Phase transitions and electrical conduction in thermal energy storage compound (n-C12H25NH3)2CdCl4

Differential scanning calorimetry (DSC) and differential thermal analysis (DTA) are performed for the compound (n-C₁₂H₂₅NH₃)₂CdCl₄. The ac conductivity σ_(ω,T), and the complex dielectric permittivity ?*_(ω,T) are measured as a function of temperature (100 K < T < 375 K) and at some selected frequencies (3 → 100 kHz). Two structural phase transitions are detected at T = (330 ± 1) K and T = (343 ± 1) K as minor and major transitions, respectively. The analysis of the measured electrical parameters reveals that the frequency-dependent conductivity obeys the power law, and the quantum mechanical tunneling (QMT) model is the main conduction mechanism in the low-temperature phase (LTP; phase III). The role of hydrogen bond N–H…Cl as a trigger force for phase transitions has been discussed. While the LTP is of the order–disorder type, the high-temperature phase (HTP) or phase I seems to be conformational and represents the main transition.     

The \bar{\partial }-Equation on an Annulus Between Two Strictly q-Convex Domains with Smooth Boundaries

In this paper, we study the global boundary regularity of the \(\bar{\partial }\) - equation on an annulus domain \(\Omega \) between two strictly \(q\) -convex domains with smooth boundaries in \(\mathbb{C }^n\) for some bidegree. To this finish, we first show that the \(\bar{\partial }\) -operator has closed range on \(L^{2}_{r, s}(\Omega )\) and the \(\bar{\partial }\) -Neumann operator exists and is compact on \(L^{2}_{r,s}(\Omega )\) for all \(r\ge 0\) , \(q\le s\le n-q- 1\) . We also prove that the \(\bar{\partial }\) -Neumann operator and the Bergman projection operator are continuous on the Sobolev space \(W^{k}_{r,s}(\Omega )\) , \(k\ge 0\) , \(r\ge 0\) , and \(q\le s\le n-q-1\) . Consequently, the \(L^{2}\) -existence theorem for the \(\bar{\partial }\) -equation on such domain is established. As an application, we obtain a global solution for the \(\bar{\partial }\) equation with Hölder and \(L^p\) -estimates on strictly \(q\) -concave domain with smooth \(\mathcal C ^2\) boundary in \(\mathbb{C }^n\) , by using the local solutions and applying the pushing out method of Kerzman (Commun Pure Appl Math 24:301–380, 1971).     

Sur un problème de capitulation du corps ℚ\sqrt {p_1 p_2 } , i dont le 2-groupe de classes est élémentaire

Let p ₁ ≡ p ₂ ≡ 1 (mod 8) be primes such that \(\left( {\tfrac{{p_1 }} {{p_2 }}} \right) = - 1\) and \(\left( {\tfrac{2} {{a + b}}} \right) = - 1\) , where p ₁ p ₂ = a ²+b ². Let \(i = \sqrt { - 1} \) , d = p ₁ p ₂, \(\Bbbk = \mathbb{Q}(\sqrt {d,} i),\Bbbk _2^{(1)} \) be the Hilbert 2-class field and \(\Bbbk ^{(*)} = \mathbb{Q}(\sqrt {p_1 } ,\sqrt {p_2 } ,i)\) be the genus field of \(\Bbbk \) . The 2-part \(C_{\Bbbk ,2} \) of the class group of \(\Bbbk \) is of type (2, 2, 2), so \(\Bbbk _2^{(1)} \) contains seven unramified quadratic extensions \(\mathbb{K}_j /\Bbbk \) and seven unramified biquadratic extensions \(\mathbb{L}_j /\Bbbk \) . Our goal is to determine the fourteen extensions, the group \(C_{\Bbbk ,2} \) and to study the capitulation problem of the 2-classes of \(\Bbbk \) .     

Pointwise Stabilization of a Hybrid System and Optimal Location of Actuator

We consider a pointwise stabilization problem for a model arising in the control of noise. We prove that we have exponential stability for the low frequencies but not for the high frequencies. Thus, we give an explicit polynomial decay estimation at high frequencies that is valid for regular initial data while clarifying that the behavior of the constant which intervenes in this estimation there, functions as the frequency of cut. We propose a numerical approximation of the model and study numerically the best location of the actuator at low frequencies.     

Application of lower-bound direct method to large-scale problems

In this paper, a lower-bound direct method is presented for the large-scale problems. This method is based on the statical shakedown analysis and nonlinear mathematical programming. Here, the interior point method combined with the method of difference of convex functions (IPDCA) is used to solve large-scale problems. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Spectroscopic and thermal investigations of poly(vinylidene fluoride) films composites with LaNi3Co2

Poly(vinylidene fluoride) (PVDF) and LaNi₃Co₂ were composites in various combinations by using melting technique. Morphological and physical properties of both the surface and interface of poly(vinylidene fluoride)/ LaNi₃Co₂ composite films have been investigated. FTIR and XRD diffraction analysis evidenced the increase of α, β and γ‐ PVDF crystalline phases. The bands at 888 and 1414 cm^‐1 were assigned to γ‐phase of PVDF. Maximum value of the relative amount of β‐phase was observed at 35 and 60% FL. This result was confirmed by X‐ray diffraction (XRD) and differential scanning calorimetry (DSC) analysis. Maximum value of degree of crystallinity was observed at 15% Filling level (FL). Morphology of SEM consists of two different size rings and spherulites. DSC was used to identify the melting temperature, the order of reaction and the activation energy of melting. A sharp endothermic peak at T_m ≈ 444 K due to melting and T₂ ≈ 360 K due to α‐relaxation/transition. Maximum values of magnetoresistance (MR) observed from range (243 to 238K) are due to reorientation of dipoles in a process associated with the glass transition temperature of PVDF. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the maximal unramified pro-2-extension of certain cyclotomic $$\mathbb {Z}_2$$ Z 2 -extensions

Periodica Mathematica Hungarica - In this paper, we establish a necessary and sufficient criterion for a finite metabelian 2-group G whose abelianized $$G^{ab}$$ is of type $$(2, 2^m)$$ , with...     

Some characterizations of a new metal–organic framework (n-C14H29NH3)2CdCl4 and the role of hydrogen bonding

A cadmium-based organic–inorganic hybrid (n-C₁₄H₂₉NH₃)₂CdCl₄ is synthesized and characterized, thermally and dielectrically. The differential scanning calorimetery (DSC) and the differential thermal analysis (DTA) thermograms were performed in a suitable range of temperature. The general feature of each thermogram indicates that the hybrid undergoes two structural phase transitions at T_major ≈ 351.5?K and T_minor ≈ 344.66?K in addition to an intermediate temperature which is located at ≈346.8?K. For further confirmation of the observed phase transitions, the complex dielectric permittivity ε* (ω,T)?=?ε′(ω,T) – iε″(ω,T) and ac conductivity σ_ac(ω,T) were accurately measured in the wide range of temperature 100?K<T<400?K at some suitable range of frequencies. The data evidenced the existence of such transitions. Comparison with other hybrids reveals the absence of the odd–even effect whereas the transition temperature increases with the increase of the chain length. The mechanism of proton transfer and kink defects was outlined.     

Generalized n-tuple colorings of a graph: A counterexample to a conjecture of Brigham and Dutton

In their papers (Technical Report CS-TR 50, University of Central Florida, 1980; J. Combin. Theory Ser. B32 (1982), 90–94) Brigham and Dutton introduce the notion of (n : i)-chromatic numbers of a graph, a generalization of Stahl's nth chromatic numbers (J. Combin. Theory Ser. B20, (1976), 185–203). The (n : i)-chromatic number of a graph G, denoted by χ_nⁱ(G), is the smallest integer m such that each vertex of G can be colored with a set of n colors in {1, 2,…, m} in such a way that any two adjacent vertices have exactly i colors in common. Brigham and Dutton conjecture at the end of loc cit that for all integers n and i with 0 ≤ i ≤ n ? 1, and for every graph G, χ_nⁱ⁺¹(G) ≤ χ_nⁱ(G). We prove this conjecture in some special cases and disprove it in the general case.