Effects of local thickness defects on the buckling of micro-beam

A buckling model of Timoshenko micro-beam with local thickness defects is established based on a modified gradient elasticity.By introducing the local thickness defects function of the micro-beam,the variable coefficient differential equations of the buckling problem are obtained with the variational principle.Combining the eigensolution series of the complete micro-beam with the Galerkin method,we obtain the critical load and buckling modes of the micro-beam with defects.The results show that the depth and location of the defect are the main factors affecting the critical load,and the combined effect of boundary conditions and defects can significantly change the buckling mode of the micro-beam.The effect of defect location on buckling is related to the axial gradient of the rotation angle,and defects should be avoided at the maximum axial gradient of the rotation angle.The model and method are also applicable to the static deformation and vibration of the micro-beam.

Conjunctival flap with auricular cartilage grafting: a modified Hughes procedure for large full thickness upper and lower eyelid defect reconstruction

AIM:To investigate the suitability of a modified Hughes procedure,which consists of conjunctival flap with auricular cartilage grafting in reconstructing large full thickness upper and lower eyelid defect.METHODS:Patients with full thickness eyelid carcinoma involving more than 50%margin length who underwent surgical resection were retrospectively reviewed in the study.The defects were reconstructed using conjunctival flap with auricular cartilage grafting,covered with myocutaneous flap above.Followed-up time ranged from 12 to 24 mo.Outcomes were classified as“good”,“fair”,and“poor”by evaluating the margin appearance,eyelid appearance,and complications.RESULTS:A total of 42 patients were enrolled in the study(26 males,16 females,mean age,68.6±7.7 y,range:53 to 82 y).The mean defect widths measured 23.2±2.9 mm(range,17 to 28 mm).The mean posterior lamellar defect height was 5.5±1.3 mm(4 to 8 mm).Thirty-seven patients had a“good”outcome(88.1%),5 patients had a“fair”outcome(11.9%),and no one had a“poor”outcome.CONCLUSION:Conjunctival flap with auricular cartilage grafting and myocutaneous flap grafting is an effective procedure in reconstructing large full thickness upper and lower eyelid defect.It can not only achieve satisfied reconstruction,but also preserve intact tarsal plate of the opposite eyelid,avoiding retraction or entropion.