To fulfill the demands of applications under severe operational conditions,alloys should possess outstanding wear resistance at elevated temperatures.A Ti-Hf-Nb-V based refractory high entropy alloy(RHEA)was successfu...To fulfill the demands of applications under severe operational conditions,alloys should possess outstanding wear resistance at elevated temperatures.A Ti-Hf-Nb-V based refractory high entropy alloy(RHEA)was successfully produced using the directed energy deposition(DED)technique,which avoided the formation of fatal defects and showcased well-performed mechanical properties across a broad temperature spectrum.Strategic design of the oxidation sequence enabled the early formation of oxide nanolayers,which can form a polycrystalline oxide nanocoating under a complex stress condition to drastically reduce the wear rate from 2.69×10^(-4) mm^(3)·(N·m)^(−1) at room temperature to 6.90×10^(-7) mm^(3)·(N·m)^(−1) at 600℃.These results indicate that the application of additive manufacturing to fabricate RHEAs with superior wear resistance at high temperatures paves the way for the development of functional coatings designed to withstand extreme conditions.展开更多
Nanopore direct RNA sequencing(DRS)provides the direct access to native RNA strands with full-length information,shedding light on rich qualitative and quantitative properties of gene expression profiles.Here with Nan...Nanopore direct RNA sequencing(DRS)provides the direct access to native RNA strands with full-length information,shedding light on rich qualitative and quantitative properties of gene expression profiles.Here with NanoTrans,we present an integrated computational framework that comprehensively covers all major DRS-based application scopes,including isoform clustering and quantification,poly(A)tail length estimation,RNA modification profiling,and fusion gene detection.In addition to its merit in providing such a streamlined one-stop solution,NanoTrans also shines in its workflow-orientated modular design,batch processing capability,all-in-one tabular and graphic report output,as well as automatic installation and configuration supports.Finally,by applying NanoTrans to real DRS datasets of yeast,Arabidopsis,as well as human embryonic kidney and cancer cell lines,we further demonstrate its utility,effectiveness,and efficacy across a wide range of DRS-based application settings.展开更多
Serveral methods for the pararrel acquisition of a PN sequence in a baseband direct sequence spread spectrum system are investigated. Four different kinds of schemes are considered: the optimal estimation scheme, the ...Serveral methods for the pararrel acquisition of a PN sequence in a baseband direct sequence spread spectrum system are investigated. Four different kinds of schemes are considered: the optimal estimation scheme, the locally optimal estimation scheme, the optimal testing searches and the locally optimal testing scheme. In the four kinds of parallel acquisition schemes, the expressions for the probability of error are given and compared with the actual error probabilities obtained via Monte Carlo simulation. We also outline a technique that can be suboptimal because of a large amount of hardware and computation when using the parallel acquisition schemes.展开更多
According to the requirements of the high-sensitivity acquisition of Direct Sequence Spread Spectrum(DSSS) signals under ultrahigh dynamic environments in space communications, a three-dimensional joint search of the ...According to the requirements of the high-sensitivity acquisition of Direct Sequence Spread Spectrum(DSSS) signals under ultrahigh dynamic environments in space communications, a three-dimensional joint search of the phase of Pseudo-Noise-code(PN-code),Doppler frequency and its rate-of-change is presented to achieve high sensitivity in sensing high-frequency dynamics. By eliminating the correlation peak loss caused by ultrahigh Doppler frequency and its rate-of-change offset,the proposed method improves the acquisition sensitivity by increasing the non-coherent accumulation time. The validity of the algorithm is proved by theoretical analysis and simulation results. It is shown that signals with a carrier- to-noise ratio as low as 39 dBHz can be captured with high performance when the Doppler frequency is up to ±1 MHz and its rate-of-change is up to ±200 kHz/s.展开更多
Aiming at improving acquisition performance for direct sequence spread spectrum （DSSS） signals, a new acquisition algorithm based on fast Fourier transform （FFT） is proposed. The code phases are parallel searched ...Aiming at improving acquisition performance for direct sequence spread spectrum （DSSS） signals, a new acquisition algorithm based on fast Fourier transform （FFT） is proposed. The code phases are parallel searched throughout the Doppler frequency domain. Since the influence of Doppler frequency errors on peak-to- average ratios of correlation power shows a pattern similar to the sinc function, it is our belief that by judging on peak-to-average ratios for different Doppler frequency errors false alarm probabilities should be lowered. Analyses have supported the underlying principle of this new algorithm. Simulation results have also indicated that the new algorithm can effectively improve the acquisition performance for DSSS signals.展开更多
A novel direct sequence （DS） design method for suppressing the narrowband interference in DS spread spectrum ultra-wideband receivers is proposed. The method has low computational complexity and can be easily implem...A novel direct sequence （DS） design method for suppressing the narrowband interference in DS spread spectrum ultra-wideband receivers is proposed. The method has low computational complexity and can be easily implemented in practical systems. Simulation results prove that the proposed method is effective to suppress the narrowband interference. Therefore, the integrity of both the ultra-wide bandwidth and the narrowband systems can be highly enhanced.展开更多
Performances of BPSK, balanced quaternary modulation, dual quaternary modulation and complex quaternary modulation in direct sequence spectrum spread (DS SS) system are discussed in this paper. Based on the crit...Performances of BPSK, balanced quaternary modulation, dual quaternary modulation and complex quaternary modulation in direct sequence spectrum spread (DS SS) system are discussed in this paper. Based on the criterion the power of original signal is the same, it is shown that complex quaternary modulation has the best performance, and dual quaternary modulation degrades 2dB. Moreover, the frequency efficient of the two modulations is 2bit/Hz. Balanced quaternary has the same performance as BPSK with frequency efficient 1bit/Hz.展开更多
For direct sequence spread spectrum (DSSS) communication systems suffering interference, it is known that code-aided interference suppression technique outperforms all of the previous linear or nonlinear methods. In t...For direct sequence spread spectrum (DSSS) communication systems suffering interference, it is known that code-aided interference suppression technique outperforms all of the previous linear or nonlinear methods. In this paper, we proposed an improved code-aided technique which can improve the system performance greatly by using the eigenvector sign (EVS) spreading sequence which depends on the statistical characteristics of the interference and the thermal noise.展开更多
A novel kind of multidimension symbol/sequence trellis coded modulation (TCM) based on TCM of lower coding rate has been constructed. The redundancy of this new kind of TCM is provided not only by the modulated symbo...A novel kind of multidimension symbol/sequence trellis coded modulation (TCM) based on TCM of lower coding rate has been constructed. The redundancy of this new kind of TCM is provided not only by the modulated symbol sequence but also by the PN sequences for spreading spectrum as well. The performance of direct sequence spread spectrum multiple access (DS/SSMA) system with this symbol/sequence TCM over flat Rayleigh fading channel has been investigated by theoretical analysis and numerical simulation. The results obtained in this research demonstrate the performance improvements of this system in comparison with that of the DS/SSMA system with conventional TCM under the same conditions.展开更多
It is a necessary step to estimate the spreading sequence of direct sequence spread spectrum （DSSS） signal for blind despreading and demodulation in non-cooperative communications. Two innovative and effective detec...It is a necessary step to estimate the spreading sequence of direct sequence spread spectrum （DSSS） signal for blind despreading and demodulation in non-cooperative communications. Two innovative and effective detection statistics are proposed to implement the synchronization and spreading sequence estimation procedure. The proposed algorithm also has a low computational complexity with only linear additions and modifications. Theoretical analysis and simulation results show that the algorithm performs quite well in low SNR environment, and is much better than all the existing typical algorithms with a comprehensive consideration both in performance and computational complexity.展开更多
This paper presents an approach of singular value de- composition plus digital phase lock loop to solve the difficult problem of blind pseudo-noise （PN） sequence estimation in low signal to noise ratios （SNR） dire...This paper presents an approach of singular value de- composition plus digital phase lock loop to solve the difficult problem of blind pseudo-noise （PN） sequence estimation in low signal to noise ratios （SNR） direct sequence spread spectrum （DS-SS） signals with residual carrier. This approach needs some given parameters, such as the period and code rate of PN sequence. The received signal is firstly sampled and divided into non-overlapping signal vectors according to a temporal window, whose duration is two periods of PN sequence. An autocorrelation matrix is then computed and accumulated by those signal vectors one by one. The PN sequence with residual carrier can be estimated by the principal eigenvector of the autocorrelation matrix. Further more, a digital phase lock loop is used to process the estimated PN sequence, it estimates and tracks the residual carrier and removes the residual carrier in the end. Theory analysis and computer simulation results show that this approach can effectively realize the PN sequence blind estimation from the input DS-SS signals with residual carrier in lower SNR.展开更多
An approach based on discrete Karhunen-Loeve transformation of the DS/SS signals is proposed to estimate PN sequence in lower S/N ratio DS/SS signals. Characteristics of self-organization and principle components extr...An approach based on discrete Karhunen-Loeve transformation of the DS/SS signals is proposed to estimate PN sequence in lower S/N ratio DS/SS signals. Characteristics of self-organization and principle components extraction of unsupervised neural networks are exploited adequately. Theoretical analysis and experimental results are provided to show that this approach can work well on the lower S/N ratio input signals.展开更多
To estimate the spreading sequence of the direct sequence spread spectrum (DSSS) signal, a fast algorithm based on maximum likelihood function is proposed, and the theoretical derivation of the algorithm is provided. ...To estimate the spreading sequence of the direct sequence spread spectrum (DSSS) signal, a fast algorithm based on maximum likelihood function is proposed, and the theoretical derivation of the algorithm is provided. By simplifying the objective function of maximum likelihood estimation, the algorithm can realize sequence synchronization and sequence estimation via adaptive iteration and sliding window. Since it avoids the correlation matrix computation, the algorithm significantly reduces the storage requirement and the computation complexity. Simulations show that it is a fast convergent algorithm, and can perform well in low signal to noise ratio (SNR).展开更多
B.Subtilis expression plasmids generally require a stringent Shine Dalgarno Sequence(SDS). Site directed mutagenesis was explored to change the Shine Dalgarno Sequence from AAAAATGGGG (mutant type) to AAAAAGGGGG (...B.Subtilis expression plasmids generally require a stringent Shine Dalgarno Sequence(SDS). Site directed mutagenesis was explored to change the Shine Dalgarno Sequence from AAAAATGGGG (mutant type) to AAAAAGGGGG (wild type) in recombinant plasmid PSM604. The single base substitution made the plasmid with wild SDS unstable in structure and segregation. The interaction of SDS with subtilisin leader sequence of PSM604 might be responsible for the instability of plasmid.展开更多
In this paper, a new approach is proposed to estimate pseudo noise(PN) sequence in the lower SNR DS/SS signals blindly. This method utilizes the characteristics of self-organization, principal components analysis and ...In this paper, a new approach is proposed to estimate pseudo noise(PN) sequence in the lower SNR DS/SS signals blindly. This method utilizes the characteristics of self-organization, principal components analysis and extraction of unsupervised neural networks adequately, in addition to its higher-speed operation ability, successfully solve the difficult problem about PN sequence blind estimation. The theoretic analysis and experimental results show that this approach can work very well on lower SNR input signals.展开更多
Over the past decade,nanopore sequencing has experienced significant advancements and changes,transitioning from an initially emerging technology to a significant instrument in the field of genomic sequencing.However,...Over the past decade,nanopore sequencing has experienced significant advancements and changes,transitioning from an initially emerging technology to a significant instrument in the field of genomic sequencing.However,as advancements in next-generation sequencing technology persist,nanopore sequencing also improves.This paper reviews the developments,applications,and outlook on nanopore sequencing technology.Currently,nanopore sequencing supports both DNA and RNA sequencing,making it widely applicable in areas such as telomere-to-telomere(T2T)genome assembly,direct RNA sequencing(DRS),and metagenomics.The openness and versatility of nanopore sequencing have established it as a preferred option for an increasing number of research teams,signaling a transformative influence on life science research.As the nanopore sequencing technology advances,it provides a faster,more costeffective approach with extended read lengths,demonstrating the significant potential for complex genome assembly,pathogen detection,environmental monitoring,and human disease research,offering a fresh perspective in sequencing technologies.展开更多
The Pb39 Bi25 Sn36 alloy was directionally solidified at varied withdrawal rates followed by quenching.From metallographic observation,composition analysis and differential scanning calorimetry(DSC)analysis,the solidi...The Pb39 Bi25 Sn36 alloy was directionally solidified at varied withdrawal rates followed by quenching.From metallographic observation,composition analysis and differential scanning calorimetry(DSC)analysis,the solidification sequence of Pb39 Bi25 Sn36 alloy was characterized.The Sn-dendrite is observed as the primary phase during solidification,followed by theβ(Pb7 Bi3)/Sn divorced eutectic.At lower temperatures,theβ(Pb7 Bi3)/Sn binary eutectic is formed in the interdendritic region.However,the quasi-peritectic reaction[L+α-Pb→β(Pb7 Bi3)+Sn]does not occur as the prediction based on ternary phase diagram analysis,which can be attributed to the unequilibrium solidfication condition.Moreover,the as-cast microstructure is significantly refined with the increasing withdrawal rates.The quenched sample only exhibits the lamellar structure of Sn,β(Pb7 Bi3)and Bi phases.The results can provide instructions to optimize the as-cast microstructure of ternary alloys with quasi-peritectic reaction.展开更多
An idea of estimating the direct sequence spread spectrum（DSSS） signal pseudo-noise（PN） sequence is presented. Without the apriority knowledge about the DSSS signal in the non-cooperation condition, we propose a s...An idea of estimating the direct sequence spread spectrum（DSSS） signal pseudo-noise（PN） sequence is presented. Without the apriority knowledge about the DSSS signal in the non-cooperation condition, we propose a self-organizing feature map（SOFM） neural network algorithm to detect and identify the PN sequence. A non-supervised learning algorithm is proposed according the Kohonen rule in SOFM. The blind algorithm can also estimate the PN sequence in a low signal-to-noise（SNR） and computer simulation demonstrates that the algorithm is effective. Compared with the traditional correlation algorithm based on slip-correlation, the proposed algorithm＇s bit error rate（BER） and complexity are lower.展开更多
An optimun search algorithm for the coherent acquisition in direct-sequence spread-spectrum （DSSS） receivers is proposed and analyzed in this paper. The system consists of two major parts： a phase region estimator ...An optimun search algorithm for the coherent acquisition in direct-sequence spread-spectrum （DSSS） receivers is proposed and analyzed in this paper. The system consists of two major parts： a phase region estimator and a phase alignment detector. We use an auxiliary sequence to correlate the incoming signal in the phase region estimator. Since the cross-correlation value between the auxiliary sequence and the incoming PN signal has linear magnitude, and can provide the direction for the phase updating, an optimum search algorithm, try and error method, can be adopted to obtain the phase region information of the incoming signal. The mean acquisition time is derived through the signal flow graph theory. The time is compared with that of the conventional serial search scheme, and the results show that the proposed scheme can achieve coarse acquisition significantly faster than the conventional scheme.展开更多
Intensive fish farming systems in Brazil have increased the disease incidence, mainly of bacterial origin, due to higher stocking density, high organic matter levels and poor quality of the aquatic environment that ca...Intensive fish farming systems in Brazil have increased the disease incidence, mainly of bacterial origin, due to higher stocking density, high organic matter levels and poor quality of the aquatic environment that causes high mortality rates during outbreaks. The identification of pathogenic species using a fast and reliable method of diagnosis is essential for successful epidemiological studies and disease control. The present study evaluated the use of direct colony PCR in combination with 16S rRNA gene sequencing to diagnose fish bacterial diseases, with the goal of reducing the costs and time necessary for bacterial identification. The method was successful for all 178 isolates tested and produced bands with the same intensity as the standard PCR performed using pure DNA. In conclusion, the genetics methods allowed detecting the most common and important pathogens in Aquaculture, including 12 species of occurrence in Brazilian fish farms. The results of the present study constitute an advance in the available diagnostic methods for bacterial pathogens in fish farms.展开更多
基金supported by Guangdong Major Project of Basic and Applied Basic Research,China(No.2019B030302010)the Joint Research Scheme sponsored by the Research Grants Council of the Hong Kong Special Administrative Region,China and National Natural Science Foundation of China(Nos.N_PolyU523/20 and 52061160483)+4 种基金the National Natural Science Foundation of China(Nos.52104362,52071222,52471179,52471180 and 52001221)the National Key R&D Program of China(No.2022YFA1603800)the National Key Research and Development Program of China(No.2021YFA0716302)Guangdong Provincial Quantum Science Strategic Initiative(No.GDZX2301001)Guangdong Basic and Applied Basic Research,China(No.2020B1515130007).
文摘To fulfill the demands of applications under severe operational conditions,alloys should possess outstanding wear resistance at elevated temperatures.A Ti-Hf-Nb-V based refractory high entropy alloy(RHEA)was successfully produced using the directed energy deposition(DED)technique,which avoided the formation of fatal defects and showcased well-performed mechanical properties across a broad temperature spectrum.Strategic design of the oxidation sequence enabled the early formation of oxide nanolayers,which can form a polycrystalline oxide nanocoating under a complex stress condition to drastically reduce the wear rate from 2.69×10^(-4) mm^(3)·(N·m)^(−1) at room temperature to 6.90×10^(-7) mm^(3)·(N·m)^(−1) at 600℃.These results indicate that the application of additive manufacturing to fabricate RHEAs with superior wear resistance at high temperatures paves the way for the development of functional coatings designed to withstand extreme conditions.
基金facility support from the Single-Molecule Sequencing Platform at Sun Yat-sen University Cancer Center.This work is supported by the National Natural Science Foundation of China(32070592 to JXY,32000395 to JL,82272789 to LZ)Guangdong Basic and Applied Basic Research Foundation(2022A1515010717 and 2019A1515110762 to JXY and 2022A1515011873 to JL)+2 种基金Guangdong Pearl River Talents Program(2019QN01Y183 to JXY,2021QN02Y168 to JL)Guangzhou Municipal Science and Technology Bureau(202102020938 to JL)Young Talents Program of Sun Yat-sen University Cancer Center(YTP-SYSUCC-0042 to JXY and YTP-SYSUCC-0040 to JL)。
文摘Nanopore direct RNA sequencing(DRS)provides the direct access to native RNA strands with full-length information,shedding light on rich qualitative and quantitative properties of gene expression profiles.Here with NanoTrans,we present an integrated computational framework that comprehensively covers all major DRS-based application scopes,including isoform clustering and quantification,poly(A)tail length estimation,RNA modification profiling,and fusion gene detection.In addition to its merit in providing such a streamlined one-stop solution,NanoTrans also shines in its workflow-orientated modular design,batch processing capability,all-in-one tabular and graphic report output,as well as automatic installation and configuration supports.Finally,by applying NanoTrans to real DRS datasets of yeast,Arabidopsis,as well as human embryonic kidney and cancer cell lines,we further demonstrate its utility,effectiveness,and efficacy across a wide range of DRS-based application settings.
文摘Serveral methods for the pararrel acquisition of a PN sequence in a baseband direct sequence spread spectrum system are investigated. Four different kinds of schemes are considered: the optimal estimation scheme, the locally optimal estimation scheme, the optimal testing searches and the locally optimal testing scheme. In the four kinds of parallel acquisition schemes, the expressions for the probability of error are given and compared with the actual error probabilities obtained via Monte Carlo simulation. We also outline a technique that can be suboptimal because of a large amount of hardware and computation when using the parallel acquisition schemes.
基金supported by the Youth Science Fund,National Natural Science Foundation of China under Grant No.61102130
文摘According to the requirements of the high-sensitivity acquisition of Direct Sequence Spread Spectrum(DSSS) signals under ultrahigh dynamic environments in space communications, a three-dimensional joint search of the phase of Pseudo-Noise-code(PN-code),Doppler frequency and its rate-of-change is presented to achieve high sensitivity in sensing high-frequency dynamics. By eliminating the correlation peak loss caused by ultrahigh Doppler frequency and its rate-of-change offset,the proposed method improves the acquisition sensitivity by increasing the non-coherent accumulation time. The validity of the algorithm is proved by theoretical analysis and simulation results. It is shown that signals with a carrier- to-noise ratio as low as 39 dBHz can be captured with high performance when the Doppler frequency is up to ±1 MHz and its rate-of-change is up to ±200 kHz/s.
基金Sponsored by the National "863" Program Project (1010021310XXX)
文摘Aiming at improving acquisition performance for direct sequence spread spectrum （DSSS） signals, a new acquisition algorithm based on fast Fourier transform （FFT） is proposed. The code phases are parallel searched throughout the Doppler frequency domain. Since the influence of Doppler frequency errors on peak-to- average ratios of correlation power shows a pattern similar to the sinc function, it is our belief that by judging on peak-to-average ratios for different Doppler frequency errors false alarm probabilities should be lowered. Analyses have supported the underlying principle of this new algorithm. Simulation results have also indicated that the new algorithm can effectively improve the acquisition performance for DSSS signals.
文摘A novel direct sequence （DS） design method for suppressing the narrowband interference in DS spread spectrum ultra-wideband receivers is proposed. The method has low computational complexity and can be easily implemented in practical systems. Simulation results prove that the proposed method is effective to suppress the narrowband interference. Therefore, the integrity of both the ultra-wide bandwidth and the narrowband systems can be highly enhanced.
基金ThisprojectwassupportedbytheKeyProjectoftheNaturalScienceFoundationofChina (No .6 98310 30 )
文摘Performances of BPSK, balanced quaternary modulation, dual quaternary modulation and complex quaternary modulation in direct sequence spectrum spread (DS SS) system are discussed in this paper. Based on the criterion the power of original signal is the same, it is shown that complex quaternary modulation has the best performance, and dual quaternary modulation degrades 2dB. Moreover, the frequency efficient of the two modulations is 2bit/Hz. Balanced quaternary has the same performance as BPSK with frequency efficient 1bit/Hz.
基金the National Natural Science Foundation of China (No. 60772100)
文摘For direct sequence spread spectrum (DSSS) communication systems suffering interference, it is known that code-aided interference suppression technique outperforms all of the previous linear or nonlinear methods. In this paper, we proposed an improved code-aided technique which can improve the system performance greatly by using the eigenvector sign (EVS) spreading sequence which depends on the statistical characteristics of the interference and the thermal noise.
文摘A novel kind of multidimension symbol/sequence trellis coded modulation (TCM) based on TCM of lower coding rate has been constructed. The redundancy of this new kind of TCM is provided not only by the modulated symbol sequence but also by the PN sequences for spreading spectrum as well. The performance of direct sequence spread spectrum multiple access (DS/SSMA) system with this symbol/sequence TCM over flat Rayleigh fading channel has been investigated by theoretical analysis and numerical simulation. The results obtained in this research demonstrate the performance improvements of this system in comparison with that of the DS/SSMA system with conventional TCM under the same conditions.
基金supported by the Specialized Research Fund for the Doctoral Program of Higher Education (20060003032)
文摘It is a necessary step to estimate the spreading sequence of direct sequence spread spectrum （DSSS） signal for blind despreading and demodulation in non-cooperative communications. Two innovative and effective detection statistics are proposed to implement the synchronization and spreading sequence estimation procedure. The proposed algorithm also has a low computational complexity with only linear additions and modifications. Theoretical analysis and simulation results show that the algorithm performs quite well in low SNR environment, and is much better than all the existing typical algorithms with a comprehensive consideration both in performance and computational complexity.
基金supported by the National Natural Science Foundation of China (10776040 60602057)+4 种基金Program for New Century Excellent Talents in University (NCET)the Project of Key Laboratory of Signal and Information Processing of Chongqing (CSTC2009CA2003)the Natural Science Foundation of Chongqing Science and Technology Commission (CSTC2009BB2287)the Natural Science Foundation of Chongqing Municipal Education Commission (KJ060509 KJ080517)
文摘This paper presents an approach of singular value de- composition plus digital phase lock loop to solve the difficult problem of blind pseudo-noise （PN） sequence estimation in low signal to noise ratios （SNR） direct sequence spread spectrum （DS-SS） signals with residual carrier. This approach needs some given parameters, such as the period and code rate of PN sequence. The received signal is firstly sampled and divided into non-overlapping signal vectors according to a temporal window, whose duration is two periods of PN sequence. An autocorrelation matrix is then computed and accumulated by those signal vectors one by one. The PN sequence with residual carrier can be estimated by the principal eigenvector of the autocorrelation matrix. Further more, a digital phase lock loop is used to process the estimated PN sequence, it estimates and tracks the residual carrier and removes the residual carrier in the end. Theory analysis and computer simulation results show that this approach can effectively realize the PN sequence blind estimation from the input DS-SS signals with residual carrier in lower SNR.
文摘An approach based on discrete Karhunen-Loeve transformation of the DS/SS signals is proposed to estimate PN sequence in lower S/N ratio DS/SS signals. Characteristics of self-organization and principle components extraction of unsupervised neural networks are exploited adequately. Theoretical analysis and experimental results are provided to show that this approach can work well on the lower S/N ratio input signals.
基金supported by Joint Foundation of and China Academy of Engineering Physical (10676006)
文摘To estimate the spreading sequence of the direct sequence spread spectrum (DSSS) signal, a fast algorithm based on maximum likelihood function is proposed, and the theoretical derivation of the algorithm is provided. By simplifying the objective function of maximum likelihood estimation, the algorithm can realize sequence synchronization and sequence estimation via adaptive iteration and sliding window. Since it avoids the correlation matrix computation, the algorithm significantly reduces the storage requirement and the computation complexity. Simulations show that it is a fast convergent algorithm, and can perform well in low signal to noise ratio (SNR).
文摘B.Subtilis expression plasmids generally require a stringent Shine Dalgarno Sequence(SDS). Site directed mutagenesis was explored to change the Shine Dalgarno Sequence from AAAAATGGGG (mutant type) to AAAAAGGGGG (wild type) in recombinant plasmid PSM604. The single base substitution made the plasmid with wild SDS unstable in structure and segregation. The interaction of SDS with subtilisin leader sequence of PSM604 might be responsible for the instability of plasmid.
文摘In this paper, a new approach is proposed to estimate pseudo noise(PN) sequence in the lower SNR DS/SS signals blindly. This method utilizes the characteristics of self-organization, principal components analysis and extraction of unsupervised neural networks adequately, in addition to its higher-speed operation ability, successfully solve the difficult problem about PN sequence blind estimation. The theoretic analysis and experimental results show that this approach can work very well on lower SNR input signals.
基金financially supported by the Natural Science Foundation of China(32470055 and U23A20148)the China Postdoctoral Science Foundation(2024M753580)the Agricultural Science and Technology Innovation Program(CAAS-ZDRW202308)。
文摘Over the past decade,nanopore sequencing has experienced significant advancements and changes,transitioning from an initially emerging technology to a significant instrument in the field of genomic sequencing.However,as advancements in next-generation sequencing technology persist,nanopore sequencing also improves.This paper reviews the developments,applications,and outlook on nanopore sequencing technology.Currently,nanopore sequencing supports both DNA and RNA sequencing,making it widely applicable in areas such as telomere-to-telomere(T2T)genome assembly,direct RNA sequencing(DRS),and metagenomics.The openness and versatility of nanopore sequencing have established it as a preferred option for an increasing number of research teams,signaling a transformative influence on life science research.As the nanopore sequencing technology advances,it provides a faster,more costeffective approach with extended read lengths,demonstrating the significant potential for complex genome assembly,pathogen detection,environmental monitoring,and human disease research,offering a fresh perspective in sequencing technologies.
基金National Natural Science Foundation of China(No.51604222)China Postdoctoral Science Foundation(No.152064),Strong Industrial Base Project of China(No.TC160A310-18)+1 种基金Xi'an University of Science and Technology for Excellent Young Teachers Research Program(No.2018YQ2-12)Excellent Projects funded by Science and Technology Activities for Overseas Students in Shaanxi Province(No.2018047).
文摘The Pb39 Bi25 Sn36 alloy was directionally solidified at varied withdrawal rates followed by quenching.From metallographic observation,composition analysis and differential scanning calorimetry(DSC)analysis,the solidification sequence of Pb39 Bi25 Sn36 alloy was characterized.The Sn-dendrite is observed as the primary phase during solidification,followed by theβ(Pb7 Bi3)/Sn divorced eutectic.At lower temperatures,theβ(Pb7 Bi3)/Sn binary eutectic is formed in the interdendritic region.However,the quasi-peritectic reaction[L+α-Pb→β(Pb7 Bi3)+Sn]does not occur as the prediction based on ternary phase diagram analysis,which can be attributed to the unequilibrium solidfication condition.Moreover,the as-cast microstructure is significantly refined with the increasing withdrawal rates.The quenched sample only exhibits the lamellar structure of Sn,β(Pb7 Bi3)and Bi phases.The results can provide instructions to optimize the as-cast microstructure of ternary alloys with quasi-peritectic reaction.
基金supported by the National Natural Science Foundation of China under Grant No.61271168
文摘An idea of estimating the direct sequence spread spectrum（DSSS） signal pseudo-noise（PN） sequence is presented. Without the apriority knowledge about the DSSS signal in the non-cooperation condition, we propose a self-organizing feature map（SOFM） neural network algorithm to detect and identify the PN sequence. A non-supervised learning algorithm is proposed according the Kohonen rule in SOFM. The blind algorithm can also estimate the PN sequence in a low signal-to-noise（SNR） and computer simulation demonstrates that the algorithm is effective. Compared with the traditional correlation algorithm based on slip-correlation, the proposed algorithm＇s bit error rate（BER） and complexity are lower.
文摘An optimun search algorithm for the coherent acquisition in direct-sequence spread-spectrum （DSSS） receivers is proposed and analyzed in this paper. The system consists of two major parts： a phase region estimator and a phase alignment detector. We use an auxiliary sequence to correlate the incoming signal in the phase region estimator. Since the cross-correlation value between the auxiliary sequence and the incoming PN signal has linear magnitude, and can provide the direction for the phase updating, an optimum search algorithm, try and error method, can be adopted to obtain the phase region information of the incoming signal. The mean acquisition time is derived through the signal flow graph theory. The time is compared with that of the conventional serial search scheme, and the results show that the proposed scheme can achieve coarse acquisition significantly faster than the conventional scheme.
基金thank the State of Sao Paulo Research Foundation(FAPESP-Process 2011/07951-5)for the financial support.
文摘Intensive fish farming systems in Brazil have increased the disease incidence, mainly of bacterial origin, due to higher stocking density, high organic matter levels and poor quality of the aquatic environment that causes high mortality rates during outbreaks. The identification of pathogenic species using a fast and reliable method of diagnosis is essential for successful epidemiological studies and disease control. The present study evaluated the use of direct colony PCR in combination with 16S rRNA gene sequencing to diagnose fish bacterial diseases, with the goal of reducing the costs and time necessary for bacterial identification. The method was successful for all 178 isolates tested and produced bands with the same intensity as the standard PCR performed using pure DNA. In conclusion, the genetics methods allowed detecting the most common and important pathogens in Aquaculture, including 12 species of occurrence in Brazilian fish farms. The results of the present study constitute an advance in the available diagnostic methods for bacterial pathogens in fish farms.
