bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two-Dimensional Computer Simulation of Salinity Gradient Solar Pond Operation
Authors: Mehdizadeh Minoo , Ahmadi Goodarz 
Published: December 2014

This study is concerned with computer modeling of flow and thermal analysis of solar ponds with a salinity gradient. Solar ponds have been used as an efficient and environmentally friendly approach for collection of solar energy for low temperature thermal applications. A two-dimensional unsteady computational fluid dynamic (CFD) model was developed and used for numerical study of stability analysis of the pond, as well as heat and mass transfer in the salt gradient solar ponds. Salinity gradient was created in order to stabilize the pond and to restrict convective motions induced by buoyancy driven solar radiation heating during the period of operation.
Fluent® commercial software was enhanced with the implementation of User Defined Functions (UDF) and was used in these simulations. The user defined scalar model was included for analyzing the convection and diffusion of the salt concentration in the solar pond. In addition, user defined functions were developed for relating the water density to temperature and salt concentration, as well as, the amount of solar radiation absorption in the solar pond as functions of thermo-physical properties. In the absence of flow exchange, the natural convection in the pond was simulated and the stability of the pond was verified. Development of salt concentration was also studied, and time evolution of temperature distribution in a small scale salinity gradient solar pond was analyzed. For the case of flow exchange at the bottom of the pond, the energy production was evaluated, and the temperature, concentration and flow field were simulated.
Thermal Modeling of a Wireline Tool for Ultra-High Temperatures
Authors: Sur Aritra , Kouchmeshky Babak , Satti Rajani 
Published: December 2014

The drive to obtain more accurate petrophysical information from deeper wells has led to the demand for operating various downhole tools at higher temperatures for longer time periods. If the borehole temperature reaches values higher than 175°C, it is considered a high temperature (HT) well. In HT wells, reliability of the electronic components of the logging tools is a major concern. One way to address the concern is through using a thermal flask to reduce the heat flow rate from the formation to the tool and evenly distribute the heat generated by the internal electronic components.
Optimizing the design of the aforementioned thermal flask is very important in providing a longer operative time for the tool before the temperature of the sensitive electronic parts reaches a critical threshold. To obtain the sensitive parameters for designing the flask, the thermal transport inside the tool must be accurately modeled.
In this work, high fidelity FEA and CFD-based transient thermal models are developed for thermal transport in a flask for an ultra-high temperature wireline tool. Two models with different levels of complexity are presented. The models are verified by experimental results and the physical insights obtained from them presented. The predictive capability of the models is used to provide recommendations for safe operating time for various environmental conditions which prevail in the formations. The results obtained from the models can also be used for optimizing the performance of the future generation of the tool and reducing the amount of time spent in unnecessary trip outs.
A Performance Prediction Model for Low-Speed Centrifugal Fans
Authors: Lee Yu-Tai , Wolfe Tristan , Slipper Michael E. 
Published: December 2014

A generalized model for mapping the trend of the performance characteristics of a double-discharge centrifugal fan is developed based on the work by Casey and Robinson (C&R) which formulated compressor performance maps for tip-speed Mach numbers ranging from 0.4 to 2 using test data obtained from turbochargers with vaneless diffusers. The current paper focuses on low-speed applications for Mach number below 0.4. The C&R model uses four non-dimensional parameters at the design condition including the flow coefficient, the work input coefficient, the tip-speed Mach number and the polytropic efficiency, in developing a prediction model that requires limited geometrical knowledge of the centrifugal turbomachine. For the low-speed fan case, the C&R formulas are further extended to a low-speed, incompressible analysis.
The effort described in this paper begins by comparing generalized results using efficiency data obtained from a series of fan measurements to that using the C&R model. For the efficiency map, the C&R model is found to heavily depend on the ratio of the flow coefficient at peak efficiency to that at the choke flow condition. Since choke flow is generally not applicable in the low-speed centrifugal fan operational environment, an alternate, but accurate estimation method based on fan free delivery derived from the fan test data is presented. Using this new estimation procedure, the modified C&R model predicts reasonably well using the double-discharge centrifugal fan data for high flow coefficients, but fails to correlate with the data for low flow coefficients. To address this undesirable characteristic, additional modifications to the C&R model are also presented for the fan application at low flow conditions.
A Reynolds number correction is implemented in the work input prediction of the C&R model to account for low-speed test conditions. The new model provides reasonable prediction with the current fan data in both work input and pressure rise coefficients. Along with the developments for the efficiency and work input coefficient maps, the use of fan shut-off and free delivery conditions are also discussed for low-speed applications.
Shared-Memory Parallelization for Two-Way Coupled Euler-Lagrange Modeling of Bubbly Flows
Authors: Ma Jingsen , Hsiao Chao-Tsung , Chahine Georges L. 
Published: December 2014

Cavitating bubbly flows are encountered in many engineering problems involving propellers, pumps, valves, ultrasonic biomedical applications, … etc. In this contribution an OpenMP parallelized Euler-Lagrange model of two-phase flow problems and cavitation is presented. The two-phase medium is treated as a continuum and solved on an Eulerian grid, while the discrete bubbles are tracked in a Lagrangian fashion with their dynamics computed. The intimate coupling between the two description levels is realized through the local void fraction, which is computed from the instantaneous bubble volumes and locations, and provides the continuum properties. Since, in practice, any such flows will involve large numbers of bubbles, schemes for significant speedup are needed to reduce computation times. We present here a shared-memory parallelization scheme combining domain decomposition for the continuum domain and number decomposition for the bubbles; both selected to realize maximum speed up and good load balance. The Eulerian computational domain is subdivided based on geometry into several subdomains, while for the Lagrangian computations, the bubbles are subdivided based on their indices into several subsets. The number of fluid subdomains and bubble subsets are matched with the number of CPU cores available in a share-memory system. Computation of the continuum solution and the bubble dynamics proceeds sequentially. During each computation time step, all selected OpenMP threads are first used to evolve the fluid solution, with each handling one subdomain. Upon completion, the OpenMP threads selected for the Lagrangian solution are then used to execute the bubble computations. All data exchanges are executed through the shared memory. Extra steps are taken to localize the memory access pattern to minimize non-local data fetch latency, since severe performance penalty may occur on a Non-Uniform Memory Architecture multiprocessing system where thread access to non-local memory is much slower than to local memory.
This parallelization scheme is illustrated on a typical non-uniform bubbly flow problem, cloud bubble dynamics near a rigid wall driven by an imposed pressure function.
Preliminary Fluid Dynamic Analysis of Turbulent Flat and Ribbed Square Duct via CFD Approach
Authors: Mereu Riccardo , Lampitella Paolo , Inzoli Fabio 
Published: December 2014

A preliminary numerical study of the fluid dynamic behavior of flat and ribbed square duct is presented. Fluid dynamics of two configurations is analyzed via Reynolds Averaged Navier Stokes (RANS) modeling in order to underline the main characteristics of each configuration and to give some information at global and local level. This kind of modeling is used as base for setting up a more detailed analysis such as Direct Numerical Simulation (DNS).
Flat and ribbed square duct with a Reynolds number based on bulk velocity and hydraulic diameter of 10320 (Reτ=600 for the flat configuration) are analyzed and the results of the flat configuration are compared with available results obtained via DNS approach.
The ribbed square duct is characterized by a two-pass configuration (aligned ribs in the top and bottom walls), with the duct height about six times the height of the obstacles for a blockage ratio of about 30%. Finally a pitch ratio (rib spacing to rib height) of 10 is used in order to obtain a k-type roughness permitting the flow to reattach before the next obstacle.
Advanced U-RANS and RANS models such as Reynolds Stress Models (RSM), Explicit Algebraic Stress Models (EASM), v2f, and two-equation low Reynolds models have been used and compared.
In this direction the validated results obtained for the smooth square duct are used to select the most appropriate RANS models and to evaluate their performance for a ribbed square duct at the same Reynolds number.
A periodic configuration including one rib and considering the flow fully developed is used to reduce computational costs. The results of the ribbed square duct are hence analyzed in order to evaluate characteristics such as domain and mesh size.
Comprehensive Soft Impact Damage Methodology for Advanced High Bypass Ratio Turbofan Engines
Authors: Song Yangkun , Bayandor Javid 
Published: December 2014

Foreign object strikes are one of the major aviation incidents that cause tremendous risk to both the aircraft and passengers, the adverse implications of which can ripple through the aviation industry. The demand for air transportation has been on the rise, leading to foreign object ingestion into the engines becoming one of the most threatening scenarios. In January 2009, Flight 1549 took off from LaGuardia Airport in New York City and struck a flock of Canadian Geese during takeoff. Both engines ingested birds, resulting in mid-air catastrophic engine failure. Fortunately, none of the damaged engine components penetrated into the cabin and the aircraft successfully completed an emergency landing on the Hudson River without incurring any casualties.
In this work, explicit finite element strategies have been adopted to model the Fluid-Solid Interactions (FSI) present in a bird ingestion scenario. Taking into account the fluidic composition of bird bodies, a proper methodology to model the Fluid-Solid Interaction was implemented. The investigations were aimed to understand the significance of impact force histograms in an accurately represented model, analyze shockwave propagations and reflections during the impact window, and perform parametric studies to highlight a superior representation for the Fluid-Solid Interaction (FSI). The paper presents a modern explicit finite element methodology adopted to accurately model bird ingestion into a complex turbomachinery forward section and analyze subsequent failure sequencing of the relevant structural components within the system.
Steady-State and Unsteady Simulations of a High Velocity Jet Into a Venturi Shaped Pipe
Authors: Semlitsch Bernhard , Laurendeau Estelle , Mihăescu Mihai 
Published: December 2014

A jet pump consists mainly of a convergent-divergent Venturi shaped duct where a primary stream is applied with the role of entraining a secondary jet. Due to their simple and reliable concept, jet pumps are used in miscellaneous applications. Performance optimization of a jet pump has to be performed for various operation conditions. Thus, numerically robust and cheap models, able to predict accurately the performance parameters of such devices are necessary. Reynolds Averaged Navier-Stokes based formulations are computationally efficient to predict the performance of a jet pump. However, these simulations rely on turbulence closure coefficients, which need to be validated with experimental observations. Large Eddy Simulation solves the most energetic structures in the flow field and it can be used to capture the flow dynamics. On the experimental side, confined geometries challenge the investigation capabilities to capture the flow field accurately and in all the details.
The flow field in the jet pump is investigated using Large Eddy Simulation approach and a steady state Reynolds Averaged Navier-Stokes formulation. The flow field solutions obtained with the two numerical tools are compared. A reasonable agreement for the velocity and pressure contours could be achieved. However, the turbulence kinetic energy distribution and the entrained mass flow rate are predicted to be distinct. The difference in entrained mass flow rate leads to differences in jet pump efficiency estimation.
Design and Experimental Study on the Surge Performance Improvement by the Effects of Bleed Slot Casing of a Centrifugal Compressor
Authors: Kim Hong Won , Chung Jae Hoon , Lee Hyo Seong , Choi Min Ouk 
Published: December 2014

The primary design goal of a compressor is focused on improving efficiency. Secondary objective is to widen the compressor’s operating range. This paper presents a numerical and experimental investigation of the influence of the bleed slot to enlarge operating range for the 1.2MW class centrifugal compressor installed in a turbocharger. The main design parameters of the bleed slot casing are upstream slot position, inlet pipe slope, downstream slot position and width. The DOE (design of experiment) method was carried out to optimize the casing design. Numerical analyses were done by the commercial code ANSYS-CFX based on the three dimensional Reynolds-averaged Navier-Stokes equations. From the analysis, as the downstream slot position and width are smaller and upstream position is located away from impeller inlet, efficiency and pressure ratio are increased.
Experimental works were done with and without the bleed slot casing. The simulation results were in good agreement with the test data. In case without the bleed slot casing, the surge margin value came out to be only 11.8% but with the optimized bleed slot design, the surge margin reached 23%. Therefore, the surge margin increase of 11.2% was achieved.
Colonization in the Photic Zone and Subsequent Changes during Sinking Determine Bacterial Community Composition in Marine Snow
Authors: Thiele Stefan , Fuchs Bernhard M. , Amann Rudolf , Iversen Morten H. 
Published: December 2014

ABSTRACT

Due to sampling difficulties, little is known about microbial communities associated with sinking marine snow in the twilight zone. A drifting sediment trap was equipped with a viscous cryogel and deployed to collect intact marine snow from depths of 100 and 400 m off Cape Blanc (Mauritania). Marine snow aggregates were fixed and washed
in situ
to prevent changes in microbial community composition and to enable subsequent analysis using catalyzed reporter deposition fluorescence
in situ
hybridization (CARD-FISH). The attached microbial communities collected at 100 m were similar to the free-living community at the depth of the fluorescence maximum (20 m) but different from those at other depths (150, 400, 550, and 700 m). Therefore, the attached microbial community seemed to be “inherited” from that at the fluorescence maximum. The attached microbial community structure at 400 m differed from that of the attached community at 100 m and from that of any free-living community at the tested depths, except that collected near the sediment at 700 m. The differences between the particle-associated communities at 400 m and 100 m appeared to be due to internal changes in the attached microbial community rather than
de novo
colonization, detachment, or grazing during the sinking of marine snow. The new sampling method presented here will facilitate future investigations into the mechanisms that shape the bacterial community within sinking marine snow, leading to better understanding of the mechanisms which regulate biogeochemical cycling of settling organic matter.
Engineering of Glarea lozoyensis for Exclusive Production of the Pneumocandin B
0
Precursor of the Antifungal Drug Caspofungin Acetate
Authors: Chen Li , Yue Qun , Li Yan , Niu Xuemei , Xiang Meichun , Wang Wenzhao , Bills Gerald F. , Liu Xingzhong , An Zhiqiang 
Published: December 2014

ABSTRACT

Pneumocandins produced by the fungus
Glarea lozoyensis
are acylated cyclic hexapeptides of the echinocandin family. Pneumocandin B
0
is the starting molecule for the first semisynthetic echinocandin antifungal drug, caspofungin acetate. In the wild-type strain, pneumocandin B
0
is a minor fermentation product, and its industrial production was achieved by a combination of extensive mutation and medium optimization. The pneumocandin biosynthetic gene cluster was previously elucidated by a whole-genome sequencing approach. Knowledge of the biosynthetic cluster suggested an alternative way to produce exclusively pneumocandin B
0
. Disruption of
GLOXY4
, encoding a nonheme, α-ketoglutarate-dependent oxygenase, confirmed its involvement in
l
-leucine cyclization to form 4
S
-methyl-
l
-proline. The absence of 4
S
-methyl-
l
-proline abolishes pneumocandin A
0
production, and 3
S
-hydroxyl-
l
-proline occupies the hexapeptide core's position 6, resulting in exclusive production of pneumocandin B
0
. Retrospective analysis of the
GLOXY4
gene in a previously isolated pneumocandin B
0
-exclusive mutant (ATCC 74030) indicated that chemical mutagenesis disrupted the
GLOXY4
gene function by introducing two amino acid mutations in GLOXY4. This one-step genetic manipulation can rationally engineer a high-yield production strain.
Improved Antimicrobial Activities of Synthetic-Hybrid Bacteriocins Designed from Enterocin E50-52 and Pediocin PA-1
Authors: Tiwari Santosh Kumar , Sutyak Noll Katia , Cavera Veronica L. , Chikindas Michael L. 
Published: December 2014

ABSTRACT

Two hybrid bacteriocins, enterocin E50-52/pediocin PA-1 (EP) and pediocin PA-1/enterocin E50-52 (PE), were designed by combining the N terminus of enterocin E50-52 and the C terminus of pediocin PA-1 and by combining the C terminus of pediocin PA-1 and the N terminus of enterocin E50-52, respectively. Both hybrid bacteriocins showed reduced MICs compared to those of their natural counterparts. The MICs of hybrid PE and EP were 64- and 32-fold lower, respectively, than the MIC of pediocin PA-1 and 8- and 4-fold lower, respectively, than the MIC of enterocin E50-52. In this study, the effect of hybrid as well as wild-type (WT) bacteriocins on the transmembrane electrical potential (ΔΨ) and their ability to induce the efflux of intracellular ATP were investigated. Enterocin E50-52, pediocin PA-1, and hybrid bacteriocin PE were able to dissipate ΔΨ, but EP was unable to deplete this component. Both hybrid bacteriocins caused a loss of the intracellular concentration of ATP. EP, however, caused a faster efflux than PE and enterocin E50-52. Enterocin E50-52 and hybrids PE and EP were active against the Gram-positive and Gram-negative bacteria tested, such as
Micrococcus luteus
,
Salmonella enterica
serovar Enteritidis 20E1090, and
Escherichia coli
O157:H7. The hybrid bacteriocins designed and described herein are antimicrobial peptides with MICs lower those of their natural counterparts. Both hybrid peptides induce the loss of intracellular ATP and are capable of inhibiting Gram-negative bacteria, and PE dissipates the electrical potential. In this study, the MIC of hybrid bacteriocin PE decreased 64-fold compared to the MIC of its natural peptide counterpart, pediocin PA-1. Inhibition of Gram-negative pathogens confers an additional advantage for the application of these peptides in therapeutics.
Clearance of Escherichia coli O157:H7 Infection in Calves by Rectal Administration of Bovine Lactoferrin
Authors: Kieckens E. , Rybarczyk J. , De Zutter L. , Duchateau L. , Vanrompay D. , Cox E. 
Published: December 2014

ABSTRACT

Enterohemorrhagic
Escherichia coli
(EHEC) strains, of which
E. coli
O157:H7 is the best-studied serotype, are an important group of foodborne pathogens causing severe illness in humans worldwide. The main reservoirs for EHEC are ruminants, mostly cattle, which harbor the bacteria in their intestinal tracts without showing clinical symptoms. In this study, we used bovine lactoferrin, a natural occurring bactericidal and immunomodulating protein, as an antibacterial agent against EHEC infection in cattle. Nine 3-month-old Holstein-Friesian calves were experimentally infected with EHEC (strain NCTC12900). Three animals received a daily rectal spray treatment with bovine lactoferrin, three animals received an oral treatment, and three animals served as a control group. Blood samples were collected weekly and fecal samples twice weekly to monitor antibody responses and fecal excretion, respectively. Animals in the rectal group ceased shedding within 26 days of the experimental treatment and remained negative. This beneficial effect of bovine lactoferrin was not observed in the oral group, where animals were still shedding at the time of euthanasia (day 61). All groups developed serum responses, but no clear differences could be observed between the groups. However, the results indicate that the use of bovine lactoferrin as a rectal treatment can be a useful strategy to preclude further transmission of EHEC infections from cattle to humans.
Interventions targeting the elderly population to reduce emergency department utilisation: a literature review
Authors: Fan Lijun , Lukin William , Zhao Jingzhou , Sun Jiandong , Hou Xiang-Yu 
Published: December 2014

ObjectiveHigh utilisation of emergency department (ED) among the elderly is of worldwide concern. This study aims to review the effectiveness of interventions targeting the elderly population in reducing ED utilisation.MethodsMajor biomedical databases were searched for relevant studies. Qualitative approach was applied to derive common themes in the myriad interventions and to critically assess the variations influencing interventions’ effectiveness. Quality of studies was appraised using the Effective Public Health Practice Project (EPPHP) tool.Results36 studies were included. Nine of 16 community-based interventions reported significant reductions in ED utilisation. Five of 20 hospital-based interventions proved effective while another four demonstrated failure. Seven key elements were identified. Ten of 14 interventions associated with significant reduction on ED use integrated at least three of the seven elements. All four interventions with significant negative results lacked five or more of the seven elements. Some key elements including multidisciplinary team, integrated primary care and social care often existed in effective interventions, while were absent in all significantly ineffective ones.ConclusionsThe investigated interventions have mixed effectiveness. Our findings suggest the hospital-based interventions have relatively poorer effects, and should be better connected to the community-based strategies. Interventions seem to achieve the most success with integration of multi-layered elements, especially when incorporating key elements such as a nurse-led multidisciplinary team, integrated social care, and strong linkages to the longer-term primary and community care. Notwithstanding limitations in generalising the findings, this review builds on the growing body of evidence in this particular area.