• 산업공학
• /
• 제13권2호
• /
• pp.157-165
• /
• 2000

In this paper, an efficient method is proposed to place the cooling lines(CLS) and ejector pins(EPS) of mold design. The other components of mold, except CLS and EPS, can be generated automatically by batch processing. But the placements and sizes of CLS and EPS depend on the shapes of a part, so that the design works of CLS and EPS should be processed interactively. Using the pre-defined reference points, the positions of CLS and EPS can be determined interactively. By the proposed method, the interference occurred during placing CLS and EPS can be avoided, and the proper lengths of them can be calculated automatically. The information of the positions and lengths are stored in BOM database for generating a machining data. The proposed method is implemented with Unigraphics API functions and C language, tested on Unigraphics V15.

• 열처리공학회지
• /
• 제32권1호
• /
• pp.17-28
• /
• 2019

Jominy hardenability curves of low alloy steel containing less than 5 wt.% of alloying elements in total were calculated by applying Scheil's rule of additivity to pre-calculated isothermal transformation curve. Isothermal transformation curve for each phase in steel was approximated as a simple mathematical equation by using Kirkaldy's approach and all coefficients in the equation were estimated from experimental temperature-time-transformation (TTT) and/or continuous cooling transformation (CCT) data in the literature. Then jominy test with simple boundary conditions was performed in computer by applying the finite difference scheme. The resultant cooling curves at each location along a longitudinal direction of Jominy bar were applied to calculate phase fractions as well as mechanical properties such as micro Vickers hardness. The simulated results were compared with experimental CCT data and Jominy curves in the literature.

• 한국축산식품학회지
• /
• 제33권3호
• /
• pp.390-394
• /
• 2013

The aim of this study was to determine the optimal storage condition of pre-packed Hanwoo beef without freezing. Hanwoo loin was purchased from a local distributor at 48 h after slaughter, then sliced in $1.5{\pm}0.5$ cm thickness, and packed in a polyethylene (PE) tray covered with linear low-density polyethylene (LLDPE) film. The studied factors to set the optimal storage condition were chamber temperature (5, 2.5 and $-1^{\circ}C$ for 14 d), cooling method (direct and indirect cooling system), and ultraviolet (UV) light irradiation for beef surface sterilization (0, 30, 60, and 120 min). The changes of pH, thiobarbituric acid reactive substances (TBARS) and number of aerobic bacteria were measured during storage. Beef samples stored in $-1^{\circ}C$ showed the minimal increasing rate in TBARS and microbial growth. After 15 d of storage, there was no significant difference in pH and TBARS values. However, the microbial population of beef stored in direct type cooling chamber ($4.25{\pm}0.66$ Log CFU/g) was significantly lower than that of beef stored in indirect type chamber ($6.47{\pm}0.08$ Log CFU/g) (p<0.05). After 4 d of storage, 60 or 120 min UV light irradiated beef samples showed significantly lower microbial population, and at 14 d of storage, 60 min UV irradiated beef sample showed significantly lower microbial population ($3.14{\pm}0.43$ Log CFU/g) than control ($4.46{\pm}0.13$ Log CFU/g) (p<0.05). However, TBARS values of 60 or 120 min UV light irradiated beef samples were significantly higher than non-irradiated beef sample after 4 d of storage (p<0.05).

• Asian-Australasian Journal of Animal Sciences
• /
• 제23권3호
• /
• pp.355-365
• /
• 2010

The aim of this study was to investigate the effect of supplemental recombinant bovine somatotropin (rbST) and cooling with misters and fans on renal function in relation to regulation of body fluids in different stages of lactation in crossbred Holstein cattle. Ten, 87.5% crossbred Holstein cattle were divided into two groups of 5 animals each, housing in a normal shaded barn (NS) and in a shaded barn with a mister-fans cooling system (MF). The experiment in each group was divided into 3 phases, early- (Day 75 postpartum), mid- (Day 135 postpartum), and late stage of lactation (Day 195 postpartum). The pre-treatment study was conducted on the starting day of each stage of lactation and the treatment study was performed after the end of the pre-treatment, during which the animal was injected with 500 mg of rbST (POSILAC) every 14 days for three times. During the study, ambient temperature at the hottest period daily in the MF barn was significantly lower, while relative humidity was higher than that of the NS barn. The temperature humidity index (THI) in both barns ranged from 79-85 throughout the periods of study. Cows in the MF barn showed a lower rectal temperature and respiration rate as compared with cows in the NS barn. The effect of rbST administration increased both rectal temperature and respiration rates of cows housed in either the NS or MF barn. Milk yield significantly increased in cows treated with rbST in all stages of lactation. Increases in mammary blood flow, accompanied by increases of total body water (TBW), extracellular fluid (ECF), blood volume (BV) and plasma volume (PV), were observed in both groups of cows receiving rbST in all stages of lactation. No alterations of renal blood flow and glomerular filtration rate were observed in cows receiving rbST, but decreases in urinary excretion and fractional excretion of sodium, potassium and chloride ions appeared to correlate with reduction in the rate of urine flow and osmolar clearance during rbST administration. These results suggest that the effect of rbST supplementation to cows housed either in NS or MF barns on body fluid volume expansion is attributable to changes in the rate of electrolyte excretion by the kidney. The increased availability of renal tubular reabsorption of sodium, potassium and chloride ions during rbST treatment was a major factor in retaining body water through its colligative properties in exerting formation of an osmotic force mechanism.

• Journal of Advanced Marine Engineering and Technology
• /
• 제24권1호
• /
• pp.41-48
• /
• 2000

The characteristics of a combined cycle for the production of fresh water and air-conditioning was analyzed. The combined cycle consisted of an open water cycle and a $CO_2$ refrigeration cycle interlinked in the pre-heater of the water cycle, which is the condenser of the refrigeration cycle. The oprating conditions and criteria for the fresh water production and air-conditioning was described and their effects on the total system were evaluated. The results indicated an increase of desalinated water with the increase of hot water temperature, which resulted in the decrease of cooling capacity of the refrigeration system in this study. However, the energy saving correspond to the pre-heating of the water cycle by the condensing of the refrigeration system shows the avilable advantage of the proposed cycle as compared to other single purpose plants for desalination.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집A
• /
• pp.91-96
• /
• 2000

Glass fiber reinforced thermoplastic composites were manufactured by Rapid Press Consolidation Technique(RPCT) as functions of temperature, pressure and time in pre-heating, consolidation and solidification sections during the manufacturing processing. It was found that the material property is greatly affected by pre-heating temperature under vacuum, mold temperature and molding pressure. Among them, the temperature In the mold was the most critical factor in determining the mechanical properties and the molded conditions of specimen. The crystallinity of PET matrix was also investigated by differential scanning calorimetry(DSC) measurements for various processing conditions. The level of crystallinity($X_c$) depended strongly on the mold temperature, cooling rate and the type of composite. The difference in $X_c$ is believed to be one of important factors in characterizing the mechanical properties.

• 한국안전학회지
• /
• 제18권4호
• /
• pp.39-43
• /
• 2003

An experimental study was conducted to develop and understanding of fracture behavior of ceramic thermal barrier coating when subjected to a thermal shock loading. The thermal loading was applied using a 1.5kW $CO_2$ laser. In the experiments, beam-shaped specimens were subjected to a high heat flux for 4sec and cooling of 7sec in air. The interface crack length was increased as the crack density, the surface pre-crack legth and the coating thickness were increased. The center surface crack length was increased as the maximum surface temperature got higher and the surface pre-crack length for shorter.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.280-281
• /
• 2006

Powder grades pre-alloyed with 1.5-3 wt% chromium can be successfully sintered at the conventional temperature $1120^{\circ}C$ although well-monitored sintering atmospheres are required to avoid oxidation. Mechanical properties of the Cr-alloyed PM grades are enhanced by a higher sintering temperature in the range $1120-1250^{\circ}C$, due to positive effects from pore rounding, increased density and more effective oxide reduction. Astaloy CrM (Fe-3 wt% Cr-0.5 wt% Mo) with 0.6 wt% graphite added obtains an ultimate tensile strength of 1470 MPa and an impact strength of 31 J at density $7.1\;g/cm^3$, after sintering at $1250^{\circ}C$ followed by cooling at $2.5^{\circ}C/s$ and tempering.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.138-139
• /
• 2006

Sintered steels are materials characterized by residual porosity, whose dimension and morphology strongly affect the fatigue crack growth behaviour of the material. Prismatic specimens were pressed at $7.0\;g/cm^3$ from Astaloy CrM powder and sintered varying the sintering temperature and the cooling rate. Optical observations allowed to evaluate the dimensions and the morphology of the porosity and the microstructural characteristics. Fatigue tests were performed to investigate the threshold zone and to calculate the Paris law. Moreover $K_{Ic}$ tests were performed to complete the investigation. Both on fatigue and $K_{Ic}$ samples a fractographic analysis was carried out to investigate the crack path and the fracture surface features. The results show that the Paris law crack growth exponent is around 6.0 for $1120^{\circ}C$ sintered and around 4.7 for $1250^{\circ}C$ sintered materials. The same dependence to process parameters is not found for $K_{Ith}$.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2006년도 추계학술대회 논문집
• /
• pp.193-194
• /
• 2006