Changes in Sedimentation Rate of Tidal Flat and Environmental Significance at Qidong Foreland of the Yangtze Estuary

The sedimentation rate is an important environmental parameter to understand the evolution of coastal geomorphology. The tidal flat around Qidong foreland is located in the junction between Yangtze Estuary and Jiangsu coast,where the land-ocean interactions are strong and highly sensitive to environmental changes. The QDZ-1 core sediments collected at Qidong foreland was analyzed for137 Cs dating and grain size.The results showed that silt is the main sedimentary type with a trend of gradually fining from the bottom to the top,conforming to the sedimentation characteristic of the silt muddy tidal flat. The sedimentation rate could be divided into three distinct stages: 1963 to 1986 was 2. 61 cm/yr,1963 to 2011 was 1. 82 cm/yr,and 1986 to 2011 was 1. 10 cm/yr. Based on these,further explanation was made for the significance of environmental changes. According to the estimation of sedimentation rate,the impact of extreme environmental change was reflected by the sudden increase in sand proportion at the depth of 172. 5 cm. Since the introduction of Spartina alterniflora in the 1970 s,it has played an important role in tidal flat development. The tidal flat has a high sedimentary rate during this time. With continuous accretion of the tidal flat,low tidal flat turns to high tidal flat,the sedimentation rate gradually declines,and tidal flat sedimentation appears.

数学拟合法应用于旋耕机结构设计研究

针对旋耕机在作业时存在耕深不够、碎土效果差及土地平整效果差等问题,将数学拟合法应用于旋耕机,对其结构设计进行研究。为了提升旋耕机的作业效果,对旋耕机的结构参数进行优化设计,包括对旋耕机的参数进行分析,并建立旋耕装置的数学模型。为了验证旋耕机的性能,对其进行了旋耕性能试验和旋耕后农田碎土率测定试验。试验结果表明:旋耕机的耕深、地表平整度和碎土率均达到合格指标,作业效果良好。

平板热管式锂离子电池热管理系统仿真分析研究

锂离子电池是航空混合电推进系统的关键子系统,本文针对基于平板热管的航空锂离子电池热管理方案进行设计与性能评估。针对一款锂离子电池模组进行建模与验证,初步设计平板热管方案并进行仿真分析;在原方案基础上,对平板热管散热翅片进行结构优化设计并开展了实验验证,结果表明:优化后的方案可提高系统对流换热量。以优化后的平板热管为基础,结合航空器高空巡航工况的环境温度,平板热管换热性能将得到进一步提升:电池平均温度可降低10.6℃,降幅达18.83%。与水冷方案相比,平板热管优化方案散热能力与之相当,系统减重30%、能耗降低约63%。

基于输配电价的用户定价策略选择模型的构建

近期,国家发展和改革委员会下发了第三监管周期省级电网输配电价,并调整了两部制电价执行的范围,对符合条件的用户赋予了选择执行单一制、两部制输配电价定价策略的选择权,而如何选择定价策略可以更具备经济性,成为困扰用电客户的难题。为此,基于当前的输配电价及相关电费计算规则,分析影响用户定价策略选择的关键因素,定义相关参数作为变量,根据现行输配电价计算定价策略经济性临界曲线,构建了一套输配电价定价策略比选模型,并通过典型用户对模型进行了验证,为用户科学合理选择输配电价定价策略提供了一套可行的方案。

平屋面摩擦速度的数值模拟研究

建筑屋面的摩擦速度是决定其风致迁移雪荷载的重要因素。该文采用CFD(computational fluid dynamics)方法模拟了平屋面的摩擦速度,并结合其分布特征分析了屋面积雪传输率、侵蚀通量和暴露系数随跨度的变化趋势。为验证CFD方法的湍流模型对平屋面摩擦速度模拟的影响,将数值模拟结果与Irwin探头风洞试验进行了对比,结果表明Realizable k-ε湍流模型的模拟结果与风洞试验最为接近。根据4种不同跨度屋面的CFD模拟结果发现,当屋面跨度与高度之比为4时,屋面平均摩擦速度最小;并且随着跨度的增大,屋面摩擦速度最小值所在的位置和积雪沉积的区域均逐渐向迎风侧屋檐靠近。同时发现,屋面积雪的平均侵蚀通量随着跨度的增大而减小,屋面积雪传输率和雪荷载暴露系数则随着跨度的增大而增大。

通过压延涂布工艺制造中心加热型加热烟草芯材的过程控制研究

主要论述通过压延涂布工艺制造中心加热型加热烟草芯材的过程控制,该工艺过程是将涂布物料施涂于烟用基材与底膜之间,并通过压延辊将烟用基材与底膜进行压延贴合,使涂布物料被均匀地压延在基材表面,而后经过烘干工序处理,再将涂布后基材与底膜进行剥离,得到最终成品。对压延涂布工艺核心工序的控制逻辑进行梳理,进而对过程控制进行研究探讨,旨在明晰工艺原理、把握控制环节,掌握分析问题和解决问题的思路与方法,提高加热不燃烧烟草制品生产制造技术和产品质量稳定性。

144型高性能转向节预锻件优化设计与精锻工艺研究

144型转向节是中重型高端商用车转向部件中的核心零件,其对延伸率和断面收缩率均有严格要求,根据传统锻造工艺理论设计的预锻方案不能满足断面收缩率要求,研究其预锻件的优化设计与精锻终成形工艺对于获得合格锻件具有重要意义。首先采用经典塑性成形理论分析了基于传统方法设计的预锻件存在的问题,然后基于损伤理论提出了其预锻件结构的优化设计方法,同时提出了基于平面薄飞边的精锻终成形工艺。应用结果表明,生产的144型转向节精密锻件阶梯杆部的关键技术指标延伸率A≥12.5%,断面收缩率Z≥50%,超过了国外客户所提技术指标的要求。

平板集热器冬季高流速运行数值模拟研究

针对平板集热器(FPSC)冬季热水收集温度不足等问题提出高流速运行方案,以期提高系统的集热性能以及全年利用率.通过CFD技术数值模拟FPSC系统在不同流速工况下(0.02~0.15 kg/s)各组件温度的变化情况,计算系统的集热效率,结合温度云图对比高流速运行的优势.结果显示,高流速运行能够减少集热损失,具有更佳的集热性能.

平坦型和全聋型单侧难治性突发性耳聋患者纯音和言语识别率分析

目的 分析平坦型和全聋型单侧难治性突发性耳聋患者的纯音测听和言语识别率特点。方法 选取2016年1月至2022年1月于淮安市第二人民医院(徐州医科大学附属淮安医院)就诊的平坦型和全聋型难治性突发性耳聋患者132例,所有患者均为单耳发病,分别检测并记录患者的纯音测听和言语识别率,按照发病年龄和听力损失程度进行分组,并进行统计分析。结果 与对照组105例健康体检者听力相比较,观察组132例患者中,轻度12例(9.09%)、中度30例(22.73%)、重度50例(37.88%)、极重度40例(30.30%),不同程度听力损失患者言语识别率比较差异有统计学意义(P<0.05);少年7例(5.30%)、青年32例(24.24%)、中年65例(49.24%)、老年28例(21.21%),不同年龄之间的听力损失比较差异有统计学意义(P<0.05),不同年龄间言语识别率差异有统计学意义(P<0.05);不同性别之间的听力损失比较差异无统计学意义(P>0.05),不同性别之间言语识别率差异无统计学意义(P>0.05)。结论 听力损失程度及年龄可以显著影响言语识别率,两者呈负相关,年龄越大,听力损失越重,言语识别率越低,老年人最为明显;而平坦型和全聋型单侧难治性突聋患者的听力损失与性别无关,多为中度以上听力损失,重度及极重度居多,中年人发病率最高。

伏龙大桥工程路线与阻水率设计总结

伏龙大桥受地理位置限制,有许多控制设计的关键因素需从方案阶段就开始充分考虑。为使防洪评价报告能顺利通过相关审批,在桥梁路线优化设计时,就要充分考虑关键因素阻水率的影响,规划路线经过局部优化,以避免大斜交。从方案设计到施工图阶段,阻水率这一指标在路线优化和总体方案确定的过程中,起到了决定性作用。防洪评价过程中的阻水率对设计路线和方案近乎有“一票否决权”。故从方案阶段开始关注阻水率,避免了方案返工。优化阻水率可从跨径、桥墩尺寸、与水流夹角等方面进行。

Risk factors associated with missed colorectal flat adenoma: A multicenter retrospective tandem colonoscopy study

AIM: To determine the miss rate for colorectal flat adenomas during colonoscopy and the risk factors.METHODS: Flat adenomas are frequently missed during colonoscopy. However, the risk factors that influence their miss rates are unclear. This was a multicenter,retrospective study in which patients diagnosed with colorectal adenomas at a diagnostic colonoscopy and followed within 3 mo by a second therapeutic colonos-copy were pooled out from the established database. The "per-patient" and "per-adenoma" adenoma miss rates(AMR) for overall adenomas and flat adenomas, and patient-, adenoma-, and procedure-related risk factors potentially associated with the "per-adenoma" AMR for flat adenomas were determined.RESULTS: Chromoscopy and high-definition colonoscopy were not taken under consideration in the study. Among 2093 patients with colorectal adenomas, 691(33.0%) were diagnosed with flat adenomas, 514 with concomitant protruding adenomas and 177 without. The "per-patient" AMR for flat adenomas was 43.3%(299/691); the rates were 54.3% and 11.3%, respectively, for those with protruding adenomas and those without(OR = 9.320, 95%CI: 5.672-15.314, χ2 = 99.084, P < 0.001). The "per-adenoma" AMR for flat adenomas was 44.3%(406/916). In multivariate analysis, older age, presence of concomitant protruding adenomas, poor bowel preparation, smaller adenoma size, location at the right colon, insufficient experience of the colonoscopist, and withdrawal time < 6 min were associated with an increased "per-adenoma" AMR for flat adenomas. The AMR for flat adenomas was moderately correlated with that for overall adenomas(r = 0.516, P < 0.0001). The AMR for flat adenomas during colonoscopy was high.CONCLUSION: Patient's age, concomitant protruding adenomas, bowel preparation, size and location of adenomas, proficiency of the colonoscopist, and withdrawal time are factors affecting the "per-adenoma" AMR for flat adenomas.

Impact of Human Activities on Depositional Process of Tidal Flat in Quanzhou Bay of China

As a very important component of a coastal system,tidal flats come to be a focus of the studies on land-ocean interaction in the coastal zone because those areas are subjected to intense human activities and are highly sensitive to the global change.The Quanzhou Bay,located along the middle part of Fujian coast of China,covers about 136.4km2,and the area of coastal wetland in the entire bay from intertidal to subtidal with 6m of water depth accounts for 96% of the total area.Seven short cores were collected and divided in situ with the interval of 5cm on the coastal wetlands of Quanzhou Bay on April 19,2006.The sediment samples were scattered and the grain sizes were measured by using Mastersizer 2000.Human beings' activities on tidal flat have disturbed the vertical distribution of sediments in stratigraphic sequence and accelerated the sedimentation rates.Grain size analysis results show that the grain size diameters increase and sediment becomes worse sorted towards the sea under the strong human disturbance;Spartina alterniflora can play a role of trapping the fine sediment;but near the bank,the sediment becomes coarse and there are two peak values on frequency curve influenced by the sandpile.The trough formed by human activities along the coastline changes the transport path of water and suspended sediment.The sediments are transported through the trough and deposit in it during the flood;the ebb flow is retarded by the flow output through the adjacent trough,and the deposited sediment can not be re-suspended;then,the sedimentation rate increases.In situ observation show that the sedimentation rate is about 8-10cm/yr.

Distribution of ^137Cs and ^210Ppb in sediments of tidal flats in north Jiangsu Province

Seven cores were collected from different sediment zones of tidal flats at Xin- yanggang in north Jiangsu province in August 2007. Sediment grain-size distribution and radioisotopes of ^137Cs and ^210Ppb analysis were carried out for these cores. Sediment rates of the cores and radioisotopes distribution in surface sediment in different zones of the tidal flat were calculated from the ^137Cs and ^210Ppb activities in sediments cores. The results indicated that each tidal zone had experienced different evolution phases, hydrological dynamics in the tidal flats made the grain-size of the surface sediment change gradually. ^137Cs and ^210Ppb activities on the superficial layer of the cores varied spatially and the reason was discussed. On tidal flats, the fluctuation of ^137Cs and ^210Ppb activities in the cores reflected the special sedimentary characteristics. Vegetation affects the grain-size distribution and the vertical profiles of ^137Cs and ^210Ppb in the upper depths. ^137Cs and ^210Ppb chronology got the comparable average sediment rates on the tidal flat. The characteristics of ^137Cs and ^210Ppb in the cores reflected various depositional dynamical environments in different tidal zones and gave information on the different evolvement phases of the tidal zones. Based on the information of grain-size distribution, texture of the cores, sediment rates and topography, the evolution lines of the tidal flat were reconstructed.

Structure and Flow Characteristics of Flat Fan Nozzles with a Single Orifice Formed by a Rectangular Cut

The flat fan nozzle with a single orifice formed by a rectangular cut at the nozzle exit through a semi-ellipsoid blind end was developed. The flow rate characteristic of the nozzle was analyzed. Theoretical analysis shows that the discharge coefficient of the nozzle is a function of the ratio of the projected exit flow area to the cross sectional area of the nozzle input section. Water spraying experiment results show that the discharge coefficient increases with the increase of the ratio of the projected exit flow area to the cross sectional area of the nozzle input section when the rectangular cut depth doesn't exceed the distance from the center of the hemisphere to the nozzle end; conversely,the discharge coefficient decreases with the increase of the ratio; for a given nozzle,the discharge coefficient varies with Reynolds number.

冲击荷载下土体动力响应与加载速率效应研究

为揭示土体在冲击荷载作用下的动态响应特征,运用自主研发的附加激发力式平板动力载荷试验系统(flat dynamic load test,简称FDLT试验)对广州大学城区内两种典型土体(砂土和黏土)进行了不同荷载大小和加载速率的FDLT试验,获取了土体在冲击荷载下的荷载-时程曲线、位移-时程曲线、荷载-位移曲线的3种关系曲线。建立了动态变形模量与加载速率的经验公式,对比分析了两种土体在冲击荷载作用下的加载速率效应。研究表明:(1)砂土的FDLT试验存在一个充电量临界值,在该充电量冲击试验过程中,加载速率对砂土的动态强度及变形有较大的影响,而对黏土在本次试验条件下未有明显影响。(2)加载速率对黏土与砂土的位移响应的相同之处在于,最大荷载和最大位移均随加载速率的增大而提高;不同之处在于,黏土达到位移峰值时间会随加载速率增大而延长,而砂土达到位移峰值时间随加载速率增大呈现先增加后减小的规律。(3)土体的动态变形模量与加载速率曲线呈对数变化关系。本研究成果可为土体动力特性研究、土的动静参数换算和工程设计提供依据。

聚氯乙烯平板膜的制备及性能研究

主要介绍了在制备平板膜的实验教学中,采用聚氯乙烯作为膜材料进行制备,这不仅降低了实验教学的成本,同时还提高了平板膜的性能。对表面活性剂含量、聚合物浓度对平板膜的膜通量和截留率等基本性能的影响进行了研究,取得了比较满意的结果。

1ZS-4200型水田振捣起浆平地机的设计与试验

针对水田耕整农艺要求,设计了一种能够一次作业完成碎土、根茬压埋、根系生长土层起浆以及平地等多道工序的水田振捣起浆平地机,主要由机械传动装置、机械式高频激振机构、圆弧埋茬梳齿、船型拖板以及新型隔震传动装置组成。通过分析确定了机械传动装置参数,并设计了水田振捣起浆机的机械式高频激振机构和圆弧埋茬梳齿。田间试验表明:当机械式高频激振机构的激振频率为43Hz、机具前进速度为3km/h时,埋茬率为90.6%,平整度为20mm,泥浆度为1.30g/cm 3,综合指标达到最佳,满足水田耕整的农艺要求。

亲水改性超薄平板热管传热性能

高性能电子器件的发展需要厚度更薄、传热性能更高的传热装置。热管依靠内部工质相变潜热来传递热量,具有热导率高、均温效果好等特点,广泛应用于电子器件的散热。本文制作了厚度为0.6mm的超薄平板热管,热管壳体内部和铜丝网均作亲水改性处理,丝网加工出蒸汽通道来实现气液共面以降低流动阻力。搭建热管性能测试平台,在自然对流冷却条件下研究去离子水、乙醇两种工质和不同充液率对超薄平板热管传热性能的影响。结果表明:经过化学改性改善了管壳和铜丝网对去离子水的浸润性,同时提高了铜丝网的毛细力,亲水改性后去离子水热管热导率相比改性前提升了19.53%;两种工质填充的热管的最佳充液率都是1.0,在控制蒸发段最高温度小于80℃的情况下允许输入的最大功率为6W;去离子水填充的热管表现出更好的热性能。