Small Irregularities Research Articles

Entropy generation in the woven mesh regenerator filler of cryocoolers

The regenerator is a key component of a pulse tube cryocooler, and is also a major contributor to irreversibility and losses in the cryocooler. In this study a method for the assessment of losses in cryocooler regenerators based on entropy generation is proposed. Pore-level CFD simulations are performed for woven mesh regenerator filler by defining periodically repeating unit cells. Simulations are performed for steady-state (uni-directional) as well as periodic flows. It is shown that entropy generation in periodic flow is higher than in steady flow, and is sensitive to operating parameters as well as small geometric irregularities. It is proposed that by optimization of the microstructure of regenerator fillers the entropy generation and losses can be minimized.

Ionospheric anomaly detection and Indian ionospheric climatology from GAGAN receivers

The ionospheric anomalies are often responsible for compromising the accuracy and performance of Global Navigation Satellite System (GNSS). GPS Aided Geo Augmented Navigation (GAGAN) is the autonomous Space Based Augmentation System of India which serves to provide timely error detection and correction for the corrupted GNSS signals in aircrafts. This paper discusses a Maximum Minimum Eigen (MME) detector to identify the ionosphere induced errors in the GNSS signals. Data has been collected from 24 different GAGAN receivers spread over the length and breadth of India from January to December, 2015. The climatology of ionospheric anomaly over India, has been established using the MME detector. This paper discusses the spatio-temporal dependence of ionospheric anomalies over India. The observations indicate an increased ionospheric activity in the course of equinoxes and a comparitively quiet ionosphere in the course of solstices. A higher number of ionospheric disturbance incidents have been noticed closer to the anomaly crest. The results from the MME detector have been verified against the Rate of Total Electron Content (TEC) Index (ROTI) values and S4 observations for the year 2015 at the 24 GAGAN TEC stations. The disturbance climatology obtained from MME detector, ROTI and S4 exhibit a high correlation. However, the outcome of the MME detector clearly shows that it is capable of picking up even small irregularities in the ionospheric TEC.

On the tradeoff between sensitivity and specificity in bus bunching prediction

Bus bunching resulting from initially small headway irregularities is a widely-known and studied problem. A variety of headway-prediction approaches, as well as corrective strategies, have been developed to identify and correct headway irregularity in real time. Instead of predicting an exact value for future headways, this study explores a probabilistic predictive methodology to forecast whether or not a bus will be bunched during its dwelling at a downstream stop, using a logistic regression model based on GPS records of buses at least k stops upstream to allow for sufficient time to possibly implement control strategies. A case study is conducted on a circular bus route in Kyoto City. Compared to two headway-based prediction approaches using linear regression and support vector machine, the superior performance of the proposed tool in detecting bunching is illustrated by Receiver Operator Characteristic (ROC) analysis. The high reliability in long-term prediction gives adequate time for operators to employ countermeasures. Besides, the proposed method provides operators with tradeoff options. We find that a bunching-averse operator can obtain 95% “sensitivity”, that is the ratio of correctly identified bunching events, at the cost of decreasing “specificity”, which is the ratio of correct non-bunching predictions over all events. This is true even if the prediction horizon is more than 10 stops.

IDEASSat: A 3U CubeSat mission for ionospheric science

The Ionospheric Dynamics Exploration and Attitude Subsystem Satellite (IDEASSat/ INSPIRESat-2) is a three-unit (U) CubeSat developed with the objective of providing in-situ measurements of the Earth’s ionosphere in order to quantify both global scale ionospheric variability and small scale irregularities. The science payload is the Compact Ionospheric Probe (CIP) - an all in one in-situ plasma sensor developed at Taiwan National Central University (NCU), which is the miniaturized version of the larger Advanced Ionospheric Probe (AIP) that is carried and operational aboard the 450 kg FORMOSAT-5 spacecraft. The spacecraft has been developed by NCU in partnership with the International Satellite Program in Research and Education (INSPIRE) consortium, and is funded by the Taiwan National Space Organization (NSPO), Ministry of Science and Technology, and Ministry of Education as part of the first national effort to encourage small satellite development at Taiwan universities. The development of IDEASSat offers students a hands-on opportunity to learn about space science and technology and will work in conjunction with FORMOSAT-5 and INSPIRESat-1 to provide ionospheric observations spanning different altitudes and local times. The IDEASSat spacecraft subsystems are a combination of commercial off the shelf (COTS) and self-developed components designed by NCU in partnership with other INSPIRE member universities. IDEASSat is expected to be launched in late 2020. In this report, we describe the IDEASSat mission and spacecraft design, as well as unique lessons learned as part of the development process.

Pneumohydraulic spring with adaptive self-adjusting damper for suspension of a high-speed tracked vehicle and its calculation procedure

Currently, a further increase in the mobility of high-speed vehicles is largely limited by the existing suspension systems, which mainly have unregulated characteristics, and the developed adjustable suspension systems with external control are very complex, expensive and less reliable. Therefore, the development of relatively simple and reliable self-adjusting suspensions for high-speed machinery is an urgent task. At the Department of Automatic Installations of Volgograd State Technical University an original design of an air-hydraulic spring (AHS) with an adaptive self-regulating damper for suspension of a high-speed tracked vehicle (HSTV) was developed. A feature of its adaptive damper is the provision of a two-stage inelastic resistance depending on the amplitude, frequency and direction of oscillation, which can significantly reduce the acceleration of the «shaking» and heating of AHS when the HSTV moves along small irregularities, as well as practically eliminate suspension breakdowns when large vertical and angular vibrations occur at the vehicles body when driving on large bumps or springboards with a takeoff of the rollers from the supporting surface. These modes of operation are ensured by installing two spring-loaded step plungers in the serial AHS body, which in a static position and with small spring lift open an additional throttle channel, which significantly reduces the inelastic resistance of the suspension, and at large strokes they block this channel, thereby significantly increasing damping fluctuations. Due to the fact that these plungers are equipped with a system for delaying their movement in the opposite direction, the increased resistance is maintained for several periods of oscillation. The article also presents an engineering methodology and a numerical example of determining the parameters of the main elements of an adaptive self-regulating damper, the elastic and damping characteristics of the AHS taking into account the operation of the pressure relief valve and the rebound check valve.

Radiomics-Based Prediction of Long-Term Treatment Response of Vestibular Schwannomas Following Stereotactic Radiosurgery.

Stereotactic radiosurgery (SRS) is one of the treatment modalities for vestibular schwannomas (VSs). However, tumor progression can still occur after treatment. Currently, it remains unknown how to predict long-term SRS treatment outcome. This study investigates possible magnetic resonance imaging (MRI)-based predictors of long-term tumor control following SRS. Retrospective cohort study. Tertiary referral center. Analysis was performed on a database containing 735 patients with unilateral VS, treated with SRS between June 2002 and December 2014. Using strict volumetric criteria for long-term tumor control and tumor progression, a total of 85 patients were included for tumor texture analysis. All patients underwent SRS and had at least 2 years of follow-up. Quantitative tumor texture features were extracted from conventional MRI scans. These features were supplied to a machine learning stage to train prediction models. Prediction accuracy, sensitivity, specificity, and area under the receiver operating curve (AUC) are evaluated. Gray-level co-occurrence matrices, which capture statistics from specific MRI tumor texture features, obtained the best prediction scores: 0.77 accuracy, 0.71 sensitivity, 0.83 specificity, and 0.93 AUC. These prediction scores further improved to 0.83, 0.83, 0.82, and 0.99, respectively, for tumors larger than 5 cm. Results of this study show the feasibility of predicting the long-term SRS treatment response of VS tumors on an individual basis, using MRI-based tumor texture features. These results can be exploited for further research into creating a clinical decision support system, facilitating physicians, and patients to select a personalized optimal treatment strategy.

Discussion

Discussion

Dispersion Process in Sewer Pipes with Sediments and Deposits

This paper describes the dispersion process in sewer pipes, which is from the hydraulic point of view a prismatic stream channel with relatively constant roughness of streambed. In such hydraulic conditions should the effect of “dead zones” not occur, but this effect was observed during the field experiments. The reason for this was the presence of bed sediments and deposits, which form together with other small obstacles irregularities in the sewer pipe such dead zones. Dead zones are areas with small flow velocities, which act as a zone with transient (temporary) storage, where the pollution is accumulated and released gradually later. This process modifies the dispersion process in sewer systems and causes irregularities in the transport process. Field experiments were performed in a straight sewer section and also in the part with directional changes of sewer line, both under dry weather flow conditions, i.e. with relatively low pipe filling, discharges and velocities. Sewer pipes had a low slope, so a lot of deposits and sediments were present. Paper presents the results of field experiments and analyse the impacts of sediments and deposits in sewer system on the transport and dispersion process, which is reflected in the value of dispersion coefficient. In the case of sewer pipelines, the most important is the longitudinal dispersion coefficient DL. Comparing the values of DL in the straight part and in the part with directional changes, DL values in the straight part were higher than from the section with directional changes. The maximal value of the dimensionless longitudinal dispersion coefficient p reached 25.2 in a straight section; in the part with the directional changes p it was up to 39.3. This result indicates that in the straight part of the sewer line, the longitudinal dispersion of the substance is dominant in the total dispersion process, whereas in the sewer part with directional changes, the transversal (lateral) dispersion contributes to the whole mixing process (dispersion process is also influenced by the velocity gradient in the transverse direction). Within the measured channel section, there were three directional changes - angles of 90°, 135° and 105°. The influence of the direction change angle to the longitudinal dispersion coefficient within the performed measurements has not been clearly determined yet.

Encapsulation of Fatty Oils into Electrospun Nanofibers for Cosmetic Products with Antioxidant Activity

Active compounds derived from pomegranate and sea-buckthorn were encapsulated into polylactide (PLA-based fibers) and poly(vinyl-pirrolidone) (PVP-based fibers) nanofibers using electrospinning technique. The focus was on the antioxidant activity of prepared nonwovens. Morphology, thermal, and mechanical properties were also examined. Due to the different physical and chemical properties of the basic polymers, the obtained results indicate that PLA-based fibers have better antioxidant activity than PVP-based ones. All prepared samples were formed from bead-less continuous fibers networks, but in the case of PLA-based samples some small irregularities in the structure occurred. Mechanical properties were improved with the addition of active compounds in most of the cases, while thermal properties were slightly affected. Preserved antioxidant activity of active compounds by encapsulation and good material properties significant for manipulation, make these functional materials promising candidates for application in cosmetics.

Statistical features of TEC and ionospheric scintillation over the low latitude of China

In this paper, a new index is established which is defined by the standard deviation of total electron content (TEC) fluctuation and denoted by the symbol σtec. It is demonstrated that the index σtec is equivalent to the phase scintillation index and can serve as an indicator of the strength of the phase scintillation. The receiver transiently loses lock on the signal, leading to cycle slips and jumps in the TEC time series. In order to obtain continuous TEC data in the situation of the disturbed ionosphere, a batch processing method is developed to detect and correct cycle slip. Based on the methods mentioned above, we investigate the statistical features of the phase scintillations and cycle slips by means of the data from a scintillation observation network in the south-central region of China during 2012–2015. The results show that the variations of phase scintillation occurrences with local time and season display very similar features to those of the cycle slip occurrences, implying that cycle slips are closely related to phase scintillations. Phase scintillations occur mainly during the night, most frequently before midnight and seldom in the daytime. It is found that phase scintillations occur mainly in equinox months but seldom in solstice months in the crest of the ionization equatorial anomaly and its adjacent regions, and an equinoctial asymmetry that phase scintillations occur more frequently in Spring than in Autumn is also found. Besides, a comparison of the TEC fluctuation index (σtec) and amplitude scintillation index (S4) indicates that there is close relation between the σtec and S4, indicating the co-existence of large and small scale irregularities in equatorial irregularity structures.

A Compressible Fluid Flow with Double-Deck Structure Inside an Axially Symmetric Wavy-Wall Pipe

The problem of viscous compressible fluid flow in an axially symmetric pipe with small periodic irregularities on the wall is considered for large Reynolds numbers. An asymptotic solution with double-deck structure of the boundary layer and unperturbed core flow is obtained. Numerical investigations of the influence of the density of the core flow on the flow behavior in the near-wall region are presented.

Using a 2D shallow water model to assess Large-Scale Particle Image Velocimetry (LSPIV) and Structure from Motion (SfM) techniques in a street-scale urban drainage physical model

Physically-based numerical modelling of surface processes in urban drainage, such as pollutant wash-off or the assessment of flood risks, requires appropriate calibration and terrain elevation data to properly simulate the overland flows and thus to achieve useful results. Accordingly, this study aims to obtain an accurate representation of the runoff generated by three different rain intensities, 30, 50 and 80 mm/h, in a full-scale urban drainage physical model of 36 m2. The study focuses firstly on applying the Structure from Motion (SfM) photogrammetric technique to carry out a high-resolution and accurate topographic survey. This topography was implemented in a 2D shallow water model and the results were compared with those obtained using traditional data point measured topography. Negligible differences were found when comparing the two models with measured discharges at the physical model gully pots. However, significant differences were obtained in the velocity distributions, especially in the shallowest flow areas where drainage channels of a few millimeters’ depth appeared in the high resolution topographic survey. Results from the numerical model were compared with overland flow velocities, determined by applying a modified Large Scale Particle Image Velocimetry (LSPIV) methodology using fluorescent particles. With the SfM topography, the 2D model was able to obtain a better representation of the experimental data, since small scale irregularities of the pavement surface could be represented in the model domain. At the same time, LSPIV was presented as a very suitable tool for the accurate measurement of runoff velocities in urban drainage models, avoiding the interference of raindrop features in the recorded images and with overland water depths in the order of few millimeters.

Characteristics of ionospheric scintillation climatology over Indian low-latitude region during the 24th solar maximum period

The amplitude and phase of L-band satellite signals are fluctuated randomly due to small scale electron density irregularity structures in the ionosphere which result in fleeting variations, known as ‘ionospheric scintillations’. The Global Navigation Satellite System (GNSS) is a profound remote sensing tool to monitor, model and forecast the ionospheric weather conditions. In this paper, the GNSS amplitude scintillation data has been analyzed during the year 2013 at Bengaluru (12.9°N, 77.59°E) and Lucknow (26.8467°N, 80.9462°E) stations to reinforce climatology of ionospheric scintillation over Indian low-latitude region. The probability of scintillation occurrence and their variations over equatorial and Equatorial Ionization Anomaly (EIA) regions in India are analyzed during various geomagnetic quiet and disturbed days, months and seasons. The annual occurrence of amplitude scintillations are mapped with the function of local time. It is observed from the experimental results that the probability of scintillations occurrences is higher over EIA region than over the equatorial region. The probability of scintillations is higher during March equinox and December solstice, and lowest during June solstice. Distribution of scintillations is intense during post–sunset period. The maximum percentage of scintillation occurrences at the two stations are recorded in November. Moreover, the highest percentage of scintillation occurrences took place on storm day (March 17, 2013) at the two stations. This work would be helpful for understanding the features of GNSS amplitude scintillations over Southern and Northern Indian regions. Moreover, these kinds of investigations are helpful for developing new algorithms to nowcast and forecast ionospheric scintillations over Indian Sub-continent.

Формирование локального патриотизма прошлого: информационный баланс коммуникативно-текстовой среды

The article is devoted to the study of the information balance of the communicative-textual environment of regional media in the context of the construction of local patriotism of the past. Information balance is considered as a parameter of ecological safety of the environment. Local patriotism is understood as the attitude of the subject and the object of patriotism formed in different spheres as a result of social interaction. An integrative approach is used, which provides the possibility of synthesis of achievements of eco- and sociolinguistics, reference to the analysis of linguistic and non-linguistic phenomena, attraction of the results obtained in different spheres of knowledge. The completeness of reflection of event content in the text space of mass media, types of facts reflected in publications, superstructure of the text are investigated. It is shown that characteristics of the information balance determine the impact on the cognitive sphere of the subject of patriotism. The following features of information balance are established: weak differentiation of regional mass media; the small number and irregularity of publications on the past of the region; the prevalence of reports on commemorative practices and, as a consequence, the frequency of special redistribution of content elements between the elements of the superstructure of the text; the limited repertoire of reactualized fragments of the past; the predominant representation of one type of facts. The article describes the negative impact of non-compliance with the principle of balance on the optimality of impact in the discursive construction of local patriotism of the past.

Neurodynamic compensatory mechanisms of visual impairment and biomechanical indicators of running in an elite athlete in the paralympic sprint

Introduction. The study of visual dysfunction compensatory mechanisms is of great importance both for the Paralympic athletes, as well as for people suffering from such dysfunctions, especially in cases when analyzer disorders occurred in adulthoodt, and natural adaptation mechanisms could not be included in the process of growth and development of the body. The aim: to identify potential compensatory mechanisms of visual impairment in an elite athlete in the Paralympic sprint based on an analysis of the biomechanical characteristics of running and neurodynamic indicators. Material and methods. A highly qualified athlete participated in the study, specializing in short-distance running and long jump among athletes with visual impairment (category T12). The individual characteristics of the psychophysiological state and the results in running for 60, 80,100, 120, 200 m were analyzed and the biomechanical characteristics of the run for 100 m were determined. In total, 36 series of measurements of each indicator were carried out for 5 months. Results. It is shown that the athlete being examined is an atypical sprinter from the point of view of the properties of the nervous system, development and maintenance of speed at a distance, some biomechanical characteristics of running. The subject athlete is a representative of a mobile and strong type of nervous system, which allows her to maintain a higher speed at a distance compared to other athletes for a longer time, which can be considered as a potential reserve. The role of the auditory analyzer at the time of the examination of the female athlete as a compensatory mechanism of visual dysfunction was not identified. The presence of a small irregularity in the change in the speed and acceleration of the movement of the ankle and knee joints, observed in some steps when lowering the limb after hip removal, was revealed. Conclusin. Revealed a high reliable relationship between the neurodynamic and biomechanical characteristics of the examined female athlete. Improving the biomechanics of running by focusing on the work of a kinestatic analyzer can give an increase in speed at a distance while maintaining it almost to the finish.

Bending and branching of calcite laths in the foliated microstructure of pectinoidean bivalves occurs at coherent crystal lattice orientation

Foliated calcite is widely employed by some important pteriomorph bivalve groups as a construction material. It is made from calcite laths, which are inclined at a low angle to the internal shell surface, although their arrangement is different among the different groups. They are strictly ordered into folia in the anomiids, fully independent in scallops, and display an intermediate arrangement in oysters. Pectinids have particularly narrow laths characterized by their ability to change their growth direction by bending or winding, as well as to bifurcate and polyfurcate. Electron backscatter analysis indicates that the c-axes of laths are at a high, though variable, angle to the growth direction, and that the laths grow preferentially along the projection of an intermediate axis between two a-axes, although they can grow in any intermediate direction. Their main surfaces are not particular crystallographic faces. Analyses done directly on the lath surfaces demonstrate that, during the bending/branching events, all crystallographic axes remain invariant. The growth flexibility of pectinid laths makes them an excellent space-filling material, well suited to level off small irregularities of the shell growth surface. We hypothesize that the exceptional ability of laths to change their direction may be promoted by the mode of growth of biogenic calcite, from a precursor liquid phase induced by organic molecules.

Relationship between the anisotropy tensor calculated through global and object measurements in high‐resolution X‐ray tomography on cellular and composite materials

Structural anisotropy of two-phase materials can be evaluated through global measurements, as volume orientation or mean-intercept length methods do, or through statistics performed on a set of individual measurements. This last procedure is encouraged by recent improvements in the spatial resolution of conventional X-ray tomography. In this paper, the above-described approaches were compared in three case studies: a foam subjected to an in situ compression test, a second foam with a completely different cell morphology and a plastic material reinforced with short fibres. The approach based on the subdivision into distinguishable objects of the considered material phase has proved to be more sensitive in highlighting small deformations in the structure or small irregularities in an otherwise isotropic structure. On the other hand, the other approach is more general and is always usable. The two methods for calculating the fabric tensor tend to converge as the average anisotropy of individual objects in the statistical population increases. The use of Lambert's cylindrical equal-area projection of cell/fibre directions or local volume orientations is suggested, because the density of points is preserved from the sphere to the plane surface. Finally, a quick vector method to evaluate the anisotropy of the directions distribution has been presented, by defining a coherence index of the average direction.

Experimentally validated CFD simulations predicting wind effects on photovoltaic modules mounted on inclined surfaces

Computational Fluid Dynamics (CFD) and wind tunnel experiments were used to study wind flow over PV modules attached to inclined surfaces. Wind velocities were investigated at various positions on a test module, for five wind speeds varying from 1 to 5 m s−1. After validation the CFD model was used to study the effects air gaps and wall cavities under the module have on the airflow over the module. Data were measured for two air gaps, 3.5 cm and 5.5 cm thick, and for three cavity depths ranging from 0 cm to 9 cm. The 3.5 cm air gap resulted in lower near-surface wind speeds over the PV module. This will result in less wind-generated cooling of the module, and consequently, in a lower electrical performance. The wall cavities did not affect the magnitude of the wind speed over the module but generated an increased deflection of the wind towards the lateral sides of the module. They also created clockwise and anti-clockwise eddies next to the PV setup and in the cavity itself. The study shows that in CFD simulations for PV applications, even small irregularities in the PV setup should be included in the model to predict reliable results.

Direct-SV radiation produced by land-based P-sources — Part 1: Surface sources

We use finite-difference modeling to illustrate direct-P and direct-SV radiation produced by land-based, vertical-displacement sources such as vertical vibrators and vertical impacts, sources that reflection seismologists have used for decades to image subsurface targets. We are particularly interested in understanding the nature of SV radiation that these sources create. Such insight will be important for those in the seismic interpretation community who are interested in S-wave reflection seismology. One distinction between our work and that of earlier investigators is that we go beyond traditional assumptions that a propagation medium has a flat surface and is isotropic and homogeneous throughout the model space. Instead, we use models composed of small finite-difference cells that allow earth anomalies with dimensions of only a few feet to be near a source station. These small irregularities are expressed as variations in propagation velocities in a small population of model cells, or as slight changes in surface elevation. These small, realistic, near-source irregularities cause robust direct-SV illumination to travel in near-vertical takeoff angles from a surface-based source station and to often travel in true-vertical takeoff angles. We also depart from the conventional practice of calculating direct-P and direct-SV radiation produced by only a single vertical vibrator. Instead, we model direct-P and direct-SV illumination produced by arrays of 2, 3, and 4 inline vertical vibrators. We find that vibrator arrays create SV-mode beam forming that causes a rich amount of direct-SV radiation to occur inside the critical takeoff-angle cone below a source station that extends from [Formula: see text] to [Formula: see text] from vertical. We consider our source-radiation models to be more realistic representations of conditions encountered in actual seismic field practice than previous models that use oversimplified earth conditions. Our purpose is to provide interpreters information that will let them decide if common, surface-based, land sources such as vertical vibrators can be used to illuminate geologic targets with direct-P and direct-SV illuminating wavefields rather than limiting the use of these sources to P-wave imaging only, as has been standard practice for several decades. Our results indicate that vertical vibrators and vertical impacts produce illuminating wavefields that are appropriate for imaging deep geologic targets. Our models apply to the total family of surface-based, vertical-displacement sources, which includes vertical vibrators and accelerated weight drops.

51‐1: Optimal Fast‐Response LCD for High‐Definition Virtual Reality Head Mounted Display

The fast response LCD is necessary for high‐definition and high‐refresh rate virtual‐reality head mounted displays. In this study, fast‐response properties were achieved by SLC‐IPS. High transmittance and stable switching were obtained using a one‐side branch structure with small irregularities in the electrode.