大型粮仓深层粮食扦样器设计与使用

针对传统扦样设备的弊端,研发了一款可移动、便携式粮食扦样器,并在广东省储备粮管理总公司东莞直属库进行了应用试验.结果表明,通过使用该扦样器,实现了大型粮食库仓深层粮食扦样的机械自动化,有效降低了仓储作业人员劳动强度,提高了扦样效率,达到了粮食仓储环节高装粮深度粮食样品取得到,取得轻松,取得精准的目标,为粮食储存期间质量...     

采样器与A／D转换器非同步问题的研究

本文详细地阐述了用单片机控制的巡回检测装置在通道设计时,如何解决采样 器与Ａ／Ｄ转换器的不同步的方法．从而使装置测出的显示值接近真实值,而不会引起由 于采样器与Ａ／Ｄ转换器异步时产生的测量误差．     

合采油井分层产出状况监测技术

文章介绍了一种新型的在合采油井正常生产状态下分层腔式取样及测压技术;阐述了腔式取样器的机械结构、取样工艺原理,以及通过原油烃色谱指纹分析技术利用标准模版监测周边合采油井分层产能状态的技术。     

推移质采样器模型试验与相似条件

通过MB—2、YZ—80和TR—2三种有代表性的推移质采样器模型试验,得出不同采样器口门断面中垂线流速分布规律,首次测出采样器绕流阻力系数随采样器雷诺数的变化规律,定量分析了采样器采样效率分别随模型相对边界宽度、相对淹没深度、采样器雷诺数、反映推移质运动强度的水流参数以及相对充盈度等因素变化的规律,并提出了采样器模型试验必须遵循的相似准则。     

水利水电工程地质勘察中取土器及取样方法探讨

在水利水电工程地质勘察中，原状土样采取的成功与否，决定了定量评价岩土体工程性能的准确性。本文详细分析了影响原状土样采取的五个主要因素：钻孔质量；钻探方法；取土器；取土方法；封存及搬运。     

Development of an Indoor Air Sampler for Polycyclic Aromatic Compounds

We have developed a new air sampler for collecting parriculate and gas phase polycyclic aromatic compounds (PAC). This sampler was designed to collect a 25 m³ volume of air at a constant sampling rate of 34 l/min over a 12-hour sampling penod. The 25 m³ sample volume is necessary to achieve the desired nglm³ detection limit for PAC. The 34 l/min sampling rate is estimated to cause less than a 5% reduction in the indoor contaminant concentrations. The sampler pump is a I/4 horsepower vacuum pump in an acoustically shielded fan-cooled enclosure and is relatively quiet. The pump draws air through a 47 mm teflon impregnated glass fibre filter for collection of particulate-phase PAC followed by a cartridge containing XAD-4 resin in front and back sections (2.5 g each) for collection of gas-phase PAC. In a pilot field study the mean breakthrough from the front sorbent section to the back section was less than 1% for each of 14 species of gas phase PAC except biphenyl which had a mean breakthrough of 3.7%. The pressure drop increase across the filter is linear up to a loading of 6 mg and causes less than a 10% reduction in the sample flow rate. The sampler was successfully demonstrated in a pilot field test with air temperatures as high as 30°C.     

Bayesian estimation of the Gaussian mixture GARCH model

Bayesian inference and prediction for a generalized autoregressive conditional heteroskedastic (GARCH) model where the innovations are assumed to follow a mixture of two Gaussian distributions is performed. The mixture GARCH model can capture the patterns usually exhibited by many financial time series such as volatility clustering, large kurtosis and extreme observations. A Griddy-Gibbs sampler implementation is proposed for parameter estimation and volatility prediction. Bayesian prediction of the Value at Risk is also addressed providing point estimates and predictive intervals. The method is illustrated using the Swiss Market Index.     

A 14-bit Current-Steering DAC with Current-Mode Deglitcher

A 14-bit current-steering DAC utilizing parallel current memories operating as a deglitcher is presented. The high linearity of the current memories is based on a memory MOS transistor biased in the triode region and a bootstrapped sampling switch. The prototype circuit is implemented using a 0.35-m BiCMOS (SiGe) technology and it occupies 5.7 mm² of silicon area. According to measurements, THD is –66.8 dBc with a 9.1-MHz input signal and 30-MHz clock frequency. Two-tone test gives intermodulation levels below 68 dBFS at 40-MS/s sampling rate. The power dissipation is 370 mW from a 3-V supply.     

Comparison of MCMC Methods for Estimating Stochastic Volatility Models

This article investigates performances of MCMC methods to estimate stochastic volatility models on simulated and real data. There are two efficient MCMC methods to generate latent volatilities from their full conditional distribution. One is the mixture sampler and the other is the multi-move sampler. There is another efficient method for latent volatilities and all parameters called the integration sampler, which is based on the mixture sampler. This article proposes an alternative method based on the multi-move sampler and finds evidence that it is the best method among them.JEL classification C22     

A case study of personal exposure to nitrogen dioxide using a new high sensitive diffusive sampler

Personal NO(2) exposure measurements were achieved during two campaigns in a large northern France city. These campaigns were following an innovating approach based on sequential exposure measurements by diffusive samplers distinguishing four categories of microenvironments ("home", "other indoor places", "transport" and "outdoors"). The objective of these campaigns was to obtain NO(2) personal exposure data in different microenvironments and to examine the determinants of personal exposure to this pollutant. Each campaign comprised two 24-h sampling periods: one during a working day and the second during the weekend. The average total NO(2) personal exposure ranged from 17 microg m(-3) for the summer weekend samplings to 38 microg m(-3) for the winter weekday samplings. The highest levels were found in transports and outdoors, the intermediate ones in other indoor places and the lowest in homes. Despite their weak levels, indoor environments contributed for more than 78% to total NO(2) personal exposure because of more time spent in these living places. A Multiple Correspondence Analysis (MCA) highlighted the determinants of NO(2) personal exposure in the "home" and "transport" microenvironments. This led to a classification of NO(2) personal exposure levels according to different means of transport: from the lowest to the highest exposure levels, train, tramway or underground, bicycle, car or motorcycle. In homes, the rise of NO(2) personal exposures is mainly due to the use of gas stoves and gas heating and the absence of automatic airing system. A classification of NO(2) personal exposure levels was set up according to the characteristics of homes. An analysis of correlations between the home NO(2) personal exposures and outdoor concentrations measured by fixed ambient air monitoring stations showed weak relations suggesting that the data of these stations are poor predictors of NO(2) personal exposures in homes.