Incidence And Risk Factor Analysis For Swelling After Apical Microsurgery

The aim of this prospective observational cohort study is to evaluate developing periapical swelling after apical microsurgery and determine potential risk factors. Ninety-eight apical microsurgery patients were selected for this study. Before surgery, bone shadow volume and density of pathological tissue were measured by CBCT. The other variables (age, gender, operative teeth number, fistula, preoperative swelling, drug use and pre-surgery root canal treatments) were assessed during examination. Swelling degree was confirmed by questionnaires for patients on the 1st, 7th, 14th, and 21st days respectively after surgery. Statistical analyses were performed to identify predictors for swelling. Majority of patients reported moderate (45.9%) or severe (34.7%) swelling on day 1, and moderate (44.9%) or mild (45.9%) on day 7. 99% patients had no or mild swelling on day 14. The average swelling level peaked on day 1 postoperatively and gradually decreased. Of statistical significance, age, bone shadow volume and density of pathological tissue acted as predictors of swelling(P<0.05). However, there was no significant difference in gender, tooth number, fistula, preoperative swelling, drug use, or pre-surgery root canal treatments (P > 0.05). We conclude that younger patients with larger shadow volume and density were significantly more likely to develop swelling after apical microsurgery.

Mitigating the effects of boom occlusion on automated aerial refueling through shadow volumes

In-flight refueling of unmanned aerial vehicles (UAVs) is critical to the United States Air Force (USAF). However, the large communication latency between a ground-based operator and his/her remote UAV makes docking with a refueling tanker unsafe. This latency may be mitigated by leveraging a tanker-centric stereo vision system. The vision system observes and computes an approaching receiver’s relative position and orientation offering a low-latency, high frequency docking solution. Unfortunately, the boom – an articulated refueling arm responsible for physically pumping fuel into the receiver – occludes large portions of the receiver especially as the receiver approaches and docks with the tanker. The vision system must be able to compensate for the boom’s occlusion of the receiver aircraft. We present a novel algorithm for mitigating the negative effects of boom occlusion in stereo-based aerial environments. Our algorithm dynamically compensates for occluded receiver geometry by transforming the occluded areas into shadow volumes. These shadow volumes are then used to cull hidden geometry that is traditionally consumed, in error, by the vision processing and point registration pipeline. Our algorithm improves computer-vision pose estimates by 44% over a naïve approach without shadow volume culling.

Hybrid Silhouette Detection for Real-Time Shadow Volume

In shadow volume, the most expensive computation is silhouette detection. In this paper, the triangular algorithm (TA) and visible-non-visible (VnV) algorithm that are famous algorithms to detect the outline of occluder are renewed. In this paper, we proposed a hybrid algorithm based on TA and VnV, namely Hybrid Silhouette Detection (HSD) algorithm. HSD is an improved algorithm that can recognize silhouette for generating real-time shadow volume. Our algorithm involves detecting silhouette and decreases the cost of implementation for shadow volume rendering. The last shadow volume algorithm using stencil buffer is rewritten and an algorithm for shadow volume using HSD with respect of culling invisible parts of scene is proposed. An accurate mathematical comparison between TA, VnV and HSD algorithms is undertaken. The obtained results confirm superiority of our proposed algorithm in terms of processing and rendering time. Our algorithm can be used in virtual environment to increase the frame

The Research and Implementation of Illumination Technology in the 3D GIS Visualization

Building mountains as the basic model for illumination model in the system of 3DGIS visualization. The establishing of this model adopts the approach of the global illumination model combine with the local reflection model and also the combination of shading and shadow. Complete the drawing of the shadow in the global illumination model ,using the shadow algorithm of Ray tracing as the main algorithm for drawing shadow, take advantage of shadow volume algorithm as the additional algorithm for shadow; complete the drawing of the shading in the local reflection model ,using the Blinn proportion algorithm as the main algorithm. Select the single ideal fixed point source as the light source of the illumination model. The results of this experimental show that the approach of combination of global and local model is feasible, the selection of the shadow and shading algorithms are also can reference.