Tree Buffers

In runtime verification, the central problem is to decide if a given program execution violates a given property. In online runtime verification, a monitor observes a program’s execution as it happens. If the program being observed has hard real-time constraints, then the monitor inherits them. In the presence of hard real-time constraints it becomes a challenge to maintain enough information to produce error traces, should a property violation be observed. In this paper we introduce a data structure, called tree buffer, that solves this problem in the context of automata-based monitors: If the monitor itself respects hard real-time constraints, then enriching it by tree buffers makes it possible to provide error traces, which are essential for diagnosing defects. We show that tree buffers are also useful in other application domains. For example, they can be used to implement functionality of capturing groups in regular expressions. We prove optimal asymptotic bounds for our data structure, and validate them using empirical data from two sources: regular expression searching through Wikipedia, and runtime verification of execution traces obtained from the DaCapo test suite

In-situ neutron diffraction study of micromechanical shear failure in an aerospace composite

Glass fibre reinforced polypropylene (GF/PP) composite is a well-established material system for fabricating bistable composite tape-spring (CTS) structure. It is light-weight and multifunctional, and has attracted growing interest in shape-adaptive and energy harvesting systems in defence, civil and especially aerospace engineering. The factors governing its bistability have been well-understood; whist there is limited research concerning the micromechanics and microstructural failure. In this research, we investigate the failure mechanisms of the GF/PP composite. This is achieved by performing in-situ neutron diffraction on composite specimens using the ENGIN-X neutron diffractometer at Rutherford Appleton Laboratory. Shear failures are characterised at both macroscopic and microscopic scales. Elastic and viscoelastic strain evolutions at different levels reveal the micromechanical shear failure. The failure mechanisms are then proposed, which will benefit optimisation of structural design and structural integrity of the CTS in aerospace applications

In-situ multiscale shear failure of a bistable composite tape-spring

A bistable composite tape-spring (CTS) is stable in both the extended and coiled configurations, with fibres oriented at ±45°. It is light weight and multifunctional, and has attracted growing interest in shape-adaptive and energy harvesting systems in defence-, civil- and, especially aerospace engineering. The factors governing its bistability have been well-understood, but there is limited research concerning the mechanics of structural failure: here, we investigate the shear failure mechanisms in particular. We perform in-situ neutron diffraction on composite specimens using the ENGIN-X neutron diffractometer at Rutherford Appleton Laboratory (STFC, UK), and shear failure is characterised at both macroscopic and microscopic scales. Elastic and viscoelastic strain evolutions at different strain levels reveal the fundamentals of micromechanical shear failure, and their temperature dependency. Multiscale shear failure mechanisms are then proposed, which will benefit the optimisation of structural design to maintain structural integrity of CTS in aerospace applications.ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Science and Technology Facilities Council (STFC), Grant no. RB1910213 Innovate UK, ‘‘Large Landing Gear of the Future: Bistable Composite Technologies’’, Grant no. 113077 EPSRC, "NRFIS", Grant no. EP/P013848/

The effects of dynamic compression on the development of cartilage grafts engineered using bone marrow and infrapatellar fat pad derived stem cells.

Bioreactors that subject cell seeded scaffolds or hydrogels to biophysical stimulation have been used to improve the functionality of tissue engineered cartilage and to explore how such constructs might respond to the application of joint specific mechanical loading. Whether a particular cell type responds appropriately to physiological levels of biophysical stimulation could be considered a key determinant of its suitability for cartilage tissue engineering applications. The objective of this study was to determine the effects of dynamic compression on chondrogenesis of stem cells isolated from different tissue sources. Porcine bone marrow (BM) and infrapatellar fat pad (FP) derived stem cells were encapsulated in agarose hydrogels and cultured in a chondrogenic medium in free swelling (FS) conditions for 21 d, after which samples were subjected to dynamic compression (DC) of 10% strain (1 Hz, 1 h d(-1)) for a further 21 d. Both BM derived stem cells (BMSCs) and FP derived stem cells (FPSCs) were capable of generating cartilaginous tissues with near native levels of sulfated glycosaminoglycan (sGAG) content, although the spatial development of the engineered grafts strongly depended on the stem cell source. The mechanical properties of cartilage grafts generated from both stem cell sources also approached that observed in skeletally immature animals. Depending on the stem cell source and the donor, the application of DC either enhanced or had no significant effect on the functional development of cartilaginous grafts engineered using either BMSCs or FPSCs. BMSC seeded constructs subjected to DC stained less intensely for collagen type I. Furthermore, histological and micro-computed tomography analysis showed mineral deposition within BMSC seeded constructs was suppressed by the application of DC. Therefore, while the application of DC in vitro may only lead to modest improvements in the mechanical functionality of cartilaginous grafts, it may play an important role in the development of phenotypically stable constructs.Funding was provided by the European Research Council Starter Grant (StemRepair—Project number 258463) and a SFI President of Ireland Young Researcher Award (08/Y15/B1336)

EQ-5D-3L Derived Population Norms for Health Related Quality of Life in Sri Lanka

Background Health Related Quality of Life (HRQoL) is an important outcome measure in health economic evaluation that guides health resource allocations. Population norms for HRQoL are an essential ingredient in health economics and in the evaluation of population health. The aim of this study was to produce EQ-5D-3L-derived population norms for Sri Lanka. Method A population sample (n =  780) was selected from four districts of Sri Lanka. A stratified cluster sampling approach with probability proportionate to size was employed. Twenty six clusters of 30 participants each were selected; each participant completed the EQ-5D-3L in a face-to-face interview. Utility weights for their EQ-5D-3L health states were assigned using the Sri Lankan EQ-5D-3L algorithm. The population norms are reported by age and socio-economic variables. Results The EQ-5D-3L was completed by 736 people, representing a 94% response rate. Sixty per cent of the sample reported being in full health. The percentage of people responding to any problems in the five EQ-5D-3L dimensions increased with age. The mean EQ-5D-3L weight was 0.85 (SD 0.008; 95%CI 0.84-0.87). The mean EQ-5D-3L weight was significantly associated with age, housing type, disease experience and religiosity. People above 70 years of age were 7.5 times more likely to report mobility problems and 3.7 times more likely to report pain/discomfort than those aged 18-29 years. Those with a tertiary education were five times less likely to report any HRQoL problems than those without a tertiary education. A person living in a shanty was 4.3 more likely to have problems in usual activities than a person living in a single house. Conclusion The population norms in Sri Lanka vary with socio-demographic characteristics. The socioeconomically disadvantaged have a lower HRQoL. The trends of population norms observed in this lower middle income country were generally similar to those previously reported in high income countries

5D gravity and the discrepant G measurements

It is shown that 5D Kaluza-Klein theory stabilized by an external bulk scalar field may solve the discrepant laboratory G measurements. This is achieved by an effective coupling between gravitation and the geomagnetic field. Experimental considerations are also addressed.Comment: 13 pages, to be published in: Proceedings of the 18th Course of the School on Cosmology and Gravitation: The gravitational Constant. Generalized gravitational theories and experiments (30 April-10 May 2003, Erice). Ed. by G. T. Gillies, V. N. Melnikov and V. de Sabbata, (Kluwer), 13pp. (in print) (2003

Application advances of artificial intelligence algorithms in dynamics simulation of railway vehicle

The application examples and domestic and foreign literatures using artificial intelligence algorithm for railway vehicle system dynamics simulation were reviewed. The machine learning and deep learning algorithms commonly used in railway vehicle dynamics simulation were summarized, and the application classifications of the 2 algorithms in railway vehicle system dynamics modelling and simulation were concluded and interpreted. According to railway vehicle system dynamics modelling, dynamics performance prediction and dynamics performance optimization, the advantages and limitations of applying artificial intelligence algorithms in force-elements modelling and simulation, track irregularity prediction, running stability prediction, noise prediction, crosswind safety prediction, running safety prediction, suspension optimization, wheel-rail matching optimization, structure optimization, and active and semi-active control were discussed in detail. The problems of applications of artificial intelligence algorithms in railway dynamics simulation were lack of training samples, generalization ability and interpretability. The development directions and key research contents of the interdisciplinary research between artificial intelligence and vehicle system dynamics were given. Research result shows that the hybrid modelling theory combining classical mechanics and artificial intelligence algorithms can be as a key research direction in the future. There is great potential to use the artificial intelligence algorithms to solve the random uncertainty in stochastic dynamics and improve the performance of stochastic dynamics. The artificial intelligence algorithms combinated with optimization algorithms can exploit their advantages in the dynamics performance optimization.

Generating MHV super-vertices in light-cone gauge

We constructe the $\mathcal{N}=1$ SYM lagrangian in light-cone gauge using chiral superfields instead of the standard vector superfield approach and derive the MHV lagrangian. The canonical transformations of the gauge field and gaugino fields are summarised by the transformation condition of chiral superfields. We show that $\mathcal{N}=1$ MHV super-vertices can be described by a formula similar to that of the $\mathcal{N}=4$ MHV super-amplitude. In the discussions we briefly remark on how to derive Nair's formula for $\mathcal{N}=4$ SYM theory directly from light-cone lagrangian.Comment: 25 pages, 7 figures, JHEP3 style; v2: references added, some typos corrected; Clarification on the condition used to remove one Grassmann variabl

Measurement of Rashba and Dresselhaus spin-orbit magnetic fields

Spin-orbit coupling is a manifestation of special relativity. In the reference frame of a moving electron, electric fields transform into magnetic fields, which interact with the electron spin and lift the degeneracy of spin-up and spin-down states. In solid-state systems, the resulting spin-orbit fields are referred to as Dresselhaus or Rashba fields, depending on whether the electric fields originate from bulk or structure inversion asymmetry, respectively. Yet, it remains a challenge to determine the absolute value of both contributions in a single sample. Here we show that both fields can be measured by optically monitoring the angular dependence of the electrons' spin precession on their direction of movement with respect to the crystal lattice. Furthermore, we demonstrate spin resonance induced by the spin-orbit fields. We apply our method to GaAs/InGaAs quantum-well electrons, but it can be used universally to characterise spin-orbit interactions in semiconductors, facilitating the design of spintronic devices