2016/2017冬中国气温偏暖的基本特征及可能成因

利用中国740余站观测的月平均2 m气温资料以及NCEP/NCAR再分析资料,通过动力学诊断的方法,对2016—2017年中国冬季异常偏暖现象进行了研究。结果发现：中国2016—2017年冬季气温偏暖主要是由于西伯利亚高压和阿留申低压偏弱导致东亚冬季风偏弱,在中国存在异常的偏南风。阿留申低压偏弱由两个因素引起,一是由于阿留申群岛地区的海温偏低,冷源对应异常高压导致阿留申低压偏弱;二是阿留申低压在东亚副热带高空西风急流出口区以北,然而该冬季高空西风急流出口区位置偏南,导致阿留申地区偏离急流出口减压区,从而导致阿留申低压偏弱。此外,西风带偏北,中高纬亚洲大陆上空以纬向环流为主,不利于冷空气南下。     

放牧压力对草原砂质栗钙土微生物量C,N,P影响的研究

对不同放牧压力下草原砂质栗钙土微生物量C、N、P进行较为系统地研究。结果表明：就土壤原土来看,随着放牧压力的增大,土壤微生物量C,N先增加后减少;土壤微生物量C在放牧率2.67只羊/hm2时相对较高,微生物量P随着放牧压力的增大逐渐降低。     

基于结构洞指数的网络节点重要度评估

运用双阶差分模型探究了并购与新建投资模式下公司避税效应的非对称性，并进一步从事后的视角探究该非对称性是否是影响企业投资模式选择的显著影响因素。研究发现：相比于新建投资，并购增加了收购方会计利润应税所得差异，且实质性地降低了其所得税实际有效税率，这表明不同投资模式下公司避税效应存在理论预期的非对称性。进一步研究发现，改变企业会计利润应税所得差异以及会计利润应税所得操纵程度是影响企业投资模式选择的重要因素。从事后的视角来看，企业很可能为了获取更大程度的公司避税效应而选择并购行为。     

冷却塔混凝土粗糙度对平均风压系数的影响

采用CFD方法研究全尺寸双曲冷却塔表面混凝土粗糙度对风压系数的影响.在规范规定的粗糙度范围内，分别对表面混凝土光滑以及表面混凝土有不同粗糙度高度的冷却塔全尺寸模型进行了数值模拟.将不同工况下的风压系数计算值与以往文献的风洞试验和现场实测数据进行了比较.研究结果表明：冷却塔全尺寸CFD模拟虽然解决了雷诺数相似问题，但纯粹的光滑壁面冷却塔在CFD计算中得到的平均风压系数比实际值偏离较大；在冷却塔全尺寸CFD模拟中必须考虑实际冷却塔表面的粗糙度对其平均风压系数的影响.     

基于霍尔效应的微小压强测量装置的设计与实现

针对化工液体的微小压强测量中所存在的测量复杂、精度低的问题，设计一种基于霍尔效应的测量流体微小压强变化的装置。该测量装置通过前端受力装置来承受液体压强的变化而产生一定的位移，并转换成霍尔电动势，经放大调理电路，最后接电压表显示相应的电压值。根据输出电压与液体压强之间的关系即可得到相应深度的压强大小。在实验中，电压表精确到1mV，最小可测量到0.792Pa的压强变化，其测量精度较高。该装置体积小、通用性强，具有较好的应用前景。     

基于叶气温差的生育中期冬小麦水分亏缺诊断研究

为了获取叶片尺度基于叶气温差的冬小麦生育中期水分亏缺诊断阈值,分析了冬小麦叶气温差的典型日变化及其与土壤水分、空气温度及太阳辐射等因子的相互关系,揭示了冬小麦叶气温差对光合气体交换参数的影响,确定了冬小麦叶片水分利用效率较适宜的非气孔限制值及叶气温差范围。结果表明,冬小麦叶气温差在不同的土壤水分条件下表现出不同的日变化规律,随光量子通量增加而升高,随土壤水分、气温增加而降低;4、5和6月冬小麦叶片水分利用效率较适宜的非气孔限制值范围分别为0.7~1.3、1.1~2.0和0.9~1.5,叶气温差控制范围分别为-1.2~0.4、-1.5~-1和-1.25~-0.9℃。     

Genotypic Variation for Tolerance to Transient Drought During the Reproductive Phase of Brassica rapa

Brassica rapa L. is a genetically diverse parent species of the allotetraploid species, oilseed rape (B. napus) and a potential source of drought tolerance for B. napus. We examined the effect of a 13‐day drought stress period during the early reproductive phase, relative to a well‐watered (WW) control, on subsequent growth and development in nine accessions of B. rapa and one accession of Brassica juncea selected for their wide morphological and genetic diversity. We measured leaf water potential, stomatal conductance, water use, and leaf and bud temperatures during the stress period and aboveground dry weight of total biomass at maturity. Dry weight of seeds and reproductive tissue were not useful measures of drought tolerance due to self‐incompatibility in B. rapa. The relative total biomass (used as the measure of drought tolerance in this study) of the 10 accessions exposed to drought stress ranged from 47 % to 117 % of the WW treatment and was negatively correlated with leaf‐to‐air and bud‐to‐air temperature difference when averaged across the 13‐day stress period. Two wild‐type (B. rapa ssp. sylvestris) accessions had higher relative total and non‐reproductive biomass at maturity and cooler leaves and buds than other types. We conclude that considerable genotypic variation for drought tolerance exists in B. rapa and cooler leaves and buds during a transient drought stress in the early reproductive phase may be a useful screening tool for drought tolerance.     

不同通风工艺在浅圆仓中应用的研究

在对大豆进行冬季通风作业时,采用正压上行压入式、负压下行吸出式和先负压后正压三种作业方式分阶段进行通风,充分的利用自然冷源,达到降温目的,通过对比三种作业方式的降温效果、水分损耗、降温能耗、人工投入等,并根据粮情,找出最合适的通风方式。     

Whistle signal variations among three Indo-Pacific humpback dolphin populations in the South China Sea: a combined effect of the Qiongzhou Strait's geographical barrier function and local ambient noise?

Geographic variations in the dolphin whistles could be useful in assessing association and isolation among populations. Whistle of free-ranging Indo-Pacific humpback dolphins (Sousa chinensis) among the Pearl River Estuary (PRE), Leizhou Bei (LZB) and Sanniang Bay (SNB) populations were investigated. A total of 2850 whistles with legible fundamental contour were extracted and 15 acoustic parameters were measured. Contrary to SNB, PRE and LZB had the same relative proportion of tonal type compositions with flat and sine representing the most frequent types. The generalized linear model analysis showed significant acoustic difference among populations and tonal types. All frequency parameters in SNB were significantly higher than those in PRE and LZB, where no significant variation was observed in most of the parameters either at the population level or within each tonal type. Canonical discriminant functions analysis showed a smaller difference between PRE and LZB than between PRE and SNB and between LZB and SNB. Compared with previous recordings, recent recordings demonstrated a consistent pattern of becoming higher in whistle frequency parameters in both LZB and SNB populations, suggesting that noise pollution in LZB and SNB increasing with time according to the acoustic niche hypothesis. Dolphin whistle's geographic variations could be shaped by the combined function of the geographical barrier function of the Qiongzhou strait and local ambient noise. Considering the isolated condition and the relatively smaller population size of the humpback dolphin in the SNB, more effective and proactive conservation actions should be taken to prevent the extinction of small populations.     

Atmospheric humidity and genotype are key determinants of the diurnal stomatal conductance pattern

Great understanding of the genotypic difference in diurnal stomatal conductance (g_s) pattern and the key determinants of the pattern is important for saving water by adopting cultivars appropriately. Fifteen wheat genotypes were studied under different soil conditions and various meteorological conditions with pot cultivation in rain shelter for two years. Genotype and air humidity were found to be key determinants of diurnal g_s pattern. All genotypes under low relative humidity (LRH) and most genotypes under high relative humidity (HRH) displayed a gradual decline pattern from morning through the afternoon. Under moderate relative humidity (MRH), all genotypes present a single-peak curve pattern, but they differed in peak time, which may lead to unreliable g_s comparison between genotypes and get ostensible contrasting materials. The stomatal conductance was significantly different among genotypes under LRH and the increased g_s magnitude is also significantly different when it was compared between LRH and HRH. The present results provide new thinking for selecting and adopting appropriate cultivars with specific stomata traits for the area with various meteorological conditions.