Search

Asian countries rely massively on rice to feed and sustain its massive population. For long the staple food has provided nourishment to the masses and the classes. Rice is grown in large quantities in Asian countries. A by-product of its cultivation is its husk. The husk of the rice grain is mainly utilized as a fuel for the boilers in the rice mills. The uncontrolled burnt rice husk referred to as rice husk ash consists majorly of silica. silica is used in a wide variety of commercial and industrial applications. Use of rice husk ash in various products serves to reduce the pollution caused by its pileup in localities especially close to the rice mills. More sustainable and an affordable source of Si would benefit the society rather than disposing rice husk ash in the fields and landfills. This brief review provides insights into the synthesis, applications, and properties of rice husk ash incorporated products either directly in the as received conditions or under modified conditions.

Multi‐carrier waveforms have several advantages over single‐carrier waveforms for radar communication. Employing multi‐carrier complementary phase‐coded (MCPC) waveforms in radar applications has recently attracted significant attention. MCPC radar signals take advantage of orthogonal frequency division multiplexing properties, and several authors have explored the use of MCPC signals and the difficulties associated with their implementation. The sidelobe level and peak‐to‐mean‐envelope‐power ratio (PMEPR) are the key issues that must be addressed to improve the performance of radar signals. We propose a scheme that applies pattern‐based scaling and geometric progression methods to enhance sidelobe and PMEPR levels in MCPC radar signals. Numerical results demonstrate the improvement of sidelobe and PMEPR levels in the proposed scheme. Additionally, autocorrelations are obtained and analyzed by applying the proposed scheme in extensive simulation experiments.

Drilling is the most common operation that is performed on the composite material to facilitate the fastening of a composite with other components in an assembly. The present investigation investigates the most significant parameter that affects the quality of the drilled hole in glass fiber-reinforced composites. Epoxy resin is used in the matrix phase. Aluminum powder is used as a filler material in the epoxy matrix to reduce delamination. Laminated composites were fabricated by the hand-layup process with 0%, 3%, and 6 vol% aluminum fillers. Holes were drilled in the composites with the help of a computer numerical controlled drilling machine equipped with a dynamometer. Spindle speeds of 1000, 3000, and 5000 rpm, and feed rates of 50, 100, and 150 mm min−1 were the variables involved in the study. The thrust force and torque experienced during the machining process were measured. An artificial neural network model was executed using python programing language. The data obtained from the model was optimized using genetic algorithm to arrive the optimized machining conditions that would result in least delamination due to drilling.

Despite the advantages of high contaminant removal, operational flexibility, and technical advancements offered, the undesirable fouling property of membranes limits their durability, thus posing restrictions on their usage. An enormous struggle is underway to conquer this major challenge. Most of the earlier reviews include the basic concepts of fouling and antifouling, with respect to particular separation processes such as ultrafiltration, nanofiltration, reverse osmosis and membrane bioreactors, graphene-based membranes, zwitterionic membranes, and so on. As per our knowledge, the importance of nanofiber membranes in challenging the fouling process has not been included in any record to date. Nanofibers with the ability to be embedded in any medium with a high surface to volume ratio play a key role in mitigating the fouling of membranes, and it is important for these studies to be critically analyzed and reported. Our Review hence intends to focus on nanofiber membranes developed with enhanced antifouling and biofouling properties with a brief introduction on fabrication processes and surface and chemical modifications. A summary on surface modifications of preformed nanofibers is given along with different nanofiller combinations used and blend fabrication with efficacy in wastewater treatment and antifouling abilities. In addition, future prospects and advancements are discussed.

With the growing demand for fuel and simultaneous pollution caused by the use of traditional fuel sources, the quest for clean energy source is the biggest challenge forward. Thus, has given way to...

Design of experiments and analysis of variance techniques have been used in the current study to examine the wear behavior of aluminum-silicon/multi-walled carbon nanotubes nanocomposite. Variables that are considered for the assessment of wear included multi-walled carbon nanotubes concentration, applied load, operating speed, distance traversed, and temperature. Results have shown that the 0.5 wt.% multi-walled carbon nanotubes reinforced aluminum-silicon alloy had the highest wear resistance. Systematic examination of variables showed that the applied load is the dominating factor that influenced the wear behavior. The improved wear resistance of the nanocomposite was found due to the reinforcement of the multi-walled carbon nanotube.

International audience; Heavy metal removal from water resources is essential for environmental protection and the production of safe drinking water. In this direction, Zinc doped Aluminium Oxide (Zn:Al2O3) nanoparticles were incorporated into Polysulfone (PSf) to prepare mixed matrix membranes for the efficient removal of heavy metals from water. These Zn:Al2O3 nanoparticles prepared by the solution combustion method have a very high surface area (261.44 m2/g) with an approximate size of 50 nm. X-ray Photoelectron Spectroscopy analysis showed that the Al and Zn were in +3 and + 2 oxidation states, respectively. Cross-sectional Scanning Electron Microscopy images revealed the finger-like morphology and porous nature of the membranes. In this study, the optimum loading amount of Zn:Al2O3 nanoparticles was determined. Synthesized membranes showed enhanced hydrophilicity, surface charge, and porosity, which enabled the removal of arsenic and lead with efficiencies of 87% and 98%, respectively. A study of the antifouling properties carried out at various pressures with a feed solution containing Bovine Serum Albumin (BSA) showed 98.4% of flux recovery ratio and reusability up to three continuous cycles. Moreover, this work demonstrates a rational design of novel mixed matrix membranes exhibiting characteristics of hydrophilicity, surface charge, and porosity adequate to realize the efficient removal of heavy metals.

Cooling behaviour of steels in quench media is of great importance as this controls phase transformations, heat transfer and the stress evolution. The heat extraction ability of each quenchant is different because of varying thermophysical properties and wetting behaviour. The quenchants should be selected in such a way that they provide uniform cooling of steel. In the present investigation, quenching experiments were carried out with Inconel 600, EN19, EN24, EN31 steel grades in distilled water, servo oil, carbonated distilled water and 10% PAG. The cooling curve analysis of the quenching process was carried out with temperature data recorded during quenching. This measured temperature–time data were used to estimate the heat flux by inverse modelling without considering the effect of phase transformation. The crack propensity was quantified using the quench uniformity ratio. The hardness distribution observed during quenching in carbonated distilled water was observed to be more uniform compared to other quench media.

Introduction Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder. It is a multi-factorial disease with a variety of identified causes including age, male gender, obesity, craniofacial and upper airway abnormalities. We would like to describe a patient who had severe OSA following application of Halo traction, which significantly improved following the removal of the device. Report of Cases: 14-year-old male with medical history of spina bifida, chiari malformation s/p decompression, shunted hydrocephalus and severe scoliosis, was admitted to the hospital for anterior spinal discectomy L2-S1 and Halo application with traction for scoliosis. He previously had nocturnal polysomnogram (NPSG) in 2017 that demonstrated very mild mixed apnea with an apnea hypopnea index (AHI) of 5.5. Because central apneas were very brief and clustered in REM, family elected to repeat a study rather than treat. In 2019, he had a follow up study with complaints of snoring and thirst, and this demonstrated an AHI of 21 with 29 brief central apneas and 72 hypopneas, 1 obstructive apnea. He had a T&A and turbinate ablation and due to the global pandemic did not undergo repeat sleep study. During admission for his anterior spinal discectomy and Halo, he demonstrated persistent night time hypoxia. A split night sleep study showed evidence of severe OSA with pretreatment AHI of 94.4, oxygen nadir 86%. Continuous positive airway pressure (CPAP) was initiated at 5 cm of water and titrated to 11 cm of water. On CPAP of +11 severe obstructive events continued with an AHI of 40.6, oxygen nadir 92%. A bilevel positive airway pressure (BIPAP) titration study the subsequent night started at pressures of 12/6 and titrated to 21/9 with respiratory rate of 12 yet demonstrated AHI of 51, oxygen nadir 89%. Study transitioned to average volume assisted pressure support (AVAPS) with IPAP max of 26, IPAP minimum of 12 EPAP of 9, tidal volume of 175ml, rate of 12 with inadequate control of his obstructive events with an AHI of 24.8, minimum oxygen saturations of 91. While hospitalized, he remained on AVAPS with normal capillary blood gases. Halo traction was removed 2 weeks following his surgery with plan was to send him home on AVAPS and repeat NPSG in 6 weeks. However, as a result of COVID pandemic/Philips recall, CPAP was the only device available for home use, so CPAP therapy at +8 cm was trialed overnight, demonstrating oxygen nadir of 92% and a normal capillary blood gas in the morning. Patient was then discharged home on CPAP of +8 cm of water. He returned back to sleep center for a BIPAP titration study to re-establish BIPAP/AVAPS settings, as his inpatient sleep study had shown severe OSA. During the sleep study, he was started on BIPAP 12/6 and he remained on it throughout the night with 0 central and 0 obstructive events. As he did well, he was advised to continue CPAP +8 with plans to repeat the sleep study off CPAP. In clinic follow up, he reported mild skin breakdown and occasionally waking unrefreshed. Conclusion As our patient did significantly better following the removal of Halo traction device, it is likely that Halo traction device caused fixed over flexion of the cervical spine that resulted in decrease in his airway diameter, which further worsened during his sleep, and caused severe OSA. Support (If Any)

Rising demand for bone implants has led to the focus on future alternatives of alloys with better biocompatibility and mechanical strength. Thus, this research is dedicated to the synthesis and investigation of new compositions for low-alloyed Ti-based compounds, which conjoin relatively acceptable mechanical properties and low elastic moduli. In this regard, the structural and mechanical properties of &alpha, + &beta, Ti-Fe-Cu-Sn alloys are described in the present paper. The alloys were fabricated by arc-melting and tilt-casting techniques which followed subsequent thermo-mechanical treatment aided by dual-axial forging and rolling procedures. The effect of the concentrations of the alloying elements, and other parameters, such as regimes of rolling and dual-axial forging operation, on the microstructure and mechanical properties were thoroughly investigated. The Ti94Fe1Cu1Sn4 alloy with the most promising mechanical properties was subjected to thermo-mechanical treatment. After a single rolling procedure at 750 &deg, C, the alloy exhibited tensile strength and tensile plasticity of 1300 MPa and 6%, respectively, with an elastic modulus of 70 GPa. Such good tensile mechanical properties are explained by the optimal volume fraction balance between &alpha, and &beta, phases and the texture alignment obtained, providing superior alternatives in comparison to pure &alpha, titanium alloys.

The effect of nanomaterial coating on heat transfer characteristics of a copper substrate during pool boiling with distilled water (>99.9 %) was studied. The peak on the pool boiling curve between nucleate and transition boiling is termed the critical heat flux. Multi-walled carbon nanotubes and graphene were used to obtain coatings on the copper substrate. Experiments were carried out at atmospheric pressure. The results showed enhanced critical heat flux for the coated substrates. Graphene-coated copper showed the highest critical heat transfer characteristics compared with that on bare and multi-walled carbon nanotube-coated substrates. The study has significant implications for the enhancement of heat transfer during quench heat treatment.

Herein, an attempt has been made to prepare a novel membrane with good efficiency for removal of heavy metal ions namely lead (Pb), cadmium (Cd) and chromium (Cr). 4-amino benzoic acid (ABA) was covalently grafted onto the poly vinyl chloride (PVC) backbone by CN bond to enhance the hydrophilicity. 1H NMR and ATR-IR spectroscopy analysis confirmed the chemical modification of PVC. Further the modified polymer was blended in different compositions with polysulfone (PSf) for optimization. Morphological changes that occurred in blend membranes, due to the incorporation of modified PVC was studied by AFM and SEM techniques. The effect on hydrophilicity and performance of blends owing to incorporation of modified PVC was evaluated by water uptake, contact angle and flux studies. The density of functional groups in blends was analyzed by its ion-exchange capacity. Batch wise filtration of metal ions was carried out and the effect of pressure, feed pH and interference of ions was thoroughly investigated. Essentially, 100% rejection was obtained for all the metal ions in acidic pH with a productivity of 2.56l/m2h. The results were correlated with the results of commercially available NF 270 membrane under the same operating conditions.

The report aims to develop and use sunlight-active catalyst-membrane to reduce toxic Cr (VI) to less toxic Cr (III) and to reject Cr (III) from Cr contaminated water. Polysulfone and TiO2 nanoparticles were hybridized, to induce a bifunctional efficacy of metal ion reduction and separation. Reduction of Cr (VI) results in the formation of Cr (III), which is larger in size facilitating rejection. Hybrid membranes possess superior hydrophilicity and permeability with an added advantage of enhanced metal ion reduction and rejection. Photoreduction of Cr (VI) requires the presence of acid to avoid accumulation of holes and hydroxyl radicals in the reaction medium. Cr (III) solution obtained after photoreduction was subjected to direct filtration without any pretreatment, so as to obtain complete Cr-free water.

Poly vinyl chloride (PVC) is functionalized using L-cysteine to get a zwitterionic effect. The obtained zwitterionic effect of L-cysteine induced PVC facilitated its utilization as separation membrane for complete As (V) removal. The functionalization was evidenced by ATR-IR, NMR spectroscopy and blended with polysulfone (PSf) in optimum composition to get a mechanically stable membrane. With a view to further enhance the charges of the blend; it was further made into a composite membrane by using TiO 2 nano fillers. The prepared membranes were characterized by XRD, EDX, SEM and ion exchange capacity (IEC). Water uptake (WU), contact angle (CA) and pure water flux (PWF) were analyzed to study the changed hydrophilicity and productivity of the membranes. Further these membranes were evaluated for removal of As (V) ions in various experimental conditions. The dual effect of zwitterion and TiO 2 NPs was profoundly deliberated. The membrane was found to work efficiently throughout the complete range of pH. Molecular weight cut-off study indicated that all the membranes belong to ultrafiltration range. The rejection efficiency was observed to be majorly governed by the charge on the membrane and a maximum of 85% arsenic rejection was achieved thus, signifying the development of zwitterionic membranes for potential removal of high concentration of arsenic in surface and ground waters unlike the existing membranes that are presently applied for ppb concentrations.

Inorganic metal oxide semiconductor-based photocatalyst plays key role in the photocatalytic process for applications such as environmental pollution (air and water) and hydrogen generation, due to their physico-chemical and photocatalytic properties. However, they are only active under ultraviolet irradiation, and it is a major drawback of oxide-based photocatalysts. The designing of visible-light-driven photocatalysts based on metal oxides is very important for the highly efficient photocatalytic process.

Distilled water and polyalkylene glycol (PAG)-based aqueous quenchants of 5 and 10 vol.% with and without carbonation were prepared and used as heat transfer media during immersion quenching. Cooling curves were recorded during quenching of an inconel 600 cylindrical probe instrumented with multiple thermocouples. It was observed that the vapor stage duration was prolonged and the wetting front ascended uniformly for quenching with carbonated media. The cooling data were analyzed by determining the critical cooling parameters and by estimating the spatially dependent probe/quenchant interfacial heat flux transients. The study showed significantly reduced values of heat transfer rate for carbonated quenchants compared to quenchants without carbonation. Further, the reduction was more pronounced in the case of PAG-based carbonated quenchants than carbonated distilled water. The results also showed the dependence of heat transfer characteristics of the carbonated media on polymer concentration. The effect of quench uniformity on the microstructure of the material was assessed.

Near-complete removal of heavy metals, namely Cd(II), Cr(VI) and Pb(II), has been attempted by a membrane purification process using a blend of modified polyvinyl chloride (PVC) and polysulfone (PSf), prepared by the diffusion induced phase separation (DIPS) method. The prepared novel material was characterized by NMR, ATR-IR spectroscopy and DSC. The sulphonyl groups incorporated into PVC enhance the hydrophilicity and are substantiated by water uptake, contact angle (CA) and flux studies. The obtained properties of the blend membrane like increased surface roughness and porosity are observed from AFM and SEM analysis. An enhanced rejection of ∼95% which is about 1.15, 1.41 and 1.37 times better than the commercially available NF 270 membrane was observed, for Cd(II), Cr(VI) and Pb(II) respectively. The work was further extended to study the antifouling property and the interference of other existing metal ions on the performance. An improved antifouling property with 98.5% rejection for bovine serum albumin (BSA) and a 75.6% flux recovery ratio (FRR) was achieved. The study gains significance in exploring the incorporation of sulphonyl groups in to polymers, to enhance membrane performance.

A hydrophobic, ultrafiltration (UF), polysulfone (PSf) was reformed into a hydrophilic polymer by introducing amine groups via chemical modification. The amination was achieved by nitration to PSf followed by reduction using Na2S2O4. The modified polymer (aPSf) was characterized by NMR spectroscopy, ATR-IR, DSC and TGA. aPSf was further made into a composite membrane by using nano fillers. The prepared membranes were characterized by XRD, SEM and ion exchange capacity (IEC). The transformation in phase of TiO2 from anatase to rutile due to excess internal strain caused by amine groups was revealed by XRD patterns. Water uptake (WU), contact angle (CA) and pure water flux (PWF) were analyzed to study the hydrophilicity and performance of the membranes. These membranes were further considered for a novel approach of chromium removal by rejection/separation process. Essentially 100% separation was achieved depending on the surface charge properties of membrane, dosage of nano fillers, pH and interference of counter ions on rejection process.

Lead halide perovskites have shown great potential in photovoltaic and optoelectronic devices due to their high brightness, defect tolerance, tunable emission wavelength, high color purity and near-unity luminescence quantum yield. Conversely, lead halide perovskites (LHP) show poor stability, which received strong criticism despite other promising characteristics. The poor stability attracted much research resulting in various modifications to enhance the stability and photoluminescence quantum yield (PLQY). The review outlines the basic structural and optical properties along with the conventional method of LHP synthesis and its drawbacks. Simultaneously discusses about factors responsible for instability like crystal structure, moisture, solvent, light and temperature. The review exclusively focuses on the recent research on core-shell LHP modification strategy to improve the stability and PLQY and its application in LED devices.

TiO2 nanoparticles (NPs), functionalized poly vinyl chloride (PVC) and polysulfone (PSf) were assembled together in different compositions to fabricate composite membranes with potential application in Cr (VI) and antifouling treatment. Here, TiO2 nanoparticles were synthesized via sol-gel process and Poly vinyl chloride chemically altered with 4-amino benzoic acid. Functionalized PVC was blended uniformly throughout PSf matrix rendering the yellowish-orange color and porous structure giving better productivity. TiO2 NPs were studied for optimum concentration to provide the excess charge for Cr (VI) rejection. SEM images revealed the porous finger like structure within the membranes and the molecular weight cutoff confirmed the ultrafiltration nature of the membranes. Composites showed good wetting behavior with contact angle (between 67 and 76°) and swelling behavior (≈50–79%). Cr (VI) aqueous rejection and the key parameters namely pressure, pH, filler TiO2 concentration and BSA protein were studied in detail. Maximum of 87 ± 5% rejection of Cr (VI) was obtained with productivity of 6.5 L/m2h at 100 kPa pressure in acidic medium. While the antifouling experiments indicated incorporation of TiO2 NPs increased the flux recovery ratio, presence of BSA protein in feed solution showed binding effects with Cr2O72− anions. The membranes showed good reusability for continuous 3 cycles maintaining the rejection efficiency above 70 ± 5% at the end of 3rd cycle.

The potential of filter paper as a substrate material and 4-aminophenyl sulfone (APS) as a novel monomer for TFC fabrication is explored for the first time. A novel polyamide selective layer was developed using APS and trimesoyl chloride by interfacial polymerization, whereas the control TFC was prepared by replacing APS with m-phenylenediamine. Formation of the interfacial selective layer was verified by ATR-IR spectra and the stability of the selective surface coatings was discussed by investigating the monomer interaction. Surprisingly, after polymerization, interconnected, cross-linked structure of two monomers was observed. Desalination studies were carried out in FO mode and PRO mode using NH4HCO3 as a draw solution. Maximum of 90% and 95% rejection was obtained for NaCl and Na2SO4 salts with a flux of 2.51 and 2.17 LMH respectively. The separation efficiency of the prepared TFC membrane was compared against the likes of a commercial TFC membrane under the same conditions.

The present research work is aimed at the estimation of quench severity Polyalkylene Glycol (PAG) polymer quenchants having varying concentrations. An Inconel600 probe instrumented with thermocouples was used for this purpose. The thermal history at various locations in the probe was used as an input to the inverse heat conduction model. The inverse analysis yields spatially dependent heat flux transients. The quench severity was assessed using the Grossmann technique. The wetting kinematics of quenching was studied by cooling curve analysis. The severity of quenching as measured by the Grossmann’s technique was found to be higher for polymer quenchants. However, the heat flux transients estimated by the inverse technique and rewetting times measured form the cooling curve analysis suggested comparable and uniform heat transfer with polymer quenchants compared to water quenchants.

Quench heat treatment consists of rapid cooling of steel alloys after austenetization by subjecting them to cooling in a suitable cooling medium. At the heart of quench treatment is the transient heat transfer that occurs between the metal surface and the quenchant at their interface. This governs the quality of the component as it influences phase transformation, residual quench stresses and mechanical properties developed. In the present research work, spatially dependent transient heat flux in the axial direction was estimated using cooling curve analyses coupled with inverse heat conduction technique. A standard Inconel 600 probe instrumented with multiple thermocouples and heated to 865°C was quenched in distilled water (DW) and DW based multi walled carbon nanotubes (MWCNT) quench media. For evaluating the cooling performance, nanoquenchants with concentrations of 0.01, 0.1 and 1.0g/lt. were prepared. The cooling rate curve calculated from the measured temperature at the geometric center of the probe and the estimation of spatially dependent heat fluxes showed that the heat extraction during quenching with MWCNT nanoquenchant (0.1g/lt.) was higher than the other quenchants. The measured values of thermal conductivity and viscosities of quenchants did not show any significant variation.

The unique feature of MCPC signal is pulse diversity along with high range resolution where each pulse in each frequency is complementary to one another. These properties play an important role in attracting the interests of researchers in designing waveform for radar systems. Multifrequency radar signal uses N subcarriers simultaneously with each subcarrier is phase coded by N completely different sequences that comprises a complementary set. In this paper we propose a new approach to generate MCPC signal using direct computation method which has lower computational complexity in comparison with the conventional method.

Hydrophobic polysulphone (PSf) was reformed into a hydrophilic polymer by sulphonation (via electrophilic substitution) and was subsequently made into a composite by incorporating nano titania to reduce Cr (VI) in the concentrated feed to Cr (III), thus eliminating the hazards of Cr (VI). The modified polymer and its composites were characterized by spectroscopic and microscopic techniques. The composite membranes exhibited enhanced hydrophilicity and flux and were evaluated for the rejection of chromium. The effect of pH and interference of counter ions towards rejection was studied. The charges fixed on the surface of the membrane due to titania, support ionic interactions and facilitated the rejection process. Essentially, rejection of up to 98% was achieved. The innovation of using a bifunctional membrane for the rejection of Cr (VI) together with the removal of its toxicity by photocatalytic reduction, leading to the potential recovery of Cr (III), highlight the uniqueness of this work.

Herein we present a new approach for the complete removal of Cr(VI) species, through reduction of Cr(VI) to Cr(III), followed by adsorption of Cr(III). Reduction of chromium from water is an important challenge, as Cr(IV) is one of the most toxic substances emitted from industrial processes. Chitosan (CS) thin films were developed on plain polysulfone (PSf) and PSf/TiO2 membrane substrates by a temperature-induced technique using polyvinyl alcohol as a binder. Structure property elucidation was carried out by X-ray diffraction, microscopy, spectroscopy, contact angle measurement, and water uptake studies. The increase in hydrophilicity followed the order: PSfPSf/TiO2PSf/TiO2/CS membranes. Use of this thin-film composite membrane for chromium removal was investigated with regards to the effects of light and pH. The observations reveal 100 % reduction of Cr(VI) to Cr(III) through electrons and protons donated from OH and NH2 groups of the CS layer; the reduced Cr(III) species are adsorbed onto the CS layer via complexation to give chromium-free water.

The present work involves the assessment of quench performance of aqueous-copper oxide nanofluids. Distilled water-based copper oxide nanofluids of concentrations 0.01, 0.05, 0.1 and 1.0 vol.% were prepared by a two-step process. Cooling curves analysis was carried out using an Inconel probe that was instrumented with thermocouples. The recorded temperature data during experiments was used to estimate spatiotemporal heat flux transients by solving inverse heat conduction problem. Quenching of probe in nanofluids resulted in longer vapour phase stage duration compared to distilled water. The addition of nanoparticles altered the peak flux and the time of its occurrence. Rewetting temperatures were found to be lower for nanofluids. The measured thermal conductivities and viscosities showed similar values for all quench media.