Evidence of Electron-Hole Imbalance in WTe2 from High-Resolution Angle-Resolved Photoemission Spectroscopy

WTe2 has attracted a great deal of attention because it exhibits extremely large and non-saturating magnetore- sistance. The underlying origin of such a giant magnetoresistance is still under debate. Utilizing laser-based angle-resolved photoemission spectroscopy with high energy and momentum resolutions, we reveal the complete electronic structure of WTe2. This makes it possible to determine accurately the electron and hole concentrations and their temperature dependence. We find that, with increasing the temperature, the overall electron concen- tration increases while the total hole concentration decreases. It indicates that the electron-hole compensation, if it exists, can only occur in a narrow temperature range,and in most of the temperature range there is an electron-hole imbalance. Our results are not consistent with the perfect electron-hole compensation picture that is commonly considered to be the cause of the unusual magnetoresistance in WTe2. We identify a fiat band near the Brillouin zone center that is close to the Fermi level and exhibits a pronounced temperature dependence. Such a fiat band can play an important role in dictating the transport properties of WTe2. Our results provide new insight on understanding the origin of the unusual magnetoresistance in WTe2.

陕西韩城芝川古代冶铁遗址初步考察

韩城芝川古代冶铁遗址位于陕西省渭南市韩城芝川镇芝西村,遗存面积超4000 m^(2),考古年代为西汉。科研团队对该遗址开展冶金考古田野调查并采集到炉渣、陶片等遗物,使用扫描电镜及能谱(SEM-EDS)、金(矿)相显微观察等手段对采集到的18个冶炼遗物进行成分分析和显微结构观察。结果表明,16个炉渣为硅钙铝系高钙低铁炉渣,基体主要为玻璃相、偶见铁橄榄石,其产品是生铁,应为生铁冶炼炉渣。1个炉渣为高铁渣,以浮氏体为主、间有铁橄榄石和极少量玻璃相;1个样品的块状金属为熟铁,很可能为生铁炒钢的遗物。该遗址主要是生铁冶炼遗址,同时进行炒钢冶金活动,是迄今发现陕西渭南地区最早的生铁炒钢遗址。

水田搅浆方式对水稻根系生长及产量的影响

为揭示水田不同搅浆方式对寒区水稻根系形态结构和生理活性的影响及其与产量形成之间的关系,本研究以龙粳31为试验材料,设置旱平免搅浆(HP)、水平地免搅浆(SP)、常规搅浆(CK)3种搅浆方式进行对比试验,对各生育期水稻根系形态结构指标、根系生理活性指标、干物质量及产量进行测定。结果表明:水稻根系形态指标在抽穗扬花期趋于稳定,与CK相比,HP处理下的总根长、根表面积、根体积和平均直径分别显著增加14.1%、8.79%、7.16%和4.06%,SP处理下仅总根长显著增加6.43%。水稻根系生理活性指标在抽穗扬花期达到最大值,与CK相比,HP和SP分别使根系氧化活力显著增加16.1%和5.51%,根系伤流强度显著增加10.2%和5.74%。同时,与CK相比,HP和SP的水稻产量分别显著提高7.65%和4.03%。综上所述,HP能够明显改善根系形态,促进根系生长,提高根系生理活性,进而促进水稻植株地上部生长和产量的增加。

新郑地区汉代墓葬出土铁器的科技研究

对河南新郑郑韩故城及周边地区墓葬出土的6件铁器进行科技检测,采用了金相、扫描电镜及能谱分析(SEM-EDS)两种试验方法,对样品进行金相组织观察及夹杂物成分分析。样品种类包括剑、带钩、削、铲。经分析样品均为生铁及生铁制钢制品,其中三件为铸铁脱碳制品,一件白口铁制品,一件韧性铸铁制品及一件炒钢制品。出土铁器的制作工艺有明显区别,选择性使用了锻打、退火等加工工艺;其中存在铸铁脱碳钢样品具有高锰特征,可能与使用含锰矿石冶炼有关。通过检测与分析,中原地区在汉代时期(王莽新朝至东汉中期)仍沿袭战国时期制铁工艺,进一步了解该时期制铁工艺发展情况。

山西翼城冶南汉代冶铁遗址初步调查

冶南遗址位于山西省临汾市翼城县冶南村,面积约1.2 km^(2),考古年代为西汉。采用X射线荧光分析仪(EDX)、扫描电镜及能谱分析仪(SEM-EDS)、金(矿)相显微镜等对冶南遗址采集的6个炉渣和2个金属铁块进行了基体成分和显微组织检测分析。结果表明,6个炉渣样品为硅钙铝系低铁渣;2个铁块样品为熟铁,可能是生铁炒钢产品。判断该遗址为生铁冶炼遗址,同时也是生铁炒钢遗址。该遗址是目前山西地区确认的第一处大型生铁冶炼及炒钢的汉代官铁遗址。

Electronic structure and ultraviolet spectra of p-C_(6)H_(4)-C_(20)

Geometry optimization of p-C_(6)H_(4)-connected cyclo[20]carbon(p-C_(6)H_(4)-C_(20))was carried out at M062X/6-311G(d,p)level,three kinds of bond orders(Mayer,Laplacian,and Wiberg),electron-hole distributions,localized orbital locators(LOL),and infrared(IR)spectrum were also performed at the same level.Based on TD-DFT M062X/6-311G(d,p)method,the first 20 excited states and ultraviolet(UV)spectra of p-C_(6)H_(4)-C_(20) were calculated.Calculation results of π-electron delocalization analyses prove thatπ-electron delocalization of p-C_(6)H_(4)-C_(20) is more likely to occur on shorter C-C bonds rather than longer C-C bonds,and inside/outside of the ring plane rather than above/below the ring plane.Two absorption peaks of p-C_(6)H_(4)-C_(20) locate at about 319 nm and 236 nm,respectively.

A Simple Mechanism for Generating a Geomagnetic Field

On the basis of the ideal gas model, the polarization of charges in the mantle was obtained, a physical and mathematical model was constructed, and estimated calculations of the dipole mode of the Earth’s magnetic field were performed, taking into account the speed of its angular rotation, the parameters of density and temperature, the chemical composition, the ionization potential, the dielectric constant and the percentage of the main chemical compounds of the mantle substance.

Effects of puddling on percolation and rice yields in rainfed lowland paddy cultivation: Case study in Khammouane province, central Laos

We investigated the effects of puddling on percolation and rice yields in rainfed lowland paddy cultivation. We selected a study village in Khammouane province, central Laos, and set up non-puddling and puddling plots from high to low positions. Even when puddling was conducted carefully, the ponding water in the plots disappeared in the case of little rainfall. Further, percolatifons during the later periods of rice growth increased drastically. Therefore, it is difficult to overcome drought stresses only by conducting puddling. We also compared the water conditions in the non-puddling and puddling plots. In the puddling plots at high position and low position along a stream, the number of days without ponding water in the puddling plots was less than that in the non-puddling field in July, suggesting the possibility of a different transplanting date. We tried to estimate the effects of transplanting date on the rice yields and found that transplanting 15 days earlier leads to an increase of 0.5 t/ha in the rice yields. Moreover, the profits from the increased yields exceed the puddling costs considerably, leading to a definite increase in income. Because the transplanting date has no effects in the fields with high ground water, puddling is effective in paddy fields where ponding does not occur to a significant degree.

Process control based on double-side image sensing of keyhole puddle for the VPPA welding of aluminum alloys

The double side image sensing of the keyhole puddle in the variable polarity plasma arc welding of aluminum alloys has been investigated in this paper, to extract the characteristically geometrical size of the keyhole and to realize the feedback controlling for weld formation in the welding process. Some geometrical sizes of the visible keyhole in the front and back images such as the width, height, area, etc. can be used to monitor both the keyhole puddle and the weld formation in the welding process. Under the condition of the varied heat sink, varied gap and misalignment, the trend from normal welding to cutting can be reflected from the variations of geometrical sizes of the keyhole puddle respectively. The keyhole area, the keyhole height and the shape parameters of the keyhole puddle are the key parameters which reflect the trend from normal welding to cutting when meeting the condition of the varied heat sink, varied gap and misalignment respectively. The algorithm for the image processing of the keyhole puddle and the periphery extracting of the visible keyhole developed in the paper can be used to determine real timely the geometrical sizes of the visible keyhole. Artificial neural network is applied to establish the model for predicting the geometrical sizes of the back keyhole puddle. The inputs of the model are the geometrical sizes of the front keyhole puddle and the weld parameters, the outputs of the model are the geometrical sizes of the back keyhole puddle. The model can be used to control the stability of keyhole and the weld formation.

Effect of Puddling and Compaction on Water Requirements of Rice at Hamelmalo, Eritrea

Eritrean farmers can cultivate rice by harvesting runoff from >82% available non-agricultural land in agricultural watersheds for crop use and reducing percolation through optimization of tillage. Experiments were conducted with NERICA rice, N11, to optimize irrigation requirements and puddling and compaction to reduce percolation. Experimental field was adjacent to Anseba River at downstream end of the watershed and a pond on the upstream to intercept runoff. Irrigation treatments were runoff farming with maximum runoff application depth of 10 mm (I1), and 50 mm irrigation two (I2), five (I3), and seven (I4) days after disappearance of ponded water in main plots and puddling by one (T1), two (T2) and three (T3) passes of puddler and compaction by three (T4), four (T5) and five (T6) passes of 600 kg roller in sub plots in 3 replications. Soil profile was loam in the surface 0.45 m and coarse sandy loam below forming porous belt. Soil submergence was difficult to maintain, but water table was developed in soil profile due to inflow of seepage from the river and pond. Depth to the water table was within 1.5 ± 0.1 m for >2 months and receded down to 1.7 m by crop maturity. Soil wetness was near field capacity around 0.7 m depth and increased below due to natural sub-irrigation from the water table. Rice roots penetrated 0.8 m in the puddled plots and 0.7 m in the compacted plots. Residual soil moisture of 135 - 146 mm·m-1 after rice harvesting provides opportunity for planting rapeseed mustered following rice. Puddling was superior to compaction in loam soil. Puddling twice and irrigation 50 mm 7 days after ponded water vanished from surface was sufficient for optimum rice grain yield of 4346 kg·ha-1 and straw yield of 4458 kg·ha-1. Optimum puddling and irrigation schedules reduced crop duration by 6 days without significantly affecting yield. Production function showed that rice grain yield of 4789 kg ha-1 could be obtained by 1009 mm applied water through rainfall and irrigation.

广东罗定船步铁炉村古代冶金遗址初步研究

铁炉村冶金遗址位于广东省罗定市船步镇铁炉村附近的丘陵脚底,遗存面积约200 m^(2)。本团队从2013年至今开展多次田野调查并取样。采用扫描电镜及能谱分析(SEM-EDS)、金(矿)相、加速器质谱(AMS)碳十四断代等研究手段,对铁炉村遗址的7个炉渣和2个金属铁块样品进行了成分和显微组织的检测分析,对1份木炭样品开展^(14)C检测。研究结果表明,该遗址既是生铁冶炼遗址又是生铁炒钢冶金遗址。生铁冶炼炉渣是铁硅铝系高硅低铁渣。遗址遗存的大块金属样品的显微组织为铁素体,磷偏析严重,为生铁炒钢产品;其相对应的炒钢炉渣为铁硅铝系高铁渣。此类高铁渣基体局部留存有大量浮氏体等。该遗址为迄今我国发现的第一处明确遗存有古代炒钢冶金产品的遗址。该遗址遗存的竖炉及生铁冶炼炉渣、炒铁炉、炒钢产品及其冶金炉渣等一整套较为齐全证据链的生铁冶炼及生铁炒钢冶金遗物,目前国内仅见一处,将为确立古代生铁炒钢渣的鉴别标准等提供重要的科学资料。AMS-14 C检测结果显示,遗址至晚距今570±25(BP)(约元中至明初)开始钢铁冶金活动。

黑龙江阿城西川冶铁遗址初步调查研究

西川冶铁遗址位于黑龙江省阿城市小岭镇西川屯300 m处,面积约5000 m^(2),考古年代为金代。2021年7月对该遗址进行了田野考察取样。采用X射线荧光仪、金(矿)相显微镜等手段对西川冶铁遗址17个冶炼炉渣、炉壁残块等样品进行基体成分分析和显微结构观察。结果表明,西川冶铁遗址为生铁冶炼遗址,生铁炉渣类型为硅锰铁铝钙多元系炉渣,生铁炉渣中铁颗粒的显微结构以片状石墨和珠光体为主。炉渣样品中的高铁炉渣可能为生铁炒钢渣。

基于自注意和对抗学习的道路场景水体检测方法

无人驾驶车辆近年来一直是研究的热点.无人车运行环境复杂、不确定因素多,尤其当其意外驶入水坑、泥潭等地形时可能直接导致抛锚,造成不可估量的损失,因此水体检测对无人车的运行有着重要意义.借助深度网络的强大学习能力,本文首先将反射注意力单元和自注意力机制相结合,并在(U shape Network,U-Net)模型基础上添加残差卷积块和上采样卷积模块,得到了新的道路场景水体区域检测模型(U shape Network with Attention for Road,URA-Net),该模型能够更好地捕捉特征依赖关系,提高水体语义特征的表示能力.进一步,本文提出了一种基于双生成器对抗学习的训练模型(Redundant With Dual Generative Adversarial Network,RWD-GAN),它对URA-Net稍做修改,拓展成两个生成器,通过在对抗网络框架下让生成器与鉴别器、生成器与生成器之间实现对抗学习,促进不同网络模型之间的信息传递.在公开数据集上的大量实验表明URA-Net达到了87.18%的F1指标,而RWD-GAN模型能够进一步提高水体检测的精度,使提升到了88.54%,URA-Net和RWD-GAN均超出现有深度网络水体检测方法的性能表现.

基于5个数据库的黄脊竹蝗研究进展可视化分析

为深入了解黄脊竹蝗的研究动态和热点,本文利用中国知网、万方数据和维普中文期刊服务平台、CAB abstracts和Web of science^(TM)5个数据库,采用Vosviewer软件对黄脊竹蝗的研究进行了可视化分析。结果表明,关于黄脊竹蝗的文献最早发表于1935年,近10年是相关研究发文量的高峰期。黄脊竹蝗相关文献最主要的媒介是学术期刊,占所有文献的79.38%;《湖南林业科技》是发文量最多的期刊。练佑明、舒金平、王浩杰和蒋国芳等作者发表文章数量名列前茅,练佑明以第一作者发表了11篇中文论文,蒋国芳发表的外文文献最多,这些学者的工作都促进了国际和国内的学术交流。黄脊竹蝗的研究热点与可持续治理高度相关,尤其侧重生物防治和生物学特性。

Synthesis,characterization and photocatalytic performance of rod-shaped Pt/PbWO_4 composite microcrystals

Rod-shaped PbW O4 microcrystals of length 1 μm were fabricated by a hydrothermal route and subsequent calcination. Pt nanoparticles（NPs） of different contents（0.5 wt%,1 wt% and 2 wt%） were subsequently deposited on the PbW O4 microcrystals,producing robust Pt/PbW O4 composite microcrystals. The PbW O4 microcrystals and Pt/PbW O4 photocatalysts were characterized by X-ray diffraction,N2 sorption measurements,scanning electron microscopy,transmission electron microscopy,and X-ray photoelectron,photoluminescence,Fourier-transform infrared,and ultraviolet-visible diffuse reflectance spectroscopies. The photocatalytic performances of the catalysts were evaluated by the consecutive photocatalytic degradation of acid orange II dye. The Pt/PbW O4 composite microcrystals exhibited high photocatalytic activity and stability. The deposition of Pt NPs produced surface plasmon resonance（SPR）,which induced a large visible light absorption. A Pt NP content of 1-2 wt% resulted in an ~2 times increase in photocatalytic activity,compared with the activity of Pt/PbW O4. The crystal structure and high crystallinity of PbW O4 resulted in its favorable photocatalytic property,and the SPR effect of the Pt NPs promoted visible light harvesting. The Pt NPs also enhanced the separation of photo-generated electrons and holes,which further promoted the photocatalytic reaction.

基于逆向工程的搅浆刀作业性能界定与关键设计参数研究

水田搅浆是基于稻作制度的独立机械化作业环节,搅浆刀是进行搅浆农艺处理的专用刀具,但目前缺乏针对搅浆的农艺界定及搅浆刀专用设计参数研究。本文利用逆向工程技术获取搅浆刀的关键几何参数,并对搅浆作业和搅浆刀的设计方法进行定义。通过与常规旋耕刀(R245)进行分析对比提出搅浆刀的专用设计参数,进而通过田间试验进一步探讨搅浆刀的设计方法。结果表明,搅浆刀的楔面入土效应是保障其水田搅浆性能的关键,该效应所对应的搅浆刀设计参数被定义为侧切刃楔角,侧切刃楔角与侧切刃刀面宽度2个关键设计参数决定了搅浆刀入土过程的侧向搅浆作业强度。与R245旋耕刀相比,侧切刃楔角是搅浆刀设计的显著特点,搅浆刀的侧切刃静态楔角高于动态楔角,而R245的侧切刀面是一平直刀面(楔角为0°),在正切刃区域,搅浆刀与旋耕刀的楔角变化基本一致。基于田间土壤条件的原位台架试验进一步证明了搅浆刀专用设计参数对保障起浆、水田埋草等性能的优越性。

黄脊竹蝗引诱剂的筛选及应用

[目的]优化黄脊竹蝗引诱剂配方,更好地实现黄脊竹蝗的有效控制。[方法]配制不同的引诱剂,通过林间诱杀试验测定不同配方毒饵对黄脊竹蝗的诱杀效果。[结果]Na Cl 2%+NH_4HCO_3 10%+Indole 5‰配方所制成毒饵诱杀黄脊竹蝗效果最好,24 h内的诱杀量可达639.4±48.14头·诱捕器-1,其次是2%Na Cl+10%NH_4HCO_3 配方,平均诱杀量达580.8±40.36头·诱捕器-1,与发酵人尿的诱杀量差异不显著(P>0.05),应用时间显著影响各配方的诱杀效果。Na Cl和NH_4HCO_3 是人尿引诱黄脊竹蝗的关键物质,挥发物Indole对诱杀具有增效作用。[结论]应用人工配制的引诱剂诱杀黄脊竹蝗能显著降低林间成虫的种群数量,且能杀死大量雌虫,可用于林间黄脊竹蝗防治。

铝合金等离子弧焊穿孔熔池正面图象检测与处理

研制了一套窄带复合滤光图象传感系统，从铝合金等离子弧焊焊接工件正面检测到部分小孔溶池的清晰图象。采用Ｇａｕｓ滤波，Ｐｒｅｗｉｔ边缘检测和图象错位边缘检测等方法准确提取出可视小孔熔池的小孔宽度和面积等几何信息。

平面流铸技术熔潭的特性

平面流铸技术是制取非晶态合金薄带的快速凝固技术之一，在其喷嘴辊轮间隙的熔潭的特 性决定了薄带制取的成败和薄带的质量．对平面流铸技术熔潭特性的研究状况进行了分析，详细阐 述了熔潭中的波动及金属薄带和淬冷辊轮间界面热交换系数的确定，并对平面流铸技术进一步的 研究提出了新的思路，对于其他薄带制取技术的深入研究有所启发．

氯化钠和碳酸氢铵溶液对黄脊竹蝗的引诱效果

黄脊竹蝗Ceracris kiangsu是中国南方地区重要的竹子食叶害虫。为深入理解黄脊竹蝗趋尿行为的机制,通过林间录像系统测定了黄脊竹蝗对不同质量浓度钠盐(1.0,5.0,10.0,20.0 g·L-1)及铵盐(1.0,2.0,4.0,8.0,10.0,25.0,50.0,75.0,150.0 g·L-1)溶液的行为反应,同时进行了钠盐及铵盐溶液的林间诱捕试验。结果表明:钠盐及铵盐的质量浓度会显著影响黄脊竹蝗的趋泥行为(P<0.05),1.0 g·L-1的碳酸氢铵和1.0 g·L-1氯化钠溶液即可激发黄脊竹蝗的趋泥行为,随着质量浓度的升高,黄脊竹蝗访问铵盐及钠盐次数逐渐增多;黄脊竹蝗成虫对经75.0 g·L-1的碳酸氢铵或10.0 g·L-1氯化钠溶液处理的滤纸有明显的选择偏好(P碳酸氢铵=0.032,P氯化钠=0.043)。林间诱杀试验表明:挥发性铵盐的诱蝗量显著高于钠盐的诱蝗量(P<0.01),挥发性物质在黄脊竹蝗趋泥行为中发挥着重要作用。