公私合营(PPP)项目市场需求风险分担研究

对PPP项目市场需求风险的影响因素、分担偏好、参与者的管理能力等问题进行探讨,以实例提出PPP项目市场需求风险完全由政府承担、政府与私人投资者共同承担及私人投资者承担的三种模式。在此基础上提出风险分担中政府所应承担的责任,以及市场分担与项目竞争强度的关系等观点,以期为政府后续PPP项目市场需求风险的管理提供参考和借鉴。     

Cobalt powdersintering industry (stone cutting diamond wheels): a study of environmental-biological monitoring, workplace improvement and health surveillance

This communication deals with an aspect of occupational hygiene in a factory producing granite cutting diamond wheels by sintering, in moulds, of fine cobalt powder. The factory has been studied between 1988 and 1991; the Department of Preventive and Occupational Medicine of the Local Sanitary Unit of Reggio Emilia has followed the evolution of the local exhaust ventilation equipment supplied by the employer in that period. At the same time, the following measurements and observations were carried out: (a) cobalt exposure by personal sampling, (b) airborne cobalt measurements by area sampling, (c) biological monitoring of cobalt in urine, (d) health surveillance.     

Human response to blast-induced vibration and air-overpressure: an Indian scenario

Ground vibration (V_max) and air-overpressure/noise (p) are some of the negative effects of blasting. The associated human annoyance and complaints are expected to show an increasing trend in the future as there is no economically viable alternative to blasting in mines in India.A study of the human response to blasting in four mining localities across India has shown that the response is not simply political, as frequently assumed. It has been found that irrespective of those questioned, a basic concern for the safety of property was the main response. There was a greater response from the middle-aged and middle-educated while fewer women than men responded. Assuming that a 100% negative response from the inhabitants will translate into complaints, a methodology is suggested to take account of the human response criteria when considering blasting within 400 m of habitations.     

Spatial patterns of cadmium and lead deposition on and adjacent to National Park Service lands in the vicinity of Red Dog Mine, Alaska

Heavy metal escapement associated with ore trucks is known to occur along the DeLong Mountain Regional Transportation System (DMTS) haul road corridor in Cape Krusenstern National Monument, northwest Alaska. Heavy metal concentrations in Hylocomium splendens moss (n = 226) were used in geostatistical models to predict the extent and pattern of atmospheric deposition of Cd and Pb on Monument lands. A stratified grid-based sample design was used with more intensive sampling near mine-related activity areas. Spatial predictions were used to produce maps of concentration patterns, and to estimate the total area in 10 moss concentration categories. Heavy metal levels in moss were highest immediately adjacent to the DMTS haul road (Cd > 24 mg/kg dw; Pb > 900 mg/kg dw). Spatial regression analyses indicated that heavy metal deposition decreased with the log of distance from the DMTS haul road and the DMTS port site. Analysis of subsurface soil suggested that observed patterns of heavy metal deposition reflected in moss were not attributable to subsurface lithology at the sample points. Further, moss Pb concentrations throughout the northern half of the study area were high relative to concentrations previously reported from other Arctic Alaska sites. Collectively, these findings indicate the presence of mine-related heavy metal deposition throughout the northern portion of Cape Krusenstern National Monument. Geospatial analyses suggest that the Pb depositional area extends 25 km north of the haul road to the Kisimilot/Iyikrok hills, and possibly beyond. More study is needed to determine whether higher moss heavy metal concentrations in the northernmost portion of the study area reflect deposition from mining-related activities, weathering from mineralized Pb/Zn outcrops in the broader region, or a combination of the two. South of the DMTS haul road, airborne deposition appears to be constrained by the Tahinichok Mountains. Heavy metal levels continue to diminish south of the mountains, reaching a minimum in the southernmost portion of the study area near the Igichuk Hills (45 km from the haul road). The influence of the mine site was not studied.     

Bioaccumulation potential of polycyclic aromatic hydrocarbons in Daphnia pulex

The bioaccumulation potentials by aquatic biota from aqueous solution were determined for seven polycyclic aromatic hydrocarbons (PAH). The PAH were tested usingDaphnia pulex and consisted of the following compounds: naphthalene, anthracene, phenanthrene, pyrene, 9-methylanthracene, benz(a)anthracene and perylene. Bioaccumulation kinetics were described as a first order approach to equilibrium in a two-compartment model (water and Daphnia), using a two-stage technique to estimate uptake and elimination rates, while accounting for decreasing aqueous concentrations. Estimates of equilibrium concentration factors were obtained by two methods: (1) evaluating the kinetic model as t tends to infinity and (2) direct measurement of concentration factor at t =24 h.Estimations of equilibrium concentration factors obtained by the two methods were in good agreement, and increased dramatically with increasing molecular weight within the series of compounds. The calculated n-octanol-water partition coefficient was shown to be a good predictor of bioaccumulation potential of PAH in Daphnia. PAH were concentrated from a high of about 10,000-fold for benz(a)anthracene to a low of about 100-fold for naphthalene.     

Characteristics and stabilities of residues from the Wheal Jane constructed wetlands

The characteristics and solubilities of residues formed during effluent treatment at the Wheal Jane constructed wetland facility in Cornwall, UK are described. The constructed wetland treats an acidic (pH 3 to 4) mine discharge enriched in iron (<100 mg/l), zinc (<80 mg/l), manganese (<20 mg/l) and arsenic (<2 mg/l). The processing strategy adopted at the site is to remove elements selectively from the mine water in distinct unit process operations and concentrate the iron and base metals into residues within the circuits. Solubility tests conducted on the materials from the aerobic and anaerobic cells attempt to simulate future possible leaching processes within landfill sites used for ultimate disposal. The tests used in the evaluation included TCLP, MARG, washing and column leaching. The aerobic solids overall have very low solubilities which are well below the TCLP thresholds for As, Cd and Pb. The TCLP results for these toxic elements are supported by the washing and column test work. The anaerobic substrates are carbonaceous in nature, composed of straw, wood pulp and manure. They contain minimal amounts of toxic compounds and are considered to be less of a disposal problem. Ochre precipitated at a pH of 3-4 in the aerobic cells contains significant concentrations of arsenic (>0.1%). This element is carcinogenic, and such residues are classified as hazardous waste under current UK landfill regulations. This classification does not take into consideration the solubility of the material but is based solely on the bulk chemical composition.     

A Power-Supply Unit for Pulsed Lasers without a Storage Capacitor

A power-supply unit for pulsed lasers that are pumped by low- and medium-power flashlamps with long pump pulses that does not require a capacitive storage unit is described. The pump-pulse duration is limited by the radiation and thermal stability of the active elements and pump lamps. A functional diagram of the power-supply unit and a circuit diagram of its power system are presented. The basic parameters and elements of this unit, as well as the results of using a laser with the described power supply in experiments, are presented.     

3D Monte Carlo simulation of grain growth in friction stir welding

Journal of Mechanical Science and Technology - The 3D fluid model was used to simulate the friction stir welding process. Three-dimensional Monte Carlo model with nucleation in each MC step was...     

Fabrication and characterization of poly(methyl methacrylate)/CaCu3Ti4O12 composites

Composites comprising Poly(Methyl Methacrylate) (PMMA) and CaCu₃Ti₄O₁₂ (CCTO) via melt mixing followed by hot pressing were fabricated. These were characterized using X‐ray diffraction, thermo gravimetric, scanning electron microscopy, and Impedance analyzer for their structural, morphology, and dielectric properties. Composites were found to have better thermal stability than that of pure PMMA. The composite, with 38 Vol % of CCTO (in PMMA), exhibited remarkably low dielectric loss at high frequencies and the low frequency relaxation is attributed to the space charge polarization/MWS effect. Theoretical models were employed to rationalize the dielectric behavior of these composites. At higher temperatures, the relaxation peak shifts to higher frequencies, due to the merging of both β and α relaxations into a single dielectric dispersion peak. The AC conductivity in the high frequency region was attributed to the electronic polarization. POLYM. ENG. SCI., 54:551–558, 2014. © 2013 Society of Plastics Engineers