2A12-T4铝合金再填充搅拌摩擦点焊过程中的材料流动行为和微观组织演变

In this study, we used the stop-action technique to experimentally investigate the material flow and microstructural evolution of alclad 2A12-T4 aluminum alloy during refill friction stir spot welding. There are two material flow components, i.e., the inward- or outward-directed spiral flow on the horizontal plane and the upward- or downward-directed flow on the vertical plane. In the plunge stage, the flow of plasticized metal into the cavity is similar to that of a stack, whereby the upper layer is pushed upward by the lower layer. In the refill stage, this is process reversed. As such, there is no obvious vertical plasticized metal flow between adjacent layers. Welding leads to the coarsening of S (Al₂CuMg) in the thermo-mechanically affected zone and the diminishing of S in the stir zone. Continuous dynamic recrystallization results in the formation of fine equiaxed grains in the stir zone, but this process becomes difficult in the thermo-mechanically affected zone due to the lower deformation rate and the pinning action of S precipitates on the dislocations and sub-grain boundaries, which leads to a high fraction of low-angle grain boundaries in this zone.     

Wave drag of rapidly and horizontally moving Rankine ovoid in uniformly stratified fluid

A theory on the wave drag as the Rankine ovoids moving horizontally, uniformly and rapidly in uniformly vertical stratified fluid （or ocean） is presented. A mass source resulting from the theory in a uniform fluid is used to model a hydrodynamic interaction between the Rankine ovoid and stratification. Theoretical results show that there exists an asymptotic state of the drag in supercritical regimes where internal Froude numbers are large. When the Rankine ovoid reduces to a sphere, the result we obtained is in good agreement with the previous theoretical and experimental results. An experiment on the elongated Rankine ovoid is also carried out to validate the theoretical results.     

Simulation and evaluation of the quality and availability of typical GLI ocean image

ADEOS-II satellite will be launched in the near future. It collocates many remote sensing instruments in the same platform. Among them, Global Image (GLI) is considered to be a main sensor which will play a key role. In order to understand the characteristics of future GLI ocean color images, a simulation and evaluation of the quality and availability of GLI typical ocean image has been done. In the paper, we first introduce the simulation models briefly, and simulate typical cases of radiance images at visible channels, in which the radiance distribution is based on geographic location, the satellite orbital parameters and sensor properties. A method, complex signal noise ratio (CSNR) to evaluate the image quality and availability, is developed according to the characteristics of image. Meanwhile, a series of CSNR images are generated from the simulated radiance components for different cases, which can be used to evaluate the quality and availability of GLI images before the ADEOS-II is placed in orbit. Finally, the quality and availability of GLI images are quantitatively analyzed by the simulated CSNR data. The results will be beneficial to the people who are in charge of GLI mission or plan to use the data from GLI.     

A quasi-global 1/10° eddy-resolving ocean general circulation model and its preliminary results

In this study,a quasi-global(excluding the Arctic Ocean) eddy-resolving ocean general circulation model(OGCM) is established based on the latest version of the LASG/IAP Climate system Ocean Model(LICOM2.0).The horizontal resolution and vertical resolution are increased to 1/10° and 55 layers,respectively.Forced by the surface fluxes from the reanalysis and observed data,the model has been integrated for approximately 20 model years(20 a).During the last 8 a,the model is driven by daily mean wind stresses from QuikSCAT and heat fluxes from reanalysis data from 2000 to 2007.The basic performance of the OGCM is analyzed using the last 8 a simulation output.Compared with the simulation of the coarse-resolution OGCM,the eddy-resolving OGCM not only better simulates the spatial-temporal features of mesoscale eddies and the paths and positions of western boundary currents but also reproduces the large meander of the Kuroshio Current and its interannual variability.Another aspect,namely,the complex structures of equatorial Pacific currents and currents in the coastal ocean of China,are better captured due to the increased horizontal and vertical resolution.     

A fingerprint feature extraction algorithm based on curvature of Bezier curve

Fingerprint feature extraction is a key step of fingerprint identification. A novel feature extraction algorithm is proposed in this paper, which describes fingerprint feature with the bending information of fingerprint ridges. Ridges in the specific region of fingerprint images are traced firstly in the algorithm, and then these ridges are fit with Bezier curve. Finally, the point that has the maximal curvature on Bezier curve is defined as a feature point. Experimental results demonstrate that this kind of feature points characterize the bending trend of fingerprint ridges effectively, and they are robust to noise, in addition, the extraction precision of this algorithm is also better than the conventional approaches.     

A non-commutative time-frequency tomography

The characterization of non-stationary signal requires joint time and frequency information. However, time and frequency are a pair of non-commuting variables that cannot constitute a joint probability density in the time-frequency plane. The time-frequency distributions have difficult interpretation problems arising from negative and complex values or spurious components. In this paper, we get time-frequency information from the marginal distributions in rotated directions in the time-frequency plane. The rigorous probability interpretation of the marginal distributions is without any ambiguities. This time-frequency transformation is similar to the computerized axial tomography (CT or CAT) and is applied to signal analysis and signal detection and reveals a lot of advantages especially in the signal detection of the low signal/noise (S/N).     

Recent progress of deep seismic experiments and studies of crustal structure in northern South China Sea

The South China Sea (SCS) is one of the largest marginal seas in the western Pacific. Its northern part has the features of a passive continental margin. The studies of deep crustal structure in this area are very important for understanding the tectonic nature, evolution history, basin formation of the northern margin, and the origin of the SCS. In the past decades, the deep seismic experiments of crustal studies in the northern SCS have gone through three stages, namely the sonobuoy, two-ship Expanding Spread Profile (ESP), and Ocean Bottom Hydrophone/Seismometer (OBH/OBS). Along the continental slope, the sonobuoy experiments provided useful information about the velocity structure of the upper crust, while the ESP data recorded for the first time the seismic signals from deep crustal structure and Moho interface. And the OBH/OBS profiles revealed the crustal structure in much greater detail. This paper first gives a brief historical review of these deep seismic experiments and studies, then a summary of the latest progress and important research results. The remaining problems and suggestions for further research work are presented as conclusive remarks.     

Passive seismic experiment and ScS wave splitting in the southwestern subbasin of South China Sea

The seismic experiment of 3D array of OBS in the southwestern sub-basin of the South China Sea(SCS) is briefly introduced in this paper.The data analysis of broadband OBS shows that totally 93 earthquakes with magnitude of Ms 6.0-6.9 and 10 earthquakes with magnitude above Ms 7.0 were recorded in high quality during this experiment,especially the catastrophic earthquake Ms 9.0 occurred in the east sea area of Japan on March 11,2011.The anisotropy parameters inversion of ScS wave of four events above Ms 7.0 indicates that the fast direction of shear wave is N58°E parallel to the ceased spreading ridge of the southwestern sub-basin of SCS(the slow direction is S35°E perpendicular to the spreading ridge),which means the spreading ridge is under compressing stress at present and the cessation of seafloor spreading is related to such stress field as well.     

Improved MFCC-Based Feature for Robust Speaker Identification

The Mel-frequency cepstral coefficient (MFCC) is the most widely used feature in speech and speaker recognition. However, MFCC is very sensitive to noise interference, which tends to drastically degrade the performance of recognition systems because of the mismatches between training and testing. In this paper, the logarithmic transformation in the standard MFCC analysis is replaced by a combined function to improve the noisy sensitivity. The proposed feature extraction process is also combined with speech enhancement methods, such as spectral subtraction and median-filter to further suppress the noise. Experiments show that the proposed robust MFCC-based feature significantly reduces the recognition error rate over a wide signal-to-noise ratio range.     

Ocean primary productivity estimation of China Sea by remote sensing

Ocean primary productivity is a key parameter in the research of globalcarbon cycle, ocean biological resources, and in evaluation of the feature and quality of ocean biological environment. Traditional shipboard measurement which is costly and time-consuming is impossible to obtain the spatial and temporal information on primary productivity on a large scale in a short period of time. Satellite remote sensing is an effective strategy to acquire the ocean information in near real time. Here we propose a model special for China Sea based on the concept of primary productivity using in situ primary productivity and environmental data from 1984 to 1990, and discuss every modeling parameter which can be retrieved by remote sensing in detail. The reliability of this model is tested by in situ data, and the comparison of other primary productivity models is made. We also analyze the temporal and spatial distribution of China Sea primary productivity in 2000. From our analysis the satellite remote sensing data have been proved very useful for ocean primary productivity study.     

交叉能量矩阵在海底地震仪水平分量旋转中的应用

海底地震仪(OBS)地震数据为4个分量:1个垂直分量,2个水平分量和1个水听器.OBS采集数据为共接收点数据,即炮点沿测线移动而检波点不动,这就导致同一采集系统中道与道之间不具有一致的振幅和极化方向,从而道与道之间振幅能量不一致,这一问题的解决是通过水平分量旋转完成的.利用x,y分量构成的交叉能量矩阵求解其最大本征特征向量值,从而确定极化方向进行水平分量旋转.通过实际OBS数据应用得到了很好的应用效果,且计算速度快,缩短了处理周期.     

国产海底地震探测装备技术研发与应用

为研究深部壳幔结构、海底地震活动性和实现地震海啸预警,需要在海底布设海底地震仪开展地震观测。深海海底地震仪因涉及地震传感器、深水水听计、声学换能器与耐压封装等先进国际技术,我国高性能深海海底地震仪长期是空白。对此,中国科学院地质与地球物理研究所通过多年持续核心技术攻关和多次深海试验验证,解决了数字调零宽带地震传感技术、全海深陶瓷压电水听传感技术、软硬协同优化低功耗采集技术和万米高可靠性释放回收技术等关键技术难题,自主成功研发了包括便携式海底地震仪、宽频带海底地震仪与实时海底地震仪等系列海底地震探测装备（统称为IGG-OBS）。实验结果表明：自主研发的IGG-OBS仪器装备达国际先进水平;近年来在多个科考航次中发挥支撑作用,总计投放达1400余台次,综合回收率大于90%;通过在洋中脊、海山、俯冲带等多种复杂海底区的实际观测,数据质量合格率>98%,具备复杂构造成像能力,已进入实质性应用阶段,为我国深海科考、大洋调查及近海灾害预警监测等提供了关键技术支撑。     

Identification and analysis of shear waves recorded by three-component OBSs in northeastern South China Sea

Structure models associated with P- and S-wave velocities contain considerable amount of information on lithology and geophysical properties, which can be used to better understand the complexity of the deep crustal structure. However, records of converted shear waves are less due to the speciality of seismic survey at sea and the rigorous generated conditions. The study on shear waves has always been a weakness for studying the deep crustal structures of South China Sea （SCS）. In this paper, eleven three-component OBSs were deployed along the Profile OBS-2001 in northeastern SCS. After the data processing of polarization and band-pass filter, converted S-wave phases were identified in the radical component records of nine OBSs. Taking the OBS7 as an example, identification and analysis of converted shear waves were presented and discussed in detail. A few phase groups, such as PwSc, PgSs, PnSc, ProS, and PwSn, were found coming from the deep crust or Moho interface by simple theoretical model calculation and ray-tracing simulation. The results not only provide the underlying basis for studies of S-wave velocity structure and Poisson＇s ratio structure, but also reveal the relationship between crustal petrology and seismology, which will be of importance for making full use of S-wave information in the future.     

南海碳循环：通量、调控机理及其全球意义

 基于多年观测研究,南海CO₂源汇及其时空格局的总体特征是：南海海盆是大气CO₂的弱源区,年均海-气CO₂通量为2.1±0.3 mmol·m^-2·d^-1;而南海北部陆架是碳汇区,年均CO₂通量为-2.2±3.5 mmol·m^-2·d^-1;南海总体上每年向大气释放的碳量为1330万±1880万t。由于南海位于陆地-大洋交界带,存在多个界面过程,根据物质交换发生的不同界面,可将南海海盆和北部陆架视为大洋主控型边缘海（OceMar）和河流主控型陆架海（RiOMar）。这两类系统分别接受大洋和河流输入的外源无机碳和营养盐,经由一系列动力过程进入真光层后同时被生物消耗,无机碳和营养盐之间的“竞争”最终决定CO₂源汇格局。在南海海盆,无机碳相对过剩,部分以CO₂形式向大气释放,即为源;而在南海北部陆架,无机碳相对不足,系统需从大气补充CO₂,即为汇。南海碳循环机理及其框架对于更好地理解全球其他陆架边缘海系统具有重要的借鉴意义。     

Intraseasonal variability of the subsurface temperature observed in the South China Sea (SCS)

Using Morlet wavelet transform we investi- gated the intraseasonal variability of the subsurface tem- perature in the SCS by analyzing ATLAS mooring data ob- tained during the South China Sea Monsoon Experiment (SCSMEX). It is found for the first time that subsurface temperature in the SCS exists intraseasonal variability, par ticularly in winter. The strongest intraseasonal variability ranges from 50 to 100 m with its maximum amplitude about 1.0-2.0℃. The subsurface temperature intraseasonal vari- ability in the SCS is primarily induced by local wind stress curl via adjusting the vertical displacement of thermocline. It reveals the important characteristic of intraseasonal varia- tions in the SCS upper ocean vertically.     

基于被动太赫兹波图像的图像分割技术

研究被动太赫兹波图像的图像分割算法. 针对被动太赫兹波图像水平和竖直方向平滑程度不同的特点,提出了一种改进的高斯-拉普拉斯算子,不同于传统高斯-拉普拉斯算子各向同性的特点,改进的算子在水平和垂直方向上对边缘具有不同的检测尺度. 实验表明,利用该算子可以将被动太赫兹波图像中的人和隐匿物品自动分割,能够准确、快速地对可疑的隐匿物品进行定位,使被动太赫兹波成像技术满足实际应用的需求.      

利用光泵磁共振测芜湖地区的地磁场

光泵磁共振是利用光抽运效应来研究原子超精细结构塞曼能级间的磁共振．根据光磁共振原理,利用光泵磁共振实验对共振信号进行检测,观测水平磁场和垂直磁场对共振信号的影响．分别通过两种方法测量出地磁场的水平分量和垂直分量,进而将二者合成,得出芜湖地区地磁场强度大小．     

Recycled dehydrated lithosphere observed in plume-influenced mid-ocean-ridge basalt

A substantial uncertainty in the Earth's global geochemical water cycle is the amount of water that enters the deep mantle through the subduction and recycling of hydrated oceanic lithosphere. Here we address the question of recycling of water into the deep mantle by characterizing the volatile contents of different mantle components as sampled by ocean island basalts and mid-ocean-ridge basalts. Although all mantle plume (ocean island) basalts seem to contain more water than mid-ocean-ridge basalts, we demonstrate that basalts associated with mantle plume components containing subducted lithosphere--'enriched-mantle' or 'EM-type' basalts--contain less water than those associated with a common mantle source. We interpret this depletion as indicating that water is extracted from the lithosphere during the subduction process, with greater than 92 per cent efficiency.