基于受激增益与自发衰减的激发-探测显微技术

基于激发-探测显微技术研究受激增益与自发衰减现象。采用脉冲二极管激光器(λ_(pu)=635 nm作为激发光束)与锁模掺钛蓝宝石激光器(λ_(pr)=780 nm作为探测光束)。受激增益部分,发射光束在频率f_1被调制,利用光电二极管作为探测器(PDA 36A,Thorlabs),探测光被相应地解调来提取透射方向的信号;自发损耗部分,探测光束在频率f_2被调制,从探测荧光由光电倍增管以反射模式解调自发损耗信号。所有情形下使用高性能锁模放大器(HF2LI,Zurich Instruments)。锁模放大器的输出信号接着输入扫描单元的A/D通道用于图像重构。扫描速率设为频率500 Hz,与锁模放大器1.99 ms的时间常数相匹配。由解调荧光信号获取背景大大减少的荧光寿命和光学部分属于散粒噪声的图像。另外,此技术改善信噪比,提高类似多光子显微镜的穿透深度,无须昂贵的飞秒激光器。

营销术种种

营销术种种高崇明，周立早探测术。随着科技进步，老商品的造型、功能、耐用、节能、携便、流行、款式等方面都在不断改进，新创制的商品将不断出现。对于改进与创新的商品能否被消费者接受，并能尽快实现其使用价值，这就要求生产者或销售者都要附设试产、试销探测点。例...

内镜神经外科手术技术百年应用与研究进展

百年来神经内镜手术设备和神经内镜技术日新月异,内镜神经外科手术技术从单纯内镜手术到多种神经外科新技术的联合应用都取得了巨大进展。神经内镜相关器械设备的研究开发:神经内镜可以与激光、立体定向仪、显微镜、B超、导航系统等相融合,拓展应用领域提高手术质量。随着医学科学的发展,神经内镜与神经导航系统、术中超声探测系统、激光系统、人工智能机器人系统相互结合技术体系的不断成熟,以及我国熟练掌握神经内镜手术技术医师队伍的不断壮大,内镜神经外科一定会创造无限美好的未来。

10 kV电力电缆故障检测相关技术问题探讨

在整个电力系统当出现中,电缆的作用是相当巨大的,可以说是电力系统的主动脉。在电力系统长期的运行过程当中,由于运行的损耗加上各种故障问题,电缆会出现一定的问题,比如老化以及过热等现象,造成供电故障的发生,因此需要对电力电缆的故障检测法进行分析,并且采取针对性的措施解决。文章首先对10 kV电力电缆故障原因和分类进行了分析,其次对10 kV电力电缆故障的检测方法进行了分析。最后以实例进行了说明。

腹腔镜在胃肠外科的应用

自1987年法国医师 Mouret 首次完成腹腔镜胆囊切除术以来,腹腔镜技术在世界范围内广泛普及并形成一门新的学科一腹腔镜外科学.腹腔镜是集电学、光学等高科技为一体的一门新的技术,最初用于胆囊的切除,随着对腹腔镜认识的提高、

Ultrafast Carrier Dynamics in CdSe/CdS/ZnS Quantum Dots

The intra- and inter-band relaxation dynamics of CdSe/CdS/ZnS core/shell/shell quantum dots are investigated with the aid of time-resolved nonlinear transmission spectra which are obtained using femtosecond pump-probe technique. By selectively exciting the core and shell carrier, the dynamics are studied in detail. Carrier relaxation is found faster in the conduction band of the CdS shell （about 130 fs） than that in the conduction band of the CdSe core （about 400 fs）. From the experiments it is distinctly demonstrated the existence of the defect states in the interface between the CdSe core and the CdS shell, indicating that ultrafast spectroscopy might be a suitable tool in studying interface and surface morphology properties in nanosystems.

乳腺癌前哨淋巴结显像的临床价值

目的:探讨乳腺癌前哨淋巴结(SLN)显像的临床价值。方法:91例T1-2N0期乳腺肿瘤术前或局部手术后在患者瘤体上方的皮下注射了99mTc-人血清白蛋白(55.5 MBq/0.5ml)或在瘤周乳腺组织注射99mTc-硫胶体(92.5 MBq,/4ml),其中63例进行了乳腺淋巴显像,70例于注射后2-16小时、在腋淋巴清扫术前进行了术中γ探头引导下的乳腺SLN活检。结果:两种示踪剂均能快速显示淋巴结,以0.5h显像结果为准,SLN显像成功率为81％(51/63),13.7％(7/51)的SLN放射性强度低于第二个淋巴结,其中证实85.7％(6/7)存在转移。乳腺内、外侧部肿瘤的内乳SLN出现率为38.5％(5/13)、26.3％(10/38)。SLN活检成功率为95.7％(67/70),SLN数量1.6±1.1只(1-5只)。SLN预测腋窝淋巴结转移的灵敏度、特异性、准确性、PPV和NPV分别为82.75％(24/29)、100％(38/38)、92.53％(62/67)、100％(24/24)和88.37％(38/43)。结论:乳腺前哨淋巴结显像可以了解所显淋巴结的质与量以帮助活检者正确定位SLN,观察乳腺癌淋巴引流个体变异以引导活检部位和制定辅助治疗方案。

硅低速刻蚀和钨膜刻蚀研究

针对半导体器件研制过程中等离子体刻蚀工艺的具体需要 ,研究了硅的低速率刻蚀和钨薄膜的刻蚀 .得到了加磁场条件下刻蚀速率与刻蚀气体流量、射频功率的关系曲线 .得到了不加磁场时不同刻蚀气体流量下钨的刻蚀速率 ,以及在刻蚀气体中掺杂不同比例氧气时硅的刻蚀速率 .对上述结果加以简单的讨论并给出了符合工艺要求的刻蚀条件 .

Fault detection of excavator’s hydraulic system based on dynamic principal component analysis

In order to improve reliability of the excavator's hydraulic system, a fault detection approach based on dynamic principal component analysis(PCA) was proposed. Dynamic PCA is an extension of PCA, which can effectively extract the dynamic relations among process variables. With this approach, normal samples were used as training data to develop a dynamic PCA model in the first step. Secondly, the dynamic PCA model decomposed the testing data into projections to the principal component subspace(PCS) and residual subspace(RS). Thirdly, T2 statistic and Q statistic performed as indexes of fault detection in PCS and RS, respectively. Several simulated faults were introduced to validate the approach. The results show that the dynamic PCA model developed is able to detect overall faults by using T2 statistic and Q statistic. By simulation analysis, the proposed approach achieves an accuracy of 95% for 20 test sample sets, which shows that the fault detection approach can be effectively applied to the excavator's hydraulic system.

Evaluating some factors that affect feasility of using ground penetrating radar for landmine detection

Ground penetrating radar （GPR） is one of the promising technologies that can be used to detect landmines. Many factors may affect the ability of GPR to detect landmines. Among those factors are： 1） the type of landmine material （metallic or plastic）, 2） conditions of the host soil （soil texture and soil moisture）, and 3） the radar frequency utilized. The impact of these factors on the ability of GPR to detect landmines is investigated by studying their effect on the dielectric permittivity contrast between the landmine and the host soil, as well as on the attenuation of the radar waves. The impact of each factor was theoretically reviewed and modeled using the Matlab and Mathcad software packages. Results of the computer modeling were correlated with GPR data acquired for metallic and plastic landmine types. It was found that the ability of GPR to detect landmines depends to a great extent on the landmine type, water content of the host soil, utilized radar frequency, and soil texture. The landmines are much easier to detect than plastic landmines for any soil conditions and any radar frequency. Increasing the soil＇s moisture content, regardless of soil texture, eases the detection of the plastic landmine and worsens the detection of the metallic mines. Increasing the percentage of clay in the soil causes the same effect as the moisture content. However, higher radar frequency delivers better results for landmine detection as long as the percentage of clay and the moisture content in the soil remains low. The results of this study are expected to help in selecting optimum radar antennae and data acquisition parameters depending on the landmine type and environmental conditions.

Crack detection using a frequency response function in offshore platforms

Structural cracks can change the frequency response function (FRF) of an offshore platform. Thus, FRF shifts can be used to detect cracks. When a crack at a specific location and magnitude occurs in an offshore structure, changes in the FRF can be measured. In this way, shifts in FRF can be used to detect cracks. An experimental model was constructed to verify the FRF method. The relationship between FRF and cracks was found to be non-linear. The effect of multiple cracks on FRF was analyzed, and the shift due to multiple cracks was found to be much more than the summation of FRF shifts due to each of the cracks. Then the effects of noise and changes in the mass of the jacket on FRF were evaluated. The results show that significant damage to a beam can be detected by dramatic changes in the FRF, even when 10% random noise exists. FRF can also be used to approximately locate the breakage, but it can neither be efficiently used to predict the location of breakage nor the existence of small hairline cracks. The FRF shift caused by a 7% mass change is much less than the FRF shift caused by the breakage of any beam, but is larger than that caused by any early cracks.

Frequency-Feedback Based Islanding Detection Algorithm for Micro-Grid

The unintentional islanding of micro-grid may cause negative impacts on distribution loads and distributed generations,so it must be detected within the acceptable duration.In this paper a new islanding detection algorithm is proposed.This algorithm introduces the frequency feedback method by the reactive power compensation to derive the frequency continuous shift. Accordingly,the islanding can be detected by monitoring the frequency within 0.1 s.The simulation results prove that this algorithm has extremely small non-detection zone,and meanwhile it presents an excellent islanding detection speed as well.

Measurement of oil volume fraction and velocity distributions in vertical oil-in-water flows using ERT and a local probe

This paper presents the use of a high performance dual-plane electrical resistance tomography (ERT) system and a local dual-sensor conductance probe to measure the vertical upward oil-in-water pipe flows in which the mean oil volume fraction is up to 23.1%. A sensitivity coefficient back-projection (SBP) algorithm was adopted to reconstruct the flow distributions and a cross correlation method was applied to obtain the oil velocity distributions. The oil volume fraction and velocity distributions obtained from both measurement techniques were compared and good agreement was found, which indicates that the ERT tech- nique can be used to measure the low fraction oil-water flows. Finally, the factors affecting measurement precision were discussed.

Non-contact inspection for inner surface of small-diameter pipes based on laser-PSD

A new non-contact inspection technique based on laser-PSD （position sensitive detector） to inspect the inner surface of small-diameter pipe is proposed,and the corresponding sensor has been developed. After being reflected by two mirrors in series,a laser beam is projected onto the inner wall of a pipe as a small light spot and is read by a two-dimensional PSD. Based on the signals from the PSD and the structure parameters of the sensor,the spot position on the wall can be calculated in a local 3D coordinate system. The spot controlled by the micro-motor driven mirrors will scan a closed section ring on the inner wall of the pipe to obtain the relative coordinates of all the sampled points. The data will be then processed through data segmentation and least square fitting,to reconstruct the section curve used for obtaining the radius and the defect description of the section. Driven by a micro-pipe robot,the sensor can inspect a long curved pipe and obtain its 3-D reconstruction. An inspection system based on this technique can detect the mini-diarneter pipe with an inner diameter of 9.5 mm-10.5 mm and a curvature radius larger than 100 mm at a measurement accuracy of the inner surface defect of ±0.1 mm.

Comparison of Kuqa foreland basin with Persian Gulf Basin in salt tectonics

Compared Kuqa foreland basin with Persian Gulf Basin in development of salt layers, salt tectonics, and the relation between salt tectonics and hydrocarbon, it is concluded that the salt diapirs are relative to hydrocarbon. Searching salt diapirs and related traps in Kuqa foreland basin is important. The forming mechanism of salt tectonic in Kuqa foreland basin is different from that of Hormuz Series, but similar to that of Lower Fars Series/Gachsaran Formation. Inspired by the role of salt tectonics of Lower Fars Series/Gaehsaran Formation in hydrocarbon accumulation, the authors considered that the exploration below salt layer should be enforced, and the traps below salt layer in the southern part of the Kuqa foreland basin would be found where salt layer is thicker. On the contrary, the traps should be found both above and below the salt layer in front of the northern mountain where salt layer is thin. The Triassic and Jurassic source rocks are rich in this area with great exploration prospective.

An entropy-based unsupervised anomaly detection pattern learning algorithm

Currently, most anomaly detection pattern learning algorithms require a set of purely normal data from which they train their model. If the data contain some intrusions buried within the training data, the algorithm may not detect these attacks because it will assume that they are normal. In reality, it is very hard to guarantee that there are no attack items in the collected training data. Focusing on this problem, in this paper, firstly a new anomaly detection measurement is proposed according to the probability characteristics of intrusion instances and normal instances. Secondly, on the basis of anomaly detection measure, we present a clustering-based unsupervised anomaly detection patterns learning algorithm, which can overcome the shortage above. Finally, some experiments are conducted to verify the proposed algorithm is valid.

Damage detection of frames using the increment of lateral displacement change

The method proposed in this paper is based on the fact that the damage in different types of structural members has distinctive influence on the structural stiffness. The intrinsic mechanical property of the structure is tapped and fully utilized for damage detection. The simplified model of the flexibility of frames treats the individual storeys as springs in series and the frame as an equivalent column. It fully considers the main deformation of all beams and columns in the frame. The deformation property of the simplified model accorded well with that of the actual frame model. The obtained increment of lateral displacement change (IOLDC) at the storey level was found to be very sensitive to the local damage in the frame. A damage detection method is pro- posed using the IOLDCs as the damage identification parameters. Numerical examples demonstrate the potential applicability of this method.

An analysis of the multi-fold method for GPR exploration

Multi-fold technology is widely applied in seismic exploration as a method of enhancing useful signals and suppressing noise interference to greatly increase the signal to noise ratio （S/N）. The authors introduce it to ground-penetrating radar （GPR） surveys and compare the experimental results to the conventional profiling method to demonstrate the feasibility and advantages of the technique for GPR exploration. Based on the experimental data, the authors summarize the GPR wave propagation rules and the parameters of multi- fold acquisition and processing. It is proven to be a useful attempt to enrich the GPR survey technology.

Vegetation field spectrum denoising via lifting wavelet transform

Field spectrum pretreatment experiments were carried out, and denoising numerical experiment via lifting wavelet transform （LWT） was designed, and several famous test signals including blocks, bumps, heavy sine and doppler were processed via Lw＇r in these experiment. And the field spectrum was processed via Lw＇r. Experiments proved that SNRG-tO-SNRN curves have similar feature and they all have a peak. And SNRG of almost all employed wavelets have higher value with SNRN between 0 and 20 dB. When signal is at high SNR, the SNRG is very little, and the MSED of denoised signal became little by little. LWT is more suite to denoise the low SNR or heavy noise contaminated signals. Bior4.4 have wider SNRN interval for denoising comparing with other five wavelets, includ- ing haar, db6, sym6, bior2.2 and bior3.3. Original field spectrum is processed by 3 stage liftings based on bior4.4 to denoise the trivial noise-contaminated regions. On processing the water band signal, logarithm transform is firstly taken. And then the spectrum is denoised via LWT based on bior4.4. The results show that an excellent denoised spectrum can be get, especially between 350 nm and 1 800 nm, and between 1 960 nm to 2 500 nm. While there is still a bump around 1 900 nm, this maybe due to the spectrum machine＇s limited precision.

A graph based system for multi-stage attacks recognition

Building attack scenario is one of the most important aspects in network security.This paper pro-posed a system which collects intrusion alerts,clusters them as sub-attacks using alerts abstraction,ag-gregates the similar sub-attacks,and then correlates and generates correlation graphs.The scenarios wererepresented by alert classes instead of alerts themselves so as to reduce the required rules and have the a-bility of detecting new variations of attacks.The proposed system is capable of passing some of the missedattacks.To evaluate system effectiveness,it was tested with different datasets which contain multi-stepattacks.Compressed and easily understandable Correlation graphs which reflect attack scenarios were gen-erated.The proposed system can correlate related alerts,uncover the attack strategies,and detect newvariations of attacks.