Piatetski-Shapiro meets Chebotarev

[No abstract available

Effect of dual-permeability structure in a porous media on heat and mass transfer by natural convection

Bu çalışmanın amacı, içerisinde ısı ve kütle üretimi olan ve geçirgenliğin tektürel olmadığı gözenekli ortamda doğal taşınımla ısı ve kütle geçişini Darcy-Brinkmam modeli kullanarak incelemektir. İki boyutlu akışkana doymuş gözenekli ortamdaki akış için Soret ve Dufour etkisi ihmal edilmiş ve yoğunluk için Boussinesq yaklaşımı kullanılmıştır. Elde edilen boyutsuz korunum denklemleri hücre merkezli sonlu hacimler yöntemi ile ayrıklaştırılmıştır. Boyutsuz akım fonksiyonları “Succesive Over Relaxation”; boyutsuz derişiklik, enerji ve çevrinti taşınım denklemleri “Alternating Direction Implicit” yöntemleri ile çözülmüştür. Farklı geçirgenliğe sahip bölgelerin gözenekli ortamdaki ısı ve kütle geçişine etkisini incelemek için iki farklı geçirgenli yapıyı temsil edecek altı farklı model oluşturulmuştur. Bu modellerin geçirgenlik değerleri 10-7ve 10-4 olmak üzere iki farklı Darcy sayısı (Da) ile temsil edilmiştir. Yapılan sayısal çalışmalarda gözeneklilik (ε=0.4), Prandtl sayısı (Pr=0.7), boyut oranı (A=1), Lewis sayısı (Le=10), yüzdürme oranı (N=2) sabit tutulmuştur. Farklı Rayleigh sayıları (Ra) kullanılarak yapılan incelemenin sonuçları, akım fonksiyonu, eşderişiklik ve eşsıcaklık eğrileri kullanılarak sunulmuştur. Sonuçlar, ayrıca Nusselt (Nu), Sherwood (Sh) sayılarının ve normalize edilmiş derişiklik değerlerinin değişimi dikkate alınarak değerlendirilmiştir. Çalışmada, ikili geçirgenli yapı ile oluşturulan modellerin ısı ve kütle geçişi üzerindeki etkilerinin yüksek Rayleigh sayıları için farklılaştığı sonucuna varılmış. Ayrıca, düşey eksen boyunca oluşturulan ikili geçirgenli yapı, yatay eksen boyunca oluşturulan ikili geçirgenli yapıdan daha etkili olmuştur. Bunun sebebi geçirgen kısmın tamamının yüksek Darcy sayısına sahip olmasıdır.  Anahtar Kelimeler: Doğal taşınım, gözenekli ortam, Darcy-Brinkman modeli, geçirgenlik, Darcy sayısı, Rayleigh sayısı.The main objective of this work is to investigate the effect of the structure of double permeability on double diffusive natural convection. The permeability, K, is the measure of the flow conductance of the porous medium. In this study, two main cases are taken into account. In the first main case, the cavity has homogenous permability in everywhere and in the other main case; the cavity has two regions with different permeability values. The permeability of the porous medium can be represented by Darcy number, since Darcy number depends on the permeability, directly (Da=K/L2). Therefore, Darcy number is used instead of the permeability for all cases. The natural convective flow with heat and mass transfer for porous media, saturated with two dimensional fluid, having heat and mass production in solid phase was investigated by using Darcy-Brinkman model. The fluid is assumed to be a normal Boussinesq fluid that is the density variations upon temperature and concentration at constant pressure. Soret and Dufour effects on heat and mass diffusion were neglected. The cavity is cooled from all the walls, where as the right wall is partially permeable and other boundaries are impermeable. The double-diffusive natural convection in a porous cavity with partially permeable wall is analyzed by solving mass, momentum, vorticity, energy and concentration balance equations, using the Brinkman extension of the classical Darcy equation. A cell-centered finite volume scheme is applied to solve the governing equations. The stream function field is calculated by using a Successive Over Relaxation method (SOR). The grid layout was arranged by utilizing collocated grid procedure, while the power law-differencing scheme was adopted for heat, mass fluxes and vorticity transfer in the fluid domain. The iterative procedure is performed with the Alternating Direction Implicit method (ADI). For benchmarking purpose, the accuracy of the numerical code was checked in the case of double diffusive convection within a differentially heating square porous enclosure subject to a concentration difference, C, and a temperature difference, T in the horizontal direction using the results reported in Goyeau et al. (1996). The results concern mass transfer due to purely thermal natural convection (N=0) for Darcy model (Da=10-7). When the Darcy number is small enough (Da 10-7) the numerical results obtained with the Brinkman model are in agreement with Darcy's law (Bennacer et al., 2001). The average Nu and Sh numbers are in good agreement with those published in the references. The grid was selected as a trade off between numerical accuracy, stability, and computational time. A non-uniform grid (64x64) was used in all calculations. Heat and mass transfer characteristics as isoconcentration lines, streamlines, isotherms, average Sherwood numbers and Nusselt numbers were studied for different values of Rayleigh number and the structures of double permeability. The main findings of this investigation are as follow: The concentration gradients in all cases are larger according to the medium with (Da 10-7) homogenous permeability. On the other hand, the temperature gradients in all cases are smaller according to the medium with (Da 10-7) homogenous permeability. In case 3 and case 6, the Darcy number of the medium is 10-7 in 75 %. Therefore heat and mass transfer characteristics as isoconcentration lines, streamlines, isotherms, average Sherwood numbers and Nusselt numbers were expected  to be  similar, but  not seen any similarities between case 3 and case 6. There are similarities only between case 6 and case 0 for the concentration gradients and the average Sherwood numbers. The average Nusselt numbers for six cases are nearly similar. Also, the average Nusselt number increases as the Rayleigh number increases for all cases. The maximum changing of Nusselt number is seen at case 5, the minimum changing is case 0. As the Rayleigh number increases, the amount of the leakage from the cavity also increases. As a result, the leakage from the cavity has higher values in the double permeability cases that the Darcy number of the bottom region of the cavity is 10-7 in 75 % (case 6). Keywords: Natural convection, porous medium, permeability, Darcy number, Rayleigh number, Darcy-Brinkman model.

OpenVirtualObjects: An open set of standardized and validated 3D household objects for virtual reality-based research, assessment, and therapy

Virtual reality (VR) technology provides clinicians, therapists, and researchers with new opportunities to observe, assess, and train behavior in realistic yet well-controlled environments. However, VR also comes with a number of challenges. For example, compared to more abstract experiments and tests on 2D computer screens, VR-based tasks are more complex to create, which can make it more expensive and time-consuming. One way to overcome these challenges is to create, standardize, and validate VR content and to make it openly available for researchers and clinicians. Here we introduce the OpenVirtualObjects (OVO), a set of 124 realistic 3D household objects that people encounter and use in their everyday lives. The objects were rated by 34 younger and 25 older adults for recognizability, familiarity, details (i.e., visual complexity), contact, and usage (i.e., frequency of usage in daily life). All participants also named and categorized the objects. We provide the data and the experiment- and analysis code online. With OVO, we hope to facilitate VR-based research and clinical applications. Easy and free availability of standardized and validated 3D objects can support systematic VR-based studies and the development of VR-based diagnostics and therapeutic tools

OpenVirtualObjects (OVO): An open set of standardized and validated 3D household objects for virtual reality-based research, assessment, and therapy

Virtual reality (VR) technology provides clinicians, therapists, and researchers with new opportunities to observe, assess, and train behaviour in realistic yet well-controlled environments. However, VR also comes with a number of challenges. For example, compared to more abstract experiments and tests on 2D computer screens, VR-based tasks are more complex to create, which can make it more expensive and time-consuming. One way to overcome these challenges is to create, standardize, and validate VR content and to make it openly available for researchers and clinicians. Here we introduce the OpenVirtualObjects (OVO), a set of 124 realistic 3D household objects that people encounter and use in their everyday lives. The objects were rated by 34 younger and 25 older adults for recognizability, familiarity, details (i.e., visual complexity), contact, and usage (i.e., frequency of usage in daily life). All participants also named and categorized the objects. We provide the data and the experiment- and analysis code online. With OVO, we hope to facilitate VR-based research and clinical applications. Easy and free availability of standardized and validated 3D objects can support systematic VR-based studies and the development of VR-based diagnostics and therapeutic tools

Photodegradation of carbendazim sensitized by aromatic ketones

Carbendazim (1) is a benzimidazole extensively used as post-harvest fungicide on fruits and vegetables. The aim of the present work is to study the photodegradation of I sensitized by aromatic ketones, with special attention to mechanistic aspects and to the possible detoxification associated with photochemical treatment. Laser flash photolysis (LPF) lambda(exc) = 355 nm of xanthone (XA) and anthraquinone (AQ) was performed in MeCN solutions, in the presence of 1. A new transient absorbing at lambda(max) 500 and 320 nm was obtained and assigned to the semioxidized radical cation 1(+center dot). An exergonic thermodynamics for electron transfer quenching was confirmed by means of the Rehm-Weller equation. The same species was observed by direct LFP of 1 at 266 nm in polar solvents. Conversely, when a deoxygenated solution of 1 was submitted to LFP in cyclohexane the transient spectrum presented a band with maximum at 380 nm; it was assigned to the triplet excited state ((3)1*) on the basis of energy transfer to oxygen and beta-carotene. The photodegradation of 1 was achieved using XA and AQ as electron acceptors in a solar-simulator, in aerated aqueous medium; the reaction was faster with XA. Formation of a new photoproduct was initially observed; its structure was assigned as carbendazim N-C5 dimer (2). A balance of the total organic carbon (TOC) after prolonged irradiation indicated that mineralization does not occur to a significant extent, pointing to oxidative fragmentation of 1 and 2 to give a variety of low molecular weight products. To check whether the observed photodegradation of 1 results in a decreased toxicity, biological assays were performed using an established model based on the inhibition of mobility of Daphnia magna. The results demonstrate that photodegradation leads to a diminished toxicity, indicating that the photoproducts are less toxic than the parent compound. (C) 2013 Elsevier B.V. All rights reserved.Financial support from the MICINN (Grant: CTQ2010-19909) and the Generalitat Valenciana (Prometeo Program) is gratefully acknowledged.Jornet Olivé, MD.; Castillo López, MÁ.; Sabater Marco, C.; Tormos Faus, RE.; Miranda Alonso, MÁ. (2013). Photodegradation of carbendazim sensitized by aromatic ketones. Journal of Photochemistry and Photobiology A: Chemistry. 256:36-41. https://doi.org/10.1016/j.jphotochem.2013.02.004S364125