Error field penetration in J-TEXT tokamak based on two-fluid drift-MHD model

An externally generated resonant magnetic perturbation can induce complex non-ideal MHD responses in their resonant surfaces.We have studied the plasma responses using Fitzpatrick's improved two-fluid model and program LAYER.We calculated the error field penetration threshold for J-TEXT.In addition,we find that the island width increases slightly as the error field amplitude increases when the error field amplitude is below the critical penetration value.However,the island width suddenly jumps to a large value because the shielding effect of the plasma against the error field disappears after the penetration.By scanning the natural mode frequency,we find that the shielding effect of the plasma decreases as the natural mode frequency decreases.Finally,we obtain the m/n=2/1 penetration threshold scaling on density and temperature.

On the Transition Regime of Nonlinear Error Field Penetration in Toroidal Plasmas

The error field penetration is numerically studied in the frame of the visco-resistive magnetohydrodynamics（MHD） model.A transition scaling is obtained to link the Rutherford and Waelbroeck regimes in the nonlinear phase of error field penetration process.Furthermore,a transition density scaling of[br/BT]critne1/2 obtained in accord with recent experimental observations in the J-TEXT tokamak.

An Analysis of Ripple and Error Fields Induced by a Blanket in the CFETR

The Chinese Fusion Engineering Tokamak Reactor （CFETR） is an important intermediate device between ITER and DEMO. The Water Cooled Ceramic Breeder （WCCB） blanket whose structural material is mainly made of Reduced Activation Ferritic/Martensitic （RAFM） steel, is one of the candidate conceptual blanket design. An analysis of ripple and error field induced by RAFM steel in WCCB is evaluated with the method of static magnetic analysis in the ANSYS code. Significant additional magnetic field is produced by blanket and it leads to an increased ripple field. Maximum ripple along the separatrix line reaches 0.53% which is higher than 0.5% of the acceptable design value. Simultaneously, one blanket module is taken out for heating purpose and the resulting error field is calculated to be seriously against the requirement.

A Conceptual Design Study for the Error Field Correction Coil Power Supply in JT-60SA

This paper describes a conceptual design study for the circuit configuration of the Error Field Correction Coil （EFCC） power supply （PS） to maximize the expected performance with reasonable cost in JT-60SA. The EFCC consists of eighteen sector coils installed inside the vacuum vessel, six in the toroidal direction and three in the poloidal direction, each one rated for 30 kA-turn. As a result, star point connection is proposed for each group of six EFCC coils installed cyclically in the toroidal direction for decoupling with poloidal field coils. In addition~ a six phase inverter which is capable of controlling each phase current was chosen as PS topology to ensure higher flexibility of operation with reasonable cost.

Numerical simulation and experiment of error field measurement using luminous trace of electron beam in SST-1

In contrast to the earlier experiments conducted in other machines, here, in SST-1 the error field measurement experiment is performed with a filled gas pressure ~8×10^-4 mbar which helped to create a luminescent toroidal beam of electron path originated due to impact excitation and guided by the toroidal magnetic field. Beam path deviations are observed and recorded from radial and top ports using visible range cameras. Such creation and detection of the electron beam path differs from the earlier works where the gun emitted electron beam deviation in ultrahigh vacuum was detected on a collector-grid/fluorescent screen. In the present experiment, large beam deviations were observed. Later investigation of the experimental set-up reveals existence of a possible source of radial electric field in between the source and the vacuum vessel which are separately grounded. Thus, to understand the observed phenomena, experiments are numerically modeled with deviated TF coil set, PF coil set and the electron source location. A particle tracing code is used to follow the electron path in the magnetic field generated by the coil set of interest. Simulation results suggest that the large deviation corresponds to the E×B drifts and not due to the large field errors. Toroidally averaged field errors of the SST-1 TF coils at toroidal field of B0?=?15 kG are negligibly small ~B0?×?10^-6 or less, which should not adversely affect the plasma performance.

Accurate and rapid error estimation on global gravitational field from current GRACE and future GRACE Follow-On missions

Firstly, the new combined error model of cumulative geoid height influenced by four error sources, including the inter-satellite range-rate of an interferometric laser （K-band） ranging system, the orbital position and velocity of a global positioning system （GPS） receiver and non-conservative force of an accelerometer, is established from the perspectives of the power spectrum principle in physics using the semi-analytical approach. Secondly, the accuracy of the global gravitational field is accurately and rapidly estimated based on the combined error model; the cumulative geoid height error is 1.985× 10^-1 m at degree 120 based on GRACE Level 1B measured observation errors of the year 2007 published by the US Jet Propulsion Laboratory （JPL）, and the cumulative geoid height error is 5.825 × 10^-2 m at degree 360 using GRACE Follow-On orbital altitude 250 km and inter-satellite range 50 km. The matching relationship of accuracy indexes from GRACE Follow-On key payloads is brought forward, and the dependability of the combined error model is validated. Finally, the feasibility of high-accuracy and high-resolution global gravitational field estimation from GRACE Follow-On is demonstrated based on different satellite orbital altitudes.

Far-Field Pattern Reconstruction from Positioning Errors Affected Near-Field Data Acquired via Helicoidal Scanning

In this paper, an effective technique to compensate the positioning errors in a near-field—far-field (NF-FF) transformation with helicoidal scanning for elongated antennas is presented and validated both numerically and experimentally. It relies on a nonredundant sampling representation of the voltage measured by the probe, obtained by considering the antenna as enclosed in a cylinder ended in two half-spheres. An iterative scheme is used to reconstruct the helicoidal NF data at the points fixed by the representation from the acquired irregularly spaced ones. Once the helicoidal data have been retrieved, those needed by a classical NF-FF transformation with cylindrical scanning are efficiently evaluated by using an optimal sampling interpolation algorithm. Some numerical tests, assessing the accuracy of the approach and its stability with respect to random errors affecting the data, are reported. Experimental tests performed at the Antenna Characterization Lab of the University of Salerno further confirm the validity of the proposed technique.

焦平面图像制导导弹对地面目标截获概率计算

针对图像制导导弹的目标探测和精确制导的需求,研究基于矩形焦平面探测器的图像制导导弹转入末制导时对地面目标的截获概率。根据导弹的高度姿态和探测器参数推导对地面探测的不规则四边形视场(Irregular Quadrilateral Detection Field,IQDF)的解析解和简化的矩形探测视场(Simplified Rectangular Detection Field,SRDF)模型,确定影响目标截获概率的主要误差源。利用条件概率思想,将目标截获概率分解为导弹状态概率和当前状态下目标落入地面视场概率,并利用有限元分割算法推导出目标落入地面视场概率,从而建立多源误差下的目标截获概率模型。通过仿真分析在IQDF和SRDF下主要误差源对目标落入地面视场概率的影响,并在多源误差下将推导的目标截获概率与蒙特卡洛方法仿真结果进行对比,验证了目标截获概率计算方法的有效性。

Calculation of angular glint in near field utilizing graphical electromagnetic computing

The angular glint in the near field plays an important role on radar tracking errors. To predict it more efficiently for electrically large targets, a new method based on graphical electromagnetic computing （GRECO） is proposed. With the benefit of the graphic card, the GRECO prediction method is faster and more accurate than other methods. The proposed method at the first time considers the special case that the targets cannot be completely covered by radar beams, which makes the prediction of radar tracking errors more self-contained in practical circumstances. On the other hand, the process of the scattering center extraction is omitted, resulting in possible angular glint prediction in real time. Comparisons between the simulation results and the theoretical ones validate its correctness and value to academic research and engineering applications.

Multi-camera calibration method based on minimizing the difference of reprojection error vectors

In order to achieve a high precision in three-dimensional（3D） multi-camera measurement system, an efficient multi-cameracalibration method is proposed. A stitching method of large scalecalibration targets is deduced, and a fundamental of multi-cameracalibration based on the large scale calibration target is provided.To avoid the shortcomings of the method, the vector differencesof reprojection error with the presence of the constraint conditionof the constant rigid body transformation is modelled, and mini-mized by the Levenberg-Marquardt （LM） method. Results of thesimulation and observation data calibration experiment show thatthe accuracy of the system calibrated by the proposed methodreaches 2 mm when measuring distance section of 20 000 mmand scale section of 7 000 mm × 7 000 mm. Consequently, theproposed method of multi-camera calibration performs better thanthe fundamental in stability. This technique offers a more uniformerror distribution for measuring large scale space.

DOA estimation for mixed signals with gain-phase error array

Most of the direction of arrival(DOA) estimation methods often need the exact array manifold, but in actual applications,the gain and phase of the channels are usually inconsistent, which will cause the estimation invalid. A novel direction finding approach for mixed far-field and near-field signals with gain-phase error array is provided. Based on simplifying the space spectrum function by matrix transformation, DOA of far-field signals is obtained. Consequently, errors of the array are acquired according to the orthogonality of far-field signal subspace and noise subspace.Finally, DOA of near-field signals can be estimated. The method merely needs one-dimensional spectrum searching, so as to improve the computational efficiency on the premise of ensuring a certain accuracy, simulation results manifest the effectiveness of the method.

A Model Study of Three-Dimensional Wind Field Analysis from Dual-Doppler Radar Data

A three-dimensional wind field analysis sollware based on the Beigng-Gucheng dual-Doppler weather radar system has been built, and evaluated by using the numerical cloud model producing storm flow and hydrometeor fields. The effects of observation noise and the spatial distribution of wind field analysis error are also investigated.

Decreasing the error in the measurement of the ecosystem effective leaf area index of a Pinus massoniana forest

Decreasing the forest ecosystem leaf-area index error(LAIe)helps accurately estimate the growth and light energy utilization of aboveground foliage.Analyzing light transmission in forest ecosystems can effectively determine LAIe.The LAI-2200 plant canopy analyzer(PCA)is used extensively for rapid field-effective LAI(LAIe)measurements and primarily to measure forest canopy LAIe values.However,sometimes this parameter must also be measured in forests with small clearings.In this study,we used the LAI-2200 PCA to obtain one A-value and four B-values each for the canopy,herbaceous layer,and forest ecosystem LAIe.Field measurements showed that the three LAIe types were obviously different.In certain quadrats,the average herbaceous layer(Dicranopteris dichotoma Bernh.)LAIe apparently exceeded that of the Pinus massoniana forest ecosystem.The sources of this error were measuring and recording A-value readings for small canopies and underestimating the ecosystem LAIe.We obtained similar coefficients of determination for both the pre-recomputation and post-recomputation of the canopy and forest ecosystem LAIe(R^2C 0.96 and R^2C 0.99,respectively);thus,the error was decreased.Measuring field LAIe with the LAI-2200 PCA and recomputation should compensate for LAIe underestimation in complex forest ecosystems.

绝对式纳米时栅传感器栅尺污染误差分析与抑制方法研究

针对服役状态下油污降低位移传感器精度和可靠性的问题,本文基于绝对式纳米时栅传感器,开展了栅尺油污污染误差分析与抑制方法研究。首先阐述了绝对式纳米时栅传感器测量原理;其次建立了栅尺油污污染的数学理论模型和电场仿真模型。通过理论和仿真分析表明:均匀油污污染对传感器没有影响,非均匀油污污染主要引入一次谐波误差,并且误差随着污染油污的厚度和宽度的增加而增加;最后搭建实验平台验证了以上理论分析的正确性。同时提出差动结构,有效抑制了一次谐波误差,提高了传感器抗污能力。研究油污造成的误差影响对提高传感器环境适应性有重要意义,同时也为提高传感器长期可靠性和增强环境适应性提供了理论基础。

胸部肿瘤三维适形调强放疗摆位误差相关因素分析

分析胸部肿瘤患者行三维适形调强放疗(IMRT)时产生摆位误差的相关因素,以准确计算出临床靶区(CTV)外放边界(摆位扩边(SM)值),从而实现安全放疗.以莆田学院附属医院接受IMRT治疗的83例胸部恶性肿瘤患者为研究对象,应用体位固定技术及电子射野影像装置(EPID)测量比较胸部恶性肿瘤IMRT的摆位误差,采用多元线性回归分析方法对摆位误差相关因素进行分析,进而分类计算出其SM值.结果显示,83例受试者在X轴、Y轴、Z轴上的SM值分别为0.31、0.28、0.28 cm;靶区定位、性别及肺容量分别为Y轴个体随机误差、Z轴个体系统误差、Z轴个体随机误差的独立影响因素.这表明肿瘤患者行IMRT治疗时靶区定位、性别及肺容量在不同方向上影响其摆位误差.

Spherical Near-Field - Far-Field Transformation for Quasi-Planar Antennas from Irregularly Spaced Data

An effective near-field - far-field (NF - FF) transformation with spherical scanning for quasi-planar antennas from irregularly spaced data is developed in this paper. Two efficient approaches for evaluating the regularly spaced spherical samples from the nonuniformly distributed ones are proposed and numerically compared. Both the approaches rely on a nonredundant sampling representation of the voltage measured by the probe, based on an oblate ellipsoidal modelling of the antenna under test. The former employs the singular value decomposition method to reconstruct the NF data at the points fixed by the nonredundant sampling representation and can be applied when the irregularly acquired samples lie on nonuniform parallels. The latter is based on an iterative technique and can be used also when such a hypothesis does not hold, but requires the existence of a biunique correspondence between the uniform and nonuniform samples, associ- ating at each uniform sampling point the nearest irregular one. Once the regularly spaced spherical samples have been recovered, the NF data needed by a probe compensated NF - FF transformation with spherical scanning are efficiently evaluated by using an optimal sampling interpolation algorithm. It is so possible to accurately compensate known posi- tioning errors in the NF - FF transformation with spherical scanning for quasi-planar antennas. Some numerical tests assessing the accuracy and the robustness of the proposed approaches are reported.

有限视场下的攻击时间和角度多约束制导律

针对精确打击任务存在导引头视场受限这一过程约束的制导问题,提出了一种考虑视场限制以及攻击角度和时间多种约束的制导律.首先,在以比例导引项实现精确命中的基础上,利用最优控制理论,采用弹目距离加权控制能耗形式的指标函数,设计了攻击角度控制项,并推导了相应的剩余飞行时间解析预测表达式.其次,基于最优误差动力学方法,设计了攻击时间相关的控制项,保证了攻击时间误差的有限时间收敛.同时,针对导引头视场有限的问题,分析了各控制项对前置角收敛性的影响,利用特定的限制函数确保前置角在整个制导过程中始终处于有效视场内,并给出了前置角的有界性及收敛性证明.数学仿真结果验证了所提出制导律对多约束制导问题的有效性.

海水环境光场水下辐照度测量光学设计

为了实现海洋环境光场水下辐照度测量光学设计,根据海洋辐射传输理论,对海洋环境下行辐照度、上行辐照度进行估算,完成海洋环境光场辐照度测量模块光学设计,并对其测量能力、姿态误差校正能力进行仿真分析,分析了探测器光敏面面积和透射窗口相对探测器的张角对测量能力的影响、横摇测量误差和纵倾测量误差对姿态测量误差影响,并得到横摇误差可采用动态水平法利用数据处理手段消除,纵倾测量误差可用对称排布的双辐照度探头测量模式消除的结论。海洋环境光场水下辐照度测量的光学设计,为水下实现目标环境光学特性测量奠定了技术支撑。