15,331 research outputs found
Vibration behaviors of thermally postbuckled anisotropic plates using first-order shear deformable plate theory
No full textVibration behaviors of thermally postbuckled anisotropic plates are investigated. The finite element method is used for the analysis of thermal postbuckling and natural vibration of thermally postbuckled plates. The finite element model is based on the first-order shear deformable plate theory (FSDT) and von Karman strain-displacement relation to account for large deflection. Critical buckling temperature and the corresponding mode shape are determined from Euler buckling problem. In order to solve the thermal-postbuckling problem, the initial nonlinear stiffness is determined from estimated deflection of scaled buckling mode shape. The converged deflection at any temperature change is obtained using the Newton-Raphson method. The vibration analysis of thermally postbuckled plates are performed using the tangent stiffness obtained from the converged deflection. The effect of fiber orientation angle and aspect ratio on postbuckling and vibration behaviors are studied for simply supported laminated plates subject to steady-state uniform temperature increase. (C) 1997 Elsevier Science Ltd
VIBRATION ANALYSIS OF ANISOTROPIC PLATES WITH ECCENTRIC STIFFENERS
No full textThe analysis of vibration characteristics of anisotropic plates with eccentric stiffeners has been performed using the finite element method based on the shear deformable plate theory. The stiffeners are modeled as a beam element based on Timoshenko beam theory. The present analysis presents the effects of fiber orientation, dimension and location of the stiffener on the vibration characteristics of anisotropic stiffened plates. The stiffened plates are composed of graphite-epoxy(AS1/3501-6) composite laminate with a symmetric stacking sequence. The present finite element model uses nine-node quadrilateral elements for the skin plate and three-node quadratic elements for the stiffener. The solution of the eigenvalue problems has been obtained by the subspace iteration method. The results obtained by the present finite element model are compared with previous results for the stiffened isotropic plates. Also, the result of the present beam model for the stiffener made of composite material is compared with that of the shell model. This result shows that the present model for the stiffened plate gives quite accurate results. The size, fibre orientation angle and location of the stiffener affect the natural frequencies and mode shapes of the stiffened anisotropic plate
Vibration analysis of stiffened laminated plates including thermally postbuckled deflection effect
No full textVibration characteristics of stiffened laminated plates are investigated considering postbuckled deflection effect due to thermal load. The finite element method is used for the analysis of thermal postbuckling and natural vibration of stiffened plates in the posebuckling range. The finite element model is based on the first order shear deformable plate theory (FSDT) for a skin panel and Timoshenko beam theory for stiffeners. iron Karman strain-displacement relation is used to account for a large deflection. Critical buckling temperature and the corresponding mode shape are determined from Euler buckling problem. In order to solve the thermal-postbuckling problem, the initial nonlinear stiffness is determined from an estimated deflection of scaled buckling mode shape. The converged deflection at any temperature change is obtained using the Newton-Raphson method. The vibration analyses of stiffened laminated plates in the postbuckling range are performed using the tangent stiffness obtained from the converged deflection. The effects of the stiffener size, the number of stiffeners, and lamination scheme on vibration characteristics are studied for stiffened laminated plates subject to steady-state uniform temperature increase
Supersonic flutter analysis of stiffened laminated plates subject to thermal load
No full textFlutter analysis of stiffened laminated plates has been performed. The purpose of this study is to analyze the flutter characteristics of stiffened plates subject to thermal load. The first order shear deformable plate and Timoshenko beam theories are used for the finite element modelling of a skin panel and stiffeners respectively. The von Karman non-linear strain-displacement relation is used to account for large deflections. First order piston theory is used for modelling aerodynamic loads. The Newton-Raphson iteration method and complex eigenvalue solver with the LUM/NTF approximation method are used to obtain the postbuckled deflection and flutter information respectively. The Guyan reduction method and mode tracing procedure are employed for an efficient analysis. The effects of various parameters, such as the stiffening scheme, lamination angle, boundary conditions, and temperature gradient on flutter characteristics are investigated through some numerical examples. From these examples, it can be shown that the selection of a proper stiffening scheme results in great improvements of flutter characteristics of laminated panels without introducing considerable weight penalty. (C) 1999 Academic Press
THROUGHPUT-DELAY AND STABILITY ANALYSIS OF AN ASYNCHRONOUS SPREAD SPECTRUM PACKET RADIO NETWORK
No full textA continuous-time Markov chain model for an asynchronous spread spectrum packet radio network is presented. The network consists of N fully connected nodes and the radios in all nodes are identical. Packets arrive at each node and are retransmitted when lost, both according to Poisson processes with different rates, and packet lengths are exponential in distribution. A simple threshold approximation is used to account for the multiuser interference, and the preamble collision probability at receiving radios to account for the capture effect. The approximate analysis gives results which are very close to those obtained by simulations in most cases. The network stability conditions are discussed and the bistable behavior of the network is demonstrated. Results are given which show the effects on throughput and packet delay performance of the network according to the variations of the network size, the packet retransmission rate, the preamble collision probability at receiving radios, and the threshold value of the radio channel capacity
Controlled Decomposition Strategy for Complex Spatial Objects
No full textThis work was supported by the National Geographic Information Systems Technology
Development of the Ministry of Science and Technology of Korea
Intrusion of a DNA repair protein in the RNome world: is this the beginning of a new era?
No full textClinical Handover in Context: Risks and Protections Across a Hospital Patient’s Journey
No full textOne weekday afternoon an 18-year-old patient, we’ll call her Belinda Page,1 arrives at the emergency department of a busy tertiary teaching hospital, complaining of shortness of breath and chest pain due to a flare-up of her asthma. During the six hours Belinda spends in the emergency department she develops additional symptoms – weakness and numbness, particularly down her left side. She undergoes an emergency MRI, x-rays and other tests but the emergency department night registrar, Dr Ken Lee – a relatively junior non-English speaking background doctor – cannot reach a diagnosis. Under pressure to move patients out of the emergency department as quickly as possible, during the night he calls the senior neurology consultant, Dr Richard Lancer, who declines to admit Belinda before reviewing her. Dr Lee then calls the Ward M consultant, Dr Allenanda, who reluctantly agrees to admit Belinda to a general medical assessment ward, until the neurology staff can review her the next day. Over the next day we observed and recorded as many of the interactions with and about Belinda as we could, including consultations and examinations, formal and informal discussions about her case and nursing and medical handovers. The first occurred at 8 am the next morning when, after working a 12-hour shift, Dr Lee fronted up to a large auditorium to give the whole-of-hospital medical handover of all the patients he had admitted overnight. He sat on a solitary chair placed front and center of the auditorium, almost as if he were to be interrogated. In the tiered rows of seats facing him sat those members of the hospital’s day shift medical staff who had the time and motivation to attend (attendance is not compulsory). On this morning, about 25 doctors were present, ranging from interns to senior consultants. They included the two female registrars from Ward M (Dr Pantani and Dr Lingren) and a male cardiology consultant (Dr Davidson). The neurology consultant Dr Lancer arrived about five minutes into this handover. While Dr Lee delivered his handover, referring to a sheet of handwritten notes, another doctor stood at the computer console, front right of the auditorium, and projected the patient’s x-ray, test results and scans on the front screen. Below we reproduce a transcript of this five-minute handover
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