Search

In this work, the impacts of OFF-state gate bias (VGS,OFF) on dynamic on-resistance (RON) are systematically investigated in commercial Schottky-type p-GaN Gate high-electron-mobility transistors (HEMTs). Double-pulse tester (DPT) and PIV system are adopted to evaluate the dynamic RON with various OFF-state gate and drain bias (VDS,OFF) under hard- and soft-switching conditions. More negative VGS,OFF can aggravate the dynamic RON degradation under both soft- and hard-switching, especially when switching with a high VDS,OFF. The impacts of VGS,OFF on switching transients and OFF-state stress are investigated separately to reveal the underlying mechanisms, which are found to be associated with the generation and movements of holes. OFF-state gate bias of the voltage-driving scheme needs to be carefully considered according to the identified mechanisms in terms of dynamic on-resistance degradation.

A physical-layer secure data encryption algorithm is proposed and demonstrated using chaotic constellation mapping associated with probabilistic shaping (PS) for orthogonal frequency division multiplexing passive optical networks (OFDM-PONs). The constellation of the encrypted data is uniformly distributed after chaotic diffusion in quadratic-amplitude modulation (QAM) mapping, to eliminate the statistical characteristics, where a key space of ~10231 is created by a 4-dimensional hyper digital chaos. Moreover, PS is introduced to improve the OFDM signal transmission. A 9.4 Gb/s encrypted PS-16-QAM OFDM signal transmission is successfully demonstrated over 20 km standard single-mode fiber (SSMF), where the gain of receiver sensitivity is ~2 dB (bit-error rate @ 10−3) using PS.

We report a 16.8 Tb/s true random number generator (TRNG) based on amplified spontaneous emission (ASE) of Erbium-doped fiber amplifier (EDFA), which is sliced into 42 parallel channels by an arrayed waveguide grating (AWG). The true randomness of ASE is enhanced and guaranteed by a novel extraction approach utilizing two orthogonal polarized components of ASE. Consequently, the random number generation rate (RNGR) can be significantly increased via higher sampling rate. The experimental results show that, the single-channel RNGR of 400 Gb/s is achieved, while the overall RNGR is 16.8 Tb/s for the full ASE spectrum. The proposed TRNG is of great significance in the field of secret key distribution and confidential communication.

We present the high-speed physical-layer secure key generation and distribution in fiber networks. A key generation rate of 2.7 Gb/s is achieved over 10 km single-mode fiber using a specifically-designed bidirectional polarization scrambler.

Poverty remains one of the long-term chronic dilemmas facing the sustainable development of human society during the 21st century. The spatiotemporal dynamics of poor regions, particularly in developing countries, is crucial for realizing fundamental sustainable development goals (SDGs). For decades, many scholars have sought to accurately measure, identify and alleviate poverty at different geographical scales. However, reliable data about the estimation of poverty remain scarce for developing countries, hindering efforts to accurately identify poverty. This paper utilizes the Defense Meteorological Satellite Program Operational Linescan System (DMSP/OLS) sensor nighttime light imagery to identify poor counties in China from 1992 to 2013. Using 16 statistical and spatial features extracted from this nighttime light imagery and using 96 poor counties and 96 nonpoor counties from 2010 as the classification sample, we describe the spatiotemporal dynamics of poor counties based on a random forests approach. Our study finds that the number of poor counties is decreasing in a fluctuating pattern and that contiguous poverty-stricken areas are becoming fragmented. The reduction in poor counties exhibits a manner of moving horizontally from the eastern regions to the central and western parts of China, while the number of poor counties in the central and western regions has decreased around the central cities or areas. The Aihui-Tengchong Line is not the dividing line in the distribution of poor counties in China, which means that China's poor can also be found in areas with relatively high population density. Together, the findings reveal that the key to reducing regional poverty is the development of regional economies and the implementation of national macro policies. This paper provides references for formulating antipoverty strategies for each county and offers new insights into poverty estimation and regional sustainable development for other developing countries.

In this work, the impacts of OFF-state gate bias (V GS,OFF ) on the dynamic on-resistance (R ON ) are investigated in the commercial Schottky-type p-GaN gate high-electron-mobility transistor (HEMT). A more negative V GS,OFF could aggravate the dynamic R ON degradation, especially when switching with a large OFF-state drain bias. In addition, the dependence of dynamic R ON on the high drain bias also varies with V GS,OFF . The underlying mechanism is suggested to be associated with the generation and movement of holes, which are both strongly affected by V GS,OFF .

The development of China’s manufacturing industry has received global attention. However, research on the distribution pattern, changes, and driving forces of the manufacturing industry has been limited by the accessibility of data. This study proposes a method for classifying based on natural language processing. A case study was conducted employing this method, hotspot detection and driving force analysis, wherein the driving forces industrial development during the “13th Five-Year plan” period in Jiangsu province were determined. The main conclusions of the empirical case study are as follows. 1) Through the acquisition of Amap’s point-of-interest (POI, a special point location that commonly used in modern automotive navigation systems.) data, an industry type classification algorithm based on the natural language processing of POI names is proposed, with Jiangsu Province serving as an example. The empirical test shows that the accuracy was 95%, and the kappa coefficient was 0.872. 2) The seven types of manufacturing industries including the pulp and paper (PP) industry, metallurgical chemical (MC) industry, pharmaceutical manufacturing (PM) industry, machinery and electronics (ME) industry, wood furniture (WF) industry, textile clothing (TC) industry, and agricultural and food product processing (AF) industry are drawn through a 1 km× 1km projection grid. The evolution map of the spatial pattern and the density field hotspots are also drawn. 3) After analyzing the driving forces of the changes in the number of manufacturing industries mentioned above, we found that manufacturing base, distance from town, population, GDP per capita, distance from the railway station were the significant driving factors of changes in the manufacturing industries mentioned above. The results of this research can help guide the development of manufacturing industries, maximize the advantages of regional factors and conditions, and provide insight into how the spatial layout of the manufacturing industry could be optimized.

A point to multi-point physical-layer secure key generation and distribution (SKGD) scheme is proposed and demonstrated in passive optical networks (PONs), where the optical line terminal (OLT) broadcasts optical lights with fast fluctuating states of polarization (SOPs) to the optical network units (ONUs). The highly correlated key waveforms are shared between OLT and ONUs, and the high-level security of the SKGD scheme is guaranteed by the high sensitivity of SOP dynamics associated with the specific fiber links. As a proof of concept, a 3.9 Gb/s SKGD is achieved over 11 km single-mode fiber, where a Sagnac interferometer-based polarization scrambler is constructed as the high-speed random source. Moreover, the generated key sequences are verified to be error free and truly random. The proposed SKGD scheme offers a flexible solution for security enhancement in PONs, and is also compatible with the current PON infrastructure.

A kind of polarized chromatic plasmonic film is proposed based on subwavelength grating structure, which enables “blue transmission” for the transverse electric light and “red transmission” for the transverse magnetic light. Metal–insulator–metal plasmonic waveguiding and metallic nanowire scattering are revealed to be responsible for the chromatic shift. Based upon the unique transmission spectrum characteristics of such films, polarized chromatic plasmonic tags (PCPTs) can be flexibly fabricated by patterning dielectric grating templates with designed figures and depositing appropriate thickness of metal. These PCPTs, simultaneously possessing directly visible unpolarized transmission colors and concealed distinct polarization‐dependent color shift, can be widely used as anti‐counterfeiting tags with higher security than the diffractive types of holograms.

The limitations of individual level interventions in changing behaviors to improve global maternal, newborn and child health have generated more interest in the patterns of social influence and decision making embedded in families, friends and communities. The purpose of this study is to expand the understanding of village dynamics in India and how first degree social and advice networks and cognitive perceptions of 185 recently delivered women (RDW) in areas with and without women&rsquo, s Self-Help Groups (SHGs) affect immediate breastfeeding. Data was collected in 6 blocks and 36 villages in Uttar Pradesh, India. The expansion of RDW&rsquo, s social worlds and creation of social capital through the organization of Self-Help Groups in their villages allowed us to examine basic relationships and advice formation as well as perceptions of interconnectedness of known groups. RDW living in SHG villages and blocks had consistently higher numbers of relationship ties, health advice ties and higher density of health advice networks than RDW living in the non-SHG areas. RDW&rsquo, s perceived knowing ties were also significantly higher between family and health workers in the SHG areas with related higher immediate breastfeeding rates. These results suggest that SHGs can accelerate community social capital and promote more accountability in the health system to engage with families and support the change from traditional to more evidence-based health practices.

Separating lights into different paths according to the polarization states while keeping their respective path’s polarizations with high purification is keen for polarization multiplex in optical communications. Metallic nanowire gratings with multi-slits in a period are proposed to achieve polarized beam splitters (PBSs) in reflection and diffraction. The setting of multi-slits largely reduces the reflection of photons with a transverse magnetific field via the plasmonic waveguiding effect, which leads to highly polarized output lights with extinction ratio larger than 20 dB in each channel. The proposed reflection/diffraction PBSs enrich the approaches to control the polarization states with the advantages of wide incident angles and flexible beam splitting angles.