• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권11호
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• pp.577-585
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• 2003

This paper proposes a new speed sensorless control method of a permanent magnet synchronous motor using an instantaneous reactive power. 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 estimation error, the estimated speed is compensated by using an instantaneous reactive power. 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.

• 한국물환경학회지
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• 제23권6호
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• pp.913-919
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• 2007

This study was conducted to develop a model equation to estimate the delivered point and nonpoint pollutant loads, which are critical factor to determine the water quality of watersheds. The model equation was developed by considering various factors such as biological removal and delivered distance of pollutants, basin shape and geomorphic runoff condition. The parameters for the model equation were estimated in 3 periods, which are October to March, April to June, and July to September. As a parameter, ${\alpha}_p$, ${\alpha}_n$, ${\beta}$, a and b for $BOD_5$-delivered pollutant loads were estimated to be 0.010~0.0155, 0.051, -0.033, 0.018~0.050 and 0.93, respectively. For T-N, ${\alpha}_p$, ${\alpha}_n$, ${\beta}$ a and b were estimated to be 0.0060~0.0140, 0.014, -0.02, 0.044~0.079 and 0.93, respectively. The same parameters for T-P were estimated to be 0.0160, 0.014, -0.0250, 0.015 and 1.21, respectively. The relationship, $E^2$ (Model efficiency), between observed and calculated delivered pollutant loads showed 0.65 for $BOD_5$, 0.81 for T-N, and 0.66 for T-P, respectively. Consequently, the model equation is effective to estimate delivered pollutant loads for TMDL.

• Journal of Trauma and Injury
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• 제36권4호
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• pp.337-342
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• 2023

Purpose: This study aimed to compare the resting energy expenditure (REE) measured using indirect calorimetry with that estimated using predictive equations in severe trauma patients to determine the appropriate caloric requirements. Methods: Patients admitted to the surgical intensive care unit between January 2020 and March 2023 were included in this study. Indirect calorimetry was used to measure the patients' REE values. These values were subsequently compared with those estimated using predictive equations: the weight-based equation (rule of thumb, 25 kcal/kg/day), Harris-Benedict, Ireton-Jones, and the Penn State 2003 equations. Results: A total of 27 severe trauma patients were included in this study, and 47 indirect calorimetric measurements were conducted. The weight-based equation (mean difference [MD], -28.96±303.58 kcal) and the Penn State 2003 equation (MD, - 3.56±270.39 kcal) showed the closest results to REE measured by indirect calorimetry. However, the REE values estimated using the Harris-Benedict equation (MD, 156.64±276.54 kcal) and Ireton-Jones equation (MD, 250.87±332.54 kcal) displayed significant differences from those measured using indirect calorimetry. The concordance rate, which the predictive REE differs from the measured REE value within 10%, was up to 36.2%. Conclusions: The REE values estimated using predictive equations exhibited substantial differences from those measured via indirect calorimetry. Therefore, it is necessary to measure the REE value through indirect calorimetry in severe trauma patients.

• Imaging Science in Dentistry
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• 제46권1호
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• pp.1-7
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• 2016

Purpose: This study assessed the accuracy of age estimates produced by a regression equation derived from lower third molar development in a Thai population. Materials and Methods: The first part of this study relied on measurements taken from panoramic radiographs of 614 Thai patients aged from 9 to 20. The stage of lower left and right third molar development was observed in each radiograph and a modified Gat score was assigned. Linear regression on this data produced the following equation: Y=9.309+1.673 mG+0.303S (Y=age; mG=modified Gat score; S=sex). In the second part of this study, the predictive accuracy of this equation was evaluated using data from a second set of panoramic radiographs (539 Thai subjects, 9 to 24 years old). Each subject's age was estimated using the above equation and compared against age calculated from a provided date of birth. Estimated and known age data were analyzed using the Pearson correlation coefficient and descriptive statistics. Results: Ages estimated from lower left and lower right third molar development stage were significantly correlated with the known ages (r=0.818, 0.808, respectively, $P{\leq}0.01$). 50% of age estimates in the second part of the study fell within a range of error of ${\pm}1year$, while 75% fell within a range of error of ${\pm}2years$. The study found that the equation tends to estimate age accurately when individuals are 9 to 20 years of age. Conclusion: The equation can be used for age estimation for Thai populations when the individuals are 9 to 20 years of age.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.381-384
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• 2002

This study aims to propose the new strength equation of concrete by penetration test. There are not only few estimate strength equation of concrete, but also many problems to apply them to the real structure because of speed, cost, easiness, structual damage, reliability and so on. For this study, there performed a series of test and proposed a strength equation as follows ; fc = 5661 - 219.5d ＋ $2.17d^2 (단, R^2 = 98.6%$) fc : estimated compressive strength of concrete by kgf/$cm^2$ d: penetrated depth of concrete by mm.

• Journal of Power Electronics
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• 제12권5호
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• pp.748-757
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• 2012

In a sensorless control system with a Permanent Magnet Synchronous Motor (PMSM), the angular position of the rotor flux can be estimated by a voltage equation. However, the estimated angle may be inaccurate due to various causes. In this paper, it was comprehensively analyzed how various causes affect the angle error. As a result of the analysis, an error equation intuitively describing these relationships was derived. The parameter errors of a PMSM and the non-ideal properties of the driving system were identified as error-causing factors. To demonstrate the validity of the error equation, PMSMs were tested at various operating points. The variations in angle errors could be well explained with the error equation.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제9권1호
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• pp.111-123
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• 2005

Here, the Fredholm integral equation with Hilbert kernel is solved numerically, using two different methods. Also the error, in each case, is estimated.

• 한국관개배수논문집
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• 제14권1호
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• pp.41-49
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• 2007

In this study, Kajiyama equation and SWAT model were used to estimate the available water resources from 1967 to 2003 at the small scale watershed, located in Dongnae-Myeon, Chunchen, Gangwon. The annual average streamflow for dry years estimated using the Kajiyama equation and the SWAT model were $2,593,779m^3$ and $2,579,162m^3$. The annual average streamflow for wet years were $7,223,804m^3$ and $7,035,253m^3$, respectively. The annual arrange streamflow for the entire 36 year period were $14,868,601m^3$ and $14,214,292m^3$, respectively. The coefficient of determination ($R^2$) and the Nash-Sutcliffe coefficient for comparison between Kajiyama and SWAT were 0.90 and 0.79, respectively. The comparison indicates that the Kajiyama equation and the SWAT model can be used to estimate the streamflow at th study watershed with reasonable accuracy, although the estimated values were not compared with measured streamflow data, which is not available at the small scale study watershed. However, the Kajiyama equation is recommended for estimating available water resources at Dongnae-Myeon watershed because of its ease-of-use and reasonable accuracy compared with the SWAT model, requiring numerous model input and expensive GIS software in operating the model

• 한국수자원학회논문집
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• 제37권6호
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• pp.479-485
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• 2004

이 연구에서는 일교차를 이용하여 일평균 증발산량을 산정한다. 이를 위하여 Thornton과 Running(1999)의 일평균 태양 복사열 산정을 위한 경험식을 이용하여 태양복사열을 계산하여 이를 현장 자료와 비교한 결과 비교적 정확한 범위 내에 있다는 것을 확인하였다. 이렇게 산정된 일평균 태양 복사열을 증발산량의 계산을 위해 Priestly Taylor 공식과 Penman 공식에 적용함으로써 현장에서의 정확성과 사용가능성을 확인해 보고자 하였다. 그 결과로 태양 복사열에 중점을 둔 Priest-Taylor 공식은 과다추정하는 경향을 보이나, Penman 공식은 비교적 정확한 증발산량의 산정을 보여 줌으로써 기상 관측 자료가 풍부하지 않은 지역에서의 사용가능성을 보여주었다. 또 계산된 증발산량을 일단위 온도만을 이용하여 증발산량을 산정하는 Hargreaves 공식과 비교하여 각 공식의 장단점을 공학적 측면에서 알아보고자 하였다.

• 수산경영론집
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• 제51권2호
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• pp.51-69
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• 2020

The purpose of this study is to construct an outlook model that is consistent with the "Fisheries Outlook" monthly published by the Fisheries Outlook Center of the Korea Maritime Institute(KMI). In particular, it was designed as a partial equilibrium model limited to abalone items, but a model was constructed with a dynamic ecological equation model(DEEM) system taking into account biological breeding and shipping time. The results of this study are significant in that they can be used as basic data for model development of various items in the future. In this study, due to the limitation of monthly data, the market equilibrium price was calculated by using the recursive model construction method to be calculated directly as an inverse demand. A model was built in the form of a structural equation model that can explain economic causality rather than a conventional time series analysis model. The research results and implications are as follows. As a result of the estimation of the amount of young seashells planting, it was estimated that the coefficient of the amount of young seashells planting from the previous year was estimated to be 0.82 so that there was no significant difference in the amount of young seashells planting this year and last year. It is also meant to be nurtured for a long time after aquaculture license and limited aquaculture area(edge style) and implantation. The economic factor, the coefficient of price from last year was estimated at 0.47. In the case of breeding quantity, it was estimated that the longer the breeding period, the larger the coefficient of breeding quantity in the previous period. It was analyzed that the impact of shipments on the breeding volume increased. In the case of shipments, the coefficient of production price was estimated unelastically. As the period of rearing increased, the estimation coefficient decreased. Such result indicates that the expected price, which is an economic factor variable and that had less influence on the intention to shipments. In addition, the elasticity of the breeding quantity was estimated more unelastically as the breeding period increased. This is also correlated with the relative coefficient size of the expected price. The abalone supply and demand forecast model developed in this study is significant in that it reduces the prediction error than the existing model using the ecological equation modeling system and the economic causal model. However, there are limitations in establishing a system of simultaneous equations that can be linked to production and consumption between industries and items. This is left as a future research project.