Fine Mesh Screen Research Articles

Cultivation of algae and nutrient removal in a waste heat utilization process

A process providing a beneficial use for waste heat and excess nutrients in the cooling waters of nuclear reactors and fossil-fueled power generating plants has been developed. The process involves the cultivation of selected strains of thermotolerant microalgae in heated discharge waters and the subsequent harvesting of the algal biomass for nutrient removal, recovery of energy and fertilizer, and extraction of high value products. The design of such a process is presented for a large cooling reservoir receiving a discharge of 1091−1 d−1 of secondary cooling water containing 100 μg 1−1 of available P and 400 μg 1−1 of available N. Based on this nutrient load, with a 1% P content in the algal biomass and a productivity of 10 g m−2 d −1, a 100 ha region would be needed for the process. Hydraulic barriers (submerged plastic curtains) would isolate the 100 ha algal production area “cultivation zone” in the influent end of the reservoir to create a hydraulic and thermal environment conductive to the selective growth of filamentous, thermotolerant, nitrogen-fixing, blue-green algae. The algal culture would be inoculated into the thermal plume and harvested near the distal barrier of the cultivation zone with rotating, backwashed, fine mesh screens (“microstrainers”). A portion of the harvested biomass would be recycled to the inoculation site to maintain a dense culture. This process could mitigate both thermal and nutrient loadings on receiving bodies of water.

Laser Diffraction Measurements of the Parameters of Fine-Mesh Woven Textiles

There are problems in determining the warp and weft density, cover factor, and other characteristics of woven fabrics. A laser diffraction measuring technique is pro posed for determining warp and weft density, cover factor, orthotropy, and weave perfection of fine-mesh screen wovens. The applicability of the proposed method is demonstrated using two examples of screen wovens, Nybolt and Kontis.

Screening of concentrates for removal of contaminants at Cyprus Thompson Creek

Laboratory test work, pilot plant testing and plant experience with wet, fine-mesh screens are discussed. High-frequency, low-amplitude, fine-mesh, wet screens were installed on the 6th cleaner concentrate stream. These screens produce a 60% oversize recovery split of the molybdenite concentrate that is of leached equivalent quality. The under size stream is leached with hot ferric chloride to remove lead and copper contaminants before roasting or shipment to sulfide customers. This plant modification is a good example of using existing technology in an unconventional flow sheet to yield significant cost savings.

Pressure drop in the SHOOT superfluid helium acquisition system

Central to the upcoming Superfluid Helium On-Orbit Transfer (SHOOT) demonstration is the fluid acquisition system. The main component of the system is a rectangular cross-section gallery area with one side fabricated from a fine mesh screen. He II enters through the screen and is delivered to a fountain effect pump. A model is proposed to predict the pressure drop as fluid flows through the screen and an expression is derived for the required gallery arm length as a function of flow rate demand. The model is compared with measurement of pressure drop in a full scale SHOOT gallery arm operated with flow rates of up to 850 dm 3 h −1. The tests were conducted in the University of Wisconsin horizontal liquid helium flow facility to minimize gravitational effects.

The role of the external mycelial network in the effect of soil disturbance upon vesicular-arbuscular mycorrhizal colonization of maize.

This study examined the mechanism by which vesicular-arbuscular (VA) mycorrhizal colonization of young maize (Zea mays L.) plants is inhibited by soil disturbance. Attention focussed upon the role of the external mycelial network. Plastic cylinders were divided into a central and two outer compartments by a fine nylon mesh screen which was impervious to roots but not to mycorrhizal hyphae. Soil was packed into each compartment and maize plants grown in the outer compartments over a series of 3-week cycles, leaving root-free central sections. Prior to a final growth cycle, the root-free soil in the central compartment was either disturbed and repacked or left undisturbed. In a third treatment the hyphal connections between the outer and central sections were severed, while leaving the soil in all sections undisturbed. Plants were then grown in the central compartments. Mycorrhizal colonization and shoot P and Zn concentrations of plants grown in the root-free zones were substantially reduced by disturbance of the soil. The reduction in colonization was similar to that found in control pots in which the root system and mycelial network were disturbed. This suggested that destruction of the hyphal network is an important component in the disturbance phenomenon. Removal of hyphal connections with roots in the outer compartments had no effect on colonization or nutrient absorption. Isolation of the mycelial network from the root system from which it had originated did not then seem to affect its infectivity. The mycelial network appears to be an important component of the inoculum potential of an undisturbed soil and it is likely that its destruction is directly responsible for much of the effect of soil disturbance upon mycorrhizal colonization. Evidence is presented indicating that the undisrupted mycelial network may also increase the nutrient absorption capacity independent of the degree of colonization.

A wind tunnel metabolism chamber with small volume and good air flow characteristics

A wind tunnel metabolism chamber is described which has a low (4.2 to 1) ratio of total to working volume to facilitate respiratory gas exchange measurements on unrestrained animals. Fine mesh screens smooth air flow to obtain 2% RMS turbulence and +or-5% uniformity. Simultaneous combinations of air temperature from -10 to 50 degrees C and wind from 0 to 3.6 m s-1can be maintained indefinitely. A window admits simulated solar radiation to the working section.

Noninvasive ion-drag velocimeter

A device is described which, while mounted flush with a wall bounding a streaming insulating fluid, can be used to deduce the velocity profile with respect to the coordinate normal to the wall. Ions, injected into the stream through a fine-meshed screen having a controlled potential V, migrate upstream along trajectories that sample the velocity profile. By means of finely divided electrodes that are also in the wall, the location, V, demarcating those ions that make it back to the upstream wall from those swept downstream is measured as a function of V. An algorithm is developed for deducing the velocity profile from the data ( V, Y). It is shown to be readily implemented with a microcomputer, which could oversee making the measurements.

Pressure drop and He II flow through fine mesh screens

Fluid acquisition systems for He II transfer devices will utilise gallery arms to ensure that the fluid encounters the pump inlet. In near term experiments such as Superfluid Helium on Orbit Transfer (SHOOT), the preferred configuration consists of several rectangular channels which have one side made from a Dutch weave stainless steel screen having 325 × 2300 wires per inch. The effective pore diameter for this screen is about 5 μm. The present paper reports on measurements of pressure drop across a screen when it is subjected to a flow of liquid helium. The experiment measures the time rate of change of the level in two different helium reservoirs connected by a screen-blocked channel. Results with normal helium are compared with predictions based on the Armour-Cannon equations. The He II data show considerable deviation from the classical result. A discussion of the He II pressure drop results in terms of two fluid hydrodynamics is included.

Design considerations for a micro- g superfluid helium fluid acquisition system

The general description, operation and design of a superfluid helium (SFHe) fluid acquisition system (FAS) for use under micro-gravity conditions is presented. For the type of FAS considered here, where fine-mesh woven screens are used to retain flowing SFHe within a gallery arm (flow) channel, those forces which determine the flow dynamics are the micro- g accelerations, liquid surface tension and tensile strength and cumulative pressure drops along a flow path that begins at the bulk liquid and ends at the entrance to a pump. For this case, the dimensionless number, N T, is written as the ratio between the pressure drop across the screen and the surface tension forces at the screen for low fluid velocities. Static Bond number measurements have been taken for SFHe using 325 × 2300 twilled Dutch screen and have indicated a screen pore hydraulic radius, r H, of 3.1 × 10 −4 cm. A design equation incorporating r H, channel dimensions and residual liquid relates N T to the various flow losses at low fluid velocities. The results show that in principle it is possible to design a micro- g SFHe FAS for steady-state flow conditions.

Hydrodynamic resistance and refracting effect of a fine-mesh screen

An attempt has been made to carry out a systematic study of the hydrodynamic resistance and refracting properties of screens and screen packs on the basis of both a generalization of the existing data and additional experiments with broad variation of the principal characteristics of the screens and the values of the Reynolds number. A universal law of resistance, valid on the interval 1 < Ree < 105, is obtained for screens and combinations of screens (matrices) is investigated in detail; Gol'dshtik's theoretical relation for the index of refraction of the streamlines is shown to be correct. The relation obtained for the hydrodynamic resistance coefficient and the index of refraction of screens and matrices can be used for apparatus design purposes.

Electrostatic Shielding of a Charged Conducting Sphere by a Fine-Mesh Grounded Screen

The physical system considered is a charged conducting sphere held at a fixed absolute potential via a battery or some other power source. Another sphere, concentric with and larger than the first, is fabricated out of a fine-mesh screen and this outer screen is grounded. The objective is to calculate the effectiveness of the screen in reducing the electrostatic field at points outside of the system. A derivation based on elementary principles of electrostatics will show that the shielding effectiveness of the screen can be expressed in terms of the separation between the two spheres and another quantity, represented in the paper by B, that is an intrinsic property of the screen. Approximations will be used that require the screen to have a mesh size that is fine compared to other dimensions of the system. In particular, characteristic distances between mesh wires must be smaller (by an amount that was not numerically evaluated in this paper) than the separation between the charged sphere and the spherical screen shield. For a sufficiently simple mesh weave, B can be calculated. More generally, B for a given screen can be measured by measuring the capacitance per unit area and separation between a flat piece of the screen and a parallel metal plate. This method of measuring B is described in the report.

Improved Brightness of the ATA Injector

with an A-K gap of about 13 cm. There was no grid used during the experiment. The cathode was surrounded by a Pierce correcting shroud and the typical gap voltage was about 2.5 MeV. Our initial tests of the field emission cathodes were done using a woven carbon yarn that was laced through a fine mesh screen and then trimmed to a uniform height. Using these “tufted” cathodes, it was easy to vary the number of emission sites per square centimeter. We also varied the geometry of these cathodes by giving the screen a slight convex shape so that the center of the cathode was about 1 cm closer to the anode plane than the edge of the cathode.

Flow of liquids through screens: Relationship between pressure drop and flow rate

The flow of both Newtonian liquids and shear-thinning polymer solutions through fine mesh screens has been studied and results have been expressed as a loss coefficient-Reynolds number relationship. A single correlation covers both types of fluids over Reynolds numbers ranging from 10 −5 to 5.

HYPHAL UPTAKE AND TRANSPORT OF NITROGEN FROM TWO 15N‐LABELLED SOURCES BY GLOMUS MOSSEAE, A VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGUS *

SUMMARYCelery (Apium graveolens L.) plants were grown in pots in which the root system was separated from the soil in a side chamber by a fine mesh screen. The side chamber was treated with either an organic (ground plant tissue) or inorganic [(NH4)2SO4] source of 15N. Mycorrhizal (Glomus mosseae) and control (non‐mycorrhizal) plants were exposed to 15N over a period of 30 days (inorganic‐15N) or 88 days (organic‐16N). Mycorrhizal and control plants did not differ in shoot dry weight or shoot P content. Dry weight of root was reduced in the mycorrhiza treatments. Mycorrhizal plants derived significantly (P= 0.01) more 16N, from both N sources, than did control plants. In the inorganic‐N treatment, 15N in mycorrhizal plants was significantly (P= 0.001) and positively correlated with percent mycorrhizal fungal colonization (r= 0.58), number of hyphal crossings (±10 μ diameter) through the mesh into the area of 15N placement (r= 0.76), total length of hyphae per gram of soil (r= 0.74), and length of hyphae of 5 μ diameter in the soil (r= 0.77). No correlations were found between the 16N content of mycorrhizal plants and any parameter in the organic‐N treatment. The 16N content of control plants was not correlated with hyphal length in the outer chamber and there were no hyphal crossings of the size ( 10 μ diameter) which was counted for the mycorrhiza treatments. The presence of the organic matter (ground plant tissue) increased the total length of saprophytic hyphae per gram of soil but decreased the number of vesicular‐arbuscular mycorrhizal fungal hyphae crossing into the area of 16N placement. The mean flux of N through the hyphae of G. mosseae was 7.42 × 10−8 mol N cm−2 s−1 for the inorganic‐N treatment over a 30‐day period, and 1.74 × 10−8 mol N cm−2 s−1 for the organic‐N treatment over an 88‐day period.

Gas flow across a wet screen: analogy to a relief valve with hysteresis

The flow of gas through a wet fine-mesh screen is analysed in terms of the capillary forces of the liquid wetting the screen and the pressure difference across the screen thickness driving the gas flow. Several different types of time-dependent flow are shown to be possible. The most interesting type is one in which the pressure difference opens small channels in the liquid, which are then closed rapidly by the wetting action of the liquid. The opening and closing exhibit hysteresis, and the flow is highly oscillatory.

Diffusion classification of submicron aerosols. An “in‐stack” diffusion classifier has been designed, constructed, calibrated, and field‐tested

An in-stack diffusion classifer has been designed, constructed, calibrated and field tested. The classifier utilizes a very fine-mesh stainless-steel wire screen for the actual aerosol classification. The in-stack unit uses five stages operated in parallel, each sampling at the same fixed flow rate, to provide five simultaneous size-classified aerosol samples. These samples are collected out on filter media for subsequent weight gain determination and for chemical analysis. Sampling rates are maintained through each stage by using carefully matched critical orifices. The entire unit is housed in a stainless steel cylinder of 25-cm length and 7.5-cm outer diameter. 5 references, 4 figures. (JMT)

Advances in Well Completion Technology

Distinguished Author Series articles are general, descriptiverepresentations that summarize the state of the art in an area of technology bydescribing recent developments for readers who are not specialists in thetopics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and presentspecific details only to illustrate the technology. Purpose: to informthe general readership of recent advances in various areas of petroleumengineering. "You can't hurt a good well." This old maxim of the oil industry should belaid to rest. Some of the most important advances in well completion technologyduring the 1970's were made in formation damage prevention. It behooves us totake advantage of these advances because operators using cleaner completionfluids and better completion practices are making wells with better productionrates practices are making wells with better production rates and lowerpressure drawdowns than ever before. Much of this success in obtaining higherproductivities can be attributed to awareness that formation damage is a realproblem. A hydrocarbon-bearing formation is like a sand filter. A sand filterbecomes plugged as it performs its job of removing solids from a fluid. Afilter made of a typical U.S. gulf coast Miocene sand would have pore sizesranging from 2 to 10 mu m; dirty water pumped through it would be cleanedeffectively. Solids larger than 10 mu m would be stopped right at the surfaceof the sand filter and particles sized from about 0.5 to 10 mu m would betrapped throughout the sand. Only solids smaller than 0.5 mu m might passthrough the sand, but they would be so small that they wouldn't be visible.That filtering process is exactly what happens in wells when fluid is lost to aformation. Solids larger than the pore sizes of the formation are trapped inthe perforations or on the face of the formation. Particles perforations or onthe face of the formation. Particles about the same size as the formation poresare carried out into the formation where they are likely to be trapped. Largersolids may come back out of the well when it is put on production, but many ofthese solids will remain trapped. If the well has been gravel packed, practically all the solids will remain trapped. packed, practically all thesolids will remain trapped. In any case, the permeability of the formation willbe less than if these solids were not present. The problem of formation damageby solids becomes even more apparent when we consider how small perforationsare and how little dirt it takes to fill them completely. About 5 lbm (2.3 kg)of solids will fill 20 average-size perforations. Only 14 bbl (2.2 m3) of waterwith 0.1 wt % solids content will fill 20 perforations with dirt completely.This reasonably perforations with dirt completely. This reasonably assumes thatmost of the dirt is stopped by the formation sand and remains in theperforations as the fluid flows into the formation. Filter Considerations One major method to reduce plugging of a formationand perforations with solids is plugging of a formation and perforations withsolids is the use of filters to clean completion and workover fluids. Cartridgefilters are the most common means of removing solids from these fluids. Theyare on most wellsites now and have reduced formation damage greatly, but theyare not a cure-all. Polypropylene filters have proved to be the most reliabletype. Polypropylene cartridge filters are rated usually from 1 to 200 mu m withthe most common ratings being 2, 5, 10, 20, and 50 mu m. This implies thatthese filters will remove all the solids larger than their micron rating. Forinstance, a 2-mu m filter might be expected to remove all particles larger than2 mu m diameter. This is absolutely wrong! At best these filters can removeonly 90% of the solids from a fluid, and solids much larger than the filterrating pass through. Some of the practices that have been found to enhance theability of these filters to remove solids are to (1) use low flow rates throughthe filters, (2) remove the largest solids and the bulk of the solids from thefluids before filtering, (3) stop bypassing of fluids around the cartridges, and (4) change the filters when they begin to plug. The maximum flow ratethrough a set of 16 or 18 filter cartridges should be 1 bbl/min (0.159 m3/min).These are the numbers of cartridges commonly found in one filter unit. Tofilter fluid at higher rates requires either multiple filter units connected inparallel or larger filter containers such as those used by Amoco Production Co.at High Island with 65 cartridges. Production Co. at High Island with 65cartridges. The larger particles and the bulk of the solids should be removedfrom the fluid by settling tanks, shakers with fine mesh screens, mud cleaners, or hydrocyclones. Bypassing of fluids around the filter cartridges is a commonproblem.

Parasites of the bald eagle (Haliaeetus leucocephalus) of North America.

Information concerning parasites of the bald eagle (Haliaeetus leucocephalus) in North America is relatively sparse. Since the bald eagle in parts of the United States is an endangered species, collection of eagles for parasito!ogical study is difficult. There have been several singular reports of parasites found in oron bald eagles in the literature. However, Kocan and Locke (1974, J. Wild!. I)is. 10: 8-10) reported the first survey of helminths collected from dead and moribund bald eagles they examined from 1963-1971. Since dead and moribund eagles are collected and submitted to the National Wildlife Health Laboratory (NWHL) for necropsy to determine factors that con tribute to their mortality, the opportunity was provided to collect and identify en doparasites and ectoparasites observed during routine necropsy. This paper summarizes the parasites found in bald eagles examined from 1979-1981. Parasite specimens were obtained from a total of 84 bald eagles collected from 18 states. All helminth parasites were fixed in AFA (alcohol-formalinacetic acid). Trematodes and acanthocephala were stained with Semichon’s carmine and mounted. Nematodes were cleared in glycerine. Ectoparasites were fixed in 70% alcohol and cleared in 1014 KOH before being mounted. Wet smears made from intestinal scrapings were examined at 140 and 1000X magnification to detect the presence of protozoan parasites. Bald eagle specimens submitted to NWHL were not used exclusively for parasitological examinations, thus metazoan parasite specimens were collected by sight. Fine-mesh screens were not used. Parasites recovered from bald eagle hosts are shown in Table 1. One protozoan, two genera of Trematoda, one genus of Acanthocephala, seven genera of Nematoda, and three genera of Mallophaga were reported. New host records are indicated in the table by an asterisk. Female Contracaecum found without males or those that were found as larval stages were identified only to

Cattle, House Fly Control in Bovine Manurewith Oral Insecticide Treatments, 1978

Abstract Eight Hereford heifers weighing 300-350 kg were used in this study. Treatments, each using 2 heifers, consisted of CGA 72662, an insect growth inhibitor, fed at 0.25 and 0.5 mg/kg of animal body weight per day and Rabon oral larvicide fed at 1.5 mg/kg of animal body weight per day. A fourth group of 2 heifers served as untreated controls. The feed mixes fed were prepared by thoroughly mixing the appropriate amounts of CGA 72662 (3% premix) and Rabon oral larvicide (7.76% premix) with a feed mixture con-taining 7 parts cracked corn and 1 part supplement in a Hobart mixer. Trie heifers were penned separately and individually fed at a rate of 3.6 kg of mixed ration per day. Beginning Sept 18, cattle were fed untreated feed the first week, treated feed the second week, and untreated feed again the third week. Manure samples were taken at days 1,3,5 and 7 before, during and after feeding the treated feed. Portions of each sample were placed in two 118 ml plastic cups. Each cup was seeded with 10 first-instar laboratory reared house fly larval, fitted with fine mesh screen, and held for 3 weeks for adult emergence.

Feeding and maintenance of Simulium mexicanum (Diptera: Simuliidae) in the laboratory.

Methods were developed to feed, maintain, and refeed Simulium mexicanum black flies in the laboratory. Flies were aspirated as they came to feed on horses and calves. The flies were held overnight at 4 °C and then attempts made to induce them to feed. Few black flies fed on serum in capillary tubes or through an artificial membrane. Approximately 1/3 of the flies tested fed on rabbits, hamsters, suckling mice, and guinea pigs. Guinea pigs were used most extensively, and 5% to over 80% of the black flies fed. Large cages were unsatisfactory for maintenance of flies after feeding. Survival was best when the flies were individually kept in 4-ml (1-dram) shell vials with fine-mesh screen tops. The vials were kept in beakers covered with wet gauze. The insectary temperature was reduced from 22 °–26 °C to 18 °–22 °C and survival at 1 week increased from 0.5% to 17%, and maximum survival improved from 8 to 18 days. Approximately ½ the black flies that previously fed on guinea pigs and were maintained for 8 or more days refed on other guinea pigs, hamsters, or suckling mice. Three flies were induced to refeed a 3rd time on suckling mice 4–5 days following the 2nd feeding. This method, thus, allows both VEE virus replication and transmission experiments.