Comprehensive three-dimensional gas chromatography with parallel factor analysis

Development of a comprehensive, three-dimensional gas chromatograph (GC3) instrument is described. The instrument utilizes two six-port diaphragm valves as the interfaces between three, in-series capillary columns housed in a standard Agilent 6890 gas chromatograph fitted with a high data acquisition rate flame ionization detector. The modulation periods for sampling column one by column two and column two by column three are set so that a minimum of three slices (more commonly four or five) are acquired by the subsequent dimension resulting in both comprehensive and quantitative data. A 26-component test mixture and quantitative standards are analyzed using the GC3 instrument. A useful methodology for three-dimensional (3D) data analysis is evaluated, based on the chemometric technique parallel factor analysis (PARAFAC). Since the GC3 instrument produces trilinear data, we are able to use this powerful chemometric technique, which is better known for the analysis of two-dimensional (2D) separations with multichannel detection (e.g., GC x GC-TOFMS) or multiple samples (or replicates) of 2D data. Using PARAFAC, we mathematically separate (deconvolute) the 3D data "volume" for overlapped analytes (i.e., ellipsoids), provided there is sufficient chromatographic resolution in each of the three separation dimensions. Additionally, PARAFAC is applied to quantify analyte standards. For the quantitative analysis, it is demonstrated that PARAFAC may provide a 10-fold improvement in the signal-to-noise ratio relative to a traditional integration method applied to the raw, baseline-corrected data. The GC3 instrument obtains a 3D peak capacity of 3500 at a chromatographic resolution of one in each separation dimension. Furthermore, PARAFAC deconvolution provides a considerable enhancement in the effective 3D peak capacity.     

Wavelet packet modulation for wireless communications

As proven by the success of OFDM, multicarrier modulation has been recognized as an efficient solution for wireless communications. Waveform bases other than sine functions could similarly be used for multicarrier systems in order to provide an alternative to OFDM. In this paper, we study the performance of wavelet packet transform modulation (WPM) for transmission over wireless channels. This scheme is shown to be overall quite similar to OFDM but with some interesting additional features and improved characteristics. A detailed analysis of the system's implementation complexity as well as an evaluation of the influence of implementation‐related impairments are also reported. Copyright © 2004 John Wiley & Sons, Ltd.     

A detailed calculation of the auger lifetime in p-type HgCdTe

There has been recent experimental evidence that showed, in heavily doped p-type HgCdTe, the lifetime may be limited by the Auger 7 recombination mechanism. We have performed a detailed calculation of both the Auger 7 and Auger 1 lifetimes as a function of Cd composition (x), temperature (T), and doping (N_A). Compared with those done 20 years ago, the depth and breadth of these calculations result in a significant increase in the accuracy of the predictions. We present here the Auguer 7 lifetime for two different compositions, x=0.305 and x=0.226 over a range of temperature extending from 60 K to 300 K and for acceptor doping from 10¹⁵ cm⁻³ to 10¹⁸ cm⁻³. The calculated results for MWIR (x=0.305) are in reasonably good agreement with recent experiments performed on MWIR HgCdTe at 77 K over a range of doping. In addition, we calculated γ (≡ τ_A7 /τ_A1) with the same doping, composition (x ≈ 0.22), for a range of temperatures (40–80 K) and found γ=3–6.     

Visualization of Babble–Speech Interactions Using Andrews Curves

Visualizing multidimensional data such as the mel frequency cepstral coefficients (MFCCs) proves difficult, especially when the number of dimensions is greater than 3. As a result, it becomes extremely difficult to spot trends in high-dimensional signal interactions. Andrews curves seam to aid in the process of performing graphical analysis of high-dimensional data. This study examines the properties of the babble in the feature domain as well as the effect of the babble noise on the MFCCs of clean speech. Experiments have been conducted using two babble models: the overlapping conversation model and the overlapping speaker model. The purpose of this paper was to provide an insight into the effect of the babble noise on the first thirteen MFCCs of clean speech through the use of Andrews curves. The investigations of this paper give a visual comparison of the signals to expose trends, which the conventional visualization methods do not. The use of Andrews curves not only allows the signal to be observed, but also allows for a statistical comparisons between signals. With a better understanding of the difference between the models, it would be possible to develop systems, which are more robust in babble-corrupted environment.     

Two‐layer LMDS system architecture: DAVIC‐based approach and analysis

Despite the growing interest for LMDS systems there have been only a few commercial implementations until now especially outside of the U.S.A. The use of hierarchical structure through two‐layer networking has been even rarer. In many cases LMDS systems have strong advantages against their competitors to cover the last mile. In this article, we review and analyze the standards currently available and describe the European two‐layer trial system developed in 1996–2000. We show why further development towards IP based LMDS is useful in the future. Most of our recommendations are based on results derived from the European Union supported research project CABSINET. It had the aim of demonstrating the viability of a 40 GHz cellular digital television system with a return channel to offer interactive services. Two systems were tested: a line of sight link using QPSK, and a non‐line of sight with COFDM modulation scheme. In the RF‐subsystems, the greatest difficulty of any viable LMDS system is to obtain a moderately low price for the user receiver, while fulfilling the hard OFDM requirements in terms of phase noise, stability and spectrum restrictions. Several options have been studied in order to design the subsystems with the smallest cost. This paper will present the architectures of the transmitters, nomadic terminals, and the design of the IF/RF subsystems for both types of modulations. The discussion is focused on system engineering and selections required in order to build a full two‐layer LMDS system. Copyright © 2002 John Wiley & Sons, Ltd.     

Reasoning and the weighting of attributes in attitude judgments.

Two experiments examined processes by which analyzing reasons may influence attitude judgments. Participants made multiple liking judgments on sets of stimuli that varied along 6 a priori dimensions. In Study 1, the stimulus set consisted of 64 cartoon faces with 6 binary-valued attributes (e.g., a straight vs a crooked nose). In Study 2, the stimuli were 60 digitized photographs from a college yearbook that varied along 6 dimensions uncovered through multidimensional scaling. In each experiment, half of the participants were instructed to think about the reasons why they liked each face before making their liking rating. Participants' multiple liking ratings were then regressed on the dimension values to determine how they weighted each dimension in their liking judgments. The results support a process whereby reasoning leads to increased variability and inconsistency in the weighting of stimulus information. Wilson's model of the disruptive effects of reasoning on attitude judgments ( e.g., T. D. Wilson, D. S. Dunn, D. Kraft, & D. J. Lisle, 1989 ) is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Linking Performance and Collective Action—the Case of the Office du Niger Irrigation Scheme in Mali

Increasing irrigation efficiency in irrigation schemes has always been high on the agenda of policy makers. Despite quite some ‘social’ experiments, whereby large portions of management were carried over to the farmer level, results often remained disappointing. This paper explores why this came about for a case study in the Office du Niger irrigation scheme in Mali. Since Irrigation Management Transfer, farmers are responsible for the tertiary level, but collective action for water management remains below expectations. This paper applies an analytical framework based on the conceptual model developed by van Noordwijk et al. (Conserv Ecol 5:21, 2002) and proceeding in two steps. Firstly, an interview-based stakeholder analysis assesses the objectives and mental models of farmers and the central management regarding water management. It appears from the interviews that the central management wants to increase irrigation efficiency through fully-fledged collective action, whereas farmers value the latter only when it favours easy irrigation. Secondly, the relation between collective action and performance was tested through a field study on a sample of 36 tertiary blocks. Results indicate that only collective action at the inlet of the tertiary canal, currently implemented on less than a third of the tertiary blocks, increases irrigation efficiency (with 14%). Collective action for water allocation is implemented within almost three quarters of tertiary blocks and effectively reduces irrigation problems. However, if they lack the necessary social capital, not all farmers can establish collective action when needed. Based on this analysis, the paper proposes a mix of incentives and measures to resolve the conflict between farmers and the central management to their mutual benefit.     

Aplasia and hypoplasia of the vestibulocochlear nerve: diagnosis with MR imaging

PURPOSE: To introduce aplasia or hypoplasia of the vestibulocochlear nerve (VCN) as a possible cause of hearing loss and to identify the magnetic resonance (MR) imaging characteristics of this entity. MATERIALS AND METHODS: In seven patients with congenital deafness or unexplained sensorineural hearing loss, MR imaging enabled diagnosis of aplasia or hypoplasia of the VCN. Axial (0.7-mm) three-dimensional Fourier transformation-constructive interference in steady state (3DFT-CISS) images and parasagittal reconstruction images perpendicular on the course of the VCN were obtained. Twenty normal inner ears were also studied; their findings were compared with those of the patients. RESULTS: The facial nerve and inferior and superior vestibular and cochlear branches of the VCN were identified on the MR images in the 20 normal inner ears. Aplasia of the VCN was detected in two patients with normal labyrinths but with a severe stenosis of the internal auditory canal. A common VCN with absence of the cochlear branch was found bilaterally in two patients with a congenital malformation of the labyrinth. A common VCN with absence or hypoplasia of the cochlear branch was found in three patients with normal internal auditory canals and labyrinths. CONCLUSION: Submillimetric gradient-echo images (eg, 3DFT-CISS) should always be used to exclude aplasia or hypoplasia of the cochlear branch of the VCN in all cochlear implant candidates and patients with congenital deafness. This entity, which can occur with or without associated labyrinthine malformation, should be confirmed in two planes.