What can possibly go wrong? Anticipatory work in space operations

This paper explores how different forms of anticipatory work contribute to reliability in high-risk space operations. It is based on ethnographic field work, participant observation and interviews supplemented with video recordings from a control room responsible for operating a microgravity greenhouse at the International Space Station (ISS). Drawing on examples from different stages of a biological experiment on the ISS, we demonstrate how engineers, researchers and technicians work to anticipate and proactively mitigate possible problems. Space research is expensive and risky. The experiments are planned over the course of many years by a globally distributed network of organizations. Owing to the inaccessibility of the ISS, every trivial detail that could possibly cause a problem is subject to scrutiny. We discuss what we label anticipatory work: practices constituted of an entanglement of cognitive, social and technical elements involved in anticipating and proactively mitigating everything that might go wrong. We show how the nature of anticipatory work changes between planning and the operational phases of an experiment. In the planning phase, operators inscribe their anticipation into technology and procedures. In the operational phase, we show how troubleshooting involves the ability to look ahead in the evolving temporal trajectory of the ISS operations and to juggle pre-planned fixes along these trajectories. A key objective of this paper is to illustrate how anticipation is shared between humans and different forms of technology. Moreover, it illustrates the importance of including considerations of temporality in safety and reliability research.     

Measuring information systems success: models,dimensions, measures,and interrelationships

Since DeLone and McLean (D&M) developed their model of IS success, there has been much research on the topic of success as well as extensions and tests of their model. Using the technique of a qualitative literature review, this research reviews 180 papers found in the academic literature for the period 1992–2007 dealing with some aspect of IS success. Using the six dimensions of the D&M model – system quality, information quality, service quality, use, user satisfaction, and net benefits – 90 empirical studies were examined and the results summarized. Measures for the six success constructs are described and 15 pairwise associations between the success constructs are analyzed. This work builds on the prior research related to IS success by summarizing the measures applied to the evaluation of IS success and by examining the relationships that comprise the D&M IS success model in both individual and organizational contexts.     

CO2 heat pump systems

After the CFCs and the HCFCs were deemed unfit as working fluids in refrigeration, air conditioning, and heat pump applications, there has been a renaissance for carbon dioxide technology. Heat pumps is one of the application areas where theoretical and experimental investigations are now performed by an increasing number of research institutions and manufacturers. This paper gives an overview of some of the current activities in the CO₂ heat pump field. Discussed are the important characteristics of the transcritical CO₂ process applied to heat pumps, and also discussed are theoretical and experimental results from several heat pump applications. Provided that calculations and system designs are performed on the premises of the working fluid, and that test plants are constructed and operated to fully exploit the specific characteristics of both the fluid and the transcritical process, the results show that CO₂ is an attractive alternative to the synthetic fluids. Competitive products may be launched in the near future.     

Accelerated climate ageing of building materials, components and structures in the laboratory

Building materials, components and structures have to fulfil many functional demands during the lifetime of a building. Therefore, it is important to require satisfactory durability of these materials, components and structures. In fact, one single material failure may jeopardize whole components as well as structures. Unfortunately, experience shows that building products too often do not satisfy the various requirements after a relatively short period of use, i.e. the expected service life is considerably shorter than foreseen. This results in increased and large costs due to increased maintenance, extensive replacements of the specific building products and any possible consequential building damages. In addition, health hazards with respect to both risk and consequence may also become an issue. To avoid this, the solution is to apply building products which have properly documented adequate and satisfactory long-term durability. That is, building products which have been subjected to long-term natural outdoor climate exposure or appropriate accelerated climate ageing in the laboratory. This study examines the main climate exposures and how these may be reproduced in the laboratory in various ways. Thus, crucial properties of building products and their durability towards climate strains may be investigated within a relatively short time frame compared with natural outdoor climate ageing. Examples of miscellaneous climate ageing laboratory apparatuses, ageing methods and building product properties to be tested before, during and after ageing are given. A calculation method for estimating acceleration factors is also discussed. Various ageing examples are shown and discussed. A special note is made towards accelerated climate ageing of new and advanced materials being developed. Hence, this study addresses durability and the versatile and powerful application of accelerated climate ageing which is an all too overlooked field within materials science and engineering.     

Disassembly and Mislocalization of AQP4 in Incipient Scar Formation after Experimental Stroke

There is an urgent need to better understand the mechanisms involved in scar formation in the brain. It is well known that astrocytes are critically engaged in this process. Here, we analyze incipient scar formation one week after a discrete ischemic insult to the cerebral cortex. We show that the infarct border zone is characterized by pronounced changes in the organization and subcellular localization of the major astrocytic protein AQP4. Specifically, there is a loss of AQP4 from astrocytic endfoot membranes that anchor astrocytes to pericapillary basal laminae and a disassembly of the supramolecular AQP4 complexes that normally abound in these membranes. This disassembly may be mechanistically coupled to a downregulation of the newly discovered AQP4 isoform AQP4ex. AQP4 has adhesive properties and is assumed to facilitate astrocyte mobility by permitting rapid volume changes at the leading edges of migrating astrocytes. Thus, the present findings provide new insight in the molecular basis of incipient scar formation.     

Development of large-scale hydrogen liquefaction processes from 1898 to 2009

This paper presents a review of the development of large-scale hydrogen liquefaction processes throughout the world from 1898 to 2009. First, there is a concise literature review including numerous past, present, and future designs given such as the first hydrogen liquefaction device, long time ago simple theoretical processes, today's actual plants with efficiencies 20–30%, a list of the capacity and location of every hydrogen liquefaction plant in the world, and some modern more efficient proposed conceptual plants with efficiencies 40–50%. After that, further information about the development and improvement potential of future large-scale liquid hydrogen liquefaction plants is given. It is found that every current plant is based on the pre-cooled Claude system, which is still the same as was 50 years ago with little improvement. Methods to resolve the challenges of the future plants include proposing completely new configurations and efficient systems coupled with improved efficiencies of the main system components such as compressors, expanders, and heat exchangers. Finally, a summary and comparison of the process efficiencies are described, including a newly proposed Multi-component Refrigerant (MR) system being developed by NTNU and SINTEF Energy Research AS.     

Purification of north Brazilian kaolin by selective flocculation

The main kaolin deposits in north Brazil present are contaminated with colored titanous impurities. Conventional beneficiation processes do not completely remove TiO₂. The difficulty in separation is mainly due to the ultra-fine size of the minerals.This work presents a study of an alternative kaolin purification method based on selective adsorption of soluble polymers. In the process, flocs were generated by interaction of anionic polyacrylamide with titanous impurities and were separated from the kaolin suspension through sedimentation.     

Carbon Cathode Wear in Aluminium Electrolysis Cells

JOM - Autopsies of six spent potlinings with different carbon cathode block grades, amperage regimes and cell designs were conducted at three separate smelters to reveal possible mechanisms causing...     

An evaluation of the Norwegian Salmonella surveillance and control program in live pig and pork

Population data and apparent prevalence data from the Salmonella surveillance and control program in pigs (NSSCP) from 1998 and 1999 were used in a simulation model to evaluate the efficacy of the program. The model consists of three parts: modelling of individual prevalence at the abattoir (abattoir part), modelling of the number of sampled herds of different sizes when carcasses are randomly sampled at the abattoir (sampling strategy part) and finally, modelling of the within herd prevalence (within herd part). A total of 136,550 sows and 2,866,550 finishing pigs slaughtered, 4446 herds and 11 herds positive for Salmonella in 1994/1995-2000 were included in the abattoir part, sampling strategy part and the within herd part of the model, respectively. The abattoir part showed an average estimated prevalence of Salmonella in sows and finishing pigs of (median) 0.4% (5-95 percentiles = 0.03-2%) and 0.1% (0.04-0.2%) respectively. The estimated number of infected sow carcasses that entered the market was 502 (37-2157) while the estimated number of finishing pig carcasses was 2919 (1218-5771). The probability of being sampled for the 10% smallest herds was (mean) 1.9% (1.6-2.2), to 25% (24.7-26.5%) for the 10% largest herds. The within herd prevalence was estimated to be from 1% to 4% for Norwegian pig herds. The conclusions drawn from this evaluation are that the NSSCP does not have any significant consumer protection effect, and that the documentation could be done more effectively using the herd rather than the individual animal as the unit of sampling. Sampling should focus on the larger herds supplying most of the meat on the market and on herds that produce breeding sows and piglets and thus can contribute to the spread of Salmonella among herds.     

A MIXTURE MODEL CLASSIFIER AND ITS APPLICATION ON THE BIOMEDICAL TIME SERIES

This article presents a methodology based on the mixture model to classify the real biomedical time series. The mixture model is shown to be an efficient probabilistic density estimation scheme aimed at approximating the posterior probability distribution of a certain class of data. The approximation is conducted by employing a weighted mixture of a finite number of Gaussian kernels whose parameters and mixing coefficients are estimated iteratively through a maximum likelihood method. A database of the real electrocardiogram (ECG) time series of out-of-hospital cardiac arrest patients suffering ventricular fibrillation (VF) with known defibrillation outcomes was adopted to evaluate the performance of this model and confirm its efficiency compared with other classification methods.