The gait pattern of exoskeleton control conflicting with the human operator’s (the pilot) intention may cause awkward maneuvering or even injury. Therefore, it has been the focus of many studies to help decide the proper gait operation. However, the timing for the recognization plays a crucial role in the operation. The delayed detection of the pilot’s intent can be equally undesirable to the exoskeleton operation. Instead of recognizing the motion, this study examines the possibility of identifying the transition between gaits to achieve in-time detection. This study used the data from IMU sensors for future mobile applications. Furthermore, we tested using two machine learning networks: a linearfFeedforward neural network and a long short-term memory network. The gait data are from five subjects for training and testing. The study results show that: 1. The network can successfully separate the transition period from the motion periods. 2. The detection of gait change from walking to sitting can be as fast as 0.17 s, which is adequate for future control applications. However, detecting the transition from standing to walking can take as long as 1.2 s. 3. This study also find that the network trained for one person can also detect movement changes for different persons without deteriorating the performance.
In this study, temperature-dependent current-voltage characteristics and electroluminescence (EL) spectra of GaN/InGaN multiple-quantum well light-emitting diodes (LEDs), which were sliced down to a few micrometers by focused ion beam technique, were researched. Compared with electrical property of broad-area LEDs, relatively larger recombination current in the temperature-dependent current-voltage (I-V) characteristics of slice LEDs was observed, indicating that most of defects created by ion damage were activated under elevated temperatures. However, approximately constant peak wavelength of slice LEDs at high current density is attributed to the competition effects of charge screening and joule heating.Recently, wide bandgap GaN-based materials have been used to develop high performance devices such as light-emitting and laser diodes. 1-3 Even though device performances have been continuously boosted during the past decade, a number of problems have still remained unsolved, such as efficiency droop 4-6 at high injection current density and emission wavelength shifting with injection current. The latter case arises from the divergence effect of spontaneous and piezoelectric polarizations in the quantum wells (QWs) causing the reduction of internal quantum efficiency due to a reduced overlapping between the electron and hole wave functions. Novel InGaN QWs with large optical matrix element 7-9 and surface plasmon LEDs 10,11 have been popular solutions for charge separation issue recently. For an InGaN-based LED under current injection condition, there are two competing mechanisms that determine the emission wavelength. That is, the red shift of the spectrum due to joule heating induced bandgap renormalization tends to be counteracted by the blue shift due to charge screening. However, the situation may change with device's size and/or injection current density. Recently, great interest in one-dimension (1D) semiconductor nanostructure for nanoscale electronic and optoelectronic device applications, 12-16 has led to the utilization of homogeneous, p-n junction, heteroepitaxial nanowires, and nanorods in several nano device prototypes. From the geometry of above-mentioned devices, quantum confinement stark effect (QCSE) can be alleviated by shrinking the device's size. 15,16 The E-beam writer and dual-beam focused ion beam system (DB-FIB) are two popular tools to fabricate the nanoscale devices. Although the E-beam writer can't etch large volume of material, it can achieve a fine surface or structure of the material. The FIB, which has been used for decades in nano fabrication, utilizes high voltage to accelerate the gallium (Ga) ions which are focused by the electromagnetic lens. This precision engineering tool uses focused energetic ions to produce an ion beam that impacts the material surface at a desired point; however, FIB etching also has side effects of surface damage caused by highly energetic ions and redeposition which occurs during the milling process. Considering these facts, using the FIB technique ca...
This study investigated technologies related to a smart-card display and its wireless charging system, where the wireless receiver in the smart card receives not only the data but also the power required for the display circuitry. The goal of this research was to achieve the required energy transfer during the extremely short reading time when a person swipes his or her smart card. This paper describes the design considerations and the analysis procedures of the transmitter and receiver pair for an electronic paper (E-paper) display. A series of magnetic simulations as well as experimental tests were conducted to investigate the various design factors. The design considerations included the shape and effect of using ferromagnetic cores, the component design for frequency tuning, the geometric arrangements, and the number of turns of the coils. A novel design for power transmission is then proposed using a ferromagnetic core to enhance its energy efficiency. In experiments the transmitter unit provided 250 mW of power to the transmitter antenna. The resultant transmission efficiency (S21) was ¡5.1 dB over a distance of 4.3 mm. Experimental results show that the smart card receives 220 mW, representing a high transmission efficiency of 88%.
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