Highly Weak-light Sensitive and Dual-band Switchable Photodetector Based on CuI/Si Unilateral Heterojunction

In recent years,copper iodide(CuI)is an emerging p-type wide bandgap semiconductor with high intrinsic Hall mobility,high optical absorption and large exciton binding energy.However,the spectral response and the photoelectric conversion efficiency are limited for CuI-based heterostructure devices,which is related to the difficulty in fabrication of high-quality CuI thin films on other semiconductors.In this study,a p-CuI/n-Si photodiode has been fabricated through a facile solid-phase iodination method.Although the CuI thin film is polycrystalline with obvious structural defects,the CuI/Si diode shows a high weak-light sensitivity and a high rectification ratio of 7.6×10^(4),indicating a good defect tolerance.This is because of the unilateral heterojunction behavior of the formation of the p^(+)n diode.In this work,the mechanism of photocurrent of the p^(+)n diode has been studied comprehensively.Different monochromatic lasers with wavelengths of 400,505,635 and 780 nm have been selected for testing the photoresponse.Under zero-bias voltage,the device is a unilateral heterojunction,and only visible light can be absorbed at the Si side.On the other hand,when a bias voltage of-3 V is applied,the photodiode is switched to a broader“UV-visible”band response mode.Therefore,the detection wavelength range can be switched between the“Visible”and“UV-visible”bands by adjusting the bias voltage.Moreover,the obtained CuI/Si diode was very sensitive to weak light illumination.A very high detectivity of 10^(13)-1014 Jones can be achieved with a power density as low as 0.5μW/cm^(2),which is significantly higher than that of other Cu-based diodes.These findings underscore the high application potential of CuI when integrated with the traditional Si industry.

全球化视野下的中产阶级之辨

二战以来,中产阶级研究逐渐成为西方的显学。世纪之交,中国中产阶层成为国内外学者的关注焦点。在全球一体化时代,厘清西方中产阶级的发展脉络、阶级性格及社会功能,对于我们正确认识中产阶级政治社会功能的多元性,培育积极、理性、平和的中国中产阶层,大有裨益。

Non-liD Recommender Systems： A Review and Framework of Recommendation Paradigm Shifting

While recommendation plays an increasingly critical role in our living, study, work, and entertainment, the recommendations we receive are often for irrelevant, duplicate, or uninteresting products and ser- vices. A critical reason for such bad recommendations lies in the intrinsic assumption that recommend- ed users and items are independent and identically distributed （liD） in existing theories and systems. Another phenomenon is that, while tremendous efforts have been made to model specific aspects of users or items, the overall user and item characteristics and their non-IIDness have been overlooked. In this paper, the non-liD nature and characteristics of recommendation are discussed, followed by the non-liD theoretical framework in order to build a deep and comprehensive understanding of the in- trinsic nature of recommendation problems, from the perspective of both couplings and heterogeneity. This non-liD recommendation research triggers the paradigm shift from lid to non-liD recommendation research and can hopefully deliver informed, relevant, personalized, and actionable recommendations. It creates exciting new directions and fundamental solutions to address various complexities including cold-start, sparse data-based, cross-domain, group-based, and shilling attack-related issues.

Multi-core optimization for conjugate gradient benchmark on heterogeneous processors

Developing parallel applications on heterogeneous processors is facing the challenges of 'memory wall',due to limited capacity of local storage,limited bandwidth and long latency for memory access. Aiming at this problem,a parallelization approach was proposed with six memory optimization schemes for CG,four schemes of them aiming at all kinds of sparse matrix-vector multiplication (SPMV) operation. Conducted on IBM QS20,the parallelization approach can reach up to 21 and 133 times speedups with size A and B,respectively,compared with single power processor element. Finally,the conclusion is drawn that the peak bandwidth of memory access on Cell BE can be obtained in SPMV,simple computation is more efficient on heterogeneous processors and loop-unrolling can hide local storage access latency while executing scalar operation on SIMD cores.

Heterogeneous dynamic modeling and simulation of an industrial ethylene oxide reactor experiencing catalyst deactivation

This paper investigates steady-state and dynamic simulation of an industrial fixed-bed ethylene oxide reactor. A mathematical heterogeneous one-dimensional model is developed for simulation of reactor performance in the presence of long term deactivation of silver/a-alumina catalyst. In this paper, steady-state model of the reactor is solved and results of steady state simulation are fed to dynamic simulator as initial condition. When results of dynamic simulation are compared with industrial reactor data, it is found that there were good agreements between simulation results and industrial data. The proposed model is also validated by industrial process data for a period of 1100 operating days.

Characterizing Landscape Spatial Heterogeneity in Multisensor Images with Variogram Models

Most evaluation of the consistency of multisensor images have focused on Normalized Difference Vegetation Index （NDVI） products for natural landscapes, often neglecting less vegetated urban landscapes. This gap has been filled through quantifying and evaluating spatial heterogeneity of urban and natural landscapes from QuickBird, Satellite pour l＇observation de la Terre （SPOT）, Ad- vanced Spacebome Thermal Emission and Reflection Radiometer （ASTER） and Landsat Thematic Mapper （TM） images with variogram analysis. Instead of a logarithmic relationship with pixel size observed in the corresponding aggregated images, the spatial variability decayed and the spatial structures decomposed more slowly and complexly with spatial resolution for real multisensor im- ages. As the spatial resolution increased, the proportion of spatial variability of the smaller spatial structure decreased quickly and only a larger spatial structure was observed at very coarse scales. Compared with visible band, greater spatial variability was observed in near infrared band for both densely and less densely vegetated landscapes. The influence of image size on spatial heterogeneity was highly dependent on whether the empirical sernivariogram reached its sill within the original image size. When the empirical semivariogram did not reach its sill at the original observation scale, spatial variability and mean characteristic length scale would increase with image size; otherwise they might decrease. This study could provide new insights into the knowledge of spatial heterogeneity in real multisen- sor images with consideration of their nominal spatial resolution, image size and spectral bands.

Thermoelectric transport across graphene/hexagonal boron nitride/graphene heterostructures

We report thermoelectric transport measurements across a graphene/hexagonal boron nitride （h-BN）/graphene heterostructure device. Using an AC lock-in technique, we are able to separate the thermoelectric contribution to the I-V characteristics of these important device structures. The temperature gradient is measured optically using Raman spectroscopy, which enables us to explore thermoelectric transport produced at material interfaces, across length scales of just 1-2 nm. Based on the observed thermoelectric voltage （AV） and tem- perature gradient （AT）, a Seebeck coefficient of -99.3 μV/K is ascertained for the heterostructure device. The obtained Seebeck coefficient can be useful for understanding the thermoelectric component in the cross-plane I-V behaviors of emerging 2D heterostructure devices. These results provide an approach to probing thermoelectric energy conversion in two-dimensional layered heterostructures.

The emergence, development and regional differences of mixed farming of rice and millet in the upper and middle Huai River Valley, China

Mixed farming of rice and millet is one of the basic agricultural modes in the upper and middle Huai River Valley(HRV). According to the latest data, this agricultural mode appeared during the middle and late Peiligang Culture(7.8–7.0 ka BP) in the upper HRV, and then became a common subsistence economy in the end of the Neolithic(5.0–4.0 ka BP) in both the upper and middle HRV. However, it is still not clear how this mixed farming developed in the upper HRV after its occurrence, nor are the regional differences in the development of mixed farming between the upper and middle HRV during the Neolithic completely understood. In this paper, flotation and starch analyses were conducted on samples from eight archaeological sites in the upper and middle HRV. The results indicate that the mixed farming of rice and millet first appeared in the later phase of the middle Neolithic in the regions of the Peiligang Culture, then developed quite rapidly in the late Neolithic(6.8–5.0 ka BP), finally becoming the main subsistence economy at the end of the Neolithic in the upper HRV. However, there are obvious differences in the emergence and development of agriculture between the middle and upper HRV. Rice farming was the only agricultural system during the middle Neolithic, lasting until the end of the Neolithic, when mixed farming appeared in the middle HRV. Furthermore, although mixed farming appeared in both the upper and middle HRV during the end of the Neolithic, the roles of rice, foxtail millet and broomcorn millet in the subsistence economy were not the same. In general, millet was more widely cultivated than rice in the upper HRV, but rice occupied the same or a slightly more prominent position in the middle HRV at the end of the Neolithic. These results are significant for understanding the process of agricultural development and transformation, as well as human adaptation to climatic and cultural variability duringthe Neolithic.

In situ construction of heterostructured bimetallic sulfide/phosphide with rich interfaces for high-performance aqueous Zn-ion batteries

It is still challenging to develop suitable cathode structures for high-rate and stable aqueous Zn-ion batteries.Herein,a phosphating-assisted interfacial engineering strategy is designed for the controllable conversion of NiCo_(2)S_(4) nanosheets into heterostructured NiCoP/NiCo_(2)S_(4) as the cathodes in aqueous Zn-ion batteries.The multicomponent heterostructures with rich interfaces can not only improve the electrical conductivity but also enhance the diffusion pathways for Zn-ion storage.As expected,the NiCoP/NiCo_(2)S_(4) electrode has high performance with a large specific capacity of 251.1 mA h g^(−1) at a high current density of 10 A g^(−1) and excellent rate capability(retaining about 76%even at 50 A g^(−1)).Accordingly,the Zn-ion battery using NiCoP/NiCo_(2)S_(4) as the cathode delivers a high specific capacity(265.1 mA h g^(−1) at 5 A g^(−1)),a long-term cycling stability(96.9%retention after 5000 cycles),and a competitive energy density(444.7W h kg^(−1) at the power density of 8.4 kW kg^(−1)).This work therefore provides a simple phosphating-assisted interfacial engineering strategy to construct heterostructured electrode materials with rich interfaces for the development of high-performance energy storage devices in the future.