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As a basic building block, the THz wave absorber has intense imaging, sensing, and nondestructive testing applications. There are several methods for tuning THz absorbers, including electricity modulation, light modulation, mechanical tuning, using phase change materials, liquid crystal, flexible materials, MEMS technology, and thermally tuning vanadium dioxide. The choice of tuning method depends on the specific application and the desired performance characteristics of the THz absorber. In this work, we report a theoretical description of mechanically tunable THz absorber based on overlapping periodic arrays of graphene nano‐disks. The basis of this work is based on the movement of a dielectric surface covered on both sides with graphene disks. This surface moves on a fixed plane while the distance between these two surfaces is free space. Also, the fixed surface consists of a relatively thick layer of gold at the bottom, dielectric on it, and graphene disk patterns on the dielectric. Now, by moving the movable surface in the horizontal direction, it is possible to adjust the amount of absorption in different frequencies of the terahertz (THz) band. Additionally, an equivalent RLC circuit model is developed and theoretical results match with simulated data. The proposed mechanically tunable THz absorber can be exploited in various emerging applications such as sensing due to its capability of covering all of the THz gap and beyond with multiple absorption peaks. [ABSTRACT FROM AUTHOR]

Nowadays cascode structures or vertical arrangements of MOSFETs can not satisfy demands regarding high gain amplifiers. As a direct result, the only promising choice turns to Multi‐stage amplifiers via cascading gain stages. The challenge here is stability issues which shows itself by different frequency compensation. All problem starts with increasing number of nodes and consequent poles. The poles degenerate phase of system and need to be controlled. In this work, a five‐stage amplifier is targeted for a new and efficient frequency compensation technique. The major contribution of proposed approach is using only two Miller capacitors with considerable small values (10 pF) compared to load capacitor (500 pF). This achieved via exploiting two differential active stages which intensify Miller effect and provide capability to share Miller capacitor at multiple loops simultaneously. The proposed amplifier with corresponding frequency compensation is described symbolically while a circuit level implementation is performed via HSPICE circuit simulator and TSMC 0.18 μm CMOS technology. Based on simulation results, the proposed amplifier expresses a DC gain of 195 dB, a gain bandwidth product of 15.2 MHz, a phase margin of 90°, and a power dissipation of 570 μW. [ABSTRACT FROM AUTHOR]

Nanocomposite film performance parameters, including barrier and mechanical properties for packaging films, can be affected by variables such as the type and the concentration of nanoparticles. In food packaging, it is desired to develop optimal films to maintain the freshness of food for longer periods. In this investigation, polyvinyl alcohol (PVA) nanocomposite films were prepared by solution casting method with different combinations of Montmorillonite (MMT) platelets and titanium oxide (TiO2) spherical nanoparticles. A support vector machine (SVM) was implemented to study the thin nanocomposite films' behavior to changes in the independent variables. The SVM model predicted oxygen transmission rate (OTR), water vapor permeability (WVP|), Young ̓s Modulus (YM), total color difference (ΔE), opacity, tensile strength (TS), and elongation at the breakpoint (EB) with an error of less than 6.4%. A Genetic Algorithm (GA) was applied to find the optimal nanoparticle concentration to achieve the optimum film performance. Results have clearly shown that the optimum film performance depends on the type and the concentration of nanoparticles. In this investigation, results showed that the optimum loading of nanoparticles should be between 0.5 and 1.0 wt% for TiO2 and 2.5–3.5 wt% for MMT. [ABSTRACT FROM AUTHOR]

The need to increase agricultural production in proportion to population growth and water crisis management requires initiatives that can increase the quantity and quality of crops by using soil moisture storage methods while preserving the environment. According to problem presented, in order to simulate the temperature, humidity and radiation of the farm environment, a control system, along with laboratory facilities were designed and constructed. Then, the production and evaluation of different types of soil mulches from biodegradable and petroleum polymers were performed by aiming investigate the effect of these soil mulches on soil temperature and moisture at different depths. Produced mulches were placed in a laboratory soil bed. The average molecular weight, the gel content and the percentage of elongation at the breakpoint for biodegradable mulches were 4906.56 g mol-1, 4.68% and 4.63%, respectively and the mean values of tensile strength and the percentage of elongation before the ultraviolet aging process were 13.41MPa and 396.71%, respectively. Acceptable values of statistical indicators were calculated with the response surface method. In conclusion of the soil temperature and humidity changes for different types of mulch, the velocity of temperature rise is reduced in deep levels due to the resistance made by soil moisture. The amount of moisture reduction for dark and uncoated mulch by moving from surface to depth was far more when compared to other mulches, and there was no significant change at the depth of transparent mulches. [ABSTRACT FROM AUTHOR]

A simulation model was developed for secondary tillage and sowing operations in autumn, using discrete event simulation technique in Arena® simulation software (Version 14). Eight machinery sets were evaluated on a 50-hectare farm. Total costs including fixed-costs, variable costs and timeliness costs were calculated for each machinery set. Timeliness costs were estimated for 21-years period on daily basis (Daily Work method) and compared with another method (Average Work method) based on the equation proposed by ASAE Standards, EP 496.3FEB2006. The Inputs of the model were machinery sets, field size, machines performances and daily soil workability state. The optimization criteria were the lowest costs and lowest standard deviation in daily work method plus the lowest costs based on average work method. The validity of the model was evaluated by comparing the output of the model with field observed data collected from various farms. Results revealed that there was no significant difference (P > 0.01) between the observed and predicted finish day. [ABSTRACT FROM AUTHOR]

In this study, the mechanical properties of the skin and flesh of cantaloupe were determined by individual experiments and then finite element simulation was developed for cantaloupe fruit under compression loading. The applied deformations were equal to 10, 20 and 30% of rupture deformation or 4.5, 9 and 13.5 mm, respectively. The results showed that the internal tissue of fruit reached to yield point in 20% of whole deformation or in force 90 N and the internal failure occurred with no visibility. The statistical comparison of finite element method results with experimental data was performed. The results showed finite element method was able to determine the force threshold of internal bruising for cantaloupe. [ABSTRACT FROM PUBLISHER]