Changes in the yield of chlorophyll a from dissolved available inorganic nitrogen after an enrichment event—applications for predicting eutrophication in coastal waters

An understanding of the dynamic relationship between nitrogen supply and the formation of phytoplankton biomass is important in predicting and avoiding marine eutrophication. This relationship can be expressed as the short-term yield q of chlorophyll from dissolved available inorganic nitrogen (DAIN), the sum of nitrate, nitrite and ammonium. This paper communicates the results of a continuous culture nitrate enrichment experiment undertaken to investigate the cumulative yield of chlorophyll from DAIN (q). The purposes of the study were: to acquire a better understanding of the relationship between chlorophyll formation and DAIN; to obtain values that could be used in models for predicting eutrophication. The results of a time series experiment carried out using microplankton (all organisms <200 μm in size) indicate that the parameter q does not have a single value but is affected by the ecophysiological response of phytoplankton to changing nutrient status after an enrichment event. It is also dependent on changes in the allocation of nitrogen between autotrophs and heterotrophs. The value of yield obtained at the height of the bloom can be represented by q (max) (2.35 μg chl (μmol N)⁻¹). The post-bloom, steady state value of q can be represented by q_eq (0.95 μg chl (μmol N)⁻¹). The microcosm steady state yield was not significantly different from the median value obtained from synoptic studies of Scottish west coast waters. It is proposed that q_eq is the most appropriate value for assessing the general potential for eutrophication resulting from continuous nutrient enrichment into coastal waters. It is further proposed that q (max) be used for cases of sporadic enrichment and where a short burst of unrestricted growth may be detrimental.     

Instability of sand–silt mixtures

The instability of the sand–silt mixtures with different amount of fines contents were studied in this paper. It showed that the slope of the instability lines increases with the increasing relative densities, and it approaches the slope of the failure line (steady state line) at a high relative density. The relationship between the peak stress ratio and the intergranular void ratio can be described by a common curve for all the mixtures with fines contents less than the transitional fines content. There may also exist a unique curve for the relationship between the peak stress ratio and interfine void ratio for the mixtures with fines contents higher than the transitional fines content. If the yield strength ratio is used instead of the peak stress ratio, the relationships can be characterized in the same way.     

不同气候生态棉区化学调控适宜期的试验及其应用

在山东省气候条件下,棉花生长发育主要受热量条件制约。由积温推算出在不同气候生态棉区以及不同品种、种植方式、密度和产量水平下的棉田物候期,由此得到相应棉田各次化调期,可改变田间小气候,提高成铃率10%～15%,单铃重增加0.3～0.9 g,使棉田因蕾期缩短而改变播期及种植品种,扩大麦棉两熟种植区域,提高棉花品质。     

富裕县农田土壤湿度变化及其对玉米发育期和产量的影响

本文旨在分析黑龙江省富裕县农田土壤相对湿度对玉米发育期和产量的影响,以期为松嫩平原西部玉米生产提供科学参考。以黑龙江省富裕县为研究区域,利用1982—2017年土壤相对湿度资料、1995—2017年玉米发育期资料、玉米产量资料,采用对比分析、相关分析、Mann-Kendall突变检验法,分析土壤相对湿度变化特征,研究土壤相对湿度对玉米发育期和产量的影响。结果表明：富裕县近36 a土壤相对湿度呈增加—减小—增加的趋势。播种期—出苗期、拔节期—抽雄期、乳熟期—成熟期土壤干旱平均每4—6 a一遇,抽雄期—乳熟期每2—3 a一遇,出苗期—拔节期土壤基本无旱。各发育期土壤相对湿度减小的突变年在1987年前后,增加的突变年在2013年前后。20世纪80年代土壤较适宜,干旱轻,90年代土壤相对湿度迅速下降,干旱最重,之后随着年代的推移土壤干旱逐渐减轻。玉米主要发育期中播种期—出苗期、出苗期—拔节期土壤干旱对产量影响较小,拔节期—成熟期是土壤干旱影响产量的主要时期。     

Extreme pressure due to expanded cylindrical and spherical cavity in a limitless medium: applications in soil mechanics

The extreme net pressure resulting from an expansion in a cylindrical or spherical cavity within a limitless medium is studied. Performing the static and kinematic approaches of yield design theory, analytical solutions of the extreme net pressure are established for cohesive–frictional as well as for purely cohesive medium. In the case of a cylindrical cavity, the identification between the analytical extreme net pressure and limit net pressure leads to the prediction of shear strength characteristics of soil. As useful result, in soil mechanics, the assessment of correlations using pressuremeter data has been discussed. Also, some assumptions for designing foundations, from pressuremeter data, have been highlighted.     

Effects of Activated Irrigation Water on Soil Physicochemical Properties and Crop Growth and Analysis of the Probable Pathway

With the problem of shortage of water resources becoming increasingly prominent, the improvement of production efficiency of agricultural water resources in China has become an important research content of modern irrigated agriculture. The technology of activated irrigation water provides a new way to excavate the physiological production potential of irrigation water and improve the comprehensive efficacy of irrigation water in agro-ecosystems. In this study, the research progress of the variable characteristics of physicochemical properties of activated irrigation water, the transport and transformation of soil material by activated irrigation water, and the promotion of crop growth by activated irrigation water were comprehensively analyzed. On this basis, according to the basic theories of soil physics, crop physiology, and material transport dynamics, the effects of activated irrigation water on soil material transport, soil material transformation, water and nutrition uptake by root, and crop yield formation and the probable pathway were analyzed. The key problems of basic science and applied technology in the future research are put forward to provide reference for the scientific and reasonable utilization of activated irrigation water technology.     

春小麦干热风灾害监测指标与损失评估模型方法探讨——以宁夏引黄灌区为例

利用小麦干热风观测资料和产量统计年鉴，结合民政部门灾害历史资料，运用产量逐级分离模拟和给定初始聚类中心的逐步筛选聚类分析方法，分别确定了宁夏引黄灌区春小麦两类干热风灾害等级判别指标，并建立了各自的等级判别方程；通过小麦抽穗扬花前的气候模拟，分离出灌浆期间两类干热风影响的产量；根据不同时期小麦受不同程度的灾害对产量的综合影响建立了综合灾害等级查询表和灾损评估模型，代入灾害综合等级，实现了监测和产量损失评估。     

弯曲法测岩石抗拉强度

岩石抗拉强度非常重要,它是岩土工程、地质工程中设计、施工和检验的重要依据之一,但抗拉强度的测试方法多数都不可靠,应引起足够重视。该文专门针对弯曲试验法,分析了不可靠的原因。     

Numerical study of effect of fluke inclination on behavior of drag anchor in clay with linearly increasing shear strength under unidirectional and combined loading

Drag anchor is a widely used anchor type in offshore engineering for the mooring system. The prediction of the anchor trajectory installation and the final position is important for anchor selection in design. The existing method using yield envelope method for trajectory prediction ignored the shallow anchor behavior but applied the deep yield envelope from a deeply embedded horizontal fluke in uniform clay for the whole drag-in installation process. However, the anchor fluke embedment depth and inclination angle change continually during installation in clay with linearly increasing shear strength soil profile in practice. Studies on the effect of fluke inclination angle on the anchor behavior in clay with such non-uniform soil profile under unidirectional and combined loading are important and necessary for the improvement of the yield envelope method to ensure a reasonable prediction. The current 2D finite element studies investigate the anchor behavior for inclined fluke in clay with linearly increasing shear strength under unidirectional vertical, horizontal and rotational loadings first. Then the effects of the fluke inclination angle, soil non-homogeneity and embedment depth ratio on the shallow yield envelopes are investigated. It is found that the effect of fluke inclination angle on the vertical capacity factors for anchor in clay with non-uniform and uniform soil profile is largely different. The resultant large impact on the yield envelopes shown here illustrates the importance of considering the fluke inclination angle and soil non-homogeneity in the prediction of anchor trajectory using yield envelope method.     

陆良石槽河煤矿充水因素及漏水量估算

石槽河煤矿位于断陷盆地中,可采煤层M3位于最低排泄基准面之下,无法自流排水,矿坑水主要来自煤层顶板、河水渗流及降水渗入。计算获得矿井漏水量为4472m3／d（正常）和6411m3／d雨季。