Rietveld refinement study of nanocrystalline copper doped zirconia

Structural studies of Cu-doped zirconia samples with varying Cu content have been carried out. Copper-zirconia samples containing 2-20 mol% Cu were prepared by the co-precipitation technique using tetramethylammonium hydroxide as the precipitating agent and calcined at 773 K in air. The powder XRD data following Rietveld refinement revealed stabilization of zirconia in both tetragonal and cubic phases for all the samples with some monoclinic impurity phase. A decrease in the unit cell parameters of the cubic and tetragonal phase indicates incorporation of copper in the zirconia lattice of both the phases. An increase in the copper concentration (up to 20 mol%) stabilizes zirconia into the cubic phase at the expense of the tetragonal phase, with a decrease in the crystallite size (6-8 nm). Rietveld refinement of the high temperature XRD data reveals that both cubic and tetragonal phases exist up to 723 K with the cubic phase dominating (80% at 723 K). At temperature higher than 723 K, cubic phase gets transformed into the tetragonal phase, which further transforms into the monoclinic phase at 1173 K. At 1173 K, copper comes out of the cubic zirconia lattice forming a separate copper oxide phase and only the tetragonal and monoclinic polymorphs of zirconia exist.     

Analysis of nonlinearly elastic cantilever snap beams for assembly of plastic parts

Accounting for the nonlinear stress-strain behavior of plastics is important for good design of a snap joint. A constitutive equation for approximating the nonlinear stress-strain behavior of plastics is introduced in this paper. The equations for the stress, strain, and deflection of a cantilever beam, based upon the newly introduced constitutive equation are presented. In comparison with the experimental results, the cantilever deflection predicted from the nonlinear analysis is found to be about 50% more accurate than the corresponding predictions from the linear analysis.     

An electron spin resonance study of Mn2+ doped calcium hydrazine carboxylate monohydrate

Single crystals of calcium hydrazine carboxylate, monohydrate have been studied by ESR of Mn²⁺ doped in the calcium sites. X-band ESR indicated a large crystal field splitting necessitating experiments at Q band. The analysis shows two magnetically inequivalent (but chemically equivalent) sites withg _xx = 2.0042±0.0038,g _yy=2.0076 ±0.0029,g _zz=2.0314±0.001,A _zz=0.0099±0.0002 cm⁻¹,A _xx=0.0092±0.0002 cm⁻¹,A _yy=0.0082±0.0002 cm⁻¹,D=3/2D _zz=0.0558±0.0006 cm⁻¹, andE=1/2 (D _yy−D _yy)=0.0127±0.0002 cm⁻¹. One of the principal components of the crystal field, (D _zz), is found to be along the Ca ↔ Ca direction in the structure and a second one, (D _xx), along the perpendicular to the plane of the triangle formed by three neighbouring calciums. TheA tensor is found to have an orientation different from that of theg andD tensors reflecting the low symmetry of the Ca²⁺ sites.     

Building Resilience Through Disaster Waste Management-UN Environment's Experiences and Approaches（特约稿）

Integrating disaster waste issue is a critical component of making humanitarian action fit for the future, anticipating global risks and challenges such as increased vulnerability due to climate change and environmental degradation. This requires a fundamental shift towards a model that not only strengthens the response to crises but also learns and adapts in order to anticipate and act before such waste garnered. This article conducted analyses on the characteristics of disasters in the past two decades. Uncertainties confound disaster waste management, including the timing and magnitude of each disaster, and the amounts and types of waste that will be generated. For these reasons alone, disaster waste management must be an integral part of development planning and processes. Making 10 years since the 2008 Wenchuan earthquake, this article highlights that disaster waste management is not only debris clearance or waste management following a disaster, but also includes prevention and pre-disaster preparedness aspects in terms of enhancing resilience of local communities. Such "mainstreaming" ensures that disaster waste management (DWM) will be treated as a priority issue, on an ongoing basis. Based on UN Environment''s experiences and approaches, this paper emphasises that preparedness is the key, and that priority should be accorded to integrating disaster contingency planning in national and city level waste management strategies as well as mainstreaming waste management issues within broader disaster preparedness and response plans and actions. It is envisaged that the issues presented and the gaps identified in this paper will provide a basis for future comprehensive and cohesive research on disaster waste management. In turn, this research can lead to better preparedness and response on disaster waste management.     

Bulk Heterojunction Solar Cells: Impact of Minor Structural Modifications to the Polymer Backbone on the Polymer–Fullerene Mixing and Packing and on the Fullerene–Fullerene Connecting Network

The morphology of the active layer of a bulk heterojunction solar cell, made of a blend of an electron‐donating polymer and an electron‐accepting fullerene derivative, is known to play a determining role in device performance. Here, a combination of molecular dynamics simulations and long‐range corrected density functional theory calculations is used to elucidate the molecular‐scale effects that even minor structural changes to the polymer backbone can have on the “local” morphology; this study focuses on the extent of polymer–fullerene mixing, on their packing, and on the characteristics of the fullerene–fullerene connecting network in the mixed regions, aspects that are difficult to access experimentally. Three representative polymer donors are investigated: (i) poly[(5,6‐difluoro‐2,1,3‐benzothiadiazol‐4,7‐diyl)‐alt‐(3,3′″‐di(2‐octyldodecyl)‐2,2′;5′,2″;5″,2′″‐quaterthiophen‐5,5′″‐diyl)] (PffBT4T‐2OD); (ii) poly[(2,1,3‐benzothiadiazol‐4,7‐diyl)‐alt‐(3,3′″‐di(2‐octyldodecyl)‐2,2′;5′,2″;5″,2′″‐quaterthiophen‐5,5′″‐diyl)] (PBT4T‐2OD), where the fluorine atoms in the benzothiadiazole moieties of PffBT4T‐2OD are replaced with hydrogen atoms; and (iii) poly[(2,2′‐bithiophene)‐alt‐(4,7‐bis((2‐decyltetradecyl)thiophen‐2‐yl)‐5,6‐difluoro‐2‐propyl‐2H‐benzo[d][1,2,3]triazole)] (PT2‐FTAZ), where the sulfur atoms in the benzothiadiazole moieties of PffBT4T‐2OD are replaced with nitrogen atoms carrying a linear C₃H₇ side‐chain; these polymers are mixed with the phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) acceptor. This study also discusses the nature of the charge‐transfer electronic states appearing at the donor–acceptor interfaces, the electronic couplings relevant for the charge‐recombination process, and the electron‐transfer features between neighboring PC₇₁BM molecules.     

Synthesis and evaluation of interaction parameters of synthetic elastin‐derived polypentapeptide with poly(vinylpyrrolidone) in solution and solid phase

The parent repeating sequence of elastin, poly(GVGVP) has been synthesized by solution phase method and characterized by 13C and ¹H‐NMR spectroscopy. The poly(GVGVP) and poly(vinyl pyrrolidone) (PVP) interactions have been examined in solution phase by the viscometric method at 24 °C. The interaction parameters such as α, β, µ, and Δ[η]_m indicated the miscible nature of poly(GVGVP)/PVP blends. Immiscibility occurred when the quantity of poly(GVGVP) is lesser than 60%. In the solid phase, Fourier transform infrared spectroscopic scrutiny of the thin films of poly(GVGVP)/PVP blends indicated the presence of strong intermolecular interaction such as hydrogen bonds linking the blend components. This result was further supported by glass transition temperature (T_g), scanning electron microscopic, and X‐ray diffraction studies. The blending of poly(GVGVP) with PVP may provide an opportunity to produce new materials for potential biomedical applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46699.     

Electrical conductivity of chromium substituted copper ferrites

Electrical conductivity of copper–chromium (Cu–Cr) ferrites of various compositions have been investigated as a function of composition and temperature. Plots of log (σT) versus 10³/T are almost linear and have shown a transition near the Curie temperature. The activation energy in the ferrimagnetic region is in general less than that in the paramagnetic region. An attempt is made to explain the conduction mechanism in Cu–Cr ferrites.     

Subspace tracking with adaptive threshold rank estimation

In frequency and direction of arrival (DOA) tracking problems, singular value decomposition (SVD) can be used to track the signal subspace. Typically, for a problem sizen, only a few, sayr dominant eigencomponents need to be tracked, wherern. In this paper we show how to modify the Jacobi-type SVD to track only ther-dimensional signal subspace by forcing the (n-r)-dimensional noise subspace to be spherical. Therby, the computational complexity is brought down fromO(n²) toO(nr) per update. In addition to tracking the subspace itself, we demonstrate how to exploit the structure of the Jacobi-type SVD to estimate the signal subspace dimension via a simple adptive threshold comparison technique. Most available computationally efficient subspace tracking algorithms rely on off-line estimation of the signal subspace dimension, which acts as a bottleneck in real-time parallel implementations. The noise averaged Jacobi-type SVD updating algorithm presented in this paper is capable of simultaneously tracking the signal subspace and its dimension, while preserving both the low computational cost ofO(nr) and the parallel structure of the method, as demonstrated in a systolic implementation. Furthermore, the algorithm tracks all signal singular values. Their squares are estimates of the powers in the orthogonal modes of the signal. Thus, applications of the algorithm are not limited to only DOA and frequency tracking where information about the powers of signal components is not exploited.     

Energy-Efficient Load Balancing Strategy for Wireless Sensor Networks using Quasi-oppositional based Jaya Optimization

Wireless Personal Communications - The area of wireless sensor networks (WSNs) has gained significant attention from researchers due to its expansive range of applications, such as industrial...     

An intelligent internet of things-based secure healthcare framework using blockchain technology with an optimal deep learning model

The Journal of Supercomputing - Today, the internet of things (IoT) is becoming more common and finds applications in several domains, especially in the healthcare sector. Due to the rising demands...