Relationships between Artemisia ordosica communities and environmental factors following sand-dune stabilization in the Mu Us desert,northwest China

Artemisia ordosica is an excellent sand-fixing shrub for sand stabilization in northwestern China. Sand dune stabilization, a critically important process, leads changes in abiotic factors, such as soil structure and nutrient contents. However, the effects of factors on an A. ordosica community following sand stabilization remain unclear. In this study, we used canonical correspondence analysis （CCA） to examine the relationships between A. ordosica communities and environmental factors at three habitats： semi-fixed dune （SF）, fixed dune with low-cov- erage biological soil crust （F）, and fixed dune with high- coverage biological soil crust （FC） in Mu Us desert. The mean height and coverage of plants increased with sand stabilization, while species diversity and richness increased initially and then reduced significantly. Correlation analysis and CCA revealed that slope, soil organic carbon, and nutrient contents, proportion of fine soil particles, soil moisture, and thickness of biological soil crust were all highly correlated with vegetation characteristics. These environmental factors could explain 40.42 % of the vege- tation-environment relationships at the three habitats. The distribution of plant species was positively related to soil moisture in the SF dune. Soil moisture, soil nutrient, and fine-particle contents mainly affected plants distribution in the F dune. In the FC dune, distribution of plant species was positively and negatively correlated with the thickness of biological soil crust and soil moisture at a depth 0-20 cm, respectively. The dominance value of typical steppe species increased significantly following sand-dune stabilization and relations between species and samples in CCA ordination bi-plots showed that perennial grasses could invade the A. ordosica community on FC, indicating A. ordosica communities had a tendency to change into typical steppe vegetation with the further fixation. We conclude that the significant differentiation not only occurred in community characteristics, but also in the relationships between vegetation and environmental factors among the three stages of dune fixation. So, restoration of degraded dune ecosystems should be based on habitat conditions and ecological needs.

Geotechnical methods of reinforcement of slopes near railroads

In order to generate well-based design decisions on reinforcement of landslide slopes and road embankment slopes, a system of combined geotechnical analysis of geological conditions is suggested which includes topographic and geo- physical survey, and laboratory studies of soils using infra-red spectroscopy methods. Calculations of slopes＇ deflected modes are carried out with taking into account elastic and elasto-plastic behavior of soil, and the presence of supporting man-made constructions. Results of the application of the system suggested may be used as criteria for the classification of landslide slopes along permanent ways according to the degree of danger when used for transportation.

Underground storage tank blowout analysis:Stability prediction using an artificial neural network

Most geotechnical stability research is linked to“active”failures,in which soil instability occurs due to soil self-weight and external surcharge applications.In contrast,research on passive failure is not common,as it is predominately caused by external loads that act against the soil self-weight.An earlier active trapdoor stability investigation using the Terzaghi’s three stability factor approach was shown to be a feasible method for evaluating cohesive-frictional soil stability.Therefore,this technical note aims to expand“active”trapdoor research to assess drained circular trapdoor passive stability(blowout condition)in cohesive-frictional soil under axisymmetric conditions.Using numerical finite element limit analysis(FELA)simulations,soil cohesion,surcharge,and soil unit weight effects are considered using three stability factors(Fc,Fs,and Fγ),which are all associated with the cover-depth ratio and soil internal friction angle.Both upper-bound(UB)and lower-bound(LB)results are presented in design charts and tables,and the large dataset is further studied using an artificial neural network(ANN)as a predictive model to produce accurate design equations.The proposed passive trapdoor problem under axisymmetric conditions is significant when considering soil blowout stability owing to faulty underground storage tanks or pipelines with high internal pressures.

Optimum Design for a Low Noise Amplifier in S-Band

An optimum design of a low noise amplifier （LNA） in S-band working at 2-4 GHz is described. Choosing FHC40LG high electronic mobility transistor （HEMT）, the noise figure of the designed amplifier simulated by Microwave Office is no more than 1.5 dB, meanwhile the gain is no less than 20 dB in the given bandwidth. The simulated results agree with the performance of the transistor itself well in consideration of its own minimum noise figure （0.3 dB） and associated gain （15.5 dB）. Simultaneously, the stability factor of the designed amplifier is no less than 1 in the given bandwidth.

Improved formulations of the CR and KR methods for structural dynamics

Although the Chen-Ricles（CR）method and the Kolay-Ricles（KR）method have been applied to conduct pseudodynamic tests,they have both been found to have some adverse numerical properties,such as conditional stability for stiffness hardening systems and an unusual overshoot in the steady-state response of a high-frequency mode.An improved formulation for each method can be achieved by using a stability amplification factor to boost the unconditional stability range for stiffness hardening systems and a loading correction term to eliminate the unusual overshoot in the steady-state response of a high-frequency mode.The details for developing improved formulations for each method are shown in this work.

Impact of parameter fluctuations on RF stability performance of DG tunnel FET

This paper presents the impact of parameter fluctuation due to process variation on radio frequency （RF） stability performance of double gate tunnel FET （DG TFET）. The influence of parameter fluctuation due to process variation leads to DG TFET performance degradation. The RF figures of merit （FoM） such as cut-off frequency （ft）, maximum oscillation frequency （fmax） along with stability factor for different silicon body thickness, gate oxide thickness and gate contact alignment are obtained from extracted device parameters through numerical simulation. The impact of parameter fluctuation of silicon body thickness, gate oxide thickness and gate contact alignment was found significant and the result provides design guidelines ofDG TFET for RF applications.

Stability performance of optimized symmetric DG-MOSFET

This article presents the bias and geometry optimization procedure for the radio frequency （RF） stability performance of nanoscale symmetric double-gate metal-oxide semiconductor field-effect transistors （DG- MOSFETs）. The stability model can provide hints for optimizing the DG-MOSFET under an RF range. The device parameters are extracted for different bias and geometry conditions through numerical simulation, and the RF figures of merit such as cut-off frequency （ft） and maximum oscillation frequency （fmax）, along with stability factor, are calculated for an optimized structure. The proposed structure exhibits good RF stability performance.

Intrinsic stability of an HBT based on a small signal equivalent circuit model

Intrinsic stability ofthe heterojunction bipolar transistor （HBT） was analyzed and discussed based on a small signal equivalent circuit model. The stability factor of the HBT device was derived based on a compact T-type small signal equivalent circuit model of the HBT. The effect of the mainly small signal model parameters of the HBT on the stability of the HBT was thoroughly examined. The discipline of parameter optimum to improve the intrinsic stability of the HBT was achieved. The theoretic analysis results of the stability were also used to explain the experimental results of the stability of the HBT and they were verified by the experimental results.

Frequency stability of InP HBT over 0.2 to 220 GHz

The frequency stabilities of lnP DHBTs in a broadband over 1 to 220 GHz are investigated. A hybrid π-topology small-signal model is used to accurately capture the parasitics of devices. The model parameters are extracted from measurements analytically. The investigation results show that the excellent agreement between the measured and simulated data is obtained in the frequency range 200 MHz to 220 GHz. The dominant parameters of the π-topology model, bias conditions and emitter area have significant effects on the stability factor K. The HBT model can be unconditionally stable by reasonable selection of the proper bias condition and the physical layout of the device.

DNA End Resection:Facts and Mechanisms

DNA double-strand breaks（DSBs）,which arise following exposure to a number of endogenous and exogenous agents,can be repaired by either the homologous recombination（HR）or non-homologous end-joining（NHEJ） pathways in eukaryotic cells.A vital step in HR repair is DNA end resection,which generates a long 30single-stranded DNA（ss DNA） tail that can invade the homologous DNA strand.The generation of 30 ss DNA is not only essential for HR repair,but also promotes activation of the ataxia telangiectasia and Rad3-related protein（ATR）.Multiple factors,including the MRN/X complex,C-terminal-binding protein interacting protein（Ct IP）/Sae2,exonuclease 1（EXO1）,Bloom syndrome protein（BLM）/Sgs1,DNA2 nuclease/helicase,and several chromatin remodelers,cooperate to complete the process of end resection.Here we review the basic machinery involved in DNA end resection in eukaryotic cells.