Combustion characteristics of gaseous inverse O₂/H₂ coaxial jet flames in a single-element model combustor

Kim, Tae Young,Choi, Sun,Kim, Young Hoo,Ahn, Yeong Jong,Kim, Hee Kyung,Kwon, Oh Chae Elsevier 2018 ENERGY Vol.155 No.-

<P><B>Abstract</B></P> <P>To effectively design hydrogen (H<SUB>2</SUB>)/oxygen (O<SUB>2</SUB>) liquid rocket engines through understanding the combustion characteristics of H<SUB>2</SUB>/O<SUB>2</SUB> bipropellants, fundamental studies for the bipropellants in different phases are needed. This study is focused on the combustion characteristics of inverse gaseous O<SUB>2</SUB>/H<SUB>2</SUB> coaxial jet flames in a single-element model combustor as a preliminary step for succeeding studies of injection at different phases in the combustor, visualizing flame structure by direct imaging, OH<SUP>∗</SUP> chemiluminescence and OH planar laser-induced fluorescence. With increasing Reynolds number (Re), the frequency of occurrence of the local flame extinction increases and the length of the disconnected OH reaction zone is extended. The OH layer thickness increases downstream, while it is almost constant where the local flame extinction occurs and decreases with increasing Re due to the enhanced strain and scalar-dissipation rates. The excessive flame wrinkledness increases the local flame strain rate and results in the local flame extinction, exhibiting the tendency of increasing and then decreasing flame surface density with increasing Re. The probability density function of OH intensity quantifies the fluctuation intensity of OH radicals and the possibility of the local flame extinction. A useful database is provided for modeling the combustion of H<SUB>2</SUB>/O<SUB>2</SUB> bipropellants under different phases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A useful database for modeling the H<SUB>2</SUB>/O<SUB>2</SUB> bipropellant combustion is provided. </LI> <LI> Local flame extinction frequently occurs at high Reynolds number (<I>Re</I>). </LI> <LI> OH probability density function indicates the possibility of local extinction. </LI> <LI> Flame surface density increases and then decreases with increasing <I>Re</I>. </LI> <LI> Strong burning of O<SUB>2</SUB>/H<SUB>2</SUB> causes laminar-like combustion near the injector lip. </LI> </UL> </P>

포스트모던 관광의 지속가능성에 관한 연구

오정준(Oh, Jeong-Joon),이후석(Lee, Hoo-Suk) 한국관광연구학회 2003 관광연구저널 Vol.17 No.1

Postmodern tourism has been conceived as environmentally-friendly tourism and thus sustainable tourism. In reality, however, postmodern tourism tends to have a negative impact on the environment and lives of indigenous people. The purpose of this study is to analyze sustainability of so-called postmodern tourism and to suggest a new direction for postmodern tourism through a case study of Ahbu Oh-Rum in Jeju Island. The case study suggests that economic benefits to and social-cultural impacts on the indigenous people of the development of postmodern tourism in Ahbu oh-rum is very few, while environmental destruction has been increased. For instance, soil erosion resulted from trampling is found in many slopes, and a number of cows are infertile due to tourists' interference. As a result, indigenous p대ple, especially who work at a meadow, prohibit tourists from visiting their meadow because of tourists' negative impact on cows. The case study also finds that Ahbu Oh-Rum destination lucks or destination management systems to conserve the environment of the destination and basic facilities such as tourist roads, visitors centers, and interpretation services for tourists. Therefore, the destination management systems and the basic facilities are necessary to improve the sustainability of postmodern tow-ism in terms of economic revenue and conservation of the environment.

수학과 동기유발을 위한 학습자료의 활용에 관한 연구

오후진,이유심 공주대학교 과학교육연구소 2002 과학교육연구 Vol.33 No.-

본 연구는 수학에 흥미가 적거나 소극적인 태도를 가진 학생에게 동기유발 학습자료를 적용한 결과 문제 해결능력이 개선될 수 있는지에 대해 연구했다. 이 자료의 적용으로 학생은 더 많은 흥미와 적극적인 태도, 그리고 수학과 학력이 보다 나아짐을 보였다. 본 연구의 결론은 다음과 같다. 1. 잘 개발된 동기유발 학습자료를 수업에 활용함에 따라 수업시간이 보다 활발해졌다. 2. 생동감 있는 수업 분위기가 조성되어 자신감, 흥미, 태도 면에서 긍정적인 변화를 가져왔고, 게다가 수학의 중요성도 인식하게 되었다. 3. 적극적인 학습의욕을 가지게 되어 학습 집중력이 강화되었으며, 수학과 학력을 신장시킬 수 있었다. The purpose of this study is to investigate the results from applying stimulative teaching materials to the class which consists of the students who have little interest or negative attitude in mathematics so that they can improve their problem-solving ability. With the application of these materials, students have showed more interest, positive attitude and better achievement in mathematics. The conclusions from the results of the study are as follows. 1. Students took part in the activities more in the class where interesting and well-developed teaching materials were used. 2. Students got changed positively with the live class atmosphere in the aspects of confidence, interest, and attitude and recognized the importance of mathematics as well. 3. Students began to be more active and highly motivated in the class, which got to be intensive gradually and led them to the improvement in mathematics.

두 모수에 대한 가우스 과정의 증분은 얼마나 큰가?

오호세 慶南專門大學 1998 論文集 Vol.26 No.1

수학과 그룹별 자기 주도 학습이 문제해결능력 신장에 미치는 영향 : 중학교 2학년 과정을 중심으로 Gentered to the 2nd Grade curriculum of Middle School

오후진,김태흥 한국학교수학회 2001 韓國學校數學會論文集 Vol.4 No.2

In its seventh revision to start in 2001, mathematics will have a new emphasis in the middle school curriculum. Mathematics subject is now composed of practical things in the use of mathematics. Also, the future of new generation, which has been known as the information age, places much focus on problem-solving in order to collect, analyze, synthesize, and judge various kinds informations. This demand of problem-solving ability is not only related with mathematical education but, along the entire educational process, its related to actual life. With this change of social structure, the importance of school education is increasing rapidly. Therefore, in order to grow abilities and create new knowledge, adapted this new method of self-oriented learning in groups to middle school 2nd graders for one year, the results were as follow : 1. Students developed their ability of the use of mathematical terms and signs correctly. 2. Students' mathematical knowledge and problem-solving ability improved as they had increased interest in mathematics. 3. Students' peership was enhanced through their communication and cooperative activities in groups during the class. 4. Students themselves were more willing to volunteer and participate during the class.

수학학습에 대한 불안요인 연구

오후진,이종배 한국학교수학회 2000 韓國學校數學會論文集 Vol.3 No.1

The purpose of this study is to investigate the degree of anxiety factors for learning mathematics and look into the reason of anxiety of mathematics and show the method of eliminating negative and anxious factors in elementary school, secondary school and high school. To have learner take an interest in learning mathematics, develop the positive attitude about learning mathematics and maximize the effect of learning of mathematics, three kinds of hypotheses are established as follows: 1.There would be difference in anxiety factor of learning mathematics according to elementary school, secondary school and high school. 2.There would be difference in anxiety factor of learning mathematics according to sex. 3.There be difference in anxiety factor of learning mathematics according to the level of achievement. The results of this study are as follows: 1.Hypotheses I was testified. The anxiety factor between mathematics learning and mathematics teacher was significant difference according to elementary school, secondary school and high school. 2.Hypotheses II was testified. The result of hypotheses II was significant difference only in high school. The anxiety factor of mathematics teacher was significant difference according to boy student and girl student. 3.Hypotheses III was testified. The anxiety factor of mathematics, teacher and test was significant difference only in elementary school and high school.

Fuzzy 측도에 관하여

오후진 공주대학교 사범대학 과학교육연구소 1996 과학교육연구 Vol.27 No.1

여러개념으로 정의되어 연구한 Fuzzy 측도들을 동일개념(unified concept)으로 접근(approach)하려는 것이 주된 목표이다. 흥미있는 결과로서, 1. [0,M]-측도([0,M]-valued measure)는 m(A)=ρ(1A)로 놓으면 ⊥-분해측도(⊥-decomposable measure)가 될 수 있다. 2. 가능측도(possibility measure)는 연산 t-코노름 ⊥을 연산 ∨로 바꾸어 놓으면 [0,M]-valued measure)가 될 수 있다.

교사 양성을 위한 미국의 교사 자격제도 : 일리노이스주와 조지아주

오후진 공주대학교 과학교육연구소 2004 과학교육연구 Vol.35 No.-

미국에서는 공교육이 주의 고유사무로 되어 있기 때문에 공교육학교의 교원을 양성하는 기관도 각주에 따라서 그 적정성이 공인되었다고 하는 것이 제일 조건이 된다. 교원양성기관은 거의 모든 종류의 대학이 포함된다. 입학의 조건은 대학에 따라서 다소 차이가 있으나 ①인정된 고교를 졸업하여야 하는 것을 기초조건으로 하고, ②졸업시 학급성적과 순위가 참작되며, ③고교로부터의 추천서 및 ④대학입학 시험위원회에서 행하는 학력적성검사의 결과가 참작된다. 수업연한은 사범대학은 4년, 교양대학의 교육과는 4년, 종합대학과 교육대학은 4∼5년으로 되어 있다. 미합중국의 교사 교육은 규정상 4년제 대학과정에서 이루어지며, 졸업 직전 6개월간은 전부 또는 부분적으로 실습을 하게 되는데, 모두 대학에서 관장한다. 모든 교사 교육 프로그램은 기본적으로 “교양교육, 전문교육 그리고 전공교육” 세 부분으로 구성되어 있다. 50개주 중에서 14개주는 석사학위(MA)를 교사 자격의 기준으로 정하고 있으며, 그 교육기간은 5년이다. 그러나 그 교육내용은 4년제와 크게 다를 바 없다. 다양성과 다원적인 개방성을 지니고 있는 미국의 교사 교육의 내용을 미국 연방의 차원에서 인지할 수 있는, 교사 교육의 기준을 중심으로, 종합하여 분석 정리하고 일리노이스주와 조지아주의 교사교육에 대하여 제시한다. Illinois has two means by which individuals may be certificated. All Persons seeking a first certificate in Illinois must complete an approved teacher education program, either in Illinois or in another state. Through the approved program process, institutions which have certification programs approved by the State Teacher Certification Board define the courses which the candidate must complete in order to certified at the grade level and subject of the candidate's interest. The institution recommends the candidate for the certificate upon the candidate's completion of the program requirements. The other means of certification in Illinois is by a transcript evaluation of credits to verify completion of the minimum requirements for the certificate. However, this route to certification for Early Childhood, Elementary, High School and Special certificates is open only to persons who are in one of the following categories: (1) They hold an Illinois teaching certificate and have teaching experience in Illinois public or private schools. (2) They hold a valid out-of-state certificate comparable to the certificate they seek in Illinois. (3) They have completed an out-of-state approved teacher education program in the area of certification sought in Illinois. Georgia offers certification in a variety of fields with specific subjects or grade levels assigned to each field. Certificates are organized by type according to the school personnel function. Certificate types include Teaching, Service, and Leadership; the type of certificate dictates in what capacity the educator may serve. Teaching fields consist of Early Childhood Education(P-5), Middle Childhood(4-8), Secondary Fields(7-12) and P-12 Fields(Special Education, Art, Music, etc.) Service fields and Leadership fields allow the educator to serve at all grade levels (P-12). In addition to full certification fields, endorsements to certificates are offered in teaching, service, and leadership areas. Vocational certificates are also available at the request of Georgia employer in specific trade and technical fields. All certificates are classified in one of three categories. The Clear Renewable Certificate indicates all professional requirements for certification in the field have been met. Conditional Certificates are issued at the request of a Georgia employer when one or more conditions have to be met in order to be issued the Clear Renewable Certificate. Life Certificates were discontinued in 1974; however, Georgia educators issued life certification before 1974 may continue to use these certificates.

수학학습에 대한 불안요인 연구

吳厚鎭,李鍾培 공주대학교 사범대학 과학교육연구소 2000 과학교육연구 Vol.31 No.1

본 연구는 초등학교, 중학교, 고등학교 학생을 대상으로 학생이 학습과정에서 지니게 되는 수학에 대한 불안정도를 조사해 보고 수학에 대한 부정적인 태도를 지니거나 큰 불안감을 갖게 되는 이유를 규명하며, 부정적 요소, 불안의 요소를 제거하기 위한 방안을 모색해 보고자 하였다. 그래서 학생이 수학을 학습하는 데 있어 교과에 대한 긍정적 태도와 바람직한 자세를 지니게 하고 수학학습의 효과를 높이며 아울러 학생 스스로 수학에 대한 흥미와 관심을 지닐 수 있도록 하는데 목적을 두고 다음과 같은 세 가지 연구문제를 설정하여 수학불안과 관련하여 본 연구의 문제에 대하여 분석하여 얻어진 결과는 다음과 같다. 첫째, 초·중학교의 학교 급별에 따른 수학 교과에 대한 불안요인과 수학교사에 대한 불안용인에서는 유의미한 차이가 있는 것으로 나타났으며, 중학교 학생들의 불안요소가 가장 큰 것으로 나타났다. 그러나, 수학시험에 대한 불안요인에서는 학교 급별 간 유의미한 차이가 없었다. 둘째, 남, 여 성별로 분석을 해 본 결과 수학교사에 대한 불안요인에서만 유의미한 차이가 있었음을 알 수 있었다. 셋째, 성취수준별로 분석을 해 본 결과 수학교과에 대한 불안요인, 수학교사에 대한 불안요인, 수학시험에 대한 불안요인에서 모두 유의미한 차이가 있었다. 그러나 중학교에서는 수학교과에 대한 불안요인에서만 유의미한 차이가 있었다. 한편, 수학불안에 대한 불안요인들을 각 문항별로 살펴본 결과 불안 요인 중 교사에 대한 불안요인에서 설명위주의 수업은 학생들의 흥미를 떨어지게 하여 수학성취수준을 하락시키는 근본적인 이유라고 판단되며, 교사의 언행이 학생들의 학업성취도 및 수학 불안요인에 상당히 큰 의미로 작용하고 있다는 사실을 알 수 있었다. The purpose of this study is to investigate the degree of anxiety factors for learning mathematics and look into the reason of anxiety of mathematics and show the method of eliminating negative and anxious factors in elementary school, secondary school and high school. To have learner take an interest in learning mathematics, develop the positive attitude about learning mathematics and maximize the effect of learning of mathematics, three kinds of hypotheses are established as follows: 1. There would be difference in anxiety factor of learning mathematics according to elementary school, secondary school and high school. 2. There would be difference in anxiety factor of learning mathematics according to sex. 3. There be difference in anxiety factor of learning mathematics according to the level of achievement. The results of this study are as follows: 1. Hypotheses Ⅰ was testified. The anxiety factor between mathematics learning and mathematics teacher was significant difference according to elementary school, secondary school and high school. 2. Hypotheses Ⅱ was testified. The result of hypotheses Ⅱ was significant difference only in high school. The anxiety factor of mathematics teacher was significant difference according to boy student and girl student. 3. Hypotheses Ⅲ was testified. The anxiety factor of mathematics, teacher and test was significant difference only in elementary school and high school.

수평 2중관 열교환기내에서 R-22와 그 대체냉매의 응축 열전달 특성

오후규,박기원,문정욱,노건상,이상훈 麗水水産大學校産業技術硏究所 1997 産業基術硏究所 論文集 Vol.6 No.-

Compared experimental results for forced convection condensation of R-22 and its alternative refrigerants inside a horizontal smooth tube are presented. The pure refrigerant, azeotropic refrigerant mixtures and binary and ternary non-azeotropic refrigerant mixtures are used as the test fluids and a double pipe heat exchanger is used. The refrigerant mass flow rate and temperatures were measured. Using the data, the heat flux, quality and local and mean heat transfer coefficients for the condensation have been obtained. Local heat transfer coefficients for R-22 and its alternative refrigerants were measured at top, side and bottom of the test tube. The results indicated that the heat transfer coefficient of pure and azeotropic refrigerant mixtures was higher than at top of the tube. Non-azeotropic refrigerant mixtures, however, were higher than side and top of the tube. Mean heat transfer coefficients for non-azeotropic refrigerant mixtures increased with refrigerant mass velocity and quality, but were considerably lower that of pure refrigerant and azeotropic refrigerant mixtures.