The sound velocity in liquid binary mixtures of <Emphasis Type="Italic">n</Emphasis>-alkanes

The method of direct measurement of the time of pulse transmission is used for investigating the sound velocity in liquid binary mixtures of n-alkanes, namely, n-hexane + n-hexadecane, n-octane + n-hexadecane, and n-decane + n-hexadecane in the range of temperatures from 298 to 433 K and pressures from 0.1 to 100.1 MPa. The maximal error of measurements is 0.1%. It is for the first time that experimental data for mixtures of n-octane + n-hexadecane and n-decane + n-hexadecane are obtained.     

Effects of Ni co-doping concentrations on dielectric and magnetic properties of (Co,Ni) co-doped SnO<Subscript>2</Subscript> nanoparticles

In this work, the dielectric and magnetic properties of (Co, Ni) co-doped SnO₂ nanoparticles were studied using ac impedance spectroscopy and magnetic properties measurement system or quantum design superconducting quantum interference device. Results showed that dielectric constant (ε _r ), dielectric loss (ε″), and ac electrical conductivity (σ _AC ) are strongly frequency dependent. A decrease in frequency was accompanied with an increase in ε _r and ε″ values, whereas, a decrease in the dielectric constant was observed with the increase of Ni co-doping concentration. It was found that the dielectric constant and dielectric loss values decrease, whilst AC electrical conductivity increases with increase in co-doping concentration. Magnetization measurements revealed that the Ni co-doped SnO₂ samples exhibits room temperature ferromagnetism. The results illustrate that (Co, Ni) co-doped SnO₂ nanoparticles have an excellent dielectric, magnetic properties, and high electrical conductivity than those of co-doped samples reported previously, indicating that these (Co, Ni) co-doped SnO₂ materials can be suitable for the purpose of high frequency device and spintronic applications.     

Test Specific Uncertainty Analysis of Zirconia-Dolerite Ball Plate by Monte Carlo Simulation

An improvised Zirconia-Dolerite ball plate artefact is manufactured, which computes different geometric errors of CMM in three different plane positions (XY, YZ and ZX). Uncertainty measurement of this artefact will affect calibration of CMM. CMM undergoing periodic interim checks by ball plate measurement needs to compute uncertainty analysis over a calibration period. This requires repetitive measurements of artefact, involving great measurement cost. An attempt has been made in this research work to devise Monte Carlo framework (MCF) for analyzing the uncertainty of ball plate measurement. The presented MCF requires less repetitive measurement at actual. This work also made possible to find preferable zones of measuring areas of CMM including volumetric measurement, explaining novelty of the research work. In the present test specific CMM, demonstrated MCF recommends seldom use of lower left corner of CMM.     

Calibration Method and Uncertainty Assessment of a High-Temperature GHP Apparatus

In this research, a calibration method of a high-temperature guarded hot plate (GHP) apparatus was proposed in order to improve the measurement accuracy of thermal conductivity. The measurement uncertainties of this GHP apparatus were assessed to validate the reliability of this calibration method. The temperature difference across the guarded gap was set as the bias value to eliminate the heat exchange over the guarded gap. The effects of the thermal expansion and pressure of the apparatus on thickness were investigated to revise the measurement results of in-situ thickness and meter area, respectively. The assessed uncertainty indicated that the related expanded uncertainty approximately increased with the increase in testing temperature and the calibration method should be valid in the temperature range. The contribution of each factor on the combined uncertainty showed that the temperature distribution in plane direction was the main factor in influencing the measurement of thermal conductivity.     

A direct method of thermal time constant measurement for lithium tantalate based terahertz pryroelectric detectors

Thermal time constant (τ _th ) is one of the most important parameters of pyroelectric detectors (PEDs). However, unlike other parameters such as voltage responsivity (R _v ), noise equivalent power and specific detectivity (D*), measurement of τ _th of lithium tantalate (LT) based PEDs was seldom reported in literatures. In this work, a convenient direct method for the measurement of τ _th was presented according to theoretical analysis and simulation result. Afterwards, this method was successfully applied to practical measurement of a homemade current mode terahertz (THz) LT based PED, of which τ _th was measured to be about 882 ms. To verify the measured result, τ _th was also calculated from the measured voltage-time curves according to its theoretical expression, which agrees well with the measured one. Compared with indirect measurement of τ _th through frequency response curves of PEDs, the direct method is simpler and more accurate. Furthermore, this method suggested an easy way for the measurement of pyroelectric coefficient of PEDs.     

Magnetic Behaviors of Ferromagnetic Semiconductor Zn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Cr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Te Grown by MBE

The magnetic and structural properties of MBE-grown films of Zn_1?xCr _x Te were investigated. The magnetization versus magnetic field (M–H) measurement of Zn_1?xCr _x Te (x = 0.01–0.17) showed clear hysteresis loop at low temperatures. The ferromagnetic transition temperature (T_C) estimated from the Arrott-plot analysis increased almost linearly with the Cr composition (x) up to 275 K at x = 0.17. However, in the magnetization versus temperature (M–T) measurement, the irreversibility between the zero-field-cooled (ZFC) and field-cooled (FC) processes was observed. This is typically observed in the magnetic random system such as spin-glass or superparamagnetic phase. In the high resolution transmission microscopy (HRTEM) observations, structural defects such as stacking faults and polycrystalline-like structure were observed at high Cr compositions, whereas any apparent precipitates of different phases were not seen in all the range of Cr compositions examined. The correlation of the observed magnetic randomness with the local structural defects was discussed.     

Symmetry of Two-Electron States in Unconventional Superconductors

A group-theoretical approach is developed to constructing two-electron states in the basis of one-electron states of crystals. Such states correspond to Cooper pairs in superconductors and pseudogap states (at T* > T _c ). The theory is applied to unconventional superconductors: heavy-fermion and high-T _c materials. Comparison of theoretical results with experimental data is used to gain insight into the structure of two-electron states in these materials.     

Modelling and analysis of South Indian temple structures under earthquake loading

The gopuram (multi-tiered entrance gateway) and the mandapam (pillared multi-purpose hall) are two representative structural forms of South Indian temples. Modelling and seismic analysis of a typical 9-tier gopuram and, 4- and 16-pillared mandapam of the 16th century AD Ekambareswar Temple in Kancheepuram, South India, are discussed. The seismic input is based on a probabilistic seismic hazard analysis of the archaeological site. Two modelling strategies, namely lumped plasticity and distributed plasticity modelling, and three analysis approaches, namely linear dynamic, non-linear, static and dynamic analyses were adopted for the seismic assessment of the gopuram. Unlike slender masonry towers, the vulnerable part of the gopuram could be at the upper levels, which is attributable to higher mode effects, and reduction in cross section and axial stresses. Finite element and limit analysis approaches were adopted for the assessment of the mandapam. Potential collapse mechanisms were identified, and the governing collapse of lateral load, calculated based on limit theory, was compared with the seismic demand as a safety check. Simple relations, as a means of rapid preliminary seismic assessment, are proposed for the mandapam.     

Investigation of ITS-90 Inconsistencies in Overlap Region of the Water-indium,Water-tin,and Water-zinc Sub-ranges

One of the significant uncertainties in Standard Platinum Resistance Thermometer (SPRT) calibration by fixed-points method is Type I non-uniqueness (sub-range inconsistencies). Sub-ranges water-tin (W ₉ ) and water-indium (W ₁₀ ) lies in the water-zinc (W ₈ ) sub-range of the International Temperature Scale of 1990. Therefore, three sub-range inconsistencies [W ₈ and W ₉ (SRI _8–9 ), W ₈ and W ₁₀ (SRI _8–10 ), and W ₉ and W ₁₀ (SRI _9–10 )] occur. This paper investigated these inconsistencies using the calibration data of 12 SPRTs from six manufacturers. The result shows that the magnitude of the inconsistency for SRI _8–9 , SRI _8–10 , and SRI _9–10 are about 2.5, 2.2 and 1.8 mK, respectively.     

Lattice Energy Determination for Polycrystalline Oxide Ceramics and Single-Crystalline Counterparts

The compositional dependence of lattice energies for polycrystalline specimens of spinel ferrite systems, Zn _x Co_1?x Fe₂ O ₄ (x = 0.0–0.6); slowly cooled and quenched systems of CuAl _x Fe_2?x O ₄ (x = 0.0–0.6); high-energy ball milled mixed ferrite composition, Ni_0.5Zn_0.5Fe₂ O ₄ (0–9 h); garnet system, Y_3?x Fe_{5 + x} O ₁₂ (x = 0.0–0.5); manganite perovskite system, La_1?x Ca _x MnO₃ (x = 0.0–1.0); and superconducting systems, Bi_1.7?x Pb_0.3Al _x Sr₂Ca₂Cu₃ O ₁₀ (x = 0.0–0.3), Bi_1.7?x Pb_0.3Ga _x Sr₂CaCu₂ O ₈ (x = 0.0–0.3), and Bi₂Sr₂CaCu₂ O ₈+0??5 % Ag ⁺ addition has been evaluated, making use of mean sound velocity data and employing Kudriavtsev’s approach. It is found that for all the systems, lattice energy decreases, and it is explained based on the change in structural and microstructural parameters as a function of substitution. The lattice energies for single-crystalline counterparts have been computed using four different estimation models based on Kapustinskii method, molecular volume and X-ray density, connectivity indices, and chemical hardness. The observed difference between the two has been discussed in the light of grain and grain boundary contributions and presence of pores and microcracks in polycrystalline materials. A simple model suggested for lattice energy determination for complex oxide compositions based on the oxide additivity rule was found to be quite satisfactory.     

Development and Characterization of a Diaphragm-Shaped Force Transducer for Static Force Measurement

There are different types of force transducers, used over the years, comprising of different principles and have different grades of uncertainty. Force transducers may be analog or digital and may be strain gauged, tuning fork type, piezoresistive type, Hall Effect based etc. Though different types of force transducers have been developed in last few decades, still strain gauged force transducers are used over the larger scale due to practical viability and reliability for force measurement. The paper describes low-cost indigenous development of a force transducer, which has been developed for a nominal capacity of 5 kN with ease of design and manufacturing. It has strain gauges applied at suitable locations to form a Wheatstone bridge. The force transducer has been calibrated according to the standard calibration procedures based on ISO 376 and IS 4169 standards. Measurement results and an uncertainty analysis have been presented. The uncertainty of measurement of the force transducer is found up to 0.06%. The paper also discusses the implications of applying multiple strain gauges at a single location in series to enhance the sensitivity of the force transducer. Two strain gauges are arranged in series for the given location and the sensitivity of the force transducer is enhanced. It also indicates that the uncertainty of measurement of the force transducer in such case is enhanced up to 0.05% or better to make force transducer suitable for most of metrological and industrial applications.     

Microstructural and Magnetic Features of SrFe<Subscript>12</Subscript><Emphasis Type="Italic">O</Emphasis><Subscript>19</Subscript> Materials Synthesized from Different Fuels by Sol-Gel Auto-Combustion Method

The nanocrystalline SrFe₁₂ O ₁₉ materials were prepared by a sol-gel auto-combustion method using different fuels such as citric acid, dextrose, aniline, and hexamine. The combustion product obtained from all the fuels except from that of aniline show a single phase of SrFe₁₂ O ₁₉ materials upon annealing at 1000 ^°C/2 h. The combustion product obtained from aniline as fuel shows SrFe₁₂ O ₁₉ as the main phase with α-Fe₂ O ₃ as impurity. No notable change in lattice parameters is observed due to variation in fuels for SrFe₁₂ O ₁₉ materials. With a little change in the NIR relative reflectance (72–85 %) on fuels, the different SrFe₁₂ O ₁₉ materials display high NIR reflectance in the wavelength range, 1500–2500 nm. The photoluminescence emission spectra of SrFe₁₂ O ₁₉ materials reveal a broad emission peak at ～350 nm which is reminiscent to the Ba-based hexaferrite, BaFe₁₂ O ₁₉. The FESEM images expose quite dissimilar morphology for the various fuels used in the synthesis of SrFe₁₂ O ₁₉ materials. Hysteresis loops for all the nanocrystalline SrFe₁₂ O ₁₉ materials observed under the applied field of ±1.5 T at room temperature exhibit hard ferromagnetic property. The SrFe₁₂ O ₁₉ materials produced from glycine and aniline as fuels exhibit highest and lowest M _s values of 61.3 and 50.5 emu/g, respectively.     

Explanation of Non-linear In-Plane Resistivity and Hall Coefficient in the Normal State of Cuprates: Polaronic Approach

We present a theoretical study of the in-plane resistivity ρ _{a b} (T) and Hall coefficient R _H (T) within the polaronic model and precursor pairing scenario by considering a two-component charge carrier picture in the normal state of high-temperature superconducting cuprates (HTSC). Here, we use a Boltzmann-equation approach and extended BCS-like model to compute ρ _{a b} (T) and R _H (T) in the τ-approximation. The opening of the pseudogap (PG) in the normal state of the cuprates should affect their transport properties. We have found that the transition to the PG regime and the effective conductivity of charge carriers in the normal state are responsible for the pronounced non-linear temperature dependence of ρ _{a b} and R _H . With the two-component model analysis, we conclude that the opening of the BCS-like PG, while the non-linear temperature dependence of ρ _{a b} and R _H could be understood as a consequence of pairing fluctuations in the PG state of cuprate superconductors. The calculated results for ρ _{a b} (T) and R _H (T) were compared with the experimental data obtained for various hole-doped cuprates. For all the considered cases, a good quantitative agreement was found between theory and experimental data. We also show that the energy scales of the binding energies of charge carriers are identified by PG crossover temperature on the cuprate phase diagram.     

Effect of Cu-Co-Zr Doping on the Properties of Strontium Hexaferrites Synthesized by Sol-Gel Auto-combustion Method

In the present study, we have synthesized tri-substituted strontium hexaferrites SrFe _(12?2x)Cu _x/2Co _x/2Zr _x O ₁₉ (x= 0.0 ?1.0, Δx= 0.2) by sol-gel auto-combustion route. The effect of this triple doping has been studied on the structural, dielectric, and magnetic properties of M-type strontium hexaferrite nanoparticles. The characterization of these materials has been done by XRD, FT-IR, VSM, SEM, EDS, and impedance analyzer. Single-phase formation is confirmed at 800 ^°C. Real permittivity decreases while loss tangent increases with increase in substitution. The observed results propose these prepared ferrites for applications in filters, antennas, isolator, circulators, etc.     

Dynamic Stiffness Assessment of Construction Materials by the Resonant and Non-resonant Methods

Dynamic stiffness of pavement surfaces is a structural property related to surface vibration and traffic noise. It is one of the mechanisms involved in tire/road noise generation. An equipment for measuring dynamic stiffness was designed and built to perform in-situ nondestructive testing on road surfaces. Laboratory studies on samples are presented to compare different measurement procedures. Measurements of the dynamic stiffness were carried out by the Resonant and Non-resonant Method. Moreover, a Dynamic Stiffness Index is proposed in order to compare the stiffness of the studied samples. Construction materials with different characteristics were studied, from resilient materials for acoustic insulation to rigid materials for pavement construction. Results show that the Non-resonant Method is more suitable for dynamic stiffness measurements, since this method could be carried out on real pavements, and both, driving point and transfer functions could be measured simultaneously. Little dynamic stiffness differences were found among road construction materials, compared to those of the resilient materials. However, the presented testing procedures are able to establish differences among these materials.     

Irreversibility Line Measurement and Vortex Dynamics in High Magnetic Fields in Ni- and Co-Doped Iron Pnictide Bulk Superconductors

The de-pinning or irreversibility lines were determined by ac susceptibility, magnetization, radio-frequency proximity detector oscillator (PDO), and resistivity methods in Ba(Fe_0.92Co_0.08)₂As₂ ( T _c = 23.2 K), Ba(Fe_0.95Ni_0.05)₂As₂ ( T _c = 20.4 K), and Ba(Fe_0.94Ni_0.06)₂As₂ ( T _c = 18.5 K) bulk superconductors in ac, dc, and pulsed magnetic fields up to 65 T. A new method of extracting the irreversibility fields from the radio-frequency proximity detector oscillator induction technique is described. Wide temperature broadening of the irreversibility lines, for any given combination of ac and dc fields, is dependent on the time frame of measurement. Increasing the magnetic field sweep rate (dH/dt) shifts the irreversibility lines to higher temperatures up to about dH/d t = 40,000 Oe/s; for higher dH/dt, there is little impact on the irreversibility line. There is an excellent data match between the irreversibility fields obtained from magnetization hysteresis loops, PDO, and ac susceptibility measurements, but not from resistivity measurements in these materials. Lower critical field vs. temperature phase diagrams are measured. Their very low values near 0 T indicate that these materials are in mixed state in nonzero magnetic fields, and yet the strength of the vortex pinning enables very high irreversibility fields, as high as 51 T at 1.5 K for the Ba(Fe_0.92Co_0.08)₂As₂ polycrystalline sample, showing a promise for liquid helium temperature applications.     

Synthesis,Structure, and Superconductivity of (La1.5Pb0.5−<Emphasis Type="Italic">x</Emphasis>Sr<Emphasis Type="Italic">x</Emphasis>)CuO<Emphasis Type="Italic">z</Emphasis>

The substitution of strontium for lead in the material (La_1.5Pb_0.5?xSr _x )CuO _z , x = 0–0.15 has been carried out. A stable and reproducible single phased superconducting materials can be obtained inside an evacuated quartz tube. The X-ray diffraction pattern shows that the superconducting phase can be indexed on the basis of an orthorhombic symmetry (F_mmm) for x = 0 and on the basis of tetragonal symmetry (I_4/mmm) for x > 0. The transition temperature T _c increases as the strontium substitution parameter x increases. We observed the maximal T _c around x = 0.15 with 38 K with fairly large Meissner volume fraction of 38% (FC).     

Development of a spinodal decomposition model for the example of a heterostructure based on silicon carbide polytypes

The transition region of a 3C-SiC/4H-SiC heterostructure constituted by layers of the 3C and 4H polytypes has been studied. A previously proposed spinodal decomposition model was used to estimate the thickness ratio of 4H and 3C layers in comparison with the image furnished by transmission electron microscopy.     

Multiscale bifurcation and stability of multilattices

A lattice-level model is developed for active materials, such as shape memory alloys, that undergo martensitic phase transformations. The model is investigated using equilibrium path following and bifurcation techniques. It is shown that a multiscale stability criterion is essential for correctly interpreting the stability of crystal equilibrium configurations under both thermal- and stress-loading conditions. A two-stage temperature-induced phase transformation is predicted from a cubic B2 phase to an orthorhombic Cmmm phase to a final orthorhombic B19 phase. Under stress-loading conditions, martensitic transformations from the B2 austenite phase to a number of possible martensite phases are identified. These include reconstructive transformations to B11, B33, and C2/m structures and proper transformation to a C2/m monoclinic phase which displays characteristic tension-compression asymmetry. The prediction of both temperature-induced and stress-induced proper martensitic transformations indicates the likelihood that the current model will exhibit shape memory behavior.