基于PI法的门源MS6.4地震前震中附近地震热点图像异常变化研究

基于1980年以来青海省和甘肃省区域地震台网的定位地震目录，分析了研究区最小完备震级，选取空间网格尺度为0.2°×0.2°、地震活动异常学习时间段和预测时间段均为3 a，应用图像信息（PI）法，分析了门源M_S6.4地震发生前震中附近地震热点图像的异常变化过程。结果表明，在2013年1月1日至2016年1月1日的预测时间窗内，冷龙岭断裂和祁连山北缘断裂附近存在明显的地震热点，且地震热点图像颜色偏深，发震概率较高，向前滑动至2014年1月1日至2017年1月1日，2015年1月1日至2018年1月1日和2016年1月1日至2019年1月1日3个预测时间窗，此两断裂附近仍存在地震热点，地震热点图像颜色逐渐由深变浅，而门源M_S6.4地震就落在PI法得到的地震热点内。门源M_S6.4地震前存在明显的地震热点，且地震热点相对集中，地震热点图像颜色由深变浅，震后消失；在祁连山北缘断裂附近，地震热点持续存在，分布较集中，地震热点图像颜色也呈由深变浅的过程。未来需关注祁连山北缘断裂，附近有发生强震的可能。     

基于探针底物法的高效液相色谱-串联质谱法测定蚯蚓体内4种CYP同工酶活力及其应用北大核心CSCD

基于探针底物法,将蚯蚓微粒体悬浮液加入至含有混合探针底物香豆素(50μmol·L^(-1))、安非他酮(25μmol·L^(-1))、阿莫地喹(50μmol·L^(-1))、右美沙芬(5μmol·L^(-1))的孵育体系中(微粒体蛋白质量浓度需控制在32~96 mg·L^(-1)内),于37℃孵育20 min后,加入甲醇终止反应,静置10 min后过0.22μm滤膜,采用高效液相色谱-串联质谱法测定对应的代谢物7-羟基香豆素、羟基-安非他酮、N-脱乙基阿莫地喹、右啡烷的生成量。根据相应代谢物的生成量分别评价蚯蚓CYP2A6、CYP2B6、CYP2C8及CYP2D6酶活力。采用Acquity UPLC HSS T3柱作为分离柱,以不同体积比的含1 mmol·L^(-1)乙酸铵的0.05%(φ)甲酸溶液和甲醇的混合溶液作为流动相进行梯度洗脱,串联质谱中采用电喷雾离子源正离子模式和多反应监测模式检测,并用基质匹配法配制混合标准溶液系列。结果显示:7-羟基香豆素、羟基-安非他酮、N-脱乙基阿莫地喹、右啡烷的质量浓度均在2.5~50μg·L^(-1)内与其对应的峰面积呈线性关系;对空白样品进行3个浓度水平的加标回收试验,回收率为73.7%~103%,日内相对标准偏差(RSDs,n=5)为2.1%~11%,日间RSDs(n=5)为4.6%~10%。方法用于分析分别暴露于多壁碳纳米管染毒土壤(暴露组)和普通土壤(对照组)21 d后蚯蚓体内4种CYP同工酶的活力,CYP2C8酶活力明显高于CYP2A6、CYP2B6及CYP2D6,暴露组中CYP2A6及CYP2C8酶活力显著(P<0.05)高于对照组,而CYP2B6及CYP2D6酶活力与对照组的无显著性差异,因此推测可将CYP2A6及CYP2C8作为一套生物标记物,用于定性诊断土壤的多壁碳纳米管污染。     

Detecting molecular vibrational modes of side chains and endpoints in nanoscale proteins with graphene plasmon

Monitoring the chemical and structural changes in protein side chains and endpoints by infrared(IR)spectroscopy is important for studying the chemical reaction and physical adsorption process of proteins.However, the detection of side chains and endpoints in nanoscale proteins is still challenging due to its weak IR response. Here, by designing a double layered graphene plasmon sensor on MgF_2/Si substrate in the IR fingerprint region, we detect the vibrational modes in side chains and endpoints(1397 cm~(-1) and 1458 cm~(-1)) of monolayer protein. The sensor could be applied on biochemistry to investigate the physical and chemical reaction of biomolecules.     

可观测度的探讨及其在捷联惯导系统可观测性分析中的应用

可观测度是为了分析线性系统中组合状态的可观测程度而提出来的,在卡尔曼滤波的滤波效果分析中得到了应用。文中先对已有的两种可观测度分析方法进行了简述,并且分析了两种方法的等价性;然后从理论上分析了此描述方法的不全面性。通过典型例子说明了理论分析的结果,给出了一种更全面的描述系统可观测组合状态可观测度的方法,并且用新的描述方式分析了捷联惯导系统的各状态可观测度。结果表明,该数值刻画方式能够定量的给出系统状态可观测的程度,是解析分析方法的很好的补充。     

水声通信中基于信道辨识的盲turbo均衡方法

水声信道多途效应明显,造成接收信号存在严重的码间干扰(ISI,Intersymbol interference)。基于最小均方误差(MMSE,Minimum mean square error)准则的turbo均衡器级联了均衡和信道译码,能够有效去除ISI,并获得优良的性能。由于水声信道的时变性,传统MMSE-turbo均衡需要周期性的训练序列,以实现连续可靠的通信。训练序列虽然提高了通信的可靠性,但降低了信息的有效传输速率。因此,为提高通信效率,本文提出了一种盲turbo均衡方法,该方法通过引入新的盲信道辨识器来同时获得信道估计响应和已去除部分ISI的初步均衡输出信号,并为turbo均衡提供初始的响应参数和比特软信息。与水声通信中应用较多的盲判决反馈均衡器(DFE,Decision feedback equalizer)相比,海上实验结果证明本文提出的盲turbo均衡方法抗信道多途衰落的能力较强,并且与传统MMSE-turbo均衡相比无需训练序列,因此提高了信息的有效传输速率。     

生物降解材料聚丙交酯的合成及相对分子质量测定——综合性研究型实验设计

介绍一个综合性研究型实验——生物降解材料聚丙交酯的合成及其相对分子质量的测定.整个实验过程不仅包含了有机化学实验的基本操作,而且还涉及当前材料化学领域的研究热点及科研分析方法,是一个涵盖内容丰富,适合高年级应用化学专业学生的综合性实验.     

Analysis of dynamic features in intersecting pedestrian flows

This paper focuses on the simulation analysis of stripe formation and dynamic features of intersecting pedestrian flows.The intersecting flows consist of two streams of pedestrians and each pedestrian stream has a desired walking direction.The model adopted in the simulations is the social force model, which can reproduce the self-organization phenomena successfully. Three scenarios of different cross angles are established. The simulations confirm the empirical observations that there is a stripe formation when two streams of pedestrians intersect and the direction of the stripes is perpendicular to the sum of the directional vectors of the two streams. It can be concluded from the numerical simulation results that smaller cross angle results in higher mean speed and lower level of speed fluctuation. Moreover, the detailed pictures of pedestrians' moving behavior at intersections are given as well.     

Ultra-compact graphene plasmonic filter integrated in a waveguide

Graphene plasmons have become promising candidates for deep-subwavelength nanoscale optical devices due to their strong field confinement and low damping. Among these nanoscale optical devices, band-pass filter for wavelength selection and noise filtering are key devices in an integrated optical circuit. However, plasmonic filters are still oversized because large resonant cavities are needed to perform frequency selection. Here, an ultra-compact filter integrated in a graphene plasmonic waveguide was designed, where a rectangular resonant cavity is inside a graphene nanoribbon waveguide. The properties of the filter were studied using the finite-difference time-domain method and demonstrated using the analytical model. The results demonstrate the band-pass filter has a high quality factor(20.36) and electrically tunable frequency response. The working frequency of the filter could also be tuned by modifying the cavity size. Our work provides a feasible structure for a graphene plasmonic nano-filter for future use in integrated optical circuits.     

利用加速度反馈的大型光电设备主轴控制技术

随着光电跟踪设备的大型化,在系统的惯量增大的同时,机械谐振频率一般会降低,此时控制系统的带宽设计将受到限制,而且大型的光电设备更容易受到风阻、地基振动等各种干扰的影响,从而降低系统的控制精度。由于惯性测量元件——加速度计直接感受被测对象的受力情况,通过引入加速度反馈控制回路,在不增大系统带宽的前提下,中低频段的扰动抑制传递函数幅值下降约25 dB。理论、仿真和实验三方面均验证了该控制方式的有效性。     

Passenger management strategy and evacuation in subway station under Covid-19

Under the background of Covid-19 sweeping the world, safe and reasonable passenger flow management strategy in subway stations is an effective means to prevent the spread of virus. Based on the social force model and the minimum cost model, the movement and path selection behavior of passengers in the subway station are modeled, and a strategy for passenger flow management to maintain a safe social distance is put forward. Take Qingdao Jinggangshan Road subway station of China as the simulation scene, the validity of the simulation model is verified by comparing the measured value and simulation value of the time required for passengers from getting off the train to the ticket gate. Simulation results indicate that controlling the time interval between incoming passengers at the entrance can effectively control the social distance between passengers and reduce the risk of epidemic infection. By comparing the evacuation process of passengers under different initial densities, it is found that the greater the initial density of passengers is, the longer the passengers are at risk social distance. In the process of passenger emergency evacuation, the stairs/escalators and ticket gates are bottleneck areas with high concentration of passenger density, which should be strictly disinfected many times on the basis of strictly checking the health code of incoming passengers and controlling the arrival time interval. The simulation results of this paper verify the harmfulness of passenger emergency evacuation without protective measures, and provide theoretical support for the operation and management of subway station under the epidemic situation.