The tailoring process in the German V-Model

V-Model is the Software Development Standard of the German Federal Authorities and is to be used for all projects in defense and commercial areas. The standard has been in use since summer 1992. V-Model is a life cycle process model that consists of activities and products for software development, quality assurance, configuration management and project management. Explained in this paper is the selection process (tailoring) of the activities and products for specific project needs. Tailoring is achieved by means of deletion conditions for activities or by means of tailoring forms for various project types.     

Vergleich von Nachweisverfahren für Stutzen in Zylinderschalen unter Innendruck und äußeren Lasten

Various methods for the verification of nozzles in cylindrical shells are described and the results of an example are compared. The example is carried out according to DIN EN 13445‐3, Sect. 16.5, in which the maximum permissible loads from internal pressure, axial force as well as moments in the longitudinal and circumferential direction are calculated. The results are compared with finite element computations performed with a 3D shell model, both with linear‐elastic material behavior and as limit‐load analyzes with ideal‐elastic ideal‐plastic material behavior.     

Copper-silica and copper-alumina alloys of high temperature interest

Utilizing relatively coarse copper powders and several sizes of silica and alumina powders, alloys containing up to 10 volume pct of oxide were made. The alloys were prepared by mechanical mixing of powders, followed by cold hydrostatic pressing, sintering, and hot extrusion. Measurements were made of room temperature tensile properties, recrystallization temperature, creep rupture properties from 250° to 450°C, and resistivity. In addition, metallographic studies were made of the resultant structures. Of particular interest was the stability of the structure with respect to temperature, time, and stress.     

Final solidification,centre segregation and precipitation phenomena in continuously cast round billets

Archimedes’ principle was applied to strand lengths of up to 14 m of round 177 mm diameter billets to determine cavity volume V (in cm³/m) for a series of tubemaking steels. Under steady state casting conditions, V depends primarily on the chemical composition and solidification behaviour of the steels. Averages ranged up to in an extreme case (bearing steel; v_C = 2.0 m/min). Stopping the strand and abrupt lowering of withdrawal speed made it possible to artificially induce individual shrinkage cavities with peak values of V = 45 cm³/m. In the round mould, subsequent necking of the liquid crater is initiated in this process. Whisker-like and icicle-like dendrites can be observed in horizontally formed macroscopic shrinkage cavities. The liquid crater is broken off by periodic bridging (the mini-lingot model). As permeability decreases, the bridges deflect downward in a U-shape under the ferrostatic load. The residual inter-dendritic melt is squeezed out in this plastic deformation process. Some bridges ultimately break. This interpretation is based on comprehensive CMA studies and concentration maps. Cores taken from the centre of a strand of bearing steel were submitted to various heat treatments between 1100 and 1350°C. Homogenization occurs below solidus (T < 1225°C). Carbides dissolve and sulfides become globular. Spatial segregation, on the other hand, increases, above solidus. In the extreme case at 1350°C/30 h, the residual melt at the grain boundaries migrates practically completely from the surface zone to the centre of the cylindrical sample (40 mm diameter). The propellent forces for this macro-heterogenization are provided by the activity gradient from the cylindrical surface to the centre and minimization of interface energy γ/I.     

Modelling the dynamics of landscape transformations and population growth in the highlands of Ethiopia using remote-sensing data

This study models landscape transformations and settlement dynamics in a highland area of Ethiopia over a 56 year period (1957–2013). The analyses were performed using aerial photographs, satellite images, and field data. The remotely sensed images were geometrically and radiometrically corrected. Visual interpretation of aerial photographs and supervised classification of multispectral satellite images using the maximum likelihood algorithm were chosen for land-cover mapping. The population size was estimated by counting the houses on the aerial photographs and on the high-resolution images, and by direct census. The overall trend showed an increase of cropland and a decrease of other types of land cover. Landscape transformation rates recently slowed down due to ownership and policy restrictions. The average cropland holding size per family has decreased from 2.6 to 1.1 ha due to the exponential growth of the population. The relationship between settlement and cropland expansion is statistically significant. Models of logistic growth were fitted to the cropland area, and models of exponential and logistic growth to the population development to estimate the carrying capacity. The concomitant increase of population and the decrease of cropland per head resulted in a shortage of food and energy, highlighting the importance of policy decisions on land management.     

AMPK Prevents Palmitic Acid-Induced Apoptosis and Lipid Accumulation in Cardiomyocytes

Palmitic acid, a main fatty acid (FA) in human nutrition, can induce apoptosis of cardiomyocytes. However, a specific combination of palmitic, myristic and palmitoleic acid (CoFA) has been reported to promote beneficial cardiac growth. The aim of this study was to investigate the relevance of CoFA for cardiac growth and to delineate the underlying signaling pathways of CoFA and palmitic acid treatment. CoFA treatment of C57Bl/6 mice increased FA serum concentrations. However, morphologic and echocardiographic analysis did not show myocardial hypertrophy. Cell culture studies using rat ventricular cardiomyocytes revealed an increased phosphorylation of AMP activated protein kinase α (AMPKα) to 155 ± 19% and its target acetyl-CoA-carboxylase to 177 ± 23% by CoFA. Treatment with myristic acid also increased AMPKα phosphorylation to 189 ± 32%. Palmitic acid did not activate AMPKα but increased expression of the FA translocase CD36 (FAT/CD36) to 163 ± 23% and adipose-differentiation-related-protein (ADRP), a sensitive marker of lipid accumulation, to 168 ± 42%. This was associated with an increased phosphorylation of the stress-activated-protein-kinase/Jun-amino-terminal-kinase (SAPK/JNK) to 173 ± 27%. In CoFA-treated cells, phosphorylation of SAPK/JNK was unaltered. FACS analysis revealed increased apoptosis to 159 ± 5% by palmitic acid but not by CoFA. AMPK activator AICAR (5-aminoimidazole-4-carboxamide ribonucleotide) prevented up-regulation of ADRP and increased apoptosis by palmitic acid. Confirming these findings, inhibition of AMPK by compound C in CoFA-treated cardiomyocytes resulted in an increased expression of ADRP to 154 ± 27%, FAT/CD36 to 167 ± 28% and apoptosis to 183 ± 12%. These data reveal that AMPK activation plays an important role in prevention of palmitic acid-induced apoptosis and lipid accumulation in cardiomyocytes.     

Untersuchungen zum Kondensationsmechanismus von Copolymerisaten mit freien und verkappten Methylolamidgruppen

According to trials with model compounds the annexed methylol amide groups in N-hydroxymethyl acryl amide polymers are linked with each other by ether and methylene bridges under elimination of water and formaldehyde. The proton catalysis favours methylene cross-linking. Part of the methylol groups escape the cross-linking reaction by reforming of carbonamide groups. The purely thermal condensation of the methylol ethers occurs by elimination of alcohol and leads to a cross-linking by N-substituted methylene-bis-carbonamide groups, while in the presence of protons alkyl formal additionally develops under formation of methylene bridges.     

Energieträger aus nachwachsenden Rohstoffen

Energy from regenerable raw materials. In the long run, some of the agricultural areas in the Federal Republic of Germany will no longer be needed for food production, and could therefore be used for growing raw material plants in order to provide various sources of energy, such as wood, rape seed oil, ethanol, methanol, and biogas. With this indirect use of the solar power accumulated in the plants, the overall expenditure for fossilized fuel energy to produce these energy sources is lower than the amount of primary energy that can be substituted. Based on the assumption that 20% of farmland will be used to grow regenerable raw materials, it would be possible to replace approximately 7 million tons of coal equivalent (SKE) by wood or approximately 4 million tons of coal equivalent (SKE) by ethanol from sugar beet or methanol from wood. In the case of alcohol production from sugar beet, the total energy efficiency including the regenerative part of energy of about 74%, is lower than in the ethanol synthesis. At present, use of biomasses as an energy source is feasible only in a few rare cases, and can only be achieved if the regenerable raw materials are considered as an alternative to surplus food production or to the strategy of gradually using less acreage for growing food.