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Marble sludge wastes (MSW) are investigated as solid precursor for the production of low-temperature calcium silicate hydrate (CSH). Calcined powder of MSW is ball-milled with rice husk ash (RHA) and the slurries are treated in oven at 100C for 24 hours in a context where water evaporation is minimized. The initial CaO:SiO2 molar ratio varies from 1 to 3 (CS, C2S and C3S) and the solution used for the preparation of the calcium silicate hydrate presents NaOH with concentration of 0, 1, 2 and 3 N. FTIR, XRD, Particle size distribution, BET surface area and Environmental Scanning Electron Microscope (ESEM) permitted to confirm the formation of CxS (x = 1, 2, 3) and CSH at 100C through pozzolanic reactions. The increase of the alkalinity of the solution improved the silica dissolution and enhances the formation of CxS and CSH up to 2N. Further increase of the alkalinity affected the silica polymerization, the particle size and the concentration of CxS and CSH into the final matrix. Precursor with CaO:SiO2 = 1 seem to promote more monomers while 2CaO:SiO2 and 3CaO:SiO2 resulted in orthosilicate chains and interlayer respectively. The high reactivity and fine particles (ϕ < 32 nm) of CSH obtained appeared promising for the design of low-cost, environmentally-friendly and sustainable binders as well as others engineering applications including refractory precursors, hydroceramics, insulating matrices, filtration and catalysis.

In this paper, we extend the Amplify-and-Forward cooperative diversity scheme to the context of impulse radio ultra wideband (IR-UWB). In particular, we present the construction of three families of minimal-delay and totally-real distributed algebraic space-time (ST) codes suitable for IR-UWB. The first family encodes adjacent symbols and is based on totally-real cyclic division algebras. The second family encodes the pulses used to transmit one information symbol and permits to achieve high performance levels with lower complexity. Both families of codes achieve full rate, full diversity with non-vanishing determinants for various number of relays. These schemes can be associated with pulse position modulation (PPM), pulse amplitude modulation (PAM) and hybrid pulse position and amplitude modulation (PPM-PAM). The third family of codes is information-lossless and does not require any pulse repetitions. It is specific to M-PPM-M'-PAM with M ges 3 and for all values of M'. Simulations performed over realistic indoor UWB channels are provided to verify the theoretical results.

In this paper, we extend the Amplify-and-Forward cooperative diversity scheme to the context of impulse radio ultra-wideband. In particular, we present the construction of two families of distributed algebraic space-time codes. The first family is based on totally real cyclic division algebras. The second family encodes the pulses used to transmit one information symbol and permits to achieve high-performance levels with lower complexity. Both families of codes achieve full rate, full diversity with non-vanishing determinants with various numbers of relays. Simulations performed over realistic indoor UWB channel models show important performance gains.

Ultra-wideband (UWB) technology has recently attracted the entire wireless community with its great potential for short-range and high data-rate communications. On the other hand, multiantenna (or multiple-input multiple-output) techniques are considered as an effective way to improve the link reliability and transmission rate. In this paper, both aspects are studied through a complete UWB single-input multiple-output (SIMO) channel sounding campaign. The time-domain channel sounder with its antenna array is firstly detailed. Secondly, measurement results will be used to describe interesting antenna array effects and channel behavior (like correlation results and underlying spatial diversity). Finally, in order to show the utility of spatial diversity in UWB systems, the performance of a SIMO system with a Rake receiver will be presented through bit error rate simulations based on measurement results.

Resume La necessite de faire communiquer des robots en environnement hostile (de type centrale nucleaire) a conduit le cea-letl a valoriser ses connaissances de l'etalement de spectre par sequence directe. Cette technique permet en effet de tirer profit des trajets multiples qui ne manquent pas d'affecter les transmissions radio classiques, grâce a une structure de reception originale et un traitement de diversite. D'abord realisees a partir d'un filtre a ondes acoustiques de surface, les recepteurs mis au point ont ensuite utilise des circuits numeriques dedies prenant en compte tout le traitement bande de base, La souplesse apportee permet des lors d'envisager des structures de reception multiutilisateurs orientees haut debit(jusqu'a 10 Mbits/s). Toutes ces recherches trouvent ainsi leurs applications dans des domaines varies: la video-surveillance et les communications sol-train dans le metro, les communications tete queue pour les trains hyper-lourds en sont quelques exemples.

The Golden code is a 2/spl times/2 space-time code that achieves the best known performance with all constellations carved from /spl Zopf/[i]. In this letter, we present the construction of a new coding scheme for 2M-ary biorthogonal pulse position modulations (BPPM) with M/spl ges/4. The proposed code satisfies all of the construction constraints of the Golden code and it has the additional advantage of being totally real making it suitable for low cost carrier-less ultra-wideband terminals. Namely, this totally real construction achieves full rate and full diversity with the best known coding gain and without any shaping losses for 2M-BPPM with M/spl ges/4.

We describe our approach and latest results for Raytheon's RELI (Robust Electric Laser Initiative) program. Our architecture leverages a slab-based, Master Oscillator / Power Amplifier (MOPA) architecture based on Raytheon's unique planar waveguide amplifier. Technical objectives for this effort are to demonstrate > 25 kW output with excellent beam quality and an electrical to optical efficiency > 30%. The planar waveguide architecture provides compact packaging and is inherently scalable to 100 kW or greater in a single beam line. We report on the latest progress and test results for the program.

In this paper, we study the achievable diversity-multiplexing gain (D-MG) tradeoffs over the IEEE 802.15.3a channel model. In particular, we give an exact expression of the D-MG tradeoff for single antenna systems. This expression is based on a statistical model of the integrated energy of the considered channels. At a second time, we evaluate lower and upper bounds on the D-MG tradeoffs of multi-antenna systems. This formulation gives us more insights on the real potential of multi-antenna techniques with UWB systems. It is shown that even though the asymptotical diversity gain has an infinite value, the multi-antenna techniques can be very beneficial in the practical range of signal-to-noise ratios.

In this paper, we present a new full rate scheme for exploiting diversity in multi-antenna ultra-wideband (UWB) systems. The independent data streams that are transmitted simultaneously from the different antennas are rendered orthogonal by the use of modified Hermite pulses. At a second time, appropriate real rotations enhance the transmit diversity level. We also consider, for the first time, the problem of Maximum Likelihood (ML) detection with multi-dimensional PPM and hybrid PPM-PAM constellations that can be used in conjunction with the proposed scheme.

In this paper, we examine the impact of spatial diversity on ultra-wideband (UWB) systems. This diversity is exploited by deploying two antennas at the UWB terminals. For single-antenna systems, spatial diversity is exploited in a distributed manner where a neighboring node can help the source in delivering its message to a destination. In particular, two space-time (ST) coding schemes are proposed. The first one is optimal among all totally-real codes having a constant transmitted energy per antenna. Unlike the classical approach of constructing ST codes over infinite fields, the second construction takes the structure of 2-dimensional constellations into consideration in order to propose an appropriate modulation-specific code. These schemes are associated with multi-antenna arrays and with virtual arrays based on the amplify-and-forward (AF) strategy.

In this paper, we extend the Amplify-and-Forward (AF) co-operative diversity scheme to the context of impulse radio ultra wideband (IR-UWB). In particular, we apply a space-time (ST) coding scheme based on totally-real cyclic division algebras in order to achieve full diversity with no data rate losses. At a second time, the pulse repetitions are exploited in order to enhance the performance of the first scheme and to propose a new scheme that achieves comparable performance with lower complexity. These schemes are associated with pulse position modulation (PPM), pulse amplitude modulation (PAM) and hybrid pulse position and amplitude modulation (PPM-PAM).

The golden code (Belfiore, 2005) is a 2 x 2 space-time (ST) code that achieves the best known performance with all constellations carved from Zopf[i]. On the other hand, impulse radio (IR) time-hopping (TH) ultra wideband (UWB) is a carrier-less baseband transmission technique. Therefore, being complex-valued, the golden code can not be associated with IR-UWB systems. In this paper, we propose a new ST code that satisfies all of the construction constraints of the golden code and that has the additional advantage of being totally real making it suitable for low cost carrier-less UWB terminals. Unlike the golden code that can be associated with all constellations carved from Zopf[i], the proposed code is optimal with binary pulse position modulation (PPM) which is a popular modulation scheme for TH-UWB. Moreover, the proposed scheme permits to achieve full transmit diversity with hybrid pulse position and amplitude modulations (PPAM) having two modulation positions.

In this paper, we extend the Decode-and-Forward cooperative diversity scheme to the context of impulse radio ultra-wideband (IR-UWB). We develop coherent and non-coherent schemes that exploit the spatial diversity in a distributed manner among the different terminals of a wireless network. These schemes are specific to IR-UWB and they take advantage of the pulse repetitions used to convey each information symbol. If Nf is the number of pulses per symbol, the coherent scheme is based on joint symbol and pulse coding and it achieves full diversity with any number of relays for Nf > 1. The non-coherent scheme is based on pulse coding and it achieves full diversity with a maximum number of Nf ? 1 relays.

In this paper, we propose a new space time (ST) coding scheme for time hopping (TH) ultra wideband (UWB) systems. The proposed scheme encodes the pulses used to transmit one information symbol. This permits to achieve full rate and full diversity with a non-vanishing coding gain for all number of transmit antennas. The proposed code shows to be the optimal extension of the codes constructed from cyclic division algebras when inter-pulse coding is performed

This paper presents the construction of new totally-real space-time coding schemes suited for carrier-less ultra-wideband transmissions. These schemes are associated with pulse position modulation and with hybrid pulse amplitude and position modulation where the input data is modulated onto both the pulse amplitudes and positions. The new schemes have a uniform average transmitted energy per antenna and achieve full rate and full diversity with hybrid M-PPM-M'-PAM for all values of M' and for M ges 3, M ges 5 and {M = 5, M ges 7} with n = 2, 3 and 4 transmit antennas respectively

In this paper, the advantage of applying space-time (ST) coding on ultra wideband (UWB) systems is discussed. In order to achieve very high data rates and important performance gains combined pulse position modulation (PPM) and pulse amplitude modulation (PAM) constellations along with full diversity and full rate ST codes are used at the transmitter side. The proposed coding-decoding scheme takes into account the nature of the highly frequency selective channel and the multi-dimensional constellation. Furthermore, the coding gain is optimized over different constellations and the possibility of compromising performance to lower peak-to-average power ratios (PAPR) is discussed. Moreover, for simplified receiver structures, V-BLAST decoding scheme was adapted to multi-dimensional signals. Results show considerable performance gains and better immunity against inter symbol interference (ISI) and multi user interference (MUI).

In this paper, we propose two transmit diversity schemes for ultra-wideband time-hopping (UWB-TH) communications. The performance of these schemes is evaluated for binary antipodal signalling over real UWB channels. The first proposed scheme assigns orthogonal codes to the M transmit antennas and is capable of achieving the maximum transmit diversity of M with no data rate loss compared to single antenna UWB systems. The second scheme is the extension of Alamouti's space-time (ST) code to UWB communications. Simulations and semi-analytical evaluations of the error probability show that giving rise to both spatial and multipath diversity by associating these schemes with partial or selective combining Rake receivers (PRake or SRake) can result in considerable performance gains.

Osteoporosis is a serious global health problem for the future, that is why improving diagnostic methods and prevention of this disease could be helpful.To assess the effects of calcium supplementations combined with Vitamin D on bone mineral density (BMD) and bone mineral content (BMC) in a representative sample of peri- and post-menopausal women in a double-blind, a randomized, controlled trial was untaken.A total of 120 women aged over 45 were included in a randomised placebo-controlled, double-blind trial on the effect of a daily dietary supplementation of calcium and Vitamin D on bone mineral density and bone mineral content; over a 30-month period.Dietary intake assessment; dual-energy X-ray absorptiometry to measure total body and segmental bone mineral density and bone mineral content at beginning of the study and every 15 months were undertaken.There was no significant change in dietary calcium or Vitamin D intakes in either of the treatment groups during the 30-month intervention period. The change in total BMD in the calcium group was significantly different from that in the placebo group (P0.005). The placebo group lost a total BMD at a rate of about 0.4% per year. There was an inverse correlation between BMD and age.The effect of calcium and Vitamin D supplementation on bone mineral density of calcium has been demonstrated in this group of young adult women. Our results showed the positive effect of calcium and Vitamin D supplementation in women both peri- and post-menopausal status; for this reason a supplementation of calcium and Vitamin D should be recommended as a strategic option in helping to prevent early postmenopausal bone loss.

The performance prediction and simulation of new communication and positioning systems based on UWB technology require an important effort to reach a deep knowledge of the physical channel. The multipath nature of the indoor channel is the limiting factor for positioning accuracy and communication capabilities of UWB systems in real environments, in particular ISI for high data rate applications. Most of the measurement performed to characterise the UWB channel have been performed in the time-domain by using a sampling oscilloscope with resolution greater than 1 ns. This paper describes a frequency approach based on a vector network analyser with a subnanosecond resolution in accordance with usually UWB pulse width. After an introduction the measurement technique is described and the performances of the sounding chain evaluated. Then an experimental methodology is proposed in order to assess the channel characteristics at different scale levels (small, medium, large). Finally the statistical post-processing for the future measurements is described.

LETI, a laboratory of the French Atomic Energy Commission, has built several direct sequence spread spectrum systems using SAW devices, the binary data rate of these systems goes from 256 kbit/s up to 8 Mbits/s and the frequency range is large (from 900 MHz up to 60 GHz). Taking into account its knowledge of this particular field of radio communications in multipath environments, LETI has designed a powerful programmable single chip that is able to perform as the matched filter of a direct spread spectrum receiver, the delay line of a differential demodulator, the demodulation, the data generation and the clock recovery.

Different code division multiple access (CDMA) receiver architectures have already been proposed such as the maximum-likelihood or the decorrelating detectors. However these architectures are too complex to be implemented. Some other solutions based on subtractive interference cancellation (IC), which meanwhile have better performance than conventional detectors, are particularly attractive for hardware implementation. After a description and comparison of different IC methods, this article focuses on the implementation of a parallel interference cancellation receiver. A dedicated integrated component (ASIC), called CESSIUM, which integrates, in a single chip, all the required functions for such architecture is then described.

Presents recent radio communications research work carried out by LETI (Laboratoire d'Electronique, de Technologie et d'Instrumentation), which is a laboratory belonging to the French Atomic Energy Commission. At the outset, a team from the LETI was involved in a programme to develop robot intervention in hostile environments. One of the first problems to be solved was to find a reliable and robust radio modulation technique for multi-path environments. In this type of situation, conventional radio solutions are unsuccessful and provide only extremely low data rates. The performance of wireless transmissions is much poorer than conventional communications using cables and they have to cope with a transmission channel that is subject to much more interference. In particular, multi-path transmission of radio waves leads to interference phenomena such as widening of the channel impulse response, fading and Doppler noise, which reduce the quality of the transmission. A novel reception structure, implementing direct-sequence spread-spectrum techniques combined with a diversity system, actually benefits from the multi-path phenomena which usually damage conventional radio transmissions. The first receivers developed were based on a surface acoustic wave filter and were subsequently replaced by dedicated digital circuits that perform all the base band processing. The resulting flexibility has made the design of CDMA and high-data-rate wireless systems possible. This research has potential applications in a wide variety of areas, e.g. video surveillance and track-to-train communications in underground systems and factory communications for machine synchronisation.

Direct sequence spread spectrum (DSSS) modulations have been widely used in different application fields over the past few years. Their main assets are now well known : reliability, robustness, communication privacy. The main drawback is a low spectrum efficiency due to spectrum spreading. This paper addresses a new base-band transceiver dedicated to point to point DSSS communications. This ASIC called VICASSO (Versatile Integrated Circuit for Advanced Spread Spectrum mOdulations) can be configured in many ways to suit a broad range of applications. First, in order to improve spectrum efficiency, M-ary orthogonal keying (MOK) and multi codes (MC) techniques have been implemented. Then, to face out inter symbol interference (ISI), a code hopping (CH) technique has been used. Many configurations mixing these modulations are available leading to a very flexible approach. VICASSO enables the end user to choose the best trade-off between data rate, robustness and spectrum efficiency for a given application. The functional description of the ASIC, its hardware features and its performance are detailed in this paper.

The direct sequence spread spectrum (DSSS) modulation technique has been widely used for a number of years. For point-to-point applications, LETI has proposed the concept of a matched filter receiver able to take into account all the propagation path signals implementing a diversity combining method. The proven interest, in different kinds of environments, of this original architecture had led to the development of a family of flexible ASICs. First this paper describes two ASICs (ICARE and VICASSO), developed in 1999. Then, special attention will be given to the implementation of an asynchronous code division multiple access (CDMA) receiver. The advanced CDMA architecture developed is based on co-channel interference cancellation (IC) schemes, which meanwhile have better performance than conventional detectors and are particularly attractive for hardware implementation. Finally, this article will focus on a synchronous CDMA receiver architecture.

This work shows the results of a study of the proliferation of bone tissue in the mouth.It was carried out on a sample of 530 persons who were natives of Central American countries, 179 males and 154 females, evaluating the rate of appearance of these formations depending on age, sex, racial group, and their location within the jaw.It was observed that 38% of the total sample showed hard tissue proliferation in the mouth. Of these cases, 158 (80%) were located in the superior maxilla and 48 (20%) of the cases in the jaw. Of which, 52 were men (25%) and 154 women (75%). This proliferation has greater incidence in the black race, in university students and liberal professions. The most frequent are torus palatinus and bilateral torus mandibularis.The Central American population shows a high incidence of hard tissue proliferations in the mouth; a radiological study is sufficient for their detection.

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This study was conducted to determine whether inhibition of hepatic glucose-6 phosphatase is involved in the mechanism of suppression of hepatic glucose production during the postprandial period. We studied the time course of changes in the enzyme activity by refeeding food-deprived rats with nonpurified diet. The Vmax of the enzyme, assayed in homogenates from livers freeze-clamped in situ in anesthetized 48-h unfed rats (12.3 +/- 0.15 U/g wet liver, mean +/- SEM, n = 6) was progressively decreased upon refeeding: 11.1 +/- 0.5, 8.5 +/- 0.4 and 7.9 +/- 0.5 U/g, in rats refed for 90, 180 (P0.01) and 360 min (P0.01), respectively. The Km of the enzyme was not affected by refeeding. No inhibition of the enzyme was observed in microsomes purified from these homogenates, suggesting a metabolite-induced inhibition mechanism. To assess the role of insulin in the inhibition, we assayed the glucose-6 phosphatase activity in similarly processed liver homogenates from food-deprived rats perfused with insulin at physiological and supraphysiological concentrations, whereas plasma glucose was maintained at the basal level by adapted glucose perfusion (euglycemic clamps). No inhibition of glucose-6 phosphatase was found under these conditions, suggesting that insulin cannot by itself account for the inhibition observed in the refeeding experiments. These data constitute the first demonstration of the inhibition of glucose-6 phosphatase activity during the postprandial period.

The authors present wideband measurements of outdoor radio channels operating within a 2 GHz frequency band around a 60 GHz carrier. Statistical analyses such as the RMS delay spread and cumulative distribution function (CDF) of the received signal envelope are presented. Investigations into the multipath effect and data rate limitation are discussed.

In this paper, we present two space-time schemes for exploiting diversity in multi-antenna impulse radio ultra wide-band (IR-UWB) systems when neither the transmitter nor the receiver has access to channel state information. The first scheme encodes the pulses of the same data symbol by a combination of differential phase shift keying and permutation codes and can be associated with any number of transmit and receive antennas. The second scheme encodes different symbols with two transmit antennas. These schemes are associated with Rake receivers and achieve full spatial and multi-path diversity with no data rate loss for constant-modulus multi-dimensional constellations. Adaptive versions of these schemes are also presented and shown to approach the performance of coherent receivers in stationary indoor channels.