Effects of sleep loss on team decision making: motivational loss or motivational gain?

OBJECTIVE: To examine the effects of 30 hr of sleep loss and continuous cognitive work on performance in a distributed team decision-making environment. BACKGROUND: To date, only a few studies have examined the effect of sleep loss on distributed team performance, and only one other to our knowledge has examined the relationship between sleep loss and social-motivational aspects of teams (Hoeksema-van Orden, Gaillard, & Buunk, 1998). METHOD: Sixteen teams participated; each comprised 4 members. Three team members made threat assessments on a military surveillance task and then forwarded their judgments electronically to a team leader, who made a final assessment on behalf of the team. RESULTS: Sleep loss had an antagonistic effect on team decision-making accuracy and decision time. However, the performance loss associated with fatigue attributable to sleep loss was mediated by being part of a team, as compared with performing the same task individually - that is, we found evidence of a "motivational gain" effect in these sleepy teams. We compare these results with those of Hoeksema-van Orden et al. (1998), who found clear evidence of a "social loafing" effect in sleepy teams. CONCLUSION: The divergent results are discussed in the context of the collective effort model (Karau & Williams, 1993) and are attributable in part to a difference between independent and interdependent team tasks. APPLICATION: The issues and findings have implications for a wide range of distributed, collaborative work environments, such as military network-enabled operations.     

On the Identifiability of Finite Mixtures Based on the Union of Logarithmic Series and Discrete Rectangular Families

In this paper, finite mixtures of the union of Logarithmic Series and Discrete Rectangular families are proved to be identifiable. The sufficient condition for the identifiability of finite mixtures given by Atienza et al. (Metrika 63:215–221, 2006) is applied instead of mostly used Teicher’s condition (Teicher, Ann Math Stat 34: 1265–1269, 1963). The choice of distribution is made in order to stress the fact that, contrarily to Teicher’s approach, Atienza et al.’s theorem being used does apply to heterogeneous parametric families.     

New fast hybrid matrix multiplication algorithms

New hybrid algorithms are proposed for multiplying (n × n) matrices. They are based on Laderman’s algorithm for multiplying (3 × 3)-matrices. As compared with well-known hybrid matrix multiplication algorithms, the new algorithms are characterized by the minimum computational complexity. The multiplicative, additive, and overall complexities of the algorithms are estimated.     

Reliability study of hermetic wafer level MEMS packaging with through-wafer interconnect

In this paper, we developed a hermetic wafer level packaging for MEMS devices. Au–Sn eutectic bonding technology in a relatively low temperature is used to achieve hermetic sealing, and the vertical through-hole via filled with electroplated copper for the electrical connection is also used. The MEMS package has the size of 1 mm × 1 mm × 700 μm, and a square loop Au–Sn metallization of 70 μm in width for hermetic sealing. The robustness of the package is confirmed by several tests such as shear strength test, reliability tests, and hermeticity test. The reliability issues of Au–Sn bonding technology, and copper through-wafer interconnection are discussed, and design considerations to improve the reliability are also presented. By applying O₂ plasma ashing and fabrication process optimization, we can achieve the void-free structure within the bonding interface. The mechanical effects of copper through-vias are also investigated numerically and experimentally. Several factors which could induce via hole cracking failure are investigated such as thermal expansion mismatch, via etch profile, copper diffusion phenomenon, and cleaning process. Alternative electroplating process is suggested for preventing Cu diffusion and increasing the adhesion performance of the electroplating process.     

Design of CWDM multiplexers based on series coupled ring resonators: analysis, potential and prospects on MEMS fabrication technologies

New designs for a 1 × 4 and a 1 × 8 CWDM multiplexers based on cascaded groups of series coupled ring resonators (Little et al. in J Lightwave Technol 15:998–1005, 1997; IEEE Photon Technol Lett 10:2263–2265, 2004; Hryniewicz et al. in IEEE Photon Technol Lett 12:320–322, 2000) are presented. Compared to other integrated optical alternatives such as MMI phasars (Paiam and MacDonald in Appl Opt 36: 5097–5108, 1997), cascaded Mach–Zehnder interferometers (Wang and He in J Lightwave Technol 23:1284–1290, 2005) and cascaded AWG (Dragone in IEEE Photon Technol Lett 3:812–815, 1991; Uetsuka in IEEE J Sel Top Quant Electron 10:393–402, 2004), the proposed circuits offer superior performance in their very sharp roll-off factor that exceeds 0.75, their reduced crosstalk level that lies below −60 dB and their negligible insertion loss for the 1 × 4 design. For the 1 × 8 design, the worst case insertion loss is 4 dB. However, the performances obtained exhibit passband ripples in the order of 5 dB, and besides, they are not very tolerant to fabrication errors. Being designed for SOI technology, the proposed circuits are compact as the circuit areas are 130 × 130 and 90 × 150 μm² for the 1 × 4 and 1 × 8 designs, respectively. They also have a high potential for MEMS tunability.     

Active Environments: Sensing and Responding to Groups of People

Most environments are passive– deaf, dumb and blind, unaware of their inhabitants and unable to assist them in a meaningful way. However, with the advent of ubiquitous computing – ever smaller, cheaper and faster computational devices embedded in a growing variety of “smart” objects – it is becoming increasingly possible to create active environments: physical spaces that can sense and respond appropriately to the people and activities taking place within them. Most of the early ubiquitous computing applications focus on how individuals interact with their environments as they work on foreground tasks. In contrast, this paper focuses on how groups of people affect and are affected by background aspects of their environments.     

An improved block size selection method based on macroblock movement characteristic

The H.264 video compression standard supports seven variable block sizes ranging from 4 × 4 to 16 × 16 for one Macro Block (MB) with 16 × 16 size to conduct motion estimation (ME) and compensation. This new feature achieves significant coding gain at the cost of huge computation complexity. Dozens of fast mode decision algorithms with fast block size selection have been proposed to reduce complexity. In this paper, we propose an improved fast block size selection method based on MB movement characteristic. The Motion Vector (MV) and block residual are employed to analyze the movement characteristic of one MB novelly. Then the movement characteristic is used to decide whether and how to merge or split the MB for encoding. Experimental results show that this method speeds up mode decision procedure dramatically with negligible compression performance degradation.

A micro cycloid-gear system fabricated by multi-exposure LIGA technique

 In this paper, a prototype of 2 mm-diameter micro-cycloid gear system fabricated by the multi-exposure LIGA technique is presented. The gear system is composed of a casing and three vertically stacked disks and gears. Each part consists of three different levels. The first level, 40 μm high, was fabricated by UV-lithography, and the second as well as the third level, 195 μm and 250 μm high respectively, were processed by aligned deep X-ray lithography (DXL). The alignment error between two DXL-processed layers has been measured to be within ±5 μm range. As a result of the height control process, the deviation of structural height has been maintained within ±3 μm range for the UV-lithography-processed structures, and ±10 μm for the DXL-processed structures. Preliminary tests of gear assembly have been implemented with 125 μm-diameter commercially available glass fiber, and the further efforts are being carried out.     

Tree Expressions for Information Systems

The discernibility matrix is one of the most important approaches to computing positive region, reduct, core and value reduct in rough sets. The subject of this paper is to develop a parallel approach of it, called ＂tree expression＂. Its computational complexity for positive region and reduct is O（m^2 × n） instead of O（m × n^2） in discernibility-matrix-based approach, and is not over O（n^2） for other concepts in rough sets, where rn and n are the numbers of attributes and objects respectively in a given dataset （also called an ＂information system＂ in rough sets）. This approach suits information systems with n ≥ m and containing over one million objects.     

Social Presence as a Multi‐Dimensional Group Construct in 3D Virtual Environments

One of the key challenges of distributed teams is the lack of social presence resulting from multiple work locations. Virtual environments (VEs) have been viewed as a collaboration tool for distributed teams that can enhance social presence via shared collaboration space and avatars. We observed, recorded, and analyzed the VE meetings of a globally distributed team. Data were analyzed through quantitative and qualitative content analysis. Our findings show that in the meetings, social presence was a situational phenomenon that constantly varied in strength. Social presence occurred as either a subgroup or group phenomenon, which at times coexisted at both levels. In particular, 2 of the 3 subdimensions of social presence, psychological involvement and behavioral engagement, were observable in team interaction.     

Combining Markov-Chain Analysis and Drift Analysis

In their seminal article Droste, Jansen, and Wegener (Theor. Comput. Sci. 276:51–82, 2002) consider a basic direct-search heuristic with a global search operator, namely the so-called (1+1) Evolutionary Algorithm ((1+1) EA). They present the first theoretical analysis of the (1+1) EA’s expected runtime for the class of linear functions over the search space {0,1} ⁿ . In a rather long and involved proof they show that, for any linear function, the expected runtime is O(nlog n), i.e., that there are two constants c and n′ such that, for n≥n′, the expected number of iterations until a global optimum is generated is bounded above by c⋅nlog ₂ n. However, neither c nor n′ are specified—they would be pretty large. Here we reconsider this optimization scenario to demonstrate the potential of an analytical method that makes use of the distribution of the evolving candidate solution over the search space {0,1} ⁿ . Actually, an invariance property of this distribution is proved, which is then used to obtain a significantly improved bound on the drift, namely the expected change of a potential function, here the number of bits set correctly. Finally, this better estimate of the drift enables an upper bound on the expected number of iterations of 3.8nlog ₂ n+7.6log ₂ n for n≥2.     

Sustaining a Community Computing Infrastructure for Online Teacher Professional Development: A Case Study of Designing Tapped In

Community computing has recently grown to become a major research area in human–computer interaction. One of the objectives of community computing is to support computer supported cooperative work among distributed collaborators working toward shared professional goals in online communities of practice. A core issue in designing and developing community computing infrastructures – the underlying socio-technical layer that supports communitarian activities – is sustainability. Many community computing initiatives fail because the underlying infrastructure does not meet end user requirements; the community is unable to maintain a critical mass of users consistently over time; it generates insufficient social capital to support significant contributions by members of the community; or, as typically happens with funded initiatives, financial and human capital resource become unavailable to further maintain the infrastructure. Based on more than nine years of design experience with Tapped In – an online community of practice for education professionals – we present a case study that discusses four design interventions that have sustained the Tapped In infrastructure and its community to date. These interventions represent broader design strategies for developing online environments for professional communities of practice.     

Trust perceptions of online travel information by different content creators: Some social and legal implications

Consumers are increasingly turning to the online environment to provide information to assist them in making purchase decisions related to travel products. They often rely on travel recommendations from different sources, such as sellers, independent experts and, increasingly, other consumers. A new type of online content, user-generated content (UGC), provides a number of legal and social challenges to providers and users of that content, especially in relation to areas such as defamation, misrepresentation and social embarrassment. This paper reports research that examined the level of trustworthiness of online travel information from these different sources. The study used a survey of Australian travel consumers (n = 12,000) and results support the notion that there are differences in the level of trust for online travel information from different sources. Respondents ‘tended to agree’ that they trusted information provided by travel agents, information from commercial operators and comments made by travellers on third party websites. However, the highest level of trust was afforded to information provided on State government tourism websites. These results suggest that greater trust is placed in online travel comments when they are on a specific travel website than when they are on a more generic social networking website. However, respondents were ‘not sure’ that they trusted comments made by travellers on weblogs and on social networking sites. Some 88% of respondents that had not visited UGC websites (or were unsure if they had) indicated that they thought that UGC would be useful in the future – suggesting that they feel that any concerns they may have in relation to legal and social problems resulting from its use will be resolved.     

Virtuality in human supervisory control: assessing the effects of psychological and social remoteness

Virtuality would seem to offer certain advantages for human supervisory control. First, it could provide a physical analogue of the 'real world' environment. Second, it does not require control room engineers to be in the same place as each other. In order to investigate these issues, a low-fidelity simulation of an energy distribution network was developed. The main aims of the research were to assess some of the psychological concerns associated with virtual environments. First, it may result in the social isolation of the people, and it may have dramatic effects upon the nature of the work. Second, a direct physical correspondence with the 'real world' may not best support human supervisory control activities. Experimental teams were asked to control an energy distribution network. Measures of team performance, group identity and core job characteristics were taken. In general terms, the results showed that teams working in the same location performed better than teams who were remote from one another.     

Exploring and mitigating social loafing in online communities

The motivation to share members’ knowledge is critical to an online community’s survival and success. Previous research has established that knowledge sharing intentions are based on group cohesion. Several studies also suggested that social loafing behavior will seriously corrode group cohesion. Therefore, social loafing is a key obstacle to fostering online community development. Although substantial studies have been performed on the critical factors that affect social loafing in the learning group, those on online communities are still lacking. By integrating two perspectives, social capital and perceived risk, a richer understanding of social loafing behavior can be gained. In the research model, social ties and perceived risk have been driven by anonymity, offline activities, knowledge quality, and media richness. Social ties and perceived risk are hypothesized to affect social loafing in the online community, which, in turn, is hypothesized as negatively affecting group cohesion. Data collected from 323 online users in online communities provide support for the proposed model. The study shows that social loafing is a significant negative predictor of the users’ group cohesion. The study also shows that social ties and perceived risk are important components of social loafing. Anonymity, offline activities, knowledge quality, and media richness all have strong effects on social ties and perceived risk in the online community. Implications for theory and practice and suggestions for future research are discussed.     

Heteroepitaxial growth of Pt (0 0 1) films on SrTiO3 by pulsed laser deposition

 New functional materials are being considered having in perspective an important role in the development of microsystems. In particular, in an experiment of pulsed laser deposition (equipped with in situ reflection high-energy diffraction of the growth surface) thin Pt epitaxial layers have been deposited on SrTiO₃ (0 0 1) substrates. It is shown that thin single-crystal layers of metallic Pt (0 0 1) can be heteroepitaxially grown on SrTiO₃ (0 0 1). Furthermore complex SrTiO₃–Pt–SrTiO₃ heteroepitaxial structures have been deposited. This result is of relevant importance for the growth of new functional materials consisting of heteroepitaxial structures involving both complex oxides and standard metals. These materials may reasonably open up new prospects in the field of microsystem technologies. Received: 31 March 1999/Accepted: 12 April 1999     

SU-8 as resist material for deep X-ray lithography

 A new negative tone resist for deep X-ray lithography is presented. This resist is a nine parts to one mixture of the EPON SU-8 resin with 2,2-bis-(3,5-dichloro-4-hydroxyphenyl)propane (Tetrachlorobisphenol A, TCBA), the latter acting as the photoinitiator. The resist was irradiated at the synchrotron source of DCI at LURE. It was dried for 7 to 20 days beforehand over silica gel while under a light vacuum (20 mbar). Best results for a 150 μm high resist were obtained with a X-ray bottom dose of 3 kJ cm⁻³ and a post exposure bake at 33 °C. Differential Scanning Calorimetry measurements (DSC) determined the glass transition temperature of the resist. The glass transition for the undried, loose resist was 34.7 °C, and it was 28.7 °C when the resist was pressed on a silicon substrate. For a sample of the dried resist, the glass transition was 33.4 °C for the loose resist and 29.8 °C when it was pressed on a Silicon substrate. CD measurements were made on top surface of a set of 100 μm long columns structures, which were produced in 150 μm of this resist. These structures have a constant 100 μm pitch, and the structures themselves varied in width from 20 to 17 μm. For these structures, the CD was calculated to be 0.15 ± 0.03 μm. Received: 8 February 2000/Accepted: 3 March 2000     

Novel Uses of Pinch Gloves™ for Virtual Environment Interaction Techniques

The usability of three-dimensional (3D) interaction techniques depends upon both the interface software and the physical devices used. However, little research has addressed the issue of mapping 3D input devices to interaction techniques and applications. This is especially crucial in the field of Virtual Environments (VEs), where there exists a wide range of potential 3D input devices. In this paper, we discuss the use of Pinch Gloves™ – gloves that report contact between two or more fingers – as input devices for VE systems. We begin with an analysis of the advantages and disadvantages of the gloves as a 3D input device. Next, we present a broad overview of three novel interaction techniques we have developed using the gloves, including a menu system, a text input technique, and a two-handed navigation technique. All three of these techniques have been evaluated for both usability and task performance. Finally, we speculate on further uses for the gloves.     

Cyanate ester based resin systems for snap-cure applications

 Resin compositions comprising cyanate ester have been demonstrated to be useful as die attach adhesives, underfills and encapsulants, where the characteristics of the resins can be varied in a wide range by copolymerization with functionalized comonomers such as epoxies, phenols, rubbers, thermoplastics and others. To reach a combination of properties such as long pot life, short cure time and high glass transition temperature, we encapsulated small particles of effective hardeners to make them insoluble and non-reactive when mixed with the resin at room temperature. Pot lifes of more than 3 months could be reached, whereas the same cyanate ester gels and becomes solid within 30 min at room temperature, if the neat hardener is used instead of the capsules. At a certain elevated temperature, which mainly depends on the structure of the hardener, the capsules open and the curing reaction starts immediately. Low-temperature systems with cure times less than 5 min at 80 °C reach glass temperatures of about 140 °C, and a glass transition temperature of 220 °C after 10 s cure can be achieved with another combination. The developed snap cure resin systems can be easily mixed with a lot of common additives such as minerals, tougheners, metallic powders and others to cover a wide range of performance characteristics for use as adhesives, underfills, encapsulants and the like. Received: 15 May 2001/Accepted: 15 October 2001     

Sex role stereotyping is hard to kill: A field experiment measuring social responses to user characteristics and behavior in an online multiplayer first-person shooter game

Sex role stereotyping by players in first-person shooter games and other online gaming environments may encourage a social environment that marginalizes and alienates female players. Consistent with the social identity model of deindividuation effects (SIDE), the anonymity of online games may engender endorsement of group-consistent attitudes and amplification of social stereotyping, such as the adherence to gender norms predicted by expectations states theory. A 2 × 3 × 2 virtual field experiment (N = 520) in an online first-person shooter video game examined effects of a confederate players’ sex, communication style, and skill on players’ compliance with subsequent online friend requests. We found support for the hypothesis that, in general, women would gain more compliance with friend requests than men. We also found support for the hypothesis that women making positive utterances would gain more compliance with friend requests than women making negative utterances, whereas men making negative utterances would gain more compliance with friend requests than men making positive utterances. The hypothesis that player skill (i.e., game scores) would predict compliance with friend requests was not supported. Implications for male and female game players and computer-mediated communication in online gaming environments are discussed.