相变墙体冬季传热性能评价及相变参数优化

本文从相变墙体冬季的传热过程出发,提出“保温因子”和“放热因子”评价其传热性能。然后,利用热阻法建立相变墙体在冬季的传热模型,并利用单因素分析的方法研究相变墙体内外层热阻和相变温度对“保温因子”和“放热因子”的影响,结果显示当相变墙体的作用是保温的情况下,相变层应布置在墙体的外侧,相变温度应该接近室内空气温度。当相变墙体的作用是放热的情况下,相变层应布置在墙体的内侧,相变温度应该尽量高一些。本研究可以为相变墙体的应用提供理论支持。

Thermodynamic re-assessment of Fe-Ti binary system

The Fe-Ti binary system was re-assessed using the CALPHAD method in order to improve the capability of being extrapolated to a ternary or higher-order system. Compared with previous assessments, the main focus was put on the thermodynamic description of the two intermetallic compounds Fe2Ti and FeTi. The C14_Laves phase Fe2Ti was described by the two-sublattice model, which is widely used at present. By checking the homogeneity range on the boundary of the ternary systems involving the binary, the phase boundary of this compound was further confirmed. The FeTi phase with a BCC_B2 crystal structure was treated as the ordered phase of the BCC_A2 phase and a unified Gibbs energy function was used to describe both the ordered and disordered phases. Reproduction of the specific heat capacities of these compounds was another aspect paid particular attention to. Comprehensive comparisons of the calculated and experimental results regarding the phase diagram and thermodynamic properties show a good agreement between them and prove the validity of the present thermodynamic description.

Fabrication of TiO_2(B)/anatase heterophase junctions in nanowires via a surface-preferred phase transformation process for enhanced photocatalytic activity

Heterojunction fabrication is one of the most effective strategies for enhancing the photocatalytic performance of semiconductor photocatalysts. Here, TiO2（B）/anatase nanowires with interfacial heterostructures were prepared through a three-step synthesis method, including hydrothermal treatment, H＋ exchange, and annealing. The phase structures of the nanowires in the bulk and on the surface during the annealing process were monitored by XRD and UV-Raman spectroscopy, respectively. SEM and TEM results indicate that the TiO2（B） nanowires partially collapse and transform into anatase during the annealing process and the heterophase junction structure is formed simultaneously. On the basis of the phase structure together with morphology data, a phase-transformation mechanism was proposed. Photocatalytic activity was evaluated by hydrogen production and pollutant-degradation assays. The optimized structure of the photocatalyst contains 24% TiO2（B） in the bulk and 100% anatase on the surface. The charge-carrier behavior during the photocatalytic process was investigated by photocurrent, electrochemical impedance spectroscopy（EIS）, and photoluminescence（PL） spectroscopy, which revealed that the heterophase-junction structure in the bulk was responsible for the highly efficient charge separation and transportation, etc.; the anatase on the surface took control of the high surface-reaction activity.

Comparison of signal reconstruction under different transforms

A newalgorithm, called Magnitude Cut, to recover a signal from its phase in the transform domain, is proposed.First, the recovery problem is converted to an equivalent convex optimization problem, and then it is solved by the block coordinate descent（ BCD） algorithm and the interior point algorithm. Finally, the one-dimensional and twodimensional signal reconstructions are implemented and the reconstruction results under the Fourier transform with a Gaussian random mask（ FTGM）, the Cauchy wavelets transform（ CWT）, the Fourier transform with a binary random mask（ FTBM） and the Gaussian random transform（ GRT） are also comparatively analyzed. The analysis results reveal that the M agnitude Cut method can reconstruct the original signal with the phase information of different transforms; and it needs less phase information to recover the signal from the phase of the FTGM or GRT than that of FTBM or CWT under the same reconstruction error.

Phase Transitions Induced by Top-Priority of Randomization

We study the characteristics of phase transition to take the top-priority of randomization in the rules of NaSch model （i.e. noise-first model） into account via computing the relaxation time and the order parameter. The scaling exponents of the relaxation time and the scaling relation of order parameter, respectively, are obtained.

双管程热交换器强化传热研究

研发一种双管程热交换器(液/液),以强化传热技术为基础,从换热温度、流体流速、蒸发量和最小换热温差4个方面进行协同优化设计。通过相变优化、驻点优化技术,该换热器换热能力可提高30%,同时增强了抗堵塞和耐腐蚀能力。