A Material Perspective on Consequence of Deformation Heating During Stamping of DP Steels

Recent studies showed that, during stamping of high strength steels at industrially relevant production rates, local temperature in the blank may rise up to 200°C – 300°C due to deformation heating. Moreover, die temperature may also rise up to 100°C – 150°C for progressive stamping dies. Based on the common assumption that the blank softens as the temperature increases, thermal softening creates a margin in Forming Limit Diagram (FLD) and therefore the FLD determined at room temperature can safely be used for those cases. In this article, the validity of this assumption on DP590 steel is questioned by high temperature tensile tests (RT - 300°C) at various strain rates (10-3 s-1 – 1 s-1). The results indicated a decrease both in uniform and total elongation in 200°C – 300°C range together with several other symptoms of Dynamic Strain Aging (DSA) at all strain rates. Concurrent with the DSA, the simulated FLD confirms the lower formability at high temperature and strain rates. Thus, it is concluded FLD determined at RT may not be valid for the investigated steels

Is song processing distinct and special in the auditory cortex?

Is the singing voice processed distinctively in the human brain? In this Perspective, we discuss what might distinguish song processing from speech processing in light of recent work suggesting that some cortical neuronal populations respond selectively to song and we outline the implications for our understanding of auditory processing. We review the literature regarding the neural and physiological mechanisms of song production and perception and show that this provides evidence for key differences between song and speech processing. We conclude by discussing the significance of the notion that song processing is special in terms of how this might contribute to theories of the neurobiological origins of vocal communication and to our understanding of the neural circuitry underlying sound processing in the human cortex

Two-element antenna-active phase shifter packaging at 77 GHz

This work presents a low cost and wire-bonded active phase shifter chip to RF circuitry on PCB board packaging for implementing a two-element phased array antenna at 77 GHz. The 1.5 mm and times; 1.1 mm chip is embedded in RO3003 PCB board and its GSG ports are wire-bonded to CPW lines that are expanded to feed the patch antenna on the PCB board. A low loss CPW to microstrip line transition is designed to exploit and transmit the signal from the GSG pads on the chip to the microstrip line on the PCB. The beam of the two-element array can be steered between and plusmn;20 and deg; by controlling the DC bias voltage of the active phase shifter chip

A COMPARATIVE ANALYSIS OF 802.11b AND 802.11g NETWORK

Recent advances in wireless technology has led to the introduction of new devices utilizing the 2.4GHz industrial scientific and medical (ISM) unlicensed band traditionally used by Wireless LANS (WLAN). The increasing demand of higher data rate in WLANs has prompted the continual emergence of different 802.11 protocols with increased performance. Interoperability and coexistence between these networks become key issues and must be catered for, to guarantee satisfactory performance of both networks. 802.11 refer to a family of specifications developed by the International Institute of Electrical Electronics Engineering (IEEE) for wireless LAN technology. IEEE accepted the specification for 802.11 in 1997. Wireless Local Area Network (WLAN) has become popular in the home due to ease of installation, and the increasing popularity of laptop computers. WLAN is based on IEEE 802.11 standard and is also known as Wireless Fidelity (Wi-Fi) [1]. In this paper, the comparative analysis of IEEE 802.11b and IEEE 802.11g networks are x-rayed. KEYWORDS: 802.11b, 802.11g, WLAN, IEEE, OFDM, LRWPANS, Wireless Fidelity, Wireless Medium Access Control, Physical Layer

Embedding complete binary trees in product graphs

This paper shows how to embed complete binary trees in products of complete binary trees, products of shuffle-exchange graphs, and products of de Bruijn graphs with small dilation and congestion. In the embedding results presented here the size of the host graph can be fixed to an arbitrary size, while we define no bound on the size of the guest graph. This is motivated by the fact that the host architecture has a fixed number of processors due to its physical design, while the guest graph can grow arbitrarily large depending on the application. The results of this paper widen the class of computations that can be performed on these product graphs which are often cited as being low-cost alternatives for hypercubes. © J.C. Baltzer AG, Science Publishers

Probabilistic System Availability Model and Prevailing Factors for 33kV Primary Power Distribution Feeders in Nigeria

Outage and complimentary load flow analyses of a selected 33kV primary distribution network in Ughelli Delta State, Nigeria, were carried out to depict feeder availability obtainable in the country. Outage and load flow analyses were carried out using parametric statistics and Newton-Raphson computation algorithm respectively. The results provide model distribution of monthly feeder availability, contributions of outage factors and normal load flow values. It was concluded that: monthly feeder availability represented using normal probability distribution function of; shows that overcurrent and earth faults contribute to outage duration, taking 5% to 12% of the month outage duration respectively; coupled with significant line losses and weak voltage profile. Recommendations proposed include: replacement of weak or failed elements and insulations in the systems with new and modern ones to mitigate especially earth faults in the short term; planning for immediate increase in system capacity to accommodate the power demand effectively for present and forecast periods to eliminate load shedding, overload events, and high technical losses; maintenance practice at the planning and execution stages to mitigate failure events and repair time. Keywords – fault, outage, probability, load flow, availability, distribution network

1 mJ pulse bursts from a Yb-doped fiber amplifier

Cataloged from PDF version of article.We demonstrate burst-mode operation of a polarization-maintaining Yb-doped fiber amplifier capable of generating 60 mu J pulses within bursts of 11 pulses with extremely uniform energy distribution facilitated by a novel feedback mechanism shaping the seed of the burst-mode amplifier. The burst energy can be scaled up to 1 mJ, comprising 25 pulses with 40 mu J average individual energy. The amplifier is synchronously pulse pumped to minimize amplified spontaneous emission between the bursts. Pulse propagation is entirely in fiber and fiber-integrated components until the grating compressor, which allows for highly robust operation. The burst repetition rate is set to 1 kHz and spacing between individual pulses is 10 ns. The 40 mu J pulses are externally compressible to a full width at half-maximum of 600 fs. However, due to the substantial pedestal of the compressed pulses, the effective pulse duration is longer, estimated to be 1.2 ps. (C) 2012 Optical Society of Americ

Yeni bir insansız hava aracının (SUAVİ) prototip üretimi ve algılayıcı-eyleyici entegrasyonu

Bu çalısmada, dört-döner rotoru ile helikopter gibi dikine kalkıs ve inis yapabilen aynı zamanda da uçak gibi uzun menzil yatay uçus yeteneğine sahip yeni bir insansız otonom hava aracının mekanik ve aerodinamik tasarımı, karbon kompozit imalatı, algılayıcı eyleyici sistem entegrasyonu ve uçus deneyleri anlatılmıstır. Gelistirilen sistem ve içinde kullanılan algılayıcı eyleyici entegrasyonunun basarımı benzetim ve deneylerle doğrulanmıstır