scholarly journals High-accuracy thrust measurements of the EMDrive and elimination of false-positive effects

Author(s):  
M. Tajmar ◽  
O. Neunzig ◽  
M. Weikert

AbstractThe EMDrive is a proposed propellantless propulsion concept claiming to be many orders of magnitude more efficient than classical radiation pressure forces. It is based on microwaves, which are injected into a closed tapered cavity, producing a unidirectional thrust with values of at least 1 mN/kW. This was met with high scepticism going against basic conservation laws and classical mechanics. However, several tests and theories appeared in the literature supporting this concept. Measuring a thruster with a significant thermal and mechanical load as well as high electric currents, such as those required to operate a microwave amplifier, can create numerous artefacts that produce false-positive thrust values. After many iterations, we developed an inverted counterbalanced double pendulum thrust balance, where the thruster can be mounted on a bearing below its suspension point to eliminate most thermal drift effects. In addition, the EMDrive was self-powered by a battery-pack to remove undesired interactions due to feedthroughs. We found no thrust values within a wide frequency band including several resonance frequencies and different modes. Our data limit any anomalous thrust to below the force equivalent from classical radiation for a given amount of power. This provides strong limits to all proposed theories and rules out previous test results by at least two orders of magnitude.

2017 ◽  
Author(s):  
G. Lohmann ◽  
J. Stelzer ◽  
K. Müller ◽  
E. Lacosse ◽  
T. Buschmann ◽  
...  

AbstractReproducibility is generally regarded as a hallmark of scientific validity. It can be undermined by two very different factors, namely inflated false positive rates or inflated false negative rates. Here we investigate the role of the second factor, i.e. the degree to which true effects are not detected reliably. The availability of large public databases and also supercomputing allows us to tackle this problem quantitatively. Specifically, we estimated the reproducibility in task-based fMRI data over different samples randomly drawn from a large cohort of subjects obtained from the Human Connectome Project. We use the full cohort as a standard of reference to approximate true positive effects, and compute the fraction of those effects that was detected reliably using standard software packages at various smaller sample sizes. We found that with standard sample sizes this fraction was less than 25 percent. We conclude that inflated false negative rates are a major factor that undermine reproducibility. We introduce a new statistical inference algorithm based on a novel test statistic and show that it improves reproducibility without inflating false positive rates.


2011 ◽  
Vol 2011 (CICMT) ◽  
pp. 000091-000098
Author(s):  
Tobias Kühnlein ◽  
Silvan Poller ◽  
Martin Rauscher ◽  
Alexander Klonczynski

Piezo multilayer ceramics are increasingly used under extreme condition such as high pressures in engine injection systems. The mechanical stability and reliability of the ceramic multilayer is of major importance for proper operation. Critical functional defects are caused by material fracture and flaw extension in the device. The flaw propagation in PZT-multilayer ceramics under mechanical load was examined using impedance spectroscopy and three-point-bending studies. Initial flaws were generated by applying a sinus ac-field on the specimens. The cracks were successively promoted and after the release of the external mechanical load the impedance spectroscopy was conducted. As a measure for flaw extension, the shift in the resonance frequencies and the sub-resonance height of the impedance spectroscopy was used. A functional dependence of the resonance frequency and the phase shift on the crack length was found. The crack propagation was studied on flaws starting at the positive and negative electrode, respectively. The maximum fracture strength as well as the crack path depends on the electrode potentials. The variation in the fracture strength was caused by the different observed fracture mode: interface cracking, matrix-cracking and a combination of both. The morphology of the fracture faces was ascribed to an anisotropic behaviour, which is created by the sample processing, e.g. the poling process. A modified poling procedure with a lower poling temperature was analysed, which yielded a reduction of the anisotropy of the electrode strength. Impedance spectroscopy was found as a reliable measurement tool for automated flaw detection in PZT-multilayer ceramics.


2020 ◽  
Author(s):  
Jan Walleczek ◽  
Von Stillfried

A general commentary by Walleczek and von Stillfried (2020) was recently published in Frontiers in Psychology. The present work provides an account of (i) the detailed research record and (ii) the main arguments behind the commentary for the purpose of full transparency and disclosure. For historical overview, Walleczek and von Stillfried (2019) had previously reported (i) the absence of any true-positive effects and (ii) the presence of one false-positive effect in a commissioned replication study of the Radin double-slit (DS) experiment on observer consciousness. In their subsequent misrepresentations, Radin et al. (2019, 2020) regrettably used the malpractice of undisclosed HARKing, i.e., undisclosed hypothesizing after the results are known. HARKing can increase greatly the risk of false-negative or false-positive conclusions. Specifically, Radin et al. (2019, 2020) deviated in two major ways from the pre-specified protocol for this commissioned study, which (i) was agreed to by Radin before data collection was started (Radin, 2011) and (ii) included data encryption to prevent the use of p-hacking and HARKing. First, Radin et al. (2019) violate the original research design by reporting a so-called “true-positive outcome of a secondary planned hypothesis”. Contrary to the claim by Radin et al. (2019, 2020), that hypothesis was not, however, part of the planned test strategy, but, instead, the associated statistical analysis – a chi-square test – was chosen by Radin sometime after the planned statistical analysis had been completed and the data unblinded. Second, Radin et al. (2019, 2020) violate the funder-approved research design in an additional way by falsely claiming that the newly developed protocol, i.e., the advanced meta-experimental protocol (AMP), implements a non-predictive test strategy when – in fact – the AMP-based test strategy is strictly predictive. Put simply, Radin et al. (2019, 2020) are mistaken that the funder-approved hypotheses posited the random occurrence of effects for the test categories in this replication experiment; instead, a different specific prediction was tested in each of the eight planned test categories, and true-positive effects were predicted to occur for only two (12.5%) of the 16 possible measurement outcomes of the eight planned single-test categories. Therefore, in the predictive single-testing regime, a statistical correction for non-predictive, i.e., random, multiple testing would not be appropriate and would thus violate the AMP-based strategy, which was implemented in the commissioned study based upon the planned outcome predictions as pre-specified in Radin (2011). Neither of these post-hoc changes by Radin et al. (on the basis of HARKing) were disclosed in Radin et al. (2019, 2020) and both these changes violate the funder-approved, original methodology agreed upon in Radin (2011) and pre-specified in the research contract. In summary, the present work reconfirms that – exactly as reported in Walleczek and von Stillfried (2019) – “the false-positive effect, which would be indistinguishable from the predicted true-positive effect, was significant at p = 0.021 (σ = −2.02; N = 1,250 test trials)” and “no statistically significant effects could be identified” in those two groups for which true-positives were predicted to occur. These observations are consistent also with an independent statistical reanalysis of the Radin DS-experiment by Tremblay (2019) and a replication attempt by Guerrer (2019). Tremblay reported significant false-positives in control groups and Guerrer found significant effects with post-hoc analyses only, but null results only when using the planned confirmatory analysis. As a general recommendation, the authors call for the implementation of advanced control-test strategies, including novel approaches from the metascience reform movement, for empirically detecting and preventing uncontrolled false-positive effects in parapsychological research.


1997 ◽  
Vol 131 (4) ◽  
pp. 371-382 ◽  
Author(s):  
Douglas M. Klieger ◽  
Kimberly K. Siejak

2012 ◽  
Vol 7 (6) ◽  
pp. 531-536 ◽  
Author(s):  
Harold Pashler ◽  
Christine R. Harris

We discuss three arguments voiced by scientists who view the current outpouring of concern about replicability as overblown. The first idea is that the adoption of a low alpha level (e.g., 5%) puts reasonable bounds on the rate at which errors can enter the published literature, making false-positive effects rare enough to be considered a minor issue. This, we point out, rests on statistical misunderstanding: The alpha level imposes no limit on the rate at which errors may arise in the literature (Ioannidis, 2005b). Second, some argue that whereas direct replication attempts are uncommon, conceptual replication attempts are common—providing an even better test of the validity of a phenomenon. We contend that performing conceptual rather than direct replication attempts interacts insidiously with publication bias, opening the door to literatures that appear to confirm the reality of phenomena that in fact do not exist. Finally, we discuss the argument that errors will eventually be pruned out of the literature if the field would just show a bit of patience. We contend that there are no plausible concrete scenarios to back up such forecasts and that what is needed is not patience, but rather systematic reforms in scientific practice.


Author(s):  
A. A. Sabirzyanov ◽  

In this paper, an inertial device of the simplest design is proposed, which allows us to visually analyze the principle of its operation. The device is a radio-controlled car placed on the bottom of a long light cardboard box. The box is on the table. Using the remote control, the car accelerates and collides with one of the walls. On impact, the box moves across the table. Next, the car is taken to the opposite wall by the remote control without a collision. Then the process is repeated, as a result of which the device jerks along the table in one direction (in the example - to the right). The advantage of this method of control is that it is contactless, the disadvantage is that it is manual. In the framework of classical mechanics, the average speed of the box movement on the table is calculated. It depends on the ratio of the mass of the car and the box, the proportion of weight that falls on the driving wheels, the coefficient of friction between the wheels and the bottom of the box, the coefficient of friction between the box and the table, the difference in the length of the box and the car. It is shown that the average speed with a decrease in the friction force on the side of the support should first increase, and with a further decrease in friction - decrease. A condition is found under which the dependence of the average velocity on the friction force has a maximum.


2016 ◽  
Vol 64 (2) ◽  
pp. 333-338
Author(s):  
M. Sikoń

Abstract In this work, the Cosserat medium is analyzes as a set of atoms. These atoms are under the action of a mechanical load. The statistical analysis is preceded by a description of a single atom using classical mechanics and quantum mechanics. The behavior of the atoms in the field generated by mechanical change of the interatomic distance is shown as a phenomenon which can explain the Cosserat mechanics in a continuum.


2020 ◽  
Vol 32 (1) ◽  
pp. 16-28 ◽  
Author(s):  
Alwathiqbellah Ibrahim ◽  
Geofrey Yamomo ◽  
Ryan Willing ◽  
Shahrzad Towfighian

Triboelectric energy harvesting is a relatively new technology showing promise for biomedical applications. This study investigates a triboelectric energy transducer for potential applications in total knee replacement both as an energy harvester and a sensor. The sensor can be used to monitor loads at the knee joint. The proposed transducer generates an electrical signal that is directly related to the periodic mechanical load from walking. The proportionality between the generated electrical signal and the load transferred to the knee enables triboelectric transducers to be used as self-powered active load sensors. We analyzed the performance of a triboelectric transducer when subjected to simulated gait loading on a joint motion simulator. Two different designs were evaluated: one made of Titanium on Aluminum (Ti-PDMS-Al) and the other made of Titanium on Titanium (Ti-PDMS-Ti). The Ti-PDMS-Ti design generates more power than Ti-PDMS-Al and was used to optimize the structural parameters. Our analysis found these optimal parameters for the Ti-PDMS-Ti design: external resistance of 304 MΩ, a gap of 550 µm, and a thickness of the triboelectric layer of 50 µm. Those parameters were optimized by varying resistance, gap, and the thickness while measuring the power outputs. Using the optimized parameters, the transducer was tested under different axial loads to check the viability of the harvester to act as a self-powered load sensor to estimate the knee loads. The forces transmitted across the knee joint during activities of daily living can be directly measured and used for self-powering, which can lead to improving the total knee implant functions.


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