56 resultados para Forecast

em Chinese Academy of Sciences Institutional Repositories Grid Portal


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The paper demonstrates the nonstationarity of algal population behaviors by analyzing the historical populations of Nostocales spp. in the River Darling, Australia. Freshwater ecosystems are more likely to be nonstationary, instead of stationary. Nonstationarity implies that only the near past behaviors could forecast the near future for the system. However, nonstionarity was not considered seriously in previous research efforts for modeling and predicting algal population behaviors. Therefore the moving window technique was incorporated with radial basis function neural network (RBFNN) approach to deal with nonstationarity when modeling and forecasting the population behaviors of Nostocales spp. in the River Darling. The results showed that the RBFNN model could predict the timing and magnitude of algal blooms of Nostocales spp. with high accuracy. Moreover, a combined model based on individual RBFNN models was implemented, which showed superiority over the individual RBFNN models. Hence, the combined model was recommended for the modeling and forecasting of the phytoplankton populations, especially for the forecasting.

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In this paper, the codes of Pattern Informatics (PI) method put forward by Rundle et al. have been worked out according to their algorithm published, and the retrospective forecast of PI method to North China (28.0 degrees-42.0 degrees N, 108.0 degrees-125.0 degrees E) and to Southwest China (22.0 degrees-28.3 degrees N, 98.0 degrees-106.0 degrees E) has been tested. The results show that the hit rates in different regions show a great difference. In Southwest China, 32 earthquakes with M(L)5.0 or larger have occurred during the predicted time period 2000-2007, and 26 out of the 32 earthquakes occurred in or near the hot spots. In North China, the total number of M(L)5.0 or larger was 12 during the predicted time period 2000-2007, and only 3 out of the 12 earthquakes occurred in or near the hot spots. From our results, we hold that if the PI method could be applied to all kinds of regions, the parameters associated with time points and time windows should be chosen carefully to obtain the higher hit rate. We also found that the aftershocks in a strong earthquake sequence affect the PI results obviously. Copyright (c) 2009 John Wiley & Sons, Ltd.

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In this paper, the codes of Pattern Informatics (PI) method put forward by Rundle et al. have been worked out according to their algorithm published, and the retrospective forecast of PI method to North China (28.0 degrees-42.0 degrees N, 108.0 degrees-125.0 degrees E) and to Southwest China (22.0 degrees-28.3 degrees N, 98.0 degrees-106.0 degrees E) has been tested. The results show that the hit rates in different regions show a great difference. In Southwest China, 32 earthquakes with M(L)5.0 or larger have occurred during the predicted time period 2000-2007, and 26 out of the 32 earthquakes occurred in or near the hot spots. In North China, the total number of M(L)5.0 or larger was 12 during the predicted time period 2000-2007, and only 3 out of the 12 earthquakes occurred in or near the hot spots. From our results, we hold that if the PI method could be applied to all kinds of regions, the parameters associated with time points and time windows should be chosen carefully to obtain the higher hit rate. We also found that the aftershocks in a strong earthquake sequence affect the PI results obviously. Copyright (c) 2009 John Wiley & Sons, Ltd.

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In order to explore a prior warning to catastrophic rupture of heterogeneous media, like rocks, the present study investigates the relationship between surface strain localization and catastrophic rupture. Instrumented observations on the evolution of surface strain field and the catastrophic rupture of a rock under uniaxial compression were carried out. It is found that the evolution of surface strain field displays two phases: at the early stage, the strain field keeps nearly uniform with weak fluctuations increasing slowly; but at the stage prior to catastrophic rupture, a certain accelerating localization develops and a localized zone emerges. Based on the measurements, an analysis was performed with local mean-field approximation. More importantly, it is found that the scale of localized zone is closely related to the catastrophic rupture strain and the rupture strain can be calculated in accord with the local-mean-field model satisfactorily. This provides a possible clue to the forecast of catastrophic rupture. (c) 2007 Elsevier Ltd. All rights reserved.

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采用量纲分析的方法,讨论了环与杆高速碰撞时影响杆被击断的主要因素,分别给出了相对临界速度、临界方位角及环的临界厚度与主要物理参数的函数关系,并通过计算机仿真确定这种函数关系。

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对比了背投领域几种主要技术的原理和性能特点,同时介绍了多媒体投影系统所需要的各类光学薄膜的作用,参数和光学性能;并针对该领域国内外最新研究状况进行了调研,给出了现在所面临的关键技术难题并对其发展前景做了预测。

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Resonant tunnelling diodes with different structures were grown. Their photoluminescence spectra were investigated. By contrast, the luminescence in the quantum well is separated from that of other epilayers. The result is obtained that the exciton of the luminescence in the quantum well is partly come from the cap layer in the experiment. So the photoluminescence spectrum is closely related to the electron transport in the resonant tunnelling diode structure. This offers a method by which the important performance of resonant tunnelling diode could be forecast by analysing the integrated photoluminescence intensities.

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软件开发是智力密集型产业,人力资源在软件开发中扮演着极其重要的角色,不同的人在相同的设备上,可以生产出质量和功能完全不同的产品,其生产效率甚至可以相差数十倍,Boehm的COCOMO模型发现团队质量是目前项目成功最大的决定因素。在软件开发中,人力资源的离职是无法避免的,总会有人因为人为或非人为的原因而离职。不同的研究人员对人力资源离职进行统计率研究表明,人力资源的离职率高达33%~80%之间,平均雇员受雇时间仅为15~36个月,而且人力资源的离职往往会给公司带来很高的成本,使人力资源离职风险成为软件开发极其重要的一种风险。虽然现在软件开发过程比以前更成熟,人员的离职仍然会给项目带来严重的影响,甚至会给项目带来毁灭性的打击。 在人员高离职率的情况下,量化项目中的每个人在任一时间点的离职对项目造成的影响,对项目管理者来说是很有参考意义的,它可以帮助项目管理人员客观地了解目前项目的人力资源离职风险情况。本文在深入细致地研究了国内外研究现状的基础上,提出了一种基于任务的人力资源离职风险预测研究。 本文的主要内容包括: 第一、提出了基于任务的人力资源离职风险预测模型。通过建立项目计划任务模型、人力资源模型、任务分配模型,来对项目开发进行描述,使模型能够适用于大多数的软件开发项目; 第二、针对现有人力资源风险管理主要依靠主观判断和个人经验的弱点,将项目参与者离职对项目造成的影响(项目延迟时间和项目成本超支)量化,给项目风险管理者提供客观的数据支持,作为企业和项目进行人力资源风险管理的依据; 第三、对基于任务的人力资源离职风险研究进行实例化分析。通过一个实际的项目实例,来分析本研究的实际使用过程。并对实例的研究结果进行分析,给出了一些降低人力资源离职风险的切实可行的措施。 第四、设计和开发了一个基于任务的人力资源离职风险预测系统,提高人力资源风险管理的效率和准确性。

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土壤是疏松多孔体,具有存蓄和调节土壤水分的功能。就目前黄土高原土壤水库及其影响因子进行了评述,重点阐述了土壤水库功能及其与三个主要影响因子(气象因子、植被因子、土壤因子)的关系,并对今后的研究做了展望。土壤水库下边界的界定、不同因子对土壤水库的影响以及土壤水库模型的构建等都有待进一步的研究。

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岷江上游是我国十分典型的山地生态脆弱区。该地区的生态环境意义十分重大,既是长江上游生态屏障的重要组成部分,更是成都平原的重要生态屏障和水源生命线,其生态环境状况直接影响成都平原水资源的质量和数量,以至影响到整个岷江流域甚至整个长江上游的生态环境与社会经济发展。本论文通过3S技术手段,应用转移矩阵、景观指数和Kappa指数系列方法对岷江上游的景观变化从1974到2000年进行了综合分析,同时应用CLUE-S模型在有无“天然林保护工程”两个预案下对该区域2001到2020年的景观变化进行了预测。然后,应用基于能值理论进行改进的生态足迹方法和传统生态足迹方法对岷江上游地区的1982到2000的生态承载力进行了分析,以反映研究区的生态环境质量和可持续发展情况;应用多元统计方法和CLUE-S模型预测的结果预测了研究区2001到2020年的生态足迹和生态承载力。对岷江上游地区的景观格局和生态承载力的变化进行分析和预测得到如下主要结论: 1. 岷江上游地区景观在1974到2000年间格局变化并不十分显著,景观由少数几种景观类型所控制,各景观类型有不断趋于平均化的趋势,但速度缓慢,景观的破碎化程度越来越严重。研究区的景观变化以有林地的不断减少和其它景观类型的相应增加为特点,主要的景观变化发生在有林地、灌木林地、草地、耕地和经济林地之间。此时间段内的景观林地的面积不断减少,大部分转化为灌木林地和草地,使得其面积相应增加。耕地和经济林地面积不断增长,增长速度最为迅速。 2. 在有无“天然林保护工程”两种预案下,有林地向着不同的方向发展,有林地变化情况的不同导致其它景观类型的变化不同。在“无天保”预案下,林地面积不断减少,灌木林地、草地和耕地面积不断增长,景观的破碎化程度不断加剧,斑块形状更加不规划,景观的连通性不断下降。在“天保”预案下,林地面积有增长趋势,灌木林地和草地面积有所下降,耕地面积有下降趋势,景观的破碎化程度有减小的趋势,景观形状变得更加规则,景观的连通性也将得到改善。由此,“天然林保护工程”对景观格局未来变化有着决定性的作用。 3. 岷江上游地区的生态足迹从1982到2000年间呈缓慢的上升趋势,表明研究区内居民的生活水平不断提高,但速度缓慢。虽然研究区在研究时期内的生态承载力大于需求,但生态承载力呈明显的下降趋势,造成这种情况的主要原因是由于资源的不合理利用方式造成的,特别是对森林的过度采伐。连续的木材采伐给岷江上游地区脆弱的生态系统带来严重后果,导致了林地面积减小、森林质量下降、水土流失加剧和泥石流频繁发生。 4. 对于生态足迹和生态承载力在两个预案的预测表明到2020年为止岷江上游地区仍为可持续发展状态。在“无天保”预案下,生态承载力不断下降,生活足迹不断上升,研究区向不可持续的方向发展;在“天保”预案下,生态承载力在2003年后开始逐渐上升,同时,由于木材采伐被禁止,导致岷江上游地区的生态足迹大为下降,研究区将向更加可持续的方向发展。由两种预案的结果对比可以发现1998年开始实施的“天然林保护工程”能够扭转岷江上游地区未来的生态承载力变化方向。生态承载力可以反映生态系统的质量,说明该政策的实施可以有效改善岷江上游地区未来的生态系统。 5. 传统生态足迹方法应用的生物生产能力数据为常量,所以它能够有效地比较不同年份和不同区域间消费数据的变化情况。实际土地需求法应用的生物生产能力和均衡因子均根据研究区实际数据计算得到,其反映研究区的实际情况更为有效。应用能值对生态足迹方法进行改进,改变了传统生态足迹以生物圈为限制的不足。本文改进的方法-区域能值足迹法能够有效地反映研究区的实际情况,同时又能够将科技进步所带来的影响加以考虑。

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21世纪中国将进入工业化与城市化快速发展阶段,随着经济全球化与竞争国际化,产业集群开始成为经济发展的主流,以临港产业为代表的沿海经济带开发建设已成为发达国家的重要经验和国内沿海省市的主导区域战略,辽宁沿海经济带的开发建设将进一步加大沿海地区与周边地区及内地的资源信息交换,人口的大量流入、城市化进程的加快等都可能对沿海区域的生态环境质量和可持续发展与生态安全产生重要影响。 论文通过3S技术手段,应用转移矩阵、土地利用度量公式、景观空间格局分析和Kappa 指数系列方法对1988~2007 年辽宁沿海经济带的景观变化进行了综合分析,同时应用CLUE-S 模型在有无“辽宁沿海经济带开发建设规划”两个预案下对该区域2008~2020 年的景观变化进行了预测。应用生态足迹理论与方法对研究区1990~2006年的生态足迹与生态承载力进行了分析,以反映研究区可持续发展情况;应用时间序列(ARMA)与支持向量机(SVM)预测了研究区2007~2020年生态足迹与生态承载力变化。并对研究区进行了基于生态足迹的区域生态安全动态分析及预测研究,最后提出了研究区生态安全对策,得到如下主要结论: (1)辽宁沿海经济带在1988~2007年间景观格局变化并不十分显著,景观由少数几种景观类型所控制,各景观类型有不断趋于平均化的趋势,但速度较慢,景观的破碎化程度越来越严重。土地利用度逐步增大,反映在景观变化上,是以建设用地的持续扩张与耕地以及林地、水域面积缩小为特点,其中建设用地在景观类型转换中发挥着越来越重要的作用。主要的景观变化发生在耕地、林地、水域与建设用地之间。 (2)在有无“规划”两种预案下,景观变化的趋势基本一致,但变化幅度有明显差别。两种预案下耕地都趋于减少,但“规划预案”降幅更大一些。建设用地逐渐增加,但“规划预案”扩张更快,面积更多。建筑用地变化情况的不同导致其它景观类型变化的不同。两种预案下景观的破碎化程度均有减小的趋势,斑块形状趋于规则,景观的连通性也在逐年增大,其中在“规划预案”中表现得更为显著。 (3)辽宁沿海经济带从1990~2006年间的人均生态足迹与生态承载力均呈逐渐增大趋势,且生态足迹需求明显大于生态承载力,生态赤字在逐渐增大,研究区内的生态负荷已超过了其生态容量,现有的区域发展模式是不可持续的。其中生态足迹需求增大主要来自能源足迹需求增大,而生态承载力的增加主要是因为水域类面积的增加。17年间研究区的人均万元GDP生态足迹均有不同程度的下降趋势,表明该区域的资源利用效率在逐渐提高。 (4)过去17年来,辽宁沿海经济带的生态压力指数变化趋势为先升后降,区域生态安全经历了生态较安全、稍不安全、较不安全和稍不安全等阶段,表明该区域生态安全正在逐步改善。生态占用指数与生态经济协调指数均呈逐步增大的趋势,表明研究区的社会经济发展程度和人民消费水平正在走向较富裕阶段,该区域社会经济发展与生态环境的协调性也在逐渐改善。 (5)两种预案下,辽宁沿海经济带未来14年的人均生态足迹与人均生态承载力均有逐渐增大的趋势,且人均生态足迹均超过了其人均生态承载力,存在不同程度的生态赤字,发展模式仍将是不可持续的,其中“规划预案”下的发展模式更加不可持续。 (6)两种预案下,研究区未来14年的生态安全均处于稍不安全状态,其中“规划预案”的生态压力更小一些。两种预案下研究区的生态占用指数和生态经济协调指数均有逐年增大的趋势,区域经济均将从较富裕阶段走向很富裕阶段,经济增长与生态环境的协调程度也由较好阶段步入很好阶段。其中“规划预案”下的区域经济增长更快,与生态环境的协调性将更好一些。 (7)三种方案可以降低研究区“规划预案”下的生态压力指数,实现区域的生态安全。其中同时提高研究区的生态承载力,降低生态足迹的方案更为合理可行,既保障了区域安全,又实现了区域的可持续发展目标。 (8)要保障研究区未来14年的生态安全,建议规划增加水域面积,推进区域热电联产,发展清洁能源并推动区域间资源互补共享。

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太子河流域位于辽河中下游,区内分布有我国重要的钢铁、石化和粮食生产基地,是辽宁社会和经济发达地区。当前,太子河流域水资源短缺、水污染和地下水超采问题突出,水资源已成为制约当地社会经济持续、健康、稳定发展的重要因素。针对当前太子河流域严峻的水资源开发利用态势,论文提出了水资源实时评价的内容和方法,根据水资源实时监控管理的实际需要,将水资源实时评价分为汛末水资源实时评价和汛前水资源实时评价两部分。其中汛末评价主要是为计划用水和节约用水服务,而汛前评价主要是为抗旱减灾服务。在实时评价基础上,将水资源实时预报分为面向实时管理的水资源实时预报和面向实时调度的水资源实时预报两部分。建立了基于人工神经网络的地表径流实时预报模型和基于数值模拟技术的地下水可开采量(可供水量)实时预报模型,并进行了模型的率定、识别和验证。此外,借助由水资源实时预报模型和水资源实时管理模型构成的水资源实时预报管理祸合计算模式及计算流程,经模型祸合迭代计算,得出了太子河流域枯水期(2001~2002年度)水资源实时管理方案。上述研究成果,可以为辽宁太子河流域实现“计划用水和节约用水”提供决策依据,并可为北方干旱、半干旱地区流域水资源的“统一管理、动态管理和科学管理”提供可借鉴模式。

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土地利用是人类根据土地质量特性来开发利用土地,创造财富,满足人类生产和生活的需要,同时改善环境,满足人类生存需要的过程。土地利用总体规划是对未来各类用地在空间上、时间上作出总体的协调的预先安排,不仅受到一定历史背景的制约,同时也受影响于当前的社会经济发展情况。但是,国内传统的土地利用总体规划往往从狭窄的技术经济观点出发,对远期的生态环境问题、社会问题缺少考虑,将新的用地尽量安排在最便捷、最经济的地方。 由于土地利用总体规划对环境影响具有长期性、复杂性、综合性、有时还有不可逆转性等特点,迫切需要在编制土地利用总体规划时对规划区与土地利用有关的环境影响进行科学研究,把环境保护纳入土地利用活动的计划、决策和规划实施中,促进土地资源持续、协调的利用。为更好地进行土地利用总体规划环境影响评价必须首先建立相应的评价指标体系,而目前国内关于该项研究的理论和实践的相关报道都较少。 本论文在综述国内外土地利用总体规划环境影响评价的理论与实践的基础上,在国内第一批开展了相关领域的案例研究,采用理论研究和案例分析相结合的研究方法对土地利用总体规划环境影响评价方法和指标体系进行了研究,对邛崃市土地利用总体规划进行了环境影响评价,其研究的主要内容和论点如下: (1)第一次根据FAO 确定的五大原则,引入了生态用地的概念并按照价值模型构建了以土地资源可持续利用为目标的县级土地利用总体规划环境影响评价的指标体系。以生产性、稳定性、保护性、经济活力、社会可接受性五个方面作为指标层来度量土地利用总体规划的环境影响,并选取了土地利用率、土地整理率、水面指数、生态用地面积比例、耕地转化率、建设用地产值指数、公众满意度等21 个元指标作为具体的评价指标。该指标体系强调了规划方案的公众参与,便于充分吸收公众的意见和建议;并且评价指标获取容易,实用性较强。 (2)在土地利用总体规划环境影响评价方法上进行了有益的探索和尝试,由于土地利用总体规划环境影响评价的主要对象是几个拟定的规划方案,所以采用综合评分法(包括特尔斐法和层次分析法)和公众参与相结合的评价方法。应用上述指标体系和评价方法对邛崃市土地利用总体规划的三个方案进行了评价筛选,高方案最终得分为92.049;中方案最终得分为91.028;而低方案最终得分为95.541,为最优方案。 (3)开展了对土地利用总体规划替代方案和公众参与机制的研究,对公众参与的方式、程序及主要内容从理论和实践两方面进行了有益的尝试,收到了良好的效果。 (4)对邛崃市土地利用总体规划进行了环境影响评价,根据邛崃市的具体情况,对规划实施后可能造成的环境正、负面影响进行了分析和预测,提出了预防或者减轻不良环境影响的对策和措施。 Land use is a process, which is to develop land according to its mass property. Bycreating the wealth and improving the environment, it can meet the need of production,life and human survival. Land use planning, as a planning form to guide land use, issubject to the historical background, and influenced by development of economic andsociety. The land use planning in the past, from narrow economic technology view,lacking of concerning ecologic environmentand social problem, arranged new land in the most convenient and economic place. Because of complexity, comprehensive and sometimes irreversible characteristicsof environmental impact caused by land use planning which has been implemented, it isneed to carry on scientific research on environmental impact related to land use as theland use planning is forming, to bring environmental protection within the plan, policymaking and implementing of land use activity, promoting the sustainment, harmonious use of land resource. This paper, taking the readjustment of land use planning in Qionglai as an example,assessed its environmental impact of land use planning. The main contents and results arepresented as follows: (1) On the basis of the five criterions of AFO, for the first time propose county classoverall planning of land uses SEA index by inducting ecological land use andestablishing the Value factor system, according to Productivity criterion,Stabilitycriterion,Sheltered criterion,Economic livingness criterion,Social acceptabilitycriterion,the environmental impact of land use system was assessed by using Valuemodel. Through identifying the factors of environmental impact of land use planning, thepaper established the factor system of SEA of land use planning. From the land usefactors, 21 factors was chosen to assess the environmental impact degree of land useplanning, such as, index of land use degree, the rate of land collating, index of watersurface, the rate of ecological use land, cultivated land conversion ratio, forest landconversion ratio, public satisfaction degree and so on. These indexes make a point thatpublic participation of plan project fully absorb public idea and propose and the index easily get, better utility. (2) Attempt useful assessment method system of SEA of land use planning. In viewof there are no or almost no inevitable contact among the factors of SEA of land useplanning,we use AHP (Analytic Hierarchy Process) as the main assess method . Thereare three plans are compared in this paper apply the foregoing index and assessmentmethod. The high plan finally score is 92.049,while the middle plan is 91.028. The lowplan score is 95.541,is the best one,as the selected plan. (3) Carry on the research of the alternative scheme of overall planing of land useand public participation,to the fashion ,procedure and object matter carry out helpfulattempt from theory to practice,the results is good. (4)Took place SEA of Qionglai County overall planing of land use,according to thecircumstance of Qionglai,we analyze and forecast the positive and negative affect afterthe plan implement,and put forward the countermeasure and means to prevent or abatebad environmental impact.

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Hunhe, Taizihe rivers originating from the east mountain areas of Liaoning Province are the biggest tributaries of the left bank of Liaohe River. From the initial stage of New China to the early 1990s, the frequency of flood damage had decreased, but recently the disasters have upgraded and changed from trunk stream to tributary basins. In July 1995, Dongzhouhe, a tributary of Hunhe River, suffered from a heaviest flood since establishing the document of floods in Hunhe basin. Meanwhile, a peak discharge, almost beyond double defending ability, occurred at Dadongshanpu Station of Beishahe River, a tributary of Taizihe River. Besides the continued heavy rainstorm, no controllable water conservancy projects and ecological damages caused by quickly decreasing forest cover and water and soil loss are the two main causes of flood damage. In addition, the low flood protection standard is also one of causes. According to the above analyses, some strategies of synthetic controlling for flood damages were put forward: 1) Establishing the system of ecological engineering to defend floods and reduce disasters; 2)Setting up storage and detention areas; 3) Establishing flood controlling information system; 4) Improving the accuracy of media short period and short period rainstorm forecast and flood forecast; 5) Insurance of flood protection.