Cong Hu

Discrimination of genetically modified sugar beets based on terahertz spectroscopy

The objective of this paper was to apply terahertz (THz) spectroscopy combined with chemometrics techniques for discrimination of genetically modified (GM) and non-GM sugar beets. In this paper, the THz spectra of 84 sugar beet samples (36 GM sugar beets and 48 non-GM ones) were obtained by using terahertz time-domain spectroscopy (THz-TDS) system in the frequency range from 0.2 to 1.2 THz. Three chemometrics methods, principal component analysis (PCA), discriminant analysis (DA) and discriminant partial least squares (DPLS), were employed to classify sugar beet samples into two groups: genetically modified organisms (GMOs) and non-GMOs. The DPLS method yielded the best classification result, and the percentages of successful classification for GM and non-GM sugar beets were both 100%. Results of the present study demonstrate the usefulness of THz spectroscopy together with chemometrics methods as a powerful tool to distinguish GM and non-GM sugar beets.

Intermolecular vibrational modes and H-bond interactions in crystalline urea investigated by terahertz spectroscopy and theoretical calculation

The characteristic absorption spectra of crystalline urea in 0.6-1.8 THz region have been measured by terahertz time-domain spectroscopy at room temperature experimentally. Five broad absorption peaks were observed at 0.69, 1.08, 1.27, 1.47 and 1.64 THz respectively. Moreover, density functional theory (DFT) calculation has been performed for the isolated urea molecule, and there is no infrared intensity in the region below 1.8 THz. This means that single molecule calculations are failure to predict the experimental spectra of urea crystals. To simulate these spectra, calculations on a cluster of seven urea molecules using M06-2X and B3LYP-D3 are performed, and we found that M06-2X perform better. The observed THz vibrational modes are assigned to bending and torsional modes related to the intermolecular H-bond interactions with the help of potential energy distribution (PED) method. Using the reduced-density-gradient (RDG) analysis, the positions and types of intermolecular H-bond interactions in urea crystals are visualized. Therefore, we can confirm that terahertz spectroscopy can be used as an effective means to detect intermolecular H-bond interactions in molecular crystals.

Sensitive distinction between herbs by terahertz spectroscopy and a metamaterial resonator

ABSTRACT Terahertz spectroscopy, combined with a metamaterial resonator, was used to distinguish varieties of herbs that look alike to the naked eye. The metamaterial resonator, based on an ohm-ring, was experimentally demonstrated to exhibit two significant resonant peaks in the range from 0.2 to 1.4 THz. The resonant peaks were shifted to lower frequency with changes of the surface permittivity, and this feature was applied to identify varieties of herbs. In the experiment, different borneols were effectively identified according to the different degree of redshift. This work demonstrates that metamaterial resonator is a sensitive tool for terahertz spectral sensing, and shows a new detection method for different herbs.

Research on Synchronization Technology Based on IEEE1588 Protocol

With the rapid development of network technology, Distributed test system is widely applied in the test field, and clock synchronization in the system is the key issues in distributed test system. Meanwhile, with the development of testing techniques, distributed test has higher requirement for precision of the synchronization. Since the IEEE1588 protocol promulgated, it provides a feasible way to realize the requirement. This paper firstly analyzes the basic principle of IEEE1588, and then puts forward a scheme to implement IEEE1588 by using hardware timestamp. Finally, optimizes the method of PTP (precision time protocol) synchronization adjustment and builds experimental platform to verify the effect of optimization. Experiments prove that the scheme is feasible, and the clock synchronization precision can achieve a level of sub-microsecond.

Research on Monitoring System of Environment in Switchgear

When high voltage electrical equipment running in electrical transformer station, heating, electrical accident would be caused by some factors, for example, the temperature of switch node higher then alarm, discharge with high humidity, condensation of electrical equipment. Therefore, the implementation on-line monitoring for high voltage electrical equipment has become the important problem needed to solve. This paper analyzes the effect of node temperature and the humidity in the switchgear failure, and designs temperature/humidity environment monitoring terminal with low power controller and integrated temperature/humidity sensor. The RS485 interface is used as the communication channel to exchange information with monitor server. In monitor computer, a server is working to collect real time environment information from each terminal and provides web service for user in internet. Experimental results show that this system can realize the contact temperature and humidity environment online monitoring, display, alarm and other functions, and has good scalability and maintainability.

1553B Bus Interface Driver Software Design and Implement Based on RTX

In order to solve the application problem of 1553B bus under RTX, we design 1553B bus interface driver software based on RXT, system operating environment are Windows XP and RTX real-time extension module, it can solve the issues of 1553B bus real-time drive under RXT and ensure the real-time and fault-tolerant character of bus interface drive software.

Design of Waveform Generator Based on GPIB Interface

Firstly, the GPIB technology is introduced in this paper, and then the method of hardware and software designing is discussed in detail. The GPIB interface function is realized by using upD7210. With the specific program, the DDS chip AD9962 is controlled by ARM processor of 32-bit to implement the waveform generation. The waveform generator has been used to build automation test system based on GPIB interface, and the experiments show that the waveform generator has the advantages of high speed, low cost, and excellent dynamic performance.

Research on Key Technologies of LXI Class C Instrument

This paper briefly introduces the features and technical points of the new generation of instrument bus LXI (Lan eXtension for Instrument). Taking the deep study of LXI standard, VXI-11 protocol, RPC principles and SCPI commands as the research base, the structure of LXI Class C instrument is analysized, and the LXI Class C instrument key technologies--discovery mechanism and instrument command interpretation mechanism were especially highlighted. Moreover, the discovery mechanism and instrument command interpretation mechanism were implemented in the platform of S3C2410/Linux embedded system, and were successfully validated through Agilent IO Libraries Suite.