How does the concept of a period relate to the study of waves and oscillations?5 answersPeriods in the study of waves and oscillations play a crucial role in understanding their fundamental characteristics. The concept of a period refers to the time taken for a wave or an oscillation to complete one full cycle. Various research works have delved into determining periods in different contexts. For instance, a study by Sato et al. demonstrates how oscillations in the Earth's magnetosphere following sudden impacts can be explained using a simple model with no free parameters, showcasing the importance of understanding period characteristics. Additionally, Kontomaris and Malamou propose a simplified method for determining the period of nonlinear oscillations using computational tools, making it accessible for introductory physics courses. These insights highlight the significance of periods in analyzing and predicting wave and oscillatory behaviors across different scientific domains.
Is coronary artery bifurcation angle measurement using coronary CT angiography accurate?5 answersCoronary artery bifurcation angle measurement using coronary CT angiography has been shown to be accurate in several studies. One study found a strong correlation between the true and measured bifurcation angles using CT angiography. Another study demonstrated that CT angiography can identify morphological changes in coronary artery sclerosis with comparable results to the reference method of intravascular ultrasound. Additionally, a study comparing CT angiography to invasive coronary angiography found that CT angiography by bifurcation angle measurement showed significant improvement in the diagnosis of calcified plaques, with diagnostic value comparable to invasive coronary angiography. These findings suggest that coronary CT angiography can accurately measure coronary artery bifurcation angles and provide valuable information for the assessment of coronary artery disease.
What is period doubling in FSI?4 answersPeriod doubling in FSI refers to a universal bifurcation phenomenon observed in various nonlinear systems. It is characterized by the system evolving with a period that is twice that of the driving force or parameter. In the context of ultrafast laser systems, period doubling bifurcations have been observed in dissipative solitons, leading to spectral pulsations and instabilities. These bifurcations can be triggered by self-phase modulation and can exhibit complex combinations with other bifurcations, resulting in entrainment phenomena and the coexistence of multiple pulsating frequencies. In the context of rock friction, period doubling bifurcation of stress drop has been observed due to macroscopic heterogeneity of the sliding surface, resulting in alternating strain release along the fault. In the quantum realm, period doubling has been studied in periodically driven many-body open quantum systems, where the classical period doubling manifests as period-one dynamics in the quantum steady state.
What is period doubling?5 answersPeriod doubling refers to a universal bifurcation phenomenon in nonlinear systems where a system transitions from a stable state to a state with two alternating periods. It is a significant phenomenon observed in various fields, including nonlinear science and laser systems. In the context of ultrafast lasers, period doubling has been studied extensively, and its physical origin has been a topic of debate. In the context of phonation, period doubling is observed in creaky voice, where two alternating periods with distinct voice qualities and pitches are produced. In the context of oscillators, period doubling can lead to complex dynamical behaviors, such as mixed-mode oscillations, which consist of large amplitude spikes followed by small amplitude peaks. In the context of multimode fiber lasers, period doubling is observed to affect the pulse train modulation and output beam profile. Perception studies have also investigated period doubling in voice and found that the degree of modulation between the two alternating periods influences the perceived pitch.
What are the mathematical expressions for vortex-induced-vibrations, galloping, and flutter, in flow-induced-vibrations?3 answersVortex-induced vibrations (VIV) are motions induced on structures by irregularities in fluid flow. The mathematical expressions for VIV are not explicitly mentioned in the abstracts provided. Galloping is observed in non-circular cylinders and the abstract by Park et al.mentions a mathematical model used to estimate fluid forces during VIV and soft galloping. However, the specific mathematical expressions for galloping are not provided. Flutter, another type of flow-induced vibration, is not mentioned in the abstracts.
When is second order ODE oscillatory?5 answersSecond-order ODEs can exhibit oscillatory behavior under certain conditions. The oscillatory properties of these equations depend on various factors such as the form of the equation, the presence of delay or advanced arguments, and the behavior of the functions involved. Several papers have studied the oscillation properties of second-order ODEs. Hassan et al. propose new oscillation criteria for noncanonical second-order dynamic equations on time scales. Džurina establishes a comparison theorem for deducing oscillation of noncanonical nonlinear differential equations. Aloui investigates the oscillation properties of solutions to a nonlinear scalar second-order ODE. Baculíková introduces new oscillatory criteria for second-order noncanonical differential equations with delay arguments. Li and Rogovchenko study the oscillatory behavior of solutions to second-order nonlinear neutral differential equations. These papers provide valuable insights into the conditions under which second-order ODEs exhibit oscillatory behavior.