Showing papers by "Stevens Institute of Technology published in 2006"

Hands-on, simulated, and remote laboratories: A comparative literature review

Abstract: Laboratory-based courses play a critical role in scientific education. Automation is changing the nature of these laboratories, and there is a long-running debate about the value of hands-on versus simulated laboratories. In addition, the introduction of remote laboratories adds a third category to the debate. Through a review of the literature related to these labs in education, the authors draw several conclusions about the state of current research. The debate over different technologies is confounded by the use of different educational objectives as criteria for judging the laboratories: Hands-on advocates emphasize design skills, while remote lab advocates focus on conceptual understanding. We observe that the boundaries among the three labs are blurred in the sense that most laboratories are mediated by computers, and that the psychology of presence may be as important as technology. We also discuss areas for future research.

Microplasmas and applications

Abstract: Atmospheric-pressure, non-equilibrium plasmas are susceptible to instabilities and, in particular, to arcing (glow-to-arc transition). Spatially confining the plasma to dimensions of 1 mm or less is a promising approach to the generation and maintenance of stable, glow discharges at atmospheric-pressure. Often referred to as microdischarges or microplasmas, these weakly-ionized discharges represent a new and fascinating realm of plasma science, where issues such as the possible breakdown of 'pd scaling' and the role of boundary-dominated phenomena come to the fore. Microplasmas are generated under conditions that promote the efficient production of transient molecular species such as the rare gas excimers, which generally are formed by three-body collisions. Pulsed excitation on a sub-microsecond time scale results in microplasmas with significant shifts in both the temperatures and energy distribution functions associated with the ions and electrons. This allows for the selective production of chemically reactive species and opens the door to a wide range of new applications of microplasmas. The implementation of semiconductor and microelectronics and MEMs microfabrication techniques has resulted in the realization of microplasma arrays as large as 250,000 devices. Fabricated in silicon or ceramics with characteristic device dimensions as small as 10 µm and at packing densities up to 104 cm−2, these arrays offer optical and electrical characteristics well suited for applications in medical diagnostics, displays and environmental sensing. Several microplasma device structures, including their fundamental properties and selected applications, will be discussed.

Adaptive channel allocation spectrum etiquette for cognitive radio networks

Abstract: In this work, we propose a game theoretic framework to analyze the behavior of cognitive radios for distributed adaptive channel allocation. We define two different objective functions for the spectrum sharing games, which capture the utility of selfish users and cooperative users, respectively. Based on the utility definition for cooperative users, we show that the channel allocation problem can be formulated as a potential game, and thus converges to a deterministic channel allocation Nash equilibrium point. Alternatively, a no-regret learning implementation is proposed for both scenarios and it is shown to have similar performance with the potential game when cooperation is enforced, but with a higher variability across users. The no-regret learning formulation is particularly useful to accommodate selfish users. Non-cooperative learning games have the advantage of a very low overhead for information exchange in the network. We show that cooperation based spectrum sharing etiquette improves the overall network performance at the expense of an increased overhead required for information exchange.

Applicant reactions to selection procedures

Abstract: We note that applicant reactions to selection procedures may be of practical importance to employers because of influences on organizations’attractiveness to candidates, ethical and legal issues, and possible effects on selection procedure validity and utility. In Study 1, after reviewing sample items or brief descriptions of 14 selection tools, newly hired entry-level managers (n= 110) and recruiting/employment managers (n= 44) judged simulations, interviews, and cognitive tests with relatively concrete item-types (e.g., vocabulary, standard written English, mathematical word problems) to be significantly more job related than personality, biodata, and cognitive tests with relatively abstract item-types (e.g., quantitative comparisons, letter sets). A measure of new managers’cognitive abilities was positively correlated with their perceptions of the job relatedness of selection procedures. In Study 2, applicant reactions to a range of entry-level to professional civil service examinations (assessed immediately after tasting the exam) were positively related to (procedural and distributive) justice perceptions and willingness to recommend the employer to others (assessed one month after the exam, n= 460).

Middleware: middleware challenges and approaches for wireless sensor networks

Abstract: Using middleware to bridge the gap between applications and low-level constructs is a novel approach to resolving many wireless sensor network issues and enhancing application development. This survey discusses representative WSN middleware, presenting the state of the research

System of Systems - the meaning of of

Abstract: We present distinguishing characteristics (i.e. autonomy, belonging, connectivity, diversity, and emergence), that can help us to recognize or to realize a System of Systems (SoS). The principle differentiation that we make between a thing being either a 'system' or a SoS focuses on the nature of a system's composition. We will distinctly define this set of distinguishing characteristics which will include a set of cross references from our literature research where we believe others are articulating our chosen differentiating characteristics. We conclude by summarizing the difference in these terms in a fundamental sense, one that impacts their structure, behavior and realization, and the distinction comes from the manner in which parts and relationships are gathered together and therefore in the nature of the emergent whole.

Are Investors Influenced by How Earnings Press Releases are Written

Abstract: Earnings press releases are an important means by which many firms communicate to investors. This study examines whether investors are influenced by how earnings press releases are written - the tone and other stylistic attributes - using actual earnings press releases and archival capital markets data in a standard short-window event study. To measure the tone and other stylistic aspects of press releases, I use elementary computer-based content analysis. Tone is measured using a frequency count of positive or negative words. Other stylistic aspects are the overall length of the press release, the overall percentage of numbers versus words, and the complexity of the words used. Results suggest that tone of earnings press releases influences investors' reactions to earnings. An explanation for this result is provided by prospect theory (Tversky and Kahneman, 1981, 1986), which predicts that framing financial performance in positive terms, will cause investors to think about the results in terms of increases relative to reference points. Limited evidence is presented that other stylistic attributes of earnings press releases affect investors' reactions to earnings.

Generalized deviations in risk analysis

Abstract: General deviation measures are introduced and studied systematically for their potential applications to risk management in areas like portfolio optimization and engineering. Such measures include standard deviation as a special case but need not be symmetric with respect to ups and downs. Their properties are explored with a mind to generating a large assortment of examples and assessing which may exhibit superior behavior. Connections are shown with coherent risk measures in the sense of Artzner, Delbaen, Eber and Heath, when those are applied to the difference between a random variable and its expectation, instead of to the random variable itself. However, the correspondence is only one-to-one when both classes are restricted by properties called lower range dominance, on the one hand, and strict expectation boundedness on the other. Dual characterizations in terms of sets called risk envelopes are fully provided.

Adsorption Mechanism of Arsenic on Nanocrystalline Titanium Dioxide

Abstract: Arsenate [As(V)] and arsenite [As(III)] interactions at the solid-water interface of nanocrystalline TiO2 were investigated using electrophoretic mobility (EM) measurements, Fourier transform infrared (FTIR) spectroscopy, extended X-ray absorption fine structure (EXAFS) spectroscopy, and surface complexation modeling. The adsorption of As(V) and As(III) decreased the point of zero charge of TiO2 from 5.8 to 5.2, suggesting the formation of negatively charged inner-sphere surface complexes for both arsenic species. The EXAFS analyses indicate that both As(V) and As(III) form bidentate binuclear surface complexes as evidenced by an average Ti-As(V) bond distance of 3.30 A and Ti-As(III) bond distance of 3.35 A. The FTIR bands caused by vibrations of the adsorbed arsenic species remained at the same energy levels at different pH values. Consequently, the surface complexes on TiO2 maintained the same nonprotonated speciation at pH values from 5 to 10, and the dominant surface species were (TiO)2AsO2- and (TiO)2AsO- for As(V) and As(III), respectively. The surface configurations constrained with the spectroscopic results were formulated in the diffuse layer model to describe the adsorption behavior of As in the pH range between 4 and 12. The study suggests that TiO2 is an effective adsorbent for As removal due to its high surface area and the presence of high affinity surface hydroxyl groups.

Dynamic spectrum access in open spectrum wireless networks

Abstract: One of the reasons for the limitation of bandwidth in current generation wireless networks is the spectrum policy of the Federal Communications Commission (FCC). But, with the spectrum policy reform, open spectrum wireless networks, and spectrum agile radios are set to drive next general wireless networks. In this paper, we investigate continuous-time Markov models for dynamic spectrum access in open spectrum wireless networks. Both queueing and no queueing cases are considered. Analytical results are derived based on the Markov models. A random access protocol is proposed that is shown to achieve airtime fairness. A distributed version of this protocol that uses only local information is also proposed based on homo egualis anthropological model. Inequality aversion by the radio systems to achieve fairness is captured by this model. These protocols are then extended to spectrum agile radios. Extensive simulation results are presented to compare the performances of fixed versus agile radios.

Priority Based Dynamic Spectrum Access with QoS and Interference Temperature Constraints

Abstract: We study the problem of dynamic spectrum access by secondary users with minimum signal to interference noise ratio (quality of service (QoS)) and interference temperature constraints. A non-linear optimization problem with the objective to maximize the total transmitting rate of the secondary users is formulated. The non-linear optimization is solved efficiently using geometric programming techniques. When not all the secondary links can be supported with their QoS requirement, a reduced complexity search algorithm is introduced to find the optimal subset of allowable links. Secondary users may belong to different priority classes. Accessing opportunities should be proportional to priorities. Therefore, we defined a secondary spectrum sharing potential game which takes these priority classes into consideration. The Nash equilibria of this potential game are reached by distributed sequential play. The efficiency of the Nash equilibria solutions are characterized. Finally, the performances of both the reduced complexity algorithm and the sequential play are examined through simulations.

Where Polyelectrolyte Multilayers and Polyelectrolyte Complexes Meet

Abstract: We summarize existing knowledge and present some new results on the relationship between polyelectrolyte multilayer (PEM) growth and phase behavior of polyelectrolyte complexes (PECs) in solution. Detailed understanding of competition between surface and solution as applied to PEMs requires selective labeling of polymers and/or the application of techniques that allow chemically specific monitoring of film components, such as in-situ ATR−FTIR spectroscopy. The trends observed with multilayers directly follow from the properties of PECs in solution. Effects of a number of parameters, such as the type of interacting polyelectrolyte chains, the ratio of their lengths, and ionic strength and pH of deposition solutions, on the likelihood of the multilayer stability or erosion are considered. Polycations with high density of primary amino groups and polyanions with SO3- or SO4- groups show the strongest interpolyelectrolyte binding, resulting in inhibited chain exchange within PECs and/or PEMs. With weakly boun...

A Bayesian game approach for intrusion detection in wireless ad hoc networks

Abstract: In wireless ad hoc networks, although defense strategies such as intrusion detection systems (IDSs) can be deployed at each mobile node, significant constraints are imposed in terms of the energy expenditure of such systems. In this paper, we propose a game theoretic framework to analyze the interactions between pairs of attacking/defending nodes using a Bayesian formulation. We study the achievable Nash equilibrium for the attacker/defender game in both static and dynamic scenarios. The dynamic Bayesian game is a more realistic model, since it allows the defender to consistently update his belief on his opponent's maliciousness as the game evolves. A new Bayesian hybrid detection approach is suggested for the defender, in which a lightweight monitoring system is used to estimate his opponent's actions, and a heavyweight monitoring system acts as a last resort of defense. We show that the dynamic game produces energy-efficient monitoring strategies for the defender, while improving the overall hybrid detection power.

Microbial activity in soils frozen to below-39 degrees C

Abstract: Recent research on life in extreme environments has shown that some microorganisms metabolize at extremely low temperatures in Arctic and Antarctic ice and permafrost. Here, we present kinetic data on CO2 and (CO2)-C-14 release from intact and C-14-glucose amended tundra soils (Barrow, Alaska) incubated for up to a year at 0 to -39 degrees C. The rate of CO2 production declined exponentially with temperature but it remained positive and measurable, e.g. 2-7 ng CO2-C cm(-3) soil d(-1), at -39 degrees C. The variation of CO2 release rate (v) was adequately explained by the double exponential dependence on temperature (T) and unfrozen water content (W) (r(2)> 0.98): v=A exp(lambda T+kW) and where A, lambda and k are constants. The rate of (CO2)-C-14 release from added glucose declined more steeply with cooling as compared with the release of total CO2, indicating that (a) there could be some abiotic component in the measured flux of CO2 or (b) endogenous respiration is more cold-resistant than substrate-induced respiration. The respiration activity was completely eliminated by soil sterilization (1 h, 121 degrees C), stimulated by the addition of oxidizable substrate (glucose, yeast extract), and reduced by the addition of acetate, which inhibits microbial processes in acidic soils (pH 3-5). The tundra soil from Barrow displayed higher below-zero activity than boreal soils from West Siberia and Sweden. The permafrost soils (20-30 cm) were more active than the samples from seasonally frozen topsoil (0-10 cm, Barrow). Finding measurable respiration to -39 degrees C is significant for determining, understanding, and predicting current and future CO2 emission to the atmosphere and for understanding the low temperature limits of microbial activity on the Earth and on other planets. (c) 2005 Elsevier Ltd. All rights reserved. (Less)

Poly(methacrylic acid) Hydrogel Films and Capsules: Response to pH and Ionic Strength, and Encapsulation of Macromolecules

Abstract: Hydrogen-bonded multilayers of a neutral polymer (poly(N-vinylpyrrolidone), PVPON) with poly(methacrylic acid) (PMAA) were used as templates to introduce cross-links between PMAA layers using carbodiimide chemistry and ethylenediamine as a cross-linking agent. Upon exposure to high pH, PVPON is completely released from the hydrogel matrix, producing surface-attached PMAA hydrogels. When such hydrogels are deposited at the surface of silica particles, and the particle core is subsequently dissolved, hollow one-component hydrogel capsules are produced. PMAA hydrogel films and hollow capsules underwent reversible, large (factors of 2 or 3) changes in size in response to changes in solution pH and/or ionic strength. The capsules were used for entrapment and storage of macromolecules such as 500 kDa FITC-dextran by “locking” the capsule wall with an electrostatically associating polycation, poly-N-ethyl-4-vinylpyridinium bromide (QPVP). The release of the encapsulated macromolecules was achieved under high sal...

Antecedents and Consequences of Unlearning in New Product Development Teams

Abstract: Unlearning, which first appeared almost 30 years ago as a subprocess of the organizational learning process, has received only limited attention in the literature. Rather than building on empirical research, the existing scholarship is largely anecdotal, aimed at reviewing the literature and generating new insights. Further, unlearning studies tend to analyze the organizational level and neglect smaller units such as work groups and teams. To address this gap in the understanding of unlearning, this article empirically investigates unlearning in work groups in general and new product development (NPD) teams in particular. This study, based on the literature of organizational memory and change, operationalized team unlearning as changes in beliefs and routines during team-based projects and then discussed the importance of unlearning behavior in NPD teams. Specifically it was argued that unlearning guards beliefs and routines against rigidity to cope with environmental turbulence. This is of particular note when rigid product development procedures and group beliefs inhibit the reception and evaluation of new market and technology information and reduce the value of perceived new information. To test the antecedents and consequences of the team unlearning model, 319 NPD teams were investigated. Using structural equation modeling, it was found that (1) team crisis and anxiety have a direct impact on team unlearning; (2) environmental turbulence also has a direct impact on both team crisis and anxiety and team unlearning; and (3) after team beliefs and project routines have changed, implementing new knowledge or information positively affects new product success. Specifically, the findings revealed that changes in team members’ collective beliefs in accordance with environmental changes and the in-process planning or adjustment of project work activities and procedures as the projects evolve enable teams to develop and launch new products successfully. Also, results indicated that team crisis and anxiety in NPD projects assist team members in revising their previous beliefs and routines when project teams are performing in turbulent environments. This article suggests that managers can enhance team unlearning by (1) creating a sense of urgency by introducing an artificial crisis; and (2) avoiding the groupthink phenomena by bringing in an outsider to challenge existing policies and procedures, and training the team on lateral thinking. In addition, managers can plan project activities in a flexible manner that allows changes as the project evolves to facilitate team unlearning. However, managers should also be cautious when promoting team unlearning. Without careful and considerable evaluation, change in beliefs and routines can cause information/knowledge loss.

Priority-based congestion control in wireless sensor networks

Abstract: In wireless sensor networks (WSNs), congestion occurs, for example, when nodes are densely distributed, and/or the application produces high flow rate near the sink due to the convergent nature of upstream traffic. Congestion may cause packet loss, which in turn lowers throughput and wastes energy. Therefore congestion in WSNs needs to be controlled for high energy-efficiency, to prolong system lifetime, improve fairness, and improve quality of service (QoS) in terms of throughput (or link utilization) and packet loss ratio along with the packet delay. This paper proposes a node priority-based congestion control protocol (PCCP) for wireless sensor networks. In PCCP, node priority index is introduced to reflect the importance of each node. PCCP uses packet inter-arrival time along with packet service time to measure a parameter defined as congestion degree and furthermore imposes hop-by-hop control based on the measured congestion degree as well as the node priority index. PCCP controls congestion faster and more energy-efficiency than other known techniques.

Portfolio optimization with stochastic dominance constraints

Abstract: We consider the problem of constructing a portfolio of finitely many assets whose return rates are described by a discrete joint distribution. We propose a new portfolio optimization model involving stochastic dominance constraints on the portfolio return rate. We develop optimality and duality theory for these models. We construct equivalent optimization models with utility functions. Numerical illustration is provided.

Loop Current warming by Hurricane Wilma

Abstract: [1] Hurricanes mix and cool the upper ocean, as shown here in observations and modeling of the Caribbean Sea and the Gulf of Mexico during the passage of hurricane Wilma. Curiously, the upper ocean around the Loop Current warmed prior to Wilma's entrance into the Gulf. The major cause was increased volume and heat transports through the Yucatan Channel produced by storm-induced convergences in the northwestern Caribbean Sea. Such oceanic variability may have important impacts on hurricane predictions.

Hydrogen‐Bonded Layer‐by‐Layer Polymer Films

Abstract: New developments in the area of hydrogen‐bonded layer‐by‐layer assembly composed of weak polyelectrolytes are reviewed, with emphasis on self‐assembly in an aqueous environment. Advances in fundamental understanding of polymer layering at surfaces are addressed. The effects of molecular weight of polymers, ionic strength, pH, and temperature on growth and post‐self‐assembly response of hydrogen‐bonded films are summarized and contrasted with trends known for electrostatically assembled films. Deposition of hydrogen‐bonded films onto particulate substrates and properties of produced capsules are discussed. Strategies to stabilize hydrogen‐bonded multilayers at neutral and basic pH through crosslinking and response properties of produced ultrathin hydrogel films deposited onto flat substrates or comprising the wall of capsules are also described. The potential of hydrogen‐bonding self‐assembly in surface modification and functionalization, in construction of responsive functional containers and membranes, o...

Learning Process in New Product Development Teams and Effects on Product Success: A Socio-Cognitive Perspective

Abstract: The study purports to develop and empirically test a model of team learning process and its effects on team performance in new product development teams. Using the socio-cognitive theory of learning in groups and organizations, several hypotheses were tested to show that the primer components of social cognition (that is, information acquisition, information dissemination, information implementation, unlearning, thinking, intelligence, improvisation, sense-making, and memory) form an interactive process model of the team earning phenomenon. By studying 165 new product development projects, it was shown: (i) that the eight primer socio-cognitive factors of information acquisition, information dissemination, information implementation, memory, thinking, improvisation, unlearning, and sense-making constitute interrelated sub-components of a higher-order team information-processing construct; (ii) that team intelligence is positively related to components of team information-processing; and (iii) that information-processing facilitates new product success primarily through the positive effects of superior information implementation. Theoretical and managerial implications of the study findings are discussed.

Privacy-preserving queries on encrypted data

Abstract: Data confidentiality is a major concern in database systems. Encryption is a useful tool for protecting the confidentiality of sensitive data. However, when data is encrypted, performing queries becomes more challenging. In this paper, we study efficient and provably secure methods for queries on encrypted data stored in an outsourced database that may be susceptible to compromise. Specifically, we show that, in our system, even if an intruder breaks into the database and observes some interactions between the database and its users, he only learns very little about the data stored in the database and the queries performed on the data. Our work consists of several components. First, we consider databases in which each attribute has a finite domain and give a basic solution for certain kinds of queries on such databases. Then, we present two enhanced solutions, one with a stronger security guarantee and the other with accelerated queries. In addition to providing proofs of our security guarantees, we provide empirical performance evaluations. Our experiments demonstrate that our solutions are fast on large-sized real data.

Transactive Memory System in New Product Development Teams

Abstract: With the increasing popularity of collective memory in the group behavior literature, the transactive memory system (TMS) attracts many researchers and practitioners from different fields, in particular, small group research. Nevertheless, the application of the theory of TMS on new product development teams is surprisingly scant. We argue that the TMS leverages the notion of project-team memory, which is mostly equated with mechanistic memory or electronic documents and databases, by facilitating an interpersonal awareness of who knows what and who has appropriate and adequate skills and expertise, and then receiving information from that person. We then empirically test the effects of TMS on new product development outcomes including mediating and moderating factors, i.e., the collective mind and environmental turbulence, respectively. By investigating 79 Turkish new product development project teams, we found that: 1) the TMS has a positive impact on team learning and speed-to-market; 2) the collective mind (i.e., team members’ attention to interrelating actions) mediates relations between the TMS, team learning, and speed-to-market; and 3) team learning and speed-to-market mediates relations between the TMS and new product success. Further, the moderating effect of environmental turbulence is investigated between the TMS, and team learning and speed-to-market. We found that the impact of the TMS on: 1) speed-to-market is negative when market and technology turbulence associated with the environment is high and 2) team learning changes quadratically with respect to the market and technology turbulence. Theoretical and managerial implications of the study findings are discussed.