• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.382-386
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• 2002

The tapping is machining process that makes a female screw on the parts to be assembly together. It is used for the high-speed tapping machine with synchronizing function for the high productivity. This paper describes the development of the ultra high-speed tapping machine with 10,000rpm. The key factors in the tapping speed are the acceleration/deceleration velocity and the synchronizing errors between the spindle motor and feeding motor. To minimizing acceleration/deceleration time, the low inertia spindle with synchronous built-in servo motor is developed. To minimizing synchronizing errors, the tapping cycle algorithm under open architecture CNC environment is optimized. The developed tapping machine has 0.13sec/10,000rpm in acceleration/deceleration time and the synchronizing error below 4.0%. It has 0.55sec for cycle time of one female screw, M3 tap, 2 times depth of tap diameter.

• Proceedings of the KSRS Conference
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• 1999.11a
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• pp.135-139
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• 1999

Wind velocity is one of the primary variables for describing atmospheric state from GMS-5. And its accurate depiction is essential for operational weather forecasting and for initialization of NWP(Numerical Weather Prediction) models. The aim of this research is to incorporate imagery from other available spectral channels and examine the error characteristics of winds derived from these images. Multi spectral imagery from GMS-5 was used for this purpose and applied to Korean region with together BoM(Bureau of Meteorology). The derivation of wind velocity estimates from low and high resolution visible, split window infrared, and water vapor images, resulted in improvements in the amount and quality of wind data available for forecasting.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.6
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• pp.773-787
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• 2003

There are variations in the temperature Held due to urban heat island and anthropogenic heating so that regional scale meteorological field is changed. Therefore we simulate and predict the regional climate change according to surface characteristics through regional meteorological model. This study investigates the regional meteorological field by urbanization that influences in local circulation system using CSU-RAMS and simulates dry deposition velocity (V$_{d}$) using PNU/DEM which includes surface characteristics (such as albedo, surface hydrology and rough-ness length etc.) with calculated meteorological field. During the summer, horizontal distributions of V$_{d}$ were simulated using CSU-RAMS and PNU/DEM at Busan metropolitan area. The estimated values of V$_{d}$ were larger in forest and agricultural areas than water areas since ozone with low water solubility is destroyed slowly at wet surface or water.water.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.12
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• pp.897-901
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• 2010

A silencer has been widely used for the purpose of suppressing the noises propagated from duct of air conditioning system. The absorption type silencer is usually applied to reduce the noise with high frequency bandwidth. On the order hand, the resonance type silencer is applied to reduce the noise with low-middle frequency bandwidth. The insertion loss of silencer is measured in the reverberation room. The cut-off frequency of reverberation room is 100 Hz. The insertion loss of absorption type silencer is more larger than that for resonance type silencer regardless of changing the flow velocity.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.312-316
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• 2004

In this study, a spatial 3-dof haptic mechanism is implemented. The implemented mechanism does not employ the gear transmissions as velocity reducers for all three joints but uses wire-based transmissions, thereby it is able to minimize the frictions significantly. Also, by employing the structure of the four-bar mechanism to drive third joint from close to the base, the mechanism is able to minimize the inertia effect from the third actuator very effectively. Its kinematic analysis such as position and velocity analyses are performed first. Then, its operating software development, hardware implementation, and the related interfaces between a PC and the implemented Haptic device are completed. To evaluate its potential and its performance as a haptic device, a experiment generating a virtual constraint in a operational task space is conducted and preliminary results are discussed.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.245-250
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• 2001

Ultrasonic pulse velocity(UPV) is a useful tool for examining the property of early-age mortar or concrete. Thus, UPV has been used for a long time to characterize setting and hardening of cementitious materials. In this study, in order to investigate the characteristics of setting for mortar, UPV was measured using automatic monitoring system up to 3 days after casting. Test results show that UPV of high water to binder ratio(w/b) mortar remained constant at the beginning of hydration and then abruptly began to increase. However, UPV of low w/b mortar gradually increase due to setting retard caused by use of superplasticizer. Furthermore, the development of UPV for mortar with fly ash is slower than that of mortar without fly ash. It was concluded that the property change of mortar or concrete, such as setting and hardening can be assessed by monitoring of UPV.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.176-178
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• 2003

This paper presents a new velocity estimation strategy of a non-salient permanent magnet synchronous motor(PMSM) drive without high frequency signal injection or special PWM pattern. This approach is based on the d-axis current regulator output voltage of the drive system which has the information of rotor position error. The rotor velocity can be estimated through a rotor position tracking PI controller that controls the position error to aero. For zero and low speed operation, the PI gains of rotor position tracking controller have a variable structure. The PI tuning formulas are derived by analyzing this control system using the frequency domain specifications such as phase margin and bandwidth assignment.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.76-78
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• 1994

Owing to the discover of oxide superconducting over critical temperature100K, it is being made experimentally somewhere under the possibility that there is superconducting magnet by cooling liquid nitrogen. The issues of thermal stability and quench process of Low-Tc superconductor has been studied and used application of oxide superconducting magnets. However the quench propagation property of oxide superconductor, especially experimental data about thermal behavior has not been reported yet. Therefore we measured the effect of temperature dependance of quench propagation velocity, Vq, by using the short samples made up of silver sheathed Bismuth-family (2223phase) superconducting oxide tape.

• Journal of the Korean Society of Safety
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• v.9 no.3
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• pp.60-66
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• 1994

The purpose of this study is to compare the combustability of the formed high density polyethylene (HDPE) with the low density polyethlyene(LDPE). That is, the easiness of ignition is examined by using the methods with Oxygen Index(OI) Tester and ventilation parameter, and the combustion velocity of these polyethylenes is measured by changing the size and shape of opening area. As the result of it, the oxygen index of HDPE, in a ignition, is required more than LDPE. Then, the concentration distribution of CO by combustion is increased when the opening area is small, but, in the same opening area, LDPE tends to increase more than HDPE. In addition, as the ratio of height to width of opening area is increased, combustion velocity becomes faster relatively. In consequence, when it is generally considered, the combustability of LDPE is better than HDPE.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.4
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• pp.75-81
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• 1997

This study was performed to evaluate the engineering properties of surlightweight polymer concrete using synthetic lightweight aggregate. The following conclusions were drawn; 1. The unit weight was in the range of 0.849~0.969t/$m^3$, the unit weights of those concrete were decreased by 58 ~ 63% than that of the normal cement concrete. 2. The highest strength was achieved by $P_1$, and compressive strength was increased by 93% and bending strength by 364% than that of the normal cement concrete, respectively. 3. The ultrasonic pulse velocity was in the range of 2, 346~2, 702m/s, which was low compared to that of the normal cement concrete. 4. The dynamic modulus of elasticity was in the range of $1.561{\times} 10{^5}~1.916{\times} 10{^5}kgf/cm^2$, which was approximately 52~98% of that of the normal cement concrete. 5. The compressive and bending strength were increased with the increase of unit weight. But, the dynamic modulus of elasticity and ultrasonic pulse velocity were decreased with the increase of unit weight.