A Novel Stress Characterization Technique for the Development of Low-Stress Ohmic Contacts to HgCdTe

HgCdTe material intended for long-wavelength infrared detection is particularly susceptible to damage from stress. As a result, an ideal ohmic contact needs to have good adhesion and low specific contact resistance. The contact should act as a diffusion barrier and induce the least amount of stress in the underlying material. In this paper we present a set of stress measurements from different ohmic contact materials deposited on short- and long-wavelength HgCdTe films grown by liquid-phase epitaxy (LPE). Using a new experimental technique we remove the substrate and measure the stress induced on single- and multilayered HgCdTe cantilevers. To interpret our results, we develop a theoretical model that describes the physics of elastic deformation in HgCdTe layers. Our model is based on classical thin-plate bending theory and explicitly takes into account the realistic boundary conditions that are present in the experimental setup by using a variational approach.     

A new medium for determining the total plate count in food

SimPlate for Total Plate Count-Color Indicator (TPC-CI, IDEXX Laboratories, Inc., Westbrook, Me.) is a new medium that incorporates the redox dye resazurin to detect and quantify bacteria in food. Enumeration is achieved by the most probable number method using a SimPlate device. Viable bacteria are detected in each well of the SimPlate device by the biochemical reduction of resazurin, which is blue, to the pink resorufin or the clear dihydroresorufin indicators. Results after 24 h of incubation for TPC-CI are highly correlated with standard plate count agar after 48 h of incubation. Correlation coefficients from studies conducted at five laboratories ranged from 0.94 to 0.98 in side-by-side comparisons against standard plate count agar. Four additional test sites, using alternative methods for determining the aerobic plate count in food, reported similar results in comparison studies (r = 0.91 to 0.97). The slopes from linear regression analysis at all sites ranged from 0.91 to 0.98, with y intercepts ranging from 0.11 to 0.84. Samples used for the validation of TPC-CI included raw food products (i.e., liver and grains), which may contain natural enzymes that interfere with enzyme-based detection methods. No interference was seen from the foods tested. These results suggest that TPC-CI is a suitable alternative to existing plate count methods and has reduced incubation time.     

The construction of reflective practice in key policy documents in England

This article presents an analysis of the construction of reflection in relation to teacher's practice to be found in some key documents designed to present or implement the current educational policy in England and Wales. There is evidence in these key texts that there is a potentially fruitful approach to the harnessing of reflection and reflective practice in the pursuit of given goals. This is however in tension with bureaucratic and political imperatives to control and those imperatives win out in the actual implementation documents. In so far as these actually determine the experience of teachers training for the Literacy Hour, then in practice teachers will feel that their own reflection is considerably censored rather than legitimated.     

Distributed detection of replica node attacks with group deployment knowledge in wireless sensor networks

Several protocols have been proposed to mitigate the threat against wireless sensor networks due to an attacker finding vulnerable nodes, compromising them, and using these nodes to eavesdrop or undermine the operation of the network. A more dangerous threat that has received less attention, however, is that of replica node attacks, in which the attacker compromises a node, extracts its keying materials, and produces a large number of replicas to be spread throughout the network. Such attack enables the attacker to leverage the compromise of a single node to create widespread effects on the network. To defend against these attacks, we propose distributed detection schemes to identify and revoke replicas. Our schemes are based on the assumption that nodes are deployed in groups, which is realistic for many deployment scenarios. By taking advantage of group deployment knowledge, the proposed schemes perform replica detection in a distributed, efficient, and secure manner. Through analysis and simulation experiments, we show that our schemes achieve effective and robust replica detection capability with substantially lower communication, computational, and storage overheads than prior work in the literature.     

Making the team [project team building and leadership]

The author outlines the role of team building and team leadership in successful project management. Different teams work in radically dissimilar environments, although it can be argued that it is the project team environment that is the most complex to analyse, as each project is unique and the conditions for team selection and motivation are often less than ideal. All this implies an overwhelming case for giving more attention to the art and science of project team building. A variety of factors are invoked in building high-performing teams, including the contributions made by individual members, leadership, communications and internal power relationships. Each of these will have an effect on whether or not your team performs successfully. The characteristics of individual team members can be categorised by a combination of nine distinct roles. These comprise: plant, resource investigator, co-ordinator, shaper, monitor evaluator, team-worker, implementer, completer/finisher and specialist. Their contributions and weaknesses are outlined. Three styles of leadership are also briefly discussed: laissez-faire, transactional and transformational     

An MRI Receiver Coil Produced by Inkjet Printing Directly on to a Flexible Substrate

Inkjet printing has been used to produce resonant radio frequency coils that are comparable to those produced by conventional printed circuit board (PCB) methods. The coils, which consist of a conductive loop and in-series capacitors, form part of a receiver circuit that is used for magnetic resonance imaging (MRI). The resonant circuit is selective at the predetermined frequency of 400 MHz. The required electrical components (resistor, capacitor, and inductor) were produced by inkjet printing, with scaling experiments for resistor and capacitor performed before the complete loops with integrated capacitors were printed. Numerical simulation was used to determine the required values for the components. The inkjet printed circuit was combined with a small tuning and matching board before being connected to a network analyzer and the MRI hardware. With a matching of ${-}$ 38 dB at 400 MHz the achieved results were comparable to those from standard PCB techniques. The performance of the inkjet printed component as a receiver device for nuclear magnetic resonance and MRI was verified by imaging reference phantoms and a whole kiwifruit; it compares favorably to standard MRI devices. Inkjet printing can, therefore, be considered a feasible technique for producing MRI receiver circuits on flexible substrates.      

Improved safety and efficacy in adaptive control of arterial bloodpressure through the use of a supervisor

A dual approach to adaptive control of arterial blood pressure using sodium nitroprusside is presented. In the clinical environment, a controller must be aggressive to achieve specific step response characteristics (less than 10 min setting time, less than 10 mm Hg overshoot), yet conservative enough to prevent overreactions to large disturbances, which are common in both the operating room and the intensive care unit. These mutually exclusive requirements make it difficult to design a closed-loop controller for this environment. To prevent possible overreactions while maintaining proper step response, an aggressive adaptive controller has been designed to achieve the desired step response, and a supervisor has been designed around the adaptive controller to limit potential overreactions in the presence of disturbances. Simulations and dog experiments demonstrate the potential for increased safety and efficacy using this dual approach to the control of a complex physiological system     

Improved track following in magnetic disk drives using adisturbance observer

Improving the position control of the disk drive read/write heads is an important step in increasing the storage capacity of a drive, especially in the presence of internal and external disturbances. To address this problem, the typical feedback loop of a disk drive servo system was augmented with a disturbance observer. The disturbance observer uses the position error signal and a nominal model of the plant to create an estimate of the disturbance. This estimate is then used to compensate for the disturbance effects. No additional sensors are required, which is particularly relevant in products such as disk drives where cost is a major concern. The effectiveness of the disturbance observer in rejecting shock and vibration disturbances is demonstrated in simulation and shake table experiments. The vibration experiments showed a decrease in the position error of 61%-96% at frequencies below 100 Hz. The maximum position error due to an experimental shock disturbance was decreased by 59%. The effects of noise in the position error signal are also discussed     

Time-varying analysis-synthesis systems based on filter banks andpost filtering

Perfect reconstruction (PR) time-varying analysis-synthesis filter banks are those in which the filters are allowed to change from one set of PR filter banks to another as the input signal is being processed. Such systems have the property that, in the absence of coding, they faithfully reconstruct every sample of the input. Various methods have been reported for the time-varying filter bank design; all of them, however, utilize structures for conventional PR filter banks. These conventional structures that have been applied in the past result in different limitations in each method. This paper introduces a new structure for exactly reconstructing time-varying analysis-synthesis filter banks. This structure consists of the conventional filter bank followed by a time-varying post filter. The new method requires neither the redesign of the analysis sections nor the use of any intermediate analysis filters during transition periods. It provides a simple and elegant procedure for designing time-varying filter banks without the disadvantages of the previous methods