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This research idea is based on the energy dissipation of sound waves through the inter/intra-structural spaces of the raised surface patterns on the woven cotton fabrics in order to achieve an eco-friendly acoustic material affordable for the public using abundant and cheap precursors via accessible, cost-effective, safe, and clean methods. The first idea is decorating the fabrics with bio-waste-based biomaterials with the use of three different size fish scales. Remarkable enhanced control on sound pollution more than four times (333%) on average over a wide frequency range (63–6400 Hz), reaching about 9.5 and 11 times at frequencies of 3000 and 4000, and up to an 85–100% reduction in sound pollution over frequency ranges of 2000–4000 Hz were recorded in a consistent trend with the fish scale morphologies. Rewarding numerous advantages of this clean production technique, the creation of seven patterns designed with the use of sequins is also investigated. One of the seven designed patterns is a bioinspired design imitating the fish scale pattern as a biomimetic design. This investigation revealed the effect of combining the change in direction of sequins sewn on the surface of the fabric in both circular (C.A.) and radial designs. In this way, by creating the appropriate patterns on the fabric, the average sound absorption coefficient increased by more than four times (330%) as compared to the control over a wide frequency range (63–6400 Hz), reaching more than 8 times enhancement at some frequencies, e.g., 500 Hz for C.A.

In this study, the effects of alloy elements, oxide phases, and created intermetallic compounds of aluminum alloy foams with different percentages of silicon, zinc, and combinations of both these elements were investigated on the compressive properties and fracture behavior of these foams. The results showed that the addition of alloying elements formed intermetallic compounds in the structure of the foam, and the number of intermetallic compounds increased with increasing the percentage of these elements which causes inconsistency between these compounds and base materials. All these factors changed the failure mechanism of these foams so that the failure behavior of pure aluminum foam and zinc-containing foams was a ductile failure, whereas the failure behaviors of silicon-containing foam samples were brittle. The Al–4%Si–4%Zn sample had the highest compressive strength among all of the fabricated samples due to the uniformly distributed intermetallic compounds in the cell wall of these samples, whereas the Al–8%Si, Al–8%Si–4%Zn, and Al–8%Si–8%Zn foam samples were more brittle than the other fabricated foam samples due to the more formation of brittle compounds such as CaAl2Si2and their accumulation in a certain area which reduced the compressive strength of these foams. Also, it was observed that the energy absorption capacity and yield strength of pure aluminum foam generally increased with the addition of alloy elements due to the increase in the amount of created intermetallic compounds in the structure of these foams.

The melt-foaming method is a commercial process to produce metallic foams. In the present research, closed-cell aluminum foams with different silicon and zinc contents (4%Si-4%Zn, 4%Si-8%Zn, 8%Si-4%Zn, 8%Si-8%Zn) using the calcium as a viscosity enhancer and calcium carbonate(CaCo3) as a foaming agent by the melt-foaming method was successfully prepared. The compression test was used to determine the effects of the combination of silicon and zinc elements on the compressive behavior of fabricated foams. According to the x-ray diffraction analysis, the SiO2, CaAl2Si2, Ca14Al10Zn6O35,and Ca3Al4ZnO10phases have been created by adding silicon and zinc elements in samples. Phases and intermetallic compounds created in the cell walls of Al-4%Si-4%Zn and Al-4%Si-8%Zn samples have a uniform distribution which increased the strength and energy absorption of these foams. The results show that the CaAl2Si2brittle phase is present in the structure of Al-8%Si-4%Zn and Al-8%Si-8%Zn samples also, the formation of the needle-shaped structures and intermetallic compounds has reduced the strength of these foams.

The intense applied thermal gradients during the welding process leads to the variation in the properties of the weld zone and its surrounding areas. In this regard, determining the local mechanical properties and evolved microstructures of the weld and its surrounding zones are essential in the evaluation of welded structures. In this study, the local mechanical properties of Al2024 friction-stir-welded joints were precisely examined. Digital image correlation (DIC) technique using uniform stress (USM) and virtual field methods (VFM) were utilized to evaluate the local mechanical properties. The local stress-strain curves were plotted for different weld regions using local strain from the DIC technique. It was observed that the advancing side of the thermo-mechanically affected zone (TMAZ) had the lowest values of Young’s modulus and yield strength (YS), approximately 9% and 31% of the base metal, respectively. Effects of welding parameters, such as tool rotational and traverse speeds, were also taken into account. The plotted local stress-strain curve for the fractured region of welded specimens at lower rotational speed illustrated a higher strength and elongation. Furthermore, lower rotational and also higher traverse speeds resulted in the reduction of the grain size.

High-altitude test facilities are usually used to evaluate the performance of space mission engines. The supersonic exhaust diffuser, a main part of high-altitude test facility, provides the required test cell vacuum conditions by self-pumping the nozzle exhaust gases to the atmosphere. However, the plume temperature is often much higher than the temperature the diffuser structure is able to withstand, usually above 2500 K. In this study, an efficient cooling system is designed and analyzed to resolve the thermal problem. A water spray cooling technique is preferred among various existing techniques. Here, a new algorithm is developed for a spray cooling system for a supersonic exhaust diffuser. This algorithm uses a series of experimental and geometrical relationships to resize the governing parameters and remove the required heat flux from the diffuser surface. The efficiency of the newly designed cooling system is evaluated via numerical simulations. The utilized numerical technique is based on the discrete-phase method. Various computational studies are accomplished to enhance the accuracy of numerical prediction and validation. The present numerical study is validated using experimental results. The results show that the realizable k-ɛmethod is superior compared to other Reynolds-averaged Navier–Stokes models.

An experimental study was carried out on an axisymmetric supersonic inlet with external compression in order to investigate the buzz phenomenon at different angles of attack and mass flow rates. The model was equipped with accurate and high-frequency pressure sensors, and the tests were conducted at Mach numbers varying from 1.8 to 2.5, for various angles of attack. Shadowgraph visualization technique, together with a high-speed camera, was used to provide the visual description of the shock structure in front of the inlet and to study the characteristics of buzz. Furthermore, pressure distribution over the spike surface was measured using several pressure sensors. Frequency of the buzz and shock displacement were measured by inspection of visualization pictures in each test. The obtained data from shadowgraphs were compared with those obtained from pressure measurements, and good agreement was found between them. The results revealed that for a moderate value of mass flow rate, the frequency of shock oscillation decreases as Mach number increases. Further, by increasing angle of attack, the shock displacement of oscillation will increase. At non-zero angles of attack, the displacement and frequency of shock motion show different behaviors on the leeward and windward sides of the body.

The chemical modification of spherical sub-100 nm silica nanoparticles with 3-aminopropyltriethoxysilane and subsequent reaction with acacen (the Schiff base ligand derived from the condensation of acetylacetone and ethylenediamine) and MoO2(acac)2precursor produced MoO2acacen@APTSNPs. The characterization of the obtained material was performed by Fourier transform infrared, inductively coupled plasma optical emission spectroscopy, nitrogen adsorption–desorption measurements, thermogravimetric analysis, and scanning electron microscopy, which indicated that the molybdenum complex is successfully supported on the SCMNPs support. The epoxidation of olefins with tert-butyl hydroperoxide in the presence of MoO2acacen@APTSNPs was carried out with good activities and selectivities under reflux and ultrasonic irradiation conditions.

One of the most common objectives in single-machine scheduling problems is the minimisation of total tardiness. Due to the non-deterministic polynomial-time hard nature of this problem, different heuristic and metaheuristic algorithms have been employed to solve it. In this article, an integer programming model with non-monotonic time-dependent job processing times is developed in which deterioration and learning considerations are incorporated simultaneously. A hybrid genetic algorithm-tabu search (GA-TS) approach is employed to solve the problem. Also, to improve the performance of the GA, Taguchi method is used for parameter tuning. Lastly, in an attempt to validate the proposed model, different test problems are generated randomly and solved by both the hybrid GA-TS and an optimisation software, and thereafter a comparison is performed between the results obtained by them. According to the results, the developed approach has potential to yield near-optimum solutions in large-sized problems. To the best of our knowledge, this is the first study that considers non-monotonic time-dependent processing times, deterioration and learning effect simultaneously in a single-machine scheduling problem with the objective of total tardiness minimisation.

This paper presents the first study of the modulation of polar mesospheric winter echoes (PMWE) by artificial radio wave heating using computational modeling and experimental observation in different radar frequency bands. The temporal behavior of PMWE response to HF pump heating can be employed to diagnose the charged dust layer associated with mesospheric smoke particles. Specifically, the rise and fall time of radar echo strength as well as relaxation and recovery time after heater turn‐on and turnoff are distinct parameters that are a function of radar frequency. The variation of PMWE strength with PMWE source region parameters such as electron‐neutral collision frequency, photodetachment current, electron temperature enhancement ratio, dust density, and radius is considered. The comparison of recent PMWE measurements at 56 MHz and 224 MHz with computational results is discussed, and dust parameters in the PMWE generation regime are estimated. Predictions for HF PMWE modification and its connection to the dust charging process by free electrons is investigated. The possibility for remote sensing of dust and plasma parameters in artificially modified PMWE regions using simultaneous measurements in multiple frequency bands are discussed. First study of HF PMWE heating and predicted turn‐on overshoot effectFirst comprehensive comparison of PMWE heating observations with computational modelTwo‐frequency radar measurements can lead to estimate dust density and radius

•The concept of power system strength is discussed in relation to the behaviour of Inverter- Based Resources (IBRs) in weak parts of the grid.•State of the art power system strength assessment methodologies are provided along with research gaps.•Derivation to explain the relation between the Short Circuit Ratio (SCR) and the static voltage stability.•A novel power system strength index is proposed to assess power system strength with the presence of reactive power injection from Static Var Compensator and other Inverter-based Resources.•The new proposed index, which is derived from the Short Circuit Ratio (SCR), is validated on both positive sequence modelling and Electro-Magnetic Transient type software.

In this article, nonlinear vibration of protein microtubules in cytosol with internal flow is studied. Based on the Euler–Bernoulli beam theory with von Kármán nonlinearity type and using Hamilton’s principle, the equations of motion for fluid-conveying microtubules are derived. The size effect is taken into account using Eringen’s nonlocal elasticity theory; moreover, the effect of an elastic surrounding filament network and the surface traction of cytosol are studied. The governing differential equations for vibration response of microtubules are solved using the differential quadrature method. The nonlinear frequency response of microtubules, considering the effect of microtubule properties, size effect, the surrounding elastic media, and the fluid motion are reported in this article. It has been found that the effect of nonlocal parameter on the vibration behavior and instability of the embedded microtubule conveying fluid are significant. In this regard, we need to point out that the critical flow velocity for a range of nonlocality parameter from 0 to 2 nm varies between 41 and 47 m/s, which should be avoided due to instability of the microtubule system. Therefore, they should be taken into account in the design of nano/micro-devices for measuring density of a fluid, such as drugs flowing through such microtubules, with great applications in biomechanics.

A numerical code for supersonic intake design with a proper simulation of the normal and/or oblique shocks, boundary layer development, interaction of the shock and the boundary layer, as well as prediction of the flow separation is of great help to the designers. In this research, a numerical code is developed to solve the inner and outer flow fields of the intake and validated with various experimental tests. The intake is an axisymmetric external compression one. Roe scheme and new schemes, AUSM+-up (for all speed) and Advection Upstream Splitting Method with Pressure-Based Weight function (AUSMPW), are used to compute the convective fluxes. The original version of the AUSMPW scheme has serious problems concerning the stability and accuracy. In this investigation, several modifications are implemented to the original version of the AUSMPW scheme for the first time which resulted in a better stability and accuracy. Turbulent viscosity coefficient is computed using the Baldwin–Lomax algebraic model. The numerical results are compared well with the experimental data. It is further found that the Roe scheme has the best accuracy; however, the AUSM+-up (for all speed) scheme is numerically very efficient.

Glutathione-S-Transferase (GST) subtype α and π are differentially expressed in adult liver tissue. Objective of the study was if GST α and p may serve as predictive markers for liver surgery, especially transplantations. 13 patients receiving living donor liver transplantation (LDLT) and their corresponding donors were analyzed for standard serum parameters (ALT, AST, gGT, bilirubin) as well as GST-α and -π before LDLT and daily for 10 days after LDLT. Patients (R) and donors (D) were grouped according to graft loss (R1/D1) or positive outcome (R2/D2) and above named serum parameters were compared between the groups. R1 showed significantly increased GST-α and significantly lower GST-π levels than R2 patients or the donors. There was a positive correlation between GST-α and ALT, AST as well as bilirubin and a negative correlation to γGT. However, γGT correlated positively with GST-π. Graft failure was associated with combined low GST-π levels in donors and their recipients before living donor liver transplantation. Our data suggest that high GST-α serum levels reflect ongoing liver damage while GST-P indicates the capacity and process of liver regeneration. Additionally, GST-π may be useful as marker for optimizing donor and recipient pairs in living donor liver transplantation.

: In this paper monthly trends of vertical wind profiles within and above an urban area with complex topography (Tehran) have been investigated using data from a Sodar, a 100-m and two 28-m towers and some surface stations. It includes the occurrence, evolution, dissipation time, peak time and maximum height for katabatic–anabatic winds due to topography, return flow and urban circulation. Vertical distributions of wind and the heat and momentum fluxes up to 600 m were also considered. The vertical wind profiles which have diurnal and seasonal variations show southwesterly daily anabatic wind and northeasterly nocturnal katabatic wind. Daily vertical wind profile structure which has two layers and two jets contains a decrease approximately at 300–400 m which may be due to the return flow and a daily thermal convective flow in the urban convergent terrain. At night the nocturnal wind profile structure, in the majority of months, has two layers and sometimes three layers containing northeasterly flows. In two layers structure, a decrease can be seen between two layers. In three layers structure, the middle layer has a different direction that indicates the return flow and urban circulation more clearly. Katabatic flows also develop in successive phases varying from 1 to 3 phases in different months. Investigation on surface wind demonstrates that in cold months a drainage flow from a valley located in the west of the station can affect wind speed and direction especially at evening transition time. These flow patterns can influence the way air pollutants disperse in this area.

The oxidation of sponge iron products and its destructive effects on iron content as well as other properties have been considered by ferrous technologists for a long time. In this investigation, a unique new low temperature method of preventing and/or retarding the oxidation of direct reduced iron is introduced. Experimental results from laboratory and pilot plant tests show the success of the method which has been named cold briquetting of sponge iron. The optimum condition for briquetting is achieved at 80 kN (Lcm)-1, 6% binder, 10% sponge iron fines and 4% anthracite. While hot briquetted iron has become a successful method for the new generation of iron reduction plants, cold briquetting of sponge iron could become a suitable technique to protect direct reduced iron products against oxidation for traditional iron reduction units.

The effects of hydrogen on the yielding and the ductility of niobium have been studied in the temperature range between 373 and 78 K. Tensile tests were undertaken on single- and poly-crystal specimens containing hydrogen ranging between 30 and 230 ppm wt. at a strain rate of 1.7 X 10-4s-1. The fracture surfaces of specimens tested were also examined by means of an SEM. At higher hydrogen concentrations, two ductility maxima were observed in the temperature dependence of the uniform strain of both single- and poly-crystals. The positions of these maxima on the temperature scale varied as a function of the amount of hydrogen dissolved. One of the maxima is found to occur at higher temperatures in single crystals than in polycrystals. Analysis of results obtained indicates the presence of two distinct mechanisms responsible for the loss of ductility in noibium with hydrogen. One mechanism is operative at the onset of embrittlement, and is sensitive to the presence of grain boundaries. The second mechanism predominates at temperatures of the second ductile-brittle transition, and is associated with the precipitation of the hydride phase. This mechanism has similar effects on both single and poly-crystals.

Previous studies have shown that the interaction of carboxylic acid groups with the amine functionalities of aryl amines, especially secondary and tertiary aryl amines, can lead to the free-radical polymerization of acrylic monomers such as methyl methacrylate. In this study, the Michael addition reaction of primary and secondary aryl amines with acrylic monomers such as acrylic acid (AA) was investigated. Equivalent amounts of either p-toluidine (PT) or N-phenylglycine (NPG) and AA were combined in polar solvents such as ethanol. The reactions were conducted at ambient (23°C) or near-ambient (37–60°C) temperatures. Samples (about 3–5 mg) of these products were then trimethylsilylated with a solution consisting of 0.4 mL of bis(trimethylsilyl)trifluoroacetamide (BSTFA) and 0.4 mL of acetonitrile by heating for 30 min at 140°C under N2. These derivatives were characterized by gas chromatography–mass spectrometry (GC–MS). The GC–MS analyses suggest that 1 mol of the primary amine PT had reacted with 2 mol of AA to yield the expected N-p-tolyliminodipropionic acid. Similarly, the secondary amine NPG added to 1 mol of AA yielded the corresponding mixed iminodiacid, N-phenyliminoacetic–propionic acid. It would appear that the Michael reaction of primary and secondary amines with acrylic monomers may offer a general, facile synthetic route to a variety of tertiary amines. Aryl amino acids of the type synthesized in this study may find use in a number of dental applications, e.g., as surface-active adhesive agents and as polymerization initiators or activators. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 67:1545–1551, 1998

It is found that niobium is an excellent diffusion barrier to Al and Si that is thermally much more stable than titanium.

Metallurgical, electrical, and reliability studies are performed for an Al‐0.5% Cu/Ti bilayer interconnecting metallization structure used in 1.2 μm DRAM and SRAM integrated circuit devices.