Application of Direct Assimilation of ATOVS Microwave Radiances to Typhoon Track Prediction

In order to solve the difficult problem of typhoon track prediction due to the sparsity of conventional data over the tropical ocean, in this paper, the No. 0205 typhoon Rammasun of 4-6 July 2002 is studied and an experiment of the typhoon track prediction is made with the direct use of the Advanced TIROS-N Operational Vertical Sounder (ATOVS) microwave radiance data in three-dimensional variational data assimilation. The prediction result shows that the experiment with the ATOVS microwave radiance data can not only successfully predict the observed fact that typhoon Rammasun moves northward and turns right, but can also simulate the action of the fast movement of the typhoon, which cannot be simulated with only conventional radiosonde data. The skill of the typhoon track prediction with the ATOVS microwave radiance data is much better than that without the ATOVS data. The typhoon track prediction of the former scheme is consistent in time and in location with the observation. The direct assimilation of

Prediction of Hidden Granites in the Luziyuan Area of Yunnan Province and the Prospecting Direction

The Fe-Pb-Zn-Cu polymetallic deposits in the Luziyuan area, are of a sedimentary-reformed type related with magmatic hydrothermalism. Previous researches have suggested that the mineralization is closely related to the hidden granites, but little is known about these granites including their burial depth and scale, which has limited the establishment of prospecting models and the optimization of prospecting targets. Geophysical methods have a great exploration depth, and have played a unique role in the prediction of hidden granites. It is shown that granites have low density and high resistivity,

FORMING PRINCIPLE OF TWO SIDE-DIRECTION BURR AND IT'S PREDICTION IN METAL CUTTING

The burr is one of the common phenomena occurring i n metal cutting operations The mathematical mechanical model of two side dir ection burr formation and transformation is established with plane stress strain theory,based on the orthogonal cutting The main laws of formation and change of the burr are revealed,and it is confirmed by experiment result,which first realizes prediction of the forming and changing of the two side direction burr in metal cutting operation.

Minimum Distortion Direction Prediction-based Fast Half-pixel Motion Vector Search Algorithm

A minimum distortion direction prediction-based novel fast half-pixel motion vector search algorithm is proposed, which can reduce considerably the computation load of half-pixel search. Based on the single valley characteristic of half-pixel error matching function inside search grid, the minimum distortion direction is predicted with the help of comparative results of sum of absolute difference(SAD) values of four integer-pixel points around integer-pixel motion vector. The experimental results reveal that, to all kinds of video sequences, the proposed algorithm can obtain almost the same video quality as that of the half-pixel full search algorithm with a decrease of computation cost by more than 66%.

Sintering zone prediction in direct metal laser sintering by finite element method

A three-dimensional finite element thermal model in direct metal laser sintering(DMLS) including the effect of powder-to-solid transition were established to predict sintering zone, which benefited the determination of suitable process parameters in DMLS. The nonlinear transient model of the metals thermal conductivity for powder-to-solid transition was developed. The model uses solid thermal properties of material in liquid-phase zone, transitional ones in sintering or sintered zone and powder ones in unsintered zones of powder bed to predict, respectively. Sintering zone boundary was estimated by maximum temperature history profile. Experiments were carried out using multi-component Cu-based metal powder. Compared experimental and predicted results, the mean error of sintering depth and width are 7.8% and 14.4%, respectively, which confirms the accuracy of the FEM prediction.

Improving RNA secondary structure prediction using direct coupling analysis

Secondary structures of RNAs are the basis of understanding their tertiary structures and functions and so their predictions are widely needed due to increasing discovery of noncoding RNAs.In the last decades,a lot of methods have been proposed to predict RNA secondary structures but their accuracies encountered bottleneck.Here we present a method for RNA secondary structure prediction using direct coupling analysis and a remove-and-expand algorithm that shows better performance than four existing popular multiple-sequence methods.We further show that the results can also be used to improve the prediction accuracy of the single-sequence methods.

Trajectory Control: Directional MWD Inversely New Wellbore Positioning Accuracy Prediction Method

The deviation control of directional drilling is essentially the controlling of two angles of the wellbore actually drilled, namely, the inclination and azimuth. In directional drilling the bit trajectory never coincides exactly with the planned path, which is usually a plane curve with straight, building, holding, and dropping sections in succession. The drilling direction is of course dependant on the direction of the resultant forces acting on the bit and it is quite a tough job to hit the optimum target at the hole bottom as required. The traditional passive methods for correcting the drilling path have not met the demand to improve the techniques of deviation control. A method for combining wellbore surveys to obtain a composite, more accurate well position relies on accepting the position of the well from the most accurate survey instrument used in a given section of the wellbore. The error in each position measurement is the sum of many independent root sources of error effects. The relationship between surveys and other influential factors is considered, along with an analysis of different points of view. The collaborative work describes, establishes a common starting point of wellbore position uncertainty model, definition of what constitutes an error model, mathematics of position uncertainty calculation and an error model for basic directional service.

Application of ATOVS Microwave Radiance Assimilation to Rainfall Prediction in Summer 2004

Experiments are performed in this paper to understand the influence of satellite radiance data on the initial field of a numerical prediction system and rainfall prediction. First, Advanced Microwave Sounder Unit A （AMSU-A） and Unit B （AMSU-B） radiance data are directly used by three-dimensional variational data assimilation to improve the background field of the numerical model. Then, the detailed effect of the radiance data on the background field is analyzed. Secondly, the background field, which is formed by application of Advanced Television and Infrared Observation Satellite Operational Vertical Sounder （ATOVS） microwave radiance assimilation, is employed to simulate some heavy rainfall cases. The experiment results show that the assimilation of AMSU-A （B） microwave radiance data has a certain impact on the geopotential height, temperature, relative humidity and flow fields. And the impacts on the background field are mostly similar in the different months in summer. The heavy rainfall experiments reveal that the application of AMSU-A （B） microwave radiance data can improve the rainfall prediction significantly. In particular, the AMSU-A radiance data can significantly enhance the prediction of rainfall above 10 mm within 48 h, and the AMSU-B radiance data can improve the prediction of rainfall above 50 mm within 24 h. The present study confirms that the direct assimilation of satellite radiance data is an effective way to improve the prediction of heavy rainfall in the summer in China.

Model Predictive Control-Based Direct Torque Control for Matrix Converter-Fed Induction Motor with Reduced Torque Ripple

To reduce the torque ripple in motors resulting from the use of conventional direct torque control(DTC),a model predictive control(MPC)-based DTC strategy for a direct matrix converter-fed induction motor is proposed in this paper.Two new look-up tables are proposed,these are derived on the basis of the control of the electromagnetic torque and stator flux using all the feasible voltage vectors and their associated switching states.Finite control set model predictive control(FCS-MPC)has then been adopted to select the optimal switching state that minimizes the cost function related to the electromagnetic torque.Finally,the experimental results are shown to verify the reduced torque ripple performance of the proposed MPC-based DTC method.

An Empirical Method for Prediction of Hypersonic Rarefied Flow-Field Structure

Numerical simulations are presented about the effects of gas rarefaction on hypersonic flow field.Due to the extremely difficult experiment,limited wind-tunnel conditions and high cost,most problems in rarefied flow regime are investigated through numerical methods,in which the direct simulation Monte-Carlo(DSMC)method is widely adopted.And the unstructured DSMC method is employed here.Flows around a vertical plate at a given velocity 7 500 m/s are simulated.For gas rarefaction is judged by the free-stream Knudsen number(Kn),two vital factors are considered:molecular number density and the plate′s length.Cases in which Kn varies from 0.035 to13.36 are simulated.Flow characters in the whole rarefied regime are described,and flow-field structure affected by Knis analyzed.Then,the dimensionless position D*of a certain velocity in the stagnation line is chosen as the marker of flow field to measure its variation.Through flow-field tracing and least-square numerical method analyzing,it is proved that hypersonic rarefied flow field expands outward linearly with the increase of 1/2Kn.An empirical method is proposed,which can be used for the prediction of the hypersonic flow-field structure at a given inflow velocity,especially the shock wave position.

Methods and applications of RNA contact prediction

The RNA tertiary structure is essential to understanding the function and biological processes. Unfortunately, it is still challenging to determine the large RNA structure from direct experimentation or computational modeling. One promising approach is first to predict the tertiary contacts and then use the contacts as constraints to model the structure. The RNA structure modeling depends on the contact prediction accuracy. Although many contact prediction methods have been developed in the protein field, there are only several contact prediction methods in the RNA field at present. Here, we first review the theoretical basis and test the performances of recent RNA contact prediction methods for tertiary structure and complex modeling problems. Then, we summarize the advantages and limitations of these RNA contact prediction methods. We suggest some future directions for this rapidly expanding field in the last.

Experimental Verification of Fault Predictions in High Pressure Hydraulic Systems

In this paper a model of a high pressure hydraulic system was developed to simulate the effect of increased internal leakages inside the hydraulic cylinder and the 4/2 way directional control valve and to calculate the main parameters of the hydraulic system under various loads through the use of leakage-simulating throttle valves. After the completion of modeling, the throttle valves that simulate the internal leakages were calibrated and a number of test runs were performed for the cases of normal operation and the operation with increased internal leakages. The theoretical predictions were compared against the experimental results from an actual hydraulic test platform installed in the laboratory. In all cases, modeling and experimental data curves correlate very well in form, magnitude and response times for all the system’s main parameters. This proves that the present modeling can be used to accurately predict various faults in hydraulic systems, and can thus be used for proactive fault finding in many cases, especially when the defective component is not easily detected and obvious at first sight.

Model Predictive Direct Torque Control of Permanent Magnet Synchronous Motor (PMSM) with Online Parameter Estimation Based on Extended Kalman Filter

Aiming at the torque and flux ripples in the direct torque control and the time-varying parameters for permanent magnet synchronous motor (PMSM), a model predictive direct torque control with online parameter estimation based on the extended Kalman filter for PMSM is designed. By predicting the errors of torque and flux based on the model and the current states of the system, the optimal voltage vector is selected to minimize the error of torque and flux. The stator resistance and inductance are estimated online via EKF to reduce the effect of model error and the current estimation can reduce the error caused by measurement noise. The stability of the EKF is proved in theory. The simulation experiment results show the method can estimate the motor parameters, reduce the torque, and flux ripples and improve the performance of direct torque control for permanent magnet synchronous motor (PMSM).

Direct Model Predictive Control of Noninverting Buck-boost DC-DC Converter

In this paper, direct model predictive control(DMPC) of the noninverting buck-boost DC-DC converter with magnetic coupling between input and output is proposed. Unlike most of the other converters, the subject converter has the advantage of exhibiting minimum phase behavior in the boost mode. However, a major issue that arises in the classical control of the converter is the dead zone near the transition of the buck and boost mode. The reason for the dead zone is practically unrealizable duty cycles, which are close to zero or unity, of pulse width modulation(PWM) near the transition region. To overcome this issue, we propose to use DMPC. In DMPC, the switches are manipulated directly by the controller without the need of PWM.Thereby, avoiding the dead zone altogether. DMPC also offers several other advantages over classical techniques that include optimality and explicit current constraints. Simulations of the proposed DMPC technique on the converter show that the dead zone has been successfully avoided. Moreover, simulations show that the DMPC technique results in a significantly improved performance as compared to the classical control techniques in terms of response time, reference tracking, and overshoot.

The NE Directed Seismicity Belt in Tibet after the M_S8.1 Nepal Earthquake and Its Predictive Significance

After the 2015 M_S8. 1 Nepal earthquake,a strong and moderate seismicity belt has formed in Tibet gradually spreading along the northeast direction. In this paper,we attempt to summarize the features and investigate the primary mechanism of this behavior of seismic activity,using a 2-D finite element numerical model with tectonic dynamic settings and GPS horizontal displacements as the constraints. In addition,compared with the NEtrending seismicity belt triggered by the 1996 Xiatongmoin earthquake,we discuss the future earthquake hazard in and around Tibet. Our results show that: the NE-directed seismicity belt is the response of enhanced loading on the anisotropic Qinghai-Tibetan plateau from the Indian plate and earthquake thrusting. Also,this possibly implies that a forthcoming strong earthquake may fill in the gaps in the NE-directed seismicity belt or enhance the seismic hazard in the eastern( the north-south seismic zone) and western( Tianshan tectonic region) parts near the NE-directed belt.

胆总管结石患者ERCP术后早期胆道感染的动态预测工具开发及验证

目的开发胆总管结石患者经内镜逆行性胰胆管造影术(ERCP)后发生早期胆道感染(PEEBI)的预测工具,以期辅助临床进行ERCP术前决策和术后早期个性化干预。方法采用观察性双向队列研究方法,选取某医院接受ERCP的胆总管结石住院患者,分别采用有向无环图(DAGs)和最小绝对收缩与选择算子法(LASSO)进行基于logistic回归的PEEBI预测,比较预测模型,并进行内外部验证。结果2020年1月1日—2023年9月30日,共纳入接受ERCP的胆总管结石患者2121例,其中77例(3.6%)发生了PEEBI,且主要集中在术后前2天(66.2%)。影响PEEBI的主要因素为非医源的患者相关因素,即糖尿病(OR=2.43,95%CI:1.14~4.85)、胆管恶性肿瘤(OR=3.95,95%CI:1.74~8.31)和十二指肠乳头憩室(OR=4.39,95%CI:1.86~9.52)。DAGs模型较LASSO模型的综合判别能力高3.0%(P=0.007),且DAGs模型外部验证中的区分性能(D=0.133,P=0.894)和校准性能(χ^(2)=5.499,P=0.703)均表现良好。结论本研究构建的DAGs模型具有良好的预测性能,临床可在该工具的协助下采取针对性的围手术期早期预防措施,以减少PEEBI的发生。

基于累积置信规则库推理的台风灾害直接经济损失预测

针对台风灾害直接经济损失预测问题,现有的解决方法大多是基于时间序列或评估数据的预测模型,忽略了在建模过程中对历史数据的应用和模型的可解释性。鉴于此,该文将扩展置信规则库模型(EBRB)应用于台风灾害直接经济损失预测,并针对可能存在规则过量和组合爆炸问题,提出基于聚类方法与证据推理(ER)相结合的累积置信规则库(C-BRB)台风灾害经济损失预测模型。最后基于收集到的台风灾害数据进行直接经济损失预测,并通过与已有研究成果进行比较,验证基于C-BRB的台风灾害直接经济损失预测模型的有效性和可行性。

基于CNN-BiGRU-Attention的短期电力负荷预测

针对目前电力负荷数据随机性强,影响因素复杂,传统单一预测模型精度低的问题,结合卷积神经网络(Convolutional neural network,CNN)、双向门控循环单元(Bi-directional gated recurrent unit,BiGRU)以及注意力机制(Attention)在短期电力负荷预测上的不同优点,提出一种基于CNN-BiGRU-Attention的混合预测模型。该方法首先通过CNN对历史负荷和气象数据进行初步特征提取,然后利用BiGRU进一步挖掘特征数据间时序关联,再引入注意力机制,对BiGRU输出状态给与不同权重,强化关键特征,最后完成负荷预测。试验结果表明,该模型的平均绝对百分比误差(Mean absolute percentage error,MAPE)、均方根误差(Root mean square error,RMSE)、判定系数(R-square,R~2)分别为0.167%、0.057%、0.993,三项指标明显优于其他模型,具有更高的预测精度和稳定性,验证了模型在短期负荷预测中的优势。

计及弱磁效应的直驱式波浪发电系统变系数模型预测控制策略

为提高波浪发电系统(wave energy converter,WEC)能量捕获效率,并保证其在运行过程中满足系统的各种约束条件,该文以平均捕获功率最优为目标,提出计及弱磁效应的直驱式波浪发电系统变系数模型预测控制(model predictive control,MPC)策略。针对波浪激励力过大导致的变流器输出电压过调制问题,将弱磁控制引入优化算法,在满足发电机弱磁极限的前提下增大发电系统的运行范围,提高WEC的能量捕获效率。此外,基于仿真分析,发现了规则波下MPC目标函数的正则系数与平均捕获功率的对应关系。在此基础上,引入快速傅里叶变换(fast Fourier transformation,FFT)与叠加定理,构建了适用于不规则波输入的直驱式WEC变系数MPC控制策略。仿真结果表明,在不规则波浪下,所提方案能在满足系统约束条件的同时,有效提高能量捕获效率。

新世纪以来我国铀矿地质科技创新重要进展及展望

新世纪以来,我国铀矿地质勘查领域重大理论和技术创新成果,极大地改变了我国砂岩型、热液型铀矿的找矿思路、找矿方向,引领、支撑了系列找矿重大突破,重塑了铀矿勘查新格局。文章首先分析了我国20余年来铀矿地质科研布局的总体思路与演进方向;然后总结了铀矿重大基础地质与成矿理论研究进展,系统凝练了地质、物化探、遥感、钻探工艺、分析测试等领域的技术创新及核心勘查装备研制成果,梳理了铀资源预测评价技术研究进展及应用成效;最后,在重大基础前沿和成矿理论、先进铀矿勘查技术研发、非常规核能裂变资源勘查技术研究、数字铀矿勘查技术开发等方面提出了未来10~15年主要发展趋势和方向,指出在“双碳”目标和核能大发展对铀资源保障需求背景下,必须继续坚持并加强铀矿地质科技创新,高质量引领和推动“新区、新层位、新类型、新深度”找矿突破。