Performance of Hybrid Direct-Sequence Time-Hopping Ultrawide Bandwidth Systems over Nakagami-m Fading Channels

This paper investigates and compares the performance of various ultrawide bandwidth (UWB) systems when communicating over Nakagami-m fading channels. Specifically, the direct-sequence (DS), time-hopping (TH) and hybrid direct-sequence time-hopping (DS-TH) UWB systems are considered. The performance of these UWB systems is studied associated with employing the conventional single-user correlation detector or minimum mean-square error (MMSE) multiuser detector. Our simulation results show that the hybrid DS-TH UWB system may outperform a corresponding pure TH-UWB or pure DS-UWB system in terms of the achievable error performance. Given the total spreading gain of the hybrid DS-TH UWB system, there is an optimal setting of the TH spreading factor and DS spreading factor, which results in the best error performance

Reduced-rank adaptive least bit-error-rate detection in hybrid direct-sequence time-hopping ultrawide bandwidth systems

Design of high-efficiency low-complexity detection schemes for ultrawide bandwidth (UWB) systems is highly challenging. This contribution proposes a reduced-rank adaptive multiuser detection (MUD) scheme operated in least bit-errorrate (LBER) principles for the hybrid direct-sequence timehopping UWB (DS-TH UWB) systems. The principal component analysis (PCA)-assisted rank-reduction technique is employed to obtain a detection subspace, where the reduced-rank adaptive LBER-MUD is carried out. The reduced-rank adaptive LBERMUD is free from channel estimation and does not require the knowledge about the number of resolvable multipaths as well as the knowledge about the multipaths’ strength. In this contribution, the BER performance of the hybrid DS-TH UWB systems using the proposed detection scheme is investigated, when assuming communications over UWB channels modeled by the Saleh-Valenzuela (S-V) channel model. Our studies and performance results show that, given a reasonable rank of the detection subspace, the reduced-rank adaptive LBER-MUD is capable of efficiently mitigating the multiuser interference (MUI) and inter-symbol interference (ISI), and achieving the diversity gain promised by the UWB systems

Adaptive detection in ultrawide bandwidth wireless communication systems

The main motivation of this thesis is to design low-complexity high-efficiency pulse-based ultrawide bandwidth (UWB) systems with reasonable bit-error-rate (BER) performance. The thesis starts with proposing a new pulse-based UWB system, namely the hybrid direct-sequence time-hopping (DS-TH) UWB system. This novel pulse-based UWB system is capable of inheriting the advantages of both the pure direct-sequence (DS)-UWB and pure time-hopping (TH)-UWB systems, while avoiding their disadvantages. Furthermore, this hybrid DS-TH UWB scheme can be easily converted to the pure DS-UWB or pure TH-UWB scheme. The BER performance of the hybrid DS-TH UWB systems employing either correlation or minimum mean-square error (MMSE) detection is investigated. From our studies it can be found that both the correlation and MMSE detectors have the capability to make use of the multipath diversity. The correlation detector does not have the capability to remove multiuser interference (MUI) and inter-symbol interference (ISI), while the MMSE detector is capable of mitigating efficiently both the ISI and MUI. While for single-user scenario the correlation detector is near-optimum and has low-complexity, it is shown that for multi-user scenarios theMMSE detector must be employed in order to achieve a reasonable BER performance. However, in this case the complexity of the hybrid DS-TH UWB system is found to be extreme. Furthermore, in order to implement MMSE detection, the signature waveforms, delays and complete channel knowledge of all the active users are required to be known by the receiver, which make the MMSE detection impractical. In practical channels obtaining the channel knowledge is highly challenging, since the received UWB signals usually consist of a huge number of resolvable multipaths and the energy conveyed by each resolvable multipath is usually very low.In order to mitigate the above mentioned problems of the MMSE detection, then, in this thesis a range of training-based adaptive detectors are investigated in the context of the hybrid DS-TH UWB systems. In detail, in this thesis a brief introduction to the literature of adaptive detection is first provided, followed by the philosophies of least mean-square (LMS), normalised least-mean squares (NLMS) and recursive least square (RLS) algorithms. In our study decision directed (DD) approaches are also introduced to the adaptive detectors to improve the BER performance and spectral-efficiency of the hybrid DS-TH UWB systems. Our studies show that the complexity of the adaptive LMS and adaptive NLMS detectors may be even lower than that of the conventional correlation detector. For the RLS adaptive detector, our studies show that, if it is initialised properly, it is capable of attaining a faster convergence rate than the LMS and NLMS adaptive detectors. In this case, the RLS adaptive detector requires less number of training bits, and hence provides higher spectral-efficiency than the LMS and NLMS adaptive detectors for the hybrid DS-TH UWB systems. Furthermore, the RLS adaptive detector is more robust and has more degrees of freedom than the LMS and NLMS adaptive detectors. However, the complexity of the RLS adaptive detector is still too high to be implemented in practical UWB systems.In order to further reduce the complexity of the RLS adaptive detector, rank-reduction techniques are introduced. With the aid of reduced-rank techniques, the filter size can be efficiently reduced, which in turn reduces the number of parameters required to be estimated. Consequently, the convergence speed, tracking ability and robustness of the RLS adaptive detector can be improved. In this thesis, three classes of reduced-rank techniques are investigated associated with the RLS adaptive detector, which are derived based on the principles of principal components analysis (PCA), crossspectral metric (CSM) and Taylor polynomial approximation (TPA), respectively. Our study and simulation results show that, given a sufficient rank of the detection subspace on which the RLS adaptive detector is operated, the reduced-rank RLS adaptive detector is capable of achieving a similar BER performance as the corresponding full-rank RLS adaptive detector, while with a detection complexity that is significantly lower than that of the fullrank RLS adaptive detector. Furthermore, our studies shown that the TPA-based reduced-rank RLS adaptive detector constitutes one of the highly efficient detection schemes for the pulse-based UWB systems. The TPA-based reduced-rank RLS adaptive detector is usually capable of attaining the full-rank BER performance with a very low rank, which is typically in the range of 5 ? 8, regardless of the system size in terms of the spreading factor, number of resolvable multipaths and the number of users supported by the UWB systems.Finally, in this thesis we summarise our discoveries and provide discussion on the possible future research issues

Optimal Parameters for Nonlinear Hirota-Satsuma Coupled KdV System by Using Hybrid Firefly Algorithm with Modified Adomian Decomposition

In this paper, several parameters of the non-linear Hirota-Satsuma coupled KdV system were estimated using a hybrid between the Firefly Algorithm (FFA) and the Modified Adomian decomposition method (MADM). It turns out that optimal parameters can significantly improve the solutions when using a suitably selected fitness function for this problem. The results obtained show that the approximate solutions are highly compatible with the exact solutions and that the hybrid method FFA_MADM gives higher efficiency and accuracy compared to the classic MADM method

Coil embolization of wide neck cerebral aneurysms using balloon remodeling technique-initial experience in pakistan

The balloon remodeling technique [BRT] was developed for neuroendovascular treatment of wide-necked cerebral aneurysms. Herein, we describe our initial experience of aneurysm embolization using BRT in Pakistan with the new double-lumen balloon catheters (Sceptor C and Ascent) and Hyperform balloon micro catheter and discuss its benefits

Endovascular treatment of spontaneous indirect high flow carotid cavernous fistula with a covered stent.

The treatment of symptomatic carotid-cavernous fistulas [CCF] has been historically treated in the developed world through the endovascular route. We report our first case of using a covered stent in a patient with spontaneous CCF. Method: Single patient with spontaneous indirect high flow CCF treated with a covered stent. We present retrospective analysis of technical success, initial and 6-month follow-up angiography and clinical outcome. Result: The stent was successfully navigated and deployed covering the CCF orifice. Immediate post stent deployment angiography showed marked reduction in flow and complete occlusion at 6-months. Clinically, patient showed near-complete recovery at 6 months. Conclusion: With proper neuroendovascular training and experience, use of a covered stent is cost effective and feasible for the treatment of CCFs in under developed countries

Evaluation of the effects of Adenotonsillar Hypertrophy on the Craniofacial development by using CT scans

이 연구의 목적은 computerized tomography (CT)를 이용하여 adenoid hypertrophy patients and tonsillar hypertrophic patients 으로 분류되어 있는 어린이들의 두개안면의 비율을 평가하는 것이다. 이 후향연구의 총 63 명 환자는 대상으로 다음과 같은 그룹으로 나누어져 있다: control group (C group)에 17 명 (10 명 남성과 7 명 여성; 평균 나이, 5.18 ± 1.51 세), adenoid hypertrophy group (A group)에 15 명 (10 명 남성과 5 명 여성; 평균 나이, 5.13 ± 1.41 세), tonsillar hypertrophy group (T group)에 15 명 (9 명 남성과 6 명 여성; 평균 나이, 5.27 ± 1.44 세) 그리고 adenotonsillar hypertrophy group (AT group)에 16 명 (8 명 남성과 8 명 여성; 평균 나이, 5.00 ± 1.41 세). 4 그룹의 사이의 다음 측정치의 차이를 one-way ANOVA 와 post-hoc Scheffe test 으로 통하여 비교하였다: inter-gonion width, inter-J width, nasal cavity width, maxillary inter-canine width, maxillary inter-molar width, palatal depth, maxillary arch length, and nasion-crest of the alveolar bone between the central incisors (N-Cr). Inter-Gonion width 가 T 와 AT group 에서 C group 보다 통계적으로 유의성이 있는 차이로 작았다 (p < 0.05). Inter-J width 가 AT group 에서 T group 보다 통계적으로 유의성이 있는 차이로 작았다 (p < 0.05). Maxillary inter-molar width 가 A 와 AT group 에서 T group 보다 통계적으로 유의성이 있는 차이로 작았다 (p < 0.05). 결과를 통하여 tonsillar hypertrophy 가 3-7 세 나이의 어린이들의 inter-gonion width 를 유의성이 있게 제한할 수 있음을 확인할 수 있었다. adenoid hypertrophy 가 3-7 세 나이의 어린이들의 maxillary width 와 maxillary inter-molar width 를 유의성이 있게 제한할 수 있음을 확인할 수 있었다. The aim of this study was to evaluate craniofacial proportions in children classified into adenoid and tonsillar hypertrophic patients, by using a systematic reproduceable method for the assessment, utilizing computerized tomography (CT) scans. This retrospective study included a total of 63 subjects (age range, 3-7 years) who were distributed as the following: control group (C group) had 17 subjects (10 males and 7 females; mean age, 5.18 ± 1.51 years), adenoid hypertrophy group (A group) had 15 subjects (10 males and 5 females; mean age, 5.13 ± 1.41 years), tonsillar hypertrophy group (T group) had 15 subjects ( 9 males and 6 females; mean age, 5.27 ± 1.44 years), and adenotonsillar hypertrophy group (AT group) had 16 subjects (8 males and 8 females; mean age, 5.00 ± 1.41 years). The differences in the following measurements between the four groups were compared using one-way ANOVA test and post-hoc Scheffe test: inter-gonion width, inter-J width, nasal cavity width, maxillary inter-canine width, maxillary inter-molar width, palatal depth, maxillary arch length, and nasion-crest of the alveolar bone between the central incisors height (N-Cr). The inter-Gonion width was smaller in T and AT groups compared to the C group (p < 0.05). The inter-J width was significantly smaller in AT group compared to T group (p < 0.05). The maxillary inter-molar width was significantly smaller in A and AT groups compared to T group (p < 0.05). The results indicate that the tonsillar hypertrophy led to a reduction of the inter-gonion width in young children aged between 3 to 7 years old. The adenoid hypertrophy led to a reduction of the inter-J width and the maxillary inter-molar width in young children aged between 3 to 7 years old. Both the tonsillar and adenoid hypertrophy did not have any other significant effect within the scope of the current study.open석

Behavior of Walls and Piles in Cohesive Soils Under Cyclic Loads

The nonlinear cyclic behavior of a soil-structure system has a significant influence on the mechanical response of this system. The cyclic response of soil-structure system has been studied experimentally and analytically. However, the results of these studies are not yet reproducing the applicability of key aspects of soil-structure behavior concepts in practice. A key prerequisite is to model the cyclic response in a facilitative and realistic way. There are several constitutive models in the literature that are available for cumulative responses, but they need many soil tests for calibration and they can be used under specific numerical codes and can be only executed by specialists. To overcome these difficulties, this research develops a simplified constitutive model (a kinematic hardening constitutive model with Von Mises failure criterion) for analyzing nonlinear plastic response of a soil-structure system subjected to cyclic loading. In addition, cumulative deformations are an essential aspect of the performance of walls and piles/caissons under cyclic loading. Therefore, reasonable estimates of the cumulative plastic displacements of structures in cohesive soils are necessary, particularly for soils which the cyclic influence may be significant. For example, the cumulative wall displacements that increase over time as the system is subjected to repeated live loading from trains passing near wall, in addition to the vertical settlements under the train track. Studying the effects of cyclic loading of railroads on the soil-wall system is necessary to improve train safety when a soil-wall system is near the tracks. As a second example, while pile and caisson anchors and foundations for offshore structures, such as wind turbines and the oil/gas exploration and production facilities have been the focus of considerable attention with respect to monotonic load capacity, much less attention has been given to cumulative displacements under cyclic loading. This issue is particularly crucial for inclined loading, since cumulative displacements can lead to loss of embedment of the caisson or pile. Since stress-strain behavior of soils is inelastic even at small strains, analyses based on linear elasticity, or on elastoplastic models that assume purely elastic behavior beneath the ultimate yield surface, cannot predict the cumulative soil deformations. Hence, an analysis that takes inelastic soil behavior at low stress levels into account, such as a bounding surface plasticity model, is required to predict cumulative displacements under cyclic loading. A cyclic nonlinear elastoplastic soil spring model has been applied to predict the monotonic and cyclic nonlinear p-y curve of piles in soft clay during the cyclic loading. Predictions of pile performance based on the kinematic hardening constitutive model used in this research are shown to match the centrifuge test results better than predictions based on the widely used API soil springs. This proposed spring model can overcome the limitations of the API clay model and can be implemented with either MATLAB or as UEL (User-defined elements) subroutine in ABAQUS/Standard. Predictions based on the spring model developed in this research shows good agreement with the measurements of cumulative displacement and soil stiffness from centrifuge tests involving cyclic loading of a single pile in soft clay

An Enhanced Approach of Image Steganographic Using Discrete Shearlet Transform and Secret Sharing

               في الآونة الأخيرة، جعل الإنترنت المستخدمين قادرين على نقل الوسائط الرقمية بطريقة أسهل. على الرغم من هذه السهولة للإنترنت، إلا أنه قد تؤدي إلى العديد من التهديدات التي تتعلق بسرية محتويات الوسائط المنقولة مثل مصادقة الوسائط والتحقق من تكاملها. لهذه الأسباب ، يتم استخدام أساليب إخفاء البيانات والتشفير لحماية محتويات الوسائط الرقمية. في هذه الورقة البحثية ، تم اقتراح طريقة معززة لإخفاء المعلومات بالصور مع التشفير المرئي. يتم تشفير الشعار السري (صورة ثنائية) بالحجم (128 × 128) عن طريق تطبيق التشفير البصري (2 out 2 share) لتوليد مشاركتين سريتين. أثناء عملية التضمين ، يتم تقسيم الصورة غطاء RGB بحجم (512 × 512) إلى ثلاث طبقات (الأحمر والأخضر والأزرق). يتم تحويل الطبقة الزرقاء باستخدام التحويل Shearlet المتقطع للحصول على معاملاتها. يتم تضمين المشاركة السرية الأولى في معاملات الطبقة الزرقاء المحولة للحصول على صورة الاخفاء. في عملية الاستخراج ، يتم استخراج المشاركة السرية الأولى من معاملات الطبقة الزرقاء لصورة الاخفاء وثم يتم تطبيق عملية XOR عليها مع المشاركة السرية الثانية لإنشاء الشعار السري الأصلي. وفقًا للنتائج التجريبية ، فإن الطريقة المقترحة قد حققت افضل نسبة من عدم الوضوح لصورة الاخفاء بقدرة الحمولة الصافية تساوي (1 bpp). أصبح الشعار السري أكثر أمانًا باستخدام التشفير المرئي (2 out 2 share)  والمشاركة السرية الثانية كمفتاح خاص ايضاً.  Recently, the internet has made the users able to transmit the digital media in the easiest manner. In spite of this facility of the internet, this may lead to several threats that are concerned with confidentiality of transferred media contents such as media authentication and integrity verification. For these reasons, data hiding methods and cryptography are used to protect the contents of digital media. In this paper, an enhanced method of image steganography combined with visual cryptography has been proposed. A secret logo (binary image) of size (128x128) is encrypted by applying (2 out 2 share) visual cryptography on it to generate two secret share. During the embedding process, a cover red, green, and blue (RGB) image of size (512x512) is divided into three layers (red, green and blue). The blue layer is transformed using Discrete Shearlet Transform (DST) to obtain its coefficients. The first secret share is embedded at the coefficients of transformed blue layer to obtain a stego image. At extraction process, the first secret share is extracted from the coefficients of blue layer of the stego image and XORed with the second secret share to generate the original secret logo. According to the experimental results, the proposed method is achieved better imperceptibility for the stego image with the payload capacity equal to (1 bpp). In addition, the secret logo becomes more secured using (2 out 2 share) visual cryptography and the second secret share as a private key