Quarterwave microstrip antenna on a ferrimagnetic substrate

Experiment conducted on a microstrip quarterwave antenna structure on a typical ferrite substrate reveals reduction in size, interesting radiation characteristics and a broadband nature over a wide range of frequencies in the lower UHF region.     

Long wavelength GRIN-SCH MQW lasers incorporating graded GaAlInAs confinement layers

We report the growth and characterisation of the first GaAllnAs based GRIN-SCH MQW lasers operating at 1.3 and 1.6μm. In these devices, GaAllnAs barriers and either GalnAs or GaAllnAs wells have been used for the 1.6 and 1.3μm lasers, respectively, together with true continuously graded composition GaAlInAs regions for the confinement layers. The excellent structural quality of the active and confinement regions and control of wavelength uniformity has been confirmed. Buried ridge lasers fabricated from the GRIN-SCH MQW wafers lased at 1.3 and 1.6μm with CW threshold currents of 65 and 30 mA, respectively.     

Emission properties of Spindt-type cold cathodes with differentemission cone material

Emission properties of thin film field emission array cathodes with molybdenum, hafnium, diamond-like carbon, and lanthanum hexaboride cones were investigated. Each array consisted of 681 holes and cones (microcells), spaced on 10-μm centers on a silicon substrate. At work functions of more than 5 eV carbon cones had the lowest operating voltage-less than 50 V-due to the high value of the form factor of the cones, which have a sharp ribbed pyramidal shape. However, high current density was not achieved with such cathodes because of the low conductance of this type of diamond-like carbon. Different approaches to increase transconductance provided by one cell are discussed     

A novel magnetic random access memory design using square ring elements for the hard layer

The behavior of narrow permalloy square rings under the influence of a magnetic field was studied using magnetic force microscopy (MFM). Two stable states of opposite polarity at remanence and simple switching were observed. We propose a design for the hard layer of magnetic random access memory (MRAM) that uses these states in square rings for data storage.     

A small-molecule organic semiconductor

The electrical conductivity and optical properties of bis-diethylaminokumarin have been investigated. The electrical conductivity of the compound exhibited three-dimensional hopping conduction in the temperature range 295–321 K. The compound shows a typical semiconductor property, and its semiconducting property results from delocalization of the π-electrons in the structure. To determine the optical band gap of the compound, an optical absorption study was made in the wavelength range 250–600 nm. The optical study revealed that the optical transition is the allowed indirect one. The electronic parameters, such as the electrical conductivity at room temperature σ₂₅, activation energy E, and optical band gap E_g of the compound are 1.46×10^?5 S/cm, 0.42 eV, and 2.46 eV, respectively. These values are in agreement with electronic parameters of organic semiconductors.     

Design and control of a microrobotic system using magneticlevitation

Presents a prototype microrobot based on magnetic principles. Miniature items are to be transported and assembled in hazardous environments. A microrobot can be remotely operated with 3 DOF in an enclosed environment by transferring magnetic energy and optical signals from outside. The magnetic drive unit consists of 8 electromagnets (4 pairs), 2 permanent magnets, a return yoke and a pole piece. The microrobot is manipulated under the pole piece by regulating magnetic field. It consists of a magnetic head, a body (electronic circuit and batteries), and copper alloy ribbon ringers. A shape memory alloy actuator activates the fingers by illuminating/extinguishing several LED. PID controls were applied. To cope with uncertainties and variations in payload masses, an adaptive control law was also employed for positioning along the z axis to enable the controller parameters to be adjusted in real-time. Effectiveness of the control was verified by the results of several experiments. The microrobot has a net mass of 8.1 g and it can elevate and manipulate objects with masses up to 1.5 g within a volume of 29×29×26 mm³ with a precision of 0.05 mm     

A design of experiment analysis of serial EEPROM endurance

The results of a study using a design of experiments approach to examine the effects of environmental operating conditions on serial EEPROM endurance are presented. The conditions studied in the experiment were operating temperature, applied voltage, device type, array usage, write cycles per day, data pattern, and write pulse width. An ANOVA table showing the significant effects and an estimation of the value of the effects using an error minimization technique is presented. While the techniques presented are relatively simple, they may be useful as a quick check of acceleration effects in EEPROM endurance cycling, without the use of extensive factorial experiments. The results show temperature, array size and voltage to be the most important effects on EEPROM endurance cycling. The temperature effect matches other published data.     

Si(hhm) surfaces: Templates for developing nanostructures

Semiconductors - The fabrication of ordered low-dimensional structures on clean and metal-atom-decorated stepped Si(557) and Si(556) surfaces is discussed. The formation conditions and atomic...     

Noniterative blind data restoration by use of an extracted filter function

A signal-processing algorithm has been developed where a filter function is extracted from degraded data through mathematical operations. The filter function can then be used to restore much of the degraded content of the data through use of a deconvolution algorithm. This process can be performed without prior knowledge of the detection system, a technique known as blind deconvolution. The extraction process, designated self-deconvolving data reconstruction algorithm, has been used successfully to restore digitized photographs, digitized acoustic waveforms, and other forms of data. The process is noniterative, computationally efficient, and requires little user input. Implementation is straightforward, allowing inclusion into many types of signal-processing software and hardware. The novelty of the invention is the application of a power law and smoothing function to the degraded data in frequency space. Two methods for determining the value of the power law are discussed. The first method assumes the power law is frequency dependent. The function derived comparing the frequency spectrum of the degraded data with the spectrum of a signal with the desired frequency response. The second method assumes this function is a constant of frequency. This approach requires little knowledge of the original data or the degradation.     

Angle- and size-dependent characteristics of incoherent Raman and fluorescent scattering by microspheres. 1. General expressions

A dipole model is used to simulate incoherent Raman and fluorescent scattering by microspheres. The use of the addition theorem for spherical harmonics circumvents the need to evaluate double sums in the final formulas, thereby drastically reducing computational effort. Special attention is paid to consideration of backscattering geometry, which is important for lidar applications. The formulas derived for backscattering geometry decrease the computation time for size parameter x approdximately 100 by a factor of 200 compared with the time for calculations performed at other angles.