• Title, Summary, Keyword: Analytical method

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Comparison of a Groundwater Simulation-Optimization Numerical Model with the Analytical Solutions (해안지하수개발 최적화수치모델과 해석해의 비교연구)

  • Shi, Lei;Cui, Lei;Lee, Chan-Jong;Park, Nam-Sik
    • Proceedings of the Korea Water Resources Association Conference
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    • pp.905-908
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    • 2009
  • In the management of groundwater in coastal areas, saltwater intrusion associated with extensive groundwater pumping, is an important problem. The groundwater optimization model is an advanced method to study the aquifer and decide the optimal pumping rates or optimal well locations. Cheng and Park gave the analytical solutions to the optimization problems basing on Strack's analytical solution. However, the analytical solutions have some limitations of the property of aquifer, boundary conditions, and so on. A simulation-optimization numerical method presented in this study can deal with non-homogenous aquifers and various complex boundary conditions. This simulation-optimization model includes the sharp interface solution which solves the same governing equation with Strack's analytical solution, therefore, the freshwater head and saltwater thickness should be in the same conditions, that can lead to the comparable results in optimal pumping rates and optimal well locations for both of the solutions. It is noticed that the analytical solutions can only be applied on the infinite domain aquifer, while it is impossible to get a numerical model with infinite domain. To compare the numerical model with the analytical solutions, calculation of the equivalent boundary flux was planted into the numerical model so that the numerical model can have the same conditions in steady state with analytical solutions.

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Analytical solution of a contact problem and comparison with the results from FEM

  • Oner, Erdal;Yaylaci, Murat;Birinci, Ahmet
    • Structural Engineering and Mechanics
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    • v.54 no.4
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    • pp.607-622
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    • 2015
  • This paper presents a comparative study of analytical method and finite element method (FEM) for analysis of a continuous contact problem. The problem consists of two elastic layers loaded by means of a rigid circular punch and resting on semi-infinite plane. It is assumed that all surfaces are frictionless and only compressive normal tractions can be transmitted through the contact areas. Firstly, analytical solution of the problem is obtained by using theory of elasticity and integral transform techniques. Then, finite element model of the problem is constituted using ANSYS software and the two dimensional analysis of the problem is carried out. The contact stresses under rigid circular punch, the contact areas, normal stresses along the axis of symmetry are obtained for both solutions. The results show that contact stresses and the normal stresses obtained from finite element method (FEM) provide boundary conditions of the problem as well as analytical results. Also, the contact areas obtained from finite element method are very close to results obtained from analytical method; disagree by 0.03-1.61%. Finally, it can be said that there is a good agreement between two methods.

A Study on PCB Analysis of Insulating Oil in Waste Condenser (폐콘덴서의 절록유 중에 함유된 PCB 분석에 관한 연구)

  • 김귀자;박재주
    • Environmental health and toxicology
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    • v.4 no.1_2
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    • pp.11-17
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    • 1989
  • A quantitative analytical method of highly concentrated PCB is established in the research. With the quantitative analytical method PCB of insulating oil was examined. The following conclusions are derived from this research. 1. The recovery ratio was 95.7% with the quantitative analytical method, which indicates it can be used for the analysis of PCB. 2. PCB concentration of insulation oil in waste condenser was found to be 21.2% thru 13.85% , which was highly concentrated. 3. PCB insulation oil in waste condenser was same as PCB-42.

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Studies on the Terpenoids in the Volatile Constituents of Liaoning Schisandra Chinensis Baillon

  • Hou, Dongyan;Zhang, Weihua;Hui, Ruihua
    • Analytical Science and Technology
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    • v.8 no.4
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    • pp.505-509
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    • 1995
  • The terpenoids in the volatile constituents of Liaoning Shcisandra Chinesis Baillon have been determined by the analytical method of GC/MS. Thirty terpenoids molecular structure were characterized. They are 11.89% monterpenes, 4.60% monoterpene oxides, 58.74% sesquiterpene hydrocarbons, and 1.62% oxygen-containing sesquiterpenoids in the total volatile constituents quantified by chromatograph. Among them, the sesquiterpene make up the characteristic constituents. Every terpenoid constituent percent content was obtained using area normalization method of HP-59970 chemstation.

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Comparison of Sampling and Analytical Methods for Determining Airborne Hexavalent Chromium -Limit of Detection, Accuracy and Precision of Analytical Procedures (공기중 6가 크롬 측정 방법 비교 -검출한계, 정확도 및 정밀도-)

  • 신용철;이병규;이지태
    • Journal of Korean Society for Atmospheric Environment
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    • v.18 no.1
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    • pp.39-49
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    • 2002
  • In this study, limits of detection (LOD), accuracy and precision of four sampling/ analytical methods were evaluated and compared for the determination of airborne hexavalent chromium, Cr (VI). The methods include : (1) a combination of the National Institute for Occupational Safety and Health (NIOSH) Method 7600/U. S. Environmental Protection Agency (EPA) Method 218.6 (NIOSH/EPA Method) proposed by Shin and Paik, 2) two impinger methods using 2% NaOH/3% Na$_2$CO$_3$. (3) same as (2) but with 0.02 N NaHCO$_3$absorbing solution, and (4) the Occupational Safety and Health (OSHA) Method ID-215. An ion chromatograph/visible absorbance detector was used for the analysis of Cr (VI) in sample solution. Limit of detection (LOD) , analytical accuracy, and precision were also tested using Cr (VI) spike samples. Recoveries (as index of accuracy) and coefficient of variation (CV) (as a index of precision) were determined. Two-way ANOVA and Turkey's test were performed to test the significance in differences among recoveries and CVs of the methods. In all the methods, the peaks of Cr (VI) were separated sharply on chromatograms and exhibited a strong linearity with Cr (VI) concentrations in solution. The correlation coefficients of calibration curves typically ranged from 0.9997 to 0.9999, and the analytical LODs from 0.025 to 0.1$\mu\textrm{g}$/sample. All the method had good sensitivities and linearities between Cr (VI) levels and peak areas. The accuracies (% mean recoveries) of the methods ranged from 80.1 to 104.2%, while the precisions (pooled coefficient of variation) ranged from 3.16 to 4.43%. The impinger methods showed higher recoveries ( > 95%) than those of the PVC filter methods (the OSHA Method and the NIOSH/EPA Method). It was assumed that Cr (VI) on PVC filter was exposed to air and reduced to trivalent chromium, Cr (III), whereas it was stabilized in alkali solution contained in impinger. Thus, a special treatment of Cr (VI) samples collected on PVC filters may be required.

A Study on the Optimal Analytical Method for the Determination of Urinary Arsenic by Hydride Generation-Atomic Absorption Spectrometry (HG-AAS법에 의한 요중 비소의 최적 분석법에 관한 연구)

  • Lee, Jong-Wha;Lee, Ui-Seon;Hong, Sung-Chul;Jang, Bong-Ki
    • Journal of Environmental Health Sciences
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    • v.35 no.5
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    • pp.402-410
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    • 2009
  • This study was carried out to examine the optimal analytical method for determination of urinary toxic arsenic (inorganic arsenic and its metabolites) by HG-AAS (hydride generation-atomic absorption spectrometry). In the analysis of SRMs (standard reference materials), method E (addition of 0.4% L-cysteine to pre-reductant and use 0.04M HCl as carrier acid) showed the most accurate results compared with the reference values. In the analysis of 30 urinary samples, analytical results were significantly different depend on the component of pre-reductant and the concentration of carrier acid. When the concentration of carrier acid was higher, the analytical result was lower. The recovery rates of MMA (monomethylarsonic acid) and DMA (dimethylarsenic acid) were varied by the concentration of pre-treatment acid and carrier acid and hydride generation reagents. When the concentration of carrier acid was 1.62 M (5% HCl), the recovery rates of DMA was 1%. The recovery rates of MMA and DMA in method E (=V) were 102% and 100%, respectively. The results of this study suggest that the component and concentration of pre-reductant and carrier acid must be carefully adjusted in the analysis of urinary arsenic, and method E is recommendable as the most precise analytical method for determination of urinary toxic arsenic.

Cogging Torque Reduction Design of Permanent Magnet Motor Using Analytical Method (해석적인 방법을 이용한 Cogging Torque 저감을 위한 영구자석형 전동기 형상 설계)

  • Fang, Liang;Lee, Byeong-Hwa;Hong, Jung-Pyo
    • Proceedings of the KIEE Conference
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    • pp.676_677
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    • 2009
  • In this paper, an analytical method used for predicting the magnetic field distribution and cogging torque characteristic in a permanent magnet synchronous motor (PMSM) is presented. The magnetic field is analyzed with the space harmonic analysis, and the cogging torque is calculated based on the air-gap field distribution and slot-opening effect considered by relative permeance. The validity of the presented analytical method is confirmed by 2-dimensional finite element analysis (FEA). Then this analytical method combines with response surface methodology (RSM) is applied to the prototype PMSM model rebuilding in order to minimize the cogging torque. Finally, an optimized PMSM model is built and the cogging torque reduction is confirmed by FEA.

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Analysis of Symmetric and Periodic Open Boundary Problem by Coupling of FEM and Fourier Series

  • Kim, Young Sun
    • Journal of Magnetics
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    • v.18 no.2
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    • pp.130-134
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    • 2013
  • Most electrical machines like motor, generator and transformer are symmetric in terms of magnetic field distribution and mechanical structure. In order to analyze these problems effectively, many coupling techniques have been introduced. This paper deals with a coupling scheme for open boundary problem of symmetric and periodic structure. It couples an analytical solution of Fourier series expansion with the standard finite element method. The analytical solution is derived for the magnetic field in the outside of the boundary, and the finite element method is for the magnetic field in the inside with source current and magnetic materials. The main advantage of the proposed method is that it retains sparsity and symmetry of system matrix like the standard FEM and it can also be easily applied to symmetric and periodic problems. Also, unknowns of finite elements at the boundary are coupled with Fourier series coefficients. The boundary conditions are used to derive a coupled system equation expressed in matrix form. The proposed algorithm is validated using a test model of a bush bar for the power supply. And the each result is compared with analytical solution respectively.

Repairability Performance and Restoring Force Characteristics of Damaged H-shaped Steel Members after Repair

  • Mori, Kenjiro;Ito, Takumi;Sato, Hanako;Munemura, Hiroka;Matsumoto, Takeshi;Choi, Changhoon
    • International Journal of High-Rise Buildings
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    • v.4 no.1
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    • pp.57-64
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    • 2015
  • Recently, new keywords such as "Resilience" and "Repairability" have been discussed from the perspective of the sustainability of damaged structures after a severe disaster. To evaluate the repairability and recovery of structures, it is necessary to establish an analytical method that can simulate the behavior of repaired structures. Furthermore, it is desirable to establish an evaluation method for the structural performance of repaired structures. This study investigates the repairability and recovery of steel members that are damaged by local buckling or cracks. This paper suggests a simple analytical model for repaired steel members, in order to simulate the inelastic behavior and evaluate the recoverability of the structural performance. There is good agreement between the analytical results and the test results. The proposed analytical method and model can effectively evaluate the recoverability.

A unified solution for vibration analysis of plates with general structural stress distributions

  • Yang, Nian;Chen, Lu-Yun;Yi, Hong;Liu, Yong
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.8 no.6
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    • pp.615-630
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    • 2016
  • Complex stress distributions often exist in ocean engineering structures. This stress influences structural vibrations. Finite Element Methods exhibit some shortcomings for solving non-uniform stress problems, such as an unclear physical interpretation, complicated operation, and large number of computations. Analytical methods research considers mainly uniform stress problems, and often, their methods cannot be applied in practical marine structures with non-uniform stress. In this paper, an analytical method is proposed to solve the vibration of plates with general stress distributions. Non-uniform stress is expressed as a special series, and the stress influence is inserted into a vibration equation that is solved through decoupling to obtain an analytical solution. This method has been verified using numerical examples and can be used in arbitrary stress distribution cases. This method requires fewer computations and it provides a clearer physical interpretation, so it has advantages in some qualitative research.