Top PDF The physical nature of weak shock reflection

The physical nature of weak shock reflection

The physical nature of weak shock reflection

Abstract Recent high-resolution numerical studies of weak shock reflections have shown that a complex flow structure exists behind the triple point which consists of multiple shocks, expansion fans and triple points. This region had not been detected earlier in experimental observations or numerical studies of weak shock reflections due to the small size of this region. New components were designed and built to modify an existing large-scale shock tube in order to obtain experimental observations to validate the numerical results. The shock tube produced a large, expanding cylindrical incident wave which was reflected off a 15° corner on the roof of the section to produce a weak shock Mach reflection with a large Mach stem in the test section. The shock tube was equipped with PCB high-speed pressure transducers and digital scope for data acquisition, and a schlieren optical system to visualise the region behind the triple point. The tests were conducted over a range of incident wave Mach numbers (M 12 = 1.060-1.094) and produced Mach
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Weak shock wave  reflections from concave curved surfaces

Weak shock wave reflections from concave curved surfaces

Figure 9.6a) shows a shadowgram of a MR that was captured in this study. It is at the native resolution, 240 pixels per inch, at which all pictures in the study were captured with the 12.1 megapixel CCD of the Fujifilm S3 Pro camera. At this resolution, the incident shock wave is approximately 6 pixels in thickness, and the flow features are clearly defined. At half the resolution shown in Figure 9.6b), the incident shock is about 4 pixels thick followed by 3 pixels thick at 90 pixels per inch for Figure 9.6c) and 1 pixel thick at 60 pixels per inch respectively in the last image. In Figure 9.6d), it is difficult to distinguish where the reflected shock wave is meeting the incident shock wave and the reflection could be mistaken for a RR. Thus it can be deduced that any flow features equal in size or smaller than the pixel size of the image cannot be distinguished with any certainty. With the imaging system laid out as it was, the physical size of the area covered by a single pixel in the images captured for this study is approximately 0.0625mm by 0.0625mm. This limitation also implies that any deviation in angle, such as the angle of the Mach stem, smaller than the thickness of the shockwave, would not be clearly distinguishable.
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The diffraction, reflection and propagation of cylindrical shock wave segments

The diffraction, reflection and propagation of cylindrical shock wave segments

In addition to shock reflection there is interest in the dynamics of shock waves; that is not to say that the two are mutually exclusive, since to understand shock reflection one needs to know about shock dynamics. Navier Stokes’ equations or Euler’s equations can be used to address the dynamics of shock waves; however, Whitham’s Geometric Shock Dynamics [ 13 ] offers a third alternative which is less computer intensive in relation to numerical solutions and also gives clearer insight into the physical processes occurring in the shock phenomena being studied. While Euler’s equations are an inviscid approximation to Navier Stokes’ equations and both take into account the flow field ahead of and behind the shock wave, Geometric Shock Dynamics (GSD) considers only the shock’s front. By ignoring post shock conditions, GSD sets itself as an approximate theory. Approximate as it may be, it is still able to predict some of shocks’ behaviour, particularly strong shocks. Further research has been done to improve GSD’s accuracy in the weak shock regime.
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Cross-correlation of weak lensing and gamma rays: implications for the nature of dark matter

Cross-correlation of weak lensing and gamma rays: implications for the nature of dark matter

weak lensing data from the Canada–France–Hawaii Telescope Lensing Survey (CFHTLenS), the Red Cluster Sequence Lensing Survey (RCSLenS), and the Kilo Degree Survey (KiDS). We present the first measurement of tomographic weak lensing cross-correlations and the first application of spectral binning to cross-correlations between gamma rays and weak lensing. The measurements are performed using an angular power spectrum estimator while the covariance is estimated using an analytical prescription. We verify the accuracy of our covariance estimate by comparing it to two internal covariance estimators. Based on the non- detection of a cross-correlation signal, we derive constraints on weakly interacting massive particle (WIMP) dark matter. We compute exclusion limits on the dark matter annihilation cross-section σ ann v, decay rate dec and particle mass m DM . We find that in the absence of
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The physical nature of spiral wave patterns in sunspots

The physical nature of spiral wave patterns in sunspots

Since the mechanism does not require additional assumptions such as the flux tube twisting or rotation, we expect that such SWPs may be generally detected in any sunspots. As we accumulate the observation of those patterns, we can infer more physical parameters in sunspots such as propagating speed of fast wave and depth of the wave driving source. Furthermore, those wave patterns can be considered as the evidence of the internal excitation of 3-min oscillations in sunspots. Further study of the SWPs may provide us with the clues to how magneto-convection inside a sunspot generates such waves.
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Strong  Authenticity  with  Leakage  under  Weak   and  Falsifiable  Physical  Assumptions

Strong Authenticity with Leakage under Weak and Falsifiable Physical Assumptions

Our contribution. The goal of this paper is to bridge the above theory gap (i.e., seeking for some well-defined leakage assumptions on the block cipher that allows the leakage-resilient MAC security reductions) while also enabling more modular security guarantees that may degrade gracefully when the physical assumption is respected only to some extent. Our answer to this challenge is Strong Unpredictability in the presence of Leakages for a (T)BC, henceforth abbreviated as SUL2. In detail, it captures the hardness of providing a fresh input/output pair for the (T)BC even having access to its leaking oracle and leaking inverse oracle (following the notations of [17], the variant without leaking inverse oracle would be SUL1). It can be viewed as a natural extension of the unpredictable block cipher assumption introduced by Dodis and Steinberger [12,13].
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Solar wind proton reflection and injection to the ACR regime at the parallel termination shock

Solar wind proton reflection and injection to the ACR regime at the parallel termination shock

with the ion bulk velocity U, which is the first moment of the ion distribution function. This expression was derived from the Euler equation for the case of a high-Mach num- ber shock. Nevertheless, it is also at a lower Mach number a reasonable formulation for the force term in Eq. (1) since it describes the deceleration of a proton as the consequence of a gradient in the bulk velocity profile. This means, a par- ticle with velocity w at position s is decelerated by the same amount as a particle with velocity U (s) at the position s due to the external force. In the Euler equation, a quiet parallel magnetic background field has no influence on the plasma flow. Furtheron, we take only electrostatic plasma waves as a consequence of a two-stream instability into account and, hence, the magnetic field does not play a role (except for its
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The causes and nature of the June 2016 protests in the city of Tshwane: A practical theological reflection

The causes and nature of the June 2016 protests in the city of Tshwane: A practical theological reflection

Other factors conducive to violence, according to Abrahams (2010:514), include poverty informed by a disparity in income between the rich and poor, poor service delivery, overcrowding in squatter camps, lack of housing and widespread unemployment. Abrahams continues to say that poverty and inequality are the most crucial social dynamics that have contributed to South Africa’s South Africa has recently experienced a series of public protests. The common element is that violence is becoming evident in these protests. This article uses the June 2016 protests in the city of Tshwane as an example to address the root causes of such protests. On 20 June 2016, the African National Congress (ANC) announced that the city of Tshwane mayoral candidate for the 3 August 2016 municipal elections in South Africa is the former public works minister and ANC National Executive Committee member, Thoko Didiza. Consequently, public protests in the city of Tshwane emerged immediately after this announcement. These public protests were very violent, such as protesters killed one another, burned buses, looted shops and barricaded roads. The root causes of these violent protests are identified as factionalism, tribalism, sexism, economic exclusion and patronage politics. The purpose of this article is a practical theological reflection on the root causes of June 2016 protests in the city of Tshwane. The main aim of this article is a practical theological solution to the general problem of violent protests.
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Physical, psychological and emotional effects of
nature based affordances of green physical activity

Physical, psychological and emotional effects of nature based affordances of green physical activity

indoors cycling (10% of maximal capacity below ventilatory threshold and 5% above) for 15 minutes cycling. This study found that the music-only and music-nature video conditions led to the highest valence and enjoyment scores during and after exercise regardless of intensity. It was worth noting that higher scores of happiness were observed in the two nature-based conditions compared to the self-selected entertainment condition. However, the post hoc test (i.e. Bonferroni correction) failed to identify the sources of differences which might due to the strict control of familywise error rate when correcting the level of significance. It was taken into consideration that Bonferroni correction was more conservative in the type I error rate for each comparison, it also increased the chance to overlook a genuine differences in the data (Field, 2009). Hence, it was difficult to identify the source of difference. It could be deduced the all the three conditions contributed to the condition effect but further investigation might be required. Participants experienced lower level of anxiety, dejection, and anger but higher level of excitement in all three exercise designs after twenty minutes of running supporting the notion that exercise has positive emotional benefits. This results were in line with the extant research about the emotional benefits of green PA (Akers et al., 2012; Calogiuri et al., 2016b; Jones et al., 2014; Pretty et al., 2005) but not with other studies (Duncan et al., 2014; Wood, Caroline, Jules, Gavin, & Jo, 2013). No emotional benefits of green PA were proposed when the target groups were children or adolescents instead of adults. Results from children and adolescents have found inconsistent outcomes which were contrary to adults on the benefits of mood. Wood et al. (2013) recruited twenty-five adolescents to assess the effects of viewing nature or building views while cycling demonstrating improvements on mood due to exercise but no effects of viewing different environmental scenes. Duncan et al. (2014) also found similar results that children did not report positive mood changes by cycling while viewing a green environment video compared to exercise alone. These authors provided an explanation that younger generation might have lower connectedness to nature than the old generation (Duncan et al., 2014; Wood et al., 2013). Nowadays the young generation may be relatively less connected to nature and spend more time on screen-based activities, such as watching TV, surfing the Internet or social websites and playing smart phone games (Rideout, Foehr, & Roberts, 2010). This assumption requires further investigations in the future research.
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Courant Friedrichs' Hypothesis and Stability of the Weak Shock Wave Satisfying the Lopatinski Condition

Courant Friedrichs' Hypothesis and Stability of the Weak Shock Wave Satisfying the Lopatinski Condition

problem appeared in recent years in [8-12]. Briefly speaking, it was shown in [8-12] that in the case of a strong shock wave (for compactly supported initial data!) the perturbation arrives to the wedge's vertex as time increases having the growth r  (   0 ) or a logarith- mic growth in space variables, and this causes instability of the steady-state solution under consideration.

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2) the stochastic reflection of the system’s physics. The associated physical

2) the stochastic reflection of the system’s physics. The associated physical

system’ conditions are created when the components are installed into the system. It is assumed, that in the system some mutual interactions occur. As a result, in the considered system, side-effects of each component performance, influence physics of failure mechanism of the remaining unit. The components failure mechanism has two parallel aspects: 1) the reality aspect, based on engineering devices and / or underlying physical and chemical processes that eventually lead to each unit’s failure, and 2) the stochastic reflection of the system’s physics. The associated physical phenomena are often too complex and complicated to be followed and efficiently handled for the reliability prediction purposes.
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GRB 060418 and 060607A: the medium surrounding the progenitor and the weak reverse shock emission

GRB 060418 and 060607A: the medium surrounding the progenitor and the weak reverse shock emission

cussed by Roming et al. (2006). To account for this fail- ing detection, it is widely considered that the reverse shock emission would be very weak if the outflow is highly magne- tized (Kennel & Coronitti 1984). As shown in the numerical calculation of Fan, Wei & Wang (2004; Fig 1 therein), for the magnetized reverse shock, its peak optical/IR emission increases with σ for σ ≤ 0.1, then decreases for larger σ, where σ refers to the ratio of the magnetic energy density to the particle energy density of the GRB outflow. Quite similar results have also been obtained in the analytical in- vestigation of Zhang & Kobayashi (2005). In principle, the non-detection of the optical flashes could be interpreted if σ ≫ 1. This conclusion motivated Molinari et al. (2007) to suggest these two GRB outflows might be magnetized. How- ever, in this work we show that for these two bursts, the absence of the IR flashes are actually consistent with the standard external reverse shock model (Sari & Piran 1999a; M´esz´ aros & Rees 1999; Kobayashi 2000) and thus render the magnetized outflow model unnecessary or alternative.
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Transiting exoplanets: From planet statistics to their physical nature

Transiting exoplanets: From planet statistics to their physical nature

et al., this volume) and HAT (Bakos et al., this volume)) presented 17 new planets. The Kepler team (Holman et al. 2010) discussed 2 transiting planets (Kepler 9 b and c) orbiting in the same planetary system. These planets show for the first time clear transit timing variations. They also provided indications of a possible third planet on a short period orbit. Kepler-9 d was detected only after the transit timing varia- tion signal from the two planets already-discovered in this system was removed. It is still difficult to rule out all false-positive contaminations, but recent work supports its planet nature even though its mass can not be derived yet (Torres et al. 2011). In 2010, the Kepler-mission released a first list of planet candidates which then triggered the detection of further transiting planets and a white dwarf from rv follow-up of these can- didates (H´ebrard et al., this volume; Ehrenreich et al. 2010). Furthermore, a planetary system with 7 planets was announced by the rv-team in Geneva (Lovis et al. 2010), including a small super-Earth planet of only 1.4 M Earth sin i. This non-exhaustive list
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Walking in the shoes of others:  Critical reflection in community sport management and physical activity

Walking in the shoes of others: Critical reflection in community sport management and physical activity

Doing things in this way is not easy, and the methods/activities adopted by Mentro Allan presented numerous challenges at every stage of the community management process. For example in the current economic climate, care workers are being asked to work longer hours for less money, which made it difficult for Mentro Allan to encourage them to spend time with the partipants in order to build positive relationships. The lack of available time and poor wages also made care workers reluctant to undertake the relevant training and take many of the ‘risks’ often associated with outdoor activity. Problems also arose when engaging particular groups in these environments. For instance, young people were often reluctant to wear appropriate outdoor clothing for fear of appearing ‘unfashionable’, BME women refused to travel alone due to cultural values regarding gender, and individuals on welfare benefits, particularly those with a mental health condition, were anxious about engaging in public physical activity for fear of being accused of benefit ‘scrounging’ (i.e. you are on a mountain bike, why are you claiming benefits?). However, by engaging with their ‘sociological imaginations’, planners were able to come up with a range of simple yet effective solutions to these problems, including staff training, the use of ‘doorstep’ locations and adopting a ‘graduated approach’ to ensure that people developed their confidence and fitness over time. In doing this, Mentro Allan was able to actively challenge negative stereotypes whilst ensuring maximum buy-in to each activity.
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Reverence to Nature and Reflection of Indian milieu in selected writings of Ruskin Bond: A short story writer

Reverence to Nature and Reflection of Indian milieu in selected writings of Ruskin Bond: A short story writer

Bond passionately radiates his fiction with evoking images of landscapes, hilly terrains, water spots, mountain cascades, the rippling and gurgling brooks, trees, host of birds and medley of animals. This diverse phenomenon of nature and its manifestations are not set in contrast with each other but in concordance and the euphony create an ecstatic state. The salient feature of Bond’s treatment of nature is its uniformity. The gentle soul of Bond experiences strange and captivating beauty and sensation in every aspect of nature – trivial or significant, beautiful or ugly. Pantheistic Bond asserts that every part of nature has its own value and own role to play. As for Bond, the trees and plants assumed the role of guardian-spirit after his parents’ separation and soon after his father’s tragic demise. In the stories like “My Father’s Trees in Dehra”, “When You Can’t Climb Any More”, and “Coming Home to Dehra” he imagines his father coming back to life through new shoots. The story “The Funeral”, gives a moving account of his father’s death. The priest’s cold voice and the coffin going deep into the entrails of the earth and ghastly silence spread around, cast a depressing impact on the young boy who could hardly understand it. Here, nature emerges as a healing force to dissipate his gloom and loneliness. The innocent boy imagines to elude death with the help of nature.
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Forseeability of nervous shock to a 'primary victim' who suffers no physical injury

Forseeability of nervous shock to a 'primary victim' who suffers no physical injury

Applying these conditions to the case before him, he argued, 'The defendant can be liable only if the hypothetical reasonable man in his position should have foreseen that the plaintiff,[r]

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A critical reflection on the threat from human insiders--its nature, industry perceptions, and detection approaches

A critical reflection on the threat from human insiders--its nature, industry perceptions, and detection approaches

Another threat that causes great concern is IP theft. In this attack, insiders use their access to steal valuable company data, including trade secrets, business information, source code and customer information [11]. There are several key features of this type of attack. First, the target tends to be product information, proprietary software and source code (these are clear targets in CMU-CERT studies [12]). Also, attacks appear more likely to be conducted by technical personnel (e.g., scientists and engineers) [6] and using technical means (54% of insiders used either email, remote access channel or network file transfer [11]) rather than physical theft of prototypes, for example. Finally, a majority of these thefts are committed by employees with legitimate access to the stolen IP; almost 75% stole material they had authorized access to [12]. Although 75% is a strong statistic and it is therefore very tempting to monitor only these individuals for this attack, yet as other articles have highlighted (e.g., the case of the foreign national who stole Ford secrets worth in excess of $50 million [13]), insiders with no legitimate access are also causing a great deal of harm.
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Weak Relationships between Stint Duration, Physical and Skilled Match Performance in Australian Football

Weak Relationships between Stint Duration, Physical and Skilled Match Performance in Australian Football

are provided by commercial performance analysis companies (Sullivan et al., 2014b). However, there is less standardization in the measurement of skilled output comparative to physical. Skilled output can be measured by quantifying the number of involvements or actions completed by each player. Involvements may include kicks, handballs and other actions considered important to match success by AF coaching staff. The amount of time each player spends on the field and on the bench is available as a measure of temporal output (Bradley and Noakes, 2013). Potentially due to a combination of cognitive (Tenenbaum and Bar-Eli, 1993) and physiological fatigue (Aughey, 2010), it is unlikely that players can maintain an optimal level of physical and skilled output for an entire match (Thelen and Smith, 1994; Aughey, 2010). In AF, a decrement in physical output has been observed for each quarter completed (Coutts et al., 2010), with a 3% reduction in meterage per minute for every 2 min spent on field during rotations longer than 5 min (Montgomery and Wisbey, 2016). Similarly, the level of skilled involvements for players also likely declines as the duration of a match increases. Recent research has examined how work rate, time on field and situational factors, including the number of stoppages, interact to affect skilled involvement (Sullivan et al., 2014a,b). Although factors influencing the skilled output of players have been identified to date (Sullivan et al., 2014a,b), research assessing how these factors may aid match-day stint/rotation strategies remains to be examined. Measures of skilled, physical and temporal output could be modeled to identify how the skilled output of a team and individual responds to change in temporal and physical output.
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Honoring Epimenides of Crete (±Δx): From Quantum Paradoxes, through Weak Measurements, to the Nature of Time

Honoring Epimenides of Crete (±Δx): From Quantum Paradoxes, through Weak Measurements, to the Nature of Time

reading macroscopic. In order to provide an accurate result, the pointer must have a certain momentum. This way, when our particle interacts with it, the reading (in terms of momentum change) would be unambiguous. Unfortunately, the amplified interaction with this pointer results in an irreversible change of the measured system – the so-called collapse. As opposed to this ordinary "strong" measurement, weak measurement creates a loose coupling to a quantum pointer whose momentum is highly uncertain, and again the pointer reading is being amplified by the same mechanism. This combination of weak coupling and noisy reading naturally gives a very small amount of information, but also a negligible change of its dynamics. It is on the ensemble level that weak measurement gains the desired precision, overcoming its inherent inaccuracy to the extent of even surpassing the limits of ordinary quantum measurement. By the Large Numbers Law, if x i (the different
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The Gem (gravity-em)theory : The Unification Of The Strong, Em , Weak ,and Gravity Forces Of Nature

The Gem (gravity-em)theory : The Unification Of The Strong, Em , Weak ,and Gravity Forces Of Nature

Abstract—This manuscript presents the initial results of the GEM (Gravity-Electro-Magnetism) theory which unifies the four forces of nature. The two long range forces Gravity and Electro- Magnetism are first unified, and out of this unification also proceeds the unification of the short range Weak and Strong Forces. They are unified under the two postulates that: 1. Gravity fields are an array of electromagnetic cells and 2. The separate appearance of Gravity and EM fields from each other is correlated with the separation of protons and electrons from each other as they emerge from the Planck scale with the appearance of a compact or hidden dimension. In the Standard Model all massive particles are charged and move freely at short distances and even photons spend time as charged particles. The quark-electron split occurs based on the asymmetry in dimensionality between space and time. The proton mass is found by assuming Planckian neutral pion fields inside the proton. The theory produces the value of G: the Newton gravitation constant, and the proton mass accurately from the Planck scale with no free parameters. The theory produces the values of the masses, charges and spins for the pions of the Strong Force and the W and Z bosons of the Weak Force as quantum Mie scatterings off the compact dimension structures associated with the proton and electron masses. The Higgs Boson mass follows from similar formalism. The GEM theory extends the Standard Model to include Gravitation. The theory predicts a short lived, neutral spin 0 particle will be found at approximately 22MeV, that matter can emerge from the bare vacuum, and that a basic cosmic parameter is the number 42.8503.
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