A Four Slot Dual Feed and Dual Band Reconfigurable Antenna for Fixed Satellite Service Applications

A dual feed and dual-band reconfigurable antenna is designed, analyzed, and prototyped in this work for fixed satellite service communication applications. The designed model occupies the compact dimension of 24X21X1.2 mm on FR4 substrate and provides an input impedance of 50 ohms at both ports. The proposed model offers additional circular polarization characteristics at both the resonating bands. The PIN diode-based switching conditions, and the frequency reconfigurability analysis in both simulation and measurement are almost match. The combination of dual-band resonance, frequency reconfigurable nature, and compact dimension makes this model an attractive candidate in the specified field with considerable gain (8.5 dB) and efficiency (80%)

Tests on light gage steel diaphragms

This report supplements and extends the scope of Report No. 319, ;lStructural Performance of Light Gage Steel Diaphragms , by Dr. Larry D. Luttrell. Eleven static load tests were conducted on 22 gage narrow rib roof decks to investigate the effect of length of the diaphragm, type of welding, and diaphragm material tensile properties on the shear stiffness and strength of the diaphragm. The behavior of a diaphragm under reversed load at two different levels) one at 0.4 x ultimate static load and the other at 0.6 x ultimate static load was explored by conducting five tests. The tests at a high level of reversed load (0.6 x Pu) were motivated by the fact that during earthquakes and blasts structures are subjected to high levels of reversed load for a few cycles. Three static load tests were performed on standard corrugated diaphragms to supplement the tests done by Dr. Luttrell and reported in Report No. 319 so as to formulate the strength (Plf.) of a diaphragm without intermediate fasteners* as a function of its thickness. It is confirmed by the above investigations that the shear stiffness of a diaphragm is dependent mainly on the length of the diaphragm, and the type and spacing of fasteners. The strength of a diaphragm is seen to be dependent mainly on the thickness of the diaphragm, and the type and spacing of the • The definition is the same as in Report 319. fasteners. Five cycles of reversed load at +0.6 x ultimate load of an identical diaphragm under static load resulted in a maximum reduction of 25% in strength of the diaphragm

Design of I-shaped beams and columns with diaphragm bracing

Cold-formed steel panels often are used as wall sheathing, roof decking or floor decking in steel framed buildings or pre-engineered metal buildings. Diaphragms formed by interconnecting these panels have considerable in-plane shear resistance, and can be utilized as bracing against buckling for individual members of a steel frame. For wall columns the diaphragm may be either directly attached or connected to girts which in turn are connected to the columns. A procedure is presented for the design of I-section beams and columns with diaphragm or diaphragm-girt bracing. The procedure is based on the ultimate load capacity of fully braced members, utilizing a conservative estimate of the shear strength and shear rigidity of the diaphragm. Design examples are included. The utilization of existing wall, floor or roof diaphragms as bracing for individual beams and columns can eliminate the need for other types of bracing, and/or reduce required member sizes. Thus it contributes to economical design

Design recommendations for diaphragm-braced beams, columns and wall-studs

INTRODUCTION Light gage steel panels are often used as wall sheathing, roof decking or floor covering in steel framed buildings. These panels carry loads normal to their plane by virtue of their bending strength. Also, diaphragms formed by interconnecting such panels can resist shear deformation in their plane. Because of this shear resisting capacity, diaphragms can be very effective in bracing columns and beams of a steel frame against lateral buckling and, thus, increase the load carrying capacity of these members. For wall columns, such diaphragm bracing may be either directly attached or connected to girts which in turn are connected to the columns. The ribs of the panels must be perpendicular to the members to which they are attached. These diaphragms as wall, roof or floor, must be present in any event, and therefore, are available at no extra cost. If properly utilized for bracing, they can lead to economical design of beams and columns. Research has been conducted at Cornell University since 1961* (1),(2),(3) to determine the increased load carrying capacities of beams and columns due to diaphragm or diaphragmgirt bracing. Based on the results of the investigation to date, recommendations are made in this report for the design of beams and columns considering the effect of diaphragm braci~g. * Superscripts in parentheses refer to the numbers in the References. Design criteria are given in Part 2; the general design procedure in Part 3, and the specific design formulae in Part 4 are illustrated by some practical examples in Part 5. The design procedure suggested herein is based on the ultimate load capacity of the beams or columns, utilizing a conservative estimate of the strength and rigidity of the diaphragm bracing. Effectiveness of diaphragm bracing or diaphragm-girt bracing in preventing lateral buckling of beams and columns depends on its two fundamental characteristics: (1) rigidity, and (2) strength. In general, it is not economical to provide anything less than fUll bracing, where full bracing is defined as bracing such that any increase in rigidity or strength of diaphragm will not cause any substantial increase in the load carrying capacity of the braced members. Therefore, the design procedure in this report is limited to only fullyli braced beams and columns. The procedure is based on analyses of I-section beams under uniform moment, and I-section columns under axial load. These analyses have been substantiated by tests of thirtyfive diaphragm-braced assemblies as reported in the references. Information regarding the load carrying capacities of beams and columns with less than full bracing can be obtained from Reference 3. The capacity of channel and Z-section beams SUbjected to uniform moment also is discussed in Reference 3. Cantilever beams and channel and Z-section beams subjected to loads in the plane of the web are currently under investigation. Light wall studs braced by wallboard on one or both faces are no different basically from columns braced by light steel diaphragms. In order to make the methods developed here applicable to such wall studs, the Appendix gives a few typical test values for diaphragm rigidity and strength of customary types of wallboard

A Novel Energy Aware Clustering Mechanism with Fuzzy Logic in MANET Environment

A Mobile Ad Hoc Networks (MANETs) comprises of the vast range of devices such as sensors, smart phones, laptops and other mobile devices that connect with each other across wireless networks and collaborate in a dispersed fashion to offer network functions in the absence of a permanent infrastructure. The Cluster Head (CH) selection in a clustered MANET is still crucial for lowering each node's energy consumption and increasing the network's lifetime. However, in existing clustering mechanism trust of the all nodes are presumed those causes increased challenge in the MANET environment. Security is a crucial factor when constructing ad-hoc networks. In a MANET, energy consumption in route optimization is dependent on network resilience and connectivity. The primary objective of this study is to design a reliable clustering mechanism for MANETs that takes energy efficiency into account. For trusted energy-efficient CH in the nodes, a safe clustering strategy integrating energy-efficient and fuzzy logic based energy clustering is proposed to address security problems brought about by malicious nodes and to pick a trustworthy node as CH. To improve the problem findings Bat algorithm (BAT) is integrated with Particle Swarm Optimization (PSO). The PSO technique is inspired because it imitates the sociological characteristics of the flock of the birds through random population. The BAT is a metaheuristic algorithm inspired by microbat echolocation behavior that uses pulse average with global optimization of the average path in the network. Hybrid Particle Swarm Optimization (HPSO) and BAT techniques are applied to identify the best route between the source and destination. According to the simulation results, the suggested Fuzzy logic Particle Swarm Optimization BAT (FLPSO-BAT) technique has a minimum latency of 0.0019 milliseconds, with energy consumption value of 0.09 millijoules, maximal throughput of 0.76 bits per sec and detection rate of 90.5% without packet dropping attack

Crustal Heating and Quiescent Emission from Transiently Accreting Neutron Stars

Nuclear reactions occurring deep in the crust of a transiently accreting neutron star efficiently maintain the core at a temperature >5e7 K. When accretion halts, the envelope relaxes to a thermal equilibrium set by the flux from the hot core, as if the neutron star were newly born. For the time-averaged accretion rates typical of low-mass X-ray transients, standard neutrino cooling is unimportant and the core thermally re-radiates the deposited heat. The resulting luminosity has the same magnitude as that observed from several transient neutron stars in quiescence. Confirmation of this mechanism would strongly constrain rapid neutrino cooling mechanisms for neutron stars. Thermal emission had previously been dismissed as a predominant source of quiescent emission since blackbody spectral fits implied an emitting area much smaller than a neutron star's surface. However, as with thermal emission from radio pulsars, fits with realistic emergent spectra will imply a substantially larger emitting area. Other emission mechanisms, such as accretion or a pulsar shock, can also operate in quiescence and generate intensity and spectral variations over short timescales. Indeed, quiescent accretion may produce gravitationally redshifted metal photoionization edges in the quiescent spectra (detectable with AXAF and XMM). We discuss past observations of Aql~X-1 and note that the low luminosity X-ray sources in globular clusters and the Be star/X-ray transients are excellent candidates for future study.Comment: 5 pages, 2 ps figures, uses AASTEX macros. To appear in ApJ letters, 10 September 1998. Revised to conform with journal; minor numerical correction

Bright flares from the X-ray pulsar SWIFT J1626.6-5156

We have performed a timing and spectral analysis of the X-ray pulsar SWIFT J1626.6-5156 during a major X-ray outburst in order to unveil its nature and investigate its flaring activity. Epoch- and pulse-folding techniques were used to derive the spin period. Time-average and pulse-phase spectroscopy were employed to study the spectral variability in the flare and out-of-flare states and energy variations with pulse phase. Power spectra were obtained to investigate the periodic and aperiodic variability. Two large flares, with a duration of ~450 seconds were observed on 24 and 25 December 2005. During the flares, the X-ray intensity increased by a factor of 3.5, while the peak-to-peak pulsed amplitude increased from 45% to 70%. A third, smaller flare of duration ~180 s was observed on 27 December 2005. The flares seen in SWIFT J1626.6-5156 constitute the shortest events of this kind ever reported in a high-mass X-ray binary. In addition to the flaring activity, strong X-ray pulsations with Pspin=15.3714+-0.0003 s characterise the X-ray emission in SWIFT J1626.6-5156. After the major outburst, the light curve exhibits strong long-term variations modulated with a 45-day period. We relate this modulation to the orbital period of the system or to a harmonic. Power density spectra show, in addition to the harmonic components of the pulsation, strong band-limited noise with an integrated 0.01-100 Hz fractional rms of around 40% that increased to 64% during the flares. A weak QPO (fractional rms 4.7%) with characteristic frequency of 1 Hz was detected in the non-flare emission. The timing (short X-ray pulsations, long orbital period) and spectral (power-law with cut off energy and neutral iron line) properties of SWIFT J1626.6-5156 are characteristic of Be/X-ray binaries

The Be/X-ray transient 4U 0115+63/V635 Cas I. A consistent model

We present photometry and high SNR spectroscopy in the classification region of V635 Cas, the optical counterpart to the transient X-ray pulsator 4U 0115+63, taken at a time when the circumstellar envelope had disappeared. V635 Cas is classified as a B0.2Ve star at a distance of 7-8 kpc. We use the physical parameters derived from these observations and the orbit derived from X-ray observations to elaborate a model of the system based on the theory of decretion discs around Be stars. We show that the disc surrounding the Be star must be truncated by the tidal/resonant interaction with the neutron star and cannot be in a steady state. This explains many of the observed properties of 4U 0115+63. In particular, because of this effect, under normal circumstances, the neutron star cannot accrete from the disc, which explains the lack of regular Type I outbursts from the source.Comment: 10 pages, 6 figures, uses aa.cls. To appear in Astronomy and Astrophysics Main Journa

Discovery of a Be/X-ray Binary Consistent with the Position of GRO J2058+42

GRO J2058+42 is a 195 s transient X-ray pulsar discovered in 1995 with BATSE. In 1996, RXTE located GRO J2058+42 to a 90% confidence error circle with a 4' radius. On 20 February 2004, the region including the error circle was observed with Chandra ACIS-I. No X-ray sources were detected within the error circle, however, 2 faint sources were detected in the ACIS-I field-of-view. We obtained optical observations of the brightest object, CXOU J205847.5+414637, that had about 64 X-ray counts and was just 0.3' outside the error circle. The optical spectrum contained a strong H alpha line and corresponds to an infrared object in the 2MASS catalog, indicating a Be/X-ray binary system. Pulsations were not detected in the Chandra observations, but similar flux variations and distance estimates suggest that CXOU J205847.5+414637 and GRO J2058+42 are the same object. We present results from the Chandra observation, optical observations, new and previously unreported RXTE observations, and a reanalysis of a ROSAT observation.Comment: 18 pages, 6 figures, Accepted for publication in the Astrophysical Journa