Extremal basic frequency of non-homogeneous plates

In this paper we propose two numerical algorithms to derive the extremal principal eigenvalue of the bi-Laplacian operator under Navier boundary conditions or Dirichlet boundary conditions. Consider a non-homogeneous hinged or clamped plate $\Omega$, the algorithms converge to the density functions on $\Omega$ which they yield the maximum or minimum basic frequency of the plate

Damage characterization of aircraft fuselage using vibrothermography technique-review and analysis

Vibrothermogrphy is a promising non-destructive technique that uses ultrasonic elastic waves to detect damages and is typically applied in the aerospace and automotive industries. This technique allows for defect selective imaging using thermal waves that are generated by ultrasound waves. In this paper, vibrothermography technique was applied to the aircraft fuselage to detect its damage. The influence of the damage on the temperature distribution at the damage region on the aluminum was investigated by finite element technique. Comprehensive understanding in edge crack in fuselage heating caused by local friction between crack surfaces was obtained

3D TEXTILE PREFORMS AND COMPOSITES FOR AIRCRAFT STRCUTURES: A REVIEW

Over the last decades, the development of 3D textile composites has been driven the structures developed to overcome disadvantages of 2D laminates such as the needs of reducing fabrication cost, increasing through-thickness mechanical properties, and improving impact damage tolerance. 3D woven, stitched, knitted and braided preforms have been used as composites reinforcement for these types of composites. In this paper, advantages and disadvantages of each of them have been comprehensively discussed. The fabric architects and their specification in particular stitched preforms and their deformation mode for aerospace applications have been reviewed. Exact insight into various types of damage in textile preforms and composite that have the potential to adversely affect the performance of composite structure along with their inspection using NDT techniques have been elaborated. The research review reported in this paper can be very valuable to researchers to release the 3D composite behaviour under different loading conditions and also to get familiar with the manufacture of high quality textile composite for aircraft structures

Imperfection-Aware Design of CNFET Digital VLSI Circuits

Carbon nanotube field-effect transistor (CNFET) is one of the promising candidates as extensions to silicon CMOS devices. The CNFET, which is a 1-D structure with a near-ballistic transport capability, can potentially offer excellent device characteristics and order-of-magnitude better energy-delay product over standard CMOS devices. Significant challenges in CNT synthesis prevent CNFETs today from achieving such ideal benefits. CNT density variation and metallic CNTs are the dominant type of CNT variations/imperfections that cause performance variation, large static power consumption, and yield degradation. We present an imperfection-aware design technique for CNFET digital VLSI circuits by: 1) Analytical models that are developed to analyze and quantify the effects of CNT density variation on device characteristics, gate and system levels delays. The analytical models, which were validated by comparison to real experimental/simulation data, enables us to examine the space of CNFET combinational, sequential and memory cells circuits to minimize delay variations. Using these model, we drive CNFET processing and circuit design guidelines to manage/overcome CNT density variation. 2) Analytical models that are developed to analyze the effects of metallic CNTs on device characteristics, gate and system levels delay and power consumption. Using our presented analytical models, which are again validated by comparison with simulation data, it is shown that the static power dissipation is a more critical issue than the delay and the dynamic power of CNFET circuits in the presence of m-CNTs. 3) CNT density variation and metallic CNTs can result in functional failure of CNFET circuits. The complete and compact model for CNFET probability of failure that consider CNT density variation and m-CNTs is presented. This analytical model is applied to analyze the logical functional failures. The presented model is extended to predict opportunities and limitations of CNFET technology at todays Gigascale integration and beyond.\u2

Third-space encounters and unexpected forms of resistance in Amy Tan's The Joy Luck Club

This paper sets out to investigate Amy Tan's The Joy Luck Club, a liminal work written in-between cultures, in the light of Homi Bhabha's concept of the third space as a site of transformation and transvaluation. It is argued that Tan's novel is implicated in unexpected forms of resistance as a result of its placement in the borderland of cultures. Thus, exploring the discursive fissures and ideological ruptures inscribed in the novel, the authors seek to bring to fore how the very mainstream accounts of Chinese culture and orientalist archive of knowledge in which the work is embedded are contested in the third-space enounters between subjects of different cultures. Orientalism, Western feminism, American Dream, and multiculturalism are some of the major discourses whose truthfulness and serenity are shown to be precarious and open to questioning, hence the recuperation of the subaltern's voice through this contrapuntal reading

Reliability and Reliability-based Sensitivity Analyses of Steel Moment-Resisting Frame Structure subjected to Extreme Actions

The ground external columns of buildings are vulnerable to the extreme actions such as a vehicle collision. This event is a common scenario of buildings' damages. In this study, a nonlinear model of 2-story steel moment-resisting frame (SMRF) is made in OpenSees software. This paper aims investigating the reliability analysis of aforementioned structure under heavy vehicle impact loadings by Monte Carlo Simulation (MCS) in MATLAB software. To reduce computational costs, meta-model techniques such as Kriging, Polynomial Response Surface Methodology (PRSM) and Artificial Neural Network (ANN) are applied and their efficiency is assessed. At first, the random variables are defined. Then, the sensitivity analyses are performed using MCS and Sobol's methods. Finally, the failure probabilities and reliability indices of studied frame are presented under impact loadings with various collision velocities at different performance levels and thus, the behavior of selected SMRF is compared by using fragility curves. The results showed that the random variables such as mass and velocity of vehicle and yield strength of used materials were the most effective parameters in the failure probability computation. Among the meta-models, Kriging can estimate the failure probability with the least error, sample number with minimum computer processing time, in comparison with MCS

Presenting a model for evaluating the performance of financial accelerators of companies accepted on the Iranian Stock

Financial accelerators and optimizing their performance have always been one of the most important issues in organizations and companies. This mixed (qualitative-quantitative) research was conducted with the aim of providing a model for evaluating the performance of financial accelerators for companies accepted on the Iranian Stock Exchange. This study was conducted using a mixed method (qualitative-quantitative) in which 21 variables of the model were extracted in the qualitative section and interviews were conducted with 19 experts and determining the relationship between variables to achieve the model in the quantitative part based on interpretive structural modeling (ISM).Qualitative and quantitative data analysis was the achievement of a five-level model that the most influential variables of this model in the fifth level of company Prosperity and recession and asymmetric information and the variables of market constraints, financial cost situation, financing mechanism, financial performance forecast, Short-term interest rates, financial friction, changes in net valuable, insurance costs and credit channels in the first level of this model were the most influential variables of this model, other variables are also connective variables.Serious attention to the period and level of prosperity and recession of companies and if possible the use of appropriate financial methods to predict the period of prosperity and recession can significantly improve the performance of financial accelerators. Also, due to the high effect of asymmetric financial information, the quality and timeliness of this information also affects the performance of financial accelerators