System Of Strings Research Articles

Laboratory studies of the impact of non-breaking waves on a horizontal emerged deck

The horizontal elements of maritime structures are susceptible to both wave impact and resulting vibrations. These vibrations can lead to a partial or complete failure of structures and require detailed investigations. To address this issue, laboratory experiments were conducted in a wave flume. The aim of this study was to investigate the problem of standing wave impact underneath a horizontal deck. The main focus was on the effect of the wave-induced vertical forces on the global response of the structure. The physical model of the deck was installed above a still water level in front of a vertical barrier. The model was supported by a system of strings and springs. The mechanical system had one degree of freedom corresponding to a small rotational displacement around rear deck edge. Among other physical parameters, the impact pressure generated under the structure due to wave impact was measured. The high sampling frequency of the data acquisition system allowed to capture momentary slamming pressure. The systems of accelerometers and displacement gauges were installed to measure induced vibrations. Thorough analysis of the influence of wave parameters and the deck clearance on the structure response was performed based on the measurements. The rapid slamming force increase, recorded at the moment of impact is not revealed in the dynamic response of the plate.

Multiview Incomplete Knowledge Graph Integration with application to cross-institutional EHR data harmonization

Objective:The growing availability of electronic health records (EHR) data opens opportunities for integrative analysis of multi-institutional EHR to produce generalizable knowledge. A key barrier to such integrative analyses is the lack of semantic interoperability across different institutions due to coding differences. We propose a Multiview Incomplete Knowledge Graph Integration (MIKGI) algorithm to integrate information from multiple sources with partially overlapping EHR concept codes to enable translations between healthcare systems. Methods:The MIKGI algorithm combines knowledge graph information from (i) embeddings trained from the co-occurrence patterns of medical codes within each EHR system and (ii) semantic embeddings of the textual strings of all medical codes obtained from the Self-Aligning Pretrained BERT (SAPBERT) algorithm. Due to the heterogeneity in the coding across healthcare systems, each EHR source provides partial coverage of the available codes. MIKGI synthesizes the incomplete knowledge graphs derived from these multi-source embeddings by minimizing a spherical loss function that combines the pairwise directional similarities of embeddings computed from all available sources. MIKGI outputs harmonized semantic embedding vectors for all EHR codes, which improves the quality of the embeddings and enables direct assessment of both similarity and relatedness between any pair of codes from multiple healthcare systems. Results:With EHR co-occurrence data from Veteran Affairs (VA) healthcare and Mass General Brigham (MGB), MIKGI algorithm produces high quality embeddings for a variety of downstream tasks including detecting known similar or related entity pairs and mapping VA local codes to the relevant EHR codes used at MGB. Based on the cosine similarity of the MIKGI trained embeddings, the AUC was 0.918 for detecting similar entity pairs and 0.809 for detecting related pairs. For cross-institutional medical code mapping, the top 1 and top 5 accuracy were 91.0% and 97.5% when mapping medication codes at VA to RxNorm medication codes at MGB; 59.1% and 75.8% when mapping VA local laboratory codes to LOINC hierarchy. When trained with 500 labels, the lab code mapping attained top 1 and 5 accuracy at 77.7% and 87.9%. MIKGI also attained best performance in selecting VA local lab codes for desired laboratory tests and COVID-19 related features for COVID EHR studies. Compared to existing methods, MIKGI attained the most robust performance with accuracy the highest or near the highest across all tasks. Conclusions:The proposed MIKGI algorithm can effectively integrate incomplete summary data from biomedical text and EHR data to generate harmonized embeddings for EHR codes for knowledge graph modeling and cross-institutional translation of EHR codes.

Higher dimensional Bianchi type-I string cosmological model in f(R) theory of gravity

In this paper, we have studied Bianchi type-I string cosmological model by combining Kaluza-Klein (KK) theory and f(R) theory of gravity which is an extension of 5-dimensional KK string cosmological models. We have used equation of state in the form of p-string or Takabayasi string given by ρ=(1+ω)λ, where ρ and λ denote the rest density of energy cloud of strings, and the tension density of the system of strings, respectively and ω is a constant. In order to get physically significant and viable solution various forms of the function f(R) are assumed, in this paper we assume f(R)=R+αR2 (e.g. Astashenok et al. (2017) [1]), where α is real number. Some physical and geometrical properties of the model are also discussed.

Fractal-like Mechanical Resonators with a Soft-Clamped Fundamental Mode.

Self-similar structures occur naturally and have been employed to engineer exotic physical properties. We show that acoustic modes of a fractal-like system of tensioned strings can display increased mechanical quality factors due to the enhancement of dissipation dilution. We describe a realistic resonator design in which the quality factor of the fundamental mode is enhanced by as much as 2 orders of magnitude compared to a simple string with the same size and tension. Our findings can open new avenues in force sensing, cavity quantum optomechanics, and experiments with suspended test masses.

Energy decay and control for a system of strings elastically connected in parallel

In the present paper, we study energy decay and exact boundary controllability for a system of n one‐dimensional linear wave equations coupled in parallel. The control obtained is a square integrable of the Neuman type for initial data with finite energy. The controllability time is near optimal value. We treat the case of control in the whole boundary and also in part of it.

Exact charges from heterotic black holes

We derive exact relations to all orders in the α′ expansion for the charges of a bound system of heterotic strings, solitonic 5-branes and, optionally, a Kaluza-Klein monopole. The expressions, which differ from those of the zeroth-order supergravity approximation, coincide with the values obtained when only the corrections of quadratic order in curvature are included. Our computation relies on the consistency of string theory as a quantum theory of gravity; the relations follow from the matching of the Wald entropy with the microscopic degeneracy. In the heterotic frame, the higher-curvature terms behave as delocalized sources that introduce a shift between near-horizon and asymptotic charges. On the other hand, when described in terms of lower-dimensional effective fields, the solution carries constant charges over space which coincide with those of the asymptotic heterotic fields. In addition, we describe why the Gauss-Bonnet term, which only captures a subset of the relevant corrections of quadratic order in curvature, in some cases succeeds to reproduce the correct value for the Wald entropy, while fails in others.

Exact boundary controllability and its applications for a coupled system of quasilinear wave equations with dynamical boundary conditions

A constructive method with modular structure is used to obtain the local exact boundary controllability for a coupled system of quasilinear wave equations with local or non-local dynamical boundary conditions. Some applications are given for the chain-like or star-like system of strings coupled via elastic springs, and of strings coupled via Maxwell-type and Kelvin-type viscoelastic springs, respectively.

Book Review: The Inka Empire: A Multidisciplinary Approach edited by Izumi Shimada

Izumi Shimada, ed. The Inka Empire: A Multidisciplinary Approach . Austin: University of Texas Press, 2015. Pp. 392. $75.00; ISBN: 978-0-292-76079-0. The Inka Empire or Tawantinsuyu (the Quechua name for the “realm of four parts”) was the largest political system to develop in the New World. Tawantinsuyu extended over 2,000,000 square kilometers and encompassed at least 86 ethnic groups from Argentina and Chile to the current border between Ecuador and Colombia. Intriguingly, the Inka ruled their empire without wheeled technologies, markets, money, or phonetic writing systems. Instead, they kept the records of the empire in a complex system of knotted strings called khipus . For that reason, much of what we know of this interesting polity comes from post-conquest sources. This breathtaking collaborative volume, edited by Izumi Shimada, seeks to offer a holistic vision of the Inka empire, placing different disciplines, methods, sources, and perspectives in dialogue. It includes 19 chapters by 23 authors that consider linguistic and genetic evidence along with material culture and historical documents to study Inka origins, imperial infrastructure, administrative strategies, agricultural technology, accounting, architecture and landscape intervention, and political organization, among other aspects. The volume is divided into five parts, prefaced by a useful introductory chapter by Shimada that lays out the book’s aims and …

Axions from strings: the attractive solution

We study the system of axion strings that forms in the early Universe if the Peccei-Quinn symmetry is restored after inflation. Using numerical simulations, we establish the existence of an asymptotic solution to which the system is attracted independently of the initial conditions. We study in detail the properties of this solution, including the average number of strings per Hubble patch, the distribution of loops and long strings, the way that different types of radiation are emitted, and the shape of the spectrum of axions produced. We find clear evidence of logarithmic violations of the scaling properties of the attractor solution. We also find that, while most of the axions are emitted with momenta of order Hubble, most of the axion energy density is contained in axions with energy of order the string core scale, at least in the parameter range available in the simulation. While such a spectrum would lead to a negligible number density of relic axions from strings when extrapolated to the physical parameter region, we show that the presence of small logarithmic corrections to the spectrum shape could completely alter such a conclusion. A detailed understanding of the evolution of the axion spectrum is therefore crucial for a reliable estimate of the relic axion abundance from strings.

Collectivity without plasma in hadronic collisions

We present a microscopic model for collective effects in high multiplicity proton–proton collisions, where multiple partonic subcollisions give rise to a dense system of strings. From lattice calculations we know that QCD strings are transversely extended, and we argue that this should result in a transverse pressure and expansion, similar to the flow in a deconfined plasma. The model is implemented in the Pythia8 Monte Carlo event generator, and we find that it can qualitatively reproduce the long range azimuthal correlations forming a near-side ridge in high multiplicity proton–proton events at LHC energies.

Rotating Space Elevators: A New Venue in Space Elevator Physics

The physics of Space Elevators connecting the Earth with outer space has recently attracted increased attention, in part due to the discovery of ultra-strong materials such as carbon nanotubes and diamond nano-thread structures. In this article we review a new venue in space elevator physics: Rotating Space Elevators (RSE) [Golubovic, L. & Knudsen, S. (2009). Classical and statistical mechanics of celestial scale spinning strings: Rotating space elevators. Europhysics Letters 86(3), 34001.]. The RSE is a double rotating system of strings reaching outer space. Objects sliding along the RSE string (sliding climbers) do not require internal engines or propulsion to be transported far away from the Earth's surface. The RSE thus solves a major problem in the space elevator technology which is how to supply the energy to the climbers moving along the string. RSE strings exhibit interesting nonlinear dynamics and statistical physics phenomena. Satellites and spacecraft carried by sliding climbers can be released (launched) along RSEs. RSE strings can host space stations and research posts. Sliding climbers can be then used to transport useful loads and humans from the Earth to these outer space locations.

Nonstationary vibrations of strings and their systems contacting with different concentrated loads

Nonstationary vibrations of strings and their systems, caused by a finite numbers of concentrated loads, are considered. External forces can be simulated by nonstationary concentrated loads. We can use nonstationary concentrated loads to simulate the external forces and reactions, conformed to influence of mass or dampers. A generalized layout of research was built for system of strings, where all strings intersect a common one. A method for constructing the system of equations is given. The system consists of one-dimensional wave equations for several strings. The system is closed by additional relations in contact points. The obtained system is the system of Volterra integral equations. The system is reduced to block matrix equation after discretization. The problem of nonstationary string vibrations with two joined dampers is solved as an example.

Strange metals from quantum geometric fluctuations of interfaces

Our current understanding of strongly correlated electron systems is based on a homogeneous framework. Here we take a step going beyond this paradigm by incorporating inhomogeneity from the beginning. Specifying to systems near the Mott metal-insulator transition, we propose a real space picture of itinerant electrons functioning in the fluctuating geometries bounded by interfaces between metallic and insulating regions. In 2+1-dimensions, the interfaces are closed bosonic strings, and we have a system of strings coupled to itinerant electrons. When the interface tension vanishes, the geometric fluctuations become critical, which gives rise to non-Fermi liquid behavior for the itinerant electrons. In particular, the poles of the fermion Green's function can be converted to zeros, indicating the absence of propagating quasiparticles. Furthermore, the quantum geometric fluctuations mediate Cooper pairing among the itinerant electrons, indicating the intrinsic instability of electronic systems near the Mott transition.

Cognition around the world

Cognition around the world

Estimating parameters of fragments forming at penetration of periodic system of strings into a semi-infinite target

An elastic–plastic model for a high-velocity penetration of periodic system of strings into a semi-infinite target is proposed. The model allows one to estimate the size, velocity and kinetic energy of the fragments forming at the penetration. The results obtained are compared with known experimental data for aluminum projectile interaction with meshes.

On spectral method in the axial channeling theory

The quantization of the transverse motion energy in the continuous potentials of atomic strings and planes can take place under passage of fast charged particles through crystals. The energy levels for electron moving in axial channeling regime in a system of parallel atomic strings (for instance, [110] strings of a silicon crystal) are found in this work for the electron energy of order of several tens of MeV, when a total number of energy levels becomes large (up to several hundreds). High resolution of the spectral method used for energy level search has been demonstrated. Hence this method could be useful for investigation of quantum chaos problem.

The Superconductivity of the Double Correlated Linear Aggregations of Holes in the Cuprates

Here I extend my last work about the origin of the pseudo-gaps in underdoped cuprates (arXiv: cond-mat. 1011.3206), to include the mechanism of superconductivity. This is done by adapting the formalism of the double correlations in systems with nested Fermi surfaces to the semi one dimensional system of strings of holes. It is proposed that magnetic interaction is crucial for the establishment of the pseudogap and the high temperature superconductivity. It is shown that superconductivity disturbs the completeness of the strings of holes, and creates fluctuations in their shapes. This, in turn, reduces the magnetic interaction and the pseudogap order.

On the use of the Varignon frame for single facility Weber problems in the presence of convex barriers

This paper presents a new experimental approach to the Weber problem in the presence of convex barriers by using the Varignon frame. The Varignon frame is a mechanical system of strings, weights and a board with holes that has been used to identify an optimal location for the classical Weber problem. We show through analytical results that the same analog can also be used for some of the Weber problems in the presence of barriers. Some examples from the literature are revisited through experiments. Findings are compared to those found in the literature. Practical use of the analog is discussed as it provides rapid solutions, allows for flexibility, and enables one to visualize the problem.

Education as Re-Embedding: Stroud Communiversity, Walking the Land and the Enduring Spell of the Sensuous

How we know, is at least as important as what we know: Before educationalists can begin to teach sustainability, we need to explore our own views of the world and how these are formed. The paper explores the ontological assumptions that underpin, usually implicitly, the pedagogical relationship and opens up the question of how people know each other and the world they share. Using understandings based in a phenomenological approach and guided by social constructionism, it suggests that the most appropriate pedagogical method for teaching sustainability is one based on situated learning and reflexive practice. To support its ontological questioning, the paper highlights two alternative culture’s ways of understanding and recording the world: Those of the Inca who inhabited pre-Columbian Peru, which was based on the quipu system of knotted strings, and the complex social and religious system of the songlines of the original people of Australia. As an indication of the sorts of teaching experiences that an emancipatory and relational pedagogy might give rise to, the paper offers examples of two community learning experiences in the exemplar sustainable community of Stroud, Gloucestershire in the United Kingdom where the authors live.

MODIFIED SCHEME OF CRYSTALLINE UNDULATOR

The new scheme of crystalline undulator based on coherent bremsstrahlung from above barrier relativistic electrons interacting with a system of atomic strings periodically deformed by acoustic wave is proposed and studied in the work. The possibility to generate X-rays in the range of about 10 keV and more by electrons with energies of about 100 MeV is shown. Spectral-angular density of the emission being considered may be six times greater than ordinary CB.