from the Fig.16 and the Fig.17, respectively. And, if $Kco{\cdot}Ka{\geq}1.0,$ then Ks=0, otherwise, Ks value was estimated by using the relation; $Ks=1-Kco{\cdot}Ka$. 9. Into type formular, $r_t=\frac{R_{24}}{24}(\frac{b}{\sqrt{t}+a})$, was the best fit one to estimate the probable rainfall intensity when daily rainfall and rainfall durations are given as input data, The coefficient a and b are shown on the Table 16. 10. Japanese type formular, $I_t=\frac{b}{\sqrt{t}+a}$, was the best fit one to estimate the probable rainfall intensity when the rainfall duration only was given. The coefficient a and b are shown on the Table 17. 11. Effective rainfall, Re, was estimated by using following relationships; Re=D, if $R-D\geq}0$, otherwise, Re=R. 12. The difference of rainfall amount from soil moisture depletion was considered as the amount of drainage required. In this case, when Wd=O, Equation 24 was used, otherwise two to three days of lag time was considered and correction was made by use of storage coefficient. 13. To evaluate the model, measured data and estimated data was compared, and relative error was computed. 5.5 percent The relative error was 5.5 percent. 14. By considering the water budget in Jinju area, it was shown that the evaporation amount was greater than the rainfall during period of October to March in next year. This was the behind reasonning that the improvement of surface drainage system is needed in Jinju area.

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The Research of Storage Capacity & Sedimentation of Reservoirs in HONAM Province (호남지방에 저수지의 매몰상황과 저수량에 관한 조사연구(농학계))

  • 이창구
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.13 no.2
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    • pp.2262-2275
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    • 1971
  • Fourteenes rervoirs maintained by the local land improvement associations in the province of Chullabuk-Do and 20 reservoir maintained by thos in the province of Chullanam-Do, were surveyed in connection with a correction between storage capacity and sediment deposit. In addition to this survey, 3,347 of small reservoir, that lie scattered around in the above-mentioned two provinces were investigated by using existing two provinces were investigated by using existing records pertaining to storage capacity in the office of City and country, respectively. According to this investigation the following comclusions are derived. 1. A sediment deposition rate is high, being about $10.63m^3/ha$ of drainage area, and resulting in the average decreasc of storage capaity by 27.5%. This high rate of deposition coule be mainly attributed to the serve denudation of forests due to disorderly cuttings of trees. Easpecially, in small reservoir, an original average design storage depth of 197mm in irrigation water depth is decreased to about 140mm. 2. An average unit storage depth of 325.6mm as the time of initial construction is decreased to 226mm at present. This phenomena causes a greater shortage irrigation water, since it was assumed that original storage quantity was already in short. 3. Generally speaking, seepage rates through dam abutment intakepipe, etc, are high due to insufficient maintenance and management of reservoir. 4. It is recommended that sediment deposit should be dredged when a reservoir is dry in drought. 5. Farmers usually waste excessive irrigation water. 6. Water saving methods should be practiced by applying only necessary water for growing stage of rice. 7. In are as where water defficiency for irrigation is severe, a soil moisture content should be kept at about 70% by applying water once in several days. 8. Tube wells should be provided so as to exploit ground water and subsurface current below stream bed as much as possible. 9. If an intake weir was constructed, a water collection well should be built for the use in drought. 10. Water conservation should be forced by converting devastated forests contained in the drainage area of reservoir to protected forests so as to take priority of yrefor estation, gully control, the prohibition of disorderly cutting of trees, etc. 11. Collective rice nurseries should be adopted, and it should be recommended that irrigation water for rice nurseries is supplied by farmer themselves. 12. Sediment desposit in reservoir should be thoroughly dreged so as to secure a original design storage capacity. 13. The structure of overflow weir should be automatic so as to freely control flood level and not to increase dam height.

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Extracting Beginning Boundaries for Efficient Management of Movie Storytelling Contents (스토리텔링 콘텐츠의 효과적인 관리를 위한 영화 스토리 발단부의 자동 경계 추출)

  • Park, Seung-Bo;You, Eun-Soon;Jung, Jason J.
    • Journal of Intelligence and Information Systems
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    • v.17 no.4
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    • pp.279-292
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    • 2011
  • Movie is a representative media that can transmit stories to audiences. Basically, a story is described by characters in the movie. Different from other simple videos, movies deploy narrative structures for explaining various conflicts or collaborations between characters. These narrative structures consist of 3 main acts, which are beginning, middle, and ending. The beginning act includes 1) introduction to main characters and backgrounds, and 2) conflicts implication and clues for incidents. The middle act describes the events developed by both inside and outside factors and the story dramatic tension heighten. Finally, in the end act, the events are developed are resolved, and the topic of story and message of writer are transmitted. When story information is extracted from movie, it is needed to consider that it has different weights by narrative structure. Namely, when some information is extracted, it has a different influence to story deployment depending on where it locates at the beginning, middle and end acts. The beginning act is the part that exposes to audiences for story set-up various information such as setting of characters and depiction of backgrounds. And thus, it is necessary to extract much kind information from the beginning act in order to abstract a movie or retrieve character information. Thereby, this paper proposes a novel method for extracting the beginning boundaries. It is the method that detects a boundary scene between the beginning act and middle using the accumulation graph of characters. The beginning act consists of the scenes that introduce important characters, imply the conflict relationship between them, and suggest clues to resolve troubles. First, a scene that the new important characters don't appear any more should be detected in order to extract a scene completed the introduction of them. The important characters mean the major and minor characters, which can be dealt as important characters since they lead story progression. Extra should be excluded in order to extract a scene completed the introduction of important characters in the accumulation graph of characters. Extra means the characters that appear only several scenes. Second, the inflection point is detected in the accumulation graph of characters. It is the point that the increasing line changes to horizontal line. Namely, when the slope of line keeps zero during long scenes, starting point of this line with zero slope becomes the inflection point. Inflection point will be detected in the accumulation graph of characters without extra. Third, several scenes are considered as additional story progression such as conflicts implication and clues suggestion. Actually, movie story can arrive at a scene located between beginning act and middle when additional several scenes are elapsed after the introduction of important characters. We will decide the ratio of additional scenes for total scenes by experiment in order to detect this scene. The ratio of additional scenes is gained as 7.67% by experiment. It is the story inflection point to change from beginning to middle act when this ratio is added to the inflection point of graph. Our proposed method consists of these three steps. We selected 10 movies for experiment and evaluation. These movies consisted of various genres. By measuring the accuracy of boundary detection experiment, we have shown that the proposed method is more efficient.

Heavy Metals of Landfilled Biomass and Their Environmental Standard, Including CCA-treated Wood for Eco-housing Materials (방부처리 목재를 포함한 토양매립 바이오메스의 중금속 함량과 안전성 문제)

  • Lim, Kie-Pyo;Lee, Jong-Tak;Bum, Jung-Won
    • Journal of the Korean Wood Science and Technology
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    • v.34 no.4
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    • pp.37-45
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    • 2006
  • Recently, wood-framed houses has been built in the Korea for pension. Wood is good material for human healthy, while the construction lumbers are treated with preservative such as CCA (chromated copper arsenate), which contain some toxic elements for human body. However, if the waste woody biomass treated with various heavy metals, which has been collected from house construction or demolition, was fired in the field, and incinerated or landfilled after mass collection, such components will result in the toxic air pollutants in the burning or land fills, and spreaded into other areas. So the careful selection of wood and chemicals are required in advance for house construction, in particular, for environment-friendly housings. Therefore, this study was carried out to determine the content of toxic heavy metals in woody materials such as domestic hinoki and imported hemlock treated with CCA for housing materials, and the post-treated wood components such as organic fertilizer, sludge, dry-distilled charcoal and carbonized charcoal, to be returned finally into soil. The results are as follows. 1) The chemical analysis of toxic trace elements in various solid biomass required accurate control and management of laboratory environment, and reagents and water used, because of the error of data due to various foreign substances added in various processing and transporting steps. So a systematic analyzers was necessary to monitor the toxic pollutants of construction materials. 2) In particular, the biomass treated with industrial biological or thermal conditions such as sludge or charcoals was not fully dissolvable after third addition of $HNO_3$ and HF. 3) The natural woody materials such as organic fertilizer, sludge. and charcoals without any treatment of preservatives or heavy metal components were nontoxic in landfill because of the standard of organic fertilizers, even after thermal or biological treatments. 4) The CC A-treated wood for making the construction wood durable should not be landfilled, because of its higher contents of toxic metals than the criterion of organic fertilizer for agriculture or of natural environment. So the demolished waste should be treated separately from municipal wastes.

Improvement of Shelf-life and Quality in Fresh-Cut Tomato Slices:

  • Hong Ji Heun
    • Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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    • 2004.10a
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    • pp.67-72
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    • 2004
  • Quality of fresh-cut tomato slices was compared during cold storage under various modified atmosphere packaging conditions. Chilling injury of slices in containers sealed with Film A was higher than with Film B; these films had oxygen transmission rates of 87.4 and 60.0 ml $h^{-1}\;m^{-2}\;atm^{-1}$ at $5^{\circ}C\;and\;99\%$ RH, respectively. While slices in containers with an initial atmospheric composition of air, $4\%\;CO_2+1\;or\;20\%\;O_2,\;8\%\;CO_2+1\;or\;20\%\;O_2,\;or\;12\%\;CO_2+20\%\;O_2$ showed fungal growth, slices in containers with $12\%\;CO_2+1\%\;O_2$ did not. Low ethylene in containers enhanced chilling injury. Modified atmosphere packaging provided good quality tomato slices with a shelf-life of 2 weeks or more at $5^{\circ}C$. Experiments were conducted to compare changes in quality of slices of red tomato (Lycopersicon esculentum Mill. 'Sunbeam') fruit from plants grown using black polyethylene or hairy vetch mulches under various foliar disease management systems including: no fungicide applications (NF), a disease forecasting model (Tom-Cast), and weekly fungicide applications (WF), during storage at $5^{\circ}C$ under a modified atmosphere. Slices were analyzed for firmness, soluble solids content (SSC), titratable acidity (TA), pH, electrolyte leakage, fungi, yeasts, and chilling injury. With both NF and Tom-Cast fungicide treatments, slices from tomato fruit grown with hairy vetch (Vicia villosa Roth) mulch were firmer than those from tomato fruit grown with black polyethylene mulch after 12 days storage. Ethylene production of slices from fruit grown using hairy vetch mulch under Tom-Cast was about 1.5- and 5-fold higher than that of slices from WF and NF fungicide treatments after 12 days, respectively. The percentage of water-soaked areas (chilling injury) for slices from tomato fruit grown using black polyethylene mulch under NF was over 7-fold that of slices from tomato fruit grown using hairy vetch under Tom-Cast. When stored at $20^{\circ}C$, slices from light-red tomato fruit grown with black polyethylene or hairy vetch mulches both showed a rapid increase in electrolyte leakage beginning 6 hours after slicing. However, slices from tomato fruit grown using the hairy vetch mulch tended to have lower electrolyte leakage than those grown with black polyethylene mulch. These results suggest that tomato fruit from plants grown using hairy vetch mulch may be more suitable for fresh-cut slices than those grown using black polyethylene mulch. Also, use of the disease forecasting model Tom-Cast, which can result in lower fungicide application than is currently used commercially, resulted in high quality fruit for fresh-cut processing. Experiments were conducted to determine if ethylene influences chilling injury, as measured by percentage of slices exhibiting water-soaked areas in fresh-cut tomato slices of 'Mountain Pride' and 'Sunbeam' tomato (Lycopersicon esculentum Mill.). Ethylene concentration in containers without ventilation significantly increased during storage at $5^{\circ}C$, whereas little or no accumulation of ethylene occurred in containers with one or six perforations. Chilling injury was greatest for slices in containers with six perforations, compared to slices in containers with one perforation, and was over 13-fold greater than that of slices in control containers with no perforations. An experiment was also performed to investigate the effectiveness of including an ethylene absorbent pad in containers on subsequent ethylene accumulation and chilling injury. While ethylene in the no-pad controls increased continually during storage of both 'Mountain Pride' and 'Sunbeam' tomatoes at $5^{\circ}C$ under modified atmosphere conditions, no increase in accumulation of ethylene was observed in containers containing ethylene absorbent pads throughout storage. The ethylene absorbent pad treatment resulted in a significantly higher percentage of chilling injury compared with the no-pad control. In studies aimed at inhibiting ethylene production using AVG during storage of slices, the concentration of ethylene in control containers (no AVG) remained at elevated levels throughout storage, compared to containers with slices treated with AVG. Chilling injury in slices treated with AVG was 5-fold greater than that of controls. Further, we tested the effect of ethylene pretreatment of slices on subsequent slice shelf-life and quality. In slices treated with ethylene (0, 0.1, 1, or $10\;{mu}L\;L^{-1}$) immediately after slicing, ethylene production in non-treated controls was greater than that of all other ethylene pre-treatments. However, pretreatment of slices 3 days after slicing resulted in a different pattern of ethylene production during storage. Ihe rate of ethylene production by slices treated with 1 L $L^{-1}$ ethylene 3 days after slicing was greater during storage than any of the other ethylene treatments. With slices pre-treated with ethylene, both immediately and 3 days after slicing, the rate of ethylene production tended to show an negative correlation with chilling injury. Chemical name used: 1-aminoethoxyvinylglycine (AVG).

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Survey on the Sodium Contents of Nursery School Meals in Gyeonggi-Do (경기도지역 어린이집의 단체급식 중 나트륨 함량 실태조사 연구)

  • Jung, Hong-Rae;Lee, Myung-Jin;Kim, Ki-Cheol;Kim, Jung-Boem;Kim, Dae-Hwan;Kang, Suk-Ho;Park, Jong-Suk;Kwon, Kwang-Il;Kim, Mee-Hye;Park, Yong-Bae
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.39 no.4
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    • pp.526-534
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    • 2010
  • The prevalence rate for chronic diseases such as obesity, diabetes, hypertension etc. caused by the increment of national income and the change of food life according to the globalization in Korea have been increased. Especially excess sodium intake may contribute to the development of hypertension, increasing cardiovascular disease risk. The objective of this study was to investigate sodium intake of nursery school meals in Gyeonggi-Do, and to construct database for lesser sodium intake policy. Survey consisted of 601 sample intakes of sodium in summer and in winter. A food weighed record method was used for measuring food intakes. Average intakes of ten children per nursery school were measured. The sodium contents of meals were analyzed by ICP-OES (inductively coupled plasma-optical emission spectrometer) after acid digestion by microwave. The sodium contents on food groups showed that sources (693 mg/100 g), grilled foods (689 mg/100 g) and kimchies (643 mg/100 g) had respectively higher sodium contents and the average sodium intake per meal was $582\pm204$ mg. The sodium contents of soups & hot soups and kimchies had 37.5% and 15.8% of total sodium intakes per meal, respectively. Sodium intakes per meal in summer and winter showed 572.3 mg and 592.3 mg, respectively. Regional ranking of sodium intakes showed the ascending order of apartment (514.3 mg/meal), rural region (540.5 mg/meal), multiplex house (635.9 mg/meal) and industrial complex (696.4 mg/ meal). A habit of excessive sodium intakes in childhood will threaten their health when they grow up to be adults; thus lesser intake of sodium per meal is needed for children in nursery school.

Reaction Mechanism and Curing Characteristics of Chicken Feather-Based Adhesives and Adhesive Properties of Medium-Density Fiberboard Bonded with the Adhesive Resins (닭털로 제조한 접착제의 반응기작 및 경화 특성과 이를 이용하여 제조한 중밀도섬유판의 접착 특성)

  • Yang, In;Park, Dae-Hak;Choi, Won-Sil;Oh, Sei Chang;Ahn, Dong-uk;Han, Gyu-Seong
    • Korean Chemical Engineering Research
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    • v.55 no.3
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    • pp.385-394
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    • 2017
  • In this study, reaction mechanism and curing characteristics of adhesives formulated with NaOH- and $H_2SO_4$-hydrolyzed chicken feather (CF) and formaldehyde-based crosslinkers were investigated by FT-IR and DSC. In addition, adhesive properties and formaldehyde emission of medium-density fiberboards (MDF) applied with the adhesives were measured. CF-based adhesives having a solid content of 40% and over were very viscous at $25^{\circ}C$, but the viscosity reduced to $300{\sim}660m{\cdot}Pa{\cdot}s$ at $50^{\circ}C$. Consequently, the adhesives could be used as a sprayable resin. Through the FT-IR spectra of liquid and cured CF-based adhesives, addition reaction of methylol group and condensation reaction between the functional groups with the use of formaldehyde-based crosslinkers were identified. From the analysis of DSC, it was elucidated for CF-based adhesives to require a higher pressing temperature or longer pressing time comparing to commercial urea-formaldehyde (C-UF) resin. MDF bonded with CF-based adhesives, which was formulated with 5% NaOH-hydrolyzed CF (CF-AK-5%) and PF of formaldehyde to phenol mole ratio of 2.5 (PF-2.5), and pressed for 8 min had higher MOR and IB than those with other CF-based adhesives. MOR and IB of MDF bonded with the CF-based adhesives regardless of formulation type and pressing time were higher than those with C-UF resin. When the values compared with the minimum requirements of KS standard, IB exceeded the KS standard in all formulations and pressing time, but MOR of only MDF bonded with CF-AK-5% and PF-2.5 and pressed for 8 min satisfied the KS standard. What was worse, 24-TS of MDF bonded with all CF-based adhesives did not satisfied the KS standard. However, MOR and 24-TS can be improved by increasing the target density of MDF or the amount of wax emulsion, which is added to improve the water resistance of MDF. Importantly, the use of CF-based adhesives decreased greatly the formaldehyde emission. Based on the results, we reached the conclusion that CF-based adhesives formulated under proper conditions had a potential as a sprayable resin for the production of wood panels.