ABSTRACT 2D molecular ferroelectrics have attracted much attention due to their advantages such as low cost, easy processing, and structural tunability. However, the impacts of alkyl chain length on their bandgap, ferroelectric, and photoelectric properties remain unclear. Herein, we present a novel 2D molecular ferroelectric [C 6 N 2 H 18 ]PbI 4 with a P c polar monoclinic structure, a direct bandgap of 2.30 eV, a room‐temperature ferroelectricity with a maximum polarization ( P m ) of 3.5 µC cm −2 . Remarkable polarization‐enhanced photoelectric performance has been achieved, yielding a maximum V oc of ∼ 0.72 V and J sc of ∼ 5.62 µA cm −2 . The impacts of chain length of diverse alkylamines spacer cations on bandgap, ferroelectric, and photoelectric of the homologous APbI 4 system (A for 1,4‐diaminobutane, 1,6‐hexamethylenediamine, and 1,8‐diaminooctane) have been systematically investigated. The elongation of alkyl chain length induces a gradual decline in P m , while simultaneously expanding the optical bandgap and notably enhancing device stability. This work provides a new perspective for the performance optimization of 2D molecular ferroelectrics toward next‐generation optoelectronic devices.

The In2S3 attracts considerable interest owing to its favorable bandgap and superior photoelectric properties, and emerges as a highly promising candidate host for the realization of intermediate band. Herein, the electronic structures of group IV elements (Si, Ge, Sn, and Pb) and group V elements (P, As, Sb, and Bi)-doped In2S3 have been systematically investigated with the hybrid density functional calculations. For all impurity semiconductors, an intermediate band is introduced within the bandgap of In2S3 host. In particular, the generated intermediate band is isolated, delocalized and partially occupied with the incorporation of Ge and Pb dopants. It is interesting that a transition from indirect to quasi-direct bandgap is also observed in Pb-doped In2S3 semiconductor. The intermediate band primarily originates from the hybridization of dopant-ns and S-3p states. Due to the presence of the intermediate band, the optical absorption capacity of IB-containing semiconductor is significantly enhanced. The photoelectric conversion efficiency eta of the Ge-doped In2S3 intermediate band solar cell is estimated to reach as high as 56.7%, which exceeds the Shockley-Queisser efficiency limit (40.7%). Hence, these theoretical results would provide valuable guidance for the design of In2S3-based intermediate band semiconductors for photovoltaic applications.

As a vital part of the water tower of Asia, water cycle changes in the Pamir Plateau have significant impacts on the climate of the arid inland regions of Central Asia. Using the high-precision precipitation dataset known as TPHiPr, a significant wetting trend in spring and a drying trend in summer over the Pamir Plateau from 1979 to 2020 is identified in this study. Further analysis reveals that dynamic factors are more important than thermodynamic factors in driving these precipitation trends throughout both seasons. The dynamic factors are closely linked to the anticyclonic trend in spring and the cyclonic trend in summer, both of which are influenced by long-term trends in atmospheric circulation. Furthermore, the warming trend of sea surface temperature (SST) in the North Atlantic (NA) may impact atmospheric circulation over the Pamir Plateau. In spring, the pronounced meridional gradient of potential vorticity over the NA facilitates the northward propagation of the wave train induced by the warm SST along the great circle path, resulting in an anticyclonic trend over the Pamir Plateau. In summer, the wave train excited by the heat source at 60 degrees N propagates eastward along the jet stream, leading to a cyclonic anomaly over the Pamir Plateau. The results were also verified in the Atlantic-pacemaker simulations. Overall, this study highlights the distinct wave trains induced by the NA SST warming trend in spring and summer. These distinct wave trains provide different dynamic conditions contributing to the observed drying and wetting trends over the Pamir Plateau.

Study region: Altay region in Northwest China. Study focus: The frequency, intensity, and impacts of spring snowmelt flood disasters have changed significantly. However, there is still a limited understanding of snowmelt floods and their causes in Altay. In this study, we focus on the essential characteristics of 49 spring snowmelt flood disasters and explore the related atmospheric circulation anomalies and local thermal conditions that contributed to extreme temperature rises, triggering warming-type flood events. New hydrological insights for the region: From 1984-2018, spring warming-type snowmelt floods predominated in Altay. These floods were associated with a deep high-pressure system over northern Central Asia, which intensified and shifted northward leaing to positive geopotential height anomalies. Additionally, southeasterly anomalies at 850 hPa significantly influenced these events. Zonal cross-sections of average air temperature and vertical circulation anomalies exhibit positive and descending motion anomalies, with the 0 degrees C layer height rises. The thermal conditions in spring show distinct characteristics, including enhanced upward energy flux from the surface, which favors to local warming in both March and April. In May, downward motion due to reduced cloud cover, resulting in an increase in net shortwave radiation flux reaching the surface. These results provide valuable insights for further exploration of the precursor signals associated with snowmelt floods in the Altay.

BackgroundGALAD model is a statistical model used to estimate the possibility of hepatocellular carcinoma (HCC) in patients with chronic liver disease. Many studies with other ethnic populations have shown that it has high sensitivity and specificity. However, whether this model can be used for Chinese patients remains to be determined. Our study was conducted to verify the performance of GALAD model in a Chinese cohort and construct a new model that is more appropriately for Chinese populations.MethodsThere are total 512 patients enrolled in the study, which can be divided into training set and validation set. 80 patients with primary liver cancer, 139 patients with chronic liver disease and 87 healthy people were included in the training set. Through the ROC(receiver operating characteristic) curve analysis, the recognition performance of GALAD model for liver cancer was evaluated, and the GAADPB model was established by logistic regression, including gender, age, AFP, DCP, total protein, and total bilirubin. The validation set (75 HCC patients and 130 CLD patients) was used to evaluate the performance of the GAADPB model.ResultThe GALAD and GAADPB achieved excellent performance (area under the receiver operating characteristic curve [AUC], 0.925, 0.945), and were better than GAAP, Doylestown, BALAD-2, aMAP, AFP, AFP-L3%, DCP and combined detection of AFP, AFP-L3 and DCP (AUCs: 0.894, 0.870, 0.648, 0.545, 0.879, 0.782, 0.820 and 0.911) for detecting HCC from CLD in the training set. As for early stage of HCC (BCLC 0/A), GAADPB had the best sensitivity compared to GALAD, ADP and DCP (56.3%, 53.1%, 40.6%, 50.0%). GAADPB had better performance than GALAD in the test set, AUC (0.896 vs 0.888).ConclusionsThe new GAADPB model was powerful and stable, with better performance than the GALAD and other models, and it also was promising in the area of HCC prognosis prediction. Further study on the real-world HCC patients in China are needed.

This study performed an observational analysis to examine the interdecadal variation in the frequency of extreme high-temperature events (EHEs) during spring over the western Tianshan mountain, China, which were characterized by relatively fewer (more) EHEs during 1983–1996 (2000–2015). A composite analysis indicated that the interdecadal increase in EHEs is closely related to a deep dynamic anomalous Iranian high. Under the control of this high system, the water vapor content decreased over the western Tianshan mountains, and atmospheric circulation was dominated by a descending motion. Both were attributed to the decreased cloud cover, inducing a cloud-forced net solar radiation increase. The short-wave radiation flux and sensible heat flux reaching the surface increased, and the net surface heat flux increased cumulatively, which was conducive to the surface temperature increase and EHE occurrence. The anomalous Iranian high responsible for ECEs occurrence was related to the air-sea interaction over the Atlantic and Indo-Pacific. The latitudinal sea surface temperature (SST) difference between the tropical western Pacific and the western Indian Ocean directly strengthens the Walker circulation and thus enhances the Iranian high. In addition, the anomalous Iranian high was affected by the atmospheric wave trains at middle latitude, which was triggered by the warm anomaly of the Atlantic SST.

As a major source of moisture in Central Asia (CA), snowfall may significantly impact agriculture and economics in CA. The study has investigated the dominant modes of snowfall frequency during winter over CA and associated mechanisms. The first EOF mode (EOF1) of snowfall frequency corresponds to a homogeneous pattern over CA. In contrast, the second EOF mode (EOF2) is characterized by reversed anomalies over northern and southern CA. The mechanisms of the interannual variation of the two leading modes are different. EOF1 is influenced by the sea surface temperature anomalies (SSTA) over the North Atlantic and eastern tropical Pacific. Positive SSTA in the eastern tropical Pacific may stimulate a zonal wave train that propagates eastward and induce an anomalous cyclone in CA. The anomalous cyclone associated with ascending motions and water vapor transport convergence can contribute to increased snowfall frequency over CA. Besides, the interaction between the North Atlantic Oscillation and North Atlantic triple SSTA may also strengthen the zonal wave train. EOF2 is affected by the stratospheric polar vortex which is related to the wave reflections in winter. The wave reflections may strengthen the coupling of atmospheric circulation in the stratosphere and the troposphere, inducing a positive (negative) geopotential height anomaly over southern (northern) CA. These geopotential height anomalies may contribute to increased and decreased synoptic-scale wave activity over northern and southern CA which is conducive to the dipole mode of snowfall frequency over CA.

Despite significant advances in seasonal climate forecasts, the reliability of both dynamical and empirical models for the Indian Ocean Dipole (IOD) prediction is still limited to a lead time of one season or less. In this study, the skill of the NCEP Climate Forecast System version 2 (CFSv2) for the IOD prediction during the period 1982–2014 is evaluated. The results indicate that the model performance for the IOD prediction is the worst in spring among the four seasons, which is manifested in the fact that a skilful prediction of spring IOD event is limited to a lead time of only about 1–2 months. To improve the forecast of spring IOD events, a physical‐empirical (PE) model and a convolutional neural network (CNN) model are established in the present study. The IOD in April–May–June (AMJ) is taken as the predictand, and the CFSv2‐predicted sea surface height (SSH) in AMJ and the observed Laptev sea ice in the preceding December are used as the two predictors. The original CFSv2‐predicted IOD time series has an insignificant correlation with the observed IOD time series with a temporal correlation coefficient (TCC) of 0.03; the PE model (CNN model) can largely improve the IOD prediction with a TCC of 0.74 (0.77) between the PE‐model‐predicted (CNN‐model‐predicted) IOD and the observed IOD during AMJ. Thus, the PE model and the CNN model developed in the present study can be applied to improve the IOD predictions from numerical models in the future.

The CdIn2S4 semiconductor is considered a potential host for the implementation of intermediate band solar cells due to its ideal bandgap value and excellent photoelectric property. In this paper, the electronic structures of group IV elements (Si, Ge, Sn, and Pb)-doped CdIn2S4 have been investigated by using hybrid density functional calculations. In the case of Ge, Sn, and Pb doping, an isolated and partially occupied intermediated band with delocalized characteristics could be created in the bandgap of the host. The results of the projected density of states reveal that the intermediated band is derived from the hybridization between the S-3p and dopant-ns states. Thanks to the assistance of the impurity band, the optical absorption ability of the intermediate band semiconductor is greatly enhanced. Based on the detailed balance theory, the theoretical efficiencies of intermediate band solar cells made by Ge- and Pb-doped CdIn2S4 are estimated to be 45.0% and 49.2%, respectively, which are superior to the Shockley and Queisser limit (40.7%) of a single junction photovoltaic device. Moreover, the experimental synthesis of these impurity semiconductors is relatively feasible because substitutional doping at the octahedral position is energetically favorable. These findings would be helpful to the development of a high-efficiency intermediate band solar cell.

The summer season raindrop size distribution (DSD) characteristics and their important applications, based on a PARSIVEL2 disdrometer installed in Zhaosu over the western Tianshan Mountains, China, in 2020–2021 are studied. Our analysis reveals that, for total rainfall and different rainfall types, the DSD in Zhaosu follows the normalized gamma distribution model, and convective rainfall has a higher raindrop concentration than stratiform rainfall at all diameters. For stratiform rainfall, the mean value of mass-weighted mean diameter (Dm) is lower than that of convective DSD, while the mean value of normalized intercept parameter (log10 Nw) is higher than that of convective DSD, and the summer season convective rainfall in Zhaosu is continental convective rainfall according to the conventional classification, which is characterized by relatively larger Dm and lower log10 Nw values. The derived µ–∧ relation in Zhaosu exhibits some differences from those reported in eastern, southern, and northern China and the Tibetan Plateau. Furthermore, derived Z–R relations for stratiform and convective rainfall in Zhaosu are compared with those from other regions. Analysis shows that the empirical relation of Z = 300R1.4 (widely used), strongly overestimates the R of convective precipitation in Zhaosu. The C-band polarimetric radar rainfall estimation relations are derived, and the R(Zh,Zdr) and R(Kdp,Zdr) relations perform the best in quantitative precipitation estimation. Moreover, the empirical Dm–Zku and Dm–Zka relations are derived, which are beneficial to the improvement of rainfall retrieval algorithms of the GPM DPR. Lastly, rainfall kinetic energy relations proposed in this study can be used to better assess rainfall erosivity. The empirical relationships of DSD evaluated in this study provide an opportunity to (1) improve rainfall retrieval algorithms for both ground-based and remote sensing radars and to (2) enhance rainfall kinetic energy estimates in rainfall erosivity studies based on disdrometer and GPM DPR.

Characteristics of orographic raindrop size distribution (DSD) in the Tianshan Mountains, China are studied based on second-generation OTT Particle Size Velocity disdrometer installed at the top (Tianchi, 43.88°N, 88.12°E, 1941.8 m above sea level) and the foot stations (Urumqi, 43.79°N, 87.65°E, 935 m above sea level) from June to August 2020 and 2021. For the overall rainfall, the concentration of drops of all sizes in Tianchi is greater than that in Urumqi. Furthermore, in both regions, small drops (diameter < 1 mm) primarily contributed to the total number concentration, and both small drops and mid-size drops (1 ≤ diameter ≤ 3 mm) had important contributions to the rainfall rate. For the DSD of different rain rate classes, the concentration of mid-size drops is higher in the first two rain rate classes in Urumqi than that in Tianchi, while the opposite is true when the rain rate exceeds 5 mm h−1. Meanwhile, the concentration of small drops is higher in the first two rain rate classes in Tianchi than that in Urumqi, while the opposite is true for small drops in partial diameter, as the rain rate class increases. In addition, two kinds of rainfall kinetic energy (rainfall kinetic energy flux: KEtime and the rainfall kinetic energy content: KEmm) and various rainfall kinetic energy-rainfall intensity relations (KEtime/KEmm –R relations) were derived based on DSD data. Further, the possible thermo-dynamical and microphysical processes that cause the dissimilarities in DSD between Urumqi and Tianchi are also discussed in this work. Affected by the difference in altitude between the top and the foot stations, the foot station had relatively hotter and drier conditions in the near-surface layer than the top station during the rainfall period, so the evaporation rate of small drops was higher at the foot station than that at the top station, resulting in fewer small drops at the foot station. Meanwhile, lower black body temperature, and stronger seeder-feeder mechanism at the top station during the rainfall period may be partly responsible for more mid-size drops and large size drops (diameter > 3 mm) at the top station

Site preferences of Eu2+ ions on the Ba2+ sites and the Ca2+ sites were discovered in the mixed cation borosilicate Ba2CaB2Si4O14 (BCBSO). Eu2+ ions are more likely to locate on the Ba2+ sites over the Ca2+ sites according to the Density Functional Theory (DFT) calculation and the photoluminescence spectrum analysis. The emission band centered at 408 nm was confirmed to be generated from the Eu2+ ions located on the Ba2+ sites, while the emission band centered at 548 nm was considered to be generated from the Eu2+ ions on the Ca2+ sites. Dual sites occupation results in a collective emission band covering 380 nm-780 nm in BCBSO:Eu phosphors. By further doping with Sr2+ ions, crystal environment of the luminescence centers could be well modulated, resulting in the tunable emission from yellow to white under UV excitation. The photoluminescence quantum yield was significantly improved from 17.9% to 36.8%. Finally, a series of white LEDs with tunable CCT (from 5132 K to 3402 K) and high Ra (reach up to 89.6) were obtained using the Ba2(1-y/3)Ca(1-y/3)SryB2Si4O14:0.03Eu single-phase white light emission phosphors.

In this study, the grounded-based Ka-band millimetre-wave cloud radar (MMCR) is used to analyse the cloud characteristics over the western Tianshan mountains. The cloud top height (CTH) obtained by MMCR is verified by comparing it with the Fengyun-4A (FY-4A) observations. Overall, the MMCR-obtained CTHs are attenuated and lower than the FY-4A-obtained CTHs under precipitation conditions. Thus, the FY-4A data is used to complement MMCR data when there is rainfall. The diurnal, seasonal variation and vertical structures of the cloud are further examined using the combination of MMCR and FY-4A. The result indicates that the CTH and cloud base height (CBH) are highest in summer and lowest in winter. Also, clouds tend to form frequently at night in spring, summer, and winter. Although in autumn, clouds tend to form most frequently in the morning. This may be related to the diurnal variation of temperature, humidity, wind speed, and wind direction. Moreover, the CTHs occur most frequently at heights of 8-9 km in spring and autumn, 9-10 km in summer, and 7-8 km in winter. The high CTHs caused by the strong convective activities in summer may be related to sufficient water vapour transport. These corrected CTH data are also used to classify cloud types, the results indicate that the proportion of high clouds is highest in summer, while the proportion of medium clouds is lower than in the other three seasons. Also, the average CTH of the low, medium, and high clouds is highest in summer and lowest in winter.

The intermediate band semiconductor of AgGa1-xCrxS2 is investigated by the first principles calculations and further confirmed by the experimental results. The band structures of pure and Cr-doped crystals were calculated and it is shown that the crystal with a direct energy band gap of about 0.95 eV for AgGaS2. Because of Cr dopant, a metallic intermediate band (IB) is successfully formed in the host. From the partial density of states (PDOS) of Cr-doped AgGaS2, the IB mainly comes from the hybridization of the Cr-3d and S-3p states. Based on the theoretical predications, the Cr-doped AgGaS2 is synthesized by the high-temperature solid state reaction. Two extra absorption responses are detected in the absorption spectra. The optical absorption coefficients are enhanced in the visible radiation range due to the formation of metallic and isolated IB. Therefore, Cr-doped AgGaS2 with an intermediate band is suggested as a potential material to enhance the efficiency of solar cells.

A novel quaternary oxysulfide, FeOCuS has been successfully synthesized with a tetragonal anti-PbO-type structure and a visible-light bandgap of about 1.37 eV. Driven by only a 0.4 V bias voltage under simulated AM 1.5 G illumination, a high photocurrent density of 3.89 mA cm-2 has been achieved, revealing the potential optoelectronic applications.

研究表面接枝碳纳米管(CNTs)的电阻焊发热元件对热固性复合材料焊接头的增强作用.利用玻璃纤维增强聚醚酰亚胺(GF/PEI)薄片制备表面塑化的碳纤维增强双马树脂(CF/BMI)层合板;继而利用表面接枝CNTs的不锈钢网作为电阻焊的发热元件进行焊接.对接枝不同处理时长CNTs的不锈钢网的焊接件进行单搭接拉伸剪切实验,以评估焊接头的强度.结果表明:不锈钢网表面的浸润性明显改善,焊接头的强度得到显著提升.断口分析显示,在CNTs的增强作用下,失效模式由被焊接件表面纤维的轻微破坏转变为塑化薄层的完全撕裂.

静电纺丝技术是一种新颖、高效且简单的制备连续纳米纤维的方法,纳米复合纤维膜的优异特点赋予了纳米吸波剂新的吸波通道.本文采用静电纺丝工艺制备Fe3O4/PEK-C纳米复合纤维膜,利用SEM和TGA表征纳米复合纤维膜的微观形貌和热稳定性,用矢量网络分析仪测试样品在8.2-12.4 GHz的电磁参数与吸波性能.结果表明,Fe3O4/PEK-C纳米复合纤维膜呈现出超细纤维彼此交织构成的立体网络结构,其热稳定性、复介电常数和复磁导率均随着Fe3O4含量的增加而增加,介电损耗和磁损耗得到加强.当纳米复合纤维膜的厚度为1.8 mm时,其反射损耗在整个测试波段均处于-5 dB以下,-10 dB以下有效吸收频宽为2 GHz,频率在8.6 GHz处吸收强度达到最大值-15.4 dB.预期可作为隐身复合材料的吸波功能层.

The performance requirements for Global Navigation Satellite Systems (GNSS) are becoming more demanding as the range of mission-critical vehicular applications, including the Unmanned Aerial Vehicle (UAV) and ground vehicle-based applications, increases. However, the accuracy and reliability of GNSS in some environments, such as in urban areas, are often affected by non-line-of-sight (NLOS) signals and multipath effects. It is therefore essential to develop an effective fault detection scheme that can be applied to GNSS observations so as to ensure that the vehicle positioning can be calculated with a high accuracy. In this paper, we propose an online dataset based faulty GNSS measurement detection and exclusion algorithm for vehicle positioning that takes account of the NLOS/multipath affected scenarios. The proposed algorithm enables a real-time online dataset based fault detection and exclusion scheme, which makes it possible to detect multiple faults in different satellites simultaneously and accurately, thereby allowing real-time quality control of GNSS measurements in dynamic urban positioning applications. The algorithm was tested with simulated/artificial step errors in various scenarios in the measured pseudoranges from a dataset acquired from a UAV in an open area. Furthermore, a real-world test was also conducted with a ground-vehicle driving in a dense urban environment to validate the practical efficiency of the proposed algorithm. The UAV based simulation exhibits a fault detection rate of 100% for both single and multi-satellite fault scenarios, with the horizontal positioning accuracy improved to about 1 metre from tens of metres after fault detection and exclusion. The ground vehicle-based real test shows an overall improvement of 26.1% in 3D positioning accuracy in an urban area compared to the traditional least square method.

This study investigates the relationship and underlying mechanisms between the Indian Ocean Dipole (IOD) and Arctic sea ice. The results reveal that the preceding December sea ice over the Laptev Sea plays an important role in the formation of positive IOD conditions during April–June (AMJ). In years with positive December Laptev sea ice anomalies, the zonal wavenumber-1 (ZWN1) planetary wave component is stimulated at middle and high latitudes. The high-latitude ZWN1 propagates upward to the stratosphere and downward to the troposphere in December, affects the atmospheric circulation over the North Atlantic, and further leads to a warm sea surface temperature anomaly (SSTA) that persists until the following February. The mid-latitude ZWN1 propagates upward to the stratosphere in January and downward to the troposphere in February, contributing to the positive 200-hPa geopotential height anomaly (GPHA) in the subtropical Atlantic. The ascending anomaly induced by the warm SSTA and the positive 200-hPa GPHA in the subtropical Atlantic in February are favorable for effective Rossby wave source formation and stimulate an atmospheric wave train that forms an anomalous cyclone over the northern Arabian Sea, which contributes to enhanced convection over North India, stimulating an anomalous anticyclone over East India and leading to reduced convection over the northeastern Indian Ocean in March. The reduced convection over the northeastern Indian Ocean may lead to strengthened equatorial easterly winds and further contribute to positive IOD conditions in AMJ. These findings indicate that December Laptev sea ice may contribute to AMJ IOD conditions.

采用氧气介质阻挡放电(DBD)等离子体处理PBO纤维表面,用以改善PBO纤维与双马来酰亚胺(BMI)树脂之间的界面粘结性能.结果 表明,用氧气等离子体处理PBO纤维能大幅度提高PBO/BMI复合材料的层间剪切强度(ILSS)值,最佳处理条件为功率30 W/m3、时间24s,ILSS值从43.9 MPa提高到62.0 MPa.经过氧气DBD等离子体处理的PBO纤维其表面的氧含量明显提高,氮含量变化不大,甚至在过度处理时降低;官能团-O-C=O基团的含量从0提高到3.16％,-C-O-的含量也明显提高;在氧气DBD等离子体处理后的PBO纤维表面产生大量凹凸不平和沟壑,使纤维表面的粗糙度提高.而表面氧含量的提高和表面形貌与粗糙度的变化,是PBO/BMI复合材料ILSS值提高的重要原因.单丝拉伸实验结果表明,适当的DBD等离子体处理不会对PBO纤维表面产生不良影响,不影响其在复合材料中的作用.