• Industrial Engineering and Management Systems
• /
• 제13권4호
• /
• pp.369-382
• /
• 2014

This paper introduces a new multi-product multi-period multi-objective aggregate production planning problem. The proposed problem is modeled using multi-objective mixed-integer mathematical programming. Three objective functions, including minimizing total cost, maximizing customer services level, and maximizing the quality of end-product, are considered, simultaneously. Several constraints such as quantity of production, available time, work force levels, inventory levels, backordering levels, machine capacity, warehouse space and available budget are also considered. Some parameters of the proposed model are assumed to be qualitative and modeled using fuzzy sets. Then, a fuzzy goal programming approach is proposed to solve the model. The proposed approach is applied on a real-world industrial case study of a color and resin production company called Teiph-Saipa. The approach is coded using LINGO software. The efficacy and applicability of the proposed approach are illustrated in the case study. The results of proposed approach are compared with those of the existing experimental methods used in the company. The relative dominance of the proposed approach is revealed in comparison with the experimental method. Finally, a data dictionary, including the way of gathering data for running the model, is proposed in order to facilitate the re-implementation of the model for future development and case studies.

• Wind and Structures
• /
• 제31권1호
• /
• pp.43-57
• /
• 2020

Considering the wind barriers induced aerodynamic characteristic variations of both bridge deck and trains, this paper studies the effects of wind barriers on the safety and stability of trains as they run through an urban rail transit cable-stayed bridge which tends to be more vulnerable to wind due to its relatively low stiffness and lightweight. For the bridge equipped with wind barriers of different characteristics, the aerodynamic coefficients of trains and bridge decks are obtained from wind tunnel test firstly. And then, the space vibration equations of the wind-train-bridge system are established using the experimentally obtained aerodynamic coefficients. Through solving the dynamic equations, one can calculate the dynamic responses both the trains and bridge. The results indicate that setting wind barriers can effectively reduce the dynamic responses of both the trains and bridge, even though more wind forces acting on the bridge are caused by wind barriers. In addition, for urban rail transit cable-stayed bridges located in strong wind environment, the wind barriers are recommended to be set with 20% porosity and 2.5 m height according to the calculation results of cases with wind barriers porosity and height varying in two wide ranges, i.e., 10% - 40% and 2.0 m to 4.0 m, respectively.

• Steel and Composite Structures
• /
• 제28권4호
• /
• pp.509-516
• /
• 2018

The differential quadrature (DQ) and teaching-learning based optimization (TLBO) methods are coupled to introduce a hybrid numerical method for maximizing fundamental natural frequency of laminated composite skew plates. The fiber(s) orientations are selected as design variable(s). The first-order shear deformation theory (FSDT) is used to obtain the governing equations of the plate. The equations of motion and the related boundary conditions are discretized in space domain by employing the DQ method. The discretized equations are transferred from the time domain into the frequency domain to obtain the fundamental natural frequency. Then, the DQ solution is coupled with the TLBO method to find the maximum frequency of the plate and its related optimum stacking sequences of the laminate. Convergence and applicability of the proposed method are shown and the optimum fundamental frequency parameter of the plates with different skew angle, boundary conditions, number of layers and aspect ratio are obtained. The obtained results can be used as a benchmark for further studies.

• The Journal of the Acoustical Society of Korea
• /
• 제21권2E호
• /
• pp.81-90
• /
• 2002

Single absorbing materials and Helmholtz resonators have limited absorption characteristics over limited frequency ranges due to their structures and properties. Porous materials are highly absorptive for mid and high frequency ranges, while they have little sound absorption for low frequency sounds. Helmholtz resonators are generally used to absorb sound energy for a specified frequency range. Hence they have limited capability in controlling the overall acoustic properties of a space. Not much has been known about useful finishing materials which have enough rigidity and absorption over broad frequency range, in spite of wide demands from acoustic designers and consultants. The present work measured and analyzed absorption characteristics of a slit absorber by varying surface materials, depths of air gap, dimensions of slat and slit widths. It was found that the narrower the slit width, the larger the absorptions over the wide frequency ranges and the pattern was dependent on the presence of porous material. Narrower slat's width tend to increase the slit absorber's absorption more or less. Absorption coefficients at low frequency ranges were dramatically improved (from 0.23 to 0.56) by increasing air gap when porous materials were present.

• 대한수학회논문집
• /
• 제35권2호
• /
• pp.371-399
• /
• 2020

Let P_s := 𝔽₂[x₁, x₂, …, x_s] = ⊕_n⩾0(P_s)_n be the polynomial algebra viewed as a graded left module over the mod 2 Steenrod algebra, ${\mathfrak{A}}$. The grading is by the degree of the homogeneous terms (P_s)_n of degree n in the variables x₁, x₂, …, x_s of grading 1. We are interested in the hit problem, set up by F. P. Peterson, of finding a minimal system of generators for ${\mathfrak{A}}$-module P_s. Equivalently, we want to find a basis for the 𝔽₂-graded vector space ${\mathbb{F}}_2{\otimes}_{\mathfrak{A}}$ P_s. In this paper, we study the hit problem in the case s = 5 and the degree n = 5(2^t - 1) + 6 · 2^t with t an arbitrary positive integer.

• 대한수학회논문집
• /
• 제32권3호
• /
• pp.661-676
• /
• 2017

Let T be a bounded linear operator acting on a complex Hilbert space ${\mathfrak{H}}$. In this paper we introduce the class, denoted ${\mathcal{Q}}(A(k),m)$, of operators satisfying $T^{m{\ast}}(T^{\ast}{\mid}T{\mid}^{2k}T)^{1/(k+1)}T^m{\geq}T^{{\ast}m}{\mid}T{\mid}^2T^m$, where m is a positive integer and k is a positive real number and we prove basic structural properties of these operators. Using these results, we prove that if P is the Riesz idempotent for isolated point ${\lambda}$ of the spectrum of $T{\in}{\mathcal{Q}}(A(k),m)$, then P is self-adjoint, and we give a necessary and sufficient condition for $T{\otimes}S$ to be in ${\mathcal{Q}}(A(k),m)$ when T and S are both non-zero operators. Moreover, we characterize the quasinilpotent part $H_0(T-{\lambda})$ of class A(k) operator.

• 한국주거학회논문집
• /
• 제24권6호
• /
• pp.81-92
• /
• 2013

Recently, the interest in the mixed-use development of various urban planning facilities has been increased, but the interest in the Mixed-use development of bus depots that is closely related to our daily life is insufficient circumstance so far. Accordingly, this study aims to realize the necessity for the mixed-use development of bus depots as methods to improve the living environment and use efficiently the land, and to suggest reasonable development directions by analyzing their physical character after classifying bus depots according to their position in the residential area. As the results of study, bus depots have different properties according to their position in residential area and have the problem of space shortage. Also, many things such as location of entrances, the finish method of edge of bus depot's area are affected by the surrounding environment. So development plan to consider the each condition is required.

• Structural Engineering and Mechanics
• /
• 제50권2호
• /
• pp.151-161
• /
• 2014

In this paper, fuel tank of the locomotive ER 24 has been studied. Firstly the behavior of fuel and air during the braking time has been investigated by using a two-phase model. Then, the distribution of pressure on the surface of baffles caused by sloshing has been extracted. Also, the fuel tank has been modeled and analyzed using Finite Element Method (FEM) considering loading conditions suggested by the DIN EN 12663 standard and real boundary conditions. In each loading condition, high stressed areas have been identified. By comparing the distribution of pressure caused by sloshing phenomena and suggested loading conditions, optimization of the tank has been taken into consideration. Moreover, internal baffles have been investigated and by modifying their geometric properties, search of the design space has been done to reach the optimal tank. Then, in order to reduce the mass and manufacturing cost of the fuel tank, Non-dominated Sorting Genetic Algorithm (NSGA-II) and Artificial Neural Networks (ANNs) have been employed. It is shown that compared to the primary design, the optimized fuel tank not only provides the safety conditions, but also reduces mass and manufacturing cost by %39 and %73, respectively.

• 대한수학회지
• /
• 제45권2호
• /
• pp.435-453
• /
• 2008

In this paper, by using q-deformed bosonic p-adic integral, we give $\lambda$-Bernoulli numbers and polynomials, we prove Witt's type formula of $\lambda$-Bernoulli polynomials and Gauss multiplicative formula for $\lambda$-Bernoulli polynomials. By using derivative operator to the generating functions of $\lambda$-Bernoulli polynomials and generalized $\lambda$-Bernoulli numbers, we give Hurwitz type $\lambda$-zeta functions and Dirichlet's type $\lambda$-L-functions; which are interpolated $\lambda$-Bernoulli polynomials and generalized $\lambda$-Bernoulli numbers, respectively. We give generating function of $\lambda$-Bernoulli numbers with order r. By using Mellin transforms to their function, we prove relations between multiply zeta function and $\lambda$-Bernoulli polynomials and ordinary Bernoulli numbers of order r and $\lambda$-Bernoulli numbers, respectively. We also study on $\lambda$-Bernoulli numbers and polynomials in the space of locally constant. Moreover, we define $\lambda$-partial zeta function and interpolation function.

• Journal of applied mathematics & informatics
• /
• 제12권1_2호
• /
• pp.81-105
• /
• 2003

This paper deals with the very interesting problem about the influence of piecewise smooth boundary conditions on the distribution of the eigenvalues of the negative Laplacian in R$^3$. The asymptotic expansion of the trace of the wave operator (equation omitted) for small ｜t｜ and i=√-1, where (equation omitted) are the eigenvalues of the negative Laplacian (equation omitted) in the (x$^1$, x$^2$, x$^3$)-space, is studied for an annular vibrating membrane $\Omega$ in R$^3$together with its smooth inner boundary surface S$_1$and its smooth outer boundary surface S$_2$. In the present paper, a finite number of Dirichlet, Neumann and Robin boundary conditions on the piecewise smooth components (equation omitted)(i = 1,...,m) of S$_1$and on the piecewise smooth components (equation omitted)(i = m +1,...,n) of S$_2$such that S$_1$= (equation omitted) and S$_2$= (equation omitted) are considered. The basic problem is to extract information on the geometry of the annular vibrating membrane $\Omega$ from complete knowledge of its eigenvalues by analysing the asymptotic expansions of the spectral function (equation omitted) for small ｜t｜.