Dynamic interactions between accommodation and convergence

Frequency-domain equations were derived for the current dual-interaction model of accommodation and convergence control, and its adaptive behavior was related to the system's parameters. Contrary to predictions based on the steady-state performance of the model [18], dynamic analysis showed that the AC/A is sensitive to the method of measurement and a procedure is established for its reliable determination. Additionally, the results provided theoretical support for the empirical finding that low AC/A and CA/C ratios are associated with high accommodative and convergence adaptation, respectively [15]. The derived equations should help future studies relate the physiological behavior of accommodative and convergence to specific model parameters.     

CSRS-MAC: Cluster Based Synchronous Radio Scheduling MAC Protocol Using Carrier Sense Multiple Access for Wireless Sensor Network

Wireless Personal Communications - Wireless sensor network is gaining popularity due to its large-scale deployment in Internet of Things. The constraints of resources influence the protocol design...     

Analysis of dynamic magnetic resonance images

Dynamic magnetic resonance (MR) imaging with contrast agents is a very promising technique for studying tissue perfusion in vivo. A temporal series of magnetic resonance images of the same slice are acquired following the injection of a contrast agent into the blood stream. The image intensity depends on the local concentration of the contrast agent, so that tissue perfusion can be studied by the image series. A new method of analyzing such series is described here. Nonparametric linear regression is used for modeling the image intensity along the series on a pixel by pixel basis. After modeling, some relevant quantities describing the time series are obtained and displayed as images. Due to its flexibility, this approach is preferred to parametric modeling when pathology is present since this can induce a wide spread of patterns for the pixel image intensity along time. Results of the application of the method to series of dynamic magnetic resonance images from ischaemic rat brains after the injection of the susceptibility agent Sprodiamide Inj. (Dy-DTPA-BMA) are shown and compared to results from a related known method.     

A monolithic DC temperature compensation bias scheme for multistageHEMT integrated circuits

This work benchmarks the first demonstration of a multistage monolithic HEMT IC design which incorporates a DC temperature compensated current-mirror bias scheme. This is believed to be the first demonstrated monolithic HEMT bias scheme of its kind. The active bias approach has been applied to a 2-18 GHz five-section low noise HEMT distributed amplifier which achieves a nominal gain of 12.5 dB and a noise figure <2.5 dB across a 2-18 GHz band, The regulated current-mirror scheme achieves better than 0.2% current regulation over a 0-125°C temperature range, The RF gain response was also measured over the same temperature range and showed less than 0.75 dB gain degradation. This results in a -0.006 dB/°C temperature coefficient which is strictly due to HEMT device G_m variation with temperature. The regulated current-mirror circuit can be employed as a stand-alone V_gs-voltage reference circuit which fan be monolithically applied to the gate bias terminal of existing HEMT ICs for providing temperature compensated performance, This monolithic bias approach provides a practical solution to DC bias regulation and temperature compensation for HEMT MMICs which can improve the performance, reliability, and cost of integrated microwave assemblies (IMAs) used in space-flight military applications     

Advanced Call Scheduling for Testing a Telecommunications Network

This paper describes an advanced scheduling system and method for generating large volumes of calls to be used for testing a telecommunications network. The system is capable of preparing large-scale and complex network tests by viewing the task as a scheduling problem. The various requirements of the scheduling problem are analysed and represented as constraints or optimisation criteria. A fast heuristic method is proposed for solving the problem. The approach is based on a greedy algorithm for constructing solutions and it incorporates limited backtracking and dynamic value-ordering heuristics. The algorithm and system are currently being used for call charge verification in BT's PSTN and CSP networks.     

116-fs soliton source based on an Er-Yb codoped waveguide amplifier

A passively mode-locked soliton ring fiber laser is investigated that utilizes a 4.5-cm erbium-ytterbium (Er-Yb) codoped waveguide amplifier as the gain element. The resulting short cavity (1.3 m of fiber) eliminates multipulsing behaviour and reduces the effects of resonant sidebands, enabling generation of 116-fs solitons with a pulse energy of 160 pJ at a fundamental repetition rate of 130 MHz     

A comparison of the trap properties and locations within GaAs fieldeffect transistors measured under different bias conditions

The activation energy and capture cross section of traps found in GaAs field effect transistors (GaAs FETs) have been measured with both ohmic channel and current saturation bias using a variety of transient, frequency dispersion, and noise spectroscopy techniques. With current saturation bias these effects have been seen in both the transconductance and the output conductance. The results for all methods and bias conditions are compared with those found by others. The relative sensitivity of the techniques and the location of the traps are discussed     

An oil import fee and drilling activity in the USA : A comment

Edward F. Renshaw's [5] recent analysis of the impact of a $5/bbl oil import fee on drilling activity in the USA is re-examined. Specifically, this comment shows: (i) the initial stimulus to the US rotary rig count of 420 new rigs would not completely disappear over the next five years, but last much longer; (ii) the initial employment impact would be more than twice as large as Renshaw suggested (39 060 rather than 18 480); and (iii) the relevant social cost per new job (excluding transfers) could be as small as $19 200, more than 80 times smaller than Renshaw's estimate of $1.6 million.     

Dielectric characterization of low-loss materials a comparison oftechniques

Measurements on low-loss materials using closed and open cavity resonators, and dielectric resonator methods are presented. Results indicate that consistent measurement results can be obtained with a number of well-characterized fixtures. Uncertainties associated with each method are addressed. Measurements also were performed on materials used in previous intercomparisons