Field Measurements of Influence of Sand Transport Rate on Structure of Wind-sand Flow over Coastal Transverse Ridge

The structure of wind-sand flow under different total sand transport rates was measured with field vertical anemometer and sand trap on the crest of typical coastal transverse ridge in Changli Gold Coast of Hebei Province, which is one of the most typical coastal aeolian distribution regions in China and famous for the tall and typical coastal transverse ridges. The measurement results show that, on the conditions of approximate wind velocities and same surface materials and environments, some changes happen to the structure of wind-sand flow with the increase of total sand transport rate on the crest of coastal transverse ridge. First, the sand transport rates of layers at different heights in the wind-sand flow increase, with the maximum increase at the height layer of 4-8cm. Second, the ratios of sand trans-port rates of layers at different heights to total sand transport rate decrease at the low height layer (0-4cm), but increase at the high height layer (4-60cm). Third, the distribution of the sand transport rate in the wind-sand flow can be expressed by an exponential function at the height layer of 0-40cm, but it changes from power function model to ex-ponential function model in the whole height layer (0-60cm) and changes into polynomial function model at the height layer of 40-60cm with the increase of total sand transport rate. Those changes have a close relationship with the limit of sand grain size of wind flow transporting and composition of sand grain size in the wind-sand flow.

Effect of Energy Density and Gas Velocity on Transport Rate of Ions

In order to study the effect of the parameters such as the energy density and the gas velocity on the transport rate of ions, the applied force and the motion law of charged particles in the electric field of corona discharges at atmospheric pressure is investigated in this paper. As a result, when the gas velocity is raised from 1.5 m/s to 25 m/s for an energy density of 0.4 mJ/cmz, the ionic transport rate increases from 5.4 × 10^8/cm^3. s to 8× 10^10/cm^3 .s, which is an increase of over two orders of magnitude. However, in the zones of streamer and glow discharges, the effect of the input energy density and the energy density of gas ionization on the transport rate is below one order of magnitude. In conclusion, the increase of charged particle momentum can be a major factor in raising the transport rate and reducing the volume of the plasma sources.

Effect of upward seepage on bedload transport rate

The paper presents an investigation of injection effects on the bedload transport rate. According to dimensional analysis, two dimensionless groups, an Einstein＇s parameter group and a modified densimetric Froude number group, were chosen to examine how injection affects the bedload transport rate. Experimental studies were conducted in an open-channel flume with an upward seepage zone. The sediment particles used for the test were 0.9 mm in diameter. The experimental results show that an increase in the injection velocity causes a reduction in the shear velocity excess, which is defined as the difference between the shear and critical shear velocities, leading to a reduction in the bedload transport rate. The equation for predicting the bedload transport rate in the presence of upward seepage was derived empirically. The proposed prediction method is suitable for engineering practice, since it only requires the undisturbed flow condition, properties of sediment particles, and the injection velocity.

Nonlinear Analysis of Bedload Transport Rate of Paroxysm Debris Flow

The evolution characteristics of bedload transport feature of paroxysm debris flow have been studied by means of both theory analysis and experimental data.The analysis based on the flume experiment data of a sand pile model as well as a large amount of field data of debris flow clearly shown that the statistical distribu- tion for the main variable of the sand pile made of non-uniform sand (according the sand pile experiment,φ≥2.55) conform to the negative power law,that means the non-uniform sand syste...

Bed Load Transport Rate in Scouring and Armoring Process of Non-uniform Sediment River Bed

Flume experiments were carried out to study bed load transport rate during rive bed scouring and ar- moring.A theoretical differential equation linking the transport rate to the probability of incipient motion of non-uniform sediment is solved.The transport rate is shown to decrease exponentially with time,according to the theory,which is in good agreement with the experiment data.

CALCULATION MODELS FOR THE SUSPENDED SEDIMENT TRANSPORT RATE

The calculation accuracy of the suspended sediment transport rate relies on that of the vertical distribution of the particle concentration,the particle velocity distribution and the reference concentration.In view of the limitations of the previons formulas for both the velocity and the concentration distributions,general expressions are introduced to the calculation of sus- pended sediment transport rate.Based on these analyses,a simple and practical calculation model is given in the present paper.

THE NONLINEAR CUSP-CATASTROPHE MODEL OF THE SEDIMENT TRANSPORT RATE

In the catastrophe theory of nonlinear science, the intensity of water flow Θ and the coefficient of non uniform sediment m are regarded as two bound variables, and the intensity of bed load transport Φ as the state variable in the motion of non uniform sediment in cusp catastrophe model. Based on the standard equation of the cusp catastrophe theory, the relation equation between the intensity of bed load transport Φ and the intensity of water flow Θ has been derived by used coordinate transform and topology transform. The equation of bed load transport rate was built on the cusp catastrophe theory of nonlinear science. The others are applied to verify this equation, that the results calculated by the cusp catastrophe equation agree well with the other equations. This indicates that the cusp catastrophe equation is reasonable, and the results fully reflect the characteristics of threshold motion and transport of non uniform sediment. The purpose of this paper is to explore the incipient motion and transport laws of non uniform sediment from the viewpoint of nonlinear science.

A transport-rate model of wind-blown sand

Sand transport by wind plays an important role in environmental problems.Formulating the sand-transport rate model has been of continuing significance,because the majority of the existing models relate sand-transport rate to the wind-shear velocity.However,the wind-shear velocity readapted to blown sand is difficult to determine from the measured wind profiles when sand movement occurs,especially at high wind velocity.Detailed wind tunnel tests were carried out to reformulate the sand-transport rate model,followed by attempts to relate sand-transport rate to parameters of wind velocity,threshold shear-velocity,and grain size.Finally,we validated the model based on the data from field observations.

Estimation of Sand Transportation Rate for Fixed and Semi-Fixed Dunes Using Meteorological Wind Data

Taibus County, Inner Mongolia, China, lies in a farming-pastoral ecotone, where severe wind erosion and various aeolian sand hazards are prevalent and fixed and semi-fixed sand dunes occur frequently. This study was conducted to investigate the relationships between sand transportation rate and wind speed for the fixed and semi-fixed sand dunes based on field measurements. The annual quantity of soil erosion by wind was estimated using meteorological wind data. The results indicated that the sand transportation rate in Taibus County in 2000 was 57.38 kg cm-1 year-1 for the semi-fixed dunes and 4.56 kg cm-1 year-1 for the fixed dunes. The total duration of erosive winds covered 12.5% of the time of the year, and spring posed the highest potential of sand transportation. Wind with low speed (≤ 17 m s-1) and high frequency plays a dominant role in sand transportation, while strong wind (≥ 17 m s-1) with low frequency significantly enhanced the sand transportation. Erosive wind speed, directions, and frequency were three crucial dynamic factors influencing sand hazards in the farming-pastoral ecotone. The dominant factors intensifying sand and dust storms in Taibus County might be related to the favorable wind condition in combination with the durable drought, which led to land desertification and vegetation degradation.

ON THE CONVERGENCE RATE OF A CLASS OF REACTION HYPERBOLIC SYSTEMS FOR AXONAL TRANSPORT

In this paper, we consider a class of reaction hyperbolic systems for axonal trans- port arising in neuroscience which can be regarded as hyperbolic systems with relaxation. We prove the BV entropy solutions of the hyperbolic systems converge toward to the unique entropy solution of the equilibrium equation at the optimal rate O（√δ） in L1 norm as the relaxation time δ tends to zero.

泸定6.8级地震公路抢通保通方案

2022年9月5日,四川泸定发生6.8级地震,公路沿线诱发了大量的地质灾害,造成多处公路损坏或断道,极大地影响了抗震救灾工作。快速摸清震区公路网的受损情况和抢通保通难度,对震后救援至关重要。为此,对震区公路受损情况进行调查,会同地方交通部门完成公路的抢通保通任务。调查发现了507处受损点,公路灾害以崩塌滑坡为主,占总灾害的90%以上。公路灾害具有数量多、规模小、连片分布的特点,公路震害与地震烈度正相关,与断层距离、河流距离负相关。在不利因子组合下,公路震害程度明显加剧,局部位置的公路受损率可达到92.5%。在抢通保通阶段,利用龙头石及大岗山电站的库区水运资源,快速建立5处码头,建立起通往震中的生命通道,让应急队伍快速进入灾区,让伤员第一时间运送出来;灾后交通网的重建充分利用水运资源,不追求道路等级与路线指标,公路重建以提高公路的抗灾能力及韧性为目标。

全社会物流成本的影响因素及下降空间测算

为了给有效降低全社会物流成本提供理论支持,支撑政府精准施策,首先,在深入剖析物流成本核算方法和衡量指标的基础上,系统分析了产业结构、产品价值、供需分布、流通速率、运输效能等因素的影响作用和影响趋势。然后,针对社会物流总费用与国内生产总值(GDP)的比率这一衡量指标,基于关联产业占比、工业增加值率、平均运距、存货周转天数、公路货物周转量占比5个关键参数建立了回归预测模型,对2024—2030年各影响因素贡献度开展预测分析。结果显示:2030年物流总费用与GDP的比率将降至12.36%;2024—2030年,关联产业占比贡献度将从20.9%波动降低至-0.48%;工业增加值率贡献度将从47.91%持续上升至78.39%;存货周转天数贡献度将从9.86%小幅上升至11.17%左右;平均运距贡献度将从33.49%持续下降至7.59%;公路货物周转量占比贡献度将从-12.15%稳定上升至3.33%。最后,基于测算成果,针对交通物流领域的降本工作提出推动交通物流融入现代化产业体系、推进新质生产力赋能、优化交通基础设施及重大生产力布局、引领构建现代流通体系、优化调整运输结构和促进多式联运发展等建议,为我国交通物流业的持续健康发展提供支撑。

不确定运价下长江集装箱多式联运路径优化

为充分贴合长江集装箱多式联运场景,在分析长江多式联运组织特点的基础上,考虑不确定运价及不同航段航道通航条件影响,以包含运输周转成本、碳排放成本和时间成本在内的总成本最小化为目标,构建不确定条件下长江集装箱多式联运路径优化模型,并设计蒙特卡洛仿真与改进的狼群算法实现模型求解,最后通过算例分析验证改进的狼群算法的有效性。算例分析结果表明,公路运输能有效控制运输的时间成本,铁路与水路运输在运输经济性与绿色性方面更具优势。在长江航道通航能力与最大中转次数限制下,运输任务将选择较高成本运输方案以满足航道与托运人要求。

高速公路货车空车差异化费率优化的双层规划方法

为解决高速公路货车由计重收费调整为按车型收费导致货车空车分流的问题,本文建立一种基于双层规划模型的货车空车分车型差异化费率优化方法。首先,以高速公路经营主体实现收费收益最大化为目标构建上层规划模型,考虑高速公路通行效率提升及增量货车空车增加的管养支出;其次,以道路使用者实现出行效用最大化为目标构建下层规划模型,构建基于逻辑回归模型和随机效用最大化理论的货车空车出行效用函数,分析货车空车特性变量对出行效用的影响;然后,采用多层神经网络模型及三次艾尔米特插值法,预测不同费率优惠下高速公路货车空车增量交通量,作为上下层联系变量;最后,以高速公路与平行老路构成的运输通道为例,采用内存受限的拟牛顿优化算法(L-BFGS-B)求解高速公路货车空车分车型最优费率。结果表明:高速公路费率折扣率对货车空车各车型出行选择影响最为显著;此外,车籍地对一类、四类货车空车出行选择影响较大,运输类型对二类、三类和六类货车空车出行选择影响较大;与现行费率方案相比,优化后的费率方案年度增加通行费收入3941万元,高速公路通行效率提升4.17%,货车空车平均每车出行效用增加3.51。

鱼类运输应激反应及其对存活率影响研究进展

【目的】探讨促进活鱼类运输产业中关注的提高存活率问题的解决方案。【方法】在理解鱼类应激生理反应的基础上,对适用于运输中的应激指标进行分类,分析其应用局限性和发展趋势;保活运输过程中的应激源可分为温度、拥挤、溶氧、氨氮、盐离子、振动和噪声等,综述不同应激源对应激指标和存活率的影响。【结果与结论】在保活运输过程中,应当系统、全面地分析多项应激指标,总结其趋势和相互关联,以正确判定应激反应的强度;同时考虑鱼种、季节、鱼体大小、运输时间等因素的影响,进而制定适宜的保活方式,提高鱼的存活率。

硫铅处理下伴矿景天对铅的耐受性与积累性研究

【目的】探明土壤在硫(S)铅(Pb)处理下,伴矿景天生长性状变化情况及对重金属Pb的耐受性与积累性,为Pb污染土壤植物修复提供依据。【方法】以伴矿景天为研究对象,采用随机区组试验,研究不同Pb浓度[Pb(CH_(3)COO)_(2)为0 mg、200 mg、400 mg、800 mg、1600 mg]和S浓度(Na_(2)SO_(4)为0 mg、50 mg、100 mg)对伴矿景天的株高、叶长、叶宽、根长、地上干重、根干重和Pb含量的影响及Pb耐受性和富集性的响应。【结果】在相同Pb浓度处理下,随S浓度增加,伴矿景天株高、叶长和根长整体呈增高趋势,在Pb 0 mg/kg、S 100 mg/kg处理下,根长最长,达6.50 cm。地上部干重以Pb 1600 mg/kg、S 50 mg/kg处理最小,根干重以Pb 1600 mg/kg、S 100 mg/kg处理最小。地上部Pb含量以Pb 1600 mg/kg、S 50 mg/kg处理最大,为1654.88 mg/kg;根系Pb含量以Pb 800 mg/kg、S 50 mg/kg处理最大,为1070.42 mg/kg。伴矿景天地上部干重与根干重呈极显著正相关关系,叶长与叶宽呈极显著正相关关系。伴矿景天的Pb富集系数在相同S浓度下,随Pb浓度增加而减小,转运系数、转运量系数总体随Pb浓度增加而减小;在相同Pb浓度处理下,富集系数随S浓度增高而增加,富集系数、转运系数和转运量系数、迁移率最高分别为11.04、2.88、30.64和74.24%。【结论】伴矿景天在铅胁迫下外施硫可缓解地上部、根生物量和株高的减少,并提高植株对铅的富集系数,外施硫是促进伴矿景天吸收重金属的有力措施。

双排高立式尼龙网阻沙障与草方格固沙障的优化配置及防沙效益

[目的]针对双排高立式尼龙网阻沙障与草方格固沙障联合应用,开展风洞试验研究,以优化联合沙障中尼龙网阻沙障孔隙度配置及探究各孔隙度下联合沙障的防沙效益。[方法]基于风洞模拟试验数据,开展不同孔隙度(40%,45%,55%)联合沙障,在不同风速下的风速流场、空气动力学粗糙度、摩阻风速、输沙率随高度和阻沙率方面的变化特征研究。[结果](1)相同风速下尼龙网阻沙障孔隙度40%时,联合沙障弱风区面积最大;(2)随着尼龙网阻沙障孔隙度的增大,空气动力学粗糙度和摩阻风速减小,相同风速和相同位置时,40%孔隙度下联合沙障空气动力学粗糙度和摩阻风速值最大;(3)风速增加地表输沙率也增加,联合沙障内部与背风侧输沙率随高度增加呈指数型递减,输沙主要集中在0~12 cm高度内;(4)风速大小与沙障阻沙率呈现负相关变化;阻沙率与孔隙度之间也呈负相关关系,孔隙度为40%的联合沙障具有较高阻沙率;双排高立式尼龙网阻沙措施与草方格固沙措施联合之间还存在阻沙率叠加。[结论]40%孔隙度的双排高立式尼龙网和草方格的阻固联合可以实现较优的配置与防沙效益。

推荐施肥量下控释肥替代普通尿素提高高粱产量和氮肥生产力

【目的】高粱生产中氮肥施用不合理,氮肥利用效率低,研究适宜重庆地区高粱种植的控释氮肥减施比例,在减少氮肥用量的同时,确保高粱稳产高产,提高肥料利用效率。【方法】田间定位试验于2021、2022年在重庆永川进行,供试高粱品种为晋渝糯3号和金糯粱1号。设置6个处理,分别为不施氮肥(CK);习惯尿素施肥量(U,N 180 kg/hm^(2));尿素推荐施用量(U1,减N 20%,N 144 kg/hm^(2));控释氮肥减施氮量20%(C1,N144 kg/hm^(2));控释氮肥减施氮量30%(C2,N 126 kg/hm^(2));控释氮肥减施氮量40%(C3,N 108 kg/hm^(2))。在高粱开花期和成熟期,调查干物质积累量和转运量,成熟期调查植株和籽粒氮素含量、生物量、产量及产量构成因素。【结果】开花期和成熟期高粱干物质积累量均以C1和U1处理最高,C1处理成熟期干物质积累量又显著高于U1。C1处理叶片花前干物质转运量显著高于U。花后干物质积累量C1处理显著高于其他处理,U1和C2处理显著高于U处理。C1处理晋渝糯3号和金糯粱1号花后干物质积累量对籽粒的贡献率较U分别显著提高了11.54%和12.41%。C1处理的高粱产量最高(晋渝糯3号6611 kg/hm^(2),金糯粱1号5690 kg/hm^(2)),较其他施氮处理显著提高了5.40%~18.66%;其次为C2和U1处理,二者的产量均显著高于U和C3处理。各施氮处理的氮肥生理利用率(NPE)差异不显著;减氮处理间氮肥农学利用率(NAE)无显著差异,氮肥偏生产力(NPFP)差异显著,其NAE和NPFP均显著高于习惯施氮处理U;控释肥各减氮处理的NPFP显著高于普通氮肥推荐量处理U1。C1处理较U处理大幅提高了NAE、NPFP和氮肥利用率(NUE),晋渝糯3号分别提高了58.54%、39.61%和59.28%,金糯粱1号分别提高了80.97%、48.30%和63.08%;与U1处理相比,晋渝糯3号的NPFP、NUE分别提高了5.38%和22.19%,金糯粱1号分别提高了5.82%和4.42%。【结论】推荐施氮量下,用控释肥替代普通氮肥增加了高粱开花期和成熟期干物质积累量,提高了叶片花前干物质转运量和花后干物质积累量及其对籽粒的贡献率,提升了高粱产量和氮肥利用效率,可作为西南地区高粱生产的推荐氮肥施用方式。

碳中和背景下的海洋微生物呼吸速率测定方法研究进展

全球气候变化与人类活动导致的CO_(2)排放息息相关。海洋是净吸收大气CO_(2)的重要环境,因此影响海洋碳存储能力的生物地球化学过程成为研究热点。海洋微生物的呼吸作用是调节碳“源-汇”转换的关键生物过程之一,呼吸速率是海区碳收支研究的重要参照指标。依据不同生物化学原理,海洋领域研发了多种微生物呼吸速率测定方法。依据海洋水文环境和微生物群落等不同应用场景的差异,使得采用一种或多种方法准确测定呼吸速率具有重要意义。文章着重陈述了各种呼吸速率测定的原理、优缺点和适用范围等,系统分析了常规测定方法和前沿测定技术,为碳中和背景下的海洋碳汇关键过程解析提供技术选择的理论支撑。

不同沿岸输沙率计算公式对比分析

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