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This paper reports the improvement of internal-quantum efficiency in GaN-based light-emitting diodes grown on the 2000-nm-period patterned-sapphire substrates with a larger post-duty cycle under the same etching depth.
High-speed permanent magnet motors (HSPMMs) have gained ever-increasing interests in high speed direct-drive applications due to their advantages of high-power density, small size and high efficiency. However, the low stator inductance of the HSPMM causes large current ripple in the stator current, therefore brings additional iron loss. The Modular multilevel converter (MMC) increases both voltage...
Since its inception, the Kalman filter, which represents the optimal estimator for linear, Gaussian state space models, has been adopted for a wide array of practical applications due to its efficient, recursive formulation. At the same time, the field of nonlinear time series analysis has produced powerful methods for filtering time series with deterministic dynamics. These nonlinear filters differ...
A C-band broadband polarization reconfigurable antenna array is introduced to enhance the spectrum efficiency and transmission capacity. This antenna array provides four kinds of polarization switching modes, including horizontal-polarization, vertical-polarization, left circularly-polarization and right circularly-polarization. Simulation results are presented and discussed, the performance verify...
We present a simple method to minimize the gain roll-off of the Rotman lens antenna with wide scans. Phase gradient transmission lines are used to neutralize a precipitous drop in the power efficiency of Rotman lens when the scan angle increases. To validate the proposed method, a Rotman lens antenna at X band with 8 beam ports and 9 array ports are designed and simulated. The results show that the...
In this paper, a novel single-pole-double-throw (SPDT) switch based on the ring structure is proposed, which can be applied in the multi-beam antenna arrays system. Different from the conventional SPDT switch, its reliability can be enhanced further for it does not involve any state of total reflection. Moreover, it can also perform as a power divider under the proper bias voltage.
The antenna structure generating orbital angular momentum (OAM) beam with small divergence angle is described in this paper. Luneberg lens, always used to generate high gain beam, is utilized in this structure to focus the OAM beam generated by the source. Luneberg lens is discretized into layers. With simulations, the OAM beam's divergence angle with 19 degree is successfully decreased to 5 degree,...
Gyro wheel, a new kind of spacecraft attitude control and measurement device, could work as actuators as well as sensors at the same time. With this characteristic, Gyro wheel could reduce the size, mess and cost of the spacecraft attitude control system. It is of great significance for the development of the small satellite. Based on the Euler dynamics equation, the gyrowheel is modeled and both...
In this paper, the task of Mission 7 of International Aerial Robotics Competition (IARC) is investigated. The quadrotor is required to autonomously navigate in a GPS-denied environment, and accomplish physical interaction with ground moving targets. In order to estimate the position of the quadrotor, a multi-sensor-compensation based method is designed and individual measurement errors are compensated...
In this paper, a landing control problem is investigated in which a quadrotor is required to autonomously land on a desired area of a ground moving target. In order to guarantee the reliability and continuity of the target recognition, the path planning of the quadrotor has to be considered under the constraints of its position, velocity and acceleration. Due to the affection of the velocity measurement...
Gyrowheel is a unique attitude control device to measure external rates of the spacecraft body as well as provide momentum control. To ensure the external rate sensing accuracy of Gyrowheel, study of the accurate characterization of the currents in the torque coils is performed in this paper. Components of the current signals and the sources of them are analyzed, and an effective filtering method...
GyroWheel is an innovative aerospace device which integrates the function of attitude determination and control. Due to the special structure of flex-gimbal suspension system, GyroWheel rotor have three degrees of freedom. As most other rotating machineries, the dynamic unbalance issue also exists in GyroWheel system, which is caused by the uneven mass distribution of rotor. The couple unbalance leads...
Driver fatigue is one of the main causes of traffic accidents. An early warning system for driver fatigue can effectively reduce the incidence of accidents. This study uses continuous physiological data to train a fatigue analyzer such that it learns the pattern change. As a result, the system can predict fatigue beforehand. For the purpose of early warning, the weights in weighted moving average...
This paper presents a method for designing linear-phase square-root (SR) FIR digital filters that alleviate the effect of receiver timing uncertainty by the quadratically constrained quadratic programming. As in the previous work, we take the “roughness” of the hybrid analog/FIR-SR filter impulse response as the cost function and the filter's stopband attenuation and the system's tolerable ISI as...
Magnetic flux leakage (MFL) inspection is one of the most commonly used nondestructive testing (NDE) technologies. This paper proposes a novel method for classifying the MFL response segments based on convolution neural network (CNN). In order to skip the procedure of saving the normalized MFL segment and save some computing time, a normalization layer is added to the proposed model. Moreover, the...
Robot Coverage Path planning (i.e., the process of providing full coverage of a given domain by one or multiple robots) is a classical problem in the field of robotics and motion planning. The goal of such planning is to provide nearly full coverage while also minimize duplicately visited area. In this paper, we focus on the scenario of path planning on general surface, including planar domains with...
This work develops a cloud-fog computing architecture for information-centric Internet-of-Things (IoT) applications with job classification and resource scheduling functions. The two designed functions support quality of service (QoS) by classifying IoT applications and scheduling computing resources. An innovative scheduling mechanism is developed to optimize the dispatch of cloud and fog resources...
In this paper, we present a microfluidic chip-based method for high-throughput formation and long-term culture of embryoid bodies (EBs). The microfluidic chip is designed to be a stand-alone device whose operation can be performed by a manual pipette, making it easy to use in a regular biology laboratory setup. We show that uniform-sized mouse EBs can be formed after 1 day of culture in the microfluidic...
This paper reported the growth of semi-polar GaN epi-layers on (0001) c-plane nano-sized patterned-sapphire substrates (c-NPSSs). In addition, the impact of c-NPSSs on the quality of semi-polar film had also been studied.
By varying the arrangements of patterned sapphire substrates, the stress-induced bandgap widening of GaN-based epitaxial layers can be acquired. Photoluminescence and Raman results demonstrate a linear relationship of blue-shift with the increase of residual stress.
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