Al-Mg-Si合金의 時效擧動에 미치는 加工熱處理의 影響

趙顯麒,李基大,朴定國 慶北大學校 1980 論文集 Vol.30 No.-

Effects of Thermo-Mechanical Treatment(TMT) on ageing behaviours in Al-Mg-Si alloy is investigated by means of tensile test, hardness measurements and transmission electron microscopy. The maximum 0.2% proof stress of the TMT materials in final ageing is higher by 10%∼20% than that of the two-step aged materials. The strength of TMT materials also increases more rapidly than that of two-step aged materials. The maximum 0.2% proof stress of the TMT materials with pre-ageing is higher than that of the TMT materials without pre-ageing. The strength of TMT materials increases with rising pre-ageing temperature, and it decreases with rising final-ageing temperature. Consequently, this type of TMT would have some practical significance in improving the mechanical properties of 6061 alloy.

일방향 응고시킨 Al-Fe 2원 공정합금의 응고조직과 기계적성질에 미치는 Zr 첨가의영향

趙顯麒,林相元 慶北大學校 1989 論文集 Vol.47 No.-

Effects of Zr addition on structure and mechanical properties in unidirectionally solidifed Al-Fe eutectic alloy have been carried out by means of scanning electron micrography and the measurement of hardness and tensile strength. Especially, effects of Zr addition on ageing behaviours and precipitate distributions have been also conducted by the observation of transmission electron microscope. At first, by the addition of Zr, the eutectic fibre produced were very fine but, as the growth rate increase, the mechanical properties were somewhat deteriorated at room temperature by misalignment of fibre due to constitutional supersooling. On the other hand, Al_3Zr phases were precipitated in interface of matrix/fibre by the ageing at 365℃ for 50 hrs and these phase contributed to increase the mechanical properties remarkablely from RT to 500℃. This results deduced that the shear slip in interface was suppressed by Al_sZr precipitates which mitigated the difference of heat expansion coefficient between matrix and fibre.

6063 押出材의 T_5處理에 관하여

趙顯麒,鄭潾相 慶北大學校 1974 論文集 Vol.18 No.-

The effective heat treatment of 6063 extruded alloys has been investigated by means of microhardness test, tensile strength test and examination of microstructure. The results are summarized as follows: (1) The ideal range of T_5 heat treatment is 8∼12 hrs. at 160∼180℃ for 6063 extruded alloys. (2) The effective range of T_5 heat treatment for improving the productability is that 1∼2hrs at about 200℃ after primary heat treatment for 1 hr. at 160∼170℃. We had to devote much of our attention to the planning of the T_5 heat treatment furnace; for example, the ideal arrangement of. heat source, the consideration of heat radiation and convection, etc.

연쇄상구균을 실험감염시킨 넙치치어의 병리조직학적 관찰

조성환,류시윤,김현수,박배근,김덕환,손화영,윤원기,신창호 충남대학교 수의과대학 동물의과학연구소 1999 動物醫科學硏究誌 Vol.7 No.-

Pathological observations were examined after abdominal inoculation in 7∼8㎝ sized flounder (Paralichthys olivaceus) with 1X10^7 cfu/㎖ of Streptococcus faecalis. The infected flounder were clinically observed and weighed a fish body at 0, 5, 10, 15, 20, 25, 30 days post inoculation. In infected group, mortality were 70% and feed efficiency were 7.2%. In non-infected group, mortality were 10% and feed efficiency were 18.2%. Macroscopically, the significant lesions were characterized by protrusions and opacity of the eyes and ulcer of the caudal pecuncle. Histopathologically, the lesions were observed a degeneration. necrosis and inflammatory cells in muscle of the caudal peduncle and a degeneration and necrosis of the rod cells and detached retina from the black pigmented layer

돼지생식기호흡기 증후군(PRRS) 바이러스 감염시킨 돼지 기관의 병리학적 관찰

조성환,김현수,윤원기,전무형,류시윤,박배근,손화영,김무강 충남대학교 수의과대학 동물의과학연구소 1996 動物醫科學硏究誌 Vol.4 No.-

The porcine reproductive and respiratory syndrome virus was inoculated into swine tracheal organ culture. The ballooning degeneration of the tracheal ciliated epithelium and a decrease of ciliary activity from the tracheal organs infected with PRRS virus were observed one day post-infection(PI). Tracheal epithelium showed degeneration and focal necrosis 2 days PI. Epithelial necrosis and loss of cilia and epithelial cells became more severe 3 and 4 days PI. An entire loss of cilia and epithelial cells were recognized 4 days PI, however, control tracheal organs were normal during the period of the experiment except a little decrease of ciliary activities with time..

一方向凝固시킨 Al-Cu-Mg共晶合金의 機械的 性質에 미치는 時效의 影響

趙顯驥,康晃鎭,趙美子 慶北大學校 1982 論文集 Vol.33 No.-

The microstructure and mechanical properties of unidirectionally solidified Al-Cu-Mg eutectic alloys have been studied in as-grown and aged condition. After unidirectionally solidification, specimens of solution treated and quenched eutectic were at 180°, 230°, 260℃ in a salt bath for various time. The results obtained are as follows; 1) Precipitation on hardening of the ductile phase is a feasible mechanism for strengthening of composites. 2) Mechanical Testing of the tenary eutectic has shown that composite is strengthened about 30 to 50% by ageing. 3) Tensile and compression strength of this composites are 25 and 70kg/㎟ by ageing treatment in growth 0.1mm/min. 4) The unidirectionally solidified structure are changed by ageing. It seems that the low Cu and Mg solute atoms are likely due to epitaxial precipitation onto CuAl_2 lamellar respectively.

4종 전자근관장측정기의 정확성과 일관성에 관한 in vitro 연구

조재현,금기연,이승종 대한치과보존학회 2006 Restorative Dentistry & Endodontics Vol.31 No.5

이번 연구는 서로 다른 4개의 전자근관장측정기의 정확성을 측정하고 각각 0.5지점과 Apex지점에서의 일관성을 비교하고자 하였다. 40개의 발치된 상하악 소구치를 대상으로 치수강 개방 후 alginate model에 고정시키고 근관장을 측정하였다. 사용된 전자근관장측정기는 Root ZX (Morita, Tokyo, Japan), SmarPex (META, Seoul, Korea), Elements Diagnostic Unit (SybronEndo, CA, USA), E-Magic Finder Deluxe (S-Denti, Seoul, Korea)이다. 먼저 모든 치아에서 4개의 전자근관장측정기를 사용하여 0.5지점과 Apex지점에서 근관장을 측정하여 한 치아당 8개의 측정값을 얻었다. 다음으로 치아를 각 전자근관장측정기당 10개씩 4개의 그룹으로 나누어, 각각 제조사의 지시대로 Root ZX, Elements Diagnostic Unit 및 E-Magic Finder Deluxe는 "0.5"지점에서, SmarPex는 ''Apex" 지점에서 file을 치아에 cement로 고정시켰다. 이후 치근단부 4 mm를 삭제하여 100배율의 Image ProPlus로 관찰하여 file 끝에서 주근단공의 외연까지의 실제거리를 측정한 후, 4개의 전자근관장측정기의 0.5지점 및 Apex지점에서 file 끝과 주근단공 사이의 거리를 계산하여 비교하였다. 그 결과 Root ZX와 E-Magic Finder는 실험군 100%, SmarPex는 90%, Elements Diagnostic Unit는 70%에서 주근단공과의 거리가 임상적 허용범위인 土0.5 mm 이내에 있었다. 또한 각 전자근관장측정기마다 0.5지점과 Apex지점에서의 근관장의 표준편차와 사분위 범위를 구하여 두 지점간의 일관성을 비교한 결과, Root ZX, E-Magic Finder는 0.5지점과 Apex지점에서 비슷한 일관성을 보였으며 SmarPex와 Elements Diagnostic unit는 Apex지점에서 0.5지점보다 더 높은 일관성을 보였다. 전자근관장측정기는 근관 내의 조건에 관계없이 근첨협착부에서 항상 일정한 거리를 재현해 낼 수 있는 일관성이 중요하므로, 이렇게 0.5지점 또는 Apex지점에서의 일관성이 증명된다면 실제 임상에서 사용할 때 전자근관장에서 일정한 거리를 가감하여 사용할 수 있다. The purpose of this study was to evaluate the accuracy and the consistency of four different electronic apex locators in an in vitro model. Fourty extracted premolars were used for the study. Four electronic apex locators (EAL) were Root ZX, SmarPex, Elements Diagnostic Unit (EDU), and E-Magic Finder Deluxe (EMF). After access preparation, the teeth were embedded in an alginate model and the length measurements were carried out at "0.5" and "Apex" mark using four EALs. The file was cemented at the location of the manufacturers' instruction (Root ZX, EDU, EMF: 0.5 mark, SmarPex: Apex mark). The apical 4mm of the apex was exposed and the distance from the file tip to the major foramen was measured by Image ProPlus (× 100). The distance from the file tip to the major foramen was calculated at 0.5 and Apex mark and the consistency of 0.5 and Apex mark was compared by SD and Quartile of Box plots. In this study, Root ZX and EMF located the apical constriction accurately within ± 0.5 mm in 100%, whereas SmarPex and EDU located in 90% and in 70% respectively. For Root ZX and EMF, there was no significant difference between the consistency of 0.5 and Apex mark. However, for the EDU and SmarPex, Apex mark was more consistent than 0.5 mark. From the evaluation of the consistency in this study, for Root ZX and EMF, both 0.5 and Apex mark can be used as a standard mark. And for EDU and SmarPex, the Apex mark can be recommended to be used as a standard mark.

다중 제어루프에 의한 자기부상용 DC-DC 전원장치에 관한 연구

조주현,조정민,전기영,이상집,이승환,오봉환,이훈구,한경희 明知大學校 産業技術硏究所 2004 産業技術硏究所論文集 Vol.23 No.-

The author present a modified multi-loop algorithm including feedforward for controlling a 55kW step down chopper in the power supply of Maglev. The control law for the duty cycle consists of three terms. The first is the feedforward term which compensates for variations in the input voltage. The second term consists of the difference between the slowly moving inductor current and output current. The third term consists of proportional and integral terms involving the perturbation in the output voltage. This perturvation is derived by subtracting the desired output voltage from the actual output voltage. The proportional and integral action stabilizes the system and minimizes output voltage error. In order to verify the validity of the proposed multi-loop controller, simulation study was tried using Matlab simulink.

Cu-Al-Ni 합금에 있어서 시효에 따른 감쇠능의 변화

조현기,박철규 경북대학교 산업기술연구소 1987 産業技術硏究誌 Vol.14 No.-

The effects of ageing on specific damping capacity in Cu-Al-Ni alloy were carried out by the torsional pendulum testing method with the computer system. The critical range of the reverse martensitic transformation was checked by measuring adiabatic scanning calorimeter and the microstructure was observed by the optical microscope. The extent of specific damping capacity in the region of the reverse martensitic transformation increases with the amount of matrix and martensitic interface. The peak of specific damping capacity appears when the amount of martensites becomes 50% The peak of specific damping capacity decreases according to ageing due to the stabilization of martensites and the decreasing rate of specific damping capacity increases. Specific damping capacity depends on the strain amplitude and non-elastic additional strain is hysteresis type. The high level of specific damping capacity found in Cu-Al-Ni alloy is most likely to due to the reversible movement of interfacial and twin boundaries on exposure to alternating stresses.

Al-Cu-Mg合金의 時效析出에 미치는 豫備時效의 影響

趙顯麒,洪俊杓,全在英 경북대학교 공과대학 1983 工大硏究誌 Vol.12 No.-

The influences of preageing on age-precipitation in Al-2.02t% Cu-1.1wt% Mg alloy have been investigated by means of measurements of hardness, tensile strength and electrical resistivity and transmission electron microscopy. The results obtained are summarized as follows. The two-step aged alloy is more age-hardenable than the onestep aged alloy in early stage of ageing. It is because of the formation and growth of solute atom cluster and GPB zones. The maximum hardness and strength of the alloy aged 200℃ is obtained by preaged at 100℃. It is because of fine and dense distribution of S'metastable phase. The hardness and strength are remarkably decreased with sufficient ageing time after preageing at room temperature and 170℃. It is because of the formation and coarsening of S'metastable phase by the preageing.