Small Relaxation Research Articles

Pressure and temperature dependence of the electric modulus and loss factor of Poly(vinyl alcohol)/Poly(vinylidene fluoride) blends reinforced with Nano - Graphene platelets

Poly(vinyl alcohol)/Poly(vinylidene fluoride) blends reinforced with Nano - Graphene Platelets render piezoelectric by combining uniaxial plastic deformation end polarization. Comparative Broadband Dielectric Spectroscopy on fresh and piezoelectric specimens were carried oud at various temperature and hydrostatic pressure states. Dc conductivity, which results from inter-NGP fluctuation induced tunneling of electrons through the effective potential barrier set by the polymer, involves two charge transfer mechanisms. The shift of the glass transition temperature and the temperature triggering a kinetic process due to the enhancement of the mobility of water molecules bound to PVA, upon pressure are detected indirectly through associated changes to the conductivity modes. NGP filling induces a couple of interfacial charge trapping. Relaxations exhibit different thermodynamics and different dependencies for fresh and piezoelectric specimens on pressure. Hydrostatic compression of heterogeneous matter results in an inhomogeneous internal stress field, whereas stress is locally amplified. In PNC, small scale relaxation is disturbed by the spatial fluctuation of the internal stress field. Rendering the PVdF grains piezoelectric, local stress amplification induces fluctuations of the local electric field. Fluctuations (of the internal stress or electric field) affect rather a short-range charge relaxation, rather than macroscopic dc conductivity.

Components and physical properties of hydrogels modulate inflammatory response and cartilage repair.

Collagen and hyaluronic acid are commonly applied in cartilage tissue engineering, yet there has been limited investigation into their inflammatory response, a crucial factor in articular cartilage repair. This study aimed to evaluate the impact of components and physical properties of hydrogels on inflammatory response and cartilage repair. Three kinds of hydrogels with comparable storage moduli at low frequencies were designed and fabricated, namely, methacrylic anhydride-modified hyaluronic acid hydrogel (HAMA), methacrylic anhydride-modified type I collagen hydrogel (CMA) and unmodified type I collagen hydrogel (Col). HAMA hydrogel was unfavorable for adhesion and spreading of BMSCs. Furthermore, HAMA hydrogel stimulated rapid migration and pro-inflammatory M1 polarization of macrophages, leading to persistent and intense inflammation, which was unfavorable for cartilage repair. CMA and Col hydrogels possessed the same component and facilitated the adhesion, spreading and proliferation of BMSCs. Compared with CMA hydrogel, Col hydrogel induced rapid migration and moderate M1 polarization of macrophages at the early stage of injury, which was mainly influenced by its fast dissolution rate, small pore size fiber network structure and rapid stress relaxation. In addition, the phenotype of macrophages timely transformed into anti-inflammatory M2 due to the properties of the collagen component, which shortened the duration of inflammation and enhanced cartilage repair. The results indicated that moderate macrophage activation adjusted by hydrogel components and physical properties was critical in modulating inflammation and cartilage regeneration.

Диэлектрическо-спектроскопическая сепарация характеристик механизмов проводимости в нанкристаллическх пленках AgI

The study of the frequency dependence of the components of the complex permittivity of thin (100 nm) nanocrystal silver iodide (AgI) films revealed the presence of two different types of relaxation processes, sharply differing in their relaxation times: tau1<<tau2. It is established that the small relaxation time of tau1 is the time of formation of a stable configuration of the internal electric field when the external high-frequency sinusoidal electric field is shielded by a system of free conduction electrons. On the contrary, a long relaxation time of tau2 characterizes the process of shielding a low-frequency external field by a system of quasi-free silver ions. It is shown that the temperature dependence of the numerical value of tau1(T) has a thermal hysteresis with a loop, the position of the heating and cooling branches of which coincides with the temperature region of the forward and reverse phase transitions in the AgI film: semiconductor-superionic and superionic-semi-conductor. The results of calculating the parameters of dielectric spectra in the framework of Debye theory are presented, demonstrating good agreement with the parameters of the proposed electrical circuit of the film sample calculated by the complex impedance method

IMMUNER: Integrated Multimodal Mobility Under Network Disruptions

Targeting at improving door-to-door accessibility, efficiency and reducing environmental impact, recent decades have witnessed vigorous development of multimodal transport. Coupled through passenger transfer, the failure of one mode, however, is likely to cause cascading disruptions to the complete system. Therefore, to maintain safe and efficient operations, the integrated recovery of the multimodal transportation system becomes an important, timely topic, given increasingly complex schedule interactions. This study proposes a mathematical model to handle the integrated recovery problem of multimodal transportation network by minimizing the passenger travel cost and mode recovery cost under failures of multiple critical infrastructures. For a case study on air/HSR interaction in China, our model incorporates decisions in terms of aircraft recovery, railway timetable rescheduling, and passenger routing with realistic constraints (e.g. max travel time, max transfer time). A column-and-row generation based heuristic solution algorithm is developed in order to solve the complex model with given computational budgets. Results reveal that real-world test disruption scenarios can be solved within 20 minutes with a small relaxation gap. A significant amount of passenger traveling time can be reduced in contrast to a sequential recovery approach with independent reaction decisions for each transport mode. This work contributes towards the development of support tools for integrated disruption management of multimodal transportation.

Bowing-alleviated continuous bandgap engineering of wafer-scale WS2xSe2(1-x) monolayer alloys and their assembly into hetero-multilayers

Bandgap engineering of compound semiconductors and the fabrication of bandgap-modulated heterostructures are important for enabling the development of modern optoelectronics. However, these engineering processes are challenging for two-dimensional (2D) semiconductors of transition metal dichalcogenides, particularly on a large scale. Herein, we report the wafer-scale homogeneous growth of composition-modulated WS2xSe2(1-x) alloys with a continuously tunable bandgap using metal–organic chemical vapor deposition. Well-optimized growth produces monolayer films with excellent homogeneity over the entire wafer. The substitutional atomic chalcogen (S, Se) concentration in WS2xSe2(1-x) alloys is precisely controlled by varying the flow rate of the metal–organic precursors, leading to a bandgap modulation from 1.67 to 2.05 eV, as determined from absorbance spectra. Notably, the optical bandgap of WS2xSe2(1-x) alloys exhibits a nearly linear relationship with the chalcogen composition, implying a low bowing effect. This bowing-alleviated bandgap modulation is attributed to the small lattice mismatch, strain relaxation, and thermodynamic miscibility in the WS2xSe2(1-x) alloys, as confirmed by density-functional theory calculations. Furthermore, the fabrication of hetero-multilayers by stacking differently alloyed films is demonstrated. The produced heterostructure film exhibits a broad spectral absorbance distinct from that of the individual layers. The findings of this study provide insights for the advancement of versatile design of functional 2D optoelectronics.

Micronewton shear rheometer performing SAOS using 2 mg of sample

Rheological measurements typically require at least 20–50 mg of sample. We set up a miniaturized sliding-plates shear rheometer (mgRheo) that requires only 2 mg sample or even less. We designed a flexure-based force-sensing device that could measure force ranging from the micronewton to millinewton scale, e.g., 40 μN–400 mN for one particular spring constant. The setup was strain-controlled by a piezostage and could perform standard rheological tests such as small amplitude oscillatory shear, step strain, and stress relaxation. The accuracy and consistencies were evaluated on polydimethylsiloxane viscoelastic standard, entangled poly(hexyl methacrylate), and polystyrene. The obtained phase angles quantitatively agreed with those from commercial rheometers. The exact values of the modulus are prone to the overfilling of the sample. The storage G′ and loss G″ moduli from the mgRheo were systematically higher than those from commercial rheometers (i.e., within 5% with careful trimming or 30% with excessive overfilling). Between 102 and 106 Pa, G′ and G″ were in good agreement with commercial rheometers. Such a setup allowed for general rheometric characterizations, especially obtaining linear viscoelasticity on soft matters that are synthetically difficult to obtain in a large quantity.

Theoretical Understanding of thermoelectric energy conversion efficiency in Lead-Free halide double perovskites showing intrinsic defect tolerance

Thermoelectric devices based on the Seebeck effect can directly convert waste heat to electricity, but the demand for better thermoelectric materials remains unfulfilled. The lead-free halide double perovskites have recently shown promises for their stability and environment-friendly nature, but impacts from intrinsic defects (vacancies and anti-sites) on their thermoelectric performance remains elusive. Combing first-principle calculations, the Boltzmann transport theory, and the defect formation theory, we investigate the thermoelectric properties of lead-free double perovskite Cs2NaInCl6, taking the intrinsic defects into consideration. Our results demonstrate that the pristine Cs2NaInCl6 presents thermodynamic, mechanical, and dynamic stability. The band edges are mainly comprised of the electrons from In and Cl atoms. Furthermore, the double perovskite has an ultra-low lattice thermal conductivity and a high Seebeck coefficient, while showing a small charge carrier relaxation time and electric conductivity. Promisingly, the maximum ZT values can reach as high as ∼ 1.36 and ∼ 1.44 at 800 K temperature, respectively, with optimal extrinsic carrier concentrations of ∼ 1.9 × 1019 and 5.8 × 1020 cm−3 for N- and P-type carriers (holes and electrons), and the maximum power generation efficiency can reach ∼ 14% (for P-type) when the hot-side temperature is 800 K. Among various intrinsic defect types, we determine the preferable defect types in Cs2NaInCl6 based on the minimal defect formation energy criteria. The free carriers can be switched from N- to P-type under these two preferable defects, respectively, with Cl and Na vacancies. Even under a very high defect concentration of 2.1 × 1019/cm3 considered here, the extra carrier concentrations induced by the defects are only ∼ 1017 cm−3 at 800 K, showing strong defect tolerance in carrier concentration. This work suggests that lead-free halide double perovskites are promising thermoelectric materials, and they show strong intrinsic defect tolerance that prevents a negative impact on the extrinsic doping-controlled carrier concentrations.

Reduced Graphene Oxide-Based Dielectric Nanocomposites with Small Dielectric Relaxation Times for Emerging Dielectric Electronics with High-Frequency Performance Demands

Reduced Graphene Oxide-Based Dielectric Nanocomposites with Small Dielectric Relaxation Times for Emerging Dielectric Electronics with High-Frequency Performance Demands

Effect of vibrational modes on electron transfer directionality: Photosynthetic reaction centers.

It is shown in the example of the photosynthetic reaction centers (RCs) that the electron transfer can be directed by vibrational modes into the needed site where it is localized. In the case of the RC, it is the low vibrational mode that produces such an effect. We find that the electron transfer unidirectionality in the photosynthetic reaction center can be determined by the asymmetry in the reorganization energy of the vibrational modes at high temperatures. We also numerically solve generalized master equationsfor various vibration relaxation times. The results are compared with the solution of master equations. It is shown that for small relaxation times, the non-Markovian electron transfer kinetics gives similar results as the Markovian approximation, but the results are significantly different for the long vibration relaxation times.

Correlation between small polaron tunneling relaxation and donor ionization in Ga2O3

Pulsed laser deposition is employed to fabricate as-grown amorphous and post-growth annealed crystalline β-Ga2O3 films. The films annealed at temperatures above 600 °C are found to exhibit a pure monolithic phase with a bandgap of 4.7 eV. The thermally activated donor ionization and dielectric relaxation of these films are systematically investigated by temperature-dependent DC and AC conductivity measurements, and complex electric modulus analysis. A donor level at ∼180 meV below the conduction band edge and a small polaron tunneling (SPT) relaxation with an activation energy of ∼180 meV are observed in the as-grown amorphous Ga2O3 film but not in the monolithic β-Ga2O3 film. The SPT occurs between donor sites with its thermal relaxation of polarization being associated with the thermal ionization of the donor state. Thermal annealing of the amorphous films removes the 180 meV donors as well the corresponding SPT relaxation.

Evaluation of spasmolytic effects of naringenin on ileum contraction and intestinal charcoal meal transit: Involvement of ATP-sensitive K+ channels

Introduction: Naringenin is a flavonoid constituent of many herbal plants, including citreous fruits. Biological studies have suggested various therapeutic effects for naringenin, including protective effects on gastrointestinal (GI) motility. The present study was performed to investigate the involvement of ATP-sensitive K+ channels on the effect of naringenin in rat ileum motility. Methods: Ileum contractions were induced by either KCl or acetylcholine (ACh) in vitro. Inhibitory concentration-response curves were constructed for naringenin and diazoxide after exposure of rat isolated ileum to KCl (20mM) or ACh (500nM). The relaxant effects of naringenin and diazoxide were also examined in the presence of glibenclamide. Furthermore, oral effects of diazoxide (25 mg/kg) and naringenin (25, 50 mg/kg) were also assessed on the intestinal charcoal meal transit in mice (n=10) in the absence and presence of glibenclamide (50 mg/kg). Results: Diazoxide and naringenin in a concentration-dependent manner inhibited ileum contractions induced by low bath concentration of KCl (20mM). However, both drugs had no effect on contractions induced by a high concentration of KCl (160mM). The inhibitory effects of diazoxide and naringenin were blocked by glibenclamide. Oral administration of diazoxide and naringenin significantly reduced the intestinal transit of charcoal meal. The delay in the intestinal transit was blocked by the oral dose of glibenclamide. The effect of naringenin on the rat intestinal strip pre-contracted with the KCl was relatively similar to that of ATP-sensitive K+ channel opener (diazoxide). Conclusion: This research supports that ATP-sensitive K+ channels are involved in the rat small intestinal smooth muscles relaxation induced by naringenin.

Significantly suppressed thermal transport by doping In and Al atoms in gallium nitride.

Thermal transport plays a key role in the working stability of gallium nitride (GaN) based optoelectronic devices, where doping has been widely employed for practical applications. However, it remains unclear how doping affects thermal transport. In this study, based on first-principles calculations, we studied the doping effect on the thermal transport properties of GaN by substituting Ga with In/Al atoms. The thermal conductivities at 300 K along the in-plane(out-of-plane) directions of In- and Al-doped GaN are calculated to be 7.3(8.62) and 12.45(11.80) W m-1 K-1, respectively, which are more than one order of magnitude lower compared to that of GaN [242(239) W m-1 K-1]. From the analysis of phonon transport properties, we find that the low phonon group velocity and small phonon relaxation time dominate the degenerated thermal conductivity, which originated from the strong phonon anharmonicity of In/Al-doped GaN. Furthermore, by examining the crystal structure and electronic properties, the lowered thermal conductivity is revealed lying in the strong polarization of In-N and Al-N bonds, which is due to the large difference in electronegativity of In/Al and N atoms. The results achieved in this study have guiding significance to the thermal transport design of GaN-based optoelectronic devices.

Spinel-MgMn2O4 nanofibers: An attractive material for high performance aqueous symmetric supercapacitor

It is a known fact that morphology greatly influences the energy storage performance of a material. In this work, spinel magnesium manganese oxide (MgMn2O4) having nanofibric morphology has successfully been prepared for the first time using a versatile and cost-effective electrospinning technique. The morphology and the pore size are altered and optimized by varying the process parameters in the electrospinning process, and their corresponding effect on supercapacitive properties are also studied thoroughly. The aligned, mesoporous, and high aspect ratio of spinel-MgMn2O4 nanofiber exhibit the specific capacitance of ∼345 Fg−1 at 1 Ag−1 and 250 Fg−1 at 4 Ag−1 as well as demonstrate an outstanding rate capability and good capacity retention (∼90%) after 10,000 successive cycles at 4 Ag−1 in a three-electrode configuration. The improved energy storage performance of MgMn2O4 active material on graphite substrate is ascribed to its nanofibric morphology with interconnected particles having pores/voids in between, which impart a higher diffusion coefficient (D= 3.226 × 10−10 cm2s−1) and a small relaxation time constant (τ = 0.1 s). The quantitative capacitive contribution generating from EDLC and/or the surface pseudocapacitance reactions and the contribution from diffusion-controlled redox reactions to the total current have also been determined. The assembled symmetric all-solid-state supercapacitor (ASSSC) shows the high specific energy of ∼30 W h kg−1 at the specific power of ∼510 W kg−1 in the potential window of 0.0 V to 2 V with PVA-H2SO4 gel electrolyte. This performance is superior to that exhibited by many ASSSC reported recently. Two ASSSC devices connected in series can light up parallelly connected 55 red LEDs for more than 3 min, indicating practical applicability of our designed symmetric supercapacitor in electronics appliances. The outstanding electrochemical performance of the MgMn2O4 nanofiber reveals its potential to be a promising electrode material for supercapacitors.

PENGARUH KESADARAN WAJIB PAJAK, PEMAHAMAN PSAK EMKM DAN RELAKSASI PAJAK TERHADAP KEPATUHAN WAJIB PAJAK PELAKU USAHA MIKRO KECIL MENENGAH DI KOTA YOGYAKARTA

This study aims to test whether taxpayer awareness, understanding of Understanding Financial Accounting Standards of Small and Medium Micro Eentitas and tax relaxation to the compliance of small and medium micro enterprises taxpayers. The population in this study is Small and Medium Micro Enterprises in Yogyakarta. Sampling techniques in this study use convenience sampling. Data collection is done by disseminating questionnaires in the form of google form through whatsap application to respondents. The number of questionnaires processed as many as 62 questionnaires, from google form. The data was analyzed using multiple linear regression analysis. The results of this study show that taxpayer awareness and tax relaxation have a positive and significant effect on taxpayer compliance. Meanwhile, understanding the Understanding of Financial Accounting Standards of Small and Medium Micro Eentitas negatively affects taxpayer compliance.

Construction of High-Performance Carbene–Metal–Amide-Like TADF Materials: A Theoretical Study

Thermally activated delayed fluorescence (TADF) molecules based on carbene–metal–amides (CMAs) have attracted tremendous attention, but it remains a great challenge for the rational design of such materials due to the lack of reliable molecular construction guidelines. In this work, we perform a computational investigation to design CMA-based TADF materials by elucidating how the location (α, β) and number of nitrogen atoms in carbolines affect the TADF properties. Four promising CMA-based TADF molecules with both small splitting energy and large fluorescence oscillator strength were successfully designed. Moreover, it was found that β-position with one and two N atoms are promising in achieving improved TADF performance in light of their small geometric relaxations, low energy barriers for electron injection, small singlet–triplet splitting energies, facile intersystem crossing, and efficient fluorescence radiative rates. These theoretical understandings could give an in-depth physical insight into the structure–performance relationship of CMA-based luminescent materials, providing important guidance for the exploration of high-performance TADF molecules.

Different Effects of Mg and Si Doping on the Thermal Transport of Gallium Nitride

Mg and Si as the typical dopants for p- and n-type gallium nitride (GaN), respectively, are widely used in GaN-based photoelectric devices. The thermal transport properties play a key role in the thermal stability and lifetime of photoelectric devices, which are of significant urgency to be studied, especially for the Mg- and Si-doped GaN. In this paper, the thermal conductivities of Mg- and Si-doped GaN were investigated based on first-principles calculations and phonon Boltzmann transport equation. The thermal conductivities of Mg-doped GaN are found to be 5.11 and 4.77 W/mK for in-plane and cross-plane directions, respectively. While for the Si-doped GaN, the thermal conductivity reaches the smaller value, which are 0.41 and 0.51 W/mK for in-plane and cross-plane directions, respectively. The decrease in thermal conductivity of Mg-doped GaN is attributed to the combined effect of low group velocities of optical phonon branches and small phonon relaxation time. In contrast, the sharp decrease of the thermal conductivity of Si-doped GaN is mainly attributed to the extremely small phonon relaxation time. Besides, the contribution of acoustic and optical phonon modes to the thermal conductivity has changed after GaN being doped with Mg and Si. Further analysis from the orbital projected electronic density of states and the electron localization function indicates that the strong polarization of Mg-N and Si-N bonds and the distortion of the local structures together lead to the low thermal conductivity. Our results would provide important information for the thermal management of GaN-based photoelectric devices.

Unveiling the origins of low lattice thermal conductivity in 122-phase Zintl compounds

The intrinsically low lattice thermal conductivity κL is essentially important for thermoelectric technology to maintain large working temperature difference, in order to enlarge the output power. In principle, high density and complex structure at atomic and nano scale are typical features for thermoelectric materials with low lattice thermal conductivities (κLs). However, many 122-phase Zintl compounds with promising thermoelectric properties defy these paradigms. They adopt three relatively simple structures with comparably small mean atomic mass, while these compounds exhibit considerably low lattice thermal conductivities κLs. Herein we unveil the origins of low κLs in 122-phase Zintl compounds, ascribed from the important aspects including atomic constituents, their arrangements and chemical bonding. The coupling between the acoustic branches and low-frequency optical branches, as well as the anisotropic chemical bonding are responsible for the high anharmonicity, favoring for the low phonon velocity and small relaxation time. This work offers a guidance to design high-performance Zintl thermoelectric materials with ultralow lattice thermal conductivity.

A macroscopic traffic model based on relaxation time

A macroscopic model based on analogies with Little’s Law is proposed. The relaxation time is employed to characterize changes in density. This change is large for a small relaxation time and large interactions between vehicles occur. The relaxation time encompasses driver behavior which includes the time to perceive and process traffic situations and the resulting actions. Thus, it incorporates the perception and reaction time of a driver. The proposed model is evaluated for a transition caused by a bottleneck on a road and is compared with Zhang model. Performance results are presented which show that traffic evolution with the proposed model is more realistic than with the Zhang model.

Spin-wave localization and guiding by magnon band structure engineering in yttrium iron garnet

In spintronics, the propagation of spin-wave excitations in magnetically ordered materials can also be used to transport and process information. One of the most popular materials in this regard is the ferrimagnetic insulator yttrium iron garnet due its exceptionally small spin-wave damping parameter. While the small relaxation rate allows for large propagation length of magnetic excitations, it also leads to nonlocality of the magnetic properties. By imaging spin waves, their band structure is mapped with high-frequency resolution using a magneto-optic super-Nyquist sampling technique. In doing so, wave-vector selection is shown to suppress dispersion effects to a large extent, allowing for local measurements of spin relaxation. Moreover, we demonstrate even higher control of magnon propagation by employing the wave-vector selectivity near an avoided crossing of different spin-wave modes where the group velocity approaches zero. Here the local engineering of the dispersion allows us to construct magnonic waveguides, and at the same time it reveals the local relaxation properties.

An ultra-compressible piezoresistive strain and pressure sensor based on RGO-CNT-Melamine foam composite for biomedical sensing

Many heitherto reported compressive piezoresistive foam sensors suffer from variable sensitivity over large compression range, limiting the applicability of the sensor for a narrow range of motion. This is because the area of contact between conductive foam struts is very small and varies linearly over only a small compression range. We resolved this problem by fabricating an ultracompressive foam sensor with large area conductive flakes using facile technique of soak-drying Melamine foam with the conducting aqueous RGO-CNT ink. Sensor exhibited a constant gauge factor (GF) 1.6 over a large and highly linear compression range (∼2% to 60 %) and detected both small and large body movements with superior detectability. Besides that all vital features of a tiny signal such as pulse waveform were delineated due to the excellent low pressure (<5 kPa) sensitivity 0.22 kPa−1 and the small relaxation time of 19 ms. The sensor showed a stable and repeatable performance over 11000 cycles. Its operation is also tested over a wide range of ambient temperature (-7 ℃ to 140 ℃) and humidity (25%–82%, RH) and even under water with no major deterioration in performance.