Self-interference Cancellation in Full-duplex Wireless Systems

Ahmed, Elsayed Ahmed Elsayed University of California, Irvine 2014 해외박사(DDOD)

Due to the tremendous increase in wireless data traffic, one of the major challenges for future wireless systems is the utilization of the available spectrum to achieve better data rates over limited spectrum. Currently, systems operate in what is termed "Half Duplex Mode", where they are either transmitting or receiving, but never both using the same temporal and spectral resources. Full-duplex transmission promises to double the spectral efficiency where bidirectional communications is carried out over the same temporal and spectral resources. The main limitation impacting full-duplex transmission is managing the strong self-interference signal imposed by the transmit antenna on the receive antenna within the same transceiver. Several recent publications have demonstrated that the key challenge in practical full-duplex systems is un-cancelled self-interference power caused by a combination of hardware imperfections, especially Radio Frequency (RF) circuits' impairments. In this thesis, we consider the problem of self-interference cancellation in full-duplex systems. The ultimate goal of this work is to design and build a complete, real-time, full-duplex system that is capable of achieving wireless full-duplex transmission using practical hardware platforms. Since RF circuits' impairments are shown to have significant impact on the self-interference cancellation performance, first, we present a thorough analysis of the effect of RF impairments on the cancellation performance, with the aim of identifying the main performance limiting factors and bottlenecks. Second, the thesis proposes several impairments mitigation techniques to improve the overall self-interference cancellation capability by mitigating most of the transceiver RF impairments. In addition to impairments mitigation, two novel full-duplex transceiver architectures that achieve significant self-interference cancellation performance are proposed. The performance of the proposed techniques is analytically and experimentally investigated in practical wireless environments. Finally, the proposed self-interference cancellation techniques are used to build a complete full-duplex system with a 90% experimentally proven full-duplex rate improvement compared to half-duplex systems.

Morphological Quality Assessment of Seed using Radiographic Image Analysis

Md. Raju Ahmed Chungnam National University 2020 국내박사

국문초록 방사선 이미지 분석을 통한 씨앗 종자의 형태학적 품질 평가 MD. Raju Ahmed 충남대학교 대학원 바이오시스템공학과 생물자원 및 환경제어공학전공 (지도교수 : 조병관) 본 논문은 씨앗 종자의 품질 평가에 방사선 이미지(raiographic image) 분석 기술을 응용하였으며 이를 통해 씨앗의 품질과 형태학적 패턴을 파악하고자 하였다. 본 연구의 혁신성은 다음과 같다. X-ray와 micro CT를 종자 내부 품질 검정을 위해 사용하였으며, 종자 선별을 위해 가장 적합한 이미지 처리와 특징 추출을 진행하였다. 또한 획득한 특징에서 최상의 분류 정확도를 획득하기위해 여러 종류의 분류자(classifier) 모델을 연구에 활용하였다. 이후 기존 머신러닝 기반의 분류기와 딥러닝 전이학습 기반으로 학습시킨 분류기의 정확도를 비교하였다. 최종적으론 이러한 연구를 기반으로 X-ray 2D 투영 이미지 종자 품질 예측 소프트웨어를 개발하였다. 본 연구의 세부 내용은 다음과 같다. 현재 대부분의 연구에서는 해당 연구년도에 재배되거나 인공적인 방법에 의해 노화시킨 샘플을 사용한다. 하지만 본 연구에서는 이와 달리 자연 노화(5-6년)된 씨앗 종자를 실험에 사용하였다. 첫번째 연구는 씨앗 종자 내부 구조의 패턴과 발아 행동의 상관관계를 확인하기 위해 진행되었다. 실험에는 머스크 멜론과 수박 종자를 사용하였으며, 이미지 획득을 위해 X-ray와 CT를 사용하였다. 일원분산분석(one-way analysis of variance: ANOVA) 결과 정상 생존 가능 종자와 비 생존/비정상 생존 가능 종자의 종자 외피 두께에 유의미한 차이가 없음을 보여주었으나, 배아와 내부 공기 공간 면적의 비교에서 유의적인 차이가 발견되었다(p<0.05). 정상 생존 종자는 내부에 큰 배아와 적은 공기 공간을 가지고 있었던 반면, 비 생존/비정상 종자의 경우 정상에 비해 상대적으로 작은 배아 크기와 내부 공간을 가짐이 확인되었다. 두번째 연구에서는 X-ray와 CT를 이용한 머스크 멜론 씨의 분류를 진행하였다. 재분할된 CT 이미지 5장(3 XY-평면, 1 XZ-평면, 1 YZ-평면)을 각기 다른 종류의 특징추출(local binary pattern, Gabor, local Fourier (FFT), texture, contrast, Haralick textural (Tx) features)방법에 적용하였으며, 이후 대비 강조(contrast enhancement)와 노이즈 제거 후 3가지 분류기를 이용해 우수한 성능의 분류기를 찾고자 하였다. 이중 18개의 특징과 Fisher discriminant object 함수를 적용한 10-fold cross-validation선형 판별 분석 (Linear discriminant analysis: LDA) 모델에서 91.5%로 정확도가 가장 높게 나타났다. 세번째 연구는 고추 씨에서 각기 다른 유형의 질감 패턴이 발견됨에 따라 명암도 동시 발생행렬(gray-level co-occurrence matrix: GLCM)을 이용하여 종자의 CT 이미지로부터 특징을 추출하였으며, 추출된 특징들에 대하여 분류 알고리즘을 개발하였다. 고추 씨에 대한 부분 최소자승 판별 분석(Partial least-squares discriminant analysis: PLS-DA)시88.7%의 정확도를 획득하였으며, 이중 서로 다른 각도에서 추출한 7개의 특징들이 고추씨앗 분류에 유의한 것으로 나타났다. 네번째 연구에서는 X-ray 2D 투영 영상 기법을 이용한 딥러닝 기반의 전이 학습 접근법을 이용하여 분류 모델을 개발하고 그 결과를 기존의 머신러닝 기반의 분류기 결과와 비교하였다. 기존 머신러닝 기반 LDA 분류기는 48개 특징을 이용한 10-fold cross-validation에서 가장 높은 정확도(83.65%)를 얻었다. 반면 딥러닝 전이학습에서는 ResNet-50이 단순 Conv-Nets(84.52%)보다 높은 86.29%의 정확도를 보였다. 결론적으로 ResNet-50이 가장 높은 분류 정확도를 보였다. 마지막 연구에서는 X-ray 영상 분석 및 종자 선별을 위한 맞춤형 소프트웨어를 개발하였다. X-ray 영상은 씨앗 종자 내부의 형태학적 평가에 적합하였으며, 본 프로그램에서는 이를 이용해 종자의 화학적 조성, 유전적 영향, 휴지상태 평가, 그리고 또한 발아에 실패할 것으로 예측되는 종자에 대해 모델에 의해 평가되고 선별된다. 결론적으로 본 연구에 따르면, X-ray 기법은 종자 내부 형태를 기반으로 한, 종자 품질 검사에 적합하였으며, 이에따라 종자 회사 및 종자 재배자에 유익할 것으로 판단된다.

Search strategies for radar target localization

Abdel-Samad, Ayman Ahmed University of Minnesota 2001 해외박사(DDOD)

In this thesis we consider a discretized version of the problem of optimal beam-forming, or radar transmit and receive pattern design. This is done for stationary radar target localization in the presence of white Gaussian noise while the target is equally likely to be in one of <italic>M</italic> discrete two-dimensional cells. This work falls under the area of optimal search, which addresses optimal allocation of effort in search problems. This arises in many areas such as the radar target localization problem that we address here, fault location in circuits, localization of mobile stations in wireless networks and Internet information searches. We propose two new approaches for beam-form design in target localization problems. The first is a finite-horizon approach in which we design the beam-form off-line with the goal of minimizing the probability of error after exactly <italic> L</italic> observations. We choose to maximize an objective function that is a point-wise infimum of all Kullback-Leibler Information Numbers (KLINs) between the <italic>M</italic> hypotheses. The second is an adaptive approach in which the beam-form is optimized after each observation to minimize the probability of incorrectly localizing the target after the next observation is acquired. In general, the adaptive approach has a better performance than the finite-horizon one. Both approaches provide an optimal trade-off between available resources, like time and signal to noise ratio (SNR), and performance. We also proposed a novel hierarchical radar target localization scheme in which the search cells are logically arranged as an <italic>m</italic>-ary search tree. Off-line allocation of available observations among the tree levels reduces to the Knapsack problem. We introduce an unconstrained solution that serves as a benchmark for the other approaches. In another approach we impose a constraint that allows us to dynamically allocate the available observations. Under this setup we propose two strategies. The first is based on the use of the multi-hypothesis sequential probability ratio test (MSPRT). The second is a look-ahead strategy which gears the search based on the expected probability of error for the next observation. In conclusion, the hierarchical localization scheme offers means to capitalize on available SNR to reduce search time.

Use of Non-inertial Coordinates and Implicit Integration for Efficient Solution of Multibody Systems

Aboubakr, Ahmed K University of Illinois at Chicago 2014 해외박사(DDOD)

Development of computational methods, formulations, and algorithms to study interconnected bodies that undergo large deformation, translational, and rotational displacements has been the focus of previous multibody system (MBS) investigations. MBS dynamics is used in the study and dynamic modeling of various systems such as structural, mechanical, and biological systems, as a result, it has a wide range of applications in industry. For this reason, the development of efficient and accurate computational methods, formulations, and algorithms to study MBS dynamics, is the main focus of this thesis. The thesis discusses the concept of non-inertial coordinates using railroad examples. Furthermore the thesis presents efficient implementation of implicit integration methods for the solution of stiff MBS differential/algebraic equations, and demonstrates this implementations using complex examples that include rigid and flexible bodies such as tracked vehicles. The use of the non-inertial coordinates can be advantages in many applications, as will be introduced in this thesis. Inertial coordinates have generalized inertia forces associated with them, while the non-inertial coordinates have no generalized inertia forces. In order to avoid having a singular inertia matrix and/or high frequency oscillations, the second derivatives of the non-inertial coordinates are not used when formulating the system equations of motion in this study. In this case, the system coordinates are partitioned into two distinct sets; inertial and non-inertial coordinates, leading to a formulation similar to the one used in the case of non-generalized coordinates. The use of the principle of virtual work leads to a coupled system of differential and algebraic equations expressed in terms of the inertial and non-inertial coordinates. The differential equations are used to determine the inertial accelerations which can be integrated to determine the inertial coordinates and velocities. The non-inertial coordinates are determined by using an iterative algorithm to solve a set of nonlinear algebraic force equations obtained using quasi-static equilibrium conditions. The non-inertial velocities are determined by solving these algebraic force equations at the velocity level. The non-inertial coordinates and velocities enter into the formulation of the generalized forces associated with the inertial coordinates. Using the concept of non-inertial coordinates and the resulting differential/algebraic equations obtained in this thesis leads to significant reduction in the numbers of state equations, system inertial coordinates, and constraint equations; and allows avoiding a system of stiff differential equations that can arise because of the relatively small mass. Large and complex multibody systems that include flexible bodies, and contact/impact pairs are governed by stiff equations. The use of explicit integration for solving the stiff equations can be very inefficient. Therefore the use of implicit numerical integration in the case of stiff MBS equations has been recommended. Therefore, it is one of the main objectives of this work is to develop a new and efficient implementation of the two-loop implicit sparse matrix numerical integration (TLISMNI) method proposed for the solution of constrained rigid and flexible multibody system (MBS) differential and algebraic equations. The TLISMNI method has desirable features that include avoiding numerical differentiation of the forces, allowing for an efficient sparse matrix implementation, and ensuring that the kinematic constraint equations are satisfied at the position, velocity and acceleration levels. In this method, a sparse Lagrangian augmented form of the equations of motion that ensures that the constraints are satisfied at the acceleration level is first used to solve for all the accelerations and Lagrange multipliers. The generalized coordinate partitioning or recursive methods can be used to satisfy the constraint equations at the position and velocity levels. In order to improve the efficiency and robustness of the TLISMNI method, the simple iteration and the Jacobian-Free Newton-Krylov approaches are used in this investigation. The new implementation is tested using several low order formulas that include Hilber--Hughes--Taylor (HHT) method, which includes numerical damping, L- stable Park, A-stable Trapezoidal, and A-stable BDF methods. Discussion on which method is more appropriate to use for a certain application is provided. The thesis also discusses TLISMNI implementation issues including the step size selection, the convergence criteria, the error control, and the effect of the numerical damping. The use of the computer algorithm described in this thesis is demonstrated by solving complex rigid and flexible tracked vehicle models, railroad vehicle models, and very stiff structure problems. The results, obtained using these low order formulas, are compared with the results obtained using the explicit Adams-predictor-corrector method. Using the TLISMNI method, which does not require numerical differentiation of the forces and allows for an efficient sparse matrix implementation, for solving complex and stiff structure problems leads to significant computational cost saving. (Abstract shortened by UMI.).

Import and function of inner envelope proteins from chloroplasts : von Ahmed Mohamed Kamal Ahmed Nada

Nada, Ahmed Mohamed Kamal Ahmed Ludwig-Maximilians-Universita@t Mu@nchen 2005 국내박사

Angular Super-Resolution of Small Baseline Structured Light Field Images Using Convolutional Neural Network

SALEM, AHMED DIEFY AHMED 충북대학교 2022 국내박사

온라인 음식 주문 시 문화적 차원이 고객 판매 촉진 수단에 미치는 영향

Islam Ahmed Mahmoud Ahmed 충북대학교 2019 국내석사

While e-business is rapidly spreading, there has also been growth in online food ordering, therefore, most online food ordering platforms are fighting to attract more customers. In this context, most of the platforms use sales promotions to increase customer purchase intention. The purpose of this study is to explore the moderating effect of culture dimensions on consumer sales promotion tool preferences and customer’s purchase intention. This study utilizes the Hofstede culture study applied in two countries: Egypt and Korea. Primary data were used, with a total of 196 respondents selected from Egypt and Korea (98 respondents each from Egypt and Korea). Data analysis was performed using SPSS and Smart PLS. The findings indicate that there are significant relationships between culture dimensions and customer sales promotion tool preferences. The findings will contribute to allowing platforms to choose the sales promotion tools which consumers prefer, based on understanding their culture dimensions background.

Toxoplasma gondii suppresses silver nanoparticle-induced cell death of human retinal epithelial pigment cells via p38 MAPK

Hassan Ahmed Hassan Ahmed Ismail 충남대학교 대학원 2013 국내박사

톡소포자충(Toxoplasma gondii)은 숙주세포의 apoptosis에 대한 저항성을 증가시키는데 은나노입자 (AgNPs) 처치시 망막세포에서의 기작은 아직까지 밝혀지지 않았다. 본 연구는 AbNPs에 의한 망막색소상피세포(ARPE-19) 손상시 톡소포자충의 세포 보호 효과를 규명하기 위해 apoptosis-regulating molecule 및 MAPK signaling pathway를 MTT법, DNA fragmentation, Tunnel법, caspase cleavage 등을 관찰하였다. AgNPs 처치에 대한 의한 세포사멸에 효과를 알아 본 결과, Bcl-2 level이 감소하였으며, mitochondira에서 cytochrome으로 cytochrome c가 유리되었다. 또한 caspase-3, caspase-9 및 poly ADP-ribose polymerase (PARP)의 발현이 증가 되었다. 톡소포자충 감염 세포에서, Bcl-2 발현은 증가되었으며 은나노입자 처치한 톡소포자충감염세포에서 , caspase-3, caspase-9 및 PARP의 발현이 억제되었다. 은나노입자 처치시 ERK1/2, JNK1/2 및 p38 MAPK 발현이 증가되었다. p38 억제제인 SB203580 처치시 세포사가 억제되었으며나 ERK1/2 억제제인 PD98059와 JNK1/2 억제제인 SP600125는 아무런 영향을 미치지 않았다. 톡소포자충 감염은 reactive oxygen species (ROS)에 의한 세포사를 억제하였으며, 망막상피세포의 세포사를 보호하기 위한 숙주 세포의 modulation에 관여하였다. As an obligate intracellular parasite, Toxoplasma gondii depends completely on host cells for its survival and propagation; thus host cell invasion is an essential process in the parasite's biology. In order to survive intracellularly the parasite developed numerous mechanisms to suppress different proapoptotic signaling cascades of its host cell. In this study, we investigated the cytotoxic effects of silver nanoparticles (AgNP) on T. gondii tachyzoite and human retinal pigment epithelial cells (ARPE-19). Cell viability was measured by MTT assay, and apoptosis was determined by measuring reactive oxygen species (ROS), DNA fragmentation, Tunel assay and caspase cleavage. Specific MAPK inhibitors were used to analyze the signaling involved in cell death of AgNP-treated and pre-infected cells. AgNP-treated cells exhibited caspase-9, -3, PARP cleavage, and Bcl-2 levels were decreased with time dependently. AgNPs-treatment activated ERK1/2, JNK1/2 and p38 MAPK. In addition, the selective p38 inhibitor SB203580 suppressed AgNPs-induced apoptosis and activation of caspase-3, -9, and poly ADP-ribose polymerase (PARP), whereas ERK1/2 inhibitor PD98059 and JNK1/2 inhibitor SP600125 had no effect. Apoptosis and DNA cleavage were inhibited in T. gondii pre-infected AgNP-treated cells. However, the cytotoxic effects were diminished by specific p38 inhibitor SB203580. These results demonstrated that AgNP-induced oxidative stress increased ROS generation, caspase activation, and cell damage in ARPE-19 cells, which was significantly suppressed by T. gondii

Facial Motor Imagery and Its Effect on Bell’s palsy - an fMRI Study

Ramy Sayed Ahmed Ahmed Soliman 경희대학교 대학원 2017 국내석사

Purpose: Many studies concluded that motor imagery is an effective mental practice for physical movement enhancement, and also that facial movement may lead to increased activity in attention and sensory-motor areas in order to improve the facial motor performance in Bell’s palsy patients. So we aimed to investigate facial motor imagery correlation with brain neural activity and to test the effect of it for Bell’s palsy rehabilitation as well as investigating brain areas responsible for increasing Bell’s palsy recovery rate. Methods: Two fMRI experiments were done: first experiment with 34 normal, and 14 Bell’s palsy subjects, and the second experiment with 15 Bell’s palsy subject longitudinal study for 3 months. The paradigm consisted of mouth and forehead motor imagery with 2 seconds animation movie and inter-stimulus interval of 9.81±1.6 seconds. General linear model and unpaired T-test were done and for the Bell’s palsy group we flipped the individual maps for those who had right side Bell’s palsy, so that the right hemisphere represents paretic side. Also, a correlation analysis was applied to correlate brain activity with a Bell’s palsy recovery index. Results: Interestingly, mouth motor imagery in both normal and Bell’s palsy subjects showed activation in M1, SI, superior temporal sulcus, superior temporal gyrus, and supplementary motor area which are the main sensory-motor areas shown in facial motor execution. Also, mouth motor imagery in Bell’s palsy subjects induced greater activity in contralateral sensory-motor areas (M1, SI, premotor cortex, and SII) compared to normal subjects, and Bell’s palsy recovery index was positively correlated with sensory-motor areas while doing facial motor imagery. Conclusion: Facial motor imagery shares similar activation in sensory-motor areas with the facial motor execution, and Bell’s palsy facial motor imagery has greater activity in contralateral sensory-motor areas than normal subjects. Besides, increasing Bell’s palsy recovery index induces more activation in main sensory-motor brain areas which could be a measure for treatment effectivity as shown with facial motor imagery. Thus, it could be speculated that facial motor imagery could be helpful in Bell’s palsy rehabilitation and its combination with facial motor execution for rehabilitation can be studied in future.

(An) adaptive bayesian network for 3D object recognition

Mohammed Naguib Mohammed Ahmed Abou El-Ela, Ahmed Sungkyunkwan University 2014 국내석사

Classification of an object under various environmental conditions is a challenge for developing a reliable service robot. In this work, we list the possible causes for classification problems and design an adaptive recognition system that is aware of environmental conditions. We show problems of using simple Naïve Bayesian classifier and decide to adapt Tree-Augmented Naïve (TAN) Bayesian Network as a basis for our work. We separate feature space into binary TRUE/FALSE regions which allows us to drive Bayesian inference prior conditional probabilities from statistical database. We go further using TRUE/FALSE regions to estimate expected posteriori probabilities of each object under online specific conditions. These expectations are then used to select optimal feature sets under this environment and autonomously reconstruct Bayesian Network. Experimental results, validation and comparison show the performance of the proposed system.