Reliability evaluation of IGBT power module on electric vehicle using big data

There are challenges to the reliability evaluation for insulated gate bipolar transistors(IGBT)on electric vehicles,such as junction temperature measurement,computational and storage resources.In this paper,a junction temperature estimation approach based on neural network without additional cost is proposed and the lifetime calculation for IGBT using electric vehicle big data is performed.The direct current(DC)voltage,operation current,switching frequency,negative thermal coefficient thermistor(NTC)temperature and IGBT lifetime are inputs.And the junction temperature(T_(j))is output.With the rain flow counting method,the classified irregular temperatures are brought into the life model for the failure cycles.The fatigue accumulation method is then used to calculate the IGBT lifetime.To solve the limited computational and storage resources of electric vehicle controllers,the operation of IGBT lifetime calculation is running on a big data platform.The lifetime is then transmitted wirelessly to electric vehicles as input for neural network.Thus the junction temperature of IGBT under long-term operating conditions can be accurately estimated.A test platform of the motor controller combined with the vehicle big data server is built for the IGBT accelerated aging test.Subsequently,the IGBT lifetime predictions are derived from the junction temperature estimation by the neural network method and the thermal network method.The experiment shows that the lifetime prediction based on a neural network with big data demonstrates a higher accuracy than that of the thermal network,which improves the reliability evaluation of system.

单原子修饰原子簇的多配位Cu基催化剂上CO_(2)高选择性电还原CO的研究

随着可再生能源发电成本的持续下降和电催化技术的迅猛发展,人们开始重新审视能源燃料和化学品的生产方式.近年来,H2O和CO_(2)等小分子的电催化转化反应已成为研究热点.特别是,CO_(2)还原反应(CO_(2)RR)作为将CO_(2)电化学还原为高附加值产品的一项变革性的技术,备受关注.在CO_(2)RR的众多产物中,CO具有重要的地位,它可以通过费托合成工艺直接用于合成醇、醛、酮、酸及烃等化工产品.然而,将CO_(2)电催化转化为CO在整体效率方面仍面临诸多挑战.因此,设计并制备高效、经济且耐用的电催化剂已成为CO_(2)RR领域发展的研究重点.本文采用简单的配体辅助负载策略制备了铜单原子修饰的铜原子簇催化剂(Cu SA/ACs).球差校正的高角度环形暗场扫描透射电子显微镜结果表明,铜以单原子和原子簇的形式存在.采用X射线吸收精细结构谱和X射线光电子能谱(XPS)分析了铜原子的电子和配位结构,证明了Cu-N键和Cu-Cu键的存在.电化学性能测试表明,与铜单原子催化剂(Cu SACs)相比,Cu SA/ACs催化剂展现了较好的CO_(2)RR性能,其CO的转化法拉第效率从27.15%提高到98.94%,电流密度是Cu SACs的3.6倍.此外,将该催化剂组装成流动电解池,在600 mA cm-2的高电流密度下,CO选择性达到93.06%,阴极的最高能量效率达61.9%,优于大多数CO_(2)还原制备CO的催化剂.为了明确铜单原子组分引入对铜原子簇性能提升的原因,通过电化学原位红外光谱研究催化剂在服役条件下的表面物种吸附.结果表明,Cu SACs催化剂的单原子活性中心在CO_(2)RR过程中受到H2析出反应的困扰,活性中心表面的吸附物种主要为H2O而不是CO_(2),从而导致CO_(2)还原性能较差;在Cu SA/ACs催化剂表面,其活性中心由单原子和原子簇协同组成,CO_(2)主要吸附在原子簇上,单原子和原子簇协同作用促进了H2O的解离过程,为CO_(2)质子化提供丰富的活性氢,进一步加快CO_(2)RR的反应动力学.密度泛函计算和差分电荷密度分析结果表明,单原子的引入优化了原子簇的局域电子结构,诱导d带中心靠近费米能级,从而优化了*COOH中间体的形成能和CO的脱附过程.综上,本文通过合理的活性位点设计实现了多位点的耦合协同,提升了铜基催化剂对于CO_(2)RR的催化活性,优化了铜基催化剂上CO_(2)到CO的选择性,通过机理研究加深了对铜基催化剂上CO_(2)转化模式的认识,为设计高效催化剂提供新思路.

Improved multi-scale inverse bottleneck residual network based on triplet parallel attention for apple leaf disease identification

Accurate diagnosis of apple leaf diseases is crucial for improving the quality of apple production and promoting the development of the apple industry. However, apple leaf diseases do not differ significantly from image texture and structural information. The difficulties in disease feature extraction in complex backgrounds slow the related research progress. To address the problems, this paper proposes an improved multi-scale inverse bottleneck residual network model based on a triplet parallel attention mechanism, which is built upon ResNet-50, while improving and combining the inception module and ResNext inverse bottleneck blocks, to recognize seven types of apple leaf(including six diseases of alternaria leaf spot, brown spot, grey spot, mosaic, rust, scab, and one healthy). First, the 3×3 convolutions in some of the residual modules are replaced by multi-scale residual convolutions, the convolution kernels of different sizes contained in each branch of the multi-scale convolution are applied to extract feature maps of different sizes, and the outputs of these branches are multi-scale fused by summing to enrich the output features of the images. Second, the global layer-wise dynamic coordinated inverse bottleneck structure is used to reduce the network feature loss. The inverse bottleneck structure makes the image information less lossy when transforming from different dimensional feature spaces. The fusion of multi-scale and layer-wise dynamic coordinated inverse bottlenecks makes the model effectively balances computational efficiency and feature representation capability, and more robust with a combination of horizontal and vertical features in the fine identification of apple leaf diseases. Finally, after each improved module, a triplet parallel attention module is integrated with cross-dimensional interactions among channels through rotations and residual transformations, which improves the parallel search efficiency of important features and the recognition rate of the network with relatively small computational costs while the dimensional dependencies are improved. To verify the validity of the model in this paper, we uniformly enhance apple leaf disease images screened from the public data sets of Plant Village, Baidu Flying Paddle, and the Internet. The final processed image count is 14,000. The ablation study, pre-processing comparison, and method comparison are conducted on the processed datasets. The experimental results demonstrate that the proposed method reaches 98.73% accuracy on the adopted datasets, which is 1.82% higher than the classical ResNet-50 model, and 0.29% better than the apple leaf disease datasets before preprocessing. It also achieves competitive results in apple leaf disease identification compared to some state-ofthe-art methods.

高空抛物罪的司法适用省思

《中华人民共和国刑法修正案(十一)》将高空抛物行为单独入罪,体现了党和国家对保障人民群众“头顶上的安全”的高度重视。司法实践中,认定高空抛物罪存在内涵和边界不够清晰明确的问题。一方面,对于符合犯罪构成的行为,要依法予以严厉打击;另一方面,要准确区分民事侵权行为与刑事犯罪行为、此罪与彼罪,避免过度适用,从而真正贯彻立法本意。同时,要进一步加强法律监督与宣传引导,防止泛化而成为“口袋罪名”,真正打击高空抛物犯罪行为,维护人民群众合法权益。

Inflammation in diabetic retinopathy: possible roles in pathogenesis and potential implications for therapy

Diabetic retinopathy, characterized as a microangiopathy and neurodegenerative disease, is the leading cause of visual impairment in diabetic patients. Many clinical features observed in diabetic retinopathy, such as capillary occlusion, acellular capillaries and retinal non-perfusion, aggregate retinal ischemia and represent relatively late events in diabetic retinopathy. In fact, retinal microvascular injury is an early event in diabetic retinopathy involving multiple biochemical alterations, and is manifested by changes to the retinal neurovascular unit and its cellular components. Currently, intravitreal anti-vascular endothelial growth factor therapy is the firstline treatment for diabetic macular edema, and benefits the patient by decreasing the edema and improving visual acuity. However, a significant proportion of patients respond poorly to anti-vascular endothelial growth factor treatments, indicating that factors other than vascular endothelial growth factor are involved in the pathogenesis of diabetic macular edema. Accumulating evidence confirms that low-grade inflammation plays a critical role in the pathogenesis and development of diabetic retinopathy as multiple inflammatory factors, such as interleukin-1β, monocyte chemotactic protein-1 and tumor necrosis factor-α, are increased in the vitreous and retina of diabetic retinopathy patients. These inflammatory factors, together with growth factors such as vascular endothelial growth factor, contribute to blood-retinal barrier breakdown, vascular damage and neuroinflammation, as well as pathological angiogenesis in diabetic retinopathy, complicated by diabetic macular edema and proliferative diabetic retinopathy. In addition, retinal cell types including microglia, Müller glia, astrocytes, retinal pigment epithelial cells, and others are activated, to secrete inflammatory mediators, aggravating cell apoptosis and subsequent vascular leakage. New therapies, targeting these inflammatory molecules or related signaling pathways, have the potential to inhibit retinal inflammation and prevent diabetic retinopathy progression. Here, we review the relevant literature to date, summarize the inflammatory mechanisms underlying the pathogenesis of diabetic retinopathy, and propose inflammation-based treatments for diabetic retinopathy and diabetic macular edema.

两步法制备MoSe_(2)薄膜的结构与摩擦学性能

为了扩大固体润滑剂MoSe_(2)的应用领域,采用两步法制备MoSe_(2)薄膜。首先通过磁控溅射法在基底上沉积MoSe_(x)预制层,随后在Se蒸气中进行硒化处理得到MoSe_(2)薄膜。研究溅射和硒化过程对薄膜结构和摩擦学性能的影响。结果表明,两步法所制备的MoSe_(2)薄膜呈(002)晶面平行于基底的择优取向,结晶度得到提高。所制备的MoSe_(2)薄膜在空气环境下具有良好的耐磨性和润滑性能,其最低平均摩擦因数为0.0443,比磨损率为1.03×10^(−5) mm^(3)/(N·m)。此外,还探讨了MoSe_(2)薄膜的润滑机理,可通过黏附机制和填充修复机制起到减摩润滑的作用。

p‑Type Two‑Dimensional Semiconductors:From Materials Preparation to Electronic Applications

Two-dimensional(2D)materials are regarded as promising candidates in many applications,including electronics and optoelectronics,because of their superior properties,including atomic-level thickness,tunable bandgaps,large specific surface area,and high carrier mobility.In order to bring 2D materials from the laboratory to industrialized applications,materials preparation is the first prerequisite.Compared to the n-type analogs,the family of p-type 2D semiconductors is relatively small,which limits the broad integration of 2D semiconductors in practical applications such as complementary logic circuits.So far,many efforts have been made in the preparation of p-type 2D semiconductors.In this review,we overview recent progresses achieved in the preparation of p-type 2D semiconductors and highlight some promising methods to realize their controllable preparation by following both the top-down and bottom-up strategies.Then,we summarize some significant application of p-type 2D semiconductors in electronic and optoelectronic devices and their superiorities.In end,we conclude the challenges existed in this field and propose the potential opportunities in aspects from the discovery of novel p-type 2D semiconductors,their controlled mass preparation,compatible engineering with silicon production line,high-κdielectric materials,to integration and applications of p-type 2D semiconductors and their heterostructures in electronic and optoelectronic devices.Overall,we believe that this review will guide the design of preparation systems to fulfill the controllable growth of p-type 2D semiconductors with high quality and thus lay the foundations for their potential application in electronics and optoelectronics.

Defects and asymmetries in the visual pathway of non-human primates with natural strabismus and amblyopia

Strabismus and amblyopia are common ophthalmologic developmental diseases caused by abnormal visual experiences. However, the underlying pathogenesis and visual defects are still not fully understood. Most studies have used experimental interference to establish diseaseassociated animal models, while ignoring the natural pathophysiological mechanisms. This study was designed to investigate whether natural strabismus and amblyopia are associated with abnormal neurological defects. We screened one natural strabismic monkey(Macaca fascicularis) and one natural amblyopic monkey from hundreds of monkeys, and retrospectively analyzed one human strabismus case. Neuroimaging, behavioral,neurophysiological, neurostructural, and genovariation features were systematically evaluated using magnetic resonance imaging(MRI), behavioral tasks, flash visual evoked potentials(FVEP),electroretinogram(ERG), optical coherence tomography(OCT), and whole-genome sequencing(WGS), respectively. Results showed that the strabismic patient and natural strabismic and amblyopic monkeys exhibited similar abnormal asymmetries in brain structure, i.e., ipsilateral impaired right hemisphere. Visual behavior, visual function, retinal structure, and fundus of the monkeys were impaired. Aberrant asymmetry in binocular visual function and structure between the strabismic and amblyopic monkeys was closely related, with greater impairment of the left visual pathway.Several similar known mutant genes for strabismus and amblyopia were also identified. In conclusion,natural strabismus and amblyopia are accompanied by abnormal asymmetries of the visual system,especially visual neurophysiological and neurostructural defects. Our results suggest that future therapeutic and mechanistic studies should consider defects and asymmetries throughout the entire visual system.

Experimental study on 3D internal penny-shaped crack propagation in brittle materials under uniaxial compression

Fractures are widely present in geomaterials of civil engineering and deep underground engineering.Given that geomaterials are usually brittle,the fractures can significantly affect the evaluation of underground engineering construction safety and the early warning of rock failure.However,the crack initiation and propagation in brittle materials under composite loading remain unknown so far.In this study,a three-dimensional internal laser-engraved cracking technique was applied to produce internal cracks without causing damage to the surfaces.The uniaxial compression tests were performed on a brittle material with internal cracks to investigate the propagation of these internal cracks at different dip angles under compression and shear.The test results show that the wing crack propagation mainly occurs in the specimen with an inclined internal crack,which is a mixed-ModeⅠ–Ⅱ–Ⅲfracture;in contrast,ModeⅠfracture is present in the specimen with a vertical internal crack.The fractography characteristics of ModeⅢfracture display a lance-like pattern.The fracture mechanism in the brittle material under compression is that the internal wing cracks propagate to the ends of the whole sample and cause the final failure.The initial deflection angle of the wing crack is determined by the participation ratio of stress intensity factors KII to KI at the tip of the internal crack.

α-硫辛酸对糖尿病大鼠肾脏的保护作用及其可能的机制

目的观察α-硫辛酸(ALA)对糖尿病大鼠肾脏的保护作用,并探讨其可能的作用机制。方法复制糖尿病大鼠模型,分为糖尿病组(DM组)、糖尿病硫辛酸组(ALA组),并设置正常对照组(NC组)。实验6周后处死全部大鼠,测定相应生化指标和相关氧化应激指标;HE、Masson染色观察肾组织的形态变化;免疫组织化学和Western blot检测大鼠肾组织中核转录共抑制因子(SnoN)、转化生长因子(TGF-β_1)、Collagen I、Collagen IV表达水平。结果 (1)DM组大鼠肾重/体重、血糖、血总胆固醇、三酰甘油、24 h尿蛋白均高于NC组,ALA组除了血糖外以上其余指标均低于DM组。(2)DM组总抗氧化物酶活性(T-AOC)、总超氧化物歧化酶活性(T-SOD)、过氧化氢酶活性(CAT)低于NC组,丙二醛含量(MDA)增多;ALA组T-AOC、T-SOD、CAT活性高于DM组,MDA含量降低。(3)病理检查显示,DM组大鼠出现肾纤维化改变,ALA组肾纤维化病变明显改善。(4)免疫组织化学和Western blot结果显示:与NC组相比,DM组大鼠SnoN蛋白水平降低,TGF-β_1、Collagen I和Collagen IV增高;与DM组相比,ALA组SnoN蛋白水平升高,TGF-β_1、Collagen I和Collagen IV降低。结论α-硫辛酸可以增强DM大鼠肾脏的抗氧化能力,上调SnoN蛋白的表达,从而抑制TGF-β_1信号通路而减少细胞外基质沉积,对糖尿病大鼠肾脏起到保护作用。

血小板/淋巴细胞比值对急性ST段抬高型心肌梗死患者PCI术后心肌无复流的预测价值

目的探讨血小板/淋巴细胞比值(PLR)对急性ST段抬高型心肌梗死(STEMI)患者经皮冠脉介入术(PCI)后心肌无复流的预测价值。方法选取2014年10月-2018年10月蚌埠市第二人民医院收治的STEMI患者118例,详细记录病史和体格检查结果,检测血小板计数(PLT)、淋巴细胞计数(LY),计算PLR;评估PCI术中情况,记录术中梗死相关动脉的病变情况,采用Gensini积分评价冠状动脉病变程度,采用TIMI血流分级将患者分为正常复流组(TIMI 3级)和无复流组(TIMI 0~2级)。结果两组患者年龄、性别构成比、高血压、糖尿病、吸烟、卒中、发病时间、Killip分级构成比比较,差异均无统计学意义(P >0.05);无复流组患者PLT、PLR和Gensini积分高于正常复流组(P <0.05),其余指标两组间比较,差异均无统计学意义(P >0.05),相关性分析显示PLR与Gensini积分呈正相关(r=0.581,P=0.006);多因素Logistic回归结果显示:PLR高[OR=2.737(95% CI:1.433,5.227)]和Gensini积分高[OR=1.490(95% CI:1.087,2.042)]为影响PCI术后心肌无复流的危险因素。ROC曲线分析结果显示以PLR为诊断模型变量,曲线下面积为0.751,以最大约登指数计算的诊断阈值为188.21,预测无复流的敏感性为70%,特异性为73%。结论 PLR与STEMI患者冠状动脉病变程度呈正相关,PLR对PCI术后心肌无复流具有一定的的预测价值。

High-frequency (50 Hz) electroacupuncture ameliorates cognitive impairment in rats with amyloid beta 1–42-induced Alzheimer＇s disease

Acupuncture has been shown to ameliorate cognitive impairment of Alzheimer’s disease.Acupoints and stimulation frequency influence the therapeutic effect of electroacupuncture.Rat models of Alzheimer’s disease were established by injecting amyloid beta 1–42（Aβ_（1–42））into the bilateral lateral ventricles.Electroacupuncture at 2,30,and 50 Hz was carried out at Baihui（GV20;15°obliquely to a depth of 2mm）and Shenshu（BL23;perpendicularly to 4–6 mm depth）,once a day for 20 minutes（each）,for 15 days,taking a break every 7 days.The Morris water maze test was conducted to assess the learning and memory.The expression levels of glycogen synthase kinase-3β（GSK-3β）,p Ser9-GSK-3β,p Tyr216-GSK-3β,amyloid precursor protein and Aβ_（1–40） in the hippocampus were determined by western blot assay.Results demonstrated that electroacupuncture treatment at different frequencies markedly improved learning and memory ability,increased synaptic curvatures,decreased the width of synaptic clefts,thickened postsynaptic densities,and downregulated the expression of GSK-3β,amyloid precursor protein,and Aβ_（1–40）.pSer9-GSK-3βexpression markedly decreased,while p Tyr216-GSK-3βexpression increased.High-frequency（50 Hz）electroacupuncture was more effective than low（2 Hz）or medium-frequency（30 Hz）electroacupuncture.In conclusion,electroacupuncture treatment exerts a protective effect against Aβ_（1–42）-induced learning and memory deficits and synapse-ultrastructure impairment via inhibition of GSK-3βactivity.Moreover,high-frequency electroacupuncture was the most effective therapy.

Spectral CT imaging as a new quantitative tool? Assessment of perfusion defects of pulmonary parenchyma in patients with lung cancer

Objective： This study investigated the capability of dual-energy spectral computed tomography （CT） to quantitatively evaluate lung perfusion defects that are induced by central lung cancer. Methods： Thirty-two patients with central lung cancer underwent CT angiography using spectral imaging. A univariate general linear model was conducted to analyze the variance of iodine concentration/CT value with three factors of lung fields. A paired t-test was used to compare iodine concentrations and CT values between the distal end of lung cancer and the corresponding area in the contralateral normal lung. Results： Iodine concentrations increased progressively in the far, intermediate and near ground sides in the normal lung fields at 0.60±0.28, 0.93±0.27 and 1.25±0.38 mg/mL, respectively （P〈0.001）. The same trend was observed for the CT values [-（840.64±49.08）, -（812.66±50.85） and -（760.83±89.17） HU, P〈0.001]. The iodine concentration （0.70±0.42 mg/mL） of the lung field in the distal end of lung cancer was significantly lower than the corresponding area in the contralateral normal lung （1.19±0.62 mg/mL） （t=-7.23, P〈0.001）. However, the CT value of lung field in the distal end of lung cancer was significantly higher than the corresponding area in the contralateral normal lung [-（765.29±93.34） HU vs. -（800.07±76.18） HU, t=3.564, P=0.001]. Conclusions： Spectral CT imaging based on the spectral differentiation of iodine is feasible and can quantitatively evaluate pulmonary perfusion and identify perfusion defects that are induced by central lung cancer. Spectral CT seems to be a promising technique for the simultaneous evaluation of both morphological and functional lung information.

Diffusion-tensor imaging as an adjunct to dynamic contrastenhanced MRI for improved accuracy of differential diagnosis between breast ductal carcinoma in situ and invasive breast carcinoma

Objective： To determine the value of diffusion-tensor imaging （DTI） as an adjunct to dynamic contrastenhanced magnetic resonance imaging （DCE-MRI） for improved accuracy of differential diagnosis between breast ductal carcinoma in situ （DCIS） and invasive breast carcinoma （IBC）. Methods： The MRI data of 63 patients pathologically confirmed as breast cancer were analyzed. The conventional MRI analysis metrics included enhancement style, initial enhancement characteristic, maximum slope of increase, time to peak, time signal intensity curve （TIC） pattern, and signal intensity on FS- T2WI. The values of apparent diffusion coefficient （ADC）, directionally-averaged mean diffusivity （D^vg）, exponential attenuation （EA）, fractional anisotropy （FA）, volume ratio （VR） and relative anisotropy （RA） were calculated and compared between DCIS and IBC. Multivariate logistic regression was used to identify independent factors for distinguishing IBC and DCIS. The diagnostic performance of the diagnosis equation was evaluated using the receiver operating characteristic （ROC） curve. The diagnostic efficacies of DCE- MRI, DWI and DTI were compared independently or combined. Results： EA value, lesion enhancement style and TIC pattern were identified as independent factor for differential diagnosis of IBC and DCIS. The combination diagnosis showed higher diagnostic efficacy than a single use of DCE-MRI （P=0.02）, and the area of the curve was improved from 0.84 （95% CI, 0.67-0.99） to 0.94 （95% CI, 0.85-1.00）. Conclusions： Quantitative DTI measurement as an adjunct to DCE-MRI could improve the diagnostic performance of differential diagnosis between DCIS and IBC compared to a single use of DCE-MRI.

Oxaliplatin plus S-1 or capecitabine as neoadjuvant or adjuvant chemotherapy for locally advanced gastric cancer with D2lymphadenectomy: 5-year follow-up results of a phase II-III randomized trial

Objective： To compare the effect of neoadjuvant chemotherapy （NACT） with adjuvant chemotherapy （ACT） using oxaliplatin plus S-1 （sex） or capecitabine （CapeOX） on gastric cancer patients with D2 lymphadenectomy. Methods： This was a two-by-two factorial randomized phase Ⅱ-Ⅲ trial, and registered on ISRCTN registry （No. ISRCTN12206108）. Locally advanced gastric cancer patients were randomized to neoadjuvant sex, neoadjuvant CapeOX, adjuvant sex, or adjuvant CapeOX arms. Primary analysis was performed on an intention- to-treat （ITT） basis using overall survival （OS） as primary endpoint. Results： This trial started in September 2011 and closed in December 2012 with 100 patients enrolled. Treatment completion rate was 56%, 52%, 38% and 30% in the four arms, respectively. NACT group had fewer dropouts due to unacceptable toxicity （P=0.042）. Surgical complication rate did not differ by the four groups （P=0.986）. No survival signifcant difference was found comparing NACT with ACT （P=0.664; 5-year-OS： 70% vs. 74% respectively）, nor between the sex and CapeOX groups （P=0.252; 5-year-OS： 78% vs. 66% respectively）. Subgroup analysis showed sex significantly improved survival in patents with diffuse type （P=0.048）. Conclusions： No significant survival difference was found between NACT and ACT. sex and CapeOX had good safety and efficacy as neoadjuvant regimens. Diffuse type patients may survive longer due to sex.

一维碳纳米管/二维二硫化钼混合维度异质结的原位制备及其电荷转移性能

一维(1D)材料与二维(2D)材料的结合可形成独特的混合维度异质结,其在继承2D/2D范德瓦尔斯异质结的独特物性之外,还具有丰富的堆叠构型,为进一步调控异质结的结构及性能提供了新的可操控自由度。p型1D单壁碳纳米管(SWCNT)与n型2D二硫化钼(MoS_(2))的结合,为调控异质结的能带结构及器件性能提供了丰富的选择。本文直接在高密度、手性窄分布的SWCNT定向阵列及无序薄膜表面原位生长MoS_(2),制备出高质量1D SWCNT/2D MoS_(2)混合维度异质结。深入分析形核点的表面形貌与结构,提出了“吸附-扩散-吸附”生长机制,用于解释混合维度异质结的生长。利用拉曼光谱分析,证实SWCNT与MoS_(2)间存在显著的电荷转移作用,载流子可在界面处快速传输,为后续基于此类1D/2D异质结的新型电子及光电器件的设计与制备提供了新思路。

Fracture of two three-dimensional parallel internal cracks in brittle solid under ultrasonic fracturing

Similar to hydraulic fracturing(HF), the coalescence and fracture of cracks are induced within a rock under the action of an ultrasonic field, known as ultrasonic fracturing(UF). Investigating UF is important in both hard rock drilling and oil and gas recovery. A three-dimensional internal laser-engraved crack(3D-ILC) method was introduced to prefabricate two parallel internal cracks within the samples without any damage to the surface. The samples were subjected to UF. The mechanism of UF was elucidated by analyzing the characteristics of fracture surfaces. The crack propagation path under different ultrasonic parameters was obtained by numerical simulation based on the Paris fatigue model and compared to the experimental results of UF. The results show that the 3D-ILC method is a powerful tool for UF research.Under the action of an ultrasonic field, the fracture surface shows the characteristics of beach marks and contains powder locally, indicating that the UF mechanism includes high-cycle fatigue fracture, shear and friction, and temperature load. The two internal cracks become close under UF. The numerical result obtained by the Paris fatigue model also shows the attraction of the two cracks, consistent with the test results. The 3D-ILC method provides a new tool for the experimental study of UF. Compared to the conventional numerical methods based on the analysis of stress-strain and plastic zone, numerical simulation can be a good alternative method to obtain the crack path under UF.

Inducing Flow Velocities to Manage Fish Reproduction in Regulated Rivers

Conservation of endangered or economic fish and control of invasive fish is a great challenge of hydraulic engineering worldwide.Flow velocity has been recognized to affect the spawning of fishes delivering drifting eggs in rivers.However,solid scientific supports and associated mechanisms to establish quantitative relations between flow velocity and fish reproduction,taking into account spawning,fertilizing,hatching,as well as surviving,are lacking.In this paper,we quantified the relationship between flow velocity and reproduction of Chinese carps through both lab and field experiments.The results showed that a minimum velocity was required to trigger Hypophthalmichthys molitrix(H.molitrix)releasing eggs,and a velocity range was preferred to sustain spawning activity.However,the embryo incubation and larvae development of H.molitrix were found to be inhibited with the increase in flow velocity.Considering the requirements of spawning and hatching,as well as larvae surviving,an optimized flow velocity processes was identified for the reproduction of H.molitrix in rivers.These findings were of great significance to the adaptive operation of reservoirs to create reasonable and precise ecological flows for managing fish reproduction,as shown by the promising results in the engineering application to the Three Gorges Reservoir.

Feasibility of differentiating T3 from T4a gastric cancer in different Lauren classification by determining serosa invasion：Diagnostic performance of high enhanced serosa sign

Objective： To study the value of high enhanced serosa sign on contrast-enhanced computed tomography（CT）in differentiating T3 from T4a gastric cancer in different Lauren classification.Methods： This study included 276 consecutive patients with surgically confirmed p T3 or p T4a gastric cancers.The pre-operative CT images were reviewed by two radiologists blinded. The demonstration of the high enhanced serosa on CT between T3 and T4a was compared with chi-square test. The diagnostic performance of this sign on CT in the differentiation of T4a from T3 in different Lauren classification was calculated.Results： The accuracy, sensitivity, specificity, positive predictive value（PPV） and negative predictive value（NPV） for the judgement of serosa invasion using the high enhanced serosa sign on CT was 74.6%, 63.7%, 83.6%,76.0% and 73.8% by one radiologist and 76.4%, 66.1%, 84.9%, 78.1% and 75.4% by the other radiologist.Compared to the intestinal-type, the sensitivity of the judgement of serosa invasion using the high enhanced serosa sign on CT in diffuse-type was significant higher（80% in both readers）, while the specificity trended to be lower（65.9% and 80.5%, respectively）. There is no significant difference in the accuracy of diagnosis between intestinaltype and diffuse-type of gastric cancers（the P-values of two radiologists were 0.968, 0.591, respectively）. The combination of the high enhanced serosa sign with conventional CT signs is significant different in diagnosis of T3 and T4a（P〈0.001）. The diagnostic accuracy was increased in both radiologists after the combination. The two readers achieved substantial agreement, with Kappa coefficient of 0.63, P〈0.001.Conclusions： The high enhanced serosa sign on CT is associated with serosa involvement. The sensitivity of the judgement of serosa invasion using this sign on CT in diffuse-type was significant higher than that in intestinal-type.

Strong and ductile Al−Zn−Mg−Zr alloy obtained by equal angular pressing and subsequent aging

An ultrafine-grained Al−Zn−Mg−Zr alloy with superior mechanical performance was obtained by high passes of equal angular pressing(ECAP)and subsequent aging.After 8 ECAP passes and aging,the yield strength(YS)and ultimate tensile strength(UTS)of the solid-solutioned alloy are significantly improved from(98±10)and(226±7)MPa to(405±9)and(427±9)MPa,respectively.A large elongation is also maintained((17.4±2.5)%).The microstructure features including grain refinement,morphology of precipitates,and dislocation density,were revealed with multiscale characterizations,including transmission electron microscopy,electron backscattered diffraction,and X-ray diffraction.After 8 passes of ECAP,the original coarse elongated grains are refined to a unique bimodal grain structure consisting of ultrafine equiaxed and lath-like grains.Additionally,the effects of ECAP and subsequent aging on the strengthening contribution of a variety of strengthening mechanisms,such as dislocation strengthening and precipitation strengthening,were discussed in detail.