External Dump Research Articles

A colony-level response to disease control in a leaf-cutting ant.

Parasites and pathogens often impose significant costs on their hosts. This is particularly true for social organisms, where the genetic structure of groups and the accumulation of contaminated waste facilitate disease transmission. In response, hosts have evolved many mechanisms of defence against parasites. Here we present evidence that Atta colombica, a leaf-cutting ant, may combat Escovopsis, a dangerous parasite of Atta's garden fungus, through a colony-level behavioural response. In A. colombica, garden waste is removed from within the colony and transported to the midden--an external waste dump--where it is processed by a group of midden workers. We found that colonies infected with Escovopsis have higher numbers of workers on the midden, where Escovopsis is deposited. Further, midden workers are highly effective in dispersing newly deposited waste away from the dumping site. Thus, the colony-level task allocation strategies of the Atta superorganism may change in response to the threat of disease to a third, essential party.

Charging magnet for the floating coil of LDX

The charging coil (C-coil) for the joint Columbia University/MIT Levitated Dipole Experiment (LDX) is under development jointly by MIT and the Efremov Institute. The NbTi superconducting C-coil serves to charge/discharge inductively the floating superconducting magnet to/from 2277 A when it is resting in the charging port at the bottom of the LDX vacuum vessel. The C-coil is designed for 3200 charge-discharge cycles. The solenoid magnet is installed in a low heat leak liquid helium cryostat with a warm bore of more than 1 m. The magnet protection system has an external dump resistor, which dissipates most of the 12 MJ stored during a quench.

Quench propagation and protection analysis of the ATLAS Toroids

The ATLAS superconducting magnet system consists of the Barrel Toroid, two End Cap Toroids and the Central Solenoid. However, the Toroids of eight coils each are magnetically separate systems to the Central Solenoid. The Toroids are electrically connected in series and energized by a single power supply. The quench protection system is based on the use of relatively small external dump resistances in combination with quench-heaters activated after a quench event detection to initiate the internal dump of stored energy in all the coils. A rather strong quench-back effect due to eddy-currents in the coil casings at the transport current decay is beneficial for the quench protection efficiency in the event of heater failures. The quench behaviour of the ATLAS Toroids was computer simulated for normal operation of the quench protection system and its complete non-operation (failure) mode.

Die Richtlinie über Europäische Betriebsräte in der Anwendung: Das Beispiel VOLKSWAGEN

Zusammenfassung Mehrere Jahre nach der Verabschiedung der Richtlinie 94/45/EG über Europäische Betriebsräte existieren nun erste Umsetzungsergebnisse. Vor dem Hintergrund der allgemein formulierten Kritik an der Wirksamkeit der Regulierung und den Gremien wird in diesem Artikel der Europäische Konzernbetriebsrat bei Volkswagen als “best practice” Beispiel dargestellt. Die Falluntersuchung zeichnet sich dadurch aus, daß nicht nur die Aussagen vieler Kritiker über die Wirkungslosigkeit der Gremien und der daraus resultierenden Gefahr konzerninternen und -externen Social Dumpings relativiert werden. Vielmehr wird herausgearbeitet, daß es darüber hinaus sogar zum Export von Elementen hoher Partizipationsstandards innerhalb eines Konzerns in niedriger regulierte Standorte kommen kann.

Quench description by the characteristic time constants

The problem of a quench consequences of superconducting windings is considered. Inherent features of a quench behavior can be described by three characteristic time constants: (1) the normalization time t/sub n/ when normal zone would propagate over all winding volume provided transport current I/sub 0/ is kept constant, (2) the time of the current decay t/sub i/ provided the winding resistance R/sub 0/ is kept constant, and (3) the time of current decay t/sub n/ due to an external dump resistance R/sub e/. In a simple model where the normal zone velocities in longitudinal and transverse directions are proportional to the decaying current, a quench behavior (hot spot temperature, maximum internal voltage and stored energy evacuation efficiency) is analysed in dimensionless form depending upon the dimensionless time constants /spl tau//sub i/=t/sub i//t/sub n/ and /spl tau//sub e/=t/sub e//t/sub n/. It is shown that the active protection is efficient only if /spl tau//sub e/ 1 the internal voltages are dangerous. These results are confirmed by numerical examples which also show that the normalization time t/sub n/ is the most important parameter in the description of quench behavior.

96/03906 New method of fault location on double-circuit two-terminal transmission lines

A new quench protection method for superconducting magnets is presented. The method utilizes ZnO arresters as external dump resistors instead of conventional resistors. The ZnO arresters, which are widely used in power systems to limit overvoltages, can be used as the energy absorbing element with a constant discharge voltage. By introducing the ZnO arresters, both the discharge time and the heat dissipation in the superconducting magnet are reduced. The authors carried out some experiments using small experimental magnets. The results show that the ZnO arrester works as a dump resistor for a superconducting magnet and it is confirmed that the heat dissipation in the superconducting magnet with ZnO arresters is about one-third smaller than that with conventional dump resistors for the same maximum transient voltage.

Qualitative and quantitative variations of the groundwaters from the vicinity of Tarnobrzeg resulting from sulphur mining : J. Malinowski & M. Perek, Kwartalnik Geologiczny, 38(3), 1994, pp 593–601

The groundwaters of the Quaternary horizon have become quantitatively and qualitatively degraded over an area of about 150 km2 of underground sulphur melting in Jeziorko and in the open pit Machow. Within the mining fields of Jeziorko and nearby areas the groundwaters display an increase in the content of sulphates and chlorides resulting from the pumping of salt waters into the Tertiary beds. The degradation of groundwater resources is an effect of the dewatering of the open pit Machow. In Jeziorko sulphate migration into consumption waters of the Quaternary is observed. The aquifers under the external dump have also been degraded. The sulphates and chlorides which penetrate the groundwaters within the Quaternary sediments, are quickly diluted and their extent is limited. After complete exploitation of the Jeziorko mine the groundwaters of Quaternary deposits may retrieve their primary quality.

Quench protection of superconducting magnet using ZnO arrester

A new quench protection method for superconducting magnets is presented. The method utilizes ZnO arresters as external dump resistors instead of conventional resistors. The ZnO arresters, which are widely used in power systems to limit overvoltages, can be used as the energy absorbing element with a constant discharge voltage. By introducing the ZnO arresters, both the discharge time and the heat dissipation in the superconducting magnet are reduced. The authors carried out some experiments using small experimental magnets. The results show that the ZnO arrester works as a dump resistor for a superconducting magnet and it is confirmed that the heat dissipation in the superconducting magnet with ZnO arresters is about one-third smaller than that with conventional dump resistors for the same maximum transient voltage.

Magnetically Confined Kinetic-Energy Storage Ring using Attractive Levitation

A design concept is presented for a magnetically confined kinetic-energy storage ring (MCKESR) using attractive levitation. Key features of the design include passive ring orbital stability by the method of alternating gradients, a continuous ring to minimize major loading fluctuations, and an external dump chamber that preserves the stationary components in case of loss of confinement. The rotating ring acts as a rotor of a synchronous motor/generator, with permanent magnets mounted on the ring interacting with copper coils that are connected to a cycloconverter to provide power input/output. For a MCKESR device capable of providing diurnal load leveling to utilities, material costs appear reasonable.

The Design, Construction, and Operation Update of the ISABELLE Ring Magnets

This report updates the various designs and prototypes tested since the last Conference. Included are the operational data of a subassembly of the old 200 × 200 GeV machine design as well as the latest larger prototype ring magnets with their strong points and shortcomings. The working line coil system design presently seems to be nearly completed, having gone through major revisions to increase its possible operational range. One of the major design goals of the magnet series, that of each unit being able to absorb their own energy, seems to be well in hand. This feature enables the magnet string to be protected without external intervention, i.e., without external energy dump or driving the magnet winding normal by an active external circuit. Simply stated, this means that the magnet's L/R time constants during quench are short enough to prevent thermal damage. There are two series of prototypes. The first type is the so called Standard which will become the ring magnet for ISABELLE. The second is that in which various characteristics and/or limits of various parameters are explored. Various parameters such as specific heat of the windings, increased metal packing fractions, and resistivity of turns (in the normal state) are bracketed. The 400 × 400 GeV version of ISABELLE1 requires acold aperture of 13.09 cm, quadrupole magnetic length of 1.6 m, and dipole length of 4.65 m at a peak dipole field of 5.0 T. Two machine size dipoles and one quadrupole are being presently tested.

Target Stations and Beam Dumps for the CERN SPS

The design of the absorber blocks for internal and external dumping of the SPS proton beam is discussed. In addition, the external target stations for slow and fast extracted proton beams are described.