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As a replacement for highly flammable and volatile organic liquid electrolyte, solid polymer electrolyte shows attractive practical prospect in high-energy lithium metal batteries. However, unsatisfied interface performance and ionic conductivities are two critical challenges. A common strategy involves introducing organic solvents or plasticizers, but this violates the original intention of security design. Here, an electrolyte concept called liquid polymer electrolyte without any small molecular solvents is proposed for safe and high-performance batteries, based on the design of a room-temperature liquid-state brush-like polymer as the sole solvent of lithium salts. This liquid polymer electrolyte is non-flammable and exhibits high ionic conductivity (1.09 × 10 −4  S cm −1 at 25 °C), significant lithium dendrite suppression, and stable long-term cycling over a wide operating temperature range ( ≥ 1000 cycles at 60 °C and 90 °C). Moreover, the pouch cell can resist thermal abuse, vacuum environment, and mechanical abuse. This electrolyte and design strategy are expected to provide enlightening ideas for the development of safe and high-performance polymer electrolytes. Although solid polymer electrolytes show promise as alternatives to organic liquid electrolytes, they are hampered by interface and ionic conduction issues. Here, the authors develop a solvent-free liquid polymer electrolyte to enhance the safety and electrochemical performance of lithium metal batteries.

Composite solid‐state electrolytes (CSEs) using Li1+xAlxTi2‐x(PO4)3 (LATP) as active fillers offer promising prospects for large‐scale lithium metal batteries (LMBs) applications due to their high environmental stability, cost‐effectiveness, and improved safety. However, the challenges persist owing to high interfacial resistance with electrodes and instability with lithium metal. Herein, self‐assembly nanofiber/polymers/LATP composite quasi‐solid electrolytes (SL‐CQSEs) are reported through in situ polymerization of precursor solution containing vinylene carbonate (VC), fluoroethylene carbonate (FEC), lithium bis(trifluoromethanesulfonic) imide (LiTFSI) in a porous and flexible self‐supporting skeleton (SSK) consisting of 2‐(3‐(6‐methyl‐4‐oxo‐1,4‐dihydropyrimidin‐2‐yl)ureido)ethyl methacrylate (UPyMA)’s self‐assembly nanofiber (SAF), poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) and LATP. Anion‐anchoring/hydrogen‐bonding competition and intercomponent multiscale‐coupling effects on SL‐CQSEs are found, which contribute to their incombustibility, excellent room‐temperature ionic conductivity (1.03 mS cm−1), wide electrochemical window (5.1 V), good interfacial compatibility, and lasting inhibition of lithium dendrites. LiFePO4/Li cells with SL‐CQSEs not only exhibit high‐rate performance and long‐term cycling stability, with a capacity retention of 90.4% at 1C and 87% even at 4C after 1000 cycles, but also can resist fire and mechanical abuse, highlighting the potential applications of SL‐CQSEs for high‐performance and safety LMBs. A novel self‐assembly fiber (SAF)/polymers/LATP composite quasi‐solid electrolytes based on TFSI‐ anchoring and intermolecular hydrogen bonding competitive and multiscale coupling effects, named SL‐CQSE, which possesses the perfect reconciliation of facilitating Li+ migration, inducing stable SEI layer construction, and strengthening mechanical properties, is in situ prepared. Non‐inflammable CQSE‐20 and anions‐induced Li3N/LiF‐rich inorganic/organic hybrid SEI endow lithium batteries with excellent electrochemical performance and superior fire safety.

Dear Editor, PIWI-interacting RNAs （piRNAs） are germ cell-specific small non-coding RNAs that are essential for silenc- ing transposable elements. Substantial efforts in the past decade have led to an understanding of how piRNAs are made. Primary piRNA biogenesis is initiated with transcription of piRNA precursors, followed by cleavage into piRNA intermediates, and finally, maturation by 3＇ end trimming and 2＇-O-methylation. Secondary piRNA biogenesis occurs through an amplification loop （ping pong pathway）; the piRNA pools generated through pri- mary processing guide MILI protein to cleave the target RNA for piRNA generation in a feed-forward loop that accelerates production of the piRNAs. Papi/Tdrkh has been implicated in processing the 3＇ ends of piRNAs [1, 2], however,

A two-way satellite time and frequency transfer（TWSTFT） device equipped in the BeiDou navigation satellite system（BDS）can calculate clock error between satellite and ground master clock. TWSTFT is a real-time method with high accuracy because most system errors such as orbital error, station position error, and tropospheric and ionospheric delay error can be eliminated by calculating the two-way pseudorange difference. Another method, the multi-satellite precision orbit determination（MPOD）method, can be applied to estimate satellite clock errors. By comparison with MPOD clock estimations, this paper discusses the applications of the BDS TWSTFT clock observations in satellite clock measurement, satellite clock prediction, navigation system time monitor, and satellite clock performance assessment in orbit. The results show that with TWSTFT clock observations, the accuracy of satellite clock prediction is higher than MPOD. Five continuous weeks of comparisons with three international GNSS Service（IGS） analysis centers（ACs） show that the reference time difference between BeiDou time（BDT） and golbal positoning system（GPS） time（GPST） realized IGS ACs is in the tens of nanoseconds. Applying the TWSTFT clock error observations may obtain more accurate satellite clock performance evaluation in the 104 s interval because the accuracy of the MPOD clock estimation is not sufficiently high. By comparing the BDS and GPS satellite clock performance, we found that the BDS clock stability at the 103 s interval is approximately 10.12, which is similar to the GPS IIR.

Time synchronization between ground and satellites is a key technology for satellite navigation system. With dual-channel sat- ellite, a method called Two-Way Common-View （TWCV） satellite time transfer for Compass system is proposed, which com- bines both characteristics of satellite common-view and two-way satellite-ground time transfer. By satellite-ground two-way pseudo-range differencing and two stations common-view differencing, this TWCV method can completely eliminate the in- fluence of common errors, such as satellite clock offset, ephemeris errors, troposphere delay and station coordinates errors. At the same time, ionosphere delay related to signal frequency is also weakened significantly. So the precision of time transfer is improved much more greatly than before. In this paper, the basic principle is introduced in detail, the effect of major errors is analyzed and the practical calculation model in the Earth-fixed coordinate system for this new method is provided. Finally, experiment analysis is conducted with actual Compass observing data. The results show that the deviation and the stability of the satellite dual channel can be better than 0.1 ns, and the accuracy of the two-way common-view satellite time transfer can achieve 0.4 ns. All these results have verified the correctness of this TWCV method and model. In addition, we compare this TWCV satellite time transfer with the independent C-band TWSTFT （Two-Way Satellite Time and Frequency Transfer）. It shows that the result of the TWCV satellite time transfer is in accordance with the C-band TWSTFT result, which further sug- gests that the TWCV method is a remote high precision time transfer technique. The research results in this paper are very im- portant references for the development and application of Compass satellite navigation system.

In order to study the stress of box-girder web under prestressing, and confirming the internal stress distribution of the web, analyzing of vertical prestressed box girder, curved beam prestressed sensitivity under the webs. Establishing finite element model of the box-girder webs vertical prestressing effect is analyzed, results show that the principal tensile stress of the web is sensitive to the vertical prestress, applying the vertical prestress can effectively reduce the principal tensile stress of the web; with the decrease of the effective vertical prestress, the neutral axis above the principal compressive stress decreases rapidly, while below the neutral axis decreases relatively slow; Under the same vertical preloading stress level, the roots of cross section of the compressive stress of web reserves than L/4 section of the web.

Proper development of plant roots is critical for primary physiological functions,including water and nutrient absorption and uptake,physical support,and carbohydrate storage（Zhang et al.,2010）.Crop root systems act as the key organ for sensing and response to abiotic and biotic stresses.

Aiming at regional services,the space segment of COMPASS （Phase I） satellite navigation system is a constellation of Geostationary Earth Orbit （GEO）,Inclined Geostationary Earth Orbit （IGSO） and Medium Earth Orbit （MEO） satellites.Precise orbit determination （POD） for the satellites is limited by the geographic distribution of regional tracking stations.Independent time synchronization （TS） system is developed to supplement the regional tracking network,and satellite clock errors and orbit data may be obtained by simultaneously processing both tracking data and TS data.Consequently,inconsistency between tracking system and TS system caused by remaining instrumental errors not calibrated may decrease navigation accuracy.On the other hand,POD for the mixed constellation of GEO/IGSO/MEO with the regional tracking network leads to parameter estimations that are highly correlated.Notorious example of correlation is found between GEO＇s orbital elements and its clock errors.We estimate orbital elements and clock errors for a 3GEO＋2IGSO constellation in this study using a multi-satellite precise orbit determination （MPOD） strategy,with which clock error elimination algorithm is applied to separate orbital and clock estimates to improve numerical efficiency.Satellite Laser Ranging （SLR） data are used to evaluate User Ranging Error （URE）,which is the orbital error projected on a receiver＇s line-of-sight direction.Two-way radio-wave time transfer measurements are used to evaluate clock errors.Experimenting with data from the regional tracking network,we conclude that the fitting of code data is better than 1 m in terms of Root-Mean-Square （RMS）,and fitting of carrier phase is better than 1 cm.For orbital evaluation,difference between computed receiver-satellite ranging based on estimated orbits and SLR measurements is better than 1 m （RMS）.For clock estimates evaluation,2-hour linear-fitting shows that the satellite clock rates are about 1.E-10 s/s,while receiver clock rates are about 1×10 13-1×10 12 s/s.For the 72-hour POD experiment,the average differences between POD satellite clock rates estimates and clock measurements based on TS system are about 1×10 13 s/s,and for receiver clock rates,the differences are about 1×10 15 s/s.

<正>Dear Editor,Proper development of plant roots is critical for primary physiological functions,including water and nutrient absorption and uptake,physical support,and carbohydrate storage(Zhang et al.,2010).Crop root systems act as the key organ for sensing and response to abiotic and biotic stresses.Previous studies of crop root system development suggest that increased lateral root formation(LRF)could stimulate

The traditional data envelopment analysis（DEA）, bootstrap-DEA and Malmquist models are employed to measure different tourism efficiencies and their spatial characteristics of 61 cities in six coastal urban agglomerations in eastern China. The following conclusions are drawn.（1） The comprehensive efficiency（CE） of urban tourism using the bootstrap-DEA model is lower than the CE level using the DEA-CRS model, which confirms the significant tendency of the DEA-CRS model to overestimate results.（2） The geometric CE averages of urban tourism in the Yangtze River Delta（YRD） and the Pearl River Delta（PRD） have changed from ineffective to effective since 2000, the averages in the Beijing-TianjinHebei（BTH） and the Shandong Peninsula（SDP） have changed from ineffective to moderately effective since 2000, and those in the Central and Southern Liaoning（CSL） and the West Bank of Taiwan Strait（WBTS） have been ineffective since 2000.（3） The CE values of urban tourism in the PRD, the YRD, the BTH and the SDP have been slightly affected by the pure technical efficiency（PTE）, whereas the CE values in the CSL and the WBTS have been slightly affected by the scale efficiency（SE） since 2000.（4） Spatially, the range of geometric averages of the total factor productivity（TFP） for the PRD, the YRD, the BTH, the SDP, the WBTS and the CSL has decreased sequentially, while the one for most cities in six urban agglomerations has exhibited a downward trend since 2000.（5） Collectively, the natural conditions, the economic policies and the tourism capital drive the SE change of urban tourism of the CSL and the WBTS. The tourism enterprises for increasing returns to scale and imitating innovative technology have an effect on the CE change of urban tourism in the BTH and the SDP. The tourism market competition drives the PTE change of urban tourism in the PRD and the YRD. Although the PTE and the SE of urban tourism in six coastal urban agglomerations suffer from uncertain events, the CE maintained overall sound momentum since 2000.