Temperature Uniformity of Wafer on a Large-Sized Susceptor for a Nitride Vertical MOCVD Reactor

The effect of coil location on wafer temperature is analyzed in a vertical MOCVD reactor by induction heating.It is observed that the temperature distribution in the wafer with the coils under the graphite susceptor is more uniform than that with the coils around the outside wall of the reactor.For the case of coils under the susceptor,we find that the thickness of the susceptor,the distance from the coils to the susceptor bottom and the coil turns significantly affect the temperature uniformity of the wafer.An optimization process is executed for a 3-inch susceptor with this kind of structure,resulting in a large improvement in the temperature uniformity.A further optimization demonstrates that the new susceptor structure is also suitable for either multiple wafers or large-sized wafers approaching 6 and 8 inches.

Hand gesture tracking algorithm based on visual attention

In the majority of the interaction process, the operator often focuses on the tracked 3D hand gesture model at the ＂interaction points＂ in the collision detectionscene, such as ＂grasp＂ and ＂release＂ and objects in the scene, without paying attention to the tracked 3D hand gesture model in the total procedure. Thus in this paper, a visual attention distribution model of operator in the ＂grasp＂, ＂translation＂, ＂release＂ and other basic operation procedures is first studied and a 3D hand gesture tracking algorithm based on this distribution model is proposed. Utilizing the algorithm, in the period with a low degree of visual attention, a pre-stored 3D hand gesture animation can be used to directly visualise a 3D hand gesture model in the interactive scene; in the time period with a high degree of visual attention, an existing ＂frame-by-frame tracking＂ approach can be adopted to obtain a 3D gesture model. The results demonstrate that the proposed method can achieve real-time tracking of 3D hand gestures with an effective improvement on the efficiency, fluency, and availability of 3D hand gesture interaction.

Brain Tumor Segmentation of HGG and LGG MRI Images Using WFL-Based 3D U-Net

The semantic segmentation of a brain tumor is the essential stage in medical treatment planning. Due to the different characteristics of tumors, one of the main difficulties in image segmentation is the severe imbalance between classes. Also, a dataset with imbalanced classes is a common problem in multimodal 3D brain MRIs. Despite these problems, most studies in brain tumor segmentation are biased toward the overrepresented tumor class (majority class) and ignore the small size tumor class (minority class). In this paper, we propose an improved loss function Weighted Focal Loss (WFL), based on 3D U-Net to enhance the prediction of brain tumor segmentation. Using our proposed loss function (WFL) solves the imbalance between classes and the imbalance between weights by giving higher weights to the minority and lower weights to the majority. After assigning these weights to different pixel values, our work is able to resolve pixel degradation, which is one of the limitations of the loss function during model training. Based on our experiments, the proposed function (WFL) on the 3D U-Net model for high-grade glioma (HGG) and low-grade glioma (LGG) in the Brain Tumor Segmentation Challenge (BraTS) 2019 dataset has shown promising results for tumor core (TC), whole tumor (WT) and enhanced tumor (ET) with average dice scores of HGG: 0.830, 0.913, 0.815 and Dice scores of LGG for TC: 0.731, WT: 0.775 and ET: 0.685. Moreover, we deployed our training on BraTS 2020 in which we obtained mean Dice scores of HGG: TC: 0.843, WT: 0.892, ET: 0.871 and Dice scores of LGG: 0.7501, 0.7985, 0.6103 for TC, WT and ET, respectively.

Tunnel visible light communication system utilizing frequency domain pre-equalization technique

Simultaneously improving the communication speed and equalizing the nonlinear frequency response are still challenging for tunnel visible light communication(TVLC)system.Here,we propose and numerically investigate a frequency domain pre-equalization scheme for discrete multitone(DMT)modulation TVLC system.The amplitude of each subscriber is appropriately pre-equalized by optimized nonlinear compensation parameters.Simulation results demonstrate that our proposed equalization technique can resist the channel attenuation of the signal high-frequency part and further flatten the nonlinear channel response.Without forward error correction technique,the bit error ratio(BER)performance can reach 7.66×10^(-6)in a 2.05 Gbit/s DMT-TVLC system.

Research on unified recognition model and algorithm for multi-modal gestures

In gesture recognition,static gestures,dynamic gestures and trajectory gestures are collectively known as multi-modal gestures.To solve the existing problem in different recognition methods for different modal gestures,a unified recognition algorithm is proposed.The angle change data of the finger joints and the movement of the centroid of the hand were acquired respectively by data glove and Kinect.Through the preprocessing of the multi-source heterogeneous data,all hand gestures were considered as curves while solving hand shaking,and a uniform hand gesture recognition algorithm was established to calculate the Pearson correlation coefficient between hand gestures for gesture recognition.In this way,complex gesture recognition was transformed into the problem of a simple comparison of curves similarities.The main innovations:1) Aiming at solving the problem of multi-modal gesture recognition,an unified recognition model and a new algorithm is proposed;2) The Pearson correlation coefficient for the first time to construct the gesture similarity operator is improved.By testing 50 kinds of gestures,the experimental results showed that the method presented could cope with intricate gesture interaction with the 97.7% recognition rate.