Wideband data-independent beamforming for subarrays

The desire to operate large antenna arrays for e.g. RADAR applications over a wider frequency range is currently limited by the hardware, which due to weight, cost and size only permits complex multipliers behind each element. In contrast, wideband processing would have to rely on tap delay lines enabling digital filters for every element.As an intermediate step, in this thesis we consider a design where elements are grouped into subarrays, within which elements are still individually controlled by narrowband complex weights, but where each subarray output is given a tap delay line or finite impulse response digital filter for further wideband processing. Firstly, this thesis explores how a tap delay line attached to every subarray can be designed as a delay-and-sum beamformer. This filter is set to realised a fractional delay design based on a windowed sinc function. At the element level, we show that designing a narrowband beam w.r.t. a centre frequency of wideband operation is suboptimal,and suggest an optimisation technique that can yield sufficiently accurate gain over a frequency band of interest for an arbitrary look direction, which however comes at the cost of reduced aperture efficiency, as well as significantly increased sidelobes. We also suggest an adaptive method to enhance the frequency characteristic of a partial wideband array design, by utilising subarrays pointing in different directions in different frequency bands - resolved by means of a filter bank - to adaptively suppress undesired components in the beam patterns of the subarrays. Finally, the thesis proposes a novel array design approach obtained by rotational tiling of subarrays such that the overall array aperture is densely constructed from the same geometric subarray by rotation and translation only. Since the grating lobes of differently oriented subarrays do not necessarily align, an effective grating lobe attenuation w.r.t. the main beam is achieved. Based on a review of findings from geometry,a number of designs are highlight and transformed into numerical examples, and the theoretically expected grating lobe suppression is compared to uniformly spaced arrays.Supported by a number of models and simulations, the thesis thus suggests various numerical and hardware design techniques, mainly the addition of tap-delay-line per subarray and some added processing overhead, that can help to construct a large partial wideband array close in wideband performance to currently existing hardware.The desire to operate large antenna arrays for e.g. RADAR applications over a wider frequency range is currently limited by the hardware, which due to weight, cost and size only permits complex multipliers behind each element. In contrast, wideband processing would have to rely on tap delay lines enabling digital filters for every element.As an intermediate step, in this thesis we consider a design where elements are grouped into subarrays, within which elements are still individually controlled by narrowband complex weights, but where each subarray output is given a tap delay line or finite impulse response digital filter for further wideband processing. Firstly, this thesis explores how a tap delay line attached to every subarray can be designed as a delay-and-sum beamformer. This filter is set to realised a fractional delay design based on a windowed sinc function. At the element level, we show that designing a narrowband beam w.r.t. a centre frequency of wideband operation is suboptimal,and suggest an optimisation technique that can yield sufficiently accurate gain over a frequency band of interest for an arbitrary look direction, which however comes at the cost of reduced aperture efficiency, as well as significantly increased sidelobes. We also suggest an adaptive method to enhance the frequency characteristic of a partial wideband array design, by utilising subarrays pointing in different directions in different frequency bands - resolved by means of a filter bank - to adaptively suppress undesired components in the beam patterns of the subarrays. Finally, the thesis proposes a novel array design approach obtained by rotational tiling of subarrays such that the overall array aperture is densely constructed from the same geometric subarray by rotation and translation only. Since the grating lobes of differently oriented subarrays do not necessarily align, an effective grating lobe attenuation w.r.t. the main beam is achieved. Based on a review of findings from geometry,a number of designs are highlight and transformed into numerical examples, and the theoretically expected grating lobe suppression is compared to uniformly spaced arrays.Supported by a number of models and simulations, the thesis thus suggests various numerical and hardware design techniques, mainly the addition of tap-delay-line per subarray and some added processing overhead, that can help to construct a large partial wideband array close in wideband performance to currently existing hardware

Salinity tolerance and associated salinity tolerance mechanisms of four turfgrasses

2001 Fall.Covers not scanned.Includes bibliographical references.The need for salinity tolerant turfgrasses is increasing because of the increased use of effluent or other low quality water for turfgrass irrigation. Greenhouse container and hydroponic experiments were conducted to determine the relative salinity tolerance, growth characteristics, and physiological responses (especially water and ion relations) of 'Challenger' Kentucky bluegrass (Poa pratensis L.) (KBG), 'Arid' tall fescue (Festuca arundinacea Schreb) (TF), 'Fults' alkaligrass (Puccinellia distans (L.) Parl.) (AG), and saltgrass (Distichlis spicata (Torr.) Beetle) (SG). Salinity treatments were applied for 8 weeks using 1NaCl:1CaCl2 solution at 2.0, 4.7, 9.4, 14.1, 18.8, and 23.5 dS/m. Based on data on shoot dry mass, KBG, TF, AG, and SG experienced a 50% shoot growth reduction at 5.5, 14.2, 23.0, and 34.5 dS/m, respectively, suggesting the ranking of salinity tolerance was SG > AG > TF > KBG. Leaf firing of KBG, TF, and AG increased as salinity increased, but no injury was noticeable in SG. Salinity caused root cortex cells to collapse in KBG at 14.1 dS/m and in TF at 23 .5 dS/m. Alkaligrass and SG only had a few cell collapses even at 23.5 dS/m. Osmotic adjustment (OA) occurred in all species under salinity stress. However, in KBG and TF, the contribution of Na+ and Cl- to OA increased and became the major contributors at high levels of salinity, whereas Na+ and Cl- contributions to OA in SG were maintained at stable levels as salinity increased from 4.7 to 23 .5 dS/m. As salinity increased, the contribution of unidentified osmolytes to OA increased in SG and decreased in KBG and TF. The proportion of K+ to OA in AG and TF was lower than SG but higher than KBG. The ability to maintain a K+/Na+ ratio close to or above 1 appeared to be important for these grasses to tolerate high salinity. Saltgrass, AG, TF, and KBG could maintain a shoot K+/Na+ ratio of 1 when salinity levels were less than 22.3, 13.6, 7.4, and 3.7 dS/m, respectively. Salt glands present in SG, root growth stimulation of SG and AG, maintenance of high root to shoot ratio in TF, synthesis of compatible solutes, regulation of ion concentrations, and maintenance of high K+/Na+ ratio in shoots are important salinity tolerance mechanisms among these grasses

Low-cost and accurate broadband beamforming based on narrowband sub-arrays

Simplified broadband beamformers can be constructed by sharing a single tapped-delay-line within a narrowband subarray. This paper discusses the use of fractional delay filters to a steering in the digital domain. For the narrowband subarrays, an optimisation approach is proposed to maintain an off-broadside look direction constraint as best as possible across a given frequency range. We demonstrate the advantage that this approach has for generating beamformers with accurate off-broadside look direction compared to a benchmark

Reality of Supervisors’ Clinical Supervision Practice in Kuwaiti Public Schools

Teachers’ classroom performance is an important aspect of the learning process. Improving teaching quality lies at the heart of this process, in which evaluation is thought to oversee the quality of classroom instruction. This study aims to examine the practice of clinical supervision by general supervisors in Kuwaiti public schools. To this end, it adopted a descriptive methodology using Serkesian’s (2011) questionnaire as a data collection instrument. The sample consisted of 169 teachers who were randomly chosen from different public schools in different educational districts across Kuwait. Data was processed and codified by using Statistical Package for Social Science software. The results showed that most teachers view their supervisors’ clinical supervision practice positively, and no statistically significant differences were found in their responses with regard to their gender, specialization, educational level, and work experience. However, some clinical supervision areas have been neglected, such as conducting preconferences. helping to resolve classroom management problems, and aiding in lesson planning. Therefore, this study calls on supervisors to direct more of their efforts on these aspects. Keywords: clinical supervision, supervision, teachers, Kuwaiti public schools, instructio

Grating lobe suppression in rotationally tiled arrays

Uniform placement of array elements limits its maximum frequency due to the formation of grating lobes. While non-uniform element or subarray spacing have significantly lower grating lobes, it reduces aperture efficiency and leads to arrays that are difficult to design and manufacture. We propose a modular asymmetric convex-shaped subarray to construct the array by rotation and translation, filling the aperture without overlaps or gaps. This new approach can achieve lower grating lobes compared to uniform array geometries. It can also lower design, manufacturing and operation costs by offering interoperable subarrays and provide array size flexibility

Continuing medical education as a national strategy to improve access to primary care in Saudi Arabia

The purpose of this study was to describe the development, implementation, and evaluation of an educational program in family medicine for general practitioners in Saudi Arabia from 2009 to 2011. A continuing medical education program called Family Medicine Education (FAME) was developed with 7 modules each consisting of 12-14 hours of teaching to be delivered in 3 day blocks, over 45 days. Twenty percent (2,761) of all general practitioners participated in the FAME program. Initial assessment of the program showed significant improvement of knowledge from scores of 49% on a pre-test to 89% on post-tests. FAME program in Saudi Arabia facilitated primary care physicians’ knowledge

An Alternative Conceptual Corporate Governance Framework for High-Context Cultures: A Case for the Islamic & Arabian Middle East

The distinctiveness of Islam and the reaction toward the domination of the Western ideologies on the rest of the world especially on Islamic nations generated a movement among many scholars toward applying Islamic principals in the field of corporate governance. Islam is the dominant religion in the Middle Eastern region. This region consist of two major blocs the Arab League and most importantly the GCC. Thus, the cultural, political and legal environments have a significant impact on both profit and non-profit organisations. The proposed concept is generated by considering; the narrowness of the Agency theory illustrated by its limited explanations of such complexity associated with corporate governance issues yet its greatness of simplicity in regards to accountability; the Stakeholders theory serves wider views and shares many aspect with Islam yet this theory by nature suffers from practical complexity; Institutional theory are considered to ensure some degree of stability in the concept by considering the importance of the Islamic corporate supervisory institution in developing a sustainable Islamic corporate governance standards

Financial Development and Economic Growth in Developing Countries: Evidence from Saudi Arabia

This study investigates the long-term and short-term relationships between capital market development and economic growth in the Kingdom of Saudi Arabia (KSA) for the period from January 1993 to December 2009. It employs a wide range of vector autoregression (VAR) models to evaluate the importance and impact of capital market development on economic growth. We used real GDP growth rates and None Oil GDP as proxies for economic growth and the stock market index (SMI), the bank credits to the private sector (BCP) and the broad money supply (M2) as proxies for the capital market development. The VAR models indicate a positive and significant long-term causal relationship between capital market development and economic growth. Granger causality tests show that economic growth Granger-cause capital market development and vice versa when using the real GDP growth rate variables. The study implications are as follows. Firstly, investment in real economic activities leads to economic growth. Secondly, the stock market might hinder economic growth due to its volatile and international risk sharing nature, low free-floating share ratio, number of listed companies and the domination of Saudi Individual Stock Trades (SIST) characteristics. Thirdly, policymakers should seek to minimise stock market volatility and fluctuations, increase both the free-floating share ratio and number of listed companies and shift investment domination toward corporate investors by considering its effect on economic growth when formulating economic policies. Fourthly, the banking sector might hinder economic growth due to its lack of small and medium enterprises lending and shareholder concentration issues. Finally, policymakers should seek to encourage banks toward more involvement in small and medium enterprises SMEs’ lending, which will strengthen the private sector role

Wideband 2-Dimensional scanning planar subarray

Achieving frequency invariance in antenna array requires linear-phase system to maintain frequency independent time lag. For example True Time Delay or tapped delay line. In this paper, the array elements are divided into subarrays. Then all subarrays are steered towards the desired azimuth direction, while the wideband property is preserved by exploiting the subarray two-dimensional structure as a sensor delay line. Each subarray pattern is then individually rotated around the desired elevation direction. Eventually superposition of subarrays is maximally constructive towards the desired direction and partially constructive or destructive everywhere else. Two frequency invariant beamformers are used. These are inverse DFT and Least squares. Results are compared with wideband wideband one-dimensional pattern syntheses of the same design methods in power concentration