In this paper, recommended spiral passive micromixer was designed and simulated. spiral design has the potential to create and strengthen the centrifugal force and the secondary flow. A series of simulations were carried out to evaluate the effects of channel width, channel depth, the gap between loops, and flowrate on the micromixer performance. These features impact the contact area of the two fluids and ultimately lead to an increment in the quality of the mixture. In this study, for the flow rate of 25 μl/min and molecular diffusion coefficient of 1×10-10 m2/s, mixing efficiency of more than 90% is achieved after 30 (approximately one-third of the total channel length). Finally, the optimized design fabricated using proposed 3D printing method.

In this research, in order to investigate the effect of the piezoelectric patch which is used as a sensor or actuator in rotating flexible structures such as a helicopter blade, the free vibrations of the rotating rectangular sheet with and without the piezoelectric patch have been presented. First-order shear deformation theory is considered for plate displacement and piezoelectric field. Considering the effect of Coriolis acceleration, centrifugal acceleration and centrifugal in-plane forces, the equations of motion are derived from Hamilton's principle and the electromechanical couple equation is obtained from Maxwell's equation. For piezoelectric, two electrical conditions, open circuit and closed circuit, which are used in sensors and actuators, respectively, have been considered. The equations are discretized with the help of the Numerical method of generalized differential squares and the matrices of inertia mass, eccentricity, Coriolis and stiffness matrix are obtained. Natural frequency values for beam and rotating plate have been compared in Abaqus software. Also, the values obtained from the Numerical solution in MATLAB have been verified with articles and ABAQUS, which have high accuracy. The effect of parameters such as hub radius, rotation speed, sheet thickness, aspect ratio, piezoelectric patch thickness and applied voltage on the natural frequency of the system has also been investigated.

Plastic hinge properties play a crucial role in predicting the nonlinear response of structural elements. The plastic hinge region of reinforced concrete normal beams has been previously studied experimentally and analytically. The main objective of this research is to evaluate the behavior of the plastic hinge region of reinforced concrete deep beams and its comparison with normal beams through finite element simulation. To do so, ten beams contain six deep beams, and four normal beams, under concentrated and uniformly distributed loading, are investigated. Lengths in the plastic hinge region involving curvature localization, rebar yielding, and concrete crushing zones are studied. The results indicate that the curvature localization zone is not suitable for the prediction of plastic hinge length in reinforced concrete deep beams. Based on the results it can be stated that in simply supported normal beams the concrete crushing zone is focused on the middle span, but in simply supported deep beams by creating a compression strut between loading place and support, the concrete crushing zone spreads along the compression trajectory. The rebar yielding zone of simply supported beams increases as the loading type is changed from the concentrated load at the middle to the uniformly distributed load.

We address the throughput maximization problem for downlink transmission in DF-relay-assisted cognitive radio networks (CRNs) based on simultaneous wireless information and power transfer (SWIPT) capability. In this envisioned network, multiple-input multiple-output (MIMO) relay and secondary user (SU) equipment are designed to handle both radio frequency (RF) signal energy harvesting and SWIPT functional tasks. Additionally, the cognitive base station (CBS) communicates with the SU only via the MIMO relay. Based on the considered network model, several combined constraints of the main problem complicate the solution. Therefore, in this paper, we apply heuristic guidelines within the convex optimization framework to handle this complexity. First, consider the problem of maximizing throughput on both sides of the relay separately. Second, each side progresses to solve the complex problem optimally by adopting strategies for solving sub-problems. Finally, these optimal solutions are synthesized by proposing a heuristic iterative power allocation algorithm that satisfies the combinatorial constraints with short convergence times. The performance of the optimal proposed algorithm (OPA) is evaluated against benchmark algorithms via Numerical results on optimality, convergence time, constraints’ compliance, and imperfect channel state information (CSI) on the CBS-PU link.

محاسبه نرخ تغییرات یا به عبارتی مشتق گیری از سیگنال های دیجیتال همواره از مهم ترین چالش های موجود در زمینه پردازش سیگنال های دیجیتال بوده است. این در حالی است که در کاربردهای مختلف به ناچار باید به مشتق گیری از سیگنال های دیجیتال پرداخت. در بسیاری از کاربردها استفاده از روش های مرسوم مشتق گیری ناکارآمد است و منجر به افزایش شدید خطا و نویز تا حدود چند ده برابر می شوند. در این مقاله محاسبه سرعت از روی داده های همراه با نویز و گسسته در متغیر حالت مکان با روش های مختلف از لحاظ تئوری و عملی بررسی و مقایسه و در ادامه بهترین روش محاسبه نرخ تغییرات (مشتق گیری) برای کاربرد مذکور استخراج شده است. با بررسی های انجام شده ملاحظه می شود که روش فیلتر کالمن مناسب ترین عملکرد را در کمینه کردن مجموع مربعات خطا برای کاربرد محاسبه مشتق از داده های جی. پی. اس. دارد و به خوبی با فیلتر مناسب داده ها آثار نویز و خطا را از بین می برد. استفاده از روش فیلتر کالمن دارای حالت گذرای مناسب نیست. این مشکل با اصلاح روش و به کارگیری فیلتر کالمن تطبیقی با وزن دهی مناسب به داده های عملکرد حالت گذرا را نیز تا حد خوبی بهبود داده است. نتایج حاصل از اعمال الگوریتم های مورد بحث روی داده های واقعی جی. پی. اس. برای استخراج بردار سرعت لحظه ای گزارش شده است.

در این مقاله برای اولین بار پیاده سازی و اجرای الگوریتم های موازی بر روی شبکه های مش (Mesh) و فوق مکعبی (Hypercube) برای حل سیستم های خطی تاپلیتز توسط روش (PCG) Preconditioned Conjugate Gradient  ارایه گردیده است. ارزش تمام الگوریتم های ارایه شده محا سبه و بهینه بودن آن اثبات می گردد. همچنین اجرای الگوریتم های ارایه شده در نرم افزار PVM) Parallel Virtual Machine) و محاسبه زمان اجرای تکرار و کارایی آنها با توجه به مثال های عددی برای ماتریس های تاپلیتز ارایه شده است.

Automatic topic detection seems unavoidable in social media analysis due to big text data which their users generate. Clustering-based methods are one of the most important and up-to-date categories in topic detection. The goal of this research is to have a wide study on this category. Therefore, this paper aims to study the main components of clustering-based-topic-detection, which are embedding methods, distance metrics, and clustering algorithms. Transfer learning and consequently pretrained language models and word embeddings have been considered in recent years. Regarding the importance of embedding methods, the efficiency of five new embedding methods, from earlier to recent ones, are compared in this paper. To conduct our study, two commonly used distance metrics, in addition to five important clustering algorithms in the field of topic detection, are implemented by the authors. As COVID-19 has turned into a hot trending topic on social networks in recent years, a dataset including one-month tweets collected with COVID-19-related hashtags is used for this study. More than 7500 experiments are performed to determine tunable parameters. Then all combinations of embedding methods, distance metrics and clustering algorithms (50 combinations) are evaluated using Silhouette metric. Results show that T5 strongly outperforms other embedding methods, cosine distance is weakly better than other distance metrics, and DBSCAN is superior to other clustering algorithms.

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