• Journal of Biosystems Engineering
• /
• v.20 no.3
• /
• pp.226-235
• /
• 1995

An unmanned speed sprayer was developed using a remote control and an inductive cable guidance systems to protect operators and environment from hazardous pesticides. The sprayer consists of a remote control system, an induction system, obstacle detectors, control actuators and an one-chip microcomputer. The sprayer can be operated by the induction guidance and/or remote control. The following summarize characteristics of the developed speed sprayer. 1) Both the remote control and the induction guidance operation were possible with the developed speed sprayer. 2) Sixteen functions of the forwarding, backing, halting, steering, 3-way valve for nozzles and fan operating etc. were utilized on the remote control system. 3) It was concluded that the DTMF method, having less transmitting error, performed better than the FSK method for an agricultural remote controller. A radio station may be necessary. 4) The digital inductive guidance system, consisting of five low-impedance detection coils and a window comparator circuit, performed better than the analog detecting system, guiding route using inductive voltage differential from tow detection coils.

• Earthquakes and Structures
• /
• v.26 no.1
• /
• pp.31-48
• /
• 2024

In order to get a better understanding of seismic performance of exterior beam-column joint, reciprocating loading tests with variable loading speeds or axial forces were carried out. The main findings indicate that only few cracks exist on the surface of the joint core area, while the plastic hinge region at the beam end is seriously damaged. The damage of the specimen is more serious with the increase of the upper limit of variable axial force. The deflection ductility coefficient of specimen decreases to various degrees after the upper limit of variable axial force increases. In addition, the higher the loading speed is, the lower the deflection ductility coefficient of the specimen is. The stiffness of the specimen decreases as the upper limit of variable axial force or the loading speed increase. Compared to the influence of variable axial force, the influence of the loading speed on the stiffness degradation of the specimen is more obvious. The cumulative energy dissipation and the equivalent viscous damping coefficient of specimen decrease with the increase of loading speed. The influence of variable axial force on the energy dissipation of specimen varies under different loading speeds. Based on the truss model, the biaxial stress criterion, the Rankine criterion, the Kent-Scott-Park model, the equivalent theorem of shearing stress, the softened strut-and-tie model, the controlled slip theory and the proposed equations, a calculation method for the shear capacity is proposed with satisfactory prediction results.

• Journal of Bio-Environment Control
• /
• v.16 no.4
• /
• pp.291-296
• /
• 2007

This study was conducted to investigate the effects of horizontal air flow produced by circulation fans on horizontal and vertical profiles of meteorological factors. The three-dimensional distributions of air speed, air temperature, relative humidity and carbon dioxide $(CO_2)$ concentration were measured with and without the fans in operation. The uniformity of the spatial distribution of meteorological factors decreased as the outside air temperature decreased. In "fans off" condition, spatial variations of $4.7^{\circ}C$ in air temperature, 19% in relative humidity were detected. When the fans were operated, these variations were reduced to 2.2 and 6.3%, respectively. As the fan capacity increased, the difference in air temperature among sampling points decreased. The fan capacity of $0.0104m^3{\cdot}s^{-1}{\cdot}m^{-2}$ was enough to obtain a reasonable air flow in greenhouse. The vertical profiles of air temperature and $CO_2$ concentration were reasonably uniform regardless of measurement height and fan capacity. Further researches on the position of fans to reduce the difference in air temperature along the width and the effects of using a larger number of smaller fans are required.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.3
• /
• pp.221-231
• /
• 2021

In the present study, numerical simulation was performed to investigate aerodynamic characteristics of a ducted fan-upper/lower vanes system in hover. Sensitivity analysis of aerodynamic forces for a system component was conducted with the deflection angle of upper vanes varying but at the constant rotational speed and the collective pitch angle of fan blades. Then, vane control performance and duct airload distributions were analyzed in detail to physically understand operating mechanisms of individual vane and interference effect between duct and vanes. Finally, new control concept of operating upper vanes has been proposed to improve the control performance of the full configuration. It is found that the side force and rolling moment of upper vanes increase linearly with the variation of those deflection angle; however, the total side force is significantly small due to the reaction force acted on the duct. It is also found that upper vanes close to the duct contraction side have a key role in changing vane control forces. It is revealed that the duct suction pressure is induced by the interaction with the suction side of upper vanes, while duct pressure recovery by the interaction with the pressure side, leading to increase in duct asymmetric force. When four upper vanes are kept in situ at 0° deflection angle or removed, the total control performance was improved with duct asymmetric force reduced and the total magnitude of roll remarkably increasing up to 80%.

• Journal of agriculture & life science
• /
• v.46 no.2
• /
• pp.101-106
• /
• 2012

Fans have been used to reduce heat stress of Hanwoo in summer, but a criterion to determine to operate or not operate them has not been developed yet. Therefore, this study was carried out to establish a criterion of fan operation to reduce heat stress of Hanwoo in summer. Respiration rate of Hanwoo, air temperature, wind speed and relative humidity were collected from Hanwoo farms in summer, 2010 and these data were used to analyze relationship between respiration rate and air temperature, relationship between respiration rate and wind speed, and relationship between respiration rate and relative humidity and so on. The results of this study that air temperature when is over $23^{\circ}C$ and wind speed is below 0.8 m/s affected the respiration rate of Hanwoo. On the other hand, relative humidity did not affect the respiration rate when is below 60%. The results of this study recommend that fans should be operated to reduce the heat stress of Hanwoo, when only air temperature in farm is over $23^{\circ}C$.

• Journal of Biosystems Engineering
• /
• v.25 no.1
• /
• pp.39-46
• /
• 2000

This work was conducted to study the operating characteristics of a grinding system designed to obtain fine rice husk ash powder. To find better utilizing of rice husk, a valuable by-product from rice production, once the rice husk was incinerated and the thermal energy was recovered from the furnace, the ash was fed and pulverized in the grinding system resulting a fine powder to be used as a supplementary adding material to the portland cement manufacturing . The rice husk ash grinding system consisted of a high speed centrifugal fan for the preliminary coarse milling and a dry-type stirred ball mill for the subsequent fine grinding . Total grinding time 9 5, 15, 30, 45 min), impeller speed (250, 500, 750 rpm) , and mixed ratio (4.8, 7.9, 14.9) were three operating factors examined for the performance of a stirred ball mill used for the fine grinding of ash. With the stirred ball mill used in this study, the minimum attianable mean diameter of rice husk ash powder appeared to be 2 ${\mu}{\textrm}{m}$. During the find grinding, the difference in specific surface area of powder showed an increase and the grinding energy efficiency decreased with the increase in total grinding time, impeller speed ,and mixed ratio. For the operating conditions employed , the resulting mean diameter of fine ash powder, specific energy input, and grinding energy efficiency were in the range of 1.79 --16.04${\mu}{\textrm}{m}$, 0.072-5.226kWh/kg, an d1.11-12.15$m^2$/Wh, respectively. Grinding time of 30 min , impeller speed of 750 rpm, and mixed ratio of 4.8 were chosen as the best operating conditions of the stirred ball mill for fine grinding . At these conditions, mean particle diameter of the fine ash, grinding energy efficiency, grinding throughtput, and specific energy input were 2.73${\mu}{\textrm}{m}$, 3.95$m^2$/Wh, 0.25kg/h, and 1.22kWh/kg, respectively.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.19 no.8
• /
• pp.809-815
• /
• 2009

The previous work(Cheong et al., 2006) where the characteristics of acoustic emissions of wind turbines has been investigated according to the methods of power regulation, has showed that the acoustic power of wind turbine using the stall control for power regulation is more correlated with the wind speed than that using the pitch control. In this paper, basically extending this work, the noise generation characteristics of large modern upwind wind turbines are experimentally indentified according to the power regulation methods. To investigate the noise generation mechanisms, the distribution of noise sources in the rotor plane is measured by using the beam-forming measurement system(B&K 7768, 7752, WA0890) consisting of 48 microphones. The array results for the 660 kW wind turbine show that all noise is produced during the downward movement of the blades. This result show good agreement with the theoretical result using the empirical formula with the parameters: the convective amplification; trailing edge noise directivity; flow-speed dependence. This agreement implies that the trailing edge noise is dominant over the whole frequency range of the noise from the 660 kW wind turbine using the pitch control for power regulation.

• The KSFM Journal of Fluid Machinery
• /
• v.19 no.6
• /
• pp.5-13
• /
• 2016

Three-dimensional unsteady numerical analysis has been performed to observe aerodynamic characteristics of a H-rotor. Generally, the structure of the H-rotor is simple but the aerodynamic characteristics are exceptionably complicated since the angle of attacks and incident velocities to a blade are considerably varied according to the azimuth angles and solidities. The blade in the upwind revolution between 0 to 180 degree obtains aerodynamic energy from the free stream but the blade in the downwind revolution between 180 to 360 degree does not. When the rotating speed increases, the blade in the downwind revolution accelerates the air around the blade like a fan and it consumes the energy and shows negative torque in the area. On the other hand, the direction of the free stream is bent because of the interaction between blade the free stream. Therefore, the operation point (highest power coefficient) appears at a lower tip-speed-ratio what it is expected.

• Journal of Biosystems Engineering
• /
• v.29 no.5 s.106
• /
• pp.433-440
• /
• 2004

Worldwide consumption of vegetable soybean has been increasing recently, but in the process of vegetable soybean production, threshing and separation work accounts fur about $80\%$ of overall labor. Therefore, developing of the vegetable soybean thresher is necessary to reduce the cost of labor. The main objective of this study is to acquire the basic in-formations for design of the vegetable soybean thresher which is suitable for domestic circumstances. We made the experimental system to investigate the threshing and separating performance at the several speeds of threshing cylinder and separating blower according to the kinds of threshing tooth. The result are as follows; Threshing performance of vegetable soybean thresher was shown as the best in case the threshing tooth made of rubber which has the 80 of Shore hardness was used at the circumference speed of cylinder of 5.8$\~$8.1m/s. Also separating cleaning performance of vegetable soybean thresher was shown as the best at more than 1,300 rpm of blower speed and $60\~80\%$ of opening ratio of suction port.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.26 no.4
• /
• pp.351-356
• /
• 2017

The resistance of printed patterns for electrodes fabricated using printing technology should be minimized. This parameter depends on the pattern width and thickness; however, from the viewpoint of printability, the printed patterns should be printed at the designed width. The resistance of the printed patterns as well as printability is affected by various printing conditions. In this paper, the printing condition is optimized to minimize the resistance of electrodes printed by the roll-to-roll gravure method. This is done by considering the spread ratio of pattern width as a parameter of printability using design experiments. The drying temperature, dryer fan speed, and printing speed are selected as effective factors for the experiment objective. The optimized conditions are obtained and reproducibility test using these demonstrates that the optimized conditions can produce low-resistance electrodes for printability of the pattern width.