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.

Experimental study on bed-load sediment transport under irregular wave and current combined flow

Using an irregularly oscillating tray and flume, a series of experiments are completed to evaluate bed-load sediment transport rate under irregular wave -current coexistent field. Testing conditions include three interaction angles 0', 45', 90' and two kinds of median sizes (0.38 and 1.10 mm). The results of transport rate show that the net sediment transport rate can be expressed approximately as the function of the maximum bottom shear stress of waves, mean shear stress of current and the grain size.

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.

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.

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.

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.

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...

ANALYSIS OF SALTATION CHARACTERISTICS OF BED-LOAD TRANSPORT IN FLOWING WATER

The study of bed-load transport is of great significance both in theory and in practice.This paper discusses the saltation of bed-load solid grains in flowing water.Experiments and theoretic analysis have been made by means of high-speed photographing and advanced data processing technique with a combined method based on mechanical and statistical theories.It indicates that the saltation is the main form of the bed-load transport under ordinary flowing conditions.In the meantime,taking suecessive saltation as the mod- el of bed-load transport,systematic analysis has been made with regard to the kinematic properties and mechanism of saltation.The statistical analysis shows that the probability density functions of the relative height and length of saltation are in conformity with Γ-type distribution,while the probability density func- tions of the relative velocities of saltation are in conformity with the Gaussian distribution.

Theoretical research on the transport and ionization rate coefficients in glow discharge dusty plasma

The electron kinetic model for investigating the transport and ionization rate coefficients of argon glow discharge dusty plasma is developed from the Boltzmann equation.Both of the electron-neutral and electron-dust collisions are considered as collision terms in the kinetic equation.The kinetic equation is simplified by employing the local approximation and nonlocal approach under the same discharge conditions,and the corresponding simplified kinetic equations are known as local and nonlocal kinetic equations respectively.Then the electron energy distribution function(EEDF)is obtained by numerically solving the local and nonlocal kinetic equations and the dust charging equations simultaneously.Based on the obtained EEDFs,the effective electron temperature,electron mobility,electron diffusion coefficient and ionization rate coefficient are calculated for different discharge conditions.It is shown that the EEDFs calculated from the local kinetic model clearly differ from the nonlocal EEDFs and both the local and nonlocal EEDFs are also clearly different with Maxwellian distributions.The appearance of dust particles results in an obvious decrease of high energy electrons and increase of low energy electrons when axial electric field is low.With the increase of axial electric field,the influence of dust particles on the EEDFs becomes smaller.The electron mobility and diffusion coefficients calculated on the basis of local and nonlocal EEDFs do not differ greatly to the dust-free ones.While,when dust density nd=10^6 cm^?3,the electron mobility increases obviously compared with the dust-free results at low axial electric field and decreases with the increasing axial electric field until they are close to the dust-free ones.Meanwhile,electron diffusion coefficients for dusty case become smaller and decrease with the increasing axial electric field.The ionization rate coefficients decrease when dust particles are introduced and they approach the dust-free results gradually with the increasing axial electric field.

Study of fate and transport of chromium in unsaturated zonesaturated zone

Effluent irrigation can ease the water shortage area agricultural water shortage,and waste-water recycling,as well as bring a series of scientific and socio-economic issues,such as environmentalissues,food safety,sustainable development and so on,which has attracted the attention of people.So,paper to Kaifeng city several important dirt irrigation district for

Amodified numerical model for moisture-salt transport in unsaturated sandy soil under evaporation

Soil salinization,caused by salt migration and accumulation underneath the soil surface,will corrode structures.To analyze the moisture-salt migration and salt precipitation in soil under evaporation conditions,a mathematical model consisting of a series of theoretical equations is briefly presented.The filling effect of precipitated salts on tortuosity factor and evaporation rate are taken into account in relevant equations.Besides,a transition equation to link the solute transport equation before and after salt precipitation is proposed.Meanwhile,a new relative humidity equation deduced from Pitzer ions model is used to modify the vapor transport flux equation.The results show that the calculated values are in good agreement with the published experimental data,especially for the simulation of volume water content and evaporation rate of Toyoura sand,which confirm the reliability and applicability of the proposed model.

Science Accelerates the Modernization of Communications and Transport

Scientific progress has greatly improved the technical level of China’s highway and waterway transport in the past ten years. In order to modernize communications and transport and raise competitive power of enterprises as early as possible, the Ministry of Communications has decided to add more scientific investment, planning to double the annual expense on scientific investment during the Ninth Five-year Plan period compared to the Eighth Five-year

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.

黄土高原径流侵蚀功率输沙模型的改进

水土流失对流域生态危害严重,输沙量模拟和预测可以为流域水土流失防治提供依据,因此精确的输沙模型是流域水土流失治理的重要工具。为了精确模拟变化环境下黄土高原年输沙量,该研究基于黄土高原19个水文站的径流和输沙数据,通过随机森林变量重要性度量方法评估年径流侵蚀功率、淤地坝指数、淤地坝相对指数、归一化植被指数、不透水地面积等因子对流域年输沙量的影响,使用非线性最小二乘法估算年输沙模型参数,对比分析不同因子组合的年输沙模型精度,提出适用性较强的黄土高原年输沙模型,据此开展年输沙量变化贡献率分析。结果表明:1)以幂函数形式构建的仅含径流侵蚀功率单因子输沙模型精度与流域面积有显著的负相关关系,相关系数为-0.505(P<0.05),模型精度随着流域面积增大而下降,在面积大于7000 km^(2)的流域适用性较差;2)年径流侵蚀功率、淤地坝指数及不透水地面积因子组合建立的多因子年输沙模型在黄土高原适用性最佳,模型在率定期纳什效率系数平均值为0.84,均方根误差平均值为0.21亿t,在验证期纳什系数平均值为0.79,均方根误差平均值为0.27亿t。3)影响研究流域年输沙量变化的因素依次是:年径流侵蚀功率、不透水地面积和淤地坝指数。研究可以为黄土高原不同区域水土流失防治和生态治理工作提供理论支撑。

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。

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。

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。

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。

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。