• Progress in Medical Physics
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• v.7 no.1
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• pp.53-64
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• 1996

Purpose: The purposes of this paper are to develop a theoretical basis that the beam directions should be considered when the mechanical accuracy of teletherapy machine is evaluated by the star pattern test, to develop methods using asymmetric field in length to simulate beam direction for the case that beam direction does not appear on film. Method: In evaluating mechanical rotational accuracy of the gantry of teletherapy unit by the star pattern test, the direction of radiation beams was considered. A star pattern using some narrow beams was made. Density profiles at 10cm far from estimated gantry axis on the star pattern were measured using an optical densitometer. On each profile, one coordimate of a beam axis was determined. A pair of coordinates on a beam axis form an equation of the axis. Assume that a unit vector equation omitted is with same direction as radiation beam and a vector equation omitted is a vector directing to the beam axis from the estimated gantry axis. Then, a vector product equation omitted ${\times}$ equation omitted is an area vector of which the absolute value is equal to the distance from the estimated gantry axis to the beam axis. The coordinate of gantry axis was obtained by using least-square method for the area vectors relative to the average of whole area vectors. For the axis, the maximum of absolute value of area vectors would be an accuracy of the gantry rotation axis. For the evaluation of mechanical accuracies of collimator and couch axes for which beam direction could not be depicted on a star pattern test film, narrow beams asymmetric in field length was used to simulate beam direction. Result: For a star test pattern to evaluate the mechanical accuracy of rotational axes of a telectherapy machine, the result considering beam direction was different from that ignoring beam direction. For the evaluation of mechanical accuracies of collimator and couch axes by means of a star pattern test, narrow asymmetric beams could simulate beam direction. Conclusion: When a star pattern test is used to evaluate the mechanical accuracy of a teletherapy unit, beam direction must be considered or simulated, and quantitatively evaluated.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.363-365
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• 2006

This paper proposes an estimation method for a circulating current of a Y-${\Delta}$ Transformer. The delta winding current can be decomposed into the two components i.e. a non-circulating component and a circulating component. The former can be estimated using the line currents. However, the latter can not be estimated directly using the line currents. A first order differential equation for the circulating current is derived by applying the Kirchhoff's voltage law on the loop of the delta side. The circulating current can be estimated by the solving the differential equation. The performance of the proposed algorithm is investigated under various conditions including magnetic inrush and over-excitation. The algorithm can estimate the circulating current very accurately even under magnetic inrush and over-excitation.

• Journal of Korean Society on Water Environment
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• v.22 no.4
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• pp.619-625
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• 2006

Amount of soil loss is important information for the proper water quality management, In this research, annual average soil loss of the Geum River basin was estimated using RUSLE (Revised Universal Soil Loss Equation) and GIS (Geographic Information System). Input data were manipulated using ArcGIS ver. 8.3. From crop field which constitute 8.2% of the Geum River Basin, annual average soil loss was estimated as 53.6 ton/ha/year. From the rice paddy field which constitutes 20% of the Geum River Basin, soil loss was estimated as 33.5 ton/ha/year, In comparison, forestry area which constitutes 61.8% of the basin discharged 2.8 ton/ha/year, It could be known from this research that appropriate measures should be implemented to prevent excessive soil loss from the agricultural areas.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.65.1-65.1
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• 2010

Thermal performance tests of solar thermal collectors include determination of coefficient parameters in an efficiency equation. The parameters can be estimated using regression method to minimize an objective function as sum of differences between measured efficiency data and regressed efficiency equation. However, this conventional approach doesn't consider measurement uncertainties. In this presentation, a method to determine regression parameters in the efficiency equation and uncertainties of the parameters is described with mainly mathematical expressions based on literature reviews. In the method, parameters in the equation for collector efficiency can be determined using regression analysis with a weighting factor in the objective function. The weighting factor can be uncertainties of the differences between measured and fitted efficiencies. To evaluate the approach, performance estimation of a solar collector using the efficiency equation with uncertainties is compared to the result using the conventional efficiency equation by a simulated way for a case in one of previous studies.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.3
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• pp.356-362
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• 2010

This research studied the bio-methane potential of several waste biomass materials as alternative sources for biogas production, and the laboratory procedure for measuring the biochemical methane potential was described. The wastes from four agro-industries (sewage, livestock, food wastewater treatment sludge and cattle rumen substance generating in slaughter house) were evaluated as substrates for the assay of biochemical methane potential. In order to estimate the ultimate methane yield, two empirical equations (modified Gompertz equation and exponential equation) was investigated. The ultimate methane yield of sewage, livestock, food sludge and lumen substance estimated by the modified Gompertz equation were 0.086, 0.147, 0.146, and 0.121 L $CH_{4}\;g^{-1}\;VS_{added}$, respectively. The ultimate methane yield estimated by the exponential equation were 0.109, 0.246 and 0.174 L $CH_{4}\;g^{-1}\;VS_{added}$ in sewage, livestock sludge and lumen substance. And the ultimate methane yield estimated by the exponential equation showed more high values in the range of 26.7 ~67.3% than the ultimate methane yield estimated by the modified Gompertz equation.

• Journal of Korean Society of Disaster and Security
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• v.15 no.1
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• pp.35-46
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• 2022

In this study, the amount of debris flow was calculated through the empirical equations of RUSLE, NILIM, and Marchi, which are widely used to calculate areas affected by debris flow, and debris flow measured through precise measurements and field surveys was compared. The RUSLE method over estimated by 2.13 times in the average sense compared with the measured sediment quantify and Marchi's empirical equation over estimated by 2.83 times while NILIM's empirical equation 1.26 times, which is the lowest error among the three empirical equation.

• Journal of Korean Society of Transportation
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• v.12 no.1
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• pp.55-73
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• 1994

The objective of this research is to evaluate the pedestrian signal time involving green and flashing green times. The minimum pedestrian green indication should give time for pedestrian to start crossing safely, and the flashing green indication should give time to complete the crossing. An average pedestrian crossing speed of 1.1(m/s) was estimated by analyzing the field data which was slower than the 1.2(m/s) currently used. Furthermore, the study proposed that design speed for the flashing green time should be slow speed for considerations pedestrian safety, not the average speed. The 0.78-1.01(m/s) of pedestrian speed was estimated at the elementary school areas that indicated 0.2(m/s) slower than the other areas. The pedestrian starting time (perception/reaction time) and time headway from front to back of herd was estimated to determine minimum pedestrian green time. the pedestrian starting time was estimated to determine minimum pedestrian green time. The pedestrian starting time was ranged 2.52-4.29 seconds. The time interval between the pedestrian rows was found to be 1.25-1.86 seconds, which declines as the pedestrian rows increases, The equation to calculate the pedestrian signal, which declines as the pedestrian rows increases. The equation to calculate the pedestrian signal time is proposed using the pedestrian starting time, the time interval between the pedestrian rows, and pedestrian crossing speed given area types (commercial, business, mixed, and elementary school areas), number of both-directional pedestrians for a cycle, crosswalk length and width.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.4
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• pp.247-254
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• 2004

The mechanical informations such as the rotor speed and angle are required to operate the Cylindrical Permanent Magnet Synchronous Motor(PMSM). A resolver or encoder is typically used to supply the mechanical informations. This position sensor adds length to the machine, raises system cost, increases rotor inertia and requires additional devices. As the result, there has been a significant interest in the development of sensorless strategies to eliminate the position sensor. This paper presents an implementation of the new sensorless speed comtrol scheme for a PMSM. In the proposed algorithm, the line currents are estimated by a observer and the estimated speed can be yielded from the voltage equation because the information of speed is included in back emf. But the speed estimation error between the estimated and the real speeds is occured by errors due to measuring the motor parameters and sensing the line current and the input voltage. To minimize the speed estimations error, the estimated speeds are compensated by using an instantaneous reactive power in synchronously rotating reference frame. In this paper, the proposed algorithm is not affected by mechanical motor parameters because the mechanical equation is not used. The effectiveness of algorithm is confirmed by the experiments.

• Journal of Korean Society of Forest Science
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• v.85 no.1
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• pp.56-65
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• 1996

Current volume tables might underestimate or overestimate the volumes of individual trees in a specific region because the tables were made using the data from broad region. This study provides a statistical method of local correction, which is the ratio-of-means estimator, when the table is applied to the data from a specific region. Data used in this study were 411 trees of Larix leptolepis from Hongchon region. Five statistical models for individual tree volume equation were evaluated based on 3 evalation criteria and the best equation fitted to the data from Hongchon region was selected. The volume estimated by the selected equation was then compared with the volume estimated by the current volume table. From the ratio-of-means estimate based on the volumes estimated by selected equation and by current volume table, the local correction was made. The correction equation was $V_{Hongchon}=1.078$ $V_{volume\;table}$. It is also proved that the correction equation can simply and precisely estimate tree volumes of Larix leptolepis in Hongchon region using the current volume table.

• Journal of Nutrition and Health
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• v.45 no.6
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• pp.511-521
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• 2012

The purposes of this study were to assess the physical activity level (PAL) and the total daily energy expenditure (TEE) as well as to evaluate the validity of prediction equation for the estimated energy requirement (EER) in normal weight and overweight or obese children and adolescents. The subjects comprised of 100 healthy Korean students aged between 7-18. The anthropometric data was collected. PAL was calculated from the physical activity diary by the 24-hour recall method, and the resting metabolic rate (RMR) was measured by an open-circuit indirect calorimetry using a ventilated hood system. Daily energy expenditure was PAL multiplied by RMR. EER was calculated by using the prediction equation published in KDRIs. There was no significant difference in the means of age and height between the 46 obese subjects and 54 nonobese subjects. The weight and BMI of the obese group (60.2 kg, $25.3kg/m^2$) were significantly higher than those of the nonobese group (42.4 kg, $18.4kg/m^2$). However, PAL was not significantly different between the two groups (nonobese 1.45, obese 1.46). TEE of the obese group (2,212 kcal/day) was significantly higher than that of the nonobese group (1,774 kcal/day). EER (individual PA) and EER (light PA) were significantly higher than TEE (p < 0,001); however, EER (sedentary PA) was not significantly different with TEE in the two groups. These results showed that the levels of physical activity were the same as the sedentary activity both in the nonobese and obese Korean students; moreover, the predictive equation for EER published in KDRI overestimated the TEE of Korean children and adolescents. Therefore, in further research, a new predictive equation for EER should be developed for Korean children and adolescents through the doubly labeled water method.