An Improved Parameters Extraction Method for Dumbbell-Shaped Defected Ground Structure

The paper presents an improved equivalent circuit parameters extraction method for the dumbbell-shaped defected ground structure (DGS). The new extraction parameters equations are obtained in closed-form expressions, which contain S11 and S21. The DGS unit with center frequency of 5 GHz is designed and fabricated on a TLX substrate with thickness of 1 mm and dielectric constant of 2.55. The circuit simulated results are in good agreement with the measured results. This parameters extraction method can be widely used for the design and analysis of DGS .

Spinal dumbbell-shaped epidural cavernous hemangioma (CM):report of nine surgical cases and literature review

Background:Spinal dumbbell-shaped epidural cavernous malformation (CM) is a rare, hypervascular entity frequently misdiagnosed for other lesions, leading to unexpected intraoperative bleeding and suboptimal resection. Our study aims to elucidate the demographics, management strategy, and outcome of this vascular disease.Methods:Retrospective review of patients seen in Beijing Tiantan Hospital with symptomatic dumbbell-shaped epidural CM from 2008 to 2013. All lesions were pathologically confirmed after resection. The clinical manifestations, radiographic features, and treatment modalities of these cases were analyzed.Results:We included 9 consecutive patients. Average age was 58 ± 12 years (range:34-79 years), with 66.7％male. Locations of the CMs were:thoracic (n=7, 77.8％), cervical (n=1, 11.1％), and cervicothoracic junction (n=1, 11.1％). Only one case presented with acute manifestations while others experienced chronic progressive spinal cord symptoms. The initial clinical diagnoses were:schwannoma (n=6, 66.7％), cavernous hemangioma (CM) (n=1, 11. 1％), meningioma (n=1, 11.1％), and angioma (n=1, 11.1％). Total resection was achieved in six patients (66.7％), and partial resection in the other three patients (33.3％). Average intraoperative blood loss was 400 ± 300 ml (range:100-1000 ml). During an average follow-up of 71 ± 21 months (range:29-94 months), excellent outcome was achieved in seven cases (77.8％), one partially improved (11.1％), and one deteriorated (11.1％). No patients experienced recurrence of symptoms.Conclusions:Spinal dumbbell-shaped epidural CM is a benign vascular malformation that should be differentiated from other dumbbell-shaped lesions. Accurate preoperative diagnose is challenging as no specific radiographic marker has been established. Total surgical resection should be recommended.

Influences of the Shape of Magnetic Material on the Magnetoelectric Properties of the PZT/Metglas Composite

In this paper,the influences of the shape of magnetic material on the magnetoelectric（ME）properties of PZT/Metglas magnetoelectric（ME）composites have been investigated.The results indicate that,with the decrease of the waist length（L w）of the dumbbell-shaped Metglas,the magnetic flux density in the center region and ME coefficients（αME）of the composites increase,while the optimal bias magnetic field H dc decreases on the contrary.In an AC magnetic field of 1 k Hz,the maximumαME（αMax）of the composite with L w=20 mm exhibits 1.3 times larger than that of the one with L w=50 mm,and the optimal H dc deceases by 15%.At the resonant frequencies of each composites,αMax is enhanced by1.3 times as L w decreases from 50 to 20 mm.The simulation made by Comsol Multiphysics and the theoretical analysis based on an equivalent magnetic circuit confirm the experimental results.