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Behavioral observation plays an essential role in the diagnosis of Autism Spectrum Disorder (ASD) by analyzing children's atypical patterns in social activities (e.g., impaired social interaction, restricted interests, and repetitive behavior). To date, this process still heavily relies on the questionnaire survey, clinical observation, or retrospective video analysis, leading to high demand for professionals with massive labor costs. This article proposes a standardized platform for stimulating, gathering, analyzing, modeling, and interpreting human behavioral data in the application of computer-aided ASD diagnosis. By a structured assessment process, the proposed system can automatically evaluate children's multiple social interaction skills using the captured audio-visual data and provide the final diagnostic suggestions. We collect a multimodal behavioral database of 95 participants (71 children with ASD and 24 age-matched typical controls) in a real clinic environment, the Third Affiliated Hospital of Sun Yat-sen University, China. On the clinical database, our proposed computer-aided ASD diagnosis system obtains an accuracy of 88.42% for identifying ASD children with an average age of 24 months, representing a performance comparable to top-level human experts. As a unified and replicable solution, it has good potential to be promoted to less developed areas with limited high-quality medical resources. [ABSTRACT FROM AUTHOR]

As a major limitation for power scaling of high power narrow linewidth fiber master oscillator power amplifiers (MOPAs), Stimulated Brillouin Scattering (SBS) induced self-pulsing in polarization maintaining (PM) fiber amplifiers is well characterized and analyzed in this paper by comparing different white noise signal (WNS) phase-modulated modes in experiments. It is found that the self-pulsing effect is not observed in the PM-amplifier with single-frequency laser seed injection, and cascaded WNS modulation provides superior self-pulsing suppression than single WNS modulation with similar output linewidth. Moreover, the experimental results indicate that the self-pulsing threshold can hardly be predicted only by the output linewidth or the defined SBS threshold in a WNS phase modulated fiber amplifier system. As self-pulsing is originated from the spectral spikes in WNS modulated system, we theoretically analyzed characteristics of these spikes in different phase-modulation modes. It indicates the spectral peak intensity can be reduced by cascaded modulation, for which self-pulsing can be suppressed. The theoretical predictions agree well with the experimental results. At the same time, in order to suppress the mode instability effect, a plum blossom shaped bending mode selection device is used in this high-power narrow linewidth fiber amplifier system. Finally, a 32 GHz cascaded WNSs modulated, over than 2.5 kW linearly polarized all-fiber amplifier with a slope efficiency of 86.7% is demonstrated. The polarization extinction ratio (PER) is measured larger than 14 dB and the beam quality factor M2 maintains lower than 1.3 in the power scaling process. [ABSTRACT FROM AUTHOR]

For a general multi-coil magnetic coupling wireless power transfer (MC-WPT) system with different coil properties and non-negligible cross couplings, there is no analytical solution that connects the resonant frequencies of the system to its electric parameters. Establishing such a generalized analytical solution not only permits quantitative analysis of resonant points but also provides a generic platform for the physical interpretation of resonance. For this purpose, a novel modeling and analysis method of integrating time domain and frequency domain is proposed in this paper, with that all possible resonant points of arbitrary coil MC-WPT systems can be quickly and accurately determined. First, an accurate state-space model of a general MC-WPT system with arbitrary number of transmitters, repeaters, and receivers is established and the analytical current response on each circuit is derived. Then, several key system concepts about resonance are elucidated, based on which the generalized analytical expressions of resonant points of MC-WPT systems, including resonant frequencies and corresponding powers and efficiencies, are derived. Furthermore, the physical interpretation along with the mathematic relationships of several key easy-confusing concepts are deduced, which provides a systematic theoretical criteria for the selection of operating frequency to achieve the resonant states for MC-WPT systems. [ABSTRACT FROM AUTHOR]

Platinum disulfide (PtS2) has recently drawn extensive research interest due to its excellent electronic properties, controllable bandgap over a broad range, and high air stability. Herein, we demonstrate the generation of mode-locked ultrafast laser pulses by using PtS2 nanosheets for the first time, which were fabricated by ultrasonic exfoliation followed by the centrifugation process. The fabricated PtS2 saturable absorber (SA) was used within two different fiber laser systems. Ultrafast laser pulses with pulse duration of 2.1 ps, 3-db bandwidth of 2.5 nm, and repetition rate of 15.04 MHz were produced from an Er-doped fiber laser system with an operational wavelength of 1.572 μm. Additionally, a mode-locking pulse train with repetition rate of 11.2 MHz was obtained by using the fabricated PtS2 SA within Yb-doped fiber laser system with operational wavelength of ∼1 μm. It is expected that these results will trigger further research with wide potential applications of PtS2 in the field of nonlinear optics and ultrafast photonics. [ABSTRACT FROM AUTHOR]

To reveal the general characteristic of the maximum power transfer points of magnetic coupling wireless power transfer (MC-WPT) systems, and to quickly and accurately determine all possible maximum power transfer points for arbitrary coil MC-WPT systems, a novel theoretical analysis method is proposed in this paper. Based on the modal theory, an accurate time-domain model of an n-coil MC-WPT system is established and the analytical current response on each coil is derived. According to the current response of the load, a detailed power spectrum distribution is presented, based on which the mathematic expressions of all possible maximum power transfer points, including the maximum output powers and corresponding operating frequencies, are deduced. The theoretical results are verified in experiment prototypes practically. The experimental results show that: 1) the output power reaches its maximum value at the modal frequencies rather than the designed natural frequency of the resonators in MC-WPT systems; 2) there are n modal frequencies of an n-coil MC-WPT system. The analysis results provide useful information to choose the operating frequency for practical MC-WPT systems with arbitrary number of coils. [ABSTRACT FROM AUTHOR]

An important feature of an inductive power transfer (IPT) system is its power transfer efficiency and capability can be significantly affected by the load and the magnetic coupling variations. Therefore, identifying the load and the mutual inductance is essential to improve the system performance. This paper proposes a load and mutual inductance identification method for IPT systems with parallel-compensated power pickups based only on the information detected from the primary side. The proposed method can be implemented for primary resonant circuits whether they are series or parallel tuned, or with a hybrid compensation, such as an LCL configuration. An identification model is established according to the steady-state characteristics of the system. Identification results are obtained based on mathematical derivations and analyses. The proposed identification method is realized without any extra communication or control, and both the simulation and experimental results have verified its feasibility. [ABSTRACT FROM AUTHOR]

The dependence of the spectral broadening characteristics on the number of longitudinal modes is studied experimentally in a bi-directional pumping fiber amplifier. It is found that the linewidth of the amplifier decreases with reducing the longitudinal mode number of the seed source. In this letter, we present a 68 pm-linewidth kilowatt-level fiber laser using a simple master oscillator power amplifier structure. Meanwhile, we theoretically analyze the spectral broadening characteristics of the seeds with different longitudinal mode numbers. The conclusions are in agreement with the experimental results. This provides a simple and efficient method for obtaining the high power narrow linewidth fiber laser used in spectral beam combining. [ABSTRACT FROM AUTHOR]

Capacitive power transfer (CPT) systems based on high-frequency electric field coupling have attracted much attention recently due to their simplicity and low eddy-current losses. This paper proposes a mixed-resonant topology consisted of a Π-CLC resonant circuit on the primary side and a T-CLC circuit on the secondary side for multiple pickups constant current output applications. The voltage gain, current gain, and zero phase angle frequency at different operating modes of Π-CLC and T-CLC circuits are analyzed by fundamental frequency approximation, and the conditions leading to a constant output current independent of loads are determined. Based on the analysis, a design method to determine the resonant network parameters is proposed according to the required output current of each pickup. A prototype with three pickups has been designed and built, and both simulation and experimental results have demonstrated that the proposed multiple-pickup CPT system can output a constant current at each operating power pickup against the load variations of itself and others. [ABSTRACT FROM AUTHOR]

WS2 layered material offers a great potential for the development of next generation laser photonic devices due to its strong layer absorption compared with graphene. The passively Q-switched Nd:YVO4 laser operating at 1064 nm was first demonstrated by using layered tungsten disulfide WS2 saturable absorber SA, which was fabricated by using radio frequency magnetron sputtering method. The fabrication method is scalable and capable of producing large size sample with high uniformity. Besides, the thickness of produced sample can be well-controlled by adjusting sputtering time. A stable Q-switched laser operation is achieved by using this home made few layers WS2-SA within a diode-pumped Nd:YVO4 laser cavity. The maximum average output power obtained is 19.6 mW corresponding to a repetition rate of 135 kHz, a pulse duration of 2.3 μs and single pulse energy of 145 nJ. This result proves the promising Q-switching performance of the fabricated WS2-SA. [ABSTRACT FROM PUBLISHER]

The theoretical design and experiment research on the YAG/Nd:YAG/YAG composite ceramic slab laser amplifier were conducted. The numerical analysis was used to obtain the design of YAG/Nd:YAG/YAG composite ceramic slab. A high optical quality composite ceramic slab with two different doping concentrations was fabricated successfully. The double-pass extracted power in composite ceramic slab laser amplifier reached 7.08 kW, and the optical-to-optical conversion efficiency increased to 39.2% under the total diode pump power of 18.06 kW. The depolarization of single-pass transmission was about 3.2% and the peak and valley of the transmission wave-front distortion among the center 26.1-mm region in the width direction of the laser slab was less than 0.5 μm at the double-pass extracted power of 7.08 kW. [ABSTRACT FROM PUBLISHER]

Nonideal frequency problems can occur in a wireless power transfer system due to multiple soft-switching frequencies and frequency bifurcation. To make the system work at an ideal frequency with high-power transfer capability and efficiency, a method based on waveform identification is proposed. First, the space state model of a SP type WPT system is built, and the waveforms at ideal and nonideal working frequencies are obtained based on the stroboscopic mapping theory. Second, according to the characteristics of these waveforms, the swing door algorithm is improved by waveform distortion rate and fast Fourier transformation, which is used to recognize nonideal waveforms. Then, a control strategy based on “online self-determined optimization” is proposed to deal with the problem. Finally, the results of simulation and experiments show that the method proposed in this paper can identify the waveforms at nonideal frequency and find an ideal working frequency for the WPT system. [ABSTRACT FROM AUTHOR]

This paper proposed a novel wireless power transfer system with full-duplex communication on a shared channel for capacitively coupled power transfer systems. For the analysis of power and signal transmission, a frequency-domain model of the power and signal channels is established. Based on this model, the signal transfer characteristic of the channel and the influence of power flow on the signal channel are analyzed. Moreover, to ensure the power and signal transfer without unacceptable interference or attenuation, a parameters selection method of the communication channel is developed. In addition, an interference suppression strategy by taking the interference from the ipsilateral channel into consideration is proposed. To suppress the interference effectively, an estimation of the ipsilateral channel output signal is made. Then, the signal from the opposite channel is demodulated by removing the estimated values of the interference. Both simulation and experimental results showed have proven the correctness and effectiveness of the proposed wireless power and signal transfer method. Finally, it has demonstrated that the designed channel can transfer 100 W of power, and a full-duplex communication can be well achieved with different data rates in two directions when both two data rates are set within 200 kb/s. [ABSTRACT FROM AUTHOR]

In order to improve the power transfer efficiency and ensure the space cleanliness of power transfer direction in inductive coupled wireless power transfer (WPT) system, a new U-coil WPT system is proposed. Based on the mutual inductance coupling theory, a new methodology for ensuring that a U-coil system is more energy efficient than a two-coil counterpart is presented in this paper. The theoretical proof and the conditions for meeting the objective are derived and practically verified in a practical prototype. The experimental results show: 1) comparing with two-coil system, power transfer efficiency can be improved more than ten times by using U-coil system; and 2) with the same power transfer efficiency principle, the dimension of primary and load coils in U-coil system shrinks at least 66% comparing with that of two-coil system. The U-coil system not only improves power transfer efficiency but also ensures the cleanliness of the space along the energy transfer direction. [ABSTRACT FROM AUTHOR]