On Finite Element Vibration Analysis of Carbon Nanotubes

In this chapter, a finite element formulation is proposed to study the natural frequencies of double-walled carbon nanotubes modeled as, both, local and nonlocal Euler-Bernoulli beams, coupled with van der Waals interaction forces. The formulation uses Galerkin-weighted residual approach and employs Hermite cubic polynomial function to derive the linear eigenvalue problem. Natural frequencies are found for clamped-free, clamped-clamped and simply supported-simply supported boundary conditions. The results are in good agreement with the formulations found in the literature. The effect of nonlocal factor on the natural frequencies of the system is found out by comparing local and nonlocal results. Additionally, the universality of the proposed model is proven by application to a double-elastic Euler-Bernoulli beam. This formulation paves way for Finite Element Method (FEM) analysis of multi-walled CNTs—either locally or nonlocally

Hanbury Brown and Twiss Interferometry with Twisted Light

The rich physics exhibited by random optical wave fields permitted Hanbury Brown and Twiss to unveil fundamental aspects of light. Furthermore, it has been recognized that optical vortices are ubiquitous in random light and that the phase distribution around these optical singularities inprints a spectrum of orbital angular momentum onto a light field. We demonstrate that random fluctuations of light give rise to the formation of correlations in the orbital angular momentum components and angular positions of pseudothermal light. The presence of these correlations is manisfested through distinct interference structures in the orbital angular momentum-mode distribution of random light. These novel forms of interference correspond to the azimuthal analog of the Hanbury Brown and Twiss effect. This family of effects can be of fundamental importance in applications where entanglement is not required and where correlations in angular position and orbital angular momentum suffice. We also suggest that the azimuthal Hanbury Brown and Twiss effect can be useful in the exploration of novel phenomena in other branches of physics and astrophysics.Comment: Science Advance

DJELOVANJE MIJEŠANJA I RAZINE UKLJUČIVANJA SOJINOG ULJA I NJEGOVE ZAKISELJENE SAPUNASTE SMJESE NA REZULTATE BROJLERA

This study was conducted to investigate the effect of diets containing blends of soy oil and its acidulated soapstock on broiler performance. Six hundred 7–day-old Ross broiler chicks were assigned to factorial arrangement (2×5) with 2 levels of oil (3 , 6%) and 5 blends of soy oil and its soapstock (100:0, 75:25, 50:50, 25:75 and 0:100) with 4 replicates in a completely randomized design . The levels of inclusion of fat in diets had a significant effect on feed intake and feed conversion ratio(FCR), and birds fed diets containing 3% of fat had higher weight gain and better FCR (P<0.05). Weight gain and feed conversion ratio were significantly (P<0.05) affected by the blending ratio of soy oil and its acidulated soapstock. The soy oil: soapstock ratio of 0:100, in diet resulted in significantly lower weight gain, but there were not any significant differences between other blending ratios on weight gain and FCR. The interaction effects of fat levels× blending ratio of soy oil and its acidulated soapstock were significant on weight gain and FCR in the whole rearing period. The weight gain of birds receiving diets containing 6% of fat with the 0:100 (soy oil: soapstock) were significantly lower (P < 0.05) than those in the other treatments. It was concluded that the acidulated soy oil soapstock could be used as an energy source in broiler diets, and the soy oil replaced witht its soapstock by 75% in the whole rearing period.Ovaj je rad proveden radi istraživanja djelovanja obroka sa soijnim uljem i njegovom zakiseljenom sapunastom smjesom na rezultate brojlerskih pilića. Šest 7 dana starih brojlerskih pilića linije Ross svrstano je u faktorijalni red (2x5) s dvije količine ulja (3%,6%) i 5 mješavina sojinog ulja i njegove sapunaste smjese (100:0, 75:25, 50:50, 25:75 i 0:100) s 4 ponavljanja u potpuno slučajnom planu. Razine uključivanja masnoće u obroke imale su značajan učinak na uzimanje hrane i omjer konverzije hrane (FCR), te su pilići hranjeni obrocima s 3% masnoće imali veći prirast tjelesne mase i bolji FCR (P<0.05). Na prirast tjelesne mase i omjer konverzije hrane značajno je djelovao omjer miješanja sojinog ulja i njegove zakiseljene sapunaste smjese (P<0.05). Omjer sojino ulje: sapunasta smjesa od 0:100 u obrocima rezultirao je značajno nižim prirastom tjelesne mase ali nije bilo nikakve druge značajne razlike između drugih omjera miješanja na prirast tjelesne mase i na FCR. Djelovanje interakcije razine masti x omjer miješanja sojinog ulja i zakiseljene sapunaste smjese bilo je značajno na prirast tjelesne mase i FCR u čitavom razdoblju uzgoja. Prirast tjelesne mase pilića koji su dobivali obroke sa 6% masti s 0:100 (sojino ulje : sapunasta smjesa) bio je značajno niži (P<0,05) od prirasta pilića u drugim tretiranjima. Zaključuje se da bi se zakiseljena sapunasta smjesa sojinog ulja mogla upotrijebiti kao izvor energije u obrocima brojlera a sojino ulje nadomjestiti sa 75% sapunaste smjese u čitavom uzgojnom razdoblju

Progress and challenges in electrically pumped GaN-based VCSELs

The Vertical-Cavity Surface-Emitting Laser (VCSEL) is an established optical source in short-distance optical communication links, computer mice and tailored infrared power heating systems. Its low power consumption, easy integration into two-dimensional arrays, and low-cost manufacturing also make this type of semiconductor laser suitable for application in areas such as high-resolution printing, medical applications, and general lighting. However, these applications require emission wavelengths in the blue-UV instead of the established infrared regime, which can be achieved by using GaN-based instead of GaAs-based materials. The development of GaN-based VCSELs is challenging, but during recent years several groups have managed to demonstrate electrically pumped GaN-based VCSELs with close to 1 mW of optical output power and threshold current densities between 3-16 kA/cm2. The performance is limited by challenges such as achieving high-reflectivity mirrors, vertical and lateral carrier confinement, efficient lateral current spreading, accurate cavity length control and lateral optical mode confinement. This paper summarizes different strategies to solve these issues in electrically pumped GaN-VCSELs together with state-of-the-art results. We will highlight our work on combined transverse current and optical mode confinement, where we show that many structures used for current confinement result in unintentionally optically anti-guided resonators. Such resonators can have a very high optical loss, which easily doubles the threshold gain for lasing. We will also present an alternative to the use of distributed Bragg reflectors as high-reflectivity mirrors, namely TiO2/air high contrast gratings (HCGs). Fabricated HCGs of this type show a high reflectivity (>95%) over a 25 nm wavelength span

Life-history and population dynamic of the White treads fish, Holothuria leucospilota in the Iranian part of the Oman Sea with a note on its conservation and management

In the present study, the Life-history and population dynamic characteristics of Holothuria leucospilota were evaluated in the Iranian part of the Oman Sea by sampling at nine sites, including Ramin, Kachoo, Aliabady, Beries, Beries plane, Pasabandar, Tis, Pozm and Gurdium from March 2017 to March 2018. Biometric data of 862 specimens were obtained, and the growth and mortality indices, including infinite length (L? = 50.5 cm), growth coefficient (K = 0.51 (yr-1)), growth performance index (? = 3.11), natural mortality (M = 0.94(yr-1)), fishing mortality (F = 0.56 (yr-1)), total mortality (Z = 1.50±0.12 (yr-1)) and exploitation coefficient (E = 0.36 (yr-1)) and time zero (-0.27) were calculated. Mean of relative production per recruitment (Y' / Rp), relative biomass per recruitment (B' / Rp) and exploitation rate (U) of the studied population of H. leucospilota were 0.02, 0.30, and 0.28, respectively. Mean GSI and maturity stage indicated that the spawning seasons were June (spring) and December (autumn). The mean size at first sexual maturity (LM50) was 246 mm for males, 220 mm for females and 225 mm for both sexes. The results of the current work showed that the studied H. leucospilota stock had not yet reached to overfished’ status