共查询到19条相似文献,搜索用时 390 毫秒
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本文阐明了在产品设计定型阶段和小批量生产过程中对印制板电路组件进行筛选的必要性,并提出了进行印制板电路组件筛选需要注意的问题。 相似文献
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为了能够提高电力系统运行过程中的可靠性,基于振动信号研究了电力系统变压器中出现的机械故障诊断方法.分析了BIM定位不同测点下的振动信号,利用时域频谱图对比分析了相同相、不同位置和不同相、相同位置的振动信号基频幅值.提出了基于小波包变换的振动信号故障特征提取方法,将信号特征转化为数值特征,为变压器机械故障的智能诊断提供了... 相似文献
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印制板蚀刻液再生及铜回收技术与设备 总被引:2,自引:0,他引:2
《中国环保产业》2008,(3):63-64
由深圳市拓鑫环保设备有限公司开发的印制板蚀刻液再生及铜回收技术与设备,适用于印制板三废的治理。主要技术内容 一、基本原理利用含重金属溶液的选择性分离技术,对含铜废水中的铜进行选择性分离,使蚀刻废液得以再生循环利用的同时,获得高纯度的金属铜板。针对线路板生产蚀刻过程的特点,高效利用蚀刻废液中残留的有用成分,去除废液中影响蚀刻效果的成分,形成了分离铜、蚀刻液再生、电解铜、蚀刻液循环利用的技术方案,使因铜离子浓度过高而失去蚀刻功能的废液得以再生,同时获得高纯度铜板。对低含铜废水则是把其中的铜选择性分离,电解制成铜板,从而达到减少污染、回收资源的目的。 相似文献
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战术导弹电子设备热设计研究 总被引:3,自引:0,他引:3
由于战术导弹高可靠性的要求,可靠性设计中的热设计问题越来越引起人们的重视。导弹电子设备,安装空间有限,安装密度高,加上密封要求,所以要求进行精心的热设计。本文根据工程实践的再认识,介绍了弹上电子设备的元器件、印制板和机箱等热设计的方法。 相似文献
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计算机键盘有用信号电磁截获的传统方法是基于宽带接收机完成的,这种方法较复杂且需要较多的设备和空间。为使键盘截获技术向小型化和实用化过渡,提出了使用基于软件无线电的解码技术及基于存储示波器全频谱远场截获。首先,基于频谱对比的方法对有用信号的频段进行初判,然后对截获的全频域信号中包含有敏感信息的频段基于软件无线电的方法进行带通滤波和解调。最后,使用一种能够精确判别按键信息的解码方法,通过预先设计的程序来实现信息的截获。实验结果表明计算机键盘有用信号电磁截获实现实用化和小型化是有一定可行性的,并且能够得到比较精确的结果。 相似文献
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《资源开发与市场》2016,(6)
为了满足水下传感器节点远距离声通信的需求,解决节点发射功率自适应调节和信号在功率放大过程中频谱再生的问题,设计了一种适用于水声通信的程控线性功率放大设备,包括微控处理器和依次连接的一级控制模块、电压放大模块、二级控制模块、功率放大模块和阻抗匹配模块。通过数字开关与电阻组成数字电阻以分压方式对电压放大和功率放大模块的输入信号进行控制,进而控制输出功率;采用线性功率放大器集成芯片进行功率放大,保证信号的无失真传输;通过阻抗匹配变压器,驱动水声换能器工作,以获得最佳的输出功率。实验结果表明,本功放对16-18k Hz频段0—1VPP的交流信号可以进行无失真放大,并且输出功率、程控功能等均能满足系统设计要求。 相似文献
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Gabi N. Waite Stéphane J. P. Egot-Lemaire Walter X. Balcavage 《The Environmentalist》2011,31(2):107-113
Over the past decades, strong evidence has accumulated that low-frequency electromagnetic fields (EMFs) can be useful in treating
human pathologies, such as bone fractures, soft tissue illnesses, and pain. Common strategies for the design of commercial
therapeutic devices are to generate EMFs that simulate body endogenous EMFs, or EMFs that resonate with a particular biological
process, such as the natural motions of ions. We recently came across a biologically active commercial EMF signal that seems
to be different. The signal is generated by summing the fundamental frequencies and harmonics of several periodic base signals
which remain proprietary to the company. When first examined in the time domain, the signal resembled electronic noise; however,
when critically analyzed, the signal is not identical with noise. Rather, it is a highly complex waveform exhibiting a very
wide range of values for the time derivative of the magnetic field density (dB/dt) and a beat frequency in the Extremely Low-Frequency
range. In this paper, we speculate on the mechanism of action of this and similar signals. We consider it less likely that
cells, or cell components, act like filters to extract and couple with individual signals that make up the complex EMF signal.
Consequently, we favor the possibility that with the signal discussed here cells respond to the very complex signal and that
the biological response can be modified by the presence of a beat in the signal, in this case a low-frequency beat. More generally,
this would suggest the hypothesis that biological processes can be regulated by noise-like signals and that the effects of
a noisy signal can be modified by the presence of signal repetition patterns, such as beats. Given the very small energy that
signals like these can transduce into a biological system, biological effects can be expected only when the molecular processes
involved are poised so that the available energy leads to molecular reactions that achieve the activation state for the reaction. 相似文献
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Ramazan Caner Sayan 《Local Environment》2017,22(12):1510-1525
Environmental justice frameworks predominantly focus on exploration of socio-environmental inequalities faced by racial, ethnic, religious, cultural and low-income groups. This article aims to expand this mainstream focus of the environmental justice concept on these groups by conceptualising urban/rural division as a group difference, based on which rural communities face with socio-environmental burdens of environmental policies in relation to their urban counterparts. It is based on the analysis of Turkey’s small-scale hydroelectricity power plant (HPP) development policies, referring to the planning and constructions of approximately 1500 hydropower plants across the country, along with country’s modernist agenda, i.e. achievement of economic development, social progress and urban transformation of Turkey. These power plants are also strongly associated with numerous socio-economic, environmental and cultural impacts on local rural communities and local environments with dozens of local opposition movements, while favouring needs, interests and lifestyles of urban communities. This point deserves a systematic conceptualisation within the environmental justice frameworks as it helps to further explain deep causes of socio-environmental inequalities particularly in developing country contexts. Thus, this article is built on such a conceptualisation arguing the necessity to integrate urban/rural division as a separate group difference to environmental justice frameworks by examining modernisation and urbanisation nexus in Turkey’s small-scale HPP development process. 相似文献
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Eleni Nanou Vassilis Tsiafakis E. Kapareliotis Charalabos Papageorgiou Andreas Rabavilas Christos Capsalis 《The Environmentalist》2005,25(2-4):173-179
Summary The effects of electromagnetic fields (EMF) emitted by cellular phones on human electroencephalogram (EEG) were studied during
an auditory memory task. The experimental method and the experimental setup are introduced as a credible measurement method
of EEG. 19 normal subjects (10 women and 9 men) performed the memory task both with and without exposure to a 900 MHz signal,
emitted by a dipole antenna placed near the subjects' head. The energy of the EEG signals was calculated at the time domain.
A Fourier transform of the EEG signals was done and the EEG energy was also calculated at the frequency domain. As the Parseval's
theorem anticipates the energies were identical. The EEG energy was found concentrated at the four basic bands (α (8–13 Hz),
β(14–30 Hz), δ (0–4 Hz) and θ(5–7 Hz)). The primary concern of the present study was the gender related influence of EMF on
the spectral energy of EEG. The results show evidence of a strong gender—radiation interaction effect on the EEG energy and
on the peak amplitudes within each of the four rhythms. Without radiation the spectral power of males is greater than of females,
while under exposure the situation is reversed. Under the influence of EMF the spectral power of the males EEG is decreased
while that of the females is increased. In conclusion both the baseline EEG and the changes effected to the EEG power spectrum
under the influence of EMF seem to be gender dependent. 相似文献
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Optimizing phosphorus characterization in animal manures by solution phosphorus-31 nuclear magnetic resonance spectroscopy 总被引:1,自引:0,他引:1
Turner BL 《Journal of environmental quality》2004,33(2):757-766
A procedure involving alkaline extraction and solution 31P nuclear magnetic resonance (NMR) spectroscopy was developed and optimized for the characterization of P in animal manures (broiler, swine, beef cattle). Inclusion of ethylenediaminetetraacetic acid (EDTA) in the alkaline extraction solution recovered between 82 and 97% of the total P from the three manures, which represented a significant improvement on recovery in NaOH alone. Low concentrations of paramagnetic ions in all manure extracts meant that relatively long delay times (> 5 s) were required for quantitative analysis by solution 31P NMR spectroscopy. The manures contained inorganic orthophosphate, orthophosphate monoesters, orthophosphate diesters, and inorganic polyphosphates, but results were markedly influenced by the concentration of NaOH in the extractant, which affected both spectral resolution and the apparent P composition of the extracts. For example, extraction of swine manure and broiler litter with 0.5 M NaOH + 50 mM EDTA produced remarkable spectral resolution that allowed accurate quantification of the four signals from phytic acid, the major organic P compound in these manures. In contrast, more dilute NaOH concentrations produced considerable line broadening that obscured individual signals in the orthophosphate monoester region of the spectra. Spectral resolution of cattle manure extracts was relatively unaffected by NaOH concentration. Improvements in spectral resolution of more concentrated NaOH extracts were, however, compromised by the disappearance of phospholipids and inorganic polyphosphates, notably in swine and cattle manure extracts, which indicated either degradation or a change in solubility. The optimum extraction conditions will therefore vary depending on the manure type and the objectives of the study. Phytic acid can be accurately quantified in swine manure and broiler litter by extraction with 0.5 M NaOH + 50 mM EDTA, while a more dilute NaOH concentration should be used for complete P characterization or comparison among different manure types. 相似文献
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Clement Loo 《Journal of Agricultural and Environmental Ethics》2014,27(5):787-809
This paper argues that the definition of food justice must be defined in more participatory terms. Current accounts of food justice tend to emphasize distributional inequalities. However, there is broad recognition that these distributional inequalities are the result of participative inequalities and that the participation of marginalized groups in advocacy plays an important role in creating just food systems. In addition, thinking of food justice in more participative terms also suggests a more well-rounded and comprehensive approach to dealing with inequalities within the food system. One manner in which the concept of food justice can be redefined to better capture the importance of participative justice is by considering what is required for informed consent. 相似文献
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Community participation, ownership and cost sharing are key components of Tanzania's water policy, in common with the broad international consensus on water governance. However these policy goals are difficult to achieve, beset with paradoxes and their benefits may be overstated, both in terms of efficiency of resource management and equality of outcomes. This article draws on longitudinal ethnographic research of a village water supply in Tanzania to explore two issues: the contested nature of community ownership and the complex evolution of a ‘community‐owned’ institution. The evidence from the Uchira Water Users Association leads us to question some of the simplistic assumptions made concerning the capacity of local communities to manage service delivery and to balance equity and sustainability principles. The limitations of ‘bottom‐up’ and demand led approaches need to be recognised without discrediting their potential for challenging inequalities. The article concludes with a consideration of some of the tensions in community‐driven development, which raises some important questions about the role of the State and external agencies in setting and enforcing equity criteria in community‐managed initiatives. 相似文献
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Gordon Mcgranahan Joseph Leitman Charles Surjadi 《Journal of Environmental Planning and Management》1998,41(4):505-518
Understanding neighbourhood conditions can play an important role in urban environmental management, especially when environmental services are lacking and new approachesare being debated. This paper describes and evaluates three research methods for assessing some of the environmentalproblems facing low income households and communities: (1) broad spectrum household surveys; (2) participatory rapid assessment; and (3) contingent valuation. As part of the study upon which this paper is based, the techniques were applied on a small scale in Jakarta. The paper finds that each technique can provide important and often complementaryinsights. The broad spectrum survey is particularly suitable to broad based planning, participatory appraisal to NGO initiatives and contingent valuation to utility pricing decisions. 相似文献