检索结果-南通市图书馆

A novel model-based multivariable framework for aircraft gas turbine engine limit protection control

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2021年第12期34卷 57-72页

作者： Shuwei PANG Soheil jafari Theoklis NIKOLAIDIS Qiuhong LI Jiangsu Province Key Laboratory of Aerospace Power System Nanjing University of Aeronautics and AstronauticsNanjing 210016China Propulsion Engineering Center School of AerospaceTransport and ManufacturingCranfield UniversityBedford MK43 OALUK

Control technologies are innovated to satisfy increasingly complicated control demands of gas turbine *** terms of limit protection control,a novel model-based multivariable limit protection control method,which is achieved by adaptive command reconstruction and multiplecontrol loop selection and switch logic,is proposed in this paper to address the problem of balancing smaller thrust loss and safe operations by comparing with widely-used Min-Max *** different combination modes of control loops,which represent the online control loop of last time instant and that of current time instant,is *** command reconstructions are designed for these modes,which is based on static gain conversion of amplitude beyond limits by using an onboard *** double-prediction based control loop selection and switch logic is developed to choose a control loop appropriately by comparing converted amplitude beyond limits regardless of one or more parameters tending to exceed *** proposed method is implemented in a twin-spool turbofan engine to achieve limit protection with direct thrust control,and the loss of thrust is improved by about 30% in comparison with the loss of thrust caused by Min-Max logic when limit protection control is activated,which demonstrates the effectiveness of the proposed method.

关键词： Amplitude conversion Command reconstruction Gas turbine engine Limit protection control Multivariable control Onboard prediction

Global stability and optim al control of a two-patch tuberculosis epidemic model using fractional-order derivatives

在线全文

学校读者我要写书评

暂无评论

International Journal of Biomathematics 2020年第3期13卷 1-27页

作者： Hossein Kheiri Mohsen jafari Faculty of Mathematical Sciences University of Tabriz TabrizIran

In this paper,we propose a fractional-order and two-patch model of tuberculosis(TB)epidemic,in which susceptible,slow latent,fast latent and infectious individuals can travel freely between the patches,but not under treatment infected individuals,due to medical *** obtain the basic reproduction number Ro for the model and extend the classical LaSalle's invariance principle for fractional differential *** show that if R0l,we obtain sufficient conditions under which the endernic equilibrium is unique and globally asymptotically *** extend the model by inclusion the time-dependent controls(effective treatment controls in both patches and controls of screening on travel of infectious individuals between patches),and formulate a fractional optimal control problem to reduce the spread of the *** numerical results show that the use of all controls has the most impact on disease control,and decreases the size of all infected compartments,but increases the size of susceptible compartment in both ***,also,investigate the impact of the fractional derivative order a on the values of the controls(0.7≤α≤1).The results show that the maximum levels of effective treatment controls in both patches increase when a is reduced from l,while the maximum level of the travel screening control of infectious individuals from patch 2 to patch 1 increases when o limits to 1.

关键词： Patch models fractional optimal control global stability tuberculosis epidemic

Optimal control of a fractional-order model for the HIV/AIDS epidemic

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Biomathematics 2018年第7期11卷 59-81页

作者： Hossein Kheiri Mohsen jafari Faculty of Mathematical Sciences University of Tabriz TabrizIran

In this paper,we present a general formulation for a fractional optimal control problem (FOCP),in which the state and co-state equations are given in terms of the left fractional *** develop the forward-backward sweep method (FBSM)using the Adamstype predictor-corrector method to solve the *** present a fractional model for transmission dynamics of human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS)with treatment and incorporate three control efforts (effective use of condoms,ART treatment and behavioral change control)into the model aimed at controlling the spread of HIV/AIDS *** necessary conditions for fractional optimal control of the disease are derived and *** numerical results show that implementing all the control efforts increases the life time and the quality of life those living with HIV and decreases significantly the number of HIV-infected and AIDS ***,the maximum levels of the controls and the value of objective functional decrease when the derivative order a limits to 1(0.7≤a <1).In addition,the effect of the fractional derivative order a (0.7≤a <1)on the spread of HIV/AIDS epidemic and the treatment of HIV-infected population is *** results show that the derivative order a can play the role of using ART treatment in the model.

关键词： Fractional optimal control diseases modeling numerical simulation HIV/AIDS dynamics

Reduced-dimensional MPC controller for direct thrust control

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2022年第4期35卷 66-81页

With the development of the aircraft gas turbine engine, a control system should be able to achieve effective thrust control to gain better operability. The main contribution of this paper is to develop a novel direct thrust control approach based on an improved model predictive control method through a strategy that reduces the dimension of control sequence. It can not only achieve normal direct thrust control tasks but also maximize the thrust level within the safe operation boundaries. Only the action of switching the objective functions is required to achieve the switch of these two thrust control modes while there is no modification to the control structure. Besides,a shorter control sequence is defined for multivariable control by updating only one control variable at every simulation time instant. Therefore, the time requirement for the solving process of the optimal control sequence is reduced. The proposed controller is implemented to a twin-spool *** are conducted in the wide flight envelope, and results show that the average timeconsumption can be reduced up to 65% in comparison with the standard model predictive control,and the thrust can be increased significantly when maximum thrust mode is implemented by using engine limit margins.

关键词： Computation time Direct thrust control Gas turbine engine Model predictive control Thrust optimization

Investigation of Pirnia’s orientation theory (Roon) in Yazd Qajar houses

在线全文

学校读者我要写书评

暂无评论

Frontiers of Architectural Research 2023年第5期12卷 906-922页

作者： Hatef jafari Sharami Department of Architecture and Urbanism University of EyvanekeyEyvanekeySemnanIran

This paper carefully explains Pirnia’s theory regarding the orientation of traditional Iranian cities and buildings(Roon)and investigates the factors involved in this historic architectural *** this purpose,40 traditional Yazd Qajar houses were under *** of which are in the Rasteh Roon and close to the southwest direction,and only five contradict the direction that Pirnia had *** the primeval data indicated the theory is strengthening,the investigation followed the fundamental factors behind this *** the perspective of analysis and discussion on involved factors(climate,topography,aqueducts,urban arteries,politics,trade routes,privacy,noise,view,and religion),it turns out that the direction of the wind and sun had negligible impacts on this orientation,and architects of the Qajar era in Yazd old city did not care about these climate *** seems religious factors were more ***,despite being approvingly referenced in many scientific studies,Pirnia’s orientation theory(Roon)dthe efforts of past Iranian architects to orient buildings in a specific direction due to their unique knowledge of region and climate factorsdbecomes not solid.

关键词： Building orientation Roon theory Pirnia Qajar Yazd houses

Integration of light and hormone signaling pathways in the regulation of plant shade avoidance syndrome

在线全文

学校读者我要写书评

暂无评论

aBIOTECH 2021年第2期2卷 131-145页

作者： Yang Liu Feresheeh jafari Haiyang Wang Biotechnology Research Institute Chinese Academy of Agricultural SciencesBeijing 100081China State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources South China Agricultural UniversityGuangzhou 510642China Guangdong Laboratory for Lingnan Modern Agriculture Guangzhou 510642China

As sessile organisms,plants are unable to move or escape from their neighboring competitors under high-density planting ***,they have evolved the ability to sense changes in light quantity and quality(such as a reduction in photoactive radiation and drop in red/far-red light ratios)and evoke a suite of adaptative responses(such as stem elongation,reduced branching,hyponastic leaf orientation,early flowering and accelerated senescence)collectively termed shade avoidance syndrome(SAS).Over the past few decades,much progress has been made in identifying the various photoreceptor systems and light signaling components implicated in regulating SAS,and in elucidating the underlying molecular mechanisms,based on extensive molecular genetic studies with the model dicotyledonous plant Arabidopsis ***,an emerging synthesis of the field is that light signaling integrates with the signaling pathways of various phytohormones to coordinately regulate different aspects of *** this review,we present a brief summary of the various cross-talks between light and hormone signaling in regulating *** also present a perspective of manipulating SAS to tailor crop architecture for breeding high-density tolerant crop cultivars.

关键词： Arabidopsis Shade avoidance syndrome(SAS) Light Hormones Signaling

Utilisation of turboelectric distribution propulsion in commercial aviation:A review on NASA's TeDP concept

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2021年第11期34卷 48-65页

作者： Mosab ALRASHED Theoklis NIKOLAIDIS Pericles PILIDIS Soheil jafari Turboelectric Engineering Group Cranfield CampusCranfield UniversityBedfordshire MK43 OALUK

Emissions produced by the aviation industry are currently a severe environmental threat;therefore,aviation agencies and governments have set emission targets and formulated plans to restrict emissions within the next *** aircraft technology is being considered to meet these *** importance of these technologies lies in their advancements in terms of aircraft life cycles and environmental *** to these advancements,hybrid electric systems with more than one power source have become promising for the aviation industry,considering that the growth of air traffic is projected to double in the next *** technologies have given future hybrid fans and motor-fan engines potential as alternative power ***,Turboelectric Distributed Propulsion(TeDP)is discussed in terms of power distribution and power *** fundamentals of turbofan and turboshaft engines are presented along with their electricitygeneration *** is discussed from a design viewpoint,with a detailed discussion of different types of hybrid electric and turboelectric *** of proposed TeDP aircraft models and numerical modelling tools used to simulate the performance of TeDP models are ***,innovative turboelectric systems in which electric power savers and mechanical gear changers have been discarded for weight optimisation are presented along with other prospective models,engines,approaches,and *** findings of this review indicate the knowledge gaps in the field of numerical modelling for NASA’s TeDP and its capability to increase the efficiency by up to 24%with a 50%reduction in emissions relative to those of conventional gas turbines.

关键词： Futuristic propulsion systems Hybrid aircraft engines Numerical modelling and simulation Turboelectric distributed propulsion Turboelectric power

Engineering interfacial band hole extraction on chemical-vapor-deposited MoS 2/CdS core-shell heterojunction photoanode:The junction thickness effects on photoelectrochemical performance

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2023年第36期167卷 107-118页

作者： Zhiyuan Peng Yilu Su Maziar jafari Mohamed Siaj Department of Chemistry and Biochemistry Universitédu QuébecàMontréalMontréalQC H3C 3P8Canada

Heterojunction fabrication is a promising strategy that can greatly boost the charge carrier separation and improve the solar-to-hydrogen conversion efficiency of photoelectrochemical(PEC)***,such technology still suffers from limited contact *** this study,the chemical vapor deposition(CVD)technique was for the first time used to construct the CdS/MoS_(2)heterojunction photoanode with a unique core-shell nanoarchitecture,in which a continuous crystalline MoS_(2)nanosheet layer was grown directly on one-dimensional(1D)oriented CdS nanorods(NRs)in a plane-to-plane stacking *** optimization of junction thickness with adjustable MoS_(2)loading from mono to a few layers was achieved by experimental parameters *** characterizations show that the MoS_(2)shell plays a dual role as an optical absorption booster for more photo-exciton generation and a surface passivator of trap ***,the formed heterojunction helps regulate the unidirectional charge migration for a significantly suppressed electron-hole recombination process,which synergistically contributes to higher quantum yield and *** a result,the optimized CdS/MoS_(2)heterojunction photoanode with 3-layered MoS_(2)wrapping exhibits the highest photocurrent density and photoconversion efficiency,over a two-fold increase,compared to those of pristine CdS and the previously reported CdS/MoS_(2)***,due to the rapid hole extraction from CdS and transferred surface oxidation sites,the present CdS/MoS_(2)heterostructure demonstrates better corrosion resistance and higher *** present work is expected to provide a versatile platform for exploiting the CVD technique to develop other MoS_(2)-based heterojunction photoelectrodes with extensive PEC applications.

关键词： Photoelectrochemical Hydrogen evolution Heterojunction fabrication Photoanode Cadmium sulfide Molybdenum sulfide

Kaempferol attenuates cognitive deficit via regulating oxidative stress and neuroinflammation in an ovariectomized rat model of sporadic dementia

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Neural Regeneration Research 2018年第10期13卷 1827-1832页

作者： Somayeh Kouhestani Adele jafari Parvin Babaei Cellular and Molecular Research Center Faculty of MedicineGuilan University of Medical Sciences Department of Physiology Faculty of MedicineGuilan University of Medical Sciences Neuroscience Research Center Guilan University of Medical Sciences

Alzheimer＇s disease（AD） is associated with oxidative stress, and ultimately results in cognitive deficit. Despite existing literature on the pathophysiology of AD, there is currently no cure for AD. The present study investigated the effects of kaempferol（Kmp） isolated from the extract of Mespilus germanica L.（medlar） leaves on cognitive impairment, hippocampal antioxidants, apoptosis, lipid peroxidation and neuro-inflammation markers in ovariectomized（OVX） rat models of sporadic AD. Kaempferol, as the main flavonoid of medlar extract has been previously known for anti-oxidative, anti-inflammatory and anti-neurotoxic effects. Thirty-two female Wistar rats were ovariectomized, and randomly divided into four groups： sham, OVX ＋ saline, OVX ＋ streptozotocin（STZ）＋ saline, OVX ＋ STZ ＋ Kmp. Animals received intracerebroventricular injection of STZ（3 mg/kg, twice with one day interval） to establish models of sporadic AD. Intraperitoneal injection of Kmp（10 mg/kg） for 21 days was performed in the OVX ＋ STZ ＋ Kmp group. Spatial learning and memory of rats were evaluated using a Morris water maze. Finally, brain homogenates were used for biochemical analysis by enzyme-linked immunosorbent assay. The results showed a significant improvement in spatial learning and memory as evidenced by shortened escape latency and searching distance in Morris water maze in the OVX ＋ STZ ＋ Kmp group compared with the OVX ＋ STZ group. Kmp also exhibited significant elevations in brain levels of antioxidant enzymes of superoxide dismutase and glutathione, while reduction in tumor necrosis factor-α and malondialdehyde. Our results demonstrate that Kmp is capable of alleviating STZ-induced memory impairment in OVX rats, probably by elevating endogenous hippocampal antioxidants of superoxide dismutase and glutathione, and reducing neuroinflammation. This study suggests that Kmp may be a potential neuroprotective agent against cognitive deficit in AD.

关键词： Alzheimer's disease oxidative stress neuroinflammation Mespilus germanica L. Kaempferol neural regeneration