• Advances in environmental research
• /
• 제7권1호
• /
• pp.29-37
• /
• 2018

A simple mathematical model for predicting fixed bed adsorption dynamics is described. The model is characterized by a linear adsorption isotherm and a linear driving force expression for mass transfer. Its analytic solution can be approximated with an algebraic equation in closed form which is easily evaluated by spreadsheet computation. To demonstrate one application of the fixed bed model, a previously published adsorption system is used as a case study in this work. The adsorption system examined here describes chromium breakthrough in a fixed bed adsorber packed with imidazole functionalized adsorbent particles and is characterized by a nonlinear adsorption isotherm. However, the equilibrium behavior of the fixed bed adsorber is in essence governed by a linear adsorption isotherm due to the use of a low influent chromium concentration. It is shown that chromium breakthrough is predicted reasonably well by the fixed bed model. The model's parameters can be easily extracted from independent batch experiments. The proposed modeling approach is very simple and rapid, and only Excel is used for computation.

• 대한치과보철학회지
• /
• 제18권1호
• /
• pp.15-35
• /
• 1980

The purpose of this study was to investigate stresses in the various components of fixed partial dentures restoring the posterior teeth of the lower jaw, and to measure quantitatively the effects of certain modifications in structural design on the stresses in the restorations using two-dimensional photoelasticity. Two-dimensional photoelastic methods were used in this study. Several models of fixed partial dentures were constructed. Shoulder less margins and anatomic occlusal reduction were incorporated in Model 1. Rounded shoulders and flat occlusal reduction were incorporated in Model 2, while Model 3 was a cantilever fixed partial denture. Other similar fixed partial dentures were constructed with V and U notches deliverately included in the region of the fixed joints for comparative reasons. The birefringent materials used in this study were PSM-1 and PSM-5 in standard sheets. PSM-1 was used for constructing the substructure, and PSM-5 was used in making the components of the fixed partial dentures. The two materials were used in the construction of composite photoelastic models. Improved artificial stone was used to represent dental cement in luting the composite photoelastic models. Static loading procedures were used at preplanned sites to represent occlusal loads in the mouth. 35 mm color and B/W film were used to record isochromatics in accordance with photoelastic procedures. Data reduction was performed using the grid method, which helped in, the mathematical integration procedure (Shear difference method) to separate the principal stresses. The results were as follows. 1. Fixed partial dentures do not function in bending as a symmetrical beam. Alternate areas of tension and compression were demonstrated when multiple contact loading was used. 2. The weakest part in posterior fixed partial dentures is the fixed joint. 3. (1) Models I and modified Model I were loaded on the pontic using a 50 pound vertical static load. The shear stress near the posterior fixed joint in Model 1 (U notches) was+129.4 p.s.i., and at the same fixed joint in modified Model 1 (V notches) was+239.4 p.s.i. The concentration of stress in fixed joint was reduced by 50% when U notches replaced the V notches. (2) Modified Model 2 was loaded using a multiple contact loader at a total load of 125 pounds. The difference between the principal stresses (${\sigma}_1-{\sigma}_2$), shear stress, at the V notches was+600 p.s.i., and at the U notches was+3l7 p.s.i. The shear stress was reduced by 50% when U notches replaced the V notches. V-grooves at the fixed joints should be avoided, and should be replaced by regular shaped U-grooves. 4. Cantilever fixed partial dentures had much higher stresses at the fixed joint than fixed partial dentures that were attached at both ends.

• Journal of the Korean Statistical Society
• /
• 제25권4호
• /
• pp.499-514
• /
• 1996

Consider an additive regression model of Y on X = (X$_1$,X$_2$,. . .,$X_p$), Y = $sum_{j=1}^pf_j(X_j) + $\varepsilon$$, where $f_j$s are smooth functions to be estimated and $\varepsilon$ is a random error. If $X_j$s are fixed design points, we call it the fixed design additive model. Since the response variable Y is observed at fixed p-dimensional design points, the behavior of the nonparametric regression estimator depends on the design. We propose a fixed design called permutation fixed design, and fit the regression function by the kernel method. The estimator in the permutation fixed design achieves the univariate optimal rate of convergence in mean squared error for any p $\geq$ 2.

• Industrial Engineering and Management Systems
• /
• 제11권2호
• /
• pp.183-187
• /
• 2012

In this paper, we study the fixed charge transportation problem with uncertain variables. The fixed charge transportation problem has two kinds of costs: direct cost and fixed charge. The direct cost is the cost associated with each source-destination pair, and the fixed charge occurs when the transportation activity takes place in the corresponding source-destination pair. The uncertain fixed charge transportation problem is modeled on the basis of uncertainty theory. According to inverse uncertainty distribution, the model can be transformed into a deterministic form. Finally, in order to solve the uncertain fixed charge transportation problem, a numerical example is given to show the application of the model and algorithm.

• Communications for Statistical Applications and Methods
• /
• 제23권2호
• /
• pp.179-187
• /
• 2016

The fixed effects panel probit model faces "incidental parameters problem" because it has a property that the number of parameters to be estimated will increase with sample size. The maximum likelihood estimation fails to give a consistent estimator of slope parameter. Unlike the panel regression model, it is not feasible to find an orthogonal reparameterization of fixed effects to get a consistent estimator. In this note, a hierarchical Bayesian model is proposed. The model is essentially equivalent to the frequentist's random effects model, but the individual specific effects are estimable with the help of Gibbs sampling. The Bayesian estimator is shown to reduce reduced the small sample bias. The maximum likelihood estimator in the random effects model is also efficient, which contradicts Green (2004)'s conclusion.

• 콘크리트학회논문집
• /
• 제12권5호
• /
• pp.81-92
• /
• 2000

A fixed angle softened truss model has been developed in order to predict both shear strength and deformation of reinforced concrete members. The model takes into account the contribution of concrete by accuming the angle of cracks in the postcracking concrete that coincides with the reinforced concrete principal compressive angle determined by the applied stresses. Therefore, this model is capable of predicting the contribution of concrete from the govering equilibrium and compatibility equations including the shear stress and strain developed along concrete diagonal crack. However, the model has a limiting range to be applicable for reinforced concrete members. This research proposes a new algorthm of fixed angle softened truss model capable of removing the limitation of applicability. The proposed algorithm adopts a new conception of constitutive laws. The average normal stresses of concrete in the x- y- directions can be calculated by transforming the principal stresses of concrete. The proposed algorthm is verified by comparing to the test results.

• Journal of applied mathematics & informatics
• /
• 제38권5_6호
• /
• pp.519-532
• /
• 2020

In this paper, we first propose a new total variation-based regularization model for image restoration. We next propose a fixed-point-like method for solving the new image restoration model, and then we provide convergence analysis for the fixed-point-like method. To evaluate the feasibility and efficiency of the fixed-point-like method for the new proposed total variation-based regularization model, we provide numerical experiments for several test problems.

• Journal of Welding and Joining
• /
• 제18권4호
• /
• pp.28-37
• /
• 2000

In this paper the LNG vessel of the Moss type which is capable of lifting 15,261 tons is investigated in the view point of the pressure vessel preliminary design using the finite element method. The Pressure vessel design is based on the equivalent stress levels due to the internal pressure. The finite element model of the spherical pressure vessel is configured using 4 noded quadrilateral shell element. The finite element analysis program NASTRAN and ANSYS 5.5are implemented. The design is compared with the three kinds of the boundary condition : first, where the equator of the pressure vessel is fixed, and where the top and is fixed, and, the bottom end is fixed, respectively. A comparison is presented between the results obtained by the finite element model and by the prototype production model. Additionally just below position(case 1 & case 2) of equator ring was carried out by using ANSYS 5.5. The results show that the vessel design based on the stress is acceptable at the preliminary design.

• 한국ITS학회 논문지
• /
• 제14권1호
• /
• pp.85-93
• /
• 2015

기존의 교통사고모형은 수집된 데이터에 대한 추정된 모수가 고정되어있다고 가정하여 교통량이나 기하구조의 길이와 폭 등은 설치형태와 관계없이 동일한 값을 적용하는 고정효과모형을 이용하여 개발하였다. 하지만 고정효과를 이용한 모형은 모형을 통해 추정된 계수의 표준오차 값이 과소 추정되거나 각 계수의 t-값이 과도하게 산정되어 모형의 설명력이 낮아지게 된다. 이를 극복하기 위하여 교통량, 기하구조, 그리고 관측되지 않은 다른 요인 등에 대한 이질성을 고려한 임의효과모형을 활용하여 모형을 개발할 수 있다. 본 연구에서는 임의효과모형의 효용성을 파악하고자 대전광역시 주요 89개 교차로를 대상으로 데이터를 수집하여 임의효과와 고정효과를 이용한 음이항 회귀모형을 개발하고 이를 비교 분석하였다. 모형개발 결과 년평균일교통량, 제한속도, 차로수, 우회전 전용차로 설치유무, 전방신호등 설치유무 등이 유효한 설명변수로 나타났으며 모형의 설명력을 비교해보면 로그-우도함수값이 임의효과에서 -1537.802로 고정효과의 로그-우도함수값 -1691.327보다 모형 설명력이 좋은 것으로 나타났으며 우도비의 경우 임의효과에서 0.279로 고정효과의 0.207보다 개선된 것으로 나타나 임의효과를 이용한 모형이 고정효과를 이용한 모형보다 우수한 것으로 나타났다.

• 경영과학
• /
• 제23권3호
• /
• pp.1-11
• /
• 2006

This study investigates empirically on the business analysis of fixed mobile convergence telecommunication service. As for the stage of empirical analysis, the process was carried out in the order elaboration of a test model, selection of sample, empirical analysis and interpretation of result. We report our Preliminary results on the fixed mobile convergence telecommunication service demand pattern forecasting by Bass model. The results show that the fixed mobile convergence telecommunication service may sustain profitability over the next ten years in the market. In conclusion, the practical implication of the result attained by this study is that in order to create a fixed mobile convergence in the korean business world, practical tools such as WiBro service is no less important than fixed service and Mobile service, and that users may be rightfully encouraged to adopt WiBro service.