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참여정부가 출범하면서 경찰처에서는 2003년 3월부터 본청과 각 지방경찰청 단위로 보직공모제를 실시하였다. 보직공무제는 보직관리를 행함에 있어 소속 경찰기관내에서 공개모집을 통하여, 인사행정의 투명성과 공정성을 높이고, 우수 경찰공무원의 활용을 극대화하고자 실시한 것이다. 그러나 경찰청이 처음으로 실시한 인사제도인 만큼 많은 문제점이 노정되었고, 이 제도의 정착을 위해서는 이번 실시를 계기로 실태에 대한 분석이 요구된다. 본 논문에서는 보직공모제도가 현실적으로 어떠한 의미가 있으며, 공모, 자격심사, 최종선발이라는 3가지 구성요소를 기초로 하여 실제로 어떻게 이루어지는가 고찰한다. 또한 2003년 3월부터 경찰청 및 각 지방경찰청 단위로 실시한 보직공모제도의 실시현황과 실태를 검토·분석해 보고, 보직공모제가 가진 문제점과 개선방안을 제시해 본다.
二種狀態의 fibre, 즉 fibre에 미리 aluminum-coating을 한것과 하지 않은 상태의 fibre를 가지고 製造한 알루미늄-鋼纖維複合材料에 對해서 機械的性質 및 塑性擧動을 Instron 인장시험기에 의해서 조사하였다. fibre에 aluminum-coating을 하지않고 製造한 알루미늄-鋼纖維複合材料의 引張强度는 fibre 含量의 增加와 더불어 直線的으로 增加하지만, 複合則에 의한 推定値보다는 약간 작다. aluminum-coating을 하지 않은 fibre를 가지고 製造한 알루미늄-鋼纖維複合材料는 비록 fibre와 matrix 間의 界面接着이 不完全하드래도, aluminum-coating을 行한 fibre를 가지고 製造한 複合材料보다도 높은 强度와 좋은 延性의 組合을 보여준다. 後者의 경우에 있어서 强度와 延性의 組合이 나쁜 理由는, aluminum-coating에 의해서 生成된 fibre 周邊部의 金屬間化合物이 塑性變形中에 crack 發生源으로 作用하기 때문이다. Two types of aluminum-steel fiber composite were prepared by a casting method; one was fabricated with aluminum-coated steel fiber, and the other the aluminum-uncoated steel fiber. Then the mechanical properties and plastic behaviors of these composites were investigated by Instron machine. The ultimate tensile strength of aluminum-uncoated steel fiber composite increases linearly with increasing fiber content. However, the values of the composite tensile strength do not agree with the theoretical values indicated by the rule of mixture. The aluminum-uncoated steel fiber composite shows a better combination of tensile strength and elongation than the aluminum-coated steel fiber composite, though the bond between fiber and matrix of the former composite is poorer than that of the latter. This is considered to be attributed to the intermetallic compound formed on the surface of the aluminum-coated steel fiber, which is brittle and acts as a crack nucleation source during plastic deformation.
The effects of thermal cycling treatment on mechanical properties and transformation temperatures of Fe-20%Mn alloy were studied. With increasing number of the thermal cycling between room temperature and 260℃, the amount of ε martensite sharply increased up to 3 cycles and showed parabolic increase beyond 3 cycles, but the amount of γ austenite showed exactly the reverse. When the alloy was deformed to fracture at room temperature, the amount of ε martensite decreased but α′ martensite increased gradually with thermal cycling. On the other hand, γ could not be found except ε and α′ martensites in the fractured samples. As the number of thermal cycling increased, the hardness, UTS and YS of the alloy increased, the ε martensite plate became finer, a large number of dislocations were introduced in γ parent phase, and M_s was lowered.
Flake graphite cast irons with the high damping capacity have been used for the control of vibration and noise occurring in the members of various mechanical structures under vibrating conditions. However, the damping capacity which is morphological characteristics of graphite is one of the important factors in reducing the vibration and noise, but hardly any work has deal with this problem. Therefore, the authors have examined the damping capacity of various cast irons with alloying elements and studied the influences of the matrix structures, mechanical properties and morphological characteristics of graphite. The main results obtained are as follows: Effects of Sb on the damping capacities and mechanical properties have been investigated in 3.6%C-0.2%Ni gray cast iron. At 0.02%Sb, specific damping capacity showed the maximum value, and deceased with further increase in Sb content. Mechanical properties showed opposite trend with the damping capacity. And then, effects of Ti on the damping capacities and mechanical properties have been investigated in 3.6%C-0.2%Ni-0.02%Sb gray cast iron. Specific damping capacity increased with increase in Ti content. Graphite length also showed same behavior. Tensile strength increased with Ti content due to refinement of pearlite. In the case of 0.14%Ti addition in 3.6%C-0.2%Ni-0.02Sb cast iron, specific damping capacity and tensile strength was 36% and 25kgf/㎟ which are higher than 32% and 15kgf/㎟ at 3.6%C-0.2%Ni cast iron respectively.
The objective of this study is to investigate the effect of solution-treatment temperature on the microstructure and damping capacity of a martensitic Fe-7%Ni-0.4%C alloy. The size of lath increased from 0.3㎛ to 0.55㎛ with increasing the solution-treatment temperature from 700 to 1100℃. In addition, the size of block, packet, and austenite grain had tendency to increase with increasing solution-treatment temperature. The damping capacity of the Fe-7%Ni-0.4%C martensitic alloy decreased with increasing the solution treatment temperature. The reason is not attributed to the increase in the size of lath, block, packet, and austenite grain, but to the increase in vacancy concentration which hinders dislocation motion.
Dilatometric experiment and thermodynamic calculation have been performed to determine M_s, A_s and driving forces for γ→ε martensitic transformation of Fe-Mn alloys. The transformation temperatures(M_s, A_s, T_o) were decreased with increasing manganese content and were newly formulated as a function of manganese content. Driving force for γ→ε martensitic transformation was increased from -75J/mole to -105J/mole with increasing manganese content from 15wt.% to 25wt.%. Transformation temperature hysteresis(A_s-M_s) was also increased from 50K to 80K with increasing mangenese content from 15wt.% to 25wt.%. The small driving force(-75J/mole-105J/mole) and small ΔT(50K∼80K) for γ→ε martensitic transformation indicated that Fe-Mn alloys behave like thermoelastic martensitic alloys : We would like to call them semi-thermoelastic martensitic alloys.