Canadian developments in superconducting Maglev and linear synchronous motors

Canadian developments in the application of superconducting magnets for levitation, synchronous propulsion, and guidance of high speed inter-city ground transport are described. At 480 km h^?1 a 100 passenger vehicle weighing 300 kN is levitated 15 cm clear of a flat guideway (minimizing ice and snow accumulation) by eight 3.85 × 10⁵ ampere-turns 100 × 30 cm magnets interacting with eddy currents induced in two 80 × 1 cm aluminium strips. The variable speed LSM uses fifty 5 × 10⁵ ampere-turns 40 × 150 cm magnets interacting with split three-phase windings energized in 5 km sections and phase angle controlled to give 72% efficiency and 0.82 power factor. A lateral restoring force of 10⁴ N cm^?1 is produced by the propulsion magnets interacting with the levitation strip edges and with flat null-flux loops overlying the LSM windings. A review of cryogenic systems indicates that isochoric dewar operation is best suited for Maglev vehicles. The test facility, using stationary full-scale superconducting magnets and guideway components mounted on a 100 km h^?1 vertical axis 7.6 m diameter wheel, is now fully operational and LSM tests are being performed.     

X-ray technique for observation of ice lens growth in partially frozen,saturated soil

This paper reports observations on ice lens growth in partially frozen, saturated soil, and applications for the measurement of hydraulic conductivity in the frozen zone. The authors developed an experimental apparatus using an X-ray technique to observe the ice lens growth and measure the amount of dilatation due to the ice segregation in the sample (Yoneyama et al., 1983). The water flow rate was determined with the displacement of the lead spheres embedded in the sample under several overburden pressures and temperature gradients. The hydraulic conductivity in the frozen zone of the sample was calculated from the water flow rates in the frozen zone under the assumptions that (1) the water flow in the frozen zone could be described by the Darcy flow equation, (2) the generalized Clapeyron equation could be used to describe temperature-pressure relations and (3) ice pressure was equal to the overburden pressure behind the final ice lens. With decreases within a wider range of lower temperatures (?1 to ?10°C) than has ever been reported, the calculated hydraulic conductivities were found to decrease rapidly from 10^?11 to 10^?13 cm/s. It was also observed that the hydraulic conductivity did not depend greatly on the applied load.     

OPTIMAL OPERATION OF MULTI-QUALITY WATER SUPPLY SYSTEMS-I: INTRODUCTION AND THE Q-C MODEL

One of three complementary models for optimal operation of multi-quality water supply systems is presented. The other two models are the subject of companion papers. The model, which is known as the Q-C (flow-quality) model, includes mass continuity of water and constituents. However, the hydraulic constraints do not appear explicitly. To prevent infeasibilities or unreasonable hydraulic conditions arising from the lack of hydraulic constraints, limits and a cost are associated with the flow in each pipe. The constraints in the model include dilution conditions which depend on flow direction. These dilution conditions are introduced into the model by an exponential function, resulting in a smooth continuous nonlinear programming problem, which is transformed into an equivalent problem and solved by a modified projected gradient method. The method is insensitive to scaling of variables, and the computational complexity depends only slightly on the number of water quality parameters. The method is demonstrated by application to two examples: the solution for a small network is presented in detail, and main results are shown for a larger one. The results of these two applications indicate the method's applicability to real networks.     

Experimental study on the prevention of microbial fouling accumulation on a Ni-Cu-P modified heat exchange surface

Microbial fouling on heat exchange surface is common for large amount of microorganisms in circulating cooling water. In this article, a modified surface technology is used to suppress and reduce the accumulation of microbial fouling on the heat transfer surface. Firstly a Ni-Cu-P modified surface is prepared by electroless plating, and a Ni-P surface applied commonly in industry is also prepared as a comparison. With the help of the designed and constructed experimental system for dynamic monitoring of microbial fouling, the microbial fouling tests of the Ni-Cu-P, Ni- P and carbon steel surface are carried out. The results show that the Ni-Cu-P modified surface has excellent antifouling performance. Compared with carbon steel, the microbial fouling on the Ni-P and Ni-Cu-P modified surface are decreased by 90.6 % and 92.0 % respectively. Further the effects of temperature, flow rate, and initial bacterial concentration on microbial fouling heat resistance of Ni-Cu-P modified surface are investigated and analyzed. With the cooling water inlet temperature increasing (25–40 °C), the fouling heat resistance of the Ni-Cu-P modified surface is increased first and then reduced. With the flow rate increasing (0.2 m/s-0.3 m/s), the fouling heat resistance of Ni-Cu-P modified surface is decreased by 78.3 %. With the initial bacteria concentration in cooling water increasing (8.364 × 10⁹ CFU/mL −51.456 × 10⁹ CFU/mL), the fouling heat resistance is increased by 57.4 % accordingly. By rationally adjusting the operating conditions, such as regulating the temperature of cooling water far away from the suitable temperature of bacteria and increasing the flow rate of circulating cooling water as much as possible, the accumulation of microbial fouling on the Ni-Cu-P modified surface can be further reduced, allowing for long-term cleaning and effective heat transfer of the Ni-Cu-P modified heat exchange surface.     

Minimizing residence times by rerouting flows to improve water quality in distribution networks

Management of water quality is a major issue for water companies, especially as many systems are old and have excess capacity. A methodology which uses an evolutionary algorithm to minimize water age, and hence improve water quality, is presented in this article. A steady-state model is used to find the water age at various nodes of a network. Three parameters are derived from these nodal age values to represent quality for the entire network. The evolutionary algorithm reconfigures the network by selecting a set of pipes for closure. The optimal network configuration is achieved when the chosen water age parameter is minimized subject to maintaining connectivity and hydraulic feasibility in the network. The methodology is applied to an example network to identify the age parameter that best represents quality over the entire network. The evolutionary model is then applied to re-route flows in a real water distribution network and the results are compared with those from the unmodified network. The validity of the use of steady-state hydraulics is tested by conducting an extended period simulation (EPS) on these results.     

Autohydrogenotrophic denitrification of drinking water using a polyvinyl chloride hollow fiber membrane biofilm reactor

A hollow fiber membrane biofilm reactor (MBfR) using polyvinyl chloride (PVC) hollow fiber was evaluated in removing nitrate form contaminated drinking water. During a 279-day operation period, the denitrification rate increased gradually with the increase of influent nitrate loading. The denitrification rate reached a maximum value of 414.72 g N/m³ d (1.50 g N/m² d) at an influent NO₃⁻–N concentration of 10 mg/L and a hydraulic residence time of 37.5 min, and the influent nitrate was completely reduced. At the same time, the effluent quality analysis showed the headspace hydrogen content (3.0%) was lower enough to preclude having an explosive air. Under the condition of the influent nitrate surface loading of 1.04 g N/m²d, over 90% removal efficiencies of the total nitrogen and nitrate were achieved at the hydrogen pressure above 0.04 MPa. The results of denaturing gel gradient electrophoresis (DGGE), 16S rDNA gene sequence analysis, and hierarchical cluster analysis showed that the microbial community structures in MBfR were of low diversity, simple and stable at mature stages; and the beta-Proteobacteria, including Rhodocyclus, Hydrogenophaga, and beta-Proteobacteria HTCC379, probably play an important role in autohydrogenotrophic denitrification.     

模拟海深条件下提升阀流动特性的实验研究

水压传动技术应用于深海环境可以直接从海洋中吸水加压，高压水作功之后可以直接排入海洋，不需要水箱和回水管道，大大简化了系统，具有独特的优势。然而，在深海作业时，液压元件的工况同陆地相比有较大的差异，海深压力相当于在元件出口加了一个背压。文中用背压来模拟海水压力，对以水作介质时背压对提升阀口流量特性的影响进行了实验研究。研究结果表明，背压使得流量饱和更容易发生；有背压时的流量系数比没有背压时的流量系数大；当阀芯和阀座有叠合时，背压对阀口流量特性的影响比阀芯和阀座没有叠合时的影响大。     

The usefulness of diffusion-weighted imaging for differentiating portal vein thrombus from tumour embolus

To investigate the usefulness of diffusion-weighted imaging (DWI) for differentiating bland portal vein thrombus from tumour thrombus. Fifteen patients with clinical comprehensive diagnoses of portal vein thrombus were analysed retrospectively. The thrombus signal intensity on 21 DWI slices and apparent diffusion coefficient (ADC) values were analysed quantitatively. The portal vein thrombus was divided into four types (low/low, high/low, low/high, and high/high) based on the DWI/ADC ratios between the thrombus and liver parenchyma (rDWI and rADC, respectively). Twenty patients with portal vein tumour thrombi were used for comparison as controls. The average ADC value for the bland thrombus was 1.84?±?0.70?×?10^?3?mm²?s^?1 (range: 0.46–2.77?×?10^?3?mm²?s^?1), and was 2.18?±?0.51?×?10^?3?mm²?s^?1 (range: 1.39–2.82?×?10^?3?mm²?s^?1) for the liver parenchyma; the rADC was therefore 0.90?±?0.45 (range: 0.26–1.86). The tumour thrombi were high/low and high/high type. The average ADC for the tumour thrombus was 1.25?±?0.26?×?10^?3?mm²?s^?1 (range: 0.68–1.67?×?10^?3?mm²?s^?1), and 1.56?±?0.33?×?10^?3?mm²?s^?1 (range: 1.11–2.34?×?10^?3?mm²?s^?1) for the liver parenchyma; the rADC was therefore 0.82?±?0.16 (range: 0.39–1.08). There was no statistical difference in rADC values and rDWI/rADC classification performance between the bland and tumour thrombi. The ADC difference between portal vein bland and tumour thrombi was statistically significant, but the ADC values of bland thrombi have a wider range, which contains the ADC values of tumour thrombi with a narrower range. The elevated ADC values of the liver parenchyma adjacent to portal vein emboli may be helpful for the diagnosis of bland thrombi.     

Microbiological quality and shelf-life of chilled cod fillets in vacuum-skin and modified atmosphere packaging

The microbiological quality and shelf-life of fresh cod fillets (Gadus morhua) packed under modified atmospheres (CO₂/N₂/O₂, 40:20:40) were compared to air and vacuum-skin packed fillets. Packed fillets were kept at 0 ± 1°C and chemical and microbiological analyses as well as sensory assessment were carried out after 4, 6 and 8 days. The decomposition process was evaluated through microbial and enzymatic proteolysis by means of total volatile nitrogen measurement, acetic acid values, surface pH and organoleptic tests. The microbiological quality was established by evaluating the growth of microbial species responsible for spoilage (total bacteria count. Gram-negative bacteria, H₂S-producers) and identifying isolated species. Modified atmosphere packaging gave the best results and the high oxygen content did not affect the microbiological quality in the presence of 40% carbon dioxide. Vacuum-skin packed fillets gave less satisfactory results owing to poor chemical and microbiological indices, even if they we-e always better than fillets maintained in air.     

Moisture content of polyethylene coated solid fibreboard after industrial lamination

Solid fibreboard is used mainly in highly demanding packaging applications. One solid fibreboard quality having six paper and paperboard layers, a thickness of 1.7 mm and polyethylene coating was studied. Several material tests on liquid water and water vapour penetration were done to assess the environmental moisture sources that change the material moisture content after the lamination process. The in‐plane diffusion coefficient of the combined board was determined based on an integrated unsteady state moisture transport equation and moisture sorption measurements. The transverse diffusion coefficient of the polyethylene coated kraft paper and the solid fibreboard medium were based on water vapour transmission rate measurements. The original moisture content of the solid fibreboard sheet was measured gravimetrically 2 days after the lamination at the mill. The results show that high relative humidity (RH) conditions during the transportation (4°C/90% RH) change the moisture content of the transportation box made from a solid fibreboard sheet very little in 8 days. Local moister (or drier) areas are created near the sheet edges due to in‐plane moisture transport through open material edges. The in‐plane diffusivity for the solid fibreboard grade in question was 5.87 × 10^?10 m²/s. Copyright © 2011 John Wiley & Sons, Ltd.     

Experimental investigation of evaporation heat transfer coefficient and pressure drop of R-410A in a multiport mini-channel

The evaporation heat transfer coefficient and pressure drop of R-410A flowing through a horizontal aluminium rectangular multiport mini-channel having 3.48 mm hydraulic diameter are experimentally investigated. The test runs are performed at mass flux ranging between 200 and 400 kg/m² s. The heat fluxes are between 5 and 14.25 kW/m² and the saturation temperatures range between 10 and 30 °C. The pressure drop across the test section is directly measured by a differential pressure transducer. The effects of the imposed wall heat flux, mass flux, vapour quality, and saturation temperature on the evaporation heat transfer and pressure drop are also discussed. The results from the present experiment are compared with those obtained from the existing correlation. New correlations for the evaporation heat transfer coefficient and pressure drop of R-410A flowing through a multiport mini-channel are proposed for practical applications.     

Monodisperse CNT Microspheres for High Permeability and Efficiency Flow‐Through Filtration Applications

Carbon nanotube (CNT)‐based filters have the potential to revolutionize water treatment because of their high capacity and fast kinetics in sorption of organic, inorganic, and biological pollutants. To date, CNT filters either rely on CNTs dispersed in liquids, which are difficult to recover and cause safety concerns, or on CNT buckypaper, which offers high efficiency, but suffers from an intrinsic trade‐off between filter permeability and capacity. Here, a new approach is presented that bypasses this trade‐off and achieves buckypaper‐like efficiency combined with filter‐column‐like permeability and capacity. For this, CNTs are first assembled into porous microspheres and then are packed into microfluidic column filters. These microcolumns exhibit large flow‐through filtration efficiencies, while maintaining membrane permeabilities an order of magnitude larger then CNT buckypaper and specific permeabilities double that of activated carbon for similar flowrates (232 000 L m^?2 h^?1 bar^?1, 1.23 × 10^?12 m²). Moreover, in a test to remove sodium dodecyl sulfate (SDS) from water, these microstructured CNT columns outperform activated carbon columns. This improved filtration efficiency and permeability is an important step toward a broader implementation of CNT‐based filtration devices.     

Neutron Radioscopic Measurement of Water Adsorption Coefficients in Aerogels

Abstract

In this work, neutron radioscopy was utilized to investigate water vapor uptake by a hydrophilic silica aerogel. Aerogel is an unusual porous material, produced by a sol-gel process that results in a solid material with a unique microstructure composed of nanometer-size particles and pores. Aerogels have an extraordinarily large internal surface area which is accessible via open pores, making them candidates for filters and gas adsorption media.

The water vapor deposition was modeled both analytically and computationally, and an estimate for adsorption coefficients for water vapor in aerogel yielded 1.08 × 10^-3 ± 2.58 × 10^-4 cm²/s. Initial tests to measure water vapor uptake from moist air were very successful. Dry air was bubbled through water and then flowed past an aerogel. The aerogel was shown to uptake the water vapor readily from moist air. After uptake, the aerogel dried out rapidly in dry air. This phenomenon was repeatable, indicating that the aerogel could be reused with little change in its sorption properties. Neutron radiography was shown to be an effective nondestructive method for evaluating the real-time movement of water vapor in aerogel, as deposition patterns can be analyzed quantitatively as a function of time and penetration distance into the aerogel.     

The cryopumping of water vapour in the continuum pressure region

Pumping speed measurements in the continuum pressure region, P>10^?3 torr, have been made for water vapour impinging on copper spheres and coils cooled to liquid nitrogen temperatures. Water vapour flow rates between 0.06 mg s^?1 and 420 mg s^?1 were used. The volumetric pumping speed was constant over the pressure range 2 × 10^?3 torr to 2 × 10^?2 torr and was, as expected, higher than that obtained in the free molecular flow region. Above 2 × 10^?2 torr the pumping speed decreased and possible reasons for this were investigated and are discussed. These included the effects of inadequate heat transfer from the liquid nitrogen refrigerant to the cryopump, a poor thermal conductivity of the cryodeposit, and an impurity, nitrogen gas, in the water vapour.     

Experimental results for a hydraulic refrigeration system using n-butane

The hydraulic refrigeration system (HRS) is a vapor-compression system that accomplishes the compression and condensation of the refrigerant in a unique manner, by entraining refrigerant vapor in a down-flowing stream of water and utilizing the pressure head of the water to compress and condense the refrigerant. A multi-stage HRS was designed, fabricated, and tested using n-butane as the refrigerant. In general, both the refrigeration rate and the coefficient of performance (COP) increased with a corresponding decrease in the compression fluid temperature of the third and final stage. The refrigeration rate and COP were also found to increase with a corresponding increase in evaporator temperature. The predictions of an enhanced model incorporating two-phase hydraulic losses show excellent agreement with the experimental data with a maximum error of ±20%. The results of the experimental investigation indicate that the HRS offers an attractive and feasible alternative to conventional vapor-compression systems, especially in applications where direct-contact heat exchange in the evaporator is desirable.     

Impact of dynamic loading on backcalculated stiffness of rigid airfield pavements

The objective of this paper was to evaluate the deterioration of Portland Cement Concrete (PCC) slabs throughout trafficking. A full-scale accelerated pavement testing at the National Airport Pavement Test Facility (NAPTF) was conducted on Construction Cycle 6 (CC6) on rigid pavements with low, medium and high flexural strengths on both a concrete and asphalt stabilised base. Heavy Weight Deflectometer (HWD) testing was conducted on the test sections to backcalculate the stiffness of the layers. The majority of PCC deterioration occurred roughly within the first 1500–2000 passes of trafficking. On average, the MRS-1 (low flexural strength) PCC elastic modulus was found to decrease by 20%, from 5.0–.4 × 10⁶ (34.5–37.2 GPa) to 4.0–4.3 × 10⁶ psi (27.6–29.7 GPa), whereas the PCC elastic modulus of MRS-2 and MRS-3 was found to decrease by 17% and 22%, respectively. However, neither the MRS-2 nor MRS-3 elastic modulus was found to drop below 5.0 × 10⁶ psi (34.5 GPa) after 15,000 passes.     

On the Possibility of Blocking Technological Pipelines of Nuclear Power Plants by Freezing Ice Locks in the Pipes

We consider some problems whose solution is required for the substantiation of the applicability of the method of local freezing of a working liquid in pipeline systems of nuclear power plants used for the purposes of maintenance or hydraulic tests. We present the results of evaluation of the pressure of ice caused by an ice lock formed in the pipe upon the inner wall of the pipeline and estimate the resistance to the displacement of the lock for the case of loading of the pipeline by the pressure of the liquid. We propose a procedure and describe an experimental test bench for the determination of the influence of thermal cycling (293 77 K) on the mechanical characteristics of the material of an element of a full-scale pipeline subjected to repeated freezing of ice locks with subsequent loading by testing pressure under conditions quite close to actual operating conditions.     

Simulations and modeling of radioactivity buildup due to corrosion products in ion exchanger and filters of a typical PWR

A set of coupled first-order differential equations have been developed to simulate the corrosion product activity in ion exchanger and filters of a typical pressurized water reactor (PWR). Computer program CPAIR-RC has been modified for the current study to include the effect of nonlinear acceleration of corrosion on corrosion product activities. Simulations for five corrosion products ⁵⁹Fe, ⁹⁹Mo, ⁵⁶Mn, ⁵⁸Co, and ⁶⁰Co have been carried out. Simulation results show that the activities due to ⁵⁹Fe, ⁹⁹Mo, and ⁵⁶Mn saturate within approximately 1000 h of reactor operation. However, the activities due to ⁵⁸Co and ⁶⁰Co keep on accumulating in the ion exchanger of PWR during this time. The activity buildup in the ion exchanger due to ⁵⁶Mn starts after 77 h of reactor operation. When flow rate perturbations are introduced by decreasing flow rate to 40% of rated value, the activity due to ⁵⁶Mn saturates at the value of 1.27 × 10⁻³ μCi cm⁻³. For the case of nonlinearly acceelerating corrosion with a pump coast down, the activity for ⁵⁹Fe shows an initial drop with a decrease in flow rates. The activity drops from 2.37 × 10⁻² to 2.33 × 10⁻² μCi cm⁻³ before the reactor scram. The corrosion product activities calculated by the CPAIR-RC program are compared with some of the experimental data available in literature and show fair agreement. Published in Russian in Radiokhimiya, 2009, Vol. 51, No. 1, pp. 40–46. The test was submitted by the authors in English.     

Wearable Microfluidic Diaphragm Pressure Sensor for Health and Tactile Touch Monitoring

Flexible pressure sensors have many potential applications in wearable electronics, robotics, health monitoring, and more. In particular, liquid‐metal‐based sensors are especially promising as they can undergo strains of over 200% without failure. However, current liquid‐metal‐based strain sensors are incapable of resolving small pressure changes in the few kPa range, making them unsuitable for applications such as heart‐rate monitoring, which require a much lower pressure detection resolution. In this paper, a microfluidic tactile diaphragm pressure sensor based on embedded Galinstan microchannels (70 µm width × 70 µm height) capable of resolving sub‐50 Pa changes in pressure with sub‐100 Pa detection limits and a response time of 90 ms is demonstrated. An embedded equivalent Wheatstone bridge circuit makes the most of tangential and radial strain fields, leading to high sensitivities of a 0.0835 kPa^?1 change in output voltage. The Wheatstone bridge also provides temperature self‐compensation, allowing for operation in the range of 20–50 °C. As examples of potential applications, a polydimethylsiloxane (PDMS) wristband with an embedded microfluidic diaphragm pressure sensor capable of real‐time pulse monitoring and a PDMS glove with multiple embedded sensors to provide comprehensive tactile feedback of a human hand when touching or holding objects are demonstrated.     

EXPERIMENTAL STUDY OF DUST FILTRATION IN SURFACE-TYPE NONWOVENS

ABSTRACT

Surface type nonwovens are widely used in industrial dust control. Recently, they have been utilized in some engine air filtration applications as automotive filters, heavy-duty engine self-cleaning filters or safety filters. Because of their mechanical strength and regenerative ability they are a perfect material for applications where filter replacement is a problem. On the other hand, the random distribution of fibers and needle punching may result in pinhole formation during dust loading, especially at high aerosol velocities. As a result, the seepage mechanism is common in applications involving fine solid aerosols.

In the inertia dominated region, the collection efficiency of particles depends on the adhesion probability. When particle momentum increases, the efficiency decreases. In general, there is no agreement between filtration theory and experiment when the Stokes number is greater than one.

Filter efficiency increases with dust loading when the filter medium is a good dust cake supporter. In this case, dust reentrainment, causing seepage, may occur at high aerosol velocities and pressure drops. In contrast, reentrainment in nonwovens can take place even at lower aerosol velocities and dust loadings. It is difficult to predict conditions favorable for dust reentrainment and pinhole formation. This process depends on media geometry, dust particle size distribution, and aerosol flow parameters.

This paper discusses filter performance of surface-type nonwovens exposed to polydisperse dusts. Filter efficiency and pressure drop are discussed as functions of aerosol velocity, dust loading, and dust particle size distribution.