下一代无线网络架构

无线局域网(WLAN)技术为家庭和企业用户描绘了美好的蓝图,也吸引着众多半导体和系统设备厂商涌入这一市场。WLAN技术的不断演变,将标准制订团体、互操作性论坛(互操作性是市场进一步接受的关键要求)、产品OEM厂商和相应的半导体厂商紧密联系在一起。     

Impact of climate variability on tropospheric ozone

A simulation with the climate-chemistry model (CCM) E39/C is presented, which covers both the troposphere and stratosphere dynamics and chemistry during the period 1960 to 1999. Although the CCM, by its nature, is not exactly representing observed day-by-day meteorology, there is an overall model's tendency to correctly reproduce the variability pattern due to an inclusion of realistic external forcings, like observed sea surface temperatures (e.g. El Ni?o), major volcanic eruption, solar cycle, concentrations of greenhouse gases, and Quasi-Biennial Oscillation. Additionally, climate-chemistry interactions are included, like the impact of ozone, methane, and other species on radiation and dynamics, and the impact of dynamics on emissions (lightning). However, a number of important feedbacks are not yet included (e.g. feedbacks related to biogenic emissions and emissions due to biomass burning). The results show a good representation of the evolution of the stratospheric ozone layer, including the ozone hole, which plays an important role for the simulation of natural variability of tropospheric ozone. Anthropogenic NO(x) emissions are included with a step-wise linear trend for each sector, but no interannual variability is included. The application of a number of diagnostics (e.g. marked ozone tracers) allows the separation of the impact of various processes/emissions on tropospheric ozone and shows that the simulated Northern Hemisphere tropospheric ozone budget is not only dominated by nitrogen oxide emissions and other ozone pre-cursors, but also by changes of the stratospheric ozone budget and its flux into the troposphere, which tends to reduce the simulated positive trend in tropospheric ozone due to emissions from industry and traffic during the late 80s and early 90s. For tropical regions the variability in ozone is dominated by variability in lightning (related to ENSO) and stratosphere-troposphere exchange (related to Northern Hemisphere Stratospheric dynamics and solar activity). Since tropospheric background chemistry is regarded only, the results are quantitatively limited with respect to derived trends. However, the main results are regarded to be robust. Although the horizontal resolution is rather coarse in comparison to regional models, such kind of simulations provide useful and necessary information on the impact of large-scale processes and inter-annual/decadal variations on regional air quality.     

A method for correction of cosine errors in measurements of spectral UV irradiance

One of the sources contributing to the overall uncertainty of spectral UV radiation measurements is the cosine error of the spectroradiometer. It leads to measurement errors that depend on atmospheric conditions and on solar zenith angle, and thus time of the day and season. Though the foreoptics of modern instruments are designed such as to minimize cosine errors, there remain deviations from the ideal cosine response. We have worked out a method to further reduce that remaining cosine error in global spectral irradiance. This method was applied to spectra of global UV radiation taken with a Brewer spectroradiometer. The only additional input data needed to apply the method of cosine correction to spectral irradiance data are concurrent broad-band UV-B radiation measurements of diffuse and global radiation recorded with filter UV instruments, which are used to estimate the optical thickness referred to global UV radiation for the time when the spectral scan is taken. The method takes account of the variable conditions of cloudiness and turbidity. In the case of measurements taken with Brewer instrument No. 30, the cosine corrected global UV-B radiation was higher than the measured irradiance by 9–20%, and even its daily totals turned out to be higher than the uncorrected radiation by 13–18%. An estimate of the uncertainty of ±4 to ±8% was derived from a theoretical approach as well as from model calculations using a radiative transfer model.     

SEM imaging of the cell structure of dislocation networks in cold worked cu single crystals

In certain metallurgical applications of SEM, such as the observation of deformation effects, and the recovery and recrystallization processes in bulk specimens, it is of special interest to obtain information about local inhomogeneities of the dislocation densities in a sample. This can be obtained using TEM on thin foils. Previously information on distortion in cold-worked specimens was obtained by measuring the dependence of the deterioration of the resolution of the selected area channelling patterns (SACP) on the degree of deformation. This method, however, is not applicable to highly deformed materials. Direct SEM imaging of the cell structure of the dislocation network has been achieved without resolving single dislocations by using a suitable arrangement of specimen and detector, such that only backscattered electrons (BSE) leaving the surface at a large angle to the normal contribute to the image signals. The signal-to-noise ratio was improved to the degree that it was possible 1) to image the cell structure of the dislocation network and 2) on heating the specimens, to record the growth of recrystallized regions with TV-frame frequency. The imaging of the cell structure gives qualitative information about the degree of crystal deformation and the crystallographic direction of grain boundary motion during recrystallization.     

Influence of molsidomine on exercise-ECG'S In coronary insufficiency (author's transl)

Molsidomine was shown to have a strong pain-relieving action in 22 coronary patients investigated one hour after oral intake of 2 mg of the substance. During comparable maximal exercise load the ST interval lowering was reduced from an average of 0.22 mV to 0.09 mV (P less than 0.0005). At the termination of exercise it was still reduced from 0.23 mV to 0.12 mV (P less than 0.0005). At the same time the exercise tolerance increased from 570 to 717 Watt-minutes (P less than 0.0025). Pectanginal complaints were clearly reduced at the same exercise loads, 11 patients became symptom-free at the same load. Even when exercise loading was stopped at higher loads a decrease of the severity of angina pectoris could be shown. Seven patients became symptom-free at that stage. The heart rate was not influenced markedly at rest and during exercise. Systolic blood pressure was reduced from 135 mm Hg to 118 mm Hg (P less than 0.0005), and in comparable submaximal loads from 177 to 165 mm Hg (P less than 0.005).     

Emotions over time: Synchronicity and development of subjective, physiological, and facial affective reactions to music.

Most people are able to identify basic emotions expressed in music and experience affective reactions to music. But does music generally induce emotion? Does it elicit subjective feelings, physiological arousal, and motor reactions reliably in different individuals? In this interdisciplinary study, measurement of skin conductance, facial muscle activity, and self-monitoring were synchronized with musical stimuli. A group of 38 participants listened to classical, rock, and pop music and reported their feelings in a two-dimensional emotion space during listening. The first entrance of a solo voice or choir and the beginning of new sections were found to elicit interindividual changes in subjective feelings and physiological arousal. Quincy Jones' "Bossa Nova" motivated movement and laughing in more than half of the participants. Bodily reactions such as "goose bumps" and "shivers" could be stimulated by the "Tuba Mirum" from Mozart's Requiem in 7 of 38 participants. In addition, the authors repeated the experiment seven times with one participant to examine intraindividual stability of effects. This exploratory combination of approaches throws a new light on the astonishing complexity of affective music listening. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Verschleiss-schutzschichten auf Hartmetallen

Titanium-containing hard metals of ISO grades P01, P10, P25 and M15 were heat treated at temperatures in the range 1150–1350 °C under nitrogen at pressures of 1 bar and 65 bar. The treatment under nitrogen was performed immediately after the sintering process. Each nitrogen treatment produced nitrogen-containing coatings of different thicknesses. The structure of these layers was investigated using X-rays, metallography and microprobe analysis. During testing of the tool life the specimens showed large improvements in crater wear resistance and in some cases in flank wear resistance too. A deterioration in the toughness behaviour of the tips was not observed. An increased nitrogen pressure would further improve the tool life behaviour.     

Instruments for broad-band UV radiation measurements

UV instruments using interference filters or glass filters for the selection of three wavelength regions (310–320 nm, 315–391 nm, and 296–388 nm) and photocells have been developed and manufactured at the Meteorological Observatory Potsdam. The design and principle of the instruments are described. Method and problems of calibration are discussed. First results of continuous UV radiation measurements will be discussed in a separate paper.     

Acoustic properties of particle/polymer composites for ultrasonic transducer backing applications

The acoustic impedance and attenuation in composites made of particle fillers loaded in polymer matrices for transducer backing applications is investigated. The acoustic impedance of tungsten/vinyl composites was modeled, and an experimental matrix identifying variables that contribute to composite attenuation was established. The variable included the particle type, the particle size and volume fraction of a filler, the physical characteristics of the polymer matrix, and the processing route that determined the composite connectivity. Experimental results showed that with an increase in filler particle size or a decrease in volume fraction of filler, there is an increase in composite attenuation. Overall, the various types of filler, the polymer matrix, and the interface between the two contribute to attenuation in the composite, as confirmed by the acoustic properties and the microstructural analysis.