The influence of friction stir welding tool shape on quality of AZ31 Magnesium welding product

Magnesium is one type of material that can be used as a base metal in welding. Magnesium has superior properties, including low density, good ductility, medium strength and excellent corrosion resistance. Because of its properties, the metal is widely used, ranging from household goods to aircraft components. These base metals are categorised as mild when viewed from the specific gravity of magnesium (1.74 g/cm3 and 1.83 g/cm3). Welding is the process of merging two or more base metals which are merged at the contact surface with or without additives or fillers. Welding is divided into two main categories, Liquid and Solid-State Welding. Friction Stir Welding (FSW) is an example of Solid-State Welding (Non-Fusion Welding). FSW is a friction welding process that twists the tool by utilising heat energy and pressing without additives or fillers until the base metal is in a phase change. The welding process in this study used the cone and spiral shape with a tool rotation at 2000 rpm and a welding speed of 16 mm/min. The tests carried out are tensile and hardness testing. This study found that the tool shape, tool rotation, and welding speed significantly affect the mechanical properties of the welded AZ31 magnesium. The spiral shape will make the welding area wider. Although the cone shape will have a small area, the weld will look perfect with good tensile strength, while the hardness values for the two tool shapes are almost the same, but the cone shape is better.

Design of Miniaturized and Polarization-Insensitive Double-Layer Frequency Selective Surface Based on Meander Lines

The work presented in this paper concerns a method for the miniaturized frequency selective surface (FSS) based on the meander lines. A miniaturized dual-bandstop FSS structure based on meander lines with spiral-shape is proposed and simulated. The equivalent circuit and current distributions are introduced to explain the FSS performance. The size of the unit cell is 10 mm, which is about 0.037 wavelength at the first resonant frequency. Simulation results indicate that the proposed FSS has a frequency shift smaller than 1% for different polarizations with an oblique incident angle of 60°. A prototype of the FSS is fabricated and measured. The measurement results show that the FSS is polarization-insensitive and angle-insensitive.

A method to determine the accuracy of shape setting thin, spirally shaped Nitinol wires

Electric stimulation of the auditory nerve using a cochlear implant (CI) is presumed to be superior when the electrode array (EA) is placed close to the inner wall of the cochlea. Nitinol is investigated as an actuator that enables an intracochlear shape change of the EA from a straight configuration (also necessary for the insertion) to a spiral shape fitting to the inner wall. As shape setting of the thin Nitinol wires is crucial, a method to quantify the accuracy of the shape setting is presented. To measure the trained shape of thin Nitinol wires (ø 100 μm) a contactless, optical method was developed. For each wire, a photomicrograph was captured and processed using a custom Matlab algorithm. Threshold based segmentation followed by morphological operations to remove artefacts were applied to extract the wire’s shape. Utilizing an iterative closest point (ICP) algorithm the actual shape was registered to the desired spiral path. Finally, the root mean squared error describing the deviation between both spirals was calculated as a measure for the “shape error” (εshape). In total 147 Nitinol wires of 16 batches were analyzed to quantify the reliability of the shape setting procedure. The proposed method was successfully applied in all samples. On average εshape was 0.06 ± 0.02 mm. Deviation from the desired shape was < 0.1 mm (< 0.15 mm) in 95% (99%) of the samples. In summary, the presented method is suitable to control the trained shape of thin Nitinol wires. Furthermore, our results confirm a high reliability of the shape setting procedure used for our thin Nitinol actuators intended for future applications in CI EAs.

Mechanical Properties and Microstructure of Shotcrete under High Temperature

High temperature is recognized as one of the extreme environments in the application of shotcrete which significantly deteriorate the performance of shotcrete. This paper reviews the mechanical properties and microstructure of shotcrete under high temperature. First of all, this paper reviews the cause of formation of high ground temperature. Based on these causes, the author establishes a heat transfer model with a spiral shape by introducing a multidimensional morphological formula into the heat conduction process. Then, the paper reviews the influence of high temperature on the mechanical and micro properties of shotcrete, the cooling technology under high temperature, and the optimization research technology of shotcrete. The author discusses the influence of high temperature on the thermal parameters and the deformation of shotcrete from the perspective of thermodynamics. Multiple studies have shown that the irregular movement and disorderly overlapping of molecules in the shotcrete caused by the high temperature environment result in the premature termination of the hydration reaction of cement in shotcrete. Finally, the author suggests the challenges of high-temperature shotcrete in term of the process structure, performance optimization, and application in special engineering fields. The research in this paper intends to give guidance to those conducting shotcrete research under high temperature, and to promote the further development of shotcrete technology.

Compact TSA with Anti-Spiral Shape and Lumped Resistors for UWB Applications

A novel compact tapered-slot-fed antenna (TSA) with anti-spiral shape and lumped resistors is presented for ultra-wideband (UWB) applications. Unique coplanar waveguide (CPW) to coplanar strip (CPS) feeding structure and exponential slot are designed to ensure the continuous current propagation and good impedance matching. With a pair of anti-spiral-shaped structure loadings at the end of the antenna, the radiation performance in lower operating band can be enhanced obviously. The typical resistor loading technique is applied to improve the time domain characteristics and expand the bandwidth. The fabricated prototype of this proposed antenna with a size of 53 × 63.5 mm2 was measured to confirm simulated results. The proposed antenna has S11 less than −10 dB in the range of 1.2–9.8 GHz, and the group delay result is only 0.4 ns. These findings indicate the proposed antenna can be taken as a promising candidate in UWB communication field.

Rainbow Archimedean spiral emission from optical fibres

We demonstrate a new practical approach for generating multicolour spiral-shaped beams. It makes use of a standard silica optical fibre, combined with a tilted input laser beam. The resulting breaking of the fibre axial symmetry leads to the propagation of a helical beam. The associated output far-field has a spiral shape, independently of the input laser power value. Whereas, with a high-power near-infrared femtosecond laser, a visible supercontinuum spiral emission is generated. With appropriate control of the input laser coupling conditions, the colours of the spiral spatially self-organize in a rainbow distribution. Our method is independent of the laser source wavelength and polarization. Therefore, standard optical fibres may be used for generating spiral beams in many applications, ranging from communications to optical tweezers and quantum optics.

Helicobacter pylori Infection: Diagnosis and Therapy

Helicobacter pylori (H. pylori) is a spiral shape gram-negative bacillus and have flagella for motility in mucus environment. H. pylori is microaerophilic organism, slow growing and requires complex growth media in vitro. H. pylori infecting more than 50% populations in worldwide. Prevalence of H. pylori infection is higher in developing countries compared to developed one, and indicates that socioeconomic and living standard may play a major role in the distribution. This study aims to provide an overview of how to diagnose and manage Helicobacter pylori infection. This study reviewed various sources then reviewed as a literature review. The most successful regimens are triple and quadruple combinations, which consist of a PPI and two or three antibiotics for 7 – 14 days. Patient’s compliance and the use of drug to which strain of H. pylori has not acquired resistance are the most important factors in successful H. pylori treatment.

Parallel and Series Connection of Dark Electric Current in Liquid and Second Law of Thermodynamics

Liquid in contact with two asymmetrical spiral-shape aluminum electrodes behaves like a still weak source of electrical energy. Almost the only way to increase the efficiency of such a source of electrical energy is to reduce internal resistance. Reducing internal resistance is equivalent to using multiple sources of electrical energy connected in series or in parallel. To check this for such unusual sources it is first necessary to study the properties of each source, which is the voltage drop across the load resistance and the internal resistance of each source. Detailed analysis of experimental data shows that the process of forming the dark current is different from a chemical one.