Thermal performance of a solar assisted horizontal ground heat exchanger

This paper presents an experimental study of a solar assisted horizontal ground heat exchanger system (HGHEs) operating as a daily heat storage unit. Initially, several soils were assessed as sensible heat storage mediums, with sand and gravel selected as the most appropriate. Then, a HGHEs was designed and connected to a 15m2 test room with a heating load of 1kW at Nottingham Trent University. Heating cables, simulating solar input, were used to heat the soil in the HGHEs to 70℃, then a heat transfer fluid (HTF), was circulated through a closed loop heat exchanger to extract the stored heat. The parameters of soil backfill and HTF mass flow rate were investigated in the HGHEs. Several output flowrates ranging between 0.1 to 0.6L/min were tested, producing discharge times varying between a few hours to a few days. The HTF mass flowrate was found to be the most significant parameter, affecting the HGHEs thermal capacity and heat exchange rates. The sand filled HGHE produced approximately 50% more hot water (T>35℃) during a longer duration achieving an efficiency of 78% compared to the gravel filled HGHE with a lower system efficiency of 58%. Insulating the HGHE system was found to reduce heat losses and avoid temperature fluctuations in the HGHEs. Overall, the results show the hot water quantity, temperature range and duration produced from the system were in line with low temperature district heating guidelines and can be applied to some household heating applications incorporating low flows and low temperatures

Recycling construction and industrial landfill waste material for backfill in horizontal ground heat exchanger systems

This research experimentally and numerically investigates the possibility of recycling some low cost construction and industrial waste landfills materials as potential backfills in horizontal ground heat exchangers (HGHE). The aim of this study was to compare the temperature distribution development in different backfill materials with respect to time. The tested materials include sand, crushed basalt, broken brick, crushed concrete, and metallic by-products including copper slag, aluminium slag, mill-scale and iron ores (fine and pellets). Initial thermal testing on these materials in an environmental climatic chamber indicated concrete and crushed brick had similar performance to sand, whereas metallic materials had better performance by up to 77% improvement compared to sand. Various percentages of the backfill material (20, 40, 60, 80 and 100%) blended with the remaining percentage of sand showed that the higher the percentage addition of the waste material, the better the heat storage of the enhanced sand. Particle size distribution was also a significant parameter in backfill selection, where medium sized particle sizes (1.18-2 mm) performed 92% better compared to course and fine gradations of the same material. An experimental set-up of a HGHE system was then constructed and filled with the best performing backfill materials to determine the heat storage and release processes on the thermal performance of the system. The paper also reports results from a transient three-dimensional finite volume model developed in ANSYS Fluent 17.2 computational fluid dynamic (CFD) software of a thin section of a HGHE. The experimental and numerical model were used to predict and analyse the temperature distribution developing within the surrounding backfill material with respect to charging (heating) and discharging (extracting heat) modes of the HGHE. Results obtained from both experimental and numerical studies show the temperature range and duration of hot water produced from the system were in line with low temperature space heating guidelines and that mill-scale, copper slag and aluminium slag were the best backfill materials, where the thermal capacity of the HGHE system can be doubled using these materials, compared to the use of sand alone. Congruence between the numerical simulations and experimental data was found

Design and Hardware Implementation of a Speech Cipher System

Digital ciphering of speech signals based on one of modern cryptography algorithms, called the Rijndael algorithm, is studied and presented in this paper. The algorithm meets most of the requirements of security level in recent applications. A system to encrypt speech files recorded with Sound Blaster Card of a personal computer was proposed and simulated successfully using MATLAB® language.  Subjective measure and objective measure using segmental spectral signal-to-noise ratio, were used to test the proposed system performance. In these tests residual intelligibility of the encrypted speech and quality of the recovered speech were calculated and assessed. Finally, a hardware implementation of the above cipher system has been proposed using the TMS320-C30. The real time requirements from the speech cipher system have been computed in terms of execution time together with factors affecting such implementation. The results show the capability of the cipher system to be implemented using the DSP device suggested. Furthermore, the results of hardware implementation also show the security of the system is very close to that of the simulated version

Adaptive Discrete Filters for Telephone Channels Based on the Wavelet Packet Transform

The wavelet transform provides good and in many times excellent results when used as a basic block transform in many systems such as electronic, communication, medical and even chemical systems. The paper uses the wavelet packet transform to adjust the tap gains of the adaptive filter used in channel equalization and estimation. The results using the wavelet technique achieve good improvements in convergence time over the ordinary LMS algorithm. The two systems were compared on full mathematical and simulation basis. Learning curves for adaptive channel equalization and adaptive channel estimation using wavelet packet transform with different mother functions, different level decompositions, different step sizes, different levels of signal to noise ratio, different telephone channels and different filter sizes were compared with conventional LMS adaptive channel equalization and channel estimation. The simulation results carried out using the MATLAB package version 6.1, demonstrate the efficiency of the proposed technique

Adaptive Evolution of the Myo6 Gene in Old World Fruit Bats (Family: Pteropodidae)

PMCID: PMC3631194This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Photocatalytic Degradation of Organic Pollutants in Water Using Graphene Oxide Composite

Developing sustainable and less-expensive technique is always challenging task in water treatment process. This chapter explores the recent development of photocatalysis technique in organic pollutant removal from the water. Particularly, advantages of graphene oxide in promoting the catalytic performance of semiconductor, metal nanoparticle and polymer based photocatalyst materials. Owing to high internal surface area and rapid electron conducting property of graphene oxide fostering as backbone scaffold for effective hetero-photocatalyst loading, and rapid photo-charge separation enables effective degradation of pollutant. This chapter summaries the recent development of graphene oxide composite (metal oxide, metal nanoparticle, metal chalcogenides, and polymers) in semiconductor photocatalysis process towards environmental remediation application

Fog computing security: a review of current applications and security solutions

Fog computing is a new paradigm that extends the Cloud platform model by providing computing resources on the edges of a network. It can be described as a cloud-like platform having similar data, computation, storage and application services, but is fundamentally different in that it is decentralized. In addition, Fog systems are capable of processing large amounts of data locally, operate on-premise, are fully portable, and can be installed on heterogeneous hardware. These features make the Fog platform highly suitable for time and location-sensitive applications. For example, Internet of Things (IoT) devices are required to quickly process a large amount of data. This wide range of functionality driven applications intensifies many security issues regarding data, virtualization, segregation, network, malware and monitoring. This paper surveys existing literature on Fog computing applications to identify common security gaps. Similar technologies like Edge computing, Cloudlets and Micro-data centres have also been included to provide a holistic review process. The majority of Fog applications are motivated by the desire for functionality and end-user requirements, while the security aspects are often ignored or considered as an afterthought. This paper also determines the impact of those security issues and possible solutions, providing future security-relevant directions to those responsible for designing, developing, and maintaining Fog systems

In Vitro and In Vivo Anti-Inflammatory Activity of 17-O-Acetylacuminolide through the Inhibition of Cytokines, NF-κB Translocation and IKKβ Activity

BACKGROUND AND PURPOSE: 17-O-acetylacuminolide (AA), a diterpenoid labdane, was isolated for the first time from the plant species Neouvaria foetida. The anti-inflammatory effects of this compound were studied both in vitro and in vivo. EXPERIMENTAL APPROACH: Plant extracts were initially tested against LPS-stimulated release of tumor necrosis factor alpha (TNF-α) from murine macrophages (RAW264.7 cells). Based on bioassay-guided fractionation, the active compound was identified as AA. AA was tested for its ability to reduce nitric oxide (NO) production, and the inducible nitric oxide synthase (iNOS) expression. The inhibition of a panel of inflammatory cytokines (TNF, IL-1β, IL-6, KC, and GM-CSF) by AA was assessed at the expression and the mRNA levels. Moreover, the effect of AA on the translocation of the transcription factor nuclear factor kappa B (NF-κB) was evaluated in LPS-stimulated RAW264.7 cells and in TNF-stimulated L929 cells. Subsequently, AA was tested in the inhibitor of NF-κB kinase beta (IKKβ) activity assay. Lastly, the anti-inflammatory activity of AA in vivo was evaluated by testing TNF production in LPS-stimulated Balb/c mice. KEY RESULTS: AA effectively inhibited TNF-α release with an IC(50) of 2.7 µg/mL. Moreover, AA significantly inhibited both NO production and iNOS expression. It significantly and dose-dependently inhibited TNF and IL-1β proteins and mRNA expression; as well as IL-6 and KC proteins. Additionally, AA prevented the translocation of NF-κB in both cell lines; suggesting that it is acting at a post receptor level. This was confirmed by AA's ability to inhibit IKKβ activity, a kinase responsible for activating NF-κB, hence providing an insight on AA's mechanism of action. Finally, AA significantly reduced TNF production in vivo. CONCLUSIONS AND IMPLICATIONS: This study presents the potential utilization of this compound, as a lead for the development of an anti-inflammatory drug