Strategies to realize decentralized manufacture through hybrid manufacturing platforms

Centralized factory dominance has led to optimization and set-up for manufacture of a sole product or product-range. In-house efficacy of such systems has been greatly improved due to lean six-sigma methodologies; however, wider scale distribution and supply has undergone little to no transformation over the past century. Research pertaining to distributed manufacture, cloud-manufacture and reconfigurable systems have provided several decentralized models using traditional manufacturing capabilities. Due to practical limitations they have not been fully realized to date. This paper outlines the emerging concept and scope for hybrid manufacturing platforms – systems using a plurality of processes on a single motion platform, to manufacture products in a decentralized network. Necessity of on-machine inspection is highlighted, outlining the potential of generic artifact machine calibration and verification of parts made. A robust experimental method using a novel hybrid manufacturing approach is used to realize the post-process adaptation of subsequent parts and demonstrates significant improvement with adapted features being cut within 15 μm of nominal position, compared to the original 300 μm error. Social, economic and environmental ramifications of adopting such a system are highlighted. The combination of several key processes will allow users to manufacture parts with minimal intervention. A move to personal fabrication would allow greater customization and convenience for the end user; however, the issues of copyright and loss of economy of scale would inhibit mass uptake in the near-future. Growing interest by enthusiasts and early adopters will continue to make an impact on the way the populace views manufacture.     

童话的建造 2010年上海世博会丹麦馆构筑实录

文章通过对丹麦馆的结构设计、材料选择和施工过程的介绍,试图将丹麦馆的中国建造还原给读者。     

论中华造物观中的“木道”

侧重从材美、工巧和审美三个方面来论述木制器物文化,及其形成的“木道” 审美情趣,从而进一步论述了“以人为本,物我融一”的设计理念。     

Investigation of solid particle number measurement: Existence and nature of sub-23 nm particles under PMP methodology

A Particle Measurement Program (PMP) compliant system, an AVL advanced particle counter (APC) and an alternative volatile particle removal system, a catalytic stripper (CS) were evaluated and compared for measuring solid particle number (PN) emissions. The evaluations and comparisons were conducted using sulfuric acid and hydrocarbon particles as model volatile particles in laboratory tests, and diluted exhaust from a diesel particle filter (DPF)-equipped heavy-duty diesel vehicle operated on a heavy-duty chassis dynamometer under steady speed conditions at two different engine loads. For the laboratory test, both the APC and CS removed more than 99% of the volatile particles in terms of PN when using aerosols composed of pure sulfuric acid or hydrocarbons. When using laboratory test aerosols consisting of mixtures of sulfuric acid and hydrocarbons more than 99% of the particles were removed by the APC but the surviving particles were no longer entirely volatile, 12–14% were solid. For the chassis dynamometer test, PN emissions between 3 and 10 nm downstream the APC were ∼2 and 7 times higher than the PN emissions of particles above 10 nm at the 74% and 26% engine load, respectively. At the 26% engine load, PN level of the 3–10 nm particles downstream the APC were significantly higher than that in the dilution tunnel, demonstrating that the APC was making 3–10 nm particles. The PN emission of 3–10 nm particles downstream the APC was related to the heating temperature of the APC evaporation tube, suggesting these particles are artifacts formed by renucleation of semivolatiles. Considerably fewer particles between 3 to 10 nm were seen downstream of the CS for both engine loads due mainly to removal of semivolatile material by the catalytic substrates, although some of this difference could be attributed to diffusion and thermophoretic losses. The findings of this study imply that improvement of the current PMP protocol would be necessary if the PMP were to be used in other applications where the PN emissions of particles below 23 nm are important.     

Efficient sign based normalized adaptive filtering techniques for cancelation of artifacts in ECG signals: Application to wireless biotelemetry

In this paper, several simple and efficient sign based normalized adaptive filters, which are computationally superior having multiplier free weight update loops are used for cancelation of noise in electrocardiographic (ECG) signals. The proposed implementation is suitable for applications such as biotelemetry, where large signal to noise ratios with less computational complexity are required. These schemes mostly employ simple addition, shift operations and achieve considerable speed up over the other least mean square (LMS) based realizations. Simulation studies shows that the proposed realization gives better performance compared to existing realizations in terms of signal to noise ratio and computational complexity.     

A method for the reduction of skin marker artifacts during walking : Application to the knee

Previous studies have demonstrated the importance of joint angle errors mainly due to skin artifact and measurement errors during gait analysis. Joint angle errors lead to unreliable kinematics and kinetic analyses in the investigation of human motion. The purpose of this paper is to present the Joint Averaging Coordinate System (JACS) method for human gait analysis. The JACS method is based on the concept of statistical data reduction of anatomically referenced marker data. Since markers are not attached to rigid bodies, different marker combinations lead to slightly different predictions of joint angles. These different combinations can be averaged in order to provide a “best” estimate of joint angle. Results of a gait analysis are presented using clinically meaningful terminology to provide better communication with clinical personal. In order to verify the developed JACS method, a simple three-dimensional knee joint contact model was developed, employing an absolute coordinate system without using any kinematics constraint in which thigh and shank segments can be derived independently. In the experimental data recovery, the separation and penetration distance of the knee joint is supposed to be zero during one gait cycle if there are no errors in the experimental data. Using the JACS method, the separation and penetration error was reduced compared to well-developed existing methods such as ACRS and Spoor & Veldpaus method. The separation and penetration distance ranged up to 15 mm and 12 mm using the Spoor & Veldpaus and ACRS method, respectively, compared to 9 mm using JACS method. Statistical methods like the JACS can be applied in conjunction with existing techniques that reduce systematic errors in marker location, leading to an improved assessment of human gait.     

能量熵与峰值窗口结合去除眼电伪迹研究

为改进传统独立分量分析自动去除眼电伪迹算法中存在识别眼电分量速度慢、需采集同步参考眼电信号、丢失脑电信号问题,提出一种不需要参考眼电信号的眼电伪迹自动识别去除方法。利用FastICA分解出独立分量,计算各独立分量频谱能量熵,以频谱能量熵值作为判据识别出眼电分量;然后使用峰值窗口分离出眼电分量中存在的脑电信号,与其他独立分量进行拼接;利用FastICA逆变换重构出去眼电伪迹的脑电信号。实验结果表明：该方法能准确快速自动地去除眼电伪迹,并较好地保留其他的脑电信号成分;频谱能量熵识别眼电伪迹平均用时为0.01?s,准确率为98％,适用于实时EOG去除。     

一种X射线射束硬化校正方法

在医学CT成像系统中,X射线源发出的X射线是多能的,若直接对其进行传统方法的重建,会导致射束硬化,使重建的图像出现“杯状”或“条状”伪影,降低图像质量,干扰诊断等问题,因此需要对CT硬化伪影进行校正。本文提出了一种射束硬化伪影的校正方法,利用近似材料衰减系数与x射线能量的关系,通过从原始重建图像中减去伪影图像来获得校正后的图像。该方法不需要先验知识。数值实验表明,该方法能有效、快速地校正射束硬化伪影。     

基于多模态局部转向核的脑部多发性硬化检测算法研究

容积效应和伪影现象是MR影像处理中的重要影响因素,单模态处理方法易受两者影响。提出一种改进的基于多模态局部转向核的方法来检测大脑中的多发性硬化。该方法利用多模态脑MR影像和大脑近似轴对称的先验知识来进行大脑情况的变化检测。局部转向核能够度量像素与其周围环境的相似程度,因此该方法将局部转向核作为特征,用余弦相似性来衡量差异性。实验结果表明,多模态的引入减少了容积效应和伪影现象,改善了检测效果。     

Correcting capacitive displacement measurements in metrology applications with cylindrical artifacts

Metrology applications commonly require non-contact, capacitive sensors for displacement measurements due to their nanometer resolution. In some metrology applications, for example, the measurement of roundness and spindle error motion, the displacements of stationary and rotating cylindrical artifacts are measured. Error from using a conventionally calibrated sensor with a non-flat (e.g., cylindrical) target is typically neglected, but these errors cannot be ignored for nanometer-level accuracy. The capacitance between a sensor and a cylindrical target is less than that of a sensor with a flat target, which causes four effects. As the diameter of the target shrinks, the sensitivity of the sensor increases, the sensing range decreases, the sensing range shifts towards the target, and the nonlinearity increases. These errors can be greatly reduced by either calibrating sensors with the correct target surface or by determining corrections for post-processing data. This paper quantifies and experimentally verifies these errors for a commonly used sensor, and a simulation of a nanometer-level measurement of out-of-roundness and spindle error motion demonstrates that measurement accuracy is improved with corrected sensitivities.