Multilevel hybrid split-step implicit tau-leap

In biochemically reactive systems with small copy numbers of one or more reactant molecules, the dynamics is dominated by stochastic effects. To approximate those systems, discrete state-space and stochastic simulation approaches have been shown to be more relevant than continuous state-space and deterministic ones. In systems characterized by having simultaneously fast and slow timescales, existing discrete space-state stochastic path simulation methods, such as the stochastic simulation algorithm (SSA) and the explicit tau-leap (explicit-TL) method, can be very slow. Implicit approximations have been developed to improve numerical stability and provide efficient simulation algorithms for those systems. Here, we propose an efficient Multilevel Monte Carlo (MLMC) method in the spirit of the work by Anderson and Higham (SIAM Multiscal Model. Simul. 10(1), 2012). This method uses split-step implicit tau-leap (SSI-TL) at levels where the explicit-TL method is not applicable due to numerical stability issues. We present numerical examples that illustrate the performance of the proposed method.     

Effect of the storage tank thermal insulation on the thermal performance of an integrated collector storage solar water heater (ICSSWH)

The thermal behavior of an integrated collector storage solar water heater (ICSSWH) is numerically studied using CFD simulations. Based on the good agreement between the numerical results and the experimental data from literature, we propose a geometrical change allowing limiting the main disadvantage of this solar system which is its high night losses due to the non-insulated storage tank surface. A second 3D CFD model of an ICSSWH in which the storage tank is partially insulated is developed and three values of this tank thermal insulated fraction are studied. Numerical results show that the partially insulated tank based ICSSWH presents lower thermal losses during the night and this night thermal losses coefficient is reduced from 14.6 to 11.64 W K^?1 for the tank thermal insulation fraction τ = 1/4. Similarly, the modified system presents the advantage of its lower thermal losses even during the day. Regarding the thermal production, it is seen that the modified system presents higher water temperature at night and that for all the tank thermal insulation fractions. Concerning the operation of this modified system during the day, the water temperature is lower during the day and that up to 16 h but the water temperature which achieves 324 K for the storage tank thermal insulation fraction τ = 1/8 still sufficiently high to satisfy a family hot water needs.     

Thermal analysis, Raman spectroscopy and complex impedance analysis of Cu2+-doped KDP

Raman spectroscopy and differential thermal analysis (DTA) and thermogravimetric analysis have been carried out on Cu-doped KH₂PO₄ (Cu-KDP). X-ray diffraction powder data reveal that the structure of the KDP crystal does not change with the additive Cu²⁺ ion. DTA analysis and Raman study of Cu-KDP as a function of temperature reveal that this compound undergoes two phase transitions at about Ttr =453 and 473 K. The electrical conductivity measurements on polycrystalline pellet of Cu-KDP (5) are performed from room temperature (RT) up to 495 K. Only one phase transition is observed at 470 K. The activation energy in the migration is 0.42 eV in the temperature range from RT to 470 K. For temperature above 470 K, the activation energy of the superprotonic phase is 1.87 eV.     

A new organically templated magnesium sulfate: structure, spectroscopic analysis, and thermal behaviour

A new magnesium sulfate templated by 2-methylpiperazine, (C₅H₁₄N₂)[Mg(H₂O)₆](SO₄)₂, was prepared by the slow evaporation method. The obtained crystals were investigated by the Raman and FTIR spectroscopy and crystallographically characterised by single-crystal X-ray diffraction. The compound crystallises in the monoclinic system, space group P2₁/n. Supramolecular network of this hybrid material consists of Mg²⁺ cations octahedrally coordinated by six water molecules, sulfate tetrahedra and protonated and disordered diamine linked together by two types of hydrogen bonds: OW—H…O and N—H…O. Dehydration of the title compound takes place in three steps. Thermal decomposition of the anhydrous phase consists in the loss of the organic moiety and one sulfate group leading to the formation of magnesium sulfate.     

Synthesis,Crystal Structure,and Characterization of A New Hydrogen Phosphate Templated By 3-Aminophenyl Sulfone

Abstract

The synthesis and crystal structure of a new noncentosymmetric compound with the general formula: [C₄₈H₅₁N₈O₈S₄](HPO₄)H₂PO₄ are reported. The structure, determined by single-crystal X-ray diffraction at 150 K can be described as organic layers [C₄₈H₅₁N₈O₈S₄]³⁺ parallel to the (a and c) plane between which the inorganic groups consisting of H₂PO₄ ^? and HPO₄ ^2? entities are inserted as inorganic layers. In this atomic arrangement, H-bonds and Vander-Waals interactions between the different species play an important role in the tridimensional network cohesion. Solid-state ¹³C and ³¹P MAS NMR spectroscopies are in agreement with the X-ray structure.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

New transition metal sulfates templated by 1,4-butanediamine, (C4H14N2)[MII(H2O)6](SO4)2·4H2O (MII: Co,Ni): Structure,reactivity and thermal decomposition

Two new hybrid materials, (C₄H₁₄N₂)[M^II(H₂O)₆](SO₄)₂·4H₂O (M^II: Co (I), Ni (II)), have been synthesised by slow evaporation method at room temperature and crystallographically characterized. They crystallise isotypically in the monoclinic system, space group P2₁/n, with the following unit-cell parameters a = 9.2285(3), b = 11.3333(4), c = 10.6693(4) Å, β = 109.004(2)°, Z = 2 and V = 1055.07(6) Å³ for I and a = 9.2127(2), b = 11.3182(2), c = 10.6434(2) Å, β = 109.094(1)°, Z = 2 and V = 1048.74(4) Å³ for II. The structure of the two supramolecular compounds consists of metallic cation octahedrally coordinated to six water molecules, sulfate anions, 1,4-butanediammonium cation and water molecules linked together via two types of hydrogen bonds, O–H?O and N–H?O. The two compounds are not stable at room temperature and their partial dehydration depends on the humidity of the environment. The thermal decomposition of precursors, studied by thermogravimetric analysis (TG) and temperature-dependent X-ray diffraction (TDXD), shows successive intermediate hydrates and crystalline anhydrous compounds upon dehydration.     

Conductivity relaxation parameters of some H and K conducting in the polycrystalline compound KDyHP3O10

Polycrystalline samples of KDyHP₃O₁₀ was obtained by heating for 12 hour at 553 K a mixture containing K₂CO₃, Dy₂O₃ and H₃PO₄. Samples were characterized through X-ray diffraction, examined by IR vibrational spectroscopy and impedance and modulus spectroscopy techniques. The conductivity relaxation parameters of some H⁺ and K⁺ conducting in this compound have been determined from an analysis of ac conductivity data measured in a wide temperature range. Transport properties in this material appears as due to H⁺ and K⁺ ions hopping mechanism. The stretched exponential function exp[−(t/τ_σ)^β] has been used to describe the conductivity relaxation. The relaxation parameters have been investigated as a function of the nature of mobile ions. The results obtained are shown to be in good agreement with the predictions of the Ngai coupling model.