امیرکبیر
سال:1384 | دوره:16 | شماره:ب-63 |تعداد مقالات:8

A new computational procedure based on two Spring-Mass-Damper-Dashpot (SMDD) and Spring-Mass- Damper (SMD) models representing contact behavior between the impactor and the plate are presented to study the low velocity impact phenomenon of sandwich plates comprising of a transversely flexible core and laminated composite face-sheets. The interaction between the impactor and the plate is modeled with the help of a new system having three-degree of-freedom, consisting of spring-mass-damper-dashpot or spring mass- damper. The plate may be subjected to initial in-plane biaxial normal and shear stresses along the edges of the plate. Impact is assumed to occur normally over the top or the bottom face-sheets, at arbitrary location. The boundary conditions of the top and the bottom face-sheets are independent. The effects of transverse flexibility of the core and structural damping of the plate are considered in the proposed models. Based on these models, the analytic functions describing the contact force, the transverse deflections of the impactor and the plate are derived. The effects of some parameters such as plate aspect ratio, boundary conditions, initial in-plane biaxial stresses, and impact location are examined in details.

A new control strategy for attitude maneuver of an elastic spacecraft is presented. Adaptive sliding mode control scheme with a synthesized Hybrid Sliding Surface (HSS) is used to overcome the difficulties arising from measurement of flexible dynamics coordinates. The excitation of flexible modes that frequently happens in the conventional sliding mode is minimized by using the synthesized sliding surface. The model of the spacecraft considered as rigid central hub and two flexible appendages. Collocated actuators and sensors are placed on the rigid central hub. Stability proof of the overall closed-loop system is given via Lyapunov analysis. Asymptotical tracking control of the multi-axis attitude motion and suppression of the elastic deformations are accomplished. Numerical simulations show the effectiveness of the proposed control scheme.

Designing of the road map for competitive strategic planning based on changing situations on Iranian day by- day planned companies is the main objective of this study. HCMS 4 model's design presenting a complementary to validated traditional models. Observing new factors, which have effects on preparation of strategic plans and their sequential order in HCMS' model is the platform of presented road map in this paper.Study review shows preparation of strategic planning using SWOTS technique for internal analysis to find strengths and weaknesses requires more factors than introduced in traditional models. Factors needed such as, Critical Success Factors, Key Performance Indicators, Organizational Excellence measures, Corporate Life Cycles' Diagnosis, Balance Score Cards measures, World Class Manufacturing measures and Core Competency findings. On the other hand, Porter Analysis, Industry attractive analysis, Stakeholders' fringe benefits for observing organizational opportunities and threats require additional subjects than introduced in existing matrix's standard elements. To achieve organizational master and main strategies, addition to complex combination of strengths, weaknesses, opportunities and threats need more actions such as, Life Cycle analysis and ADL6 matrix outcomes. It is inevitable, for selection and ranking of introduced strategies, forecast of external and internal factors' trends and evaluating strategies with trends and Evaluation Matrix take place. Description of mentioned requirements, the outcomes and their order is developing and presenting as the HCMS model's road map, in this paper.