Virtual Flows Research Articles

Calculation of the Virtual Resources Flows Condensed in Grain in Gansu Province

Increasing shortage of water and land resources is an uncontroversial fact with population growth and economic development in Gansu Province.How to alleviate the pressure of water and land resources is a major issue faced by decision-makers.Based on the concept of virtual water and virtual land,in this paper a matrix of virtual resources flows condensed in grain and an outline of virtual resources trade are developed through the grain supply and demand at different consumption levels in Gansu Province in 2005 and the next decades.The result shows that the ultimate output of grain in Gansu Province in 2005 could satisfy a per capita grain consumption of 300 kg only.In order to achieve the ample and well-off grain consumptions,it needs to import grain of 6.80×105~1.97×106 t from other provinces or foreign countries.It is predicted that the inter-regional virtual flows of water and land resources condensed in grain will be 4.23×109~6.74×109 m3 and 6.00×105~9.44×105 hm2 respectively by 2020.In a long-term,the trend of virtual resources flows from the Hexi Corridor to the ecological regions in the central and southern parts of Gansu Province will not be significantly changed.The virtual resources trade provides a new choice for guaranteeing the food security and alleviating the shortage of resources in Gansu Province.

On the general form of the law of dynamics

The dynamics of Lagrangian systems is formulated with a differential geometric approach and according to a new paradigm of the calculus of variations. Discontinuities in the trajectory, non-potential force systems and linear constraints are taken into account with a coordinate-free treatment. The law of dynamics, characterizing the trajectory in a general non-linear configuration manifold, is expressed in terms of a variational principle and of differential and jump conditions. By endowing the configuration manifold with a connection, the general law is shown to be tensorial in the velocity of virtual flows and to depend on the torsion of the connection. This result provides a general expression of the E ULER–L AGRANGE operator. P OINCARÉ and L AGRANGE forms of the law are recovered as special cases corresponding, respectively, to the connection induced by natural and mobile reference frames. For free motions, the geodesic property of the trajectory is directly inferred by adopting the L EVI-C IVITA connection induced by the kinetic energy.

Virtual Decomposition Control of a Planar Flexible-Link Robot

Use of flexible link robots is motivated by applications featuring lightweight or long arms. However, the control problem faces strong technical challenges resulting from the complex dynamics. In this paper, the virtual decomposition control (VDC) approach is applied for the first time to address the technical challenges of this thorny problem mainly resulting from the dynamic coupling effects among flexible links. In view of the VDC approach, the control problem of a multiple-flexible-link robot is no more complex than the control problem of individual flexible links subject to kinematics constraints. A planar beam governed by Euler-Bernoulli equation is studied as an example for simplicity. A possible extension to robots with multiple flexible links is theoretically possible by creating appropriate virtual power flows at the two ends of each beam. The validity of the theoretical results is verified by simulations with respect to two typical space systems in planar motion.

In and Out of the House. Housing Hau in Sønderborg and Frederikssund

This article deals with houses and objects. Based on anthropological fieldwork on materiality in two well-off neighbourhoods in Denmark, the starting point are localisations of global flows in the privacy of houses. Filters and control showed out to be a major theme concerning the passages of things in and out of houses; these passages follow two rules: “something in means something else out” and “what comes in must be activated”. Openness and transparency showed out to be important themes concerning the house; there is a tendency towards large windows, few inner walls and large rooms, which are both poly-functional and poly-social. Furthermore, the filtering mechanisms for objects and the openness of the house are related to virtual flows from computers, telephones and televisions. Classical anthropological theories are used to understand this subject matter: the concept of haul (the spirit of the thing), exchange and social relations at large.

Virtual-Flow Multipath Algorithms for MPLS

Multiprotocol Label Switching (MPLS) can improve the routing efficiency of Internet Protocol (IP) networks through its intrinsic Traffic Engineering (TE) capabilities. In this paper, a centralised and a distributed virtual-flow routing algorithms are proposed, which aggregate IP flows entering the MPLS domain and optimally partition them among virtual flows that are routed on multiple paths. The routing algorithms dynamically select multiple Label Switched Paths (LSPs), taking into account the available bandwidth of links in the network to balance the traffic load and avoid network congestion. The multipath routing problem is formulated as a Multicommodity Network Flow (MCNF) problem, and is solved by implementing online the Dantzig Wolfe decomposition method. The proposed multipath algorithms are shown through simulations to outperform single-path routing solutions, such as the Constraint Shortest Path First (CSPF) and the Bandwidth-Based Shortest Path (BSPR) routing algorithms.

LTCP

In this paper, we propose Layered TCP (LTCP for short), a set of simple modifications to the congestion window response of TCP to make it more scalable in highspeed networks. LTCP modifies the TCP flow to behave as a collection of virtual flows to achieve more efficient bandwidth probing. The number of virtual flows emulated is determined based on the dynamic network conditions by using the concept of virtual layers , such that the convergence properties and RTT-unfairness behavior is maintained similar to that of TCP. In this paper, we provide the intuition and the design for the LTCP protocol modifications and evaluation results based on ns-2 simulations and Linux implementation. Our results show that LTCP has promising convergence properties, is about an order of magnitude faster than TCP in utilizing high bandwidth links, employs few parameters and retains AIMD characteristics

Economic analysis of water resources in Japan: using factor decomposition analysis based on input-output tables

This article explores the cause-and-effect relationship between the exports of manufactured goods and water resources (virtual water). Little is known about virtual water flows in relation to Japan’s exports of manufactured goods. The research is based on the Japanese input-output tables and factor decomposition analysis (1980–2000). Virtual water exports include both “direct” water exports (the water utilized to manufacture final goods) and “indirect” water exports (the water required to produce intermediate goods). In the analysis, the change in virtual water exports is decomposed into three determinant factors: the direct water coefficient change, indirect water coefficient change, and export volume change. The findings imply that the export volume change was the most influential factor in determining the total volume of Japanese virtual water exports in the early 1980s; however, the volume of indirect water change exerts a stronger influence on the massive virtual water exports now and is greatly affected by subsidiaries. Manufacturers depend on the supply of water from developing countries to enhance their competitive strengths. Thus, the article suggests possible changes in virtual water trade flows between Japan and other countries.

Virtual water flows and trade liberalization

The linkages between agricultural trade and water resources need to be identified and analyzed to better understand the potential impacts that a full liberalization, or lack thereof, will have on water resources. This paper examines trade of virtual water embodied in agricultural products for most countries of the world. The main purpose of the paper, however, is to examine the impact of trade liberalization on virtual-water trade in the future. Based on a simulation of global agricultural trade, a scenario of full liberalization of agriculture was used to assess the net effect of virtual water flows from the relocation of meat and cereals' trade. The paper also identifies the main reasons behind the changes in the magnitude and direction of the net virtual water trade over time, and shows that virtual water trade flows are independent of water resource endowments, contrary to what the Heckscher-Ohlin Theorem states. Finally, based on a formal model, some input demand functions at the country level are estimated. The estimates of the income and agricultural support elasticities of demand for import of virtual water have the expected sign, and are statistically significant. Variables found to have some explanatory power of the variance of virtual water imports are average income; population; agriculture as value added; irrigated area, and exports of goods and services.

Recurring Surfaces: Architecture in the Experience Economy

Architecture today is split. Arrayed on the one hand are varied, intelligent, and often provocative investigations into the making of form. New materials, new design processes, virtuoso manipulations of irregular geometries, whole new metaphors for the generation of form, surprising borrowings from unlikely sources: each of these characterizes some of the most innovative design thinking of our time. Equally, architects working with self-imposed formal constraints and strict spatial orders have brought minimalist modernism to new levels, while others speculate on the future of architecture in a world increasingly dominated by visual media and virtual flows of information.

Adaptive control of mixed rigid/flexible joint robot manipulators based on virtual decomposition

A modular approach, called virtual decomposition, is applied to adaptive control of robot manipulators with mixed rigid/flexible joints. The system is virtually decomposed into the held object, the links, and the rigid/flexible joints. Each subsystem is controlled independently with decentralized parameter adaptation, while the dynamic interactions between the subsystems are completely represented by virtual power flows (VPFs) which are independent of the dynamics of the subsystems. The equivalence between a rigid joint control and a flexible joint control is established, since they dedicate the same dynamic interactions with their connecting links. Each subsystem is assigned a nonnegative accompanying function which takes care of its dynamics. The system Lyapunov function is formed by considering the VPFs without considering the dynamics of the subsystems. Lyapunov asymptotic stability is guaranteed. Finally, simulation results are presented.

Further appreciation of a control system for chemical reactions residing in virtual energy flows through the bio-system

The argument has been advanced in previous papers that the radiative field of classical electromagnetics is a special case of envelopment of space itself (termed here ‘non-reap’ or ‘imaginary energy’) by waves of this field according to the formalism of Clark Maxwell (termed here ‘real energy’) and that, in its non-enveloped state, the virtual field is of special significance for the functioning bio-system.This paper summarizes evidence from a preceding paper from the areas of physical chemistry and theoretical physics to validate the presence of just such a radiationless, non-enveloped virtual field of space elements dissipating matter of inanimate and animate types. As discussed, the non-enveloped field is subject to envelopment by magnetic fields and by the heat part of the electromagnetic spectrum. It is reasoned that the envelopment process itself is concerned with a thrust-delivering atomic and molecular movement so familiar in bio-system function.The virtual stream develops from the polyatom and polymer state so that wavelengths of its components are greater than those wavelengths associated with individual atoms or molecules. The division between the two wavelength types is set for purposes of this quasi-mechanical approach to space elements at the heat part of the spectrum. Properties of control and stability over atomic and molecular systems derive from this wavelength advantage.Irrespective of wavelength, the virtual system is operative free of heat and of the magnetic field. In the presence of appropriate threshold values, these enveloping agents then manifest an arrangement of space elements in real energy or radiative terms. Events during these transitions confer important physical properties on all matter but they are more highly developed and the control they exercise more subtle in animate matter.

A mathematical framework for the analysis and management of power transactions under open access

Several models are being considered by the power industry for competition under open access transmission. Each alternative offers a radically different solution which must be evaluated, not only in terms of economic benefits, but also in terms of impact on power system security. This paper therefore presents a general mathematical framework for the analysis and management of power transactions under open access subject to system security constraints. The framework introduces the notions of a virtual network of transactions and the transactions matrix, both describing virtual power flows among financial entities. Finally, this paper shows how the transactions selected by the market forces are influenced by the security requirements of the physical network.

Virtual decomposition based control for generalized high dimensional robotic systems with complicated structure

This paper presents a systematic adaptive control strategy which can accomplish a variety of control objectives (position control, internal force control, constraints,and optimizations) for the generalized high-dimensional robotic systems (GHDRS) without restriction on target systems. Based on the concept of virtual decomposition by which a GHDRS is virtually decomposed into several objects and base-floating open chains, the motion control problem of the original system is converted into that of each object and that of each open chain, individually, while the internal force control as well as the constraint force control may be performed with respect to each object only. This feature makes it possible to implement the control algorithm of each subsystem in modularly structured hardware which can be integrated to form any specific robot controller dedicated to a specific application. In the sense of Lyapunov, it is declared that the dynamic coupling between every two physically connected subsystems can be completely represented by the so-called virtual power flows (VPFs) at the cutting points between them. Asymptotic stability of the complete system can be ensured by choosing the system Lyapunov function as the sum of all nonnegative accompanying functions assigned for the subsystems. Some possible applications based on the proposed approach are discussed. Finally, computer simulations of two PUMA 560 arms transporting a common object along a prespecified trajectory are carried out to verify the stability and robustness issues of the system.

Minimal constraints for a joint-probability distribution associated to microsystems

A general continuity equation in the (q, p)-space is stated for virtual flows from Liouville’s complete theorem,i.e. not reduced to a Hamiltonian form. The comparison with the Schrodinger equation permits to disclose the minimal conditions imposed by this equation upon a joint-probability distribution functionP(q, p,t) associated to a microsystem.