Design and implementation of wideband baluns for Archimedean spiral antennas

The demand for high-speed data services for portable device has become a driving force for development of advanced broadband access technologies. Despite recent advances in broadband wireless technologies, there remain a number of critical issues to be resolved. One of the major concerns is the implementation of compact antennas that can operate in a wide frequency band. Spiral antenna has been used extensively for broadband applications due to its planar structure, wide bandwidth characteristics and circular polarisation. However, the practical implementation of spiral antennas is challenged by its high input characteristic impedance, relatively low gain and the need for balanced feeding structures. Further development of wideband balanced feeding structures for spiral antennas with matching impedance capabilities remain a need. This thesis proposes three wideband feeding systems for spiral antennas which are compatible with wideband array antenna geometries. First, a novel tapered geometry is proposed for a symmetric coplanar waveguide (CPW) to coplanar strip line (CPS) wideband balun. This balun can achieve the unbalanced to balanced transformation while matching the high input impedance of the antenna to a reference impedance of 50 . The discontinuity between CPW and CPS is accommodated by using a radial stub and bond wires. The bandwidth of the balun is improved by appropriately tapering the CPW line instead of using a stepped impedance transformer. Next, the tapered design is applied to an asymmetric CPW to propose a novel asymmetric CPW to CPS wideband balun. The use of asymmetric CPW does away with the discontinuities between CPW and CPS without having to use a radial stub or bond wires. Finally, a tapered microstrip line to parallel striplines balun is proposed. The balun consists of two sections. One section is the parallel striplines which are connected to the antenna, with the impedance of balanced line equal to the antenna input impedance. The other section consists of a microstrip line where the width of the ground plane is gradually reduced to eventually resemble a parallel stripline. The taper accomplishes the mode and impedance transformation. This balun has significantly improved bandwidth characteristics. Characteristics of proposed feeding structures are measured in a back-to-back configuration and compared to simulated results. The simulated and measured results show the tapered microstrip to parallel striplines balun to have more than three octaves of bandwidth. The tapered microstrip line to parallel striplines balun is integrated with a single Archimedean spiral antenna and with an array of spiral antennas. The performance of the integrated structures is simulated with the aid of electromagnetic simulation software, and results are compared to measurements. The back-to-back microstrip to parallel strip balun has a return loss of better than 10 dB over a wide bandwidth from 1.75 to 15 GHz. The performance of the microstrip to parallel strip balun was validated with the spiral antennas. The results show the balun to be an effective mean of feeding network with a low profile and wide bandwidth (2.5 to 15 GHz) for balanced spiral antennas.

Quality metrics for assessing security-critical computer programs

Existing secure software development principles tend to focus on coding vulnerabilities, such as buffer or integer overflows, that apply to individual program statements, or issues associated with the run-time environment, such as component isolation. Here we instead consider software security from the perspective of potential information flow through a program’s object-oriented module structure. In particular, we define a set of quantifiable "security metrics" which allow programmers to quickly and easily assess the overall security of a given source code program or object-oriented design. Although measuring quality attributes of object-oriented programs for properties such as maintainability and performance has been well-covered in the literature, metrics which measure the quality of information security have received little attention. Moreover, existing securityrelevant metrics assess a system either at a very high level, i.e., the whole system, or at a fine level of granularity, i.e., with respect to individual statements. These approaches make it hard and expensive to recognise a secure system from an early stage of development. Instead, our security metrics are based on well-established compositional properties of object-oriented programs (i.e., data encapsulation, cohesion, coupling, composition, extensibility, inheritance and design size), combined with data flow analysis principles that trace potential information flow between high- and low-security system variables. We first define a set of metrics to assess the security quality of a given object-oriented system based on its design artifacts, allowing defects to be detected at an early stage of development. We then extend these metrics to produce a second set applicable to object-oriented program source code. The resulting metrics make it easy to compare the relative security of functionallyequivalent system designs or source code programs so that, for instance, the security of two different revisions of the same system can be compared directly. This capability is further used to study the impact of specific refactoring rules on system security more generally, at both the design and code levels. By measuring the relative security of various programs refactored using different rules, we thus provide guidelines for the safe application of refactoring steps to security-critical programs. Finally, to make it easy and efficient to measure a system design or program’s security, we have also developed a stand-alone software tool which automatically analyses and measures the security of UML designs and Java program code. The tool’s capabilities are demonstrated by applying it to a number of security-critical system designs and Java programs. Notably, the validity of the metrics is demonstrated empirically through measurements that confirm our expectation that program security typically improves as bugs are fixed, but worsens as new functionality is added.

Critical time scales for advection–diffusion–reaction processes

The concept of local accumulation time (LAT) was introduced by Berezhkovskii and coworkers in 2010–2011 to give a finite measure of the time required for the transient solution of a reaction–diffusion equation to approach the steady–state solution (Biophys J. 99, L59 (2010); Phys Rev E. 83, 051906 (2011)). Such a measure is referred to as a critical time. Here, we show that LAT is, in fact, identical to the concept of mean action time (MAT) that was first introduced by McNabb in 1991 (IMA J Appl Math. 47, 193 (1991)). Although McNabb’s initial argument was motivated by considering the mean particle lifetime (MPLT) for a linear death process, he applied the ideas to study diffusion. We extend the work of these authors by deriving expressions for the MAT for a general one–dimensional linear advection–diffusion–reaction problem. Using a combination of continuum and discrete approaches, we show that MAT and MPLT are equivalent for certain uniform–to-uniform transitions; these results provide a practical interpretation for MAT, by directly linking the stochastic microscopic processes to a meaningful macroscopic timescale. We find that for more general transitions, the equivalence between MAT and MPLT does not hold. Unlike other critical time definitions, we show that it is possible to evaluate the MAT without solving the underlying partial differential equation (pde). This makes MAT a simple and attractive quantity for practical situations. Finally, our work explores the accuracy of certain approximations derived using the MAT, showing that useful approximations for nonlinear kinetic processes can be obtained, again without treating the governing pde directly.

Legal education and the 'idealistic student': using Foucault to unpack the critical legal narrative

It appears that few of the students holding ‘socially idealistic’ goals upon entering law school actually maintain these upon graduation. The critical legal narrative, which explains and seeks to act upon this shift in the graduate’s ‘legal identity’, posits that these ideals are repressed through power relations that create passive receptacles into which professional ideologies can be deposited, in the interests of those advantaged by the social and legal status quo. Using the work of Michel Foucault, this paper unpacks the assumptions underpinning this narrative, particularly its arguments about ideology, power, and the subject. In doing so, it will argue this narrative provides an untenable basis for political action within legal education. By interrogating this narrative, this paper provides a new way of understanding the construction of the legal identity through legal education, and a new basis for political action within law school.

Power in legal education : a (new) critical and analytical approach

This article explores power within legal education scholarship. It suggests that power relations are not effectively reflected on within this scholarship, and it provokes legal educators to consider power more explicitly and effectively. It then outlines in-depth a conceptual and methodological approach based on Michel Foucault’s concept of ‘governmentality’ to assist in such an analysis. By detailing the conceptual moves required in order to research power in legal education more effectively, this article seeks to stimulate new reflection and thought about the practice and scholarship of legal education, and allow for political interventions to become more ethically sensitive and potentially more effective.

History of critical criminology in Australia

Those working in the critical criminology tradition have been centrally concerned with the social construction, variability and contingency of the criminal label. The concern is no less salient to a consideration of critical criminology itself and any history of critical criminology (in Australia or elsewhere) should aim itself to be critical in this sense. The point applies with equal force to both of the terms ‘critical’ and ‘criminology’. The want of a stable theoretical object has meant that criminology itself needs to be seen not as a distinct discipline but as a composite intellectual and governmental hybrid, a field of studies that overlaps and intersects many others (sociology, law, psychology, history, anthropology, social work, media studies and youth studies to name only a few). In consequence, much of the most powerful work on subjects of criminological inquiry is undertaken by scholars who do not necessarily define themselves as criminologists first and foremost, or at all. For reasons that should later become obvious this is even more pronounced in the Australian context. Although we may appear at times to be claiming such work for criminology, our purpose is to recognize its impact on and in critical criminology in Australia.

Turbulence measurements in a small subtropical estuary under king tide conditions

In natural waterways and estuaries, the understanding of turbulent mixing is critical to the knowledge of sediment transport, stormwater runoff during flood events, and release of nutrient-rich wastewater into ecosystems. In the present study, some field measurements were conducted in a small subtropical estuary with micro-tidal range and semi-diurnal tides during king tide conditions: i. e., the tidal range was the largest for both 2009 and 2010. The turbulent velocity measurements were performed continuously at high-frequency (50Hz) for 60 h. Two acoustic Doppler velocimeters (ADVs) were sampled simultaneously in the middle estuarine zone, and a third ADV was deployed in the upper estuary for 12 h only. The results provided an unique characterisation of the turbulence in both middle and upper estuarine zones under the king tide conditions. The present observations showed some marked differences between king tide and neap tide conditions. During the king tide conditions, the tidal forcing was the dominant water exchange and circulation mechanism in the estuary. In contrast, the long-term oscillations linked with internal and external resonance played a major role in the turbulent mixing during neap tides. The data set showed further that the upper estuarine zone was drastically less affected by the spring tide range: the flow motion remained slow, but the turbulent velocity data were affected by the propagation of a transient front during the very early flood tide motion at the sampling site. © 2012 Springer Science+Business Media B.V.

Job satisfaction and intention to leave among critical care nurses in Saudi Arabia

Aim The purpose of this study was to examine the relationship between registered nurses’ (RN) job satisfaction and their intention to leave critical care nursing in Saudi Arabia. Background Many studies have identified critical care areas as stressful work environments for nurses and have identified factors contributing to job satisfaction and staff retention. However, very little research has examined these relationships in the Saudi context. Design and Methods This study utilised an exploratory, cross-sectional survey design to examine the relationship between RN job satisfaction and intention to leave at King Abdul-Aziz University Hospital, Saudi Arabia. Respondents completed a self-administered survey including demographic items and validated measures of job satisfaction and intention to leave. A convenience sample of 182 RNs working in critical care areas during the data collection period were included. Results Regression analysis predicting RN intention to leave found that demographic variables including age, parental status and length of ICU experience, and three of the job satisfaction subscales including perceived workload, professional support and pay and prospects for promotion, were significantly associated with the outcome variable. Conclusion This study adds to the existing literature on the relationship between job satisfaction and intention to leave critical care areas among RNs working in Saudi Arabia. These findings point to the need for management and policy interventions targeting nurses’ workloads, professional support and pay and promotion in order to improve nurse retention.

Re-examining the evidence in radiation dermatitis management literature : an overview and a critical appraisal of systematic reviews

Purpose: To provide an overview and a critical appraisal of systematic reviews (SRs) of published interventions for the prevention/management of radiation dermatitis. Methods and Materials: We searched Medline, CINAHL, Embase, and the Cochrane Library. We also manually searched through individual reference lists of potentially eligible articles and a number of key journals in the topic area. Two authors screened all potential articles and included eligible SRs. Two authors critically appraised and extracted key findings from the included reviews using AMSTAR (the measurement tool for “assessment of multiple systematic reviews”). Results: Of 1837 potential titles, 6 SRs were included. A number of interventions have been reported to be potentially beneficial for managing radiation dermatitis. Interventions evaluated in these reviews included skin care advice, steroidal/nonsteroidal topical agents, systemic therapies, modes of radiation delivery, and dressings. However, all the included SRs reported that there is insufficient evidence supporting any single effective intervention. The methodological quality of the included studies varied, and methodological shortfalls in these reviews might create biases to the overall results or recommendations for clinical practice. Conclusions: An up-to-date high-quality SR in the prevention/management of radiation dermatitis is needed to guide practice and direction for future research. We recommend that clinicians or guideline developers critically evaluate the information of SRs in their decision making.

In Praise of Critical Criminology

This short essay examines the relationship between academic research and policy with particular emphasis on the question of whether a critical criminology can engage in academic critique at the same time as engaging in policy oriented research. Recognising that critical criminology falls between theory and politics criminologists are urged to adopt pragmatic, strategic positions as they negotiate their role in contentious debates and practical minefi elds. It is concluded that a critical criminology must try not only to think the unthinkable about crime, but also to speak the unspeakable about the conditions in which and by which it is known.

Contemporary Critical Criminology

The concept of critical criminology – that crime and the present day processes of criminalization are rooted in the core structures of society – is of more relevance today than it has been at any other time. Written by an internationally renowned scholar, Contemporary Critical Criminology introduces the most up-to-date empirical, theoretical, and political contributions made by critical criminologists around the world. In its exploration of this material, the book also challenges the erroneous but widely held notion that the critical criminological project is restricted to mechanically applying theories to substantive topics, or to simple calling for radical political, economic, cultural, and social transformations. This book is an essential source of reference for both undergraduate and postgraduate students of Criminology, Criminal Theory, Social Policy, Research Methodology, and Penology.