In this paper, we report that reversals of the large-scale circulation in two-dimensional Rayleigh–Bénard (RB) convection can be suppressed by imposing sinusoidally distributed heating to the bottom plate. We examine how the frequency of flow reversals depends on the dimensionless wavenumber $k$ of the spatial temperature modulation with various modulation amplitude $A$. For sufficiently large $k$, the flow reversal frequency is close to that in the standard RB convection under uniform heating. However, when $k$ decreases, the frequency of flow reversal gradually becomes lower and can even be largely reduced. Furthermore, we examine the growth of the corner roll and the global flow structure based on Fourier mode decomposition, and reveal that the size of the corner roll diminishes as the wavenumber decreases. The reason is that the regions occupied by the cold phase can absorb heat from the hot plumes and thus lower their temperature, which reduces the corner roll's kinetic energy input provided by the buoyancy force, and weakens the feeding process of the corner rolls. This results in the locking of the corner roll into a smaller region near the corner, making it harder for a reversal to occur. Using the concept of horizontal convection caused by non-uniform heating, we find a relevant parameter $k/A$ to describe briefly how the reversal frequency depends on wavenumber and modulation amplitude. The present work provides a new way to control the flow reversals in RB convection through modifying temperature boundary conditions.

We describe the motivation and design details of the ‘Phase II’ upgrade of the Murchison Widefield Array radio telescope. The expansion doubles to 256 the number of antenna tiles deployed in the array. The new antenna tiles enhance the capabilities of the Murchison Widefield Array in several key science areas. Seventy-two of the new tiles are deployed in a regular configuration near the existing array core. These new tiles enhance the surface brightness sensitivity of the array and will improve the ability of the Murchison Widefield Array to estimate the slope of the Epoch of Reionisation power spectrum by a factor of ∼3.5. The remaining 56 tiles are deployed on long baselines, doubling the maximum baseline of the array and improving the array u, v coverage. The improved imaging capabilities will provide an order of magnitude improvement in the noise floor of Murchison Widefield Array continuum images. The upgrade retains all of the features that have underpinned the Murchison Widefield Array’s success (large field of view, snapshot image quality, and pointing agility) and boosts the scientific potential with enhanced imaging capabilities and by enabling new calibration strategies.

The crystal–melt interfacial free energy is an important quantity governing many kinetic phenomena including solidification and crystal growth. Although general calculation methods are available, it is still difficult to obtain the interfacial energies that differ only slightly due to anisotropy. Here, we report such a calculation of Al crystal–melt interfacial energy based on the general framework of the capillary fluctuation method (CFM). The subtle dependence of both the melting temperature and interfacial free energy at melting temperature on the crystal interface orientation was examined. For Al, the average melting temperature is obtained at 934.79 ± 5 K and the orientationally averaged mean interfacial free energy is 98.35 mJ/m2. In addition, the anisotropy of the interfacial free energy is found weak, nevertheless with the values ranked as γ100 > γ110 > γ111.

In the past 10 years, under the common problems of unemployment of people with a higher education and the devaluation of diplomas, the concepts and practices of higher education governance have emerged and have gradually been embedded in university operations. Higher education in Taiwan faces the same problems as the rest of the world. Thus, guided by policies of the Taiwanese Ministry of Education (TMOE) and fuelled by the media, the education-job gap is becoming a discursive truth. With this background, the TMOE has invested numerous resources to establish an information system (IS) that attempts to guide the direction of university education using information technology. If the IS is poorly designed, the scope of its side effects and harm will be magnified by a massive number of IS users and the characteristics of procedure standardisation. We suggest another form of action — IS competition, in which more positive social changes can be created. Based on the analysis of the available data, the action of IS competition does have a positive impact on society.

A complete classification is given of pentavalent symmetric graphs of order $30p$, where $p\ge 5$ is a prime. It is proved that such a graph ${\Gamma }$ exists if and only if $p=13$ and, up to isomorphism, there is only one such graph. Furthermore, ${\Gamma }$ is isomorphic to $\mathcal{C}_{390}$, a coset graph of PSL(2, 25) with ${\sf Aut}\, {\Gamma }=\mbox{PSL(2, 25)}$, and ${\Gamma }$ is 2-regular. The classification involves a new 2-regular pentavalent graph construction with square-free order.

The Lower Yangtze foreland basin is situated to the northwest of the early Palaeozoic Wuyi–Yunkai orogen in South China. To demonstrate its provenance history and the denudation of the orogen, seven sandstone samples were collected from the upper Ordovician to Silurian strata for U–Pb dating. The zircons show a broad range of ages that can be linked with the ages of specific units in the Wuyi–Yunkai orogen. The zircon spectra in the late Ordovician samples are similar to those in the pre-orogenic strata, suggesting a recycled source. The dominant age population of 880–740 Ma in the early Llandovery samples indicates that the middle Neoproterozoic volcanic rocks were the primary source. A significant age population of 460–425 Ma in the late Llandovery to Wenlock samples reflects the fact that the synorogenic magmatic and metamorphic rocks were exposed to provide detritus. The youngest zircons from the uppermost Silurian strata yield an age of 425 Ma, which approximates the inferred depositional age. This age, together with available biostratigraphic data, indicates that the foreland basin was formed 448–425 Ma ago. We surmise a possible link between the Wuyi–Yunkai orogen and the Appalachian–Caledonian orogen based on the geological constraints and palaeomagnetic data.

A survey of the Milky Way disk and the Magellanic System at the wavelengths of the 21-cm atomic hydrogen (H i) line and three 18-cm lines of the OH molecule will be carried out with the Australian Square Kilometre Array Pathfinder telescope. The survey will study the distribution of H i emission and absorption with unprecedented angular and velocity resolution, as well as molecular line thermal emission, absorption, and maser lines. The area to be covered includes the Galactic plane (|b| < 10°) at all declinations south of δ = +40°, spanning longitudes 167° through 360°to 79° at b = 0°, plus the entire area of the Magellanic Stream and Clouds, a total of 13 020 deg2. The brightness temperature sensitivity will be very good, typically σT≃ 1 K at resolution 30 arcsec and 1 km s−1. The survey has a wide spectrum of scientific goals, from studies of galaxy evolution to star formation, with particular contributions to understanding stellar wind kinematics, the thermal phases of the interstellar medium, the interaction between gas in the disk and halo, and the dynamical and thermal states of gas at various positions along the Magellanic Stream.

The multi-mode approximation is presented to compute the interior wave function of Schrödinger equation. This idea is necessary to handle the multi-barrier and high dimensional resonant tunneling problems where multiple eigenvalues are considered. The accuracy and efficiency of this algorithm is demonstrated via several numerical examples.

X-ray topography data are compared with photodiode responsivity maps to identify potential candidates for electron trapping in high purity, single crystal diamond. X-ray topography data reveal the defects that exist in the diamond material, which are dominated by non-electrically active linear dislocations. However, many diamonds also contain defects configurations (groups of threading dislocations originating from a secondary phase region or inclusion) in the bulk of the wafer which map well to regions of photoconductive gain, indicating that these inclusions are a source of electron trapping which affect the performance of diamond X-ray detectors. It was determined that photoconductive gain is only possible with the combination of an injecting contact and charge trapping in the near surface region. Typical photoconductive gain regions are 0.2 mm across; away from these near-surface inclusions the device yields the expected diode responsivity.

Dental remineralization may be achieved by mediating the interactions between tooth surfaces with free ions and biomimetic peptides. We recently developed octuplet repeats of aspartate-serine-serine (DSS-8) peptide, which occurs in high abundance in naturally occurring proteins that are critical for tooth remineralization. In this paper, we evaluated the possible role of DSS-8 in dentin remineralization. Human dentin specimens were demineralized, exposed briefly to DSS-8 solution, and then exposed to concentrated ionic solutions that favor remineralization. Dentin nano-mechanical behaviors, hardness and elastic modulus, at various stages of treatment were determined by nanoindentation. The phase, microstructure and morphology of the resultant surfaces were characterized using grazing incidence X-ray diffraction, variable pressure scanning electron microscopy, and atomic force microscopy, respectively. Nanoindentation results show that DSS-8 remineralization effectively improves the mechanical and elastic properties of native dentin. Moreover, the hardness and elastic modulus for the DSS-8 treated dentin were significantly higher than surfaces remineralized without DSS-8.

Dental remineralization may be achieved by mediating the interactions between tooth surfaces with free ions and biomimetic peptides. We recently developed octuplet repeats of aspartate-serine-serine (DSS-8) peptide, which occurs in high abundance in naturally occurring proteins that are critical for tooth remineralization. In this paper, we evaluated the possible role of DSS-8 in enamel remineralization. Human enamel specimens were demineralized, exposed briefly to DSS-8 solution, and then exposed to concentrated ionic solutions that favor remineralization. Enamel nano-mechanical behaviors, hardness and elastic modulus, at various stages of treatment were determined by nanoindentation. The phase, microstructure and morphology of the resultant surfaces were characterized using the grazing incidence X-ray diffraction (GIXD), variable pressure scanning electron microscopy (VPSEM), and atomic force microscopy (AFM), respectively. Nanoindentation results show that the DSS-8 remineralization effectively improves the mechanical and elastic properties for demineralized enamel.

High-average-current linear electron accelerators require photoinjectors capable of delivering tens to hundreds of mA average current, with peak currents of hundreds of amps. Standard photocathodes face significant challenges in meeting these requirements, and often have short operational lifetimes in an accelerator environment. We report on recent progress toward development of secondary emission amplifiers for photocathodes, which are intended to increase the achievable average current while protecting the cathode from the accelerator.

The amplifier is a thin diamond wafer which converts energetic (few keV) primary electrons into hundreds of electron-hole pairs via secondary electron emission. The electrons drift through the diamond under an external bias and are emitted into vacuum via a hydrogen-terminated surface with negative electron affinity (NEA). Secondary emission gain of over 200 has been achieved. Two methods of patterning diamond, laser ablation and reactive-ion etching (RIE), are being developed to produce the required geometry. A variety of diagnostic techniques, including FTIR, SEM and AFM, have been used to characterize the diamonds.

A simple novel route to synthesize aqueous tantalum and niobium precursors has been developed using cheap and stable Nb2O5 or Ta2O5 as starting source, based on basic flux technique. Various analytical techniques have been employed to characterize the purity, and thermal decomposition features of the precursors. Using home-made Ta and Nb precursors, several photocatalysts and ferroelectric powders such as LiNbO3, LiTaO3, Sr0.75Ba0.25Nb2O6, and SrBi2Ta2O9 have been prepared at lower processing temperature by a polymerizable complex route successfully.

Zr/Ti an Hf/Ti composite nitrate were developed as single-source precursors for deposition of multi-component metal oxide films. X-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) analyses confirmed that ZrxTi1-xO2 and HfxTi1-xO2 films were successfully prepared by the CVD technique from these composite precursors. The Zr/Ti nitrate can be taken as a solid solution of the individual Zr and Ti nitrate, and the Zr/Ti molar ratio in as-deposited ZrxTi1-xO2 films is nicely consistent with that of the precursor. The Hf/Ti nitrate appears to be a mixture of the Zr and Ti nitrates and the composition of the as-deposited HfxTi1-xO2 films depends remarkably on the heating time of precursor. Both ZrxTi1-xO2 and HfxTi1-xO2 films exhibit trading-off properties between band gap and dielectric constant, which suggesting that ZrxTi1-xO2 and HfxTi1-xO2 can be the promising candidates for gate dielectric application to improve the scalability and reduce the leakage current of the next generation complementary metal-oxide-semiconductor transistor (CMOS) devices.