Wideband spectrum sensing using step-sampling based on the multipath nyquist folding receiver

Wideband spectrum sensing with a high-speed analog-digital converter(ADC) presents a challenge for practical systems.The Nyquist folding receiver(NYFR) is a promising scheme for achieving cost-effective real-time spectrum sensing,which is subject to the complexity of processing the modulated outputs.In this case,a multipath NYFR architecture with a step-sampling rate for the different paths is proposed.The different numbers of digital channels for each path are designed based on the Chinese remainder theorem(CRT).Then,the detectable frequency range is divided into multiple frequency grids,and the Nyquist zone(NZ) of the input can be obtained by sensing these grids.Thus,high-precision parameter estimation is performed by utilizing the NYFR characteristics.Compared with the existing methods,the scheme proposed in this paper overcomes the challenge of NZ estimation,information damage,many computations,low accuracy,and high false alarm probability.Comparative simulation experiments verify the effectiveness of the proposed architecture in this paper.

Two chemical mutagens modulate the seed germination,growth,and phenotypic characteristics of Chinese fir(Cunninghamia lanceolata)

Chinese fir(Cunninghamia lanceolata(Lamb.)Hook),a fast-growing and economically important timber tree species in China,is widely used in construction,furniture,and paper manufacture but has a long breeding cycle.Chemical mutagens,such as ethyl methane sulfonate(EMS)and sodium azide(SA),are widely used in crops such as rice,wheat,cotton,soybean and sugarcane but their utility for tree breeding is unknown.In this study we examined the effects of EMS and S A on Chinese fir seed germination and growth.Chinese fir seeds were treated with the two chemical mutagens;were planted in Jiangle County,Fujian Province,China;and their heights were measured from 2011 to2017.The concentrations and durations of treatment with the two chemical mutagens were significantly associated with the Chinese fir seedling and mortality rates,as well as with the heights of trees from the seedling stage to 3 years old.We also generated 127 mutants with abnormal branches and reproductive growth.We report here the effects of two chemical mutagens on Chinese fir breeding;our data will contribute to knowledge of the utility of EMS and SA in forestry.

Genetic diversity and population structure of Robinia pseudoacacia from six improved variety bases in China as revealed by simple sequence repeat markers

Robinia pseudoacacia is an important afforesta-tion tree introduced to China in 1878.In the present study,we examined the genetic diversity among 687 strains rep-resenting four improved varieties and two secondary prov-enances,comprising 641 clones and 46 seedlings.Ninety-one simple sequence repeats(SSRs)were selected through segregation analysis and polymorphism characterization,and all sampled individuals were genotyped using well-characterized SSR markers.After excluding loci with non-neutral equilibrium,missing locus data and null alleles,we used 36 primer pairs to assess the genetic diversity of these germplasm resources,revealing vast genetic differentiation among the samples,with an average of 8.352 alleles per locus and a mean Shannon′s index of 1.302.At the popula-tion level,the partitioning of variability was assessed using analysis of molecular variance,which revealed 93%and 7%variation within and among collection sites,respectively.Four clusters were detected using structure analysis,indi-cating a degree of genetic differentiation among the six populations.Insights into the genetic diversity and structure of R.pseudoacacia provide a theoretical basis for the con-servation,breeding and sustainable development in China.

Scientific land greening under climate change: Theory, modeling, and challenges

Anthropogenic land greening is a vital strategy to combat the global warming crisis.However,the changing external environment and endowment factors may constrain the effectiveness of land greening.It remains unclear how to quantify and optimize land greening strategies scientifically.This article reviewed the theoretical foundations of land greening,pointing out that climate governance and human settlement quality improvement have gradually become the two core objectives of land greening since the 2oth century.Multi-source and multi-scale experimental and observational surveys are important techniques for detecting and evaluating long-term land greening in the context of climate change,especially by forming experimental and observational networks.The theoretical mechanisms of interactions among climate,humans,and vegetation were also explored.For modeling approaches,hybrid modeling based on Earth system coupling theory may be the most promising but challenging approach.Four main challenges of scientific land greening were also discussed,including knowledge gaps related to land greening mechanisms,unclear multifaceted effects of land greening,lack of forward-looking quantitative assessment,and difficulties in evaluating synergies and trade-offs among assessment targets.Based on these,a strategic framework was proposed,including systematic observation,mechanism research,expectation assessment,and scientific planning for scientific greening programs in the Guangdong-Hong Kong-Macao Greater Bay Area.This review underscored the importance of proactively implementing land greening programs and provided guidelines for scientific greening based on cutting-edge theory and methods.