Temperature Variation Of Frequency Research Articles

Unveiling the characteristics of MgAl0.5Fe1.5O4 spinel ferrite: A study of structural, optical, and dielectric properties

Aluminium-doped magnesium ferrite (MAFO) has garnered significant interest due to its recently observed low microwave loss properties, making it invaluable for applications at high-frequency operations, including fields like spintronics and magnonics. This study delves into the optical and dielectric properties of MgAl0.5Fe1.5O4 synthesized via a conventional solid-state method followed by sintering at 1350 °C for 6 hrs. The X-ray diffraction analysis confirmed the formation of pure, single-phase MAFO spinel ferrite with the lattice constant of 8.313 Å. The Williamson–Hall (W-H) method was employed to determine the crystallite size and strain from X-ray diffraction data, resulting in values of 115.4 nm and 9.37 × 10–4, respectively. UV–visible spectroscopy was used to determine the optical properties, revealing a band gap of 2.38 eV and an average refractive index of 2.09 for the investigated spinel ferrite. The dielectric properties including capacitance, dielectric constant (ε), dielectric loss, ac conductivity, complex impedance, and modulus of MAFO sample were studied as a function of frequency for various temperatures. This comprehensive analysis sheds light on the previously undiscovered traits in the material's transport phenomena and optical attributes, opening an exciting and active field of research into its other physical properties.

Persistent effect of temperature on GDP identified from lower frequency temperature variability

It is well established that temperature variability affects a range of outcomes relevant to human welfare, including health, emotion and mood, and productivity across a number of economic sectors. However, a critical and still unresolved empirical question is whether temperature variation has a long-lasting effect on economic productivity and, therefore, whether damages compound over time in response to long-lived changes in temperature expected with climate change. Several studies have identified a relationship between temperature and gross domestic product (GDP), but empirical evidence as to the persistence of these effects is still weak. This paper presents a novel approach to isolate the persistent component of temperature effects on output using lower frequency temperature variation. The effects are heterogeneous across countries but collectively, using three different GDP datasets, we find evidence of persistent effects, implying temperature affects the determinants of economic growth, not just economic productivity. This, in turn, means that the aggregate effects of climate change on GDP may be far larger and far more uncertain than currently represented in integrated assessment models used to calculate the social cost of carbon.

Synthesis, Growth and Characterization of a Non-Linear Optical Crystal: Glycine Lead acetate (GLA)

A new non-linear optical material, glycine lead acetate (GLA) was synthesized and crystal was grown by slow evaporation growth technique at constant temperature from its aqueous solution. The Lattice Parameters for the grown crystal were determined using single crystal XRD. The crystalline nature of new crystal was confirmed by powder XRD pattern. The Presence of various functional groups has been identified by using FTIR Spectral analysis ranging between 500 and 4000 cm−1. The UV – Vis – NIR Spectroscopic study revealed that the grown crystal has good optical transmittance and the band gap energy was calculated to be 5.17ev. The thermal stability of the complex was studied by TG- DTA analysis and found that it is stable up to 214°C. The dielectric constant and dielectric loss has been studied as a function of frequency for various temperatures. The Second harmonic generation behaviour of GLA Crystal was tested by Kurtz –Perry powder technique and it is found to be 1.12 times than that of KDP Crystal.

Growth and characterization of L-tyrosine magnesium chloride single crystal: A promising NLO crystal

New single Crystal of L-Tyrosine Magnesium Chloride (LTMC) was grown from aqueous solution by slow evaporation solution technique (SEST). The grown crystal was subjected to single crystal X-ray diffraction study which confirms that the grown crystal is orthorhombic system with the space group Pmn21. The grown crystals were characterized by Fourier Transform Infrared (FTIR) spectroscopic analysis to find the different modes of vibration due to various functional groups present in LTMC. The transmission spectrum of LTMC was recorded by UV–Vis spectrometer in the range between 200 nm and 800 nm which addressed the grown crystal has good optical transparency in the entire visible region and its energy band gap was determined. The thermal stability of the crystal was determined from thermo gravimetric and differential thermo analysis (TG-DTA) curve. The dielectric constant and dielectric loss has been studied as a function of frequency for various temperatures and the results were discussed in details. The frequency dependence of AC/DC conductivity studies for different temperature was carried out. The photoconductive behavior of the material is also investigated and the grown crystal has positive photoconductive nature. Mechanical strength of the grown crystal was estimated by using Vicker’s hardness test. The presence of second harmonic generation (SHG) for the grown crystal was confirmed by Kurtz Perry powder technique. All these studies indicate that the LTMC crystal can be considered as a potential candidate for the fabrication of optoelectronic devices.

Climate warming differently affects Larix decidua ring formation at each end of a French Alps elevational gradient

The ongoing global warming tends to reduce Larix decidua radial growth and ring wood density at the bottom of an elevational gradient in the French Alps, while it has a less marked effect at the top. The ongoing climate warming affects most tree species across their biogeographic distribution range. The bottom and the top of an elevational gradient are appropriate environments to observe the effect of climate warming in contrasted temperature conditions. To retrospectively study the effect of the ongoing climate warming on Larix decidua trees located in warm and cold conditions, i.e., at the bottom (1200 m) and the top (2300 m) of an elevational gradient, respectively. Dendroecological analysis of two groups of Larix decidua trees located at very low (1200 m) and very high (2300 m) elevations. Construction of climatic response curves for annual ring variables. Decomposition of the variance of the response models into their high and low frequency components. At Briancon, in the French Alps, the increase of the daily maximum temperature during the last 50 years is already almost 3 °C for the March–October period. The results reveal contrasted behaviors at both ends of the investigated elevational gradient. Basal area increment, ring width, and their earlywood and latewood components increase or level off at the top of the gradient, while they all strongly decrease at the bottom. At the bottom, the low frequency warming effect explains the recent ring width decrease, with no influence of the high frequency temperature variation. At the top, both the low frequency warming effect and the high frequency temperature effect explain each about half of the ring width variation encompassed by the model. Latewood density displays the same trend as ring width, while earlywood density decreases at both ends of the gradient. Such opposed trends of the radial growth time trends between the top (2300 m) and the bottom (1200 m) of the gradient reflects the respectively favorable and unfavorable effects of climate warming at such ends of this Larix decidua elevational gradient. We propose that the strong ring width decrease observed at the warmer bottom announces a coming dieback. The corresponding wood density decrease will affect wood hydraulic properties in a way that is unclear.

Selection of optimal proxy locations for temperature field reconstructions using evolutionary algorithms

In the Era of exponential data generation, increasing the number of paleoclimate records to improve climate field reconstructions might not always be the best strategy. By using pseudo-proxies from different model ensembles, we show how biologically-inspired artificial intelligence can be coupled with different reconstruction methods to minimize the spatial bias induced by the non-homogeneous distribution of available proxies. The results indicate that small subsets of records situated over representative locations can outperform the reconstruction skill of the full proxy network, even in more realistic pseudo-proxy experiments and observational datasets. These locations highlight the importance of high-latitude regions and major teleconnection areas to reconstruct annual global temperature fields and their responses to external forcings and internal variability. However, low frequency temperature variations such as the transition between the Medieval Climate Anomaly and the Little Ice Age are better resolved by records situated at lower latitudes. According to our idealized experiments a careful selection of proxy locations should be performed depending on the targeted time scale of the reconstructed field.

Investigation of non linear optical tyrosine cadmium chloride single crystals grown by solution growth technique

A Novel semi-organic nonlinear optical single crystal of tyrosine cadmium chloride (TCC) has been grown by slow evaporation solution growth technique. The lattice parameters and crystal system were determined from the single crystal X-ray diffraction. The crystalline nature of the grown crystal TCC is confirmed by using powder X-ray diffraction technique. Fourier Transform Infrared (FTIR) confirms the various functional groups present in the grown crystal. The optical absorbance of electromagnetic radiation was studied through UV–Vis spectrum. The thermal behavior of the grown crystal has been investigated by DTA and TGA analysis. The dielectric constant and dielectric loss have been studied as a function of frequency for various temperatures and the result was discussed in detail. The frequency dependence of ac conductivity for different temperatures was studied. The photoconductivity studies confirm that the TCC crystal has negative photo conducting nature. The mechanical properties of the grown crystals have been studied using Vickers micro hardness. Surface morphology of TCC was studied using Scanning Electron Microscope. Nonlinear optical characteristics of TCC have been studied using Q-switched Nd:YAG laser. The second harmonic generation conversion efficiency of TCC is 5.14 times more than that of KDP and it is the highest value in the amino acid family so far reported.

Growth, spectral, thermal, electrical, mechanical and nonlinear optical properties of organic single crystal 4–Amino–(1–methylphenyl) pyridinium bromide

A recently identified organic nonlinear optical material, 4–Amino–(1–methylphenyl) pyridinium bromide (4A1MPB) was synthesized and attempts were made to grow good quality single crystal by slow evaporation solution growth technique which crystallizes in orthorhombic system with a non–centrosymmetric space group P212121. Studies such as microanalysis and powder XRD were performed for this material to ascertain its composition and phase respectively. The FT–IR spectral study, which was performed to analyze and assign the vibrational frequencies, enumerated various characteristic functional groups present in the crystal. The NLO efficiency was measured by Kurtz and Perry powder technique using Nd:YAG laser of wavelength 1064nm and it was found to be about 0.73 times that of standard KDP material. TG/DTA and DSC analyses showed that the grown crystal was thermally stable up to about 197°C. The UV–vis–NIR spectral data and fluorescence spectrum of the crystal were recorded to explore its optical transmission and emission properties respectively. The dielectric constant, dielectric loss, and ac conductivity of the grown crystal were evaluated as a function of frequency for various temperatures. The photoconducting nature of the grown crystal was analyzed and confirmed to be positive. The hardness studies were performed on (001) plane of the crystal at room temperature using Vickers micro-hardness tester, from which mechanical stability was analyzed through the classical Meyer’s relation that revealed the moderate hardness of the title compound.

Effective chemical route for the synthesis of thiophenol stabilized cadmium sulphide (CdS) quantum dots: compact discussions on the structural, morphological, optical and dielectric properties

This article describes the synthesis of CdS quantum dots by conventional chemical precipitation technique using thiophenol as a stabilizer. Structural information, crystallite size, lattice strain and dislocation density were determined by powder XRD analysis. FTIR analysis confirms the functional groups present in the synthesized CdS nanoparticles. FESEM and TEM analyses were used to investigate the morphology, particle size, phase identification and particle size distribution of the CdS nanoparticles. EDX analysis gives the elemental composition of the title compound. UV–vis-NIR reflectance spectroscopy brings out the nano-regime nature and bandgap of the resultant CdS product. Photoluminescence analysis describes the various emission properties of CdS quantum dots. The emission spectrum was analyzed through Commission International de I’Eclairage (CIE) 1931 chromaticity diagram to explore the dominant emission from the CdS quantum dots. DLS analysis gives out the information regarding secondary particle size of CdS nanoparticles. Dielectric study gives the relation between the dielectric constant and frequency for various temperatures. This work may help to develop a better understanding of solution growth mechanism and stabilizing nature of nanoparticles through chemical synthesis technique. The CdS nanoparticles are useful for the photovoltaic device applications.

Scale-dependent climatic drivers of human epidemics in ancient China

A wide range of climate change-induced effects have been implicated in the prevalence of infectious diseases. Disentangling causes and consequences, however, remains particularly challenging at historical time scales, for which the quality and quantity of most of the available natural proxy archives and written documentary sources often decline. Here, we reconstruct the spatiotemporal occurrence patterns of human epidemics for large parts of China and most of the last two millennia. Cold and dry climate conditions indirectly increased the prevalence of epidemics through the influences of locusts and famines. Our results further reveal that low-frequency, long-term temperature trends mainly contributed to negative associations with epidemics, while positive associations of epidemics with droughts, floods, locusts, and famines mainly coincided with both higher and lower frequency temperature variations. Nevertheless, unstable relationships between human epidemics and temperature changes were observed on relatively smaller time scales. Our study suggests that an intertwined, direct, and indirect array of biological, ecological, and societal responses to different aspects of past climatic changes strongly depended on the frequency domain and study period chosen.

Study on growth, structural, optical, thermal and mechanical properties of organic single crystal ethyl p-amino benzoate (EPAB) grown using vertical Bridgman technique

Ethyl p-aminobenzoate (EPAB) single crystal was grown using vertical Bridgman technique (VBT). The crystal system of grown crystal was identified, and lattice parameters have been measured from the powder X-ray diffraction (PXRD). The optical transparency of EPAB single crystal was 55%, and the cut-off wavelength was found to be 337nm. The thermal stability of EPAB single crystal was analyzed by thermogravimetric analysis. Etching studie were carried out for the grown crystal using different solvents, and etch pit density (EPD) was calculated and compared. Vickers microhardness (Hv) measurements revealed that EPAB belongs to the category of soft material. The dielectric studies reveal that the dielectric constant and dielectric loss of grown crystal decreases with increasing frequency for various temperatures. The third-order nonlinear optical property of EPAB was investigated and compared with other organic crystals. The evaluation of third-order optical properties such as nonlinear refractive index (n2), nonlinear absorption (β) and third-order nonlinear susceptibility (χ3) have found to be in the range of 10−11m2/W, 10−4m/W and 10−5esu respectively. The Laser damage threshold energy of EPAB was measured using Nd: YAG laser. The blue emission of the grown crystal was identified by photoluminescence (PL) spectra measurements. The second harmonic generation (SHG) for the grown EPAB crystal was confirmed by Kurtz powder technique.

Air-Ground Temperature Coupling: Analysis by Means of Thermal Orbits

Long-term measurements of air, near-surface (soil) and ground temperatures that were collected between 1994 and 2013 at the drill site of the Geothermal Climate Change Observatory (Prague) were analyzed to understand the relationship between these variables and to reveal the mechanisms of heat transport at the land-atmosphere boundary layer. The 2D Thermal Orbit (TO) method was applied to detect regularities that were hidden in noisy and highly variable temperature time series. The results showed that the temperatures at shallow depths were affected by surface air temperature (SAT) variations on seasonal and annual time scales and could be regarded as an accurate proxy for low frequency temperature variations at the Earth’s surface. Only low-frequency/ high-amplitude surface temperature variations penetrate into the subsurface because of strong damping and the filtering effect of the ground surface. The borehole temperatures have good potential to capture temperature variations (periodicities) over long time scales that cannot be detected in the SAT series themselves because of the interference of higher frequency noise. The TO technique is a useful and powerful tool to quickly obtain diagnostics of the presence of long periodicities in borehole temperature time series.

Effect of Mn doping on crystal structure, dielectric and magnetic ordering of Bi0.8Ba0.2FeO3 multiferroic

Bi0.8Ba0.2Fe1−xMnxO3 (x=0.0, 0.1, and 0.2) multiferroics were synthesized by the conventional solid state reaction method. Structural characterization was performed using powder X-ray diffraction at room temperature which shows that all samples possess a rhombohedrally distorted perovskite structure described by the space group R3c. Rietveld refinement confirmed a good agreement between the observed and calculated patterns. Magnetic measurements were carried out at room temperature up to a field of 15kOe. Ba and Mn co-substitution transformed antiferromagnetic BFO into ferromagnetic. This transformation is related to partial modification in the structure. Dielectric response of all synthesized samples was analyzed in the frequency range 10Hz to 5MHz at different temperatures by impedance/gain phase analyzer. The value of dielectric constant and dielectric loss show dispersion at low frequency for various temperatures in all the samples. For 10% substitution of Mn, έ increases and tanδ decreases significantly.

Analysis on the Growth and Characterization of a Non-linear Optical Single Crystal: L-Cystine Dihydrobromide

Nonlinear optical single crystals of L-cystine dihydrobromide (LCHB) have been grown by slow evaporation method. Single crystal X-ray diffraction analysis revealed the crystal system and lattice parameter values. Powder X-ray diffraction analyses have been carried out and the diffraction patterns have been indexed. Fourier transform infrared (FTIR) analysis confirms the various functional groups present in the grown crystal. The thermal behavior of the grown crystal was investigated by DTA and TGA analysis. The optical properties of the crystals were determined using UV-Visible transmittance spectrum. The dielectric constant and dielectric loss of the crystal are studied as a function of frequency for various temperatures. The SHG efficiency of the crystal is studied using the Kurtz and Perry technique.

Synthesis, growth and characterization of non linear optical Bisthiourea ammonium chloride single crystals by slow evaporation technique

A new semi-organic nonlinear optical crystal of Bisthiourea Ammonium Chloride (BTAC) has been grown by slow evaporation technique. The crystal system and lattice parameters were determined from X-ray diffraction. Fourier Transform Infrared (FTIR) studies confirm the various functional groups present in the grown crystal. The transmittance and absorbance of electromagnetic radiation is studied through UV–Visible spectrum. The thermal behavior of the grown crystals has been investigated by TG/DTA analysis. The dielectric constant and dielectric loss has been studied as a function of frequency for various temperatures and the result were discussed in detail. The SEM analysis was also done and it revealed the surface morphology of BTAC crystal. The second harmonic generation has been confirmed by the Kurtz powder test and it is found to be 1.4 times more than that of KDP crystal.

A model for predicting the creep-fatigue life under stepped-isothermal fatigue loading

A model is developed herein for predicting the fatigue life of creep-fatigue damage interaction, which is induced by combined high frequency mechanical loading and low frequency temperature variation, i.e. stepped-isothermal fatigue loading. The model is derived from continuum damage mechanics. In the model, the interaction between creep and fatigue damage is considered to be nonlinear. To validate the proposed model, a cast aluminum alloy is fatigue tested at 200–350°C and 350–400°C. The results show that good agreement can be achieved between predicted life and experimental data.

Turnover Temperature Point in Extensional-Mode Highly Doped Silicon Microresonators

This paper demonstrates the existence of a local zero temperature coefficient of frequency (i.e., turnover point) in extensional-mode silicon microresonators, fabricated on highly n-type-doped substrates and aligned to the [100] crystalline orientation. It is shown through both theoretical analysis and finite-element simulation that the turnover point in thin-film piezoelectric-on-silicon (TPoS) resonators is a function of doping concentration and orientation. Moreover, the turnover point can be adjusted by changing the thickness ratio of Si and the piezoelectric film (e.g., AlN) in the resonant structure. In order to experimentally validate this result, similar resonators are fabricated on silicon-on-insulator substrates, and the temperature variation of frequency is measured. An overall temperature-induced frequency variation of less than 245 ppm is measured over the range of -40 °C-85 °C for an ~ 25-MHz TPoS resonator aligned to the [100] plane. This is more than a 15-times reduction with respect to the uncompensated conventional silicon resonators reported before. This work is a significant step toward strengthening silicon's position as an alternative resonator technology in the quartz-dominated stable oscillator market.

Crystal growth and characterization of L-valine cadmium acetate a semiorganic NLO crystals

A new semiorganic nonlinear optical material, L-valine cadmium acetate, was grown successfully from aqueous solution by slow evaporation method. The grown crystals characterized by using Powder X-ray diffraction analysis confirms the structure of the grown title compound. The functional groups have been identified using FTIR spectral data. Transmittance compound was analyzed by using UV-vis spectrum. The thermal behavior of the grown crystal was determined with the aid of thermogravimetric analysis (TGA), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The dielectric constant was studied as a function of frequency for various temperatures. The grown crystal has positive photoconductivity nature. The fluorescence spectrum of the crystal was recorded and its optical band gap is about 3.4479eV. Second order nonlinear optical property of the grown crystal has been confirmed by modified Kurtz–Perry powder second harmonic generation (SHG) test.

Growth and characterization of l-histidine cadmium chloride monohydrate a semiorganic nonlinear optical crystals

l-histidine cadmium chloride monohydrate (LHCCM), a semiorganic nonlinear optical material was grown from aqueous solution by slow solvent evaporation method at room temperature. The LHCCM crystals were characterized by X-ray powder diffraction analysis. The presence of functional groups was identified through fourier transform infrared spectroscopy. Thermogravimetric and differential thermal analysis confirms that the crystal is stable up to 277°C. The dielectric constant was studied as a function of frequency for various temperatures. The mechanical properties of the grown crystals have been studied using Vickers microhardness tester. The second harmonic generation behavior of LHCCM crystal was tested by modified Kurtz–Perry powder technique.

Synthesis, dielectric and magnetic characteristics of poly(1-vinyl-1,2,4-triazole) (PVTri)–barium hexaferrite composite

The production of PVTri–BaFe 12O 19 composites was carried out by in situ polymerization of PVTri in the presence of synthesized BaFe 12O 19 particles. Crystalline phase was determined as BaFe 12O 19 by XRD analysis and thermal analysis revealed an inorganic content of ∼45% in the composite. SEM and TEM analyses showed strongly agglomerated particles in the range of 200 nm to several micrometers in the composite. The dielectric function of the various temperatures showed frequency dependency in a reciprocal power law. The dissipation (or loss) of energy stored within the composite was found to obey the reciprocal rule of power law of the frequency dependency. The real part of electrical modulus formalism increased exponentially with frequency for various temperatures, reaching a constant value and finally saturated. The imaginary part showed a reciprocal power law against the applied frequency and shifted to higher frequency at elevated temperatures. Magnetization measurements revealed substantially lower saturation magnetization of the composite material as compared to the bulk barium ferrite powders, possibly due to pinning of some of the surface spins by the adsorption of the PVTri molecules to the surface of the BaFe 12O 19.