水蓄冷运行控制分析

随着空调蓄冷技术的不断发展,它已逐渐在节能效果、经济效益和社会效益等方面展现出强大的生命力和广阔的市场。主要探讨了自然分层蓄冷形式,该方式利用温度和密度不同的原理,通过斜温层分隔高、低温水。必须严格进行水蓄冷系统的运行控制,否则极易打破其自然分层的规律。     

Strain-Induced Deformation in Magnesia–Alumina Layered Composites

Ceramic beams are induced in situ to form complex shapes at elevated temperature without the application of an external stress. This process has been demonstrated for thin alumina substrates coated with a layer of magnesia. The internal strain causing the substrates to deform at elevated temperature arises as a consequence of strain mismatch accompanying the penetration of the coating into the substrate. The magnitude of the deformation depends on the amount of coating applied, on the thickness of the substrate, on the density of the substrate, and on the temperature. During exposure of the beams to elevated temperature, the magnesia coating reacts with the alumina substrate to form the spinel phase; the resulting volume change accompanying the phase transformation is likely the predominant driving force for deformation.     

Preparation of phenolic resin derived 3-D ordered macroporous carbon

Three-dimensionally ordered long-range macroporous carbon structures were prepared using commercially available phenolic resin by utilizing sacrificial colloidal silica crystalline arrays as templates that were subsequently removed by HF etching after pyrolysis in an argon atmosphere. SEM, TEM, and BET were employed to characterize the morphology and the surface area of the porous carbon structures. The pore size (150–1000 nm) and BET surface area, which reflect pore volume (298.6 m²/g (1.32 cm³/g) ∼ 93.7 m²/g (0.12 cm³/g)), of the macroporous carbon structures produced were approximately proportional to the size (150–1000 nm) of the sacrificial silica sphere templates used (annealing temp. 550°C). The achieved 550 nm porous carbon structures were examined to function as potential catalyst carriers and were successfully impregnated with Ag or Pt-Ru on their inner walls after borohydride reduction at room temperature. In addition, porous carbon patterns were fabricated using the ‘micromolding in capillary’ technique, which has potential applications in the microreaction technology.     

乳液聚合中单体醋酸乙烯酯与保护胶体聚乙烯醇的接枝反应研究

研究了以聚乙烯醇为保护胶体的醋酸乙烯乳液聚合中,聚乙烯醇与单体的接枝反应。探讨了引发剂用量、聚合反应温度、保护胶体聚合度等因素对接枝反应的影响。     

Influence of amorphous silica on the hydration of tricalcium aluminate

Amorphous silica influences tricalcium aluminate (C₃A) hydration both in pastes and in suspensions. Two heat peaks are found by isothermal calorimetry during the paste hydration of C₃A. The addition of amorphous silica causes the second heat peak to shift towards shorter reaction times and become more pronounced. In suspensions, the change in ion concentration in the water phase is not influenced by the presence of amorphous silica except that the change in concentration occurs more quickly. Quantitative X-ray analysis shows that more 3CaO.Al₂O₃.6H₂O is present in suspensions containing amorphous silica than in silica-free suspensions at equal hydration times.     

A study on the factors for improving the ethanol production from Jerusalem artichoke by Kluyveromyces fragilis

This study is to investigate the factors influencing the alcohol production byKluyveromyces fragilis using the juice of Jerusalem Artichoke tubers. The cell growth rate and ethanol production rate were stimulated by aeration and by the addition of unsaturated fatty acids and the cell mass production and the ethanol production were substantially improved. It was found that oxygen and unsaturated fatty acids added played a decisive role on the increase of alcohol tolerance of yeast.     

High catalytic activity of PdOx/MnO2 for CO oxidation and importance of oxidation state of Mn

PdO_x/MnO₂ has been examined as a catalyst for CO oxidation using a conventional flow reactor at reaction temperatures between 50 and 150°C. In the reaction conditions of GHSV (gashourlyspacevelocity) of 1.22 × 10⁵/h and CO concentration of 2000 ppm, PdO_x/MnO₂ showed higher catalytic activity compared with PdO_x/Mn₂O₃, which had been previously reported as an effective catalyst due to the cooperative action of Pd and Mn₂O₃ for this reaction. The reason for higher activity of PdO_x/MnO₂ than PdO_x/Mn₂O₃ has been investigated using TPR (temperatureprogrammed reduction) and XPS studies. TPR showed that PdO_x/MnO₂ could be reduced by CO at much lower temperature than PdO_x/Mn₂O₃. During the experiment of reduction and oxidation, XPS showed that the valence of Mn in the PdO_x/MnO₂ was between 4+ and 3+, which is higher than that of Mn in the PdO_x/Mn₂O₃ catalyst of which the valence has been reported to be between 3+ and 2+. It is known that in this catalyst system the support supplies oxygen onto Pd, where the oxidation occurs with adsorbed CO, and the ability of the support to provide oxygen improves the performance of the catalyst. Therefore, it was concluded that the readiness of MnO₂ to be reduced with maintaining a higher oxidation state showed higher CO oxidation activity than Mn₂O₃ as support for PdO_x.     

胶层厚度对拉伸试样应力分布影响的数值分析

运用弹塑性有限元法研究了胶层厚度对承受拉伸载荷的对接接头胶层内应力分布的影响．三维有限元法数值分析的结果表明，随胶层厚度减小，胶层中正应力SZ与剪应力SYZ的分布趋于均匀；而对正应力SY而言，胶层厚度为0．15mm时，其边缘峰值应力最低。     

Synthesis of biodegradable PU/PEGDA IPNs having micro-separated morphology for enhanced blood compatibility

Summary New biodegradable hydrophobic polyurethane (PU)/hydrophilic poly (ethylene glycol) diacrylate (PEGDA) IPN was simultaneously synthesized with changing the molecular weight of PEGDA to investigate the effect of crosslinking density on the degree of phase separation. PU was modified using biodegradable poly(-caprolactone)diol and the hydroxy group of PEG was substituted to crosslinkable acrylate group having double bond, which induce photo-polymerization. The sturucture of PEGDA was confirmed by NMR. Because the reaction rate of PEGDA was faster than that of PU, the continuous matrix of the micro-separated PU/PEGDA IPNs having amphiphilic character was made of hydrophilic PEGDA-rich phase. All IPNs have sea-island morphology resulting from the suppressed phase separation. The effect of the degree of phase separation on blood compatibility was investigated.     

The onset of Taylor-Görtler vortices in impulsively decelerating swirl flow

The onset of hydrodynamical instability induced by impulsive spin-down to rest in a cylinder containing a Newtonian fluid is analyzed by using propagation theory. It is well-known that the primary transient swirl flow is laminar, but with initial high velocities secondary motion sets in at a certain time. The dimensionless critical time Τ_c to mark the onset of instability is presented here as a function of the Reynolds number Re. Available experimental data indicate that for large Re deviation of the velocity profiles from their momentum diffusion occurs starting from a certain time Τ≈4Τ_c. This means that secondary motion is detected at this characteristic time. It seems evident that during Τ_c⪯Τ⪯4Τ_c, secondary motion is relatively very weak and the primary diffusive momentum transfer is dominant.