实际联合动力循环有限时间热力学研究

基于有限时间内传热不可逆情况,用有限时间热力学方法建立了内可逆内燃机循环与斯特林循环相结合的联合动力装置的热力学模型,导出了以压缩比、温度比等循环参数表示的联合循环功率和效率表达式,通过对温度比（斯特林循环吸热温度与内燃机循环初始放热温度的比值）的数值计算分析,验证了温度比对联合循环功率和效率的影响,以及联合循环功率与效率之间的关系。该分析结果对联合循环动力装置的性能研究具有实际指导意义。     

黄河三小间水情自动测报系统遥测站供电系统设计计算

供电系统是水情自动测报系统遥测站的心脏，可靠与否至关重要。黄河三小间水情自动测报系统过几年的使用，效果良好，证明其供电系统方案正确、设计合理。本文介绍了黄河三小间水情自动测报系统遥测站供电系统的方案选择和太阳能电池、蓄电池容量的计算。     

Three-dimensionally Ordered Macroporous Phosphotungstic Acid/SiO<Subscript>2</Subscript> for Efficient Catalytic Oxidative Desulfurization

Three-dimensionally ordered (3DOM) macroporous phosphotungstic acid/SiO₂ (HPW/SiO₂) materials were prepared by using colloidal crystal as templates and applied for oxidative desulfurization (ODS) of the model fuel oil. The obtained HPW/SiO₂ materials were characterized through scanning electron microscopy, powder X-ray diffraction, N₂ sorption, and Fourier transform infrared spectroscopy. The results indicated that 3DOM HPW/SiO₂ possessed hierarchical pore architectures which contained ordered macropores and disordered mesopores, with the Keggin type HPW embedded in the framework of pore structure. The removal rate of dibenzothiophene (DBT) could reach 100% under the optimum conditions, moreover. The performance was only slightly decreased for the regenerated catalyst after 7 cycles.     

Different Frequency Synchronization Theory and Its Frequency Measurement Practice Teaching Innovation Based on Lissajous Figure Method

According to the requirement of multi-parameter time and frequency measurement without frequency normalization,a different frequency synchronization theory is proposed based on Lissajous figure method and the variation law of Lissajous figure which are used in practice teaching of frequency measurement.The theory can achieve high-precision transmission and comparison of time and frequency and precise locking and tracking of phase and frequency,improve the level of scientific research on time and frequency for postgraduate,and promote practice teaching innovation of time frequency measurement for undergraduate.Utilizing the ratio of horizontal and vertical inflection point of the Lissajous figure,the nominal frequency of the measured signal is precisely calculated.The frequency deviation between the measured frequency and its nominal frequency can be obtained by combining the turning cycle of the Lissajous figure.By observing the phase relationship between the frequency standard signal and the measured signal,the accurate measurement of the frequency isimplemented.Experimental results show that the direct measurement and comparison better than the 10-11 order of magnitude with common frequency source can be fmished between any signal frequencies.The frequency measurement method based on the theory has the advantage of simple operation,quick measurement speed,small error,low noise and high measurement precision.It plays an important role in time synchronization,communications,metrology,scientific research,educational technology practice and equipment and other fields.     

Robust design optimization with bivariate quality characteristics

In robust design optimization, if Taguchi quality loss function is employed, its expectation is minimized. When multiple quality characteristics exist, their covariances appear in the expectation and usually require numerical integrations. In this work, we propose an analytical robust design approach without numerical integrations to problems with bivariate quality characteristics. The quality characteristics are assumed to be functions of independent normal random variables with small uncertainties. Because the uncertainties are small, the functions are linearized with good accuracy. Analytical equations are then derived for the expected quality loss. The approach is efficient because no numerical integrations are needed. It is applied to the robust synthesis of a four-bar linkage.     

Synthesis of Plastic Mg-Based Bulk-Metallic-Glass Matrix Composites by Bridgman Solidification

The microstructures of the in-situ Mg-based bulk-metallic-glass (BMG) matrix composites synthesized by the copper-mold casting are inhomogeneous, and the optimized mechanical properties are usually realized through alloy composition design. In this article, Mg-based BMG matrix composites containing uniform flake-shaped precipitates with a fixed composition of Mg₇₀Cu_8.33Ni_8.33Gd_8.33Zn₅ were synthesized by the Bridgman solidification. Adjusting the withdrawal velocities controlled the size and volume fractions of the precipitates in the composites, and large plasticity was obtained by controlling the cooling condition only. Thus, the Bridgman solidification is an effective way not only to fabricate the homogeneous BMG matrix composites but also to tailor and optimize their mechanical properties.     

Effects of pressure and vibration on the thermal decomposition of cubic Ti1-x Al x N, Ti1-x Zr x N, and Zr1-x Al x N coatings: a first-principles study

Thermodynamic properties as well as the miscibility gap (binodal) and spinodal decompositions of the cubic Ti_1-x Al _x N, Ti_1-x Zr _x N, and Zr_1-x Al _x N coating alloys have been computed using first-principles calculations. Herein, the cluster expansion method and especially the special quasirandom structure are employed to describe the disordered alloys. The effects of pressure and lattice vibration on the miscibility gaps and spinodal decompositions of the above alloys have been investigated by means of Helmholtz free energy with the vibrational contribution depicted with the Debye-Grüneisen model. It is found that the application of hydrostatic pressure promotes the isostructural decomposition of Ti_1-x Al _x N, Ti_1-x Zr _x N, and Zr_1-x Al _x N alloys, whereas the vibrational contribution decreases the consolute temperature of the phase separation. Our results indicate that the improved age-hardening behavior of cubic Ti_1-x Al _x N coatings with the addition of Zr arises from the enlarged composition range of binodal and spinodal curves at specified temperatures. Our results are in good agreement with the available experimental data and provide a useful insight into the investigation of age-hardening and characterization of Ti–Al–Zr–N-based coatings for high-temperature applications.     

Effect of sodium silicate pretreatment on phosphate layer: Morphology and corrosion resistance behavior

Phosphating is a widely adopted treatment in industry for many purposes. In this paper, carbon steel was pretreated with sodium silicate before phosphating. X‐ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical measurements were used to evaluate the pretreatment effect by sodium silicate on the phosphating layer. The results demonstrate that the phosphate layer pretreated by sodium silicate has a better corrosion resistance as compared with the un‐pretreated ones. More compact and uniform coatings composed of finer crystals were obtained with the pretreatment of sodium silicate.