Recent advances in radar technology

The technical developments and advances that have taken place thus far are reviewed in those areas impacting future phased array active aperture radar systems. The areas covered are printed circuit antennas and antenna arrays, GaAs MMIC design and fabrication leading to affordable transmitter-receiver (T-R) modules, and novel hardware and software developments. The use of fiber-optic distribution networks to interconnect the monolithically integrated optical components with the T-R modules is discussed. Beamforming and sidelobe control techniques for active phased array systems are also examined.

Jouko Turkan Teatterikorkeakoulun kauden yhteiskunnallinen kontekstuaalisuus vuosina 1982 - 1985

The subject of my doctoral thesis is the social contextuality of Finnish theater director, Jouko Turkka's (b. 1942) educational tenure in the Theater Academy of Finland 1982 1985. Jouko Turkka announced in the opening speech of his rectorship in 1982 that Finnish society had undergone a social shift into a new cultural age, and that actors needed new facilities like capacity, flexibility, and ability for renewal in their work. My sociological research reveals that Turkka adapted cultural practices and norms of new capitalism and new liberalism, and built a performance environment for actors' educational work, a real life simulation of a new capitalist workplace. Actors educational praxis became a cultural performance, a media spectacle. Turkka's tenure became the most commented upon and discussed era in Finnish postwar theater history. The sociological method of my thesis is to compare information of sociological research literature about new capitalist work, and Turkka's educational theater work. In regard to the conceptions of legitimation, time, dynamics, knowledge, and social narrative consubstantial changes occurred simultaneously in both contexts of workplace. I adapt systems and chaos theory's concepts and modules when researching how a theatrical performance self-organizes in a complex social space and the space of Information. Ilya Prigogine's chaos theoretic concept, fluctuation, is the central social and aesthetic concept of my thesis. The chaos theoretic conception of the world was reflected in actors' pedagogy and organizational renewals: the state of far from equilibrium was the prerequisite of creativity and progress. I interpret the social and theater's aesthetical fluctuations as the cultural metaphor of new capitalism. I define the wide cultural feedback created by Turkka's tenure of educational praxis, and ideas adapted from the social context into theater education, as an autopoietic communicative process between theater education and society: as a black box, theater converted the virtual conception of the world into a concrete form of an actor's psychophysical praxis. Theater educational praxis performed socially contextual meanings referring to a subject's position in the social change of 1980s Finland. My other theoretic framework lies close to the American performance theory, with its close ties to the social sciences, and to the tradition of rhetoric and communication: theater's rhetorical utility materializes quotidian cultural practices in a theatrical performance, and helps the audience to research social situations and cultural praxis by mirroring them and creating an explanatory frame.

Interfaces and traps in pentacene field-effect transistor

The equivalent circuit parameters for a pentacene organic field-effect transistor are determined from low frequency impedance measurements in the dark as well as under light illumination. The source-drain channel impedance parameters are obtained from Bode plot analysis and the deviations at low frequency are mainly due to the contact impedance. The charge accumulation at organic semiconductor-metal interface and dielectric-semiconductor interface is monitored from the response to light as an additional parameter to find out the contributions arising from photovoltaic and photoconductive effects. The shift in threshold voltage is due to the accumulation of photogenerated carriers under source-drain electrodes and at dielectric-semiconductor interface, and also this dominates the carrier transport. The charge carrier trapping at various interfaces and in the semiconductor is estimated from the dc and ac impedance measurements under illumination. (c) 2010 American Institute of Physics. doi: 10.1063/1.3517085]

Nanoscale ZnO/CdS heterostructures with engineered interfaces for high photocatalytic activity under solar radiation

Semiconductor based nanoscale heterostructures are promising candidates for photocatalytic and photovoltaic applications with the sensitization of a wide bandgap semiconductor with a narrow bandgap material being the most viable strategy to maximize the utilization of the solar spectrum. Here, we present a simple wet chemical route to obtain nanoscale heterostructures of ZnO/CdS without using any molecular linker. Our method involves the nucleation of a Cd-precursor on ZnO nanorods with a subsequent sulfidation step leading to the formation of the ZnO/CdS nanoscale heterostructures. Excellent control over the loading of CdS and the microstructure is realized by merely changing the initial concentration of the sulfiding agent. We show that the heterostructures with the lowest CdS loading exhibit an exceptionally high activity for the degradation of methylene blue (MB) under solar irradiation conditions; microstructural and surface analysis reveals that the higher activity in this case is related to the dispersion of the CdS nanoparticles on the ZnO nanorod surface and to the higher concentration of surface hydroxyl species. Detailed analysis of the mechanism of formation of the nanoscale heterostructures reveals that it is possible to obtain deterministic control over the nature of the interfaces. Our synthesis method is general and applicable for other heterostructures where the interfaces need to be engineered for optimal properties. In particular, the absence of any molecular linker at the interface makes our method appealing for photovoltaic applications where faster rates of electron transfer at the heterojunctions are highly desirable.

Ultrasonic spray pyrolysis of CZTS solar cell absorber layers and characterization studies

CZTS (Copper Zinc Tin Sulphide) is a wide band gap quartnery chalcopyrite which has a band gap of about 1.45 eV and an absorption coefficient of 10(4) cm(-1); thus making it an ideal material to be used as an absorber layer in solar cells. Ultrasonic Spray Pyrolysis is a deposition technique, where the solution is atomized ultrasonically, thereby giving a fine mist having a narrow size distribution which can be used for uniform coatings on substrates. An Ultrasonic Spray Pyrolysis equipment was developed and CZTS absorber layers were successfully grown with this technique on soda lime glass substrates using aqueous solutions. Substrate temperatures ranging from 523 K to 723 K were used to deposit the CZTS layers and these films were characterized using SEM, EDAX and XRD. It was observed that the film crystallized in the kesterite structure and the best crystallites were obtained at 613 K. It was observed that the grain size progressively increased with temperature. The optical band gap of the material was obtained as 1.54 eV.

An integrated model for optimal reservoir operation for irrigation of multiple crops

An integrated model is developed, based on seasonal inputs of reservoir inflow and rainfall in the irrigated area, to determine the optimal reservoir release policies and irrigation allocations to multiple crops. The model is conceptually made up of two modules, Module 1 is an intraseasonal allocation model to maximize the sum of relative yields of all crops, for a given state of the system, using linear programming (LP). The module takes into account reservoir storage continuity, soil moisture balance, and crop root growth with time. Module 2 is a seasonal allocation model to derive the steady state reservoir operating policy using stochastic dynamic programming (SDP). Reservoir storage, seasonal inflow, and seasonal rainfall are the state variables in the SDP. The objective in SDP is to maximize the expected sum of relative yields of all crops in a year. The results of module 1 and the transition probabilities of seasonal inflow and rainfall form the input for module 2. The use of seasonal inputs coupled with the LP-SDP solution strategy in the present formulation facilitates in relaxing the limitations of an earlier study, while affecting additional improvements. The model is applied to an existing reservoir in Karnataka State, India.

Covalent Grafting of Polydimethylsiloxane over Surface-Modified Alumina Nanoparticles

The synthesis of ``smart structured'' conducting polymers and the fabrication of devices using them are important areas of research. However, conducting polymeric materials that are used in devices are susceptible to degradation due to oxygen and moisture. Thus, protection of such devices to ensure long-term stability is always desirable. Polymer nanocomposites are promising materials for the encapsulation of such devices. Therefore, it is important to develop suitable polymer nanocomposites as encapsulation materials to protect such devices. This work presents a technique based on grafting between surface-decorated gamma-alumina nanoparticles and polymer to make nanocomposites that can be used for the encapsulation of devices. Alumina was functionalized with allyltrimethoxysilane and used to conjugate polymer molecules (hydride-terminated polydimethylsiloxane) through a platinum-catalyzed hydrosilylation reaction. Fourier transform infrared spectroscopy, X-ray-photoelectron spectroscopy, and Raman spectroscopy were used to characterize the surface chemistry of the nanoparticles after surface modification. The grafting density of alkene groups on the surface of the modified nanoparticles was calculated using CHN and thermogravimetric analyses. The thermal stability of the composites was also evaluated using thermogravimetric analysis. The nanoindentation technique was used to analyze the mechanical characteristics of the composites. The densities of the composites were evaluated using a density gradient column, and the morphology of the composites was evaluated by scanning electron microscopy. All of our studies reveal that the composites have good thermal stability and mechanical flexibility and, thus, can potentially be used for the encapsulation of organic photovoltaic devices.

Open-source tools for enhancing full-text searching of OPACs Use of Koha, Greenstone and Fedora

Purpose - There are many library automation packages available as open-source software, comprising two modules: staff-client module and online public access catalogue (OPAC). Although the OPAC of these library automation packages provides advanced features of searching and retrieval of bibliographic records, none of them facilitate full-text searching. Most of the available open-source digital library software facilitates indexing and searching of full-text documents in different formats. This paper makes an effort to enable full-text search features in the widely used open-source library automation package Koha, by integrating it with two open-source digital library software packages, Greenstone Digital Library Software (GSDL) and Fedora Generic Search Service (FGSS), independently. Design/methodology/approach - The implementation is done by making use of the Search and Retrieval by URL (SRU) feature available in Koha, GSDL and FGSS. The full-text documents are indexed both in Koha and GSDL and FGSS. Findings - Full-text searching capability in Koha is achieved by integrating either GSDL or FGSS into Koha and by passing an SRU request to GSDL or FGSS from Koha. The full-text documents are indexed both in the library automation package (Koha) and digital library software (GSDL, FGSS) Originality/value - This is the first implementation enabling the full-text search feature in a library automation software by integrating it into digital library software.

Robust controller for an autonomous small refrigeration unit

The authors describe the constructional features of a controller for operating an autonomous refrigeration unit powered by a field of photovoltaic panels and backed up by a generator set. The controller enables three voltage levels of operation of an inverter to meet the start, run and off cycle conditions of the refrigerator compressor. The algorithm considers several input and output parameters and status signals from each subsystem of the unit to deduce a control strategy. Such units find application for storage of vaccines and life-saving medicines requiring uninterrupted refrigeration, in medical shops, rural health centres, veterinary laboratories etc.

Analytical solutions for heat transfer during cyclic melting and freezing of a phase change material used in electronic or electrical packaging

In this paper we develop an analytical heat transfer model, which is capable of analyzing cyclic melting and solidification processes of a phase change material used in the context of electronics cooling systems. The model is essentially based on conduction heat transfer, with treatments for convection and radiation embedded inside. The whole solution domain is first divided into two main sub-domains, namely, the melting sub-domain and the solidification sub-domain. Each sub-domain is then analyzed for a number of temporal regimes. Accordingly, analytical solutions for temperature distribution within each subdomain are formulated either using a semi-infinity consideration, or employing a method of quasi-steady state, depending on the applicability. The solution modules are subsequently united, leading to a closed-form solution for the entire problem. The analytical solutions are then compared with experimental and numerical solutions for a benchmark problem quoted in the literature, and excellent agreements can be observed.

Synthesis and Self-Assembly of Donor-Acceptor-Donor Based Oligothiophenes and Their Optoelectronic Properties

In this work, the synthesis of an oligothiophene having a donor acceptor donor (D-A-D) chromophore with hydrogen bonding groups is described. The D-A-D molecule was demonstrated to self-organize via intermolecular H-bonding between barbituric acid units. Interactions between the oligothiophene subunits were also found to be important, affording nanoribbons that could be observed by atomic force and transmission electron microscopy. The applicability of the oligothiophene for organic electronic applications was investigated by fabricating organic field-effect transistors (OFETs) and organic photovoltaic devices. The OFET measurements yielded p-type mobility of 7 x 10(-7) cm(2)/(Vs), and when blended with C(60)-PCBM, the photovoltaic efficiency was observed to be 0.18%.

Influence of the highest occupied molecular orbital energy level of the donor material on the effectiveness of the anode buffer layer in organic solar cells

Efficiency of organic photovoltaic cells based on organic electron donor/organic electron acceptor junctions can be strongly improved when the transparent conductive Anode is coated with a Buffer Layer (ABL). Here, the effects of a metal (gold) or oxide (molybdenum oxide) ABL are reported, as a function of the Highest Occupied Molecular Orbital (HOMO) of different electron donors. The results indicate that a good matching between the work function of the anode and the highest occupied molecular orbital of the donor material is the major factor limiting the hole transfer efficiency. Indeed, gold is efficient as ABL only when the HOMO of the organic donor is close to its work function Phi(Au). Therefore we show that the MoO(3) oxide has a wider field of application as ABL than gold. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

An experimental study on fracture process zone in high strength concrete beams

An attempt has been made to experimentally investigate the fracture process zone (FPZ) using Acoustic Emission (AE) method in High Strength Concrete (HSC) beams subjected to monotonically increasing load. Stress waves are released during the fracture process in materials, which cause acoustic emissions. AE energy released during the fracture of notched HSC beam specimens during Three Point Bend (TPB) tests is measured and is used to investigate the FPZ in the notched HSC beams having 28-day compressive strength of 78.0 MPa. The specimens are tested by Material Testing System (MTS) of 1200 KN capacity employing Crack Mouth Opening Displacement (CMOD) control at the rate of 0.0004 mmlsec in accordance with RILEM recommendations. A brief review on AE technique applied to concrete fracture is presented. The fracture process zone developed and the AE energy released during the fracture process in high strength concrete beam specimens are presented and discussed. It was observed that AE events containing higher energy are located around the notch tip. It may be possible to relate AE energy to fracture energy of concrete.

Adaptive Filtering Technique and DSP Based Implementation for High-Speed Distance Protection

The paper presents an adaptive Fourier filtering technique and a relaying scheme based on a combination of a digital band-pass filter along with a three-sample algorithm, for applications in high-speed numerical distance protection. To enhance the performance of above-mentioned technique, a high-speed fault detector has been used. MATLAB based simulation studies show that the adaptive Fourier filtering technique provides fast tripping for near faults and security for farther faults. The digital relaying scheme based on a combination of digital band-pass filter along with three-sample data window algorithm also provides accurate and high-speed detection of faults. The paper also proposes a high performance 16-bit fixed point DSP (Texas Instruments TMS320LF2407A) processor based hardware scheme suitable for implementation of the above techniques. To evaluate the performance of the proposed relaying scheme under steady state and transient conditions, PC based menu driven relay test procedures are developed using National Instruments LabVIEW software. The test signals are generated in real time using LabVIEW compatible analog output modules. The results obtained from the simulation studies as well as hardware implementations are also presented.

MAX: A Multi Objective Memory Architecture eXploration Framework for Embedded Systems-on-Chip

Today's feature-rich multimedia products require embedded system solution with complex System-on-Chip (SoC) to meet market expectations of high performance at a low cost and lower energy consumption. The memory architecture of the embedded system strongly influences these parameters. Hence the embedded system designer performs a complete memory architecture exploration. This problem is a multi-objective optimization problem and can be tackled as a two-level optimization problem. The outer level explores various memory architecture while the inner level explores placement of data sections (data layout problem) to minimize memory stalls. Further, the designer would be interested in multiple optimal design points to address various market segments. However, tight time-to-market constraints enforces short design cycle time. In this paper we address the multi-level multi-objective memory architecture exploration problem through a combination of Multi-objective Genetic Algorithm (Memory Architecture exploration) and an efficient heuristic data placement algorithm. At the outer level the memory architecture exploration is done by picking memory modules directly from a ASIC memory Library. This helps in performing the memory architecture exploration in a integrated framework, where the memory allocation, memory exploration and data layout works in a tightly coupled way to yield optimal design points with respect to area, power and performance. We experimented our approach for 3 embedded applications and our approach explores several thousand memory architecture for each application, yielding a few hundred optimal design points in a few hours of computation time on a standard desktop.