Al-Cu-Mu 주조합금의 피로성질에 미치는 Sn 첨가의 영향

김경현,김정대,김인배,Kim, Kyung-Hyun,Kim, Jeung-Dae,Kim, In-Bae 한국재료학회 2002 한국재료학회지 Vol.12 No.4

Effect of Sn addition on the fatigue properties of Al-Cu-Mn cast alloy was investigated by low and high cycle fatigue tests. Fatigue life showed the maximum value of 5450cycles in the Al-Cu-Mn alloy containing 0.10%Sn, but decreased rapidly beyond 0.20% of Sn additions. It was found that the fatigue strength was 132MPa and fatigue ratio was 0.31 in the alloy containing 0.10%Sn. Metallographic observation revealed that the fatigue crack initiated at the surface and propagated along the grain boundary. This propagation path was attributed to the presence of PFZ along the grain boundary. The tensile strength increased from 330MPa in 7he Sn-free Al-Cu-Mn cast alloy to 429MPa in the alloy containing 0.10%Sn. But above 0.20%Sn additions, tensile strength was decreased by the segregation of Sn.

Al-10%Si-0.3%Mg 합금에서 Sr 첨가가 미세조직 및 기계적 성질에 미치는 영향

김경현,이정무,정신검 ( Kyung Hyun Kim,Jung Moo Lee,Shin Kum Jung ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.1

N/A The effects of strontium content as modifier on microstructure and mechanical properties were studied in Al-10%Si-0.3%Mg cast alloys. There were not big differences in the form of eutectic Si particle and its morphology depending on adding amount of strontium, but the alloy modified by 0.012%Sr had shown the higher values than the alloy modified 0.038%Sr in strength, elongation and impact value.

웹 기반 문제중심학습 프로그램 개발과 학업성취에 미치는 효과 분석

김경현,정미경,최운필,Kim, Kyung-Hyun,Jung, Mi-Kyong,Choi, Un-Phil 한국정보교육학회 2005 정보교육학회논문지 Vol.9 No.1

Establishing problem-based leaning(PBL) that is one type of constitutional learning models is meaningful not only for finding the diversity of WBI types but also for being the specific example of constitutional usage of WBI. This paper shows the development of web-based and problem-based learning program for 6th grade students of elementary school and finds its effect on their studies achievement. There were two classes of traditional lessons and one class of web-based and problem-based lessons. It performed a test with the classes for science lesson. It was found that web-based and problem-based learning is more effective on the improvement of studies achievement. There was meaningful difference in studies achievement according to ICT utilization ability. Web-based and problem-based learning statistically had a meaningful effect on the improvement of ICT utilization ability.

Al-10%Si-0.3%Mg 주조재의 보수용접에 따른 내구특성 연구

김경현,이정무 ( Kyung Hyun Kim,Jung Moo Lee ) 한국주조공학회 1994 한국주조공학회지 Vol.14 No.6

N/A The effects of weld repair on the durability in Al-10%Si-0.3%Mg castings were evaluated. The strength and fracture toughness in fusion zone were higher than those in the base metal by rapid cooling of fusion zone after welding. There were no significant differences between fatigue properties in castings and weld repaired specimen as the results of low cycle fatigue and rotating bending fatigue test. Therefore it was concluded that weld repairing did not have any significant effect on the mechanical properties of castings.

MBE로 성장된 Al_0.25Ga_0.75As/In_0.2Ga_0.8As pHEMT 에피구조의 RTA에 따른 전도 특성

김경현,홍성의,백문철,조경익,최상식,양전욱,심규환,Kim, Kyung-Hyun,Hong, Sung-Ui,Paek, Moon-Cheol,Cho, Kyung-Ik,Choi, Sang-Sik,Yang, Jeon-Wook,Shim, Kyu-Hwan 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.7

We have investigated $Al_{0.25}Ga_{0.75}As/In_{0.2}Ga_{0.8}As$ structures for pseudomorphic high electron mobility transistor(pHEMT), which were grown by molecular beam epitaxy(MBE) and consequently annealed by rapid thermal anneal(RTA), using Hall measurement, photoluminescence, and transmission electron microscopy (TEM). According to intensity and full-width at half maximum maintained stable at the same energy level, the quantized energy level in $Al_{0.25}Ga_{0.75}As/In_{0.2}Ga_{0.8}As$ quantum wells was independent of the RTA conditions. However, the Hall mobility was decreased from $6,326cm^2/V.s\;to\;2,790cm^2/V.s\;and\;2,078cm^2/V.s$ after heat treatment respectively at $500^{\circ}C\;and\;600^{\circ}C$. The heat treatment which is indispensable during the fabrication procedure would cause catastrophic degradation in electrical transport properties. TEM observation revealed atomically non-uniform interfaces, but no dislocations were generated or propagated. From theoretical consideration about the mobility changes owing to inter-diffusion, the degraded mobility could be directly correlated to the interface scattering as long as samples were annealed below $600^{\circ}C$ lot 1 min.

반성적 성찰활동에 기반한 사이버 학습상담이 초등학생의 학습동기 및 학습습관에 미치는 효과

김경현,도은경,Kim, Kyung-Hyun,Do, En-Kyeong 한국정보교육학회 2009 정보교육학회논문지 Vol.13 No.2

This study examines the effects of cyber learning counseling based on self-reflective activities on learning motivation and habits of elementary students. From the above processes, following findings could be drawn: First, the cyber learning counseling based on self-reflective activities turned out to have positive effects on promoting the motivation of elementary students for learning. Positive impacts were found in 4 sub-factors of motivation for learning, that are, attention, relevance, conviction and satisfaction that were enhanced after cyber counseling for learning was given. Second, the cyber learning counseling based on self-reflective activities were found to have positive effects on changing elementary students' habit of learning. After cyber learning counseling was carried out, Positive impacts were visible in sub-factors of learning habit which are the behavioral indexes of applying learning skill and student-initiated behavior.

아르곤/이산화탄소 혼합가스의 유도 결합 플라즈마를 이용한 이산화탄소 분해 연구

김경현,김관용,이효창,정진욱,Kim, Kyung-Hyun,Kim, Kwan-Yong,Lee, Hyo-Chang,Chung, Chin-Wook 한국전력공사 2015 KEPCO Journal on electric power and energy Vol.1 No.1

유도 결합 플라즈마를 활용하여 $Ar/CO_2$ 혼합가스에서 이산화탄소를 분해하는 연구이다. 고밀도 플라즈마를 발생시키기 위해 Ar 가스를 첨가하였고 이산화탄소 분해율을 측정하기 위해 광학적 광량 측정법을 사용 하였다. 유도 결합 플라즈마를 방전시키고 인가 전력, 압력, 혼합가스 비율을 변경하가며 단일 랭뮤어 프로브를 이용해 플라즈마 변수를 얻고 방출 분광기로 얻은 빛의 스펙트럼을 이용하여 분해율을 측정하였다. 측정된 플라즈마 변수로부터 $CO_2$ 유도 결합 플라즈마의 소스 특성을 확인했고 $CO_2$ 분해 메커니즘은 플라즈마 변수에 직접적인 영향을 받기 때문에 그 상관관계를 분석하였다. Decomposition of carbon dioxide is studied using $Ar/CO_2$ mixture inductively coupled plasmas (ICP). Argon gas was added to generate plasma which has high electron density. To measure decomposition rate of $CO_2$, optical emission actinometry is used. Changing input power, pressure and mixture ratio, the plasma parameters and the spectrum intensity were measured using single Langmuir probe and spectroscope. The source characteristic of Carbon dioxide ICP observed from the obtained plasma parameters. The decomposition rate is evolved depending on the reaction and discharge mode. This result is analyzed with both the measurement of the plasma parameters and the dissociation mechanism of $CO_2$.

아우구스투스 황제와 수도 로마

김경현(Kim Kyung-hyun) 호서사학회 2008 역사와 담론 Vol.0 No.50

카눌레이우스 입법안의 성격에 관한 재고

김경현 ( Kim Kyung Hyun ) 한국서양고대역사문화학회 ( 구 한국서양고대사학회 ) 2012 서양고대사연구 Vol.30 No.-

기원전 445년, 호민관 가이우스 카눌레이우스(Canuleius)는 귀족과 평민 간의 통혼 금지를 철회하는 법안을 평민회에서 통과시켰다. 또한 그는 자신의 동료 호민관들과 함께 두 명의 콘술 중 한 명은 평민 중에서 선출되어야만 한다는 법안을 제출했다. 귀족들은 평민이 콘술에 선출되는 것을 막기 위해 호민관들과 타협하였으며, 결국 귀족뿐만 아니라 평민도 선출될 수 있는 새로운 정무관인 콘술러 트리뷴(consular tribune)직이 설치되었다. 통혼금지의 철회와 콘술러 트리뷴직의 설치는 공화국 초기의 ‘신분투쟁’의 역사에서 평민의 승리로 오랫동안 간주되어 왔다. 왜냐하면 전자는 귀족의 사회적 배타성을 무너뜨림으로써 형식적이지만 법 앞에서의 평등을 초래하였던 것처럼 보였기 때문이다. 반면에 후자는 평민들에게 정치적 문호를 개방함으로써 귀족과 평민이 국가 행정을 공유하기 시작했다고 평가되었기 때문이다. 그럼에도 불구하고 카눌레이우스 법안들을 귀족에 대한 평민의 승리로 해석하는 것을 잠시 유보할 필요가 있다. 카눌레이우스가 법을 제정한 목적과 그 법의 결과가 일치하지 않기 때문이다. 귀족과 평민의 통혼금지가 철회되었음에도 불구하고 통혼의 사례가 발견되고 있지 않다. 사료에서 확인되고 있는 통혼의 사례는 법안이 제출된 지 거의 80년이 지나서야 처음으로 나타났다. 또 콘술러 트리뷴직이 새롭게 설치되었다고는 하지만, 그 직책의 이용과 심지어 직책의 인원도 확실하게 정해지지 않았으며, 더욱이 평민의 선출이 허용되었음에도 불구하고 선출되었던 자들은 대부분 귀족들이었다. 일부 현대학자들은 법 제정의 목적과 결과 사이의 불일치를 사료의 신뢰성을 부인하는 증거로 제시하고 있지만, 이런 접근은 너무 단순하다고 할 수 있다. 그 불일치가 과연 무엇을 의미하는 지를 고찰해야만 한다. 이를 위해서는 카눌레이우스의 법안들을 재고찰할 필요가 있다. 첫째, 통혼에 관한 카눌레이우스법안은 평민회에서 통과되었지만 아직 법적 구속력을 가지고 있지 못하였을 것이다. 그 법안이 효력을 가지게 되었을 시점은 아마도 귀족만이 선출될 수 있었던 정무관직과 신관직이 평민에게 개방되었을 때였을 것이다. 둘째, 귀족과 평민이 합의 끝에 콘술러 트리뷴직이라는 새로운 직책을 설치하였지만, 기원전 408년까지는 콘술직과 교대로 이용되었으며, 기원전 405년부터 기원전 367년까지는 거의 매년 6명의 콘술러 트리뷴들이 선출되었다. 그러나 이 새로운 직책에 선출된 평민들의 수는 매우 적었다. 법 제정의 목적과 결과 사이의 차이는 다음과 같이 이해될 수 있다. 첫째, 평민운동이 귀족에 의한 사회적․정치적 독점현상을 와해시키려 하였기 때문에, 강경파 귀족들이 강력하게 반발하였다고 할 수 있다. 다시 말해서 귀족은 통혼금지를 철회하는 법안이 법적 구속력을 갖는 데 비협조적이었을 뿐만 아니라 새로운 직책에 평민이 선출되는 것을 방해하는데 성공적이었던 것 같다. 둘째, 호민관을 위시한 평민 지도자들이 귀족들에 의해 지배되고 있던 기존의 체제에 편입되기를 희망함으로써, 평민운동이 자발적이고 의식적인 그룹으로서의 평민에 의한 운동이라는 정체성을 상실했던 것 같다. 다시 말해서 평민지도자들의 바램만을 반영하고 있는 카눌레이우스 법안들 때문에 일반 평민들은 그들의 요구에 적극적으로 호응하지 않았을 것이다. 통혼금지를 철회하는 법안이 법적 구속력이 가지지 못한 것과 콘술러 트리뷴직에 평민이 선출되지 못했던 것은 우연이 아니라 평민들의 적극적이 지지가 결여되어 있었기 때문일 것이다. 결론적으로 카눌레이우스의 입법안들은 야누스(Janus)의 두 얼굴을 가지고 있다고 할 수 있다. 그것들은 비록 형식적이지만 법 앞에서 평등의 원칙을 선언했다는 점에서 평민운동의 승리로 간주될 수도 있다. 그러나 다른 한편으로는 평민운동이 귀족의 사회적·정치적 독점을 공격하고 부유한 평민지도자들의 정치적 참여를 지향함으로써, 강경파 귀족의 강력한 반발을 유발시켰을 뿐만 아니라 스스로 평민운동의 정체성을 훼손시켜, 평민운동을 위기에 처하게 했다고 할 수도 있다. 이런 위기는 평민운동이 앞으로 나아갈 방향을 제시하였던 것 같다. 다시 말해서, 평민지도자와 일반 평민 간의 협조만이 평민운동을 승리로 이끌 수 있다는 교훈을 제공한 것 같다. 평민운동에서 중요한 것은 평민운동을 지휘하는 부유한 평민지도자들 그리고 그들에게 지지를 제공하는 일반 대중 각각이 아니라 그들 간의 진정한 이해와 긴밀한 협조였던 것이다. 기원전 367년 호민관 리키니우스(Licinius)와 섹스티우스(Sextius)가 콘술에 관한 법안과 공유지와 부채에 관한 경제적 법안들이 반드시 민회에서 함께 통과되어야 한다고 강력하게 주장했던 것은 카눌레이우스 법안들과 관련된 평민운동의 문제점을 잘 인식하고 있었기 때문일 것이다. In 445 BC, the plebeian tribune Canuleius carried a bill abolishing the eleventh Table prohibiting intermarriage (conubium) between the patricians and the plebeians. With his fellow tribunes, he also proposed another bill that the plebeians should be elected for one of the two annually elected consuls. To prevent the plebeians from obtaining the consulship, the patricians reached an agreement with the plebeian tribunes to create a new magistrate called the consular tribune, which was to be composed of several persons from the plebeians as well as the patricians. The lift of the ban on intermarriage and the establishment of the consular tribunate have been long regarded as a plebeian victory in the history of ‘the Struggle of the Orders’ in the early Roman Republic. It is because the former seemed to bring about a kind of formal equality before the law by breaking down the social exclusiveness of the patricians, and the latter seemed to give the plebeians a share in the administration of the state by opening the political door. Nevertheless, such a view in terms of ‘a plebeian victory’ against the patricians should be reserved for a while. It is because the ostensible purposes and results of the Canuleian bills are not in accord. Not a single case of intermarriage between the patricians and the plebeians was found, until after nearly 80 years had passed since the ban on intermarriage had been lifted. Also even though the patricians and the plebeians agreed to create the consular tribunate, its employment and memberships were not fixed. Moreover, regardless the fact that the plebeians were allowed to be elected, most of the chosen consular tribunes were the patricians. Some modern scholars regard the disagreement between the purposes and results of the Canuleian legislations as a evidence to refuse the credibility of the ancient sources. But this approach is too easy and simple. What such a disagreement means should be discussed. For this, it is necessary to reconsider the Canuleian legislations. Firstly, the legislation lifting the ban on conubium seemed to have a legal force binding the whole population not in the beginning but around the period when the patrician magistracies and priesthoods were open to the plebeians. Secondly, the new magistracy, though created, was alternated with the old existing consulship before 408 BC and at most times six consular tribunes were annually elected from 405 to 367 BC. However, the number of the plebeians who were elected as a consular tribune was very few. Disagreement between the purpose and results of the Canuleian legislations could be understood as follows. Firstly, the hard-line and purist patricians may have oppressed the plebeian movement violently as soon as it requested a share with the patricians in matters of legislation or religious and political life by breaking down the social and political exclusiveness of the patricians. In other words, the patricians probably would have tried and succeeded in preventing the plebeians from being elected as a consular tribune and refrained from giving a legal force to the Canuleian legislation on the intermarriage. Secondly. the plebeian movement itself may have lost its identity as a voluntary and conscious political group as the plebeian leaders including the plebeian tribunes sought to be allowed into the existing system ruled by the patricians. In other words, the normal plebeians probably would not have hailed the Canuleian bills as it was only in accord with the needs of its leaders. This also explains why the legislation lifting the ban on the intermarriage lacked legal power and only very few plebeians were elected as the consular tribunes. In conclusion, the Canuleian legislations could be regarded as a plebeian victory in pronouncing the equality, though formal, before the law. It also reveals the crisis of the plebeian movement in that it not only caused the patrician violent resistance but defamed its identity of its own accord. This was because they attacked the social and political monopoly of the patricians and requested that the wealthy plebeian leaders to be admitted into the existing system ruled by the patricians. This crisis would have showed the future plebeian movements the way to go. In other words, it gives a historical lesson that outcome of plebeian movements depends on the cooperation between the wealthy plebeian leaders and the normal plebeians. What is important in the plebeian movements is the real understanding and close cooperation between them rather than segregating themselves into ‘the wealthy and noble plebeians’ and ‘the masses’. It is not a coincidence that Licinius and Sextius the plebeian tribunes of 367 BC struggled to insist on passing the legislation on the revival of the dual consulate and the legislations of the public land and debt together in the assembly. It is likely that they tried and succeeded in linking the interests of the masses with those of their own small class, because they recognized the problems of the Canuleian legislations as a plebeian movement well.

그리스 역사(서술)의 기원

김경현(Kim, Kyung-Hyun) 한국서양고전학회 2006 西洋古典學硏究 Vol.25 No.-