Acceleration Factor

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Estimating the parameters of Weibull distribution and the acceleration factor from hybrid partially accelerated life test

Estimating the parameters of Weibull distribution and the acceleration factor from hybrid partially accelerated life test

In this paper I have considered the classical inference procedure for the unknown parameters of the Weibull distribution and the acceleration factor when the data are hybrid censored from step-stress partially accelerated life tests. It is observed that the maximum likelihood estimators can not be obtained in closed form and I have proposed to use the Newton–Raphson as an iterative method to compute them. The approximate confidence intervals of the model parameters are also con- structed. The performances of the estimators are investigated by Monte Carlo simulations and it is observed that they are quite satisfactory. Finally, as a future work, further studies of finding optimal censoring schemes and another important as- pect, namely goodness of fit test from hybrid censored data should be addressed. More work is needed in those directions. Acknowledgments
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Parallel imaging: is GRAPPA a useful acquisition tool for MR imaging intended for volumetric brain analysis?

Parallel imaging: is GRAPPA a useful acquisition tool for MR imaging intended for volumetric brain analysis?

The HERMES MultiModality program was also used for hippocampus volume measurement using a manual out- lining technique. Analysis was performed using only images acquired with acceleration factor two. A single trained operator performed all measurements. The bor- ders of both left and right hippocampi were delineated on each image slice from posterior to anterior to generate a series of regions of interest (ROIs). The first ROI was drawn on the slice where crus of the fornix could be seen in full profile. The measurements ended where the hip- pocampus disappeared under the amygdala. The summed volume of each ROI gave the hippocampus volume. The complete evaluation of whole brain segmentation and hippocampus volume measurement was performed on data of each patient acquired on two separate occa- sions.
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Acceleration of tissue phase mapping with sensitivity encoding at 3T

Acceleration of tissue phase mapping with sensitivity encoding at 3T

One volunteer underwent a black blood prepared, respiratory gated, cardiac phase resolved 3D anatomical and velocity encoded acquisition. For maximal accelera- tion a SENSE acceleration factor of R = 4 was chosen. Data were acquired on a 3T whole body MR scanner (Achieva 3.0T, Philips, Best, The Netherlands) with a 32 [2 × 4 ×4] channel phased array cardiac coil. The acqui- sition protocol is listed in table 1.

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Hydrogen Enhanced Fatigue Crack Growth Rates in a Ferritic Fe-3wt%Si Alloy

Hydrogen Enhanced Fatigue Crack Growth Rates in a Ferritic Fe-3wt%Si Alloy

Figure 3: a) Fatigue crack growth rate curves of Fe3%Si material in air and under different load ration and frequency levels. Red curves indicate test in air and blue curves indicates in-situ electrochemically charged tests. Full markers indicate test conducted at R=0.1 while empty markers the ones at R=0.5. Round, square and triangle markers indictes test carried out at 10 Hz, 1 Hz and 0.1 Hz, respectively. b) Table reporting the Paris law constants C and m obtained at different conditions. The acceleration factor for K=16 MPa√m is also reported.
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Improving the Reliability of a Domestic  Refrigerator Compressor Subjected to  Repetitive Loading

Improving the Reliability of a Domestic Refrigerator Compressor Subjected to Repetitive Loading

As a reliability quantitative specification, parametric accelerated life testing was used to assess the reliability of a newly designed compressor of a commercial refrigerator subjected to repetitive stresses. A generalized life-stress failure model and new sample size equation with a new load concept were derived starting with the basic refrigeration cycle. The sample size equation with the acceleration factor also enabled the parametric accelerated life testing to quickly evaluate the expected lifetime. The design of this testing should help an engineer uncover the design parame- ters affecting reliability during the design process of the compressor system. Consequently, it should help companies improve product reliability and avoid recalls due to the product failures in the field. A newly designed compressor in a commercial refrigerator was used as a test case.
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Two-stage estimation to adjust for treatment switching in randomised trials: a simulation study investigating the use of inverse probability weighting instead of re-censoring

Two-stage estimation to adjust for treatment switching in randomised trials: a simulation study investigating the use of inverse probability weighting instead of re-censoring

AF: Acceleration factor; CI: Confidence interval; HR: Hazard ratio; HTA: Health technology assessment; IPCW: Inverse probability of censoring weights; ITT: Intention to treat; MSM: Margi[r]

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Trade with time zone differences: factor market implications

Trade with time zone differences: factor market implications

In the existing trade literature, however, relatively few attempts have been made to address the effect of trade with time zone differences on labor markets. The main purpose of this study is to illustrate, with a simple two-factor (skilled labor and unskilled labor) trade model, how a time-saving improvement in business-services trade benefitting from dif- ferences in time zones can have an impact on national factor markets. For these purposes, we extend Marjit’s (2007) framework into the case with the night-shift work. By doing so, we intend to capture the situation where the night-shift work in one country is replaced by the day-shift work in another country. In other words, we will show that, trade with time zone differences will result in shifts of the relative supplies and demands for skilled labor around the globe.
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Probabilistic seismic hazard assessment of the historical peninsula of Istanbul

Probabilistic seismic hazard assessment of the historical peninsula of Istanbul

According to the Turkish seismic design code the design acceleration value for first-degree earthquake zone of Turkey is defined as 0.40 g. In this study, the bedrock peak accelera- tion value reaches 0.40 g according to a 10 % probability of exceedance. In cases where there are thick soil layers over bedrock, the earthquake wave will undergo ground amplifi- cation until it reaches the ground surface especially in soft clay layers and fill, which results in a surface peak ground acceleration value much higher than 0.40 g. Therefore, it is recommended that a more realistic acceleration value be de-
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Climbing flight performance and load carrying in lesser dog faced fruit bats (Cynopterus brachyotis)

Climbing flight performance and load carrying in lesser dog faced fruit bats (Cynopterus brachyotis)

wing stroke amplitude wingspan wingbeat frequency the magnitude of acceleration due to gravity induced velocity correction factor body mass induced hovering power kinetic power climbing [r]

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The Acceleration Of Tooth Movement: A Review

The Acceleration Of Tooth Movement: A Review

distraction devices usually custom made to cater to each patient’s individual needs are used for rapid canine retraction (Kurt et al., 2010). DAD is found to reduce treatment time by 50%. And it is feasible in dental practice (Liou and Huang 1998). However it poses some disadvantages in the form of invasiveness and aggressiveness. It’s a bit costly compared to the other options available. The acceleration in some of the studies was seen for few months and then declined to the same level (Gurgan et al., 2005). (Table 3)

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The acceleration dilemma : can English law accommodate constructive acceleration?

The acceleration dilemma : can English law accommodate constructive acceleration?

Whilst the American doctrine seems to be a useful tool to resolve an otherwise complex legal problem, it does not rely on established common law principles due its origin in U.S. appeal board decisions. Even American authors suggest that more conventional grounds for such claims are ‘implied contract’ (Cibinic et al., 2006) or breach of contract (Barry Bramble & Callahan, 2011; Gusman, 1974). Gusman argues that the use of the ‘fictional’ constructive acceleration doctrine in place of more orthodox common-law grounds limits a contractor’s rights to an equitable remedy under the contract, when ‘the measure of recovery should be governed by the remedy of damages or restitution’ (1974, p. 243). In American government contracts, this limitation restricts foreseeable consequential costs, which would otherwise be recoverable in a claim for common-law damages (Cibinic et al., 2006).
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Alternative vehicle electronic architecture for individual wheel control

Alternative vehicle electronic architecture for individual wheel control

vertical acceleration sensor 3 lateral acceleration sensor 1 lateral acceleration sensor 2 longitudinal acceleration sensor steering angle sensor yaw rate sensor rear wheel spin sensor 1[r]

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Application of pre-stressed SMA-based tuned mass damper to a timber floor system

Application of pre-stressed SMA-based tuned mass damper to a timber floor system

Timber floor is a common structural system utilised around the world, as such flooring materials can add benefits to construction; for example, they are light-weight, pre-fabricated and environmentally friendly because of their carbon storage capacities. However, human activities and machine operations can cause excessive vibrations in timber floors. Such excessive vibration can lead to building occupants experiencing uncomfortable sensations or even feeling anxious, which is a problem that designers should address (Hu et al., 2001, Smith and Chui, 1988, Thelandersson and Larsen, 2003). In order to investigate how to reduce timber floor vibration, several studies have examined the design criteria for this type of floor (Smith and Chui, 1988, Kalkert et al., 1995, Foschi et al., 1995, Al-Foqaha'a et al., 2001). The traditional passive approach requires the floor natural frequency to be higher than 8 Hz, which avoids resonance with human- induced vibration and requires less root mean square (RMS) acceleration response. With the development of vibration control techniques, studies on tuned mass damper (TMD) systems have been conducted in order to assess their application in floor systems as a more effective vibration reduction approach, with various levels of success (Breukelman and Haskett, 2001, Setareh et al., 2007, Baxter and Murray, 2003).
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Greenfield tunnelling in sands: the effects of soil density and relative depth

Greenfield tunnelling in sands: the effects of soil density and relative depth

to achieve a target value of C/D. The adopted Ng level of each test is reported in Table 1, where N is the centrifuge acceleration scale factor. The centrifuge package includes a strong box, soil, a model tunnel and a tunnel volume control system (refer to Marshall (2009), Zhou (2014) and Franza (2016) for full details). A dry silica sand known as Leighton Buzzard fraction E was used for testing. The model tunnel consisted of a cylinder with enlarged ends covered by a sealed latex sleeve. The annular gap between the sleeve and cylinder was filled with water. The tunnelling process (i.e. V l,t ) was
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Wing inertia and whole body acceleration: an analysis of instantaneous
aerodynamic force production in cockatiels (Nymphicus hollandicus)
flying across a range of speeds

Wing inertia and whole body acceleration: an analysis of instantaneous aerodynamic force production in cockatiels (Nymphicus hollandicus) flying across a range of speeds

Our model treats each wing section as a point mass. This is a reasonable assumption given the concentration of mass in each strip at the leading edge in the bone and muscle rather than in the feathers extending posterior and the large number of wing slices we employed (Van den Berg and Rayner, 1995). We merged the mass information from the standard wing with the 3-D kinematics by computing the position of each wing strip in each video frame, then distributing the appropriate number of strips between the shoulder, wrist and wingtip. We then derived the acceleration of each wing section in the global frame of reference by taking the 2nd derivative of a quintic spline fit between the successive positions of each wing strip. The resulting X-, Y- and Z-axis section accelerations were used (1)
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Level locomotion in wood ants: evidence for grounded running

Level locomotion in wood ants: evidence for grounded running

acceleration in the x-direction acceleration in the y-direction acceleration in the z-direction bipedal spring-loaded inverted pendulum centre of mass kinetic energy potential energy tot[r]

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The rebound of the body during uphill and downhill running at different speeds

The rebound of the body during uphill and downhill running at different speeds

The changes observed in uphill running are similar to those observed in old men running (Cavagna et al., 2008b). In older subjects, the average upward acceleration ( a v;ce ) is lower than in younger ones, leading to a symmetric rebound. According to these authors, the lower force attained during contact by the old subjects may be explained in part by the loss of muscular strength (e.g. Doherty, 2003). Similarly, the strategy adopted while running uphill could be due to the limits set by the muscular strength and/or power. Furthermore, in uphill running, the GRF vector is farther from the leg joint centres (DeVita et al., 2007). Thus, the slope of the terrain alters the muscle mechanical advantage by creating longer lever arms, and leads to higher joint torques and power outputs (Roberts and Belliveau, 2005). Therefore, decreasing T might be a beneficial strategy to limit the muscular moments and to reduce the mechanical load applied to the MTU.
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Computation of vertically averaged velocities in irregular sections of straight channels

Computation of vertically averaged velocities in irregular sections of straight channels

and Shiono (2007), Tang and Knight (2008) and Omran and Knight (2010). Apart from SKM, some other methods for analysing the conveyance capacity of compound chan- nels have been proposed. For example, Ackers (1993) for- mulated the so-called empirical coherence method. Lam- bert and Sellin (1996) suggested a mixing length approach at the interface whereas, more recently, Cao et al. (2006) reformulated flow resistance through lateral integration us- ing a simple and rational function of depth-averaged veloc- ity. Bousmar and Zech (1999) considered the main chan- nel/floodplain momentum transfer proportional to the prod- uct of the velocity gradient at the interface times the mass discharge exchanged through this interface due to turbulence. This method, called EDM (exchange divided method), also requires a geometrical exchange correction factor and turbu- lent exchange model coefficient for evaluating discharge.
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Improving a non linear model for simulating sand waves
An idealized modelling study on the effect of including suspended sediment and a critical condition for bed load transport on sand wave predictions in the North Sea

Improving a non linear model for simulating sand waves An idealized modelling study on the effect of including suspended sediment and a critical condition for bed load transport on sand wave predictions in the North Sea

It could also be that flow separation plays a role in the development of sand waves in shelf seas. Paarlberg (2007) studied the effect of flow separation on subaqueous dunes in sandy river beds. They state that flow separation already occurs in a non-permanent form over dunes with maximum lower leeside slopes of 14°. In another article (Paarlberg et al., 2009), they use a critical leeside slope of 10°, which means that flow separation occurs in their model when the leeside slope is over 10°. This means that it is unlikely that flow separation should play a role here, as the measured maximum slopes are in the order of 5°. The flow in a river is unidirectional, while the flow in a coastal shelf sea is oscillating. This means that flow separation will possibly only occur when a large residual current is present, because it takes a while to develop and this will not happen when the flow is just oscillating. Another small issue is that the shapes of the sand waves found in this research do not correspond with the shapes shown in the measurements. The measurements show sand waves that are more sharp-crested (Besio et al., 2004; van Santen et al., 2011). Németh et al. (2007) mentioned that sharper crested waves develop when . In this research only has been used and it was named for simplicity. The value of was set to zero in this research. The total slope factor ( )
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Design of Measurement Memory System Based on MEMS Acceleration Sensor

Design of Measurement Memory System Based on MEMS Acceleration Sensor

The control display module includes a storage unit and a communication unit, completes real-time reading and storage of the acceleration, and uses the serial com- munication circuit to upload the data to the computer. This module uses a micropro- cessor DSP (Digital Signal Processor) which is capable of high-speed digital signal processing operations. DSP adopts the Harvard structure, has independent program space and data space, whose program space and data space access simultaneously through an independent data bus. Built-in high-speed multipliers and enhanced multi- stage pipelines enable high-speed data processing capabilities. The DSP also provides highly specialized instruction sets that increase the speed of operation. The charac- teristics of the DSP greatly increase its computing power and processing power, so that it can well meet the requirements for fast, accurate, real-time processing and control of signals.
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