bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparative study on electric and gas engine heat pump
Authors: Kuryło Konrad , Ruciński Adam
Published: December 2019

The paper compares heat pumps driven by electric motors (EHP) with heat pumps driven by gas engines (GEHP). GEHPs are still a novelty on the Polish HVACR market - therefore, the subject of the study is to indicate whether in Polish climatic conditions their use is profitable. A thorough analysis of the energy consumption of selected devices was carried out due to the consumption of utilities needed for their propulsion and the related costs. This has been done by calculating seasonal efficiency coefficients and using an innovative method of comparative modifiers allowing for unification of the performance of EHP and GEHP pumps. The results obtained include average energy efficiency coefficients, operating costs and payback times. Discussion of the calculation results proved that under certain assumptions GEHP pumps may be competitive with EHP heat pumps due to the possibility of managing waste heat at high temperatures.
Optimal operation of a hybrid-energy microgrid with energy storage system
Authors: Elgamal Mohamed , Korovkin Nikolay V. , Refaat Ahmed , Elmitwally Akram
Published: December 2019

In this paper, a day-ahead profit-maximizing energy management scheme for a grid-tied microgrid operation is proposed. The microgrid contains various types of distributed energy resources (DERs) and an inverter-interfaced battery-bank storage system. The average of day-ahead hourly forecasted data for loads, wind speed, and solar radiation are inputted into the framework of energy management (EMF). To optimize the microgrid performance, EMF determines the hourly dispatch of reactive and active power for each DER. Also, it specifies the discharging and charging times of the energy storage system and the onload tap changer position setting of the transformer connected to the main grid. The main aim is to maximize the revenue of microgrid meeting all technical limitations. The main grid can sell/buy reactive and active powers to/from the microgrid with a variable daily energy price of the market. A collective rule base-BAT algorithm is implemented as a solver of the energy management optimization problem for a grid-tided microgrid. Furthermore, the ability of the suggested EMF is proved in comparison with recent approaches.
Identification of sustainability of road safety improvement in Russian cities with a population of more than 1 million people
Authors: Petrov Artur
Published: December 2019

The article examines the issues of assessing the sustainability of road safety improvement process in Russian cities with a population of more than 1 million people. In 2015...2018 a sharp decrease in the overall level of road traffic accidents in the Russian Federation was recorded. However, in different regions and cities of the country this positive process runs extremely heterogeneously, with various speeds and different levels of qualitative changes in the field of road safety. The T-Wilcoxon criterion is an instrument, used in analyzing accident rate statistics, which can help in the argumentation of the opinion on the sustainability of this process or, vice versa, on the chaotic state and weak expression. On the example of accident rate statistics in Russian cities with a population of more than 1 million people, the article proves that improvement of road safety can be characterized as sustainable.
Analysis and regulation of the stress-strain state of structures with reliability
Authors: Tryapitsin Yurii , Pakhomov Viktor , Voinov Sergei
Published: December 2019

It is offered an algorithm for analysis and regulation of the stress-strain state of building constructions and soils of the foundations of structures at designing, building and exploitation, at setting of the mode of exploitation for providing of the required level of reliability, when tensions in them differ from calculation values. Possible options for secured or unsecured reliability are considered. The algorithm consists in determining the necessary decrease in the design stresses or increase the bearing capacity of structure. Offered algorithm is an estimation of necessary displacement of density of distribution of current tension or density of distribution of bearing strength for the achievement of the required level of reliability of the constructions and soil of base of the structure. Further research will be devoted to the consideration of case with unsecured reliability, for which it is necessary to assess the necessary displacement of the distribution density of the existing stresses or the distribution density of the bearing capacity to achieve the required level of reliability of the building constructions and soil of base of the structure.
Monitoring the dustiness of the gymnasium
Authors: Kalinina N.E. , Zhegalova M.N. , Skivko A.V. , Martynova E.V.
Published: December 2019

This article presents an experimental study of the concentration of fine dust in a covered sports facility using the example of a sports gym using a HANDHELD-3016 aerosol particle counter. The monitoring data of indoor air was analyzed and graphically presented in graphs of the integral function of the distribution of dust particles over the diameters. The concentration of fine dust at different time intervals during the training of the sports section was compared. The dependence of the distribution of dust particles over the measurement heights on the intensity of the workout was studied. Recommendations on improving air quality in a sports-type room during classes were provided. Changes in the indicators of external respiration during the training session was analysed.
Snow insulation and conservation systems
Authors: Ter-Zakaryan Karapet , Grigoryan Armen , Medvedev Andrey , Efimov Boris , Poserenin Aleksey
Published: December 2019

Various aspects of application of polyethylene foam implemented for roof thermal insulation within the frame of one of the sports venues and, closely, the realization of insulation systems for cold conservation on the territory of public sports facilities, particularly for snow storage conservation within ski resorts have been regarded in this article. Additional demands are placed on thermal insulating material for suchlike constructions. Apart from high thermo technical properties, the material should involve hermeticity, lightness, easy mounting and maintenance, durability, bacterial and fungal resistance and temperature differential resistance. The examination results concerning properties and particularities of application of non-cross-linked polyethylene foam within the scope of production of insulation coatings protecting the snow from melting are given in the article. It has been established that being the part of insulation system polyethylene foam preserves the accuracy of mechanical and thermo physical characteristics. Taking all functional particularities of insulation systems implementation into consideration, the principles of protection and conservation of snow covering have been developed being realized on the mountainsides and plateaus of ski resorts. Polyethylene foam rolls have been connected in a butt joint and mechanically fixed. As a result, a seamless insulating coating - thermal blanket has been formed, which covered the entire mountainside. Maintenance of insulation system is performed during the off-season between March and September in the period of stable positive temperatures.
GIS analysis of promising landing sites for manned flight to Mars
Authors: Kuziakina Marina , Gura Dmitry , Zverok Dmitry
Published: December 2019

Remote sensing provides data that can be used in a variety of projects. One such project is the preparation for sending a manned flight to Mars. Before the departure of the expedition it is very important to carefully select a place of high scientific value and a high security level for the members of the flight. Remote sensing methods allow getting the whole set of necessary data, which will later be used for the flight equipment properly, as well as to adapt the lander design. Currently, robotic probes that send the collected information to Earth are engaged in the collection of the necessary data. There, the data, in turn, can be processed by specialists, as well as provided for the general public for informational purposes only.
On the search of a potential displacement surface with the use of the local variation method
Authors: Makeeva Tamara , Trofimov Vitaly
Published: December 2019

The purpose of the article is to develop some basic conceptual provisions, algorithm and method of the search of the surface of the smallest resistance to shift, based on the minimization of durability functionality. The algorithm uses the approach, based on the direct iteration of various trial displacement surfaces and the selection of the surface with the minimum functionality value from these surfaces with the method of local variations. The coefficients allowing to estimate the possibility of rocks destruction at various sites of this surface are offered. The results of the search of a potential destruction surface for a pit board are given as an example.
Innovative development of the region through the formation of a technological cluster
Authors: Lapteva Svetlana
Published: December 2019

The issues of creation and functioning of technology parks, the development of innovative policies of the state, the problems of implementing innovative projects in the construction industry are discussed in the paper. Some statistical data reflecting the degree of development of this form of stimulating society to innovative development are presented. The author gives recommendations to facilitate the process of transferring the construction industry to an innovative path of development, as well as solving a number of emerging economic problems.
Key directions of development of measures to improve the reliability of electrical power systems
Authors: Jalilov R.B. , Latipov S.T. , Aslanova G.N. , Akhmedov A.A. , Shayimova S.P.
Published: December 2019

The article covers the study of measures aimed to improving the reliability of electrical power systems at the present stage. It considers the integration of the global electricity industry. The article analyzes the latest technical work in the field of automation, such as Smart Grid and intelligent power systems.
On the system of key indicators for monitoring the compliance with requirements of the Russia’s Energy Security Doctrine in terms of reliable fuel and energy supply to domestic consumers of energy resources
Authors: Senderov Sergey , Rabchuk Viktor
Published: December 2019

The paper is devoted to the problem of forming a system of indicators for monitoring the fulfilment of the requirements of the Russian Energy Security Doctrine, approved by the President of the Russian Federation in 2019, in terms of ensuring reliable fuel and power supply to energy consumers within the country. The main threats to energy security are described from the standpoint of ensuring the reliability of fuel and power supply to the regions of Russia and the country as a whole. Relevant indicators of federal and regional review levels are presented.
Digitalization of heat energy accounting as a means of improving the reliability of heat supply
Authors: Akhmetova I.G. , Lapin K.V. , Akhmetov T. R. , Balsamova E. Yu.
Published: December 2019

Annotation

The paper considers the issue of improving the reliability of heat networks due to timely detection of deviations of actual operating conditions from the normative-sections of the heat network located in a humid environment, intensifying the processes of external corrosion of metal. The use of the software complex in real time analyzing and notifying about the operating conditions of thermal networks, deviations from the normative values is proposed. A method for automated calculation of normative values of coolant temperature is developed.
Assessment of reliability and safety of work large pumps of machine irrigation systems
Authors: Kamalov Tоlyagan , Halikov Solixjon
Published: December 2019

The article provides an assessment of the reliability and safety of large pumps of machine irrigation systems in case of violations occurring in abnormal conditions and mechanical malfunctions of pump elements.
Procedure of selecting the priorities when constructing new most important facilities in the Russian energy sector in the context of materialization of strategic energy security threats
Authors: Rabchuk Viktor , Senderov Sergey
Published: December 2019

The paper is devoted to finding ways to solve the problem of a scientifically based approach to the selection of priorities in the construction of new most important energy facilities in Russia for the future up to 15 years. The perspective scales of realization of strategic threats to the energy security of Russia are characterized. A list of subtasks that should be solved to form a methodology for solving the problem is shown.
Long-term availability of generation capacity in the market-driven electric power industry
Authors: Khamisov Oleg V. , Podkovalnikov Sergei V. , Semenov Konstantin A.
Published: December 2019

The study investigates the issues of long-term availability of generation capacity in a market environment. The expansion of the electric power industry is analyzed, taking into account its one-product and two-product structural organization as well as its splitting into separate generation companies pursuing their own economic interests in an imperfect market. A case study is provided.
Use of phasor measurements for modeling FACTS at the electric power system state estimation
Authors: Kolosok Irina , Korkina Elena , Tikhonov Aleksandr
Published: December 2019

As the Smart Grid is being developed in the Russian Federation, a need in FACTS arises at resolving the issues of increasing the transmission capacity of electric power lines, voltage control, etc. The paper considers the issues of installing phasor measurement units (PMU) at the FACTS for the electric power system state estimation of (EPS SE). The relevance of the paper is explained by the mandatory introduction of PMUs at newly commissioned power engineering facilities (PEF) scheduled for 2020 and farther. PMUs registering voltage and current phasors at FACTS allow increasing the precision of results of the EPS SE problem and improving the electric modes at the considered PEF.
Best overall dimensions of synchronous generator with permanent magnets for small power wind plants and micro hydropower plants
Authors: Pirmatov Nurali , Tosheva Shaxnoza , Toshev Sherzod
Published: December 2019

The overall dimensions of a synchronous generator with permanent magnets are determined by its main dimensions - the length lp and active part of the rotor with a diameter Dp , so the larger the air gap, the smaller the magnetic induction in it and vice versa. The force of gravity, in turn, will also depend on the air gap. The structurally incorporated unevenness of the air gap leads to an increase in the attractive force in the place of the smallest gap value, which leads to the appearance of a bending moment. As a result, the disc skews and the load on the bearings increases.
Modeling of reliability of power supply systems with autonomous energy source
Authors: Ershov M.S. , Jalilov R.B. , Shayimova S.P. , Choriyev A.I. , Charieva M.R.
Published: December 2019

The methodology for calculating the reliability of power supply systems with autonomous and mixed energy sources has been considered. Autonomous sources are widely used in industrial power supply systems as primary, backup or emergency sources. The functioning and interchangeability of these systems has features that affect the reliability of power supply. The proposed methodology is based on the method of semi-Markov random processes and can be used for comparative analysis of the reliability of options for power supply systems. The methodology has been brought to software implementation and is accompanied by an example of calculating the reliability of the power supply system for stationary marine oil production platforms.
Increase of Transient Stability Level of Gas Turbine Power Plant Using FACTS
Authors: Solodyankin Sergey , Pazderin Andrey
Published: December 2019

The article is devoted to the development of the mathematical models of modern devices of flexible alternating current transmission systems (FACTS) when calculating the modes and stability of power systems and to the analysis of influence of the specified devices on transient stability of the generators. The considered scheme contains the generators with the gas turbine drive that have electromechanical parameters providing lower level of transient stability compared to units of higher power rating, which in some cases requires implementation of measures for transient stability enhancement. As examples of FACTS the following devices have been considered: compensating device based on voltage- sourced converter (STATCOM), static synchronous series compensator (SSSC) and the unified power flow controller (UPFC). The known examples of mathematical models of FACTS devices vary in complexity. For a preliminary assessment of the effectiveness of the FACTS devices, it is proposed to use simplified models that adequately reflect their impact on transients. The use of models made it possible to establish a positive impact of the devices on transient stability of generating equipment in case of short circuits in the electric network. The important conclusion here is that the use of the UPFC device based on two converters (with a corresponding increase in cost) compared to one converter device (STATCOM or SSSC) slightly increases the level of transient stability and the limit time of short circuit disconnection. The proposed method of simulating the FACTS devices is suitable for numerical calculations of transient processes in electric power systems, in particular, to estimate the impact on the transient stability level of the parallel operation of power plants in case of disturbances.
Placement of shunt reactors in high-voltage network using fuzzy constraints
Authors: Hashimov Arif , Guliyev Huseyngulu , Babayeva Aytek
Published: December 2019

In recent years, controlled shunt reactors (CSR) relevant to the class of FACTS facilities have been widely used to control voltage modes and reactive power flows in the high-voltage electrical network. The selection of location, as well as the definition of the law of CSR control in the conditions of stochastic variability of the operation mode of high-voltage power transmission, are associated with numerous technical and economic factors. At the same time, such constraint conditions as ease of use, performance efficiency, purpose and location in the system, as well as the period of commissioning should be taken into account. In the proposed procedure these factors are considered as fuzzy constraints. The procedure of CSR placement in the 330 kV electrical network of Azerenergy system for control of reactive power flows taking into account the mentioned fuzzy constraints is proposed. The obtained simulation results confirm the advantage of the proposed procedure.
Operational reliability of low-voltage asynchronous motors at asymmetrical supply voltage
Authors: Romanova Victoria , Khromov Sergey
Published: December 2019

Issues of operating modes of 4A series asynchronous squirrel-cage motors and AI serried motors at asymmetrical supply voltage for different values of motor shaft load are considered on the basis of simulation using Matlab software package and Simulink package. In the simulation, currents in asynchronous motor phases were evaluated as a function of K2U, KZ, and based on these results, permissible operation parameters were evaluated for induction motors. The results obtained are the basis for technical solutions aimed at improving operational reliability of asynchronous motors, they will allow taking into account permissible operating parameters of asynchronous motors not only in the design, but also in operation in power supply systems of various facilities.
Method of resource saving of cable production recycables
Authors: Tsypkina Victoria , Madrakhimov Daniyar
Published: December 2019

The article discusses development of recycling technologies of cabling and wiring products with justification for the relevance of the cable waste use in the process as part of the closed technological cycle of cabling and wiring products manufacture. Sources of waste generation are analysed. Issues of uninterrupted operation and reliability of technological equipment, efficiency of the recycling process and problems of the development of processing technologies in cable production are highlighted.
Improvement of algorithms for voltage circuits fault detection in relay protection terminal of 6-35 kV electrical networks
Authors: Vukolov Vladimir , Obalin Mikhail , Petrov Anton
Published: December 2019

Issues of increase of consumer power supply reliability by prevention of protection device false operation and unreasonable tripping of the protected network element at malfunction of measuring voltage transformer secondary circuits are considered. Options for implementation in relay protection microprocessor terminals of advanced blocking algorithms in case of voltage circuits fault are proposed.
On application of semi-Markov processes superposition to energy systems modeling
Authors: Obzherin Yuriy E. , Sidorov Stanislav M. , Nikitin Mikhail M.
Published: December 2019

One of the important tasks of the theory of reliability and efficiency of energy systems is the task of creating information systems for managing energy systems and the transition to intelligent management and engineering. The solution to this problem is possible based on the construction of mathematical models relating to various aspects of the structure and functioning of these systems. The paper, using the example of a superposition of independent semi-Markov processes constructed in the works of V.S. Korolyuk, A.F. Turbin, examines the possibilities of using semi-Markov processes with a common phase state space for modeling energy systems; an illustrative example of the application of this approach is given.
Topological algorithm for forming nodal stresses of complex networks energy systems
Authors: Akhmetbaev D.S. , Dzhandigulov A.R. , Akhmetbaev A.D.
Published: December 2019

The paper presents a new topological algorithm for the formation of nodal stresses of complex networks of power systems. The first step of the described algorithm is the search and determination of the values of all possible and specific trees of the graph corresponding to a given network of the power system. The well-known advantage of the topological approach compared to matrix methods, which allows one to obtain the final solution of non-linear equations of the steady state, has led to the development of many methods and corresponding software implementations. The paper provides a comparative analysis of the advantages and disadvantages of these methods. The main computational complexity of these methods is the search for 2 trees for each tree, which are obtained from it by dividing into two parts by removing any branch. A completely new topological approach that does not require finding 2 trees was proposed by one of the authors. The process of this method consists of the following steps: finding all possible graph trees, selecting specific graph trees, calculating the network node voltage. The work offers a unique algorithm for the implementation of these stages, which are implemented and tested at the software level. The result of the execution of the software package is the calculation of the steady state of a complex electric network using the distribution coefficients of the driving currents.
Electromagnetic safety of high voltage traction networks
Authors: Buyakova Natalya , Zakaryukin Vasilij , Kryukov Andrey
Published: December 2019

The article provides procedure for simulation modeling of traction power supply systems which allows analyzing electromagnetic safety conditions in perspective high voltage traction net- works. Modeling of electromagnetic fields in the Fazonord software application proved that 50 kV traction system is characterized by the highest electromagnetic strength at a height of 1.8 m above the ground surface, while 2x25 kV system is characterized by the lowest one. Traditional traction system with 27.5 kV voltage is the worst in terms of magnetic field strength, while 2x50 kV is the best; auto- transformer systems of traction power supply create magnetic fields due to demagnetizing effect of power leads.
Intellectualization of determination of electrical loads in city electric networks
Authors: Saidkhodjaev A.G. , Ametova B. Kh. , Mamutov M. M.
Published: December 2019

This article illustrates new methods for automatically fixing and determining the calculation loads of electrical consumers, in particular the maximum load. The accuracy in the calculations is increased taking into account several factors affecting the maximum load values. It also offers a method and algorithm determination of the maximum electrical loads in urban electrical loads.
Features stabilization of the consumer current using electro-ferromagnetic circuits
Authors: Rafikova G.R. , Ruzinazarov M.R. , Makhmutkhonov S.K.
Published: December 2019

Electromagnetic ferromagnetic oscillatory circuits having falling sections on the amplitude characteristics formed the basis of stabilizers based on the principle of summing the currents of individual branches. A distinctive feature of such stabilizers is that the current remains unchanged both when the load resistance changes, so when the input voltage varies over a wide range. This is required by devices such as electromagnets of physical instruments, electromagnetic lenses of electron microscopes, instruments for emitting nuclear paramagnetic resonance, instruments and devices of various automation schemes, measuring and computing equipment, as well as many electrotechnological processes. Therefore, current stabilization has long attracted the attention of many researchers, and this is still one of the important problems of electrical engineering. The curve shape of the proposed current stabilizer is close to a sinusoid, the power factor is very high, since the device operates in capacitive mode.
Method for determining the maximum load of consumers in city power supply systems
Authors: Saidkhodjaev A.G. , Najimova A.M. , Bijanov A.K.
Published: December 2019

In this article, we propose a new method for determining the maximum load of electric consumers in urban electric networks, which differs from existing methods in more accurate and reliable determination of the maximum loads. Based on the determination of the maximum loads of the objects of urban electrical networks, it is concluded that the proposed methods are determined by high accuracy and minor errors.
Non-contact voltage relay for switching windings of a boost transformer
Authors: Usmanov E.G. , Rasulov A.N. , Bobojanov M.K. , Karimov R.Ch.
Published: December 2019

In power supply systems the change in the magnitude of the voltage degrades the operation of electrical appliances right up to their failure. The proposed scheme of a contactless voltage relay based on a contactless voltage relay with switching the windings of a booster step-up transformer with a time delay allows switching the windings of a magnetizing booster transformer with a voltage change at the consumer terminals. Analytical studies of a non-autonomous non-linear dynamic circuit, which is the basis of the proposed device based on the classical method of solving a differential equation, which determines the nature of the voltage change for controlling thruster switches. The change of energy parameters of the proposed stabilizer depending on the voltage is given. The article considers the principle of operation of the proposed scheme of a contactless switching device based on a contactless voltage relay that switches the windings of a booster step-up transformer. An analytical study of a non-autonomous nonlinear dynamic circuit, which is the basis of the proposed device and the characteristics uc = f t required for switching the thruster is presented.
The role of information in power management tasks
Authors: Rakhmonov I.U. , Reymov K.M. , Shayumova Z.M.
Published: December 2019

The more complex the system designed to serve the person, the higher the requirements for its high-quality functioning and its reliability itself. Reliability monitoring should reach the level of the highest “survivability” if we consider systems such as “power systems”, i.e. systems whose services mankind does not intend to refuse in the foreseeable future. The presence of naturally wearing elements and seed details actualizes the issue of developing a certain “reliability index” and, accordingly, the procedure for its calculation and current display. Below we will consider possible solutions to the problems posed by the example of the electric power system. Since we are talking about “information”, first of all, on the basis of rigorous mathematical calculations, we will try to establish a connection between the measurement information and the so-called Shannon information. Summing up the above, we can outline the goals of research in the near future.
Method of choosing the unification of cable sections of electric network cables under conditions of load development uncertainty
Authors: Taslimov A.D. , Berdishev A.S. , Melikuziev M.V. , Rakhimov F.M.
Published: December 2019

The article analyzes the optimization criteria used in the conditions of uncertainty of the initial information, selects the number and values of standard cable sections under uncertainty, the development of the load over time using the minimax criteria of Wald and Savage, and also makes recommendations on the number and values of standard sections of distribution cables electrical networks
Method of selecting parameters of cable lines distributive networks 10 kv in uncertainty conditions
Authors: Taslimov A.D. , Berdishev A.S. , Melikuziev M.V. , Rakhimov F.M.
Published: December 2019

The article discusses the task of selecting the optimal number of types and values of standard cable sections of urban distribution electric power supply systems under conditions of uncertainty of electric load development using zoning method and proves the expediency of using a very limited number of standard cable sections (application of one or two standard cable sections at wide range of load DNsity variation).
The composition of natural waters of some source rivers of the republic of Uzbekistan, used in the thermal power engineering and the results of the experimental researches at preliminary and ion exchange treatment of water
Authors: Yusupaliev R. , Yunusov B.Kh. , Azimova M.M.
Published: December 2019

The article describes the possibility of use of the natural waters for generation of steam at thermal electric power stations. The chemical composition of some source rivers of the Republic of Uzbekistan is provided as well as its influence to the processing of water and contamination of the steam in the thermal energy engineering. The conditions of the preliminary chemical treatment of the natural water at TashTPP with the use of aluminum sulphate are described, as well as the experimental unit for production of the coagulant in the preliminary treatment and clarification of water; the experimental data on treatment of water with ions of chloride using the new ionites of type ASH-64 and ASH-64M, which were synthetized by the scientists of the Tashkent national university.
Self-starting of pump units when extinguishing voltage in the energy saving mode
Authors: Abidov Kudrat , Zaripov Odiljon
Published: December 2019

The article discusses the main processes that occur during the self-start of pumping units of pumping stations of systems of machine lifting for irrigation, ensuring the rational use of electricity, pumping equipment and irrigation water.
Green One-Pot Asymmetric Synthesis of Peptidomimetics via Sequential Organocatalyzed Aziridination and Passerini Multicomponent Reaction
Authors: dos Santos Deborah A. , da Silva Allan R. , Ellena Javier , da Silva Cecilia C. P. , Paixão Marcio W. , Corrêa Arlene G.
Published: December 2019

Peptidomimetics containing an aziridine moiety have been reported as potent cysteine protease inhibitors. In this sense, the development of stereoselective and sustainable synthetic strategies to obtain three-membered N-heterocyclic compounds has gained importance in the last decades. In this work, an efficient method was designed to achieve highly functionalized aziridine peptidomimetics via a sequential reaction, which involves the organocatalytic aziridination of α,β-unsaturated aldehydes followed by the Passerini multicomponent reaction in an environmentally friendly solvent mixture (ethanol: water).
Visible-Light-Induced Arene C(sp2)–H Lactonization Promoted by DDQ and tert-Butyl Nitrite
Authors: Wang Yiqing , Wang Shengpeng , Chen Bajin , Li Meichao , Hu Xinquan , Hu Baoxiang , Jin Liqun , Sun Nan , Shen Zhenlu
Published: December 2019

A visible-light photocatalytic aerobic oxidative lactonization of arene C(sp2)–H bonds proceeds in the presence of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and tert-butyl nitrite (TBN). Under the optimized conditions, a range of 2-arylbenzoic acids is converted into the corresponding benzocoumarin derivatives in moderate to excellent yields. This method is characterized by its atom economy, mild reaction conditions, the use of a green oxidant and metal-free catalysis.
Time delay in the swing equation: A variety of bifurcations
Authors: Scholl T. H. , Gröll L. , Hagenmeyer V.
Published: December 2019

The present paper addresses the swing equation with additional delayed damping as an example for pendulumlike systems. In this context, it is proved that recurring sub- and supercritical Hopf bifurcations occur if time delay is increased. To this end, a general formula for the first Lyapunov coefficient in second order systems with additional delayed damping and delay-free nonlinearity is given. Insofar, the paper extends the results about the stability switching of equilibria in linear time delay systems from Cooke and Grossman. In addition to the analytical results, periodic solutions are numerically dealt with. The numerical results demonstrate how a variety of qualitative behaviors are generated in the simple swing equation by only introducing time delay in a damping term.
Effects of interface-potential smoothness and wavefunction delocalization on Auger recombination in colloidal CdSe-based core/shell quantum dots
Authors: Hou Xiaoqi , Li Yang , Qin Haiyan , Peng Xiaogang
Published: December 2019

Auger nonradiative recombination dominates decay of multicarrier states in high quality colloidal quantum dots (QDs) and thus is critical for many of their optical and optoelectronic applications. Controlling interface-potential smoothness and wavefunction delocalization are proposed as two main strategies for Auger engineering in core/shell QDs. Here, a series of CdSe-based core/shell QDs with nearly ideal optical quality of their single-exciton states are developed and applied for studying biexciton quantum yields and Auger nonradiative recombination rates. Comparative experiments find that the interface-potential smoothness has little influence on biexciton quantum yield and Auger rates of these core/shell QDs with the same CdS outer shells. In contrast, with a fixed total size of the series of QDs, the decreasing hole wavefunction delocalization can increase the Auger rates of positive trions by ∼400%. A mild decrease in electron wavefunction delocalization among the series of QDs results in a small increase in the Auger rates of negative trions (∼50%). Smoothing the core/shell interface can indeed affect the Auger rates, but this is by the way of altering wavefunction delocalization. These findings highlight the importance of control of wavefunction delocalization among the strategies of Auger engineering and provide guidelines for rational design QDs for applications.
Conformal Killing initial data
Authors: García-Parrado Alfonso , Khavkine Igor
Published: December 2019

We find necessary and sufficient conditions ensuring that the vacuum development of an initial dataset of Einstein’s field equations admits a conformal Killing vector. We refer to these conditions as conformal Killing initial data (CKID), and they extend the well-known Killing initial data (KID) that have been known for a long time. The procedure used to find the CKID is a classical argument, which is reviewed and presented in a form that may have an independent interest, based on identifying a suitable propagation identity and checking the well-posedness of the corresponding initial value problem. As example applications, we review the derivation of the KID conditions as well as give a more thorough treatment of the homothetic KID conditions than was previously available in the literature.
On the Holway-Weiss debate: Convergence of the Grad-moment-expansion in kinetic gas theory
Authors: Cai Zhenning , Torrilhon Manuel
Published: December 2019

Moment expansions are used as a model reduction technique in kinetic gas theory to approximate the Boltzmann equation. Rarefied gas models based on so-called moment equations have become increasingly popular recently. However, in a seminal paper by Holway [“Existence of kinetic theory solutions to the shock structure problem,” Phys. Fluids 7(6), 911–913 (1965)], a fundamental restriction on the existence of the expansion was used to explain subshock behavior of shock profile solutions obtained by moment equations. Later, Weiss [“Comments on ‘Existence of kinetic theory solutions to the shock structure problem’ [Phys. Fluids 7, 911 (1964)],” Phys. Fluids 8(6), 1689–1690 (1996)] argued that this restriction does not exist. We will revisit and discuss their findings and explain that both arguments have a correct and an incorrect part. While a general convergence restriction for moment expansions does exist, it cannot be attributed to subshock solutions. We will also discuss the implications of the restriction and give some numerical evidence for our considerations.
Non-monotonic dependence of fluid dissipation on fluid density in fluid-coupled nanoresonators
Authors: Pial Turash Haque , Wang Yanbin , Das Siddhartha
Published: December 2019

Recent studies on fluid-coupled nanoresonators (represented by argon-filled carbon nanotubes or CNTs) have shown nonintuitive variation of the fluid dissipation (Dflu) with fluid density (ρ*) at high-frequency oscillations. In this letter, we propose a physical mechanism that can explain such a behavior. We identify that argon atoms are in the disordered (ordered) state within the CNTs at small (large) ρ*. For low-frequency oscillations, i.e., for oscillations with large characteristic excitation time scales, the argon atoms, at both large and small ρ*, have enough time to dissipate all the energy added from the imposed oscillations. But for high-frequency oscillations, i.e., for oscillations with small characteristic excitation time scales, while the argon atoms in the disordered state (low density) can dissipate all the energy in that small time, those in the ordered state (high density) cannot dissipate all the energy (and hence stores some energy) in that time. This explains the nonmonotonic density-dependence of Dflu in argon-filled CNTs at high frequency. We also explain this nonmonotonic density-dependence of Dflu from the corresponding Deborah number (De). De represents the ratio of the fluid relaxation to the excitation time scales. The relaxation time of CNT-confined argon increases with ρ*. Therefore, for a large-frequency (or a small excitation time) oscillation, De becomes large and the fluid starts losing its fluidity and shows solidlike (“elastic”) characteristics. This viscoelastic behavior ensures a partial storage (without dissipation) of the imposed oscillation, which in turn explains the nonmonotonic variation of Dflu with ρ* for large-frequency oscillations.
Implicit self-consistent electrolyte model in plane-wave density-functional theory
Authors: Mathew Kiran , Kolluru V. S. Chaitanya , Mula Srinidhi , Steinmann Stephan N. , Hennig Richard G.
Published: December 2019

The ab initio computational treatment of electrochemical systems requires an appropriate treatment of the solid/liquid interfaces. A fully quantum mechanical treatment of the interface is computationally demanding due to the large number of degrees of freedom involved. In this work, we develop a computationally efficient model where the electrode part of the interface is described at the density-functional theory (DFT) level, and the electrolyte part is represented through an implicit solvation model based on the Poisson-Boltzmann equation. We describe the implementation of the linearized Poisson-Boltzmann equation into the Vienna Ab initio Simulation Package, a widely used DFT code, followed by validation and benchmarking of the method. To demonstrate the utility of the implicit electrolyte model, we apply it to study the surface energy of Cu crystal facets in an aqueous electrolyte as a function of applied electric potential. We show that the applied potential enables the control of the shape of nanocrystals from an octahedral to a truncated octahedral morphology with increasing potential.
Simple method for asymmetric twin-field quantum key distribution
Authors: Wang Wenyuan , Lo Hoi-Kwong
Published: December 2019

Twin-field quantum key distribution (TF-QKD) can beat the linear bound of repeaterless QKD systems. After the proposal of the original protocol, multiple papers have extended the protocol to prove its security. However, these works are limited to the case where the two channels have equal amount of loss (i.e. are symmetric). In a practical network setting, it is very likely that the channels are asymmetric due to e.g. geographical locations. In this paper we extend the ‘simple TF-QKD’ protocol to the scenario with asymmetric channels. We show that by simply adjusting the two signal states of the two users (and not the decoy states) they can effectively compensate for channel asymmetry and consistently obtain an order of magnitude higher key rate than previous symmetric protocol. It also can provide 2–3 times higher key rate than the strategy of deliberately adding fibre to the shorter channel until channels have equal loss (and is more convenient as users only need to optimize their laser intensities and do not need to physically modify the channels). We also perform simulation for a practical case with three decoy states and finite data size, and show that our method works well and has a clear advantage over prior art methods with realistic parameters.
Spin-dependent radiative deflection in the quantum radiation-reaction regime
Authors: Geng X S , Ji L L , Shen B F , Feng B , Guo Z , Han Q Q , Qin C Y , Wang N W , Wang W Q , Wu Y T , Yan X , Yu Q , Zhang L G , Xu Z Z
Published: December 2019

A new spin-dependent deflection mechanism is revealed by considering the spin-correlated radiation-reaction force during laser-electron collision. We found that such deflection originates from the non-zero work done by the radiation-reaction force along the laser polarization direction in each half-period, which is larger/smaller for spin-anti-paralleled/spin-paralleled electrons. The resulted anti-symmetric deflection is further accumulated when the spin-projection onto the laser magnetic field is reversed in adjacent half-periods. The discovered mechanism dominates over the Stern–Gerlach deflection for electrons of several hundreds of MeV and 10 PW-level laser peak power. The results provide a new perspective to study the strong-field QED physics in quantum radiation-reaction regime and an approach to leverage the study of radiation-dominated and strong-field QED physics via particle spins.
Homogeneity trend on social networks changes evolutionary advantage in competitive information diffusion
Authors: Liu Longzhao , Wang Xin , Zheng Yi , Fang Wenyi , Tang Shaoting , Zheng Zhiming
Published: December 2019

Competitive information diffusion on large-scale social networks reveals fundamental characteristics of rumor contagions and has profound influence on public opinion formation. There has been growing interest in exploring dynamical mechanisms of the competing evolutions recently. Nevertheless, the impacts of homogeneity trend, which determines powerful collective human behaviors, remains unclear. In this paper, we incorporate homogeneity trend into a modified competitive ignorant-spreader-ignorant rumor diffusion model with generalized population preference. Using microscopic Markov chain approach, we first derive the phase diagram of competing diffusion results on Erdös–Rényi graph and examine how competitive information spreads and evolves on social networks. We then explore the detailed effects of homogeneity trend, which is modeled by a rewiring mechanism. Results show that larger homogeneity trend promotes the formation of polarized ‘echo chambers’ and protects the disadvantaged information from extinction, which further changes or even reverses the evolutionary advantage, namely, the difference of stable proportions of the competitive information. However, the reversals may happen only when the initially disadvantaged information has stronger transmission ability, owning diffusion advantage over the other one. Our framework provides profound insight into competing dynamics with homogeneity trend, which may pave ways for further controlling misinformation and guiding public belief systems. Moreover, the reversing condition sheds light on designing effective competing strategies in many real scenarios.
Quantum-classical correspondence and mechanical analysis of a classical-quantum chaotic system*
Authors: Bi Haiyun , Qi Guoyuan , Hu Jianbing , Wu Qiliang
Published: December 2019

Quantum-classical correspondence is affirmed via performing Wigner function and a classical-quantum chaotic system containing random variables. The classical-quantum system is transformed into a Kolmogorov model for force and energy analysis. Combining different forces, the system is divided into two categories: conservative and non-conservative, revealing the mechanical characteristic of the classical-quantum system. The Casimir power, an analysis tool, is employed to find the key factors governing the orbital trajectory and the energy cycle of the system. Detailed analyses using the Casimir power and an energy transformation uncover the causes of the different dynamic behaviors, especially chaos. For the corresponding classical Hamiltonian system when Planck’s constant ħ → 0, the supremum bound of the system is derived analytically. Difference between the classical-quantum system and the classical Hamiltonian system is displayed through trajectories and energies. Quantum-classical correspondences are further demonstrated by comparing phase portrait, kinetic, potential and Casimir energies of the two systems.
Shallow Well Water Salinity Viewed From Distance Of Well To CoastLine And Ground Water Level Elevation In Purus Padang Village
Authors: Chairi M , Purba W , Boy W , Imani R , Melasari J
Published: December 2019

The coastal environment is an area that always changes. It depends on the power balance between topography, rocks, and its nature with tidal and wind waves. Progress in the Purus sub-district resulted in an increase in the amount of groundwater demand. If this happens, it can cause a drawdown so that the well water of the residents feels brackish or feels salty. This study aims to determine the salinity of shallow well water when viewed from the distance of the well to the coastline (x1) and groundwater level (x2) in Purus Padang Village. This type of research is field research (field research), using a quantitative approach. The sample was taken as many as 18 wells in Purus. The results showed that the salinity of well water occurred unevenly in Purus Village. If the distance of the well is further away from the coast, the salinity value will be lower. If the depth (height) of the water table is getting farther away from the sea level, the salinity value will be higher. For consumption, the salinity content in Purus Village is still within normal limits (<250 mg/l). The spread of salinity is caused by the flow of surface water.