Ultrafast Fiber Lasers
Iniewski Krzysztof in Integrated Microsystems, 2017
Things are a little different when working at the 1 μm region. Conventionally, ultrashort pulse mode-locked fiber lasers operating at wavelengths below 1.3 μm pose a challenge in that there is no simple all-fiber-based solution for dispersion compensation in this wavelength regime. Dispersion is a phenomenon that causes the separation of a wave into spectral components with different wavelengths, due to the dependence of the component’s speed on its wavelength (i.e., wavelength-dependent index of refraction). Normal dispersion is the dispersion in which the refractive index decreases monotonically and continuously with increasing wavelength; anomalous dispersion is the opposite. For wavelengths above 1.3 μm, several types of fibers exist exhibiting either normal or anomalous dispersion; by splicing different lengths of fibers together, one can obtain a cavity with adjustable overall dispersion. Below 1.3 μm, only normal dispersion fibers existed; so previous researchers used bulk devices (e.g., grating pairs and prisms) to provide an adjustable amount of dispersion for the cavity. Unfortunately, these devices require the coupling of the fiber into a bulk device, which results in a laser that is highly sensitive to alignment and thus the environment.
Statistics You Need
Saif Aldeen Saleh AlRyalat, Shaher Momani in A Beginner's Guide to Using Open Access Data, 2019
Descriptive statistics are used to describe the basic features of the data in a study. They provide simple summaries about a sample to help us to simplify large amounts of data in a sensible way. There are three major characteristics of a single variable that we tend to look at in descriptive statistics: distribution, central tendency, and dispersion. Distribution is a summary of the frequency of individual values or ranges of values for a variable. Central tendency is an estimate of the center of distribution of values by using mean, median, and mode. Dispersion is the spread of the values around the central tendency, represented by range, variance, and standard deviation (SD). These will be further discussed later in this chapter in the section “Statistical Analyses.”
Multiphoton imaging of the retina
Pablo Artal in Handbook of Visual Optics, 2017
This parameter is related to the shape of the spectral amplitude distribution. For example, for pulses with Gaussian spectral profiles, the time-bandwidth product is 0.44. While shorter pulses improve the probability of two-photon absorption, there is a trade-off associated with the broader spectral bandwidth. The refractive indices of optical media are dependent on the wavelength of light propagating through them; this is known as dispersion. Dispersion causes different wavelengths to propagate at different velocities that spread the pulse in time and in turn reduces the probability of two-photon absorption. Broadband pulses could also suffer from chromatic aberration, which can cause different spectral components to focus at different focal planes. Additionally, the combination of chromatic aberration and dispersion can affect the spatiotemporal profile of ultrashort pulses near the focal plane, a phenomenon known as propagation time delay (Bor, 1988; Kempe et al., 1992). For singlet lenses, radially dependent dispersion delays radial components of the beam differently, consequently preventing light at the exit pupil from arriving at the focal region at the same time. This can affect the realistically achievable lateral and axial resolution from such imaging systems.
Adsorption and sensing of an anticancer drug on the boron nitride nanocones; a computational inspection
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Chao Wang, Lizhen Shen, Liang Wu
The method most DFT used nowadays to calculate ground-state electronic structure calculations of atoms, molecules, and solid-state materials. This calculation based on the first and second Hohenberg-Kohn theorems. Also, the Thomas-Fermi approximation and Kohn-Sham equations were used for evaluating the ground-state energy. Furthermore, the exchange-correlation energy contribution to the Kohn-Sham equations can be approximated by the local density approximation or several other approximations. When used functional and basis set with low accuracy the obtained results was may be very different from the experimental values. For solving this problem was used B3LYP functional and basis set 6-31 (d) with high accuracy. Also, it was applied dispersion term to calculate intermolecular interaction energies. The dispersion was used this article as follows:
Orally administered self-emulsifying drug delivery system in disease management: advancement and patents
Published in Expert Opinion on Drug Delivery, 2021
Vijay Mishra, Pallavi Nayak, Nishika Yadav, Manvendra Singh, Murtaza M. Tambuwala, Alaa A. A. Aljabali
The rate of self-emulsification is usually determined by keeping self-emulsifying formulations (pre-concentrate) in a capsule and it to a sufficient amount of water or bio-relevant media. The rate of dispersion is determined by visually. Light microscopy is used to observe the process of self-emulsification. The USP XXII dissolution apparatus can be used for determining the efficiency of oral nanoemulsion or microemulsion. In this case, sample formulation (1 mL) is mixed with water (500 mL) at temperature of 37 ± 1°C. For continuous agitation stainless steel dissolution paddle has been utilized with the stirring speed 100 rpm and the time is noted for the emulsion formation. The precipitation and the phase separation of resultant mixture are checked at different time intervals (2, 4, 6, 8, 12, 24 h). Grading system, used for evaluating the in vitro performance [34] is given below:
Analyzing clustered count data with a cluster-specific random effect zero-inflated Conway–Maxwell–Poisson distribution
Published in Journal of Applied Statistics, 2018
Hyoyoung Choo-Wosoba, Somnath Datta
This simulation section contains three types of investigations into the finite sample behaviors of our inferential methodology. First, we study the behaviors of the point estimators in terms of their bias and variance. We also study the performance of approximating normal distribution-based confidence intervals for the parameter of interest using two types of variance estimates. Next we conduct a power analysis for a statistical test for a regression effect based on an approximate Wald test; one again both variance estimates have been attempted to standardize the test statistic. The third subsection contains the simulation results for the zero-inflation test. We study the size/power of the test for three choices of the dispersion parameter corresponding to three types of dispersion patterns.
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