The self-focusing condition of a charged particle beam in a resistive plasma

The self-focusing condition of a charged particle beam in a resistive plasma has been studied. When plasma heating is weak, the beam focusing is intensified by increasing the beam density or velocity. However, when plasma heating is strong, the beam focusing is only determined by the beam velocity. Especially, in weak heating conditions, the beam trends to be focused into the centre as a whole, and in strong heating conditions, a double-peak structure with a hollow centre is predicted to appear. Furthermore, it is found that the beam radius has a significant effect on focusing distance: a larger the beam radius will result in a longer focusing distance. Simulation results also show that when the beam radius is large enough, filamentation of the beam appears. Our results will serve as a reference for relevant beam–plasma experiments and theoretical analyses, such as heavy ion fusion and ion-beam-driven high energy density physics.

Smartphone videoscopy: Recent progress and opportunities for biosensing

Smartphone is emerging as a portable analytical biosensing platform in many point-of-care (POC) applications such as disease diagnostics, environmental monitoring, and food toxin screening. With the recent advancement of imaging technologies on the smartphone, the manual control of acquisition settings (e.g., exposure time, frame rate, focusing distance, etc.) has already been expanded from the photo to the video capturing mode. In modern smartphone models, high frame rate (above 100 fps) can be achieved to bring in a new temporal dimension to the smartphone-supported POC tests by recording high-definition videos. This opens up a new analytical method defined as smartphone videoscopy. In this review, the recent development of smartphone videoscopy is summarized based on different POC applications. Representative examples of smartphone videoscopy systems and how these time-dependent measurements could open up new opportunities for POC diagnostics are discussed in detail. The advances demonstrated so far illustrate the promising future of smartphone videoscopy in biosensing, POC diagnostics, and time-resolved analysis in general.

Real-time per-pixel focusing method for light field rendering

Light field rendering is an image-based rendering method that does not use 3D models but only images of the scene as input to render new views. Light field approximation, represented as a set of images, suffers from so-called refocusing artifacts due to different depth values of the pixels in the scene. Without information about depths in the scene, proper focusing of the light field scene is limited to a single focusing distance. The correct focusing method is addressed in this work and a real-time solution is proposed for focusing of light field scenes, based on statistical analysis of the pixel values contributing to the final image. Unlike existing techniques, this method does not need precomputed or acquired depth information. Memory requirements and streaming bandwidth are reduced and real-time rendering is possible even for high resolution light field data, yielding visually satisfactory results. Experimental evaluation of the proposed method, implemented on a GPU, is presented in this paper.

Ultrasound Axicon: Systematic Approach to Optimize Focusing Resolution through Human Skull Bone

The use of axicon lenses is useful in many high-resolution-focused ultrasound applications, such as mapping, detection, and have recently been extended to ultrasonic brain therapies. However, in order to achieve high spatial resolution with an axicon lens, it is necessary to adjust the separation, called stand-off (δ), between a conventional transducer and the lens attached to it. Comprehensive ultrasound simulations, using the open-source k-Wave toolbox, were performed for an axicon lens attached to a piezo-disc type transducer with a radius of 14 mm, and a frequency of about 0.5 MHz, that is within the range of optimal frequencies for transcranial transmission. The materials properties were measured, and the lens geometry was modelled. Hydrophone measurements were performed through a human skull phantom. We obtained an initial easygoing design model for the lens angle and optimal stand-off using relatively simple formulas. The skull is not an obstacle for focusing of ultrasound with optimized axicon lenses that achieve an identical resolution to spherical transducers, but with the advantage that the focusing distance is shortened. An adequate stand-off improves the lateral resolution of the acoustic beam by approximately 50%. The approach proposed provides an effective way of designing polydimethylsiloxane (PDMS)-based axicon lenses equipped transducers.

CONVERGENCE TUNING OF SOLAR POWER FOR ENHANCED ENERGY HARVESTING

There is a crucial need for sustainable progress in the field of energy saving in rational time. This paper shows the effect of solar energy in photovoltaic with a Fresnel convex Lens. With the use of this Lens it has been studied that there is unbelievable improvement in various parameters of photovoltaic nature. With the use of the Fresnel lens the concentration of the system has been enhanced in commendable time. In order to diminish the losses from reflection, proper photon management has been implemented. This paper describes an approach in scheming of concentrator module. Small size sub-module ,each of which 2×2 cm2 aperture and 15cm focusing distance are united in a fully hermetic module which is resistance to the environmental effects. Fresnel’s Lens has a composite construction and comprise of a silicate glass and a thin refractive profile made of transparent silicon. These advances concern the two main mechanisms of the system, the optics and the cell, as well as their mixing inside a complete module. The projected system can help in reducing the dependency by fossils fuel in the environment.

Optimization and Analysis of Alvarez Lens

Alvarez lens is one of the free form lens designs. After optimized, the focusing distance curve of Alvarez lens keeps smoothly when Δd increased. We also found the effects of the affective factors, and the good performances of geometric image and illumination surface analysis.

Electron Beam Welding of Duplex Stainless Steel with Regulated Heat Input

This paper analyses the current state of welding duplex stainless steel (DSS). Despite of well-known procedures of welding DSS by standard methods, nowadays modern technologies brings several issues. Electron beam welding showed the problems with achieving the similar phase composition to base metal. By changing the focusing distance and using the post-heating it was possible to bring extra heat input to weld joint what promoted the creation of austenite. Post-heating was performed by additional electron beam pass. By modification of welding procedure it was possible to obtain the phase composition very similar to base metal.