热载流子多结太阳能电池CdSe/CdS核壳量子点和纳米片的声子瓶颈效应机理

热载流子多结太阳能电池(HCMJSC)是热载流子及叠层电池概念相结合而提出的一种较有前景的第三代太阳能电池之一,其理论效率在一个标准太阳条件(即1000 W/m 2,25℃)下将高于65%,远高于32%的单节硅基电池极限效率。该型电池主要包括一个宽带隙的顶结薄膜和一个适中带隙的厚底结基底,以分别高效吸收利用高能和低能光子。其广泛应用于光电器件的宽带隙CdSe/CdS低维材料体系(如量子点、纳米片等)有望成为顶结薄膜的合适候选材料。然而,该材料体系中的声子瓶颈效应(PBE)机理目前尚不明晰。文章主要研究了CdSe/CdS核壳量子点(QDs)和纳米片(NPLs)中的PBE机理;通过稳态光致发光(SSPL)和皮秒时间分辨尺度光致发光(ps-TRPL)技术,计算该材料体系的热弛豫系数(Q th),从而定量分析激发载流子的弛豫速率,同时阐述了PBE和量子点中常见的俄歇复合之间的耦合关系,最终系统研究了QDs和NPLs中载流子弛豫过程机理,提出HCMJSC的发展路径和建议。

龙云灌区新建水源工程正常蓄水位方案比选

水库正常蓄水位方案比选是确定水库规模的一个重要环节,关系到工程实施的经济性和可行性。本文以广西玉林市龙云灌区工程为例,研究提出了串联水库正常蓄水位方案比选的原则和方法,得出了经济合理的正常蓄水位成果。

基于NPLS技术的可压缩湍流机理实验研究新进展

可压缩湍流机理的实验研究是一件难度很大的工作,其主要的难度在于高时空分辨率的可压缩湍流结构非接触精细测试技术和低噪声的高速风洞设备技术.近几年来,由于在低噪声的超声速、高超声速风洞研究和可压缩流动精细结构测量技术研究方面取得的重要进展及其在可压缩湍流机理研究方面的应用,超声速流动转捩与湍流的机理研究取得了较大的进展.本文介绍了最近几年高速流动非接触精细测试技术,尤其是基于纳米粒子的平面激光散射技术(nano-tracer planar laser scattering,NPLS)、背景导向纹影技术(background oriented schlieren,BOS)和超声速流场的粒子图像测速技术(particle image velocimetry,PIV)的研究进展和发展前景,以及基于这些技术,在可压缩湍流机理实验研究方面的进展和发展前景,其中包括在超声速混合层转捩、超声速绕流与尾流结构、超声速边界层转捩、激波边界层干扰等典型流场的机理研究方面,以及气动光学机理研究方面的研究进展.最后,展望了目前湍流机理实验研究对湍流工程模型研究的可能贡献.

三维高光谱NPLS模型用于冬小麦估产的初步研究

以35个实验小区,8个生育期的冬小麦田间测量冠层反射高光谱组成三维数据信息阵,采用多维偏最小二乘(multiway partial least squares,NPLS)算法建立了冬小麦亩产量估产模型。模型用于对13个实验小区产量预测分析,预测值与实际值的相关系数r为0.936 6,平均相对误差为4.44%,说明模型的预测效果较好,对实际的估产工作有一定的指导意义。

NPLS流场测量技术在高超声速风洞中纳米粒子跟随性数值仿真

从描述粒子运动的微观层次出发,采用双向耦合技术,建立了一种适用于稀薄条件下两相流动的DSMC数值模拟方法。对相间相互作用进行解耦处理,实现了气固两相间动量和能量相互作用的模拟。采用基于DSMC方法的稀薄两相流双向耦合算法,对NPLS测量技术高超声速流场测量中纳米粒子的跟随性进行了数值研究。通过Φ50nmTiO2粒子在不同高超声速流场条件下气相-纳米粒子两相流场的仿真,表明在稀薄度很小的流场中,纳米粒子的跟随性很好。而随着流场稀薄度增加,流场中纳米粒子的跟随性降低,纳米粒子在流场中的分布与气相流场分布差异变大,通过NPLS测量得到的激光散射信号不能反映流场结构。

NPLS技术及其在高速飞行器气动研究中的应用(英文)

近年来,与高速飞行器相关的超声速/高超声速流动受到了极大关注。这类流动所具有的非定常性、强梯度和可压缩性对试验研究提出了挑战。纳米示踪的平面激光散射技术(NPLS)是2005年由作者所在的研究团队研发的非接触光学测试技术。它能够获得超声速三维流场的某个剖面的瞬态流动结构,并且具有较高的时空分辨率。目前,许多研究结果表明NPLS是研究超声速湍流的一项非常有效的技术。近年来,作者应用NPLS技术在超声速湍流研究中取得了较大的进展,并且基于NPLS开发了其它几种技术,比如基于NPLS的密度场测量技术(NPLS-DT),能够获得超声速流动的密度场信息并还能进一步得到雷诺应力分布。本文介绍了NPLS技术并回顾了其在超声速边界层、激波/边界层相互作用等流动中的应用。由于能够获得雷诺压力和湍动能等统计量,NPLS技术有望在发展可压缩湍流模型的研究中发挥作用。

NPLS技术在高超声速边界层转捩研究中的应用

基于纳米粒子示踪平面激光散射技术(Nano-tracer-based Planar Laser Scattering,NPLS)是作者自主研发的一种流动显示与精细测量技术。在超声速条件下,NPLS技术具有很高的时空分辨率和信噪比,已经成功应用于超声速复杂流动现象的精细测量,包括超声速混合层、超声速平板边界层、超声速压缩拐角、激波边界层干扰等。近年来,该技术被进一步应用到高超声速边界层转捩研究中。本文主要介绍了NPLS技术在高超声速静音风洞喷管边界层流态测量、高超声速圆锥边界层转捩以及三角翼边界层转捩等研究中的应用。高超声速条件下NPLS研究结果与高频传感器、温敏漆等测试技术得到的结论一致性较好,表明NPLS技术在高超声速边界层转捩研究中具有良好的应用前景。

二维相关近红外谱结合NPLS-DA判别掺杂牛奶的研究

将二维相关近红外谱与多维偏最小二乘判别分析方法结合起来,建立了掺杂牛奶与纯牛奶的判别模型.分别配置掺杂尿素牛奶(1～20g/L)和掺杂三聚氰胺牛奶(0.01～3g/L)样品各40个,采集纯牛奶及掺杂牛奶样品的近红外光谱.在量化二维相关近红外同步谱的基础上,采用多维偏最小二乘判别分析法分别建立了掺杂尿素、掺杂三聚氰胺及两种掺杂牛奶与纯牛奶的判别模型对未知样品进行判别,其判别正确率分别为95%、90%和92.5%,并与偏最小二乘判别和隐变量正交投影判别建模方法进行了比较.结果表明:多维偏最小二乘判别分析法具有更强的预测能力可推广到其它食品的掺杂检测中.

Radiative Blood-Based Hybrid Copper-Graphene Nanoliquid Flows along a Source-Heated Leaning Cylinder

Variant graphene,graphene oxides(GO),and graphene nanoplatelets(GNP)dispersed in blood-based copper(Cu)nanoliquids over a leaning permeable cylinder are the focus of this study.These forms of graphene are highly beneficial in the biological and medical fields for cancer therapy,anti-infection measures,and drug delivery.The non-Newtonian Sutterby(blood-based)hybrid nanoliquid flows are generalized within the context of the Tiwari-Das model to simulate the effects of radiation and heating sources.The governing partial differential equations are reformulated into a nonlinear set of ordinary differential equations using similar transformational expressions.These equations are then transformed into boundary value problems through a shooting technique,followed by the implementation of the bvp4c tool in MATLAB.The influences of various parameters on the model’s nondimensional velocity and temperature profiles,reduced skin friction,and reduced Nusselt number are presented for detailed discussions.The results indicated that Cu-GNP/blood and Cu-GO/blood hybrid nanofluids exhibit the lowest and highest velocity distributions,respectively,for increased nanoparticles volume fraction,curvature parameter,Sutterby fluid parameter,Hartmann number,and wall permeability parameter.Conversely,opposite trends are observed for the temperature distribution for all considered parameters,except the mixed convection parameter.Increases in the reduced skin friction magnitude and the reduced Nusselt number with higher values of graphene/GO/GNP nanoparticle volume fraction are also reported.Finally,GNP is identified as the superior heat conductor,with an average increase of approximately 5%and a peak of 7.8%in the reduced Nusselt number compared to graphene and GO nanoparticles in the Cu/blood nanofluids.

NPL4靶向抑制剂双硫仑对T细胞肿瘤泛素-蛋白酶体通路相关基因表达的影响

目的我们前期的研究表明,双硫仑(disulfiram,DSF)通过核蛋白定位蛋白4同源物(nuclear protein localization protein 4 homolog,NPL4)介导的泛素-蛋白酶体通路发挥抗T细胞肿瘤[主要包括急性T淋巴白血病(T-cell acute lymphoblastic leukemia,T-ALL)和T细胞淋巴瘤(T-cell lymphoma,TCL)]的作用。本研究旨在探讨双硫仑对T细胞肿瘤中泛素-蛋白酶体通路相关基因表达的调节作用,为T细胞肿瘤的精准靶向治疗提供依据。方法应用0.4μM双硫仑处理T-ALL细胞株Jurkat 48 h,采用转录组测序分析显著性差异表达的基因,并采用10例T细胞肿瘤样本(GZFPH数据集)进行实时荧光定量PCR验证差异基因相对表达水平。最后,从TARGET和GSE58445数据库中下载262例T-ALL和140例TCL的转录组测序数据进行生存分析。结果0.4μM双硫仑处理Jurkat细胞48 h后,在泛素-蛋白酶体通路中,有86个下调和35个上调的基因;其中,单因素Cox回归和生存曲线分析发现,仅有泛素结合酶E2 J1(ubiquitin conjugating enzyme E2 J1,UBE2J1)基因的低表达与TARGET和GSE58445数据集中T-ALL和TCL患者的不良预后相关(P<0.05)。将UBE2J1的表达水平、年龄和性别纳入单因素和多因素Cox回归分析,结果提示UBE2J1的低表达是T-ALL和TCL患者的独立预后影响因子(P<0.05)。结论双硫仑可调控UBE2J1基因的表达,其低表达与T细胞肿瘤患者的不良预后相关,为进一步阐明双硫仑的抗肿瘤作用及其调控的UBE2J1基因作为T细胞肿瘤的危险分层的分子标志物提供理论依据。

基于NPLS的静压比对高超声速光学头罩冷却气膜影响作用研究

超声速冷却气膜是应用于高超声速成像制导飞行器上的一项关键技术,静压比是影响超声速冷却气膜流场发展的重要因素。为研究静压比对该流场的影响规律,在M6高超声速风洞中采用基于纳米粒子的平面激光散射技术,对不同静压比下的马赫数3超声速冷却气膜流场进行了实验研究,获得了流场的瞬态流动显示图像。通过瞬态流动显示图像分析,研究了高超声速主流与超声速喷流之间边界面的发展过程;通过分形维数及间歇性分析,研究了静压比对湍流化程度的影响。结果表明在波系结构、喷流厚度及湍流化程度等方面,静压比对超声速冷却气膜产生了明显的影响:气膜总体厚度和静压比正相关,欠压状态和匹配状态气膜厚度增长先慢后快,过压状态先快后慢;欠压状态和匹配状态湍流破碎因子在流场前段普遍小于过压状态,但其沿流向增长较快,最终压力匹配状态湍流破碎因子最大,湍流化程度最高。

Surfactant-decorated graphite nanoplatelets(GNPs) reinforced aluminum nanocomposites: sintering effects on hardness and wear

The exceptional properties of graphene make it ideal as a reinforcement to enhance the properties of aluminum matrices and this critically depends on uniform dispersion. In this study, the dispersion issue was addressed by sonication and non-covalent surface functionalization of graphite nanoplatelets（GNPs） using two types of surfactant： anionic（sodium dodecyl benzene sulfate（SDBS）） and non-ionic polymeric（ethyl cellulose（EC））. After colloidal mixing with Al powder, consolidation was performed at two sintering temperatures（550 and 620°C）. The structure, density, mechanical and wear properties of the nanocomposite samples were investigated and compared with a pure Al and a pure GNPs/Al nanocomposite sample. Noticeably, EC-based 0.5 wt% GNPs/Al samples showed the highest increment of 31% increase in hardness with reduced wear rate of 98.25% at 620°C, while a 22% increase in hardness with reduced wear rate of 96.98% at 550°C was observed, as compared to pure Al. Microstructural analysis and the overall results validate the use of EC-based GNPs/Al nanocomposites as they performed better than pure Al and pure GNPs/Al nanocomposite at both sintering temperatures.

Effect of graphene nanoplatelets(GNPs)addition on strength and ductility of magnesium-titanium alloys

Effect of graphene nanoplatelets(GNPs)addition on mechanical properties of magnesium–10wt%Titanium(Mg–10Ti)alloy is investigated in current work.The Mg-(10Ti+0.18GNPs)composite was synthesized using the semi powder metallurgy method followed by hot extrusion.Microstructural characterization results revealed the uniform distribution of reinforcement(Ti+GNPs)particles in the matrix,therefore(Ti+GNPs)particles act as an effective reinforcing filler to prevent the deformation.Room temperature tensile results showed that the addition of Ti+GNPs to monolithic Mg lead to increase in 0.2%yield strength(0.2%YS),ultimate tensile strength(UTS),and failure strain.Scanning Electron Microscopy(SEM),Energy-Dispersive X-ray Spectroscopy(EDS)and X-Ray Diffraction(XRD)were used to investigate the surface morphology,elemental dispersion and phase analysis,respectively.

Mechanical properties of graphene nanoplatelets reinforced 7075 aluminum alloy composite fabricated by spark plasma sintering

A 0.3wt%graphene nanoplatelets(GNPs)reinforced 7075 aluminum alloy matrix(7075 Al)composite was fabricated by spark plasma sintering and its strength and wear resistance were investigated.The microstructures of the internal structure,the friction surface,and the wear debris were characterized by scanning electron microscopy,X-ray diffraction,and Raman spectroscopy.Compared with the original 7075 aluminum alloy,the hardness and elastic modulus of the 7075 Al/GNPs composite were found to have increased by 29%and 36%,respectively.The results of tribological experiments indicated that the composite also exhibited a lower wear rate than the original 7075 aluminum alloy.

Ab initio calculation of the growth of Te nanorods and Bi_2Te_3 nanoplatelets

In this paper the growth mechanism of a Te/Bi2Te3 novel structure is studied by ab-initio calculations. The results show that the growth of Te nanorods is determined by the adsorption energy of Te atoms on different crystalline Te surfaces. The adsorption energy of Te on the Te （001） surface is 3.29 eV, which is about 0.25 eV higher than that of Te on the Te （110）. This energy difference makes the preferential growth direction along the 〈 001 〉 direction. In addition, the higher surface energy of Bi2Te3 （110） and the lattice misfit between crystalline Bi2We3 and Te along 〈 001 〉 direction are considered to explain the growth of the Bi2Te3 nanoplatelets, in which Volmer-Weber model is used. The theoretical results are in agreement with experimental observation.

Curing Kinetics, Mechanical Properties and Thermal Stability of Epoxy/Graphene Nanoplatelets(GNPs) Powder Coatings

Epoxy/graphene nanoplatelets（GNPs） powder coatings were fabricated using ultrasonic predispersion of GNPs and melt-blend extrusion method. The isothermal curing kinetics of epoxy/GNPs powder coating were monitored by means of real-time Fourier transform infrared spectroscopy（FT-IR） with a heating cell. The mechanical properties of the epoxy/GNPs cured coatings had been investigated, by evaluating their fracture surfaces with field-emission scanning electron microscopy（FE-SEM） after three-point-bending tests. The thermal stability of the epoxy/GNPs cured coatings was studied by thermo-gravimetric analysis（TGA）. The isothermal curing kinetics result showed that the GNPs would not affect the autocatalytic reaction mechanism, but the loading of GNPs below 1.0 wt % additive played a prompting role in the curing of the epoxy/GNPs powder coatings. The fracture strain, fracture toughness and impact resistance of the epoxy/GNPs cured coatings increased dramatically at low levels of GNPs loading（1 wt %）, indicating that the GNPs could improve the toughness of the epoxy/GNPs powder coatings. Furthermore, from FE-SEM studies of the fracture surfaces, the possible toughening mechanisms of the epoxy/GNPs cured coatings were proposed. TGA result showed that the incorporation of GNPs improved the thermal stability of the cured coatings. Hence, the GNPs modified epoxy can be an efficient approach to toughen epoxy powder coating along with improving their thermal stability.

Edge sulfurized graphene nanoplatelets via vacuum mechano-chemical reaction for lithium–sulfur batteries

Lithium–sulfur batteries have great potential for high energy applications due to their high capacities,low cost and eco-friendliness. However, the particularly rapid capacity decay owing to the dissolution and diffusion of polysulfide intermediate into the electrolyte still hamper their practical applications.And the reported preparation procedures to sulfur based cathode materials are often complex, and hence are rather difficult to produce at large scale. Here, we report a simple mechano-chemical sulfurization methodology in vacuum environment applying ball-milling method combined both the chemical and physical interaction for the one-pot synthesis of edge-sulfurized grapheme nanoplatelets with 3D porous foam structure as cathode materials. The optimal sample of 70%S–Gn Ps-48 h(ball-milled 48 h) obtains 13.2 wt% sulfur that chemically bonded onto the edge of Gn Ps. And the assembled batteries exhibit high initial discharge capacities of 1089 mAh/g at 0.1 C and 950 mAh/g at 0.5 C, and retain a stable discharge capacity of 776 mAh/g after 250 cycles at 0.5 C with a high Coulombic efficiency of over 98%. The excellent performance is mainly attributed to the mechano-chemical interaction between sulfur and grapheme nanoplatelets. This definitely triggers the currently extensive research in lithium–sulfur battery area.

Effect of Graphene Nanoplatelets Presence on the Thermal and Mechanical Properties of Polypropylene Fibers Produced by Melt Spinning

In aiming to obtain fibers with enhanced thermal and mechanical properties,graphene based textile fibers with 144 filaments were developed using an approach in which the PP/GnP(polypropylene/graphene nanoplatelets)nanocomposite was employed as conductive material in a fiber with circular cross-section geometry.The kinetics of thermal degradation was evaluated by the Broido method using thermogravimetric analysis(TGA).Activation energy was enhanced from 260.6 kJ·mol^-1 to 337.4 kJ·mol^-1 compared to the neat PP.GnP increased the thermal stability of the PP,slowing its degradation by thermal depolymerization.Furthermore,the degree of crystallization declined as the GnP content increased,reducing the tenacity of the yarn,but improving its elastic modulus from 91.9 to 95.9 cN/tex,being a promising alternative to produce smart textiles.In conclusion,it has been confirmed that GnP loading up to 1%(w/w)can be incorporated into polypropylene by melt spinning and that the resulting nanocomposite fibers are suitable for several applications in the textile industry.

Structure and Mechanical Properties of Waterborne Polyurethane-based Composites Filled with Self-assembled Supramolecular Nanoplatelets

New composites of waterborne polyurethane （WPU） as a matrix were prepared by incorporating rigid supramolecular nanoplatelets （SNs） as filler, which were self-assembled by the selective inclusion of β-cyclodextrin （β-CD） onto poly（propylene oxide） （PPO） segment in the poly（ethylene oxide）- block-PPO-block-poly（ethylene oxide） （PEO-b-PPO-b-PEO）. It is worth noting that, when the loading level of SN is lower than 3wt%, the SNs with moderate PEO length result in the simultaneous increase in strength, elongation and Young＇s modulus in contrast with neat WPU. If there is no stretching free PEO chain, both strength and elongation decrease in spite of an increase in Young＇s modulus. However, too long PEO chains result in the decrease of mechanical performances while the relatively higher loading-level of SNs also inhibits the enhancement of strength and elongation.

Mild-temperature Synthesis of Covellite Copper Sulfide Hexagonal Nanoplatelets via the Hydrothermal Route

Covellite CuS hexagonal nanoplatelets were prepared by a simple hydrothermal process at mild temperature, using sodium dodecyl benzene sulfonate （SDBS） as an assisting reagent. The products were characterized by X-ray powder diffraction （XRD）, transmission electron microscopy （TEM） and UV-vis absorption spectroscopy. An energy-dispersive X-ray spectrometer （EDS） was used to analyze the elementary compositions of the intermediate products. A possible formation mechanism of hexagonal nanoplatelets is discussed, using TEM observations.