Intermittency Effects Research Articles

Sensitivity Analysis of Chaotic Systems Using Unstable Periodic Orbits

A well-behaved adjoint sensitivity technique for chaotic dynamical systems is presented. The method arises from the specialisation of established variational techniques to the unstable periodic orbits of the system. On such trajectories, the adjoint problem becomes a time periodic boundary value problem. The adjoint solution remains bounded in time and does not exhibit the typical unbounded exponential growth observed using traditional methods over unstable non-periodic trajectories (Lea et al., Tellus 52 (2000)). This enables the sensitivity of period averaged quantities to be calculated exactly, regardless of the orbit period, because the stability of the tangent dynamics is decoupled effectively from the sensitivity calculations. We demonstrate the method on two prototypical systems, the Lorenz equations at standard parameters and the Kuramoto-Sivashinky equation, a one-dimensional partial differential equation with chaotic behaviour. We report a statistical analysis of the sensitivity of these two systems based on databases of unstable periodic orbits of size 10^5 and 4x10^4, respectively. The empirical observation is that most orbits predict approximately the same sensitivity. The effects of symmetries, bifurcations and intermittency are discussed and future work is outlined in the conclusions.

Intermittent Stimulation of the Nucleus Basalis of Meynert Improves Working Memory in Adult Monkeys

Dysfunction in the brain's cholinergic systems results in working memory and executive function impairments. The source of acetylcholine for the neocortex is the Nucleus Basalis of Meynert. We tested whether electrical activation of this nucleus would improve executive function in young adult monkeys. Continuous stimulation led to consistent performance impairments. In contrast, intermittent stimulation led to supranormal working memory performance. Optimal performance was achieved with delivery of 200 microsecond biphasic pulses at a frequency of 60 pulses per second, for 20 seconds every minute. Effects onset and offset within three minutes. Pharmacological experiments suggested both intermittent and continuous stimulation effects depended on cholinergic activation. Donepezil, a cholinesterase inhibitor, improved performance to supranormal levels in animals already impaired by continuous electrical stimulation. The same treatment did not impact performance while animals received intermittent stimulation. Administration of either nicotinic or muscarinic acetylcholine receptor antagonists prevented intermittent stimulation from altering performance. In the months after stimulation testing began, animal performance, measured in sessions without stimulation, improved. Over these months, the working memory delay at which animals achieved 80% correct performance increased three to fivefold. Our results show that cholinergic activation by deep brain stimulation enhances working memory performance and is a candidate treatment for losses in executive function in aging and Alzheimer's Disease.

Galaxy dynamo in inhomogeneous interstellar medium

In some galaxies there are magnetic fields of several microgauss. Their evolution is connected with dynamo mechanism which is based on joint action of alpha-effect and differential rotation. The equations of the dynamo theory usually include some averaged kinematic characteristics of the interstellar turbulence. This approach is quite suitable for galaxies with "calm" interstellar medium. As for the galaxies with intensive star formation or supernovae explosions it will not give proper results. For this case the HII regions are quite small, exist for small-time and their localization can be assumed random. So it is useful to take the dynamo equations with random coefficients, which take one of two values (the first one is connected with HI regions, and the second one - with HII). We have studied the magnetic field evolution in the stochastic dynamo model for some typical cases. From the mathematical point of view, the results show some special effects. Firstly, the magnetic field evolution demonstrates the intermittency effect: higher statistical moments of the field grow faster than the lower ones. Moreover, the magnetic field in this model can have large fluctuations, so we have also described the correlation function of the field.

Transient analysis, exergy and thermo-economic modelling of façade integrated photovoltaic/thermal solar collectors

This paper presents a detailed exergetic and technoeconomic analysis of a Building Integrated PhotoVoltaic Thermal (BIPVT) system. BIPVT system, consisting of flat-plate PVT solar collectors, is integrated in the south facing façade of a non-residential high-rise building. BIPVT collectors produce: i) thermal energy for space heating purposes, by a radiant floor system; ii) Domestic Hot Water (DHW); iii) electricity. Electric air-to-water heat pumps/chillers and a condensing gas fired boiler are used as auxiliary systems for space heating/cooling and DHW, respectively. In addition, the system also includes an electricity storage system coupled to the BIPVTs in order to mitigate the effects of solar energy intermittency and to obtain a virtually grid-independent system.In order to compare the proposed BIPVT system to a conventional building, a reference building model, i.e. without BIPVTs, energy storage and radiant floor, is considered. Here, the space heating and cooling energy is supplied by air-to-water heat pumps (one for each floor), DHW is produced by a condensing boiler and electricity is supplied by the national grid. The comparison is performed for three thermal zones, well representative of the thermal behaviour of the whole building. In this paper, a detailed dynamic simulation model is developed by means of well-known tool TRNSYS 17, in order to predict the transient behaviour of BIPVT system. Energy and exergy balances are taken into account to determine, for the 1-year operation, the exergy destructions and exergetic efficiencies of each of the investigated components. The economic viability of the proposed system is also discussed and the resulted Simple Pay Back period is about 4 years. From the carried out exergy analysis, the average exergetic efficiency of electricity storage system is about 90%, whereas the condensing boiler one is close to 2% all year long. In addition, an exergy analysis on the proposed BIPVT system located in several European weather zones is also carried out, as well as a suitable exergy analysis is performed by varying the capacity of the electricity storage system. Such analyses aim to assess the weather condition and the size of electricity storage effects on the destroyed exergy and exergetic efficiency of BIPVT collectors and electricity storage, respectively. It resulted that, the highest destroyed exergy of BIPVT occurs in Larnaca (150 MWh/year) vs the lowest one in Belfast (87 MWh/year), whereas the BIPVT collectors exergetic efficiencies range from 8.4% for Larnaca to 8.8% for Belfast.

The influence of flow permanence and drying pattern on macroinvertebrate biomonitoring tools used in the assessment of riverine ecosystems

Temporary rivers comprise a significant proportion of river networks globally and their prevalence is expected to increase as a result of future climate change and anthropogenic water resource pressures. Despite this, the influence of drying events on freshwater biomonitoring tools within temporary rivers has received limited research attention within temperate environments. This study examines the effects of flow permanence and longitudinal drying patterns on selected biomonitoring indices used within the United Kingdom to assess the ecological status of waterbodies within the context of the Water Framework Directive. These indices are based on faunal tolerances and preferences to nutrient enrichment (BMWP, ASPT and Ntaxa) and flow velocity (Family LIFE). Long-term biomonitoring data from four rivers within southern England were examined, two of which dry longitudinally from the headwaters and two that dry within the mid-reaches. The results demonstrate that all of the biomonitoring indices examined differed significantly between each ‘hydrological class’ (i.e. temporary versus perennial reaches), with those based on absolute scores (BMWP and Ntaxa) displaying greater differences compared to those derived using scores standardized by the number of taxa recorded (ASPT and Family LIFE). The individual influence of drying pattern did not have a significant effect on any biomonitoring index. However, the interaction between the hydrological class and drying pattern significantly influenced all biomonitoring indices, indicating that the effect of flow intermittency on the metrics examined differed between drying patterns. Flow permanence explained a greater amount of statistical variation compared to the hydrological class and highlights the importance of the duration of flowing conditions on biomonitoring indices. The results indicate that flow intermittency has a significant effect on freshwater biomonitoring tools and highlights the need to incorporate this knowledge into existing management and environmental policy frameworks to prevent the misclassification of the ecological status of temporary streams.

Dissipative-convergent intermittency in dynamics of tidal waves in estuaries

The effect of dissipative-convergent intermittency in dynamics of tidal waves in estuaries is described. The effect manifests itself in spatial modulation of the tide amplitude. The effects of convergent channel and turbulent friction are competitive in dynamics of tidal waves in bays, gulfs, and estuaries. This manifests itself in the alternating excess of the action of one effect over another as the tidal wave penetrates deep the estuary. The effect of dissipative-convergent intermittency is manifested most completely in “strange” bays in which the mean water depth is commensurable with the Stokes layer thickness. It is shown that the spatial distribution of the tidal wave amplitude has a minimum in the convergent channel. If the minimum point lies beyond the estuary, then the effect of convergent channel predominates and the wave height increases to the vertex. If the minimum point lies in the neighborhood of the estuary vertex then the effect of turbulent friction predominates along the entire bay length and the wave height decreases to the bay vertex. Finally, if the minimum point finds itself in the middle part of the estuary, then the case of the “strange” bays arises, namely, in such bays the wave height decreases to crossing the minimum point and begins increases again after its passage. The local increase in the tidal wave amplitude can be manifested further in the mouth of the inflowing river.

Effects of chronic pollution and water flow intermittency on stream biofilms biodegradation capacity.

A mesocosm case study was conducted to gain understanding and practical knowledge on biofilm emerging contaminants biodegradation capacity under stressor and multiple stressor conditions. Two real life scenarios: I) biodegradation in a pristine intermittent stream experiencing acute pollution and II) biodegradation in a chronically polluted intermittent stream, were examined via a multifactorial experiment using an artificial stream facility. Stream biofilms were exposed to different water flow conditions i.e. permanent and intermittent water flow. Venlafaxine, a readily biodegradable pharmaceutical was used as a measure of biodegradation capacity while pollution was simulated by a mixture of four emerging contaminants (erythromycin, sulfisoxazole, diclofenac and imidacloprid in addition to venlafaxine) in environmentally relevant concentrations. Biodegradation kinetics monitored via LC-MS/MS was established, statistically evaluated, and used to link biodegradation with stress events. The results suggest that the effects of intermittent flow do not hinder and may even stimulate pristine biofilm biodegradation capacity. Chronic pollution completely reduced biodegradation in permanent water flow experimental treatments while no change in intermittent streams was observed. A combined effect of water flow conditions and emerging contaminants exposure on biodegradation was found. The decrease in biodegradation due to exposure to emerging contaminants is significantly greater in streams with permanent water flow suggesting that the short and medium term biodegradation capacity in intermittent systems may be preserved or even greater than in perennial streams.

The Jarvik 2000 left ventricular assist device as a bridge to transplantation: Japanese Registry for Mechanically Assisted Circulatory Support

The Jarvik 2000 ventricular assist device features a miniaturized intraventricular pump and an intermittent low-speed function that facilitates aortic valve opening. Despite its long history, little is known about the Jarvik device with regard to post-implantation outcomes. Prospectively collected data from 13 participating hospitals were extracted from the Japanese Registry for Mechanically Assisted Circulatory Support database to analyze mortality, morbidity and de-novo aortic regurgitation. Data on 83 patients who underwent implantation of the Jarvik 2000 were reviewed. Median support duration was 191 (maximum 758) days. All recipients underwent implantation as a bridge to transplantation. Overall survival proportions at 1 and 2 years were 85.0% and 79.3%, respectively. Nine patients were in INTERMACS Level 1, and 28 patients were on mechanical circulatory support at the time of implantation. Causes of death included stroke, infection and device malfunction. Three patients had their device removed: 2 at the time of heart transplantation and 1 after recovery of the left ventricle. Common adverse events included major bleeding (27.7%), new infection (31.3%), stroke (20.5%) and device malfunction (20.5%). De-novo aortic regurgitation was observed in 17 patients, 6 of whom developed at least moderate regurgitation during follow-up. Mid-term survival after Jarvik 2000 implantation was satisfactory and comparable to that reported by other national and international registries (INTERMACS and IMACS) for continuous-flow LVADs. De novo aortic regurgitation occurred despite the intermittent low-speed effect of this device, with some recipients experiencing progressive worsening of aortic regurgitation within 2 years post-implantation.

Bed Rest and Intermittent Centrifugation Effects on Human Balance and Neuromotor Reflexes.

The effects of repeated centrifugation in association with head-down tilt (HDT) bed rest (BR) on the mediation of basic reflexes associated with the major postural muscles was investigated as a potential countermeasure for maintaining balance control and neuromotor reflex function. There were 15 male volunteers who were exposed to 21 d of 6° HDT-BR. Eight were treated with daily 1-h artificial gravity (AG) exposures aboard a short radius centrifuge that provided 1-g footward loading at heart level. The other seven served as HDT-BR control subjects. Balance control was assessed using a standard computerized dynamic posturography (CDP) protocol that was modified by adding low-frequency pitch-plane head movements. Neuromotor reflex function was assessed using tendon stretch reflexes (MSR) and functional stretch reflex (FSR) data collected from the triceps surae muscle group. CDP performance was degraded by HDT-BR in both groups (ranging from 24 to 26%), but was unaffected by AG. BR also degraded MSR and FSR functions in both groups, with increased peak reflex latencies between 1.5 and 1.95 ms, but AG maintained pre-BR latencies for the MSR subjects. AG exposure did not modify balance control from pre-BR responses, but did help prevent decrements in FSR latencies post-BR.Paloski WH, Reschke MF, Feiveson AH. Bed rest and intermittent centrifugation effects on human balance and neuromotor reflexes. Aerosp Med Hum Perform. 2017; 88(9):812-818.

Occupational Hearing Loss from Non-Gaussian Noise.

Noise levels are truly continuous in relatively few occupations, with some degree of intermittency the most common condition. The sound levels of intermittent noise are often referred to as non-Gaussian in that they are not normally distributed in the time domain. In some conditions, intermittent noise affects the ear differently from continuous noise, and it is this assumption that underlies the selection of the 5-dB exchange rate (ER). The scientific and professional communities have debated this assumption over recent decades. This monograph explores the effect of non-Gaussian noise on the auditory system. It begins by summarizing an earlier report by the same author concentrating on the subject of the ER. The conclusions of the earlier report supported the more conservative 3-dB ER with possible adjustments to the permissible exposure limit for certain working conditions. The current document has expanded on the earlier report in light of the relevant research accomplished in the intervening decades. Although some of the animal research has supported the mitigating effect of intermittency, a closer look at many of these studies reveals certain weaknesses, along with the fact that these noise exposures were not usually representative of the conditions under which people actually work. The more recent animal research on complex noise shows that intermittencies do not protect the cochlea and that many of the previous assumptions about the ameliorative effect of intermittencies are no longer valid, lending further support to the 3-dB ER. The neurologic effects of noise on hearing have gained increasing attention in recent years because of improvements in microscopy and immunostaining techniques. Animal experiments showing damage to auditory synapses from noise exposures previously considered harmless may signify the need for a more conservative approach to the assessment of noise-induced hearing loss and consequently the practice of hearing conservation programs.

Algunos hechos estilizados y explicativos sobre el diferencial y la discriminación salarial por sexo en México, 1987-2015

This paper aims to analyze some stylized and explanatory facts about income differentials by monthly and hourly income in Mexico for the period 1987-2015. The explanatory power of human capital theory, synthesized in years of schooling, training and experience, is evaluated using the Blinder-Oaxaca methodology, which weighs the explanatory factors of endowments, full wage discrimination and factors not considered represented by the constants. The results show, in general, that the endowments of human capital have a temporary and partial effect, so that the trends of the hourly and monthly long-term earnings differentials are mainly explained by the behavior of wage discrimination and endowments of years of experience. Schooling as a factor of discrimination was relevant only for the period prior to the 1995 economic crisis and nafta, while the training factor has small and intermittent effects throughout the period of analysis.

Effect of intermittent heating on the heat transfer performance of supercritical R134a flowing in a pipe

Heat transfer performance of supercritical fluid is unique due to the significant variance of the thermo-physical properties of fluids around the pseudo-critical temperature. Aiming at exploring the effect of intermittent heating on heat transfer to supercritical fluid, experimental and numerical study on supercritical R134a flowing upward in an inner diameter 7mm and 2.3m long intermittent heated pipe have been carried out. The pipe is heated by Joel effect and 0.3m-long part in the middle of pipe can be short-circuited. The test is carried out at 4.3MPa and the mass flux is 600kg/(m2s). The heat flux ranges from 20 to 40kW/m2. The Re number varies between 4.1×104 and 2.1×105. It’s found that the variance of HTC (heat transfer coefficient) due to the intermittent heating effect and the length of the pipe where heat transfer affected by the intermittent heating effect at low, medium and high heat fluxes is different. Heat transfer enhancement is observed at the downstream of no-heating section for all three kinds of cases. The enhancement due to the intermittent heating effect at the heat transfer deterioration case (heat transfer deterioration happens if the pipe is uniformly heated under the same heat flux, inlet pressure and temperature) is much stronger than that at the normal heat transfer case (heat transfer deterioration does not happen if the pipe is uniformly heated under the same heat flux, inlet pressure and temperature). The maximum HTC ratio for the heat transfer deterioration case is as high as 90%. Moreover, the location where heat transfer deterioration happens is shifted by the intermittent effect. The length affected by the development of boundary layer due to intermittent heating effect is about 40 diameters for the normal heat transfer case and it is increased to 90 diameters for the heat transfer deterioration case since the heat transfer deterioration region is shifted further downstream. With the assistance of numerical simulation results using k-ω SST turbulence model, the reason for heat transfer enhancement and the shift of heat transfer deterioration is discussed.

Cluster-delay consensus in multi-agent systems via pinning leader-following approach with intermittent effect

ABSTRACTIn this paper, the cluster consensus problem with delays of first-order nonlinear multi-agent systems is studied through pinning leader-following approach with periodic intermittent effect. The graph of the networked system is assumed to be directed and weakly connected. A new type of pinning consensus protocol with intermittent effect is designed according to the ways in which the agents link, specifically, the agents in each cluster are divided into three subsets due to the orientation of their topological degree, and each subset of agents is controlled by an individual law. A redefined notion on cluster consensus with two sorts of time delays is proposed in this article. Some consensus criteria are derived to guarantee that the agents in the same cluster asymptotically follow the virtual leader with a delay, while agents in different clusters reach consensus with delays via following their leaders. Some numerical simulations are given to illustrate the effectiveness of the theoretical results.

Intermittent hypercapnic hypoxia during sleep does not induce ventilatory long-term facilitation in healthy males.

Intermittent hypoxia-induced ventilatory neuroplasticity is likely important in obstructive sleep apnea pathophysiology. Although concomitant CO2 levels and arousal state critically influence neuroplastic effects of intermittent hypoxia, no studies have investigated intermittent hypercapnic hypoxia effects during sleep in humans. Thus the purpose of this study was to investigate if intermittent hypercapnic hypoxia during sleep induces neuroplasticity (ventilatory long-term facilitation and increased chemoreflex responsiveness) in humans. Twelve healthy males were exposed to intermittent hypercapnic hypoxia (24 × 30 s episodes of 3% CO2 and 3.0 ± 0.2% O2) and intermittent medical air during sleep after 2 wk washout period in a randomized crossover study design. Minute ventilation, end-tidal CO2, O2 saturation, breath timing, upper airway resistance, and genioglossal and diaphragm electromyograms were examined during 10 min of stable stage 2 sleep preceding gas exposure, during gas and intervening room air periods, and throughout 1 h of room air recovery. There were no significant differences between conditions across time to indicate long-term facilitation of ventilation, genioglossal or diaphragm electromyogram activity, and no change in ventilatory response from the first to last gas exposure to suggest any change in chemoreflex responsiveness. These findings contrast with previous intermittent hypoxia studies without intermittent hypercapnia and suggest that the more relevant gas disturbance stimulus of concomitant intermittent hypercapnia frequently occurring in sleep apnea influences acute neuroplastic effects of intermittent hypoxia. These findings highlight the need for further studies of intermittent hypercapnic hypoxia during sleep to clarify the role of ventilatory neuroplasticity in the pathophysiology of sleep apnea.NEW & NOTEWORTHY Both arousal state and concomitant CO2 levels are known modulators of the effects of intermittent hypoxia on ventilatory neuroplasticity. This is the first study to investigate the effects of combined intermittent hypercapnic hypoxia during sleep in humans. The lack of neuroplastic effects suggests a need for further studies more closely replicating obstructive sleep apnea to determine the pathophysiological relevance of intermittent hypoxia-induced ventilatory neuroplasticity.

A qualitative study on psychological experience of patients with neurogenic bladder in spinal cord injury undergoing intermittent catheterization

Objective To explore the psychological experience of patients with neurogenic bladder in spinal cord injury undergoing intermittent catheterization and provide references for better implementation of bladder function training. Methods Using the phenomenological method of qualitative research, 12 patients with neurogenic bladder in spinal cord injury in orthopedic department of one hospital in Beijing from July 2016 to October 2016 were surveyed by in-depth interviews. Experience and feelings of patients in the process of catheterization were analyzed. Results Experience and demands were mainly divided into three themes. First, patients undergoing intermittent catheterization had different types of psychological reactions including exclusion and disgust, fear and anger, depression and loneliness, acceptance and customization. Second, different intermittent catheterization effects resulted in different feelings including frustration and happy due to failing and success. Third, patients had expectation of establishing a perfect medical system and coping with support mechanisms of family and society. Conclusions Psychological experience of patients has a process of changing. They behave different psychological feelings with failing or success of catheterization. The doctors and nurses should provide health education and technical guidance as well as psychological counseling for the patients, understand and respect their emotional needs, establish appropriate supporting system and improve their compliance. Key words: Spinal cord injury; Neurogenic bladder; Intermittent catheterization; Qualitative study

Performance Analysis of Neural Network Training Algorithms and Support Vector Machine for Power Generation Forecast of Photovoltaic Panel

Current energy policies are encouraging the connection of power generation based on low-polluting technologies, mainly those using renewable sources to distribution networks. The photovoltaic (PV) systems have experienced a great growth around the word in last years. Hence, it becomes increasingly important to understand technical challenges, facing high penetration of PV systems at the grid, especially considering the effects of intermittence of this source on the power quality, reliability and stability of the electric distribution system. In another hand, the connections of distributed generators, by PV panels, changes voltage profile at low voltage power systems. This fact can affect the distribution networks on which they are attached causing overvoltage, undervoltage, frequency oscillations and changes in protection design. In order to predict these disturbs, because of this PV penetration, this article aims to analyze seven training algorithms used in artificial neural networks for temporal prediction of the generated active power and thus the state of the distribution network in which these microgenerators are connected and, then compare its best results with the Support Vector Machine (SVM) technique. As a result it was concluded that 3 algorithms are suitable for this type of analysis with the best performance among the seven analyzed was the Bayesian Regularization and that Artificial Neural Networks are more suitable for this problem than the SVM.

Gibbs Measures on Mutually Interacting Brownian Paths under Singularities

AbstractWe are interested in the analysis of Gibbs measures defined on two independent Brownian paths in ℝd interacting through a mutual self‐attraction. This is expressed by the Hamiltonian with two probability measures μ and ν representing the occupation measures of two independent Brownian motions. We will be interested in a class of potentials V that are singular, e.g., Dirac‐ or Coulomb‐type interactions in ℝ3, or the correlation function of the parabolic Anderson problem with white noise potential.The mutual interaction of the Brownian paths inspires a compactification of the quotient space of orbits of product measures, which is structurally different from the self‐interacting case introduced in [27], owing to the lack of shift‐invariant structure in the mutual interaction. We prove a strong large‐deviation principle for the product measures of two Brownian occupation measures in such a compactification and derive asymptotic path behavior under Gibbs measures on Wiener paths arising from mutually attracting singular interactions. For the spatially smoothened parabolic Anderson model with white noise potential, our analysis allows a direct computation of the annealed Lyapunov exponents, and a strict ordering of them implies the intermittency effect present in the smoothened model. © 2017 Wiley Periodicals, Inc.

Water abstraction affects abundance, size-structure and growth of two threatened cyprinid fishes.

Hydrologic alteration is a major threat to freshwater biota, and particularly fish, in many river courses around the world. We analyzed and compared the effects of water abstraction on two threatened cyprinid fishes of contrasting ecology (the Mediterranean barbel Barbus meridionalis and the Catalan chub Squalius laietanus) in a Mediterranean stream. We compared abundance, size-structure, growth, and condition of both species across perennial and artificially intermittent reaches affected by water abstraction. Both species were less abundant, had scarce large individuals, and displayed slower growth rates (length-at-age) in intermittent reaches, showing clear detrimental effects of water diversion. Mixed-effect models of scale increments showed variation among individuals and among sites, years and age classes for both species. The larger-sized, water-column species (chub) disappeared or was rare in many intermittent reaches. The barbel present in intermittent reaches showed better somatic condition than in sites with permanent flow, perhaps due to reduced competition after rewetting or colonization by better fitted individuals. This benthic, rheophilic species seems more resilient to moderate water abstraction than chub. Many effects of water flow intermittency were only detected on fish life-history traits when accounting for natural, often non-linear, variation, along upstream-downstream gradients. Our results suggest that abundance was the strongest indicator of effects of water abstraction on fish populations, whereas condition was a more labile trait, rapidly recovering from anthropogenic disturbance.

A semi-analytical solution for 2-D axisymmetric modeling of repetitive pulse laser heating with body absorption

In the forthcoming paper (Chen et al., 2017), we presented an analytical solution for two-dimensional (2-D) modeling of repetitive pulse laser heating with surface absorption using the method of separation of variables combining with Laplace transform. But in practice, it often confronts the body absorption for the laser heating. Unfortunately, the above method due to the surface absorption is no longer suitable to the body absorption. In this paper, a semi-analytical solution for 2-D axisymmetric modeling of repetitive pulse laser heating with body absorption is obtained using the integral transform method. The method is validated by comparing with the results of existing finite element method. Temperature distributions for different repetitive pulses heating Silicon are modeled, and some physical mechanisms of repetitive pulses heating are analyzed. Results show that: repetitive pulse laser heating has obvious temperature intermittent cumulation effect; in the thin layer of material surface vicinity, temperature rises due to absorption of irradiated energy dominates over the conduction energy transport from surface to vicinity, and as the depth increases, the absorption decreases, whereas the conduction enhances; the shape of radial distribution of temperature is similar to that of the radial distribution of laser intensity for both Gaussian and flat top laser.

Geomagnetic variation peculiarities at middle latitudes of the East European Platform

The results of instrumental observations of geomagnetic variations at the Mikhnevo midlatitudinal observatory of Institute of Geosphere Dynamics of the Russian Academy of Sciences (54.9595° N; 37.7664° E) are presented and discussed. The main periodicities of the local background variations of geomagnetic field are determined. Variations of ~ 27 days have been registered, as well as periodicities with periods of ~6–9, 12–14, 60 days, and a semiannual periodicity. It has been shown that the background geomagnetic variation periodicities have a sporadic and scaling character. An alternating effect of increasing and degradation periods in geomagnetic variation intensity (the intermittency effect) is found.