Prediction of spiralling in BTA deep-hole drilling: estimating the system's eigenfrequencies

One serious problem in deep-hole drilling is the formation of a dynamic disturbance called spiralling which causes holes with several lobes. Since such lobes are a severe impairment of the bore hole quality the formation of spiralling has to be prevented. Gessesse et al. [2] explain spiralling by the coincidence of bending modes and multiples of the rotation frequency. They derive this from an elaborate finite elements model of the process. In online measurements we detected slowly changing frequency patterns similar to those calculated by Gessesse et al. We therefore propose a method to estimate the parameters determining the change of frequencies over time from spectrogram data. This significantly simplifies the explanation of spiralling for practical applications compared to finite elements models which have to be correctly modified for each machine and tool assembly. It turns out that this simpler model achieves to explain the observed frequency patterns quite well. We use this for estimating the variation of the frequencies as good as possible. This opens up the opportunity to prevent spiralling by e.g. changing the rotary frequency. --

Modelling and Understanding of Chatter

Recent analysis in chatter modelling of BTA deep-hole drilling consisted in phenomenological modelisation of relationships between the observed time series and appearance of chatter during the process. Using the newly developed MEWMA control chart [4, 5], it has even been possible to predict the occurence of chatter about 30 to 50 mm in advance (i.e. up to one minute before the chatter starts). Unfortunately, no relationships between the machine and model parameters have been detected. Therefore, in this paper a physical model of the boring bar is taken into account. Simulation studies of the regenerative process are performed. These simulated time series show the same characteristics as the data recorded during the drilling process and thus support the validity of our model. By running such simulations, we intend to find strategies for chatter prevention in future work. --

Multiple roles for Plasmodium berghei phosphoinositide-specific phospholipase C in regulating gametocyte activation and differentiation

Critical events in the life cycle of malaria parasites are controlled by calcium-dependent signalling cascades, yet the molecular mechanisms of calcium release remain poorly understood. The synchronized development of Plasmodium berghei gametocytes relies on rapid calcium release from internal stores within 10 s of gametocytes being exposed to mosquito-derived xanthurenic acid (XA). Here we addressed the function of phosphoinositide-specific phospholipase C (PI-PLC) for regulating gametocyte activation. XA triggered the hydrolysis of PIP2 and the production of the secondary messenger IP3 in gametocytes. Both processes were selectively blocked by a PI-PLC inhibitor, which also reduced the early Ca2+ signal. However, microgametocyte differentiation into microgametes was blocked even when the inhibitor was added up to 5 min after activation, suggesting a requirement for PI-PLC beyond the early mobilization of calcium. In contrast, inhibitors of calcium release through ryanodine receptor channels were active only during the first minute of gametocyte activation. Biochemical determination of PI-PLC activity was confirmed using transgenic parasites expressing a fluorescent PIP2/IP3 probe that translocates from the parasite plasmalemma to the cytosol upon cell activation. Our study revealed a complex interdependency of Ca2+ and PI-PLC activity, with PI-PLC being essential throughout gamete formation, possibly explaining the irreversibility of this process

Ubiquitous Computing. Summary

Ubiquitous computing - the complex electronic networking of things that communicate - is considered a promising innovation path worldwide. Intensive R&D activities and political strategies are aimed at promoting practical technologies and applications. Where do we currently stand on the path to the "Internet of Things"? Which practical projects already show the potential that can be exploited by implementing the basic idea of ubiquitous computing? What technical, legal and social challenges must be overcome to achieve this - and what can be the contribution of politics? In the light of these questions, the authors analyse the status quo and the perspectives of ubiquitous computing and illustrate their findings with examples from trade, logistics and health care, among others. the fascinating "Brownie technology" of ubiquitous computing must, however, still be comprehensively made fit by those involved in business, society and politics if its applications are really to become economically attractive, socially acceptable and helpful in overcoming social problems

Effect of electron-beam treatment on the properties of high speed steel

Results of research influence of the modes of electron beam processing on structure and properties of P6M5 high-speed cutting steel are presented in article. On the basis of pilot studies, the optimum mode of electron beam processing of high-speed cutting steel is chosen. It is experimentally defined that after electron beam processing the microhardness of P6M5 high-speed cutting steel increases to 950 MPa and wear resistance increases to 1,3 times in comparison with initial material. It is established that electron beam processing allows receiving the modified layer with a high hardness and high resistance to abrasive wear. Substantial increase of microhardness and wear resistance of high-speed cutting steels after electron beam processing shows prospects of application of this way of processing for increase of operability of the cutting tools from high-speed cutting steels

User-Centric Secure Data Sharing: Exploration of Concepts and Values

Data we handle and generate when using Internet-based services reveals information on our behavior and values. Access control to this data most often lies in the hands of service or storage providers. With regard to the value ladenness of data sharing in particular, we propose to shift the focus back to the user by introducing the concept of User-Centric Secure Data Sharing (UC-SDS). The UC-SDS approach aims at combining technologies and methodologies from the fields of secure data sharing, secure data outsourcing and value-oriented design. In this paper, we discuss design alternatives using the example of car telemetry data, considering their value interdependencies with particular emphasis on the legal context. Our work indicates that through combination of available building blocks, a higher level of user-centricity in access control is possible than we are used to today

Genetic and transcriptional analysis of phosphoinositide-specific phospholipase C in Plasmodium

Phosphoinositide-specific phospholipase C (PI-PLC) is a major regulator of calcium-dependent signal transduction, which has been shown to be important in various processes of the malaria parasite Plasmodium. PI-PLC is generally implicated in calcium liberation from intracellular stores through the action of its product, inositol-(1,4,5)-trisphosphate, and is itself dependent on calcium for its activation. Here we describe the plc genes from Plasmodium species. The encoded proteins contain all domains typically found in PI-PLCs of the δ class but are almost twice as long as their orthologues in mammals. Transcriptional analysis by qRT-PCR of plc during the erythrocytic cycle of P. falciparum revealed steady expression levels that increased at the late schizont stages. Genetic analysis in the P. berghei model revealed that the plc locus was targetable but that plc gene knock-outs could not be obtained, thereby strongly indicating that the gene is essential during blood stage development. Alternatively, we attempted to modify plc expression through a promoter exchange approach but found the gene to be refractory to over-expression indicating that plc expression levels might additionally be tightly controlled

Spiralling in BTA-deep-hole drilling : models of varying frequencies

One serious problem in deep-hole drilling is the formation of a dynamic disturbance called spiralling which causes holes with several lobes. Since such lobes are a severe impairment of the bore hole the formation of spiralling has to be prevented. Gessesse et al. (1994) explain spiralling by the coincidence of bending modes and multiples of the rotary frequency. They derive this from an elaborate finite elements model of the process. In online measurements we detected slowly changing frequency patterns similar to those calculated by Gessesse et al. We therefore propose a method to estimate the explanation of spiralling in practice because the finite elements model has to be correctly modified for each machine and tool assembly while the statistical method uses observable measurements. Estimating the variation of the frequencies as good as possible opens up the opportunity to prevent spiralling by e.g. changing the rotary frequency. --