合金工具鋼의 最適熱處理

黃慶周,李在鉉,郭士濩 조선대학교 생산기술연구소 1993 生産技術硏究 Vol.15 No.2

This paper aims to find out the optimum heat-treatment condition for alloy tool steels (STS3). The influence of heat-treating temperature and time on the impact resisntance and hardness best suitable for the STS3 alloy tool steel was investigated. Tempering heat-treatment following oil quenching at 830℃ to 65℃ was carried out at each temperature 100, 200, 400, and 600℃ for 1, 3, 5, and 10 hrs, The values of impact resistance and hardness were measured by Charpy impact tester and Vickers hardness tester. The results obtained are summarized as follows : 1) Both impact resistance value, 1.6㎏ - m/㎠ and hardness,830 Hv best suitable for this alloy tool steel were obtained at 200℃ for 1 hour-tempering. 2) The value of impact resistance increases as tempering temperature rises from l00℃ to 600℃. 3) Hardness reveals the highest value at 100℃, but tempering temperature abruptly decreases above around 400℃ and up to 600℃. That's because the longer and higher temperature permitted the development of larger and fewer coalescent carbides.

주축 런아웃이 절삭흔과 표면거칠기에 미치는 영향에 관한 연구

황영국,이춘만,임경진,하재용,신성우 한국공작기계학회 2006 한국공작기계학회 추계학술대회논문집 Vol.2006 No.-

The radial error motion of a machine tool cutter/spindle system is critical to the dimensional accuracy of the parts to be machined. This paper presents an investigation into spindle run-out effects on cutting mark and surface roughness. We experimented the effects of spindle run-out on surface roughness in flat-end milling by cutting AL 7075 workpiece in various cutting conditions. In order to analyze the effects of run-out on the surface roughness, the spindle's radial error motions was measured by mounting a sphere target onto the spindle as a reference. From the experimental results, it was found that spindle run-out makes a directive effects on surface roughness in flat-end milling.

불소이온에 따른 치과용 티타늄의 표면조도에 관한 연구

황경란,김철위 대한치과기재학회 1996 대한치과재료학회지 Vol.23 No.2

Titanium has a number of advantages, such as light weight, adequate strength, good corrosion resitance, excellent biocompatibility and reasonable price. Therefore, the wrought forms of titanium metals have been widely utilized in the dental field, including orthodontic wire and endosseous dental implants. Titanium exhibits exellent resistance to to most corrosive agents, but its passivated oxide layer is susceptible to halogens - especially fluorine and fluoride compounds. Prophylactic fluids and gels containing fluorides cause corrosion and surface alterations of titanium implant or prostheses. This study described the effects of fluoride ion on surface roughness of titanium. Five kinds of metals such as 2 kinds of commercially pure titanium, titanium-alumium-vanadium alloy, nickel-titanium and cobalt-chromium-molybdenum alloy were used. Alloys were embedded in cold-curing acrylic resin and polished with silicone carbide paper from # 800 to # 1,200. Specimens were cleaned with ethanol before further treatment. The surface roughness were measured for 0,1,5,10,20,40 minuite storage in sodium fluoride gel (1.23%, 0.62%, 0.41% fluoride ion) after rinsing with distilled water using surface roughness tester (Surtronic 3P, Rank Tayler Hobson, England). From the experiment, the following results were obtained: 1. The surface roughness of commercially pure titanium increased with fluoride concentration and storage time (p<0.01). 2. The surface roughness of titanium-allumium-vanadium alloy increased with fluoride concentration in 1.23% and 0.62% (p<0.01) and strage time but there was no significant difference with storage time in 0.41% fluoride ion (p>0.01). 3. In case of nickel-titanium alloy there was no significant difference in surface roughness depending on used fluoride concentration and storage time(p>0.01). 4. In case of cobalt-chromium- molybdenum alloy there was no significant difference in surface roughness in all experimental conditions(p>0.01).

新品種 밀 "早光"의 沓裏作 播種期 및 播種量에 관한 硏究

黃鍾奎,崔京求,陳星桂 全北大學校 1979 論文集 Vol.21 No.-

This experiment was carried out under different seeding dates(October 10, Oct. 20 or November 10) and seeding rates (20, 30, 35 ℓ 10a) from 1976 to 1977 in Iri in order to study the suitable seeding date and seeding rate for Jokwang, the newly developed wheat variety, in double cropping paddy field. 1. Number of days to seedling emergence both on Oct. 20 and Oct. 30 were 14 days, but that of Nov. 10 was prolonged due to comparatively low temperature and about 37 days. 2. The heading date and the maturing date seemed to be shortened by 1 or 2 days in accordance with the earlier seeding date and the larger amount of seeding. 3. Number of panicles per square meter seeded on Oct. 20 was 506 which marked the most among the three seeding dates. 30ℓ 10a plot showed the most in panicle number among three seeding rates. 4. Number of grains per panicles was increased by 1 or 2 grains with hastened seeding date, but it was decreased by 2 or 3 grains with the increase in seeding rate. 5. The weight of 1,000 grains of the plots both seeded on Oct. 20 and Oct. 30 was about 38.0 g. and that of Nov. 10 was 35.0g. On the other hand, there were almost negligible differences in 1,000 grains weight between seeding rates at the same seeding date. 6. The yield of the plot seeded on Oct. 20 was 359 ㎏ 10a which marked the highest among the three seeding dates. Among seeding rates, 30 ℓ/10a plot showed the highest yield of 351 ㎏ 10a. However, the highest yield among all treatments, seeding dates and seeding rates, was 382 ㎏ 10a which was obtained from the plot seeded on Oct. 20 with the seeding rate of 30 ℓ/10a. 7. Therefore, it was considered that the suitable seeding date for Jokwang, the newly developed wheat variety, in double cropping paddy field in Iri area was Oct. 20 and its seeding rate was 30ℓ/10a.

유전알고리즘을 이용한 모델추종형 퍼지제어기 설계

황기현,문경준,김문수,원태현 동의공업대학 1998 論文集 Vol.24 No.1

In this paper, a reference model following control system using a fuzzy logic controller (FLC) is proposed. A reference model whose response does not overshoot and has a fast rise time is designed. A FLC is designed to follow as close as possible the response of the reference model. The proposed design method has the robustness and the optimal tracking property under modeling error, disturbance and parameter perturbations. The proposed designing method is compared using a PD controller throughout the experiment. The effectiveness of the proposed designing method is verified through computer simulation and experiments for the second-order and the first-order reference model.

水稻品種間의 近綠度에 關한 硏究

黃鍾圭,金鎭淇,崔京求 全北大學校 1976 論文集 Vol.18 No.-

This investigation was aimed to clarify the mutual relationship between 54 major rice varieties bred in Korea or introduced from Japan. The coefficient of relationship was computed by Sakai's method and the results are as follows; 1. The 54 major varieties are origined from 28 ancestor varieties composing of 23 varieties from Japan, three from China, one from Philippine and one from Indonesia. Out of ancestors Aikoku and Asahi, both from Japan, are most closely related to the major varieties. 2. The lately bred varieties have much more ancestors than the earlier ones. For example, newly bred varieties Mangyeong and Akibare both have 12 ancestors, while earlier bred variety, Pungog has only one ancestor. 3. The 54 major varieties are related to each other by 90 percent of the total 1431 combinations, out of which 70 percentage have the coefficient of relationship from 0.0001 to 0.3.

광에너지 총량에 따른 광중합 콤포짓트레진과 콤포머의 중합도에 관한 연구

황경란,이용근,임범순,김철위 대한치과기재학회 2000 대한치과재료학회지 Vol.27 No.4

Dental composite resin is filler added, particle reinforced composite material, and the usage range had been enlarged in the posterior restoration through improvement of physical properties. Recently, resin modified glassionomer and compomer are used for various purposes. The degree of polymerization of cross-liked polymer has great importance in determining the mechanical properties and clinical availability of materials. Residual carbon-carbon double bonds have been implicated in causing reduced wear resistance, strength and color stability. The degree of polymerization is an important factor for longevity of a restoration. However the higher the degree of polymerization in resin composites, the higher the shrinkage will result. It has been elucidated that the degree of polymerization was significantly affected by the intensity of the curing light, wavelength of light and irradiation time. In this experiment, 16 kinds of restorative materials such as five kinds of universal composite resin, five kinds of condensable composite resin, two kinds of flowable composite resin, and four kinds of compomer were used. This study examined the effect of light intensity and irradiation time on the polymerization behavior such as the heat release during polymerization and the rate of polymerization by DSC (differential scanning calorimeter), and the degree of double bond conversion by FT-IR. With DSC, the irradiation modes were three different light intensity of 300, 400, 600 ㎽/㎠ and for 40 seconds. With FT-IR, the levels of irradiation energy were 1,500, 40,000, 8,000, 16,000 and 24,000 mJ/㎠ by combining the light intensity of 300, 400, 600 ㎽/㎠ and irradiation time of 5, 10, 20 and 40 seconds. From this experiment, The following results were obtained : 1.In the DSC result, heat of polymerization of composite resin was 23.22∼55.17J/gram and exothermic energy of compomer was 26.50∼52.68 J/gram 2.At the isothermal condition of 27℃, there were exothermal peaks at 40.812∼44.724 seconds from the start of irradiation. The percentage of polymerization by released heat was 19.12∼49.44% after 18 seconds, 37.23∼82.07% after 36 seconds, and 93.57∼98.53% after 54 seconds from the start of irradiation. 3.From FT-IR, the degree of polymerization of composite resin was 17.17∼60.91% and that of compomer was 7.74∼40.82%, and the degree of final conversion was influenced by the kinds of restorative materials and the irradiation energy(p<0.01). 4.As the irradiation energy was increased from 1,500 mJ/㎠ to 16,000 mJ/㎠, the degree of conversion was increased also. However, the degree of final conversion was no significant differences with the irradiation energy of 24,000 mJ/㎠ and 16,000 mJ/㎠(p>0.05). The wavenumber of absorbance peak of aromatic double bond was similar regardless of the restorative materials, and appeared around 1606.67∼1610.67 cm-1. The absorbance peak of aliphatic double bond appeared around 1636.64∼1638.52 cm-1 from FT-IR.

【영아보육프로그램】자료 개발 연구

황해익,임재택,김정신,송연숙,이경화,김남희 부산대학교 영유아보육연구소 1998 영유아보육연구 Vol.4 No.-

This study aimed to develop Materials for (The Infant Educare Program) (Dept. of Health & Welfare, 1996). Infant educare Materials were developed through following procedures: 1) analysis of reference and other educare materials 2) content analysis of (The Infant Educare Program) 3) developing materials and 4)testing and revising materials by professionals. Infant educare Materials that developed in this study were constituted of 12 kinds in 5 areas - Materials for management of daycare center, the nursery stories for infants, musical materials for infants, play things for infants, and educational materials for parents. First, materials for management of daycare center were considered various conditions whithin daycare centers and were compased of 2 kinds - diary for educare plan and diskettes for documents. Second, the nursery stories for infants were compased of materials for 3 stages-the weaning stage, the toddling stage, and the independent stage. Similarly, musical materials for infants were composed of 3 stages. And play things for infants were composed of 2 kinds - play things to be easily founded and easily making play things. Finally, educational materials for parents were composed of 2 kinds - guide book for parents education and diskettes for communication with parents. It is needed that persistent attention from professionals in developing and testing materials for infant educare. Also, further educational implications were discussed

Jacobi 반복법을 이용한 합성 근사 구조재해석

황진하,김경일 충북대학교 건설기술연구소 2002 建設技術論文集 Vol.21 No.1

A design-oriented structural reanalysis method is presented in this paper. The new combined approximation method is based on combining the computed terms of Jacobi iteration and coefficients of a reduced basis method. Some examples are demonstrated to show the validity and efficiency of the present study. Satisfactory results compared to the exact method show that the proposed method is worth being incorporated into the design procedures of the large structural systems. This method can improves the total efficiency when they are appropriately used according to the design informations for the redesign process of large scale structures. The numerical results for some trusses show the validity and usability of the method.

복지권으로서 교육권 보장을 위한 『장애인 등에 대한 특수교육법』

황정보,이선재,안병주,강경희,김청아 국립특수교육원 2007 특수교육연구 Vol.14 No.2

결핍에서 오는 필요의 개념은 장애인에게 복지권으로서 교육받을 권리를 가장 잘 말해주고 있다. 장애인은 신체적·인지적 손상으로 발생하는 기본적인 생존적 필요의 충족뿐만 아니라 동시에 교육기회 균등이나 개인차의 고려 등을 통해 무지로부터 벗어날 수 있는 보편적 필요가 충족되어야 함을 논의하였다. 장애인들에게 이러한 결핍에 따른 필요를 충족시켜 줄 이론적 근거가 롤즈(J. Rawls)의 정의론이라 할 수 있다. 정의론의 '차등의 원칙'에 따르면, 교육에 있어 비장애인과 장애인 중 먼저 최소 수혜자인 장애인의 교육복지를 우선하여 극대화할 필요성을 제시함으로써, 그들의 교육권 보장을 위한 이론적 근거에 대한 정당화를 논의하였다. 기존의 특수교육진흥법은 '국가가 교육할 권리'를 가지는 국가 주도적 교육이었다면, 「장애인 등에 대한 특수교육법」 제정은 수년간 장애인의 교육권 확보를 위해 애쓴 장애인 교육 주체들이 노력 끝에 '교육받을 권리'를 찾게 된 의미 있는 결실로 평가되어 진다. The concept of need which comes from lack represents well the right to education as welfare rights to individuals with disabilities. It is necessary to meet the universal need of individuals with disabilities such as an equal opportunity for education and the consideration for individual difference as well as their substantial need. The rationale which may satisfy the need associated with the lack can be J. Rawls's a Theory of Justice. The difference principle by Rawls presents the need of the educational welfare of individuals with disabilities(the least advantaged) to take precedence over that of the non-disabled and be maximized, it is considered that he created the rationale that makes secure their right to education. While established Special Education Promotion Law was national-driven education that state had to the education right, the enactment of 'the Special Education Law for the Individuals with Disabilities, etc.' can be a significant fruit which takes back 'the right to education by citizens' by the educational subjects of the individuals with disability who have taken pains to secure their right to education for years.