• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.1118-1120
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• 1997

This paper presents a simple method for evaluating of voltage stability using the line flow equation. Line flow equations ($P_{ij}$, $Q_{ij}$) are comprised of state variable, $V_i$, ${\delta}_i$, $V_j$ and ${\delta}_j$, and line parameter, r and x. Using the feature of polar coordinate, these becomes one equation with two variables, $V_i$ and $V_j$. Moreover, if bus j is slack or generater bus, which is specified voltage magnitude, it becomes one equation with one variable $V_i$, that is, may be formulated with the second-order equation for $V_i^2$. Therefore, multiple load flow solutions may be obtained with simple computation, and the formulated equation used for approximately evaluating of voltage stability limit considering line flow sensitivity. The proposed method was validated to 2-bus and IEEE 6-bus system.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.4
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• pp.219-225
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• 2003

Recently, electric power demands tend to be increased continuously. In this situation, current states of power systems must be definitely recognized to operate power systems stably and economically. Also, corrective actions must be performed for the violation of bus voltage and line overload. It is desirable that the situations of violation are promptly removed to operate power systems effectively. This paper deals with the development of guidance system for voltage and overload correction on base case using Generator-Voltage Sensitivity List(GVSL) and Generator Shifter Factor List(GSFL). Also, to show the superiority and economical efficiency of the proposed application, we applied the proposed guidance system to the Kwangyang Steel Works' Power Systems.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.251-254
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• 2003

A voltage stability assessment consists of the contingency screening, voltage stability analysis, and counter measures. A widely used index for the voltage stability assessment of power system is the reactive power margin. It shows some factors of voluntariness as following the status of power system and load levels for the target analyzing area. Therefore, it has a demerit that the absolute amounts of reactive power margin is not to be applied by the quantized margin criterion. This paper selects a vulnerable area by assigning the voltage instability for the particular contingency for the selection of vulnerable area in the respect of the investigation of reactive power margin or VQVI as an index of V-Q margin sensitivity in order to overcome the demerit. This will be able to grasp the V-Q margin sensitivity for the target analyzing area by presenting the ratio of power margin between the margin before and after contingency as following the calculation of reactive power margin. The presented method is applied to the voltage stability assessment for the Metropolitan area of 2003 KEPCO summer peak system.

• The Journal of the Korea Contents Association
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• v.19 no.4
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• pp.368-380
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• 2019

This study proposes a method to evaluate the performance of a detector by analyzing the dynamic step wedge and histogram according to the change of the tube voltage and sensitivity when using the Automatic Exposure Control (AEC). The performance of a detector was evaluated by measuring X-ray quality, Entrance Surface Dose (ESD), tube current, dynamic range corresponding to detector sensitivities of S200, S400, S800, S1000 per tube voltage of 60, 70, 81, 90 kVp. As a results, all of the qualities satisfied the acceptance criteria, and the Entrance Surface Dose and tube current were decreased stage by stage as sensitivity was set higher. In the dynamic step wedge, the observable dynamic range has also increased as tube voltage became higher. The histogram showed the quantization separation phenomena as the tube voltage was set higher. The higher the sensitivity, the more the underflow and overflow occurred in which the amount of information on both ends of the histogram was lost. In conclusion, the deterioration in the performance of the detector was found to be insufficient to realize the change of the tube voltage and sensitivity when using the Automatic Exposure Control, and it is useful to use dynamic step wedge and histogram in evaluating detector performance evaluation.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.6
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• pp.115-120
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• 2008

There are many typesof accelerometer sensor. There was mainly used high-g accelerometer to obtain data for vehicle in crash test. Accelerometer was mounted on test vehicle with mounting blocks. Test result can be influenced by condition of mounting i.e. bonding material and type of block. These influences can be evaluated to variation of sensitivity in calibration test. In this paper, Calibration test were carried out for 3 types of bonding material i.e. stud, beewax and double side tape. Other factor was taken into consideration by 3-types for mounting block. All test was conducted by sinusoidal signal vibrator up to 4500Hz. In order to investigate influence for sensitivity from different input voltage in the calibrator, the same test was repeated. Test results were compared with standard accelerometer data. Relative sensitivities and phases were showed small difference in sensitivity for bonding materials with one block, but significant one for another block and different input voltage below 1000Hz.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1431-1433
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• 1995

This paper describes the characteristics of Si Hall sensors fabricated on a SOI(Si-on-insulator} structure, in which the SOI structure was forrmed by SDB(Si-wafer direct bonding) technology. The Hall voltage and the sensitivity of implemented Si Hall devices show good linearity with respect to the applied magnetic flux density and supplied current. The product sensitivity of the SDB SOI Hall device is average $600V/A{\cdot}T$. In the temperature range of 25 to $300^{\circ}C$, the shifts of TCO(Temperature Coefficient of the Offset Voltage) and TCS(Temperature Coefficient of the product Sensitivity) are less than ${\pm}6.7{\times}10^{-3}/^{\circ}C$ and ${\pm}8.2{\times}10^{-4}/^{\circ}C$, respectively. From these results, Si Hall sensors using the SOI structure presented here are very suitable for high-temperature operation.

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.2
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• pp.180-185
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• 2017

In this research, we proposed the simple and efficient method to calculate the shear stresses by using the mid-point measurements in ${\pm}45^{\circ}$ semiconductor resistor-sensor pair. Compared to the previous works, the measurements became much simpler by combining the approximation theory with the technique of mid-point measurement. In addition, we proposed another novel method for the stress calculation in which we could increase the sensitivity of the stress sensor by controlling the applied voltage between the sensor-pair. For the applied voltage of 8 V, the sensitivity showed a significant increase by 100%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05b
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• pp.27-30
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• 2002

Photoconductor for direct detection flat-panel imager present a great materials challenge, since their requirements include high X -ray absorption, ionization and charge collection, low leakage current and large area deposition. Selenium is practical material. But it needs high thickness and high voltage in selenium for high ionization rate. We report comparative studies of detector sensitivity. One is an a-Se with $70{\mu}m$ thickness on glass. The other has hybrid layer of depositting ZnS phosphor with $100{\mu}m$ on a-Se. The leakage current of hybrid is similar to it of a-Se, but photocurrent is lager than a-Se. Both of them have high spatial resolution, but hybrid has higher sensitivity than a-Se at comparable bias voltage.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.12
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• pp.1870-1877
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• 1990

The electromagnetic properties of P- and n-channel split drain magnetic sensitive MOSFET fabricated using 2\ulcorner design rules and CMOS process technology has been investigated. The achieved output voltage in the double drain MOSFET was 160mV at 10\ulcorner drain current and magnetic flux density of 10kG, and the sensitivity was 1.6x10**3 V/A\ulcornerG. A further higher sensitivity was obtained by introducing a third drain in the split region. In this case, the triple drain MOSFET showed a much higher sensitivity of 2x10**3 V/A\ulcornerG under the same condition. Also, the linearity of output voltage vs. magnetic flux density was excellent.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.190-193
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• 2001

This paper presents a linear programming based Optimal Reactive Power Dispatch (ORPD) problem using modified sensitivity method. The proposed model minimizes the real power losses and improves the voltage profiles in the system with consideration of voltage and reactive power constraints. The method employs modified sensitivity relationships of power systems to establish both the objective function for minimizing the system losses and the system performance sensitivities relating dependent and control variables. The proposed algorithm has been evaluated with the IEEE 6-bus and IEEE 30-bus systems.