• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.614-615
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• 2010

The propellants distribution of an oxidizer rich preburner was predicted by a simplified physical approach. The Mixing head is composed of honeycomb array of 7 fuel injectors and 24 oxidizer injectors. The OF ratio of the mixing head is 15. As results, the OF ratio of the central area is about 9 and the OF ratio of the wall area is about 30.

• Journal of the Korean GEO-environmental Society
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• v.13 no.6
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• pp.19-26
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• 2012

In this study, geotechnical tests including unconfined compression test were carried out to evaluate the ground improvement effect of the hardening agent, which has been developed by using inter-chemical reactions between slag, fly ash, phosphogypsum and bypass dust on the weathered granite soil and dredged marine clay. Test results show that the strength of weathered granite soil mixed with hardening agent B-2, which uses phosphogypsum as an activator, is higher than that of B-1, which uses bypass dust as an activator. Strengths of B-1 & B-2 hardening agent mixed soil show only 44%~60% of strength of OPC(Ordinary Portland Cement, OPC) mixed soil. However, since B-1 and B-2 agents are made of industrial by-products, they seem economically more effective than ordinary portland cement as well as other present hardening agents. Test results on dredged marine clay show that unconfined compression strength increases with amount of agent and curing days. Unconfined compression strength of 14% B-1 agent mixed soil increases linearly with curing days and reaches only 40% of OPC mixed soil. While unconfined compression strength of 14% B-2 agent mixed soil increases exponentially and reaches 133% of OPC mixed soil. Relationship between deformation modulus and unconfined compression strength of B-1 and B-2 mixed soil can be expressed as $E_{50}=(20{\sim}47)_{qu,28}$, which is similar with lower limit of OPC mixed dredged marine clay.

• Korean journal of applied entomology
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• v.54 no.2
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• pp.99-109
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• 2015

Insecticidal and antifeeding activities of 29 commercialized eco-friendly organic products for managing plant diseases and insect pests against Plutella xylostella larvae, Spodoptera exigua larvae, Frankliniella occidentalis adults, and Myzus persicae adults were tested using spraying and leaf dipping bioassays under laboratory conditions. Products containing 60% Sophora extract (EOIS) and mixtures (EOISm) with Sophora extract, Stemona japonica extract, Melia azedarach extract, and Nepeta cataria extract as well as mixtures (EOISc) with Sophora extract, Chenopodium ambrosioides extract, and Melia azedarach extract as active ingredients showed strong insecticidal activity at recommended concentration against P. xylostella larvae. At half concentration, their insecticidal activities were decreased under 50%. The EOIS gave good insecticidal activity against S. exigua larvae and also showed 85% and 95% insecticidal activity at 24 and 48 hours after treatment to F. occidentalis adults, respectively. For M. persicae adults, EOISm and mixtures (EOIR) containing rape seed extract, neem extract, and castar oil produced 93% and 68% insecticidal activity, but their activities did not be increased at double concentration. EOISm only showed 100% contact toxicity against M. persicae adults exposed to dipping leaves. Interestingly, the insecticidal activity of EOIR and EOICi (citronella oil and derris extract) against M. persicae adults was increased with exposed time and concentration. In addition, EOICe (cedar oil), EOIS, EOISm, EOISc, EOIM (microorganism), EOIR, EOIPe (plant extract), and EOIT (tea tree extract) gave strong antifeeding activity against S. exigua and P. xylostella larvae. EOIB, EOIBs, EOIM, EOICi, and EOIMc showed above 70% antifeeding activity to the lepidopteran larvae. These results indicate that mixtures containing 2 to 3 plant extracts with Sophora extract show good activities against insect pests, although the difference of insecticidal and antifeeding activities was produced depending on both a tested insect species and an active ingredient or concentration.

• Korean Journal of Weed Science
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• v.6 no.1
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• pp.59-66
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• 1986

This experiment was conducted with pot trial to evaluate effects of pretilachlor [2-chloro-2', 6'-diethyl-N(n-propoxythyl) acetanilide], pyrazoxyfen [ 1,3-dimethyl-4-(2,4-dichloro benzoyl)-5-phenacyloxy-pyrazole], pyrazolate (4-(2,4-dichloro benzoyl)-1,3-dimethyl-pyrazol-5-yl-p-toluenesulphonate] and their combinations on Echinochloa crew-galli. Herbicides were treated with different dosages under 3 cm water depth at 1st and 2nd leaf stages of E. crus-galli. E. crus-galli showed stunted symptom by treatment of pretilachlor and etiolation by treatment of pyrazoxyfen or pyrazolate after 4 days from treatment. Stunting and chlorosis degrees of E. crusgalli increased with high dosage of all herbicides at lst and 2nd leaf stage. Combination of pyrazoxyfen+pretilachlor (6+1.5)G or pyrazolate+pretilachlor (6+1.5)G showed positive synergistic effect of herbicidal action on E. crus-galli, therefore these combinations can control E. crux galli in paddy field with lower dosage than each single treatment of herbicides. Herbicidal effect of pyrazoxyfen on E. crus-galli was similar to pyrazolate in single treatment and combination with pretilachlor.

• The Bimonthly Magazine for Agrochemicals and Plant Protection
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• v.4 no.8
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• pp.16-24
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• 1983

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.11a
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• pp.470-473
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• 2011

본 연구에서는 산업현장에서 에폭시 강화촉진제, 도로용 첨가제 등으로 많이 사용되고 있는 경화제(M.E.K)의 혼합비에 따른 자연발화 위험성을 알아보고 산업 현장의 화재 예방을 위한 기초자료로 제공하고자 하였다. M.E.K와 에포비아 수지를 각기 다른 비율로 혼합한 상태에서 시간경과에 따른 시료의 온도변화 와 유증기 발생 및 자연발화 여부를 관찰한 결과 합성수지와 경화제의 혼합시 경화제가 5% 이상으로 혼합될 경우 혼합 수지의 내부온도가 약 $40^{\circ}C$ 이상으로 상승하면서 발포 현상과 함께 다량의 유증기가 발생하였고, 유증기가 발생된 모든 조건에 대하여 자연발화 여부는 확인할 수 없었다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1999.04a
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• pp.2-2
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• 1999

액체추진제 로켓엔진에서 분사기의 미립화 및 혼합 특성과 그에 따른 연소 특성은 성능과 안정성을 결정하는 중요한 파라미터이며 분사기는 제한된 설계 조건하에서 최대의 열방출율을 발휘하도록 설계되어야 한다. 여기서 연소효율은 연료와 산화제의 혼합특성과 충돌 분무의 미립화의 정도에 의해 결정되므로 충돌 분무 유동성의 혼합, 미립화 특성과 이에 따른 인조성능 특성을 명확하게 밝힘으로써 최대 엔진성능을 위한 설계가 가능하게 된다. 분사기의 설계에는 분사요소형태, 분사공의 형상 및 유동시스템 등이 포함되며 특히 분사요소 형태의 선택에는 추진제, 연소실냉각방법, 연소실 형상, 자동조건 및 엔진의 수명 등이 중요한 제한조건으로 고려된다. 이런 형태의 분사 요소들 중, 충돌형 분사기는 저장성 추진제를 사용하는 중, 저추력의 액체추진제 로켓엔진에 주로 사용된다. 이 분사형태는 미립화 성능이 높지 않고, 분사공 직경 및 운동량비에 따른 혼합성능이 만감하며 blow apart 등에 의한 열부하 혹은 안정성에 대한 문제가 있으나 양호한 혼합효율, 신뢰성과 제작의 용이함으로 인하여 광범위하게 사용된다.

• Korean Journal of Environmental Agriculture
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• v.27 no.1
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• pp.66-71
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• 2008

Phosphorus transfer from agricultural soils to surface waters is an important environmental issue. Fly ash and phospho-gypsum which are industrial by-product were investigated as a means of reducing dissolved phosphorus in arable soil. To determine the optimum mixing ratio of fly ash(FA) and phospho-gypsum(PG) for reducing dissolved reactive P(DRP) in soil, various mixture ratio of FA and PG were mixed with two soil. The DRP content and pH in soils were analysed after 3 weeks incubation under flooding condition. Although DRP content in soils was significantly decreased by FA-PG mixture compared with control, there were no significant difference among the FA and PG mixture ratio of 75:25, 50:50, and 25:75. The mixture of 75% FA and 25% PG was selected for field test. A field experiment was carried out to evaluate the reducing DRP content in paddy soil to which 0(NPK), 20(FG 20), 40(FG 40), and 60(FG 60) Mg $ha^{-1}$ of the mixture were applied. The DRP content was reduced by 31% at the application rate of 60 Mg $ha^{-1}$. In contrast to deceasing DRP, Ca-P content increased significantly with the mixture application rate. After rice harvesting, available $SiO_2$, P, and exchangeable Ca content in soil increased significantly with application rate due to high content of Si, P, and Ca in the mixture. Mixtures of fly ash and gypsum should reduce P loss from paddy soil and increase soil fertility.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.3
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• pp.47-57
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• 2011

All solid rocket propellants are divided in two basic classes according to chemical state: homogeneous(double base) and heterogeneous (composite). Today, composite propellants are extensively used as power sources covering the range from gas generators and small rocket systems to large launch vehicles in space programs. The development of composite rocket propellants in the past was mainly directed to thermoset polymers. But, the thermoset composite propellants have the complication in formulation and fabricating process to adapt to rocket system requirements. In contrast to the thermoset propellant, the PVC plastisols composite propellants have the advantages in the view of loss in manufacturing process, low cost of raw material, and stability of the handling process even though moderate ballistic and mechanical properties. It is predicted that the application field of this class will be used more widely than any other classes.

• Journal of Digital Convergence
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• v.20 no.1
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• pp.87-94
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• 2022

The reform of the mixed ownership system of vocational colleges in China is an important driving force in the development of vocational education. The purpose of this study is to discuss the operation direction of the reorganization of the mixed ownership system of vocational colleges at this stage in accordance with the guidelines for vocational education reform in China. Therefore, this study analyzed the necessity and existing problems of reforming the mixed ownership system of vocational colleges using literature research methods. As a result of the study, it was found that the reform of the mixed ownership system of vocational colleges should be continuously developed by preparing measures in terms of legal support, providing incentives, and improving the evaluation system. This study has academic and practical significance in that it suggests the need to reform the mixed ownership system of Chinese vocational colleges, analyzes problems, and prepares policy measures.