scholarly journals Intelligent lightweight structures for hybrid machine tools

2020 ◽  
Vol 14 (5-6) ◽  
pp. 583-600
Author(s):  
H. -Christian Möhring ◽  
Matthias Müller ◽  
Jens Krieger ◽  
Jörg Multhoff ◽  
Christian Plagge ◽  
...  
Keyword(s):  
Machine Tools ◽  
Dynamic Stiffness ◽  
Ministry Of Education ◽  
Mass Reduction ◽  
Joint Project ◽  
Lightweight Structures ◽  
Thermal Boundary Conditions ◽  
The Us ◽  
Precise Machine ◽  
Operational Time

AbstractIn order to improve the competitiveness on the global machine tool markets, a permanent development of new solutions and optimization of existing technologies is necessary. Besides traditional business areas, like Europe, Asia and the US, emerging countries provide interesting potential. Currently, the setup and operation of precise machine tools in these areas possesses some challenges. As an example, the foundation of the machines is often not as stable as assumed during the layout and design phase. Furthermore, the thermal boundary conditions are often characterized by much higher differences of the ambient temperature during the daily operational time compared to European conditions. These influences affect especially the performance of medium sized machine tools. Within the joint project HYBRIDi, funded by the Federal Ministry of Education and Research (BMBF) supported by the Projektträger Karlsruhe (PTKA), partners from industry and research created, realized and investigated new intelligent lightweight machine slide structures in order to overcome the named challenges. In particular, two variants of a hybrid material z-slide (RAM) with integrated sensors were built and analyzed with respect to advantages in terms of mass reduction, static and dynamic stiffness, dynamic positioning accuracy as well as thermal behavior. This paper presents the developments and results of the project.

¡A La Huelga! Secondary Students, School Strikes, and the Power of Educational Activism in 1970s Nicaragua

2020 ◽  
Vol 77 (4) ◽  
pp. 601-631
Author(s):  
Claudia Rueda
Keyword(s):  
Secondary School ◽  
Secondary Students ◽  
Quality Of Education ◽  
Ministry Of Education ◽  
Democratic Schools ◽  
Joint Project ◽  
The Press ◽  
To Come ◽  
Student Demands

ABSTRACTThe year 1976 was a violent one in Nicaragua. In an effort to quash the Sandinista guerrillas, the dictator Anastasio Somoza Debayle had declared a state of siege, suspending constitutional guarantees, muzzling the press, and unleashing the Guardia Nacional. Despite the dangers of dissent, thousands of students across the country walked off their secondary school campuses that year to protest poor funding, inept teachers, and oppressive administrators. This article examines this series of strikes to uncover the ways in which teenagers managed to organize their schools and communities in spite of the repression that marked the final years of the Somoza regime. Analyzing student documents, Ministry of Education records, and newspaper reports, this article argues that in the context of a decades-long dictatorship, student demands for more democratic schools opened a relatively safe pathway for cross-generational activism that forced concessions from the Somoza regime. By the 1970s, secondary schools had come to reflect the state's authoritarianism and mismanagement, and widespread educational deficiencies brought students and parents together in a joint project to demand better schools. Battles over the quality of education, thus, showcased the power of an organized citizenry and laid the groundwork for the revolutionary mobilizations that were to come.

Experimental Research Regarding the Influence of Hydraulic Resistances on the Hydrostatic Guideways Stiffness

2014 ◽  
Vol 657 ◽  
pp. 475-479
Author(s):  
Marius Pascu ◽  
Gheorghe Stan
Keyword(s):  
Machine Tool ◽  
Hydraulic Resistance ◽  
Experimental Research ◽  
Machine Tools ◽  
Dynamic Stiffness ◽  
Experimental Results ◽  
Graphical Form ◽  
Experimental Setup ◽  
Experimental Database ◽  
Supply Circuit

A very important factor for the hydrostatic guideways is given by the presence of the restrictor on the supply circuit, whose hydraulic resistance may have important effects on the lubricant film behaviour and implicitly, on the static and dynamic stiffness of the system. This paper presents a new method of experimental research regarding the hydrostatic guideway stiffness, depending on the hydraulic resistances values which supply each pocket. During the experiments which approach the influence of the hydraulic resistances values of the restrictors on the hydrostatic guideway stiffness, a centered constant loads of 20, 50 and 100 [daN] was used. The experiments were carried out on an experimental setup composed of an open hydrostatic guideway, having the pocket dimensions of 150x88 [m, supplied with liquid under pressure through means of a pack of adjustable restrictors. The obtained experimental results are presented in both tabular and graphical form and constitute an experimental database which can be used by the machine tools designers and manufacturers. The paper contains recommendations regarding the usage of hydraulic resistances values depending on the machine tool type and size. Also, from the obtained results, recommendations can be made with regard to the type of restrictors to be used, so that the lubricant filtration grade is comprised between admissible values.

Cross-linguistic perspectives on the development of text-production abilities

2002 ◽  
Vol 5 (1) ◽  
pp. 1-43 ◽  
Author(s):  
Ruth A. Berman ◽  
Ludo Verhoeven
Keyword(s):  
Lead Author ◽  
Project Director ◽  
Joint Project ◽  
Text Production ◽  
Graduate Research ◽  
The Us ◽  
Research Assistants

The studies reported in this volume of WL&L (5: 1–2, 2002) all derive from a joint project entitled “Developing literacy in different contexts and in different languages”, funded by the Spencer Foundation, Chicago. The study encompasses seven languages — Dutch, English, French, Hebrew, Icelandic, Spanish, and Swedish — for which data were collected in Europe, Israel, and the US by graduate research assistants in education, linguistics, and psychology, under the supervision of a project director in each country — each of whom is listed as a first or “lead” author in the articles which follow the introduction to this collection.

Experimental Research on Self-Alignment Design Principle of a Large-Scale Precise Machine Bed

2010 ◽  
Vol 102-104 ◽  
pp. 306-310
Author(s):  
Zhan Hui Yan ◽  
Yi Cao ◽  
Jun Yi Yu
Keyword(s):  
Experimental Research ◽  
Machine Tools ◽  
Thermal Deformation ◽  
Large Scale ◽  
Design Principle ◽  
Simulation Experiment ◽  
Good Precision ◽  
Key Points ◽  
Machined Parts ◽  
Precise Machine

In order to eliminate thermal deformation of large-scale precise machine tools caused by ambient temperature change, self-alignment design principle and key points are proposed for a large-scale precise machine tools, Self-alignment simulation experiment, machined parts experiment and compared results for self-alignment rail grinder and other similar products are analysed, the present analysis show that self-alignment rail grinder has many advangtages of good precision, straightness stability.

scholarly journals Vibration Damping Analysis of Lightweight Structures in Machine Tools

Materials ◽  
2017 ◽  
Vol 10 (3) ◽  
pp. 297 ◽  
Author(s):  
Francesco Aggogeri ◽  
Alberto Borboni ◽  
Angelo Merlo ◽  
Nicola Pellegrini ◽  
Raffaele Ricatto
Keyword(s):  
Machine Tools ◽  
Vibration Damping ◽  
Lightweight Structures

scholarly journals INVESTIGATION OF NOISE TRANSMISSION OF A MACHINE TOOL ENCLOSURE

2019 ◽  
Vol 19 (3) ◽  
pp. 5-17
Author(s):  
Friedrich BLEICHER ◽  
Christoph REICHL ◽  
Felix LINHARDT ◽  
Peter WIMBERGER ◽  
Christoph HABERSOHN ◽  
...  
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Dynamic Stiffness ◽  
Measuring Method ◽  
Work Piece ◽  
Noise Emission ◽  
Mechatronic Systems ◽  
Major Interest ◽  
Noise Transmission ◽  
Moving Parts

Machine tools are highly integrated mechatronic systems consisting of dedicated mechanic design and integrated electrical equipment - in particular drive systems and the CNC-control - to realize the complex relative motion of tool towards work piece. Beside the process related capabilities, like static and dynamic stiffness as well as accuracy behavior and deviation resistance against thermal influence, safety aspects are of major interest. The machine tool enclosure must fulfill multiple requirements like retention capabilities against the moving parts of broken tools, lose work pieces or clamping components. In regular use, the noise emission have to be inhibited at the greatest possible extent by the machine tool enclosure. Nevertheless, the loading door and the moving parts of the workspace envelope are interfaces where noise transmission is harder to be avoided and therefore local noise emissions increase. The aim of the objective investigation is to analyse the noise emission of machine tools to determine the local noise transmission of a machine tool enclosure by using arrays of microphones. By the use of this measuring method, outer surfaces at the front, the side and on the top of the enclosure have been scanned. The local transient acoustic pressures have been recorded using a standard noise source placed on the machine table. In addition, an exemplary manufacturing process has been performed to analyse the frequency dependent location resolved sound emissions.

scholarly journals English Language Writing Centres in Japanese Universities: What do Students Really Need?

2010 ◽  
pp. 17-31
Author(s):  
Jim McKinley
Keyword(s):  
Liberal Arts ◽  
English Language ◽  
Language Education ◽  
Ministry Of Education ◽  
English Language Education ◽  
Attitudes Toward Writing ◽  
The Us ◽  
Language Writing ◽  
Efl Students ◽  
Students Attitudes

The installation of English language writing centres in Japanese universities is a relatively recent event—the first ones established with funding from the Ministry of Education in 2004. Because of the EFL writing context, setting up a writing centre requires consideration of students’ needs and cultural expectations of writing and writing centres. In general, writing centres that have been established in Japanese universities follow a structure similar to those in the US. This raises the question as to whether or not this is appropriate for the particular needs of EFL students and the obstacles they face. For this study, in order to explore students’ attitudes toward writing centres and the role they play in writing education, interview data was collected from students of English composition in two different departments at a university in Japan well known for its English language education: the English department, which does not have a writing centre, and the liberal arts department, which has one of the first writing centres established in Japan.

scholarly journals Development of the common standard for revenue recording as a part of the US GAAP and IAS/IFRS systems convergence

2009 ◽  
Vol 57 (6) ◽  
pp. 29-44
Author(s):  
Hana Bohušová
Keyword(s):  
Comparative Analysis ◽  
Revenue Recognition ◽  
New Approach ◽  
Joint Project ◽  
Starting Point ◽  
Significant Difference ◽  
The Us ◽  
Limited Application ◽  
General Standard ◽  
Us Gaap

The most significant difference between US GAAP and IFRSs is in the area of general approach. IFRSs are based on basic accounting principles1 with limited application guidance, US GAAPs are based especially on rules with specific application guidance. FASB and IASB initiated their joint project on revenue recording to converge IFRS and US GAAP in this area. The main objective of this paper is comparative analysis of revenue recognition under both systems, evaluation of the most significant differences in revenue recognition and measurements as a starting point for the preparation of the new general standard for revenue recognition and the new approach to the revenue recognition development.In this paper, the current approaches to revenue recognition under both systems are compared. The most significant difference is the general approach to revenue recognition. There is the Conceptual Framework where revenue is defined, two standards on revenue recognition and interpretations concerning revenue recognition and measurement in the IAS/IFRS. On the other hand, there are many standards and guidance concerning revenue in the US GAAP. Revenue is defined in the Statements of Financial Accounting concepts (CON 5, CON 6). There is not any general standard for revenue recognition under the US GAAP. The most significant differences in revenue recognition concern the long-term contracts and deferred payments. Despite this difference, there are many similarities between both systems.Based on the results of the comparative analysis which was done in the paper, a new approach for re­ve­nue recognition based on principles for the new general standard for revenue recognition common for both systems is being developed.

scholarly journals Analysis of Dynamic Characteristics for Machine Tools Based on Dynamic Stiffness Sensitivity

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2260
Author(s):  
Chunhui Li ◽  
Zhiqiang Song ◽  
Xianghua Huang ◽  
Hui Zhao ◽  
Xuchu Jiang ◽  
...  
Keyword(s):  
Machine Tool ◽  
Dynamic Characteristics ◽  
Machine Tools ◽  
Dynamic Stiffness ◽  
Variable Stiffness ◽  
Structural Vibration ◽  
Dynamic Experiment ◽  
Machine Tool Structure ◽  
Analysis Experiment ◽  
Five Axis

Dynamic parameters are the intermediate information of the entirety of machine dynamics. The differences between components have not been combined with the structural vibration in the cutting process, so it is difficult to directly represent the dynamic characteristics of the whole machine related to spatial position. This paper presents a method to identify sensitive parts according to the dynamic stiffness-sensitivity algorithm, which represents the dynamic characteristics of the whole machine tool. In this study, two experiments were carried out, the simulation verification experiment (dynamic experiment with variable stiffness) and modal analysis experiment (vibration test of five-axis gantry milling machine). The key modes of sensitive parts obtained by this method can represent the position-related dynamic characteristics of the whole machine. The characteristic obtained is that the inherent properties of machine-tool structure are independent of excitation. The method proposed in this paper can accurately represent the dynamic characteristics of the whole machine tool.

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