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A metasurface reflector-backed wideband planar antenna is designed for millimeter-wave (mmWave) applications. A simple meandering structure is used for radiation element design, while the back side consists of a partial ground plane and parasitic elements. The utilization of meander-shaped element led to small antenna dimensions. The partial ground plane is used to achieve wide bandwidth, while the parasitic elements are used to improve the impedance matching toward higher frequency bands. To achieve high gain and directional radiation characteristics, an array of metasurfaces is placed behind the radiating element. It is observed from the simulated results that the proposed antenna system offers 17.72 GHz of impedance bandwidth in the operating range of 22.28–40 GHz, while the measured impedance bandwidth is noted to be 15.8 GHz, ranging from 23 to 38.8 GHz. Furthermore, it is observed that a metasurface-based planar antenna tends to achieve a peak gain of ≈9 dBi in the band of interest.
Studies up to great extent have focused on investigating the possible consequences of supervisor incivility in organizations; however, surprisingly very little research has concentrated on its antecedents. Drawing on affective event theory, the aim of this study is to identify how role overload may cause the supervisor behavior uncivil toward their subordinates in the project environment by examining the mediating role of emotional exhaustion and moderating effect of time consciousness. Data were collected from both supervisors and their immediate subordinates from project-based organizations of Pakistan. After data consolidation, the final sample was 296 supervisor–subordinate dyads. The results revealed that supervisor role overload and emotional exhaustion is positively related with supervisor incivility and emotional exhaustion mediates this relationship. Time consciousness moderates the link between supervisor role overload and emotional exhaustion. The practical and theoretical implications of our findings are provided.
This study reported the justification and selection of acceptable γ criteria with respect to low (6 MV) and high (15 MV) photon beams for intensity-modulated radiation therapy quality assurance (IMRT QA) using the Gafchromic external beam therapy 3 (EBT3) film.
Materials and methods
Five-field step-and-shoot IMRT was used to treat 16 brain IMRT patients using the dual-energy DHX-S linear accelerator (Varian Medical System, Palo Alto, CA, USA). Dose comparisons between computed values of the treatment planning system (TPS) and Gafchromic EBT3 film were evaluated based on γ analysis using the Film QA Pro software. The dose distribution was analysed with gamma area histograms (GAHs) generated using different γ criteria (3%/2 mm, 3%/3 mm and 5%/3 mm) for the 6 and 15 MV photon beams, to optimise the best distance-to-agreement (DTA) criteria with respect to the beam energy.
From the comparison between the dose distributions acquired from the TPS and EBT3 film, a DTA criterion of 3%/2 mm showed less dose differences (DDs) with passing rates up to 93% for the 6 MV photon beams, while for the 15 MV a relaxed DTA criterion of 5%/3 mm was consistent with the DD acceptability criteria with a 95% passing rate.
Our results suggested that high-energy photon beams required relaxed DTA criteria for the brain IMRT QA, while low-energy photon beams showed better results even with tight DTA criteria.
This work reports our study to commission a radiochromic film dosimetry system using the timely EBT3 film. We carried out dosimetric evaluations on different characteristics of photon beams (e.g., flatness, symmetry and penumbra) in radiation dose delivery.
Materials and Methods
A Varian linear accelerator producing 6 and 15 MV photon beams with 120 multi-leaf collimator was used in this study. PTW ionisation chamber was used to measure the beam characteristics such as symmetry, flatness and penumbra and these measurements were used to commission the radiochormic EBT3 film dosimetry system. The results of irradiated films were analysed using the radiochromic film QA Pro software 2016.
The measured film doses were analysed at two different colour channels (green and red) using two scanning geometries (i.e., upper or lower side of film facing the scanner light source) at two dose levels (10 and 40 Gy). The difference between the ionisation chamber and film results was found insignificant and within the acceptable range as per the World Health Organisation standard.
Results of the comparison between the ionisation chamber and film measurements show that our radiochormic EBT3 film dosimetry system is reliable and cost-effective in the output measurement of a linear accelerator. Our measurements confirm that our EBT3 film dosimetry agreed well with the ionisation chamber, and can be used as a re-validation tool for linear accelerator quality control.
Magneto polymer matrix composites (MPMC) is a new class of magnetic polymer materials which are being developed and under investigation as potential materials for tomorrow’s aircraft structures. It encompasses magnetic, particulate strengthening (dispersion strengthening) as well as fiber reinforcement/strengthening characteristics which are sought out to be utilized toward making efficient future aerospace composite materials. Various types of ferrites including barium, cobalt, iron, and strontium were explored for being used in making new composites. Here a comprehensive review of the synthesis, structure, properties, thermodynamics, surface chemistry, and phase transformations of individual ferrites and clusters of ferrites as fillers is presented. In particular a discussion about the rational control of the mechanical, physical, thermal, electrical, and magnetic properties of magneto polymer matrix composites through surface functionalization, modification, emulsification/compounding/blending, heat treatment (phase transformation and separation), and control of processing conditions (temperature, pressure and geometry of mold) is provided. These smart materials have a wide range of potential applications in medicine, drug delivery, bio imaging, bio marking, tissue engineering, electromagnetic interference (EMI) and electromagnetic force (EMF) shielding, and as competent materials for aerospace structural applications.
Bulk metallic glass and their composites are unique new materials which have superior mechanical and structural properties as compared to existing conventional materials. Owing to this, they are potential candidates for tomorrow’s structural applications. However, they suffer from disadvantages of poor ductility and little or no toughness which render them brittle and they manifest catastrophic failure on the application of force. Their behavior is dubious and requires extensive experimentation to draw conclusive results. In present study, an effort has been made to overcome this pitfall by simulation. A quantitative mathematical model based on KGT theory has been developed to describe nucleation and growth of second phase dendrites from melt in glassy matrix during solidification. It yields information about numerical parameters necessary to understand the behaviour of each individual element in multicomponent sluggish slurry and their effect on final microstructural evolution. Model is programmed and simulated in MATLAB®. Its validation is done by comparison with identical curves reported in literature previously for similar alloys. Results indicate that the effect of incorporating all heat transfer coefficients at macroscopic level and diffusion coefficients at microscopic level play a vital role in refining the model and bringing it closer to actual experimental observations. Two types of hypo and eutectic systems namely Zr65Cu15Al10Ni10 and Zr47.5Cu45.5Al5Co2 respectively were studied. Simulation results were found to be in good agreement with prior simulated and experimental values.
Theoretical studies have been performed on the interaction of short
laser pulse with metals. The results of the theoretical model indicate
that heat conduction would not be uniform from focal spot or crater at the
surface of target metal, when an ultra short laser will interact with the
metal. The electromagnetic radiations of laser induce electric field
inside the target that is responsible for the induction of current
density, which causes electronic heat conduction in the direction of
current density. Such an effect is dominant for laser pulse having
duration less than of the order of sub-picoseconds. This mode will open a
new significant field of study to discuss laser metal interaction for
ultra short laser pulses.
This paper represents the results of a study of angular distribution
of laser produced ions (LPI) of Al, Cu, and Ag. The angular distribution
is studied by CR-39 (SSNTD) and ion assisted sputtering experiments. A
Q-Switched Nd:YAG laser (1.064 μm, 1.1 MW) with 10 mJ pulsed energy
was used to produce the Ag ions, which were detected by CR-39 detector
mounted at −17.5°, 0°, 17.5°, 30°, 60°, and
90° from the normal to the target placed at a distance of 9 cm from
the target. Etched CR-39 detectors then observed under the Motic DMB
Series optical microscope. A bunch of ions was detected along the normal
of target due to self generated collimation of ions. This is termed as
Forward Peaking of Laser Produced Ions. Similar results were also observed
from sputtering of polished Al substrate by laser produced ions of Cu and
Sputtering of polished Cu substrate by laser produced ions of Al. The
surface morphology of the ion irradiated samples were observed under the
Scanning Electron microscope (SEM) S 300 Hi-tech. Formation of a circular
damage on the surface of the substrates by irradiation conforms the ions
collimation along the normal or Forward Peaking of ions.
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