Research on Pulsar Time Steered Atomic Time Algorithm Based on DPLL

In today’s society,there is a wide demand for high-precision and high-stability time service in the fields of electric power,communication,transportation and finance.At present,the time standard in various countries is mainly based on atomic clocks,but the frequency drift of atomic clocks will affect the long-term stability performance.Compared with atomic clocks,millisecond pulsars have better long-term stability and can complement with the excellent short-term stability of atomic clocks.In order to improve the long-term stability of the atomic timescale,and then improve the timing accuracy,this paper proposes an algorithm for steering the atomic clock ensemble(ACE)by ensemble pulsar time(EPT)based on digital phase locked loop(DPLL).First,the ACE and EPT are generated by the ALGOS algorithm,then the ACE is steered by EPT based on DPLL to calibrate the long-term frequency drift of the atomic clock,so that the generated steered atomic time follows both the short-term stability characteristics of ACE and the long-term stability characteristics of EPT,and finally,the steered atomic time is used to calibrate the local cesium clock.The experimental results show that the long-term stability of atomic time after steering is improved by 2 orders of magnitude compared with that before steering,and the daily drift of a local cesium clock after calibration is less than 9.47 ns in 3 yr,3 orders of magnitude higher than that before calibration on accuracy.

Naphthodithiophene-based donor materials for solution processed organic solar cells

As an emerging donor building block,naphthodithiophene（NDT） is causing more concerns in the field of organic semiconductors.With the rigid and coplanar molecule structure,NDT will exhibit more application space relying on its own advantage for facilitating the charge carrier transport.In this review article,we have summarized the development progress on the NDT-based donor materials for solution processed organic solar cells.Discussions and comments on those representative NDT type materials about structure and property are also presented.

Unusual presentation of urachal adenocarcinoma with genitourinary cutaneous metastasis

Dear Editor, The urachus, which is a vestigial structure between the dome of the bladder and umbilicus, usually, retracts from the bladder before birth. However, the urachal remnant was continuous with the bladder cavity even in adults in 32% of bladder in one autopsy study.1 For this reason, tumors may develop from the remnants, most of which are well-differentiated mucinous adenocarcinomas, which is a rare form of vesical malignancy, accounting for 〈 1% of all bladder cancers. Although local spread to the peritoneum is common at presentation, distant metastases without local recurrence are rarely detected following surgical excision of clinically localized disease. To the best of our knowledge,