开孔剂对多孔氧化铝支撑体的影响

研究了开孔剂对a-Al2O3多孔道氧化铝支撑体的影响,发现开孔剂的种类及质量分数对支撑体的性能有重要影响,选择合适的开孔剂种类及质量分数可使氧化铝支撑体的纯水通量提高2～3倍。     

三峡工程高掺量粉煤灰混凝土碳化性能研究

研究了不同掺量粉煤灰混凝土碳化速率及其碳化前后强度和抗渗性的变化 ,分析了粉煤灰掺量和火山灰反应与粉煤灰混凝土碳化速率的关系 ,讨论了粉煤灰混凝土碳化前后强度和抗渗性变化的原因。     

Strength, durability and micro-structural aspects of high performance volcanic ash concrete

This paper presents the results of investigations to assess the suitability of using volcanic ash (VA) as a cement replacement material to produce high performance concrete. Tests were conducted on concrete mixtures replacing 0 to 20% by mass of ordinary Portland cement (OPC) by VA. The performance of high performance volcanic ash concrete (HPVAC) mixtures was evaluated by conducting comprehensive series of tests on fresh and hardened properties as well as durability. The mechanical properties were assessed by compressive strength, while durability characteristics were investigated by rapid chloride permeability (RCP), drying shrinkage (DS), mercury intrusion porosimetry (MIP), differential scanning calorimetry (DSC) and microhardness tests. HPVACs showed better durability properties compared to control concrete with 0% VA. The improved performance of HPVACs was attributed to the refinement of pore structure, and pozzolanic action of VA. HPVAC having a minimum 28-day compressive strength of 60 MPa can be obtained by replacing up to 20% (by mass) of cement by VA. Development of non-expensive and environmentally friendly HPVAC with acceptable strength and durability characteristics (as illustrated in this study) is extremely helpful for the sustainable development and rehabilitation of volcanic disaster areas around the world.     

大掺量粉煤灰对混凝土渗透性的影响

以粉煤灰代替３０％的水泥，在水胶比为０．３０、０．３３、０．３６及０．３９的情况下，分别试验了用水量及胶凝材料用量变化下混凝土的强度和渗透性。试验结果表明，与不掺粉煤灰的混凝土比较，掺粉煤灰混凝土的渗透性都明显降低，３０天龄期时最大可降低至５０．７％，７０天时可降低至２２．３％；为了获得较低的渗透性而采取较低的水胶比时，不掺粉煤灰的混凝土应用降低用水量的办法有利，掺粉煤灰的混凝土用提高总胶凝材料用量的办法更好     

Nanocomposites based on polyethylene and Mg-Al layered double hydroxide. I. Synthesis and characterization

Low density polyethylene (LDPE)/Mg-Al layered double hydroxide (LDH) nanocomposites have been synthesized with different compositions by melt-mixing technique using maleic anhydride grafted polyethylene as compatibilizer. LDH has been modified by sodium dodecylbenzene sulfonate using reconstruction method and characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The nanocomposites are characterized by different techniques such as, transmission electron microscopy (TEM), XRD and rheology. The TEM analysis shows a complex nature of particle dispersion in the polymer matrix with wide distribution of particles sizes and shapes. The rheological analysis showed significant changes in linear viscoelastic responses of the composites, even at very low concentration (2 phr) of LDH materials, in comparison to the pure polymer in low frequency regime in dynamic frequency sweep experiments. These changes are related to the LDHs-polymer chains interactions resulting in network-like structure.     

Effects of personal,psychosocial and occupational factors on low back pain severity in workers

Low back pain (LBP) remains the most common work-related musculoskeletal disorder (WMSD). While most of the LBP research has focused on occupational risk factors, other underlying causal mechanisms may exist since not all workers performing the same task develop an injury. Previous research has identified three primary risk factor categories for LBP (occupational, personal and psychosocial factors); however, few studies have investigated the impact of cross categorical risk factor interactions on LBP. The objective of this study was to investigate the effects of occupational, personal and psychosocial factors, and their interactions, on LBP severity in a population of workers currently suffering from LBP. Sixty LBP patients recruited for the study through local physicians and local announcements, completed questionnaires relating to identified occupational, personal and psychosocial risk factors, and completed an Oswestry Disability Index (ODI). Multiple regression models for predicting LBP severity were developed for each risk factor category and for a combined risk factor model (which included factors from all three risk factor categories) that included two-way interactions. Results showed that the final model consisted of both main effects and interaction terms between risk factor categories and had an adjusted R² value of 0.85, a significant improvement over models developed for the individual categories. These findings illustrate the need to consider all three broad categories of risk factors simultaneously in predicting injury status and in developing effective potential intervention efforts.     

Recent studies of self-condensation and co-condensation of melamine-formaldehyde resins; cure at low temperatures

Self-condensation: recent research on the chemical pathways by which alcoholated melamine-formaldehyde (MF) resins react with themselves and on the product structures is summarized. Model compound studies suggest that bridges are less stable than widely thought unless they are in hexahydro-1,3,5-triazine ring structures. In acyclic structures they are probably less stable than bridges. Co-condensation: studies of how the composition of MF resins influences the rates of reaction with poly(ol) co-reactant show that MF resins that contain very low levels of and/or functionality are quite reactive. Reactivities of a variety of poly(ester) and acrylic coreactants were studied. By combining reactive MF resins with reactive co-reactants one can formulate high solids enamels that cure by co-condensation in 30 min at 50 to 65 °C with 0.5 parts per hundred (phr) of p-toluenesulfonic acid (p-TSA) catalyst. Cure at 25 °C appears feasible with higher catalyst levels.     

A phosphorus budget of a poultry farm and a dairy farm in the southeastern U.S., and the potential impacts of diet alterations

Current and potential environmental problems associated with P transport from lands receiving high application rates of animal waste are a major concern. Phosphorus management strategies are needed to reduce P loading on land. This study was conducted to compare on-farm P budgets for a modern broiler farm and a dairy farm under traditional diets and management practices. Phosphorus inputs, recycling and outputs were assessed for both farms. A typical broiler and a dairy farmer from North Carolina were interviewed and pertinent information for the study was obtained, in cooperation with extension agents, and other professionals associated with the farms. The annual on-farm P surplus for the broiler farm was 6,380 kg, while that for the dairy farm was 1,141 kg. This corresponds to an annual application of 65 kg P ha^–1 for the broiler farm and 20 kg P ha^–1 for the dairy farm in excess of removal. The potential for reducing P surpluses by the addition of phytase enzymes and/or the use of low phytic acid corn (Zea mays L.) feed in the broiler farm diet was also assessed. Estimates by animal nutritionists indicate that feed supplementation with phytase enzyme can reduce the broiler farm's P surplus by 33%. The use of low phytic acid corn can reduce the surplus by 49% and a combination of the two can reduce the surplus by 58%. In this study, the incorporation of soybean (Glycine max (L.) Merr.) and alfalfa (Medicago sativa) land into the waste utilization plan of the dairy farm decreases the annual P surplus from 20 to 9 kg P ha^–1. The use of new feed technology and expanding waste application to a larger land base can significantly alter the P budgets of broiler and dairy farms and reduce P surpluses, minimizing the risk of environmental problems.     

低挥发分煤在新型干法窑生产中的应用

对劣质煤、低挥发分煤的燃烧特性分析,工艺设备分析,提出预分解窑烧劣质煤、低挥发分煤的可能性、必要性,为我公司烧劣质煤、无烟煤打下了基础。     

RTM二维径向流动模型的理论概况及研究

综述了牛顿流体在放置了各向同性和各向异性预制件的RTM平板模具中二维径向恒流和恒压渗流的流动模型.对各个模型的可测量物理量之间的关系通过求解其解析解进行了必要的拓展补充推导和研究分析,对传统的二维解析方程进行了拓展和改进,提供了在不透明模具中测定渗透率的方法.即在恒流条件下利用压力传感器和恒流泵测定预制件的二维渗透率;或者在恒压条件下利用数字流量计和压力表测得二维渗透率.这些解析解的关系式也可用于实验预估模具中的压力分布及充模时间等.