基于液位测量系统的定时器的开发

本文基于液位测量系统设计开发了定时器,其中 IC555用于不稳定模式。使用数字存储振荡器(DSO)测量的定时器输出波形接通时间的脉冲宽度,即电容器充电时间(T C ),与同轴圆柱形电容换能器的电容成线形比例,且该电容随着液位的变化而线性变化。因此,我们获得了电容器充电时间与液位的线性关系,该设计的优点是输入-输出具有线性关系,尺寸小,便于携带,成本低,且不受环境温度影响,它还可用于测量各种工业中液体或固体的介电常数。     

Graphene nanoplate and multiwall carbon nanotube–embedded polycarbonate hybrid composites: High electromagnetic interference shielding with low percolation threshold

This study has reported the preparation of polycarbonate (PC)/graphene nanoplate (GNP)/multiwall carbon nanotube (MWCNT) hybrid composite by simple melt mixing method of PC with GNP and MWCNT at 330°C above the processing temperature of the PC (processing temperature is 280°C) followed by compression molding. Through optimizing the ratio of (GNP/MWCNT) in the composites, high electromagnetic interference shielding effectiveness (EMI SE) value (∼21.6 dB) was achieved at low (4 wt%) loading of (GNP/MWCNT) and electrical conductivity of ≈6.84 × 10⁻⁵ S.cm⁻¹ was achieved at 0.3 wt% (GNP/MWCNT) loading with low percolation threshold (≈0.072 wt%). The high temperature melt mixing of PC with nanofillers lowers the melt viscosity of the PC that has helped for better dispersion of the GNPs and MWCNTs in the PC matrix and plays a key factor for achieving high EMI shielding value and high electrical conductivity with low percolation threshold than ever reported in PC/MWCNT or PC/graphene composites. With this method, the formation of continuous conducting interconnected GNP‐CNT‐GNP or CNT‐GNP‐CNT network structure in the matrix polymer and strong π–π interaction between the electron rich phenyl rings and oxygen atom of PC chain, GNP, and MWCNT could be possible throughout the composites. POLYM. COMPOS., 37:2058–2069, 2016. © 2015 Society of Plastics Engineers     

Upshot of strata movement during underground mining of a thick coal seam below hilly terrain

Underpinning-based simultaneous extraction was successfully used to extract more than 90% of thick and contiguous sections of a coal seam at Chirimiri mine, lying below a hill cap with a rapid change in depth of cover and is placed above the surrounding ground level. The last few panels of the mine encountered strata control problems during the depillaring. Underground instrumentation and observations showed that the last phase depillaring of the property near the free surface of the hill slope experienced shearing of overlying strata along two incompetent layers. Field investigations revealed that large amount of lateral movement due to the hilly nature of the overlying strata is the main source of the problem. A simple two-dimensional study on a simulated model also demonstrated the occurrence of the problem during working below an unconfined rock mass of hilly nature. Different evidences were collected from the site to identify the main horizons and the direction of lateral movement and, accordingly, two different strata management plans, one for each section, were successfully executed to overcome the encountered strata control problems. Field investigations in the rest of the panels of the site showed favourable impact of the adopted strata management plan.     

Ferroelectric Phase Stability Studies in Spray Deposited KNO3:PVA Composite Films

The composite films of potassium nitrate (KNO₃):poly(vinyl alcohol) (PVA) have been prepared at different temperatures by spray-deposition technique. Ferroelectric hysteresis loops were traced at room temperature for the composite films using modified Sawyer and Tower circuit. The X-ray diffraction studies confirm the existence of ferroelectric phase III of KNO₃ in the composite films at the room temperature, where this phase in pure KNO₃ films is known to exist in the temperature range 110°–124°C. The composite films deposited at 200°C shows the optimum remanent polarization, P _r∼17 μC/cm². The P _r was studied in the frequency range 10 Hz–1 kHz. The stability of the P _r in the composite films exhibits improved fatigue compared with that of quenched KNO₃ films. The capacitance–voltage ( C – V ) characteristics exhibits butterfly features which supports the presence of ferroelectric phase in the composite films. The atomic force microscopy images show that the composite films have uniform dispersion of KNO₃ particles in the PVA matrix.     

Two end variable singularity boundary elements and their applications in crack–crack interaction problems

Two new boundary elements have been proposed for simulation of variable order singularities at the two ends of an element in two dimensions. The first can model the variable order strain singularity at both the ends of the element. The second element can do both the strain and traction singularities simultaneously. The elements are useful for studying the interaction of singularities as in the case of multiple neighbouring cracks in a domain. They are employed here for the computation of stress intensity factors (SIFs) in the crack–crack interaction problems. To improve the accuracy of such computations further a modified crack closure integral (MCCI) based method for mechanical and/or thermal loading is presented. Examples of mode I crack and mixed mode problems under mechanical loading are studied to illustrate the performance of the proposed elements and the MCCI‐based calculations. The effects of the order of Gauss quadrature associated with such elements on the accuracy of the SIFs are also reported. Copyright © 2000 John Wiley & Sons, Ltd.     

Graft copolymerization of acrylonitrile onto poly(vinyl alcohol) in presence of air using ceric ammonium nitrate‐natural gums

In an attempt to overcome the problem of polymerization of vinyl monomers in presence of oxygen, polymerization was done by using some plant gums. The effect of some plant gums were studied on the graft copolymerization of acrylonitrile (AN) on to poly(vinyl alcohol) using ceric ammonium nitrate (CAN) as initiator in presence of air. Percent of grafting was determined as a function of nitric acid, concentration of monomer, time, and temperature. The rate of polymerization and maximum grafting (151%) were high compared with those in absence of the gum both in air of even in an inert atmosphere. Thus, it was definitely observed that the graft copolymerization is affected by the gum. From the differential scanning calorimetric (DSC) studies the glass‐transition temperature Tg of polyacrylonitrile (PAN) is found to be 56°C. Thermal stabilities were checked by thermogravimetric analysis (TGA) and this indicated that the grafted copolymers were resistant to moisture absorption. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1586–1590, 2000     

A rigid poly(amidehydrazide): Morphology and mechanical behavior

A wholly aromatic all-para oriented poly(amidehydrazide) has been prepared from N,N′-bis(4-aminobenzoyl)hydrazine and terephthaloyl dichloride by solution polycondensation. Films of the polymer were prepared by two processes, viz. a wet and a dry process, by using its solution in N,N-dimethylacetamide/LiCl. Optical anisotropy, surface morphology and tensile properties of the films were studied. Polarizing optical microscopic study reveals that the films prepared by the dry process have more pronounced birefringent characteristics and greater nematic order than the films prepared by the wet process. The birefringent characteristics in the films become more and more prominent with increase in polymer inherent viscosity. Scanning electron microscopic study reveals that when the LiCl content in the polymer solution used for the film casting is low (1 wt.-%), the corresponding films, prepared either by the wet or by the dry process, have smooth surfaces. But when the LiCl content is high (>1 wt.-%), only the wet process produces films with smooth surface, whereas there are microvoids on the surface of the films prepared by the dry process. Regarding the tensile study, in general, the films prepared by the dry process have higher strength and modulus, but lower elongation than the films prepared by the wet process due to a greater extent of retention of orientation in the films prepared by the dry process. The strength and modulus of the films are found to increase with increase in the polymer inherent viscosity.     

Epoxy-based multilayers for flame resistant flexible polyurethane foam (FPUF)

Flexible polyurethane foam (FPUF), a widely used cushioning and comfort component for homeware and automobile industries if tailored for flame resistance, can exhibit enhanced market value. With the view to preparing such protective films, multilayered coating composed of montmorillonite (MMT) and triphenyl phosphate (tPP) along with polyethyleneimine (PEI), poly[(o-cresyl glycidyl ether)-co-formaldehyde] (CNER), tPP solution and MMT suspension was deposited via layer-by-layer technique so as to suppress the flammability of FPUF. A comparative study applying “cone test” revealed that multilayered coatings having PEI(CNER/NH₂-MMT/PEI)_n and PEI(CNER/NH₂₋MMT/tPP)_n architectures, where “n” signifies the number of layer pairs, exhibited remarkable decrease in “peak heat release rate” (pHRR) of 20 and 25%, respectively, as compared to uncoated FPUF. Moreover, these coatings showed a 50% reduction in “fire growth rate index” (FIGRA) when compared to uncoated FPUF. This significant decrease in FIGRA after a specific combination of epoxy-clay features that such multilayered coatings can be used to protect the underlying FPUF due to the labyrinth effect offered by MMT and accelerated char formation by tPP. Furthermore, the evolution of volatile gases upon combustion of multilayered coated foam decreased due to the inhibition of oxygen permeation owing to the protective effect of the coating. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48890.     

Solid Lipid Curcumin Particles Protect Medium Spiny Neuronal Morphology,and Reduce Learning and Memory Deficits in the YAC128 Mouse Model of Huntington’s Disease

Huntington’s disease (HD) is a genetic neurodegenerative disorder characterized by motor, cognitive, and psychiatric symptoms, accompanied by massive neuronal degeneration in the striatum. In this study, we utilized solid lipid curcumin particles (SLCPs) and solid lipid particles (SLPs) to test their efficacy in reducing deficits in YAC128 HD mice. Eleven-month-old YAC128 male and female mice were treated orally with SLCPs (100 mg/kg) or equivalent volumes of SLPs or vehicle (phosphate-buffered saline) every other day for eight weeks. Learning and memory performance was assessed using an active-avoidance task on week eight. The mice were euthanized, and their brains were processed using Golgi-Cox staining to study the morphology of medium spiny neurons (MSNs) and Western blots to quantify amounts of DARPP-32, brain-derived neurotrophic factor (BDNF), TrkB, synaptophysin, and PSD-95. We found that both SLCPs and SLPs improved learning and memory in HD mice, as measured by the active avoidance task. We also found that SLCP and SLP treatments preserved MSNs arborization and spinal density and modulated synaptic proteins. Our study shows that SLCPs, as well as the lipid particles, can have therapeutic effects in old YAC128 HD mice in terms of recovering from HD brain pathology and cognitive deficits.     

Palladium-Catalysed Amide-Directed Ligand Free C8-Olefination of 1-Naphthamides for the synthesis of 2,3-dihydro-1H-benzo[de]isoquinolin-1-ones

This work describes the palladium(II)-catalyzed regioselective C8-H olefination of 1-naphthamides. Interestingly, naphthamide fused lactam 2,3-dihydro-1H-benzo[de]isoquinolin-1-one derivatives were also synthesized in the case of a particular class of napthamides. This protocol was found well compatible with a diverse range of acrylates and styrenes leading to product formation in good yields along with a wide functional group tolerance. The developed strategy was further applied to the synthesis of different drug derivatives.