• Korean Journal of Agricultural Science
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• v.16 no.2
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• pp.212-224
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• 1989

This paper reports results of an investigation to determine properties of superplasticizered fly ash concrete. The mixture proportions of fly ash were 0, 10, 20 and 30%, by weight of cement, and superplasticizer was added as a percentage of fly ash, 0, 0.6, 12 and 1.8%. To investigate the effective use of the superplasticized fly ash concrete, the basic data were analyzed. The results obtained were summarized as follows : 1. The unit water content was decreased by 1%, 6% and increased by 2% to the ratio of addition of fly ash 10%, 20%, 30%, respectively, but in case of the superplasticized fly ash concrete, it was decreased by 3~16%, 4~14% and 10~17%, at 0.6, 12, and 1.8% dosage of superplasticizer, respectively. 2. In the properties of the fresh fly ash concrete, the slump loss was reduced with the ratio of replacement of fly ash increased, and with times went by. When using superplasticizer in fly ash substituting concrete, the fludity in the concrete was not decreased. 3. The compressive strength of fly ash concrete at early ages was lower than that of ordinary concrete. At the later age of 28 days, the compressive strength with 20% addition of fly ash was increased than that of ordinary concrete. In cased of 10%, 30% addition of fly ash, the compressive strength were reduced. From this, it was proved that the optimum amount of fly ash appears to be about 20%. The compressive strength at all ages of superplasticized fly ash concrete was significantly higher than that of fly ash concrete, with increasing fly ash content. 4. In case of the tensile strength, the effects of the increasing strength with the ages were similar to those of the compressive strtength, and at the later ages was seen a decreasing tendency of strengths. 5. The correlation between compressive and tensile strength of superplasticized fly ash concrete was highly significant. The multiple regression equations of compressive and tensile strength were obtained on a function of the mixture proportion of fly ash and the addition of superplasticizer. The relation between compressive and tensile strength is higher than for ordinary concrete. The strength ratio is 7~11, and it is higher than that of ordinary concrete, 8~10. 6. Bulk density was decreased by 1~3% compared with ordinary concrete with the mixture proportion of fly ash increased, 10~30%, and decreased by 1~2% with the superplasticizer added 0.6~1.8%.

• Korean Journal of Agricultural Science
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• v.14 no.2
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• pp.232-247
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• 1987

Three rice varietis, Dongjinbyeo, Daecheongbyeo and Chucheongbyeo, which are leading cultivars in the Chungnam area, were planted to determine their effects of mixture on the plant characteristics and the blast occurrence. The summary obtained is as follows; 1. The heading dates of each cultivars were not affected by the mixing culture. Only a day was delayed in heading date of Chucheongbyeo under commonly standard fertilizer level. 2. The effects of cultivar mixture on the plant height was high when low level of fertilizer were applied. Of the cultivar mixture, the mixing of Dongjinbyeo and Daecheongbyeo shoed 5.1% of plant height increase. The effects of mixture on the tillering number were apparent only under the standard fertilizer level. The mixture of Dongjinbyeo and Chucheongbyeo was effective in increasing the tillering number up to 5.7% over mean tillering number of each cultivars. 3. The stem height tended to increase as the fertilizer level increased and the effects of cultivar mixture on the stem height was high. The stem height of mixture of Dongjinbyeo and Daecheongbyeo was highest compared with other mixture cropping. On the contrary, the panicle length was shortened as the fertilizer level decreased and cultivars were mixed. Among the cultivar mixtures, the mixture of Dongjinbyeo and Daecheongbyeo showed the most effectives of increasing the panicle length. 4. The total dry weight of mixed and pure cultivars were compared. The mixture of two cultivars was effective in increasing the dry weight of rice upto 3.5% over the average of dry weight of each cultivars. When three cultivars were mixed, there were 8.5% of dry weight increase over not mixed cultivars. The effects of mixture on the dry weight were more apparent under standard fertilizer level. 5. The rates of Neck and Node and Branch Blast occurrence were reduced when cultivars were mixed, and their reduction rates were 11.7% and 14.0%, respectively. The occurrence of Blasts was also decreased under the lowest fertilizer level than the standard fertilizer level. The least Blast occurrence was obtained when Dongjinbyeo and Daecheongbyeo were mixed cropped. 6. Significantly high number of spikelets of per square meter was observed when Chucheongbyeo and Dongjinbyeo were mixed. However, the spikelets of panicle were the lowest when Chucheongbyeo and Dongjinbyeo were mixed. The number of panicles per square meter was increased as the fertilizer levels increased, while the number of spikelets per panicle increased as the fertilizer level decreased. 7. The effects of mixture on the maturing were apparent regardless of the fertilizer level. The 1000 grain weight was higher when lower level of fertilizer was applied. The effects of cultivar mixture on the 1000 grain weight were more apparent in the plots of Chucheongbyeo and Dongjinbyeo mixture and three cultivar mixture. 8. The grain yield increased when cultivars mixed. The increment under mixing cropping was 4.6% over mono cropping. The effects of cultivar mixture on the yield increase were more apparent under lower levels of fertilizer application. The highest yield increase was obtained when Chucheongbyeo and Daecheongbyeo were mixed, and the rate of yield increase was 6.8% over mono-cropping. 9. The grain yield was highly correlated with number of panicles per square meter and dry weight. There was not any significant relationships found among grain yield, spikelets of panicle and ripening percentage.

• Korean Journal of Agricultural Science
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• v.15 no.2
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• pp.143-152
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• 1988

This study was conducted to obtain basic data which affected engine performance of the power tiller being widely used in the rural area. Among the various factors affected engine performance, only flywheel weight was considered as the major factor in this study. Fuel consumption ratio, motoring loss, torque, vibration and mechanical efficiency of the engine tested were measured and analyzed on the four levels of flywheel weight (32.2, 29.7, 26.4, 24.2 kg). The results obtained were as follows: 1. The maximum output of 6 and 7.5 kW engine was 7.43 kW and 7.85 kW respectively. When flywheel weight was reduced from 32.2 kg to 24.2 kg, output power of the engine was increased 0.27 kW in 6 kW engine and increased 0.39 kW in 7.5 kW engine. 2. The fuel consumption ratio was decreased from 300.8 to 296.8 g/kW-hr in 6 kW engine and decreased from 313.6 to 312.8 g/kW-hr in 7.5 kW engine when the flywheel weight was reduced from 32.2 kg to 24.2 kg. 3. The mechanical efficiencies of the engine was increased from 76.1 to 76.8% in 6 kW engine and increased from 76.7 to 77.0% in 7.5 kW engine when the flywheel weight was reduced from 32.2 kg to 24.2 kg. 4. When the flywheel weight was reduced from 32.2 kg to 24.2 kg, a tendency of a little decrease of vibration at X- and Z-axis in 6 kW engine and of a little increase of vibration at Y-axis in 6 kW engine and all directions in 7.5 kW engine was observed. 5. Motoring losses was decreased from 2.33 to l.76 kW in 6 kW engine and decreased from 2.46 to 1.84 kW in 7.5 kW engine when the flywheel weight was reduced from 32.2 kg to 24.2 kg. From the above results and the flywheel weight calculated theoretically, it was recommendable that the flywheel weight should be reduced about 7 kg in 6 kW engine and about 10 kg in 7.5 kW engine, respectively.

• Korean Journal of Agricultural Science
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• v.11 no.1
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• pp.146-159
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• 1984

This study was the contrast of the compressive strength, the tensile strength, the reducing ratio and the flow of mortar using dispersing agent and high fluid admix. 1. The admix ratio of chemical admixtures espressing maximum strength appeared the same result high fluid admix SP was 0.6%, the dispersing agents LG and C211 were 0.2%, SK was 0.3%, C376 was 0.5%. But two or three times more than standard quantity made the strength's fast lowness, which influenced bad to wateriness and retard the soli-dification. 2. When proper quantity of chemical admixture was used, the increment of compressive strength was as follows. High fluid admix SP was 40.7% and the average increasing rate of dispersing agents(C211 was 19.5%, LG was 19.1%, C376 was 17.9%) was 18.7% more than normal mortar in the codition of 7 days. Also, in the condition of 28 days, high fluid admix SP was about 24.4% and the average of dispersing agents(LG was 21.1%, C211 was 16.4%, SK was 11.1%, C376 was 7.6%) was 14.1%. 3. When proper quantity of chemical admixture was used, the increment of tensile strength was as follows. High fluid admixture SP was 26.6% and the average increasing agents(SK was 16.0%, C376 was 14.7%, LG was 10%, C211 was 5.8%) was 11.6%. Also, in the condition of 28 days, high fluid admix SP was 16.5% and the average increasing rate of dispersing agents(LG was 19.1%, SK was 10.6%, C211 was 10.1%, C376 was 8.7%) was 12.1%. 4. As for the reducing ratio of each dispersing agent, he flow of mortar was less than the slump of concrete. That is; the reducing ratio of concrete was 15% adding each dispersing agent, but the reducing ratio of mortar was in the range of from 5.8% to 13.5% in 1 : 1 mixture, from 7.6% to 14.2% in 1 : 2, from 9.5% to 18.8% in 1 : 3. 5. The fluidity of each chemical admixture was as follows. High fluid admix SP in the condition of 1: 1 and 1 : 2 showed the best result than other dispersing agent and 1 : 3 showed the same result like other agents. Therefore these good dispersing agents were suitable in the prepact concrete construction using intrusion mortar.

• Korean Journal of Agricultural Science
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• v.16 no.2
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• pp.169-178
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• 1989

The study was carried out to elucidate the feedback mechanism on the hypothalamo-hypophyseal system from the functional changes of ovary in female rats. One hundred and forty-four mature female rats were lloted into the three groups; ovariectoimzed group, estradiol treated group and intact control group. The varies of 48 heads of rat were completely removed. Forty eight heads of rat were administered with $200{\mu}g$ of estradiol benzoate every 48 hours. Serum FSH, LH and prolactin levels were determined with radioimmunoassay method at 3,6,12,24 ours, and 5,10, and 15days after treatment. The rats were necropsied to measure the weights of hypophysis and to examin the histological changes in the organs. The results obtained were as follows: The weights of hypophysis were increased after ovariectomy and decreased after estradiol injection. The differences in hypophysis weights were significant between the group from 5 days after treatment. The histological changes in hypophysis were appeared from 5th day after ovariectomy. Proliferation and hypertrophy began to occur in basophilic from 10th day after ovariectomy, chromophobes were slightly hypertrophied and acidophilic cells were atrophied. In estradiol injected rats the histological findings were appeard to be contrary to those of ovariectomized rats. Serum FSH levels significantly changed after ovariectomy and estradiol injection and were higher in both the treated groups than in the intact control group. Within 18 hours after treatment the level was the highest in ovariectomized group, and thereafter the highest level was found in estradiol treated gorup. In ovariectomized rats the levels were rapidly increased 3 hours after treatment and maximum levels were found 18 hours after treatment. In estradiol treated rats the levels started to increase 18 hours after treatment and reached maximum levels 24 hours treatment. 4. Serum LH levels started to increase 3 hours after ovariectomy and estradiol injection and reached maximum levels 12 hours after ovariectomy and 24 hours after estradiol injection. There were significant differences in LH levels between the groups in each observation time. Up to 18 hours after treatment levels were higher in ovariectomized rats than in estradiol treated rats. but thereafter the levels were higher in estradiol treated rats than in ovariectomized rats. The multiple range test showed that a significant difference in LH levels was not found between ovariectomized group and estradiol treated group 18 hours and 5 days after treatment. 5. Serum prolactin levels were significantly changed after ovariectomy and estradiol injection. The levels were lower in ovariectomized rats than in intact control rats.

• Korean Journal of Agricultural Science
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• v.16 no.2
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• pp.179-200
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• 1989

Mucor miehei rennet(MR) was added as calf rennet(CR) substitutes in the fixed amounts of mixed rennets in making Camembert cheese. The conditions in the variations of chemical composition: water-soluble nitrogen, non-caseinic nitrogen, non-proteinic nitrogen, amino nitrogen, ammoniacal nitorgen, electrophoresis, molecular fractionation, mineral distribution, texture characterisitics, free amino acids and free fatty acids, were checked up with the sensory test and the chesse yields at each ripening period. The results obtained by investigating the utility of Mucor rennet were summarized as follows: 1. CR chesse, MR cheese and the mixed-rennet chesse failed to show any significant difference in their yields of 15%. 2. The contents of protein, fat and ash in MR cheese gave lower value than CR cheese did and with progress of ripening lactose decreased rapidly after 14 days of ripening. The difference among the rate of addition of mucor rennet was not recognized. 3. The WSN contents of 5 fresh sample chesse were from 14.7% to 17.3% and WSN increased from 39.7% to 41.0% with progress of ripening. After 21 days of ripening MR chesse had more WSN than CR cheese did. In NCN and ammoniacal nitrogen MR cheese showed higher value. 4. As the ripening progressed, MR chesse showed more cystein, phenylalanine and proline than CR chesse did but it failed to show any increase in aspartic acid, threonine and glutamic acid etc. 5. In the content of free fatty acid MR chesse showed higher value than CR cheese did and with the progress of ripening fatty acids increased from 8.36 mEq to 26.36 mEq but did not show any significant difference in the cheese types by the coagulant ratio. 6. Ca contents in the sample chesse were 0.238-0.27%, Mg 0.019-0.022%, Na 0.910-1.047%, and K 0.175-0.200%. The important non-sedimentable Ca in casein remained from 61 % to 77% without regard the ripening periods and added-rennets and Mg remained from 59.1% to 92.5% in non-sedimentable and water-soluble conditions. 7. In the fractionation of protein by ultrafilteration, MW> $5{\times}10^4$ decresed from 95% at the beginning period of ripening to 45% and MW< $10^4$ increased from 0.2% to 38% and definite caseinolysis was shown in all samples. 8. All the cheese showed to different electrophoretic patterns for the added-amounts of mucor rennet in the 14 days of ripenig. In the 28 days or ripening, MR cheese kept some bands on the patterns compared with CR cheese. 9. In vitro digestibility increased from 81.48-94.81 % to 94.47-98.61% but failed to show any significant difference in the cheese types by the coagulant ratio. 10. In hardness, MR cheese showed lower value compared with CR cheese as the ripening progressed. 11. The results of the sensory test failed to show any difference in flora rind, feelings in mouth and hands, deep structure, flavor and bitterness between CR Camembert cheese and MR Camembert chesse.

• Korean Journal of Agricultural Science
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• v.9 no.1
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• pp.303-313
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• 1982

The study was conducted to find out the concentrations of sex hormones and the contents of metabolites in serum, and the changes of weights and tissues on ovary, thyroid gland and adrenal gland according to gestation period in rabbit. The results were summarized as follows: 1. The ovary weights were increased significantly with the time e lapse after gestation and recovered normally at 5 days after parturition. In the histological changes of ovary, the lutein cells were hypertrophied and the secretory granules were increased actively until 3 weeks after gestation, and then a trophied thereafter. 2. The thyroid gland weights at all observation times were higher than those in control group, and the significance was recognized at 1, 3 and 4 weeks after gestation. The histological features of the secretory epithelium were the hyper trophic and columnar condition stimulating the functional state from 1 week after gestation. 3. The adrenal gland weights in experimental group were recognized significantly at 4 weeks after gestation, but showed higher than those in control group at all observation times. The zona fasciculata and zona reticularis of the gland showed the slight hypertrophic condition, but the zona glomeerulosa and adrenal medulla did not find out any particular changes. 4. The serum concentrations of progesterone and LH reached a peak level at 2 weeks and 1 week after geestation respectively, and rapidly began to decline thereafter. 5. The serum concentrations of estradiol-$17{\beta}$ and FSH were not detected below 20.0 pg/ml and 1.3 mIU/ml respectively. 6. The contents of total protein and non-protein nitrogen nitrogen were decreased gradually with the time elapse after gestation, but the significant differences were recognized from 3 weeks. 7. The total lipids were not changed markedly until 3 weeks, but increased significantly at 4 weeks after gestation and at 5 days after parturition. 8. The serum cholesterol tended to be decreased until 3 weeks, but increased at 4 weeks after gestation and at 5 days after parturition. 9. The serum calcium showed a continuous decrease during the gestation period, but the significant differences were recognized at 3 and 4 weeks. The serum phosphorus also had a significant decrease at 4 weeks after gestation.

• Korean Journal of Agricultural Science
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• v.9 no.1
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• pp.284-302
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• 1982

Development of protein resources as food has been a big issue especially in Southeast Asia region, and intake of protein is also insufficient in Korea. To cope with this shortage of protein resources and its improvement together with increased production of high nutritive animal protein, studies were carried out on feeding of Korean native goats. In the experiments were made absorption of carbohydrate and volatile fatty acid in miniature rumen, and absorption of amino acid in rumen as in vivo were conducted as part of studies on nutritional absorption in rumen. Those nutritional for improvement of feeding and management as described above are summarized as following. 1. According to the result of test on the nutritional absorption of native goat by means of miniature rumen method, absorption ratio of VFA measured at 0.5, 1 and 2 hours after injection of nutrition showed propionic acid 70-86%, acetic acid 74-87%, and lactic acid 76-89%. In the absorption of organic substances, ethyl alcohol of 0.5% showed 29-87% and lactic acid of 0.1M showed 12-27% of absorption ratio. 2. Result of absorption measurement in rumen from L-type free amino acid injection in the content of rumen vein showed lower rate at menthionine-free group compared to whole-egg amino acid injection in the content of rumen vein showed lower rate at methioine-free group compared to whole-egg amino acid group, and high absorption ratio was observed at methionine 3 times group and urea added group. Deficiency of methionine caused no change of the content in mucous membranes. 3. Absorption of amino acid in rumen muscular layer showed equal tendency as in the mucous membrane without exerting any influence of methionine deficiency. At the methionine3-times group, content of methionine and glutamine were increased by 14.7 and 4.4 times as compared to whole-egg amino acid group, an absorption ratio of glutamine, proline and valine were increased at urea added group. 4. In general, concentration of amino acid in rumen vein plasma was lower than in rumen mucous membrane and muscular layer. Absorption ratio of amino acid is decreased due to methionine deficiency, and tripling of methionine or urea adding caused increment of amino acid. Absorption pattern is thus varied depending on the composition of amino acid. 5. At the urea added group, content of ammonia-N, amino-N and urea were increased in rumen muscular layer. As the inside of goat's rumen was unable to clean thoroughly, investigation was made on remaining bacteria, however, variation of ammonia-N was affected by these bacterial content. 6. Variation in rumen structure by differential absorption of amino acid was observed by general microscope and fluorescent microscope. According to the result of observation in the methionine 3 times group, single cylinder epithelium of mucous membrane showed rather thin, and it was thick at urea added group though no significant differences existed among test groups in submucous membrane and muscular layer.

• Korean Journal of Agricultural Science
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• v.3 no.1
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• pp.95-104
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• 1976

This study was conducted to test the harvesting operation of two kinds of rice varieties such as Milyang #15 and Tong-il with a imported two furrow Japanese combine and was performed to find out the operational accuracy of it, the adaptability of this machine, and the feasibility of supplying this machine to rural area in Korea. The results obtained in this study are summarized as follows; 1. The harvesting test of the Milyang #15 was carried out 5 times from the optimum harvesting operation was good regardless of its maturity. The field grain loss ratio and the rate of unthreshed paddy were all about 1 percent. 2. The field grain loss of Tong-il harvested was increased from 5.13% to 10.34% along its maturity as shown in Fig 1. In considering this, it was needed that the combine mechanism should be improved mechanically for harvesting of Tong-il rice variety. 3. The rate of unthreshed paddy of Tong-il rice variety of which stem was short was average 1.6 percent, because the sample combine used in this study was developed on basisof the long stem variety in Japan, therefore some ears owing to the uneven stem of Tong-il rice could nat reach the teeth of the threshing drum. 4. The cracking rates of brown rice depending mostly upon the revolution speed of the threshing drum(240-350 rpm) in harvesting of Tong-il and Milyang #15 were all below 1 percent, and there was no significance between two varieties. 5. Since the ears of Tong-il rice variety covered with its leaves, a lots of trashes was produced, especially when threshed in raw materials, and the cleaning and the trashout mechanisms were clogged with those trashes very often, and so these two mechanisms were needed for being improved. 6. The sample combine of which track pressure was $0.19kg/cm^2$ could drive on the soft ground of which sinking was even 25cm as shown in Fig 3. But in considering the reaping height adjustment, 5cm sinking may be afford to drive the combine on the irregular sinking level ground without any readjustment of the resaping height. 7. The harvesting expenses per ha. by the sample combine of which annual coverage area is 4.7 ha. under conditions that the yearly workable days is 40, percentage of days being good for harvesting operation is 60%, field efficiency is 56%, working speed is 0.273m/sec, and daily workable hours is 8 hrs is reasonable to spread this combine to rural area in Korea, comparing to the expenses by the conventional harvesting expenses, if mechanical improvement is supplemented so as to harvest Tong-il rice. 8. In order to harvest Tong-il rice, the two furrow combine should be needed some mechanical improvements that divider can control not to touch ears of paddy, the space between the feeding chain and the thrshing drum is reduced, trash treatment apparatus must be improved, fore and rear adjust-interval is enlarged, and width of track must be enlarged so as to drive on the soft ground.

• Korean Journal of Agricultural Science
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• v.17 no.1
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• pp.34-44
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• 1990

The study was carried out to elucidate the effects of ovarian function on the thyroid gland, adrenal gland and uterus in female rats. One hundred and forty-four mature female rats were allotted into the three groups ; ovariectomized group, estradiol treated group and intact control group. The ovaries of 48 heads of rats were completely removed. Forty eight heads of rats were administered with $200{\mu}g$ of estradiol benzoate every 48 hours. Serum estradiol-$17{\beta}$ and progesterone levels were determined with radioimmunoassay method at 3, 6, 12, 24 hours and 5, 10, 15 days after treatment. The rats were necropsied to measure weights of thyroid gland, adrenal gland and uterus and to examine the histological changes in the organs. The results obtained were as follows ; 1. Serum estradiol-$17{\beta}$ levels were rapidly decreased below 27.20pg/ml 18 hours after ovariectomy. In estradiol treated rats the levels were rapidly increased 18 hours after treatment, but thereafter slowly decreased. The significant differences in the estradiol level were found between the group at every observation time. 2. Serum progesterone levels were significantly decreased after ovariectomy and estradiol injection. The lowest level was found in the group of ovariectomized rats. 3. The weights of thyroid glands decreased in ovariectomized rats rather than in intact rats 5 days after treatment. The weights tended to increase after estradiol injection but significant differences between the groups were seen on 10th and 15th days. 4. In the histological findings of thyroid glands, follicular epithelial cells were changed to be squamous 5 days after ovariectomy and accompanied pyknosis 10 days and karyorrhexis 15 days after ovariectomy. On the contrary follicular epithelial cells were changed to be columnar with hypertrophy 10 days after estradiol injection. 5. The significant differences in adrenal gland weights were recognized between all the groups 5 and 15 days after treatment in ovariectomized rats were lighter than intact rats and the adrenal gland weights were rather heavier in estradiol treated rats. 6. The days after ovariectomy the adrenal glands were atrophied accompanying with pyknosis in the cortical cells of zona fasciculata. The cells in zona fasciculata and zona reticularis started to hypertrophy 5 days after estradiol injection, but no changes were found in the zona glomerulosa of adrenal cortex and in the adrenal medulla. 7. The significant differences in uterus weights were recognized between the groups at each observation time. After ovariectomy the uterus weights decreased rapidly but after estradiol injection they increased rapidly. 8. Through histological examination of uterus, the atrophy and degeneration started to occur in endometrium and lamina propria 12 hours after ovariectomy, and in myometrium one day after ovariectomy, and the changes progressed rapidly after that. On the contrary, the myometrium was proliferated and hypertrophied from 12 hours after estradiol-$17{\beta}$ injection.