Deformation measurement by single spherical near-field intensity measurement for large reflector antenna

This paper presents a new method to obtain the deformation distribution on the main reflector of an antenna only by measuring the electric intensity on a spherical surface with the focal point as the center of the sphere, regardless of phase. Combining the differential geometry theory with geometric optics method, this paper has derived a deformation-intensity equation to relate the surface deformation to the intensity distribution of a spherical near-field directly. Based on the finite difference method (FDM) and Gauss-Seidel iteration, deformation has been calculated from intensity simulated by geometrical optics (GO) and physical optics (PO) methods, respectively, with relatively small errors, which prove the effectiveness of the equation proposed in this paper. By means of this method, it is possible to measure the deformation only by scanning the electric intensity of a single hemispherical near-field whose area is only about 1/15 of the aperture. The measurement only needs a plane wave at any frequency as the incident wave, which means that both the signals from the outer space satellite and the far-field artificial beacon could be used as the sources. The scanning can be realized no matter what attitude and elevation angle the antenna is in because the size and angle of the hemisphere are changeable.

Problem of Determining the Anisotropic Conductivity in Electrodynamic Equations

For a system of electrodynamic equations, the inverse problem of determining an anisotropic conductivity is considered. It is supposed that the conductivity is described by a diagonal matrix σ(x) = $${\text{diag}}({{\sigma }_{1}}(x),{{\sigma }_{2}}(x)$$, σ3(x)) with $$\sigma (x) = 0$$ outside of the domain Ω = $$\{ x \in {{\mathbb{R}}^{3}}|\left| x \right| < R\} $$, $$R > 0$$, and the permittivity ε and the permeability μ of the medium are positive constants everywhere in $${{\mathbb{R}}^{3}}$$. Plane waves coming from infinity and impinging on an inhomogeneity localized in Ω are considered. For the determination of the unknown functions $${{\sigma }_{1}}(x)$$, $${{\sigma }_{2}}(x)$$, and $${{\sigma }_{3}}(x)$$, information related to the vector of electric intensity is given on the boundary S of the domain Ω. It is shown that this information reduces the inverse problem to three identical problems of X-ray tomography.

Selective effect of irreversible electroporation on parenchyma of the pancreas and its vascular structures - an in vivo experiment on a porcine model

Irreversible electroporation is a local, non-thermal ablation method, where short electrical pulses of high voltage lead to changes in cell membrane permeability and cell death. Recent experimental studies have shown that it does not lead to damage of blood vessels, nerves, bile duct or ureters. The aim of our experimental study was to evaluate the negative effect of irreversible electroporation regarding damage to the vascular wall and porcine pancreatic tissue. Irreversible electroporation of the pancreas was performed in 6 pigs after medial laparotomy. Irreversible electroporation was applied to each pig to the splenic lobe of the pancreas in order to assess damage to the pancreatic tissue and to the duodenal lobe of the pancreas to assess damage to the vascular structure of the pancreatic tissue. Higher ablation electric intensity (minimum 500 V/cm – maximum 1,750 V/cm, step 250 V/cm) in 90 μs pulses was utilized on each pig. After 7 days, macroscopic and microscopic evaluations of en bloc resected specimen (pancreas with duodenum) were performed. During 7 post-ablation days, no deaths or clinical worsening occurred in any of the pigs. Necrotic changes in the pancreatic tissue were recorded at an electric intensity of 750 V/cm. Changes in the outer layers of the wall of the arteries and veins occurred at 1,000 V/cm. Transmural vascular wall damage was not recorded in any case. Irreversible electroporation allows for relatively efficient cell death in the target tissues. Our independent experimental work confirms the safety of this method towards vascular structures located in the ablation zone.

Electropolishing Parameters for Nickel Coating Replacement of Hard Disk Actuator Arm

For hard disk drives (HDD), loose particles that are trapped between the head and disk during HDD operations can create damages to HDD. As a result, a nickel coating is used to minimize their loose particles. However, nickel is one of many carcinogenic metals known to be an environmental and occupational pollutant. Therefore, an electropolishing technique is proposed to replace a nickel coating process. To do experiments, a stainless steel actuator arm is set as an anode, a steel plate is set as a cathode, and a sulfuric acid is used as an electrolyte. With a design of experiment (DOE) technique, four parameters of the electropolishing technique which are an electrolyte concentration, an electrolyte temperature, a polishing time, and an electric intensity, are tested. The experiment result shows that the electrolyte concentration and electric intensity are not made any change for loose particles counts with liquid particle counter (LPC) testing whereas only two parameters which are the electrolyte temperature and polishing time play significant roles for LPC values. The lower LPC shows the smaller percentage of HDD failure. From these Box-Behnken DOE experiments, the optimal solution is 90 Celsius of the electrolyte temperature and 40 minutes of the polishing time. Although, the electrolyte concentration and electric intensity are not made any impact for LPC but they are set as a standard to be 0.2 mol/l and 0.25 A/cm2 consequently. With these parameters, the predicted LPC is only 442,106 counts/part. This LPC is still in an accepted level standard that will not cause failure to HDD. This means that the electropolishing technique initially can be used to replace a nickel coating process without loose particles.