Sharif Digital Repository

We are concerned with an open shop scheduling problem having sequence-dependent setup times. A novel bi-objective possibilistic mixed-integer linear programming model is presented. Sequence-dependent setup times, fuzzy processing times and fuzzy due dates with triangular possibility distributions are the main constraints of this model. An open shop scheduling problem with these considerations is close to the real production scheduling conditions. The objective functions are to minimize total weighted tardiness and total weighted completion times. To solve small-sized instances for Pareto-optimal solutions, an interactive fuzzy multi-objective decision making (FMODM) approach, called TH... 

The problem of spacecraftformation control and reconfiguration for halo orbit around the second libration point (L2) of the Sun-Earth Three Body (TB) system is investigated. Station keeping, reconfigu-ration and precision formation control of spacecrafts on halo orbits are performed via the use of the nonlinear Integral Sliding Mode (ISM) method as well as the optimal closed loop Linear Quadratic Regulator(LQR) approach. In this regard the nonlinear relative dynamics of deputy-chief spacecrafts are derived within the concept of the three body problem. The behavior of the two controllers are compared for different tasks of the formation mission in order to determine the more preferred... 

A Digital Delta Sigma Modulator (DDSM) is a Finite State Machine (FSM); it is implemented using finite precision arithmetic units and the number of available states is finite. The DDSM always produces a periodic output signal when the input is constant. This paper proposes a novel method of applying periodic dither to a DDSM in order to obtain minimized spurious tones. The effects of adding the pseudorandom dither signal in different stages within the proposed Multi-Stage noise Shaping (MASH) modulator are expressed in the equations, and the results are compared. We present results regarding the periodicity of the quantization noise produced by a MASH modulator with a constant input and a... 

Purpose - Digital Delta Sigma Modulator (DDSM) is used widely in electronic circuits including Radars, class-D power amplifiers and fractional frequency synthesizers. The purpose of this paper is to propose an implementation for MASH DDSMs named as Multi Modulus Reduced Complexity (MMRC) architecture. Design/methodology/approach - This architecture will use a very simple pseudorandom Linear Feedback Shift Register (LFSR) dither signal with period N-d to randomize the digital MMRC modulator used for fractional frequency synthesizers. Using error masking methodology, the MMRC modulator can decrease the hardware consumption and increase accuracy of the fractional frequency synthesizer. Rules... 

Smart water flooding as a developing technique utilizes modified water chemistry in terms of salinity and composition to prepare the best-suited brine composition for a specific brine/oil/rock system to obtain higher oil recovery efficiency. Huge amount of unrecovered oil is expected to be remained in carbonate reservoirs; however, few research works on incremental oil recovery during smart water injection in carbonate cores at reservoir condition are reported. Several core flooding tests using one of the Iranian carbonate reservoir rock are conducted to check the effectiveness of smart water injection for more oil recovery efficiency. The results reaffirm the positive effect of sulfate ions... 

A typical scientist has no responsibility other than to explain how a natural event occurred. However, when a philosopher asks about the conditions under which a scientist’s explanation is true, he is, in fact, raising an ultimate question, the concept which Karl Popper used for the first time. Answering this question requires that no elements are neglected in the explanation, and no significant factors in the explanation are overlooked. In other words, in explaining a phenomenon, at any level of its explanation, there should be no remainder. These requirements can be achieved through the full explanation. In the present article, by drawing on concepts such as theory-ladenness of... 

To differentiate between the laws of nature and accidental generalizations, we must adopt a view of necessity that is capable of being realized in relationships existing among natural objects. In neo-Sadraian Islamic philosophy, metaphysical necessity is accepted as part of the cause-effect relationship. This paper compares the neo-Sadraian interpretation of necessity and necessitarian theories about the laws of nature, particularly essentialism and universal theory. By resorting to specific forms al-shûrat al-naw’iyyah, the origin of the essential properties of natural objects, I argue that neo-Sadraians have proposed a perspective on metaphysical necessity that is epistemologically a... 

Some proponents of new atheism, including Dawkins, claim that religion, especially Islam, is the cause of the war because it encourages divisiveness and labeling. In this article, in the first step, I will show that Islam is not the cause of war, but rather it is a misconception of Islam that is the cause of divisiveness and eventually war. Then, I will demonstrate that the COVID-19 pandemic and its impact on societies and religious behaviors somehow could, and still can, modify this misconception and blur divisions. This effect occurs in two ways: firstly, a pandemic creates common human problems for all people worldwide, making people more aware of their common points that Islam refers to... 

The contact line dynamics is an important phenomenon in natural and industrial processes and is still a challenging problem. The complexity of this problem in computational simulations is much more than theoretical and experimental works. In this paper, a color-gradient (CG) lattice Boltzmann method (LBM) for simulating wetting phenomena and the dynamics of contact line in two-phase flows with very high density-ratio (∼ 1000 was used. This method applies a multi-relaxation time (MRT) collision operator to enhance the stability of numerical scheme. Both static and dynamic contact angles were enforced at the wall through geometrical wetting boundary condition. Note, the main nobility of this... 

Micro-scale systems have gained considerable attention in recent years and a large amount of researches have been done in this field. In this study, the hydrodynamic interference of a droplet is comprehensively investigated under surface acoustic waves. This paper reveals the effects of some control parameters such as wave amplitude and wave frequency on the dynamical behavior of droplet. For these purposes, a two-dimensional multiple-relaxation-time color-gradient model lattice Boltzmann method is developed. This model is first validated by dynamical behaviors of a droplet subjected to shear flow. Moreover, displacement of a droplet affected by surface acoustic waves is comprehensively... 

Several types of research are performed on flow control and this fact highlights the importance of this topic. Over the last two decades, actuators based on acoustic waves have attracted much attention and have been used in widespread applications from mixing to pumping. This paper reveals the effects of some control parameters such as wave amplitude and wave frequency on the dynamical behavior of a sessile drop in order to change the flow characteristics. For this purpose, the removal of water from surfaces and drop movement against gravity are considered. Flow dynamics is simulated using lattice Boltzmann method. The results show that the drop can be removed from the surface in a short... 

The gut-brain axis is believed to constitute a bidirectional communication mechanism that affects both mental and digestive processes. Recently, the role of the gut microbiota in cognitive performance has been the focus of much research. In this paper, we discuss the effects of gut microbiota and nutrition on spatial memory and learning. Studies have shown the influence of diet on cognitive capabilities such as spatial learning and memory. It has been reported that a high-fat diet can alter gut microbiota which subsequently leads to changes in spatial learning and memory. Some microorganisms in the gut that can significantly affect spatial learning and memory are Akkermansia muciniphila,... 

Selling correlated products faces the sellers with the cross-selling, which is a key factor in managing revenue and costs of the sellers. Cross-selling is a phenomenon which happens when the demands of products are correlated so that the demand for one of the correlated products automatically initiates demand of another. In these cases, different selling tactics such as bundling, tying, mixed bundling, etc. are applied to sell the items. In this paper, an integrated pricing-inventory model for two complementary products under three selling strategies is developed. In the first model, it is assumed that the seller sells the products separately while those are packed and sold as bundling in... 

Selling correlated products faces the sellers with the cross-selling, which is a key factor in managing revenue and costs of the sellers. Cross-selling is a phenomenon which happens when the demands of products are correlated so that the demand for one of the correlated products automatically initiates demand of another. In these cases, different selling tactics such as bundling, tying, mixed bundling, etc. are applied to sell the items. In this paper, an integrated pricing-inventory model for two complementary products under three selling strategies is developed. In the first model, it is assumed that the seller sells the products separately while those are packed and sold as bundling in... 

In this paper, a new constructive auto-associative neural network performing nonlinear principal component analysis is presented. The developed constructive neural network maps the data nonlinearly into its principal components and preserves the order of principal components at the same time. The weights of the neural network are trained by a combination of Back Propagation (BP) and Genetic Algorithm (GA) which accelerates the training process by preventing local minima. The performance of the proposed method was evaluated by means of two different experiments that illustrated its efficiency. ©2007 IEEE  

The harmonic displacement response of a beam is utilized as the input signal function in wavelet analysis. Sudden changes in the spatial variation of transformed response identify the location of damages and defects. The damage incurred causes a change in the stiffness or mass of the beam. This causes a localized singularity which can be identified by a wavelet analysis of the displacement response. In this article, it is shown that using harmonic response is superior to the static deflection response and this approach is more effective in the presence of noise and more sensitive to the versatility of the applied harmonic loads. © 2007 SAGE Publications  

In the last decades, much attention has been paid to the design of multi-speaker voice conversion. In this work, a new method for voice conversion (VC) using nonlinear principal component analysis (NLPCA) is presented. The principal components are extracted and transformed by a feed-forward neural network which is trained by combination of Genetic Algorithm (GA) and Back-Propagation (BP). Common pre- and post-processing approaches are applied to increase the quality of the synthesized speech. The results indicate that the proposed method can be considered as a step towards multi-speaker Voice conversion. © 2007 IEEE  

In this paper, by using first-principle density functional theory (DFT) combined with non-equilibrium Green's function (NEGF), thermally induced spin current in zigzag and armchair Antimonene Nanoribbon (SbNR) is investigated. Also, we obtain higher spin current in Armchair nanoribbon (ANR) than zigzag nanoribbon (ZNR), because the start energy of transmission for ANR is closer to the Fermi level than ZNR. The results show that the device has a perfect spin Seebeck effect under temperature difference without gate voltage or bias voltage. For the ANR configuration, the competition between spin up holes and spin down electrons leads to negative differential behavior of charge current, which is...