Sharif Digital Repository

Conjugated linoleic acid (CLA) is one of the most physiological active fatty acids due to its positive effect on prevention of diseases such as obesity, hyperlipidemia, atherosclerosis and cancer. The aim of this study was to optimize the production of conjugated linoleic acid (CLA)% in alkali isomerization of safflower oil including 71% linoleic acid (LA) using response surface methodology (RSM). The effect of three reaction variables such as temperature, reaction time and amount of KOH on CLA production was investigated using design-expert software. The optimal condition determined at this point, 72% total CLA with the yield of 84% temperature reaction time and the amount of KOH were 187.6... 

Conjugated Linoleic Acid (CLA), Glycerol (G) and sunflower oil blends with varying concentration were subjected to enzymatic esterification using a 1, 3-specific immobilized lipase. CLA was used as acyl due to its purported health benefits. The transesterified lipids were evaluated for free fatty acids (FFA) and composition of fatty acids by gas chromatography. Lipozyme RM IM is preferred for enzymatic esterification because of more CLA incorporation and less free fatty acids at the end of reaction than Lipozyme TL IM. Response surface methodology (RSM) was used to determine the effects of three variables Glycerol concentration, reaction temperature, and amount of enzyme on the lipase... 

Conjugated Linoleic Acid (CLA) was produced from castor oil using washed cells of Lactobacillus plantarum PTCC 1058 and Lactobacillus plantarum subsp. plantarum PTCC1745 as the catalyst. Under the optimal reaction conditions, the washed cells of Lactobacillus plantarum PTCC1058 produced 1661.26 mg of CLA/L reaction mixture (36% yield of production) from 4.6 mg/ml of castor oil after using 15% (w/v) cell for 121 h. The resulting CLA was a mixture of two CLA isomers, cis-9, trans-11 (or trans-9, cis-11)-octadecadienoic acid (CLA1, 44% of total CLA) and trans-10, cis-12-octadecadienoic acid (CLA2, 46% of total CLA). The total production of CLA is extracellular in all of the reactions performed... 

Palm oil (PO) and sunflower oil (SFO) blends with varying proportions were subjected to enzymatic interesterification (EIE) using a 1,3-specific immobilised lipase. The interesterified blends were evaluated for their slip melting point (SMP), solid fat content (SFC) at 10-40°C, p-anisidine value, peroxide value, free fatty acids (FFA), induction period of oxidation at 110°C (IP110) and composition of fatty acids by gas chromatography. Under EIE treatment, the blends of PO and SFO in different proportions (20:80, 40:60, 50:50, 60:40 and 80:20) had saturated and unsaturated fatty acid content in the range of 37.6-52.0% and 48.0-62.4%, respectively. The blends showed a considerable reduction in... 

In this paper, the multiuser performance of a multicarrier frequency-hopping (MC-FH)CDMA system employing non-coherent detection is evaluated. We derive the bit error rate of the system for both uncoded and coded systems in AWGN and slowly frequency-selective Rayleigh fading channel, based on Gaussian distribution assumption for the decision variable. We use a practical low-rate convolutional error correcting code, which does not require any extra bandwidth further than what is needed by the uncoded scheme. Our numerical results indicate that the coded scheme significantly outperforms the uncoded scheme in both AWGN and fading channels. Furthermore, it is observed that the performance... 

In this paper, we evaluate and compare the multiuser performance of the multicarrier frequency-hopping (MCFH) CDMA system using coherent and non-coherent detections in AWGN and slowly frequency-selective Rayleigh fading channels in a downlink application. For fair comparison, we use BFSK modulation for both cases. Our numerical results indicate that in both AWGN and fading channels, the coherent detection sub-stantially outperforms the non-coherent detection. Furthermore, it has been realized that the performance enhancement due to the diversity order is only observable for coherent detection  

Data traffic is increasing in recent years and small cell densification is a promising solution for handling the consequences of this growth. However, it faces with backhual' constraint which limits its efficiency. Caching the popular files near to the small base stations (SBSs) is an effective technique which decreases usage of backhual links. In this paper, we model the network by a graph and propose a new popular files' placement based on graph coloring for which different powerful solutions and algorithms have been presented in the literature. In this respect, we propose an algorithm to fill the caches of SBSs with the popular files and show the efficiency of our proposed algorithm... 

Caching the popular files in the memories of small base stations (SBSs) is an effective solution to the limited capacity of wireless backhaul links. The efficiency of caching depends on the proper design of the content placement. This is more challenging when the SBSs have overlapped coverage and especially when the users are also mobile. In this letter, we exploit the concept of graph-coloring and model the connection between SBSs and users as well as user mobilities, through a weighted graph in which SBSs are its vertices, and propose some algorithms to color it effectively. Then, we fill the memory of colored SBSs with popular content accordingly. © 1967-2012 IEEE  

Employing femtocell technology noticeably improves both the indoor coverage and the overall cellular network's capacity. In the downlink scenario, when macrocell users (MUs) are far from the macro base station (MBS) and close to the femto access points (FAPs), the transmitted signals of FAPs to their users cause severe interference on MUs. One solution to overcome this issue is serving MUs by neighbouring FAPs. Generally femtocells are selfish and have no desire to allocate their resources to MUs. In this study, a framework to motivate femtocells to share their free resources with MUs is proposed. In this framework, the femtocells are assumed to belong to a specific unit. The unit encourages... 

Recently, caching of the popularity video files in the caches near to the users has been proposed as a promising way to reduce data traffic. These caches can be considered as the nodes which their transmission ranges are limited but have significant storage capacity and are known as the helper nodes. To evaluate the performance and efficiency of the caches, a suitable model for their distributions should be taken into account. Stochastic geometry is a useful tool for modeling these nodes. In this paper, the helper nodes and users are distributed according to the Poisson point process distribution. However, to manage the interferences and their access to a distributed cache, the helper nodes... 

The strengthening behavior of particle reinforced metal-matrix composites is primarily attributed to the dislocation strengthening effect and the load transfer effect. To account for these two effects in a unified way, a new multi-scale approach is developed in this paper incorporating the aspect ratio effect into the geometrically necessary dislocation strengthening relationships. By making use of this multi-scale approach, the deformation behavior of metal-matrix composites (MMCs) and metal-matrix nanocomposites (MMNCs) as a function of size, volume fraction, aspect ratio, etc. of the particles has been investigated. Comparison with the previously proposed models and the available... 

Traditionally, the frequency spectrum is licensed to users by government agencies in a fixed manner where the licensee has exclusive right to access the allocated band. However, with increasing demand for the spectrum and scarcity of vacant bands, a spectrum policy reform seems inevitable. Meanwhile, recent measurements suggest the possibility of sharing spectrum among different parties subject to interference-protection constraints. In order to enable access to an unused licensed spectrum, a secondary user has to monitor licensed bands and opportunistically transmit whenever no primary signal is detected. Spectrum-sharing between a primary licensee and a group of secondary users has been... 

In this paper, a decentralized controller for trajectory tracking of modular and reconfigurable robot manipulators is developed. The proposed control scheme uses joint-torque sensory feedback; also sliding mode control is employed to make both position and velocity tracking errors of robot manipulators globally converging to zero. Proposed scheme also guarantees that all signals in closed-loop systems will be bounded. In contrast to some of prior works in this scheme, each controller uses a smooth law to achieve its purposes. In this method, each controller uses only local information for producing control law hence separated controller can be used to control each module of manipulator and... 

The most important disadvantage of swinging interferometers is that the optical path difference created in them is a nonlinear function of the rotation angle. In this paper, two new swinging interferometers are presented which have good linearity and provide a larger path difference in response to the rotation angle compared to other interferometers. This makes them suitable for applications such as high-resolution spectroscopy, and precision micro and nanopositioning. In one of these two interferometers, the optical path difference is created by rotation of a system composed of four mirrors, and in the other one it is created by rotation of a system consisting of two mirrors. They are not... 

Rolling-element bearing (REB) failure is one of the general damages in rotating machinery. In this manner, the correct prediction of remaining useful life (RUL) of REB is a crucial challenge to move forward the unwavering quality of the machines. One of the main difficulties in implementing data-driven methods for RUL prediction is to choose proper features that represent real damage progression. In this article, by using the outcomes of frequency analysis through the Envelope method, the initiated/existed defects on the ball bearings are identified. Also, new features based on developing faults of ball bearings is recommended to estimate RUL. Early-stage faults in ball bearings usually...