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Investigation of the plenum configuration effect on the maldistribution of liquid and gas phases in upflow packed bed reactors using Gamma-ray densitometry (GRD)

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Chemical Engineering Research and Design 2025年 218卷 481-494页

作者： Youssef Yatimi Ahmed Alalou Muthanna H. Al-Dahhan Multiphase Flow and Reactors Engineering & Education Laboratory (mFReel) Linda and Bipin Doshi Department of Chemical and Biochemical Engineering Missouri University of Science and Technology Rolla MO 65409 USA Applied Organic Chemistry Laboratory Faculty of Sciences and Technologies Sidi Mohammed Ben Abdellah University Fez B.P. 2202 Morocco Department of Nuclear Engineering and Radiation Science Missouri University of Science and Technology Rolla MO 65409 USA Applied Chemistry and Engineering Research Center of Excellence (ACER CoE) Mohammed VI Polytechnic University (UM6P) Lot 660 Hay Moulay Rachid Ben Guerir 43150 Morocco

The objective of this study was to investigate the effect of five plenum designs on the distribution of the flowing phases in the plenum itself and within the packed catalysts’ bed of the reactor. The line-averaged gas and liquid holdups were measured in the plenum at nine radial positions ( r / R = 0 , ± 0.225 , ± 0.45 , ± 0.675 , ± 0.9 ), and under two superficial inlet gas velocities ( 0.07 and 0.17 m / s ) using the inhouse developed, non-invasive gamma-ray densitometry (GRD). With the same measurement conditions, the line-averaged dynamic liquid holdups were estimated in the packed catalysts’ bed at two axial levels ( Z / D = 0.1 , 1.56 ) . The results show that, with a plenum design containing four or five deflectors, an enhanced distribution uniformity of the liquid and gas phases can be obtained in the plenum and in the fully developed region of the packed catalysts’ bed. With these two plenum designs, the increase of the superficial inlet gas velocity was found to significantly increase the chaotic flow of the gas and liquid in the regions where the flow is not fully developed. However, it did not affect the level of the liquid in the plenum, indicating the applicability of these plenum designs for several U-PBR applications requiring high gas holdups.

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Nonlinear Sliding Manifold for High Performance Lateral Guidance of UAV 36

Nonlinear Sliding Manifold for High Performance Lateral Guid...

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第36届中国控制会议

作者： Syed Ussama Ali Raza Samar M.Zamurad Shah Center of Excellence in Science and Applied Technologies （CESAT）

ISBN: (纸本)9781538629185

This paper presents a novel guidance algorithm for UAVs to follow a 2-D ground track by controlling the lateral cross track deviations. The guidance framework based on sliding mode theory is presented to solve the two dimensional path-following problem. To control the lateral track error of the vehicle during flight, the guidance algorithm generates reference bank angle commands for the vehicle control system i.e., by executing roll maneuvers. Novel nonlinear high performance sliding surface is proposed to reduce the lateral cross track error efficiently. Subsequently, 1storder sliding mode guidance logic is then devised using the proposed manifold for generating reference bank angle commands. Stability of the proposed nonlinear manifold is proved using Lyapunov *** boundedness is proved to avoid saturation of control signals. Effectiveness of the proposed algorithm is shown via simulation results for a research scaled YAK-54 UAV. Different scenarios（consisting of both small and large lateral errors）in simulation validates the proposed guidance framework and illustrates the effectiveness of the algorithm.

关键词： Manifolds Unmanned aerial vehicles Stability analysis Sliding mode control Kinematics Switches

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UAV Lateral Path Following: Nonlinear Sliding Manifold for Limited Actuation 36

UAV Lateral Path Following: Nonlinear Sliding Manifold for L...

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第36届中国控制会议

作者： Syed Ussama Ali Raza Samar M.Zamurad Shah Center of Excellence in Science and Applied Technologies (CESAT)

ISBN: (纸本)9781538629185

The lateral guidance objective is to derive the cross track error towards zero with graceful and stable maneuvers and then to keep it as minimum as possible. A nonlinear sliding surface based lateral guidance scheme is proposed here for Unmanned Aerial Vehicles(UAVs) application with limited actuation. Following the inner(control) and outer(guidance)loop structure, the proposed guidance scheme resides in outer loop and generates reference bank angle commands for the inner control loop. The proposed 1 order SMC algorithm based on nonlinear sliding surface is derived using the kinematic equations for bank-to-turn vehicles. Mathematical proof of existence of sliding mode and actuation boundedness of the closed-loop is also provided. The proposed guidance and control system performance is verified via simulation results for different scenario. A high fidelity nonlinear 6-degrees-offreedom(6-dof) scaled Yak-54 UAV mathematical model is used for flight simulations. Simulation results validated the effectiveness and performance of the proposed lateral guidance scheme.

关键词： Stability analysis Unmanned aerial vehicles Manifolds Actuators Mathematical model Sliding mode control Robustness

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Leveraging Occlusion Sensitivity for Malicious Code Localization 21

Leveraging Occlusion Sensitivity for Malicious Code Localiza...

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21st International Bhurban Conference on applied sciences and Technology, IBCAST 2024

作者： Rizwan, Muhammad Babar, Faiza Sarwar, Sohail Center of Excellence in Science & Applied Technologies Islamabad Pakistan

ISBN: (纸本)9798331516680

Malware injection attacks represent a significant threat to the security of computer systems and networks, necessitating robust detection and mitigation strategies. This paper investigates the efficacy of convolutional neural networks (CNNs) in detecting malicious files, employing a novel approach that utilizes occlusion sensitivity analysis. By converting Portable Executable (PE) files into image representations through N-Gram Pixel Mapping, we assess the ability of CNNs to accurately classify malicious code segments. Our methodology includes a comprehensive evaluation of a dataset sourced from MalwareBazaar, comprising over 1,000 malware-infected files across various families. The results reveal that while CNN models such as MalConv demonstrate resilience and improved recall after occlusion analysis, other models like PE-Classifier and DeepMalware exhibit performance declines, indicating their sensitivity to feature occlusion. These findings underscore the importance of advanced machine learning techniques in enhancing malware detection accuracy, particularly in recognizing zero-day threats and obscured malicious code. The paper contributes to the ongoing discourse on malware detection, offering insights into effective strategies for improving cybersecurity through AI-driven methodologies. © 2024 IEEE.

关键词： Sensitivity analysis

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Engineering grain boundaries in monolayer molybdenum disulfide for efficient water-ion separation

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science (New York, N.Y.) 2025年第6735期387卷 776-782页

作者： Shen, Jie Aljarb, Areej Cai, Yichen Liu, Xing Min, Jiacheng Wang, Yingge Wang, Qingxiao Zhang, Chenhui Chen, Cailing Hakami, Mariam Fu, Jui-Han Zhang, Hui Li, Guanxing Wang, Xiaoqian Chen, Zhuo Li, Jiaqiang Dong, Xinglong Shih, Kaimin Huang, Kuo-Wei Tung, Vincent Shi, Guosheng Pinnau, Ingo Li, Lain-Jong Han, Yu Physical Sciences and Engineering Division (PSE) King Abdullah University of Science and Technology (KAUST) Thuwal Saudi Arabia School of Materials Science and Engineering Nanyang Technological University 50 Nanyang Avenue Singapore Department of Physics King Abdulaziz University Jeddah Saudi Arabia KAUST Catalysis Center King Abdullah University of Science and Technology (KAUST) Thuwal Saudi Arabia Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM) Nanjing Tech University (NanjingTech) Nanjing China Shanghai Applied Radiation Institute Shanghai Key Laboratory of Atomic Control and Application of Inorganic 2D Supermaterials Shanghai University Shanghai China Department of Mechanical Engineering University of Hong Kong Pok Fu Lam Road Hong Kong China Department of Civil Engineering University of Hong Kong Pok Fu Lam Road Hong Kong China Imaging and Characterization Core Lab King Abdullah University of Science and Technology (KAUST) Thuwal Saudi Arabia Department of Chemical System Engineering School of Engineering University of Tokyo Tokyo Japan Center for Electron Microscopy South China University of Technology Guangzhou China School of Emergent Soft Matter South China University of Technology Guangzhou China Catalyst Center of Excellence (CCoE) Research and Development Center Saudi Aramco Dhahran Saudi Arabia Center for Sustainability and Energy Technologies Chang Gung University Taoyuan Taiwan Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources Qinghai Institute of Salt Lakes Chinese Academy of Sciences Xining Qinghai China University of Chinese Academy of Sciences Wenzhou China

Two-dimensional (2D) materials have long been considered as ideal platforms for developing separation membranes. However, it is difficult to generate uniform subnanometer pores over large areas on 2D materials. We report that the well-defined eight-membered ring (8-MR) pores, typically formed at the boundaries of two antiparallel grains of monolayer molybdenum disulfide (MoS2), can serve as molecular sieves for efficient water-ion separation. The density of grain boundaries and, consequently, the number of 8-MR pores can be tuned by regulating the grain size. Optimized MoS2 membranes outperformed the state-of-the-art membranes in forward osmosis tests by demonstrating both ultrahigh water/sodium chloride selectivity and exceptional water permeance. Creating precise pore structures on atomically thin films through grain boundary engineering presents a promising route for producing membranes suitable for various applications.

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The Effect of Affine and Extended Affine Equivalence Class Against Various Cryptographic Profile 21

The Effect of Affine and Extended Affine Equivalence Class A...

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21st International Bhurban Conference on applied sciences and Technology, IBCAST 2024

作者： Khalid, Ijaz Hassan, Zohaib Rasheed, Haroon Ul Center of Excellence in Science and Applied Technologies Islamabad Pakistan Islamabad Pakistan

ISBN: (纸本)9798331516680

S-boxes play a crucial role in various symmetric primitives by substituting a certain number of input bits in a nonlinear way to achieve optimal security bounds. To attain these optimal security bounds, researchers explore the Affine and Extended Affine (EA) equivalence classes. In this research, we investigate the effect of Affine and EA equivalence classes on different Cryptographic Properties (CPs). CPs like Differential Uniformity (DU), Algebraic Degree (AD), Strict Avalanche Criterion (SAC), Nonlinearity (NL), Autocorrelation (AC), and Linear Structure (LS) remain invariant under Affine and EA transformations, while other cryptographic properties like Branch Number (BN), Number of Terms in Interpolation Polynomials (NIP), bijectivity, Side Channel Profile (SCP), and some hybrid CPs are not preserved under the EA class. These results highlight the importance of careful selection of Affine and EA parameters during the design process to achieve strong resistance against a range of statistical and differential attacks. © 2024 IEEE.

关键词： Equivalence classes

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A Mathematical Model of a UAV Spark-Ignition Engine for the Design of Control Methods

A Mathematical Model of a UAV Spark-Ignition Engine for the ...

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SAE Automotive Technical Papers, WONLYAUTO 2022

作者： Amin, Maliha Kazmi, Ijaz Hussain Khan, Abdul Qayyum Electrical Engineering Pakistan Institute Of Engineering Pakistan Center Of Excellence In Science And Applied Technologies Pakistan

This paper presents a real-time, nonlinear, control-oriented model for a two-stroke, spark-ignition aircraft engine. The safety and reliability of unmanned aerial vehicles (UAVs) are vital for their large-scale usage. Therefore, the design of control systems for normal as well as abnormal operation of UAVs is very essential. Timely detection and isolation of faults in an engine can save the aircraft from catastrophic consequences. Modeling is the first stage in the majority of control methods. This model is designed to be able to accurately and in real-time predict the output of an aircraft engine. Using existing modeling knowledge, a mean-value engine model is developed in this paper. The engine model consists of five submodels named the throttle body model, air dynamics model, fuel dynamics model, rotational dynamics model, and atmospheric model. The first four submodels are responsible for an accurate description of engine dynamics, while the atmospheric model covers the variation in the aerial environment. The simulation model is constructed using the MATLAB Simulink environment. The proposed engine model is validated with available data of a real UAV engine. The model is as generic as possible and can be employed as a simulation tool for control analysis and the implementation of model-base fault diagnosis schemes for UAV engines. ©

关键词： Internal combustion engines

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Implementation of data interpolation for reducing data points with frequency content preservation in narrowband detection displays

Implementation of data interpolation for reducing data point...

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2014 11th International Bhurban Conference on applied sciences and Technology, IBCAST 2014

作者： Waqas, Kashif Tahir, Aqdas Bin Hamid, Umar National University of Computer and Emerging Science FAST Islamabad Pakistan Center of Excellence in Science and Applied Technologies Islamabad Pakistan

ISBN: (纸本)9781479923199

Representation of data points on displays is one of the trickiest part regarding underwater surveillance systems. The data points are mostly large in numbers than the number of pixels to represent them on displays. This makes the data processing domain more interesting to correctly map these data points on displays. The biggest challenge while reducing these data points is preservation of correct information. Mostly simple averaging and linear mapping do not ensure correct content preservation. The content preservation is guaranteed by the use of more complex mathematical techniques such as quadratic equations, sum of trigonometric functions etc. These complex mathematical techniques certainly ensure correct preservation of data while reducing its size for mapping it on displays. One of the well-known data fitting techniques is 'Spline Interpolation'. This technique guarantees correct representation of data points and uses 4th order quadratic equations to correctly deal with data points. The use of quadratic equations makes it heavy on processing end in terms of real time processing constraints. In this context there is a need to have some technique that not only reduces data points correctly but also keeps in view the timing constraints of real time operation. This paper presents a novel technique that meets all the real time processing constraints and keeps the integrity of data intact. This technique can reduce data points up to hundreds of times with correct preservation of data content and frequency information. This technique has been tested on several different scenarios of narrowband detection displays and provided good results. These results clearly show the robustness and accuracy of the proposed technique in comparison to other technique like 'Spline Interpolation'. © 2014 IEEE.

关键词： Functions

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GaN-Based Low Noise Flat Gain Amplifier for X-Band Applications 21

GaN-Based Low Noise Flat Gain Amplifier for X-Band Applicati...

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21st International Bhurban Conference on applied sciences and Technology, IBCAST 2024

作者： Nawaz, Muhammad Imran Zafar, Salahuddin Akoglu, Busra Cankaya Aras, Erdem Ozbay, Ekmel Bilkent University Nanotechnology Research Center Ankara Turkey Centres of Excellence in Science and Applied Technologies Islamabad Pakistan

ISBN: (纸本)9798331516680

This paper describes the design of a low noise amplifier (LNA) monolithic microwave integrated circuit based on GaN-on-SiC technology. The amplifier operates in the frequency range of 9.5 -11.5 GHz. The design topology and careful choice of HEMTs ensure high gain and low output power at 1-dB compression point (P1dB). P1dB and saturated output power (Psat) have a direct relation with each other. The low Psat feature is desired to safely integrate GaN LNAs with subsequent circuitry in the radar receiver systems. The proposed LNA consists of two stages, having 300 μm periphery at the first stage and 200 mum periphery at the second stage. The low periphery device provides better gain, lower output power, and hence lower P1dB. The amplifier provides a gain of 20.9 dB with +/- 0.2 dB gain ripple. Its input and output reflection coefficients are better than -9.6 dB and -11 dB, respectively. The overall chip size is 2.9 mm x 1.5 mm. © 2024 IEEE.

关键词： III-V semiconductors

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Innovative Design, Prototyping, Integration of an Opening Mechanism and electronics for Enhanced Stability and Manoeuvrability in a Tandem Wing Tube-Launched UAV 4

Innovative Design, Prototyping, Integration of an Opening Me...

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4th International Conference on Digital Futures and Transformative technologies, ICoDT2 2024

作者： Martins, Muhammad Hasnain Khan Arif, Muhammad Arslan Iqbal, Sohail Moiz, Abdul Islam, Asad Rasheed, Sheikh Muhammad Muneeb Hamid Abbas, Hussain Air University Department of Mechanical and Aerospace Engineering Islamabad Pakistan Center of Excellence in Science & Applied Technologies Pakistan

ISBN: (纸本)9798350391862

This paper presents the design, prototyping, and integration of an innovative opening mechanism for a tandem wing tube-launched unmanned aerial vehicle (UAV) to enhance its stability and maneuverability. The study incorporates computational fluid dynamics (CFD), finite element method (FEM), and wind tunnel testing to validate the UAV's. A prototype of the tandem wing UAV has been successfully fabricated and final model is fabricated through 3D printing. The opening mechanism, a crucial component for the UAV's functionality, has been meticulously implemented to optimize aerodynamic performance, ensuring improved stability and maneuverability during flight operations. We have also integrated the necessary electronics to enable autonomous flight capabilities. Flight testing has been conducted to test the experimental performance of the UAV. This UAV design represents an advancement in tube-launched unmanned aerial vehicle technology, with the potential for various military and civilian applications. © 2024 IEEE.

关键词： Computational fluid dynamics

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