Showing papers by "Illinois Institute of Technology published in 1995"

Short-term generation scheduling with transmission and environmental constraints using an augmented Lagrangian relaxation

Abstract: This paper proposes a new approach based on augmented Lagrangian relaxation for short term generation scheduling problems with transmission and environmental constraints. In this method, the power system constraints, e.g. load demand, spinning reserve, transmission capacity and environmental constraints, are relaxed by using Lagrangian multipliers, and quadratic penalty terms associated with power system load demand balance are added to the Lagrangian objective function. Then, the decomposition and coordination technique is used, and nonseparable quadratic penalty terms are replaced by linearization around the solution obtained from the previous iteration. In order to improve the convergence property, the exactly convex quadratic terms of decision variables are added to the objective function as strongly convex, differentiable and separable auxiliary functions. The overall problem is decomposed into N subproblems, multipliers and penalty coefficients are updated in the dual problem and power system constraints are satisfied iteratively. The corresponding unit commitment subproblems are solved by dynamic programming, and the economic dispatch with transmission and environmental constraints is solved by an efficient network flow programming algorithm. The augmented Lagrangian relaxation method enhanced by the decomposition and coordination techniques avoids oscillations associated with piece-wise linear cost functions. Numerical results indicate that the proposed approach is fast and efficient in dealing with numerous power system constraints. >

Projection-based spatially adaptive reconstruction of block-transform compressed images

Abstract: At the present time, block-transform coding is probably the most popular approach for image compression. For this approach, the compressed images are decoded using only the transmitted transform data. We formulate image decoding as an image recovery problem. According to this approach, the decoded image is reconstructed using not only the transmitted data but, in addition, the prior knowledge that images before compression do not display between-block discontinuities. A spatially adaptive image recovery algorithm is proposed based on the theory of projections onto convex sets. Apart from the data constraint set, this algorithm uses another new constraint set that enforces between-block smoothness. The novelty of this set is that it captures both the local statistical properties of the image and the human perceptual characteristics. A simplified spatially adaptive recovery algorithm is also proposed, and the analysis of its computational complexity is presented. Numerical experiments are shown that demonstrate that the proposed algorithms work better than both the JPEG deblocking recommendation and our previous projection-based image decoding approach. >

IRT-Based Internal Measures of Differential Functioning of Items and Tests

Abstract: Internal measures of differential functioning of items and tests (DHFIT) based on item response theory (IRT) are proposed. Within the DFIT context, the new differential test functioning (DTF) index leads to two new measures of differential item functioning (DIF) with the following properties: (1) The compensatory DIF (CDIF) indexes for all items in a test sum to the DTF index for that test and, unlike current DIF procedures, the CDIF index for an item does not assume that the other items in the test are unbi ased ; (2) the noncompensatory DIF (NCDIF) index, which assumes that the other items in the test are unbiased, is comparable to some of the IRT-based DIP indexes; and (3) COIF and NCDIF, as well as DTF, are equally valid for polytomous and multidimensional IRT models. Monte carlo study results, comparing these indexes with Lord's χ2 test, the signed area measure, and the unsigned area measure, demonstrate that the DFIT framework is accu rate in assessing DTF, COIF, and NCDIF.

A parallel genetic algorithm for the set partitioning problem

Abstract: In this dissertation we report on our efforts to develop a parallel genetic algorithm and apply it to the solution of the set partitioning problem--a difficult combinatorial optimization problem used by many airlines as a mathematical model for flight crew scheduling. We developed a distributed steady-state genetic algorithm in conjunction with a specialized local search heuristic for solving the set partitioning problem. The genetic algorithm is based on an island model where multiple independent subpopulations each run a steady-state genetic algorithm on their own subpopulation and occasionally fit strings migrate between the subpopulations. Tests on forty real-world set partitioning problems were carried out on up to 128 nodes of an IBM SP1 parallel computer. We found that performance, as measured by the quality of the solution found and the iteration on which it was found, improved as additional subpopulations were added to the computation. With larger numbers of subpopulations the genetic algorithm was regularly able to find the optimal solution to problems having up to a few thousand integer variables. In two cases, high-quality integer feasible solutions were found for problems with 36,699 and 43,749 integer variables, respectively. A notable limitation we found was the difficulty solving problems with many constraints.

Information Processing and Social Competence in Chronic Schizophrenia

Abstract: The relationship between social competence and information processing among individuals with chronic schizophrenia was investigated. Thirty-eight inpatients participated in a role play test of social competence and completed a battery of information-processing tasks. Information processing was found to be significantly related to social competence, even after controlling for patient demographics, chronicity, and symptomatology. Higher global social competence was related to more efficient early information processing on a continuous performance/span of apprehension task. Composite indices of specific social competence (i.e., paralinguistic and nonverbal skills) were related to other aspects of information processing (e.g., reaction time). Implications for behavioral assessment and cognitive rehabilitation are discussed.

A Methanol Impermeable Proton Conducting Composite Electrolyte System

Abstract: The concept of a proton conducting, methanol impermeable composite electrolyte system is demonstrated. A three‐layered laminar electrolyte consisting of a dense, methanol impermeable protonic conductor sandwiched between proton permeable electronically insulating layers permits the selective transport of protons while eliminating methanol crossover to the cathode. We demonstrate the selectivity of the composite electrolyte using palladium foil sandwiched between two Nafion™ polymer membranes. The open‐circuit voltage for an fuel cell utilizing this composite electrolyte is unaffected by introduction of methanol to the fuel stream, whereas conventional polymer electrolyte cells suffer severe degradation of performance due to methanol crossover.

Implantable drug delivery apparatus

Abstract: An implantable drug delivery apparatus including a housing that has a housing chamber. An outer deformable body having a reserve chamber is mounted within the housing chamber. An inner deformable body having a dispensing chamber is mounted within the reserve chamber. A dispensing valve is actuated to an open position to allow a fluidic drug to flow from the dispensing chamber, through the dispensing valve and through a catheter into a body of a patient. The fluidic drug is discharged from the dispensing chamber at a dispensing mass flowrate which is greater than a refilling mass flowrate of the fluidic drug passing from the reserve chamber to the dispensing chamber, when the dispensing valve is in an open position. When the dispensing valve is in a closed position, the fluidic drug is prevented from discharging from the dispensing chamber while a recharging amount of the fluidic drug is capable of flowing from the reserve chamber to the dispensing chamber, until the dispensing chamber is at least partially filled. The outer deformable body is normally forced or urged in a direction or manner that tends to reduce a volume of the reserve chamber.

Regularized constrained total least squares image restoration

Abstract: In this paper, the problem of restoring an image distorted by a linear space-invariant (LSI) point-spread function (PSF) that is not exactly known is formulated as the solution of a perturbed set of linear equations. The regularized constrained total least-squares (RCTLS) method is used to solve this set of equations. Using the diagonalization properties of the discrete Fourier transform (DFT) for circulant matrices, the RCTLS estimate is computed in the DFT domain. This significantly reduces the computational cost of this approach and makes its implementation possible even for large images. An error analysis of the RCTLS estimate, based on the mean-squared-error (MSE) criterion, is performed to verify its superiority over the constrained total least-squares (CTLS) estimate. Numerical experiments for different errors in the PSF are performed to test the RCTLS estimator. Objective and visual comparisons are presented with the linear minimum mean-squared-error (LMMSE) and the regularized least-squares (RLS) estimator. Our experiments show that the RCTLS estimator reduces significantly ringing artifacts around edges as compared to the two other approaches. >

The contingency model of leadership effectiveness: Its levels of analysis

Abstract: The contingency model of leadership effectiveness (Fiedler, 1978) has been the basis for an extensive body of research. During the last three decades, numerous studies have supported its propositions (Peters, Hartke, & Pohlmann, 1985; Strube & Garcia, 1981), but the model has also elicited strong criticisms. This article argues that the contingency model was one of the first models in leadership research that was theoretically multi-level and methodologically multi-source. New evidence and alternative perspectives are offered to address the issues concerning the conceptual definitions of the model's components, which have often been the subject of debate. The discussion concludes with productive avenues for future research in the paradigm and its potential contributions to leadership training and development within a multi-level framework.

A practical resource scheduling with OPF constraints

Abstract: This paper presents an efficient approach to short term power system resource scheduling based on the augmented Lagrangian relaxation method. The problem is divided into two stages, the commitment stage and the constrained economic dispatch stage. The proposed mathematical model incorporates optimal power flow (OPF) constraints in the unit commitment stage. By OPF constrains, the authors refer to the relevant active power constraints that are incorporated in the constrained economic dispatch stage (i.e. transmission capacity constraints, fuel and various regulated emission requirements). The inclusion of OPF constraints in the commitment stage will improve the feasibility of the constrained economic dispatch solution. Other unit commitment constraints such as spinning and operating reserve requirements, power balance as well as other relevant local constraints (i.e. unit ramping rates, upper and lower generation limits, minimum up and down times) are taken into account in the proposed model. As a larger number of constraints are dealt with, a more rigorous method is introduced for updating Lagrange multipliers to improve the solution convergence. A software package which addresses energy management systems requirements is developed and tested.

Conflict Analysis for Prediction of Fatal Crash Locations in Mixed Traffic Streams

Abstract: This paper presents a midblock conflict study which was undertaken to explore the relationship between fatal crash sites and conflict rates. Peak hour traffic at fourteen selected locations was video taped. Trained observers recorded traffic compositions at midblock, average space mean speeds by modes and conflicts by type and mode. The studies showed a weak crash-conflict association. Comparison of conflict data for various sites, and for different combinations of conflict types revealed that the presence of only a few non-motorized modes can cause conflicts between motorized vehicles and non-motorized vehicles. The study did not provide a conclusive relationship between midblock conflicts and fatal crash sites, but the conflict studies provided useful insights into the interaction between different traffic entities present in the traffic streams.

Analysis of differential item functioning in translated assessment instruments

Abstract: The usefulness of three IRT-based methods and the Mantel-Haenszel technique in evaluating the measure ment equivalence of translated assessment instruments was investigated. A 15-item numerical test and an 18- item reasoning test that were originally developed in English and then translated to French were used. The analyses were based on four groups, each containing 1,000 examinees. Two groups of English-speaking ex aminees were administered the English version of the tests; the other two were French-speaking examinees who were administered the French version of the tests. The percent of items identified with significant differ ential item functioning (DIF) in this study was similar to findings in previous large-sample studies. The four DIF methods showed substantial consistency in identi fying items with significant DIF when replicated. Sug gestions for future research are provided.

Analysis of cell-to-bubble attachment in sparged bioreactors in the presence of cell-protecting additives.

Abstract: To investigate the mechanisms of cell protection provided by medium additives against animal cell injury in sparged bioreactors, we have analyzed the effect of various additives on the cell-to-bubble attachment process using CHO cells in suspension. Cell-to-bubble attachment was examined using three experimental techniques: (1) cell-bubble induction time analysis (cell-to-bubble attachment times); (2) forming thin liquid films and observing the movement and location of cells in the thin films; and (3) foam flotation experiments. The induction times we measured for the various additives are as follows: no additive (50 to 500 ms), polyvinyl pyrrolidone (PVP: 20 to 500 ms), polyethylene glycol (PEG: 200 to 1000 ms), 3% serum (500 to 1000 ms), polyvinyl alcohol (PVA: 2 to 10 s), Pluronic F68 (5 to 20 s), and Methocel (20 to 60 s). In the thin film formation experiments, cells in medium with either F68, PVA, or Methocel quickly flowed out of draining thin liquid films and entered the plateau border. When using media with no additive or with serum, the flow of cells out of the thin liquid film and film drainage were slower than for media containing Pluronic F68. PVA, or Methocel. With PVP and PEG, the thin film drainage was much slower and cells remained trapped in the film. For the foam flotation experiments, a separation factor (ratio of cell concentration in the foam catch to that in the bubble column) was determined for the various additives. In the order of increasing separation factors (i.e., increasing cell attachment to bubbles), the additives are as follows: Methocel, PVA, Pluronic F68, 3% serum, serum-free medium with no additives, PEG, and PVP. Based on the results of these three different cell-to-bubble attachment experiments, we have classified the cell-protecting additives into three groups: (1) Pluronic F68, PVA, and Methocel (reduced cell-to-bubble attachment); (2) PEG and PVP (high or increased cell-to-bubble attachment); and (3) FBS (reduced cell attachment butslower drainage films compared with F68, PVA, and Methocel with some cell entrapment in those films). These phenomena are discussed in relation to the interfacial properties of the media reported in a companion Study (this issue). © 1995 John Wiley & Sons Inc.

Interfacial properties of cell culture media with cell-protecting additives.

Abstract: In an effort to identify key rheological properties that contribute to cell protection against shear damage, we have measured surface shear and dilatationai viscosities, dynamic surface tension, foaminess, and foam stability for media containing cell-protecting additives. In a companion article,(18) we found that cell-to-bubble attachment was decreased in media containing Methocel, Pluronic F68, or polyvinyl alcohol (PVA). In medium containing polyethylene glycol (PEG) or potyvinyl-pyrrolidone (PVP), attachment was increased. PEG, PVP, serum (FBS), and serum albumin (BSA) increased the surface viscosity of the air/medium surface (thus, producing a more rigid interface), whereas F68 and PVA lowered it greatly. Foaming experiments showed that Methocel, PEG, PVA, and F68 decreased the foam half-life while FBS, BSA, and PVP were foam stabilizers. Interestingly, the foam stability of CHO cell suspensions decreased significantly for cell concentrations higher than ca. 2 x 10(6) cells/mL. Nonviable CHO cells reduced foam stability further. Dynamic surface tension values of the media tested were found significantly differentfrom their static surface tension values. The interfacial properties measured and the results presented in the companion study suggest that the additives that lower dynamic surface tension the most (Methocel, F68, and PVA) correlate well with reduced cell-to-bubble attachment, and thus, cell protection. Reduced dynamic surface tension with these additives implies faster surfactant adsorption, mobile interfaces, lower surface viscosity, and foam destabilization. Because PEG and PVP resulted in increased cell-to-bubble attachment and had different interfacial properties, a different mechanism (compared with Methocel, PVP, and F68) is apparently responsible for their protective effect. Finally, cell protection offered by FBS and BSA is attributed to the foam stabilization properties provided by these additives. (c) 1995 John Wiley & Sons Inc.

AI approach to optimal VAr control with fuzzy reactive loads

Abstract: This paper presents an artificial intelligence (AI) approach to the optimal reactive power (VAr) control problem. The method incorporates the reactive load uncertainty in optimizing the overall system performance. The artificial neural network (ANN) enhanced by fuzzy sets is used to determine the memberships of control variables corresponding to the given load values. A power flow solution determines the corresponding state of the system. Since the resulting system state may not be feasible in real-time, a heuristic method based on the application of sensitivities in an expert system is employed to refine the solution with minimum adjustments of control variables. Test cases and numerical results demonstrate the applicability of the proposed approach. Simplicity, processing speed and ability to model load uncertainties make this approach a viable option for online VAr control. >

Throughput and fairness properties of asynchronous data transfer methods in the IEEE 802.11 MAC protocol

Abstract: To satisfy the needs of wireless data networking, study group 802.11 was formed under IEEE project 802 to recommend an international standard for wireless local area networks (WLANs). A key part of standard are the medium access control (MAC) protocols needed to support asynchronous and time bounded delivery of data frames. We conduct a performance evaluation of the asynchronous data transfer protocols that are a part of the proposed IEEE 802.11 standard taking into account the decentralized nature of communication between stations, the possibility of "capture", and presence of "hidden stations". We compute the system throughput and evaluate the fairness properties of the proposed MAC protocols and evaluate the impact of spatial characteristics on the performance of the system. Further, extensive numerical results are presented.

Gaussian limit for critical oriented percolation in high dimensions

Abstract: In this paper, we consider the spread-out oriented bond percolation models inZ d ×Z withd>4 and the nearest-neighbor oriented bond percolation model in sufficiently high dimensions. Let η n ,n=1, 2, ..., be the random measures defined onR d by $$\eta _n (A) = \sum\limits_{x \in Z^d } {1_A (x/\sqrt n )1_{\{ (0,0) \to (x,n)\} } } $$ The mean of η n , denoted by\(\bar \eta _n \), is the measure defined by $$\bar \eta _n (A) = E_p [\eta _n (A)]$$ We use the lace expansion method to show that the sequence of probability measures\([\bar \eta _n (R^d )]^{ - 1} \bar \eta _n \) converges weakly to a Gaussian limit asn→∞ for everyp in the subcritical regime as well as the critical regime of these percolation models. Also we show that for these models the parallel correlation length\(\xi (p)~|p_c - p|^{ - 1} \) asp⇆pc

Third‐order nonlinear optical response in a multilayered phthalocyanine composite

Abstract: The third‐order nonlinear optical properties of multilayered films containing 23% by weight of an axially modified silicon phthalocyanine derivative have been measured by degenerate four‐wave mixing at 532 nm with 70 ps full width at half maximum pulses. The average χ(3)of the films measured at (1.33±0.15) ×10−11 esu using CS2 as a standard and the cubic hyperpolarizability 〈γ〉 was calculated at (1.97±0.22)×10−32esu. The degenerate four‐wave mixing signal profile indicates that the films have a response time better than 70 ps.

An automaton model for scheduling constraints in synchronous machines

Abstract: We present a finite-state model for scheduling constraints in digital system design. We define a two-level hierarchy of finite-state machines: a behavior FSM's input and output events are partially ordered in time; a register-transfer FSM is a traditional FSM whose inputs and outputs are totally ordered in time. Explicit modeling of scheduling constraints is useful for both high-level synthesis and verification-we can explicitly search the space of register-transfer FSM's which implement a desired schedule. State-based models for scheduling are particularly important in the design of control-dominated systems. This paper describes the BFSM I model, describes several important operations and algorithms on BFSM's and networks of communicating BFSM's, and illustrates the use of BFSM's in high-level synthesis. >

Antibody covalently bound film immunobiosensor

Abstract: A biosensor comprising a substrate material, at least one antibody covalently immobilized on the substrate material, and a pair of metal contact electrodes for measuring the impedance of the biosensor. A process for producing a biosensor in accordance with this invention as well as a process for utilizing the biosensor are also disclosed.

Cloning and expression of the Vitreoscilla hemoglobin gene in pseudomonads: effects on cell growth

Abstract: The gene (vgb) encoding the hemoglobin (VtHb) of Vitreoscilla sp. was cloned into a broad-host-range vector and stably transformed into Pseudomonas putida, Pseudomonas aeruginosa, and Xanthomonas maltophilia. vgb was stably maintained and expressed in functional form in all three species. When growth of the P. aeruginosa and X. maltophilia transformants in Luria-Bertani medium was compared with that of each corresponding untransformed strain, the VtHb-producing strains reached slightly higher maximum viable cell numbers, had significantly increased viability after extebded times in culture, and, like E. coli that produces VtHb, had significantly lower respiration rates. The VtHb-producing strain of P. putida also reached a slightly higher maximum viable cell number than its corresponding untransformed strain, but was significantly less viable after extended times in culture and, unlike the case in E. coli, had a generally higher respiration rate than the untransformed strain. When growth was monitored by absorbance, the results were similar to those obtained with viable cell counts.