Symbol Timing Recovery Algorithms and Their Evaluation for Burst Communication

This paper reviews and presents the simulationresults on the performance of four alternative symboltiming offset estimation algorithms for burst modecommunication. Two basically different approaches are taken to the problem. The first approach isbased on the concept of maximum likelihood estimation,of which two basic varieties are derived and evaluated.These are referred to as the data-driven and the non-data-driven versions. In thedata-driven mode, either the decision symbols from theoutput of the demodulator or a number of known referencesymbols may be used to drive the algorithm. The maximum likelihood algorithms generate an error signalthat can be used in a closed-loop control system toadjust the phase of the sampling clock to the optimumsymbol sampling instant. The second approach uses the basic signal processing technique of tonefiltering using effectively the discrete Fouriertransform. The tone filtering approach results in thedirect estimation of the optimum symbol sampling phase and hence is more of an open-loop approach. Thesimulation results indicate that excellent performanceis achieved with this kind of open-loop approach, evenat low signal to noise ratios and in the presence of some frequency offset as long as the symboltiming offset does not exceed 90% from its optimumpoint. It is also shown that by choosing the propersampling rate, this algorithm results in a simple IIR filtering implementation with one pole that isvery efficient from a processing point ofview.     

玻璃纤维/木塑混杂复合材料及其协同增强效应

将固体废弃物中的高密度聚乙烯(HDPE)回收后与废弃的木纤维以及短切玻璃纤维进行复合,成功地制备出混杂型木塑复合材料。研究结果表明,采用长径比较大的L型玻璃纤维增强时,木塑复合材料的弯曲强度、弯曲模量以及冲击强度同时得到提高,而采用长径比较小的玻璃纤维增强时,弯曲性能和冲击强度均呈现下降趋势。玻璃纤维增强木塑复合材料的主要破坏模式为玻璃纤维的拔出、玻璃纤维断裂、界面脱粘等。在玻璃纤维/木纤维/HDPE混杂体系中由于组元之间的协同增强作用,形成了特殊的三维网络结构,木塑复合材料的力学性能得到显著改善。     

A simple frequency‐domain method for stress analysis of stall‐regulated wind turbines

A simple method, based in the frequency domain, was developed for calculating the dynamic response of a stall‐regulated wind turbine. Emphasis is placed on two aspects of the method, which are necessary in order to obtain a reasonable linearization of behavior when the blades are stalled. First, the tangential (in‐plane) component of turbulence is included, in addition to the axial component. Second, the linearized relationship between lift coefficient and angle‐of‐attack is adjusted to account for the effects of dynamic stall: separate linearizations are used for excitation and damping of vibration. A thorough comparison is made between linear and non‐linear dynamic‐stall methods, with the conclusion that the accuracy of the linear method depends upon the frequency and amplitude of oscillation. The linear dynamic‐stall method is accurate at blade vibrational frequencies, but it can be inaccurate at frequencies in the vicinity of 1P or below, when the angle‐of‐attack oscillates with an amplitude of 3° or more. Load spectra of a Nordtank 500 turbine, calculated using the frequency‐domain method, are compared with measurements. The frequency‐domain method provides estimates of load spectra and aerodynamic damping (stability) that are useful for preliminary design and optimization, but the method lacks sufficient accuracy and generality to be used for certification. Copyright © 2011 John Wiley & Sons, Ltd.     

Transport mode preferences,risk perception and worry in a Norwegian urban population

The main aim of the present study was to compare risk perception among Norwegians (n = 512) living in the region of Oslo. This study was part of an ERANET 13 project entitled PETRIS, Perception of transport risk in France and Norway. The data collection was carried out in January 2011. The response rate was 51 percent. The results showed that respondents, divided in two groups according to their transport mode preferences, assessed differently risk perception in public and private transportation. Respondents who preferred collective transportation assessed the probability of experiencing criminality in collective transport modes as higher than those who preferred private modes. They were also more worried of experiencing accidents, criminality, and terror attacks in collective transportation. The relationship between transport mode preferences and use, risk perception and worry are discussed.     

A study on physical and mechanical properties for soft to firm clays in Yangon area – Properties of clays deposit at the sedimentary basins in Myanmar

Recently, a great deal of foreign investment has been entered into construction of the social infrastructure of Myanmar. Many construction projects are therefore on-going, and these are especially planned in the Yangon area. While these construction booms are increasing, existing studies on the geotechnical problems in the Yangon area such as problematic soils like soft clays are limited at present. Information on soil properties has also not been shared and has been confined to individual projects. In this paper, the boring and laboratory tests carried out in the Yangon area are selected and focused upon among the tests carried out in Myanmar. Laboratory test results for clay deposits in the Yangon area are analyzed and the differences in soil properties between different sedimentary basins and sub-areas divided by the Tertiary sediment ridge that runs from north to south at the center of Yangon are clarified together with a comparison to the clays found in other countries, which have been previously investigated.     

Anodic bonding of glass to aluminium

Anodic bonding of glass to aluminium may provide a higher degree of freedom in device design. In this paper, a systematic variation of the bonding parameters for the aluminium–glass bond is presented. Hermetic seals with strengths of 18.0 MPa can be achieved using a 50–100-nm-thick bonding aluminium layer, and bonding at 300–400°C applying a voltage of 1,000–1,500 V for 20 min. With these parameters, bond yields above 95.1% were obtained on 17 wafers. The bonds survived extensive thermal ageing without significant degradation. The possibility of bonding glass to an aluminium layer with buried, electrically isolated conductors underneath is also demonstrated.     

Hydrogen thresholds as indicators of dehalorespiration in constructed treatment wetlands

Anaerobic degradation of cis-1,2-dichloroethene (cis-1,2-DCE) and 1,2-dichloroethane (1,2-DCA) was studied in microcosms derived from a laboratory-scale upflow treatment wetland system used to biodegrade chlorinated compounds present in groundwater from a Superfund site. Dechlorination kinetics of cis-1,2-DCE (0.94-1.57 d(-1)) and 1,2-DCA (0.15-0.71 d(-1)) were rapid, and degradation proceeded to completion with ethene or ethane as terminal dechlorination products. Hydrogen concentrations, measured simultaneously during dechlorination, were significantly different for the two compounds, approximately 2.5 nM for cis-1,2-DCE and 38 nM for 1,2-DCA. Methanogenesis proceeded during the degradation of 1,2-DCA when H2 concentrations were high but not during the dechlorination of cis-1,2-DCE when H2 concentrations were below published thresholds for methanogenesis. A 16S rRNA gene-based approach indicates that microorganisms closely related to Dehalococcoides ethenogenes were present and that they were distributed throughout the bottom, middle, and top of the upflow treatment wetland system. These results coupled with consideration of hydrogen thresholds, degradation kinetics, daughter products, and measurements of methanogenesis strongly suggest that halorespirers were responsible for dechlorination of cis-1,2-DCE and that 1,2-DCA dechlorination was co-metabolic, likely mediated by acetogens or methanogens. Rapid dechlorination potential was distributed throughout the wetland bed, both within and below the rhizosphere, indicating that reductive dechlorination pathways can be active in anaerobic environments located in close spatial proximity to aerobic environments and plants in treatment wetland systems.     

High accuracy peak location and amplitude spectral estimation via tuning APES method

In this paper, we introduce a new approach to the method of non-parametric adaptive spectral analysis by using the Amplitude and Phase Estimation (APES) method, and taking into account the small sample errors of the sample covariance matrix. This approach is referred to as Adaptive Tuning Amplitude and Phase Estimation method (ATAPES). The main advantage of the ATAPES algorithm is its elimination of biased estimation exists with APES method, which is a biased peak location and corresponding problem of the biased amplitude estimation. The ATAPES method provides more accurate peak location and amplitude estimation with higher resolution than APES method.