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The Periodic Law of Chemistry is one of the great discoveries in cultural history. Elements behaving chemically similar are empirically merged in groups G of a Periodic Table, each element with G valence electrons per neutral atom, and with upper limit G for the oxidation and valence numbers. Here, we report that among the usually mono- or di-valent s-block elements (G = 1 or 2), the heaviest members (87Fr, 88Ra, 119E, and 120E) with atomic numbers Z = 87, 88, 119, 120 form unusual 5- or 6-valent compounds at ambient conditions. Together with well-reported basic changes of valence at the end of the 6d-series, in the whole 7p-series, and for 5g6f-elements, it indicates that at the bottom of common Periodic Tables, the classic Periodic Law is not as straightforward as commonly expected. Specifically, we predict the feasible experimental synthesis of polyvalent [RaL− n] (n = 4, 6) compounds. [ABSTRACT FROM AUTHOR]

This paper proposes a co-design method of dynamic output feedback control law and periodic event-triggered control (PETC) strategy to tolerate a maximum allowable number of successive packet dropouts (MANSDs) in networked control systems (NCSs). For the purpose of striking a balance between saving limited communication resources and reducing complexity of the transmission implementation, we present the periodic event-triggering mechanism (PETM), in which the triggering conditions only needs to be monitored at each event-verifying instant. In NCSs, packets often suffer from some interference in network transmission, such as packet losses. For packet dropouts, we introduce a dropout variable and model the whole closed-loop systems as a hybrid system. Furthermore, some stability conditions for co-design are given by a novel Lyapunov function and stability theorems of hybrid systems, and the explicit designs parameters of controller and triggering conditions are presented to ensure L 2 stability. Finally, two illustrated examples are given to show the effectiveness of the proposed design methods. • A co-design method of PETM and control law is proposed to save network resource. • The method aims at achieving desired stability properties while tolerating a MANSD. • The method provides less conservation results than the emulation-based approach. • The overall system is modeled based on the hybrid system framework. • By using a modified Young's inequality, rigorous stability analysis is provided. [ABSTRACT FROM AUTHOR]

Consider chemical elements as a system, we create an undirected chemical network with 99 elements and 1916 edges from Chemspider, a website that provide search engines to collect compounds. Using this network and the network that we used in our previous work with 97 elements and 2198 edges, we found that RootedPageRank, a link prediction tool in complex network, can be used to predict potential binary compounds, because the changing trend of PageRank probability of each element in these networks all follow the periodic law, despite of the difference of scale of these networks. The accuracy test indicates that at least 7 among top 10 predicted compoundss in one network can be verified using the compoundss in the other network or in other chemical database, proving that this method can be used to provide guidance in finding potential binary compounds, suggesting that we can study chemical properties from the view of complex network. [ABSTRACT FROM AUTHOR]

The underground roadway of the Buertai Coal Mine adopts the double-roadway layout. Double-roadway layout mode has a roadway that is affected by repeated mining, called reserved roadways. The reserved roadway is strongly affected by mining, and the strata behaviors appear violently. This paper studies the strata behaviors that occur in auxiliary haulage roadway (AHR) during the mining of panel 42106. By analyzing geological conditions, mining influencing factors, and roadway layout, the mechanism of strong rock behavior has been clarified. Then, based on the theoretical analysis, we put forward the treatment method for the manifestation of strong strata behaviors by using hydraulic fracturing technology to break the key stratum. In this way, the high stress of the surrounding rock can be reduced by forcing the hard roof to be broken. After the application of hydraulic fracturing technology, we monitored the deformation of roadways and the periodic weighting law of the working face. The strength of strata behaviors has significantly weakened, and the application of this technology ensures the safe production of coal mines. [ABSTRACT FROM AUTHOR]

The objective of this work is to elaborate a new version of a game used to teach periodic law. To accomplish this, it is necessary to make some decisions regarding two equally important aspects: the need to define what is to be taught about the disciplinary content, and to improve the mechanics of a game, which already has two previous versions. Aiming to decide the approach to teach, we searched the historical milestones from which the concepts: element, atom, periodic law, and periodic properties, underlying the representations of the law were modeled. Then, an analysis was carried out from the epistemological and ontological dimensions that allowed us to define which would be the periodic properties used in the game. The intention was to propose an approach that prioritizes chemical theories and models over physical ones without forgetting the contributions of this discipline that could facilitate the definitions and understanding of the concepts. Regarding the periodic tables to be used as game boards, the aesthetic sense of the idea underlying the different representations was defined as a selection criterion. Concerning the development of the new game mechanics, it was modified so that learning takes place during the game and not only at a later stage. [ABSTRACT FROM AUTHOR]

Gas drainage is an important measure to ensure energy safety in coal mines. However, for mines with high gas content and low permeability, the critical question is how to enhance the drainage effect of drilling. By using the self‐unloading pressure effect on the coal body in front of the mine, the permeability of the coal body can be improved, which facilitates gas drainage. Therefore, establishing the fluid–solid model of gas‐bearing coal mass under the influence of mining, this paper simulates the advanced self‐pressure‐relief range in front of the coal working face and the permeability of coal seam at different heights. Through simulations and field tests, the reasonableness of the advanced self‐pressure‐relief gas drainage was verified, and the spatial and temporal characteristics of the gas drainage from the borehole were quantified and analyzed. The results show that the width of the advanced self‐pressure‐relief zone after simulated mining is 25 m, the vertical permeability of the coal seam increases first and then decreases with the increase of the height from the floor, and the maximum permeability of the layer is 2.6 m from the floor, which is 8.62 times higher than the initial permeability; the gas drainage effect of test boreholes has a periodic law with the coal seam recovery, which, divided into the initial drainage stage, the scalar volume of gas drainage increase stage, and the scalar volume of gas drainage decay stage. At a distance from the working face 20–40 m, the boreholes' scalar volume of gas drainage increased by 3.89 times compared with the initial drainage stage, and the scalar drainage volume of the boreholes through the seam increased by 8.01 times compared with the initial drainage stage; in the section of increasing scalar volume of drainage, the gas drainage volume of the boreholes at different heights of the coal seam had obvious "stratification" phenomenon. The test boreholes were optimally placed in the middle of the seam at the lower end. The study provides a reference for self‐pressure‐relief gas drainage technology and optimization of borehole placement. [ABSTRACT FROM AUTHOR]

Copyright of China Rural Water & Hydropower is the property of China Rural Water & Hydropower Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to study the migration characteristics and strata behavior law of mining-induced rocks in fully mechanized caving face of coal mine, taking the actual geological mining of Longwanggou Coal Mine as the background, using computer software (KSPB) to identify the location of key strata. The physical similar material simulation test was used to monitor the movement characteristics of mining-induced rocks by using the internal displacement sensor (IDS) and distributed optical fiber sensor (DOFS). A three-dimensional physical model of 3.6 m × 2.0 m × 2.0 m was built; the internal displacement of rock was measured by IDS. BOTDA distributed optical fiber was used to monitor the dynamic movement and deformation law of coated rock. Finally, the two monitoring results were compared and analyzed. The results show that: (1) the displacement curve of the fractured rock mass in the key strata shows a "stepped" increase; (2) based on the analysis of displacement continuous monitoring results, the strata behavior law of working face is obtained. The first weighting interval of 61601 working face is 90 cm, and the periodic weighting steps are 105 cm, 115 cm, 135 cm, 150 cm, 165 cm, 180 cm, 215 cm, and 240 cm; (3) the average strain of fiber is proposed. The first weighting and periodic weighting laws of the working face are represented by the average strain, which are consistent with the experimental phenomena. The first weighting in the average strain curve shows the first mutation peak, and the periodic weighting shows the periodic mutation peak change of the average strain curve. [ABSTRACT FROM AUTHOR]

When an axial-flow pump is running, there is a very complex flow inside the runner. Based on the two-way fluid–structure coupling method, this paper simulated the forward and reverse operating conditions of an axial-flow pump and calculated the dynamic stress distribution on the blade surface. The stress load spectrum was loaded onto the blade, and fatigue characteristic analysis was carried out to obtain the fatigue life and damage of the blade. This research shows the following: under different working conditions, the dynamic stress is concentrated at the root of the blade, and its amplitude decreases with the increase in the flow rate; at the same time, the change in stress with time shows a periodic change law. Under the working conditions of the turbine, the main frequency is the rotational frequency, and the secondary frequency is composed of multipliers of the rotational frequency, which is obviously affected by the number of blades; the fatigue damage and stress distribution are consistent, and the damage is the most serious at the stress concentration point. The research results of this paper can provide theoretical guidance for the structural design and safe operation of axial-flow pumps. [ABSTRACT FROM AUTHOR]

A series of new charge transfer (CT) chromophores of "α-diimine-MII-catecholate" type (where M is 3d-row transition metals—Cu, Ni, Co) were derived from 4,4′-di-tert-butyl-2,2′-bipyridyl and 3,6-di-tert-butyl-o-benzoquinone (3,6-DTBQ) in accordance with three modified synthetic approaches, which provide high yields of products. A square-planar molecular structure is inherent for monomeric [CuII(3,6-Cat)(bipytBu)]∙THF (1) and NiII(3,6-Cat)(bipytBu) (2) chromophores, while dimeric complex [CoII(3,6-Cat)(bipytBu)]2∙toluene (3) units two substantially distorted heteroleptic D-MII-A (where D, M, A are donor, metal and acceptor, respectively) parts through a donation of oxygen atoms from catecholate dianions. Chromophores 1–3 undergo an effective photoinduced intramolecular charge transfer (λ = 500–715 nm, extinction coefficient up to 104 M−1·cm−1) with a concomitant generation of a less polar excited species, the energy of which is a finely sensitive towards solvent polarity, ensuring a pronounced negative solvatochromic effect. Special attention was paid to energetic characteristics for CT and interacting HOMO/LUMO orbitals that were explored by a synergy of UV-vis-NIR spectroscopy, cyclic voltammetry, and DFT study. The current work sheds light on the dependence of CT peculiarities on the nature of metal centers from various groups of the periodic law. Moreover, the "α-diimine-MII-catecholate" CT chromophores on the base of "late" transition elements with differences in d-level's electronic structure were compared for the first time. [ABSTRACT FROM AUTHOR]

In philosophy, the empirical success of a science is often explained by the fact that it has managed to discover some law(s) of nature. This line of thought has not been thoroughly explored with respect to chemistry. The aim of this paper is to fill this gap by showing how we could think about laws in chemistry. Specifically, it briefly presents how laws of nature are understood in philosophy of science. It then discusses two case studies from chemistry—the periodic table and chemical reactions—and explains how general ideas about law-hood can be applied to these cases. Lastly, it presents research questions and philosophical problems that arise by considering chemistry from the perspective of laws. This analysis illustrates that there is value in thinking about laws in chemistry. [ABSTRACT FROM AUTHOR]

Brucellosis is a chronic infectious disease caused by brucellae or other bacteria directly invading human body. Brucellosis presents the aggregation characteristics and periodic law of infectious diseases in temporal and spatial distribution. Taking major European countries as an example, this study established the temporal and spatial distribution sequence of brucellosis, analyzed the temporal and spatial distribution characteristics of brucellosis, and quantitatively predicted its epidemic law by using different traditional or machine learning models. This paper indicates that the epidemic of brucellosis in major European countries has statistical periodic characteristics, and in the same cycle, brucellosis has the characteristics of piecewise trend. Through the comparison of the prediction results of the three models, it is found that the prediction effect of long short-term memory and convolutional long short-term memory models is better than autoregressive integrated moving average model. The first mock exam using Conv layer and data vectorizations predicted that the convolutional long short-term memory model outperformed the traditional long short-term memory model. Compared with the monthly scale, the prediction of the trend stage of brucellosis can achieve better results under the single model prediction. These findings will help understand the development trend and liquidity characteristics of brucellosis, provide corresponding scientific basis and decision support for potential risk assessment and brucellosis epidemic prevention and control, and reduce the loss of life and property. [ABSTRACT FROM AUTHOR]

Incentivizing businesses to lower carbon emissions and trade back excess carbon allowances paved the way for rapid growth in carbon credit ETFs. The use of carbon allowances as a hedging alternative fueled this rally further, causing a shift to speculation and forming repetitive bubbles. Speculative bubbles are born from euphoria, yet, they are relatively predictable, provided their pattern matches the log periodic power law (LPPL) with specific stylized facts. A "Minsky moment" identifies a clear speculative bubble as a signal of financial system instability, while a "Social bubble" is regarded as relatively positive, increasing in the long run, infrastructure spending and development. The aim of this paper is to investigate whether various carbon credit bubbles during the pandemic period caused financial instability or had a positive impact ("Minsky" or "Social"). Particularly, we investigate the carbon credit bubble behavior in the ETF prices of KRBN, GRN (Global Carbon Credit tracking ETFs), and the SOLCARBT index during the COVID-19 pandemic period by adopting the log-periodic power law model (LPPL) methodology, which has been widely used, over the past decade, for detecting bubbles and crashes in various markets. In conclusion, these bubbles are social and propelled by the newfound interest in carbon credit trading, for obvious reasons. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Direito da Cidade is the property of Editora da Universidade do Estado do Rio de Janeiro (EdUERJ) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the field of frontier research, information security has received a lot of interest, but in the field of information security algorithm, the introduction of decimals makes it impossible to bypass the topic of calculation accuracy. This article creatively proposes the definition and related proofs of double parameters fractal sorting matrix (DPFSM). As a new matrix classification with fractal properties, DPFSM contains self-similar structures in the ordering of both elements and sub-blocks in the matrix. These two self-similar structures are determined by two different parameters. To verify the theory, this paper presents a type of $2\times 2$ DPFSM iterative generation method, as well as the theory, steps, and examples of the iteration. DPFSM is a space position transformation matrix, which has a better periodic law than a single parameter fractal sorting matrix (FSM). The proposal of DPFSM expands the fractal theory and solves the limitation of calculation accuracy on information security. The image encryption algorithm based on DPFSM is proposed, and the security analysis demonstrates the security. DPFSM has good application value in the field of information security. [ABSTRACT FROM AUTHOR]

Detached eddy simulation was used to numerically compute the leeward vortex flow field on a blunt-headed rotating body. The effects of changes in the angle of attack and flight velocity on the evolutionary law of the counter-rotating vortexes and the fluctuation characteristics of the lateral force coefficient were analyzed. The results show that the counter-rotating vortexes on the leeward surface of the blunt-headed rotating body gradually separate from the wall along the direction from the tail to the head of the projectile as the angle of attack increases. In addition, it shows a periodic variation law of alternating expansion and detachment of the unilateral separated vortex. When the angle of attack is greater than 30°, the fluctuation amplitude of the lateral force coefficient initially rises and then drops with an increase in the angle of attack, while the fluctuation frequency keeps increasing. The maximum amplitude and corresponding frequency of the lateral force coefficient under the main fluctuation remain in the range of 100–230 Hz and have a linear positive feedback relationship with the flight Mach number. With the angle of attack and flight velocity as independent variables, the fittings were performed on the varying laws of maximum amplitude and the corresponding frequency of the lateral force coefficient under the main fluctuation. An unsteady calculation equation for the lateral force coefficient under the change in coupling with the angle of attack and flight velocity was established. [ABSTRACT FROM AUTHOR]

For new medical β titanium implants, the surface micro texture processing technology is a difficult problem. To solve this problem, a new method of ultrasonic elliptical vibration cutting (UEVC) is adopted in this paper. The mechanism of material removal in ultrasonic elliptical vibration cutting is explored for different cutting paths. By means of simulation and experimentation, the material removal mechanism of ultrasonic elliptical vibration cutting medical β titanium alloy is revealed with respect to the aspects of cutting deformation, stress distribution, force and thermal variation, and chip formation mechanism. The results show that: (1) The cutting temperature and cutting force in the UEVC process obey the law of periodic change, and the maximum point of cutting force appears ahead of the maximum point of cutting temperature. (2) The material removal process of UEVC is a "press–shear–pull" composite cutting process. The tool squeezes the material to form the chips. Under the action of high temperature, the material is removed by adiabatic shear. (3) The difference of UEVC paths will affect the removal mode of materials and form different surface morphology. (4) For different cutting paths, compressive stress is distributed at the lowest point of the machining pit, and tensile stress is distributed at the protrusion position. [ABSTRACT FROM AUTHOR]

The concept of agricultural innovation ecosystem in county areas was defined by reviewing the literature on agricultural innovation systems and innovation ecosystems. Combined with the urgent demand for agricultural innovation-driven development, a multidimensional agricultural innovation ecosystem was established in county areas. From the life-cycle perspective, the evolution law of agricultural innovation ecosystems in county areas was analyzed, and the evaluation system was constructed from four aspects: subjects, network, resources, and the environment. Then, the fuzzy technique for order preference by similarity to an ideal solution approach was used to determine the evolution stage of the system. It was found that the agricultural innovation ecosystem in county areas includes three ecological layers of microsubjects, meso-interfaces, and the macroenvironment. The microsubjects exchange material, energy, and information, with the macroenvironment more effectively depending on the carrier function of meso-interfaces. The system shows periodic laws in the process of spiraling evolution, gestation, growth, maturity, and recession, where different stages of the system exhibit different characteristics. Through an empirical analysis of the apple industry of Neiqiu County, Shunping County, and Yi County in Hebei province, the innovation ecosystems formed around the apple industry in the three counties were judged to be in the maturity stage, growth stage, and growth stage, respectively. The evaluation results are consistent with the actual situation, which effectively verified the scientific nature and effectiveness of the theoretical model and the evolutionary evaluation index system. [ABSTRACT FROM AUTHOR]

Consideration has been given to laminar flow of a liquid with constant properties in a channel on whose surface the temperature or density of the heat flux vary with time by a periodic law. An analytical solution to the problem of convective heat transfer in general form has been obtained, using which it has been established that heat transfer ceases to depend on the axial coordinate away from the inlet of the heated portion. Relations have been found to calculate stabilized heat transfer. It has been shown that at a high frequency of the process, a nonstationary stabilized heat-transfer coefficient varies noticeably over the period, however, its stabilization with time occurs as the frequency is reduced. Data on fully stabilized heat transfer have been given for various shapes of the channel, flow regimes, and boundary conditions. [ABSTRACT FROM AUTHOR]

This paper studies the exponential stabilization on the infinite dimensional system with impulse controls, where the impulse instants appear periodically. The first main result shows that the exponential stabilizability of the control system with a periodic feedback law is equivalent to one kind of weak observability inequalities. The second main result presents that, in the setting of a discrete LQ problem, the exponential stabilizability of control system with a periodic feedback law is equivalent to the solvability of an algebraic Riccati-type equation which was built up in Qin et al. (2021) [18] for finite dimensional system. As an application, some sufficient and necessary condition for the exponential stabilization of an impulse controlled system governed by coupled heat equations is given. [ABSTRACT FROM AUTHOR]

The presented work is devoted to the analysis of the modern stage of development of the theory periodic properties of chemical elements as a fundamental aspect of scientific worldpicture. Studying of the phenomenon of periodic properties of chemical elements has gone far beyond chemistry. It should be taken into account that even today, after the creation of two quantum theories of the electronic structure of the atom, after a century of experience in the study of chemical elements and the experimental discovery of antihydrogen, this problem is far from being exhausted. The generalization of theoretical and experimental studies of the quantum-mechanical aspects of the chemical properties of matter, the first results of the study of antimatter made it possible to set a hypothesis of the existence of a new fundamental characteristic of chemical element and to formulate the Periodic Law adequately – in keeping with modern concepts.

The author expresses critical remarks regarding the article by O.V. Mikhailov on teaching the topic “Mendeleev’s Periodic law” by at the national research University. Some specific errors of O.V. Mikhailov relating to historical-scientific and quantum-chemical issues are indicated. The article also presents a general critical assessment of his approach to teaching.

This article discusses an optical reflection-based method for equipment anomaly detection that enhances weak signals and has high sensitivity to abnormalities. Automatic warp knitting machine yarn breakage detection, which has become an acknowledged difficulty in the textile field, is achieved. To the best of our knowledge, this is the first time that visual inspection has been applied to yarn breakage detection in weaving. Furthermore, based on the periodicity of the yarn distribution and the periodic motion law of the machine, the combined wavelet and Seasonal and Trend decomposition using locally weighted regression (LOESS) (STL) decomposition method is proposed for yarn breakage detection. Finally, the efficiency and accuracy of the proposed method are verified experimentally. Our research is a successful application of reflection characteristics to the anomaly detection of non-Lambertian objects, which has implications for the high-precision anomaly detection of precision equipment. [ABSTRACT FROM AUTHOR]

A large variety of periodic tables of the chemical elements have been proposed. It was Mendeleev who proposed a periodic table based on the extensive periodic law and predicted a number of unknown elements at that time. The periodic table currently used worldwide is of a long form pioneered by Werner in 1905. As the first topic, we describe the work of Pfeiffer (Naturwiss. 8:984–991, 1920), who refined Werner's work and rearranged the rare-earth elements in a separate table below the main table for convenience. Today's widely used periodic table essentially inherits Pfeiffer's arrangements. Although long-form tables more precisely represent electron orbitals around a nucleus, they lose some of the features of Mendeleev's short-form table to express similarities of chemical properties of elements when forming compounds. As the second topic, we compare various three-dimensional (3D) helical periodic tables that resolve some of the shortcomings of the long-form periodic tables in this respect. In particular, we explain how the 3D periodic table "Elementouch" (Maeno in Periodic-table-of-the-elements stationery. Design No. 1149493, Japan Patent Office. https://www.j-platpat.inpit.go.jp/d0000, 2001), which combines the s- and p-blocks into one tube, can recover features of Mendeleev's periodic law. Finally we introduce a topic on the recently proposed nuclear periodic table based on the proton magic numbers (Hagino and Maeno in Found Chem 22:267–273, 2020). Here, the nuclear shell structure leads to a new arrangement of the elements with the proton magic-number nuclei treated like noble-gas atoms. We show that the resulting alignments of the elements in both the atomic and nuclear periodic tables are common over about two thirds of the tables because of a fortuitous coincidence in their magic numbers. [ABSTRACT FROM AUTHOR]

The group-based method of classification of chemical elements for definition of their place in the Mendeleev’s periodic system of elements is considered. The arrangement of energetic elements in periods according to the diagram of experimentally defined atomic electron shells is compared to energy levels of elements estimated from the Madelung-Klechkovsky lexicographic ordering rules. It is shown that for adequate description of the set of elements in the framework of approach based on the use of the group method, the changig the peculiarirties of the eigenvalues degeneration of the electron hamiltonian describing a hydrogen-like system is necessary. For this, it is sufficient to include into the hamiltonian a term containing operator of squared orbital momentum.

Copyright of Educacao e Pesquisa is the property of Faculdade de Educacao da Universidade de Sao Paulo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To effectively monitor and control the severe mining-induced rockburst in deep fault area, the fault activation law and the mechanical essence of rockburst induced by crossing fault mining were studied through theoretical analysis, microseismic monitoring, field investigation, and other methods; numerical simulation was employed to verify the obtained fault activation law and the mechanical nature. First, the distribution of microseismic sources at different mining locations and the fault activation degree were analyzed. According to the microseismic frequency and the characteristics of the energy stage, the fault activation degree was divided into three stages: fault stress transfer, fault pillar stress behavior, and fault structure activation. It was determined that the impact disaster risk was the strongest in the stage of the fault pillar stress behavior. Based on the periodic appearance law of microseisms in fault area, three types of conceptual models of fault-type rockburst were proposed, and the rockburst carrier system model of "roof-coal seam-floor" in the fault area was established. The mechanical essence of fault-type rockburst was obtained as follows: under the action of fault structure, the static load of the fault coal pillar was increased and superimposed with the active dynamic load of the fault, leading to high-strength impact disaster. Finally, the prevention and treatment concepts of fault-type rockburst were proposed. The monitoring and prevention measures of fault-type rockburst were taken from two aspects: the monitoring and characterization of fault rockburst and weakening control of the high static load of the fault coal pillar and dynamic load of fault activation. The proposed concepts and technical measures have been verified in the working face 14310 of Dongtan Coal Mine with sound results. The research results have a guiding significance for the prevention and control of rockburst in a similar mining face under crossing fault mining. [ABSTRACT FROM AUTHOR]

With the gradual development of deep mining, heat hazard has become an increasingly prominent problem, which poses a great threat to the coal mine production. In order to reduce the heat hazard effectively, it is necessary to investigate the temperature distribution characteristics and regulation of the surrounding rock of the mine tunnels. Based on field measurement data from a Chinese coal mine, the present study probes into the dynamic law of periodic variation of the heat regulation circle (HRC) in surrounding rocks, which is featured by the serious heat hazard, and further reveals the evolution characteristics of the physical range of HRC and the temperature field distribution. By analyzing field data, it can be concluded that a total of five typical distribution models of HRC of surrounding rocks are summarized. Influencing factors concerning thermophysical properties, thermal environment conditions of the stratum, and boundary conditions play important roles and affect the formation of such five models. A mathematical model of heat regulation and energy storage of surrounding rocks in a mine tunnel is proposed. Calculations of air temperature–regulating capability of HRC and evaluating its cooling storage capacity are also demonstrated. Using the HRC in rocks for cooling underground ventilation may be a good and green engineering practice for coal mines. [ABSTRACT FROM AUTHOR]

This article discusses the mathematizing of the chemical periodic system as a grid, which leads to a quadratic function or "binódica function" formed by pairs of periods or binodos (dyads). We describe the periodic law as an increasing function of the principal quantum number (n). It works subject to the dialectical laws that generate; first: gradual quantitative changes: (2n2), with "duplication" of periods: (2n2, 2n2). Second: radical quantitative changes: (4n2), with the emergence of new quantum transitions, growth and a change in the format of the binodos (qualitative change). We use analytical and graphic methods to mathematize Mendeleev's law, making the size of the binodos (Y) and the continuous series (Z) depend on the number of the binode (B), which is the same quantum number (n). Likewise, we show a graphic representation, in 2D, of a continuous and self-similar spiral function of the elements, in a geometric growth pattern. [ABSTRACT FROM AUTHOR]

This study explores the full set of handwritten and printed materials associated with the 1869 publication of the first version of Dmitrii Mendeleev's periodic system of elements: "An Attempt at a System of Elements Based on Their Atomic Weight and Chemical Affinity." Using innovative historical research methods, the author has been able to refute the publication date traditionally associated with the first version of the periodic table, as well as to establish an accurate chronology of its subsequent publications. This task was made possible through the discovery of previously unknown handwritten materials in Mendeleev's personal archive and the Russian State Historical Archive. This typographical analysis of the first publication of Mendeleev's periodic table represents a rare and unusual opportunity in the history of science: it gives us the chance to observe how, in the process of publishing the results of a scientific study, a researcher comes to realize that what he has discovered is, in fact, a major scientific breakthrough and begins to take the necessary steps toward establishing his scientific priority. [ABSTRACT FROM AUTHOR]

Active magnetic bearings (AMBs) are being continuously explored for industrial applications mainly because of their friction-free operation. However, if a rotor-shaft-AMB system is used in applications such as turbo engine of an aircraft or in the propeller shaft of a ship, it would be subject to parametric excitation because of the moving base of the system. Parametric excitation is known to cause instability in systems. This paper addresses the issue of such flexible rotor-AMB system and performs the parametric stability analysis. A novel control law based on the constitutive relationship of a viscoelastic material called the four-element control law is developed. Because of the presence of periodic base motion terms in the system state matrix, the system can be classified as a linear periodic system. Thus, the stability analysis is carried out using Floquet–Liapunov theory on stability of periodic system, for which an approximate state transition matrix is first found and stability of the system is then decided based on the absolute value of eigenvalue. Three different base motions (roll, pitch, and yaw) were considered for evaluating the performance of the proposed control law. Simulation results reveal that the proposed control law has better stability characteristics than the proportional-integral-derivative (PID) control law. [ABSTRACT FROM AUTHOR]

• A simplified joint model is established based on surface springs and tangential surface damping. • A joint parameter identification method for a bolted CFRC thin-walled structure is proposed. • A combined nonlinear parameter tracking model is proposed to capture the material and joint nonlinearity. • The nonlinear vibration behaviors of a bolted CFRC plate are accurately predicted without relying on experimental data. • The analysis of time-varying stiffness and damping reveals the mechanical mechanism of the joint interface. Based on the material nonlinearity of carbon fiber reinforced composites (CFRC) obtained in previous work, including frequency and strain dependence of material parameters, the nonlinear dynamical behaviors of the bolt-connected CFRC plate are further studied in this paper. A joint parameter identification method for a bolt-connected CFRC thin-walled structure is proposed, which can accurately identify the nonlinear mechanical parameters of the joint interface while removing the influence of the CFRC-material nonlinearity. A combined nonlinear parameter tracking model is proposed to capture the CFRC-material and joint nonlinearity of a bolt-connected CFRC thin-walled structure. Specifically, a bolt-connected CFRC plate is taken as an analysis case, and the nonlinear time domain responses are solved by the Newmark method. Meanwhile, the mechanism of nonlinear mechanical behavior for the joint under different forced vibration states is further explained by obtaining the periodic variation law of joint parameters. The nonlinear dynamics analysis for the bolt-connected CFRC plate shows that: The proposed combined nonlinear parameter tracking model effectively tracks material parameters and joint parameters, and the proposed simplified joint model can effectively simulate the mechanical behavior of micro-slip and macro-slip of the joint through parameter tracking. Considering the influence of combined nonlinearity, the dynamical model of the bolt-connected CFRC plate can accurately reproduce nonlinear vibration responses observed in the experiment. [Display omitted] [ABSTRACT FROM AUTHOR]

• Experiments of mechanical deformation were conducted on LiF specimens. • The Acoustic Signals emitted during the deformation experiments were recorded. • Two log periodic power law models were used to fit the data of the energy released. • The results of the fittings produced from the two different models were compared. • The comparison showed that one of the two models provides more reliable results. The deformation of solid materials up to the point of fracture is followed by acoustic emission (AE) signals. The cumulative acoustic energy released during such a process seems to generally follow a power law form, which is compatible with the view that the fracturing process is a phenomenon with developing critical dynamics. In the present work, the cumulative energy released by the AE signals emitted during the deformation of LiF samples has been calculated and fitted by two different fitting functions, which are both power laws decorated with log-periodic corrections. The comparison of the produced results would lead to the conclusion of whether each one of the two equations can produce valid acoustic energy release modeling, which can describe the fracturing procedure of solid materials and its underlying mechanics. It should be noted that one of the models managed to fit the experimental data more accurately in the majority of the cases studied. We show that both of the studied log-periodic models managed to acceptably fit the data, which means that this field of study could possible lead to new methods of predicting the time point of a material's failure. In conclusion, this comparative study reveals that these models could be a valuable tool in cases of monitoring materials or structures being under load at the region of their mechanical tolerance. [ABSTRACT FROM AUTHOR]

Atomic structure and the Periodic Table are key elements in Science Education, as they constitute a bridge between Physics an Chemistry, and because of the epistemic value of the historic process of their construction. We describe a Project-Based Learning sequence where students reproduce the inductive process to construct the Periodic Table through several inquiry cycles. The activity ends up with the celebration of a scholar scientific congress where students make predictions on the physical and chemical properties of several elements. We analize the learning outomes and students perspectives on the sequence in the frame of the development of the scientific competence. [ABSTRACT FROM AUTHOR]

In this article, the author reviews literature concerning the great Mendeleev’s achievements in the seventies of the XIX century, i.e. discovery of the periodic law and fulfillment of his early predictions of unknown elements. Special attention was paid to the references concerning these achievements by chemists – authors of the English, German, and French chemical books in 1871 – 1917. This review was enriched with: 1) selected facts from Mendeleev’s life and scientific activity; 2) Mendeleev’s stay abroad and participation in some celebrities, and 3) a list of the authors of his biography in Russia and other countries in the world.

The s, p, d and f blocks of the elements, as delimited by Charles Janet in 1928, can be represented as parallel slices of a regular tetrahedron. They also fit neatly on to the surface of a sphere. The reasons for this are discussed and the possible objections examined. An attempt is made to see whether there are philosophical implications of this unexpected geometrical regularity. A new tetrahedral design in transparent plastic is presented. [ABSTRACT FROM AUTHOR]

In this article, the author reviews literature concerning the great Mendeleev's achievements in the seventies of the XIX century, i.e. discovery of the periodic law and fulfillment of his early predictions of unknown elements. Special attention was paid to the references concerning these achievements by chemists - authors of the English, German, and French chemical books in 1871 - 1917. This review was enriched with: 1) selected facts from Mendeleev's life and scientific activity; 2) Mendeleev's stay abroad and participation in some celebrities, and 3) a list of the authors of his biography in Russia and other countries in the world. [ABSTRACT FROM AUTHOR]

The existence of periodic solutions in Γ-symmetric Newtonian systems x ¨ = − ∇ f ( x ) can be effectively studied by means of the Γ × O ( 2 ) -equivariant gradient degree with values in the Euler ring U ( Γ × O ( 2 ) ) . In this paper we show that in the case of Γ being a finite group, the Euler ring U ( Γ × O ( 2 ) ) and the related basic degrees are effectively computable using Euler ring homomorphisms, the Burnside ring A ( Γ × O ( 2 ) ) , and the reduced Γ × O ( 2 ) -degree with no free parameters. We present several examples of Newtonian systems with various symmetries, for which we show existence of multiple periodic solutions. We also provide exact value of the equivariant topological invariant for those problems. [ABSTRACT FROM AUTHOR]

Pesticide residues in wine were analyzed by liquid chromatography–tandem mass spectrometry. Retentions are modelled by structure–property relationships. Bioplastic evolution is an evolutionary perspective conjugating effect of acquired characters and evolutionary indeterminacy–morphological determination–natural selection principles; its application to design co-ordination index barely improves correlations. Fractal dimensions and partition coefficient differentiate pesticides. Classification algorithms are based on information entropy and its production. Pesticides allow a structural classification by nonplanarity, and number of O, S, N and Cl atoms and cycles; different behaviours depend on number of cycles. The novelty of the approach is that the structural parameters are related to retentions. Classification algorithms are based on information entropy. When applying procedures to moderate-sized sets, excessive results appear compatible with data suffering a combinatorial explosion. However, equipartition conjecture selects criterion resulting from classification between hierarchical trees. Information entropy permits classifying compounds agreeing with principal component analyses. Periodic classification shows that pesticides in the same group present similar properties; those also in equal period, maximum resemblance. The advantage of the classification is to predict the retentions for molecules not included in the categorization. Classification extends to phenyl/sulphonylureas and the application will be to predict their retentions.

Superlattice-like (SLL) phase-change films provide more controllable parameters for the optimization of the performance of phase-change films, including the thickness of each constituent layer, the thickness ratio of two constituent layers and cycle number of periodicity. The effects of the first two parameters on the performance of SLL films have been studied widely. However, the influence of last parameter, cycle number of periodicity, was studied sparsely. In this study, we have studied the period number effect on crystallization temperature of SLL [Ge/Ge8Sb92]n films, and designed and fabricated a series of superlattice-like (SLL) [Ge/Ge8Sb92]n phase-change films. Their crystallization behaviors are studied by the measurement of temperature-dependent sheet resistance. We find that crystallization temperature decreases with increasing cycle number of periodicity, revealing period-cycle-number modulation effect. However, such the effect cannot be explained by current interface effect model. We test the existence of periodic structures of the crystallized SLL films by coherent acoustic phonon (CAP) spectroscopy. Apparent folded CAP modes related to SLL nanostructures are observed, implying the existence of excellent periodic structures or no alloying within one period in crystallized SLL films. Therefore, such period number manipulation effect cannot be explained by the cooperative effects of interface and alloying effects either, implying new mechanisms to be unveiled. We tentatively propose two kinds of possible long-range effects, built-in electric field and strain effects. Based on strain effect, our results can be explained phenomenologically. [ABSTRACT FROM AUTHOR]