Selection of elastomeric membranes for the removal of volatile organics from water

A wide range of homogeneous elastomeric membranes has been prepared using dicumylperoxide as a general cross-linking agent. The membranes have been used for both equilibrium sorption measurements and steady-state pervaporation experiments to study solution-diffusion phenomena in the removal of volatile organic components from aqueous solutions. Pervaporation experiments have been performed under identical hydrodynamic conditions in order to fix the boundary layer mass transfer coefficient at a constant and known value. For comparison of the permeabilities of different pervaporation membrane materials, this is of utmost importance. A wide range of selectivity factors up to a value of 100,000 are obtained, whereas usually the permeabilities for the organic component are in the range of 10-10-10-9m2/s and 10-14-10-12m2/s for water. The permeation and sorption data obtained for the various elastomers have been related to the chemical and physical nature of the elastomers through the solubility parameter and the glass transition temperature, respectively. Both diffusional and sorption effects seem to be important, determining the water-transport behavior in the elastomeric membranes. The solubility of the organic component appears to be independent of this combined solubility parameter. Differences in the permeabilities of the organic component can primarily be ascribed to structural parameters in the membrane material, like degree of unsaturation and presence of steric side groups

Academics in control: supporting personal performance for teaching-related activities

Academics are under pressure because of entrepreneurial constraints, such as budgets and cost-oriented objectives, and educational demands, such as for more flexibility and for offering courses online or with online components. Based on the results of a series of studies of desired and actual performance, and evaluations of responses to a set of prototypes of a Personal Performance Support Tool, a final prototype version of the tool was developed to research the effects the tool can have on the performance and job satisfaction of academics, especially for their teaching-related activities

Study of the Effect of Transport Current and Combined Transverse and Longitudinal Fields on the AC Loss in NET Prototype Conductors

AC losses in cables carrying DC as well as AC transport currents at different DC background fields up to 2T have been measured on three types of Nb3Sn subcables in a new test facility. In this facility it is possible to apply sinusoidal transverse AC fields up to dB/dt=5T/s and longitudinal AC fields up to dB/dt=30T/s separately and simultaneously. The AC loss is measured with a calorimetric method. Simultaneously applied transverse and longitudinal fields can result in a loss which exceeds the added contributions of the separate applied AC fields. Within the measured range it is about correct (within 10%) to add the loss components due to DC transport current up to 10 kA and both applied transverse and longitudinal AC fields. The measured total loss is always above the sum of the loss component

Case studies in reconstruction efficiency of current distribution in CICC's by self field measurements

The measurements of the self magnetic field by means of Hall sensors (HS) in the vicinity of a superconducting cable-in-conduit conductor (CICC) is often used to study current distribution effects. It is possible that current imbalance may affect the performance of CICC's and therefore knowledge of the current distribution is needed. Recently a model was presented to approximate the current distribution inside a conductor. Basically, the inverse problem must be solved in which the input data usually are the experimentally measured values of the local magnetic field, the location and orientation of the HS's and the geometry of the line or segment currents. All these, together with the adopted algorithm, determine the accuracy of the reconstruction procedure. In the present study the impact of two basic orientations of the HS: polar-symmetric and plane-parallel on the current reconstruction efficiency is performed for the analytical model developed in Twente. For the case study, a 36 strands CICC and a mock-up conductor are considered. The influence of the experimental errors and geometrical errors on the model output is also investigated

Finite element models applied in active structural acoustic control

This paper discusses the modeling of systems for active structural acoustic control. The finite element method is applied to model structures including the dynamics of piezoelectric sensors and actuators. A model reduction technique is presented to make the finite element model suitable for controller design. The reduced structural model is combined with an acoustic model which uses the radiation mode concept. For a test case consisting of a rectangular plate with one piezo patch the model reduction technique is validated. The results show that the an accurate prediction of both the structural and acoustic response is predicted by the reduced model. The model is compact requiring small simulation times, which makes it attractive for control system design. Finally the control performances for both structural and acoustic error criteria are presented

The Effect of Inter-bundle Resistive Barriers on Coupling Loss, Current Distribution and DC Performance in ITER Conductors

The role of inter-bundle resistive barriers (metal sheet wraps), introduced to reduce the inter-bundle coupling loss in multistage cabled Cable-In-Conduit Conductors (CICC) for the International Thermonuclear Experimental Reactor (ITER) is evaluated, based on results gained recently on short sample experiments in the Twente Cable Press and SULTAN. The obvious benefit of limiting the inter bundle coupling loss unavoidably goes together with impeding the redistribution of nonuniform currents in the coil winding introduced at the terminations, as well as reduction of the heat exchange between the bundles. Six-element numerical electromagnetic code simulations are presented that qualitatively explain the effect of wraps on the DC performance, strongly depending on the testing geometry. The computations illustrate that wraps can reduce the DC performance in short sample tests. At the same time simulations of the Poloidal Field Coil Insert (PFCI), with a winding length of 50 m, have shown that omitting sub-stage wraps, can even degrade the DC performance of coils due to the short current transfer length in combination with current nonuniformity causing peak voltages in the most overloaded petals

Optimization strategy for actuator and sensor placement in active structural acoustic control

In active structural acoustic control the goal is to reduce the sound radiation of a structure by means of changing the vibrational behaviour of that structure. The performance of such an active control system is to a large extent determined by the locations of the actuators and sensors. In this work an approach is presented for the optimization of the actuator and sensor locations. The approach combines a numerical modelling technique, for predicting the control performance, and genetic optimization, to find the optimal actuator and sensor locations. The approach is tested for a setup consisting of clamped rectangular plate with a piezoelectric actuator and either structural or acoustic sensors. The results show that a control system with optimal actuator and sensor configuration outperforms an arbitrary chosen configuration in terms of reduction in radiated sound power

The influence of Lorentz force on the ac loss in sub-size cable-in-conduit conductors for ITER

The cable-in-conduit superconductors for the ITER coils have operating current in excess of 40 kA and function under last ramp conditions and fields up to 13 T. The transverse Lorentz force acting on strands may reduce the effective contact resistance between strands in the cable and as a consequence, the coupling loss will increase. This influence is investigated with a sub-size jacketed cable having 81 Cr-coated Nb3Sn strands. The AC loss is measured with a sinusoidal and trapezoidal magnetic field superimposed to a stationary background field of 1 or 2 T while the cable carries a constant transport current up to about 30 kA. The AC loss is determined by a pick-up coil system and partly with a calorimeter for calibration purposes. The nτ at 0 current declines after cyclic loading, from 9 ms in the virgin state to 2 ms after several loads. The increase of the interstrand coupling loss due to Lorentz effects, accompanied by resistance-hysteresis and relaxation effects as observed in the loss are discussed. The total loss increases considerably due to interference of transport current and induced coupling currents with rising transport current and DC field