bluuebunny/crossref_metadata_2025 huggingface dataset:
Successful Dynamic Closure Test Using Controlled Flow Back in the Vaca Muerta Formation
Authors: Varela R. A. , Maniere J. L.
Published: May 2016

The Vaca Muerta formation is a shale oil and gas reservoir under active tectonics created by the Andes which are compressing the basin in an east to west direction and creates a varying stress regime both in horizontal and vertical directions. Additionally, this formation is composed of alternating layers of three litho-types with contrasted mechanical properties. These are organic shale, carbonate and ash beds. Slippage or debonding at weak-strong interfaces separating laminations is suspected to further contribute to the development of horizontal fracture components or T-Shape fractures during hydraulic fracturing when the fracturing pressure reaches the overburden (Zhang et al. 2007).

Selecting the proper landing position of horizontal wells in these compressive environments depends not only on the reservoir quality but also in selecting a layer which combines lower stress with sufficient vertical connectivity, thus minimizing detrimental effect from T-Shape propagation behavior.

Closure pressure can be obtained by performing a Dynamic in Situ Stress Test by force-closing the fracture (Nolte 1979; Raaen and Brudy, 2001). To this effect, YPF initiated in 2015 a campaign of in situ stress measurements across the Quintuco-Vaca Muerta system in vertical exploration and pilot wells. The objective was not only to predict a more accurate mud weight window to drill through the Vaca Muerta but mostly to measure as best as possible the difference between the overburden and the minimum horizontal stress to build a mechanical earth model accurate enough to help select better landing points for horizontal wells.

There are 3 scales at which dynamic closure tests are performed. At the smallest scale, a micro-fracture is created by pumping a little amount of drilling fluid at few liters/minute in 1m open hole isolated between straddle packers. At the largest scale, in a cased-hole perforated well, the dynamic closure test is performed as part of fracturing data acquisition before fracture operation: at this scale the test involves tens of bbls pumped at 5-10 bpm. Finally stress can be measured during Extended Leakoff Test (ELOT or XLOT) acquired in open hole at the casing shoe. After a literature review of the development of the flow back method this paper presents extensive details and operational procedure recommendations that were obtained from successful XLOT combining multiple cycles with injection, forced flow back and reopening sequence in the Neuquén basin.
The Begu Zulu vertical flute
Authors: Veenstra A.J.F.
Published: May 2016

In assessing the steps in the evolution in the construction of the vertical flute, the most important transition is from the flute with no whistle-head system, through the rudimentary whistle-head stage, to the whistle-head proper as manifest in the recorder and penny-whistle.
African music in Rhodesian native eduction
Authors: McHarg James
Published: May 2016

Being the transcription of a talk recently given by the author to a group of visiting educationists at the Leverhulme Conference in Southern Rhodesia. There are, in addition, certain intrinsic qualities in African folk music which make its preservation or cultivation a difficult matter in these days of easy communications. Father A.M. Jones, of Northern Rhodesia, who has given long years to the study of African music, refers to these difficulties in his critical essay, “The Study of African Musical Rhythm”. He describes an attempt to record, in notation, an African song by what he calls the Direct Method.
Wandering from pitch
Authors: (Brother) Basil Basil
Published: May 2016

Several writers have expressed their views in this Journal about a natural phenomenon: the wandering from pitch of their singers. I have also before me a leading Church Music Magazine in which a writer is at pains to give devices to overcome this difficulty especially with child choirs. From a long experience with choral groups in several countries, my own views are at variance with almost every writer on the subject. It may even come as a surprise if I say that African singers, even children or a whole congregation, can keep pitch when they are accompanied (by the harmonium, for instance, provided they can hear it enough); and that any musician who can transpose, or has a transpositor keyboard, could obviate the tendency in his singers. I do not find it a problem. But a few simple ‘rules’ should be observed.
African music within its social setting
Authors: Tracey Hugh
Published: May 2016

The social setting of present day African Folk Music varies from that of the most remote tribes tucked away in the vast forests, almost oblivious of the outside world, to the homes of the towns people, some of them in the second and third generation of urban families, often of mixed tribal parentage and forming a new lower and middle class of skilled and semi-skilled industrial workers. There is a correspondingly wide range of musics to be found on the Continent from the most complex folk melodies and rhythms to the simplicities of imported dance music. Folk music in the countryside is still by far the most widespread kind of music making in Africa, but because it is practised largely off the beaten track, it is not so well known as town and institutional musics which have been encouraged to steal the limelight. There is a remarkable variety of styles and manners of performance of folk music which ranges from the great xylophone bands of the Chopi in the South-East to the merest fragments of melody by simple folk such as the Pigmies of the Ituri Forest.
Report on the I.L.A.M. Nyasaland recording tour (May 7th to June, 1958)
Authors: Tracey Hugh
Published: May 2016

Our first objective on this tour was to discover what music might still be available in the two Southern districts of Southern Rhodesia, Chibi and Gutu, on our way up to Nyasaland via Fort Victoria and Salisbury. To test the prevalence of local music we went to two of the regions where I had first recorded in 1931, twenty-seven years ago, the one at Chief Takawarasha’s kraal, Chibi, and the other at the Alheit Mission, Gutu. In both places there were several African people who clearly remembered my previous visit and some who possessed my recordings which were made at that time and had been pressed and published by Columbia. Since most of the 1931 artists had already died, they were especially delighted to have their voices still on discs and they expressed their belated understanding of what we were doing for African people through our recordings which, they said, they had not appreciated at the time.
Changing times
Authors: Rhodes Willard
Published: May 2016

Ethnomusicologists and students of African music have too often become involved in the technicalities of music as an art, forgetting that it is one of the most spontaneous and revealing expressions of the inner life of the individual and the social group to which he belongs. Melville J. Herskovits, one of the first anthropologists to recognise the importance of music in culture, writes, “But it is at the core of anthropological thinking that each problem investigated be recognised as only one manifestation of one segment of man’s complex culture, and that it be studied with full consciousness of its wide implications.” In discussing the comparative study of music outside the Euro- American culture sphere he states, “For its implications lead us to some of the most fundamental truths about the nature and function of culture, and suggest the importance of the contributions that investigations carried on in this field can make to the study of culture as a whole.”
The future of music in Basutoland
Authors: Tracey Hugh
Published: May 2016

There is a popular impression among the general public that folk music is a thing of the past and of no modern importance. This no doubt arises from a misconception of the function of music in society and also from the notion that the practice of European folk musics is a revivalist art, and, therefore, African music must fall into the same category. This is far from the truth which, in this case, is hidden under a mass of false assumptions and prejudices. There are two good reasons, the one cultural and the other social, why the authentic country music of Basutoland, like other African musics elsewhere, should be studied carefully and enlisted into the ranks of modern community services. Before discussing this we must comprehend the motives of those persons, black and white alike, who see in the destruction of a local musical form a sense of ‘progress’.
The Aku-Ahwa and Aku-Maga post-burial rites of the Jukun peoples of northern Nigeria
Authors: Lane Michael
Published: May 2016

The records of the Jukun peoples of Northern Nigeria are as vague as those of most Nigerian tribes with the exception, perhaps, of the Fulani and the Hausa. It is thought that in the mid-fifteenth century they occupied the whole of the north-eastern corner of Nigeria and according to Fulani records they had gained the whole of the north two centuries later. One hundred years of glorious rule ended when they were defeated by the Fulani. Now they are only some 25,000 strong and they have been pushed back to the little triangular area round the banks of the Benue, Katsina and Donga rivers. Anthropologists suspect that the Jukun originally came from the Sudan and the greatest authority on the tribe, C. K. Meek, has called his major work about them “A Sudanese Kingdom”. The Jukun religion is based on the divine right of kingship, their king being referred to as “Aku”, meaning “Souls of the Dead”, while Sir Wallis Budge quotes the names “Khu” or “Aaku” given to the ancient Egyptian beatified souls. Another fact in our search for proof of this ancestry is the importance that is laid on the sun. Although it cannot be said that, like the Pharaohs, the king is the only son of the sun god, it is certainly true to say that the Jukun “Aku” is indeed the son of one of the gods. The most important of the gods is still the sun god and thus . . .? However, whether proven or not, it is interesting that in spite of centuries of mingling with the semi-Bantu people of the Middle Belt the Jukun have retained many characteristics which justify anthropological suspicions.
"African music", a lecture given at Natal University
Authors: Cope Trevor
Published: May 2016

The music of Africa is so different from our own music that we are unable to appreciate it until we know where that difference lies and therefore what to listen for. It is no use listening for the harmonies based upon the triads of the major and minor scales when listening to African music. Similarities there are, particularly in the melodic aspect of music. Neither European nor African music is characterised by a high development of melody, such as we find in the rich melodic ornamentation of Indian music. The Indian scale is arranged into a large number of modes (as against our two modes, major and minor) and the octave is divided into 24 quarter-tones (as against our 12 semi-tones), and this gives full scope to the flair for ornamentation to be found not only in the music of India, but also in the wonderful weaving and in other aspects of culture. The intricate patterns of a carpet are analogous to the melodic embellishments of a song; and think of the dome of a Hindu temple.
The lost valley: a feature programme for broadcasting
Authors: Tracey Hugh , Tracey Peggy
Published: May 2016

Based upon the story of that part of the great Zambezi Valley in Southern Africa which has recently been submerged beneath the waters of the Kariba Dam.
African and European musical culture in the Federation of Rhodesia and Nyasaland
Authors: Sibson A.R.
Published: May 2016

As a result of the emergence of Africa from its long isolation from the rest of the world and of the growing impact of Western civilization on the indigenous inhabitants of this continent, a considerable body of enlightened opinion is concerning itself with efforts to ensure that the worthwhile elements of African culture are not submerged in a flood of “culture”, manufactured—-often for purely commercial reasons—-in other parts of the world. In those countries of Africa where the white man, if present at all, is a temporary resident, there is much to be said for encouraging Africans to develop their music along purely indigenous lines, avoiding, as far as possible, any external influences that might be foreign to a society of their own making. In countries like the Federation of Rhodesia and Nyasaland and, particularly, in Southern Rhodesia, the permanent presence of a large white population makes it virtually impossible to keep the cultures in water-tight compartments and efforts to do so are likely to be doomed to failure. Indeed, it is questionable whether such efforts should be made, even if there was any hope of success, since the whole motive underlying the enormous political and sociological experiment which is beginning to gain momentum in the Federation, is one that visualises rapprochement between the races rather than the maintenance of rigid separation.
The sociology of recording in Africa south of the Sahara
Authors: Wachsmann Klaus
Published: May 2016

In recent years, at conferences on the welfare of folk music, much comment could be heard on the rapidity and thoroughness of the changes which affect society today. However, there was no witch-hunting; the mood was not to blame but to understand. Although there was a feeling that it was pointless to resist this kind of change, there was also some mental reservation that some good might be done if the disruption of continuity in folk music could be prevented, at least in some small measure, without interfering with its evolution. Needless to say, that at these congresses the tension between those who wished to promote stability in tradition and those who wholeheartedly wanted a new era of a new kind of folk music, could only be felt as an undercurrent. But the division has led to the formation of strange alliances. Those intent on a positive attitude to rapid change, moved perhaps by a social gospel promising a new and happier world, found themselves shoulder to shoulder with those who simply realised that popular entertainment in the garb of folk tradition sold well. On the other side, the supporters of continuity and authenticity found themselves agreeing with African nationalists and the scholars, united in a deep concern for the achievements of a tradition which both believed to have deep roots. From this common platform they opposed the extravagant claims of the ‘entertainment-first’ school. The African Music Society reflects this view when it speaks of music offered by the gramophone companies in Africa, “with a strongly exotic flavour . . . featuring for the most part selections of popular American and European origin.”
On Construction of Bit-Interleaved Coded Modulation Systems with Iterative Decoding
Authors: Mai Quoc Khanh , Dinh The Cuong , Hashimoto Takeshi
Published: May 2016

A new construction of Bit-Interleaved Coded Modulation systems with Iterative Decoding (BICM-ID) is proposed to achieve the best performance over white additive Gaussian noise (AWGN) channels, assuming that the ideal feedback (IF) holds for iterative decoding. For a class of so-called regular IF mappings, new upper bounds for error probabilities are presented for both cases of BICM-ID systems using overall and in-line interleaving. Search results for component Recursive Systematic Convolutional (RSC) codes with and without puncturing are reported for 4-PSK and 8-PSK signal sets.
Improving the Behavior of an Electro-Optic Modulator by Controlling Its Temperature
Authors: Bui Dang Thanh , Nguyen Lam Duy , Journet Bernard
Published: May 2016

The purpose of this paper is to present the improvement of the stability of an electro-optic modulator obtained from its temperature control. A digital system based on PSOC microcontroller and a small power amplifier has been developed. The behavior of the modulator can be observed by the way of its nonlinear properties. Thanks to the improved thermal stability, it is possible to reduce significantly the drift of the electro-optic modulator.
ACO-Based Multi-User Detection in Cooperative CDMA Networks
Authors: Jahromi Ali Jafarnia , Abdizadeh Mohammad T.
Published: May 2016

In this paper, the cooperative diversity is investigated in the uplink of a Code Division Multiple Access (CDMA) network in which users cooperate by relaying each other’s messages toward the Base Station (BS). It is assumed that the spreading waveforms are not orthogonal and hence, Multiple Access Interference (MAI) exists at the relay nodes as well as the BS. MAI degrades the signal quality at both relays and BS and decreases the cooperative diversity gain. To alleviate this problem, an Ant Colony Optimization (ACO) based Multi-User Detector (MUD) has been proposed to efficiently combine the received signals from the direct and relay paths and sub-optimally extract transmitted bits at the BS. The computational complexity of proposed algorithm is significantly lower than that of the Maximum Likelihood (ML) detector. More explicitly, for a cooperative network supporting 15 users, the computational complexity of the proposed ACO algorithm is a factor of 103 lower than that of the optimum Bayesian detector. Simulation results show that the performance of the proposed ACO-based detector can closely approach the maximum diversity in terms of BER and efficiently cancel the MAI at the BS.
Bit-Interleaved Coded Modulation Systems with Iterative Decoding and Partial Reusing QAM Signal Points
Authors: Tuan Nguyen Quang , Trinh Do Quoc , Nam Tran Xuan , Cuong Dinh The
Published: May 2016

A new method of reusing a subset of an M-QAM signal constellation is presented for Bit-Interleaved Coded Modulation systems with Iterative Decoding (BICM-ID). In addition to the remapping of high-energy signals to low-energy signals in order to save the average signal energy as a shaping technique known so far, a new scheme of remapping low-energy signals to high-energy signals is proposed in order to gain the equivalent distance when decoding bits, often called the Squared Euclidean Weights (SEW). Numerical analysis and simulation results show that the partial reuse of the signals in the BICM-ID system with 16-QAM can improve the system performance in terms of lowering the bit error rate in the error floor region.
Theoretical Foundations of Mobile Flexible Networks
Authors: Debbah Mérouane
Published: May 2016

The general framework of Mobile Flexible Networks (MFN) is to design dense self-organizing, self-healing and self-energy harvesting secure networks where terminals and base stations interact and self-adapt in an intelligent manner without the need of a central controller or with the right amount of regulation to let the agents in the network exploit fully the degrees of freedom. The design depends mainly on the mobility pattern as in highly mobile environments, intelligence at the terminal reduces the cost of signaling whereas for fixedling whereas for fixed (non-mobile) networks, all the intelligence can be put on the network side. One of the big challenges is to find how to optimally split the intelligence between cognitive terminals and cognitive networks. In this paper, we discuss the challenges ahead and provide some research directions to develop the theoretical foundations of these networks.
On the Practical Implementation of VFDM-based Opportunistic Systems: Issues and Challenges
Authors: Maso Marco , Cardoso Leonardo S. , Bastug Ejder , Linh-Trung Nguyen , Debbah Mérouane , Ozdemir Ozgur
Published: May 2016

Vandermonde-subspace frequency division multiplexing (VFDM) is a physical layer technique for cognitive two-tiered networks, allowing for the coexistence of an orthogonal frequency division multiplexing (OFDM) legacy system and a cognitive secondary system in a time division duplex mode. It consists of a linear null-space precoder used by the secondary transmitter to effectively cancel the interference towards one or more primary receivers, while guaranteeing a non-negligible rate to a served secondary receiver. In this work, we propose an implementation of an experimental test-bed using the new SDR4All platform developed at the Alcatel-Lucent Chair on Flexible Radio (SUPELEC) to take a step towards a proof of concept of a VFDM-based system. We focus on the secondary link, where an opportunistic transmitter/receiver pair communicates over moderately frequency selective channels, characterized by very short root mean square (r.m.s.) delay spreads and non uniform power delay profiles (PDP). The obtained results show the practical feasibility of a VFDM transmission over a secondary link. However, a significant bit error rate (BER) loss with respect to the previously shown achievable theoretical performance is evident. A thorough analysis of the structure of the VFDM precoder is carried out and the impact of the channel characteristics on the performance of the opportunistic system is discussed. Numerical findings demonstrate that the potential BER drop can be addressed by designing a suitable flexible receiver able to deal with the effect induced by non uniform PDP and short r.m.s. delay spread channels.
Standard-Compliant Content Adaptation in IPTV Systems
Authors: Thang Truong Cong , Kang Jung Won , Pham Ngoc Nam , Pham Anh T.
Published: May 2016

IPTV, which is based on the universal IP infrastructure, has the inherent nature of heterogeneity in terms of content, networks, terminals, and users. An important solution to cope with such heterogeneity is content adaptation. This paper reviews the standardization issues related to content adaptation in IPTV standards. We first describe the basic architecture of content adaptation and its integration into the ITU-T IPTV architecture. Then typical methods of content adaptation in practical IPTV systems are discussed in detail. Especially, we highlight the standard metadata tools that are potential to support adaptation methods within ITU-T IPTV architecture. Some recent developments in other standard bodies are also discussed.
Improving the Performance of Concatenated Convolutional Codes in the Error Floor Region
Authors: Dinh The Cuong , Tran Xuan Nam , Huynh Huu-Tue
Published: May 2016

The idea of the Bit-Interleaved Coded Modulation with Iterative Decoding (BICM-ID) is applied to classic schemes of both parallel and serial concatenation of convolutional codes (PCCC and SCCC) with Binary Phase Shift Keying (BPSK) modulation. Simulation results show that slightly modified PCCC and SCCC schemes provide significant improved performance of the encoder in the error floor region in terms of much lower bit error rate (BER).
A Hybrid of T-Dipole and Quasi-Yagi Antenna for Dual-band WLAN Access Point
Authors: Ta Son Xuat , Park Ikmo , Dao-Ngoc Chien
Published: May 2016

In this paper, a hybrid of T-dipole and quasi-Yagi antenna is presented for using in dual-band Wireless Local Area Network (WLAN) access point. The antenna is made up of combination of T-dipole and quasi-Yagi antenna structures, which are distinctly designed to operate at 2.4 and 5.5 GHz frequency bands. A simply integrated balun that consists of a curved microstrip line and a circular slot to allow broadband characteristic is used to feed the antenna. The final antenna design presents measured bandwidths (RL ≤ − 10 dB) of 2.35 – 2.55 GHz and 4.30 – 6.56 GHz which cover completely the two bands of WLAN. Simulated and measured results of peak gain and radiation patterns in both E- and H-plane validate potential of the design.
Minimalist Self-Organization in Wireless Networks
Authors: Roy Sébastien , Leroux Philippe
Published: May 2016

Many fields of human endeavour, such as biology and the theory of complex systems, are now embracing the concept of self-organization based on local actions leading to a desirable global emergent behavior. While many examples, both natural and artificial, can be found of such self-organized systems, the relationship between the local rules and the global behavior remains elusive and no systematic procedure is known to engineer a specific global result. Given the increasing pervasiveness of wireless networks of all sorts, including ad hoc networks competing within narrow unlicensed bands and wireless sensor networks, self-organization could constitute the next defining paradigm in wireless communications. It can be shown that a set of heuristic principles can be leveraged to engineer a self-organized connection-oriented wireless network with minimal complexity. Such a system requires no centralization of information, yet achieves a nearly optimal global state with only a modest amount of local signaling. It will naturally and jointly balance the many parameters related to radio resource management, exhibiting great adaptability, fault tolerance and scalability.
Blind Identification for Communication Signals: An Approach Exploiting Sampling Phase Diversity
Authors: Racine Emmanuel , Grenier Dominic
Published: May 2016

This paper presents a second-order blind channel estimation algorithm for digital communication signals under natural asynchronous conditions where no synchronization exists between transmitting and receiving antennas. The approach exploits sampling phase diversity provided by the cyclostationary nature of the received signals as an advantageous means of constructing multiple sets of distinct autocorrelation matrices evaluated at equals time lags. Channel estimation is then performed via joint diagonalization of a set of differential autocorrelation target matrices, avoiding the need of noise power or statistical distribution estimation. A broad set of simulation experiments is presented in distinctive signal contexts as a means of supporting and evidencing the potential of the proposed estimation method.
Improving Delay-Based Data Dissemination Protocol in VANETs with Network Coding
Authors: Mirani Farhan H. , Busson Anthony , Adjih Cedric
Published: May 2016

In vehicular ad hoc networks (VANETs), for a large number of applications, the destination of relevant information such as alerts, is the whole set of vehicles located inside a given area. Therefore dissemination with efficient broadcast is an essential communication primitive. One of the families of broadcast protocols suitable for such networks, is the family of delay-based broadcast protocols, where farthest receivers retransmit first and where transmissions also act as implicit acknowledgements. For lossless networks, such protocols may approach the optimum efficiency. However with realistic loss models of VANET wireless communication, their performance is noticeably degraded. This is because packet losses have a double effect: directly on the amount of successfully received packets and indirectly with implicit acknowledgement misses. In this article, in order to combat the effects of packet losses, we combine delay-based broadcast with network coding, through a new protocol: Delay-based Opportunistic Network Coding protocol (DONC). By design, DONC aims at cancelling the twofold effects of packet and implicit acknowledgement losses. We describe the details of the DONC protocol, and we study its behavior, with realistic models and simulations. Results illustrate the excellent performance of the protocol.
Lattice-Reduction-Aided Detection with Successive Interference Cancelation for Multiuser Space-Time Block Coded Systems
Authors: Nguyen Tien Duc , Le Quang Duc , Tran Xuan Nam , Fujino Tadashi
Published: May 2016

Effective detectors with low-complexity are considered for the Alamouti’s multiuser space-time block coded (STBC) systems. Viewing the noiseless received signals from Q users as a lattice with basis vectors being the columns of the total channel matrix H, we apply lattice reduction to transform the original basis into a nearly orthogonal one which improves the decision regions against noise. Then, linear detection using zero-forcing (ZF) and minimum-mean-square-error (MMSE) methods is performed on the transformed basis to detect transmitted signals from the Q users. These lattice-reduction-aided (LRA) linear detectors significantly improve BER of the linear detectors and, more importantly, allow us to achieve full diversity at high Eb/N0 regions.
Interference Analysis for OFDM Transmissions in the Presence of Time-Varying Channel Impairments
Authors: Nguyen-Duy-Nhat Vien , Nguyen-Le Hung , Tang-Tan Chien
Published: May 2016

This paper is concerned with the detrimental effect of phase noise on the performance of orthogonal frequency division multiplexing (OFDM) transmissions over time-selective channels. In the literature, most of the existing papers analyze the performance of OFDM systems in the presence of either time-selective channels or phase noise. Unlike the existing studies, this paper formulates an approximate expression of signal-to-interference-plus-noise ratio (SINR) at an OFDM receiver in the presence of both phase noise and time-selective channel response. The formulated SINR expression can be used as a guideline in determining appropriate OFDM transmission settings under a given quality-of-service (QoS) requirement. To illustrate the tightness of the approximate SINR formulation, empirical and theoretical values of SINR under different OFDM system settings are presented in this paper.
A Comprehensive Model for Performance Analysis of APD-based FSO Systems using M-PPM Signaling in Atmospheric Turbulence
Authors: Pham Hien T. T. , Dang Ngoc T.
Published: May 2016

In this paper, a model of Gaussian pulse propagation over atmospheric turbulence channel is used to comprehensively analyze the performance of APD-based free-space optical communication (FSO) systems using M-PPM signaling. This model is able to simultaneously take into account all effects of atmospheric turbulence including attenuation, intensity fluctuation, and pulse broadening, which has not been considered in previous works. In addition, the impacts of APD shot noise, background noise, and thermal noise are included in our analysis. The numerical results show that the main factor that limits the system performance is intensity fluctuation. However, when M is large enough, optical pulse is so short that the effect of pulse broadening becomes dominant. By using APD receiver, bit-error rate is improved significantly. Finally, based on channel capacity, we are able to determine the maximum transmission length of the system.
A Comparative Survey on 3D Models Retrieval Methods
Authors: Ali Sarah , Tran Trung-Thien , Laurendeau Denis
Published: May 2016

In computer vision many studies have been conducted in order to perform the matching and comparison of 3D models of objects. The main goal of matching is to group the models into different categories according to their similarity in order to allow their retrieval for recognition purposes and for further usage. So, in most of the cases, the comparison is run on a large dataset containing various models whether they belong to the same type of object or not and generally having similar or different shapes and poses. The objects’ nature and characteristics are important factors to be taken into consideration before performing the comparison step. We distinguish between two main categories of objects: rigid objects and deformable objects whose treatment and handling differ in the modeling as well as in the comparison phases. In this paper, we will be focusing on the comparison of deformable objects, and thus dealing with objects whose shapes might vary in different instances. For this purpose two main approaches used in the retrieval of 3D deformable models will be reviewed and implemented: the spectral approach and the bag-of-features approach. The deformation or variation in shape involves different aspects depending on the type of object. It could be a change in the posture of an articulated or bendable model, or it could result from a variation (loss or gain) in the total mass leading to a change in the surface and thus in the shape of the object. Even more complex situations occur when both cases are combined together.
On The Performance of Underlay Relay Cognitive Networks
Authors: Ho-Van Khuong , Bao Vo Nguyen Quoc
Published: May 2016

The bit error rate (BER) performance of underlay relay cognitive networks in the presence of Rayleigh fading is thoroughly analyzed in this paper. New exact and asymptotic analytic expressions under consideration of both interference power constraint and maximum transmit power constraint are derived in closed-form and are extensively corroborated by Monte-Carlo simulations. These expressions facilitate in evaluating effectively the network performance behaviour in key operation parameters as well as in optimizing system parameters. A multitude of analytical results expose that underlay relay cognitive networks experience the performance saturation phenomena while their performance considerably depends on the number of hops for the linear network model. Additionally, optimum relay position is significantly dependent of maximum transmit power, maximum interference power, and licensee location. Moreover, the appropriate order of locating unlicensees with different maximum transmit power levels can dramatically improve the network performance.
Improved Time and Frequency Synchronization Algorithm for 802.11a Wireless Standard based on the SIGNAL Field
Authors: Nguyen Cong Luong , Mokraoui Anissa , Duhamel Pierre , Linh-Trung Nguyen
Published: May 2016

Time and frequency synchronization in the IEEE 802.11a OFDM (Orthogonal Frequency Division Multiplexing) wireless communication system is addressed in this paper. Usually synchronization algorithms rely only on training sequences specified by the standard. To enhance the synchronization between stations, we propose to extract known information by both the transmitter and the receiver at the IEEE 802.11a physical layer to be then exploited by the receiver in addition to the training sequences. Indeed the parts of the identified SIGNAL field are either known or predictable from the RtS (Request to Send) control frame when the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) mechanism is triggered jointly to bit-rate adaptation algorithms to the channel. Moreover the received RtS control frame allows the receiver to estimate the channel before time synchronization stage improving then the performance of the proposed synchronization algorithm. Simulation results show that the performance of the proposed synchronization algorithm is improved as compared to existing algorithms.
3D Reconstruction using Kinect Sensor and Parallel Processing on 3D Graphics Processing Unit
Authors: Le-Tien Thuong , Luong Marie , Ho Thai Phu , Tran Viet Dai
Published: May 2016

One of depth cameras such as the Microsoft Kinect is much cheaper than conventional 3D scanning devices, thus it can be acquired for everyday users easily. However, the depth data captured by Kinect over a certain distance is of low quality. In this work, we implement a set of algorithms allowing users to capture 3D surfaces by using the handheld Kinect. As a classic alignment algorithm such as the Iterative Closest Point (ICP) does not show efficacy in aligning point clouds that have limited overlapped regions, another coarse alignment using the Sample Consensus Initial Alignment (SAC-IA) is incorporated in to the registration process in order to ameliorate 3D point clouds’ fitness. Two robust reconstruction methods namely the Alpha Shapes and the Grid Projection are also implemented to reconstruct 3D surface from registered point clouds. The experimental results have shown the efficiency and applicability of of our blueprint. The constructed system obtains acceptable results in a few minutes with a low price device, thus it may practically be an useful approach for avatar generations or online shoppings.
A New Decoding Algorithm based on Equivalent Parity Check Matrix for LDPC Codes
Authors: Hung Nguyen Tung
Published: May 2016

The article introduces a new LDPC decoding algorithm based on Equivalent Parity Check Matrix. Simulation results show that the new LDPC decoding algorithm can improve LDPC decoding performance. Compared to some other improvements, the new LDPC decoding algorithm, which is simpler, can detect errors and be applied to LDPC codes for great-length LDPC codes.
A Novel Non-Stationary Channel Model Utilizing Brownian Random Paths
Authors: Borhani Alireza , Pätzold Matthias
Published: May 2016

This paper proposes a non-stationary channel model in which real-time dynamics of the mobile station (MS) are taken into account. We utilize Brownian motion (BM) processes to model targeted and non-targeted dynamics of the MS. The proposed trajectory model consists of both drift and random components to capture both targeted and non-targeted motions of the MS. The Brownian trajectory model is then employed to provide a non-stationary channel model, in which the scattering effects of the propagation area are modelled by a non-centred one-ring geometric scattering model. The starting point of the motion is a fixed point in the propagation environment, whereas its terminating point is a random point along a predetermined drift. The drift component can be controlled by a so-called drift parameter. Tracking the MS on the proposed Brownian path allows us to derive the local angles-of-arrival (AOAs) and local angles-of-motion (AOMs), which are expressed by stochastic processes rather than random variables. We compute the first-order densities of the AOA and AOM processes in closed form. The local power spectral density (PSD) of the Doppler frequencies and the autocorrelation function (ACF) of the complex channel gain are also provided. Given a walking speed scenario, the analytical results are demonstrated and explained in depth. It turns out that the proposed Brownian path model results in a non-stationary non-isotropic channel model. The proposed geometry-based channel model is very useful for the performance analysis of mobile communication systems under non-stationary conditions.
Jointly Optimal Precoder and Power Allocation for an Amplify-and-Forward Half-Duplex Relay System
Authors: Rodríguez Leonardo J. , Tran Nghi H. , Le-Ngoc Tho
Published: May 2016

This paper investigates the optimal precoder design and power allocation between the source and relay for a half-duplex single-relay non-orthogonal amplify-and-forward (NAF) system. Based on the pair-wise error probability (PEP) analysis, an optimal class of 2 × 2 precoders is first derived for the traditional power allocation scheme, where one-third of the system power is spent at the relay node, while two-thirds are spent at the source node. Different from optimal unitary precoders proposed earlier, the derived class of precoders indicates that the source should spend all its power transmitting a superposition of the symbols in the broadcast phase, while being silent in the cooperative phase, for optimal asymptotic performance. We then further address the problem of jointly optimal precoder and power allocation for the system under consideration. It is shown that the total power should be equally distributed to the source and the relay, and the source should again spend no power during the cooperative phase for the best asymptotic performance. Analytical and simulation results reveal that the proposed precoders not only exploit full cooperative diversity, but also provide significant coding gain over the optimal unitary precoders. For instance, a coding gain of around 1dB can be attained at the practical BER level of 10 − 5 for various modulation schemes.
High Performance Direction Finding Algorithm Based on Phase Locked Loop
Authors: Thanh Han Trong , Yem Vu Van
Published: May 2016

Using Phase Locked Loop based single channel Direction Finding (DF) system to estimate the bearing angle or the coordinates of an incoming radio signal(s) has much more advantages than multiple receiver system does in many practical scenarios such as mobile communication. This method utilizes a bank of Phase Locked Loops (PLLs) to calculate the differential phase of signal received by an M-element uniform circular antenna array with a commutative switch followed by single channel Software Defined Radio (SDR) receiver. One important factor when using conventional phase locked loop is the requirement of the small convergence rate of the algorithm compared to the switching cycle. In order to achieve small convergence rate, we propose a method for DOA estimation with low computation complexity that improves significantly the performance of conventional PLLs system. An analysis of the challenges of computation complexity in this algorithm is presented. The simulation results for DOA estimation using the proposed structure with low complexity are shown to verify the performance of the system.
An Overview of H.264 Hardware Encoder Architectures Including Low-Power Features
Authors: Nguyen Ngoc-Mai , Bui Duy-Hieu , Dang Nam-Khanh , Beigne Edith , Lesecq Suzanne , Vivet Pascal , Tran Xuan-Tu
Published: May 2016

H.264 is the most popular video coding standard with high potent coding performance. For its efficiency, the H.264 is expected to encode real-time and/or high-definition video. However, the H.264 standard also requires highly complex and long lasting computation. To overcome these difficulties, many efforts have been deployed to increase encoding speed. Besides, with the revolution of portable devices, multimedia chips for mobile environments are more and more developed. Thus, power-oriented design for H.264 video encoders is currently a tremendous challenge. This paper discusses these trends and presents an overview of the state of the art on power features for different H.264 hardware encoding architectures. We also propose the VENGME’s design, a particular hardware architecture of H.264 encoder that enables applying low-power techniques and developing power-aware ability. This low power encoder is a four-stage architecture with memory access reduction, in which, each module has been optimized. The actual total power consumption, estimated at Register-Transfer-Level (RTL), is only 19.1 mW.
Analysis and Simulation of MRC Diversity Reception in Correlated Composite Nakagami-Lognormal Fading Channels
Authors: Nguyen Dinh Thong , Nguyen Quoc Tuan , Lam Sinh Cong
Published: May 2016

The physical meaning of the composite Nakagami-lognormal fading model is not well understood by many researchers using the model. The signal power transfer and transform at the interface between the global lognormal shadowing sub-channels and the local Nakagami multipath sub-channels in the presence of correlation between these diversity sub-channels is rather complex. This is the main reason why a thorough analysis or a simulation model is absent to date for the case of correlated composite Nakagami-lognormal diversity channels. This paper presents a novel technique for the estimation of the probability density function (PDF) of the signal-to-noise (SNR) at the output of a maximum ratio combining (MRC) receiver operating in correlated composite diversity fading channels. The PDF is estimated using the recently proposed two-point lossless moment generating function (MGF) matching technique and a closed-form expression for the bit-error rate (BER) for QPSK signal is consequently presented using the Gauss-Hermite polynomial approximation. The paper also presents the complex Monte-Carlo simulation model for the MRC reception and BER counting in correlated composite Nakagami-lognormal fading channels.
Noncoherent Receiver for Decode-and-Forward Cooperative Systems with Multi-Antenna Equipped Destination
Authors: Nguyen Ha X. , Ho Cuu V. , Thai Chan Dai Truyen
Published: May 2016

This paper studies a maximum energy selection receiver for an adaptive decode-and-forward (DF) cooperative wireless system with multiple-antenna equipped destination. In particular, the destination selects the maximum output from all the outputs of the square-law detectors to perform the detection of the transmitted information. A close-form expression for the bit-error-rate (BER) is analytically derived when the system is deployed with binary frequency-shift keying (BFSK) modulation. The thresholds used at the relays to address the issue of error propagation are optimized to minimize the BER. While finding the optimal thresholds requires information on the average signal-to-noise ratios (SNRs) of all the transmission links in the system, the approximate thresholds at each relay that require only information on the average SNR of the source-corresponding relay are investigated. It is also derived that the system achieves a full diversity order with the approximate thresholds. Finally, both analytical and simulation results are provided to verify our analysis.
A Low Cost and Low Power Consumption Automatic Water Meter Reading System: Hardware Investigation and Network Design
Authors: Nguyen Lap-Luat , Huynh Huu-Tue , Nguyen Tuan-Duc
Published: May 2016

This paper presents a low power consumption and low cost automatic data collection network for water meter application. Based on transmission performance and power consumption, several low cost sub-GHz wireless transceivers are analyzed and compared, and consequently a suitable hardware is chosen. The associated network protocol stack is also examined. To construct the automatic collecting data mechanism, we consider a cluster based wireless sensor network (WSN) where routers and a GPRS gateway are used to link each cluster to a data collection center. Advantages of this proposed configuration are the simple implementation, low cost and low power consumption. By using the Monte Carlo simulation technique, packet delivery ratio and power consumption for different topologies are investigated. Based on obtained results, the optimum network topology for automatic water meter reading in a typical urban environment is finally proposed.
Multiple-Symbol Differential Detection for Spatial Modulation
Authors: Nguyen Thu Phuong , Le Minh Tuan , Tran Xuan Nam
Published: May 2016

Approximately 3 dB Signal-to-Noise Ratio (SNR) loss is always paid with conventional Differential Spatial Modulation (DSM) as compared to coherent Spatial Modulation (SM). In this paper, a Multiple-Symbol Differential Detection (MSDD) technique is proposed for DSM systems to mitigate the loss due to differential detection. The new scheme can greatly narrow the 3 dB performance gap by extending the observation interval for differential decoding. The technique uses maximum-likelihood sequence detection instead of traditional symbol-by-symbol detection, and is carried out on the slow, flat Rayleigh fading channel. A generalized decision metric is derived for an observation interval of arbitrary length. It is shown that for a moderate number of symbols, MSDD provides approximately 1.5 dB performance improvement over the conventional differential detection. In addition, a closed-form pairwise error probability and approximate bit error probability (BEP) are derived for multiple-symbol differential spatial modulation. Results show that the theoretical BEP matches well the simulated one. The BEP is shown to converge asymptotically with the number of symbols in the observation interval to that of the differential scheme with coherent detection.
A Study on Determinants of Share Prices of Service Sector Companies
Authors: Kedia Naresh
Published: May 2016

Service industry has maximum contribution to the GDP of India. The share prices of this sector have a significant impact on both retail and institutional investors. This study significantly shows the determinants of share prices of companies representing service industry. The objective of the study is to find relationship between different factors, effecting share prices (specifically in service sector). Determinants taken are EPS, DVS, P/E Ratio etc.