Numerical and experimental investigation of inward tube electromagnetic forming

In this work, experimental and numerical simulation of high-speed inward forming of tubes on a die in electromagnetic forming (EMF) system using a compression coil is presented. A 2D axi-symmetric electromagnetic model is used to calculate magnetic field and magnetic forces. Modified loose-coupled simulations of electromagnetic and structural aspects of EMF process are reported and emphasized in this paper. During the simulation, in each time step, the transient magnetic forces are obtained from the electromagnetic model and used as input load to the mechanical model. Based on the calculated deformation, in each step, the tube geometry in the electromagnetic model is updated to calculate the electromagnetic forces in proceeding step. Tube material, AA 6061-T6, is assumed to obey the Johnson-Cook (J-C) rate-dependent model. Displacement and thickness variations of workpieces along the tube length are presented and discussed experimentally and numerically. The results demonstrate that various workpiece zones could be thickened or thinned based on various process parameters. In addition, it is seen that the increase of discharge voltage decreases the thickness at die radius and reverses the thickening trend at tip of the bead.     

Extraction of Lycopene from Tomato Paste by Ursodeoxycholic Acid Using the Selective Inclusion Complex Method

Lycopene, a precursor of β‐carotene with well‐known antioxidant activity and powerful health properties, can be found in many natural products such as tomato (Lycopersicon esculentum), watermelon, red pepper, and papaya. Many separation methods have been reported for extracting lycopene from its sources. The inclusion complex is an effective method for extraction and purification of organic chemicals. This procedure has 2 main components: host and guest molecules. In this study, lycopene (guest) was extracted from tomato paste by ursodeoxycholic acid, the inclusive agent (host). The molecular structure of the extracted lycopene was then confirmed by ¹HNMR and its purity was evaluated using high‐performance liquid chromatography and UV‐Vis spectrophotometry methods, in comparison with a standard product. The results indicated that the proposed separation method was very promising and could be used for the extraction and purification of lycopene from tomato paste.     

Improvement of ECAP process by imposing ultrasonic vibrations

The International Journal of Advanced Manufacturing Technology - In a few last decades, equal-channel angular pressing (ECAP) has been one of the most prominent procedures for fabrication of...     

高振动石英晶体振荡器

新的设备特性使苛刻应用中的频率控制更稳固 我们通常认为在电子系统中,石英晶体振荡器是最易碎的元件之一.     

Gaze stability for liveness detection

Spoofing attacks on biometric systems are one of the major impediments to their use for secure unattended applications. This paper explores features for face liveness detection based on tracking the gaze of the user. In the proposed approach, a visual stimulus is placed on the display screen, at apparently random locations, which the user is required to follow while their gaze is measured. This visual stimulus appears in such a way that it repeatedly directs the gaze of the user to specific positions on the screen. Features extracted from sets of collinear and colocated points are used to estimate the liveness of the user. Data are collected from genuine users tracking the stimulus with natural head/eye movements and impostors holding a photograph, looking through a 2D mask or replaying the video of a genuine user. The choice of stimulus and features are based on the assumption that natural head/eye coordination for directing gaze results in a greater accuracy and thus can be used to effectively differentiate between genuine and spoofing attempts. Tests are performed to assess the effectiveness of the system with these features in isolation as well as in combination with each other using score fusion techniques. The results from the experiments indicate the effectiveness of the proposed gaze-based features in detecting such presentation attacks.     

Pulse shaping fiber laser at 1.5 μm

In this paper we present, for the first time to our knowledge, a new pulse shaping technology (modulation schemes for seed laser) used to mitigate pulse narrowing effect and SBS effect in a high energy Er:Yb codoped fiber master oscillator power amplifier system at 1.5 μm to obtain longer pulse duration and higher energy. An average power of over 1.3 W and a pulse energy of over 0.13 mJ were obtained at 10 kHz repetition rate with a pulse duration of 200 ns and near-diffraction-limited beam quality (M(2)<1.2).     

Improvement of the flow formulation by recovery of the hydrostatic pressure using the finite point method

Most of the existing numerical methods based on penalty technique, lead to pressure fields, which are not satisfactory especially when crude meshes are used. The present work for the first time, using a simple and effective finite point approach approximates the total hydrostatic stresses. By this new technique, the nodal hydrostatic pressure values are calculated so that the gradient of hydrostatic pressure satisfies the equilibrium equation, with regard to the current distribution of deviatoric stresses. This approach is verified using a cantilever beam with known analytical stress field. It is also applied to a typical 2D axisymmetric bulk metal forming process. The calculated pressure field is then compared with available solutions. The results of the present approach are very encouraging. Copyright © 2005 John Wiley & Sons, Ltd.     

Experimental determination of the transmission of a mini-orange β-spectrometer

A method is described to determine the efficiency (transmission) of a mini-orange type β-spectrometer in the energy range of (here) 500–1800 keV with an accuracy of about 5%.The method combines data taken with a continuous β-spectrum (⁹⁰Sr) with those from discrete electron lines (conversion lines of ²⁰⁷Bi). With simple assumptions concerning the backscattering of electrons from the Si(Li) detector, the two sets of data yield a unique continuous curve for the transmission as a function of energy which allows the in-beam determination of unknown conversion coefficients, e.g. after (p, p′) or (p, n)-reactions.     

Crow Algorithm for Irrigation Management: A Case Study

Water Resources Management - This study employed a new evolutionary algorithm namely, the crow algorithm (CA), to optimize reservoir operation and minimize irrigation water deficit. Comprehensive...