Evaporative cooling technologies for greenhouses: a comprehensive review

Excessive heat generation by the high solar radiation is the major issue for agricultural greenhouses in hot climatic regions. This issue has been of great concern to summer greenhouses and has continuously been under study. Effective cooling of greenhouses has to be undertaken to minimize the issue. There are several techniques of greenhouse cooling and among them, evaporative cooling has completely revolutionized the system of cooling in greenhouses since the nineteenth century and still it is being used around the world. The current paper presents a review study covering the past and the latest kinds of evaporative cooling techniques, which have been utilizing for agricultural greenhouses in summer. The paper attempted to show the performance characteristics of the individual cooling systems, like fan-pad systems, fog-cooled systems, roof cooling systems, dissector pad-fan systems, two-stage cooling system and seawater greenhouse systems. A brief survey of literature revealed that evaporative cooling could be applicable to any environmental condition to reduce greenhouse excess thermal load depending upon the types of the system. Finally, some innovative cooling ideas have been given for further studies

General Relativistic Spectra from Accretion Disks around Rapidly Rotating Neutron Stars

We compute spectra from accretion disks around rapidly rotating neutron stars. The full effect of general relativity is considered for the structure calculation of the stars. We take into account the Doppler shift, gravitational redshift and light-bending effects in order to compute the observed spectra. To facilitate direct comparison with observations, a simple empirical function is presented which describes the numerically computed spectra well. This function can in principle be used to distinguish between the Newtonian spectra and the relativistic spectra. We also discuss the possibility of constraining neutron star's equation of state using our spectral models.Comment: 2 pages, to appear in the proceedings of 'The Physics of Cataclysmic Variables and Related Objects', Goettingen, August 5-10, 200

Microclimatic Modeling and Analysis of a Fog-Cooled Naturally Ventilated Greenhouse

In the present paper, a thermal model has been presented for predicting the thermal environment inside a fog cooled naturally ventilated greenhouse. Experiments were conducted on a polyethylene covered greenhouse having 250 m2 ground area located at Coochbehar (latitude: 26.2o N, longitude: 89oE), West Bengal, India. The greenhouse was cooled by intermittent fogging with three distinct fogging cycles during the experiments. The greenhouse air temperature profiles as predicted by theoretical model were validated for different fogging cycle configurations. The model prediction and experimental results build up a good match (co-efficient of correlation was in range of 0.85 to 0.97). It was observed that fogging cycle configuration (spray time and spray interval combination) influences greatly the cooling performance of the fogging system. Further analysis revealed that greenhouse temperature could be maintained 2-5oC below the ambient temperature by employing suitable fogging cycle, maintaining the relative humidity within acceptable level

Performance Study of a Floricultural Greenhouse Surrounded by Shallow Water Ponds

In the present paper, an innovative low energy-intensive evaporative cooling system has been proposed for greenhouse application in near-tropical regions dominated by hot climate. The system can operate under dual- ventilation mode to maintain a favourable microclimate inside the greenhouse. A single ridge type un-even span greenhouse has been considered, targeting a few species of Indian tropical flowers. The greenhouse has a continuous roof vent as well as adjustable side vents and is equipped with exhaust fans on top and roll-up curtains on the sides. The greenhouse is surrounded by shallow water ponds outside its longitudinal walls and evaporative surfaces partially cover the free water surface. Inside the pond, low cost evaporative surfaces are so placed that they form air channels. Thus, outside air flows through the channels formed by the wetted surfaces over the water surface and undergoes evaporative cooling before entering the greenhouse. A simplified theoretical model has been presented in this paper to predict the inside greenhouse air temperature while ambient weather data are used as model inputs. The study reveals that during average radiation periods, the greenhouse can depends solely on natural ventilation and during peak radiation hours fan-induced ventilation is needed to maintain the required level of temperature. It is seen that under dual-ventilation mode greenhouse, temperature can be kept 3-6 oC lower than ambient temperature when saturation effectiveness is 0.7 and with 75% shading.Article History: Received February 25th 2017; Received in revised form April 14th 2017; Accepted May 4th 2017; Available onlineHow to Cite This Article: Misra, D. and Ghosh, S. (2017) Performance Study of a Floricultural Greenhouse Surrounded by Shallow Water Ponds. International Journal of Renewable Energy Development, 6(2), 137-144.https://doi.org/10.14710/ijred.6.2.137-14

Properties of unique hard X-ray dips observed from GRS 1915+105 and IGR J17091-3624 and their implications

We report a comprehensive study on spectral and timing properties of hard X-ray dips uniquely observed in some so-called variability classes of the micro-quasars GRS 1915+105 and IGR J17091-3624. These dips are characterized by a sudden decline in the 2.0-60.0 keV X-ray intensity by a factor of 4-12 simultaneous with the increase in hardness ratio by a factor of 2-4. Using 31 observations of GRS 1915+105 with RXTE/PCA, we show that different behavior are observed in different types of variability classes, and we find that a dichotomy is observed between classes with abrupt transitions vs those with smoother evolution. For example, both energy-lag spectra and frequency-lag spectra of hard X-ray dips in classes with abrupt transitions and shorter dip intervals show hard-lag (hard photons lag soft photons), while both lag spectra during hard dips in classes with smoother evolution and longer dip intervals show soft-lag. Both lag time-scales are of the order of 100-600 msec. We also show that timing and spectral properties of hard X-ray dips observed in light curves of IGR J17091-3624 during its 2011 outburst are consistent with the properties of the abrupt transitions in GRS 1915+105 rather than smooth evolution. A global correlation between the X-ray intensity cycle time and hard dip time is observed for both abrupt and smooth transition which may be due to two distinct physical processes whose time-scales are eventually correlated. We discuss implications of our results in the light of some generic models.Comment: 17 pages, 5 figures, accepted for publication in the Astrophysical Journa

In Vivo Channel Characterization for Dengue Virus Infection

Dengue, a mosquito-borne viral disease, poses a global threat owing to the unavailability of any specific therapeutics. Since prevention is only restricted to vector control, a clear understanding of Dengue Virus (DENV) transmission within an infected host is essential. The dynamics of DENV transmission addressed in light of molecular communication paradigm is promising in providing crucial information accounting for disease control that can lead to development of novel approaches to clear the virus infection. In this work, we model the DENV transmission inside the body from the point of a mosquito bite to the targeted organs as a communication system. Based on the physiological processes involved in the transmission of DENV through the layers of skin and vascular systems, we identify and propose a channel model. By considering the dynamics of virus transmission through the channel, we analyze and calculate different channel phenomena, such as path loss and channel noise, and obtain an analytical expression for the capacity of the proposed channel model. The uncertainty in signal transmission is modeled and evaluated owing to the innate and adaptive immune response in the channel. We performed in-silico experiments for validation and provided numerical analysis for the channel characteristics. Our analysis revealed that the attenuation offered in the cutaneous channel does not result in significant signal loss. We also observed that the variations in the channel capacity is not substantially affected by the injection probabilities of the virus

SmartARM: A smartphone-based group activity recognition and monitoring scheme for military applications

© 2017 IEEE. In this paper we propose SmartARM-A Smartphone-based group Activity Recognition and Monitoring (ARM) scheme, which is capable of recognizing and centrally monitoring coordinated group and individual group member activities of soldiers in the context of military excercises. In this implementation, we specifically consider military operations, where the group members perform similar motions or manoeuvres on a mission. Additionally, remote administrators at the command center receive data from the smartphones on a central server, enabling them to visualize and monitor the overall status of soldiers in situations such as battlefields, urban operations and during soldier's physical training. This work establishes-(a) the optimum position of smartphone placement on a soldier, (b) the optimum classifier to use from a given set of options, and (c) the minimum sensors or sensor combinations to use for reliable detection of physical activities, while reducing the data-load on the network. The activity recognition modules using the selected classifiers are trained on available data-sets using a test-train-validation split approach. The trained models are used for recognizing activities from live smartphone data. The proposed activity detection method puts forth an accuracy of 80% for real-time data

Privacy-preserving blockchain based IoT ecosystem using attribute-based encryption

© 2017 IEEE. The Internet of Things (IoT) has penetrated deeply into our lives and the number of IoT devices per person is expected to increase substantially over the next few years. Due to the characteristics of IoT devices (i.e., low power and low battery), usage of these devices in critical applications requires sophisticated security measures. Researchers from academia and industry now increasingly exploit the concept of blockchains to achieve security in IoT applications. The basic idea of the blockchain is that the data generated by users or devices in the past are verified for correctness and cannot be tampered once it is updated on the blockchain. Even though the blockchain supports integrity and non-repudiation to some extent, confidentiality and privacy of the data or the devices are not preserved. The content of the data can be seen by anyone in the network for verification and mining purposes. In order to address these privacy issues, we propose a new privacy-preserving blockchain architecture for IoT applications based on attribute-based encryption (ABE) techniques. Security, privacy, and numerical analyses are presented to validate the proposed model

Temperature Profiles of Accretion Disks around Rapidly Rotating Neutron Stars in General Relativity and Implications for Cygnus X-2

We calculate the temperature profiles of (thin) accretion disks around rapidly rotating neutron stars (with low surface magnetic fields), taking into account the full effects of general relativity. We then consider a model for the spectrum of the X-ray emission from the disk, parameterized by the mass accretion rate, the color temperature and the rotation rate of the neutron star. We derive constraints on these parameters for the X-ray source Cygnus X-2 using the estimates of the maximum temperature in the disk along with the disk and boundary layer luminosities, using the spectrum inferred from the EXOSAT data. Our calculations suggest that the neutron star in Cygnus X-2 rotates close to the centrifugal mass-shed limit. Possible constraints on the neutron star equation of state are also discussed.Comment: 18 pages, 9 figs., 2 tables, uses psbox.tex and emulateapj5.sty. Submitted to Ap