Browsing by Author "Chen, Jian"
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- Accurate frequency estimation with phasor anglesChen, Jian (Virginia Tech, 1994-04-04)A power system should always operate in a balanced and stable condition at its designed frequency. Any significant upset of this balance will produce a change in the power system frequency. It is the responsibility of the monitoring and protective devices to detect and restore the system to the equilibrium operating condition at the nominal frequency as soon as it is practical to do so. An accurate measurement of both frequency deviation and rate of change of frequency will greatly facilitate the restoration process. In this thesis, a recursive algorithm for precise frequency and rate of change of frequency measurement is presented. The algorithm consists of three major steps. First, a rough frequency estimation for a data window is computed using a second order least error square approximation on the phasor angles of the input waveform. Then, a resampling based on the rough frequency estimation is carried out, followed by another second order least error square approximation to obtain the final results. The results of simulations using this approach are provided.
- Design and Evaluation of Domain-Specific Interaction Techniques in the AEC Domain for Immersive Virtual EnvironmentsChen, Jian (Virginia Tech, 2006-10-25)Immersive virtual environments (VEs) are broadly applicable to situations where a user can directly perceive and interact with three-dimensional (3D) virtual objects. Currently, successful interactive applications of VEs are limited. Some interactive applications in the AEC (architecture / engineering / construction) domain have not yet benefited from applying VEs. A review of prior work has suggested that 3D interaction has not reached a level that meets real-world task requirements. Most interaction techniques pay little attention to the application contexts. When designers assemble these techniques to develop an interactive system, the interfaces often have very simple and not highly useful UIs. In this work, we describe a domain-specific design approach (DSD) that utilizes pervasive and accurate domain knowledge for interaction design. The purpose of this dissertation is to study the effects of domain knowledge on interaction design. The DSD approach uses a three-level interaction design framework to represents a continuous design space of interaction. The framework has generative power to suggest alternative interaction techniques. We choose the AEC domain as the subject of study. Cloning and object manipulation for massing study are the two example tasks to provide practical and empirical evidences for applying the DSD. This dissertation presents several important results of the knowledge use in the DSD approach. First, the DSD approach provides a theoretical foundation for designing 3D interaction. Techniques produced using DSD result in more useful real-world applications, at least in the domain of AEC. Second, the three-level interaction design framework forms a continuum of design and expands our understanding of 3D interaction design to a level that addresses real-world use. Third, this research proposes an integrated system design approach that integrates DSD and the usability engineering process. Fourth, this work produces a large set of empirical results and observations that demonstrate the effectiveness of domain-knowledge use in designing interaction techniques and applications. Finally, we apply domain-specific interaction techniques to real world applications and create a fairly complex application with improved usefulness.
- Designing Explicit Numeric Input Interfaces for Immersive Virtual EnvironmentsChen, Jian; Bowman, Douglas A.; Wingrave, Chadwick A.; Lucas, John F. (Department of Computer Science, Virginia Polytechnic Institute & State University, 2004)User interfaces involving explicit control of numeric values in immersive virtual environments have not been well studied. In the context of designing three-dimensional interaction techniques for the creation of multiple objects, called cloning, we have developed and tested a dynamic slider interface (D-Slider) and a virtual numeric keypad (VKey). Our cloning interface requires precise number input because it allows users to place objects at any location in the environment with a precision of 1/10 unit. The design of the interface focuses on feedback, constraints, and expressiveness. Comparative usability studies have shown that the newly designed user interfaces were easy to use, effective, and had a good quality of interaction. We describe a working prototype of our cloning interface, the iterative design process for D-Slider and V-Key, and lessons learned. Our interfaces can be re-used for any virtual environment interaction tasks requiring explicit numeric input.
- Domain-Specific Design of 3D Interaction Techniques: An Approach for Designing Useful Virtual Environment ApplicationsChen, Jian; Bowman, Douglas A. (MIT Press, 2009-10-01)Few production virtual environment (VE) applications involve complex three-dimensional (3D) interaction. Our long-term collaboration with architects and engineers in designing 3D user interfaces (3D UIs) has revealed some of the causes: existing interaction tasks and/or techniques are either too generic when isolated from the application context, or too specific to be reusable. We propose a new design approach called domain-specific design (DSD) that sits between the generic and specific design approaches, with an emphasis on using domain knowledge in 3D interaction techniques. We also describe an interaction design framework encompassing generic, domain-specific, and application-specific interaction tasks and techniques. This framework can be used by designers to think of ways to produce domain-specific interaction techniques. We present a particular DSD method, and demonstrate its use for the design of cloning techniques in a structural engineering application. Results from empirical studies demonstrate that interaction techniques produced with domain knowledge in mind outperformed other techniques by improving task efficiency, work flow, and usefulness of the 3D UI.
- Evaluation of the Effectiveness of Cloning Techniques for Architectural Virtual EnvironmentsChen, Jian; Bowman, Douglas A. (Department of Computer Science, Virginia Polytechnic Institute & State University, 2005-09-01)We made the first attempt towards building effective domain-specific interaction techniques for a cloning task. Five interaction techniques were designed and evaluated considering different aspects of domain requirements and human limitations. We demonstrated their effectiveness of designed techniques in two usability studies. The results suggested that no single technique is best for all task conditions. Techniques designed for cloning improved the domain task performance profoundly. The work suggests a further direction: passing domain knowledge to the design process to increase the usefulness of VEs.
- Interfaces for Cloning in Immersive Virtual EnvironmentsChen, Jian; Bowman, Douglas A.; Lucas, John F.; Wingrave, Chadwick A. (Department of Computer Science, Virginia Polytechnic Institute & State University, 2004)Three-dimensional objects in many application domains, such as architecture and construction, can be extremely complex and can consist of a large number of components. However, many of these complex objects also contain a great deal of repetition. Therefore, cloning techniques, which generate multiple spatially distributed copies of an object to form a repeated pattern, can be used to model these objects more efficiently. Such techniques are important and useful in desktop three-dimensional modeling systems, but we are not aware of any cloning techniques designed for immersive virtual environments (VEs). In this paper, we present an initial effort toward the design and development of such interfaces. We define the design space of the cloning task, and present five novel VE interfaces for cloning, then articulate the design rationale. We have also performed a usability study intended to elicit subjective responses with regard to affordance, feedback, attention, perceived usefulness, ease of use, and ease of learning in these interfaces. The study resulted in four major conclusions. First, slider widgets are better suited for discrete than for continuous numeric input. Second, the attentional requirements of the interface increase with increased degrees-of-freedom associated with widgets. Third, users prefer constrained widget movement, although more degrees-of-freedom allow more efficient parameter setting. Finally, appropriate feedback can reduce the cognitive load. The lessons we learned will influence our continuing design of cloning techniques, and these techniques will ultimately be applied to VE applications for design, construction, and prototyping.
- Testbed Evaluation of Navigation and Text Display Techniques in an Information-Rich Virtual EnvironmentChen, Jian; Pyla, Pardha S.; Bowman, Douglas A. (Department of Computer Science, Virginia Polytechnic Institute & State University, 2003)Information-Rich Virtual Environment (IRVE) is a virtual environment (VE) that is enhanced with the addition of related abstract information. Such an environment conveys rich information set that can make the VE more useful if provided with a useful interface and efficient interaction techniques. This motivates our current research goals to investigate the interface and interaction issues involved in IRVE. The fundamental question is how to access and display information in an effective way. This paper presents the first controlled experiment using a travel testbed based on our text layout taxonomy. We investigated two manipulation-based navigation techniques: Hand-Centered Object Manipulation Extending Ray0casting (HOMER) and Go-Go based navigation, and two text layout techniques; within-the-world display (WWD) and heads-up display (HUD). Four search tasks with repeated measures were performed to measure subjects performance in a densely packed environment. We found that using Go-Go based navigation combined with HUD techniques is significantly better than the other three combinations for difficulty search tasks. HUD enabled better performance than WWD and Go-Go technique enabled better performance than HOMER technique ro most of the tasks. Also users preferred the combination of Go-Go and HUD for all tasks. Such results on their own, or combined with specific application characteristics, can provide valuable design guidelines for IRVEs.
- Usability of Tablet PC as a Remote Control Device for Biomedical Data VisualizationNarayan, Michael; Chen, Jian; Pérez-Quiñones, Manuel A. (Department of Computer Science, Virginia Polytechnic Institute & State University, 2004)Interaction through multi-platform user interfaces (MPUIs), is increasingly being used in battlefield applications, telemedicine, classroom education, and engineering applications. Some of the uniqueness of these non-traditional user interfaces lies in the division of information between multiple displays and the remote control of information (e.g., using one computer to control a remote display). We preformed an exploratory study to compare three different setups: a Tablet PC with a traditional desktop, a Tablet PC with a large screen display (LSD) combination, and a desktop computer. The results showed that many users preferred the familiar Microsoft Windows widgets available on the Tablet PC; users often had difficulty generalizing their experiences' when using the Tablet PC; and the form factor of the Tablet PC worked in favor and against the user in different conditions. Our results indicate that while there are yet problems to overcome, generic handheld devices can make highly effective remote controls for virtual environments.