23,549 research outputs found
Control-system techniques for improved departure/spin resistance for fighter aircraft
Some fundamental information on control system effects on controllability of highly maneuverable aircraft at high angles of attack are summarized as well as techniques for enhancing fighter aircraft departure/spin resistance using control system design. The discussion includes: (1) a brief review of pertinent high angle of attack phenomena including aerodynamics, inertia coupling, and kinematic coupling; (2) effects of conventional stability augmentation systems at high angles of attack; (3) high angle of attack control system concepts designed to enhance departure/spin resistance; and (4) the outlook for applications of these concepts to future fighters, particularly those designs which incorporate relaxed static stability
Theory and Simulation of the diffusion of kinks on dislocations in bcc metals
Isolated kinks on thermally fluctuating (1/2) screw, edge and
(1/2) edge dislocations in bcc iron are simulated under zero stress
conditions using molecular dynamics (MD). Kinks are seen to perform stochastic
motion in a potential landscape that depends on the dislocation character and
geometry, and their motion provides fresh insight into the coupling of
dislocations to a heat bath. The kink formation energy, migration barrier and
friction parameter are deduced from the simulations. A discrete
Frenkel-Kontorova-Langevin (FKL) model is able to reproduce the coarse grained
data from MD at a fraction of the computational cost, without assuming an a
priori temperature dependence beyond the fluctuation-dissipation theorem.
Analytic results reveal that discreteness effects play an essential r\^ole in
thermally activated dislocation glide, revealing the existence of a crucial
intermediate length scale between molecular and dislocation dynamics. The model
is used to investigate dislocation motion under the vanishingly small stress
levels found in the evolution of dislocation microstructures in irradiated
materials
Simulator study of stall/post-stall characteristics of a fighter airplane with relaxed longitudinal static stability
A real-time piloted simulation was conducted to evaluate the high-angle-of-attack characteristics of a fighter configuration based on wind-tunnel testing of the F-16, with particular emphasis on the effects of various levels of relaxed longitudinal static stability. The aerodynamic data used in the simulation was conducted on the Langley differential maneuvering simulator, and the evaluation involved representative low-speed combat maneuvering. Results of the investigation show that the airplane with the basic control system was resistant to the classical yaw departure; however, it was susceptible to pitch departures induced by inertia coupling during rapid, large-amplitude rolls at low airspeed. The airplane also exhibited a deep-stall trim which could be flown into and from which it was difficult to recover. Control-system modifications were developed which greatly decreased the airplane susceptibility to the inertia-coupling departure and which provided a reliable means for recovering from the deep stall
Selfâcompassion, selfâ forgiveness, suicidal ideation and selfâharm: a systematic review
Selfâcompassion has been implicated in the aetiology and course of mental health with evidence suggesting an association between greater selfâcompassion and lower emotional distress. However, our understanding of the nature and extent of the relationship between selfâcompassion and selfâharm (selfâinjury regardless of suicidal intent) or suicidal ideation remains unclear. This review, therefore, aimed to critically evaluate the extant literature investigating this relationship. To do so, a systematic search, including terms synonymous with selfâcompassion, was conducted on three main psychological and medical databases (Web of Science, PsycINFO and Medline). Only studies investigating selfâcompassion or selfâforgiveness and selfâharm or suicidal ideation were found to be relevant to the review. 18 studies were included in the final narrative synthesis. Heterogeneity of studies was high and the majority of studies were quantitative and crossâsectional (n=16) in design. All studies reported significant associations between higher levels of selfâforgiveness or selfâcompassion and lower levels of selfâharm or suicidal ideation. Several studies suggested that selfâcompassion or selfâforgiveness may weaken the relationship between negative life events and selfâharm. In conclusion, this review highlights the potential importance of selfâcompassion in the aetiology of suicidal thoughts and selfâharm. We discuss the clinical and research implications
Endogenous Versus Exogenous Shocks in Complex Networks: an Empirical Test Using Book Sale Ranking
Are large biological extinctions such as the Cretaceous/Tertiary KT boundary
due to a meteorite, extreme volcanic activity or self-organized critical
extinction cascades? Are commercial successes due to a progressive reputation
cascade or the result of a well orchestrated advertisement? Determining the
chain of causality for extreme events in complex systems requires disentangling
interwoven exogenous and endogenous contributions with either no clear or too
many signatures. Here, we study the precursory and recovery signatures
accompanying shocks, that we test on a unique database of the Amazon sales
ranking of books. We find clear distinguishing signatures classifying two types
of sales peaks. Exogenous peaks occur abruptly and are followed by a power law
relaxation, while endogenous sale peaks occur after a progressively
accelerating power law growth followed by an approximately symmetrical power
law relaxation which is slower than for exogenous peaks. These results are
rationalized quantitatively by a simple model of epidemic propagation of
interactions with long memory within a network of acquaintances. The slow
relaxation of sales implies that the sales dynamics is dominated by cascades
rather than by the direct effects of news or advertisements, indicating that
the social network is close to critical.Comment: 5 pages including 3 figures final version published in Physical
Review Letter
Bringing the Inside Out and the Outside in: The Therapeutic Relationship in Compassion Focused Therapy Chairwork
Chairwork is a central component in Compassion Focused Therapy (CFT). Despite its importance, there has been no prior research on the relational factors underpinning the application of chairwork in CFT. There is also a general paucity of research on the role of the therapeutic relationship in chairwork across modalities. This paper analyses data from interviews with 21 clients following a CFT chairwork intervention to ascertain how relational factors influenced their experience of this method. An Interpretative Phenomenological Analysis (IPA) found three main themes: 1) direction and coaching during enactment; 2) externalisation: bringing the inside out and outside in; 3) regulation and trust: the relational requirements to âlet goâ. The implications of these findings, both for the delivery and training of chairwork, are then discussed in the context of CFT
âAn ethnographic seductionâ: how qualitative research and Agent-based models can benefit each other
We provide a general analytical framework for empirically informed agent-based simulations. This methodology provides present-day agent-based models with a sound and proper insight as to the behavior of social agents â an insight that statistical data often fall short of providing at least at a micro level and for hidden and sensitive populations. In the other direction, simulations can provide qualitative researchers in sociology, anthropology and other fields with valuable tools for: (a) testing the consistency and pushing the boundaries, of specific theoretical frameworks; (b) replicating and generalizing results; (c) providing a platform for cross-disciplinary validation of results
Rapidly driven nanoparticles: Mean first-passage times and relaxation of the magnetic moment
We present an analytical method of calculating the mean first-passage times
(MFPTs) for the magnetic moment of a uniaxial nanoparticle which is driven by a
rapidly rotating, circularly polarized magnetic field and interacts with a heat
bath. The method is based on the solution of the equation for the MFPT derived
from the two-dimensional backward Fokker-Planck equation in the rotating frame.
We solve these equations in the high-frequency limit and perform precise,
numerical simulations which verify the analytical findings. The results are
used for the description of the rates of escape from the metastable domains
which in turn determine the magnetic relaxation dynamics. A main finding is
that the presence of a rotating field can cause a drastic decrease of the
relaxation time and a strong magnetization of the nanoparticle system. The
resulting stationary magnetization along the direction of the easy axis is
compared with the mean magnetization following from the stationary solution of
the Fokker-Planck equation.Comment: 24 pages, 4 figure
How one experiences and embodies compassionate mind training influences its effectiveness.
This paper explores indicators of practice quality of a brief compassion mind training (CMT) intervention and their impact on the development of an inner sense of oneâs compassionate self (CS) and a range of self-report measures. Participants were randomly assigned to one of two conditions: compassionate mind training (CMT; nâ=â77) and wait-list control. Participants in the CMT condition practiced a range of CMT practices during 2Â weeks. Each week, participants completed a feedback questionnaire, measuring practice frequency, helpfulness and embodiment of the practices in everyday life. Self-report measures of compassion, positive affect, shame, self-criticism, fears of compassion and psychopathological symptoms were also completed at pre and post. Practice frequency was associated with the frequency and easiness of embodiment of the CS. Perceived helpfulness of the practices was related to greater embodiment of the CS and to increases in compassion, reassured self, relaxed and safe affect and decreases in self-criticism. The embodiment variables of the CS were associated with higher compassion for the self, for others and from others and with improvements in reassured self, safe affect and compassionate goals. Embodiment of the CS and perceived helpfulness of the practices predicted compassion for the self and experience of compassion from others at post-intervention. Perceiving compassion cultivation practices as helpful and being able to embody the CS in everyday life is key to foster self-compassion and the experience of receiving compassion from others, as well as to promote feelings of safeness, contentment and calmness.Portuguese Foundation for Science and Technology (FCT) Compassionate Mind Foundation charit
The factor structure of the Forms of Self-Criticising/Attacking & Self-Reassuring Scale in thirteen distinct populations
There is considerable evidence that self-criticism plays a major role in the vulnerability to and recovery from psychopathology. Methods to measure this process, and its change over time, are therefore important for research in psychopathology and well-being. This study examined the factor structure of a widely used measure, the Forms of Self-Criticising/Attacking & Self-Reassuring Scale in thirteen nonclinical samples (Nâ=â7510) from twelve different countries: Australia (Nâ= 319), Canada (Nâ= 383), Switzerland (Nâ= 230), Israel (Nâ=â476), Italy (Nâ=â389), Japan (Nâ=â264), the Netherlands (Nâ=â360), Portugal (Nâ=â764), Slovakia (Nâ=â1326), Taiwan (Nâ=â417), the United Kingdom 1 (Nâ=â1570), the United Kingdom 2 (Nâ=â883), and USA (Nâ=â331). This study used more advanced analyses than prior reports: a bifactor item-response theory model, a two-tier item-response theory model, and a non-parametric item-response theory (Mokken) scale analysis. Although the original three-factor solution for the FSCRS (distinguishing between Inadequate-Self, Hated-Self, and Reassured-Self) had an acceptable fit, two-tier models, with two general factors (Self-criticism and Self-reassurance) demonstrated the best fit across all samples. This study provides preliminary evidence suggesting that this two-factor structure can be used in a range of nonclinical contexts across countries and cultures. Inadequate-Self and Hated-Self might not by distinct factors in nonclinical samples. Future work may benefit from distinguishing between self-correction versus shame-based self-criticism.Peer reviewe
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