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This study presents a novel shape-morphing wheel that enables to not only traverse flat ground quickly in a circular configuration but also overcome obstacles like steps effectively in a transformed configuration. The proposed wheel mechanism has two degrees-of-freedoms (DOFs) to change its wheel radius and the tilting angle of its lobe simultaneously in response to obstacles of various sizes. The kinematic requirements for the 2-DOF shape-morphing wheel mechanism are first defined. Then, the proper mechanisms for the proposed wheel mechanism are exhaustively searched. As a result, five mechanisms are selected in combination with four-bar mechanism to synchronize the motions of wheel lobes. From the kinematic viewpoints including the singularity, transformation range and interference, the characteristics of selected mechanisms are analyzed extensively, and a novel 2-DOF shape-morphing wheel mechanism has been successfully constructed.

As a non-contact measurement technology with high data acquisition efficiency, photogrammetry is an ideal choice for collecting the data needed in the safety evaluation of port hoisting machinery. However, the radius fitting result accuracy cannot meet the requirements of safety assessment due to the limitation of the port crane itself and the working environment characteristics, when the existing photogrammetry method is used to measure the rotary body structure represented by the portal crane slewing mechanism. In order to solve this problem, an iterative optimization algorithm for weighted radius prediction for the photogrammetry of the slewing mechanism of port hoisting machinery is proposed in this paper. First, the algorithm uses the generalized multi-line rendezvous model to transform the radius fitting problem into the multi-line intersection point prediction problem, which lays a theoretical basis for the subsequent algorithm implementation. Second, by introducing a weighting algorithm based on the camera optical distortion model, the algorithm optimizes the accuracy of radius fitting results. In addition, through the quantitative evaluation method of fitting accuracy based on weighted algorithm, the algorithm also establishes a set of iterative rules to balance the accuracy of measurement results and the execution efficiency of the algorithm. Finally, this paper designs theoretical verification tests and simulation engineering tests based on the characteristics of the algorithm and the engineering practice of port hoisting machinery photogrammetry. The experimental results demonstrate that the algorithm described in this paper can significantly improve the accuracy of radius fitting results when the data quantity is small and the data quality is poor compared with the traditional algorithm.

A terahertz (THz) superimposed perfect vortex (SPV) beam is generated by using a designed superimposed optimal phase element (SOPE) at 0.3 THz. As the superimposed topological charge changes, the ring radius of THz SPV beams remains almost constant in the experiment, whose relative error is only 0.96%. The perfect vortex property is confirmed. The intensity profile of THz SPV beams is a ring with equally spaced breakpoints. The superimposed topological charge carried can be judged directly by identifying the number of breakpoints. The ring radius is linearly related to the radial wave vector, which can be adjusted. Such THz SPV beams have promising applications for THz fiber communication systems based on vortex beams.

In order to solve the problem of low spraying efficiency and excessive paint waste caused by overspray when the robot automatically sprays irregular plane, a method of spray trajectory planning with boundary-constrained considering spray gun changing posture is proposed. The static spraying model of the spray gun with variable posture, and the dynamic spraying model of the spray gun along the arc path are established separately, an optimization method for the symmetry of coating distribution based on the variable spray angle when the gun spraying along the arc path is proposed. Orthogonal experiment method based on numerical simulation is used to clarify the influence of boundary curve shape and spray gun posture on boundary constraint distance, the prediction of the value range of the boundary constraint distance at the boundary of different curvature radius is realized. Within the range of the value of the boundary constraint, combined with the equal division method of the plane intercept line and the distance search method, a boundary constraint spray path generation algorithm is established by setting a uniform boundary constraint distance value. Finally, a multivariable spraying parameter optimization algorithm based on PSO is established, the spraying velocity, spraying height and spraying angle in the dynamic spraying process are solved, and the coating uniformity is optimized. The effectiveness and feasibility of the proposed spray trajectory planning method is verified by robot spraying experiment for any irregular plane.

In this paper, the wideband characterization of the propagation channel in circular metallic indoor environments is addressed, regarding Body Area Networks and 5G small cells, an analytical model for the dependence of the mean delay and the average delay spread on the circle radius, the working frequency and the distance between the transmitter and the receiver being proposed. The derivation of the model is initially done analytically, based on optical physics, after which simulation results allow to obtain the values of the coefficients. The simulator was previously assessed with measurements at 2.45 GHz in a passenger ferry room with a circular shape. For a random positioning of the transmitter and the receiver, and a given distance between them, it is observed that the mean delay and the delay spread increase linearly with the radius; furthermore, the mean delay increases quadratically with the distance, while the delay spread has a concave parabolic behavior, with the maximum being at a distance equal to the radius. In a practical case, regarding the positioning of an Access Point inside the room, it is recommended that it is done at the circle center, in order to reduce delay spread.

The stirrer design is important in a reverberation chamber measurement system. Previous study shows that the rotating radius of the stirrer plays a key role for the stirrer performance. However, to identify the contribution from the structure, optimizing the stirrer structure while keeping the stirring volume unchanged is necessary. In this paper, when the stirring volume is kept invariant, we show that the detailed structure of stirrers can be optimized to improve the performance but the effect is not significant. A comparative study is given to confirm the effect of zigzag boundaries on the stirrers. Both simulations and measurements confirm the performance improvement, key performance indicators such as field uniformity and correlated angles are simulated and measured.

We report the effects of gold nanoparticles (GNP) on the enhancement of the dose effect and double-strand break (DSB) induction for X-ray monoenergies (10 keV–2 MeV). The overall relative biological effectiveness (RBE) was defined as the product of dose and DSB enhancement. The cellular doses and energy spectra were computed using the PENELOPE (PENetration and Energy LOss of Positrons and Electrons) code. The DNA damage yields were estimated using the MCDS (Monte Carlo damage simulation) code. Considering the production of Auger electrons induced by 7mg/ml GNP, we found that dose enhancement at the 30 keV was ~4.0 for cells with radius $4~\mu \text{m}$ . The DSB induction increased as GNP concentrations increased and was dependent on X-ray energy. These findings demonstrated that the maximum RBE was attained at 30–40 keV and therefore this energy range would be more efficient in cancer cell killing.

The low permeability conglomerate rock has a strong heterogeneity with a wide range of pore radius from submillimeter to nanometer. The traditional digital rock technology is based on micro-CT image with a resolution up to 0.5 µm, which leads to a lower porosity and higher permeability than the laboratory measurements. This paper proposed a new image upscaling method to capture the heterogeneity, and the conglomerate rock in the southern margin of Junggar, Xinjiang Oilfield, was used for validation. The micro-CT scan of the core plug was carried out to obtain the submillimeter porosity (with a resolution of 10-20 μm), and subsamples with a physical size of 1-3 mm3 were taken to obtain the micro-porosity (with a resolution of 1-2 μm). Then a small amount of samples was analyzed with a magnification of 500×, 5000× using scanning electron microscope (SEM) to obtain the nano-porosity image (with a resolution of 20-200 nm). The features of four-scale porosities are integrated to obtain the total porosity of the core plug, and the Brinkman method is used to calculate the permeability based on the multi-scale model. The results obtained by the image upscale method match the experimental data very well, which improves the digital rock technology for the industry practice.

Significant amount of lately research is focused on improving performance of Darrieus type vertical-axis wind turbines (VAWT). This research explains the impact of rotor blade radius on tip-speed ratio, rotational frequency, starting wind speed, manufacturing costs and performance coefficient of Darrieus VAWT. To support the proposed explanations, a prototype with variable rotor blade radius was developed and tested in a wind tunnel. The conclusion is that blade radius should be decreased as much as possible until performance coefficient starts decreasing.

With the current trend towards high-power density electric machines, rotors are being pushed closer to their structural limits. While finite element analysis tools are capable of calculating rotor stresses, there exists a need for accurate and rapid analytical modeling for use in population-based machine design optimizations. This paper presents an analytical model for calculating the stresses due to centrifugal and thermal loading in a surface mounted permanent magnet rotor retained using a composite rotor sleeve. The primary contribution of this paper is the normalization of this model by the outer rotor radius and its use to identify normalized design trends. Using rotor tip speed, the results from the normalized model can be generalized to analyze machines for a wide range of rated speeds. A method for determining optimal rotor sleeve geometry is presented and a generalized design case study is used to validate this model with a finite element analysis tool. Finally, the relationship between maximum rotor tip speed, magnet thickness, and temperature rise is demonstrated using the normalized model. This relationship illustrates an important trade off between magnetic loading and rotor tip speed.

We proposed a U-shaped optical fiber sensor formed by using self-made 3D-printed mold. Compared to previous fabrication methods of U-shaped fiber sensors, the utilized 3D-printed mold can not only effectively control the radius of U-shaped structure but also enhance the mechanical strength of the sensor by filling PDMS into the mold. The measured displacement sensing performance for the fabricated U-shaped fiber sensor with bending radius of 10mm can realize high displacement sensing sensitivity of 53 pm/μm, and the temperature response is −0.51 nm/°C.

The research on characteristics of a single layer differentially-fed quadrature ultra-wide band (UWB) antenna with polarization diversity is discussed in this research work. This antenna has two pairs of identical circular disk-shaped monopoles, along with octagonal ground slots which achieves a good impedance bandwidth. The antenna has a dimension of 54×54×1.6 mm3 and it is modelled on a single side of the substrate. The antenna employs differential feeding using microstrip feed lines to achieve polarization diversity. The effects of feed width (W f ), feed length (L f ), circle radius (r) and ground slot width (W g ) on antenna’s performance are evaluated and simulation results are analyzed. The proposed antenna has a VSWR band of 107 % (2.2 GHz - 10.6 GHz) and provides cross-polarization of −19 dB. A prototype of this antenna is modelled and evaluated; the test observations are close to experimental results. The proposed antenna exhibits nearly bidirectional radiation pattern both in E-plane and H-plane for moderate gain. The findings illustrate that the proposed antenna with these features is an optimal solution for wireless devices in UWB systems.

Cu-Cu joints have potential in high performance electric product. Although the voids in the bonding interface was observed, there was no report on the size distribution and evolution of voids due to ripening. In this paper, the void size distribution under 200 °C for 30, 60 and 120 min is obtained by a specific direction. The average void diameter is 49 nm, 70 nm, and 96 nm for the joint annealed for 30, 60, and 120 min, respectively. A simple kinetic model of ripening is developed, and the relationship between radius and annealing time is in good agreement with experimental data.

This paper discusses the effects of variation of the radius of the ground plane on the performance of a water Dielectric Resonator Antenna. The antenna has been simulated using CST and the radiation parameters have been observed in the frequency range of 0.5 GHz to 8 GHz. The radiation parameters observed are beamwidth, Main Lobe Magnitude, Main Lobe Direction, Angular Width, and Side Lobe Level. Statistical analysis of the DRA’s radiation parameters exhibit minimum variance when radius of the ground plane is 30 mm and frequency range is 4 GHz to 8 GHz, thus appropriate for C-Band applications.

The indirect illumination system with diffuse reflection light-emitting diode (LED) is widely applied in various fields that require high illumination uniformity. On the basis of the Lambertian characteristic of LEDs and the ideal diffuse surface, a design method that features a multiple diffuse reflectance freeform surface is proposed and its related mathematical model is established in this paper. A nonlinear algebraic equation is solved to redistribute the energy emitted by the LED to a uniformity illuminated scene. The outline of the diffuse surface is obtained by solving equations numerically. With the use of the ray tracing software TracePro, simulation results show that the effect is generally the best and the uniformity and efficiency are significantly improved compared with other methods when the proportion between the radius of the target surface and the distance between the LED light source and the target surface is 1:4.

In this paper, a simple design for extending the range of a Wireless Power Transfer (WPT) system is presented. The design consists of a traditional Conformal Strongly Coupled Magnetic Resonance (CSCMR) system that incorporates a repeater resonator, known as the U-loop resonator. Simulated and measured results show that the proposed system with the U-loop provides larger efficiency at transfer distances beyond its original optimal efficiency, achieving a peak efficiency of greater than 70% at a distance equivalent to the diameter of the U-loop, up to distances of 480 mm. The proposed system can also maintain efficiencies greater than 60% irrespective of the angular position of the receiver (RX) around the U-loop.

Orbital angular momentum (OAM) generation based on metasurfaces has attracted tremendous interest due to its potential in capacity enhancement of high-speed wireless communication systems. Reconfigurability is one of the key desired characteristics for the design of future metasurfaces. In this paper, a metasurface taking advantage of vanadium dioxide (VO2) is proposed. The proposed design can generate a non-diffractive OAM beam and achieve the multiple reconfigurability of the topological charge, beam radius, beam deflection angle. The operation frequency can be adjusted by controlling the state of VO2 at terahertz (THz) region. Simulation results demonstrate that the designed metasurface can generate a non-diffractive OAM beam with tunable topological charge and beam radius, propagating along ±x or ±y directions with the controllable deflection angle between 6.74° and 44.77°, ranging from 0.69 THz to 0.79 THz.

This study proposes a dual-circularly polarized Reduced-Surface-Wave (RSW) antenna which has a compact and simple structure by the integration of a via-loaded annular-ring (VLAR)-RSW antenna with a branch-line coupler. The fundamental characteristics of a VLAR-RSW antenna are analyzed through simulations in detail. In general, stronger mutual coupling between RSW antennas occurs in comparison with conventional patch antennas when the element spacing is small, since the effect of the close physical distance becomes larger than the effect of surface wave suppression. It is shown that the VLAR antenna can reduce the mutual coupling than the conventional antenna by selecting the appropriate radius at each element spacing, even when the element spacing is small. A matching circuit is generally required for an annular-ring antenna because of the high input impedance when exciting the TM11 mode. In contrast, for the VLAR-RSW antenna, impedance matching is feasible without a matching circuit by adjusting the distance between the feed position and the shorting vias. Measured results show the performance of the developed dual-circularly polarized antenna is in agreement with the simulation. At 5.8GHz, the measured axial ratios of both polarizations are smaller than 0.6dB and the measured isolation between ports is about 29 dB. Moreover, it is shown that the developed antenna reduces mutual coupling than the conventional patch antenna because of the effect of suppressing surface waves.

The magnetic field sensitivity is the main source of errors in a fiber optic gyroscope (FOG) and the polarization-maintaining (PM) optical fiber coil is a major sensitive source. In this paper, a theory that an orthogonal magnetic field vertical to the light propagating direction in a PM optical fiber coil can induce a non-Faraday nonreciprocal phase difference in a FOG is presented. The theoretical simulation and experimental results show that the orthogonal magnetic drift proportional to the orthogonal magnetic field is the main cause of the axial magnetic field sensitivity in a FOG, which is closely related to the skeleton radius of the optical fiber coil and depends neither on the fiber coil’s size nor the shape. Furthermore, the orthogonal magnetic field sensitivity will increase with decreasing skeleton radius. Aiming at the application demand of miniaturized gyroscope, the research results of this paper have certain guiding significance and engineering application value.

At present, solenoid (helical) coils are widely used in various researches, especially electromagnetic forming (EMF), due to their advantages of simple manufacture and high magnetic field strength. However, in the study of EMF, there are still some defects in the high precision calculation of solenoid coils in the magnetic field the main reason is that the solenoid coil is of non-axisymmetric structure, which is generally equivalent to the 2-D or 3-D axisymmetric structure in practical research. Not only can it ignore the effect of the pitch effect of the solenoid coil, but also causes a certain deviation in the calculation of the magnetic field. Hence, this paper establishes 5 helical coils and 3-D axisymmetric finite element coils models with different layers for comparative analysis. The simulation results show that the magnetic flux density distribution deviation of helical coil and the 3-D axisymmetric coil is small and can be ignored when the coil layers are 1 or 2 layers. However, the number of linear circles increasing, the deviation between the two increases obviously. Therefore, in the study of EMF, the effect of solenoid coil pitch effect on magnetic field calculation can be ignored when the layers, radius and pitch of helical coils are used less whereas the effect of solenoid coil pitch effect on magnetic field calculation must be considered when the layers, radius and pitch of helical coils are used more.

Fiber optic taper is an important component in the CCD coupling, television imaging and night vision device. Increasing need in high-resolution picture transmission devices requires better quality of high-ratio fiber optic taper. The resulting taper shape is important as it affects transmission properties of fiber optic taper. This paper develops a physical model for analyzing the high-ratio fiber optic taper time-dependent fabricating process. Based on the physical model, the evolution of the taper's neckdown profile is analyzed. Simulation results demonstrate that viscosity of materials, furnace geometry, temperature distribution in the furnace and the external tensile force will strongly affect the drawing process. The final shape of fiber optic taper depends on material properties and heating profile. The tensile force, which will affect the evolution process, has a minor influence on the taper's final shape. Based on the understanding of the above analysis, an improved drawing design can be proposed for fabricating large radius fiber optic taper with high ratio.

In this paper, an analytical model is presented to calculate the low frequency magnetic shielding effective (SE) of the spherical shell with a circular aperture and finite conductivity. This model is obtained by the combination of two submodels: the finite conductivity shell without the aperture, and the perfect conductor shell with the aperture. Both the submodels have existing analytical solutions. The first submodel represents the diffusion effect of magnetic field penetration through the conducting shell, and the second one denotes the aperture effect of magnetic field leakage through the aperture. The total magnetic field is the superposition of these from the two submodels. Calculation results are provided for an aluminum spherical shell of radius 0.1m for frequencies between 10Hz and 1MHz. The results are in good agreement with these form 2D axisymmetric finite element simulations. It is shown that there is a critical frequency. Below this frequency, the diffusion effect is dominant and the SE enhances with the increase of frequency. Above this frequency, the aperture effect is dominant and the SE keeps unchanged with the variation of frequency. In addition, the phase shift characteristics are also analyzed for the two effects respectively, and are employed to elucidate the mechanism of the resonance phenomenon of the SE around the critical frequency. Further, the effect of aperture depth is investigated numerically, which shows that increasing the depth has similar effect on SE like reducing aperture radius.

We propose a potentially practical scheme for realizing ultrasensitive size sensor of a single metallic nanoparticles (MNP) in a hybrid nonlinear microcavity. This is achieved by exploiting a well-established microcavity-engineered plasmonic resonance, where a degenerate parametric amplifier (DPA) is embedded into the microcavity driven by a strong pump field and a weak probe pulse. It is shown that the transmission spectrum of the probe pulse exihibits a two-peak splitting and the splitting width depends on the radius. The radius of a single MNP can be inferred from the transmission spectrum by monitoring the width between two peaks. Using experimentally achievable parameters, we identify the detection sensitivity of the sensor can reach approximately 0.198 THz/nm for detecting and sizing of individual MNPs as small as 10 nm in radius.

Electromagnetic forming has attracted more and more attention in the advanced manufacturing field as a promising technology to improve the formability of lightweight alloys at room temperature. Electromagnetic forming employs the electromagnetic force between the drive coil and the workpiece to complete the forming. The low conductivity materials such as titanium alloy usually cannot gain enough electromagnetic force to deformation due to the low induced current on the workpiece. The forming performance of low conductivity material can be improved using high conductivity driver sheet which increases the eddy current and the forming force acted on the workpiece. Some efforts to improve and optimize the performance of the electromagnetic driven forming were made. In this study, a copper driver ring for the electromagnetic driven forming of titanium alloy is proposed based on the electromagnetic force distribution. The effect of the radial dimension of the driver ring on the forming result is studied with the numerical simulation model which is verified by the experiment. It is found that the outer radius of the driver ring mainly effects the maximum forming depth, and the inner radius of the driver ring influences the forming profile of the workpiece. The numerical results suggest that the forming depth can be improved and the forming contour can be adjusted while the proposed driver ring is applied in electromagnetic driven forming.

Propagation of a surface discharge on water is evaluated using simulation results of the voltage/current waveforms and discharge contact area. Voltage/current waveforms are calculated using an exponential function which assumes the resistance of water decreases with increasing discharge contact area. A conductive disk having a given potential is used to model the discharge contact area and the temporal variation of the radius of the disk is discussed as the discharge propagation. The calculation in the current field is replaced by a calculation of the electrostatic field using the similarity between current and electrostatic fields. The calculation of the electrostatic field is conducted by a charge simulation method. The discharge phenomena are classified into two stages which are the breakdown of needle-to-water gap and the surface discharge propagation on water. The electrostatic field calculation at needle-to-water gap is performed to determine the initial discharge contact area. Expansion of the contact area in the creepage direction, is evaluated by the electric field calculation at the edge of the conductive disk. The expansion terminates when the field becomes lower than 26 kV/cm. The velocity of the expansion increases with the applied voltage. The maximum contact radius increases with decreasing conductivity of water under the same applied voltage. The tendency of simulation results of the expansion of the contact area are consistent with the previous observation results of the discharge propagation., IEEE Transactions on Dielectrics and Electrical Insulation, 26(2), pp.439-446; 2019

The investigation of the He-induced W "fuzz" electrical properties was carried out. For the research, an automated experimental setup was designed. The setup was based on a vacuum chamber operated under high vacuum condition (~10-7 Pa). The vacuum diode under investigation comprised of a flat W "fuzz" cathode with an area of about 1 cm2 and a 2 mm radius cylindrical copper anode rounded with a 2 mm radius hemisphere. The cathode-anode distance was ~100 µm. The voltage applied was up to 10 kV. An HV power supply was controlled employing the DAC/ADC module "LCardTM E20-10". This module registered automatically currents and voltages of interest also. As the result, the data on the dielectric strength of the diode with the W "fuzz" cathode were obtained. The effect of the cathode conditioning was demonstrated. An increase in the breakdown electric field strength from about 4•105 V/cm for the very first breakdown up to 9•105 V/cm for the 20th breakdown was registered. In addition, the emissive characteristics of the W "fuzz" cathode were studied in accordance with the Fowler-Nordheim theory. The estimated value of the electric field enhancement factor β near the cathode surface was found to be ~60 before the breakdown and ~80 after the breakdown. The obtained β values were somewhat smaller than the ones obtained by other research groups for the nanostructured W cathodes. This fact should be investigated additionally.

In recent years, a large number of radio base stations and antenna towers have been built in Shenzhen. The height of antenna tower is usually tens of meters, which may increase the probability of lightning strike. The lightning environment of radio base stations has been analyzed by the data accumulated by the lightning location system of Guangdong-Hongkong-Macao. The results show that the lightning occurrence probability in the surrounding domain cannot be increased by signal tower. The lightning parameter is basically the same in inner domain (177 m radius) and outer domain (177–250 m radius). The lightning parameter in the domain around radio base stations which were analyzed is also basically the same as those in Shenzhen.

In order to realize the intelligent inspection of bend tube processing defects, such as the wrinkles and the ovality, a 3D scanning device composed of a linear translation stage and four uniformly distributed laser profilers (LPs) is built in this paper. For the external calibration of this type of device, the major contribution of this paper are: 1) A 3D calibration object composed of three non-collinear target balls (TBs) is designed. Even if the scanning angle of each LP is limited, there are still common geometric features. 2) A frame-by-frame fusion method for scan data from multiple LPs that only requires one set of rail parameters is proposed to avoid the introduction of multiple sets of rail errors that affect equipment calibration and data fusion. When calculating the parameters, the shape error of the TBs after fusing the scan data of each LP is taken as the objective function, and the nonlinear least square method is used to solve the problem. Finally, the scan data fusion can maintain the accuracy and stability of the shape. The fitting error of the TB with a nominal radius of 19.05mm does not increase with the increase of the guideway stroke, the average fitting error of the radius is stable at about 0.0014mm, and the average RMSE of the surface point is stable at about 0.0426mm.

Because the liquid crystal material has fluidity and electrical control characteristics, it is suitable for conformal phased array design, this paper designed a cylindrical conformal phased array antenna based on liquid crystal material. The designed conformal phased array antenna has a center frequency of 15GHz, a 5×5 uniform array, and a cylindrical radius of 80mm, which can achieve gradient gain scanning (14.17dBi-21.4dBi), and the scanning range is ±30°. The designed antenna array has certain practical prospects.

Till recently, measurements of the magnetic field in gas-puff z-pinch implosions were limited to low density and temperatures typically found at very early times and outside the pinch radius ( r≥ 9 mm and t≤ −90 ns). However, recent, more accurate measurements 1 at higher densities and temperatures at various R and Z-locations on the generator at the Weizmann Institute of Science (WIS) have yielded information close to stagnation and beyond. These measurements seem to be inconsistent with earlier 2D radiation-magneto-hydrodynamics simulations using MACH2-TCRE as well as simple snowplow models when using the inductive current notch, pinch length the pinch radius.

New measurements of the magnetic field at several axial position along the column of an imploding plasma column, as a function of radius and time are presented. The optical configuration, efficient in UV-visible light collection, provided simultaneous radial measurement points, along with revoking the use of Abel-inversion in the analysis. These measurements help to assess the true inductance of the plasma column during the implosion, following our previous studies 1 , where there was no satisfactory explanation to the current turnover (“notch”). 2D MHD simulations are presented for the initial gas flow, including the details of the recessed regions in the cathode- anode structure. Synthetic images and the calculated azimuthal magnetic field distribution at stagnation are compared with the previous and present measurements of the field and current profiles.

The interaction of an ultra-intense, ultra-short laser pulse with nano-rods is investigated. The nano-rods consist of two materials with different mass. The interaction leads to the ionisation of the nano-rods and their consecutive Coulomb explosion. A number of simulations are performed to understand the nonlinear optical properties of the electronic subsystem interacting with the driver laser. It is shown that the dynamics of the Coulomb explosions can be controlled by changing the cylinder radius, the cylinder density, the gap between the cylinders, and the laser parameters. The simulations are performed with the help of the plasma simulation code (PSC), which is a Particle-In-Cell (PIC) code. The PSC solves the Vlasov-Maxwell system of equations that describes the time evolution of the particle distribution functions.

Vortex field can be generated by the phase modulated circular transducer array. However, the side lobe of the beam may interfere the transmission and reception of the signals. In order to reduce the influence of side lobe, a phased modulated concentric ring array is proposed in this paper to produce the vortex field with low side lobe. By exploring the far-field radiation patterns of the concentric ring array with different inner circle radius, the number of array elements and the initial phase, we obtain the suitable array arrangement with better radiation pattern. This paper should be of positive significance to the development of underwater sound field detection and identification technology.

Ultrasound sources of an appropriate size and controllable power are crucial for extensive investigations and applications, especially in exploratory experiments needing precise ultrasound stimulations. We designed an acoustic wave funnel (AWF) that changes the ultrasound source to a suitable size and acts as a small ultrasound source suited for widespread experiments and applications. The AWF consists of three parts—two cladded waveguides of different radii connected by a hollow cone. The larger waveguide has the same radius as the transducer, whereas the radius of the smaller waveguide is set for application requirements. Using the cone, the AWF squeezes the acoustic wave from the large transducer into the small output port and produces a small intense acoustic source. Both theoretical analyses and numerical simulations show that AWF works efficiently and exhibits a pretty amplification factor. The AWF is effective and practical in providing a miniaturized acoustic wave source with high intensity. These results indicate that, when requiring a miniaturized ultrasound source in experiments and applications, the AWF is a practical and reliable device.

Through the hydrophone measurement of acoustic fields, this paper experimentally illustrates the spatial distributions of the focusing amplitudes and deviations of a 6144-element fully-electronically focused HIFU phased array with an element spacing of λ/2, and further evaluates its −6 dB focus-steering region. In the measured region of a cylinder 30 mm above the array and with a radius of 90 mm and a height of 170 mm, the ultrasonic spatial focusing is achieved via the acoustic ray theory to compensate each element's initial emitting phase. Experimental results show that the maximal and minimal ones of all maximal peak-to-peak voltages in the measured region are 2.59 V and 0.78 V, respectively. The maximal total, radial and axial focusing deviations are 4.41 mm, 3.71 mm and 3.60 mm, respectively. Besides, considering the maximal peak-to-peak voltages of all focuses decreasing by no more than 6 dB relative to the maximum of 2.59 V, the −6 dB focus-steering region will be at least a cylinder with a radius of 70 mm and a height of 170 mm. In such a region, the minimal one of the maximal peak-to-peak voltages is 1.33 V, while the maximal total, radial and axial focusing deviations are 3.62, 3.06 and 3.60 mm, respectively. Therefore, this 6144-element HIFU phased array shows outstanding ability in fully-electronic ultrasound focusing.

In this paper, the mechanical behavior of silicon nanowires with the hollow-core geometry was investigated using molecular dynamics simulation. The pristine Si nanowires are considered as references to compare the mechanical properties of the hollow-core structures. Our results show that hollow-core silicon nanowires with a cavity volume fraction above 50% have a larger fracture strain compared to nanowires with a smaller cavity. Under uniaxial tensile loading, the computed Young’s modulus decreases as the radius of cylindrical cavity in nanowire increases. To understand the mechanical behavior of hollow-core Si nanowires, the structural evolution of the nanowire with different cavity volume fraction was investigated. It is established that the structure of nanowires with a cavity volume of more than 50% is completely amorphous. We have shown that structural changes in nanowires are the root cause of changes in their mechanical behavior.

The frequency dependencies for the diagonal components of the polarizability tensor of the metallic nanotubes have been obtained. The different approaches to the considering of the surface scattering of electrons have been analyzed. The calculations have been performed for the nanotubes Au, Ag, Cu, Al. It has been established that the location of the maximums of the polarizability and the scattering cross-section depend on the radius of the dielectric core and on the thickness of the metallic nanotube.

In this paper, a mode converter from a rectangular waveguide TE 10 mode to a circular waveguide HE 11 mode for W-band is proposed. The power experiment has confirmed the designed mode converter. The converter consists of two parts: one is to convert the TE 10 mode in the rectangular waveguide into the TE 11 mode in the circular waveguide by using a square-circle transition; the second is based on the coupled wave theory, the TE 11 mode is converted into a Gaussian distributed HE 11 mode by using the waveguide wall smooth radius structure. The mode converter has a simple structure, easy to machine, and avoids the disadvantage of the corrugated mode converter which is prone to breakdown. Through the power experiment, the designed mode converter coincide with the simulation results.

An efficient method for rapid, non-contact scanning of human cornea is presented. The optics utilize two, 101.6-mm diameter off-axis parabolic mirrors fed by a goniometrically scanned, planar mirror. An evaluation system at 650 GHz was built and demonstrated ~ 1.5 mm beam radius on target and ~ 30° x 30° field of view. The system was inspired by confocal laser scanning principles and represents a system design where image acquisition time is limited by SNR, not mechanical translation.

In this paper, an electron-optical system for a Q-band traveling-wave tube (TWT) is proposed to meet the demand of future wireless communications. Based on the electron beam parameters required for the Q-band TWT, a dual-anode electron gun and periodic permanent magnet (PPM) focusing configuration are designed. The CST simulation results show that the beam voltage, current and waist radius of the pencil electron beam are 8.7 kV, 70 mA, and 0.135 mm, respectively. The electron beam can transport through the helix slow-wave structure with a length of more than 100 mm and the static beam transmission can reach over 99.8% in CST simulation.

Using radiofrequency (rf) for heating and levitation of alloy samples is greatly simplified by a passive element, the slotted cold crucible (similar to Faraday shield for rf plasma ion sources), which if properly designed can shape and concentrate the axial (non static) magnetic field profile. The effect is better represented and verified in 3D simulations (very time consuming) as shown here, even if some simplified 1D and 2D models may help understanding. Boundary conditions at large radius are discussed. Moreover, the sensitivity to important parameters (levitated weight vs frequency and power, sizes of crucible, sample conductivity, radius of sample to skin depth ratio) are demonstrated in a schematized 3D geometry, easily parametrized. Finally complete 3D simulation of a realistic design (adequate for clean alloy melting) are also reported.

The exact analytical solution to the problem of scattering of an oblique electromagnetic wave by a metal cylinder in a cold resonant magnetoplasma is found. It is shown that a quasi-electrostatic wave, which wavelength is much smaller than the radius of cylinder, is scattered mostly in the forward direction in terms of energy.

We present the design of a thermal isolator, based on a simple gap in a standard rectangular waveguide with external circular profile. The proposed solution allows to achieve high return loss and low insertion loss by a suitable selection of the of the external radius of the waveguide circular profile, which determines the waveguide wall thickness. High robustness to misalignment is obtained, improving the performance of a recently published work in the same topic.

A magnetized plasma strongly interacts with microwaves, when their angular frequency $\omega$ is around the electron cyclotron resonance (ECR) one, that is $\Omega=e\vert \mathrm{B}^{s}\vert /m_{e}$ , with $\mathrm{B}^{s}$ the static flux density. The case of small ion sources with $\mathrm{B}^{s}\cong 0.5$ to 1 T, where wavelength and plasma chamber radius are comparable, is studied with full wave equations, assuming a collision rate $v$ and a plasma of given density. Wave initially launched in the TE mode from a waveguide (TE 11 for a circular waveguide), aligned with the axis $z$ of a cylindrical plasma chamber and of $\mathrm{B}^{s}$ , are partially converted to $E_{z}$ waves; use of azimuthal symmetry to consider only the $m=1$ component is discussed. Large reflections are sometimes observed as a function of ratio of plasma angular frequency $\omega_{p}(z)$ and $\omega$ , possibly due to model simplification (density constant in $x$ and $y$ ). Extension to off-axis waveguides (perhaps rectangular or coaxial) is mentioned.

This paper focuses on developing an adaptation algorithm for hypotrochoid spiral dynamic optimization using linear adaptive spiral radius and angle by dynamically varying the value for each iteration based on the fitness function value. The adaptive algorithm will help obtain the optimal search point compared to fixed radius and angle in conventional methods. The spiral radius and angle effect show that the spiral movement with a negative radius will boost the process of escaping from converging at local optima. The statistical results on various benchmark functions show that the proposed optimization has performed better than spiral dynamic, adaptive spiral dynamic, and hypotrochoid spiral dynamic algorithms.

Capacitance Level Sensor (CLS) is used to measure liquid level in many of the process industries. The main objective of the work is to optimize a design of novel helical electrode of CLS, in order to enhance the sensitivity and reduce the time response of sensor. The main effecting parameters of the design are considered to be pitch and radius of inner electrode of CLS. These parameters are directly affected on sensor output and time response. If the pitch is considered to be zero, then the helical sensor acts as a cylindrical CLS exhibiting higher response time and higher capacitance output. And if the pitch is considered to be infinity (66 cm in our case) then helical CLS acts as parallel plate CLS exhibiting lower capacitance output and lower time response. Hence the pitch and radius of inner electrode are optimized using Taguchi optimization method. Results showed that pitch of 2.64 cm and 1.08 cm radius of inner electrode gives maximum capacitance output and lower time response as related to that of existing CLS.

The paper presents results of mathematical modeling of transmission and reflection coefficients of a rectangular waveguide with a ferrite probe for selective microwave wattmeters of multimode power. The mathematical modeling was performed for the case of three lower wave types propagating at the multimode operation of the rectangular waveguide in a frequency range of 10–16 GHz. The general equations of transmission and reflection coefficients are given. Change in the radius of the spherical ferrite probe was established not to cause changes in the reflection coefficient depending on the position of this ferrite probe in the waveguide. Only the numerical values of the curve peaks on the graph change. The larger is the radius, the greater are the reflection coefficients. The dependence of the transfer and reflection coefficients on different values of the resonance curve half-width was also investigated. The transmittance was shown to depend weakly on the constant magnetization.

Superdirective antenna can realize high channel capacity of multiple-input multiple-output system (MIMO). The optimization of superdirective scattering by a novel weighting optimizing goal and Dirac-Delta function model is proposed. Both main-lobe and side-lobe characteristics of the lobe are optimized. Compared with the traditional optimization method, which only takes the main-lobe characteristic into consideration, the directivity has improved by 50% (from 6.0 to 9.0). Meanwhile, the radius of the scattering object is only $0.1 \lambda_{0}$, which indicates this antenna is a super-directive antenna.

We develop a model for a dielectric-coated perfectly conducting cylinder, as imaged by a wideband millimeter-wave radar security scanning system. This model images concealed dielectric objects, when attached to realistically curved body parts, including the human arm or leg. The model is compared to that of a planar dielectric slab on a perfectly conducting plane, and it is proven to be nearly identical for dielectrics with thickness of less than half the cylinder radius.