A Steam-Plasma Igniter for Aluminum Powder Combustion

High-temperature ignition is essential for the ignition and combustion of energetic metal fuels,including aluminum and magnesium particles which are protected by their highmelting-temperature oxides.A plasma torch characterized by an ultrahigh-temperature plasma plume fulfills such high-temperature ignition conditions.A new steam plasma igniter is designed and successfully validated by aluminum power ignition and combustion tests.The steam plasma rapidly stabilizes in both plasma and steam jet modes.Parametric investigation of the steam plasma jet is conducted in terms of arc strength.A high-speed camera and an oscilloscope method visualize the discharge characteristics,and optical emission spectroscopy measures the thermochemical properties of the plasma jet.The diatomic molecule OH fitting method,the Boltzmann plot method,and short exposure capturing with an intensified charge coupled device record the axial distributions of the rotational gas temperature,excitation temperature,and OH radical distribution,respectively.The excitation temperature at the nozzle tip is near 5500 K,and the gas temperature is 5400 K.     

Influences of tool plunge speed and tool plunge depth on friction spot joining of AA5454-O aluminum alloy plates with different thicknesses

AA5454-O aluminum alloy plates with the thicknesses of 1.4 and 1.0 mm were friction-spot-joined (FSJed).The plunge speed of the joining tool was changed in a range of 100 500 mm/min under a constant rotation speed of 500 r/min.The plunge depth was ranged from 1.6 mm to 2.2 mm.The tool plunge speed did not make a remarkable effect on the surface appearance and macro-structure of the FSJed zone.The average hardness of the FSJed zone was greater than or equal to that of the base metal.However,there was no remarkable tendency in the average hardness change of the FSJed zone in spite of the variation in the tool plunge speed and tool plunge depth.The increase of the tool plunge depth resulted in the increase of the tensile shear load.However,the change of the tool plunge speed did not lead to the remarkable variation in the tensile shear load of the FSJed plates.It was noteworthy that the FSJed plate exhibited the highest tensile shear load of about 4.0 kN.     

Development of a dimensionless parameter for characterization of dielectric barrier discharge devices with respect to geometrical features

Non-thermal plasma (NTP) devices produce excited and radical species that have higher energy levels than their ground state and are utilized for various applications.There are various types of NTP devices,with dielectric barrier discharge (DBD) reactors being widely used.These DBD devices vary in geometrical configuration and operating parameters,making a comparison of their performance in terms of discharge power characteristics difficult.Therefore,this study proposes a dimensionless parameter that is related to the geometrical features,and is a function of the discharge power with respect to the frequency,voltage,and capacitance of a DBD.The dimensionless parameter,in the form of a ratio of the discharge energy per cycle to the gap capacitive energy,will be useful for engineers and designers to compare the energy characteristics of devices systematically,and could also be used for scaling up DBD devices.From the results in this experiment and from the literature,different DBD devices are categorized into three separate groups according to different levels of the energy ratio.The larger DBD devices have lower energy ratios due to their lower estimated surface discharge areas and capacitive reactance.Therefore,the devices can be categorized according to the energy ratio due to the effects of the geometrical features of the DBD devices,since it affects the surface discharge area and capacitance of the DBD.The DBD devices are also categorized into three separate groups using the Kriegseis factor,but the categorization is different from that of the energy ratio.     

Kinematic design of an anthropomimetic 7-DOF cable-driven robotic arm

In this paper, an anthropomimetic design of a 7-DOF dexterous robotic arm is proposed. Similar to the human arm, the arm consists of three sequentially connected modules, i.e., a 3-DOF shoulder module, a 1-DOF elbow module, and a 3-DOF wrist module. All three arm modules are also driven by cables in order to mimic the driving scheme and functionality of the human muscles. This paper addresses three critical design analysis issues, i.e., the displacement analysis, the tension-closure analysis, and the workspace analysis. A closed-form solution approach is presented for the forward displacement analysis, while the inverse displacement solution is obtained through an efficient optimization algorithm, in which both task-decomposition and dimension-reduction techniques are employed. An effective tension-closure analysis algorithm is also formulated based on the theory of convex analysis. The orientation workspace for the 3-DOF shoulder and wrist modules are then analyzed using a new equi-volumetric partition scheme based on the intuitive Tilt-and-Torsion angle parameterization. An optimization approach is then investigated for the kinematic design of the three joint modules, in which the design objective is to maximize the matched workspace of the robotic arm joints with that of the human arm joints. A research prototype of the 7-DOF cable-driven robotic arm has also been developed in order to demonstrate the anthropomimetic design concept. With a lightweight structure of 1 kg, the cable-driven robotic arm can carry a payload of 5 kg and has motion repeatability of±2.5mm.     

Effects of poly‐γ‐glutamic acid on the physicochemical characteristics of skim milk yoghurt

The physicochemical and sensory properties of skim milk yoghurts containing poly‐γ‐glutamic acid (PGA) at different levels (0.0025, 0.005 and 0.01%) were evaluated. Addition of PGA up to 0.01% to reconstituted skim milk (11%, w/v) did not affect the growth of lactic acid bacteria or the development of titratable acidity in yoghurt, whereas full‐fat control yoghurt had reduced acid production. No changes were found in viable cell counts of PGA yoghurts during storage (4 weeks at 4 °C). The addition of PGA (0.005%) significantly decreased syneresis in skim milk yoghurt and did not cause any undesirable effects in sensory acceptability.     

Performance of signal‐to‐noise ratio estimation for scanning electron microscope using autocorrelation Levinson–Durbin recursion model

A new technique to quantify signal‐to‐noise ratio (SNR) value of the scanning electron microscope (SEM) images is proposed. This technique is known as autocorrelation Levinson–Durbin recursion (ACLDR) model. To test the performance of this technique, the SEM image is corrupted with noise. The autocorrelation function of the original image and the noisy image are formed. The signal spectrum based on the autocorrelation function of image is formed. ACLDR is then used as an SNR estimator to quantify the signal spectrum of noisy image. The SNR values of the original image and the quantified image are calculated. The ACLDR is then compared with the three existing techniques, which are nearest neighbourhood, first‐order linear interpolation and nearest neighbourhood combined with first‐order linear interpolation. It is shown that ACLDR model is able to achieve higher accuracy in SNR estimation.     

Landau damping of twisted waves in Cairns distribution with anisotropic temperature

The consideration of orbital angular momentum of an electric field(twisted mode) is applied to the kinetic theory of plasma. The linearized Vlasov–Poisson equation is solved for the anisotropic thermal distributed bi-Maxwellian and Cairns distributions of electrons to obtain the damping rates of twisted waves. The dispersion relation and Landau damping of Langmuir twisted modes are obtained. The presence of twisted modes opens up two more possibilities in Landau damping and dispersion relations. This may generate a mixture with ion sound waves. It seems to play the role of a control parameter of Landau damping.     

A New Approach for Manufacturing a High Porosity Ti-6Al-4V Scaffolds for Biomedical Applications

Titanium and its alloys are currently considered as one of the most important metallic materials used in the biomedical applications, due to their excellent mechanical properties and superior biocompatibility. In the present study, a new effective method for fabricating high porosity titanium alloy scaffolds was developed. Porous Ti-6Al-4V scaffolds are successfully fabricated with porosities ranging from 30% to 70% using spaceholder and powder sintering technique. Based on its acceptable properties, spherical carbamide particles with different diameters （0.56, 0.8, and 1mm） were used as the space-holder material in the present investigation. The Ti-6Al-4V scaffolds porosity is characterized by using scanning electron microscopy. The results show that the scaffolds spherical-shaped pores are depending on the shape, size and distribution of the space-holder particles. This investigation shows that the present new manufacturing technique is promising to fabricate a controlled high porosity and high purity Ti-6Al-4V scaffolds for hard tissue replacement.