Effect of V cut in perforated twisted tape insert on heat transfer and fluid flow behavior of tube flow: An experimental study

ABSTRACT

Present study investigates the heat transfer and friction characteristics of heat exchanger tube fitted with perforated twisted tape (PTT) insert having V cuts. A copper tube of 1 m length and 0.032 m inner diameter is used as test section to collect the experimental data by varying the twist ratio of PTT from 2 to 6 for the Reynolds number range of 2,700–23,400. V cuts are introduced in the PTT and the V-cut relative pitch ratio is varied from 1 to 2. The maximum thermo-hydraulic performance parameter is found to be 1.58.     

An interpretation of the g factors for the tetragonally-compressed Cr centers in YVO4 and YPO4 crystals

The g factors g_∥ and g_⊥ for the tetragonally-compressed (CrO₄)³⁻ clusters in YMO₄ (M=V, P) crystals are calculated from the high-order perturbation formulas based on the two-mechanism model for the compressed d¹ tetrahedra with the ground state |d_z²〉. From the calculated values and by considering a small admixture of the first excited state |d_x²−y²〉 to the ground state |d_z²〉 due to the vibrational motion of ligands (which leads a twinkling compressed tetrahedron to become an elongated one), the observed g_∥ and g_⊥ for Cr⁵⁺ centers in YMO₄ crystals are explained reasonably. The difficulty of the large deviations of g_∥ from g_e (≈2.0023) in the two systems is therefore removed and the above dynamic effect may be the cause which results in the large deviation of g_∥ from g_e for some (CrO₄)³⁻ clusters in crystals.     

On Weierstrass semigroups and sets: a review with new results

In this work we present a survey of the main results in the theory of Weierstrass semigroups at several points, with special attention to the determination of bounds for the cardinality of its set of gaps. We also review results on applications to the theory of error correcting codes. We then recall a generalization of the concept of Weierstrass semigroup, which is the Weierstrass set associated to a linear system and several points. We finish by presenting new results on this Weierstrass set, including some on the cardinality of its set of gaps.      

High-power continuous-wave operation of a diode-pumped laser at

The continuous-wave laser properties of an efficient diode-pumped Nd:GdVO₄ crystal operating at formed with a simple plane-concave cavity have been studied. With the incident pump power of 21 W, an output power of 6.9 W was obtained, giving an optical conversion efficiency of 32.8% and a slope efficiency of 35.3%. The laser characterization of two different Nd³⁺-doped concentration of Nd:GdVO₄ crystals were studied.     

-extension of Lie triple systems

In this paper, we introduce the notion of T^*-extension of a Lie triple system. Then we show that T^*-extension is compatible with nilpotency, solvability, and it preserves in certain sense the decomposition properties. In addition, we investigate the equivalence of T^*-extensions using cohomology. Finally, we show that every finite-dimensional nilpotent metrised Lie triple system over an algebraically closed field is the T^*-extension of an appropriate quotient system.     

Successive iteration and positive symmetric solution for a Sturm–Liouville-like four-point boundary value problem with a -Laplacian operator

In this paper, we consider the following Sturm–Liouville-like four-point p-Laplacian boundary value problem with the nonlinear term f depending on the first-order derivative subject to the boundary conditions By using a monotone iterative technique, the existence of symmetric positive solutions and corresponding iterative schemes are obtained.     

4-(5-溴-2-噻唑偶氮)间苯二酚反相阳离子对HPLC测定痕量铌、钒、铑、铬

本文报道新试剂4-(5-溴-2-噻唑偶氮)间苯二酚(5-Br-TAR)为柱前衍生试剂,以阳离子表面活性剂作为对离子试剂,用含15 mmol／L的pH 5.8的乙酸-乙酸钠缓冲溶液、0.05 mmol／L溴化钠、10 mmol／L TBA·Br的乙腈-甲醇-水(42 : 13：45,V／V／V)三元体系为流动相,在C8柱上25min内HPLC测定了Nb(V)、V(V)、Rh(Ⅲ)和Cr(Ⅵ)的5-BR-TAR螯合物。当SNR=2时,检出限分别为Nb(V)1.0、V(V)1.6、Rh(Ⅲ)0.9和Cr(Ⅵ)1.9μg／L。该方法用于测定污水中的铬和钒,结果良好。     

Manipulating OH−-Mediated Anode-Cathode Cross-Communication Toward Long-Life Aqueous Zinc-Vanadium Batteries

The anode-cathode interplay is an important but rarely considered factor that initiates the degradation of aqueous zinc ion batteries (AZIBs). Herein, to address the limited cyclability issue of V-based AZIBs, Al₂(SO₄)₃ is proposed as decent electrolyte additive to manipulate OH⁻-mediated cross-communication between Zn anode and NaV₃O₈ ⋅ 1.5H₂O (NVO) cathode. The hydrolysis of Al³⁺ creates a pH≈0.9 strong acidic environment, which unexpectedly prolongs the anode lifespan from 200 to 1000 h. Such impressive improvement is assigned to the alleviation of interfacial OH⁻ accumulation by Al³⁺ adsorption and solid electrolyte interphase formation. Accordingly, the strongly acidified electrolyte, associated with the sedated crossover of anodic OH⁻ toward NVO, remarkably mitigate its undesired dissolution and phase transition. The interrupted OH⁻-mediated communication between the two electrodes endows Zn||NVO batteries with superb cycling stability, at both low and high scan rates.     

V2O5电致变色薄膜的Raman光谱

近年来,通过向过渡金属氧化物薄膜注入Ｌｉ 制作可调节光透过率的电变色器件已越来越引起广泛的重视[1、2].由于Ｖ2Ｏ5薄膜的稳定性差,限制了它在实际中的应用.因此,为了获得变色效率高、稳定性和可逆性能好的Ｖ2Ｏ5薄膜,使用了多种制备方法,如磁控溅射法[3、6]、电化学沉积法[7、8]、溶胶凝胶法[9、10]、旋涂法[11、12]、真空蒸镀法[13、14]等.但是,无论那种方法都要解决Ｖ2Ｏ5本身在Ｈ2Ｏ或醇等的电解质溶液中电致变色时的溶解问题,通常采用控制薄膜的沉积温度或者退火处理来提高薄膜的电致变色性能[3、4、11].为了探明薄膜结构与电致变色…     

Darstellung und spektroskopische Eigenschaften von Nitridophthalocyaninatorhenium(V)

Preparation and Spectroscopical Properties of Nitridophthalocyaninatorhenium(V) Nitridophthalocyaninatorhenium(V) ([ReNPc^2?]) is prepared by the reaction of dirheniumheptoxide with ammoniumiodide in molten 1,2-dicyano-benzene. The diamagnetic complex is chemically und thermically extremely stable. In the Uv-vis spectra the typical π-π*-transitions of the Pc^2? ligand are observed. Extra bands in the solid state spectrum are due to strong excitonic coupling of ca. 2.8 kK. In the resonance Raman spectra the intensity of the Re≡N stretching vibration (v(Re≡N)) at 969 cm^?1 is selectively enhanced by laser excitations above 19.0 kK. v(Re≡N) is a dominant m.i.r. absorption at 976 cm^?1.