Studying optical and nonlinear optical properties of synthesized azo dyes doped in polymer and liquid crystal using birefringence and Z‐ scan techniques

The authors report the effect of the structure of new synthesized photo‐responsive azo dyes, based on N‐benzyl‐N‐ethyl‐aniline on their optical and nonlinear optical properties, when doped in polymer and liquid crystal (LC) hosts. Anisotropic response of dyes doped with polymer polymethyl methacrylate is studied using photo‐induced birefringence experiment and the optical nonlinearity of dyes doped in LC 5CB is measured using z‐scan technique. A correlation is established between dipole moment and optical/nonlinear optical response, which makes it possible to develop molecular design strategies to create structures with suitable anisotropic response and nonlinearity in various host systems for different applications. It is also shown how very little change in the structure of the dye may cause severe changes in the dipole moment and its nonlinear response. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Operand Width Aware Hardware Reuse: A low cost fault-tolerant approach to ALU design in embedded processors

This paper presents a low cost fault-tolerant technique so called OWHR (Operand Width Aware Hardware Reuse) to ALU design in embedded processors. The OWHR technique is motivated by two facts: (1) Many of the produced and consumed values are narrow-width values in the embedded processors, i.e. they have leading zeros or ones in their most significant bits. This indicates that only a fraction of the circuit is performing useful operations when a particular arithmetic or logic circuit in the ALU is operating on narrow-width values; (2) other circuits of the ALU are not used, when a particular arithmetic or logic circuit is being utilized to perform a specific operation in the ALU in the embedded processors. To exploit the first fact for fault tolerance purpose, the unused parts of a particular arithmetic or logic circuit can be used to provide redundant computations. The second fact also offers us assisting the other unused arithmetic circuits of the ALU to provide redundant computation while a particular arithmetic circuit is being used to perform a specific operation. In this paper, we have implemented a 32-bit ALU protected by the OWHR technique using VHDL and we have extracted the results of power and performance overheads using Synopsis Design and Power Compiler. To do this, we have profiled the input operands of the adder and multiplier units by running some programs of MiBench embedded suite benchmark on an ARM processor performance mode. We have then applied the profiled operands to the implemented ALU to extract the power and performance overheads. The simulation results show that the proposed technique is capable of correcting about 56% of errors in the adder circuit and about 88% of errors in multiplier circuit while having the ability of detecting 100% of errors in the both of the circuits. Beside its high level of reliability, it offers the benefits of low power, and area overheads.     

Approximate design and performance of the robust control charts for monitoring dispersion in Phase I

This article designs and studies the approximate performance of robust dispersion charts, namely, MAD chart, S_n chart, and Q_n chart, in Phase I analysis (recently developed in the literature). The proposed limits are based on false alarm probability for monitoring the dispersion of a process in Phase I analysis. The charting constants are determined to achieve the required nominal FAP (FAP₀). The performance of these structures is evaluated in (i) the attained false alarm rate and (ii) the probability of signals for out‐of‐control situations. The analysis shows that the proposed design of Phase I robust dispersion charts correctly controls the FAP and shows a good performance in detecting the shifts in the process variation. An illustrative example is used to explain the practical implementation of these limits.     

Identifying Critical Components of a Public Transit System for Outbreak Control

Modern public transport networks provide an efficient medium for the spread of infectious diseases within a region. The ability to identify components of the public transit system most likely to be carrying infected individuals during an outbreak is critical for public health authorities to be able to plan for outbreaks, and control their spread. In this study we propose a novel network structure, denoted as the vehicle trip network, to capture the dynamic public transit ridership patterns in a compact form, and illustrate how it can be used for efficient detection of the high risk network components. We evaluate a range of network-based statistics for the vehicle trip network, and validate their ability to identify the routes and individual vehicles most likely to spread infection using simulated epidemic scenarios. A variety of outbreak scenarios are simulated, which vary by their set of initially infected individuals and disease parameters. Results from a case study using the public transit network from Twin Cities, MN are presented. The results indicate that the set of transit vehicle trips at highest risk of infection can be efficiently identified, and are relatively robust to the initial conditions of the outbreak. Furthermore, the methods are illustrated to be robust to two types of data uncertainty, those being passenger infection levels and travel patterns of the passengers.     

Investigation of Microstructure Properties and Quantitative Metallography by Different Etchants in the Service-Exposed Nickel-Based Superalloy Turbine Blade

In this study, the effect of etchant type and etching conditions on the root and airfoil microstructure of a service-exposed IN738 turbine blade has been investigated. The microstructure of superalloy components used at high temperatures, in addition to the usual microstructural changes, experiences deterioration in micrometer dimensions. In order to investigate these changes, electrochemical etching was performed on the samples with the chemical solution including 80% phosphoric acid, solution containing Cr₂O₃ and 55% glycerol. Chemical etching was performed with marble and etchant solution containing 60% glycerol. The results in terms of specifying the deterioration effects on microstructure of the blade applied at high temperature, the amount of γ′ phase and the best etchant were investigated. Among the solutions used for chemical etching, the solution containing 10 ml HNO₃, 50 ml HCl and 60 ml glycerol was appropriate for detection of segregations and dendrites, and among the electrochemical etching solutions, the Cr₂O₃ solution was found suitable for specifying γ′ precipitates’ morphology by scanning electron microscopy. In this research, the results of the quantitative analysis of the images provided by these etchants were also investigated.     

Fabricating boron nitride nanosheets from hexagonal BN in water solution by a combined sonication and thermal-assisted hydrolysis method

Boron nitride nanosheets (BNNSs) have unique and excellent thermal, electrical, and mechanical properties. But, their low efficiency in the production methods restricts their applications in the study of researchers. Hence, we reported a study in which BNNSs were successfully produced through a simple, affordable, and high-efficiency method. In this approach, hexagonal boron nitride block (h-BN) was firstly examined in aqueous solution under sonication (120 min) to produce hydroxyl functionalization and; furthermore, to penetrate water molecules between the layers. Then, with the explosion of the water molecules into the h-BN layers in the presence of heat, the space between the layers was increased. Finally, with the exfoliation of bulk h-BN layers through the ultrasonic irradiation, the ultrathin BNNSs were produced with an efficiency of 37%. The TEM and AFM images confirmed that the obtained BNNSs have mainly consisted of nanosheets with a thickness in the range of 3–8 nm. The results of UV–Vis analysis of BNNSs compared to h-BN showed a strong absorption peak at 204 nm^?1, which confirmed the presence of nanosheets. Also, other analyses, including XRD, BET, and FT-IR, confirmed the structure of BNNSs.     

On Infinite Horizon Optimal Control Problems with a Feed Forward Neural Network Scheme

Neural Processing Letters - In this paper, a class of infinite-horizon nonlinear optimal control problems is considered. The main idea is to convert the infinite horizon problem to an equivalent...