Parallel asynchronous systems and image processing algorithms

A new hardware approach to implementation of image processing algorithms is described. The approach is based on silicon devices which would permit an independent analog processing channel to be dedicated to evey pixel. A laminar architecture consisting of a stack of planar arrays of the device would form a two-dimensional array processor with a 2-D array of inputs located directly behind a focal plane detector array. A 2-D image data stream would propagate in neuronlike asynchronous pulse coded form through the laminar processor. Such systems would integrate image acquisition and image processing. Acquisition and processing would be performed concurrently as in natural vision systems. The research is aimed at implementation of algorithms, such as the intensity dependent summation algorithm and pyramid processing structures, which are motivated by the operation of natural vision systems. Implementation of natural vision algorithms would benefit from the use of neuronlike information coding and the laminar, 2-D parallel, vision system type architecture. Besides providing a neural network framework for implementation of natural vision algorithms, a 2-D parallel approach could eliminate the serial bottleneck of conventional processing systems. Conversion to serial format would occur only after raw intensity data has been substantially processed. An interesting challenge arises from the fact that the mathematical formulation of natural vision algorithms does not specify the means of implementation, so that hardware implementation poses intriguing questions involving vision science

Parallel asynchronous hardware implementation of image processing algorithms

Research is being carried out on hardware for a new approach to focal plane processing. The hardware involves silicon injection mode devices. These devices provide a natural basis for parallel asynchronous focal plane image preprocessing. The simplicity and novel properties of the devices would permit an independent analog processing channel to be dedicated to every pixel. A laminar architecture built from arrays of the devices would form a two-dimensional (2-D) array processor with a 2-D array of inputs located directly behind a focal plane detector array. A 2-D image data stream would propagate in neuron-like asynchronous pulse-coded form through the laminar processor. No multiplexing, digitization, or serial processing would occur in the preprocessing state. High performance is expected, based on pulse coding of input currents down to one picoampere with noise referred to input of about 10 femtoamperes. Linear pulse coding has been observed for input currents ranging up to seven orders of magnitude. Low power requirements suggest utility in space and in conjunction with very large arrays. Very low dark current and multispectral capability are possible because of hardware compatibility with the cryogenic environment of high performance detector arrays. The aforementioned hardware development effort is aimed at systems which would integrate image acquisition and image processing

Theory of transient spectroscopy of multiple quantum well structures

A theory of the transient spectroscopy of quantum well (QW) structures under a large applied bias is presented. An analytical model of the initial part of the transient current is proposed. The time constant of the transient current depends not only on the emission rate from the QWs, as is usually assumed, but also on the subsequent carrier transport across QWs. Numerical simulation was used to confirm the validity of the proposed model, and to study the transient current on a larger time scale. It is shown that the transient current is influenced by the nonuniform distribution of the electric field and related effects, which results in a step-like behavior of the current. A procedure of extraction of the QW emission time from the transient spectroscopy experiments is suggested.Comment: 5 pages, 4 figures, to be published in J. Appl. Phy

TIME ON THE MARKET OF RESIDENTIAL CONDOMINIUM UNITS WITH PRE-SALE ARRANGEMENT IN COLOMBO DISTRICT

The purpose of this paper is to study the time on market (TOM) for residential condominium units under pre sales arrangements and what key factors drive that TOM. The contextual understanding of previous studies on TOM for residential properties confined for properties sold either in the secondary market or properties where construction is completed. This study focuses on the relationships among TOM, listed price, and basic property characteristics of residential condominium units sold under the provisional condominium plan in Colombo, Sri Lanka. Following non-probability sampling technique, this study examines TOM of 189 pre-sale residential condominium units in Colombo district which came into market between 2016 January to 2019 January. Developers were approached to collect required data such as transaction price, transaction date, final listed date listed price, number of bedrooms, number of bathrooms, floor area, floor level, construction completion, discounting rates likewise. Data analysis followed descriptive statistics, Pearson Correlation, and multiple regression model. The analysis highlighted that from January-2016 to January-2019, TOM of provisional residential condominiums of Colombo varied from 12.76 to 5.51 months. The results further highlighted that the TOM of a pre-sale provisional residential condominium unit is a function of floor area, number of bathrooms, level of the unit, construction completion & discount rate. The study highlights that during the period considered, the floor area units of 744sqft at the initial stage of construction with a discount rate between 10% to 20% from the listed price can predicted to have the lowest TOM.. Keywords: Time on the Market; Pre-sale; Residential Condominium Units; Listed Price; TransactionPrice

Characteristics of a tunneling quantum-dot infrared photodetector operating at room temperature

We report high-temperature (240–300 K)(240–300K) operation of a tunneling quantum-dot infrared photodetector. The device displays two-color characteristics with photoresponse peaks at ∼ 6 μm∼6μm and 17 μm17μm. The extremely low dark current density of 1.55 A/cm21.55A∕cm2 at 300 K300K for 1 V1V bias is made possible by the tunnel filter. For the 17 μm17μm absorption, the measured peak responsivity is 0.16 A/W0.16A∕W (300 K)(300K) for a bias of 2 V2V and the specific detectivity D*D* is 1.5×107 cm Hz1/2/W1.5×107cmHz1∕2∕W (280 K)(280K) for a bias of 1 V1V. Excellent performance characteristics are also measured for the 6 μm6μm photoresponse.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87841/2/191106_1.pd

Terahertz detection with tunneling quantum dot intersublevel photodetector

The characteristics of a tunnel quantum dot intersublevel photodetector, designed for the absorption of terahertz radiation, are described. The absorption region consists of self-organized In0.6Al0.4As/GaAsIn0.6Al0.4As∕GaAs quantum dots with tailored electronic properties. Devices exhibit spectral response from 20 to 75 μm20to75μm ( ∼ 4 THz)(∼4THz) with peak at ∼ 50 μm∼50μm. The peak responsivity and specific detectivity of the device are 0.45 A/W0.45A∕W and 108 cm Hz1/2/W108cmHz1∕2∕W, respectively, at 4.6 K4.6K for an applied bias of 1 V1V. Response to terahertz radiation is observed up to 150 K150K.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87819/2/031117_1.pd

A Review on the Comparative Analysis of Synthetic Insect Repellents and Essential Oil Based Sustained-release Insect Repellent Formulations

The necessity of developing insect repellents with highly effective sustained release properties has attracted more attention due to the vast spread of arthropod-borne diseases such as dengue and malaria, which must be controlled with proper measures, and also due to the devastating damage caused by severe infestation of insect pests on crops and stored food. Natural and synthetic insect repellents are used against insect vectors and insect pests. Topical insect repellent formulations should be less toxic, less irritant, and less skin permeable. Irrespective of the type and form of the repellent, the mechanism of action depends on the formation of a vapour barrier/ odour barrier, that would deviate the insect from reaching the host. Synthetic insect repellents are highly efficient but due to their high toxicity, degradation resistance, and bio accumulation, they raise environmental and ecological issues. Due to the adverse effects caused by synthetic insect repellents, more attention is given to insect repellents consisting of natural products.Essential oils are among the widely used natural insect repellents available due to their biocompatibility and non-toxicity. High volatility of essential oils is the major problem that hampers the application of essential oils as insect repellent agents. The high volatility that reduces the length of application, and its activity can be successfully addressed by the formulation of slow-release insect repellent composites by incorporating essential oils into adsorbing or encapsulating matrices. Zeolites, montmorillonite, β-cyclodextrin, polymeric materials, and electrospun nanomaterials are commonly used to develop slow-release formulations with essential oils. Among these, polymeric microcapsules are the most extensively studied and developed slow-release insect repellent systems that are based on natural and synthetic active compounds. Key words: Formulation, Insects, Microcapsules, Repellents, Zeolit

Eco-Friendly Alternatives for Storage Pest Management:Leaves of Ruta Graveolens (Aruda) as a Repellent Against the Rice Weevil, Sitophilus Oryzae L.

In view of worldwide interest and greater public awareness in finding plant products as the most promising and ecologically safer alternatives for synthetic insecticides in post-harvest protection of stored rice, present study was undertaken to explore the potential of leaves of Ruta graveolens (Aruda) as a repellent against S.oryzae infestations. Leaf powder and solvent extracts of R. graveolens were evaluated for their contact and fumigant repellent properties against seven day old S. oryzae adults. In contact repellency test, weevils (20 each) were exposed to 1.0 g, 3.0 g, 5.0 g, and 7.0 g of leaf powder mixed with white raw rice grains in a modified cup bioassay apparatus. Fumigation repellency of leaf powder was tested using same dosages and the number of weevils in a fumigation-repellency chamber. Number of weevils that moved from the bioassay chamber was recorded one hour after weevil introduction. Leaves of R. graveolens were extracted in hexane, ethyl acetate, methanol, distilled water and different concentrations 10, 50, 100% (v/v) were assessed separately to evaluate repellent activity by means of an area preference bioassay. In all experiments, ten weevils for each were tested and the number repelled was recorded 30 minutes after weevil introduction. Highest contact and fumigant repellent effects were elicited by 7.0 g of leaf powder resulting 96% and 95% respectively, whilst lowest dose also produced more than 50% repellency indicating extremely strong repellent action of the plant powder. In comparison, aqueous extract exhibited the most potent repellent activity (91%) while other extracts were producing over 70% repellent effects on weevils at the concentration of 100% (v/v). Overall findings of the study suggest that both powder and extracts of R. graveolens leaves could be used as eco-friendly agents for post-harvest rice protection. KEYWORDS: Ruta graveolens, Sitophilus oryzae, stored rice, leaf powder, repellen

Optical interference and nonlinearities in quantum-well infrared photodetectors

Abstract The e ects of optical interference in quantum-well infrared photodetectors (QWIPs) caused by re ection of radiation from the metal contact are investigated. It is shown that interference leads to strong deterioration of QWIP characteristics (responsivity, noise, and noise equivalent power (NEP)) if signal photocurrent is larger than the dark current or background current. This is caused by the nonuniform distribution of the photogeneration rate, electric ÿeld, and all other microscopic physical quantities. As a result, the photocurrent gain and photoionization e ciency are decreased, while the noise gain is increased with respect to their values for uniform excitation. Several puzzling experimental e ects -a strong increase of the QWIP NEP for high-power heterodyne operation and temperature dependence of QWIP responsivity -can be explained by the model described above.