Virtual item purchase behavior in virtual worlds: an exploratory investigation

Virtual worlds, such as Second Life, World of Warcraft and Everquest, have demonstrated huge economic potential. In such virtual worlds, virtual items are bought and sold between individuals for real money. However, little empirical research has been conducted into players’ purchase behavior in virtual worlds. To help us gain a better understanding of factors influencing purchase behavior in virtual worlds, we embarked on an exploratory study. Four focus groups were conducted with 24 participants, selected according to demographic and experiential characteristics. Preliminary empirical evidence suggests that factors including effort expectancy, character competency, the quality of the virtual world system, social influence, virtual item resources, personal real resources, performance expectancy, and self-actualization are important for predicting virtual item purchase behavior in virtual worlds. The results showed that virtual item purchase behavior in virtual worlds has considerable variability involving a range of factors at different stages.     

Realistic real-time sound re-synthesis and processing for interactive virtual worlds

We present new GPU-based techniques for implementing linear digital filters for real-time audio processing. Our solution for recursive filters is the first presented in the literature. We demonstrate the relevance of these algorithms to computer graphics by synthesizing realistic sounds of colliding objects made of different materials, such as glass, plastic, and wood, in real time. The synthesized sounds can be parameterized by the object materials, velocities, and collision angles. Despite its flexibility, our approach uses very little memory, since it essentially requires a set of coefficients representing the impulse response of each material sound. Such features make our approach an attractive alternative to traditional CPU-based techniques that use playback of pre-recorded sounds.     

Approach for automatic font outline generation of NüShu

针对点阵字形存储量大、缩放字形质量难以保证的缺点, 对将女书点阵字形自动转换成曲线轮廓字形的方法进行了研究。首先提取女书轮廓数据; 然后提出了一种基于最大误差值的特征点提取方法; 最后用直线和二次Bezier曲线拟合字形轮廓段, 存储曲线轮廓数据, 从而得到用曲线描述的女书字形。实验结果表明, 该方法计算简单, 大大减少了存储空间, 拟合出来的曲线和原字形轮廓一致, 同时也消除了因手写而造成的毛刺现象, 为在计算机中处理女书奠定了基础。     

A methodology for the generation of planar models for multibody chain drives

To overcome the difficulty on building manually complex models of chain drives, this work proposes a comprehensive methodology to build multibody models of any general chain drive automatically from a minimal set of data. The proposed procedure also evaluates the initial positions and velocities of all components of the drive that are consistent with the kinematic joints or with the contact pairs used in the model. In this methodology, all links and sprockets are represented by rigid bodies connected to each other either by ideal or by clearance revolute joints. The clearance revolute joint contact is further extended to handle the contact between the chain rollers and the sprocket teeth exact profiles. A suitable cylindrical continuous contact law is applied to describe the interaction on all contact pairs. One of the complexities of the computational study of roller chain drives is the large number of bodies in the system and the dynamics of the successive engagement and disengagement of the rollers with the sprockets. Each time a roller engages or disengages with a sprocket tooth, the number of rigid bodies in contact changes. The search for the contact pairs is recognized as one of the most time consuming task in contact analysis. This work proposes a procedure to specify the contact pairs and their update during the dynamic analysis optimizing the computational efficiency of the contact search. The methodologies adopted result in a general computer program that is applied and demonstrated in a generic chain drive that can be used in industrial machines, vehicle engines or any other type of mechanical system.     

Dwelling in Second Life? A phenomenological evaluation of online virtual worlds

In previous research on virtual worlds, the question of whether virtual space can be evaluated just like “real world” space has not been fully addressed. This paper challenges the perceived commonsensical set of assumptions through which virtual world activities are usually unpacked and proposes a new method of evaluating virtual worlds based on Martin Heidegger’s phenomenology. Various focus groups conducted in the virtual world Second Life confirmed that a phenomenological paradigm is more appropriate to fully make sense of and leverage this new medium. Besides questioning the relevancy of dealing with virtual worlds as if they were parallel spaces, this paper, by leveraging a new conceptualization of virtual worlds, also offers suggestions for new online qualitative methodologies.     

A demand-driven virtual disk prefetch mechanism for seamless mobility of personal computing environments

In this paper, we propose a demand-driven virtual disk (VD) prefetch mechanism—DPM—to improve the performance of virtual machine (VM) at destination site for mobile personal computing environments. DPM uses an extended CoW (Copy-on-Write) virtual block device to split the traditional monolithic large-sized VD image into multiple small-sized SVD (Software Virtual Disk) images at a basic granularity of a single kind of software. Based on the fine-grained VD splitting, DPM uses an access frequency and dynamic priority-based prefetch target identifying-APTI algorithm to identify the SVDs of the software being used by the user at destination site, and prefetches those SVDs by utilizing P2P transportation mechanism at background. We have built a prototype to realize DPM on Xen virtual machine monitor (VMM). Experiments on the prototype show that DPM can effectively improve the VM performance at an unexpected destination site without any cached VD state, being helpful in achieving seamless mobility of personal computing environments in distributed virtual machine environments.     

Automatic generation of temporal planning domains for e-learning problems

AI Planning & Scheduling techniques are being widely used to adapt learning paths to the special features and needs of students both in distance learning and lifelong learning environments. However, instructors strongly rely on Planning & Scheduling experts to encode and review the domains for the planner/scheduler to work. This paper presents an approach to automatically extract a fully operational HTN planning domain and problem from a learning objects repository without requiring the intervention of any planning expert, and thus enabling an easier adoption of this technology in practice. The results of a real experiment with a small group of students within an e-Learning private company in Spain are also shown.     

Asymmetric trajectory generation and impedance control for running of biped robots

An online asymmetric trajectory generation method for biped robots is proposed to maintain dynamical postural stability and increase energy autonomy, based on the running stability criterion defined in phases. In a support phase, an asymmetric trajectories for the hip and swing leg of the biped robots is obtained from an approximated running model with two springless legs and a spring-loaded inverted pendulum model so that the zero moment point should exist inside the safety boundary of a supporting foot, and the supporting leg should absorb large reaction forces, take off and fly through the air. The biped robot is under-actuated with six degrees of under-actuation during flight. The trajectory generation strategies for the hip and both legs in a flight phase use the approximated running model and non-holonomic constraints based on the linear and angular momenta at the mass center. Next, we present an impedance control with a force modulation strategy to guarantee a stable landing on the ground and simultaneously track the desired trajectories where the desired impedance at the hip link and both legs is specified. A series of computer simulations for two different types of biped robots show that the proposed running trajectory and impedance control method satisfy the two conditions for running stability and make the biped robot more robust to variations in the desired running speed, gait transitions between walking and running, and parametric modeling errors. We have examined the feasibility of this method with running experiments on a 12-DOF biped robot without arms. The biped robot could run successfully with average forward speed of about 0.3359 [m/s]. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.

Hybrid BFOA–PSO algorithm for automatic generation control of linear and nonlinear interconnected power systems

In the bacteria foraging optimization algorithm (BFAO), the chemotactic process is randomly set, imposing that the bacteria swarm together and keep a safe distance from each other. In hybrid bacteria foraging optimization algorithm and particle swarm optimization (hBFOA–PSO) algorithm the principle of swarming is introduced in the framework of BFAO. The hBFOA–PSO algorithm is based on the adjustment of each bacterium position according to the neighborhood environment. In this paper, the effectiveness of the hBFOA–PSO algorithm has been tested for automatic generation control (AGC) of an interconnected power system. A widely used linear model of two area non-reheat thermal system equipped with proportional-integral (PI) controller is considered initially for the design and analysis purpose. At first, a conventional integral time multiply absolute error (ITAE) based objective function is considered and the performance of hBFOA–PSO algorithm is compared with PSO, BFOA and GA. Further a modified objective function using ITAE, damping ratio of dominant eigenvalues and settling time with appropriate weight coefficients is proposed to increase the performance of the controller. Further, robustness analysis is carried out by varying the operating load condition and time constants of speed governor, turbine, tie-line power in the range of +50% to ?50% as well as size and position of step load perturbation to demonstrate the robustness of the proposed hBFOA–PSO optimized PI controller. The proposed approach is also extended to a non-linear power system model by considering the effect of governor dead band non-linearity and the superiority of the proposed approach is shown by comparing the results of craziness based particle swarm optimization (CRAZYPSO) approach for the identical interconnected power system. Finally, the study is extended to a three area system considering both thermal and hydro units with different PI coefficients and comparison between ANFIS and proposed approach has been provided.     

Augmented &; Virtual Reality applications in the field of logistics

Changing basic conditions in the field of logistics requires intuitive planning methods as well as new ways of supporting and educating the operative staff. VR and AR show a great promise for that.

Coverage-guided test generation for continuous and hybrid systems

In this paper, we describe a formal framework for conformance testing of continuous and hybrid systems, using the international standard ‘Formal Methods in Conformance Testing’ FMCT. We propose a novel test coverage measure for these systems, which is defined using the star discrepancy notion. This coverage measure is used to quantify the validation ‘completeness’. It is also used to guide input stimulus generation by identifying the portions of the system behaviors that are not adequately examined. We then propose a test generation method, which is based on a robotic motion planning algorithm and is guided by the coverage measure. This method was implemented in a prototype tool that can handle high dimensional systems (up to 100 dimensions).     

The physiological mirror—a system for unconscious control of a virtual environment through physiological activity

This paper introduces a system for real-time physiological measurement, analysis, and metaphorical visualization within a virtual environment (VE). Our goal is to develop a method that allows humans to unconsciously relate to parts of an environment more strongly than to others, purely induced by their own physiological responses to the virtual reality (VR) displays. In particular, we exploit heart rate, respiration, and galvanic skin response in order to control the behavior of virtual characters in the VE. Such unconscious processes may become a useful tool for storytelling or assist guiding participants through a sequence of tasks in order to make the application more interesting, e.g., in rehabilitation. We claim that anchoring of subjective bodily states to a virtual reality (VR) can enhance a person’s sense of realism of the VR and ultimately create a stronger relationship between humans and the VR.     

A High Order Compact Scheme for the Pure-Streamfunction Formulation of the Navier-Stokes Equations

In this paper we continue the study, which was initiated in (Ben-Artzi et al. in Math. Model. Numer. Anal. 35(2):313–303, 2001; Fishelov et al. in Lecture Notes in Computer Science, vol. 2667, pp. 809–817, 2003; Ben-Artzi et al. in J. Comput. Phys. 205(2):640–664, 2005 and SIAM J. Numer. Anal. 44(5):1997–2024, 2006) of the numerical resolution of the pure streamfunction formulation of the time-dependent two-dimensional Navier-Stokes equation. Here we focus on enhancing our second-order scheme, introduced in the last three afore-mentioned articles, to fourth order accuracy. We construct fourth order approximations for the Laplacian, the biharmonic and the nonlinear convective operators. The scheme is compact (nine-point stencil) for the Laplacian and the biharmonic operators, which are both treated implicitly in the time-stepping scheme. The approximation of the convective term is compact in the no-leak boundary conditions case and is nearly compact (thirteen points stencil) in the case of general boundary conditions. However, we stress that in any case no unphysical boundary condition was applied to our scheme. Numerical results demonstrate that the fourth order accuracy is actually obtained for several test-cases.     

Energizing business transactions in virtual worlds: an empirical study of consumers’ purchasing behaviors

Virtual marketplaces for products and services have become major profit sources in virtual worlds (VWs). The large quantity and growth of virtual product transactions and their platform providers’ profits have made it critical to understand consumer purchasing behavior in VWs. However, as open-ended VWs such as Second Life have environments that differ from those of other online communities, the underlying mechanisms of consumers’ e-commerce behavior may not explain their VW behavior. Therefore, this study examines consumers’ VW behavior by considering three categories of factors influencing their purchasing behavior: the platform context (i.e., technical characteristics such as interactivity and vividness and social characteristics such as involvement), product context (i.e., product value), and virtual experience (i.e., flow and satisfaction). This study examines how these factors affect consumers when they purchase virtual products. Its results highlight the importance of flow experience in consumers’ VW behavior. Interactivity, vividness, and involvement are found to affect consumers’ virtual experience—flow, and involvement exhibits a significantly stronger influence on flow. Flow and involvement are found to affect product value, and flow exerts a stronger influence than involvement on product value. Flow and product value directly impact consumers’ willingness to purchase, whereas satisfaction with the virtual world experience, which is significantly affected by flow, is not associated with willingness to purchase. The results further indicate that product value is more influential on willingness to purchase than is flow. After describing the study’s contributions to both research and practice, I conclude the paper by presenting avenues for future research.     

Virtual Observations: a software tool for contextual observation and assessment of user’s actions in virtual reality

Virtual Reality - In this paper, we present ‘Virtual Observation’ (VO) a software tool for contextual observation and assessment of user’s directly from within the virtual reality...     

A Comparison of Closed World Assumptions

In this Paper.we introduce a notion of the family of closed world assumptions and compare several well-known closed world approaches in the family to the extent to whic an incomplete database is com pleted.     

A Comparison of Closed World Assumptions

In this paper, we introduce a notion of the family of closed world assumptions and compare severalwell-known closed world approaches in the family to the extent to which an incomplete database is com-pleted.