Horizontal cellular oscillations caused by time-periodic resonant thermal forcing in weakly nonlinear Darcy-Bénard convection

The onset of Rayleigh-Bénard convection in a horizontally unbounded saturated porous medium is considered. Particular attention is given to the stability of weakly nonlinear convection between two plane horizontal surfaces heated from below. The primary aim is to study the effects on postcritical convection of having small amplitude time-periodic resonant thermal forcing. Amplitude equations are derived using a weakly nonlinear theory and they are solved in order to understand how the flow evolves with changes in the Darcy-Rayleigh number and the forcing frequency. When convection is stationary in space, it is found to consist of one of two different types depending on its location in parameter space: either a convection pattern where each cell rotates in the same way for all time with a periodic variation in amplitude (Type I) or a pattern where each cell changes direction twice within each forcing period (Type II). Asymptotic analyses are also performed (i) to understand the transition between convection of types I and II; (ii) for large oscillation frequencies and (iii) for small oscillation frequencies. In a large part of parameter space the preferred pattern of convection when the layer is unbounded horizontally is then shown to be one where the cells oscillate horizontally—this is a novel form of pattern selection for Darcy-Bénard convection

Radiation pattern reconfigurable fm antenna

In this work, a radiation pattern reconfigurable antenna design using compact printed spiral monopoles that operates at 102 MHz is reported. The proposed antenna changes its radiation behaviour that responds towards a desired direction with the use of RF switches. The antenna is printed on a 76.6mm × 50mm PCB layer providing more than 20MHz bandwidth at -10 dB threshold and is easily fabricated with low manufacturing cost. The antenna was also simulated on 500mm × 500mm ground plane that represents the roof top of a vehicl

Plasmon-enhanced second harmonic generation in semiconductor quantum dots close to metal nanoparticles

We report the enhancement of the optical second harmonic signal in non-centrosymmetric semiconductor CdS quantum dots, when they are placed in close contact with isolated silver nanoparticles. The intensity enhancement is about 1000. We also show that the enhancement increases when the incoming laser frequency $\omega$ is tuned toward the spectral position of the silver plasmon at $2\omega$, proving that the silver nanoparticle modifies the nonlinear emission.Comment: 5 pages, 5 figure

Domestic wastewater treatment using multi-layer constructed wetlands: an overview

Domestic wastewater is generated from residential, institutional, commercial, and industrial establishments is disposed of via drainage and sewers. Usually, the wastewater is not treated from the primary sewage treatment and gets discharged to drainage without initial treatment. Thus, it is necessary to create an environmentally-friendly method to reduce any pollution issues. This chapter provides insights into overview from previous studies about characteristics of domestic wastewater, results of the treatments using the multi-layer constructed wetlands, type of plants for vegetation wetlands, and parameters needed for the optimisation the multi-layer constructed wetlands. As the low-cost and affordable technology systems, the multi-layer constructed wetlands are the potential alternative to achieve the treatment efficiency

Amphibian Lampbrush Chromosome Loops: Correlative Light Microscopy, Transmission Electron Microscopy, and Scanning Electron Microscopy Observations

The RNP matrix of landmark loops in Pleurodeles waltlii lampbrush chromosomes have been examined by light microscopy, transmission and scanning electron microscopy. This study shows that in normal loops as well as granular, globular and dense loops, the RNP matrices are composed of one basic structure: an RNP particle with a diameter of 30 nm. The scanning electron microscope study also clarified the spatial arrangement of the various types of RNP matrices. The specific morphology of the RNP matrices is due to i) the progressive packaging of transcription products and ii) a concomitant and gradual coiling of the loop axis

PEMBINAAN TAMAN DESA RAMAH ANAK

Kegiatan ini dilaksanakan di Desa Sibuak Kecamatan Tapung, Kabupaten Kampar dalam bentuk pendampingan dan pembinaan untuk pemberdayaan masyarakat, khususnya perangkat desa, pemuda karang taruna, tokoh desa, organisai sosial desa, serta masyarakat umum desa. Tahapan kegiatan yang dilakukan untuk kegiatan pembinaan dan pendampingan, yaitu; (a) rekonsiderasi, (b) Periapan, (c) sosialisasi, (d) tahap pelaksanaan pembinaan, dan (e) tahap evaluasi dan pelaporan. Diketahui bahwa daya serap masyarakat terhadap materi pembinaan dan pendampingan tentang taman desa ramah anak tergolong baik, karena tingkat pemahaman peserta sebesar 83,99% sangat baik, 14,13% tergolong kurang baik dan hanya 1,19% yang tergolong tidak baik. Hasil survey tanggapan mitra terhadap kegiatan yang dilakukan menunjukkan bahwa hasil yang sangat baik, dengan pembuktian bahwa semua unsur yang terlibat berharap kegiatan ini untuk dilanjutkan lagi. Taman desa ramah anak ditujukan untuk mengoptimalkan pemanfaatan fasilitas taman semua kalangan di desa Sibuak.

Prediction of Soil Anisotropic Stress-Strain Behaviour Incorporating Shear Strength Using Improvise Normalised Stress-Strain Method

Currently the soil anisotropic stress-strain behaviour can be predicted accurately at any effective stress using the Rotational Multiple Yield Surface Framework. This framework incorporates the developed of mobilised shear strength within the body of the soil mass whenever the soil is subjected to anisotropic compression. However the accuracy of the framework can be improvised since the failure axial strain is not unique but increases as the effective stress increases. This improved method s call normalised strain method. This method is applied to predict the stress-strain behaviour of granitic residual soil grade V from Kuala Kubu Baharu. The improve accuracy of this method will be presented in comparison with the conventional method

Horizontal cellular oscillations caused by time-periodic resonant thermal forcing in weakly nonlinear Darcy-Bénard convection

The onset of Rayleigh-Bénard convection in a horizontally unbounded saturated porous medium is considered. Particular attention is given to the stability of weakly nonlinear convection between two plane horizontal surfaces heated from below. The primary aim is to study the effects on postcritical convection of having small amplitude time-periodic resonant thermal forcing. Amplitude equations are derived using a weakly nonlinear theory and they are solved in order to understand how the flow evolves with changes in the Darcy-Rayleigh number and the forcing frequency. When convection is stationary in space, it is found to consist of one of two different types depending on its location in parameter space: either a convection pattern where each cell rotates in the same way for all time with a periodic variation in amplitude (Type I) or a pattern where each cell changes direction twice within each forcing period (Type II). Asymptotic analyses are also performed (i) to understand the transition between convection of types I and II; (ii) for large oscillation frequencies and (iii) for small oscillation frequencies. In a large part of parameter space the preferred pattern of convection when the layer is unbounded horizontally is then shown to be one where the cells oscillate horizontally—this is a novel form of pattern selection for Darcy-Bénard convection