A brief history of mobile communication in Europe

Since the introduction of mobile telephony in the early 1950s in Europe, US and Japan the demand for this service exploded. It seems that the latent demand for mobile telecommunication services for decade’s continued to be very strong. After the introduction of cellular technology the capacity of the services became able to meet the massive demand. Next and future generations of mobile telecommunication technologies bring increased transmission speed and more versatile services. This forces network operators to organise multi sourced information flows supplied by service providers to increase the network effect of the system instead of providing the network infrastructure and leave the content to the users as in pure voice telephony. The drivers and inhibitors behind the emergence and recent developments of mobile telecommunications systems in Europe, are highlighted in this paper. Liberalisation of the telecom markets in Europe drove new entrants to the market and curbed excessive pricing. However, in recent years the lack of challenging service is the main cause for the wavering development of newer generations of mobile telecommunication services.     

Hydrocracking Marlim vacuum residue with natural limonite. Part 2: experimental cracking in a slurry-type continuous reactor

Disposable Australian iron-slurry (AL) and NiO-MoO₃-Al₂O₃ (NiMo) catalysts were used in hydrocracking experiments to convert Marlim vacuum residue (ML-VR) in a slurry-bed continuous flow reactor at temperatures of 440-460 °C, under a hydrogen pressure of 14.7 MPa and an LHSV of 0.5. The degree of conversion ranged from 54 to 83%, depending on the reaction temperature and catalyst used, with AL giving more complete conversion than NiMo. AL also proved more active in the removal of nickel. Hydrogen consumption was linearly correlated with conversion regardless of the catalyst used.     

Long-term experience with an automatic process control for nitrogen removal in membrane bioreactors

The alternating processes applied in membrane bioreactors for municipal wastewater treatment may be an attractive option to reduce the energy consumptions and optimize carbon and nitrogen removal. However, the knowledge of these systems is often based on empirical results so to discourage the plant operators for its adoption. This paper discusses and compares the empirical evidence coming from two different alternating membrane bioreactors, a demonstration and a full-scale one. The two plants treat two real municipal wastewaters, rather different for both C:N ratio and degree of biodegradability of the influent organics. Nine steady-state runs have been carried out in the demonstration plant, while a one whole year operation has been considered for the full-scale system. Combining the results of the two MBRs, it was found that the alternating process was able to adjust automatically and adequately the aeration of the biological reactor with a nitrogen loading rate in the range 0.05–0.18 kgN m⁻³ d⁻¹ and C:N mass ratios greater than 5–6. As a result, the use of the available carbon source, with concern to the total nitrogen removal, was as low as 0.1 kg of total nitrogen removed per kg of total influent COD. Effluent total nitrogen met the standard for reuse with specific energy consumptions in the range 85–109 gTN_removed per kWh_consumed. Considering the usual loading conditions of the municipal wastewater treatment plants in Italy, membrane bioreactors operating alternating processes may be implemented to increase the nitrogen treatment capacity of existing plants and achieve the standards for reuse.     

Upgrading and dewatering of raw tropical peat by hydrothermal treatment

In this study, hydrothermal upgrading and dewatering of raw tropical peat derived from Pontianak, West Kalimantan-Indonesia was evaluated at temperatures ranging from 150 to 380 °C, a maximum final pressure of 25.1 MPa and a residence time of 30 min. The moisture content of the raw peat was approximately 90 wt.%. Raw peat was hydrothermally upgraded without the addition of water in the laboratory scale. The yield of the solid products was between 53.0 and 99.7 wt.% and the effective calorific value of hydrothermally dewatered peat was between 17,290 and 29,209 kJ/kg following hydrothermal upgrading. In addition, the oxygen content in the solid product was varied from 38.4 to 15.6 wt.% after upgrading, while the carbon content from 55.2 to 77.8 wt.%. The hydrothermally upgraded peat fuel product also had an equilibrium moisture content of 2.3 wt.% and a maximum equilibrium moisture content of 17.6 wt.%. Upgraded peat is characteristically resistant to moisture adsorption at high humidity, which makes it promising for fuel based combustion. The change in the carbon-functional groups and their properties, as determined by FTIR and ¹³C NMR, are discussed in terms of the hydrothermal upgrading and dewatering process.     

PLC和电液换向阀在机械调速器改造中的应用

本文通过CT-40改造,拆除接力器以上所有机械控制柜部分,保留调速器基础及油压装置,采用以PLC为控制核心和数字式电液换向阀的微机调速系统,每台节约技改经费5万左右。     

基于STi7162的高清机顶盒设计

设计了一种基于STi7162芯片的低成本高清机顶盒,介绍了机顶盒的基本硬件组成、存储子系统和外围接口设计,对机顶盒软件系统架构也进行了简单说明。对设计的基于双Loader的机顶盒软件升级方案进行了重点介绍,详细介绍了升级方案的组成、Flash分区设计、升级条件检测和数据更新过程。实际测试结果表明,所设计的升级方案稳定可靠,可满足复杂的用户升级环境需求。     

Performance improvement of absorption heat transformer

In this study, a mathematical model of absorption heat transformer (AHT) operating with the aqua/ammonia was developed to simulate the performance of these systems coupled to a solar pond in order to increase the temperature of the useful heat produced by solar ponds and used a special ejector located at the absorber inlet. By the use of the ejector, the obtained absorber pressure becomes higher than the evaporator pressure and thus the system works with triple-pressure-level. The ejector has two functions: (i) aids pressure recovery from the evaporator and (ii) upgrades the mixing process and the pre-absorption by the weak solution of the ammonia coming from the evaporator. The other advantage of the system with ejector is increased absorber temperature. Therefore, pressure recovery and pre-absorption in the ejector improves the efficiency of the AHT. Under the same circumstances, when compared to an AHT with and without an ejector, the system's COP and exergetic coefficient of performance (ECOP) were improved by 14% and 30%, respectively and the circulation ratio (f) was reduced by 57% at the maximum efficiency condition. Due to the reduced circulation ratio, the system dimensions can be reduced; consequently, this decreases overall cost. The maximum upgrading of the solar pond's temperature by the AHT was obtained at 57.5 °C and gross temperature lift at 97.5 °C with coefficients of performance of about 0.5. The maximum temperature of the useful heat produced by the AHT was 150 °C. In addition, exergy losses for each component in the system were calculated at different working temperatures and the results of both systems with and without an ejector were compared. Exergy analysis emphasised that both the losses and irreversibilities have an impact on the system performance and exergy analysis can be used to identify the less efficient components of the system. Exergy analyses also showed that the exergy loss of the absorber of AHT with ejector was higher than those of other components.     

褐煤干选、干燥、成型一体化工艺技术开发研究

阐述了褐煤的特点、储量及利用中存在的问题,分析了发展褐煤提质加工技术对国家节能减排、发展低碳经济具有十分重要的意义;针对国内外现有的褐煤提质加工技术发展状况及存在的问题,提出了褐煤干选、干燥、成型一体化提质工艺技术,并阐述了该工艺技术流程、主要研究内容及其具有的其他工艺无法比拟的一些优点;文章还对原褐煤处理能力为50 t/h的提质系统进行了提质工艺参数计算和工艺设备投资估算,并论述了该工艺技术广阔的市场发展空间。     

等应力束技术的设计与施工

文章首先介绍了等应力束技术的工程背景及特点;然后结合东洋河大桥升级加固工程,介绍了等应力束技术设计中的关键技术如总体张拉工艺、纵向张拉设备、纵向张拉端、横向张拉设备及装置、预应力钢束的起弯点和落弯点处的构造等;介绍了应力束技术施工及施工过程中出现的问题和应对措施,如精确控制钢束张拉应力,单点张拉和双点张拉的差别,首孔横张顺序对预应力效果的影响等。