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Concurrent generation and amplification of longitudinal and bending waves using defective phononic crystals

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Applied Mathematics and Mechanics(English Edition) 2025年第2期46卷 269-288页

作者： s.h.JO Department of Mechanical Robotics and Energy Engineering Dongguk University

Defective phononic crystals (PnCs) have enabled spatial localization and quantitative amplification of elastic wave energy. Most previous research has focused on applications such as narrow-bandpass filters, ultrasonic sensors, and piezoelectric energy harvesters, typically operating under the assumption of an external elastic wave incidence. Recently, a novel approach that uses defective PnCs as ultrasonic actuators to generate amplified waves has emerged. however, the existing studies are limited to the generation of either longitudinal or bending waves, with no research addressing the concurrent generation of both. hence, this paper proposes a straightforward methodology for the concurrent generation and amplification of both wave types utilizing defect modes at independent defect-band frequencies. Bimorph piezoelectric elements are attached to the defect, with each element connected to independent external voltage sources. By precisely adjusting the magnitude and temporal phase differences between the voltage sources, concurrently amplified wave generation is achieved. The paper highlights the advantages of the proposed analytical model. This model is both computationally timeefficient and accurate, in comparison with the COMsOL simulation results. For instance,in case studies, the analytical model reduces the computational time from one hour to mere seconds, while maintaining acceptable error rates of 1%in peak frequencies. This concurrent wave-generation methodology opens new avenues for applications in rotating machinery fault diagnosis, structural health monitoring, and medical imaging.

关键词： phononic crystal (PnC) defect concurrent generation piezoelectric ultrasonic actuator O328 O346

Job burnout among critical care nurses in the eastern province of saudi Arabia

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Frontiers of Nursing 2025年第1期12卷 67-78页

作者： Mahmoud abdel hameed shahin Associate Professor of Medical-surgical and Critical Care Nursing Nursing DepartmentPrince Sultan Military College of Health SciencesDhahranKSA

Objectives:Nurses working in critical care units may encounter substantial work-related strain,and elevated levels of stress can lead to burnout,ultimately impacting both the quality of nursing care and their overall working *** study aimed to assess job burnout and determine the factors that contribute to it among critical care nurses in the Eastern Province of saudi ***:This study employed a descriptive,exploratory,cross-sectional research design.A total of 220 nurses employed in the critical care units of 5 private hospitals in the eastern region were selected for participation in this study using a convenience sample *** electronic survey was distributed to critical care nurses in the Eastern Province who satisfied the specified inclusion *** job burnout questionnaire utilized in this study was derived from previously conducted research,which has been established as a reliable and valid survey *** process of data analysis was conducted utilizing the sPss *** scientific research conducted on human subjects adhered rigorously to all ethical ***:The highest percentage of nurses at the critical care units reported experiencing moderate levels of job *** exhibiting greater levels of professional experience demonstrated a statistically significant reduction in overall burnout scores when compared to their less experienced ***,within the realm of sociodemographic factors,it was found that the only significant independent predictor for job burnout was the level of experience among critical care ***:The prevalence of burnout among nurses in critical care settings was found to be significant,with most participants reporting moderate levels of burnout which can yield significant ramifications for nurses and healthcare ***,healthcare organizations must accord primacy to the welfare of their staff and adopt proactive strategies to

关键词： critical care eastern province job burnout nurses predictors saudi Arabia

Geological, Engineering Geological and hydrogeological Characteristics of the Knowledge Economic City, Al Madinah Al Munawwarah, KsA

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Geomaterials 2025年第1期15卷 40-55页

作者： Mutasim A. M. Ez Eldin Tareq saeid Al Zahrani Gabel Zamil Al-Barakati Ibrahim Mohamed Alharthi Marwan Mohamed Al saikhan Waleed abdel aziz Al Aklouk Waheed Mohamed saeid Ba Amer Programme of Engineering Geology Center of Applied Geology Saudi Geological Survey Jeddah Kingdom of Saudi Arabia Department of Engineering Geology College of Petroleum Geology and Minerals University of Bahri Khartoum Sudan Zamzam studies and Research Center Saudi Geological Survey Jeddah Kingdom of Saudi Arabia

The Knowledge Economic City (KEC) of Al Madinah Al Munawwarah is one of the major projects and represents the cornerstone for the new development activities for Al Madinah. The study area contains different geological units dominated by basalt and overlain by surface deposits. The surface soils vary in thickness and can be classified into well-graded sAND with silt and gravel (sW-sM), silty sAND with gravel (sM), silty GRAVEL with sand (GM), and sandy sILTY clay (CL-ML). The subsurface soil obtained from the drilled boreholes can be classified into poorly graded GRAVEL (GP), well-graded GRAVEL with sand (GW), poorly graded GRAVEL with silt (GP-GM), silty CLAYEY gravel with sand (GC-GM), silty sAND with gravel (sM), silt with sAND (ML), and silty CLAY with sand (CL-ML), sandy lean CLAY (CL), and lean CLAY (CL). The relative density of the deposit and the different gravel sizes intercalated with the soil influenced the standard Penetration Test (sPT) values. The sPT N values are high and approach refusal even at shallow depths. The shallow refusal depth (0.10 to 0.90 m) of the Dynamic Cone Penetration Test (DCPT) was observed. Generally, the soil can be described as inactive with low plasticity and dense to very dense consistency. The basalt of the KEC site is characterized by slightly (W2) to highly (W4) weathering, their strength ranges from moderate (s4) to very strong (s2), and the Rock Quality Designation (RQD) ranges from very poor (R5) to excellent (R1). The engineering geological map of the KEC characterized the geoengineering properties of the soil and rock materials and classified them into many zones. The high sulphate (sO42−) and chloride (Cl−) contents in groundwater call for protective measures for foundation concrete. The current study revealed that geohazard(s) mitigation measures concerning floods, volcanic eruptions, and earthquakes should be considered.

关键词： Engineering Geology Knowledge Economic City Petrographic Description Rock and soil Investigations

Free vibration and transient response of double curved beams connected by intermediate straight beams

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Applied Mathematics and Mechanics(English Edition) 2025年第1期46卷 37-62页

作者： R.A.JAFARI-TALOOKOLAEI h.GhANDVAR E.JUMAEV s.KhATIR T.CUONG-LE school of Mechanical Engineering Babol Noshirvani University of Technology Department of Mechanical Engineering Faculty of Engineering New Uzbekistan University University of Business and science Center for Engineering Application and Technology solutions Ho Chi Minh City Open University

This paper investigates the free vibration and transient response of interconnected structures including double curved beams and intermediate straight beams,which are all constructed from functionally graded porous(FGP) materials. The strain potential and kinetic energies of each beam along with the work done by the external force are calculated. Additionally, a higher-order beam element is introduced to derive stiffness and mass matrices, along with the force vector. The curved and straight beams are discretized, and their assembled stiffness, mass matrices, and force vectors, are *** conditions at the joints are used to derive the total matrices of the entire structure. subsequently, the natural frequencies and transient response of the system are determined. The accuracy of the mathematical model and the self-developed computer program is validated through the comparison of the obtained results with those of the existing literature and commercial software ANsYs, demonstrating excellent ***, a comprehensive study is conducted to investigate the effects of various parameters on the free vibration and transient response of the considered structure.

关键词： double curved beam finite element method functionally graded porous (FGP) material intermediate straight beam O313 vibration analysis

An investigation into the physical assessment abilities of critical care nurses in an internationally recognized hospital

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Frontiers of Nursing 2025年第1期12卷 99-106页

作者： Gideon Victor Faisal aziz Jamal hussain Noman Iqbal shifa Tameer-e-Millat University Shifa College of NursingIslamabadPakistan Center for Biomarker Research in Medicine Medical University of GrazGrazAustria Intensive Care Unit PAEC General HospitalIslamabadPakistan Intensive Care Nursing IslamabadNursing CollegeBhara KahuIslamabadPakistan

Objective: Physical assessment is an indispensable and pivotal skill that nurses must aptly monitor, evaluate, and deliver timely care, particularly in the context of critically ill patients. however, studies have revealed instances where nurses demonstrate inaccurate practices. This study is aimed to measure the physical assessment skills of critical care nurses and the differences between levels of nursing education. Methods: A descriptive cross-sectional study was conducted involving a simple random sample of 101 nurses employed in critical care units. Results: Of the 101 participants, 56.4% were identified as female and 43.6% were male. In the sample, 71.0% held a diploma in nursing, while 29.0% held a Bachelor of science in Nursing (BsN). Vital signs, orientation, and skin assessments were performed correctly in ≥90% of cases, whereas the majority (≥60%) did not correctly assess neck veins, homan’s signs, breath sounds, heart sounds, and bowel sounds. Only ≤10% of participants accurately executed these assessments. significant associations were found between sex and pain (P=0.034), as well as between the type of education and closure of the health assessment (P=0.041). Further, female nurses scored 10.0 ± 2.3, and male nurses 8.5 ± 2.5, diploma holders scored 9.4 ± 1.8, and BsN holders scored 9.3 ± 2.7 at the global rating. Conclusions: The presence of an existing gap in the accurate assessment of patients poses a potential risk to patient care. It is essential to investigate the factors contributing to this gap and to develop strategies to address it, thereby enhancing the quality of physical assessment and ultimately improving patient care.

关键词： critical care nursing nurses patient physical assessment

Attitude dynamics and control of spacecraft using geomagnetic Lorentz force

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Research in Astronomy and Astrophysics 2015年第1期15卷 127-144页

作者： Yehia A.abdel-aziz Muhammad shoaib National Research Institute of Astronomy and Geophysics (NRIAG) Helwan Cairo 11721Egypt University of hail Department of Mathematics PO BOX 2440 Kingdom of Saudi Arabia

Attitude stabilization of a charged rigid spacecraft in Low Earth Orbit using torques due to Lorentz force in pitch and roll directions is considered. A spacecraft that generates an electrostatic charge on its surface in the Earth’s magnetic field will be subject to perturbations from the Lorentz force. The Lorentz force acting on an electrostatically charged spacecraft may provide a useful thrust for controlling a spacecraft’s orientation. We assume that the spacecraft is moving in the Earth’s magnetic field in an elliptical orbit under the effects of gravitational, geomagnetic and Lorentz torques. The magnetic field of the Earth is modeled as a non-tilted dipole.A model incorporating all Lorentz torques as a function of orbital elements has been developed on the basis of electric and magnetic fields. The stability of the spacecraft orientation is investigated both analytically and numerically. The existence and stability of equilibrium positions is investigated for different values of the charge to mass ratio（α＊）. stable orbits are identified for various values of α＊. The main parameters for stabilization of the spacecraft are α＊and the difference between the components of the moment of inertia for the spacecraft.

关键词： space vehicles atmospheric effects celestial mechanics kinematics and dynamics

Equilibria of a charged artificial satellite subject to gravitational and Lorentz torques

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Research in Astronomy and Astrophysics 2014年第7期14卷 891-902页

作者： Yehia A.abdel-aziz Muhammad shoaib National Research Institute of Astronomy and Geophysics (NRIAG) HelwanCairo 11721Egypt University of hail Department of MathematicsPO Box 2440Kingdom of Saudi Arabia

The attitude dynamics of a rigid artificial satellite subject to a gravity gradient and Lorentz torques in a circular orbit are considered. Lorentz torque is developed on the basis of the electrodynamic effects of the Lorentz force acting on the charged satellite＇s surface. We assume that the satellite is moving in a Low Earth Orbit in the geomagnetic field, which is considered to be a dipole. Our model of torque due to the Lorentz force is developed for an artificial satellite with a general shape, and the nonlinear differential equations of Euler are used to describe its attitude orientation. All equilibrium positions are determined and conditions for their existence are *** numerical results show that the charge q and radius ρ0of the center of charge for the satellite provide a certain type of semi-passive control for the attitude of the satellite. The technique for this kind of control would be to increase or decrease the electrostatic screening on the satellite. The results obtained confirm that the change in charge can affect the magnitude of the Lorentz torque, which can also affect control of the satellite. Moreover, the relationship between magnitude of the Lorentz torque and inclination of the orbit is investigated.

关键词： space vehicles -- atmospheric effects -- celestial mechanics -- kine-matics and dynamics

Encoderless Five-phase PMa-synRM Drive system Based on Robust Torque-speed Estimator with super-twisting sliding Mode Control

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CEs Transactions on Electrical Machines and systems 2023年第1期7卷 54-62页

作者： Ghada A.abdel aziz Rehan Ali Khan Power Electronics and Energy Conversion Department Electronics Research InstituteCairo11843Egypt Department of Electrical Engineering University of Science&TechnologyBannu28100Pakistan IEEE

In this paper,a robust torque speed estimator(RTsE)for linear parameter changing(LPC)system is proposed and designed for an encoderless five-phase permanent magnet assisted synchronous reluctance motor(5-phase PMa-synRM).This estimator is utilized for estimating the rotor speed and the load torque as well as can solve the speed sensor fault problem,as the feedback speed information is obtained directly from the virtual *** addition,this technique is able to enhance the 5-phase PMa-synRM performance by estimating the load torque for the real time *** stability analysis of the proposed estimator is performed via schur complement along with Lyapunov ***,for improving the 5-phase PMa-synRM performance,five super-twisting sliding mode controllers(sT-sMCs)are employed with providing a robust response without the impacts of high chattering problem.A super-twisting sliding mode speed controller(sT-sMsC)is employed for controlling the PMa-synRM rotor speed,and four super-twisting sliding mode current controllers(sT-sMCCs)are employed for controlling the 5-phase PMa-synRM *** stability analysis and the experimental results indicate the effectiveness along with feasibility of the proposed RTsE and the sT-sMsC with sT-sMCCs approach for a 750-W 5-phase PMa-synRM under load disturbance,parameters variations,single open-phase fault,and adjacent two-phase open circuit fault conditions.

关键词： Five-phase permanent magnet assisted synchronous reluctance motor Encoderless control supertwisting sliding mode control Torque-speed estimator

Adaptive Gain Tuning Rule for Nonlinear sliding-mode speed Control of Encoderless Three-phase Permanent Magnet Assisted synchronous Motor

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CEs Transactions on Electrical Machines and systems 2023年第3期7卷 301-310页

作者： Ghada A.abdel aziz Rehan Ali Khan IEEE Power Electronics and Energy Conversion Department Electronics Research InstituteCairo 11843Egypt Department of Electrical Engineering University of Science&TechnologyBannuPakistan.

In this paper, an adaptive gain tuning rule is designed for the nonlinear sliding mode speed control(NsMsC) in order to enhance the dynamic performance and the robustness of the permanent magnet assisted synchronous reluctance motor(PMa-syn RM) with considering the parameter uncertainties. A nonlinear sliding surface whose parameters are altering with time is designed at first. The proposed NsMsC can minimize the settling time without any overshoot via utilizing a low damping ratio at starting along with a high damping ratio as the output approaches the target set-point. In addition, it eliminates the problem of the singularity with the upper bound of an uncertain term that is hard to be measured practically as well as ensures a rapid convergence in finite time, through employing a simple adaptation law. Moreover, for enhancing the system efficiency throughout the constant torque region, the control system utilizes the maximum torque per ampere technique. The nonlinear sliding surface stability is assured via employing Lyapunov stability theory. Furthermore, a simple sliding mode estimator is employed for estimating the system uncertainties. The stability analysis and the experimental results indicate the effectiveness along with feasibility of the proposed speed estimation and the NsMsC approach for a 1.1-k W PMa-syn RM under different speed references, electrical and mechanical parameters disparities, and load disturbance conditions.

关键词： Permanent magnet assisted synchronous reluctance motor Nonlinear sliding mode speed control speed estimation Parameter uncertainties sliding mode estimator