Showing papers by "Illinois Institute of Technology published in 1992"

Methods for choosing the regularization parameter and estimating the noise variance in image restoration and their relation

Abstract: The application of regularization to ill-conditioned problems necessitates the choice of a regularization parameter which trades fidelity to the data with smoothness of the solution. The value of the regularization parameter depends on the variance of the noise in the data. The problem of choosing the regularization parameter and estimating the noise variance in image restoration is examined. An error analysis based on an objective mean-square-error (MSE) criterion is used to motivate regularization. Two approaches for choosing the regularization parameter and estimating the noise variance are proposed. The proposed and existing methods are compared and their relationship to linear minimum-mean-square-error filtering is examined. Experiments are presented that verify the theoretical results. >

Relationships of Work Stressors with Aggression, Withdrawal, Theft and Substance Use: An Exploratory Study

Abstract: Based on findings from the domain of organizational frustration, the conceptual similarity between stress and frustration, and the functional similarity between frustrated events and work stressors, the relationships of behaviours (aggression, withdrawal, theft and substance use) with work stressors and affective reactions were investigated. Relations between reported stressors and behaviours were strongest for the more directly aggressive actions (sabotage, interpersonal aggression, and hostility and complaints), and for intention to quit. Relations with theft and absence were modest. None of the stressors correlated with reported substance use at work. Among the relations between affective reactions and the reported behaviours, anger and job satisfaction correlated with all behaviours except substance use at work. Hierarchical regression results further showed that the observed associations between stressors and behaviours were not attributed to affective variables for most cases.

Dense, vertical gas‐solid flow in a pipe

Abstract: The hydrodynamics of gas-solid flow, usually referred to as circulating fluidizedbed flow, was studied in a 7.5-cm clear acrylic riser with 75-μm FCC catalyst particles. Data were obtained for three central sections as a function of gas and solids flow rates. Fluxes were measured by means of an extraction probe. Particle concentrations were measured with an X-ray densitometer. In agreement with previous investigators, these data showed the flow to be in the core-annular regime, with a dilute rising core and a dense descending annular region. However, unlike the previous studies conducted worldwide, the data obtained in this investigation allowed us to determine the viscosity of the suspension. The viscosity was a linear function of the volume fraction of solids. It extrapolates to the high bubbling-bed viscosities.

Closed-loop class E transcutaneous power and data link for MicroImplants

Abstract: The use of a multifrequency transmitter coil driver based on the class E topology is described. The development of a high-Q approximation, which simplifies the design procedure is presented. A closed-loop controller to compensate for transmitter and receiver variations, and a method of data modulation using synchronous frequency shifting are described. The closed-loop class E circuit shows great promise, especially for circuits with unusually low coefficients of coupling. Currents of several amperes, at radio frequencies, can easily and efficiently be obtained. >

Dynamics of pounding when two buildings collide

Abstract: A formulation and solution of the multiple-degree-of-freedom equations of motion for pounding between two multistorey buildings are presented. Pounding occurs at rigid horizontal diaphragms in each building. The theory is implemented into a microcomputer program and sample earthquake analyses involving pounding between 15-storey and 8-storey buildings are performed. The influence of building separation, relative mass, and contact location properties are assessed. Conclusions are drawn regarding response behaviour trends that are relevant to other actual pounding situations.

Effect of oil on foam stability: Aqueous foams stabilized by emulsions

Abstract: The interactions between oil drops and the foam lamella were investigated by following the aging phenomena (i.e., drainage, bubble disproportionation, and rupture) of foams containing emulsified oils. It was found that the stability of the film (“pseudoemulsion film”) between an oil drop and an air/water surface was an important factor for the stability of foams containing emulsified oils. The mechanism of foam stability in the presence of stable emulsions was investigated for the case where the pseudoemulsion film was stable. It was found that these emulsions accumulated within the Plateau borders of the draining foam, thus inhibiting foam drainage. As a result, the foams were found to be stabilized by emulsified oil. Important parameters which affect foam stability, such as oil volume fraction, drop size, and oil phase density, were identified and the effect of these parameters on foam stability was experimentally verified. It was found that the stability increased with the oil fraction in the foam. The foam stability was found to go through a minimum as a function of drop size, due to competing effects of emulsion viscosity at smaller drop sizes and the higher accumulation of oil at larger drop sizes. The density of the oil phase directly influenced the oil accumulation and thus the foam stability.

On the definition of a probabilistic normed space

Abstract: In this paper we give a new definition of a probabilistic normed space. This definition, which is based on a characterization of normed spaces by means of a betweenness relation, includes the earlier definition of A. N. Serstnev as a special case and leads naturally to the definition of the principal class of probabilistic normed spaces, the Menger spaces.

A decomposition approach to nonlinear multi-area generation scheduling with tie-line constraints using expert systems

Abstract: The authors propose a rigorous method to treat multiarea generation scheduling with tie line limits. An expert system was used for obtaining the initial solution. As the generation scheduling problem involves unit commitment and economic dispatch, the method adopts an iterative procedure to deal with these two phases. The hourly load demand and the area power generation will cause the tie flows to change. To maintain the operation security in every area, the spinning reserve should comply with the area power generation rather than its load demand. After economic dispatch, it is necessary to adjust the unit commitment in each area for preserving the spinning reserve requirements. Heuristics were used to modify the generation unit combinations. The objective is to find an economic generation schedule for a multiarea system. The interchange transactions among areas represent the transportation problem, embedded within the nonlinear optimization process. The equivalent system concept is adopted, and the transmission losses are included in this study. A four-area system with each area consisting of 26 units was used to test the efficiency of the proposed algorithm. >

Psychosocial Concomitants of Children's Feeding Disorders

Abstract: Compared behavior problems, child developmental skills, home environment, and parent emotional distress for 50 families of children aged 11-70 months with differing etiologies of feeding disorders (FD). Results showed that psychosocial functioning differed across FD classifications. Children with nonorganic characteristics to FD had more behavior problems compared to those with only organic FD. Children with primarily or only organic FD displayed lower developmental skills and their parents had higher emotional distress than children with primarily nonorganic FD. High parent distress was associated with older children who had poor feeding skills, less positive disciplinary practices, and higher social status. The findings imply that clinical services to families often are warranted and that service needs vary depending on the nature of FD. Mixed organic and nonorganic FD occurred in the majority of children, which supports the need for more detailed classification than an organic-nonorganic dichotomy used in prior research.

A class of order statistic LMS algorithms

Abstract: Conventional gradient-based adaptive filters, as typified by the well-known LMS algorithm, use an instantaneous estimate of the error-surface gradient to update the filter coefficients. Such a strategy leaves the algorithm extremely vulnerable to impulsive interference. A class of adaptive algorithms employing order statistic filtering of the sampled gradient estimates is presented. These algorithms, dubbed order statistic least mean squares (OSLMS), are designed to facilitate adaptive filter performance close to the least squares optimum across a wide range of input environments from Gaussian to highly impulsive. Three specific OSLMS filters are defined: the median LMS, the average LMS, and the trimmed-mean LMS. The properties of these algorithms are investigated and the potential for improvement demonstrated. Finally, a general adaptive OSLMS scheme in which the nature of the order-statistic operator is also adapted in response to the statistics of the input signal is presented. It is shown that this can facilitate performance gains over a wide range of input data types. >

The properties and applications of amperometric gas sensors

Abstract: The properties and applications of amperometric gas sensors are reviewed. An introductory discussion of the general mechanism of electrochemical gas reactions and an outline of the construction of amperometric gas sensors is presented. The performance of sensors and the relationship of the sensor's performance to the materials of construction and sensor components are described. The analytical characteristics of a sensor such as sensitivity, selectivity, response time and noise are intimately related to the materials chosen for membranes, conductive electrolytes, and active electrocatalysts, as well as the choice of effective operating conditions. The applications of amperometric gas sensors to specific analytical problems are discussed in the context of required performance. Finally, this article points out technical gaps and the future direction of amperometric gas sensor research including some potential applications. References that are relevant to the field of amperometric gas sensors are summarized in a table which contains the author's name, the electrochemical reaction, and an exemplary application.

Unsteady pressure field and vorticity production over a pitching airfoil

Abstract: The unsteady pressure field and the accompanying variations in the flux of spanwise vorticity from the surface were measured over a range of dimensionless pitch rates for a two-dimensional NACA 0012 airfoil model undergoing a single pitch-up motion. The results were examined to identify the mechanisms that play key roles in the initiation, development, growth, and movement of the dynamic-stall vortex. The unsteady pressure distribution over the airfoil was dominated by three features, whose emergence and evolution were used to distinguish between two classes of behavior, corresponding to low and high pitch rates. Further, it was found that the flux of vorticity from the surface originated primarily from five concentrated regions or sources, the majority of which were located over the forward portion of the airfoil surface. The behavior of vorticity flux from these sources was related to the interacting mechanisms responsible for the development of the flowfield. The change of these features in the pressure and surface vorticity flux variations with the pitch rate is described.

A stochastic approach to small disturbance stability analysis

Abstract: A systematic approach to the construction of stochastic models of electric power systems for small disturbance stability analysis is presented. In this study, the cumulative effects of small-magnitude random fluctuations of electrical loads are considered as sources of eventual loss of stability, and a security measure is derived to determine the small-disturbance stability limits of the stochastic system. The electric power system models were tested on a 30-bus power system and compared according to the relative effects of load fluctuations on the proposed security measure. >

Prioritized DCT for compression and progressive transmission of images

Abstract: An approach is based on the block discrete cosine transform (DCT). The novelty of this approach is that the transform coefficients of all image blocks are coded and transmitted in absolute magnitude order. The resulting ordered-by-magnitude transmission is accomplished without sacrificing coding efficiency by using partition priority coding. Coding and transmission are adaptive to the characteristics of each individual image. and therefore, very efficient. Another advantage of this approach is its high progression effectiveness. Since the largest transform coefficients that capture the most important characteristics of images are coded and transmitted first, this method is well suited for progressive image transmission. Further compression of the image-data is achieved by multiple distribution entropy coding, a technique based on arithmetic coding. Experiments show that the approach compares favorably with previously reported DCT and subband image codecs. >

The response and symmetry properties of a cylinder wake subjected to localized surface excitation

Abstract: Symmetric and antisymmetric periodic disturbances introduced directly into the boundary layer on a circular cylinder at low Reynolds number are shown by experiment to be capable of modifying the vortex formation process and changing the vortex shedding frequency. Spectral measurements have shown that the antisymmetric vortex shedding mode is strongly coupled to the symmetric first harmonic mode. When symmetric excitation is applied, three different shapes of the mean velocity profiles can be identified as the forcing amplitude is increased. At low forcing amplitudes nonlinear interaction between the forcing field and the natural wake oscillator produces sum and difference modes. Symmetric forcing with intermediate-amplitude disturbances suppresses the natural shedding frequency, and the dominant vortex shedding energy appears as a sinuous mode at half the excitation frequency. At high symmetric forcing amplitudes a threshold is reached, above which the large-scale vortices do not form. The symmetries of the combination modes follow two simple rules based on the symmetries of the interacting modes. The symmetry rules provide an explanation for the fundamental difference in wake structure that occurs between symmetric forcing and antisymmetric forcing.

A near perfect stable random access protocol for a broadcast channel

Abstract: A near perfect stable random access protocol for a broadcast channel, the distributed queuing random access protocol (DQRAP), is presented and evaluated. The DQRAP protocol utilizes minislots to provide ternary channel feedback and two distributed queues to resolve contention and to schedule the transmission of messages. Modeling and simulation indicate that the DQRAP protocol, using as few as three minislots, achieves a performance level which approaches that of a hypothetical perfect scheduling protocol, i.e., the M/D/1 system, with respect to throughput and delay. The DQRAP protocol is stable and not sensitive to propagation delay and thus offers the potential of improved performance over current protocols in satellite, metropolitan and packet radio networks. >

Demulsification of water in oil emulsions using water soluble demulsifiers

Abstract: The possibility of using a water soluble,as opposed to the conventional oil soluble demulsifier, to destabilize a w/o emulsion in crude oil has been explored. It was found experimentally that a surfactant soluble in the water (dispersed) phase could destabilize the emulsion. Polymer molecules with varying HLB's and molecular weights and structure were synthesized and these compounds were added to the water phase to destabilize the water/crude oil emulsions. Molecules with a high percentage of hydrophilic groups and low molecular weights showed very good demulsifying abilities.

A Spectral Difference Method to Estimate Building Separations to Avoid Pounding

Abstract: A method to estimate the likely minimum building separation necessary to preclude seismic pounding is presented. The method is based on random vibration theory. The accuracy is demonstrated by numerical experiments using 9 artificial and 6 actual earthquake records. The relation between the minimum separation, period, height, damping and earthquake type are discussed. Example applications of the theory are presented. The effects of inelastic hysteretic building behavior are also discussed.

Microbial, Enzymatic, and Chemical Changes During Storage of Fresh and Processed Orange Juice

Abstract: Microbial, enzymatic, and chemical comparisons were made on orange juice stored at 4°C without pasteurization, with light pasteurization (66°C, 10 sec) directed at vegetative microorganisms, and with full pasteurization (90°C, 60 sec) directed at the heat stable isozyme of pectinesterase. Effects of oxygen-barrier and nonbarrier packaging were also examined. Oxygen-barrier packaging did not benefit unpasteurized juice. However, lightly and fully pasteurized juices in barrier cartons exhibited lower microbial counts, greater ascorbic acid retention, and apparent slowing of cloud loss by the third week of storage. During the first 22 days storage, microbial, cloud, sugar, and ascorbic acid values for lightly pasteurized juice were similar to those of juice receiving full pasteurization.