Mesh Cover Research Articles

Researches on the Generation of Three-Dimensional Manifold Element under FEM Mesh Cover

Three-dimensional manifold element generation and contact detection algorithm between blocks are the bottleneck for the development of three-dimensional numerical manifold method (NMM). For building mathematics cover, the technology of three-dimensional finite element mesh generation is utilized in the paper. Aiming at the characteristics of complex formation and difficult identification of three-dimensional manifold block, three-dimensional manifold cutting technology is developed. It is important to achieve the coding of mathematical cover (MC) and physical cover (PC) for NMM, which directly determines the correctness of three-dimensional manifold element generation. Based on the character that the coding of three-dimensional manifold is the same as two-dimensional field essentially, coding algorithm of PC system proposed by Dr. Shi is extended to be three-dimensional. A three-dimensional manifold cutting program 3D MC.f90 is developed in this paper, which can generate an arbitrary three-dimensional manifold element under tetrahedral and hexahedral mesh cover. Several examples are made, and results show that three-dimensional manifold block shape and the coding of manifold node and element generated by three-dimensional manifold cutting program all agree well with the definition of three-dimensional manifold element.

Polymeric mesh for durable infra-red transparent convection shields: Applications in cool roofs and sky cooling

Polyethylene (PE) mesh is shown to strongly suppress convective gain at night and to have a high black body transmittance, making it suited to use in radiative cooling. Advantages over previous non-porous cover systems include; self-supporting for large areas, good mechanical stability, low cost, retractable, and a long outdoor lifetime. This study compares performance with a PE mesh cover to that of an impermeable PE cover and to no cover. Convective suppression and net cooling for different wind speeds and ambient temperatures are examined. The impact of such a mesh on night sky cooling rates for a mesh over water, then over a roof is presented. For the roof the associated rise in surface temperature is also measured and modelled in the daytime. Effective permeabilities are not the same as geometric permeability. They are extracted by comparing simulation results with data and are found to depend only weakly on wind speed. They are most sensitive to magnitude and sign of the difference between roof and ambient temperatures. They differ significantly between night and day, that is for convective warming and cooling respectively.

Hyperpnoeic response independent of limb movements at exercise onset in mice

We have shown that constant-load treadmill exercise in mice produces an abrupt ventilatory increase to a maximal level at exercise onset. We examined what caused this abrupt response. We measured ventilation during 30-min constant-load exercise on a treadmill, below the lactate threshold, in conscious mice. Video analysis showed that hyperpnoea started before locomotion began. Incremental changes in speed did not further increase ventilation during the early phase of exercise. Next, we measured ventilatory responses to a sudden movement of the treadmill belt on which the mice were kept in a stationary position by a mesh cover. Hyperpnoea started concurrently with the sudden belt movement. In the absence of locomotion, ventilation increased to the extent reached during exercise hyperpnoea. Finally, the abrupt response showed plasticity but was attenuated by experience. The present study shows the importance of factors independent of limb movements in the hyperpnoeic response during the early phase of treadmill exercise in mice.

Effects of substrate and shading on the growth of two submerged macrophytes

Excessive nutrient loading may cause a shift from submerged macrophyte dominance to free-floating macrophyte dominance. Tolerance and persistence of submerged plants in response to shade may be key characteristics in determining when/if such a shift occurs in shallow eutrophic lakes. This study examines how the cover of floating macrophyte (Lemna minor) and shade of dark mesh affect the growth and photosynthetic efficiency of two submerged plants (Vallisneria natans and Myriophyllum spicatum) on different nutrient substrates. We found that low- and mid-cover intensities generally enhanced the leaf/shoot growth of both submerged plants under all cover and substrate types. The relative growth rates (RGR) were slightly enhanced under the treatment of Lemna with low- and mid-intensity cover on both nutrient-rich substrates. The leaf/shoot growth and RGR of both submerged macrophytes generally increased more under Lemna cover than mesh cover. The photosynthetic efficiency (Fv/Fm value) typically increased with the duration of treatment and the cover densities. In addition, these two macrophytes with contrasting growth forms have markedly different growth and survival strategies in response to covers. These results strengthen the hypothesis that submerged plants can successfully develop under a low-intensity cover of floating vegetation on nutrient-rich substrate.

Neuroendocrine carcinoma of the thymus gland with sternal invasion

Large-cell neuroendocrine carcinoma of the thymus is a rare cancer that is more aggressive than other thymic epithelial tumors with poorer prognosis. We report one such case in a 44-year-old male patient with invasion into the upper 2/3rd of the sternum but no endocrinopathy. Complete enbloc resection of the tumor with adherent pericardium, upper 2/3rd of the sternum and mediastinal lymphadenectomy was performed. The chest wall was reconstructed with polypropylene mesh and bilateral pectoralis major muscle advancement flap cover. A search of PubMed database with user query words 'neuroendocrine carcinoma, thymus gland, sternal invasion' revealed no case report in the literature of thymic neuroendocrine carcinoma with invasion of the sternum.

The Mini-Missouri Trawl: A Useful Methodology for Sampling Small-Bodied Fishes in Small and Large River Systems

ABSTRACT Sampling has been conducted in small to large rivers of the Midwest and northeastern United States to determine the usefulness of a modified Missouri trawl designed to increase species detection of small-bodied fish species. We modified the Missouri trawl, which is a 4.8 m standard two-seam slingshot balloon trawl with a small mesh cover, by reducing the size (to a 2.44 m) and cover. The modified Missouri trawl (a.k.a. the mini-Missouri trawl) increased the number of small-bodied aquatic species of concern captured over that of previously used gears. For instance, shoal chub (Macrhybopsis hyostoma) had only been captured in the St. Croix River of Minnesota at three locations since 1960, yet we sampled it at 14 new locations in September, 2004 employing this methodology. Because of our success in these diverse and numerous systems, we believe this is a useful methodology for sampling the benthic fish community in many aquatic systems when other sampling methods are difficult to use because of water depths and/or velocities.

Evaluation and in situ assessment of photodegradation of polyaromatic hydrocarbons in semipermeable membrane devices deployed in ocean water

Semipermeable membrane devices (SPMDs) were deployed in water using four different methods: a typical SPMD cage with and without a mesh cover, a bowl chamber and without any protection. In addition to routinely used performance reference compounds (PRCs), perdeuterated dibenz[ a, h]anthracene was added. Due to its high sampler to water partition coefficient no measurable clearance due to diffusion was expected during the deployment period, hence any observed loss could be attributed to photodegradation. The loss of PRCs was measured and SPMD-based water concentrations determined. Results showed that a typical SPMD deployment cage covered with mesh provided the best protection from photodegradation. Samplers which had undergone the highest photodegradation underestimated PAH water concentrations by up to a factor of 5 compared to the most protected SPMDs. This study demonstrates that the potential for photodegradation needs to be addressed when samplers are deployed in water of low turbidity.

Structural integrity of ferrocement panels exposed to fire

The structural fire integrity performance of a ferrocement jacket was experimentally determined based on its flexural characteristics and damage after exposure to fire. The main parameters investigated were the volume fraction of wire mesh and mortar cover. A sandwich-sample configuration was adopted to simulate the actual conditions of exposure to fire in which the maximum temperature of 1060 °C was reached within 3 h. Tests showed that a ferrocement jacket was a satisfactory fire protection material due to its post-fire strength compared with that of plain mortar. Although an increase in wire mesh content significantly improved the mechanical properties of ferrocement under normal conditions, after fire exposure the content of wire mesh was no longer significant and higher volume fractions of wire mesh resulted in in-plane cracking. Mortar covers had negligible influence on the mechanical properties of ferrocement jackets under both normal and after fire exposures. However more visible fire damage occurred in ferrocement with thinner mortar cover.

A field investigation into the effects of progressive rainfall-induced soil seal and crust development on runoff and erosion rates: The impact of surface cover

Surface crusts and seals can form from a variety of processes, both physical and biological, and have the potential to alter runoff and erosion, especially in regions with low vegetation covers. Despite the obvious links between seals and crusts these features have rarely been considered together. This study uses rainfall simulation experiments to investigate interrill soil crust and seal development in response to structural (or raindrop-impact-induced) and depositional (or runoff-induced) processes on a semiarid piedmont in southern New Mexico, USA, which has undergone substantive vegetation change (replacement of grasses by shrubs) over the last 100 years. The study design incorporates six double-paired runoff plots divided into four subplots, each of which was exposed to three rainfall simulation events. Crust development on these plots was assessed using penetration-resistance measurements while seal development was assessed using runoff coefficients. The penetration-resistance data indicate that subplots directly exposed to raindrop impacts (uncovered plots) have crusts that are ∼ 40% stronger than those positioned beneath a mesh cover (covered plots) that intercepts the kinetic energy of the rainfall. The crusts exposed to raindrop-impacts increased in strength following each simulation, whereas the crusts on the covered surfaces reached a plateau after two events. Runoff data indicate that seal development does not directly mirror crust formation. Runoff coefficients increased after each rainfall simulation event but were not significantly different between the covered and uncovered plots. Rather, the presence of stone lags or litter on the soil surface influenced the relation between runoff and seal development. Sediment yields from uncovered surfaces exceeded those from covered surfaces, indicating that raindrop impacts contribute to the delivery of sediment into flows. The results of this study indicate that the loss of vegetation cover on the piedmont has increased the extent of surface crust and seal development but that those crusts may be playing an important role in mitigating erosion.

Effectiveness of a Plastic Mesh Substrate Cover for Reducing the Effects of Common Carp on Aquatic Ecosystems

AbstractA great deal of effort has been directed at eliminating or controlling common carp Cyprinus carpio populations, but these efforts have had limited success. We assessed the effectiveness of an alternative approach, using plastic‐mesh substrate covers, to reduce environmental effects of common carp, Multiple trophic levels were monitored in 0.06‐ha enclosures in experimental ponds that contained either common carp with mesh covers, common carp with no mesh covers, no common carp with mesh covers, or neither fish nor mesh covers. Macroinvertebrates and macrophytes were also sampled over a 1‐year period in six field sites with paired mesh cover and control plots. Common carp significantly increased turbidity (NTU) and total phosphorus (μg/L), decreased macrophyte cover (%), altered the relative abundance of zooplankton taxa (N/L), and suppressed macroinvertebrate abundance (N/m2) in ponds. In contrast, carp did not significantly affect either total nitrogen (μg/L) or phytoplankton (μg/L) concentrations. Mesh substrate covers did not significantly reduce any effects of common carp in the pond enclosures. Abundances of macroinvertebrates and macrophytes also did not differ between field plots with and without mesh covers. The lack of effective reduction of common carp‐induced effects limits the usefulness of mesh substrate covers as a tool for habitat restoration.

Simulation-based investigation of the paired-gear method in cod-end selectivity studies

In this paper, the paired-gear and covered cod-end methods for estimating the selectivity of trawl cod-ends are compared. A modified version of the cod-end selectivity simulator PRESEMO is used to simulate the data that would be collected from a paired-gear experiment where the test cod-end also had a small mesh cover. Thus, estimates of the selectivity parameters of the test cod-end can be made using both the paired-gear method and the covered cod-end method. These estimates are compared and, as it is assumed that the covered cod-end method is objective, we conclude that the paired-gear method is biased. We demonstrate that extreme parameter estimates as well as discrepancies between the paired-gear and covered cod-end experiments do not necessarily reflect physical or biological mechanisms. We believe that this phenomenon may help explain cases in the literature where the covered cod-end and paired-gear methods produce different estimates of cod-end selectivity.

내부에 그루브와 스크린 메쉬를 갖는 평판 스트립형 히트파이프의 열성능에 대한 실험적 연구

The thermal performance of a flat-strip heat pipe with inner grooves and the screen mesh cover was investigated experimentally. The heat pipes were made of 2024 aluminum alloy of which the dimensions were 30(W) x 4(T) x 150(L) ㎜. The cross sectional dimensions of inner groove were 0.4 x 0.9㎜ and the space between grooves was 0.6㎜. To enhance the capillary force, fine screen meshes were attached to cover the grooved inner surface. In the grooved heat pipes without screen mesh cover, the maximum thermal load of 180 W (12 W/㎠) was achieved for operating temperature below 130℃ at horizontal position. The beat pipes with screen mesh cover showed the thermal resistances less than one third of those without screen mesh cover, and showed less fluctuation in the thermal resistance values. Furthermore, the thermal performance of the former exhibited less dependence on the tilt angle and the fill charge ratio.

Effect of Insect Exclusion on the Incidence of Yellow Vine Disease and of the Associated Bacterium in Squash.

Yellow vine (YV) of cucurbits, associated with a phloem-limited bacterium, causes rapid wilting and death in affected plants. In a previous study, experimental insecticide-treated plots had a lower incidence of YV than untreated plots, suggesting that insects were involved in the transmission of the bacterium. In the study reported here, we compared the incidence of YV and polymerase chain reaction (PCR) detection of the YV bacterium in noncovered squash plants (Cucurbita pepo var. melopepo) with plants covered with fine-mesh fabric secured in such a way that insects were excluded. Rows of squash were covered with row mesh cover that was stretched over hoops and anchored in the soil. The row cover was removed after 40 or 50 days, at which time all plants were sampled destructively by harvesting the crown and root. In the first experiment, 3% of the noncovered plants had foliar symptoms, 7% were positive with the use of Dienes' stain, and 25% were positive when analyzed by PCR with specific primers. No covered plants were positive by any detection method, and no plants in the second experiment had foliar symptoms or tested positive with Dienes' stain. However, 20% of noncovered and 0% of covered plants were PCR positive. These data support the hypothesis that insects were involved in the transmission of the bacterium.

Esophageal Stent with Antireflux Valve for Tumors Involving the Cardia: Work in Progress

To describe an esophageal stent with a polyester mesh cover and an antireflux valve, and to assess its efficacy in the treatment of patients with inoperable tumors of the gastric cardia. Thirteen patients with adenocarcinoma of the cardia, two patients with squamous cell carcinoma, and three patients with recurrent carcinoma of the gastric fundus after surgery were treated by placement of an esophageal stent with an antireflux valve. The spiral Z stent has a porous, polyester mesh cover and an antireflux sleeve made of pliable polyurethane at its lower end. Placement of the stent was successful in all patients, and their dysphagia disappeared or significantly improved. All were able to swallow solid food, and no patient reported significant reflux or "gas bloat" syndrome prior to death or the end of follow-up. Two patients only complained of minor heartburn. Follow-up barium swallow studies showed the absence of significant gastroesophageal reflux in all patients. No stent migration occurred. The esophageal stent with antireflux valve has been effective in the treatment of malignant obstruction of the cardia and allowed good esophageal passage without migration and major gastroesophageal reflux.

Experimental Study of the Histocompatibility of Covered Expandable Metallic Stents in the Trachea

To evaluate the histocompatibility of four different materials used to cover expandable metallic stents. Prospective, randomized, unblinded study. Animal research laboratory of Kurume University. Twenty 12- to 18-kg mongrel dogs. Handmade Gianturco-type stents with six bends, 20 mm in length, and 15 to 20 mm in diameter were covered using four different materials: polypropylene mesh, silicone-coated mesh, polyester mesh, and ePTFE. Covered stents were inserted into the trachea after i.v. anesthesia. Five animals were used in each group. Postinsertion status was observed using clinical and bronchoscopy measures 7, 14, 28, and 56 days after intervention. Eight weeks after stent insertion, the tracheal specimens were studied pathologically. A scoring system was used to evaluate the histocompatibility of covered stents in each study group. The mean of clinical scores in the polypropylene group was 1.84+/-0.36, which was significantly higher than those in the groups of silicone, polyester, and ePTFE. The means of histopathologic scores in the polypropylene group and the silicone group were 1.60+/-0.55, which were significantly higher than those in groups of polyester and ePTFE. Polypropylene mesh cover was more suitable than silicone-coated mesh, polyester mesh, and ePTFE because of its excellent histocompatibility.

The bicycle spoke injury: an avoidable accident?

A prospective study of the bicycle spoke injury over a 1-year period included a total of 71 spoke injuries. Of these, 67 injuries occurred on an adult bicycle and four occurred on a child's bicycle. All children sustained ankle and foot injuries, which consisted of contusion and superficial abrasion (N = 45), skin loss (N = 10), skin laceration (N = 4), and undisplaced fractures (N = 12). A biomechanical study was conducted to investigate the use of a protective cover over the wheel to prevent the foot from slipping between the spokes. Wind resistance studies showed that a cover with a mesh size of 10 mm hexagonal could prevent this and at the same time stop the cover from acting as a sail if a flat cover without holes was used instead. The mesh cover, however, will prevent the toes from entering between the spokes but will not prevent the foot from becoming jammed between the wheel and the fork. To prevent this, a plastic shield to bridge the gap between the fork and the horizontal upright has been designed. With these modifications, the bicycle spoke injury can become an injury of the past.

Demersal pair trawl cod-end selectivity models

Experiments to examine the selectivity of Scottish demersal pair trawls were carried out using a new version of the covered cod-end technique. The small mesh cover was supported by flexible hoops designed to hold the cover netting clear of the test cod-end and thus reduce masking of the cod-end meshes by the cover. Two typical Scottish 447 kW North Sea pair trawlers were chartered for this work and the test cod-ends were fitted directly to their trawl gear. Combinations of three mesh sizes and three cod-end diameters were tested and catches of haddock, whiting and cod sampled. Both mesh size and cod-end diameter had a higly significant effect on selectivity, with 50% retention lengths increasing with increasing mesh size and decreasing cod-end diameter. Models quantifying these effects were developed.

Enamel microhardness change and plaque pH measurements in an intra-oral model in humans.

Changes in plaque pH and microhardness of bovine enamel slabs were evaluated with a seven-day intra-oral cariogenicity test (ICT). The test enamel slabs were mounted in prosthetic appliances with a Dacron mesh cover for enhancement of microbial colonization. Three percent solutions of sucrose, sorbitol, and xylitol were evaluated as four daily extra-oral immersions of 10 min each, for seven days, and the results were compared with baseline experiments (no daily immersions). The pH was measured with antimony electrodes on one-day and seven-day ICT plaque samples that were challenged with a one-minute immersion in the studied substrates. Plaque samples in the baseline experiments were challenged with 3% sucrose. The enamel softening was assessed with measurements of microhardness. Sucrose challenge caused pH depression with both the baseline and the sucrose-immersed plaque. Sorbitol and xylitol challenge did not depress the plaque pH. Compared with the baseline, sucrose immersions caused enamel softening; sorbitol and xylitol did not.

A new quantitative grab for sampling benthos

A new quantitative grab for sampling benthos is described. It is constructed of stainless steel to retard corrosion, and incorporates six features designed to make it outperform other grabs: 1) a frame support; 2) counter-weighted arms; 3) overlapping buckets; 4) upright posts on the frame for addition of weights; 5) a fine mesh cover on each bucket; and 6) a moving elliptical pivot point. These features result in high reliability compared to other grabs, and a somewhat quadrangular bite profile. The model in use digs to 6 cm depth over the entire area sampled, and penetrates to a maximum of 11.5 cm.

Net selectivity studies in the Northern Ireland Nephrops fishery

The effect on catch composition of a large mesh lifter net fitted to a trawl cod-end was investigated in the Northern Ireland Nephrops fishery in the north west Irish Sea (ICES area Vila). Two experiments were conducted using chartered commercial fishing vessels. In the first experiment, parallel hauls showed there to be no significant difference in the Ncphrops size distribution caught by nets with and without a lifter net. The result of the second experiment, in which the cod-end was fitted with a small mesh cover to retain escaping Nephrops, did not suggest that the cod-end meshes were blinded by the lifter. Field data are contrasted with those from theoretical studies of mesh obstruction.