bluuebunny/crossref_metadata_2025 huggingface dataset:
Understanding the chemical contribution to the enhancement mechanism in SERS: Connection with Hammett parameters
Authors: Trivedi Dhara J. , Barrow Brendan , Schatz George C.
Published: September 2020

The enhancement mechanism due to the molecule–surface chemical interaction in surface-enhanced Raman scattering (SERS) has been characterized using a theoretical approach based on time dependent density functional theory. This includes a systematic study of the chemical mechanism (CM) to the SERS enhancement for halogen substituted benzenethiols interacting with a silver cluster. Changing the halogen on benzenethiol enables us to systematically modulate interactions between the benzenethiol ring and the metal cluster. We observe a decrease in the CM enhancement factor with an increase in the atomic number of the halogen for para-substitutions. For meta-substitutions, there is no such trend. However, the results scale linearly with the Hammett parameters for both meta and para halogens, which provides an important predictive tool for interpreting chemical enhancements. We also study the effect of solvation on the CM, showing that there is a systematic increase in enhancement with the increasing solvent dielectric constant. The correlation of CM with other properties, such as the amount of charge transfer between adsorbate and metal and the excitation energies of charge transfer states, is much less predictive than the Hammett parameter correlation.
Upper-class romance: homogamy at the apex of the class structure
Authors: Toft Maren , Jarness Vegard
Published: September 2020

This article focuses on social closure by way of marital homogamy within the upper class. It offers new insights into the social structuring of romantic partnerships, while drawing on research on assortative mating and contemporary elite and class analysis. The analysis is based on detailed data covering the entire Norwegian population. Our main point of focus is the upper class, whose patterns of partner choice have been little studied. By drawing on Bourdieu’s model of the social space, we move beyond conventional operationalisations of class. The analysis demonstrates that romantic partnerships within the upper class are structured along three dimensions of class: (i) vertical inter-class closure (upper-class individuals are disproportionately more likely to have partners in upper-class positions); (ii) horizontal intra-class closure (a tendency for marrying within the same upper-class fraction); (iii) closure by class trajectory (upwardly mobile newcomers are disproportionately more unlikely to have upper-class partners). We also demonstrate how class divisions intersect with gender divisions. Among the men, there are important differences between the upper-class fractions: the cultural fraction is more homogamous than the other fractions, and the economic fraction is comparatively more likely to have partners from lower down in the class structure.
New Zealand blackcurrant extract enhances muscle oxygenation during repeated intermittent forearm muscle contractions in advanced and elite rock climbers
Authors: Fryer Simon , Giles David , Bird Ellis , Stone Keeron , Paterson Craig , Baláš Jiří , Willems Mark E. T. , Potter Julia A. , Perkins Ian C.
Published: September 2020

Anthocyanin‐rich New Zealand blackcurrant (NZBC) may improve forearm muscle oxygenation and enhance performance in high‐level rock climbers. As such, using a double‐blind, randomised, cross‐over design study, twelve participants performed an oxidative capacity assessment, and two successive exhaustive exercise trials (submaximal forearm muscle contractions at 60% of their maximal volitional contraction). Each visit was conducted following 7‐days intake of 600 mg·day−1 NZBC extract or placebo. Oxidative capacity was estimated by calculating the oxygen half time recovery using near infrared spectroscopy. Time to exhaustion (s), impulse (kg·s), and minimum tissue saturation index (min‐TSI %) were assessed during both the exercise trials. Muscle oxidative capacity was greater with NZBC (mean difference [MD] = 5.3 s, 95% confidence intervals [95% CI] = 0.4–10.2 s; p = 0.036; Cohen's d = 0.94). During the exercise trials, there was an interaction for min‐TSI % (time x condition, p = 0.046; = 0.372), which indicated a greater level of oxygen extraction during trial two with NZBC extract (MD = 9%, 95% CI = 2‐15%) compared to the placebo (MD = 2%, 95% CI = 1–7%). There was a decrease in time to exhaustion (p <0.001, = 0.693) and impulse (p = 0.001, = 0.672) in exercise trial two, with no effect of NZBC extract. In high‐level rock climbers 7‐days NZBC extract improves forearm muscle oxygenation with no effect on isolated forearm muscle performance.
ATP synthase: Evolution, energetics, and membrane interactions
Authors: Nirody Jasmine A. , Budin Itay , Rangamani Padmini
Published: September 2020

The synthesis of ATP, life’s “universal energy currency,” is the most prevalent chemical reaction in biological systems and is responsible for fueling nearly all cellular processes, from nerve impulse propagation to DNA synthesis. ATP synthases, the family of enzymes that carry out this endless task, are nearly as ubiquitous as the energy-laden molecule they are responsible for making. The F-type ATP synthase (F-ATPase) is found in every domain of life and has facilitated the survival of organisms in a wide range of habitats, ranging from the deep-sea thermal vents to the human intestine. Accordingly, there has been a large amount of work dedicated toward understanding the structural and functional details of ATP synthases in a wide range of species. Less attention, however, has been paid toward integrating these advances in ATP synthase molecular biology within the context of its evolutionary history. In this review, we present an overview of several structural and functional features of the F-type ATPases that vary across taxa and are purported to be adaptive or otherwise evolutionarily significant: ion channel selectivity, rotor ring size and stoichiometry, ATPase dimeric structure and localization in the mitochondrial inner membrane, and interactions with membrane lipids. We emphasize the importance of studying these features within the context of the enzyme’s particular lipid environment. Just as the interactions between an organism and its physical environment shape its evolutionary trajectory, ATPases are impacted by the membranes within which they reside. We argue that a comprehensive understanding of the structure, function, and evolution of membrane proteins—including ATP synthase—requires such an integrative approach.
Deflection angle and shadow behaviors of quintessential black holes in arbitrary dimensions
Authors: Belhaj A , Benali M , El Balali A , El Moumni H , Ennadifi S-E
Published: September 2020

Motivated by M-theory/superstring inspired models, we investigate certain behaviors of the deflection angle and the shadow geometrical shapes of higher dimensional quintessential black holes associated with two values of the dark energy (DE) state parameter, being

ω
=
−

1

3

and

ω
=
−

2

3

. Concretely, we derive the geodesic equation of photons on such backgrounds. Thanks to the Gauss–Bonnet theorem corresponding to the optical metric, we compute the leading terms of the deflection angle in the so-called weak-limit approximation. After that, we inspect the effect of DE and the space–time dimension d on the calculated optical quantities. Introducing DE via the field intensity c and the state parameter ω, we find that the shadow size and the deflection angle increase by increasing values of the field intensity c. However, we observe that the high dimensions decrease such quantities for ω-models exhibiting similar behaviors. Then, we consider the effect of the black hole charge, on these optical quantities, by discussing the associated behaviors. The present investigation recovers certain known results appearing in ordinary four dimensional models.
Nuclear explosions: a study
Authors: Khan F A
Published: September 2020

The incident neutron energy dependence of the neutron multiplication rate constant α is studied for 235U- and 239Pu-based nuclear explosions. At high neutron energy, α comes out to be about 10 generations/shake for both 235U and 239Pu. In addition, the photon gas model seems to hold well for the very early stage of a nuclear explosion as one is able to reproduce the yield (20.4 ± 2.4) kiloton for the Trinity test.
Quantum surfing
Authors: Rasinskaitė D , Strange P
Published: September 2020

Here we report a project in which time-dependent supersymmetry has been employed to derive a new potential and eigenfunctions that satisfy the Schrödinger equation. The supersymmetry method is outlined and we apply it to a wavefunction obeying the free-particle Schrödinger equation. This leads to an exactly soluble model in which a quantum particle is seen to ‘surf’ on a time-dependent potential. The model can be solved and understood within both classical and quantum mechanics and the relationship between the two approaches is discussed. The mathematics of this formalism is accessible to a final year British undergraduate making supersymmetry derived Hamiltonians suitable as a final year theoretical physics research project.
Effect of interfiber bonding on the rupture of electrospun fibrous mats
Authors: Chavoshnejad Poorya , Alsmairat Ohood , Ke Changhong , Razavi Mir Jalil
Published: September 2020

Electrospun fibrous mats have a wide range of applications, and characterizing their mechanical behavior is an important task. In addition to the mechanical properties of the individual fibers, other factors can alter the overall mechanical behavior of the mat. In this study, we use computational and experimental methods to investigate the effect of interfiber bonding on the failure and rupture of typical fibrous mats. A non-linear finite element model of a mat is simulated with randomly distributed fibers with different porosities. The percentage of bonding between intersecting fibers is controlled by an auxiliary code. The results reveal that interfiber bonding increases the stiffness of the mat, and the toughness of the mat increases as well. Interestingly, a large percentage of interfiber bonding at a predefined porosity of a mat does not increase the elastic modulus of the mat, nor does it have considerable effects on the failure behavior. Moreover, the effect of interfiber bonding increases with a mat’s porosity. The findings of this study could help tune the mechanical properties of fibrous mats used for different applications.
Bound fermion states in pinned vortices in the surface states of a superconducting topological insulator
Authors: Deng Haoyun , Bonesteel N , Schlottmann P
Published: September 2020

By analytically solving the Bogoliubov–de Gennes equations we study the fermion bound states at the center of the core of a vortex in a two-dimensional superconductor. The superconducting states are induced via proximity effect between an s-wave superconductor and the surface states of a strong topological insulator. The strong spin–orbit coupling locks the spin perpendicular to the momentum (Rashba interaction). A zero-energy Majorana state arises together with an equally spaced (

Δ

∞

2

/

E

F

) sequence of fermion excitations. The spin–momentum locking is key to the formation of the Majorana state. We present analytical expressions for the energy spectrum and the wave functions of the bound states. The wave functions fall off exponentially with the distance ρ from the core of the vortex as

exp

[

−

∫

0

ρ

d

ρ

′

Δ

(

ρ

′

)

/

v

F

]

. An analytic expression for the local density of states (LDOS) for the bound states is obtained. The particle–hole symmetry is broken in the LDOS as a consequence of the spin–orbit coupling. The spin-polarization of the bound states is discussed. We also obtain the energy shifts of the bound states in a small magnetic field. A unitary transformation relating the model with Rashba interaction to the Dirac Hamiltonian is presented.
Loss tolerant quantum absorption measurement
Authors: Okamoto Ryo , Tokami Yuta , Takeuchi Shigeki
Published: September 2020

The quantum statistics of entangled photon pairs promise greater performance for absorption measurements than can be achieved classically. However, the performance of a quantum approach is easily degraded under a loss of photons caused by experimental limitations. Here, we propose a loss-tolerant quantum scheme using quantum destructive interference in a nonlinear interferometer. Our theoretical results show that the loss-tolerant quantum scheme surpasses the conventional quantum scheme under photon loss at the detection stage. We demonstrate how photon losses at optical paths and mode-mismatches in a nonlinear interferometer affect the performance of our scheme. We also propose a hybrid approach to cope with the case where the quantum destructive interference is imperfect, and show that the hybrid scheme always surpasses the conventional quantum scheme.
Production of energetic protons, deuterons, and neutrons up to 60 MeV via disruption of a current-carrying plasma column at 3 MA
Authors: Klir D , Shishlov A V , Kokshenev V A , Jackson S L , Rezac K , Cherdizov R K , Cikhardt J , Dudkin G N , Fursov F I , Krasa J , Kravarik J , Kubes P , Kurmaev N E , Munzar V , Ratakhin N A , Turek K , Varlachev V A
Published: September 2020

Acceleration of ions to multi-MeV energies is investigated in various plasma devices to better understand processes in astrophysical plasmas and to develop efficient accelerators for a variety of applications. This paper reports the production of proton, deuteron, and electron beams in a z-pinch—a cylindrically symmetric plasma column that is compressed by its own magnetic field. For this work, the GIT-12 pulsed-power generator was used to drive a novel configuration of z-pinch that dramatically enhanced ion acceleration associated with disruption of the current by instabilities in the compressed plasma. During the disruption of 3 MA current, hydrogen ions were accelerated up to at least 50 MeV, which is almost a hundred-times the ion energy provided by the generator driving voltage of 0.6 MV. Under optimal conditions, the total numbers of hydrogen ions with energies above 20 and 50 MeV were 4 × 1013 and 1011, respectively. Accelerated deuterons produced one 20 ns (full width at half maximum) pulse of fast neutrons via D(d, n)3He and other nuclear reactions. A maximum neutron output of (1.0 ± 0.2) × 1012 neutrons/sr was observed downstream, i.e., in the anode to cathode direction. In this direction, the maximum neutron energy reached 58 ± 7 MeV. Both ion and neutron beams in our experiment reached an end-point energy of about 60 MeV, which is the highest value observed in pulsed-power devices. A localized peak voltage of ≳60 MV was driven by the inductive energy that was stored around the plasma column and that was extracted during a sub-nanosecond current drop. Considering the natural occurrence of current-carrying columns in laboratory and space plasmas, the current interruption observed in z-pinches could represent a more general physical process that contributes to the efficient conversion of magnetic energy into the energy of particle beams in various plasmas.
Ultra-fast two-qubit ion gate using sequences of resonant pulses
Authors: Torrontegui E , Heinrich D , Hussain M I , Blatt R , García-Ripoll J J
Published: September 2020

We propose a new protocol to implement ultra-fast two-qubit phase gates with trapped ions using spin-dependent kicks induced by resonant transitions. By only optimizing the allocation of the arrival times in a pulse train sequence the gate is implemented in times faster than the trapping oscillation period T < 2π/ω. Such gates allow us to increase the number of gate operations that can be completed within the coherence time of the ion-qubits favoring the development of scalable quantum computers.
Twin-field quantum key distribution with passive-decoy state
Authors: Teng Jun , Lu Feng-Yu , Yin Zhen-Qiang , Fan-Yuan Guan-Jie , Wang Rong , Wang Shuang , Chen Wei , Huang Wei , Xu Bing-Jie , Guo Guang-Can , Han Zheng-Fu
Published: September 2020

Twin-Field quantum key distribution (TF-QKD) and its variants, e.g. phase-maching QKD, sending-or-not-sending QKD, and no phase post-selection TFQKD promise high key rates at long distance to beat the rate distance limit without a repeater. The security proof of these protocols are based on decoy-state method, which is usually performed by actively modulating a variable optical attenuator together with a random number generator in practical experiments, however, active-decoy schemes like this may lead to side channel and could open a security loophole. To enhance the source security of TF-QKD, in this paper, we propose passive-decoy based TF-QKD, in which we combine TF-QKD with the passive-decoy method. And we present a simulation comparing the key generation rate with that in active-decoy, the result shows our scheme performs as good as active decoy TF-QKD, and our scheme could reach satisfactory secret key rates with just a few photon detectors. This shows our work is meaningful in practice.
Heterogeneity and ‘memory’ in stem cell populations
Authors: Stumpf Patrick S , Arai Fumio , MacArthur Ben D
Published: September 2020

Modern single cell experiments have revealed unexpected heterogeneity in apparently functionally ‘pure’ cell populations. However, we are still lacking a conceptual framework to understand this heterogeneity. Here, we propose that cellular memories—changes in the molecular status of a cell in response to a stimulus, that modify the ability of the cell to respond to future stimuli—are an essential ingredient in any such theory. We illustrate this idea by considering a simple age-structured model of stem cell proliferation that takes account of mitotic memories. Using this model we argue that asynchronous mitosis generates heterogeneity that is central to stem cell population function. This model naturally explains why stem cell numbers increase through life, yet regenerative potency simultaneously declines.
Identification of Gas Flow Regimes in Adiabatic Microtubes by means of Wall Temperature Measurements
Authors: Kashiwagi R , Hong C , Asako Y , Morini G L , Faghri M
Published: September 2020

There exists the laminar flow, transitional flow, turbulent flow and choked flow regimes in a microtube gas flow. Development of a non-invasive identification method of the flow regimes within a microdevice is expected. This paper demonstrated how the internal gas flow regimes can be identified by measuring the distribution of the external wall temperature of the microchannel along the flow direction. A series of experiments were conducted by using nitrogen as working fluid through a stainless steel micro-tube with an inner diameter of 523 µm and a fused silica micro-tube having a diameter of 320 µm. The experiments were performed by fixing the back pressure at the exit of the microchannel at the atmospheric value and by varying the inlet pressure in order to modify the gas flow regime. In order to measure the external wall temperature along the microtube, two or three bare type-K thermocouples with a diameter of 50 µm were attached to the micro-tube external surface by using a high conductivity epoxy. In the case of the microtube having a diameter of 523 µm, local pressures were measured at three local pressure ports along the microtube. The pressure ports were placed on the opposite side of the tube wall where three thermocouples were attached. The microtube external wall was thermally insulated with foamed polystyrene to prevent heat gain or loss from the surrounding. The experimental results show that the wall temperature decreases in the laminar flow regime, increases in the transitional flow regime, decreases in the turbulent flow regime and it stays nearly constants in the choked flow regime. The behavior of the average Fanning friction factor and the local Mach number can be explained by identifying the flow regime. It is clarified that the microtube external wall temperature is a reliable indicator of the flow regime.
Numerical analysis of double-layered microchannel heat sinks with different microchannel heights
Authors: Savino S , Nonino C
Published: September 2020

A numerical parametric analysis is carried out to investigate the thermal performance of double-layered microchannel heat sinks for different values of the relative channel height and fixed values of the total pumping power, with the additional constraint that the pressure drop be the same in the two layers in order to allow a much simpler header design, which can only include a single inlet and a single outlet. Single-layered microchannel heat sinks are also considered for additional comparisons. The computed results show that, in the hypothesis of this work (i) the ratio of the heights of the upper and lower microchannels only has a marginal effect on the overall thermal resistance but a significant influence on the temperature uniformity of the bottom (heated) surface and (ii) a better temperature uniformity is achieved when the heights of the upper microchannels are larger than those of the lower ones.
CFD simulation of turbulent flows over wire-wrapped nuclear reactor bundles using immersed boundary method
Authors: Cervone Antonio , Chierici Andrea , Chirco Leonardo , Da Vià Roberto , Giovacchini Valentina , Manservisi Sandro
Published: September 2020

A preliminary study for lead-bismuth eutectic (LBE) turbulent flows over wire-wrapped nuclear reactor bundles is performed. The 19-pin hexagonal bundle geometry, representative of NACIE-UP facility and adopted in the MYRRHA reactor [1, 2], is considered. The presence of the helical wire wrap has a strong effect on flow patterns inside the bundle geometry, with induced secondary flows and enhanced mixing [3]. From a computational point of view, the wire-wrapped geometry model is much more complex to realize than the bare rod configuration and simplified models are often used [4, 5]. In order to overcome the difficulties of the model generation, an hybrid body fitted immersed boundary method is used. A computational grid that fits the presence of bundle pins is generated, as for the case of the bare rod configuration, allowing a better control of mesh resolution in the regions close to wall boundaries. The immersed boundary method is used to model the presence of the helical wire wrap so that its effect on fluid motion can be taken into account.
Design and implementation of a modulating test plant to assess the performance of innovative cross-flow heat recovery units for air conditioning system: preliminary results.
Authors: Bonfiglio C , Bozzoli F , Cattani L , Pagliarini G , Rainieri S. , Vilar França M , Vocale P
Published: September 2020

Nowadays global warming has increased consciousness of the dangers of energy wastefulness: in the last 50 years the temperature of the Earth’s surface rose by approximately 1 °C. The building sector is responsible for a very high percentage of world carbon emissions and with the increasing of the request for comfort, heating, ventilation and air conditioning, buildings energy consumption is rapidly growing. Consequently, it appears fundamental the role played by the improvement of buildings energy performance within global policies of emissions reduction. In this context an increasing attention is given to the energy waste reduction in tertiary sector: bars, offices, restaurants, meetings, shops, school buildings, gyms and in general in the buildings in which the minimization of the energy dissipation is requested. The present study is part of the NANOFANCOIL project (POR-FESR 2014-2020): one of the objectives was the design and implementation of a modulating test plant to assess the performance of innovative cross-flow heat recovery units for air conditioning system. This experimental setup was mainly composed by two climatic chambers that enabled to simulate the environmental conditions of interest. The temperature could vary from -20°C to 0°C and from 10°C to 30°C for the cold and the hot chamber, respectively (i.e. the outdoor and the indoor environment). Moreover, the climatic chamber that simulates the indoor environment could be controlled also in terms of humidity thanks to a steam humidifier that guaranteed 5 kg/h of vapour. Preliminary results about the heat transfer behaviour of a cross-flow heat recovery unit (air-to-air) for controlled mechanical ventilation systems that employs mini-channels in order to increase performance and reduce size and costs are presented here.
Measurements of Spectrally Averaged Absorptivity and Emissivity for a Selective Solar Absorber in High Vacuum Under Direct Solar Illumination
Authors: Alessandro C D’ , De Maio D , De Luca D , Musto M , Di Gennaro E , Rotondo G , Dalena D , Russo R
Published: September 2020

The innovative ultra-high vacuum technology applied to solar thermal flat panels, allows to reach high operating temperatures (up to 200 °C) without concentration, cutting out both convective and conductive thermal losses of the internal gas. The system losses are mainly due to the radiative energy emitted by the absorber. In this paper, a power balance equation has been used to perform the best fit of the data recorded with the absorber first exposed to the Sun illumination (up to the stagnation temperature, typically above 300 °C) and then cooled down by using an opaque shield. In particular, the fitting procedure is useful to evaluate the spectrally averaged absorptivity and the temperature dependent spectrally averaged emissivity of the absorber in a realistic operating condition.
An experimental study on the transient thermal response of an electronic equipment box for UAV remote sensing applications
Authors: Tanda G
Published: September 2020

An experimental study of the transient thermal characteristics of an electronic equipment box is presented. The box is designed to house devices typically used for UAV-based remote sensing applications. Different cooling systems, aimed at maintaining all the components within their allowable temperature limits for the duration (15-20 min) of each UAV flight, have been considered. They include forced convection of external or internal air and use of storage units (cold gel packs) inside the box. Experiments indicated that a mixed active/passive technique consisting in the combination of cold gel packs and internal ventilation, without any air renewal, provides the most suitable cooling condition.
Numerical modelling of a PV-T collector working as evaporator in a solar assisted heat pump
Authors: Zanetti E , Del Col D
Published: September 2020

A numerical study of a PV-T collector working as an evaporator for a solar assisted heat pump is presented. The work has been realized in the framework of the SolairHP project for the study of a reversible dual source heat pump. The main objective is to increase the seasonal coefficient of performance of the heat pump compared to an air source heat pump and reduce the overall electrical consumption by including a solar collector-evaporator. A mathematical steady state model of the solar evaporator device has been realized in Matlab environment: it considers the energy and mass fluxes in three dimensions by working a discretization of the main surfaces of the PV sandwich and of the absorber plate (roll-bond plate). The input of the model are the ambient conditions (irradiance components and air temperature), the thermodynamic conditions of the refrigerant at the inlet (enthalpy and mass flowrate) and the circuitation. The main results of the model are the electric and thermal efficiency, the conditions of the refrigerant all along the channels and the temperature distribution on the PV-T surfaces. The numerical model has been used in the design procedure of the solar evaporators to be coupled to a 8 kW heat pump working with R32. A preliminary seasonal analysis on the PV-T evaporator has been realized in order to evaluate the advantage of the dual source system.
Towards DES/DDES computation of the flow field and heat transfer adopting elliptic relaxation and local correlation based transition approaches
Authors: D’Alessandro V , Giammichele L , Lops C , Ricci R
Published: September 2020

As Large–Eddy Simulation (LES) shall remain too expensive in the following few decades for the ever increasing number of engineering complexities, researches have shifted much of the attention and effort to hybrid formulations incorporating Reynolds–Averaged Navier– Stokes (RANS) equations and LES in a certain ways. The long term goal of this research activity is to develop accurate hybrid RANS/LES methods. These approaches are particularly appealing in massively separated flows since they offer good prediction performance and they can be considered a good trade–off, in terms of computational resources, if compared with standard LES techniques. In particular with this work we want to deeply investigate Detached–Eddy Simulation (DES) based on: (i) elliptic relaxation turbulence model; (ii) Spalart Allmaras local correlation based transition model (LCTM). Specifically, we analyze v2–f DES approach for the convective heat transfer around a sphere at Re = 5000 (with Pr = 0.71) and we compare these results with the so called delayed version of the model. At the same time we also investigate the LCTM version of the SA model, in the DES context.
Numerical Simulations of the flow field within a 1:10 Aspect Ratio duct at intermediate Re
Authors: Vignati Federica , Fustinoni Damiano , Gramazio Pasqualino , Vitali Luigi , Niro Alfonso
Published: September 2020

Numerical simulations are carried on to study the fluid-dynamical features of a smooth duct with aspect ratio of 10. The duct is operated with an incompressible, newtonian fluid, whose Reynolds number, computed over the hydraulic diameter and bulk velocity, ranges from 470 to 14500, encompassing laminar and turbulent flow. To capture the details of all the flow scales, Direct Numerical Simulations are performed, by means of a code developed at Politecnico di Milano. The adopted code is a finite-difference, structured grid solver, that includes a mass flow rate correction. The latter guarantees high accuracy in the calculation of unsteady flows, or during the transition to turbulent regime, and it allows to check the consistency of numerical results.

Both global parameters –including the friction factor and the identification of the laminar-to-turbulent transition and local flow features, e.g., corner vortexes, are investigated and presented in this work. Preliminary analyses agree fairly well with literature data and with experimental results obtained at ThermALab of Politecnico di Milano.

The final goal of this work, including a deep integration between the numerical and the experimental setup, is to carry on detailed investigations of the fluid-dynamical and thermal characteristics of ribbed ducts, in the perspective of heat transfer enhancement and pressure drop reduction.
Increased efficiency of combined heat and power plants by utilizing waste heat for resorption chillers and their combination with hydrocarbon chillers
Authors: Ziegler O , Hesse U , Thomas C
Published: September 2020

The use of waste heat has long been a topic to increase the efficiency of large-scale industrial processes, but it is becoming as well important in the commercial sector and in small and medium-sized industrial plants. For a sustainable and decentralized energy supply it is necessary to utilize all exergy flows much more than before. Particularly in decentralized combined heat and power (CHP) plants, the annual coefficient of performance is low due to seasonal temperature fluctuations, as the generated heat cannot be used or can only be used partly during the summer and transitional months. Interface technologies such as sorption technology can be used to further increase the utilization rate of such CHP plants and provide cooling capacity at the same time. This concept allows the utilization of previously unused waste heat to generate cooling in the temperature range from -6°C to 15°C, without the necessity of significant amounts of electric energy for the operation of additional compression refrigeration systems. In a pilot project funded by the German Federal Ministry of Economic Affairs and Energy, a thermally driven refrigeration plant with a small cooling capacity of maximum 25 kW using the resorption principle was evolved under these aspects and installed in a supermarket. Special focus is given to the flexibility of the plant technology as well as to the potentials of combinations of thermally and electrically driven chillers with natural refrigerants such as hydrocarbons and ammonia and the integration of thermal storage for temporal decoupling or discontinuous availability of heat and cooling load.
Confined Copolymer Structures
Authors: Pezzutti Aldo D. , Hernández Hugo
Published: September 2020

Bulk morphologies of diblock copolymers have been extensively studied in literature both experimentally and theoretically. Depending on the composition of the blocks it is comprised of, the bulk structures correspond to lamellae, gyroids, cylinder hexagonal arrangements and BCC structures of spheres. Recent research has shown that confinement is a powerful tool to break the symmetry of a structure, and obtain new shapes, different from those of the bulk.

The process of forming new morphologies by confinement in nano-droplets, created from a dewetting process, was simulated. The structures obtained showed a great similarity with the experimental results present in the literature.

The developed model captures the fundamental interactions that determine the dynamics of the phase separation process of the confined copolymer system between a rigid substrate and a free surface.
Study of acoustic characteristics of the swirling flow generated in ejector
Authors: Vekteris V , Styra A , Mokshin V , Turla V , Viselga G , Tetsman I
Published: September 2020

The article deals with changes in the density of pulsating water and air flow generated in pulsating flow ejector. Transformation of the fluid motion equation to Lighthill’s equation describing density change and acoustic radiation of the flow is presented. Calculation results demonstrate suitability of the ejector to cause acoustic agglomeration and effectively remove iron particles from potable water.
Methods and tools for teaching programming at university
Authors: Kasyanov Victor N. , Kasyanova Elena V.
Published: September 2020

The paper is devoted to the methods and tools for teaching programming developed in the A.P. Ershov Institute of Informatics Systems. Practical work on programming and an introductory course of programming on the basis of the Zonnon language are considered. The paper also describes the development of an adaptive system for distance learning and a visual cloud system that supports parallel and functional programming.
A Novel Technique for Optimization of Statistical Decisions under Parametric Uncertainty through Invariant Statistical Embedding and Averaging in Terms of Pivotal Quantities
Authors: Nechval N. A. , Berzins G. , Nechval K. N. , Danovics V.
Published: September 2020

In the present paper, a new technique of invariant embedding of sample statistics in a decision criterion (performance index) and averaging this criterion via pivotal quantity is proposed for intelligent constructing efficient (optimal, uniformly non-dominated, unbiased, improved) statistical decisions under parametric uncertainty. The technique of invariant statistical embedding and averaging in terms of pivotal quantities (ISE&APQ) is independent of the choice of priors and represents a novelty in the theory of statistical decisions. It allows one to eliminate unknown parameters from the problem and to find the efficient statistical decision rules, which often have smaller risk than any of the well-known decision rules. To illustrate the proposed technique of ISE&APQ, application examples are given.
ml-experiment: A Python framework for reproducible data science
Authors: Molner Domenech Antonio , Guillén Alberto
Published: September 2020

Nowadays, data science projects are usually developed in an unstructured way, which makes it difficult to reproduce. It is also hard to move from an experimental environment to production. Operational workflows such as containerization, continuous deployment, and cloud orchestration allow data science researchers to move a pipeline from a local environment to the cloud. Being aware of the difficulties of setting those workflows up, this paper presents a framework to ease experiment tracking and operationalizing machine learning by combining existent and well-supported technologies. These technologies include Docker, Mlflow, Ray, among others. The framework provides an opinionated workflow to design and execute experiments either on a local environment or the cloud. ml-experiment includes: an automatic tracking system for the most famous machine learning libraries: Tensorflow, Keras, Fastai, Xgboost and Lightgdm, first-class support for distributed training and hyperparameter optimization, and a Command Line Interface (CLI) for packaging and running projects inside containers.
Evaluation of the effectiveness of the soil-cement with hydrophobized surface for road construction
Authors: Kuyukov S , Testeshev A , Zhigailov A , Shmatok V
Published: September 2020

The paper presents an assessment of the effectiveness of the use soil-cement with hydrophobized surface by conducting a feasibility study. The work performed theoretical studies and the calculation part. The object of study is a soil-cement with hydrophobized surface at the base in road foundation of the road. The subject of the study is the economic efficiency of the use of modified soil-cement. Theoretical studies are based on the choice of methodology for assessing the economic efficiency of the use of this material with its subsequent description. The calculation part includes determining the benefits of road users, current and one-time costs from the use of various constructions of pavement for the billing period. The result of the calculations is a graph of the dependence of the economic efficiency of various structures on traffic intensity. The use of soil-cement with hydrophobized surface will reduce economic costs in the construction of roads, increase the speed and quality of work, increase the overhaul time of roads of federal and regional significance.
Influence of light aggregate on structure formation of lightweight concrete
Authors: Larsen O A , Bulgakov B I , Gafarov R M , Melikhov D O
Published: September 2020

Recycling of glass industry waste is relevant in the world today. It is caused by the increase of environmental problems and devastation of natural resources. One of the option of cullet recycling is production of foamed lightweight glass aggregate. It is energy efficient material with size up to 75 mm, irregular shape and relatively low strength. High specific surface area of aggregate leads to increase the cement consumption to achieve acceptable concrete compaction. This article presents the results of size gradings selection of coarse foamed glass aggregate and its water demand in concrete mix. The determination of structure formation period and water demand of foamed glass aggregate are presented. The influence of particle size distribution of lightweight aggregate on structure formation period of lightweight concrete is established. The density and compressive strength of structural lightweight concrete with foamed lightweight glass aggregate are 1468 kg/m3 and 19 MPa, respectively. The density and strength of insulating lightweight concrete are 1167 kg/m3 and 10 MPa, respectively. The cement consumption of structural and insulating concrete is 260 kg and 254 kg, respectively.
Calculation of shear stresses in the soil of the subgrade using empirical plasticity conditions
Authors: Aleksandrov A , Dolgih G , Kalinin A
Published: September 2020

The aim of the work is to replace the criterion of the original Mohr – Coulomb criterion with an empirical plasticity condition in which the limit state arises at deformation εlim<15 %. As a result of the analysis of experimental data on testing soils by triaxial compression, an empirical plasticity criterion is obtained. The limiting state by the empirical criterion occurs when the sample is deformed by 10–12%. The shear stresses calculated by this plasticity condition exceed the shear stresses calculated by the Mohr – Coulomb criterion. Therefore, the application of the proposed criterion in the calculation of pavement by shear resistance in the soil of the subgrade requires an increase in the thickness of the structural layers, compared with the traditional calculation, which is based on Mohr – Coulomb.
Building energy modeling as a mandatory requirement of cooperative housing projects
Authors: Larionov A , Smirnova E , Larionova Y
Published: September 2020

Energy modeling of buildings reduces sales risks in the sense that it contributes to expanding the spheres of business, hi-tech production, innovations and information telecommunication technologies, improve the state of the environment. Until recently, the risks of “equity holders” were quite high despite the insurance system and bankruptcy procedure in accordance with the federal law. The process of cooperative housing projects did not prevent from frankly fraudulent schemes. Regulatory authorities have established strict requirements for the legitimate use of homebuyer’s assets, having formed the interaction with developers in electronic format. Among the pressing issues of organization and management of construction, one of the most significant is the problem of shared housing construction and efficient pricing management since the strategic approach of urban development and housing and utilities infrastructure depends on its decision. Depending on the problems facing a developer at various stages of its activity, the assessment of its reliability seems to be the most controversial. The tendency towards the destruction of the institutional fundamentals of housing was clearly marked; the implementation of most housing projects has been questioned. The system of standards for energy modeling allows the use of data for optimal pricing in order to avoid risks and harmonize relations between developers and shareholders at an early stage of the project. Building energy modeling as a mandatory requirement of cooperative housing projects are aimed at the construction of eco-friendly, economically- and energy-efficient buildings and entire districts convenient for living with the use of biopositive architectural and planning design concepts.
Current issues of energy efficiency in water consumption and discharge, and environmental safety in St Petersburg
Authors: Smirnova E
Published: September 2020

The author attempts to determine current issues energy efficiency in water consumption and discharge, and environmental safety in the field of construction activities. A methodological rationale for measures to increase in water consumption efficiency is given. Mass discharges of polluted wastewater by industrial enterprises and utilities infrastructure, diffuse runoff from urban areas, industrial sites and agricultural fields result in total pollution of surface and many underground water sources in St Petersburg. The scenario for 2030 based on a predictable number population of approximately 6.5 mn people and a specific rate of drinking water consumption of 160 l/day is considered optimal. There is one paradox: efficiency enhancement measures would have to stabilize tariffs for water use and disposal, but they are actually rising. The author analizes a number of priority measures are required to provide for the stable operation of the water use and disposal system in public utilities and urban enterprises. Author’s concept of the utilities infrastructure functioning involves the introduction of public private partnerships. To stabilize tariffs for water use and disposal, it is necessary to implement public private partnerships. However, it shall be carefully reasoned on the basis of full information and statistics on the housing and utilities infrastructure operation.
Block diagram of the automatic model of technical documentation
Authors: Baratov D , Aripov N , Muxiddinov O , Jumanov X
Published: September 2020

The article explores the features of electronic document management of technical documentation of railway automation and telemechanics. The article deals with the synthesis of mathematical models of electronic document management of technical documentation of railway automation and telemechanics. For this purpose, the real processes of creation, verification and use of technical documentation were examined using the example of the process of accounting and control of railway automation and telemechanics devices, which made it possible to identify a structural diagram of a formalized model of technical documentation. A model of electronic document management of technical documentation is created using the mathematical apparatus of finite state machines. A block diagram of an automaton model of technical documentation is developed. The proposed block diagram of a formalized model of technical documentation consists of matrices of external microoperations, internal microoperations, code creation for the following microcomponents. The number of internal states of the firmware is completely determined by the number of logic elements of the algorithms. The size of the matrices depends on the number of operators and logical conditions in the logic circuits of the algorithms.
Business center construction project as the model of resource-saving building
Authors: Luchkina V V
Published: September 2020

Design with resource-saving technologies has become an important part of the Terms of Reference for the project, and environmental friendliness has become a key core of the business center marketing strategy. The purpose of research was to develop the business center construction project as the model of resource-saving building. The research results are the following tasks: to create the comfortable environment for lessees and guests: thermal and visual comfort, air exchange quality; to ensure high energy efficiency of the building; to reduce the resource consumption costs to maximum (energy, water and heat). In the research, the project concept and business plan were developed, the project risks analysis was conducted and the project economic efficiency assessment was performed. In the course of research, the calculations of the full life cycle cost of the building were analyzed and made. The following technical characteristics on internal and external lighting, heat supply of the building, comfortable environment, heat exchange quality, water treatment and re-use, and energy-efficient elevators were considered. The project comprises the land improvement plan for adjacent territory, including introduction of the “green” roof technology to into operation. In the project, the risk of excess water consumption and damage of finishing materials and equipment were brought to minimum. It is planned to have separate accounting of the energy, water and heat by various lessees, floors and functional areas of the business center. The readings will be recorded by the automated control and dispatch system of the building. This will make it possible to conduct a detail results analysis, keep statistics and set the goals to reduce the resource consumption.