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Alumina-titanium composites have shown good mechanical properties which makes them promising for orthopedic applications. The placement of an orthopedic implant involves an invasive procedure which stimulates a localized inflammatory response causing an acidic environment around the implant. This makes the study on corrosion more critical. Therefore, the aim of the present paper was to study the corrosion behavior of the composites with 75 vol% and 50 vol% Ti content (with alumina balance) fabricated by Spark Plasma Sintering under acidic condition representing inflammation and in two elapsed times (1 h and 1-day) using polarization and electrochemical impedance spectroscopy tests. For comparison, the experiments were also conducted in normal physiological solution after 1 h, and pure Ti (100vol%Ti) was fabricated by the same process and analyzed, similarly. Furthermore, behavior of the samples was studied after 48 days of immersion in the acidic and normal solutions using SEM, ATR-FTIR, AFM, and ICP-OES. The results of corrosion tests showed very good passivation behavior of 100vol%Ti and the composite containing 75vol.%Ti. The superiority of the 75vol.%Ti composite in corrosion characteristics in both solutions was also found. Its corrosion resistance was 20.3 MΩcm

Biomaterials are continuously being developed to overcome the drawbacks of existing materials and provide improved function in artificial organs. Currently Co-Cr based alloys are used in many medical applications such as hip and knee implants which still require modification to better perform. In this article, therefore, the influence of tungsten allying element on electrochemical corrosion resistance and biocompatibility behaviour of a recently developed Co-30Cr-4Mo-1Ni alloy composition were investigated. The tungsten modified alloys were prepared by using a high temperature vertical vacuum casting technique at five different weight percentages (0-4wt.% tungsten). The electrochemical corrosion behaviour of all the samples under NaCl solution was studied by using potentiodynamic scan method. The corrosion characteristics were investigated in terms of corrosion potential (Ecorr) and corrosion current density (Icorr). From the results of the analysis, it was observed that out of all samples, an alloy with 2wt.% of tungsten in composition (i.e. Co-30Cr-4Mo-1Ni-2W) exhibited better corrosion resistance. Furthermore, histopathological evaluations in subcutaneous tissue were performed in rats according to the standard ISO 10993 to examine the biocompatibility of the prepared samples. The results showed no evidence of inflammatory cell migration, no epidermal necrosis, no vacuolar degeneration of basal cell, no adnexal atrophy and vesicle formation of any samples. The obtained findings indicate that Co-30Cr-4Mo-1Ni-2W can be used in biomedical applications including femoral component of hip and knee implants.

Microbiological screening of tissue allografts is crucial to prevent the transmission of bacterial and fungal infections to transplant recipients. Klebsiella was the most prevalent and resistant contaminating microorganism observed in our setting in the Iranian Tissue Bank. This study was conducted to determine the presence of extended-spectrum β-lactamase (ESBL) genes, antimicrobial resistance patterns of Klebsiella pneumoniae isolates, and their clonal relationships in allograft materials. K. pneumoniae contaminating bone and other tissue allografts recovered from deceased donors were identified and ESBL isolates were detected using a phenotypic confirmatory method. Antimicrobial susceptibility testing was carried out using the disk diffusion method. Distribution of ESBL genes and molecular typing were performed using polymerase chain reaction (PCR) and Repetitive-element (rep-PCR) methods. Of 3828 donated tissues, 51 (1.3%) were found contaminated by K. pneumoniae isolates. Compared to tissue allografts from brain-dead, heart-beating tissue donors, allografts from donors with circulatory cessation were associated with a higher risk of K. pneumoniae contamination [odds ratio (OR), 1.2 (CI 95% 0.9–2.3) (P value < 0.001)]. Half of the isolates produced ESBL, and the rate of susceptibility to cephalosporins was 51%. Among isolates, 22 (43.1%) harbored CTX-M, 31 (60.8%) SHV, and 9 (17.6%) harbored TEM types. The rep-dendrogram indicated that clones having identical or related strains with a similar antibiotype were isolated in the same period. This study provides evidence that a single clone of K. pneumoniae contaminated tissue allografts recovered from many different donors. A single clone found on tissues from several donors suggests contamination of tissues from a single source such as the tissue recovery process and environment. Genomic DNA testing and clonality of contaminating bacteria using molecular methods can focus the epidemiologic investigation on the tissue allograft recovery process including a search for contamination of the tissue recovery room environment, recovery staff, recovery equipment, reagents, solutions and supplies.

The trend in biomaterials development has now headed for tailoring the properties and making hybrid materials to achieve the optimal performance metrics in a product. Modern manufacturing processes along with advanced computational techniques enable systematical fabrication of new biomaterials by design strategy. Functionally graded materials as a recent group of hybrid materials have found numerous applications in biomedical area, particularly for making orthopedic prostheses. This article, therefore, seeks to address the following research questions: (RQ1) What is the desired structure of orthopedic hybrid materials? (RQ2) What is the contribution of the literature in the development of hybrid materials in the field of orthopedic research? (RQ3) Which type of manufacturing approaches is prevalently used to build these materials for knee and hip implants? (RQ4) Is there any inadequacy in the methods applied?

Objective: An appropriate psychological intervention to promote the level of the psychological health of patients with a coronary heart has a great importance. The principal intention of the current study was to study the efficacy of the behavioral-cognitive group therapy on the quality of life of the cases with a coronary heart illness. Method: The current research was a quasi-test via posttest-pretest that was used by the checking team. Hence, 24 patients with coronary heart disease were selected by using the convenience sampling technique and were placed in experimental and control groups in Shahid Rajaee Heart Center in Tehran. Both groups were pretested by using a demographic questionnaire and a quality of life questionnaire. Afterwards, the experimental group trained for eight sessions of cognitive-behavioral group therapy, and the control group gained no interference. Later, both groups were post-tested, and the acquired information was examined by using inferential and descriptive statistical methods accompanied by SPSS 21 software. Findings: The results indicated that the cognitive-behavioral group therapy training significantly increases the quality of life of cases with coronary heart problems. Conclusion: The conclusions of the existing research were that due to the high level of the effectiveness of the cognitive-behavioral group therapy training, its low cost and high acceptability by the patients, especially when it was performed in a group, it had a significant positive impact on the enhancement of the quality of life in cases of coronary heart illness.

Objective: an appropriate psychological intervention to promote the level of the public health and mental well-being of nurses has a great importance. This investigation was aimed to study the effectiveness of stress management training on the psychological welfare of nurses in Imam Khomeini Hospital. Methodology: this study was quasi-experimental with pretest-posttest that used a control group. Hence, 40 of the nurses in Imam Khomeini Hospital were selected by using a convenience sampling method and placed in the experimental group and the control group. Both groups were pretested by using psychological well-being 84-question scale. Afterwards, the experimental group was trained for ten sessions under stress management skill exercise, and the check group got no intervention. Next, both societies were post-tested, and the acquired data were analyzed by using inferential and descriptive statistical methods accompanied by SPSS 21 software. Findings: the results indicated that stress management training significantly led to the promotion of psychological well-being in nurses (p < 0.001). Conclusion: it was found from the research that due to the high level of effectiveness of stress management training, its low cost, and its high acceptability by the patients, especially when it was performed in a group, had a significant positive impact on the promotion of psychological well-being in nurses.

Orthopaedic prostheses still suffer from limited lifetime which imposes revision surgery with the associated risks involved. This, to some extent, is related to the vulnerability of the biomaterials used for their fabrication that are commonly single-constituent and uniform. Therefore, hybrid biomaterials such as composites and functionally graded materials (FGMs) are being developed to overcome the shortcomings of available biomaterials. The present paper focuses on the study of the structural, physical and mechanical properties of a FGM made of alumina-titanium fabricated by spark plasma sintering (SPS). The corresponding composites of the individual FGM layer were also fabricated. After sintering, the structural, mechanical and physical tests were carried out. The microstructural analysis using X-ray diffraction revealed the presence of Ti

One of the most important tools for improving the relative efficiencies of any organization is to establish suggestion system. Having a reliable system, which could reflect all employees’ comments and concerns, helps managers take necessary actions to remove any possible obstacle in the system. In this paper, we measure efficiency and effectiveness of suggestion system in the National Iranian Oil Products Distribution. We also provide practical suggestions for improvement and necessary actions required to review the system. The proposed study of this paper uses a sample of 297 people from 1294 employees who work in different position for some of the regional offices of this firm in north part of Iran. The study has used two separate questionnaires, where the first one consists of 40 questions in Likert scale trying to measure the efficiency and effectiveness of the suggestion system. In addition, we use another questionnaire to rank important factors detected in the first stage. The results of questionnaires have been analyzed using different statistical tests.

Article history: Received May 14, 2012 Received in Revised form June, 26, 2012 Accepted 2 August 2012 Available online August 9 2012 Performance measurement plays an essential role on management of governmental agencies especially when profitability is not the primary concern and we need to consider other important factors than profitability such as customer satisfaction, etc. In this paper, we propose a multi-criteria decision making method to rank different national Iranian oil refining and distribution companies. The proposed study of this paper uses six factors including per capita supply, energy cost, physical productivity of labor, staff participation, quality control inspection of stations and education per capita. The proposed study uses Entropy to find the relative importance of each criterion and TOPSIS to rank 37 alternatives based on cities and three regions. The results of the implementation of our method indicate that central regions close to capital city of the country maintains the highest ranking (0.9122) while southern regions maintains the lowest comes in the lowest priority (0.0569) and the northern region is in the middle (0.7635). © 2012 Growing Science Ltd. All rights reserved.

The chemical composition of the volatile fraction obtained by head-space solid phase microextraction (HS-SPME), single drop microextraction (SDME) and the essential oil obtained by cold-press from the peels of C. sinensis cv. valencia were analyzed employing gas chromatography-flame ionization detector (GC-FID) and gas chromatography-mass spectrometry (GC-MS). The main components were limonene (61.34 %, 68.27 %, 90.50 %), myrcene (17.55 %, 12.35 %, 2.50 %), sabinene (6.50 %, 7.62 %, 0.5 %) and ?-pinene (0 %, 6.65 %, 1.4 %) respectively obtained by HS-SPME, SDME and cold-press. Then a quantitative structure-retention relationship (QSRR) study for the prediction of retention indices (RI) of the compounds was developed by application of structural descriptors and the multiple linear regression (MLR) method. Principal components analysis was used to select the training set. A simple model with low standard errors and high correlation coefficients was obtained. The results illustrated that linear techniques such as MLR combined with a successful variable selection procedure are capable of generating an efficient QSRR model for prediction of the retention indices of different compounds. This model, with high statistical significance (R2 train = 0.983, R2 test = 0.970, Q2 LOO = 0.962, Q2 LGO = 0.936, REP(%) = 3.00), could be used adequately for the prediction and description of the retention indices of the volatile compounds.

Designing mostly involves complex problem-solving and the need to consider many different options. Design support tools facilitate the process of obtaining optimum solutions such as the most appropriate choice of material for the component of a product. Multi-criteria decision-making (MCDM) methods are useful when multi-criteria need to be considered simultaneously. MCDM can be further categorized as multi-objective decision-making, usually appropriate for design problems, and multi-attribute decision-making that typically fits better to materials selection problems. The strategic combination of materials science and computational modeling and analysis plays a key role in evaluating the performance metrics necessary to support materials selection and design.

The screening methods available for materials selection range from simple manual procedures to sophisticated computer-based packages, as either stand-alone, or linked to materials’ properties databases, or integrated with other design support tools. Of all the current methods available, the most popular way of screening materials is via the use of materials selection charts (the so-called “Ashby” method). The charts allow a direct comparison to be easily made between different material properties, or a limited combination of material properties, via the use of performance indices. Multi-criteria decision-making techniques can also be applied when a large number of materials’ selection criteria need to be considered simultaneously.

During the design process for a product, materials are either selected or designed to meet the desired requirements. In material selection the outcome is that typically the ideal solution is not always chosen. Also, because of the conflicting nature of materials characteristics, improvement of material properties usually does not meet the expected requirements, hence material design benefits from multi-objective optimization. However, despite the complexity, the final product can benefit from simultaneous material and structural optimization.

Multi-Criteria Decision-making (MCDM) has the potential for improving all areas of decision-making in engineering, from design to manufacture, but is especially beneficial for applications in high technology market sectors, where product differentiation and competitive advantage are often achieved by just very small gains in material performance. The full capability of MCDM methods are realized by their ability to simultaneously consider material, process, and shape for complex materials selection problems. It is essential therefore to expand the scope of MCDM methods to a wide range of engineering applications and feedback the experience to improve materials selection. The need to handle uncertainty and make compromises are recurring practical design issues and the effective manipulation of data ranges is critical to more effective use of MCDM in materials selection and design. The selection of more advanced materials, and materials with tailored properties, particularly composites and multi-functional materials, is a significant area that is beginning to take advantage of MCDM. With the current emphasis on materials design and modeling, it is desirable in future versions of computer simulation software to include multi-criteria analysis capability.

The selection of materials at all stages of the product design process requires effective decision-making. The nature of the problem is both complex and varying from having to consider a large number of available materials and vague information in the early design stages to a small number of acceptable materials and detailed information in the later design stages. The inclusion of hybrid materials and newly developed materials although offering the potential of enhanced performance can further exacerbate the problem. To fully satisfy the design requirements, decision-making support is essential to correctly select the most appropriate design, materials, and manufacturing processes in the design and development of new engineering products.

Ten detailed practical examples, or case studies, have been chosen to explain and impart a better understanding of the methods described in the previous chapters. The first example describes the problem of selecting materials for a hip joint prosthesis, which includes target criteria. The process of obtaining three types of weightings, ranking with comprehensive VIKOR and extended TOPSIS methods, and the aggregation process for optimal materials selection has been exhibited in this example. The second example, which includes the target value of criteria as well as interval data in some criteria, describes the problem of selecting materials for the femoral component of a total knee replacement. The third to fifth examples are all related to materials selection and design of knee prostheses. The third example is the design and multi-objective optimization of a functionally graded material for the femoral component of knee prosthesis. The fourth example deals with materials selection and design optimization problem, and the fifth example is a simultaneous material and design selection problem, while demonstrating the role of quality function deployment (QFD) in design decision-making. The sixth example is a typical engineering problem, selecting materials using interval data, in this case to repair aircraft structures. The seventh example uses a mechanical turnbuckle assembly to introduce the concept of multiple component materials selection. In addition, it tries to reveal cost uncertainty in the early stages of the design process. The eighth example explains the place of multiple attribute decision-making (MADM) in the lightweight design of a thin-walled tube for the energy absorption structure in a motorcar. A strategy for decision-making, in the presence of a difference between physical and simulation experiments, is also highlighted in this example. The ninth example describes the use of fuzzy MADM when selecting materials for a motorcar dashboard. The last example discusses selecting hard coating materials to resist wear.

Multi-Attribute Decision-Making methods have become accepted for determining the choice of materials when the “lowest price” approach does not realize the optimum result. These methods are especially useful for high technology markets, where product differentiation and competitive advantage are often achievable with just small gains in material performance. The strategy of applying objective and subjective weightings for all types of criteria is described in materials selection as well as a method to incorporate them. The whole process for optimal decision-making in materials selection includes selecting the proper ranking method, as well as the aggregation method for situations when there are a lot of similar alternatives. As a result, a systematic approach to optimal materials selection is explained that will be beneficial to materials engineers and designers.

Satisfying consumers in all expected quality dimensions is the major challenge in product design. In the integrated chain of actions for developing new, or improving existing products, creativity is considered to be essential. The process of selecting the best material to fulfill the desired requirements deals with a lot of trade-offs. An increased requirement for the production of high-quality products implies the need to use modern approaches for modeling and analyzing customer expectations as well as contemporary computing facilities for supporting decision-making about the selection of materials, processing and design. Applying lean design principles in the material design/selection phase can help in better translating the customer’s requirements, cost saving goals, faster time-to-market, increasing quality, and innovating industries.

We report on a study of the Tehran Price Index (TEPIX) from 2001 to 2006 as an emerging market that has been affected by several political crises during the recent years, and analyze the non-Gaussian probability density function (PDF) of the log returns of the stocks' prices. We show that while the average of the index did not fall very much over the time period of the study, its day-to-day fluctuations strongly increased due to the crises. Using an approach based on multiplicative processes with a detrending procedure, we study the scale-dependence of the non-Gaussian PDFs, and show that the temporal dependence of their tails indicates a gradual and systematic increase in the probability of the appearance of large increments in the returns on approaching distinct critical time scales over which the TEPIX has exhibited maximum uncertainty., Comment: 5 pages, 5 figures. Accepted to appear in IJMPC

We propose a method for analyzing the data for the rates of exchange of various currencies versus the U.S. dollar. The method analyzes the return time series of the data as a Markov process, and develops an effective equation which reconstructs it. We find that the Markov time scale, i.e., the time scale over which the data are Markov-correlated, is one day for the majority of the daily exchange rates that we analyze. We derive an effective Langevin equation to describe the fluctuations in the rates. The equation contains two quantities, D ð1Þ and D ð2Þ , representing the drift and diffusion coefficients, respectively. We demonstrate how the two coefficients are estimated directly from the data, without using any assumptions or models for the underlying stochastic time series that represent the daily rates of exchange of various currencies versus the U.S. dollar. r 2007 Elsevier B.V. All rights reserved.

The AutoRegressive Conditional Heteroskedasticity (ARCH) and its generalized version (GARCH) family of models have grown to encompass a wide range of specifications, each of them is designed to enhance the ability of the model to capture the characteristics of stochastic data, such as financial time series. The existing literature provides little guidance on how to select optimal parameters, which are critical in efficiency of the model, among the infinite range of available parameters. We introduce a new criterion to find suitable parameters in GARCH models by using Markov length, which is the minimum time interval over which the data can be considered as constituting a Markov process. This criterion is applied to various time series and its results support the known idea that GARCH(1, 1) model works well.

The purpose of this article is to investigate the effect of overvalued equity on the relationship between audit quality and earning quality. In this article audit firm size, auditor industry specialization and auditor tenure were used as audit quality variable. The sample population consists of 189 companies listed in Tehran stock Exchange during the period 2008 to 2012. To test the hypotheses, OLS in Eviews has been used and investigation method of data is panel. The results show a reverse relationship between all audit quality variables and absolute discretionary accruals indicating that high audit quality causes higher earning quality. But the existence of overvalued equity cause decreasing or reversing of these relationships, in other words, when a firm is highly valued the accruals’ decreasing effect of high quality auditors is reduced.

Contact pressure in the knee joint is a key element in the mechanisms of knee pain and osteoarthritis. Assessing the contact pressure in tibiofemoral joint is a challenging mechanical problem due to uncertainty in material properties. In this study, a sensitivity analysis of tibiofemoral peak contact pressure to the material properties of the soft tissue was carried out through fractional factorial and Box-Behnken designs. The cartilage was modeled as linear elastic material, and in addition to its elastic modulus, interaction effects of soft tissue material properties were added compared to previous research. The results indicated that elastic modulus of the cartilage is the most effective factor. Interaction effects of axial/radial modulus with elastic modulus of cartilage, circumferential and axial/radial moduli of meniscus were other influential factors. Furthermore this study showed how design of experiment methods can help designers to reduce the number of finite element analyses and to better interpret the results.

We study localization of elastic waves in two-dimensional heterogeneous solids with randomly distributed Lam�� coefficients, as well as those with long-range correlations with a power-law correlation function. The Matin-Siggia-Rose method is used, and the one-loop renormalization group (RG) equations for the the coupling constants are derived in the limit of long wavelengths. The various phases of the coupling constants space, which depend on the value $��$, the exponent that characterizes the power-law correlation function, are determined and described. Qualitatively different behaviors emerge for $��1$. The Gaussian fixed point (FP) is stable (unstable) for $��1$). For $��, 13 pages, 4 figures

These days smart phones have changed the concept of mobile platform. Due to rapid growth in affordability, increased sensory and computational power has opened the ways for some interesting applications like activity recognition, gaming, navigation/tracking, augmented reality etc. In all these applications orientation of mobile phone is very important, once we know the correct orientation of the device, it becomes easy to develop such applications. Orientation can be determined by sensor fusion of accelerometer and magnetometer but it provides good accuracy as long as device is stationary or not moving linearly and also it suffers from surrounding magnetic interference. Orientation estimation systems often use gyroscope to increase reliability and accuracy. Although gyroscopes provide a quick response to change in angles and do not have problems like interference, they suffer from bias and integration errors which introduce drift in signal. In this paper an efficient and less complicated approach is utilized which minimizes the drift and noise in output orientation. In most of smart phone navigation applications these days, it is assumed that mobile is at fixed position like holding in hand facing forward, in trouser/jacket pocket or attached to waist. But if we assume that mobile position is changing arbitrary then situation becomes complicated. The goal of this work is to find accurately the direction of movement of a pedestrian while holding mobile in any position. In this work an accelerometer based approach is presented for pedestrian direction of movement estimation.

These days, most of the smartphones come with integrated MEMS (Microelectromechanicalsystems) sensors like accelerometer, magnetometer, gyros etc. It has opened the ways to use them for location based applications. The big advantage of these sensor based navigation system is that they are environment independent in contrast to other existing positioning technologies. A lot of work is already done on fixed position sensor based systems where sensors are either attached to foot or belt. This work is focussed on developing a smartphone based pedestrian dead reckoning (PDR) system. The big issue with smartphone’s sensor based PDR system is that the position of mobile is not deterministic in contrast to fixed position inertial measuring unit. In this work, three different modes of smartphone placement (Idle, Handheld and Listening) are investigated and accelerometer and magnetic sensors are used for step detection and heading determination respectively. Various step detection and stride length estimation methods are implemented and a comparison is given at the end.

We use drift and diffusion coefficients to reveal interactions between different oscillatory processes underlying a complex signal and apply the method to EEG delta and theta frequencies in the brain. By analysis of data recorded from rats during anaesthesia we consider the stability and basins of attraction of fixed points in the phase portrait of the deterministic part of the retrieved stochastic process. We show that different classes of dynamics are associated with deep and light anaesthesia, and we demonstrate that the predominant directionality of the interaction is such that theta drives delta.

We use drift and diffusion coefficients to reveal interactions between different oscillatory processes underlying a complex signal and apply the method to EEG delta and theta frequencies in the brain. By analysis of data recorded from rats during anaesthesia we consider the stability and basins of attraction of fixed points in the phase portrait of the deterministic part of the retrieved stochastic process. We show that different classes of dynamics are associated with deep and light anaesthesia, and we demonstrate that the predominant directionality of the interaction is such that theta drives delta.

Based on extensive new numerical simulations, we show that Chu's arguments and objections against our previous results are invalid. In addition, we explain the origin of the differences between our results and the previous ones, obtained based on a simple model of one-dimensional disordered materials.

We consider two coupled phase oscillators in the presence of proportional ("common") and independent white noises. The global synchronization properties of the system are analytically studied via the Fokker-Planck equation. When the "effective coupling" is big compared to the common noises, the former favors and the latter hinder synchronization. On the contrary, when the coupling is small compared to the proportional noises, we find that the latter induce synchronization, optimally when their intensities are big and in the n:m synchronization ratio. Furthermore, in such case a small value of the coupling is better for synchronization. Finally, we show that synchronization, which is a global property, must not be studied via local stability such as with Lyapunov exponents., Comment: 5 pages, 4 figures, revtex. Added an example that shows that synchronization, which is a global property, must not be studied by means of a local stability analysis such as via Lyapunov exponents. Other changes of medium importance were made as well

Markovian analysis is applied to derive nonlinear stochastic equations for the reconstruction of heart rate and respiration rate variability data. A model of their 'phase' interactions is obtained for the first time, thereby gaining new insights into the strength and direction of the cardiorespiratory phase coupling. The reconstructed model can reproduce synchronisation phenomena between the cardiac and the respiratory systems, including switches in synchronisation ratio. The technique is equally applicable to the extraction of the multi-dimensional couplings between many interacting subsystems.