Development of custom lead shield and strainer for targeted irradiation for mice in the gamma cell chamber

We presented a development of a custom lead shield and mouse strainer for targeted irradiation from the gamma-cell chamber. This study was divided into two parts i.e., to (i) fabricate the shield and strainer from a lead (Pb) and (ii) optimize the irradiation to the mice-bearing tumour model with 2 and 8 Gy absorbed doses. The lead shielding was fabricated into a cuboid shape with a canal on the top and a hole on the vertical side for the beam path. Respective deliveries doses of 28 and 75 Gy from gamma-cell were used to achieve 2 and 8 Gy absorbed doses at the tumour sites.

Enhanced Light-Harvesting in Single Rectangular Silicon Nanowires

Light-harvesting of single nanowires is very crucial to enhance conversion efficency of solar cells. Here, we systematically examined light-harvesting of single rectangular nanowires and found that light-harvesting of rectangular nanowires is increased contrasted with that of square nanowires, which is because decreasing the horizontal side can strengthen the leaky mode resonances and increasing the vertical side can increase the length of the light path. Numerical results showed that the photocurrent of single rectangular silicon nanowires is dramatically enhanced by 82.9% or 276.5% in comparison with that of square nanowires with the same vertical side (1000 nm) or horizontal side (100 nm), respectively. This work indicates that light-harvesting of single nanowires can be improved by decreasing the symmetry from the square to rectangular nanowires.

Improving Absorption in Single Silicon Nanowires by Symmetry-breaking Design from Square to Rectangular Cross-section

Light absorption in single nanowires (NWs) is one of the most crucial factors for photovoltaic applications. In this paper, we carried out a detailed investigation of light absorption in single rectangular NWs (RNWs). We show that the RNWs exhibit improved light absorption compared with the square NWs (SNWs), which can be attributed to the symmetry-breaking structure that can increase the light path length by increasing the vertical side and the enhanced leaky mode resonances (LMRs) by decreasing the horizontal side. We found that the light absorption in silicon RNWs can be enhanced by engineering the horizontal and vertical sides, the photocurrent is significantly increased by 276.5% or 82.9% compared with that of the SNWs with the same side length as the horizontal side of 100 nm or the vertical side of 1000 nm, respectively. This work provides an effective way for designing high-efficiency single NW photovoltaic devices based on the symmetry breaking from the SNWs to RNWs.

Effect of Nanoparticles and Base Fluid Types on Natural Convection in a Three-Dimensional Cubic Enclosure

Convective heat transfer using nanofluids play an important role in thermal applications such as heat exchangers, automotive industries, and power generation. In this work, a numerical analysis is conducted to examine the heat transfer of nanofluid in three-dimensional differentially heated cavity. The finite volume method-based SIMPLEC algorithm is used to solve the system of the mass, momentum, and energy transfer governing equations. The left and the right vertical side walls of the cube are maintained at constant temperatures T C and T H , respectively. The remaining walls of the cube are insulated. Effective thermal conductivity and viscosity of the nanofluid are determined using Brinkman and Maxwell models, respectively. Studies are carried out for three types of nanoparticles and volume fractions of nanoparticles ( 0 – 5 % ). The effects of two binary liquid mixtures as a base fluid (propylene glycol-water and ethylene glycol-water) are also examined. Results show an enhancement of 13 % for Al2O3-EG in comparison to pure ethylene glycol in the case of Ra = 10 3 . In addition, heat transfer enhancement was increased with the rise of nanoparticle volume fractions.

Inhibition and Hydrodynamic Analysis of Twin Side-Hulls on the Porpoising Instability of Planing Boats

A comparative analysis of the hydrodynamic performance of a planing craft in the monomer-form state (MFS) and trimaran-form state (TFS) was performed, and the inhibition mechanism of twin side-hulls on porpoising instability was evaluated based on the numerical method. A series of drag tests were conducted on the monomer-form models with different longitudinal locations of the center of gravity (Lcg); the occurrence of porpoising and the influence of Lcg on porpoising by the model was discussed. Then, based on the Reynolds-averaged Navier–Stokes (RANS) solver and overset grid technology, numerical simulations of the model were performed, and using test data, the results were verified by incorporating the whisker spray equation of Savitsky. To determine how the porpoising is inhibited in the TFS, simulations for the craft in the MFS and TFS when porpoising were performed and the influence of side-hulls on sailing attitudes and hydrodynamic performance at different speeds were analyzed. Using the full factor design spatial sampling method, the influence of longitudinal and vertical side-hull placements on porpoising inhibition were deliberated, and the optimal side-hull location range is reported and verified on the scale of a real ship. The results indicate that the longitudinal side-hull location should be set in the ratio (a/Lm) range from 0.1 to 0.3, and vertically, the draft ratio (Dd/Tm) should be less than 0.442. Following these recommendations, porpoising instability can be inhibited, and lesser resistance can be achieved.

How universal is the vibration-velocity controlled granular convection?

Recently, a number of articles have reported that granular convection induced by continuous vibration is controlled by vibration velocity, in contrast with some previous studies. We have reported such an example for the Brazil nut effect when the vibration is given discontinuously, using a one-layer granular bed in a cell with down-facing side walls. Here, we report the effect of vibration phase and wall friction using the same experimental system, to confirm rising motion of an intruder induced by granular convection is again governed by vibration velocity. We compare two different cases of vibration phase for giving intermittent vibration cycles, and found one, in which granular packing is well established before grains start to lose contacts due to vibration, provides distinctly high reproducibility. We further control the side wall friction using a microfabrication technique, and found that significantly high reproducibility is attained in a cell with vertical side walls when a millimeter texture is introduced on the side walls. Our results indicate that the granular convection is universally controlled by vibration velocity. The present study opens a way to conduct highly reproducible experiments on granular dynamics, which is indispensable for deep physical understanding of granular flow and segregation.

Light Management in Single Rectangular Silicon Nanowires for Photovoltaic Applications

Light management in single nanowires (NWs) is of great importance for photovoltaic applications. However, square NWs (SNWs) can limit their light-trapping ability due to high geometrical symmetry. In this work, we present a detailed study of light management in single silicon NWs with a rectangular cross-section (RNWs). We demonstrate that the RNWs exhibit significantly enhanced light-harvesting compared with the SNWs, which can be attributed to the symmetry-broken structure that can orthogonalize the direction of light illumination and the leaky mode resonances (LMRs). That is, the rectangular cross-section can simultaneously increase the light path length by increasing the vertical side and reshape the LMR modes by decreasing the horizontal side. We found that the light absorption can be engineered via tuning the horizontal and vertical sides, the photocurrent is significantly enhanced by 276.5% or 82.9% in comparison with that of the SNWs with the same side length as the horizontal side of 100 nm or the vertical side of 1000 nm, respectively. This work advances our understanding of how to improve light-harvesting based on the symmetry breaking from the SNWs to RNWs and provides an effective way for designing high-efficiency single NW photovoltaic devices.

Stability Analysis of Jointed Rock Slope by Strength Reduction Technique considering Ubiquitous Joint Model

In order to study the failure mechanism and assess the stability of the inlet slope of the outlet structure of Lianghekou Hydropower station, the strength reduction method considering the ubiquitous joint model is proposed. Firstly, two-dimension numerical models are built to investigate the influence of the dilation angle of ubiquitous joints, mesh discretization, and solution domain size on the slope stability. It is found that the factor of safety is insensitive to the dilation angle of ubiquitous joints and the solution domain size but sensitive to the mesh discretization when the number of elements less than a certain threshold. Then, a complex three-dimension numerical model is built to assess the stability of the inlet slope of the outlet structure of Lianghekou Hydropower station. During the strength reduction procedure, the progressive failure process and the final failure surface of the slope are obtained. Furthermore, the comparison of factors of safety obtained from strength reduction method and analytical solutions indicates that the effect of vertical side boundaries plays an important role in the stability of jointed rock slope, and the cohesive force is the main contribution to the resistant force of vertical side boundaries.

Effect of the Direction of Uniform Horizontal Magnetic Field on the Linear Stability of Natural Convection in a Long Vertical Rectangular Enclosure

The effect of the direction of external horizontal magnetic fields on the linear stability of natural convection of liquid metal in an infinitely long vertical rectangular enclosure is numerically studied. A vertical side wall is heated and the opposing vertical wall is cooled both isothermally, whereas the other two vertical walls are adiabatic. A uniform horizontal magnetic field is applied either in the direction parallel or perpendicular to the temperature gradient. In this study, the height of the enclosure is so long as to neglect the top and bottom effects where returning flow takes place, and thus the basic flow is assumed to be a parallel flow and the temperature field is in heat conduction state. The Prandtl number is limited to the value of 0.025 and horizontal cross-section is square. The natural convection is monotonously stabilized as increase in the Hartmann number when the applied magnetic field is parallel to the temperature gradient. However, when the applied magnetic field is perpendicular to the temperature gradient, it is once destabilized at a certain low Hartmann number, but it is stabilized at high Hartmann numbers.

A Novel Asymmetric Patch Reflectarray Antenna with Ground Ring Slots for 5G Communication Systems

The narrow bandwidth and low gain performances of a reflectarray are generally improved at the cost of high design complexity, which is not a good sign for high-frequency operation. A dual resonance asymmetric patch reflectarray antenna with a single layer is proposed in this work for 5G communication at 26 GHz. The asymmetric patch is developed from a square patch by tilting its one vertical side by a carefully optimized inclination angle. A progressive phase range of 650° is acquired by embedding a circular ring slot in the ground plane of the proposed element for gain improvement. A 332-element, center feed reflectarray is designed and tested, where its high cross polarization is suppressed by mirroring the orientation of asymmetric patches on its surface. The asymmetric patch reflectarray offers a 3 dB gain bandwidth of 3 GHz, which is 4.6% wider than the square patch reflectarray. A maximum measured gain of 24.4 dB has been achieved with an additional feature of dual linear polarization. Simple design with wide bandwidth and high-gain of asymmetric patch reflectarray make it suitable to be used in 5G communications at high frequencies.