关于推进黄河立法工作的思考

经过长期的积累和探索,黄河的立法时机趋向成熟。通过对黄河立法必要性和可行性的分析,论证了黄河流域立法工作的必要和紧迫。同时,论述了黄河立法过程中应遵循的基本原则,并在此基础上对应建立的法律制度提出建议,为解决黄河治理、开发、保护和管理中存在的问题提供思路。     

强化企业内部管理 提高质量体系认证的有效性

产品质量的提高在于对企业内部质量体系的有效运行、审核和管理评审。企业为了满足顾客对产品不断增长、变化的需要,就必须不断完善质量运行体系,不断提高产品及服务质量。     

在ISO 9002质量管理体系中对采购分供方的选择与管理

介绍中海石油平台制造公司采用ISO9002质量体系对采购分供方进行选择与管理。     

大庆油田勘探测井数据的管理与应用

为了加强对大庆油田勘探测井资料的管理,提出了以Finder、LogDB数据库为核心管理软件,实现勘探测井数据全数字化管理的管理模式.依托现代计算机技术、网络技术,建立了测井数据银行.     

Laser perforated fuel cell diffusion media. Part I: Related changes in performance and water content

In this study, cathode-side, bi-layered diffusion media (DM) samples with micro-porous layer were perforated with 300 μm laser-cut holes (covering 15% of the surface area in a homogenous pattern) using a ytterbium fiber laser to investigate the effect of structural changes on the gas and water transport. Under reduced humidity conditions (50% inlet relative humidity on the anode and cathode), the perforated DM were observed to increase the potential by an average of 6% for current densities ranging from 0.2 to 1.4 A cm⁻². However, the perforated DM showed reduced performance for current densities greater than 1.4 A cm⁻² and at all currents under high-humidity conditions. Neutron radiography experiments were also performed to understand the changes in liquid water retention characteristics of DM due to the laser perforations. Significant water accumulation and water redistribution were observed in the perforated DM, which helps explain the observed performance behavior. The results indicate that the perforations act as water pooling and possible channeling locations, which significantly alter the water condensation, storage, and transport scheme within the fuel cell. These observations suggest that proper tailoring of fuel cell DM possesses significant potential to enable fuel cell operations with reduce liquid overhead and high performance.     

Bi-modal water transport behavior across a simple Nafion membrane

The development of predictive mathematical models for water management in polymer electrolyte membrane fuel cells requires detailed understanding of water distribution and water transport across the Nafion layer. The anisotropic microstructure of Nafion suggests the measurement of water content and mass transport should be along the fuel cell functional direction, i.e. across the membrane. Non-invasive, high resolution, microscopy measurements of this type are very challenging.We report here the calibration of a minimal mathematical model for diffusive water transport in Nafion against data from high-resolution water content maps determined with a new magnetic resonance imaging methodology developed for this purpose. A mock fuel cell was designed to permit well-controlled wetting and drying boundary conditions. With no chemical potential driving force involved, we assume the water transport behavior will be dominated by diffusion. Moreover we show that, in this context, our model is mathematically equivalent to the traditional permeation models based upon saturation dependent pressure gradients via a capillary pressure ansatz.The non-linear equilibrium water distribution across the Nafion membrane measured in this work suggests a bi-modal diffusivity. The model constructed associates distinct transport behaviors to water contents above and below a critical threshold, consistent with a rearrangement of a micro-structural pore network. The experimental observation and the model prediction agree with the primary features of Weber's model of Nafion, which predicts distinct modes of transport for hydration fronts traversing the through-plane direction of the membrane.     

An index-based risk assessment model for hydrogen infrastructure

This study focuses on the development of a risk assessment model associated with the safety of a hydrogen infrastructure system. The safety of hydrogen infrastructure is one of the crucial pre-requisites for a sustainable economy and accordingly, its design should be made based upon the performance to investigate and evaluate the risks from or out of the required infrastructure. In order to support strategic decision-making for safe hydrogen infrastructure, this study proposes an appropriate index-based risk assessment model. The model evaluates the hydrogen infrastructure using the relative risk ranking of the hydrogen activities such as hydrogen production, storage and transportation, and the relative impact levels of regions. The relative risk rankings of the hydrogen activities are rated a quantitative risk analysis, whereas the relative impact level of regions is rated based on the regional characteristics such as population density. With consideration of regional characteristics, the proposed model makes it possible not only to assess the risks of processes and technologies associated with hydrogen but also to compare the relative safety levels of the hydrogen infrastructures made up with various hydrogen activities. In order to show the features and capabilities of the model, four future hydrogen infrastructure scenarios in Korea are examined in the study. The result shows that distributed production, and mass storage and transportation via liquefied hydrogen facility are relatively safer than centralized production, and compressed-gaseous hydrogen storage and transportation, respectively.     

Comparison of biomass feedstock supply and demand in Northeast Italy

This study uses Geographical Information Systems (GIS) to estimate woody biomass supply and demand in Northeast Italy. Demand is estimated using census data on boilers and supply calculations are derived from data on timber harvests and mill operations. The analysis is done with GIS using Large Scale Analysis at a broader resolution (for the entire region) and Small Scale Analysis at a finer resolution (for the Primiero valley only), with added information on tree species, road networks and logging systems. From large scale analysis demand results to be about 163 000 MWh, corresponding to about 71 000 tonnes per year of fuel, with a moisture content of 50 percent. As shown by results from a small scale analysis, the Primiero valley has a deficit of 21 400 MWh. A more thorough analysis shows that 93 percent of logging operations can be performed with cable cranes and that high quality chips derived from forest biomass amount to only 335 MWh of energy (20 percent of the total). The deficit calculated at a small scale confirms the value obtained in the large scale calculation.Analysis of the demand-supply balance will be helpful for decision makers and politicians and should be taken into account when allocating subsidies for new boilers or district heating.     

Assessment of potential bioenergy from coppice forests trough the integration of remote sensing and field surveys

A spatially explicit knowledge of forest resources is essential to support the sustainable use of wood as a fuel for producing energy (firewood).This paper describes the integrated use of remotely sensed data and sample based forest inventories to derive a biomass map for coppice forest, resulted estimated potential biomass available is contrasted with local domestic consumptions at the municipality level. The test was carried out in an environmentally and socially homogeneous district of Apennine Mountains (Alto Molise, south-central Italy) coupling multispectral high resolution Landsat 7 ETM+ satellite imagery and a local forest inventory trough the application of the non-parametric estimation procedure k-Nearest Neighbours (k-NN). Several forest management scenarios were applied in order to evaluate their impact on the potential availability of firewood from coppice forests.The paper introduces data and methods used and presents the achieved results both in terms of the accuracy of the biomass map produced by k-NN and of the relationship between the potential availability and demand for firewood.These results demonstrated that k-NN is able to estimate the biomass of coppice forest in the test area with an accuracy level comparable with recent similar application of k-NN carried out in Boreal regions (RMSE of 25.6%).The application of different forest management scenarios have a significant impact on local estimated firewood balance between potential supply from coppice forests and demand for domestic consumption, depending of the scenarios the net balance changed up to 84%.     

Firewood yield and profitability of a traditional Daniellia oliveri short-rotation coppice on fallow lands in Benin

Sub-Saharan Africa has a great diversity of local coppicing species which are exploited in traditional short coppice systems for firewood. Biomass yield and profitability of these systems as well as their responses to silvicultural improvement are little known. This study evaluated the firewood yield and the profitability of a traditional Daniellia oliveri short-rotation coppice on fallow lands in central Benin. Two weed management options were considered: (1) the weedy option, usually practiced by locals, which experienced grass competition and bushfires, and (2) the weed-free option, which consisted in periodic removal of grasses and other species. Destructive measurements and allometric equations were used to estimate biomass yield in 12 plots over 42 months. A cost-benefit analysis model based on the net present value and the benefit-cost ratio was used to compare the profitability of the two management options. Biomass accumulation rate averaged 1.08 ± 0.20 tonnes of dry matter ha⁻¹ year⁻¹ (t DM ha⁻¹ year⁻¹) in weedy conditions. Weed removal improved 3.5 times this rate in weed-free plots (3.83 ± 0.47 t DM ha⁻¹ year⁻¹). After 42 months, total biomass reached 3.67 ± 0.65 t DM ha⁻¹ in weedy plots and 11.63 ± 0.76 t DM ha⁻¹ in weed-free plots. Most of the biomass (≥88%) was marketable in local markets. Coppice exploitation was profitable after 24 months for both management options. Weed removal improved the profits three times. A sensitivity analysis showed that both options were still profitable with up to 25% increase of labour and transport costs, 25% decrease of biomass price and 12% increase of the discount rate.