以高瓦数数字放大器进行设定

数字放大器技术自问世以来已有长足的进展,现在已普遍应用于日常生活中各个层面的产品,包括DVD接收器、平板电视及MP3基座.比较各通道的功率级耗电量,即可明显看出这一先进的技术所发挥的性能.     

Monitoring the status of forests and rangelands in the Western United States using ecosystem performance anomalies

The effects of land management and disturbance on ecosystem performance (i.e. biomass production) are often confounded by those of weather and site potential. The current study overcomes this issue by calculating the difference between actual and expected ecosystem performance (EEP) to generate ecosystem performance anomalies (EPA). This study aims to delineate and quantify average EPA from 2000–2009 within the Greater Platte and Upper Colorado River Basins, USA. Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index (NDVI) images averaged over the growing season (GSN) served as a proxy of actual ecosystem performance. Yearly EEP was determined with rule-based piecewise regression tree models of abiotic data (climate, soils, elevation, etc.), independently created for each land cover. EPA were calculated as the residuals of the EEP to GSN relationship, and characterized as normal performing, underperforming, and overperforming at the 90% confidence level. Validation revealed that EPA values were related to biomass production (R ² = 0.56, P = 0.02) and likely to the proportion of biomass removed by livestock in the Nebraska Sandhills. Overall, 60.6% of the study area was (normal) performing near its EEP, 3.0% was severely underperforming, 5.0% was highly overperforming, and the remainder was slightly underperforming or overperforming. Generally, disturbances such as fires, floods, and insect damage, in addition to high grazing intensity, result in a negative EPA. Conversely, mature stands and appropriate management often result in positive EPA values. This method provides information critical to land managers to evaluate the appropriateness of previous management practices and restoration efforts and quantify disturbance impacts. Results are at a scale sufficient for many of the large management units of the region and for locating areas needing further investigation. Applications of EPA data to monitoring invasive species, grazing impacts, and vulnerability to plant community shifts have been suggested by land management professionals.     

SoC微处理器推动便携式医疗设备创新发展

便携式医疗设备正不断改进数以百万计患者的医疗保健条件。诸如血糖监测仪、心率检测仪、可吞咽胃肠（GI）道检测仪以及止痛植入物等众多设备都在不断提升慢性或急性疾病患者的生活质量。便携式自动除颤器可以挽救急病患者的生命。运动手表不仅能够无线记录用户的心率、测量距离、进行脚步计数，而且还可实现能最大限度发挥有氧训练优势的其它功能。未来几年中，还将陆续推出众多能显著改善医疗实施及其效果的创新型医疗应用产品。     

Structural invariance of constitutively active and inactive mutants of acanthamoeba myosin IC bound to F-actin in the rigor and ADP-bound states

The three single-headed monomeric myosin I isozymes of Acanthamoeba castellanii (AMIs)-AMIA, AMIB, and AMIC-are among the best-studied of all myosins. We have used AMIC to study structural correlates of myosin's actin-activated ATPase. This activity is normally controlled by phosphorylation of Ser-329, but AMIC may be switched into constitutively active or inactive states by substituting this residue with Glu or Ala, respectively. To determine whether activation status is reflected in structural differences in the mode of attachment of myosin to actin, these mutant myosins were bound to actin filaments in the absence of nucleotide (rigor state) and visualized at 24-A resolution by using cryoelectron microscopy and image reconstruction. No such difference was observed. Consequently, we suggest that regulation may be affected not by altering the static (time-averaged) structure of AMIC but by modulating its dynamic properties, i.e., molecular breathing. The tail domain of vertebrate intestinal brush-border myosin I has been observed to swing through 31 degrees on binding of ADP. However, it was predicted on grounds of differing kinetics that any such effects with AMIC should be small [Jontes, J. D., Ostap, E. M., Pollard, T. D. & Milligan, R. A. (1998) J. Cell Biol. 141, 155-162]. We have confirmed this hypothesis by observing actin-associated AMIC in its ADP-bound state. Finally, we compared AMIC to brush-border myosin I and AMIB, which were previously studied under similar conditions. In each case, the shape and angle of attachment to F-actin of the catalytic domain is largely conserved, but the domain structure and disposition of the tail is distinctively different for each myosin.     

In the realm of agents

Stit theory (a logic of seeing-to-it-that) is applied to cases involving many agents. First treated are complex nestings of stits involving distinct agents. The discussion is driven by the logical impossibility of a sees to it that b sees to it thatQ in the technical sense, even though that seems to make sense in everyday language. Of special utility are the concepts of forced choice, of the creation of deontic states, and of probabilities. Second, joint agency, both plain and strict (every participant is essential) is given a rigorous treatment. A central theorem is that strict joint agency is itself agentive.     

Case Study: Model to Simulate Regional Flow in South Florida

South Florida has a complex regional hydrologic system that consists of thousands of miles of networked canals, sloughs, highly pervious aquifers, open areas subjected to overland flow and sheet flow, agricultural areas and rapidly growing urban areas. This region faces equally complex problems related to water supply, flood control, and water quality management. Advanced computational methods and super fast computers alone have limited success in solving modern day problems such as these because the challenge is to model the complexity of the hydrologic system, while maintaining computational efficiency and acceptable levels of numerical errors. A new, physically based hydrologic model for South Florida called the regional simulation model (RSM) is presented here. The RSM is based on object oriented design methods, advanced computational techniques, extensible markup language, and geographic information system. The RSM uses a finite volume method to simulate two-dimensional (2D) surface and groundwater flow. It is capable of working with unstructured triangular and rectangular mesh discretizations. The discretized control volumes for 2D flow, canal flow and lake flow are treated as abstract “water bodies” that are connected by abstract “water movers.” The numerical procedure is designed to work with these and many other abstractions. An object oriented code design is used to provide robust and highly extensible software architecture. A weighted implicit numerical method is used to keep the model fully integrated and stable. A limited error analysis was carried out and the results were compared with analytical error estimates. The paper describes an application of the model to the L-8 basin in South Florida and the strength of this approach in developing models over complex areas.     

集成知识是电源技术的发展趋势

随着 IC 技术演进步伐的加快,低功耗技术变得更为复杂,也日益依赖于 IC 之间的交互性。通过将高效与智能相结合,半导体技术在节能领域中正扮演着极为关键的角色。有的系统有一些必须持续工作的简单功能,如果这些功能由配合 DSP 工作的 MCU 完成,则通常可实现更低的功耗。功耗更低的工作模式可降低电源管理 IC 本身的损耗,而借助这种工作模式和改进后的工艺技术,电源管理 IC 及相关组件的效率可获得进一步提升。     

Fracture resistant super hard materials and hardmetals composite with functionally designed microstructure

Polycrystalline diamond and other hard materials are widely used in earth boring, mining, and construction tool applications. Chipping and fracture resistance is often improved by various means at the expense of hardness and wear resistance. This trade-off between wear resistance and chipping resistance hinders the development of hard and super hard materials for many industrial applications. A new approach, characterized as “hard materials composites with functionally designed microstructure” including polycrystalline diamond and cemented tungsten carbide, is discussed. The functionally designed microstructure offers enhanced chipping resistance and toughness without significantly sacrificing wear resistance.     

Crack Shielding in Ce-TZP/Al2O3 Composites: Comparison of Fatigue and Sustained Load Crack Growth Specimens

Crack shielding stress intensities in in situ loaded compact tension specimens of two types of ceria-partially-stabilized zirconia/alumina (Ce-TZP/Al₂O₃) composites with prior histories of subcritical crack growth in sustained and tension-tension fatigue loading were directly assessed using laser Raman spectroscopy. Crack-tip stress fields within the transformation zones were measured by measuring a stress-induced frequency shift of a peak corresponding to the tetragonal phase. The peak shift as a function of the applied stress was separately calibrated using a ball-on-ring flexure test. Total crack shielding stress intensity was estimated from the far-field applied stress intensity and the local crack-tip stress intensity assessed from the measured near-crack-tip stresses. The shielding stress intensities were consistently lower in the fatigue specimens than in the sustained load crack growth specimens. The reduced crack shielding developed in the fatigue specimens was independently confirmed by measurements of larger crack-opening displacement under far-field applied load as compared to the sustained load crack growth specimens. Thus, diminished crack shielding was a major factor contributing to the higher subcritical crack growth rates exhibited by the Ce-TZP/Al₂O₃ composites in tension–tension cyclic fatigue. Calculations of zone shielding considering only the dilatational strains in the transformation zones accounted for 81% and 86% of the measured values in the sustained load crack growth specimens, but significantly overestimated the shielding in the fatigue specimens. Possible reasons for the diminished crack shielding in the fatigue specimens are discussed.