Fetch effect on the developmental process of aeolian sand transport in a wind tunnel

As the sand mass flux increases from zero at the leading edge of a saltating surface to the equilibrium mass flux at the critical fetch length,the wind flow is modified and then the relative contribution of aerodynamic and bombardment entrainment is changed.In the end the velocity,trajectory and mass flux profile will vary simultaneously.But how the transportation of different sand size groups varies with fetch distance is still unclear.Wind tunnel experiments were conducted to investigate the fetch effect on mass flux and its distribution with height of the total sand and each size group in transportation.The mass flux was measured at six fetch length locations(0.5,1.2,1.9,2.6,3.4 and 4.1 m)and at three free-stream wind velocities(8.8,12.2 and 14.5 m/s).The results reveal that the total mass flux and the mass flux of each size group with height can be expressed by q=aexp(–bh),where q is the sand mass flux at height h,and a and b are regression coefficients.The coefficient b represents the relative decay rate.Both the relative decay rates of total mass flux and each size group are independent of fetch length after a quick decay over a short fetch.This is much shorter than that of mass flux.The equilibrium of the relative decay rate cannot be regarded as an equilibrium mass flux profile for aeolian sand transport.The mass fluxes of 176.0,209.3 and 148.0μm size groups increase more quickly than that of other size groups,which indicates strong size-selection of grains exists along the fetch length.The maximal size group in mass flux(176.0μm)is smaller than the maximal size group of the bed grains(209.3μm).The relative contribution of each size group to the total mass flux is not monotonically decreasing with grain size due to the lift-off of some small grains being reduced due to the protection by large grains.The results indicate that there are complex interactions among different size groups in the developmental process of aeolian sand transport and more attention should be focused on the fetch effect because it has different influences on the total mass flux,the mass flux profile and its relative decay rate.

The Fractional Power Law of Wind Wave Growth in Deep Water for Short Fetch

Combining the 3/2 power law proposed by Toba with the significant wave energy balance equation for wind waves, wave growth in deep water for short fetch is investigated. It is found that the variations of wave height and period with fetch have the form of power function with fractional exponents 3/8 and 1/4 respectively. Using these exponents in the power functions and through data fitting, the concise wind wave growth relations for short fetch are obtained.

Vibration Analysis of Fetching Carton Mechanism of Square Carpets Packaging

In this paper,according to the cantilever beam of fetching carton mechanism in square packaging machine, considering the impact of motion of air cylinder on it,its dynamics model and finite element model are built by using ANSYS. This paper not only acquires the deformation distribution,stress distribution and natural frequency of the cantilever beam in the static state; but also gets the dynamic response curve in the maximum deformation and the dynamic stress response curve in the near of the maximum stress during the motion of air cylinder. Result shows that no matter static state or dynamic state,deformation of the cantilever in the fetching carton mechanism is acceptable. The design of mechanism is reliable and its motion is also stable; no resonance can occur on the cantilever beam.

bring、take、get、fetch和carry的用法小议

bring、take、get、fetch和carry都有“携带”、“搬运”之意,但是,它们却表示动作的方向不同,同学们用起来极易混淆,先就它们各词的用法归纳如下: 1.take一般指携带或搬运的东西离说话的人而去。如:

Fetching the First Bucket of Water In a New Year in Kamba

Tibetans in Kamba (referring to Qamdo and Tibetan areas in Sichuan, Yunnan and Qinghai) have developed many habits and customs unique to themselves. Fetching the First Bucket of Water in a New Year is a case in point.

利用FETCH/WRITE方式实现PC机与S7PLC的直接通讯

介绍了西门子S7系统PLC和计算机通讯的几种方式,着重阐述了FETCH/WRITE通讯方式的组态配置、原理、报文格式等内容;同时描述了计算机通讯模块的TCP/IP Socket通讯的原理、程序流程图、多线程操作、以及如何利用VC++2005实现整个同模块。

Experimental Study of Wave Energy Spectrum in Shallow Water

Wave energy spectrum in shallow water can be studied in wind wave channel in combination with irregular wave- maker. Fetch length is successfully extended and by 'Relay' method the corresponding spectrum pattern and the wind velocity scale are obtained.

Axios和Fetch数据传输效率分析

本文主要是模拟实际使用场景,使用Axios和Fetch方法进行定量数据的传输,从Browse到Server,模拟实际数据传输过程,根据结果深度分析两种方式下网络数据的传输运行效率,为今后在系统运用中选择哪种方式进行数据传输提供一个参考。

Effect of air－sea temperature difference on the momentum exchange between air and sea for fetch－limited cases

The atmospheric boundaly layer over sea surface is simplified as mixed convection of turbulent boundary lay er flow over a horizontal plate, and the momentum exchange between wind and waves is also included in the model. Ef fects of wind speed, air-sea temperature difference and fetch on the momentum exchange between air and sea are re vealed. The turbulence model used in calculating boundary layer is an extended version of the Van Driest mixing lengthmodel, and a combined theoretical and semi-empirical approach is employed in estimating the effect of ocean waves. Forfetch-limited cases, i. e. wind blows off sea shore for a limited distance. fetch plays a fundamental role in the air-sea mo mentum exchange under different air-sea temperature conditions, which is not discussed in previous studies.

Similarities of Some Wind Input and Dissipation Source Terms

Wind input parameterizations proposed by Jeffreys, Sverdrup and Munk, and Plant are analyzed. It is found by analogy that the similarity of integrals of the three wind input parameterizations exists. Wave breaking dissipation parameterizations proposed by Tsikunov, Hasselmann, and Phillips are also analyzed. Likewise it is found by analogy that the similarity of integrals of the three dissipation parameterizations exists. The similarities of wind input and dissipation are applied to the investigation of the fetch-limited growth of wind waves, together with the 3/2 power law presented by Toba. Some semi-empirical formulas concerning the growth of wave height and period with fetch are presented. The results from the formulas are in good agreement with previous field observations.

Simultaneous Multithreading Fault Tolerance Processor

Transient fault detection mechanism is added to simultaneous multithreading architecture. By exploiting both ILP (Instruction Level Parallelism) and TLP (Thread Level Parallelism), Simultaneous Multithreading (SMT) Fault Tolerance Processor can be expected to achieve better tradeoff between performance and hardware cost than traditional Fault Tolerance Processors. Detailed simulations of 3 of SPEC95 benchmarks show that executing two redundant programs on the fault-tolerant microarchitecture takes only 40%–61%longer than running a single version of the program. The new instruction fetch algorithm enhances the performance by 0.4%～1%to most of the benchmarks we choose randomly.

Analysis of the Smart Player’s Impact on the Success of a Team Empowered with Machine LeAnalysis of the Smart Player’s Impact on the Success of a Team Empowered with Machine Learningarning

The innovation and development in data science have an impact in all trades of life.The commercialization of sport has encouraged players,coaches,and other concerns to use technology to be in better position than r their opponents.In the past,the focus was on improved training techniques for better physical performance.These days,sports analytics identify the patterns in the performance and highlight strengths and weaknesses of potential players.Sports analytics not only predict the performance of players in the near future but it also performs predictive modeling for a particular behavior of a player in the past.The impact of a smart player on the success of a team is always a big question mark before the start of a match.The fans always want to know performance analysis of these superstar players and they always are interested to get to know more about their favorite player and they always have high hopes from their favorite player.Machine learning(ML)based techniques help in predicting the performance of an individual player as well as for the whole team.The statistics are very vital and useful for management,fans,and expert analysis.In our proposed framework,the adaptive back propagation neural network(ABPNN)model is used for the prediction of a player’s performance.The data is collected from football websites,and the results are stored in the cloud for fast fetching of data.They can be retrieved anywhere in the world through cloud storage.The results are computed with 94%accuracy and the performance of the smart player is formulated for the success of a team.

A Whitecap Coverage Model Based on the Surface Slope For Criterion of Wave Breaking

Using the limit surface slope as a criterion of wave breaking, a simple model for estimating the spatial fraction of breaking surface of sea at an instant, which is regarded as the whitecap coverge in this paper, is analytically derived from the probability density of surface slope based on Gaussian statistics. The resulting fraction is found depending on the fourth moment of wave spectum, m(4), as well as the critical threshold of surface slope. By expressing the fourth moment in terms of the Neumann spectrum, a formula linking the fraction and wind speed for fully developed sea states is obtianed. Another formula relating the fraction to both wind speed and fetch (or duration) is achieved by expressing m, in terms of the Krylov spectrum and applying the empirical relationships used in the SMB ocean wave predicting technique. A comparison between these results and the field data of whitecap coverage collected by Monahan and O'Muircheartuigh shows an encouraging agreement.

英语新教材高一(上)练习册中fetch的误用

关于 bring、fetch、take、carry 这四个动词的区别,无论是老教材,还是新教材,讲述得都很详细,也很清楚。可是,新教材高一（上）的练习册第80—81页却出现了这样两道题:2.The boy CalTle to fetch the ball.They said that it was<sub><sub><sub><sub>their,theirs. （Exercise 3,p,80）

“go/Come to fetch”结构真的是误用吗?

《英语知识》1999年第6期在《英语新教材高一(上)练习册中 fetch的误用》(下简称《误用》)一文中指出:go/come to fetch 结构是误用。笔者认为这种说法已经过时,特写此文予以补正。在《误用》一文中作者引用国内外权威词典 Longman Dictionary ofContemporary English(1993年版)中对 fetch 的解释作为例证,说明 goto fetch 结构不对。这看上去很有说明力。

基于react-native的移动端周界入侵定位系统

随着社会经济地快速发展,所带来地安全隐患也在逐渐增多,设计一款移动端周界入侵定位系统具有重要意义.本文为了降低APP开发复杂度,提升开发效率的同时,兼顾原生移动应用的优势,将采用react-native技术来实现监测地图上显示出入侵点及相关入侵点的信息详情,并通过跳转到第三方平台来实时看到监控画面,除此之外,为了能够更好地分析出入侵的具体情况,将通过echats图表的形式进行展示.此款APP的服务器采用nodejs进行搭建,综合采用socket和fetch技术实现服务端和移动端的实时通信和控制.经APP测试结果表明,基于react-native技术所实现的周界入侵定位系统具有开发效率高、运行效率快以及安全稳定等特点.

The varying fetch effect of aeolian sand transport above a gobi surface and its implication for gobi development process

The Gobi deserts are important landscapes and major sandstorm source areas in arid northwestern China.Unsaturated sand flow and decreasing sand supply capacity is well known as the basic characteristics of gobi surface,but relatively little attention has been paid to the fetch effect of sand transport which is closely related to sand supply and indicative of wind erosion process in gobi.Using a field experiment,we investigated the spatial and temporal variations on a manually disturbed gobi surface downwind a sand-blocking belt and a sand-fixing belt by measuring the sand transport rate and the height profile of flux density at different fetch lengths during a sequence of wind erosion events.Results showed that the sand supply capacity determined the critical fetch length(Lc)for the sand transport rate so that the fetch effect varied with wind erosion proceeding due to depletion of erodible material.The height profile of flux density above the surface followed two distributions:an exponential decrease with increasing height,which commonly occurred above the newly treated gobi surface during the early wind erosion events;or a Lorentzian distribution with a peak flux at a certain height,which often happened in the later wind erosion events.The varying fetch effect,decreasing sand transport rates,and the nonerodible area expanded downwind are an epitome of the gobi development and expansion process from the perspective of wind erosion.