Flow and sound fields of scaled high-speed trains with different coach numbers running in long tunnel

Segregated incompressible large eddy simulation and acoustic perturbation equations were used to obtain the flow field and sound field of 1:25 scale trains with three,six and eight coaches in a long tunnel,and the aerodynamic results were verified by wind tunnel test with the same scale two-coach train model.Time-averaged drag coefficients of the head coach of three trains are similar,but at the tail coach of the multi-group trains it is much larger than that of the three-coach train.The eight-coach train presents the largest increment from the head coach to the tail coach in the standard deviation(STD)of aerodynamic force coefficients:0.0110 for drag coefficient(Cd),0.0198 for lift coefficient(Cl)and 0.0371 for side coef-ficient(Cs).Total sound pressure level at the bottom of multi-group trains presents a significant streamwise increase,which is different from the three-coach train.Tunnel walls affect the acoustic distribution at the bottom,only after the coach number reaches a certain value,and the streamwise increase in the sound pressure fluctuation of multi-group trains is strengthened by coach number.Fourier transform of the turbulent and sound pressures presents that coach number has little influence on the peak frequencies,but increases the sound pressure level values at the tail bogie cavities.Furthermore,different from the turbulent pressure,the first two sound pressure proper orthogonal decomposition(POD)modes in the bogie cavities contain 90%of the total energy,and the spatial distributions indicate that the acoustic distributions in the head and tail bogies are not related to coach number.

The Probability of Pairwise Shared Ancestry and the Expected Number of Pairs of k-th Cousins in a Population Sample

An analytical solution is derived for the probability that a random pair of individuals from a panmictic population of size N will share ancestors who lived G generations previously. The analysis is extended to obtain 1) the probability that a sample of size s will contain at least one pair of (G - 1)th cousins;and 2) the expected number of pairs of (G - 1)th cousins in that sample. Solutions are given for both monogamous and promiscuous (non-monogamous) cases. Simulation results for a population size of N = 20,000 closely approximate the analytical expectations. Simulation results also agree very well with previously derived expectations for the proportion of unrelated individuals in a sample. The analysis is broadly consistent with genetic estimates of relatedness among a sample of 406 Danish school children, but suggests that a different genetic study of a heterogenous sample of Europeans overestimates the frequency of cousin pairs by as much as one order of magnitude.

Impacts of the sampling design on the abundance index estimation of Portunus trituberculatus using bottom trawl

In the survey of fishery resources,the sampling design will directly impact the accuracy of the estimation of the abundance.Therefore,it is necessary to optimize the sampling design to increase the quality of fishery surveys.The distribution and abundance of fisheries resource estimated based on the bottom trawl survey data in the Changjiang River(Yangtze River)Estuary-Hangzhou Bay and its adjacent waters in 2007 were used to simulate the"true"situation.Then the abundance index of Portunus trituberculatus were calculated and compared with its true index to evaluate the impacts of different sampling designs on the abundance estimation.Four sampling methods(including fixed-station sampling,simple random sampling,stratified fixed-station sampling,and stratified random sampling)were simulated.Three numbers of stations(9,16 and 24)were assumed for the scenarios of fixed-station sampling and simple random sampling without stratification.While 16 stations were assumed for the scenarios with stratification.Three reaction distances(1.5 m,3 m and 5 m)of P.trituberculatus to the bottom line of trawl were also assumed to adapt to the movement ability of the P.trituberculatus for different ages,seasons and substrate conditions.Generally speaking,compared with unstratified sampling design,the stratified sampling design resulted in more accurate abundance estimation of P.trituberculatus,and simple random sampling design is better than fixed-station sampling design.The accuracy of the simulated results was improved with the increase of the station number.The maximum relative estimation error(REE)was 163.43%and the minimum was 49.40%for the fixed-station sampling scenario with 9 stations,while 38.62%and 4.15%for 24 stations.With the increase of reaction distance,the relative absolute bias(RAB)and REE gradually decreased.Resource-intensive area and the seasons with high density variances have significant impacts on simulation results.Thus,it will be helpful if there are prior information or pre-survey results about density distribution.The current study can provide reference for the future sampling design of bottom trawl of P.trituberculatus and other species.

Seismological study on the crustal structure of Tengchong volcanic-geothermal area

Based upon the deep seismic sounding profile conducted in the Tengchong volcanic-geothermal area, a two-dimensional crustal P velocity structure is obtained by use of the finite-difference inversion and the forward travel-time fitting method. The crustal model shows that there is a low velocity zone in upper crust in the Tengchong area, which may be related to the volcanic-geothermal activities, and two intracrustal faults (the LonglingRuili fault and Tengchong fault) exist on the profile, where the Tengchong fault may extend to the Moho discontinuity. Meanwhile, based on teleseismic data recorded by a temporary seismic network, we obtained the S-wave velocity structures beneath the RehaiRetian region in the Tengchong area, which show the low S-wave velocity anomaly in upper crust. The authors discuss the causes of Tengchong volcanic eruption based on the deep crustal structure. The crustal structure in the Tengchong volcanic-geothermal area is characterized by low P-wave and S-wave velocity, low resistivity, high heat-flow value and low Q value. The P-wave velocity in the upper mantle is also low. For this information, it can be induced that the magma in the crust is derived from the upper mantle, and the low velocity anomaly in upper crust in the Tengchong area may be related to the differentiation of magma. The Tengchong volcanoes are close to an active plate boundary and belong to plate boundary volcanoes.

On Spatial Distribution Pattern of Broccoli Clubroot Disease and and the Sampling Technique

[Objective] To further improve the prediction and forecast and continuous control ability of broccoli clubroot disease. [Methods] The spatial distribution pattern of diseased or infected plants was analyzed using the least square method, fre- quency distribution, aggregation index, m＊-m regression analysis and Taylor＇s pow- er law model. [Result] The field distribution of broccoli plants with clubroot disease tended to be aggregated distribution, m＇-m regression analysis showed that the el- ementary composition of the spatial distribution of diseased or infected plants was individual colony, the individuals attracted each other; the disease had obvious dis- ease focus in the field, and the individual colony showed uniform distribution pattern in the field. Taylor＇s power law showed that the spatial pattern of individual dis- eased or infected plant with clubroot disease tended to be uniform distribution with the increase of the density. On the basis of this, Iwao optimal theoretical sampling model and sequential sampling model were established, namely N =273.954 1/m- 59.698 5, To （N）=0.368 4N±1.926 8√N, respectively, it meant that when surveying N plants, if the accumulative incidence rate exceeded upper bound, the field can be set as control object; if the accumulative incidence rate didn＇t reach lower bound, it can be set as uncontrol field; if the accumulative incidence rate was between upper bound and lower bound, it should be surveyed continuously until the maximum sample size （mo=0.368 4） appeared, that was, the disease incidence was 15%, so the sampling number should be 684 plants. [Conclusion] The research results had very important instructive meaning for disease control.

Impacts of sampling design on the abundance estimation of Portunus trituberculatus using crab pots

Fishery-independent surveys can provide high-quality data and support fishery assessment and management.Optimization of sampling design is crucial to increase the quality of fishery surveys.Crab pots are important fishing gears used to catch crabs.We analyzed the impacts of sampling design of crab pots on the abundance of Portunus trituberculatus in the Changjiang(Yangtze)River estuary to the Hangzhou Bay and its adjacent waters in East China Sea.The crab pots were cylindrical,240 mm in height and 600 mm in diameter of the iron ring.Our sampling designs(including fixed-station sampling,simple random sampling,stratified fixed-station sampling,and stratified random sampling),three number of stations(9,16,and 24),and three numbers of crab pots(500,1000,and 3000)were simulated and compared with the“true”abundance that obtained from bottom trawl surveys in the study area in 2007.The scenarios with 16 stations were set in stratification as a control group for comparison with unstratified designs.Results show that simple random sampling can obtain more stable results than fixed-station sampling in the abundance estimation of P.trituberculatus.In addition,stratified sampling resulted in more accurate abundance than unstratified sampling.The accuracy of the simulated results improved with the increase of the number of stations.No remarkable differences in the results were found among the scenarios of different number of crab pots at each station.However,resource-intensive areas exerted great impacts on simulation results.Thus,prior information or pre-survey results about resource abundance and density distribution are necessary.This study may serve as a reference for future sampling designs of crab pots of P.trituberculatus and other species.

The Precision Estimate of Multi-Fractal Methods of Time Sequence of Earthquakes

At present,there are many methods of calculating seismic time-fractal.However,there isn’t aquantitative result about the precision of every method.So,in this Paper,we use the digitalimitation of theoretic model to solve precision estimate problems of calculating the precision ofone dimension distribution of theoretic models with Cantor multi-fractal set,we obtained someresults as follows:(1)There exists many problems such as rules,numbers of samples,basicpoint selection,the diffence resulted from different methods and so on.(2)The fixed-massmethod(MAS)and the minimal spanning tree method(MST)can give good structure charac-teristics with different q value,while the counting-boxes method can’t.And the error of thefixed-radius method(RAD)in the range of-q is too big.(3)There are scale problems of rulesfor multi-fractal,it is objective reflection for non-rule area.(4)MST has the boundary prob-lem,while MAS and RAD don’t.(5)With increasing sample number,the precision of allfractal-dimension values

A thin film ^(10)B sample for measuring the atom number

In order to measure differential cross sections of the 10B(n,α)7Li reaction induced by MeV neutrons using the forward-backward coincidence method, a thin film 10B sample was designed and the 10B atom number was determined with a reference 10B film sample. Alpha counts of the 10B(nth,α)7Li reaction from the 10B thin film and the reference sample were measured using a gridded ionization chamber and thermal neutrons, which were moderated and thermalized by paraffin from fast neutrons produced in D(d,n)3He reaction on a 4.5 MV Van de Graaff. The neutron flux was normalized by measuring the fission yield of a small 238U fission chamber.

Theoretical and Experimental Research on the Sound Field in A Finite Duct

Based upon the theoretical analysis of the sound field in a finite duct and the spatialsampling principle,this paper applies the adaptive filtering technique to the measurement of thesound field in the duct with the distribution patterns of standing waves in the direction of thewaveguide and high—order wavefront on the cross section of the duct measured and the acousticmode theory proved by experimental results.

Properties of sound attenuation around a two-dimensional underwater vehicle with a large cavitation number

Due to the high speed of underwater vehicles, cavitation is generated inevitably along with the sound attenuation when the sound signal traverses through the cavity region around the underwater vehicle. The linear wave propagation is studied to obtain the influence of bubbly liquid on the acoustic wave propagation in the cavity region. The sound attenuation coefficient and the sound speed formula of the bubbly liquid are presented. Based on the sound attenuation coefficients with various vapor volume fractions, the attenuation of sound intensity is calculated under large cavitation number conditions. The result shows that the sound intensity attenuation is fairly small in a certain condition. Consequently, the intensity attenuation can be neglected in engineering.

Optimal Recovery of Functions on the Sphere on a Sobolev Spaces with a Gaussian Measure in the Average Case Setting

In this paper, we study optimal recovery （reconstruction） of functions on the sphere in the average case setting. We obtain the asymptotic orders of average sampling numbers of a Sobolev space on the sphere with a Gaussian measure in the Lq （S^d-1） metric for 1 ≤ q ≤ ∞, and show that some worst-case asymptotically optimal algorithms are also asymptotically optimal in the average case setting in the Lq （S^d-1） metric for 1 ≤ q ≤ ∞.

A Modified Sampling Synthesis for a Realistic Simulation of Wind Instruments—The Design and Implementation

Sampling synthesis is one of the most practical and widely used approaches among the various sound synthesis methods used for creating a realistic simulation of acoustic instruments. Using numerous high quality sound samples it is possible to reproduce a sound of almost any musical instrument, including subtle variations caused by the registers of an instrument or through the use of different articulation techniques and dynamic levels. However, this method has some disadvantages. Firstly, with high fidelity reproduction systems, the repeatability of samples becomes quickly apparent for more experienced listeners. This is sometimes manually corrected by switching between several different samples of the same note. Secondly, it is standard approach to record and reproduce each note separately. It prevents samplers from reproducing natural note transitions, making fluent, connected articulations, such as legato, unnatural. Finally, samplers provide a very limited number of sound parameters to control. Therefore, it is difficult to introduce a set of purposeful fluctuations of selected parameters uniquely attributable to human performances. A synthesis system which addresses the aforementioned problems has been developed at the Academy of Music in Krakow (Poland) for a group of wind instruments as part of a symphony orchestra. The system is based on a large collection of non-standard samples. Samples contain short sequences of notes instead of single notes. In order to use them, a number of techniques have been implemented to allow the seamless connecting of recorded sequences and the control of note durations as well as tempo and dynamics envelopes. Decision-making algorithms and signal processing are applied to create melodic figures by choosing, modifying, and connecting fragments of samples, while keeping natural note transitions intact. The problem of mimicking human performances is addressed by implementing a set of performance rules. It allows to introduce context-dependent variations into the regular playback of the material contained in the musical notation to properly shape the expression of musical structures, similarly to that of live performances by musicians. This article presents the main modules of the modified sampling synthesis system designed by us as well as its general structure and principle of operation. The modules are responsible for performing musical score analyses, an automatic selection and connection of sound samples, and the application of performance rules.

The Impact of Selected Parameters of a Modified Sampling Synthesis on the Result of Its Auditory Assessment

One of the main shortcomings of standard sampling synthesis is the very limited number of sound parameters that are user-controllable. In the most general case, the user can choose a particular pitch, duration, and amplitude. If the sampler allows control over articulation, it simply switches from one sound sample to another. This makes fine-tuning of musical performances demanding and time-consuming if not an impossibility altogether. A synthesis system has been developed at the Academy of Music in Krakow, Poland. It uses a large collection of samples that contain short sequences of notes. The system implements a number of techniques to seamlessly connect recorded sequences, to control note durations as well as the tempo and the dynamics envelopes. Samples are automatically chosen, modified, and connected to keep the recorded, natural note transitions intact. The system uses performance rules to introduce variations into the regular playback akin to live performances by musicians. A user can either control the parameters manually or choose a desired expression and leave the particular decisions to the system. However, it is necessary to examine which parameters have the greatest impact on the listeners’ impression and determine useful values. 15 expert listeners compared and evaluated variants of musical performances produced by the synthesis system with different sets of parameters. The paper discusses a selection of the examined parameters, the test methods employed and the results obtained.

Listening Problems ChineseE Students Face and SuffestionsS for Solving ThemM

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SOUND RADIATION FROM PLATES ON ELASTIC FOUNDATION UNDER ACTION OF MOVING LINE FORCES

An analysis is made of the problem of sound radiation from infinite one-dimensional plateson elastic foundation, when the plates are subjected to the action of harmonic line forces movingat subsonic speeds (M 【 1). The expressions of nondimensional sound power are formulated andthe asymptotic forms of sound power in the low frequency regions are derived. The radiatedsound power is shown as a function of the stiffness of elastic foundation, in terms of stiffness fac-torψ, the moving speed of line force, in terms of Math number M, and the frequency, in termsof wavenumber ratio γ . The effects of the parameter ψ in conjunction with the parameters Mand γ on the radiated sound power level and the phenomenon of coincidence radiation are alsoinvestigated in detail.

Fault Diagnosis of 5G Networks Based on Digital Twin Model

Fault diagnosis of 5G networks faces the challenges of heavy reliance on human experience and insufficient fault samples and relevant monitoring data.The digital twin technology can realize the interaction between virtual space and physical space through the fusion of model and data,providing a new paradigm for fault diagnosis.In this paper,we first propose a network digital twin model and apply it to 5G network diagnosis.We then use an improved Average Wasserstein GAN with Gradient Penalty(AWGAN-GP)method to discover and predict failures in the twin network.Finally,we use XGBoost algorithm to locate the faults in physical network in real time.Extensive simulation results show that the proposed approach can significantly increase fault prediction and diagnosis accuracy in the case of a small number of labeled failure samples in 5G networks.

样品尺寸对脉冲穿透法声速测量误差的影响

岩心的声速测量能够提供关键的储层地质信息,对储层评价和地质模型构建具有实际应用价值。脉冲穿透法是一种常用的声速测量方法,但它要求样品尺寸远大于波长(约10倍)。当特殊场景如需在测井信号主频8~20 kHz下测量样品声速时,被测样品长达数米,不仅制备困难,还存在声波信号衰减大的问题。关于试样尺寸能否缩小或能缩小到什么程度的定量研究很少见到公开报道。该文将数值模拟和实验测量相结合,系统定量地研究了圆柱状样品长度及直径与波长之间的比值对脉冲穿透法声速测量精度的影响。研究表明:为确保脉冲穿透法声速测量的准确性,建议样品沿传播方向上的长度不低于4倍声波波长,横向尺寸不低于2倍波长。研究结果突破了传统脉冲穿透法要求样品尺寸远大于波长的限制,为优化声速测量方法和提高测量精度提供了理论支持。

基于概率建模的分层产液劈分方法

传统产液劈分方法无法考虑层间干扰及注水井和邻井的影响,难以准确判断井下实际状况。同时,海上油田产液剖面测试成本高,常规的机器学习方法面临样本数量少的问题。基于此,提出一种基于贝叶斯神经网络和极限梯度提升算法的多层合采产液劈分混合学习模型。概率方法可以识别预测中的不确定性,通过将神经网络与概率建模结合,进行分层产液数据分布特征挖掘,结合主控因素分析,混合学习算法可以实现小层产液量的准确预测,可以依据较少的数据获得更为稳健的模型。为验证所提方法的有效性,将其应用于实际油田某区块进行产液剖面预测。结果表明:相比KH劈分方法在计算中劈分系数固定,不会随着生产过程波动,所提出的方法可从历史数据中学习,预测精度达到87.9%,预测结果更加逼近真实单层产液量。

山东烟田烟蚜种群动态与空间分布

烟蚜在山东烟田发生普遍,危害严重。研究山东烟田烟蚜种群动态与空间分布对于提高山东烟田烟蚜预测测报准确率以及有效防控该害虫具有重要意义。试验开展了烟蚜的田间种群消长动态调查,并应用5个聚集度指标(丛生指数I,聚块指标m^(*)/m,久野指标Ca,扩散系数C,负二项分布K值)和2种回归方法(Iwao回归分析法与Toylar幂法则)研究其空间分布特征。结果表明,2020—2021年烟田烟蚜的种群动态均为双峰型曲线:第1个高峰出现在5月下旬至6月上旬,第2个高峰出现在7月上中旬。在垂直分布上,烟草植株上部叶片的烟蚜数量占比(49.07%~70.29%)显著高于中部叶片(27.64%~33.71%)和下部叶片(1.64%~19.85%)。数据分析结果显示,I(1.733 2~42.703 0)>0,m^(*)/m(2.368 3~10.414 2)>1,Ca(1.368 3~9.414 2)>0,C(2.733 2~43.703 0)>1,0<K(0.106 2~0.730 8)<8;在Iwao回归方程中,β(4.578 65)>1,α(0.190 57)>0,在Toylar幂法则回归方程中,lga(0.691 65)>0,b(1.817 05)>1,说明调查期间烟蚜种群呈聚集分布,分布的基本成分是个体群。利用空间分布参数确定了烟蚜的理论抽样数,并提出合理的田间抽样技术,即在烟田内采用“Z”字形取样法,每点选取烟草5~10株、每株烟草调查上中部叶片2~4片。

输入基岩地震波数量对土层地震反应影响研究

以成都某地铁站点工程场地为例,采用一维等效线性化方法,将人工合成的不同超越概率下各20条相互独立的地震波作为基岩输入地震动时程,进行了土层地震反应计算,并对计算结果进行了分析研究,得出结论:1)通过对土层地震反应结果的计算分析,给出了PGA、T_(g)和S_(a)(T)值计算结果参数的变异系数和随概率档的变化规律,并验证了上述各参数均值都服从正态分布。2)对于Ⅱ级和地震小区划工作,目前业内较为普遍地采用3条基岩地震波作为土层地震反应计算基岩输入地震动时程的做法和现行地震安评国标的规定,至少采用3条基岩地震波作为输入地震动时程下限数量的规定已不能满足要求,需要增加,建议增加到最少采用15条基岩输入地震波,以保证地震安评工作所提供的场地设计地震动参数更加可靠。