Simple Physical Approach Research Articles

A Facile Route Preparation of Fe3O4/MWCNT/ZnO/PANI Nanocomposite and its Characterization for Enhanced Microwave Absorption Properties

AbstractWith increasing concerns regarding the potential health risks associated with microwave‐based technology, researchers have been actively investigating materials with impressive microwave absorption properties. In this study, a synthesis and investigation of a nanocomposite, named Fe3O4/MWCNT/ZnO/PANI, consisting of magnetite (Fe3O4), multi‐walled carbon nanotube (MWCNT), zinc oxide (ZnO), and polyaniline (PANI) as a microwave‐absorbing material, was carried out for the first time. The nanocomposite was prepared through a simple physical mixing approach and demonstrated tunable microwave absorption, making it highly suitable for shielding applications. Structural analysis techniques, including X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), and scanning electron microscopy with energy‐dispersive X‐ray analysis (SEM‐EDAX), confirmed the presence of all components in the nanocomposite. Moreover, ultraviolet‐visible spectroscopy (UV‐Vis) further verified the formation of nanocomposite components and revealed an adjustable optical bandgap ranging from 2.86 to 3.34 eV. Impressively, the nanocomposite exhibited promising microwave absorption properties, with a minimum reflection loss (RL) of −32.66 dB for the nanocomposite containing 37.50 % PANI by weight, and a maximum electromagnetic bandwidth (EB) of 2.26 GHz for the nanocomposite containing 44.44 % PANI by weight, indicating its potential as an effective shielding material. Furthermore, a modified theory combining transmission line, Landau‐Lifshits, and Drude‐Lorentz theories was introduced to extract complex relative permittivity and permeability, providing insights into the role of polyaniline in enhancing the microwave absorption properties of the nanocomposite as measured by reflection loss (RL).

Synthesis and Characterization of Physically Mixed V2O5.CaO as Bifunctional Catalyst for Methyl Ester Production from Waste Cooking Oil

Synthesis of the solid bifunctional vanadium-calcium mixed oxides catalyst was accomplished by application of a simple physical mixing approach. In this work, we compared the catalytic activity of CaO and 2%V2O5.CaO catalyst. Various characterization methods, such as X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR), BET surface area, and temperature-programmed desorption (TPD) of CO2 and NH3, were involved in studying the newly synthesized catalysts. The presence of CaO, CaCO3, and Ca(OH)2 compounds in the synthesized catalyst were detected by XRD and FTIR analysis. The existence of 2% V2O5 on the CaO catalyst surface was demonstrated by XRF analysis. From TPD-NH3, TPD-CO2, and BET surface area analysis, it was known that the 2% V2O5-CaO catalyst had a higher total number of acid-base sites and surface area than the CaO catalyst. In the fatty acid methyl esters (FAME) production from waste cooking oil (WCO) with higher free fatty acid (FFA), CaO could only catalyze the transesterification reaction. In contrast, 2%V2O5-CaO could successfully catalyze both the esterification of FFA and the transesterification of triglyceride (TG) simultaneously in a one-step reaction process. Thus, these results prove that 2%V2O5.CaO can act as a bifunctional catalyst in the production of biodiesel from WCO. Moreover, the synthesized 2%V2O5.CaO catalyst could achieve a maximum FAME yield of 51.30% under mild reaction conditions, including a 20:1 methanol to oil molar ratio, 60 °C reaction temperature, 1 wt% of catalyst loading, and 3 hours of reaction time.

Solar irradiation on the rear surface of bifacial solar modules: a modeling approach

The transition in the energy sector has started with the growing population leading to the growing energy demands. The use of photovoltaic (PV) technologies has become a crucial way to meet energy demand. There are many ongoing studies for increasing the efficiency of commercial PV modules. One way to increase the energy yield of the PV modules is to use bifacial solar panels by capturing the rear side illumination as well. One of the challenges for estimating the bifacial module performances is to calculate the solar irradiation impinging on the rear side. Many models presented up to now require high computational power, and they are challenging to implement real-life conditions. In this paper, a simple physical modeling approach is presented to calculate the rear side solar irradiation incident on the bifacial modules. For the rear side irradiance estimation, the maximum difference between the measured and calculated rear side irradiance value is approximately 10 W/m2. The model does not require high computational skills since it is neither focused on the view factor nor ray tracing methodologies but instead uses solar geometry. The yield of the module is also modeled, calculated, and compared with the measurements.

A potential proxy for seasonal hypoxia: LA-ICP-MS Mn/Ca ratios in benthic foraminifera from the Yangtze River Estuary

We have examined the possible use of Mn/Ca ratios in benthic foraminifera as a proxy for hypoxia, which has increasingly become a serious environmental issue in many coastal zones. We collected samples from the Yangtze River Estuary, one of the largest and most intense seasonally hypoxic zones in the world. In order to obtain high quality Mn/Ca data, unaffected by contamination, we examined two different cleaning protocols and instrument-based analysis methods. Our results showed that a relatively simple physical cleaning approach coupled to laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) provided excellent results on single specimens. Our observations were comparable to ICP analyses of solutions made up from dozens or even hundreds of specimens and involving complicated sample pretreatments. Using the LA methodology, we analyzed Mn/Ca ratios from living Florilus decorus (F. decorus) specimens from stations in the Yangtze River Estuary with varying bottom water dissolved oxygen (DO) concentrations. Our results showed that Mn/Ca ratios in penultimate chambers of living benthic foraminifera are sensitive to bottom water DO concentrations. We also observed significant variations of both Mn/Ca and Mg/Ca ratios from different chambers within foraminiferal shell specimens. These fluctuations were likely a response to changing ambient water DO and temperature during the specimen’s growth history. Combined use of foraminiferal Mn/Ca ratios together with other proxies could provide a powerful tool for historical reconstruction of low oxygen conditions in seasonal hypoxia areas.

Oxidized multiwalled carbon nanotubes coated fibers for headspace solid-phase microextraction of amphetamine-type stimulants in human urine

Carbon nanotubes (CNTs) have attracted a lot of attention as effective sorbents due to their strong sorption properties and several potential applications in many fields. In this work, the acid oxidized multiwalled carbon nanotubes (MWCNTs-COOH) was coated onto a stainless steel wire by a simple physical adhesion approach to develop solid-phase microextraction (SPME) fibers. By combination of the MWCNTs-COOH coated fiber-based headspace SPME and gas chromatography-mass spectrometry (GC–MS), the developed method demonstrates a good enhancement factor (288–651), low limits of detection (LODs, 0.2–1.3μg/L) for determination of amphetamine-type stimulant drugs (ATSs) in urine samples. The recoveries of the spiked ATSs (5, 50 and 500μg/L) were in the range of 88–107%, the calibration curve was linear for concentrations of analytes in the range from 0.5 to 1000μg/L (R=0.963–0.999). Furthermore, single fiber repeatability and fiber-to-fiber reproducibility were in the range of 2.3%–6.2% (n=6) and 5.7%–9.8% (n=3), respectively. The MWCNTs-COOH coated fiber is highly thermally stable and can be used over 150 times. The method was successfully applied to the forensic determination of amphetamine (AMP) and methamphetamine (MAMP) in human urine samples and satisfactory results were achieved.

Linearized inversion methods for three-dimensional electromagnetic imaging in the multiple scattering regime

In optical or microwave computational tomography, the sample permittivity is reconstructed numerically from the measurements of its scattered field for various illuminations. When the light sample interaction involves multiple scattering, the relationship between the scattered field and the permittivity is non-linear and a direct reconstruction is not possible. Using a simple physical approach, adapted to the three-dimensional vectorial electromagnetic framework, we derive an iterative inversion technique, based on the linearization of the scattering operator, for imaging (possibly anisotropic) targets in the multiple scattering regime. We investigate the performances of different approximations of this operator accounting for more or less multiple scattering. Our method is applied to the reconstruction of targets in the microwave domain using experimental data.

Multi-scale patterns formed by sodium sulphate in a drying droplet of gelatin: experiment and simulation in 2-dimensions

We present a study of patterns, formed in drying drops of aqueous gelatin solution containing sodium sulphate. The patterns are highly complex, consisting of a hierarchical sequence of rings which form concentric bands as well as dendritic crystalline aggregates. We try to explain the origin of the rings and the dendritic growth from them, from a simple physical approach using the advection diffusion equations. We implement a finite difference scheme in 2-dimensions to simulate the experimental results. The effect on pattern formation using different solutions are examined by variation of contact angle and diffusivity. Our model can explain the growth dynamics of a complex pattern that covers several length scales, from the nano scale of single crystals, to the micro scale of dendrites and finally rings that are of the scale of centimeters.

Modification of Tennant and Wetted Perimeter Methods in Simindasht Basin, Tehran Province

Environmental Flow Requirement (EFR) is defined as the flow that is necessary to ensure the existence of habitats in water resources systems. EFR is defined in rivers as flow index commonly. Tennant method is the most popular hydrological method in rivers and based on the historic flow data. The most common method of hydraulic rating method is the wetted perimeter method. Habitat simulation techniques attempt to assess environmental flow requirements on the basis of detailed analyses of the suitability of instream physical habitat. Investigation of the relationship between simple approaches and physical habitat simulation approach and presentation of new recommendations based on the hydraulic and hydrological data can be very useful in estimation of environmental flow in planning phase of river projects. Main objective of present research are modification of Tennant and wetted perimeter methods and providing more reliable recommendations in Simindasht basin in Tehran province which Rainbow Trout is dominant species. Based on the results, in April to September 60% of mean annual flow (MAF) and in October to March 120% of MAF can provide sustainable habitats approximately. Also common wetted perimeter method estimates EFR more than real instream flow need of target species. This method will assess the suitable value for environmental flow on 86% of the maximum wetted perimeter approximately. But based on Physical habitat analysis mean suitable environmental flow will be assess in 63% of the maximum wetted perimeter. Hence modification of wetted perimeter based on physical habitat analysis can reduce instream flow need significantly.

Contactless Transport and Mixing of Liquids on Self-Sustained Sublimating Coatings.

Controlled handling of liquids and colloidal suspensions as they interact with surfaces, targeting a broad palette of related functionalities, is of great importance in science, technology, and nature. When small liquid volumes (drops on the order of microliters or nanoliters) need to be processed in microfluidic devices, contamination on the solid/liquid interface and loss of liquid due to adhesion on the transport channels are two very common problems that can significantly alter the process outcome, for example, the chemical reaction efficiency or the purity and the final concentration of a suspension. It is, therefore, no surprise that both levitation and minimal contact transport methods-including nonwetting surfaces-have been developed to minimize the interactions between liquids and surfaces. Here, we demonstrate contactless surface levitation and transport of liquid drops, realized by harnessing and sustaining the natural sublimation of a solid-carbon-dioxide-coated substrate to generate a continuous supporting vapor layer. The capability and limitations of this technique in handling liquids of extreme surface tension and kinematic viscosity values are investigated both experimentally and theoretically. The sublimating coating is capable of repelling many viscous and low-surface-tension liquids, colloidal suspensions, and non-Newtonian fluids as well, displaying outstanding omniphobic properties. Finally, we demonstrate how sublimation can be used for liquid transport, mixing, and drop coalescence, with a sublimating layer coated on an underlying substrate with prefabricated channels, conferring omniphobicity using a simple physical approach (i.e., phase change) rather than a chemical one. The independence of the surface levitation principle from material properties, such as electromagnetic, thermal or optical, surface energy, adhesion, or mechanical properties, renders this method attractive for a wide range of potential applications.

A zeolitic imidazolate framework based nanoporous carbon as a novel fiber coating for solid-phase microextraction of pyrethroid pesticides

A high-surface-area nanoporous carbon (NPC) has been successfully synthesized by using the metal-organic framework ZIF-90 as both the template and precursor together with furfuryl alcohol as a secondary carbon source. The prepared ZIF-90 templated NPC (ZIF-90-NPC) was then coated onto a stainless steel wire by a simple physical adhesion approach to prepare solid-phase microextraction (SPME) fiber. By coupling the ZIF-90-NPC coated fiber-based SPME with gas chromatography-microelectron capture detection (GC-μECD), the developed method gave a large enhancement factor (984-2869), low limit of detection (0.1–0.5ngg−1) and good linearity (0.3–50ngg−1) for the determination of some pyrethroid pesticides (bifenthrin, fenpropathrin, cyhalothrin, permethrin, cyfluthrin, flucythrinate, fenvalerate and deltamethrin) from different fruits and vegetables. The relative standard deviations (RSDs) for six replicate extractions of the pyrethroids by the ZIF-90-NPC coated fiber ranged from 4.3% to 8.0%. The recoveries of the spiked pyrethroids (5ngg−1 and 20ngg−1) from fruit and vegetable samples were in the range of 88.0–104.0% and 86.0–103.5% with the RSDs ranging from 4.8% to 12.9% and 5.0–10.8%, respectively. Besides, the ZIF-90-NPC coated fiber was stable enough for 100 extraction cycles without a significant loss of extraction efficiency. The method was successfully applied to the determination of the pyrethroids in fruit and vegetable samples.

Regular Hexagonal Gold Nanoprisms Fabricated by a Physical Method: Toward Use as Ultrasensitive Surface‐Enhanced Raman Scattering Substrates

A simple physical approach to prepare gold (Au) nanoparticles with sharp edges for increasing surface‐enhanced Raman scattering (SERS) response is presented. The shape evolution process of Au nanoparticles under different fabrication conditions is studied, and a thermodynamic model is adopted to explain the shape transition. Single‐crystalline Au nanoprisms with regular hexagonal shape can be formed at a certain annealing temperature. Coating of these Au nanoprisms with graphene causes them to exhibit a SERS enhancement of 60x. This is the first demonstration of a physical approach to fabricate regular hexagonal Au nanoprisms that exhibit an ultrasensitive SERS effect. Furthermore, the local field distribution of a series of Au nanoprisms with different sizes is simulated to better understand their ultrasensitive SERS performance.

Multi-scale patterns formed by sodium sulphate in a drying droplet of gelatin

We present a study of patterns, formed in drying drops of aqueous gelatin solution containing sodium sulphate. The patterns are highly complex, consisting of a hierarchical sequence of rings which form concentric bands as well as dendritic crystalline aggregates. When the preparation of the complex fluid is done by mixing an aqueous solution of the salt with an aqueous solution of gelatin prepared separately, another feature is observed in the pattern on the dried out drop. This is a viscous fingering pattern, superposed on the series of rings. We try to explain the origin of these two features from a simple physical approach.

Clinical neurological examination vs electrophysiological studies: Reflections from experiences in occupational medicine.

Seventy-five percent of upper limb disorders that are related to work are regarded as diagnostically unclassifiable and therefore challenging to the clinician. Therefore it has been generally less successfully to prevent and treat these common and frequently disabling disorders. To reach a diagnosis requires the identification of the responsible pathology and the involved tissues and structures. Consequently, improved diagnostic approaches are needed. This editorial discusses the potentials of using the clinical neurologic examination in patients with upper limb complaints related to work. It is argued that a simple but systematic physical approach permits the examiner to frequently identify patterns of neurological findings that suggest nerve afflictions and their locations, and that electrophysiological studies are less likely to identify pathology. A diagnostic algorithm for the physical assessment is provided to assist the clinician. Failure to include representative neurological items in the physical examination may result in patients being misinterpreted, misdiagnosed and mistreated.

Simulated real-time soft shadow in mixed reality using fuzzy logic

This paper presents fuzzy logic in computer graphics to generate soft shadows in virtual environments and augmented reality. A very short overview on hard shadow generation is introduced. Shadow volume which is a conventional technique to create hard shadow is the base algorithm for our approach to show hard shadows in crisp set. A new technique with help of shadow maps for generating soft shadows using fuzzy logic is used. Fuzzy logic could change the concept of soft shadows into mathematically simple forms. Conversion of the soft shadows into fuzzy logic could change some parts of complex calculation to a simple physical based approach for increasing the speed of rendering. ARToolkit is used for geometric tracking as well as stencil buffer. A credible soft shadow is produced by splitting the wide light source into many parts.

Electrochemical behavior of cuprous oxide–reduced graphene oxide nanocomposites and their application in nonenzymatic hydrogen peroxide sensing

In this paper, three approaches including physical adsorption, in situ reduction, and one pot synthesis were developed to fabricate cuprous oxide–reduced graphene oxide (Cu2O–rGO) nanocomposites. These nanocomposites were characterized by XRD, SEM, Raman spectrum and electrochemical methods. The composite with different morphologies and components fabricated from these three methods displayed much enhanced performance for the catalytic reduction of H2O2 than the single component Cu2O. Among these Cu2O–rGO nanocomposites, the product prepared through the simple physical adsorption approach (i.e. Cu2O–rGOpa) showed a slightly better performance than the other two composites. A wider linear range (0.03–12.8mM), higher sensitivity (19.5μA/mM) and better stability were achieved on the Cu2O–rGOpa based sensor than Cu2O based sensor for accurate detection of H2O2.

Simple Physical Approach to Reducing Frictional and Adhesive Forces on a TiO2 Surface via Creating Heterogeneous Nanopores

A simple physical strategy to reduce the frictional and adhesive forces on TiO(2) films was proposed by constructing mesoporous TiO(2) films with heterogeneously distributed nanopores on the film surfaces. In comparison, TiO(2) films with densely packed nanoparticles were also prepared. The crystal structure and morphology of the films were characterized with Raman spectroscopy, field emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM). It was found that the TiO(2)(B) phase exists in the mesoporuos TiO(2) films but not in the densely packed films. The existence of TiO(2)(B) plays a significant role in creating and maintaining the nanopores in the mesoporous TiO(2) films. The frictional and adhesive forces were measured on both films using AFM. The mesoporous films exhibit two typical adhesion forces of around 3 and 12 nN in the force distribution profile whereas the densely packed films show only one around 12 nN. The frictional coefficients were 2.6 × 10(-3) and 6.7 × 10(-2) for the mesoporous and densely packed TiO(2) films, respectively. A model based on the atomic structures of a thin film of water molecules adsorbed on TiO(2) surfaces leading to hydrophobic effects was proposed to understand the lower frictional and adhesive forces observed on the mesoporous TiO(2) films. This simple physical approach to reducing the frictional and adhesive forces on TiO(2) films could have broad applications to a variety of surface coatings.

Entropy, Extropy and the Physical Driver of Irreversibility

ABSTRACT We point out that the fundamental irreversibility of Nature requires the introduction of a suitable measure for the distance from equilibrium. We show that entropy, which is widely held to be such a measure, suffers from the problem that it does not have a physical meaning, since it is introduced on the basis of mathematical arguments. As a consequence, the basic physics beyond irreversibility has remained obscure. We present here a simple but transparent physical approach for solving the problem of irreversibility. This approach shows that extropy, the fundamental thermodynamic variableintroducedbyKatalinMartinas,isthesuitablemeasureforthedistancefromequilibrium,since it corresponds to the actual driver of irreversible processes. Since extropy explicitly contains in its definition all the general thermodynamic forces that drive irreversible processes, extropy is the suitable physical measure of irreversibility. KEY WORDS extropy, irreversibility, entropy, equilibrium , non-equilibrium, thermodynamics

A Simple Physical Approach to Study Spectrum of Baryons

The exact solution of Schrödinger equation corresponding to a baryonic system is the main interest in the present work. We take into account both quadratic and Coulomb terms in the potential relation. Next, after presenting an exact solution, we have calculated the spin and isospin effects in both ground and excited states. The results are comparable with experimental data.

Synthesis and optical properties of S-doped ZnO nanowires

S-doped ZnO nanowires with an average diameter of 80 nm and length up to several tens of micrometers were produced through a simple physical evaporation approach. The nanowires had a single-crystal hexagonal structure and grew along the [102] direction. Photoluminescence (PL) measurements showed that the doping of sulfur shifted the PL spectrum peak towards short wavelengths, and the doping quantity was found responsible for the different characteristics.

Regular Keplerian motions in classical many-body systems

A clear and simple physical approach to the explanation of exact particular solutions of the classical many-body problem is suggested. When the motion of individual bodies coupled by mutual gravitational forces in a many-body system occurs along conic sections, each body can be treated as moving not under the pull of the other moving bodies, but rather under a stationary central inverse-square gravitational field. These solutions describing possible amazingly simple (Keplerian) many-body motions are illustrated by computer simulations. Some pedagogical and philosophical aspects of the problem are discussed.