Prediction of Grain Structure of Thin Bronze Slab Produced by Horizontal Continuous Casting

Yong‑You Kim,Hee‑Soo Kim 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.2

The grain structure of a thin bronze slab produced by horizontal continuous casting was investigated using heat-transfercalculation and cellular automaton (CA). The composition of the bronze was Cu–22wt%Sn, which has been widely used inKorean history. The solid form of Cu–22wt%Sn was assumed as a single phase for simplicity. To simulate the macrostructureof the alloy, the heat transfer in the horizontal continuous casting was calculated as a steady-state one-dimensional lumpedsystem. The CA was used for simulating the grain structure. Since the temperature profile was in the steady state, the cellinformation was shifted along the casting direction at a rate of one cell per time step during the simulation. The grainswere nucleated at the slab surface and grown as columnar grains. The effects of the process parameters, such as initial melttemperature and casting speed, on the grain structure of the slab were investigated. It was found that the casting speed is acritical factor determining the angle between the columnar grains and the casting direction.

부산시 용호동 정책이주단지 주거공간의 내·외부 변용 특성에 관한 연구

김용운(Kim, Yong-Woon),유재우(You, Jae-Woo) 대한건축학회 2014 대한건축학회 학술발표대회 논문집 Vol.34 No.2

측두하악관절 내장증 환자의 자기공명영상에서 관절 원판의 전방 이동에 관한 연구

유하식,문창수,조병욱,이열,이용찬,이한욱 大韓顎顔面成形再建外科學會 1993 Maxillofacial Plastic Reconstructive Surgery Vol.15 No.3

Tempormandibular Joint pain and dysfunction is a common and important clinical problem. With the recent advances in imaging technology, radiologists have made major contribution to the understanding of TMJ disease. The MRI has several advantages over the conventional imaging methods. It is possible to obtain surprisingly precise images of internal hard and soft tissues with MRI. It is not invasive without ionizing radiation. The abnormal disk position has been thought as the cause of TMJ internal derangement. But there are few methods to relate disk position to TMJ internal derangement quantatively. The object of our study is to determine the amount of anterior displacement fo articular disk in symptomatic patients related each symptoms. Using the method of Dr. Drace, we studied the 38 joints of 22 persons with susceptable TMJ internal derangement. 1. In determining the anterior displacement of TMJ articular disk, the junction between the posterior band and bilaminar zone was useful. 2. The mean anterior displacement of disk in reduction group and without reduction gouop were 51.0 and 81.1 respectively. The difference was significant. 3. In the mean anterior displacement of disk, the pain without clicking group showed 84.8 and the clicking and pain group 70.8, the clicking group respectively.

운동전·후 淸暑益氣湯 투여방법이 2,000m 달리기시 선수들의 운동피로회복에 미치는 영향

유종만,이규성,강명신,오재근,최용어 韓國體育大學校附屬 體育科學硏究所 1994 韓國體育大學校附屬 體育科學硏究所論文集 Vol.13 No.1

The purpose of this study was to investigate the effects of two different chung-seo-ik-gi-tang administration types on fatigue induced during 2,000 m running in 12 healthy-male elite boxer. All subjects were divided randomly with two groups, Pre-administration Group(A: N=7) and Pre- and Post-administration Group(B: N=7) and performed 2,000 m maximal running. The blood samples were collected from antecubital vein by 10ml syranges(6ml/each) at before exercise, immediately after exhaustion, recover-10 min, recover-20 min and recover-30 min. These samples were used to analyze for the level of glucose, lactate, TG, LDH, pH, HCO₃?, Na??, K??. The statistically analyzed results of various blood parameters were summarized as follow, 1. Plasma glucose were not showed significant difference between two groups. but glucose lwvel at post-exercise and rest-30 min in B group wes significantly decreased. 2. Lactate accumulation in B group was significantly decreased at post-exercise and rest-30 min.. And lactate level at rest-30 min. was showed significant difference between two gruops. 3. Serum LDH response to 2,000 m running at post-exercise and recovary periods was showed significant changes in B group. 4. Venous pH at post-exercise, HCO₃? at post-exercise and rest-30 min. in A group and pH at post-exercise and rest-10, 20 min., HCO₃? at post-exercise were showed significant changes. But there were not showed significant difference between two groups. 5. K?? level in B group was showed significant difference compared to A group. And also K?? level at rest-30 min. in B group was showed significant change. The results indicated that Chung-seo-ik-pi-tang had the effects of ergogenic aids on fatigue and recovery during 2,000 m maximal running.

건강한 한국인에서의 배변 조영술 소견

나용호,장명규,김태현,김형언,유광현,진경민 大韓消化器病學會 1995 大韓消化器病學會誌 Vol.27 No.3

SCM 435 구조용강의 플라즈마 질화에 관한 연구

유용주,김인수,이재식 울산대학교 1996 공학연구논문집 Vol.27 No.2

본 연구는 SCM 435 구조용강을 450∼650℃의 온도범위에서 NH₃가스유량을 0.5∼2.1 l/min로 변화시키고, 20∼110분 동안 플라즈마 질화처리하여 강 표면에 생성된 경화층의 두께와 경도 및 조직을 조사하였다. 반응온도 550℃, NH₃1.65 l/min.에서 110분 동안 질화 하였을 경우 생성된 질화층의 두께는 260㎛으로써, 화합물층은 16㎛ 이며, 확산층은 224㎛로 이것이 최대의 질화층이었다. 한편, 반응온도 600℃, NH₃1.65 l/min. 가스유량에서 50분간 반응하였을때 24㎛의 최대 화합물층을 얻을 수 있었다. 또한 화합물층은 450℃와 500℃에서는 r'- Fe₄N-α-Fe로, 550℃에서는 r'-Fe₄N+ε- Fe₃N으로, 600℃이상에서는 r-Fe₄N+α-Fe로 구성되어있는 혼합상이었다. 550℃,NH₃1.65 l/min. 에서 80분 동안 질화처리하였을때 생성된 질화층의 최대 표면경도는 Hv 988이었다. The plasma nitriding of SCM 435 structural steel has been studied at the temperature between 450℃ and 650℃ with gas flow rate of NH₃ 0.5 to 2.1 l/min. for 20 to 110 minutes. The phases of compound layer formed below 500℃ and above 600℃ was mixture of r'-Fe₄N and ε- Fe₂₄N phases, while the phases formed 550 was r' - FeN and - Fe N phases. The hardness of nitrided layer formed at 550℃ with gas flow rate of NH₃ 1.65 l/min. for 80minutes was Hv 988. The thickness of nitrided layer formed at 550℃ with gas flow rate of NH 1.65 l/min. for 110minutes was 260㎛. The nitriede layer was composed of 16㎛ compound layer and 244㎛ diffusion layer.

建設技能 人力 確保 및 育成方案에 關한 基礎的 硏究

유영식,김을용 大田産業大學校 1996 한밭대학교 논문집 Vol.13 No.0201

Seeking the elevation of constructional skill standards, to cope with the construction market opening and domestic business upturn elastically, Shall materialize an all-out management plan of cultivation constructional technical manpower and expert manpower to expedite using the manpower cultivated.

EMF 측정법에 의한 Cu-Co-O System의 열역학적 연구

유용주,이재식 울산대학교 1990 연구논문집 Vol.21 No.1

고체 전해질인 (ZrO₂+ CaO)를 사용하여 구성된 다음과 같은 galvanic cell들을 이용한 EMF를 측정함으로써, Cu₂O, CuO, CoO의 Cu₂CoO₃생성에 대한 자유에너지 값을 얻었으며, Cell(1) Ni, NiO/ZrO₂(+CaO)/Cu, Cu₂O Cell(2) Ni, NiO/ZrO₂(+CaO)/CuO, Cu₂O Cell(3) Co, CoO/ZrO₂(+CaO)/Ni, NiO Cell(4) Co, CoO/ZrO₂(+CaO)/Cu, Cu₂O Cell(5) Cu, Cu₂O, CoO/ZrO₂(+CaO)/Cu,Cu₂O Cell(6) Cu₂O, CoO, Cu₂CoO₃/ZrO₂(+CaO)/Cu, Cu₂O Cell(7) CuO, Cu₂O, Cu₂CoO₃/ZrO₂(+CaO)/Cu, Cu₂O 그 결과들은 아래와 같다. △ G˚??, Cu₂O=-40548+17.494 T cal/mole(970-1258K) △ G˚??, CuO=-36062+20.084 T cal/mole(1162-1332K) △ G˚??, CoO=-56680+17.394 T cal/mole(1126-1326K) 그리고 2 CuO+CoO=Cu₂CoO₃반응에 대한 △G˚=-1618+0.9838 T cal/mole(1162-1332K)이며, 계산된 Cu₂CoO₃의 생성에 대한 자유에너지 값은 △G˚, Cu₂CoO₃=-130423+58.542T cal/mole이다. 그리고 Cu₂CoO₃에 대한 Cu₂O와 CuO의 용해도는 매우 작았다. The equilibrium oxygen pressures of the binary and threephase regions [Cu-O], [Co-O], [Cu, Cu₂O, CoO], [Cu₂O, CoO, Cu₂CoO₃] and [CuO, Cu₂O, Cu₂CoO₃]were measured as a function of temperature by the solid oxide electrolyte (ZrO₂+ CaO) electromotive force method. The galvanic cells used were as follow: Cell(1) Ni, NiO/ZrO₂(+CaO)/Cu, Cu₂O Cell(2) Ni, NiO/ZrO₂(+CaO)/CuO, Cu₂O Cell(3) Co, CoO/ZrO₂(+CaO)/Ni, NiO Cell(4) Co, CoO/ZrO₂(+CaO)/Cu, Cu₂O Cell(5) Cu, Cu₂O, CoO/ZrO₂(+CaO)/Cu, Cu₂O Cell(6) Cu₂O, CoO, Cu₂CoO₃/ZrO₂(+CaO)/Cu, Cu₂O Cell(7) CuO, Cu₂O, Cu₂CoO₃/ZrO₂(+CaO)/Cu, Cu₂O The results were expressed by the following equations: G˚??, Cu₂O=-40548+17.494 T cal/mole(970-1258K) G˚??, CuO=-36062+20.084 T cal/mole(1162-1332K) G˚??, CoO=-56680+17.394 T cal/mole(1126-1326K) The measured Gibbs energy of the reaction 2 CuO+CoO=Cu₂CoO₃was found to be -1618+0.9838 T cal/mole(1162-1332K). The evaluated Gibbs energy of formation of △G˚, Cu₂CoO was found to be -130423+58.542T cal/mole. The solubility of Cu₂CoO₃in Cu₂O or CuO is very small.

연속파형 Nd:YAG 레이저를 이용한 SM45C 용접특성

유영태,노경보,오용석 朝鮮大學校 機械技術硏究所 2002 機械技術硏究 Vol.5 No.2

The Nd:YAG laser in combination with the optical fiber increase the automation and the flexibility of a whole industry. The Nd:YAG laser welding process in one of the most advanced manufacturing technologies owing to its high speed and penetration. This paper describes the weldability of SM45C carbon steel for machine structural use by Nd:YAG laser. Major process parameters were position of focus, travel speed and laser power. The results showed that peneration depth of the weld was increased with increasing applied laser power. Microstructural examinations and calculations and indicated that the microstructure of the laser weld, which experienced very high heating and cooling cycle during welding process. The results of this study provide application possibility of Nd:YAG laser welding for SM45C carbon steel

소목(Caesalpinia sappan) 추출물의 Streptococcus mutans에 대한 성장, 산생성, 부착 및 비수용성 글루칸 합성 억제에 미치는 영향

유용욱,유현희,김윤정,유미선,서세정,이황,이흥수 대한구강보건학회 2003 大韓口腔保健學會誌 Vol.27 No.2

Streptococcus mutans is known as the causative bacterial playing the most important role in forming plaque and it is being noticed as major causative bacteria of dental caries. Therefore, development of more effective, substantial and safe preventive agent against dental caries and periodontal disease is honestly required. The present study was designed to investigate the effect of chloroform extract(CE), n-butanol extract(BE),methanol extract(ME) and water extract(WE) of Caesalpinia on the growth, acid production, adhesion, and insoluble glucan synthesis of Streptococcus mutans. The CE, BE, ME and WE decreased the growth and acid production of S.mutans than that of control, especially, the ME was more effective than other extracts. The effect of CE, BE, ME and WE on the adherences to saliva-coated hydroxyapatite bead(S-HA) were evaluated. At the concentration of 2,000 ㎍/㎖, the CE showed 32% rate of bacterial adherence to S-HA, whereas, other extracts of the same concentration producedgreater than 50% rate. The CE and BE were significantly decreased the reduction rates of water insoluble glucan formation from sucrose by crude glucosyltransferase of S.mutans. Thus, the application of C. sappan can be considered a useful and a practical method for the prevention of dental caries.