Local pressure for inhomogeneous fluids

A simple solution to the serious problem of specimen contamination in the electron microscope is presented. This is accomplished by the introduction of clean helium into the vacuum exactly at the specimen position. The local pressure gradient thus established inhibits the migration of hydrocarbon molecules to the specimen surface. The high ionization potential of He permits the use of relatively large volumes of the gas, without interfering with gun stability. The contamination rate is reduced on metal samples by a factor of 10.

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Integral equation approximations for inhomogeneous fluids: functional optimization

Molecular Physics ◽

10.1080/002689798166936 ◽

1998 ◽

Vol 95 (3) ◽

pp. 601-619

Author(s):

MICHAEL R. BUSH M. J. BOOTH A. D. J. HAYMET

Keyword(s):

Integral Equation ◽

Functional Optimization ◽

Inhomogeneous Fluids

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Healing venous ulcers with different modalities of leg compression

Phlebologie ◽

10.1055/s-0037-1622150 ◽

2006 ◽

Vol 35 (05) ◽

pp. 349-355 ◽

Cited By ~ 9

Author(s):

E. O. Brizzio ◽

G. Rossi ◽

A. Chirinos ◽

I. Cantero ◽

G. Idiazabal ◽

...

Keyword(s):

Wound Care ◽

Univariate Analysis ◽

Compression Therapy ◽

Healing Time ◽

Clinical Parameters ◽

Compression Stockings ◽

Local Pressure ◽

Ulcer Size ◽

Venous Ulcers ◽

Unexpected Findings

Summary Background: Compression therapy (CT) is the stronghold of treatment of venous leg ulcers. We evaluated 5 modalities of CT in a prospective open pilot study using a unique trial design. Patients and methods: A group of experienced phlebologists assigned 31 consecutive patients with 35 venous ulcers (present for 2 to 24 months with no prior CT) to 5 different modalities of leg compression, 7 ulcers to each group. The challenge was to match the modality of CT with the features of the ulcer in order to achieve as many healings as possible. Wound care used standard techniques and specifically tailored foam pads to increase local pressure. CT modalities were either stockings Sigvaris® 15-20, 20-30, 30-40 mmHg, multi-layer bandages, or CircAid® bandaging. Compression was maintained day and night in all groups and changed at weekly visits. Study endpoints were time to healing and the clinical parameters predicting the outcome. Results: The cumulative healing rates were 71%, 77%, and 83% after 3, 6, and 9 months, respectively. Univariate analysis of variables associated with nonhealing were: previous surgery, presence of insufficient perforating and/or deep veins, older age, recurrence, amount of oedema, time of presence of CVI and the actual ulcer, and ulcer size (p <0.05-<0.001). The initial ulcer size was the best predictor of the healing-time (Pearson r=0.55, p=0.002). The modality of CT played an important role also, as 19 of 21 ulcers (90%) healed with stockings but only 8 of 14 with bandages (57%; p=0.021). Regression analysis allowed to calculate a model to predict the healing time. It compensated for the fact that patients treated with low or moderate compression stockings were at lower risk of non-healing. and revealed that healing with stockings was about twice as rapid as healing with bandages. Conclusion: Three fourths of venous ulcers can be brought to healing within 3 to 6 months. Healing time can be predicted using easy to assess clinical parameters. Irrespective of the initial presentation ulcer healing appeared more rapid with the application of stockings than with bandaging. These unexpected findings contradict current believes and require confirmation in randomised trials.

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Considerations about mass and energy flow in discontinuous evaporating crystallizers

Sugar Industry ◽

10.36961/si17686 ◽

2016 ◽

pp. 514-516

Author(s):

Martin Bruhns

Keyword(s):

Energy Flow ◽

Static Pressure ◽

Bubble Formation ◽

Boiling Temperature ◽

Vapor Bubbles ◽

Local Pressure ◽

Heating Steam ◽

Flow Changes ◽

Local Superheating ◽

Local Supersaturation

The massecuite circulates in a loop within the evaporating crystallizing vessel. The massecuite flows upwards through the heating tubes. In the room above the calandria the massecuite flow changes its direction to radial inwards and then to vertical downwards. An impeller in the central tube forces the circulation. Below the calandria the main direction of flow is radially outwards until threads of the massecuite stream enter the heating tubes in upwards direction. Within the tubes heat is transferred to the massecuite. At low temperature differences between heating steam and massecuite and higher levels of the massecuite in the crystallizer vapor bubbles are not found in the tubes. Vapor bubbles can be formed at a massecuite level in the crystallizer where the temperature of the massecuite is higher than the local boiling temperature of water, which depends on the local pressure (including the static pressure of the massecuite at this point) and the boiling point elevation of the mother liquor. The surface tension of the liquid is a resistance against the bubble formation, which has to be overcome by the local superheating i.e. the part of the enthalpy of the massecuite exceeding the local boiling temperature. The formation and the flow of the bubbles change the density of the massecuite/bubbles mixture and has an influence on the massecuite flow. The formation of a vapour bubble is connected with a local drop of the massecuite temperature which changes the local supersaturation. Today the heat transfer into the magma is quite well known but the process of bubble formation is quite unknown. Some basic considerations about the formation of bubbles and its influence on local supersaturation based on calculation of heat and mass balances and models of bubble formation are be given and discussed. Experiments for basic investigations are proposed.

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Comparative Assessment of Tubular Ceramic, Spiral Wound, and Hollow Fiber Membrane Microfiltration Module Systems for Milk Protein Fractionation

Foods ◽

10.3390/foods10040692 ◽

2021 ◽

Vol 10 (4) ◽

pp. 692

Author(s):

Roland Schopf ◽

Florian Schmidt ◽

Johanna Linner ◽

Ulrich Kulozik

Keyword(s):

Hollow Fiber ◽

Milk Protein ◽

Hollow Fiber Membrane ◽

Comparative Assessment ◽

Transmission Factor ◽

Transmembrane Pressure ◽

Protein Fractionation ◽

Flow Conditions ◽

Local Pressure ◽

Spiral Wound

The fractionation efficiency of hollow fiber membranes (HFM) for milk protein fractionation was compared to ceramic tubular membranes (CTM) and spiral wound membranes (SWM). HFM combine the features of high membrane packing density of SWM and the more defined flow conditions and better control of membrane fouling in the open flow channel cross-sections of CTM. The aim was to comparatively analyze the effect of variations in local pressure and flow conditions while using single industrially sized standard modules with similar dimensions and module footprints (module diameter and length). The comparative assessment with varied transmembrane pressure was first applied for a constant feed volume flow rate of 20 m3 h−1 and, secondly, with the same axial pressure drop along the modules of 1.3 bar m−1, similar to commonly applied crossflow velocity and wall shear stress conditions at the industrial level. Flux, transmission factor of proteins (whey proteins and serum caseins), and specific protein mass flow per area membrane and per volume of module installed were determined as the evaluation criteria. The casein-to-whey protein ratios were calculated as a measure for protein fractionation effect. Results obtained show that HFM, which so far are under-represented as standard module types in industrial dairy applications, appear to be a competitive alternative to SWM and CTM for milk protein fractionation.

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Design and Optimization of a Centrifugal Pump for Slurry Transport Using the Response Surface Method

Machines ◽

10.3390/machines9030060 ◽

2021 ◽

Vol 9 (3) ◽

pp. 60

Author(s):

Khaled Alawadhi ◽

Bashar Alzuwayer ◽

Tareq Ali Mohammad ◽

Mohammad H. Buhemdi

Keyword(s):

Response Surface ◽

Centrifugal Pump ◽

Industrial Applications ◽

Pump Efficiency ◽

Optimized Design ◽

Centrifugal Pumps ◽

Local Pressure ◽

Design And Optimization ◽

Geometry Characteristic ◽

Line Design

Since centrifugal pumps consume a mammoth amount of energy in various industrial applications, their design and optimization are highly relevant to saving maximum energy and increasing the system’s efficiency. In the current investigation, a centrifugal pump has been designed and optimized. The study has been carried out for the specific application of transportation of slurry at a flow rate of 120 m3/hr to a head of 20 m. For the optimization process, a multi-objective genetic algorithm (MOGA) and response surface methodology (RSM) have been employed. The process is based on the mean line design of the pump. It utilizes six geometric parameters as design variables, i.e., number of vanes, inlet beta shroud, exit beta shroud, hub inlet blade draft, Rake angle, and the impeller’s rotational speed. The objective functions employed are pump power, hydraulic efficiency, volumetric efficiency, and pump efficiency. In this reference, five different software packages, i.e., ANSYS Vista, ANSYS DesignModeler, response surface optimization software, and ANSYS CFX, were coupled to achieve the optimized design of the pump geometry. Characteristic maps were generated using simulations conducted for 45 points. Additionally, erosion rate was predicted using 3-D numerical simulations under various conditions. Finally, the transient behavior of the pump, being the highlight of the study, was evaluated. Results suggest that the maximum fluctuation in the local pressure and stresses on the cases correspond to a phase angle of 0°–30° of the casing that in turn corresponds to the maximum erosion rates in the region.

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Sedimentation in homogeneous and inhomogeneous fluids using SPH

International Journal of Multiphase Flow ◽

10.1016/j.ijmultiphaseflow.2015.02.004 ◽

2015 ◽

Vol 72 ◽

pp. 155-164 ◽

Cited By ~ 12

Author(s):

Jihoe Kwon ◽

Joseph J. Monaghan

Keyword(s):

Inhomogeneous Fluids

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Seasonal food habits of the four-horned antelope (Tetracerus quadricornis de Blainville, 1816) in tropical deciduous forests of Aravalli mountain range, Rajasthan, Western India

The Journal of Basic and Applied Zoology ◽

10.1186/s41936-020-00193-9 ◽

2020 ◽

Vol 81 (1) ◽

Author(s):

Ramchandra Meghwal ◽

Chhaya Bhatnagar ◽

Vijay Kumar Koli

Keyword(s):

Plant Species ◽

Forest Fires ◽

Habitat Management ◽

Fleshy Fruit ◽

Feeding Strategies ◽

Western India ◽

Mountain Range ◽

Local Pressure ◽

Dendrocalamus Strictus ◽

Helicteres Isora

Abstract Background Feeding strategies assessment of endangered species during food limited seasons is important in order to understand their niche and advise effective habitat management steps. We assessed the four-horned antelope (Tetracerus quadricornis) seasonal diet from April 2014 to March 2015, in three wildlife sanctuaries in western India, namely, Sitamata, Kumbhalgarh, and Phulwari-ki-nal Wildlife Sanctuaries. Opportunistic focal animal sampling method was used in five 1 km paths in each sanctuary to take feeding observations. Each transect was walked three times a day (morning 06:00-10:00 h; mid-day 10:00-14:00 h; evening 15:00-18:00 h), 1 day a month, during 12 months, with a total of 540 surveys divided between 15 paths. The diet data was categorized into different plant categories. Results A total of 532 feeding records from 85 animal sightings were noted with a mean (± SD) of 14.78 ± 10.04 feeding records/month. Feeding was observed on 63 plant species belonging to 23 families. The highest feeding records noted were on trees (60.91%) in the diet followed by shrubs (20.49%), grasses (16.92%), forbs (1.50%), and climbers (0.18%) respectively. Most of the plant species consumed were from Fabaceae (n = 17) and Poaceae (n = 12) families. The overall browse-grass ratio was 83.08-16.92% (88.02-11.98% for Sitamata WLS; 82.11-17.89% for Kumbhalgarh WLS; 79.10-20.90% for Phulwari-ki-nal WLS). Leaves were the most consumed part of the plants (64.10%), followed by dry fruit (16.55%), fleshy fruit (13.34%), flowers (2.82%), buds (2.06%), and twigs (1.13%) respectively. Use of fleshy fruits, dry fruits, and trees showed significant seasonal dietary difference (P < 0.05) in all three sanctuaries. Conclusions Tetracerus quadricornis was found to consume more browse species than grasses. We recommend conservation and promotion of natural plant regeneration, in particular for the plant species that were the most consumed by four-horned antelope, namely, Aristida adscensionis, Dendrocalamus strictus, Dichrostachys cinerea, Acacia leucophloea, Butea monosperma, Helicteres isora, Ziziphus nummularia, and Ziziphus xylopyrus. Conservation of grassland patches, minimizing local pressure, and planning, construction, and maintenance of fire lines prior to timing of forest fires would help to protected T. quadricornis habitat in all three sanctuaries.

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