scholarly journals The effect of assembly and static unbalance on reaction wheel assembly bearing harmonics

2020 ◽  
Author(s):  
Cameron Hodge ◽  
Alessandro Stabile ◽  
Guglielmo Aglietti ◽  
Guy Richardson
Keyword(s):  
Rotational Speed ◽  
Significant Variation ◽  
Test Rig ◽  
Reaction Wheel ◽  
Top Down ◽  
Engine Order ◽  
Resonance Frequencies ◽  
Manufacturing Parameters ◽  
Different Levels ◽  
Motor Disturbances

AbstractReaction wheel assemblies (RWA) are well-known major sources of microvibrations, whilst they have been studied thoroughly and many disturbance types can be reasonably modelled, bearing disturbances and how their amplitude evolves with the RWA rotational speed are not at the same level of confidence. Whilst studies have been carried out, many of the test rigs used do not truly show the bearing harmonic development, either due to interference from other disturbances such as structural modes or are not representative of an RWA. This study aims to design and validate a test rig which alleviates those issues by moving the resonance frequencies out of a range of interest and isolating the motor disturbances. Using this test rig, it was possible to observe many engine order development without any inference and start to investigate some of the effects some manufacturing parameters can have. The two studied and discussed in this paper were the effect of reassembly and static unbalance. Investigating the microvibration signature at different levels ranging from a top-down to individual harmonics it showed a clear significant variation between disturbance amplitudes.

scholarly journals The Role of Figurative Complexity in the Comprehension and Appreciation of Advertisements

2018 ◽  
Vol 40 (6) ◽  
pp. 957-991 ◽  
Author(s):  
Paula Pérez-Sobrino ◽  
Jeannette Littlemore ◽  
David Houghton
Keyword(s):  
Significant Variation ◽  
Processing Time ◽  
Consumer Response ◽  
Cross Cultural ◽  
Cultural Variation ◽  
Perceived Effectiveness ◽  
The Uk ◽  
Linguistic Backgrounds ◽  
Different Levels

Abstract To date, research in advertising has focussed almost exclusively on metaphor, with linguists and marketing scholars paying very little attention to alternative types of figurative expression. Beyond the finding that metaphor leads to an increased appreciation of advertisements, there has been surprisingly little research into how consumer response is affected by metonymy, or by metaphor–metonymy interactions. In this article, we present findings from a study that investigated the depth to which participants (n = 90) from a range of cultural and linguistic backgrounds (the UK, Spain, and China) were found to process 30 real-world adverts featuring creative metaphor and metonymy in multimodal format. We focus on the cross-cultural variation in terms of time taken to process, appreciation and perceived effectiveness of adverts, and on individual differences explained by different levels of need for cognition. We found significant variation in the understanding of advertisements containing metaphor, metonymy, and combinations of the two, between subjects and across nationalities in terms of (i) processing time, (ii) overall appeal, and (iii) the way in which participants interpreted the advertisements.

scholarly journals Modularity and derivation in Functional Discourse Grammar

2017 ◽  
Vol 33 (1) ◽  
pp. 1-23
Author(s):  
Daniel GARCÍA VELASCO
Keyword(s):  
Central Issue ◽  
Top Down ◽  
Basic Principles ◽  
External Constraints ◽  
Language Structure ◽  
Maximal Depth ◽  
Linguistic Representations ◽  
Discourse Grammar ◽  
Theory Of Language ◽  
Different Levels

ABSTRACT Functional Discourse Grammar (FDG) is a typologically-based theory of language structure which is organized in levels, layers and components. In this paper, I will claim that FDG is modular in Sadock’s sense, as it presents four independent levels of representation with their own linguistic primitives each. For modular grammars, the relation between the different levels (more technically, the nature of the interfaces) is a central issue. It will be shown that FDG is a top-down grammar which follows two basic principles in its dynamic implementation: Depth-first and Maximal depth. Together with external constraints, these principles conspire to create linguistic representations which are psychologically adequate and which allow levels to be circumvented if necessary, thus simplifying representations and creating mismatches among them.

scholarly journals Effect of Mulch and Different Levels of N and K on the Growth and Yield of Onion

2013 ◽  
Vol 21 (1-2) ◽  
pp. 39-46 ◽  
Author(s):  
KS Islam ◽  
MHA Miah ◽  
SU Ahmed
Keyword(s):  
Yield Components ◽  
Significant Variation ◽  
Growth And Yield ◽  
Nitrogen Level ◽  
Straw Mulch ◽  
Yield And Yield Components ◽  
Different Levels ◽  
Bulb Yield

An experiment was conducted to study the effect of mulch (non-mulch and straw mulch) and different levels of nitrogen (0, 40, 80 and 120 kg ha-1) and potassium (0, 37.5, 75 and 112.5 kg ha-1) on the growth and yield of onion. Plants grown with straw mulch gave higher bulb yield (10.89 t ha-1) which showed 13.79% increase over non-mulch. Nitrogen increased the bulb yield significantly.The highest nitrogen level gave the highest bulb yield (12.13 t ha-1), which was 41.54% increase over control. Potassium increased bulb yield compared to control, but its different levels had identical results on yield. Nitrogen and mulch together produced significant variations. The Nitrogen at the highest level (120 kg ha-1) along with straw mulch gave the highest yield (13.31 t ha-1). Potassium together with mulch also exhibited significant variation on yield and yield components. Plants grown with the highest level of potassium (112.5 kg ha-1) along with straw mulch gave the highest bulb yield (11.58 t ha-1). Nitrogen and potassium as 120 kg N ha-1 × 75.0 kg K ha-1 gave the highest bulb yield (13.07 t ha-1). Nitrogen and potassium at their maximum levels with straw mulch gave the highest bulb yield (14.67 t ha-1).DOI: http://dx.doi.org/10.3329/pa.v21i1-2.16747 Progress. Agric. 21(1 & 2): 39 - 46, 2010

Strategies of LMS Implementation at German Universities

2012 ◽  
pp. 522-541
Author(s):  
Carola Kruse ◽  
Thanh-Thu Phan Tan ◽  
Arne Koesling ◽  
Marc Krüger
Keyword(s):  
Academic Staff ◽  
Federal State ◽  
Top Down ◽  
Lower Saxony ◽  
Online Tool ◽  
General Aspects ◽  
The University ◽  
Different Levels ◽  
German Federal State ◽  
German Universities

In Germany, a learning management system (LMS) has become an everyday online tool for the academic staff and students at almost every university. Implementing an LMS, however, can be very different depending on the university. We introduce some general aspects on the strategies at German universities on how to implement an LMS. These aspects are mainly influenced by two main approaches, the top-down and bottom-up approach, which determine the decisions and actions on different levels at the university. In order to show how the strategies are carried out, we are presenting three case studies from universities based in the German federal state of Lower Saxony. We are going to reveal that both approaches play a part in each strategy, however differently weighted. It becomes clear that networking and collaboration plays a crucial role, not only concerning the technical development of the LMS software but also in organisational and educational terms.

Strategies of LMS Implementation at German Universities

2012 ◽  
pp. 315-334
Author(s):  
Carola Kruse ◽  
Thanh-Thu Phan Tan ◽  
Arne Koesling ◽  
Marc Krüger
Keyword(s):  
Academic Staff ◽  
Federal State ◽  
Top Down ◽  
Lower Saxony ◽  
Online Tool ◽  
General Aspects ◽  
The University ◽  
Different Levels ◽  
German Federal State ◽  
German Universities

In Germany, a learning management system (LMS) has become an everyday online tool for the academic staff and students at almost every university. Implementing an LMS, however, can be very different depending on the university. We introduce some general aspects on the strategies at German universities on how to implement an LMS. These aspects are mainly influenced by two main approaches, the top-down and bottom-up approach, which determine the decisions and actions on different levels at the university. In order to show how the strategies are carried out, we are presenting three case studies from universities based in the German federal state of Lower Saxony. We are going to reveal that both approaches play a part in each strategy, however differently weighted. It becomes clear that networking and collaboration plays a crucial role, not only concerning the technical development of the LMS software but also in organisational and educational terms.

scholarly journals Experimental Study on the Dynamic Performance of Water-Lubricated Rubber Bearings with Local Contact

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Wu Ouyang ◽  
Xuebing Zhang ◽  
Yong Jin ◽  
Xiaoyang Yuan
Keyword(s):  
Rotational Speed ◽  
Dynamic Performance ◽  
Water Film ◽  
Mixed Lubrication ◽  
Contact Friction ◽  
Specific Pressure ◽  
Test Rig ◽  
Identification Method ◽  
Bearing Stiffness ◽  
Rubber Bearings

Accurate dynamic characteristic coefficients of water-lubricated rubber bearings are necessary to research vibration of ship propulsion system. Due to mixed lubrication state of water-lubricated rubber bearings, normal test rig and identification method are not applicable. This paper establishes a test rig to simulate shaft misalignment and proposes an identification method for water-lubricated rubber bearings, which utilizes rotor unbalanced motion to produce self-excited force rather than artificial excitation. Dynamic performance tests under different conditions are operated. The results show that when rotational speed is less than 700 r/min, even if specific pressure is 0.05 MPa, it is difficult to form complete water film for the rubber bearing which was investigated, and contact friction and collision of the shaft and bearing are frequent. In the mixed lubrication, water film, rubber, and contact jointly determine dynamic characteristics of water-lubricated rubber bearings. The contact condition has a significant effect on the bearing stiffness, and water film friction damping has a significant effect on bearing damping. As for the particular investigated bearing, when rotational speed is in the range of 400~700 r/min and specific pressure is in the range of 0.03~0.07 MPa, bearing stiffness is in the range of 5.6~10.06 N/μm and bearing damping is in the range of 1.25~2.02 Ns/μm.

Dynamics of Species and Size Structures of Phytoplankton at Different Levels of Bottom-Up and Top-Down Effects in Experimental Conditions

2019 ◽  
Vol 12 (3) ◽  
pp. 245-253 ◽  
Author(s):  
E. G. Sakharova ◽  
I. Yu. Feniova ◽  
Z. I. Gorelysheva ◽  
M. Rzepecki ◽  
I. Kostshevska-Shlakovska ◽  
...  
Keyword(s):  
Top Down ◽  
Experimental Conditions ◽  
Bottom Up ◽  
Different Levels

Spracherhalt als Prozess: Elemente des kirchlichen Sprachmanagements bei den katholischen Sorben

2015 ◽  
Vol 2015 (232) ◽  
Author(s):  
Goro Christoph Kimura
Keyword(s):  
Language Maintenance ◽  
Language Shift ◽  
Management Theory ◽  
Actual Process ◽  
Language Management ◽  
Top Down ◽  
Language Maintenance And Shift ◽  
The Church ◽  
Different Levels

AbstractIn contrast to language shift, language maintenance appears to be a static phenomenon. Yet this article displays language maintenance as a process, applying the Language Management Theory. On the ground of a case study at a Catholic Sorbian parish in eastern Germany, the study shows that the Sorbian language is maintained in the church through numerous minute interventions at different levels. The findings suggest that the actual process of language maintenance and shift is much more complex than the conventional dualism of “top-down” vs. “bottom-up” assumes. It is argued that in order to get a more reliable understanding of how language maintenance and shift is attained, it is necessary to pay due attention to the interplay of various processes between and within simple and organized management.

Influence of Gas Feeding Position on the Performance of Radial-Inflow Hydrostatic Gas Ultra-Short Journal Bearings

2016 ◽  
Author(s):  
Chao Nie ◽  
Xiaojun Yan ◽  
Xia Chen
Keyword(s):  
Rotational Speed ◽  
Cfd Simulation ◽  
Journal Bearing ◽  
Maximum Speed ◽  
Test Rig ◽  
Thrust Bearings ◽  
Axial Stability ◽  
Speed Measurement ◽  
Gas Leaks ◽  
Better Than

To investigate the influence of gas feeding position on the performance of radial-inflow hydrostatic gas ultra-short (with a L/D value as 0.1) journal bearing two rotor-bearing system test rigs with two different feeding positions (central feeding and bottom feeding) for the journal bearing were designed. A rotor measurement system with an original rotational speed measurement program is built. Rotation experiments to measure the maximum rotational speed of rotors under different inlet pressure of journal bearing were conducted. It was found that, the rotor supported by the central feeding journal bearing worked better, and achieved a maximum rotational speed of 40000 rpm, (83.74m/s for the tip speed). While the test rig with bottom feeding journal bearing could not function well. To verify the reasons behind the failure mentioned above, the flow condition in the journal clearance and the rotor bottom clearance was analyzed by the CFD simulation. It shows that most of the journal bearing gas “leaks” into the rotor bottom clearance in the bottom feeding bearing test rig, disarranging the axial stability of the rotor and the normal functioning of the thrust bearings. In conclusion, the central feeding radial-inflow journal bearing is better than the bottom feeding one, for the better operability and higher maximum speed. And an ideal feeding position is supposed to make the journal bearing does not influence the axial stability of the rotor and the functioning of the thrust bearings.

On the Performance of Porous Sound Absorbent Ceramic Lining in a Combustion Chamber Test Rig

2013 ◽  
Author(s):  
Hans-Christoph Ries ◽  
Mateus Vieira Carlesso ◽  
Christian Eigenbrod ◽  
Stephen Kroll ◽  
Kurosch Rezwan
Keyword(s):  
Combustion Chamber ◽  
Sound Pressure Level ◽  
Gas Turbines ◽  
Sound Pressure ◽  
Porous Ceramic ◽  
Pressure Level ◽  
Test Rig ◽  
Resonance Frequencies ◽  
Lean Premixed ◽  
Ceramic Lining

This paper discusses the potential of using porous ceramic lining as insulating material in combustion chambers with respect to their sound absorbent ability to suppress thermoacoustic instabilities. For this purpose a combustion chamber test rig was developed and different types of ceramic linings were tested. The examined range of power was between 40 and 250 kW and the air-propane equivalence ratio was between 1.2 and 2.0. The overall sound pressure level and frequency domain of a lean premixed swirl stabilized and piloted burner are presented. The resonance frequencies and sound pressure levels are obtained and compared for the different combustion chamber linings. The results show a significant decrease in overall sound pressure level by up to 23.5 dB for sound absorbent lining in comparison to the common sound reflecting combustion chamber lining. In summary, sound absorbent ceramic combustion chamber lining can contribute to improve the stability of lean premixed gas turbines.

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