Immersed boundary simulation of flow through arterial junctions

The present work demonstrates implementation of a mass-conserving sharp-interface immersed boundary for simulation of flows in branched arterial geometries. A simplistic two-dimensional arterial junction is considered to capture the preliminary flow physics in the aortic regions. Numerical solutions are benchmarked against established available experimental PIV results in Ensley et al (Annu. Thorac. Surg. 68(4):1384–1390, 1999) and numerical predictions in Gilmanov and Sotiropoulos (J. Comput. Phys. 207(2):457–492, 2005) and de Zelicourt et al (Comput. Fluids 38(9):1749–1762, 2009). Simulations are further carried out for pulsated flows and effects of blockages near the junctions (due to stenosis or atherosclerosis). Instabilities in the flow structures near the junction and the resulting changes in the downstream pulsation frequency were observed. These changes account for the physiological heart defects that arise from the poorly working valve (due to blockage), giving rise to chest pain and breathing instability, and can potentially be used as a detection tool for arterial diseases.     

On the rates of convergence for moments convergence in regression models

In one-dimensional regression models, we establish a rate for the rth moment convergence \((r \geqslant 1)\) of the ordinary least-squares estimator involving explicitly the regressors, answering to an open question raised lately by Afendras and Markatou (Test 25:775–784, 2016). An extension of the classic Theorem 2.6.1 of Anderson (The statistical analysis of time series, Wiley, New York, 1971) is also presented.     

EM Radiation Sensor: Bulk SQUID Made from Polycrystalline HTSC

The micro-contacts in the granules of the high-temperature superconductor (HTSC) films and other polycrystalline objects after transition to the SC state would then be similar to a bulk superconducting quantum interference device (SQUID), with the point S-N-S state greatly enhancing the sensitivity to electromagnetic radiation and can be used as of the application for much higher resolution than ever before possible (Braginsky, NATO ASI Series, 329, 235 (1996); Bray, J. Supercond. Novel Magn., 21, 335–341 (2008); Cantor, Supercoduct. & Cryoelectronics, 2000). Production of SQUIDs based on thin films is a very complicated technological process, requiring very expensive equipment. Use of the composite (HTSC powder + epoxy matrix), compressed SC powder, and thick films for SQUID fabrication should be very much simpler. The range of frequencies that can by detected with such a device will depend on the circuit parameters and may be extended to the microwave or infrared regimes (Braginsky, NATO ASI Series, 329, 235 (1996); Jurga et al. Acta Phys Pol A, 114, (2007); Jurga et al., Acta Phys Pol A, 114, (2007)). The advantage of the bulk SQUID based on HTSC-YBa₂Cu₃O _x , BiSr₂Ca₂Cu₃O _X , B(Pb)iSr₂Ca₂Cu₃O _X , and NdBaCo _X (powder + epoxy matrix, compressed SC powders, and thick films) is the non-selective nature of the spectral characteristics over a wide frequency range, high sensitivity, and quick response. For suppressing the large noise resulting from the maximal instability of electromagnetic properties at the SC, insulator transition is employed a differentiation procedure of the measurements signal.     

Test on the linear combinations of mean vectors in high-dimensional data

In this study, we propose a procedure for simultaneous testing \(l (l\ge 1)\) linear relations on \(k(k\ge 2)\) high-dimensional mean vectors with heterogeneous covariance matrices, which extends the result derived by Nishiyama et al. (J Stat Plan Inference 143(11):1898–1911, 2013) and does not need the normality assumption. The newly proposed test statistic is motivated by Bai and Saranadasa (Statistica Sinica 6(2):311–329, 1996) and Chen and Qin (Ann Stat 38(2):808–835, 2010). As a special case, our result could be applied to multivariate analysis of variance, that is, testing the equality of k high-dimensional mean vectors.     

A citation-based cross-disciplinary study on literature ageing: part II—diachronous aspects

In the first part of our study (Zhang and Glänzel in Scientometrics, 2017) we provided a view of the literature ageing based on a synchronous approach. Taking up the ideas by Egghe (Scientometrics 27(2):195–214, 1993) and Glänzel et al. (Scientometrics 109(3):2165–2179, 2016) we extend our study in the second part by applying a diachronous approach on the basis of citing literature. For this purpose we used the Prospective Price Index which was recently introduced by Glänzel et al. (Scientometrics 109(3):2165–2179, 2016). Finally, we compare the two aspects of literature ageing. In particular, we analyze the correlation between the share of recent references and the share of fast response, and found a generally positive correlation between both aspects at different levels of aggregation (subfields, major fields and the individual paper level). However, the consistence varies among different aggregations. For examples, on the level of subject fields, Chemistry, Biology, Neuroscience & Behavior are found with evidently better ranks by Prospective Price Index than Price Index, indicating their faster ageing process in the mirror of citations than references, while Engineering and Social sciences are found with the opposite ageing features. At the journal level, we observed a striking divergence between the reference and citation ageing patterns in some cases. Thus several journals proved ‘hard’ from the perspective of information sources (cited papers) but, at the same time, rather ‘soft’ in the light of information targets (citing papers).     

Letter to the editor: Dimensionless citation indicators

Bornmann and Leydesdorff (Scientometrics, 2018.  https://doi.org/10.1007/s11192-018-2682-1) make an excellent case to use normalized citation based indicators instead of the h-index. In this Letter to the Editor we point out that h/P, p/P and i/P are all very simple and intuitive dimensionless citation indicators where h is the Hirsch h-index, p the performance index of Prathap, and i the value of impact as measured by the ratio of citations C to Publications P.     

Strain-injection and crack-path field techniques for 3D crack-propagation modelling in quasi-brittle materials

This paper presents a finite element approach for modelling three-dimensional crack propagation in quasi-brittle materials, based on the strain injection and the crack-path field techniques. These numerical techniques were already tested and validated by static and dynamic simulations in 2D classical benchmarks [Dias et al., in: Monograph CIMNE No-134. International Center for Numerical Methods in Engineering, Barcelona, (2012); Oliver et al. in Comput Methods Appl Mech Eng 274:289–348, (2014); Lloberas-Valls et al. in Comput Methods Appl Mech Eng 308:499–534, (2016)] and, also, for modelling tensile crack propagation in real concrete structures, like concrete gravity dams [Dias et al. in Eng Fract Mech 154:288–310, (2016)]. The main advantages of the methodology are the low computational cost and the independence of the results on the size and orientation of the finite element mesh. These advantages were highlighted in previous works by the authors and motivate the present extension to 3D cases. The proposed methodology is implemented in the finite element framework using continuum constitutive models equipped with strain softening and consists, essentially, in injecting the elements candidate to capture the cracks with some goal oriented strain modes for improving the performance of the injected elements for simulating propagating displacement discontinuities. The goal-oriented strain modes are introduced by resorting to mixed formulations and to the Continuum Strong Discontinuity Approach (CSDA), while the crack position inside the finite elements is retrieved by resorting to the crack-path field technique. Representative numerical simulations in 3D benchmarks show that the advantages of the methodology already pointed out in 2D are kept in 3D scenarios.     

Linear Response of One-Dimensional Liquid $$^4\hbox {He}$$ to External Perturbations

We study the response of one-dimensional liquid \(^4\hbox {He}\) to weak perturbations relying on the dynamical structure factor, \(S(q,\omega )\), recently obtained via ab-initio techniques (Bertaina et al. in Phys Rev Lett 116:135302, 2016). We evaluate the drag force, \(F_\mathrm{v}\), experienced by an impurity moving along the system with velocity v and the static response function, \(\chi (q)\), describing the density modulations induced by a periodic perturbation with wave vector q.     

Theory of <Emphasis Type="Italic">d</Emphasis>-Wave High Temperature Superconductivity in the Cuprates Involving Non-linear Lattice Modes

The transition mechanism in high temperature cuprate superconductors is an outstanding puzzle. A previous suggestion on the role of non-linear local lattice instability modes on the microscopic pairing mechanism in high temperature cuprate superconductors (Lee, J. Supercond. Nov. Magn. 23(3), 333; 2009) is re-examined to provide a viable mechanism for superconductivity in these cuprates via an unusual lattice vibration in which an electron is predominantly interacting with a non-linear Q ₂ mode of the oxygen clusters in the CuO₂ planes. It is shown that the interaction has explicit d-wave symmetry and leads to an indirect coupling of d-wave symmetry between electrons. As a follow-up of Lee (J. Supercond. Nov. Magn. 23(3), 333; 2009), in this paper, we report detailed derivation of the superconducting gap equation and numerical solutions for the transition temperature as inherently integrated into the so-called extended Hubbard model (EHM). A unique feature in the EHM is that the transition temperature has an inherent k-dependence. In addition, superconducting gap solutions are restrained to specific regions in the first Brillouin zone (1BZ). It is very feasible to expect that the EHM naturally inherits a huge parameter space in which experimentally measured results, such as the well-known superconducting dome and the phase diagram from electronic Raman scattering (Sacuto et al., Rep. Prog. Phys. 76(2), 022502; 2013) can be accommodated. The EHM model hence offers a viable venue to search for or confirm any signature in k-point-sensitive experimental measurements.     

A Material History of Electroshock Therapy

The article considers the history of electroshock therapy as a history of medical technology, professional cooperation and business competition. A variation of a history from below is intended; though not from the patients’ perspective (Porter, Theory Soc 14:175–198, 1985), but with a focus on electrodes, circuitry and patents. Such a ‘material history’ of electroshock therapy reveals that the technical make-up of electroshock devices and what they were used for was relative to the changing interests of physicians, industrial companies and mental health politics; it makes an intriguing case for the Social Construction of Technology theory (Bijker et al., The social construction of technological systems: new directions in the sociology and history of technology. MIT Press, Cambridge, MA, 1987).     

The parameters governing the coefficient of dispersion of cubes in rotating cylinders

Axial dispersion of cubic particles in horizontal, rotating cylinders was investigated using discrete element modelling simulations. We found that, similar to the behavior of spheres, the axial dispersion coefficient of cubes depends on (1) the rotational speed of the cylinder \({\omega }\), (2) the acceleration due to gravity g and (3) the particle size d, satisfying the relationship \({D}_\mathrm {ax}\propto {\omega }^{1-2{\lambda }}{g}^{{\lambda }}{d}^{2-{\lambda }}\) with \({\lambda }\approx 0.15\) (\({\lambda }\approx 0.1\) for beds of spheres) (Third et al. in Powder Technol 203:510–517, 2010). This observation suggested that, although particle shape influences significantly the rate of axial dispersion (cubes disperse almost twice as fast as spheres of equal volume), the parameters controlling the coefficient of dispersion are independent of particle shape.     

A computationally efficient algorithm to simulate the butt curl deformation in casting processes

The aim of this work is to present a computationally efficient algorithm to simulate the butt curl deformation. In our previous articles [1, 2] the nonlinearities due to the viscoplastic law and the contact condition with the bottom block were solved by means of duality methods involving two multipliers. In [1] these multipliers were computed with a fixed point algorithm and in [2] with a generalized Newton’s method. In this work we improve the viscoplastic algorithm by means of a generalized duality method with variable parameters. We will present numerical results showing the applicability of the resultant algorithm to casting processes.     

The Viscosities of Dilute Kr,Xe, and CO$$_$$ Revisited: New Experimental Reference Data at Temperatures from 95 K to 690 K

Previously reported, but also unpublished experimental data of our group for the viscosities of dilute krypton, xenon, and carbon dioxide, obtained in the range from 295 K to a maximum of 690 K using oscillating-disk viscometers, were re-evaluated and corrected or extrapolated to the limit of zero density (\(\eta _0\)). The combined standard uncertainty of the data is 0.1 % at room temperature and 0.2 % at higher temperatures. For krypton and carbon dioxide, our \(\eta _0\) data were compared with \(\eta _0\) values theoretically calculated using the kinetic theory and highly accurate ab initio potentials for the krypton atom pair and the CO\(_2\) molecule pair, but also with recent experimental \(\eta _0\) data from the literature. Our data for krypton differ up to 690 K from the theoretical values by \(-0.10\,\%\) to \(+0.28\,\%\), whereas that of Lin et al. (Fluid Phase Equilib. 418:198, 2016) show deviations of +(0.04 to 0.20) % at temperatures from 243 K to 393 K, in each case proving that experiment and theory are in consistent agreement. The re-evaluated \(\eta _0\) data for xenon were compared with recent data from the literature and with calculated values resulting from the HFD-B potential for xenon via the corresponding-states principle to verify that they are reference values. For carbon dioxide, \(\eta _0\) values obtained from 26 re-evaluated isotherms and from eight isotherms of Schäfer et al. (J Chem Thermodyn 89:7, 2015) between 253 K and 473 K are mutually consistent with ab initio calculated and subsequently scaled viscosity values of Hellmann (Chem Phys Lett 613:633, 2014). The isotherms of Schäfer et al. are especially suitable for determining the initial density dependence of the viscosity. Concomitantly inferred reduced second viscosity virial coefficients were checked against two theoretical approaches of the Rainwater–Friend theory.     

New aspects for friction coefficients of finite granular avalanche down a flat narrow reservoir

This work examines the bulk internal friction coefficient, \(\mu \), and effective wall friction coefficient, \(\mu _w\), for finite number of nearly identical dry glass spheres in avalanche down a narrow inclined reservoir of smooth frictional bed using a validated discrete element scheme. Instantaneous deviatoric strain rate tensor \(\dot{\gamma }^d_{ij}\) and stress tensor \(\tau _{ij}\) are computed locally to evaluate a three-dimensional constitutive model developed based on the rheology of steady homogeneous surface flows. On one side, the algebraic \(\mu -I\) relation conforms to conventional relation for glass beads, \(\mu =0.34+0.31/(1+0.15/I)\) (Jop et al. in J. Fluid Mech. 541:167–192, 2005, Midi in Eur. Phys. J. E 14:341–365, 2004, Jop in Comptes Rendus Phys. 16:62–72, 2015), when the inertial number \(I>I_{c}=2\times 10^{-2}\). The assumption of collinear \(\tau _{ij}\) and \(\dot{\gamma }^d_{ij}\), however, does not hold and such misalignment agrees to the findings in non-uniform inhomogeneous flows (Cortet et al. in Europhys. Lett. 88(1):14001, 2009). Below \(I_c\), we observe a decaying \(\mu -I\) as found in slowly deforming rheology tests and a simplified model is developed in view of shear-induced dilatation upon yielding. Non-constant effective wall friction coefficient is measured to grow in time and with I towards the sphere-wall sliding friction coefficient in the contact model while preserving the depth-weakening feature as in confined steady surface flows (Richard et al. in Phys. Rev. Lett. 101:248002, 2008, Brodu et al. in Phys. Rev. E 87:022202, 2013). The fact that rotation at one sphere center can divert surface relative velocity across the contact area to render lower sliding friction is considered to develop a model describing how \(\mu _w\) drops with the ratio between rotation-induced velocity and sliding velocity, \(\varOmega \). The simulation data compares fairly well to the predicted monotonic decay of \(\mu _w\) with \(\varOmega \).     

Partial permutation decoding for MacDonald codes

We show how to find s-PD-sets of the minimal size \(s+1\) for the \(\left[ \frac{q^n-q^u}{q-1},n,q^{n-1}-q^{u-1}\right] _q \) MacDonald q-ary codes \(C_{n,u}(q)\) where \(n \ge 3\) and \(1 \le u \le n-1\). The construction of [6] can be used and gives s-PD-sets for s up to the bound \(\lfloor \frac{q^{n-u}-1}{(n-u)(q-1)} \rfloor -1\), of effective use for u small; for \(u \ge \lfloor \frac{n}{2} \rfloor \) an alternative construction is given that applies up to a bound that depends on the maximum size of a set of vectors in \(V_u(\mathbb {F}_q)\) with each pair of vectors distance at least 3 apart.     

Censored linear model in high dimensions

Censored data are quite common in statistics and have been studied in depth in the last years [for some references, see Powell (J Econom 25(3):303–325, 1984), Murphy et al. (Math Methods Stat 8(3):407–425, 1999), Chay and Powell (J Econ Perspect 15(4):29–42, 2001)]. In this paper, we consider censored high-dimensional data. High-dimensional models are in some way more complex than their low-dimensional versions, therefore some different techniques are required. For the linear case, appropriate estimators based on penalised regression have been developed in the last years [see for example Bickel et al. (Ann Stat 37(4):1705–1732, 2009), Koltchinskii (Bernoulli 15:799–828, 2009)]. In particular, in sparse contexts, the \(l_1\)-penalised regression (also known as LASSO) [see Tibshirani (J R Stat Soc Ser B 58:267–288, 1996), Bühlmann and van de Geer (Statistics for high-dimensional data. Springer, Heidelberg, 2011) and reference therein] performs very well. Only few theoretical work was done to analyse censored linear models in a high-dimensional context. We therefore consider a high-dimensional censored linear model, where the response variable is left censored. We propose a new estimator, which aims to work with high-dimensional linear censored data. Theoretical non-asymptotic oracle inequalities are derived.     

Comparison of the Argon Triple-Point Temperature in Small Cells of Different Construction

The argon triple point (\(T_{90} = 83.8058\,\hbox {K}\)) is a fixed point of the International Temperature Scale of Preston-Thomas (Metrologia 27:3, 1990). Cells for realization of the fixed point have been manufactured by several European metrology institutes (Pavese in Metrologia 14:93, 1978; Pavese et al. in Temperature, part 1, American Institute of Physics, College Park, 2003; Hermier et al. in Temperature, part 1, American Institute of Physics, College Park, 2003; Pavese and Beciet in Modern gas-based temperature and pressure measurement, Springer, New York, 2013). The Institute of Low Temperature and Structure Research has in its disposal a few argon cells of various constructions used for calibration of capsule-type standard platinum resistance thermometers (CSPRT) that were produced within 40 years. These cells differ in terms of mechanical design and thermal properties, as well as source of gas filling the cell. This paper presents data on differences between temperature values obtained during the realization of the triple point of argon in these cells. For determination of the temperature, a heat-pulse method was applied (Pavese and Beciet in Modern gas-based temperature and pressure measurement, Springer, New York, 2013). The comparisons were performed using three CSPRTs. The temperatures difference was determined in relation to a reference function \(W(T)=R(T_{90})/R(271.16\hbox {K})\) in order to avoid an impact of CSPRT resistance drift between measurements in the argon cells. Melting curves and uncertainty budgets of the measurements are given in the paper. A construction of measuring apparatus is also presented in this paper.     

Solubility Prediction of Active Pharmaceutical Compounds with the UNIFAC Model

The crystallization from solution of an active pharmaceutical ingredient requires the knowledge of the solubility in the entire temperature range investigated during the process. However, during the development of a new active ingredient, these data are missing. Its experimental determination is possible, but tedious. UNIFAC Group contribution method Fredenslund et al. (Vapor–liquid equilibria using UNIFAC: a group contribution method, 1977; AIChE J 21:1086, 1975) can be used to predict this physical property. Several modifications on this model have been proposed since its development in 1977, modified UNIFAC of Dortmund Weidlich et al. (Ind Eng Chem Res 26:1372, 1987), Gmehling et al. (Ind Eng Chem Res 32:178, 1993), Pharma-modified UNIFAC Diedrichs et al. (Evaluation und Erweiterung thermodynamischer Modelle zur Vorhersage von Wirkstofflöslichkeiten, PhD Thesis, 2010), KT-UNIFAC Kang et al. (Ind Eng Chem Res 41:3260, 2002), \(\ldots \) In this study, we used UNIFAC model by considering the linear temperature dependence of interaction parameters as in Pharma-modified UNIFAC and structural groups as defined by KT-UNIFAC first-order model. More than 100 binary datasets were involved in the estimation of interaction parameters. These new parameters were then used to calculate activity coefficient and solubility of some molecules in various solvents at different temperatures. The model gives better results than those from the original UNIFAC and shows good agreement between the experimental solubility and the calculated one.