A microwave characterization at UHF band of a ferroelectric hafnium zirconium oxide metal-ferroelectric-metal (MFM) capacitors for varactor applications has been performed. By using an impedance reflectivity method, a complex dielectric permittivity was obtained at frequencies up to 500 MHz. Ferroelectric Hf0.5Zr0.5O2 of 10 nm thickness has demonstrated a stable permittivity switching in the whole frequency range. A constant increase of the calculated dielectric loss is observed, which is shown to be an effect of electric field distribution on highly resistive titanium nitride (TiN) thin film electrodes. The C-V characteristics of a “butterfly” shape was also extracted, where the varactors exhibited a reduction of capacitance tunability from 18.6% at 10 MHz to 15.4% at 500 MHz.
A ridge-channel AlGaN/GaN high-electron mobility transistor (HEMT) utilizing selective-area growth and epitaxial lateral overgrowth (ELO) technique is proposed in this work to achieve high-performance normally-off devices. It has a c-plane platform for the source and the drain contacts, and sidewalls of lattice plane for the gate contact. The sidewalls have characteristics of weak polarization and thin barrier, which are advantageous for realizing normally-off operation. Two ridge HEMTs with triangular and trapezoid channel are designed. Theoretical simulation demonstrates a threshold voltage of 0.03 V for the sidewall channel with reduced polarization and barrier thickness, and a threshold voltage of 1.1–1.3 V for the ridge HEMTs assuming no polarization charge in sidewall channel. The ridge-channel device also exhibits high saturation drain current. The ELO-based ridge-channel opens a new way to achieve normally-off AlGaN/GaN HEMT.
Abstract As a bridge linking propagating waves and surface waves, reflective metasurfaces (with metal cladding at the bottom) play a significant role in the field of beam steering. The feasibility and flexibility to control electromagnetic waves by reflective metasurfaces depend on the recognition of their physical properties by researchers. As for bianisotropic reflective metasurfaces, however, the effective-medium characteristics cannot be appropriately described by conventional methods, which entail both transmission and reflection coefficients. Here, a robust method based on simplex S-parameters is proposed to retrieve constitutive effective parameters (CEPs) for bianisotropic reflective metasurfaces. By illuminating the transverse electric-polarization plane waves on a split-ring unit cell normally and obliquely, the CEPs can be calculated with only S11 parameters. To demonstrate the effectiveness of the retrieval results, an analysis of small incident angles is employed to examine the consistency of both the x- and y-directions effective impedance and determine the accurate range of the incident angles. Moreover, the sensitivity of the retrieval results to S-parameters is also sufficiently discussed. This method is beneficial for the applications of one-side complex materials, e.g., dual-function reflective metasurfaces, multichannel reflectors, excitation of spoof space plasmon polaritons, and ground-penetrating-radar applications.
In contrast to agricultural settings, the process of urbanization in the pastoral regions of China are largely driven by long-term influences of ecological conservation and the provision of social services. Consequently, many of the herders who have migrated into nearby secondary urban centers depend on resources from pastoral regions to support their livelihoods, forming complex patterns of rural–urban linkages. While current literature has discussed the processes of herder out-migration and their implications on rural and urban livelihood development, few studies have examined the linkages between the herders living in the pastoral regions and those who have out-migrated to urban regions and their importance in rural livelihood transformation. Based on past studies, we argue that, in a changing pastoral social–ecological system, herders living in both rural and urban regions depend on each other to support their livelihoods through three types of mobility: (1) livestock mobility, (2) herder mobility, and (3) resource mobility. However, what innovative institutions in rangeland resource management and herder economic cooperation can do to help maintain these three types of mobility to sustain rural livelihood development, becomes a critical challenge. Innovative community cooperative institutions developed by pastoral communities from the Tibetan Plateau and Inner Mongolia may be able to offer new perspective and insight on how to better maintain rural–urban linkages in the processes of urbanization in pastoral regions. In this current study will present the two cases of innovative institutions and the roles they play in facilitating the three types of mobility to address livelihood challenges. While current studies recommend an increase of government subsidies, provision of vocational training, and social insurance that help herders better adapt to urban livelihood, we argue that rangeland management and community economic cooperation in innovative institutions are needed to facilitate the mobility of livestock, resources, and the herder population, and maybe only then the livelihood challenges that migrated herders are facing will be addressed effectively.
Interpreting subjectivity in causal relations takes effort: Subjective, claim-argument relations are read slower than objective, cause-consequence relations. In an eye-tracking-while-reading experiment, we investigated whether connectives and stance markers can play a facilitative role. Sixty-five Chinese participants read sentences expressing a subjective causal relation, systematically varied in the use of stance markers (no, attitudinal, epistemic) in the first clause and connectives (neutral suoyi “so”, subjective kejian “so”) in the second clause. Results showed that processing subjectivity proceeds highly incrementally: The interplay of the subjectivity markers is visible as the sentence unfolds. Subjective connectives increased reading times, irrespective of the type of stance marker being used. Stance markers did, however, facilitate the processing of modal verbs in subjective relations. We conclude that processing subjectivity involves evaluating how the argument supports the claim and that connectives, modal verbs, and stance markers function as processing instructions that help readers achieve this evaluation.
Artificial neural networks (ANNs), like convolutional neural networks (CNNs), have achieved the state-of-the-art results formanymachine learning tasks. However, inference with large-scale full-precision CNNs must cause substantial energy consumption and memory occupation, which seriously hinders their deployment on mobile and embeddedsystems. Highly inspired from biological brain, spiking neural networks (SNNs) are emerging as new solutions because of natural superiority in brain-like learning and great energy efficiency with event-driven communication and computation. Nevertheless, training a deep SNN remains a main challenge and there is usually a big accuracy gap between ANNs and SNNs. In this paper, we introduce a hardware-friendly conversion algorithm called “scatter-and-gather” to convert quantized ANNs to lossless SNNs, where neurons are connected with ternary {−1,0,1} synaptic weights. Each spiking neuron is stateless and more like original McCulloch and Pitts model, because it fires at most one spike and need be reset at each time step. Furthermore, we develop an incremental mapping framework to demonstrate efficient network deployments on a reconfigurable neuromorphic chip. Experimental results show our spiking LeNet on MNIST and VGG-Net on CIFAR-10 datasetobtain 99.37% and 91.91% classification accuracy, respectively. Besides, the presented mapping algorithm manages network deployment on our neuromorphic chip with maximum resource efficiency and excellent flexibility. Our four-spike LeNet and VGG-Net on chip can achieve respective real-time inference speed of 0.38 ms/image, 3.24 ms/image, and an average power consumption of 0.28 mJ/image and 2.3 mJ/image at 0.9 V, 252 MHz, which is nearly two orders of magnitude more efficient than traditional GPUs.
Cooking has been proven to be a significant source of primary organic aerosol, especially in megacities. However, the formation of secondary organic aerosol (SOA) derived from cooking emissions is still poorly understood. In this work, four prevalent Chinese domestic cooking types involving complicated cuisines and various cooking methods were chosen to conduct a lab simulation for SOA formation using a Gothenburg potential aerosol mass reactor (Go: PAM). After samples had been aged under OH exposures of 4.3–27.1 × 1010 molecules cm–3 s, the domestic cooking SOA was characterized by mass growth potentialities (1.81–3.16), elemental ratios (O/C = 0.29–0.41), and mass spectra. Compared with other organic aerosol (OA), domestic cooking SOA is a kind of less oxidized oxygenated OA (LO-OOA) with a unique oxidation pathway (alcohol/peroxide pathway) and mass spectra (characteristic peaks at m/z 28, 29, 41, 43, 44, 55, and 57). This study is expected to identify the cooking SOA under actual cooking conditions, which could contribute to the formulation of pollution source control as well as the health risk assessment of exposure to cooking fumes.
