Seismic evaluation and analysis of high-voltage substation disconnect switches

Disconnect switches are one of the components of an electrical substation that are vulnerable to the effects of earthquake shaking. Three vertical-break and two horizontal-break 230 kV switches of porcelain and composite construction were tested on a triaxial earthquake simulator in various configurations. Three-pole switches were mounted on a stiff, low-profile frame and tested according to the industry standard IEEE-693-1997. The vulnerable components of the switches were the aluminum spacers at the base of the switch posts and the welded post-blade connections and the bolted connections at the base of the posts. Single-degree-of-freedom models of the switch insulator posts were developed using experimental data to establish the amplification of seismic demand on the switches when mounted on frames of different heights and stiffness.     

Diel and lateral patterns of zooplankton distribution in the St. Lawrence River

While the four‐dimensional nature of river ecosystems has been recognized for nearly two decades, the role of lateral complexity has rarely been factored into studies of zooplankton ecology. We examined the importance of hydrologic retention areas (slackwaters) near islands and embayments of the St. Lawrence River for densities, fecundity, and diel migration of planktonic microcrustaceans. Densities of cladocera and copepods (nauplii and adult stages of cyclopoids and calanoids) were sampled from surface and deeper layers both at night (2100–0100 h, near the new moon) and during the day (1000–1400 h) for channel (deep‐fast), offshore (shallow‐slower), and inshore (shallow‐stagnant) habitats. Average zooplankton densities increased laterally from the main channel into the slackwaters with the exception of calanoid copepods, which peaked in the intermediate depths and flows of the offshore habitats. Although the ratio of males to females for the calanoid Eurytemora affinis and the cladoceran Bosmina spp. did not differ among habitats, a greater percentage of ovigerous cladoceran females were present in slackwaters than in channel habitats. Densities of microcrustaceans were generally greater during the night than day, suggesting diel vertical migration. By demonstrating both lateral and diel differences in the spatial distribution of riverine zooplankton, we refute the view of large rivers as well‐mixed homogenous systems. To the contrary, the two non‐random patterns that we document imply that there is an abiotic template that at least microcrustacean potamoplankton can exploit. In turn this suggests more research into the ecological significance of the pelagic structure of other large rivers like the St. Lawrence is justified. Copyright © 2007 John Wiley & Sons, Ltd.     

HACCP-based program for on-farm food safety for pig production in Australia

The standard Codex HACCP approach was modified to allow a hazard analysis and critical control point determination to be conducted at an industry level and then used to determine the appropriate on-farm food safety control measures for pig production in Australia. A detailed risk-based profile with hazard identification, hazard characterisation and levels of microbial contamination for production and primary processing was used as a major technical resource to inform HACCP determinations. The process resulted in the identification of Critical Control Points for control of a specific physical hazard (non-recovered broken needles) and prevention of violations of Maximum Residue Limits with agricultural and veterinary chemicals. In relation to the identified microbiological hazards, it was noted that there are numerous Good Agricultural Practices (GAP) to prevent and/or reduce their risk and these controls would also need to be a feature of any on-farm food safety program. By applying a HACCP-based approach it was determined that the application of a set of Good Agricultural Practices on-farm would be effective in ensuring low risk. It was, therefore, concluded that on-farm food safety programs may not warrant full (i.e. Codex compliant) HACCP plans at the individual enterprise level provided appropriate GAP is in place. The results provide pig producers and the Australian pig industry with the elements of a HACCP-based food safety system that are scientifically justifiable, understandable and realistic to apply. These features are essential elements that underpin successful implementation and compliance by industry.     

下扬子地区中上二叠统页岩有机孔发育特征

下扬子地区中上二叠统发育一套海陆过渡相页岩,其显微组成与海相页岩存在明显的差异,为了研究该套页岩有机孔的发育特征及影响因素,开展了有机岩石学、扫描电镜、氩离子抛光扫描电镜、气测孔隙度和压汞等相关分析。研究表明,中上二叠统页岩中有机孔整体发育较好,但不同有机质组分中孔隙的发育存在明显的差别,具体表现为镜质体内孔隙发育差,固体沥青内发育少量孤立的孔隙,腐泥质内具有丰富的孔隙。黄铁矿或黏土矿物常与有机质形成有机/矿物复合体,复合体内有机孔普遍发育较好,可能与黄铁矿或黏土矿物促进有机质生烃和分解有关。中上二叠统页岩TOC含量与比表面积之间存在明显的线性正相关性,但与孔隙度之间具有复杂的关系,当w（TOC）<6.16%时,孔隙度随TOC含量的增加而增加,而当w（TOC）>6.16%时,孔隙度普遍较低且与TOC含量之间存在微弱的负相关性。孔径分布特征也揭示高TOC页岩的中—大孔体积明显低于低TOC页岩。页岩孔隙结构发育特征表明,TOC含量越高、固体沥青组分以及贫氢组分的含量越高,这些组分占据的矿物孔隙越多,降低了页岩总的孔隙空间,且TOC含量越高,页岩越易被压实,造成中大孔塌陷,进一步降低了页岩的孔隙度。     

Impact of the condition of storage of tartaric acid solutions on the production and stability of glyoxylic acid

The production and stability of glyoxylic acid was followed during the storage of tartaric acid solutions under various conditions. The solutions were prepared both with and without ethanol. Quantification of glyoxylic acid and other oxidation products, including hydrogen peroxide and formic acid, were performed using ion exclusion chromatography. Glyoxylic acid was only detected in tartaric acid samples that had been stored outdoors and sunlight was identified as the critical component of outdoor storage that allowed its formation. The hydrogen peroxide and glyoxylic acid generated under these conditions were of limited stability due to their reaction with each other to produce formic acid. The concentration of the glyoxylic acid was greatly increased when ethanol was omitted from the sample matrix. Copper(II) enhanced the stability of glyoxylic acid but slowed its production. The reaction pathway responsible for the sunlight-induced production and subsequent stability of glyoxylic acid is discussed.     

Emphasizing conflict resolution versus conflict avoidance during schedule generation

Classical planning systems attempt to solve a planning problem by avoiding possible conflicts before the actions are put on a timeline. This is computationally very expensive and the search for all possible future conflicts may be prohibitive. A conflict resolution approach can check for immediate conflicts and try conflict resolution strategies as each activity is put on a timeline without regard for possible future conflicts. A more practical approach is to use a combination of conflict avoidance and conflict resolution based upon heuristics which limit the amount of search required when either is used. Because humans are not good at solving problems which require complex lookahead, this combined approach, with emphasis on conflict resolution, is what human schedulers actually use when they develop schedules. A system which simulates this human approach to scheduling has been developed at NASA's Goddard Space Flight Center for scheduling satellite activities. This system, which includes the Planning And Resource Reasoning (PARR) shell, allows expert schedulers to specify conflict resolution strategies as well as conflict avoidance strategies to be used during the scheduling process. PARR has been used since May 1987 to schedule the Tracking and Data Relay Satellite System services for the Earth Radiation Budget Satellite. PARR will also be used to schedule platform resources on the Explorer Platform, scheduled for launch in early 1992. This paper describes the advantages of using a combined conflict avoidance and resolution approach in a satellite scheduling system.     

Controllable transmission of information in excitable media: The 2+ medium

In this paper we address the problem of how to implement directed dispatching of information in homogeneous excitable media. To do this, we surveyed cellular automaton models which reveal spatial oscillating patterns of excitation. Thus we discovered a medium where any element at rest was excited if just two of its nearest neighbours were excited. A medium of this kind, the 2⁺ medium, does not support the spreading of ordinary autowaves, but in its evolution one can find compact movable groups of excited states. Here we demonstrate that such solitary waves with particle-like behaviour will change their velocity vectors as a result of external singular stimulation. Thus they can be used as objects with controllable movement which transmit information in disordered surroundings. The results of this work can be utilised in the design of molecular computers.