A numerical model study on multi-species harmful algal blooms coupled with background ecological fields

Based on systematized physical, chemical, and biological modules, a multi-species harmful algal bloom （HAB） model coupled with background ecological fields was established. This model schematically embod-ied that HAB causative algal species and the background ecological system, quantified as total biomass, were significantly different in terms of the chemical and biological processes during a HAB while the inter-action between the two was present. The model also included a competition and interaction mechanism between the HAB algal species or populations. The Droop equation was optimized by considering tempera-ture, salinity, and suspended material impact factors in the parameterization of algal growth rate with the nutrient threshold. Two HAB processes in the springs of 2004 and 2005 were simulated using this model. Both simulation results showed consistent trends with corresponding HAB processes observed in the East China Sea, which indicated the rationality of the model. This study made certain progress in modeling HABs, which has great application potential for HAB diagnosis, prediction, and prevention.

Vertical development of a Prorocentrum donghaiense bloom in the coastal waters of the East China Sea: coupled biophysical numerical modeling

Algal blooms caused by Prorocentrum donghaiense occurred frequently in the East China Sea （ECS） during spring in recent years. In this study, a coupled biophysical model was used to hindcast a massive P. donghaiense bloom that occurred in 2005 and to determine the factors influencing bloom initiation and development. The model comprised the Regional Ocean Modeling System tailored for the ECS that utilized a multi-nested configuration and a population dynamics model for 19. donghaiense. Comparisons between simulations and observations revealed that the biological model is capable of reproducing the characteristics of 19. donghaiense growth under different irradiances and phosphorus limitation scenarios. The variation of intracellular phosphorus and the effects of 19. donghaiense on ambient nutrients conditions were also reproduced. The biophysical model hindcasted the hydrodynamics and spatiotemporal distributions of the P. donghaiense bloom reasonably well. Bloom development was consistent with observations reported in earlier studies. The results demonstrate the capability of the model in capturing subsurface incubation during bloom initiation. Then model＇s hindcast solutions were further used to diagnose the factors controlling the vertical distribution. Phosphate appeared to be one of the factors controlling the subsurface incubation, whereas surface wind fields played an important role in determining P. donghaiense distribution. The results highlight the importance of nutrient-limitation as a mechanism in the formation of P. donghaiense subsurface layers and the dispersing of P. donghaiense blooms. This coupled biophysical model should be improved and used to investigate 19. donghaiense blooms occurring in different scenarios.

Mathematical model of heat transfer for bloom continuous casting

A mathematical model for heat transfer during solidification in continuous casting of automobile steel, was established on researching under the influence of the solidifying process of bloom quality of CCM in the EAF steelmaking shop, at Shijiazhuang Iron and Steel Co. Ltd. Several steel grades were chosen to research, such as, 40Cr and 42CrMo. According to the results of the high temperature mechanical property tests of blooms, the respective temperature curves for controlling the solidification of different steels were acquired, and a simulating software was developed. The model was verified using two methods, which were bloom pinshooting and surface strand temperature measuring experiments. The model provided references for research on the solidifying process and optimization of a secondary cooling system for automobile steel. Moreover, it was already applied to real production. The calculated temperature distribution and solidification trend of blooms had offered a reliable theory for optimizing the solidifying process of blooms, increasing withdrawal speed, and improving bloom quality. Meanwhile, a new secondary cooling system was designed to optimize a secondary cooling water distribution, including choice and arrangements of nozzles, calculation of cooling water quantity, and so on. 2008 University of Science and Technology Beijing. All rights reserved.

A niche model to predict Microcystis bloom decline in Chaohu Lake, China

Cyanobacterial blooms occur frequently in lakes due to eutrophication. Although a number of models have been proposed to forecast algal blooms, a good and applicable method is still lacking. This study explored a simple and effective mathematical-ecological model to evaluate the growth status and predict the population dynamics of Microcystis blooms. In this study, phytoplankton were collected and identified from 8 sampling sites in Chaohu Lake every month from July to October, 2010. The niche breadth and niche overlap of common species were calculated using standard equations, and the potential relative growth rates of Microcystis were calculated as a weighted-value of niche overlap. In July, the potential relative growth rate was 2.79 (a.u., arbitrary units) but then rapidly declined in the following months to -3.99 a.u. in September. A significant correlation (R=0.998, P<0.01) was found in the model between the net-increase in biomass of Microcystis in the field and the predicted values calculated by the niche model, we concluded that the niche model is suitable for forecasting the dynamics of Microcystis blooms. Redundancy analysis indicated that decreases in water temperature, dissolved oxygen and total dissolved phosphorus might be major factors underlying bloom decline. Based on the theory of community succession being caused by resource competition, the growth and decline of blooms can be predicted from a community structure. This may provide a basis for early warning and control of algal blooms.

沉浸式3D虚拟仿真实验平台构建

为解决传统实践教学在时间、空间上的局限性,增强实践教学的互动性,以虚拟智慧城市中的物联网创新应用为研究对象,结合虚拟现实技术,在实验内容和教学模式中融入价值创造和创业素养,构建融入“创新实验路径”和“多层次综合实验项目”的物联网专业沉浸式3D虚拟仿真实验平台。采用布鲁姆教学目标分类法设计3D虚拟仿真实验教学目标,并按照IAPVE的实施模型,构建基于3D虚拟仿真实验平台的教学实施模型和考核评价模型。实施结果表明,该3D虚拟仿真实验平台及教学实施和考核评价模型可指导实践教学改革,实现学生综合能力的全面协同提升。

水体富营养化响应规律与水华预警方法研究进展

水体富营养化问题日益严峻,这种现象导致了浮游植物的异常增长,释放有害的藻毒素,造成了水体的污染,并对动植物乃至人类造成了危害。与之相关的,水体通常流动缓慢,连通性差,水流停滞时间较长,使得这些水体更容易受到富营养化的影响,也使水华风险升高。针对水华的产生机理,深入探讨了水动力因素、水环境因素和气象因素的影响。水动力因素包括水体的流速、流量和水体扰动等情况,它们共同决定了藻类的积聚程度;水环境因素包括水温、溶解氧、营养盐浓度以及酸碱度等,它们将直接影响浮游藻类的生长;气象因素如气温、风力等会改变水体的温度,从而对水华的形成和发展产生影响。还依据江河湖库水体的特点,探讨了数值模型和数据驱动模型在水华预测中的应用,数值模型在水华预测中的应用是通过模拟水体中的环境因素,来预测水华的发生和发展趋势;数据驱动模型以数据挖掘算法和统计技术为基础,利用机器学习方法,通过分析和识别监测数据、图片与水华的对应关系,进行迭代学习,创建其与水华爆发的预测联系。它们为探究水体状况、预测水华事件提供了有效工具,二者相耦合的方法对水华的精准预测有着重要意义,也是未来研究的发展趋势,有助于水资源管理者更好地对其进行调控,提高预测精度和水质管理的效率以减少水华的发生。

基于布隆过滤器的零知识集成员证明效率提升

针对区块链中数据的安全验证问题(数据的动态增加导致零知识集成员证明参数更新频繁、参数生成和验证时间变长),进行了创新性的完善。提出了一种新型的数据存储模型,结合优化的跳表索引,提高了数据验证的安全性和效率。实验结果表明,基于布隆过滤器的新型数据存储模型和外部索引,虽然增加了空间复杂度,但是借助预校验机制,提高了约45%的安全校验速度。此外,优化后的时间跳表总体上提高了约50%的区块检索速度,并且索引更新更加便捷。

“BOPPPS+BLOOM”模型在课程教学设计中的应用

近年来北美流行的BOPPPS教学模型在国内课程教学中得到了广泛的应用。BOPPPS模型中很重要的一个过程是明确教学目标。那么如何科学的设立教学目标呢?BLOOM认知模型作为一种思维技巧模型,对提升学生思维层次,为设立科学合理的教学目标提供了理论指导。本文旨在有机的融合BOPPPS教学模型以及BLOOM认知模型,以"惯性传感器技术"课程为案例,探究"BOPPPS+BLOOM"模型在课程教学设计中的应用,为创新教学方法提供一种有益的补充。

Numerical simulation of an algal bloom in Dianshan Lake

A hydrodynamic model and an aquatic ecology model of Dianshan Lake,Shanghai,were built using a hydrodynamic simulation module and the water quality simulation module of Delft3D,which is an integrated modelling suite offered by Deltares. The simulated water elevation,current velocity,and direction were validated with observed data to ensure the reliability of hydrodynamic model. The seasonal growth of different algae was analyzed with consideration of observed and historical data,as well as simulated results. In 2008,the dominant algae in Dianshan Lake was Bacillariophyta from February to March,while it was Chlorophyta from April to May,and Cyanophyta from July to August. In summer,the biomass of Cyanophyta grew quickly,reaching levels much higher than the peaks of Bacillariophyta and Chlorophyta. Algae blooms primarily occurred in the stagnation regions. This phenomenon indicates that water residence time can influence algal growth significantly. A longer water residence time was associated with higher algal growth. Two conclusions were drawn from several simulations: reducing the nutrients inflow had little effect on algal blooms in Dianshan Lake; however,increasing the discharge into Dianshan Lake could change the flow field characteristic and narrow the range of stagnation regions,resulting in inhibition of algal aggregation and propagation and a subsequent reduction in areas of high concentration algae.

基于遥感影像的多方法评估氮元素对太湖水华影响

氮元素与太湖水华暴发有强相关性,是太湖水华暴发的重要因子.论文基于多源数据深入探讨了氮元素对太湖蓝藻水华暴发的影响机制.结果显示,氮元素通过营养盐释放和循环利用推动水华暴发,与蓝藻生长之间构成正反馈.高水温下,蓝藻生长与反硝化过程对硝态氮的竞争,削弱了反硝化微生物的脱氮效果,导致太湖水华持续化.相关性分析表明,不同形态氮与叶绿素a之间存在显著相关.论文从多层次、多角度解析氮元素与太湖水华暴发的关联机制,研究结果可为水体生态修复和水环境管理决策提供科学依据.

基于Bloom Filter的云内容路由优化

随着国家三网融合战略的进一步推进,传统的"广播式"媒体内容分发模式已无法满足用户日益增长的双向"互动式"业务需求。利用云计算技术构建媒体云内容分发网络,实现媒体内容的弹性部署、高效分发来解决该问题,已成为下一代广电网络(NGB)的核心内容。在构建媒体云网络过程中,如何进一步改善用户的响应时延是必须考虑的因素。文中在此背景下,提出利用全局Bloom Filter优化媒体云网络中的内容路由。通过两种优化路由设计,使用户的平均响应时延得到有效下降。并采用排队网络对传统以及优化后的路由策略进行理论建模,使用OMNeT++网络仿真器对提出的路由策略进行仿真。其结论与仿真结果一致性良好。结果显示,优化后的路由策略,在不同的场景下,最多可节省65.2%的平均响应时延。

Nutrient-controlled growth of Skeletonema costatum : an applied model

To model Skeletonema costatum blooms and their relationship with environmental parameters in situ, a S. costatum-specifi c zero-dimensional box model based on the mechanistic model Eco3M was established using physiological features. The parameters were calibrated using experimental counterparts, and simulations were compared with published laboratory fi ndings. The resulting normalized objective function(NOF) values are less than 1.0(and in most cases less than 0.58) and the values for the slope γ(between 0.656 7–1.127 4) and R 2(between 0.806 8–0.971) are close to 1.0 for most of the sub-fi gures. This indicates good agreement between simulated and measured data and suggests that the model reproduces the general characteristics of S. costatum growth and use of nutrients under different N- or P-limiting conditions. The model is appropriate for further applications and can be used to test more scenarios using other nutrients.

喂钢带碳浓度对连铸大圆坯宏观偏析的影响

结晶器喂钢带工艺是提高大截面连铸坯中心质量的有效方法之一.本文发展了液相-柱状晶-等轴晶三相体积平均凝固模型,探究了喂入钢带的碳浓度对连铸大圆坯凝固组织结构及宏观偏析分布的影响规律.结果表明:喂入钢带的碳浓度会极大地影响等轴晶与柱状晶的生长,碳浓度过低或过高均会降低喂钢带对等轴晶体积分数提高的效果.通过调控钢带溶质浓度可以直接影响铸坯内溶质浓度及分布,喂入1.0倍钢液碳浓度(r_(C)=1.0)的钢带对连铸坯宏观偏析的改善效果最佳,其中铸坯径向碳极差和宏观偏析指数极值差分别为0.165 7%和38.36%.

Optimization of strand and final electromagnetic stirrers of round bloom casters with multiple sections

Strand electromagnetic stirring（S-EMS） and final electromagnetic stirring（F-EMS） are the main methods used to improve the center porosity and segregation for round blooms. To optimize the stirring conditions, nail shooting tests were conducted for three sections of large round blooms with diameters of ф380 mm, ф450 mm, and ф600 mm. Acid leaching and sulfur print tests were used to investigate the shell thickness. Based on the results of nail shooting tests, a mathematical model of solidification was established, and the variation of shell thickness and the central solid fraction were exactly calculated by the model. By taking all sections into account, the locations of S-EMS and F-EMS were optimized for each section. In the results, the macro-segregation of various sections is improved after the locations of S-EMS and F-EMS systems are changed.

Development and Application of a Marine Ecosystem Dynamic Model

A nutrient-phytoplankton-zooplankton-detritus （NPZD） type of marine ecosystem model was developed in this study,and was further coupled to a three-dimensional primitive-equation ocean circulation model with a river discharge model and a solar radiation model to reproduce the dynamics of the low nutrition level in the Bohai Sea （BS）.The simulation results were validated by observations and it was shown that the seasonal variation in the phytoplankton biomass could be characterized by the double-peak structure,corresponding to the spring and summer blooms,respectively.It was also found that both nitrogen and phosphate declined to the lowest level after the onset of the summer bloom,since the large amounts of nutrients were exhausted by phytoplankton for photosynthesis,and the concentrations of nutrients could resume in winter after a series of the biogeochemical-physical processes.By calculating the nitrogen/phosphorus （N/P） ratio,it is easy to see that the phytoplankton dynamics is nitrogen-limited as a whole in BS,though the phosphorus limitation may occur in the Yellow River （YR） Estuary where the input of riverine nitrogen is much more than that of phosphate.

Spectral Models for Improving Atmospheric Correction Results in Complex Oceanic Waters around India

Atmospheric correction over turbid and productive waters continues to be problematic and often results in excessive errors in retrieved water-leaving radiance and bio-geo-physical products. This may be likely due to overestimation of La + Lra (atmospheric signal due to aerosol and Rayleigh scattering) in the visible and thus reduction in Lw which appears as an elevated pigment concentration. Spectral models for reconstructing the atmospherically distorted data are developed and their results are thoroughly validated with in-situ data from a wide range of waters. Good agreement was found between the retrieved products and in-situ data. Our results indicate that the new spectral models have the potential to improve the accuracy of ocean colour retrievals in optically complex waters, and can become an important part of the processing of data from ocean colour sensors (e.g., Ocean colour monitor OCM2) with only two near-infrared bands (i.e., 765 and 865 nm).

Physical Hydrography and Algal Bloom Transport in Hong Kong Waters

In sub-tropical coastal waters around Hong Kong, algal blooms and red tides are usually first sighted in the Mirs Bay, in the eastern waters of Hong Kong. A calibrated three-dimensional hydrodynamic model for the Pearl River Estuary （Delft3D） has been applied to the study of the physical hydrography of Hong Kong waters and its relationship with algal bloom transport patterns in the dry and wet seasons. The general 3D hydrodynamic circulation and salinity structure in the partially-mixed estuary are presented. Extensive numerical surface drogue tracking experiments are performed for algal blooms that are initiated in the Mirs Bay under different seasonal, wind and tidal conditions. The probability of bloom impact on the Victoria Harbour and nearby urban coastal waters is estimated. The computations show that： i） In the wet season （May - August）, algal blooms initiated in the Mirs Bay will move in a clockwise direction out of the bay, and be transported away from Hong Kong due to SW monsoon winds which drive the SW to NE coastal current; ii） In the dry season （November- April）, algal blooms initiated in the northeast Mirs Bay will move in an anti-clockwise direction and be carried away into southern waters due to the NE to SW coastal current driven by the NE monsoon winds; the bloom typically flows past the east edge of the Victoria Harbeur and nearby waters. Finally, the role of hydrodynamic transport in an important episodic event -- the spring 1998 massive red tide -- is quantitatively examined. It is shown that the strong NE to E wind during late March to early April, coupled with the diurnal tide at the beginning of April, significantly increased the probability of bloom transport into the Port Shelter and East Lamma Channel, resulting in the massive fish kill. The results provide a basis for risk assessment of harmful algal bloom （HAB） impact on urban coastal waters around the Victoria Habour.