单色仪能量检测系统的设计

针对原子吸收分光光度计单色仪模块的光能检测,设计一套能量采集系统.由光电倍增管将元素灯发出的光能信号转换成脉动弱电压信号;设计二级放大电路及滤波电路,将弱脉动电压信号放大为直流电压信号,提高信号传输中的抗干扰性;采用高精度的AD转换器进行模数转换,并进行相应的软件滤波处理,得到高精度的能量信号;最后由上位机通过CAN总线与微控制器进行通信获取能量并进行吸光度处理.实际应用结果表明:该检测模块具有精度高、信噪比低和实时性好等优点,提高了系统的检测性能.

Development status and prospect of cold chain logistics of fruits,vegetables,and agricultural products based on intelligent technology

The cold chain in the production area of fruits and vegetables is the primary link to reduce product loss and improve product quality,but it is also a weak link.With the application of big data technology in cold chain logistics,intelligent devices,and technologies have become important carriers for improving the efficiency of cold chain logistics in fruit and vegetable production areas,extending the shelf life of fruits and vegetables,and reducing fruit and vegetable losses.They have many advantages in fruit and vegetable pre-cooling,sorting and packaging,testing,warehousing,transportation,and other aspects.This article summarizes the rapidly developing and widely used intelligent technologies at home and abroad in recent years,including automated guided vehicle intelligent handling based on electromagnetic or optical technology,intelligent sorting based on sensors,electronic optics,and other technologies,intelligent detection based on computer vision technology,intelligent transportation based on perspective imaging technology,etc.It analyses and studies the innovative research and achievements of various scholars in applying intelligent technology in fruit and vegetable cold chain storage,sorting,detection,transportation,and other links,and improves the efficiency of fruit and vegetable cold chain logistics.However,applying intelligent technology in fruit and vegetable cold chain logistics also faces many problems.The challenges of high cost,difficulty in technological integration,and talent shortages have limited the development of intelligent technology in the field of fruit and vegetable cold chains.To solve the current problems,it is proposed that costs be controlled through independent research and development,technological innovation,and other means to lower the entry threshold for small enterprises.Strengthen integrating intelligent technology and cold chain logistics systems to improve data security and system compatibility.At the same time,the government should introduce relevant policies,provide necessary financial support,and establish talent training mechanisms.Accelerate the development and improvement of intelligent technology standards in the field of cold chain logistics.Through technological innovation,cost control,talent cultivation,and policy guidance,we aim to promote the upgrading of the agricultural industry and provide ideas for improving the quality and efficiency of fruit and vegetable cold chain logistics.

Optical molecular imaging for detection of Barrett's-associated neoplasia

Recent advancements in the endoscopic imaging of Barrett's esophagus can be used to probe a wide range of optical properties that are altered with neoplastic progression.This review summarizes relevant changes in optical properties as well as imaging approaches that measures those changes.Wide-field imaging approaches include narrow-band imaging that measures changes in light scattering and absorption,and autofluorescence imaging that measure changes in endogenous fluorophores.High-resolution imaging approaches include optical coherence tomography,endocytoscopy,confocal microendoscopy,and high-resolution microendoscopy.These technologies,some coupled with an appropriate contrast agent,can measure differences in glandular morphology,nuclear morphology,or vascular alterations associated with neoplasia.Advances in targeted contrast agents are further discussed.Studies that have explored these technologies are highlighted;as are the advantages and limitations of each.

Analysis of I-V Thermal Characteristic on GaN-based p-i-n Ultraviolet Detector

The I-V characteristic of GaN-based p-i-n ultraviolet detector is presented. It is measured at different temperatures and analyzed with changing temperature. The ideality factor of the device is 2.09 at room temperature. The maximum ideality factor is 2.14 at 100 ℃, which declines above 100 ℃, and the minimum ideality factor is 1.26 at 300 ℃. The coefficient of forward voltage vs. temperature is -1.97 mV/℃ with a forward current of 1 mA. Based on double injection model, the deep lying impurity activation energy in the i-region is 0.1 343 eV.

A Method of Peak Detecting for Nanosecond Pulse in Optical Performance Monitoring System

In optical performance monitoring system,the analog to digital converter is needed to detect the peak of nanosecond pulse and get the signal envelope.A scheme based on a designed anti-aliasing filter and analog to digital converter is proposed to broaden the nanosecond pulse and make it easier for the analog to digital converter to catch the peak of the nanosecond pulse.The experimental results demonstrate that,with the proposed scheme,the optical performance system needs less time to get the recovered eye-diagram of high speed optical data signal,and is robust to phase mismatch in the analog to digital converter circuit.

Quantitative Surface Chirality Detection with Sum Frequency Generation Vibrational Spectroscopy： Twin Polarization Angle Approach

Here we report a novel twin polarization angle （TPA） approach in the quantitative chirality detection with the surface sum-frequency generation vibrational spectroscopy （SFG-VS）. Generally, the achiral contribution dominates the surface SFG-VS signal, and the pure chiral signal is usually two or three orders of magnitude smaller. Therefore, it has been difficult to make quantitative detection and analysis of the chiral contributions to the surface SFG- VS signal. In the TPA method, by varying together the polarization angles of the incoming visible light and the sum frequency signal at fixed s or p polarization of the incoming infrared beam, the polarization dependent SFG signal can give not only direct signature of the chiral contribution in the total SFG-VS signal, but also the accurate measurement of the chiral and achiral components in the surface SFG signal. The general description of the TPA method is presented and the experiment test of the TPA approach is also presented for the SFG-VS from the S- and R-limonene chiral liquid surfaces. The most accurate degree of chiral excess values thus obtained for the 2878 cm^-1 spectral peak of the S- and R-limonene liquid surfaces are （23.7±0.4）% and （-25.4±1.3）%, respectively.

DNA template-synthesized silver nanoparticles:A new platform for high-performance fluorescent biosensing of biothiols

To develop the high-performance fluorescent bio-sensors, the metal nanoparticles were employed as nanoquenchers and at- tracted reasonable attention in the design of fluorescent biosensors. In this work, silver nanoparticles （AgNPs） were obtained via reduction of Ag＋ on FAM-labeled DNA template. For the tight binding between AgNPs and DNA, the tem- plate-synthesized AgNPs turned out high quenching efficiency and could be applied as super nanoquenchers to establish the biosensing platform for fluorescent detection. As an example, the template-synthesized DNA-AgNPs conjugates were em- ployed in sensing thiols. By forming S-Ag bonds, thiols interact intensely with AgNPs and replace the FAM-labeled DNA off from the surface of AgNPs, resulting in a fluorescence enhancement. Besides the advantages of lower background and higher signal-to-background ratio （S/B）, the conjugates present better stability, making them applicable in complicated biological fluids. To further evidence the feasibility of sensing thiols in real samples, the thiols in human urine were detected. The total amount of free thiols found in human urine was ranging from 229 μM to 302μM with the proposed sensor. To conclude the reliability, low content of Cys was added and the recovery was 98%-103%.