• Proceedings of the KIEE Conference
• /
• 2004.07c
• /
• pp.2090-2092
• /
• 2004

In this paper, the new measurement methodology of characteristics of the vibratory micro gyroscope using Quality factor and the resonant displacement was proposed. Because the Quality factor has a large error under the high Quality factor condition, it is difficult to analyze the characteristics of the vacuum packaged vibratory micro gyroscopes with the Quality factor. We analyzed mechanical characteristics of gyroscope with the value of Quality factor. We described measurement errors of mechanical characteristics of micro gyroscopes. The measured value of Quality factor is 47532 and error range of Quality factor is from -29.8 % to 73.9 %. The value of resonant displacement is 3.4${\mu}m$ and the measurement error is 2.9 %. From the result of Quality factor degradation and resonant displacement degradation, 1698 days and 1503 days were estimated as Time To Failure (TTF), respectively. The range of estimation error of Quality factor degradation and resonant displacement degradation is calculated from 1246 days to 1832 days and from 1456 days to 1537 days, respectively. We can analyze the characteristics of the vibratory gyroscope using the quality factor when the Quality factor is smaller than 10,000. Also we can analyze that using the resonant displacement when the Quality factor is larger than 10,000.

• Tribology and Lubricants
• /
• v.26 no.1
• /
• pp.7-13
• /
• 2010

This experimental study presents tribological characteristics under boundary lubrication contacts associated with electrorheolocal (ER) fluid. ER fluid is prepared by using phosphorated starch particles and silicone oil. Experimental apparatus of tribological tester is designed and constructed to evaluate tribological characteristics of pin specimens. Wear tests under boundary lubrication of ER fluid are experimentally performed under consideration of several operational factors such as normal load, sliding distance, sliding speed and specimen materials: steel, copper and aluminum. After wear test, microscopic surface changes of the worn pin specimens are analyzed in order to investigate measured wear characteristics by using the scanning electron microscope (SEM) as well as surface profilometer. In addition, the chemical wear characteristics are investigated by using energy dispersive x-ray spectroscopy (EDS). Moreover, friction coefficient measurements under different materials of pin specimens are conducted for the tribological investigations. In order to verify the effect of starch phosphate particles in ER fluid, the wear test results with ER fluid are compared with test results with only silicone oil. The results clearly present that the phosphorated starch based ER fluid shows the stabilized wear as well as friction characteristics after run-in operations, but the wear rate under ER fluid is increased.

• Progress in Superconductivity and Cryogenics
• /
• v.23 no.4
• /
• pp.61-69
• /
• 2021

This paper presents the analysis and experiment results on the electrical and thermal characteristics of metal insulation (MI) REBCO racetrack coil, which was wound with stainless steel (SS) tape between turn-to-turn layers, under rotating magnetic field and conduction cooling system. Although the field windings of superconducting rotating machine are designed to operate on a direct current, they may be subjected to external magnetic field due to the unsynchronized armature windings during electrical or mechanical load fluctuations. The field windings show the voltage and magnetic field fluctuations and the critical current reduction when they are exposed to an external magnetic field. Moreover, the cryogenic cooling conditions are also identified as the factors that affect the electrical and thermal characteristics of the HTS coil because the characteristic resistance changes according to the cryogenic cooling conditions. Therefore, it is necessary to investigate the effect of external magnetic field on the electrical and thermal characteristics of MI-SS racetrack coil for further development reliable HTS field windings of superconducting rotating machine. First, the major components of the experiment test (i.e., HTS racetrack coil construction, armature winding of 75 kW class induction motor, and conduction cooling system) were fabricated and assembled. Then, the MI racetrack coil was performed under liquid nitrogen bath and conduction cooling conditions to estimate the key parameters (i.e., critical current, time constant, and characteristic resistance) for the test coil in the steady state operation. Further, the test coil was charged to the target value under conduction cooling of 35 K then exposed to the rotating magnetic field, which was generated by three phrase armature windings of 75 kW class induction motor, to investigate the electrical and thermal characteristics during the transient state.

• Journal of Environmental Health Sciences
• /
• v.46 no.6
• /
• pp.726-734
• /
• 2020

Objectives: The aim of this study was to analyze and classify the characteristics of potential damage from hazardous chemical accidents in 229 administrative units in South Korea by reflecting the social and environmental characteristics of areas where chemical accidents can occur. Methods: A number of indicators were selected through preceding studies. Factor analysis was performed on selected indicators to derive factors, and cluster analysis was performed based on the factor scores. Results: As a result of the cluster analysis, 229 administrative units were divided into three clusters, and it was confirmed that each cluster had its own characteristics. Conclusions: The first cluster, "areas at risk of accident occurrence and spread of damage" was a type with a high potential for accident damage and a high density of hazardous facilities. The second cluster, "Urban infrastructure damage hazard areas" appeared to be a cluster with high urban development characteristics. Finally, the third cluster 'Urban and environmental damage hazard areas' appeared to be a cluster with an excellent natural environment. This study went further from the qualitative discussion related to existing chemical accidents to identify and respond to accident damage by reflecting the social and environmental characteristics of the region. Distinct from the previous studies related to the causes of accidents and the response system, it is meaningful to conduct empirical research focusing on the affected areas by analyzing the possibility of accident damage in reflection of the social and environmental characteristics of the community.

• ETRI Journal
• /
• v.27 no.5
• /
• pp.563-568
• /
• 2005

A motion-control chip contains major functions that are necessary to control the position of each motor, such as generating velocity command profiles, reading motor positions, producing control signals, driving several types of servo amplifiers, and interfacing host processors. Existing motion-control chips can only generate velocity profiles of fixed characteristics, typically linear and s-shape smooth symmetric curves. But velocity profiles of these two characteristics are not optimal for all tasks in industrial robots and automation systems. Velocity profiles of other characteristics are preferred for some tasks. This paper proposes a motion-control chip to generate velocity profiles of desired acceleration and deceleration characteristics. The proposed motion-control chip is implemented with a field-programmable gate array by using the Very High-Speed Integrated Circuit Hardware Description Language and Handel-C. Experiments using velocity profiles of four different characteristics will be performed.

• International Journal of Aeronautical and Space Sciences
• /
• v.14 no.1
• /
• pp.19-29
• /
• 2013

This paper deals with the study of buckling, vibration, and parametric instability characteristics in a damaged cross-ply and angle-ply laminated plate like beam under in-plane harmonic loading, using the finite element approach. Damage is modelled using an anisotropic damage formulation, based on the concept of reduction in stiffness. The effect of damage on free vibration and buckling characteristics of a thin plate like beam has been studied. It has been observed that damage shows a strong orthogonality and in general deteriorates the static and dynamic characteristics. For the harmonic type of loading, analysis was carried out on a thin plate like beam by solving the governing differential equation which is of Mathieu-Hill type, using the method of multiple scales (MMS). The effects of damage and its location on dynamic stability characteristics have been presented. The results indicate that, compared to the undamaged plate like beam, heavily damaged beams show steeper deviations in simple and combination resonance characteristics.

• Journal of Advanced Marine Engineering and Technology
• /
• v.25 no.3
• /
• pp.573-580
• /
• 2001

When investigating optimum design of the evaporator in the refrigeration and heat pump systems, there is still lack of data for the dynamic characteristics of the evaporator, This is due to the fact that the static characteristics in the evaporator are absolutely difficult to measure and are burdened with uncertainties. In this study, the simulation works for static characteristics in the evaporator of small air conditioner are carried out to obtain the data of dynamic characteristics. In the simulation, the test evaporator is divided by two-phase evaporating region and single-phase heating region. The major parameters are refrigerant flow rate, heat transfer coefficient of air, air velocity and air temperature. The results show that the calculation method for tube length is an easy-to-use to model analysis of static characteristics and to determine state of refrigerant in the evaporator. The effects of the four parameters on the length of evaporating completed point and heat flow rate to the evaporator are clarified.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.19 no.5
• /
• pp.491-498
• /
• 2009

This paper deals with structural analysis and vibration characteristics of scaffolding structures with a hoist according to payloads. In order to analyze the vibrational and structural characteristics for 20-step scaffolding structure, structural and vibrational characteristics for 2-step scaffolding structure were compared with some experimental results. The numerical results for natural frequencies of scaffolding structures have a good agreement with experimental ones. Through the numerical analysis, firstly, it is shown that the maximum stress of scaffolding structures is lower than von-mises yield criteria when four persons with total weight of 280 kgf are working at the top of the scaffolding structures. Secondly, vibration characteristics including natural frequencies and modes for scaffolding structures are shown in case of various kinds of moving masses.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.117-120
• /
• 2007

The floor slabs of building structures are often subjected to the periodic force which is induced by vibrating machines or human activity(walking, jumping, running etc). These periodic forces cause excessive oscillation. In order to examine the dynamic characteristics of floor slabs, the dynamic characteristics test is accomplished. Generally, the Impact Hammer and Dynamic Exciter test is used to dynamic characteristics test. But the Impact Hammer test is not suitable to apply in building slabs. In this paper, It compared the performance of the Exciter and Impact Hammer test for dynamic characteristics analysis of floor slabs.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.543-548
• /
• 2006

This paper presents the vibration characteristics of scaffolding structures with a hoist according to payloads. In order to analyze the vibrational and structural characteristics for 20-step scaffolding structure, structural and vibrational characteristics for 2-step scaffolding structure were compared with some experimental results. The numerical results for natural frequencies of scaffolding structures have a good agreement with experimental ones. Through the numerical analysis, firstly, it is shown that the maximum stress of scaffolding structures is lower than von-mises yield criteria when four persons with total weight of 280kgf are working at the top of the scaffolding structures. Secondly vibration characteristics including natural frequencies and modes for scaffolding structures are shown in case of various kinds of moving masses.