Dual-mode and stacked concentric ring patch antenna-arrays

A dual mode concentric ring patch antenna is discussed which is suitable for vehicles operating with mobile satellite communication systems. It is operated at two modes, the TM21 and TM41 modes, which possess conical radiated beams. Switching between these modes provides omnidirectional azimuth coverage with elevation beam steering

Performance of microstrip loop antenna arrays

A number of mobile satellite systems are proposed for service in the late 1990s. A study of concentric annular ring arrays is reported in which the rings are excited in various modes, resulting in toroidal beams pointing at different elevation angles. Switching between modes can provide a degree of beam steering. The gain of a single patch was 5-7 dB typically. However, this was found to be sensitive to the size of the ground plane on which it was mounted and this variation in gain has been investigated. A theoretical study is presented of a 4 element stacked array of concentric ring elements in which a degree of beam steering is attained by switching mode

Three-Dimensional Force Characterizations in Maxillary Molar Distalization: A Finite Element Study

Class II malocclusion is a very common condition in orthodontic patients. The reaction force and moment on the teeth induced by a maxillary segmental distalizer (MSD) are essential for understanding tooth movement, tipping, and rotation. This work quantified the three-dimensional (3D) reaction force and moment on canine and molar teeth induced by three different MSDs: the JVBarre (JVB), Carriere Motion 3D (CM3D), and CM3D Clear. A patient-specific mandibular model was reconstructed based on cone-beam computed tomography (CBCT) images. Each of the three MSDs was implanted using finite element analysis (FEA). The reaction force and moment were obtained. The results show that the JVB induced less extrusion force (15% less), tipping (90% less), and rotational moment (70% less) on the canine, compared with the other two CM3Ds. However, the JVB induced a relatively larger extrusion force, tipping, and rotational moment on the molar due to the hook location changing from the end to the middle of the bar. These observations were consistent with the 3D stress distribution of the MSDs. The mechanical understanding from this work may shed light on the optimal design of MSDs