宁南黄土丘陵区旱地作物水分平衡特征与水分生态适应性研究

依据田间试验结果 ,对宁南黄土丘陵区主要作物水分平衡特征与水分生态适应性进行定量评价。结果表明 ,夏熟作物全生育期水分满足率 ,干旱年份为 5 5 9%～ 6 3 8% ,丰水年份为84 1%～ 86 4 % ;秋熟作物全生育期水分满足率 ,干旱年份为 6 7 7%～ 79 0 % ,丰水年份为92 1%～ 95 1%。水分生态适应性因作物类型和降水条件而存在差异 ,秋熟作物水分生态适应性指数高于夏熟作物 ,丰水年份的作物水分生态适应性指数高于干旱年份。旱地 6种主要作物的水分生态适应性指数排序依次为 :谷子 >马铃薯 >糜子 >胡麻 >豌豆 >春小麦。研究结果可为制定合理的旱区种植制度决策方案提供理论依据     

天然气水露点与含水量的换算

在天然气水露点与含水量的换算过程中,涉及天然气状态方程、气液相平衡、气体混合规则等多步计算,参数多且需要迭代求解,整个计算过程相当复杂。为此,提出了一种快速、准确的天然气水露点与含水量的换算方法:选用PR状态方程,并基于GB/T22634-2008提供的关联关系曲线,通过相平衡理论导出计算气、液相的逸度系数公式,最后迭代求解。给出了整个换算过程的详细计算步骤,该计算方法的适用范围可扩展至0.1MPa≤p≤30MPa,-50℃≤t≤40℃。实际算例结果表明:该换算方法在压力范围为0.1～5MPa内计算结果准确性较高,当压力超过8MPa时,计算不确定度有待进一步分析。     

滇西北兰科植物海拔分布格局

根据实际调查和整理相关文献资料,确定滇西北兰科植物409种,其分布的海拔范围为650～4700m;并按400m划分海拔段,共9个梯度,分析其垂直分布格局。结果表明：滇西北兰科植物的垂直分布格局呈“中间膨胀型”或“单峰型”,随着海拔升高,各海拔段兰科植物的数量依次为92、167、194、223、192、159、129、58、32种,其中1051—3000m海拔范围的物种多样性较高;相邻海拔段兰科植物种类相似性系数较高,海拔段相隔越远,相似性系数越小;生活型以地生兰为主,1051～1450m海拔段附生兰种类较为丰富,1851～3450m海拔段地生兰种类较为丰富,各海拔段腐生兰种类较少;1851—2250m海拔段区系成分最多,物种数为223种,占该区域兰科植物总数的54．52％;该区域的区系平衡点在海拔2115m左右,生活型平衡点在海拔2050m左右。     

多层住宅楼中实木地板实际含水率的调查

对南京市城区数栋多层住宅楼、近百户家庭安装的实木地板的含水率进行了实地调查.结果表明,朝南房间靠近窗口和阳台处的地板含水率均较低,朝北房间和客厅近窗口位置,地板的含水率较高;除了楼房底层,在相同楼层内同一树种实木地板的使用含水率差异不明显;含水率随楼层高度的增加而降低.调查结果为生产企业合理控制实木地板产品含水率范围提供参考.     

Influence of felling season,drying method and within-tree location on the brinell hardness and equilibrium moisture content of wood from 27–35-year-old Betula pendula

The Brinell hardness and equilibrium moisture content (EMC) were measured from thinning-aged silver birch wood. Wood material both from the trees harvested in the first commercial thinning and from trees remaining on site after the thinning was included. The average Brinell hardness was 19.40 MPa. It correlated significantly with the basic density of wood. With respect to the distance from the pith, the Brinell hardness of air-dried wood was higher than that of artificially dried wood. The average EMC of the conditioned (20°C, 65% relative humidity) wood was 12.0%. The EMC of the wood also varied, with the EMC being higher for air-dried wood than for kiln-dried wood. EMC was the highest at a distance of 30–40 mm from the pith, decreasing towards both pith and log surface. Seasonal variation in both the Brinell hardness and the EMC of the wood was found. It was presumed to be a consequence of season-dependent physiological changes in trees.     

Experimental studies on the impact of an increased dose of anionic salts on the metabolism of dairy cows

Summary

This study was initiated to investigate the influence of a daily dose of anionic salts (AS) above the valid upper limit at present on metabolism of dairy cows. Eleven non‐pregnant and non‐lactating Holstein‐Friesian crossbred cows with a permanent rumen cannula were used in a study with a controlled feeding design. The initial daily dose was 2500 meq/day, which resulted in a Dietary Cation Anion Difference (DCAD) of ‐211 meq/kg dry matter. Every seven days, the daily dose was raised by 500 meq. If a cow stopped eating, the application of AS was stopped and these cows were monitored over the next seven days. On day 30 another batch of hay, having the same DCAD but higher concentrations of minerals and energy, was fed. Blood and urine samples were taken to monitor acid‐base balance and calcium concentrations. Acid‐base balance was strongly influenced by AS. Blood pH dropped steadily and reached values around 7.23. Urine pH dropped quickly below 6 and remained at that level regardless of the increased dosage of AS. Net acid base excretion (NABE) fell continuously with the increase of the dosage of AS and reached values below ‐200 mmol/l. Calcium concentrations in the serum were nearly stable, but those in urine increased sharply and remained on an elevated level with increasing doses of AS. A few days before the individual cow's refusal of feed intake, calcium excretion in urine decreased. The majority of cows stopped eating while consuming a diet containing 3500 to 4000 meq AS except two animals who consumed up to 6000 meq/day AS but they received the better hay in the second half of the treatment period. In this time pH in blood increased slowly. NABE remained stable on a low level at ‐100 mmol/l. The results showed that with an increasing amount of AS fed the risk of clinical acidosis increased. The decreasing urine concentrations of calcium indicate a breakdown of the compensation capability of the single cow. Besides the dose of AS fed, the quality of the feed stuff might be another factor concerning the tolerance of cows against AS.     

Chemical modification of wood: A short review

Abstract

For most markets for wood, it is used without any treatments or modifications. When wood is used in adverse environments, it may be treated with chemicals to help prevent decay, improve water resistance, reduce the effects of ultraviolet radiation or increase fire retardancy. Many of these treatments involve the use of toxic or corrosive chemicals that can harm the environment. Chemical modification of wood provides an alternative by providing protection against water, decay, UV and thermal degradations by bonding chemicals to the cell wall polymers that do not leach out. Dimensional stability and decay resistance are two major properties that can be greatly improved by simple reactions with acetic anhydride.     

高温水热处理对毛竹材颜色和平衡含水率的影响

为提高竹制品加工利用水平,以高温水为传热介质,在温度为120℃、130℃、140℃、150℃,160℃,时间为60min、90min、120min的密闭条件下对毛竹（Phyllostachys heterocycla）进行高温热处理,以饱和蒸汽压控制试验的压力环境,研究毛竹材在不同水热处理条件下颜色及平衡含水率的变化。结果表明,随着热处理温度的升高和时间的延长,毛竹材表面颜色由明黄色向深咖啡色转变,红绿色品指数（a*）略微上升后下降,趋向于绿色,黄蓝色品指数（b*）逐步下降,趋向于蓝色。总体色差（ΔE*）增大,明度（L*）下降,竹材平衡含水率下降拐点出现在140℃,与热处理时间相比,热处理温度对竹材颜色及平衡含水率的影响更显著。     

汇率变化对我国农业产业的影响——基于农业部门局部均衡模型

为研究汇率浮动与中国农产品市场波动之间的关系,采用全球农产品市场局部均衡模型,设定5种货币贬值和升值的情景方案,通过静态模拟方法,评估不同货币的汇率变化对中国农业产业的影响。结果显示,人民币贬值时,进口商品变的更加昂贵,进口减少,国内产品的需求增加,刺激国内产出增加。从具体产品来看,人民币贬值对稻谷、小麦、玉米、牛肉、猪肉和奶粉产量的影响较大。当人民币升值,中国农业受到的影响与贬值情况相反。主要农业贸易伙伴国货币汇率变动则首先影响该国产品的进出口量,进而影响产品的世界价格,再通过进出口将价格传导到中国,最终引起中国相关产品的生产、消费和贸易量的变动。中国受到较大影响的是从这些国家进口份额较大的产品,其中欧元、澳元、新西兰元和巴西雷亚尔汇率变动将主要引起中国牛肉、猪肉、奶粉、小麦和大豆进口量和产量的变化。     

长江流域土壤水量平衡与植被旱度研究

以流域为研究单元,采用水量平衡与估算法相结合的参考蒸散修正模型,定量分析了长江流域九个区域的不同水平年的土壤水分动态、植被耗水量、水分亏缺量及植被旱度。结果表明:长江中下游流域植被旱度较大,特别是偏枯年。不同区域四季干旱规律、干旱程度不同,各有特点。长江流域的水量平衡中水分蒸散是主要的输出形式。因蒸散力较大,所以植被旱度较大,植被恢复要充分考虑其水分条件,选择合适条件的物种。