A compact ACS-fed dual-band monopole antenna for LTE,WLAN/WiMAX and public safety applications

In this paper, a compact asymmetric coplanar strip (ACS)-fed printed monopole antenna for dual frequency operation is presented. The proposed antenna is composed of an ACS-fed monopole structure and two semi circle shaped radiating branches, which occupies a very small size of 13.4 × 22.7 mm² including the ground plane. By properly selecting the length and position of these branches, two desired operating bands can be achieved and tuned independently. The simulated and measured return loss results shows that the proposed antenna can be used for long term evolution 2500 (2500–2690 MHz), WLAN 5.2 GHz (5.15–5.35 GHz)/5.8 GHz (5.725–5.825 GHz), WiMAX 5.5 GHz (5.28–5.85 GHz) and 4.9 GHz (4.94–4.99 GHz) public safety applications. The omnidirectional and bidirectional radiation pattern characteristics in H-plane and E-plane of the proposed antenna along with acceptable peak gain make the best suitable candidate for the above intended applications.     

Top-down proteomic analysis by MALDI-TOF profiling: Concentration-independent biomarkers

Although numerous protein biomarkers have been correlated with advanced disease states, no new clinical assays have been developed. Goals often anticipate disease-specific protein changes that exceed values among healthy individuals, a property common to acute phase reactants. This review considers somewhat different approaches. It focuses on intact protein isoform ratios that present a biomarker without change in the total concentration of the protein. These will seldom be detected by peptide level analysis or by most antibody-based assays. For example, application of an inexpensive method to large sample groups resulted in observation of several polymorphisms, including the first structural polymorphism of apolipoprotein C1. Isoform distribution of this protein was altered and was eventually linked to increased obesity. Numerous other protein isoforms included C- and N-terminal proteolysis, changes of glycoisoform ratios and certain types of sulfhydryl oxidation. While many of these gave excellent statistical correlation with advanced disease, clinical utility was not apparent. More important may be that protein isoform ratios were very stable in each individual. Diagnosis by longitudinal analysis of the same individual might increase sensitivity of protein biomarkers by 20-fold or more. Protein changes that exceed the range of values found among healthy individuals may be uncommon.     

Modeling expert problem solving in a game of chance: a Yahtzee© case study

Although developments on software agents have led to useful applications in automation of routine tasks such as electronic mail filtering, there is a scarcity of research that empirically evaluates the performance of a software agent versus that of a human reasoner, whose problem-solving capabilities the agent embodies. In the context of a game of a chance, namely Yahtzee©, we identified strategies deployed by expert human reasoners and developed a decision tree for agent development. This paper describes the computer implementation of the Yahtzee game as well as the software agent. It also presents a comparison of the performance of humans versus an automated agent. Results indicate that, in this context, the software agent embodies human expertise at a high level of fidelity.     

FireFly: a cross-layer platform for real-time embedded wireless networks

We propose a cross-layer approach with tightly-coupled time synchronization for real-time support and predictable lifetime in battery-operated sensor networks. Our design spans a sensor hardware platform with hardware-based global time synchronization, a TDMA link layer protocol with collision-free multi-hop support and node scheduling algorithms for maximum concurrency and streaming. Our dual-radio sensor platform, FireFly, features an IEEE 802.15.4 transceiver and supports global time synchronization indoors by using an AM radio carrier-current method and an atomic clock receiver for outdoors. A TDMA-based link protocol, RT-Link, leverages the hardware for fixed and mobile nodes with a near-optimal and predictable node lifetime of over 2 years. It outperforms comparable sensor network link protocols such as B-MAC and S-MAC in terms of end-to-end latency and throughput and node lifetime across all duty cycle ratios. Operating over RT-Link is MAX, a scheduling framework which offers optimal transmission concurrency and bandwidth management for networks with regular structure. Through analysis and experiments we show that global time sync is a robust, economical and scalable alternative to in-band software-based techniques. To illustrate the capabilities and flexibility of our platform, we describe our experiences with two-way voice streaming over multiple hops. We have deployed a 42-node network with sub-100 μs synchronization accuracy in the NIOSH experimental coal mine for people-tracking and voice communication.

Common-input models for multiple neural spike-train data

Recent developments in multi-electrode recordings enable the simultaneous measurement of the spiking activity of many neurons. Analysis of such multineuronal data is one of the key challenge in computational neuroscience today. In this work, we develop a multivariate point-process model in which the observed activity of a network of neurons depends on three terms: (1) the experimentally-controlled stimulus; (2) the spiking history of the observed neurons; and (3) a hidden term that corresponds, for example, to common input from an unobserved population of neurons that is presynaptic to two or more cells in the observed population. We consider two models for the network firing-rates, one of which is computationally and analytically tractable but can lead to unrealistically high firing-rates, while the other with reasonable firing-rates imposes a greater computational burden. We develop an expectation-maximization algorithm for fitting the parameters of both the models. For the analytically tractable model the expectation step is based on a continuous-time implementation of the extended Kalman smoother, and the maximization step involves two concave maximization problems which may be solved in parallel. The other model that we consider necessitates the use of Monte Carlo methods for the expectation as well as maximization step. We discuss the trade-off involved in choosing between the two models and the associated methods. The techniques developed allow us to solve a variety of inference problems in a straightforward, computationally efficient fashion; for example, we may use the model to predict network activity given an arbitrary stimulus, infer a neuron's ring rate given the stimulus and the activity of the other observed neurons, and perform optimal stimulus decoding and prediction. We present several detailed simulation studies which explore the strengths and limitations of our approach.     

Magnetic properties of Cu-Cd ferrite investigated by Mössbauer spectroscopy

Samples of the copper-cadmium ferrite series Cd _x Cu_1–x Fe₂O₄ (x=0 to 1) have been investigated by means of Mössbauer spectroscopy at 77 K. Mössbauer spectra forx=0.0 to 0.7 suggest the existence of two hyperfine fields, one due to the Fe³⁺ tetrahedral ions (A-sites) and the other due to the Fe³⁺ octahedral ions (B-sites), while forx=0.8 it shows relaxation behaviour and forx0.9 it exhibits a paramagnetic quadrupole doublet. The systematic dependence of the isomer shifts, line widths, quadrupole interactions and nuclear magnetic fields of⁵⁷Fe³⁺ ions in both A and B sites has been determined as a function of cadmium content. The variation of nuclear magnetic fields at the A and B sites is explained on the basis of the A-B and B-B supertransferred hyperfine interactions. Analysis of the average Mössbauer line widths as a function of cadmium concentration suggests that the relaxation spectrum observed atx=0.8 (77 K) is possibly due to domain wall oscillations. It has been found here that QS (B) increases from CuFe₂O₄to CdFe₂O₄ as the cadmium concentration is increased.     

Proactive thermal management in green datacenters

The increasing demand for faster computing and high storage capacity has resulted in an increase in energy consumption and heat generation in datacenters. Because of the increase in heat generation, cooling requirements have become a critical concern, both in terms of growing operating costs as well as their environmental and societal impacts. Presently, thermal management techniques make an effort to thermally profile and control datacenters’ cooling equipment to increase their efficiency. In conventional thermal management techniques, cooling systems are triggered by the temperature crossing predefined thresholds. Such reactive approaches result in delayed response as the temperature may already be too high, which can result in performance degradation of hardware.     

Synthesis, characterization and a.c. conductivity of polypyrrole/Y2O3 composites

Conducting polymer composites of polypyrrole/yttrium oxide (PPy/Y₂O₃) were synthesized byin situ polymerization of pyrrole with Y₂O₃ using FeCl₃ as an oxidant. The Y₂O₃ is varied in five different weight percentages of PPy in PPy/Y₂O₃ composites. The synthesized polymer composites are characterized by infrared and X-ray diffraction techniques. The surface morphology of the composite is studied by scanning electron microscopy. The glass transition temperature of the polymer and its composite is discussed by DSC. Electrical conductivity of the compressed pellets depends on the concentration of Y₂O₃ in PPy. The frequency dependent a.c. conductivity reveals that the Y₂O₃ concentration in PPy is responsible for the variation of conductivity of the composites. Frequency dependent dielectric constant at room temperature for different composites are due to interfacial space charge (Maxwell Wagner) polarization leading to the large value of dielectric constant. Frequency dependent dielectric loss, as well as variation of dielectric loss as a function of mass percentage of Y₂O₃ is also presented and discussed.     

Total radiation dose at geostationary orbit

Active semiconductor components in satellites are sensitive to accumulated ionization radiation dose. Radiation dose and shielding estimations for electronic components are usually carried out using NASA models of space radiation particle flux. Accurate measurement of accumulated dose during the life of a satellite is essential for optimizing radiation shielding design for electronic components. Dosimeters were designed using radiation sensitive field-effect transistors (RADFETs) and accumulated dose at geostationary orbit was measured. Radiation dose as measured by these dosimeters with spherical aluminum shields are presented and compared with NASA model doses.     

A comparative dielectric relaxation study of PMN–PT and PMN–PZ ceramics using impedance spectroscopy

AC-impedance spectroscopic studies in the temperature range of 30–400 °C are carried out on solid solutions of lead magnesium niobate (PMN) with lead titanate (PT) and lead zirconate (PZ), both of them in the 65/35 atomic ratio. For PMN–PT this corresponds to the morphotropic phase boundary composition (with normal ferroelectric behaviour), and for PMN–PZ it is near the phase boundary between normal ferroelectric and relaxor ferroelectric compositions. The variation of dielectric permittivity with temperature at different frequencies shows normal ferroelectric and relaxor-like dependence for PMN–PT and PMN–PZ, respectively. Temperature-dependent spectroscopic modulus plots reveal a much broader peak for PMN–PZ compared to that for PMN–PT, which is consistent with the dielectric behaviour. PMN–PT shows nearly ideal Debye behaviour below T_m (the temperature of the permittivity maximum) and the behaviour departs from ideality above T_m, whereas non-ideal Debye behaviour is seen both below and above T_m for PMN–PZ. Complex modulus plots fit well with two depressed semicircles and three depressed semicircles, respectively, for PMN–PT and PMN–PZ. The relaxation observed in the spectroscopic plots around 1 MHz for PMN–PT has been assigned to polarisation relaxation expected for normal-sized domains. No such relaxation could be observed for PMN–PZ around 1 MHz because of the mesoscopic domain sizes.