3 research outputs found
Characteristics Evaluation of Welding Zones of Cast Steel for Piston Crown Usage Welded by 1.25Cr-.5Mo Filler Metal
μΈκ³μ μΈ μ κ°μ μμΉμΌλ‘ μ°λ£λΉκ° μλ±ν¨μ λ°λΌ C μ€μ λ₯Ό μ¬μ©νλ λν μ λ° λμ €κΈ°κ΄ μ°λ£λ λμ± μ μ§ν λμ΄ μ°λ£μ체μ λΉμ€μ λ¬Όλ‘ λΆμλ¬Όμ ν¨λ λν μ¦κ° λμλ€. κ·Έλ¦¬κ³ μ΄λ¬ν 쑰건μμ μ΄μ νλ λμ €κΈ°κ΄μ κ²½μ° μ μ§ μ€μ μ μ¬μ©μΌλ‘ μΈν μ€λ¦°λλΌμ΄λμ νΌμ€ν€ ν¬λΌμ΄μ λ§ νμ λ§λ©Έ μ¦λ λ° μ€μ μ€μ ν¨μ λμ΄ μλ λ°λλ(V)κ³Ό μ ν©(S)μ μν κ³ μ¨λΆμκ³Ό μ μ¨λΆμ λ±μΌλ‘ μΈν΄ μ€λ¦°λν€λμ μμκ³Ό κ· μ΄ λ°μ λ±μ΄ μΌκΈ°λκ³ μλ€. λμ±μ΄ μ°μμ€μ ꡬμ±νλ μ£Όμν μμμΈ νΌμ€ν€ μλΆλ νλ©΄ μ¨λκ° μ μΌ λμ λΆμκΈ°μμμ μλλλ©° λν μ°μνλ°μ μν κ°ν λ°λ³΅ 좩격μ λ°κ³ μλ λμμ μ°μ κ°μ€λ₯Ό λμμμ΄ λ°°μΆνλ€. λΏλ§ μλλΌ νΌμ€ν€ ν¬λΌμ΄ μμ νΌμ€ν€μ λμμλ λ°λ³΅μ΄λμΌλ‘ νΌμ€ν€ ν¬λΌμ΄μ λΆμμΌλ‘ μΈν λ§λ©Έμ νΌν μ μλ μν©μ΄λ€. νΌμ€ν€ ν¬λΌμ΄μ κ³ μ¨ νμμμ λ°λ³΅ 좩격과 μλ ₯μΌλ‘ μΈν 물리μ μΈ λ§λ©Έκ³Ό μ κΈ°ννμ λΆμμΌλ‘ μΈν λΆμμμ±λ¬Όμ μ°μμ μν λ§λ©Έλμ΄ μ¦λ λκ³ μλ€. λ°λΌμ μ μ ν μ€λ¦°λ ν€λ, νΌμ€ν€ ν¬λΌμ΄ λ° λ°°κΈ° λ°ΈλΈμ μμλΆλΆμ 보μμ©μ μ ν΅νμ¬ μ¬μ¬μ©ν¨μΌλ‘μ¨ μλͺ
μ°μ₯μ λ°λ₯Έ κ²½μ μ μΈ ν¨κ³Όλ₯Ό μ»κ³ μλ€.
μ΄μ²λΌ μμλ νΌμ€ν€ ν¬λΌμ΄μ 보μμ©μ λΏλ§ μλλΌ μΌλ°μ μΌλ‘ κ°κ΅¬μ‘°λ¬Όμ μ μμλ μ¬λ¬ κ°μ§ μ©μ λ²μ΄ μ¬μ©λκ³ μλ€. λ°λΌμ μ§κΈκΉμ§ μ λ°κ³Ό κ΄λ ¨λ κ°κ΅¬μ‘°λ¬Όμ μ μμ μ©μ μΌλ‘ ν κ²½μ°, μ΄λ° ꡬ쑰물μ μ©μ λΆμ λν κΈ°κ³μ νΉμ±κ³Ό λΆμ λ±μ κ΄ν μ°κ΅¬λ λ§μ΄ λ°νλκ³ μλ€. κ·Έλ¦¬κ³ μκΈ°ν λΆνλ€μ μλͺ
μ°μ₯μ μν 보μμ©μ μ λν΄μλ λ€μν μ©μ λ°©λ²μ΄ μ¬μ©λμ΄μ§κ³ μλ€. κ·Έλ¬λ μ΄λ€ μ©μ λ°©λ²μ λ°λΌ 보μ μ©μ μ νμμ κ²½μ° λͺ¨μ¬μ μ©μ κΈμμ κΈ°κ³μ μ±μ§κ³Ό λ΄μμ± λΉκ΅ νκ° λ±μ λν μ°κ΅¬κ²°κ³Όλ κ±°μ μλ μ€μ μ΄λ€.
λ³Έ μ°κ΅¬μμλ νΌμ€ν€ ν¬λΌμ΄μ μ£Όκ°μΌλ‘ μ μν κ²½μ°, μ€μ μ£Όκ°μ ν λΆλΆμ λͺ¨μ¬λ‘ νκ³ μ¬κΈ°μ 1.25Cr-0.5Moμ μ©μ λ΄μΌλ‘ νΌλ³΅μν¬μ©μ (SMAW: Shielded Metal Arc Welding)μ νμμ κ²½μ° λͺ¨μ¬μ μ΄μν₯λΆ λ° μ©μ κΈμμ λ΄μμ± λΉκ΅ νκ°λ₯Ό μ κΈ°ννμ μΈ μΈ‘λ©΄μμ λΉκ΅ κ³ μ°°νμλ€. λ°λΌμ λ³Έ μ°κ΅¬μ κ²°κ³Όλ νΌμ€ν€ μ£Όκ°μ νμ 1.25Cr-0.5Moμ μ©μ λ΄μΌλ‘ νΌλ³΅μν¬μ©μ (SMAW: Shielded Metal Arc Welding)μ νμμ κ²½μ° κ° μ©μ λΆμμ λν κΈ°κ³μ λ° λ΄μμ±μ μ°¨μ΄μ νΉμ±μ λΉκ΅ κ³ μ°°ν¨μΌλ‘μ¨ μ΅μ μ μ©μ μ¬λ£μ μ¬μ© κ°λ₯μ±μ λν μ°Έκ³ μλ£λ₯Ό μ 곡νλλ° κ·Έ μλ―Έκ° ν΄ κ²μΌλ‘ μ¬λ£λλ€. λΏλ§ μλλΌ νν΄ μ€μΈ μ λ°μμ λΆκ°νΌνκ² λ³΄μμ©μ μ ν κ²½μ° μ°κ°μ©μ λ΄μ μ¬μ©νλ κ²½μ°κ° μλλ° λ³Έ μ°κ΅¬μμλ 1.25Cr-0.5Mo μ©μ λ΄κ³Ό λͺ μ’
λ₯μ μ°κ°μ©μ λ΄μ λν κΈ°κ³μ λ° λ΄μ νΉμ±μ κ²°κ³Όμ λΉκ΅ κ³ μ°°νμ¬ λ³΄μλ€. κ·Έλ¬λ―λ‘ 1.25Cr-0.5Moμ μ©μ λ΄κ³Ό μ°κ°μ©μ λ΄μ κΈ°κ³μ λ° λ΄μνΉμ±μ λΉκ΅λ ν₯ν 보μμ©μ μ λν μ μ΅ν μ°Έκ³ μλ£λ₯Ό μ κ³΅ν΄ μ€ κ²μΌλ‘ κΈ°λλλ€.Recently a fuel oil of the diesel engine for the marine ship is being changed with heavy oil of low quality as the oil price is higher more and more. Therefore the wear and corrosion in all parts of the engine such as cylinder liner, piston crown, spindle and seat ring of exhaust valves are predominantly increased with using of heavy oil of low quality. In particular the degree of wear and corrosion of piston crown is more seriously compared to the other parts of the engine due to operating in severe environment such as the high temperature of exhaust gas and repeating impact. Thus the repair weldment of the piston crown is a unique method to prolong the its life in a economical point of view.
By the way, their parts on the ships job site is often being actually welded with electrodes of mild steel. However, in the case welded with the electrode of mild steel, the mechanical property and corrosion resistance of welding zone would be worse than other electrode.
In this study, the cast steel material for piston crown as a base metal was welded with 1.25Cr-0.5Mo electrode. And each welding zone, that is, the mechanical and corrosion characteristics of base metal(BM), heat affected zone(HAZ) and weld metal(WM) were investigated using such as measuring of Vickers hardness, corrosion potential, polarization curve, cyclic voltammogram and impedance in 35% H2SO4 solution. And the morphology of corroded surface was also observed by micro photograph. The base metal zone exhibited higher value of hardness compared to the heat affected and weld metal zones. The corrosion potential of the base metal indicated a lower value than those of heat affected and weld metal zones, however, the corrosion resistance of the base metal zone was better compared to heat affected and weld metal. Consequently, it is considered that the lower corrosion potential, the lower hardness, the corrosion resistance is to become better more and more. Furthermore, in the case welded by 1.25Cr-0.5Mo electrode to the cast steel material for piston crown, we can see that their mechanical properties and corrosion resistance in the welding zones were significantly to be better compared to the case welded by the electrode with mild steel.List of Tables β
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List of Figures β
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Abstract β
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1. μ λ‘ 1
2. μ΄λ‘ μ λ°°κ²½ 3
2.1 λΆμμ μ΄λ‘ 3
2.1.1 λΆμμ μ κΈ°ννμ μ리 6
2.1.2 μκ·Ήκ³Ό μκ·Ήμ μ μ 9
2.1.3 λΆμμ λ°μ 10
2.1.4 κΈ°μ λ ₯ κ³μ΄κ³Ό κ°λ°λ κ³μ΄ 12
2.1.5 λΆμμ μ§μ μ’
λ₯ 15
2.1.6 λΆμμ μ’
λ₯ 18
2.1.7 μ μ(Potential) 23
2.1.8 μ μ-pHλ 26
2.1.9 λΆκ·Ή(Polarization) 28
2.1.10 μνΌλμ€(Impedance) 33
2.2 μ©μ μ κ°μ 40
2.2.1 μ©μ μ μμ 40
2.2.2 μ©μ μ μ리 40
2.2.3 μ©μ μ μμ¬ 41
2.2.4 μ©μ λ²μ λΆλ₯ 42
2.2.5 μ©μ μ νΉμ± 43
2.2.6 μ©μ μ μμ© 44
2.2.7 μ©μ λΆμ μ±μ§ 45
2.3 νΌμ€ν€ ν¬λΌμ΄μ μ©μ κ°μ 45
2.3.1 νΌμ€ν€ ν¬λΌμ΄μ μ¬μ§ 45
2.3.2 νΌμ€ν€ ν¬λΌμ΄μ μμ 46
2.3.3 νΌμ€ν€ ν¬λΌμ΄μ 보μ μ©μ 48
3. μ°κ΅¬κ²°κ³Ό λ° κ³ μ°° 50
3.1 μ¬λ£ λ° μ€νλ°©
Analysis of Teaching Practice Guidance of Science Cooperating Teachers in the Perspective of the CHAT
νμλ
Όλ¬Έ (μμ¬) -- μμΈλνκ΅ λνμ : μ¬λ²λν κ³Όνκ΅μ‘κ³Ό(ννμ 곡), 2021. 2. λ
Ένν¬.μ΄ μ°κ΅¬μμλ κ³Όνκ΅μ¬μ κ΅μ‘μ€μ΅ μ§λ κ³Όμ μ CHATμ νμ©νμ¬ μ¬μΈ΅μ μΌλ‘ λΆμνμλ€. μμΈνΉλ³μμ μμ¬ν μ¬λ²λνμ λΆμ€νκ΅μμ 근무νλ 2λͺ
μ κ³Όνκ΅μ¬κ° μ°κ΅¬μ μ°Έμ¬νμλ€. κ΅μ‘μ€μ΅μ μ°Έκ΄νμ¬ μ§λ κ³Όμ κ³Ό μμ
μ κ΄μ°°νμκ³ , κ΄λ ¨ λ¬Έμ μλ£λ₯Ό μμ§νμμΌλ©°, κ΅μ‘μ€μ΅μ μ , μ€, νμ λ°κ΅¬μ‘°νλ λ©΄λ΄μ μ€μνμλ€. μ§μμ λΉκ΅ λ°©λ²μΌλ‘ μμ§ν μλ£λ₯Ό λΆμνμλ€. λΆμ κ²°κ³Ό, κ΅κ³Ό μ§λκ΅μ¬μ μμ
μ€ μνμ§λ λν μ€μνμμΌλ©° κ΅κ³Ό μ€λ¦¬μν
μ΄μ
μ μ€μ΅ μ μλ μΆκ°λ‘ μ΄λ£¨μ΄μ§ νμκ° μμλ€. μλΉκ³Όνκ΅μ¬μμ λΆμ
μ μ§λκ΅μ¬μ μ
무 λΆλ΄μ λκΈ°λ νμλ€. μ±μ μ λ―Όκ°ν νμλ€κ³Ό κ°μ΄ 곡λ체 μμμ μν₯μΌλ‘ νμ νκ°λ₯Ό μ§λνμ§ λͺ»νλ κ²½μ°κ° μμλ€. λ κ΅μ¬μ κ΅μ‘μ€μ΅μ μνΈνλ ₯μ μΌλ‘ μ΄λ£¨μ΄μ Έ μλΉκ΅μ¬λ§μ΄ μλλΌ μ§λκ΅μ¬, νμλ€ λͺ¨λμκ² κΈμ μ μΌλ‘ μμ©νμλ€. λν, λ κ΅μ¬μ νλ체κ³μμλ ꡬ체μ μΈ μ§λ λ°©μμ λΆμ¬μ μλΉκ΅μ¬μ λν μ΄ν΄ λΆμ‘±μΌλ‘ μΈν λͺ¨μμ΄ λνλ¬λ€. μ΄λ λ κ΅μ¬μ κ΅μ‘μ€μ΅ μ§λμ μ΄λ €μμ κ°μ Έμκ³ , λμκ°μλ μλΉκ΅μ¬λ€μ΄ μ€μ΅ μ€μ κ²ͺλ μ΄λ €μμΌλ‘ μ΄μ΄μ§κΈ°λ νμλ€. λ κ΅μ¬λ λμμ λ°©λ²μΌλ‘ λͺ¨μμ ν΄κ²°νκ³ μ νμμΌλ©° κ΅μ‘μ€μ΅ μ§λλ₯Ό μν νμ€νλ μ§μΉ¨, μ§λκ΅μ¬λ€μ΄ μλ‘ νλ ₯ν μ μλ νκ²½, μ¬λ²λνκ³Όμ κΈ΄λ°ν μ°κ³ λ±μ μꡬνμλ€. μ΄μμ μ°κ΅¬ κ²°κ³Όλ₯Ό λ°νμΌλ‘ κ΅μ‘μ€μ΅μ κ°μ νκΈ° μν λ°©μμ λ
Όμνμλ€.In this study, we investigated science cooperating teacher's guidance of teaching practice in the perspective of the CHAT. Two science teachers working for schools affiliated with a college of education in Seoul took part in this study. Visiting the entire teaching practice, we observed the processes of guidance and the lessons and collected materials related. Semi-structured interviews were also conducted before, during and after teaching practice. All the data were analyzed by using the constant comparative method. The analyses of the results revealed that student guidance during the lessons was also important. And the curriculum orientation needed to be carried out before teaching practice. The division of labor with pre-service teachers relieved teachers of work burden. Teachers failed to guide assessment of students due to influences of community element such as students who were sensitive to grades. In both cases, teaching practice were so collaborative that valuable not only for pre-service teachers but also for teachers and students. Two teachers' activity system showed contradictions due to the lack of specific manuals for guidance and the lack of understanding of pre-service teachers. These contradictions brought about difficulties in their guidance, which in turn led to the difficulties experienced by pre-service teachers during teaching practice. They attempted to resolve contradictions in alternative ways and required standardized manuals for guidance, environments in which teachers could collaborate, and close connections with a college of education. Based on the results, we suggest some ways to improve teaching practice.I. μλ‘ 1
1.1 μ°κ΅¬μ νμμ± 1
1.2 μ°κ΅¬μ λ΄μ© λ° μ°κ΅¬ λ¬Έμ 5
1.3 μ°κ΅¬μ μ νμ 6
1.4 μ©μ΄μ μ μ 7
II. μ΄λ‘ μ λ°°κ²½ 8
2.1 κ΅μ‘μ€μ΅ 8
2.1.1 κ΅μ‘μ€μ΅μ μμ λ° ν¨κ³Ό 8
2.1.2 κ΅μ‘μ€μ΅ μμ λ° κ³Όμ 10
2.2 κ΅μ‘μ€μ΅ μ§λκ΅μ¬ 12
2.2.1 κ΅μ‘μ€μ΅ μ§λκ΅μ¬ 12
2.2.2 κ΅μ‘μ€μ΅ μ§λκ΅μ¬μ μν₯λ ₯ 14
2.2.3 κ΅μ‘μ€μ΅ μ§λκ΅μ¬μ κ΄λ ¨λ μ νμ°κ΅¬ 16
2.3 λ¬Ένμμ¬μ νλμ΄λ‘ (CHAT) 18
2.3.1 λ¬Ένμμ¬μ νλμ΄λ‘ 18
2.3.2 κ΅μ‘μ°κ΅¬μμ CHATμ νμ© 22
III. μ°κ΅¬ λ°©λ² 24
3.1 μ°κ΅¬ μ°Έμ¬μ λ° μ°κ΅¬μ λ§₯λ½ 24
3.2 μ°κ΅¬ μ μ°¨ λ° μλ£ μμ§ λ°©λ² 25
3.3 κ²°κ³Ό λΆμ λ°©λ² 26
IV. μ°κ΅¬ κ²°κ³Ό λ° λ
Όμ 28
4.1 νλ체κ³μ μμ λΆμ 28
4.1.1 주체 28
4.1.2 κ°μ²΄ 30
4.1.3 곡λ체 34
4.1.4 κ·μΉ 36
4.1.5 λΆμ
39
4.1.6 λꡬ 41
4.2 νλμ²΄κ³ μμμ μνΈμμ© λΆμ 43
4.2.1 νμ νκ° μ§λ 43
4.2.2 μνΈνλ ₯μ μΌλ‘ μ΄λ£¨μ΄μ§ κ΅μ‘μ€μ΅ 45
4.3 νλ체κ³μ λνλ λͺ¨μ λΆμ 47
4.3.1 ꡬ체μ μΈ μ§λ λ°©μμ λΆμ¬λ‘ μΈν λͺ¨μ 47
4.3.2 μλΉκ΅μ¬μ λν μ΄ν΄ λΆμ‘±μΌλ‘ μΈν λͺ¨μ 50
V. κ²°λ‘ λ° μ μΈ 54
μ°Έκ³ λ¬Έν 57
ABSTRACT 65
νλͺ©μ°¨ 0
κ΅μ‘μ€μ΅ μ§λκ΅μ¬μ μν 13
νλ체κ³λ₯Ό ꡬμ±νλ 6κ°μ§ κ΅¬μ± μμ 18
μ§λκ΅μ¬ νλ체κ³μ 6κ°μ§ μμ 26
κ·Έλ¦Όλͺ©μ°¨ 0
μ 1μΈλ νλμ΄λ‘ 19
μ 2μΈλ νλμ΄λ‘ 20
μ 3μΈλ νλμ΄λ‘ 20
μ§λκ΅μ¬ Bμ μ€λ¦¬μν
μ΄μ
μλ£ 30
νμνκ° μ§λμ λν Aμ νλμ²΄κ³ 43
μνΈνλ ₯μ κ΅μ‘μ€μ΅μ λν Aμ Bμ νλμ²΄κ³ 45
ꡬ체μ μΈ μ§λλ°©μ λΆμ λ‘ μΈν νλ체κ³μ λͺ¨μ 47
μλΉκ³Όνκ΅μ¬μ λν μ΄ν΄ λΆμ‘±μΌλ‘ μΈν νλ체κ³μ λͺ¨μ 50Maste
Pre-service Science Teachersβ Difficulties in Teaching Practice: Focused on the Perspectives of Pre-service Teachers and Cooperating Teachers
μ΄ μ°κ΅¬μμλ κ΅μ‘μ€μ΅μμ λνλλ μλΉκ³Όνκ΅μ¬μ μ΄λ €μμ μλΉκ΅μ¬μ μ§λκ΅μ¬μ κ΄μ μμ μ‘°μ¬νμλ€. μμΈνΉλ³μμ μμ¬ν μ¬λ²λν ννκ΅μ‘κ³Όμ μ¬νμ€μ΄λ©° κ΅μ‘μ€μ΅μ μ°Έμ¬ν 9λͺ
μ μλΉκ΅μ¬μ μ΄λ€μ μ§λκ΅μ¬ 2λͺ
μ΄ μ°κ΅¬μ μ°Έμ¬νμλ€. κ΅μ‘μ€μ΅μ κ΄μ°°νκ³ λ¬Έμ μλ£λ₯Ό μμ§νμμΌλ©° λ©΄λ΄μ μ€μνμλ€. κ·Όκ±° μ΄λ‘ μ λΆμ λ°©λ²μ λ°λΌ μμ§ν μλ£λ₯Ό λΆμνμλ€. λΆμ κ²°κ³Ό, μλΉκ΅μ¬λ€μ μ€ν μμ
μ μ€λΉνκ³ μ€ννλ κ³Όμ μμ μ΄λ €μμ κ²ͺμμΌλ©°, μ΄λ μ¬λ²λνμμ μ€Β·κ³ λ±νκ΅ μ€νκ³Ό κ΄λ ¨λ κ΅μ‘μ΄ λΆμ‘±νκ³ μ€μ΅ νκ΅μ νκ²½μ΄ λ―μ€κΈ° λλ¬Έμ΄μλ€. μλΉκ΅μ¬λ€μ νμ μ€μ¬ νλμμ λνλλ νμλ€μ λ€μν λ°μμ μ νλ©° μ΄λ €μμ κ²ͺμκ³ μ΄μ λ°λΌ νμλ€μ ν΅μ νκ³ μ νμλ€. μ§λκ΅μ¬λ€μ μλΉκ΅μ¬μ μμ¨μ±μ 보μ₯νκΈ° μν΄ κ΅¬μ²΄μ μΈ λμμ μ 곡νμ§ μμκ³ μ΄λ‘ μΈν΄ μλΉκ΅μ¬λ€μ μ΄λ €μμ κ²ͺμλ€. κ³Όν λμ리 νλμ μ§λν΄ λ³΄λ κ²μ μλΉκ΅μ¬λ€μκ² μλ―Έ μλ κ²½νμ΄μμΌλ μλΉκ΅μ¬μ μ§λκ΅μ¬ λͺ¨λμκ² λΆλ΄μΌλ‘ μμ©νμλ€. μ°κ΅¬ κ²°κ³Όκ° κ°λ κ΅μ‘μ ν¨μμ κ΅μ‘μ€μ΅ κ°μ μ μν μμ¬μ μ λ
Όμνμλ€.
In this study, pre-service science teachers' difficulties in teaching practice were investigated from the perspectives of pre-service teachers and cooperating teachers. Nine pre-service teachers who were attending a department of chemistry education at a college of education in Seoul and participated in teaching practice, and two of their cooperating teachers participated in the study. Teaching practice were observed, documentary data were collected, and interviews were conducted. The collected data were analyzed using analysis method of grounded theory. As results of the analysis, the pre-service teachers had difficulties in preparing and executing lessons which include experiments, because education related to experiments in middle and high schools was insufficient at the college of education and environments of cooperating school were unfamiliar to them. They had difficulties in encountering various responses from students in student-centered activities and tried to control students. Cooperating teachers did not provide specific assistance to ensure the autonomy of pre-service teachers, so that pre-service teachers suffered. Guiding science club activities was a meaningful experience to pre-service teachers, but it was a burden on both pre-service teachers and cooperating teachers. Educational implications of these findings were discussed.N