A low-cost remote sensing system for agricultural applications

This research develops a low cost remote sensing system for use in agricultural applications. The important features of the system are that it monitors the near infrared and it incorporates position and attitude measuring equipment allowing for geo-rectified images to be produced without the use of ground control points. The equipment is designed to be hand held and hence requires no structural modification to the aircraft. The portable remote sensing system consists of an inertia measurement unit (IMU), which is accelerometer based, a low-cost GPS device and a small format false colour composite digital camera. The total cost of producing such a system is below GBP 3000, which is far cheaper than equivalent existing systems. The design of the portable remote sensing device has eliminated bore sight misalignment errors from the direct geo-referencing process. A new processing technique has been introduced for the data obtained from these low-cost devices, and it is found that using this technique the image can be matched (overlaid) onto Ordnance Survey Master Maps at an accuracy compatible with precision agriculture requirements. The direct geo-referencing has also been improved by introducing an algorithm capable of correcting oblique images directly. This algorithm alters the pixels value, hence it is advised that image analysis is performed before image georectification. The drawback of this research is that the low-cost GPS device experienced bad checksum errors, which resulted in missing data. The Wide Area Augmented System (WAAS) correction could not be employed because the satellites could not be locked onto whilst flying. The best GPS data were obtained from the Garmin eTrex (15 m kinematic and 2 m static) instruments which have a highsensitivity receiver with good lock on capability. The limitation of this GPS device is the inability to effectively receive the P-Code wavelength, which is needed to gain the best accuracy when undertaking differential GPS processing. Pairing the carrier phase L1 with the pseudorange C/A-Code received, in order to determine the image coordinates by the differential technique, is still under investigation. To improve the position accuracy, it is recommended that a GPS base station should be established near the survey area, instead of using a permanent GPS base station established by the Ordnance Survey.

Verification of the indoor GPS system, by comparison with calibrated coordinates and by angular reference

This paper details work carried out to verify the dimensional measurement performance of the Indoor GPS (iGPS) system; a network of Rotary-Laser Automatic Theodolites (R-LATs). Initially tests were carried out to determine the angular uncertainties on an individual R-LAT transmitter-receiver pair. A method is presented of determining the uncertainty of dimensional measurement for a three dimensional coordinate measurement machine. An experimental procedure was developed to compare three dimensional coordinate measurements with calibrated reference points. The reference standard used to calibrate these reference points was a fringe counting interferometer with the multilateration technique employed to establish three dimensional coordinates. This is an extension of the established technique of comparing measured lengths with calibrated lengths. The method was found to be practical and able to establish that the expanded uncertainty of the basic iGPS system was approximately 1 mm at a 95% confidence level. Further tests carried out on a highly optimized version of the iGPS system have shown that the coordinate uncertainty can be reduced to 0.25 mm at a 95% confidence level.

Relating two simultaneous events in discourse: the role of on-goingness devices in L1 Tunisian Arabic, L1 French and L2 French by Tunisian learners

Our PhD study focuses on the role of aspectual marking in expressing simultaneity of events in Tunisian Arabic as a first language, French as a first language, as well as in French as a second language by Tunisian learners at different acquisitional stages. We examine how the explicit markers of on-goingness qa:’id and «en train de» in Tunisian Arabic and in French respectively are used to express this temporal relation, in competition with the simple forms, the prefixed verb form in Tunisian Arabic and the présent de l’indicatif in French. We use a complex verbal task of retelling simultaneous events sharing an interval on the time axis based on eight videos presenting two situations happening in parallel. Two types of simultaneity are exploited: perfect simultaneity (when the two situations are parallel to each other) and inclusion (one situation is framed by the second one). Our informants in French and in Tunisian Arabic have two profiles, highly educated and low educated speakers. We show that the participants’ response to the retelling task varies according to their profiles, and so does their use of the on-goingness devices in the expression of simultaneity. The differences observed between the two profile groups are explained by the degree to which the speakers have developed a habit of responding to tasks. This is a skill typically acquired during schooling. We notice overall that the use of qa:’id as well as of «en train de» is less frequent in the data than the use of the simple forms. However, qa:’id as well as «en train de» are employed to play discursive roles that go beyond the proposition level. We postulate that despite the shared features between Tunisian Arabic and French regarding marking the concept of on-goingness, namely the presence of explicit lexical, not fully grammaticalised markers competing with other non-marked forms, the way they are used in the discourse of simultaneous events shows clear differences. We explain that «en train de» plays a more contrastive role than qa:’id and its use in discourse obeys a stricter rule. In cases of the inclusion type of simultaneity, it is used to construe the ‘framing’ event that encloses the second event. In construing perfectly simultaneneous events, and when both «en train de» and présent de l’indicatif are used, the proposition with «en train de» generally precedes the proposition with présent de l’indicatif, and not the other way around. qa:id obeys, but to a less strict rule as it can be used interchangeably with the simple form regardless of the order of propositions. The contrastive analysis of French L1 and L2 reveals learners’ deviations from natives’ use of on-goingness devices. They generalise the use of «en train de» and apply different rules to the interaction of the different marked and unmarked forms in discourse. Learners do not master its role in discourse even at advanced stages of acquisition despite its possible emergence around the basic and intermediate varieties. We conclude that the native speakers’ use of «en train de» involves mastering its role at the macro-structure level. This feature, not explicitly available to learners in the input, might persistently present a challenge to L2 acquisition of the periphrasis.

L1 to teach L2:complexities and contradictions

This article uncovers the complexities and contradictions inherent in making decisions about L1 use in the English language classroom. Through an analysis of data from classrooms in a Cypriot context and from interviews with Cypriot teachers, a number of functions for L1 use are identified, as are the teachers' rationales for using L1 for different functions. Teachers' decision making, it emerges, is often complex, based on either what they perceive as their students' affective needs or on their cognitive processes.What ismore, teachers often under-report or differently report their use of L1 in the classroom, contradicting beliefs by their actions. The construct of guilt is offered to explain these complexities and contradictions in the teachers' use of L1 in this study. We conclude by suggesting that teachers should be supported in finding local solutions to local teaching problems, so that they better understand and exploit the resources available to them. © The Author 2010. Published by Oxford University Press; all rights reserved.

All-optical nonlinear signal processing at a RZ receiver

We propose a novel all-optical signal processor for use at a return-to-zero receiver utilising loop mirror intensity filtering and nonlinear pulse broadening in normal dispersion fibre. The device offers reamplification and cleaning up of the optical signals, and phase margin improvement. The efficiency of the technique is demonstrated by application to 40 Gbit/s data transmission.

Novel real-time homodyne coherent receiver using a feed-forward based carrier extraction scheme for phase modulated signals

We report a novel real-time homodyne coherent receiver based on a DPSK optical-electrical-optical (OEO) regenerator used to extract a carrier from carrier-less phase modulated signals based on feed-forward based modulation stripping. The performance of this non-DSP based coherent receiver was evaluated for 10.66Gbit/s BPSK signals. Self-homodyne coherent detection and homodyne detection with an injection-locked local oscillator laser was demonstrated. The performance was evaluated by measuring the electrical signal-to-noise (SNR) and recording the eye diagrams. Using injection-locking for the LO improves the performance and enables homodyne detection with optical injection-locking to operate with carrier-less BPSK signals without the need for polarization multiplexed pilot-tones.

Time domain all-optical nonlinear signal processing to enhance the performance of a RZ receiver

We have proposed a new technique of all-optical nonlinear pulse processing for use at a RZ optical receiver, which is based on an AM or any device with a similar function of temporal gating/slicing enhanced by the effect of Kerr nonlinearity in a NDF. The efficiency of the technique has been demonstrated by application to timing jitter and noise-limited RZ transmission at 40 Gbit/s. Substantial suppression of the signal timing jitter and overall improvement of the receiver performance has been demonstrated using the proposed method.

An RZ DPSK receiver design with significantly improved dispersion tolerance

We show an improved DPSK receiver design which can increase useful dispersion tolerance by up to a factor of two. The increased dispersion tolerance is achieved through optimization of the optical filter at the receiver and the delay of the Mach-Zehnder interferometer. In this paper we fully explain the concept, quantify the gain and provide an explanation for the operation of the receiver. © 2007 Optical Society of America.

Novel asymmetrical filtered 40 Gb/s NRZ-DPSK receiver design in a 50GHz grid

We present a novel differential phase shift keying receiver design under strong optical filtering. The receiver design is based on the different offset filtering performances of the output ports of the NRZ-DPSK Mach Zehnder Interferometer. The asymmetrical filtered receiver design can significantly increase performance by 2 dB in calculated Q for an OSNR of 15 dB.

Performance improvement of asymmetrical filtered 40GB/s RZ-DPSK receiver design-strong filtering considerations

We present a novel differential phase shift keying receiver design under strong optical filtering. The receiver design is based on asymmetrical filtering at the destructive port of the Mach Zehnder Interferometer. The asymmetrical filtered receiver design can significantly increase performance by 2 to 4.7dB in calculated "Q".

Time domain all-optical signal processing at a RZ optical receiver

We propose a new all-optical signal processing technique to enhance the performance of a return-to-zero optical receiver, which is based on nonlinear temporal pulse broadening and flattening in a normal dispersion fiber and subsequent slicing of the pulse temporal waveform. The potential of the method is demonstrated by application to timing jitter-and noise-limited transmission at 40 Gbit/s. © 2005 Optical Society of America.

Linguistic identifiers of L1 Persian speakers writing in English:NLID for authorship analysis

This research focuses on Native Language Identification (NLID), and in particular, on the linguistic identifiers of L1 Persian speakers writing in English. This project comprises three sub-studies; the first study devises a coding system to account for interlingual features present in a corpus of L1 Persian speakers blogging in English, and a corpus of L1 English blogs. Study One then demonstrates that it is possible to use interlingual identifiers to distinguish authorship by L1 Persian speakers. Study Two examines the coding system in relation to the L1 Persian corpus and a corpus of L1 Azeri and L1 Pashto speakers. The findings of this section indicate that the NLID method and features designed are able to discriminate between L1 influences from different languages. Study Three focuses on elicited data, in which participants were tasked with disguising their language to appear as L1 Persian speakers writing in English. This study indicated that there was a significant difference between the features in the L1 Persian corpus, and the corpus of disguise texts. The findings of this research indicate that NLID and the coding system devised have a very strong potential to aid forensic authorship analysis in investigative situations. Unlike existing research, this project focuses predominantly on blogs, as opposed to student data, making the findings more appropriate to forensic casework data.

Performance improvement of asymmetrical filtered 40GB/s RZ-DPSK receiver design-strong filtering considerations

We present a novel differential phase shift keying receiver design under strong optical filtering. The receiver design is based on asymmetrical filtering at the destructive port of the Mach Zehnder Interferometer. The asymmetrical filtered receiver design can significantly increase performance by 2 to 4.7dB in calculated "Q".

Gain switched multi-carrier transmitter and pilot tone based receiver for long reach access networks

A novel and cost effective long reach PON downlink scenario is proposed employing a multi-carrier transmitter and pilot tone aided direct detection at the receiver. Error free performance with QPSK and 50km transmission is presented. © 2012 OSA.