Characterization of CuInS2 thin films prepared by electrodeposition and sulfurization with photoluminescence spectroscopy

Potentiostatic electrodeposition and sulfurization techniques were used to prepare polycrystalline CuInS₂ thin films. X-ray diffraction and photoresponse measurements in a photoelectrochemical cell (PEC) revealed that photoactive polycrystalline CuInS₂ films can be deposited on Ti substrate. Photoluminescence (PL) spectroscopy was used to investigate the prepared thin films and optically characterize them. PL spectra revealed the defect structure of the samples with an acceptor energy level at 109 meV above the valance band and a donor energy level at 71 meV below the conduction band. The CuInS₂ thin films prepared in this investigation are observed to be In-rich material with n-type electrical conductivity.     

Sulphidation of electrodeposited cuprous oxide thin films for photovoltaic applications

Electrodeposited cuprous oxide thin films on indium-doped tin oxide (ITO) substrates were sulphided by exposing them to a spray of aqueous solution of sodium sulphide or to a mixture of hydrogen sulphide and nitrogen gases. Both methods produced light darker and darker films having different photovoltaic characteristics in a solar cell structure. The photovoltages produced by the light darker films under AM 1.5 illumination was negative as compared to the positive photovoltages produced by the darker films. Spectral response measurements revealed that most of the light darker films produced positive photovoltages in the shorter wavelengths and negative photovoltages in the longer wavelengths. However, some of the light darker films produced only the negative photovoltage for the entire spectral range and their photovoltaic properties were comparatively better. Darker films resulted in only the positive photovoltages in the entire spectral range. As a result of the sulphidation, the bulk crystal structure of the cuprous oxide thin films was not changed, however, the interfacial characteristics of the solar cell structure were modified.     

A generalised solution for generating stepper motor speed profiles in real time

We present a new low-complexity algorithm for controlling a stepper motor to rotate with constant acceleration or deceleration. It can be operated on a basic low-end microcontroller and does not require any data tables. Also, it does not have the limitation of the motor having to start from standstill. The algorithm was tested using a small robot programmed to move and change acceleration ‘on the run’. The theoretical foundations for further improving the timing accuracy of the algorithm were also derived.     

Sigiri: uniform resource abstraction for grids and clouds

With the maturation of grid computing facilities and recent explosion of cloud computing data centers, midscale computational science has more options than ever before to satisfy computational needs. But heterogeneity brings complexity. We propose a simple abstraction for interaction with heterogeneous resource managers spanning grid and cloud computing and on features that make the tool useful for the midscale physical or natural scientist. Key strengths of the abstraction are its support for multiple standard job specification languages, preservation of direct user interaction with the service, removing the delay that can come through layers of services, and the predictable behavior under heavy loads. Copyright © 2012 John Wiley & Sons, Ltd.     

PostBits: using contextual locations for embedding cloud information in the home

Placing information at specific locations in the home provides rich and intuitive ways for people to cope with information, as they leverage semantics of the locations within the home. However, there is no deeper investigation yet on how users would embed digital cloud-based information into various locations in their homes, partly because previous systems were not robust enough to be deployed in real settings for an extended period of time. To this end, we have developed PostBits, a system of display blocks that integrate cloud information with contextually rich physical space. PostBits were designed for long battery life, robust communication and simple interactions, to enable a field deployment. A field study was conducted with 6 families, each using the system in their home for 1 week. We have identified patterns and strategies of how users embed cloud information at contextual locations in the home, and reflect on future design opportunities.     

Evaluation and Enhanced Use of Light Emitting Diodes for Hydroponics

Hydroponic farming is a viable and economical farming method,which can produce safe and healthy greens and vegetables conveniently and at a relatively low cost....     

Evaluation and Enhanced Use of Light Emitting Diodes for Hydroponics

Hydroponic farming is a viable and economical farming method, which can produce safe and healthy greens and vegetables conveniently and at a relatively low cost. It is essential to provide supplemental lighting for crops grown in greenhouses to meet the daily light requirement, Daily Light Integral (DLI). The present paper investigates how effectively and efficiently LEDs can be used as a light source in hydroponics. It is important for a hydroponic grower to assess the requirement of photosynthetically active radiation (PAR) or the Photosynthetic Photon Flux Density (PPFD), in a greenhouse, and adjust the quality and quantity of supplemental lighting accordingly. A Quantum sensor (or PAR sensor) can measure PAR more accurately than a digital light meter, which measures the light intensity or illuminance in the SI unit Lux, but a PAR sensor is relatively expensive and normally not affordable by an ordinary farmer. Therefore, based on the present investigation and experimental results, a very simple way to convert light intensity measured with a Lux meter into PAR is proposed, using a simple conversion factor (41.75 according to the present work). This allows a small-scale hydroponic farmer to use a simple and inexpensive technique to assess the day to day DLI values of PAR in a greenhouse accurately using just an inexpensive light meter. The present paper also proposes a more efficient way of using LED light panels in a hydroponic system. By moving the LED light panels closer to the crop, LED light source can use a fewer number of LEDs to produce the same required daily light requirement and can increase the efficiency of the power usage to more than 80%. Specifically, the present work has determined that it is important to design more efficient vertically movable LED light panels with capabilities of switching individual LEDs on and off, for the use in greenhouses. This allows a user to control the number of LEDs that can be lit at a particular time, as required. By doing so it is possible to increase the efficiency of a LED lighting system by reducing its cost of the electricity usage.     

Study of annealing effects of cuprous oxide grown by electrodeposition technique

Low temperature electrochemical deposition of cuprous oxide from aqueous solutions has been investigated. X-ray diffraction, scanning electron microscopy, optical absorption, and photo-response of liquid/cuprous oxide junctions have been used to study the deposits' crystallographic, morphological, optical, and electrical properties. Effects of annealing in air have been studied using the above mentioned methods. As-deposited cuprous oxide exhibits a direct band gap of 2.0 eV, and shows an n-type behaviour when used in an liquid/solid junction. Annealing below 300°C enhances the n-type photocurrent produced by the junction. Type conversion occurs after heat treatments in air at temperatures above 300°C. No apparent bulk structure changes have been observed during annealing below this temperature, but heat treatments above this temperature produce darker films containing cupric oxide and its complexes with water.     

Infoshare : Design and Implementation of Scalable Multimedia Signage Architecture for Wireless Ubiquitous Environments

Digital signage systems have found many interesting applications in the realms of advertising, entertainment and education. One of the most prevalent challenging issues faced by current Local Area Network (LAN) based Digital signage network architectures is that their difficulty in porting to wireless ubiquitous environments. While popularity of wireless LANs promotes such architectural improvement, Traditional thin/thick client based architectures suffer inefficiency and scalability issues introduced by use of proprietary signage content formats. Use of such content formats to store signage contents is less optimal since it could lead to content redundancy, difficulty in creating, managing signage contents and scalability issues. As a solution for this issue we propose a Smart Client based digital signage architecture that uses XAML (an XML based declarative GUI language) contents for expressing its signage displays. While Smart Clients can better tolerate communication disruptions which are quite frequent in wireless environments, use of XAML based open content format promotes use of simple tools and variety of devices for signage content creation and management over the Internet in a ubiquitous environment. We successfully applied this generic architecture to a prototype digital signage system called Infoshare and report its robustness in withstanding network disruptions. We evaluate the easiness of editing XAML based signage contents by comparing Infoshare with a popular LAN based digital signage system which uses proprietary content formats. We demonstrate scalability of Infoshare signage service in terms of hardware resources by deploying it in different hardware platforms.