Showing papers by "University of Notre Dame published in 1998"

Stability theory for hybrid dynamical systems

Abstract: We first formulate a model for hybrid dynamical systems which covers a very large class of systems and which is suitable for the qualitative analysis of such systems. Next, we introduce the notion of an invariant set for hybrid dynamical systems and we define several types of (Lyapunov-like) stability concepts for an invariant set. We then establish sufficient conditions for uniform stability, uniform asymptotic stability, exponential stability, and instability of an invariant set of hybrid dynamical systems. Under some mild additional assumptions, we also establish necessary conditions for some of the above stability types (converse theorems). In addition to the above, we also establish sufficient conditions for the uniform boundedness of the motions of hybrid dynamical systems (Lagrange stability). To demonstrate the applicability of the developed theory, we present specific examples of hybrid dynamical systems and we conduct a stability analysis of some of these examples.

Picosecond Dynamics of Silver Nanoclusters. Photoejection of Electrons and Fragmentation

Abstract: Silver colloids of particle diameter 40−60 nm have been synthesized using a chemical reduction method in aqueous medium. These nanoclusters are photoactive and exhibit transient bleaching in the 400−500 nm region followed by a strong absorption in the visible−near-infrared region when subjected to 355 nm laser-pulse excitation. The transient bleaching of the surface plasmon absorption band is a monophotonic process, while the absorption growth in the red region is a biphotonic process arising from the photoejection of electrons. The 40−60 nm clusters were observed to break up into smaller clusters (5−20 nm) with 355 nm laser-pulse excitation. The choice of excitation wavelength provides the size selectivity in the fragmentation of the clusters. For example, when the excitation wavelength was switched to 532 nm, only larger (or irregularly shaped) particles were found to break up.

An experimental study of MR dampers for seismic protection

Abstract: In this paper, the efficacy of magnetorheological (MR) dampers for seismic response reduction is examined. To investigate the performance of the MR damper, a series of experiments was conducted in which the MR damper is used in conjunction with a recently developed clipped-optimal control strategy to control a three-story test structure subjected to a one-dimensional ground excitation. The ability of the MR damper to reduce both peak responses, in a series of earthquake tests, and rms responses, in a series of broadband excitation tests, is shown. Additionally, because semi-active control systems are nonlinear, a variety of disturbance amplitudes are considered to investigate the performance of this control system over a variety of loading conditions. For each case, the results for three clipped-optimal control designs are presented and compared to the performance of two passive systems. The results indicate that the MR damper is quite effective for structural response reduction over a wide class of seismic excitations.

Super-resolution from image sequences-a review

Abstract: Growing interest in super-resolution (SR) restoration of video sequences and the closed related problem of construction of SR still images from image sequences has led to the emergence of several competing methodologies. We review the state of the art of SR techniques using a taxonomy of existing techniques. We critique these methods and identified areas which promise performance improvements.

Relationships Among Risk, Incentive Pay, and Organizational Performance

Abstract: In this study, we extended agency-based research by examining the role of risk in the structure of managerial compensation and its relationship to organization performance. Our results suggest that...

A longitudinal look at the relation between depression and anxiety in children and adolescents.

Abstract: Elementary school students (n = 330) and their parents (n = 228) participated in a 3-year longitudinal study of the temporal relation between anxiety and depressive symptoms in children. Every 6 months, children and parents completed depression and anxiety questionnaires for a total of 6 waves. Structural equation modeling revealed that individual differences on all measures were remarkably stable over time. Nevertheless, high levels of anxiety symptoms at 1 point in time predicted high levels of depressive symptoms at subsequent points in time even after controlling for prior levels of depression symptoms. These findings were consistent across self- and parent reports. Results support the temporal hypothesis that anxiety leads to depression in children and adolescents.

Carbon, nitrogen, and phosphorus mineralization in northern wetlands

Abstract: We examined rates of C, N, and P mineralization in soils from 16 northern Minnesota wetlands that occur across an ombrotrophic–minerotrophic gradient. Soils were incubated at 30°C under aerobic and anaerobic conditions for 59 wk, and the results were fit with a two-pool kinetic model. Additionally, 39 different soil quality variables were used in a principal components analysis (PCA) to predict mineralization rates. Mineralization of C, N, and P differed significantly among wetland types, aeration status (aerobic vs. anaerobic), and their interaction term. Despite low total soil N and P, there was a rapid turnover of the nutrient pools in ombrotrophic sites, particularly under aerobic conditions. On a volumetric basis, C and N mineralization increased in a predictable manner across the ombrotrophic–minerotrophic gradient, largely due to increasing soil bulk density. However, P mineralization per cubic centimeter remained relatively high in the bogs. The higher total P content of more minerotrophic soils a...

negotiating with Yourself and Losing: Making Decisions with Competing Internal Preferences

Abstract: The field of organizational behavior includes the study of how individuals organize and manage conflict among themselves. Less visible has been the study of conflicts occurring within individuals. We propose that one form of intrapersonal conflict is the result of tension between what people want to do versus what they think they should do. We argue that this want/should distinction helps to explain the “multiple-selves” phenomenon and a recently discovered group of preference reversals noted in behavioral decision and organizational behavior research. We develop a history of knowledge on intrapersonal conflict, discuss how conflicts between what one wants to do and what one should do result in inconsistent behavior, connect this pattern of inconsistency to recent literature on joint versus separate preference reversals, and outline prescriptions for the management of intrapersonal conflict.

Applications of error-control coding

Abstract: An overview of the many practical applications of channel coding theory in the past 50 years is presented. The following application areas are included: deep space communication, satellite communication, data transmission, data storage, mobile communication, file transfer, and digital audio/video transmission. Examples, both historical and current, are given that typify the different approaches used in each application area. Although no attempt is made to be comprehensive in the coverage, the examples chosen clearly illustrate the richness, variety, and importance of error-control coding methods in modern digital applications.

Exploring children's emotional security as a mediator of the link between marital relations and child adjustment

Abstract: Guided by the emotional security hypothesis, this study examined whether links between marital relations and children's adjustment were mediated by children's emotional security, as evidenced by their emotional reactivity (e.g., vigilance, distress), regulation of exposure to parent affect (avoidance, involvement), and internal representations in the context of interparental relations. Multiple methods and contexts were used to assess 6- to 9-year-olds' emotional security in response to standardized, simulated conflicts involving parents. Latent variable path analysis supported a theoretical pathway whereby marital dysfunction was linked with adjustment problems as mediated by response processes indicative of emotional insecurity in relation to parental conflicts. Emotional reactivity and internal representations were most closely linked with marital relations and child adjustment, especially with regard to internalizing symptoms. The importance of understanding children's emotional security in the context of the marital subsystem is discussed.

Insecure Property Rights and Government Ownership of Firms

Abstract: We develop a theory of the ownership of firms in an environment without secure property rights against state encroachment. "Private ownership" leads to excessive revenue hiding and "state ownership" (i.e., national government ownership) fails to provide incentives for managers and local governments in a credible way. Because "local government ownership" integrates local government activities and business activities, local government may better serve the interests of the national government, and thus local government ownership may credibly limit state predation, increase local public goods provision, and reduce costly revenue hiding. We use our theory to interpret the relative success of local government-owned firms during China's transition to a market economy.

Combustion Synthesis of Advanced Materials: Principles and Applications

Abstract: Combustion synthesis is an attractive technique to synthesize a wide variety of advanced materials including powders and near-net shape products of ceramics, intermetallics, composites, and functionally graded materials. This method was discovered in the former Soviet Union by Merzhanov et al. (1971). The development of this technique by Merzhanov and coworkers led to the appearance of a new scientijc direction that incorporates both aspects of combustion and materials science. At about the same time, some work concerning the combustion aspects of this method was also done in the United States (Booth, 1953; Walton and Poulos, 1959; Hardt and Phung, 1973). However, the full potential of combustion synthesis in the production of advanced materials was not utilized. The scientijc and technological activity in thejeld picked up in the United States during the 1980s. The signijcant results of combustion synthesis have been described in a number of review articles (e.g., Munir and Anselmi-Tamburini, 1989; Merzhanov, I990a; Holt and Dunmead, 1991; Rice, 1991; Varma and Lebrat, 1992; Merzhanov, 1993b; Moore and Feng, 1995). At the present time, scientists and engineers in many other countries are also involved in research and further development of combustion synthesis, and interesting theoretical, experimental, and technological results have been reported from various parts of the world (see SHS Bibliography, 1996). This review article summarizes the state of the art in combustion synthesis, from both the scientijc and technological points of view. In this context, we discuss wide-ranging topics including theory, phenomenology, and mechanisms of product structure formation, as well as types and properties of product synthesized, and methods for large-scale materials production by combustion synthesis technique.

Set-membership filtering and a set-membership normalized LMS algorithm with an adaptive step size

Abstract: Set-membership identification (SMI) theory is extended to the more general problem of linear-in-parameters filtering by defining a set-membership specification, as opposed to a bounded noise assumption. This sets the framework for several important filtering problems that are not modeled by a "true" unknown system with bounded noise, such as adaptive equalization, to exploit the unique advantages of SMI algorithms. A recursive solution for set membership filtering is derived that resembles a variable step size normalized least mean squares (NLMS) algorithm. Interesting properties of the algorithm, such as asymptotic cessation of updates and monotonically non-increasing parameter error, are established. Simulations show significant performance improvement in varied environments with a greatly reduced number of updates.

Spectroscopy and Dynamics of Nanometer-Sized Noble Metal Particles

Abstract: Electron−phonon coupling in 11 ± 2 nm diameter Au particles and 10 ± 3 nm and 50 ± 10 nm Ag particles has been examined by ultrafast pump−probe spectroscopy. The observed relaxation times are strongly dependent on the pump laser power. At the lowest pump powers used, the time constants for relaxation are 0.8 ± 0.1 ps for the 11 nm Au particles, 1.1 ± 0.1 ps for the 10 nm Ag particles, and 1.0 ± 0.1 ps for the 50 nm Ag particles. The measured relaxation times are similar to those for bulk metals, which implies that there are no size-dependent effects in the dynamics for particles in this size region. The transient absorption/bleach recovery signals for the particles were modeled using the theory developed by Rosei et al. (Surf. Sci. 1973, 37, 689). These calculations yield the transient absorption spectrum as a function of the temperature of the electron distribution. The time dependence of the electronic temperature after pump laser excitation was calculated using the two-temperature model for electron−ph...

Predicting impact of freshwater exotic species on native biodiversity: Challenges in spatial scaling

Abstract: Global homogenization of biota is underway through worldwide introduction and establishment of nonindigenous (exotic) species. Freshwater ecologists should devote more attention to exotic species for two reasons. First, exotics provide an opportunity to test hypotheses about what characteristics of species or habitats are related to successful establishment or invasibility, respectively. Second, predicting which species will cause large ecological change is an important challenge for natural resource managers. Rigorous statistical relationships linking species characteristics to probability of establishment or of causing ecological impacts are needed. In addition, it is important to know how reliable different sorts of experiments are in guiding predictions. We address this issue with different spatial scales of experiments testing the impact of two predators on native snail assemblages in northern Wisconsin USA lakes: an exotic crayfish, the rusty crayfish (Orconectes rusticus); and a native fish predator, the pumpkinseed sunfish (Lepomis gibossus). For the crayfish, laboratory experiments, a field cage experiment, and a snapshot survey of 21 lakes gave consistent results: the crayfish reduced abundance and species richness of native snails. Laboratory and field experiments suggested that pumpkinseed sunfish should have a similar impact, but the lake survey suggested little impact. Unfortunately, no algorithms exist to guide scaling up from small-scale experiments to the whole-lake, long-term management scale. To protect native biodiversity, management of freshwater exotic species should be targeted on lakes or drainages that are both vulnerable to colonization by an exotic, and that harbour endemic species. Management should focus on preventing introduction because eradication after establishment is usually not possible.

Institutional Environment, Community Government, and Corporate Governance: Understanding China's Township-Village Enterprises

Abstract: We study China's township-village enterprises (TVEs) from an organizational perspective with a focus on governance. Unlike most previous studies, we interpret the firm boundaries of TVEs at the community level rather than the enterprise level. From this perspective, we analyze the central role that community governments play in TVE governance as an organizational response to the imperfect institutional environment of both state and market. Specifically, we show that the community government's involvement in TVEs helps overcome the problems of state predation and under-financing of private enterprises. We also explain why TVE governance leads to harder budget constraints than state-owned enterprises.

Radiolytic Control of the Size of Colloidal Gold Nanoparticles

Abstract: Solutions containing KAu(CN)2 (∼5 × 10-4 M), methanol (0.3 M), and nitrous oxide (2.5 × 10-2 M) are γ-irradiated in the presence of colloidal gold (∼6 × 10-5 M; mean particle size, 15 nm). The hydroxymethyl radicals, •CH2OH, which are generated in these solutions, reduce Au(I) in Au(CN)2-, and the reduced gold is completely deposited on the gold seeds to yield larger particles. The particle growth is followed spectrophotometrically and by electron microscopy. A mechanism is proposed in which the radicals transfer electrons to the gold particles and Au(CN)2- is subsequently reduced by the stored electrons directly at the surface of the particles. In further steps of particle enlargement, Au(CN)2- is reduced in solutions in which the gold particles synthesized in the preceding step serve as seeds, the result being larger and larger gold particles up to 120 nm. The reduction yield is discussed with respect to side reactions of the radicals, such as mutual deactivation and gold-catalyzed H2 formation. The rad...

Asset Pricing with Distorted Beliefs: Are Equity Returns Too Good to Be True?

Abstract: We study a Lucas asset pricing model that is standard in all respects representative agent's subjective beliefs about endowment growth are distorted. Using constant-relative-risk-aversion (CRRA) utility a CRRA coefficient below ten that exhibit, on average, excessive pessimism over expansions and excessive optimism over" contractions, our model is able to match the first and second moments of the equity premium and" risk-free rate, as well as the persistence and predictability of excess returns found in the data."

Fathering over Time: What Makes the Difference?.

Abstract: This article examines how much fathers participate in child care, an important component of domestic duties, and factors related to it It has the advantage of longitudinal data, so that it is possible to look at changes in fathers' participation and factors affecting changes and continuities over time The data come from the 1987-1988 and 1992-1993 National Surveys of Families and Households The sample is restricted to White, two-parent families with at least one child younger than 5 years of age at the time of the first survey The analyses control for the number of children and the gender of the child for whom there is fathering information Based on prior theories and research, the study variables related to fathers' child care include performance of household tasks, their marital quality, gender role ideologies, perceptions of the fairness of the division of domestic labor and the mothers' childcare hours The labor-force variables are the husbands' and wives' hours of paid employment, as well as the earned incomes of husbands and wives The findings indicate that hours on the job keep some men from active fathering, but if they begin taking care of young children, a continuing pattern is established Mothers' child-care hours are positively related to fathers' child care, and fathers do more with sons The discussion places the findings in theoretical context Key Words: child care, childrearing, fathering, parenting, paternal involvement One of the continuing, contentious issues in the research on families has been the division of household labor Early studies (Blood & Wolfe, 1960) showed that wives performed the majority of domestic tasks, presumably including child care Since these reports, an increasing proportion of women have entered the paid labor force, thereby adding breadwinning to their housekeeping and child-care responsibilities Despite this change, there is little evidence that men are doing more around the house to compensate for their wives holding jobs, as well as taking care of domestic responsibilities (Hochschild, 1989) Men's household participation would make for more of a balance in the family's division of labor Critics of this argument note that husbands may do less around the house than their job-holding wives, but they tend to have longer hours on the job (Perry-Jenkins & Folk, 1994; Pleck, 1985) Thus, many men have less time off the job to devote to domestic tasks than do their employed wives Although some recent studies have shown that the gender gap in family housework is diminishing (eg, Pittman, Solheim, & Blanchard, 1996), research indicates a continuing discrepancy in the performance of domestic tasks, even when both spouses are employed full-time (Barnett & Shen, 1997; Wright, 1997; see also, Pleck, 1997, p 85) This research is devoted to looking at the lessexplored topic of men's activities as fathers The research has the advantage of longitudinal data so that the seldom studied issue of factors related to continuities or discontinuities in fathering can be examined In addition, these data avoid the possible confounding of the age of the child and the age cohort of fathers Different ages of respondents who have different parenting expectations due to the historical era in which they grew up and the different ages of their children make this a possible problem in cross-sectional studies (Parke, 1995, p 43) Because there has been some research that suggests housework and child care may have different antecedents (Ishii-Kuntz & Coltrane, 1992), this study concerns specific factors related to fathers who look after their children The focus is on variations in the extent of fathers' child-care activities and what seems to be related to these activities RELEVANT THEORY Despite a growing body of literature on factors that influence fathers' involvement in the lives of their children, psychologist, Ross D Parke (1996) writes, "Surprisingly, we know much more about what fathers do than why they do it" (p …

Misrepresentation and Expectations of Misrepresentation in an Ethical Dilemma: The Role of Incentives and Temptation

Abstract: An investigation of ethical decision making in a negotiation context revealed that focal actors' incentives influenced not only their misrepresentation, but also their expectations of their opponen...

Spatial Resolution Enhancement of Low-Resolution Image Sequences A Comprehensive Review with Directions for Future Research

Abstract: Recent years have seen growing interest in the problem of super-resolution restoration of video sequences. Whereas in the traditional single image restoration problem only a single input image is available for processing, the task of reconstructing super-resolution images from multiple undersampled and degraded images can take advantage of the additional spatiotemporal data available in the image sequence. In particular, camera and scene motion lead to frames in the source video sequence containing similar, but not identical information. The additional information available in these frames make possible reconstruction of visually superior frames at higher resolution than that of the original data. In this paper we review the current state of the art and identify promising directions for future research. The authors are with the Laboratory for Image and Signal Analysis (LISA), University of Notre Dame, Notre Dame, IN 46556. E-mail: rls@nd.edu .

Accountability horizontal e novas poliarquias

Abstract: The poliarchies developed in the western world have been shaped by three different political traditions: the liberal, the republican and the democratic. The liberal and republican traditions foster horizontal accountability, a crucial feature of those poliarchies wich is not to be found in the new democracies. After discussing what this absence implies ways of generating horizontal accountability in the latter are suggested.

The Joint Effect of Management's Prior Forecast Accuracy and the Form of Its Financial Forecasts on Investor Judgment

Abstract: We examine how investor reaction to management earnings forecasts is a joint function of the form of the forecast and management's perceived credibility. In a laboratory experiment involving 126 individual investors, we compare investors' earnings predictions and their confidence therein after receiving point and closed range forecasts issued by managements whose previous forecasting accuracy is known to be either high or low. We used point and range forecasts, because they differ in the degree to which they communicate management's uncertainty about the future. We use management's prior forecasting accuracy as a measure of management's credibility, because prior research has documented the importance of this factor when considering the usefulness of management's voluntary forecasts. Our results show that, as expected, investors' earnings predictions are responsive to management's forecasts. However, as we hypothesized, forecast form did not influence investors' earnings estimates. In contrast, investors' confidence in their earnings predictions was influenced by the form of management's forecasts, but this effect emerged only when management was previously accurate in their forecasting. A similar interactive pattern was found in the dispersion of investors' predictions about the company's future earnings. Finally, consistent with the hypothesis that confidence is an important determinant of investor behavior, we find that investors' judgments of future stock price appreciation are a positive function of both unexpected earnings and the change in their confidence. Our study extends the literature on management forecasts by empirically testing the joint influence of management's credibility (i.e., forecasting accuracy) and forecast form. The prior literature has argued that both factors should be important, but has not delineated whether or how these two factors might interact. We present a theoretical framework that indicates when both factors should influence investor judgment.

Neighborhood Social Context and Racial Differences in Women's Heart Disease Mortality

Abstract: Compared to white women, black women experience similar rates of heart disease morbidity, but higher rates of heart disease mortality. This puzzling relationship may be due to several factors working at varied levels to affect each race. For example, the high heart disease mortality rate may be due to individual health or socioeconomic risk factors or to social structural factors. We conduct a multi-level analysis to address these issues, using data from a newly released data file that links the National Health Interview Survey with death certificate information from the National Death Index, and with additional community level data from the 1990 Census STF-3A files. We are primarily interested in the effects of female-headship rates in the census tracts on coronary heart disease mortality (CHD) among black and white women. We find that women who live in communities with high concentrations of female-headed families are more likely to die of heart disease, net of other characteristics. For younger women, the effect appears to be routed primarily through poverty whereas for older women the effect of female-headship rates remains, net of other census tract characteristics. This study, then, highlights the importance of examining the effect of neighborhoods and their social content on mortality.

Literacy Instruction in 10 Fourth-Grade Classrooms in Upstate New York

Abstract: Literacy instruction was observed in 6 fourth-grade and 4 fifth-grade classrooms over the course of 1 year. Using the method of constant comparison, commonalities among classrooms were identified in the areas of reading instruction, writing instruction, instructional materials, instructional goals, management, and classroom motivational orientation. Teachers in all classrooms provided a combination of authentic reading and writing experiences and explicit skills instruction. Dimensions of difference among classrooms were also identified with respect to the same set of instructional components. One important way that the classrooms differed was with respect to the methods and materials that each teacher considered to be the core of his or her pedagogy (e.g., one teacher's instruction centered on trade books and process writing, another's on cooperative exploration as part of theme-driven instruction). There were also some striking omissions noted in the instruction observed, including a lack of instruction...

Creating Contexts for Involvement in Mathematics.

Abstract: Students' (21 girls, 21 boys) self-reports of involvement in mathematics were related to instructional strategies observed in their upper-elementary classrooms. Students in high involvement classrooms reported challenges and skills as above average and matched, whereas students in low involvement classrooms reported skills as exceeding challenges. Students in high involvement classrooms also reported significantly more positive affect. Discourse analyses of instruction in high involvement classrooms revealed that teachers scaffolded instruction (i.e., negotiated understanding, transferred responsibility, and fostered intrinsic motivation). Instruction in low involvement classrooms was characterized by Initiation-Response-Evaluation sequences, emphasis on procedures, and extrinsic motivation strategies. Results imply that involvement can be socially constructed through whole class instruction and that researchers should give more attention to measuring and understanding situated motivation.