Periodic isolator is well known for its wave filtering characteristic.While in middle and high frequencies,the internal resonances of the periodic isolator are evident especially when damping is small.This study propo...Periodic isolator is well known for its wave filtering characteristic.While in middle and high frequencies,the internal resonances of the periodic isolator are evident especially when damping is small.This study proposes a novel aperiodic vibration isolation for improving the internal resonances control of the periodic isolator.The mechanism of the internal resonances control by the aperiodic isolator is firstly explained.For comparing the internal resonances suppression effect of the aperiodic isolator with the periodic isolator,a dynamic model combing the rigid machine,the isolator,and the flexible plate is derived through multi subsystem modeling method and transfer matrix method,whose accuracy is verified through the finite element method.The influences of the aperiodicity and damping of the isolator on the vibration isolation performance and internal resonances suppression effect are investigated by numerical analysis.The numerical results demonstrate that vibration attenuation performances of the periodic isolator and aperiodic isolator are greatly over than that of the continuous isolator in middle and high frequencies.The aperiodic isolator opens the stop bandgaps comparing with the periodic isolator where the pass bandgaps are periodically existed.The damping of the isolator has the stop bandgap widening effect on both the periodic isolator and the aperiodic isolator.In addition,a parameter optimization algorithm of the aperiodic isolator is presented for improving the internal resonances control effect.It is shown that the vibration peaks within the target frequency band of the aperiodic isolator are effectively reduced after the optimization.Finally,the experiments of the three different vibration isolation systems are conducted for verifying the analysis work.展开更多
This phenomenological qualitative study explored the lived experiences of employees at Maryland's Historically Black Colleges and Universities(HBCUs)concerning internal control systems through the theoretical lens...This phenomenological qualitative study explored the lived experiences of employees at Maryland's Historically Black Colleges and Universities(HBCUs)concerning internal control systems through the theoretical lenses of the COSO framework and employee engagement theory.Using semi-structured interviews with faculty and staff who had worked at the institution for more than three years,the research investigated how employees perceive leadership tone,risk assessment processes,policy implementation,communication channels,and evaluation mechanisms related to internal controls.The study revealed five major themes that characterize employee experiences with internal control systems at this HBCU.Leadership communication was found to be hierarchical but inclusive,though marked by inconsistent communication of ethical values and significant resource constraints affecting implementation.Risk management practices were predominantly reactive rather than proactive,with limited systematic risk assessment processes that focused more on academic risks than operational vulnerabilities.Policy implementation was characterized by unclear separation of duties,substantial workload imbalances,and limited resources that compromised effective control activities.Communication challenges emerged as a critical weakness,with participants describing information sharing as inconsistent,unclear,and selective,compounded by significant technology obstacles in accessing necessary information.The evaluation and improvement processes were found to be limited and primarily driven by external accreditation requirements rather than systematic internal monitoring,resulting in reactive responses to issues rather than proactive enhancement.The findings contribute to the limited research on internal control systems within HBCUs by providing phenomenological insights into how structural constraints including funding limitations,unclear role delineation,and reactive management approaches create barriers to implementing robust internal control systems.Despite institutional commitment to inclusive leadership and student success,the study reveals that addressing these challenges requires not only increased resources but also structural changes to workload distribution,communication practices,and a shift toward more proactive risk management and monitoring procedures.The research provides evidence-based insights for HBCU administrators seeking to strengthen internal control implementation while maintaining institutional mission and cultural values.展开更多
This paper investigates the reliability of internal marine combustion engines using an integrated approach that combines Fault Tree Analysis(FTA)and Bayesian Networks(BN).FTA provides a structured,top-down method for ...This paper investigates the reliability of internal marine combustion engines using an integrated approach that combines Fault Tree Analysis(FTA)and Bayesian Networks(BN).FTA provides a structured,top-down method for identifying critical failure modes and their root causes,while BN introduces flexibility in probabilistic reasoning,enabling dynamic updates based on new evidence.This dual methodology overcomes the limitations of static FTA models,offering a comprehensive framework for system reliability analysis.Critical failures,including External Leakage(ELU),Failure to Start(FTS),and Overheating(OHE),were identified as key risks.By incorporating redundancy into high-risk components such as pumps and batteries,the likelihood of these failures was significantly reduced.For instance,redundant pumps reduced the probability of ELU by 31.88%,while additional batteries decreased the occurrence of FTS by 36.45%.The results underscore the practical benefits of combining FTA and BN for enhancing system reliability,particularly in maritime applications where operational safety and efficiency are critical.This research provides valuable insights for maintenance planning and highlights the importance of redundancy in critical systems,especially as the industry transitions toward more autonomous vessels.展开更多
On January 3,the United States launched a military operation against the sovereign nation of Venezuela.“capturing”its president,Nicolas Maduro.This event is far from a mere isolated"law enforcement operation&qu...On January 3,the United States launched a military operation against the sovereign nation of Venezuela.“capturing”its president,Nicolas Maduro.This event is far from a mere isolated"law enforcement operation";it represents a blatant challenge to the international legal system centered around the United Nations Charter and a thorough and dangerous trampling of the fundamental principles of intemmational relations.展开更多
Extensive studies on nonlinear dynamics of gear systems with internal excitation or external excitation respectively have been carried out.However,the nonlinear characteristics of gear systems under combined internal ...Extensive studies on nonlinear dynamics of gear systems with internal excitation or external excitation respectively have been carried out.However,the nonlinear characteristics of gear systems under combined internal and external excitations are scarcely investigated.An eight-degree-of-freedom(8-DOF)nonlinear spur gear-rotor-bearing model,which contains backlash,transmission error,eccentricity,gravity and input/output torque,is established,and the coupled lateral-torsional vibration characteristics are studied.Based on the equations of motion,the coupled spur gear-rotor-bearing system(SGRBS)is investigated using the Runge-Kutta numerical method,and the effects of rotational speed,error fluctuation and load fluctuation on the dynamic responses are explored.The results show that a diverse range of nonlinear dynamic characteristics such as periodic motion,quasi-periodic motion,chaotic behaviors and impacts exhibited in the system are strongly attributed to the interaction between internal and external excitations.Significantly,the changing rotational speed could effectively control the vibration of the system.Vibration level increases with the increasing error fluctuation.Whereas the load fluctuation has an influence on the nonlinear dynamic characteristics and the increasing excitation force amplitude makes the vibration amplitude increase,the chaotic motion may be restricted.The proposed model and numerical results can be used for diagnosis of faults and vibration control of practical SGRBS.展开更多
The start-up current control of the high-speed brushless DC（HS-BLDC） motor is a challenging research topic. To effectively control the start-up current of the sensorless HS-BLDC motor, an adaptive control method is ...The start-up current control of the high-speed brushless DC（HS-BLDC） motor is a challenging research topic. To effectively control the start-up current of the sensorless HS-BLDC motor, an adaptive control method is proposed based on the adaptive neural network（ANN）inverse system and the two degrees of freedom（2-DOF） internal model controller（IMC）. The HS-BLDC motor is identified by the online least squares support vector machine（OLS-SVM） algorithm to regulate the ANN inverse controller parameters in real time. A pseudo linear system is developed by introducing the constructed real-time inverse system into the original HS-BLDC motor system. Based on the characteristics of the pseudo linear system, an extra closed-loop feedback control strategy based on the 2-DOF IMC is proposed to improve the transient response performance and enhance the stability of the control system. The simulation and experimental results show that the proposed control method is effective and perfect start-up current tracking performance is achieved.展开更多
A modified two-degrees-of-freedom( M-TDOF) internal model control( IMC) method is proposed for non-square systems with multiple time delays and right-half-plane( RHP) zeros. In this method,pseudo-inverse is introduced...A modified two-degrees-of-freedom( M-TDOF) internal model control( IMC) method is proposed for non-square systems with multiple time delays and right-half-plane( RHP) zeros. In this method,pseudo-inverse is introduced to design the internal model controller,and a desired closed-loop transfer function is designed to eliminate the unrealizable factors of the derived controller. In addition,set-point tracking and load-disturbance rejection of each process are separately controlled by two controllers. The simulation results show that in addition to high decoupling performance and robustness,the proposed control method also effectively improves loaddisturbance rejection and simultaneously optimizes the input tracking performance and disturbance rejection performance by selecting the parameters of controllers. Furthermore,the higher tolerance of model mismatch is achieved in this paper.展开更多
The nuclides inhaled during nuclear accidents usually cause internal contamination of the lungs with low activity.Although a parallel-hole imaging system,which is widely used in medical gamma cameras,has a high resolu...The nuclides inhaled during nuclear accidents usually cause internal contamination of the lungs with low activity.Although a parallel-hole imaging system,which is widely used in medical gamma cameras,has a high resolution and good image quality,owing to its extremely low detection efficiency,it remains difficult to obtain images of inhaled lung contamination.In this study,the Monte Carlo method was used to study the internal lung contamination imaging using the MPA-MURA coded-aperture collimator.The imaging system consisted of an adult male lung model,with a mosaicked,pattern-centered,and anti-symmetric MURA coded-aperture collimator model and a CsI(Tl)detector model.The MLEM decoding algorithm was used to reconstruct the internal contamination image,and the complementary imaging method was used to reduce the number of artifacts.The full width at half maximum of the I-131 point source image reconstructed by the MPAMURA coded-aperture imaging reached 2.51 mm,and the signal-to-noise ratio of the simplified respiratory tract source(I-131)image reconstructed through MPA-MURA coded-aperture imaging was 3.98 dB.Although the spatial resolution of MPA-MURA coded-aperture imaging is not as good as that of parallel-hole imaging,the detection efficiency of PMA-MURA coded-aperture imaging is two orders of magnitude higher than that of parallel-hole collimator imaging.Considering the low activity level of internal lung contamination caused by nuclear accidents,PMA-MURA coded-aperture imaging has significant potential for the development of lung contamination imaging.展开更多
This paper proposes a two-to-one internal resonance to widen the bandwidth of vibratory energy harvesters.To describe the improved characteristic,an electromagnetic spring-pendulum harvester is designed.Approximate an...This paper proposes a two-to-one internal resonance to widen the bandwidth of vibratory energy harvesters.To describe the improved characteristic,an electromagnetic spring-pendulum harvester is designed.Approximate analytical solutions of the electromechanical coupled system are carried out by introducing the method of multiple scales,and the frequency response relationships of the displacement and the current are obtained.The character of broadband harvesting performance is examined,the two peaks and double jump phenomena for variation of design parameters were observed.The effect of key control parameters on the harvesters bandwidth is considered,and the nonlinear behaviors of the harvester are validated via numerical results.展开更多
Pipe-in-pipe(PIP)structures are widely used in offshore oil and gas pipelines to settle thermal insulation issues.A PIP structure system usually consists of two concentric pipes and one softer layer for thermal insula...Pipe-in-pipe(PIP)structures are widely used in offshore oil and gas pipelines to settle thermal insulation issues.A PIP structure system usually consists of two concentric pipes and one softer layer for thermal insulation consideration.The total response of the system is related to the dynamics of both pipes and the interactions between these two concentric pipes.In the current work,a theoretical model for flow-induced vibrations of a PIP structure system is proposed and analyzed in the presence of an internal axial flow and an external cross flow.The interactions between the two pipes are modeled by a linear distributed damper,a linear distributed spring and a nonlinear distributed spring along the pipe length.The unsteady hydrodynamic forces due to cross flow are modeled by two distributed van der Pol wake oscillators.The nonlinear partial differential equations for the two pipes and the wake are further discretized by the aid of Galerkin’s technique,resulting in a set of ordinary differential equations.These ordinary differential equations are further numeri cally solved by using a fourth-order Runge-Kutta integration algorithm.Phase portraits,bifurcation diagrams,an Argand diagram and oscillation shape diagrams are plotted,showing the existence of a lock-in phenomenon and figure-of-eight trajectory.The PIP system subjected to cross flow displays some interesting dynamical behaviors different from that of a single-pipe structure.展开更多
In this paper, an iterative learning control algorithm is proposed for discrete linear time-varying systems to track iterationvarying desired trajectories. A high-order internal model(HOIM) is utilized to describe the...In this paper, an iterative learning control algorithm is proposed for discrete linear time-varying systems to track iterationvarying desired trajectories. A high-order internal model(HOIM) is utilized to describe the variation of desired trajectories in the iteration domain. In the sequel, the HOIM is incorporated into the design of learning gains. The learning convergence in the iteration axis can be guaranteed with rigorous proof. The simulation results with permanent magnet linear motors(PMLM) demonstrate that the proposed HOIM based approach yields good performance and achieves perfect tracking.展开更多
In the present study a numerical model developed by Lynett and Liu （2002） is modified to include density difference in a stratified two-layer fluid in a three-dimensional internal wave domain. The internal solitary ...In the present study a numerical model developed by Lynett and Liu （2002） is modified to include density difference in a stratified two-layer fluid in a three-dimensional internal wave domain. The internal solitary wave （ISW） in the model is assumed to be weakly nonlinear and weakly dispersive, and the viscosity effects at all boundaries are ignored. The governing equations based on the Navier-Stokes and Euler equations are solved for internal solitary wave propagation over variable seabed topography. Theoretical formulations are established, from which analytical solutions are obtained, in addition to numerical results. Wave profiles from previous experimental studies are compared with the numerical results from the present analytical solutions. Numerical models developed on the basis of the present analytical solutions are better than those developed by Lynett and Liu （2002）. The results of numerical modeling agree well with the experimental data.展开更多
AIM:To compare the outcomes of four adjuvants used for internal limiting membrane(ILM)peeling in macular hole surgery,including indocyanine green(ICG),brilliant blue G(BBG),triamcinolone(TA)and trypan blue(TB),through...AIM:To compare the outcomes of four adjuvants used for internal limiting membrane(ILM)peeling in macular hole surgery,including indocyanine green(ICG),brilliant blue G(BBG),triamcinolone(TA)and trypan blue(TB),through systematic review and random-effects Bayesian network Meta-analysis.METHODS:PubMed,Cochrane library databases and Web of Science were searched until August 2018 for clinical trials comparing the above four adjuvants.ORs for postoperative best corrected visual acuity(BCVA)improvement and primary macular hole closure rates were compared between the different adjuvants.RESULTS:Twenty-seven eligible articles were included.For postoperative BCVA improvement,results of BBGassisted peeling were significantly more favorable than those of ICG(WMD 0.08,95%credible interval 0.01-0.16)and TA ranked highest.No significant differences were found between any other two groups in postoperative BCVA improvement.For postoperative primary macular hole closure rates,BBG ranked highest.However,no significant differences were shown between any two groups.CONCLUSION:TA and BBG are the optimum adjuvants for achieving postoperative BCVA improvement macular hole surgery with adjuvant-assisted ILM peeling.Among all adjuvants,the use of BBG is associated with the highest postoperative macular hole closure rate.展开更多
The dynamics differential equations are constructed, and the initial conditions are also given. Simulation shows the following conclusions： The water pressure in cylinder has great instantaneous pulsation and phase s...The dynamics differential equations are constructed, and the initial conditions are also given. Simulation shows the following conclusions： The water pressure in cylinder has great instantaneous pulsation and phase step when outlet valve or inlet valve opens, but is more gently in other time; The volume efficiency is influenced by the output pressure slightly, and decreases as the working rotational speed increases; When the inherent frequency of the valves is integer multiple of the working frequency, the volume efficiency of system will decrease evidently.展开更多
A novel control scheme of active disturbance rejection internal model control(ADRIMC) is proposed to improve the anti-interference ability and robustness for the dead-time process. The active anti-interference concept...A novel control scheme of active disturbance rejection internal model control(ADRIMC) is proposed to improve the anti-interference ability and robustness for the dead-time process. The active anti-interference concept is introduced into the internal model control(IMC) by analyzing the relationship between IMC and disturbance observer control(DOB). Further, a design process of disturbance filter is presented to realize the active anti-interference ability for ADRIMC scheme. The disturbance filter is used to estimate an equivalent disturbance consisting of both external disturbances and internal disturbances caused by model mismatches.Simulation results demonstrate that the proposed method possesses a good disturbance rejection performance, though losing some partial dynamic performance. In other words, the proposed method shows a tradeoff between the dynamic performance and the system robust.展开更多
The characteristic and mechanism of parachlorophenol(4-CP) degradation in an internal electrolysis system were investigated. The degradation rate of 4-CP was higher in acid solution than that of in neutral or alkaline...The characteristic and mechanism of parachlorophenol(4-CP) degradation in an internal electrolysis system were investigated. The degradation rate of 4-CP was higher in acid solution than that of in neutral or alkaline solution. Addition of activated carbon could make 4-CP easier be degraded by the surface contact catalysis. The dissolved oxygen in solution could take part in the electrode reaction and intensify the degradation of 4-CP. By the analysis of intermediates of degradation of 4-CP, it could be conferred that 4-CP was broken through the bond beside hydroxy firstly, then the bond beside chloride was broken and the chloride was dechlorinated simultaneously. Most intermediate products were glycerine, ethane diacid and acetic acid, while very few 1,4-butanedial and alcohols were found.展开更多
In this study, the vibrations of multiple stepped beams with cubic nonlinearities are considered. A three-to-one internal resonance case is investigated for the system. A general approximate solution to the problem is...In this study, the vibrations of multiple stepped beams with cubic nonlinearities are considered. A three-to-one internal resonance case is investigated for the system. A general approximate solution to the problem is found using the method of multiple scales （a perturbation technique）. The modulation equations of the amplitudes and the phases are derived for two modes. These equations are utilized to determine steady state solutions and their stabilities. It is assumed that the external forcing frequency is close to the lower frequency. For the numeric part of the study, the three-to-one ratio in natural frequencies is investigated. These values are observed to be between the first and second natural frequencies in the cases of the clamped-clamped and clamped-pinned supports, and between the second and third natural frequencies in the case of the pinned-pinned support. Finally, a numeric algorithm is used to solve the three-to-one internal resonance. The first mode is externally excited for the clamped-clamped and clamped-pinned supports, and the second mode is externally excited for the pinned-pinned support. Then, the amplitudes of the first and second modes are investigated when the first mode is externally excited. The amplitudes of the second and third modes are investigated when the second mode is externally excited. The force-response, damping-response, and .frequency- response curves are plotted for the internal resonance modes of vibrations. The stability analysis is carried out for these plots.展开更多
Objective To assess the feasibility of internal suspension technique in retroperitoneal robot-assisted laparoscopic partial nephrectomy(rRAPN)with a new robotic platform called KangDuo Surgical Robot-01(KD-SR-01)syste...Objective To assess the feasibility of internal suspension technique in retroperitoneal robot-assisted laparoscopic partial nephrectomy(rRAPN)with a new robotic platform called KangDuo Surgical Robot-01(KD-SR-01)system(Suzhou KangDuo Robot Co.,Ltd.,Suzhou,China)and discuss its surgical technique.Methods A 44-year-old male patient was admitted with a 2.5 cm tumor on dorsolateral upper pole of the left kidney.The R.E.N.A.L.nephrometry score of this patient was 4x.This patient underwent rRAPN with KD-SR-01.The perinephric fat between the tumor and Gerota's fascia was preserved,which was used for internal suspension traction during tumor resection.Postoperative follow-up data were collected.Results The surgery was successfully carried out with a duration of 127 min,in which the docking time was 6 min 25 s and console time was 60 min.The warm ischemia time was 19 min 53 s,and the estimated blood loss was 0 mL.The pathological histology showed a pathological tumor stage 1a clear cell renal cell carcinoma,with a negative surgical margin.The World Health Organization/International Society of Urological Pathology(WHO/ISUP)grade of this patient was Grade 2.No recurrence was observed during the 6-month follow-up.Conclusion Internal suspension in rRAPN is feasible and effective with use of the new robotic system KD-SR-01.展开更多
The 1:2 internal resonance of coupled dynamic system with quadratic and cubic nonlinearities is studied. The normal forms of this system in 1 :2 internal resonance were derived by using the direct method of normal for...The 1:2 internal resonance of coupled dynamic system with quadratic and cubic nonlinearities is studied. The normal forms of this system in 1 :2 internal resonance were derived by using the direct method of normal form. In the normal,forms, quadratic and cubic nonlinearities were remained. Based on a new convenient transformation technique, the 4-dimension bifurcation equations were reduced to 3-dimension. A bifurcation equation with one-dimension was obtained. Then the bifurcation behaviors of a universal unfolding were studied by using the singularity theory. The method of this paper can be applied to analyze the bifurcation behavior in strong internal resonance on 4-dimension center manifolds.展开更多
Background: Pelvic fracture combined with massive bleeding(PFCMB) is a complex issue in clinical practice. Currently, the use of angiography and embolization for the treatment of PFCMB obtains good results. The aim of...Background: Pelvic fracture combined with massive bleeding(PFCMB) is a complex issue in clinical practice. Currently, the use of angiography and embolization for the treatment of PFCMB obtains good results. The aim of this study is to observe the effects of early internal iliac artery embolization on the systemic inflammatory response syndrome(SIRS) in dogs with simulated-pelvic-fracture combined with massive bleeding.Methods: Twenty adult dogs were randomly divided into an embolization group(EG) and a control group(CG). For the two groups, heart rate, respiratory rate and body temperature and other physiological variables were measured, and IL-6, TNF-α and arterial blood gas levels were monitored. These variables were assayed every 30 min until death in the CG, while dogs in the EG underwent arterial angiography after 60 min of modeling. The internal iliac artery was embolized on the injured side.Results: The average time to SIRS in the CG was 3.56 h, occurring at a rate of 90%(9/10) within 24 h, with a mortality rate of 50%(5/10); the average time to SIRS for the EG was 5.33 h, occurring at a rate of 30%(3/10) within 24 h, with a mortality rate of 10%(1/10). When SIRS occurred in the EG, the mean plasma IL-6 level was 52.66±7.38pg/ml and the TNF-ps, tα level was 11.45±2.72ng/ml, showing a significant difference with those of the CG(P<0.05). In the two grouhe respiratory rate and leukocyte levels were higher at each monitored time after modeling than those before modeling; the mean arterial pressure, levels of hemoglobin and oxygen partial pressure were significantly lower at each time point after modeling than those before modeling except for the mean arterial pressure at 0h in EG; the platelet levels at 4 and 8h were higher than those before modeling; and the differences were statistically significant(P<0.05). In the EG, the mean arterial pressure, heart rate, respiratory rate and hemoglobin levels at 2, 4 and 8h were lower than those at 0h; the levels of leukocytes, platelets and carbon dioxide partial pressure at 4 and 8h after modeling were higher than those at 0h, and the differences were statistically significant(P<0.05, P<0.01); in the CG after modeling, the mean arterial pressure, levels of hemoglobin and carbon dioxide partial pressure at 2, 4 and 8h were lower than those at 0h; the levels of heart rate and leukocytes were higher than those before modeling; the respiratory rate and platelet levels at 4 and 8h were higher than those at 0h; and the differences were statistically significant(P<0.05). The levels of the mean arterial pressure and hemoglobin at 4 and 8h and the p H values at 8h after modeling in the EG were significantly higher than those in the CG, while the heart rate and respiratory rate at 4 and 8h were significantly lower than those in the CG. The p H values at 8h after modeling were significantly lower than those of the other monitored times in the CG(P<0.05, P<0.01). The two groups had elevated levels of alkaline phosphatase after injury induction.Conclusion: Through the use of an on-spot interventional treatment cabin, early internal iliac artery embolization can control bleeding associated with pelvic fractures, delay the occurrence of SIRS, and improve the success rate of the treatment of pelvic fracture combined with bleeding.展开更多
基金supported by the National Key Research and Development Plan of China (Grant No.2023YFB3406302)Guangdong Basic and Applied Basic Research Foundation (Grant No.2024A1515011126)the Key Research and Development Plan of Shanxi (Grant No.2024GH-ZDXM-29)。
文摘Periodic isolator is well known for its wave filtering characteristic.While in middle and high frequencies,the internal resonances of the periodic isolator are evident especially when damping is small.This study proposes a novel aperiodic vibration isolation for improving the internal resonances control of the periodic isolator.The mechanism of the internal resonances control by the aperiodic isolator is firstly explained.For comparing the internal resonances suppression effect of the aperiodic isolator with the periodic isolator,a dynamic model combing the rigid machine,the isolator,and the flexible plate is derived through multi subsystem modeling method and transfer matrix method,whose accuracy is verified through the finite element method.The influences of the aperiodicity and damping of the isolator on the vibration isolation performance and internal resonances suppression effect are investigated by numerical analysis.The numerical results demonstrate that vibration attenuation performances of the periodic isolator and aperiodic isolator are greatly over than that of the continuous isolator in middle and high frequencies.The aperiodic isolator opens the stop bandgaps comparing with the periodic isolator where the pass bandgaps are periodically existed.The damping of the isolator has the stop bandgap widening effect on both the periodic isolator and the aperiodic isolator.In addition,a parameter optimization algorithm of the aperiodic isolator is presented for improving the internal resonances control effect.It is shown that the vibration peaks within the target frequency band of the aperiodic isolator are effectively reduced after the optimization.Finally,the experiments of the three different vibration isolation systems are conducted for verifying the analysis work.
文摘This phenomenological qualitative study explored the lived experiences of employees at Maryland's Historically Black Colleges and Universities(HBCUs)concerning internal control systems through the theoretical lenses of the COSO framework and employee engagement theory.Using semi-structured interviews with faculty and staff who had worked at the institution for more than three years,the research investigated how employees perceive leadership tone,risk assessment processes,policy implementation,communication channels,and evaluation mechanisms related to internal controls.The study revealed five major themes that characterize employee experiences with internal control systems at this HBCU.Leadership communication was found to be hierarchical but inclusive,though marked by inconsistent communication of ethical values and significant resource constraints affecting implementation.Risk management practices were predominantly reactive rather than proactive,with limited systematic risk assessment processes that focused more on academic risks than operational vulnerabilities.Policy implementation was characterized by unclear separation of duties,substantial workload imbalances,and limited resources that compromised effective control activities.Communication challenges emerged as a critical weakness,with participants describing information sharing as inconsistent,unclear,and selective,compounded by significant technology obstacles in accessing necessary information.The evaluation and improvement processes were found to be limited and primarily driven by external accreditation requirements rather than systematic internal monitoring,resulting in reactive responses to issues rather than proactive enhancement.The findings contribute to the limited research on internal control systems within HBCUs by providing phenomenological insights into how structural constraints including funding limitations,unclear role delineation,and reactive management approaches create barriers to implementing robust internal control systems.Despite institutional commitment to inclusive leadership and student success,the study reveals that addressing these challenges requires not only increased resources but also structural changes to workload distribution,communication practices,and a shift toward more proactive risk management and monitoring procedures.The research provides evidence-based insights for HBCU administrators seeking to strengthen internal control implementation while maintaining institutional mission and cultural values.
基金supported by Istanbul Technical University(Project No.45698)supported through the“Young Researchers’Career Development Project-training of doctoral students”of the Croatian Science Foundation.
文摘This paper investigates the reliability of internal marine combustion engines using an integrated approach that combines Fault Tree Analysis(FTA)and Bayesian Networks(BN).FTA provides a structured,top-down method for identifying critical failure modes and their root causes,while BN introduces flexibility in probabilistic reasoning,enabling dynamic updates based on new evidence.This dual methodology overcomes the limitations of static FTA models,offering a comprehensive framework for system reliability analysis.Critical failures,including External Leakage(ELU),Failure to Start(FTS),and Overheating(OHE),were identified as key risks.By incorporating redundancy into high-risk components such as pumps and batteries,the likelihood of these failures was significantly reduced.For instance,redundant pumps reduced the probability of ELU by 31.88%,while additional batteries decreased the occurrence of FTS by 36.45%.The results underscore the practical benefits of combining FTA and BN for enhancing system reliability,particularly in maritime applications where operational safety and efficiency are critical.This research provides valuable insights for maintenance planning and highlights the importance of redundancy in critical systems,especially as the industry transitions toward more autonomous vessels.
文摘On January 3,the United States launched a military operation against the sovereign nation of Venezuela.“capturing”its president,Nicolas Maduro.This event is far from a mere isolated"law enforcement operation";it represents a blatant challenge to the international legal system centered around the United Nations Charter and a thorough and dangerous trampling of the fundamental principles of intemmational relations.
基金Supported by National Natural Science Foundation of China(Grant No.51475084)
文摘Extensive studies on nonlinear dynamics of gear systems with internal excitation or external excitation respectively have been carried out.However,the nonlinear characteristics of gear systems under combined internal and external excitations are scarcely investigated.An eight-degree-of-freedom(8-DOF)nonlinear spur gear-rotor-bearing model,which contains backlash,transmission error,eccentricity,gravity and input/output torque,is established,and the coupled lateral-torsional vibration characteristics are studied.Based on the equations of motion,the coupled spur gear-rotor-bearing system(SGRBS)is investigated using the Runge-Kutta numerical method,and the effects of rotational speed,error fluctuation and load fluctuation on the dynamic responses are explored.The results show that a diverse range of nonlinear dynamic characteristics such as periodic motion,quasi-periodic motion,chaotic behaviors and impacts exhibited in the system are strongly attributed to the interaction between internal and external excitations.Significantly,the changing rotational speed could effectively control the vibration of the system.Vibration level increases with the increasing error fluctuation.Whereas the load fluctuation has an influence on the nonlinear dynamic characteristics and the increasing excitation force amplitude makes the vibration amplitude increase,the chaotic motion may be restricted.The proposed model and numerical results can be used for diagnosis of faults and vibration control of practical SGRBS.
基金co-supported by the National Major Project for the Development and Application of Scientific Instrument Equipment of China (No. 2012YQ040235)
文摘The start-up current control of the high-speed brushless DC（HS-BLDC） motor is a challenging research topic. To effectively control the start-up current of the sensorless HS-BLDC motor, an adaptive control method is proposed based on the adaptive neural network（ANN）inverse system and the two degrees of freedom（2-DOF） internal model controller（IMC）. The HS-BLDC motor is identified by the online least squares support vector machine（OLS-SVM） algorithm to regulate the ANN inverse controller parameters in real time. A pseudo linear system is developed by introducing the constructed real-time inverse system into the original HS-BLDC motor system. Based on the characteristics of the pseudo linear system, an extra closed-loop feedback control strategy based on the 2-DOF IMC is proposed to improve the transient response performance and enhance the stability of the control system. The simulation and experimental results show that the proposed control method is effective and perfect start-up current tracking performance is achieved.
基金Sponsored by the Fundamental Research Funds for the Central Universities(Grant No.N110304008)the National Natural Science Foundation of China(Grant No.61374137)
文摘A modified two-degrees-of-freedom( M-TDOF) internal model control( IMC) method is proposed for non-square systems with multiple time delays and right-half-plane( RHP) zeros. In this method,pseudo-inverse is introduced to design the internal model controller,and a desired closed-loop transfer function is designed to eliminate the unrealizable factors of the derived controller. In addition,set-point tracking and load-disturbance rejection of each process are separately controlled by two controllers. The simulation results show that in addition to high decoupling performance and robustness,the proposed control method also effectively improves loaddisturbance rejection and simultaneously optimizes the input tracking performance and disturbance rejection performance by selecting the parameters of controllers. Furthermore,the higher tolerance of model mismatch is achieved in this paper.
基金the Ministry of Science and Technology,People’s Republic of China(No.2012YQ180118)the National Natural Science Foundation of China(No.41874121)the Sichuan Science and Technology Program(No.2018JY0181).
文摘The nuclides inhaled during nuclear accidents usually cause internal contamination of the lungs with low activity.Although a parallel-hole imaging system,which is widely used in medical gamma cameras,has a high resolution and good image quality,owing to its extremely low detection efficiency,it remains difficult to obtain images of inhaled lung contamination.In this study,the Monte Carlo method was used to study the internal lung contamination imaging using the MPA-MURA coded-aperture collimator.The imaging system consisted of an adult male lung model,with a mosaicked,pattern-centered,and anti-symmetric MURA coded-aperture collimator model and a CsI(Tl)detector model.The MLEM decoding algorithm was used to reconstruct the internal contamination image,and the complementary imaging method was used to reduce the number of artifacts.The full width at half maximum of the I-131 point source image reconstructed by the MPAMURA coded-aperture imaging reached 2.51 mm,and the signal-to-noise ratio of the simplified respiratory tract source(I-131)image reconstructed through MPA-MURA coded-aperture imaging was 3.98 dB.Although the spatial resolution of MPA-MURA coded-aperture imaging is not as good as that of parallel-hole imaging,the detection efficiency of PMA-MURA coded-aperture imaging is two orders of magnitude higher than that of parallel-hole collimator imaging.Considering the low activity level of internal lung contamination caused by nuclear accidents,PMA-MURA coded-aperture imaging has significant potential for the development of lung contamination imaging.
基金supported by the National Natural Science Foundation of China(Grants 11632008,11702119,and 11972173)the Natural Science Foundation of Jiangsu Province(Grant BK20170565)+1 种基金the Qing Lan Project of Jiangsu Provincethe Training program for Young Talents of Jiangsu University.
文摘This paper proposes a two-to-one internal resonance to widen the bandwidth of vibratory energy harvesters.To describe the improved characteristic,an electromagnetic spring-pendulum harvester is designed.Approximate analytical solutions of the electromechanical coupled system are carried out by introducing the method of multiple scales,and the frequency response relationships of the displacement and the current are obtained.The character of broadband harvesting performance is examined,the two peaks and double jump phenomena for variation of design parameters were observed.The effect of key control parameters on the harvesters bandwidth is considered,and the nonlinear behaviors of the harvester are validated via numerical results.
基金The work was supported by the National Natural Science Foundation of China(Grant 11622216).
文摘Pipe-in-pipe(PIP)structures are widely used in offshore oil and gas pipelines to settle thermal insulation issues.A PIP structure system usually consists of two concentric pipes and one softer layer for thermal insulation consideration.The total response of the system is related to the dynamics of both pipes and the interactions between these two concentric pipes.In the current work,a theoretical model for flow-induced vibrations of a PIP structure system is proposed and analyzed in the presence of an internal axial flow and an external cross flow.The interactions between the two pipes are modeled by a linear distributed damper,a linear distributed spring and a nonlinear distributed spring along the pipe length.The unsteady hydrodynamic forces due to cross flow are modeled by two distributed van der Pol wake oscillators.The nonlinear partial differential equations for the two pipes and the wake are further discretized by the aid of Galerkin’s technique,resulting in a set of ordinary differential equations.These ordinary differential equations are further numeri cally solved by using a fourth-order Runge-Kutta integration algorithm.Phase portraits,bifurcation diagrams,an Argand diagram and oscillation shape diagrams are plotted,showing the existence of a lock-in phenomenon and figure-of-eight trajectory.The PIP system subjected to cross flow displays some interesting dynamical behaviors different from that of a single-pipe structure.
基金supported by National Basic Research Program of China(973 Program)(No.2012CB316400)National Natural Science Foundation of China(Nos.61171034 and 61273134)
文摘In this paper, an iterative learning control algorithm is proposed for discrete linear time-varying systems to track iterationvarying desired trajectories. A high-order internal model(HOIM) is utilized to describe the variation of desired trajectories in the iteration domain. In the sequel, the HOIM is incorporated into the design of learning gains. The learning convergence in the iteration axis can be guaranteed with rigorous proof. The simulation results with permanent magnet linear motors(PMLM) demonstrate that the proposed HOIM based approach yields good performance and achieves perfect tracking.
文摘In the present study a numerical model developed by Lynett and Liu （2002） is modified to include density difference in a stratified two-layer fluid in a three-dimensional internal wave domain. The internal solitary wave （ISW） in the model is assumed to be weakly nonlinear and weakly dispersive, and the viscosity effects at all boundaries are ignored. The governing equations based on the Navier-Stokes and Euler equations are solved for internal solitary wave propagation over variable seabed topography. Theoretical formulations are established, from which analytical solutions are obtained, in addition to numerical results. Wave profiles from previous experimental studies are compared with the numerical results from the present analytical solutions. Numerical models developed on the basis of the present analytical solutions are better than those developed by Lynett and Liu （2002）. The results of numerical modeling agree well with the experimental data.
文摘AIM:To compare the outcomes of four adjuvants used for internal limiting membrane(ILM)peeling in macular hole surgery,including indocyanine green(ICG),brilliant blue G(BBG),triamcinolone(TA)and trypan blue(TB),through systematic review and random-effects Bayesian network Meta-analysis.METHODS:PubMed,Cochrane library databases and Web of Science were searched until August 2018 for clinical trials comparing the above four adjuvants.ORs for postoperative best corrected visual acuity(BCVA)improvement and primary macular hole closure rates were compared between the different adjuvants.RESULTS:Twenty-seven eligible articles were included.For postoperative BCVA improvement,results of BBGassisted peeling were significantly more favorable than those of ICG(WMD 0.08,95%credible interval 0.01-0.16)and TA ranked highest.No significant differences were found between any other two groups in postoperative BCVA improvement.For postoperative primary macular hole closure rates,BBG ranked highest.However,no significant differences were shown between any two groups.CONCLUSION:TA and BBG are the optimum adjuvants for achieving postoperative BCVA improvement macular hole surgery with adjuvant-assisted ILM peeling.Among all adjuvants,the use of BBG is associated with the highest postoperative macular hole closure rate.
基金This project is supported by National Natural Science Foundation of China(No.10342003).
文摘The dynamics differential equations are constructed, and the initial conditions are also given. Simulation shows the following conclusions： The water pressure in cylinder has great instantaneous pulsation and phase step when outlet valve or inlet valve opens, but is more gently in other time; The volume efficiency is influenced by the output pressure slightly, and decreases as the working rotational speed increases; When the inherent frequency of the valves is integer multiple of the working frequency, the volume efficiency of system will decrease evidently.
基金Project(61273132)supported by the National Natural Foundation of ChinaProject(20110010010)supported by Higher School Specialized Research Fund for the Doctoral Program,China
文摘A novel control scheme of active disturbance rejection internal model control(ADRIMC) is proposed to improve the anti-interference ability and robustness for the dead-time process. The active anti-interference concept is introduced into the internal model control(IMC) by analyzing the relationship between IMC and disturbance observer control(DOB). Further, a design process of disturbance filter is presented to realize the active anti-interference ability for ADRIMC scheme. The disturbance filter is used to estimate an equivalent disturbance consisting of both external disturbances and internal disturbances caused by model mismatches.Simulation results demonstrate that the proposed method possesses a good disturbance rejection performance, though losing some partial dynamic performance. In other words, the proposed method shows a tradeoff between the dynamic performance and the system robust.
文摘The characteristic and mechanism of parachlorophenol(4-CP) degradation in an internal electrolysis system were investigated. The degradation rate of 4-CP was higher in acid solution than that of in neutral or alkaline solution. Addition of activated carbon could make 4-CP easier be degraded by the surface contact catalysis. The dissolved oxygen in solution could take part in the electrode reaction and intensify the degradation of 4-CP. By the analysis of intermediates of degradation of 4-CP, it could be conferred that 4-CP was broken through the bond beside hydroxy firstly, then the bond beside chloride was broken and the chloride was dechlorinated simultaneously. Most intermediate products were glycerine, ethane diacid and acetic acid, while very few 1,4-butanedial and alcohols were found.
基金supported by the Scientific and Technical Research Council of Turkey (TUBITAK) under project No. 104M427
文摘In this study, the vibrations of multiple stepped beams with cubic nonlinearities are considered. A three-to-one internal resonance case is investigated for the system. A general approximate solution to the problem is found using the method of multiple scales （a perturbation technique）. The modulation equations of the amplitudes and the phases are derived for two modes. These equations are utilized to determine steady state solutions and their stabilities. It is assumed that the external forcing frequency is close to the lower frequency. For the numeric part of the study, the three-to-one ratio in natural frequencies is investigated. These values are observed to be between the first and second natural frequencies in the cases of the clamped-clamped and clamped-pinned supports, and between the second and third natural frequencies in the case of the pinned-pinned support. Finally, a numeric algorithm is used to solve the three-to-one internal resonance. The first mode is externally excited for the clamped-clamped and clamped-pinned supports, and the second mode is externally excited for the pinned-pinned support. Then, the amplitudes of the first and second modes are investigated when the first mode is externally excited. The amplitudes of the second and third modes are investigated when the second mode is externally excited. The force-response, damping-response, and .frequency- response curves are plotted for the internal resonance modes of vibrations. The stability analysis is carried out for these plots.
文摘Objective To assess the feasibility of internal suspension technique in retroperitoneal robot-assisted laparoscopic partial nephrectomy(rRAPN)with a new robotic platform called KangDuo Surgical Robot-01(KD-SR-01)system(Suzhou KangDuo Robot Co.,Ltd.,Suzhou,China)and discuss its surgical technique.Methods A 44-year-old male patient was admitted with a 2.5 cm tumor on dorsolateral upper pole of the left kidney.The R.E.N.A.L.nephrometry score of this patient was 4x.This patient underwent rRAPN with KD-SR-01.The perinephric fat between the tumor and Gerota's fascia was preserved,which was used for internal suspension traction during tumor resection.Postoperative follow-up data were collected.Results The surgery was successfully carried out with a duration of 127 min,in which the docking time was 6 min 25 s and console time was 60 min.The warm ischemia time was 19 min 53 s,and the estimated blood loss was 0 mL.The pathological histology showed a pathological tumor stage 1a clear cell renal cell carcinoma,with a negative surgical margin.The World Health Organization/International Society of Urological Pathology(WHO/ISUP)grade of this patient was Grade 2.No recurrence was observed during the 6-month follow-up.Conclusion Internal suspension in rRAPN is feasible and effective with use of the new robotic system KD-SR-01.
文摘The 1:2 internal resonance of coupled dynamic system with quadratic and cubic nonlinearities is studied. The normal forms of this system in 1 :2 internal resonance were derived by using the direct method of normal form. In the normal,forms, quadratic and cubic nonlinearities were remained. Based on a new convenient transformation technique, the 4-dimension bifurcation equations were reduced to 3-dimension. A bifurcation equation with one-dimension was obtained. Then the bifurcation behaviors of a universal unfolding were studied by using the singularity theory. The method of this paper can be applied to analyze the bifurcation behavior in strong internal resonance on 4-dimension center manifolds.
基金supported by the Key Project of the"Twelfth FiveYear Plan"for Medical Science and Technology Research of People’s Liberation Army(BWS12J006)the Scientific Key Project of Liaoning Province(2011225006)
文摘Background: Pelvic fracture combined with massive bleeding(PFCMB) is a complex issue in clinical practice. Currently, the use of angiography and embolization for the treatment of PFCMB obtains good results. The aim of this study is to observe the effects of early internal iliac artery embolization on the systemic inflammatory response syndrome(SIRS) in dogs with simulated-pelvic-fracture combined with massive bleeding.Methods: Twenty adult dogs were randomly divided into an embolization group(EG) and a control group(CG). For the two groups, heart rate, respiratory rate and body temperature and other physiological variables were measured, and IL-6, TNF-α and arterial blood gas levels were monitored. These variables were assayed every 30 min until death in the CG, while dogs in the EG underwent arterial angiography after 60 min of modeling. The internal iliac artery was embolized on the injured side.Results: The average time to SIRS in the CG was 3.56 h, occurring at a rate of 90%(9/10) within 24 h, with a mortality rate of 50%(5/10); the average time to SIRS for the EG was 5.33 h, occurring at a rate of 30%(3/10) within 24 h, with a mortality rate of 10%(1/10). When SIRS occurred in the EG, the mean plasma IL-6 level was 52.66±7.38pg/ml and the TNF-ps, tα level was 11.45±2.72ng/ml, showing a significant difference with those of the CG(P<0.05). In the two grouhe respiratory rate and leukocyte levels were higher at each monitored time after modeling than those before modeling; the mean arterial pressure, levels of hemoglobin and oxygen partial pressure were significantly lower at each time point after modeling than those before modeling except for the mean arterial pressure at 0h in EG; the platelet levels at 4 and 8h were higher than those before modeling; and the differences were statistically significant(P<0.05). In the EG, the mean arterial pressure, heart rate, respiratory rate and hemoglobin levels at 2, 4 and 8h were lower than those at 0h; the levels of leukocytes, platelets and carbon dioxide partial pressure at 4 and 8h after modeling were higher than those at 0h, and the differences were statistically significant(P<0.05, P<0.01); in the CG after modeling, the mean arterial pressure, levels of hemoglobin and carbon dioxide partial pressure at 2, 4 and 8h were lower than those at 0h; the levels of heart rate and leukocytes were higher than those before modeling; the respiratory rate and platelet levels at 4 and 8h were higher than those at 0h; and the differences were statistically significant(P<0.05). The levels of the mean arterial pressure and hemoglobin at 4 and 8h and the p H values at 8h after modeling in the EG were significantly higher than those in the CG, while the heart rate and respiratory rate at 4 and 8h were significantly lower than those in the CG. The p H values at 8h after modeling were significantly lower than those of the other monitored times in the CG(P<0.05, P<0.01). The two groups had elevated levels of alkaline phosphatase after injury induction.Conclusion: Through the use of an on-spot interventional treatment cabin, early internal iliac artery embolization can control bleeding associated with pelvic fractures, delay the occurrence of SIRS, and improve the success rate of the treatment of pelvic fracture combined with bleeding.
