“Biped”: a dance with virtual and company dancers. 1

Merce Cunningham's “Biped” is a new and unique modern dance. The choreography integrates computer-captured virtual dance movement so directly and naturally as to root the entire piece in today's time and space. The animations derive from a complex process, beginning with computerized motion-capture sessions. “Biped” reveals an openness and curiosity applied to computer technology that makes us anticipate new possibilities rather than honor the past. This is a dance conceived entirely for performance as much within a computer as on stage, yet executed without sacrificing any of the human emotion and movement that makes dance survive as a fine-art form     

Explorations into virtual architecture: a HIT Lab gallery

We depend on, and remain overloaded by vast amounts of information. Immersed in a chaotic sea of global data, we must organize this information so that we can interact intuitively and without anxiety from overload or confusion. Enter the architect. Architecture and digital media today, particularly virtual reality technologies, integrate in many ways. Virtual reality promises new venues for designers to conceive, represent, and communicate their ideas, as well. as the opportunity to design spaces not intended for the physical world. Versed in designing and constructing physical environments, architects can create virtual, 3D informational relationships in ways that people can relate to instinctively. This 3D “cyberspace” content must be designed, consciously shaped, and constructed. Architects are just now understanding how to apply their design skills in the virtual world, to design and build “virtual architecture”     

Some principles for designing a wide-area WDM optical network

We explore design principles for next-generation optical wide-area networks, employing wavelength-division multiplexing (WDM) and targeted to nationwide coverage. This optical network exploits wavelength multiplexers and optical switches in routing nodes, so that an arbitrary virtual topology may be embedded on a given physical fiber network. The virtual topology, which is used as a packet-switched network and which consists of a set of all-optical “lightpaths”, is set up to exploit the relative strengths of both optics and electronics-viz. packets of information are carried by the virtual topology “as far as possible” in the optical domain, but packet forwarding from lightpath to lightpath is performed via electronic switching, whenever required. We formulate the virtual topology design problem as an optimization problem with one of two possible objective functions: (1) for a given traffic matrix, minimize the network-wide average packet delay (corresponding to a solution for present traffic demands), or (2) maximize the scale factor by which the traffic matrix can be scaled up (to provide the maximum capacity upgrade for future traffic demands). Since simpler versions of this problem have been shown to be NP-hard, we resort to heuristic approaches. Specifically, we employ an iterative approach which combines “simulated annealing” (to search for a good virtual topology) and “flow deviation” (to optimally route the traffic-and possibly bifurcate its components-on the virtual topology). We do not consider the number of available wavelengths to be a constraint, i.e., we ignore the routing of lightpaths and wavelength assignment for these lightpaths. We illustrate our approaches by employing experimental traffic statistics collected from NSFNET     

Comment on “A rigorous explanation for the resonancesobserved in the scattering from spherical ice particles” [andreply]

In their paper on the “fine scale resonant structure that has been observed both in Mie scattering calculations and in measurements”, Papatsoris and Watson (see ibid., vol.42, p.1350, 1994) state, “various physical explanations have been sought in the past, none of them entirely satisfactory. In this paper, we show that these resonances are directly related to the excitation of the eigenfrequencies of the ice particles, when considered as dielectric resonators.” The most recent prior work in which they mention spheres is a paper written in 1980 regarding surface waves. The authors appear to be unfamiliar with the relevant literature. Papatsoris and Watson reply that qualitative physical explanations for the fine structure of the scattered field form dielectric spheres have been available for many years. They prefer the work of Metz and Dettmar (1963) as being representative as an explanation of the ripple structure. They solved the transcendental equations for ice and presented a comparison between the natural and scattering resonances. They believe that the physical insight offered by their physical explanation is of value     

The “missing” damage-temperature relationship in theChallenger Incident

Communication is a major part of an engineer's work at all levels, and should be considered a fundamental part of total quality management in any industrial process. The communication's failures encountered in the Challenger Incident (flight 51-L, January, 1986) can be generalized to show how to examine critical features in engineering design and service. Since the publication of the Report of the Rogers Commission on the Challenger Incident, there has been a widespread consensus on the conclusion that the engineers failed to demonstrate what they felt, i.e., that temperature was a critical factor in the rubber O-rings' performance. Based on experimental data concerning the “severity-weighted” total number of incidents of O-ring erosion, heating and blow-by proposed by Tufte on the 22 flights before flight 51-L, the paper shows that a power-law function would have been a good estimate of the damage-temperature relationship. The formula agrees qualitatively and quantitatively with physical theory applied to the critical element of the shuttle, the boosters O-rings. For flight 51-L, it would have predicted an average damage well beyond the engineering safety “factor of three”. The formula has been obtained in a rational and objective way and it is based on experimental data: it should have convinced NASA officials to delay the launch, and avoided the last and fatal communication failure in a long sequence     

An infrastructure for social software

In a virtual world, as DVE (distributed virtual environment) applications are often called, logistic support must be supplied by software. As the range of DVE applications expands, they will need software support of a kind rarely envisioned by previous generations of programmers. A new breed of programs is required: social software. The overriding point of social software is not simulation but conversation. Its applications are not substitutes for real-world interaction, but extensions of it. Its “worlds” are not virtual in the customary sense; they are real media for meeting others online. Designers of social software are less concerned with how well their on-screen objects mimic real-world objects than with how well they connect their users to each other. Simulation environments can be thought of as being like the “preview” mode of a word processor, designed to match the look of a printed document. Social environments, by comparison, are like hypertext, opening up avenues of communication that were unforeseen in the media that preceded them. The disparate programs meant for virtual worlds will need a common platform to underpin widespread social interaction     

Comments on “Hall Effect Imaging” [and reply]

Recently, Wen, Shah, and Balaban (The Encyclopedia of Physics, 2nd ed., New York, VCH, 1990) presented two novel and elegant methods for imaging electrical conductivity. In their first method, they placed a conducting sample in a steady magnetic field and applied an ultrasound pulse. The resulting motion of the conductor in the magnetic field produced a measurable voltage. In their second method, they applied a high-frequency voltage to a conducting sample in a steady magnetic field and recorded the ultrasound signal. Here, Roth and Wikswo make two points about this work: 1) The “Hall effect” is not the physical basis for Wen et al.'s techniques, and 2) their work has close experimental and theoretical connections to previous studies of magnetoacoustic imaging. In their reply, disagreeing with Roth et al., Wen and Balaban say that they did not propose two imaging methods. Their paper presented two realizations, the forward and reverse modes, of the same imaging method. They are the reciprocal versions of the same linear electrodynamic process, namely, the conversion between electrical energy and mechanical energy by the Lorentz force. In reply to Roth et al.'s statement that “the name “Hall effect imaging” is misleading” Wen and Balaban say that they extended the idea of the classical Hall effect to describe “Hall-effect imaging” because the initial motion of the charges is not driven by an electric field but by direct mechanical force     

Comments on “General Fourier solution and causality inattenuating media” by R.E. Duren

For original paper, see IEEE Trans. Electromagn. Compat., vol.35, no.1, p.43-8 (1994). When applying mathematics to physical problems one must satisfy the mathematical axioms and in addition the physical laws. Neither the mathematical axioms nor the physical laws can be listed comprehensively, but one does not need to concern oneself too much with mathematical axioms as long as one does not make a mathematical mistake. The physical laws must be introduced into a mathematical model of a physical process, which implies that one must know which physical laws are important in any particular case and one must be sure to actually introduce them. Confusion is caused by the practice of using physical sounding terms in applied mathematics. For instance, R.E. Duren calls a function of time “causal” if it is zero for values of the time variable below a certain threshold. No law prevents one from doing so, but such “causal” functions have no evident connection with the causality law of physics and no results about physical causality should be derived from them. How does one know that the causality law is a physical law that has to be introduced and not a mathematical axiom that is satisfied as long as one calculates correctly? To answer this question the present author considers the causality law in the following form: every effect requires a sufficient cause that occurred a finite time earlier (Harmuth, 1993). The use of the term “time” shows that one is dealing with a physical concept. Pure mathematics has no time variable or spatial variable but it has complex variables     

基于虚拟现实的三维户型展示系统

通过3DStudio MAX结合Cosmo World、VrmlPad和Java语言制作虚拟场景,嵌入网页来展示小区户型及其周边环境,在二维导航图中实现视点跳转、实时导航,在虚拟环境中进行交互操作,使人们对三维小区户型和其周边环境具有强烈的身临其境感,增强了宣传效果。     

Behind the scenes of virtual reality: vision and motion

The phrase “Concealing Telecommunications Networks” is first introduced as an ultimate philosophical concept in human-to-human or physically evolving “multimedia” communications by employing the same face-to-face mode that is used in natural communications. Then virtual reality (VR) technologies and their current applications are introduced, followed by an introduction of cutting-edge research on “Teleconferencing with Realistic Sensations”, which is a communications system that conceals the existence of telecommunications networks. Next, research activities on “vision” and “motion”, the most important underlying human functions supporting technologies such as VR, are presented. These activities consist of 1) a perception model that explains how human beings mentally reconstruct 3-D shapes from 2-D information projected on the retina, and 2) research on the close relationship between the senses, i.e., auditory and visual perception, visual information, and muscular motion stimuli. As a practical application, an example of measuring eye movements for early detection of Alzheimer's disease is briefly introduced. Finally, some fundamental problems with stereoscopic 3-D displays on 2-D screens, which can make them more fatiguing than the natural environment, are discussed     

Polarization-independent δ-strained semiconductor opticalamplifiers: a tight-binding study

We present a tight-binding analysis of the polarization dependence of GaAs δ-strained semiconductors optical amplifiers. Our approach allows us to account for band nonparabolicity, valence band mixing, as well as thin layer perturbations, overcoming the natural limitations of standard techniques based on the envelope function formalism. We explain how thin strained GaAs layers embedded in a lattice-matched InGaAsP-InGaAs quantum well can he used to achieve polarization-insensitive optical amplification. The theory is also applied to other structures providing optical amplification, showing how the concept of “virtual barriers” can lead to high polarization insensitivity     

基于Visua1C#2010的变频器上位机的设计开发

为了提高变频器自动化测试水平,提升生产效率,提出了在VisuaIC#2010开发环境下变频器上位机的设计方案。本文着重介绍了在上位机中如何利用NI Measurement Studio波形控件进行的虚拟示波器设计的方法,对通讯传输的动态数据如何实现波形化显示进行了详细分析说明。     

Network transparency: the plaNET approach

Fast packet-switching has been chosen as the basis for future high speed, “universal” networks. The successful deployment of such networks will clearly depend on a wide range of factors such as cost and technology, but the authors believe that foremost among all is how well they will support existing and future applications. Emphasizing an application oriented perspective is one of the main motivation of the paper. The authors denote by “transparency” the ability of a network to transport application information while altering or manipulating it as little as possible, and believe it will be key to the acceptance of high-speed networks. While the concept is clearly not new, they articulate the need for it and illustrate its feasibility and the advantages it affords through the example of the plaNET network. In particular, they argue that a “transparent” data transfer mechanism can be provided that is both compatible with current standard proposals such as ATM and frame relay, and offers applications the choice of the data transfer mode that best meet their needs. A number of examples are used to illustrate these claims     

An alternative to the biomagnetic forward problem in arealistically shaped head model, the “weightedvertices”

The “weighted vertices” (WV), an alternative in solving the biomagnetic forward problem (BFP) for a realistically shaped head (RSH) model are presented. This proposed approach differs from the others in the way some terms in the governing integral equations are defined. The effects that WV has on important issues such as the “auto solid angle” and “stability of equations” are discussed. Two variants of the WV approach, i.e., the “linear weight” and the “quadratic weight”, have been developed, and comparison of results produced by these two approaches shows that the implementation of quadratic elements to evaluate the integral produces significant improvements. This study is done with a focus on magnetic rather than electric phenomena, so a homogeneous conductor has been used in the numerical example. However, the thoughts behind this proposed method can be easily extended for cases where inhomogeneous conductors are involved. Significant improvement in the accuracy of the forward problem has been observed by use of the WV approach     

Spawning networks

The deployment of new network architectures, services, and protocols is often manual, ad hoc, and time-consuming. We introduce “spawning networks,” a new class of programmable networks that automate the life cycle process for the creation, deployment, and management of network architectures. These networks are capable of spawning distinct “child” virtual networks with their own transport, “parent's” network resources and in isolation from other spawned networks. Spawned child networks represent programmable virtual networks and support the controlled access to communities at users with specific connectivity, security, and quality of service requirements. In this article we present a framework for the realization of spawning networks based on the notion of the Genesis Kernel, a virtual network operating system capable of creating distinct virtual network architectures on the fly. We discuss the motivation and principles that underpin spawning networks and focus on the design of the transport, programming and life cycle environments, which comprise the main architectural components of the Genesis Kernel     

Electrostatic “fractional” image methods for perfectlyconducting wedges and cones

Engheta (1996) introduced a definition for the electric charge “fractional-order” multipoles using the concept of fractional derivatives and integrals. Here, we utilize that definition to introduce a detailed image theory for the two-dimensional (2-D) electrostatic potential distributions in front of a perfectly conducting wedge with arbitrary wedge angles, and for the three-dimensional potential in front of a perfectly conducting cone with arbitrary cone angles. We show that the potentials in the presence of these structures can be described equivalently as the electrostatic potentials of sets of equivalent “image” charge distributions that effectively behave as “fractional-order” multipoles; hence, the name “fractional” image methods. The fractional orders of these so-called fractional images depend on the wedge angle (for the wedge problem) and on the cone angle (for the cone problem). Special cases where these fractional images behave like the discrete images are discussed, and physical justification and insights into these results are given     

The “packing” and the “scheduling packet”switch architectures for almost all-optical lossless networks

This paper proposes two almost all-optical packet switch architectures, called the “packing switch” and the “scheduling switch” architecture, which when combined with appropriate wait-for-reservation or tell-and-go connection and how control protocols provide lossless communication for traffic that satisfies certain smoothness properties. Both switch architectures preserve the order of packets that use a given input-output pair, and are consistent with virtual circuit switching, The scheduling switch requires 2klogT+k² two-state elementary switches (or 2klogT+2klogk elementary switches, if a different version is used) where k is the number of inputs and T is a parameter that measures the allowed burstiness of the traffic. The packing switch requires very little processing of the packet header, and uses k²logT+klogk two-state switches. We also examine the suitability of the proposed architectures for the design of circuit switched networks. We find that the scheduling switch combines low hardware cost with little processing requirements at the nodes, and is an attractive architecture for both packet-switched and circuit-switched high-speed networks     

Multimedia interchange using SGML/HyTime. I. Structures

HyTime is a standard neutral markup language for representing hypertext, multimedia, hypermedia and time-based documents in terms of their logical structure. Documents represented in HyTime conform fully to the ISO Standard Generalized Markup Language (SGML). In effect, HyTime extends SGML by adding certain syntactic conventions called SGML architectural forms, with which it represents certain semantic constructs. HyTime cannot be understood or evaluated without understanding, at least to some extent, the significance and usefulness of the SGML standard on which it is based. This article examines the structure of the two standards. HyTime places unprecedented demands on document processing systems-demands which they have yet to meet. For example, a full implementation of HyTime would allow one to create a hyperlink to whatever happens to be going on at a particular time and/or place in a finite coordinate space (FCS), even if the event, location and time are not yet known, because of binding-time issues. HyTime allows a document to specify where and/or when the results of traversing a hyperlink will be rendered. HyTime provides constructs for specifying how events scheduled in one FCS are to be “projected” onto another, e.g. from a 3D FCS to a 2D FCS, or from a virtual measurement domain to a real one     

Author's reply to comments on “Propagation of EM pulsesexcited by electric dipole in a conducting medium”

It is not surprising that our paper attracted Dr. Wait's interest, since this subject is one of his many contributions. We mentioned that previous studies are “incomplete” because they report either magnetic fields or electric fields excited by a step-junction excitation that is only a special case (as reaffirmed by Dr. Wait). We presented both electric and magnetic fields excited by an impulsive excitation from which the EM field excited by any arbitrary excitation can be obtained by a convolution. This information was needed because we attempted to find the optimal excitation that can excite a maximum electric field. In our humble opinion, our solution is “exact” because we solved Maxwell's equation exactly within the assumption of frequency independent conductivity and permittivity. The adjective “complete” means that we have presented complete expressions for both the electric and magnetic fields. It is not our intention in using these adjectives to be immodest     

The effect of reward structures on allocating shared staffresources among interdependent software projects: an experimentalinvestigation

Organizational theorists have long proposed the use of organizational reward structures to enhance coordination between interdependent projects. In practice, however, the structuring of reward schemes has been problematic, leading in many cases to dysfunctional behavior. The purpose of the reported research is to investigate the impact of different reward structures on the allocation of shared staff resources among interdependent software projects. The research question was explored in the context of a role-playing project simulation game. Experimental dyads played the roles of managers on two concurrent software projects sharing a limited staff resource. Two reward structures were tested, one that rewarded subjects for maximizing their own outcome (an “individualistic orientation”) and the other rewarded subjects for maximizing joint outcome (a “cooperative orientation”). The results suggest that reward structures lead to greater interaction and to more effective strategies for utilizing the organization's staff resource, but they do not lead to less self-interested behavior. The findings of the current study extend the literature on reward structures beyond group performance on physical tasks to dynamic decision making