Thermally Stimulated Depolarisation Studies of Methyl Acrylic Acid (MAA) Doped Ethyl Cellulose (EC)

Thermally stimulated depolarisation current (TSDC) of polarised samples of methyl acrylic acid (MAA) doped ethyl cellulose (EC) films of about 25 µm thickness has been recorded as a function of temperature, electric field, heating rates and storage times. Two current maxima in positive direction and found around 60 and 110oC for doped sample with ethyl cellulose. FTIR of doped EC are represented the different phenomena of TSDC. Thermal sampling technique showed that the relaxation is distributed. Differentia thermal analysis gave a second-order transition at bout 345K because of good correlation between both thermal techniques it is concluded that the TSD peak is associated with glass transition of the polymer, and therefore it involves the motion of large parts of the polymer chains.

CJT effective potential approach to analyze the nature of phase transition of thermal QED$$_3$$ at finite volume

Based on the Cornwall–Jackiw–Tomboulis effective potential and the truncated Dyson–Schwinger equations, the nature of phase transition of thermal QED$$_3$$ 3 at finite volume is investigated. We show that, with the rise of temperature, the system undergoes a second-order transition in the chiral limit, and remains exhibiting the second-order with small fermion mass, while it switches to a crossover when the fermion mass exceeds a critical value about $$m_{c}$$ m c , which diminishes with the increasing volume size and tends to zero in infinite volume.

Large Low-Field Reversible Magnetocaloric Effect in Itinerant-Electron Hf1-xTaxFe2 Alloys

First-order isostructural magnetoelastic transition with large magnetization difference and controllable thermal hysteresis are highly desirable in the development of high-performance magnetocaloric materials used for energy-efficient and environmental-friendly magnetic refrigeration. Here, we demonstrate large magnetocaloric effect covering the temperature range from 325 K to 245 K in Laves phase Hf1-xTaxFe2 (x = 0.13, 0.14, 0.15, 0.16) alloys undergoing the magnetoelastic transition from antiferromagnetic (AFM) state to ferromagnetic (FM) state on decreasing the temperature. It is shown that with the increase of Ta content, the nature of AFM to FM transition is gradually changed from second-order to first-order. Based on the direct measurements, large reversible adiabatic temperature change (ΔTad) values of 2.7 K and 3.4 K have been achieved under a low magnetic field change of 1.5 T in the Hf0.85Ta0.15Fe2 and Hf0.84Ta0.16Fe2 alloys with the first-order magnetoelastic transition, respectively. Such remarkable magnetocaloric response is attributed to the rather low thermal hysteresis upon the transition as these two alloys are close to intermediate composition point of second-order transition converting to first-order transition.

The Beauty of Twist-Bend Nematic Phase: Fast Switching Domains, First Order Fréedericksz Transition and a Hierarchy of Structures

The twist-bend nematic phase (NTB) exhibits a complicated hierarchy of structures responsible for several intriguing properties presented here. These are: the observation of a fast electrooptic response, the exhibition of a large electroclinic effect, and the observation of an unusual pattern of the temperature dependence of birefringence of bent-shaped bimesogens in parallel-rubbed planar-aligned cells. These unusual effects inspired the use of highly sophisticated techniques that led to the discovery of the twist-bend nematic phase. Results of the optical retardation of a parallel-rubbed planar-aligned cell show that the ‘heliconical angle’ (the angle the local director makes with the optical axis) starts increasing in the high temperature N phase, it exhibits a jump at the N–NTB transition temperature and continues to increase in magnitude with a further reduction in temperature. The liquid crystalline parallel-rubbed planar-aligned and twist-aligned cells in this phase exhibit fascinating phenomena such as a demonstration of the beautiful stripes and dependence of their periodicity on temperature. The Fréedericksz transition in the NTB phase is found to be of the first order both in rubbed planar and homeotropic-aligned cells, in contrast to the second order transition exhibited by a conventional nematic phase. This transition shows a significant hysteresis as well as an abrupt change in the orientation of the director as a function of the applied electric field. Hierarchical structures are revealed using the technique of polymer templating the structure of the liquid crystalline phase of interest, and imaging of the resulting structure by scanning electron microscopy.

ANALISIS PENJUALAN DAN PERSAINGAN AIR MINERAL KEMASAN BOTOL SELAMA PANDEMI COVID-19 DI KOTA MEDAN MENGGUNAKAN RANTAI MARKOV ORDE DUA

Markov chain is a method used to identify variables in the present, which is based on past variables in order to obtain an estimate of the probability of these variables in the future. The CoVid-19 virus outbreak has also had a negative impact on economic problems, because this pandemic resulted in a decrease in sales of mineral water. in bottles that experienced a decline in sales results during the COVID-19 pandemic. The formulation of the problem of how companies compete during Covid-19 which continues to experience a decline in sales? . Based on the results of this study, there is a large chance of a second order transition, namely AQUA products in September, which is 61%, an increase of 0.39% from October, in October it was 61.39, a decline of 0.02% so that in November it was 61.37% while Le Mineral products in September were 39%, decreased 0.39% from October, October was 38.61%, experienced a fix in November so November was 38.61%.

The Maxwell crossover and the van der Waals equation of state

The well-known Maxwell construction1 (the equal-area rule, EAR) was devised for vapor liquid equilibrium (VLE) calculation with the van der Waals (vdW) equation of state (EoS)2. The EAR generates an intermediate volume between the saturated liquid and vapor volumes. The trajectory of the intermediate volume over the coexistence region is defined here as the Maxwell crossover, denoted as the M-line, which is independent of EoS. For the vdW or any cubic3 EoS, the intermediate volume corresponds to the “unphysical” root, while other two corresponding to the saturated volumes of vapor and liquid phases, respectively. Due to it’s “unphysical” nature, the intermediate volume has always been discarded. Here we show that the M-line, which turns out to be strictly related to the diameter4 of the coexistence curve, holds the key to solving several major issues. Traditionally the coexistence curve with two branches is considered as the extension of the Widom line5,6-9. This assertion causes an inconsistency in three planes of temperature, pressure and volume. It is found that the M-line is the natural extension of the Widom line into the vapor-liquid coexistence region. As a result, the united single line coherently divides the entire phase space, including the coexistence and supercritical fluid regions, into gas-like and liquid-like regimes in all the planes. Moreover, along the M-line the vdW EoS finds a new perspective to access the second-order transition in a way better aligning with observations and modern theory10. Lastly, by using the feature of the M-line, we are able to derive a highly accurate and analytical proximate solution to the VLE problem with the vdW EoS.

Study of the magnetic properties and magnetocaloric effects in (Ho0.85RE0.15)3Pd2 (RE=Y and Gd) compounds

The crystal structure, magnetic and magnetocaloric properties of the [Formula: see text] (RE=Y and Gd) compounds were investigated. Both of the compounds crystallize in a single phase with a tetragonal [Formula: see text]-type structure (space group [Formula: see text]/mbm) and undergo a second-order transition from ferromagnetic (FM) state to paramagnetic (PM) state. In the PM region, the reciprocal susceptibilities both obey the Curie–Weiss law. The paramagnetic Curie temperatures [Formula: see text] for [Formula: see text] and [Formula: see text] were determined to be 4.9 K and 3.2 K, and the corresponding effective magnetic moments [Formula: see text] are 10.3 [Formula: see text]/RE and 10.5 [Formula: see text]/RE, respectively. Under a field change from 0 T to 5 T, the maximum values of [Formula: see text] for the [Formula: see text] and [Formula: see text] compounds are determined to be [Formula: see text] and [Formula: see text], with the corresponding RC values of [Formula: see text] and [Formula: see text], respectively.

Скачкообразные процессы магнитного разупорядочения, стимулированные магнитным полем в системах со структурной неустойчивостью

A theoretical analysis of the features of structural and magnetostructural first-order phase transitions in magnetocaloric helimagnetic alloys of the Mn_{1-x}Cr_{x}NiGe system has been carried out. To describe the observed displacive structural transitions hex(P6_{3}/mmc)<->orth(P_{nma}), we used the local soft mode model in the approximation of a biased harmonic oscillator. In the absence of a magnetic field, the emergence of a helimagnetic order as a structurally induced second-order transition was described in the framework of the Heisenberg model, taking into account the dependence of the exchange integrals on the structural order parameters and elastic strains. In the presence of a magnetic field, it was found that the approximation of the characteristic temperatures for the helimagnetic HM(P_{nma}) and lability temperatures of the hexagonal paramagnetic PM(P6_{3}/mmc) states, due to the influence of the magnetic field, leads to the appearance of previously unexplored peripheral magnetostructural first-order phase transitions with insignificant magnetization jumps that increase with increasing magnetic induction.In this case, as the pressure increases to 4 kbar with constant induction of the magnetic field, the peripheral transitions transform into reversible first-order magnetostructural transitions, and at even higher pressures (10-14 kbar) into full-fledged first-order magnetostructural transitions with magnetization jumps comparable with maximum value of magnetization. Experimental pressure studies of the temperature dependences of magnetization in static magnetic fields with an induction of up to 1 T and a pressure of up to 14 kbar confirm the theoretical results.