Impedance of a monopole antenna over a ground plane and immersed in a magnetoplasma

A treatment of the input impedance of a monopole antenna over a ground plane covered with a magnetoplasma with any arbitrary direction of the static magnetic field is presented. The analysis is restricted to a cold plasma with uniaxial and quasi-static approximations. It has been found that for parallel and perpendicular directions of the static magnetic field with respect to the ground plane perfect mirror reflections can be obtained. For other directions of the static magnetic field, the reflection is birefringent so that the monopole impedance becomes modified over a dipole impedance. These modifications can be significant under hyperbolic plasma conditions. A short and a long monopole were considered. From laboratory measurements of a long monopole impedance, the resonance cone and the resonances corresponding to the antenna length have been observed.     

Marketing importance and marketing performance measurement of architecture firms in Singapore: an exploratory study

While marketing is a known element of successful practice, architects are yet to be convinced of its full potential. Little was known about the marketing practice in architectural firms in Singapore. Attempts were made to determine the realities of formalized marketing approaches and their importance to architectural firms in Singapore through a questionnaire survey (where 95 architectural firms participated) and follow-up interviews. A total of 34 usable responses were collected. This was investigated using the ‘Architecture Business Development Process’ as a framework, which found evidence to suggest that marketing has been recognized as an important component of architectural practice in Singapore. The results show that the adoption of the ‘marketing concept’ in the architecture profession is still in its formative stages. Architectural firms – and small and medium ones in particular – need to fully capitalize on this area of business knowledge in order to influence, command and understand the market for them to remain financially viable as a practice. Despite little attention being paid to measuring the performance of marketing outcomes, almost all the respondents and interviewees acknowledged its increasing importance. With greater corporate governance, these firms are beginning to realize the significance of marketing, and are evaluating their practices to ride the market for success. This move indicates a positive step in bridging the disparities between architecture practice and design.     

Mechanical properties of carbon fiber/epoxy composites: Effects of number of plies,fiber contents,and angle‐ply layers

Multi‐axial multi‐ply fabric (MMF) composites are becoming increasingly popular as reinforcing materials in high‐performance composites due to their high mechanical properties. This work aimed to study the effects of three variable parameters including fiber contents, numbers of plies, and layer orientations on the mechanical properties of MMF composites. Unidirectional carbon fibers and a two‐part epoxy resin were employed to produce the composite laminates using the manual lay‐up process. It was found that the mechanical properties of composites made with 5‐ply were slightly greater than 3‐ply composites. However, there was no highly significant difference between them. Generally, the angle‐ply of the composites showed the greatest effect on the mechanical properties compared with number of plies and layer orientations. The significant improvements in mechanical properties of the composites were further supported using scanning electron microscopy (SEM). Morphologies of the tensile fracture surfaces of composites revealed that the presence of fiber pulled out results in the creation of voids between the fibers and matrix polymer. This causes the mechanical properties of the composites to be reduced. Finally, the enhancement of mechanical properties of composites clearly confirmed that angle‐ply layer (0°,?35°,0°,+35°,0°) had the most significant reinforcing effect among other parameters evaluated. POLYM. ENG. SCI., 54:2676–2682, 2014. © 2013 Society of Plastics Engineers     

Enhancing the Stability of CuO Thin-Film Photoelectrodes by Ti Alloying

A major drawback for CuO as an efficient photocathode in photoelectrochemical (PEC) water splitting is its instability in aqueous solution. In this paper, we report that Ti alloying can enhance the stability of CuO in PEC water splitting but at the cost of reduced crystallinity and optical absorption, and therefore reduced photocurrent. We further report that a balance between the stability and photocurrent can be realized by a bilayer configuration—a thin Ti-alloyed CuO layer on a pure CuO thin film. Our results indicate that the thickness of the top Ti-alloyed CuO layer should be optimized to realize the best stability and photocurrent.     

Structural,Dielectric, and Magnetic Properties of Ba-Doped Multiferroic Bismuth Ferrite

The main focus of the research was to correlate the microstructure with dielectric and magnetic properties of Bi1-xBaxFeO3 samples. Bi1-xBaxFeO3 samples(x = 0.1, 0.2 and 0.3) were synthesized by the conventional solid-state reaction method using nano-powders of Bi2O3, Fe2O3, and BaCO3. Thereafter, field emission scanning electron microscope and X-ray diffraction(XRD) techniques were used to examine the structure and phase of the samples. Phase analysis by XRD indicated that the single-phase perovskite structure was formed with possible increment in lattice parameter with increasing Ba doping. Complex permeability(u'iand u'i) measured using impedance analyzer confirmed the increase in magnetic property with increasing Ba doping. Finally, dielectric constant(k) was analyzed as a function of temperature at different frequencies. Dielectric constant as high as 2900 was attained in this research for Bi0.8Ba0.2FeO3 sample due to reduction in leakage current at this composition.     

Fabrication and Characterization of CZTS Thin Films Prepared by the Sulfurization of RF-Sputtered Stacked Metal Precursors

In this work, Cu₂ZnSnS₄ (CZTS) thin films were prepared by the sulfurization of metal precursors deposited sequentially via radio frequency magnetron sputtering on Mo-coated soda-lime glass. The stack order of the precursors was Mo/Zn/Sn/Cu. Sputtered precursors were annealed in sulfur atmosphere with nine different conditions to study the impact of sulfurization time and substrate temperature on the structural, morphological, and optical properties of the final CZTS films. X-ray fluorescence was used to determine the elemental composition ratio of the metal precursors. Final CZTS films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). XRD and EDS were combined to investigate the films’ structure and to identify the presence of secondary phases. XRD analysis indicated an improvement in film crystallinity with an increase of the substrate temperature and annealing times. Also indicated was the minimization and/or elimination of secondary phases when the films experienced longer annealing time. EDS revealed slight Sn loss in films sulfurized at 550°C; however, an increase of the sulfurization temperature to 600°C did not confirm these results. SEM study showed that films treated with higher temperatures exhibited dense morphology, indicating the completion of the sulfurization process. The estimated absorption coefficient was on the order of 10⁴ cm^?1 for all CZTS films, and the values obtained for the optical bandgap energy of the films were between 1.33 eV and 1.52 eV.     

Susceptibility of Rhyzopertha dominica to ionizing radiation

The effects of ionizing radiation doses between 1 and 20 krad on all stages of Rhyzopertha dominica were studied. Adult emergence from treated eggs and larvae was prevented by 4 and 8 krad respectively. Doses up to 20 krad to pupae only slightly reduced the emergence of adults. However there was considerable (up to 30 per cent) mortality of the adults within 8 hours of eclosion. The 20 krad dose caused very high mortality of adults from irradiated pupae and of irradiated adults within 3–5 weeks. Complete sterility, as evidenced by the lack of an F₁ generation, was induced in pupae by a dose of 14 krad and in adults by 11·5 krad.     

Centimeter‐Scale and Visible Wavelength Monolayer Light‐Emitting Devices

Monolayer 2D transition metal dichalcogenides (TMDCs) have shown great promise for optoelectronic applications due to their direct bandgaps and unique physical properties. In particular, they can possess photoluminescence quantum yields (PL QY) approaching unity at the ultimate thickness limit, making their application in light‐emitting devices highly promising. Here, large‐area WS₂ grown via chemical vapor deposition is synthesized and characterized for visible (red) light‐emitting devices. Detail optical characterization of the synthesized films is performed, which show peak PL QY as high as 12%. Electrically pumped emission from the synthetic WS₂ is achieved utilizing a transient‐mode electroluminescence device structure, which consists of a single metal–semiconductor contact and alternating gate fields to achieve bipolar emission. Utilizing this aforementioned structure, a centimeter‐scale ( ≈ 0.5 cm²) visible (640 nm) display is demonstrated, fabricated using TMDCs to showcase the potential of this material system for display applications.