基于分形理论的黄河内蒙古段河势演变特征及其与凌汛灾害关联研究

寒区河道凌汛灾害河势“弯道效应”的量化评估十分重要。基于分形理论提出河道横断面-纵剖面-平面多维度河势分形维数计算方法及其物理机制，并探讨黄河内蒙古段不同维度河势演变分形特征及其与凌汛灾害的关联关系。结果表明，黄河内蒙古段不同维度河势均具有多尺度自相似分形特征，且具有多年记忆周期的长程相关性；冰坝（严重性冰塞）发生频次与河道主槽弯曲分形维数呈正相关指数型函数关系，与河相系数、深泓点高程和河段平均底坡分形维数负相关，与水深-面积分形维数正相关，总体表明冰坝灾害更易发生于主槽偏移摆动大、蜿蜒曲折、河湾发育程度高的宽浅型弯曲河道，研究成果可为凌汛期冰塞冰坝灾害易发河段诊断及预测提供重要理论依据。     

三峡水库运行后宜昌-城陵矶河段冲刷重心下移与时空演变

三峡大坝下游河道的冲刷发展影响着长江中下游的防洪、航运及区域经济发展。本文以宜昌至城陵矶河段约400 km长河段为研究对象,基于2002—2018年河道的来水来沙、泥沙粒径和横断面形态观测资料,计算并分析河道垂向冲淤、横向摆动、平滩面积、平滩水深和冲淤量的变化,根据河道平面形态将研究河段划分为32个子河段,对子河段平均平滩面积和平滩水深的变化速率进行分级,引入空间聚类分析方法,对冲刷强度等级最高的河段在时空尺度上分布进行聚类分析,研究河道冲刷重心的时空迁移规律。结果表明,三峡水库运用后下游河道经历了蓄水初期冲刷较强（2003—2007）、175 m正常蓄水运用后冲刷减弱（2008—2012）和上游梯级水库运用后冲刷增强（2013—2018）的三个阶段;空间上,宜昌至枝城及上荆江河段普遍冲刷,以弯曲型为主的下荆江河道以冲为主,但冲淤交替频繁,同时冲淤强度具有随时间衰减的特点;冲刷重心具有向下游迁移的趋势,在三峡水库蓄水初期冲刷重心向下迁移较快,之后减缓,上游梯级水库运用后,冲刷重心下移速率明显加快,之后再次减缓,2003—2018年冲刷重心平均下移速率约7.5 km/a。     

浔江防洪堤对西江中下游洪水的归槽影响

基于河道洪水演算原理,建立符合河流水力特性及其变化规律的边滩滞洪水库调节法流量演算模型、校正因数法水位演算模型,利用实测洪水和防洪堤资料进行归槽或还原演算,综合分析防洪堤对洪水归槽的影响。保护区滞洪容积占次洪水总量9．50％的浔江防洪堤对西江中下游洪水过程的归槽影响大于对洪峰的归槽影响,而且洪水类型和干支流组合不同,影响的程度也不相同：对流量过程、洪峰流量影响的最大归槽流量、最大归槽流量比重分别为3680m^3／s、9．63％,2700m^3／s、5．90％,对水位过程、洪峰水位影响的最大变幅为0．60、0．22m。浔江防洪堤造成的洪水归槽并未显著改变西江中下游洪水特性,干支流洪水遭遇、区间降雨和雨洪重叠仍然是形成西江中下游大洪水的主要因素,西江中下游洪涝频繁是气候和流域环境变化综合影响的结果。     

长江口澄通河段床沙粒度特征分析

为了进一步研究长江口水土资源和岸线开发利用工作对该段河床演变和水动力变化的影响,根据2012年及2013年枯水期长江口澄通河段两次大范围床沙取样监测成果,分析了各主支汊床沙的物质组成,粒度分布及丰枯水年粒度特征。结果表明：澄通河段主槽砂粒粗,浅滩砂粒细;主汊砂粒粗,支汊砂粒细;总体上,从上游向下游床沙粒度逐渐变细;主槽及主汊区域床沙类型主要为细砂及粉砂质砂,支汊及浅滩区域床沙类型主要为砂质粉砂及黏土质粉砂;2012年,全河段床沙的粒度组成表现为,砂含量大于粉砂含量,粉砂含量大于黏土含量。     

三峡水库175 m试验性蓄水过程水文泥沙分析

为掌握三峡水库175 m试验性蓄水过程中库区水位、流量、含沙量变化过程,通过三峡库区寸滩、清溪场、万县、朱沱（三）水文站实测的水位、流量、含沙量、水面比降资料,分析了蓄水过程中三峡库区沿程水面比降、库区水文站的水位流量关系、含沙量变化、库区冲淤变化等。分析结果为认识掌握三峡水库175 m蓄水后库区水文泥沙的变化规律积累了资料,对探索三峡库区水文泥沙的监测方式和分析研究将具有积极作用。     

试析学生德育记实考评的做法

本文从思想工作应该“康事实做”出发,讨论如何做好大学生德育纪实考评工作,提出了应该“思想到位”以提高认识,“措施到位”以建立规范,“工作到位”以保证落实。     

黄河内蒙古段冰情的自适应神经网络预报

运用数理统计理论的互相关分析方法,对黄河内蒙古段冰情信息时间序列进行分析,筛选出了冰情信息的预报因子,建立了冰情预报的自适应BP神经网络模型。预报结果表明:流凌日期为乙等预报方案,封河日期为甲等预报方案,开河日期为丙等预报方案。     

Effects of age and gender on maximum voluntary range of motion of the upper body joints

The maximum voluntary range of motion (ROM) of the major joints of the upper body was studied in a seated position and compared between young and elderly subjects. A total of 41 subjects (22 young male and female subjects aged 25 to 35 years, 19 elderly male and female subjects aged 65 to 80 years) took part in the experiment. In total, 13 maximum voluntary joint motions were performed by each subject. Age was found to have a non-uniform effect on the ROM of the joints investigated in this study. Its effect on ROM was joint specific and motion specific. The highest loss in ROM was observed in the neck and trunk, especially for neck extension, lateral flexion and axial rotation as well as for trunk lateral flexion and axial rotation. No significant age differences were observed in the elbow and wrist joint ROMs. The effect of gender on joint ROM was much weaker than that of age. Only four among the 26 joint ROMs investigated in this study were significantly different between the two gender groups.     

Prediction of recent bank retreat processes at typical sections in the Jingjiang Reach

The Jingjiang Reach is experiencing continuous channel degradation owing to operation of the Three Gorges Project(TGP)in2003.Significant retreat processes at composite riverbanks have occurred at local sites of this reach,which may influence the stability of the river regime and the effect of existing river training works.Therefore,bank retreat plays a key role in fluvial processes of the Jingjiang Reach,and it is necessary to predict the long-term processes of bank retreat at typical sections in the reach.In this study,various factors influencing bank retreat in the Jingjiang Reach are investigated,based on bank erosion processes at four sections and the corresponding flow and sediment conditions.It is discovered that fluvial erosion intensity is a dominant factor in controlling the processes of bank retreat in the reach,although other factors,such as bank soil properties,can also influence bank retreat.The bankfull width at a section with severe bank erosion since 2002 is defined as being equal to the sum of the bankfull width in 2002 and the accumulated bank retreat distance after 2002.The magnitude of the bankfull width can be expressed as an exponential function of the previous 5-year average fluvial erosion intensity during flood seasons.The accumulated distances of bank retreat at four sections over the period 2002–2012 are predicted using the proposed empirical relationships,with the calculated bank retreat processes agreeing well with observed data.     

金沙江建库对重庆河段泥沙淤积的影响

通过平面二维水沙数学模型,分析了金沙江建库前后重庆河段的泥沙淤积情况.结果表明,金沙江无库情况下,重庆河段在水库运用初期出现累积性淤积,随着水库运行时间增加,部分浅滩河段可能产生碍航问题;金沙江建库后,整个重庆河段长江干流呈现冲刷趋势,但支流金沙碛河段淤积情况和上游无库时差别不大.