Cooling Strategies for Greenhouses in Summer: Control of Fogging by Pulse Width Modulation

The possibilities for improving the control of greenhouse fogging systems, were studied by comparing several combinations of ventilation cooling techniques, shade screening and low-pressure fogging. The study was divided into three parts: experiments, modelling and simulations. In the first part of the paper, ten combinations of five cooling techniques were tested during the summers of 2002 and 2003 in a 132m2 greenhouse with a steel structure and a single-layer methacrylate cover located in Madrid, Spain. An analysis of variance of the climatic parameters was carried out to determine which combinations produced significant differences in inside temperature or relative humidity. Comparing the values for the inside to outside temperature difference, the combination of a shade screen and above-screen fogging achieved a difference in temperature almost the same as that for under-screen fogging, but the relative humidity was significantly lower. In the second part of the study a dynamic model was developed (2002) and validated (2003). The mean absolute error obtained for inside temperature was similar in the fit and the validation and it was less than 1.5 1C in both cases. The model was used to simulate the inside air temperature for a fog system working without shading, and above and under a shade screen. Control algorithms were developed for reducing system water consumption. In the three cases a simple on/off control with a fixed fogging cycle was compared with a pulse width modulation (PWM) strategy, in which the duration of the fogging pulse was increased as a function of inside temperature. The strategies with PWM applied to the fog system were able to reduce water consumption by 8–15% with respect to the strategies with a fixed fogging cycle

Giant radiation heat transfer through the micron gaps

Near-field heat transfer between two closely spaced radiating media can exceed in orders radiation through the interface of a single black body. This effect is caused by exponentially decaying (evanescent) waves which form the photon tunnel between two transparent boundaries. However, in the mid-infrared range it holds when the gap between two media is as small as few tens of nanometers. We propose a new paradigm of the radiation heat transfer which makes possible the strong photon tunneling for micron thick gaps. For it the air gap between two media should be modified, so that evanescent waves are transformed inside it into propagating ones. This modification is achievable using a metamaterial so that the direct thermal conductance through the metamaterial is practically absent and the photovoltaic conversion of the transferred heat is not altered by the metamaterial.Comment: 4 pages, 3 figure

Prescription Patterns of Antidepressants: The Effect of the Black Box Warning among Pediatric Patients

Introduction: Our aim was to investigate the prescription patterns of antidepressant in the southern Israel during the years 2000 to 2005, before and after the FDA black box warning issued regarding the prescription of antidepressants in children. Patients and methods: A cross sectional study. Data regarding prescription of anti-depressant drugs was examined retrospectively. All information was obtained from the computerized databases of the Clalit Health care services, southern county. Data was analyzed by using descriptive statistics, and analytical statistics. Multi-variate analysis was performed when applicable.Results: When comparing the prescription rate of fluoxetine and fluvoxamine versus other SSRI’s included in the health agencies warnings during the years mentioned, there was a gradual increase in the percentage of the other SSRI’s until 2003 from 12.2% in 2000 to 64.2% in 2003 and then a reversal of this trend from 51.9% in 2004 to 47.8% in 2005.Discussion and conclusions: This study shows that the CSM advice has not had a significant effect in reversing the rising prevalence of antidepressant prescribed to children and adolescents in primary care. It has however changed the choice of antidepressant medication chosen within the group of SSRI’s

Chaotic to ordered state transition of cathode-sheath instabilities in DC glow discharge plasmas

Transition from chaotic to ordered state has been observed during the initial stage of a discharge in a cylindrical dc glow discharge plasma. Initially it shows a chaotic behavior but increasing the discharge voltage changes the characteristics of the discharge glow and shows a period substraction of order 7 period $\to$ 5 period $\to$3 period $\to$1 period i.e. the system goes to single mode through odd cycle subtraction. On further increasing the discharge voltage, the system goes through period doubling, like 1 period $\to$ 2 period $\to$ 4 period. On further increasing the voltage, the system goes to stable state without having any oscillations.Comment: chathode-sheath, instabilities, chaos, period-subtraction, bifurcation, dc-discharg

Retention of Re in metakaolin based geopolymer in the presence of an organic reductant – an experimental study

The goal of this research was to examine the change in redox sensitive contaminant retention and leaching behavior from a model geopolymer system, during oxidation and carbonation, in the presence of an organic reductant. The behavior of redox sensitive elements under variable environmental conditions is specifically important for understanding the leaching of radionuclides retained in geopolymeric materials (e.g. Tc) that are soluble when oxidized and insoluble under reducing conditions. An alkali-activated metakaolin geopolymer with high silica/alumina ratio was selected as a model material. Rhenium was selected as the model redox sensitive element, which exhibits a large valence (-3 to +7) and solubility range. Rhenium was introduced in its most oxidized form (VII) as Re2S7. Ascorbic acid was used as a reducing agent during geopolymer casting due to its high solubility and homogeneous distribution within the matrix. Cylindrical monoliths were cured for 90 days under an inert atmosphere (N2) and then aged for 60 days under 98% N2 + 2% CO2 or CO2 deficient air, at a constant relative humidity (68%). The samples were then subjected to EPA 1313 pH dependent leaching test and EPA 1315 monolith leaching test. Leachates were analyzed using DOC and ICP techniques. XRD and SEM – EDS imaging and analyses were used to characterizes the solids Results show that Re has precipitated as ReS2 (IV) in the matrix. The pH dependent leaching test show that Re was released homogenously throughout most of the pH range (3-12). However, the retention of the material aged under CO2 deficient air was three times lower, indicating that the main effect on leaching from this material is of the oxidation process. The natural pH values were 11.3 and 12 for the material aged under 2% CO2 and for material aged under CO2 deficient air respectively, indicating minor carbonation in the former, however, no carbonate minerals were detected in the matrix. Monolith leaching results show that the geopolymers aged under CO2 deficient air have retained significantly less Re (0.24% leaching) relative to the sample aged under 2% CO2 (0.07wt % leaching). -log(diffusivity) values were in the order of 15 and 16 for CO2 deficient air and 2% CO2 respectively. There is a clear positive correlation between the amount of Re and DOC released from the samples, where their amounts are significantly larger for the samples aged under CO2 deficient air, indicating that the main Re-release mechanism from these samples is related to chelation to organic species under oxidizing conditions

Multimedia delivery in the future internet

The term “Networked Media” implies that all kinds of media including text, image, 3D graphics, audio and video are produced, distributed, shared, managed and consumed on-line through various networks, like the Internet, Fiber, WiFi, WiMAX, GPRS, 3G and so on, in a convergent manner [1]. This white paper is the contribution of the Media Delivery Platform (MDP) cluster and aims to cover the Networked challenges of the Networked Media in the transition to the Future of the Internet. Internet has evolved and changed the way we work and live. End users of the Internet have been confronted with a bewildering range of media, services and applications and of technological innovations concerning media formats, wireless networks, terminal types and capabilities. And there is little evidence that the pace of this innovation is slowing. Today, over one billion of users access the Internet on regular basis, more than 100 million users have downloaded at least one (multi)media file and over 47 millions of them do so regularly, searching in more than 160 Exabytes1 of content. In the near future these numbers are expected to exponentially rise. It is expected that the Internet content will be increased by at least a factor of 6, rising to more than 990 Exabytes before 2012, fuelled mainly by the users themselves. Moreover, it is envisaged that in a near- to mid-term future, the Internet will provide the means to share and distribute (new) multimedia content and services with superior quality and striking flexibility, in a trusted and personalized way, improving citizens’ quality of life, working conditions, edutainment and safety. In this evolving environment, new transport protocols, new multimedia encoding schemes, cross-layer inthe network adaptation, machine-to-machine communication (including RFIDs), rich 3D content as well as community networks and the use of peer-to-peer (P2P) overlays are expected to generate new models of interaction and cooperation, and be able to support enhanced perceived quality-of-experience (PQoE) and innovative applications “on the move”, like virtual collaboration environments, personalised services/ media, virtual sport groups, on-line gaming, edutainment. In this context, the interaction with content combined with interactive/multimedia search capabilities across distributed repositories, opportunistic P2P networks and the dynamic adaptation to the characteristics of diverse mobile terminals are expected to contribute towards such a vision. Based on work that has taken place in a number of EC co-funded projects, in Framework Program 6 (FP6) and Framework Program 7 (FP7), a group of experts and technology visionaries have voluntarily contributed in this white paper aiming to describe the status, the state-of-the art, the challenges and the way ahead in the area of Content Aware media delivery platforms

Registration of 3D Fetal Brain US and MRI

We propose a novel method for registration of 3D fetal brain ultrasound and a reconstructed magnetic resonance fetal brain volumes. The reconstructed MR volume is first segmented using a probabilistic atlas and an ultrasound-like image volume is simulated from the segmentation of the MR image. This ultrasound-like image volume is then affinely aligned with real ultrasound volumes of 27 fetal brains using a robust block-matching approach which can deal with intensity artefacts and missing features in ultrasound images. We show that this approach results in good overlap of four small structures. The average of the co-aligned US images shows good correlation with anatomy of the fetal brain as seen in the MR reconstruction

Exact closed form analytical solutions for vibrating cavities

For one-dimensional vibrating cavity systems appearing in the standard illustration of the dynamical Casimir effect, we propose an approach to the construction of exact closed-form solutions. As new results, we obtain solutions that are given for arbitrary frequencies, amplitudes and time regions. In a broad range of parameters, a vibrating cavity model exhibits the general property of exponential instability. Marginal behavior of the system manifests in a power-like growth of radiated energy.Comment: 17 pages, 7 figure