改性栲胶高温堵剂的性能评价

研发了适用于高温低渗油田调剖堵水的改性落叶松栲胶堵剂。基础配方（以质量计）为：6．0％磺化落叶松栲胶＋2．5％～3．0％甲醛＋1．0％～1．5％促进剂＋水．pH值8～10。基础配方堵剂溶液25℃、35001／s黏度为1．5mPa·s；温度由120℃升至180℃时，成胶时间由7．5h缩短至约4h；从成胶时间和代表凝胶强度的突破真空度确定其适用的pH值范围为4～10；外加NaCI特别是CaCl2使其成胶时间缩短，突破真空度在NaCI加量≤50g／L时下降幅度很小。NaCl加量为100g／L时仍不低于66kPa。减少任一组分用量而保持其他组分用量不变，均使堵剂溶液成胶时间缩短，通过改变各组分用量和加盐量可在很大范围内调节堵剂溶液的成胶时间。堵剂在120℃放置48h后质量变化小于5％，在180℃放置120h后质量变化小于8％。堵剂凝胶在250℃的5％盐酸、5％苛性钠、10％NaCl溶液中至少可稳定存在6h。加入原油量超过10％的堵剂溶液不能成胶，因而该堵剂有一定选择性。在2支填砂管封堵实验中，封堵率为98．5％和97．6％，突破压力梯度为25．3和36，4MPa／m。讨论了栲胶与甲醛的交联反应。图7表1参5。     

Tributary confluences are dynamic thermal refuges for a juvenile salmonid in a warming river network

As rivers warm, cold‐water fish species may alleviate thermal stress by moving into localized thermal refuges such as cold‐water plumes created by cool tributary inflows. We quantified use of two tributary confluence plumes by juvenile steelhead, Oncorhynchus mykiss, throughout the summer, including how trout positioned themselves in relation to temperature within confluence plumes. At two confluences, Cedar and Elder creeks, along the South Fork Eel River, California, USA, we monitored temperatures using in situ logger grids throughout summer 2016. Fish were counted within confluences via snorkel surveys five times a day on 5 days at each site. We found diel and seasonal dependence on confluence use by steelhead, especially at the Cedar Creek confluence, where mainstem temperatures exceeded 28°C. At this site, fish moved into the confluence on the warmest days and warmest times of the day. Fish observed within the Cedar Creek confluence plume were most common in locations between 20–22°C, rather than the coldest locations (14.5°C). At Elder Creek, where mainstem temperatures remained below 24°C, there was little relationship between mainstem temperature and steelhead presence in the confluence plume. At both sites, steelhead distribution within plumes was influenced by spatial variation of temperature and mean temperature in surveyed grid cells. Our results show that cool tributaries flowing into warmer mainstem reaches (over 24°C) likely create important thermal refuges for juvenile steelhead. As mainstem rivers warm with climate change, cool‐water tributary inputs may become more important for sustaining cold‐water salmonids near the southern end of their range.     

Properties and H2 production ability of Pt photodeposited on the anatase phase transition of nitrogen-doped titanium dioxide

The effect of calcination temperature on the properties and H₂ production ability of nitrogen-doped (N-doped) titanium dioxide (TiO₂) photodeposited with 0.2 wt% Pt (platinum) was studied. The increase in crystallinity of pre-calcinated N-doped TiO₂ initiated at temperatures higher than 131 °C transformed the morphology from anomalous nanostructure to texture composed of nanoparticles and enhanced the specific surface areas. At 200-400 °C, the anatase peaks gradually became sharper and the visible light absorption region decreased due to the growth of crystallites and the decrease of N-doping content, respectively. Maximum H₂ production was reached when N-doped TiO₂ was calcined at 200 °C followed by Pt photodeposition. The maximum condition is brought about by the formation of textures consisting of nanoparticles and a broad absorption region, thus creating superior active sites for photocatalytic H₂ production.     

HCFC22-based absorption cooling systems,part III: Effects of different absorbers and condenser temperatures

Generally in a vapour absorption refrigeration system (VARS) heat rejection temperatures at absorber (T_a) and condenser (T_c) are taken to be equal. However, different temperatures can exist when the cooling water flows in series through the two components. Under such situations, it is essential to know which of T_a and T_c has greater influence on the performance of the VARS. Here the influence of different T_a and T_c on the performance of a single-stage VARS working with HCFC22 as a refrigerant and three organic solvents, namely DMA, DMF and DEMTEG, as absorbents is studied. Results are obtained over a wide range of operating temperatures. To improve the performance of HCFC22-based VARS, results reveal that (i) the cooling water in parallel pipe connections should be used at low values of temperatures at evaporator, cooling water and heat source, and (ii) cooling water should first flow through condenser and then through the absorber when evaporator and heat source temperatures are high over the complete range of cooling water temperatures. COP_th is more sensitive to T_c than to T_a.     

Measurements of laminar burning velocities and onset of cellular instabilities of methane–hydrogen–air flames at elevated pressures and temperatures

An experimental study on laminar burning velocities and onset of cellular instabilities of the premixed methane–hydrogen–air flames was conducted in a constant volume combustion vessel at elevated pressures and temperatures. The unstretched laminar burning velocity and Markstein length were obtained over a wide range of hydrogen fractions. Besides, the effects of hydrogen addition, initial pressure and initial temperature on flame instabilities were analyzed. The results show that the unstretched flame propagation speed and the unstretched laminar burning velocity are increased with the increase of initial temperature and hydrogen fraction, and they are decreased with the increase of initial pressure. Early onset of cellular instability is presented and the critical radius and Markstein length are decreased with the increase of initial pressure, indicating the increase of hydrodynamic instability with the increase of initial pressure. Flame instability is insensitive to initial temperature compared to initial pressure. With the increase of hydrogen fraction, significant decrease in critical radius and Markstein length is presented, indicating the increase in both diffusional-thermal and hydrodynamic instabilities as hydrogen fraction is increased.     

Electrolysis of humidified methane to hydrogen and carbon dioxide at low temperatures and voltages

Considerable amounts of hydrogen are produced from fossil fuels. In recent years, natural gas and biogas have received attention as important feedstocks for hydrogen production, because methane, their main component, is hydrogen rich and readily available. Methane steam reforming is the major industrial route for hydrogen production, but requires high temperature due to endothermic nature of the reaction. This report presents a new green technology for the efficient and ecological production of hydrogen from methane. A humidified methane was electrolyzed to hydrogen and carbon dioxide at low onset cell voltages (ca. 0.3–0.4 V), depending on the temperature (150–250 °C). Almost all currents were used for the production of hydrogen and carbon dioxide. Hydroxyl radicals generated from water vapor during the electrolysis played an important role as an active oxygen for the methane oxidation reaction at the anode. This is the first report on the production of hydrogen from methane at both low temperatures and voltages.     

Compressive strength and microstructure of alkali-activated fly ash/slag binders at high temperature

This paper reports the results of the compressive strength and microstructure of various alkali-activated binders at elevated temperatures of 300 and 600 °C. The binders were prepared by alkali-activated low calcium fly ash/ground granulated blast-furnace slag at ratios of 100/0, 50/50, 10/90 and 0/100 wt.%. Specimens free of loading were heated to a pre-fixed temperature by keeping the furnace temperature constant until the specimens reached a steady state. Then the specimen was loaded to failure while hot. XRD, SEM and FTIR techniques were used to investigate the microstructural changes after the thermal exposure. The fly ash-based specimen shows an increase in strength at 600 °C. On the other hand, the slag-based specimen gives the worst high-temperature performance particularly at a temperature of 300 °C as compared to ordinary Portland cement binder. This contrasting behaviour of binders is due to their different binder formulation which gives rise to various phase transformations at elevated temperatures. The effects of these transformations on the compressive strength are discussed on the basis of experimental results.     

Influences of different comminution methods on maceral segregations,ignition, and pyrolysis of superfine pulverized coal

The same bituminous coal is grinded by three representative grinding systems, respectively. Tendencies of maceral segregations in three systems are analyzed. The influences of maceral segregations on ignition temperatures and flash pyrolysis products are compared and discussed.     

来自牛半腱肌肌束膜和肌内膜胶原蛋白热力学特性分析

探讨牛半腱肌肉肌束膜和肌内膜胶原蛋白热力特性的热诱导变化。牛半腱肌肉分别采用水浴和微波加热到内部终点温度分别为20、40、50、60、70、80℃和90℃,用示差扫描量热法研究肌束膜和肌内膜胶原蛋白热力特性(起始、最高和最终热收缩温度)在热处理过程中的变化。结果表明：牛半腱肌肉肌束膜和肌内膜胶原蛋白的热收缩温度在两种热处理方式间都存在显著差异,在两种热处理方式中,内部终点温度60℃是影响肌束膜和肌内膜胶原蛋白热收缩温度的关键加热温度。热诱导的肌束膜和肌内膜胶原蛋白热力特性的变化是水浴和微波加热牛肉胶原蛋白热收缩温度存在差异的主要原因。