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Bifurcation structure of a swept-source laser
摘要： We numerically analyze a delay differential equation model of a short-cavity semiconductor laser with an intracavity frequency-swept filter and reveal a complex bifurcation structure responsible for the asymmetry of the output characteristics of this laser. We show that depending on the direction of the frequency sweep of a narrow-band filter, there exist two bursting cycles determined by different parts of a continuous-wave solutions branch.
关键词： delay differential equation,frequency-swept filter,swept-source laser,semiconductor laser,bifurcation structure
更新于2025-09-19 17:13:59
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Primary percutaneous coronary intervention for a left main bifurcation lesion without stenting using excimer laser with optical coherence tomography guidance: a case report
摘要： Optimal strategy for treating bifurcation lesions or lesions with large thrombus in left main disease remains elusive. Excimer laser coronary angioplasty (ELCA) is a therapeutic option for thrombotic lesions in acute coronary syndrome. A 68-year-old man with chest pain was transferred to our emergency department, and subsequently diagnosed as inferior ST-segment elevation myocardial infarction (STEMI). Emergent coronary angiography revealed a 75% stenosis in the left main trunk (LMT). Optical coherence tomography (OCT) showed massive thrombus at the distal LMT to the ostial left anterior descending artery (LAD) and left circumflex artery (LCx). ELCA was performed in the three directions from LMT to proximal LAD, proximal LCx, and obtuse marginal branch. OCT after ELCA showed reduction of thrombus and no apparent plaque rupture or calcification, implying that coronary thrombosis was caused by OCT-defined plaque erosion. Intracoronary electrocardiogram of the LCx showed ST-segment elevation which corresponded to inferior ST-segment elevation, whereas no intracoronary electrocardiogram ST-segment elevation was detected for LAD. Taking all of the data including angiographic appearance, OCT-derived residual lumen size and residual thrombus volume, and strategic options into consideration, we completed percutaneous coronary intervention without stent deployment. He has been free from any cardiac events thereafter for 8 months. Optimal strategy of coronary intervention for bifurcation lesions, especially LMT bifurcations, remains elusive. ELCA may have a potential to safely reduce intracoronary thrombus in patients presenting with acute coronary syndrome with OCT guidance.
关键词： Plaque erosion,Excimer laser coronary angioplasty,Case report,Bifurcation,Left main disease,Stentless
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Transparent WO <sub/>x</sub> window layers for silicon based heterojunction solar cells
摘要： As a major application domain of vascular ultrasound, the carotid artery has long been the subject of anthropomorphic phantom design. It is nevertheless not trivial to develop walled carotid phantoms that are compatible for use in integrative imaging of carotid wall motion and flow dynamics. In this paper, we present a novel phantom design protocol that can enable efficient fabrication of walled carotid bifurcation phantoms with: 1) high acoustic compatibility; 2) artery-like vessel elasticity; and 3) stenotic narrowing feature. Our protocol first involved direct fabrication of the vessel core and an outer mold using computer-aided design tools and 3-D printing technology; these built parts were then used to construct an elastic vessel tube through investment casting of a polyvinyl alcohol containing mixture, and an agar-gelatin tissue mimicking slab was formed around the vessel tube. For demonstration, we applied our protocol to develop a set of healthy and stenosed (25%, 50%, and 75%) carotid bifurcation phantoms. Plane wave imaging experiments were performed on these phantoms using an ultrasound scanner with channel-level configurability. Results show that the wall motion dynamics of our phantoms agreed with pulse wave propagation in an elastic vessel (pulse wave velocity of 4.67 ± 0.71 m/s measured at the common carotid artery), and their flow dynamics matched the expected ones in healthy and stenosed bifurcation (recirculation and flow jet formation observed). Integrative imaging of vessel wall motion and blood flow dynamics in our phantoms was also demonstrated, from which we observed fluid-structure interaction differences between healthy and diseased bifurcation phantoms. These findings show that the walled bifurcation phantoms developed with our new protocol are useful in vascular imaging studies that individually or jointly assess wall motion and flow dynamics.
关键词： carotid bifurcation phantom,vessel wall motion,integrative imaging,Blood flow dynamics
更新于2025-09-19 17:13:59
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Bifurcation of finitely deformed thick-walled electroelastic spherical shells subject to a radial electric field
摘要： This paper is concerned with the bifurcation analysis of a pressurized electroelastic spherical shell with compliant electrodes on its inner and outer boundaries. The theory of small incremental electroelastic deformations superimposed on a radially finitely deformed electroelastic thick-walled spherical shell is used to determine those underlying configurations for which the superimposed deformations do not maintain the perfect spherical shape of the shell. Specifically, axisymmetric bifurcations are analyzed, and results are obtained for three different electroelastic energy functions, namely electroelastic counterparts of the neo-Hookean, Gent and Ogden elastic energy functions. For the neo-Hookean energy function it was reported previously that for the purely mechanical case axisymmetric bifurcations are possible under external pressure only, no bifurcation solutions being possible for internally pressurized spherical shells. In the case of an electroelastic neo-Hookean model bifurcation under internal pressure becomes possible when the potential difference between the electrodes exceeds a certain value, which depends on the ratio of inner to outer undeformed radii. Results obtained for the three classes of model are significantly different and are illustrated for a range of fixed values of the potential difference. Although of less practical significance, results are also shown for fixed charges, and these are both different between the models and different from the case of fixed potential difference.
关键词： neo-Hookean,Ogden,spherical shell,potential difference,Gent,fixed charges,electroelastic,bifurcation
更新于2025-09-16 10:30:52
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Numerical study of Riskena??Nummedala??Grahama??Haken instability in mid-infrared Fabrya??P??rot quantum cascade lasers
摘要： We review our recent theoretical studies on multimode instabilities in Fabry–Pérot cavity mid-infrared quantum cascade lasers (QCLs) caused by parametric excitation of Rabi flopping oscillations. Numerical simulations are based on the semiclassical traveling wave Maxwell–Bloch equations. QCLs with a few mm cavity without an absorber exhibit intermittent RNGH self-pulsations, while regular self-pulsations are possible in short-cavity QCLs, with the cavity length of 100 μm or smaller. However, the second threshold in short-cavity QCLs is significantly increased compared to the values for a few mm long devices. We provide here a new insight on RNGH instability via bifurcation analysis of the output waveform and studies of the recurrence period density entropy. We propose an interpretation of the broadening/narrowing of the optical spectrum of a QCL i.e. switching the RNGH instability on and off observed in experiment.
关键词： Quantum cascade laser,RNGH instability,Self-pulsations,Bifurcation diagram,Spatial hole burning
更新于2025-09-16 10:30:52
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Design Rules for Producing Cardiovascular Stents by Selective Laser Melting: Geometrical Constraints and Opportunities
摘要： Additive Manufacturing (AM) has risen great interest in biomedical applications, for its flexibility and the possibility of producing patient-customized devices. Customization has high importance to limit inflammation and rejection. Moreover, some occlusions may take place in bifurcation sites, which require the insertion of multiple stents, increasing the risk and complexity of the procedure. Selective Laser Melting (SLM) can be exploited to realize metallic stents with geometries not depending on tubular precursor, allowing the study of devices with new shapes, such as for occlusions in high-tortuosity vessels and in bifurcated arteries. The geometrical flexibility of SLM is largely exploited for large components, while for small implants such as cardiovascular stents it has not been studied in depth. Accordingly, this work analyses the geometrical requirements of cardiovascular stents starting from traditional meshes and identifies design rules for AM. Initially, traditional stent meshes are analysed to assess their feasibility in layer-by-layer production by SLM. An accurate investigation of the limitations imposed by the powder-bed process nature, the powder size and the laser spot diameter is performed, considering the relationship with stent dimensions, cell shape and strut inclinations. Finally, a set of design rules for SLM of stents are defined. These rules are used to design novel meshes producible with an industrial SLM system using cobalt-chromium powder. In particular, tubular stents are produced in expanded and semi-crimped configurations. Additionally, multi-branch stents were designed and produced to prove the capability of the process for bifurcation applications.
关键词： Cobalt-chromium alloy,Selective laser melting,Design for additive manufacturing,Additive manufacturing,Bifurcation
更新于2025-09-12 10:27:22
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Comparison of diagnostic performance in assessing the rewiring position into a jailed side branch between online 3D reconstruction systems version 1.1 and 1.2 derived from optical frequency domain imaging
摘要： The three-dimensional reconstruction of optical coherence tomography and optical frequency domain imaging (3D-OCT/OFDI) helps optimize bifurcation percutaneous coronary interventions (PCIs) with side branch (SB) dilatation by identifying the optimal rewiring position. 3D-OCT/OFDI’s diagnostic performance for assessing the rewiring position into a jailed SB is unknown. We retrospectively evaluated the diagnostic performances of a conventional (ver. 1.1) and a new (ver. 1.2) online 3D-OFDI reconstruction system based on an offline 3D reconstruction system’s performance. We analyzed 45 patients’ 52 OFDI pullbacks with main vessel stenting followed by rewiring into a jailed SB for coronary bifurcation lesions. We counted the undetected stent struts in the polygon of confluence as the stent detection performance. We assessed the diagnostic agreement regarding the rewiring position into a jailed SB by the three 3D reconstruction systems. The percentage of undetected struts and the diagnostic agreement of ver.1.2 were significantly better than those of ver.1.1 [5.1 ± 5.1% vs. 30.2 ± 14.2%; p < 0.0001, and 94.2% (49/52) vs. 76.9% (40/52); p = 0.0120]. The new online 3D-OFDI reconstruction system provides better diagnostic performance than the conventional online system for assessing the rewiring position into a jailed SB.
关键词： Three-dimensional reconstruction,Agreement comparison,Coronary bifurcation stenting,Optical frequency domain imaging,Kissing balloon inflation
更新于2025-09-12 10:27:22
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Neuromorphic dynamics with optically injected quantum dot lasers
摘要： Optically injected quantum dot lasers display many unique nonlinear phenomena and are in particular, excellent testbeds for different forms of excitability. We analyse the recent discovery of Type II excitability in such devices. An optothermal instability leads to the phenomenon and while an underlying Hopf bifurcation is ultimately responsible for the observation, intriguingly there are two potential routes: One via a subcritical bifurcation and an associated bistable region and the other via a supercritical bifurcation and an associated canard explosion.
关键词： optothermal instability,quantum dot lasers,Type II excitability,canard explosion,Hopf bifurcation
更新于2025-09-11 14:15:04
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Study on nonlinear dynamic behavior and stable operation region of single-phase photovoltaic inverter
摘要： In order to design a photovoltaic inverter with excellent performance, the second-order photovoltaic inverter circuit model under current loop proportional control is established in this paper, the discrete iterative model of system is also obtained. The nonlinear behavior of system is analysed in detail through bifurcation diagram, folding diagram and the phase diagram of output current (i) and output voltage (uc). The simulation model is constructed in Matlab/Simulink, and the correctness of theoretical analysis is verified through time domain waveform and phase-space map. The influence of bifurcation and chaos on system spectrum is analysed from the frequency domain. According to the Jacobian matrix of system, the stable operation region of system is given. The experiment shows that the correct selection of circuit parameters is important for the stable operation of system.
关键词： nonlinear dynamic behavior,stable operation region,chaos,bifurcation,photovoltaic inverter
更新于2025-09-11 14:15:04
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Dynamic relaxation oscillations in a nonlinearly driven quartz crystal
摘要： We demonstrate thermo-mechanical relaxation oscillations in a strongly driven quartz crystal. Dynamic bifurcation leads to two stable oscillation states with a distinct electrical impedance. Slow Joule-heating, which shifts the susceptibility of the crystal, provides a feedback that leads to thermally induced oscillations in which the amplitude of the crystal is modulated by a relaxation cycle. The frequency of the relaxation cycle is roughly a million times lower than the resonance frequency of the crystal, and it can be adjusted by the detuning from the critical point for dynamic bifurcation. The experimental observations are reproduced by a simple model that takes into account the slow dynamics of the system.
关键词： dynamic bifurcation,Joule-heating,feedback,thermo-mechanical relaxation oscillations,quartz crystal
更新于2025-09-10 09:29:36