bluuebunny/crossref_metadata_2025 huggingface dataset:
An Enhanced Mathematical Model for Investigating the Dynamic Loading of a Slewing Crane
Authors: Jerman B
Published: June 2006

A fatigue analysis of a structure is nowadays a common part of the design process. One of the fundamental pieces of information for ensuring the high quality of the analysis is details of the dynamic loading of the structure. This information can be provided by means of a simulation using an appropriate mathematical model. In this article, a new mathematical model of a slewing crane is presented on the basis of the experiences gained with a previously developed model. Only the slewing motion that produces the spatial oscillation of the payload is considered, as this motion has received less attention than the translation of the suspension point. The mathematical model takes into account the non-linear nature of the swinging motion for large angles and the non-linearity of the power transmission to ensure sufficient accuracy. The structure's elasticity and damping, the friction in the main bearing, and the air resistance were also taken into account. The angles of swinging of the payload and the dynamic forces acting on the steel structure of the crane during payload transport were obtained. Measurements on an actual model of a crane were carried out for the purpose of confirmation of the mathematical model. The comparison of the results was executed and a good greement between the predicted and the measured values was observed.
Machine Tool Axis Dynamics
Authors: Whalley R , Ebrahimi M , Abdul-Ameer A A
Published: June 2006

The independent axis dynamics of machine tools that employ long slender lead screws, bearings, and workpiece saddles, mounted on supporting slides, will be considered. Distributed-lumped parameter techniques will be used for system analysis and in the model formulation procedures. Realizations that encompass combined torsional and tension loading will be incorporated. Specific, integrated, distributed-lumped machine tool configurations will be derived and described in block diagram form. Simulation studies illustrating the dynamic signature of a machine tool axis drive, when operated at various feed rates, together with the measured results will be presented. The effect of changes in the effective lead-screw length on the workpiece surface finish will be commented on.
SRI: A Scalable Rule Induction Algorithm
Authors: Pham D T , Afify A A
Published: June 2006

Rule induction as a method for constructing classifiers is particularly attractive in data mining applications, where the comprehensibility of the generated models is very important. Most existing techniques were designed for small data sets and thus are not practical for direct use on very large data sets because of their computational inefficiency. Scaling up rule induction methods to handle such data sets is a formidable challenge. This article presents a new algorithm for rule induction that can efficiently extract accurate and comprehensible models from large and noisy data sets. This algorithm has been tested on several complex data sets, and the results prove that it scales up well and is an extremely effective learner.
Numerical Sensitivity and View Factor Calculation Using the Monte Carlo Method
Authors: Vujičić M. R. , Lavery N. P. , Brown S. G. R.
Published: June 2006

In radiative heat transfer simulations, the geometrical view (configuration, form) factor plays a crucial role. Several different methods (deterministic and non-deterministic) such as integration, the Monte Carlo method, and the Hemi-Cube method have been introduced to calculate view factors in recent years. In this article, the Monte Carlo method combined with the finite-element (FE) technique is investigated. Results describing the relationships among different discretization schemes, number of rays used for the view factor calculation, CPU time, accuracy, and two origins of emanating rays are presented. The interesting case where reduced accuracy is obtained with increased refinement of FE mesh is discussed.
Residual Thermal Stresses Simulation of Television Panel in the Forming Process. Part 2: Simulations and Validation
Authors: Zhou H. M. , Feng W , Geng T , Li D. Q.
Published: June 2006

To obtain the temperature history data of the part taken for residual stresses analysis, a numerical simulation has been developed for the part cooling during the TV panel forming process. In the simulation, a local one-dimensional transient analysis in the thickness direction is adopted, which employs the finite-difference method. The renormalization-group turbulence model is applied for jet impinging cooling. By applying the numerical analysis system described in Part I, the residual stresses in the formed TV panel part are predicted. Experimental comparison is employed to verify the proposed models and methods. The temperatures were measured by a thermographic camera and the residual stresses were measured using the birefringence. On the whole, the predictions are encouraging. The agreement between measured temperatures and simulation results is very good, with the maximum deviation within 5 per cent. The residual stresses trends of the experimental results indicated a similar behaviour over most of specimen thickness. Also, the results showed about the same magnitude of predicted stresses in specimen.
Profile Cutting on Alumina Ceramics by Abrasive Waterjet. Part 1: Experimental Investigation
Authors: Wang J , Liu H
Published: June 2006

An experimental investigation is presented of the various cutting performance measures, such as the kerf taper and depth of cut, in profile cutting on an 87 per cent alumina ceramic by abrasive waterjet (AWJ) over a wide range of process parameters. It is found that the taper angles on the two kerf walls produced in cutting AWJ of profiles are different in magnitude and exhibit different trends as the profile curvature radius varies. Moreover, the depth of cut increases with an increase in the curvature radius and approaches its maximum in straight cutting. The other process variables affect the cutting process in a way similar to that in straight cutting. Recommendations are finally made for the selection of process parameters in AWJ profile cutting of alumina ceramics. Predictive mathematical models for the major cutting performance measures that are essential for the optimization of the AWJ cutting process are reported in the subsequent part of this investigation.
Laser Forming of Plates Using Two Sequent Scans of Different Intervals
Authors: Shen H , Shi Y , Yao Z
Published: June 2006

Laser forming of metal plates offers the advantages of requiring no external forces, cost reduction, and increasing flexibility. It also enables forming of some materials and shapes that are impossible by using the traditional methods. This article presents a finite-element model (FEM) for two-scan laser forming with different intervals along the same path. On the basis of the proposed model, the FEM simulation of the temperature and displacement fields is studied. The simulated results show that the plastic deformation is larger if the interval between the first scan and the second scan is short, which aids the bending process because of the heat retained in the plate.
A Case Study of the Five-Point Double-Toggle Mould Clamping Mechanism
Authors: Lin W Y , Shen C L , Hsiao K M
Published: June 2006

This work attempts to enhance the performances of the stroke ratio and/or thrust saving of the conventional and Fanuc five-point double-toggle mould clamping mechanisms, at the cost of increasing the offset and varying the cross-head height and loosening the initial transmission performance within an acceptable extent, on condition that the overall horizontal length cannot exceed the one of the original design in the work of Lin and Hsiao [1]. In addition, to show the effect of the initial transmission performance and the effect of the combination of the offset and the crosshead height individually, the present and previous designs in the work of Lin and Hsiao without loosening the initial transmission performance are also presented. The parameter study in the work of Lin and Hsiao is extended to synthesize the conventional and Fanuc linkages and to find the optimal dimensions in the programming discrete domain. The kinematic stick diagrams in the open and closed positions for the original and present designs are shown, which may see some features of the profiles of the toggle linkages with the larger stroke ratio and/or thrust saving and the difference between the two designs.
Many-Degree-Of-Freedom Mechanism Combination in Automated Conceptual Design of Mechanism Systems
Authors: Tang L
Published: June 2006

This article presents the mechanism combination's modes, fundamentals, reasoning rules, and realization methods in the automated conceptual design of mechanism systems. According to the combination form between two function units, with the aid of morphology matrix, applying a recursive mode of mechanism combination and the reasoning system based on set theory, the function units' solutions in the form of combination mechanisms can conveniently be generated. The theory and method presented in this article can simplify the process of mechanism combination and the reasoning rules and are suitable for the combination between not only single-degree-of-freedom mechanisms, but also many-degree-of-freedom mechanisms. They have successfully been applied to the software development of automated conceptual design of mechanism systems.
Structural study of elements of Tetrahymena telomerase RNA stem–loop IV domain important for function
Authors: Richards Rebecca J. , Wu Haihong , Trantirek Lukas , O'Connor Catherine M. , Collins Kathleen , Feigon Juli
Published: June 2006

Tetrahymena telomerase RNA (TER) contains several regions in addition to the template that are important for function. Central among these is the stem–loop IV domain, which is involved in both catalysis and RNP assembly, and includes binding sites for both the holoenzyme assembly protein p65 and telomerase reverse transcriptase (TERT). Stem–loop IV contains two regions with high evolutionary sequence conservation: a central GA bulge between helices, and a terminal loop. We solved the solution structure of loop IV and modeled the structure of the helical region containing the GA bulge, using NMR and residual dipolar couplings. The central GA bulge with flanking C–G base pairs induces a ∼50° semi-rigid bend in the helix. Loop IV is highly structured, and contains a conserved C–U base pair at the top of the helical stem. Analysis of new and previous biochemical data in light of the structure provides a rationale for some of the sequence conservation in this region of TER. The results suggest that during holoenzyme assembly the protein p65 recognizes a bend in stem IV, and this binding to central stem IV helps to position the structured loop IV for interaction with TERT and other region(s) of TER.
Structure–function analysis of Plasmodium RNA triphosphatase and description of a triphosphate tunnel metalloenzyme superfamily that includes Cet1-like RNA triphosphatases and CYTH proteins
Authors: Gong Chunling , Smith Paul , Shuman Stewart
Published: June 2006

RNA triphosphatase catalyzes the first step in mRNA capping. The RNA triphosphatases of fungi and protozoa are structurally and mechanistically unrelated to the analogous mammalian enzyme, a situation that recommends RNA triphosphatase as an anti-infective target. Fungal and protozoan RNA triphosphatases belong to a family of metal-dependent phosphohydrolases exemplified by yeast Cet1. The Cet1 active site is unusually complex and located within a topologically closed hydrophilic β-barrel (the triphosphate tunnel). Here we probe the active site of Plasmodium falciparum RNA triphosphatase by targeted mutagenesis and thereby identify eight residues essential for catalysis. The functional data engender an improved structural alignment in which the Plasmodium counterparts of the Cet1 tunnel strands and active-site functional groups are located with confidence. We gain insight into the evolution of the Cet1-like triphosphatase family by noting that the heretofore unique tertiary structure and active site of Cet1 are recapitulated in recently deposited structures of proteins from Pyrococcus (PBD 1YEM) and Vibrio (PDB 2ACA). The latter proteins exemplify a CYTH domain found in CyaB-like adenylate cyclases and mammalian thiamine triphosphatase. We conclude that the tunnel fold first described for Cet1 is the prototype of a larger enzyme superfamily that includes the CYTH branch. This superfamily, which we name “triphosphate tunnel metalloenzyme,” is distributed widely among bacterial, archaeal, and eukaryal taxa. It is now clear that Cet1-like RNA triphosphatases did not arise de novo in unicellular eukarya in tandem with the emergence of caps as the defining feature of eukaryotic mRNA. They likely evolved by incremental changes in an ancestral tunnel enzyme that conferred specificity for RNA 5′-end processing.
A three-hybrid screen identifies mRNAs controlled by a regulatory protein
Authors: Seay Daniel , Hook Brad , Evans Katie , Wickens Marvin
Published: June 2006

RNA–protein interactions are important in many biological contexts. Identification of the networks that connect regulatory proteins to one another and to the mRNAs they control is a critical need. Here, we use a yeast three-hybrid screening approach to identify RNAs that bind a known RNA regulatory protein, the Saccharomyces cerevisiae PUF protein, Mpt5p. The assay selects RNAs that bind in vivo using simple phenotypes and reporter genes. It enables rapid analyses of the affinity and specificity of the interaction. We show that the method identifies mRNAs that are genuinely regulated by the protein in vivo, and that it complements biochemical strategies, yielding a set of mRNAs that overlap with, but are distinct from, those obtained by biochemical means. The approach we describe facilitates construction of protein–RNA linkage maps.
Polyamine-regulated unproductive splicing and translation of spermidine/spermine N1-acetyltransferase
Authors: Hyvönen Mervi T. , Uimari Anne , Keinänen Tuomo A. , Heikkinen Sami , Pellinen Riikka , Wahlfors Tiina , Korhonen Arja , Närvänen Ale , Wahlfors Jarmo , Alhonen Leena , Jänne Juhani
Published: June 2006

Spermidine/spermine N1-acetyltransferase (SSAT), the rate-controlling enzyme in the interconversion of spermidine and spermine, is regulated by polyamines and their analogs at many levels of gene expression. Recently, SSAT pre-mRNA has been shown to undergo alternative splicing by inclusion of an exon that contains premature termination codons. In the present study, we show that alterations in the intracellular polyamine level resulted in a change in the relative abundance of SSAT transcripts. Addition of polyamines or their N-diethylated analogs reduced the amount of the variant transcript, whereas polyamine depletion by 2-difluoromethylornithine or MG-132 enhanced the exon inclusion. Experiments performed with protein synthesis inhibitors and siRNA-mediated down-regulation of Upf1 protein verified that the variant transcript was degraded by nonsense-mediated mRNA decay (NMD). Interestingly, several proteins have been shown to regulate their expression by alternative splicing-coupled NMD, termed regulated unproductive splicing and translation (RUST). Our present results suggest that in the case of SSAT, RUST is mediated by polyamines, and this system functions to fine-tune the polyamine metabolism.
Conventional 3′ end formation is not required for NMD substrate recognition in Saccharomyces cerevisiae
Authors: Baker Kristian E. , Parker Roy
Published: June 2006

The recognition and rapid degradation of mRNAs with premature translation termination codons by the nonsense-mediated pathway of mRNA decay is an important RNA quality control system in eukaryotes. In mammals, the efficient recognition of these mRNAs is dependent upon exon junction complex proteins deposited on the RNA during pre-mRNA splicing. In yeast, splicing does not play a role in recognition of mRNAs that terminate translation prematurely, raising the possibility that proteins deposited during alternative pre-mRNA processing events such as 3′ end formation might contribute to the distinction between normal and premature translation termination. We have utilized mRNAs with a 3′ poly(A) tail generated by ribozyme cleavage to demonstrate that the normal process of 3′ end cleavage and polyadenylation is not required for mRNA stability or the detection of a premature stop codon. Thus, in yeast, the distinction between normal and premature translation termination events is independent of both splicing and conventional 3′ end formation.
Modeling and Performance Analysis of a Finite-Buffer Queue with Batch Arrivals, Batch Services, and Setup Times: The MX/GY/1/K + B Queue with Setup Times
Authors: Chang Seok Ho , Choi Dae Won
Published: June 2006

In this paper, we consider a finite-buffer MX/GY/1/K + B queue with setup times, which has a wide range of applications. The primary purpose of this paper is to discuss both exact analytic and computational aspects of this system. For this purpose, we present a modern applied approach to queueing theory. First, we present a set of linear equations for the stationary queue-length distribution at a departure epoch based on the embedded Markov-chain technique. Next, using two simple approaches that are based on the conditioning of the system states and discrete renewal theory, we establish two numerically stable relationships for the stationary queue-length distributions at three different epochs: departure, random, and arrival. Finally, based on these relationships, we present useful performance measures of interest such as the moments of the stationary queue lengths at three different epochs, the blocking probability, the mean delay in queue, and the probability that the server is busy, with computational experience.
Integer Programming and Constraint Programming in Solving a Multimachine Assignment Scheduling Problem with Deadlines and Release Dates
Authors: Sadykov Ruslan , Wolsey Laurence A.
Published: June 2006

We consider both branch-and-cut and column-generation approaches for the problem of finding a minimum-cost assignment of jobs with release dates and deadlines to unrelated parallel machines. Results are presented for several variants both with and without constraint programming. Among the variants, the most effective strategy is to combine a tight and compact, but approximate, mixed integer programming (MIP) formulation with a global constraint testing single machine feasibility. Instances with up to nine machines and 54 jobs have been solved. All the algorithms have been implemented in the Mosel modeling and optimization language.
Optimization in Object Caching
Authors: Dutta Kaushik , Soni Samit , Narasimhan Sridhar , Datta Anindya
Published: June 2006

Modern applications are built using object-oriented (OO) principles. Unfortunately, OO technologies, though they add tremendous functionality and flexibility to applications, require significant computational power, which greatly affects the performance and scalability of the applications. Caching objects in memory is a popular way to solve this problem, but the available memory in systems is limited and not sufficient to store each instance of every enterprise application object. Deciding which instances of which objects should be cached is a two-stage process. The first stage is selecting the objects, and the second stage is selecting the object instances. The second stage, typically referred to as a replacement policy, occurs at run-time and has been widely studied. The focus of this paper is the first stage: selecting objects whose instances are candidates for caching at run-time. In current systems, this critical step is performed in an ad hoc manner. We build a nonlinear mathematical model for this problem, develop a feasible solution procedure based on genetic algorithms, and demonstrate its effectiveness by comparing the solution quality to lower bounds obtained using a Lagrangian-relaxation-based method.
Integer Linear Programming Models for Global Routing
Authors: Behjat Laleh , Vannelli Anthony , Rosehart William
Published: June 2006

Modern integrated circuit design involves the layout of circuits consisting of millions of switching elements or transistors. Due to the sheer complexity of the problem, optimizing the connectivity between transistors is very difficult. The circuit interconnection is the single most important factor in performance criteria such as signal delay, power dissipation, circuit size, and cost. These factors dictate that interconnections, i.e., wires, be made as short as possible. The wire-minimization problem is generally formulated as a sequence of discrete optimization subproblems that are known to be NP-hard. Hence, they can only be solved approximately using meta-heuristics. These methods are computationally expensive and the quality of the solution depends to a great extent on an appropriate choice of starting configuration and modeling techniques. In this paper, new modeling techniques are used to solve the routing problem formulated as an integer programming problem. The main contribution of this paper is a proposed global routing heuristic that combines the wire length, channel congestion, and number of pins in routes to find the best wiring layout of a circuit. By adding information such as channel congestion and the number of pins in each route as well as the wire length, the quality of the solution is improved. In addition, the solutions of the large relaxed linear programming problems are skewed towards a zero-one solution, resulting in faster convergence. The developed LP models in this paper are useful when solving the global routing problem for two reasons; first, the new interior-point algorithms to solve the LP problem are polynomial in time. Second, “near optimal wiring” is obtained in polynomial time without performing randomized rounding.
A Data-Mining-Based Prefetching Approach to Caching for Network Storage Systems
Authors: Fang Xiao , Liu Sheng Olivia R. , Gao Wei , Iyer Balakrishna R.
Published: June 2006

The need for network storage has been increasing rapidly owing to the widespread use of the Internet in organizations and the shortage of local storage space due to the increasing size of applications and databases. Proliferation of network storage systems entails a significant increase in the number of storage objects (e.g., files) stored, the number of concurrent clients, and the size and number of storage objects transferred between the systems and their clients. Performance (e.g., client-perceived latency) of these systems becomes a major concern. Previous research has explored techniques for scaling up the number of storage servers involved to enhance the performance of network storage systems. However, adding servers to improve system performance is an expensive solution. Moreover, for a WAN-based network storage system, the bottleneck for its performance improvement typically is not caused by the load of storage servers, but by the network traffic between clients and storage servers. This paper introduces an Internet-based network storage system named NetShark and proposes a caching-based performance-enhancement solution for such a system. The proposed performance-enhancement solution is validated using a simulation.
A Projection-Based Reduction Approach to Computing Sensitivity of Steady-State Response of Nonlinear Circuits
Authors: Pai Praveen , Gad Emad , Achar Ramachandra , Nakhla Michel , Khazaka Roni
Published: June 2006

This paper presents a new algorithm for computing the sensitivity of steady-state responses of nonlinear circuits with respect to an arbitrary network parameter. The proposed algorithm is based on circuit-reduction techniques obtained through nonlinear-projection approaches. The main idea in the proposed sensitivity-computation algorithm is based on projecting the adjoint system of equations onto a subspace of smaller dimension. Continuation methods are then applied on the reduced system to trace the solution trajectory of the adjoint system in the reduced space. We show that once the steady-state solution has been obtained using nonlinear order reduction, the computational cost required to compute sensitivity is only a limited number of forward/backward substitutions. Numerical examples are presented to demonstrate the accuracy and efficiency of the proposed algorithm.
Using Eigenvectors to Partition Circuits
Authors: Kucar Dorothy , Vannelli Anthony
Published: June 2006

Many fields, ranging from bioinformatics to databases to large-scale integrated circuits, deal with the interrelation between elementary objects. Objects are represented as vertices and the relationships between them are represented as nets (edges that connect two or more vertices) in the form of a hypergraph. We seek a placement of vertices that groups like objects and separates unlike objects. This involves separating related objects into a few, possibly disjoint, blocks. These hypergraph-partitioning problems are NP-hard so cannot be solved exactly, except for very small instances. We develop and use a numerical technique based on eigenvector decomposition of the connectivity matrix associated with the circuit netlist to partition hypergraphs emanating from circuit netlists. The eigenvector components of the circuit connectivity matrix are then used to determine vertex coordinates in one dimension that are then rounded in some fashion to determine block assignments. The inherent difficulty with eigenvector techniques is that the eigenvector components tend to cluster, making it difficult to determine correct block assignments. Our technique uses weights on nets, vertices, and fixed vertices to obtain a more “discrete” placement of vertices, making it easier to determine correct block assignments.
Antibody Arrays: Technical Considerations and Clinical Applications in Cancer
Authors: Sanchez-Carbayo Marta
Published: June 2006

Antibody arrays represent one of the high-throughput techniques that are able to detect multiple proteins simultaneously. One of the main advantages of this technology over other proteomic approaches is that the identities of the measured proteins are known or can be readily characterized, allowing a biological interpretation of the results. Features such as lower sample volume and antibody concentration requirements, higher format versatility, and reproducibility support the increasing use of antibody arrays in cancer research. Clinical applications include disease marker discovery for diagnosis, prognosis, and drug response, characterization of signaling and protein pathways, and modifications associated with disease development and progression. This report presents an overview of technical issues of the main antibody array formats and various applications in cancer research. Antibody arrays are high-throughput tools that improve the functional characterization of molecular bases for disease. Furthermore, identification and validation of protein expression patterns, characteristic of cancer progression, and tumor subtypes may intervene and improve tailored therapies in the clinical management of cancer patients.
Car Backlight Position and Fog Density Bias Observer-Car Distance Estimates and Time-to-Collision Judgments
Authors: Buchner Axel , Brandt Martin , Bell Raoul , Weise Judith
Published: June 2006

Objective: A series of experiments assessed biases in perceived distance that occur while driving as a function of the backlight position of the car ahead and fog density. Background: V. Cavallo, M. Colomb, and J. Doré (2001) have shown that smaller horizontal backlight separation and fog may result in increased estimates of the distance between an observer and a car of which only the backlights are visible. They also predicted that raising the height of the car backlights would lead to increasing distance estimates. Method: Distance perception was assessed in both static and dynamic computer-simulated scenarios in which the distance estimates were performed using a familiarized analog scale or using time-to-collision judgments for both pairs of backlights and single backlights. Results: In a series of five experiments, the horizontal separation and fog density effects were replicated. In addition, distance estimates were consistently larger with higher than with lower vertical backlight positions. Conclusion: There is reason to believe that biases in distance perception may be augmented by car backlight positions and by low-visibility weather conditions. Application: Car designers should take backlight placement seriously. Speed-dependent car-to-car distance control systems seem desirable to counteract biases in distance perception.
Reading in the Dark: Effects of Age and Contrast on Reading Speed and Comprehension
Authors: Mitzner Tracy L. , Rogers Wendy A.
Published: June 2006

Objective: To explore the effects of contrast reduction on younger and older adults' reading behavior and to examine whether readers rely on word predictability to compensate for poor contrast. Background: Poor contrast can degrade text and may influence reading behavior. Readers may compensate for visual degradation of text by taking advantage of word predictability. Method: In Experiment 1, 5 younger and 5 older adults read sentences presented with 10 levels of contrast. In Experiment 2, 40 younger and 40 older adults read high-, medium-, and low-contrast sentences that varied in target word predictability (high vs. low). Results: Relative to those of younger adults, older adults' reading rates were more slowed by low contrast; comprehension was less influenced by contrast (i.e., not significantly). Older adults read high-predictability words faster and comprehended them better than low-predictability words, significantly so for high- and medium-contrast sentences. Younger adults comprehended high-predictability words significantly better than low-predictability words for high- and low-contrast sentences. Conclusion: Low contrast was more detrimental for older adults. High-predictability words benefited older adults by significantly reducing their reading times and benefited all readers by significantly increasing their comprehension. Application: The current findings demonstrate the benefit of adequate contrast and word predictability for optimal text design to facilitate both reading times and reading comprehension.
Automation Failures on Tasks Easily Performed by Operators Undermine Trust in Automated Aids
Authors: Madhavan Poornima , Wiegmann Douglas A. , Lacson Frank C.
Published: June 2006

Objective: We tested the hypothesis that automation errors on tasks easily performed by humans undermine trust in automation. Background: Research has revealed that the reliability of imperfect automation is frequently misperceived. We examined the manner in which the easiness and type of imperfect automation errors affect trust and dependence. Method: Participants performed a target detection task utilizing an automated aid. In Study 1, the aid missed targets either on easy trials (easy miss group) or on difficult trials (difficult miss group). In Study 2, we manipulated both easiness and type of error (miss vs. false alarm). The aid erred on either difficult trials alone (difficult errors group) or on difficult and easy trials (easy miss group; easy false alarm group). Results: In both experiments, easy errors led to participants mistrusting and disagreeing more with the aid on difficult trials, as compared with those using aids that generated only difficult errors. This resulted in a downward shift in decision criterion for the former, leading to poorer overall performance. Misses and false alarms led to similar effects. Conclusion: Automation errors on tasks that appear “easy” to the operator severely degrade trust and reliance. Application: Potential applications include the implementation of system design solutions that circumvent the negative effects of easy automation errors.
Modeling Driver Behavior in a Cognitive Architecture
Authors: Salvucci Dario D.
Published: June 2006

Objective: This paper explores the development of a rigorous computational model of driver behavior in a cognitive architecture--a computational framework with underlying psychological theories that incorporate basic properties and limitations of the human system. Background: Computational modeling has emerged as a powerful tool for studying the complex task of driving, allowing researchers to simulate driver behavior and explore the parameters and constraints of this behavior. Method: An integrated driver model developed in the ACT-R (Adaptive Control of Thought-Rational) cognitive architecture is described that focuses on the component processes of control, monitoring, and decision making in a multilane highway environment. Results: This model accounts for the steering profiles, lateral position profiles, and gaze distributions of human drivers during lane keeping, curve negotiation, and lane changing. Conclusion: The model demonstrates how cognitive architectures facilitate understanding of driver behavior in the context of general human abilities and constraints and how the driving domain benefits cognitive architectures by pushing model development toward more complex, realistic tasks. Application: The model can also serve as a core computational engine for practical applications that predict and recognize driver behavior and distraction.
A Tactile Cockpit Instrument Supports the Control of Self-Motion During Spatial Disorientation
Authors: van Erp Jan B. F. , Groen Eric L. , Bos Jelte E. , van Veen Hendrik A. H. C.
Published: June 2006

Objective: We investigated the effectiveness of a tactile torso display as a counter-measure to spatial disorientation (SD) and compared inside-out and outside-in codings. Background: SD is a serious threat to military as well as civilian pilots and aircraft. Considerable effort has been put into SD countermeasures such as training programs and advanced cockpit displays. Tactile displays have been considered a promising technology. Method: Twenty-four participants were assigned to the two coding groups (12 per group and matched for age and gender). We used a rotating chair to build up a state of SD by rotating participants around their yaw axis followed by a sudden stop. During the following recovery phase a random disturbance signal was added to the chair's orientation. Participants actively controlled their orientation and were instructed to maintain a stable orientation. Results: Statistical analyses revealed that recovery from SD was improved with support of the tactile instrument, but tracking performance was reduced. The effects were the same whether the instrument was available full time or during the recovery phase only. There were no differences between outside-in and inside-out coding. Conclusion: The present study demonstrates the potential of tactile cockpit instruments in controlling SD, even in the presence of strong but misleading self-motion information from the vestibular sense. Application: Actual or potential applications of this research include spatial disorientation countermeasures for pilots, divers, and astronauts.
Stepping Onto Raised, Laterally Compliant Structures: A Biomechanical Study of Age and Gender Effects in Healthy Adults
Authors: Yang Bing-Shiang , Ashton-Miller James A.
Published: June 2006

Objective: To investigate the effects of gender and age on the kinematics and kinetics associated with stepping onto, and balancing on, a raised structure with lateral compliance. Background: Falls from a stepladder tipping sideways are associated with considerable socioeconomic costs. Method: Ten young women (YF) and 10 young men (YM), aged 23 to 29 years, and 10 older men (OM) aged 66 to 75 years were asked to step up onto one of two raised structures with increasing lateral compliance (C1 and C2), presented in sets of six trials separated by up to 12 rigid (C0) structure trials. Results: Structural compliance (C1 or C2) significantly affected step duration ( p < .05) and lateral weight transfer velocity ( p < .01). Significant age ( p < .001) and gender ( p < .05) differences were found in step duration and center of mass adjustments: With increasing structural compliance, participants required more time (YM: 15%; YF ranged from 33% to 45%; OM 35%-37%) to complete the step-up movement. Conclusion: Increasing age and structural compliance were both associated with larger and longer-lasting structural oscillations that increase the risk for a lateral fall. Application: Older adults, in particular, should not hurry their movements on raised structures. Actual or potential applications of this research include additional safety instructions for ladder users and considerations of structural compliance for designers and authors of national or international standards for raised structures.
Time-to-Collision Judgments Under Realistic Driving Conditions
Authors: Kiefer Raymond J. , Flannagan Carol A. , Jerome Christian J.
Published: June 2006

Objective: This study examined perceived time to collision (TTC) with automobile drivers under realistic approach, rear-end crash scenario conditions. Background: TTC refers to the time before impact if prevailing conditions continue. Method: In this test track study involving 51 drivers ranging from 20 to 70 years old, the driver's vision was occluded at either 3.6 or 5.6 s TTC during an in-lane approach to a lead vehicle. Drivers provided TTC estimates by pressing a button the instant they felt that they would have collided with the vehicle ahead. Results: Results indicated that TTC was consistently underestimated. The TTC ratio (perceived TTC/actual TTC) increased as driver speed decreased and as relative speed increased. These ratios were largely unaffected by age, gender, actual TTC, viewing time (1 s vs. continuous), and the presence of an eyes-forward, mental addition distraction task. Conclusion: Overall, these results suggest that under these low TTC conditions drivers estimate TTC in a relatively uniform fashion and that they are capable of providing this estimate based on a brief glimpse to the vehicle ahead. Application: These results are being used to develop an alert timing approach for a forward collision warning system intended to assist drivers in avoiding rear-end crashes with the vehicle ahead.
Erratum: “Effect of magnetite particle size on adsorption and desorption of arsenite and arsenate” [J. Mater. Res. 20, 3255 (2005)]
Authors: Yean S. , Cong L. , Yavuz C.T. , Mayo J.T. , Yu W.W. , Falkner J.C. , Kan A.T. , Colvin V.L. , Tomson M.B.
Published: June 2006

The purpose of this erratum is to correct the omission of a coauthor, Joshua C. Falkner, Department of Chemistry, Rice University, Houston, Texas.
Dielectric characteristics and diffuse ferroelectric phase transition in Sr4La2Ti4Nb6O30 tungsten bronze ceramics
Authors: Zhu X.L. , Chen X.M. , Liu X.Q. , Yuan Y.
Published: June 2006

In this work, Sr4La2Ti4Nb6O30 ceramics with tetragonal filled tungsten bronze structure were prepared, and the dielectric characteristics and ferroelectric transition were investigated. The room-temperature dielectric constant of the present ceramics showed very weak frequency dependency; it decreased from 570.4 to 561.7 when the frequency varied from 200 Hz to 1 MHz, and a comparatively low-dielectric loss was observed (in the order of 10−3). Unlike the situation for Ba4Ln2Ti4Nb6O30 (Ln = La, Nd and Sm), Sr4La2Ti4Nb6O30 ceramics showed a diffuse ferroelectric phase transition, and the diffuseness exponent γ was 1.61. Moreover, the obvious frequency dispersion was observed over a broad frequency range from 200 Hz to 1 MHz, and the maximum dielectric constant temperature Tmax shifted to higher temperatures with increasing frequency. The dielectric data agreed closely with the Vogel–Fulcher relationship. We concluded that tungsten bronze Sr4La2Ti4Nb6O30 has the relaxor ferroelectric nature.
Preparation of a polymer-intercalated layered manganese oxide nanocomposite through a delamination/reassembling process
Authors: Liu Zong-Huai , Kang Liping , Yang Zupei , Wang Zenglin , Ooi Kenta
Published: June 2006

Layered manganese oxide nanocomposite (PQN2MO) with Polyquaternium-2 (PQN2) incorporated between manganese oxide sheets was synthesized through a delamination/reassembling process. The synthesized material was characterized by powder x-ray diffraction (XRD), elemental analysis, thermal analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy observation. XRD analysis showed that the expansion of the interlayer depended on the amount of PQN2 intercalated; the largest expansion was 0.94 nm, corresponding to a layer of PQN2 chains existing in the interlayer at an angle of about 30°. Chemical analysis results indicated that the tetramethylammonium (TMA+) ions in the interlayer were partly replaced by PQN2 polycations by an ion exchange mechanism, resulting in a nanocomposite in which TMA+ ions and PQN2 polycations simultaneously existed in the interlayer. The intercalated PQN2 polycations were selectively extracted, and TMA+ ions were stable enough to remain in the interlayer against the acid treatment. PQN2MO nanocomposite was composed of platelike nanocomposite particles.
Role of submicron residual fillers in improving optical reflectance of barrier rib glasses for plasma display panels
Authors: Shin Hyunho , Kim Sang-Gon , Park Jong-Sung , Jung Hyun Suk , Hong Kug Sun , Kim Hyungsun
Published: June 2006

The improvement of optical reflectance of BaO–ZnO–B2O3–SiO2 (BZBS) glass by the addition of various types of micron-scale crystalline fillers (TiO2, SiO2, ZrO2, Al2O3, MgO, and cordierite) was investigated for application of the materials to barrier ribs of plasma display panels. The fillers were partially dissolved during sintering, yielding an increased local volume of the fillers in the submicron range, filler rearrangement along boundaries of sintered glass frits, and rather irregular and rugged filler shapes differing from the original morphologies. The measured optical reflectance of the various filler added specimens was within the 30–70% range, which was much higher than the predicted values (less than 10%) based on the rule of mixture of the refractive index. Here we report that the high reflectance of the barrier rib glass for plasma display panels is explained by light scattering by the increased submicron portion of the partially dissolved residual fillers, the size of which is similar to the visual spectrum range (0.4–0.7 μm). The order of reflectance improvement among different types of filler-embedded specimens was consistent with that of the degree of dispersion of the residual fillers in the glass matrix.
Silicoaluminum carbonitride ceramic resist to oxidation/corrosion in water vapor
Authors: Wang Yiguang , Fei Weifeng , Fan Yi , Zhang Ligong , Zhang Wenge , An Linan
Published: June 2006

The oxidation behavior of polymer-derived SiAlCN ceramic in a water vapor environment was studied at 1400 °C. The oxidation and corrosion rates of the SiAlCN are much lower than those of SiCN and pure silicon-based ceramics. The material retains about 75% of its original strength after exposure in water vapor for 300 h at 1400 °C. It is believed that the superior resistance of the SiAlCN to water vapor-related oxidation and corrosion is due to the formation of an aluminum-doped silica layer, in which the aluminum has reduced the activity of the silica.
Microwave-assisted combustion synthesis of Ni powder using urea
Authors: Sahu Ranjan K. , Ray A.K. , Das S.K. , Kailath A.J. , Pathak L.C.
Published: June 2006

A novel microwave-assisted combustion method was used to prepare Ni powder. The method involves the combustion reaction of nickel nitrate and urea as a fuel in the microwave field. The initiation of the exothermic peak of the combustion reaction was found to vary as a function of urea content. The microwave-prepared Ni powder was characterized using x-ray diffraction (XRD), scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, thermogravimetric (TG) analysis, differential thermal analysis (DTA), and magnetic measurement. The XRD pattern revealed that the Ni powder crystallizes with the cubic phase when the molar ratio of fuel to nitrate is varied between 5:1 and 6:1. Above or below that molar ratio, NiO phase coexists as an impurity along with the Ni phase. The magnetization value of Ni measured at room temperature is 53.5 Am2/kg, which is close to the value observed for commercial Ni powder (55.0 Am2/kg). The mechanism for the formation of the Ni and NiO phase is discussed based on the infrared, TG, and DTA data. The method shows that highly pure Ni powder can be prepared using urea as a fuel and microwaves as a source of energy via the solution combustion method.
Effects of strain hardening and residual stress in impression on the instrumented indentation technique
Authors: Liu L.Z. , Bao Y.W. , Zhou Y.C.
Published: June 2006

Finite element analyses were carried out to simulate the loading, unloading, and reloading processes of indentation tests. It was found that the validity of applying the elastic contact theory to the indentation unloading process is strongly related to the strain hardening and residual stress in impression. It is the combination of strain hardening and residual stress that causes the unloading or reloading curves to show elastic loading in the range from zero to the maximum load whereas the reloading curve on the impression without strain hardening and residual stress shows elastic–plastic loading in the same range. These computations indicate that applying the elastic contact theory to the unloading or reloading processes, the fundamental prerequisite of the instrumented indentation technique, is valid because of the existence of strain hardening and residual stress. The mechanism of this hardening effect is discussed through energy analysis.
Transmission electron microscopy study of epitaxial InN thin films grown on c-plane sapphire
Authors: Lu C.J. , Duan X.F. , Lu Hai , Schaff William J.
Published: June 2006

High-quality epitaxial InN thin films grown on (0001) sapphire with GaN buffer were characterized using transmission electron microscopy. It was found that the GaN buffer layer exhibits the (0001) Ga polarity and the InN film has In-terminated polarity. At the InN/GaN interface, there exists a high density of misfit dislocation (MD) array. Perfect edge threading dislocations (TDs) with (1/3)〈1120〉 Burgers vectors are predominant defects that penetrate the GaN and InN layers. Pure screw and mixed TDs were also observed. Overall, the TD density decreases during film growth due to annihilation and fusion. The TD density in GaN is as high as ∼1.5 × 1011 cm−2, and it drops rapidly to ∼2.2 × 1010 cm−2 in InN films. Most half-loops in GaN are connected with MD segments at the InN/GaN interface to form loops, while some TD segments threaded the interface. Half-loops were also generated during the initial stages of InN growth.
Formation, evolution, and degradation of nanostructured covalent thin films deposited by low-energy cluster beam deposition
Authors: D'Urso Luisa , Scalisi A. Alessandro , Altamore Corinna , Compagnini Giuseppe
Published: June 2006

Low-energy cluster beam deposition (LECBD) is considered an intriguing technique for obtaining thin layers with well-defined structures at the nano- and mesoscale levels, allowing novel optical, electronic, and magnetic properties. The produced layers are highly porous and extremely reactive due to the high surface to volume ratio and must be characterized with in situ techniques to study their original composition and their evolution once exposed to reactive gases. In this work, we present a general overview and some results on the formation, evolution, and deposition of silicon and carbon cluster beams produced using a laser vaporization source.