Stainless Steel Screen Research Articles

Plasma synthesized doped B powders for MgB2 superconductors

Gas phase plasma synthesis methods have been used to prepare nano-scale particles of C doped boron powder that are well suited for powder-in-tube (PIT) fabrication of superconducting wire. Mixtures of H2, BCl3, and CH4 gas are injected into an induction plasma where doped boron powder is formed and collected on a stainless steel screen. The particles typically are ∼20nm in size and collect into lacy agglomerates in the 1–50μm size range. Pressed pellets of these powders heated in a Mg atmosphere are transformed to the MgB2 phase at temperatures ranging from 600°C to 1200°C. Critical current densities, Jc, at 5K run from about 106A/cm2 at self-field to 4×104A/cm2 at 7T. At 20K, Jc ranges from 5×105A/cm2 at self-field to about 104A/cm2 at 3T. Samples of pure B powder and B with 7.4%C powder were prepared as PIT wires having a combination Fe inner jacket and a cupro-nickel outer jacket. These PIT Jc values are lower than, but comparable to the pressed pellet values. The PIT samples can be reacted in times on the order of 10min and still exhibit greater than 105A/cm2 at 5K and 2T.

Specimen Capsules For Critical-Point Drying

Abstract Since we do a lot of small-sample critical-point drying (CPD) for SEM, we assemble our own drying capsules which can be manufactured easily in quantity. Materials' cost at current prices is about $10 for 50 capsules. About 25 capsules can be manufactured in an hour. The completed capsule consists of a small polypropylene chamber with fine-mesh, stainless-steel screen caps at each end that allow easy exchange of solvents. shows the steps ofthe assembly process. The base of one capsule is cut off with a razor blade, the cap of a second capsule, for a bottom (Figure 1a). Chamber length can be 5 to 14mm. One-quarter-inch holes are punched through the center of each cap using a paper punch whose spring/detente has been removed to pass the caps' rim (Figure 1b). A sheet-metal shim punch is used to create 3/8" disks of 60-mesh stainless steel wire cloth.

Creation of plasma density transitions short compared to the plasma skin depth

A plasma based electron beam source apparatus is described which creates a plasma with two distinct density regions separated by a transition which is shorter than the plasma skin depth kp−1 of either region. This sharp density modulation is achieved by using a perforated stainless steel screen to filter half of a diffusing plasma column. A simple physical model predicts that the length of the plasma density transition will vary with the distance from the screen. For a weakly magnetized plasma, the transition length will be twice the distance, on a line normal to the screen plane, from the screen edge to the location where the transition is measured. The plasma column is generated using an argon discharge plasma source. It has a peak density of approximately 3.5×1013cm−3 and a full width half maximum width of 5 cm. The discharge source utilizes a 7.5 cm diameter LaB6 disk cathode heated to 1300 °C using a graphite heater. The plasma column is filtered with a 78μm thick stainless steel sheet with 152μm holes and 21% open area. Plasma density transitions with lengths between 0.74 and 0.95kp−1 were measured.

High frequency two-stage pulse tube cryocooler with base temperature below 20 K

High frequency (30–50 Hz) multi-stage pulse tube coolers that are capable of reaching temperatures close to 20 K or even lower are a subject of recent research and development activities. This paper reports on the design and test of a two-stage pulse tube cooler which is driven by a linear compressor with nominal input power of 200 W at an operating frequency of 30–45 Hz. A parallel configuration of the two pulse tubes is used with the warm ends of the pulse tubes located at ambient temperature. For both stages, the regenerator matrix consists of a stack of stainless steel screen. At an operating frequency of 35 Hz and with the first stage at 73 K a lowest stationary temperature of 19.6 K has been achieved at the second stage. The effects of input power, frequency, average pressure, and cold head orientation on the cooling performance are also reported. An even lower no-load temperature can be expected from the use of lead or other regenerator materials of high heat capacity in the second stage.

Low cost and high performance screen laminate regenerator matrix

A laminate screen matrix regenerator with 47 elements has been designed, analyzed, fabricated and tested. The laminate was fabricated from stainless steel screen sheets that were stacked on top of each other at certain angular orientation and then bonded at high temperature and pressure environment utilizing a sintering process. This laminate is a porous structure media with highly repeatable properties that can be controlled by varying mesh size, weave type, wire size and laminate sheet to sheet orientation. The flow direction in relation to the weave plan can be varied by cutting a cylindrical or rectangular laminate element along or across the weave. The regenerator flow resistance, thermal conductance losses, dead volume, surface area and heat transfer coefficient are analyzed. Regenerator cost and performance comparison data between the conventional widely used method of stacked screens and the new stacked laminate matrix regenerator is discussed. Also, a square stainless steel screen laminate was manufactured in a way which permits gas to flow along the screen wire instead of across it.

Configuration of a Bioreactor for Milk Lactose Hydrolysis

Permeabilized microbial cells can be used as a crude enzyme preparation for industrial applications. Immobilization and process recycling can compensate for the low specific activity of this preparation. For biomass immobilization, the common support is alginate beads; however, its low surface area and the low biomass concentration limit the activity. We here describe a biocatalyst consisting of a paste of permeabilized Kluyveromyces lactis cells gelled with manganese alginate over a semicircular stainless steel screen. A ratio of wet permeabilized biomass to alginate of 50:4 (wt/wt) resulted in a paste with maximum immobilized β-galactosidase activity and maximum gel biomass retention. The biocatalysts retained activity better when stored in milk at 4°C than in 50% glycerol. The unused biocatalysts stored in milk did not lose activity after 50 d. However, repeated use of the same biocatalyst 40 times resulted in almost 50% loss of activity. A bioreactor design with two different conditions of operation were tested for milk lactose hydrolysis using this biocatalyst. The bioreactor was operated at 40°C as packed bed or with recirculation, similar to a continuous stirred tank reactor. The continuous system with recirculation resulted in 82.9% lactose hydrolysis at a residence time of 285.5min (flow of 2.0 ml/min), indicating the potential of this system for processing low lactose milk, or even in processing other substrates, using an appropriate biocatalyst.

Process development for the removal of copper from wastewater using ferric/limestone treatment

The removal of copper from wastewater by ferric/limestone coagulation followed by screen filtration was carried out at a laboratory scale. The optimum coagulant (FeCl3) dose and working pH were 50 mg// of Fe(m) and pH 7.5, respectively, through jar tests. For the efficient removal of copper from wastewater, we developed a novel process including the co-precipitation of copper with FeCl3, alkalization in a limestone aeration bed, and separation of precipitates in a sedimentation tank coupled with internal stainless steel screen filter. The performance results showed that removal of copper from the solution was over 99.5%. The pH was effectively maintained over 7.5 in limestone bed during the whole process. Ferric hydroxide/copper aggregates were removed over 99% by stainless steel screen filter of 1,450 mesh. Periodic air backwashing alleviated fouling of the filter surface.

FORMATION OF CARBON NANOTUBES ON CARBON PAPER AND STAINLESS STEEL SCREEN BY OHMICALLY HEATING CATALYTIC SITES

A newly designed gas phase thermal decomposition reactor, ohmically heating the catalytic sites, has been used to synthesize multiwall carbon nanotubes (MWCNTs) on carbon paper and stainless steel screen. Co-Ni catalyst particles were dispersed by a silane intermediate layer adsorbed onto the carbon fibers or the stainless steel threads of the supports. MWCNTs were obtained on both substrates by a tip grown mechanism. They are about 20 μm in length and 15–50 nm in diameter. A methanol pretreatment of the carbon fibers significantly increased the density of the tubes on the carbon paper, but the same treatment had a negative effect on stainless steel. The MWCNTs, which adhere firmly to the carbon paper and the stainless steel screen, may find applications as electrodes in fuel cells, sensors and in photonics.

Effects of preheating and operation conditions on combustion in a porous medium

The effects of preheating conditions (including the critical energy content, the firing rate, and the equivalence ratio) on the initiation and extinction of a super-adiabatic combustion (SAC) in a steady flow of propane/air mixture through a stack of stainless steel screens (an inert porous medium) are investigated. It is found that there are critical conditions for the initiation and extinction of a SAC in the steady flow through the inert porous column. The critical preheating energy required to initiate a SAC is found to decrease with the increase of the preheating equivalence ratio, the preheating firing rate, and the operational equivalence ratio. After the initiation of a SAC, two combustion modes (i.e., stable combustion mode and push-forward combustion mode) have been observed. These combustion modes are determined by the operational conditions.

A new continuous biofilm bioreactor for immobilized oil-degrading filamentous fungi

A new type of horizontal biofilm bioreactor for continuous bioconversion of emulsified oily substrate by immobilized growing biofilm of filamentous fungi was designed, constructed, and feasibility tested. The new reactor design provides "self"-immobilization of homogenized mycelium leading to even biofilm development. This was accomplished by using stainless steel screens of optimal mesh, mounted in parallel and stretching outward from a main rotating axis of a biological rotating contractor. Each screen was equipped with a pair of stainless steel blades mounted on supports allowing for continuous biofilm "shaving" beyond a predetermined thickness, thus retaining freshly growing active biofilm surface. The feasibility of the new bioreactor was demonstrated by decalactone production from emulsified castor oil by immobilized filamentous fungi (Tyromyces sambuceus). The combination of oriented metal screens and moving blades was found to be highly effective for a model system in maintaining stable substrate emulsion in the reactor in either batchwise or continuous processing, as well as maintaining biofilm thickness with continuous removal of excess growing hyphae.

Pot soil air composition in conditions of high soil moisture and its influence on chrysanthemum growth

Chrysanthemums were grown in 15.2 cm standard pots in a heavy mix of clay loam soil+sphagnum peat moss (2:1). A fine texture mix was used to accentuate undesirable gas profiles in the soil. Soil air was analyzed at five depths in the soil profile. In one set of tests, water was applied to the top of the pot at a matrix potential in the center of the soil profile of −5 kPa. The average gas concentrations in soil air in the top and bottom fifths of soil were for O 2—20.0 and 14.5%, for CO 2—0.8 and 2.4%, and for C 2H 4—0 and 0.08 μl dm −3. Smooth concentration gradients of each gas occurred from top to bottom of the soil profile. The composition of soil air changed greatly during the drying cycle. At soil moisture tensions of −0.7, −2.5, and −5 kPa in the center of the soil profile, the gas concentrations in the lowest fifth of soil were for O 2—9.6, 15.3, and 20.3%, and for CO 2—4.5, 3.5, and 0.6%, respectively. Thus, soil atmospheric conditions for plant growth were poorest immediately after watering and continuously improved up to the time of watering. When pots of chrysanthemum were watered by capillary action from mats, the average concentration of gases in soil air in the lowest fifth of soil were 5.8% O 2, 3.6% CO 2, and 0.38 μl dm −3 C 2H 4. This gas profile was less desirable for growth than the profile found in top-watered pots. Unlike the situation in top-watered pots, the gas concentrations in mat-watered pots were stable. Roots in top-watered pots were restricted to the upper two thirds of the soil ball, and were distributed evenly in the inner part of the soil and at the periphery. Roots of mat-watered plants developed further down the vertical periphery of the pot than roots of top-watered plants, but they did not grow inside the ball. Chrysanthemum plants were grown through a hole in the side wall of each of five 3.9 cm tall by 15.2 cm diameter plastic rings stacked vertically and separated by stainless steel screens that allowed for passage of water but not roots. Water was applied to the top of these cylinder stacks. The largest plants developed in the top ring with progressively smaller plants at lower depths. Plants in the lower two rings developed interveinal chlorosis and did not reach commercial size.

熱音響冷凍機 可視化によるパルス管冷凍機内の流動状態の観察

We tried to observe the flow behavior in typical pulse tube refrigerators (i.e., basic, orifice and double-inlet pulse tube refrigerators) using a smoke-wire flow visualization technique, and discuss the fundamental flow behavior in those pulse tube refrigerators. The pulse tube is made of a transparent acrylate tube having the effective length of 280mm, an inner diameter of 16mm and a wall thickness of 4mm. The regenerator is composed of a stainless-steel housing and a bakelite tube, 18mm in diameter and 168mm long packed with 770 discs of 100-mesh stainless-steel screen. The reservoir has a volume of about 3×10-4m3, which is 5.5 times larger than the pulse tube volume. Air is used as the working gas and pressure oscillation is generated by introducing pressurized air of about 0.2MPa into the rotary valve and releasing it to the atmosphere. Visualization is done under the conditions of frequency of 5Hz and compression ratio of about 1.2.The flow behavior throughout the pulse tube during one cycle is cleared. It was found that typical velocity profiles of the viscous oscillating flow are observed for all pulse tube refrigerators, and that the orifice and double-inlet types have larger velocity and displacement compared to the basic one. It was also found that the thickness of velocity boundary layer for oscillating flow is estimated to be about 30% of the radius of the pulse tube. Secondary streaming in the pulse tube, which flows in the direction from cold- to hot-end in the core region and the opposite direction in the boundary region, was recognized for all refrigerators.

熱音響冷凍機 大出力４バルブ型パルス管冷凍機の開発

A single-stage four-valve pulse tube cryocooler with a large cooling power at 80K has been built and tested. The cryocooler has a regenerator stacked with stainless-steel screen disks of 250 mesh and a pulse tube 200mm long. A rotary valve unit directly united to the hot end of the cold head is employed to control the mass flow at the hot ends of the regenerator and pulse tube. Three kinds of pulse tube, 18, 28 and 38mm in diameter, were prepared for investigating the influence of pulse tube size on cooling performance. The cryocooler with the pulse tube of 28mm in diameter delivered a cooling power of 33.5W at 80K, and reached a no-load temperature of 20.5K at a cycle frequency of 1.8Hz. This paper gives the initial experimental results and a brief discussion.

Electroflotation for groundwater decontamination

An electroflotation device was built using a platinum-clad columbium screen as anode, and a stainless steel screen as cathode. A rock salt solution was used as the electrolyte, generating hypochlorite to oxidize cyanide, and hydroxides to form metal hydroxide precipitates which were carried to the top of the electroflotation device by the rising gas bubbles. The device was used successfully to remove Ni, Zn, Pb, Cu CN in a polluted groundwater obtained from directly under a contaminated site, meeting the pretreatment standards of the pollutants for the local POWT sewer system. The cost of an electroflotation device plus a sand filter compares favorably with a conventional treatment system using cyanide oxidation/alkaline precipitation/ polymeraided clarification.

Photochemical production of low-molecular-weight carbonyl compounds in seawater and surface microlayer and their air-sea exchange

Abstract Coastal and oceanic surface microlayer samples were collected using a stainless steel screen, along with subsurface bulk seawater, and were analyzed for low-molecular-weight (LMW) carbonyl compounds, including formaldehyde, acetaldehyde, propanal, glyoxal, methylglyoxal, glyoxylic acid and pyruvic acid. The enrichment factor in surface microlayer compared to corresponding subsurface seawater ranged from 1.2 to 21. A time-series measurement at a coastal site showed strong diurnal variations in concentrations of the LMW carbonyl compounds in the surface microlayer and in the enrichment factor, with maxima in the early afternoon and minima in the early morning. Exposure of samples to sunlight resulted in the higher yields of these compounds in the surface microlayer than in the bulk seawater, by a factor of 1.1–25, suggesting that the higher photoproduction rate of LMW carbonyl compounds in the surface microlayer accounts for the majority of the observed enrichment in these samples. Potential sinks include biological uptake and mixing. Air-sea exchange may be a source for soluble compounds and a sink for less soluble compounds. The enrichment of the LMW carbonyl in surface microlayer may alter their net air-sea exchange direction e.g., from the ocean as a potential sink to a source for atmospheric acetaldehyde and acetone. The residence times of the LMW carbonyl compounds in the microlayer were estimated to be on the order of tens of seconds to minutes using a modified two-layer model. However, to maintain the observed microlayer enrichment factor, the residence time should be on the order of ~ 1 hour. This prolonged residence time may be due to organic enrichment in the surface microlayer (‘organic film’) which inhibited molecular transfer of carbonyl compounds into and out of the microlayer. The deviated behavior from model prediction may also be due to changes in the apparent partition coefficients of these species as a result of thier physical and chemical interactions with organic matrix in the surface microlayer.

Enhancement of pool boiling heat transfer in a horizontal water layer through surface roughness and screen coverage

An experimental investigation was carried out to study the augmentation of heat transfer in saturated pool boiling of a liquid water layer on a heated horizontal stainless steel plate by roughing the surface and/or covering it with a single layer of stainless steel screen. The results were presented in terms of the boiling curves. Effects of various parameters – the surface roughness, liquid level and size of the stainless steel mesh on the boiling heat transfer were examined in detail. The measured data clearly indicated that a lowering of the liquid level from 60 to 5 mm in water depth causes heat transfer reduction. Roughing the surface was found to sig- nificantly enhance the heat transfer. Use a layer of metal screen to cover the heated surface was shown to substantially augment the heat transfer especially for a shallow water layer if the mesh size is comparable with the bubble departure diameter. Covering the rough surface with the metal mesh, however, reduced the heat transfer.

Two-Phase Flow in a Flooded-Bed Filter

Abstract Two-phase flow in a flooded-bed filter was characterized by measuring the pressure drop as a function of liquid and air flow rates for two types of filter media. The two types of filter media tested were felt fabric and woven stainless steel screens. For typical operating conditions, the two-phase flow through the filter media was neither laminar nor turbulent. It could be described by a transition region in which the pressure drop was proportional to the nth power of air velocity, with n between 1 and 2. In the absence of water the flow was turbulent, where n was close to 2. Some of the physical properties like porosity and specific surface area were estimated to characterize the filter media.

Separating oil from oil-water emulsions by electroflotation technique

The separation of finely dispersed oil from oil-water emulsions was carried out in an electroflotation cell which has a set of electrodes, a lead anode and stainless steel screen cathode. The effect of operating parameters on the performance of the batch cell was examined. The parameters investigated are electrical current, oil concentration, flotation time and flocculant agent concentrations. A well-fitted empirical correlation represents the change in percentage oil removal with wide range of operating conditions was obtained. The oil separation reached 65% at optimum conditions; 75% in the presence of NaCl (3.5% by wt. of solution); and 92% with the presence of NaCl and at optimum concentration of flocculant agent. Electrical energy consumption varied from 0.5 to 10.6 KWh/m 3 according to experimental conditions. An equation relates the K with I was obtained. The general form of the equation is K = constant ( I) n ; where the n values are 0.6 4 and 0.62 for solutions with and without NaCl, respectively. The previous relation is valid only for current values from 0.3 to 1.2 A. The effect of emulsion flow rate on the separation process was determined on continuous scale.

Experimental and modeling studies of 220Rn decay products in outdoor air near the ground surface

Measurements of the concentrations of 220Rn gas and its short-lived decay products ( 216Po, 212Pb, 212Bi) in attached-to-aerosol and unattached states were carried out at a semi-arid field site in central New Mexico under varying atmospheric conditions. A high volume air sampler (100 L min −1), with a single 635 mesh stainless steel screen (50% penetration for 4 nm particles) and a glass fiber filter, were employed. Analysis of the 105 outdoor measurements yielded the following average values: 9 Bq m −3 for the 220Rn activity concentration; 22 nJ m −3 for the concentration of potential alpha energy, 0.03 for the equilibrium factor, 0.15 for the unattached fraction of potential alpha energy, and 14 nSv h −1 for the effective dose rate. The measurements were interpreted using the computer code TPOUT, which applies one-dimensional eddy transport to calculate the vertical concentrations of 220Rn and its decay products as a function of atmospheric stability, aerosol concentration, terrain roughness, and surface wind speed. This code successfully predicted the observed trends of unattached and attached decay products concentrations with height, and demonstrated the importance of the mixing height and the rate of vertical transport for controlling breathing level dose. Projection of the present results to conditions typical of temperate climates suggests an average annual outdoor effective dose from 220Rn decay products of about 0.025 mSv, which is a significant component of the total outdoor dose.

A Method for Isolation and Partial Purification of Trichinella spiralis Nurse Cells

Invasion of vertebrate muscle cells by larvae of Trichinella spiralis is accompanied by redifferentiation of the host myofiber into a novel structure called the nurse cell. The nurse cell protects and nurtures the enclosed parasite during its long stay in host muscle. It is anatomically independent of the surrounding uninfected muscle cells and can be isolated from host tissue by mechanical or enzymatic means. Current methods employed for this purpose have yielded only small numbers of nurse cells. An apparatus designed to isolate large numbers of nurse cells and a method for removal of all free larvae and most host muscle debris is described. Homogenization and trypsin digestion of muscle tissue was followed by passage of muscle/parasite suspensions maintained at 37 C through a jacketed glass column fitted with a 40-mesh stainless steel screen at the top and a Nitex screen with 150-microns-diameter pores at the bottom. Nurse cells were retained by the Nitex screen. Density gradient centrifugation using Percoll removed all free larvae and most contaminating muscle debris from nurse cell suspensions. The large quantities of nurse cells made available by this method will allow evaluation of the molecular biology, nutrition, biochemistry, and metabolism of the enclosed parasite and of the Trichinella-modified host muscle cell.