Pemodelan Matematik Kinerja Pengering Surya Efek Rumah Kaca (ERK)-Hibrid Menggunakan Rak Berputar secara Vertikal

Makalah ini menyajikan uji unjuk kerja dan pemodelan matematik pengering energi surya (ERK)-Hibrid menggunakan rak berputar secara vertikal. Pengering terdiri dari bangunan rumah kaca berukuran (1100 × 860 × 1300) mm dengan delapan buah rak dan sistim pemanas tambahan yang terdiri dari kolektor plat datar (1,04 m2), tangki penyimpan air panas (197 liter) dan penukar panas. Untuk mengetahuikinerja pengering energi surya, dilakukan lima kali percobaan variasi kecepatan putar rak (1, 4, 7, 10 ) rpm dan tanpa pemutaran rak. Bahan yang dipergunakan pada pengujian adalah kapulaga lokal (Amomum cardamomum Wild). Masing-masing percobaan seberat 9 sampai dengan 10 kg. Rata-rata suhu air tangki penyimpan panas bervariasi dari 50,0 sampai dengan 55,0 °C suhu ruang pengering antara 38,9 sampai dengan 45,9 °C, sedangkan kelembaban relatif (RH) ruang pengering berkisar antara 32,1 sampai dengan 47,4 %. Perlakuan pemutaran rak berpengaruh terhadap keseragaman suhu bahan maupun kadar air pada masing rak pengering. Pada perlakuan pemutaran 1 rpm (percobaan II), didapatkan kondisi terbaik (suhu bahan maupun kadar air yang paling seragam). Dengan kecepatan putar rak yang semakin meningkat menyebabkan nilai ragam suhu bahan maupun kadar air semakin meningkat. Untuk melakukan simulasi unjuk kerja dilakukan pemodelan matematik berdasarkan pindah panas dan massa serta pendekatan pengeringan lapisan tipis. Persamaan diselesaikan secara numerik menggunakan finite difference Euler dengan bantuan bahasa pemrograman Visual Basic Aplication (VBA) Excell. Validasi dilakukan dengan membandingkan antara perhitungan hasil pemodelan (data prediksi) dengan data hasil pengukuran (data observasi). Kriteria kevalidan ditentukan dengan melihat nilai koefisien determinasi (R2), nilai RMSD maupun nilai MAPD. Pemodelan matematik yang telah dibangun dapat menggambarkan dengan tepat Perubahan suhu air tangki penyimpan panas, suhu ruang pengering, suhu bahan maupun penurunan kadar air

Reducing multiphoton ionization in a linearly polarized microwave field by local control

We present a control procedure to reduce the stochastic ionization of hydrogen atom in a strong microwave field by adding to the original Hamiltonian a comparatively small control term which might consist of an additional set of microwave fields. This modification restores select invariant tori in the dynamics and prevents ionization. We demonstrate the procedure on the one-dimensional model of microwave ionization.Comment: 8 page

Modeling meander morphodynamics over self-formed heterogeneous floodplains

This work addresses the signatures embedded in the planform geometry of meandering rivers consequent to the formation of floodplain heterogeneities as the river bends migrate. Two geomorphic features are specifically considered: scroll bars produced by lateral accretion of point bars at convex banks and oxbow lake fills consequent to neck cutoffs. The sedimentary architecture of these geomorphic units depends on the type and amount of sediment, and controls bank erodibility as the river impinges on them, favoring or contrasting the river migration. The geometry of numerically generated planforms obtained for different scenarios of floodplain heterogeneity is compared to that of natural meandering paths. Half meander metrics and spatial distribution of channel curvatures are used to disclose the complexity embedded in meandering geometry. Fourier Analysis, Principal Component Analysis, Singular Spectrum Analysis and Multivariate Singular Spectrum Analysis are used to emphasize the subtle but crucial differences which may emerge between apparently similar configurations. A closer similarity between observed and simulated planforms is attained when fully coupling flow and sediment dynamics (fully-coupled models) and when considering self-formed heterogeneities that are less erodible than the surrounding floodplain

Ideally embedded space-times

Due to the growing interest in embeddings of space-time in higher-dimensional spaces we consider a specific type of embedding. After proving an inequality between intrinsically defined curvature invariants and the squared mean curvature, we extend the notion of ideal embeddings from Riemannian geometry to the indefinite case. Ideal embeddings are such that the embedded manifold receives the least amount of tension from the surrounding space. Then it is shown that the de Sitter spaces, a Robertson-Walker space-time and some anisotropic perfect fluid metrics can be ideally embedded in a five-dimensional pseudo-Euclidean space.Comment: layout changed and typos corrected; uses revtex

Plant roots steer resilience to perturbation of river floodplains

Freshwater ecosystems along river floodplains host among the greatest biodiversity on Earth and are known to respond to anthropic pressure. For water impounded systems, resilience to changes in the natural flow regime is believed to be bi-directional. Whether such resilience prevents the system from returning to pristine conditions after the flow regime changes reverse is as yet unclear, though widely documented. In this work we show that temporal irreversibility of river floodplains to recover their status may be explained by the dynamics of riparian water-tolerant plant roots. Our model is a quantitative tool that will benefit scientists and practitioners in predicting the impact of changing flow regimes on long-term river floodplain dynamics

Excitation of Small Quantum Systems by High-Frequency Fields

The excitation by a high frequency field of multi--level quantum systems with a slowly varying density of states is investigated. A general approach to study such systems is presented. The Floquet eigenstates are characterized on several energy scales. On a small scale, sharp universal quasi--resonances are found, whose shape is independent of the field parameters and the details of the system. On a larger scale an effective tight--binding equation is constructed for the amplitudes of these quasi--resonances. This equation is non--universal; two classes of examples are discussed in detail.Comment: 4 pages, revtex, no figure

Disorder-induced critical behavior in driven diffusive systems

Using dynamic renormalization group we study the transport in driven diffusive systems in the presence of quenched random drift velocity with long-range correlations along the transport direction. In dimensions $d\mathopen< 4$ we find fixed points representing novel universality classes of disorder-dominated self-organized criticality, and a continuous phase transition at a critical variance of disorder. Numerical values of the scaling exponents characterizing the distributions of relaxation clusters are in good agreement with the exponents measured in natural river networks

The Dynamics of a Meandering River

We present a statistical model of a meandering river on an alluvial plane which is motivated by the physical non-linear dynamics of the river channel migration and by describing heterogeneity of the terrain by noise. We study the dynamics analytically and numerically. The motion of the river channel is unstable and we show that by inclusion of the formation of ox-bow lakes, the system may be stabilised. We then calculate the steady state and show that it is in agreement with simulations and measurements of field data.Comment: Revtex, 12 pages, 2 postscript figure

Diffusive Ionization of Relativistic Hydrogen-Like Atom

Stochastic ionization of highly excited relativistic hydrogenlike atom in the monochromatic field is investigated. A theoretical analisis of chaotic dynamics of the relativistic electron based on Chirikov criterion is given for the cases of one- and three-dimensional atoms. Critical value of the external field is evaluated analitically. The diffusion coefficient and ionization time are calculated.Comment: 13 pages, latex, no figures, submitted to PR

Waarnemingen van Bruinvissen in maart 2013 vanaf een zandzuiger in het slijkgat bij Ouddorp

Jaarlijks spoelen in Nederland honderden bruinvissen dood aan op de kust. Onderzoek heeft laten zien dat “scherp trauma" (snij- en rijtwonden, amputaties) veelvuldig voorkomt. Vanaf 2005 hadden gemiddeld 14.4% van de gestrande bruinvissen scherp trauma, met uitschieters tot 20.5% in 2012 en 21.4% in 2010. Veel gevallen van scherp trauma worden gemeld van de kop van Goeree, in de eerste maanden van het jaar. Dieren worden hier vaak ernstig verminkt, maar in verse toestand gevonden. Dit doet vermoeden dat deze dieren vlak onder de kust gewond zijn geraakt. De eerste verminkte bruinvissen werden rond Ouddorp opgemerkt in 2006 (Leopold & Camphuysen 2006) en zijn sindsdien jaarlijks gevonden, al waren er in 2011 opvallend weinig in vergelijking met andere jaren. De aantallen lagen in 2012 en 2013 fors hoger dan in eerdere jaren