Showing papers by "University of Maryland, College Park published in 2000"

A Theoretical Extension of the Technology Acceptance Model: Four Longitudinal Field Studies

Abstract: The present research develops and tests a theoretical extension of the Technology Acceptance Model (TAM) that explains perceived usefulness and usage intentions in terms of social influence and cognitive instrumental processes. The extended model, referred to as TAM2, was tested using longitudinal data collected regarding four different systems at four organizations ( N = 156), two involving voluntary usage and two involving mandatory usage. Model constructs were measured at three points in time at each organization: preimplementation, one month postimplementation, and three months postimplementation. The extended model was strongly supported for all four organizations at all three points of measurement, accounting for 40%--60% of the variance in usefulness perceptions and 34%--52% of the variance in usage intentions. Both social influence processes (subjective norm, voluntariness, and image) and cognitive instrumental processes (job relevance, output quality, result demonstrability, and perceived ease of use) significantly influenced user acceptance. These findings advance theory and contribute to the foundation for future research aimed at improving our understanding of user adoption behavior.

Emerging adulthood. A theory of development from the late teens through the twenties.

Abstract: Emerging adulthood is proposed as a new conception of development for the period from the late teens through the twenties, with a focus on ages 18-25. A theoretical background is presented. Then evidence is provided to support the idea that emerging adulthood is a distinct period demographically, subjectively, and in terms of identity explorations. How emerging adulthood differs from adolescence and young adulthood is explained. Finally, a cultural context for the idea of emerging adulthood is outlined, and it is specified that emerging adulthood exists only in cultures that allow young people a prolonged period of independent role exploration during the late teens and twenties.

The Promise of Entrepreneurship as a Field of Research

Abstract: To date, the phenomenon of entrepreneurship has lacked a conceptual framework. In this note we draw upon previous research conducted in the different social science disciplines and applied fields of business to create a conceptual framework for the field. With this framework we explain a set of empirical phenomena and predict a set of outcomes not explained or predicted by conceptual frameworks already in existence in other fields.

The genome sequence of Drosophila melanogaster

Abstract: The fly Drosophila melanogaster is one of the most intensively studied organisms in biology and serves as a model system for the investigation of many developmental and cellular processes common to higher eukaryotes, including humans. We have determined the nucleotide sequence of nearly all of the approximately 120-megabase euchromatic portion of the Drosophila genome using a whole-genome shotgun sequencing strategy supported by extensive clone-based sequence and a high-quality bacterial artificial chromosome physical map. Efforts are under way to close the remaining gaps; however, the sequence is of sufficient accuracy and contiguity to be declared substantially complete and to support an initial analysis of genome structure and preliminary gene annotation and interpretation. The genome encodes approximately 13,600 genes, somewhat fewer than the smaller Caenorhabditis elegans genome, but with comparable functional diversity.

Determinants of Perceived Ease of Use: Integrating Control, Intrinsic Motivation, and Emotion into the Technology Acceptance Model

Abstract: Much previous research has established that perceived ease of use is an important factor influencing user acceptance and usage behavior of information technologies. However, very little research has been conducted to understand how that perception forms and changes over time. The current work presents and tests an anchoring and adjustment-based theoretical model of the determinants of system-specific perceived ease of use. The model proposes control (internal and external--conceptualized as computer self-efficacy and facilitating conditions, respectively), intrinsic motivation (conceptualized as computer playfulness), and emotion (conceptualized as computer anxiety) as anchors that determine early perceptions about the ease of use of a new system. With increasing experience, it is expected that system-specific perceived ease of use, while still anchored to the general beliefs regarding computers and computer use, will adjust to reflect objective usability, perceptions of external control specific to the new system environment, and system-specific perceived enjoyment. The proposed model was tested in three different organizations among 246 employees using three measurements taken over a three-month period. The proposed model was strongly supported at all points of measurement, and explained up to 60% of the variance in system-specific perceived ease of use, which is twice as much as our current understanding. Important theoretical and practical implications of these findings are discussed.

Economics and Identity

Abstract: This paper considers how identity, a person's sense of self, affects economic outcomes. We incorporate the psychology and sociology of identity into an economic model of behavior. In the utility function we propose, identity is associated with different social categories and how people in these categories should behave. We then construct a simple game-theoretic model showing how identity can affect individual interactions. The paper adapts these models to gender discrimination in the workplace, the economics of poverty and social exclusion, and the household division of labor. In each case, the inclusion of identity substantively changes conclusions of previous economic analysis.

Time flies when you're having fun: cognitive absorption and beliefs about information technology usage 1

Abstract: Extant explanations of why users behave in particular ways toward information technologies have tended to focus predominantly on instrumental beliefs as drivers of individual usage intentions. Prior work in individual psychology, however, suggests that holistic experiences with technology as captured in constructs such as enjoyment and flow are potentially important explanatory variables in technology acceptance theories. In this paper, we describe a multi-dimensional construct labeled cognitive absorption and defined as a state of deep involvement with software. Cognitive absorption, theorized as being exhibited through the five dimensions of temporal dissociation, focused immersion, heightened enjoyment, control, and curiosity, is posited to be a proximal antecedent of two important beliefs about technology use: perceived usefulness and perceived ease of use. In addition, we propose that the individual traits of playfulness and personal innovativeness are important determinants of cognitive absorption. Based on the conceptual definition of this construct, operational measures for each dimension are developed. Using the World Wide Web as the target technology, scale validation indicates that the operational measures have acceptable psychometric properties and confirmatory factor analysis supports the proposed multi-dimensional structure. Structural equation analysis provides evidence for the theorized nomological net of cognitive absorption. Theoretical and practical implications are offered

Knowledge flows within multinational corporations

Abstract: Pursuing a nodal (i.e., subsidiary) level of analysis, this paper advances and tests an overarching theoretical framework pertaining to intracorporate knowledge transfers within multinational corporations (MNCs). We predicted that (i) knowledge outflows from a subsidiary would be positively associated with value of the subsidiary’s knowledge stock, its motivational disposition to share knowledge, and the richness of transmission channels; and (ii) knowledge inflows into a subsidiary would be positively associated with richness of transmission channels, motivational disposition to acquire knowledge, and the capacity to absorb the incoming knowledge. These predictions were tested empirically with data from 374 subsidiaries within 75 MNCs headquartered in the U.S., Europe, and Japan. Except for our predictions regarding the impact of source unit's motivational disposition on knowledge outflows, the data provide either full or partial support to all of the other elements of our theoretical framework. Copyright © 2000 John Wiley & Sons, Ltd.

W/sup 4/: real-time surveillance of people and their activities

Abstract: W/sup 4/ is a real time visual surveillance system for detecting and tracking multiple people and monitoring their activities in an outdoor environment. It operates on monocular gray-scale video imagery, or on video imagery from an infrared camera. W/sup 4/ employs a combination of shape analysis and tracking to locate people and their parts (head, hands, feet, torso) and to create models of people's appearance so that they can be tracked through interactions such as occlusions. It can determine whether a foreground region contains multiple people and can segment the region into its constituent people and track them. W/sup 4/ can also determine whether people are carrying objects, and can segment objects from their silhouettes, and construct appearance models for them so they can be identified in subsequent frames. W/sup 4/ can recognize events between people and objects, such as depositing an object, exchanging bags, or removing an object. It runs at 25 Hz for 320/spl times/240 resolution images on a 400 MHz dual-Pentium II PC.

Non-parametric Model for Background Subtraction

Abstract: Background subtraction is a method typically used to segment moving regions in image sequences taken from a static camera by comparing each new frame to a model of the scene background. We present a novel non-parametric background model and a background subtraction approach. The model can handle situations where the background of the scene is cluttered and not completely static but contains small motions such as tree branches and bushes. The model estimates the probability of observing pixel intensity values based on a sample of intensity values for each pixel. The model adapts quickly to changes in the scene which enables very sensitive detection of moving targets. We also show how the model can use color information to suppress detection of shadows. The implementation of the model runs in real-time for both gray level and color imagery. Evaluation shows that this approach achieves very sensitive detection with very low false alarm rates.

Thinking about Mechanisms

Abstract: The concept of mechanism is analyzed in terms of entities and activities, organized such that they are productive of regular changes. Examples show how mechanisms work in neurobiology and molecular biology. Thinking in terms of mechanisms provides a new framework for addressing many traditional philosophical issues: causality, laws, explanation, reduction, and scientific change.

"It is what one does": why people participate and help others in electronic communities of practice

Abstract: Advances in information and communication technologies have fundamentally heightened organizational interest in knowledge as a critical strategic resource. However, organizations are finding that members are often reluctant to exchange knowledge with others in the organization. This paper examines why. We review current knowledge management practices and find that organizations are treating knowledge as a private good, owned either by the organization or by organization members. We propose that knowledge can also be considered a public good, owned and maintained by a community. When knowledge is considered a public good, knowledge exchange is motivated by moral obligation and community interest rather than by narrow self-interest. We provide support for the public good perspective by providing results from a survey examining why people participate and share knowledge in three electronic communities of practice. The results indicate that people participate primarily out of community interest, generalized reciprocity and pro-social behavior.

Integrating Justice and Social Exchange: The Differing Effects of Fair Procedures and Treatment on Work Relationships

Abstract: This research investigated whether procedural and interactional justice affect work-related outcomes through different social exchange relationships. The findings extend previous research by demons...

Virioplankton: viruses in aquatic ecosystems

Abstract: The discovery that viruses may be the most abundant organisms in natural waters, surpassing the number of bacteria by an order of magnitude, has inspired a resurgence of interest in viruses in the aquatic environment. Surprisingly little was known of the interaction of viruses and their hosts in nature. In the decade since the reports of extraordinarily large virus populations were published, enumeration of viruses in aquatic environments has demonstrated that the virioplankton are dynamic components of the plankton, changing dramatically in number with geographical location and season. The evidence to date suggests that virioplankton communities are composed principally of bacteriophages and, to a lesser extent, eukaryotic algal viruses. The influence of viral infection and lysis on bacterial and phytoplankton host communities was measurable after new methods were developed and prior knowledge of bacteriophage biology was incorporated into concepts of parasite and host community interactions. The new methods have yielded data showing that viral infection can have a significant impact on bacteria and unicellular algae populations and supporting the hypothesis that viruses play a significant role in microbial food webs. Besides predation limiting bacteria and phytoplankton populations, the specific nature of virus-host interaction raises the intriguing possibility that viral infection influences the structure and diversity of aquatic microbial communities. Novel applications of molecular genetic techniques have provided good evidence that viral infection can significantly influence the composition and diversity of aquatic microbial communities.

Contextual supports and barriers to career choice: A social cognitive analysis.

Abstract: Summary The foregoing review of the career barriers literaturepresents a mixed picture. On the one hand, students andworkers do perceive barriers to their career progress; but onthe other hand, barrier ratings are often found to besomewhat modest in size and have not been shown to beconsistently related to important career outcome or processvariables in the mostly student samples in which they havebeen studied. This is not to say that barriers are notconsequential for many Individuals. Indeed, they are likelyto be especially salient for those who have been victimizedby various forms of oppression. However, several concep-tual and methodological issues—such as the manner inwhich barriers have been defined, failure to consider thecontext and temporal specificity of barriers, noncorrespon-dence between barriers and outcome criteria (in terms ofcontent and developmental task), infrequent attention tomediating and moderating variables, understudy of nonstu-dent samples, and use of designs that do not explorepotential causal effects of barriers—may have partly ob-scured the impact of perceived barriers and the mechanismsthrough which they affect career behavior.Despite these considerations, recent career barriers re-search has constructed an important conceptual and method-ological foundation for further inquiry, and the program-matic research of Swanson, McWhirter, and Luzzo and theircolleagues has been particularly pivotal. In the remainder ofthis article, we attempt to build on this foundation, offering amodest set of suggestions for future research on careerbarriers and their conceptual partner, career supports. Thesesuggestions are premised on the need to clarify or elaboratecertain aspects of SCCT having relevance for the conceptu-alization and assessment of contextual variables.

Mutual Fund Performance: An Empirical Decomposition into Stock-Picking Talent, Style, Transactions Costs, and Expenses

Abstract: We use a new database to perform a comprehensive analysis of the mutual fund industry. We find that funds hold stocks that outperform the market by 1.3 percent per year, but their net returns underperform by one percent. Of the 2.3 percent difference between these results, 0.7 percent is due to the underperformance of nonstock holdings, whereas 1.6 percent is due to expenses and transactions costs. Thus, funds pick stocks well enough to cover their costs. Also, high-turnover funds beat the Vanguard Index 500 fund on a net return basis. Our evidence supports the value of active mutual fund management.

Energy conserving routing in wireless ad-hoc networks

Abstract: An ad-hoc network of wireless static nodes is considered as it arises in a rapidly deployed, sensor-based, monitoring system. Information is generated in certain nodes and needs to reach a set of designated gateway nodes. Each node may adjust its power within a certain range that determines the set of possible one hop away neighbors. Traffic forwarding through multiple hops is employed when the intended destination is not within immediate reach. The nodes have limited initial amounts of energy that is consumed at different rates depending on the power level and the intended receiver. We propose algorithms to select the routes and the corresponding power levels such that the time until the batteries of the nodes drain-out is maximized. The algorithms are local and amenable to distributed implementation. When there is a single power level, the problem is reduced to a maximum flow problem with node capacities and the algorithms converge to the optimal solution. When there are multiple power levels then the achievable lifetime is close to the optimal (that is computed by linear programming) most of the time. It turns out that in order to maximize the lifetime, the traffic should be routed such that the energy consumption is balanced among the nodes in proportion to their energy reserves, instead of routing to minimize the absolute consumed power.

Is Anyone Doing the Housework? Trends in the Gender Division of Household Labor

Abstract: Time-diary data from representative samples ofAmerican adults show thatthenumber ofoverall hours ofdomestic labor (excluding child care andshopping) has continued to decline steadily and predictably since 1965. This finding is mainly due todramatic declines among women (both in and out of thepaidlabor market), whohave cuttheir housework hours almostin halfsince the 1960s: abouthalfofwomen's 12-hour-per­ week decline can beaccountedfor bycompositional shifts - such asincreased labor force participation, later marriage, andfewer children. In contrast, men's housework time has almost doubled during thisperiod (to thepointwhere menwere responsible for a third ofhousework in the 1990s), and only about15% of theirfive-hour-per­ week increase can be attributed to compositional factors. Parallel results on gender differences in housework were obtained from theNational Survey of Families and Households estimate data, even though these producefigures 50%higher thandiary data. Regression results examiningfactors related to wives' andhusbands' housework hours showmore support for the time-availability and relative-resource models of household production thanfor thegender perspective, although there issome support for thelatter perspective aswell.

DNA sequence of both chromosomes of the cholera pathogen Vibrio cholerae

Abstract: Here we determine the complete genomic sequence of the Gram negative, g-Proteobacterium Vibrio cholerae El Tor N16961 to be 4,033,460 base pairs (bp). The genome consists of two circular chromosomes of 2,961,146 bp and 1,072,314 bp that together encode 3,885 open reading frames. The vast majority of recognizable genes for essential cell functions (such as DNA replication, transcription, translation and cell-wall biosynthesis) and pathogenicity (for example, toxins, surface antigens and adhesins) are located on the large chromosome. In contrast, the small chromosome contains a larger fraction (59%) of hypothetical genes compared with the large chromosome (42%), and also contains many more genes that appear to have origins other than the g-Proteobacteria. The small chromosome also carries a gene capture system (the integron island) and host ‘addiction’ genes that are typically found on plasmids; thus, the small chromosome may have originally been a megaplasmid that was captured by an ancestral Vibrio species. The V. cholerae genomic sequence provides a starting point for understanding how a free-living, environmental organism emerged to become a significant human bacterial pathogen.

Age differences in technology adoption decisions: implications for a changing work force

Abstract: This research investigated age differences in individual adoption and sustained usage of technology in the workplace using the theory of planned behavior. User reactions and technology usage behavior were studied over a 5-month period among 118 workers being introduced to a new software system. At 2 points of measurement, compared to older workers, younger workers' technology usage decisions were more strongly influenced by attitude toward using the technology. In contrast, older workers were more strongly influenced by subjective norm and perceived behavioral control, although the effect of subjective norm diminished over time. These findings were robust, even after controlling for key confounding variables identified in prior organizational behavior research (i.e., income, occupation, and education levels). Theoretical and practical implications for understanding the effects of aging on technology adoption and usage in the workplace are discussed.

Nutritional constraints in terrestrial and freshwater food webs

Abstract: Biological and environmental contrasts between aquatic and terrestrial systems have hindered analyses of community and ecosystem structure across Earth's diverse habitats. Ecological stoichiometry1,2 provides an integrative approach for such analyses, as all organisms are composed of the same major elements (C, N, P) whose balance affects production, nutrient cycling, and food-web dynamics3,4. Here we show both similarities and differences in the C:N:P ratios of primary producers (autotrophs) and invertebrate primary consumers (herbivores) across habitats. Terrestrial food webs are built on an extremely nutrient-poor autotroph base with C:P and C:N ratios higher than in lake particulate matter, although the N:P ratios are nearly identical. Terrestrial herbivores (insects) and their freshwater counterparts (zooplankton) are nutrient-rich and indistinguishable in C:N:P stoichiometry. In both lakes and terrestrial systems, herbivores should have low growth efficiencies (10–30%) when consuming autotrophs with typical carbon-to-nutrient ratios. These stoichiometric constraints on herbivore growth appear to be qualitatively similar and widespread in both environments.

From Micro to Meso: Critical Steps in Conceptualizing and Conducting Multilevel Research

Abstract: Although interest in multilevel organizational theory, research, and methods has been on the rise in recent years, vigorous debates in the literature regarding appropriate ways to conceptualize and...

Maternal employment and time with children: dramatic change or surprising continuity?

Abstract: Despite the rapid rise in mothers’ labor force participation, mothers’ time with children has tended to be quite stable over time. In the past, nonemployed mothers’ time with children was reduced by the demands of unpaid family work and domestic chores and by the use of mother substitutes for childcare, especially in large families. Today employed mothers seek ways to maximize time with children: They remain quite likely to work part-time or to exit from the labor force for some years when their children are young; they also differ from nonemployed mothers in other uses of time (housework, volunteer work, leisure). In addition, changes in children’s lives (e.g., smaller families, the increase in preschool enrollment, the extended years of financial dependence on parents as more attend college) are altering the time and money investments that children require from parents. Within marriage, fathers are spending more time with their children than in the past, perhaps increasing the total time children spend with parents even as mothers work more hours away from home.

Implications of loyalty program membership and service experiences for customer retention and value

Abstract: Companies that offer loyalty reward programs believe that their programs have a long-run positive effect on customer evaluations and behavior. However, if loyalty rewards programs increase relationship durations and usage levels, customers will be increasingly exposed to the complete spectrum of service experiences, including experiences that may cause customers to switch to another service provider. Using cross-sectional, time-series data from a worldwide financial services company that offers a loyalty reward program, this article investigates the conditions under which a loyalty rewards program will have a positive effect on customer evaluations, behavior, and repeat purchase intentions. The results show that members in the loyalty reward program overlook or discount negative evaluations of the company vis-a-vis competion. One possible reason could be that members of the loyalty rewards program perceive that they are getting better quality and service for their price or, in other words, “good value.”

On the construction of energy-efficient broadcast and multicast trees in wireless networks

Abstract: The wireless networking environment presents formidable challenges to the study of broadcasting and multicasting problems. After addressing the characteristics of wireless networks that distinguish them from wired networks, we introduce and evaluate algorithms for tree construction in infrastructureless, all-wireless applications. The performance metric used to evaluate broadcast and multicast trees is energy-efficiency. We develop the broadcast incremental power algorithm, and adapt it to multicast operation as well. This algorithm exploits the broadcast nature of the wireless communication environment, and addresses the need for energy-efficient operation. We demonstrate that our algorithm provides better performance than algorithms that have been developed for the link-based, wired environment.