Experimental Determination of Cutting Forces and Surface Roughness when Turning 50CrV4 Steel (SAE 6150) and Modelling with the Artificial Neural Network Approach

In this experimental study, 50CrV4 (SAE 6150) steel parts were subjected to machining test using coated and uncoated carbide cutting tools through single point turning operation. The turning tests were performed at various cutting parameters (cutting speed, feed rate and depth of cut). In the light of these parameters, cutting forces and surface roughness values obtained were determined. A suitable cutting force measurement dynamometer was used for measuring the three cutting force components. The surface roughness values were also measured. The results of experiments were modelled with artificial neural network system. The relation between the cutting forces and surface roughness values was defined.     

Sympathoexcitation from the rostral ventrolateral medulla is mediated by spinal NMDA receptors

These studies examined the role of spinal N-methyl-D-aspartic acid (NMDA) receptors in mediating sympathoexcitation evoked by stimulation of neurons in the rostral ventrolateral medulla (RVLM). In urethane-anesthetized rats, blood pressure, heart rate, and splanchnic sympathetic nerve activity (SNA) were recorded. The NMDA receptor antagonist D-2-amino-7-phosphonoheptanoic acid (D-AP7) was administered to the spinal cord via intrathecal (IT) catheter. Blockade of spinal NMDA receptors reduced arterial blood pressure, heart rate, and SNA. Spinal administration of D-AP7 markedly attenuated the pressor and sympathoexcitatory responses evoked by L-glutamate stimulation of the RVLM. The small increases in heart rate evoked by stimulation of the RVLM were not affected by IT administration of D-AP7. These results indicate that NMDA receptors in the spinal cord mediate the pressor and sympathoexcitatory responses evoked by activation of a bulbospinal pathway originating from the RVLM. Moreover, these data suggest that excitatory amino acid neurotransmitters and NMDA receptors in the spinal cord play an important role in the maintenance and regulation of SNA and cardiovascular function.     

Recognition by prototypes

A scheme for recognizing 3D objects from single 2D images under orthographic projection is introduced. The scheme proceeds in two stages. In the first stage, the categorization stage, the image is compared to prototype objects. For each prototype, the view that most resembles the image is recovered, and, if the view is found to be similar to the image, the class identity of the object is determined. In the second stage, the identification stage, the observed object is compared to the individual models of its class, where classes are expected to contain objects with relatively similar shapes. For each model, a view that matches the image is sought. If such a view is found, the object's specific identity is determined. The advantage of categorizing the object before it is identified is twofold. First, the image is compared to a smaller number of models, since only models that belong to the object's class need to be considered. Second, the cost of comparing the image to each model in a class is very low, because correspondence is computed once for the whole class. More specifically, the correspondence and object pose computed in the categorization stage to align the prototype with the image are reused in the identification stage to align the individual models with the image. As a result, identification is reduced to a series of simple template comparisons. The paper concludes with an algorithm for constructing optimal prototypes for classes of objects.     

W-CDMA Uplink Practical Capacity and Interference Statistics of Rural Highways Cigar-Shaped Microcells with Imperfect Power Control and Finite Transmitted Power

The capacity and the interference statistics of the sectors of the cigar-shaped W-CDMA microcell are studied. A model of 5 microcells is used to analyze the uplink. The microcells are assumed to exist in rural zones. The capacity and the interference statistics of the microcell are studied for different sector range, different antenna side lobe levels, different values of the break point distance, different values of the propagation parameter s ₂ and different standard deviation of the power control error.     

Bit rate of HSDPA in tunnel’s cigar-shaped microcells

This paper presents the bit rate of High Speed Downlink Packet Access (HSDPA) mode for cigar-shaped microcells deployed at tunnels. The hybrid propagation loss model with log-normal shadowing is used to calculate the signal to interference plus noise ratio taking into account the expected value and the variance of the interference. A model of ten cigar-shaped microcells is used in the analysis. The effect of the propagation parameters on the HSDPA performance (coverage and bit rate) is studied. It is found that, with a sector transmitted power of 1 W, a sector with a range of 1 km can be deployed with the worst case propagation parameters values. It is shown that it is impossible to support more than 6 HSDPA codes for full coverage within the sector what ever the power assigned to the HSDPA service.     

Propagation Loss Measurement of Wireless Body Area Network at 2.4 GHz and 3.35 GHz Bands

The main purpose of this work is to measure and analyze the propagation loss of the Wireless Body Area Network (WBAN) in frequency and time domain at two frequency bands, namely 2.4 GHz band with 80 MHz bandwidth and 3.35 GHz band with 500 MHz bandwidth. Four different scenarios (front to front, front to back, front to off-body node and back to off-body node) using many antenna´s locations on the body are used to investigate the channel response (path loss) of WBAN. It is found that the front to front channels and the front to off-body node channels have a low fading. The front to back channels and the back to off-body node channels have a high fading that can be approximated by the Distorted Rayleigh fading. Thus the WBAN range for the front to off-body node scenario is more than the range of the back to off-body node scenario.

     

Human Body Shadowing at 28 GHz

Wireless Personal Communications - It is well known that human body shadowing is a significant propagation effect in indoor communications especially at frequencies higher than 10 GHz....     

W-CDMA uplink capacity and interference statistics of cigar-shaped microcells in over-ground train service with imperfect power control and finite transmitted power

The capacity and the interference statistics of the sectors of the shaped Wideband Code Division Multiple Access (W-CDMA) microcells serving over-ground trains are studied. A model of five microcells is used to analyze the uplink. The capacity and the interference statistics of the microcell are studied for different antenna sidelobe levels and different sector ranges. In the study, imperfect power control and limited transmitted power are assumed. The effect of the power assigned to the uplink pilot is taken into account. It is shown that, the sector capacity depends on the train’s position. The uplink sector capacity limits (upper and lower) are presented. The lower capacity limit is given as a function of the sector range and the sidelobe level of the directive antenna used in each sector.     

WCDMA downlink capacity of cigar-shaped microcells for long tunnels

In this paper, the Wideband Code Division Multiple Access (WCDMA) downlink capacity and the interference statistics of long tunnel cigar-shaped microcells are analyzed. The hybrid model of propagation is used in the analysis where a model of 10 cigar-shaped microcells is used. The downlink capacity is given for different sector radio R, break point distance R _b and propagation parameters (s and γ). It is found that the effect of changing the value of the propagation parameter s is very small. Also, it is noticed that, increasing the propagation parameter γ will increase the sector downlink. It is found that, the effect of changing the break point distance R _b is quasi null. Finally it is noticed that the imperfect power control reduces the downlink capacity by 4 %.     

Direct liquid fuel cells: A review

Direct liquid fuel cells (DLFCs) are one of the most promising types of fuel cells due to their high energy density, simple structure, small fuel cartridge, instant recharging, and ease of storage and transport. Alcohols such as methanol and ethanol were the most common types of fuel used, although glycols and acids are also used. The main problem that arose in direct liquid fuel cells (DLFCs) was the high cost of the catalyst and the high catalyst loading. Other issues, such as fuel crossover, cathode flooding, the generation of various side products, fuel safety and unproven long-term durability, must also be solved to improve the performance of DLFCs. More research studies were required to increase its performance and foster commercialization. Currently, there were some commercial products using direct methanol fuel cells (DMFCs) and direct ethanol fuel cells (DEFCs), but the other types of DLFCs were generally still in the research stage. This paper aims to review the different types of liquid fuels directly used in fuel cells and identify their properties, challenges and applications.