bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Constrained Level Set Method for Simulating the Formation of Liquid Bridges
Authors: He Dongdong , Huang Huaxiong 
Published: May 2012

AbstractIn this paper, we investigate the dynamic process of liquid bridge formation between two parallel hydrophobic plates with hydrophilic patches, previously studied in [1]. We propose a dynamic Hele-Shaw model to take advantage of the small aspect ratio between the gap width and the plate size. A constrained level set method is applied to solve the model equations numerically, where a global constraint is imposed in the evolution [2] stage together with local constraints in the reinitialization [3] stage of level set function in order to limit numerical mass loss. In contrast to the finite element method used in [2], we use a finite difference method with a 5th order HJWENO scheme for spatial discretization. To illustrate the effectiveness of the constrained method, we have compared the results obtained by the standard level set method with those from the constrained version. Our results show that the constrained level set method produces physically reasonable results while that of the standard method is less reliable. Our numerical results also show that the dynamic nature of the flow plays an important role in the process of liquid bridge formation and criteria based on static energy minimization approach has limited applicability.
Inertial Frame Independent Forcing for Discrete Velocity Boltzmann Equation: Implications for Filtered Turbulence Simulation
Authors: Premnath Kannan N. , Banerjee Sanjoy 
Published: May 2012

AbstractWe present a systematic derivation of a model based on the central moment lattice Boltzmann equation that rigorously maintains Galilean invariance of forces to simulate inertial frame independent flow fields. In this regard, the central moments, i.e. moments shifted by the local fluid velocity, of the discrete source terms of the lattice Boltzmann equation are obtained by matching those of the continuous full Boltzmann equation of various orders. This results in an exact hierarchical identity between the central moments of the source terms of a given order and the components of the central moments of the distribution functions and sources of lower orders. The corresponding source terms in velocity space are then obtained from an exact inverse transformation due to a suitable choice of orthogonal basis for moments. Furthermore, such a central moment based kinetic model is further extended by incorporating reduced compressibility effects to represent incompressible flow. Moreover, the description and simulation of fluid turbulence for full or any subset of scales or their averaged behavior should remain independent of any inertial frame of reference. Thus, based on the above formulation, a new approach in lattice Boltzmann framework to incorporate turbulence models for simulation of Galilean invariant statistical averaged or filtered turbulent fluid motion is discussed.
A Coupled Approach for Fluid Dynamic Problems Using the PDE Framework Peano
Authors: Neumann Philipp , Bungartz Hans-Joachim , Mehl Miriam , Neckel Tobias , Weinzierl Tobias 
Published: May 2012

AbstractWe couple different flow models, i.e. a finite element solver for the Navier-Stokes equations and a Lattice Boltzmann automaton, using the framework Peano as a common base. The new coupling strategy between the meso- and macroscopic solver is presented and validated in a 2D channel flow scenario. The results are in good agreement with theory and results obtained in similar works by Latt et al. In addition, the test scenarios show an improved stability of the coupled method compared to pure Lattice Boltzmann simulations.
High Efficient Numerical Simulation of Infrared Radiation from a Hot Exhaust Nozzle
Authors: Hu Haiyang , Bai Peng , Wang Qiang 
Published: May 2012

AbstractA coupled model, capable of simulating transonic flow, solid heat conduction, species transport, and gas radiation, is developed that provides better computational treatment of infrared radiation from hot exhaust nozzles. The modeling of gas radiation is based on a statistical narrow-band correlated-k analysis, whose parameters are deduced from the HITEMP line-by-line database. To improve computational efficiency, several methods are employed. A mixed analytical-numerical algorithm is described for the stiffness of the two-equation turbulence model and an alternating direction implicit pretreatment for the ill-conditioned matrix appearing in the coupled problem of flow and solid heat conduction. Moreover, an improved multigrid method and a symmetry plane treatment of the radiation transfer-energy equations are also introduced. Four numerical simulations are given to confirm the efficiency and accuracy of the numerical method. Finally, an account of the aerothermodynamics and infrared characteristics for two types of nozzles are presented. The infrared radiation intensity of the Chevron ejecting nozzle is clearly smaller than that of the common axisymmetric ejecting nozzle. All computations can be performed on a personal computer.
Modified Upwinding Compact Scheme for Shock and Shock Boundary Layer Interaction
Authors: Liu Chaoqun , Lu Ping , Oliveira Maria , Xie Peng 
Published: May 2012

AbstractStandard compact scheme and upwinding compact scheme have high order accuracy and high resolution, but cannot capture the shock which is a discontinuity. This work developed a modified upwinding compact scheme which uses an effective shock detector to block compact scheme to cross the shock and a control function to mix the flux with WENO scheme near the shock. The new scheme makes the original compact scheme able to capture the shock sharply and, more importantly, keep high order accuracy and high resolution in the smooth area which is particularly important for shock boundary layer and shock acoustic interactions. Numerical results show the scheme is successful for 2-D Euler and 2-D Navier-Stokes solvers. The examples include 2-D incident shock, 2-D incident shock and boundary layer interaction. The scheme is robust, which does not involve case related parameters.
Fast Multipole Accelerated Boundary Integral Equation Method for Evaluating the Stress Field Associated with Dislocations in a Finite Medium
Authors: Zhao Degang , Huang Jingfang , Xiang Yang 
Published: May 2012

AbstractIn this paper, we develop an efficient numerical method based on the boundary integral equation formulation and new version of fast multipole method to solve the boundary value problem for the stress field associated with dislocations in a finite medium. Numerical examples are presented to examine the influence from material boundaries on dislocations.
High Order Schemes on Three-Dimensional General Polyhedral Meshes — Application to the Level Set Method
Authors: Pringuey Thibault , Cant R. Stewart 
Published: May 2012

AbstractIn this article, we detail the methodology developed to construct arbitrarily high order schemes — linear and WENO — on 3D mixed-element unstructured meshes made up of general convex polyhedral elements. The approach is tailored specifically for the solution of scalar level set equations for application to incompressible two-phase flow problems. The construction of WENO schemes on 3D unstructured meshes is notoriously difficult, as it involves a much higher level of complexity than 2D approaches. This due to the multiplicity of geometrical considerations introduced by the extra dimension, especially on mixed-element meshes. Therefore, we have specifically developed a number of algorithms to handle mixed-element meshes composed of convex polyhedra with convex polygonal faces. The contribution of this work concerns several areas of interest: the formulation of an improved methodology in 3D, the minimisation of computational runtime in the implementation through the maximum use of pre-processing operations, the generation of novel methods to handle complex 3D mixed-element meshes and finally the application of the method to the transport of a scalar level set.
A Spectral Iterative Method for the Computation of Effective Properties Of Elastically Inhomogeneous Polycrystals
Authors: Bhattacharyya Saswata , Heo Tae Wook , Chang Kunok , Chen Long-Qing 
Published: May 2012

AbstractWe report an efficient phase field formalism to compute the stress distribution in polycrystalline materials with arbitrary elastic inhomogeneity and anisotropy The dependence of elastic stiffness tensor on grain orientation is taken into account, and the elastic equilibrium equation is solved using a spectral iterative perturbation method. We discuss its applications to computing residual stress distribution in systems containing arbitrarily shaped cavities and cracks (with zero elastic modulus) and to determining the effective elastic properties of polycrystals and multilayered composites.
Computer Simulation of Helium Effects in Plutonium During the Aging Process of Self-Radiation Damage
Authors: Ao Bingyun , Chen Piheng , Shi Peng , Wang Xiaolin , Hu Wangyu , Wang Liang 
Published: May 2012

AbstractDue to α radioactive decay Pu is vulnerable to aging. The behavior of He in Pu is the foundation for understanding Pu self-radiation damage aging. Molecular dynamics technique is performed to investigate the behavior of defects, the interaction between He and defects, the processes of initial nucleation and growth of He bubble and the dependence of He bubble on the macroscopical properties of Pu. Modified embedded atom method, Morse pair potential and the Lennard-Jones pair potential are used for describing the interactions of Pu-Pu, Pu-He and He-He, respectively. The main calculated results show that He atoms can combine with vacancies to form Hevacancy cluster (i.e., the precursor of He bubble) during the process of self-radiation as a result of high binding energy of an interstitial He atom to vacancy; He bubble’s growth can be dominated by the mechanism of punching out of dislocation loop; the swelling induced by He bubble is very small; grain boundaries give rise to an energetically more favorable zone for the interstitial He atom and self-interstitial atom accumulation than for vacancy accumulation; the process of He release can be identified as the formation of release channel induced by the cracking of He bubble and surface structure.
Runge-Kutta Discontinuous Galerkin Method Using Weno-Type Limiters: Three-Dimensional Unstructured Meshes
Authors: Zhu Jun , Qiu Jianxian 
Published: May 2012

AbstractThis paper further considers weighted essentially non-oscillatory (WENO) and Hermite weighted essentially non-oscillatory (HWENO) finite volume methods as limiters for Runge-Kutta discontinuous Galerkin (RKDG) methods to solve problems involving nonlinear hyperbolic conservation laws. The application discussed here is the solution of 3-D problems on unstructured meshes. Our numerical tests again demonstrate this is a robust and high order limiting procedure, which simultaneously achieves high order accuracy and sharp non-oscillatory shock transitions.
Surgical Treatment Modalities for Complicated Aneurysms and Pseudoaneurysms of Arteriovenous Fistulas
Authors: Belli Sedat , Parlakgumus Alper , Colakoglu Tamer , Ezer Ali , Yildirim Sedat , Moray Gokhan , Haberal Mehmet 
Published: May 2012

Purpose This study was designed to determine the clinical presentation, characteristics, and management of aneurysm/pseudoaneurysm formation (APF) in dialysis access fistulas. Methods The treatment methods and outcomes of 31 patients who underwent surgery for APF in dialysis access fistulas were retrospectively reviewed over a 9-year period. Results We performed 1558 operations for arteriovenous fistulas (AVFs) between 2000 and 2009 at our centre. Of the 1558 operations, 35 were carried out for APFs (2.2%) on 31 patients. Thirty of these operations were restorative. Twenty-two (71%) of these patients had their original access done elsewhere, and all corrective surgeries were performed at our hospital. Approximately 52% of the subjects were female, with a mean age of 45.7 ± 17 years. The mean duration of end-stage renal disease was 70.2 ± 51.5 months. The mean number of AVFs per patient was 2.2 ± 1.5. Synthetic grafts were used in five patients (16.1%). Most of the procedures were left-sided (67.7%) and brachial-cephalic fistulas (48.3%). Among 31 complications, 22 were arterial/venous aneurysms (71%) and nine were pseudoaneurysms (29%). Fourteen patients (46.6%) were treated by excision of the aneurysm and primary suture repair. The post-intervention primary patencies for all revised APFs were 68%, 56%, and 52% at 1, 6, and 12 months, respectively. Dysfunction of AVF (16.1%) and bleeding (12.9%) were the most encountered complications after aneurysmectomy. Conclusion Reformative operations should be considered in cases of urgency and irresponsiveness to endovascular surgery rather than closing the fistulas directly, as it prolongs the duration of AVF patency.
Advances in the electrical stunning and bleeding of ostriches
Authors: Hoffman LC 
Published: May 2012

AbstractThe stunning of ostriches (Struthio camelus) has traditionally been carried out with hand-held tongs whilst birds are held in a restraining area by applying pressure normally from behind by gently pushing on the tail feathers. The area is often a V-shaped structure, high enough that the stunning operator is not kicked. After stunning, the birds are rocked backwards and a rubberised leg clamp placed over the legs at the tarso-metatarsal bone allowing the birds to be chain-shackled by the big toes. This stunning procedure has been replaced by a new restraining and stunning mechanism which completely envelops the ostrich in a padded clamp holder. Double-padded sides restrain the bird's upper thighs and a rubberised foot clamp holds the feet so there is no physical damage to the bird. As the bird is electrically stunned with electrodes placed both sides of the head, the entire stunning box rotates 180° so that toe clamps can be applied without any danger to the stunning operators. Within 20 s of stunning, the birds are bled by means of a complete ventral cut to the neck and/or by thoracic sticking.
Evidence for pain in decapod crustaceans
Authors: Elwood RW 
Published: May 2012

AbstractVast numbers of decapods are used in human food and currently subject to extreme treatments and there is concern that they might experience pain. If pain is indicated then a positive change in the care afforded to this group has the potential to produce a major advance in animal welfare. However, it is difficult to determine pain in animals. The vast majority of animal phyla have a nociceptive ability that enables them to detect potential or actual tissue damage and move away by a reflex response. In these cases there is no need to assume an unpleasant feeling that we call pain. However, various criteria have been proposed that might indicate pain rather than simple nociception. Here, with respect to decapod crustaceans, four such criteria are discussed: avoidance learning, physiological responses, protective motor reactions and motivational trade-offs. The evidence from various experiments indicates that all four criteria are fulfilled and the data are thus consistent with the idea of pain. The responses cannot be explained by nociception alone but, it is still difficult to state categorically that pain is experienced by decapods. However, the evidence is as strong for this group as it is for fish but the idea that fish experience pain has broader acceptance than does the idea of decapod pain. A taxonomic bias is evident in the evaluation of experimental data.
Auditing animal welfare and making practical improvements in beef-, pork- and sheep-slaughter plants
Authors: Grandin T 
Published: May 2012

AbstractA welfare audit that utilises numerically scored, animal-based outcome measures has been used successfully by McDonald's and other restaurant companies for over ten years. In 2010, audit data from two restaurant companies indicated that all 30 of their North American plants rendered 95% or more of the cattle insensible with a single shot from a captive-bolt gun. Eight pork plants that used electrical stunning placed the tongs correctly on 99% or more of the pigs. All animals were insensible prior to hoisting. In 32 beef plants, the percentage of cattle vocalising in the stunning area was 5% or less. In 94% of the beef plants and 86% of the pork plants, none of the animals fell during handling. The worst falling score was 2% in two of the plants. High standards were attained by making simple changes. To improve welfare, plant managers did the following: improved stunner maintenance; installed non-slip floors in stun boxes and unloading ramps; and trained employees. To reduce balking and improve animal movement, the following modifications were made: illumination of dark race entrances; moving of lamps to eliminate reflections; reducing equipment noise; stopping employee yelling; installation of solid sides on races or shields to prevent animals from seeing activity outside the facility; and the elimination of air blowing in the faces of approaching animals. Employees were trained to use behavioural principles of animal handling such as the point of balance and the flight zone. The five numerically scored outcome measures in this audit are critical control points that can detect a variety of problems. They are: i) the percentage of animals stunned effectively with a single application of the stunner; ii) the percentage of animals falling during handling must be 1% or less to pass; iii) the percentage of pigs or cattle vocalising (moo, bellow, squeal) in the stun box or while entering into the stun box must be 5% or less to pass (vocalisation scoring is not used for sheep); iv) the percentage of animals moved with an electric goad; and v) the percentage of animals rendered insensible before hoisting must be 100% to pass an audit. An animal is scored as either silent or as a vocaliser and whether stunned correctly with a single application or not stunned correctly. The audit also contains a list of banned practices that will result in an automatic failure. To maintain improvements in handling, 23 plants have installed video cameras that are monitored by auditors viewing the footage over the internet. These external auditors perform numerical scoring at random times throughout the day. Video auditing over the internet is an important new tool for improving welfare.
Preliminary evaluation of the effectiveness of captive-bolt guns as a killing method without exsanguination for horned and unhorned sheep
Authors: Gibson TJ , Ridler AL , Lamb CR , Williams A , Giles S , Gregory NG 
Published: May 2012

AbstractThe current study aims to make welfare-based recommendations for gun/cartridge combinations and shooting positions that will ensure death of the sheep (horned, unhorned, rams and ewes), without the need for either sticking or pithing. The study examined the pathophysiology of captive-bolt gun (CBG) injuries that result in incomplete concussion leading to death. Behavioural, brainstem and cranial/spinal responses were examined along with gross pathology in 489 animals (116 polled ewes, 134 horned ewes, 117 polled rams and 122 horned rams) following a variety of CBG-cartridge combinations. Shooting horned rams was more challenging than unhorned sheep, partly because minor movements of the head at the time of shooting can result in deflection of the gun by the horns. Marksmanship was the definitive factor: 100% of animals that showed signs of incomplete concussion were found to have been shot incorrectly. The findings will have application when it is necessary to kill sheep on farms for disease control or euthanasia purposes.
Stress at slaughter in cattle: role of reactivity profile and environmental factors
Authors: Terlouw EMC , Bourguet C , Deiss V 
Published: May 2012

AbstractDuring slaughter, cattle may be exposed to many potentially stress-inducing factors, of emotional and physical nature. A series of studies aimed to identify factors that may contribute to slaughter stress. During reactivity tests testing emotional stressors, Blond d’Aquitaine bulls were more reactive than Angus and Limousin bulls. However, no breed differences were found for stress indicators at slaughter. Indicators of post mortem (PM) muscle metabolism were correlated with stress reactions at slaughter, and with behavioural reactions and heart rates during the reactivity tests, including a sudden event and handling. Similarly, in Normand cull cows, stronger behavioural and physiological reactions during the slaughter procedure were associated with faster PM muscle metabolism. Reactions during the reactivity tests were also correlated with stress indicators at slaughter. A Principal Component Analysis indicated that the first and second axes were correlated with reactions to non-familiarity and to social isolation, respectively. Both axes were correlated with stress indicators at slaughter, suggesting that these two aspects contribute significantly to the emotional stress at slaughter. These experiments indicate that stress reactivity at slaughter may be predicted from behavioural and emotional stress reactions during reactivity tests. A third experiment found that compared with normally fed cows, 30-h food-deprived cows showed stronger startle and fear responses in response to a sudden event. Within a group subjected to a physical-effort treatment, compared to normally fed heifers, food-deprived heifers were more reactive to human exposure. This shows that the reactions to a given stressor may increase due to the presence of other stressors. Thus, in cattle, novelty, social disturbances and sudden events may contribute to slaughter stress and the simultaneous presence of several stressors during the slaughter period may exacerbate stress reactions.
Veterinary certificates for emergency or casualty slaughter bovine animals in the Republic of Ireland: are the welfare needs of certified animals adequately protected?
Authors: Cullinane M , O’Sullivan E , Collins G , Collins DM , More SJ 
Published: May 2012

AbstractAll emergency and casualty bovines in the Republic of Ireland that are deemed to be fit for human consumption must be accompanied to the slaughterhouse by an official veterinary certificate (VC). Cullinane et al (2010) conducted a review of bovine cases consigned under veterinary certification to emergency (ES) and casualty (CS) slaughter in the Republic of Ireland during 2006 to 2008. The current paper further evaluates these results, with emphasis on the period of validity, transport distance and transport conditions, and considers whether the current VC adequately protects welfare. Of 1,255 veterinary certificates, the median time between certification and slaughter was 1 (minimum 0, maximum 452) day, with one-fifth in excess of three days. The median straight-line distance between farm and slaughterhouse was 22 km; 82 and 98% study animals were transported distances of no more than 40 and 100 km, respectively. In 27% of VCs, no slaughterhouse was designated; hence the transport distance was not limited. In 77% of all cases, the disability/injury was related to the locomotor system, including 35% with limb fractures. Veterinary certification of the latter as being fit for transport appears to have been in contravention of animal transport and welfare legislation. The welfare of animals would be improved if each VC included a certified period of validity. In future, veterinary certificates should state clearly a maximum period of validity between certification and slaughter, a maximum distance that the animal should be transported and a minimum level of comfort under which the animal must be transported. Historically, in the Republic of Ireland, there was no suitable non-transport alternative available to cattle producers wanting to salvage an otherwise healthy animal that had suffered an accident or injury resulting in acute pain. An alternative is now available, with the introduction of an on-farm emergency slaughter policy.