Silveira, Raquel Kelner; Coelho, Antônio Roberto Barros; Pinto, Flávia Cristina Morone; de Albuquerque, Amanda Vasconcelos; de Melo Filho, Djalma Agripino; de Andrade Aguiar, José Lamartine
2016-08-01
The use of meshes for treatment of hernias continues to draw attention of surgeons and the industry in the search of an ideal prosthesis. The purpose of this work is to use meshes manufactured from bacterial cellulose, evaluate their organic tissue interaction and compare with an expanded polytetrafluorethylene (ePTFE's) prosthesis used to repair acute defect of muscle aponeurotic induced in rats. Forty-five male Wistar rats were classified using the following criteria: (1) surgical repair of acute muscle aponeurotic defect with perforated bacterial cellulose film (PBC; n = 18); (2) compact bacterial cellulose film (CBC; n = 12) and (3) ePTFE; (n = 15). After postoperative period, rectangles (2 × 3 cm) including prosthesis, muscles and peritoneum were collected for biomechanical, histological and stereological analysis. In all cases, the maximum acceptable error probability for rejecting the null hypothesis was 5 %. Between PBC and CBC samples, the variables of strain (P = 0.011) and elasticity (P = 0.035) were statistically different. The same was found between CBC and ePTFE (elasticity, P = 0.000; strain, P = 0.009). PBC differed from CBC for giant cells (P = 0.001) and new blood vessels (P = 0.000). In conclusion, there was biological integration and biomechanical elasticity of PBC; therefore, we think this option should be considered as a new alternative biomaterial for use as a bio prosthesis. PMID:27379627
Sub-aponeurotic fluid collections in infancy
International Nuclear Information System (INIS)
AIM: To describe the radiological features and natural history of sub-aponeurotic fluid collections presenting after the neonatal period. MATERIALS AND METHODS: All cases of sub-aponeurotic scalp fluid collection presenting to the radiology department between June 1996 and June 2000 were reviewed. Note was made of the birth history, the radiographic and ultrasound features and the natural history (including any treatment) of the collection. RESULTS: Seven cases of sub-aponeurotic fluid collections were identified. There were six infants who presented 3·5-18 weeks (mean nine weeks) after delivery, four of whom had had ventouse-assisted delivery. The last case was in a seven-year-old child who presented one month after minor head trauma. Clinical examination revealed non-tender, soft, mobile and fluctuant scalp swellings in all patients. Ultrasound identified sonolucent fluid collections of between 5 and 24 mm depth in the sub-aponeurotic space. No skull fractures were identified. Six patients were treated conservatively and one had fluid aspirated and a compression bandage applied. All cases resolved 2-24 weeks after diagnosis and there were no long-term sequelae. CONCLUSION: Sub-aponeurotic scalp collections presenting after the neonatal period are usually associated with ventouse-assisted delivery ultrasound is useful for diagnosis. The condition is benign and resolution occurs with conservative treatment. Hopkins, R.E. et al. (2002)
Axelrod's Model with Surface Tension
Pace, Bruno
2012-01-01
In this work we propose a subtle change in Axelrod's model for the dissemination of culture. The mechanism consists of excluding non-interacting neighbours from the set of neighbours out of which an agent is drawn for potential cultural interactions. Although the alteration proposed does not alter topologically the configuration space, it yields significant qualitative changes, specifically the emergence of surface tension, driving the system in some cases to metastable states. The transient behaviour is considerably richer, and cultural regions have become stable leading to the formation of different spatio-temporal structures. A new metastable "glassy" phase emerges between the globalised phase and the polarised, multicultural phase.
Modelling Tension Stiffening in Reinforced Concrete Structures
DEFF Research Database (Denmark)
Christiansen, Morten Bo; Nielsen, Mogens Peter
1997-01-01
Part I of the present thesis deals with crack formation in reinforced concrete and the phenomenon of tension stiffening in concrete tension rods reinforced with deformed bars.Two physical models are presented for uniaxial tension, and they are modified for application on beams subjected to pure...... crack widths predicted by the models are compared with experimental data from tests on tension rods as well as flexural beams.In the light of the simple assumptions made and the random nature of cracking, the accordance between the models and the test data is quite good.Part II of the present thesis...... the light of the simple assumptions, quite good accordance is found.Part III of the thesis deals with the deformations of a beam symmetrically loaded by two concentrated forces. In the shear-flexure beam model it is assumed that the load is carried by means of a stringer system and a diagonal stress...
Dynamical Modeling of Surface Tension
Brackbill, Jeremiah U.; Kothe, Douglas B.
1996-01-01
In a recent review it is said that free-surface flows 'represent some of the difficult remaining challenges in computational fluid dynamics'. There has been progress with the development of new approaches to treating interfaces, such as the level-set method and the improvement of older methods such as the VOF method. A common theme of many of the new developments has been the regularization of discontinuities at the interface. One example of this approach is the continuum surface force (CSF) formulation for surface tension, which replaces the surface stress given by Laplace's equation by an equivalent volume force. Here, we describe how CSF formulation might be made more useful. Specifically, we consider a derivation of the CSF equations from a minimization of surface energy as outlined by Jacqmin (1996). This reformulation suggests that if one eliminates the computation of curvature in terms of a unit normal vector, parasitic currents may be eliminated. For this reformulation to work, it is necessary that transition region thickness be controlled. Various means for this, in addition to the one discussed by Jacqmin (1996), are discussed.
A continuum method for modeling surface tension
Brackbill, J. U.; Kothe, D. B.; Zemach, C.
1992-01-01
In the novel method presented for modeling the effects of surface tension on fluid motion, the interfaces between fluids with different, color-represented properties are finite-thickness transition regions across which the color varies continuously. A force density proportional to the surface curvature of constant color is defined at each point in the transition region; this force-density is normalized in such a way that the conventional description of surface tension on an interface is recovered when the ratio of local transition-reion thickness to local curvature radius approaches zero. The properties of the method are illustrated by computational results for 2D flows.
Surface tension in Kac glass models
International Nuclear Information System (INIS)
In this paper we study a distance-dependent surface tension, defined as the free-energy cost for putting metastable states at a given distance. This will be done in the framework of a disordered microscopic model with Kac interactions that can be solved in the mean-field limit
Surface Tension in Kac Glass Models
Zarinelli, Elia; Franz, Silvio
2009-01-01
In this paper we study a distance-dependent surface tension, defined as the free-energy cost to put metastable states at a given distance. This will be done in the framework of a disordered microscopic model with Kac interactions that can be solved in the mean-field limit.
Toward a general psychological model of tension and suspense
Directory of Open Access Journals (Sweden)
Moritz eLehne
2015-02-01
Full Text Available Tension and suspense are powerful emotional experiences that occur in a wide variety of contexts (e.g., in music, film, literature, and everyday life. The omnipresence of tension experiences suggests that they build on very basic cognitive and affective mechanisms. However, the psychological underpinnings of tension experiences remain largely unexplained, and tension and suspense are rarely discussed from a general, domain-independent perspective. In this paper, we argue that tension experiences in different contexts (e.g., musical tension or suspense in a movie build on the same underlying psychological processes. We discuss key components of tension experiences and propose a domain-independent model of tension and suspense. According to this model, tension experiences originate from states of conflict, instability, dissonance, or uncertainty that trigger predictive processes directed at future events of emotional significance. We also discuss possible neural mechanisms underlying experiences of tension. The model provides a theoretical framework that can inform future empirical research on tension phenomena.
Toward a general psychological model of tension and suspense.
Lehne, Moritz; Koelsch, Stefan
2015-01-01
Tension and suspense are powerful emotional experiences that occur in a wide variety of contexts (e.g., in music, film, literature, and everyday life). The omnipresence of tension and suspense suggests that they build on very basic cognitive and affective mechanisms. However, the psychological underpinnings of tension experiences remain largely unexplained, and tension and suspense are rarely discussed from a general, domain-independent perspective. In this paper, we argue that tension experiences in different contexts (e.g., musical tension or suspense in a movie) build on the same underlying psychological processes. We discuss key components of tension experiences and propose a domain-independent model of tension and suspense. According to this model, tension experiences originate from states of conflict, instability, dissonance, or uncertainty that trigger predictive processes directed at future events of emotional significance. We also discuss possible neural mechanisms underlying tension and suspense. The model provides a theoretical framework that can inform future empirical research on tension phenomena. PMID:25717309
Managing Tensions Between New and Existing Business Models
DEFF Research Database (Denmark)
Sund, Kristian J.; Bogers, Marcel; Villarroel Fernandez, Juan Andrei;
2016-01-01
Exploring new business models may be a good way to stay competitive, but doing so can create tensions internally, in areas such as organizational structure and competition for resources. Companies exploring business model innovation may not recognize the inevitability of these tensions and thus b...
Managing Tensions Between New and Existing Business Models
DEFF Research Database (Denmark)
Sund, Kristian J.; Bogers, Marcel; Villarroel, J. Andrei;
2016-01-01
The search for new business models forces established companies to experiment with organizational designs — and leads to tensions that should be anticipated and carefully managed.......The search for new business models forces established companies to experiment with organizational designs — and leads to tensions that should be anticipated and carefully managed....
Surface tension in the dilute Ising model. The Wulff construction
Wouts, Marc
2008-01-01
We study the surface tension and the phenomenon of phase coexistence for the Ising model on $\\mathbbm{Z}^d$ ($d \\geqslant 2$) with ferromagnetic but random couplings. We prove the convergence in probability (with respect to random couplings) of surface tension and analyze its large deviations : upper deviations occur at volume order while lower deviations occur at surface order. We study the asymptotics of surface tension at low temperatures and relate the quenched value $\\tau^q$ of surface t...
Longitudinal Multilevel Modeling of Facial Pain, Muscle Tension, and Stress.
Glaros, A G; Marszalek, J M; Williams, K B
2016-04-01
The role of masticatory muscle activation on pain in temporomandibular muscle and joint disorders (TMJD) is controversial. This single-group, prospective panel study examined the relationships among masticatory muscle tension, emotional distress, and TMJD pain in a sample of 7,023 observations obtained from 171 individuals using longitudinal multilevel modeling. Three main hypotheses were tested. The first posited that emotional distress and muscle tension directly influenced pain (hypothesis 1a: Distress → TMJD Pain; hypothesis 1b: Muscle Tension → TMJD Pain). The second posited that emotional distress directly influenced muscle tension (Distress → Muscle Tension), and the third posited that the effect of emotional distress on pain was mediated by muscle tension (Distress → Muscle Tension → TMJD pain). We also examined the fit of the data to possible alternative models. All the data used in this study were collected via an experience sampling methodology. The fit of the preferred models was better than that of the alternative models, with the preferred models explaining large proportions of the data, especially for level 2 variance (hypothesis 1a = 41% variance; hypothesis 1b = 69% variance; hypothesis 2 = 48% variance). In the mediation model, the addition of muscle tension to the model reduced the impact of emotional distress. The findings support a causal role for masticatory muscle tension in TMJD pain. Clinically, the results suggest that addressing tension and other oral parafunctions in those diagnosed with TMJDs should be an important part of the conservative, noninvasive care of individuals diagnosed with the myofascial pain or arthralgia of TMJD. PMID:26758381
Classical solutions for Hele-Shaw models with surface tension
Escher, Joachim; Simonett, Gieri
1997-01-01
It is shown that surface tension effects on the free boundary are regularizing for Hele-Shaw models. This implies, in particular, existence and uniqueness of classical solutions for a large class of initial data. As a consequence, we give a rigorous proof of the fact that homogeneous Hele-Shaw flows with positive surface tension are volume preserving and area shrinking.
Modified levator aponeurotic advancement with delayed postoperative office revision.
Mauriello, J A; Abdelsalam, A
1998-07-01
The results of a "modified" levator aponeurotic advancement were reviewed to determine the appropriate indications and optimum timing for office revision after blepharoptosis repair. The levator advancement was modified as follows: 1) elimination of epinephrine from the local anesthetic so as not to stimulate the Müller muscle, 2) use of a 6-0 silk rather than a monofilament nonabsorbable suture to secure the advanced levator to avoid possible cheese-wiring and late recurrence, and 3) excision of a strip of preseptal orbicularis muscle just above the tarsal border to create surgically apposed "raw" surfaces for a firm attachment of the "advanced" levator. Office adjustments were delayed for at least 8 days after surgery and were performed as late as 14 days after surgery. Of the 122 consecutive aponeurotic advancements in 110 patients (12 bilateral cases), five (4.1%) patients were candidates for revision in that the operated eyelid was greater than 1 mm from desired height. All such eyelids were undercorrected by 2.0 mm to 2.5 mm. Four of the five underwent revision at 8, 11, and 14 days (two patients) after surgery. The fifth patient did not undergo revision. Four patients with overcorrections from 2.0 mm to 2.5 mm resolved with eyelid massage. It is concluded that the number of office revisions may be reduced if delayed for at least 8 days after surgery. This delay allows for resolution of postoperative edema and objective prediction of final eyelid position. The advantages of this "modified" levator advancement procedure are discussed. PMID:9700735
Modelling of tension stiffening for normal and high strength concrete
DEFF Research Database (Denmark)
Christiansen, Morten Bo; Nielsen, Mogens Peter
1998-01-01
substantial contribution to the stiffness, a phenomenon which is generally referred to as tension stiffening. The present paper describes a new theory of tension stiffening. It is based on a simple physical model for pure tension, which works with three different stages of crack generation. In a simplified...... form the model is extended to apply to biaxial stress fields as well. To determine the biaxial stress field, the theorem of minimum complementary elastic energy is used. The theory has been compared with tests on rods, disks, and beams of both normal and high strength concrete, and very good results...
The critical tension in the 6D Cascading DGP model
Sbisa', Fulvio
2014-01-01
We investigate the presence of ghosts in the Cascading DGP model. We start by discussing the problem of the cosmological late time acceleration, and we introduce the modified gravity approach. We then focus on brane induced gravity models and in particular on the Cascading DGP model. We consider a specific realization of the latter model, and we study first order perturbations around pure tension solutions. In the scalar sector of a 4D scalar-vector-tensor decomposition, the dynamics on the 4D brane can be described by a master equation where a critical tension emerges in a suitable 4D limit. We give a geometrical interpretation of this critical tension, and explain its relevance for the presence of ghosts in the theory. We comment on the difference between our result and the one present in the literature, and stress its importance regarding the phenomenological viability of the model. We finally provide a numerical check which confirms the validity of our analysis.
Mohamad Javad Kamali; Zakarya Kamali; Gholamhossein Vatankhah
2015-01-01
Thermodynamic modeling of surface tension of different electrolyte systems in presence of gas phase is studied. Using the solid-liquid equilibrium, Langmuir gas-solid adsorption, and ENRTL activity coefficient model, the surface tension of electrolyte solutions is calculated. The new model has two adjustable parameters which could be determined by fitting the experimental surface tension of binary aqueous electrolyte solution in single temperature. Then the values of surface tension for other...
The critical tension in the Cascading DGP model
International Nuclear Information System (INIS)
We study the behaviour of weak gravitational fields in the 6D Cascading DGP model using a bulk-based approach. To deal with the ambiguity in the thin limit of branes of codimension higher than one, we consider a specific regularization of the internal structure of the branes where the 5D brane can be considered thin with respect to the 4D one. We consider the solutions corresponding to pure tension sources on the 4D brane, and study perturbations at first order around these background solutions. We adopt a 4D scalar-vector-tensor decomposition, and focus on the scalar sector of perturbations. We show that, in a suitable 4D limit, the trace part of the 4D metric perturbations obeys a decoupled equation which suggests that it is a ghost for background tensions smaller than a critical tension, while it is a healthy field otherwise. We give a geometrical interpretation of the existence of the critical tension and of the reason why the relevant field is a ghost or not depending on the background tension. We however find a value of the critical tension which is different from the one already found in the literature. Differently from the results in the literature, our analysis implies that, choosing the background tension suitably, we can construct ghost-free models for any value of the free parameters of the theory. We suggest that the difference lies in the procedure used to evaluate the pillbox integration across the codimension-2 brane. We confirm the validity of our analysis by performing numerically the integration in a particular case where the solution inside the thick cod-2 brane is known exactly. We stress that the singular structure of the perturbation fields in the nested branes set-ups is very subtle, and that great care has to be taken when deriving the codimension-2 junction conditions
The critical tension in the Cascading DGP model
Sbisà, Fulvio
2014-01-01
We study the behaviour of weak gravitational fields in the 6D Cascading DGP model using a bulk-based approach. To deal with the ambiguity in the thin limit of branes of codimension higher than one, we consider a specific regularization of the internal structure of the branes where the 5D brane can be considered thin with respect to the 4D one. We consider the solutions corresponding to pure tension sources on the 4D brane, and study perturbations at first order around these background solutions. We adopt a 4D scalar-vector-tensor decomposition, and focus on the scalar sector of perturbations. We show that, in a suitable 4D limit, the trace part of the 4D metric perturbations obeys a decoupled equation which suggests that it is a ghost for background tensions smaller than a critical tension, while it is a healthy field otherwise. We give a geometrical interpretation of the existence of the critical tension and of the reason why the relevant field is a ghost or not depending on the background tension. We howeve...
Electrochemotherapy for the treatment of recurring aponeurotic fibromatosis in a dog
Spugnini, Enrico P; Di Tosto, Giovanni; Salemme, Scirin; Pecchia, Luca; Fanciulli, Maurizio; Baldi, Alfonso
2013-01-01
This paper reports the clinical findings, histopathology, and clinical outcome of a rare case of aponeurotic fibromatosis in a dog. The dog was treated with 4 courses of electrochemotherapy using the drugs cisplatin and bleomycin. There was complete remission and the dog was still disease-free after 18 months.
Electrochemotherapy for the treatment of recurring aponeurotic fibromatosis in a dog.
Spugnini, Enrico P; Di Tosto, Giovanni; Salemme, Scirin; Pecchia, Luca; Fanciulli, Maurizio; Baldi, Alfonso
2013-06-01
This paper reports the clinical findings, histopathology, and clinical outcome of a rare case of aponeurotic fibromatosis in a dog. The dog was treated with 4 courses of electrochemotherapy using the drugs cisplatin and bleomycin. There was complete remission and the dog was still disease-free after 18 months. PMID:24155455
Modeling of electrophysiology and tension development in the human heart
Seemann, Gunnar
2005-01-01
Comprehension of the beating of the human heart is important for cardiac research and will improve many clinical applications. Simulations based on models describing cardiac electro-mechanics can acquire insights into this behavior. This work focuses on the mathematical reconstruction of electrophysiology, excitation conduction, and tension development in the human heart on the cellular and the tissue level. The tissue models represent accurate anatomical shapes of the atria and the ventr...
Directory of Open Access Journals (Sweden)
Mohamad Javad Kamali
2015-01-01
Full Text Available Thermodynamic modeling of surface tension of different electrolyte systems in presence of gas phase is studied. Using the solid-liquid equilibrium, Langmuir gas-solid adsorption, and ENRTL activity coefficient model, the surface tension of electrolyte solutions is calculated. The new model has two adjustable parameters which could be determined by fitting the experimental surface tension of binary aqueous electrolyte solution in single temperature. Then the values of surface tension for other temperatures in binary and ternary system of aqueous electrolyte solution are predicted. The average absolute deviations for calculation of surface tension of binary and mixed electrolyte systems by new model are 1.98 and 1.70%, respectively.
Huang, BK; Campos, JC; Ghobrial, P; Peschka, M; Pretterklieber, ML; Skaf, AY; Chung, CB; Pathria, MN
2013-01-01
The fascia lata, or deep fascia of the thigh, is a complex anatomic structure that has not been emphasized as a potential source of pelvic and hip pain. This structure represents a broad continuum of fibrous tissue about the buttock, hip, and thigh that receives contributions from the posteriorly located aponeurotic fascia covering the gluteus medius muscle and from the more laterally located iliotibial band (ITB). At the pelvis and hip, the ITB consists of three layers that merge at the lowe...
Filopodial-Tension Model of Convergent-Extension of Tissues
Swat, Maciej H.; Glazier, James A.
2016-01-01
In convergent-extension (CE), a planar-polarized epithelial tissue elongates (extends) in-plane in one direction while shortening (converging) in the perpendicular in-plane direction, with the cells both elongating and intercalating along the converging axis. CE occurs during the development of most multicellular organisms. Current CE models assume cell or tissue asymmetry, but neglect the preferential filopodial activity along the convergent axis observed in many tissues. We propose a cell-based CE model based on asymmetric filopodial tension forces between cells and investigate how cell-level filopodial interactions drive tissue-level CE. The final tissue geometry depends on the balance between external rounding forces and cell-intercalation traction. Filopodial-tension CE is robust to relatively high levels of planar cell polarity misalignment and to the presence of non-active cells. Addition of a simple mechanical feedback between cells fully rescues and even improves CE of tissues with high levels of polarity misalignments. Our model extends easily to three dimensions, with either one converging and two extending axes, or two converging and one extending axes, producing distinct tissue morphologies, as observed in vivo. PMID:27322528
Surface tension model for surfactant solutions at the critical micelle concentration
Burlatsky, S. F.; Atrazhev, V. V.; Dmitriev, D. V.; Sultanov, V. I.; Timokhina, E. N.; Ugolkova, E. A.; Tulyani, S.; Vincitore, A.
2013-01-01
A model for the limiting surface tension of surfactant solutions (surface tension at and above the critical micelle concentration, cmc) was developed. This model takes advantage of the equilibrium between the surfactant molecules on the liquid/vacuum surface and in micelles in the bulk at the cmc. An approximate analytical equation for the surface tension at the cmc was obtained. The derived equation contains two parameters, which characterize the intermolecular interactions in the micelles, ...
Molecular modelling and simulation of the surface tension of real quadrupolar fluids
Werth, Stephan; Klein, Peter; Küfer, Karl-Heinz; Horsch, Martin; Hasse, Hans
2014-01-01
Molecular modelling and simulation of the surface tension of fluids with force fields is discussed. 29 real fluids are studied, including nitrogen, oxygen, carbon dioxide, carbon monoxide, fluorine, chlorine, bromine, iodine, ethane, ethylene, acetylene, propyne, propylene, propadiene, carbon disulfide, sulfur hexafluoride, and many refrigerants. The fluids are represented by two-centre Lennard-Jones plus point quadrupole models from the literature. These models were adjusted only to experimental data of the vapour pressure and saturated liquid density so that the results for the surface tension are predictions. The deviations between the predictions and experimental data for the surface tension are of the order of 20 percent. The surface tension is usually overestimated by the models. For further improvements, data on the surface tension can be included in the model development. A suitable strategy for this is multi-criteria optimization based on Pareto sets. This is demonstrated using the model for carbon d...
Organization of atomic bond tensions in model glasses
Kustanovich, T.; Rabin, Y.; Olami, Z.
2002-01-01
In order to understand whether internal stresses in glasses are correlated or randomly distributed, we study the organization of atomic bond tensions (normal forces between pairs of atoms). Measurements of the invariants of the atomic bond tension tensor in simulated 2D and 3D binary Lennard-Jones glasses, reveal new and unexpected correlations and provide support for Alexander's conjecture about the non-random character of internal stresses in amorphous solids.
Calculation of Surface Tensions of Polar Mixtures with a Simplified Gradient Theory Model
DEFF Research Database (Denmark)
Zuo, You-Xiang; Stenby, Erling Halfdan
1996-01-01
Key Words: Thermodynamics, Simplified Gradient Theory, Surface Tension, Equation of state, Influence Parameter.In this work, assuming that the number densities of each component in a mixture across the interface between the coexisting vapor and liquid phases are linearly distributed, we developed a...... surface tensions of 34 binary mixtures with an overall average absolute deviation of 3.46%. The results show good agreement between the predicted and experimental surface tensions. Next, the SGT model was applied to correlate surface tensions of binary mixtures containing alcohols, water or/and glycerol...
Corresponding-States and Parachor Models for the Calculation of Interfacial Tensions
DEFF Research Database (Denmark)
Zuo, You-Xiang; Stenby, Erling Halfdan
1997-01-01
A generalized corresponding-states model based on two reference fluids and a parachor correlation were developed for the prediction of interfacial tensions for non-polar and weakly polar pure fluids and mixtures. Pure methane and n-octane were chosen as reference fluids of the corresponding......, interfacial tension, reference fluids....
International Nuclear Information System (INIS)
To describe the aponeurotic expansion of the supraspinatus tendon with anatomic correlations and determine its prevalence in a series of patients imaged with MRI. In the first part of this HIPAA-compliant and IRB-approved study, we retrospectively reviewed 150 consecutive MRI studies of the shoulder obtained on a 1.5-T system. The aponeurotic expansion at the level of the bicipital groove was classified as: not visualized (type 0), flat-shaped (type 1), oval-shaped and less than 50 % the size of the adjacent long head of the biceps section (type 2A), or oval-shaped and more than 50 % the size of the adjacent long head of the biceps section (type 2B). In the second part of this study, we examined both shoulders of 25 cadavers with ultrasound. When aponeurotic expansion was seen at US, a dissection was performed to characterize its origin and termination. An aponeurotic expansion of the supraspinatus located anterior and lateral to the long head of the biceps in its groove was clearly demonstrated in 49 % of the shoulders with MRI. According to our classification, its shape was type 1 in 35 %, type 2A in 10 % and type 2B in 4 %. This structure was also identified in 28 of 50 cadaveric shoulders with ultrasound and confirmed at dissection in 10 cadavers (20 shoulders). This structure originated from the most anterior and superficial aspect of the supraspinatus tendon and inserted distally on the pectoralis major tendon. The aponeurotic expansion of the supraspinatus tendon can be identified with MRI or ultrasound in about half of the shoulders. It courses anteriorly and laterally to the long head of the biceps tendon, outside its synovial sheath. (orig.)
Directory of Open Access Journals (Sweden)
Sílvio H.M. de Almeida
2004-08-01
Full Text Available INTRODUCTION: Aponeurotic sling surgeries can evolve with obstruction or voiding dysfunction in 5 to 20% of patients. There are few studies on factors that could possibly predispose to voiding difficulties or urinary retention. The objective of this work is to identify these potential clinical or urodynamic factors. MATERIALS AND METHODS: Records from 130 patients who underwent aponeurotic sling surgeries were reviewed. All patients underwent a throughout urodynamic study during pre-operative investigation. The variables studied were age above 65 years, previous pelvic surgeries, concomitant surgeries, post-voiding residue higher than 100 mL, vesical obstruction (according to Blaivas-Groutz nomogram and urinary flow under 12 mL/s. Post-voiding residue was assessed on the seventh post-operative day through vesical catheterization. Recovering of spontaneous voiding after 7 post-operative days or with a residue higher than 100 mL, was regarded as voiding dysfunction. Univariate analysis was performed with qui-square test and Fisher's exact test, and multivariate analysis was performed by logistic regression with alpha = 5%. RESULTS: Age in the studied group ranged from 41 to 83 years (mean 56.7 years, with 69 (53% patients having urethral hypermobility and 61 (47% having intrinsic urethral lesion. Normal voiding occurred in 97 (75.6 % women with 7 post-operative days. The only significant variable in the univariate (p = 0.014 and multivariate (p = 0.017 analysis was post-voiding residue higher than 100 mL. CONCLUSION: Pre-operative presence of a post-voiding residual urine higher than 100 mL was the only variable predictive of voiding dysfunction.
Surface tension gradients: feasible model for gliding motility of Myxococcus xanthus.
Keller, K H; Grady, M; Dworkin, M
1983-01-01
We propose that surface tension is the driving force for the gliding motility of Myxococcus xanthus. Our model requires that the cell be able to excrete surfactant in a polar and reversible fashion. We present calculations that (i) estimate the surface tension difference across a cell necessary to move the cell at the observed rate, which is less than 10(-5) dyn/cm, an extremely small value; (ii) estimate the rate of surfactant excretion necessary to produce the required surface tension diffe...
Extrapolated renormalization group calculation of the surface tension in square-lattice Ising model
International Nuclear Information System (INIS)
By using self-dual clusters (whose sizes are characterized by the numbers b=2, 3, 4, 5) within a real space renormalization group framework, the longitudinal surface tension of the square-lattice first-neighbour 1/2-spin ferromagnetic Ising model is calculated. The exact critical temperature T sub(c) is recovered for any value of b; the exact assymptotic behaviour of the surface tension in the limit of low temperatures is analytically recovered; the approximate correlation length critical exponents monotonically tend towards the exact value ν=1 (which, at two dimensions, coincides with the surface tension critical exponent μ) for increasingly large cells; the same behaviour is remarked in what concerns the approximate values for the surface tension amplitude in the limit T→T sub(c). Four different numerical procedures are developed for extrapolating to b→infinite the renormalization group results for the surface tension, and quite satisfactory agreement is obtained with Onsager's exact expression (error varying from zero to a few percent on the whole temperature domain). Furthermore the set of RG surface tensions is compared with a set of biased surface tensions (associated to appropriate misfit seams), and find only fortuitous coincidence among them. (Author)
Dworkin, M; Keller, K H; Weisberg, D.
1983-01-01
We have presented experimental evidence to support the model that gliding motility of Myxococcus xanthus is driven by surface tension. (i) Motility is inhibited by the addition of sufficient exogenous, nontoxic surfactants to swamp out the cells' own surfactant gradient. (ii) M. xanthus does not move polystyrene latex beads over its surface. (iii) Motility is prevented by elimination of an interfacial surface tension either by embedding the cells in soft agar or by placing them at an agar-aqu...
A hybrid model to predict the onset of gas entrainment with surface tension effects
International Nuclear Information System (INIS)
The onset of gas entrainment, in a single downward oriented discharge from a stratified gas-liquid region with was modeled. The assumptions made in the development of the model reduced the problem to that of a potential flow. The discharge was modeled as a point-sink. Through use of the Kelvin-Laplace equation the model included the effects of surface tension. The resulting model required further knowledge of the flow field, specifically the dip radius of curvature prior to the onset of gas entrainment. The dip shape and size was investigated experimentally and correlations were provided to characterize the dip in terms of the discharge Froude number. The experimental correlation was used in conjunction with the theoretical model to predict the critical height. The results showed that by including surface tension effects the predicted critical height showed excellent agreement with experimental data. Surface tension reduces the critical height through the Bond number
A Surface Tension Model for Liquid Mixtures Based on NRTL Equation
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
A new equation for predicting surface tension is proposed based on the thermodynamic definition of surface tension and the expression of the Gibbs free energy of the system. Using the NRTL equation to represent the excess Gibbs free energy, a two-parameter surface tension equation is derived. The feasibility of the new equation has been tested in terms of 124 binary and 16 multicomponent systems(13-ternary and 3-quaternary) with absolute relative deviations of 0.59% and 1.55% respectively. This model is also predictive for the temperature dependence of surface tension of liquid mixtures. It is shown that, with good accuracy, this equation is simple and reliable for practical use.
Experiment and model for the surface tension of amine–ionic liquids aqueous solutions
International Nuclear Information System (INIS)
Highlights: • The surface tensions of MEA/DEA–ionic liquids aqueous solutions were measured. • The experiments were modeled satisfactorily by using a thermodynamic equation. • The temperature dependence of the surface tension was illustrated. • The effects of the mass fractions of MEA/DEA and ionic liquids were demonstrated. - Abstract: The surface tension (γ) of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4])–monoethanolamine (MEA), 1-butyl-3-methylimidazolium bromide ([Bmim][Br])–MEA, [Bmim][BF4]–diethanolamine (DEA) and [Bmim][Br]–DEA aqueous solutions was measured by using the BZY-1 surface tension meter. The temperature ranged from (293.2 to 323.2) K. The mass fraction of amines and ionic liquids (ILS) respectively ranged from 0.15 to 0.30 and 0.05 to 0.10. A thermodynamic equation was proposed to model the surface tension of amines–ILS aqueous solutions and the calculated results agreed well with the experiments. The effects of temperature, mass fraction of amines and ILS on the surface tension were demonstrated on the basis of experiments and calculations
Boyer, Hallie C; Dutcher, Cari S
2016-06-30
With statistical mechanics, an isotherm-based surface tension model for single solute aqueous solutions was derived previously (Wexler et al. J. Phys. Chem. Lett. 2013) for the entire concentration range, from infinite dilution to pure liquid solute, as a function of solute activity. In recent work (Boyer et al. J. Phys. Chem. Lett. 2015), empirical model parameters were reduced through physicochemical interpretations of both electrolyte and organic solutes, enabling surface tension predictions for systems where there is little or no data. The prior binary model is extended in the current work for the first time to treat multicomponent systems to predict surface tensions of partially dissociating organic acids (acetic, butyric, citric, formic, glutaric, maleic, malic, malonic, oxalic, propionic, and succinic acids). These organic acids are especially applicable to the study of atmospheric aqueous aerosols, due to their abundance in the atmosphere. In the model developed here, surface tension depends explicitly on activities of both the neutral organic and deprotonated components of the acid. The relative concentrations of the nondissociated and dissociated mole fractions are found using known dissociation constants. Model parameters strongly depend on molecular size, number of functional groups, O:C ratio, and number of carbons. For all organic acids in this study, fully predictive modeling of surface tensions is demonstrated. PMID:27219322
Moerman, Kevin M; Nagel, Thomas
2015-01-01
This paper discusses tension-compression asymmetry properties of Ogden hyperelastic formulations. It is shown that if all negative or all positive Ogden coefficients are used, tension-compression asymmetry occurs the degree of which cannot be separately controlled from the degree of non-linearity. A simple hybrid form is therefore proposed providing separate control over the tension-compression asymmetry. It is demonstrated how this form relates to a newly introduced generalised strain tensor class which encompasses both the tension-compression asymmetric Seth-Hill strain class and the tension-compression symmetric Ba\\v{z}ant strain class. If the control parameter is set to q=0.5 a tension-compression symmetric form involving Ba\\v{z}ant strains is obtained with the property {\\Psi}({\\lambda}_1,{\\lambda}_2,{\\lambda}_3 )={\\Psi}(1/{\\lambda}_1 ,1/{\\lambda}_2 ,1/{\\lambda}_3 ). The symmetric form may be desirable for the definition of ground matrix contributions in soft tissue modelling allowing all deviation from t...
Ternary free-energy lattice Boltzmann model with tunable surface tensions and contact angles
Semprebon, Ciro; Krüger, Timm; Kusumaatmaja, Halim
2016-03-01
We present a ternary free-energy lattice Boltzmann model. The distinguishing feature of our model is that we are able to analytically derive and independently vary all fluid-fluid surface tensions and the solid surface contact angles. We carry out a number of benchmark tests: (i) double emulsions and liquid lenses to validate the surface tensions, (ii) ternary fluids in contact with a square well to compare the contact angles against analytical predictions, and (iii) ternary phase separation to verify that the multicomponent fluid dynamics is accurately captured. Additionally we also describe how the model presented here can be extended to include an arbitrary number of fluid components.
Ternary Free Energy Lattice Boltzmann Model with Tunable Surface Tensions and Contact Angles
Semprebon, Ciro; Kusumaatmaja, Halim
2015-01-01
We present a new ternary free energy lattice Boltzmann model. The distinguishing feature of our model is that we are able to analytically derive and independently vary all fluid-fluid surface tensions and the solid surface contact angles. We carry out a number of benchmark tests: (i) double emulsions and liquid lenses to validate the surface tensions, (ii) ternary fluids in contact with a square well to compare the contact angles against analytical predictions, and (iii) ternary phase separation to verify that the multicomponent fluid dynamics is accurately captured. Additionally we also describe how the model here presented here can be extended to include an arbitrary number of fluid components.
Convergence and accuracy of kernel-based continuum surface tension models
Energy Technology Data Exchange (ETDEWEB)
Williams, M.W.; Kothe, D.B. [Los Alamos National Lab., NM (US); Puckett, E.G. [Univ. of California, Davis, CA (US)
1998-12-01
Numerical models for flows of immiscible fluids bounded by topologically complex interfaces possessing surface tension inevitably start with an Eulerian formulation. Here the interface is represented as a color function that abruptly varies from one constant value to another through the interface. This transition region, where the color function varies, is a thin O(h) band along the interface where surface tension forces are applied in continuum surface tension models. Although these models have been widely used since the introduction of the popular CSF method [BKZ92], properties such as absolute accuracy and uniform convergence are often not exhibited in interfacial flow simulations. These properties are necessary if surface tension-driven flows are to be reliably modeled, especially in three dimensions. Accuracy and convergence remain elusive because of difficulties in estimating first and second order spatial derivatives of color functions with abrupt transition regions. These derivatives are needed to approximate interface topology such as the unit normal and mean curvature. Modeling challenges are also presented when formulating the actual surface tension force and its local variation using numerical delta functions. In the following they introduce and incorporate kernels and convolution theory into continuum surface tension models. Here they convolve the discontinuous color function into a mollified function that can support accurate first and second order spatial derivatives. Design requirements for the convolution kernel and a new hybrid mix of convolution and discretization are discussed. The resulting improved estimates for interface topology, numerical delta functions, and surface force distribution are evidenced in an equilibrium static drop simulation where numerically-induced artificial parasitic currents are greatly mitigated.
International Nuclear Information System (INIS)
The surface tension of liquid Cu-Ti alloys has been measured by using the containerless technique of electromagnetic levitation and theoretically calculated in the framework of the compound formation model. Measurements have been carried out on alloys covering the entire range of composition and over the temperature range 1275-2050 K. For all investigated alloys the surface tension can be described by a linear function of the temperature with negative slope. Due to the presence of different intermetallic compounds in the solid state the surface properties of liquid Cu-Ti alloys are satisfactory described by the compound formation model.
Surface tension prediction for hydrocarbons and its application to level swell modelling.
Cumber, Peter
2002-01-28
In this article, methods for estimating surface tension are considered where the specific gravity and normal boiling point are known such as when the composition is expressed using petroleum fractions. This is of interest as surface tension is an important parameter in the calculation of outflow conditions from a two-phase vessel undergoing level swell. A new improved correlation for the parachor is presented and the improved accuracy of the surface tension and bubble rise velocity compared to when the original parachor correlation is used is assessed. Finally the sensitivity of outflow predictions to changes in the surface tension is presented for a depressurising vessel containing pentane. For the vessel depressurisation simulation where the original parachor correlation is used, two-phase venting is maintained for two-three times as long compared to when the actual parachor or improved parachor correlation is used to estimate the surface tension. This has an impact on the error in predicting the mass flow rate as a source condition for other consequence models and also in vent sizing calculations. PMID:11744200
A New Model for Prediction of Surface Tension of Pure Fluids
Institute of Scientific and Technical Information of China (English)
杨春生; 仲崇立
2004-01-01
A new model based on the theoretical work of Boudh-Hir and Mansoori was developed for prediction of surface tension of pure fluids. The new model has the advantage of not requiring densities in the calculation, and the input parameters are critical temperature and connectivity indices. A total of 209 compounds covering a wide variety of substances were used to develop the model, and the overall correlative AAD is 4.21%. To test its predictive ability, the model is further used to predict the surface tension of 25 more compounds that were not included in the model development. The overall predictive AAD is 4.07%, which illustrates that the model is reliable. The model proposed is simple and easy to apply, with good predictive accuracy.
Interface tension of the 3d 4-state Potts model using the Wang-Landau algorithm
Hietanen, A
2011-01-01
We study the interface tension of the 4-state Potts model in three dimensions using the Wang- Landau algorithm. The interface tension is given by the ratio of the partition function with a twisted boundary condition in one direction and periodic boundary conditions in all other directions over the partition function with periodic boundary conditions in all directions. With the Wang-Landau algorithm we can explicitly calculate both partition functions and obtain the result for all temperatures. We find solid numerical evidence for perfect wetting. Our algorithm is tested by calculating thermodynamic quantities at the phase transition point.
DEFF Research Database (Denmark)
Gharagheizi, Farhad; Eslamimanesh, Ali; Sattari, Mehdi;
2013-01-01
include critical temperature or temperature/critical volume/acentric factor/critical pressure/reduced temperature/reduced normal boiling point temperature/molecular weight of the compounds. Around 1,300 surface tension data of 118 random compounds are used for developing the first model (a four...
Modeling the in-plane tension failure of composite plates
Energy Technology Data Exchange (ETDEWEB)
Trinh, K.V. [Sandia National Labs., Livermore, CA (United States). Structural and Thermomechanical Modeling Dept.
1997-11-01
This study developed a modeling method to predict the final failure load of laminated composite plates which may contain cutouts and are subjected to quasi-static in-plane tensile loads. This study focused on overcoming numerical problems often encountered in analyses that exhibit significant stable damage growth in the composite materials. To keep the computational cost at a reasonable level, the modeling method uses a quasi-static solution procedure to solve composite plate problems with quasi-static load. The numerical problems in the quasi-static analyses are nonconvergence problems caused by the discontinuous material behavior from brittle fiber failure. This study adds artificial damping to the material model to suppress the discontinuous material behavior. The artificial damping essentially changes the material behavior, and could adversely change the final failure load prediction. Thus, a selective scheme for adding the damping was developed to minimize adverse damping effects. In addition, this modeling method uses multiple analyses at different levels of artificial damping to determine damping effects on the failure load prediction. Fracture strength experimental data for small coupons with small cutouts and large panels with larger cutouts available in the literature were selected and used to verify failure predictions of the developed modeling method. Results show that, without the artificial damping treatment, progressive damage analyses reasonably predicted the fracture strength of the small coupons, but severely underpredicted the fracture strength of the large panels. With the artificial damping treatment, the analyses predicted the failure load of both the small coupons and the large panels reasonably well.
Challenges, tensions and barriers to emancipatory models of student voice
Bishop, Daniel; Amsler, Sarah
2013-01-01
The demands and values of the neo-liberal market economy in western universities has changed the terrain of higher education, re-structuring managerial practices and processes and affecting the role and functions of the university and the beliefs about who can participate (Lambert, 2009). The resulting model of mass higher education is accompanied with increasing demands of students and the ideology of the student as a paying ‘customer’ or ‘consumer’, directly impacting on pedagogic practice...
Computer modelling of the surface tension of the gas-liquid and liquid-liquid interface.
Ghoufi, Aziz; Malfreyt, Patrice; Tildesley, Dominic J
2016-03-01
This review presents the state of the art in molecular simulations of interfacial systems and of the calculation of the surface tension from the underlying intermolecular potential. We provide a short account of different methodological factors (size-effects, truncation procedures, long-range corrections and potential models) that can affect the results of the simulations. Accurate calculations are presented for the calculation of the surface tension as a function of the temperature, pressure and composition by considering the planar gas-liquid interface of a range of molecular fluids. In particular, we consider the challenging problems of reproducing the interfacial tension of salt solutions as a function of the salt molality; the simulations of spherical interfaces including the calculation of the sign and size of the Tolman length for a spherical droplet; the use of coarse-grained models in the calculation of the interfacial tension of liquid-liquid surfaces and the mesoscopic simulations of oil-water-surfactant interfacial systems. PMID:26744846
A Linear Gradient Theory Model for Calculating Interfacial Tensions of Mixtures
DEFF Research Database (Denmark)
Zou, You-Xiang; Stenby, Erling Halfdan
1996-01-01
In this research work, we assumed that the densities of each component in a mixture are linearly distributed across the interface between the coexisting vapor and liquid phases, and we developed a linear gradient theory model for computing interfacial tensions of mixtures, especially mixtures...... with proper scaling behavior at the critical point is at least required.Key words: linear gradient theory; interfacial tension; equation of state; influence parameter; density profile....... containing supercritical methane, argon, nitrogen, and carbon dioxide gases at high pressure. With this model it is unnecessary to solve the time-consuming density profile equations of the gradient theory model. The model has been tested on a number of mixtures at low and high pressures. The results show...
Prototypical model for tensional wrinkling in thin sheets
Davidovitch, B.
2011-10-31
The buckling and wrinkling of thin films has recently seen a surge of interest among physicists, biologists, mathematicians, and engineers. This activity has been triggered by the growing interest in developing technologies at ever-decreasing scales and the resulting necessity to control the mechanics of tiny structures, as well as by the realization that morphogenetic processes, such as the tissue-shaping instabilities occurring in animal epithelia or plant leaves, often emerge from mechanical instabilities of cell sheets. Although the most basic buckling instability of uniaxially compressed plates was understood by Euler more than two centuries ago, recent experiments on nanometrically thin (ultrathin) films have shown significant deviations from predictions of standard buckling theory. Motivated by this puzzle, we introduce here a theoretical model that allows for a systematic analysis of wrinkling in sheets far from their instability threshold. We focus on the simplest extension of Euler buckling that exhibits wrinkles of finite length--a sheet under axisymmetric tensile loads. The first study of this geometry, which is attributed to Lamé, allows us to construct a phase diagram that demonstrates the dramatic variation of wrinkling patterns from near-threshold to far-from-threshold conditions. Theoretical arguments and comparison to experiments show that the thinner the sheet is, the smaller is the compressive load above which the far-from-threshold regime emerges. This observation emphasizes the relevance of our analysis for nanomechanics applications.
Modeling of a curvilinear planar crack with a curvature-dependent surface tension
Zemlyanova, A Y
2011-01-01
In this paper, an approach to modeling fracture incorporating interfacial mechanics is applied to the example of a curvilinear plane strain crack. The classical Neumann boundary condition is augmented with curvature-dependent surface tension. It is shown that the considered model eliminates the integrable crack-tip stress and strain singularities of order 1/2 present in the classical linear fracture mechanics solutions, and also leads to the sharp crack opening that is consistent with empirical observations.
International Nuclear Information System (INIS)
Highlights: • The effect of oxygen on the surface tension of liquid Cu was investigated. • The adsorption behavior of oxygen is presented with a thermodynamic model. • This model assumes a hypothetical binary system of Cu-“Cu2O”. • “Cu2O” is considered as an associate molecule. • Ideal adsorption model exhibits the best fit of the experimental results. - Abstract: The effect of oxygen adsorption on surface tension of liquid copper at two different temperatures (1390 and 1440 K) has been investigated. A combination of specially designed crucibles, He-Ne laser, and high-resolution photography in a highly controlled gas atmosphere was used for accurate measurements. Experimental data exhibits decreasing surface tension with increasing oxygen partial pressure. Discussion on the adsorption behavior of oxygen is presented based on thermodynamic models by assuming a hypothetical binary system of Cu-“Cu2O”, in which “Cu2O” is considered as an associate molecule. Ideal adsorption model which assumes insignificant interactions between Cu and Cu2O on the surface exhibits the best fit to the experimental results
Banerjee, S.; Hassenklover, E.; Kleijn, J.M.; Cohen Stuart, M.A.; Leermakers, F.A.M.
2013-01-01
This paper presents experimental and modeling results on water–CO2 interfacial tension (IFT) together with wettability studies of water on both hydrophilic and hydrophobic surfaces immersed in CO2. CO2–water interfacial tension (IFT) measurements showed that the IFT decreased with increasing pressur
Iida, Kei; Oyamatsu, Kazuhiro
2004-01-01
We examine whether or not the surface tension acts to increase the nucleon density in the nuclear interior within a compressible liquid-drop model. We find that it depends on the density dependence of the surface tension, which may in turn be deduced from the neutron skin thickness of stable nuclei.
Song, Kyonchan; Li, Yingyong; Rose, Cheryl A.
2011-01-01
The performance of a state-of-the-art continuum damage mechanics model for interlaminar damage, coupled with a cohesive zone model for delamination is examined for failure prediction of quasi-isotropic open-hole tension laminates. Limitations of continuum representations of intra-ply damage and the effect of mesh orientation on the analysis predictions are discussed. It is shown that accurate prediction of matrix crack paths and stress redistribution after cracking requires a mesh aligned with the fiber orientation. Based on these results, an aligned mesh is proposed for analysis of the open-hole tension specimens consisting of different meshes within the individual plies, such that the element edges are aligned with the ply fiber direction. The modeling approach is assessed by comparison of analysis predictions to experimental data for specimen configurations in which failure is dominated by complex interactions between matrix cracks and delaminations. It is shown that the different failure mechanisms observed in the tests are well predicted. In addition, the modeling approach is demonstrated to predict proper trends in the effect of scaling on strength and failure mechanisms of quasi-isotropic open-hole tension laminates.
Constitutive Model Constants for Low Carbon Steels from Tension and Torsion Data
Brar, N. S.; Joshi, V. S.; Harris, B. W.
2007-12-01
Low carbon C1010 steel is characterized under tension and torsion to determine Johnson-Cook (J-C) strength model constants. Constitutive model constants are required as input to computer codes to simulate projectile (fragment) impact on structural components made of this material. J-C model constants (A, B, n, C, and m) for the alloy are determined from tension and torsion stress-strain data. Reference tension tests are performed at a strain rate of ˜1/s at room temperature. Tests at high strain rates are performed at temperatures to 750 °C. Torsion tests at quasi-static and high strain rates are performed at both room and high temperatures. Equivalent plastic tensile stress-strain data are obtained from torsion data using von Mises flow rule and compared directly to measured tensile data. J-C strength model constants are determined from these data. Similar low carbon steels (1006, 1008, and 1020) have their J-C constants compared.
A thermodynamical model for the surface tension of silicate melts in contact with H2O gas
Colucci, Simone; Battaglia, Maurizio; Trigila, Raffaello
2016-01-01
Surface tension plays an important role in the nucleation of H2O gas bubbles in magmatic melts and in the time-dependent rheology of bubble-bearing magmas. Despite several experimental studies, a physics based model of the surface tension of magmatic melts in contact with H2O is lacking. This paper employs gradient theory to develop a thermodynamical model of equilibrium surface tension of silicate melts in contact with H2O gas at low to moderate pressures. In the last decades, this approach has been successfully applied in studies of industrial mixtures but never to magmatic systems. We calibrate and verify the model against literature experimental data, obtained by the pendant drop method, and by inverting bubble nucleation experiments using the Classical Nucleation Theory (CNT). Our model reproduces the systematic decrease in surface tension with increased H2O pressure observed in the experiments. On the other hand, the effect of temperature is confirmed by the experiments only at high pressure. At atmospheric pressure, the model shows a decrease of surface tension with temperature. This is in contrast with a number of experimental observations and could be related to microstructural effects that cannot be reproduced by our model. Finally, our analysis indicates that the surface tension measured inverting the CNT may be lower than the value measured by the pendant drop method, most likely because of changes in surface tension controlled by the supersaturation.
Lee, Deok-Sun; Sadjadi, Zeinab; Rieger, Heiko
2014-07-01
Recently, anomalous scaling properties of front broadening during spontaneous imbibition of water in Vycor glass, a nanoporous medium, were reported: the mean height and the width of the propagating front increase with time t both proportional to t(1/2). Here, we propose a simple lattice imbibition model and elucidate quantitatively how the correlation range of the hydrostatic pressure and the disorder strength of the pore radii affect the scaling properties of the imbibition front. We introduce an effective tension of liquid across neighboring pores, which depends on the aspect ratio of each pore, and show that it leads to a dynamical crossover: both the mean height and the roughness grow faster in the presence of tension in the intermediate-time regime but eventually saturate in the long-time regime. The universality class of the long-time behavior is discussed by examining the associated scaling exponents and their relation to directed percolation. PMID:25122378
Modeling of the Tension and Compression Behavior of Sintered 316L Using Micro Computed Tomography
Directory of Open Access Journals (Sweden)
Doroszko Michał
2015-06-01
Full Text Available This paper describes the method of numerical modeling of the tension and compression behavior of sintered 316L. In order to take into account the shape of the mesostructures of materials in the numerical modeling, X-ray microtomography was used. Based on the micro-CT images, three-dimensional geometrical models mapped shapes of the porosity were generated. To the numerical calculations was used finite element method. Based on the received stress and strain fields was described the mechanism of deformation of the materials until fracture. The influence of material discontinuities at the mesoscopic scale on macromechanical properties of the porous materials was investigated.
Fault Tree Model for Failure Path Prediction of Bolted Steel Tension Member in a Structural System
Directory of Open Access Journals (Sweden)
Biswajit Som
2015-06-01
Full Text Available Fault tree is a graphical representation of various sequential combinations of events which leads to the failure of any system, such as a structural system. In this paper it is shown that a fault tree model is also applicable to a critical element of a complex structural system. This will help to identify the different failure mode of a particular structural element which might eventually triggered a progressive collapse of the whole structural system. Non-redundant tension member generally regarded as a Fracture Critical Member (FCM in a complex structural system, especially in bridge, failure of which may lead to immediate collapse of the structure. Limit state design is governed by the failure behavior of a structural element at its ultimate state. Globally, condition assessment of an existing structural system, particularly for bridges, Fracture Critical Inspection becomes very effective and mandatory in some countries. Fault tree model of tension member, presented in this paper can be conveniently used to identify the flaws in FCM if any, in an existing structural system and also as a check list for new design of tension member.
Transfer matrix modeling of a tensioned piezo-solar hybrid energy harvesting ribbon
Chatterjee, Punnag; Bryant, Matthew
2015-04-01
This paper proposes a multifunctional compliant structure that can harvest electrical power from both incident sunlight and ambient mechanical energy including wind flow or vibration. The energy harvesting device consists of a slender, ribbon-like, flexible thin film solar cell that is laminated with piezoelectric patches. The harvester is mounted in longitudinal tension and subjected to a transverse wind flow to excite flow-induced aeroelastic vibrations. This paper formulates an analytic model of the bending dynamics of the device. We present a Transfer Matrix formulation that also accounts for the changes in natural frequencies and mode shapes of the system when subjected to axial loads in a beam. It also observed that mode shape obtained using TMM formulation shows numerical stability even for very high tensile loads providing results consistent with the geometric boundary conditions applied at the ends of a beam. This article also discusses about structurally modeling a piezo - solar energy harvester using TMM methodology, where a thin clampedclamped solar film is bonded with piezo patches having a much higher bending stiffness. Additionally, the effect of axial tension on the mode shape of the thin host structure of the piezo-solar ribbon is presented and it is shown how this tension can be used advantageously to affect the strain distribution of the entire structure and introduce higher strains at the piezo patches.
On the modelling of semi-insulating GaAs including surface tension and bulk stresses
Energy Technology Data Exchange (ETDEWEB)
Dreyer, W.; Duderstadt, F.
2004-07-01
Necessary heat treatment of single crystal semi-insulating Gallium Arsenide (GaAs), which is deployed in micro- and opto- electronic devices, generate undesirable liquid precipitates in the solid phase. The appearance of precipitates is influenced by surface tension at the liquid/solid interface and deviatoric stresses in the solid. The central quantity for the description of the various aspects of phase transitions is the chemical potential, which can be additively decomposed into a chemical and a mechanical part. In particular the calculation of the mechanical part of the chemical potential is of crucial importance. We determine the chemical potential in the framework of the St. Venant-Kirchhoff law which gives an appropriate stress/strain relation for many solids in the small strain regime. We establish criteria, which allow the correct replacement of the St. Venant-Kirchhoff law by the simpler Hooke law. The main objectives of this study are: (i) We develop a thermo-mechanical model that describes diffusion and interface motion, which both are strongly influenced by surface tension effects and deviatoric stresses. (ii) We give an overview and outlook on problems that can be posed and solved within the framework of the model. (iii) We calculate non-standard phase diagrams, i.e. those that take into account surface tension and non-deviatoric stresses, for GaAs above 786 C, and we compare the results with classical phase diagrams without these phenomena. (orig.)
Modeling the Restraint of Liquid Jets by Surface Tension in Microgravity
Chato, David J.; Jacqmim, David A.
2001-01-01
An axisymmetric phase field model is developed and used to model surface tension forces on liquid jets in microgravity. The previous work in this area is reviewed and a baseline drop tower experiment selected 'for model comparison. A mathematical model is developed which includes a free surface. a symmetric centerline and wall boundaries with given contact angles. The model is solved numerically with a compact fourth order stencil on a equally spaced axisymmetric grid. After grid convergence studies, a grid is selected and all drop tower tests modeled. Agreement was assessed by comparing predicted and measured free surface rise. Trend wise agreement is good but agreement in magnitude is only fair. Suspected sources of disagreement are suspected to be lack of a turbulence model and the existence of slosh baffles in the experiment which were not included in the model.
Block, Benjamin J; Virnau, Peter; Binder, Kurt
2014-01-01
As a generic example for crystals where the crystal-fluid interface tension depends on the orientation of the interface relative to the crystal lattice axes, the nearest neighbor Ising model on the simple cubic lattice is studied over a wide temperature range, both above and below the roughening transition temperature. Using a thin film geometry $L_x \\times L_y \\times L_z$ with periodic boundary conditions along the z-axis and two free $L_x \\times L_y$ surfaces at which opposing surface fields $\\pm H_{1}$ act, under conditions of partial wetting, a single planar interface inclined under a contact angle $\\theta < \\pi/2$ relative to the yz-plane is stabilized. In the y-direction, a generalization of the antiperiodic boundary condition is used that maintains the translational invariance in y-direction despite the inhomogeneity of the magnetization distribution in this system. This geometry allows a simultaneous study of the angle-dependent interface tension, the contact angle, and the line tension (which depe...
Grandis, S; Saro, A; Mohr, J J; Dietrich, J P
2016-01-01
Recent measurements of the Cosmic Microwave Background (CMB) by the Planck Collaboration have produced arguably the most powerful observational evidence in support of the standard model of cosmology, i.e. the spatially flat $\\Lambda$CDM paradigm. In this work, we perform model selection tests to examine whether the base CMB temperature and large scale polarization anisotropy data from Planck 2015 (P15) prefer any of eight commonly used one-parameter model extensions with respect to flat $\\Lambda$CDM. We find a clear preference for models with free curvature, $\\Omega_\\mathrm{K}$, or free amplitude of the CMB lensing potential, $A_\\mathrm{L}$. We also further develop statistical tools to measure tension between datasets. We use a Gaussianization scheme to compute tensions directly from the posterior samples using an entropy-based method, the surprise, as well as a calibrated evidence ratio presented here for the first time. We then proceed to investigate the consistency between the base P15 CMB data and six oth...
Theissen, David B.; Man, Kin F.
1996-01-01
The effect of surface tension is observed inmany everyday situations. For example, a slowly leaking faucet drips because the force surface tension allows the water to cling to it until a sufficient mass of water is accumulated to break free.
Directory of Open Access Journals (Sweden)
Mariane Miyashiro
2011-06-01
Full Text Available OBJECTIVES: The complexity and heterogeneity of human bone, as well as ethical issues, frequently hinder the development of clinical trials. The purpose of this in vitro study was to determine the modulus of elasticity of a polyurethane isotropic experimental model via tension tests, comparing the results to those reported in the literature for mandibular bone, in order to validate the use of such a model in lieu of mandibular bone in biomechanical studies. MATERIAL AND METHODS: Forty-five polyurethane test specimens were divided into 3 groups of 15 specimens each, according to the ratio (A/B of polyurethane reagents (PU-1: 1/0.5, PU-2: 1/1, PU-3: 1/1.5. RESULTS: Tension tests were performed in each experimental group and the modulus of elasticity values found were 192.98 MPa (SD=57.20 for PU-1, 347.90 MPa (SD=109.54 for PU-2 and 304.64 MPa (SD=25.48 for PU-3. CONCLUSION: The concentration of choice for building the experimental model was 1/1.
Modeling the tension-compression asymmetric yield behavior of β-treated Zircaloy-4
Zhai, Jinyuan; Gao, Xiaosheng; Sobotka, James C.; Webler, Bryan A.; Cockeram, Brian V.
2014-08-01
Zirconium alloys such as Zircaloy-4 are used in nuclear applications due to adequate strength, ductility and resistance to radiation damage. Recent modeling efforts have focused on improvements to the predicted elastic-plastic response, complicated by the strong strength-differential (S-D) effects in HCP materials. This study develops a pressure-insensitive, continuum plasticity model, dependent on the second and third invariants of the stress deviator (J2 and J3), with an internal variable related to the plastic strain to describe the tension-compression asymmetry of a β-treated Zircaloy-4. Plastic deformation drives isotropic and distortional hardening of the non-Mises yield surface. The proposed plasticity model has been calibrated and validated using measured results from an experimental test program. Results show that the proposed model captures the complex elastic-plastic response observed in measured load-displacement and torque-rotation curves over a range of triaxiality and Lode parameter values.
Tartakovsky, Alexandre M.; Panchenko, Alexander
2016-01-01
We present a novel formulation of the Pairwise Force Smoothed Particle Hydrodynamics (PF-SPH) model and use it to simulate two- and three-phase flows in bounded domains. In the PF-SPH model, the Navier-Stokes equations are discretized with the Smoothed Particle Hydrodynamics (SPH) method, and the Young-Laplace boundary condition at the fluid-fluid interface and the Young boundary condition at the fluid-fluid-solid interface are replaced with pairwise forces added into the Navier-Stokes equations. We derive a relationship between the parameters in the pairwise forces and the surface tension and static contact angle. Next, we demonstrate the model's accuracy under static and dynamic conditions. Finally, we use the Pf-SPH model to simulate three phase flow in a porous medium.
Energy Technology Data Exchange (ETDEWEB)
Tartakovsky, Alexandre M.; Panchenko, Alexander
2016-01-15
We present a novel formulation of the Pairwise Force Smoothed Particle Hydrodynamics Model (PF-SPH) and use it to simulate two- and three-phase flows in bounded domains. In the PF-SPH model, the Navier-Stokes equations are discretized with the Smoothed Particle Hydrodynamics (SPH) method and the Young-Laplace boundary condition at the fluid-fluid interface and the Young boundary condition at the fluid-fluid-solid interface are replaced with pairwise forces added into the Navier-Stokes equations. We derive a relationship between the parameters in the pairwise forces and the surface tension and static contact angle. Next, we demonstrate the accuracy of the model under static and dynamic conditions. Finally, to demonstrate the capabilities and robustness of the model we use it to simulate flow of three fluids in a porous material.
Surface tension in an intrinsic curvature model with fixed one-dimensional boundaries
International Nuclear Information System (INIS)
A triangulated fixed connectivity surface model is investigated by using the Monte Carlo simulation technique. In order to have the macroscopic surface tension τ, the vertices on the one-dimensional boundaries are fixed as the edges (= circles) of the tubular surface in the simulations. The size of the tubular surface is chosen such that the projected area becomes a regular square of area A. An intrinsic curvature energy with a microscopic bending rigidity b is included in the Hamiltonian. We found that the model undergoes a first-order transition of surface fluctuations at finite b, where the surface tension τ discontinuously changes. The gap of τ remains constant at the transition point in a certain range of values A/N' at sufficiently large N', which is the total number of vertices excluding the fixed vertices on the boundaries. The value of τ remains almost zero in the wrinkled phase at the transition point while τ remains negative finite in the smooth phase in that range of A/N'
About the isocurvature tension between axion and high scale inflationary models
Estevez, Mariel
2016-01-01
The present work suggests that the isocurvature tension between axion and high energy inflationary scenarios may be avoided by considering a double field inflationary model involving the hidden Peccei-Quinn Higgs and the Standard Model one. Some terms in the lagrangian we propose explicitly violate the Peccei-Quinn symmetry but, at the present era, their effect is completely negligible. The resulting mechanism allows a large value for the axion constant, of the order $f_a\\sim M_p$, thus the axion isocurvature fluctuations are suppressed even when the scale of inflation $H_{inf}$ is very high, of the order of $H_{inf}\\sim M_{gut}$. This numerical value is typical in Higgs inflationary models. An analysis about topological defect formation in this scenario is also performed, and it is suggested that, under certain assumptions, their effect is not catastrophic from the cosmological point of view.
International Nuclear Information System (INIS)
Highlights: • The surface tensions of (MDEA + ionic liquids) aqueous solutions were measured. • The experiments were modeled satisfactorily by using a thermodynamic equation. • The temperature dependence of the surface tension was illustrated. • The effects of the mass fractions of MDEA and ionic liquids were demonstrated. -- Abstract: The surface tension (γ) of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), 1-butyl-3-methylimidazolium bromide ([Bmim][Br]), (N-methyldiethanolamine(MDEA) + [Bmim][BF4]) and (MDEA + [Bmim][Br]) aqueous solutions were measured by using the BZY-1 surface tension meter. The temperature ranged from (293.2 to 323.2) K. The mass fraction of MDEA ranged from 0.35 to 0.45. A thermodynamic equation was proposed to model the surface tension of (MDEA + ionic liquids) (ILS) aqueous solutions and the calculated results agreed well with the experiments. The effects of temperature, mass fractions of MDEA and ILS on the surface tension were demonstrated on the basis of experiments and calculations
Experiment and model for the surface tension of MEA-PEG400 and DEA-PEG400 aqueous solutions
International Nuclear Information System (INIS)
Highlights: • The surface tensions of PEG400 and amine-PEG400 aqueous solutions were measured. • The experiments were modeled satisfactorily by using a thermodynamic equation. • The temperature dependence of the surface tension was illustrated. • The effects of the mass fractions of amines and PEG400 were demonstrated. -- Abstract: The surface tension (γ) of monoethanolamine (MEA)-poly(ethylene oxide) 400 (PEG400) and diethanolamine (DEA)-PEG400 aqueous solutions was measured by using the BZY-1 surface tension meter. The temperatures ranged from (298.2 to 323.2) K. The mass fraction of amines and PEG400, respectively, ranged from 0.20 to 0.30 and from 0 to 0.10. A thermodynamic equation was proposed to model the surface tension of the binary and ternary mixtures. The calculated results agreed well with the experiments. The effects of temperature, mass fraction of amines and PEG400 on the surface tension were demonstrated on the basis of experiments and calculations
Abdallah, Wael
2011-05-18
Interfacial tension (IFT) measurements of Dodecane/brine systems at different concentrations and Dodecane/deionized water subject to different Dodecane purification cycles were taken over extended durations at room temperature and pressure to investigate the impact of aging. When a fresh droplet was formed, a sharp drop in IFT was observed assumed to be a result of intrinsic impurity adsorption at the interface. The subsequent measurements exhibited a prolonged equilibration period consistent with diffusion from the bulk phase to the interface. Our results indicate that minute amounts of impurities present in experimental chemical fluids "used as received" have a drastic impact on the properties of the interface. Initial and equilibrium IFT are shown to be dramatically different, therefore it is important to be cautious of utilizing IFT values in numerical models. The study demonstrates the impact these variations in IFT have on relative permeability relationships by adopting a simple pore network model simulation.
Modeling of a Curvilinear Planar Crack with a Curvature-Dependent Surface Tension
Zemlyanova, A. Y.
2012-01-01
An approach to modeling fracture incorporating interfacial mechanics is applied to the example of a curvilinear plane strain crack. The classical Neumann boundary condition is augmented with curvature-dependent surface tension. It is shown that the considered model eliminates the integrable crack-tip stress and strain singularities of order 1/2 present in the classical linear fracture mechanics solutions, and also leads to the sharp crack opening that is consistent with empirical observations. Unlike for the case of a straight crack, for a general curvilinear crack some components of the stresses and the derivatives of the displacements may still possess weaker singularities of a logarithmic type. Generalizations of the present study that lead to complete removal of all crack-tip singularities, including logarithmic, are the subject of a future paper. © 2012 Society for Industrial and Applied Mathematics.
Navigating Tensions Between Conceptual and Metaconceptual Goals in the Use of Models
Delgado, Cesar
2015-04-01
Science education involves learning about phenomena at three levels: concrete (facts and generalizations), conceptual (concepts and theories), and metaconceptual (epistemology) (Snir et al. in J Sci Educ Technol 2(2):373-388, 1993). Models are key components in science, can help build conceptual understanding, and may also build metaconceptual understanding. Technology can transform teaching and learning by turning models into interactive simulations that learners can investigate. This paper identifies four characteristics of models and simulations that support conceptual learning but misconstrue models and science at a metaconceptual level. Ahistorical models combine the characteristics of several historical models; they conveniently compile ideas but misrepresent the history of science (Gilbert in Int J Sci Math Educ 2(2):115-130, 2004). Teleological models explain behavior in terms of a final cause; they can lead to useful heuristics but imply purpose in processes driven by chance and probability (Talanquer in Int J Sci Educ 29(7):853-870, 2007). Epistemological overreach occurs when models or simulations imply greater certainty and knowledge about phenomena than warranted; conceptualizing nature as being well known (e.g., having a mathematical structure) poses the danger of conflating model and reality or data and theory. Finally, models are inevitably ontologically impoverished. Real-world deviations and many variables are left out of models, as models' role is to simplify. Models and simulations also lose much of the sensory data present in phenomena. Teachers, designers, and professional development designers and facilitators must thus navigate the tension between conceptual and metaconceptual learning when using models and simulations. For each characteristic, examples are provided, along with recommendations for instruction and design. Prompts for explicit reflective activities around models are provided for each characteristic
A New Approach for On-Demand Generation of Various Oxygen Tensions for In Vitro Hypoxia Models
Li, Chunyan; Chaung, Wayne; Mozayan, Cameron; Chabra, Ranjeev; Wang, Ping; Narayan, Raj K.
2016-01-01
The development of in vitro disease models closely mimicking the functions of human disease has captured increasing attention in recent years. Oxygen tensions and gradients play essential roles in modulating biological systems in both physiologic and pathologic events. Thus, controlling oxygen tension is critical for mimicking physiologically relevant in vivo environments for cell, tissue and organ research. We present a new approach for on-demand generation of various oxygen tensions for in vitro hypoxia models. Proof-of-concept prototypes have been developed for conventional cell culture microplate by immobilizing a novel oxygen-consuming biomaterial on the 3D-printed insert. For the first time, rapid (~3.8 minutes to reach 0.5% O2 from 20.9% O2) and precisely controlled oxygen tensions/gradients (2.68 mmHg per 50 μm distance) were generated by exposing the biocompatible biomaterial to the different depth of cell culture media. In addition, changing the position of 3D-printed inserts with immobilized biomaterials relative to the cultured cells resulted in controllable and rapid changes in oxygen tensions (3D-printed tissues or organs, it will serve as the basis for a new generation of experimental models previously impossible or very difficult to implement. PMID:27219067
Model-based traction force microscopy reveals differential tension in cellular actin bundles.
Soiné, Jérôme R D; Brand, Christoph A; Stricker, Jonathan; Oakes, Patrick W; Gardel, Margaret L; Schwarz, Ulrich S
2015-03-01
Adherent cells use forces at the cell-substrate interface to sense and respond to the physical properties of their environment. These cell forces can be measured with traction force microscopy which inverts the equations of elasticity theory to calculate them from the deformations of soft polymer substrates. We introduce a new type of traction force microscopy that in contrast to traditional methods uses additional image data for cytoskeleton and adhesion structures and a biophysical model to improve the robustness of the inverse procedure and abolishes the need for regularization. We use this method to demonstrate that ventral stress fibers of U2OS-cells are typically under higher mechanical tension than dorsal stress fibers or transverse arcs. PMID:25748431
Surface tension of spherical drops from surface of tension
Energy Technology Data Exchange (ETDEWEB)
Homman, A.-A.; Bourasseau, E. [CEA/DAM DIF, F-91297 Arpajon Cedex (France); Stoltz, G. [Université Paris-Est, CERMICS (ENPC), INRIA, F-77455 Marne-la-Vallée (France); Malfreyt, P. [Institut de Chimie de Clermont-Ferrand, Université Blaise Pascal, UMR CNRS 6296, ICCF, BP 10448, F-63000 Clermont-Ferrand (France); Strafella, L.; Ghoufi, A., E-mail: aziz.ghoufi@univ-rennes1.fr [Institut de Physique de Rennes, Université de Rennes 1 UMR 6251 CNRS, 263 avenue Général Leclerc, 35042 Rennes (France)
2014-01-21
The determination of surface tension of curved interfaces is a topic that raised many controversies during the last century. Explicit liquid-vapor interface modelling (ELVI) was unable up to now to reproduce interfacial behaviors in drops due to ambiguities in the mechanical definition of the surface tension. In this work, we propose a thermodynamic approach based on the location of surface of tension and its use in the Laplace equation to extract the surface tension of spherical interfaces from ELVI modelling.
Surface tension of spherical drops from surface of tension
International Nuclear Information System (INIS)
The determination of surface tension of curved interfaces is a topic that raised many controversies during the last century. Explicit liquid-vapor interface modelling (ELVI) was unable up to now to reproduce interfacial behaviors in drops due to ambiguities in the mechanical definition of the surface tension. In this work, we propose a thermodynamic approach based on the location of surface of tension and its use in the Laplace equation to extract the surface tension of spherical interfaces from ELVI modelling
Institute of Scientific and Technical Information of China (English)
谷家扬; 杨建民; 吕海宁
2013-01-01
Analyzing the dynamic response and calculating the tendon tension of the mooring system are necessary for the structural design of a tension leg platform (TLP). The six-degree-of-freedom dynamic coupling responses and the mooring characteristics of TLP under random waves are studied by using a self-developed program. Results are verified by the 1:40 scaling factor model test conducted in the State Key Laboratory of Ocean Engineering at Shanghai JiaoTong University. The mean, range, and standard deviation of the numerical simulation and model test are compared. The influences of different sea states and wave approach angles on the dynamic response and tendon tension of the mooring system are investigated. The acceleration in the center and corner of the deck is forecasted.
Prediction of viscosities and surface tensions of fuels using a new corresponding states model
DEFF Research Database (Denmark)
Queimada, A.J.; Rolo, L.I.; Caco, A.I.;
2006-01-01
While some properties of diesels are cheap, easy and fast to measure, such as densities, others such as surface tensions and viscosities are expensive and time consuming. A new approach that uses some basic information such as densities to predict viscosities and surface tensions is here proposed...
Directory of Open Access Journals (Sweden)
Kyu-Sik Park
2015-01-01
Full Text Available Hanger cables in suspension bridges are partly constrained by horizontal clamps. So, existing tension estimation methods based on a single cable model are prone to higher errors as the cable gets shorter, making it more sensitive to flexural rigidity. Therefore, inverse analysis and system identification methods based on finite element models are suggested recently. In this paper, the applicability of system identification methods is investigated using the hanger cables of Gwang-An bridge. The test results show that the inverse analysis and systemic identification methods based on finite element models are more reliable than the existing string theory and linear regression method for calculating the tension in terms of natural frequency errors. However, the estimation error of tension can be varied according to the accuracy of finite element model in model based methods. In particular, the boundary conditions affect the results more profoundly when the cable gets shorter. Therefore, it is important to identify the boundary conditions through experiment if it is possible. The FE model-based tension estimation method using system identification method can take various boundary conditions into account. Also, since it is not sensitive to the number of natural frequency inputs, the availability of this system is high.
Directory of Open Access Journals (Sweden)
2008-01-01
Full Text Available El año 2007 estuvo marcado por la continuidad del crecimiento económico, por las tensiones surgidas en la implementación del esquema macroeconómico de tipo de cambio elevado con superávit fiscal y comercial (inflación y deterioro del superávit fiscal primario del sector público, por la consolidación del dominio electoral del partido oficialista Frente para la Victoria (FPV con su triunfo en las elecciones generales y legislativas, y por la territorialización y faccionalización de los principales partidos políticos nacionales. Durante 2007 se observó una mejoría de los índices socioeconómicos (desempleo, pobreza e indigencia, así como un incremento de los niveles de conflictividad sindical, principalmente en las provincias. En el plano internacional, sobresalieron la conflictiva relación con Uruguay y la continuidad de la alianza económica con Venezuela.The year 2007 was marked by the continuity of economic growth, the tensions stemming from the implementation of the macroeconomic model (i.e., inflation and decline of the public sector’s primary fiscal surplus, which rests on a high exchange rate and commercial and fiscal surplus, the consolidation of the electoral predominance of the incumbent party Frente para la Victoria (FPV in the general and legislative elections, and by the territorialization and fractionalization of the main national political parties. During 2007, it is possible to observe an improvement in the socioeconomic indicators (unemployment, poverty, and poverty line, together with an increase in the levels of labor unions’ mobilization, especially in the provinces. At the international level, two aspects stood out: the conflictive relationship with Uruguay, and the continuity of the economic alliance with Venezuela.
Energy Technology Data Exchange (ETDEWEB)
Wenman, M.R., E-mail: m.wenman@imperial.ac.u [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Price, A.J. [Faculty of Engineering and Physical Sciences (J5), University of Surrey, Guildford GU2 7XH (United Kingdom); Steuwer, A. [ESS Scandinavia, Stora Algatan 4, 22350 Lund (Sweden) and Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa); Chard-Tuckey, P.R. [Nuclear Department, Defence College of Management and Technology, HMS Sultan, Gosport, Hants PO12 3BY (United Kingdom); Crocombe, A. [Faculty of Engineering and Physical Sciences (J5), University of Surrey, Guildford GU2 7XH (United Kingdom)
2009-12-15
The aim of the work is to elucidate the influence of plasticity behaviour on the residual stress field in a ferritic reactor pressure vessel steel. To this end, we investigate two compressively pre-loaded compact tension (CT) specimens to generate a mechanical residual stress field. One specimen was subsequently pre-cracked by fatigue before both specimens were measured using high-energy synchrotron X-ray diffraction. A fine grain size microstructure (approx5-10 mum grain size) allowed a small X-ray beam slit size and therefore gauge volume. The results provide an excellent data set for validation of finite element (FE) modelling predictions against which they have been compared. The results of both mechanical testing and modelling suggest that the use of a combined hardening model is needed to accurately predict the residual stress field present in the specimen after pre-loading. Some discrepancy between the modelled crack tip stress values and those found by X-ray diffraction remain which can be partly explained by volume averaging effects in the presence of very high stress/strain gradients.
International Nuclear Information System (INIS)
The aim of the work is to elucidate the influence of plasticity behaviour on the residual stress field in a ferritic reactor pressure vessel steel. To this end, we investigate two compressively pre-loaded compact tension (CT) specimens to generate a mechanical residual stress field. One specimen was subsequently pre-cracked by fatigue before both specimens were measured using high-energy synchrotron X-ray diffraction. A fine grain size microstructure (∼5-10 μm grain size) allowed a small X-ray beam slit size and therefore gauge volume. The results provide an excellent data set for validation of finite element (FE) modelling predictions against which they have been compared. The results of both mechanical testing and modelling suggest that the use of a combined hardening model is needed to accurately predict the residual stress field present in the specimen after pre-loading. Some discrepancy between the modelled crack tip stress values and those found by X-ray diffraction remain which can be partly explained by volume averaging effects in the presence of very high stress/strain gradients.
Simplified Prediction Model for Vortex-Induced Vibrations of Top Tensioned Risers
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
According to the characteristics of deepwater top tensioned risers, a simplified model is presented to predict the multi-modal response of vortex-induced vibration (VIV) in non-uniform flow based on energy equilibrium theory and the experimental data from VIV self-excited and forced oscillations of rigid cylinders. The response amplitude of each mode is determined by a balance between the energy fed into the riser over the lock-in regions and the energy dissipated by the fluid damping over the remainders. Compared with the previous prediction models, this method can take fully account of the intrinsic nature of VIV for low mass ratio structures on lock-in regions, added mass and nonlinear fluid damping effect, etc. Moreover, it is the first time to propose the accurate calculating procedure for VIV amplitude correction factor by solving energy equilibrium equation and a closed form solution is presented for the case of a riser of uniform mass and cross-section oscillating in a uniform flow. The predicted values show a reasonable agreement with VIV experiments of riser models in stepped and sheared currents.
DOUBLE-MEDIUM CONSTITUTIVE MODEL OF GEOLOGICAL MATERIAL IN UNIAXIAL TENSION AND COMPRESSION
Institute of Scientific and Technical Information of China (English)
LIU Xiao-li; WANG Si-jing; WANG En-zhi; XUE Qiang
2006-01-01
Based on elasto-plasticity and damage mechanics, a double-medium constitutive model of geological material under uniaxial tension and compression was presented,on the assumption that rock and soil materials are the pore-fracture double-medium, and porous medium has no damage occurring, while fracture medium has damage occurring with load. To the implicit equation of the model, iterative method was adopted to obtain the complete stress-strain curve of the material. The result shows that many different distributions (uniform distribution, concentrated distribution and random distribution)of fractures in rock and soil material are the essential reasons of the daedal constitutive relations. By the reason that the double-medium constitutive model separates the material to be porous medium part, which is the main body of elasticity, and fracture medium part, which is the main body of damage, it is of important practical values and theoretical meanings to the study on failure of rock and soil or materials containing damage.
Tension of knotted surgical sutures shows tissue specific rapid loss in a rodent model
Directory of Open Access Journals (Sweden)
Klink Christian D
2011-12-01
Full Text Available Abstract Background Every surgical suture compresses the enclosed tissue with a tension that depends from the knotting force and the resistance of the tissue. The aim of this study was to identify the dynamic change of applied suture tension with regard to the tissue specific cutting reaction. Methods In rabbits we placed single polypropylene sutures (3/0 in skin, muscle, liver, stomach and small intestine. Six measurements for each single organ were determined by tension sensors for 60 minutes. We collected tissue specimens to analyse the connective tissue stability by measuring the collagen/protein content. Results We identified three phases in the process of suture loosening. The initial rapid loss of the first phase lasts only one minute. It can be regarded as cutting through damage of the tissue. The percentage of lost tension is closely related to the collagen content of the tissue (r = -0.424; p = 0.016. The second phase is characterized by a slower decrease of suture tension, reflecting a tissue specific plastic deformation. Phase 3 is characterized by a plateau representing the remaining structural stability of the tissue. The ratio of remaining tension to initial tension of phase 1 is closely related to the collagen content of the tissue (r = 0.392; p = 0.026. Conclusions Knotted non-elastic monofilament sutures rapidly loose tension. The initial phase of high tension may be narrowed by reduction of the surgeons' initial force of the sutures' elasticity to those of the tissue. Further studies have to confirm, whether reduced tissue compression and less local damage permits improved wound healing.
Medina, Tait Runnfeldt
The increasing global reach of survey research provides sociologists with new opportunities to pursue theory building and refinement through comparative analysis. However, comparison across a broad array of diverse contexts introduces methodological complexities related to the development of constructs (i.e., measurement modeling) that if not adequately recognized and properly addressed undermine the quality of research findings and cast doubt on the validity of substantive conclusions. The motivation for this dissertation arises from a concern that the availability of cross-national survey data has outpaced sociologists' ability to appropriately analyze and draw meaningful conclusions from such data. I examine the implicit assumptions and detail the limitations of three commonly used measurement models in cross-national analysis---summative scale, pooled factor model, and multiple-group factor model with measurement invariance. Using the orienting lens of the double tension I argue that a new approach to measurement modeling that incorporates important cross-national differences into the measurement process is needed. Two such measurement models---multiple-group factor model with partial measurement invariance (Byrne, Shavelson and Muthen 1989) and the alignment method (Asparouhov and Muthen 2014; Muthen and Asparouhov 2014)---are discussed in detail and illustrated using a sociologically relevant substantive example. I demonstrate that the former approach is vulnerable to an identification problem that arbitrarily impacts substantive conclusions. I conclude that the alignment method is built on model assumptions that are consistent with theoretical understandings of cross-national comparability and provides an approach to measurement modeling and construct development that is uniquely suited for cross-national research. The dissertation makes three major contributions: First, it provides theoretical justification for a new cross-national measurement model and
Gramicidin channel kinetics under tension.
Goulian, M; Mesquita, O. N.; Fygenson, D K; Nielsen, C; Andersen, O S; Libchaber, A.
1998-01-01
We have measured the effect of tension on dimerization kinetics of the channel-forming peptide gramicidin A. By aspirating large unilamellar vesicles into a micropipette electrode, we are able to simultaneously monitor membrane tension and electrical activity. We find that the dimer formation rate increases by a factor of 5 as tension ranges from 0 to 4 dyn/cm. The dimer lifetime also increases with tension. This behavior is well described by a phenomenological model of membrane elasticity in...
A MODEL FOR THE CALCULATION OF SURFACE ENERGY AND SURFACE TENSION OF LIQUID METALS
Amokrane, S.; Badiali, J.; Rosinberg, M.; Goodisman, J.
1980-01-01
Surface energy and surface tension of liquid metals are calculated by applying to liquid surface a simple appropriate form of the Lang and Kohn's approach. Resulting values are in reasonable agreement with experiments.
Three-dimensional finite element modelling of the uniaxial tension test
DEFF Research Database (Denmark)
Østergaard, Lennart; Stang, Henrik
2002-01-01
. One of the most direct methods for determination of the σ-w relationship is the uniaxial tension test, where a notched specimen is pulled apart while the tensile load and the crack opening displacement is observed. This method is appealing since the interpretation is straightforward. The method is...... examined in this paper through three dimensional finite element analyses. It is concluded that the interpretation of the uniaxial tension test is indeed straightforward, if the testing machine stiffness is sufficiently high....
International Nuclear Information System (INIS)
Calcifying aponeurotic fibroma (CAF) is a rare, benign fibroblastic tumor that typically occurs in the palms of the hands and soles of the feet, in children and adolescents. Due to its infiltrative nature, this tumor can mimic malignancy on preoperative magnetic resonance imaging (MRI) and has a predilection for local recurrence. There are very few reports in the literature that describe features of CAF on MRI, especially those arising in the foot. We present an unusual case of a CAF affecting the dorsum of the foot in a four-year-old boy
Seismic evaluation of lead caves using no-tension discrete model with interface elements
International Nuclear Information System (INIS)
This paper investigates quasi-static behavior of lead cave walls radiation shields made by stacking lead bricks. The bricks have high stiffness, whereas the joints are weak and incapable of supporting tension. Global behavior of this kind of wall is strongly influenced by size friction coefficient of the brick elements. The general finite element code ANSYS was used for the analysis of the lead caves. A series of 2-D models that spanned the range of height-to-width aspect ratios of the cave wall were constructed. Two types of contact elements were incorporated in the model. The point-to-point contact element was used to represent contact in the horizontal direction. This element permits either compression in the direction normal to the surfaces or opening of a gap. The point-to-surface contact element was chosen to represent contact in the vertical direction. This element allows sliding in addition to the compression or gap formation normal to the surface. A series of static analyses were performed for each model. A l-g. vertical acceleration representing gravity was applied. The lateral acceleration was increased until the solution would not converge. This acceleration is defined as the critical lateral acceleration. This was achieved with a set of load steps with increasing lateral load. The critical acceleration was found to depend on the wall aspect ratio. For a wall with an aspect ratio up to three, the maximum acceleration is above the required 0.1 g. The wall failure mechanisms were also identified based on the numerical results. The two failure modes are the rotation and loss of interlocking among the blocks or silding of upper layers of the wall
International Nuclear Information System (INIS)
Foamed metals have been widely used as various engineering materials, and their mechanical properties have also been drawing extensive attention. In the present paper, a new mechanical and analytical model is established for these materials with isotropic three-dimensional reticulated structure under biaxial tension, and the mathematical equation about biaxial nominal stresses is deduced for the biaxial tension at the beginning of failure of the porous body. With the relevant experiment, the relation formula is proved to be very effective. Different from the relevant theoretical system of Gibson and Ashby, the present mathematical relationship can be conveniently achieved from directly using the 'beam theory' on this mechanical and analytical model. In addition, this relationship can be further expressed as the mathematical relationship among the nominal failure 'deviatoric stress', the nominal failure 'average stress' and porosity, but the concepts of both the 'deviatoric stress' and the 'average stress' can appear just from the mathematical treatment
An experimentally validated fatigue model for wood subjected to tension perpendicular to the grain
DEFF Research Database (Denmark)
Clorius, Christian Odin; Pedersen, Martin Uhre; Hoffmeyer, Preben;
2009-01-01
This study presents an experimental investigation of fatigue in wood subjected to tension perpendicular to the grain. The study has been designed with special reference to the influence of the frequency of loading. The investigation reveals an interaction between number of load oscillations and a...
Account for the surface tension in hydraulic modeling of the weir with a sharp threshold
Directory of Open Access Journals (Sweden)
Medzveliya Manana Levanovna
Full Text Available In the process of calculating and simulating water discharge in free channels it is necessary to know the flow features in case of small values of Reynolds and Weber numbers. The article considers the influence of viscosity and surface tension on the coefficient of a weir flow with sharp threshold. In the article the technique of carrying out experiments is stated, the equation is presented, which considers the influence of all factors: pressure over a spillway threshold, threshold height over a course bottom, speed of liquid, liquid density, dynamic viscosity, superficial tension, gravity acceleration, unit discharge, the width of the course. The surface tension and liquid density for the applied liquids changed a little. In the rectangular tray (6000x100x200 spillway with a sharp threshold was established. It is shown that weir flow coefficient depends on Reynolds number (in case Re < ~ 2000 and Webers number. A generalized expression for determining weir flow coefficient considering the influence of the forces of viscosity and surface tension is received.
Directory of Open Access Journals (Sweden)
T. Hede
2011-07-01
Full Text Available Cloud condensation nuclei act as cores for water vapour condensation, and their composition and chemical properties may enhance or depress the ability for droplet growth. In this study we use molecular dynamics simulations to show that model humic-like substances (HULIS in systems containing 10 000 water molecules mimic experimental data well referring to reduction of surface tension. The model HULIS compounds investigated in this study are cis-pinonic acid (CPA, pinic acid (PAD and pinonaldehyde (PAL. The structural properties examined show the ability for the model HULIS compounds to aggregate inside the nanoaerosol clusters.
International Nuclear Information System (INIS)
The transfer of amphiphilic solutes through an interface between water and an organic solvent has been studied numerically by simulations based on a general diffusion/reaction model. This description predicts the evolution of the solute concentrations and the transfer across the liquid/liquid interface. It especially focuses on the dynamic interfacial tension evolution that can be measured by a pendant drop tensiometer. Both the bulk diffusion and the adsorption/desorption rate on both sides of the liquid interface are assumed to contribute to the global transfer kinetic. The calculations provide an understanding on how kinetic exchange at the interface and diffusion transport through the bulk determine the dynamic interfacial tension evolution. In particular, complex interfacial tension evolutions with a non-trivial behavior are predicted in some special cases when diffusion and kinetic exchange are of the same order of magnitude. Finally, this model is used to re-interpret experimental data about Triton X-100 transfer at a water-oil interface. (authors)
Macroscopic modelling of the surface tension of polymer-surfactant systems
Bell, C. G.; Breward, C. J. W.; Howell, P. D.; Penfold, J; Thomas, R.K
2007-01-01
Polymer-surfactant mixtures are increasingly being used in a wide range of applications. Weakly-interacting systems, such as SDS/PEO and SDS/PVP, comprise ionic surfactants and neutral polymers, while strongly-interacting systems, such as SDS/POLYDMDAAC and C12TAB/NaPSS, comprise ionic surfactants and oppositely charged ionic polymers. The complex nature of interactions in the mixtures leads to interesting and surprising surface tension profiles as the concentrations of polymer and surfactant...
A two-structure model of themrodynamic properties and surface tension of supercooled water
Czech Academy of Sciences Publication Activity Database
Hrubý, Jan; Holten, V.
Kyoto : Maruzen Co., Ltd, 2005 - (Nakahara, M.; Matubayasi, N.; Ueno, M.; Yasuoka, K.; Watanabe, K.), s. 241-246 ISBN 4-621-07596-9. [International Conference on the Properties of Water and Steam /14./. Kyoto (JP), 29.08.2004-03.09.2004] R&D Projects: GA AV ČR(CZ) IAA2076203 Institutional research plan: CEZ:AV0Z20760514 Keywords : supercooled water * thermodynamic properties * surface tension Subject RIV: BJ - Thermodynamic s
Head and Neck Tension Biomechanical Models for Pediatric and Small Female Populations
Pintar, Frank A.; Yoganandan, Narayan; Gennarelli, Thomas A.
1999-01-01
Although airbag technology has been beneficial to the vast majority of occupants involved in vehicular collisions, there are certain scenarios that have been identified as potentially harmful to the occupant who is improperly positioned near a deploying airbag. A deploying airbag that expands around the neck region may thrust the occupant’s head up and back causing a tension-extension mechanism of injury in the neck structures. The purpose of the present study was to evaluate this injury in s...
Abdullah, A. B. M.; Rice, Jennifer A.; Hamilton, H. R.
2014-03-01
Post-tensioned segmental bridges are common throughout the US; however, in recent years, the incidence of tendon failure in bonded post-tensioned bridges has raised questions regarding their design, construction, and maintenance. These failures have led to the investigation of the applicability of using replaceable unbonded tendons in segmental construction and new methods for monitoring their condition. This paper presents a damage detection algorithm to identify strand breakage in unbonded tendons based on the relative variation of strains in the anchorage. In unbonded construction, the anchorage assembly usually undergoes a severe stress-state condition as the entire prestressing force only passes through the deviator and end anchorage locations. The strain distribution in the anchorage mechanism, therefore, goes through significant changes in response to the breakage of an individual wire or an entire strand in a multi-strand arrangement. In this way, breakage of a post-tensioning strand can be identified by observing a non-uniform variation of the strain field over the anchorage region in contrast to a uniform variation of strains due to environmental or traffic loading. A reduced scale laboratory experiment is performed followed by an extensive finite element simulation to conduct a parametric study with wire/strand breakages at different locations on multi-strand anchorages commonly used in industry. Based on the observed strain variations from simulation, a damage detection model is proposed that enables the adoption of an automated monitoring strategy to characterize the breakage programmatically.
Shin Hyunkyoung; Cho Sangrai; Jung Kwangjin
2014-01-01
A new 5-MW floating offshore wind turbine moored by a spring-tensioned-leg was proposed for installation in about 50m water depth. Its substructure is a platform of the inverted conical cylinder type with massive ballast weight plate at the bottom. A 1:128 scale model was built for the preliminary engineering development. The model tests in waves and wind were carried out to estimate motion characteristics of this platform in the Ocean Engineering Wide Tank of the University of Ulsan. Its mo...
Koga, K.; Widom, B.
2016-06-01
We treat two different density-functional models of the structures and tensions of the interfaces between phases on approach to the tricritical point of three-phase equilibrium. The major objective is to account for some of the results of earlier experimental measurements of these tensions. The thermodynamic background is first reviewed, including representations of the properties near the critical endpoints and tricritical point and of the wetting transitions that may occur on approach to those critical points. The first of the models treated is analytically soluble. Its properties are illuminating but at the price of some artificiality paid for its analytical solubility. The second model, called model T, is in a class of those treated in the past and analyzed numerically. Some of its properties are obtained with sufficient precision to allow one to conclude with near certainty what the analytically exact results would be. This model, too, illuminates the experimental measurements. It is noted where its properties are in accord with those of the analytically soluble model and where the two differ.
A Simple Size Effect Model for Tension Perpendicular to the Grain
DEFF Research Database (Denmark)
Pedersen, M. U.; Clorius, Christian Odin; Damkilde, Lars;
2003-01-01
The strength in tension perpendicular to the grain is known to decrease with an increase in the stressed volume. Usually this size effect is explained on a stochastic basis, that is, an explanation relying on the increased probability of encountering a strength reducing flaw when the volume of the...... material under stress is increased. This paper presents an experimental investigation on specimens with a well-defined structural orientation of the material. The experiments exhibit a large size effect and the nature of the failures encountered suggests that the size effect can be explained on a...
Ivić, Stefan; Čanađija, Marko; Družeta, Siniša
2014-01-01
Static structural analysis of a pipe during laying is usually performed by use of finite element analysis tools specialized for this purpose. In this paper, Abaqus/CAE, which is a general purpose FEA software, was used for a static non-linear structural analysis of a pipe during pipe laying. The pipe is modeled as a geometrically non-linear elastic beam supported by a vessel and its stinger in the overbend region and by the seabed in the sagbend region. We propose a new method for tensioner m...
International Nuclear Information System (INIS)
Motile cells regulate their shape and movements largely by remodeling the actin cytoskeleton. Principles of this regulation are becoming clear for simple-shaped steadily crawling cells, such as fish keratocytes. In particular, the shape of the leading edge and sides of the lamellipodium-cell motile appendage-is determined by graded actin distribution at the cell boundary, so that the denser actin network at the front grows, while sparser actin filaments at the sides are stalled by membrane tension. Shaping of the cell rear is less understood. Here we theoretically examine the hypothesis that the cell rear is shaped by the disassembly clock: the front-to-rear lamellipodial width is defined by the time needed for the actin-adhesion network to disassemble to the point at which the membrane tension can crush this network. We demonstrate that the theory predicts the observed cell shapes. Furthermore, turning of the cells can be explained by biases in the actin distribution. We discuss experimental implications of this hypothesis.
Institute of Scientific and Technical Information of China (English)
WANG Zeng; MA Wen; SONG Yong-xia
2005-01-01
The description of "Jingjin" (经筋aponeurotic system or muscles or tendinomuscular structures of the 12 regular meridians) in Chapter Jingjin of book Huangdi Neijing (the Yellow Emperor's Canon of Internal Medicine) is the earliest record on nervous system. The Jingjin and channels are interdependent, and together they form the major parts of the channel-collateral system in the theory of traditional Chinese medicine (TCM). The integration of their own functions contributes to the "Qiji" (气机 functional activities) of the channel-collateral system. The Jingjin distributes in the human body regularly like channels, with starting and ending points (which goes up and down), main streams and branches, converging and connecting spots, and specific manifestations for a certain disease. Observation by modern anatomy shows that blood vessels, nerves, and lymphatic vessels accompany closely with each other to run in the human body and work together to maintain human's life activities.
Yen, Pei-Shan; Datta, Ravindra
2014-07-15
The influence of oxygen on liquid-gas surface tension of molten metals has been well-investigated experimentally and modeled theoretically via the Szyszkowski equation, derivable from the Butler molecular monolayer interface model. However, there is no corresponding model describing the experimentally observed profound effect of oxygen partial pressure on solid-liquid surface tension as well as on contact angle of molten metals on ceramic substrates. Here, we utilize the Butler-Sugimoto thermodynamic approach based on a monomolecular bilayer interface model to investigate the effect of oxygen partial pressure on liquid-gas as well as solid-liquid surface tension of molten Cu/Al2O3 and molten Ag/Al2O3 systems. It is shown that both liquid-gas and solid-liquid surface tension are a strong function of oxygen activity in the melt, which, in turn, depends on gas-phase oxygen partial pressure, in conformity with experiments. The change in solid-liquid surface tension and wetting is also greatly affected by the change in liquid-gas surface tension. This improved understanding is of practical significance in many applications. PMID:24863799
Tsagas, C G
2001-01-01
The vector nature of magnetic fields and the general relativistic geometrical interpretation of gravity lead to a unique coupling between magnetism and spacetime curvature, by effectively transferring the field properties into the spacetime itself. The key magnetic property appears to be the tension of the field lines. Combined with geometry, the magnetic tension triggers a range of rather unexpected effects with profound implications. The field suppresses or boosts density fluctuations depending on the strength of the curvature deformation. It can act as an effective cosmological constant or mimic a time-decaying quintessence. Moreover, even weak magnetic fields become key players when the curvature is strong. For instance, a seed field could halt the accelerated phase in certain inflationary models. The magnetic tension also damps gravity waves and shows an intriguing tendency to smooth out spatial curvature distortions. We describe the nature and the range of these effects and discuss their potential impli...
Directory of Open Access Journals (Sweden)
D. O. Topping
2006-11-01
Full Text Available In order to predict the physical properties of aerosol particles, it is necessary to adequately capture the behaviour of the ubiquitous complex organic components. One of the key properties which may affect this behaviour is the contribution of the organic components to the surface tension of aqueous particles in the moist atmosphere. Whilst the qualitative effect of organic compounds on solution surface tensions has been widely reported, our quantitative understanding on mixed organic and mixed inorganic/organic systems is limited. Furthermore, it is unclear whether models that exist in the literature can reproduce the surface tension variability for binary and higher order multi-component organic and mixed inorganic/organic systems of atmospheric significance. The current study aims to resolve both issues to some extent. Surface tensions of single and multiple solute aqueous solutions were measured and compared with predictions from a number of model treatments. On comparison with binary organic systems, two predictive models found in the literature provided a range of values resulting from sensitivity to calculations of pure component surface tensions. Results indicate that a fitted model can capture the variability of the measured data very well, producing the lowest average percentage deviation for all compounds studied. The performance of the other models varies with compound and choice of model parameters. The behaviour of ternary mixed inorganic/organic systems was unreliably captured by using a predictive scheme and this was composition dependent. For more "realistic" higher order systems, entirely predictive schemes performed poorly. It was found that use of the binary data in a relatively simple mixing rule, or modification of an existing thermodynamic model with parameters derived from binary data, was able to accurately capture the surface tension variation with concentration. Thus, it would appear that in order to model
Jian, Cuiying; Poopari, Mohammad Reza; Liu, Qingxia; Zerpa, Nestor; Zeng, Hongbo; Tang, Tian
2016-06-30
In this work, pendant drop techniques and molecular dynamics (MD) simulations were employed to investigate the effect of asphaltene concentrations on the interfacial tension (IFT) of the oil/water interface. Here, oil and asphaltene were represented by, respectively, common organic solvents and Violanthrone-79, and two types of concentration, i.e., bulk concentration and surface concentration, were examined. Correlations between the IFTs from experiments and MD simulations revealed that surface concentration, rather than the commonly used bulk concentration, determines the reduction of oil/water IFTs. Through analyzing the hydrogen bonding, the underlying mechanism for the IFT reduction was proposed. Our discussions here not only enable the direct comparison between experiments and MD simulations on the IFTs but also help with future interfacial studies using combined experimental and simulation approaches. The methodologies used in this work can be extended to many other oil/water interfaces in the presence of interfacially active compounds. PMID:27268710
Schafer, Rachel; Gmitro, Arthur F.
2015-03-01
Tumor regions under hypoxic or low oxygen conditions respond less effectively to many treatment strategies, including radiation therapy. A novel investigational therapeutic, NVX-108 (NuvOx Pharma), has been developed to increase delivery of oxygen through the use of a nano-emulsion of dodecofluoropentane. By raising pO2 levels prior to delivering radiation, treatment efficacy may be improved. To aid in evaluating the novel drug, oxygen tension was quantitatively measured, spatially and temporally, to record the effect of administrating NVX-108 in an orthotopic mammary window chamber mouse model of breast cancer. The oxygen tension was measured through the use of an oxygen-sensitive coating, comprised of phosphorescent platinum porphyrin dye embedded in a polystyrene matrix. The coating, applied to the surface of the coverslip of the window chamber through spin coating, is placed in contact with the mammary fat pad to record the oxygenation status of the surface tissue layer. Prior to implantation of the window chamber, a tumor is grown in the SCID mouse model by injection of MCF-7 cells into the mammary fat pad. Two-dimensional spatial distributions of the pO2 levels were obtained through conversion of measured maps of phosphorescent lifetime. The resulting information on the spatial and temporal variation of the induced oxygen modulation could provide valuable insight into the optimal timing between administration of NVX-108 and radiation treatment to provide the most effective treatment outcome.
Energy Technology Data Exchange (ETDEWEB)
Suzuki, K. [Yokohama National Univ., Yokohama (Japan). Faculty of Engineering; Akiba, H. [Toyo Construction Co. Ltd., Tokyo (Japan)
1996-12-31
The effect of surface tension on free surface flow around floating models is discussed experimentally and numerically. Three-dimensional free surface flow around vertical circular cylinders floating in a circulating water channel was visually observed, where a surface-active agent was added to water. The results are analyzed using Weber number. The numerical analysis was done for vertical cylinder and CY100 models using the Rankine source method. Weber number of at least around 120 is necessary to eliminate the effect of surface tension from free surface flow around the CY100 model. The numerical analysis for the cylinder model needs simulation with wavelength shorter than that of free surface wave used by the Rankine source method. The model for the resistance test should be at least around 7m long to eliminate the effect of surface tension at Froude number of 0.1 or higher. 15 refs., 12 figs., 2 tabs.
Wu, Jie; Yu, Sheng-Tao; Jiang, Bo-nan
1996-01-01
In this paper a numerical procedure for simulating two-fluid flows is presented. This procedure is based on the Volume of Fluid (VOF) method proposed by Hirt and Nichols and the continuum surface force (CSF) model developed by Brackbill, et al. In the VOF method fluids of different properties are identified through the use of a continuous field variable (color function). The color function assigns a unique constant (color) to each fluid. The interfaces between different fluids are distinct due to sharp gradients of the color function. The evolution of the interfaces is captured by solving the convective equation of the color function. The CSF model is used as a means to treat surface tension effect at the interfaces. Here a modified version of the CSF model, proposed by Jacqmin, is used to calculate the tension force. In the modified version, the force term is obtained by calculating the divergence of a stress tensor defined by the gradient of the color function. In its analytical form, this stress formulation is equivalent to the original CSF model. Numerically, however, the use of the stress formulation has some advantages over the original CSF model, as it bypasses the difficulty in approximating the curvatures of the interfaces. The least-squares finite element method (LSFEM) is used to discretize the governing equation systems. The LSFEM has proven to be effective in solving incompressible Navier-Stokes equations and pure convection equations, making it an ideal candidate for the present applications. The LSFEM handles all the equations in a unified manner without any additional special treatment such as upwinding or artificial dissipation. Various bench mark tests have been carried out for both two dimensional planar and axisymmetric flows, including a dam breaking, oscillating and stationary bubbles and a conical liquid sheet in a pressure swirl atomizer.
Horizon Thermodynamics and Gravitational Tension
Widom, A.; Swain, J.; Srivastava, Y. N.
2016-01-01
We consider the thermodynamics of a horizon surface from the viewpoint of the vacuum tension $\\tau =(c^4/4G )$. Numerically, $\\tau \\approx 3.026\\times 10^{43}$ Newton. In order of magnitude, this is the tension that has been proposed for microscopic string models of gravity. However, after decades of hard work on string theory models of gravity, there is no firm scientific evidence that such models of gravity apply empirically. Our purpose is thereby to discuss the gravitational tension in te...
Zhang, Zhongyang; Liao, Yiliang
2016-04-01
For structural and engineering steels, accurate modeling of stress-strain relation of ferrite phase is of particular importance, since the modeling results could benefit new material system design and process-microstructure-property analysis. Several modeling efforts have been made to achieve this target. However, few efforts have been put on the Lüders elongation behavior of ferrite. As a result, the modeling results from proposed models do not match well with experimental data, particularly at a relatively low-strain range. Furthermore, without the consideration of yield point elongation due to the formation of Lüders bands, additional calibration parameters are required to capture the stress level of stress-strain curves. In this work, a multi-stage model is developed to predict the stress-strain relation of ferrite phase steel under room temperature tension. This model is capable of capturing the grain size effect on both Lüders elongation and work-hardening behaviors of ferrite. The modeling results are extensively validated by experimental data.
Nonequilibrium interfacial tension during relaxation.
Bier, Markus
2015-10-01
The concept of a nonequilibrium interfacial tension, defined via the work required to deform a system such that the interfacial area is changed while the volume is conserved, is investigated theoretically in the context of the relaxation of an initial perturbation of a colloidal fluid towards the equilibrium state. The corresponding general formalism is derived for systems with planar symmetry and applied to fluid models of colloidal suspensions and polymer solutions. It is shown that the nonequilibrium interfacial tension is not necessarily positive, that negative nonequilibrium interfacial tensions are consistent with strictly positive equilibrium interfacial tensions, and that the sign of the interfacial tension can influence the morphology of density perturbations during relaxation. PMID:26565189
Institute of Scientific and Technical Information of China (English)
LI Jinlong; HE Changchun; MA Jun; PENG Changjun; LIU Honglai; HU Ying
2011-01-01
The equation of state（EOS）for square-well chain fluid with variable range（SWCF-VR） developed in our previous work based on statistical mechanical theory for chemical association is employed for the correlations of surface tension and viscosity of common fluids and ionic liquids（ILs）.A model of surface tension for multi-component mixtures is presented by combining the SWCF-VR EOS and the scaled particle theory and used to produce the surface tension of binary and ternary mixtures.The predicted surface tensions are in excellent agreement with the experimental data with an overall average absolute relative deviation（AAD）of 0.36%.A method for the calculation of dynamic viscosity of common fluids and ILs at high pressure is presented by combining Eyring’s rate theory of viscosity and the SWCF-VR EOS.The calculated viscosities are in good agreement with the experimental data with the overall AAD of 1.44% for 14 fluids in 84 cases.The salient feature is that the molecular parameters used in these models are self-consistent and can be applied to calculate different thermodynamic properties such as pVT,vapor-liquid equilibrium,caloric properties,surface tension,and viscosity.
Horizon Thermodynamics and Gravitational Tension
Widom, A; Srivastava, Y N
2016-01-01
We consider the thermodynamics of a horizon surface from the viewpoint of the vacuum tension $\\tau =(c^4/4G )$. Numerically, $\\tau \\approx 3.026\\times 10^{43}$ Newton. In order of magnitude, this is the tension that has been proposed for microscopic string models of gravity. However, after decades of hard work on string theory models of gravity, there is no firm scientific evidence that such models of gravity apply empirically. Our purpose is thereby to discuss the gravitational tension in terms of the conventional Einstein general theory of relativity that apparently does explain much and maybe all of presently known experimental gravity data. The central result is that matter on the horizon surface is bound by the entropy-area law by tension in the closely analogous sense that the Wilson action-area law also describes a surface confinement.
Huber, M.; Keller, F.; Säckel, W.; Hirschler, M.; Kunz, P.; Hassanizadeh, S. M.; Nieken, U.
2016-04-01
The description of wetting phenomena is a challenging problem on every considerable length-scale. The behavior of interfaces and contact lines on the continuum scale is caused by intermolecular interactions like the Van der Waals forces. Therefore, to describe surface tension and the resulting dynamics of interfaces and contact lines on the continuum scale, appropriate formulations must be developed. While the Continuum Surface Force (CSF) model is well-engineered for the description of interfaces, there is still a lack of treatment of contact lines, which are defined by the intersection of an ending fluid interface and a solid boundary surface. In our approach we use a balance equation for the contact line and extend the Navier-Stokes equations in analogy to the extension of a two-phase interface in the CSF model. Since this model depicts a physically motivated approach on the continuum scale, no fitting parameters are introduced and the deterministic description leads to a dynamical evolution of the system. As verification of our theory, we show a Smoothed Particle Hydrodynamics (SPH) model and simulate the evolution of droplet shapes and their corresponding contact angles.
A Reduced Order Model of Force Displacement Curves for the Failure of Mechanical Bolts in Tension.
Energy Technology Data Exchange (ETDEWEB)
Moore, Keegan J. [Univ. of Illinois, Urbana-Champaign, IL (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Brake, Matthew Robert [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2015-12-01
Assembled mechanical systems often contain a large number of bolted connections. These bolted connections (joints) are integral aspects of the load path for structural dynamics, and, consequently, are paramount for calculating a structure's stiffness and energy dissipation prop- erties. However, analysts have not found the optimal method to model appropriately these bolted joints. The complexity of the screw geometry causes issues when generating a mesh of the model. This report will explore different approaches to model a screw-substrate connec- tion. Model parameters such as mesh continuity, node alignment, wedge angles, and thread to body element size ratios are examined. The results of this study will give analysts a better understanding of the influences of these parameters and will aide in finding the optimal method to model bolted connections.
International Nuclear Information System (INIS)
This paper presents the theoretical analysis of a flow driven by surface tension and gravity in an inclined circular tube. A governing equation is developed for describing the displacement of a non-Newtonian fluid(Power-law model) that continuously flows into a circular tube owing to surface tension, which represents a second-order, nonlinear, non-homogeneous, and ordinary differential form. It was found that quantitatively, the theoretical predictions of the governing equation were in excellent agreement with the solutions of the equation for horizontal tubes and the past experimental data. In addition, the predictions compared very well with the results of the force balance equation for steady
Institute of Scientific and Technical Information of China (English)
GAO Fu-qiang; KANG Hong-pu
2008-01-01
The importance of the pre-tensioned force of rock bolts has been recognized by more and more researchers. To investigate the effect of pre-tensioned rock bolts on stress redistribution around roadways, a numerical analysis was carded out using FLAC3D and a special post-process methodology, using surfer, is proposed to process the numerical simulation results. The results indicate that pre-tensioned rock bolts have a significant effect on stress redistribution around a roadway. In the roof, pre-tensioned rock bolts greatly increase vertical stress; as a result, the strength of the rock mass increased significantly which results in a greater capacity of bearing a large horizontal stress. The horizontal stress decreases in the upper section of the roof, indicating that pre-tensioned rock bolts significantly reduce the coefficient and the size of the region concentration of horizontal stress. At the lateral side, pre-tensioned rock bolts greatly increase the horizontal stress; therefore, the rock mass strength significantly increases which results also in a greater capacity of bearing a large vertical stress. The greater the size of pre-tensioned force, the larger the region of stress redistribution around a roadway is affected and the higher the size of the stress on the roadway surface the more the rock mass strength increases.
Fujioka, Hideki; Halpern, David; Gaver, Donald P
2013-01-18
We developed a computational model of lung parenchyma, which is comprised of individual alveolar chamber models. Each alveolus is modeled by a truncated octahedron. Considering the force balance between the elastin and collagen fibers laying on the alveolar membrane and the pressures acting on the membrane, we computed the deformations of the parenchyma with a finite element method. We focused on the effect of surfactant on the force of parenchymal tethering an airway. As the lung inflates, the parenchyma becomes stiffer and the tethering force becomes stronger. As the alveolar surfactant concentration is reduced, the lung volume at a fixed alveolar pressure decreases, and thus, the tethering force becomes weaker. The distortion of parenchyma caused by the deformation of an airway extends widely around the airway. The displacement of parenchyma decays with distance from the airway wall, but deviates from the prediction based on a theory for a continuum material. Using results obtained from the present lung parenchyma model, we also developed a simple 1-dimensional model for parenchyma tethering force on an airway, which could be utilized for the analysis of liquid/gas transports in an axis-symmetric elastic airway. The effective shear modulus was calculated from the pressure-volume relation of parenchyma. By manipulating the pressure-volume curve, this simple model may be used to predict the parenchyma tethering force in diseased lungs. PMID:23235110
Directory of Open Access Journals (Sweden)
Vinš Václav
2014-03-01
Full Text Available The density gradient theory (GT combined with a SAFT-type (Statistical Associating Fluid Theory equation of state has been used for modeling the surface tension of associating fluids represented by a series of six alkanols ranging from methanol to 1-pentanol. The effect of nonzero dipole moment of the selected alkanols on the predicted surface tension was investigated in this study. Results of the GT + non-polar Perturbed Chain (PC SAFT equation of state were compared to predictions of GT combined with the PC-polar-SAFT, i.e. PCP-SAFT, equation. Both GT + PC-SAFT and GT + PCP-SAFT give reasonable prediction of the surface tension for pure alkanols. Results of both models are comparable as no significant difference in the modeled saturation properties and in the predicted surface tension using GT was found. Consideration of dipolar molecules of selected alkanols using PCP-SAFT had only minor effect on the predicted properties compared to the non-polar PC-SAFT model.
Hu, Bin
2015-01-01
Planck-2015 data seem to favour a large value of the lensing amplitude parameter, $A_{\\rm L}=1.22\\pm0.10$, in CMB spectra. This result is in $2\\sigma$ tension with the lensing reconstruction result, $A_{\\rm L}^{\\phi\\phi}=0.95\\pm0.04$. In this paper, we simulate several CMB anisotropy and CMB lensing spectra based on Planck-2015 best-fit cosmological parameter values and Planck blue book beam and noise specifications. We analyse several modified gravity models within the effective field theory framework against these simulations and find that models whose effective Newton constant is enhanced can modulate the CMB anisotropy spectra in a way similar to that of the $A_{\\rm L}$ parameter. However, in order to lens the CMB anisotropies sufficiently, like in the Planck-2015 results, the growth of matter perturbations is substantially enhanced and gives a high $\\sigma_8$ value. This in turn proves to be problematic when combining these data to other probes, like weak lensing from CFHTLenS, that favour a smaller ampl...
Inquiry through Modeling: Exploring the Tensions between Natural & Sexual Selection Using Crickets
Bouwma-Gearhart, Jana; Bouwma, Andrew
2015-01-01
The "Next Generation Science Standards" (NGSS Lead States, 2013) recommend that science courses engage communities of students in scientific practices that include building accurate conceptual models of phenomena central to the understanding of scientific disciplines. We offer a set of activities, implemented successfully at both the…
Navigating Tensions between Conceptual and Metaconceptual Goals in the Use of Models
Delgado, Cesar
2015-01-01
Science education involves learning about phenomena at three levels: concrete (facts and generalizations), conceptual (concepts and theories), and metaconceptual (epistemology) (Snir et al. in "J Sci Educ Technol" 2(2):373-388, 1993). Models are key components in science, can help build conceptual understanding, and may also build…
Directory of Open Access Journals (Sweden)
D. O. Topping
2007-01-01
Full Text Available In order to predict the physical properties of aerosol particles, it is necessary to adequately capture the behaviour of the ubiquitous complex organic components. One of the key properties which may affect this behaviour is the contribution of the organic components to the surface tension of aqueous particles in the moist atmosphere. Whilst the qualitative effect of organic compounds on solution surface tensions has been widely reported, our quantitative understanding on mixed organic and mixed inorganic/organic systems is limited. Furthermore, it is unclear whether models that exist in the literature can reproduce the surface tension variability for binary and higher order multi-component organic and mixed inorganic/organic systems of atmospheric significance. The current study aims to resolve both issues to some extent. Surface tensions of single and multiple solute aqueous solutions were measured and compared with predictions from a number of model treatments. On comparison with binary organic systems, two predictive models found in the literature provided a range of values resulting from sensitivity to calculations of pure component surface tensions. Results indicate that a fitted model can capture the variability of the measured data very well, producing the lowest average percentage deviation for all compounds studied. The performance of the other models varies with compound and choice of model parameters. The behaviour of ternary mixed inorganic/organic systems was unreliably captured by using a predictive scheme and this was dependent on the composition of the solutes present. For more atmospherically representative higher order systems, entirely predictive schemes performed poorly. It was found that use of the binary data in a relatively simple mixing rule, or modification of an existing thermodynamic model with parameters derived from binary data, was able to accurately capture the surface tension variation with concentration. Thus
Mobasher, Barzin
2011-01-01
The Aveston Copper and Kelly (ACK) Method has been routinely used in estimating the efficiency of the bond between the textile and cementitious matrix. This method however has a limited applicability due to the simplifying assumptions such as perfect bond. A numerical model for simulation of tensile behavior of reinforced cement-based composites is presented to capture the inefficiency of the bond mechanisms. In this approach the role of interface properties which are instrumental in the simu...
A Simple Size Effect Model for Tension Perpendicular to the Grain
DEFF Research Database (Denmark)
Pedersen, M.U.; Clorius, C.O.; Damkilde, Lars;
2003-01-01
material under stress is increased. This paper presents an experimental investigation on specimens with a well-defined structural orientation of the material. The experiments exhibit a large size effect and the nature of the failures encountered suggests that the size effect can be explained on a...... deterministic basis. Arguments for such a simple deterministic explanation of size effect is found in finite element modelling, using the orthotropic stiffness characteristics in the transverse plane of wood....
The accurate simulation of the tension test for stainless steel sheet: the plasticity model
International Nuclear Information System (INIS)
Full text: The overall aim of this research project is to achieve the accurate simulation of a hydroforming process chain, in this case the manufacturing of a metal bellow. The work is done in cooperation with the project group for numerical research at the computer centre of the University of Karlsruhe, which is responsible for the simulation itself, while the Institute for Metal Forming Technology (IFU) of the University of Stuttgart is responsible for the material modeling and the resulting differential equations to describe the material behavior. Hydroforming technology uses highly compressed fluid media (up to 4200 bar) to form the basic, mostly metallic material. One hydroforming field is tube hydroforming (THF), which uses tubes or extrusions as basic material. The forming conditions created by hydroforming are quite different from those originated by other processes as for example deep drawing. That's why today's available simulation software is not always able to show satisfying results when a hydroforming process is simulated. The partners of this project try to solve this problem with the FDEM simulation software, developed by W. Schoenauer at the University of Karlsruhe, Germany. It was designed to solve systems of partial differential equations, which in this project are delivered by the IFU. The manufacturing of a metal bellow by hydroforming leads to tensile stress in longitudinal and tangential direction and to bend load due to the shifting and rollforming process. Therefore as a first step, the standardized tensile test is simulated. For plastic deformation a material model developed by D. Banabic is used. It describes the plastic behavior of orthotropic sheet metal. For elastic deformation Hooke's law for isotropic materials is used. In permanent iteration with the simulation the used material model has to be checked for its validity and must be modified if necessary. Refs. 3 (author)
THE OLD-NEW TENSION AND THE PRODUCTIVE FORCE TRANSFORMATION MODEL
Directory of Open Access Journals (Sweden)
Dumitru – Alexandru Bodislav
2010-12-01
Full Text Available This paper will develop a theoretical and applied approach of a special case which appeared in a media company, The New York Times Company, company which ownes the newspaper with the biggest global circulation, aproxamtively 1 million copies sold daily, printed and electronic, „The New York Times”. This case represents the appearance of linking and coordination component between new (online and old (print. To have the biggest stakes, the new coordination must borrow from the initial coordionation resources. This needs a captious equilibrated balance scale. The new coordination must be distinctive from the initial one, because a new organisational design implements the phenomenon of forgetting into the initial coordinates. The two business units must be connected, although interactions between the new and the old coordination will create unavoidable frictions. Only when the new coordination is distinct and connected with the initial coordination, both will forget the previous systems and will create an intra-business, mutually beneficial borrowing. This paper will illustrate the pattern/model of elaborating/developing/implementing in a strong represented business on a market, which wants a new complementary approach to the initial model of doing business.
Kink-pair formation on dislocations within the framework of the line-tension model
International Nuclear Information System (INIS)
This article deals with the plastic deformation of crystals under an applied stress and summarizes various theoretical concepts within the framework of a model of dislocation migration in crystals. The migration of one type of dislocations in their glide plane is described within the framework of a continuum approximation. The dynamics of the physical system is treated by a Hamiltonian method describing solitonic vibrations of a one-dimensional field added by discussions of a special perturbation which models the applied stress in the glide plane of the dislocation. Dislocation migration is governed by nucleation processes. Therefore, one has to apply thermodynamical concepts in order to calculate the formation rate of the nucleation configuration of the dislocation. This is done here by mapping the solitonic field onto a Brownian particle and using Kramers' famous work on nucleation in chemical reactions. The last section is devoted to an approach involving quantum thermodynamical effects and relating them to tunnelling processes of kinks on dislocations. The method used for calculating tunnelling rates is based on Feynman's path integral method in imaginary time formulation. (author). 26 refs, 12 figs
Skin tension related to tension reduction sutures.
Hwang, Kun; Kim, Han Joon; Kim, Kyung Yong; Han, Seung Ho; Hwang, Se Jin
2015-01-01
The aim of this study was to compare the skin tension of several fascial/subcutaneous tensile reduction sutures. Six upper limbs and 8 lower limbs of 4 fresh cadavers were used. At the deltoid area (10 cm below the palpable acromion) and lateral thigh (midpoint from the palpable greater trochanter to the lateral border of the patella), and within a 3 × 6-cm fusiform area of skin, subcutaneous tissue defects were created. At the midpoint of the defect, a no. 5 silk suture was passed through the dermis at a 5-mm margin of the defect, and the defect was approximated. The initial tension to approximate the margins was measured using a tensiometer.The tension needed to approximate skin without any tension reduction suture (S) was 6.5 ± 4.6 N (Newton). The tensions needed to approximate superficial fascia (SF) and deep fascia (DF) were 7.8 ± 3.4 N and 10.3 ± 5.1 N, respectively. The tension needed to approximate the skin after approximating the SF was 4.1 ± 3.4 N. The tension needed to approximate the skin after approximating the DF was 4.9 ± 4.0 N. The tension reduction effect of approximating the SF was 38.8 ± 16.4% (2.4 ± 1.5 N, P = 0.000 [ANOVA, Scheffé]). The tension reduction effect of approximating the DF was 25.2% ± 21.9% (1.5 ± 1.4 N, P = 0.001 [ANOVA, Scheffé]). The reason for this is thought to be that the SF is located closely to the skin unlike the DF. The results of this study might be a basis for tension reduction sutures. PMID:25569413
Institute of Scientific and Technical Information of China (English)
Tao WANG; Ling-bo HOU; Zhen-jun LIU; Yan WANG; Chun-lian CHEN; Xiao XIAO; Dao-wen WANG
2007-01-01
Aim: The overexpression of the human tissue kallikrein (HK) gene can reduce blood pressure and ameliorate the secondary syndromes associated with hyper- tension in animal models. The current study was designed to investigate hy- potensive effect of intramuscular delivery of HK gene. Methods: We generated an recombinant adeno-associated virus (rAAV) vector expressing human tissue kallikrein under the control of a cytomegalovirus promoter and administered the rAAV-HK vector to a spontaneously hypertensive rat model at a dose of 1× 1010 virons/rat through intramuscular injection. Results: A persistent, high-level ex- pression of HK post-gene delivery was confirmed by ELISA. The systolic blood pressure in the rats receiving rAAV-LacZ and saline increased from 171.3 mmHg to 182.3 mmHg 28 weeks' post injection. In contrast, the delivery of the HK gene by AAV vectors attenuated the increase of the systolic blood pressure in the treated group. The systolic blood pressure was only slightly lowered (from a level of 174 mmHg to 170.5 mmHg) post-vector administration. The difference in blood pres- sure between the treated group and the control groups is statistically significant at 12.6 mmHg. The hypotensive effect of rAAV-HK persisted until the end of the testing period. In addition, a significant amelioration of cardiovascular hypertrophy, renal injury, and collagen depositions in the rAAV-HK-treated ani- mals were also observed. Conclusion: All the effects are comparable with those of intravenous delivery. Therefore, the intramuscular administration of rAAV-HK may be used in gene therapy for hypertension.
Demonstration of Surface Tension.
Rosenthal, Andrew J.
2001-01-01
Surface tension is a fundamental obstacle in the spontaneous formation of bubbles, droplets, and crystal nuclei in liquids. Describes a simple overhead projector demonstration that illustrates the power of surface tension that can prevent so many industrial processes. (ASK)
Surface tension profiles in vertical soap films
Adami, N.; Caps, H.
2013-01-01
Surface tension profiles in vertical soap films are experimentally investigated. Measurements are performed introducing deformable elastic objets in the films. The shape adopted by those objects set in the film can be related to the surface tension value at a given vertical position by numerical solving of adapted elasticity equations. We show that the observed dependency of the surface tension versus the vertical position in the soap film can be reproduced by simple modeling taking into acco...
Anisotropic surface tension of buckled fluid membrane
Noguchi, Hiroshi
2011-01-01
Solid sheets and fluid membranes exhibit buckling under lateral compression. Here, it is revealed that fluid membranes have anisotropic buckling surface tension contrary to solid sheets. Surprisingly, the surface tension perpendicular to the buckling direction shows stronger dependence than that parallel to it. Our theoretical predictions are supported by numerical simulations of a meshless membrane model. This anisotropic tension can be used to measure the membrane bending rigidity. It is al...
International Nuclear Information System (INIS)
Highlights: → Surface tension and the Gibbs-Thomson coefficient are computed for Al-based alloys. → Butler's scheme and ThermoCalc are used to compute the thermophysical properties. → Predictive cell/dendrite growth models depend on accurate thermophysical properties. → Mechanical properties can be related to the microstructural cell/dendrite spacing. - Abstract: In this paper, a solution for Butler's formulation is presented permitting the surface tension and the Gibbs-Thomson coefficient of Al-based binary alloys to be determined. The importance of Gibbs-Thomson coefficient for binary alloys is related to the reliability of predictions furnished by predictive cellular and dendritic growth models and of numerical computations of solidification thermal variables, which will be strongly dependent on the thermophysical properties assumed for the calculations. A numerical model based on Powell hybrid algorithm and a finite difference Jacobian approximation was coupled to a specific interface of a computational thermodynamics software in order to assess the excess Gibbs energy of the liquid phase, permitting the surface tension and Gibbs-Thomson coefficient for Al-Fe, Al-Ni, Al-Cu and Al-Si hypoeutectic alloys to be calculated. The computed results are presented as a function of the alloy composition.
一种纱线张力数字化仿真模型%A Digitized Simulation Model of Yarn Tension
Institute of Scientific and Technical Information of China (English)
邱海飞
2012-01-01
The CAD model of 6 - bar shedding mechanism is set up in ADAMS/View, and the kinematics simu-lation analysis for it is earned out. Hookeanspring is used to substitute for actual yam, and a virtual simulation platform which could simulate dynamic changes of yam tension is created. Trie curve of yam deflections and tension change are acquired through dynamic simulation, and the rationality and feasibility of the model is verified by comparing the simu-lation results with the measured results. In results, a new way of measuring yam tension is offered.%在ADAMS/View中建立了六连杆开口机构的CAD模型,并对其进行了运动学仿真分析.通过线性弹簧来代替实际纱线,创建了一种可以模拟纱线张力动态变化的虚拟仿真平台.通过动态仿真获得了纱线形变量和纱线张力变化曲线,并将实测结果与仿真结果进行比较,验证了该模型的合理性和可行性,为纱线张力的测试提供了一种新思路.
Osth, Jonas; Olafsdóttir, Jóna Marín; Davidsson, Johan; Brolin, Karin
2013-11-01
The objectives of this study are to generate validation data for human models intended for simulation of occupant kinematics in a pre-crash phase, and to evaluate the effect of an integrated safety system on driver kinematics and muscle responses. Eleven male and nine female volunteers, driving a passenger car on ordinary roads, performed maximum voluntary braking; they were also subjected to autonomous braking events with both standard and reversible pre-tensioned restraints. Kinematic data was acquired through film analysis, and surface electromyography (EMG) was recorded bilaterally for muscles in the neck, the upper extremities, and lumbar region. Maximum voluntary contractions (MVCs) were carried out in a driving posture for normalization of the EMG. Seat belt positions, interaction forces, and seat indentions were measured. During normal driving, all muscle activity was below 5% of MVC for females and 9% for males. The range of activity during steady state braking for males and females was 13-44% in the cervical and lumbar extensors, while antagonistic muscles showed a co-contraction of 2.3-19%. Seat belt pre-tension affects both the kinematic and muscle responses of drivers. In autonomous braking with standard restraints, muscle activation occurred in response to the inertial load. With pre-tensioned seat belts, EMG onset occurred earlier; between 71 ms and 176 ms after belt pre-tension. The EMG onset times decreased with repeated trials and were shorter for females than for males. With the results from this study, further improvement and validation of human models that incorporate active musculature will be made possible. PMID:24435725
Mayoral, E
2016-01-01
We study and predict the interfacial tension, solubility parameters and Flory-Huggins parameters of binary mixtures as functions of pressure and temperature, using multiscale numerical simulation. A mesoscopic approach is proposed for simulating the pressure dependence of the interfacial tension for binary mixtures, at different temperatures, using classical Dissipative Particle Dynamics (DPD). The thermodynamic properties of real systems are reproduced via the parametrization of the repulsive interaction parameters as functions of pressure and temperature via Molecular Dynamics simulations. Using this methodology, we calculate and analyze the cohesive density energy and the solubility parameters of different species obtaining excellent agreement with reported experimental behavior. The pressure- and temperature-dependent Flory-Huggins and repulsive DPD interaction parameters for binary mixtures are also obtained and validated against experimental data. This multiscale methodology offers the benefit of being ...
Mayoral, E; Nahmad-Achar, E
2016-03-10
We study and predict the interfacial tension, solubility parameters, and Flory-Huggins parameters of binary mixtures as functions of pressure and temperature, using multiscale numerical simulation. A mesoscopic approach is proposed for simulating the pressure dependence of the interfacial tension for binary mixtures, at different temperatures, using classical dissipative particle dynamics (DPD). The thermodynamic properties of real systems are reproduced via the parametrization of the repulsive interaction parameters as functions of pressure and temperature via molecular dynamics simulations. Using this methodology, we calculate and analyze the cohesive energy density and the solubility parameters of different species obtaining excellent agreement with reported experimental behavior. The pressure- and temperature-dependent Flory-Huggins and repulsive DPD interaction parameters for binary mixtures are also obtained and validated against experimental data. This multiscale methodology offers the benefit of being applicable for any species and under difficult or nonfeasible experimental conditions, at a relatively low computational cost. PMID:26840645
Underslung Payload Tension Control from an Autonomous Unmanned Helicopter
McCabe, Brian John
2012-01-01
A tension control algorithm for the deployment of a unmanned ground vehicle from an autonomous helicopter is designed and tested in this thesis. The physical hardware which the controller will run on is detailed. The plant model and underlying controllers are derived and modeled. The tension controller algorithm is selected, derived, and modeled. The parameters of the tension controller are chosen and simulations are run with the chosen parameters. The tension control algorithm...
Energy Technology Data Exchange (ETDEWEB)
Prowell, I.; Robertson, A.; Jonkman, J.; Stewart, G. M.; Goupee, A. J.
2013-01-01
Realizing the critical importance the role physical experimental tests play in understanding the dynamics of floating offshore wind turbines, the DeepCwind consortium conducted a one-fiftieth-scale model test program where several floating wind platforms were subjected to a variety of wind and wave loading condition at the Maritime Research Institute Netherlands wave basin. This paper describes the observed behavior of a tension-leg platform, one of three platforms tested, and the systematic effort to predict the measured response with the FAST simulation tool using a model primarily based on consensus geometric and mass properties of the test specimen.
Richards, Howard L.; Novotny, M. A.; Rikvold, Per Arne
1993-01-01
We compute by numerical transfer-matrix methods the surface free energy $\\tau(T),$ the surface stiffness coefficient $\\kappa(T),$ and the single-step free energy $s(T)$ for Ising ferromagnets with $(\\infty \\times L)$ square-lattice and $(\\infty \\times L \\times M)$ cubic-lattice geometries, into which an interface is introduced by imposing antiperiodic or plus/minus boundary conditions in one transverse direction. These quantities occur in expansions of the angle-dependent surface tension, eit...
de Castro, Marcelo Souza; Rodriguez, Oscar Mauricio Hernandez
2016-06-01
The study of the hydrodynamic stability of flow patterns is important in the design of equipment and pipelines for multiphase flows. The maintenance of a particular flow pattern becomes important in many applications, e.g., stratified flow pattern in heavy oil production avoiding the formation of emulsions because of the separation of phases and annular flow pattern in heat exchangers which increases the heat transfer coefficient. Flow maps are drawn to orientate engineers which flow pattern is present in a pipeline, for example. The ways how these flow maps are drawn have changed from totally experimental work, to phenomenological models, and then to stability analysis theories. In this work an experimental liquid-liquid flow map, with water and viscous oil as work fluids, drawn via subjective approach with high speed camera was used to compare to approaches of the same theory: the interfacial-tension-force model. This theory was used to drawn the wavy stratified flow pattern transition boundary. This paper presents a comparison between the two approaches of the interfacial-tension-force model for transition boundaries of liquid-liquid flow patterns: (i) solving the wave equation for the wave speed and using average values for wave number and wave speed; and (ii) solving the same equation for the wave number and then using a correlation for the wave speed. The results show that the second approach presents better results.
Marcucci, Lorenzo
2016-01-01
Almost 60 years ago Andrew Huxley with his seminal paper \\cite{Huxley1957} laid the foundation of modern muscle modeling, linking chemical events to mechanical performance. He described mechanics and energetics of muscle contraction through the cyclical attachment and detachment of myosin motors to the actin filament with ad hoc assumptions on the dependence of the rate constants on the strain of the myosin motors. That relatively simple hypothesis is still present in recent models, even though with several modifications to adapt the model to the different experimental constraints which became subsequently available. However, already in that paper, one controversial aspect of the model became clear. Relatively high attachment and detachment rates of myosin to the actin filament were needed to simulate the high power output at intermediate velocity of contraction. However, these rates were incompatible with the relatively slow rise in tension after activation, despite the rise should be generated by the same r...
Latorre, Marcos; Montáns, Francisco J
2016-04-01
Many biological soft tissues are structurally composed of a mostly isotropic matrix (elastin) and fibers (collagen). These fibers are not perfectly aligned but dispersed around some referential, preferred directions. In order to account for the dispersion of the fibers, a probability distribution is assumed. The Generalized Structure Tensor (GST) models perform a pre-integration of the distribution in order to achieve improved computational efficiency. The best known model of this kind is the Gasser-Ogden-Holzapfel (GOH) model. However, in these models no singular treatment of fibers is made. Whenever they suffer compression it is usual to consider that fibers should not contribute to the overall stiffness. At this point, a switch criterion is employed. This switch criterion is important because it changes the model predictions and may also result in unphysical stress predictions or strain ranges at which no compatible equilibrium solution is found. We perform an analysis of different tension-compression switch criteria from the literature for the GOH model and show relevant physical and computational drawbacks when using these criteria. In order to overcome these drawbacks, we make a new proposal which yields continuous stress solutions. In our proposal, pre-integrated expressions given in terms of the usual set of invariants take into account an average amount of fibers working either in tension or in compression for a given deformation gradient and fiber family. Two distinct switches naturally emerge from our procedure. Furthermore, we keep the appealing GST pre-integrated approach for any proposed stored energy, including that of the GOH model. PMID:26720909
Tunneling with negative tension
Marvel, Kate
2008-01-01
We describe a new family of thin-wall instantons, with negative tension bubble walls, that mediate tunneling between Minkowski or de Sitter vacua. Some of these instantons can have exponentially enhanced tunneling rates, and would dominate the Euclidean path integral, representing a severe non-perturbative instability in any theory which supports them. We give two constructions of these instantons in theories which are perturbatively stable, but violate the null energy condition. One construction uses a scalar field theory with higher-derivative kinetic term, and is similar to the Coleman-de Luccia positive tension instanton. The other construction employs a negative-tension boundary arising from Z_2 orbifolding: it resembles a "bubble of nothing" which nucleates and grows, consuming the surrounding de Sitter or Minkowski spacetime. We explain how the spectral flow for fluctutations about the thin-wall tunneling solutions automatically protects causality, for both positive and negative tension instantons. We ...
Energy Technology Data Exchange (ETDEWEB)
Matha, D.
2010-02-01
This report presents results of the analysis of a 5-MW wind turbine located on a floating offshore tension leg platform (TLP) that was conducted using the fully coupled time-domain aero-hydro-servo-elastic design code FAST with AeroDyn and HydroDyn. The report also provides a description of the development process of the TLP model. The model has been verified via comparisons to frequency-domain calculations. Important differences have been identified between the frequency-domain and time-domain simulations, and have generated implications for the conceptual design process. An extensive loads and stability analysis for ultimate and fatigue loads according to the procedure of the IEC 61400-3 offshore wind turbine design standard was performed with the verified TLP model. This report compares the loads for the wind turbine on the TLP to those of an equivalent land-based turbine. Major instabilities for the TLP are identified and described.
DEFF Research Database (Denmark)
la Cour, M; Kiilgaard, Jens Folke; Eysteinsson, T;
2000-01-01
To investigate the influence of acute changes in intraocular pressure on the oxygen tension in the vicinity of the optic nerve head under control conditions and after intravenous administration of 500 mg of the carbonic anhydrase inhibitor dorzolamide.......To investigate the influence of acute changes in intraocular pressure on the oxygen tension in the vicinity of the optic nerve head under control conditions and after intravenous administration of 500 mg of the carbonic anhydrase inhibitor dorzolamide....
Dodd, Dominic; Favaro, Ken
2006-12-01
Of all the competing objectives every company faces, three pairs stand out: profitability versus growth, the short term versus the long term, and the whole organization versus the units. In each case, progress on one front usually comes at the expense of progress on the other. The authors researched the performance of more than 1000 companies worldwide over the past two decades and found that most struggle to succeed across the three tensions. From 1983 to 2003, for example, only 32% of these companies more often than not achieved positive profitability and revenue growth at the same time. The problem, the authors discovered, is not so much that managers don't recognize the tensions--those are all too familiar to anyone who has ever run a business. Rather, it is that managers frequently don't focus on the tension that matters most to their company. Even when they do identify the right tension, they usually make the mistake of prioritizing a "lead" objective within it-for example, profitability over growth. As a result, companies often end up moving first in this direction, then in that, and then back again, never quite resolving the tension. The companies that performed best adopted a very different approach. Instead of setting a lead objective, they looked at how best to strengthen what the two sides of each tension have in common: For profitability and growth,the common bond is customer benefit; for the short term and the long, it is sustainable earnings; and for the whole and its parts, it is particular organizational resources and capabilities. The authors describe how companies can select the right tension, what traps they may fall into when they focus on one side over the other, and how to escape these traps by managing to the bonds between objectives. PMID:17183794
Institute of Scientific and Technical Information of China (English)
Yue WU; Zhao-qing CHEN; Xiao-ying SUN
2015-01-01
The aero-elastic instability mechanism of a tensioned membrane structure is studied in this paper. The response and wind velocities above two closed-type saddle-shaped tensioned membrane structures, with the same shape but different pre-tension levels, were measured in uniform flow and analyzed. The results indicate that, for most wind directions, several vibration modes are excited and the amplitude and damping ratio of the roof slowly increase with the on-coming flow velocity. However, for particular wind directions, only one vibration mode is excited, and the amplitude and damping ratio of the vibration mode increase slowly with the on-coming flow velocity. The aero-elastic instability is caused by vortex-induced resonance. On ex-ceeding a certain wind speed, the amplitude of the roof vibration increases sharply and the damping ratio of the vibration mode decreases quickly to near zero; the frequency of the vortex above the roof is locked in by the vibration within a certain wind velocity range; the amplitudes of the roof in these wind directions reach 2–4 times the amplitudes for other wind directions. The reduced critical wind speeds for the aero-elastic instability of saddle-shaped membrane structures at the first two modes are around 0.8–1.0.%目的：明确张拉膜结构风致气弹响应特征及气弹失稳机理。 创新点：1.采用无接触测量技术设计鞍形张拉膜结构气弹模型风洞试验；2.研究鞍形张拉膜结构的气弹响应特征；3.给出鞍形张拉膜结构的失稳机理。 方法：1.在风洞中测量两个形状相同但预张力不同的封闭式鞍形张拉膜结构气弹模型在不同风速下的均匀流中的位移响应及膜面上方不同高度的风速时程；2.通过对位移响应及风速时程进行分析，明确结构的响应随风速变化特征及气弹失稳原因。 结论：1.膜结构在风荷载作用下变形到平衡位置，并围绕该平衡位置
International Nuclear Information System (INIS)
Dynamic tensile tests, at speeds ranging between 10 and 50 ms-1, were carried out on two materials of different crystalline structure, in order to find a function characteristic of their plasticities and to establish whether the behavior equation used is the general equation and consistent with dynamical behavior. The work is divided into three chapters. The first chapter deals with generalities about deformation at high strain rates, together with the principal measuring methods. The second chapter presents a theoretical model based on dislocation theory which explains the behavior of a 17 per cent chromium enriched ferritic steel subjected to a high strain rate tension test. The third chapter deals experimental work carried out on pure crystalline Cu. Three stages were observed during the macroscopic deformation of the sample and a hypothesis was put forward relating them to microscopic mechanisms observed with transmission electron microscopy. (author)
Influence of surface tension on two fluids shearing instability
Banerjee, Rahul
2015-01-01
Using extended Layzer's potential flow model, we investigate the effects of surface tension on the growth of the bubble and spike in combined Rayleigh-Taylor and Kelvin-Helmholtz instability. The nonlinear asymptotic solutions are obtained analytically for the velocity and curvature of the bubble and spike tip. We find that the surface tension decreases the velocity but does not affect the curvature, provided surface tension is greater than a critical value. For a certain condition, we observe that surface tension stabilizes the motion. Any perturbation, whatever its magnitude, results stable with nonlinear oscillations. The nonlinear oscillations depend on surface tension and relative velocity shear of the two fluids.
Spontaneous tension haemopneumothorax
Directory of Open Access Journals (Sweden)
Itam Sarah
2008-10-01
Full Text Available Abstract We present a patient with sudden onset progressive shortness of breath and no history of trauma, who rapidly became haemodynamically compromised with a pneumothorax and pleural effusion seen on chest radiograph. He was treated for spontaneous tension pneumothorax but this was soon revealed to be a tension haemopneumothorax. He underwent urgent thoracotomy after persistent bleeding to explore an apical vascular abnormality seen on CT scanning. To our knowledge this is the first such case reported. Aetiology and current approach to spontaneous haemothorax are discussed briefly.
Energy Technology Data Exchange (ETDEWEB)
Fradera, J., E-mail: jfradera@ubu.es; Cuesta-López, S., E-mail: scuesta@ubu.es
2013-12-15
Highlights: • The work presented in this manuscript provides a reliable computational tool to quantify the He complex phenomena in a HCLL. • A model based on the self-consistent nucleation theory (SCT) is exposed. It includes radiation induced nucleation modelling and surface tension corrections. • Results informed reinforce the necessity of conducting experiments to determine nucleation conditions and bubble transport parameters in LM breeders. • Our findings and model provide a good qualitative insight into the helium nucleation phenomenon in LM systems for fusion technology and can be used to identify key system parameters. -- Abstract: Helium (He) nucleation in liquid metal breeding blankets of a DT fusion reactor may have a significant impact regarding system design, safety and operation. Large He production rates are expected due to tritium (T) fuel self-sufficiency requirement, as both, He and T, are produced at the same rate. Low He solubility, local high concentrations, radiation damage and fluid discontinuities, among other phenomena, may yield the necessary conditions for He nucleation. Hence, He nucleation may have a significant impact on T inventory and may lower the T breeding ratio. A model based on the self-consistent nucleation theory (SCT) with a surface tension curvature correction model has been implemented in OpenFOAM{sup ®} CFD code. A modification through a single parameter of the necessary nucleation condition is proposed in order to take into account all the nucleation triggering phenomena, specially radiation induced nucleation. Moreover, the kinetic growth model has been adapted so as to allow for the transition from a critical cluster to a macroscopic bubble with a diffusion growth process. Limitations and capabilities of the models are shown by means of zero-dimensional simulations and sensitivity analyses to key parameters under HCLL breeding unit conditions. Results provide a good qualitative insight into the helium
International Nuclear Information System (INIS)
Highlights: • The work presented in this manuscript provides a reliable computational tool to quantify the He complex phenomena in a HCLL. • A model based on the self-consistent nucleation theory (SCT) is exposed. It includes radiation induced nucleation modelling and surface tension corrections. • Results informed reinforce the necessity of conducting experiments to determine nucleation conditions and bubble transport parameters in LM breeders. • Our findings and model provide a good qualitative insight into the helium nucleation phenomenon in LM systems for fusion technology and can be used to identify key system parameters. -- Abstract: Helium (He) nucleation in liquid metal breeding blankets of a DT fusion reactor may have a significant impact regarding system design, safety and operation. Large He production rates are expected due to tritium (T) fuel self-sufficiency requirement, as both, He and T, are produced at the same rate. Low He solubility, local high concentrations, radiation damage and fluid discontinuities, among other phenomena, may yield the necessary conditions for He nucleation. Hence, He nucleation may have a significant impact on T inventory and may lower the T breeding ratio. A model based on the self-consistent nucleation theory (SCT) with a surface tension curvature correction model has been implemented in OpenFOAM® CFD code. A modification through a single parameter of the necessary nucleation condition is proposed in order to take into account all the nucleation triggering phenomena, specially radiation induced nucleation. Moreover, the kinetic growth model has been adapted so as to allow for the transition from a critical cluster to a macroscopic bubble with a diffusion growth process. Limitations and capabilities of the models are shown by means of zero-dimensional simulations and sensitivity analyses to key parameters under HCLL breeding unit conditions. Results provide a good qualitative insight into the helium nucleation
DEFF Research Database (Denmark)
Kiilgaard, Jens Folke; Pedersen, D B; Eysteinsson, T;
2004-01-01
The authors have previously reported that carbonic anhydrase inhibitors such as acetazolamide and dorzolamide raise optic nerve oxygen tension (ONPO(2)) in pigs. The purpose of the present study was to investigate whether timolol, which belongs to another group of glaucoma drugs called beta...
DEFF Research Database (Denmark)
Stein, Mari-Klara; Lim, Eric T. K.; Tan, Chee-Wee
2014-01-01
goals. Given these challenges, we set out to explore what factors contribute to ineffectiveness in multi-level IT use in the context of an online community. Our initial analysis reveals two novel concepts – frictions and tensions – that could help researchers and practitioners in better understanding...
Frederick, A. B.
This is a bibliography of literature on the subject of tension. Books, films, and periodicals with a bearing on stress, relaxation, anxiety, and/or methods of controlling stress are listed from the fields of physiology, psychology, and philosophy. New methods such as transcendental meditation and biofeedback are analyzed briefly and criteria are…
Labus, Kevin M; Puttlitz, Christian M
2016-09-01
Computational models of the brain require accurate and robust constitutive models to characterize the mechanical behavior of brain tissue. The anisotropy of white matter has been previously demonstrated; however, there is a lack of data describing the effects of multi-axial loading, even though brain tissue experiences multi-axial stress states. Therefore, a biaxial tensile experiment was designed to more fully characterize the anisotropic behavior of white matter in a quasi-static loading state, and the mechanical data were modeled with an anisotropic hyperelastic continuum model. A probabilistic analysis was used to quantify the uncertainty in model predictions because the mechanical data of brain tissue can show a high degree of variability, and computational studies can benefit from reporting the probability distribution of model responses. The axonal structure in white matter can be heterogeneous and regionally dependent, which can affect computational model predictions. Therefore, corona radiata and corpus callosum regions were tested, and histology and transmission electron microscopy were performed on tested specimens to relate the distribution of axon orientations and the axon volume fraction to the mechanical behavior. These measured properties were implemented into a structural constitutive model. Results demonstrated a significant, but relatively low anisotropic behavior, yet there were no conclusive mechanical differences between the two regions tested. The inclusion of both biaxial and uniaxial tests in model fits improved the accuracy of model predictions. The mechanical anisotropy of individual specimens positively correlated with the measured axon volume fraction, and, accordingly, the structural model exhibited slightly decreased uncertainty in model predictions compared to the model without structural properties. PMID:27214689
Shokoohi, Shirin; Naderi, Ghasem
2016-01-01
To evaluate the prediction reliability of conventional morphology predicting models, polypropylene (PP)/polyamide6 (PA6)/ethylene propylene diene monomer (EPDM) (70/15/15) ternary polymer blends compatibilized with Maleic-anhydride grafted EPDM (EPDM-g-MA) were prepared through melt blending using a twin screw extruder (TSE). Different EPDM/EPDM-g-MA ratios i.e. 100/0, 75/25, 50/50, 25/75 and 0/100 were used to prepare the ternery blend PP/(EPDM-g-MA + EPDM)/PA6 samples. The effects of compatibilizer content on the microstructures and consequently mechanical properties of prepared ternary blends were studied. Direct microstructural observations were compared to the predictions of conventional phenomenological models including spreading coefficient, minimum relative free energy, and dynamic interfacial energy. A comparison depicted the relative inaccuracy of the existing models in predicting the morphology of the present ternary system due to the ignorance of some effective parameters and/or discomfit of model assumptions. A novel predictive model was developed considering parameters ignored in conventional models. A thorough investigation of the model's validation results showed a reasonable agreement between model predictions and direct microstructural observations.
Fradera, Jorge
2013-01-01
Helium (He) nucleation in liquid metal breeding blankets of a DT fusion reactor may have a significant impact regarding system design, safety and operation. Large He production rates are expected due to tritium (T) fuel self-sufficiency requirement, as both, He and T, are produced at the same rate. Low He solubility, local high concentrations, radiation damage and fluid discontinuities, among other phenomena, may yield the necessary conditions for He nucleation. Hence, He nucleation may have a significant impact on T inventory and may lower the T breeding ratio. A model based on the self-consistent nucleation theory (SCT) with a surface tension curvature correction model has been implemented in OpenFoam(r) CFD code. A modification through a single parameter of the necessary nucleation condition is proposed in order to take into account all the nucleation triggering phenomena, specially radiation induced nucleation. Moreover, the kinetic growth model has been adapted so as to allow for the transition from a cr...
Surface Tension and Capillary Rise
Walton, Alan J.
1972-01-01
Discussion of the shortcomings of textbook explanations of surface tension, distinguishing between concepts of tension and capillary rise. The arguments require only a clear understanding of Newtonian mechanics, notably potential energy. (DF)
Directory of Open Access Journals (Sweden)
Adriana Mayon Neiva Flores
2008-03-01
Full Text Available A cefaléia do tipo tensional constitui um tipo freqüente de dor de cabeça, que tende a ocasionar uma série de comportamentos de evitação, com prejuízos físicos, sociais e psicológicos aos indivíduos afetados. O presente trabalho descreve algumas contribuições do modelo biopsicossocial de saúde para a compreensão da cefaléia do tipo tensional, descreve os tratamentos mais freqüentemente oferecidos e discute as vantagens de modalidades terapêuticas que utilizam a formulação comportamental. Destaca-se a relevância da consideração de fatores psicossociais presentes nas formas mais comuns de evolução da cefaléia do tipo tensional, o que contribui para a elaboração de planos de tratamento mais eficientes e coerentes com uma proposta realmente sistêmica e idiográfica.La cefalea del tipo tensional constituye un tipo frecuente de dolor de cabeza, que tiene la tendencia a ocasionar una serie de comportamientos de evitación, con daños físicos, sociales y psicológicos a los individuos afectados. El presente trabajo describe algunas contribuciones del modelo biopsicosocial de salud para la comprensión de la cefalea del tipo tensional, describe los tratamientos más frecuentemente ofrecidos y discute las ventajas de modalidades terapéuticas que utilizan la formulación comportamental. Se destaca la relevancia de la consideración de factores psicosociales presentes en las formas más comunes de evolución de la cefalea del tipo tensional, lo que contribuye para la elaboración de planes de tratamiento más eficientes y coherentes con una propuesta realmente sistémica e idiográfica.Tension-type headache are a frequent source of complaints in health assistance units. It tends to cause avoidance behaviors with adverse consequences in physical, psychological and social aspects. Contributions from the Bio-Psychosocial perspective are described for a better understanding of the tension-type headache problem. Study also analyzes
Surface tension and microgravity
International Nuclear Information System (INIS)
The behaviour of confined liquids on board an orbiting spacecraft is mainly driven by surface tension phenomena, which cause an apparently anomalous response of the liquid when compared with the behaviour that can be observed on an Earth laboratory provided that the amount of liquid is high enough. The reason is that in an orbiting spacecraft the different inertial forces acting on the bulk of the liquid are almost zero, causing thus capillary forces to be the dominant ones. Of course, since gravity forces are proportional to the liquid volume, whereas surface tension forces are proportional to the liquid surface, there are situations on Earth where capillarity can be the dominant effect, as it happens when very small volume liquid samples are considered. However, work with small size samples may require the use of sophisticated optical devices. Leaving aside the neutral buoyancy technique, a way of handling large liquid interfaces is by using drop towers, where the sample falls subjected to the action of Earth’s gravity. This approach is suitable when the characteristic time of the problem under consideration is much smaller than the drop time. In this work the transformation of an out-of-use chimney into a drop tower is presented. Because of the miniaturization, hardiness and low cost of current electronic devices, a drop tower can be used as an inexpensive tool for undergraduate students to experimentally analyse a large variety of surface tension driven phenomena. (paper)
Alekseenko, Elena; Kuznetsov, Konstantin; Roux, Bernard
2016-04-01
Wind stress on the free surface is the main driving force behind the circulation of the upper part of the ocean, which in hydrodynamic models are usually defined in terms of the coefficient of surface tension (Zhang et al., 2009, Davies et al., 2003). Moreover, wave motion impacts local currents and changes sea level, impacts the transport and the stratification of the entire water column. Influence of surface waves at the bottom currents is particularly pronounced in the shallow coastal systems. However, existing methods of parameterization of the surface tension have significant limits, especially in strong wind waves (Young et al., 2001, Jones et al., 2004) due to the difficulties of measuring the characteristics of surface waves in stormy conditions. Thus, the formula for calculating the coefficient of surface tension in our day is the actual problem in modeling fluid dynamics, particularly in the context of strong surface waves. In the hydrodynamic models usually a coefficient of surface tension is calculated once at the beginning of computation as a constant that depends on the averaged wind waves characteristic. Usually cases of strongly nonlinear wind waves are not taken into account, what significantly reduces the accuracy of the calculation of the flow structures and further calculation of the other processes in water basins, such as the spread of suspended matter and pollutants. Thus, wave motion influencing the pressure on the free surface and at the bottom must be considered in hydrodynamic models particularly in shallow coastal systems. A method of reconstruction of a free-surface drag coefficient based on the measured in-situ bottom pressure fluctuations is developed and applied in a three-dimensional hydrodynamic model MARS3D, developed by the French laboratory of IFREMER (IFREMER - French Research Institute for Marine Dynamics). MARS3D solves the Navier-Stokes equations for incompressible fluid in the Boussinesq approximation and with the
Energy Technology Data Exchange (ETDEWEB)
Se, R.A.G.; Lima, E.R.A.; Nele, M.; Tavares, F.W. [Federal Univ. of Rio de Janeiro (Brazil). School of Chemistry; Bostrom, M. [Linkoping Univ., Linkoping (Sweden). Dept. of Physics, Chemistry and Biology
2008-07-01
This study presented new experimental data of interfacial tension of toluene-asphaltene/water systems in the presence of different salts. In order to study the stability of emulsions caused by the presence of salts in produced water, it is important to understand the interaction of ions at the interface. It was simpler to use model systems consisting of asphaltenes dissolved in toluene because of the complexity of the interfacially active components in oil. The study involved a Brazilian crude oil in which asphaltene was precipitated with a 1:15 ratio of n-heptane and solutions of water with salts LiCl, KCl, NaCl, NaI, NaBr and KBr in concentrations of 0.10, 0.25, 0.50, 0.75 and 1.0 M. The study investigated salt mixtures NaCl/NaBr and NaCl/NaI in the proportions 0.8:0.2, 0.6:0.4, 0.4:0.6, 0.2:0.8 molar. The experimental data was modeled using a modified Poisson-Boltzmann equation that considered dispersion in order to take into account the influence of ions at the interface.
Size Effect for Normal Strength Concrete in Uniaxial Tension
Institute of Scientific and Technical Information of China (English)
李庆斌; 尹玉先
2004-01-01
This paper presents a new size effect model for normal strength concrete subjected to uniaxial tension. The model is based on two extremes, sand cement paste in uniaxial tension and a sand-cement-paste/rock interface in uniaxial tension. Uniaxial tension tests with normal strength concrete measuring the tensile strength of normal strength concrete specimens with different geometrical shapes and different ratios of the aggregate size to the characteristic dimension of the concrete specimen show a significant size effect. The theoretical size effect law prediction agrees well with the experimental data.
Jamróz, Weronika
2016-06-01
The paper shows the way enrgy-based models aproximate mechanical properties of hiperelastic materials. Main goal of research was to create a method of finding a set of material constants that are included in a strain energy function that constitutes a heart of an energy-based model. The most optimal set of material constants determines the best adjustment of a theoretical stress-strain relation to the experimental one. This kind of adjustment enables better prediction of behaviour of a chosen material. In order to obtain more precised solution the approximation was made with use of data obtained in a modern experiment widely describen in [1]. To save computation time main algorithm is based on genetic algorithms.
Murphy, Kelly E.
2011-03-01
The repair of dermal tissue is a complex process of interconnected phenomena, where cellular, chemical and mechanical aspects all play a role, both in an autocrine and in a paracrine fashion. Recent experimental results have shown that transforming growth factor -β (TGF β) and tissue mechanics play roles in regulating cell proliferation, differentiation and the production of extracellular materials. We have developed a 1D mathematical model that considers the interaction between the cellular, chemical and mechanical phenomena, allowing the combination of TGF β and tissue stress to inform the activation of fibroblasts to myofibroblasts. Additionally, our model incorporates the observed feature of residual stress by considering the changing zero-stress state in the formulation for effective strain. Using this model, we predict that the continued presence of TGF β in dermal wounds will produce contractures due to the persistence of myofibroblasts; in contrast, early elimination of TGF β significantly reduces the myofibroblast numbers resulting in an increase in wound size. Similar results were obtained by varying the rate at which fibroblasts differentiate to myofibroblasts and by changing the myofibroblast apoptotic rate. Taken together, the implication is that elevated levels of myofibroblasts is the key factor behind wounds healing with excessive contraction, suggesting that clinical strategies which aim to reduce the myofibroblast density may reduce the appearance of contractures. © 2010 Elsevier Ltd.
Blanke, Monika
2016-01-01
Motivated by the recently improved results from the Fermilab Lattice and MILC Collaborations on the hadronic matrix elements entering $\\Delta M_{s,d}$ in $B_{s,d}^0-\\bar B_{s,d}^0$ mixing, we determine the Universal Unitarity Triangle (UUT) in models with Constrained Minimal Flavour Violation (CMFV). Of particular importance are the very precise determinations of the ratio $|V_{ub}|/|V_{cb}|=0.0864\\pm0.0025$ and of the angle $\\gamma=(62.7\\pm 2.1)^\\circ$. They follow in this framework from the experimental values of $\\Delta M_{d}/\\Delta M_s$ and of the CP-asymmetry $S_{\\psi K_S}$. As in CMFV models the new contributions to meson mixings can be described by a single flavour-universal variable $S(v)$, we next determine the CKM matrix elements $|V_{ts}|$, $|V_{td}|$, $|V_{cb}|$ and $|V_{ub}|$ as functions of $S(v)$ using the experimental value of $\\Delta M_s$ as input. The lower bound on $S(v)$ in these models, derived by us in 2006, implies then upper bounds on these four CKM elements and on the CP-violating par...
Influence of surface tension on two fluids shearing instability
Banerjee, Rahul; Kanjilal, S.
2014-01-01
Using extended Layzer's potential flow model, we investigate the effects of surface tension on the growth of the bubble and spike in combined Rayleigh-Taylor and Kelvin-Helmholtz instability. The nonlinear asymptotic solutions are obtained analytically for the velocity and curvature of the bubble and spike tip. We find that the surface tension decreases the velocity but does not affect the curvature, provided surface tension is greater than a critical value. For a certain condition, we observ...
Institute of Scientific and Technical Information of China (English)
荣凯; 朱渊; 刘津浩; 徐向阳
2014-01-01
目的：介绍及评价腓肠肌前方腱膜松解治疗非痉挛性腓肠肌挛缩的手术方法及术后疗效。方法回顾性研究2006年7月至2013年7月期间，本组采用腓肠肌前方腱膜松解治疗非痉挛性腓肠肌挛缩的患者。患者术前体检Silfverskiöld试验（＋），采用Baumann入路在腓肠肌与比目鱼肌间隙之间，松解腓肠肌前方腱膜，背伸踝关节至角度满意。术前和末次随访时测量踝关节的最大被动背伸角度（膝关节伸直位和屈曲90°时），进行美国足踝医师协会后足-踝关节（AOFAS-AH）评分，并记录术后并发症情况。结果29例（35足）患者获得随访，平均年龄36.5岁（8～69岁），平均随访32.6个月（7～54个月）。其中成人扁平足11例13足，儿童扁平足4例5足，踇外翻6例8足，跖筋膜炎5例6足，创伤性马蹄足3例3足。术前和末次随访时伸膝位踝关节最大被动背伸角度分别为（-5.7°±3.2°）（-15°～3°）和（8.2°±3.7°）（-6°～17°）（P＜0.01），背伸角度平均增加13.9°。 AOFAS-AH评分由术前平均46．7分提高到末次随访的75.1分（P＜0.01）。术后马蹄足畸形复发2例（2足），无过度延长、神经血管损伤及伤口并发症发生。结论腓肠肌前方腱膜松解操作方便，术后踝关节背伸角度恢复满意，跖屈肌力良好，未见明显并发症，是治疗非痉挛性腓肠肌挛缩安全、有效的手术方法。%Objective To investigate the surgical method and the clinical results of the anterior aponeurotic recession of gastrocnemius for non-spastic gastrocnemius contraction .Methods The patients with non-spastic gastrocnemius contraction treated by the anterior aponeurotic recession of gastrocnemius during July 2007 to July 2013, were retrospectively studied .All the patients were preoperatively identified by Silfverskiold test , and received the anterior aponeurotic recession of gastrocnemius in the
Directory of Open Access Journals (Sweden)
E. O. Fors
2010-06-01
Full Text Available HUmic-LIke Substances (HULIS have been identified as major contributors to the organic carbon in atmospheric aerosol. The term "HULIS" is used to describe the organic material found in aerosol particles that resembles the humic organic material in rivers and sea water and in soils. In this study, two sets of filter samples from atmospheric aerosols were collected at different sites. One set of samples was collected at the K-puszta rural site in Hungary, about 80 km SE of Budapest, and a second was collected at a site in Rondônia, Amazonia, Brazil, during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia – Smoke Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC biomass burning season experiment. HULIS were extracted from the samples and their hygroscopic properties were studied using a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA at relative humidity (RH <100%, and a cloud condensation nucleus counter (CCNC at RH >100%. The H-TDMA measurements were carried out at a dry diameter of 100 nm and for RH ranging from 30 to 98%. At 90% RH the HULIS samples showed diameter growth factors between 1.04 and 1.07, reaching values of 1.4 at 98% RH. The cloud nucleating properties of the two sets of aerosol samples were analysed using two types of thermal static cloud condensation nucleus counters. Two different parameterization models were applied to investigate the potential effect of HULIS surface activity, both yielding similar results. For the K-puszta winter HULIS sample, the surface tension at the point of activation was estimated to be lowered by between 34% (47.7 mN/m and 31% (50.3 mN/m for dry sizes between 50 and 120 nm in comparison to pure water. A moderate lowering was also observed for the entire water soluble aerosol sample, including both organic and inorganic compounds, where the surface tension was decreased by between 2% (71.2 mN/m and 13% (63.3 mN/m.
Directory of Open Access Journals (Sweden)
E. O. Fors
2009-12-01
Full Text Available HUmic-LIke Substances (HULIS have been identified as major contributors to the organic carbon in atmospheric aerosol. The term HULIS is used to describe the organic material found in aerosol particles which resembles the humic organic material in river and sea water and in soils. In this study two sets of filter samples from atmospheric aerosols were collected at different sites. One sample was collected at the K-puszta rural site in Hungary, about 80 km SE of Budapest, and a second set of samples was collected at a site in Rondônia, Amazonia, Brazil, during the LBA-SMOCC biomass burning season experiment. HULIS were extracted from the samples, and their hygroscopic properties were studied using a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA at relative humidity (RH <100%, and a cloud condensation nucleus counter (CCNC at RH >100%. The H-TDMA measurements were carried out at a dry diameter of 100 nm and for RH ranging from 30 to 98%. At 90% RH the HULIS samples showed diameter growth factors between 1.04 and 1.07, reaching values of 1.4 at 98% RH. The cloud nucleating properties of the two sets of aerosol samples were analyzed using two types of thermal static cloud condensation nucleus counters (CCNC. Two different parameterization models were used to investigate the potential effect of HULIS surface activity, both yielding similar results. For the K-puszta winter HULIS sample, the surface tension at the point of activation was estimated to be lowered by between 34% (47.7 mN/m and 31% (50.3 mN/m for dry sizes between 50 and 120 nm in comparison to pure water. A moderate lowering was also observed for the entire water soluble aerosol sample, including both organic and inorganic compounds, where the surface tension was decreased by between 2% (71.2 mN/m and 13% (63.3 mN/m.
Interpreting expressive performance through listener judgments of musical tension
Directory of Open Access Journals (Sweden)
Morwaread Mary Farbood
2013-12-01
Full Text Available This study examines listener judgments of musical tension for a recording of a Schubert song and its harmonic reduction. Continuous tension ratings collected in an experiment and quantitative descriptions of the piece’s musical features, include dynamics, pitch height, harmony, onset frequency, and tempo, were analyzed from two different angles. In the first part of the analysis, the different processing timescales for disparate features contributing to tension were explored through the optimization of a predictive tension model. The results revealed the optimal time windows for harmony were considerably longer (~22 s than for any other feature (~1-4 s. In the second part of the analysis, tension ratings for the individual verses of the song and its harmonic reduction were examined and compared. The results showed that although the average tension ratings between verses were very similar, differences in how and when participants reported tension changes highlighted performance decisions made in the interpretation of the score, ambiguity in tension implications of the music, and the potential importance of contrast between verses and phrases. Analysis of the tension ratings for the harmonic reduction also provided a new perspective for better understanding how complex musical features inform listener tension judgments.
Rainbow surface tension analysis.
Adler, Charles L; Smith, Valen A; Haddad, Natalie M
2008-03-31
In this paper we outline a new all-optical non-contact technique for measurement of the surface tension of a Newtonian fluid. It is based on the accurate measurement of the spacing of the supernumerary fringes produced by the diffraction pattern of a laser beam transmitted through or reflected by a thin vertically-draining film of the liquid. We discuss the basic theory and application of this technique, and several issues which must be addressed before it can be used commercially. PMID:18542611
Vijayan, T.; Patil, Jagadish G.
2012-12-01
The genesis and transport of ozone (O3) are investigated in a novel plasma diode and described in this paper. The innovative cathode (K) of this axial symmetric diode which operated at the high voltage (ϕ0), has a large number of sharpened nozzles located on different radial planes of its central tubular-mast and is encircled by the anode (A). The nozzles played the dual role of oxygen (O2) injection as well as creation of high electric field (E) in the A-K gap, enabled the formation of a cold corona. Electrons in the corona under the influence of E moved towards anode, collided with O2 and created the O radicals. O in turn joined the free O2 and formed O3. The evolution of O3 here is modeled in various O2 pressure (P), electron density (ne), and temperature (T) in terms of the major reaction modes involving e, O, O2, and O3. Typical steady state O3 density attained so in P ˜ bar, ne ˜ 1015 m-3 and T ˜ 300 K is over 1025 m-3 and that of O lower ˜1020 m-3. Both the O and O3 densities increased with an enhanced ne of avalanche multiplications in corona. O3 increased also with a higher P but the temporal O reversed in trend midway and reduced with P towards the steady state. A sharp decline in diode resistance with smaller A-K gap induced finite discharge current and led to the undesired heating of corona. It is shown that the O3 density reduced with the temperature rise but O density reduced with the T rise up to 500 K and then rose modestly with the further T increase.
Effect of initial tension on mechanics of adhered graphene blisters
Liao, Pinzhen; Xu, Pei
2015-09-01
The effect of initial tension on mechanics of adhered graphene blisters is investigated by extending Hencky's solution to cases with an initial tension. The system parameters including maximum blister deflection, pressure difference across the membrane, and critical delamination pressure under various initial tensions are modeled and calculated. The dependences of critical pressure on the radius and depth of etched microcavity are also demonstrated and compared with the previous work which does not consider the initial tension. The results show that the added adhesion energy between monolayer graphene membrane and SiO2 substrate can reach 0.0954 J/m2 with a reported maximum initial tension of 2.4 N/m taken into account, which accounts for 21.2 % of the measured average value 0.45 J/m2. Thus, the initial tension should be considered in further adhesion energy measurements of graphene/substrate interfaces.
Nason, F
1981-03-01
Current efforts to provide comprehensive health care have accentuated the need for new models that integrate the biological, psychological, and social fields. One approach to meeting this need has been the development of health care teams. However, the multidisciplinary perspectives of such teams often result in tension and discord. While this tension may be partly attributable to institutional or professional biases or lack of adequate decision-making techniques, it may also be an essential diagnostic tool for exploring and integrating the paradoxes of the patient's homeostatic system. This approach captures and bridges some of the inadequacies of our prevailing knowledge base. The team's tension can be experienced as an essential empathic connectedness to the patient's life situation. Resolution of the team's internalized conflict becomes a paradigm for the patient's reintegration of his or her own paradoxical or contradictory needs. PMID:7215794
Study of branes with variable tension
Aros, Rodrigo
2016-01-01
In this work we study a brane world model with variable tension which gives rise to four dimensional cosmologies. The brane worlds obtained correspond to E\\"{o}tv\\"{o}s branes whose (internal) geometry can be casted as either a four dimensional (A)dS$_{4}$ or a standard radiation period cosmology. The matter dominated period is discussed as well.
Influence of colour symmetry on string tension
International Nuclear Information System (INIS)
The ratio of the fundamental string tension in the SU(3) pure (quarkless) gauge theory to that in the SU(2) gluonic system is estimated within a statistical model approach to the description of the QCD thermodynamics. The obtained estimation is in agreement with the lattice evaluation of the ratio. 9 refs
Feudtner, Chris
2016-05-01
My colleagues and I had been asked by a member of a clinical team to help sort through the ethics of stopping a life-sustaining intervention for a very ill child. We had already talked with the parents, the physicians, and the folks from nursing, social work, and chaplaincy. Terms like "suffering," "cruel," "compassion," and "moral distress" had been uttered, as had terms like "inappropriate," "unethical," "neglectful," and "risk-management." The group had now stuffed all of these polarizing thoughts and feelings into this cramped room with only one door. And everyone was looking at me. What skill, competency, or inner capacity must one possess to hold and manage such tension? PMID:27150423
Social and environmental tensions
DEFF Research Database (Denmark)
Saito, Moeko; Rutt, Rebecca Leigh; Chhetri, Bir Bahadur Khanal
2014-01-01
them, receive payments not only to address inequities but also for resource conservation. Drawing on a case study of a NORAD pilot project in Nepal, this paper investigates how affirmative measures adopted under the project affect different social actors and their perceptions and behaviors in relation......REDD + is a mitigation measure against global climate change that offers payments to developing countries based on the increased volume of forest carbon. It has been argued that affirmative measures should be adopted to ensure that communities, particularly the socially disadvantaged groups among...... to forests. Our case highlights the risk that the mere application of affirmative measures may give rise to difficult social and environmental tensions. Thus, this paper calls for such measures to effectively incorporate local perspectives in their designs and to be reflective, by allowing for...
Robust atomistic calculation of dislocation line tension
Szajewski, B. A.; Pavia, F.; Curtin, W. A.
2015-12-01
The line tension Γ of a dislocation is an important and fundamental property ubiquitous to continuum scale models of metal plasticity. However, the precise value of Γ in a given material has proven difficult to assess, with literature values encompassing a wide range. Here results from a multiscale simulation and robust analysis of the dislocation line tension, for dislocation bow-out between pinning points, are presented for two widely-used interatomic potentials for Al. A central part of the analysis involves an effective Peierls stress applicable to curved dislocation structures that markedly differs from that of perfectly straight dislocations but is required to describe the bow-out both in loading and unloading. The line tensions for the two interatomic potentials are similar and provide robust numerical values for Al. Most importantly, the atomic results show notable differences with singular anisotropic elastic dislocation theory in that (i) the coefficient of the \\text{ln}(L) scaling with dislocation length L differs and (ii) the ratio of screw to edge line tension is smaller than predicted by anisotropic elasticity. These differences are attributed to local dislocation core interactions that remain beyond the scope of elasticity theory. The many differing literature values for Γ are attributed to various approximations and inaccuracies in previous approaches. The results here indicate that continuum line dislocation models, based on elasticity theory and various core-cut-off assumptions, may be fundamentally unable to reproduce full atomistic results, thus hampering the detailed predictive ability of such continuum models.
Black string corrections in variable tension braneworld scenarios
da Rocha, Roldao
2012-01-01
Braneworld models with variable tension are investigated, and the corrections on the black string horizon along the extra dimension are provided. Such corrections are encrypted in additional terms involving the covariant derivatives of the variable tension on the brane, providing profound consequences concerning the black string horizon variation along the extra dimension, near the brane. The black string horizon behavior is shown to be drastically modified by the terms corrected by the brane variable tension. In particular, a model motivated by the phenomenological interesting case regarding Eotvos branes is investigated. It forthwith provides further physical features regarding variable tension braneworld scenarios, heretofore concealed in all previous analysis in the literature. All precedent analysis considered uniquely the expansion of the metric up to the second order along the extra dimension, what is able to evince solely the brane variable tension absolute value. Notwithstanding, the expansion terms ...
Surface tension and long range corrections of cylindrical interfaces
Energy Technology Data Exchange (ETDEWEB)
Bourasseau, E. [CEA/DAM DIF, F-91297 Arpajon Cedex (France); Malfreyt, P. [Université Clermont Auvergne, Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand (France); Ghoufi, A., E-mail: aziz.ghoufi@univ-rennes1.fr [Institut de Physique de Rennes, UMR 6251 CNRS, Université de Rennes 1, 263 avenue Général Leclerc, 35042 Rennes (France)
2015-12-21
The calculation of the surface tension of curved interfaces has been deeply investigated from molecular simulation during this last past decade. Recently, the thermodynamic Test-Area (TA) approach has been extended to the calculation of surface tension of curved interfaces. In the case of the cylindrical vapour-liquid interfaces of water and Lennard-Jones fluids, it was shown that the surface tension was independent of the curvature of the interface. In addition, the surface tension of the cylindrical interface is higher than that of the planar interface. Molecular simulations of cylindrical interfaces have been so far performed (i) by using a shifted potential, (ii) by means of large cutoff without periodic boundary conditions, or (iii) by ignoring the long range corrections to the surface tension due to the difficulty to estimate them. Indeed, unlike the planar interfaces there are no available operational expressions to consider the tail corrections to the surface tension of cylindrical interfaces. We propose here to develop the long range corrections of the surface tension for cylindrical interfaces by using the non-exponential TA (TA2) method. We also extend the formulation of the Mecke-Winkelmann corrections initially developed for planar surfaces to cylindrical interfaces. We complete this study by the calculation of the surface tension of cylindrical surfaces of liquid tin and copper using the embedded atom model potentials.
Surface tension and long range corrections of cylindrical interfaces
International Nuclear Information System (INIS)
The calculation of the surface tension of curved interfaces has been deeply investigated from molecular simulation during this last past decade. Recently, the thermodynamic Test-Area (TA) approach has been extended to the calculation of surface tension of curved interfaces. In the case of the cylindrical vapour-liquid interfaces of water and Lennard-Jones fluids, it was shown that the surface tension was independent of the curvature of the interface. In addition, the surface tension of the cylindrical interface is higher than that of the planar interface. Molecular simulations of cylindrical interfaces have been so far performed (i) by using a shifted potential, (ii) by means of large cutoff without periodic boundary conditions, or (iii) by ignoring the long range corrections to the surface tension due to the difficulty to estimate them. Indeed, unlike the planar interfaces there are no available operational expressions to consider the tail corrections to the surface tension of cylindrical interfaces. We propose here to develop the long range corrections of the surface tension for cylindrical interfaces by using the non-exponential TA (TA2) method. We also extend the formulation of the Mecke-Winkelmann corrections initially developed for planar surfaces to cylindrical interfaces. We complete this study by the calculation of the surface tension of cylindrical surfaces of liquid tin and copper using the embedded atom model potentials
Surface tension of molecular liquids: Lattice gas approach
Maslechko, A; Kulinskii, V
2016-01-01
The approach of global isomorphism between the fluid and the Ising model is applied to obtain an expression for the surface tension of the Lennard-Jones fluid on the basis of the information about the Ising model. This is done in a broad interval of temperatures along the phase coexistence, and is valid both in 2D and 3D. The relation between the critical amplitudes of the surface tension of the fluid and the Ising model is derived in the vicinity of the critical point. The obtained theoretical estimates agree well with the literature results for the surface tension. The methodology is demonstrated for the 2D LJ fluid on the basis of the exact solution of the 2D Ising model and is tested for the 3D LJ fluid. As a result, an expression for the surface tension without any fitting parameter is derived.
Three-Dimensional Smoothed Particle Hydrodynamics Simulation for Liquid Droplet with Surface Tension
Terissa, Hanifa; Barecasco, Agra; Naa, Christian Fredy
2013-01-01
We provide a basic method of Smoothed Particle Hydrodynamics (SPH) to simulate liquid droplet with surface tension in three dimensions. Liquid droplet is a simple case for surface tension modeling. Surface tension works only on fluid surface. In SPH method, we simply apply the surface tension on the boundary particles of liquid. The particle on the 3D boundary was detected dynamically using Free-Surface Detection algorithm. The normal vector and curvature of the boundary surface were calculat...
Handling device for stud tensioner
International Nuclear Information System (INIS)
The handling device for a stud tensioner machine used by example for fixing the reactor vessel head has an extension module, joining elements and means for displacement in vertical and horizontal axis
Interfacial Tension of Electrolyte Solutions
Levin, Yan
2000-01-01
A theory is presented to account for the increase in surface tension of water in the presence of electrolyte. Unlike the original ``grand-canonical'' calculation of Onsager and Samaras, which relied on the Gibbs adsorption isotherm and lead to a result which could only be expressed as an infinite series, our approach is ``canonical'' and produces an analytic formula for the excess surface tension. For small concentrations of electrolyte, our result reduces to the Onsager-Samaras limiting law.
Black string corrections in variable tension braneworld scenarios
Da Rocha, Roldão; Hoff da Silva, J. M.
2012-02-01
Braneworld models with variable tension are investigated, and the corrections on the black string horizon along the extra dimension are provided. Such corrections are encrypted in additional terms involving the covariant derivatives of the variable tension on the brane, providing profound consequences concerning the black string horizon variation along the extra dimension, near the brane. The black string horizon behavior is shown to be drastically modified by the terms corrected by the brane variable tension. In particular, a model motivated by the phenomenological interesting case regarding Eötvös branes is investigated. It forthwith provides further physical features regarding variable tension braneworld scenarios, heretofore concealed in all previous analysis in the literature. All precedent analysis considered uniquely the expansion of the metric up to the second order along the extra dimension, which is able to evince solely the brane variable tension absolute value. Notwithstanding, the expansion terms aftermath, further accomplished in this paper from the third order on, elicits the successive covariant derivatives of the brane variable tension, and their respective coupling with the extrinsic curvature, the Weyl tensor, and the Riemann and Ricci tensors, as well as the scalar curvature. Such additional terms are shown to provide sudden modifications in the black string horizon in a variable tension braneworld scenario.
Allen, Phillip A.; Wells, Douglas N.
2013-01-01
No closed form solutions exist for the elastic-plastic J-integral for surface cracks due to the nonlinear, three-dimensional nature of the problem. Traditionally, each surface crack must be analyzed with a unique and time-consuming nonlinear finite element analysis. To overcome this shortcoming, the authors have developed and analyzed an array of 600 3D nonlinear finite element models for surface cracks in flat plates under tension loading. The solution space covers a wide range of crack shapes and depths (shape: 0.2 less than or equal to a/c less than or equal to 1, depth: 0.2 less than or equal to a/B less than or equal to 0.8) and material flow properties (elastic modulus-to-yield ratio: 100 less than or equal to E/ys less than or equal to 1,000, and hardening: 3 less than or equal to n less than or equal to 20). The authors have developed a methodology for interpolating between the goemetric and material property variables that allows the user to reliably evaluate the full elastic-plastic J-integral and force versus crack mouth opening displacement solution; thus, a solution can be obtained very rapidly by users without elastic-plastic fracture mechanics modeling experience. Complete solutions for the 600 models and 25 additional benchmark models are provided in tabular format.
Directory of Open Access Journals (Sweden)
Sapegin V.I.
2014-11-01
Full Text Available In acute experiments on rabbits there were studied changes in oxygen tension in the intestinal wall tissues, acid-base balance and limited proteolysis and its inhibitors in intestinal venous blood, protective action of L-lysine escinat (0,15 mg/kg / single dose, thiotriazolin (25 mg/kg / single dose, aprotinin (gordox (10,000 units/kg / single dose in sequential modeling of standard levels increasing of intra-abdominal hypertension (IAH — 50, 100, 150, 200, 250, 300, 350 m H2O, and also of tolperison (mydocalm (5 mg/kg / single dose on modeling of stable 3-hour IAH 200 m H2O. The IAH modeling was performed by means of stand of our construction. Under the influence of IAH the compensated metabolic acidosis in intestinal venous blood with a compensative hyperpnoe develops, decline of oxygen tension in tissues and activating of a limited proteolysis as well as decline of its inhibitors activity in intestinal venous blood occur. By the degree of metabolic acidosis prevention investigational preparations were distributed as follows gordox > thiotriazolin = L-lysine escinat = mydocalm, and by prevention of decline of oxygen tension in tissues — thiotriazolin > L-lysine escinat > mydocalm > gordox, it is is connected with different rate of methabolic products excretion into the blood, due to the influence on blood circulation and transcapilary exchange. By the degree of prevention of proteolytic activity and inhibitory potential changes, investigational preparations were distributed as follows: gordox > mydocalm > thiotriazolin > L-lysine escinat, this is connected with inhibition of proteolysis in gordox, and in other ones – with reduction of ischemic damage of tissues. Owing to different mechanism of action thiotriazolin, L-lysine escinat and mydocalm may be simultaneously recommended for a conservative treatment of patients with intraabdominal hypertension syndrome.
Buras, Andrzej J
2016-01-01
Motivated by the recently improved lattice QCD results on the hadronic matrix elements entering $\\Delta M_{s,d}$ in $B_{s,d}^0-\\bar B_{s,d}^0$ mixings and the resulting increased tensions between $\\Delta M_{s,d}$ and $\\varepsilon_K$ in the Standard Model and CMFV models, we demonstrate that these tensions can be removed in 331 models based on the gauge group $SU(3)_C\\times SU(3)_L\\times U(1)_X$ both for $M_{Z^\\prime}$ in the LHC reach and well beyond it. But the implied new physics (NP) patterns in $\\Delta F=1$ observables depend sensitively on the value of $|V_{cb}|$. Concentrating the analysis on three 331 models that have been selected by us previously on the basis of their performance in electroweak precision tests and $\\varepsilon^\\prime/\\varepsilon$ we illustrate this for $|V_{cb}|=0.042$ and $|V_{cb}|=0.040$. We find that these new lattice data still allow for positive shifts in $\\varepsilon^\\prime/\\varepsilon$ up to $6\\times 10^{-4}$ for $M_{Z^\\prime}=3~TeV$ for both values of $$|V_{cb}|$ but for $M_{...
Surface Tension and Fingering of Miscible Interfaces
Abib, Mohammed; Liu, Jian-Bang; Ronney, Paul D.
1999-01-01
Experiments on miscible, buoyantly unstable reaction-diffusion fronts and non-reacting displacement fronts in Hele-Shaw cells show a fingering-type instability whose wavelengths (lambda*) are consistent with an interfacial tension (sigma) at the front caused by the change in chemical composition, even though the solutions are miscible in all proportions. In conjunction with the Saffman-Taylor model, the relation sigma = K/tau, where tau is the interface thickness and K approximately equal 4 +/- 2 x 10(exp -6) dyne, enables prediction of our measured values of lambda* as well as results from prior experiments on miscible interfaces. These results indicate that even for miscible fluids, surface tension is generally a more significant factor than diffusion in interfacial stability and flow characteristics.
Coarse-Grained Simulations of Membranes under Tension
Neder, Jörg; Nielaba, Peter; Schmid, Friederike
2010-01-01
We investigate the properties of membranes under tension by Monte-Carlo simulations of a generic coarse-grained model for lipid bilayers. We give a comprising overview of the behavior of several membrane characteristics, such as the area per lipid, the monolayer overlap, the nematic order, and pressure profiles. Both the low-temperature regime, where the membranes are in a gel phase, and the high-temperature regime, where they are in the fluid phase, are considered. In the gel state, the membrane is hardly influenced by tension. In the fluid state, high tensions lead to structural changes in the membrane, which result in different compressibility regimes. The ripple state, which is found at tension zero in the transition regime between the fluid and the gel phase, disappears under tension and gives way to an interdigitated phase. We also study the membrane fluctuations in the fluid phase. In the low tension regime the data can be fitted nicely to a suitably extended elastic theory. At higher tensions the elas...
On the Low Surface Tension of Lung Surfactant
Zhang, Hong; Wang, Yi E.; Fan, Qihui; Zuo, Yi Y.
2011-01-01
Natural lung surfactant contains less than 40% disaturated phospholipids, mainly dipalmitoylphosphatidylcholine (DPPC). The mechanism by which lung surfactant achieves very low near-zero surface tensions, well below its equilibrium value, is not fully understood. To date, the low surface tension of lung surfactant is usually explained by a squeeze-out model which predicts that upon film compression non-DPPC components are gradually excluded from the air–water interface into a surface-associat...
Tension leg platform project execution
Institute of Scientific and Technical Information of China (English)
Zhang Dagang; Wang Chunsheng; Zhang Tianyu
2013-01-01
The first floating platform concept design work for South China Sea is undergoing in DMAR' s office now.This tension leg platform has potential to become the first advanced floating production platform project.Project execution is always a challenge for floating system.This paper focuses on the critical elements of project execution for tension leg platform,and studies potential implications to future oil and gas exploration in South China Sea.There are many factors affecting successful execution of floating system project,including technical issues,engineering management,interface management,etc.There are also failure examples of project execution in the industry.The author has participated 28 large detailed projects and has gained extensive experience on floating projects,with ample hands-on project experiences.A detailed tension leg platform project study example and discussions in depth are presented for future project execution in China deepwater development.
Taylor, Graham J; Venkatesan, Guru A; Collier, C Patrick; Sarles, Stephen A
2015-10-14
Thickness and tension are important physical parameters of model cell membranes. However, traditional methods to measure these quantities require multiple experiments using separate equipment. This work introduces a new multi-step procedure for directly accessing in situ multiple physical properties of droplet interface bilayers (DIB), including specific capacitance (related to thickness), lipid monolayer tension in the Plateau-Gibbs border, and bilayer tension. The procedure employs a combination of mechanical manipulation of bilayer area followed by electrowetting of the capacitive interface to examine the sensitivities of bilayer capacitance to area and contact angle to voltage, respectively. These data allow for determining the specific capacitance of the membrane and surface tension of the lipid monolayer, which are then used to compute bilayer thickness and tension, respectively. The use of DIBs affords accurate optical imaging of the connected droplets in addition to electrical measurements of bilayer capacitance, and it allows for reversibly varying bilayer area. After validating the accuracy of the technique with diphytanoyl phosphatidylcholine (DPhPC) DIBs in hexadecane, the method is applied herein to quantify separately the effects on membrane thickness and tension caused by varying the solvent in which the DIB is formed and introducing cholesterol into the bilayer. Because the technique relies only on capacitance measurements and optical images to determine both thickness and tension, this approach is specifically well-suited for studying the effects of peptides, biomolecules, natural and synthetic nanoparticles, and other species that accumulate within membranes without altering bilayer conductance. PMID:26289743
Tension-induced binding of semiflexible biopolymers
Benetatos, Panayotis; Zippelius, Annette
2014-01-01
We investigate theoretically the effect of polymer tension on the collective behavior of reversibly binding cross-links. For this purpose, we employ a model of two weakly bending wormlike chains aligned in parallel by a tensile force, with a sequence of inter-chain binding sites regularly spaced along the contours. Reversible cross-links attach and detach at the sites with an affinity controlled by a chemical potential. In a mean-field approach, we calculate the free energy of the system and find the emergence of a free-energy barrier which controls the reversible (un)binding. The tension affects the conformational entropy of the chains which competes with the binding energy of the cross-links. This competition gives rise to a sudden increase in the fraction of bound sites as the tension increases. We show that this transition is related to the cross-over between weak and strong localization of a directed polymer in a pinning potential. The cross-over to the strongly bound state can be interpreted as a mechan...
Cosmic Strings with Small Tension
Halyo, Edi
2009-01-01
We describe cosmic F--term strings with exponentially small tension which are D3 branes wrapped on deformed $A_3$ singularities. We show that brane instanton effects which can be calculated after a geometric transition give rise to an exponentially small volume for the node on which the D3 branes wrap leading to a string with small tension. We generalize our description to the case of non--Abelian cosmic strings and argue that these strings are stable against monopole--anti monopole pair creation.
Quantifying the BICEP2-Planck tension over gravitational waves.
Smith, Kendrick M; Dvorkin, Cora; Boyle, Latham; Turok, Neil; Halpern, Mark; Hinshaw, Gary; Gold, Ben
2014-07-18
The recent BICEP2 measurement of B-mode polarization in the cosmic microwave background (r = 0.2(-0.05)(+0.07)), a possible indication of primordial gravity waves, appears to be in tension with the upper limit from WMAP (r < 0.13 at 95% C.L.) and Planck (r < 0.11 at 95% C.L.). We carefully quantify the level of tension and show that it is very significant (around 0.1% unlikely) when the observed deficit of large-scale temperature power is taken into account. We show that measurements of TE and EE power spectra in the near future will discriminate between the hypotheses that this tension is either a statistical fluke or a sign of new physics. We also discuss extensions of the standard cosmological model that relieve the tension and some novel ways to constrain them. PMID:25083631
The surface tension of liquid aluminium-based alloys
International Nuclear Information System (INIS)
In a systematic study, the surface tensions of the binary alloys Al-Fe and Al-Ni were investigated over a wide temperature and concentration range using electromagnetic levitation and the oscillating drop technique. Surface tensions were derived from the oscillation frequencies applying the formalism of Cummings and Blackburn. Temperature was measured by single-color pyrometry. Of particular interest in these alloys are melts corresponding to compositions of intermetallic phases, because potential ordering phenomena may influence all thermophysical properties. In both systems, an increase of the surface tension is observed at such concentrations. On the basis of partial excess Gibbs enthalpies, surface tensions can be calculated via the Butler equation and compared with experimental results. The agreement with our experimental data depends crucially on the quality of the thermodynamic potentials used. In addition, phenomenological models are also discussed, which describe the general trend correctly
Apparatus for determining surface tension
Razouk, R. E.
1978-01-01
System for studying capillary action uses pressure transducer and chart recorder instead of manometer. Apparatus enables measurements to be made under controlled atmospheres. It also may be remotely operated. These features are particularly useful when dealing with noxious liquids and for study of surface tension under high-pressure conditions that require use of all-metal apparatus.
Molecular simulation of the surface tension of real fluids
Werth, Stephan; Hasse, Hans
2016-01-01
Molecular models of real fluids are validated by comparing the vapor-liquid surface tension from molecular dynamics (MD) simulation to correlations of experimental data. The considered molecular models consist of up to 28 interaction sites, including Lennard-Jones sites, point charges, dipoles and quadrupoles. They represent 38 real fluids, such as ethylene oxide, sulfur dioxide, phosgene, benzene, ammonia, formaldehyde, methanol and water, and were adjusted to reproduce the saturated liquid density, vapor pressure and enthalpy of vaporization. The models were not adjusted to interfacial properties, however, so that the present MD simulations are a test of model predictions. It is found that all of the considered models overestimate the surface tension. In most cases, however, the relative deviation between the simulation results and correlations to experimental data is smaller than 20 %. This observation corroborates the outcome of our previous studies on the surface tension of 2CLJQ and 2CLJD fluids where a...
Tensional acoustomechanical soft metamaterials
Xin, Fengxian; Lu, Tianjian
2016-06-01
We create acoustomechanical soft metamaterials whose response to uniaxial tensile stressing can be easily tailored by programming acoustic wave inputs, resulting in force versus stretch curves that exhibit distinct monotonic, s-shape, plateau and non-monotonic snapping behaviors. We theoretically demonstrate this unique metamaterial by considering a thin soft material sheet impinged by two counter-propagating ultrasonic wave inputs across its thickness and stretched by an in-plane uniaxial tensile force. We establish a theoretical acoustomechanical model to describe the programmable mechanics of such soft metamaterial, and introduce the first- and second-order tangential stiffness of its force versus stretch curve to boundary different behaviors that appear during deformation. The proposed phase diagrams for the underlying nonlinear mechanics show promising prospects for designing tunable and switchable photonic/phononic crystals and microfluidic devices that harness snap-through instability.
Hyperelastic tension of graphene
Energy Technology Data Exchange (ETDEWEB)
Saavedra Flores, E. I., E-mail: erick.saavedra@usach.cl [Departamento de Ingeniería en Obras Civiles, Universidad de Santiago de Chile, Av. Ecuador 3659, Santiago (Chile); Ajaj, R. M. [Aeronautics and Astronautics, University of Southampton, Southampton SO171BJ (United Kingdom); Adhikari, S.; Dayyani, I.; Friswell, M. I. [College of Engineering, Swansea University, Singleton Park, Swansea SA2 8PP (United Kingdom); Castro-Triguero, Rafael [Department of Mechanics, University of Cordoba, Campus de Rabanales, Cordoba CP 14071 (Spain)
2015-02-09
In this paper, we investigate the hyperelastic tensile behaviour of single layer graphene sheets (SLGSs). A one-term incompressible Ogden-type hyperelastic model is chosen to describe the mechanical response of C-C bonds. By establishing equality between the Ogden strain-energy and the variation of the Tersoff-Brenner interatomic potential, three different geometries of SLGSs are studied under tensile loading. We compute the Young's modulus, the finite-deformation Poisson's ratio, ultimate strains, total reactions, and the variation of the potential energy per carbon atom for large strains. Numerical simulations are compared with results obtained by molecular mechanics and molecular dynamics simulations, finite elements, continuum mechanics theory, and experiments. Our predictions are validated, revealing the potential predictive capabilities of the present hyperelastic framework for the analysis of graphene in the context of infinitesimal and large deformations. The good agreement found between our calculations and the published data suggests that graphene may be described as a hyperelastic material.
Normal-tension glaucoma (Low-tension glaucoma)
Anderson Douglas
2011-01-01
Glaucoma is now considered an abnormal physiology in the optic nerve head that interacts with the level of intraocular pressure (IOP), with the degree and rate of damage depending on the IOP and presumably the degree of abnormal physiology. Diagnosis of normal-tension glaucoma (NTG), defined as glaucoma without a clearly abnormal IOP, depends on recognizing symptoms and signs associated with optic nerve vulnerability, in addition to absence of other explanations for disc abnormality and visua...
Light Scattering by Surface Tension Waves.
Weisbuch, G.; Garbay, F.
1979-01-01
This simple and inexpensive experiment is an illustration of the physical concepts of interaction between light and surface tension waves, and provides a new method of measuring surface tension. (Author/GA)
Fluoride glass: Crystallization, surface tension
Doremus, R. H.
1988-01-01
Fluoride glass was levitated acoustically in the ACES apparatus on STS-11, and the recovered sample had a different microstructure from samples cooled in a container. Further experiments on levitated samples of fluoride glass are proposed. These include nucleation, crystallization, melting observations, measurement of surface tension of molten glass, and observation of bubbles in the glass. Ground experiments are required on sample preparation, outgassing, and surface reactions. The results should help in the development and evaluation of containerless processing, especially of glass, in the development of a contaminent-free method of measuring surface tensions of melts, in extending knowledge of gas and bubble behavior in fluoride glasses, and in increasing insight into the processing and properties of fluoride glasses.
The Plastic Tension Field Method
DEFF Research Database (Denmark)
Hansen, Thomas
2005-01-01
This paper describes a calculation method for steel plate girders with transverse web stiffeners subjected to shear. It may be used for predicting the failure load or, as a design method, to determine the optimal amount of internal web stiffeners. The new method is called the plastic tension field...... method. The method is based on the theory of plasticity and is analogous to the so-called diagonal compression field method developed for reinforced concrete beams with transverse stirrups, which is adopted in the common European concrete code (Eurocode 2). Many other theories have been developed, but....... The emphasis is attached to the presentation of a design method based on the diagonal tension field theory. Also, how to determine the load-carrying capacity of a given steel plate girder with transverse web stiffeners, is briefly presented. The load-carrying capacity may be predicted by applying both...
Surface Tension Confines Cryogenic Liquid
Castles, Stephen H.; Schein, Michael E.
1989-01-01
New type of Dewar provides passive, constant-temperature cryogenic cooling for scientific instruments under normal-to low-gravity conditions. Known as Surface-Tension-Contained Liquid Cryogen Cooler (STCLCC), keeps liquid cryogen in known location inside the Dewar by trapping liquid inside spongelike material. Unique sponge material fills most of volume of inner tank. Sponge is all-silica, open-cell material similar to that used for Space Shuttle thermal-protection tiles.
Application of stud loading tension technology
International Nuclear Information System (INIS)
The author principally describes a new way to pretension studs of large diameters--stud loading tension technology, and discusses the rationale of the technology, the calculating method of tension amount, the step and the calibrating method to tension studs. The technology makes little damage on equipment, has seal assemblies uniformly forced and greatly increases the reliability of container seals
Damage development in woven fabric composites during tension-tension fatigue
DEFF Research Database (Denmark)
Hansen, U.
1999-01-01
operating fatigue damage mechanism(s). Fatigue leads to a degradation of material properties. Consequently, in connection with impact induced local stress raisers, fatigue produces continuously changing non-uniform stress fields because of stress redistribution effects. Other models addressing evolution of...... fatigue damage in composite materials have not been able to simulate evolving nonuniform stress fields. Therefore. in the second part of this paper, an analytical/numerical approach capable of addressing these issues is also proposed.......Impacted woven fabric composites were tested in tension-tension fatigue. In contrast to results from static testing, the effects of low energy impact damage in a fatigue environment were found to be the critical element leading to failure of the specimen. This difference emphasizes the need to...
Hritz, A. D.; Raymond, T. M.; Dutcher, D. D.
2016-01-01
Accurate estimates of particle surface tension are required for models concerning atmospheric aerosol nucleation and activation. However, it is difficult to collect sufficiently large volumes of atmospheric aerosol for use in typical instruments that measure surface tension, such as goniometers or Wilhelmy plates. In this work, a method that measures the surface tension of collected liquid nanoparticles using atomic force microscopy is presented. A...
The ensemble switch method for computing interfacial tensions
International Nuclear Information System (INIS)
We present a systematic thermodynamic integration approach to compute interfacial tensions for solid-liquid interfaces, which is based on the ensemble switch method. Applying Monte Carlo simulations and finite-size scaling techniques, we obtain results for hard spheres, which are in agreement with previous computations. The case of solid-liquid interfaces in a variant of the effective Asakura-Oosawa model and of liquid-vapor interfaces in the Lennard-Jones model are discussed as well. We demonstrate that a thorough finite-size analysis of the simulation data is required to obtain precise results for the interfacial tension
The ensemble switch method for computing interfacial tensions
Energy Technology Data Exchange (ETDEWEB)
Schmitz, Fabian; Virnau, Peter [Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 9, D-55128 Mainz (Germany)
2015-04-14
We present a systematic thermodynamic integration approach to compute interfacial tensions for solid-liquid interfaces, which is based on the ensemble switch method. Applying Monte Carlo simulations and finite-size scaling techniques, we obtain results for hard spheres, which are in agreement with previous computations. The case of solid-liquid interfaces in a variant of the effective Asakura-Oosawa model and of liquid-vapor interfaces in the Lennard-Jones model are discussed as well. We demonstrate that a thorough finite-size analysis of the simulation data is required to obtain precise results for the interfacial tension.
Dynamic surface tension of natural surfactant extract under superimposed oscillations.
Reddy, Prasika I; Al-Jumaily, Ahmed M; Bold, Geoff T
2011-01-01
Surfactant dysfunction plays a major role in respiratory distress syndrome (RDS). This research seeks to determine whether the use of natural surfactant, Curosurf™ (Cheisi Farmaceutici, Parma, Italy), accompanied with pressure oscillations at the level of the alveoli can reduce the surface tension in the lung, thereby making it easier for infants with RDS to maintain the required level of functional residual capacity (FRC) without collapse. To simulate the alveolar environment, dynamic surface tension measurements were performed on a modified pulsating bubble surfactometer (PBS) type device and showed that introducing superimposed oscillations about the tidal volume excursion between 10 and 70 Hz in a surfactant bubble lowers interfacial surface tension below values observed using tidal volume excursion alone. The specific mechanisms responsible for this improvement are yet to be established; however it is believed that one mechanism may be the rapid transient changes in the interfacial area increase the number of interfacial binding sites for surfactant molecules, increasing adsorption and diffusion to the interface, thereby decreasing interfacial surface tension. Existing mathematical models in the literature reproduce trends noticed in experiments in the range of breathing frequencies only. Thus, a modification is introduced to an existing model to both incorporate superimposed pressure oscillations and demonstrate that these may improve the dynamic surface tension in the alveoli. PMID:20883997
Implications of cosmic strings with time-varying tension on CMB and large scale structure
Ichikawa, Kazuhide; Takahashi, Tomo; Yamaguchi, Masahide
2006-01-01
We investigate cosmological evolution and implications of cosmic strings with time-dependent tension. We derive basic equations of time development of the correlation length and the velocity of such strings, based on the one scale model. Then, we find that, in the case where the tension depends on some power of the cosmic time, cosmic strings with time-dependent tension goes into the scaling solution if the power is lower than a critical value. We also discuss cosmic microwave background anis...
Vortex Turbulence due to the Interplay of Filament Tension and Rotational Anisotropy
Institute of Scientific and Technical Information of China (English)
JIANG Mi; MA Ping
2009-01-01
The mechanism of scroll wave turbulence is investigated in excitable media with rotational anisotropy. We adopt the Barkley model with heterogeneity in the diffusion constants. Through comparative numerical studies, we demonstrate the vortex turbulence results from the rotational anisotropy's cooperation with negative filament tension or competition with positive filament tension. The presence of rotational anisotropy can enlarge the parameter region leading to negative-tension induced wave turbulence in isotropic media.
Membrane tension and peripheral protein density mediate membrane shape transitions
Shi, Zheng; Baumgart, Tobias
2015-01-01
Endocytosis is a ubiquitous eukaryotic membrane budding, vesiculation and internalization process fulfilling numerous roles including compensation of membrane area increase after bursts of exocytosis. The mechanism of the coupling between these two processes to enable homeostasis is not well understood. Recently, an ultrafast endocytosis (UFE) pathway was revealed with a speed significantly exceeding classical clathrin-mediated endocytosis (CME). Membrane tension reduction is a potential mechanism by which endocytosis can be rapidly activated at remote sites. Here, we provide experimental evidence for a mechanism whereby membrane tension reduction initiates membrane budding and tubulation mediated by endocytic proteins, such as endophilin A1. We find that shape instabilities occur at well-defined membrane tensions and surface densities of endophilin. From our data, we obtain a membrane shape stability diagram that shows remarkable consistency with a quantitative model. This model applies to all laterally diffusive curvature-coupling proteins and therefore a wide range of endocytic proteins.
Institute of Scientific and Technical Information of China (English)
白锐; 佟绍成
2013-01-01
通过对带钢张力产生机理的分析,建立了张紧辊带钢张力的动态机理模型和状态空间模型,在此基础上,与传统的带钢张力比例—积分—微分(PID)控制方法不同,采用状态反馈和极点配置力法设计了带钢张力的多变量跟踪控制器.所设计的带钢张力跟踪控制器能够使各个带钢张力的实际值渐近跟踪相应的设定值,可获得良好的控制效果.通过仿真实验证明了本文的带钢张力模型和跟踪控制方法的有效性.%By means of the mechanism analysis for the strip tension, the dynamical mechanism model and the state space model of the strip tension of the bridling roll are proposed. Based-on these models, the multivariable tracking controller of the strip tension is designed. The proposed tracking controller is designed using the state feedback and pole assignment method, which is different with the traditional PID controller. The proposed tracking control method of the strip tension can control the actual strip tension to track asymptotically their set-points with the satisfactory performance. Simulation experiments are implemented to illustrate the efficiency of the tension model and multivariable tracking control method.
Surface tension driven convection experiment
Ostrach, Simon; Kamotani, Yasuhiro
1988-01-01
Thermocapillary flow is driven by a thermally induced surface tension variation along a liquid free surface. In the Earth-gravity environment such flows are usually overshadowed by buoyancy driven flows, but at reduced gravity conditions their influence could be significant. A comprehensive theoretical and experimental research program was stated 12 years ago and is still being continued. Past work done at Case Western Reserve University as well as work done by others is reviewed. The justification for low-gravity experiments is presented.
Sensorless tension control of shuttleless loom system based on support vector regression
Han, Dong Chang; Back, Woon Jae; Lee, Yoon Chul; Lee, Sang Hwa; Lee, Hyuk Jin; Noh, Seok Hong; Kim, Han Kil; Park, Jae Yong; Lee, Suk Gyu; Chun, Du Hwan
2005-12-01
Tension control of loom system are usually achieved by using loadcell sensor and powder clutch, which require additional mounting space, reduce the reliability in harsh environments and increase the cost of a loom system. Moreover, the physical properties of textile fabrics are very sensitive to several factors(temperature, humidity, radius change of warp beam etc.) which result in tension change. In this paper, a novel sensorless tension control of a shuttleless loom system based on SVR(Support Vector Regression) is presented. The sensorless tension algorithm of shuttleless loom system driven by servo motor which is robust to disturbance and tension variation. First, the modeling and dynamic behaviors of a shuttleless loom system is described. Then, different tension control strategies are analyzed and discussed. And finally, the validity and the usefulness of proposed algorithm are thoroughly verified through numerical simulation.
Lattice Boltzmann simulation of liquid–vapor system by incorporating a surface tension term
International Nuclear Information System (INIS)
In this study, we investigate the pseudopotential multiphase model of lattice Boltzmann method (LBM) and incorporate a surface tension term to implement the particle interaction force. By using the Carnahan–Starling (CS) equation of state (EOS) with a proper critical pressure–density ratio, a density ratio over 160000 is obtained with satisfactory numerical stability. The added surface tension term offers a flexible choice to adjust the surface tension strength. Numerical tests of the Laplace rule are conducted, proving that smaller spurious velocity and better numerical stability can be acquired as the surface tension becomes stronger. Moreover, by wall adhesion and heterogeneous cavitation tests, the surface tension term shows its practical application in dealing with problems in which the surface tension plays an important role. (paper)
The Role of Bag Surface Tension in Color Confinement
Bugaev, K A
2011-01-01
We discuss here the novel view at the color confinement which, on the one hand, allows us to find out the surface tension coefficient of quark gluon bags and, under a plausible assumption, to determine the endpoint temperature of the QCD phase diagram, on the other hand. The present model considers the confining color tube as the cylindrical quark gluon bag with non-zero surface tension. A close inspection of the free energies of elongated cylindrical bag and the confining color tube that connects the static quark-antiquark pair allows us to find out the string tension in terms of the surface tension, thermal pressure and the bag radius. Using the derived relation it is possible to estimate the bag surface tension at zero temperature directly from the lattice QCD data and to estimate the (tri)critical endpoint temperature. In the present analysis the topological free energy of the cylindrical bag is accounted for the first time. The requirement of positive entropy density of such bags leads to negative values...
Pfaffenrath, V; Wermuth, A; Pöllmann, W
1988-12-01
Tension headache (TH) is an ill-defined headache syndrome, characterized by bilateral, daily headaches with fronto-occipital localisation. TH is often accompanied by a migraine and an abuse of analgesics and/or ergotamine. In the etiology of TH vascular, muscular and psychogenic factors are assumed. Floating transitions to common migraine are discussed. The increased muscle tension is not specific for TH, but more probably a consequence of TH. In addition a decrease of the pain threshold with a deficiency of the antinociceptive system is supposed. The efficacy of tricyclic antidepressives in TH is based on potentiation of serotonergic and noradrenergic mechanisms and - besides their analgetic potencies - upon an increase of the pain threshold. TH prophylaxis is indicated if patients suffer from TH more than ten times per month. Medication are tricyclic antidepressives of the amitriptyline-type. Prophylaxis of TH can only be successful if a simultaneous abuse of analgesics and/or ergotamine is discontinued. In addition, EMG-biofeedback, as well as relaxation - and vasoconstriction training might be helpful in specific cases. PMID:3069680
Uniaxial tension and tensile creep behaviors of EPS
Institute of Scientific and Technical Information of China (English)
康颖安; 李显方; 谭加才
2008-01-01
The mechanical behavior of EPS(Expanded polystyrene) with three densities at room temperature and under tension loading was studied.The results show that EPS material is characterized by brittle behavior in the tension tests,and tensile properties of EPS increase with the increase of density.Volume fraction has no a significant effect on the modulus of these foams.The tensile creep strain increases with stress for EPS with same density,indicating that the creep behavior is of the stress dependency.And the creep behavior of EPS exhibits density dependency,which the creep strain decreases with densities for a fixed stress value.Moreover the creep behavior under the constant tension load is well in coincidence with the three-parameter solid model.
Directory of Open Access Journals (Sweden)
Mokritskaya T.P.
2014-12-01
Full Text Available Stochastic analysis of the results of different methods of obtaining and processing of information allows us to solve problems on a qualitatively different level. This is important when creating complex earth models and fields of its parameters, particularly the physical properties. Application of remote sensing methods (geophysical investigations with the registration of a single pulse intensity of the electromagnetic field of the Earth (EIEMPZ seismic profiling, is expanding. Interesting results of the joint interpretation of the results of geophysical and laboratory studies of physical soil. Interesting results of the joint interpretation of the results of geophysical and laboratory studies of physical soil. For the first time a methodology for assessing the state of the soil [3] applied for a joint interpretation of materials determine the field strength EMPZ, seismic profiling, and laboratory techniques. This has allowed to characterize the state of the geological environment and to build a model of inhomogeneous density distribution of fractured rocks at depth. In this paper we made a mathematical analysis of the results of research and talus deposits eluvial clay Taurian series, studied at one of the construction sites southern coast at a depth of 12.0 -25.0 m. Methods of statistical analysis, assessment of homogeneity and symmetrically distributed, rank correlation and multiple regression analysis described in [3]. The analysis of the spatial distribution of areas extrem value of EMPZ, heterogeneity of seismic rigidity. Statistical characteristics of indicators of physical properties reflect the genetic characteristics of the formation and the current state of silty-clay sediments of different genesis.It is proved that the regression model can be applied to interpret the state of the array in the construction of geodynamic model. It is established that the creation of forward-looking (dynamic models for the distribution of the physical
On Surface Tension for Compact Stars
Indian Academy of Sciences (India)
R. Sharma; S. D. Maharaj
2007-06-01
In an earlier analysis it was demonstrated that general relativity gives higher values of surface tension in strange stars with quark matter than neutron stars. We generate the modified Tolman–Oppenheimer–Volkoff equation to incorporate anisotropic matter and use this to show that pressure anisotropy provides for a wide range of behaviour in the surface tension than is the case with isotropic pressures. In particular, it is possible that anisotropy drastically decreases the value of the surface tension.
Etiological factors for muscle tension dysphonia
Kušar, Rozalija
2012-01-01
This thesis discusses muscle tension dysphonia and etiological factors for its emergence. Muscle tension dysphonia is a consequence of irregular formation of the sound and is connected to increased and unnecessary muscle tension and phonation, and is usually without any anatomical and peripheral neurological irregularities and also without any changes on the mucous membrane. In the theoretical part of this thesis voice disorders and various classifications of voice disorders that occur in the...
Surface tension and dynamics of fingering patterns
Magdaleno, F. X.; Casademunt, J.
1997-01-01
We study the minimal class of exact solutions of the Saffman-Taylor problem with zero surface tension, which contains the physical fixed points of the regularized (non-zero surface tension) problem. New fixed points are found and the basin of attraction of the Saffman-Taylor finger is determined within that class. Specific features of the physics of finger competition are identified and quantitatively defined, which are absent in the zero surface tension case. This has dramatic consequences f...
Influence of surface tension to mass transfer
International Nuclear Information System (INIS)
Based on the principle of pressure gradient diffusion, the mechanism of the influence of surface tension on interphase mass transfer was brought forward, and a mathematical description of the influence was presented exploringly. Finally, relating to industrial applications, the influence of surface tension on oxygen deaerating in the atomizing section and in the bubble sections was introduced, and the influence of surface tension on atomizing absorption was pointed out as well
Surface Tension Calculation of Undercooled Alloys
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Based on the Butler equation and extrapolated thermodynamic data of undercooled alloys from those of liquid stable alloys, a method for surface tension calculation of undercooled alloys is proposed. The surface tensions of liquid stable and undercooled Ni-Cu (xNi=0.42) and Ni-Fe (xNi=0.3 and 0.7) alloys are calculated using STCBE (Surface Tension Calculation based on Butler Equation) program. The agreement between calculated values and experimental data is good enough, and the temperature dependence of the surface tension can be reasonable down to 150-200 K under the liquid temperature of the alloys.
Vajoczki, Susan; Biegas, Tamara C.; Crenshaw, Melody; Healey, Ruth L.; Osayomi, Tolulope; Bradford, Michael; Monk, Janice
2011-01-01
This paper provides a review of the practices and tensions informing approaches to professional development for early career academic geographers who are teaching in higher education. We offer examples from Britain, Canada, Nigeria and the USA. The tensions include: institutional and departmental cultures; models that offer generic and…
Evolving spacetimes with purely radial tension
Directory of Open Access Journals (Sweden)
B. Nasre Esfahani
2000-12-01
Full Text Available In this study time-dependent and spherically symmetric solutions of the Einstein field equations in an anisotropic background with a purely radial tension are presented. There exist three classes of solutions,1 An open spacetime with a wormhole at its center. 2 A conical spacetime. 3 A closed spacetime. These inhomogeneous solutions are reduced to FRW spacetimes in matter-dominated era, asymptotically. Therefore, they can be used to describe local inhomogeneities that are not considered in the standard model. For the wormhole solution. it is explicity shown that the considered matter is non-exotic, that is, it does not violate the energy conditions. Also, static solutions are studied. There is only one static solution,a conical spacetime. In this case, the matter satisfies the energy condition critically.
Shell tension forces propel Dictyostelium slugs forward
International Nuclear Information System (INIS)
The Dictyostelium slug is an excellent model system for studying collective movements, as it is comprised of about 105 cells all moving together in the same direction. It still remains unclear how this movement occurs and what the physical mechanisms behind it are. By applying our recently developed 3D traction force microscopy, we propose a simple explanation for slug propulsion. Most of the forces are exerted by the sheath surrounding the slug. This secreted shell is under a rather uniform tension (around 50 mN m−1) and will give rise to a tissue under pressure. Finally, we propose that this pressure will naturally push the slug tip forwards if a gradient of shell mechanical properties takes place in the very anterior part of the raised tip. (paper)
Buschmann, C T; Tsokos, M; Kurz, S D; Kleber, C
2015-07-01
Tension pneumothorax can occur at any time during cardiopulmonary resuscitation (CPR) with external cardiac massage and invasive ventilation either from primary or iatrogenic rib fractures with concomitant pleural or parenchymal injury. Airway injury can also cause tension pneumothorax during CPR. This article presents the case of a 41-year-old woman who suffered cardiopulmonary arrest after undergoing elective mandibular surgery. During CPR the upper airway could not be secured by orotracheal intubation due to massive craniofacial soft tissue swelling. A surgical airway was established with obviously unrecognized iatrogenic tracheal perforation and subsequent development of tension pneumomediastinum and tension pneumothorax during ventilation. Neither the tension pneumomediastinum nor the tension pneumothorax were decompressed and accordingly resuscitation efforts remained unsuccessful. This case illustrates the need for a structured approach to resuscitate patients with ventilation problems regarding decompression of tension pneumomediastinum and/or tension pneumothorax during CPR. PMID:26036317
Directory of Open Access Journals (Sweden)
Y. Ma
2011-01-01
Full Text Available Arctic Ground Squirrels (AGS are classic hibernators known for their tolerance to hypoxia. AGS have been studied as a model of hypoxia with potential as a medical research model. Problem statement: Their unique resistance to the stressors of low oxygen led us to hypothesize that AGS might also be adaptable to hyperoxia. Approach: This study examined the physiological pattern associated with hyperoxia in response to brain tissue oxygen partial pressure (PtO2, brain temperature (Tbrain, global oxygen consumption (VO2 and respiratory frequency (fR using non-sedated and nonanesthetized Arctic Ground Squirrels (AGS and rats. Results: We found that 1 100% inspired oxygen (FiO2 increased the baseline values of brain PtO2 significantly in both summer euthermic AGS (24.4 ± 3.6-87.3 ± 3.6 mmHg, n=6 and in rats (18.2 ± 5.2-73.3 ± 5.2 mmHg, n = 3; PtO2 was significantly higher in AGS than in rats during hyperoxic exposure; 2 hyperoxic exposure had no effect on brain temperature in either AGS or rats, with the brain temperatures maintaining constancy before, during and after 100% O2 exposure; 3 systemic metabolic rates increased significantly during hyperoxic exposure in both euthermic AGS and rats; moreover, VO2 were significantly lower in AGS than in rats during hyperoxic exposure; 4 the respiratory rates for rats were maintained before, during and after 100% O2 exposure, while the respiratory responding patterns to hyperoxic exposure changed after exposure in AGS. AGS fR was significantly lower after hyperoxic exposure than before the exposure. Conclusion: These results suggest that hyperoxic ventilation induced PtO2 and VO2 differences between AGS and rats and led to altered respiratory patterns between these species. AGS and the rat serves as an excellent comparative model for hypoxic and hyperoxic stress studies of the brain.
Energy Technology Data Exchange (ETDEWEB)
Schwalbe, K.H. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Materialforschung
1995-12-31
The Engineering Treatment Model (ETM) relates the crack tip opening displacement (CTOD) and the J integral with the applied load or applied strain using a geometry independent, master-curve-type, equation. In the present paper, CTOD and J were examined as a function of the applied strain by means of comparing ETM predictions with earlier experimental and numerical results. A comparison was also made with a theoretical solution by Shih and Hutchinson. It was concluded that the ETM provides useful engineering approximations. (orig.)
Field Evaluation of the System Identification Approach for Tension Estimation of External Tendons
Directory of Open Access Journals (Sweden)
Myung-Hyun Noh
2015-01-01
Full Text Available Various types of external tendons are considered to verify the applicability of tension estimation method based on the finite element model with system identification technique. The proposed method is applied to estimate the tension of benchmark numerical example, model structure, and field structure. The numerical and experimental results show that the existing methods such as taut string theory and linear regression method show large error in the estimated tension when the condition of external tendon is different with the basic assumption used during the derivation of relationship between tension and natural frequency. However, the proposed method gives reasonable results for all of the considered external tendons in this study. Furthermore, the proposed method can evaluate the accuracy of estimated tension indirectly by comparing the measured and calculated natural frequencies. Therefore, the proposed method can be effectively used for field application of various types of external tendons.
Delayed tension pneumothorax complicating staphylococcal pneumonia.
Yates, S. P.; Morcos, S. K.
1988-01-01
A case is described in which a tension pneumothorax complicated staphylococcal pneumonia 11 months after its onset. The delayed and subacute/chronic nature of the tension pneumothorax is unusual. The case also highlights the difficult differential diagnosis between subpleural lung cysts and encysted pneumothorax.
Effect of Gravity on Surface Tension
Weislogel, M. M.; Azzam, M. O. J.; Mann, J. A.
1998-01-01
Spectroscopic measurements of liquid-vapor interfaces are made in +/- 1-g environments to note the effect of gravity on surface tension. A slight increase is detected at -1-g0, but is arguably within the uncertainty of the measurement technique. An increased dependence of surface tension on the orientation and magnitude of the gravitational vector is anticipated as the critical point is approached.
Tension and robustness in multitasking cellular networks.
Directory of Open Access Journals (Sweden)
Jeffrey V Wong
Full Text Available Cellular networks multitask by exhibiting distinct, context-dependent dynamics. However, network states (parameters that generate a particular dynamic are often sub-optimal for others, defining a source of "tension" between them. Though multitasking is pervasive, it is not clear where tension arises, what consequences it has, and how it is resolved. We developed a generic computational framework to examine the source and consequences of tension between pairs of dynamics exhibited by the well-studied RB-E2F switch regulating cell cycle entry. We found that tension arose from task-dependent shifts in parameters associated with network modules. Although parameter sets common to distinct dynamics did exist, tension reduced both their accessibility and resilience to perturbation, indicating a trade-off between "one-size-fits-all" solutions and robustness. With high tension, robustness can be preserved by dynamic shifting of modules, enabling the network to toggle between tasks, and by increasing network complexity, in this case by gene duplication. We propose that tension is a general constraint on the architecture and operation of multitasking biological networks. To this end, our work provides a framework to quantify the extent of tension between any network dynamics and how it affects network robustness. Such analysis would suggest new ways to interfere with network elements to elucidate the design principles of cellular networks.
Dialectical tensions in stroke survivor relationships.
Brann, Maria; Himes, Kimberly Leezer; Dillow, Megan R; Weber, Keith
2010-06-01
Stroke is an unpredictable and life-altering medical occurrence that causes immediate change in survivors' relationships. This study unearthed dialectical tensions expressed by spouses of stroke survivors and examined how those dialectical tensions compare to those experienced by stroke survivors themselves. Sixteen spouses of stroke survivors participated in interviews, and four tensions ultimately emerged: self-orientation-partner-orientation, realism-idealism, uncertainty-acceptance, and emotional release-emotional reservation. Three dialectical tensions (i.e., uncertainty-acceptance, realism-idealism, self-orientation-partner-orientation) were similar to those communicated by stroke survivors. Recognizing dialectical tensions experienced and shared can open communication lines and ultimately improve the health of individuals and their relationships. PMID:20512714
FORMULAS OF TENSION OF CONTINUOUS ROLLING PROCESS
Institute of Scientific and Technical Information of China (English)
J.Z. Zhang; X.P. Zhang
2007-01-01
The development of computer controlled continuous rolling process calls for a mathematicalexpression that can express the inequality condition of "constant flow". Tension is the link of thecontinuous rolling process. From the condition of dynamic equilibrium, a differential equation oftension is given out. On the basis of the physical rules established from the industrial practice andexperimental studies, the law of volume constancy, the linear relation of forward slip and tension,the state equation of continuous rolling, the formula of dynamic tension, and the formula of statictension have been obtained. These formulae reflect the functional relations between tensions,thickness, roll velocity, and time in the continuous rolling process. It is implied that the continuousrolling process is a gradually steady, controllable, and measurable dynamic system. An assumptionof predicting the thickness of a steel plate using these tension formulae is also put forward.
Directory of Open Access Journals (Sweden)
Moncayo Helga
2007-02-01
to the contra lateral side and tendon snapping. We propose that eccentric muscle action over time can be the basis for a low grade inflammatory condition. The general implications of this model and its relations to Zn and Se will be discussed.
An interlaminar tension strength specimen
Jackson, Wade C.; Martin, Roderick H.
1992-01-01
This paper describes a technique to determine interlaminar tension strength, sigma(sub 3c) of a fiber reinforced composite material using a curved beam. The specimen was a unidirectional curved beam, bent 90 degrees, with straight arms. Attached to each arm was a hinged loading mechanism which was held by the grips of a tensile testing machine. Geometry effects of the specimen, including the effects of loading arm length, inner radius, thickness, and width, were studied. The data sets fell into two categories: low strength corresponding to a macroscopic flaw related failure and high strength corresponding to a microscopic flaw related failure. From the data available, the loading arm length had no effect on sigma(sub 3c). The inner radius was not expected to have a significant effect on sigma(sub 3c), but this conclusion could not be confirmed because of differences in laminate quality for each curve geometry. The thicker specimens had the lowest value of sigma(sub 3c) because of poor laminate quality. Width was found to affect the value of sigma(sub 3c) only slightly. The wider specimens generally had a slightly lower strength since more material was under high stress, and hence, had a larger probability of containing a significant flaw.
The effects of solid-liquid interfacial tension on the settlement of sediment flocs
Jianglin, Z
2006-01-01
In this paper, the effects of interfacial tension between the sediment solid particle and liquid on the settlement of sediment flocs are investigated. After a discussion of mechanical and physical chemistry, we give a settling velocity expression including such dynamical information of the floc growth as interfacial tension and primary particle size \\textit{etc.}. The resulting expression indicates the average settling velocity of sediment flocs increases with increasing solid-liquid interfacial tension in a form of power law and deceases with the primary particle size. We report on a general method for analyzing settling behaviors of sediment flocs under different flocculation conditions and verify the rationality of the assumption of tension-induced flocculation by fitting typical experimental data to the electrolyte concentration-dependent sedimentation model which can follow from the relationship between interfacial tension and electrolyte concentration.
Tension-tension fatigue behavior of the Space Shuttle strain-isolation-pad material
Phillips, E. P.
1981-01-01
The room temperature fatigue behavior of 0.41-cm (0.16-in) thick strain-isolation-pad (SIP) material was explored in a series of constant- and random-amplitude loading tests. The SIP material is used on the Space Shuttle to isolate the ceramic insulating tiles from the strains and deflections of the aluminum alloy airframe. In all tests, 12.7 by 12.7 cm (5.0 by 5.0 in) SIP specimens were subjected to tension-tension loading in the through-the-thickness direction at a frequency of 10 Hz. When subjected to cyclic loading, the SIP material exhibited a monotonic increase in thickness and a monotonic increase in tensile tangent moduli. The rate of thickness growth increased with increasing test stress level and decreased with increasing number cycles endured. Power law equations were found to provide a good representation of the thickness growth rate data. Tensile tangent moduli increased by as much as 80 percent during fatigue tests. Simple cumulative damage fatigue models predicted the mean thickness growth under random-amplitude loading with reasonable accuracy (factor of 2 on life).
ANCHORING EFFECT ANALYSIS OF TENSIONED BOLTS
Institute of Scientific and Technical Information of China (English)
夏建中
1997-01-01
The paper analyses quantitatively the anchoring effect of tensioned bolts on surrounding rock strength, and defines two concepts: one is the surrounding rock strength increased amount △τ13 and the other is the strength influence factor k. The anchoring effect of tensioned bolts is considered to increase a strength increased amount △τ13 where △τ13 is the product k and tensioned load p, i. e. △τ13= kp, where k is a function of two variables x and y. The distributive properties both △τ13 and k are also discussed in the paper, obtaining some useful results for designing bolting support parameters.
Superficial tension: experimental model with simple materials
2012-01-01
En este trabajo se presenta una propuesta didáctica basada en una actividad experimental utilizando materiales de muy bajo costo, orientada a lograr que los alumnos comprendan e interpreten el fenómeno de tensión superficial conjuntamente con la importancia de la modelización en ciencias. Tiene como objetivo principal de enseñanza acercar al alumno a la mecánica de los fluidos estáticos y las fuerzas intermoleculares, combinando contenidos científicos con cuestiones cercanas al es...
Robust Tension Control of Strip for 5-Stand Tandem Cold Mills
Directory of Open Access Journals (Sweden)
Behrooz Shafiei
2014-01-01
Full Text Available Tandem cold rolling process is a nonlinear complex system with external and internal uncertainties and significant disturbances. The improvement in the quality of the final output depends on the control strategy of centerline thickness and interstand tension. This paper focuses on interstand tension control problem in 5-stand tandem cold rolling mills. Tension dynamics can be described by a nominal model perturbed by parametric uncertainties. In order to overcome the model uncertainties and external disturbances, suboptimal H∞ and μ controllers are proposed and the Hankel-norm approximation is used to reduce the order of μ controller. The performance of the proposed controllers is demonstrated by some simulations.
P-O. Legault Tremblay (Pierre-Olivier)
2015-01-01
textabstractCorporate governance in transition economies does not fit in the dominant normative models. China embodies institutional tensions between an inherited system of political governance and new laws transplanted from Western countries that empower external shareholders on capital markets.
Time-Dependent Response of Polypropylene/Clay Nanocomposites Under Tension and Retraction
DEFF Research Database (Denmark)
Drozdov, Aleksey; Christiansen, Jesper de Claville
2013-01-01
Observations are reported in relaxation tests under tension and retraction on polypropylene/clay nanocomposites with various contents of filler. A two-phase constitutive model is developed in cyclic viscoelasticity and viscoplasticity of nanocomposites. Adjustable parameters in the stress...
The Equilibrium Spreading Tension of Pulmonary Surfactant.
Dagan, Maayan P; Hall, Stephen B
2015-12-01
Monomolecular films at an air/water interface coexist at the equilibrium spreading tension (γ(e)) with the bulk phase from which they form. For individual phospholipids, γ(e) is single-valued, and separates conditions at which hydrated vesicles adsorb from tensions at which overcompressed monolayers collapse. With pulmonary surfactant, isotherms show that monolayers compressed on the surface of bubbles coexist with the three-dimensional collapsed phase over a range of surface tensions. γ(e) therefore represents a range rather than a single value of surface tension. Between the upper and lower ends of this range, rates of collapse for spread and adsorbed films decrease substantially. Changes during adsorption across this narrow region of coexistence between the two- and three-dimensional structures at least partially explain how alveolar films of pulmonary surfactant become resistant to collapse. PMID:26583569
Notch effects in uniaxial tension specimens
International Nuclear Information System (INIS)
Results of a literature survey on the effect of notches on the time-dependent failure of uniaxial tension specimens at elevated temperatures are presented. Particular attention is paid to the failure of notched specimens containing weldments
Tension Hydrothorax Related to Disseminated Endometriosis
Directory of Open Access Journals (Sweden)
AnnaKate Deal, MD
2016-01-01
Full Text Available We present the case of a 34-year-old woman presenting to the emergency department (ED with dyspnea, cough, and fever. She was found to have a tension hydrothorax and was treated with ultrasound-guided thoracentesis in the ED. Subsequent inpatient evaluation showed the patient had disseminated endometriosis. Tension hydrothorax has not been previously described in the literature as a complication of this disease.
On surface tension for compact stars
Sharma, R.; Maharaj, S. D.
2007-01-01
In an earlier treatment it was demonstrated that general relativity gives higher values of surface tension in strange stars with quark matter than neutron stars.We generate the modified Tolman-Oppenheimer-Volkoff equation to incorporate anisotropic matter and use this to show that pressure anisotropy provides for a wide range of behaviour in the surface tension than is the case with isotropic pressures. In particular it is possible that anisotropy drastically decreases the value of the surfac...
Lehle, H.; Oettel, M.
2008-01-01
We analyze the effective potential for nanoparticles trapped at a fluid interface within a simple model which incorporates surface and line tensions as well as a thermal average over interface fluctuations (capillary waves). For a single colloid, a reduced steepness of the potential well hindering movements out of the interface plane compared to rigid interface models is observed, and an instability of the capillary wave partition sum in case of negative line tensions is pointed out. For two ...
Tension-loaded bolted connections in steel structures
Skavhaug, Elin Stensrud; Østhus, Svanhild Irene
2015-01-01
The purpose of this thesis is to study the behaviour of bolted steel connections subjected to tension. Quasi-static conditions have been considered. By performing laboratory tests on single bolts and simple T-stub connections the failure modes of the bolts have been examined. Finite element models are created and validated to represent the behaviour observed in the laboratory. Different grip length configurations have been tested for a single bolt and nut assembly subjected to pure tensio...
Oxygen tension level and human viral infections
Energy Technology Data Exchange (ETDEWEB)
Morinet, Frédéric, E-mail: frederic.morinet@sls.aphp.fr [Centre des Innovations Thérapeutiques en Oncologie et Hématologie (CITOH), CHU Saint-Louis, Paris (France); Université Denis Diderot, Sorbonne Paris Cité Paris, Paris (France); Casetti, Luana [Institut Cochin INSERM U1016, Paris (France); François, Jean-Hugues; Capron, Claude [Institut Cochin INSERM U1016, Paris (France); Laboratoire d' Hématologie, Hôpital Ambroise Paré, Boulogne (France); Université de Versailles Saint-Quentin en Yvelynes, Versailles (France); Pillet, Sylvie [Laboratoire de Bactériologie-Virologie-Hygiène, CHU de Saint-Etienne, Saint-Etienne (France); Université de Lyon et Université de Saint-Etienne, Jean Monnet, GIMAP EA3064, F-42023 Saint-Etienne, Lyon (France)
2013-09-15
The role of oxygen tension level is a well-known phenomenon that has been studied in oncology and radiotherapy since about 60 years. Oxygen tension may inhibit or stimulate propagation of viruses in vitro as well as in vivo. In turn modulating oxygen metabolism may constitute a novel approach to treat viral infections as an adjuvant therapy. The major transcription factor which regulates oxygen tension level is hypoxia-inducible factor-1 alpha (HIF-1α). Down-regulating the expression of HIF-1α is a possible method in the treatment of chronic viral infection such as human immunodeficiency virus infection, chronic hepatitis B and C viral infections and Kaposi sarcoma in addition to classic chemotherapy. The aim of this review is to supply an updating concerning the influence of oxygen tension level in human viral infections and to evoke possible new therapeutic strategies regarding this environmental condition. - Highlights: • Oxygen tension level regulates viral replication in vitro and possibly in vivo. • Hypoxia-inducible factor 1 (HIF-1α) is the principal factor involved in Oxygen tension level. • HIF-1α upregulates gene expression for example of HIV, JC and Kaposi sarcoma viruses. • In addition to classical chemotherapy inhibition of HIF-1α may constitute a new track to treat human viral infections.
Czech Academy of Sciences Publication Activity Database
Součková, Monika; Klomfar, Jaroslav; Pátek, Jaroslav
2015-01-01
Roč. 83, April (2015), s. 52-60. ISSN 0021-9614 R&D Projects: GA ČR GA13-00145S; GA ČR GA101/09/0010 Institutional support: RVO:61388998 Keywords : density * surface tension * 1-alkyl-3-methylimidazolium iodide * group contribution method * parachor Subject RIV: BJ - Thermodynamics Impact factor: 2.679, year: 2014
Ice Accretion with Varying Surface Tension
Bilanin, Alan J.; Anderson, David N.
1995-01-01
During an icing encounter of an aircraft in flight, super-cooled water droplets impinging on an airfoil may splash before freezing. This paper reports tests performed to determine if this effect is significant and uses the results to develop an improved scaling method for use in icing test facilities. Simple laboratory tests showed that drops splash on impact at the Reynolds and Weber numbers typical of icing encounters. Further confirmation of droplet splash came from icing tests performed in the NaSA Lewis Icing Research Tunnel (IRT) with a surfactant added to the spray water to reduce the surface tension. The resulting ice shapes were significantly different from those formed when no surfactant was added to the water. These results suggested that the droplet Weber number must be kept constant to properly scale icing test conditions. Finally, the paper presents a Weber-number-based scaling method and reports results from scaling tests in the IRT in which model size was reduced up to a factor of 3. Scale and reference ice shapes are shown which confirm the effectiveness of this new scaling method.
Surface Tension and Adsorption without a Dividing Surface.
Marmur, Abraham
2015-11-24
The ingenious concept of a dividing surface of zero thickness that was introduced by Gibbs is the basis of the theory of surface tension and adsorption. However, some fundamental questions, mainly those related to the location of the dividing surface and the proper definition of relative adsorption, have remained open over the years. To avoid these questions, the present paper proposes to analyze an interfacial phase by defining a thermodynamic system of constant, but nonzero thickness. The interfacial phase is analyzed as it really is, namely a nonuniform three-dimensional entity. The current analysis redevelops the equation for calculating surface tension, though with different assumptions. However, the main point in the proposed model is that the thermodynamic interfacial system, due to its fixed thickness, conforms to the requirement of first-order homogeneity of the internal energy. This property is the key that allows using the Gibbs adsorption isotherm. It is also characteristic of the Gibbs dividing surface model, but has not always been discussed with regard to subsequent models. The resulting equation leads to a simple, "natural" expression for the relative adsorption. This expression may be compared with simulations and sophisticated surface concentration measurements, and from which the dependence of interfacial tension on the solution composition can be derived. Finally, it is important to point out that in order to calculate the interfacial tension as well as the relative adsorption from data on the properties of the interfacial phase, there is no need to know its exact thickness, as long as it is bigger than the actual thickness but sufficiently small. PMID:26523466
Mechanical relation for porous metal foams under complex loads of triaxial tension and compression
International Nuclear Information System (INIS)
The mechanical relation of isotropic three-dimensional reticulated porous metal foams with stochastic pores is investigated under complex loads of triaxial tension and compression. From the simplified structural model, the mathematical relationship between three nominal main stresses and porosity has been derived for this class of porous materials at failure under the above-mentioned complex loads, covering three loading conditions of biaxial tension with monoaxial compression, of biaxial compression with monoaxial tension, and of triaxial compression. Through the relevant expression from the deduction, the criterion of strength design can be further obtained for these porous materials under these multiaxial complex loadings.
Mechanical Principle of Enhancing Cell-Substrate Adhesion via Pre-Tension in the Cytoskeleton
Chen, Bin; Gao, Huajian
2010-01-01
Motivated by our earlier study on the effect of pre-tension in gecko adhesion, here we investigate whether and how pre-tension in cytoskeleton influences cell adhesion by developing a stochastic-elasticity model of a stress fiber attached on a rigid substrate via molecular bonds. By comparing the variations in adhesion lifetime and observing the sequences of bond breaking with and without pre-tension in the stress fiber under the same applied force, we demonstrate that the effect of pre-tensi...
Dependence of the surface tension on the shape of surface boundary
Koibuchi, Hiroshi
2016-01-01
We numerically check that the surface tension of membranes is independent of the shape of surface boundary. The surface tension is calculated by means of the Monte Carlo simulation technique on two types of cylinders made of rubans of size $L_1$ and $L_2$, where the rubans are the same for the projected area and different in the ratio $L_1/L_2$. The difference of the surface tension disappears in the thermodynamic limit in both models of Helfrich-Polyakov and Landau-Ginzburg.
Novel estimated surface tension data of actinide halide salts in the molten state
International Nuclear Information System (INIS)
The surface tension of ThF4, UF4 and UF6 is theoretically estimated, as function of temperature, whereas eight other halide salts only for temperature equal to their melting points. Calculations are based on a model, using statistical thermodynamics of Eyring theory. It is observed that the surface tension decreases linearly with temperature. The results are strictly compared with the available experimental data. The technique can be applied for conditions where experimental data are currently missing. The compressibility and surface tension products, of all salts under study, were also calculated
Experimental and calculated liquid-liquid interfacial tension in demixing metal alloys
Institute of Scientific and Technical Information of China (English)
Walter Hoyer; Ivan Kaban
2006-01-01
Liquid-liquid interfacial tension in binary and ternary Al-based monotectic systems has been determined experimentally with a tensiometric method in a wide temperature interval. The temperature dependence of the interfacial tension is well described by a power law function of the type σαβ～ (1 - T/Tc)δ with the critical exponent δ = 1.3 and a critical tem perature TC. Theoretical models describing the liquid-liquid interface in monotectic alloys and their applicability for calculation of the interfacial tension and its temperature dependence in binary systems are considered.
Novel estimated surface tension data of actinide halide salts in the molten state
Energy Technology Data Exchange (ETDEWEB)
Aqra, Fathi, E-mail: fathiaqra2009@hotmail.com
2014-05-01
The surface tension of ThF{sub 4}, UF{sub 4} and UF{sub 6} is theoretically estimated, as function of temperature, whereas eight other halide salts only for temperature equal to their melting points. Calculations are based on a model, using statistical thermodynamics of Eyring theory. It is observed that the surface tension decreases linearly with temperature. The results are strictly compared with the available experimental data. The technique can be applied for conditions where experimental data are currently missing. The compressibility and surface tension products, of all salts under study, were also calculated.
Oxygen tension affects lubricin expression in chondrocytes.
Hatta, Taku; Kishimoto, Koshi N; Okuno, Hiroshi; Itoi, Eiji
2014-10-01
We assessed the effects of oxygen tension on lubricin expression in bovine chondrocytes and cartilage explants and a role for hypoxia-inducible transcription factor (HIF)-1α in regulating lubricin expression was investigated using a murine chondroprogenitor cell line, ATDC5, and bovine chondrocytes isolated from superficial and middle/deep zones of femoral cartilage. ATDC5 cells and bovine chondrocytes were cultured in micromass under different oxygen tensions (21%, 5%, and 1%). ATDC5 cells and middle/deep zone chondrocytes that initially had low lubricin expression levels were also cultured with or without transforming growth factor (TGF)-β1. Quantitative reverse transcription (RT)-PCR was used to determine lubricin and chondrogenic marker gene mRNA levels and immunohistochemistry was used to assess lubricin protein expression. Explant cartilage plugs cultured under different oxygen tensions were also subjected to immunohistological analysis for lubricin. HIF-1α gene silencing was achieved by electroporatic transfer into ATDC5 cells. A low oxygen tension reduced lubricin gene expression levels in bovine superficial chondrocytes, TGF-β1-treated middle/deep zone chondrocytes, and TGF-β1-treated ATDC5 cells. Lubricin expression in explant cartilage was also suppressed under hypoxia. HIF-1α gene silencing in ATDC5 cells attenuated the lubricin expression response to the oxygen tension. These results corroborate with previous studies that the oxygen tension regulates lubricin gene expression and suggest that HIF-1α plays an important role in this regulation. The normal distribution of lubricin in articular cartilage may be due to the hypoxic oxygen environment of cartilage as it is an avascular tissue. An oxygen tension gradient may be a key factor for engineering cartilage tissue with a layered morphology. PMID:24712343
Membrane tension feedback on shape and motility of eukaryotic cells
Winkler, Benjamin; Aranson, Igor S.; Ziebert, Falko
2016-04-01
In the framework of a phase field model of a single cell crawling on a substrate, we investigate how the properties of the cell membrane affect the shape and motility of the cell. Since the membrane influences the cell dynamics on multiple levels and provides a nontrivial feedback, we consider the following fundamental interactions: (i) the reduction of the actin polymerization rate by membrane tension; (ii) area conservation of the cell's two-dimensional cross-section vs. conservation of the circumference (i.e. membrane inextensibility); and (iii) the contribution from the membrane's bending energy to the shape and integrity of the cell. As in experiments, we investigate two pertinent observables - the cell's velocity and its aspect ratio. We find that the most important effect is the feedback of membrane tension on the actin polymerization. Bending rigidity has only minor effects, visible mostly in dynamic reshaping events, as exemplified by collisions of the cell with an obstacle.
Surface tension dominates insect flight on fluid interfaces.
Mukundarajan, Haripriya; Bardon, Thibaut C; Kim, Dong Hyun; Prakash, Manu
2016-03-01
Flight on the 2D air-water interface, with body weight supported by surface tension, is a unique locomotion strategy well adapted for the environmental niche on the surface of water. Although previously described in aquatic insects like stoneflies, the biomechanics of interfacial flight has never been analysed. Here, we report interfacial flight as an adapted behaviour in waterlily beetles (Galerucella nymphaeae) which are also dexterous airborne fliers. We present the first quantitative biomechanical model of interfacial flight in insects, uncovering an intricate interplay of capillary, aerodynamic and neuromuscular forces. We show that waterlily beetles use their tarsal claws to attach themselves to the interface, via a fluid contact line pinned at the claw. We investigate the kinematics of interfacial flight trajectories using high-speed imaging and construct a mathematical model describing the flight dynamics. Our results show that non-linear surface tension forces make interfacial flight energetically expensive compared with airborne flight at the relatively high speeds characteristic of waterlily beetles, and cause chaotic dynamics to arise naturally in these regimes. We identify the crucial roles of capillary-gravity wave drag and oscillatory surface tension forces which dominate interfacial flight, showing that the air-water interface presents a radically modified force landscape for flapping wing flight compared with air. PMID:26936640
Inhomogeneous Deformation of Brain Tissue During Tension Tests
Rashid, Badar; Gilchrist, Michael D; 10.1016/j.commatsci.2012.05.030
2013-01-01
Mechanical characterization of brain tissue has been investigated extensively by various research groups over the past fifty years. These properties are particularly important for modelling Traumatic Brain Injury (TBI). In this research, we present the design and calibration of a High Rate Tension Device (HRTD) capable of performing tests up to a maximum strain rate of 90/s. We use experimental and numerical methods to investigate the effects of inhomogeneous deformation of porcine brain tissue during tension at different specimen thicknesses (4.0-14.0 mm), by performing tension tests at a strain rate of 30/s. One-term Ogden material parameters (mu = 4395.0 Pa, alpha = -2.8) were derived by performing an inverse finite element analysis to model all experimental data. A similar procedure was adopted to determine Young's modulus (E= 11200 Pa) of the linear elastic regime. Based on this analysis, brain specimens of aspect ratio (diameter/thickness) S < 1.0 are required to minimise the effects of inhomogeneous...
Transcutaneous oxygen tension in imminent foot gangrene
DEFF Research Database (Denmark)
Tønnesen, K H
1978-01-01
Transcutaneous oxygen tension at 44 degree C and maximal isotope clearance (90m Tc-pretechnetate + histramine) just proximal to the 1st toe and systolic toe blood pressure (strain gauge) were studied on a tilt table in patients with various degrees of obstructive arteriosclerotic disease. In legs......) from the arterioles into the tissue sink and counter current gas shunting. The hypoxia in spite of a positive perfusion pressure up to 50 mmHg explains our experience that ischemic ulcers in feet such low pressures never heal.......Transcutaneous oxygen tension at 44 degree C and maximal isotope clearance (90m Tc-pretechnetate + histramine) just proximal to the 1st toe and systolic toe blood pressure (strain gauge) were studied on a tilt table in patients with various degrees of obstructive arteriosclerotic disease. In legs...... with moderate obstruction, the oxygen tension reached zero at a toe systolic blood pressure of 5--10 mmHg (tilt toe up) and reached arterial oxygen tension at about 50 to 70 mmHg (tilt toe down). In legs withsevere arterial obstruction and ischaemic rest pain, oxygen tension rose from zero not before...
Renormalization group improved action for SU(3) lattice gauge theory and the string tension
International Nuclear Information System (INIS)
The expectation values of the Wilson loops and the string tension are calculated by Monte Carlo simulations for SU(3) lattice gauge theory with a renormalization group improved action, the form of which is chosen from a block spin renormalization group study and an analysis of instantions on the lattice. The string tension is about 2.5 times larger than that obtained so far for the standard model. The deconfinement phase transition temperature is also calculated roughly. (orig.)
Kolar, David R.; Hammerle, Florian; Jenetzky, Ekkehart; Huss, Michael; Bürger, Arne
2016-01-01
Background Current models of Anorexia Nervosa (AN) emphasize the role of emotion regulation. Aversive tension, described as a state of intense arousal and negative valence, is considered to be a link between emotional events and disordered eating. Recent research focused only on adult patients, and mainly general emotion regulation traits were studied. However, the momentary occurrence of aversive tension, particularly in adolescents with AN, has not been previously studied. Method 20 female ...
Filament tension and phase-locked drift of meandering scroll waves
Dierckx, Hans; Biktasheva, Irina V.; Verschelde, Henri; Panfilov, Alexander V.; Biktashev, Vadim N.
2016-01-01
Rotating scroll waves are self-organising patterns which are found in many oscillating or excitable systems. Here we show that quasi-periodic (meandering) scroll waves, which include the rotors that organise cardiac arrhythmias, exhibit filament tension when averaged over the meander cycle. With strong filament curvature or medium thickness gradients, however, scroll wave dynamics are governed by phase-locked drift instead of filament tension. Our results are validated in computational models...
Carbon speciation and surface tension of fog
Capel, P.D.; Gunde, R.; Zurcher, F.; Giger, W.
1990-01-01
The speciation of carbon (dissolved/particulate, organic/inorganic) and surface tension of a number of radiation fogs from the urban area of Zurich, Switzerland, were measured. The carbon species were dominated by "dissolved" organic carbon (DOC; i.e., the fraction that passes through a filter), which was typically present at levels of 40-200 mg/L. Less than 10% of the DOC was identified as specific individual organic compounds. Particulate organic carbon (POC) accounted for 26-41% of the mass of the particles, but usually less than 10% of the total organic carbon mass. Inorganic carbon species were relatively minor. The surface tensions of all the measured samples were less than pure water and were correlated with their DOC concentrations. The combination of high DOC and POC and low surface tension suggests a mechanism for the concentration of hydrophobic organic contaminants in the fog droplet, which have been observed by numerous investigators. ?? 1990 American Chemical Society.
Tending the tensions in co-creation
DEFF Research Database (Denmark)
Phillips, Professor MSO Louise; Nordentoft, Helle Merete; Pedersen, Lektor Christina Hee; Frølunde, Adjunkt Lisbeth; Olesen, Lektor Birgitte Ravn; Kristiansen, Lektor Marianne; Poulsen, Lektor Jørgen Bloch
2013-01-01
-for-granted positive value. In the panel we de-romanticise “co-creation” and explore how it is enacted in particular organisational contexts, concentrating on context-specific tensions arising in the meeting between different knowledge forms and interests. These include tensions BETWEEN dialogic views of knowledge co-creation...... as a process of mutual learning to be valued at least as much as the outcome AND the neoliberal instrumentalisation of creativity in the service of social innovation and economic growth. The papers build on the themes of Knowledge and Power in Collaborative Research: A Reflexive Approach (Phillips......, Kristiansen et al, Routledge, 2012), adopting a critical, reflexive approach that interrogates the tensions AND is committed to developing co-creative methods....
Tending the tensions in co-creation
DEFF Research Database (Denmark)
Phillips, Louise Jane
-for-granted positive value. In the panel we de-romanticise “co-creation” and explore how it is enacted in particular organisational contexts, concentrating on context-specific tensions arising in the meeting between different knowledge forms and interests. These include tensions BETWEEN dialogic views of knowledge co-creation...... as a process of mutual learning to be valued at least as much as the outcome AND the neoliberal instrumentalisation of creativity in the service of social innovation and economic growth. The papers build on the themes of Knowledge and Power in Collaborative Research: A Reflexive Approach (Phillips......, Kristiansen et al, Routledge, 2012), adopting a critical, reflexive approach that interrogates the tensions AND is committed to developing co-creative methods....
Surface tension of tin-lithium alloys
International Nuclear Information System (INIS)
Temperature and concentration dependences of surface tension of tin-lithium alloys in the range of temperatures 250-410 deg C and concentrations 6.3-15.0 at. % Li were measured by the big drop method. It was ascertained that lithium is a surfactant component of Sn-Li system. Positive sign of surface tension temperature coefficients suggests prevailing lithium desorption from the liquid alloy surface with temperature increase. Calculated value of maximum lithium adsorption in its alloys with tin, containing about 4 at. % Li, makes up 8.5 x 10-6 mol/m2
Surface tension of micellar block copolymer films
International Nuclear Information System (INIS)
Surface tensions of micellar block copolymers of poly(styrene-b-dimethylsiloxane) (PS-b-PDMS) films are obtained by X-ray diffuse scattering. PS-b-PDMS films on Si substrates with the thicknesses from 36 to 588 nm were investigated at temperatures of 30 - 215 .deg. C. The surface tension reflects the concentration of PDMS micelles which are preferably located at the surface. The molar fraction of PDMS micelles near the surface is estimated by using angle-resolved X-ray photoelectron spectroscopy.
A progressive reduce tension method to fabricate Bradbury-Nielsen gates with uniform tension
Kai, Ni; Zhou, Yu
2015-01-01
Bradbury-Nielsen gates (BNG) which consist of two interleaved and electrically isolated sets of wires can be used to modulate the beams of charged particles, particularly ion beams in mass spectrometry and ion mobility spectrometry. The wires of BNG with uniform tension is critical to make sure the BNG work reliable and robust. In our previous work, we have analyzed the problem of wires tension non-uniform that exists in the traditional sequentially winding methods when the metal wire's elastic modulus is much larger than insulations substrate's and developed a template-based transfer method to solve this problem. In this study, we proposed a progressive reduce tension method which does not need template to fabricate BNG with uniform tension. First input the initial parameters to calculate the final progressive reduce tension sequence (FA(i)) through program; then sequentially adjust the weight set according to FA(i) to construct a BNG with uniform tension wires through a home-built device. Wires tension non-...
Forward Kinematics Analysis and Tension Distribution of a Cable-Driven Sinking Winches Mechanism
Shao, Xingguo; Chen, Peter C Y; Zhu, Zhencai; Zi, Bin
2010-01-01
This paper concerns the forward kinematics and tension distribution of sinking winches mechanism, which is a type of four-cable-driven partly constrained parallel robot. Conventional studies on forward kinematics of cable-driven parallel robot assumed that all cables are taut. Actually, given the lengths of four cables, some cables may be slack when the platform is in static equilibrium. Therefore, in this paper, the tension state (tautness or slackness) of cables is considered in the forward kinematics model. We propose Traversal-Solving-Algorithm, which can indicate the tension state of cables, and further determine the pose of the platform, if the lengths of four cables are given. The effectiveness of the algorithm is verified by four examples. The results of this paper can be used to control sinking winches mechanism to achieve the level and stable motion of the platform, and to make the tension distribution of cables as uniform as possible.
Dynamic Simulation and Tension Compensation Research on Subsea Umbilical Cable Laying System
Institute of Scientific and Technical Information of China (English)
Guojun Bi; Shaohua Zhu; Jun Liu; Xiaoming Fang; Liquan Wang
2013-01-01
For studying the dynamic performance of subsea umbilical cable laying system and achieving the goal of cable tension and laying speed control, the rigid finite element method is used to discrete and transform the system into a rigid-flexible coupling multi-body system which consists of rigid elements and spring-damping elements. The mathematical model of subsea umbilical cable laying system kinematic chain is presented with the second order Lagrange equation in the joint coordinate system, and dynamic modeling and simulation is performed with ADAMS. The dynamic analysis is conducted assuming the following three statuses:ideal laying, practical laying under wave disturbance, and practical laying with tension compensation. Results show that motion disturbances of the laying budge under sea waves, especially with heaving and pitching, will cause relatively serious fluctuations in cable tension and laying speed. Tension compensation, i.e., active back tension torque control can restrict continuous tension increasing or decreasing effectively and rapidly, thus avoiding cable breach or buckling.
Dynamic Surface Tensions of Fluorous Surfactant Solutions
Institute of Scientific and Technical Information of China (English)
高艳安; 侯万国; 王仲妮; 李干佐; 韩布兴; 张高勇; 吕锋锋
2005-01-01
Dynamic surface properties of aqueous solutions of cationic fluorous surfactant CF3CF2CF20(CF(CF3)CF2O)2CF(CF3)CONH(CHE)3N+(C2H5)2CH3I- (abbrev. FC-4 ) were reported. The critical micelle concentration (cmc)(3.6×10-5 mol/L) and equilibdum surface tensions γeq were measured by Krtlss K12 tension apparatus. Dynamic surface tension γ(t) was measured in the range of 15 ms to 200 s using the MBP tensiometer. The surface excess Γ,as a function of concentration, was obtained from equilibrium tensiometry using the Gibbs equation. Data from these experiments were combined to analyze the γ（t) decays according to the asymptotic Ward and Tordai equation.The results show that at the initial adsorption stage, the dynamic surface tension data were all consistent with this diffusion-controlled mechanism, and at the end of the adsorption process, there were some evidences for an adsorption barrier, suggesting a mixed diffusion-controlled adsorption mechanism. Using measured quantities, the barrier strength was estimated as between 25 and 35 kJ/mol at 25℃. The surface pressure plays an important role in contributing to the barrier.
Transcutaneous oxygen tension in imminent foot gangrene
DEFF Research Database (Denmark)
Tønnesen, K H
1978-01-01
Transcutaneous oxygen tension at 44 degree C and maximal isotope clearance (90m Tc-pretechnetate + histramine) just proximal to the 1st toe and systolic toe blood pressure (strain gauge) were studied on a tilt table in patients with various degrees of obstructive arteriosclerotic disease. In legs...
Tension Tests On Bored Piles In Sand
DEFF Research Database (Denmark)
Krabbenhøft, Sven; Clausen, Johan; Damkilde, Lars
2006-01-01
The lengths of the bored piles varied from 2 m to 6 m and all were of a diameter of 140 mm. The piles were tested to failure in tension and the load-displacement relations were recorded. The investigation has shown pronounced differences between the load bearing capacities obtained by different d...
Normal tension glaucoma and Alzheimer disease
DEFF Research Database (Denmark)
Bach-Holm, Daniella; Kessing, Svend Vedel; Mogensen, Ulla;
2012-01-01
PURPOSE: To investigate whether normal tension glaucoma (NTG) is associated with increased risk of developing dementia/Alzheimer disease (AD). METHODS: A total of 69 patients with NTG were identified in the case note files in the Glaucoma Clinic, University Hospital of Copenhagen (Rigshospitalet...
Surface tension of undercooled liquid cobalt
International Nuclear Information System (INIS)
This paper provides the results on experimentally measured and numerically predicted surface tensions of undercooled liquid cobalt. The experiments were performed by using the oscillation drop technique combined with electromagnetic levitation. The simulations are carried out with the Monte Carlo (MC) method, where the surface tension is predicted through calculations of the work of cohesion, and the interatomic interaction is described with an embedded-atom method. The maximum undercooling of the liquid cobalt is reached at 231 K (0.13Tm) in the experiment and 268 K (0.17Tm) in the simulation. The surface tension and its relationship with temperature obtained in the experiment and simulation are σexp=1.93-0.000 33 (T-Tm) N m-1 and σcal=2.26-0.000 32 (T-Tm) N m-1 respectively. The temperature dependence of the surface tension calculated from the MC simulation is in reasonable agreement with that measured in the experiment. (author)
Measuring the surface tension of soap bubbles
Sorensen, Carl D.
1992-01-01
The objectives are for students to gain an understanding of surface tension, to see that pressure inside a small bubble is larger than that inside a large bubble. These concepts can be used to explain the behavior of liquid foams as well as precipitate coarsening and grain growth. Equipment, supplies, and procedures are explained.
Spreading of oil films on water in the surface tension regime
Energy Technology Data Exchange (ETDEWEB)
Camp, D.W.
1985-01-01
Surface tension forces will cause an oil to spread over water if the tension of the oil film (the summed surface and interfacial tensions for bulk oil films, or the equilibrium spreading tension for monomolecular films) is less than the surface tension of water. For oil films spreading in a 40 cm long channel, measurements are made of leading edge position and lateral profiles of film thickness, velocity, and tension as a function of time. Measurements of the tension profiles, important for evaluating proposed theories, is made possible by the development of a new technique based on the Wilhelmy method. The oils studied were silicones, fatty acids and alcohols, and mixtures of surfactants in otherwise nonspreading oils. The single-component oils show an acceleration zone connecting a slow-moving inner region with a fast-moving leading monolayer. The dependence of film tension on film thickness for spreading single-component oils often differs from that at equilibrium. The mixtures show a bulk oil film configuration which extends to the leading edge and have velocity profiles which increase smoothly. The theoretical framework, similarity transformation, and asymptotic solutions of Foda and Cox for single-component oils were shown to be valid. An analysis of spreading surfactant-oil mixtures is developed which allows them to be treated under this framework. An easily-used semi-empirical model is proposed which allows them to be treated under this framework. An easily-used semi-empirical model is proposed which allows accurate prediction of detailed spreading behavior for any spreading oil.
The interfacial surface tension of a quark-gluon plasma ﬁreball in a hadronic medium
Indian Academy of Sciences (India)
R Ramanathan; K K Gupta; Agam K Jha; S S Singh
2007-05-01
We calculate the interfacial surface tension of a QGP-ﬁreball in a hadronic medium in the Ramanathan et al statistical model. The constancy of the ratio of the surface tension with the cube of the critical transition temperature is in overall accordance with lattice QCD ﬁndings. It is in complete agreement with a recent MIT bag model calculation of surface tension. The velocity of sound in the QGP droplet is predicted to be in the range (0.27 ± 0.02) times the velocity of light in vacuum and this value is independent of both the value of the transition temperature and the model parameters.
Campinho, Pedro; Behrndt, Martin; Ranft, Jonas; Risler, Thomas; Minc, Nicolas; Heisenberg, Carl-Philipp
2015-01-01
Epithelial spreading is a common and fundamental aspect of various developmental and disease-related processes such as epithelial closure and wound healing. A key challenge for epithelial tissues undergoing spreading is to increase their surface area without disrupting epithelial integrity. Here we show that orienting cell divisions by tension constitutes an efficient mechanism by which the enveloping cell layer (EVL) releases anisotropic tension while undergoing spreading during zebrafish ep...
Akoglu, Haldun; Coban, Erkan; Guneysel, Ozlem
2012-01-01
Tension pneumothorax complicating a pneumoperitoneum is a rare but known entity. However, all previously published articles report an air leak through defects in the diaphragm connecting the pneumoperitoneum and the pneumothorax. Here, the case of a 36-year-old man in whom the pneumoperitoneum acted like a tension pneumothorax because of a congenital eventration of the left diaphragm without penetration is presented. Emergency needle decompression of the abdomen was performed. A gastric ulcer...
Strain analysis of nonlocal viscoelastic Kelvin bar in tension
Institute of Scientific and Technical Information of China (English)
ZHAO Xue-chuan; LEI Yong-jun; ZHOU Jian-ping
2008-01-01
Based on viscoelastic Kelvin model and nonlocal relationship of strain and stress, a nonlocal constitutive relationship of viscoelasticity is obtained and the strain response of a bar in tension is studied. By transforming governing equation of the strain analysis into Volterra integration form and by choosing a symmetric exponential form of kernel function and adapting Neumann series, the closed-form solution of strain field of the bar is obtained. The creep process of the bar is presented. When time approaches infinite, the strain of bar is equal to the one of nonlocal elasticity.
Theoretical study of line and boundary tension in adsorbed colloid-polymer mixtures
Koning, Jesper; Vandecan, Yves; Indekeu, Joseph
2014-07-01
An extended theoretical study of interface potentials in adsorbed colloid-polymer mixtures is performed. To describe the colloid-polymer mixture near a hard wall, a simple Cahn-Nakanishi-Fisher free-energy functional is used. The bulk phase behaviour and the substrate-adsorbate interaction are modelled by the free-volume theory for ideal polymers with polymer-to-colloid size ratios q = 0.6 and q = 1. The interface potentials are constructed with help from a Fisher-Jin crossing constraint. By manipulating the crossing density, a complete interface potential can be obtained from natural, single-crossing, profiles. The line tension in the partial wetting regime and the boundary tension along prewetting are computed from the interface potentials. The line tensions are of either sign, and descending with increasing contact angle. The line tension takes a positive value of 10-14-10-12 N near a first-order wetting transition, passes through zero and decreases to minus 10-14-10-12 N away from the first-order transition. The calculations of the boundary tension along prewetting yield values increasing from zero at the prewetting critical point up to the value of the line tension at first-order wetting.
Surface and interfacial tension measurement, theory, and applications
Hartland, Stanley
2004-01-01
This edited volume offers complete coverage of the latest theoretical, experimental, and computer-based data as summarized by leading international researchers. It promotes full understanding of the physical phenomena and mechanisms at work in surface and interfacial tensions and gradients, their direct impact on interface shape and movement, and their significance to numerous applications. Assessing methods for the accurate measurement of surface tension, interfacial tension, and contact angles, Surface and Interfacial Tension presents modern simulations of complex interfacial motions, such a
STRENGTH SHRINKAGE AND CREEP OF CONCRETE IN TENSION AND COMPRESSION
S A Kristiawan
2006-01-01
Strength, shrinkage and creep of concrete in tension and compression have been determined and the relationship between those properties was studied. Direct tensile tests were applied to measure those properties in tension. The relationship of creep in tension and compression was determined based on the measurement of creep at similar stress and similar stress/strength ratio. It is found that concrete deforms more in tension than in compression. Except for concrete with a higher water/cement r...
Razbin, Mohammadhosein; Zippelius, Annette
2016-01-01
We analyze the stretching elasticity of a wormlike chain with a tension discontinuity resulting from a Hookean spring connecting its backbone to a fixed point. The elasticity of isolated semiflexible filaments has been the subject in a significant body of literature, primarily because of its relevance to the mechanics of biological matter. In real systems, however, these filaments are usually part of supramolecular structures involving cross-linkers or molecular motors which cause tension discontinuities. Our model is intended as a minimal structural element incorporating such a discontinuity. We obtain analytical results in the weakly bending limit of the filament, concerning its force-extension relation and the response of the two parts in which the filament is divided by the spring. For a small tension discontinuity, the linear response of the filament extension to this discontinuity strongly depends on the external tension. For large external tension $f$, the spring force contributes a subdominant correct...
Separation anxiety: Stress, tension and cytokinesis
International Nuclear Information System (INIS)
Cytokinesis, the physical separation of a mother cell into two daughter cells, progresses through a series of well-defined changes in morphology. These changes involve distinct biochemical and mechanical processes. Here, we review the mechanical features of cells during cytokinesis, discussing both the material properties as well as sources of stresses, both active and passive, which lead to the observed changes in morphology. We also describe a mechanosensory feedback control system that regulates protein localization and shape progression during cytokinesis. -- Highlights: ► Cytokinesis progresses through three distinct mechanical phases. ► Cortical tension initially resists deformation of mother cell. ► Late in cytokinesis, cortical tension provides stress, enabling furrow ingression. ► A mechanosensory feedback control system regulates cytokinesis.
Separation anxiety: Stress, tension and cytokinesis
Energy Technology Data Exchange (ETDEWEB)
Mohan, Krithika [Department of Electrical and Computer Engineering, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218 (United States); Iglesias, Pablo A., E-mail: pi@jhu.edu [Department of Electrical and Computer Engineering, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218 (United States); Robinson, Douglas N., E-mail: dnr@jhmi.edu [Department of Cell Biology, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205 (United States)
2012-07-15
Cytokinesis, the physical separation of a mother cell into two daughter cells, progresses through a series of well-defined changes in morphology. These changes involve distinct biochemical and mechanical processes. Here, we review the mechanical features of cells during cytokinesis, discussing both the material properties as well as sources of stresses, both active and passive, which lead to the observed changes in morphology. We also describe a mechanosensory feedback control system that regulates protein localization and shape progression during cytokinesis. -- Highlights: Black-Right-Pointing-Pointer Cytokinesis progresses through three distinct mechanical phases. Black-Right-Pointing-Pointer Cortical tension initially resists deformation of mother cell. Black-Right-Pointing-Pointer Late in cytokinesis, cortical tension provides stress, enabling furrow ingression. Black-Right-Pointing-Pointer A mechanosensory feedback control system regulates cytokinesis.
Fatigue in tension perpendicular to the grain
DEFF Research Database (Denmark)
Clorius, Christian Odin; Pedersen, Martin Bo Uhre; Hoffmeyer, Preben;
1999-01-01
Traditinally fatigue resistance is quantified as number of cycles to failure at a given stress level. A previous study by the authors showed that fatigue in compression parallel to the grain is governed partly by duration of load and partly by an effect of loading, i.e. a combination of a creep...... mechanism and a mechanism connected to damage introduce in the loading sequences. The purpose of the present study is to disentangle the effect of duration of load from the effect of load oscillation in fatigue in tension perpendicular to the grain. Fatigue experiments are made on small specimens and on...... made on dowel type connections that have tension perpendicular to the grain as limiting strength parameter. Is is concluded that no significant influence of duration of load is observed when the fatigue resistance of small specimens at 0.01 Hz and 0.1 Hz are compared. A weak but inconclusive time...
Fatigue In Tension Perpendicular to the Grain
DEFF Research Database (Denmark)
Clorius, Christian Odin; Pedersen, Martin Uhre; Hoffmeyer, Preben;
2004-01-01
Traditionally fatigue resistance is quantified as number of cycles to failure at a given stress level. A previous study by the authors showed that fatigue in compression parallel to the grain is governed partly by duration of load and partly by an effect of loading, i.e. a combination of a creep...... mechanism and a mechanism connected to damage introduced in the loading sequences. The purpose of the present study is to disentangle the effect of duration of load from the effect of load oscillation in fatigue in tension perpendicular to the grain. Fatigue experiments are made on small specimens and on...... made on dowel type connections that have tension perpendicular to the grain as limiting strength parameter. It is concluded that no significant influence of duration of load is observed w hen the fatigue resistance of small specimens at 0.01 Hz and 0.1 Hz are compared. A weak but inconclusive time...
International Nuclear Information System (INIS)
Highlights: • Surface tension of binary mixtures of alcohol/DMSO determined. • Surface mole fraction and surface thermodynamic parameters were calculated. • The surface tension data of binary mixtures were correlated with FLW, LWW and MS models. -- Abstract: Surface tensions of binary mixtures of DMSO (dimethyl sulphoxide) with a series of long chain aliphatic alcohols (1-propanol, 1-butanol, and 1-hexanol) were measured as a function of composition using the ring detachment method in the temperature range between (288.15 and 328.15) K. The surface tension results are used to describe quantitatively the nature, properties, and compositions of surface layers in binary liquid mixtures. The temperature influence on the behaviour of surface tensions and surface properties of binary mixtures has often been used to obtain information about solute structural effects on DMSO. The surface tension of the above mentioned binary systems were correlated with empirical and thermodynamic based models. The average relative error obtained from the comparison of experimental and calculated surface tension values for 15 binary systems with three models is less than 1%. In addition to finding more information about the surface structure of binary mixtures, surface mole fraction was calculated using an extended Langmuir model (EL). The temperature dependence of σ at fixed composition of solutions was used to estimate surface enthalpy, Hs, and surface entropy, Ss. The results provide information on the molecular interactions between the unlike molecules that exist at the surface and the bulk
FINDING TRUTH IN COLOMBIA: EPISTEMOLOGICAL TENSIONS
Directory of Open Access Journals (Sweden)
Laly Catalina Peralta Gonzalez
2011-11-01
Full Text Available The purpose of this paper is to analyze the right of truth in order to elucidate the complexity and tensions involved in defining what ‘truth’ means in transitional contexts. Following this purpose, it explores the experience undergone by the women of San Carlos (Antioquia in the Centro de Acercamiento para la Reparación y la Reconciliación.
Vortices and the SU(3) string tension
Kovács, T. G.; Tomboulis, E. T.
1998-01-01
We present simulation results comparing the SU(3) heavy quark potential extracted from the full Wilson loop expectation to that extracted from the expectation of the Wilson loop fluctuation solely by elements of Z(3). The two potentials are found to coincide. This agreement is stable under multiple smoothings of the configurations which remove short distance fluctuations, and thus reflects long-distance physics. It strongly indicates that the asymptotic string tension arises from thick center...
Critical-path tensioning by specialist supervision
International Nuclear Information System (INIS)
Reactor pressure vessel head retensioning is on the critical path during outages, so when an unexpected outage occurred before planned tensioner system maintenance had been done at Niagara Mohawk Power Corporation's Nine Mile BWR Station I, the tool manufacturer was asked to send a service specialist to oversee the entire detensioning and retensioning sequence. The supervisor sent was able to deal with several minor problems as they occurred, ensuring that the entire procedure went smoothly and within schedule. (author)
Projecting Tension in Virtual Environments through Lighting.
Seif El-Nasr, Magy; Zupko, Joseph; Almeida, Priya
2006-01-01
Interactive synthetic environments are currently used in a wide variety of applications, including video games, exposure therapy, education, and training. Their success in such domains relies on their immersive and engagement qualities. Filmmakers and theatre directors use many techniques to project tension in the hope of affecting audiences’ affective states. These techniques include narrative, sound effects, camera movements, and lighting. This paper focuses on temporal variation of lightin...
Dynamic Transitions of Surface Tension Driven Convection
Dijkstra, Henk,; Sengul, Taylan; Wang, Shouhong
2011-01-01
We study the well-posedness and dynamic transitions of the surface tension driven convection in a three-dimensional (3D) rectangular box with non-deformable upper surface and with free-slip boundary conditions. It is shown that as the Marangoni number crosses the critical threshold, the system always undergoes a dynamic transition. In particular, two different scenarios are studied. In the first scenario, a single mode losing its stability at the critical parameter gives rise to either a Type...
2-rational Cubic Spline Involving Tension Parameters
Indian Academy of Sciences (India)
M Shrivastava; J Joseph
2000-08-01
In the present paper, 1-piecewise rational cubic spline function involving tension parameters is considered which produces a monotonic interpolant to a given monotonic data set. It is observed that under certain conditions the interpolant preserves the convexity property of the data set. The existence and uniqueness of a 2-rational cubic spline interpolant are established. The error analysis of the spline interpolant is also given.
Surface Tension Demonstration Aboard the ISS
2003-01-01
Astronaut Donald R. Pettit, Expedition Six NASA ISS science officer, photographed this view of a surface tension demonstration using water that is held in place by a metal loop. The experiment took place in the Destiny laboratory on the International Space Station (ISS). The Expedition Six crew was delivered to the station via the Space Shuttle Orbiter Endeavor STS-113 mission which was launched on November 23, 2002.
Surface tension confined liquid cryogen cooler
Castles, Stephen H. (Inventor); Schein, Michael E. (Inventor)
1989-01-01
A cryogenic cooler is provided for use in craft such as launch, orbital, and space vehicles subject to substantial vibration, changes in orientation, and weightlessness. The cooler contains a small pore, large free volume, low density material to restrain a cryogen through surface tension effects during launch and zero-g operations and maintains instrumentation within the temperature range of 10 to 140 K. The cooler operation is completely passive, with no inherent vibration or power requirements.
Scaling for Interfacial Tensions near Critical Endpoints
Zinn, Shun-Yong; Fisher, Michael E.
2004-01-01
Parametric scaling representations are obtained and studied for the asymptotic behavior of interfacial tensions in the \\textit{full} neighborhood of a fluid (or Ising-type) critical endpoint, i.e., as a function \\textit{both} of temperature \\textit{and} of density/order parameter \\textit{or} chemical potential/ordering field. Accurate \\textit{nonclassical critical exponents} and reliable estimates for the \\textit{universal amplitude ratios} are included naturally on the basis of the ``extende...
Noncontact surface tension measurement by drop rotation
Rhim, Won-Kyu; Ishikawa, Takehiko
2001-01-01
Validity of the surface tension measurement technique that was proposed by Elleman et al. was experimentally verified. The technique was based on Brown and Scriven's work on the shape evolution of rotating drops. Molten tin and aluminum drops were levitated in high vacuum by the electrostatic levitator and rotated by applying a rotating magnetic field. This technique offers an alternative technique for those liquids where the drop oscillation technique cannot be used. As a demonstration, the ...
Acute Tension Pneumothorax Following Cardiac Herniation after Pneumonectomy
Daniel Steinmann; Eva Rohr; Andreas Kirschbaum
2010-01-01
A tension pneumothorax is one of the main causes of cardiac arrest in the initial postoperative period after thoracic surgery. Tension pneumothorax and cardiac herniation must be taken into account in hemodynamically unstable patients after pneumonectomy. We report an unusual case of successful treatment of acute tension pneumothorax following cardiac herniation and intrathoracic bleeding after pneumonectomy.
Li, Z.; Schwier, A. N.; Sareen, N.; McNeill, V. F.
2011-11-01
The reactive uptake of carbonyl-containing volatile organic compounds (cVOCs) by aqueous atmospheric aerosols is a likely source of particulate organic material. The aqueous-phase secondary organic products of some cVOCs are surface-active. Therefore, cVOC uptake can lead to organic film formation at the gas-aerosol interface and changes in aerosol surface tension. We examined the chemical reactions of two abundant cVOCs, formaldehyde and acetaldehyde, in water and aqueous ammonium sulfate (AS) solutions mimicking tropospheric aerosols. Secondary organic products were identified using Aerosol Chemical Ionization Mass Spectrometry (Aerosol-CIMS), and changes in surface tension were monitored using pendant drop tensiometry. Hemiacetal oligomers and aldol condensation products were identified using Aerosol-CIMS. Acetaldehyde depresses surface tension to 65(±2) dyn cm-1 in pure water (a 10% surface tension reduction from that of pure water) and 62(±1) dyn cm-1 in AS solutions (a 20.6% reduction from that of a 3.1 M AS solution). Surface tension depression by formaldehyde in pure water is negligible; in AS solutions, a 9% reduction in surface tension is observed. Mixtures of these species were also studied in combination with methylglyoxal in order to evaluate the influence of cross-reactions on surface tension depression and product formation in these systems. We find that surface tension depression in the solutions containing mixed cVOCs exceeds that predicted by an additive model based on the single-species isotherms.
Nuclear myosin I regulates cell membrane tension
Venit, Tomáš; Kalendová, Alžběta; Petr, Martin; Dzijak, Rastislav; Pastorek, Lukáš; Rohožková, Jana; Malohlava, Jakub; Hozák, Pavel
2016-01-01
Plasma membrane tension is an important feature that determines the cell shape and influences processes such as cell motility, spreading, endocytosis and exocytosis. Unconventional class 1 myosins are potent regulators of plasma membrane tension because they physically link the plasma membrane with adjacent cytoskeleton. We identified nuclear myosin 1 (NM1) - a putative nuclear isoform of myosin 1c (Myo1c) - as a new player in the field. Although having specific nuclear functions, NM1 localizes predominantly to the plasma membrane. Deletion of NM1 causes more than a 50% increase in the elasticity of the plasma membrane around the actin cytoskeleton as measured by atomic force microscopy. This higher elasticity of NM1 knock-out cells leads to 25% higher resistance to short-term hypotonic environment and rapid cell swelling. In contrast, overexpression of NM1 in wild type cells leads to an additional 30% reduction of their survival. We have shown that NM1 has a direct functional role in the cytoplasm as a dynamic linker between the cell membrane and the underlying cytoskeleton, regulating the degree of effective plasma membrane tension. PMID:27480647
STRAIN-CONTROLLED BIAXIAL TENSION OF NATURAL RUBBER: NEW EXPERIMENTAL DATA
Pancheri, Francesco Q.
2014-03-01
We present a new experimental method and provide data showing the response of 40A natural rubber in uniaxial, pure shear, and biaxial tension. Real-time biaxial strain control allows for independent and automatic variation of the velocity of extension and retraction of each actuator to maintain the preselected deformation rate within the gage area of the specimen. Wealso focus on the Valanis-Landel hypothesis that is used to verify and validate the consistency of the data.Weuse a threeterm Ogden model to derive stress-stretch relations to validate the experimental data. The material model parameters are determined using the primary loading path in uniaxial and equibiaxial tension. Excellent agreement is found when the model is used to predict the response in biaxial tension for different maximum in-plane stretches. The application of the Valanis-Landel hypothesis also results in excellent agreement with the theoretical prediction.
Huang, Hu; Zhao, Hongwei; Shi, Chengli; Hu, Xiaoli; Cui, Tao; Tian, Ye
2013-09-01
In this paper, a tension stress loading unit is designed to provide tension stress for brittle materials by combining the piezo actuator and the flexible hinge. The structure of the tension stress loading unit is analyzed and discussed via the theoretical method and finite element simulations. Effects of holding time, the installed specimen and hysteresis of the piezo actuator on output performances of the tension stress loading unit are studied in detail. An experiment system is established by combing the indentation testing unit and the developed tension stress loading unit to characterize indentation response of single crystal silicon under tension stress. Experiment results indicate that tension stress leads to increasing of indentation displacement for the same inden-tation load of single crystal silicon. This paper provides a new tool for studying indentation response of brittle materials under tension stress.
Energy Technology Data Exchange (ETDEWEB)
Charbonnier, D.
2004-12-15
The physical phenomena observed in turbomachines are generally three-dimensional and unsteady. A recent study revealed that a three-dimensional steady simulation can reproduce the time-averaged unsteady phenomena, since the steady flow field equations integrate deterministic stresses. The objective of this work is thus to develop an unsteady deterministic stresses model. The analogy with turbulence makes it possible to write transport equations for these stresses. The equations are implemented in steady flow solver and e model for the energy deterministic fluxes is also developed and implemented. Finally, this work shows that a three-dimensional steady simulation, by taking into account unsteady effects with transport equations of deterministic stresses, increases the computing time by only approximately 30 %, which remains very interesting compared to an unsteady simulation. (author)
Aerodynamic and Nonlinear Dynamic Acoustic Analysis of Tension Asymmetry in Excised Canine Larynges
Devine, Erin E.; Bulleit, Erin E.; Hoffman, Matthew R.; McCulloch, Timothy M.; Jiang, Jack J.
2012-01-01
Purpose: To model tension asymmetry caused by superior laryngeal nerve paralysis (SLNP) in excised larynges and apply perturbation, nonlinear dynamic, and aerodynamic analyses. Method: SLNP was modeled in 8 excised larynges using sutures and weights to mimic cricothyroid (CT) muscle function. Weights were removed from one side to create tension…
A High Rate Tension Device for Characterizing Brain Tissue
Rashid, Badar; Gilchrist, Michael; 10.1177/1754337112436900
2013-01-01
The mechanical characterization of brain tissue at high loading velocities is vital for understanding and modeling Traumatic Brain Injury (TBI). The most severe form of TBI is diffuse axonal injury (DAI) which involves damage to individual nerve cells (neurons). DAI in animals and humans occurs at strains > 10% and strain rates > 10/s. The mechanical properties of brain tissues at these strains and strain rates are of particular significance, as they can be used in finite element human head models to accurately predict brain injuries under different impact conditions. Existing conventional tensile testing machines can only achieve maximum loading velocities of 500 mm/min, whereas the Kolsky bar apparatus is more suitable for strain rates > 100/s. In this study, a custom-designed high rate tension device is developed and calibrated to estimate the mechanical properties of brain tissue in tension at strain rates < 90/s, while maintaining a uniform velocity. The range of strain can also be extended to 100% de...
Growth factor involvement in tension-induced skeletal muscle growth
Vandenburgh, Herman H.
1993-01-01
Long-term manned space travel will require a better understanding of skeletal muscle atrophy which results from microgravity. Astronaut strength and dexterity must be maintained for normal mission operations and for emergency situations. Although exercise in space slows the rate of muscle loss, it does not prevent it. A biochemical understanding of how gravity/tension/exercise help to maintain muscle size by altering protein synthesis and/or degradation rate should ultimately allow pharmacological intervention to prevent muscle atrophy in microgravity. The overall objective is to examine some of the basic biochemical processes involved in tension-induced muscle growth. With an experimental in vitro system, the role of exogenous and endogenous muscle growth factors in mechanically stimulated muscle growth are examined. Differentiated avian skeletal myofibers can be 'exercised' in tissue culture using a newly developed dynamic mechanical cell stimulator device which simulates different muscle activity patterns. Patterns of mechanical activity which significantly affect muscle growth and metabolic characteristics were found. Both exogenous and endogenous growth factors are essential for tension-induced muscle growth. Exogenous growth factors found in serum, such as insulin, insulin-like growth factors, and steroids, are important regulators of muscle protein turnover rates and mechanically-induced muscle growth. Endogenous growth factors are synthesized and released into the culture medium when muscle cells are mechanically stimulated. At least one family of mechanically induced endogenous factors, the prostaglandins, help to regulate the rates of protein turnover in muscle cells. Endogenously synthesized IGF-1 is another. The interaction of muscle mechanical activity and these growth factors in the regulation of muscle protein turnover rates with our in vitro model system is studied.
Line-tension controlled mechanism for influenza fusion.
Directory of Open Access Journals (Sweden)
Herre Jelger Risselada
Full Text Available Our molecular simulations reveal that wild-type influenza fusion peptides are able to stabilize a highly fusogenic pre-fusion structure, i.e. a peptide bundle formed by four or more trans-membrane arranged fusion peptides. We rationalize that the lipid rim around such bundle has a non-vanishing rim energy (line-tension, which is essential to (i stabilize the initial contact point between the fusing bilayers, i.e. the stalk, and (ii drive its subsequent evolution. Such line-tension controlled fusion event does not proceed along the hypothesized standard stalk-hemifusion pathway. In modeled influenza fusion, single point mutations in the influenza fusion peptide either completely inhibit fusion (mutants G1V and W14A or, intriguingly, specifically arrest fusion at a hemifusion state (mutant G1S. Our simulations demonstrate that, within a line-tension controlled fusion mechanism, these known point mutations either completely inhibit fusion by impairing the peptide's ability to stabilize the required peptide bundle (G1V and W14A or stabilize a persistent bundle that leads to a kinetically trapped hemifusion state (G1S. In addition, our results further suggest that the recently discovered leaky fusion mutant G13A, which is known to facilitate a pronounced leakage of the target membrane prior to lipid mixing, reduces the membrane integrity by forming a 'super' bundle. Our simulations offer a new interpretation for a number of experimentally observed features of the fusion reaction mediated by the prototypical fusion protein, influenza hemagglutinin, and might bring new insights into mechanisms of other viral fusion reactions.
Pumpless Transport of Low Surface Tension Liquids in Surface Tension Confined (STC) Tracks
Megaridis, Constantine; Schutzius, Thomas; Elsharkawy, Mohamed; Tiwari, Manish
2012-11-01
Surfaces with patterned wettability have potential applications in microfluidics, fog capture, pool boiling, etc. With recent fabrication advancements, surfaces with adjacent superhydrophobic and superhydrophilic regions are feasible at a reasonable cost; with properly designed patterns, one can produce microfluidic paths (a.k.a. surface tension confined or STC tracks) where a liquid is confined and transported by surface tension alone. The surface tension of water is relatively high (72 mN/m), as compared with oils (~25 mN/m) and organic solvents (~20 mN/m). This makes the design of STC channels for oils and organic solvents far more difficult. In this study, open STC tracks for pumpless transport of low-surface tension liquids (acetone, ethanol, and hexadecane) on microfluidic chips are fabricated using a large-area, wet-processing technique. Wettable, wax-based, submillimeter-wide tracks are applied by a fountain-pen procedure on superoleophobic, fluoroacrylic carbon nanofiber (CNF) composite coatings. The fabricated anisotropic wetting patterns confine the low-surface tension liquids onto the flow tracks, driving them with meniscus velocities exceeding 3 cm/s. Scaling arguments and Washburn's equation provide estimates of the liquid velocities measured in these tracks, which also act as rails for directional sliding control of mm-sized water droplets. The present facile patterned wettability approach can be extended to deposit micrometer-wide tracks.
Energy Technology Data Exchange (ETDEWEB)
Gauglitz, Phillip A.; Mahoney, Lenna A.; Blanchard, Jeremy; Bamberger, Judith A.
2011-06-10
In support of the K-Basin project, Pacific Northwest National Laboratory (PNNL) was requested to evaluate the appropriate surface tension value to use in models predicting the formation of droplets from spray leaks of K-Basin slurries. The specific issue was whether it was more appropriate to use the surface tension of pure water in model predictions for all plausible spray leaks or to use a lower value. The surface tension of K-Basin slurries is potentially affected not only by particles but by low concentrations of nonionic polyacrylamide flocculant and perhaps by contaminants with surfactant properties, which could decrease the surface tension below that of water. A lower surface tension value typically results in smaller droplets being formed with a larger fraction of droplets in the respirable size range, so using the higher surface tension value of pure water is not conservative and thus needs a strong technical basis.
Curved and diffuse interface effects on the nuclear surface tension
Kolomietz, V. M.; Lukyanov, S. V.; Sanzhur, A. I.
2011-01-01
We redefine the surface tension coefficient for a nuclear Fermi-liquid drop with a finite diffuse layer. Following Gibbs-Tolman concept, we introduce the equimolar radius R_e of sharp surface droplet at which the surface tension is applied and the radius of tension surface R_s which provides the minimum of the surface tension coefficient \\sigma. This procedure allows us to derive both the surface tension and the corresponding curvature correction (Tolman length) correctly for the curved and d...
Surface tension measurement from the indentation of clamped thin films.
Xu, Xuejuan; Jagota, Anand; Paretkar, Dadhichi; Hui, Chung-Yuen
2016-06-21
We developed an indentation technique to measure the surface tension of relatively stiff solids. In the proposed method, a suspended thin solid film is indented by a rigid sphere and its deflection is measured by optical interferometry. The film deflection is jointly resisted by surface tension, elasticity and residual stress. Using a version of nonlinear von Karman plate theory that includes surface tension, we are able to separate the contribution of elasticity to the total tension in the film. Surface tension is determined by extrapolating the sum of surface tension and residual stress to zero film thickness. We measured the surface tension of polydimethylsiloxane (PDMS) using this technique and obtained a value of 19.5 ± 3.6 mN m(-1), consistent with the surface energy of PDMS reported in the literature. PMID:27189735
Black strings from minimal geometric deformation in a variable tension brane-world
International Nuclear Information System (INIS)
We study brane-world models with variable brane tension and compute corrections to the horizon of a black string along the extra dimension. The four-dimensional geometry of the black string on the brane is obtained by means of the minimal geometric deformation approach, and the bulk corrections are then encoded in additional terms involving the covariant derivatives of the variable brane tension. Our investigation shows that the variable brane tension strongly affects the shape and evolution of the black string horizon along the extra dimension, at least in a near-brane expansion. In particular, we apply our general analysis to a model motivated by the Eötvös branes, where the variable brane tension is related to the Friedmann–Robertson–Walker brane-world cosmology. We show that for some stages in the evolution of the universe, the black string warped horizon collapses to a point and the black string has correspondingly finite extent along the extra dimension. Furthermore, we show that in the minimal geometric deformation of a black hole on the variable tension brane, the black string has a throat along the extra dimension, whose area tends to zero as time goes to infinity. (paper)
Black strings from minimal geometric deformation in a variable tension brane-world
Casadio, R.; Ovalle, J.; da Rocha, Roldão
2014-02-01
We study brane-world models with variable brane tension and compute corrections to the horizon of a black string along the extra dimension. The four-dimensional geometry of the black string on the brane is obtained by means of the minimal geometric deformation approach, and the bulk corrections are then encoded in additional terms involving the covariant derivatives of the variable brane tension. Our investigation shows that the variable brane tension strongly affects the shape and evolution of the black string horizon along the extra dimension, at least in a near-brane expansion. In particular, we apply our general analysis to a model motivated by the Eötvös branes, where the variable brane tension is related to the Friedmann-Robertson-Walker brane-world cosmology. We show that for some stages in the evolution of the universe, the black string warped horizon collapses to a point and the black string has correspondingly finite extent along the extra dimension. Furthermore, we show that in the minimal geometric deformation of a black hole on the variable tension brane, the black string has a throat along the extra dimension, whose area tends to zero as time goes to infinity.
Tension between SNeIa and BAO: current status and future forecasts
Energy Technology Data Exchange (ETDEWEB)
Escamilla-Rivera, Celia [Astrophysics, University of Oxford, DWD, Kebble Road, Oxford, OX1 3RH (United Kingdom); Lazkoz, Ruth; Salzano, Vincenzo; Sendra, Irene, E-mail: celia_escamilla@ehu.es, E-mail: ruth.lazkoz@ehu.es, E-mail: vincenzo.salzano@ehu.es, E-mail: irene.sendra@ehu.es [Fisika Teorikoaren eta Zientziaren Historia Saila, Zientzia eta Teknologia Fakultatea, Euskal Herriko Unibertsitatea, 644 Posta Kutxatila, 48080 Bilbao (Spain)
2011-09-01
Using real and synthetic Type Ia SNe (SNeIa) and baryon acoustic oscillations (BAO) data representing current observations forecasts, this paper investigates the tension between those probes in the dark energy equation of state (EoS) reconstruction considering the well known CPL model and Wang's low correlation reformulation. In particular, here we present simulations of BAO data from both the the radial and transverse directions. We also explore the influence of priors on Ω{sub m} and Ω{sub b} on the tension issue, by considering 1σ deviations in either one or both of them. Our results indicate that for some priors there is no tension between a single dataset (either SNeIa or BAO) and their combination (SNeIa+BAO). Our criterion to discern the existence of tension (σ-distance) is also useful to establish which is the dataset with most constraining power; in this respect SNeIa and BAO data switch roles when current and future data are considered, as forecasts predict and spectacular quality improvement on BAO data. We also find that the results on the tension are blind to the way the CPL model is addressed: there is a perfect match between the original formulation and that by the correlation optimized proposed in Wang (2008), but the errors on the parameters are much narrower in all cases of our exhaustive exploration, thus serving the purpose of stressing the convenience of this reparametrization.
Surface tension in the cold and dense chiral transition and astrophysical applications
Palhares, L F
2011-01-01
The surface tension of cold and dense QCD phase transitions has appeared recently as a key ingredient in different astrophysical scenarios, ranging from core-colapse supernovae explosions to compact star structure. If the surface tension is low enough, observable consequences are possible. Its value is however not known from first-principle methods in QCD, calling for effective approaches. Working within the framework of homogeneous nucleation by Langer, we discuss the steps that are needed to obtain the nucleation parameters from a given effective potential. As a model for deriving the effective potential for the chiral transition, we adopt the linear sigma model with constituent quarks at very low temperatures, which provides an effective description for the thermodynamics of the strong interaction in cold and dense matter, and predict a surface tension of Sigma ~ 5--15 MeV/fm^2, well below previous estimates. Including temperature effects and vacuum logarithmic corrections, we find a clear competition betw...
Energy Technology Data Exchange (ETDEWEB)
Lehle, H [Max-Planck-Institut fuer Metallforschung, Heisenbergstrasse 3, D-70569 Stuttgart (Germany); Oettel, M [Johannes-Gutenberg-Universitaet Mainz, Institut fuer Physik (WA 331), Staudinger Weg 7, D-55128 Mainz (Germany)
2008-10-08
We analyze the effective potential for nanoparticles trapped at a fluid interface within a simple model which incorporates surface and line tensions as well as a thermal average over interface fluctuations (capillary waves). For a single colloid, a reduced steepness of the potential well hindering movements out of the interface plane compared to rigid interface models is observed, and an instability of the capillary wave partition sum in the case of negative line tensions is pointed out. For two colloids, averaging over the capillary waves leads to an effective Casimir-type interaction which is long ranged, power-like in the inverse distance, but whose power sensitively depends on possible restrictions of the colloid degrees of freedom. A nonzero line tension leads to changes in the magnitude but not in the functional form of the effective potential asymptotics.
Lehle, H.; Oettel, M.
2008-10-01
We analyze the effective potential for nanoparticles trapped at a fluid interface within a simple model which incorporates surface and line tensions as well as a thermal average over interface fluctuations (capillary waves). For a single colloid, a reduced steepness of the potential well hindering movements out of the interface plane compared to rigid interface models is observed, and an instability of the capillary wave partition sum in the case of negative line tensions is pointed out. For two colloids, averaging over the capillary waves leads to an effective Casimir-type interaction which is long ranged, power-like in the inverse distance, but whose power sensitively depends on possible restrictions of the colloid degrees of freedom. A nonzero line tension leads to changes in the magnitude but not in the functional form of the effective potential asymptotics.
Correlations for calculating the surface tension and enthalpies of sublimation of alkali halides
International Nuclear Information System (INIS)
The capability of a new model on predicting the surface tension of molten alkali halides is described. A relationship, with a simple form of calculation, exists between the surface tension (γ) at the melting point, molar volume (V), inter-nuclear distance (D) and the enthalpy of sublimation (Es). The basic idea results from the assumption that all the parameters are constants that are usually easy to acquire. Moreover, two previous models (Furth and Schytil equations) were also checked and applied for calculating surface tension of molten salts. The three formulas have been examined for 20 salts and showed remarkable agreement between calculated and experimental data with a difference of less than 10% for most of the salts studied. The heats of sublimation of alkali halides were, theoretically, calculated and compared to literature values.
Role of nuclear surface tension coefficient in alpha decay process of the superheavy nuclei
International Nuclear Information System (INIS)
The present paper role of nuclear surface tension in alpha decay resulted from the need to improve the Isospin Cluster Model, where the excess of neutron and proton numbers are taken in account effectively of a nucleus in decay calculations. The appropriate value of nuclear surface tension coefficient in proximity potential which plays an important role to estimate the nuclear attraction between two nuclear surfaces is reviewed, in this model. The nuclear proximity force is proportional to the surface tension and its contribution necessarily should be appropriate. The synthesis of super heavy elements, formed by either of cold fusion or hot fusion process, is primarily decay through alpha-particle emission. The successive emission of alpha particles from a superheavy element ends at spontaneous fission
International Nuclear Information System (INIS)
A rigorous thermodynamic formulation of the geometric model for heterogeneous nucleation including line tension effect is missing till date due to the associated mathematical hurdles. In this work, we develop a novel thermodynamic formulation based on Classical Nucleation Theory (CNT), which is supposed to illustrate a systematic and a more plausible analysis for the heterogeneous nucleation on a planar surface including the line tension effect. The appreciable range of the critical microscopic contact angle (θc), obtained from the generalized Young’s equation and the stability analysis, is θ∞ < θc < θ′ for positive line tension and is θM < θc < θ∞ for negative line tension. θ∞ is the macroscopic contact angle, θ′ is the contact angle for which the Helmholtz free energy has the minimum value for the positive line tension, and θM is the local minima of the nondimensional line tension effect for the negative line tension. The shape factor f, which is basically the dimensionless critical free energy barrier, becomes higher for lower values of θ∞ and higher values of θc for positive line tension. The combined effect due to the presence of the triple line and the interfacial areas (fL + fS) in shape factor is always within (0, 3.2), resulting f in the range of (0, 1.7) for positive line tension. A formerly presumed appreciable range for θc(0 < θc < θ∞) is found not to be true when the effect of negative line tension is considered for CNT. Estimation based on the property values of some real fluids confirms the relevance of the present analysis
Surface tension of HFC refrigerant mixtures
Energy Technology Data Exchange (ETDEWEB)
Okada, M. [Tsukuba Coll. of Technology (Japan). Dept. of Mechanical Engineering; Shibata, T.; Sato, Y.; Higashi, Y. [Iwaki Meisei Univ. (Japan)
1999-01-01
The surface tension of refrigerant mixtures, i.e., R-410A (50 mass% R-32/50 mass% R-125), R-410B (45 mass% R-32/55 mass% R-125), R-407C (23 mass% R-32/25 mass% R-125/52 mass% R-134a), R-404A (44 mass% R-125/52 mass% R-143a/4 mass% R-134a), and R-507 (50 mass% R-125/50 mass% R-143a), has been measured and correlated in the present study. Although the first three mixtures are very important as promising replacements for R-22 in air-conditioners and heat-pumps and the last two are promising replacements for R-502, surface tension data for these mixtures were not previously available. The measurements were conducted under conditions of coexistence of the sample liquid and its saturated vapor in equilibrium. The differential capillary rise method (DCRM) was used, with two glass capillaries with inner radii of 0.3034 {+-} 0.0002 and 0.5717 {+-} 0.0002 mm. The temperature range covered was from 273 to 323 K, and the uncertainty of measurements for surface tensions and temperatures is estimated to be at most {+-} 0.2 mN {center_dot} m{sup {minus}1} and {+-} 20 mK, respectively. A mixing rule was selected for representing the temperature dependence of the resultant data. These data were successfully represented by a mixing rule using mass fraction based on the van der Waals correlation.
International Nuclear Information System (INIS)
Tension levelling is employed in strip processing lines to minimise residual stresses resp. to improve the strip flatness by inducing small elasto-plastic deformations. To improve the design of such machines, precise calculation models are essential to reliably predict tension losses due to plastic dissipation, power requirements of the driven bridle rolls (located upstream and downstream), reaction forces on levelling rolls as well as strains and stresses in the strip. FEM (Finite Element Method) simulations of the tension levelling process (based on Updated Lagrangian concepts) yield high computational costs due to the necessity of very fine meshes as well as due to the severely non-linear characteristics of contact, material and geometry. In an evaluation process of hierarchical models (models with different modeling levels), the reliability of both 3D and 2D modelling concepts (based on continuum and structural elements) was proved by extensive analyses as well as consistency checks against measurement data from an industrial tension leveller. To exploit the potential of computational cost savings, a customised modelling approach based on the principle of virtual work has been elaborated, which yields a drastic reduction of degrees of freedom compared to simulations by utilising commercial FEM-packages.
Cuerpo y subjetividad: materiales y tensiones
Cachorro, Gabriel
2007-01-01
En este artículo se efectúa un abordaje del tema cuerpo y subjetividad a través de un ejercicio exploratorio de sus materiales y tensiones. Las preguntas posibles de formular son: ¿Qué discusiones tenemos por debajo de la subjetividad corporal?, ¿cuáles son las raíces históricas de este tema?, ¿qué problemáticas lo atraviesan? La enunciación de estos interrogantes nos ayuda a establecer la posición de investigador y a explicitar los argumentos teóricos. Se desprende de esta propuesta un mo...
OXYGEN TENSION REGULATES PREOSTEOCYTE MATURATION AND MINERALIZATION
Zahm, Adam; Bucaro, Michael; Srinivas, Vickram; Shapiro, Irving M.; Adams, Christopher S.
2008-01-01
The goal of this investigation was to test the hypothesis that low pO2 regulates bone cell mineralization. MLO-A5 and MLO-Y4 cells were cultured in monolayer and alginate scaffolds in hypoxia (2% O2) or normoxia (20% O2). Reduction of the O2 tension from 20% to 2% resulted in reduced mineralization and decreased alkaline phosphatase activity of MLO-A5 cells in both monolayer and three-dimensional cultures. Similar changes in osteogenic activity were seen when these preosteocyte-like cells wer...
Surface Tension Driven Convection Experiment Completed
Jacobson, Thomas P.; Sedlak, Deborah A.
1997-01-01
The Surface Tension Driven Convection Experiment (STDCE) was designed to study basic fluid mechanics and heat transfer on thermocapillary flows generated by temperature variations along the free surfaces of liquids in microgravity. STDCE first flew on the USML-1 mission in July 1992 and was rebuilt for the USML-2 mission that was launched in October 1995. This was a collaborative project with principal investigators from Case Western Reserve University (CWRU), Professors Simon Ostrach and Yasuhiro Kamotani, along with a team from the NASA Lewis Research Center composed of civil servants and contractors from Aerospace Design & Fabrication, Inc. (ADF), Analex, and NYMA, Inc.
Insights into high temperature tensional fracturing in silicic magma
Lamb, Oliver; Lavallée, Yan; De Angelis, Silvio; Hornby, Adrian
2015-04-01
During dome-forming eruptions, the rapid transition from effusive to explosive activity is a direct consequence of strain localisation in magma. A deformation mechanism map of magma subjected to strain localisation will help develop accurate numerical models, which, coupled to an understanding of the mechanics driving the monitored geophysical signals precursor to failure, will enhance eruption forecasts. Here we present our work where seismic data is combined with experimental work to give insights into high temperature tensional fracturing in magma. The seismic data is derived from multiple recent dome-forming eruptions including Unzen (Japan), Volcán de Colima (Mexico) and Mt. St. Helens (USA). For the analysis we implemented various methods to study temporal variations in seismicity, such as: automatic event detection, statistical analysis of time-series, waveform correlation, and singular value decomposition. Preliminary results have highlighted various processes during dome formation such as: sub-weekly cycles, clusters during spine extrusion, and variations in precursors to dome extrusion. In our experiments, samples from the above volcanoes were placed under tensional conditions at high temperatures and acoustic emissions were recorded. The data is analysed and compared to the natural seismic data so that constraints may be placed on the conditions of the natural seismogenic sources. Using a combination of field and experimental data promises a greater understanding of the processes affecting the rise of magma during an eruption. This will help with the challenge of forecasting and hazard mitigation during dome-forming eruptions worldwide.
Energy Technology Data Exchange (ETDEWEB)
Rizoug, N.
2006-02-15
This document presents a study of the electrical and energetic behaviour of super-capacitors under conditions similar to industrial applications' ones. For that, a test bench has been developed in our laboratory in order to characterize a super-capacitors' module (112 F-48 V) composed of 24 elements of 2700 F/2,3 V. The goal of this work was firstly to evaluate the precision of the existing model about the electrical and energetic characteristics and secondly to improve this precision. For that, two models representing the energetic and electrical behaviour of these components are developed. These models are obtained by a simple identification of the data measured during the cycling tests using frequency and temporal approaches. Numerous electrical and thermal data are obtained during the cycling test of the module. These data are used to observe the evolution of the equivalent capacity and resistance of several super-capacitor elements of the tested module according to the temperature. For the first 200.000 cycles, the ageing process of super-capacitors and the variation of the module parameters during all the life of this tested module are presented. This study allowed to obtain information about the degradation (R, rs and C) according to the number of cycles carried out. Finally, the tests of cycling done without balancing device (except the impedance of the measurement system) allow to observe a natural dispersion of the voltage according to the position of the components in the module. (author)
Tanaka, Ryo; Nomoto, Tomonori; Toyota, Taro; Kitahata, Hiroyuki; Fujinami, Masanori
2013-11-01
Time-resolved measurements of the interfacial tension of propagating chemical waves of the Belousov-Zhabotinsky reaction based on the iron complex catalysts were carried out without stirring by monitoring the frequency of capillary waves with the quasi-elastic laser scattering method. A delayed response of the interfacial tension with respect to absorption was found with the delay being ligand-dependent when the reaction was conducted at a liquid/liquid interface. This behavior is attributed to differences in adsorption activity of the hydrophobic metal catalyst. The delay time and the increase in interfacial tension were also reproduced by a model considering the rate constants of equilibrium adsorption. PMID:24107133
Surface Tension, Pressure Difference and Laplace Formula for Membranes
International Nuclear Information System (INIS)
The surface tension γ and the pressure difference Δp for spherical membranes are calculated using Monte Carlo simulation technique. We study the so-called tethered and uid surface discrete models that are defined on the fixed-connectivity (tethered) and dynamically triangulated (uid) lattices respectively. Hamiltonians of the models include a self-avoiding potential, which makes the enclosed volume well defined. We find that there is reasonable accuracy in the technique for the calculation of γ using the real area A if the bending rigidity κ or A/N is sufficiently large. We also find that γ becomes constant in the limit of A/N → ∞ both in the tethered and uid surfaces. The property limA/N→∞ γ = const corresponds to certain experimental results in cell biology
Tension-dependent Free Energies of Nucleosome Unwrapping
Lequieu, Joshua; Schwartz, David C; de Pablo, Juan J
2016-01-01
Nucleosomes form the basic unit of compaction within eukaryotic genomes and their locations represent an important, yet poorly understood, mechanism of genetic regulation. Quantifying the strength of interactions within the nucleosome is a central problem in biophysics and is critical to understanding how nucleosome positions influence gene expression. By comparing to single-molecule experiments, we demonstrate that a coarse-grained molecular model of the nucleosome can reproduce key aspects of nucleosome unwrapping. Using detailed simulations of DNA and histone proteins, we calculate the tension-dependent free energy surface corresponding to the unwrapping process. The model reproduces quantitatively the forces required to unwrap the nucleosome, and reveals the role played by electrostatic interactions during this process. We then demonstrate that histone modifications and DNA sequence can have significant effects on the energies of nucleosome formation. Most notably, we show that histone tails are crucial f...
How does the cortex get its folds? The role of tension-based morphogenesis
van Essen, David
The cerebral cortex is a sheet-like structure that is convoluted to varying degrees in different species and, for human cortex, shows remarkable variability across individuals - even in identical twins. This talk will discuss key biological events and physical forces involved in how the cortex gets its folds. The early stages of cortical morphogenesis are established by exquisitely regulated patterns of cellular proliferation and migration that place the right numbers of cells in an appropriate starting configuration. A major focus will be on the proposed role of mechanical tension in the next stages of morphogenesis. Does tension along apical dendrites of cortical pyramidal cells help make the cortex a sheet? Does tension along long-distance axons cause the cortex to fold? These are attractive but controversial ideas. I will suggest ways in which physicists can contribute critical models and analyses that may help distinguish the relative contributions of several mechanisms (differential proliferation, buckling of the cortical sheet, and tension-based cortical folding). Physicists can also help in evaluating the degree to which cortical circuits reflect principles of compact wiring and the putative role of tension-based morphogenesis in wiring length minimization.
Mechanical principle of enhancing cell-substrate adhesion via pre-tension in the cytoskeleton.
Chen, Bin; Gao, Huajian
2010-05-19
Motivated by our earlier study on the effect of pre-tension in gecko adhesion, here we investigate whether and how pre-tension in cytoskeleton influences cell adhesion by developing a stochastic-elasticity model of a stress fiber attached on a rigid substrate via molecular bonds. By comparing the variations in adhesion lifetime and observing the sequences of bond breaking with and without pre-tension in the stress fiber under the same applied force, we demonstrate that the effect of pre-tension is to shift the interfacial failure mode from cracklike propagation toward uniform bond failure within the contact region, thereby greatly increasing the adhesion lifetime. Since stress fibers are the primary load-bearing components of cells, as well as the basic functional units of cytoskeleton that facilitate cell adhesion, this study suggests a feasible mechanism by which cell adhesion could be actively controlled via cytoskeletal contractility and proposes that pre-tension may be a general principle in biological adhesion. PMID:20483323
Impact of interfacial tension on residual CO2 clusters in porous sandstone
Jiang, Fei; Tsuji, Takeshi
2015-03-01
We develop a numerical simulation that uses the lattice Boltzmann method to directly calculate the characteristics of residual nonwetting-phase clusters to quantify capillary trapping mechanisms in real sandstone. For this purpose, a digital-rock-pore model reconstructed from micro-CT-scanned images of Berea sandstone is filtered and segmented into a binary file. The residual-cluster distribution is generated following simulation of the drainage and imbibition processes. The characteristics of the residual cluster in terms of size distribution, major length, interfacial area, and sphericity are investigated under conditions of different interfacial tension (IFT). Our results indicate that high interfacial tension increases the residual saturation and leads to a large size distribution of residual clusters. However, low interfacial tension results in a larger interfacial area, which is beneficial for dissolution and reaction processes during geological carbon storage. Analysis of the force balance acting on the residual clusters demonstrates that trapping stability is higher in high interfacial tension case, and the interfacial tension should be a controlling factor for the trapping stability in addition to the pore geometry and connectivity. The proposed numerical method can handle the complex displacement of multicomponent systems in porous media. By using this method, we can obtain residual-cluster distributions under different conditions for optimizing the storage capacity of carbon-storage projects.
Surface tensions, viscosities, and diffusion constants in mixed component single aerosol particles
Bzdek, Bryan; Marshall, Frances; Song, Young-Chul; Haddrell, Allen; Reid, Jonathan
2016-04-01
Surface tension and viscosity are important aerosol properties but are challenging to measure on individual particles owing to their small size and mass. Aerosol viscosity impacts semivolatile partitioning from the aerosol phase, molecular diffusion in the bulk of the particle, and reaction kinetics. Aerosol surface tension impacts how particles activate to serve as cloud condensation nuclei. Knowledge of these properties and how they change under different conditions hinders accurate modelling of aerosol physical state and atmospheric impacts. We present measurements made using holographic optical tweezers to directly determine the viscosity and surface tension of optically trapped droplets containing ~1-4 picolitres of material (corresponding to radii of ~5-10 micrometres). Two droplets are captured in the experimental setup, equilibrated to a relative humidity, and coalesced through manipulation of the relative trap positions. The moment of coalescence is captured using camera imaging as well as from elastically backscattered light connected to an oscilloscope. For lower viscosity droplets, the relaxation in droplet shape to a sphere follows the form of a damped oscillator and gives the surface tension and viscosity. For high viscosity droplets, the relaxation results in a slow merging of the two droplets to form a sphere and the timescale of that process permits determination of viscosity. We show that droplet viscosity and surface tension can be quantitatively determined to within diffusion constants, vapour pressures, and reactive uptake coefficients for a mixed component aerosol undergoing oxidation and volatilisation will be discussed.
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
A quantitative structure-property relationship (QSPR) study has been made for the prediction of the surface tension of nonionic surfactants in aqueous solution.The regressed model includes a topological descriptor,the Kier & Hall index of zero order (KH0) of the hydrophobic segment of surfactant and a quantum chemical one,the heat of formation () of surfactant molecules.The established general QSPR between the surface tension and the descriptors produces a correlation coefficient of multiple determination,=0.9877,for 30 studied nonionic surfactants.
Directory of Open Access Journals (Sweden)
S. Henning
2004-11-01
Full Text Available Critical supersaturations for internally mixed particles of adipic acid, succinic acid and sodium chloride were determined experimentally for dry particles sizes in the range 40–130 nm. Surface tensions of aqueous solutions of the dicarboxylic acids and sodium chloride corresponding to concentrations at activation were measured and parameterized as a function of carbon content. The activation of solid particles as well as solution droplets were studied and particle phase was found to be important for the critical supersaturation. Experimental data were modelled using Köhler theory modified to account for limited solubility and surface tension lowering.
Flow analysis in a vane-type surface tension propellant tank
International Nuclear Information System (INIS)
Vane-type surface tension tanks are widely used as the propellant management devices in spacecrafts. This paper treats the two-phase flow inside a vane-type surface tension tank. The study indicates that the present numerical methods such as time-dependent Navier-Stokes equations, VOF model can reasonably predict the flow inside a propellant tank. It is clear that the vane geometry has important effects on transmission performance of the liquid. for a vane type propellant tank, the vane having larger width, folding angle, height of folded side and clearance is preferable if possible
Surface tension measurements of aqueous ammonium chloride (NH4Cl) in air
Lowry, S. A.; Mccay, M. H.; Mccay, T. D.; Gray, P. A.
1989-01-01
Aqueous NH4Cl's solidification is often used to model metal alloy solidification processes. The present determinations of the magnitude of the variation of aqueous NH4Cl's surface tension as a function of both temperature and solutal concentration were conducted at 3, 24, and 40 C over the 72-100 wt pct water solutal range. In general, the surface tension increases 0.31 dyn/cm per percent decrease in wt pct of water, and decreases 0.13 dyn/cm for each increase in deg C. Attention is given to the experimental apparatus employed.
Absence of surface mode in a visco-elastic material with surface tension
Nakanishi, Hiizu; Kubota, Satoshi
1998-01-01
The surface waves in the visco-elastic media with the surface tension are studied using the Voigt-Kelvin model of the visco-elasticity. It is shown that the surface mode of oscillation does not exist in the parameter region where the effect of surface tension is larger than that of the elastic stress at the surface unless the viscous stress masks the elastic stress in the bulk. In the region, the surface oscillation is suppressed and the oscillation beneath the surface diffuses after the puls...
DEFF Research Database (Denmark)
Roberts, C; Freeman, J; Samdal, O;
2009-01-01
OBJECTIVES: To describe the methodological development of the HBSC survey since its inception and explore methodological tensions that need to be addressed in the ongoing work on this and other large-scale cross-national surveys. METHODS: Using archival data and conversations with members of the...... resources, (3) accommodating analysis of trends with the need to improve and adapt questionnaire content, and (4) meeting the differing requirements of scientific and policy audiences. CONCLUSIONS: While these challenges are not trivial, the structure of the HBSC network and its long-term experience in...... working through such challenges renders it likely that HBSC can provide a model of other similar studies facing these tensions....
Hritz, Andrew D.; Raymond, Timothy M.; Dutcher, Dabrina D.
2016-08-01
Accurate estimates of particle surface tension are required for models concerning atmospheric aerosol nucleation and activation. However, it is difficult to collect the volumes of atmospheric aerosol required by typical instruments that measure surface tension, such as goniometers or Wilhelmy plates. In this work, a method that measures, ex situ, the surface tension of collected liquid nanoparticles using atomic force microscopy is presented. A film of particles is collected via impaction and is probed using nanoneedle tips with the atomic force microscope. This micro-Wilhelmy method allows for direct measurements of the surface tension of small amounts of sample. This method was verified using liquids, whose surface tensions were known. Particles of ozone oxidized α-pinene, a well-characterized system, were then produced, collected, and analyzed using this method to demonstrate its applicability for liquid aerosol samples. It was determined that oxidized α-pinene particles formed in dry conditions have a surface tension similar to that of pure α-pinene, and oxidized α-pinene particles formed in more humid conditions have a surface tension that is significantly higher.
Directory of Open Access Journals (Sweden)
Z. Li
2011-07-01
Full Text Available The reactive uptake of carbonyl-containing volatile organic compounds (cVOCs by aqueous atmospheric aerosols is a likely source of particulate organic material. The aqueous-phase secondary organic products of some cVOCs are surface-active. Therefore, cVOC uptake can lead to organic film formation at the gas-aerosol interface and changes in aerosol surface tension. We examined the chemical reactions of two abundant cVOCs, formaldehyde and acetaldehyde, in water and aqueous ammonium sulfate (AS solutions mimicking tropospheric aerosols. Secondary organic products were identified using Aerosol Chemical Ionization Mass Spectrometry (Aerosol-CIMS, and changes in surface tension were monitored using pendant drop tensiometry. Hemiacetal oligomers and aldol condensation products were identified using Aerosol-CIMS. A hemiacetal sulfate ester was tentatively identified in the formaldehyde-AS system. Acetaldehyde depresses surface tension to 65(±2 dyn cm^{−1} in pure water and 62(±1 dyn cm^{−1} in AS solutions. Surface tension depression by formaldehyde in pure water is negligible; in AS solutions, a 9 % reduction in surface tension is observed. Mixtures of these species were also studied in combination with methylglyoxal in order to evaluate the influence of cross-reactions on surface tension depression and product formation in these systems. We find that surface tension depression in the solutions containing mixed cVOCs exceeds that predicted by an additive model based on the single-species isotherms.
Ibagon, Ingrid; Bier, Markus; Dietrich, S
2016-06-22
The three-phase contact line formed by the intersection of a liquid-vapor interface of an electrolyte solution with a charged planar substrate is studied in terms of classical density functional theory applied to a lattice model. The influence of the substrate charge density and of the ionic strength of the solution on the intrinsic structure of the three-phase contact line and on the corresponding line tension is analyzed. We find a negative line tension for all values of the surface charge density and of the ionic strength considered. The strength of the line tension decreases upon decreasing the contact angle via varying either the temperature or the substrate charge density. PMID:27116050
An ALuc-Based Molecular Tension Probe for Sensing Intramolecular Protein-Protein Interactions.
Kim, Sung-Bae; Nishihara, Ryo; Suzuki, Koji
2016-01-01
Optical imaging of protein-protein interactions (PPIs) facilitates comprehensive elucidation of intracellular molecular events. The present protocol demonstrates an optical measure for visualizing molecular tension triggered by any PPI in mammalian cells. A unique design of single-chain probes was fabricated, in which a full-length artificial luciferase (ALuc(®)) was sandwiched between two model proteins of interest, e.g., FKBP and FRB. A molecular tension probe comprising ALuc23 greatly enhances the bioluminescence in response to varying concentrations of rapamycin, and named "tension probe (TP)." The basic probe design can be further modified towards eliminating the C-terminal end of ALuc and was found to improve signal-to-background ratios, named "combinational probe." TPs may become an important addition to the tool box of bioassays in the determination of protein dynamics of interest in mammalian cells. PMID:27424905
DEFF Research Database (Denmark)
Pereira, Eduardo B.; Fischer, Gregor; Barros, Joaquim A. O.
The characterization of the tensile behavior of strain hardening cementitious composites (SHCC) is of significant importance to the material design. In a previous work the tensile stress-crack opening response of different types of SHCC was characterized using notched specimens tested in direct...... tension, where a single crack was obtained and mechanically characterized by performing Single Crack Tension Test (SCTT). In this study the tensile behavior of SHCC materials is characterized under eccentric tensile load using the Compact Tension Test (CTT). The long edge notch placed in the rectangular...... results are discussed and compared to the numerically derived responses. The tensile load-displacement responses observed in the CTTs were simulated using the cohesive crack model. The tensile stress-crack opening behaviors previously obtained with the SCTT tests were utilized to derive the traction...
International Nuclear Information System (INIS)
Ion channels of excitable membranes are known to be sensitive to various kinds of stimuli, but the case of simultaneous occurrence of different stimuli is poorly understood. Here, we theoretically analyze the influence of membrane tension on the dynamics of voltage-gated ion channels of excitable membranes. To do so, we develop a modification of the well–known Hodgkin–Huxley model to study numerically the spike generation and propagation in a single and two coupled excitable cells. We find that these cells can use membrane tension to trigger sub-threshold spike propagation, to suppress spike propagation and to alter the intensity of the signal transmission. These effects indicate that cells could use membrane tension to regulate cell-to-cell communication. (paper)
Stability and evolution of low-surface-tension metal catalyzed growth of silicon nanowires
Yu, Linwei; Fortuna, Franck; O'Donnell, Benedict; Patriache, Gilles; Roca i Cabarrocas, Pere
2011-03-01
Low-surface-tension metals were predicted to be insufficient to catalyze the growth of silicon nanowires (SiNWs) in vapor-liquid-solid (VLS) mode while counter examples do exist, for example, in the tin- or indium-catalyzed SiNWs. This puzzle remains largely unresolved. We first examine the local tension-force-balance in a tin-catalyzed SiNW by using a cross-section analysis. We found that the existence of an ultrathin sidewall-spreading catalyst layer helps to stabilize the catalyst drop during growth. The predicted contact-angle evolution, by an energetic balance model, is also supported by the experimental data. These results bring critical understanding on the low-surface-tension catalyzed VLS process.
Effect of bending and tension on the voltage-current relation of Bi-2223/Ag
Ahoranta, Maria; Lehtonen, Jorma; Kováč, Pavol; Hušek, Imrich; Melišek, Tibor
2004-01-01
The critical current in a strained HTS tape degrades due to filament cracking. Here, the voltage-current characteristics of bent and tensioned Bi-2223/Ag tapes have been measured. In the case of tension the voltage characteristics were also measured over different sections of the sample to obtain local curves. Because the crack formation is stochastic the influence of stress on the distribution of the critical current along the tape length is studied with statistical methods. Attention is paid on the effect of different stress distribution caused by bending and tension. Because the local properties cannot be uniquely determined from the measured voltage-current characteristics the limits of applicability for these models are discussed. In the analysis emphasis is put on the dynamic n-value.
Effect of bending and tension on the voltage-current relation of Bi-2223/Ag
International Nuclear Information System (INIS)
The critical current in a strained HTS tape degrades due to filament cracking. Here, the voltage-current characteristics of bent and tensioned Bi-2223/Ag tapes have been measured. In the case of tension the voltage characteristics were also measured over different sections of the sample to obtain local curves. Because the crack formation is stochastic the influence of stress on the distribution of the critical current along the tape length is studied with statistical methods. Attention is paid on the effect of different stress distribution caused by bending and tension. Because the local properties cannot be uniquely determined from the measured voltage-current characteristics the limits of applicability for these models are discussed. In the analysis emphasis is put on the dynamic n-value
Visible branes with negative tension in heterotic M-theory
International Nuclear Information System (INIS)
It is shown that there exist large classes of BPS vacua in heterotic M-theory which have negative tension on the visible orbifold plane, positive tension on the hidden plane and positive tension, physical five-branes in the bulk space. Explicit examples of such vacua are presented. Furthermore, it is demonstrated that the ratio, β/ vertical bar α vertical bar, of the bulk five-brane tension to the visible plane tension can, for several large classes of such vacua, be made arbitrarily small. Hence, it is straightforward to find vacua with the properties required in the examples of the Ekpyrotic theory of cosmology - a visible brane with negative tension and β/ vertical bar α vertical bar small. This contradicts recent claims in the literature. (author)
Interfacial tension measured at high expansion rates and within milliseconds using microfluidics.
Muijlwijk, Kelly; Hinderink, Emma; Ershov, Dmitry; Berton-Carabin, Claire; Schroën, Karin
2016-05-15
To understand droplet formation and stabilisation, technologies are needed to measure interfacial tension at micrometer range and millisecond scale. In this paper, microtechnology is used, and that allows us to access these ranges and derive a model for surfactant free systems. The predicting power of the model was tested, and we found that it can be used to accurately (validated with >60 experiments) describe droplet size for a wide range of flow rates, interfacial tensions, and continuous phase viscosities. The model was used next to determine interfacial tensions in a system with hexadecane and sodium dodecylsulfate (SDS) solutions, and it was found that the model can be used for droplet formation times ranging from 0.4 to 9.4ms while using a wide range of process conditions. The method described here differs greatly from standard dynamic interfacial tension methods that use quiescent, mostly diffusion-limited situations. The effects that we measured are much faster due to enhanced mass transfer; this allows us to assess the typical time scales used in industrial emulsification devices. PMID:26930542
E. Momoniat
2005-01-01
The effects of nonuniform surface tension on the axisymmetric gravity-driven spreading of a thin viscous liquid drop are investigated. A second-order nonlinear partial differential equation modelling the evolution of the free surface of a thin viscous liquid drop is derived. The nonuniform surface tension is represented by a function Σ(r). The Lie group method is used to determine Σ(r) such that exact and approximate invariant solutions admitted by the free surface equation can be determined....
Surface tension of Nanofluid-type fuels containing suspended nanomaterials
Tanvir, Saad; Qiao, Li
2012-01-01
The surface tension of ethanol and n-decane based nanofluid fuels containing suspended aluminum (Al), aluminum oxide (Al2O3), and boron (B) nanoparticles as well as dispersible multi-wall carbon nanotubes (MWCNTs) were measured using the pendant drop method by solving the Young-Laplace equation. The effects of nanoparticle concentration, size and the presence of a dispersing agent (surfactant) on surface tension were determined. The results show that surface tension increases both with partic...
The free boundary Euler equations with large surface tension
Disconzi, Marcelo M.; Ebin, David G.
2015-01-01
We study the free boundary Euler equations with surface tension in three spatial dimensions, showing that the equations are well-posed if the coefficient of surface tension is positive. Then we prove that under natural assumptions, the solutions of the free boundary motion converge to solutions of the Euler equations in a domain with fixed boundary when the coefficient of surface tension tends to infinity.
The free boundary Euler equations with large surface tension
Disconzi, Marcelo M.; Ebin, David G.
2016-07-01
We study the free boundary Euler equations with surface tension in three spatial dimensions, showing that the equations are well-posed if the coefficient of surface tension is positive. Then we prove that under natural assumptions, the solutions of the free boundary motion converge to solutions of the Euler equations in a domain with fixed boundary when the coefficient of surface tension tends to infinity.
Surface tension with Normal Curvature in Curved Space-Time
Kumar, Himanshu; Alam, Sharf; Ahmad, Suhail
2012-01-01
With an aim to include the contribution of surface tension in the action of the boundary, we define the tangential pressure in terms of surface tension and Normal curvature in a more naturally geometric way. First, we show that the negative tangential pressure is independent of the four-velocity of a very thin hyper-surface. Second, we relate the 3-pressure of a surface layer to the normal curvature and the surface tension. Third, we relate the surface tension to the energy of the surface lay...
The law of corresponding states and surface tension of metals
International Nuclear Information System (INIS)
Full Text: Surface tension of liquid metals is one of fundamental and most important quantities in theory and practice of material processing and its temperature dependence leads to the well-known Marangoni convection. Although currently methods are sufficiently precise to measure the surface tension, there are uncertainties in experimental data and its temperature dependence mainly due to impurity, which even a trace of it strongly affects the results of measurements. The theoretical treatment from the first principles is unwieldy and not always permits one to calculate the surface tension with certainty. Another active research field deals with empirical correlation between the surface tension and bulk thermodynamic properties, which we interpret as a simple consequence of the law of corresponding states. In order to relate the surface tension and to bulk properties of liquid metals the reduced formula is derived by scaling with the melting point Tm (0) at p = 0 and atomic volume Ω02/3 at T = 0 K as macroscopic parameters for scaling ε and a characterizing the interatomic potential in metals. The reduced surface tension and the reduced surface entropy obtained in high temperature limit are discussed and compared with the experiment. The reduced temperature coefficient of the surface tension found is a universal constant for the metals of the same structure. It is shown that pressure dependence of the surface tension, so called baric coefficient of the surface tension, can be described by pressure dependence of scaling parameters Tm (p) and Ω0 (p). (author)
STRENGTH SHRINKAGE AND CREEP OF CONCRETE IN TENSION AND COMPRESSION
Directory of Open Access Journals (Sweden)
S A Kristiawan
2006-01-01
Full Text Available Strength, shrinkage and creep of concrete in tension and compression have been determined and the relationship between those properties was studied. Direct tensile tests were applied to measure those properties in tension. The relationship of creep in tension and compression was determined based on the measurement of creep at similar stress and similar stress/strength ratio. It is found that concrete deforms more in tension than in compression. Except for concrete with a higher water/cement ratio, the use of pulverised fuel ash, ground granulated blast furnace slag, superplasticizer and shrinkage reducing admixture has no effect on strength. However, they affect creep and shrinkage of concrete.
Kulinskii, Vladimir
2012-01-01
In this communication we show that the surface tension of the real fluids of the Lennard-Jones type can be obtained from the surface tension of the lattice gas (Ising model) on the basis of the global isomorphism approach developed earlier for the bulk properties.
The string tension from smeared Wilson loops at large N
International Nuclear Information System (INIS)
We present the results of a high statistics analysis of smeared Wilson loops in 4-dimensional SU(N) Yang–Mills theory for various values of N. The data is used to analyze the behavior of smeared Creutz ratios, extracting from them the value of the string tension and other asymptotic parameters. A scaling analysis allows us to extrapolate to the continuum limit for N=3,5,6 and 8. The results are consistent with a 1/N2 approach towards the large N limit. The same analysis is done for the TEK model (one-point lattice) for N=841 and a non-minimal symmetric twist with flux of k=9. The results match perfectly with the extrapolated large N values, confirming the validity of the reduction idea for this range of parameters.
The string tension from smeared Wilson loops at large N
González-Arroyo, Antonio
2012-01-01
We present the results of a high statistics analysis of smeared Wilson loops in 4 dimensional SU(N) Yang-Mills theory for various values of N. The data is used to analyze the behaviour of smeared Creutz ratios, extracting from them the value of the string tension and other asymptotic parameters. A scaling analysis allows us to extrapolate to the continuum limit for N=3,5,6 and 8. The results are consistent with a $1/N^2$ approach towards the large N limit. The same analysis is done for the TEK model (one-point lattice) for N=841 and a non-minimal symmetric twist with flux of $k=9$. The results match perfectly with the extrapolated large N values, confirming the validity of the reduction idea for this range of parameters.
Central pain processing in chronic tension-type headache
DEFF Research Database (Denmark)
Lindelof, Kim; Ellrich, Jens; Jensen, Rigmor;
2009-01-01
OBJECTIVE: Chronic tension-type headache (CTTH) affects 3% of the population. Directly and indirectly it causes high costs and considerable loss of quality of life. The mechanisms of this disorder are poorly understood and the treatment possibilities are therefore limited. The blink reflex (BR) r...... combined homotopic and heterotopic effect of the conditioning pain onto the blink reflex could account for this finding.......) reflects neuronal excitability due to nociceptive input in the brainstem. The aim of this study was to investigate nociceptive processing at the level of the brainstem in an experimental pain model of CTTH symptoms. METHODS: The effect of conditioning pain, 5 min infusion of hypertonic saline into the neck...... muscles, was investigated in 20 patients with CTTH and 20 healthy controls. In addition, a pilot study with isotonic saline was performed with 5 subjects in each group. The BR was elicited by electrical stimuli with an intensity of four times the pain threshold, with a superficial concentric electrode. We...
Neurotrophic factors in tension-type headache
Directory of Open Access Journals (Sweden)
Renan B. Domingues
2015-05-01
Full Text Available Neurotrophic factors (NF are involved in pain regulation and a few studies have suggested that they may play a pathophysiological role in primary headaches. The aim of this study was to investigate NF levels in patients with tension type headache (TTH. We carried out a cross sectional study including 48 TTH patients and 48 age and gender matched controls. Beck Depression and Anxiety Inventories, and Headache Impact Test were recorded. Serum levels of NF were determined by ELISA. There were not significant differences between NF levels between TTH patients and controls. Patients with chronic and episodic TTH had not significant differences in NF levels. The presence of headache at the time of evaluation did not significantly alter the levels of NF. Depression and anxiety scores as well as headache impact did not correlate with NF levels. Our study suggest that the serum levels of NF are not altered in TTH.
Modifying horizon thermodynamics by surface tensions
Chen, Deyou
2016-01-01
The modified first laws of thermodynamics at the black hole horizon and the cosmological horizon of the Schwarzschild de Sitter black hole and the apparent horizon of the Friedmann-Robertson-Walker cosmology are derived by the surface tensions, respectively. The corresponding Smarr relations are obeyed. For the black hole, the cosmological constant is first treated as a fixed constant, and then as a variable associated to the pressure. The law at the apparent horizon takes the same form as that at the cosmological horizon, but is different from that at the black hole horizon. The positive temperatures guarantee the appearance of the worked terms in the modified laws at the cosmological and apparent horizons. While they can disappear at the black hole horizon.
Hu, Bin; Kieweg, Sarah
2010-11-01
Gravity-driven thin film flow down an incline is studied for optimal design of polymeric drug delivery vehicles, such as anti-HIV topical microbicides. We develop a 3D FEM model using non-Newtonian mechanics to model the flow of gels in response to gravity, surface tension and shear-thinning. Constant volume setup is applied within the lubrication approximation scope. The lengthwise profiles of the 3D model agree with our previous 2D finite difference model, while the transverse contact line patterns of the 3D model are compared to the experiments. With incorporation of surface tension, capillary ridges are observed at the leading front in both 2D and 3D models. Previously published studies show that capillary ridge can amplify the fingering instabilities in transverse direction. Sensitivity studies (2D & 3D) and experiments are carried out to describe the influence of surface tension and shear-thinning on capillary ridge and fingering instabilities.
Nuclear curvature tension and the possibility of shape isomers for nuclei near Ra
International Nuclear Information System (INIS)
The shape dependence of nuclear masses is discussed. The saddle-point area of the potential energy surface has been studied. We used a semi-empiric mass formula containing a volume-, a surface-, a curvature-, a Coulomb-term as well as the shell correction term of Myers and Swiatecki (version II), the shape-dependent pairing energy as suggested by Moretto and Noerenberg and the asymmetry and compressibility terms of the droplet model of Myers and Swiatecki. The nuclear shape at the saddle-point and the 'flatness' (the width of the inverse fission oscillator) of its vicinity is calculated as a function of charge Z, atomic weight A, and the fissility parameter K, respectively. The well-known change at the K-area of Ra from constricted saddle-point shapes for light nuclei to sausage-like ones for heavy nuclei has been studied. This change is emphasized by a curvature tension and simultaneously the saddle-point area becomes very flat. For sufficiently large values of the curvature tension a small second minimum occurs, which means a small double-hump fission barrier. This is due to the different ways in which surface tension and curvature tension act on deformed nuclei. The formation of a Strutinsky minimum in a small area of nuclei near Ra is fostered to the same degree as the value of the curvature tension is increased. The Strutinsky shell correction term, however (which led to the shape isomers of very heavy nuclei predicted), is still unknown for the strongly deformed and constricted saddle-point shapes in question. Some simple other shell terms have been tried. The numerical values of the surface and curvature tensions are estimated by fitting simultaneously the fission barriers of light and heavy nuclei and using the estimate of the nuclear particle density of Seeger, ρ = 1.46 fm-3 . (author)
Directory of Open Access Journals (Sweden)
Uta König von Borstel
Full Text Available Rideability, i.e. the ease and comfort with which a horse can be ridden, is considered to be one of the most important traits in riding horses. However, at present rideability is evaluated rather subjectively in breeding horse performance tests. The aim of the present study was to evaluate the role horse behaviour as well as degree and quality of rein tension might play in judges' evaluation of horses' rideability. Mares (n=33 and stallions (n=13 from two different mare- and one stallion-testing station were observed twice during their performance test dressage training. During these rides, rein tension was measured continuously, and frequency of behaviour patterns such as head-tossing, tail swishing, and snorting was recorded. Rein tension parameters showed reasonable repeatabilities within horse-rider pairs (e.g. mean rein tension: r(2=0.61 ± 0.11; variance of rein tension: r(2=0.52 ± 0.14. Regression analysis revealed that a larger proportion of variance in rideability scores could be explained by maximum (17%, mean (16% and variance (15% of rein tension compared to horses' or riders' behavioural parameters (tail-swishing: 5% and rider's use of hands: 5%, respectively. According to mixed model analysis, rideability scores dropped (all P<0.05 with increasing mean, maximum and variability in rein tension (e.g. -0.37 ± 0.14 scores per additional 10 Newton in mean tension. However, mean rein tension differed between testing stations (P<0.0001 ranging between 9.1 ± 1.6 N in one station and 21.7 ± 1.3 N in another station. These results indicate that quantity and consistency of rein tension is either directly or indirectly an important factor for judges to derive rideability scores. Given the importance of rein tension parameters to both rider comfort and horse welfare, potentially, measurements of rein tension along with behaviour observations assessing the quality of rein contact (e.g. distinguishing a light contact from attempts to evade
Feller, S E; Pastor, R W
1996-01-01
As sketched in Fig. 1, a current molecular dynamics computer simulation of a lipid bilayer fails to capture significant features of the macroscopic system, including long wavelength undulations. Such fluctuations are intrinsically connected to the value of the macroscopic (or thermodynamic) surface tension (cf. Eqs. 1 and 9; for a related treatment, see Brochard et al., 1975, 1976). Consequently, the surface tension that might be evaluated in an MD simulation should not be expected to equal the surface tension obtained from macroscopic measurements. Put another way, the largest of the three simulations presented here contained over 16,000 atoms and required substantial computer time to complete, but modeled a system of only 36 lipids per side. From this perspective it is not surprising that the system is not at the thermodynamic limit. An important practical consequence of this effect is that simulations with fluctuating area should be carried out with a nonzero applied surface tension (gamma 0 of Fig. 2) even when the macroscopic tension is zero, or close to zero. Computer simulations at fixed surface area, which can explicitly determine pressure anisotropy at the molecular level, should ultimately lend insight into the value of gamma 0, including its dependence on lipid composition and other membrane components. As we have noted and will describe further in separate publications (Feller et al., 1996; Feller et al., manuscript in preparation), surface tensions obtained from simulations can be distorted by inadequate initial conditions and convergence, and are sensitive to potential energy functions, force truncation methods, and system size; it is not difficult, in fact, to tune terms in the potential energy function so as to yield surface tensions close to zero. This is why parameters should be tested extensively on simpler systems, for example, monolayers. The estimates of gamma 0 that we have presented here should be regarded as qualitative, and primarily
Black Strings from Minimal Geometric Deformation in a Variable Tension Brane-World
Casadio, Roberto; da Rocha, Roldao
2013-01-01
We study brane-world models with variable brane tension and compute corrections to the horizon of a black string along the extra dimension. The four-dimensional geometry of the black string on the brane is obtained by means of the minimal geometric deformation approach, and the bulk corrections are then encoded in additional terms involving the covariant derivatives of the variable brane tension. Our investigation shows that the variable brane tension strongly affects the shape and evolution of the black string horizon along the extra dimension, at least in a near-brane expansion. In particular, we apply our general analysis to a model motivated by the E\\"otv\\"os branes, where the variable brane tension is related to the Friedmann-Robertson-Walker brane-world cosmology. We show that for some stages in the evolution of the universe, the black string warped horizon collapses to a point and the black string has correspondingly finite extent along the extra dimension. Furthermore, we show that in the minimal geom...
Fowler's approximation for the surface tension and surface energy of Lennard-Jones fluids revisited
International Nuclear Information System (INIS)
We present a detailed study of the validity of Fowler's approximation for calculating the surface tension and the surface energy of Lennard-Jones fluids. To do so, we consider three different explicit analytical expressions for the radial distribution function (RDF), including one proposed by our research group, together with very accurate expressions for the liquid and vapour densities, also proposed by our group. The calculation of the surface tension from the direct correlation function using both the Percus-Yevick and the hypernetted-chain approximations is also considered. Finally, our results are compared with those obtained by other authors by computer simulations or through relevant theoretical approximations. In particular, we consider the analytical expression proposed by Kalikmanov and Hofmans (1994 J. Phys.: Condens. Matter 6 2207-14) for the surface tension. Our results indicate that the values for the surface energy in Fowler's approximation obtained by other authors are adequate, and can be calculated from the RDF models. For the surface tension, however, the values considered as valid in previous works seem to be incorrect. The correct values can be obtained from our model for the RDF or from the Kalikmanov and Hofmans expression with suitable inputs
Vassilakis, Pantelis N.
2005-04-01
Within western musical tradition, auditory roughness constitutes one of the principle perceptual correlates of dissonance. A previous study [P. N. Vassilakis, Selected Reports in Ethnomusicology, Vol. 12 (in press)] addressed the musical significance of auditory roughness within western as well as three non-western musical traditions. It introduced a new roughness estimation model that predicts successfully roughness ratings of synthesized complex diatonic dyads. For the present study, an application was created that uses the aforementioned model to estimate the roughness of natural signals with arbitrary spectra, as well as roughness profiles of short musical pieces. The application was used to examine if and how the pattern of tension and release within a stylized improvisation on the Middle Eastern mijwiz (double clarinet) relates to roughness changes. Tension/release patterns were indicated by the Lebanese improviser and expert mijwiz player (Dr. A. J. Racy) and were also obtained by both musicians and non-musicians (American-raised) in a perceptual experiment. The results suggest that auditory roughness is a good predictor of the tension/release pattern indicated by the improviser. The patterns obtained by the subjects, although not very consistent, appear to be different overall, suggesting that musical tension and release may be culture-specific concepts.
Dynamic Interfacial Tension Measurements with Microfluidic Y-Junctions
Steegmans, M.L.J.; Warmerdam, A.; Schroën, C.G.P.H.; Boom, R.M.
2009-01-01
Emulsification in microdevices (microfluidic emulsification) involves micrometer-sized droplets and fast interface expansion rates. In addition, droplets are formed in less than milliseconds, and therefore traditional tensiometric techniques cannot be used to quantify the actual interfacial tension. In this paper, monodisperse droplets formed at flat microfluidic Y-junctions were used to quantify the apparent dynamic interfacial tension during (microfluidic) emulsification. Hexadecane droplet...
On innovation patterns and value-tensions in public services
DEFF Research Database (Denmark)
Fuglsang, Lars; Rønning, Rolf
2015-01-01
the possibility of intertwined innovation patterns. Focusing public sector services, this paper agues that intertwined innovation patterns emerge within public services as a response to value-tensions. Values can be defined as measures for beneficial behaviour that guide innovation. Value-tensions in...
Tensions in the Biology Laboratory: What Are They?
Tan, Aik-Ling
2008-01-01
The purpose of this paper is to identify tensions in teacher-student interaction in a high school biology laboratory. Using micro-analytic analysis of classroom talk, the interaction between the students and a teacher working in the biology laboratory session on "Reproduction in Plants" is studied. The two tensions highlighted here are tension…
Conducting Qualitative Data Analysis: Managing Dynamic Tensions within
Chenail, Ronald J.
2012-01-01
In the third of a series of "how-to" essays on conducting qualitative data analysis, Ron Chenail examines the dynamic tensions within the process of qualitative data analysis that qualitative researchers must manage in order to produce credible and creative results. These tensions include (a) the qualities of the data and the qualitative data…
Dorzolamide increases retinal oxygen tension after branch retinal vein occlusion
DEFF Research Database (Denmark)
Noergaard, Michael Hove; Bach-Holm, Daniella; Scherfig, Erik;
2008-01-01
To study the effect of dorzolamide on the preretinal oxygen tension (RPO(2)) in retinal areas affected by experimental branch retinal vein occlusion (BRVO) in pigs.......To study the effect of dorzolamide on the preretinal oxygen tension (RPO(2)) in retinal areas affected by experimental branch retinal vein occlusion (BRVO) in pigs....
Note About Unstable D-Brane with Dynamical Tension
Kluson, J
2016-01-01
We propose an action for unstable Dp-brane with dynamical tension. We show that the equations of motion are equivalent to the equations of motion derived from DBI and WZ actions for non-BPS Dp-brane. We also find Hamiltonian formulation of this action and analyze properties of the solutions corresponding to the tachyon vacuum and zero tension solution.
FRP tendon anchorage in post-tensioned concrete structures
DEFF Research Database (Denmark)
Schmidt, Jacob Wittrup; Täljsten, Björn; Bennitz, Anders; Henning, Pedersen
Strengthening of building structures by the use of various external post-tensioning steel tendon systems, is known to be a very efficient method. However, FRP as material in external post-tensioning projects has been investigated during the last decade. The advantages for this material are the high...
Negotiating Narrative Inquiries: Living in a Tension-Filled Midst
Clandinin, D. Jean; Murphy, M. Shaun; Huber, Janice; Orr, Anne Murray
2010-01-01
The authors explore the place of tension in understanding narrative inquiry as a relational research methodology. Drawing on a narrative inquiry into children's, teachers', and families' experiences in schools shaped by achievement testing practices that flow from accountability policies, the authors show how attending to tensions is central to…
Pendant-Drop Surface-Tension Measurement On Molten Metal
Man, Kin Fung; Thiessen, David
1996-01-01
Method of measuring surface tension of molten metal based on pendant-drop method implemented in quasi-containerless manner and augmented with digital processing of image data. Electrons bombard lower end of sample rod in vacuum, generating hanging drop of molten metal. Surface tension of drop computed from its shape. Technique minimizes effects of contamination.
Thermodynamics of surface tension: application to electrolyte solution
Levin, Yan
2001-01-01
In this contribution to the special issue of the Journal of Statistical Physics dedicated to Michael Fisher on his 70'th birthday, I shall review two thermodynamically distinct routes for obtaining the interfacial tension of liquid-vapor interfaces in mixtures. A specific application to the calculation of the excess surface tension of aqueous electrolyte solutions will be presented.
The Cartesian Diver, Surface Tension and the Cheerios Effect
Chen, Chi-Tung; Lee, Wen-Tang; Kao, Sung-Kai
2014-01-01
A Cartesian diver can be used to measure the surface tension of a liquid to a certain extent. The surface tension measurement is related to the two critical pressures at which the diver is about to sink and about to emerge. After sinking because of increasing pressure, the diver is repulsed to the centre of the vessel. After the pressure is…
Surface tension of molten tin investigated with sessile drop method
Institute of Scientific and Technical Information of China (English)
LI Jing; YUAN Zhang-fu; FAN Jian-feng; KE Jia-jun
2005-01-01
The surface tension of molten tin was determined by a set of self-developed digital equipment with sessile drop method at oxygen partial pressure of 1.0 × 10-6 MPa under different temperatures, and the dependence of surface tension of molten tin on temperature was also discussed. The emphasis was placed on the comparison of surface tension of the same molten tin sample measured by using different equipments with sessile drop method. Results of the comparison indicate that the measurement results with sessile drop method under the approximate experimental conditions are coincident, and the self-developed digital equipment for surface tension measurement has higher stability and accuracy. The relationships of surface tension of molten tin and its temperature coefficient with temperature and oxygen partial pressure were also elucidated from the thermodynamic equilibrium analysis.
Decaying dark matter and the tension in $\\sigma_8$
Enqvist, Kari; Sekiguchi, Toyokazu; Takahashi, Tomo
2015-01-01
We consider decaying dark matter (DDM) as a resolution to the possible tension between cosmic microwave background (CMB) and weak lensing (WL) based determinations of the amplitude of matter fluctuations, $\\sigma_8$. We perform N-body simulations in a model where dark matter decays into dark radiation and develop an accurate fitting formula for the non-linear matter power spectrum, which enables us to test the DDM model by the combined measurements of CMB, WL and the baryon acoustic oscillation (BAO). We employ a Markov chain Monte Carlo analysis to examine the overlap of posterior distributions of the cosmological parameters, comparing CMB alone with WL+BAO. We find an overlap that is significantly larger in the DDM model than in the standard CDM model. This may be hinting at DDM, although current data is not constraining enough to unambiguously favour a non-zero dark matter decay rate $\\Gamma$. From the combined CMB+WL data, we obtain a lower bound $\\Gamma^{-1}\\ge 97$ Gyr at 95 % C.L, which is less tight th...
Behavior of Unbonded Flexible Risers Subject to Axial Tension
Institute of Scientific and Technical Information of China (English)
任少飞; 唐文勇; 郭晋挺
2014-01-01
Owing to nonlinear contact problems with slip and friction, a lot of limiting assumptions are made when developing analytical models to simulate the behavior of an unbonded flexible riser. Meanwhile, in order to avoid convergence problems and excessive calculating time associated with running the detailed finite element (FE) model of an unbonded flexible riser, interlocked carcass and zeta layers with complicated cross section shapes are replaced by simple geometrical shapes (e.g. hollow cylindrical shell) with equivalent orthotropic materials. But the simplified model does not imply the stresses equivalence of these two layers. To solve these problems, based on ABAQUS/Explicit, a numerical method that is suitable for the detailed FE model is proposed. In consideration of interaction among all component layers, the axial stiffness of an eight-layer unbonded flexible riser subjected to axial tension is predicted. Compared with analytical and experimental results, it is shown that the proposed numerical method not only has high accuracy but also can substantially reduce the calculating time. In addition, the impact of the lay angle of helical tendons on axial stiffness is discussed.
Instability due to interfacial tension in parallel liquid-liquid flow
Rodriguez, Oscar M. H.
2016-06-01
The frequent occurrence of multiphase flows in pipes has motivated a great research interest over the last decades. The particular case of liquid-liquid flow is commonly encountered in the petroleum industry, where a number of applications involve oil-water flow such as crude oil production in directional wells. However, it has not received the same attention when compared to gas-liquid flow. In addition, most of the available information has to do with flow in pipes. When it comes to flows in annular ducts the data are scanty. A general transition criterion has been recently proposed in order to obtain the stratified and core-annular flow-pattern transition boundaries in viscous oil-water flow. The proposed criterion was based on an one-dimensional two-fluid model of liquid-liquid two-phase flow. A stability analysis was carried out and interfacial tension is considered. A new destabilizing term arises, which is a function of the cross-section curvature of the interface. It is well accepted that interfacial tension favors the stable condition. However, the analysis of the new interfacial-tension term shows that it can actually destabilize the basic flow pattern, playing an important role in regions of extreme volumetric fractions. Such an interesting effect seems to be more pronounced in flows of viscous fluids and in annular-duct flow. The effect of interfacial tension is explored and the advantages of using a more complete model are discussed and illustrated through comparisons with experimental data from the literature. The evaluation of the effects of fluid viscosity and interfacial tension allows the correction and enhancement of transition models based essentially on data of pipe flow of low viscosity fluids.
Early dark energy, the Hubble-parameter tension, and the string axiverse
Karwal, Tanvi; Kamionkowski, Marc
2016-01-01
Precise measurements of the cosmic microwave background (CMB) power spectrum are in excellent agreement with the predictions of the standard $\\Lambda$CDM cosmological model. However, there is some tension between the value of the Hubble parameter $H_0$ inferred from the CMB and that inferred from observations of the Universe at lower redshifts, and the unusually small value of the dark-energy density is a puzzling ingredient of the model. In this paper, we explore a scenario with a new exotic...
DEFF Research Database (Denmark)
Korkiakoski, Samuli; Brøndsted, Povl; Sarlin, Essi; Saarela, Olli
2016-01-01
It is well known that standardised tension-tension fatigue test specimens of unidirectional (UD) glass-fibre-reinforced plastics (GFRP) laminates tend to fail at end tabs. The true fatigue life is then underestimated. The first objective of this study was to find for UD GFRP laminates a test...
Ocular Blood Flow and Normal Tension Glaucoma
Directory of Open Access Journals (Sweden)
Ning Fan
2015-01-01
Full Text Available Normal tension glaucoma (NTG is known as a multifactorial optic neuropathy characterized by progressive retinal ganglion cell death and glaucomatous visual field loss, even though the intraocular pressure (IOP does not exceed the normal range. The pathophysiology of NTG remains largely undetermined. It is hypothesized that the abnormal ocular blood flow is involved in the pathogenesis of this disease. A number of evidences suggested that the vascular factors played a significant role in the development of NTG. In recent years, the new imaging techniques, fluorescein angiography, color Doppler imaging (CDI, magnetic resonance imaging (MRI, and laser speckle flowgraphy (LSFG, have been used to evaluate the ocular blood flow and blood vessels, and the impaired vascular autoregulation was found in patients with NTG. Previous studies showed that NTG was associated with a variety of systemic diseases, including migraine, Alzheimer’s disease, primary vascular dysregulation, and Flammer syndrome. The vascular factors were involved in these diseases. The mechanisms underlying the abnormal ocular blood flow in NTG are still not clear, but the risk factors for glaucomatous optic neuropathy likely included oxidative stress, vasospasm, and endothelial dysfunction.
Surface Tension Driven Convection Experiment (STDCE)
Ostrach, S.; Kamotani, Y.
1996-01-01
This document reports the results obtained from the Surface Tension Driven Convection Experiment (STDCE) conducted aboard the USML-1 Spacelab in 1992. The experiments used 10 cSt silicone oil placed in an open circular container that was 10 cm wide and 5 cm deep. Thermocapillary flow was induced by using either a cylindrical heater placed along the container centerline or by a CO2 laser. The tests were conducted under various power settings, laser beam diameters, and free surface shapes. Thermistors located at various positions in the test section recorded the temperature of the fluid, heater, walls, and air. An infrared imager was used to measure the free surface temperature. The flow field was studied by flow visualization and the data was analyzed by a PTV technique. The results from the flow visualization and the temperature measurements are compared with the numerical analysis that was conducted in conjunction with the experiment. The compared results include the experimental and numerical velocity vector plots, the streamline plots, the fluid temperature, and the surface temperature distribution.
Whiteboards: mediating professional tensions in clinical practice.
Riley, Robin; Forsyth, Rowena; Manias, Elizabeth; Iedema, Rick
2007-01-01
In this paper we argue that whiteboards in clinical settings play a hybrid role: communicating inter- and intraprofessional directives, mediating professional tensions, and mitigating potentially face-threatening acts. The data upon which this paper is based emanate from two independently conducted ethnographic studies: the first explored a range of nurse-nurse and nurse-doctor communication practices in operating rooms, while the second explored work routines and communication methods in oncology wards. Data collection included fieldwork using observations, interviews assisted by photographic methods, and in the first study, a personal diary. A deconstructive analysis was independently undertaken. As a communication method, the use of whiteboards in clinical settings provided a focal point for the coordination of clinical work activities and for the dissemination of information to large groups of people. Whiteboards were a conduit for potentially face-threatening information in that they facilitated the policing and disciplining of staff, while distancing communicators from one another. We conclude that whiteboards are 'pseudo-synchronous' in nature, enabling 'communication at a distance'. In doing so, whiteboards may facilitate and economize clinical communication but they also perpetuate the invisibility of nurses' contribution to ensuring safe care, and they mask the symbolic violence that is committed within and between health professionals. PMID:18052816
India: environmental degradation, urban slums, political tension.
Chhabra, R
1985-09-01
This article presents an overview of stresses facing Indian society, including population pressures on land and agriculture, topsoil erosion, deforestation, flooding, unemployment, urban slums, and political unrest. Over 60% of India's arable land is estimated to suffer from environmental degradation. This has been caused both by a rapidly growing poor population seeking subsistence and by the misappropriation of natural resources by the wealthy for luxury consumption. Although deforestation is officially cited at 0.37 million acres/year, more sensitive estimates put it at 2.5 million acres/year. Deforestation and massive soil erosion have further created silting, flooding, and pollution in the plains areas of the country. Moreover, the urban population of India is expected to double in the next 15 years to reach a level of 350-400 million. At present, 20-33% of the urban population lives in slums without basic facilities. The employment crisis precipitated by increasing urbanization and migration is expected to be a major problem in the decades ahead. By the year 2000, 7.5 million people will enter the labor force annually. Demographic tension has been a major factor in recent political unrest. Language differences, inequitable access to resources, and the lack of job opportunities have been central issues in these conflicts. Unless more effective means can be found to cope simultaneously with the need to speed up development and meet the needs of a rapidly expanding population, the social and environmental fabric of India is in danger of further erosion. PMID:12313938
Directory of Open Access Journals (Sweden)
Z. Li
2011-11-01
Full Text Available The reactive uptake of carbonyl-containing volatile organic compounds (cVOCs by aqueous atmospheric aerosols is a likely source of particulate organic material. The aqueous-phase secondary organic products of some cVOCs are surface-active. Therefore, cVOC uptake can lead to organic film formation at the gas-aerosol interface and changes in aerosol surface tension. We examined the chemical reactions of two abundant cVOCs, formaldehyde and acetaldehyde, in water and aqueous ammonium sulfate (AS solutions mimicking tropospheric aerosols. Secondary organic products were identified using Aerosol Chemical Ionization Mass Spectrometry (Aerosol-CIMS, and changes in surface tension were monitored using pendant drop tensiometry. Hemiacetal oligomers and aldol condensation products were identified using Aerosol-CIMS. Acetaldehyde depresses surface tension to 65(±2 dyn cm^{−1} in pure water (a 10% surface tension reduction from that of pure water and 62(±1 dyn cm^{−1} in AS solutions (a 20.6% reduction from that of a 3.1 M AS solution. Surface tension depression by formaldehyde in pure water is negligible; in AS solutions, a 9% reduction in surface tension is observed. Mixtures of these species were also studied in combination with methylglyoxal in order to evaluate the influence of cross-reactions on surface tension depression and product formation in these systems. We find that surface tension depression in the solutions containing mixed cVOCs exceeds that predicted by an additive model based on the single-species isotherms.
International Nuclear Information System (INIS)
Highlights: ► We measure surface tension, σ, in eight systems formed by IL + water or ethanol. ► The ILs are 1-ethyl-3-methyl imidazolium alkyl sulphate, with the alkyl chain being ethyl, butyl, hexyl and octyl. ► Surface tension behaviour of mixtures with water concentration resembles surfactants. ► We calculate surface tension deviations for each system. ► We fit accurately the reduced surface pressure with the Bahe–Varela equation. - Abstract: In this work, we present surface tension experimental measurements for eight binary systems containing water or ethanol and an ionic liquid (IL) of the 1-ethyl-3-methyl imidazolium alkyl sulphate family, being the alkyl chain of the anion: ethyl, butyl, hexyl and octyl. Measurements were performed at the temperature of 25.0 °C and atmospheric pressure. All four ILs are completely miscible with water and ethanol, but for a concentration range of the octyl sulphate IL aqueous system the mixture jellifies, and so it is not possible to measure its surface tension. These measurements allow us to study the influence of the anion size on the surface tension for the pure IL compounds, and the role of the two different solvents in the surface tension behaviour. Thus, we observe that it is completely different when mixed with water or with ethanol, as also happens in other mixtures with different ionic liquids. From the experimental data, we extract surface tension deviations using the most popular definition. The calculated deviations for the ethanol based system are fitted using the Redlich–Kister equation and a novel one previously reported by us. Furthermore, we have also calculated the reduced surface pressure for the aqueous mixtures, which is fitted with good agreement using a theoretical equation obtained from the Bahe–Varela pseudo-lattice model.
Diz-Muñoz, Alba; Thurley, Kevin; Chintamen, Sana; Altschuler, Steven J.; Fletcher, Daniel A.; Weiner, Orion D.
2016-01-01
For efficient polarity and migration, cells need to regulate the magnitude and spatial distribution of actin assembly. This process is coordinated by reciprocal interactions between the actin cytoskeleton and mechanical forces. Actin polymerization-based protrusion increases tension in the plasma membrane, which in turn acts as a long-range inhibitor of actin assembly. These interactions form a negative feedback circuit that limits the magnitude of membrane tension in neutrophils and prevents expansion of the existing front and the formation of secondary fronts. It has been suggested that the plasma membrane directly inhibits actin assembly by serving as a physical barrier that opposes protrusion. Here we show that efficient control of actin polymerization-based protrusion requires an additional mechanosensory feedback cascade that indirectly links membrane tension with actin assembly. Specifically, elevated membrane tension acts through phospholipase D2 (PLD2) and the mammalian target of rapamycin complex 2 (mTORC2) to limit actin nucleation. In the absence of this pathway, neutrophils exhibit larger leading edges, higher membrane tension, and profoundly defective chemotaxis. Mathematical modeling suggests roles for both the direct (mechanical) and indirect (biochemical via PLD2 and mTORC2) feedback loops in organizing cell polarity and motility—the indirect loop is better suited to enable competition between fronts, whereas the direct loop helps spatially organize actin nucleation for efficient leading edge formation and cell movement. This circuit is essential for polarity, motility, and the control of membrane tension. PMID:27280401
Two Surface-Tension Formulations For The Level Set Interface-Tracking Method
International Nuclear Information System (INIS)
The paper describes a comparative study of two surface-tension models for the Level Set interface tracking method. In both models, the surface tension is represented as a body force, concentrated near the interface, but the technical implementation of the two options is different. The first is based on a traditional Level Set approach, in which the surface tension is distributed over a narrow band around the interface using a smoothed Delta function. In the second model, which is based on the integral form of the fluid-flow equations, the force is imposed only in those computational cells through which the interface passes. Both models have been incorporated into the Finite-Element/Finite-Volume Level Set method, previously implemented into the commercial Computational Fluid Dynamics (CFD) code CFX-4. A critical evaluation of the two models, undertaken in the context of four standard Level Set benchmark problems, shows that the first model, based on the smoothed Delta function approach, is the more general, and more robust, of the two. (author)
Whole-Body Reaching Movements Formulated by Minimum Muscle-Tension Change Criterion.
Kudo, Naoki; Choi, Kyuheong; Kagawa, Takahiro; Uno, Yoji
2016-05-01
It is well known that planar reaching movements of the human shoulder and elbow joints have invariant features: roughly straight hand paths and bell-shaped velocity profiles. The optimal control models with the criteria of smoothness or precision, which determine a unique movement pattern, predict such features of hand trajectories. In this letter on expanding the research on simple arm reaching movements, we examine whether the smoothness criteria can be applied to whole-body reaching movements with many degrees of freedom. Determining a suitable joint trajectory in the whole-body reaching movement corresponds to the optimization problem with constraints, since body balance must be maintained during a motion task. First, we measured human joint trajectories and ground reaction forces during whole-body reaching movements, and confirmed that subjects formed similar movements with common characteristics in the trajectories of the hand position and body center of mass. Second, we calculated the optimal trajectories according to the criteria of torque and muscle-tension smoothness. While the minimum torque change trajectories were not consistent with the experimental data, the minimum muscle-tension change model was able to predict the stereotyped features of the measured trajectories. To explore the dominant effects of the extension from the torque change to the muscle-tension change, we introduced a weighted torque change cost function. Considering the maximum voluntary contraction (MVC) force of the muscle as the weighting factor of each joint torque, we formulated the weighted torque change cost as a simplified version of the minimum muscle-tension change cost. The trajectories owing to the minimum weighted torque change criterion also showed qualitative agreement with the common features of the measured data. Proper estimation of the MVC forces in the body joints is essential to reproduce human whole-body movements according to the minimum muscle-tension change
Linking melodic expectation to expressive performance timing and perceived musical tension.
Gingras, Bruno; Pearce, Marcus T; Goodchild, Meghan; Dean, Roger T; Wiggins, Geraint; McAdams, Stephen
2016-04-01
This research explored the relations between the predictability of musical structure, expressive timing in performance, and listeners' perceived musical tension. Studies analyzing the influence of expressive timing on listeners' affective responses have been constrained by the fact that, in most pieces, the notated durations limit performers' interpretive freedom. To circumvent this issue, we focused on the unmeasured prelude, a semi-improvisatory genre without notated durations. In Experiment 1, 12 professional harpsichordists recorded an unmeasured prelude on a harpsichord equipped with a MIDI console. Melodic expectation was assessed using a probabilistic model (IDyOM [Information Dynamics of Music]) whose expectations have been previously shown to match closely those of human listeners. Performance timing information was extracted from the MIDI data using a score-performance matching algorithm. Time-series analyses showed that, in a piece with unspecified note durations, the predictability of melodic structure measurably influenced tempo fluctuations in performance. In Experiment 2, another 10 harpsichordists, 20 nonharpsichordist musicians, and 20 nonmusicians listened to the recordings from Experiment 1 and rated the perceived tension continuously. Granger causality analyses were conducted to investigate predictive relations among melodic expectation, expressive timing, and perceived tension. Although melodic expectation, as modeled by IDyOM, modestly predicted perceived tension for all participant groups, neither of its components, information content or entropy, was Granger causal. In contrast, expressive timing was a strong predictor and was Granger causal. However, because melodic expectation was also predictive of expressive timing, our results outline a complete chain of influence from predictability of melodic structure via expressive performance timing to perceived musical tension. (PsycINFO Database Record PMID:26594881
Directory of Open Access Journals (Sweden)
X. Li
2011-11-01
Full Text Available Atmospheric amino acids constitute an important fraction of the water-soluble organic nitrogen compounds in both marine and continental aerosols, and have been confirmed as effective cloud condensation nuclei materials in laboratory tests. We here present a molecular dynamics study of amino acids representative for the remote marine atmospheric aerosol-cloud system, in order to investigate molecular distributions, orientations and induced changes in surface tension, and to evaluate their indirect effects on optical properties of clouds. These L-amino acids, including serine, glycine, alanine, valine, methionine and phenylalanine, are categorized as hydrophilic and hydrophobic according to their affinities to water. Different amino acids show distinct effects on the surface tension; even the same amino acid has different influence on the surface tension for planar and spherical interfaces. The curvature dependence of the surface tension is modelled by a quadratic polynomial function of the inverse of droplet radius, and such relationship is used to improve the Köhler equation in predicting the critical water vapour supersaturation of the droplet activation.
Mechanical Behavior of BFRP-Steel Composite Plate under Axial Tension
Directory of Open Access Journals (Sweden)
Yunyu Li
2014-06-01
Full Text Available Combining the advantages of basalt fiber-reinforced polymer (BFRP material and steel material, a novel BFRP-steel composite plate (BSP is proposed, where a steel plate is sandwiched between two outer BFRP laminates. The main purpose of this research is to investigate the mechanical behavior of the proposed BSP under uniaxial tension and cyclic tension. Four groups of BSP specimens with four different BFRP layers and one control group of steel plate specimens were prepared. A uniaxial tensile test and a cyclic tensile test were conducted to determine the initial elastic modulus, postyield stiffness, yield strength, ultimate bearing capacity and residual deformation. Test results indicated that the stress-strain curve of the BSP specimen was bilinear prior to the fracture of the outer BFRP, and the BSP specimen had stable postyield stiffness and small residual deformation after the yielding of the inner steel plate. The postyield modulus of BSP specimens increased almost linearly with the increasing number of outer BFRP layers, as well as the ultimate bearing capacity. Moreover, the predicted results from the selected models under both monotonic tension and cyclic tension were in good agreement with the experimental data.
Evolution of melt-vapor surface tension in silicic volcanic systems: Experiments with hydrous melts
Mangan, M.; Sisson, T.
2005-01-01
We evaluate the melt-vapor surface tension (??) of natural, water-saturated dacite melt at 200 MPa, 950-1055??C, and 4.8-5.7 wt % H2O. We experimentally determine the critical supersaturation pressure for bubble nucleation as a function of dissolved water and then solve for ?? at those conditions using classical nucleation theory. The solutions obtained give dacite melt-vapor surface tensions that vary inversely with dissolved water from 0.042 (??0.003) J m-2 at 5.7 wt% H2O to 0.060 (??0.007) J m-2 at 5.2 wt% H2O to 0.073 (??0.003) J m-2 at 4.8 wt% H2O. Combining our dacite results with data from published hydrous haplogranite and high-silica rhyolite experiments reveals that melt-vapor surface tension also varies inversely with the concentration of mafic melt components (e.g., CaO, FeOtotal, MgO). We develop a thermodynamic context for these observations in which melt-vapor surface tension is represented by a balance of work terms controlled by melt structure. Overall, our results suggest that cooling, crystallization, and vapor exsolution cause systematic changes in ?? that should be considered in dynamic modeling of magmatic processes.
The Effect of String Tension Variation on the Perceived Pitch of a Classical Guitar
Directory of Open Access Journals (Sweden)
Wanda Jadwiga Lewis
2014-09-01
Full Text Available Actual motion of a vibrating guitar string is a superposition of many possible shapes (modes in which it could vibrate. Each of these modes has a corresponding frequency, and the lowest frequency is associated with a shape idealised as a single wave, referred to as the fundamental mode. The other contributing modes, each with their own progressively higher frequency, are referred to as overtones, or harmonics. By attaching a string to a medium (a soundboard capable of a response to the vibrating string, sound waves are generated. The sound heard is dominated by the fundamental mode, ‘coloured’ by contributions from the overtones, as explained by the classical theory of vibration. The classical theory, however, assumes that the string tension remains constant during vibration, and this cannot be strictly true; when considering just the fundamental mode, string tension will reach two maximum changes, as it oscillates up and down. These changes, occurring twice during the fundamental period match the frequency of the octave higher, 1st overtone. It is therefore plausible to think that the changing tension effect, through increased force on the bridge and, therefore, greater soundboard deflection, could be amplifying the colouring effect of (at least the 1st overtone.In this paper, we examine the possible influence of string tension variation on tonal response of a classical guitar. We use a perturbation model based on the classical result for a string in general vibration in conjunction with a novel method of assessment of plucking force that incorporates the engineering concept of geometric stiffness, to assess the magnitude of the normal force exerted by the string on the bridge. The results of our model show that the effect of tension variation is significantly smaller than that due to the installed initial static tension, and affects predominantly the force contribution arising from the fundamental mode. We, therefore, conclude that string
Automated wireless monitoring system for cable tension using smart sensors
Sim, Sung-Han; Li, Jian; Jo, Hongki; Park, Jongwoong; Cho, Soojin; Spencer, Billie F.; Yun, Chung-Bang
2013-04-01
Cables are critical load carrying members of cable-stayed bridges; monitoring tension forces of the cables provides valuable information for SHM of the cable-stayed bridges. Monitoring systems for the cable tension can be efficiently realized using wireless smart sensors in conjunction with vibration-based cable tension estimation approaches. This study develops an automated cable tension monitoring system using MEMSIC's Imote2 smart sensors. An embedded data processing strategy is implemented on the Imote2-based wireless sensor network to calculate cable tensions using a vibration-based method, significantly reducing the wireless data transmission and associated power consumption. The autonomous operation of the monitoring system is achieved by AutoMonitor, a high-level coordinator application provided by the Illinois SHM Project Services Toolsuite. The monitoring system also features power harvesting enabled by solar panels attached to each sensor node and AutoMonitor for charging control. The proposed wireless system has been deployed on the Jindo Bridge, a cable-stayed bridge located in South Korea. Tension forces are autonomously monitored for 12 cables in the east, land side of the bridge, proving the validity and potential of the presented tension monitoring system for real-world applications.
Climate-derived tensions in Arctic security.
Energy Technology Data Exchange (ETDEWEB)
Backus, George A.; Strickland, James Hassler
2008-09-01
Globally, there is no lack of security threats. Many of them demand priority engagement and there can never be adequate resources to address all threats. In this context, climate is just another aspect of global security and the Arctic just another region. In light of physical and budgetary constraints, new security needs must be integrated and prioritized with existing ones. This discussion approaches the security impacts of climate from that perspective, starting with the broad security picture and establishing how climate may affect it. This method provides a different view from one that starts with climate and projects it, in isolation, as the source of a hypothetical security burden. That said, the Arctic does appear to present high-priority security challenges. Uncertainty in the timing of an ice-free Arctic affects how quickly it will become a security priority. Uncertainty in the emergent extreme and variable weather conditions will determine the difficulty (cost) of maintaining adequate security (order) in the area. The resolution of sovereignty boundaries affects the ability to enforce security measures, and the U.S. will most probably need a military presence to back-up negotiated sovereignty agreements. Without additional global warming, technology already allows the Arctic to become a strategic link in the global supply chain, possibly with northern Russia as its main hub. Additionally, the multinational corporations reaping the economic bounty may affect security tensions more than nation-states themselves. Countries will depend ever more heavily on the global supply chains. China has particular needs to protect its trade flows. In matters of security, nation-state and multinational-corporate interests will become heavily intertwined.
Institute of Scientific and Technical Information of China (English)
Tae Ho Kim; David W. Fredriksson; Judson DeCew
2012-01-01
A numerical model was used to analyze the motion response and mooring tension of a submerged fish reef system.The system included a net attached to a rigid structure suspended up from the bottom with a single,high tension mooring by fixed flotation.The analysis was performed by using a Morison equation type finite element model configured with truss elements.Input forcing parameters into the model consisted of both regular and irregular waves,with and without a steady current.Heave,surge and pitch dynamic calculations of the reef structure were made.Tension response results of the attached mooring line were also computed.Results were analyzed in both the time and frequency domain in which appropriate,linear transfer functions were calculated.The influence of the current was more evident in the tension and heave motion response data.This is most likely the result of the large buoyancy characteristics of the reef structure and the length of the mooring cable.Maximum mooring component tension was found to be 13.9 kN and occurred when the reef was subjected to irregular waves with a co-linear current of 1.0 m/s velocity.The results also showed that the system had little damping (in heave) with damped natural periods of 2.8 s.This combination of system characteristics promotes a possible resonating situation in typical open sea conditions with similar wave periods.
Research on the fracture behavior of PBX under static tension
Directory of Open Access Journals (Sweden)
Hu Guo
2014-06-01
Full Text Available The fracture behavior of polymer-bonded explosive (PBX seriously affects the safety and reliability of weapon system. The effects of interface debonding and initial meso-damage on the fracture behavior of PBX under quasi-static tension are studied using numerical method. A two-dimensional representative volume element (RVE is established based on Voronoi model in which the component contents could be regulated and the particles are randomly distributed. A nonlinear damage model of polymer matrix relative to matrix depth between particles is constructed. The results show that the simulated strain-stress relation is coincident with experiment data. It is found that interface debonding leads to the nucleation and propagation of meso-cracks, and a main crack approximately perpendicular to the loading direction is generated finally. The interface debonding tends to occur in the interface perpendicular to the loading direction. There seems to be a phenomenon that strain softening and hardening alternatively appear around peak stress of stress and strain curve. It is shown that the initial damages of intragranular and interfacial cracks both decrease the modulus and failure stress, and the main crack tends to propagate toward the initial meso-cracks.
Cyclic Creep Behavior with Hold Time under Tension-Tension Loading Cycles of Grade 91 Steel
International Nuclear Information System (INIS)
Cyclic deformation behavior is very important in practice because the high-temperature structural components are exposed under the cyclic conditions of repeated loading. In the case of static creep (SC), the response of the material is simple as a static state of monotonic loading. However, in the case of cyclic creep (CC), it is complex because of a dynamic loading. So far, cyclic creep data have been rarely reported and it has not been understood well whether the cyclic creep will accelerate or retard the creep rate and creep life compared with static creep, because not only is the plastic deformation under cyclic loading drastically different from that under monotonic loading, but the cyclic creep response is also dependent on the cycling frequency, stress range, stress ratio, and hold period of cycling. Therefore, it is necessary to clarify the cyclic creep behavior influencing the creep deformation and fracture process. The cyclic creep behavior for Gr, 91 steel was investigated from a series of cyclic creep tests which was performed with various hold times and stress ratios under tension-tension loading cycles. The results showed that at the test conditions of the short hold time (HT=1 and 3 min) and higher stress ratios (R=0.90 and 0.95), the cyclic rupture time increased sharply and the creep rate decreased largely
Energy Technology Data Exchange (ETDEWEB)
NONE
2000-04-20
This facility was delivered to Acerinox S.A. (Spain) for surface property improvement, mechanical property improvement and shape correction of bright annealed materials in the end facility of No.3 BAL. Main specifications: (1) Material to be handled: stainless steel sheet (bright annealed cold-rolled steel sheet), (2) Sheet thickness and width: 0.15-2.0mm x 600-1,300mm, (3) Processing speed: 90m/min maximum, (4) Rolling mill: 4 Hi hydraulic depression system, (5) Tension leveler: 6 Hi wet system. Features: (1) Some degree of a flatness only by a skin pass mill through automatic flatness control by work roll bender, 4 Hi skin pass mill with a variable crown backup roll, and shape meter, (2) Stable dead flatness of 0.1% in elongation rate by adding a tension leveler, (3) High-quality bright annealing without any pressed flaw and roll mark by applying an advanced wiper to a skin pass mill, and applying switching control during traveling of welding points to wet leveling and skin pass leveler rolling. (translated by NEDO)
Surface tension driven processes densify and retain permeability in magma and lava
Kennedy, Ben M.; Wadsworth, Fabian B.; Vasseur, Jérémie; Ian Schipper, C.; Mark Jellinek, A.; von Aulock, Felix W.; Hess, Kai-Uwe; Kelly Russell, J.; Lavallée, Yan; Nichols, Alexander R. L.; Dingwell, Donald B.
2016-01-01
We offer new insights into how an explosive eruption can transition into an effusive eruption. Magma containing >0.2 wt% dissolved water has the potential to vesiculate to a porosity in excess of 80 vol.% at atmospheric pressure. Thus all magmas contain volatiles at depth sufficient to form foams and explosively fragment. Yet gas is often lost passively and effusive eruptions ensue. Magmatic foams are permeable and understanding permeability in magma is crucial for models that predict eruptive style. Permeability also governs magma compaction models. Those models generally imply that a reduction in magma porosity and permeability generates an increased propensity for explosivity. Here, our experimental results show that surface tension stresses drive densification without creating an impermeable 'plug', offering an additional explanation of why dense magmas can avoid explosive eruption. In both an open furnace and a closed autoclave, we subject pumice samples with initial porosity of ∼70 vol.% to a range of isostatic pressures (0.1-11 MPa) and temperatures (350-950 °C) relevant to shallow volcanic environments. Our experimental data and models constrain the viscosity, permeability, timescales, and length scales over which densification by pore-scale surface tension stresses competes with density-driven compaction. Where surface tension dominates the dynamics, densification halts at a plateau connected porosity of ∼25 vol.% for our samples. SEM, pycnometry and micro-tomography show that in this process (1) microporous networks are destroyed, (2) the relative pore network surface area decreases, and (3) a remaining crystal framework enhances the longevity of macro-pore connectivity and permeability critical for sustained outgassing. We propose that these observations are a consequence of a surface tension-driven retraction of viscous pore walls at areas of high bubble curvature (micro-vesicular network terminations), and that this process drives bulk
Design of a vapor-liquid-equilibrium, surface tension, and density apparatus
Energy Technology Data Exchange (ETDEWEB)
Holcomb, C.D.; Outcalt, S.L. [National Institute of Standards and Technology, Boulder, CO (United States)
1997-12-31
The design and performance of a unique vapor-liquid equilibrium (VLE) apparatus with density and surface tension capabilities is presented. The apparatus operates at temperatures ranging from 218 to 423 K, at pressures to 17 MPa, at densities to 1100 kg/m{sup 3}, and at surface tensions ranging from 0.1 to 75 mN/m. Temperatures are measured with a precision of {+-}0.02 K, pressures with a precision of {+-}0.1% of full scale, densities with a precision of {+-}0.5 kg/m{sup 3}, surface tensions with a precision of {+-}0.2 mN/m, and compositions with a precision of {+-}0.005 mole fraction. The apparatus is designed to be both accurate and versatile. Capabilities include: (1) the ability to operate the apparatus as a bubble point pressure or an isothermal pressure-volume-temperature (PVT) apparatus, (2) the ability to measure densities and surface tensions of the coexisting phases, and (3) the ability for either trapped or capillary sampling. We can validate our VLE and density data by measuring PVT or bubble point pressures in the apparatus. The use of the apparatus for measurements of VLE, densities, and surface tensions over wide ranges of temperature and pressure is important in equation of state and transport property model development. The use of different sampling procedures allows measurement of a wider variety of fluid mixtures. VLE measurements on the alternative refrigerant system R32/134a are presented and compared to literature results to verify the performance of the apparatus.
The influence of microstructure on surface strain distributions in a nickel micro-tension specimen
International Nuclear Information System (INIS)
This work presents an integrated experimental and modeling approach for examining the deformation of a pure nickel polycrystal utilizing micro-mechanical testing and a crystal-based elasto-viscoplastic finite-element model (CPFEM). The objective is to study the influence of microstructure on the heterogeneous deformation in polycrystalline materials, and to utilize a modeling framework to explore aspects of the deformation that are difficult or impossible to measure experimentally. To accomplish this, a micro-tension specimen containing 259 grains was created from a pure nickel foil material and deformed in uniaxial tension. After the deformation, the specimen was destructively serial sectioned in concert with electron back scattering diffraction, and these data were used to instantiate a CPFEM simulation. The material parameters in the CPFEM model were calibrated by matching the experimental macroscopic stress-strain response of the micro-tension specimen, and then the simulation results were compared with experimental surface deformations measured with digital image correlation. After validating the simulation results by comparing measured and predicted surface strain distributions, a parametric study of the influence of both crystallographic texture and grain morphology is presented to better understand the influence of microstructure on the development of heterogeneous deformation in the pure nickel polycrystalline material. (paper)
Man Singh
2007-01-01
The article presents Inter Facial Tension (IFT) (ift, N m-1) of benzene-water; surface tensions (, N m-1) and viscosities (, N s m-2) of ethanol, glycerol, ethyl acetate, n-hexane, diethyl ether, chloroform, benzene, carbon tetrachloride [CCl4], formic acid, measured with Survismeter with ± 1.1x10-5 N m-1, ± 1.3x10-5 N m-1 and ± 1.1x10-6 N s m-2 accuracies respectively. Also the surface tension and viscosities of carboxymethylcellulose (CMC), dodecylbenzenesulfonicacid (DBSA) and tet...
Kim, Sung Bae; Nishihara, Ryo; Citterio, Daniel; Suzuki, Koji
2016-02-17
Optical imaging of protein-protein interactions (PPIs) facilitates comprehensive elucidation of intracellular molecular events. We demonstrate an optical measure for visualizing molecular tension triggered by any PPI in mammalian cells. Twenty-three kinds of candidate designs were fabricated, in which a full-length artificial luciferase (ALuc) was sandwiched between two model proteins of interest, e.g., FKBP and FRB. One of the designs greatly enhanced the bioluminescence in response to varying concentrations of rapamycin. It is confirmed with negative controls that the elevated bioluminescence is solely motivated from the molecular tension. The probe design was further modified toward eliminating the C-terminal end of ALuc and was found to improve signal-to-background ratios, named "a combinational probe". The utilities were elucidated with detailed substrate selectivity, bioluminescence imaging of live cells, and different PPI models. This study expands capabilities of luciferases as a tool for analyses of molecular dynamics and cell signaling in living subjects. PMID:26322739
Tension density as counter force to the Lorentz force density
Nozaki, Hiroo; Senami, Masato; Ichikawa, Kazuhide; Tachibana, Akitomo
2016-08-01
It is confirmed numerically that the tension density defined in quantum field theory is the counter force to the Lorentz force density. We take benzenedithiol in a nonequilibrium steady state as an example for the numerical demonstration of the balance between these densities. While we use simply a nonequilibrium Green’s function method for a quantum conduction state instead of computations based on quantum field theory, the balance between the tension density and the Lorentz force density can be confirmed. The tension density is free from the relaxation time ansatz and defined as a local quantity. The tension density may give a novel viewpoint to the understanding of the physics of electrical conduction.
Coulomb vs. physical string tension on the lattice
Burgio, G; Reinhardt, H; Vogt, H
2015-01-01
We investigate the precise relationship between the Coulomb and the physical (Wilson) string tension on the lattice, as the former is generally known to give an upper bound for the latter. We give evidence that the two string tensions are in a one to one correspondence at zero temperature, while they become unrelated at finite temperatures. More precisely, we show that the standard lattice calculations of the Coulomb gauge confinement scenario are always tied to the spatial string tension, which is known to survive the deconfinement phase transition and to cause screening effects in the quark-gluon plasma. Our analysis is based on the identification and elimination of center vortices which allows to control the physical string tension and study its effect on the Coulomb gauge observables. We also show how alternative definitions of the Coulomb potential may sense the deconfinement transition, although a true static Coulomb gauge order parameter for the phase transition is still elusive on the lattice.
Stress distribution and fracture behavior of beryllium compact tension specimens
International Nuclear Information System (INIS)
Compact tension specimens of beryllium (Be) were designed to study fracture behavior and mechanical properties. The local stress distribution near a notch in a compact tension specimen was measured in situ by the combination of an X-ray stress analysis and a custom-designed load device. The fracture morphology was observed by scanning electron microscopy. The result showed that the local stresses near the notch tip are much higher than in other areas, and cracking occurs first in that area. The load-crack opening displacement curve of the Be compact tension specimen was obtained, and used to calculate the fracture toughness as 15.7 MPa√m. The compact tension specimen fracture surfaces were mainly characterized by cleavage fracture over three different areas. Cleavage micro-cracks along the basal slip plane were formed at the crack tip, and their growth was controlled by the primary stress after reaching a critical length
Geometric Interpretation of Surface Tension Equilibrium in Superhydrophobic Systems
Directory of Open Access Journals (Sweden)
Michael Nosonovsky
2015-07-01
Full Text Available Surface tension and surface energy are closely related, although not identical concepts. Surface tension is a generalized force; unlike a conventional mechanical force, it is not applied to any particular body or point. Using this notion, we suggest a simple geometric interpretation of the Young, Wenzel, Cassie, Antonoff and Girifalco–Good equations for the equilibrium during wetting. This approach extends the traditional concept of Neumann’s triangle. Substances are presented as points, while tensions are vectors connecting the points, and the equations and inequalities of wetting equilibrium obtain simple geometric meaning with the surface roughness effect interpreted as stretching of corresponding vectors; surface heterogeneity is their linear combination, and contact angle hysteresis is rotation. We discuss energy dissipation mechanisms during wetting due to contact angle hysteresis, the superhydrophobicity and the possible entropic nature of the surface tension.
Tensioned Rollable Ultra-light Solar array System (TRUSS) Project
National Aeronautics and Space Administration — TRUSS is a structurally efficient solar array concept that utilizes a TRAC rollable boom and tension-stiffened structure to exceed the program requirements for very...
The effects of ambient impurities on the surface tension
Directory of Open Access Journals (Sweden)
Ponce-Torres A.
2016-01-01
Full Text Available A liquid bridge is a liquid column held captive between two coaxial and parallel solid disks. It is an excellent test bench where measuring the surface tension. In this paper, we used this fluid configuration to examine experimentally the effects of ambient impurities on the surface tension over time. For this purpose, the liquid bridge equilibrium shape was analyzed when the liquid bridge was surrounded by three environments: the uncontrolled ambient, and both air and argon encapsulated in a small glass cover. Ambient contamination produced a sharp decrease of the surface tension of ultra-pure water. The presence of an anionic surfactant in the free surface of an aqueous solution did not inhibit the action of impurities coming from the ambient. Impurities can influence the dynamical behavior of the free surface in flows dominated by the surface tension. Therefore, a careful control of that influence can be crucial in many applications of fluid mechanics.
The effects of ambient impurities on the surface tension
Ponce-Torres, A.; Vega, E. J.
2016-03-01
A liquid bridge is a liquid column held captive between two coaxial and parallel solid disks. It is an excellent test bench where measuring the surface tension. In this paper, we used this fluid configuration to examine experimentally the effects of ambient impurities on the surface tension over time. For this purpose, the liquid bridge equilibrium shape was analyzed when the liquid bridge was surrounded by three environments: the uncontrolled ambient, and both air and argon encapsulated in a small glass cover. Ambient contamination produced a sharp decrease of the surface tension of ultra-pure water. The presence of an anionic surfactant in the free surface of an aqueous solution did not inhibit the action of impurities coming from the ambient. Impurities can influence the dynamical behavior of the free surface in flows dominated by the surface tension. Therefore, a careful control of that influence can be crucial in many applications of fluid mechanics.
Surface Tension Gradients Induced by Temperature: The Thermal Marangoni Effect
Gugliotti, Marcos; Baptisto, Mauricio S.; Politi, Mario J.
2004-01-01
Surface tensions gradients were generated in a thin liquid film because of the local increase in temperature, for demonstration purposes. This is performed using a simple experiment and allows different alternatives for heat generation to be used.
Surface tension driven shaping of adhesive microfluidic channel walls
DEFF Research Database (Denmark)
Janting, Jakob; Storm, Elisabeth K.; Geschke, Oliver
2005-01-01
The feasibility of making microfluidic channels with different wall geometries using adjacent lines of dispensed adhesive between substrates has been studied. Important parameters for the geometry have been identified to be: surface tension (adhesive / substrates), adhesive viscosity / thixotropy...
Linear dispersive decay estimates for vortex sheets with surface tension
Spirn, Daniel; Wright, J. Douglas
2009-01-01
We consider the amplitude decay for the linearized equations governing irrotational vortex sheets and water waves with surface tension. Using oscillatory integral estimates, we prove that the magnitude of the amplitude decays faster than $t^−1/3$
Softening of edges of solids by surface tension
International Nuclear Information System (INIS)
Surface tension tends to minimize the area of interfaces between pieces of matter in different thermodynamic phases, be they in the solid or the liquid state. This can be relevant for the macroscopic shape of very soft solids and lead to a roughening of initially sharp edges. We calculate this effect for a Neo-Hookean elastic solid, with assumptions corresponding to actual experiments, namely the case where an initially sharp edge is rounded by the effect of surface tension felt when the fluid surrounding the soft solid (and so surface tension) is changed at the solid/liquid boundary. We consider two opposite limits where the analysis can be carried to the end, the one of a shallow angle and the one of a very sharp angle. Both cases yield a discontinuity of curvature in the state with surface tension although the initial state had a discontinuous slope. (paper)
Stability in the Stefan problem with surface tension (I)
Hadzic, Mahir; Guo, Yan
2008-01-01
We develop a high-order energy method to prove asymptotic stability of flat steady surfaces for the Stefan problem with surface tension - also known as the Stefan problem with Gibbs-Thomson correction.
Influence of Surface Tension on Nuclear Collective Properties
Goncharova, N G
2016-01-01
Rigidities of even-even nuclei were estimated and compared with nuclear charge radii. Correlation of maximal nuclear rigidities with minimal values of r0 parameters was revealed. Influence of effective surface tension on nuclear properties was discussed.
Study of necking stability in tension test of zircaloy-2, on range from 170 0 C to 620 0 C
International Nuclear Information System (INIS)
The objective of this work is to study necking behavior of Zircaloy-2 in a tension test in which the temperature range varies from 1700 C to 6200 C by means of a model. This model provides strain rate variations in the beginning of necking and the parameters in the / necking stability. A new parameter Ψ is presented which permits necking / stability description in metals by means of a simple tension test. It is also proceeded a behavioral study of ε versus ε curve after necking formation. (author)
Embedded Structural Tensions in the Organization of Japanese Advertising Production
Moeran, Brian
2009-01-01
This essay examines embedded structural tensions in the organization of Japanese advertising production. Tensions arise from the fact that an advertising campaign, like many other creative products, is produced by motley crews of personnel from both within an agency contracted to carry out the campaign (an account team) and freelance professionals hired to assist in the creative work required (a production team). The structuring of advertising account teams in Japan, Europe ...
Surface tension and related thermodynamic quantities of aqueous electrolyte solutions
Matubayasi, Norihiro
2013-01-01
Surface tension provides a thermodynamic avenue for analyzing systems in equilibrium and formulating phenomenological explanations for the behavior of constituent molecules in the surface region. While there are extensive experimental observations and established ideas regarding desorption of ions from the surfaces of aqueous salt solutions, a more successful discussion of the theory has recently emerged, which allows the quantitative calculation of the distribution of ions in the surface region. Surface Tension and Related Thermodynamic Quantities of Aqueous Electrolyte Solutions provides a d
Pulmonary Surfactant Surface Tension Influences Alveolar Capillary Shape and Oxygenation
Ikegami, Machiko; Weaver, Timothy E.; Grant, Shawn N.; Whitsett, Jeffrey A.
2009-01-01
Alveolar capillaries are located in close proximity to the alveolar epithelium and beneath the surfactant film. We hypothesized that the shape of alveolar capillaries and accompanying oxygenation are influenced by surfactant surface tension in the alveolus. To prove our hypothesis, surfactant surface tension was regulated by conditional expression of surfactant protein (SP)-B in Sftpb−/− mice, thereby inhibiting surface tension–lowering properties of surfactant in vivo within 24 hours after d...
Advanced multi-stud tensioners for Convoy plants
International Nuclear Information System (INIS)
The multiple stud tensioners for the reactor vessels of the new Emsland and Neckarwestheim 2 convoy plants in FR Germany are built to handle 52 reactor pressure vessel studs with an M210X8 thread. They are equipped with two stud turning robots and a total of four stud elongation measuring devices so as to reduce the time taken for multi-stud tensioner operations on the vessel. (author)
Simulation of two-phase flow with varying surface tension.
Lervåg, Karl Yngve
2008-01-01
This thesis is a study on the effects of varying surface tension along an interface separating two fluids. Varying surface tension leads to tangential forces along the interface. This is often called the Marangoni effect. These forces are discussed in detail, and two test cases are considered to analyse the Marangoni effect, and to verify the present implementation. The first test studies steady-state two-phase flow where the fluids are separated with plane interfaces and the flow is driv...
Landau Gauge Fixing on GPUs and String Tension
Cardoso, Nuno; Silva, Paulo J; Oliveira, Orlando
2012-01-01
We explore the performance of CUDA in performing Landau gauge fixing in Lattice SU(3), using the steepest descent method with Fourier acceleration. The code performance was tested in a Tesla C2070, Fermi architecture. We also present a study of the string tension at finite temperature in the confined phase. The string tension is extracted from the color averaged free energy and from the color singlet using Landau gauge fixing.
Landau Gauge Fixing on GPUs and String Tension
Cardoso, Nuno; Bicudo, Pedro; Silva, Paulo J.; Oliveira, Orlando
2012-01-01
We explore the performance of CUDA in performing Landau gauge fixing in Lattice QCD, using the steepest descent method with Fourier acceleration. The code performance was tested in a Tesla C2070, Fermi architecture. We also present a study of the string tension at finite temperature in the confined phase. The string tension is extracted from the color averaged free energy and from the color singlet using Landau gauge fixing.
Tension pneumothorax, is it a really life-threatening condition?
Yoon, Jeong Seob; Choi, Si Young; Suh, Jong Hui; Jeong, Jin Yong; Lee, Bae Young; Park, Yong Gue; Kim, Chi Kyung; Park, Chan Beom
2013-01-01
Background Tension pneumothorax is a life-threatening occurrence that is infrequently the consequence of spontaneous pneumothorax. The aim of this study was to identify the risk factors for the development of tension pneumothorax and its effect on clinical outcomes. Methods We reviewed patients who were admitted with spontaneous pneumothorax between August 1, 2003 and December 31, 2011. Electronic medical records and the radiological findings were reviewed with chest x-ray and high-resolution...
Rising Russian-Western Tensions in the Global Security Context
Institute of Scientific and Technical Information of China (English)
Ji Zhiye
2008-01-01
Tensions between Russia and the West have grown increasingly apparent in recent years. This can be demonstrated in Moscow's ideological confrontations with the West, the intensifying rivalry over military strategic force, the fierce geopolitical confrontation, and grave contentions over energy resources between the two. The author concludes that in short, rising Russia-US tensions can hardly be remedied. It is a matter of political significance that merits careful consideration by the international community.
Human Uterine Wall Tension Trajectories and the Onset of Parturition
Peter Sokolowski; Francis Saison; Warwick Giles; Shaun McGrath; David Smith; Julia Smith; Roger Smith
2010-01-01
Uterine wall tension is thought to be an important determinant of the onset of labor in pregnant women. We characterize human uterine wall tension using ultrasound from the second trimester of pregnancy until parturition and compare preterm, term and twin pregnancies. A total of 320 pregnant women were followed from first antenatal visit to delivery during the period 2000-2004 at the John Hunter Hospital, NSW, Australia. The uterine wall thickness, length, anterior-posterior diameter and tran...
Human uterine wall tension trajectories and the onset of parturition.
Directory of Open Access Journals (Sweden)
Peter Sokolowski
Full Text Available Uterine wall tension is thought to be an important determinant of the onset of labor in pregnant women. We characterize human uterine wall tension using ultrasound from the second trimester of pregnancy until parturition and compare preterm, term and twin pregnancies. A total of 320 pregnant women were followed from first antenatal visit to delivery during the period 2000-2004 at the John Hunter Hospital, NSW, Australia. The uterine wall thickness, length, anterior-posterior diameter and transverse diameter were determined by serial ultrasounds. Subjects were divided into three groups: women with singleton pregnancies and spontaneous labor onset, either preterm or term and women with twin pregnancies. Intrauterine pressure results from the literature were combined with our data to form trajectories for uterine wall thickness, volume and tension for each woman using the prolate ellipsoid method and the groups were compared at 20, 25 and 30 weeks gestation. Uterine wall tension followed an exponential curve, with results increasing throughout pregnancy with the site of maximum tension on the anterior wall. For those delivering preterm, uterine wall thickness was increased P < 0.05 compared with term. For twin pregnancies intrauterine volume was increased compared to singletons (P < 0.001, but wall thickness was not. There was no evidence for increased tension in those delivering preterm or those with twin gestations. These data are not consistent with a role for high uterine wall tension as a causal factor in preterm spontaneous labor in singleton or twin gestations. It seems likely that hormonal differences in multiple gestations are responsible for increased rates of preterm birth in this group rather than increased tension.
The effects of ambient impurities on the surface tension
Ponce-Torres A.; Vega E. J.
2016-01-01
A liquid bridge is a liquid column held captive between two coaxial and parallel solid disks. It is an excellent test bench where measuring the surface tension. In this paper, we used this fluid configuration to examine experimentally the effects of ambient impurities on the surface tension over time. For this purpose, the liquid bridge equilibrium shape was analyzed when the liquid bridge was surrounded by three environments: the uncontrolled ambient, and both air and argon encapsulated in a...
Method for Measuring Changes in Surface Tension on Agar
Weisberg, David S.; Dworkin, Martin
1983-01-01
The surface tension of agar surfaces was determined by measuring the contact angles formed by drops of various hydrophobic liquids on the surface and then calculating the composite surface free energy function by solving a series of simultaneous equations derived from these data. This method was used to measure the change in the surface tension of agar produced by the addition of various concentrations of albumin. The resulting curve was typical of the effect of increasing concentrations of s...
Influence of plasma on surface tension of hydrocarbons
International Nuclear Information System (INIS)
The results of studying of plasma influence on the surface tension of liquid hydrocarbons and distilled water during experiments with corona discharge are presented. The charged particles influence on the surface tension of fluids with different electrical conductivity is demonstrated. Current-voltage characteristics of corona discharge are measured. It is shown that the flow of charged particles leads to fragmentation of liquids with low conductivity into small droplets. The effect of corona discharge on the stearin combustion rate is investigated
Why is surface tension a force parallel to the interface?
Marchand, Antonin; Weijs, Joost H.; Snoeijer, Jacco H.; Andreotti, Bruno
2011-01-01
A paperclip can float on water. Drops of mercury refuse to spread on a surface. These capillary phenomena are macroscopic manifestations of molecular interactions, and can be explained in terms of surface tension. For students, the concept of surface tension is quite challenging since the microscopic intuition is often in conflict with the common macroscopic interpretations. In this paper we address a number of conceptual questions that are often encountered when teaching capillarity. By answ...
Influence of external factors on surface tension of water
International Nuclear Information System (INIS)
The influence of various external factors such as magnetization, electric discharge, electromagnetic irradiation in cantimetric range, air and osone saturation, riching by the metal ions on the surface tension coefficient of water has been experimentally investigated. It has been established that these actions lead to decreasing surface tension coefficient of drinking water. The value of this decreasing considerably has depended on nature and degree of action
Finite time singularities for water waves with surface tension
Castro, Angel; Córdoba, Diego; Fefferman, Charles; Gancedo, Francisco; Gómez-Serrano, Javier
2012-01-01
Here we consider the 2D free boundary incompressible Euler equation with surface tension. We prove that the surface tension does not prevent a finite time splash or splat singularity, i.e. that the curve touches itself either in a point or along an arc. To do so, the main ingredients of the proof are a transformation to desingularize the curve and a priori energy estimates.
Water surface tension modulates the swarming mechanics of Bacillus subtilis
Ke, Wan-Ju; Hsueh, Yi-Huang; Cheng, Yu-Chieh; Wu, Chih-Ching; Liu, Shih-Tung
2015-01-01
Many Bacillus subtilis strains swarm, often forming colonies with tendrils on agar medium. It is known that B. subtilis swarming requires flagella and a biosurfactant, surfactin. In this study, we find that water surface tension plays a role in swarming dynamics. B. subtilis colonies were found to contain water, and when a low amount of surfactin is produced, the water surface tension of the colony restricts expansion, causing bacterial density to rise. The increased density induces a quorum ...
Surface tension of liquid alumina from contactless techniques
International Nuclear Information System (INIS)
Full Text: We report new data on surface tension of liquid alumina from 2300 to 3200 K. Aerodynamic levitation of CO2 laser heated liquid drops allowed contactless measurement of vibration frequencies directly related to surface tension. Consistent data were obtained on drops of various weights ranging from 20 to 160 mg. It was also shown that oxydo-reducing character of the atmosphere does not modify sensible the results. (author)
Zero surface tension limit of viscous surface waves
Tan, Zhong; Wang, Yanjin
2012-01-01
We consider the free boundary problem for a layer of viscous, incompressible fluid in a uniform gravitational field, lying above a rigid bottom and below the atmosphere. For the "semi-small" initial data, we prove the zero surface tension limit of the problem within a local time interval. The unique local strong solution with surface tension is constructed as the limit of a sequence of approximate solutions to a special parabolic regularization. For the small initial data, we prove the global...
Flow-induced dynamic surface tension effects at nanoscale
Lukyanov, A. V.
2010-01-01
The aim of this study is to investigate flow-induced dynamic surface tension effects, similar to the well-known Marangoni phenomena, but solely generated by the nanoscale topography of the substrates. The flow-induced surface tension effects are examined on the basis of a sharp interface theory. It is demonstrated how nanoscale objects placed at the boundary of the flow domain result in the generation of substantial surface forces acting on the bulk flow.
Plastic tension of thin strip with symmetrical cut-outs
Nepershin, Rostislav I.
2016-06-01
Numerical solution of thin strip plane-stress tension with symmetrical cut-outs for Mises rigid-plastic solid is given. Limit plastic state of neck forming along the rigid-plastic boundaries induced by velocity discontinuity is considered. The problem solution can be useful for the material limit plastic formability estimation in the case of biaxial stress tension in complex thin sheet plastic forming technology.
The length–tension curve in muscle depends on lattice spacing
Williams, C. David; Salcedo, Mary K.; Irving, Thomas C.; Regnier, Michael; Daniel, Thomas L.
2013-01-01
Classic interpretations of the striated muscle length–tension curve focus on how force varies with overlap of thin (actin) and thick (myosin) filaments. New models of sarcomere geometry and experiments with skinned synchronous insect flight muscle suggest that changes in the radial distance between the actin and myosin filaments, the filament lattice spacing, are responsible for between 20% and 50% of the change in force seen between sarcomere lengths of 1.4 and 3.4 µm. Thus, lattice spacing ...
Estimating the Sensitivity of Mechanosensitive Ion Channels to Membrane Strain and Tension
Charras, G. T.; Williams, B. A.; Sims, S. M.; Horton, M.A.
2004-01-01
Bone adapts to its environment by a process in which osteoblasts and osteocytes sense applied mechanical strain. One possible pathway for the detection of strain involves mechanosensitive channels and we sought to determine their sensitivity to membrane strain and tension. We used a combination of experimental and computational modeling techniques to gain new insights into cell mechanics and the regulation of mechanosensitive channels. Using patch-clamp electrophysiology combined with video m...
Wu, You; Kharge, Angana Banerjee; Perlman, Carrie E.
2014-01-01
With proteinaceous-liquid flooding of discrete alveoli, a model of the edema pattern in the acute respiratory distress syndrome, lung inflation over expands aerated alveoli adjacent to flooded alveoli. Theoretical considerations suggest that the overexpansion may be proportional to surface tension, T. Yet recent evidence indicates proteinaceous edema liquid may not elevate T. Thus whether the overexpansion is injurious is not known. Here, working in the isolated, perfused rat lung, we quantif...
Bilirubin influence on oxidative lung damage and surfactant surface tension properties
Dani C.; Martelli E.; Tronchin M.; Buonocore G.; Longini M.; Di Filippo A; Giossi M.; Rubaltelli F.F.
2004-01-01
To study the hypothesis that hyperbilirubinemia might reduce in vivo oxidative lung damage while also diminishing lung surfactant surface tension properties during acute lung injury, we performed a randomized study in a rabbit model of acute lung injury. Twenty rabbits were randomized to receive bilirubin or saline intravenously. Acute lung injury was induced by lung lavages with saline. Lung tissue oxidation was evaluated by measuring total hydroperoxide (TH), advanced oxidation protein prod...
Spoke Dimension on the Motion Performance of a Floating Wind Turbine with Tension-Leg Platform
Wang, H. F.; Fan, Y. H.
2016-01-01
The tension-leg platform (TLP) supporting structure is a good choice for floating offshore wind turbines because TLP has superior motion dynamics. This study investigates the effects of TLP spoke dimensions on the motion of a floating offshore wind turbine system (FOWT). Spoke dimension and offshore floating TLP were subjected to irregular wave and wind excitation to evaluate the motion of the FOWT. This research has been divided into two parts: (1) Five models were designed based on differen...
Hydrodynamics and mass transfer in bubble column: Influence of liquid phase surface tension
Chaumat, Hélène; Billet, Anne-Marie; Delmas, Henri
2007-01-01
According to literature, few experiments are performed in organic solvents which are mostly used in commercial gas–liquid reactors. However, it is commonly accepted that data obtained in aqueous solution allow to predict the surface tension effects, and to model the behaviour of organic solvents. In this work, we examine the validity of this approximation. In this objective, the flows observed in two pure media having similar viscosity but different surface tension—respectively, water (ref...
Tension-Enhanced Hydrogen Evolution Reaction on Vanadium Disulfide Monolayer.
Pan, Hui
2016-12-01
Water electrolysis is an efficient way for hydrogen production. Finding efficient, cheap, and eco-friendly electrocatalysts is essential to the development of this technology. In the work, we present a first-principles study on the effects of tension on the hydrogen evolution reaction of a novel electrocatalyst, vanadium disulfide (VS2) monolayer. Two electrocatalytic processes, individual and collective processes, are investigated. We show that the catalytic ability of VS2 monolayer at higher hydrogen coverage can be efficiently improved by escalating tension. We find that the individual process is easier to occur in a wide range of hydrogen coverage and the collective process is possible at a certain hydrogen coverage under the same tension. The best hydrogen evolution reaction with near-zero Gibbs free energy can be achieved by tuning tension. We further show that the change of catalytic activity with tension and hydrogen coverage is induced by the change of free carrier density around the Fermi level, that is, higher carrier density, better catalytic performance. It is expected that tension can be a simple way to improve the catalytic activity, leading to the design of novel electrocatalysts for efficient hydrogen production from water electrolysis. PMID:26924817
Estimating intercellular surface tension by laser-induced cell fusion
International Nuclear Information System (INIS)
Intercellular surface tension is a key variable in understanding cellular mechanics. However, conventional methods are not well suited for measuring the absolute magnitude of intercellular surface tension because these methods require determination of the effective viscosity of the whole cell, a quantity that is difficult to measure. In this study, we present a novel method for estimating the intercellular surface tension at single-cell resolution. This method exploits the cytoplasmic flow that accompanies laser-induced cell fusion when the pressure difference between cells is large. Because the cytoplasmic viscosity can be measured using well-established technology, this method can be used to estimate the absolute magnitudes of tension. We applied this method to two-cell-stage embryos of the nematode Caenorhabditis elegans and estimated the intercellular surface tension to be in the 30–90 µN m−1 range. Our estimate was in close agreement with cell–medium surface tensions measured at single-cell resolution. (communication)
Surface Tension of Alcohols. Data Selection and Recommended Correlations
Mulero, A.; Cachadiña, I.; Sanjuán, E. L.
2015-09-01
In previous papers, we have proposed specific correlations to reproduce the surface tension values for several sets of fluids and for wide ranges of temperatures. In this paper, we focus our attention on alcohols and consider the available data for 152 fluids grouped into five families. We use the most recent versions of the DIPPR and DETHERM databases and also Wohlfarth and Wohlfarth's (1997) book as our main sources of data. In some cases we have also considered new data. All the data have been carefully filtered in order to discard those that are in clear disagreement with most of the available data for the same fluid. In some cases, two or more different data sets versus temperature trends were observed, and where possible we considered only one of these trends. To fit the finally selected data, we used the model currently implemented in National Institute of Standards and Technology's refprop program, calculating two, four, or six adjustable coefficients for each fluid. As a result, we proposed recommended correlations for 147 alcohols, providing mean average percentage deviations below 1.7% for each fluid, with only two exceptions: 1,2-butanediol (2.77%) and benzyl alcohol (3.20%).
Dynamical string tension in string theory with spacetime Weyl invariance
International Nuclear Information System (INIS)
The fundamental string length, which is an essential part of string theory, explicitly breaks scale invariance. However, in field theory we demonstrated recently that the gravitational constant, which is directly related to the string length, can be promoted to a dynamical field if the standard model coupled to gravity (SM+GR) is lifted to a locally scale (Weyl) invariant theory. The higher gauge symmetry reveals previously unknown field patches whose inclusion turn the classically conformally invariant SM+GR into a geodesically complete theory with new cosmological and possibly further physical consequences. In this paper this concept is extended to string theory by showing how it can be ''Weyl lifted'' with a local scale symmetry acting on target space background fields. In this process the string tension (fundamental string length) is promoted to a dynamical field, in agreement with the parallel developments in field theory. We then propose a string theory in a geodesically complete cosmological stringy background which suggests previously unimagined directions in the stringy exploration of the very early universe. (Copyright copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
The current research status of normal tension glaucoma
Directory of Open Access Journals (Sweden)
Mi XS
2014-09-01
Full Text Available Xue-Song Mi,1,2 Ti-Fei Yuan,3,4 Kwok-Fai So2,4,5 1Department of Ophthalmology, The First Affiliated Hospital of Jinan University, Guangzhou, People’s Republic of China; 2Department of Anatomy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, People’s Republic of China; 3School of Psychology, Nanjing Normal University, Nanjing, People’s Republic of China; 4Department of Ophthalmology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, People’s Republic of China; 5GHM Institute of CNS Regeneration, Jinan University, Guangzhou, People’s Republic of China Abstract: Normal tension glaucoma (NTG is a progressive optic neuropathy that mimics primary open-angle glaucoma, but lacks the findings of elevated intraocular pressure or other mitigating factors that can lead to optic neuropathy. The present review summarized the causes, genetics, and mechanisms underlying NTG in both animal models and human patients. We also proposed that the neurovascular unit is a therapeutic target for NTG management. Keywords: aging, genetics, neurovascular unit, primary open-angle glaucoma, treatment
Analysis of Percent Elongation for Ductile Metal in Uniaxial Tension
Institute of Scientific and Technical Information of China (English)
WANG Xue-bin; YANG Mei; JIANG Jian
2005-01-01
Percent elongation of ductile metal in uniaxial tension due to non-homogeneity was analyzed based on gradient-dependent plasticity. Three assumptions are used to get the analytical solution of percent elongation: one is static equilibrium condition in axial direction; another is that plastic volumetric strain is zero in necking zone;the other is that the diameter in unloading zone remains constant after strain localization is initiated. The strain gradient term was introduced into the yield function of classical plastic mechanics to obtain the analytical solution of distributed plastic strain. Integrating the plastic strain and considering the influence of necking on plastic elongation, a one-dimensional analytical solution of percent elongation was proposed. The analytical solution shows that the percent elongation is inversely proportional to the gauge length, and the solution is formally similar to earlier empirical formula proposed by Barba. Comparisons of existing experimental results and present analytical solutions for relation between load and total elongation and for relation between percent elongation and gauge lengthwere carried out and the new mechanical model for percent elongation was verified. Moreover, higher ductility,toughness and heterogeneity can cause much larger percentage elongation, which coincides with usual viewpoints.
Surface tension/thermal mismatch in a self-assembly process
International Nuclear Information System (INIS)
Surface tension is increasingly used for the self-assembly of 3D microstructures. This paper studies the use of a benzocyclobutene (BCB) photo-resist material for the out-of-plane rotation via self-assembly behavior of a silicon micro-part. The literature discusses both surface-tension self-assembly and thermal-mismatch self-assembly, but these two topics are treated separately. Due to its relatively large thermal expansion coefficient, the BCB photo-resist material exhibits both surface-tension and thermal-mismatch effects during self-assembly. Therefore, the residual stresses induced by the self-assembly process on the interface between the melting pad and the microstructure are an issue that needs clarification. In order to quantify the shear stress on the interface, a micro-cantilever test specimen is designed and fabricated by a two-mask self-assembly process using a BSOI wafer and DRIE etching. Two cantilever designs are compared, one having a single section of photo-resist coverage and the other having two sections of photo-resist coverage. The MSC/NASTRAN finite-element method with an interfacial shear-lag model is used to estimate the deflection of the cantilever beam due to residual stresses from surface tension and thermal shrinkage. A clamped-edge-body-rotation model is proposed in order to calibrate measurement results by confocal optical microscopy with numerical results. The interfacial shear between the BCB photo-resist and the silicon structure is found to range from 0.4 to 1.0 MPa due to thermal shrinkage (after soft bake and structure release). The residual stress from surface tension (after material reflow and self-assembly) depends on the thickness of the PR layer and in some cases is twice the residual stress from material mismatch. Finally, a micro-mirror design employing BCB melting pads is presented to verify a self-assembly process powered by both surface tension and thermal mismatch
Energy Technology Data Exchange (ETDEWEB)
Reyes Martinez, Oscar Alfonso
2001-02-01
In this work the problems of the transient overvoltage produced in the components that integrate the synchronous generators installed in industrial systems of medium voltage are approached. The development of a mathematical model in phase components for the synchronous generator is presented. The model includes a current saturation transformer, a system of static excitation and a scheme of grounding by low impedance through an energy cable. In the formulation the effect of the dampening windings is neglected since the interest is only to evaluate the effect of the initial transient overvoltage. Also, symmetry in the phases is considered and the saturation is neglected. The proposed mathematical model was evaluated through cases of simulation using real data of a typical industrial system. Also some tests were conducted in laboratories that, qualitatively, endorse the results obtained by simulation. Two real cases of electrical equipment fault by effect of transient overvoltage in industrial centers in Mexico were analyzed, with generators grounded through high impedance. [Spanish] En este trabajo se aborda la problematica de los sobrevoltajes transitorios producidos en los componentes que integran los generadores sincronos instalados en sistemas industriales de mediana tension. Se presenta el desarrollo de un modelo matematico en componentes de fase para el generador sincrono. El modelo incluye un transformador de corriente saturable, un sistema de excitacion estatica y un esquema de aterrizamiento por baja impedancia a traves de un cable de energia. En la formulacion se desprecia el efecto de los devanados amortiguadores debido a que solo interesa evaluar el efecto del sobrevoltaje transitorio inicial. Asi mismo, se considera simetria en las fases y se desprecia la saturacion. El modelo matematico propuesto fue evaluado a traves de casos de simulacion utilizando datos reales de un sistema industrial tipico. Tambien se realizaron algunas pruebas en laboratorios que
International Nuclear Information System (INIS)
The 'no tension' modeling technique is used to analyze the region near the earth's surface that experiences localized uplift due to the presence of a nuclear waste vault. This technique is particularly appropriate for vaults located in hard rock which generally contains numerous discontinuities near the earth's surface. In conjuction with the no-tension load transfer technique, a method for tracking the strains was incorporated and zones where fissure apertures may open to relieve tensile stresses were determined. These zones are of interest because of the permeability changes that may be expected due to the opening of fissure apertures. The extent of these zones was found to be strongly related to the in-situ stress state
Calculation method of load distribution on pipe threaded connections under tension load
Chen, Shoujun; Gao, Lianxin; An, Qi
2011-06-01
This paper presents a new calculation method that can calculate the load distribution on pipe threaded connections under tension load. On the basis of elastic mechanics, the new method was developed by analyzing each thread tooth, and a new deformation and covariant equation by making a mechanics analysis on each thread tooth was obtained. Compared with the traditional method proposed by the previous references, the new deformation and covariant equation could be used to describe the relation between the previous and the next thread tooth. By applying the new method on the sample of P-110S pipe threaded connection, the obtained results show that the load on thread tooth mainly concentrates on the four or five threads engaged and the middle teeth were not utilized well to bear the loads. The model offers a new way to calculate the loads carried on the thread teeth under tension load.