Machine acceleration time series prediction for dimensional accuracy of 3D printed parts

This study explores the influence of infill patterns on machine acceleration prediction in the realm of three-dimensional(3D)printing,particularly focusing on extrusion technology.Our primary objective was to develop a long short-term memory(LSTM)network capable of assessing this impact.We conducted an extensive analysis involving 12 distinct infill patterns,collecting time-series data to examine their effects on the acceleration of the printer’s bed.The LSTM network was trained using acceleration data from the adaptive cubic infill pattern,while the Archimedean chords infill pattern provided data for evaluating the network’s prediction accuracy.This involved utilizing offline time-series acceleration data as the training and testing datasets for the LSTM model.Specifically,the LSTM model was devised to predict the acceleration of a fused deposition modeling(FDM)printer using data from the adaptive cubic infill pattern.Rigorous testing yielded a root mean square error(RMSE)of 0.007144,reflecting the model’s precision.Further refinement and testing of the LSTM model were conducted using acceleration data from the Archimedean chords infill pattern,resulting in an RMSE of 0.007328.Notably,the developed LSTM model demonstrated superior performance compared to an optimized recurrent neural network(RNN)in predicting machine acceleration data.The empirical findings highlight that the adaptive cubic infill pattern considerably influences the dimensional accuracy of parts printed using FDM technology.

A Family of High_order Accuracy Explicit Difference Schemes for Solving 2-D Parabolic Partial Differential Equation

A family of high_order accuracy explicit difference schemes for solving 2_dimension parabolic P.D.E. are constructed. Th e stability condition is r=Δt/Δx 2=Δt/Δy 2【1/2 and the truncation err or is O(Δt 3+Δx 4).

改进D-Linknet的眼底视网膜血管分割

临床医生可通过观察眼底视网膜血管及其分支对人体是否患有疾病进行早期诊断,但由于视网膜中的血管错综复杂,模型在分割时会出现对微细血管分割精确度不足的问题。为此,提出一种结合残差模块Res2-net以及高效通道注意力机制(efficient channel attention,ECA)的D-Linknet模型。首先,利用Res2-net代替基础模型中的残差模块Res-net以提升每个网络层的感受野;其次,在Res2-net中添加一种结合压缩激励(squeeze and excitation,SE)和门通道(gated channel transformation,GCT)的注意力机制模块,改善处于复杂背景下的血管分割效果和效率;在网络的解码层加入ECA确保模型计算的性能,避免因降维导致的精度下降;最后,融合改进的模型输出图与掩膜图细化分割结果。在公开数据集DRIVE、STARE上进行分割实验,模型准确度(accuracy,AC)分别为97.11%、96.32%,灵敏度(sensitivity,SE)为84.55%、83.92%,曲线下方范围的面积(area under curve,AUC)为0.9873和0.9766,分割效果优于其他模型。实验证明了算法的可行性,为后续研究提供科学依据。

针对高转速A/D采集的自适应平滑处理方法

船舶领域常用瞬间转速测量对各类大型机械设备进行运行状态监测及信号控制,为了提高瞬时转速测量的精度,从而提高船舶设备运行控制的准确性以及设备健康状态评估的有效性,基于传统模数转换(A/D)采集的采集转速方法——测频率法和测周期法,通过对A/D转速测量点数进行多周期平滑处理,并加入转速分段测量的自适应机制,提高A/D采集瞬时高转速的精度。在进行模拟仿真与理论结果比较验证后,进一步开展在实际测量中自适应平滑处理方法对转速测量精度影响的研究。仿真及试验结果表明,采用的转速测量方法针对不同的转频均可有效降低转速测量误差,研究成果可为船舶机械设备转速测量提供一定参考。

Discrete multi-step phase hologram for high frequency acoustic modulation

Acoustic holograms can recover wavefront stored acoustic field information and produce high-fidelity complex acoustic fields. Benefiting from the huge spatial information that traditional acoustic elements cannot match, acoustic holograms pursue the realization of high-resolution complex acoustic fields and gradually tend to high-frequency ultrasound applications. However, conventional continuous phase holograms are limited by three-dimensional(3D) printing size, and the presence of unavoidable small printing errors makes it difficult to achieve acoustic field reconstruction at high frequency accuracy. Here, we present an optimized discrete multi-step phase hologram. It can ensure the reconstruction quality of image with high robustness, and properly lower the requirement for the 3D printing accuracy. Meanwhile, the concept of reconstruction similarity is proposed to refine a measure of acoustic field quality. In addition, the realized complex acoustic field at 20 MHz promotes the application of acoustic holograms at high frequencies and provides a new way to generate high-fidelity acoustic fields.

Preparation of A Novel Hybrid Type Photosensitive Resin for Stereolithography in 3D Printing and Testing on the Accuracy of the Fabricated Parts

A novel hybrid type photosensitive resin for stereolithography in 3D printing was prepared with bisphenol A type epoxy diacrylate （EA-612）, tripropylene glycol diacrylate （TPGDA）,ethoxylated trimethyolpropane triacrylate（EO3TMPTA）, cycloaliphatic diepoxide（ERL-4221）,polycaprolactonepolyol（Polyol-0301）,1-hydroxy-cyclohphenyl ketone（Irgacure184）, and a mixture of triarylsulfonium hexafluoroantimonate salts （Ar3SSbF6）. The novel hybrid type photosensitive resin was the photosensitive resin of an epoxy-acrylate hybrid system, which proceeded free radical polymerization and cationic polymerization in ultraviolet （UV） laser. Cuboid parts and double-cantilever parts were fabricated by using a stereolithography apparatus with the novel hybrid type photosensitive resin as the processing material,and the dimension shrinkage factor and the curl factor were tested. The shrinkage factor was less than 2.00%,and the curl factor was less than 8.00%, which showed that the accuracy of the fabricated parts was high with the photosensitive resin for stereolithography in 3D printing.

Accuracy Assessment of Alos W3d30, Aster Gdem and Srtm30 Dem: A Case Study of Nigeria, West Africa

Digital Elevation Models (DEMs) depict the configuration of the earth surface and are being applied in many areas in earth and environmental sciences. In this study, the accuracy of the Advanced Land Observing Satellite World 3D Digital Surface Model version 2.1 (ALOS W3D30), the Shuttle Radar Topography Mission Digital Elevation Model version 3.0 (SRTM30) and the Advanced Space borne Thermal Emission and Reflection Radiometer Global DEM version 2.0 (ASTER GDEM2) was statistically assessed using high accuracy GPS survey data. Root-Mean-Square errors of ~5.40 m, ~7.47 m and ~20.03 m were obtained for ALOS W3D30, SRTM30 and ASTER GDEM2 respectively. In further analyses, we discovered that ALOS W3D30 and SRTM30 were much more accurate in regions where the height intervals were within 201 m - 400 m and >801 m. ALOS W3D30 proved to be the most accurate DEM that best represents the topography of the earth’s surface and could be used for some earth and environmental applications in Nigeria. We recommend that this study should serve as a guide in the use of any of these DEMs for earth and environmental applications in Nigeria.

Determining the effect of relative size of sensor on calibration accuracy of TEM cells

The time-domain calibration coefficient of a D-Dot sensor should be identical across various transverse electromagnetic (TEM) cells to comply with the IEEE Std 1309. However, in our previous calibration experiments, poor consistency was observed. The size of D-Dot sensors relative to TEM cells is considered the main reason for this poor consistency. Therefore, this study aims at determining the calibration coefficient of a D-Dot sensor. We calculate the theoretical coefficient as a reference. Practical calibration experiments involve the processing of TEM cells with three different sizes. To observe the response more clearly, corresponding models are constructed and numerical simulations are performed. The numerical simulations and experimental calibration are in good agreement. To determine the calibration accuracy, we quantify the accuracy using the relative error of the calibration coefficient. By comparing the coefficients obtained, it can be concluded that the perturbation error is about 15% when the relative size is over 1/3. Further, the relative size should be less than 1/5 to obtain a relative error below 10%.

气体辅助条件下GF/PP的3D打印

在气辅3D打印中,高温气流对聚合物丝材形态产生显著影响,因此,需要深入研究其内部机理。优化设计了气辅3D打印喷嘴,采用含量为10%的玻璃纤维增强聚丙烯(GF/PP),对比研究了传统3D打印与气辅3D打印制品的表观性能和力学性能,结果表明,引入气体辅助后,减小了打印过程中的收缩变形,将3D打印制品在水平和垂直2个方向上的尺寸精度分别提高了4.3、1.7倍,形状尺寸更接近原始模型尺寸;气流的引入使高分子丝材变为滑移挤出,表面粗糙度降低至传统3D打印材料的46%,表面更加光滑平整;拉伸强度和断裂伸长率分别提高了8.24%、50.71%。在以上因素共同作用下,打印制品的表观质量和力学性能更佳。

Experimental Research on the Fabrication of Modular Devices for Drilling Using PLA for Model Parts

The objective of the work is to determine the influence of the PLA melting temperature during 3D printing on the dimensional accuracy of the model parts. Two modular drilling devices were also made using PLA model parts. The model parts were 3D printed using FDM technology and the ZMorph 2.0 hybrid 3D printer. The accuracy of 3D printing of the model part influences the realization of modular devices. In recent years, technology has evolved a lot, and the need to have the most efficient manufacturing equipment has increased. This is the reason for the development of 3D printers using FDM technology for plastic parts. The software used by these 3D printers used in FDM technology is very sophisticated, as they allow the manufacture of very precise 3D prototypes, identical to the designed 3D model, through modern additive manufacturing techniques. The quality and mechanical strength of the prototypes obtained using 3D printers is very good. The materials used by the 3D printers manufactured by FDM are cheap and accessible. These 3D printers are used to make three-dimensional objects (gears, flanges, bearings, covers, casings, mechanisms, figurines, interior and exterior design elements, architectural models, medical models).

Parallel numerical simulations for quantized vortices in Bose-Einstein condensates

We employ the parallel computing technology to study numerically the three-dimensional structure of quantized vortices of Bose-Einstein condensates, For anisotropic cases, the bending process of vortices is described in detail by the decrease of Gross-Pitaevskii energy. A completely straight vortex and the steady and symmetrical multiple-vortex configurations are obtained. We analyse the effect of initial conditions and angular velocity on the number and shape of vortices.

Comparison of the Motion Accuracy of a Six Degrees of Freedom Radiotherapy Couch with and without Weights

In this study, we compared the motion accuracy of six degrees of freedom (6D) couch for precision radiotherapy with or without weights attached to the couch. Two digital cameras were focused on the iso-center of a linear accelerator. Images of a needle which had been fixed to the 6D couch were obtained using the cameras when the couch moved in translation and rotation around each axis. The three-dimensional (3D) coordinates of the needle were calculated from coordinate values in the images. A coordinate error of the needle position relative to the theoretical position was calculated. The errors were obtained with or without a 60 kg weight attached to the 6D couch, and these errors were compared with each other. The mean distance of the 3D error vectors for the weighted test was 0.21 ± 0.11 mm, and >0.16 ± 0.09 mm for the non-weighted test (p

Optical A/D Quantizer Scheme Based on Parallel Phase Mod ulators

A high-speed and high-resolution optical A/D quantizer is proposed.Its architecture is discussed.Bit circuits are built by using the phase modulators in parallel.Based on the different character of the half-wave voltage for every phase modulator and the polarized bias design of incident light,the RF input signal is coled and transmitted in the form of optical digital signal.According to the principle of the architecture,the high-resolution quantizers with 8-bit and 12-bit,et al.are built,which operate at 100 GS/s.Their quantization noise is invariable almost with bit circuits increasing.The simulation result of 4-bit A/D quantizer is also given.

Methodology of High Accuracy and Resolution 3D Geological Model Generation and Application

By generating a high accuracy and high resolution geological model in Liuchu oil field, the technique of geological modeling is expanded and involved in primary geological study, making the sand bodies and reservoir be easily described in detail. The 3D visualization and 3D interactive editing of geological structure model are the key for modeling procedure. And a high accuracy and resolution geological model has been well applied in optimizing the production scheme.

An Analysis on Position Estimation, Drifting and Accumulated Error Accuracy during 3D Tracking in Electronic Handheld Devices

This work focuses on a brief discussion of new concepts of using smartphone sensors for 3D painting in virtual or augmented reality. Motivation of this research comes from the idea of using different types of sensors which exist in our smartphones such as accelerometer, gyroscope, magnetometer etc. to track the position for painting in virtual reality, like Google Tilt Brush, but cost effectively. Research studies till date on estimating position and localization and tracking have been thoroughly reviewed to find the appropriate algorithm which will provide accurate result with minimum drift error. Sensor fusion, Inertial Measurement Unit (IMU), MEMS inertial sensor, Kalman filter based global translational localization systems are studied. It is observed, prevailing approaches consist issues such as stability, random bias drift, noisy acceleration output, position estimation error, robustness or accuracy, cost effectiveness etc. Moreover, issues with motions that do not follow laws of physics, bandwidth, restrictive nature of assumptions, scale optimization for large space are noticed as well. Advantages of such smartphone sensor based position estimation approaches include, less memory demand, very fast operation, making them well suited for real time problems and embedded systems. Being independent of the size of the system, they can work effectively for high dimensional systems as well. Through study of these approaches it is observed, extended Kalman filter gives the highest accuracy with reduced requirement of excess hardware during tracking. It renders better and faster result when used in accelerometer sensor. With the aid of various software, error accuracy can be increased further as well.

A FAMILY OF HIGH-ORDER ACCURACY EXPLICIT DIFFERENCE SCHEMES WITH BRANCHING STABILITY FOR SOLVING 3-D PARABOLIC PARTIAL DIFFERENTIAL EQUATION

A family of high-order accuracy explict difference schemes for solving 3-dimension parabolic P. D. E. is constructed. The stability condition is r = Deltat/Deltax(2) Deltat/Deltay(2) = Deltat/Deltaz(2) < 1/2 ,and the truncation error is 0(<Delta>t(2) + Deltax(4)).

A/D量化对GPS接收机自适应天线性能的影响

A/D量化会带来干扰抑制比和输出卫星信噪比的损耗。通过估算量化噪声和干扰信号互相关矩阵的最大特征值,给出了干扰抑制比的近似表达式,而输出卫星信噪比损耗则是通过计算高斯噪声下量化信号的一阶矩和二阶矩得到的。结果表明,当选择量化间隔Δ=0.5σ(σ2为接收信道的热噪声功率)时,量化噪声近似为独立的均匀分布的白噪声,因A/D量化带来的输出卫星信噪比的损耗不大于0.1dB,干扰抑制能力几乎不受影响。计算机仿真实验也验证了所作分析。

WSN中一种DV-Hop定位精度改进算法

提出了一种DV-Hop的改进算法(RHDV-Hop算法)。该算法引入接收信号强度指示器(RSSI)测距技术代替DV-Hop算法中到锚节点一跳距离测量并采用2-D Hyperbolic算法代替DV-Hop算法中三边测量法。通过NS2对RHDV-Hop算法和DV-Hop算法以及一些已经提出的对DV-Hop算法的改进算法进行了模拟实验对比,结果表明:RHDV-Hop算法定位精度要明显好于DV-Hop算法和其他改进的DV-Hop算法。

D-InSAR技术二轨法监测矿区地表沉陷的方法研究

针对D-InSAR技术二轨法中先差分再解缠和先解缠再差分2种情况,以钱营孜矿区为例,采用ALOSPALSAR数据进行差分处理,并与地面水准观测结果进行比较,最终得出结论:两者所得沉降结果与水准观测结果沉降趋势相同,但先差分再解缠的精度要远高于先解缠再差分的精度。