International Journal of Engineering
Volume:27 Issue: 8, Aug 2014

In this study, the rheology of blood clot is measured with the help of rotational rheometer. Several shear strains (0.5, 1 and 2%) are applied with two frequencies (5 and 10 Hz) from the incipient time of clot formation and the response of the sample is measured in the form of shear stress and the phase lag which is interpreted with storage and loss moduli. In this study the ratio of loss to storage modulus is studied and the blood clot gel-point as the transition from viscoelastic fluid to viscoelastic solid is investigated. By increasing the frequency, “tan delta” decreases before the gel-point and increases after the gel-point which indicates the viscoelastic fluid and viscoelastic solid behaviour,respectively. Moreover, by increasing the shear strain, “tan delta” varies with lower rate at luidic stage (Ra1 and Ra3) and with higher rate at solid stage (Ra2 and Ra4). It is also shown that increasing the shear strain causes a delay on gel point formation.

A novel work was performed for fabrication and modification of composite nanofiltration (NF) membrane by polymerization reaction between polyethyleneimine (PEI) and triphthaloyldechloride (TPC). The main purpose of this work was water treatment. Polysulfone was the main polymer applied as substrate. The result of reaction between PEI and TPC was the formation of polyamide layer on the membrane surface. SiO2 nanoparticles were used as modification agent. The fabricated membranes were characterized by Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM), contact angle measurement and FTIR analysis. Removal ofMgSO4 as one of the dissolved salts in water was investigated and these fabricated membranes were utilized to remove MgSO4 from water. Properties of substrate in addition to properties of NF membrane such as steric-hindrance and Donnan exclusion led to a rejection of 89% for MgSO4.

Exceptional characteristics of cloud computing have replaced all traditional computing. With reduced resource management and without advance investment, it has been victorious in making the IT world to migrate towards it. Microsoft announced its office package as Cloud, which can prevent people moving from Windows to Linux. As this drift is escalating in an exponential rate, the cloudenvironment has alsobecome a target for attackers. Hence to acquire the best use of the cloud services, the security issues haveto be dealt with first. Among various security threats faced by the cloud environment, this paper focuses on the most dangerous one, Distributed Denial of Service attack, DDoS. In DDoS attack, a victim is targeted simultaneously by numerous hosts distributed across the network. An attacker compromises the vulnerable systems in the network and infects those systems with malicious code which can trigger these systems, called zombies, to send requests in huge numbers to choke the target. This type of attack can happen both at network as well as service level. Network level attack is achieved by sending simultaneous invalid or incomplete requests, whereas in service level attacks, the target will be flooded with complete request for services provided by the CSP, but with malicious intent. These two types of attack trafficshave to be filtered out at different levels. In this paper, a three phase authentication scheme, REputation based Service for Cloud User Environment (RESCUE) has been proposed that can help the cloud service provider to detect and mitigate both the aforesaid types of DDoS attacks. RESCUE, the proposed scheme authenticates the users in three different phases. The simulation results presented here exhibits the strength of the proposed method in detection and prevention of DDoS attack in cloud computing environment.

Many parameter-tuning algorithms have been proposed for training Fuzzy Wavelet Neural Networks (FWNNs). Absence of appropriate structure, convergence to local optima and low speed in learning algorithms are deficiencies of FWNNs in previous studies. In this paper, a Memetic Algorithm (MA) is introduced to train FWNN for addressing aforementioned learning lacks. In proposed MA, DifferentialEvolution (DE) is utilized as the global search. The main contributions of this paper aresummarized in three sections. (I) Proposing a new, fast and effective local search based on spatial distribution that is named Spatial Distribution Local Search (SDLS). SDLS can adjust the step size of movements toward better neighbor solutions adaptively. (II) Introducing a selection method to select appropriate individuals from current population for local refinement in MA. This property decreases the computational cost of MA and leads to tuning the local search frequency in an adaptive way. (III) Improving the selection operator in standard DE by an adaptive strategy. In this strategy, worse offspring has a chance to be replaced with its parent to prevent trapping in local optima and controlling the selection pressure. The proposed MA is compared with several training algorithms of FWNNs over some benchmark problems. Experimental results obtained, confirm the effectiveness of the proposed MA for improving the convergence rate and modeling accuracy in comparison to the other training methods.

The decision making on selection of improvement solutions was one of the obstacles hampering the success of process improvement. This paper presents the House of Improvement (HOI) model as a guideline to link decision criteria for the prioritisation of improvement solutions. Three phases in the HOI are applied to facilitate selection and to ensure that suitable and value-added solutions are chosen. Each phase includes procedures for identifying, evaluating, and analysing the elements by establishing a relationship matrix. The reliability of each relationship matrix will be tested in order to proceed to the next phase. The adopted matrices in the HOI serve as decision-making tools for analysing potential and critical problems in the production line, evaluating possible effects of the critical problems, and innovating on the necessary actions for the solution. Using a real-life case study, this paper demonstrates the applicability and suitability of the HOI model in providing prioritised solutions for production problems experienced by small and medium enterprises.

Third party service providers locate logistic hub for operating their tasks. Finding a proper location helps them to have better performance in the competitive environment. Multiple characteristics of proper location selection faces the decision maker to have a multi criteria decision making problem. Since the location decision is a long term planning, the robustness of the decision is getting more highlighted so we applied a statistical based decision making approach to reduce uncertainty effect. Hub facilities are reducing the serving cost due to economies of scale. In this paper, in order to enhance such effect we applied the clustering analysis to find similar regions by consideration of different characteristics. The approach is implemented in an Iranian case study and the validity of the approach is investigated.

Strategic planning in each organization identifies its orientation and coming priorities as all decisions to be adopted respect to the ensuing outcomes. Strategic decisions considering crucial and irreversible results should not be based on experience and judgments. This paper uses analytic network process (ANP) method for prioritization in strategic planning. ANP is mostly analogous to analytic hierarchical process (AHP) with the only difference that the latter takes into account no interdependence between criteria and hierarchal levels, but the former does. The interpretations of the experts of the Iran’s Trade Promotion Organization''s (TPO), internal and external factors have determined Strength and Weakness points, opportunities and threats (SWOT) as well as their internal communications. After all, the appropriate strategies are defined and prioritized. In this paper, as a result, prioritization of strategies using AHP and ANP methods yield different results and to judge appropriately, the necessity of surveying relationships among criteria is indicated.

This paper proposes a mixed integer programming model for single-item capacitated lot sizing problem with setup times, safety stock, demand shortages, outsourcing and inventory capacity. Due to the complexity of problem, three meta-heuristics algorithms named simulated annealing (SA), vibration damping optimization (VDO) and harmony search (HS) have been used to solve this model. Additionally, Taguchi method is conducted to calibrate the parameters of the meta heuristics and select the optimal levels of the algorithm’s performance influential factors. Computational results on a set of randomly generated instances show the efficiency of the HS against VDO and SA.

We consider competition between two decentralized supply chain networks under demand uncertainty. Each chain consists of one risk-averse manufacturer and a group of risk-averse retailers. These two chains present substitutable products to the geographical dispensed markets. The markets’ demand is a function of prices, service levels and advertising efforts of two chains. We formulate the distribution design problem of two rival chains as a two-person nonzero sum game theoretical model. Since strategic decisions of distribution network design often have priority over tactical ones, we first calculate the equilibrium of tactical decisions for each pair of distribution design scenarios and according to the presented methodology, we find Nash equilibrium solutions of distribution network scenarios for two rival chains. Eventually, to illustrate the real applications of the methodology, a numerical example is presented and analyzed.

There are many factors in coatings process which are effective in changing coatings characteristic such as voltages, duty cycle, pressure, temperatures and gas flux. In this paper, in plasma enhanced chemical vapor deposition (PECVD) technique, temperature and gas flux are two important variants which affect the coatings structure and mechanical properties. All TiC coating deposited on a hot work tool steel (H13) had a thickness of 2-3 micrometer. The investigation of TiC coatings composition and structure were done with the grazing incidence XRD, the FTIR (Fourier Transformation Infrared Spectroscopy) and the Field Emission Scanning Electron Microscopy (FE-SEM). The mechanical properties of the coatings, such as hardness, wear resistance and surface roughness were studied with Vickers hardness indentation; pin on disk wear tests and atomic force microscopy, respectively. The best mechanical properties such as a high hardness (3100 VHN), wear resistance and fracture toughness (11.3MPa. m1/2) and low surface roughness (18 nm) were related to the coating which was deposited in 450°C.

An experimental investigation was carried out to study mixed convection heat transfer from Al2O3- water nanofluid inside a vertical, W-shaped, copper-tube with uniform wall temperature. The tests covered different ranges of some involved parameters including Reynolds number, temperature and particles volume fraction. The results showed that the rate of heat transfer coefficient improved with Reynolds number for average wall temperatures of 50 and 60ºC. Additionally, the heat transfer coefficient increased slightly with an increase of the Reynolds number. Interestingly, the pressure drop of nanofluid was very close to that of base fluid. Besides, a new correlation was proposed to calculate the Nusselt number in W-shaped tubes.

In the present study, there is a need to reduce the consumption of conventional fuel and related fossil fuels. So, in order to promote the use of renewable sources such as biofuels there is a requirement for the effective evaluation of the performance of engines based on the second law of thermodynamic. In this paper, the analysis of energy, exergy, mean gas temperature and exhaust gas temperature of a compression ignition (CI) engine using diesel and Karanja methyl ester blends are done. The results are calculated at various compression ratios under full load and at different engine loads at a compression ratio of 18:1. It is observed that the exergy efficiency, mean gas temperature, brake thermal efficiency increases with increase in compression ratio as well as load. The exhaust gas temperature and destruction of exergy decreases with increase in compression ratio and increases with increase in load for all blends of fuel.

The mathematical modeling of a gas network is a powerful tool for identifying the behavior of system under different conditions. The modeling can be performed both for the steady state and unsteady state conditions. It is possible to use the fluid flow basic governing equations or the electrical analogy concept for developing the model. The second approach provides a simpler and more robust model, especially in large networks with different and numerous components. In this study, this approach has been used for studying the steady state behavior of a sample gas distribution network. The model is verified by comparing its results with some existing experimental and numerical data. The comparison shows a very good agreement between the two results.

In this study, generalized differential quadrature analysis of elastic/plastic buckling of skew thin plates is presented. The governing equations are derived for the first time based on the incremental and deformation theories of plasticity and classical plate theory (CPT). The elastic/plastic behavior of plates is described by the Ramberg-Osgood model. The ranges of plate geometries are 0.5 £ a/b £ 2.5 and 0.001 £ h/b £ 0.05 under uniaxial uniform compression or biaxial compression/tension. Generalized differential quadrature (GDQ) discretization rules in association with an exact coordinate transformation are simultaneously used to transform and discretize the equilibrium equations and the related boundary conditions. The accuracy of the results are compared with previously published results. Finally, the effects of aspect, loading and thickness ratios, skew angle, incremental and deformation theories and different types of boundary conditions on the buckling coefficient are presented. Moreover, the effect of skew angle and thickness ratio on the convergence and accuracy of the method are studied. Due to the lack of published solutions for plastic buckling of skew thin plates and the high accuracy of the present approach, the solutions obtained may serve as benchmark values for further studies.

Tensile stress-strain curve is of high importance in mechanics of materials particularly in numerical simulations of material deformations. The curve is usually obtained by experiment, but is limited by the necking phenomenon. Engineering stress-strain curve is converted to true stress- strain curvethrough simple formulas. The conversion, however, is correct up the point of necking. From this point on, the curve should be corrected taking account of stress triaxiality. Over the past several decades, a number of methods such as Bridgeman correction technique have been proposed. In this investigation a new technique based on strain energy in introduced. Strain energy is assumed to be equal to the external work in tensile test. The energy method is compared with different approaches such as Bridgeman-Leroy, Bridgeman, Davidenkov, Siebel and optimization aided numerical simulation. The results indicate that the energy method prediction is very close to numerical simulation, but at the same time it does not differ too significantly from the other approaches studied in this investigation.

The possibility of using flat plate collector in northern parts of Iran specially city of Rasht has been investigated in this paper. Due to the high humidity in the northern parts of this country, diffuse radiation plays a more important role than direct radiation. This fact can change the results of delivered solar energy and the best tilt angle of the collector compared to the sunny central cities. Therefore, maximum solar energy based on the best tilt angle is calculated first. Relative to the horizontal collector, changing the tilt angle, the daily, monthly, seasonally and yearly delivered solar energy increases16.58%, 15.84%, 15.31% and 10.79%, respectively. Then, the steady state two dimensional equation of conduction for the collector plate has been solved to obtain the length of the collector required for heating the water to a desired temperature20 meters of a typical collector 10 numbers) increases the water temperature to 66 and 85˚C in the months December and September, respectively. Mean efficiency of the collectors decreases with increasing the temperature of inlet water. That is, the efficiency of the first and tenth collectors is approximately 60% and less than 10% respectively.

Energy absorbers are used to reduce accident induced damages. Thin-walled energy absorbers are widely used in modern industries due to their high efficiency and ease of manufacturing. In this study, thinwalled stainless steel structures in quasi-hemisphere geometry were subjected under quasi-static loading using Santam 150KN apparatus. Experimental results were compared with the results of numerical simulations by LS-DYNA and it was shown that there is a good agreement between experimental and numerical results. Two different collapse types in radial and circumferential directions were observed. Also, the multi-cell quasi-hemisphere specimens from 3 to 6 cells were numerically investigated and it is observedthat increasing the number of cells increases the absorbed energy. Increasing the thickness of the quasi-hemisphere sample in smaller diameter specimens is more effective. The results showed that Sixcell specimen with the largest diameter and the minimum thickness has the most increase of Specific Absorbed Energy (SAE) with respect to simple section.

This paper focuses on effect of abrasion process on color change and reflectance factor of dyed woven fabrics containing 100% acrylic chenille yarns in weft and cotton warp yarns. Three fabrics having 12, 14 and 16 weft per centimeter were dyed with three dyes in different hues i.e. C.I. basic yellow12, C.I. basic blue41, and C.I. basic red46. Four different abrasion levels, i.e. 50,200,400 and 650 were selected to abrade samples. The results show that abrasion of samples leads to decrease of reflectance factor and increase of color change up to specific levels of abrasion, although this variation was not the same for different hues and weft densities. It was found that reflectance factor and color change of fabrics that have higher weft density were more affected by abrasion at all abrasion levels. Finally analysis of variance and multiplr linear regression was performed at 95% confidence level. According to multiple linear regression models weft density had the most dominant effect on reflectance factor. Moreover, number of abrasion cycle was the most significant parameter on color change of chenille woven fabrics. The R2-value of regression model of color change, and reflectance factor, was 0.897, 0.963 respectively, which confirms the good fitness of proposed models.