Optical transmission utilizing injection light sources

Although a large amount of work in optical transmission has been accomplished through the use of lasers, modern developments have enabled noncoherent light sources also to be used in this area with great success. In particular, injection light sources?in the form of the coherent injection laser and the noncoherent light-emitting diode (LED)?offer designers of optical transmission systems characteristics that are in many ways superior to those of other methods. The present article deals essentially with how injection light sources may be employed to transmit or ``communicate' information optically. Such optical techniques can be used not only in communication systems, in the classic RF sense, but in computer, video, telemetry, and detection systems as well.     

Seismic response of a structure subjected to rotational base excitation

A modal superposition method which can perform the seismic analysis of a structure subjected to translational and rotational base excitation is presented. Discussed are two different approaches to derive the equations of motion. In the first approach, the reference axes are fixed in space. While in the second approach, they are rigidly fixed at the base of the structure. For rotational base excitation, it is shown that the application of second approach results in equation of motion with asymmetric, time-dependent coefficient matrix due to presence of the Coriolis acceleration term.Analytic integration is used to integrate the modal equations of motion derived by the first approach. Most of the mode shapes have to be included in the time history analysis.The modal superposition method is applied to the seismic analysis of a building subjected to translational and rotational excitation. The displacement results and the computer cost of this analysis are compared with those of using the direct integration method. The computer cost associated with the modal superposition method is lower than that associated with the direct integration method.     

Virtual three-dimensional blackboard: three-dimensional finger tracking with a single camera

We present a method for three-dimensional (3D) tracking of a human finger from a monocular sequence of images. To recover the third dimension from the two-dimensional images, we use the fact that the motion of the human arm is highly constrained owing to the dependencies between elbow and forearm and the physical constraints on joint angles. We use these anthropometric constraints to derive a 3D trajectory of a gesticulating arm. The system is fully automated and does not require human intervention. The system presented can be used as a visualization tool, as a user-input interface, or as part of some gesture-analysis system in which 3D information is important.     

HEAT TRANSFER IN MULTIPHASE CONTACTORS

A procedure for the prediction of wall-bed heat transfer coefficient for bubble columns and gas-solid fluidized beds is developed on the basis of hydrodynamic behavior of these contactors. A comparison between the predicted and experimental values of heat transfer coefficient over a wide range of design and operating variables is presented. An attempt is made to analyze the occurrence of maxima in heat transfer coefficient with respect to gas velocity in the case of fluidized beds. A procedure for the calculation of the optimum superficial gas velocity is outlined.     

Simulation of bubble populations in a gas fluidized bed

The dynamics of bubble populations in a gas fluidized bed have been analyzed using a simulation technique due to the authors [11,12]. It is shown that small bubble populations arising from progressive coalescence may lead to inherent fluctuations which may be considerable. Evidently, such fluctuations could manifest in conversions in fluidized bed reactors. The results obtained were based on a model due to Argyriou, List and Shinnar[1].     

Autonomous Line Scanning for SPC Telephone Switching Systems

An Autonomous Line Scanning Unit (ALSU) for completely autonomous detection of call originations in the SPC Telephone Switching System is described. Through its own memories, ALSU maintains an up-to-date record of subscribers' statuses, detects call originations, performs 'hit timing check' and informs the Switching System of the identity of calling subscribers. The ALSU needs minimum interaction with the Central Processor, resulting in increased call handling capacity.     

Testing methods for concrete durability

Experimental techniques for measuring progressive deterioration of concrete were investigated. Specimens of pastes, mortars, and concretes were subjected to alternate wetting and drying in sodium sulfate solutions and plain water as well as freezing and thawing. The methods used to assess the effects included: changes in weight, length, and flexural strength, changes in ultrasonic pulse time, quantitative and qualitative optical microscopy, scanning electron microscopy, and energy dispersive X-ray analysis. The results of the study show that the ultrasonic pulse method can be used to detect local cracking at an early stage of formation. Of the different testing methods employed, the progressive deterioration was best reflected by the measurements of pulse time. Measurements of flexural strength also adequately reflected the state of corrosion. Measurements of weight did not consistently indicate damage, while those of length were not always reliable.     

Automated detection of ocular alignment with binocular retinal birefringence scanning

We previously developed a retinal birefingence scanning (RBS) device to detect eye fixation. The purpose of this study was to determine whether a new binocular RBS (BRBS) instrument can detect simultaneous fixation of both eyes. Control (nonmyopic and myopic) and strabismic subjects were studied by use of BRBS at a fixation distance of 45 cm. Binocularity (the percentage of measurements with bilateral fixation) was determined from the BRBS output. All nonstrabismic subjects with good quality signals had binocularity >75%. Binocularity averaged 5% in four subjects with strabismus (range of 0-20%). BRBS may potentially be used to screen individuals for abnormal eye alignment.     

Message from Dr. Carmen Andrade,RILEM president 2000–2003

RILEM Bulletin

Message from Dr. Carmen Andrade, RILEM president 2000–2003 1 September 2003     

Characterization of molecularly imprinted polymers with the Langmuir-Freundlich isotherm

The majority of binding models that have been applied to molecularly imprinted polymers (MIPs) have been homogeneous models. MIPs, on the other hand, are heterogeneous materials containing binding sites with a wide array of binding affinities and selectivities. Demonstrated is that the binding behavior of MIPs can be accurately modeled by the heterogeneous Langmuir-Freundlich (LF) isotherm. The applicability of the LF isotherm to MIPs was demonstrated using five representative MIPs from the literature, including both homogeneous and heterogeneous MIPs. Previously, such comparisons required the use of several different binding models and analyses, including the Langmuir model, the Freundlich model, and numerical approximation techniques. In contrast, the LF model enabled direct comparisons of the binding characteristics of MIPs that have very different underlying distributions and were measured under different conditions. The binding parameters can be calculated directly using the LF fitting coefficients that yield a measure of the total number of binding sites, mean binding affinity, and heterogeneity. Alternatively, solution of the Langmuir adsorption integral for the LF model enabled direct calculation of the corresponding affinity spectrum from the LF fitting coefficients from a simple algebraic expression, yielding a measure of the number of binding sites with respect to association constant Finally, the ability of the LF isotherm to model MIPs suggests that a unimodal heterogeneous distribution is an accurate approximation of the distribution found in homogeneous and heterogeneous MIPs.