Shock Waves in Plane Symmetric Spacetimes

We consider Einstein's equations coupled to the Euler equations in plane symmetry, with compact spatial slices and constant mean curvature time. We show that for a wide variety of equations of state and a large class of initial data, classical solutions break down in finite time. The key mathematical result is a new theorem on the breakdown of solutions of systems of balance laws. We also show that an extension of the solution is possible if the spatial derivatives of the energy density and the velocity are bounded, indicating that the breakdown is really due to the formation of shock waves

Intermediate inflation and the slow-roll approximation

It is shown that spatially homogeneous solutions of the Einstein equations coupled to a nonlinear scalar field and other matter exhibit accelerated expansion at late times for a wide variety of potentials $V$. These potentials are strictly positive but tend to zero at infinity. They satisfy restrictions on $V'/V$ and $V''/V'$ related to the slow-roll approximation. These results generalize Wald's theorem for spacetimes with positive cosmological constant to those with accelerated expansion driven by potentials belonging to a large class.Comment: 19 pages, results unchanged, additional backgroun

Individual tree biomass equations or biomass expansion factors for assessment of carbon stock changes in living biomass - A comparative study

AbstractSignatory countries to the United Nations Framework Convention on Climate Change (UNFCCC) and its supplementary Kyoto Protocol (KP) are obliged to report greenhouse gas emissions and removals. Changes in the carbon stock of living biomass should be reported using either the default or stock change methods of the Intergovernmental Panel on Climate Change (IPCC) under the Land Use, Land-Use Change and Forestry sector. Traditionally, volume estimates are used as a forestry measures. Changes in living biomass may be assessed by first estimating the change in the volume of stem wood and then converting this volume to whole tree biomass using biomass expansion factors (BEFs). However, this conversion is often non-trivial because the proportion of stem wood increases with tree size at the expense of branches, foliage, stump and roots. Therefore, BEFs typically vary over time and their use may result in biased estimates. The objective of this study was to evaluate differences between biomass estimates obtained using biomass equations and BEFs with particular focus on uncertainty analysis. Assuming that the development of tree fractions in different ways can be handled by individual biomass equations, BEFs for standing stock were shown to overestimate the biomass sink capacity (Sweden). Although estimates for BEFs derived for changes in stock were found to be unbiased, the estimated BEFs varied substantially over time (0.85–1.22ton CO2/m3). However, to some extent this variation may be due to random sampling errors rather than actual changes. The highest accuracy was obtained for estimates based on biomass equations for different tree fractions, applied to data from the Swedish National Forest Inventory using a permanent sample design (estimated change in stock 1990–2005: 420million tons CO2, with a standard error amounting to 26.7million tons CO2) Many countries have adopted such a design combined with the stock change method for reporting carbon stock changes under the UNFCCC/KP

Investigations of solutions of Einstein's field equations close to lambda-Taub-NUT

We present investigations of a class of solutions of Einstein's field equations close to the family of lambda-Taub-NUT spacetimes. The studies are done using a numerical code introduced by the author elsewhere. One of the main technical complication is due to the S3-topology of the Cauchy surfaces. Complementing these numerical results with heuristic arguments, we are able to yield some first insights into the strong cosmic censorship issue and the conjectures by Belinskii, Khalatnikov, and Lifschitz in this class of spacetimes. In particular, the current investigations suggest that strong cosmic censorship holds in this class. We further identify open issues in our current approach and point to future research projects.Comment: 24 pages, 12 figures, uses psfrag and hyperref; replaced with published version, only minor corrections of typos and reference

Fuchsian methods and spacetime singularities

Fuchsian methods and their applications to the study of the structure of spacetime singularities are surveyed. The existence question for spacetimes with compact Cauchy horizons is discussed. After some basic facts concerning Fuchsian equations have been recalled, various ways in which these equations have been applied in general relativity are described. Possible future applications are indicated

Sensitivity of Colding tool life equation on the dimensions of experimental dataset

In this work, 22 sets of cutting data and tool life for longitudinal turning of steel are analyzed using the Colding equation. When modeling tool life with a limited number of tool performance data points, the model error may be low for these points. Evaluating the model for test points not used when computing the model coefficients may give larger errors for these points. This work proves that the Colding model also provides sufficient precision when modelling data points not being used to create the model, and is therefore a well-functioning instrument for tool life modelling. The results also prove that for the selected data, the precision of the model can be greatly improved when the dimension of the data set is increased from 5 to 10 data points. Above 13 data points the precision improvements are negligible.Проаналізовано 22 набору режимів різання і стійкість інструменту при поздовжньому точінні стали при застосуванні моделі Колдінга. При моделюванні стійкості інструменту при обмеженій кількості даних про робочі характеристики помилка моделі може бути незначною в заданих точках. Оцінка моделі для тестових точок, які не використовуються при обчисленні коефіцієнтів моделі, може показати більші помилки в цих точках. Доведено, що модель Колдінга забезпечує достатню точність при моделюванні даних, що не використовуються для створення моделі, і тому може бути застосована для моделювання періоду стійкості інструменту. Результати також доводять, що для даних, що використовуються, точність моделі може бути значно поліпшена при збільшенні набору точок з 5 до 10, а при збільшенні понад 13 точок поліпшення точності моделювання незначні.Проанализированы 22 набора режимов резания и стойкость инструмента при продольном точении стали с применением модели Колдинга. При моделировании стойкости инструмента при ограниченном количестве данных о рабочих характеристиках ошибка модели может быть незначительной в заданных точках. Оценка модели для тестовых точек, не используемых при вычислении коэффициентов модели, может показать бóльшие ошибки в этих точках. Доказано, что модель Колдинга обеспечивает достаточную точность при моделировании данных, не используемых для создания модели, и поэтому может быть применена для моделирования периода стойкости инструмента. Результаты также доказывают, что для используемых данных точность модели может быть значительно улучшена при увеличении набора точек с 5 до 10, а при увеличении более 13 точек улучшения точности моделирования незначительны

Emotions in context: examining pervasive affective sensing systems, applications, and analyses

Pervasive sensing has opened up new opportunities for measuring our feelings and understanding our behavior by monitoring our affective states while mobile. This review paper surveys pervasive affect sensing by examining and considering three major elements of affective pervasive systems, namely; “sensing”, “analysis”, and “application”. Sensing investigates the different sensing modalities that are used in existing real-time affective applications, Analysis explores different approaches to emotion recognition and visualization based on different types of collected data, and Application investigates different leading areas of affective applications. For each of the three aspects, the paper includes an extensive survey of the literature and finally outlines some of challenges and future research opportunities of affective sensing in the context of pervasive computing

Pressure-induced structural change in liquid GaIn eutectic alloy

Synchrotron x-ray diffraction reveals a pressure induced crystallization at about 3.4 GPa and apolymorphic transition near 10.3 GPa when compressed a liquid GaIn eutectic alloy up to ~13 GPa atroom temperature in a diamond anvil cell. Upon decompression, the high pressure crystalline phaseremains almost unchanged until it transforms to the liquid state at around 2.3 GPa. The ab initiomolecular dynamics calculations can reproduce the low pressure crystallization and give some hints onthe understanding of the transition between the liquid and the crystalline phase on the atomic level.The calculated pair correlation function g(r) shows a non-uniform contraction reflected by the differentcompressibility between the short (1st shell) and the intermediate (2nd to 4th shells). It is concludedthat the pressure-induced liquid-crystalline phase transformation likely arises from the changes in localatomic packing of the nearest neighbors as well as electronic structures at the transition pressure

Detection and Identification of the Atypical Bovine Pestiviruses in Commercial Foetal Bovine Serum Batches

The recently emerging atypical bovine pestiviruses have been detected in commercial foetal bovine serum (FBS) of mainly South American origin so far. It is unclear how widely the viruses are presented in commercial FBS of different geographic origins. To further investigate the possible pestivirus contamination of commercially available FBS batches, 33 batches of FBS were obtained from ten suppliers and analysed in this study for the presence of both the recognised and the atypical bovine pestiviruses. All 33 batches of FBS were positive by real-time RT-PCR assays for at least one species of bovine pestiviruses. According to the certificate of analysis that the suppliers claimed for each batch of FBS, BVDV-1 was detected in all 11 countries and BVDV-2 was detected exclusively in the America Continent. The atypical pestiviruses were detected in 13 batches claimed to originate from five countries. Analysis of partial 5′UTR sequences showed a high similarity among these atypical bovine pestiviruses. This study has demonstrated, for the first time that commercial FBS batches of different geographic origins are contaminated not only with the recognised species BVDV-1 and BVDV-2, but also with the emerging atypical bovine pestiviruses