Low Loss Photonic Crystal Waveguide by Elliptical Unit Cell Structure

Author(s):  
Jiguang Li ◽  
Z. Huang
2014 ◽  
Vol 70 (a1) ◽  
pp. C1135-C1135
Author(s):  
Patrik Ahvenainen ◽  
Ritva Serimaa

Cellulose is the most abundant biopolymer on Earth and hence it has enormous potential as a source of renewable energy. The nanoscale properties of cellulose are also import for the wood and papermaking industries. The atomic level structure of naturally occurring cellulose Iβ allomorph is well known [1] and this atomistic model is employed in this study for the cellulose unit cell structure. The cellulose crystallinity cannot be measured directly with scattering methods, but the crystallinity of the sample can be estimated by fitting models of crystalline and amorphous contributions to the sample intensity profile. The crystallinity fitting can be enhanced by improving the cellulose fitting model or the amorphous model. We focus on the cellulose crystallite model. The nanoscale level organization of crystalline cellulose in different plant materials is less well established that the unit cell structure of cellulose Iβ. Information on the texture of the sample is obtained efficiently by measuring the sample with a two-dimensional detector. The two-dimensional diffraction pattern can be used to obtain a wealth of information in one measurement, including the crystallite size, crystallite orientation and the crystallinity of the sample. The small size of cellulose crystallites in the wood cell wall limits the information obtainable from the diffraction pattern as the diffraction peaks widen and overlap. The overlapping of certain diffraction peaks can be studied at least qualitatively by computing the diffraction patterns from crystallite models of varying dimensions. Different models for cellulose crystallite have been suggested in the literature, such as the 36 chain model [2]. We investigate how the crystallinity fitting is influenced by the selected cellulose crystallite model and evaluate the suitability of different models to experimental X-ray scattering data of plant material, wood and highly crystalline cellulose.


2019 ◽  
Vol 12 (1) ◽  
pp. 012005 ◽  
Author(s):  
Xiongbin Yu ◽  
Masaki Sugeta ◽  
Yuichiro Yamagami ◽  
Masayuki Fujita ◽  
Tadao Nagatsuma

Optik ◽  
2014 ◽  
Vol 125 (12) ◽  
pp. 2930-2933 ◽  
Author(s):  
Aayushi Wadhwa ◽  
Mukesh Kumar

2011 ◽  
Vol 82 (3) ◽  
pp. 220-241 ◽  
Author(s):  
Kadir Bilisik ◽  
Nesrin Sahbaz

The aim of this study was to understand the effects of braid pattern and the number of layers on three-dimensional (3D) braided unit cell structures. Various unit cell-based representative 3D braided preforms were developed. Data generated from these structures included unit cell dimensions, yarn angle, and yarn length in the unit cell structures. It was shown that braid patterns affected the 3D braided unit cell structures. The 1 × 1 braid pattern made fully interconnected integral 3D braided unit cell structures, whereas the 2 × 1 braid pattern created disconnected braid layers that were connected to the structures edges. When the number of layers increased, 3D braided unit cell thickness also increased. Braid pattern slightly affected the braider yarn angle, whereas the number of layers did not influence it. It was observed that the number of layers considerably affected the yarn length in the unit cell structure. Increasing the layer number from five to 10 layers created a yarn path in the unit cell edge regions called the ‘multilayer yarn length’. This yarn path was not observed below five-layer 3D braided unit cell structures. In jamming conditions, minimum jamming decreased the width of the unit cell structure, but maximum jamming increased its width. On the other hand, minimum jamming decreased the surface angle of the unit cell structure, whereas maximum jamming increased the surface angle. In addition, it was realized that jamming conditions influenced the density of the unit cell but did not affect the yarn length in the unit cell structures.


2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Muhammad Tauseef Asim ◽  
Mushtaq Ahmed

A dual layer periodically patterned metamaterial inspired antenna on a low cost FR4 substrate is designed, simulated, fabricated, and tested. The eigenmode dispersion simulations are performed indicating the left handed metamaterial characteristics and are tunable with substrate permittivity. The same metamaterial unit cell structure is utilized to fabricate a metascreen. This metascreen is applied below the proposed metamaterial antenna and next used as superstrate above a simple patch to study the effects on impedance bandwidth, gain, and radiation patterns. The experimental results of these antennas are very good and closely match with the simulations. More importantly, the resonance for the proposed metamaterial antenna with metascreen occurs at the left handed (LH) eigenfrequency of the metamaterial unit cell structure. The measured −10 dB bandwidths are 14.56% and 22.86% for the metamaterial antenna with single and double metascreens, respectively. The metascreens over the simple patch show adjacent dual band response. The first and second bands have measured −10 dB bandwidths of 9.6% and 16.66%. The simulated peak gain and radiation efficiency are 1.83 dBi and 74%, respectively. The radiation patterns are also very good and could be useful in the UWB wireless applications.


2016 ◽  
Vol 145 (17) ◽  
pp. 174706 ◽  
Author(s):  
Tobias Huempfner ◽  
Martin Hafermann ◽  
Christian Udhardt ◽  
Felix Otto ◽  
Roman Forker ◽  
...  

Sign in / Sign up

Export Citation Format

Share Document