Eight-year exploration of shrinkage in high-performance concrete

In this paper, an experimental and analytical exploration on the effect of water-binder ratio (w/b), silica fume and age on autogenous, carbonation, drying and total shrinkage of high-performance concrete (HPC) is outlined. Eight types of HPC were studied. Carbonation, internal relative humidity (RH) and strength were studied on specimens from the same batch of HPC that was used in the studies of shrinkage. The results indicate fairly good correlation between carbonation, shrinkage, w/b and RH. The type and amount of silica fume affected shrinkage.     

Treatment with the oral growth hormone secretagogue MK-677 increases markers of bone formation and bone resorption in obese young males

The effect of 2 months of treatment with the oral growth hormone (GH) secretagogue MK-677 on markers of bone metabolism was determined in healthy obese male subjects. This was a randomized, double-blind, parallel, placebo-controlled study. Twenty-four healthy obese males, 19-49 years of age, with body mass index > 30 kg/m2 were treated with MK-677 (25 mg/day; n = 12) or placebo (n = 12) for 8 weeks. MK-677 increased markers of bone formation; a 23% increase in the carboxy-terminal propeptide of type I procollagen levels and a 28% increase in procollagen III peptide levels were seen with as little as 2 weeks of MK-677 treatment (p < 0.01 and p = 0.001 vs. placebo, respectively) while a 15% increase in serum levels of osteocalcin was not detected until 8 weeks of treatment (p < 0.01 vs. placebo). Markers of bone resorption were induced within 2 weeks of treatment with MK-677; serum levels of the carboxy-terminal cross-linked telopeptide of type I collagen were increased 26% at 8 weeks (p = 0.001 vs. placebo), and urine hydroxyproline/creatinine and calcium/creatinine ratios at 8 weeks were increased by 23% (p < 0.05 vs. placebo) and 46% (p < 0.05 vs placebo), respectively, MK-677 increased serum insulin-like growth factor binding protein-5 (IGFBP-5) by 43-44% after 2-8 weeks of treatment (p < 0.01 vs. placebo). Serum IGFBP-4 was increased by 25% after 2 weeks of treatment (p < 0.001 vs. placebo) but no significant change from baseline was observed after 8 weeks of treatment. Plasma interleukin-6 was not significantly changed by active treatment. In conclusion, short-term treatment of healthy obese male volunteers with the GH secretagogue MK-677 increases markers of both bone resorption and formation. Large increases in serum levels of IGF-1 and IGFBP-5 and a transient increase in serum IGFBP-4 were found. Future long-term studies are needed to investigate if prolonged treatment with MK-677 increases bone mass.     

An Extended Replication of an Experiment for Assessing Methods for Software Requirements Inspections

We have performed an extended replication of the Porter-Votta-Basili experiment comparing the Scenario method and the Checklist method for inspecting requirements specifications using identical instruments. The experiment has been conducted in our educational context represented by a more general definition of a defect compared to the original defect list. Our study involving 24 undergraduate students manipulated three independent variables: detection method, requirements specification, and the order of the inspections. The dependent variable measured is the defect detection rate. We found the requirements specification inspected and not the detection method to be the most probable explanation for the variance in defect detection rate. This suggests that it is important to gather knowledge of how a requirements specification can convey an understandable view of the product and to adapt inspection methods accordingly. Contrary to the original experiment, we can not significantly support the superiority of the Scenario method. This is in accordance with a replication conducted by Fusaro, Lanubile and Visaggio, and might be explained by the lack of individual defect detection skill of our less experienced subjects.     

How practice produces suboptimal heuristics that render backup instruments ineffective

The operation of machines typically requires attention to instruments that signal the state of the machine. One safeguard against primary instrument malfunction is to provide backup instruments, but this works only if the operators react to malfunction by switching attention to the backups. Little is known about the effect of negative outcomes or feedback on allocation of attention to backup instruments. Four experiments demonstrated that prior practice causes operators of a simulated machine to adapt to instrument malfunction by changing to a suboptimal decision rule rather than by reallocating attention to a different set of instruments. This fallacy appears linked to the operators' failures to notice feedback that they should switch during the simulations and operators' failures to correctly interpret outcome feedback following the simulations. The results raise theoretical questions and warn interface designers not to overrate backup instruments.     

Relationship between the attenuation of downwelling irradiance at 490 nm with the attenuation of PAR (400 nm-700 nm) in the Baltic Sea

The vertical attenuation coefficient of diffuse downwelling irradiance at 490 nm (K_d 490) is a parameter that we routinely derive from SeaWiFS images of the Baltic Sea. Here, through model simulations, we examine the relationship between K_d(490), and the vertical attenuation coefficient of PAR (K_d PAR), as this later coefficient determines the light available for aquatic photosynthesis. A simple semi-analytical model is used to predict K_d(490) and K_d(PAR), as a function of the concentrations of chlorophyll, colored dissolved organic material (CDOM), suspended inorganic, and suspended organic particulate material. A series of model simulations based on variations in these optically significant constituents over a range realistic for the Baltic Sea, are used to define the relationship between the two attenuation coefficients.

Kd(PAR)=0.6677Kd^0.6763(490).     

Assessing and Understanding Efficiency and Success of Software Production

One of the goals of collectingproject data during software development and evolution is toassess how well the project did and what should be done to improvein the future. With the wide range of data often collected andthe many complicated relationships between them, this is notalways easy. This paper suggests to use production models (DataEnvelope Analysis) to analyze objective variables and their impacton efficiency. To understand the effect of subjective variables,it is suggested to apply principal component analysis (PCA).Further, we propose to combine the results from the productionmodels and the analysis of the subjective variables. We showcapabilities of production models and illustrate how productionmodels can be combined with other approaches to allow for assessingand hence understanding software project data. The approach isillustrated on a data set consisting of 46 software projectsfrom the NASA-SEL database (NASA-SEL, 1992). The data analyzedis of the type that is commonly found in project databases.     

On the internal frost resistance of self-compacting concrete, with and without polypropylene fibres

In this article experimental and numerical studies of internal frost resistance of self-compacting and normal concrete, with and without fibres, are outlined. For this purpose self-compacting concrete with low water-cement ratio was studied, with varying amounts of filler, crystalline or sedimentary, different pouring pressures and different mixing procedure with two ages at the start of testing. The concrete was frozen twice a day at ±20^∘C all around the specimen up to 300 cycles. Measurement of length, weight and internal fundamental frequency were performed at the start of testing, at 100 cycles and at 300 frost cycles. Tests were also carried out on submerged cast self-compacting concrete and on self-compacting concrete with fibres. In reference tests normal concrete was studied in parallel. In general self-compacting concrete behaved well or better than normal concrete to internal frost except for the submerged cast concrete, where large segregation occurred and low internal frost resistance followed. The main reasons for low internal frost resistance in submerged applications were probably differences in water-cement ratio in the casting due to cement, water or/and aggregate segregation. Polypropylene fibres in concrete seemed to prohibit the movement of water in the air void system so that a sudden internal collapse occurred before 300 frost cycles.     

Contradicting incentives for research collaboration

This study describes the Danish publication award system (BFI), investigates whether its built-in incentives have had an effect on publication behavior at the University of Southern Denmark, and discusses the possible future implications on researcher incentives should universities wish to measure BFI on the individual level. We analyzed publication data from the university CRIS system (Pure) and from SciVal. Several studies indicate that co-authored scholarly journal articles attract more citations than single author articles. The reason for this are not clear, however, research collaboration across institutions and countries is commonly accepted in the research community and among university managements as one way of increasing the researcher’s and institution’s reputation and impact. The BFI system is designed to award scholarly publication activity at Danish universities, especially publication in international journals of high status. However, we find that the built-in incentives leave the researcher and his or her institution with a dilemma: If the researchers optimize their performance by forming author groups with external collaborators, the optimal way of doing so for the researchers is not the optimal way seen from the perspective of the university. Our analysis shows that the typical article has 6.5 authors, two of which are internal, and that this has remained stable since the introduction of the BFI. However, there is variation across the disciplines. While ‘the Arts and Humanities’ and ‘the Social Sciences’ seem to compose author groups in a way which does not optimize the performance of the institution, both ‘Health’ and ‘the Natural Sciences’ seem to optimize according to criteria other than those specified in the BFI.