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Cylindrical shells, very commonly used in aerospace applications, are susceptible to buckling when subjected to static and dynamic or transient loads. Bucking load enhancement with minimum weight addition is an important requirement in space structures. Buckling control of space structures using piezoelectric actuators is an emerging area of research. The earlier work on enhancement of buckling load on columns reported a 3.8 times enhancement theoretically and 123% experimentally [1–2]. The enhancement was (25%) when buckling control was implemented on plates [3] using PZT actuators. Buckling control of cylindrical shells is challenging because of the uncertainties in the location of buckling and the coupling between bending and membrane action. Earlier attempt to improve the buckling load carrying capacity of the cylindrical shell did not result in a considerable increase in the buckling load [4]. This is because the buckling modes of cylindrical shell are very close to each other when compared to structures like column and plate. An optimized actuator location is hence necessary to improve the load carrying capacity of the cylindrical shells. Unlike vibration control problems where the actuators locations are optimized to minimize the structural Volume Displacement (SVD) or to maximize the energy dissipation, buckling control is aimed at controlling the critical modes of buckling and hence improving the load carrying capacity of the shells [5]. Numerical analyses are carried out, comparing different configurations used in buckling control of thin shells. Experiments are performed to support the numerical analysis as the behavior of cylindrical shells under axial compression is highly sensitive to geometric imperfections. Load – Axial shortening graphs are used to compare the performance of cylindrical shell for the various actuator configurations.

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Background: Thyroid cancers are on the rise all over the world. Studies have shown a tripling incidence of thyroid cancer in the United States in the past 35 years. Similar studies from Korea have also shown similar trends of 15 times increase in incidence. This study aims at assessing the recent trends in clinical presentation of thyroid malignancy and the efficacy of ultrasound targeted fine needle aspiration cytology (FNAC) in the diagnosis of thyroid malignancy.Methods: A cross sectional study was conducted involving 275 patients with thyroid disorders treated in the department of General Surgery at Dr. Somervell Memorial CSI Medical College, Trivandrum, India. Chi-square test was done for statistical test of significance and odds ratio for strength of association.Results: In this study group, 89% of the patients presented with swelling in front of the neck as chief complaint both in benign and malignancy. Swelling in front of the neck is the predominant symptom in thyroid malignancy. 52% of patients presented with the described symptoms of more than 6 months duration. The specificity of USG guided FNAC is 90% in diagnosing malignancy in goitre in this study group.Conclusions: The commonest symptom of thyroid malignancy was a painless swelling in the front of the neck. Most common thyroid pathology presenting as thyroid swelling was multinodular goitre. Nearly half of the patients presenting with symptoms more than 6 months had thyroid malignancy. FNAC under ultrasound guidance is an inexpensive accurate and practical investigation for evaluation of thyroid carcinomas.