Resonant tunneling diodes as sources for millimeter andsubmillimeter wavelengths

High quality resonant tunneling diodes have been fabricated and tested as sources for millimeter and submillimeter wavelengths. The devices have shown excellent I-V characteristics with peak-to-valley current ratios as high as 6:1 and current densities in the range of 50-150 kA/cm² at 300 K. Used as local oscillators, the diodes are capable of state of the art output power delivered by AlGaAs-based tunneling devices. As harmonic multipliers, a frequency of 320 GHz has been achieved by quintupling the fundamental oscillation of a klystron source     

Empirical studies in reverse engineering: state of the art and future trends

Starting with the aim of modernizing legacy systems, often written in old programming languages, reverse engineering has extended its applicability to virtually every kind of software system. Moreover, the methods originally designed to recover a diagrammatic, high-level view of the target system have been extended to address several other problems faced by programmers when they need to understand and modify existing software. The authors’ position is that the next stage of development for this discipline will necessarily be based on empirical evaluation of methods. In fact, this evaluation is required to gain knowledge about the actual effects of applying a given approach, as well as to convince the end users of the positive cost–benefit trade offs. The contribution of this paper to the state of the art is a roadmap for the future research in the field, which includes: clarifying the scope of investigation, defining a reference taxonomy, and adopting a common framework for the execution of the experiments.     

Emission and capture of electrons in multiquantum-well structures

The mechanisms of unipolar emission and capture of electrons are studied in multiquantum-well structures in relation with the quantum-well infrared photoconductors (QWIP's). We clarify the roles played by the physical parameters which appear in the different QWIP photoresponse models, i.e., the photoconductive and the photoemissive ones. We then describe the experimental procedures which allow us to independently determine these different parameters: deep level optical spectroscopy for the electron emission probability, impedance spectroscopy for the quantum-well capture velocity and thermal emission time, as well as the infrared photoconductive gain for the unipolar electron capture time. The measured dependence of these parameters on photon energy and electric field sheds light on the microscopic physical phenomena which are involved in quantum-well infrared photodetection. Theoretical results on optical phonon mediated transitions in an applied electric field from barrier to well states show good agreement with experiment at low fields but less dependence on the field. Finally, this theoretical approach allows us to connect the different parameters and solve the apparent discrepancy between the QWIP photoresponse models     

Current directions in research on understanding and preventing intoxicated aggression

The present paper describes promising research directions that emerged from a recent international conference on intoxication and aggression and from the scientific literature generally. In this overview, intoxicated aggression is seen as arising from an interactional process involving multiple contributing factors or causes. This model helps to define research directions that can further understanding and prevention. First, the societal/cultural framing of intoxication and aggression exerts a powerful influence on drinking behaviour and needs to be better understood. Another important area for research is the moderating role on alcohol-related aggression of personal factors such as predisposition to aggression and individual differences in expectations about alcohol and aggression. Research on the role of basic pharmacological effects of alcohol in increasing the likelihood of aggressive behaviour is also a critical aspect of understanding intoxicated aggression. Drinking contexts and environments play a considerable role in the relationship between intoxication and aggressive behaviour and need to be better understood. Another critical direction for future research is the study of intoxicated aggression as a process involving the interaction of the person, the situation and the effects of alcohol in natural and experimental settings. Finally, the paper highlights promising directions for research on interventions to prevent intoxicated aggression and violence.     

On-Board Check System with Speech Synthesis

By using specially developed microprocessors, and the larger, cheaper read-only memories (ROM's) now available, it is possible to store and reproduce the human voice electronically.     

Review of principal hydrocarbon-bearing basins of the South China Sea area

As a consequence of exploration for hydrocarbons, and of research programs conducted by academic and international institutions, substantial progress has been made in recent years in definition of hydrocarbon bearing basins, and those potentially so, in Southeast Asia and the South China Sea. Basins and depositional provinces now recognized include: the Thai Basin, the Malay Basin, West Natuna and Penyu Basins, Saigon (Ho Chi Minh) and Mekong (Vung Tau) Basins, East Natuna area, the Greater Sarawak Basin including Central Luconia and Balingian depositional provinces, the Baram Delta/Brunei-Sabah Basin and the Northwest Palawan Shelf. Where hydrocarbons have been encountered, the deposits are commonly associated with rocks of mid- and Upper Miocene age. Oligocene and Pliocene occurrences are locally significant.With some exceptions, most sedimentary basin-fill was deposited within continental to coastal environments. Such sediments are commonly gas-prone. Where oil-prone, there are suggestions that the oil has been generated under conditions of greater thermal maturity. Stratigraphic correlation depends largely on recognition of cyclic successions by means of integration of information derived from seismic stratigraphy, and paleontological and environmental analysis. Structures are commonly anticlinal and fault-associated; the anticlines are commonly suspected to have diapiric cores. Major transcurrent faults of regional extent may have been instrumental in formation of depositional provinces and anticlinal trends.     

A software for evaluating local accuracy in the fourier transform

With the evolution of computers toward ever increasing computing speed, the numerical algorithms implemented on such computers are more and more complex, and require a very great number of computations. The numerical errors inherent in floating-point arithmetic of the computer generate errors in the results which may be fairly great. In this paper we propose a software based on the Perturbation Method for estimating the local accuracy in the Fast Fourier Transform, both in the case of exact data (computing errors alone) and in the case of experimental data (data errors and computing errors).     

A Decision Process Implementation for Microwave Near-Field Characterization of Concrete Constituent Makeup

Determination of concrete compressive strength is one of the most important factors in the construction industry. Concrete is a mixture of cement, water, sand (fine aggregate) and rock (coarse aggregate) of various sizes. Water and cement chemically bind to form the cement paste phase of concrete, which primarily influences the compressive strength. The aggregate content mainly acts as a filler but also influences the compressive strength of concrete. Currently, there is no single method for nondestructive determination of compressive strength of concrete. As a result, the only reliable method of compressive strength measurement is to core a specimen from an existing structure and perform a compressive failure test. In recent years, studies on the reflection properties of concrete with varying material content have been performed using microwave nondestructive testing techniques. These techniques, employing open-ended rectangular waveguide probes, have shown tremendous potential for determining concrete constituent makeup. The results have demonstrated that microwave reflection property measurements of concrete as a function of varying constituent makeup, possess statistical properties that provide for a unique fingerprint. In this paper a simple decision process is proposed, based on the maximum likelihood ratio, which uses the a priori statistical distribution of microwave reflection measurements for material content determination of concrete specimens. The results show that by simply performing two sets of microwave reflection property measurements at 3 and 10 GHz, the constituent makeup of an unknown concrete specimen can be very closely determined. Subsequently, the compressive strength of the specimen could be easily determined from a simple lookup table relating constituent makeup and compressive strength, which are readily available in the industry.