Modeling of wheat crop harvesting losses

Abstract: Recognition of effective factors and using suitable mechanism of crop harvesting can reduce seed losses to an acceptable amount.  To investigate wheat crop losses due to seed moisture content and the speed of combine harvester at seed harvest time, research was carried out in G.B.P.U.A. & T., Pantnagar in 2003.  This study included three seed moisture contents (10%, 15% and 20%) and three combine working speeds (1, 2 and 2.5 km/h) based on split plot by using a randomized block design with three replications.  Finally combine working speed of 1.5 km/h and 9.16% crop moisture content was suitable for harvesting wheat crop.  Stepwise regression technique was used to develop combine losses, seed breakage, performance and threshing efficiency models from field data.  The r2 value for seed breakage, performance efficiency and threshing efficiency were 0.888, 0.676 and 0.803, respectively.   Keywords: multiple regressions, plot combine harvester, stepwise regression, seed breakag

Optimum Power Randomization for the Minimization of Outage Probability

Cataloged from PDF version of article.The optimum power randomization problem is studied to minimize outage probability in flat block-fading Gaussian channels under an average transmit power constraint and in the presence of channel distribution information at the transmitter. When the probability density function of the channel power gain is continuously differentiable with a finite second moment, it is shown that the outage probability curve is a nonincreasing function of the normalized transmit power with at least one inflection point and the total number of inflection points is odd. Based on this result, it is proved that the optimum power transmission strategy involves randomization between at most two power levels. In the case of a single inflection point, the optimum strategy simplifies to on-off signaling for weak transmitters. Through analytical and numerical discussions, it is shown that the proposed framework can be adapted to a wide variety of scenarios including log-normal shadowing, diversity combining over Rayleigh fading channels, Nakagami-m fading, spectrum sharing, and jamming applications. We also show that power randomization does not necessarily improve the outage performance when the finite second moment assumption is violated by the power distribution of the fading. © 2013 IEEE

Design of a compact SOI polarization rotator for mid-IR application

Design of a compact polarization rotator (PR) exploiting power coupling through phase matching between the TM mode of a strip waveguide (WG) and TE mode of a vertical slot WG is presented. Optimized cross sectional dimensions of the coupler have been achieved to use this device as a compact PR at 3 μm wavelength with device length of just 2 mm. We also investigate the device performance at the operating wavelength (λ) = 1.55 μm

Design and Performance Study of a Compact SOI Polarization Rotator at 1.55 mu m

We numerically design a compact silicon (Si) based polarization rotator (PR) by exploiting power coupling through phase matching between the TM mode of a Si strip waveguide (WG) and TE mode of a Si-air vertical slot WG. In such structures, the coupling occurs due to horizontal structural asymmetries and extremely high modal hybridness due to high refractive index contrast of Si-on-insulator (SOI) structure. Design parameters of the coupler have been optimized to achieve a compact PR of ~135 μm length at the telecommunication wavelength of 1.55 μm. Maximum power coupling efficiency Cm, which is studied by examining the transmittance of light, is achieved as high as 80% for both polarization conversions. Fabrication tolerances and the band width of operation of the designed PR have also been studied

An efficient polarization converter for Mid-IR wavelength

Design of a silicon-based polarization converter through phase matched power coupling between TE and TM modes is presented. Conversion efficiency up to 90% is feasible at 3 μm wavelength with device length of 536 μm

Design of a Polymer-Based Hollow-Core Bandgap Fiber for Low-Loss Terahertz Transmission

We use numerical simulations to design a hollowcore microstructured polymer optical fiber (HC-mPOF) suitable for broadband, terahertz (THz) pulse transmission with relatively low losses and small dispersion. The HC-mPOF consists of a central large air-core surrounded by periodically arranged wavelength-scale circular air holes in a hexagonal pattern, embedded in a uniform Teflon matrix. The THz guidance in this fiber is achieved by exploiting the photonic bandgap (PBG) effect. In our low index contrast Teflon-air (1.44:1) hexagonal periodic lattice, the PBG appears only for a certain range of non-zero values of the longitudinal wavevector. We have achieved PBG over a broad spectral range (bandwidth ~400 GHz) ranging from 1.65 to 2.05 THz in the proposed HC-mPOF. The achievable loss coefficient in our designed HC-mPOF is <;4 m-1 and the group velocity dispersion parameter is <;±5 ps/THz·cm over a 300-GHz bandwidth (1.65~1.95 THz)

Specialty Fibers for Terahertz Generation and Transmission: A Review

Terahertz (THz) frequency range, lying between the optical and microwave frequency ranges covers a significant portion of the electro-magnetic spectrum. Though its initial usage started in the 1960s, active research in the THz field started only in the 1990s by researchers from both optics and microwaves disciplines. The use of optical fibers for THz application has attracted considerable attention in recent years. In this paper, we review the progress and current status of optical fiber-based techniques for THz generation and transmission. The first part of this review focuses on THz sources. After a review on various types of THz sources, we discuss how specialty optical fibers can be used for THz generation. The second part of this review focuses on the guided wave propagation of THz waves for their transmission. After discussing various wave guiding schemes, we consider new fiber designs for THz transmission