酯化反应“快循环”产生的原因及对策

聚酯装置生产负荷超过100%后,酯化釜经常出现"快循环"。经过分析,PTA平均粒径的变小是引起酯化"快循环"的直接原因。通过对酯化釜浆料进料和反应温度的及时调整,合理利用2种调节手段,才能确保生产平稳,产品品质优等。

Rapid,sensitive detection of Vibrio anguillarum using loop-mediated isothermal amplification

Vibrio anguillarum is an important bacterial pathogen of aquatic organisms and a significant problem in aquatic farming. The rapid detection and identification of V. anguillarum, and other pathogens that infect marine organisms, is crucial to effective disease management. In this study, we developed a loop-mediated amplification （LAMP） assay to detect V. anguillarum in an hour in a single tube without the need for thermal cycling. Conserved regions of the metalloproteinase （empA） gene of V. anguillarum served as the targets for primer design. A fragment of the empA gene was amplified at 65℃ in the presence of the primer mixture and Bst DNA polymerase. In the optimized LAMP assay, 6.7 pg of V. anguillarum DNA could be detected. Six strains of V. anguillarum and 17 strains of non-V, anguillarum bacteria were used in this study to evaluate the species specificity of the primers. The six V. anguillarum strains gave a positive result in the LAMP assay. This method was also validated in V. anguillarum-infected fish. This LAMP method is more sensitive than PCR in the detection of V. anguillarum and shows good species specificity. The LAMP assay is therefore an effective method for the quick detection of V. anguillarum both in the laboratory and in the field.

The Situation with College Express Packaging Waste and Recycling Recommendations——Taking the Graduate School of the Chinese Academy of Social Sciences as an Example

Questionnaires and interviews are employed in this paper to investigate and analyze the situation with respect to express packaging waste at the Graduate School of the Chinese Academy of Social Sciences(GCASS).The survey results show that:(1)the campus receives a large number of express packages and there is,in turn,a considerable amount of packaging waste;(2)there are four main types of express packaging materials:paper packaging,plastic bags,wrapping tapes and package fillers;(3)neither the students nor the school perform well in the recycling of express packaging waste;(4)the samples investigated in this paper can be divided into four categories by cluster analysis,and the author infers from this that the colleges and universities with a large proportion of female students should pay more attention to the issue of recycling of express packaging waste.Several suggestions are presented based on the research results:(1)establishing a campus waste recycling system is the most efficient way to solve the problem of express packaging waste at GCASS;(2)we should advocate for green packaging and manage it from the source of waste generation because most of the express packaging material does not easily degrade naturally,and this represents a huge hidden danger to human health and the environment;(3)the school should cultivate student awareness of environmental protection.If education and penalties are implemented together,the recovery system will run better.

Construction of type-Ⅱ QC-LDPC codes with fast encoding based on perfect cyclic difference sets

In view of the problems that the encoding complexity of quasi-cyclic low-density parity-check(QC-LDPC) codes is high and the minimum distance is not large enough which leads to the degradation of the error-correction performance, the new irregular type-Ⅱ QC-LDPC codes based on perfect cyclic difference sets(CDSs) are constructed. The parity check matrices of these type-Ⅱ QC-LDPC codes consist of the zero matrices with weight of 0, the circulant permutation matrices(CPMs) with weight of 1 and the circulant matrices with weight of 2(W2CMs). The introduction of W2CMs in parity check matrices makes it possible to achieve the larger minimum distance which can improve the error-correction performance of the codes. The Tanner graphs of these codes have no girth-4, thus they have the excellent decoding convergence characteristics. In addition, because the parity check matrices have the quasi-dual diagonal structure, the fast encoding algorithm can reduce the encoding complexity effectively. Simulation results show that the new type-Ⅱ QC-LDPC codes can achieve a more excellent error-correction performance and have no error floor phenomenon over the additive white Gaussian noise(AWGN) channel with sum-product algorithm(SPA) iterative decoding.

Facile synthesis and excellent electrochemical performance of CoP nanowire on carbon cloth as bifunctional electrode for hydrogen evolution reaction and supercapacitor

In this paper, we report CoP nanowires supported on carbon cloth （CC） （CoP/CC） as a bifunctional electrode for hydrogen evolution reaction （HER） and supercapacitor. CoP/CC possess an excellent electrocatalytic performance for HER, with a Tafel slope of 56 mV/dec and a low overpotential of 68 mV to achieve a current density of 10 mAcm^-2. Remarkably, the bifunctional CoP/CC used as electrode for supercapacitor exhibit a higher specific capacitance of 674 F g^-1 at a scan rate of 5 mV s^-1 and maintains long-life cycling stability, retaining 86% of the initial capacitance after 10,000 cycles. CoP/CC will be a promising candidate as electrode for HER and supercapacitor.

A novel energy-efficient ICI cancellation technique for bandwidth improvements through cyclic prefix reuse in an OFDM system

Orthogonal frequency division multiplexing （OFDM）, a very promising technique that is leading the evolution in wireless mobile communication to sideline the bandwidth scarcity issue in spectrum allocation, is severely affected by the undesirable effects of the frequency offset error, which generates inter cartier interference （ICI） due to the Doppler shift and local oscillator frequency synchronization errors. There are many ICI cancellation techniques available in the literature, such as self-cancellation （SC）, maximum likelihood estimation （MLE）, and windowing, but they present a tradeoff between bandwidth redundancy and system complexity. In this study, a new energy-efficient, bandwidth-effective technique is proposed to mitigate ICI through cyclic prefix （CP） reuse at the receiver end. Unlike SC and MLE where the whole OFDM symbol data is transmitted in duplicate to create redundancy at the transmitter end, the proposed technique uses the CP data （which is only 20% of the total symbol bandwidth） to estimate the channel, and it produces similar results with a huge bandwidth saving. The simulation results show that the proposed technique has a significant improvement in error performance, and a comparative analysis demonstrates the substantial improvement in energy efficiency with high bandwidth gain. Therefore, it outperforms the legacy IC1 cancellation schemes under consideration.