A Study on the Forest Yield Regulation by Systems Analysis (시스템분석(分析)에 의(依)한 삼림수확조절(森林收穫調節)에 관(關)한 연구(硏究))
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- Korean Journal of Agricultural Science
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- v.4 no.2
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- pp.344-390
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- 1977
The purpose of this paper was to schedule optimum cutting strategy which could maximize the total yield under certain restrictions on periodic timber removals and harvest areas from an industrial forest, based on a linear programming technique. Sensitivity of the regulation model to variations in restrictions has also been analyzed to get information on the changes of total yield in the planning period. The regulation procedure has been made on the experimental forest of the Agricultural College of Seoul National University. The forest is composed of 219 cutting units, and characterized by younger age group which is very common in Korea. The planning period is devided into 10 cutting periods of five years each, and cutting is permissible only on the stands of age groups 5-9. It is also assumed in the study that the subsequent forests are established immediately after cutting existing forests, non-stocked forest lands are planted in first cutting period, and established forests are fully stocked until next harvest. All feasible cutting regimes have been defined to each unit depending on their age groups. Total yield (Vi, k) of each regime expected in the planning period has been projected using stand yield tables and forest inventory data, and the regime which gives highest Vi, k has been selected as a optimum cutting regime. After calculating periodic yields and cutting areas, and total yield from the optimum regimes selected without any restrictions, the upper and lower limits of periodic yields(Vj-max, Vj-min) and those of periodic cutting areas (Aj-max, Aj-min) have been decided. The optimum regimes under such restrictions have been selected by linear programming. The results of the study may be summarized as follows:- 1. The fluctuations of periodic harvest yields and areas under cutting regimes selected without restrictions were very great, because of irregular composition of age classes and growing stocks of existing stands. About 68.8 percent of total yield is expected in period 10, while none of yield in periods 6 and 7. 2. After inspection of the above solution, restricted optimum cutting regimes were obtained under the restrictions of Amin=150 ha, Amax=400ha,
Percentage recovery or fertilizer nitrogen, phosphorus and potassium by rice plant(Oriza sativa L.) were investigated at 8, 10, 12, 14 kg/10a of N, 6 kg of
Purpose In nuclear medicine examination,
A survey was made of 976 students who were selected among students of 5 middle schools at Taegu so that it could furnish basic knowledge about sex education of adolescents by analyzing students recognition of sex, acquaintance with the opposite-sex, sex-education, The survery took a month from Nov. 1, to Nov 30, 1991. The results of this study are summarized as follows. 1. The general characteristics of the surveyed students. The survey consisted of 332 boys middle school student & 325 girls middle school students, 157 male & 162 female students of coeducational middle schools. 32.9% of them were from the first grade, 33.2% from the second grade & 33.9% from the third grade. 35.7% of them believed in Buddhism, 19% Christianism and the mode of their living standard, 86.7%, fell on 34.7% of their parents engaged in commerce and they were followed by salary man and public officals, 93.1 % of the students, parents were alive. 44.9% of their fathers were graduates of high school and 42.2% of their mothers middle school. 2. Sexual maturity 89.1 % of the surveyed girls had experienced menstruation. The mode of first menstruation, 48.2%, was at the age of 13 and the mean of it was 12.9, 3.7% the surveyed boys had exprienced a wet drem before. The mode of the first wet dream, 40.0%, was at the age of 14 and the mean was 13.4. 21.3% of surveyed students had the experience of masturbation but the number of girls fell far short of that boys. The mode of the first masturbation, 37.0%, was at the age of 14 and the mean was 13.4. 3. The acquaintance and sexual relations with the opposite sex 1) Analyzing the students actual conditions with the opposite, I found out that 52.3% of them wanted to have any kind of relations with the opposite and that 30.25 had already had some kind of relations. 73.2% of the students having relations with the opposite thought the other sex merely as a friend and the number of students who were thinking that way was distributed evenly among schools. 28.8% of the students had got acquainted with the other sex through their frieds and there were not much difference between boys and girls in the method of getting acquainated with the opposite. About 35.2% of the students having relations with the opposite came from the third grade. 47.8% of them answered that the meeting place was not fixed and 26.4% answered that they were meeting their parthers outdoors. 60.7% replyed that they were not disturbed in their studies by the relations with the other sex. 2) Most of the students 79.4%, answered that they had never had sexual relations and 16.3% of the rest said that thery were expressing their feelings by grasping each other's hand. 3) 16.6% of the surveyed students asid that they had the exprience of smoking, 1.1 % of an illusion caused by inhaling chemical addhesives, 44.0% of drinking and 41.4% of warching pornographic films. 4. The knowledge and attitude about the sex 1) The distribution and analysis according to schools and grades : 64.8% of the surveyed students answered correctly to the questions about mensturation, 49.3 % did so about wet dreams, 94.3 % did so about conception, 60.6% did so about child birth, 73.9% did so about AIDS and 50.1 % did so about sexual diseases. Roughly speaking, they had not much knowledge of sexual diseases. 2) The recognition of sex according to schools and grades : 39.0% of the students said that they had worries about sex. 33.1 % of what they worried was concerned with their bodies and 26.8% was about the acqaintance and relationship with the opposite sex. The girls were much more concerned about the former and the boys the latter. 51.1 % of the students asid that they had no specific opinion of masturbation but 19.2% said that's alright if self-restrained. About the sexual intercourse before marriage, 75.7% said negatively. 5. The need for sex education most of the students, 99.4% said they needed sex education and there was not much difference in that thought among schools. And 49.7% answered that schools, families, and societies were equlally important in sex education. About half of the students, exactly 50.2%. considered it as the main reason of sex education to prevent accidents cauesd by ignorance of sex. 81.4% said that they had had some kind of sex education. Most of the educations, 87.0%, had taken place at schools but 5.2% said they were getting most of the knowledge about sex from therir friednds, juniors and seniors. 59.5% of the students who had ever had a sex education said "Just so, so" when asked of the level of their contentment but the number of students who said "satisfied" was only a few, 16.1 %. 20.7% of the survered answered that thery wanted sex education to be made in the course of home life, and 26.6 % of the students most wanted to know about the acquaintance and relationship with the oppostie sex, 29.0% preferred nurse teachers as proper councellors of sex education. The mode of their present councellors, 42.0%, was friends but only 7.6% answered they dicussed with teachers. 6. The correlation analysis between general characteristcs and sexual behaviors of the surveyed students revealed that sex had a signigicant(P<0.001) positive correlation with parents' love toward students(P<0.01), the experience of masturbation, smoking, an illusion caused by inhaling chemical adhesives and the experience of watching pornographic films. And the standard of living had a significant(P<0.01) positive correlation(P<0.01) with grade point average, parents' existence(P<0.01) and parents' love, but a significant(P<0.01) negative correlation with sexual worries. grade point average had a significant(P<0.01)negative correlation with the experience of an illusion caused by chemical adhesives(P<0.01) and smoking. Parents' existence had significant(P<0.01) positive correlations with parents' love and smoking but a significant(P<0.01) negative correlation with the experience of an illusion by chemical adhesives. There was a significant(P<0.01) negative correlations between parents' love and the experience of an illusion by chemical adhesives, and a significant(P<0.001) positive correlation among masturbation and sexual worries, smoking, an illusion by chemical adhesives and the experience of watching pornographic films. There was a significant(P<0.001) positive correlation among acquaintance with the opposite sex, smoking, the experience of an illusion by chemical adhesives and watching pornographic films. Sexual worries had significant(P<0.01) positive correlations with smoking, the experience of an illusion by chemical adhesives and watching pornographic films. smoking had a significant positive correlation with drinking the experirence of, an illusion by chemical adhesives and watching pornographic films. Finally, there was a significant(P<0.01) positive correlation between the drinking experience and the illusion experience by chemical adhesives. According to the results mentioned above, the fact is certain that there is a great need for sex education of adolescents. Therefore, it is desirable that the schools teach sexual physiology and normal positively and that sex education including hygien education be an independant course in the curriculums. Furthermore, it is essential that the schools should have enough nurse teachers to take up sex education, expand training opportunities for them and that they develop educational materials. Considering the unbalance of the level of sex educations between boys and girls, I want to suggest that all boys and girls have sex education evenly and lead happy lives by correction irrational thought about sex, that is to say, sex discrimination, Sex education programs, especially of middle school students, should be reexamined if it is to give the students effective and profitable knowledge about sex. In addition, the government should establish a policy of adolescents' sex education to have healthy opinions of sex settled nationwide.
These studies were aimed at clarification of genetic and ecological variation in culm length, panicle length and plant height of the