“双壁面射流”燃烧系统性能的试验研究

为了改善直喷柴油机的排放与经济性能,该文开发了一种直喷柴油机"双壁面射流"燃烧系统。通过试验的方法研究了燃烧室结构参数、喷油器结构参数、转速、负荷及喷油时刻等运行条件对"双壁面射流"燃烧系统燃烧过程的影响。试验结果表明:随转速的增加,着火始点向后推迟,缸压峰值呈现出先增大后减小的趋势,瞬时放热率峰值、缸内燃烧平均温度和累计放热量都降低;随负荷的增加,着火点提前,缸压峰值对应的曲轴转角向后推迟,缸压峰值、缸内燃烧平均温度和累计放热量都增加,总指示热效率随负荷的增加而降低。不同燃烧室结构参数和喷油器参数的"双壁面射流"燃烧系统燃烧持续期,在2100r/min的负荷特性中,小负荷主要受压缩比的影响,大负荷主要受预混合燃烧量的影响;总指示热效率主要受压缩比和壁面油膜生成量的影响;而NOx与碳烟排放受预混合燃烧量和贯穿度的影响。将"双壁面射流"燃烧系统静态供油提前角提前到18°CA BTDC,能实现扭矩点与功率点同为0.21BSU的低碳烟排放。     

Chemical characterization of wood and extractives of fast-growing Schizolobium parahyba and Pinus taeda

This study aims to evaluate the chemical composition of wood and extractives of Pinus taeda and Schizolobium parahyba (guapuruvu) as potential feedstock for new applications in the biorefinery industry. For this purpose, their content of α-cellulose, hemicellulose, insoluble lignin, hot water solubility, NaOH_1% solubility, inorganic materials (ash), and monomeric sugars by high-performance liquid chromatography was quantified. Attenuated total reflectance infrared spectroscopy and thermogravimetric analysis were also used to complete the physicochemical characterization of the studied woods. The extractives were obtained by soxhlet extraction with ethanol:toluene and dichloromethane and identified with pyrolysis-gas chromatography/mass spectroscopy technique. The results showed that guapuruvu wood has the higher amount of hemicellulose (16%) when compared to pine wood (10%), which resulted in higher solubility in alkali solution. Furthermore, in relation to other biomasses, the two woods presented more percentage of lignin and minor content of hemicelluloses. The P. taeda wood presented the highest percentage of extractives mainly composed of fatty acids and aromatic hydrocarbons, while guapuruvu wood had a higher percentage of phenolic compounds and also fatty acids. Both the materials have low content of extractives with dichloromethane and were mainly composed of lipophilic compounds.     

肉味香精加工技术研究与应用进展

肉味香精对改善食品风味和改良食品品质至关重要。现代食品加工高新技术对肉味香精产业的发展起着非常重要的作用,直接决定了产品质量优劣与产品的竞争优势。概述了肉味香精生产过程中常用的现代食品加工高新技术,如酶解技术、热反应技术、干燥浓缩技术、超临界萃取技术及微胶囊技术等,旨在为肉味香精的研究提供理论基础。     

用热扩散式茎流计测定园林树木蒸腾耗水量

采用热扩散式边材液流探针和环境自动监测系统对北京3种园林树木的树干液流及主要环境因子进行了一个生长季的同步观测.结果表明,3树种树干液流的日变化呈明显的单峰曲线,晴天的液流速率大于多云天和阴天,紫叶李和悬铃木的日耗水量明显大于元宝枫;对不同天气3树种每h的液流速率与相应的环境因子进行逐步回归分析.结果显示,影响3树种液流速率的主要环境因子是空气温度、空气相对湿度、辐射强度和5 cm土层温度,在不同天气里起主导作用的因子不同,环境因子与树干液流之间的数量关系能较好地预测树木的蒸腾耗水量.     

紫荆光合日进程及光响应

自然条件下使用LCA-4型便携式光合测定系统研究了紫荆连体叶片的光合日变化及光响应。结果表明:(1)净光合速率的日进程曲线呈“双峰”型,胞间CO2浓度的日进程基本与净光合速率相反,中午胞间CO2浓度增高,表明净光合速率午间降低主要受非气孔限制因素的影响。暗呼吸速率日进程为单峰曲线,中午最高。气孔阻力的日变化曲线是单谷型,午间最低。(2)一天分时段光响应试验表明,饱和光强和表观量子效率上午最高,中午最低,下午有所上升。下午的光补偿点是上午的2倍,中午则是上午的近3倍。不同时段遮光都使得气孔阻力和胞间CO2浓度升高。     

Thermal diffusion in Masson pine wood

In order to analyze the effects of the temperature gradient on moisture movement during the highly intensive microwave-vacuum drying, thermal diffusion of Masson pine wood was studied. Internal distribution of temperature and moisture in Masson pine samples sealed by epoxy resin and aluminum foil was measured, the magnitude of thermal diffusion was calculated and the influencing factors of thermal diffusion were discussed. Results showed that with the transfer of moisture toward the low temperature in wood, opposite temperature and moisture gradient occurred. The initial moisture content （MC）, temperature and time are important factors affecting this process; the thermal diffusion is in proportion to wood temperature, its initial moisture and time. The temperature and distance from hot surface is strongly linearly correlated, and the relationship between MCs at different locations and distance from the hot end surface changes from logarithmically form to exponentially form with the increase in experimental time.     

Marine temperatures experienced by postsmolts and the survival of Atlantic salmon, Salmo salar L., in the North Sea area

The survival of two Atlantic salmon stocks that inhabit rivers confluent with the North Sea was examined in respect to historical distributions of sea surface water temperatures. The rivers Figgjo and North Esk are relatively small salmon rivers in southern Norway and eastern Scotland, respectively. Wild salmon smolts have been tagged in these rivers since 1965. Tag returns were used to evaluate the survival of salmon in the North Sea. Survival rates of one-sea-winter (1SW) and 2SW fish were correlated within stocks, as well as between stocks. Survival rates were compared with the areal extent of thermal habitat in the north-eastern Atlantic Ocean. A positive correlation was found between the area of 8–10°C water in May and the survival of salmon. A reciprocal negative correlation was also found between survival and 5–7°C water in the same month. An analysis of sea surface temperature distributions for periods of good vs. poor salmon survival showed that when cool surface waters dominate the Norwegian coast and North Sea during May, salmon survival has been poor. Conversely, when the 8°C isotherm has extended northward along the Norwegian coast during May, survival has been good. The effect of water temperature distributions on the growth of postsmolts and other survival factors are discussed.     

Thermal stability of carp G-actin monitored by loss of polymerization activity using an extrinsic fluorescent probe

ABSTRACT:   The thermal stability of carp G-actin was investigated by monitoring loss of actin polymerization ability. To determine the amount of native actin remaining after heat treatment, actin was labeled with a fluorescence reagent, N-(1-pyrene)iodoacetamide. The loss of polymerization ability of carp actin during heat treatment, at between 45 and 55°C, occurred faster than that of chicken actin. The inactivation rate was influenced by concentrations of ATP and Ca²⁺ in solution. With the increase of Ca²⁺ concentration, the inactivation of carp actin was markedly suppressed. Furthermore, the activation energy of the inactivation of carp actin obtained from an Arrhenius plot was similar to that of chicken actin. These results indicated that the thermal instability of carp G-actin was due to the low affinites of ATP and Ca²⁺ for carp actin described in a previous report.     

辣椒素类物质在烤制加工和储藏中的稳定性

为了解辣椒素类物质在烤制加工和储藏过程中的稳定性,该文研究了不同加热温度和时间处理以及不同储藏条件下（常温和冷藏,真空和非真空）,野山椒中辣椒素类物质的含量变化。试验结果表明：烤制加热温度（80～180℃）及其时间（2～16 min）对辣椒素类物质的影响均显著（p<0.01）;不同储藏条件下,随着储藏时间的延长,野山椒中辣椒素类物质的含量均有不同程度下降。9个月后,真空包装冷藏的辣椒粉中辣椒素类物质含量降低了16.44%,非真空包装冷藏的降低了17.00%,真空包装常温储藏的降低了23.58%,非真空包装常温储藏的降低了24.11%,真空包装对其稳定性影响不大,低温更有利于保存辣椒素类物质。     

夏玉米冠层温度变化的时滞效应及其对土壤水分监测的影响

考虑冠层温度变化的时滞效应,可能在一定程度上能够提高土壤含水率的监测精度。该研究以灌浆期的夏玉米为研究对象,利用精密红外温度传感器（SI-411）连续监测I1（田间持水量的85%～100%）、I2（田间持水量的70%～85%）和I3（田间持水量的50%～65%）3个不同水分处理下的冠层温度,并同步获取试验地地面净辐射、大气温度、空气相对湿度等环境因子数据,以及不同水分处理小区0～10、0～20、0～30、0～40、0～60 cm不同深度处土壤含水率数据,利用高斯函数拟合冠层温度及环境因子日变化过程以此确定拟合曲线的峰值时刻,通过峰值时间差确定两者之间的时滞关系,并利用多元线性回归分析确定冠层温度的主要影响因素,最后在考虑冠层温度与主要影响因素之间时滞关系的基础上,分析冠层温度变化的时滞效应对监测土壤含水率的影响。结果表明：不同水分处理下的冠层温度峰值具有较大差异,峰值大小依次为I3、I2、I1;I1、I2、I3水分处理的冠层温度峰值时刻分别滞后净辐射约70、70、100 min,超前大气温度和相对湿度约60、60、30 min;冠层温度变化的主要影响因素为大气温度,其次为地面净辐射,最后为相对湿度;考虑时滞效应的冠气温差与土壤含水率的相关性更高,考虑时滞效应的冠气温差对土壤含水率的监测效果有一定提升。研究可为利用作物生理特性提高土壤水分监测精度提供参考。