Limited Interval Research Articles

ВИМІРЮВАННЯ ОПОРНОЇ ЧАСТОТИ ВУЗЬКОСМУГОВОГО РАДІОСИГНАЛУ ОБМЕЖЕНОЇ ТРИВАЛОСТІ

The work concerns analog-digital systems that work with radio signals emitted and received by the antenna, and these signals have a limited duration, ie are pulsed. The propagation conditions of such signals and the processes of formation of echo signals affect their amplitude, frequency and phase characteristics in such a way that they form classical narrowband signals. The operation of the system involves the determination of certain parameters of echo signals, and taking into account their pulse nature for such a definition is given a limited time interval. This means that the procedure for determining the parameters must meet the criterion of high speed, and therefore differ from the traditional, built on the use of phase-locked loop. The article is devoted to solving the problem of measuring the reference frequency of a pulsed narrowband radio signal. By analyzing the results of experimental studies, two types of errors in measuring the reference frequency of a narrowband radio signal were identified and the causes of their occurrence were established. These errors are provoked by the peculiarities of the structure of the narrowband signal. The reason for the error of the 1st type, the absolute value of which correlates with the duration of the half-cycle of the reference frequency, is the so-called phase jumps at the point of change of the sign of the bypass. The frequency of such errors within the duration of the echo signal is generally low, although it increases with increasing signal spectrum width. Type 2 errors occur due to the appearance of zones with almost completely suppressed signal amplitude, which may be the result of intrapulse interference and / or signal attenuation. Such errors also occur more often if the spectrum width is larger. A method for measuring the reference frequency of a narrowband pulsed radio signal is proposed, which is based on counting the number of half-cycles of the reference frequency on a time-limited measurement interval and removing from this procedure areas with completely suppressed signal amplitude. An auxiliary highly stable reference frequency is used to establish the numerical value of the reference frequency. The block diagram of the frequency meter and the algorithm of its operation are given, the implementation of which avoids these errors.

Iterative learning PID Controller for Permanent Magnet Linear Synchronous Motor

At present, PID controllers have been widely used to control permanent magnet linear synchronous motor(PMLSM), but PID controllers are difficult to be suitable for the occasions with high precision requirements. In order to solve the problem of high precision control, the position-speed-current three-loop control structure is adopted in this study. In the design process of the position controller, the method of combining PID and Iterative learning controller is adopted. Iterative learning control(ILC) can deal with problems in a very simple way. A dynamic system with a fairly high degree of certainty, at the same time, is highly adaptable and easy to implement. It does not rely on the precise mathematical model of the dynamic system, and is an iterative generation of optimized input signals. The Matlab simulation results show that the PMLSM under the iterative learning PID control has accurate position tracking ability. The applicable object of this control system is the controlled system with repetitive motion of industrial robot, which can effectively realize the complete tracking task in a limited time interval.

Dynamics of flame extinction in narrow channels with cold walls: Heat loss vs acceleration

Propagation of a premixed flame from a closed to an open end in micro-channels with smooth non-slip isothermal walls is considered in the context of flame extinction dynamics. Powerful exponential flame acceleration in micro-channels with adiabatic walls has been demonstrated at the initial quasi-isobaric stage of the process [Bychkov et al., Phys. Rev. E 72, 046307 (2005)]. In contrast to the previous studies, here we investigate flame propagation in channels with isothermal walls. The problem is solved by means of high-fidelity laminar numerical simulations of the complete set of the Navier–Stokes combustion equations. For most of the problem parameter sets chosen, we obtain initial flame acceleration after ignition at the closed channel end. This acceleration resembles qualitatively the adiabatic case, but it develops noticeably slower, in an approximately linear regime instead of the exponential one and persists only for a limited time interval. Subsequently, heat loss to the walls reduces the temperature and hence the volume of the burnt gas behind the flame front, which produces a reverse flow in the direction of the closed channel end. When the amount of the burnt gas becomes sufficiently large, the reverse flow stops the acceleration process and drives the flame backwards with modifications of the flame front shape from convex to concave. Eventually, the flame extinguishes. Qualitatively, the process obtained reproduces a possible combustion failure during deflagration-to-detonation transition observed in previous experiments. We investigate the key characteristics of initial flame acceleration such as the acceleration rate and the maximum speed of the flame tip.

Study on summer thermal performance of a solar ventilated window integrated with thermoelectric air-cooling system

In this paper, a thermoelectric air-cooling system was used to cool down the airflow window glazing surfaces during summer in hot climates by which cooling load of the indoors and occupant’s thermal discomfort near the window reduce. The performance of the proposed system was modeled analytically, in which the models used were validated by the literature experiment results. To determine the thermoelectric system specifications, the three features of the system including the time working interval, the number of modules, and the degree of air temperature attenuation were investigated. The results show that using the thermoelectric air cooling system for the limited time interval within hours of peak cooling load can significantly reduce the energy consumption, while using the system for a longer time interval not only cannot decrease the energy consumption but also may increase. Besides, the results reveal that the thermoelectric system with 15 modules is required to be energy efficient. On the other hand, an increase in the number of modules more than 20 has no considerable effect on energy saving. Furthermore, the percentage of energy saving is 6.5% for 5 °C air cooling and reached a maximum of 7.1% for 7 °C air cooling, while for 10 °C, this value is zero. The mean reduction of the maximum interior glazing surface temperature is 5.9 and 7.4 °C for air cooling degrees of 5 and 10 °C.

Effect of heat treatment on mechanical properties of FeMnAlC alloys

FeMnAlC alloys exhibit an attractive strength/ductility combination, low density and some of them show good oxidation behavior at high temperatures. In this paper the effect of a solubilization treatment at 1030 °C followed by aging at 550 °C on the mechanical properties of two alloys belonging to this system, has been evaluated. The results of the investigation revealed that the steel characterized by the higher quantity of Mn and Al shows, after heat treatment, the formation of intermetallic phases that make the alloy very brittle. Considering the obtained results, it is evident that optimizing the alloy chemical composition is of paramount importance to guarantee a high fracture toughness if the steel works for limited time intervals at high temperature.

A Real-Time-Link-Adaptive Operation Scheme for Maximum Energy Storage Efficiency in Resonant CM Wireless Power Receivers

The development, analysis, and experimental validation of an energy storage algorithmic scheme for performance optimization of resonant inductive power receivers are presented. Motivated by the crucial role of efficient energy storage in the next generation of brain-implantable devices, we introduce an energy management strategy in the design of wireless powering links, in which, the key performance measure is the energy stored during a limited time interval rather than the average energy delivered to the load. The presented strategy is proven analytically to yield the theoretically-maximum energy storage efficiency over a pre-determined period of time. Additionally, thanks to the algorithm's closed-form solution, the optimization can be done in real time, offering the potential for a solution that is adaptive to any variations in physical (e.g., coil separation, Rx rotation, etc.) and/or electrical (e.g., Q-factor, media conductivity, etc.) properties of the link, conditional to a low-power circuit implementation for its evaluation. The efficacy and precision of the solution obtained from the presented analytical model is confirmed with CAD-based simulation results, and later validated using experimental measurements. Our experimental results for two links with different characteristics (resonance frequency, coils size and separation, etc.) show a 52.5% and 67.5% improvement in overall energy storage efficiency compared to the standard CM receiver design in which resonance-to-charging switching is performed when the receiver's LC tank energy accumulation starts to saturate. This is while the presented method does not require any calibration and is designed to be employed by any generic current-mode receiver.

Solution of transport safety problems based on biometric systems with error-correcting coding procedures

The paper considers models and methods for solving processing biometric data at the physical and channel levels. A classification of the parameters of such systems is given and those characteristics that play a decisive role in achieving the objective function in limited time intervals are distinguished from them. The work aims to analyze the possibilities of increasing the reliability of biometric devices at the channel level by using error correction codes. The practicability and necessity of error-correcting coding mean using the permutation data decoding algorithms capable of matching biometric identification adequately. Based on the results of statistical modelling of optical communication channels, the necessary and sufficient conditions for the application of permutation decoding tools for binary codes are determined. The problem of minimizing the memory size of the cognitive map of a permutation decoder is solved by allocating the permutation orbits and using the generating combinations of loops as indexes of the reference matrices. An efficient algorithm is proposed for finding a unique orbit number and the corresponding reference matrix when the receiver generates an arbitrary permutation of characters from the set of permissible permutations.

Response of a reinforced concrete cantilever beam subject to impulse impact loads

To study the response of a RC cantilever beam subjected to impulse excitations is based computational model. Static and dynamic analysis of the computational model was performed using a software product based on the Finite Element Method. Two numerical models have been builded for static analysis. In the first model, the concrete modelled with a linear - elastic material model and the reinforcement as deformable bars. In the second model, the concrete modelled using a nonlinear model of concrete - the material model of Willam and Warnke, and the reinforcement as deformable bars. For dynamic analysis, concrete modelled as a linearly elastic material and reinforcement as deformed bars. Under impulse loading, the applied force acts for a very short but limited time interval. This article presents five cases of impulse duration. The dynamic time-history analysis used to determine the dynamic response of the RC cantilever beam under the action of time variables. This type of analysis used to determine time-varying displacements, stresses, and internal forces caused by a combination of static and dynamic (pulse and harmonic) loads. A dynamic time-history analysis used to study the dynamic response to time-varying loads. The time-determined displacements, deformations, stresses and internal forces give the behaviour and reaction of the structure at any time in the studied interval.

Investigating the article processing charge of journals in the gold open access market: A game theory approach

AbstractAs a promising solution for enhancing knowledge communication as well as alleviating financial pressure of institutional libraries, gold open access (gold OA) has attracted wide attention all over the world. But it is a hard work to fully disclose how the equilibrium article processing charge is established in the gold OA market. To deal with this challenge, this paper firstly formulates the competition among journals in this market as a three‐stage Hotelling duopoly game, which is able to reveal its dynamic and competitive features affected by academic reputation, publication delays and article processing charges of journals. Then backward induction is applied to derive the market equilibria. Finally, an empirical study with 1,346 journals is conducted to verify the credibility of the theoretical solutions. The results show that gold OA journal with relatively higher academic reputation and shorter publication delay could charge higher article processing charge. And the publication delays of gold OA journals tend to cluster together in a limited time interval.

S0532 Pre-Procedure COVID-19 Screening and SARS-CoV-2 Testing in a Large Community-Based Ambulatory Surgical Center (ASC) in SE Michigan

INTRODUCTION: The role of pre-procedure COVID-19 testing in outpatient endoscopy centers remains unclear, especially in areas with declining incidence and prevalence of infection. We developed a strategy utilizing symptom screening and SARS-CoV-2 viral RT-PCR testing in patients referred for elective endoscopy at a large community-based ASC in SE Michigan. We hypothesize that this dual screening approach will allow better detection of symptomatic and asymptomatic carriers of COVID-19. METHODS: A retrospective review of all patients referred for elective outpatient endoscopy during a 3 week period (May 20–June 12, 2020) was conducted. Patients were initially screened for exposure history and symptoms of COVID-19 at the time of procedure scheduling, again 3 days prior to the procedure, and on the actual day of the procedure. All patients were offered SARS-CoV-2 RT-PCR testing 48 hours prior to the scheduled procedure and then advised to follow CDC guidelines of social distancing, donning a face mask and frequent hand hygiene until endoscopy. Uptake of COVID-19 testing, barriers, and impact on subsequent endoscopy were evaluated. RESULTS: 718 consecutive patients were scheduled for elective outpatient endoscopy. All patients were symptom screened and 642 patients (89%) underwent COVID-19 PCR testing within 48 hours of their scheduled procedures. 2 patients reported fevers within 48 hours of their scheduled endoscopy, leading to cancellation. COVID-19 PCR testing of asymptomatic patients (n = 642) revealed no positive results. A total of 76 patients (11%) did not undergo viral testing. Barriers to COVID-19 testing included limited time interval between scheduling and procedure, patient reported challenges with travel/availability, and negative perceptions about testing. CONCLUSION: This study demonstrates the feasibility and successful implementation of a pre-procedure COVID-19 screening program in a busy endoscopy center. The dual process of clinical screening for symptomatic patients and viral testing of asymptomatic patients optimizes the likelihood of identifying pre-procedure patients with COVID-19. Although there is a low yield of positive viral tests in settings with low disease prevalence, this study forms a framework to expand pre-procedure screening and testing to enhance safety for our patients and staff during the COVID-19 pandemic.

3D-Printed Splitter for Use of a Single Ventilator on Multiple Patients During COVID-19.

During epidemics or pandemics affecting the respiratory systems, hospital equipment such as ventilators may become insufficient and different solutions can be considered. In fast spreading respiratory illnesses such as COVID-19 due to the rapidly increasing number of patients, ventilatory machine insufficiencies may appear. It may be considered to use one hospital ventilator for more than one patient by dividing the airway of the machine with a specially designed splitter. The aim of this study was to determine whether a ventilator can be modified to provide ventilation of two or more patients simultaneously by using 3D designed and manufactured splitters. A two-port and four-port splitter were designed in Autodesk Fusion 360 computer program and manufactured by 3D printer using PolyJet technology (Stratasys J750). Two sets of splitters were used to adapt to the ventilator during trial process: one for inspiratory and one for expiratory outputs. Two intensive care specialists voluntarily tried this study on themselves. It was concluded from the study that 3D designed and manufactured two-port splitter can be used to separate the airway of a single ventilator to multiple patients within a very limited indication and time interval.

Investigation of global ionospheric response of the severe geomagnetic storm on June 22-23, 2015 by GNSS-based TEC observations

The magnetosphere and ionosphere have a crucial interaction during severe geomagnetic storms. The Global Navigation Satellite System (GNSS) provides high-quality ionospheric observations with high temporal and spatial resolution, is generally preferred to investigate the ionospheric variation. In this study, the storm-time ionospheric response of the June 2015 severe storm (Dstmin = −208 nT) was investigated by the Total Electron Content (TEC) data of the Global Ionosphere Maps (GIMs), COSMIC radio occultation (RO) and a chain of International GNSS Service (IGS) stations. GIMs were used to show the global TEC variation during the storm. COSMIC RO data were also utilized to investigate the TEC variation and electron density profiles in an anomaly area with a limited time interval. GNSS TEC data of the 16 IGS stations were utilized to investigate the ionospheric variability on different latitudes of hemispheres. The results showed that intense positive phases formed in high latitudes of the Southern Hemisphere (SH) and the western longitudes of the Northern Hemisphere (NH), especially over the North Atlantic Ocean until the main phase of the storm. Besides, negative phases were observed in high latitudes and eastern longitudes of the NH. During the recovery phase of the storm, positive phases were seen in the low latitudes of the SH and the ionospheric conditions calmed down in the entire SH after the depletion of these phases. Negative phases were also observed almost wholly covered in the NH, which denser in the European-African sector. As a particular result, the electron density profiles of COSMIC RO showed that the ionospheric phases of the June 2015 storm not only related to TEC values but also the altitude of maximum electron density.

A Point Process Framework for the Characterization of Fetal Sleep States.

In the fetal period, the progressive coordination among several subsystems promotes the emergence of sleep states. For this reason, the characterization of fetal behavioral states plays a crucial role in assessing fetal wellbeing. Nevertheless, current methodologies aimed at assessing fetal sleep states over limited time intervals require visual observation of the traces. In this work, we validate a point process approach for a continuous in time characterization of fetal behavioral states. We compare traditional heart rate variability (HRV) parameters and the corresponding point process-extracted sets of time and frequency measures in a population of 39 fetuses whose fetal ECG was recorded overnight during the third trimester of gestation.Clinical Relevance- Our results provide evidence for the proposed point process framework to capture fetal HRV dynamics with a high degree of reliability, suggesting its potential application for instantaneous estimates of fetal sleep states.

Middle Paleolithic Site Sukhaya Mechёtka: the Renewal of Complex Investigations

The Sukhaya Mechёtka site, located on the northern outskirts of Volgograd, has attracted the attention of Paleolithic researchers since its discovery in 1951 by geologists A.I.Koptev and M.N. Grishchenko. The materials of the site - a collection of stone products currently kept at the MAE RAS, and chronostratigraphic information – can be considered as perfect by standards of open Paleolithic complexes. To a large extent, the site acquired such a significance due to the presence of the only one perfectly preserved cultural layer, which lies in clear stratigraphic conditions. Being densely overlapped with thick deposits, the site was preserved so well that it remained unaffected by the turbulent natural processes of the last glacial-interglacial macrocycle. Single-layer sites usually have a disadvantage comparing to multi-layer complexes in terms of the importance level of the tasks solved with their help. But the Sukhaya Mechёtka favorably differs from other sites by the measure of cultural layer being studied in the field and the potential for further studies. The stone assemblage and field documentation archives created by M.Z. Panichkina and S.N. Zamyatnin show a picture of the life of Middle Paleolithic hunters settlement taken at limited time interval. It is confirmed by preliminary results of planigraphic and technological analyzes performed with use of refitting. Sukhaya Mechёtka is a practically intact echo of an individual Neanderthal community’s life, as far as it’s possible for archaeological material of this age. However, the matter of the site’s chronology, and the time period of Sukhaya Mechёtka layer formation being determined in particular, are not completely resolved. The representations of the middle of the last century based on geological observations (Mikulino) need to be verified. The C14 dating method showed obviously an inadequately young age. OSL dating results are expected to be gained in the future.

Neurotransmitter and tryptophan metabolite concentration changes in the complete Freund\u2019s adjuvant model of orofacial pain

BackgroundThe neurochemical background of the evolution of headache disorders, still remains partially undiscovered. Accordingly, our aim was to further explore the neurochemical profile of Complete Freund’s adjuvant (CFA)-induced orofacial pain, involving finding the shift point regarding small molecule neurotransmitter concentrations changes vs. that of the previously characterized headache-related neuropeptides. The investigated neurotransmitters consisted of glutamate, γ-aminobutyric acid, noradrenalin and serotonin. Furthermore, in light of its influence on glutamatergic neurotransmission, we measured the level of kynurenic acid (KYNA) and its precursors in the kynurenine (KYN) pathway (KP) of tryptophan metabolism.MethodsThe effect of CFA was evaluated in male Sprague Dawley rats. Animals were injected with CFA (1 mg/ml, 50 μl/animal) into the right whisker pad. We applied high-performance liquid chromatography to determine the concentrations of the above-mentioned compounds from the trigeminal nucleus caudalis (TNC) and somatosensory cortex (ssCX) of rats. Furthermore, we measured some of these metabolites from the cerebrospinal fluid and plasma as well. Afterwards, we carried out permutation t-tests as post hoc analysis for pairwise comparison.ResultsOur results demonstrated that 24 h after CFA treatment, the level of glutamate, KYNA and that of its precursor, KYN was still elevated in the TNC, all diminishing by 48 h. In the ssCX, significant concentration increases of KYNA and serotonin were found.ConclusionThis is the first study assessing neurotransmitter changes in the TNC and ssCX following CFA treatment, confirming the dominant role of glutamate in early pain processing and a compensatory elevation of KYNA with anti-glutamatergic properties. Furthermore, the current findings draw attention to the limited time interval where medications can target the glutamatergic pathways.

ORAL CARE AND CHOICE OF MEDICINES FOR TREATING GINGIVITIS AND PERIODONTITIS IN CHILDREN WITH TYPE 1 DIABETES MELLITUS

The anatomical and physiological characteristics of a growing organism require a specific approach to the prevention and treatment of periodontal diseases. Not enough attention is paid toward improving the oral health of children suffering from diabetes mellitus, as well as therapeutic and prophylactic measures aimed at preserving teeth and preventing exacerbations of the inflammatory process in periodontal tissues. The results of clinical studies indicate a high prevalence of dental diseases in patients with type I diabetes mellitus; there are not enough reliable results of such indicators depending on the age and duration of this endocrine pathology, diabetic complications, hypoglycemic therapy taking into account metabolic control. Diagnosis of periodontal diseases is complicated by the peculiarities of the child’s psychological perception, caused by age-specific characteristics and the influence of common manifestations of inflammatory diseases. Children of primary school age often demonstrate increased motor activity, a hyperergic reaction even to minor negative feelings, the difficulty of adequate behaviour in an unfamiliar environment and a correct assessment of what is happening, being stressed due to the presence of many phobias associated with doctors and medical manipulations, communicative difficulties caused by staying in the spotlight, meeting new people, talking with adults. Teaching children must necessarily be accompanied by educating parents, since within limited time interval of dental appointment a doctor does not have the opportunity to fully monitor and consolidate the knowledge and skills the child has received, and this responsibility falls on parents. In this case, some attention should be paid to issues of skills, motivation as well as on the importance dental care aspects for the development of the dentofacial system, since in the vast majority of cases, parents are not enough aware on these issues. In addition to educating and fostering the motivation, it is necessary to control the level of knowledge, the frequency and quality of tooth brushing. For young children, it is necessary to do complete cleaning up the chewing group of teeth due to the low level of children’s manual skills.

Chebyshev neural network-based attitude-tracking control for rigid spacecraft with finite-time convergence

In this paper, the problem of finite-time attitude-tracking control for a rigid spacecraft is addressed. Uncertainties including unknown inertial parameters, external disturbances, actuator failures and saturation constraints are considered. Firstly, a smooth function which is different from the common saturation treatment is presented to deal with the actuator constraints. Secondly, a fast non-singular terminal sliding mode (FNTSM) manifold composed of tracking errors is constructed. To estimate the unknown function in the sliding surface derivative, Chebyshev neural network (CNN) is introduced and thus the strict assumptions on uncertainties in many related works are abolished. By designing the CNN adaptive laws, a new fault-tolerant control scheme is proposed such that the attitude tracking can be achieved within a limited time interval. Compared with the existing CNN-based achievements with finite-time convergence, the approximation errors are proved to be finite-time stable instead of uniformly ultimately bounded (UUB). Finally, simulation experiments are conducted to demonstrate the satisfactory tracking performance of the attitude controller.

Adaptive iterative learning consensus control for second-order multi-agent systems with unknown control gains

We respond to the consensus control algorithms for second-order non-linear MAS with unknown control gains in the finite time interval by adopting iterative learning control (ILC) methods in this paper. Compared to the current findings, the control gains in the proposed method are unknown functions with unknown and non-identical signs. The topology graph between the follower agents is an undirected connected graph. By referencing the Nussbaum-type function and the neural networks, the adaptive control algorithms are intended to cope with the consensus control between the agents on the limited time interval. Simulation results illustrate the efficacy of the raised algorithms.

Sapienza Space debris Observatory Network (SSON): A high coverage infrastructure for space debris monitoring

Optical observations represent a passive method for space debris tracking and monitoring. Although being constrained to limited time intervals, e.g. when the target is in sunlight and the observatory is in darkness, a debris observatory network distributed over multiple locations can improve the observational interval and favor the data integration for more consistent and significant results. The Sapienza Space Systems and Space Surveillance Laboratory (S5Lab) At Sapienza University of Rome has established Sapienza Space debris Observatory Network (SSON), an international network of optical observatories addressed at debris surveillance. The network is composed of six observatories owned and controlled by Sapienza, plus five observational sites controlled by collaborators (mainly University of Michigan and the University of Bern). The network operations have been carried out during several observations campaign, including the Tiangong-1 space station re-entry campaign performed in support of the Inter-Agency space Debris Committee (IADC). The heterogeneous capabilities of the different observatories represent an advantage for acquiring a wider set of debris monitoring data with different techniques. A strong synergy between our institution and the Italian specialized industry has also revealed to be very productive in the context of the network establishment.The present paper will describe the SSON infrastructure and the opportunities, improvements and future perspectives for research institutions or space industry of this wide observatories network will be discussed.

Design and Implement a Real-Time Detection and Defence Mechanism Against the SYN Flood Attack in Server Client System

In the digital world, maintaining information is much difficult. Without security measures and controls in place, data might be subjected to an attack. Now a day’s several attacks are evolved & Distributed Denial of Service (DDOS) is one of them. There are various categories of DDOS attack.SYN flood is addressed as one of the most dangerous attacks. In three way handshaking method a SYN packet is generated and a received ACK acknowledgement is provided to the corresponding. When the SYN packet is generated continuously from random sourcesis considered as flooding. And it’s known as SYN flood attacks. This paper is constructed with a proposed technique for the betterment of both the detection and defense techniques against it. The detection process is improved by a database added in the server for accepting random flooding for a limited time interval. And the defense algorithm is a developed design operated by scrolling the pending requests from database and checking the accessibility of the user and stop requesting otherwise. There are two parts of this research paper. The first one is to discuss extensively the various aspects of SYN Flood attack and developing the knowledge of this flooding attack mechanisms and the second one is to detect the SYN Flood attack and finding a better mitigation process through which we can reduce the loss of any information that generally happens by this deadly flooding. For saving server from crush it is important to mitigate this attack. So it may prove effective in home appliance servers like IoT, IoE that any of the fraud can't get access into the server for any harmful activity.