Analyzing the fractal feature of nickel thin films surfaces modified by low energy nitrogen ion

Fractal concepts are used to explore how different energies (10, 20 and 50 keV) and fluence of 5 × 10¹⁷ N⁺ cm^?2 affect the morphology of nickel thin film. The nickel thin film with thickness of 100 nm is prepared by electron beam evaporation technique at room temperature on stainless steel (AISI 316) substrates. The nanoscale three‐dimensional (3‐D) surface micro‐morphologies are investigated by atomic force microscopy (AFM). Interface width is used to describe the surface height fluctuations. The autocorrelation function with height‐height correlation function give the quantitative data about the morphology of surface. The value of roughness exponent and fractal dimension is computed by height‐height correlation function. Fractal measure is an important analysis which provides fundamental insights into the texture characteristics and a direct way of testing their functional role.     

Efficient Observer-Dependent Simplification in?Polygonal Domains

In this paper, we consider a special version of the well-known line-simplification problem for simplifying the boundary of a region illuminated by a point light source q, or its visibility polygon VP(q). In this simplification approach, we should take the position of q as an essential factor into account to determine the quality of the resulting simplification. For this purpose, we redefine the known distance- and area-distortion error criteria as the main simplification criteria to take into account the distance between the observer q and the boundary of VP(q). Based on this, we propose algorithms for simplifying VP(q). More precisely, we propose simplification algorithms of O(n ²) and O(n ^4/3+δ ) running time for observer-dependent distance-distortion simplification criterion and an O(n ³) simplification algorithm for observer-dependent area-distortion criterion where n is the number of vertices in VP(q). Moreover, we consider the observer-dependent distance-distortion simplification problem in the data streaming model where the vertices of VP(q) are given as a stream and only a constant amount of memory is available.     

Photonic crystal directional coupler for all-optical switching,tunable multi/demultiplexing and beam splitting applications

In this paper, we introduce a new configuration based on the combination of photonic crystal directional coupler and nonlinear electromagnetically induced transparency (EIT) phenomenon in solid-state materials. The proposed structure has the abilities of switching, tunable multi/demultiplexing and tunable power beam splitting. These applications are attainable in the same structure by modulating the refractive index of special regions via EIT effect. This effect causes a high reduction in the required optical control power for the desired refractive index change, compared to the other nonlinear methods. Band structure calculations and simulations of optical field propagation through the device are done by plane wave expansion and finite difference time domain methods, respectively. In the switching mechanism, extinction ratios of 11.38?dB in the linear regime (with the control signal being off) and 26.63?dB in the nonlinear regime (with the presence of control signal) are achievable. Also, the proposed structure operates as a two-channel multi/demultiplexer for wavelengths of 1550?nm and 1480?nm in the linear regime, for wavelengths of 1550?nm and 1600?nm in both linear and nonlinear regimes, and for wavelengths of 1480?nm and 1600?nm in the nonlinear regime (the nonlinear regime is the same as the nonlinear regime for the switching). Since different refractive indices are obtained by changing the power of the control signal, the wavelengths for multi/demultiplexer operation can be tunable. Finally, simulation results show that the suggested structure can operate as a tunable power beam splitter at the wavelength of 1550?nm.     

Prediction of compressed air transport properties at elevated pressures and high temperatures using simple method

Compressed air energy storage is a way to store energy generated at one time for use at another time. At utility scale, energy generated during periods of low energy demand can be released to meet higher demand periods. Also compressed air is a commonly used utility across most manufacturing and processing industries as its production and handling are safe and easy. Compressed air systems are critical and play a pivotal role in the proper operation of many processing facilities since most of the instruments and controls depend on pressurized instrumentation air for operation. In this work, a simple predictive tool, which is easier than current available models involving a large number of parameters, requiring more complicated and longer computations, is presented here for the prediction of transport properties (namely thermal conductivity and viscosity) of compressed air at elevated pressures as a function of temperature and pressure using a simple Arrhenius-type function. The proposed correlation predicts the transport properties of air for temperature range between 260 and 1000 K, and pressures up to 1000 bar (100 MPa). Estimations are found to be in excellent agreement with the reliable data in the literature with average absolute deviation being around 1.28% and 0.68% for thermal conductivity and viscosity respectively.     

Simulation of reversible chain transfer catalyzed polymerization (RTCP): effect of different iodide based catalysts

Monte Carlo kinetic simulation method was performed to study the reversible chain transfer catalyzed polymerization (RTCP) of styrene in 80°C. The effect of different iodide based catalysts (AI) was investigated on RTCP systems by simulating the chain length distribution, the depletion rate of polymerization ingredients, average molecular weights and the monomer conversion. In RTCP systems a narrow distribution was obtained compared to iodide-mediated polymerization. Superior reversible chain transfer reaction constants (k_a and k_da) led to a more uniform chain length distribution and a faster PDI decrement. In each RTCP system k_da/k_a ratio, designates the concentration of A* by dictating the dominant side of exchange equilibriums which specifies the number of cross-termination reactions. Addition of cross-termination reactions to the iodide-mediated polymerization system decreases the number of combination reactions leading to lower average molecular weights. Higher k_da/k_a ratios also consequences in faster catalyst depletions and lessen monomer conversions. On the other hand, PhE-I was found to deplete rapidly in RTCP systems, changing the nonlinear increase of the number average molecular weight to a linear pattern. The Monte Carlo simulation results were in a fine agreement with experimental data which were obtained from different RTCP systems.     

Chemical and Morphological Characteristics of Malaysian Cultivated Kenaf (Hibiscus cannabinus) Fiber

In this study, an attempt is made to understand the chemical and morphological characteristics of Malaysian cultivated kenaf fractions (bast, core, and whole stem). Results based on morphologyand chemical analysis indicate that bast and core fiber fractions in the kenaf are significantly different, although the chemical composition of kenaf is quite similar to the woody mass. In the case of whole stem fibers, it is concluded that the effective length of fibers from the whole stem is reasonably good for the purpose of making printing papers.     

Robust control of systems with sector nonlinearities via convex optimization: A data‐driven approach

In this paper, a new data‐driven method for designing robust controllers is proposed for systems with sector‐bounded nonlinearities and multimodel uncertainties. The results from the circle criterion are used to generate necessary and sufficient convex constraints that guarantee the stability of the closed‐loop system. The main feature of the proposed approach is that only the frequency response data of the linear part of the system is used for guaranteeing the stability of the closed‐loop nonlinear system. Additionally, a convex optimization problem is formulated to ensure performance with respect to the fundamental component of a sector‐bounded nonlinearity. The case study illustrates how the proposed method can be used to control uncertain systems that are subject to sector‐bounded nonlinearities.     

Multi-Objective Optimization of Integrated Surface and Groundwater Resources Under the Clean Development Mechanism

Acquiring sustainable water resources for water-based development of countries is the experts? concern in this field, who seek to follow the clean development mechanism (CDM) regulations and overcome water crisis through integrated water resources management (IWRM). The Great Karun River basin is one of the major basins in the Middle East. This basin, containing six of the largest reservoir dams with a cumulative power plant capacity of more than 10,500 MW generates about 93% of hydropower of Iran. The water balance of the aquifer in the study area was simulated using MODFLOW model while water resources and surface water reserves were simulated by the water evaluation and planning (WEAP) model. A separate simulation was performed with each of two models and the results of two models were coupled using a link file. The multi-objective function optimization process including the maximized supply of demands and hydropower and the minimized aquifer drawdown was completed using non-dominated sorting genetic algorithm (NSGA-II). All effective system components, such as inter-basin water transfer, integrated use of water resources, variation of irrigation network efficiencies, and the effect of water shortage were studied and analyzed under the targeted scenarios. Finally, the best scenario, which was capable to supply the future needs until time horizon of 2040 was planned for the basin considering minimization of aquifer drawdown and optimal generation of hydropower resulting in a maximum decrease in emission of greenhouse gases.

     

Sustainability assessment in the presence of undesirable factors over time: A case on gas companies

Sustainability is an essential ingredient for long-term success of firms, and its assessment has a significant impact on decision making and sustainability management. In the current paper, a data envelopment analysis-based approach is proposed to assess the sustainability of systems over several periods when undesirable outputs are present in the process. Indeed, sustainability is assessed in each period and, as a whole, simultaneously. Furthermore, social, economic, and environmental efficiency scores of multiperiod systems are evaluated in each period. The weak disposability assumption is used to handle undesirable outputs. Also, the current study concerns socio-economic, socioenvironmental, and eco-environmental factors in addition to economic, social, and environmental aspects. A real-world application on Iranian gas companies is used to illustrate the applicability of the proposed approach.