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1. chinaXiv:202206.00126 [pdf]

Low-Noise Large-Bandwidth Transimpedance Amplifier for Measuring Scanning Tunneling Shot Noise Spectra in Cryogenic STM and its Applications

梁迎新
Subjects: Engineering and technical science >> Technology of Instrument and Meter

散粒噪声是一个研究量子体系的强有力的手段。本文提出一种用于低温扫描隧道显微镜 (CryoSTM)的跨阻放大器(TIA),可满足散粒噪声测量的需要。在该TIA中,前置放大器(Pre-Amp)由超低噪声低功率低温高电子迁移率晶体管(HEMTs)构成。以1Gohm的高跨阻增益,所设计的TIA的带宽超过300 kHz。在CryoSTM中,这个TIA连同针尖-样品组件和输入信号被称为CryoSTM-TIA。它的带宽仍然超过300kHz,并且它的等效输入噪声电流功率谱密度在100 kHz小于30 (fA)2/Hz。该CryoSTM-TIA能够用于测量扫描隧道电流谱和扫描隧道微分电导谱。本文又特别阐述了如何用该CryoSTM-TIA测量量子体系的扫描隧道噪声电流功率谱和散粒噪声谱。这就使得用低温CryoSTM-TIA通过测量散粒噪声来研究各种量子体系中的新奇量子现象成为可能,例如在局域尺度中的Andreev反射、在单分子磁体中的Kondo效应,等等。特别是把它用于研究与实现拓扑量子计算有关的Majorana零能模的存在性。

submitted time 2022-06-11 Hits255Downloads133 Comment 0

2. chinaXiv:202204.00129 [pdf]

Large-area electronics enabled high resolution digital microfluidics for single cell manipulations

Siyi HU; Jingmin YE; Subao SHI; Kai JIN; Dongping WANG; Hanbin MA
Subjects: Engineering and technical science >> Biomedical Engineering

Thin-film semiconductor devices as switching elements are perfect fit for electrodes-array based digital microfluidics. With support of large-area electronics technology, high-resolution digital droplets (diameter around 100 μm) contains single cell can be generated by pre-programmable addressing signals. Single-cell generation and manipulation is a foundation of single-cell research, which demands ease of operation, multifunctional and accurate tools. Herein, we report an active-matrix digital microfluidic platform for single-cell generation and manipulation enabled by large-area electronics technology. The active device contains 26,368 electrodes that can be independently addressed to perform parallel and simultaneous droplets and even single cells manipulation. An on-chip generated single droplet volume limit of 500 pL has been reported, proving the continuous and stable movement of the droplet containing cells for over 1 hour. Furthermore, the success rate of single droplet formation can be higher than 98% and able to generate around 10 single cells within 10 seconds.  A pristine single cell generation rate of 29% is achieved without any further sorting process

submitted time 2022-04-17 Hits1595Downloads297 Comment 0

3. chinaXiv:202203.00044 [pdf]

一种根据羽流扩张角判断火箭发动机海平面排气速度的方法

袁浩翔; 闫东峰; 郭常超
Subjects: Engineering and technical science >> Physics Related Engineering and Technology

近年,火箭发动机的非接触式测量研究受到各国的关注,但是主要关注点为火箭发动机的羽流温度场或振动力学研究,并未用于测量火箭发动机的排气速度。传统排气速度测量方法设备复杂,且长期没有其他方法作为参照。因此本文提出了一种利用羽流图像中扩张角测量结果,估算火箭发动机海平面排气速度的方法,该方法结合一维可压缩绝热流模型、大气背景下的普朗特-迈耶函数和布伦特算法。本文利用该方法得到羽流扩张角-海平面排气速度关系,并将其与传统方法测量结果进行对比,验证该方法的精度。估算结果显示海平面排气速度和羽流扩张角呈线性关系,与传统方法之间的相对误差小于2%,因此,结果说明该估算方法具有较高精确度。近年,火箭发动机的非接触式测量研究受到各国的关注,但是主要关注点为火箭发动机的羽流温度场或振动力学研究,并未用于测量火箭发动机的排气速度。传统排气速度测量方法设备复杂,且长期没有其他方法作为参照。因此本文提出了一种利用羽流图像中扩张角测量结果,估算火箭发动机海平面排气速度的方法,该方法结合一维可压缩绝热流模型、大气背景下的普朗特-迈耶函数和布伦特算法。本文利用该方法得到羽流扩张角-海平面排气速度关系,并将其与传统方法测量结果进行对比,验证该方法的精度。估算结果显示海平面排气速度和羽流扩张角呈线性关系,与传统方法之间的相对误差小于2%,因此,结果说明该估算方法具有较高精确度。

submitted time 2022-03-17 Hits1811Downloads369 Comment 0

4. chinaXiv:202202.00011 [pdf]

Exact Decomposition of Multifrequency Discrete Real and Complex Signals

刘保国
Subjects: Electronics and Communication Technology >> Information Processing
Subjects: Engineering and technical science >> Engineering General Technology
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering

‘The spectral leakage (SL) from windowing and the picket fence effect (PEF) from discretization’ have been among the standard contents in textbooks for many decades. The SL and PEF would cause the distortions in amplitude, frequency, and phase of signals, which have always been of concern, and attempts have been made to solve them. This paper proposes two novel decomposition theorems that can totally eliminate the SL and PEF, they could broaden the knowledge of signal processing. First, two generalized eigenvalue equations are constructed for multifrequency discrete real signals and complex signals. The two decomposition theorems are then proved. On these bases, exact decomposition methods for real and complex signals are proposed. For a noise-free multifrequency real signal with m sinusoidal components, the frequency, amplitude, and phase of each component can be exactly calculated by using just 4m–1 discrete values and its second-order derivatives. For a multifrequency complex signal, only 2m–1 discrete values and its first-order derivatives are needed. The numerical experiments show that the proposed methods have very high resolution, and the sampling rate does not necessarily obey the Nyquist sampling theorem. With noisy signals, the proposed methods have extraordinary accuracy.

submitted time 2022-02-08 Hits3565Downloads589 Comment 0

5. chinaXiv:202110.00082 [pdf]

用于MEMS激光雷达内部时间同步的一种简单自标定方法

张雨; 遆晓光; 闫诗雨; 张斌; 漆保凌; 王春晖
Subjects: Engineering and technical science >> Optical Engineering

针对MEMS激光雷达在研发过程中的内部时间同步问题,提出了一种简单的自标定方法。首先,我们介绍了MEMS激光雷达的内部时间不对齐问题。在此基础上,提出了一种鲁棒的最小垂直梯度(MVG)先验算法,用于标定激光与MEMS反射镜之间的时间差,该时间差可以自动计算,无需任何人工参与或专门设计的合作目标。最后,在MEMS激光雷达上进行了实际实验,验证了该方法的有效性。需要注意的是,校准可以在简单的实验室环境中进行,无需任何测距设备和人工参与,这大大加快了实际应用中的研发进度。

submitted time 2021-10-21 Hits5051Downloads589 Comment 0

6. chinaXiv:202105.00077 [pdf]

二维光学刺激下的视觉感知定律

祝锐; 刘玉红; 王体春; 陈龙聪; 谢正祥
Subjects: Computer Science >> Computer Application Technology
Subjects: Medicine, Pharmacy >> Other Disciplines of Medicine and Pharmacology
Subjects: Engineering and technical science >> Optical Engineering

人类对刺激量的感知分为数量感知和质量感知。无论是韦伯-费克纳(Weber-Fechner)的对数感觉定律还是史蒂文斯(Stevens)的幂函数感觉定律,都是关于感觉量与一维亮度刺激之间定量关系的定律。图像属于具有二维亮度分布特征的刺激量。本文研究的是二维亮度刺激的质量的感知,即二维亮度刺激质量好坏程度的感知。好坏程度是一个模糊的心理学概念,因此我们需要用模糊数学的方法来量化图像视觉感知质量的好坏程度,即建立一个模糊隶属函数PQ来定量表示图像视觉质量的好与坏的程度。

submitted time 2021-05-24 Hits12779Downloads1456 Comment 0

7. chinaXiv:202004.00020 [pdf]

Printed Organic Transistors-based Impedance Biosensor

Qi Huang; Kai Jin; Yukun Huang; Zhe Liu; Linrun Feng; Xiaojun Guo; Hanbin Ma
Subjects: Engineering and technical science >> Biomedical Engineering

Electrochemical impedance biosensors measure the impedance varies of the solution during the biochemical process, so it can realize label-free biological detection. However, the biological signal to be detected is very weak, thus requiring signal amplification circuit. Printed organic thin film transistor (OTFT) has many advantages such as low cost, flexible bending, biocompatibility, which is suitable for biological detection. This work built up amplification circuit for electrochemical impedance test based on OTFT, different concentrations of phosphate buffer solution (PBS) used as test samples were measured with the above circuit. The results show that OTFT-based circuit has a good implementation of signal amplification, which lay a foundation for the application of printed OTFT in the electrochemical impedance biosensors.

submitted time 2020-04-05 Hits12865Downloads2692 Comment 0

8. chinaXiv:201812.00135 [pdf]

pCO2在哺乳动物细胞培养中的影响和应用

刘小双; 徐寒梅
Subjects: Biology >> Bioengineering
Subjects: Engineering and technical science >> Bioengineering

二氧化碳分压(pCO2)是哺乳动物细胞培养中一个重要参数,其主要来源包括细胞有氧呼吸产生的CO2、培养基中碳酸氢盐和pH控制加入的CO2。一般细胞培养中不精确控制pCO2,但是将pCO2水平维持在一定范围(30 - 80 mmHg)十分重要,pCO2过高(> 80 mmHg)和过低(< 30 mmHg)不利于细胞生长、代谢、以及蛋白生产和质量控制。大规模高密度细胞培养过程中高pCO2问题比较常见,因此工艺放大时需要考虑不同规模细胞培养中pCO2水平的差异。本文综述了哺乳动物细胞培养中pCO2对细胞生长、代谢和蛋白生产的影响,以及大规模中控制pCO2的方法。

submitted time 2018-12-11 Hits14685Downloads5086 Comment 0

9. chinaXiv:201803.00584 [pdf]

一种新型Micro-CT系统设计

张志诚; 梁晓坤; 朱轩玉; 李维振; 谢耀钦
Subjects: Engineering and technical science >> Biomedical Engineering

传统的 CT 设备由于受到系统架构的物理限制,导致最终扫描结果中运动伪影影响很大,本文依据碳纳米管的场致发射原理设计出一套工作在准静态模式下的显微CT。该系统采用 35 个碳纳米管 X 射线光源和 5 个探测器,相对于传统 CT,通过外部时序控制减少了机架的机械旋转次数和行程,大大降低了运动伪影的影响。由于重建角度是稀疏的,因此通过采用迭代重建算法模拟仿真验证了该系统的有效性。

submitted time 2018-03-15 Hits12786Downloads3291 Comment 0

10. chinaXiv:201803.00583 [pdf]

基于静息态fMRI的催眠控制呼吸研究

刘燕君; 李荣茂; 臧珊珊; 陈思宇; 谢耀钦
Subjects: Biology >> Neurobiology
Subjects: Psychology >> Cognitive Psychology
Subjects: Engineering and technical science >> Biomedical Engineering

催眠是一种被证明有效的、无害的心理学上的呼吸控制方法。文章通过对 13 位有催眠背景的心理咨询师被试进行催眠控制呼吸实验,由催眠师引导被试进行催眠,运用静息态功能磁共振的方法来研究催眠控制呼吸状态下脑功能的异常。结果显示:在催眠状态下,脑活动在视觉皮层(枕叶)、感觉运动皮层(中央前回、中央后回、布洛德曼 4、6 区)、后扣带回以及颞中回上升;在背外侧前额皮层、小脑后叶以及缘上回下降,并且在全脑大规模静息态功能网络范围内相关关系增强(正常态 r=0.64,催眠态 r=0.80)。此外,催眠状态下视觉皮层与运动皮层之间的功能连接增强。研究结果表明,视觉皮层和运动皮层在催眠控制呼吸的神经机制中发挥了重要的作用,其神经机制也可能与认知处理和感知处理密切相关。本研究结合了心理学以及脑科学进行了研究,为催眠的研究提供了一个认知脑科学的研究新视觉。

submitted time 2018-03-15 Hits13951Downloads4395 Comment 0

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