Young-Rok Yang

An Aerodynamic Shape Optimization Study to Maximize the Range of a Guided Missile

This paper describes a research of a shape optimization study to maximize a range of a guided missile with canards and tailfins. To design a guided missile for the maximum range, a shape optimization system is incorporated with a trajectory analysis and an optimization technique. In the trajectory analysis part, a component build-up method is directly connected to the equation of motion to calculate aerodynamic coefficients at every time step. In the optimization part, real coded adaptive range genetic algorithm was adopted to find out an optimum shape of the global maximum range. The shape optimization system of a guided missile for the maximum range can maximize the range of a guided missile and yield the optimum shape of canards and tailfins. The analysis results confirmed that the optimum shape thus derived extended the range of the base shape by 5.8% for the unguided case and by 21.4% for the guided case.

Effects of Early Heat Conditioning on Performance in Broilers exposed to Heat Stress

Department of Animal Biotechnology, Kangwon National University, Chooncheon 200-701, KoreaABSTRACT Heat manipulation at early age has been known to help chickens cope with heat stress later in life. The present study was conducted to determine the effects of early heat conditioning at 5 days of age on performance in broilers when re-exposed to heat stress later in life. Day-old, 256 Arbor Acre boiler chicks were housed in two identical rooms where all broilers were exposed to a 23-h light: 1-h dark cycle throughout the study and provided with feed and water ad libitum. At the age of 5 days, one group was exposed to 37for 24 hours and then returned to the temperature at which control birds were maintained (early heat condition group) while the other was maintained without heat modulation (Control). On 21 days, broilers were regrouped into 4 groups (CON+CON: control+control; CON+HS: control+heat stress; HC+CON: heat conditioning+control; HC+HS: heat conditioning+heat stress), and given 7 days for adaptation. On 28 days, birds in one room were exposed to heat stress (2131) for 3 days whereas those in the other were at room temperature. Heat stress resulted in decreased feed intake, water intake, and body weight gain (P<0.05), but increased rectal temperature and mortality (P<0.05). No beneficial effects of heat conditioning were detected when broilers were exposed to heat stress again at later in life. The present results were discussed together with other studies regarding possible differences in methods such as ages of breeders and strains, which may have resulted in the failure of heat conditioning to help broilers resist heat stress.(Key Words : broilers, early heat conditioning, heat stress)

Range Sensitivity Analysis of a Canard Controlled Missile

This study describes a range sensitivity of a canard controlled missile. An investigation was conducted into the relative importance of aerodynamic parameters on a guided missile. Also this study was analyzed by quantifying their effects on the missile range. To analyze the range sensitivity of a guided missile, a trajectory analysis program of a guided missile was developed. The range sensitivity analysis was conducted on a thrust, weight, drag and lift. The result of the range sensitivity analysis shows that the design parameters with the greatest effect on the missile range are thrust, drag, weight, and lift, in descending order of importance. The thrust on range extension is quite obvious to extend a range of a guided missile. In particular, the drag exhibited greater range sensitivity than lift at a guided flight. The result also shows that missile range could be maximized by applying the appropriate launch angle and canard pitch-up control.

Aerodynamic Characteristics of a Canard-Controlled Missile with Freely Spinning Tailfins Using a Semi-Empirical Method and a CFD Code

In this study the aerodynamic characteristics of a canard-controlled missile with freely spinning tailfins were investigated by using a semi-empirical method and a CFD code. The mean aerodynamic coefficients for the rolling and roll damping moments were first calculated and then used to predict the roll-rate of freely spinning tailfins. The calculation of roll-rate in the CFD code was carried out by combining a Chimera overset grid system and 6-DOF analysis module. The predicted roll-rate was in good agreement with the experimental data for the roll and yaw canard control inputs. It was also shown that the results are in good agreement with the prediction by a CFD code. This indicates that the semi-empirical method can be used to predict the roll-rate of a canard-controlled missile with freely spinning tailfins. ⌌圀؀㘲〮㔻ጀ䝥湥牡氠䕮杩湥敲楮最

Effects of Repeated High Ambient Temperature on Performance in Broilers Heat-Conditioned at an Early Age

Heat conditioning at an early age has been known to help chickens cope with heat stress later in life. The present study was conducted to determine the effects of heat conditioning at 5 days of age in broilers repeatedly exposed to high ambient temperature later in life. A total of 256 day-old Arbor Acre boiler chicks were housed in two identical rooms with a 23-h light/1-h dark cycle and provided with feed and water ad libitum. At 5 days of age, the birds in one room were exposed to for 24 hours, while those in the other room served as controls. On day 21, half of the birds in each room were moved into the other room so that each room contained both control and heat-conditioned birds. After a 7-day adaptation period, the birds in one room were exposed to high ambient temperature () for 3 days, whereas those in the other room were kept at normal temperature. The same 3-day exposure to high ambient temperature was repeated two weeks later. Hence, there were four treatment groups (CON+CON: control+control; CON+HS: control+high ambient temperature; HC+CON: heat conditioning+control; and HC+HS: heat conditioning+high ambient temperature). Repeated heat stress resulted in decreased feed intake, water intake, body weight gain, and spleen weight (p

COMPUTATIONAL DESIGN OF A FLUTED NOZZLE FOR ACHIEVING TARGET AERODYNAMIC PERFORMANCE

As a preliminary design study to achieve target aerodynamic performance, this work was conducted on an original nozzle with 9 flutes in order to design a fluted nozzle with 12 flutes. The thrust and rolling moment of the nozzle with 12 flutes were analyzed using a CFD code according to the depth and rotation angle of the flutes. Based on this, a fluted nozzle with 12 flutes was optimized to yield the same thrust as that of the original nozzle with 9 flutes. The response surface method was applied for shape optimization of the fluted nozzle and design variables were selected to determine the depth angle and rotation angle of the flutes. An optimized shape that led to a thrust as strong as that of the original nozzle was obtained.