Same impact momentum causes different degrees of spinal cord injury

The weight-drop impact is widely used in making animal model of spinal cord injury （SCI）. But there has not yet been an appropriate unit for the quantification of the impact. In this study, we compared the degrees of the spinal cord injury caused by weight-drop impact with the same momentum but different combinations of drop weight and drop height, in order to test whether ＂momentum＂ is capable of being the unit for the quantification of weight- drop impact. Thirty adult rats were randomly allocated to three groups and were injured with 5 g-10 cm （group A）, 10g-2.5 cm （group B） and 15 g-l.ll cm （group C） impacts with the same momentum to the spinal cord, respectively. Open-field locomotor function was evaluated using the Basso-Beattie-Bresnahan （BBB） locomotor rat- ing scale. The percentage of spared tissue area （STA） at the epicenter, and 500, 1000 and 1500 gm from the epicenter was calculated using serial sections stained by hematoxylin and eosin. As a result, the behavioral recovery （BBB scores） and the STA percentage were similar in group B and group C. However, the BBB score in group A was significantly lower than that in groups B and C at the same time point post injury. The STA percentage was signifi- cantly less and the lesion/cavity length was significantlygreater in group A than in groups B and C. These suggested that the 5 g-10 cm weight-drop impact, compared with the other two impacts with different weights and heights, caused a greater damage of the spinal cord when the momentum was the same. So, these impacts with the same momentum but different weights and drop heights cause different degrees of spinal cord injury. Momentum alone is inadequate to be the unit for the qualification of weight- drop impact and to be used to predict the extent of injury.     

Reverse leakage current in AlGaN-based ultraviolet light-emitting diodes

The reverse leakage characteristics of AlGaNbased ultraviolet light-emitting diodes fabricated on sapphire substrate are studied by temperature-variable current–voltage(I–V)measurement from 300 to 450 K.At low-reverse bias range(0–0.5 V),the reverse leakage current exhibits tunneling characteristics.Meanwhile,under a more negative reverse bias range([0.5 V),the log(I)–log(V)plots exhibit close-to-linear dependency,which is in good agreement with the transport mechanism of space-charge limited current.A phenomenological leakage current model focusing on electron transmission primarily through continuous defect band formed by linear defects like dislocations is suggested to explain the reverse current–voltage characteristics.     

Er3+/Yb3+共掺双包层光纤放大器的增益特性

基于速率方程和功率传输方程,分析了Er³⁺/Yb³⁺共掺双包层光纤放大器增益特性随光纤长度的变化及信号光、抽运光功率对放大器增益的影响,并进行了实验验证。结果表明:有源光纤长度对放大器增益有影响,大信号输入时放大器达到增益饱和对应的光纤长度更短;放大器增益随着信号光和抽运光功率不同而变化,要适当调整其大小以获得较高的放大增益。     

两步法制备性能优良的ZnO纳米线

利用热蒸发和溶液浸泡两步法制备了性能优良的ZnO纳米线，研究了这些ZnO纳米线的光致发光和场发射特性.与直接采用热蒸发方法生长的ZnO纳米线相比，由该方法得到的ZnO纳米线表现出了更好的紫外发光特性，同时发生5 nm的蓝移，场发射测试表明其开启电场和阈值电场分别达到2.3 V/μm和6.8 V/μm.该方法适用于制备光致发光和场发射性能优良的ZnO纳米线.     

窄带滤光片精确波长激光器高频调制特性研究

采用窄带滤光片作为选频元件对精确波长激光器高频调制特性进行了小信号分析.优化设计了外腔长度,兼顾了激光器的阈值特性和工作稳定性;给出了适用于外腔情况的光子寿命表达式;讨论了外腔反射率、管芯与外腔耦合效率以及外腔长度对光子寿命的影响.数值分析结果表明该类型激光器的调制响应特性主要取决于等效光子寿命,受偏置电流影响不大.当外腔反射率为72%,管芯与外腔耦合效率为80%,等效外腔长度为9.7 mm时,光子寿命为100 ps,激光器的调制带宽约为2 GHz,适合于以太网无源光网络中波分多址技术应用的需要.     

用铁砂代替Fe_2O_3制备M_x—2000软磁铁氧体

用铁砂代替Fe_2O_3,制备性能优良的软磁MnZn铁氧体,其性能如下:μ_1:2000±20％; B(H=800A/m):360-390mT;H_c:12.8-14.8A/m:T_c:160-180℃tgδ/μ(f=100KC,H=0.4A/米):21.0-27.0×10~(-6);Tkμ/μ(20-60℃):1.3-1.8×10~(-6).针对铁砂的特点,本文对用铁砂制备软磁MnZn铁氧体的工艺进行研究,得出一些规律和特点。     

Distribution,ecology, and oxygen and carbon isotope characteristics of modern planktonic foraminifers in the Makarov Basin of the Arctic Ocean

The Arctic region, with magnificent ice cover on the surface of the Arctic Ocean and adjacent seas, is not only extremely sensitive to but also has strong amplification effects on climate change. Observations during the past decades have documented substantial retreat and thinning of the Arctic sea-ice cover, a process that is accelerating. Its feedback and impact on the global climate has become an important subject of current climate change research. Calcite tests of planktonic foraminifers are major constituents in pelagic sediments, and they provide valuable materials for the reconstruction of past oceanographic conditions. However, research is still sparse in the Arctic sea area because of limited availability of the materials for investigation. Here, we present a study of modern foraminifers from the plankton tow samples taken in the Makarov Basin of the Arctic Ocean during the fourth Arctic expedition of China. We have analyzed ecological information stored in the modern planktonic foraminifers and in their stable isotope signals, and established a relationship between the distribution of the main taxa and the environment. Our main observations are as follows:(1) in the Makarov Basin, the polar species Neogloboquadrina pachyderma(sinistral coiling) dominates the [150 lm planktonic foraminiferal assemblages.(2) The planktonic foraminifers live mainly in the upper halocline at a water depth of 50–100 m and less in the depth interval of 100–200 m.(3) Temperature change in the halocline can affect the absolute abundance of planktonic foraminifers and their distribution in the water column. The warmer halocline is more favorable to the development of planktonic foraminifers.(4) A lighter d18O value(2.11 %) of N. pachyderma(sin.) is recorded in the depth interval of 100–200 m, which is likely related to the isotopically light brines separated out during sea ice freezing. The relatively heavy d18O value(1.68 %–2.68 %, average 2.27 %) in the depth interval of 50–100 m may be influenced by the low salinity water with the relatively heavy d18O value formed during the sea-ice melting in the surface layer.     

激光二极管腔体有源区长度的优化设计

由激光二极管(LD)输入、输出的关系,得到激光器腔体参数与注入电流的关系,进而给出在设计激光器时遇到的相关限制的方程,以及LD电流与某种形式的电流增益转换因子的关系,根据增益曲线上的最佳工作点可优化腔体长度参数.讨论了共面LD在固定总腔长、固定无源区长度、固定有源与无源区的长度比等条件下有源区长度的优化.     

Synthesis of urchin-like Sn–ZnO–C composite and its enhanced electrochemical performance for lithium-ion batteries

Urchin-like Sn–ZnO–C composite have been successfully prepared by thermal annealing of ZnSn(OH)6precursor in acetylene/argon gas(1/9;v/v).The phase of the urchin-like Sn–ZnO–C has been characterized by X-ray diffraction(XRD)and Raman spectrum.The images of scanning electron microscopy(SEM)and transmission electron microscope(TEM)demonstrate that the Sn–ZnO–C composite with an average of 3 lm in diameter is composed of many core–shell nanowires and carbon nanotubes emanated from the center.The thermal annealing temperature and time have crucial effects on the formation of urchin-like structure and carbon content of the Sn–ZnO–C composites.As an anode for lithium-ion batteries,the urchin-like Sn–ZnO–C composite delivers a discharge capacity of 1,034.5 mAh/g in initial cycle and 571.9 mAh/g reversible discharge capacity after 25 cycles at a current density of 50 mA/g.The superior energy storage properties highlight the urchin-like Sn–ZnO–C composite as a potential alternative anode material in lithium-ion batteries.     

Carrier-envelope phase passively stabilized near-infrared laserpulses from a dual-frequency pumped noncollinear opticalparametric amplifier

By inversing the signal and idler in a two-stagenoncollinear optical parametric amplifier which is, respec-tively, pumped by the second harmonic and fundamentalwave of femtosecond Ti：sapphire laser at repetition rate of1 kHz, the carrier-envelope phase （CEP） passively stabilizedpulses with a tunable wavelength from 1.1 to 1.6 μm areobtained with maximum energy of95 μJat 1.3 μm underthepump energy ofS00 μJ. The CEP jitter of pulses is 108 mradmeasured by anf-2finterferometer. This work demonstratesa new way to efficiently generate tunable near-infraredfemtosecond laser pulses with self-stabilized CEP.     

Multistage interband cascade photovoltaic devices with a bandgapof 0.23 eV operating above room temperature

Interband cascade （IC） photovoltaic （PV）device structures, consisting of multiple discrete InAs/GaSb superlattice absorbers sandwiched between electronand hole barriers, were grown by molecular beam epitaxy.Details of the molecular beam epitaxy growth and materialcharacterization of the structures are presented. The dis-crete absorber architecture enables certain advantages, suchas high open-circuit voltage, high collection efficiency,high operating temperature, and smooth integration ofcascade stages with different bandgaps. The two- andthree-stage ICPV devices presented in this article operate atroom temperature with substantial open-circuit voltages ata cutoff wavelength of 5.3 μm （corresponding to a bandgapof 0.23 eV）, the longest ever reported for room temperaturePV devices. The device characteristics indicate a high levelof current matching and demonstrate the advantages of theinterband cascade approach in thermophotovoltaic celldesign.     

量子阱LD有源区量子阱数目的优化设计

采用直观的载流子、光子库模型,导出半导体激光器速率方程,得到输入电流、输出光功率的关系以及激光器腔体参数与注入电流的关系,从而给出在设计激光器时遇到的相关限制的方程,以及LD电流与某种形式的电流增益转换因子的关系,根据增益曲线上的最佳工作点来优化有源区量子阱数目．给出了共面量子阱LD在固定有源长度、固定无源区长度的共面量子阱激光器的量子阱数目优化方案．     

一款工作于2.4 GHz频段的带有源负载的高性能双平衡有源混频器

对带有源负载的CMOS双平衡Gilbert有源混频器的1/f噪声、线性度与转换增益进行深入分析。这款采用PMOSFETs做负载的混频器工作于2.4 GHz频段。为降低混频器的1/f噪声, 利用双阱工艺中的寄生垂直NPN晶体管作为开关, 同时在PMOSFETs处并联最低噪声的分流电路作为负载。运用在PMOSFETs处的高性能运算放大器, 不仅为零中频输出提供了合适的直流偏置电压, 以避免下级电路的饱和, 并能够为混频器提供足够高的转换增益。同时, 在输入跨导(G_m)级电路中采用电容交叉耦合电路能够将转换增益进一步提高。为了增加混频器的线性度, 采用共栅放大器作为输入跨导级电路。这款混频器采用TSMC 0.18m 1-Poly 6-Metal RF CMOS工艺, 在1.5 V电源电压、3 mA的电流消耗下获得了17.78 dB的转换增益、13.24 dB的噪声因子和4.45 dBm输入三阶交调点的高性能。     

Tailoring soft magnetic properties of Fe-based amorphous alloys through C addition

It is known that developing Fe-based amorphous alloys with the saturation flux density(B_s) higher than 1.65 T is a major challenge.In present work,effects of C addition on magnetic properties of Fe-based amorphous alloys were systematically studied.It has been found that the addition of C can significantly increase the saturation flux density(B_s) and the magnetic flux density at 800 A/m(B_(800)) of the Fe-B-C-Si-P amorphous alloys.After the addition of C,the B_s of the amorphous alloys increase from 1.61 T(Fe_(83)B_(13)Si_3 P_1) to 1.65-1.71 T(Fe_(83)B_(13-x)C_xSi_3 P_1,x=1.5,2,3 and 4). The Fe_(83)B_(10)C_3 Si_3 P_1 amorphous alloy possesses excellent soft magnetic properties with high B_s of 1.71 T and low H_c of 1.5 A/m.It shows that density increase of the alloys and weakened metalloid-sp/metal-d bonding caused by C addition contribute to the increment of B_s.It suggests that the newly developed high-performance amorphous alloys possess great potential in application.     

Injection processing and foaming behaviors of polypropylene composite foams

A volume-adjustable cavity of molding machine for polymer foaming was fabricated with renovation of an ordinary injection molding machine. Polypropylene （PP） composite foams were prepared by chemical foaming method via the volume-adjustable cavity of the molding machine. The decompressing and short shot processes in preparing the samples were carded out to adjust the cell structure of the foamed samples. The structures that foamed insufficiently, moder- ately, and excessively were observed in these two foaming processes. The foamed PP composite samples generated in decompressing pro- cess have more desirable cell s~cture than those generated by short shot process, specifically, the cell structure with the cell size of 46.97 IJxn, cell density of 3.18x 106 cell/cm3, and cell size dispersion of 10.76 ~m was achieved in the decompressing process. A controlled foaming process was realized through the decompressing process using the injection foaming equipment with a volume-adjustable cavity. The foamed PP composite has the insufficient, moderate, and excessive foamed structures in these two foaming processes.     

The effect of spacer in hybrid white organic light emitting diodes

Two kinds of highly efficient,bright hybrid white organic light emitting diodes have been fabricated by utilizing ambipolar material 4,4-N,N-dicarbazolebiphenyl(CBP)and unipolar material N,N0-di(naphthalene-1-yl)-N,N0-diphenyl-benzidine(NPB)as the spacer,respectively.By adjusting the thickness of spacers together with effectively utilizing combinations of exciton-harnessed orangephosphorescence/blue-fluorescence,the current efficiency of optimal device with CBP spacer and device with NPB spacer are 31.0 and 38.9 cd/A,the maximum power efficiency are 23.9 and 29.1 lm/W,the maximum brightness are 87,249 and 75,501 cd/m2,and the Commission Internationale de l’Eclairage(CIE)coordinates are(0.42,0.43)and(0.47,0.44)at a voltage of 11 V,respectively.Furthermore,systematic investigations focused on the effects of spacers on device performance have been performed.By virtue of the multifunctional spacer,energy transfer between the phosphorescent and fluorescent emitters can be avoided while the carriers still can pass through this spacer bridge,which is important to realize such high device performance.In addition,a novel concept that both ambipolar materials and unipolar materials can be the promising candidates for spacers has been proposed if the thickness of spacers with high triplet energy is optimized.     

The effect of DIO additive on performance improvement of polymer solar cells

A series of polymer solar cells （PSCs） based on poly （diketopyrrolopyrrole-terthiophene） （PDPP3T） and [6,6]-phenyl-C71-butyric acid methyl ester （PC71BM） as active layer were fabricated to investigate the effect of 1,8- diiodooctane （DIO） on the performance of PSCs. The power conversion efficiency （PCE） of PSCs was increased from 3.77 % to 4.37 % for the cells with DIO additive. The underlying reason may be attributed to that DIO additive could make PC71BM more dispersive in the active layer, forming a better bicontinuous interpenetrating network for excition dissociation and charge carrier transport. There- fore, the short circuit current density （Jsc） and fill factor （FF） was increased from 8.25 to 9.18 mA/cm2 and from 67.2 % to 70.0 % for the PSCs with DIO additive compared with PSCs without DIO additive.     

CeO2 thin films grown on biaxially textured nickel (001)

CeO\-2 films have been grown on biaxially textured Ni substrates at various temperatures. The results show that CeO\-2 films without IBAD are dominated by (111) orientation from room temperature to 800℃ while the preferential orientation of CeO\-2 films with IBAD is (001) at lower deposition temperature and (111) at deposition temperature higher than 450℃. CeO\-2 films with better in_plane texture and out_of_plane orientation can be grown at 360℃ with 240 eV ion energy and 200 μA/cm\+2 ion current density.     

Sensitivity analysis of single-angle polarization reflectance observed by satellite

Two channels of the Cloud Aerosol Polarimetric Imager, onboard the TanSat-Chinese carbon dioxide observation satellite, are designed to detect the polarization state of radiation reflected by the earth-atmosphere system in a single-viewing angle. Aiming to understand how the earth and atmospheric parameters affect the polarization state of radiation, we conduct a sensitivity analysis of the polarized reflectance at the top of atmosphere （TOA） with respect to the aerosol microphysical parameters, atmo- spheric profiles, and surface polarization properties. It is found that （1） the TOA polarization reflectance at 0.66 μm is most sensitive to the real part of the aerosol complex refractive index, the mean radius of the fine mode aerosol particles, as well as atmospheric pressure and temperature profiles; （2） the TOA polarization reflectance at 1.64 μm is sensitive to the volume ratio between the coarse mode and fine mode particles as well, but it is not sensitive to atmospheric profiles; and （3） surface polarization properties have a relatively weak influence on the TOA polarization reflectance at both 0.66 and 1.64 μm.     

半导体光放大器静态增益饱和特性的理论研究

通过数值模拟对半导体光放大器（SOA）的静态增益饱和特性进行了理论研究。分别在考虑和不考虑放大的自发辐射（ASE）的情况下，给出了连续光（CW）单光束入射时SOA的增益随入射光功率、注入电流和波长的变化以及有源区内载流子浓度的分布，并且在不考虑ASE的前提下，讨论了连续光双光束入射的情况，比较了两束光同向和相向入射时SOA增益和有源区内载流子浓度分布的差别。