Carotid bifurcation calcium and correlation with percent stenosis of the internal carotid artery on CT angiography

International Nuclear Information System (INIS)

McKinney, Alexander M.; Casey, Sean O.; Teksam, Mehmet; Truwit, Charles L.; Kieffer, Stephen; Lucato, Leandro T.; Smith, Maurice

2005-01-01

The aim of this paper was to determine the correlation between calcium burden (expressed as a volume) and extent of stenosis of the origin of the internal carotid artery (ICA) by CT angiography (CTA). Previous studies have shown that calcification in the coronary arteries correlates with significant vessel stenosis, and severe calcification (measured by CT) in the carotid siphon correlates with significant (greater than 50% stenosis) as determined angiographically. Sixty-one patients (age range 50-85 years) underwent CT of the neck with intravenous administration of iodinated contrast for a variety of conditions. Images were obtained with a helical multidetector array CT scanner and reviewed on a three-dimensional workstation. A single observer manipulated window and level to segment calcified plaque from vascular enhancement in order to quantify vascular calcium volume (cc) in the region of the bifurcation of the common carotid artery/ICA origin, and to measure the extent of ICA stenosis near the origin. A total of 117 common carotid artery bifurcations were reviewed. A ''significant'' stenosis was defined arbitrarily as >40% (to detect lesions before they become hemodynamically significant) of luminal diameter on CTA using NASCET-like criteria. All ''significant'' stenoses (21 out of 117 carotid bifurcations) had measurable calcium. We found a relatively strong correlation between percent stenosis and the calcium volume (Pearson's r= 0.65, P<0.0001). We also found that there was an even stronger correlation between the square root of the calcium volume and the percent stenosis as measured by CTA (r= 0.77, P<0.0001). Calcium volumes of 0.01, 0.03, 0.06, 0.09 and 0.12 cc were used as thresholds to evaluate for a ''significant'' stenosis. A receiver operating characteristic (ROC) curve demonstrated that thresholds of 0.06 cc (sensitivity 88%, specificity 87%) and 0.03 cc (sensitivity 94%, specificity 76%) generated the best combinations of sensitivity and

Treatment of an Unusual Occurrence of a Complex Left Subclavian Artery/Left Internal Mammary Artery Bifurcation Stenosis in the Setting of Coronary Subclavian Steal Syndrome and Ischemic Left Ventricular Systolic Dysfunction

Directory of Open Access Journals (Sweden)

Michael J. Martinelli

2018-01-01

Full Text Available This case will illustrate the clinical and unique technical challenges, not previously reported, in a patient with a history of progressive left ventricular (LV systolic dysfunction, congestive heart failure (CHF, myocardial infarction (MI, and a complex bifurcation lesion of the left subclavian artery (SA involving the left internal mammary artery (LIMA in the setting of coronary subclavian steal syndrome (CSSS. The approach to this lesion is complicated by significant LIMA involvement requiring intervention directed toward both the SA and the LIMA in the presence of severe LV systolic dysfunction. This clinical scenario necessitates a careful technique, utilizing bifurcation methods similar to those used in coronary intervention.

Thrombosed persistent median artery causing carpal tunnel syndrome associated with bifurcated median nerve: A case report

International Nuclear Information System (INIS)

Salter, M.; Sinha, N. R.; Szmigielski, W.

2011-01-01

Background: Carpal tunnel syndrome is a sporadically occurring abnormality due to compression of median nerve. It is exceedingly rare for it to be caused by thrombosis of persistent median artery. Case Report: A forty two year old female was referred for ultrasound examination due to ongoing wrist pain, not relived by pain killers and mild paraesthesia on the radial side of the hand. High resolution ultrasound and Doppler revealed a thrombosed persistent median artery and associated bifurcated median nerve. The thrombus resolved on treatment with anticoagulants. Conclusions: Ultrasound examination of the wrist when done for patients with carpal tunnel syndrome should preferably include looking for persistent median artery and its patency. (authors)

Tomographic particle image velocimetry investigation of the flow in a modeled human carotid artery bifurcation

Science.gov (United States)

Buchmann, N. A.; Atkinson, C.; Jeremy, M. C.; Soria, J.

2011-04-01

Hemodynamic forces within the human carotid artery are well known to play a key role in the initiation and progression of vascular diseases such as atherosclerosis. The degree and extent of the disease largely depends on the prevailing three-dimensional flow structure and wall shear stress (WSS) distribution. This work presents tomographic PIV (Tomo-PIV) measurements of the flow structure and WSS in a physiologically accurate model of the human carotid artery bifurcation. The vascular geometry is reconstructed from patient-specific data and reproduced in a transparent flow phantom to demonstrate the feasibility of Tomo-PIV in a complex three-dimensional geometry. Tomographic reconstruction is performed with the multiplicative line-of-sight (MLOS) estimation and simultaneous multiplicative algebraic reconstruction (SMART) technique. The implemented methodology is validated by comparing the results with Stereo-PIV measurements in the same facility. Using a steady flow assumption, the measurement error and RMS uncertainty are directly inferred from the measured velocity field. It is shown that the measurement uncertainty increases for increasing light sheet thickness and increasing velocity gradients, which are largest near the vessel walls. For a typical volume depth of 6 mm (or 256 pixel), the analysis indicates that the velocity derived from 3D cross-correlation can be measured within ±2% of the maximum velocity (or ±0.2 pixel) near the center of the vessel and within ±5% (±0.6 pixel) near the vessel wall. The technique is then applied to acquire 3D-3C velocity field data at multiple axial locations within the carotid artery model, which are combined to yield the flow field and WSS in a volume of approximately 26 mm × 27 mm × 60 mm. Shear stress is computed from the velocity gradient tensor and a method for inferring the WSS distribution on the vessel wall is presented. The results indicate the presence of a complex and three-dimensional flow structure, with

Stent impact on the geometry of the carotid bifurcation and the course of the internal carotid artery

International Nuclear Information System (INIS)

Berkefeld, J.; Zanella, F.E.; Rosendahl, H.; Theron, J.G.; Guimaraens, L.; Treggiari-Venzi, M.M.

2002-01-01

A measurement system is proposed to evaluate reconstructive effects of carotid stents on the geometry of the carotid bifurcation and the course of the internal carotid artery. To describe deviations of the stenotic internal carotid artery (ICA) from the extended axis of the common carotid artery (CCA) the CCA-ICA angle is measured between the CCA midaxis and the midaxis of the stenotic ICA segment. Maximal extensions of ICA tortuosities perpendicular to the course of the CCA axis are defined as ICA offset. The measurements were applied to DSA images of 224 carotid stenoses to evaluate variation and correlation between the two parameters. Comparative pre- and post-stent evaluation was performed in two series of 55 and 31 carotid stenoses treated with Wallstents and in a historic control group of 35 stenoses treated with Strecker stents. Straight course of the ICA was associated with low angle and low offset values, whereas tortuous course of the ICA showed larger angle and offset. A moderate linear correlation between the two parameters was found. Corresponding to a straightening of the stented segment, Wallstents reduced mean angle and offset values significantly. In five cases of the second series of Wallstents, transferrals of curves above the distal stent end associated with kinks were observed, and offset remained constant or increased. Strecker stent implantation caused no significant changes of bifurcational geometry. The proposed parameters corresponded to visual aspects of ICA tortuosity and detected reconstructive effects of self-expanding Wallstents on the ICA course. The measurement system may provide a basis for geometric evaluation of different stent types or implantation concepts with the aim: to optimize anatomic recanalization results in tortuous high angle-high offset bifurcations. (orig.)

Efficacy of different types of self-expandable stents in carotid artery stenting for carotid bifurcation stenosis.

Science.gov (United States)

Liu, Ya-min; Qin, Hao; Zhang, Bo; Wang, Yu-jing; Feng, Jun; Wu, Xiang

2016-02-01

Both open and closed loop self-expandable stents were used in carotid artery stenting (CAS) for carotid bifurcation stenosis. We sought to compare the efficacy of two types of stents in CAS. The data of 212 patients treated with CAS (42 and 170 cases implanted with closed and open loop stents, respectively) for carotid bifurcation stenosis and distal filtration protection devices were retrospectively analyzed. Between closed and open loop stents, there were no significant differences in hospitalization duration, NIHSS score before and after the treatment, stenosis at 12th month, and cumulative incidence of primary endpoint events within 30 days or from the 31st day to the 12th month; while there were significant differences in hemodynamic changes and rate of difficulty in recycling distal filtration protection devices. Use of open vs. closed loop stents for carotid bifurcation stenosis seems to be associated with similar incidence of complications, except for greater rate of hemodynamic changes and lower rate of difficulty in recycling the distal filtration protection devices.

3-D flow characterization and shear stress in a stenosed carotid artery bifurcation model using stereoscopic PIV technique.

Science.gov (United States)

Kefayati, Sarah; Poepping, Tamie L

2010-01-01

The carotid artery bifurcation is a common site of atherosclerosis which is a major leading cause of ischemic stroke. The impact of stenosis in the atherosclerotic carotid artery is to disturb the flow pattern and produce regions with high shear rate, turbulence, and recirculation, which are key hemodynamic factors associated with plaque rupture, clot formation, and embolism. In order to characterize the disturbed flow in the stenosed carotid artery, stereoscopic PIV measurements were performed in a transparent model with 50% stenosis under pulsatile flow conditions. Simulated ECG gating of the flowrate waveform provides external triggering required for volumetric reconstruction of the complex flow patterns. Based on the three-component velocity data in the lumen region, volumetric shear-stress patterns were derived.

Spiral blood flow in aorta-renal bifurcation models.

Science.gov (United States)

Javadzadegan, Ashkan; Simmons, Anne; Barber, Tracie

2016-01-01

The presence of a spiral arterial blood flow pattern in humans has been widely accepted. It is believed that this spiral component of the blood flow alters arterial haemodynamics in both positive and negative ways. The purpose of this study was to determine the effect of spiral flow on haemodynamic changes in aorta-renal bifurcations. In this regard, a computational fluid dynamics analysis of pulsatile blood flow was performed in two idealised models of aorta-renal bifurcations with and without flow diverter. The results show that the spirality effect causes a substantial variation in blood velocity distribution, while causing only slight changes in fluid shear stress patterns. The dominant observed effect of spiral flow is on turbulent kinetic energy and flow recirculation zones. As spiral flow intensity increases, the rate of turbulent kinetic energy production decreases, reducing the region of potential damage to red blood cells and endothelial cells. Furthermore, the recirculation zones which form on the cranial sides of the aorta and renal artery shrink in size in the presence of spirality effect; this may lower the rate of atherosclerosis development and progression in the aorta-renal bifurcation. These results indicate that the spiral nature of blood flow has atheroprotective effects in renal arteries and should be taken into consideration in analyses of the aorta and renal arteries.

Anomalous external carotid artery-internal carotid artery anastomosis in two patients with proximal internal carotid arterial remnants

Energy Technology Data Exchange (ETDEWEB)

Kim, Chang Hun [Dept. of Neurology, Stroke Center, Myongji Hospital, Goyang (Korea, Republic of); Cho, Young Dae; Kang, Hyun Seung; Kim, Jeong Eun; Han, Moon Hee [Seoul National University Hospital, Seoul National University College of Medicine, Seoul (Korea, Republic of); Jung, Seung Chai [Dept. of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul (Korea, Republic of); Ahn, Jun Hyong [Dept. of Neurosurgery, Hallym University Sacred Heart Hospital, Hallym University College of Medicine, Anyang (Korea, Republic of)

2015-08-15

Two angiographic instances of anomalous external carotid artery (ECA) and internal carotid artery (ICA) anastomosis are described, each occurring at the C2-3 level and bearing remnants of proximal ICA. The ICA remnant of one patient (identifiable immediately upon bifurcation of the common carotid artery) was hypoplastic, and that of the other patient was an occluded arterial stump. These features are not typical of non-bifurcating ICA. The occipital artery originated from an anomalous connection in one instance and from the main trunk of the ECA (just past the ECA-ICA connection) in the other.

A numerical investigation of the functionality of coronary bifurcation lesions with respect to lesion configuration and stenosis severity.

Science.gov (United States)

Pagiatakis, Catherine; Tardif, Jean-Claude; L'Allier, Philippe L; Mongrain, Rosaire

2015-09-18

The intervention of coronary bifurcation lesions is associated with higher rates of peri- and post-procedural clinical events compared to the treatment of isolated lesions. Overall, the factors that influence the dynamics of these types of configurations are still not well understood. A geometric multiscale model, consisting of a 3D representation of the left main coronary artery bifurcation and a 0D representation of the rest of the cardiovascular system, was developed. Computational fluid dynamics simulations of the 3D domain were executed by implementing the multiscale algorithm, in order to characterize the functionality of different multilesional configurations as a function of stenosis severity. The investigation found that coronary branch steal has a significant impact on the functionality of the disease and can render a two-lesion configuration more severe compared to a three-lesion configuration. As a result of the complexity of this phenomenon, it was also suggested that certain lesion configurations could result in false negatives in diagnosis when employing a pullback pressure recording across the tandem lesions. In conclusion, this study showed that coronary bifurcation lesions are subject to intricate haemodynamic interactions which render the characterization of their functionality complex and could have significant clinical implications with regards to their diagnosis and prognosis. Copyright © 2015 Elsevier Ltd. All rights reserved.

Flow studies in canine artery bifurcations using a numerical simulation method.

Science.gov (United States)

Xu, X Y; Collins, M W; Jones, C J

1992-11-01

Three-dimensional flows through canine femoral bifurcation models were predicted under physiological flow conditions by solving numerically the time-dependent three-dimensional Navier-stokes equations. In the calculations, two models were assumed for the blood, those of (a) a Newtonian fluid, and (b) a non-Newtonian fluid obeying the power law. The blood vessel wall was assumed to be rigid this being the only approximation to the prediction model. The numerical procedure utilized a finite volume approach on a finite element mesh to discretize the equations, and the code used (ASTEC) incorporated the SIMPLE velocity-pressure algorithm in performing the calculations. The predicted velocity profiles were in good qualitative agreement with the in vivo measurements recently obtained by Jones et al. The non-Newtonian effects on the bifurcation flow field were also investigated, and no great differences in velocity profiles were observed. This indicated that the non-Newtonian characteristics of the blood might not be an important factor in determining the general flow patterns for these bifurcations, but could have local significance. Current work involves modeling wall distensibility in an empirically valid manner. Predictions accommodating these will permit a true quantitative comparison with experiment.

Renal denervation beyond the bifurcation: The effect of distal ablation placement on safety and blood pressure.

Science.gov (United States)

Beeftink, Martine M A; Spiering, Wilko; De Jong, Mark R; Doevendans, Pieter A; Blankestijn, Peter J; Elvan, Arif; Heeg, Jan-Evert; Bots, Michiel L; Voskuil, Michiel

2017-04-01

Renal denervation may be more effective if performed distal in the renal artery because of smaller distances between the lumen and perivascular nerves. The authors reviewed the angiographic results of 97 patients and compared blood pressure reduction in relation to the location of the denervation. No significant differences in blood pressure reduction or complications were found between patient groups divided according to their spatial distribution of the ablations (proximal to the bifurcation in both arteries, distal to the bifurcation in one artery and distal in the other artery, or distal to the bifurcation in both arteries), but systolic ambulatory blood pressure reduction was significantly related to the number of distal ablations. No differences in adverse events were observed. In conclusion, we found no reason to believe that renal denervation distal to the bifurcation poses additional risks over the currently advised approach of proximal denervation, but improved efficacy remains to be conclusively established. ©2017 Wiley Periodicals, Inc.

Small-bubble transport and splitting dynamics in a symmetric bifurcation

KAUST Repository

Qamar, Adnan

2017-06-28

Simulations of small bubbles traveling through symmetric bifurcations are conducted to garner information pertinent to gas embolotherapy, a potential cancer treatment. Gas embolotherapy procedures use intra-arterial bubbles to occlude tumor blood supply. As bubbles pass through bifurcations in the blood stream nonhomogeneous splitting and undesirable bioeffects may occur. To aid development of gas embolotherapy techniques, a volume of fluid method is used to model the splitting process of gas bubbles passing through artery and arteriole bifurcations. The model reproduces the variety of splitting behaviors observed experimentally, including the bubble reversal phenomenon. Splitting homogeneity and maximum shear stress along the vessel walls is predicted over a variety of physical parameters. Small bubbles, having initial length less than twice the vessel diameter, were found unlikely to split in the presence of gravitational asymmetry. Maximum shear stresses were found to decrease exponentially with increasing Reynolds number. Vortex-induced shearing near the bifurcation is identified as a possible mechanism for endothelial cell damage.

Small-bubble transport and splitting dynamics in a symmetric bifurcation.

Science.gov (United States)

Qamar, Adnan; Warnez, Matthew; Valassis, Doug T; Guetzko, Megan E; Bull, Joseph L

2017-08-01

Simulations of small bubbles traveling through symmetric bifurcations are conducted to garner information pertinent to gas embolotherapy, a potential cancer treatment. Gas embolotherapy procedures use intra-arterial bubbles to occlude tumor blood supply. As bubbles pass through bifurcations in the blood stream nonhomogeneous splitting and undesirable bioeffects may occur. To aid development of gas embolotherapy techniques, a volume of fluid method is used to model the splitting process of gas bubbles passing through artery and arteriole bifurcations. The model reproduces the variety of splitting behaviors observed experimentally, including the bubble reversal phenomenon. Splitting homogeneity and maximum shear stress along the vessel walls is predicted over a variety of physical parameters. Small bubbles, having initial length less than twice the vessel diameter, were found unlikely to split in the presence of gravitational asymmetry. Maximum shear stresses were found to decrease exponentially with increasing Reynolds number. Vortex-induced shearing near the bifurcation is identified as a possible mechanism for endothelial cell damage.

Small-bubble transport and splitting dynamics in a symmetric bifurcation

KAUST Repository

Qamar, Adnan; Warnez, Matthew; Valassis, Doug T.; Guetzko, Megan E.; Bull, Joseph L.

2017-01-01

Simulations of small bubbles traveling through symmetric bifurcations are conducted to garner information pertinent to gas embolotherapy, a potential cancer treatment. Gas embolotherapy procedures use intra-arterial bubbles to occlude tumor blood supply. As bubbles pass through bifurcations in the blood stream nonhomogeneous splitting and undesirable bioeffects may occur. To aid development of gas embolotherapy techniques, a volume of fluid method is used to model the splitting process of gas bubbles passing through artery and arteriole bifurcations. The model reproduces the variety of splitting behaviors observed experimentally, including the bubble reversal phenomenon. Splitting homogeneity and maximum shear stress along the vessel walls is predicted over a variety of physical parameters. Small bubbles, having initial length less than twice the vessel diameter, were found unlikely to split in the presence of gravitational asymmetry. Maximum shear stresses were found to decrease exponentially with increasing Reynolds number. Vortex-induced shearing near the bifurcation is identified as a possible mechanism for endothelial cell damage.

Perigraft Plug Embolization of the Internal Iliac Artery and Implantation of a Bifurcated Stentgraft: One Treatment Option for Insufficient Tubular Stentgraft Repair of a Common Iliac Artery Aneurysm

Energy Technology Data Exchange (ETDEWEB)

Goltz, Jan Peter, E-mail: janpeter.goltz@uksh.de; Loesaus, Julia; Frydrychowicz, Alex; Barkhausen, Jörg [University Hospital of Schleswig-Holstein, Department for Radiology and Nuclear Medicine (Germany); Wiedner, Marcus [University Hospital of Schleswig-Holstein, Clinic for Surgery (Germany)

2016-02-15

We report an endovascular technique for the treatment of type Ia endoleak after a plain tubular stentgraft had been implanted for a large common iliac artery aneurysm with an insufficient proximal landing zone and without occlusion of the hypogastric in another hospital. CT follow-up showed an endoleak with continuous sac expansion over 12 months. This was classified as type Ia by means of dynamic contrast-enhanced MRI. Before a bifurcated stentgraft was implanted to relocate the landing zone more proximally, the still perfused ipsilateral hypogastric artery was embolized to prevent a type II endoleak. A guidewire was manipulated alongside the indwelling stentgraft. The internal iliac artery could then be selectively intubated followed by successful plug embolization of the vessel’s orifice despite the stentgraft being in place.

Does the principle of minimum work apply at the carotid bifurcation: a retrospective cohort study

International Nuclear Information System (INIS)

Beare, Richard J; Das, Gita; Ren, Mandy; Chong, Winston; Sinnott, Matthew D; Hilton, James E; Srikanth, Velandai; Phan, Thanh G

2011-01-01

There is recent interest in the role of carotid bifurcation anatomy, geometry and hemodynamic factors in the pathogenesis of carotid artery atherosclerosis. Certain anatomical and geometric configurations at the carotid bifurcation have been linked to disturbed flow. It has been proposed that vascular dimensions are selected to minimize energy required to maintain blood flow, and that this occurs when an exponent of 3 relates the radii of parent and daughter arteries. We evaluate whether the dimensions of bifurcation of the extracranial carotid artery follow this principle of minimum work. This study involved subjects who had computed tomographic angiography (CTA) at our institution between 2006 and 2007. Radii of the common, internal and external carotid arteries were determined. The exponent was determined for individual bifurcations using numerical methods and for the sample using nonlinear regression. Mean age for 45 participants was 56.9 ± 16.5 years with 26 males. Prevalence of vascular risk factors was: hypertension-48%, smoking-23%, diabetes-16.7%, hyperlipidemia-51%, ischemic heart disease-18.7%. The value of the exponent ranged from 1.3 to 1.6, depending on estimation methodology. The principle of minimum work (defined by an exponent of 3) may not apply at the carotid bifurcation. Additional factors may play a role in the relationship between the radii of the parent and daughter vessels

Hybrid treatment of tandem, common carotid/innominate artery and ipsilateral carotid bifurcation stenoses by simultaneous, retrograde proximal stenting and eversion carotid endarterectomy: Preliminary results of a case series.

Science.gov (United States)

Illuminati, Giulio; Pizzardi, Giulia; Pasqua, Rocco; Frezzotti, Francesca; Palumbo, Piergaspare; Macrina, Francesco; Calio', Francesco

2018-04-01

Tandem stenoses of the internal carotid artery (ICA) and proximal, ipsilateral common carotid artery (CCA) or innominate artery can be treated with a hybrid approach, combining conventional carotid endarterectomy (CEA) and retrograde stenting of the proximal stenosis, through surgical exposure of the carotid bifurcation. The purpose of this study was to evaluate the results of combining eversion CEA with retrograde CCA/innominate artery stenting. From January 2015 to July 2017, 7 patients, 6 men of a mean age of 72 years (range 59-83 years) underwent simultaneous, retrograde stenting of the proximal CCA/innominate artery and an eversion CEA of the ipsilateral ICA, through surgical exposure of the carotid bifurcation, for severe tandem stenoses. The proximal stenosis involved the left proximal CCA in 4 patients, the proximal innominate artery in 2 patients and the right CCA in one patient. The procedure was performed under general anesthesia in a conventional operating room equipped with a mobile C-arm. A covered, balloon expandable stent was deployed over the proximal stenosis via a 6-F sheath directly introduced into the proximal CCA through the obliquely transected carotid bulb. After removing the sheath, debris were flushed through the carotid bulb and eversion CEA completed the procedure. Study endpoints were: postoperative stroke/mortality rate, cardiac mortality and morbidity, peripheral nerve injury, cervical hematoma, overall late survival, freedom from ipsilateral stroke and patency of arterial reconstruction. No postoperative mortality or neurologic morbidity was observed in any patient. Cervical hematomas and peripheral nerve injuries were likewise absent. At a mean follow-up of 18 months, all the patients were alive, free from neurologic events of new onset and free from restenosis. Combined proximal stenting and eversion CEA for tandem lesions seems a valid treatment, with the advantages of eversion CEA over other techniques of carotid bifurcation

Computational fluid dynamics comparisons of wall shear stress in patient-specific coronary artery bifurcation using coronary angiography and optical coherence tomography

Science.gov (United States)

Poon, Eric; Thondapu, Vikas; Chin, Cheng; Scheerlinck, Cedric; Zahtila, Tony; Mamon, Chris; Nguyen, Wilson; Ooi, Andrew; Barlis, Peter

2016-11-01

Blood flow dynamics directly influence biology of the arterial wall, and are closely linked with the development of coronary artery disease. Computational fluid dynamics (CFD) solvers may be employed to analyze the hemodynamic environment in patient-specific reconstructions of coronary arteries. Although coronary X-ray angiography (CA) is the most common medical imaging modality for 3D arterial reconstruction, models reconstructed from CA assume a circular or elliptical cross-sectional area. This limitation can be overcome with a reconstruction technique fusing CA with intravascular optical coherence tomography (OCT). OCT scans the interior of an artery using near-infrared light, achieving a 10-micron resolution and providing unprecedented detail of vessel geometry. We compared 3D coronary artery bifurcation models generated using CA alone versus OCT-angiography fusion. The model reconstructed from CA alone is unable to identify the detailed geometrical variations of diseased arteries, and also under-estimates the cross-sectional vessel area compared to OCT-angiography fusion. CFD was performed in both models under pulsatile flow in order to identify and compare regions of low wall shear stress, a hemodynamic parameter directly linked with progression of atherosclerosis. Supported by ARC LP150100233 and VLSCI VR0210.

Topography of the accessory left gastric artery (ALGA) analyzed by CT angiography from the left hepatic artery

International Nuclear Information System (INIS)

Shioyama, Yasukazu; Takasaka, Isao; Onaya, Hiroaki

2003-01-01

To avoid gastric complications when we perform transcatheter treatment via left hepatic artery, we analyzed the topography of ALGA (accessory left gastric artery) by left hepatic arteriography and CT angiography from left hepatic artery. Six hundred seventy eight cases of CT angiography were performed between 1995 and 2000. Among them, selective left hepatic arteriography was done in 85 cases. We analyzed the frequency and the course of ALGA on the hepatic angiogram and CT angiogram. ALGA were identified in eighteen (21.2 %) of the 85 cases. We classified them into eleven cases of the proximal type and six cases of the distal type. When ALGA bifurcated from the left hepatic artery very close to the bifurcation of A2 (dorsolateral branch) and A3 (ventrolateral branch), we classified them as the distal type on hepatic angiogram. On the other hand, when ALGA bifurcated from the left hepatic artery apart from the bifurcation of A2 and A3 they were classified as the proximal type. In one rare case ALGA originated from the dorsolateral branch of the left hepatic artery. ALGA were classified as the distal and proximal types. Distal type of ALGA often overlapped dorsolateral branch of the left hepatic artery, and it was sometimes difficult to notice the existence of them. We should check the existence of ALGA on the arterial phase of dynamic CT before we plan to make a transcatheter treatment from the left hepatic artery. Then we can avoid gastric complications caused by a transcatheter treatment from the left hepatic artery. (author)

Experimental Investigation of Bifurcations in a Thermoacoustic Engine

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Vishnu R. Unni

2015-06-01

Full Text Available In this study, variation in the characteristics of the pressure oscillations in a thermoacoustic engine is explored as the input heat flux is varied. A bifurcation diagram is plotted to study the variation in the qualitative behavior of the acoustic oscillations as the input heat flux changes. At a critical input heat flux (60 Watt, the engine begins to produce acoustic oscillations in its fundamental longitudinal mode. As the input heat flux is increased, incommensurate frequencies appear in the power spectrum. The simultaneous presence of incommensurate frequencies results in quasiperiodic oscillations. On further increase of heat flux, the fundamental mode disappears and second mode oscillations are observed. These bifurcations in the characteristics of the pressure oscillations are the result of nonlinear interaction between multiple modes present in the thermoacoustic engine. Hysteresis in the bifurcation diagram suggests that the bifurcation is subcritical. Further, the qualitative analysis of different dynamic regimes is performed using nonlinear time series analysis. The physical reason for the observed nonlinear behavior is discussed. Suggestions to avert the variations in qualitative behavior of the pressure oscillations in thermoacoustic engines are also provided.

Investigation of blood flow rheology using second-grade viscoelastic model (Phan-Thien-Tanner) within carotid artery.

Science.gov (United States)

Ramiar, Abas; Larimi, Morsal Momenti; Ranjbar, Ali Akbar

2017-01-01

Hemodynamic factors, such as Wall Shear Stress (WSS), play a substantial role in arterial diseases. In the larger arteries, such as the carotid artery, interaction between the vessel wall and blood flow affects the distribution of hemodynamic factors. The fluid is considered to be non-Newtonian, whose flow is governed by the equation of a second-grade viscoelastic fluid and the effects of viscoelastic on blood flow in carotid artery is investigated. Pulsatile flow studies were carried out in a 3D model of carotid artery. The governing equations were solved using finite volume C++ based on open source code, OpenFOAM. To describe blood flow, conservation of mass and momentum, a constitutive relation of simplified Phan-Thien-Tanner (sPTT), and appropriate relations were used to explain shear thinning behavior. The first recirculation was observed at t = 0.2 s, in deceleration phase. In the acceleration phase from t = 0.3 s to t = 0.5 s, vortex and recirculation sizes in bulb regions in both ECA and ICA gradually increased. As is observed in the line graphs based on extracted data from ICA, at t = 0.2 s, τyy is the maximum amount of wall shear stress and τxy the minimum one. The maximum shear stress occurred in the inner side of the main branch (inner side of ICA and ECA) because the velocity of blood flow in the inner side of the bulb region was maximum due to the created recirculation zone in the opposite side in this area. The rheology of blood flow and shear stress in various important parts (the area that are in higher rates of WSS such as bifurcation region and the regions after bulb areas in both branches, Line1-4 in Fig. 7) were also analyzed. The investigation of velocity stream line, velocity profile and shear stress in various sections of carotid artery showed that the maximum shear stress occurred in acceleration phase and in the bifurcation region between ECA and ICA which is due to velocity gradients and changes in thinning behavior of blood and

Percutaneous coronary intervention for the left main stem and other bifurcation lesions: 12th consensus document from the European Bifurcation Club.

Science.gov (United States)

Lassen, Jens Flensted; Burzotta, Francesco; Banning, Adrian P; Lefèvre, Thierry; Darremont, Olivier; Hildick-Smith, David; Chieffo, Alaide; Pan, Manuel; Holm, Niels Ramsing; Louvard, Yves; Stankovic, Goran

2018-01-20

The European Bifurcation Club (EBC) was initiated in 2004 to support a continuous overview of the field of coronary artery bifurcation interventions and aims to facilitate a scientific discussion and an exchange of ideas on the management of bifurcation disease. The EBC hosts an annual, two-day compact meeting, dedicated to bifurcations, which brings together physicians, pathologists, engineers, biologists, physicists, mathematicians, epidemiologists and statisticians for detailed discussions. Every meeting is finalised with a consensus statement that reflects the unique opportunity of combining the opinion of interventional cardiologists with the opinion of a large variety of other scientists on bifurcation management. A series of consensus sessions dedicated to specific topics, to strengthen the consensus debates and focus the discussions, was introduced at this year's meeting. The sessions comprise an intensive overview of the present literature, a pro and con debate and a voting system, to guide the consensus-building process. The present document represents the summary of the up-to-date EBC consensus and recommendations from the 12th annual EBC meeting in 2016 in Rotterdam.

Hybrid treatment of bullet embolism at the abdominal aortic bifurcation, complicated with thoracoabdominal aorta pseudoaneurysm and common iliac artery occlusion: case report

Directory of Open Access Journals (Sweden)

Patrick Bastos Metzger

2014-03-01

Full Text Available Embolization due to a firearm projectile entering the bloodstream is a rare event that is unlikely to be suspected during initial treatment of trauma patients. We describe and discuss a case of bullet embolism of the abdominal aortic bifurcation, complicated by a pseudoaneurysm of the thoracoabdominal aorta and occlusion of the right common iliac artery, but successfully treated using a combination of endovascular methods and conventional surgery.

Inverse parameter identification for a branching 1 D arterial network

CSIR Research Space (South Africa)

Bogaers, Alfred EJ

2012-07-01

Full Text Available In this paper we investigate the invertability of a branching 1 D arterial blood flow network. We limit our investigation to a single bifurcating vessel, where the material properties, unloaded areas and variables characterizing the input and output...

Clip reconstruction of a large right MCA bifurcation aneurysm. Case report

Directory of Open Access Journals (Sweden)

Giovani A.

2014-06-01

Full Text Available We report a case of complex large middle cerebral artery (MCA bifurcation aneurysm that ruptured during dissection from the very adherent MCA branches but was successfully clipped and the MCA bifurcation reconstructed using 4 Yasargill clips. Through a right pterional craniotomy the sylvian fissure was largely opened as to allow enough workspace for clipping the aneurysm and placing a temporary clip on M1. The pacient recovered very well after surgery and was discharged after 1 week with no neurological deficit. Complex MCA bifurcation aneurysms can be safely reconstructed using regular clips, without the need of using fenestrated clips or complex by-pass procedures.

Long-Term Results After Simple Versus Complex Stenting of Coronary Artery Bifurcation Lesions Nordic Bifurcation Study 5-Year Follow-Up Results

DEFF Research Database (Denmark)

Maeng, M.; Holm, N. R.; Erglis, A.

2013-01-01

Objectives This study sought to report the 5-year follow-up results of the Nordic Bifurcation Study. Background Randomized clinical trials with short-term follow-up have indicated that coronary bifurcation lesions may be optimally treated using the optional side branch stenting strategy. Methods...... complex strategy of planned stenting of both the main vessel and the side branch. (C) 2013 by the American College of Cardiology Foundation...

Variations in the origins of the thyroid arteries on CT angiography.

Science.gov (United States)

Esen, Kaan; Ozgur, Anil; Balci, Yuksel; Tok, Sermin; Kara, Engin

2018-02-01

To investigate the anatomical variations in the origins of the thyroid arteries on CT angiography images. The presence and the origins of the superior thyroid artery, the inferior thyroid artery, and the thyroidea ima artery were retrospectively evaluated based on carotid CT angiography examinations. The bifurcation level of the common carotid artery with respect to the cervical vertebrae and disc spaces was also determined. A total of 640 patients were included in the study. The right and left superior thyroid arteries arose from the external carotid artery in 413 (64.5%) and 254 (39.7%) patients, from the bifurcation of the common carotid artery in 131 (20.5%) and 148 (23.1%) patients, and from the common carotid artery in 90 (14.1%) and 226 (35.3%) patients, respectively. We could not observe the right and the left superior thyroid arteries in 6 (0.9%) and 12 (1.9%) of the patients, respectively. However, the right and left inferior thyroid arteries were not identified in 14 (2.2%) and 45 (7%) of the patients, respectively. The thyroidea ima artery was detected in 2.3% of the patients. The visualization of thyroid arteries on CT angiography images enables the anatomy of the arterial supply system of the thyroid gland to be explored in a noninvasive manner prior to surgery.

Variations in superior thyroid artery: A selective angiographic study

International Nuclear Information System (INIS)

Gupta, Pankaj; Bhalla, Ashu Seith; Thulkar, Sanjay; Kumar, Atin; Mohanti, Bidhu Kalyan; Thakar, Alok; Sharma, Atul

2014-01-01

To investigate variations in superior thyroid artery (STA) based on digital subtraction angiography (DSA). Twenty five angiography studies of 15 pts performed between June 2010 and December 2012 were retrospectively evaluated. These patients underwent DSA of the head and neck region as a part of their superselective neoadjuvant intra-arterial chemotherapy protocol for treatment of laryngeal and hypopharyngeal cancers. Depending upon the location of the tumor, unilateral or bilateral arteriograms of common carotid artery (CCA), external carotid artery (ECA), and STA were performed. Arteriograms were evaluated for the site of origin and branching pattern of STA. STA anatomy was ascribed to one of the three branching patterns. A total of 25 angiograms were evaluated, including 14 right and 11 left. On the right side, STA was noted to arise from ECA in 10 (71.5%), bifurcation of CCA in 3 (21.5%), and CCA in 1 (7%) patient. Left STA was seen to arise from ECA in 8 (72.5%), bifurcation of CCA in 2 (18.5%), and internal carotid artery (ICA) in 1 (9%) patient. Type III branching pattern (non-bifurcation, non-trifurcation) was found to be the most frequent (52%). Infrahyoid branch was found to be the most consistent in terms of its origin from STA. Origin of STA is predictable, arising from ECA in more than 70% cases. Branching pattern of STA, following origin from ECA, is, however, highly variable. Knowledge concerning the origin and branching pattern of STA is essential in enhancing precision and decreasing morbidity related to the surgical and interventional radiological head and neck procedures

Effect of aorto-iliac bifurcation and iliac stenosis on flow dynamics in an abdominal aortic aneurysm

Science.gov (United States)

Patel, Shivam; Usmani, Abdullah Y.; Muralidhar, K.

2017-06-01

Physiological flows in rigid diseased arterial flow phantoms emulating an abdominal aortic aneurysm (AAA) under rest conditions with aorto-iliac bifurcation and iliac stenosis are examined in vitro through 2D PIV measurements. Flow characteristics are first established in the model resembling a symmetric AAA with a straight outlet tube. The influence of aorto-iliac bifurcation and iliac stenosis on AAA flow dynamics is then explored through a comparison of the nature of flow patterns, vorticity evolution, vortex core trajectory and hemodynamic factors against the reference configuration. Specifically, wall shear stress and oscillatory shear index in the bulge portion of the models are of interest. The results of this investigation indicate overall phenomenological similarity in AAA flow patterns across the models. The pattern is characterized by a central jet and wall-bounded vortices whose strength increases during the deceleration phase as it moves forward. The central jet impacts the wall of AAA at its distal end. In the presence of an aorto-iliac bifurcation as well as iliac stenosis, the flow patterns show diminished strength, expanse and speed of propagation of the primary vortices. The positions of the instantaneous vortex cores, determined using the Q-function, correlate with flow separation in the bulge, flow resistance due to a bifurcation, and the break in symmetry introduced by a stenosis in one of the legs of the model. Time-averaged WSS in a healthy aorta is around 0.70 N m-2 and is lowered to the range ±0.2 N m-2 in the presence of the downstream bifurcation with a stenosed common iliac artery. The consequence of changes in the flow pattern within the aneurysm on disease progression is discussed.

Effect of aorto-iliac bifurcation and iliac stenosis on flow dynamics in an abdominal aortic aneurysm

International Nuclear Information System (INIS)

Patel, Shivam; Usmani, Abdullah Y; Muralidhar, K

2017-01-01

Physiological flows in rigid diseased arterial flow phantoms emulating an abdominal aortic aneurysm (AAA) under rest conditions with aorto-iliac bifurcation and iliac stenosis are examined in vitro through 2D PIV measurements. Flow characteristics are first established in the model resembling a symmetric AAA with a straight outlet tube. The influence of aorto-iliac bifurcation and iliac stenosis on AAA flow dynamics is then explored through a comparison of the nature of flow patterns, vorticity evolution, vortex core trajectory and hemodynamic factors against the reference configuration. Specifically, wall shear stress and oscillatory shear index in the bulge portion of the models are of interest. The results of this investigation indicate overall phenomenological similarity in AAA flow patterns across the models. The pattern is characterized by a central jet and wall-bounded vortices whose strength increases during the deceleration phase as it moves forward. The central jet impacts the wall of AAA at its distal end. In the presence of an aorto-iliac bifurcation as well as iliac stenosis, the flow patterns show diminished strength, expanse and speed of propagation of the primary vortices. The positions of the instantaneous vortex cores, determined using the Q -function, correlate with flow separation in the bulge, flow resistance due to a bifurcation, and the break in symmetry introduced by a stenosis in one of the legs of the model. Time-averaged WSS in a healthy aorta is around 0.70 N m −2 and is lowered to the range ±0.2 N m −2 in the presence of the downstream bifurcation with a stenosed common iliac artery. The consequence of changes in the flow pattern within the aneurysm on disease progression is discussed. (paper)

Effect of aorto-iliac bifurcation and iliac stenosis on flow dynamics in an abdominal aortic aneurysm

Energy Technology Data Exchange (ETDEWEB)

Patel, Shivam; Usmani, Abdullah Y; Muralidhar, K, E-mail: kmurli@iitk.ac.in [Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016 (India)

2017-06-15

Physiological flows in rigid diseased arterial flow phantoms emulating an abdominal aortic aneurysm (AAA) under rest conditions with aorto-iliac bifurcation and iliac stenosis are examined in vitro through 2D PIV measurements. Flow characteristics are first established in the model resembling a symmetric AAA with a straight outlet tube. The influence of aorto-iliac bifurcation and iliac stenosis on AAA flow dynamics is then explored through a comparison of the nature of flow patterns, vorticity evolution, vortex core trajectory and hemodynamic factors against the reference configuration. Specifically, wall shear stress and oscillatory shear index in the bulge portion of the models are of interest. The results of this investigation indicate overall phenomenological similarity in AAA flow patterns across the models. The pattern is characterized by a central jet and wall-bounded vortices whose strength increases during the deceleration phase as it moves forward. The central jet impacts the wall of AAA at its distal end. In the presence of an aorto-iliac bifurcation as well as iliac stenosis, the flow patterns show diminished strength, expanse and speed of propagation of the primary vortices. The positions of the instantaneous vortex cores, determined using the Q -function, correlate with flow separation in the bulge, flow resistance due to a bifurcation, and the break in symmetry introduced by a stenosis in one of the legs of the model. Time-averaged WSS in a healthy aorta is around 0.70 N m{sup −2} and is lowered to the range ±0.2 N m{sup −2} in the presence of the downstream bifurcation with a stenosed common iliac artery. The consequence of changes in the flow pattern within the aneurysm on disease progression is discussed. (paper)

Vessel bifurcation localization based on intraoperative three-dimensional ultrasound and catheter path for image-guided catheter intervention of oral cancers.

Science.gov (United States)

Luan, Kuan; Ohya, Takashi; Liao, Hongen; Kobayashi, Etsuko; Sakuma, Ichiro

2013-03-01

We present a method to localize intraoperative target vessel bifurcations under bones for ultrasound (US) image-guided catheter interventions. A catheter path is recorded to acquire skeletons for the target vessel bifurcations that cannot be imaged by intraoperative US. The catheter path is combined with the centerlines of the three-dimensional (3D) US image to construct a preliminary skeleton. Based on the preliminary skeleton, the orientations of target vessels are determined by registration with the preoperative image and the bifurcations were localized by computing the vessel length. An accurate intraoperative vessel skeleton is obtained for correcting the preoperative image to compensate for vessel deformation. A reality check of the proposed method was performed in a phantom experiment. Reasonable results were obtained. The in vivo experiment verified the clinical workflow of the proposed method in an in vivo environment. The accuracy of the centerline length of the vessel for localizing the target artery bifurcation was 2.4mm. These results suggest that the proposed method can allow the catheter tip to stop at the target artery bifurcations and enter into the target arteries. This method can be applied for virtual reality-enhanced image-guided catheter intervention of oral cancers. Copyright © 2013 Elsevier Ltd. All rights reserved.

Treatment of a symptomatic intrathoracic internal carotid artery

Directory of Open Access Journals (Sweden)

Christopher R. Brown

2017-09-01

Full Text Available Intrathoracic common carotid artery bifurcations are an anatomic anomaly with such rarity that only six cases have been reported to date. The true incidence of and preferred treatment options for a diseased intrathoracic common carotid artery bifurcation or internal carotid artery (ICA have not been clearly described. This case report describes a 72-year-old man who experienced a postoperative right hemispheric stoke after an aortic valve replacement, radiofrequency maze procedure, and left atrial appendage clip. Postoperative cerebrovascular evaluation revealed a severely diseased intrathoracic ICA that was treated by ligation of the diseased proximal ICA and transposition of the distal ICA to the disease-free external carotid artery. The patient provided written consent to present the history, data, and images in this manuscript.

Hemi-central retinal artery occlusion in young adults

Directory of Open Access Journals (Sweden)

Rishi Pukhraj

2010-01-01

Full Text Available Amongst the clinical presentations of retinal artery occlusion, hemi-central retinal artery occlusion (Hemi-CRAO is rarely described. This case series of four adults aged between 22 and 36 years attempts to describe the clinical profile, etiology and management of Hemi-CRAO. Case 1 had an artificial mitral valve implant. Polycythemia and malignant hypertension were noted in Case 2. The third patient had Leiden mutation while the fourth patient had Eisenmenger′s syndrome. Clinical examination and fundus fluorescein angiography revealed a bifurcated central retinal artery at emergence from the optic nerve head, in all cases. Color Doppler examination of the central retinal artery confirmed branching of the artery behind the lamina cribrosa. It is hypothesized that bifurcation of central retinal artery behind the lamina cribrosa may predispose these hemi-trunks to develop an acute occlusion if associated with underlying risk factors. The prognosis depends upon arterial recanalisation and etiology of the thromboembolic event.

Morphometry of medial gaps of human brain artery branches.

Science.gov (United States)

Canham, Peter B; Finlay, Helen M

2004-05-01

The bifurcation regions of the major human cerebral arteries are vulnerable to the formation of saccular aneurysms. A consistent feature of these bifurcations is a discontinuity of the tunica media at the apex of the flow divider. The objective was to measure the 3-dimensional geometry of these medial gaps or "medial defects." Nineteen bifurcations and 2 junctions of human cerebral arteries branches (from 4 male and 2 female subjects) were formalin-fixed at physiological pressure and processed for longitudinal serial sectioning. The apex and adjacent regions were examined and measurements were made from high-magnification photomicrographs, or projection microscope images, of the gap dimensions at multiple levels through the bifurcation. Plots were made of the width of the media as a function of distance from the apex. The media at each edge of the medial gap widened over a short distance, reaching the full width of the media of the contiguous daughter vessel. Medial gap dimensions were compared with the planar angle of the bifurcation, and a strong negative correlation was found, ie, the acute angled branches have the more prominent medial gaps. A discontinuity of the media at the apex was seen in all the bifurcations examined and was also found in the junction regions of brain arteries. We determined that the gap width is continuous with well-defined dimensions throughout its length and average length-to-width ratio of 6.9. The gaps were generally centered on the prominence of the apical ridge.

A codimension two bifurcation in a railway bogie system

DEFF Research Database (Denmark)

Zhang, Tingting; True, Hans; Dai, Huanyun

2017-01-01

In this paper, a comprehensive analysis is presented to investigate a codimension two bifurcation that exists in a nonlinear railway bogie dynamic system combining theoretical analysis with numerical investigation. By using the running velocity V and the primary longitudinal stiffness (Formula...... coexist in a range of the bifurcation parameters which can lead to jumps in the lateral oscillation amplitude of the railway bogie system. Furthermore, reduce the values of the bifurcation parameters gradually. Firstly, the supercritical Hopf bifurcation turns into a subcritical one with multiple limit...

Prediction of fibre architecture and adaptation in diseased carotid bifurcations.

LENUS (Irish Health Repository)

Creane, Arthur

2011-12-01

Many studies have used patient-specific finite element models to estimate the stress environment in atherosclerotic plaques, attempting to correlate the magnitude of stress to plaque vulnerability. In complex geometries, few studies have incorporated the anisotropic material response of arterial tissue. This paper presents a fibre remodelling algorithm to predict the fibre architecture, and thus anisotropic material response in four patient-specific models of the carotid bifurcation. The change in fibre architecture during disease progression and its affect on the stress environment in the plaque were predicted. The mean fibre directions were assumed to lie at an angle between the two positive principal strain directions. The angle and the degree of dispersion were assumed to depend on the ratio of principal strain values. Results were compared with experimental observations and other numerical studies. In non-branching regions of each model, the typical double helix arterial fibre pattern was predicted while at the bifurcation and in regions of plaque burden, more complex fibre architectures were found. The predicted change in fibre architecture in the arterial tissue during plaque progression was found to alter the stress environment in the plaque. This suggests that the specimen-specific anisotropic response of the tissue should be taken into account to accurately predict stresses in the plaque. Since determination of the fibre architecture in vivo is a difficult task, the system presented here provides a useful method of estimating the fibre architecture in complex arterial geometries.

Sex differences in intracranial arterial bifurcations

DEFF Research Database (Denmark)

Lindekleiv, Haakon M; Valen-Sendstad, Kristian; Morgan, Michael K

2010-01-01

. The female preponderance is usually explained by systemic factors (hormonal influences and intrinsic wall weakness); however, the uneven sex distribution of intracranial aneurysms suggests a possible physiologic factor-a local sex difference in the intracranial arteries....

Percutaneous reconstruction of the innominate bifurcation using the retrograde 'kissing stents' technique

International Nuclear Information System (INIS)

Nagata, Shun-ichi; Kazekawa, Kiyoshi; Matsubara, Shuko; Sugata, Sei

2006-01-01

Obstructions of the supraaortic vessels are an important cause of morbidity associated with a variety of symptoms. Percutaneous transluminal angioplasty has evolved as an effective and safe treatment modality for occlusive lesions of the supraaortic vessels. However, the endovascular management of an innominate bifurcation has not previously been reported. A 53-year-old female with a history of systematic hypertension, diabetes mellitus and hypercholesterolemia presented with left hemiparesis and dysarthria. Angiography of the innominate artery showed a stenosis of the innominate bifurcation. The lesion was successfully treated using the retrograde kissing stent technique via a brachial approach and an exposed direct carotid approach. The retrograde kissing stent technique for the treatment of a stenosis of the innominate bifurcation was found to be a safe and effective alternative to conventional surgery. (orig.)

Angiographic diagnosis of the carotid artery pseudoaneurysm

International Nuclear Information System (INIS)

Qi Yueyong; Zou Liguang; Dai Shuhua; Tan Yinghui; Li Zhongyu; Zhou Zheng

2004-01-01

Objective: To create a further understanding of the angiographic features of the carotid artery pseudoaneurysm (CAPA) and to explore the clinical diagnostic value of angiography. Methods: Sixteen cases of CAPA with clinical and angiographic data were analyzed retrospectively. The angiographic appearances in all of the patients were observed dynamically and precisely with a double blind method by two experienced radiologists together and formed a consensus interpretation. Results: Angiography provided a definite diagnosis for all cases. The parent arteries included the common carotid artery (1 case), common carotid artery bifurcation (9 cases), internal carotid artery (5 cases) and external carotid artery (1 case). The angiographic features of the CAPA were: All cases showed the contrast media retension in the aneurysms; turbulent flow within aneurysm in 9 cases; the 'jetting sign' at the leak of the parent artery in 7 cases; increase angulation of the bifurcation of internal and external carotid arteries in 12 cases. Conclusions: Angiography is the most valuable examination method in diagnosis of CAPA, and it can not only provide definite diagnosis, but also play an important role in selection of therapeutic plan. (authors)

Evaluation of the carotid artery stenosis based on minimization of mechanical energy loss of the blood flow.

Science.gov (United States)

Sia, Sheau Fung; Zhao, Xihai; Li, Rui; Zhang, Yu; Chong, Winston; He, Le; Chen, Yu

2016-11-01

Internal carotid artery stenosis requires an accurate risk assessment for the prevention of stroke. Although the internal carotid artery area stenosis ratio at the common carotid artery bifurcation can be used as one of the diagnostic methods of internal carotid artery stenosis, the accuracy of results would still depend on the measurement techniques. The purpose of this study is to propose a novel method to estimate the effect of internal carotid artery stenosis on the blood flow based on the concept of minimization of energy loss. Eight internal carotid arteries from different medical centers were diagnosed as stenosed internal carotid arteries, as plaques were found at different locations on the vessel. A computational fluid dynamics solver was developed based on an open-source code (OpenFOAM) to test the flow ratio and energy loss of those stenosed internal carotid arteries. For comparison, a healthy internal carotid artery and an idealized internal carotid artery model have also been tested and compared with stenosed internal carotid artery in terms of flow ratio and energy loss. We found that at a given common carotid artery bifurcation, there must be a certain flow distribution in the internal carotid artery and external carotid artery, for which the total energy loss at the bifurcation is at a minimum; for a given common carotid artery flow rate, an irregular shaped plaque at the bifurcation constantly resulted in a large value of minimization of energy loss. Thus, minimization of energy loss can be used as an indicator for the estimation of internal carotid artery stenosis.

Bursting oscillations, bifurcation and synchronization in neuronal systems

Energy Technology Data Exchange (ETDEWEB)

Wang Haixia [School of Science, Nanjing University of Science and Technology, Nanjing 210094 (China); Wang Qingyun, E-mail: drwangqy@gmail.com [Department of Dynamics and Control, Beihang University, Beijing 100191 (China); Lu Qishao [Department of Dynamics and Control, Beihang University, Beijing 100191 (China)

2011-08-15

Highlights: > We investigate bursting oscillations and related bifurcation in the modified Morris-Lecar neuron. > Two types of fast-slow bursters are analyzed in detail. > We show the properties of some crucial bifurcation points. > Synchronization transition and the neural excitability are explored in the coupled bursters. - Abstract: This paper investigates bursting oscillations and related bifurcation in the modified Morris-Lecar neuron. It is shown that for some appropriate parameters, the modified Morris-Lecar neuron can exhibit two types of fast-slow bursters, that is 'circle/fold cycle' bursting and 'subHopf/homoclinic' bursting with class 1 and class 2 neural excitability, which have different neuro-computational properties. By means of the analysis of fast-slow dynamics and phase plane, we explore bifurcation mechanisms associated with the two types of bursters. Furthermore, the properties of some crucial bifurcation points, which can determine the type of the burster, are studied by the stability and bifurcation theory. In addition, we investigate the influence of the coupling strength on synchronization transition and the neural excitability in two electrically coupled bursters with the same bursting type. More interestingly, the multi-time-scale synchronization transition phenomenon is found as the coupling strength varies.

Resonant Homoclinic Flips Bifurcation in Principal Eigendirections

Directory of Open Access Journals (Sweden)

Tiansi Zhang

2013-01-01

Full Text Available A codimension-4 homoclinic bifurcation with one orbit flip and one inclination flip at principal eigenvalue direction resonance is considered. By introducing a local active coordinate system in some small neighborhood of homoclinic orbit, we get the Poincaré return map and the bifurcation equation. A detailed investigation produces the number and the existence of 1-homoclinic orbit, 1-periodic orbit, and double 1-periodic orbits. We also locate their bifurcation surfaces in certain regions.

Global Hopf Bifurcation for a Predator-Prey System with Three Delays

Science.gov (United States)

Jiang, Zhichao; Wang, Lin

2017-06-01

In this paper, a delayed predator-prey model is considered. The existence and stability of the positive equilibrium are investigated by choosing the delay τ = τ1 + τ2 as a bifurcation parameter. We see that Hopf bifurcation can occur as τ crosses some critical values. The direction of the Hopf bifurcations and the stability of the bifurcation periodic solutions are also determined by using the center manifold and normal form theory. Furthermore, based on the global Hopf bifurcation theorem for general function differential equations, which was established by J. Wu using fixed point theorem and degree theory methods, the existence of global Hopf bifurcation is investigated. Finally, numerical simulations to support the analytical conclusions are carried out.

Segmental hepatic artery at hepatic hilar area. Analysis by 3 dimensional integrated image of artery, portal vein and bile duct

Energy Technology Data Exchange (ETDEWEB)

Sakai, Hisamune; Okuda, Kouji; Yoshida, Jun; Kinoshita, Hisafumi; Aoyagi, Shigeaki [Kurume Univ., School of Medicine, Kurume, Fukuoka (Japan)

2006-11-15

Multiple individual variations in running and bifurcation of the hepatic artery, biliary duct and portal vein are known in hepatic hilar area. This paper describes the examination of such arterial variations by integrating the 3D images of those vessels obtained by multidetector-row CT (MDCT). Subjects are findings from 64 patients with cholangiocarcinoma, hepatocarcinoma or cholelithiasis. MDCT dynamic scanning, and percutaneous transhepatic biliary drainage-CT and/or drip infusion cholangiography-CT with the intravenous iopamidol and/or iotroxate megulumin, were done with GE LightSpeed Ultra 16 slice type equipment to compose the 3D images. Arterial variants of the bifurcation in the right and left lobe were found to be 18 cases/62 (29%) and 13/64 (20%), respectively. The left artery running at right side of portal venous umbilical region was seen in 9/64 (14%) and right artery running ''northward'', in 9/62 (14%). Previous realization of such individual 3D arterial variations as above is necessary for the precise microsurgery of the hilar area to preserve the essential vessel. (T.I.)

Segmental hepatic artery at hepatic hilar area. Analysis by 3 dimensional integrated image of artery, portal vein and bile duct

International Nuclear Information System (INIS)

Sakai, Hisamune; Okuda, Kouji; Yoshida, Jun; Kinoshita, Hisafumi; Aoyagi, Shigeaki

2006-01-01

Multiple individual variations in running and bifurcation of the hepatic artery, biliary duct and portal vein are known in hepatic hilar area. This paper describes the examination of such arterial variations by integrating the 3D images of those vessels obtained by multidetector-row CT (MDCT). Subjects are findings from 64 patients with cholangiocarcinoma, hepatocarcinoma or cholelithiasis. MDCT dynamic scanning, and percutaneous transhepatic biliary drainage-CT and/or drip infusion cholangiography-CT with the intravenous iopamidol and/or iotroxate megulumin, were done with GE LightSpeed Ultra 16 slice type equipment to compose the 3D images. Arterial variants of the bifurcation in the right and left lobe were found to be 18 cases/62 (29%) and 13/64 (20%), respectively. The left artery running at right side of portal venous umbilical region was seen in 9/64 (14%) and right artery running ''northward'', in 9/62 (14%). Previous realization of such individual 3D arterial variations as above is necessary for the precise microsurgery of the hilar area to preserve the essential vessel. (T.I.)

Provisional versus elective two-stent strategy for unprotected true left main bifurcation lesions: Insights from a FAILS-2 sub-study.

Science.gov (United States)

Kawamoto, Hiroyoshi; Chieffo, Alaide; D'Ascenzo, Fabrizio; Jabbour, Richard J; Naganuma, Toru; Cerrato, Enrico; Ugo, Fabrizio; Pavani, Marco; Varbella, Ferdinando; Boccuzzi, Giacomo; Pennone, Mauro; Garbo, Roberto; Conrotto, Federico; Biondi-Zoccai, Giuseppe; D'Amico, Maurizio; Moretti, Claudio; Escaned, Javier; Gaita, Fiorenzo; Nakamura, Sunao; Colombo, Antonio

2018-01-01

This study sought to investigate the optimal percutaneous coronary intervention (PCI) strategy for true unprotected left main coronary artery (ULMCA) bifurcations. The FAILS-2 was a retrospective multi-center study including patients with ULMCA disease treated with second-generation drug-eluting stents. Of these, we compared clinical outcomes of a provisional strategy (PS; n=216) versus an elective two-stent strategy (E2S; n=161) for true ULMCA bifurcations. The primary endpoint was the incidence of major adverse cardiac events (MACEs) at 3-years. We further performed propensity-score adjustment for clinical outcomes. There were no significant differences between the groups in terms of patient and lesion characteristics. 9.7% of patients in the PS group crossed over to a provisional two-stent strategy. MACEs were not significantly different between groups (MACE at 3-year; PS 28.1% vs. E2S 28.9%, adjusted p=0.99). The rates of target lesion revascularization (TLR) on the circumflex artery (LCX) were numerically high in the E2S group (LCX-TLR at 3-years; PS 11.8% vs. E2S 16.6%, adjusted p=0.51). E2S was associated with a comparable MACE rate to PS for true ULMCA bifurcations. The rates of LCX-TLR tended to be higher in the E2S group although there was no statistical significance. This study sought to compare the clinical outcomes of a provisional strategy (PS) with an elective two-stent strategy (E2S) for the treatment of true unprotected left main coronary artery bifurcations. 377 Patients (PS 216 vs. E2S 161 patients) were evaluated, and 9.7% in the PS group crossed over to a two-stent strategy. E2S was associated with a similar major adverse cardiac event rate at 3-years when compared to the PS strategy (PS 28.1% vs. E2S 28.9%, p=0.99). However, the left circumflex artery TLR rate at 3-year tended to be higher in the E2S group (PS 11.8% vs. E2S 16.6%, p=0.51). Copyright © 2017 Elsevier B.V. All rights reserved.

Angiographic Assessment of the Right Hepatic Artery for Encasement by Hilar Cholangiocarcinoma: Comparison Between Antero-Posterior and Right Anterior Oblique Projections

International Nuclear Information System (INIS)

Furukawa, Hiroyoshi; Iwata, Ryoko; Moriyama, Noriyuki

2001-01-01

Purpose: To evaluate the usefulness of right anterior oblique (RAO) arteriography for evaluating encasement of the right hepatic artery (RHA) by hilar cholangiocarcinoma.Methods: Celiac arteriography was performed in both the antero-posterior (AP) and RAO projection in ten patients with cholangiocarcinoma. The lengths of the arteries between the bifurcation of the anterior and posterior branch of the liver and the following points were measured: (a) the bifurcation of the left and right hepatic artery (AP-LR), (b) the bifurcation of the proper hepatic artery and the gastroduodenal artery (AP-PG). Additionally, image quality in investigating the invasion of the RHA was evaluated.Results: On the AP images, the average lengths of AP-LR and AP-PG were 24.5 ± 5.1 mm and 30.0 ± 4.9 mm, respectively. On RAO images, the lengths were 28.2 ± 4.6 mm and 32.7 ± 4.8 mm, respectively. Every length was different between the two projections (p < 0.01). In 6 of 10 patients with hilar cholangiocarcinoma, images in RAO projections were superior to AP images for evaluation of encasement.Conclusion: We conclude that angiography obtained in the RAO projection yields images that are superior to those obtained in the conventional AP projection for assessment of RHA encasement

Flow visualisation study of spiral flow in the aorta-renal bifurcation.

Science.gov (United States)

Fulker, David; Javadzadegan, Ashkan; Li, Zuming; Barber, Tracie

2017-10-01

The aim of this study was to analyse the flow dynamics in an idealised model of the aorta-renal bifurcation using flow visualisation, with a particular focus on the effect of aorta-to-renal flow ratio and flow spirality. The recirculation length was longest when there was low flow in the renal artery and smaller in the presence of spiral flow. The results also indicate that patients without spiral flow or who have low flow in the renal artery due to the presence of stenosis may be susceptible to heightened development of atherosclerotic lesions.

Bifurcation Behavior Analysis in a Predator-Prey Model

Directory of Open Access Journals (Sweden)

Nan Wang

2016-01-01

Full Text Available A predator-prey model is studied mathematically and numerically. The aim is to explore how some key factors influence dynamic evolutionary mechanism of steady conversion and bifurcation behavior in predator-prey model. The theoretical works have been pursuing the investigation of the existence and stability of the equilibria, as well as the occurrence of bifurcation behaviors (transcritical bifurcation, saddle-node bifurcation, and Hopf bifurcation, which can deduce a standard parameter controlled relationship and in turn provide a theoretical basis for the numerical simulation. Numerical analysis ensures reliability of the theoretical results and illustrates that three stable equilibria will arise simultaneously in the model. It testifies the existence of Bogdanov-Takens bifurcation, too. It should also be stressed that the dynamic evolutionary mechanism of steady conversion and bifurcation behavior mainly depend on a specific key parameter. In a word, all these results are expected to be of use in the study of the dynamic complexity of ecosystems.

Bifurcations of optimal vector fields: an overview

NARCIS (Netherlands)

Kiseleva, T.; Wagener, F.; Rodellar, J.; Reithmeier, E.

2009-01-01

We develop a bifurcation theory for the solution structure of infinite horizon optimal control problems with one state variable. It turns out that qualitative changes of this structure are connected to local and global bifurcations in the state-costate system. We apply the theory to investigate an

Travelling waves and their bifurcations in the Lorenz-96 model

Science.gov (United States)

van Kekem, Dirk L.; Sterk, Alef E.

2018-03-01

In this paper we study the dynamics of the monoscale Lorenz-96 model using both analytical and numerical means. The bifurcations for positive forcing parameter F are investigated. The main analytical result is the existence of Hopf or Hopf-Hopf bifurcations in any dimension n ≥ 4. Exploiting the circulant structure of the Jacobian matrix enables us to reduce the first Lyapunov coefficient to an explicit formula from which it can be determined when the Hopf bifurcation is sub- or supercritical. The first Hopf bifurcation for F > 0 is always supercritical and the periodic orbit born at this bifurcation has the physical interpretation of a travelling wave. Furthermore, by unfolding the codimension two Hopf-Hopf bifurcation it is shown to act as an organising centre, explaining dynamics such as quasi-periodic attractors and multistability, which are observed in the original Lorenz-96 model. Finally, the region of parameter values beyond the first Hopf bifurcation value is investigated numerically and routes to chaos are described using bifurcation diagrams and Lyapunov exponents. The observed routes to chaos are various but without clear pattern as n → ∞.

Relação anatômica entre o nervo hipoglosso e a bifurcação carotídea Anatomical relation between the hypoglossal nerve and the carotid artery bifurcation

Directory of Open Access Journals (Sweden)

Felipe S. G. Fortes

to establish the anatomical relation between the carotid artery bifurcation and hypoglossal nerve. Study design: experimental. Material and method: Carotid artery and hypoglossal nerve dissections were carried out in 38 fresh corpses. All the individuals were placed in standard position and the dissections were performed with surgical technique. The measurements were done in centimeters and millimeters from the dissected carotid bifurcation to the XII nerve in the cervical area. Results: Twenty-six individuals were male and 12 female. The majority were whites, 30, and 8 were non-whites. The distance between hypoglossal nerve and carotid artery bifurcation ranged from 0.5 cm to 4.3 cm, with mean of 2.1 cm, median 2.0 cm and standard deviation of 0.63 cm. Neck length, age, gender and race were related with the measurements and failed to show significant statistic correlation (a > 0.05. Conclusion: In this sample there is a great anatomic variation of the distance between hypoglossal nerve and carotid artery bifurcation and there was no statistical difference concerning age, gender, race and neck length. A better understanding of the anatomic course of this nerve and its variation in relation to carotid artery bifurcation, are relevant to prevent hypoglossal nerve lesions in the carotid artery surgery.

Cutting Balloon Angioplasty in the Treatment of Short Infrapopliteal Bifurcation Disease.

Science.gov (United States)

Iezzi, Roberto; Posa, Alessandro; Santoro, Marco; Nestola, Massimiliano; Contegiacomo, Andrea; Tinelli, Giovanni; Paolini, Alessandra; Flex, Andrea; Pitocco, Dario; Snider, Francesco; Bonomo, Lorenzo

2015-08-01

To evaluate the safety, feasibility, and effectiveness of cutting balloon angioplasty in the management of infrapopliteal bifurcation disease. Between November 2010 and March 2013, 23 patients (mean age 69.6±9.01 years, range 56-89; 16 men) suffering from critical limb ischemia were treated using cutting balloon angioplasty (single cutting balloon, T-shaped double cutting balloon, or double kissing cutting balloon technique) for 47 infrapopliteal artery bifurcation lesions (16 popliteal bifurcation and 9 tibioperoneal bifurcation) in 25 limbs. Follow-up consisted of clinical examination and duplex ultrasonography at 1 month and every 3 months thereafter. All treatments were technically successful. No 30-day death or adverse events needing treatment were registered. No flow-limiting dissection was observed, so no stent implantation was necessary. The mean postprocedure minimum lumen diameter and acute gain were 0.28±0.04 and 0.20±0.06 cm, respectively, with a residual stenosis of 0.04±0.02 cm. Primary and secondary patency rates were estimated as 89.3% and 93.5% at 6 months and 77.7% and 88.8% at 12 months, respectively; 1-year primary and secondary patency rates of the treated bifurcation were 74.2% and 87.0%, respectively. The survival rate estimated by Kaplan-Meier analysis was 82.5% at 1 year. Cutting balloon angioplasty seems to be a safe and effective tool in the routine treatment of short/ostial infrapopliteal bifurcation lesions, avoiding procedure-related complications, overcoming the limitations of conventional angioplasty, and improving the outcome of catheter-based therapy. © The Author(s) 2015.

Percutaneous reconstruction of the innominate bifurcation using the retrograde 'kissing stents' technique

Energy Technology Data Exchange (ETDEWEB)

Nagata, Shun-ichi; Kazekawa, Kiyoshi; Matsubara, Shuko [Fukuoka University Chikushi Hospital, Department of Neurosurgery, Chikushino, Fukuoka (Japan); Sugata, Sei [Bironoki Neurosurgical Hospital, Shibushi, Kagoshima (Japan)

2006-08-15

Obstructions of the supraaortic vessels are an important cause of morbidity associated with a variety of symptoms. Percutaneous transluminal angioplasty has evolved as an effective and safe treatment modality for occlusive lesions of the supraaortic vessels. However, the endovascular management of an innominate bifurcation has not previously been reported. A 53-year-old female with a history of systematic hypertension, diabetes mellitus and hypercholesterolemia presented with left hemiparesis and dysarthria. Angiography of the innominate artery showed a stenosis of the innominate bifurcation. The lesion was successfully treated using the retrograde kissing stent technique via a brachial approach and an exposed direct carotid approach. The retrograde kissing stent technique for the treatment of a stenosis of the innominate bifurcation was found to be a safe and effective alternative to conventional surgery. (orig.)

Calculation of arterial wall temperature in atherosclerotic arteries: effect of pulsatile flow, arterial geometry, and plaque structure

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Kim Taehong

2007-03-01

Full Text Available Abstract Background This paper presents calculations of the temperature distribution in an atherosclerotic plaque experiencing an inflammatory process; it analyzes the presence of hot spots in the plaque region and their relationship to blood flow, arterial geometry, and inflammatory cell distribution. Determination of the plaque temperature has become an important topic because plaques showing a temperature inhomogeneity have a higher likelihood of rupture. As a result, monitoring plaque temperature and knowing the factors affecting it can help in the prevention of sudden rupture. Methods The transient temperature profile in inflamed atherosclerotic plaques is calculated by solving an energy equation and the Navier-Stokes equations in 2D idealized arterial models of a bending artery and an arterial bifurcation. For obtaining the numerical solution, the commercial package COMSOL 3.2 was used. The calculations correspond to a parametric study where arterial type and size, as well as plaque geometry and composition, are varied. These calculations are used to analyze the contribution of different factors affecting arterial wall temperature measurements. The main factors considered are the metabolic heat production of inflammatory cells, atherosclerotic plaque length lp, inflammatory cell layer length lmp, and inflammatory cell layer thickness dmp. Results The calculations indicate that the best location to perform the temperature measurement is at the back region of the plaque (0.5 ≤ l/lp ≤ 0.7. The location of the maximum temperature, or hot spot, at the plaque surface can move during the cardiac cycle depending on the arterial geometry and is a direct result of the blood flow pattern. For the bending artery, the hot spot moves 0.6 millimeters along the longitudinal direction; for the arterial bifurcation, the hot spot is concentrated at a single location due to the flow recirculation observed at both ends of the plaque. Focusing on the

Hopf bifurcation in a delayed reaction-diffusion-advection population model

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Chen, Shanshan; Lou, Yuan; Wei, Junjie

2018-04-01

In this paper, we investigate a reaction-diffusion-advection model with time delay effect. The stability/instability of the spatially nonhomogeneous positive steady state and the associated Hopf bifurcation are investigated when the given parameter of the model is near the principle eigenvalue of an elliptic operator. Our results imply that time delay can make the spatially nonhomogeneous positive steady state unstable for a reaction-diffusion-advection model, and the model can exhibit oscillatory pattern through Hopf bifurcation. The effect of advection on Hopf bifurcation values is also considered, and our results suggest that Hopf bifurcation is more likely to occur when the advection rate increases.

Description of the celiac artery in domestic pigeons (Columba livia

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Cibele Geeverghese

2012-06-01

Full Text Available This paper aimed to define the origin and distribution of the celiac artery and its collateral branches in 15 fowls from the Columba livia species, which were obtained from the Zoonosis Control Center of Brasilia, Brazil. In order to mark the arterial system of the specimens, the left brachiocephalic trunk was canullated and a colored water-latex solution was injected there. Afterwards, fowls were fixed in a 10% v/v formaldehyde solution and dissected with appropriate equipment, presenting the results described in this paper. The celiac artery originated from the ventral face of the descendent aorta. The first collateral branch arose from the celiac artery itself, forming the esophageal artery. Then, the celiac artery has bifurcated into two branches, named left and right branches of the celiac artery. The left branch emitted the proventricular ventral artery, followed by the splenic arteries, proventricular dorsal artery, and the left hepatic artery. The left branch has bifurcated into two branches, known as ventral and left gastric arteries. The right branch emitted the right hepatic artery, followed by the ileal artery and the right gastric artery. Finally, the right branch turned into the pancreaticoduodenal artery. Our findings showed a great similarity with the avian lineages of the Gallus gallus species, except for the lack of ileocecal artery, cystic branches, and dorsal gastric artery.

Bifurcation and chaos in neural excitable system

International Nuclear Information System (INIS)

Jing Zhujun; Yang Jianping; Feng Wei

2006-01-01

In this paper, we investigate the dynamical behaviors of neural excitable system without periodic external current (proposed by Chialvo [Generic excitable dynamics on a two-dimensional map. Chaos, Solitons and Fractals 1995;5(3-4):461-79] and with periodic external current as system's parameters vary. The existence and stability of three fixed points, bifurcation of fixed points, the conditions of existences of fold bifurcation, flip bifurcation and Hopf bifurcation are derived by using bifurcation theory and center manifold theorem. The chaotic existence in the sense of Marotto's definition of chaos is proved. We then give the numerical simulated results (using bifurcation diagrams, computations of Maximum Lyapunov exponent and phase portraits), which not only show the consistence with the analytic results but also display new and interesting dynamical behaviors, including the complete period-doubling and inverse period-doubling bifurcation, symmetry period-doubling bifurcations of period-3 orbit, simultaneous occurrence of two different routes (invariant cycle and period-doubling bifurcations) to chaos for a given bifurcation parameter, sudden disappearance of chaos at one critical point, a great abundance of period windows (period 2 to 10, 12, 19, 20 orbits, and so on) in transient chaotic regions with interior crises, strange chaotic attractors and strange non-chaotic attractor. In particular, the parameter k plays a important role in the system, which can leave the chaotic behavior or the quasi-periodic behavior to period-1 orbit as k varies, and it can be considered as an control strategy of chaos by adjusting the parameter k. Combining the existing results in [Generic excitable dynamics on a two-dimensional map. Chaos, Solitons and Fractals 1995;5(3-4):461-79] with the new results reported in this paper, a more complete description of the system is now obtained

A Rare Case of Atypical Renal Arteries Arrangement with Ectopic Kidneys in a Guinea Pig

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Maženský D.

2016-12-01

Full Text Available We recorded a very rare case of atypical renal arteries arrangement in a guinea pig using the corrosion technique in the study of the arterial system. The right renal artery originated from the ventral wall of the abdominal aorta at the level of the caudal aspect of the 5th lumbar vertebra. The left renal artery originated from the left common iliac artery approximately 12 mm caudally to the aortic bifurcation. The right kidney was located ventral to the aortic bifurcation and the left kidney inside the pelvic cavity between the common iliac arteries. According to the vascular pattern, we determined that the ectopic kidneys in this guinea pig were unusual. This is the first case describing bilateral ectopic kidneys in a guinea pig.

Anatomy and function relation in the coronary tree: from bifurcations to myocardial flow and mass.

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Kassab, Ghassan S; Finet, Gerard

2015-01-01

The study of the structure-function relation of coronary bifurcations is necessary not only to understand the design of the vasculature but also to use this understanding to restore structure and hence function. The objective of this review is to provide quantitative relations between bifurcation anatomy or geometry, flow distribution in the bifurcation and degree of perfused myocardial mass in order to establish practical rules to guide optimal treatment of bifurcations including side branches (SB). We use the scaling law between flow and diameter, conservation of mass and the scaling law between myocardial mass and diameter to provide geometric relations between the segment diameters of a bifurcation, flow fraction distribution in the SB, and the percentage of myocardial mass perfused by the SB. We demonstrate that the assessment of the functional significance of an SB for intervention should not only be based on the diameter of the SB but also on the diameter of the mother vessel as well as the diameter of the proximal main artery, as these dictate the flow fraction distribution and perfused myocardial mass, respectively. The geometric and flow rules for a bifurcation are extended to a trifurcation to ensure optimal therapy scaling rules for any branching pattern.

Flow patterns on spectral-domain optical coherence tomography reveal flow directions at retinal vessel bifurcations

DEFF Research Database (Denmark)

Willerslev, Anne; Li, Xiao Q; Munch, Inger C

2014-01-01

PURPOSE: To study intravascular characteristics of flowing blood in retinal vessels using spectral-domain optical coherence tomography (SD-OCT). METHODS: Examination of selected arterial bifurcations and venous sites of confluence in 25 healthy 11-year-old children recruited as an ad hoc subsample...

Bifurcation of self-folded polygonal bilayers

Science.gov (United States)

Abdullah, Arif M.; Braun, Paul V.; Hsia, K. Jimmy

2017-09-01

Motivated by the self-assembly of natural systems, researchers have investigated the stimulus-responsive curving of thin-shell structures, which is also known as self-folding. Self-folding strategies not only offer possibilities to realize complicated shapes but also promise actuation at small length scales. Biaxial mismatch strain driven self-folding bilayers demonstrate bifurcation of equilibrium shapes (from quasi-axisymmetric doubly curved to approximately singly curved) during their stimulus-responsive morphing behavior. Being a structurally instable, bifurcation could be used to tune the self-folding behavior, and hence, a detailed understanding of this phenomenon is appealing from both fundamental and practical perspectives. In this work, we investigated the bifurcation behavior of self-folding bilayer polygons. For the mechanistic understanding, we developed finite element models of planar bilayers (consisting of a stimulus-responsive and a passive layer of material) that transform into 3D curved configurations. Our experiments with cross-linked Polydimethylsiloxane samples that change shapes in organic solvents confirmed our model predictions. Finally, we explored a design scheme to generate gripper-like architectures by avoiding the bifurcation of stimulus-responsive bilayers. Our research contributes to the broad field of self-assembly as the findings could motivate functional devices across multiple disciplines such as robotics, artificial muscles, therapeutic cargos, and reconfigurable biomedical devices.

Merging flows in an arterial confluence : The vertebro-basilar junction

NARCIS (Netherlands)

Ravensbergen, J; Krijger, JKB; Hillen, B; Hoogstraten, HW

1995-01-01

The basilar artery is one of the three vessels providing the blood supply to the human brain. It arises from the confluence of the two vertebral arteries. In fact, it is the only artery of this size in the human body arising from a confluence instead of a bifurcation. Earlier work, concerning flow

Post-Treatment Hemodynamics of a Basilar Aneurysm and Bifurcation

Energy Technology Data Exchange (ETDEWEB)

Ortega, J; Hartman, J; Rodriguez, J; Maitland, D

2008-01-16

Aneurysm re-growth and rupture can sometimes unexpectedly occur following treatment procedures that were initially considered to be successful at the time of treatment and post-operative angiography. In some cases, this can be attributed to surgical clip slippage or endovascular coil compaction. However, there are other cases in which the treatment devices function properly. In these instances, the subsequent complications are due to other factors, perhaps one of which is the post-treatment hemodynamic stress. To investigate whether or not a treatment procedure can subject the parent artery to harmful hemodynamic stresses, computational fluid dynamics simulations are performed on a patient-specific basilar aneurysm and bifurcation before and after a virtual endovascular treatment. The simulations demonstrate that the treatment procedure produces a substantial increase in the wall shear stress. Analysis of the post-treatment flow field indicates that the increase in wall shear stress is due to the impingement of the basilar artery flow upon the aneurysm filling material and to the close proximity of a vortex tube to the artery wall. Calculation of the time-averaged wall shear stress shows that there is a region of the artery exposed to a level of wall shear stress that can cause severe damage to endothelial cells. The results of this study demonstrate that it is possible for a treatment procedure, which successfully excludes the aneurysm from the vascular system and leaves no aneurysm neck remnant, to elevate the hemodynamic stresses to levels that are injurious to the immediately adjacent vessel wall.

Hopf Bifurcation of Compound Stochastic van der Pol System

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Shaojuan Ma

2016-01-01

Full Text Available Hopf bifurcation analysis for compound stochastic van der Pol system with a bound random parameter and Gaussian white noise is investigated in this paper. By the Karhunen-Loeve (K-L expansion and the orthogonal polynomial approximation, the equivalent deterministic van der Pol system can be deduced. Based on the bifurcation theory of nonlinear deterministic system, the critical value of bifurcation parameter is obtained and the influence of random strength δ and noise intensity σ on stochastic Hopf bifurcation in compound stochastic system is discussed. At last we found that increased δ can relocate the critical value of bifurcation parameter forward while increased σ makes it backward and the influence of δ is more sensitive than σ. The results are verified by numerical simulations.

[Morphometrical analyze of the middle cerebral artery system at the 13-15 weeks fetuses].

Science.gov (United States)

Macovei, Georgeta Nataşa; Varlam, H; St Antohe, D

2002-01-01

Tele-encephalization process is accompanied by the appearance and progressive complication of the middle cerebral artery system. The aim of our study is to analyze the morphometrical parameters of the middle cerebral artery branches in the beginning of the edification of its system. We used 162 cerebral hemispheres from 88 fetuses aged of 13-15 weeks. Middle cerebral artery system was injected with a gelatin-China ink mixture and images recorded by means of a Zeiss surgical microscope. Parameters evaluation (length, proximal and distal diameters, external surface, volume, angles of bifurcation) was realized with KS-300 program. At this early age middle cerebral artery system has only 4-5 generations of branches usually resulting from acute angle bifurcations.

Surgical repair of a celiac artery aneurysm using a sutureless proximal anastomosis device

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Tetsuro Uchida, MD, PhD

2017-12-01

Full Text Available Some celiac artery aneurysms are not suitable for endovascular therapy. We describe the case of a 63-year-old man with a celiac trunk aneurysm extending to the hepatosplenic bifurcation. The aneurysm was resected and oversewn at the origin from the abdominal aorta. A saphenous vein bypass from the supraceliac aorta to the celiac artery bifurcation was performed using a sutureless anastomotic device (PAS-Port system; Cardica, Redwood City, Calif to create the proximal anastomosis, eliminating the need for aortic clamping. This system is thought to make direct proximal aortic anastomosis safe and easy in patients requiring surgical reconstruction of celiac artery aneurysms.

Anatomical variations of hepatic arterial system, coeliac trunk and renal arteries: an analysis with multidetector CT angiography.

Science.gov (United States)

Ugurel, M S; Battal, B; Bozlar, U; Nural, M S; Tasar, M; Ors, F; Saglam, M; Karademir, I

2010-08-01

The purpose of our investigation was to determine the anatomical variations in the coeliac trunk-hepatic arterial system and the renal arteries in patients who underwent multidetector CT (MDCT) angiography of the abdominal aorta for various reasons. A total of 100 patients were analysed retrospectively. The coeliac trunk, hepatic arterial system and renal arteries were analysed individually and anatomical variations were recorded. Statistical analysis of the relationship between hepatocoeliac variations and renal artery variations was performed using a chi(2) test. There was a coeliac trunk trifurcation in 89% and bifurcation in 8% of the cases. Coeliac trunk was absent in 1%, a hepatosplenomesenteric trunk was seen in 1% and a splenomesenteric trunk was present in 1%. Hepatic artery variation was present in 48% of patients. Coeliac trunk and/or hepatic arterial variation was present in 23 (39.7%) of the 58 patients with normal renal arteries, and in 27 (64.3%) of the 42 patients with accessory renal arteries. There was a statistically significant correlation between renal artery variations and coeliac trunk-hepatic arterial system variations (p = 0.015). MDCT angiography permits a correct and detailed evaluation of hepatic and renal vascular anatomy. The prevalence of variations in the coeliac trunk and/or hepatic arteries is increased in people with accessory renal arteries. For that reason, when undertaking angiographic examinations directed towards any single organ, the possibility of variations in the vascular structure of other organs should be kept in mind.

Experimental Investigation of Bifurcations in a Thermoacoustic Engine

OpenAIRE

Vishnu R. Unni; Yogesh M. S. Prasaad; N. T. Ravi; S. Md Iqbal; Bala Pesala; R. I. Sujith

2015-01-01

In this study, variation in the characteristics of the pressure oscillations in a thermoacoustic engine is explored as the input heat flux is varied. A bifurcation diagram is plotted to study the variation in the qualitative behavior of the acoustic oscillations as the input heat flux changes. At a critical input heat flux (60 Watt), the engine begins to produce acoustic oscillations in its fundamental longitudinal mode. As the input heat flux is increased, incommensurate frequencies appear i...

Traumatic aneurysms of the pericallosal arteries

International Nuclear Information System (INIS)

Nakstad, P.; Nornes, H.; Hauge, H.N.

1986-01-01

Of a total of 912 operated intracranial aneurysms only three were classified as traumatic (0.3%). They were found in children after severe head trauma and were all located on the pericallosal artery or its branches and not a bifurcations. Shearing forces between the falx, the arteries and the brain at the time of injury are held responsible for the development of these aneurysms. Unlike these traumatic aneurysms, 29 ''spontaneous'' pericallosal aneurysms (3.2%) in adults were located at the bifurcations of the artery. As significantly fewer reports of traumatic aneurysms have been published during the last decade than before 1976, it is suggested that some might have been overlooked as a consequence of CT replacing cerebral angiography in the neuroradiological evaluation of severe head injury. This possibility should be kept in mind, especially when dealing with children after head injury and when CT scans indicate brain damage around the falx. The possibility of overlooking traumatic pericallosal aneurysms is described by other authors and discussed further in this paper. (orig.)

Stability and bifurcation of a discrete BAM neural network model with delays

International Nuclear Information System (INIS)

Zheng Baodong; Zhang Yang; Zhang Chunrui

2008-01-01

A map modelling a discrete bidirectional associative memory neural network with delays is investigated. Its dynamics is studied in terms of local analysis and Hopf bifurcation analysis. By analyzing the associated characteristic equation, its linear stability is investigated and Hopf bifurcations are demonstrated. It is found that there exist Hopf bifurcations when the delay passes a sequence of critical values. Numerical simulation is performed to verify the analytical results

Pierce instability and bifurcating equilibria

International Nuclear Information System (INIS)

Godfrey, B.B.

1981-01-01

The report investigates the connection between equilibrium bifurcations and occurrence of the Pierce instability. Electrons flowing from one ground plane to a second through an ion background possess a countable infinity of static equilibria, of which only one is uniform and force-free. Degeneracy of the uniform and simplest non-uniform equilibria at a certain ground plan separation marks the onset of the Pierce instability, based on a newly derived dispersion relation appropriate to all the equilibria. For large ground plane separations the uniform equilibrium is unstable and the non-uniform equilibrium is stable, the reverse of their stability properties at small separations. Onset of the Pierce instability at the first bifurcation of equilibria persists in more complicated geometries, providing a general criterion for marginal stability. It seems probable that bifurcation analysis can be a useful tool in the overall study of stable beam generation in diodes and transport in finite cavities

Bifurcations of heterodimensional cycles with two saddle points

Energy Technology Data Exchange (ETDEWEB)

Geng Fengjie [School of Information Technology, China University of Geosciences (Beijing), Beijing 100083 (China)], E-mail: gengfengjie_hbu@163.com; Zhu Deming [Department of Mathematics, East China Normal University, Shanghai 200062 (China)], E-mail: dmzhu@math.ecnu.edu.cn; Xu Yancong [Department of Mathematics, East China Normal University, Shanghai 200062 (China)], E-mail: yancongx@163.com

2009-03-15

The bifurcations of 2-point heterodimensional cycles are investigated in this paper. Under some generic conditions, we establish the existence of one homoclinic loop, one periodic orbit, two periodic orbits, one 2-fold periodic orbit, and the coexistence of one periodic orbit and heteroclinic loop. Some bifurcation patterns different to the case of non-heterodimensional heteroclinic cycles are revealed.

Bifurcations of heterodimensional cycles with two saddle points

International Nuclear Information System (INIS)

Geng Fengjie; Zhu Deming; Xu Yancong

2009-01-01

The bifurcations of 2-point heterodimensional cycles are investigated in this paper. Under some generic conditions, we establish the existence of one homoclinic loop, one periodic orbit, two periodic orbits, one 2-fold periodic orbit, and the coexistence of one periodic orbit and heteroclinic loop. Some bifurcation patterns different to the case of non-heterodimensional heteroclinic cycles are revealed.

Unfolding the Riddling Bifurcation

DEFF Research Database (Denmark)

Maistrenko, Yu.; Popovych, O.; Mosekilde, Erik

1999-01-01

We present analytical conditions for the riddling bifurcation in a system of two symmetrically coupled, identical, smooth one-dimensional maps to be soft or hard and describe a generic scenario for the transformations of the basin of attraction following a soft riddling bifurcation.......We present analytical conditions for the riddling bifurcation in a system of two symmetrically coupled, identical, smooth one-dimensional maps to be soft or hard and describe a generic scenario for the transformations of the basin of attraction following a soft riddling bifurcation....

[Coronary angioplasty simultaneous with the "kissing" technique in a bifurcation lesion: use of a guidewire, and 2 monorail systems of rapid interchange].

Science.gov (United States)

Escudero, X

1996-01-01

Coronary branch occlusion complicating percutaneous coronary angioplasty has been recognized in certain bifurcation lesions. The utilization of double angioplasty systems simultaneously has been called "kissing" because the image of contact between balloons, and has been utilized as an alternative to protect the jeopardized branch or prevent snowplow lesion of the principal artery. The technological advance with the use of wide lumen catheters and low profile dilation balloons make the application of this technique possible in those type of lesions using a single guiding catheter. The present paper describes one case treated with this technique using conventional angioplasty systems in a complex bifurcating lesion of the circumflex artery. Some technical considerations about the procedure are made.

Magnetic resonance angiography of the extracranial carotid and vertebral arteries

International Nuclear Information System (INIS)

Akimura, Tatsuo; Saito, Kenichi; Nakayama, Hisato; Kashiwagi, Shiro; Kato, Shoichi; Ito, Haruhide.

1994-01-01

To evaluate the contribution of magnetic resonance angiography (MRA) in the screening study of the extracranial carotid and vertebral arteries using the conventional head and neck coils, 500 consecutive MRAs of the cervical vessels were performed using 1.5 tesla magnetic resonance unit with circularly polarized head coil. The 5 cm-thick imaging plane was placed in coronal fashion including both carotid and vertebral arteries. The imaging sequence was three-dimensional (3D) fast imaging with steady precession (FISP). In 10 patients with failed head coil examination, 10 patients with possible carotid and vertebral diseases and 10 volunteers, the extracranial carotid and vertebral arteries were examined with the Helmholtz neck coil. Both 3D- and 2D-FISP were performed in each case. The imaging plane was placed in oblique sagittal fashion. In 458 out of 500 cases (91.6%), the extracranial carotid and vertebral arteries were successfully depicted using head coil. In 20 patients with high shoulders, the carotid bifurcations were out of range of the head coil. In these cases, carotid bifurcations and the origins of the carotid and vertebral arteries were successfully revealed using a neck coil. To evaluate the stenotic lesions and tortuous vessels, 2D-FISP sequence seemed to be more suitable than 3D-FISP. Compared with conventional angiography, MRA caused overestimation of the degree of stenotic lesions. For screening examination of the extracranial carotid and vertebral arteries, most cases can be evaluated only with the conventional head coil. If depiction of the carotid bifurcation fails and the examination of carotids or vertebrals down to the aortic arch is needed, neck coil examination is required. (author)

Bifurcations sights, sounds, and mathematics

CERN Document Server

Matsumoto, Takashi; Kokubu, Hiroshi; Tokunaga, Ryuji

1993-01-01

Bifurcation originally meant "splitting into two parts. " Namely, a system under­ goes a bifurcation when there is a qualitative change in the behavior of the sys­ tem. Bifurcation in the context of dynamical systems, where the time evolution of systems are involved, has been the subject of research for many scientists and engineers for the past hundred years simply because bifurcations are interesting. A very good way of understanding bifurcations would be to see them first and study theories second. Another way would be to first comprehend the basic concepts and theories and then see what they look like. In any event, it is best to both observe experiments and understand the theories of bifurcations. This book attempts to provide a general audience with both avenues toward understanding bifurcations. Specifically, (1) A variety of concrete experimental results obtained from electronic circuits are given in Chapter 1. All the circuits are very simple, which is crucial in any experiment. The circuits, howev...

Assessment of shear stress related parameters in the carotid bifurcation using mouse-specific FSI simulations.

Science.gov (United States)

De Wilde, David; Trachet, Bram; Debusschere, Nic; Iannaccone, Francesco; Swillens, Abigail; Degroote, Joris; Vierendeels, Jan; De Meyer, Guido R Y; Segers, Patrick

2016-07-26

The ApoE(-)(/)(-) mouse is a common small animal model to study atherosclerosis, an inflammatory disease of the large and medium sized arteries such as the carotid artery. It is generally accepted that the wall shear stress, induced by the blood flow, plays a key role in the onset of this disease. Wall shear stress, however, is difficult to derive from direct in vivo measurements, particularly in mice. In this study, we integrated in vivo imaging (micro-Computed Tomography-µCT and ultrasound) and fluid-structure interaction (FSI) modeling for the mouse-specific assessment of carotid hemodynamics and wall shear stress. Results were provided for 8 carotid bifurcations of 4 ApoE(-)(/)(-) mice. We demonstrated that accounting for the carotid elasticity leads to more realistic flow waveforms over the complete domain of the model due to volume buffering capacity in systole. The 8 simulated cases showed fairly consistent spatial distribution maps of time-averaged wall shear stress (TAWSS) and relative residence time (RRT). Zones with reduced TAWSS and elevated RRT, potential indicators of atherosclerosis-prone regions, were located mainly at the outer sinus of the external carotid artery. In contrast to human carotid hemodynamics, no flow recirculation could be observed in the carotid bifurcation region. Copyright © 2015 Elsevier Ltd. All rights reserved.

Unilateral high bifurcation of brachial artery: a case report | Auwal ...

African Journals Online (AJOL)

The Profunda Brachii, Superior Ulnar Collateral and Inferior Ulnar Collateral arteries arose from the relatively short brachial arterial trunk. Although the documented incidence of this anatomical variation is low in Nigeria, its concomitant widespread documentation in other parts of the world makes it a sufficiently important ...

Quantitative angiography methods for bifurcation lesions

DEFF Research Database (Denmark)

Collet, Carlos; Onuma, Yoshinobu; Cavalcante, Rafael

2017-01-01

Bifurcation lesions represent one of the most challenging lesion subsets in interventional cardiology. The European Bifurcation Club (EBC) is an academic consortium whose goal has been to assess and recommend the appropriate strategies to manage bifurcation lesions. The quantitative coronary...... angiography (QCA) methods for the evaluation of bifurcation lesions have been subject to extensive research. Single-vessel QCA has been shown to be inaccurate for the assessment of bifurcation lesion dimensions. For this reason, dedicated bifurcation software has been developed and validated. These software...

Simple or Complex Stenting for Bifurcation Coronary Lesions: A Patient-Level Pooled-Analysis of the Nordic Bifurcation Study and the British Bifurcation Coronary Study

DEFF Research Database (Denmark)

Behan, Miles W; Holm, Niels Ramsing; Curzen, Nicholas P

2011-01-01

Background— Controversy persists regarding the correct strategy for bifurcation lesions. Therefore, we combined the patient-level data from 2 large trials with similar methodology: the NORDIC Bifurcation Study (NORDIC I) and the British Bifurcation Coronary Study (BBC ONE). Methods and Results— B...

Bifurcation theory for hexagonal agglomeration in economic geography

CERN Document Server

Ikeda, Kiyohiro

2014-01-01

This book contributes to an understanding of how bifurcation theory adapts to the analysis of economic geography. It is easily accessible not only to mathematicians and economists, but also to upper-level undergraduate and graduate students who are interested in nonlinear mathematics. The self-organization of hexagonal agglomeration patterns of industrial regions was first predicted by the central place theory in economic geography based on investigations of southern Germany. The emergence of hexagonal agglomeration in economic geography models was envisaged by Krugman. In this book, after a brief introduction of central place theory and new economic geography, the missing link between them is discovered by elucidating the mechanism of the evolution of bifurcating hexagonal patterns. Pattern formation by such bifurcation is a well-studied topic in nonlinear mathematics, and group-theoretic bifurcation analysis is a well-developed theoretical tool. A finite hexagonal lattice is used to express uniformly distri...

Detailed investigation of the bifurcation diagram of capacitively coupled Josephson junctions in high-Tc superconductors and its self similarity

Science.gov (United States)

Hamdipour, Mohammad

2018-04-01

We study an array of coupled Josephson junction of superconductor/insulator/superconductor type (SIS junction) as a model for high temperature superconductors with layered structure. In the current-voltage characteristics of this system there is a breakpoint region in which a net electric charge appear on superconducting layers, S-layers, of junctions which motivate us to study the charge dynamics in this region. In this paper first of all we show a current voltage characteristics (CVC) of Intrinsic Josephson Junctions (IJJs) with N=3 Junctions, then we show the breakpoint region in that CVC, then we try to investigate the chaos in this region. We will see that at the end of the breakpoint region, behavior of the system is chaotic and Lyapunov exponent become positive. We also study the route by which the system become chaotic and will see this route is bifurcation. Next goal of this paper is to show the self similarity in the bifurcation diagram of the system and detailed analysis of bifurcation diagram.

Bifurcation Analysis of the QI 3-D Four-Wing Chaotic System

International Nuclear Information System (INIS)

Sun, Y.; Qi, G.; Wang, Z.; Wyk, B.J. van

2010-01-01

This paper analyzes the pitchfork and Hopf bifurcations of a new 3-D four-wing quadratic autonomous system proposed by Qi et al. The center manifold technique is used to reduce the dimensions of this system. The pitchfork and Hopf bifurcations of the system are theoretically analyzed. The influence of system parameters on other bifurcations are also investigated. The theoretical analysis and simulations demonstrate the rich dynamics of the system. (authors)

Energized Oxygen : Speiser Current Sheet Bifurcation

Science.gov (United States)

George, D. E.; Jahn, J. M.

2017-12-01

A single population of energized Oxygen (O+) is shown to produce a cross-tail bifurcated current sheet in 2.5D PIC simulations of the magnetotail without the influence of magnetic reconnection. Treatment of oxygen in simulations of space plasmas, specifically a magnetotail current sheet, has been limited to thermal energies despite observations of and mechanisms which explain energized ions. We performed simulations of a homogeneous oxygen background, that has been energized in a physically appropriate manner, to study the behavior of current sheets and magnetic reconnection, specifically their bifurcation. This work uses a 2.5D explicit Particle-In-a-Cell (PIC) code to investigate the dynamics of energized heavy ions as they stream Dawn-to-Dusk in the magnetotail current sheet. We present a simulation study dealing with the response of a current sheet system to energized oxygen ions. We establish a, well known and studied, 2-species GEM Challenge Harris current sheet as a starting point. This system is known to eventually evolve and produce magnetic reconnection upon thinning of the current sheet. We added a uniform distribution of thermal O+ to the background. This 3-species system is also known to eventually evolve and produce magnetic reconnection. We add one additional variable to the system by providing an initial duskward velocity to energize the O+. We also traced individual particle motion within the PIC simulation. Three main results are shown. First, energized dawn- dusk streaming ions are clearly seen to exhibit sustained Speiser motion. Second, a single population of heavy ions clearly produces a stable bifurcated current sheet. Third, magnetic reconnection is not required to produce the bifurcated current sheet. Finally a bifurcated current sheet is compatible with the Harris current sheet model. This work is the first step in a series of investigations aimed at studying the effects of energized heavy ions on magnetic reconnection. This work differs

Analysis of stability and Hopf bifurcation for a delayed logistic equation

International Nuclear Information System (INIS)

Sun Chengjun; Han Maoan; Lin Yiping

2007-01-01

The dynamics of a logistic equation with discrete delay are investigated, together with the local and global stability of the equilibria. In particular, the conditions under which a sequence of Hopf bifurcations occur at the positive equilibrium are obtained. Explicit algorithm for determining the stability of the bifurcating periodic solutions and the direction of the Hopf bifurcation are derived by using the theory of normal form and center manifold [Hassard B, Kazarino D, Wan Y. Theory and applications of Hopf bifurcation. Cambridge: Cambridge University Press; 1981.]. Global existence of periodic solutions is also established by using a global Hopf bifurcation result of Wu [Symmetric functional differential equations and neural networks with memory. Trans Amer Math Soc 350:1998;4799-38.

Bifurcations of a periodically forced microbial continuous culture model with restrained growth rate

Science.gov (United States)

Ren, Jingli; Yuan, Qigang

2017-08-01

A three dimensional microbial continuous culture model with a restrained microbial growth rate is studied in this paper. Two types of dilution rates are considered to investigate the dynamic behaviors of the model. For the unforced system, fold bifurcation and Hopf bifurcation are detected, and numerical simulations reveal that the system undergoes degenerate Hopf bifurcation. When the system is periodically forced, bifurcation diagrams for periodic solutions of period-one and period-two are given by researching the Poincaré map, corresponding to different bifurcation cases in the unforced system. Stable and unstable quasiperiodic solutions are obtained by Neimark-Sacker bifurcation with different parameter values. Periodic solutions of various periods can occur or disappear and even change their stability, when the Poincaré map of the forced system undergoes Neimark-Sacker bifurcation, flip bifurcation, and fold bifurcation. Chaotic attractors generated by a cascade of period doublings and some phase portraits are given at last.

Bifurcation structure of parameter plane for a family of unimodal piecewise smooth maps: Border-collision bifurcation curves

International Nuclear Information System (INIS)

Sushko, Iryna; Agliari, Anna; Gardini, Laura

2006-01-01

We study the structure of the 2D bifurcation diagram for a two-parameter family of piecewise smooth unimodal maps f with one break point. Analysing the parameters of the normal form for the border-collision bifurcation of an attracting n-cycle of the map f, we describe the possible kinds of dynamics associated with such a bifurcation. Emergence and role of border-collision bifurcation curves in the 2D bifurcation plane are studied. Particular attention is paid also to the curves of homoclinic bifurcations giving rise to the band merging of pieces of cyclic chaotic intervals

Innominate artery war injury

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Ilić Radoje

2005-01-01

Full Text Available Aim. A case is reported of successfully surgically treated explosive war injury to the innominate artery. Case report. A 26 - year-old soldier was injured in combat by a fragment of mortar shell. In the field hospital, the wound gauze packing was applied, followed by orotracheal intubation and thoracic drainage. The soldier was admitted to MMA six hours later. Physical examination, on admission, revealed huge swelling of the neck, the absence of pulse in the right arm and the right common carotid artery. Chest x-ray revealed hemopneumothorax of the right side and the foreign metal body in the projection of the right sternoclavicular joint. Due to the suspicion of large vessel injury, a median sternotomy was immediately performed. Surgery revealed disrupted bifurcation of the right innominate artery, so the ligation was performed. Aortography was performed postoperatively, followed by the reconstruction of innominate bifurcation with synthetic grafts. Control aortography showed good graft patency, and the patient was discharged from the hospital in good general condition with palpable pulses and mild anisocoria as a sole neurological sequela. Conclusion. A rare and life-threatening injury was successfully managed, mainly due to the rational treatment carried out in the field hospital that helped the injured to survive and arrive to the institution capable of performing the most sophisticated diagnostic and therapeutic procedures.

Bifurcation dynamics of the tempered fractional Langevin equation

Energy Technology Data Exchange (ETDEWEB)

Zeng, Caibin, E-mail: macbzeng@scut.edu.cn; Yang, Qigui, E-mail: qgyang@scut.edu.cn [School of Mathematics, South China University of Technology, Guangzhou 510640 (China); Chen, YangQuan, E-mail: ychen53@ucmerced.edu [MESA LAB, School of Engineering, University of California, Merced, 5200 N. Lake Road, Merced, California 95343 (United States)

2016-08-15

Tempered fractional processes offer a useful extension for turbulence to include low frequencies. In this paper, we investigate the stochastic phenomenological bifurcation, or stochastic P-bifurcation, of the Langevin equation perturbed by tempered fractional Brownian motion. However, most standard tools from the well-studied framework of random dynamical systems cannot be applied to systems driven by non-Markovian noise, so it is desirable to construct possible approaches in a non-Markovian framework. We first derive the spectral density function of the considered system based on the generalized Parseval's formula and the Wiener-Khinchin theorem. Then we show that it enjoys interesting and diverse bifurcation phenomena exchanging between or among explosive-like, unimodal, and bimodal kurtosis. Therefore, our procedures in this paper are not merely comparable in scope to the existing theory of Markovian systems but also provide a possible approach to discern P-bifurcation dynamics in the non-Markovian settings.

Relative Lyapunov Center Bifurcations

DEFF Research Database (Denmark)

Wulff, Claudia; Schilder, Frank

2014-01-01

Relative equilibria (REs) and relative periodic orbits (RPOs) are ubiquitous in symmetric Hamiltonian systems and occur, for example, in celestial mechanics, molecular dynamics, and rigid body motion. REs are equilibria, and RPOs are periodic orbits of the symmetry reduced system. Relative Lyapunov...... center bifurcations are bifurcations of RPOs from REs corresponding to Lyapunov center bifurcations of the symmetry reduced dynamics. In this paper we first prove a relative Lyapunov center theorem by combining recent results on the persistence of RPOs in Hamiltonian systems with a symmetric Lyapunov...... center theorem of Montaldi, Roberts, and Stewart. We then develop numerical methods for the detection of relative Lyapunov center bifurcations along branches of RPOs and for their computation. We apply our methods to Lagrangian REs of the N-body problem....

Analysis of the flow at a T-bifurcation for a ternary unit

International Nuclear Information System (INIS)

Campero, P; Beck, J; Jung, A

2014-01-01

The motivation of this research is to understand the flow behavior through a 90° T- type bifurcation, which connects a Francis turbine and the storage pump of a ternary unit, under different operating conditions (namely turbine, pump and hydraulic short-circuit operation). As a first step a CFD optimization process to define the hydraulic geometry of the bifurcation was performed. The CFD results show the complexity of the flow through the bifurcation, especially under hydraulic short-circuit operation. Therefore, it was decided to perform experimental investigations in addition to the CFD analysis, in order to get a better understanding of the flow. The aim of these studies was to investigate the flow development upstream and downstream the bifurcation, the estimation of the bifurcation loss coefficients and also to provide comprehensive data of the flow behavior for the whole operating range of the machine. In order to evaluate the development of the velocity field Stereo Particle Image Velocimetry (S-PIV) measurements at different sections upstream and downstream of the bifurcation on the main penstock and Laser Doppler Anemometrie (LDA) measurements at bifurcation inlet were performed. This paper presents the CFD results obtained for the final design for different operating conditions, the model test procedures and the model test results with special attention to: 1) The bifurcation head loss coefficients, and their extrapolation to prototype conditions, 2) S-PIV and LDA measurements. Additionally, criteria to define the minimal uniformity conditions for the velocity profiles entering the turbine are evaluated. Finally, based on the gathered flow information a better understanding to define the preferred location of a bifurcation is gained and can be applied to future projects

Dynamic Bifurcations

CERN Document Server

1991-01-01

Dynamical Bifurcation Theory is concerned with the phenomena that occur in one parameter families of dynamical systems (usually ordinary differential equations), when the parameter is a slowly varying function of time. During the last decade these phenomena were observed and studied by many mathematicians, both pure and applied, from eastern and western countries, using classical and nonstandard analysis. It is the purpose of this book to give an account of these developments. The first paper, by C. Lobry, is an introduction: the reader will find here an explanation of the problems and some easy examples; this paper also explains the role of each of the other paper within the volume and their relationship to one another. CONTENTS: C. Lobry: Dynamic Bifurcations.- T. Erneux, E.L. Reiss, L.J. Holden, M. Georgiou: Slow Passage through Bifurcation and Limit Points. Asymptotic Theory and Applications.- M. Canalis-Durand: Formal Expansion of van der Pol Equation Canard Solutions are Gevrey.- V. Gautheron, E. Isambe...

Nonlinear stability control and λ-bifurcation

International Nuclear Information System (INIS)

Erneux, T.; Reiss, E.L.; Magnan, J.F.; Jayakumar, P.K.

1987-01-01

Passive techniques for nonlinear stability control are presented for a model of fluidelastic instability. They employ the phenomena of λ-bifurcation and a generalization of it. λ-bifurcation occurs when a branch of flutter solutions bifurcates supercritically from a basic solution and terminates with an infinite period orbit at a branch of divergence solutions which bifurcates subcritically from the basic solution. The shape of the bifurcation diagram then resembles the greek letter λ. When the system parameters are in the range where flutter occurs by λ-bifurcation, then as the flow velocity increase the flutter amplitude also increases, but the frequencies of the oscillations decrease to zero. This diminishes the damaging effects of structural fatigue by flutter, and permits the flow speed to exceed the critical flutter speed. If generalized λ-bifurcation occurs, then there is a jump transition from the flutter states to a divergence state with a substantially smaller amplitude, when the flow speed is sufficiently larger than the critical flutter speed

Bifurcation of steady tearing states

International Nuclear Information System (INIS)

Saramito, B.; Maschke, E.K.

1985-10-01

We apply the bifurcation theory for compact operators to the problem of the nonlinear solutions of the 3-dimensional incompressible visco-resistive MHD equations. For the plane plasma slab model we compute branches of nonlinear tearing modes, which are stationary for the range of parameters investigated up to now

Unruptured internal carotid artery bifurcation aneurysms: general features and overall results after modern treatment.

Science.gov (United States)

La Pira, Biagia; Brinjikji, Waleed; Burrows, Anthony M; Cloft, Harry J; Vine, Roanna L; Lanzino, Giuseppe

2016-11-01

Internal carotid artery bifurcation aneurysms (ICAbifAs) present unique challenges to endovascular and surgical operators, and little is known about their natural history. We reviewed our institution's experience with ICAbifAs studying outcomes of surgical and endovascular management and natural history. Consecutive patients with unruptured ICAbifAs evaluated and/or treated over an 8-year interval were studied. Baseline demographics, neurovascular risk factors, aneurysm location and size, clinical presentation, treatment recommendations, and outcomes were prospectively collected and retrospectively analyzed. Continuous variables were compared with Student's t test and categorical variables with Chi-square tests. Fifty-nine patients with 61 unruptured ICAbifAs were included. Seven aneurysms were treated surgically (11.5 %), 22 underwent endovascular treatment (36 %), and 32 were managed conservatively (52.5 %). In the surgical group, short- and long-term complete aneurysm occlusion rates were 100 % with no cases of perioperative or long-term permanent morbidity or treatment-related mortality. In the endovascular group, two patients (11.7 %) with giant aneurysms had perioperative thromboembolic events with transient morbidity. There was one case of aneurysm rupture at follow-up in a giant aneurysm treated with partial coil embolization. Complete/near-complete occlusion rates were 63 %. There was one case of aneurysm rupture after 114 aneurysm-years of follow-up in the conservative management group (0.89 %/year), but no ruptures were observed in small aneurysms selected for conservative management. Unruptured small ICAbifAs have a benign natural history. In patients selected for treatment, excellent results can be achieved in the vast majority of patients with judicious use of endovascular and surgical therapy.

Bifurcation analysis and stability design for aircraft longitudinal motion with high angle of attack

Directory of Open Access Journals (Sweden)

Xin Qi

2015-02-01

Full Text Available Bifurcation analysis and stability design for aircraft longitudinal motion are investigated when the nonlinearity in flight dynamics takes place severely at high angle of attack regime. To predict the special nonlinear flight phenomena, bifurcation theory and continuation method are employed to systematically analyze the nonlinear motions. With the refinement of the flight dynamics for F-8 Crusader longitudinal motion, a framework is derived to identify the stationary bifurcation and dynamic bifurcation for high-dimensional system. Case study shows that the F-8 longitudinal motion undergoes saddle node bifurcation, Hopf bifurcation, Zero-Hopf bifurcation and branch point bifurcation under certain conditions. Moreover, the Hopf bifurcation renders series of multiple frequency pitch oscillation phenomena, which deteriorate the flight control stability severely. To relieve the adverse effects of these phenomena, a stabilization control based on gain scheduling and polynomial fitting for F-8 longitudinal motion is presented to enlarge the flight envelope. Simulation results validate the effectiveness of the proposed scheme.

Intramural location and size of arterial calcification are associated with stenosis at carotid bifurcation

Energy Technology Data Exchange (ETDEWEB)

Yamada, Shigeki, E-mail: shigekiyamada3@gmail.com [Department of Neurosurgery and Stroke Center, Rakuwakai Otowa Hospital, Otowachinji-cho 2, Yamashina-ku, Kyoto 607-8602 (Japan); Department of Neurosurgery, Hamamatsu Rosai Hospital, 25 Shogen-cho, Higashi-ku, Hamamatsu city, Shizuoka 430-8525 (Japan); Interfaculty Initiative in Information Studies/Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Oshima, Marie, E-mail: marie@iis.u-tokyo.ac.jp [Interfaculty Initiative in Information Studies/Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Watanabe, Yoshihiko, E-mail: ynabe@magic.odn.ne.jp [Department of Neurosurgery, Hamamatsu Rosai Hospital, 25 Shogen-cho, Higashi-ku, Hamamatsu city, Shizuoka 430-8525 (Japan); Ogata, Hideki, E-mail: hidogata@gmail.com [Department of Neurosurgery, Hamamatsu Rosai Hospital, 25 Shogen-cho, Higashi-ku, Hamamatsu city, Shizuoka 430-8525 (Japan); Hashimoto, Kenji, E-mail: hashiken8022@yahoo.co.jp [Department of Neurosurgery, Kishiwada Municipal Hospital, 1001 Gakuhara-cho, Kishiwada city, Osaka 596-8501 (Japan); Miyake, Hidenori, E-mail: hi-miyake@hamamatsuh.rofuku.go.jp [Department of Neurosurgery, Hamamatsu Rosai Hospital, 25 Shogen-cho, Higashi-ku, Hamamatsu city, Shizuoka 430-8525 (Japan)

2014-06-15

Purpose: The purpose of this study was to investigate the association between internal carotid artery (ICA) stenosis and intramural location and size of calcification at the ICA origins and the origins of the cervical arteries proximal to the ICA. Method: A total of 1139 ICAs were evaluated stenosis and calcification on the multi-detector row CT angiography. The intramural location was categorized into none, outside and inside location. The calcification size was evaluated on the 4-point grading scale. The multivariate analyses were adjusted for age, serum creatinine level, hypertension, hyperlipidemia, diabetes mellitus, smoking and alcohol habits. Results: Outside calcification at the ICA origins showed the highest multivariate odds ratio (OR) for the presence of ICA stenosis (30.0) and severe calcification (a semicircle or more of calcification at the arterial cross-sectional surfaces) did the second (14.3). In the subgroups of >70% ICA stenosis, the multivariate OR of outside location increased to 44.8 and that of severe calcification also increased to 32.7. Four of 5 calcified carotid plaque specimens extracted by carotid endarterectomy were histologically confirmed to be calcified burdens located outside the internal elastic lamia which were defined as arterial medial calcification. Conclusions: ICA stenosis was strongly associated with severe calcification located mainly outside the carotid plaque. Outside calcification at the ICA origins should be evaluated separately from inside calcification, as a marker for the ICA stenosis. Additionally, we found that calcification at the origins of the cervical arteries proximal to the ICA was significantly associated with the ICA stenosis.

Digital subtraction angiography of carotid bifurcation

International Nuclear Information System (INIS)

Vries, A.R. de.

1984-01-01

This study demonstrates the reliability of digital subtraction angiography (DSA) by means of intra- and interobserver investigations as well as indicating the possibility of substituting catheterangiography by DSA in the diagnosis of carotid bifurcation. Whenever insufficient information is obtained from the combination of non-invasive investigation and DSA, a catheterangiogram will be necessary. (Auth.)

Stability, bifurcation and a new chaos in the logistic differential equation with delay

International Nuclear Information System (INIS)

Jiang Minghui; Shen Yi; Jian Jigui; Liao Xiaoxin

2006-01-01

This Letter is concerned with bifurcation and chaos in the logistic delay differential equation with a parameter r. The linear stability of the logistic equation is investigated by analyzing the associated characteristic transcendental equation. Based on the normal form approach and the center manifold theory, the formula for determining the direction of Hopf bifurcation and the stability of bifurcation periodic solution in the first bifurcation values is obtained. By theoretical analysis and numerical simulation, we found a new chaos in the logistic delay differential equation

Characterization of volumetric flow rate waveforms at the carotid bifurcations of older adults

International Nuclear Information System (INIS)

Hoi, Yiemeng; Xie, Yuanyuan J; Steinman, David A; Wasserman, Bruce A; Najjar, Samer S; Lakatta, Edward G; Ferruci, Luigi; Gerstenblith, Gary

2010-01-01

While it is widely appreciated that volumetric blood flow rate (VFR) dynamics change with age, there has been no detailed characterization of the typical shape of carotid bifurcation VFR waveforms of older adults. Toward this end, retrospectively gated phase contrast magnetic resonance imaging was used to measure time-resolved VFR waveforms proximal and distal to the carotid bifurcations of 94 older adults (age 68 ± 8 years) with little or no carotid artery disease, recruited from the BLSA cohort of the VALIDATE study of factors in vascular aging. Timings and amplitudes of well-defined feature points from these waveforms were extracted automatically and averaged to produce representative common, internal and external carotid artery (CCA, ICA and ECA) waveform shapes. Relative to young adults, waveforms from older adults were found to exhibit a significantly augmented secondary peak during late systole, resulting in significantly higher resistance index (RI) and flow augmentation index (FAI). Cycle-averaged VFR at the CCA, ICA and ECA were 389 ± 74, 245 ± 61 and 125 ± 49 mL min −1 , respectively, reflecting a significant cycle-averaged outflow deficit of 5%, which peaked at around 10% during systole. A small but significant mean delay of 13 ms between arrivals of ICA versus CCA/ECA peak VFR suggested differential compliance of these vessels. Sex and age differences in waveform shape were also noted. The characteristic waveforms presented here may serve as a convenient baseline for studies of VFR waveform dynamics or as suitable boundary conditions for models of blood flow in the carotid arteries of older adults

Effect of Cervical Siphon of External and Internal Carotid Arteries.

Science.gov (United States)

Singh, Rajani; Tubbs, Richard Shane

2017-10-01

Variant courses, configuration, and branching pattern of the external and internal carotid arteries, especially when curved in S-shape, are important for hemodynamic changes and clinical implications. Therefore, the aim of the study is to report abnormal cervical siphons observed in external and internal carotid arteries to explore clinical significance by review of literature and hemodynamic changes theoretically.The right common carotid artery bifurcated into external and internal carotid arteries at the level of the upper border of thyroid cartilage in a 70-year-old female cadaver. After bifurcation, the external carotid artery underwent severe tortuosity coursing through 5 bends at points A, B, C, D, and E from its origin to termination and 2 bends at A' and B' in internal carotid artery in the cervical region. The angles between inflow and out flow of the blood at the bends were measured and the change in velocity at each bend was computed for both arteries. Hemodynamic changes were calculated, compared and relevant clinical complications were theoretically correlated.The angles of 20°, 30°, 51°, 52°, 60°, and 28°, 48° were formed by 5 bends of external and 2 bends of internal carotid arteries, respectively. The curved courses of these arteries caused reduction in velocity/stasis, turbulence, and low shear stress. Such kinks might cause stroke, ischemia and mistaken for tumors and abscess in imagery leading to or otherwise producing iatrogenic repercussions. This study will be useful for anatomists, clinicians, and radiologists.

Transportation and concentration inequalities for bifurcating Markov chains

DEFF Research Database (Denmark)

Penda, S. Valère Bitseki; Escobar-Bach, Mikael; Guillin, Arnaud

2017-01-01

We investigate the transportation inequality for bifurcating Markov chains which are a class of processes indexed by a regular binary tree. Fitting well models like cell growth when each individual gives birth to exactly two offsprings, we use transportation inequalities to provide useful...... concentration inequalities.We also study deviation inequalities for the empirical means under relaxed assumptions on the Wasserstein contraction for the Markov kernels. Applications to bifurcating nonlinear autoregressive processes are considered for point-wise estimates of the non-linear autoregressive...

Delay Induced Hopf Bifurcation of an Epidemic Model with Graded Infection Rates for Internet Worms

Directory of Open Access Journals (Sweden)

Tao Zhao

2017-01-01

Full Text Available A delayed SEIQRS worm propagation model with different infection rates for the exposed computers and the infectious computers is investigated in this paper. The results are given in terms of the local stability and Hopf bifurcation. Sufficient conditions for the local stability and the existence of Hopf bifurcation are obtained by using eigenvalue method and choosing the delay as the bifurcation parameter. In particular, the direction and the stability of the Hopf bifurcation are investigated by means of the normal form theory and center manifold theorem. Finally, a numerical example is also presented to support the obtained theoretical results.

Sliding bifurcations and chaos induced by dry friction in a braking system

International Nuclear Information System (INIS)

Yang, F.H.; Zhang, W.; Wang, J.

2009-01-01

In this paper, non-smooth bifurcations and chaotic dynamics are investigated for a braking system. A three-degree-of-freedom model is considered to capture the complicated nonlinear characteristics, in particular, non-smooth bifurcations in the braking system. The stick-slip transition is analyzed for the braking system. From the results of numerical simulation, it is observed that there also exist the grazing-sliding bifurcation and stick-slip chaos in the braking system.

Emergence of the bifurcation structure of a Langmuir–Blodgett transfer model

KAUST Repository

Köpf, Michael H

2014-10-07

© 2014 IOP Publishing Ltd & London Mathematical Society. We explore the bifurcation structure of a modified Cahn-Hilliard equation that describes a system that may undergo a first-order phase transition and is kept permanently out of equilibrium by a lateral driving. This forms a simple model, e.g., for the deposition of stripe patterns of different phases of surfactant molecules through Langmuir-Blodgett transfer. Employing continuation techniques the bifurcation structure is numerically investigated using the non-dimensional transfer velocity as the main control parameter. It is found that the snaking structure of steady front states is intertwined with a large number of branches of time-periodic solutions that emerge from Hopf or period-doubling bifurcations and end in global bifurcations (sniper and homoclinic). Overall the bifurcation diagram has a harp-like appearance. This is complemented by a two-parameter study in non-dimensional transfer velocity and domain size (as a measure of the distance to the phase transition threshold) that elucidates through which local and global codimension 2 bifurcations the entire harp-like structure emerges.

Stability and Hopf bifurcation for a delayed SLBRS computer virus model.

Science.gov (United States)

Zhang, Zizhen; Yang, Huizhong

2014-01-01

By incorporating the time delay due to the period that computers use antivirus software to clean the virus into the SLBRS model a delayed SLBRS computer virus model is proposed in this paper. The dynamical behaviors which include local stability and Hopf bifurcation are investigated by regarding the delay as bifurcating parameter. Specially, direction and stability of the Hopf bifurcation are derived by applying the normal form method and center manifold theory. Finally, an illustrative example is also presented to testify our analytical results.

Stability and Hopf Bifurcation for a Delayed SLBRS Computer Virus Model

Directory of Open Access Journals (Sweden)

Zizhen Zhang

2014-01-01

Full Text Available By incorporating the time delay due to the period that computers use antivirus software to clean the virus into the SLBRS model a delayed SLBRS computer virus model is proposed in this paper. The dynamical behaviors which include local stability and Hopf bifurcation are investigated by regarding the delay as bifurcating parameter. Specially, direction and stability of the Hopf bifurcation are derived by applying the normal form method and center manifold theory. Finally, an illustrative example is also presented to testify our analytical results.

Bifurcation Analysis and Spatiotemporal Patterns in Unidirectionally Delay-Coupled Vibratory Gyroscopes

Science.gov (United States)

Li, Li; Xu, Jian

Time delay is inevitable in unidirectionally coupled drive-free vibratory gyroscope system. The effect of time delay on the gyroscope system is studied in this paper. To this end, amplitude death and Hopf bifurcation induced by small time delay are first investigated by analyzing the related characteristic equation. Then, the direction of Hopf bifurcations and stability of Hopf-bifurcating periodic oscillations are determined by calculating the normal form on the center manifold. Next, spatiotemporal patterns of these Hopf-bifurcating periodic oscillations are analyzed by using the symmetric bifurcation theory of delay differential equations. Finally, it is found that numerical simulations agree with the associated analytic results. These phenomena could be induced although time delay is very small. Therefore, it is shown that time delay is an important factor which influences the sensitivity and accuracy of the gyroscope system and cannot be neglected during the design and manufacture.

Sixth International Symposium on Bifurcations and Instabilities in Fluid Dynamics (BIFD2015)

DEFF Research Database (Denmark)

Bar-Yoseph, P. Z.; Brøns, Morten; Gelfgat, A.

2016-01-01

dynamics and remain a challenge for experimental, theoretical and computational studies. Examples of prototypical hydrodynamic instabilities are the Rayleigh–Bénard, Taylor–Couette, Bénard–Marangoni, Rayleigh–Taylor, and Kelvin–Helmholtz instabilities. A fundamental understanding of bifurcation patterns...... diseases, such as atherosclerotic and vulnerable plaques, abdominal aortic aneurisms, carotid artery disease, and pulmonary embolisms and implications for vascular interventions such as grafting and stenting. The collection of papers in this issue is a selection of the presentations given at the Sixth...

Increased Vessel Depiction of the Carotid Bifurcation with a Specialized 16-Channel Phased Array Coil at 3T

Science.gov (United States)

Tate, Quinn; Kim, Seong-Eun; Treiman, Gerald; Parker, Dennis L.; Hadley, J. Rock

2012-01-01

The purpose of this work was to design and construct a multi-channel receive-only RF coil for 3 Tesla magnetic resonance imaging of the human carotid artery and bifurcation with optimized signal to noise ratio in the carotid vessels along the full extent of the neck. A neck phantom designed to match the anatomy of a subject with a neck representing the body habitus often seen in subjects with carotid arterial disease, was constructed. Sixteen circular coil elements were arranged on a semi-rigid fiberglass former that closely fit the shape of the phantom, resulting in a 16-channel bilateral phased array coil. Comparisons were made between this coil and a typical 4-channel carotid coil in a study of 10 carotid vessels in 5 healthy volunteers. The 16-channel carotid coil showed a 73% average improvement in signal to noise ratio (SNR) at the carotid bifurcation. This coil also maintained an SNR greater than the peak SNR of the 4-channel coil over a vessel length of 10 cm. The resulting increase in SNR improved vessel depiction of the carotid arteries over an extended field of view, and demonstrated better image quality for higher parallel imaging reduction factors compared to the 4-channel coil. PMID:22777692

Heteroclinic Bifurcation Behaviors of a Duffing Oscillator with Delayed Feedback

Directory of Open Access Journals (Sweden)

Shao-Fang Wen

2018-01-01

Full Text Available The heteroclinic bifurcation and chaos of a Duffing oscillator with forcing excitation under both delayed displacement feedback and delayed velocity feedback are studied by Melnikov method. The Melnikov function is analytically established to detect the necessary conditions for generating chaos. Through the analysis of the analytical necessary conditions, we find that the influences of the delayed displacement feedback and delayed velocity feedback are separable. Then the influences of the displacement and velocity feedback parameters on heteroclinic bifurcation and threshold value of chaotic motion are investigated individually. In order to verify the correctness of the analytical conditions, the Duffing oscillator is also investigated by numerical iterative method. The bifurcation curves and the largest Lyapunov exponents are provided and compared. From the analysis of the numerical simulation results, it could be found that two types of period-doubling bifurcations occur in the Duffing oscillator, so that there are two paths leading to the chaos in this oscillator. The typical dynamical responses, including time histories, phase portraits, and Poincare maps, are all carried out to verify the conclusions. The results reveal some new phenomena, which is useful to design or control this kind of system.

Hopf bifurcations of a ratio-dependent predator–prey model involving two discrete maturation time delays

International Nuclear Information System (INIS)

Karaoglu, Esra; Merdan, Huseyin

2014-01-01

Highlights: • A ratio-dependent predator–prey system involving two discrete maturation time delays is studied. • Hopf bifurcations are analyzed by choosing delay parameters as bifurcation parameters. • When a delay parameter passes through a critical value, Hopf bifurcations occur. • The direction of bifurcation, the period and the stability of periodic solution are also obtained. - Abstract: In this paper we give a detailed Hopf bifurcation analysis of a ratio-dependent predator–prey system involving two different discrete delays. By analyzing the characteristic equation associated with the model, its linear stability is investigated. Choosing delay terms as bifurcation parameters the existence of Hopf bifurcations is demonstrated. Stability of the bifurcating periodic solutions is determined by using the center manifold theorem and the normal form theory introduced by Hassard et al. Furthermore, some of the bifurcation properties including direction, stability and period are given. Finally, theoretical results are supported by some numerical simulations

A bench top experimental model of bubble transport in multiple arteriole bifurcations

International Nuclear Information System (INIS)

Eshpuniyani, Brijesh; Fowlkes, J. Brian; Bull, Joseph L.

2005-01-01

Motivated by a novel gas embolotherapy technique, a bench top vascular bifurcation model is used to investigate the splitting of long bubbles in a series of liquid-filled bifurcations. The developmental gas embolotherapy technique aims to treat cancer by infarcting tumors with gas emboli that are formed by selective acoustic vaporization of ∼6 μm, intravascular, perfluorcarbon droplets. The resulting gas bubbles are large enough to extend through several vessel bifurcations. The current bench top experiments examine the effects of gravity and flow on bubble transport through multiple bifurcations. The effect of gravity is varied by changing the roll angle of the bifurcating network about its parent tube. Splitting at each bifurcation is nearly even when the roll angle is zero. It is demonstrated that bubbles can either stick at one of the second bifurcations or in the second generation daughter tubes, even though the flow rate in the parent tube is constant. The findings of this work indicate that both gravity and flow are important in determining the bubble transport, and suggest that a treatment strategy that includes multiple doses may be effective in delivering emboli to vessels not occluded by the initial dose

Bifurcation analysis of a discrete SIS model with bilinear incidence depending on new infection.

Science.gov (United States)

Cao, Hui; Zhou, Yicang; Ma, Zhien

2013-01-01

A discrete SIS epidemic model with the bilinear incidence depending on the new infection is formulated and studied. The condition for the global stability of the disease free equilibrium is obtained. The existence of the endemic equilibrium and its stability are investigated. More attention is paid to the existence of the saddle-node bifurcation, the flip bifurcation, and the Hopf bifurcation. Sufficient conditions for those bifurcations have been obtained. Numerical simulations are conducted to demonstrate our theoretical results and the complexity of the model.

Anomalies of radial and ulnar arteries

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Rajani Singh

Full Text Available Abstract During dissection conducted in an anatomy department of the right upper limb of the cadaver of a 70-year-old male, both origin and course of the radial and ulnar arteries were found to be anomalous. After descending 5.5 cm from the lower border of the teres major, the brachial artery anomalously bifurcated into a radial artery medially and an ulnar artery laterally. In the arm, the ulnar artery lay lateral to the median nerve. It followed a normal course in the forearm. The radial artery was medial to the median nerve in the arm and then, at the level of the medial epicondyle, it crossed from the medial to the lateral side of the forearm, superficial to the flexor muscles. The course of the radial artery was superficial and tortuous throughout the arm and forearm. The variations of radial and ulnar arteries described above were associated with anomalous formation and course of the median nerve in the arm. Knowledge of neurovascular anomalies are important for vascular surgeons and radiologists.

Stochastic Bifurcation Analysis of an Elastically Mounted Flapping Airfoil

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Bose Chandan

2018-01-01

Full Text Available The present paper investigates the effects of noisy flow fluctuations on the fluid-structure interaction (FSI behaviour of a span-wise flexible wing modelled as a two degree-of-freedom elastically mounted flapping airfoil. In the sterile flow conditions, the system undergoes a Hopf bifurcation as the free-stream velocity exceeds a critical limit resulting in a stable limit-cycle oscillation (LCO from a fixed point response. On the other hand, the qualitative dynamics changes from a stochastic fixed point to a random LCO through an intermittent state in the presence of irregular flow fluctuations. The probability density function depicts the most probable system state in the phase space. A phenomenological bifurcation (P-bifurcation analysis based on the transition in the topology associated with the structure of the joint probability density function (pdf of the response variables has been carried out. The joint pdf corresponding to the stochastic fixed point possesses a Dirac delta function like structure with a sharp single peak around zero. As the mean flow speed crosses the critical value, the joint pdf bifurcates to a crater-like structure indicating the occurrence of a P-bifurcation. The intermittent state is characterized by the co-existence of the unimodal as well as the crater like structure.

Bifurcation in a buoyant horizontal laminar jet

Science.gov (United States)

Arakeri, Jaywant H.; Das, Debopam; Srinivasan, J.

2000-06-01

The trajectory of a laminar buoyant jet discharged horizontally has been studied. The experimental observations were based on the injection of pure water into a brine solution. Under certain conditions the jet has been found to undergo bifurcation. The bifurcation of the jet occurs in a limited domain of Grashof number and Reynolds number. The regions in which the bifurcation occurs has been mapped in the Reynolds number Grashof number plane. There are three regions where bifurcation does not occur. The various mechanisms that prevent bifurcation have been proposed.

Bifurcations of Tumor-Immune Competition Systems with Delay

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Ping Bi

2014-01-01

Full Text Available A tumor-immune competition model with delay is considered, which consists of two-dimensional nonlinear differential equation. The conditions for the linear stability of the equilibria are obtained by analyzing the distribution of eigenvalues. General formulas for the direction, period, and stability of the bifurcated periodic solutions are given for codimension one and codimension two bifurcations, including Hopf bifurcation, steady-state bifurcation, and B-T bifurcation. Numerical examples and simulations are given to illustrate the bifurcations analysis and obtained results.

Bifurcation Analysis of Gene Propagation Model Governed by Reaction-Diffusion Equations

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Guichen Lu

2016-01-01

Full Text Available We present a theoretical analysis of the attractor bifurcation for gene propagation model governed by reaction-diffusion equations. We investigate the dynamical transition problems of the model under the homogeneous boundary conditions. By using the dynamical transition theory, we give a complete characterization of the bifurcated objects in terms of the biological parameters of the problem.

Hopf bifurcation in a dynamic IS-LM model with time delay

International Nuclear Information System (INIS)

Neamtu, Mihaela; Opris, Dumitru; Chilarescu, Constantin

2007-01-01

The paper investigates the impact of delayed tax revenues on the fiscal policy out-comes. Choosing the delay as a bifurcation parameter we study the direction and the stability of the bifurcating periodic solutions. We show when the system is stable with respect to the delay. Some numerical examples are given to confirm the theoretical results

Bifurcation and synchronization of synaptically coupled FHN models with time delay

International Nuclear Information System (INIS)

Wang Qingyun; Lu Qishao; Chen Guanrong; Feng Zhaosheng; Duan Lixia

2009-01-01

This paper presents an investigation of dynamics of the coupled nonidentical FHN models with synaptic connection, which can exhibit rich bifurcation behavior with variation of the coupling strength. With the time delay being introduced, the coupled neurons may display a transition from the original chaotic motions to periodic ones, which is accompanied by complex bifurcation scenario. At the same time, synchronization of the coupled neurons is studied in terms of their mean frequencies. We also find that the small time delay can induce new period windows with the coupling strength increasing. Moreover, it is found that synchronization of the coupled neurons can be achieved in some parameter ranges and related to their bifurcation transition. Bifurcation diagrams are obtained numerically or analytically from the mathematical model and the parameter regions of different behavior are clarified.

Growth hormone (GH) and atherosclerosis: changes in morphology and function of major arteries during GH treatment.

Science.gov (United States)

Pfeifer, M; Verhovec, R; Zizek, B

1999-04-01

Patients with hypopituitarism have increased carotid artery intima-media thickness and reduced arterial distensibility. The effect of 2 years of growth hormone (GH) replacement therapy on these parameters was studied in 11 GH-deficient men (age range, 24-49 years) with hypopituitarism and compared with 12 healthy, age-matched men with no evidence of pituitary or vascular disease. Before treatment the intima-media of the common carotid arteries and the carotid bifurcations were significantly thicker in patients (P < 0.001) than in the control group. Treatment with GH normalized the intima-media thickness of the common carotid artery within 6 months and of the carotid bifurcation within 3 months. The changes in intima-media thickness of the carotid artery were negatively correlated with changes in serum levels of insulin-like growth factor I during treatment. There was a significant improvement in flow-mediated, endothelium-dependent dilation of the brachial artery at 3 months, which was sustained at 6, 18 and 24 months of GH treatment (P < 0.05). Thus, GH replacement therapy in GH-deficient men reverses early morphological and functional atherosclerotic changes in major arteries, and may reduce rates of vascular morbidity and mortality.

Bifurcations in the optimal elastic foundation for a buckling column

International Nuclear Information System (INIS)

Rayneau-Kirkhope, Daniel; Farr, Robert; Ding, K.; Mao, Yong

2010-01-01

We investigate the buckling under compression of a slender beam with a distributed lateral elastic support, for which there is an associated cost. For a given cost, we study the optimal choice of support to protect against Euler buckling. We show that with only weak lateral support, the optimum distribution is a delta-function at the centre of the beam. When more support is allowed, we find numerically that the optimal distribution undergoes a series of bifurcations. We obtain analytical expressions for the buckling load around the first bifurcation point and corresponding expansions for the optimal position of support. Our theoretical predictions, including the critical exponent of the bifurcation, are confirmed by computer simulations.

Bifurcations in the optimal elastic foundation for a buckling column

Energy Technology Data Exchange (ETDEWEB)

Rayneau-Kirkhope, Daniel, E-mail: ppxdr@nottingham.ac.u [School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD (United Kingdom); Farr, Robert [Unilever R and D, Olivier van Noortlaan 120, AT3133, Vlaardingen (Netherlands); London Institute for Mathematical Sciences, 22 South Audley Street, Mayfair, London (United Kingdom); Ding, K. [Department of Physics, Fudan University, Shanghai, 200433 (China); Mao, Yong [School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD (United Kingdom)

2010-12-01

We investigate the buckling under compression of a slender beam with a distributed lateral elastic support, for which there is an associated cost. For a given cost, we study the optimal choice of support to protect against Euler buckling. We show that with only weak lateral support, the optimum distribution is a delta-function at the centre of the beam. When more support is allowed, we find numerically that the optimal distribution undergoes a series of bifurcations. We obtain analytical expressions for the buckling load around the first bifurcation point and corresponding expansions for the optimal position of support. Our theoretical predictions, including the critical exponent of the bifurcation, are confirmed by computer simulations.

The Aortic Bifurcation Angle as a Factor in Application of the Outback for Femoropopliteal Lesions in Ipsilateral Versus Contralateral Approaches.

Science.gov (United States)

Raskin, Daniel; Khaitovich, Boris; Balan, Shmuel; Silverberg, Daniel; Halak, Moshe; Rimon, Uri

2018-01-01

To assess the technical success of the Outback reentry device in contralateral versus ipsilateral approaches for femoropopliteal arterial occlusion. A retrospective review of patients treated for critical limb ischemia (CLI) using the Outback between January 2013 and July 2016 was performed. Age, gender, length and site of the occlusion, approach site, aortic bifurcation angle, and reentry site were recorded. Calcification score was assigned at both aortic bifurcation and reentry site. Technical success was assessed. During the study period, a total of 1300 endovascular procedures were performed on 489 patients for CLI. The Outback was applied on 50 femoropopliteal chronic total occlusions. Thirty-nine contralateral and 11 ipsilateral antegrade femoral were accessed. The device was used successfully in 41 patients (82%). There were nine failures, all in the contralateral approach group. Six due to inability to deliver the device due to acute aortic bifurcation angle and three due to failure to achieve luminal reentry. Procedural success was significantly affected by the aortic bifurcation angle (p = 0.013). The Outback has high technical success rates in treatment of femoropopliteal occlusion, when applied from either an ipsi- or contralateral approach. When applied in contralateral access, acute aortic bifurcation angle predicts procedural failure.

Analysis of stability and Hopf bifurcation for a viral infectious model with delay

International Nuclear Information System (INIS)

Sun Chengjun; Cao Zhijie; Lin Yiping

2007-01-01

In this paper, a four-dimensional viral infectious model with delay is considered. The stability of the two equilibria and the existence of Hopf bifurcation are investigated. It is found that there are stability switches and Hopf bifurcations occur when the delay τ passes through a sequence of critical values. Using the normal form theory and center manifold argument [Hassard B, Kazarino D, Wan Y. Theory and applications of Hopf bifurcation. Cambridge: Cambridge University Press; 1981], the explicit formulaes which determine the stability, the direction and the period of bifurcating periodic solutions are derived. Numerical simulations are carried out to illustrate the validity of the main results

Bifurcation of the spin-wave equations

International Nuclear Information System (INIS)

Cascon, A.; Koiller, J.; Rezende, S.M.

1990-01-01

We study the bifurcations of the spin-wave equations that describe the parametric pumping of collective modes in magnetic media. Mechanisms describing the following dynamical phenomena are proposed: (i) sequential excitation of modes via zero eigenvalue bifurcations; (ii) Hopf bifurcations followed (or not) by Feingenbaum cascades of period doubling; (iii) local and global homoclinic phenomena. Two new organizing center for routes to chaos are identified; in the classification given by Guckenheimer and Holmes [GH], one is a codimension-two local bifurcation, with one pair of imaginary eigenvalues and a zero eigenvalue, to which many dynamical consequences are known; secondly, global homoclinic bifurcations associated to splitting of separatrices, in the limit where the system can be considered a Hamiltonian subjected to weak dissipation and forcing. We outline what further numerical and algebraic work is necessary for the detailed study following this program. (author)

Bifurcation Control of an Electrostatically-Actuated MEMS Actuator with Time-Delay Feedback

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Lei Li

2016-10-01

Full Text Available The parametric excitation system consisting of a flexible beam and shuttle mass widely exists in microelectromechanical systems (MEMS, which can exhibit rich nonlinear dynamic behaviors. This article aims to theoretically investigate the nonlinear jumping phenomena and bifurcation conditions of a class of electrostatically-driven MEMS actuators with a time-delay feedback controller. Considering the comb structure consisting of a flexible beam and shuttle mass, the partial differential governing equation is obtained with both the linear and cubic nonlinear parametric excitation. Then, the method of multiple scales is introduced to obtain a slow flow that is analyzed for stability and bifurcation. Results show that time-delay feedback can improve resonance frequency and stability of the system. What is more, through a detailed mathematical analysis, the discriminant of Hopf bifurcation is theoretically derived, and appropriate time-delay feedback force can make the branch from the Hopf bifurcation point stable under any driving voltage value. Meanwhile, through global bifurcation analysis and saddle node bifurcation analysis, theoretical expressions about the system parameter space and maximum amplitude of monostable vibration are deduced. It is found that the disappearance of the global bifurcation point means the emergence of monostable vibration. Finally, detailed numerical results confirm the analytical prediction.

Bubble transport in bifurcations

Science.gov (United States)

Bull, Joseph; Qamar, Adnan

2017-11-01

Motivated by a developmental gas embolotherapy technique for cancer treatment, we examine the transport of bubbles entrained in liquid. In gas embolotherapy, infarction of tumors is induced by selectively formed vascular gas bubbles that originate from acoustic vaporization of vascular droplets. In the case of non-functionalized droplets with the objective of vessel occlusion, the bubbles are transported by flow through vessel bifurcations, where they may split prior to eventually reach vessels small enough that they become lodged. This splitting behavior affects the distribution of bubbles and the efficacy of flow occlusion and the treatment. In these studies, we investigated bubble transport in bifurcations using computational and theoretical modeling. The model reproduces the variety of experimentally observed splitting behaviors. Splitting homogeneity and maximum shear stress along the vessel walls is predicted over a variety of physical parameters. Maximum shear stresses were found to decrease with increasing Reynolds number. The initial bubble length was found to affect the splitting behavior in the presence of gravitational asymmetry. This work was supported by NIH Grant R01EB006476.

Nonresonant Double Hopf Bifurcation in Toxic Phytoplankton-Zooplankton Model with Delay

Science.gov (United States)

Yuan, Rui; Jiang, Weihua; Wang, Yong

This paper investigates a toxic phytoplankton-zooplankton model with Michaelis-Menten type phytoplankton harvesting. The model has rich dynamical behaviors. It undergoes transcritical, saddle-node, fold, Hopf, fold-Hopf and double Hopf bifurcation, when the parameters change and go through some of the critical values, the dynamical properties of the system will change also, such as the stability, equilibrium points and the periodic orbit. We first study the stability of the equilibria, and analyze the critical conditions for the above bifurcations at each equilibrium. In addition, the stability and direction of local Hopf bifurcations, and the completion bifurcation set by calculating the universal unfoldings near the double Hopf bifurcation point are given by the normal form theory and center manifold theorem. We obtained that the stable coexistent equilibrium point and stable periodic orbit alternate regularly when the digestion time delay is within some finite value. That is, we derived the pattern for the occurrence, and disappearance of a stable periodic orbit. Furthermore, we calculated the approximation expression of the critical bifurcation curve using the digestion time delay and the harvesting rate as parameters, and determined a large range in terms of the harvesting rate for the phytoplankton and zooplankton to coexist in a long term.

Magneto-elastic dynamics and bifurcation of rotating annular plate*

International Nuclear Information System (INIS)

Hu Yu-Da; Piao Jiang-Min; Li Wen-Qiang

2017-01-01

In this paper, magneto-elastic dynamic behavior, bifurcation, and chaos of a rotating annular thin plate with various boundary conditions are investigated. Based on the thin plate theory and the Maxwell equations, the magneto-elastic dynamic equations of rotating annular plate are derived by means of Hamilton’s principle. Bessel function as a mode shape function and the Galerkin method are used to achieve the transverse vibration differential equation of the rotating annular plate with different boundary conditions. By numerical analysis, the bifurcation diagrams with magnetic induction, amplitude and frequency of transverse excitation force as the control parameters are respectively plotted under different boundary conditions such as clamped supported sides, simply supported sides, and clamped-one-side combined with simply-anotherside. Poincaré maps, time history charts, power spectrum charts, and phase diagrams are obtained under certain conditions, and the influence of the bifurcation parameters on the bifurcation and chaos of the system is discussed. The results show that the motion of the system is a complicated and repeated process from multi-periodic motion to quasi-period motion to chaotic motion, which is accompanied by intermittent chaos, when the bifurcation parameters change. If the amplitude of transverse excitation force is bigger or magnetic induction intensity is smaller or boundary constraints level is lower, the system can be more prone to chaos. (paper)

Bifurcation analysis of the logistic map via two periodic impulsive forces

International Nuclear Information System (INIS)

Jiang Hai-Bo; Li Tao; Zeng Xiao-Liang; Zhang Li-Ping

2014-01-01

The complex dynamics of the logistic map via two periodic impulsive forces is investigated in this paper. The influences of the system parameter and the impulsive forces on the dynamics of the system are studied respectively. With the parameter varying, the system produces the phenomenon such as periodic solutions, chaotic solutions, and chaotic crisis. Furthermore, the system can evolve to chaos by a cascading of period-doubling bifurcations. The Poincaré map of the logistic map via two periodic impulsive forces is constructed and its bifurcation is analyzed. Finally, the Floquet theory is extended to explore the bifurcation mechanism for the periodic solutions of this non-smooth map. (general)

Hopf bifurcation in an Internet congestion control model

International Nuclear Information System (INIS)

Li Chunguang; Chen Guanrong; Liao Xiaofeng; Yu Juebang

2004-01-01

We consider an Internet model with a single link accessed by a single source, which responds to congestion signals from the network, and study bifurcation of such a system. By choosing the gain parameter as a bifurcation parameter, we prove that Hopf bifurcation occurs. The stability of bifurcating periodic solutions and the direction of the Hopf bifurcation are determined by applying the normal form theory and the center manifold theorem. Finally, a numerical example is given to verify the theoretical analysis

Stabilization of a percutaneously implanted port catheter system for hepatic artery chemotherapy infusion

International Nuclear Information System (INIS)

Shindoh, Noboru; Ozaki, Yutaka; Kyogoku, Shinsuke; Yamana, Daigo; Sumi, Yukiharu; Katayama, Hitoshi

1999-01-01

A port catheter system for hepatic artery infusion chemotherapy was implanted percutaneously via the left subclavian artery in 41 patients for treatment of unresectable liver metastases. The catheter tip was inserted into the gastroduodenal artery (GDA), the end hole was occluded with a guidewire fragment, and a side-hole for infusion was positioned at the bifurcation of the proper hepatic artery and the GDA. The GDA was embolized with steel coils around the infusion catheter tip via a transfemoral catheter. This procedure is designed to reduce the incidence of hepatic artery occlusion and infusion catheter dislocation.

Experimental and numerical investigations of shock wave propagation through a bifurcation

Science.gov (United States)

Marty, A.; Daniel, E.; Massoni, J.; Biamino, L.; Houas, L.; Leriche, D.; Jourdan, G.

2018-02-01

The propagation of a planar shock wave through a split channel is both experimentally and numerically studied. Experiments were conducted in a square cross-sectional shock tube having a main channel which splits into two symmetric secondary channels, for three different shock wave Mach numbers ranging from about 1.1 to 1.7. High-speed schlieren visualizations were used along with pressure measurements to analyze the main physical mechanisms that govern shock wave diffraction. It is shown that the flow behind the transmitted shock wave through the bifurcation resulted in a highly two-dimensional unsteady and non-uniform flow accompanied with significant pressure loss. In parallel, numerical simulations based on the solution of the Euler equations with a second-order Godunov scheme confirmed the experimental results with good agreement. Finally, a parametric study was carried out using numerical analysis where the angular displacement of the two channels that define the bifurcation was changed from 90° , 45° , 20° , and 0° . We found that the angular displacement does not significantly affect the overpressure experience in either of the two channels and that the area of the expansion region is the important variable affecting overpressure, the effect being, in the present case, a decrease of almost one half.

An evaluation of coronary artery lesions of Kawasaki disease and congenital heart disease using rotary three dimensional digital cardiovascular angiography

International Nuclear Information System (INIS)

Watanabe, Masanori; Ogawa, Shunichi; Kumazaki, Tatsuo; Hirayama, Tsuneo

1994-01-01

Congenital heart disease and the coronary artery lesions of children suffering from Kawasaki disease were evaluated by cardiovascular angiography using a newly developed rotary three-dimensional digital angiography method, and the usefulness of the device was examined. This method enable the observation of lesions from 144 directions within a 180 degree range depicting an image from optimal directions. In addition, the radiation exposure during one angiography was about one fifth of that of conventional cineangiography. With regard to the lesions of the coronary artery, identification of the localization of the stenotic lesions were made possible, especially at bifurcations, or the stenotic lesions overlapping with other bifurcations or coronary arteries aneurysms as well as the structure at the ostium of the left and right coronary arteries, which were difficult to identify using conventional coronary artery angiography. For the case of patient ductus arteriosus or major aortopulmonary collateral artery (MAPCA), separation and imaging of the overlap with other blood vessels through the three-dimensional observation became possible. This method is effective for the evaluation of the site, direction and morphology of these arteries. With regard to stenosis of the right ventricular outflow tract, the morphology and the degree of stenosis could be evaluated more accurately than by conventional cineangiography. In addition, the images matched well with the operative findings. This method was also effective for the diagnosis and evaluation of the stenosis at the main pulmonary artery and stenosis of the bifurcation of the right and left pulmonary arteries overlapping with the main trunk of the pulmonary artery. The problem with this method is that it cannot be used for the quantitative evaluation of the cardiac function because it cannot take images from multiple directions at the same time or cannot take temporal images from one direction. (author)

Anatomical-clinical investigations of variations of the human coronary arteries

OpenAIRE

Aida Hasanović; Faruk Dilberović; Fehim Ovčina

2003-01-01

Variations of the human coronary arteries have always attracted the attention of many researchers. A review of the literature shows that variations can cause ischemic heart disease or sudden cardiac death. The aim of the investigations was to examine the existence and clinical significance of variations of the human coronary arteries. Special attention has been focused on myocardial bridging of the coronary arteries and coronary arteriovenous fistula. Our investigations were carried out on th...

Delay-induced stochastic bifurcations in a bistable system under white noise

International Nuclear Information System (INIS)

Sun, Zhongkui; Fu, Jin; Xu, Wei; Xiao, Yuzhu

2015-01-01

In this paper, the effects of noise and time delay on stochastic bifurcations are investigated theoretically and numerically in a time-delayed Duffing-Van der Pol oscillator subjected to white noise. Due to the time delay, the random response is not Markovian. Thereby, approximate methods have been adopted to obtain the Fokker-Planck-Kolmogorov equation and the stationary probability density function for amplitude of the response. Based on the knowledge that stochastic bifurcation is characterized by the qualitative properties of the steady-state probability distribution, it is found that time delay and feedback intensity as well as noise intensity will induce the appearance of stochastic P-bifurcation. Besides, results demonstrated that the effects of the strength of the delayed displacement feedback on stochastic bifurcation are accompanied by the sensitive dependence on time delay. Furthermore, the results from numerical simulations best confirm the effectiveness of the theoretical analyses

Local and global bifurcations at infinity in models of glycolytic oscillations

DEFF Research Database (Denmark)

Sturis, Jeppe; Brøns, Morten

1997-01-01

We investigate two models of glycolytic oscillations. Each model consists of two coupled nonlinear ordinary differential equations. Both models are found to have a saddle point at infinity and to exhibit a saddle-node bifurcation at infinity, giving rise to a second saddle and a stable node...... at infinity. Depending on model parameters, a stable limit cycle may blow up to infinite period and amplitude and disappear in the bifurcation, and after the bifurcation, the stable node at infinity then attracts all trajectories. Alternatively, the stable node at infinity may coexist with either a stable...... sink (not at infinity) or a stable limit cycle. This limit cycle may then disappear in a heteroclinic bifurcation at infinity in which the unstable manifold from one saddle at infinity joins the stable manifold of the other saddle at infinity. These results explain prior reports for one of the models...

Delay-induced stochastic bifurcations in a bistable system under white noise

Energy Technology Data Exchange (ETDEWEB)

Sun, Zhongkui, E-mail: sunzk@nwpu.edu.cn; Fu, Jin; Xu, Wei [Department of Applied Mathematics, Northwestern Polytechnical University, Xi' an 710072 (China); Xiao, Yuzhu [Department of Mathematics and Information Science, Chang' an University, Xi' an 710086 (China)

2015-08-15

In this paper, the effects of noise and time delay on stochastic bifurcations are investigated theoretically and numerically in a time-delayed Duffing-Van der Pol oscillator subjected to white noise. Due to the time delay, the random response is not Markovian. Thereby, approximate methods have been adopted to obtain the Fokker-Planck-Kolmogorov equation and the stationary probability density function for amplitude of the response. Based on the knowledge that stochastic bifurcation is characterized by the qualitative properties of the steady-state probability distribution, it is found that time delay and feedback intensity as well as noise intensity will induce the appearance of stochastic P-bifurcation. Besides, results demonstrated that the effects of the strength of the delayed displacement feedback on stochastic bifurcation are accompanied by the sensitive dependence on time delay. Furthermore, the results from numerical simulations best confirm the effectiveness of the theoretical analyses.

Comparative study of Newtonian physiological blood flow through normal and stenosed carotid artery

Science.gov (United States)

Rahman, Mohammad Matiur; Hossain, Md. Anwar; Mamun, Khairuzzaman; Akhter, Most. Nasrin

2017-06-01

A numerical simulation is performed to investigate Newtonian physiological flows behavior on three dimensional idealized carotid artery (CA) and single stenosed (75% by area) carotid artery(SCA). The wall vessel is set as rigid during simulation. Bifurcated blood vessel are simulated by using three-dimensional flow analysis. Physiological and parabolic velocity profiles are set out to fix the conditions of inlet boundaries of artery. In other hand, physiological waveform is an important part of compilation and it is successfully done by utilization of Fourier series having sixteen harmonics. The investigation has a Reynolds number range of 94 to 1120. Low Reynolds number k — ω model has been used as governing equation. The investigation has been carried out to characterize the flow behavior of blood in two geometry, namely, (i) Normal carotid artery (CA) and (ii) Stenosed carotid artery (SCA). The Newtonian model has been used to study the physics of fluid. The findings of the two models are thoroughly compared in order to observe there behavioral sequence of flows. The numerical results were presented in terms of velocity, pressure, wall shear stress distributions and cross sectional velocities as well as the streamlines contour. Stenosis disturbs the normal pattern of blood flow through the artery as reduced area. At stenosis region velocity and peak Reynolds number rapidly increase and Reynolds number reach transitional and turbulent region. These flow fluctuation and turbulence have bad effect to the blood vessel which makes to accelerate the progress of stenosis.

Propagation of aortic dissection and visceral artery compromise. Three-dimensional analysis on CT angiography

International Nuclear Information System (INIS)

Minamiguchi, Hiroki

2003-01-01

The purpose of this study was to clarify the patterns of the propagation of aortic dissection with quantitative data from CT angiography and to verify the relationship between the propagation of aortic dissection and visceral artery compromise. The subjects were 67 cases (48 men, 19 women) with acute and subacute aortic dissection extending from the descending thoracic aorta to the aortic bifurcation. The mean age is 56.5±12.3 years old (range 34 to 80 years). Eight axial levels of the trunk of right pulmonary artery, left inferior pulmonary vein, coronary sinus, celiac axis, the orifice of superior mesenteric artery (SMA), the orifice of right real artery, the orifice of left renal artery and the orifice of inferior mesenteric artery were submitted to investigate the propagation of aortic dissection. The true lumen central angle was calculated in each level. The axial distance, branch angle difference and true distance between SMA and bilateral renal arteries were calculated. The trajectory of aortic dissection propagation from descending thoracic aorta to aortic bifurcation could be divided into two types of linear dissection type (n=41) and spiral dissection type (n=26). The latter were further subdivided into clockwise rotation type (n=14) and counter-clockwise rotation type (n=12). Younger age was significantly associated with the spiral dissection type as compared to older age (p=0.030). The spiral dissection type propagation pattern was found predominantly from the descending thoracic aorta to celiac axis, while at more distal levels linear type dissection was more common. The blood flow of SMA and celiac axis came from the true lumen or both lumens in all cases but single case from false lumen. The incidence (19.4%) of the right renal blood flow supplied from false lumen was lower than that (37.3%) of the left one supplied from false lumen. The shorter distance and the less angle difference between SMA and right renal artery than between SMA and left renal

Voltage stability, bifurcation parameters and continuation methods

Energy Technology Data Exchange (ETDEWEB)

Alvarado, F L [Wisconsin Univ., Madison, WI (United States)

1994-12-31

This paper considers the importance of the choice of bifurcation parameter in the determination of the voltage stability limit and the maximum power load ability of a system. When the bifurcation parameter is power demand, the two limits are equivalent. However, when other types of load models and bifurcation parameters are considered, the two concepts differ. The continuation method is considered as a method for determination of voltage stability margins. Three variants of the continuation method are described: the continuation parameter is the bifurcation parameter the continuation parameter is initially the bifurcation parameter, but is free to change, and the continuation parameter is a new `arc length` parameter. Implementations of voltage stability software using continuation methods are described. (author) 23 refs., 9 figs.

Bifurcation analysis on a generalized recurrent neural network with two interconnected three-neuron components

International Nuclear Information System (INIS)

Hajihosseini, Amirhossein; Maleki, Farzaneh; Rokni Lamooki, Gholam Reza

2011-01-01

Highlights: → We construct a recurrent neural network by generalizing a specific n-neuron network. → Several codimension 1 and 2 bifurcations take place in the newly constructed network. → The newly constructed network has higher capabilities to learn periodic signals. → The normal form theorem is applied to investigate dynamics of the network. → A series of bifurcation diagrams is given to support theoretical results. - Abstract: A class of recurrent neural networks is constructed by generalizing a specific class of n-neuron networks. It is shown that the newly constructed network experiences generic pitchfork and Hopf codimension one bifurcations. It is also proved that the emergence of generic Bogdanov-Takens, pitchfork-Hopf and Hopf-Hopf codimension two, and the degenerate Bogdanov-Takens bifurcation points in the parameter space is possible due to the intersections of codimension one bifurcation curves. The occurrence of bifurcations of higher codimensions significantly increases the capability of the newly constructed recurrent neural network to learn broader families of periodic signals.

Three-dimensional modelling of the human carotid artery using the lattice Boltzmann method: I. Model and velocity analysis

Energy Technology Data Exchange (ETDEWEB)

Boyd, J [Cardiovascular Research Group Physics, University of New England, Armidale, NSW 2351 (Australia); Buick, J M [Department of Mechanical and Design Engineering, University of Portsmouth, Anglesea Building, Anglesea Road, Portsmouth PO1 3DJ (United Kingdom)

2008-10-21

Numerical modelling is a powerful tool in the investigation of human blood flow and arterial diseases such as atherosclerosis. It is known that near wall velocity and shear are important in the pathogenesis and progression of atherosclerosis. In this paper results for a simulation of blood flow in a three-dimensional carotid artery geometry using the lattice Boltzmann method are presented. The velocity fields in the body of the fluid are analysed at six times of interest during a physiologically accurate velocity waveform. It is found that the three-dimensional model agrees well with previous literature results for carotid artery flow. Regions of low near wall velocity and circulatory flow are observed near the outer wall of the bifurcation and in the lower regions of the external carotid artery, which are regions that are typically prone to atherosclerosis.

Three-dimensional modelling of the human carotid artery using the lattice Boltzmann method: I. Model and velocity analysis

International Nuclear Information System (INIS)

Boyd, J; Buick, J M

2008-01-01

Numerical modelling is a powerful tool in the investigation of human blood flow and arterial diseases such as atherosclerosis. It is known that near wall velocity and shear are important in the pathogenesis and progression of atherosclerosis. In this paper results for a simulation of blood flow in a three-dimensional carotid artery geometry using the lattice Boltzmann method are presented. The velocity fields in the body of the fluid are analysed at six times of interest during a physiologically accurate velocity waveform. It is found that the three-dimensional model agrees well with previous literature results for carotid artery flow. Regions of low near wall velocity and circulatory flow are observed near the outer wall of the bifurcation and in the lower regions of the external carotid artery, which are regions that are typically prone to atherosclerosis.

Bifurcation structure of a model of bursting pancreatic cells

DEFF Research Database (Denmark)

Mosekilde, Erik; Lading, B.; Yanchuk, S.

2001-01-01

One- and two-dimensional bifurcation studies of a prototypic model of bursting oscillations in pancreatic P-cells reveal a squid-formed area of chaotic dynamics in the parameter plane, with period-doubling bifurcations on one side of the arms and saddle-node bifurcations on the other. The transit......One- and two-dimensional bifurcation studies of a prototypic model of bursting oscillations in pancreatic P-cells reveal a squid-formed area of chaotic dynamics in the parameter plane, with period-doubling bifurcations on one side of the arms and saddle-node bifurcations on the other....... The transition from this structure to the so-called period-adding structure is found to involve a subcritical period-doubling bifurcation and the emergence of type-III intermittency. The period-adding transition itself is not smooth but consists of a saddle-node bifurcation in which (n + 1)-spike bursting...

NUMERICAL HOPF BIFURCATION OF DELAY-DIFFERENTIAL EQUATIONS

Institute of Scientific and Technical Information of China (English)

无

2006-01-01

In this paper we consider the numerical solution of some delay differential equations undergoing a Hopf bifurcation. We prove that if the delay differential equations have a Hopf bifurcation point atλ=λ*, then the numerical solution of the equation also has a Hopf bifurcation point atλh =λ* + O(h).

Bifurcation of solutions to Hamiltonian boundary value problems

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McLachlan, R. I.; Offen, C.

2018-06-01

A bifurcation is a qualitative change in a family of solutions to an equation produced by varying parameters. In contrast to the local bifurcations of dynamical systems that are often related to a change in the number or stability of equilibria, bifurcations of boundary value problems are global in nature and may not be related to any obvious change in dynamical behaviour. Catastrophe theory is a well-developed framework which studies the bifurcations of critical points of functions. In this paper we study the bifurcations of solutions of boundary-value problems for symplectic maps, using the language of (finite-dimensional) singularity theory. We associate certain such problems with a geometric picture involving the intersection of Lagrangian submanifolds, and hence with the critical points of a suitable generating function. Within this framework, we then study the effect of three special cases: (i) some common boundary conditions, such as Dirichlet boundary conditions for second-order systems, restrict the possible types of bifurcations (for example, in generic planar systems only the A-series beginning with folds and cusps can occur); (ii) integrable systems, such as planar Hamiltonian systems, can exhibit a novel periodic pitchfork bifurcation; and (iii) systems with Hamiltonian symmetries or reversing symmetries can exhibit restricted bifurcations associated with the symmetry. This approach offers an alternative to the analysis of critical points in function spaces, typically used in the study of bifurcation of variational problems, and opens the way to the detection of more exotic bifurcations than the simple folds and cusps that are often found in examples.

Stability and Hopf bifurcations in a competitive Lotka-Volterra system with two delays

International Nuclear Information System (INIS)

Song Yongli; Han Maoan; Peng Yahong

2004-01-01

We consider a Lotka-Volterra competition system with two delays. We first investigate the stability of the positive equilibrium and the existence of Hopf bifurcations, and then using the normal form theory and center manifold argument, derive the explicit formulas which determine the stability, direction and other properties of bifurcating periodic solutions

Hopf bifurcation in a environmental defensive expenditures model with time delay

International Nuclear Information System (INIS)

Russu, Paolo

2009-01-01

In this paper a three-dimensional environmental defensive expenditures model with delay is considered. The model is based on the interactions among visitors V, quality of ecosystem goods E, and capital K, intended as accommodation and entertainment facilities, in Protected Areas (PAs). The tourism user fees (TUFs) are used partly as a defensive expenditure and partly to increase the capital stock. The stability and existence of Hopf bifurcation are investigated. It is that stability switches and Hopf bifurcation occurs when the delay t passes through a sequence of critical values, τ 0 . It has been that the introduction of a delay is a destabilizing process, in the sense that increasing the delay could cause the bio-economics to fluctuate. Formulas about the stability of bifurcating periodic solution and the direction of Hopf bifurcation are exhibited by applying the normal form theory and the center manifold theorem. Numerical simulations are given to illustrate the results.

Energetics and monsoon bifurcations

Science.gov (United States)

Seshadri, Ashwin K.

2017-01-01

Monsoons involve increases in dry static energy (DSE), with primary contributions from increased shortwave radiation and condensation of water vapor, compensated by DSE export via horizontal fluxes in monsoonal circulations. We introduce a simple box-model characterizing evolution of the DSE budget to study nonlinear dynamics of steady-state monsoons. Horizontal fluxes of DSE are stabilizing during monsoons, exporting DSE and hence weakening the monsoonal circulation. By contrast latent heat addition (LHA) due to condensation of water vapor destabilizes, by increasing the DSE budget. These two factors, horizontal DSE fluxes and LHA, are most strongly dependent on the contrast in tropospheric mean temperature between land and ocean. For the steady-state DSE in the box-model to be stable, the DSE flux should depend more strongly on the temperature contrast than LHA; stronger circulation then reduces DSE and thereby restores equilibrium. We present conditions for this to occur. The main focus of the paper is describing conditions for bifurcation behavior of simple models. Previous authors presented a minimal model of abrupt monsoon transitions and argued that such behavior can be related to a positive feedback called the `moisture advection feedback'. However, by accounting for the effect of vertical lapse rate of temperature on the DSE flux, we show that bifurcations are not a generic property of such models despite these fluxes being nonlinear in the temperature contrast. We explain the origin of this behavior and describe conditions for a bifurcation to occur. This is illustrated for the case of the July-mean monsoon over India. The default model with mean parameter estimates does not contain a bifurcation, but the model admits bifurcation as parameters are varied.

Bifurcation analysis of a delayed mathematical model for tumor growth

International Nuclear Information System (INIS)

Khajanchi, Subhas

2015-01-01

In this study, we present a modified mathematical model of tumor growth by introducing discrete time delay in interaction terms. The model describes the interaction between tumor cells, healthy tissue cells (host cells) and immune effector cells. The goal of this study is to obtain a better compatibility with reality for which we introduced the discrete time delay in the interaction between tumor cells and host cells. We investigate the local stability of the non-negative equilibria and the existence of Hopf-bifurcation by considering the discrete time delay as a bifurcation parameter. We estimate the length of delay to preserve the stability of bifurcating periodic solutions, which gives an idea about the mode of action for controlling oscillations in the tumor growth. Numerical simulations of the model confirm the analytical findings

Bifurcation and chaos in a Tessiet type food chain chemostat with pulsed input and washout

International Nuclear Information System (INIS)

Wang Fengyan; Hao Chunping; Chen Lansun

2007-01-01

In this paper, we introduce and study a model of a Tessiet type food chain chemostat with pulsed input and washout. We investigate the subsystem with substrate and prey and study the stability of the periodic solutions, which are the boundary periodic solutions of the system. The stability analysis of the boundary periodic solution yields an invasion threshold. By use of standard techniques of bifurcation theory, we prove that above this threshold there are periodic oscillations in substrate, prey and predator. Simple cycles may give way to chaos in a cascade of period-doubling bifurcations. Furthermore, by comparing bifurcation diagrams with different bifurcation parameters, we can see that the impulsive system shows two kinds of bifurcations, whose are period doubling and period halving

Stability and Hopf Bifurcation of Fractional-Order Complex-Valued Single Neuron Model with Time Delay

Science.gov (United States)

Wang, Zhen; Wang, Xiaohong; Li, Yuxia; Huang, Xia

2017-12-01

In this paper, the problems of stability and Hopf bifurcation in a class of fractional-order complex-valued single neuron model with time delay are addressed. With the help of the stability theory of fractional-order differential equations and Laplace transforms, several new sufficient conditions, which ensure the stability of the system are derived. Taking the time delay as the bifurcation parameter, Hopf bifurcation is investigated and the critical value of the time delay for the occurrence of Hopf bifurcation is determined. Finally, two representative numerical examples are given to show the effectiveness of the theoretical results.

Bifurcations of non-smooth systems

Science.gov (United States)

Angulo, Fabiola; Olivar, Gerard; Osorio, Gustavo A.; Escobar, Carlos M.; Ferreira, Jocirei D.; Redondo, Johan M.

2012-12-01

Non-smooth systems (namely piecewise-smooth systems) have received much attention in the last decade. Many contributions in this area show that theory and applications (to electronic circuits, mechanical systems, …) are relevant to problems in science and engineering. Specially, new bifurcations have been reported in the literature, and this was the topic of this minisymposium. Thus both bifurcation theory and its applications were included. Several contributions from different fields show that non-smooth bifurcations are a hot topic in research. Thus in this paper the reader can find contributions from electronics, energy markets and population dynamics. Also, a carefully-written specific algebraic software tool is presented.

Bifurcations of a class of singular biological economic models

International Nuclear Information System (INIS)

Zhang Xue; Zhang Qingling; Zhang Yue

2009-01-01

This paper studies systematically a prey-predator singular biological economic model with time delay. It shows that this model exhibits two bifurcation phenomena when the economic profit is zero. One is transcritical bifurcation which changes the stability of the system, and the other is singular induced bifurcation which indicates that zero economic profit brings impulse, i.e., rapid expansion of the population in biological explanation. On the other hand, if the economic profit is positive, at a critical value of bifurcation parameter, the system undergoes a Hopf bifurcation, i.e., the increase of delay destabilizes the system and bifurcates into small amplitude periodic solution. Finally, by using Matlab software, numerical simulations illustrate the effectiveness of the results obtained here. In addition, we study numerically that the system undergoes a saddle-node bifurcation when the bifurcation parameter goes through critical value of positive economic profit.

Bifurcation analysis on a delayed SIS epidemic model with stage structure

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Kejun Zhuang

2007-05-01

Full Text Available In this paper, a delayed SIS (Susceptible Infectious Susceptible model with stage structure is investigated. We study the Hopf bifurcations and stability of the model. Applying the normal form theory and the center manifold argument, we derive the explicit formulas determining the properties of the bifurcating periodic solutions. The conditions to guarantee the global existence of periodic solutions are established. Also some numerical simulations for supporting the theoretical are given.

Stability and bifurcation of numerical discretization of a second-order delay differential equation with negative feedback

International Nuclear Information System (INIS)

Ding Xiaohua; Su Huan; Liu Mingzhu

2008-01-01

The paper analyzes a discrete second-order, nonlinear delay differential equation with negative feedback. The characteristic equation of linear stability is solved, as a function of two parameters describing the strength of the feedback and the damping in the autonomous system. The existence of local Hopf bifurcations is investigated, and the direction and stability of periodic solutions bifurcating from the Hopf bifurcation of the discrete model are determined by the Hopf bifurcation theory of discrete system. Finally, some numerical simulations are performed to illustrate the analytical results found

Bifurcation and Control in a Singular Phytoplankton-Zooplankton-Fish Model with Nonlinear Fish Harvesting and Taxation

Science.gov (United States)

Meng, Xin-You; Wu, Yu-Qian

In this paper, a delayed differential algebraic phytoplankton-zooplankton-fish model with taxation and nonlinear fish harvesting is proposed. In the absence of time delay, the existence of singularity induced bifurcation is discussed by regarding economic interest as bifurcation parameter. A state feedback controller is designed to eliminate singularity induced bifurcation. Based on Liu’s criterion, Hopf bifurcation occurs at the interior equilibrium when taxation is taken as bifurcation parameter and is more than its corresponding critical value. In the presence of time delay, by analyzing the associated characteristic transcendental equation, the interior equilibrium loses local stability when time delay crosses its critical value. What’s more, the direction of Hopf bifurcation and stability of the bifurcating periodic solutions are investigated based on normal form theory and center manifold theorem, and nonlinear state feedback controller is designed to eliminate Hopf bifurcation. Furthermore, Pontryagin’s maximum principle has been used to obtain optimal tax policy to maximize the benefit as well as the conservation of the ecosystem. Finally, some numerical simulations are given to demonstrate our theoretical analysis.

Hopf bifurcation and chaos from torus breakdown in voltage-mode controlled DC drive systems

International Nuclear Information System (INIS)

Dai Dong; Ma Xikui; Zhang Bo; Tse, Chi K.

2009-01-01

Period-doubling bifurcation and its route to chaos have been thoroughly investigated in voltage-mode and current-mode controlled DC motor drives under simple proportional control. In this paper, the phenomena of Hopf bifurcation and chaos from torus breakdown in a voltage-mode controlled DC drive system is reported. It has been shown that Hopf bifurcation may occur when the DC drive system adopts a more practical proportional-integral control. The phenomena of period-adding and phase-locking are also observed after the Hopf bifurcation. Furthermore, it is shown that the stable torus can breakdown and chaos emerges afterwards. The work presented in this paper provides more complete information about the dynamical behaviors of DC drive systems.

Analysis of Vehicle Steering and Driving Bifurcation Characteristics

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Xianbin Wang

2015-01-01

Full Text Available The typical method of vehicle steering bifurcation analysis is based on the nonlinear autonomous vehicle model deriving from the classic two degrees of freedom (2DOF linear vehicle model. This method usually neglects the driving effect on steering bifurcation characteristics. However, in the steering and driving combined conditions, the tyre under different driving conditions can provide different lateral force. The steering bifurcation mechanism without the driving effect is not able to fully reveal the vehicle steering and driving bifurcation characteristics. Aiming at the aforementioned problem, this paper analyzed the vehicle steering and driving bifurcation characteristics with the consideration of driving effect. Based on the 5DOF vehicle system dynamics model with the consideration of driving effect, the 7DOF autonomous system model was established. The vehicle steering and driving bifurcation dynamic characteristics were analyzed with different driving mode and driving torque. Taking the front-wheel-drive system as an example, the dynamic evolution process of steering and driving bifurcation was analyzed by phase space, system state variables, power spectral density, and Lyapunov index. The numerical recognition results of chaos were also provided. The research results show that the driving mode and driving torque have the obvious effect on steering and driving bifurcation characteristics.

Association of lower extremity arterial calcification with amputation and mortality in patients with symptomatic peripheral artery disease.

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Chi-Lun Huang

Full Text Available OBJECTIVE: The clinical implication of the coronary artery calcium score (CS is well demonstrated. However, little is known about the association between lower extremity arterial calcification and clinical outcomes. METHODS AND RESULTS: Eighty-two patients with symptomatic peripheral artery disease (age 61.0±12.4 years were followed for 21±11 months. CSs, ranging from the common iliac artery bifurcation to the ankle area, were analyzed through noncontrast multidetector computed tomography images retrospectively. The primary endpoints of this study were amputation and mortality. Old age, diabetes, hyperlipidemia, and end-stage renal disease were associated with higher CSs. Patients with more advanced Fontaine stages also tended to have significantly higher CSs (p = 0.03. During the follow-up period (21±11 months, 29 (35% patients underwent amputation, and 24 (29% patients died. Among the patients who underwent amputation, there were no significant differences in CSs between the amputated legs and the non-amputated legs. In the Cox proportional hazard model with CS divided into quartiles, patients with CS in the highest quartile had a 2.88-fold (95% confidence interval [CI] 1.18-12.72, p = 0.03 and a 5.16-fold (95% CI 1.13-21.61, p = 0.04 higher risk for amputation and all-cause mortality, respectively, than those with CS in the lowest quartile. These predictive effects remained after conventional risk factor adjustment. CONCLUSION: Lower extremity arterial CSs are associated with disease severity and outcomes, including amputation and all-cause mortality, in patients with symptomatic peripheral artery disease. However, the independent predictive value needs further investigation in large scale, prospective studies.

Bifurcation scenarios for bubbling transition.

Science.gov (United States)

Zimin, Aleksey V; Hunt, Brian R; Ott, Edward

2003-01-01

Dynamical systems with chaos on an invariant submanifold can exhibit a type of behavior called bubbling, whereby a small random or fixed perturbation to the system induces intermittent bursting. The bifurcation to bubbling occurs when a periodic orbit embedded in the chaotic attractor in the invariant manifold becomes unstable to perturbations transverse to the invariant manifold. Generically the periodic orbit can become transversely unstable through a pitchfork, transcritical, period-doubling, or Hopf bifurcation. In this paper a unified treatment of the four types of bubbling bifurcation is presented. Conditions are obtained determining whether the transition to bubbling is soft or hard; that is, whether the maximum burst amplitude varies continuously or discontinuously with variation of the parameter through its critical value. For soft bubbling transitions, the scaling of the maximum burst amplitude with the parameter is derived. For both hard and soft transitions the scaling of the average interburst time with the bifurcation parameter is deduced. Both random (noise) and fixed (mismatch) perturbations are considered. Results of numerical experiments testing our theoretical predictions are presented.

Attractors near grazing–sliding bifurcations

International Nuclear Information System (INIS)

Glendinning, P; Kowalczyk, P; Nordmark, A B

2012-01-01

In this paper we prove, for the first time, that multistability can occur in three-dimensional Fillipov type flows due to grazing–sliding bifurcations. We do this by reducing the study of the dynamics of Filippov type flows around a grazing–sliding bifurcation to the study of appropriately defined one-dimensional maps. In particular, we prove the presence of three qualitatively different types of multiple attractors born in grazing–sliding bifurcations. Namely, a period-two orbit with a sliding segment may coexist with a chaotic attractor, two stable, period-two and period-three orbits with a segment of sliding each may coexist, or a non-sliding and period-three orbit with two sliding segments may coexist

Stability and Bifurcation Analysis of a Modified Epidemic Model for Computer Viruses

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Chuandong Li

2014-01-01

Full Text Available We extend the three-dimensional SIR model to four-dimensional case and then analyze its dynamical behavior including stability and bifurcation. It is shown that the new model makes a significant improvement to the epidemic model for computer viruses, which is more reasonable than the most existing SIR models. Furthermore, we investigate the stability of the possible equilibrium point and the existence of the Hopf bifurcation with respect to the delay. By analyzing the associated characteristic equation, it is found that Hopf bifurcation occurs when the delay passes through a sequence of critical values. An analytical condition for determining the direction, stability, and other properties of bifurcating periodic solutions is obtained by using the normal form theory and center manifold argument. The obtained results may provide a theoretical foundation to understand the spread of computer viruses and then to minimize virus risks.

Experimental study on blood flow patterns through the phantoms of the intracranial arterial aneurysms using color Doppler imaging

International Nuclear Information System (INIS)

Chung, Tae Sub; Jeong, Eun Kee; Rhim, Yoon Chul; Kim, Sung Bin; Lee, Dong Hoon; Kim, Dae In

1994-01-01

The occurrence, growth, thrombosis, and rupture of intracranial saccular aneurysms can be directly related to the effect of hemodynamic forces. We developed the phantom flow models and compared with the computer simulation program to analyse the flow pattern and hemodynamics that might be responsible for the intracranial arterial aneurysms. We designed the arterial phantoms of three major sites of intracranial arterial aneurysm ; 1) basilar artery tip, 2) internal carotid artery bifurcation, 3) curved area of internal carotid artery. Flow patterns in the aneurysmal portion of phantoms were evaluated with color Doppler system on the connection with automatic closed type of circulation system. Then, we compared the results with computer simulation. The hemodynamic characteristics of the phantoms were identical with those obtained by computerisation's. Three distinct zones of flow were identified by color Doppler studies on the aneurysm of the curved area of an internal carotid artery : 1) an inflow zone entering the aneurysm at the distal aspect of its orifice, 2) an outflow zone exiting the aneurysm at the proximal aspect of its orifice, 3) a central slow vortex.However, the phantoms of basilar artery tip and artery bifurcation showed a direct inflow stream at the dome of an aneurysm. Flow dynamics in the various phantoms of the aneurysms can be successfully evaluated with color Doppler imaging, and were consistent with those predicted by computer simulations

Stability and Hopf bifurcation analysis of a prey-predator system with two delays

International Nuclear Information System (INIS)

Li Kai; Wei Junjie

2009-01-01

In this paper, we have considered a prey-predator model with Beddington-DeAngelis functional response and selective harvesting of predator species. Two delays appear in this model to describe the time that juveniles take to mature. Its dynamics are studied in terms of local analysis and Hopf bifurcation analysis. By analyzing the associated characteristic equation, its linear stability is investigated and Hopf bifurcations are demonstrated. The stability and direction of the Hopf bifurcation are determined by applying the normal form method and the center manifold theory. Numerical simulation results are given to support the theoretical predictions.

Bifurcation with memory

International Nuclear Information System (INIS)

Olmstead, W.E.; Davis, S.H.; Rosenblat, S.; Kath, W.L.

1986-01-01

A model equation containing a memory integral is posed. The extent of the memory, the relaxation time lambda, controls the bifurcation behavior as the control parameter R is increased. Small (large) lambda gives steady (periodic) bifurcation. There is a double eigenvalue at lambda = lambda 1 , separating purely steady (lambda 1 ) from combined steady/T-periodic (lambda > lambda 1 ) states with T → infinity as lambda → lambda + 1 . Analysis leads to the co-existence of stable steady/periodic states and as R is increased, the periodic states give way to the steady states. Numerical solutions show that this behavior persists away from lambda = lambda 1

A case study in bifurcation theory

Science.gov (United States)

Khmou, Youssef

This short paper is focused on the bifurcation theory found in map functions called evolution functions that are used in dynamical systems. The most well-known example of discrete iterative function is the logistic map that puts into evidence bifurcation and chaotic behavior of the topology of the logistic function. We propose a new iterative function based on Lorentizan function and its generalized versions, based on numerical study, it is found that the bifurcation of the Lorentzian function is of second-order where it is characterized by the absence of chaotic region.

Bifurcation analysis and spatio-temporal patterns of nonlinear oscillations in a delayed neural network with unidirectional coupling

International Nuclear Information System (INIS)

Song Yongli; Tadé, Moses O; Zhang Tonghua

2009-01-01

In this paper, a delayed neural network with unidirectional coupling is considered which consists of two two-dimensional nonlinear differential equation systems with exponential decay where one system receives a delayed input from the other system. Some parameter regions are given for conditional/absolute stability and Hopf bifurcations by using the theory of functional differential equations. Conditions ensuring the stability and direction of the Hopf bifurcation are determined by applying the normal form theory and the centre manifold theorem. We also investigate the spatio-temporal patterns of bifurcating periodic oscillations by using the symmetric bifurcation theory of delay-differential equations combined with representation theory of Lie groups. Then the global continuation of phase-locked periodic solutions is investigated. Numerical simulations are given to illustrate the results obtained

Bifurcation Analysis and Chaos Control in a Discrete Epidemic System

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Wei Tan

2015-01-01

Full Text Available The dynamics of discrete SI epidemic model, which has been obtained by the forward Euler scheme, is investigated in detail. By using the center manifold theorem and bifurcation theorem in the interior R+2, the specific conditions for the existence of flip bifurcation and Neimark-Sacker bifurcation have been derived. Numerical simulation not only presents our theoretical analysis but also exhibits rich and complex dynamical behavior existing in the case of the windows of period-1, period-3, period-5, period-6, period-7, period-9, period-11, period-15, period-19, period-23, period-34, period-42, and period-53 orbits. Meanwhile, there appears the cascade of period-doubling 2, 4, 8 bifurcation and chaos sets from the fixed point. These results show the discrete model has more richer dynamics compared with the continuous model. The computations of the largest Lyapunov exponents more than 0 confirm the chaotic behaviors of the system x→x+δ[rN(1-N/K-βxy/N-(μ+mx], y→y+δ[βxy/N-(μ+dy]. Specifically, the chaotic orbits at an unstable fixed point are stabilized by using the feedback control method.

Bifurcation structure of a model of bursting pancreatic cells

DEFF Research Database (Denmark)

Mosekilde, Erik; Lading, B.; Yanchuk, S.

2001-01-01

. The transition from this structure to the so-called period-adding structure is found to involve a subcritical period-doubling bifurcation and the emergence of type-III intermittency. The period-adding transition itself is not smooth but consists of a saddle-node bifurcation in which (n + 1)-spike bursting...... behavior is born, slightly overlapping with a subcritical period-doubling bifurcation in which n-spike bursting behavior loses its stability.......One- and two-dimensional bifurcation studies of a prototypic model of bursting oscillations in pancreatic P-cells reveal a squid-formed area of chaotic dynamics in the parameter plane, with period-doubling bifurcations on one side of the arms and saddle-node bifurcations on the other...

Stability and Hopf Bifurcation of a Reaction-Diffusion Neutral Neuron System with Time Delay

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Dong, Tao; Xia, Linmao

2017-12-01

In this paper, a type of reaction-diffusion neutral neuron system with time delay under homogeneous Neumann boundary conditions is considered. By constructing a basis of phase space based on the eigenvectors of the corresponding Laplace operator, the characteristic equation of this system is obtained. Then, by selecting time delay and self-feedback strength as the bifurcating parameters respectively, the dynamic behaviors including local stability and Hopf bifurcation near the zero equilibrium point are investigated when the time delay and self-feedback strength vary. Furthermore, the direction of the Hopf bifurcation and the stability of bifurcating periodic solutions are obtained by using the normal form and the center manifold theorem for the corresponding partial differential equation. Finally, two simulation examples are given to verify the theory.

Von Bertalanffy's dynamics under a polynomial correction: Allee effect and big bang bifurcation

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Leonel Rocha, J.; Taha, A. K.; Fournier-Prunaret, D.

2016-02-01

In this work we consider new one-dimensional populational discrete dynamical systems in which the growth of the population is described by a family of von Bertalanffy's functions, as a dynamical approach to von Bertalanffy's growth equation. The purpose of introducing Allee effect in those models is satisfied under a correction factor of polynomial type. We study classes of von Bertalanffy's functions with different types of Allee effect: strong and weak Allee's functions. Dependent on the variation of four parameters, von Bertalanffy's functions also includes another class of important functions: functions with no Allee effect. The complex bifurcation structures of these von Bertalanffy's functions is investigated in detail. We verified that this family of functions has particular bifurcation structures: the big bang bifurcation of the so-called “box-within-a-box” type. The big bang bifurcation is associated to the asymptotic weight or carrying capacity. This work is a contribution to the study of the big bang bifurcation analysis for continuous maps and their relationship with explosion birth and extinction phenomena.

Bifurcation in the Lengyel–Epstein system for the coupled reactors with diffusion

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Shaban Aly

2016-01-01

Full Text Available The main goal of this paper is to continue the investigations of the important system of Fengqi et al. (2008. The occurrence of Turing and Hopf bifurcations in small homogeneous arrays of two coupled reactors via diffusion-linked mass transfer which described by a system of ordinary differential equations is considered. I study the conditions of the existence as well as stability properties of the equilibrium solutions and derive the precise conditions on the parameters to show that the Hopf bifurcation occurs. Analytically I show that a diffusion driven instability occurs at a certain critical value, when the system undergoes a Turing bifurcation, patterns emerge. The spatially homogeneous equilibrium loses its stability and two new spatially non-constant stable equilibria emerge which are asymptotically stable. Numerically, at a certain critical value of diffusion the periodic solution gets destabilized and two new spatially nonconstant periodic solutions arise by Turing bifurcation.

Stability and Hopf bifurcation in a delayed competitive web sites model

International Nuclear Information System (INIS)

Xiao Min; Cao Jinde

2006-01-01

The delayed differential equations modeling competitive web sites, based on the Lotka-Volterra competition equations, are considered. Firstly, the linear stability is investigated. It is found that there is a stability switch for time delay, and Hopf bifurcation occurs when time delay crosses through a critical value. Then the direction and stability of the bifurcated periodic solutions are determined, using the normal form theory and the center manifold reduction. Finally, some numerical simulations are carried out to illustrate the results found

Bifurcation theory for finitely smooth planar autonomous differential systems

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Han, Maoan; Sheng, Lijuan; Zhang, Xiang

2018-03-01

In this paper we establish bifurcation theory of limit cycles for planar Ck smooth autonomous differential systems, with k ∈ N. The key point is to study the smoothness of bifurcation functions which are basic and important tool on the study of Hopf bifurcation at a fine focus or a center, and of Poincaré bifurcation in a period annulus. We especially study the smoothness of the first order Melnikov function in degenerate Hopf bifurcation at an elementary center. As we know, the smoothness problem was solved for analytic and C∞ differential systems, but it was not tackled for finitely smooth differential systems. Here, we present their optimal regularity of these bifurcation functions and their asymptotic expressions in the finite smooth case.

Discretization analysis of bifurcation based nonlinear amplifiers

Science.gov (United States)

Feldkord, Sven; Reit, Marco; Mathis, Wolfgang

2017-09-01

Recently, for modeling biological amplification processes, nonlinear amplifiers based on the supercritical Andronov-Hopf bifurcation have been widely analyzed analytically. For technical realizations, digital systems have become the most relevant systems in signal processing applications. The underlying continuous-time systems are transferred to the discrete-time domain using numerical integration methods. Within this contribution, effects on the qualitative behavior of the Andronov-Hopf bifurcation based systems concerning numerical integration methods are analyzed. It is shown exemplarily that explicit Runge-Kutta methods transform the truncated normalform equation of the Andronov-Hopf bifurcation into the normalform equation of the Neimark-Sacker bifurcation. Dependent on the order of the integration method, higher order terms are added during this transformation.A rescaled normalform equation of the Neimark-Sacker bifurcation is introduced that allows a parametric design of a discrete-time system which corresponds to the rescaled Andronov-Hopf system. This system approximates the characteristics of the rescaled Hopf-type amplifier for a large range of parameters. The natural frequency and the peak amplitude are preserved for every set of parameters. The Neimark-Sacker bifurcation based systems avoid large computational effort that would be caused by applying higher order integration methods to the continuous-time normalform equations.

Metamorphosis of plasma turbulence-shear-flow dynamics through a transcritical bifurcation

International Nuclear Information System (INIS)

Ball, R.; Dewar, R.L.; Sugama, H.

2002-01-01

The structural properties of an economical model for a confined plasma turbulence governor are investigated through bifurcation and stability analyses. A close relationship is demonstrated between the underlying bifurcation framework of the model and typical behavior associated with low- to high-confinement transitions such as shear-flow stabilization of turbulence and oscillatory collective action. In particular, the analysis evinces two types of discontinuous transition that are qualitatively distinct. One involves classical hysteresis, governed by viscous dissipation. The other is intrinsically oscillatory and nonhysteretic, and thus provides a model for the so-called dithering transitions that are frequently observed. This metamorphosis, or transformation, of the system dynamics is an important late side-effect of symmetry breaking, which manifests as an unusual nonsymmetric transcritical bifurcation induced by a significant shear-flow drive

Measurement of carotid bifurcation pressure gradients using the Bernoulli principle.

Science.gov (United States)

Illig, K A; Ouriel, K; DeWeese, J A; Holen, J; Green, R M

1996-04-01

Current randomized prospective studies suggest that the degree of carotid stenosis is a critical element in deciding whether surgical or medical treatment is appropriate. Of potential interest is the actual pressure drop caused by the blockage, but no direct non-invasive means of quantifying the hemodynamic consequences of carotid artery stenoses currently exists. The present prospective study examined whether preoperative pulsed-Doppler duplex ultrasonographic velocity (v) measurements could be used to predict pressure gradients (delta P) caused by carotid artery stenoses, and whether such measurements could be used to predict angiographic percent diameter reduction. Preoperative Doppler velocity and intraoperative direct pressure measurements were obtained, and per cent diameter angiographic stenosis measured in 76 consecutive patients who underwent 77 elective carotid endarterectomies. Using the Bernoulli principle (delta P = 4v(2), pressure gradients across the stenoses were calculated. The predicted delta P, as well as absolute velocities and internal carotid artery/common carotid velocity ratios were compared with the actual delta P measured intraoperatively and with preoperative angiography and oculopneumoplethysmography (OPG) results. An end-diastolic velocity of > or = 1 m/s and an end-diastolic internal carotid artery/common carotid artery velocity ratio of > or = 10 predicted a 50% diameter angiographic stenosis with 100% specificity. Although statistical significance was reached, preoperative pressure gradients derived from the Bernoulli equation could not predict actual individual intraoperative pressure gradients with enough accuracy to allow decision making on an individual basis. Velocity measurements were as specific and more sensitive than OPG results. Delta P as predicted by the Bernoulli equation is not sufficiently accurate at the carotid bifurcation to be useful for clinical decision making on an individual basis. However, end

[Revascularization of the carotid and vertebral arteries in the elderly].

Science.gov (United States)

Illuminati, G; Bezzi, M; D'Urso, A; Giacobbi, D; Ceccanei, G; Vietri, F

2004-01-01

From January 1994 to July 2004, 323 patients underwent 348 revascularization of carotid bifurcation for atherosclerotic stenoses. Eighty eight patients (group A) were 75 year-old or older, whereas 235 (group B) were younger than 75 years. Postoperative mortality/neurologic morbidity rate was 1% in group A, and 1.4% in group B. At 5 years, patency and freedom from symptoms/stroke were, respectively, 91% and 92% in group A, and 89% and 91% in group B. None of these differences was statistically significant. In the same time period, 26 internal carotid arteries were revascularized in 24 patients, 75 or more aged, for a symptomatic kinking. Postoperative mortality/morbidity rate was absent, whereas, at 5 years, patency and freedom from symptoms/stroke were, respectively, 88% and 92%. Twelve vertebral arteries were revascularized in 12 patients, 75 or more aged, for invalidating symptoms of vertebrobasilar insufficiency. Postoperative mortality/neurologic morbidity rate was absent. In one case postoperative recurrence of symptoms occurred, despite a patent revascularization. Patency and freedom from symptoms/stroke were 84% and 75%, at 5 years. Revascularization of carotid and vertebral arteries in the elderly can be accomplished with good results, superposable to those of standard revascularization of carotid bifurcation in a younger patients' population.

Quantum entanglement and fixed-point bifurcations

International Nuclear Information System (INIS)

Hines, Andrew P.; McKenzie, Ross H.; Milburn, G.J.

2005-01-01

How does the classical phase-space structure for a composite system relate to the entanglement characteristics of the corresponding quantum system? We demonstrate how the entanglement in nonlinear bipartite systems can be associated with a fixed-point bifurcation in the classical dynamics. Using the example of coupled giant spins we show that when a fixed point undergoes a supercritical pitchfork bifurcation, the corresponding quantum state--the ground state--achieves its maximum amount of entanglement near the critical point. We conjecture that this will be a generic feature of systems whose classical limit exhibits such a bifurcation

Hopf bifurcation and chaos in macroeconomic models with policy lag

International Nuclear Information System (INIS)

Liao Xiaofeng; Li Chuandong; Zhou Shangbo

2005-01-01

In this paper, we consider the macroeconomic models with policy lag, and study how lags in policy response affect the macroeconomic stability. The local stability of the nonzero equilibrium of this equation is investigated by analyzing the corresponding transcendental characteristic equation of its linearized equation. Some general stability criteria involving the policy lag and the system parameter are derived. By choosing the policy lag as a bifurcation parameter, the model is found to undergo a sequence of Hopf bifurcation. The direction and stability of the bifurcating periodic solutions are determined by using the normal form theory and the center manifold theorem. Moreover, we show that the government can stabilize the intrinsically unstable economy if the policy lag is sufficiently short, but the system become locally unstable when the policy lag is too long. We also find the chaotic behavior in some range of the policy lag

Hopf Bifurcation Analysis for a Stochastic Discrete-Time Hyperchaotic System

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Jie Ran

2015-01-01

Full Text Available The dynamics of a discrete-time hyperchaotic system and the amplitude control of Hopf bifurcation for a stochastic discrete-time hyperchaotic system are investigated in this paper. Numerical simulations are presented to exhibit the complex dynamical behaviors in the discrete-time hyperchaotic system. Furthermore, the stochastic discrete-time hyperchaotic system with random parameters is transformed into its equivalent deterministic system with the orthogonal polynomial theory of discrete random function. In addition, the dynamical features of the discrete-time hyperchaotic system with random disturbances are obtained through its equivalent deterministic system. By using the Hopf bifurcation conditions of the deterministic discrete-time system, the specific conditions for the existence of Hopf bifurcation in the equivalent deterministic system are derived. And the amplitude control with random intensity is discussed in detail. Finally, the feasibility of the control method is demonstrated by numerical simulations.

Valve-Like and Protruding Calcified Intimal Flap Complicating Common Iliac Arteries Kissing Stenting

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George S. Georgiadis

2015-01-01

Full Text Available Endovascular therapy for iliac artery chronic total occlusions is nowadays associated with low rates of procedure-related complications and improved clinical outcomes, and it is predominantly used as first-line therapy prior to aortobifemoral bypass grafting. Herein, we describe the case of a patient presenting with an ischemic left foot digit ulcer and suffering complex aortoiliac lesions, who received common iliac arteries kissing stents, illustrating at final antegrade and retrograde angiograms the early recognition of a blood flow obstructing valve-like calcified intimal flap protruding through the stent struts, which was obstructing antegrade but not retrograde unilateral iliac arterial axis blood flow. The problem was resolved by reconstructing the aortic bifurcation at a more proximal level. Completion angiogram verified normal patency of aorta and iliac vessels. Additionally, a severe left femoral bifurcation stenosis was also corrected by endarterectomy-arterioplasty with a bovine patch. Postintervention ankle brachial pressure indices were significantly improved. At the 6-month and 2-year follow-up, normal peripheral pulses were still reported without intermittent claudication suggesting the durability of the procedure. Through stent-protruding calcified intimal flap, is a very rare, but existing source of antegrade blood flow obstruction after common iliac arteries kissing stents.

Dedicated bifurcation stents

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Ajith Ananthakrishna Pillai

2012-03-01

Full Text Available Bifurcation percutaneous coronary intervention (PCI is still a difficult call for the interventionist despite advancements in the instrumentation, technical skill and the imaging modalities. With major cardiac events relate to the side-branch (SB compromise, the concept and practice of dedicated bifurcation stents seems exciting. Several designs of such dedicated stents are currently undergoing trials. This novel concept and pristine technology offers new hope notwithstanding the fact that we need to go a long way in widespread acceptance and practice of these gadgets. Some of these designs even though looks enterprising, the mere complex delivering technique and the demanding knowledge of the exact coronary anatomy makes their routine use challenging.

Measurement and analysis of geometric parameters of human carotid bifurcation using image post-processing technique

International Nuclear Information System (INIS)

Xue Yunjing; Gao Peiyi; Lin Yan

2008-01-01

Objective: To investigate variation in the carotid bifurcation geometry of adults of different age by MR angiography images combining image post-processing technique. Methods: Images of the carotid bifurcations of 27 young adults (≤40 years old) and 30 older subjects ( > 40 years old) were acquired via contrast-enhanced MR angiography. Three dimensional (3D) geometries of the bifurcations were reconstructed and geometric parameters were measured by post-processing technique. Results: The geometric parameters of the young versus older groups were as follows: bifurcation angle (70.268 degree± 16.050 degree versus 58.857 degree±13.294 degree), ICA angle (36.893 degree±11.837 degree versus 30.275 degree±9.533 degree), ICA planarity (6.453 degree ± 5.009 degree versus 6.263 degree ±4.250 degree), CCA tortuosity (0.023±0.011 versus 0.014± 0.005), ICA tortuosity (0.070±0.042 versus 0.046±0.022), ICA/CCA diameter ratio (0.693± 0.132 versus 0.728±0.106), ECA/CCA diameter ratio (0.750±0.123 versus 0.809±0.122), ECA/ ICA diameter ratio (1.103±0.201 versus 1.127±0.195), bifurcation area ratio (1.057±0.281 versus 1.291±0.252). There was significant statistical difference between young group and older group in-bifurcation angle, ICA angle, CCA tortuosity, ICA tortuosity, ECA/CCA and bifurcation area ratio (F= 17.16, 11.74, 23.02, 13.38, 6.54, 22.80, respectively, P<0.05). Conclusions: MR angiography images combined with image post-processing technique can reconstruct 3D carotid bifurcation geometry and measure the geometric parameters of carotid bifurcation in vivo individually. It provides a new and convenient method to investigate the relationship of vascular geometry and flow condition with atherosclerotic pathological changes. (authors)

Codimension-2 bifurcations of the Kaldor model of business cycle

International Nuclear Information System (INIS)

Wu, Xiaoqin P.

2011-01-01

Research highlights: → The conditions are given such that the characteristic equation may have purely imaginary roots and double zero roots. → Purely imaginary roots lead us to study Hopf and Bautin bifurcations and to calculate the first and second Lyapunov coefficients. → Double zero roots lead us to study Bogdanov-Takens (BT) bifurcation. → Bifurcation diagrams for Bautin and BT bifurcations are obtained by using the normal form theory. - Abstract: In this paper, complete analysis is presented to study codimension-2 bifurcations for the nonlinear Kaldor model of business cycle. Sufficient conditions are given for the model to demonstrate Bautin and Bogdanov-Takens (BT) bifurcations. By computing the first and second Lyapunov coefficients and performing nonlinear transformation, the normal forms are derived to obtain the bifurcation diagrams such as Hopf, homoclinic and double limit cycle bifurcations. Some examples are given to confirm the theoretical results.

Critical bifurcation surfaces of 3D discrete dynamics

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Michael Sonis

2000-01-01

Full Text Available This paper deals with the analytical representation of bifurcations of each 3D discrete dynamics depending on the set of bifurcation parameters. The procedure of bifurcation analysis proposed in this paper represents the 3D elaboration and specification of the general algorithm of the n-dimensional linear bifurcation analysis proposed by the author earlier. It is proven that 3D domain of asymptotic stability (attraction of the fixed point for a given 3D discrete dynamics is bounded by three critical bifurcation surfaces: the divergence, flip and flutter surfaces. The analytical construction of these surfaces is achieved with the help of classical Routh–Hurvitz conditions of asymptotic stability. As an application the adjustment process proposed by T. Puu for the Cournot oligopoly model is considered in detail.

The Hindlimb Arterial Vessels in Lowland paca (Cuniculus paca, Linnaeus 1766).

Science.gov (United States)

Leal, L M; de Freitas, H M G; Sasahara, T H C; Machado, M R F

2016-04-01

This study aims to describe the origin and distribution of the hindlimb arterial vessels. Five adult lowland pacas (Cuniculus paca) were used. Stained and diluted latex was injected, caudally to the aorta. After fixation in 10% paraformaldehyde for 72 h, we dissected to visualize and identify the vessels. It was found out that the vascularization of the hindlimb in lowland paca derives from the terminal branch of the abdominal aorta. The common iliac artery divides into external iliac and internal iliac. The external iliac artery emits the deep iliac circumflex artery, the pudendal epigastric trunk, the deep femoral artery; the femoral artery originates the saphenous artery, it bifurcates into cranial and caudal saphenous arteries. Immediately after the knee joint, the femoral artery is called popliteal artery, which divides into tibial cranial and tibial caudal arteries at the level of the crural inter-osseous space. The origin and distribution of arteries in the hindlimb of lowland paca resembles that in other wild rodents, as well as in the domestic mammals. © 2014 Blackwell Verlag GmbH.

Comparison of branch and distally focused main renal artery denervation using two different radio-frequency systems in a porcine model.

Science.gov (United States)

Mahfoud, Felix; Pipenhagen, Catherine A; Boyce Moon, L; Ewen, Sebastian; Kulenthiran, Saarraaken; Fish, Jeffrey M; Jensen, James A; Virmani, Renu; Joner, Michael; Yahagi, Kazuyuki; Tsioufis, Costas; Böhm, Michael

2017-08-15

Anatomic placement of lesions may impact efficacy of radio-frequency (RF) catheter renal denervation (RDN). However, it is unclear if it is necessary to perform treatments post bifurcation with systems that may provide deeper penetration to achieve successful RDN. Sixteen domestic swine (n=16) were randomly assigned to 4 groups: 1) 8 lesions created in the branch arteries using the Spyral catheter (SP8); 2) 8 lesions created in the branch arteries plus 4 lesions created in the main artery using the SP catheter (SP12); 3) 8 lesions created in the main artery using the EnligHTN catheter with the distal position as close as possible to the bifurcation (EN8); and 4) 12 lesions created in the main artery using the EN catheter with the distal position as close as possible to the bifurcation (EN12). Each arm showed statistically significant changes in kidney norepinephrine (NE, ng/g) between treated kidneys vs. untreated contralateral control. There were no statistically significant differences in tissue NE% reductions across each arm based on catheter, anatomic location, & number of lesions (p=0.563): EN8 -74±34%, EN12 -95±3%, SP8 -76±16%, SP12 -82±17% (p=0.496). A total of 46 lesions were measured for lesion depth: EN main (3.3±2.8mm) vs. SP branch (2.0±1.0mm, p=0.039), SP main (2.9±1.6mm) vs. SP branch (p=0.052), and EN main vs. SP main (p=0.337). Distally-focused main renal artery treatment using the EN system appears to be equally efficacious in reducing tissue NE levels compared with SP treatment in the branches plus main renal arteries, advocating for device-specific procedure execution. Copyright © 2017 Elsevier B.V. All rights reserved.

Bifurcation and complex dynamics of a discrete-time predator-prey system involving group defense

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S. M. Sohel Rana

2015-09-01

Full Text Available In this paper, we investigate the dynamics of a discrete-time predator-prey system involving group defense. The existence and local stability of positive fixed point of the discrete dynamical system is analyzed algebraically. It is shown that the system undergoes a flip bifurcation and a Neimark-Sacker bifurcation in the interior of R+2 by using bifurcation theory. Numerical simulation results not only show the consistence with the theoretical analysis but also display the new and interesting dynamical behaviors, including phase portraits, period-7, 20-orbits, attracting invariant circle, cascade of period-doubling bifurcation from period-20 leading to chaos, quasi-periodic orbits, and sudden disappearance of the chaotic dynamics and attracting chaotic set. The Lyapunov exponents are numerically computed to characterize the complexity of the dynamical behaviors.

Invariants, Attractors and Bifurcation in Two Dimensional Maps with Polynomial Interaction

Science.gov (United States)

Hacinliyan, Avadis Simon; Aybar, Orhan Ozgur; Aybar, Ilknur Kusbeyzi

This work will present an extended discrete-time analysis on maps and their generalizations including iteration in order to better understand the resulting enrichment of the bifurcation properties. The standard concepts of stability analysis and bifurcation theory for maps will be used. Both iterated maps and flows are used as models for chaotic behavior. It is well known that when flows are converted to maps by discretization, the equilibrium points remain the same but a richer bifurcation scheme is observed. For example, the logistic map has a very simple behavior as a differential equation but as a map fold and period doubling bifurcations are observed. A way to gain information about the global structure of the state space of a dynamical system is investigating invariant manifolds of saddle equilibrium points. Studying the intersections of the stable and unstable manifolds are essential for understanding the structure of a dynamical system. It has been known that the Lotka-Volterra map and systems that can be reduced to it or its generalizations in special cases involving local and polynomial interactions admit invariant manifolds. Bifurcation analysis of this map and its higher iterates can be done to understand the global structure of the system and the artifacts of the discretization by comparing with the corresponding results from the differential equation on which they are based.

Bilateral Distal Anterior Cerebral Artery Aneurysms Mimicking So-called "Kissing Aneurysms": A Case Report

OpenAIRE

山口, 竜一; 伊藤, 宣行; 前村, 栄治; 塩川, 芳昭; 齋藤, 勇; Ryuichi, YAMAGUCHI; Nobuyuki, ITO; Eiji, MAEMURA; Yoshiaki, SHIOKAWA; Isamu, SAITO; 公立阿伎留病院脳神経外科; 公立阿伎留病院脳神経外科; 公立阿伎留病院脳神経外科; 杏林大学医学部脳神経外科; 杏林大学医学部脳神経外科

2003-01-01

A 71-year-old woman presented disturbance of consciousness due to subarachnoid hemorrhage (SAH). A computed tomography (CT) on admission revealed diffuse thick SAH and intracerebral hematoma in the right frontal lobe. Conventional angiography and three-dimensional CT angiography showed symmetrical aneurysms located on the bilateral pericallosal arteries at bifurcation of the callosomarginal arteries. The operation was performed on the next day after onset of SAH. The aneurysms were clipped vi...

The prevalence of peripheral arterial disease in middle-aged people with intellectual disabilities

NARCIS (Netherlands)

Zaal-Schuller, I. H.; Goorhuis, A. E. M.; Bock-Sinot, A.; Claassen, I. H. M.; Echteld, M. A.; Evenhuis, H. M.

2015-01-01

Peripheral arterial disease (PAD) is a manifestation of atherosclerosis below the bifurcation of the abdominal aorta. PAD increases the risk of cardiovascular disease and associated mortality. Little is known about the prevalence of PAD in middle-aged persons with intellectual disabilities (ID). We

Bifurcation analysis of a three dimensional system

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Yongwen WANG

2018-04-01

Full Text Available In order to enrich the stability and bifurcation theory of the three dimensional chaotic systems, taking a quadratic truncate unfolding system with the triple singularity equilibrium as the research subject, the existence of the equilibrium, the stability and the bifurcation of the system near the equilibrium under different parametric conditions are studied. Using the method of mathematical analysis, the existence of the real roots of the corresponding characteristic equation under the different parametric conditions is analyzed, and the local manifolds of the equilibrium are gotten, then the possible bifurcations are guessed. The parametric conditions under which the equilibrium is saddle-focus are analyzed carefully by the Cardan formula. Moreover, the conditions of codimension-one Hopf bifucation and the prerequisites of the supercritical and subcritical Hopf bifurcation are found by computation. The results show that the system has abundant stability and bifurcation, and can also supply theorical support for the proof of the existence of the homoclinic or heteroclinic loop connecting saddle-focus and the Silnikov's chaos. This method can be extended to study the other higher nonlinear systems.

Bifurcation analysis in delayed feedback Jerk systems and application of chaotic control

International Nuclear Information System (INIS)

Zheng Baodong; Zheng Huifeng

2009-01-01

Jerk systems with delayed feedback are considered. Firstly, by employing the polynomial theorem to analyze the distribution of the roots to the associated characteristic equation, the conditions of ensuring the existence of Hopf bifurcation are given. Secondly, the stability and direction of the Hopf bifurcation are determined by applying the normal form method and center manifold theorem. Finally, the application to chaotic control is investigated, and some numerical simulations are carried out to illustrate the obtained results.

Anatomical surgical arterial segments of the kidneys of Santa Inês ovines

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Antônio Chaves de Assis Neto

2007-03-01

Full Text Available The main goal of the study was describe the distribution of the renal arteries of the renal parenchyma and the proportional area of the arterial vascular system. The renal arterial vascularization in Santa Ines ovines was analyzed in fifteen pairs of organs of male adult animal, after attainment of vascular models through the techniques of corrosion and arteriography. The renal artery always appeared single, and before reaching the renal hilus, it bifurcated into sectorial dorsal and ventral arteries, giving rise to the segmentary arteries which varied from 6 to 10 in number in the right kidney and 7 to 11 in the left kidney. These vessels vascularized independent areas in each renal sector, the renal arterial segments, separated by non-vascularized planes. Bilateral symmetry of the arterial segmentation was found in 13.33% of cases. In accordance with the arterial characterization, the realization of setoriectomy and segmentectomy on the kidneys of Santa Ines ovines is therefore deemed possible.

Bifurcation theory of ac electric arcing

International Nuclear Information System (INIS)

Christen, Thomas; Peinke, Emanuel

2012-01-01

The performance of alternating current (ac) electric arcing devices is related to arc extinction or its re-ignition at zero crossings of the current (so-called ‘current zero’, CZ). Theoretical investigations thus usually focus on the transient behaviour of arcs near CZ, e.g. by solving the modelling differential equations in the vicinity of CZ. This paper proposes as an alternative approach to investigate global mathematical properties of the underlying periodically driven dynamic system describing the electric circuit containing the arcing device. For instance, the uniqueness of the trivial solution associated with the insulating state indicates the extinction of any arc. The existence of non-trivial attractors (typically a time-periodic state) points to a re-ignition of certain arcs. The performance regions of arcing devices, such as circuit breakers and arc torches, can thus be identified with the regions of absence and existence, respectively, of non-trivial attractors. Most important for applications, the boundary of a performance region in the model parameter space is then associated with the bifurcation of the non-trivial attractors. The concept is illustrated for simple black-box arc models, such as the Mayr and the Cassie model, by calculating for various cases the performance boundaries associated with the bifurcation of ac arcs. (paper)

Asymmetry of blood flow and cancer cell adhesion in a microchannel with symmetric bifurcation and confluence.

Science.gov (United States)

Ishikawa, Takuji; Fujiwara, Hiroki; Matsuki, Noriaki; Yoshimoto, Takefumi; Imai, Yohsuke; Ueno, Hironori; Yamaguchi, Takami

2011-02-01

Bifurcations and confluences are very common geometries in biomedical microdevices. Blood flow at microchannel bifurcations has different characteristics from that at confluences because of the multiphase properties of blood. Using a confocal micro-PIV system, we investigated the behaviour of red blood cells (RBCs) and cancer cells in microchannels with geometrically symmetric bifurcations and confluences. The behaviour of RBCs and cancer cells was strongly asymmetric at bifurcations and confluences whilst the trajectories of tracer particles in pure water were almost symmetric. The cell-free layer disappeared on the inner wall of the bifurcation but increased in size on the inner wall of the confluence. Cancer cells frequently adhered to the inner wall of the bifurcation but rarely to other locations. Because the wall surface coating and the wall shear stress were almost symmetric for the bifurcation and the confluence, the result indicates that not only chemical mediation and wall shear stress but also microscale haemodynamics play important roles in the adhesion of cancer cells to the microchannel walls. These results provide the fundamental basis for a better understanding of blood flow and cell adhesion in biomedical microdevices.

A COMPUTATIONAL FRAMEWORK INVOLVING CFD AND DATA MINING TOOLS FOR ANALYZING DISEASE IN CAROTID ARTERY BIFURCATION

OpenAIRE

Tabib, Mandar; Rasheed, Adil; Fonn, Eivind

2017-01-01

Cardiovascular diseases, like Carotid Artery Disease and Coronary Artery Disease (CAD) are associated with the narrowing of artery due to build-up of fatty substances and cholesterol deposits (called plaque). Carotid Artery Disease increases the chances of brain stroke. Hence, the main objective of this work is to apply computational tools to help differentiate between the healthy and unhealthy artery (with 25% stenosis) using a combination of Computational Fluid Dynamics (CFD) and data minin...

Local bifurcation analysis in nuclear reactor dynamics by Sotomayor’s theorem

International Nuclear Information System (INIS)

Pirayesh, Behnam; Pazirandeh, Ali; Akbari, Monireh

2016-01-01

Highlights: • When the feedback reactivity is considered as a nonlinear function some complex behaviors may emerge in the system such as local bifurcation phenomenon. • The qualitative behaviors of a typical nuclear reactor near its equilibrium points have been studied analytically. • Comprehensive analytical bifurcation analyses presented in this paper are transcritical bifurcation, saddle- node bifurcation and pitchfork bifurcation. - Abstract: In this paper, a qualitative approach has been used to explore nuclear reactor behaviors with nonlinear feedback. First, a system of four dimensional ordinary differential equations governing the dynamics of a typical nuclear reactor is introduced. These four state variables are the relative power of the reactor, the relative concentration of delayed neutron precursors, the fuel temperature and the coolant temperature. Then, the qualitative behaviors of the dynamical system near its equilibria have been studied analytically by using local bifurcation theory and Sotomayor’s theorem. The results indicated that despite the uncertainty of the reactivity, we can analyze the qualitative behavior changes of the reactor from the bifurcation point of view. Notably, local bifurcations that were considered in this paper include transcritical bifurcation, saddle-node bifurcation and pitchfork bifurcation. The theoretical analysis showed that these three types of local bifurcations may occur in the four dimensional dynamical system. In addition, to confirm the analytical results the numerical simulations are given.

Bifurcation and chaos response of a cracked rotor with random disturbance

Science.gov (United States)

Leng, Xiaolei; Meng, Guang; Zhang, Tao; Fang, Tong

2007-01-01

The Monte-Carlo method is used to investigate the bifurcation and chaos characteristics of a cracked rotor with a white noise process as its random disturbance. Special attention is paid to the influence of the stiffness change ratio and the rotating speed ratio on the bifurcation and chaos response of the system. Numerical simulations show that the affect of the random disturbance is significant as the undisturbed response of the cracked rotor system is a quasi-periodic or chaos one, and such affect is smaller as the undisturbed response is a periodic one.

Global Bifurcation of a Novel Computer Virus Propagation Model

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Jianguo Ren

2014-01-01

Full Text Available In a recent paper by J. Ren et al. (2012, a novel computer virus propagation model under the effect of the antivirus ability in a real network is established. The analysis there only partially uncovers the dynamics behaviors of virus spread over the network in the case where around bifurcation is local. In the present paper, by mathematical analysis, it is further shown that, under appropriate parameter values, the model may undergo a global B-T bifurcation, and the curves of saddle-node bifurcation, Hopf bifurcation, and homoclinic bifurcation are obtained to illustrate the qualitative behaviors of virus propagation. On this basis, a collection of policies is recommended to prohibit the virus prevalence. To our knowledge, this is the first time the global bifurcation has been explored for the computer virus propagation. Theoretical results and corresponding suggestions may help us suppress or eliminate virus propagation in the network.

Bifurcation and complex dynamics of a discrete-time predator-prey system

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S. M. Sohel Rana

2015-06-01

Full Text Available In this paper, we investigate the dynamics of a discrete-time predator-prey system of Holling-I type in the closed first quadrant R+2. The existence and local stability of positive fixed point of the discrete dynamical system is analyzed algebraically. It is shown that the system undergoes a flip bifurcation and a Neimark-Sacker bifurcation in the interior of R+2 by using bifurcation theory. It has been found that the dynamical behavior of the model is very sensitive to the parameter values and the initial conditions. Numerical simulation results not only show the consistence with the theoretical analysis but also display the new and interesting dynamic behaviors, including phase portraits, period-9, 10, 20-orbits, attracting invariant circle, cascade of period-doubling bifurcation from period-20 leading to chaos, quasi-periodic orbits, and sudden disappearance of the chaotic dynamics and attracting chaotic set. In particular, we observe that when the prey is in chaotic dynamic, the predator can tend to extinction or to a stable equilibrium. The Lyapunov exponents are numerically computed to characterize the complexity of the dynamical behaviors. The analysis and results in this paper are interesting in mathematics and biology.

Parametric uncertainty and global sensitivity analysis in a model of the carotid bifurcation: Identification and ranking of most sensitive model parameters.

Science.gov (United States)

Gul, R; Bernhard, S

2015-11-01

In computational cardiovascular models, parameters are one of major sources of uncertainty, which make the models unreliable and less predictive. In order to achieve predictive models that allow the investigation of the cardiovascular diseases, sensitivity analysis (SA) can be used to quantify and reduce the uncertainty in outputs (pressure and flow) caused by input (electrical and structural) model parameters. In the current study, three variance based global sensitivity analysis (GSA) methods; Sobol, FAST and a sparse grid stochastic collocation technique based on the Smolyak algorithm were applied on a lumped parameter model of carotid bifurcation. Sensitivity analysis was carried out to identify and rank most sensitive parameters as well as to fix less sensitive parameters at their nominal values (factor fixing). In this context, network location and temporal dependent sensitivities were also discussed to identify optimal measurement locations in carotid bifurcation and optimal temporal regions for each parameter in the pressure and flow waves, respectively. Results show that, for both pressure and flow, flow resistance (R), diameter (d) and length of the vessel (l) are sensitive within right common carotid (RCC), right internal carotid (RIC) and right external carotid (REC) arteries, while compliance of the vessels (C) and blood inertia (L) are sensitive only at RCC. Moreover, Young's modulus (E) and wall thickness (h) exhibit less sensitivities on pressure and flow at all locations of carotid bifurcation. Results of network location and temporal variabilities revealed that most of sensitivity was found in common time regions i.e. early systole, peak systole and end systole. Copyright © 2015 Elsevier Inc. All rights reserved.

Bifurcation and instability problems in vortex wakes

DEFF Research Database (Denmark)

Aref, Hassan; Brøns, Morten; Stremler, Mark A.

2007-01-01

A number of instability and bifurcation problems related to the dynamics of vortex wake flows are addressed using various analytical tools and approaches. We discuss the bifurcations of the streamline pattern behind a bluff body as a vortex wake is produced, a theory of the universal Strouhal......-Reynolds number relation for vortex wakes, the bifurcation diagram for "exotic" wake patterns behind an oscillating cylinder first determined experimentally by Williamson & Roshko, and the bifurcations in topology of the streamlines pattern in point vortex streets. The Hamiltonian dynamics of point vortices...... in a periodic strip is considered. The classical results of von Kármán concerning the structure of the vortex street follow from the two-vortices-in-a-strip problem, while the stability results follow largely from a four-vortices-in-a-strip analysis. The three-vortices-in-a-strip problem is argued...

Flow Velocities After Carotid Artery Stenting: Impact of Stent Design. A Fluid Dynamics Study in a Carotid Artery Model with Laser Doppler Anemometry

International Nuclear Information System (INIS)

Greil, Oliver; Kleinschmidt, Thomas; Weiss, Wolfgang; Wolf, Oliver; Heider, Peter; Schaffner, Silvio; Gianotti, Marc; Schmid, Thomas; Liepsch, Dieter; Berger, Hermann

2005-01-01

Purpose. To study the influence of a newly developed membrane stent design on flow patterns in a physiologic carotid artery model. Methods. Three different stents were positioned in silicone models of the carotid artery: a stainless steel stent (Wall-stent), a nitinol stent (SelfX), and a nitinol stent with a semipermeable membrane (MembraX). To increase the contact area of the membrane with the vessel wall, another MembranX model was modified at the outflow tract. The membrane consists of a biocompatible silicone-polyurethane copolymer (Elast-Eon) with a pore size of 100 μm. All stents were deployed across the bifurcation and the external carotid artery origin. Flow velocity measurements were performed with laser Doppler anemometry (LDA), using pulsatile flow conditions (Re = 220; flow 0.39 l/min; flow rate ratio ICA:ECA = 70:30) in hemodynamically relevant cross-sections. The hemodynamic changes were analyzed by comparing velocity fluctuations of corresponding flow profiles. Results. The flow rate ratio ICA:ECA shifted significantly from 70/30 to 73.9/26.1 in the MembraX and remained nearly unchanged in the SelfX and Wallstent. There were no changes in the flow patterns at the inflow proximal to the stents. In the stent no relevant changes were found in the SelfX. In the Wallstent the separation zone shifted from the orifice of the ICA to the distal end of the stent. Four millimeters distal to the SelfX and the Wallstent the flow profile returned to normal. In the MembraX an increase in the central slipstreams was found with creation of a flow separation distal to the stent. With a modification of the membrane this flow separation vanished. In the ECA flow disturbances were seen at the inner wall distal to the stent struts in the SelfX and the Wallstent. With the MembraX a calming of flow could be observed in the ECA with a slight loss of flow volume. Conclusions. Stent placement across the carotid artery bifurcation induces alterations of the physiologic flow

Stability Switches, Hopf Bifurcations, and Spatio-temporal Patterns in a Delayed Neural Model with Bidirectional Coupling

Science.gov (United States)

Song, Yongli; Zhang, Tonghua; Tadé, Moses O.

2009-12-01

The dynamical behavior of a delayed neural network with bi-directional coupling is investigated by taking the delay as the bifurcating parameter. Some parameter regions are given for conditional/absolute stability and Hopf bifurcations by using the theory of functional differential equations. As the propagation time delay in the coupling varies, stability switches for the trivial solution are found. Conditions ensuring the stability and direction of the Hopf bifurcation are determined by applying the normal form theory and the center manifold theorem. We also discuss the spatio-temporal patterns of bifurcating periodic oscillations by using the symmetric bifurcation theory of delay differential equations combined with representation theory of Lie groups. In particular, we obtain that the spatio-temporal patterns of bifurcating periodic oscillations will alternate according to the change of the propagation time delay in the coupling, i.e., different ranges of delays correspond to different patterns of neural activities. Numerical simulations are given to illustrate the obtained results and show the existence of bursts in some interval of the time for large enough delay.

Hopf bifurcation analysis of Chen circuit with direct time delay feedback

International Nuclear Information System (INIS)

Hai-Peng, Ren; Wen-Chao, Li; Ding, Liu

2010-01-01

Direct time delay feedback can make non-chaotic Chen circuit chaotic. The chaotic Chen circuit with direct time delay feedback possesses rich and complex dynamical behaviours. To reach a deep and clear understanding of the dynamics of such circuits described by delay differential equations, Hopf bifurcation in the circuit is analysed using the Hopf bifurcation theory and the central manifold theorem in this paper. Bifurcation points and bifurcation directions are derived in detail, which prove to be consistent with the previous bifurcation diagram. Numerical simulations and experimental results are given to verify the theoretical analysis. Hopf bifurcation analysis can explain and predict the periodical orbit (oscillation) in Chen circuit with direct time delay feedback. Bifurcation boundaries are derived using the Hopf bifurcation analysis, which will be helpful for determining the parameters in the stabilisation of the originally chaotic circuit

Axial flow velocity patterns in a normal human pulmonary artery model: pulsatile in vitro studies.

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Sung, H W; Yoganathan, A P

1990-01-01

It has been clinically observed that the flow velocity patterns in the pulmonary artery are directly modified by disease. The present study addresses the hypothesis that altered velocity patterns relate to the severity of various diseases in the pulmonary artery. This paper lays a foundation for that analysis by providing a detailed description of flow velocity patterns in the normal pulmonary artery, using flow visualization and laser Doppler anemometry techniques. The studies were conducted in an in vitro rigid model in a right heart pulse duplicator system. In the main pulmonary artery, a broad central flow field was observed throughout systole. The maximum axial velocity (150 cm s-1) was measured at peak systole. In the left pulmonary artery, the axial velocities were approximately evenly distributed in the perpendicular plane. However, in the bifurcation plane, they were slightly skewed toward the inner wall at peak systole and during the deceleration phase. In the right pulmonary artery, the axial velocity in the perpendicular plane had a very marked M-shaped profile at peak systole and during the deceleration phase, due to a pair of strong secondary flows. In the bifurcation plane, higher axial velocities were observed along the inner wall, while lower axial velocities were observed along the outer wall and in the center. Overall, relatively low levels of turbulence were observed in all the branches during systole. The maximum turbulence intensity measured was at the boundary of the broad central flow field in the main pulmonary artery at peak systole.

Bifurcation analysis of Rössler system with multiple delayed feedback

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Meihong Xu

2010-10-01

Full Text Available In this paper, regarding the delay as parameter, we investigate the effect of delay on the dynamics of a Rössler system with multiple delayed feedback proposed by Ghosh and Chowdhury. At first we consider the stability of equilibrium and the existence of Hopf bifurcations. Then an explicit algorithm for determining the direction and the stability of the bifurcating periodic solutions is derived by using the normal form theory and center manifold argument. Finally, we give a numerical simulation example which indicates that chaotic oscillation is converted into a stable steady state or a stable periodic orbit when the delay passes through certain critical values.

Stochastic bifurcation in a model of love with colored noise

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Yue, Xiaokui; Dai, Honghua; Yuan, Jianping

2015-07-01

In this paper, we wish to examine the stochastic bifurcation induced by multiplicative Gaussian colored noise in a dynamical model of love where the random factor is used to describe the complexity and unpredictability of psychological systems. First, the dynamics in deterministic love-triangle model are considered briefly including equilibrium points and their stability, chaotic behaviors and chaotic attractors. Then, the influences of Gaussian colored noise with different parameters are explored such as the phase plots, top Lyapunov exponents, stationary probability density function (PDF) and stochastic bifurcation. The stochastic P-bifurcation through a qualitative change of the stationary PDF will be observed and bifurcation diagram on parameter plane of correlation time and noise intensity is presented to find the bifurcation behaviors in detail. Finally, the top Lyapunov exponent is computed to determine the D-bifurcation when the noise intensity achieves to a critical value. By comparison, we find there is no connection between two kinds of stochastic bifurcation.

Comments on the Bifurcation Structure of 1D Maps

DEFF Research Database (Denmark)

Belykh, V.N.; Mosekilde, Erik

1997-01-01

-within-a-box structure of the total bifurcation set. This presents a picture in which the homoclinic orbit bifurcations act as a skeleton for the bifurcational set. At the same time, experimental results on continued subharmonic generation for piezoelectrically amplified sound waves, predating the Feigenbaum theory......, are called into attention....

Predicting bifurcation angle effect on blood flow in the microvasculature.

Science.gov (United States)

Yang, Jiho; Pak, Y Eugene; Lee, Tae-Rin

2016-11-01

Since blood viscosity is a basic parameter for understanding hemodynamics in human physiology, great amount of research has been done in order to accurately predict this highly non-Newtonian flow property. However, previous works lacked in consideration of hemodynamic changes induced by heterogeneous vessel networks. In this paper, the effect of bifurcation on hemodynamics in a microvasculature is quantitatively predicted. The flow resistance in a single bifurcation microvessel was calculated by combining a new simple mathematical model with 3-dimensional flow simulation for varying bifurcation angles under physiological flow conditions. Interestingly, the results indicate that flow resistance induced by vessel bifurcation holds a constant value of approximately 0.44 over the whole single bifurcation model below diameter of 60μm regardless of geometric parameters including bifurcation angle. Flow solutions computed from this new model showed substantial decrement in flow velocity relative to other mathematical models, which do not include vessel bifurcation effects, while pressure remained the same. Furthermore, when applying the bifurcation angle effect to the entire microvascular network, the simulation results gave better agreements with recent in vivo experimental measurements. This finding suggests a new paradigm in microvascular blood flow properties, that vessel bifurcation itself, regardless of its angle, holds considerable influence on blood viscosity, and this phenomenon will help to develop new predictive tools in microvascular research. Copyright © 2016 Elsevier Inc. All rights reserved.

Double Kissing Crush Versus Provisional Stenting for Left Main Distal Bifurcation Lesions: DKCRUSH-V Randomized Trial.

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Chen, Shao-Liang; Zhang, Jue-Jie; Han, Yaling; Kan, Jing; Chen, Lianglong; Qiu, Chunguang; Jiang, Tiemin; Tao, Ling; Zeng, Hesong; Li, Li; Xia, Yong; Gao, Chuanyu; Santoso, Teguh; Paiboon, Chootopol; Wang, Yan; Kwan, Tak W; Ye, Fei; Tian, Nailiang; Liu, Zhizhong; Lin, Song; Lu, Chengzhi; Wen, Shangyu; Hong, Lang; Zhang, Qi; Sheiban, Imad; Xu, Yawei; Wang, Lefeng; Rab, Tanveer S; Li, Zhanquan; Cheng, Guanchang; Cui, Lianqun; Leon, Martin B; Stone, Gregg W

2017-11-28

Provisional stenting (PS) is the most common technique used to treat distal left main (LM) bifurcation lesions in patients with unprotected LM coronary artery disease undergoing percutaneous coronary intervention. The double kissing (DK) crush planned 2-stent technique has been shown to improve clinical outcomes in non-LM bifurcations compared with PS, and in LM bifurcations compared with culotte stenting, but has never been compared with PS in LM bifurcation lesions. The authors sought to determine whether a planned DK crush 2-stent technique is superior to PS for patients with true distal LM bifurcation lesions. The authors randomized 482 patients from 26 centers in 5 countries with true distal LM bifurcation lesions (Medina 1,1,1 or 0,1,1) to PS (n = 242) or DK crush stenting (n = 240). The primary endpoint was the 1-year composite rate of target lesion failure (TLF): cardiac death, target vessel myocardial infarction, or clinically driven target lesion revascularization. Routine 13-month angiographic follow-up was scheduled after ascertainment of the primary endpoint. TLF within 1 year occurred in 26 patients (10.7%) assigned to PS, and in 12 patients (5.0%) assigned to DK crush (hazard ratio: 0.42; 95% confidence interval: 0.21 to 0.85; p = 0.02). Compared with PS, DK crush also resulted in lower rates of target vessel myocardial infarction I (2.9% vs. 0.4%; p = 0.03) and definite or probable stent thrombosis (3.3% vs. 0.4%; p = 0.02). Clinically driven target lesion revascularization (7.9% vs. 3.8%; p = 0.06) and angiographic restenosis within the LM complex (14.6% vs. 7.1%; p = 0.10) also tended to be less frequent with DK crush compared with PS. There was no significant difference in cardiac death between the groups. In the present multicenter randomized trial, percutaneous coronary intervention of true distal LM bifurcation lesions using a planned DK crush 2-stent strategy resulted in a lower rate of TLF at 1 year than a PS�

Influence of the Accuracy of Angiography-Based Reconstructions on Velocity and Wall Shear Stress Computations in Coronary Bifurcations: A Phantom Study

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Schrauwen, Jelle T. C.; Karanasos, Antonios; van Ditzhuijzen, Nienke S.; Aben, Jean-Paul; van der Steen, Antonius F. W.

2015-01-01

Introduction Wall shear stress (WSS) plays a key role in the onset and progression of atherosclerosis in human coronary arteries. Especially sites with low and oscillating WSS near bifurcations have a higher propensity to develop atherosclerosis. WSS computations in coronary bifurcations can be performed in angiography-based 3D reconstructions. It is essential to evaluate how reconstruction errors influence WSS computations in mildly-diseased coronary bifurcations. In mildly-diseased lesions WSS could potentially provide more insight in plaque progression. Materials Methods Four Plexiglas phantom models of coronary bifurcations were imaged with bi-plane angiography. The lumens were segmented by two clinically experienced readers. Based on the segmentations 3D models were generated. This resulted in three models per phantom: one gold-standard from the phantom model itself, and one from each reader. Steady-state and transient simulations were performed with computational fluid dynamics to compute the WSS. A similarity index and a noninferiority test were used to compare the WSS in the phantoms and their reconstructions. The margin for this test was based on the resolution constraints of angiography. Results The reconstruction errors were similar to previously reported data; in seven out of eight reconstructions less than 0.10 mm. WSS in the regions proximal and far distal of the stenosis showed a good agreement. However, the low WSS areas directly distal of the stenosis showed some disagreement between the phantoms and the readers. This was due to small deviations in the reconstruction of the stenosis that caused differences in the resulting jet, and consequently the size and location of the low WSS area. Discussion This study showed that WSS can accurately be computed within angiography-based 3D reconstructions of coronary arteries with early stage atherosclerosis. Qualitatively, there was a good agreement between the phantoms and the readers. Quantitatively, the

Influence of the Accuracy of Angiography-Based Reconstructions on Velocity and Wall Shear Stress Computations in Coronary Bifurcations: A Phantom Study.

Directory of Open Access Journals (Sweden)

Jelle T C Schrauwen

Full Text Available Wall shear stress (WSS plays a key role in the onset and progression of atherosclerosis in human coronary arteries. Especially sites with low and oscillating WSS near bifurcations have a higher propensity to develop atherosclerosis. WSS computations in coronary bifurcations can be performed in angiography-based 3D reconstructions. It is essential to evaluate how reconstruction errors influence WSS computations in mildly-diseased coronary bifurcations. In mildly-diseased lesions WSS could potentially provide more insight in plaque progression.Four Plexiglas phantom models of coronary bifurcations were imaged with bi-plane angiography. The lumens were segmented by two clinically experienced readers. Based on the segmentations 3D models were generated. This resulted in three models per phantom: one gold-standard from the phantom model itself, and one from each reader. Steady-state and transient simulations were performed with computational fluid dynamics to compute the WSS. A similarity index and a noninferiority test were used to compare the WSS in the phantoms and their reconstructions. The margin for this test was based on the resolution constraints of angiography.The reconstruction errors were similar to previously reported data; in seven out of eight reconstructions less than 0.10 mm. WSS in the regions proximal and far distal of the stenosis showed a good agreement. However, the low WSS areas directly distal of the stenosis showed some disagreement between the phantoms and the readers. This was due to small deviations in the reconstruction of the stenosis that caused differences in the resulting jet, and consequently the size and location of the low WSS area.This study showed that WSS can accurately be computed within angiography-based 3D reconstructions of coronary arteries with early stage atherosclerosis. Qualitatively, there was a good agreement between the phantoms and the readers. Quantitatively, the low WSS regions directly distal to

Defining Electron Bifurcation in the Electron-Transferring Flavoprotein Family.

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Garcia Costas, Amaya M; Poudel, Saroj; Miller, Anne-Frances; Schut, Gerrit J; Ledbetter, Rhesa N; Fixen, Kathryn R; Seefeldt, Lance C; Adams, Michael W W; Harwood, Caroline S; Boyd, Eric S; Peters, John W

2017-11-01

Electron bifurcation is the coupling of exergonic and endergonic redox reactions to simultaneously generate (or utilize) low- and high-potential electrons. It is the third recognized form of energy conservation in biology and was recently described for select electron-transferring flavoproteins (Etfs). Etfs are flavin-containing heterodimers best known for donating electrons derived from fatty acid and amino acid oxidation to an electron transfer respiratory chain via Etf-quinone oxidoreductase. Canonical examples contain a flavin adenine dinucleotide (FAD) that is involved in electron transfer, as well as a non-redox-active AMP. However, Etfs demonstrated to bifurcate electrons contain a second FAD in place of the AMP. To expand our understanding of the functional variety and metabolic significance of Etfs and to identify amino acid sequence motifs that potentially enable electron bifurcation, we compiled 1,314 Etf protein sequences from genome sequence databases and subjected them to informatic and structural analyses. Etfs were identified in diverse archaea and bacteria, and they clustered into five distinct well-supported groups, based on their amino acid sequences. Gene neighborhood analyses indicated that these Etf group designations largely correspond to putative differences in functionality. Etfs with the demonstrated ability to bifurcate were found to form one group, suggesting that distinct conserved amino acid sequence motifs enable this capability. Indeed, structural modeling and sequence alignments revealed that identifying residues occur in the NADH- and FAD-binding regions of bifurcating Etfs. Collectively, a new classification scheme for Etf proteins that delineates putative bifurcating versus nonbifurcating members is presented and suggests that Etf-mediated bifurcation is associated with surprisingly diverse enzymes. IMPORTANCE Electron bifurcation has recently been recognized as an electron transfer mechanism used by microorganisms to maximize

Dynamic bifurcations on financial markets

International Nuclear Information System (INIS)

Kozłowska, M.; Denys, M.; Wiliński, M.; Link, G.; Gubiec, T.; Werner, T.R.; Kutner, R.; Struzik, Z.R.

2016-01-01

We provide evidence that catastrophic bifurcation breakdowns or transitions, preceded by early warning signs such as flickering phenomena, are present on notoriously unpredictable financial markets. For this we construct robust indicators of catastrophic dynamical slowing down and apply these to identify hallmarks of dynamical catastrophic bifurcation transitions. This is done using daily closing index records for the representative examples of financial markets of small and mid to large capitalisations experiencing a speculative bubble induced by the worldwide financial crisis of 2007-08.

Bifurcation Analysis for an SEIRS-V Model with Delays on the Transmission of Worms in a Wireless Sensor Network

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Zizhen Zhang

2017-01-01

Full Text Available Hopf bifurcation for an SEIRS-V model with delays on the transmission of worms in a wireless sensor network is investigated. We focus on existence of the Hopf bifurcation by regarding the diverse delay as a bifurcation parameter. The results show that propagation of worms in the wireless sensor network can be controlled when the delay is suitably small under some certain conditions. Then, we study properties of the Hopf bifurcation by using the normal form theory and center manifold theorem. Finally, we give a numerical example to support the theoretical results.

Hopf bifurcation for tumor-immune competition systems with delay

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Ping Bi

2014-01-01

Full Text Available In this article, a immune response system with delay is considered, which consists of two-dimensional nonlinear differential equations. The main purpose of this paper is to explore the Hopf bifurcation of a immune response system with delay. The general formula of the direction, the estimation formula of period and stability of bifurcated periodic solution are also given. Especially, the conditions of the global existence of periodic solutions bifurcating from Hopf bifurcations are given. Numerical simulations are carried out to illustrate the the theoretical analysis and the obtained results.

Experimental bifurcation analysis—Continuation for noise-contaminated zero problems

DEFF Research Database (Denmark)

Schilder, Frank; Bureau, Emil; Santos, Ilmar Ferreira

2015-01-01

Noise contaminated zero problems involve functions that cannot be evaluated directly, but only indirectly via observations. In addition, such observations are affected by a non-deterministic observation error (noise). We investigate the application of numerical bifurcation analysis for studying...... the solution set of such noise contaminated zero problems, which is highly relevant in the context of equation-free analysis (coarse grained analysis) and bifurcation analysis in experiments, and develop specialized algorithms to address challenges that arise due to the presence of noise. As a working example......, we demonstrate and test our algorithms on a mechanical nonlinear oscillator experiment using control based continuation, which we used as a main application and test case for development of the Coco compatible Matlab toolbox Continex that implements our algorithms....

HIGH ORIGIN OF SUPERFICIAL ULNAR ARTERY- A CASE REPORT

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Anjana Jayakumaran Nair

2017-03-01

Full Text Available BACKGROUND High origin and superficially placed ulnar artery is a rare anatomical variant that usually arises either in the axilla or arm and runs a superficial course in the forearm, enters the hand and participates in the formation of superficial palmar arch. During routine dissection of cadavers in our department, we observed a unilateral case of high origin and superficial ulnar artery in a human male cadaver. It originated from the brachial artery in the lower third of arm 4 cm above its bifurcation. From its origin, it passed downwards along the medial aspect of forearm, superficial to the flexors, entered hand superficial to the flexor retinaculum and formed superficial palmar arch. The knowledge of existence of a superficial ulnar artery is important during vascular and reconstructive surgery and also in evaluation of angiographic images. Superficial position makes it more vulnerable to trauma and more accessible to cannulation.

Reverse bifurcation and fractal of the compound logistic map

Science.gov (United States)

Wang, Xingyuan; Liang, Qingyong

2008-07-01

The nature of the fixed points of the compound logistic map is researched and the boundary equation of the first bifurcation of the map in the parameter space is given out. Using the quantitative criterion and rule of chaotic system, the paper reveal the general features of the compound logistic map transforming from regularity to chaos, the following conclusions are shown: (1) chaotic patterns of the map may emerge out of double-periodic bifurcation and (2) the chaotic crisis phenomena and the reverse bifurcation are found. At the same time, we analyze the orbit of critical point of the compound logistic map and put forward the definition of Mandelbrot-Julia set of compound logistic map. We generalize the Welstead and Cromer's periodic scanning technology and using this technology construct a series of Mandelbrot-Julia sets of compound logistic map. We investigate the symmetry of Mandelbrot-Julia set and study the topological inflexibility of distributing of period region in the Mandelbrot set, and finds that Mandelbrot set contain abundant information of structure of Julia sets by founding the whole portray of Julia sets based on Mandelbrot set qualitatively.

Towards classification of the bifurcation structure of a spherical cavitation bubble.

Science.gov (United States)

Behnia, Sohrab; Sojahrood, Amin Jafari; Soltanpoor, Wiria; Sarkhosh, Leila

2009-12-01

We focus on a single cavitation bubble driven by ultrasound, a system which is a specimen of forced nonlinear oscillators and is characterized by its extreme sensitivity to the initial conditions. The driven radial oscillations of the bubble are considered to be implicated by the principles of chaos physics and owing to specific ranges of control parameters, can be periodic or chaotic. Despite the growing number of investigations on its dynamics, there is not yet an inclusive yardstick to sort the dynamical behavior of the bubble into classes; also, the response oscillations are so complex that long term prediction on the behavior becomes difficult to accomplish. In this study, the nonlinear dynamics of a bubble oscillator was treated numerically and the simulations were proceeded with bifurcation diagrams. The calculated bifurcation diagrams were compared in an attempt to classify the bubble dynamic characteristics when varying the control parameters. The comparison reveals distinctive bifurcation patterns as a consequence of driving the systems with unequal ratios of R(0)lambda (where R(0) is the bubble initial radius and lambda is the wavelength of the driving ultrasonic wave). Results indicated that systems having the equal ratio of R(0)lambda, share remarkable similarities in their bifurcating behavior and can be classified under a unit category.

Bifurcations of transition states: Morse bifurcations

International Nuclear Information System (INIS)

MacKay, R S; Strub, D C

2014-01-01

A transition state for a Hamiltonian system is a closed, invariant, oriented, codimension-2 submanifold of an energy level that can be spanned by two compact codimension-1 surfaces of unidirectional flux whose union, called a dividing surface, locally separates the energy level into two components and has no local recrossings. For this to happen robustly to all smooth perturbations, the transition state must be normally hyperbolic. The dividing surface then has locally minimal geometric flux through it, giving an upper bound on the rate of transport in either direction. Transition states diffeomorphic to S 2m−3 are known to exist for energies just above any index-1 critical point of a Hamiltonian of m degrees of freedom, with dividing surfaces S 2m−2 . The question addressed here is what qualitative changes in the transition state, and consequently the dividing surface, may occur as the energy or other parameters are varied? We find that there is a class of systems for which the transition state becomes singular and then regains normal hyperbolicity with a change in diffeomorphism class. These are Morse bifurcations. Various examples are considered. Firstly, some simple examples in which transition states connect or disconnect, and the dividing surface may become a torus or other. Then, we show how sequences of Morse bifurcations producing various interesting forms of transition state and dividing surface are present in reacting systems, by considering a hypothetical class of bimolecular reactions in gas phase. (paper)

Regularization of the Boundary-Saddle-Node Bifurcation

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Xia Liu

2018-01-01

Full Text Available In this paper we treat a particular class of planar Filippov systems which consist of two smooth systems that are separated by a discontinuity boundary. In such systems one vector field undergoes a saddle-node bifurcation while the other vector field is transversal to the boundary. The boundary-saddle-node (BSN bifurcation occurs at a critical value when the saddle-node point is located on the discontinuity boundary. We derive a local topological normal form for the BSN bifurcation and study its local dynamics by applying the classical Filippov’s convex method and a novel regularization approach. In fact, by the regularization approach a given Filippov system is approximated by a piecewise-smooth continuous system. Moreover, the regularization process produces a singular perturbation problem where the original discontinuous set becomes a center manifold. Thus, the regularization enables us to make use of the established theories for continuous systems and slow-fast systems to study the local behavior around the BSN bifurcation.

Codimension-Two Bifurcation Analysis in DC Microgrids Under Droop Control

Science.gov (United States)

Lenz, Eduardo; Pagano, Daniel J.; Tahim, André P. N.

This paper addresses local and global bifurcations that may appear in electrical power systems, such as DC microgrids, which recently has attracted interest from the electrical engineering society. Most sources in these networks are voltage-type and operate in parallel. In such configuration, the basic technique for stabilizing the bus voltage is the so-called droop control. The main contribution of this work is a codimension-two bifurcation analysis of a small DC microgrid considering the droop control gain and the power processed by the load as bifurcation parameters. The codimension-two bifurcation set leads to practical rules for achieving a robust droop control design. Moreover, the bifurcation analysis also offers a better understanding of the dynamics involved in the problem and how to avoid possible instabilities. Simulation results are presented in order to illustrate the bifurcation analysis.

Bifurcation diagram of a cubic three-parameter autonomous system

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Lenka Barakova

2005-07-01

Full Text Available In this paper, we study the cubic three-parameter autonomous planar system $$displaylines{ dot x_1 = k_1 + k_2x_1 - x_1^3 - x_2,cr dot x_2 = k_3 x_1 - x_2, }$$ where $k_2, k_3$ are greater than 0. Our goal is to obtain a bifurcation diagram; i.e., to divide the parameter space into regions within which the system has topologically equivalent phase portraits and to describe how these portraits are transformed at the bifurcation boundaries. Results may be applied to the macroeconomical model IS-LM with Kaldor's assumptions. In this model existence of a stable limit cycles has already been studied (Andronov-Hopf bifurcation. We present the whole bifurcation diagram and among others, we prove existence of more difficult bifurcations and existence of unstable cycles.

Bifurcation of transition paths induced by coupled bistable systems.

Science.gov (United States)

Tian, Chengzhe; Mitarai, Namiko

2016-06-07

We discuss the transition paths in a coupled bistable system consisting of interacting multiple identical bistable motifs. We propose a simple model of coupled bistable gene circuits as an example and show that its transition paths are bifurcating. We then derive a criterion to predict the bifurcation of transition paths in a generalized coupled bistable system. We confirm the validity of the theory for the example system by numerical simulation. We also demonstrate in the example system that, if the steady states of individual gene circuits are not changed by the coupling, the bifurcation pattern is not dependent on the number of gene circuits. We further show that the transition rate exponentially decreases with the number of gene circuits when the transition path does not bifurcate, while a bifurcation facilitates the transition by lowering the quasi-potential energy barrier.

Bifurcation analysis for a discrete-time Hopfield neural network of two neurons with two delays and self-connections

International Nuclear Information System (INIS)

Kaslik, E.; Balint, St.

2009-01-01

In this paper, a bifurcation analysis is undertaken for a discrete-time Hopfield neural network of two neurons with two different delays and self-connections. Conditions ensuring the asymptotic stability of the null solution are found, with respect to two characteristic parameters of the system. It is shown that for certain values of these parameters, Fold or Neimark-Sacker bifurcations occur, but Flip and codimension 2 (Fold-Neimark-Sacker, double Neimark-Sacker, resonance 1:1 and Flip-Neimark-Sacker) bifurcations may also be present. The direction and the stability of the Neimark-Sacker bifurcations are investigated by applying the center manifold theorem and the normal form theory

Nonlinear physical systems spectral analysis, stability and bifurcations

CERN Document Server

Kirillov, Oleg N

2013-01-01

Bringing together 18 chapters written by leading experts in dynamical systems, operator theory, partial differential equations, and solid and fluid mechanics, this book presents state-of-the-art approaches to a wide spectrum of new and challenging stability problems.Nonlinear Physical Systems: Spectral Analysis, Stability and Bifurcations focuses on problems of spectral analysis, stability and bifurcations arising in the nonlinear partial differential equations of modern physics. Bifurcations and stability of solitary waves, geometrical optics stability analysis in hydro- and magnetohydrodynam

Fractional noise destroys or induces a stochastic bifurcation

Energy Technology Data Exchange (ETDEWEB)

Yang, Qigui, E-mail: qgyang@scut.edu.cn [School of Sciences, South China University of Technology, Guangzhou 510640 (China); Zeng, Caibin, E-mail: zeng.cb@mail.scut.edu.cn [School of Sciences, South China University of Technology, Guangzhou 510640 (China); School of Automation Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Wang, Cong, E-mail: wangcong@scut.edu.cn [School of Automation Science and Engineering, South China University of Technology, Guangzhou 510640 (China)

2013-12-15

Little seems to be known about the stochastic bifurcation phenomena of non-Markovian systems. Our intention in this paper is to understand such complex dynamics by a simple system, namely, the Black-Scholes model driven by a mixed fractional Brownian motion. The most interesting finding is that the multiplicative fractional noise not only destroys but also induces a stochastic bifurcation under some suitable conditions. So it opens a possible way to explore the theory of stochastic bifurcation in the non-Markovian framework.

Experimental bifurcation analysis of an impact oscillator – Determining stability

DEFF Research Database (Denmark)

Bureau, Emil; Schilder, Frank; Elmegård, Michael

2014-01-01

We propose and investigate three different methods for assessing stability of dynamical equilibrium states during experimental bifurcation analysis, using a control-based continuation method. The idea is to modify or turn off the control at an equilibrium state and study the resulting behavior...

Technique and results of femoral bifurcation endarterectomy by eversion.

Science.gov (United States)

Dufranc, Julie; Palcau, Laura; Heyndrickx, Maxime; Gouicem, Djelloul; Coffin, Olivier; Felisaz, Aurélien; Berger, Ludovic

2015-03-01

, with a statistically higher rate for patients with malnutrition (P = .029), preoperative platelet count >450 ×10(9)/L (P = .0071), platelet aggregation inhibitor treatment other than clopidogrel (P = .022), preoperative deep femoral artery occlusion or stenosis >75% (P = .0064), and poor tibial runoff (P = .00042). Eversion femoral bifurcation endarterectomy is a safe, efficient, and reproducible technique for the treatment of atherosclerotic femoral lesions. Advantages are notable, especially the lack of need for prosthetic angioplasty, eliminating the risk of patch infection or pseudoaneurysms and permitting direct puncture if endovascular procedures are needed for assisted patency. Copyright © 2015 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

Bifurcations and Periodic Solutions for an Algae-Fish Semicontinuous System

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Chuanjun Dai

2013-01-01

Full Text Available We propose an algae-fish semicontinuous system for the Zeya Reservoir to study the control of algae, including biological and chemical controls. The bifurcation and periodic solutions of the system were studied using a Poincaré map and a geometric method. The existence of order-1 periodic solution of the system is discussed. Based on previous analysis, we investigated the change in the location of the order-1 periodic solution with variable parameters and we described the transcritical bifurcation of the system. Finally, we provided a series of numerical results to illustrate the feasibility of the theoretical results. These results may help to facilitate a better understanding of algal control in the Zeya Reservoir.

Codimension-two bifurcation analysis on firing activities in Chay neuron model

International Nuclear Information System (INIS)

Duan Lixia; Lu Qishao

2006-01-01

Using codimension-two bifurcation analysis in the Chay neuron model, the relationship between the electric activities and the parameters of neurons is revealed. The whole parameter space is divided into two parts, that is, the firing and silence regions of neurons. It is found that the transition sets between firing and silence regions are composed of the Hopf bifurcation curves of equilibrium states and the saddle-node bifurcation curves of limit cycles, with some codimension-two bifurcation points. The transitions from silence to firing in neurons are due to the Hopf bifurcation or the fold limit cycle bifurcation, but the codimension-two singularities lead to complexity in dynamical behaviour of neuronal firing

Codimension-two bifurcation analysis on firing activities in Chay neuron model

Energy Technology Data Exchange (ETDEWEB)

Duan Lixia [School of Science, Beijing University of Aeronautics and Astronautics, Beijing 100083 (China); Lu Qishao [School of Science, Beijing University of Aeronautics and Astronautics, Beijing 100083 (China)]. E-mail: qishaolu@hotmail.com

2006-12-15

Using codimension-two bifurcation analysis in the Chay neuron model, the relationship between the electric activities and the parameters of neurons is revealed. The whole parameter space is divided into two parts, that is, the firing and silence regions of neurons. It is found that the transition sets between firing and silence regions are composed of the Hopf bifurcation curves of equilibrium states and the saddle-node bifurcation curves of limit cycles, with some codimension-two bifurcation points. The transitions from silence to firing in neurons are due to the Hopf bifurcation or the fold limit cycle bifurcation, but the codimension-two singularities lead to complexity in dynamical behaviour of neuronal firing.

Bifurcation parameters of a reflected shock wave in cylindrical channels of different roughnesses

Science.gov (United States)

Penyazkov, O.; Skilandz, A.

2018-03-01

To investigate the effect of bifurcation on the induction time in cylindrical shock tubes used for chemical kinetic experiments, one should know the parameters of the bifurcation structure of a reflected shock wave. The dynamics and parameters of the shock wave bifurcation, which are caused by reflected shock wave-boundary layer interactions, are studied experimentally in argon, in air, and in a hydrogen-nitrogen mixture for Mach numbers M = 1.3-3.5 in a 76-mm-diameter shock tube without any ramp. Measurements were taken at a constant gas density behind the reflected shock wave. Over a wide range of experimental conditions, we studied the axial projection of the oblique shock wave and the pressure distribution in the vicinity of the triple Mach configuration at 50, 150, and 250 mm from the endwall, using side-wall schlieren and pressure measurements. Experiments on a polished shock tube and a shock tube with a surface roughness of 20 {μ }m Ra were carried out. The surface roughness was used for initiating small-scale turbulence in the boundary layer behind the incident shock wave. The effect of small-scale turbulence on the homogenization of the transition zone from the laminar to turbulent boundary layer along the shock tube perimeter was assessed, assuming its influence on a subsequent stabilization of the bifurcation structure size versus incident shock wave Mach number, as well as local flow parameters behind the reflected shock wave. The influence of surface roughness on the bifurcation development and pressure fluctuations near the wall, as well as on the Mach number, at which the bifurcation first develops, was analyzed. It was found that even small additional surface roughness can lead to an overshoot in pressure growth by a factor of two, but it can stabilize the bifurcation structure along the shock tube perimeter.

Numerical bifurcation analysis of conformal formulations of the Einstein constraints

International Nuclear Information System (INIS)

Holst, M.; Kungurtsev, V.

2011-01-01

The Einstein constraint equations have been the subject of study for more than 50 years. The introduction of the conformal method in the 1970s as a parametrization of initial data for the Einstein equations led to increased interest in the development of a complete solution theory for the constraints, with the theory for constant mean curvature (CMC) spatial slices and closed manifolds completely developed by 1995. The first general non-CMC existence result was establish by Holst et al. in 2008, with extensions to rough data by Holst et al. in 2009, and to vacuum spacetimes by Maxwell in 2009. The non-CMC theory remains mostly open; moreover, recent work of Maxwell on specific symmetry models sheds light on fundamental nonuniqueness problems with the conformal method as a parametrization in non-CMC settings. In parallel with these mathematical developments, computational physicists have uncovered surprising behavior in numerical solutions to the extended conformal thin sandwich formulation of the Einstein constraints. In particular, numerical evidence suggests the existence of multiple solutions with a quadratic fold, and a recent analysis of a simplified model supports this conclusion. In this article, we examine this apparent bifurcation phenomena in a methodical way, using modern techniques in bifurcation theory and in numerical homotopy methods. We first review the evidence for the presence of bifurcation in the Hamiltonian constraint in the time-symmetric case. We give a brief introduction to the mathematical framework for analyzing bifurcation phenomena, and then develop the main ideas behind the construction of numerical homotopy, or path-following, methods in the analysis of bifurcation phenomena. We then apply the continuation software package AUTO to this problem, and verify the presence of the fold with homotopy-based numerical methods. We discuss these results and their physical significance, which lead to some interesting remaining questions to

Computing closest saddle node bifurcations in a radial system via conic programming

Energy Technology Data Exchange (ETDEWEB)

Jabr, R.A. [Electrical, Computer and Communication Engineering Department, Notre Dame University, P.O. Box 72, Zouk Mikhael, Zouk Mosbeh (Lebanon); Pal, B.C. [Department of Electrical and Electronic Engineering, Imperial College London, SW7 2BT (United Kingdom)

2009-07-15

This paper considers the problem of computing the loading limits in a radial system which are (i) locally closest to current operating load powers and (ii) at which saddle node bifurcation occurs. The procedure is based on a known technique which requires iterating between two computational steps until convergence. In essence, step 1 produces a vector normal to the real and/or reactive load solution space boundary, whereas step 2 computes the bifurcation point along that vector. The paper shows that each of the above computational steps can be formulated as a second-order cone program for which polynomial time interior-point methods and efficient implementations exist. The proposed conic programming approach is used to compute the closest bifurcation points and the corresponding worst case load power margins of eleven different distribution systems. The approach is validated graphically and the existence of multiple load power margins is investigated. (author)

Bifurcation magnetic resonance in films magnetized along hard magnetization axis

Energy Technology Data Exchange (ETDEWEB)

Vasilevskaya, Tatiana M., E-mail: t_vasilevs@mail.ru [Ulyanovsk State University, Leo Tolstoy 42, 432017 Ulyanovsk (Russian Federation); Sementsov, Dmitriy I.; Shutyi, Anatoliy M. [Ulyanovsk State University, Leo Tolstoy 42, 432017 Ulyanovsk (Russian Federation)

2012-09-15

We study low-frequency ferromagnetic resonance in a thin film magnetized along the hard magnetization axis performing an analysis of magnetization precession dynamics equations and numerical simulation. Two types of films are considered: polycrystalline uniaxial films and single-crystal films with cubic magnetic anisotropy. An additional (bifurcation) resonance initiated by the bistability, i.e. appearance of two closely spaced equilibrium magnetization states is registered. The modification of dynamic modes provoked by variation of the frequency, amplitude, and magnetic bias value of the ac field is studied. Both steady and chaotic magnetization precession modes are registered in the bifurcation resonance range. - Highlights: Black-Right-Pointing-Pointer An additional bifurcation resonance arises in a case of a thin film magnetized along HMA. Black-Right-Pointing-Pointer Bifurcation resonance occurs due to the presence of two closely spaced equilibrium magnetization states. Black-Right-Pointing-Pointer Both regular and chaotic precession modes are realized within bifurcation resonance range. Black-Right-Pointing-Pointer Appearance of dynamic bistability is typical for bifurcation resonance.

Bifurcation magnetic resonance in films magnetized along hard magnetization axis

International Nuclear Information System (INIS)

Vasilevskaya, Tatiana M.; Sementsov, Dmitriy I.; Shutyi, Anatoliy M.

2012-01-01

We study low-frequency ferromagnetic resonance in a thin film magnetized along the hard magnetization axis performing an analysis of magnetization precession dynamics equations and numerical simulation. Two types of films are considered: polycrystalline uniaxial films and single-crystal films with cubic magnetic anisotropy. An additional (bifurcation) resonance initiated by the bistability, i.e. appearance of two closely spaced equilibrium magnetization states is registered. The modification of dynamic modes provoked by variation of the frequency, amplitude, and magnetic bias value of the ac field is studied. Both steady and chaotic magnetization precession modes are registered in the bifurcation resonance range. - Highlights: ► An additional bifurcation resonance arises in a case of a thin film magnetized along HMA. ► Bifurcation resonance occurs due to the presence of two closely spaced equilibrium magnetization states. ► Both regular and chaotic precession modes are realized within bifurcation resonance range. ► Appearance of dynamic bistability is typical for bifurcation resonance.

Bifurcation and Fractal of the Coupled Logistic Map

Science.gov (United States)

Wang, Xingyuan; Luo, Chao

The nature of the fixed points of the coupled Logistic map is researched, and the boundary equation of the first bifurcation of the coupled Logistic map in the parameter space is given out. Using the quantitative criterion and rule of system chaos, i.e., phase graph, bifurcation graph, power spectra, the computation of the fractal dimension, and the Lyapunov exponent, the paper reveals the general characteristics of the coupled Logistic map transforming from regularity to chaos, the following conclusions are shown: (1) chaotic patterns of the coupled Logistic map may emerge out of double-periodic bifurcation and Hopf bifurcation, respectively; (2) during the process of double-period bifurcation, the system exhibits self-similarity and scale transform invariability in both the parameter space and the phase space. From the research of the attraction basin and Mandelbrot-Julia set of the coupled Logistic map, the following conclusions are indicated: (1) the boundary between periodic and quasiperiodic regions is fractal, and that indicates the impossibility to predict the moving result of the points in the phase plane; (2) the structures of the Mandelbrot-Julia sets are determined by the control parameters, and their boundaries have the fractal characteristic.

Inverse bifurcation analysis: application to simple gene systems

Directory of Open Access Journals (Sweden)

Schuster Peter

2006-07-01

Full Text Available Abstract Background Bifurcation analysis has proven to be a powerful method for understanding the qualitative behavior of gene regulatory networks. In addition to the more traditional forward problem of determining the mapping from parameter space to the space of model behavior, the inverse problem of determining model parameters to result in certain desired properties of the bifurcation diagram provides an attractive methodology for addressing important biological problems. These include understanding how the robustness of qualitative behavior arises from system design as well as providing a way to engineer biological networks with qualitative properties. Results We demonstrate that certain inverse bifurcation problems of biological interest may be cast as optimization problems involving minimal distances of reference parameter sets to bifurcation manifolds. This formulation allows for an iterative solution procedure based on performing a sequence of eigen-system computations and one-parameter continuations of solutions, the latter being a standard capability in existing numerical bifurcation software. As applications of the proposed method, we show that the problem of maximizing regions of a given qualitative behavior as well as the reverse engineering of bistable gene switches can be modelled and efficiently solved.

Angiographic prevalence and pattern of coronary artery disease in women.

Science.gov (United States)

Ezhumalai, Babu; Jayaraman, Balachander

2014-01-01

There are not many studies describing the prevalence and pattern of "coronary artery disease" (CAD) in women undergoing "coronary angiography" (CAG). Hence, uncertainty thrives with regard to the angiographic prevalence and pattern of CAD in women. Our objective was to study the prevalence and pattern of CAD among women undergoing CAG. Data of 500 women who underwent CAG for suspected CAD over 3 years were retrospectively analyzed. They were classified into young group (age right coronary artery. Bifurcation lesion involving distal left main coronary artery is the most prevalent pattern of LMD. There has been a change with regard to clinical presentation and onset of risk factors for CAD at young age, but the load of atherosclerotic burden and pattern of involvement of coronary arteries have not changed in women. Copyright © 2014 Cardiological Society of India. Published by Elsevier B.V. All rights reserved.

Deformable 4DCT lung registration with vessel bifurcations

International Nuclear Information System (INIS)

Hilsmann, A.; Vik, T.; Kaus, M.; Franks, K.; Bissonette, J.P.; Purdie, T.; Beziak, A.; Aach, T.

2007-01-01

In radiotherapy planning of lung cancer, breathing motion causes uncertainty in the determination of the target volume. Image registration makes it possible to get information about the deformation of the lung and the tumor movement in the respiratory cycle from a few images. A dedicated, automatic, landmark-based technique was developed that finds corresponding vessel bifurcations. Hereby, we developed criteria to characterize pronounced bifurcations for which correspondence finding was more stable and accurate. The bifurcations were extracted from automatically segmented vessel trees in maximum inhale and maximum exhale CT thorax data sets. To find corresponding bifurcations in both data sets we used the shape context approach of Belongie et al. Finally, a volumetric lung deformation was obtained using thin-plate spline interpolation and affine registration. The method is evaluated on 10 4D-CT data sets of patients with lung cancer. (orig.)

Carotid Artery Stenting Successfully Prevents Progressive Stroke Due to Mobile Plaque

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Masahiro Oomura

2015-05-01

Full Text Available We report a case of progressive ischemic stroke due to a mobile plaque, in which carotid artery stenting successfully prevented further infarctions. A 78-year-old man developed acute multiple infarcts in the right hemisphere, and a duplex ultrasound showed a mobile plaque involving the bifurcation of the left common carotid artery. Maximal medical therapy failed to prevent further infarcts, and the number of infarcts increased with his neurological deterioration. Our present case suggests that the deployment of a closed-cell stent is effective to prevent the progression of the ischemic stroke due to the mobile plaque.

Bifurcation into functional niches in adaptation.

Science.gov (United States)

White, Justin S; Adami, Christoph

2004-01-01

One of the central questions in evolutionary biology concerns the dynamics of adaptation and diversification. This issue can be addressed experimentally if replicate populations adapting to identical environments can be investigated in detail. We have studied 501 such replicas using digital organisms adapting to at least two fundamentally different functional niches (survival strategies) present in the same environment: one in which fast replication is the way to live, and another where exploitation of the environment's complexity leads to complex organisms with longer life spans and smaller replication rates. While these two modes of survival are closely analogous to those expected to emerge in so-called r and K selection scenarios respectively, the bifurcation of evolutionary histories according to these functional niches occurs in identical environments, under identical selective pressures. We find that the branching occurs early, and leads to drastic phenotypic differences (in fitness, sequence length, and gestation time) that are permanent and irreversible. This study confirms an earlier experimental effort using microorganisms, in that diversification can be understood at least in part in terms of bifurcations on saddle points leading to peak shifts, as in the picture drawn by Sewall Wright.

Bifurcation analysis of a delay differential equation model associated with the induction of long-term memory

International Nuclear Information System (INIS)

Hao, Lijie; Yang, Zhuoqin; Lei, Jinzhi

2015-01-01

Highlights: • A delay differentiation equation model for CREB regulation is developed. • Increasing the time delay can generate various bifurcations. • Increasing the time delay can induce chaos by two routes. - Abstract: The ability to form long-term memories is an important function for the nervous system, and the formation process is dynamically regulated through various transcription factors, including CREB proteins. In this paper, we investigate the dynamics of a delay differential equation model for CREB protein activities, which involves two positive and two negative feedbacks in the regulatory network. We discuss the dynamical mechanisms underlying the induction of long-term memory, in which bistability is essential for the formation of long-term memory, while long time delay can destabilize the high level steady state to inhibit the long-term memory formation. The model displays rich dynamical response to stimuli, including monostability, bistability, and oscillations, and can transit between different states by varying the negative feedback strength. Introduction of a time delay to the model can generate various bifurcations such as Hopf bifurcation, fold limit cycle bifurcation, Neimark–Sacker bifurcation of cycles, and period-doubling bifurcation, etc. Increasing the time delay can induce chaos by two routes: quasi-periodic route and period-doubling cascade.

Stability and bifurcation analysis in a delayed SIR model

International Nuclear Information System (INIS)

Jiang Zhichao; Wei Junjie

2008-01-01

In this paper, a time-delayed SIR model with a nonlinear incidence rate is considered. The existence of Hopf bifurcations at the endemic equilibrium is established by analyzing the distribution of the characteristic values. A explicit algorithm for determining the direction of the Hopf bifurcation and the stability of the bifurcating periodic solutions are derived by using the normal form and the center manifold theory. Numerical simulations to support the analytical conclusions are carried out

Bifurcating fronts for the Taylor-Couette problem in infinite cylinders

Science.gov (United States)

Hărăguş-Courcelle, M.; Schneider, G.

We show the existence of bifurcating fronts for the weakly unstable Taylor-Couette problem in an infinite cylinder. These fronts connect a stationary bifurcating pattern, here the Taylor vortices, with the trivial ground state, here the Couette flow. In order to show the existence result we improve a method which was already used in establishing the existence of bifurcating fronts for the Swift-Hohenberg equation by Collet and Eckmann, 1986, and by Eckmann and Wayne, 1991. The existence proof is based on spatial dynamics and center manifold theory. One of the difficulties in applying center manifold theory comes from an infinite number of eigenvalues on the imaginary axis for vanishing bifurcation parameter. But nevertheless, a finite dimensional reduction is possible, since the eigenvalues leave the imaginary axis with different velocities, if the bifurcation parameter is increased. In contrast to previous work we have to use normalform methods and a non-standard cut-off function to obtain a center manifold which is large enough to contain the bifurcating fronts.

Symmetry, Hopf bifurcation, and the emergence of cluster solutions in time delayed neural networks.

Science.gov (United States)

Wang, Zhen; Campbell, Sue Ann

2017-11-01

We consider the networks of N identical oscillators with time delayed, global circulant coupling, modeled by a system of delay differential equations with Z N symmetry. We first study the existence of Hopf bifurcations induced by the coupling time delay and then use symmetric Hopf bifurcation theory to determine how these bifurcations lead to different patterns of symmetric cluster oscillations. We apply our results to a case study: a network of FitzHugh-Nagumo neurons with diffusive coupling. For this model, we derive the asymptotic stability, global asymptotic stability, absolute instability, and stability switches of the equilibrium point in the plane of coupling time delay (τ) and excitability parameter (a). We investigate the patterns of cluster oscillations induced by the time delay and determine the direction and stability of the bifurcating periodic orbits by employing the multiple timescales method and normal form theory. We find that in the region where stability switching occurs, the dynamics of the system can be switched from the equilibrium point to any symmetric cluster oscillation, and back to equilibrium point as the time delay is increased.

Symmetry, Hopf bifurcation, and the emergence of cluster solutions in time delayed neural networks

Science.gov (United States)

Wang, Zhen; Campbell, Sue Ann

2017-11-01

We consider the networks of N identical oscillators with time delayed, global circulant coupling, modeled by a system of delay differential equations with ZN symmetry. We first study the existence of Hopf bifurcations induced by the coupling time delay and then use symmetric Hopf bifurcation theory to determine how these bifurcations lead to different patterns of symmetric cluster oscillations. We apply our results to a case study: a network of FitzHugh-Nagumo neurons with diffusive coupling. For this model, we derive the asymptotic stability, global asymptotic stability, absolute instability, and stability switches of the equilibrium point in the plane of coupling time delay (τ) and excitability parameter (a). We investigate the patterns of cluster oscillations induced by the time delay and determine the direction and stability of the bifurcating periodic orbits by employing the multiple timescales method and normal form theory. We find that in the region where stability switching occurs, the dynamics of the system can be switched from the equilibrium point to any symmetric cluster oscillation, and back to equilibrium point as the time delay is increased.

Stability and Hopf bifurcation analysis of a new system

International Nuclear Information System (INIS)

Huang Kuifei; Yang Qigui

2009-01-01

In this paper, a new chaotic system is introduced. The system contains special cases as the modified Lorenz system and conjugate Chen system. Some subtle characteristics of stability and Hopf bifurcation of the new chaotic system are thoroughly investigated by rigorous mathematical analysis and symbolic computations. Meanwhile, some numerical simulations for justifying the theoretical analysis are also presented.

Bifurcation analysis and the travelling wave solutions of the Klein

Indian Academy of Sciences (India)

In this paper, we investigate the bifurcations and dynamic behaviour of travelling wave solutions of the Klein–Gordon–Zakharov equations given in Shang et al, Comput. Math. Appl. 56, 1441 (2008). Under different parameter conditions, we obtain some exact explicit parametric representations of travelling wave solutions by ...

Secondary Channel Bifurcation Geometry: A Multi-dimensional Problem

Science.gov (United States)

Gaeuman, D.; Stewart, R. L.

2017-12-01

The construction of secondary channels (or side channels) is a popular strategy for increasing aquatic habitat complexity in managed rivers. Such channels, however, frequently experience aggradation that prevents surface water from entering the side channels near their bifurcation points during periods of relatively low discharge. This failure to maintain an uninterrupted surface water connection with the main channel can reduce the habitat value of side channels for fish species that prefer lotic conditions. Various factors have been proposed as potential controls on the fate of side channels, including water surface slope differences between the main and secondary channels, the presence of main channel secondary circulation, transverse bed slopes, and bifurcation angle. A quantitative assessment of more than 50 natural and constructed secondary channels in the Trinity River of northern California indicates that bifurcations can assume a variety of configurations that are formed by different processes and whose longevity is governed by different sets of factors. Moreover, factors such as bifurcation angle and water surface slope vary with discharge level and are continuously distributed in space, such that they must be viewed as a multi-dimensional field rather than a single-valued attribute that can be assigned to a particular bifurcation.

Bifurcations and chaos of DNA solitonic dynamics

International Nuclear Information System (INIS)

Gonzalez, J.A.; Martin-Landrove, M.; Carbo, J.R.; Chacon, M.

1994-09-01

We investigated the nonlinear DNA torsional equations proposed by Yakushevich in the presence of damping and external torques. Analytical expressions for some solutions are obtained in the case of the isolated chain. Special attention is paid to the stability of the solutions and the range of soliton interaction in the general case. The bifurcation analysis is performed and prediction of chaos is obtained for some set of parameters. Some biological implications are suggested. (author). 11 refs, 13 figs

Bifurcations in the theory of current transfer to cathodes of DC discharges and observations of transitions between different modes

Science.gov (United States)

Bieniek, M. S.; Santos, D. F. N.; Almeida, P. G. C.; Benilov, M. S.

2018-04-01

General scenarios of transitions between different spot patterns on electrodes of DC gas discharges and their relation to bifurcations of steady-state solutions are analyzed. In the case of cathodes of arc discharges, it is shown that any transition between different modes of current transfer is related to a bifurcation of steady-state solutions. In particular, transitions between diffuse and spot modes on axially symmetric cathodes, frequently observed in the experiment, represent an indication of the presence of pitchfork or fold bifurcations of steady-state solutions. Experimental observations of transitions on cathodes of DC glow microdischarges are analyzed and those potentially related to bifurcations of steady-state solutions are identified. The relevant bifurcations are investigated numerically and the computed patterns are found to conform to those observed in the course of the corresponding transitions in the experiment.

Bifurcation of learning and structure formation in neuronal maps

DEFF Research Database (Denmark)

Marschler, Christian; Faust-Ellsässer, Carmen; Starke, Jens

2014-01-01

to map formation in the laminar nucleus of the barn owl's auditory system. Using equation-free methods, we perform a bifurcation analysis of spatio-temporal structure formation in the associated synaptic-weight matrix. This enables us to analyze learning as a bifurcation process and follow the unstable...... states as well. A simple time translation of the learning window function shifts the bifurcation point of structure formation and goes along with traveling waves in the map, without changing the animal's sound localization performance....

Simulation of Blood Flow and Nanoparticle Transport in a Stenosed Carotid Bifurcation and Pseudo-Arteriole

Directory of Open Access Journals (Sweden)

Graham Doig

2012-03-01

Full Text Available Numerical simulation of flow through a realistic bifurcated carotid artery geometry with a stenosis has been conducted for comparison to experimental measurements. The behaviour of simplified therapeutic nanoparticles in relatively low concentration was observed using a discrete particle approach. The role of size (diameters from 500 nm to 50 nm in determining particle residence time and the potential for both desirable and undesirable wall interactions was investigated. It was found that mean particle residence time reduced with decreasing particle diameter, and the percentage of particles experiencing one or more wall interactions increased simultaneously. Further simulations were conducted on a scaled-down version of the geometry which approximated the size and flow conditions of an arteriole with capillary branches, and in this instance the mean residence time increased with decreasing particle diameter, owing largely to the greater influence of Brownian motion. 33% of all 50 nm particles were involved in wall interactions, indicating that smaller particles would have a greater ability to target, for instance, cancerous tumours in such regions.

Fold points and singularity induced bifurcation in inviscid transonic flow

International Nuclear Information System (INIS)

Marszalek, Wieslaw

2012-01-01

Transonic inviscid flow equation of elliptic–hyperbolic type when written in terms of the velocity components and similarity variable results in a second order nonlinear ODE having several features typical of differential–algebraic equations rather than ODEs. These features include the fold singularities (e.g. folded nodes and saddles, forward and backward impasse points), singularity induced bifurcation behavior and singularity crossing phenomenon. We investigate the above properties and conclude that the quasilinear DAEs of transonic flow have interesting properties that do not occur in other known quasilinear DAEs, for example, in MHD. Several numerical examples are included. -- Highlights: ► A novel analysis of inviscid transonic flow and its similarity solutions. ► Singularity induced bifurcation, singular points of transonic flow. ► Projection method, index of transonic flow DAEs, linearization via matrix pencil.

Outcomes of the single-stent versus kissing-stents technique in asymmetric complex aortoiliac bifurcation lesions.

Science.gov (United States)

Suh, Yongsung; Ko, Young-Guk; Shin, Dong-Ho; Kim, Jung-Sun; Kim, Byeong-Keuk; Choi, Donghoon; Hong, Myeong-Ki; Jang, Yangsoo

2015-07-01

This study investigated the outcomes of single-stent vs kissing-stents techniques in asymmetric complex aortoiliac bifurcation (ACAB) lesions. We retrospectively investigated 80 consecutive patients (69 males, 66.6 ± 8.7 years) treated with a single stent and 30 patients (26 males, 67.1 ± 7.7 years) treated with kissing stents for ACAB between January 2005 and December 2012 from a single-center cohort. A ACAB lesion was defined as a symptomatic unilateral common iliac artery stenosis (>50%) combined with intermediate stenosis (30%-50%) in the contralateral common iliac artery ostium. The primary end point was the primary patency of the ACAB. The baseline clinical characteristics did not differ significantly between the single-stent and the kissing-stents group. Technical success was achieved in all patients. The single-stent group required fewer stents (1.3 ± 0.5 vs 2.3 ± 0.8; P stent group (3%) required bailout kissing stents because of plaque shift to the contralateral side. The major complication rates were 8% in single-stent vs 13% in the kissing-stent group, which was similar (P = .399). At 3 years, the single-stent and kissing-stents group had similar rates of primary patency (89% vs 87%; P = .916) and target lesion revascularization-free survival (93% vs 87%; P = .462). The single-stent technique in ACAB was safe and showed midterm outcomes comparable with those of kissing stents. Considering the benefits, such as fewer stents, less bilateral femoral access, and the availability of contralateral access for future intervention, the single-stent technique may be an advantageous treatment option in ACAB. Copyright © 2015 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

Bifurcation of rupture path by linear and cubic damping force

Science.gov (United States)

Dennis L. C., C.; Chew X., Y.; Lee Y., C.

2014-06-01

Bifurcation of rupture path is studied for the effect of linear and cubic damping. Momentum equation with Rayleigh factor was transformed into ordinary differential form. Bernoulli differential equation was obtained and solved by the separation of variables. Analytical or exact solutions yielded the bifurcation was visible at imaginary part when the wave was non dispersive. For the dispersive wave, bifurcation of rupture path was invisible.

Ternary choices in repeated games and border collision bifurcations

International Nuclear Information System (INIS)

Dal Forno, Arianna; Gardini, Laura; Merlone, Ugo

2012-01-01

Highlights: ► We extend a model of binary choices with externalities to include more alternatives. ► Introducing one more option affects the complexity of the dynamics. ► We find bifurcation structures which where impossible to observe in binary choices. ► A ternary choice cannot simply be considered as a binary choice plus one. - Abstract: Several recent contributions formalize and analyze binary choices games with externalities as those described by Schelling. Nevertheless, in the real world choices are not always binary, and players have often to decide among more than two alternatives. These kinds of interactions are examined in game theory where, starting from the well known rock-paper-scissor game, several other kinds of strategic interactions involving more than two choices are examined. In this paper we investigate how the dynamics evolve introducing one more option in binary choice games with externalities. The dynamics we obtain are always in a stable regime, that is, the structurally stable dynamics are only attracting cycles, but of any possible positive integer as period. We show that, depending on the structure of the game, the dynamics can be quite different from those existing when considering binary choices. The bifurcation structure, due to border collisions, is explained, showing the existence of so-called big-bang bifurcation points.

Bifurcation structures of a cobweb model with memory and competing technologies

Science.gov (United States)

Agliari, Anna; Naimzada, Ahmad; Pecora, Nicolò

2018-05-01

In this paper we study a simple model based on the cobweb demand-supply framework with costly innovators and free imitators. The evolutionary selection between technologies depends on a performance measure which is related to the degree of memory. The resulting dynamics is described by a two-dimensional map. The map has a fixed point which may lose stability either via supercritical Neimark-Sacker bifurcation or flip bifurcation and several multistability situations exist. We describe some sequences of global bifurcations involving attracting and repelling closed invariant curves. These bifurcations, characterized by the creation of homoclinic connections or homoclinic tangles, are described through several numerical simulations. Particular bifurcation phenomena are also observed when the parameters are selected inside a periodicity region.

Common Arterial Trunk in a 3-Day-Old Alpaca Cria

Directory of Open Access Journals (Sweden)

Tsumugi Anne Kurosawa

2016-01-01

Full Text Available A 3-day-old alpaca cria presented for progressive weakness and dyspnea since birth. Complete bloodwork, thoracic radiographs, and endoscopic examination of the nasal passages and distal trachea revealed no significant findings. Echocardiogram and contrast study revealed a single artery overriding a large ventricular septal defect (VSD. A small atrial septal defect or patent foramen ovale was also noted. Color flow Doppler and an agitated saline contrast study revealed bidirectional but primarily right to left flow through the VSD and bidirectional shunting through the atrial defect. Differential diagnosis based on echocardiographic findings included common arterial trunk, Tetralogy of Fallot, and pulmonary atresia with a VSD. Postmortem examination revealed a large common arterial trunk with a quadricuspid valve overriding a VSD. Additionally, defect in the atrial septum was determined to be a patent foramen ovale. A single pulmonary trunk arose from the common arterial trunk and bifurcated to the left and right pulmonary artery, consistent with a Collet and Edwards’ type I common arterial trunk with aortic predominance. Although uncommon, congenital cardiac defects should be considered in animals presenting with clinical signs of hypoxemia, dyspnea, or failure to thrive.

Long-term outcome in patients treated with sirolimus-eluting stents in complex coronary artery lesions: 3-year results of the SCANDSTENT (Stenting Coronary Arteries in Non-Stress/Benestent Disease) trial

DEFF Research Database (Denmark)

Kelbaek, H.; Klovgaard, L.; Helqvist, S.

2008-01-01

data of the long-term outcome of patients with complex coronary artery lesions. METHODS: We randomly assigned 322 patients with total coronary occlusions or lesions located in bifurcations, ostial, or angulated segments of the coronary arteries to have SES or BMS implanted. RESULTS: At 3 years, major...... performed between 1 and 3 years after the index treatment (p = NS). According to revised definitions, stent thrombosis occurred in 5 patients (3.1%) in the SES group and in 7 patients (4.4%) in the BMS group (p = NS); very late stent thrombosis was observed in 4 versus 1 patient. CONCLUSIONS: A continued...

Bifurcation of Jovian magnetotail current sheet

Directory of Open Access Journals (Sweden)

P. L. Israelevich

2006-07-01

Full Text Available Multiple crossings of the magnetotail current sheet by a single spacecraft give the possibility to distinguish between two types of electric current density distribution: single-peaked (Harris type current layer and double-peaked (bifurcated current sheet. Magnetic field measurements in the Jovian magnetic tail by Voyager-2 reveal bifurcation of the tail current sheet. The electric current density possesses a minimum at the point of the Bx-component reversal and two maxima at the distance where the magnetic field strength reaches 50% of its value in the tail lobe.

Subcritical Hopf Bifurcation and Stochastic Resonance of Electrical Activities in Neuron under Electromagnetic Induction

Directory of Open Access Journals (Sweden)

Yu-Xuan Fu

2018-02-01

Full Text Available The FitzHugh–Nagumo model is improved to consider the effect of the electromagnetic induction on single neuron. On the basis of investigating the Hopf bifurcation behavior of the improved model, stochastic resonance in the stochastic version is captured near the bifurcation point. It is revealed that a weak harmonic oscillation in the electromagnetic disturbance can be amplified through stochastic resonance, and it is the cooperative effect of random transition between the resting state and the large amplitude oscillating state that results in the resonant phenomenon. Using the noise dependence of the mean of interburst intervals, we essentially suggest a biologically feasible clue for detecting weak signal by means of neuron model with subcritical Hopf bifurcation. These observations should be helpful in understanding the influence of the magnetic field to neural electrical activity.

Turing instability and bifurcation analysis in a diffusive bimolecular system with delayed feedback

Science.gov (United States)

Wei, Xin; Wei, Junjie

2017-09-01

A diffusive autocatalytic bimolecular model with delayed feedback subject to Neumann boundary conditions is considered. We mainly study the stability of the unique positive equilibrium and the existence of periodic solutions. Our study shows that diffusion can give rise to Turing instability, and the time delay can affect the stability of the positive equilibrium and result in the occurrence of Hopf bifurcations. By applying the normal form theory and center manifold reduction for partial functional differential equations, we investigate the stability and direction of the bifurcations. Finally, we give some simulations to illustrate our theoretical results.

Discretizing the transcritical and pitchfork bifurcations – conjugacy results

KAUST Repository

Ló czi, Lajos

2015-01-01

© 2015 Taylor & Francis. We present two case studies in one-dimensional dynamics concerning the discretization of transcritical (TC) and pitchfork (PF) bifurcations. In the vicinity of a TC or PF bifurcation point and under some natural assumptions

Shells, orbit bifurcations, and symmetry restorations in Fermi systems

Energy Technology Data Exchange (ETDEWEB)

Magner, A. G., E-mail: magner@kinr.kiev.ua; Koliesnik, M. V. [NASU, Institute for Nuclear Research (Ukraine); Arita, K. [Nagoya Institute of Technology, Department of Physics (Japan)

2016-11-15

The periodic-orbit theory based on the improved stationary-phase method within the phase-space path integral approach is presented for the semiclassical description of the nuclear shell structure, concerning themain topics of the fruitful activity ofV.G. Soloviev. We apply this theory to study bifurcations and symmetry breaking phenomena in a radial power-law potential which is close to the realistic Woods–Saxon one up to about the Fermi energy. Using the realistic parametrization of nuclear shapes we explain the origin of the double-humped fission barrier and the asymmetry in the fission isomer shapes by the bifurcations of periodic orbits. The semiclassical origin of the oblate–prolate shape asymmetry and tetrahedral shapes is also suggested within the improved periodic-orbit approach. The enhancement of shell structures at some surface diffuseness and deformation parameters of such shapes are explained by existence of the simple local bifurcations and new non-local bridge-orbit bifurcations in integrable and partially integrable Fermi-systems. We obtained good agreement between the semiclassical and quantum shell-structure components of the level density and energy for several surface diffuseness and deformation parameters of the potentials, including their symmetry breaking and bifurcation values.

Accidental Coverage of Both Renal Arteries during Infrarenal Aortic Stent-Graft Implantation: Cause and Treatment

Directory of Open Access Journals (Sweden)

Umberto Marcello Bracale

2014-01-01

Full Text Available The purpose of this paper is to report a salvage maneuver for accidental coverage of both renal arteries during endovascular aneurysm repair (EVAR of an infrarenal abdominal aortic aneurysm (AAA. A 72-year-old female with a 6 cm infrarenal abdominal aortic aneurysm was treated by endovascular means with a standard bifurcated graft. Upon completing an angiogram, both renal arteries were found to be accidentally occluded. Through a left percutaneous brachial approach, the right renal artery was catheterized and a chimney stent was deployed; however this was not possible for the left renal artery. A retroperitoneal surgical approach was therefore carried out with a retrograde chimney stent implanted to restore blood flow. After three months, both renal arteries were patent and renal function was not different from the baseline. Both endovascular with percutaneous access via the brachial artery and open retroperitoneal approaches with retrograde catheterization are feasible rescue techniques to recanalize the accidentally occluded renal arteries during EVAR.

CISM Session on Bifurcation and Stability of Dissipative Systems

CERN Document Server

1993-01-01

The first theme concerns the plastic buckling of structures in the spirit of Hill’s classical approach. Non-bifurcation and stability criteria are introduced and post-bifurcation analysis performed by asymptotic development method in relation with Hutchinson’s work. Some recent results on the generalized standard model are given and their connection to Hill’s general formulation is presented. Instability phenomena of inelastic flow processes such as strain localization and necking are discussed. The second theme concerns stability and bifurcation problems in internally damaged or cracked colids. In brittle fracture or brittle damage, the evolution law of crack lengths or damage parameters is time-independent like in plasticity and leads to a similar mathematical description of the quasi-static evolution. Stability and non-bifurcation criteria in the sense of Hill can be again obtained from the discussion of the rate response.

Bifurcation of elastic solids with sliding interfaces

Science.gov (United States)

Bigoni, D.; Bordignon, N.; Piccolroaz, A.; Stupkiewicz, S.

2018-01-01

Lubricated sliding contact between soft solids is an interesting topic in biomechanics and for the design of small-scale engineering devices. As a model of this mechanical set-up, two elastic nonlinear solids are considered jointed through a frictionless and bilateral surface, so that continuity of the normal component of the Cauchy traction holds across the surface, but the tangential component is null. Moreover, the displacement can develop only in a way that the bodies in contact do neither detach, nor overlap. Surprisingly, this finite strain problem has not been correctly formulated until now, so this formulation is the objective of the present paper. The incremental equations are shown to be non-trivial and different from previously (and erroneously) employed conditions. In particular, an exclusion condition for bifurcation is derived to show that previous formulations based on frictionless contact or `spring-type' interfacial conditions are not able to predict bifurcations in tension, while experiments-one of which, ad hoc designed, is reported-show that these bifurcations are a reality and become possible when the correct sliding interface model is used. The presented results introduce a methodology for the determination of bifurcations and instabilities occurring during lubricated sliding between soft bodies in contact.

Allee’s dynamics and bifurcation structures in von Bertalanffy’s population size functions

Science.gov (United States)

Leonel Rocha, J.; Taha, Abdel-Kaddous; Fournier-Prunaret, D.

2018-03-01

The interest and the relevance of the study of the population dynamics and the extinction phenomenon are our main motivation to investigate the induction of Allee Effect in von Bertalanffy’s population size functions. The adjustment or correction factor of rational type introduced allows us to analyze simultaneously strong and weak Allee’s functions and functions with no Allee effect, whose classification is dependent on the stability of the fixed point x = 0. This classification is founded on the concepts of strong and weak Allee’s effects to the population growth rates associated. The transition from strong Allee effect to no Allee effect, passing through the weak Allee effect, is verified with the evolution of the rarefaction critical density or Allee’s limit. The existence of cusp points on a fold bifurcation curve is related to this phenomenon of transition on Allee’s dynamics. Moreover, the “foliated” structure of the parameter plane considered is also explained, with respect to the evolution of the Allee limit. The bifurcation analysis is based on the configurations of fold and flip bifurcation curves. The chaotic semistability and the nonadmissibility bifurcation curves are proposed to this family of 1D maps, which allow us to define and characterize the corresponding Allee effect region.

Bifurcations and degenerate periodic points in a three dimensional chaotic fluid flow

International Nuclear Information System (INIS)

Smith, L. D.; Rudman, M.; Lester, D. R.; Metcalfe, G.

2016-01-01

Analysis of the periodic points of a conservative periodic dynamical system uncovers the basic kinematic structure of the transport dynamics and identifies regions of local stability or chaos. While elliptic and hyperbolic points typically govern such behaviour in 3D systems, degenerate (parabolic) points also play an important role. These points represent a bifurcation in local stability and Lagrangian topology. In this study, we consider the ramifications of the two types of degenerate periodic points that occur in a model 3D fluid flow. (1) Period-tripling bifurcations occur when the local rotation angle associated with elliptic points is reversed, creating a reversal in the orientation of associated Lagrangian structures. Even though a single unstable point is created, the bifurcation in local stability has a large influence on local transport and the global arrangement of manifolds as the unstable degenerate point has three stable and three unstable directions, similar to hyperbolic points, and occurs at the intersection of three hyperbolic periodic lines. The presence of period-tripling bifurcation points indicates regions of both chaos and confinement, with the extent of each depending on the nature of the associated manifold intersections. (2) The second type of bifurcation occurs when periodic lines become tangent to local or global invariant surfaces. This bifurcation creates both saddle–centre bifurcations which can create both chaotic and stable regions, and period-doubling bifurcations which are a common route to chaos in 2D systems. We provide conditions for the occurrence of these tangent bifurcations in 3D conservative systems, as well as constraints on the possible types of tangent bifurcation that can occur based on topological considerations.

Hopf bifurcation in a reaction-diffusive two-species model with nonlocal delay effect and general functional response

International Nuclear Information System (INIS)

Han, Renji; Dai, Binxiang

2017-01-01

Highlights: • We model general two-dimensional reaction-diffusion with nonlocal delay. • The existence of unique positive steady state is studied. • The bilinear form for the proposed system is given. • The existence, direction of Hopf bifurcation are given by symmetry method. - Abstract: A nonlocal delayed reaction-diffusive two-species model with Dirichlet boundary condition and general functional response is investigated in this paper. Based on the Lyapunov–Schmidt reduction, the existence, bifurcation direction and stability of Hopf bifurcating periodic orbits near the positive spatially nonhomogeneous steady-state solution are obtained, where the time delay is taken as the bifurcation parameter. Moreover, the general results are applied to a diffusive Lotka–Volterra type food-limited population model with nonlocal delay effect, and it is found that diffusion and nonlocal delay can also affect the other dynamic behavior of the system by numerical experiments.

Analysis of Surgical Freedom Variation Across the Basilar Artery Bifurcation: Towards a Deeper Insight Into Approach Selection for Basilar Apex Aneurysms.

Science.gov (United States)

Tayebi Meybodi, Ali; Benet, Arnau; Rodriguez Rubio, Roberto; Yousef, Sonia; Lawton, Michael T

2018-03-03

The orbitozygomatic approach is generally advocated over the pterional approach for basilar apex aneurysms. However, the impact of the extensions of the pterional approach on the obtained maneuverability over multiple vascular targets (relevant to basilar apex surgery) has not been studied before. To analyze the patterns of surgical freedom change across the basilar bifurcation between the pterional, orbitopterional, and orbitozygomatic approaches. Surgical freedom was assessed for 3 vascular targets important in basilar apex aneurysm surgery (ipsilateral and contralateral P1-P2 junctions, and basilar apex), and compared between the pterional, orbitopterional, and orbitozygomatic approaches in 10 cadaveric specimens. Transitioning from the pterional to orbitopterional approach, the surgical freedom increased significantly at all 3 targets (P < .05). However, the gain in surgical freedom declined progressively from the most superficial target (60% for ipsilateral P1-P2 junction) to the deepest target (35% for contralateral P1-P2 junction). Conversely, transitioning from the orbitopterional to the orbitozygomatic approach, the gain in surgical freedom was minimal for the ipsilateral P1-P2 and basilar apex (<4%), but increased dramatically to 19% at the contralateral P1-P2 junction. The orbitopterional approach provides a remarkable increase in surgical maneuverability compared to the pterional approach for the basilar apex target and the relevant adjacent arterial targets. However, compared to the orbitopterional, the orbitozygomatic approach adds little maneuverability except for the deepest target (ie, contralateral P1-P2 junction). Therefore, the orbitozygomatic approach may be most efficacious with larger basilar apex aneurysms limiting the control over of the contralateral P1 PCA.

Sediment discharge division at two tidally influenced river bifurcations

NARCIS (Netherlands)

Sassi, M.G.; Hoitink, A.J.F.; Vermeulen, B.; Hidayat, H.

2013-01-01

[1] We characterize and quantify the sediment discharge division at two tidally influenced river bifurcations in response to mean flow and secondary circulation by employing a boat-mounted acoustic Doppler current profiler (ADCP), to survey transects at bifurcating branches during a semidiurnal

Stability and Hopf bifurcation on a model for HIV infection of CD4{sup +} T cells with delay

Energy Technology Data Exchange (ETDEWEB)

Wang Xia [College of Mathematics and Information Science, Xinyang Normal University, Xinyang, Henan 464000 (China)], E-mail: xywangxia@163.com; Tao Youde [College of Mathematics and Information Science, Xinyang Normal University, Xinyang, Henan 464000 (China); Beijing Institute of Information Control, Beijing 100037 (China); Song Xinyu [College of Mathematics and Information Science, Xinyang Normal University, Xinyang, Henan 464000 (China) and Research Institute of Forest Resource Information Techniques, Chinese Academy of Forestry, Beijing 100091 (China)], E-mail: xysong88@163.com

2009-11-15

In this paper, a delayed differential equation model that describes HIV infection of CD4{sup +} T cells is considered. The stability of the positive equilibrium and the existence of Hopf bifurcation are investigated. In succession, using the normal form theory and center manifold argument, we derive the explicit formulas which determine the stability, direction and other properties of bifurcating periodic solutions.

Long-Term Results after Placement of Aortic Bifurcation Self-Expanding Stents: 10 Year Mortality, Stent Restenosis, and Distal Disease Progression

International Nuclear Information System (INIS)

Houston, J. Graeme; Bhat, Raj; Ross, Rose; Stonebridge, Peter A.

2007-01-01

Purpose. To retrospectively evaluate the 10 year follow-up results in patients who had 'kissing' self-expanding stent aortic bifurcation reconstruction. Methods. Forty-three patients were treated with 'kissing' self-expanding stents for aortoiliac occlusive disease. Early follow-up with clinical and ankle brachial pressure indices (ABPI) was performed at 3, 6, 12, and 24 months and with intra-arterial digital subtraction angiography at 12-24 months; clinical and angiographic follow-up was performed for symptom recurrence up to 10 years after treatment. Retrospective record review was performed to assess mortality, clinical patency, angiographic patency, and secondary assisted patency of both stents and downstream peripheral vessels at 5 and 10 years follow-up. Results. The 2 year primary angiographic and secondary assisted stent patencies were 89% and 93%, respectively. At 10 years follow-up in 40 patients the mortality was 38% (due to myocardial infarction, stroke, chronic renal failure, malignancy, and liver failure). At 5 and 10 years follow-up the primary clinical stent patency was 82% and 68%, and the secondary assisted stent patency 93% and 86%, respectively. At 5 and 10 years, the distal vessel patency was 86% and 72%, and the secondary assisted distal vessel patency treated by surgical or endovascular techniques was 94% and 88%, respectively. At 10 years there was no limb loss. Conclusion. The long-term (10 year) results of aortic bifurcation arterial self-expanding stent placement in patients with arterial occlusive disease show a 10 year primary stent patency rate of 68% but a secondary assisted patency rate of 86%. In addition there is a high overall mortality due to other cardiovascular causes and the rate of distal disease progression and loss of patency is similar to the loss of stent patency rate

Variant anatomy of renal arteries in a Kenyan population.

Science.gov (United States)

Ogeng'o, Julius A; Masaki, Charles O; Sinkeet, Simeon R; Muthoka, Johnstone M; Murunga, Acleus K

2010-01-01

Variant anatomy of renal arteries is important in renal transplant, vascular reconstruction, and uroradiological procedures. The variations show ethnic and population differences. Data from Africans are scarce and altogether absent for Kenyans. To describe patterns of origin, trajectories and branching of renal arteries in a Kenyan population. Descriptive cross-sectional study conducted in the Department of Human Anatomy, University of Nairobi. Three hundred and fifty six kidneys from 178 cadavers and postmortem specimens were used in the study. Aorta, renal arteries and kidneys were exposed by dissection. Number, trajectories, level of branching, number of branches and point of entry into the kidney were recorded. Data was analyzed using SPSS version 16.0, and presented using macrographs, tables, and bar charts. Additional arteries occurred in 14.3% of the cases. In 82.4% of these, there was one additional artery. Fifty nine point five per cent of the double renal arteries were parallel and 7.1% crossed. Of the 305 single arteries, 76.4% showed hilar, 21.6% prehilar and 2% intraparenchymal branching. In the hilar branching, ladder type was present in 65% and fork type in 35%. Bifurcation and trifurcation were present in 59.6% and 33.1% respectively. Polar arteries were present in 16.9% cases. Over 14% of the Kenyan population may have additional renal arteries while more than 20% show early branching. Several trajectories and hilar branching patterns exist which renal transplant surgeons and radiologists should be aware of to avoid inadvertent vascular injury.

Stability of River Bifurcations from Bedload to Suspended Load Dominated Conditions

Science.gov (United States)

de Haas, T.; Kleinhans, M. G.

2010-12-01

Bifurcations (also called diffluences) are as common as confluences in braided and anabranched rivers, and more common than confluences on alluvial fans and deltas where the network is essentially distributary. River bifurcations control the partitioning of both water and sediment through these systems with consequences for immediate river and coastal management and long-term evolution. Their stability is poorly understood and seems to differ between braided rivers, meandering river plains and deltas. In particular, it is the question to what extent the division of flow is asymmetrical in stable condition, where highly asymmetrical refers to channel closure and avulsion. Recent work showed that bifurcations in gravel bed braided rivers become more symmetrical with increasing sediment mobility, whereas bifurcations in a lowland sand delta become more asymmetrical with increasing sediment mobility. This difference is not understood and our objective is to resolve this issue. We use a one-dimensional network model with Y-shaped bifurcations to explore the parameter space from low to high sediment mobility. The model solves gradually varied flow, bedload transport and morphological change in a straightforward manner. Sediment is divided at the bifurcation including the transverse slope effect and the spiral flow effect caused by bends at the bifurcation. Width is evolved whilst conserving mass of eroded or built banks with the bed balance. The bifurcations are perturbed from perfect symmetry either by a subtle gradient advantage for one branch or a gentle bend at the bifurcation. Sediment transport was calculated with and without a critical threshold for sediment motion. Sediment mobility, determined in the upstream channel, was varied in three different ways to isolate the causal factor: by increasing discharge, increasing channel gradient and decreasing particle size. In reality the sediment mobility is mostly determined by particle size: gravel bed rivers are near

Arterial Ligation for Infected Femoral Psuedo-Aneurysm in Drug Injecting Abusers

Directory of Open Access Journals (Sweden)

Mohammadzade Mohammad Ali

2009-10-01

Full Text Available Pseudo-aneurysm of the femoral artery is the most common arterial complication in drug injecting abusers. Scholars in vascular surgery have published debating statements regarding techniques of successful surgical management during last two decades. We present the results of simple arterial ligation in a series of 32 patients presenting with infected femoral pseudo-aneurysm. Most of the patients were males (89%. Young persons in the age group of 15-44 years were mostly affected. Site of lesion included common femoral artery in 65% , superficial femoral artery 28% and at bifurcation 6.2%. celulitis in 14 (53%, abscess & "ncelulitis in 6 (19%, necrosing fasciitis in 2 (6.2% and vascular abscess in 7 (22% cases were the forms of associated local infection. There was no hemorrhage, vascular thrombosis, amputation, or mortality. Claudicating were the only complications identified in 2 patients with Tripe ligation. Ligation is the optimal management for infected pseudo-aneurysms because it is easy, cost-effective, and safe. Early reconstruction is not recommended, since there is an extended infection in the location of the pseudo-aneurysm.

Usefulness of CT angiography after metallic stent implantation of the internal carotid artery

International Nuclear Information System (INIS)

Yoon, Man Won; Kim, Hyeon Chul; Kim, Jae Kyu; Seo, Jeong Jin; Jeong, Gwang Woo; Kang, Heoung Keun

1999-01-01

To evaluate the usefulness of CT angiography in patients with implantation of metallic stent for stenosed internal carotid artery. Seven patients with atherosclerotic stenosis of the internal carotid artery underwent metallic stent implantation. All were male and their ages ranged from 36 to 69 years. A total of seven stents were placed in the internal carotid artery in five patients and in the carotid bifurcation in two. Spiral CT scans were obtained and CT angiographic images were reconstructed using MPR or curved MPR techniques at a workstation. The interval between CT and conventional angiography did not exceed six days except in one patient, in whom it was 61days. CT and conventional angiography were compared for stent position with respect to the carotid bifurcation, stent deformation, intraluminal filling defect, and luminal caliber and outflow. Luminal patency of the implanted stent was measured according to NASCET(North American Symptomatic Carotid Endarterectomy Trial) criteria, and statistically processed (p>.05). The presence or absence of intrastent thrombus and vascular wall calcification was determined using axial source images. In all patients, CT angiographic findings matched those obtained by conventional angiography. Complications such as migration or deformation of an implanted stent, intraluminal filling defect, change of luminal caliber or outflow of implanted stent were not observed in any patient. In two studies in which Wilcoxon signed rank test was used, degree of stent expansion correlated closely(p=0.237). Axial source images showed that in no patient was an intrastent thrombus present, though in five, vascular wall calcification of internal carotid arteries outside the stent was noted. CT angiography is useful for the assessment of positional change, occlusion, and luminal patency of a stent-implanted internal carotid artery

Early control of distal internal carotid artery during carotid endarterectomy: does it reduce cerebral microemboli?

Science.gov (United States)

Mommertz, G; Das, M; Langer, S; Koeppel, T A; Krings, T; Mess, W H; Schiefer, J; Jacobs, M J

2010-06-01

According to the results of the large trials on carotid endarterectomy (CEA), this type of surgery is only warranted if perioperative mortality and morbidity are kept considerably low. Less attention has been paid to methods of cerebral protection during CEA, although intraoperative transcranial Doppler (TCD) can visualise intracerebral microemboli (MES) during routine carotid dissection, although MES occur throughout the CEA, only those during dissection are related to neurological outcome. Prevention of MES by means of early control of the distal internal carotid artery dislodging from the carotid artery plaque during dissection is very likely the mechanism behind an eventual benefit from this approach. Hence, the amount of MES might serve as a surrogate parameter for the risk of periprocedural neurological events. So, the aim of the present study was to evaluate whether early control of the distal carotid artery during CEA is capable of reducing the number of MES by means of a prospective randomised trial. Twenty-eight patients (29 procedures) could be prospectively included in our study. Before surgery we randomly assigned the patients to two groups: group A (N.=12): CEA by means of early control of the distal internal carotid artery; group B (N.=17): CEA with dissection of the total carotid bifurcation before clamping the arteries. Periprocedurally, we continuously monitored the cerebral blood flow in the ipsilateral middle cerebral artery by means of TCD. Pre- and postoperative morbidity were independently verified by a neurologist control of the distal internal carotid artery did not reduce the occurrence of MES during dissection of the carotid bifurcation. Also, the total number of MES throughout the procedure and postoperatively was comparable between both groups. The procedure related times as well as the clinical outcome did not differ significantly. Thus, early control of the distal internal carotid artery has got no advantage but also no disadvantage

Forced phase-locked response of a nonlinear system with time delay after Hopf bifurcation

International Nuclear Information System (INIS)

Ji, J.C.; Hansen, Colin H.

2005-01-01

The trivial equilibrium of a nonlinear autonomous system with time delay may become unstable via a Hopf bifurcation of multiplicity two, as the time delay reaches a critical value. This loss of stability of the equilibrium is associated with two coincident pairs of complex conjugate eigenvalues crossing the imaginary axis. The resultant dynamic behaviour of the corresponding nonlinear non-autonomous system in the neighbourhood of the Hopf bifurcation is investigated based on the reduction of the infinite-dimensional problem to a four-dimensional centre manifold. As a result of the interaction between the Hopf bifurcating periodic solutions and the external periodic excitation, a primary resonance can occur in the forced response of the system when the forcing frequency is close to the Hopf bifurcating periodic frequency. The method of multiple scales is used to obtain four first-order ordinary differential equations that determine the amplitudes and phases of the phase-locked periodic solutions. The first-order approximations of the periodic solutions are found to be in excellent agreement with those obtained by direct numerical integration of the delay-differential equation. It is also found that the steady state solutions of the nonlinear non-autonomous system may lose their stability via either a pitchfork or Hopf bifurcation. It is shown that the primary resonance response may exhibit symmetric and asymmetric phase-locked periodic motions, quasi-periodic motions, chaotic motions, and coexistence of two stable motions

Renal Artery Variations, Hilar Arrangement and Its Distances to Ventral Branches of Abdominal Aorta: A Morphometric Study

Directory of Open Access Journals (Sweden)

D'Souza A

2015-10-01

Full Text Available Purpose: To measure the distance of origin of renal artery in relation to the ventral branches of abdominal aorta and also to study the variations in the number and the hilar branching pattern of renal arteries. Materials and methods: The present study was carried out using ten embalmed adult cadavers. The distances were measured bilaterally from the origin of renal artery to the origin of superior and inferior mesenteric artery and the bifurcation of abdominal aorta. Results: Out of ten cadavers studied, bilateral accessory renal artery was observed in two cases. The hilar branching pattern varied from a single artery to maximum of six branches. The mean and standard deviations of the measured parameters were calculated. Conclusion: Knowledge of variations of renal artery is important for surgeons in performing many procedures and may help to avoid clinical complications in the abdominal region.

[Surgical angioplasty of the left main coronary artery].

Science.gov (United States)

Vranes, Mile; Velinović, Milos; Kocica, Mladen; Mikić, Aleksandar; Velimirović, Dusan; Djukić, Petar

2010-01-01

The conventional treatment for isolated stenosis of the left main coronary artery is bypass surgery (myocardial revascularization). However, the process of atherosclerosis is not arrested by myocardial revascularization and it will lead to the occlusion of the left main coronary artery. Revascularization will establish retrograde perfusion for 50-70% of the myocardium of the left ventricle. Direct surgical angioplasty of the left main coronary artery enables normal physiological perfusion of the whole myocardium and better myocardial function. The aim of our study is to point out a new surgical approach of treating left main coronary artery stenosis. Between October 2002 and October 2003, direct surgical angioplasty of the main left coronary artery was performed on three patients with isolated stenosis of the left main coronary artery using the anterior approach and the pericardium as a patch. The procedure was performed under total endotracheal anaesthesia and standard cardiopulmonary circulation, moderate hypothermia, anterograde St. Tomas cardioplegia and local cooling. Patients were followed clinically, echocardiographically and by load-tests. All three patients were without complications. In postoperative follow-up (54-68 months) neither angina pectoris nor electrocardiographically registered ischaemic changes were found. Load-tests performed every six months on all three patients were negative. Surgical angioplasty of isolated stenosis of the left main coronary artery is a preferred method for treating this type of coronary disease. Contraindications for this type of treatment are stenosis of the left main coronary artery with bifurcation and advanced calcification of the left main coronary artery.

Bifurcation and chaos of an axially accelerating viscoelastic beam

International Nuclear Information System (INIS)

Yang Xiaodong; Chen Liqun

2005-01-01

This paper investigates bifurcation and chaos of an axially accelerating viscoelastic beam. The Kelvin-Voigt model is adopted to constitute the material of the beam. Lagrangian strain is used to account for the beam's geometric nonlinearity. The nonlinear partial-differential equation governing transverse motion of the beam is derived from the Newton second law. The Galerkin method is applied to truncate the governing equation into a set of ordinary differential equations. By use of the Poincare map, the dynamical behavior is identified based on the numerical solutions of the ordinary differential equations. The bifurcation diagrams are presented in the case that the mean axial speed, the amplitude of speed fluctuation and the dynamic viscoelasticity is respectively varied while other parameters are fixed. The Lyapunov exponent is calculated to identify chaos. From numerical simulations, it is indicated that the periodic, quasi-periodic and chaotic motions occur in the transverse vibrations of the axially accelerating viscoelastic beam

Bifurcation of Jovian magnetotail current sheet

Directory of Open Access Journals (Sweden)

P. L. Israelevich

2006-07-01

Full Text Available Multiple crossings of the magnetotail current sheet by a single spacecraft give the possibility to distinguish between two types of electric current density distribution: single-peaked (Harris type current layer and double-peaked (bifurcated current sheet. Magnetic field measurements in the Jovian magnetic tail by Voyager-2 reveal bifurcation of the tail current sheet. The electric current density possesses a minimum at the point of the B_x-component reversal and two maxima at the distance where the magnetic field strength reaches 50% of its value in the tail lobe.

Riddling bifurcation and interstellar journeys

International Nuclear Information System (INIS)

Kapitaniak, Tomasz

2005-01-01

We show that riddling bifurcation which is characteristic for low-dimensional attractors embedded in higher-dimensional phase space can give physical mechanism explaining interstellar journeys described in science-fiction literature

Arctic melt ponds and bifurcations in the climate system

Science.gov (United States)

Sudakov, I.; Vakulenko, S. A.; Golden, K. M.

2015-05-01

Understanding how sea ice melts is critical to climate projections. In the Arctic, melt ponds that develop on the surface of sea ice floes during the late spring and summer largely determine their albedo - a key parameter in climate modeling. Here we explore the possibility of a conceptual sea ice climate model passing through a bifurcation point - an irreversible critical threshold as the system warms, by incorporating geometric information about melt pond evolution. This study is based on a bifurcation analysis of the energy balance climate model with ice-albedo feedback as the key mechanism driving the system to bifurcation points.

Bifurcation diagram features of a dc-dc converter under current-mode control

International Nuclear Information System (INIS)

Ruzbehani, Mohsen; Zhou Luowei; Wang Mingyu

2006-01-01

A common tool for analysis of the systems dynamics when the system has chaotic behaviour is the bifurcation diagram. In this paper, the bifurcation diagram of an ideal model of a dc-dc converter under current-mode control is analysed. Algebraic relations that give the critical points locations and describe the pattern of the bifurcation diagram are derived. It is shown that these simple algebraic and geometrical relations are responsible for the complex pattern of the bifurcation diagrams in such circuits. More explanation about the previously observed properties and introduction of some new ones are exposited. In addition, a new three-dimensional bifurcation diagram that can give better imagination of the parameters role is introduced

Modified jailed balloon technique for bifurcation lesions.

Science.gov (United States)

Saito, Shigeru; Shishido, Koki; Moriyama, Noriaki; Ochiai, Tomoki; Mizuno, Shingo; Yamanaka, Futoshi; Sugitatsu, Kazuya; Tobita, Kazuki; Matsumi, Junya; Tanaka, Yutaka; Murakami, Masato

2017-12-04

We propose a new systematic approach in bifurcation lesions, modified jailed balloon technique (M-JBT), and report the first clinical experience. Side branch occlusion brings with a serious complication and occurs in more than 7.0% of cases during bifurcation stenting. A jailed balloon (JB) is introduced into the side branch (SB), while a stent is placed in the main branch (MB) as crossing SB. The size of the JB is half of the MB stent size. While the proximal end of JB attaching to MB stent, both stent and JB are simultaneously inflated with same pressure. JB is removed and then guidewires are recrossed. Kissing balloon dilatation (KBD) and/or T and protrusion (TAP) stenting are applied as needed. Between February 2015 and February 2016, 233 patients (254 bifurcation lesions including 54 left main trunk disease) underwent percutaneous coronary intervention (PCI) using this technique. Procedure success was achieved in all cases. KBD was performed for 183 lesions and TAP stenting was employed for 31 lesions. Occlusion of SV was not observed in any of the patients. Bench test confirmed less deformity of MB stent in M-JBT compared with conventional-JBT. This is the first report for clinical experiences by using modified jailed balloon technique. This novel M-JBT is safe and effective in the preservation of SB patency during bifurcation stenting. © 2017 Wiley Periodicals, Inc.

An anatomical study of variations in termination of brachial artery, with its embryological basis and clinical significance

Directory of Open Access Journals (Sweden)

Deepa T. K

2016-03-01

Full Text Available The brachial artery is the main artery of the arm. It begins as the continuation of 3rd part of axillary artery, at the level of inferior border of teres major muscle. It ends at the level of the neck of radius by dividing into radial and ulnar arteries. In the present study we found higher division of brachial artery at mid arm level into its terminal branches with superficial course of radial artery. The present study was done on 51 cadavers from our dept. of Anatomy. The upper limbs of the cadaver were dissected and observed for any variations in the branching pattern of brachial artery. In the present study, a total number of 51 cadaver’s, 102 upper limbs were studied. In one male cadaver we found bilateral higher division of brachial artery, trifurcation on left side and bifurcation on right side brachial artery, with superficial course of radial artery. The knowledge of variation in origin and course of brachial artery is useful for orthopaedicians, physicians, radiologist, vascular and plastic surgeons.

Investigation of spiral blood flow in a model of arterial stenosis

OpenAIRE

Paul, M.C.; Larman, A.

2009-01-01

The spiral component of blood flow has both beneficial and detrimental effects in human circulatory system [Stonebridge PA, Brophy CM. Spiral laminar flow in arteries? Lancet 1991; 338: 1360–1]. We investigate the effects of the spiral blood flow in a model of three-dimensional arterial stenosis with a 75% cross-sectional area reduction at the centre by means of computational fluid dynamics (CFD) techniques. The standard κ–ω model is employed for simulation of the blood flow for the...

Walking dynamics of the passive compass-gait model under OGY-based state-feedback control: Analysis of local bifurcations via the hybrid Poincaré map

International Nuclear Information System (INIS)

Gritli, Hassène; Belghith, Safya

2017-01-01

Highlights: • We study the passive walking dynamics of the compass-gait model under OGY-based state-feedback control. • We analyze local bifurcations via a hybrid Poincaré map. • We show exhibition of the super(sub)-critical flip bifurcation, the saddle-node(saddle) bifurcation and a saddle-flip bifurcation. • An analysis via a two-parameter bifurcation diagram is presented. • Some new hidden attractors in the controlled passive walking dynamics are displayed. - Abstract: In our previous work, we have analyzed the passive dynamic walking of the compass-gait biped model under the OGY-based state-feedback control using the impulsive hybrid nonlinear dynamics. Such study was carried out through bifurcation diagrams. It was shown that the controlled bipedal gait exhibits attractive nonlinear phenomena such as the cyclic-fold (saddle-node) bifurcation, the period-doubling (flip) bifurcation and chaos. Moreover, we revealed that, using the controlled continuous-time dynamics, we encountered a problem in finding, identifying and hence following branches of (un)stable solutions in order to characterize local bifurcations. The present paper solves such problem and then provides a further investigation of the controlled bipedal walking dynamics using the developed analytical expression of the controlled hybrid Poincaré map. Thus, we show that analysis via such Poincaré map allows to follow branches of both stable and unstable fixed points in bifurcation diagrams and hence to explore the complete dynamics of the controlled compass-gait biped model. We demonstrate the generation, other than the conventional local bifurcations in bipedal walking, i.e. the flip bifurcation and the saddle-node bifurcation, of a saddle-saddle bifurcation, a subcritical flip bifurcation and a new type of a local bifurcation, the saddle-flip bifurcation. In addition, to further understand the occurrence of the local bifurcations, we present an analysis with a two-parameter bifurcation

Bifurcation-based approach reveals synergism and optimal combinatorial perturbation.

Science.gov (United States)

Liu, Yanwei; Li, Shanshan; Liu, Zengrong; Wang, Ruiqi

2016-06-01

Cells accomplish the process of fate decisions and form terminal lineages through a series of binary choices in which cells switch stable states from one branch to another as the interacting strengths of regulatory factors continuously vary. Various combinatorial effects may occur because almost all regulatory processes are managed in a combinatorial fashion. Combinatorial regulation is crucial for cell fate decisions because it may effectively integrate many different signaling pathways to meet the higher regulation demand during cell development. However, whether the contribution of combinatorial regulation to the state transition is better than that of a single one and if so, what the optimal combination strategy is, seem to be significant issue from the point of view of both biology and mathematics. Using the approaches of combinatorial perturbations and bifurcation analysis, we provide a general framework for the quantitative analysis of synergism in molecular networks. Different from the known methods, the bifurcation-based approach depends only on stable state responses to stimuli because the state transition induced by combinatorial perturbations occurs between stable states. More importantly, an optimal combinatorial perturbation strategy can be determined by investigating the relationship between the bifurcation curve of a synergistic perturbation pair and the level set of a specific objective function. The approach is applied to two models, i.e., a theoretical multistable decision model and a biologically realistic CREB model, to show its validity, although the approach holds for a general class of biological systems.

An investigation of an autonomic innervation of the vertebral artery using monoamine histofluorescence

Directory of Open Access Journals (Sweden)

JA Mitchell

2009-06-01

Full Text Available Blood flow to the hindbrain, via the paired vertebral arteries, must be uncompromised for adequate neurological functioning of its vital centres. Therefore, it would seem unlikely that the intracranial vertebral artery would need to vasoconstrict, thus reducing its blood flow. In order to investigate the existence and location of a noradrenaline-mediated constrictor mechanism in the wall of the intracranial vertebral artery, transverse sections of ten baboon and ten monkey vessels were stained with sucrose-potassium phosphate-glyoxylic acid (counterstained with malachite-green. This method allows the visualisation of catecholaminergic nerves when the sections are exposed to ultraviolet light. In this study of primate vascular tissue, however, none of the monkey or baboon vertebral artery sections showed the presence of noradrenergic nerves in the tunica media – tunica adventitia junction or penetrating the tunica media of the arteries. These findings indicate that the intracranial vertebral artery does not have a neurogenic vasomotor function in primates.

Anatomy of the Portal Vein Bifurcation: Implication for Transjugular Intrahepatic Portal Systemic Shunts

International Nuclear Information System (INIS)

Kwok, Philip Chong-hei; Ng, Wai Fu; Lam, Christine Suk-yee; Tsui, Polly Po; Faruqi, Asma

2003-01-01

Purpose: The relationship of the portalvein bifurcation to the liver capsule in Asians, which is an important landmark for transjugular intrahepatic portosystemic shunt, has not previously been described. Methods: The anatomy of the portal vein bifurcation was studied in 70 adult Chinese cadavers; it was characterized as intrahepatic or extrahepatic. The length of the exposed portion of the right and left portal veins was measured when the bifurcation was extrahepatic. Results: The portal vein bifurcation was intrahepatic in 37 cadavers (53%) and extrahepatic in 33 cadavers (47%). The mean length of the right and left extrahepatic portal veins was 0.96 cm and 0.85 cm respectively.Both were less than or equal to 2 cm in 94% of the cadavers with extrahepatic bifurcation. There was no correlation between the presence of cirrhosis and the location of the portal vein bifurcation(p 1.0). There was no statistically significant difference in liver mass in cadavers with either extrahepatic or intrahepatic bifurcation (p =0.40). Conclusions: These findings suggest that fortransjugular intrahepatic portosystemic shunt placement, a portal vein puncture 2 cm from the bifurcation will be safe in most cases

Occlusive Hepatic Artery Thrombus in a Deceased-Donor Liver Procured From a Donor With Blunt Abdominal Trauma Following a Road Traffic Collision Accident.

Science.gov (United States)

Ahmad, Niaz; Tahir, Wasif; Haque, Ali; Dar, Faisal; Vilca-Melendez, Hector; Srinavasan, Parthi; Heaton, Nigel

2018-04-09

Here, we describe a case of occlusive hepatic artery thrombus in a liver procured from an 18-year-old deceased donor after circulatory death. The donor had died of multiple trauma following a road traffic collision. Occlusive thrombus was found at the hepatic artery bifurcation during back-table preparation. Consequently, the liver transplant did not proceed. We suggest careful assessment of hepatic arteries of all donor livers before transplant, particularly those from donors who are involved in deceleration injuries. Transplanting such livers may lead to primary nonfunction.

FFT Bifurcation Analysis of Routes to Chaos via Quasiperiodic Solutions

Directory of Open Access Journals (Sweden)

L. Borkowski

2015-01-01

Full Text Available The dynamics of a ring of seven unidirectionally coupled nonlinear Duffing oscillators is studied. We show that the FFT analysis presented in form of a bifurcation graph, that is, frequency distribution versus a control parameter, can provide a valuable and helpful complement to the corresponding typical bifurcation diagram and the course of Lyapunov exponents, especially in context of detailed identification of the observed attractors. As an example, bifurcation analysis of routes to chaos via 2-frequency and 3-frequency quasiperiodicity is demonstrated.

EXPERIMENTAL STUDY ON SEDIMENT DISTRIBUTION AT CHANNEL BIFURCATION

Institute of Scientific and Technical Information of China (English)

G.M. Tarekul ISLAM; M.R. KABIR; Ainun NISHAT

2002-01-01

This paper presents the experimental results on the distribution of sediments at channel bifurcation.The experiments have been conducted in a physical model of channel bifurcation. It consists of a straight main channel which bifurcates into two branch channels of different widths. The test rig is a mobile bed with fixed bank. Four different noses have been used to study the phenomenon. For each nose, three upstream discharges viz. 20 l/s, 30 l/s and 40 l/s have been employed. From the measured data, discharges and sediment transport ratios per unit width are calculated in the downstream branches.These data have been set to the general nodal point relation and a set of equations has been developed to describe the distribution of sediments to the downstream branches for different nose angles.

Bifurcation theory for toroidal MHD instabilities

International Nuclear Information System (INIS)

Maschke, E.K.; Morros Tosas, J.; Urquijo, G.

1992-01-01

Using a general representation of magneto-hydrodynamics in terms of stream functions and potentials, proposed earlier, a set of reduced MHD equations for the case of toroidal geometry had been derived by an appropriate ordering with respect to the inverse aspect ratio. When all dissipative terms are neglected in this reduced system, it has the same linear stability limits as the full ideal MHD equations, to the order considered. When including resistivity, thermal conductivity and viscosity, we can apply bifurcation theory to investigate nonlinear stationary solution branches related to various instabilities. In particular, we show that a stationary solution of the internal kink type can be found

Crossing Y-stent technique with dual open-cell stents for coiling of wide-necked bifurcation aneurysms.

Science.gov (United States)

Ko, Jun Kyeung; Han, In Ho; Cho, Won Ho; Choi, Byung Kwan; Cha, Seung Heon; Choi, Chang Hwa; Lee, Sang Weon; Lee, Tae Hong

2015-05-01

Double stenting in a Y-configuration is a promising therapeutic option for wide-necked cerebral aneurysms not amenable to reconstruction with a single stent. We retrospectively evaluated the efficacy and safety of the crossing Y-stent technique for coiling of wide-necked bifurcation aneurysms. By collecting clinical and radiological data we evaluated from January 2007 through December 2013, 20 wide-necked bifurcation aneurysms. Twelve unruptured and eight ruptured aneurysms in 20 patients were treated with crossing Y-stent-assisted coiling. Aneurysm size and neck size ranged from 3.2 to 28.2mm (mean 7.5mm) and from 1.9 to 9.1mm (mean 4.5mm). A Y-configuration was established successfully in all 20 patients. All aneurysms were treated with a pair of Neuroform stents. The immediate angiographic results were total occlusion in 17 aneurysms, residual neck in two, and residual sac in one. Peri-operative morbidity was only 5%. Fifteen of 18 surviving patients underwent follow-up conventional angiography (mean, 10.9 months). The result showed stable occlusion in all 15 aneurysms and asymptomatic in-stent occlusion in one branch artery. At the end of the observation period (mean, 33.5 months), all 12 patients without subarachnoid hemorrhage had excellent clinical outcomes (mRS 0), except one (mRS 2). Of eight patients with subarachnoid hemorrhage, four remained symptom free (mRS 0), while the other four had were dependent or dead (mRS score, 3-6). In this report on 20 patients, crossing Y-stent technique for coiling of wide-necked bifurcation aneurysms showed a good technical safety and favorable clinical and angiographic outcome. Copyright © 2015. Published by Elsevier B.V.

Local stability and Hopf bifurcation in small-world delayed networks

International Nuclear Information System (INIS)

Li Chunguang; Chen Guanrong

2004-01-01

The notion of small-world networks, recently introduced by Watts and Strogatz, has attracted increasing interest in studying the interesting properties of complex networks. Notice that, a signal or influence travelling on a small-world network often is associated with time-delay features, which are very common in biological and physical networks. Also, the interactions within nodes in a small-world network are often nonlinear. In this paper, we consider a small-world networks model with nonlinear interactions and time delays, which was recently considered by Yang. By choosing the nonlinear interaction strength as a bifurcation parameter, we prove that Hopf bifurcation occurs. We determine the stability of the bifurcating periodic solutions and the direction of the Hopf bifurcation by applying the normal form theory and the center manifold theorem. Finally, we show a numerical example to verify the theoretical analysis

Local stability and Hopf bifurcation in small-world delayed networks

Energy Technology Data Exchange (ETDEWEB)

Li Chunguang E-mail: cgli@uestc.edu.cn; Chen Guanrong E-mail: gchen@ee.cityu.edu.hk

2004-04-01

The notion of small-world networks, recently introduced by Watts and Strogatz, has attracted increasing interest in studying the interesting properties of complex networks. Notice that, a signal or influence travelling on a small-world network often is associated with time-delay features, which are very common in biological and physical networks. Also, the interactions within nodes in a small-world network are often nonlinear. In this paper, we consider a small-world networks model with nonlinear interactions and time delays, which was recently considered by Yang. By choosing the nonlinear interaction strength as a bifurcation parameter, we prove that Hopf bifurcation occurs. We determine the stability of the bifurcating periodic solutions and the direction of the Hopf bifurcation by applying the normal form theory and the center manifold theorem. Finally, we show a numerical example to verify the theoretical analysis.

Bifurcation of plasma cylinder equilibrium into a stationary helical flow with magnetic islands

International Nuclear Information System (INIS)

Gubarev, V.F.; Dmitrenko, A.G.; Fesenko, A.I.

1985-01-01

Introduction of the low-hydrodynamic viscosity into the system of nonlinear MHD-equations enabled to use the bifurcation theory for the investigation into nonlinear phenomena connected with a tearing mode. The existance of a stable stationary helical flow with magnetic islands in the vicinity of a neutral curve is established. Fransfer from an axisymmetric equilibrium of a plasma cylinder to a helical one takes place only under soft conditions at both sides of the neutral curve. This result confirms the fact that the tearing mode, actually, is not an instability and may be con sidered only as a reason of formation of equilibrium with splitted magnetic surfaces. Really, changing the q 0 parameter (q 0 is the value proportional to a value of stability margin) at the plasma filament boundary a plasma equilibrium is attained corresponding to a stable branch of the bifurcation curve. In this case, a stable branch of the bifurcation curve corresponds to a helical stationary flow with magnetic islands in the instabwility region determined from the linear theory

Iterative Controller Tuning for Process with Fold Bifurcations

DEFF Research Database (Denmark)

Huusom, Jakob Kjøbsted; Poulsen, Niels Kjølstad; Jørgensen, Sten Bay

2007-01-01

Processes involving fold bifurcation are notoriously difficult to control in the vicinity of the fold where most often optimal productivity is achieved . In cases with limited process insight a model based control synthesis is not possible. This paper uses a data driven approach with an improved...... version of iterative feedback tuning to optimizing a closed loop performance criterion, as a systematic tool for tuning process with fold bifurcations....

Hepatocellular Carcinoma Supplied by the Right Lumbar Artery

International Nuclear Information System (INIS)

Miyayama, Shiro; Yamashiro, Masashi; Okuda, Miho; Yoshie, Yuichi; Sugimori, Natsuki; Igarashi, Saya; Nakashima, Yoshiko; Matsui, Osamu

2010-01-01

This study evaluated the clinical features of hepatocellular carcinoma (HCC) supplied by the right lumbar artery. Eleven patients with HCC supplied by the right lumbar artery were treated with chemoembolization. The patients' medical records were retrospectively analyzed. All patients underwent 6.7 ± 3.7 (mean ± SD) chemoembolization sessions, and the hepatic arterial branches were noted as being attenuated. The right inferior phrenic artery (IPA) was also embolized in 10 patients. The interval between initial chemoembolization and chemoembolization of the lumbar artery supply was 53.2 ± 26.9 months. Mean tumor diameter was 3.1 ± 2.4 cm and was located at the surface of S7 and S6. The feeding-branch arose proximal to the bifurcation of the dorsal ramus and muscular branches (n = 8) or from the muscular branches (n = 3) of the right first (n = 10) or second lumbar artery (n = 1). The anterior spinal artery originated from the tumor-feeding lumbar artery in one patient. All feeders were selected, and embolization was performed after injection of iodized oil and anticancer drugs (n = 10) or gelatin sponge alone in a patient with anterior spinal artery branching (n = 1). Eight patients died from tumor progression 10.1 ± 4.6 months later, and two patients survived 2 and 26 months, respectively. The remaining patient died of bone metastases after 32 months despite liver transplantation 10 months after chemoembolization. The right lumbar artery supplies HCC located in the bare area of the liver, especially in patients who undergo repeated chemoembolization, including chemoembolization by way of the right IPA. Chemoembolization by way of the right lumbar artery may be safe when the feeder is well selected.

Investigation Of Arterial Blood Pressure Level And Metabolic Indices In Patients With Arterial Hypertension At Pharmacotherapy With Antihypertensive Medicines Of Various Chemical Structure

Directory of Open Access Journals (Sweden)

G.Kh. Glybochko

2009-12-01

Full Text Available The research goal is to carry on the comparative analysis of medicines of various chemical structure, Telmisar-tan and Bisoprolol, and to reveal their effect on the arterial blood pressure level and the indices of various metabolic processes in patients with arterial hypertension. 60 out-patients with arterial hypertension (stage II risk III both males and females aged 33-55 have been under study taking Telmisartan and Bisoprolol for 3 months. While treating the patients the arterial blood pressure level control and biochemical investigations for determination the indices of metabolic processes have been carried out. The investigated medications have provided the decrease of systolic and diastolic arterial pressure parameters, the increase of concentration of total and ionized calcium, chlorine ions, urea and total bilirubin in blood plasma. Therapy with Telmisartan has shown more significant increase of potassium level in erythro-cytes, decrease of levels of natrium, glucose, glycolized hemoglobin and triglycerides and increased contents of alani-naminotransferase and aspartataminotransferase. The course of therapy with Bisoprolol has restored the normal level of magnesium in blood plasma, has not have any influence on carbohydrate and lipid metabolism, increased the level of alaninaminotransferase and significantly increased the contents of total and ionized calcium, urea and creatinine. 3-months therapy with Telmisartan and Bisoprolol has proved the decrease of systolic and diastolic arterial pressure in patients with arterial hypertension. The medications under study have had active and variable effects on metabolic indices

Bifurcations and chaos of a vibration isolation system with magneto-rheological damper

Energy Technology Data Exchange (ETDEWEB)

Zhang, Hailong [Magneto-electronics Lab, School of Physics and Technology, Nanjing Normal University, Nanjing 210046 (China); Vibration Control Lab, School of Electrical and Automation Engineering, Nanjing Normal University, Nanjing 210042 (China); Zhang, Ning [Magneto-electronics Lab, School of Physics and Technology, Nanjing Normal University, Nanjing 210046 (China); Min, Fuhong; Yan, Wei; Wang, Enrong, E-mail: erwang@njnu.edu.cn [Vibration Control Lab, School of Electrical and Automation Engineering, Nanjing Normal University, Nanjing 210042 (China)

2016-03-15

Magneto-rheological (MR) damper possesses inherent hysteretic characteristics. We investigate the resulting nonlinear behaviors of a two degree-of-freedom (2-DoF) MR vibration isolation system under harmonic external excitation. A MR damper is identified by employing the modified Bouc-wen hysteresis model. By numerical simulation, we characterize the nonlinear dynamic evolution of period-doubling, saddle node bifurcating and inverse period-doubling using bifurcation diagrams of variations in frequency with a fixed amplitude of the harmonic excitation. The strength of chaos is determined by the Lyapunov exponent (LE) spectrum. Semi-physical experiment on the 2-DoF MR vibration isolation system is proposed. We trace the time history and phase trajectory under certain values of frequency of the harmonic excitation to verify the nonlinear dynamical evolution of period-doubling bifurcations to chaos. The largest LEs computed with the experimental data are also presented, confirming the chaotic motion in the experiment. We validate the chaotic motion caused by the hysteresis of the MR damper, and show the transitions between distinct regimes of stable motion and chaotic motion of the 2-DoF MR vibration isolation system for variations in frequency of external excitation.

Bifurcations and chaos of a vibration isolation system with magneto-rheological damper

Directory of Open Access Journals (Sweden)

Hailong Zhang

2016-03-01

Full Text Available Magneto-rheological (MR damper possesses inherent hysteretic characteristics. We investigate the resulting nonlinear behaviors of a two degree-of-freedom (2-DoF MR vibration isolation system under harmonic external excitation. A MR damper is identified by employing the modified Bouc-wen hysteresis model. By numerical simulation, we characterize the nonlinear dynamic evolution of period-doubling, saddle node bifurcating and inverse period-doubling using bifurcation diagrams of variations in frequency with a fixed amplitude of the harmonic excitation. The strength of chaos is determined by the Lyapunov exponent (LE spectrum. Semi-physical experiment on the 2-DoF MR vibration isolation system is proposed. We trace the time history and phase trajectory under certain values of frequency of the harmonic excitation to verify the nonlinear dynamical evolution of period-doubling bifurcations to chaos. The largest LEs computed with the experimental data are also presented, confirming the chaotic motion in the experiment. We validate the chaotic motion caused by the hysteresis of the MR damper, and show the transitions between distinct regimes of stable motion and chaotic motion of the 2-DoF MR vibration isolation system for variations in frequency of external excitation.

Imaging platelet deposition on Dacron bifurcation grafts in man: Quantification by a dual-tracer method using 111In-labeled platelets and sup(99m)Tc-labeled human serum albumin

International Nuclear Information System (INIS)

Isaka, Yoshinari; Kimura, Kazufumi; Etani, Hideki; Uehara, Akira; Yoneda, Shotaro; Kamada, Takenobu; Kusunoki, Masahito; Kim, Teak Dong; Ohshiro, Takeshi

1986-01-01

A dual tracer technique using 111 In-labeled platelets and sup(99m)Tc-labeled human serum albumin was applied to evaluate the thrombogenicity of Dacron, bifurcation arterial grafts. The level of platelet accumulation over the whole of the graft was estimated from the ratio of 111 In-platelet radioactivity deposited on the vascular wall to these radioactivity circulating in the blood pool, i.e., the platelet-accumulation index (PAI). Furthermore, the PAI value was calculated for each pixel in digitized images and the PAI distribution image (PAI image) was reconstructed. Eighteen patients with DeBakey knitted Dacron bifurcation grafts and 11 normal volunteers were studied. Of the 18 patients, 11 had no graft occlusion (group I) and the remaining 7 (group II) had occlusion. The mean PAI value (+-SD) over the whole of the graft in group I was 32.6%+-33.7% as compared to -8.8%+-4.5% in the control group (P 2 =10.55; P<0.005). The method used for platelet imaging in the present study may be useful in the study of platelet reactions on Dacron arterial prostheses. (orig.)

Numerical bifurcation analysis of a class of nonlinear renewal equations

NARCIS (Netherlands)

Breda, Dimitri; Diekmann, Odo; Liessi, Davide; Scarabel, Francesca

2016-01-01

We show, by way of an example, that numerical bifurcation tools for ODE yield reliable bifurcation diagrams when applied to the pseudospectral approximation of a one-parameter family of nonlinear renewal equations. The example resembles logistic-and Ricker-type population equations and exhibits

A preliminary discussion of angiographic anatomy and variations of rabbit hepatic vessels and catheterization methods of hepatic artery

International Nuclear Information System (INIS)

Wang Diaodong; Yang Renjie; Zhang Hongzhi; Sun Hongliang

2006-01-01

Objective: To study the normal angiographic anatomy and variations of rabbit hepatic vessels, and explore the optimal method for hepatic artery catheterization. Methods: 30 rabbits were divided into two groups randomly. Modified surgical method and interventional method were used to catheterize hepatic artery respectively, and followed by angiography to demonstrate the normal anatomy and variations of rabbit celiac artery, hepatic artery and portal vein. Results: The route and distribution of rabbit celiac artery and hepatic artery were very different from human's. The commonly seen variation showed the differences in branching bifurcation of hepatic-gastric artery, with the incidence of 13.3%. The rates of successfully hepatic artery catheterization with surgical and interventional methods were 86.6%(13/15) and 80%(12/15) respectively (P>0.05). The surgical method will not be successful, whenever there's variation. Conclusion: The normal anatomy and variation of rabbit celiac artery and hepatic artery are quite different from human's. Both surgical and interventional catheterizations could be rather successful but possessing advantages and disadvantages of each its own. (authors)

Stability and Hopf bifurcation in a delayed model for HIV infection of CD4{sup +}T cells

Energy Technology Data Exchange (ETDEWEB)

Cai Liming [Department of Mathematics, Xinyang Normal University, Xinyang, 464000 Henan (China); Beijing Institute of Information Control, Beijing 100037 (China)], E-mail: lmcai06@yahoo.com.cn; Li Xuezhi [Department of Mathematics, Xinyang Normal University, Xinyang, 464000 Henan (China)

2009-10-15

In this paper, we consider a delayed mathematical model for the interactions of HIV infection and CD4{sup +}T cells. We first investigate the existence and stability of the Equilibria. We then study the effect of the time delay on the stability of the infected equilibrium. Criteria are given to ensure that the infected equilibrium is asymptotically stable for all delay. Moreover, by applying Nyquist criterion, the length of delay is estimated for which stability continues to hold. Finally by using a delay {tau} as a bifurcation parameter, the existence of Hopf bifurcation is also investigated. Numerical simulations are presented to illustrate the analytical results.

Hopf-pitchfork bifurcation and periodic phenomena in nonlinear financial system with delay

International Nuclear Information System (INIS)

Ding Yuting; Jiang Weihua; Wang Hongbin

2012-01-01

Highlights: ► We derive the unfolding of a financial system with Hopf-pitchfork bifurcation. ► We show the coexistence of a pair of stable small amplitudes periodic solutions. ► At the same time, also there is a pair of stable large amplitudes periodic solutions. ► Chaos can appear by period-doubling bifurcation far away from Hopf-pitchfork value. ► The study will be useful for interpreting economics phenomena in theory. - Abstract: In this paper, we identify the critical point for a Hopf-pitchfork bifurcation in a nonlinear financial system with delay, and derive the normal form up to third order with their unfolding in original system parameters near the bifurcation point by normal form method and center manifold theory. Furthermore, we analyze its local dynamical behaviors, and show the coexistence of a pair of stable periodic solutions. We also show that there coexist a pair of stable small-amplitude periodic solutions and a pair of stable large-amplitude periodic solutions for different initial values. Finally, we give the bifurcation diagram with numerical illustration, showing that the pair of stable small-amplitude periodic solutions can also exist in a large region of unfolding parameters, and the financial system with delay can exhibit chaos via period-doubling bifurcations as the unfolding parameter values are far away from the critical point of the Hopf-pitchfork bifurcation.

Hemodynamic study on flow patterns in the carotid bifurcation before and after carotid endarterectomy using cine magnetic resonance imaging

Energy Technology Data Exchange (ETDEWEB)

Yamane, Kanji; Shima, Takeshi; Okada, Yoshikazu; Nishida, Masahiro; Okita, Shinji; Hanaguri, Katsuro [Chugoku Rousai Hospital, Kure, Hiroshima (Japan)

1993-11-01

Blood flow in the cervical carotid bifurcation was investigated by cine magnetic resonance imaging. In patients with stenosis, a low-intensity stream was demonstrated from the beginning of the carotid bulb, which was more distinct in the systolic phase. In patients with stenotic carotid bifurcations,the low-intensity flow was also present but was more prominent than in the non-stenotic bifurcation. This low-intensity stream may be due to the change from steady to turbulent flow due to the geometric characteristics of the carotid bifurcation or atheromatous plaque, similar to the flow separation phenomenon in fluid dynamics because of the coincidence of location and flow pattern. After carotid endarterectomy, turbulent flow was seen at the proximal and distal ends of the endarterectomy. Close follow-up and administration of antiplatelet agents are necessary to prevent restenosis due to mural thrombosis induced by such turbulent flow. (author).

Bifurcation sets of the motion of a heavy rigid body around a fixed point in Goryatchev-Tchaplygin case

International Nuclear Information System (INIS)

Quazzani, T.H.A.; Dekkaki, S.; Kharbach, J.; Quazzani-Ja, M.

2000-01-01

In this paper, the topology of Hamiltonian flows is described on the real phase space for the Goryatchev-Tchaplygin top. By making use of Fomenko's theory of surgery on Liouville tori, it is given a complete description of the generic bifurcations of the common level sets of the first integrals. It is also given a numerical investigation of these bifurcations. Explicit periodic solutions for singular common level sets of the first integrals were determined

Stability and Bifurcation of a Computer Virus Propagation Model with Delay and Incomplete Antivirus Ability

Directory of Open Access Journals (Sweden)

Jianguo Ren

2014-01-01

Full Text Available A new computer virus propagation model with delay and incomplete antivirus ability is formulated and its global dynamics is analyzed. The existence and stability of the equilibria are investigated by resorting to the threshold value R0. By analysis, it is found that the model may undergo a Hopf bifurcation induced by the delay. Correspondingly, the critical value of the Hopf bifurcation is obtained. Using Lyapunov functional approach, it is proved that, under suitable conditions, the unique virus-free equilibrium is globally asymptotically stable if R01. Numerical examples are presented to illustrate possible behavioral scenarios of the mode.

Bifurcation and Stability Analysis of the Equilibrium States in Thermodynamic Systems in a Small Vicinity of the Equilibrium Values of Parameters

Science.gov (United States)

Barsuk, Alexandr A.; Paladi, Florentin

2018-04-01

The dynamic behavior of thermodynamic system, described by one order parameter and one control parameter, in a small neighborhood of ordinary and bifurcation equilibrium values of the system parameters is studied. Using the general methods of investigating the branching (bifurcations) of solutions for nonlinear equations, we performed an exhaustive analysis of the order parameter dependences on the control parameter in a small vicinity of the equilibrium values of parameters, including the stability analysis of the equilibrium states, and the asymptotic behavior of the order parameter dependences on the control parameter (bifurcation diagrams). The peculiarities of the transition to an unstable state of the system are discussed, and the estimates of the transition time to the unstable state in the neighborhood of ordinary and bifurcation equilibrium values of parameters are given. The influence of an external field on the dynamic behavior of thermodynamic system is analyzed, and the peculiarities of the system dynamic behavior are discussed near the ordinary and bifurcation equilibrium values of parameters in the presence of external field. The dynamic process of magnetization of a ferromagnet is discussed by using the general methods of bifurcation and stability analysis presented in the paper.

Bunch lengthening with bifurcation in electron storage rings

Energy Technology Data Exchange (ETDEWEB)

Kim, Eun-San; Hirata, Kohji [National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)

1996-08-01

The mapping which shows equilibrium particle distribution in synchrotron phase space for electron storage rings is discussed with respect to some localized constant wake function based on the Gaussian approximation. This mapping shows multi-periodic states as well as double bifurcation in dynamical states of the equilibrium bunch length. When moving around parameter space, the system shows a transition/bifurcation which is not always reversible. These results derived by mapping are confirmed by multiparticle tracking. (author)

Adaptive Control of Electromagnetic Suspension System by HOPF Bifurcation

Directory of Open Access Journals (Sweden)

Aming Hao

2013-01-01

Full Text Available EMS-type maglev system is essentially nonlinear and unstable. It is complicated to design a stable controller for maglev system which is under large-scale disturbance and parameter variance. Theory analysis expresses that this phenomenon corresponds to a HOPF bifurcation in mathematical model. An adaptive control law which adjusts the PID control parameters is given in this paper according to HOPF bifurcation theory. Through identification of the levitated mass, the controller adjusts the feedback coefficient to make the system far from the HOPF bifurcation point and maintain the stability of the maglev system. Simulation result indicates that adjusting proportion gain parameter using this method can extend the state stability range of maglev system and avoid the self-excited vibration efficiently.

Multiple bifurcations and periodic 'bubbling' in a delay population model

International Nuclear Information System (INIS)

Peng Mingshu

2005-01-01

In this paper, the flip bifurcation and periodic doubling bifurcations of a discrete population model without delay influence is firstly studied and the phenomenon of Feigenbaum's cascade of periodic doublings is also observed. Secondly, we explored the Neimark-Sacker bifurcation in the delay population model (two-dimension discrete dynamical systems) and the unique stable closed invariant curve which bifurcates from the nontrivial fixed point. Finally, a computer-assisted study for the delay population model is also delved into. Our computer simulation shows that the introduction of delay effect in a nonlinear difference equation derived from the logistic map leads to much richer dynamic behavior, such as stable node → stable focus → an lower-dimensional closed invariant curve (quasi-periodic solution, limit cycle) or/and stable periodic solutions → chaotic attractor by cascading bubbles (the combination of potential period doubling and reverse period-doubling) and the sudden change between two different attractors, etc

Border-Collision Bifurcations and Chaotic Oscillations in a Piecewise-Smooth Dynamical System

DEFF Research Database (Denmark)

Zhusubaliyev, Z.T.; Soukhoterin, E.A.; Mosekilde, Erik

2002-01-01

Many problems of engineering and applied science result in the consideration of piecewise-smooth dynamical systems. Examples are relay and pulse-width control systems, impact oscillators, power converters, and various electronic circuits with piecewise-smooth characteristics. The subject...... of investigation in the present paper is the dynamical model of a constant voltage converter which represents a three-dimensional piecewise-smooth system of nonautonomous differential equations. A specific type of phenomena that arise in the dynamics of piecewise-smooth systems are the so-called border......-collision bifurcations. The paper contains a detailed analysis of this type of bifurcational transition in the dynamics of the voltage converter, in particular, the merging and subsequent disappearance of cycles of different types, change of solution type, and period-doubling, -tripling, -quadrupling and -quintupling...

Period-doubling bifurcation and chaos control in a discrete-time mosquito model

Directory of Open Access Journals (Sweden)

Qamar Din

2017-12-01

Full Text Available This article deals with the study of some qualitative properties of a discrete-time mosquito Model. It is shown that there exists period-doubling bifurcation for wide range of bifurcation parameter for the unique positive steady-state of given system. In order to control the bifurcation we introduced a feedback strategy. For further confirmation of complexity and chaotic behavior largest Lyapunov exponents are plotted.

A CT study of the prevalence of carotid artery calcification in dental patients

International Nuclear Information System (INIS)

Yoon, Suk Ja; Lee, Jae Seo; Yoon, Woong

2006-01-01

Stroke is one of the leading causes of death in Korea. Atherosclerotic disease in the carotid artery bifurcation is the most common cause of stroke. The carotid artery calcification is easily appreciated by CT(Computed tomography). CT is often taken in a dental hospital for the diagnosis of inflammation. injury, cyst or tumor on maxillofacial region. However, there was no report of carotid artery calcification on CT in dental patients. The presence of carotid artery calcification was evaluated by an experienced radiologist on CT scans of 287 patients (166 males, 121 females, average age 42, range 6 to 86 years) and the medical history of the patient and the interpretation of CT were reviewed. Carotid artery calcification was detected on CT scans of 57 patients (19.8%; 35 males, 22 females). All the male patients with carotid artery calcification were older than 50, and all the female patients with carotid artery calcification were older than 60. Among the 57 patients, 10 had Diabetes mellitus, 20 had cardiovascular disease, 3 had history of stroke and 3 underwent radiation therapy for head and neck cancer. Carotid artery calcification was not included in the interpretation of CT of dental patients except one patient. The prevalence of carotid artery calcification on CT of dental patients was about 20% in this study. Carotid artery calcification should be included in the interpretation of CT of dental patients

Magnetic targeting to enhance microbubble delivery in an occluded microarterial bifurcation.

Science.gov (United States)

de Saint Victor, M; Carugo, D; Barnsley, L C; Owen, J; Coussios, C-C; Stride, E

2017-09-05

Ultrasound and microbubbles have been shown to accelerate the breakdown of blood clots both in vitro and in vivo. Clinical translation of this technology is still limited, however, in part by inefficient microbubble delivery to the thrombus. This study examines the obstacles to delivery posed by fluid dynamic conditions in occluded vasculature and investigates whether magnetic targeting can improve microbubble delivery. A 2D computational fluid dynamic model of a fully occluded Y-shaped microarterial bifurcation was developed to determine: (i) the fluid dynamic field in the vessel with inlet velocities from 1-100 mm s -1 (corresponding to Reynolds numbers 0.25-25); (ii) the transport dynamics of fibrinolytic drugs; and (iii) the flow behavior of microbubbles with diameters in the clinically-relevant range (0.6-5 µm). In vitro experiments were carried out in a custom-built microfluidic device. The flow field was characterized using tracer particles, and fibrinolytic drug transport was assessed using fluorescence microscopy. Lipid-shelled magnetic microbubbles were fluorescently labelled to determine their spatial distribution within the microvascular model. In both the simulations and experiments, the formation of laminar vortices and an abrupt reduction of fluid velocity were observed in the occluded branch of the bifurcation, severely limiting drug transport towards the occlusion. In the absence of a magnetic field, no microbubbles reached the occlusion, remaining trapped in the first vortex, within 350 µm from the bifurcation center. The number of microbubbles trapped within the vortex decreased as the inlet velocity increased, but was independent of microbubble size. Application of a magnetic field (magnetic flux density of 76 mT, magnetic flux density gradient of 10.90 T m -1 at the centre of the bifurcation) enabled delivery of microbubbles to the occlusion and the number of microbubbles delivered increased with bubble size and with decreasing inlet

Bifurcation structure of localized states in the Lugiato-Lefever equation with anomalous dispersion

Science.gov (United States)

Parra-Rivas, P.; Gomila, D.; Gelens, L.; Knobloch, E.

2018-04-01

The origin, stability, and bifurcation structure of different types of bright localized structures described by the Lugiato-Lefever equation are studied. This mean field model describes the nonlinear dynamics of light circulating in fiber cavities and microresonators. In the case of anomalous group velocity dispersion and low values of the intracavity phase detuning these bright states are organized in a homoclinic snaking bifurcation structure. We describe how this bifurcation structure is destroyed when the detuning is increased across a critical value, and determine how a bifurcation structure known as foliated snaking emerges.

Transradial percutaneous coronary intervention for left main bifurcation lesions using 7.5-Fr sheathless guide catheter.

Science.gov (United States)

Zhao, Huiqiang; Banerjee, Subhash; Chen, Hui; Li, Hongwei

2018-05-01

Recent studies have shown sheathless guide catheters (GCs) to be safe and effective during complex lesions such as bifurcations, chronic total occlusion (CTO), and/or calcified lesions. We investigated the feasibility and safety of using 7.5-Fr sheathless GC for transradial percutaneous coronary intervention (PCI) to treat left main bifurcation lesions.A total of 82 patients were consecutively enrolled from March 2013 to February 2016. They underwent transradial PCI for left main bifurcation lesions using the 7.5-Fr sheathless GC.The mean syntax score was 28.1 ± 6.1, and the majority (n = 55, 67.1%) was intermediate scores (23∼32). The unprotected LM disease was present in 67 of 82 patients (81.7%), and true bifurcation (Medina 1, 1, 1) was present in 46 of 82 patients (56.1%). The 2-stent technique was used in 62 of 82 patients (75.6%). The 2-stent technique included 31 cases (37.8%) of "Crush," 18 cases (22.0%) of "Cullote," and 13 (15.8%) cases of "T stent and modified T stent" (T stent). Immediate angiographic success rate was 100% (82/82), and procedural success rate was 97.6% (80/82). The vascular complications occurred in 3 patients (3/82, 3.7%).The use of 7.5-Fr sheathless GC is safe and allows PCI for complex bifurcation lesions located in the distal of left main to be performed transradially with a high success rate.

[Microsurgical anatomy importance of A1-anterior communicating artery complex].

Science.gov (United States)

Monroy-Sosa, Alejandro; Pérez-Cruz, Julio César; Reyes-Soto, Gervith; Delgado-Hernández, Carlos; Macías-Duvignau, Mario Alberto; Delgado-Reyes, Luis

2013-01-01

The anterior cerebral artery originates from the bifurcation of the internal carotid artery lateral to the optic chiasm, then joins with its contralateral counterpart via the anterior communicating artery. A1-anterior communicating artery complex is the most frequent anatomical variants and is the major site of aneurysms between 30 to 37%. Know the anatomy microsurgical, variants anatomical and importance of complex precommunicating segment-artery anterior communicating in surgery neurological of the pathology vascular, mainly aneurysms, in Mexican population. The study was performed in 30 brains injected. Microanatomy was studied (length and diameter) of A1-anterior communicating artery complex and its variants. 60 segments A1, the average length of left side was 11.35 mm and 11.84 mm was right. The average diameter of left was 1.67 mm and the right was 1.64 mm. The average number of perforators on the left side was 7.9 and the right side was 7.5. Anterior communicating artery was found in 29 brains of the optic chiasm, its course depended on the length of the A1 segment. The average length of the segment was 2.84 mm, the average diameter was 1.41 mm and the average number of perforators was 3.27. A1-anterior communicating artery complex variants were found in 18 (60%) and the presence of two blister-like aneurysms. It is necessary to understand the A1-anterior communicating artery complex microanatomy of its variants to have a three-dimensional vision during aneurysm surgery.

Malformação ílio-femoral Iliofemoral arterial malformation

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Mangala M. Pai

2006-12-01

Full Text Available Durante uma dissecção de rotina realizada em um cadáver do sexo masculino com 65 anos de idade foi constatada malformação arterial iliofemoral. A aorta abdominal estava consideravelmente deslocada lateralmente e também bifurcava em nível mais alto. A artéria ilíaca comum dividia-se uma vértebra acima do nível normal e a artéria femoral dava origem à artéria femoral profunda aproximadamente l,2 cm abaixo do ligamento inguinal, o que é consideravelmente proximal ao seu nível normal. Aqui nós apresentamos uma breve revisão de literatura e base embriológica dessas anomalias.During routine dissection, an Iliofemoral arterial malformation was noticed in a 65 year old male cadaver. The abdominal aorta was considerably laterally displaced and also bifurcated higher up. The common iliac artery divided one vertebral level higher and the femoral artery gave the profunda femoris artery about 1.2 cm below the inguinal ligament, which is considerably proximal to its usual level of origin. A brief review of literature and embryological basis of the anomalies are discussed.

Optimization Design and Application of Underground Reinforced Concrete Bifurcation Pipe

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Chao Su

2015-01-01

Full Text Available Underground reinforced concrete bifurcation pipe is an important part of conveyance structure. During construction, the workload of excavation and concrete pouring can be significantly decreased according to optimized pipe structure, and the engineering quality can be improved. This paper presents an optimization mathematical model of underground reinforced concrete bifurcation pipe structure according to real working status of several common pipe structures from real cases. Then, an optimization design system was developed based on Particle Swarm Optimization algorithm. Furthermore, take the bifurcation pipe of one hydropower station as an example: optimization analysis was conducted, and accuracy and stability of the optimization design system were verified successfully.

Bifurcation and Metamorphosis of Plasma Turbulence-Shear Flow Dynamics: the Path to the Top of the Hill

International Nuclear Information System (INIS)

Ball, R.; Dewar, R.L.; Sugama, H.

2003-01-01

The structural properties of an economical model for a confined plasma turbulence governor are investigated through bifurcation and stability analyses. Two types of discontinuous low to high confinement transition are found. One involves classical hysteresis, governed by viscous dissipation. The other is intrinsically oscillatory and non-hysteretic, and thus provides a model for observed 'dithering' transitions. This metamorphosis of the system dynamics is an important late side-effect of symmetry-breaking, which manifests as an unusual non-symmetric transcritical bifurcation induced by a significant shear flow drive

A financial market model with two discontinuities: Bifurcation structures in the chaotic domain

Science.gov (United States)

Panchuk, Anastasiia; Sushko, Iryna; Westerhoff, Frank

2018-05-01

We continue the investigation of a one-dimensional piecewise linear map with two discontinuity points. Such a map may arise from a simple asset-pricing model with heterogeneous speculators, which can help us to explain the intricate bull and bear behavior of financial markets. Our focus is on bifurcation structures observed in the chaotic domain of the map's parameter space, which is associated with robust multiband chaotic attractors. Such structures, related to the map with two discontinuities, have been not studied before. We show that besides the standard bandcount adding and bandcount incrementing bifurcation structures, associated with two partitions, there exist peculiar bandcount adding and bandcount incrementing structures involving all three partitions. Moreover, the map's three partitions may generate intriguing bistability phenomena.

Stability of small-amplitude periodic solutions near Hopf bifurcations in time-delayed fully-connected PLL networks

Science.gov (United States)

Ferruzzo Correa, Diego P.; Bueno, Átila M.; Castilho Piqueira, José R.

2017-04-01

In this paper we investigate stability conditions for small-amplitude periodic solutions emerging near symmetry-preserving Hopf bifurcations in a time-delayed fully-connected N-node PLL network. The study of this type of systems which includes the time delay between connections has attracted much attention among researchers mainly because the delayed coupling between nodes emerges almost naturally in mathematical modeling in many areas of science such as neurobiology, population dynamics, physiology and engineering. In a previous work it has been shown that symmetry breaking and symmetry preserving Hopf bifurcations can emerge in the parameter space. We analyze the stability along branches of periodic solutions near fully-synchronized Hopf bifurcations in the fixed-point space, based on the reduction of the infinite-dimensional space onto a two-dimensional center manifold in normal form. Numerical results are also presented in order to confirm our analytical results.

Bifurcation Control of Chaotic Dynamical Systems

National Research Council Canada - National Science Library

Wang, Hua O; Abed, Eyad H

1992-01-01

A nonlinear system which exhibits bifurcations, transient chaos, and fully developed chaos is considered, with the goal of illustrating the role of two ideas in the control of chaotic dynamical systems...

Stability and Hopf Bifurcation in a Computer Virus Model with Multistate Antivirus

Directory of Open Access Journals (Sweden)

Tao Dong

2012-01-01

Full Text Available By considering that people may immunize their computers with countermeasures in susceptible state, exposed state and using anti-virus software may take a period of time, a computer virus model with time delay based on an SEIR model is proposed. We regard time delay as bifurcating parameter to study the dynamical behaviors which include local asymptotical stability and local Hopf bifurcation. By analyzing the associated characteristic equation, Hopf bifurcation occurs when time delay passes through a sequence of critical value. The linerized model and stability of the bifurcating periodic solutions are also derived by applying the normal form theory and the center manifold theorem. Finally, an illustrative example is also given to support the theoretical results.

Stochastic stability and bifurcation in a macroeconomic model

International Nuclear Information System (INIS)

Li Wei; Xu Wei; Zhao Junfeng; Jin Yanfei

2007-01-01

On the basis of the work of Goodwin and Puu, a new business cycle model subject to a stochastically parametric excitation is derived in this paper. At first, we reduce the model to a one-dimensional diffusion process by applying the stochastic averaging method of quasi-nonintegrable Hamiltonian system. Secondly, we utilize the methods of Lyapunov exponent and boundary classification associated with diffusion process respectively to analyze the stochastic stability of the trivial solution of system. The numerical results obtained illustrate that the trivial solution of system must be globally stable if it is locally stable in the state space. Thirdly, we explore the stochastic Hopf bifurcation of the business cycle model according to the qualitative changes in stationary probability density of system response. It is concluded that the stochastic Hopf bifurcation occurs at two critical parametric values. Finally, some explanations are given in a simply way on the potential applications of stochastic stability and bifurcation analysis

Bifurcations of propellant burning rate at oscillatory pressure

Energy Technology Data Exchange (ETDEWEB)

Novozhilov, Boris V. [N. N. Semenov Institute of Chemical Physics, Russian Academy of Science, 4 Kosygina St., Moscow 119991 (Russian Federation)

2006-06-15

A new phenomenon, the disparity between pressure and propellant burning rate frequencies, has revealed in numerical studies of propellant burning rate response to oscillatory pressure. As is clear from the linear approximation, under small pressure amplitudes, h, pressure and propellant burning rate oscillations occur with equal period T (T-solution). In the paper, however, it is shown that at a certain critical value of the parameter h the system in hand undergoes a bifurcation so that the T-solution converts to oscillations with period 2T (2T-solution). When the bifurcation parameter h increases, the subsequent behavior of the system becomes complicated. It is obtained a sequence of period doubling to 4T-solution and 8T-solution. Beyond a certain value of the bifurcation parameter h an apparently fully chaotic solution is found. These effects undoubtedly should be taken into account in studies of oscillatory processes in combustion chambers. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

Dynamical systems V bifurcation theory and catastrophe theory

CERN Document Server

1994-01-01

Bifurcation theory and catastrophe theory are two of the best known areas within the field of dynamical systems. Both are studies of smooth systems, focusing on properties that seem to be manifestly non-smooth. Bifurcation theory is concerned with the sudden changes that occur in a system when one or more parameters are varied. Examples of such are familiar to students of differential equations, from phase portraits. Moreover, understanding the bifurcations of the differential equations that describe real physical systems provides important information about the behavior of the systems. Catastrophe theory became quite famous during the 1970's, mostly because of the sensation caused by the usually less than rigorous applications of its principal ideas to "hot topics", such as the characterization of personalities and the difference between a "genius" and a "maniac". Catastrophe theory is accurately described as singularity theory and its (genuine) applications. The authors of this book, the first printing of w...

Explicit Solutions and Bifurcations for a Class of Generalized Boussinesq Wave Equation

International Nuclear Information System (INIS)

Ma Zhi-Min; Sun Yu-Huai; Liu Fu-Sheng

2013-01-01

In this paper, the generalized Boussinesq wave equation u tt — u xx + a(u m ) xx + bu xxxx = 0 is investigated by using the bifurcation theory and the method of phase portraits analysis. Under the different parameter conditions, the exact explicit parametric representations for solitary wave solutions and periodic wave solutions are obtained. (general)

Bifurcated equilibria in two-dimensional MHD with diamagnetic effects

International Nuclear Information System (INIS)

Ottaviani, M.; Tebaldi, C.

1998-12-01

In this work we analyzed the sequence of bifurcated equilibria in two-dimensional reduced magnetohydrodynamics. Diamagnetic effects are studied under the assumption of a constant equilibrium pressure gradient, not altered by the formation of the magnetic island. The formation of an island when the symmetric equilibrium becomes unstable is studied as a function of the tearing mode stability parameter Δ' and of the diamagnetic frequency, by employing fixed-points numerical techniques and an initial value code. At larger values of Δ' a tangent bifurcation takes place, above which no small island solutions exist. This bifurcation persists up to fairly large values of the diamagnetic frequency (of the order of one tenth of the Alfven frequency). The implications of this phenomenology for the intermittent MHD dynamics observed in tokamaks is discussed. (authors)

Analytical determination of bifurcations of periodic solution in three-degree-of-freedom vibro-impact systems with clearance

International Nuclear Information System (INIS)

Liu, Yongbao; Wang, Qiang; Xu, Huidong

2017-01-01

The smooth bifurcation and non-smooth grazing bifurcation of periodic solution of three-degree-of-freedom vibro-impact systems with clearance are studied in this paper. Firstly, six-dimensional Poincaré maps are established through choosing suitable Poincaré section and solving periodic solutions of vibro-impact system. Then, as the analytic expressions of all eigenvalues of Jacobi matrix of six-dimensional map are unavailable, the numerical calculations to search for the critical bifurcation values point by point is a laborious job based on the classical critical criterion described by the properties of eigenvalues. To overcome the difficulty from the classical bifurcation criteria, the explicit critical criterion without using eigenvalues calculation of high-dimensional map is applied to determine bifurcation points of Co-dimension-one bifurcations and Co-dimension-two bifurcations, and then local dynamical behaviors of these bifurcations are further analyzed. Finally, the existence of the grazing periodic solution of the vibro-impact system and grazing bifurcation point are analyzed, the discontinuous grazing bifurcation behavior is studied based on the compound normal form map near the grazing point, the discontinuous jumping phenomenon and the co-existing multiple solutions near the grazing bifurcation point are revealed.

Patent hepatic falciform artery detected after Tc-99m-macroaggregated albumin injection on SPECT/CT prior to Yttrium-90 microsphere radioembolization: a case report

International Nuclear Information System (INIS)

Karaman, B.; Aslan, A.; Hamcan, S.; Ugurel, M.

2012-01-01

Full text: Introduction: Yttrium-90 (Y-90) microsphere radioembolization is increasingly used for the treatment of unresectable hepatocellular carcinoma and liver metastasis. Objectives and tasks: We aim to present the upper abdominal wall skin involvement detected during routine pre-therapy Technetium-99m-macroaggregated albumin (Tc-99m-MAA) on SPECT/CT due to patent hepatic falciform artery and the precautions to avoid this potential complication. Material and methods: 38-year-old male with colon cancer and multiple liver metastasis was evaluated prior to radioembolization and Tc-99 MAA was slowly hand injected at the bifurcation of the proper hepatic artery. Then, the SPECT/CT scan was performed in order to investigate the systemic shunt or gastric involvement. Results: On SPECT/CT scan, involvement of the upper abdominal wall through falciform ligament was seen. Re-evaluation of the hepatic angiogram identified a patent hepatic falciform artery arising from the left hepatic artery. Y-90 microspheres were slowly hand injected to the left hepatic artery superselectively and no extra-hepatic activity was seen on SPECT/CT scan. Conclusion: Upper abdominal pain and dermatitis are uncommon findings after radioembolization and may occur due to inadvertent delivery of Y-90 microspheres into patent hepatic falciform artery. To prevent these complications, either patent hepatic falciform artery must be embolized by coil or Y-90 injection must be performed superselectively

Hopf Bifurcation Analysis of a Gene Regulatory Network Mediated by Small Noncoding RNA with Time Delays and Diffusion

Science.gov (United States)

Li, Chengxian; Liu, Haihong; Zhang, Tonghua; Yan, Fang

2017-12-01

In this paper, a gene regulatory network mediated by small noncoding RNA involving two time delays and diffusion under the Neumann boundary conditions is studied. Choosing the sum of delays as the bifurcation parameter, the stability of the positive equilibrium and the existence of spatially homogeneous and spatially inhomogeneous periodic solutions are investigated by analyzing the corresponding characteristic equation. It is shown that the sum of delays can induce Hopf bifurcation and the diffusion incorporated into the system can effect the amplitude of periodic solutions. Furthermore, the spatially homogeneous periodic solution always exists and the spatially inhomogeneous periodic solution will arise when the diffusion coefficients of protein and mRNA are suitably small. Particularly, the small RNA diffusion coefficient is more robust and its effect on model is much less than protein and mRNA. Finally, the explicit formulae for determining the direction of Hopf bifurcation and the stability of the bifurcating periodic solutions are derived by employing the normal form theory and center manifold theorem for partial functional differential equations. Finally, numerical simulations are carried out to illustrate our theoretical analysis.

Dynamical Regimes and the Dynamo Bifurcation in Geodynamo Simulations

Science.gov (United States)

Petitdemange, L.

2017-12-01

We investigate the nature of the dynamo bifurcation in a configuration applicable to the Earth's liquid outer core : in a rotating spherical shell with thermally driven motions with no-slip boundaries. Unlike previous studies on dynamo bifurcations, the control parameters have been varied significantly in order to deduce general tendencies. Numerical studies on the stability domain of dipolar magnetic fields found a dichotomy between non-reversing dipole-dominated dynamos and the reversing non-dipole-dominated multipolar solutions. We show that, by considering weak initial fields, the above transition is replaced by a region of bistability for which dipolar and multipolar dynamos coexist. Such a result was also observed in models with free-slip boundaries in which the strong shear of geostrophic zonal flows can develop and gives rise to non-dipolar fields. We show that a similar process develops in no-slip models when viscous effects are reduced sufficiently.Close to the onset of convection (Rac), the axial dipole grows exponentially in the kinematic phase and saturation occurs by marginally changing the flow structure close to the dynamo threshold Rmc. The resulting bifurcation is then supercritical.In the range 3RacIf (Ra/Ra_c>10), important zonal flows develop in non-magnetic models with low viscosity. The field topology depends on the initial magnetic field. The dipolar branch has a subcritical behaviour whereas the multipolar branch is supercritical. By approaching more realistic parameters, the extension of this bistable regime increases (lower Rossby numbers). An hysteretic behaviour questions the common interpretation for geomagnetic reversals. Far above Rm_c$, the Lorentz force becomes dominant, as it is expected in planetary cores.

Stability and bifurcation analysis in a kind of business cycle model with delay

International Nuclear Information System (INIS)

Zhang Chunrui; Wei Junjie

2004-01-01

A kind of business cycle model with delay is considered. Firstly, the linear stability of the model is studied and bifurcation set is drawn in the appropriate parameter plane. It is found that there exist Hopf bifurcations when the delay passes a sequence of critical values. Then the explicit algorithm for determining the direction of the Hopf bifurcations and the stability of the bifurcating periodic solutions are derived, using the normal form method and center manifold theorem. Finally, a group conditions to guarantee the global existence of periodic solutions is given, and numerical simulations are performed to illustrate the analytical results found

Stability of Bifurcating Stationary Solutions of the Artificial Compressible System

Science.gov (United States)

Teramoto, Yuka

2018-02-01

The artificial compressible system gives a compressible approximation of the incompressible Navier-Stokes system. The latter system is obtained from the former one in the zero limit of the artificial Mach number ɛ which is a singular limit. The sets of stationary solutions of both systems coincide with each other. It is known that if a stationary solution of the incompressible system is asymptotically stable and the velocity field of the stationary solution satisfies an energy-type stability criterion, then it is also stable as a solution of the artificial compressible one for sufficiently small ɛ . In general, the range of ɛ shrinks when the spectrum of the linearized operator for the incompressible system approaches to the imaginary axis. This can happen when a stationary bifurcation occurs. It is proved that when a stationary bifurcation from a simple eigenvalue occurs, the range of ɛ can be taken uniformly near the bifurcation point to conclude the stability of the bifurcating solution as a solution of the artificial compressible system.

Bifurcation of the Kuroshio Extension at the Shatsky Rise

Science.gov (United States)

Hurlburt, Harley E.; Metzger, E. Joseph

1998-04-01

A 1/16° six-layer Pacific Ocean model north of 20°S is used to investigate the bifurcation of the Kuroshio Extension at the main Shatsky Rise and the pathway of the northern branch from the bifurcation to the subarctic front. Upper ocean-topographic coupling via a mixed barotropic-baroclinic instability is essential to this bifurcation and to the formation and mean pathway of the northern branch as are several aspects of the Shatsky Rise complex of topography and the latitude of the Kuroshio Extension in relation to the topography. The flow instabilities transfer energy to the abyssal layer where it is constrained by geostrophic contours of the bottom topography. The topographically constrained abyssal currents in turn steer upper ocean currents, which do not directly impinge on the bottom topography. This includes steering of mean pathways. Obtaining sufficient coupling requires very fine resolution of mesoscale variability and sufficient eastward penetration of the Kuroshio as an unstable inertial jet. Resolution of 1/8° for each variable was not sufficient in this case. The latitudinal extent of the main Shatsky Rise (31°N-36°N) and the shape of the downward slope on the north side are crucial to the bifurcation at the main Shatsky Rise, with both branches passing north of the peak. The well-defined, relatively steep and straight eastern edge of the Shatsky Rise topographic complex (30°N-42°N) and the southwestward abyssal flow along it play a critical role in forming the rest of the Kuroshio northern branch which flows in the opposite direction. A deep pass between the main Shatsky Rise and the rest of the ridge to the northeast helps to link the northern fork of the bifurcation at the main rise to the rest of the northern branch. Two 1/16° "identical twin" interannual simulations forced by daily winds 1981-1995 show that the variability in this region is mostly nondeterministic on all timescales that could be examined (up to 7 years in these 15-year

Characterizing Spatial Dynamics of Bifurcation to Alternans in Isolated Whole Rabbit Hearts Based on Alternate Pacing

Directory of Open Access Journals (Sweden)

Kanchan Kulkarni

2015-01-01

Full Text Available Sudden cardiac death instigated by ventricular fibrillation (VF is the largest cause of natural death in the USA. Alternans, a beat-to-beat alternation in the action potential duration, has been implicated as being proarrhythmic. The onset of alternans is mediated via a bifurcation, which may occur through either a smooth or a border-collision mechanism. The objective of this study was to characterize the mechanism of bifurcation to alternans based on experiments in isolated whole rabbit hearts. High resolution optical mapping was performed and the electrical activity was recorded from the left ventricle (LV epicardial surface of the heart. Each heart was paced using an “alternate pacing protocol,” where the basic cycle length (BCL was alternatively perturbed by ±δ. Local onset of alternans in the heart, BCLstart, was measured in the absence of perturbations (δ=0 and was defined as the BCL at which 10% of LV exhibited alternans. The influences of perturbation size were investigated at two BCLs: one prior to BCLstart (BCLprior=BCLstart+20 ms and one preceding BCLprior (BCLfar=BCLstart+40 ms. Our results demonstrate significant spatial correlation of the region exhibiting alternans with smooth bifurcation characteristics, indicating that transition to alternans in isolated rabbit hearts occurs predominantly through smooth bifurcation.

Bifurcation-free design method of pulse energy converter controllers

International Nuclear Information System (INIS)

Kolokolov, Yury; Ustinov, Pavel; Essounbouli, Najib; Hamzaoui, Abdelaziz

2009-01-01

In this paper, a design method of pulse energy converter (PEC) controllers is proposed. This method develops a classical frequency domain design, based on the small signal modeling, by means of an addition of a nonlinear dynamics analysis stage. The main idea of the proposed method consists in fact that the PEC controller, designed with an application of the small signal modeling, is tuned after with taking into the consideration an essentially nonlinear nature of the PEC that makes it possible to avoid bifurcation phenomena in the PEC dynamics at the design stage (bifurcation-free design). Also application of the proposed method allows an improvement of the designed controller performance. The application of this bifurcation-free design method is demonstrated on an example of the controller design of direct current-direct current (DC-DC) buck converter with an input electromagnetic interference filter.

Dynamics and Physiological Roles of Stochastic Firing Patterns Near Bifurcation Points

Science.gov (United States)

Jia, Bing; Gu, Huaguang

2017-06-01

Different stochastic neural firing patterns or rhythms that appeared near polarization or depolarization resting states were observed in biological experiments on three nervous systems, and closely matched those simulated near bifurcation points between stable equilibrium point and limit cycle in a theoretical model with noise. The distinct dynamics of spike trains and interspike interval histogram (ISIH) of these stochastic rhythms were identified and found to build a relationship to the coexisting behaviors or fixed firing frequency of four different types of bifurcations. Furthermore, noise evokes coherence resonances near bifurcation points and plays important roles in enhancing information. The stochastic rhythms corresponding to Hopf bifurcation points with fixed firing frequency exhibited stronger coherence degree and a sharper peak in the power spectrum of the spike trains than those corresponding to saddle-node bifurcation points without fixed firing frequency. Moreover, the stochastic firing patterns changed to a depolarization resting state as the extracellular potassium concentration increased for the injured nerve fiber related to pathological pain or static blood pressure level increased for aortic depressor nerve fiber, and firing frequency decreased, which were different from the physiological viewpoint that firing frequency increased with increasing pressure level or potassium concentration. This shows that rhythms or firing patterns can reflect pressure or ion concentration information related to pathological pain information. Our results present the dynamics of stochastic firing patterns near bifurcation points, which are helpful for the identification of both dynamics and physiological roles of complex neural firing patterns or rhythms, and the roles of noise.

Non-robust dynamic inferences from macroeconometric models: Bifurcation stratification of confidence regions

Science.gov (United States)

Barnett, William A.; Duzhak, Evgeniya Aleksandrovna

2008-06-01

Grandmont [J.M. Grandmont, On endogenous competitive business cycles, Econometrica 53 (1985) 995-1045] found that the parameter space of the most classical dynamic models is stratified into an infinite number of subsets supporting an infinite number of different kinds of dynamics, from monotonic stability at one extreme to chaos at the other extreme, and with many forms of multiperiodic dynamics in between. The econometric implications of Grandmont’s findings are particularly important, if bifurcation boundaries cross the confidence regions surrounding parameter estimates in policy-relevant models. Stratification of a confidence region into bifurcated subsets seriously damages robustness of dynamical inferences. Recently, interest in policy in some circles has moved to New-Keynesian models. As a result, in this paper we explore bifurcation within the class of New-Keynesian models. We develop the econometric theory needed to locate bifurcation boundaries in log-linearized New-Keynesian models with Taylor policy rules or inflation-targeting policy rules. Central results needed in this research are our theorems on the existence and location of Hopf bifurcation boundaries in each of the cases that we consider.

Analysis of the magnetohydrodynamic equations and study of the nonlinear solution bifurcations

International Nuclear Information System (INIS)

Morros Tosas, J.

1989-05-01

The nonlinear saturation of a plasma magnetohydrodynamic instabilities is studied, by means of a bifurcation theory. The work includes: an accurate mathematical method to study the MHD equations, in which the physical content is clear; and the study of the nonlinear solutions of the branch bifurcations, applied to different unstable plasma models. A scalar function representation is proposed for the MHD equations. This representation is characterized by a reference steady magnetic field and by a velocity field, which allow to write the equations for the scalar functions. An approximation method, leading to the obtention of the reduced equations applied in the instability study, is given. The cylindrical or toroidal plasmas are studied by using the nonlinear solutions bifurcation. Concerning the cylindrical plasma, the representation leads to a reduced system which enables the analytical calculations: two different steady bifurcation solutions are obtained. In the case of the toroidal plasma, an appropriate reduced equations system, is obtained. A qualitative approach of the Kink-type steady solution bifurcation, in a toroidal geometry, is performed [fr

Three dimensional nilpotent singularity and Sil'nikov bifurcation

International Nuclear Information System (INIS)

Li Xindan; Liu Haifei

2007-01-01

In this paper, by using the normal form, blow-up theory and the technique of global bifurcations, we study the singularity at the origin with threefold zero eigenvalue for nonsymmetric vector fields with nilpotent linear part and 4-jet C ∼ -equivalent toy-bar -bar x+z-bar -bar y+ax 3 y-bar -bar z,with a 0, and analytically prove the existence of Sil'nikov bifurcation, and then of the strange attractor for certain subfamilies of the nonsymmetric versal unfoldings of this singularity under some conditions

Bifurcation analysis of nephron pressure and flow regulation

DEFF Research Database (Denmark)

Barfred, Mikael; Mosekilde, Erik; Holstein-Rathlou, N.-H.

1996-01-01

One- and two-dimensional continuation techniques are applied to study the bifurcation structure of a model of renal flow and pressure control. Integrating the main physiological mechanisms by which the individual nephron regulates the incoming blood flow, the model describes the interaction between...... the tubuloglomerular feedback and the response of the afferent arteriole. It is shown how a Hopf bifurcation leads the system to perform self-sustained oscillations if the feedback gain becomes sufficiently strong, and how a further increase of this parameter produces a folded structure of overlapping period...

The period adding and incrementing bifurcations: from rotation theory to applications

DEFF Research Database (Denmark)

Granados, Albert; Alseda, Lluis; Krupa, Maciej

2017-01-01

This survey article is concerned with the study of bifurcations of piecewise-smooth maps. We review the literature in circle maps and quasi-contractions and provide paths through this literature to prove sufficient conditions for the occurrence of two types of bifurcation scenarios involving rich...

Analytical determination of the bifurcation thresholds in stochastic differential equations with delayed feedback.

Science.gov (United States)

Gaudreault, Mathieu; Drolet, François; Viñals, Jorge

2010-11-01

Analytical expressions for pitchfork and Hopf bifurcation thresholds are given for a nonlinear stochastic differential delay equation with feedback. Our results assume that the delay time τ is small compared to other characteristic time scales, not a significant limitation close to the bifurcation line. A pitchfork bifurcation line is found, the location of which depends on the conditional average , where x(t) is the dynamical variable. This conditional probability incorporates the combined effect of fluctuation correlations and delayed feedback. We also find a Hopf bifurcation line which is obtained by a multiple scale expansion around the oscillatory solution near threshold. We solve the Fokker-Planck equation associated with the slowly varying amplitudes and use it to determine the threshold location. In both cases, the predicted bifurcation lines are in excellent agreement with a direct numerical integration of the governing equations. Contrary to the known case involving no delayed feedback, we show that the stochastic bifurcation lines are shifted relative to the deterministic limit and hence that the interaction between fluctuation correlations and delay affect the stability of the solutions of the model equation studied.

Multistability and gluing bifurcation to butterflies in coupled networks with non-monotonic feedback

International Nuclear Information System (INIS)

Ma Jianfu; Wu Jianhong

2009-01-01

Neural networks with a non-monotonic activation function have been proposed to increase their capacity for memory storage and retrieval, but there is still a lack of rigorous mathematical analysis and detailed discussions of the impact of time lag. Here we consider a two-neuron recurrent network. We first show how supercritical pitchfork bifurcations and a saddle-node bifurcation lead to the coexistence of multiple stable equilibria (multistability) in the instantaneous updating network. We then study the effect of time delay on the local stability of these equilibria and show that four equilibria lose their stability at a certain critical value of time delay, and Hopf bifurcations of these equilibria occur simultaneously, leading to multiple coexisting periodic orbits. We apply centre manifold theory and normal form theory to determine the direction of these Hopf bifurcations and the stability of bifurcated periodic orbits. Numerical simulations show very interesting global patterns of periodic solutions as the time delay is varied. In particular, we observe that these four periodic solutions are glued together along the stable and unstable manifolds of saddle points to develop a butterfly structure through a complicated process of gluing bifurcations of periodic solutions

Numerical analysis of bifurcations

International Nuclear Information System (INIS)

Guckenheimer, J.

1996-01-01

This paper is a brief survey of numerical methods for computing bifurcations of generic families of dynamical systems. Emphasis is placed upon algorithms that reflect the structure of the underlying mathematical theory while retaining numerical efficiency. Significant improvements in the computational analysis of dynamical systems are to be expected from more reliance of geometric insight coming from dynamical systems theory. copyright 1996 American Institute of Physics

Bifurcation Analysis with Aerodynamic-Structure Uncertainties by the Nonintrusive PCE Method

Directory of Open Access Journals (Sweden)

Linpeng Wang

2017-01-01

Full Text Available An aeroelastic model for airfoil with a third-order stiffness in both pitch and plunge degree of freedom (DOF and the modified Leishman–Beddoes (LB model were built and validated. The nonintrusive polynomial chaos expansion (PCE based on tensor product is applied to quantify the uncertainty of aerodynamic and structure parameters on the aerodynamic force and aeroelastic behavior. The uncertain limit cycle oscillation (LCO and bifurcation are simulated in the time domain with the stochastic PCE method. Bifurcation diagrams with uncertainties were quantified. The Monte Carlo simulation (MCS is also applied for comparison. From the current work, it can be concluded that the nonintrusive polynomial chaos expansion can give an acceptable accuracy and have a much higher calculation efficiency than MCS. For aerodynamic model, uncertainties of aerodynamic parameters affect the aerodynamic force significantly at the stage from separation to stall at upstroke and at the stage from stall to reattach at return. For aeroelastic model, both uncertainties of aerodynamic parameters and structure parameters impact bifurcation position. Structure uncertainty of parameters is more sensitive for bifurcation. When the nonlinear stall flutter and bifurcation are concerned, more attention should be paid to the separation process of aerodynamics and parameters about pitch DOF in structure.

Neimark-Sacker Bifurcation and Chaos Control in a Fractional-Order Plant-Herbivore Model

Directory of Open Access Journals (Sweden)

Qamar Din

2017-01-01

Full Text Available This work is related to dynamics of a discrete-time 3-dimensional plant-herbivore model. We investigate existence and uniqueness of positive equilibrium and parametric conditions for local asymptotic stability of positive equilibrium point of this model. Moreover, it is also proved that the system undergoes Neimark-Sacker bifurcation for positive equilibrium with the help of an explicit criterion for Neimark-Sacker bifurcation. The chaos control in the model is discussed through implementation of two feedback control strategies, that is, pole-placement technique and hybrid control methodology. Finally, numerical simulations are provided to illustrate theoretical results. These results of numerical simulations demonstrate chaotic long-term behavior over a broad range of parameters. The computation of the maximum Lyapunov exponents confirms the presence of chaotic behavior in the model.

One-dimensional map lattices: Synchronization, bifurcations, and chaotic structures

DEFF Research Database (Denmark)

Belykh, Vladimir N.; Mosekilde, Erik

1996-01-01

The paper presents a qualitative analysis of coupled map lattices (CMLs) for the case of arbitrary nonlinearity of the local map and with space-shift as well as diffusion coupling. The effect of synchronization where, independently of the initial conditions, all elements of a CML acquire uniform...... dynamics is investigated and stable chaotic time behaviors, steady structures, and traveling waves are described. Finally, the bifurcations occurring under the transition from spatiotemporal chaos to chaotic synchronization and the peculiarities of CMLs with specific symmetries are discussed....

Understanding of hysteresis behaviors at the L-H-L transitions in tokamak plasma based on bifurcation concept

Energy Technology Data Exchange (ETDEWEB)

Chatthong, B. [Department of Physics, Faculty of Science, Prince of Songkla University, Hat Yai, Songkla (Thailand); Onjun, T. [School of Manufacturing Systems and Mechanical Engineering, Sirindhorn International Institute of Technology, Thammasat University, Pathum Thani (Thailand)

2016-08-15

The hysteresis behaviour at the L-H-L transitions in tokamak plasma is investigated based on bifurcation concept. The formation of an edge transport barrier (ETB) is modeled via thermal and particle transport equations with the flow shear suppression effect on anomalous transport included. The anomalous transport is modeled based on critical gradients threshold and the flow shear is calculated from the force balance equation, couples the two transport equations leading to a non-linear behaviour. Analytical investigation reveals that the fluxes versus gradients space exhibits bifurcation behaviour with s -curve soft bifurcation type. Apparently, the backward H-L transition occurs at lower values than that of the forward L-H transition, illustrating hysteresis behaviour. The hysteresis properties, i.e. locations of threshold fluxes, gradients and their ratios are analyzed as a function of neoclassical and anomalous transport values and critical gradients. It is found that the minimum heat flux for maintaining H -mode depends on several plasma parameters including the strength of anomalous transport and neoclassical transport. In particular, the hysteresis depth becomes larger when neoclassical transport decreases or anomalous transport increases. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Phase-flip bifurcation in a coupled Josephson junction neuron system

Energy Technology Data Exchange (ETDEWEB)

Segall, Kenneth, E-mail: ksegall@colgate.edu [Department of Physics and Astronomy, Colgate University, Hamilton, NY 13346 (United States); Guo, Siyang; Crotty, Patrick [Department of Physics and Astronomy, Colgate University, Hamilton, NY 13346 (United States); Schult, Dan [Department of Mathematics, Colgate University, Hamilton, NY 13346 (United States); Miller, Max [Department of Physics and Astronomy, Colgate University, Hamilton, NY 13346 (United States)

2014-12-15

Aiming to understand group behaviors and dynamics of neural networks, we have previously proposed the Josephson junction neuron (JJ neuron) as a fast analog model that mimics a biological neuron using superconducting Josephson junctions. In this study, we further analyze the dynamics of the JJ neuron numerically by coupling one JJ neuron to another. In this coupled system we observe a phase-flip bifurcation, where the neurons synchronize out-of-phase at weak coupling and in-phase at strong coupling. We verify this by simulation of the circuit equations and construct a bifurcation diagram for varying coupling strength using the phase response curve and spike phase difference map. The phase-flip bifurcation could be observed experimentally using standard digital superconducting circuitry.

Phase-flip bifurcation in a coupled Josephson junction neuron system

International Nuclear Information System (INIS)

Segall, Kenneth; Guo, Siyang; Crotty, Patrick; Schult, Dan; Miller, Max

2014-01-01

Aiming to understand group behaviors and dynamics of neural networks, we have previously proposed the Josephson junction neuron (JJ neuron) as a fast analog model that mimics a biological neuron using superconducting Josephson junctions. In this study, we further analyze the dynamics of the JJ neuron numerically by coupling one JJ neuron to another. In this coupled system we observe a phase-flip bifurcation, where the neurons synchronize out-of-phase at weak coupling and in-phase at strong coupling. We verify this by simulation of the circuit equations and construct a bifurcation diagram for varying coupling strength using the phase response curve and spike phase difference map. The phase-flip bifurcation could be observed experimentally using standard digital superconducting circuitry

Eckhaus and Benjamin-Feir instabilities near a weakly inverted bifurcation

International Nuclear Information System (INIS)

Brand, H.R.; Deissler, R.J.

1992-01-01

We investigate how the criteria for two prototype instabilities in one-dimensional pattern-forming systems, namely for the Eckhaus instability and for the Benjamin-Feir instability, change as one goes from a continuous bifurcation to a spatially periodic or spatially and/or time-periodic state to the corresponding weakly inverted, i.e., hysteretic, cases. We also give the generalization to two-dimensional patterns in systems with anisotropy as they arise, for example, for hydrodynamic instabilities in nematic liquid crystals

Study of intermittent bifurcations and chaos in boost PFC converters by nonlinear discrete models

International Nuclear Information System (INIS)

Zhang Hao; Ma Xikui; Xue Bianling; Liu Weizeng

2005-01-01

This paper mainly deals with nonlinear phenomena like intermittent bifurcations and chaos in boost PFC converters under peak-current control mode. Two nonlinear models in the form of discrete maps are derived to describe precisely the nonlinear dynamics of boost PFC converters from two points of view, i.e., low- and high-frequency regimes. Based on the presented discrete models, both the evolution of intermittent behavior and the periodicity of intermittency are investigated in detail from the fast and slow-scale aspects, respectively. Numerical results show that the occurrence of intermittent bifurcations and chaos with half one line period is one of the most distinguished dynamical characteristics. Finally, we make some instructive conclusions, which prove to be helpful in improving the performances of practical circuits

Ergodicity-breaking bifurcations and tunneling in hyperbolic transport models

Science.gov (United States)

Giona, M.; Brasiello, A.; Crescitelli, S.

2015-11-01

One of the main differences between parabolic transport, associated with Langevin equations driven by Wiener processes, and hyperbolic models related to generalized Kac equations driven by Poisson processes, is the occurrence in the latter of multiple stable invariant densities (Frobenius multiplicity) in certain regions of the parameter space. This phenomenon is associated with the occurrence in linear hyperbolic balance equations of a typical bifurcation, referred to as the ergodicity-breaking bifurcation, the properties of which are thoroughly analyzed.

Bifurcated states of the error-field-induced magnetic islands

International Nuclear Information System (INIS)

Zheng, L.-J.; Li, B.; Hazeltine, R.D.

2008-01-01

We find that the formation of the magnetic islands due to error fields shows bifurcation when neoclassical effects are included. The bifurcation, which follows from including bootstrap current terms in a description of island growth in the presence of error fields, provides a path to avoid the island-width pole in the classical description. The theory offers possible theoretical explanations for the recent DIII-D and JT-60 experimental observations concerning confinement deterioration with increasing error field

Bifurcation structure of successive torus doubling

International Nuclear Information System (INIS)

Sekikawa, Munehisa; Inaba, Naohiko; Yoshinaga, Tetsuya; Tsubouchi, Takashi

2006-01-01

The authors discuss the 'embryology' of successive torus doubling via the bifurcation theory, and assert that the coupled map of a logistic map and a circle map has a structure capable of generating infinite number of torus doublings

Experimental observation of bifurcation nature of radial electric field in CHS heliotron/torsatron

International Nuclear Information System (INIS)

Fujisawa, Akihide; Iguchi, Harukazu; Yoshimura, Yasuo; Minami, Takashi; Tanaka, Kenji; Okamura, Shoichi; Matsuoka, Keisuke; Fujiwara, Masami

1999-01-01

Several interesting phenomena, such as the formation of a particular potential profile with a protuberance around the core and oscillatory stationary states termed electric pulsation, have been discovered using a heavy ion beam probe in the electron cyclotron heated plasmas of the CHS. This paper presents experimental observations which indicate that bifurcation of the radial electric field is responsible for such phenomena; existence of an ECH power threshold to obtain the profile with a protuberance, and its striking sensitivity to density. In particular, Flip-flop behavior of the potential near the power threshold clearly demonstrates bifurcation characteristics. Bifurcation of radial electric field in neoclassical theory is presented, and its qualitative expectation is discussed in the bifurcation phenomena. The neoclassical transition time scale between two bifurcative sates is compared with the experimental observations during the electric pulsation. It is confirmed that the neoclassical transition time is not contradictory with the experimental one. (author)

Right Hepatic Artery: A Cadaver Investigation and Its Clinical Significance

Directory of Open Access Journals (Sweden)

Usha Dandekar

2015-01-01

Full Text Available The right hepatic artery is an end artery and contributes sole arterial supply to right lobe of the liver. Misinterpretation of normal anatomy and anatomical variations of the right hepatic artery contribute to the major intraoperative mishaps and complications in hepatobiliary surgery. The frequency of inadvertent or iatrogenic hepatobiliary vascular injury rises with the event of an aberrant anatomy. This descriptive study was carried out to document the normal anatomy and different variations of right hepatic artery to contribute to existing knowledge of right hepatic artery to improve surgical safety. This study conducted on 60 cadavers revealed aberrant replaced right hepatic artery in 18.3% and aberrant accessory right hepatic artery in 3.4%. Considering the course, the right hepatic artery ran outside Calot’s triangle in 5% of cases and caterpillar hump right hepatic artery was seen in 13.3% of cases. The right hepatic artery (normal and aberrant crossed anteriorly to the common hepatic duct in 8.3% and posteriorly to it in 71.6%. It has posterior relations with the common bile duct in 16.7% while in 3.4% it did not cross the common hepatic duct or common bile duct. The knowledge of such anomalies is important since their awareness will decrease morbidity and help to keep away from a number of surgical complications.

The high opening of the right bronchial artery with a non-typical course.

Science.gov (United States)

Maciejewski, R; Madej, B; Anasiewicz, A

1995-01-01

Authors describing the bronchial vessels agree to the fact that they are characterised by a great variability in regard to their number and the place where they leave aorta (1, 2, 6). The characteristic feature of the right bronchial artery is that it often forms common trunks with other vessels (mainly with the first right aortic intercostal branch or with one of the upper oesophageal arteries). It can also have a common let-out trunk with the left upper bronchial artery (4). Bearing in mind that the operations on trachea and bronchi are difficult, and that it is very important to maintain the blood supply of the walls in the operated organs we have decided to publish our observations. They refer to a case, not described before, in which the right bronchial artery left the aortic arch in a high position making the vascular supply to the front lower half of the trachea and its bifurcation. Then, it went down to the membranous part of the right bronchus.

Vascular patterns of upper limb: an anatomical study with accent on superficial brachial artery

Directory of Open Access Journals (Sweden)

David Kachlik

2011-02-01

Full Text Available The aim of the study was to evaluate the terminal segmentation of the axillary artery and to present four cases of anomalous branching of the axillary artery, the superficial brachial artery (arteria brachialis superficialis, which is defined as the brachial artery that runs superficially to the median nerve. Totally, 130 cadaveric upper arms embalmed by classical formaldehyde technique from collections of the Department of Anatomy, Third Faculty of Medicine, Charles University in Prague, were macroscopically dissected with special focus on the branching arrangement of the axillary artery. The most distal part of the axillary artery (infrapectoral part terminated in four cases as a bifurcation into two terminal branches: the superficial brachial artery and profunda brachii artery, denominated according to their relation to the median nerve. The profunda brachii artery primarily gave rise to the main branches of the infrapectoral part of the axillary artery. The superficial brachial artery descended to the cubital fossa where it assumed the usual course of the brachial artery in two cases and in the other two cases its branches (the radial and ulnar arteries passed superficially to the flexors. The incidence of the superficial brachial artery in our study was 5% of cases. The reported incidence is a bit contradictory, from 0.12% to 25% of cases. The anatomical knowledge of the axillary region is of crucial importance for neurosurgeons and specialists using the radiodiagnostic techniques, particularly in cases involving traumatic injuries. The improved knowledge would allow more accurate diagnostic interpretations and surgical treatment.

Necessary and sufficient conditions for Hopf bifurcation in tri-neuron equation with a delay

International Nuclear Information System (INIS)

Liu Xiaoming; Liao Xiaofeng

2009-01-01

In this paper, we consider the delayed differential equations modeling three-neuron equations with only a time delay. Using the time delay as a bifurcation parameter, necessary and sufficient conditions for Hopf bifurcation to occur are derived. Numerical results indicate that for this model, Hopf bifurcation is likely to occur at suitable delay parameter values.

Homoclinic bifurcation in Chua's circuit

Indian Academy of Sciences (India)

spiking and bursting behaviors of neurons. Recent experiments ... a limit cycle increases in a wiggle with alternate sequences of stable and unstable orbits via ... further changes in parameter, the system shows period-adding bifurcation when .... [21–23] transition from limit cycle to single scroll chaos via PD and then to alter-.

Equivariant bifurcation in a coupled complex-valued neural network rings

International Nuclear Information System (INIS)

Zhang, Chunrui; Sui, Zhenzhang; Li, Hongpeng

2017-01-01

Highlights: • Complex value Hopfield-type network with Z4 × Z2 symmetry is discussed. • The spatio-temporal patterns of bifurcating periodic oscillations are obtained. • The oscillations can be in phase or anti-phase depending on the parameters and delay. - Abstract: Network with interacting loops and time delays are common in physiological systems. In the past few years, the dynamic behaviors of coupled interacting loops neural networks have been widely studied due to their extensive applications in classification of pattern recognition, signal processing, image processing, engineering optimization and animal locomotion, and other areas, see the references therein. In a large amount of applications, complex signals often occur and the complex-valued recurrent neural networks are preferable. In this paper, we study a complex value Hopfield-type network that consists of a pair of one-way rings each with four neurons and two-way coupling between each ring. We discuss the spatio-temporal patterns of bifurcating periodic oscillations by using the symmetric bifurcation theory of delay differential equations combined with representation theory of Lie groups. The existence of multiple branches of bifurcating periodic solution is obtained. We also found that the spatio-temporal patterns of bifurcating periodic oscillations alternate according to the change of the propagation time delay in the coupling, i.e., different ranges of delays correspond to different patterns of neural network oscillators. The oscillations of corresponding neurons in the two loops can be in phase or anti-phase depending on the parameters and delay. Some numerical simulations support our analysis results.

The ovarian and uterine arteries in the chinchilla (Chinchilla lanigera

Directory of Open Access Journals (Sweden)

A. Cevik-Demirkana

2010-05-01

Full Text Available The purpose of this study was to describe arteries supplying the ovaries and uterus in the chinchilla. Five healthy adult female chinchillas were used. In order to reveal the arterial network by dissecting under a stereoscopic microscope, latex coloured with red ink was injected through the common carotid artery. The ovaries of the chinchilla are supplied by the arteriae ovaricae which formed end-to-end anastomoses with the cranial termination of the arteria uterina. Soon after leaving the aorta abdominalis, the arteriae ovaricae extended 2-3mm caudolaterally, then released 1 branch and extended caudally and bifurcated into 2 further branches. One of these supplied branches to fat tissue. The other branch coursed caudally and anastomosed with the arteria circumflexa ilium profunda and dispersed into fat tissue. The arteria ovarica further subdivided into 2 rami ovaricae. The origins of the uterine arteries were exclusively from the left arteria iliaca externa. The arteria uterina gave a branch to the arteria umbilicalis and consecutive branches which supplied to the ureter, urinary bladder and cranial aspects of the vagina. It also gave rise to 2-3 branches to the cervix and further supplied 10-12 meandering branches to the uterine horns. The arteria uterina gave rise to many tortuous arteries to the uterus and provided 2 further branches to the ovary.

Views on the Hopf bifurcation with respect to voltage instabilities

Energy Technology Data Exchange (ETDEWEB)

Roa-Sepulveda, C A [Universidad de Concepcion, Concepcion (Chile). Dept. de Ingenieria Electrica; Knight, U G [Imperial Coll. of Science and Technology, London (United Kingdom). Dept. of Electrical and Electronic Engineering

1994-12-31

This paper presents a sensitivity study of the Hopf bifurcation phenomenon which can in theory appear in power systems, with reference to the dynamics of the process and the impact of demand characteristics. Conclusions are drawn regarding power levels at which these bifurcations could appear and concern the concept of the imaginary axis as a `hard` limit eigenvalue analyses. (author) 20 refs., 31 figs.

Bifurcation and stability analysis of a nonlinear milling process

Science.gov (United States)

Weremczuk, Andrzej; Rusinek, Rafal; Warminski, Jerzy

2018-01-01

Numerical investigations of milling operations dynamics are presented in this paper. A two degree of freedom nonlinear model is used to study workpiece-tool vibrations. The analyzed model takes into account both flexibility of the tool and the workpiece. The dynamics of the milling process is described by the discontinuous ordinary differential equation with time delay, which can cause process instability. First, stability lobes diagrams are created on the basis of the parameters determined in impact test of an end mill and workpiece. Next, the bifurcations diagrams are performed for different values of rotational speeds.

Numerical Hopf bifurcation of Runge-Kutta methods for a class of delay differential equations

International Nuclear Information System (INIS)

Wang Qiubao; Li Dongsong; Liu, M.Z.

2009-01-01

In this paper, we consider the discretization of parameter-dependent delay differential equation of the form y ' (t)=f(y(t),y(t-1),τ),τ≥0,y element of R d . It is shown that if the delay differential equation undergoes a Hopf bifurcation at τ=τ * , then the discrete scheme undergoes a Hopf bifurcation at τ(h)=τ * +O(h p ) for sufficiently small step size h, where p≥1 is the order of the Runge-Kutta method applied. The direction of numerical Hopf bifurcation and stability of bifurcating invariant curve are the same as that of delay differential equation.

Hopf bifurcation of the stochastic model on business cycle

International Nuclear Information System (INIS)

Xu, J; Wang, H; Ge, G

2008-01-01

A stochastic model on business cycle was presented in thas paper. Simplifying the model through the quasi Hamiltonian theory, the Ito diffusion process was obtained. According to Oseledec multiplicative ergodic theory and singular boundary theory, the conditions of local and global stability were acquired. Solving the stationary FPK equation and analyzing the stationary probability density, the stochastic Hopf bifurcation was explained. The result indicated that the change of parameter awas the key factor to the appearance of the stochastic Hopf bifurcation

Electron Bifurcation: Thermodynamics and Kinetics of Two-Electron Brokering in Biological Redox Chemistry.

Science.gov (United States)

Zhang, Peng; Yuly, Jonathon L; Lubner, Carolyn E; Mulder, David W; King, Paul W; Peters, John W; Beratan, David N

2017-09-19

How can proteins drive two electrons from a redox active donor onto two acceptors at very different potentials and distances? And how can this transaction be conducted without dissipating very much energy or violating the laws of thermodynamics? Nature appears to have addressed these challenges by coupling thermodynamically uphill and downhill electron transfer reactions, using two-electron donor cofactors that have very different potentials for the removal of the first and second electron. Although electron bifurcation is carried out with near perfection from the standpoint of energy conservation and electron delivery yields, it is a biological energy transduction paradigm that has only come into focus recently. This Account provides an exegesis of the biophysical principles that underpin electron bifurcation. Remarkably, bifurcating electron transfer (ET) proteins typically send one electron uphill and one electron downhill by similar energies, such that the overall reaction is spontaneous, but not profligate. Electron bifurcation in the NADH-dependent reduced ferredoxin: NADP + oxidoreductase I (Nfn) is explored in detail here. Recent experimental progress in understanding the structure and function of Nfn allows us to dissect its workings in the framework of modern ET theory. The first electron that leaves the two-electron donor flavin (L-FAD) executes a positive free energy "uphill" reaction, and the departure of this electron switches on a second thermodynamically spontaneous ET reaction from the flavin along a second pathway that moves electrons in the opposite direction and at a very different potential. The singly reduced ET products formed from the bifurcating flavin are more than two nanometers distant from each other. In Nfn, the second electron to leave the flavin is much more reducing than the first: the potentials are said to be "crossed." The eventually reduced cofactors, NADH and ferredoxin in the case of Nfn, perform crucial downstream redox

Bifurcation of Mobility, Bifurcation of Law : Externalization of migration policy before the EU Court of Justice

NARCIS (Netherlands)

Spijkerboer, T.P.

2017-01-01

The externalization of European migration policy has resulted in a bifurcation of global human mobility, which is divided along a North/South axis. In two judgments, the EU Court of Justice was confronted with cases challenging the exclusion of Syrian refugees from Europe. These cases concern core

Bifurcation in autonomous and nonautonomous differential equations with discontinuities

CERN Document Server

Akhmet, Marat

2017-01-01

This book is devoted to bifurcation theory for autonomous and nonautonomous differential equations with discontinuities of different types. That is, those with jumps present either in the right-hand-side or in trajectories or in the arguments of solutions of equations. The results obtained in this book can be applied to various fields such as neural networks, brain dynamics, mechanical systems, weather phenomena, population dynamics, etc. Without any doubt, bifurcation theory should be further developed to different types of differential equations. In this sense, the present book will be a leading one in this field. The reader will benefit from the recent results of the theory and will learn in the very concrete way how to apply this theory to differential equations with various types of discontinuity. Moreover, the reader will learn new ways to analyze nonautonomous bifurcation scenarios in these equations. The book will be of a big interest both for beginners and experts in the field. For the former group o...

Bifurcation analysis of the simplified models of boiling water reactor and identification of global stability boundary

Energy Technology Data Exchange (ETDEWEB)

Pandey, Vikas; Singh, Suneet, E-mail: suneet.singh@iitb.ac.in

2017-04-15

Highlights: • Non-linear stability analysis of nuclear reactor is carried out. • Global and local stability boundaries are drawn in the parameter space. • Globally stable, bi-stable, and unstable regions have been demarcated. • The identification of the regions is verified by numerical simulations. - Abstract: Nonlinear stability study of the neutron coupled thermal hydraulics instability has been carried out by several researchers for boiling water reactors (BWRs). The focus of these studies has been to identify subcritical and supercritical Hopf bifurcations. Supercritical Hopf bifurcation are soft or safe due to the fact that stable limit cycles arise in linearly unstable region; linear and global stability boundaries are same for this bifurcation. It is well known that the subcritical bifurcations can be considered as hard or dangerous due to the fact that unstable limit cycles (nonlinear phenomena) exist in the (linearly) stable region. The linear stability leads to a stable equilibrium in such regions, only for infinitesimally small perturbations. However, finite perturbations lead to instability due to the presence of unstable limit cycles. Therefore, it is evident that the linear stability analysis is not sufficient to understand the exact stability characteristics of BWRs. However, the effect of these bifurcations on the stability boundaries has been rarely discussed. In the present work, the identification of global stability boundary is demonstrated using simplified models. Here, five different models with different thermal hydraulics feedback have been investigated. In comparison to the earlier works, current models also include the impact of adding the rate of change in temperature on void reactivity as well as effect of void reactivity on rate of change of temperature. Using the bifurcation analysis of these models the globally stable region in the parameter space has been identified. The globally stable region has only stable solutions and

Bifurcation analysis of the simplified models of boiling water reactor and identification of global stability boundary

International Nuclear Information System (INIS)

Pandey, Vikas; Singh, Suneet

2017-01-01

Highlights: • Non-linear stability analysis of nuclear reactor is carried out. • Global and local stability boundaries are drawn in the parameter space. • Globally stable, bi-stable, and unstable regions have been demarcated. • The identification of the regions is verified by numerical simulations. - Abstract: Nonlinear stability study of the neutron coupled thermal hydraulics instability has been carried out by several researchers for boiling water reactors (BWRs). The focus of these studies has been to identify subcritical and supercritical Hopf bifurcations. Supercritical Hopf bifurcation are soft or safe due to the fact that stable limit cycles arise in linearly unstable region; linear and global stability boundaries are same for this bifurcation. It is well known that the subcritical bifurcations can be considered as hard or dangerous due to the fact that unstable limit cycles (nonlinear phenomena) exist in the (linearly) stable region. The linear stability leads to a stable equilibrium in such regions, only for infinitesimally small perturbations. However, finite perturbations lead to instability due to the presence of unstable limit cycles. Therefore, it is evident that the linear stability analysis is not sufficient to understand the exact stability characteristics of BWRs. However, the effect of these bifurcations on the stability boundaries has been rarely discussed. In the present work, the identification of global stability boundary is demonstrated using simplified models. Here, five different models with different thermal hydraulics feedback have been investigated. In comparison to the earlier works, current models also include the impact of adding the rate of change in temperature on void reactivity as well as effect of void reactivity on rate of change of temperature. Using the bifurcation analysis of these models the globally stable region in the parameter space has been identified. The globally stable region has only stable solutions and

Quantum entanglement dependence on bifurcations and scars in non-autonomous systems. The case of quantum kicked top

International Nuclear Information System (INIS)

Stamatiou, George; Ghikas, Demetris P.K.

2007-01-01

Properties related to entanglement in quantum systems, are known to be associated with distinct properties of the corresponding classical systems, as for example stability, integrability and chaos. This means that the detailed topology, both local and global, of the classical phase space may reveal, or influence, the entangling power of the quantum system. As it has been shown in the literature, the bifurcation points, in autonomous dynamical systems, play a crucial role for the onset of entanglement. Similarly, the existence of scars among the quantum states seems to be a factor in the dynamics of entanglement. Here we study these issues for a non-autonomous system, the quantum kicked top, as a collective model of a multi-qubit system. Using the bifurcation diagram of the corresponding classical limit (the classical kicked top), we analyzed the pair-wise and the bi-partite entanglement of the qubits and their relation to scars, as a function of the critical parameter of the system. We found that the pair-wise entanglement and pair-wise negativity show a strong maximum precisely at the bifurcation points, while the bi-partite entanglement changes slope at these points. We have also investigated the connection between entanglement and the fixed points on the branch of the bifurcation diagram between the two first bifurcation points and we found that the entanglement measures take their extreme values precisely on these points. We conjecture that our results on this behavior of entanglement is generic for many quantum systems with a nonlinear classical analogue

The Absence of Sensory Axon Bifurcation Affects Nociception and Termination Fields of Afferents in the Spinal Cord

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Philip Tröster

2018-02-01

Full Text Available A cGMP signaling cascade composed of C-type natriuretic peptide, the guanylyl cyclase receptor Npr2 and cGMP-dependent protein kinase I (cGKI controls the bifurcation of sensory axons upon entering the spinal cord during embryonic development. However, the impact of axon bifurcation on sensory processing in adulthood remains poorly understood. To investigate the functional consequences of impaired axon bifurcation during adult stages we generated conditional mouse mutants of Npr2 and cGKI (Npr2fl/fl;Wnt1Cre and cGKIKO/fl;Wnt1Cre that lack sensory axon bifurcation in the absence of additional phenotypes observed in the global knockout mice. Cholera toxin labeling in digits of the hind paw demonstrated an altered shape of sensory neuron termination fields in the spinal cord of conditional Npr2 mouse mutants. Behavioral testing of both sexes indicated that noxious heat sensation and nociception induced by chemical irritants are impaired in the mutants, whereas responses to cold sensation, mechanical stimulation, and motor coordination are not affected. Recordings from C-fiber nociceptors in the hind limb skin showed that Npr2 function was not required to maintain normal heat sensitivity of peripheral nociceptors. Thus, the altered behavioral responses to noxious heat found in Npr2fl/fl;Wnt1Cre mice is not due to an impaired C-fiber function. Overall, these data point to a critical role of axonal bifurcation for the processing of pain induced by heat or chemical stimuli.

Symmetry breaking bifurcations of a current sheet

International Nuclear Information System (INIS)

Parker, R.D.; Dewar, R.L.; Johnson, J.L.

1990-01-01

Using a time evolution code with periodic boundary conditions, the viscoresistive hydromagnetic equations describing an initially static, planar current sheet with large Lundquist number have been evolved for times long enough to reach a steady state. A cosh 2 x resistivity model was used. For long periodicity lengths L p , the resistivity gradient drives flows that cause forced reconnection at X point current sheets. Using L p as a bifurcation parameter, two new symmetry breaking bifurcations were found: a transition to an asymmetric island chain with nonzero, positive, or negative phase velocity, and a transition to a static state with alternating large and small islands. These states are reached after a complex transient behavior, which involves a competition between secondary current sheet instability and coalescence

Bifurcation and Nonlinear Oscillations.

Science.gov (United States)

1980-09-28

Structural stability and bifurcation theory. pp. 549-560 in Dinamical Systems (Ed. MI. Peixoto), Academic Press, 1973. [211 J. Sotomayor, Generic one...Dynamical Systems Brown University ELECTP" 71, Providence, R. I. 02912 1EC 2 4 1980j //C -*)’ Septabe-4., 1980 / -A + This research was supported in...problems are discussed. The first one deals with the characterization of the flow for a periodic planar system which is the perturbation of an autonomous

Bifurcation routes and economic stability

Czech Academy of Sciences Publication Activity Database

Vošvrda, Miloslav

2001-01-01

Roč. 8, č. 14 (2001), s. 43-59 ISSN 1212-074X R&D Projects: GA ČR GA402/00/0439; GA ČR GA402/01/0034; GA ČR GA402/01/0539 Institutional research plan: AV0Z1075907 Keywords : macroeconomic stability * foreign investment phenomenon * the Hopf bifurcation Subject RIV: AH - Economics

Computed tomography angiography study of variations of the celiac trunk and hepatic artery in 100 patients

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Ivelise Regina Canito Brasil

Full Text Available Abstract Objective: To describe the main anatomical variations of the celiac trunk and the hepatic artery at their origins. Materials and Methods: This was a prospective analysis of 100 consecutive computed tomography angiography studies of the abdomen performed during a one-year period. The findings were stratified according to classification systems devised by Sureka et al. and Michels. Results: The celiac trunk was "normal" (i.e., the hepatogastrosplenic trunk and superior mesenteric artery originating separately from the abdominal aorta in 43 patients. In our sample, we identified four types of variations of the celiac trunk. Regarding the hepatic artery, a normal anatomical pattern (i.e., the proper hepatic artery being a continuation of the common hepatic artery and bifurcating into the right and left hepatic arteries was seen in 82 patients. We observed six types of variations of the hepatic artery. Conclusion: We found rates of variations of the hepatic artery that are different from those reported in the literature. Our findings underscore the need for proper knowledge and awareness of these anatomical variations, which can facilitate their recognition and inform decisions regarding the planning of surgical procedures, in order to avoid iatrogenic intraoperative injuries, which could lead to complications.

Computed tomography angiography study of variations of the celiac trunk and hepatic artery in 100 patients

Energy Technology Data Exchange (ETDEWEB)

Brasil, Ivelise Regina Canito; Araujo, Igor Farias de; Lima, Adriana Augusta Lopes de Araujo; Melo, Ernesto Lima Araujo; Esmeraldo, Ronaldo de Matos, E-mail: igor_farias98@hotmail.com [Universidade Estadual do Ceará (UECE), Fortaleza, CE (Brazil). Escola de Medicina

2018-01-15

Objective: To describe the main anatomical variations of the celiac trunk and the hepatic artery at their origins. Materials and methods: This was a prospective analysis of 100 consecutive computed tomography angiography studies of the abdomen performed during a one-year period. The findings were stratified according to classification systems devised by Sureka et al. and Michels. Results: The celiac trunk was 'normal' (i.e., the hepatogastrosplenic trunk and superior mesenteric artery originating separately from the abdominal aorta) in 43 patients. In our sample, we identified four types of variations of the celiac trunk. Regarding the hepatic artery, a normal anatomical pattern (i.e., the proper hepatic artery being a continuation of the common hepatic artery and bifurcating into the right and left hepatic arteries) was seen in 82 patients. We observed six types of variations of the hepatic artery. Conclusion: We found rates of variations of the hepatic artery that are different from those reported in the literature. Our findings underscore the need for proper knowledge and awareness of these anatomical variations, which can facilitate their recognition and inform decisions regarding the planning of surgical procedures, in order to avoid iatrogenic intraoperative injuries, which could lead to complications. (author)

Computed tomography angiography study of variations of the celiac trunk and hepatic artery in 100 patients

International Nuclear Information System (INIS)

Brasil, Ivelise Regina Canito; Araujo, Igor Farias de; Lima, Adriana Augusta Lopes de Araujo; Melo, Ernesto Lima Araujo; Esmeraldo, Ronaldo de Matos

2018-01-01

Objective: To describe the main anatomical variations of the celiac trunk and the hepatic artery at their origins. Materials and methods: This was a prospective analysis of 100 consecutive computed tomography angiography studies of the abdomen performed during a one-year period. The findings were stratified according to classification systems devised by Sureka et al. and Michels. Results: The celiac trunk was 'normal' (i.e., the hepatogastrosplenic trunk and superior mesenteric artery originating separately from the abdominal aorta) in 43 patients. In our sample, we identified four types of variations of the celiac trunk. Regarding the hepatic artery, a normal anatomical pattern (i.e., the proper hepatic artery being a continuation of the common hepatic artery and bifurcating into the right and left hepatic arteries) was seen in 82 patients. We observed six types of variations of the hepatic artery. Conclusion: We found rates of variations of the hepatic artery that are different from those reported in the literature. Our findings underscore the need for proper knowledge and awareness of these anatomical variations, which can facilitate their recognition and inform decisions regarding the planning of surgical procedures, in order to avoid iatrogenic intraoperative injuries, which could lead to complications. (author)

Homoclinic connections and subcritical Neimark bifurcation in a duopoly model with adaptively adjusted productions

International Nuclear Information System (INIS)

Agliari, Anna

2006-01-01

In this paper we study some global bifurcations arising in the Puu's oligopoly model when we assume that the producers do not adjust to the best reply but use an adaptive process to obtain at each step the new production. Such bifurcations cause the appearance of a pair of closed invariant curves, one attracting and one repelling, this latter being involved in the subcritical Neimark bifurcation of the Cournot equilibrium point. The aim of the paper is to highlight the relationship between the global bifurcations causing the appearance/disappearance of two invariant closed curves and the homoclinic connections of some saddle cycle, already conjectured in [Agliari A, Gardini L, Puu T. Some global bifurcations related to the appearance of closed invariant curves. Comput Math Simul 2005;68:201-19]. We refine the results obtained in such a paper, showing that the appearance/disappearance of closed invariant curves is not necessarily related to the existence of an attracting cycle. The characterization of the periodicity tongues (i.e. a region of the parameter space in which an attracting cycle exists) associated with a subcritical Neimark bifurcation is also discussed

On period doubling bifurcations of cycles and the harmonic balance method

International Nuclear Information System (INIS)

Itovich, Griselda R.; Moiola, Jorge L.

2006-01-01

This works attempts to give quasi-analytical expressions for subharmonic solutions appearing in the vicinity of a Hopf bifurcation. Starting with well-known tools as the graphical Hopf method for recovering the periodic branch emerging from classical Hopf bifurcation, precise frequency and amplitude estimations of the limit cycle can be obtained. These results allow to attain approximations for period doubling orbits by means of harmonic balance techniques, whose accuracy is established by comparison of Floquet multipliers with continuation software packages. Setting up a few coefficients, the proposed methodology yields to approximate solutions that result from a second period doubling bifurcation of cycles and to extend the validity limits of the graphical Hopf method

Voltage Stability Bifurcation Analysis for AC/DC Systems with VSC-HVDC

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Yanfang Wei

2013-01-01

Full Text Available A voltage stability bifurcation analysis approach for modeling AC/DC systems with VSC-HVDC is presented. The steady power model and control modes of VSC-HVDC are briefly presented firstly. Based on the steady model of VSC-HVDC, a new improved sequential iterative power flow algorithm is proposed. Then, by use of continuation power flow algorithm with the new sequential method, the voltage stability bifurcation of the system is discussed. The trace of the P-V curves and the computation of the saddle node bifurcation point of the system can be obtained. At last, the modified IEEE test systems are adopted to illustrate the effectiveness of the proposed method.

Endodontic-periodontic bifurcation lesions: a novel treatment option.

Science.gov (United States)

Lin, Shaul; Tillinger, Gabriel; Zuckerman, Offer

2008-05-01

The purpose of this preliminary clinical report is to suggest a novel treatment modality for periodontal bifurcation lesions of endodontic origin. The study consisted of 11 consecutive patients who presented with periodontal bifurcation lesions of endodontic origin (endo-perio lesions). All patients were followed-up for at least 12 months. Treatment included calcium hydroxide with iodine-potassium iodide placed in the root canals for 90 days followed by canal sealing with gutta-percha and cement during a second stage. Dentin bonding was used to seal the furcation floor to prevent the ingress of bacteria and their by-products to the furcation root area through the accessory canals. A radiographic examination showed complete healing of the periradicular lesion in all patients. Probing periodontal pocket depths decreased to 2 to 4 mm (mean 3.5 mm), and resolution of the furcation involvement was observed in post-operative clinical evaluations. The suggested treatment of endo-perio lesions may result in complete healing. Further studies are warranted. This treatment method improves both the disinfection of the bifurcation area and the healing process in endodontically treated teeth considered to be hopeless.

Resource competition: a bifurcation theory approach.

NARCIS (Netherlands)

Kooi, B.W.; Dutta, P.S.; Feudel, U.

2013-01-01

We develop a framework for analysing the outcome of resource competition based on bifurcation theory. We elaborate our methodology by readdressing the problem of competition of two species for two resources in a chemostat environment. In the case of perfect-essential resources it has been

Stability and Hopf Bifurcation in a Delayed SEIRS Worm Model in Computer Network

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Zizhen Zhang

2013-01-01

Full Text Available A delayed SEIRS epidemic model with vertical transmission in computer network is considered. Sufficient conditions for local stability of the positive equilibrium and existence of local Hopf bifurcation are obtained by analyzing distribution of the roots of the associated characteristic equation. Furthermore, the direction of the local Hopf bifurcation and the stability of the bifurcating periodic solutions are determined by using the normal form theory and center manifold theorem. Finally, a numerical example is presented to verify the theoretical analysis.

Bifurcations in the response of a flexible rotor in squeeze-film dampers with retainer springs

International Nuclear Information System (INIS)

Inayat-Hussain, Jawaid I.

2009-01-01

Squeeze-film dampers are commonly used in conjunction with rolling-element or hydrodynamic bearings in rotating machinery. Although these dampers serve to provide additional damping to the rotor-bearing system, there have however been some cases of rotors mounted in these dampers exhibiting non-linear behaviour. In this paper a numerical study is undertaken to determine the effects of design parameters, i.e., gravity parameter, W, mass ratio, α, and stiffness ratio, K, on the bifurcations in the response of a flexible rotor mounted in squeeze-film dampers with retainer springs. The numerical simulations were undertaken for a range of speed parameter, Ω, between 0.1 and 5.0. Numerical results showed that increasing K causes the onset speed of bifurcation to increase, whilst an increase of α reduces the onset speed of bifurcation. For a specific combination of K and α values, the onset speed of bifurcation appeared to be independent of W. The instability of the rotor response at this onset speed was due to a saddle-node bifurcation for all the parameter values investigated in this work with the exception of the combination of α = 0.1 and K = 0.5, where a secondary Hopf bifurcation was observed. The speed range of non-synchronous response was seen to decrease with the increase of α; in fact non-synchronous rotor response was totally absent for α=0.4. With the exception of the case α = 0.1, the speed range of non-synchronous response was also seen to decrease with the increase of K. Multiple responses of the rotor were observed at certain values of Ω for various combinations of parameters W, α and K, where, depending on the values of the initial conditions the rotor response could be either synchronous or quasi-periodic. The numerical results presented in this work were obtained for an unbalance parameter, U, value of 0.1, which is considered as the upper end of the normal unbalance range of most practical rotor systems. These results provide some insights

Modal bifurcation in a high-Tc superconducting levitation system

International Nuclear Information System (INIS)

Taguchi, D; Fujiwara, S; Sugiura, T

2011-01-01

This paper deals with modal bifurcation of a multi-degree-of-freedom high-T c superconducting levitation system. As modeling of large-scale high-T c superconducting levitation applications, where plural superconducting bulks are often used, it can be helpful to consider a system constituting of multiple oscillators magnetically coupled with each other. This paper investigates nonlinear dynamics of two permanent magnets levitated above high-T c superconducting bulks and placed between two fixed permanent magnets without contact. First, the nonlinear equations of motion of the levitated magnets were derived. Then the method of averaging was applied to them. It can be found from the obtained solutions that this nonlinear two degree-of-freedom system can have two asymmetric modes, in addition to a symmetric mode and an antisymmetric mode both of which also exist in the linearized system. One of the backbone curves in the frequency response shows a modal bifurcation where the two stable asymmetric modes mentioned above appear with destabilization of the antisymmetric mode, thus leading to modal localization. These analytical predictions have been confirmed in our numerical analysis and experiments of free vibration and forced vibration. These results, never predicted by linear analysis, can be important for application of high-T c superconducting levitation systems.

Sufficient conditions for a period incrementing big bang bifurcation in one-dimensional maps

International Nuclear Information System (INIS)

Avrutin, V; Granados, A; Schanz, M

2011-01-01

Typically, big bang bifurcation occurs for one (or higher)-dimensional piecewise-defined discontinuous systems whenever two border collision bifurcation curves collide transversely in the parameter space. At that point, two (feasible) fixed points collide with one boundary in state space and become virtual, and, in the one-dimensional case, the map becomes continuous. Depending on the properties of the map near the codimension-two bifurcation point, there exist different scenarios regarding how the infinite number of periodic orbits are born, mainly the so-called period adding and period incrementing. In our work we prove that, in order to undergo a big bang bifurcation of the period incrementing type, it is sufficient for a piecewise-defined one-dimensional map that the colliding fixed points are attractive and with associated eigenvalues of different signs

Sufficient conditions for a period incrementing big bang bifurcation in one-dimensional maps

Science.gov (United States)

Avrutin, V.; Granados, A.; Schanz, M.

2011-09-01

Typically, big bang bifurcation occurs for one (or higher)-dimensional piecewise-defined discontinuous systems whenever two border collision bifurcation curves collide transversely in the parameter space. At that point, two (feasible) fixed points collide with one boundary in state space and become virtual, and, in the one-dimensional case, the map becomes continuous. Depending on the properties of the map near the codimension-two bifurcation point, there exist different scenarios regarding how the infinite number of periodic orbits are born, mainly the so-called period adding and period incrementing. In our work we prove that, in order to undergo a big bang bifurcation of the period incrementing type, it is sufficient for a piecewise-defined one-dimensional map that the colliding fixed points are attractive and with associated eigenvalues of different signs.

[Sciatic nerve block "out-of-plane" distal to the bifurcation: effective and safe].

Science.gov (United States)

Geiser, T; Apel, J; Vicent, O; Büttner, J

2017-03-01

Ultrasound guided distal sciatic nerve block (DSB) at bifurcation level shows fast onset and provides excellent success rates. However, its safe performance might be difficult for the unexperienced physician. Just slightly distal to the bifurcation, the tibial nerve (TN) and common fibular nerve (CFN) can be shown clearly separated from each other. Therefore, we investigated if a block done here would provide similar quality results compared to the DSB proximally to the division, with a potentially lower risk of nerve damage. In this randomized, prospective trial, 56 patients per group received either a DSB distal to the bifurcation "out-of-plane" (dist.) or proximally "in-plane" (prox.) with 30 ml of Mepivacaine 1% each. Success was tested by a blinded examiner after 15 and 30 min respectively (sensory and motor block of TN and CFN: 0 = none, 2 = complete, change of skin temperature). Videos of the blocks were inspected by an independent expert retrospectively with regard to the spread of the local anesthetic (LA) and accidental intraneural injection. Cumulative single nerve measurements and temperature changes revealed significant shorter onset and better efficacy (dist/prox: 15 min: 3.13 ± 1.86/1.82 ± 1.62; 30 min: 5.73 ± 1.92/3.21 ± 1.88; T 15 min : 30.3 ± 3.48/28.0 ± 3.67, T 30 min . 33.0 ± 2.46/30.6 ± 3.86; MV/SD; ANOVA; p safe application of the LA, so an effective block can be done with just one injection. DSB slightly distal to the bifurcation, in an out-of-plane technique between the TN and CFN, can be done fast, effectively and safe.

A Method to Determine Oscillation Emergence Bifurcation in Time-Delayed LTI System with Single Lag

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Yu Xiaodan

2014-01-01

Full Text Available One type of bifurcation named oscillation emergence bifurcation (OEB found in time-delayed linear time invariant (abbr. LTI systems is fully studied. The definition of OEB is initially put forward according to the eigenvalue variation. It is revealed that a real eigenvalue splits into a pair of conjugated complex eigenvalues when an OEB occurs, which means the number of the system eigenvalues will increase by one and a new oscillation mode will emerge. Next, a method to determine OEB bifurcation in the time-delayed LTI system with single lag is developed based on Lambert W function. A one-dimensional (1-dim time-delayed system is firstly employed to explain the mechanism of OEB bifurcation. Then, methods to determine the OEB bifurcation in 1-dim, 2-dim, and high-dimension time-delayed LTI systems are derived. Finally, simulation results validate the correctness and effectiveness of the presented method. Since OEB bifurcation occurs with a new oscillation mode emerging, work of this paper is useful to explore the complex phenomena and the stability of time-delayed dynamic systems.

Asymmetric Bilateral Variations in the Musculocutaneous and Median Nerves with High Branching of Brachial Artery

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Vandana Tomar

2012-01-01

Full Text Available Brachial Plexus is formed by the union of the anterior rami of cervical 5, 6, 7, 8 and thoracic 1 nerves. These nerves unite and divide to form the key nerves innervating the upper limb. Variations in the course of these nerves are clinically important to anesthetists, neurologists and orthopedicians. We report bilateral variations in the arterial and neural structures in the upper limb of a 65 year old cadaver. The muscles of the arm on one side were innervated by the median nerve with absence of musculocutaneous. While on the other side the musculocutaneous nerve contributed to the formation of the median nerve. There was a presence of high bifurcation of brachial artery on both sides. Knowledge of such variations in the innervations of muscles and the arterial supply of the limbs are important to remember before performing any reconstructive procedures or interventions on the limb.

Three-dimensional modelling of the human carotid artery using the lattice Boltzmann method: II. Shear analysis

Energy Technology Data Exchange (ETDEWEB)

Boyd, J [Cardiovascular Research Group, Physics, University of New England, Armidale, NSW 2351 (Australia); Buick, J M [Mechanical and Design Engineering, Anglesea Building, Anglesea Road, University of Portsmouth, Portsmouth, PO1 3DJ (United Kingdom)

2008-10-21

Near-wall shear is known to be important in the pathogenesis and progression of atherosclerosis. In this paper, the shear field in a three-dimensional model of the human carotid artery is presented. The simulations are performed using the lattice Boltzmann model and are presented at six times of interest during a physiologically accurate velocity waveform. The near-wall shear rate and von Mises effective shear are also examined. Regions of low near-wall shear rates are observed near the outer wall of the bifurcation and in the lower regions of the external carotid artery. These are regions where low near-wall velocity and circulatory flows have been observed and are regions that are typically prone to atherosclerosis.

Three-dimensional modelling of the human carotid artery using the lattice Boltzmann method: II. Shear analysis

International Nuclear Information System (INIS)

Boyd, J; Buick, J M

2008-01-01

Near-wall shear is known to be important in the pathogenesis and progression of atherosclerosis. In this paper, the shear field in a three-dimensional model of the human carotid artery is presented. The simulations are performed using the lattice Boltzmann model and are presented at six times of interest during a physiologically accurate velocity waveform. The near-wall shear rate and von Mises effective shear are also examined. Regions of low near-wall shear rates are observed near the outer wall of the bifurcation and in the lower regions of the external carotid artery. These are regions where low near-wall velocity and circulatory flows have been observed and are regions that are typically prone to atherosclerosis.

Turing-Hopf bifurcations in a predator-prey model with herd behavior, quadratic mortality and prey-taxis

Science.gov (United States)

Liu, Xia; Zhang, Tonghua; Meng, Xinzhu; Zhang, Tongqian

2018-04-01

In this paper, we propose a predator-prey model with herd behavior and prey-taxis. Then, we analyze the stability and bifurcation of the positive equilibrium of the model subject to the homogeneous Neumann boundary condition. By using an abstract bifurcation theory and taking prey-tactic sensitivity coefficient as the bifurcation parameter, we obtain a branch of stable nonconstant solutions bifurcating from the positive equilibrium. Our results show that prey-taxis can yield the occurrence of spatial patterns.

Bifurcating Particle Swarms in Smooth-Walled Fractures

Science.gov (United States)

Pyrak-Nolte, L. J.; Sun, H.

2010-12-01

Particle swarms can occur naturally or from industrial processes where small liquid drops containing thousands to millions of micron-size to colloidal-size particles are released over time from seepage or leaks into fractured rock. The behavior of these particle swarms as they fall under gravity are affected by particle interactions as well as interactions with the walls of the fractures. In this paper, we present experimental results on the effect of fractures on the cohesiveness of the swarm and the formation of bifurcation structures as they fall under gravity and interact with the fracture walls. A transparent cubic sample (100 mm x 100 mm x 100 mm) containing a synthetic fracture with uniform aperture distributions was optically imaged to quantify the effect of confinement within fractures on particle swarm formation, swarm velocity, and swarm geometry. A fracture with a uniform aperture distribution was fabricated from two polished rectangular prisms of acrylic. A series of experiments were performed to determine how swarm movement and geometry are affected as the walls of the fracture are brought closer together from 50 mm to 1 mm. During the experiments, the fracture was fully saturated with water. We created the swarms using two different particle sizes in dilute suspension (~ 1.0% by mass). The particles were 3 micron diameter fluorescent polymer beads and 25 micron diameter soda-lime glass beads. Experiments were performed using swarms that ranged in size from 5 µl to 60 µl. The swarm behavior was imaged using an optical fluorescent imaging system composed of a CCD camera illuminated by a 100 mW diode-pumped doubled YAG laser. As a swarm falls in an open-tank of water, it forms a torroidal shape that is stable as long as no ambient or background currents exist in the water tank. When a swarm is released into a fracture with an aperture less than 5 mm, the swarm forms the torroidal shape but it is distorted because of the presence of the walls. The

Symmetry breaking bifurcations of a current sheet

International Nuclear Information System (INIS)

Parker, R.D.; Dewar, R.L.; Johnson, J.L.

1988-08-01

Using a time evolution code with periodic boundary conditions, the viscoresistive hydromagnetic equations describing an initially static, planar current sheet with large Lundquist number have been evolved for times long enough to reach a steady state. A cosh 2 x resistivity model was used. For long periodicity lengths, L p , the resistivity gradient drives flows which cause forced reconnection at X point current sheets. Using L p as a bifurcation parameter, two new symmetry breaking bifurcations were found - a transition to an asymmetric island chain with nonzero, positive or negative phase velocity, and a transition to a static state with alternating large and small islands. These states are reached after a complex transient behavior which involves a competition between secondary current sheet instability and coalescence. 31 refs., 6 figs

Experimental Study of Flow in a Bifurcation

Science.gov (United States)

Fresconi, Frank; Prasad, Ajay

2003-11-01

An instability known as the Dean vortex occurs in curved pipes with a longitudinal pressure gradient. A similar effect is manifest in the flow in a converging or diverging bifurcation, such as those found in the human respiratory airways. The goal of this study is to characterize secondary flows in a bifurcation. Particle image velocimetry (PIV) and laser-induced fluorescence (LIF) experiments were performed in a clear, plastic model. Results show the strength and migration of secondary vortices. Primary velocity features are also presented along with dispersion patterns from dye visualization. Unsteadiness, associated with a hairpin vortex, was also found at higher Re. This work can be used to assess the dispersion of particles in the lung. Medical delivery systems and pollution effect studies would profit from such an understanding.

Bifurcation of Lane Change and Control on Highway for Tractor-Semitrailer under Rainy Weather

Directory of Open Access Journals (Sweden)

Tao Peng

2017-01-01

Full Text Available A new method is proposed for analyzing the nonlinear dynamics and stability in lane changes on highways for tractor-semitrailer under rainy weather. Unlike most of the literature associated with a simulated linear dynamic model for tractor-semitrailers steady steering on dry road, a verified 5DOF mechanical model with nonlinear tire based on vehicle test was used in the lane change simulation on low adhesion coefficient road. According to Jacobian matrix eigenvalues of the vehicle model, bifurcations of steady steering and sinusoidal steering on highways under rainy weather were investigated using a numerical method. Furthermore, based on feedback linearization theory, taking the tractor yaw rate and joint angle as control objects, a feedback linearization controller combined with AFS and DYC was established. The numerical simulation results reveal that Hopf bifurcations are identified in steady and sinusoidal steering conditions, which translate into an oscillatory behavior leading to instability. And simulations of urgent step and single-lane change in high velocity show that the designed controller has good effects on eliminating bifurcations and improving lateral stability of tractor-semitrailer, during lane changing on highway under rainy weather. It is a valuable reference for safety design of tractor-semitrailers to improve the traffic safety with driver-vehicle-road closed-loop system.

Bifurcation of cubic nonlinear parallel plate-type structure in axial flow

International Nuclear Information System (INIS)

Lu Li; Yang Yiren

2005-01-01

The Hopf bifurcation of plate-type beams with cubic nonlinear stiffness in axial flow was studied. By assuming that all the plates have the same deflections at any instant, the nonlinear model of plate-type beam in axial flow was established. The partial differential equation was turned into an ordinary differential equation by using Galerkin method. A new algebraic criterion of Hopf bifurcation was utilized to in our analysis. The results show that there's no Hopf bifurcation for simply supported plate-type beams while the cantilevered plate-type beams has. At last, the analytic expression of critical flow velocity of cantilevered plate-type beams in axial flow and the purely imaginary eigenvalues of the corresponding linear system were gotten. (authors)

On the analysis of local bifurcation and topological horseshoe of a new 4D hyper-chaotic system

International Nuclear Information System (INIS)

Zhou, Leilei; Chen, Zengqiang; Wang, Zhonglin; Wang, Jiezhi

2016-01-01

Highlights: • A new 4D smooth quadratic autonomous system with complex hyper-chaotic dynamics is presented. • The stability of equilibria is observed near the bifurcation points. • The Hopf bifurcation and pitchfork bifurcation are analyzed by using the center manifold theorem and bifurcation theory. • A horseshoe with two-directional expansions in the 4D hyper-chaotic system has been found, which rigorously proves the existence of hyper-chaos in theory. - Abstract: In this paper, a new four-dimensional (4D) smooth quadratic autonomous system with complex hyper-chaotic dynamics is presented and analyzed. The Lyapunov exponent (LE) spectrum, bifurcation diagram and various phase portraits of the system are provided. The stability, Hopf bifurcation and pitchfork bifurcation of equilibrium point are discussed by using the center manifold theorem and bifurcation theory. Numerical simulation results are consistent with the theoretical analysis. Besides, by combining the topological horseshoe theory with a computer-assisted method of Poincaré maps and utilizing the algorithm for finding horseshoes in 3D hyper-chaotic maps, a horseshoe with two-directional expansions in the 4D hyper-chaotic system is successfully found, which rigorously proves the existence of hyper-chaos in theory.

Bifurcations and Patterns in Nonlinear Dissipative Systems

Energy Technology Data Exchange (ETDEWEB)

Guenter Ahlers

2005-05-27

This project consists of experimental investigations of heat transport, pattern formation, and bifurcation phenomena in non-linear non-equilibrium fluid-mechanical systems. These issues are studies in Rayleigh-B\\'enard convection, using both pure and multicomponent fluids. They are of fundamental scientific interest, but also play an important role in engineering, materials science, ecology, meteorology, geophysics, and astrophysics. For instance, various forms of convection are important in such diverse phenomena as crystal growth from a melt with or without impurities, energy production in solar ponds, flow in the earth's mantle and outer core, geo-thermal stratifications, and various oceanographic and atmospheric phenomena. Our work utilizes computer-enhanced shadowgraph imaging of flow patterns, sophisticated digital image analysis, and high-resolution heat transport measurements.

Bifurcation Regulations Governed by Delay Self-Control Feedback in a Stochastic Birhythmic System

Science.gov (United States)

Ma, Zhidan; Ning, Lijuan

2017-12-01

We aim to investigate bifurcation behaviors in a stochastic birhythmic van der Pol (BVDP) system subjected to delay self-control feedback. First, the harmonic approximation is adopted to drive the delay self-control feedback to state variables without delay. Then, Fokker-Planck-Kolmogorov (FPK) equation and stationary probability density function (SPDF) for amplitude are obtained by applying stochastic averaging method. Finally, dynamical scenarios of the change of delay self-control feedback as well as noise that markedly influence bifurcation performance are observed. It is found that: the big feedback strength and delay will suppress the large amplitude limit cycle (LC) while the relatively big noise strength facilitates the large amplitude LC, which imply the proposed regulation strategies are feasible. Interestingly enough, the inner LC is never destroyed due to noise. Furthermore, the validity of analytical results was verified by Monte Carlo simulation of the dynamics.

Equilibrium-torus bifurcation in nonsmooth systems

DEFF Research Database (Denmark)

Zhusubahyev, Z.T.; Mosekilde, Erik

2008-01-01

Considering a set of two coupled nonautonomous differential equations with discontinuous right-hand sides describing the behavior of a DC/DC power converter, we discuss a border-collision bifurcation that can lead to the birth of a two-dimensional invariant torus from a stable node equilibrium...... point. We obtain the chart of dynamic modes and show that there is a region of parameter space in which the system has a single stable node equilibrium point. Under variation of the parameters, this equilibrium may disappear as it collides with a discontinuity boundary between two smooth regions...... in the phase space. The disappearance of the equilibrium point is accompanied by the soft appearance of an unstable focus period-1 orbit surrounded by a resonant or ergodic torus. Detailed numerical calculations are supported by a theoretical investigation of the normal form map that represents the piecewise...

Impact of leakage delay on bifurcation in high-order fractional BAM neural networks.

Science.gov (United States)

Huang, Chengdai; Cao, Jinde

2018-02-01

The effects of leakage delay on the dynamics of neural networks with integer-order have lately been received considerable attention. It has been confirmed that fractional neural networks more appropriately uncover the dynamical properties of neural networks, but the results of fractional neural networks with leakage delay are relatively few. This paper primarily concentrates on the issue of bifurcation for high-order fractional bidirectional associative memory(BAM) neural networks involving leakage delay. The first attempt is made to tackle the stability and bifurcation of high-order fractional BAM neural networks with time delay in leakage terms in this paper. The conditions for the appearance of bifurcation for the proposed systems with leakage delay are firstly established by adopting time delay as a bifurcation parameter. Then, the bifurcation criteria of such system without leakage delay are successfully acquired. Comparative analysis wondrously detects that the stability performance of the proposed high-order fractional neural networks is critically weakened by leakage delay, they cannot be overlooked. Numerical examples are ultimately exhibited to attest the efficiency of the theoretical results. Copyright © 2017 Elsevier Ltd. All rights reserved.

Analysis of the magnetohydrodynamic equations and study of the nonlinear solution bifurcations

International Nuclear Information System (INIS)

Morros Tosas, J.

1989-01-01

The nonlinear problems related to the plasma magnetohydrodynamic instabilities are studied. A bifurcation theory is applied and a general magnetohydrodynamic equation is proposed. Scalar functions, a steady magnetic field and a new equation for the velocity field are taken into account. A method allowing the obtention of suitable reduced equations for the instabilities study is described. Toroidal and cylindrical configuration plasmas are studied. In the cylindrical configuration case, analytical calculations are performed and two steady bifurcated solutions are found. In the toroidal configuration case, a suitable reduced equation system is obtained; a qualitative approach of a steady solution bifurcation on a toroidal Kink type geometry is carried out [fr

Coordinating bifurcated remediation of soil and groundwater at sites containing multiple operable units

International Nuclear Information System (INIS)

Laney, D.F.

1996-01-01

On larger and/or more complex sites, remediation of soil and groundwater is sometimes bifurcated. This presents some unique advantages with respect to expedited cleanup of one medium, however, it requires skillful planning and significant forethought to ensure that initial remediation efforts do not preclude some long-term options, and/or unduly influence the subsequent selection of a technology for the other operable units and/or media. this paper examines how the decision to bifurcate should be approached, the various methods of bifurcation, the advantages and disadvantages of bifurcation, and the best methods to build flexibility into the design of initial remediation systems so as to allow for consideration of a fuller range of options for remediation of other operable units and/or media at a later time. Pollutants of concern include: metals; petroleum hydrocarbons; and chlorinated solvents

Climate bifurcation during the last deglaciation?

NARCIS (Netherlands)

Lenton, T.M.; Livina, V.N.; Dakos, V.; Scheffer, M.

2012-01-01

There were two abrupt warming events during the last deglaciation, at the start of the Bolling-Allerod and at the end of the Younger Dryas, but their underlying dynamics are unclear. Some abrupt climate changes may involve gradual forcing past a bifurcation point, in which a prevailing climate state