• Title/Summary/Keyword: Power Level Control

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Investigation on Diesel Injection Characteristics of Natural Gas-Diesel Dual Fuel Engine for Stable Combustion and Efficiency Improvement Under 50% Load Condition (천연가스-디젤 혼소 엔진의 50% 부하 조건에서 제동효율 및 연소안정성 개선을 위한 디젤 분무 특성 평가)

  • Oh, Sechul;Oh, Junho;Jang, Hyungjun;Lee, Jeongwoo;Lee, Seokhwan;Lee, Sunyoup;Kim, Changgi
    • Journal of the Korean Institute of Gas
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    • v.26 no.3
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    • pp.45-53
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    • 2022
  • In order to improve the emission of diesel engines, natural gas-diesel dual fuel combustion compression ignition engines are in the spotlight. In particular, a reactivity controlled compression ignition (RCCI) combustion strategy is investigated comprehensively due to its possibility to improve both efficiency and emissions. With advanced diesel direct injection timing earlier than TDC, it achieves spontaneous reaction with overall lean mixture from a homogeneous mixture in the entire cylinder area, reducing nitrogen oxides (NOx) and particulate matter (PM) and improving braking heat efficiency at the same time. However, there is a disadvantage in that the amount of incomplete combustion increases in a low load region with a relatively small amount of fuel-air. To solve this, sensitive control according to the diesel injection timing and fuel ratio is required. In this study, experiments were conducted to improve efficiency and exhaust emissions of the natural gas-diesel dual fuel engine at low load, and evaluate combustion stability according to the diesel injection timing at the operation point for power generation. A 6 L-class commercial diesel engine was used for the experiment which was conducted under a 50% load range (~50 kW) at 1,800 rpm. Two injectors with different spray patterns were applied to the experiment, and the fraction of natural gas and diesel injection timing were selected as main parameters. Based on the experimental results, it was confirmed that the brake thermal efficiency increased by up to 1.3%p in the modified injector with the narrow-angle injection added. In addition, the spray pattern of the modified injector was suitable for premixed combustion, increasing operable range in consideration of combustion instability, torque reduction, and emissions level under Tier-V level (0.4 g/kWh for NOx).

An Economic Factor Analysis of Air Pollutants Emission Using Index Decomposition Methods (대기오염 배출량 변화의 경제적 요인 분해)

  • Park, Dae Moon;Kim, Ki Heung
    • Environmental and Resource Economics Review
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    • v.14 no.1
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    • pp.167-199
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    • 2005
  • The following policy implications can be drawn from this study: 1) The Air Pollution Emission Amount Report published by the Ministry of Environment since 1991 classifies industries into 4 sectors, i. e., heating, manufacturing, transportation and power generation. Currently, the usability of report is very low and extra efforts should be given to refine the current statistics and to improve the industrial classification. 2) Big pollution industries are as follows - s7, s17 and s20. The current air pollution control policy for these sectors compared to other sectors are found to be inefficient. This finding should be noted in the implementation of future air pollution policy. 3) s10 and s17 are found to be a big polluting industrial sector and its pollution reduction effect is also significant. 4) The effect of emission coefficient (${\Delta}f$) has the biggest impact on the reduction of emission amount change and the effect of economic growth coefficient (${\Delta}y$) has the biggest impact on the increase of emission volume. The effect of production technology factor (${\Delta}D$) and the effect of the change of the final demand structure (${\Delta}u$) are insignificant in terms of the change of emission volume. 5) Further studies on emission estimation techniques on each industry sector and the economic analysis are required to promote effective enforcement of the total volume control system of air pollutants, the differential management of pollution causing industrial sectors and the integration of environment and economy. 6) Korea's economic growth in 1990 is not pollution-driven in terms of the Barry Commoner's hypothesis, even though the overall industrial structure and the demand structure are not environmentally friendly. It indicates that environmental policies for the improvement of air quality depend mainly on the government initiatives and systematic national level consideration of industrial structures and the development of green technologies are not fully incorporated.

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Effect of Garlic and Medicinal Plants Composites on Antioxidant Activity and Lipid Levels of Liver in Hypercholesterolemic Rats (마늘과 한약재 복합물의 항산화 활성 및 고콜레스테롤 급이 흰쥐의 간장 지질 함량에 미치는 영향)

  • Lee, Soo-Jung;Shin, Jung-Hye;Kang, Min-Jung;Yang, Seung-Mi;Ju, Jong-Chan;Sung, Nak-Ju
    • Journal of Life Science
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    • v.19 no.12
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    • pp.1769-1776
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    • 2009
  • The effects of combined garlic and medicinal plant extracts such as Gyeolmyeongja (Cassia obtusifolia Linne), Hasuo (Polygoni multiflori Radix), Youngji (Ganoderma lucium) and Sansayuk (Crataegus pinnatifida Bunge) on the antioxidant activity and lipid levels in the livers of rats fed a high cholesterol diet were analyzed. Total phenol and flavonoid contents were the highest in the Gyeolmyeongja by $151.02{\pm}5.20\;mg$/100 g and $43.69{\pm}5.58\;mg$/100 g. Electron donating ability, reducing power and hydroxyl radical scavenging activity were significantly increased when over 0.3% garlic extract was added. The antioxidant activity of linoleic acid in $\beta$- carotene increased in a dose dependant manner in response to the concentration of garlic extract. In livers of rats, the content of total lipids was significantly decreased by feeding garlic and medicinal plants composites; in particular, the group in which 0.7% garlic extract was added was the lowest. Total cholesterol was 14.95 mg/g in the control group; its level was lower in the groups fed garlic and medicinal plants composites, ranging from 11.47 to 11.86 mg/g. Triglyceride concentration was significantly decreased in the group fed 0.7% garlic extracts, with 46.42 mg/g compared to groups fed 0.3% and 0.5%. TBARS content showed a 15.8~17.6% decrease in groups fed 0.5~0.7% garlic extract and medicinal plants composites. Antioxidant activity was significantly increased in groups fed over 0.5% garlic extract compared to the control group. This study shows that garlic and medicinal plant composites intake is able to reduce the levels of liver lipids in hypercholesterolemic rats.

Aerobic Capacity and Ventilatory Response During Incremental Exercise in Elite High School Cyclist (점진부하 운동에서 중고교 엘리트 사이클 선수들의 유산소능력과 폐환기 반응)

  • Lee, Dae-Taek;Bae, Yoon-Jung
    • Journal of Life Science
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    • v.20 no.3
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    • pp.437-443
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    • 2010
  • This study was designed to examine the aerobic capacity and ventilatory response during an incremental exercise in elite high school cyclists. Twelve boys ($17{\pm}1\;yr$, $175{\pm}5\;cm$, $70{\pm}9\;kg$) participated in anthropometric measurements, incremental exercise testing, and pulmonary function tests. During incremental exercise testing using a cycle ergometer, their maximal oxygen uptake ($VO_2max$), maximal power output, ventilation, ventilatory equivalents for oxygen ($V_E/VO_2$) and carbon dioxide ($V_E/VCO_2$), respiratory rate, and tidal volume were measured. Time variables such as inspiratory time (Ti), expiratory time (Te), breathing time (Tb), and inspiratory duty cycle (Ti/Tb), as well as inspiratory flow rate ($V_T$/Ti) were assessed. Pulmonary function of vital capacity (FVC), forced expiratory volume in one second ($FEV_1$), $FEV_1$/FVC, and peak expiratory flow were evaluated. Their $VO_2max$, maximal heart rate, and Wmax were $57.5{\pm}3.9\;ml{\cdot}kg^{-1}{\cdot}min^{-1}$, $194.1{\pm}8.6\;beat{\cdot}min^{-1}$, and 452 W, respectively. $VO_2max$ was not related to any anthropometric parameters. Most ventilatory variables progressively increased with exercise intensity. As intensity increased, Ti, Tb, Tb decreased while Ti/Tb was maintained. Below an intensity of 250 W, height, weight, body mass index, and body surface were highly correlated with $V_T$/Ti and Ti/Tb (p<0.05). Collectively, $VO_2max$ appeared to be lower than adult cyclists, suggesting a different pattern of ventilatory control as age advances. Morphological characteristics were not related to $VO_2max$ in the population. Time variables of ventilatory response seemed to be related only at an exercise intensity level of less than 250 W. $V_T$/Ti may be related to exercise endurance capacity, but Ti/Tb was similar to adult cyclists.

Antioxidant and Anti-inflammatory Activities of Functional Plant Materials (항산화 및 면역 활성 증강을 위한 생약재의 탐색)

  • Lee, Soo-Jung;Shin, Jung-Hye;Lee, Hye-Jin;Tak, Hyun-Min;Kang, Min-Jung;Sung, Nak-Ju
    • Journal of Life Science
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    • v.23 no.7
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    • pp.869-878
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    • 2013
  • Eleven functional plant materials were identified via a literature search, and their antioxidant capacity and inhibitory effects on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW264.7 cells were tested. Yields from hot water extracts of the materials were the highest (52.10%) in Lycii fructus, and the yields from Phellinus linteus were the lowest (5.7%). The yields of another were 14.50-42.47%. Total phenol and flavonoids contents were the highest in P. linteus. The $EC_{50}$ values for DPPH and ABTS radical scavenging activities were lower than $100{\mu}g/ml$ for Salvia miltiorrhiza, whereas the values for P. linteus, Scutellaria baicalensis, and Paeonia lactiflora were $100-200{\mu}g/ml$. The $EC_{50}$ value for the superoxide anion radical scavenging activity of all the extracts was higher than $300{\mu}g/ml$. P. linteus for the reducing power was shown the highest activity. $Fe^{2+}$ chelating activity was the highest in the Morus alba extract. In an MTT assay, the cell viability of the RAW264.7 LPS-exposed cells was above 80% in extracts of $50{\mu}g/ml$ and above 77% in extracts of $100{\mu}g/ml$ in all the plant materials except Acanthopanax sessiliflorum. NO production in the RAW264.7 LPS-exposed cells showed a 12-fold increase compared to the control. The NO production level of all the extracts was $6.86-26.18{\mu}M$. Notably, $100{\mu}g/ml$ of S. baicalensis extract showed a remarkable decrease in NO production (72%) compared with the control. The potent antioxidant and anti-inflammatory activities of S.baicalensis, P. linteus, S. miltiorrhiza, M. alba, and P. lactiflora suggest that they are potential candidates as functional materials.

The Impacts of Need for Cognitive Closure, Psychological Wellbeing, and Social Factors on Impulse Purchasing (인지폐합수요(认知闭合需要), 심리건강화사회인소대충동구매적영향(心理健康和社会因素对冲动购买的影响))

  • Lee, Myong-Han;Schellhase, Ralf;Koo, Dong-Mo;Lee, Mi-Jeong
    • Journal of Global Scholars of Marketing Science
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    • v.19 no.4
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    • pp.44-56
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    • 2009
  • Impulse purchasing is defined as an immediate purchase with no pre-shopping intentions. Previous studies of impulse buying have focused primarily on factors linked to marketing mix variables, situational factors, and consumer demographics and traits. In previous studies, marketing mix variables such as product category, product type, and atmospheric factors including advertising, coupons, sales events, promotional stimuli at the point of sale, and media format have been used to evaluate product information. Some authors have also focused on situational factors surrounding the consumer. Factors such as the availability of credit card usage, time available, transportability of the products, and the presence and number of shopping companions were found to have a positive impact on impulse buying and/or impulse tendency. Research has also been conducted to evaluate the effects of individual characteristics such as the age, gender, and educational level of the consumer, as well as perceived crowding, stimulation, and the need for touch, on impulse purchasing. In summary, previous studies have found that all products can be purchased impulsively (Vohs and Faber, 2007), that situational factors affect and/or at least facilitate impulse purchasing behavior, and that various individual traits are closely linked to impulse buying. The recent introduction of new distribution channels such as home shopping channels, discount stores, and Internet stores that are open 24 hours a day increases the probability of impulse purchasing. However, previous literature has focused predominantly on situational and marketing variables and thus studies that consider critical consumer characteristics are still lacking. To fill this gap in the literature, the present study builds on this third tradition of research and focuses on individual trait variables, which have rarely been studied. More specifically, the current study investigates whether impulse buying tendency has a positive impact on impulse buying behavior, and evaluates how consumer characteristics such as the need for cognitive closure (NFCC), psychological wellbeing, and susceptibility to interpersonal influences affect the tendency of consumers towards impulse buying. The survey results reveal that while consumer affective impulsivity has a strong positive impact on impulse buying behavior, cognitive impulsivity has no impact on impulse buying behavior. Furthermore, affective impulse buying tendency is driven by sub-components of NFCC such as decisiveness and discomfort with ambiguity, psychological wellbeing constructs such as environmental control and purpose in life, and by normative and informational influences. In addition, cognitive impulse tendency is driven by sub-components of NFCC such as decisiveness, discomfort with ambiguity, and close-mindedness, and the psychological wellbeing constructs of environmental control, as well as normative and informational influences. The present study has significant theoretical implications. First, affective impulsivity has a strong impact on impulse purchase behavior. Previous studies based on affectivity and flow theories proposed that low to moderate levels of impulsivity are driven by reduced self-control or a failure of self-regulatory mechanisms. The present study confirms the above proposition. Second, the present study also contributes to the literature by confirming that impulse buying tendency can be viewed as a two-dimensional concept with both affective and cognitive dimensions, and illustrates that impulse purchase behavior is explained mainly by affective impulsivity, not by cognitive impulsivity. Third, the current study accommodates new constructs such as psychological wellbeing and NFCC as potential influencing factors in the research model, thereby contributing to the existing literature. Fourth, by incorporating multi-dimensional concepts such as psychological wellbeing and NFCC, more diverse aspects of consumer information processing can be evaluated. Fifth, the current study also extends the existing literature by confirming the two competing routes of normative and informational influences. Normative influence occurs when individuals conform to the expectations of others or to enhance his/her self-image. Whereas informational influence occurs when individuals search for information from knowledgeable others or making inferences based upon observations of the behavior of others. The present study shows that these two competing routes of social influence can be attributed to different sources of influence power. The current study also has many practical implications. First, it suggests that people with affective impulsivity may be primary targets to whom companies should pay closer attention. Cultivating a more amenable and mood-elevating shopping environment will appeal to this segment. Second, the present results demonstrate that NFCC is closely related to the cognitive dimension of impulsivity. These people are driven by careless thoughts, not by feelings or excitement. Rational advertising at the point of purchase will attract these customers. Third, people susceptible to normative influences are another potential target market. Retailers and manufacturers could appeal to this segment by advertising their products and/or services as products that can be used to identify with or conform to the expectations of others in the aspiration group. However, retailers should avoid targeting people susceptible to informational influences as a segment market. These people are engaged in an extensive information search relevant to their purchase, and therefore more elaborate, long-term rational advertising messages, which can be internalized into these consumers' thought processes, will appeal to this segment. The current findings should be interpreted with caution for several reasons. The study used a small convenience sample, and only investigated behavior in two dimensions. Accordingly, future studies should incorporate a sample with more diverse characteristics and measure different aspects of behavior. Future studies should also investigate personality traits closely related to affectivity theories. Trait variables such as sensory curiosity, interpersonal curiosity, and atmospheric responsiveness are interesting areas for future investigation.

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A Study on the Administrative Enhancement for Health Center Activities (보건소(保健所) 행정(行政)의 기선을 위(爲)한 연구(硏究))

  • Moon, Ok-Ryun
    • Journal of Preventive Medicine and Public Health
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    • v.3 no.1
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    • pp.97-110
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    • 1970
  • This survey was conducted to evaluate not only the present status of health center directors-their personal histories, their will to private practice in the future, their responses to governmental policies, -but also the distribution of doctorless myons, budget and subsidy, and director's opinions to the enhancement of health center activities. This survey questioned 116 health center directors and 16 health personnel from August to October of 1970 and obtained the following results; 1) The average ages of directors of kun, city, and total health centers were $43.2{\pm}7.8,\;42.1{\pm}7.7,\;and\;42.9{\pm}10.3$ respectively. 2) The average family sizes of directors of kun, city, and total health centers were $5.6{\pm}2.7,\;5.6{\pm}2.1,\;and\;5.6{\pm}2.6$ respectively. 3) Directors holding M. D. degrees were 79.3%, those holding qualified M. D. degrees ('approved director') were 20.7%. 4) M. P. H., M. S., and Ph. D. holders were 6.0%, 6.1%, and 4.3% respectively. 5) The average duration of present directorship in kun and city were 30.2 months and 20.4 months respectively. 6) The majority of directors had been employed in related fields before assuming current position : directorship at other health center 26.7%, army 22.4%, health subcenter 21.6%, private practice 19.0%. 7) Average length of directorship is 41.8 months. Average length of public health career, including health subcenter and present position, is 56.5 months. 8) Both rural and urban experience in health centers for regular directors is 16.3% and for approved directors, 12,5%. A total of 15.5% of all survey directors had experience in both rural and urban health center. 9) A total of 70.7% of health center directorships were staffed by local doctors. 10) Nearly 40% wanted to quit the directorships within 3 years and 60.3% had already experienced private practice. 11) Of the regular directors 17.4% felt strongly about devoting their lives to public health fields, but only 4.1% of the approved approved directors felt so. 12) There wire 432 doctorless myons among 996 respondent myons and 4.5 doctorless myons per kun. 13) The percentage of doctorless myon by Province are as follows, Cholla buk-do 57.2%, Cholla nam-de 55.0%, Kyungsang nam-do 52.0%, Kyungsang buk-do 49.7%, Chungchong but-do 42.4%, Kyonggi-do 32.9%. Cheju-do 30.8%, Kangwon-do 25.8%. 14) Two thirds of health critters have experienced the abscence of the director for a certain period since 1966 and the average span of the abscence was 18.2 months. 15) The percentage of doctorless myons increased proportionally with the span of the director's abscence. 16) The average budgets of health centers, kun, city and ku, were $W15.03\;million{\pm}W4.5\;million,\;W22.03\;million{\pm}W17.80\;million,\;W13.10\;million{\pm}W7.9\;million$ respectively. 17) Chunju city had the highest health budget per capita(W344) while Pusan Seo ku had the lowest(W19). 18) Director's medical subsidies are W30,000-50,000 in kun, and roughly W20,000 in city. 19) The older of priority in health center activities is T.B. control(31.1%), Family Planning and M. C. H.(28.0%), prevention of acute communicable disease and endemic disease (18.2%) and clinical care of patients(14.3%). 20) Nearly 32% opposed in principle the governmental policy of prohibiting medical doctors from going abroad. 21) Suggestions for immediate enhancing the position of director of health centers and subcenters: (1) Raise the base subsidy (48.2%), (2) Provide more opportunities for promotion (20.7%), (3) Exemption from army services(12.1%), (4) Full scholarship to medical students for this purpose only (7.8%). 22) A newly established medical school was opposed by 56.9% of the directors, however 33.6% of them approved. 23) Pertaining to the division of labor in Medicine and Pharmacy, the largest portion (31.9%) urged the immediate partial division of antibiotics and some addictive drugs to be given only by prescription. 24) More than half wanted a W70,000 level for the director's medical subsidies, white 36.2% stated W50,000. 25) Urgently needed skills in the kun are clinical pathologist (38.6%) and doctor (health center director) (25.5%); while in the city nurse (37.1%), doctors(clinical)(31.4%) and health educators(14.4%) are needed. 26) Essential treatment for the better health center administration; raising the base subsidy (22.7%), obtaining the power of personal management (19.3%) and the establishment of a Board of Health (14.3%). etc.

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The effects GeongshinhaeGihwan 1(GGT1) has on the hGHTg (human growth hormone transgenic) obese male rats' blood-antiobestic index (형질전환 비만모델 수컷 hGHTg rats에서 경신해지환(輕身解脂丸)이 혈중 항비만지표에 미치는 영향)

  • Jung, Yang-Sam;Tsung, Pei-Chin;Choi, Seung-Bae;Kim, Gyeong -Cheol;Shin, Soon-Shik
    • Herbal Formula Science
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    • v.13 no.2
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    • pp.1-16
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    • 2005
  • Objectives: To find out the effects GGTl, an antiobestic drug widely used in clinics, has on the blood-antiobestic index and the toxicity index using the data from the hGHTg obese male rats. We looked closely into both of the two indices because GGTl antiobestic effect can happen not only by pharmacological action, but also by its toxicity. Also, we verified the difference in effect between GGTl and reductil (sibutramine), which has been approved by the FDA of the United States. Methods: After performing the experiments for 8 weeks on the hGHTg obese male rats divided into three groups: the control group, the GGTl group, and the reductil (RD) group, we anesthetized the rats with Diethyl ether and took a 3ml blood sample from the heart. Then, after coagulating the blood in room temperature by using the plasma separator, we centrifuged it for 25 minutes in 3,000rpm using the high-speed refrigerated centrifuge. We kept the separated plasma in a deep freezer at $-80^{\circ}C$, and repeatedly measured the antiobestic index and the toxicity index twice using the hematology biochemistry analyzer. Also, in order to judge the indirect toxicity index, we separated liver from kidney and observed them. Results: When we looked at the results of the analysis of covariance on the measuring elements related to the antiobestic index (TC, HDL, LDL, TG, and GLU), there was no significant difference among the groups in all measuring elements. Also, the results of the analysis of covariance on the two roups (RD group and GGTl group) showed that the p-values had no significant difference under the level of significance 0.05. When we looked at the result of the analysis of covariance on the measuring elements related to the toxicity index (GOT, GPT, GGT, CREA, UA, ALB, and TP), we could see that the p-values in GPT, ALB, and TP have a significant difference among the groups. Also, the results of the analysis of covariance about the measuring elements related to the toxicity index on both groups, RD group and GGTl group, showed no significant difference in the p-values of all of the measuring elements in the two groups, RD and GGTl group. Conclusions: In conclusion, through this experiment, the safety of GGTl has been approved, and although the verification on its medical effect has not been clearly approved, when we consider the fact that it belongs to the same group as reductil, an antiobestic drug approved by the FDA of the United States, we could indirectly verify that GGTl has an antiobestic effect. We believe that when doing a sample design for a future experiment, it needs to be performed on a greater sample size based on the power analysis that needs to be performed primarily in experiments, and a more accurate verification is needed through more systematic experiment plans.

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Environment-friendly and Low-Carbon Agriculture for Demand-Supply Control and Food Security of Korean Rice (쌀 수급안정과 식량안보를 위한 친환경·저탄소 농업 전환방안)

  • Yang, Seung-Koo;Park, Pyung-Sik;Son, Jang-Hwan;An, Kyu-Nam
    • Korean Journal of Organic Agriculture
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    • v.26 no.1
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    • pp.99-128
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    • 2018
  • The cultivation area of rice as staple grains is decreasing in the domestic situation in Korea. Import volume of a duty in foreign rice is 409,000 tons for a year regardless increasing of production per unit area and decreasing of rice consumption. The total stock of rice is increasing cumulatively despite the effort for production mediation of rice. Therefore, maintenance of cultivation area and reduction of production are necessary for national foodstuffs security problems. Development of environment-friendly and low-carbon technology as alternative of global warming and aging of farm labor power is very important responsibility for descendants with creation of sustainable agriculture environment. As alternative for demand and supply stabilization of rice from all angles, first stage: extension of environment-friendly cultivation area as 17% Jeollanam-do level with maintenance of cultivation area under the present circumstances, second stage: extension of environment-friendly cultivation area as 25%, third stage: extension of environment-friendly cultivation area as 35%. From above mentioned scenario, reduction of rice production (60,000 tons), increases of production cost (59,200,000,000 Won), and reduction of income (201,500,000,000 Won) are estimated in first stage. Reduction of rice production (90,000 tons), increases of production cost (122,100,000,000 Won), and reduction of income (313,700,000,000 Won) are estimated in second stage. Reduction of rice production (380,000 tons), increases of production cost (222,000,000,000 Won), and reduction of income (464,500,000,000 Won) are estimated in third stage. From analysis results for partial tillage in transplanting cultivation complex (10ha), rice production is decreased 1.3~1.5 ton by complex. Production cost of rice is decreased and increases of income cultivation type. Gradual extension of environment-friendly agriculture and low-carbon partial tillage could be expected for environment maintenance of the territorial integrity, confidence of consumer, and high-efficiency of low-cost.

Memory Organization for a Fuzzy Controller.

  • Jee, K.D.S.;Poluzzi, R.;Russo, B.
    • Proceedings of the Korean Institute of Intelligent Systems Conference
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    • 1993.06a
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    • pp.1041-1043
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    • 1993
  • Fuzzy logic based Control Theory has gained much interest in the industrial world, thanks to its ability to formalize and solve in a very natural way many problems that are very difficult to quantify at an analytical level. This paper shows a solution for treating membership function inside hardware circuits. The proposed hardware structure optimizes the memoried size by using particular form of the vectorial representation. The process of memorizing fuzzy sets, i.e. their membership function, has always been one of the more problematic issues for the hardware implementation, due to the quite large memory space that is needed. To simplify such an implementation, it is commonly [1,2,8,9,10,11] used to limit the membership functions either to those having triangular or trapezoidal shape, or pre-definite shape. These kinds of functions are able to cover a large spectrum of applications with a limited usage of memory, since they can be memorized by specifying very few parameters ( ight, base, critical points, etc.). This however results in a loss of computational power due to computation on the medium points. A solution to this problem is obtained by discretizing the universe of discourse U, i.e. by fixing a finite number of points and memorizing the value of the membership functions on such points [3,10,14,15]. Such a solution provides a satisfying computational speed, a very high precision of definitions and gives the users the opportunity to choose membership functions of any shape. However, a significant memory waste can as well be registered. It is indeed possible that for each of the given fuzzy sets many elements of the universe of discourse have a membership value equal to zero. It has also been noticed that almost in all cases common points among fuzzy sets, i.e. points with non null membership values are very few. More specifically, in many applications, for each element u of U, there exists at most three fuzzy sets for which the membership value is ot null [3,5,6,7,12,13]. Our proposal is based on such hypotheses. Moreover, we use a technique that even though it does not restrict the shapes of membership functions, it reduces strongly the computational time for the membership values and optimizes the function memorization. In figure 1 it is represented a term set whose characteristics are common for fuzzy controllers and to which we will refer in the following. The above term set has a universe of discourse with 128 elements (so to have a good resolution), 8 fuzzy sets that describe the term set, 32 levels of discretization for the membership values. Clearly, the number of bits necessary for the given specifications are 5 for 32 truth levels, 3 for 8 membership functions and 7 for 128 levels of resolution. The memory depth is given by the dimension of the universe of the discourse (128 in our case) and it will be represented by the memory rows. The length of a world of memory is defined by: Length = nem (dm(m)+dm(fm) Where: fm is the maximum number of non null values in every element of the universe of the discourse, dm(m) is the dimension of the values of the membership function m, dm(fm) is the dimension of the word to represent the index of the highest membership function. In our case then Length=24. The memory dimension is therefore 128*24 bits. If we had chosen to memorize all values of the membership functions we would have needed to memorize on each memory row the membership value of each element. Fuzzy sets word dimension is 8*5 bits. Therefore, the dimension of the memory would have been 128*40 bits. Coherently with our hypothesis, in fig. 1 each element of universe of the discourse has a non null membership value on at most three fuzzy sets. Focusing on the elements 32,64,96 of the universe of discourse, they will be memorized as follows: The computation of the rule weights is done by comparing those bits that represent the index of the membership function, with the word of the program memor . The output bus of the Program Memory (μCOD), is given as input a comparator (Combinatory Net). If the index is equal to the bus value then one of the non null weight derives from the rule and it is produced as output, otherwise the output is zero (fig. 2). It is clear, that the memory dimension of the antecedent is in this way reduced since only non null values are memorized. Moreover, the time performance of the system is equivalent to the performance of a system using vectorial memorization of all weights. The dimensioning of the word is influenced by some parameters of the input variable. The most important parameter is the maximum number membership functions (nfm) having a non null value in each element of the universe of discourse. From our study in the field of fuzzy system, we see that typically nfm 3 and there are at most 16 membership function. At any rate, such a value can be increased up to the physical dimensional limit of the antecedent memory. A less important role n the optimization process of the word dimension is played by the number of membership functions defined for each linguistic term. The table below shows the request word dimension as a function of such parameters and compares our proposed method with the method of vectorial memorization[10]. Summing up, the characteristics of our method are: Users are not restricted to membership functions with specific shapes. The number of the fuzzy sets and the resolution of the vertical axis have a very small influence in increasing memory space. Weight computations are done by combinatorial network and therefore the time performance of the system is equivalent to the one of the vectorial method. The number of non null membership values on any element of the universe of discourse is limited. Such a constraint is usually non very restrictive since many controllers obtain a good precision with only three non null weights. The method here briefly described has been adopted by our group in the design of an optimized version of the coprocessor described in [10].

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