Miracle-dz/UniFAR-FTUs huggingface dataset:
Perturb and observe maximum power point tracking method for photovoltaic systems using duty-cycle modulation

This paper presents the implementation of perturb and observe maximum power point tracking algorithm with Duty Cycle Modulation instead of pulse width modulator for photovoltaic power generators. Like all the different methods used for tracking the maximum power point of photovoltaic system, perturb and observe method use a Pulse Width Modulation to control the DC-DC converter. Here, the Duty Cycle Modulation is used in the place of Pulse Width Modulation. A detailed analysis of the approach is proposed and simulations are performed using MATLAB/Simulink software. The results show the performance and speed at which this control reaches the maximum power point. The response times is very low and is between 0.0125s and 0.05s depending on the climatic variations. So, Duty Cycle Modulation can be used as an alternative to Pulse Width Modulation for the search of the maximum power point.
Numerical simulation of viscous, nonlinear and progressive water waves

A numerical simulation is performed to study the velocity, streamlines, vorticity and shear stress distributions in viscous water waves with different wave steepness in intermediate and deep water depth when the average wind velocity is zero. The numerical results present evidence of ‘clockwise’ and ‘anticlockwise’ rotation of the fluid at the trough and crest of the water waves. These results show thicker vorticity layers near the surface of water wave than that predicted by the theories of inviscid rotational flow and the low Reynolds number viscous flow. Moreover, the magnitude of vorticity near the free surface is much larger than that predicted by these theories. The analysis of the shear stress under water waves show a thick shear layer near the water surface where large shear stress exists. Negative and positive shear stresses are observed near the surface below the crest and trough of the waves, while the maximum positive shear stress is inside the water and below the crest of the water wave. Comparison of wave energy decay rate in intermediate depth and deep water waves with laboratory and theoretical results are also presented.
Spontaneous polarization and piezoelectric constants of III-V nitrides

The spontaneous polarization, dynamical Born charges, and piezoelectric constants of the III-V nitrides AlN, GaN, and InN are studied ab initio using the Berry-phase approach to polarization in solids. The piezoelectric constants are found to be up to ten times larger than in conventional III-V and II-VI semiconductor compounds, and comparable to those of ZnO. Further properties at variance with those of conventional III-V compounds are the sign of the piezoelectric constants ~positive as in II-VI compounds! and the very large spontaneous polarization. @S0163-1829~97! 51740-1# In this paper we report an ab initio study of the spontaneous polarization, piezoelectric constants, and dynamical charges of the III-V nitride semiconductors AlN, GaN, and InN. 1 This class of polarization-related properties is of obvious importance for the study of nitride-based piezodevices 2 and multilayer structures. In particular, knowledge of these properties allows an insightful treatment of the polarization ~and ensuing electric fields! in strained and polarized nitride junctions and superlattices under any strain condition, as discussed elsewhere. 3 From the present study, one of the first applications of the modern theory of polarization in solids 4,5 to real and ‘‘difficult’’ materials of technological interest, the nitrides emerge as highly unusual III-V materials, resembling II-VI oxides and in some respects ferroelectric perovskites. The results we report here are of special interest in view of the scarcity of the data ~both experimental and theoretical! available at present for the nitrides. In the absence of external fields, the total macroscopic polarization P of a solid is the sum of the spontaneous polarization P eq in the equilibrium structure, and of the straininduced or piezoelectric polarization dP. In the linear regime, the piezoelectric polarization is related to the strain e by
Identification of stable lentil genotypes through genotype by environment interactions on yield potential in Morocco

Genotype by environment (G×E) interaction study becomes essential for selecting high and stable yielding genotypes. Altogether 64 lentil genotypes representing improved varieties, landraces and advanced lines were evaluated under 6 environments for green cover, phenological characters, grain yield and 1000 seed weight. Variance analysis revealed highly significant effects of genotype, environment and genotype by environment interaction for all studied traits. The environment had the greatest effect with 75.7% of the total sum of squares. AMMI-GGE biplot identified 3 mega-environments where Z32 advanced lines were performed in the first one (E1, E4 and E5); Z33 was the best in the second mega-environment (E2 and E3), of which E2 (SAD18) was characterized as discriminating and representative environment for selecting adaptable genotypes. While VR4 and LR4 were the winning genotypes in the third mega-environment represented by E6. According to 7 stability methods, Z33, Z32, Z31, Z13 and G03 lines were the most stable and resilient in all environments. In addition, five landraces (PA6, LR4, LR10, LR6 and PA1) showed a high yielding potential that could be used as a source of genotype candidates to develop novel resilient varieties of lentils. Varieties VR9 was recommended for both favorable and unfavorable environments, VR6 for unfavorable and VR3 for favorable environment. Otherwise, genotypes were grouped into 3 clusters with 90% of similarity. The third one gathered the highest yielding genotypes (Z33 and Z32), which were the most stable that could be promoted for developing resilient varieties for climatic changing environments.
Correlation for Flow Boiling Heat Transfer at Low Liquid Reynolds Number in Small Diameter Channels

In view of significance of a heat transfer correlation of flow boiling under the conditions of low liquid Reynolds number or liquid laminar flow, and very few correlations in principle suitable for such flow conditions, this study is aiming at developing a heat transfer correlation of flow boiling at low liquid Reynolds number for small diameter channels. The correlation is developed based on superimposition of two main flow boiling mechanisms, namely nucleate boiling and forced convection. In the correlation, two terms corresponding to nucleate boiling and forced convection are obtained from the pool boiling correlation by Forster and Zuber and the analytical annular flow model by Hewitt and Hall-Taylor, respectively. An extensive comparison with a collected database indicates that the developed correlation works satisfactorily with mean deviation and rms errors of 19.1% and 24.3%, respectively, under many experimental conditions such as different channel geometries (circular and rectangular) and flow orientations (vertical and horizontal) for some test fluids (water, Rll, R12, and R113). A detailed discussion reveals that existing correlations for turbulent flow boiling such as Chen 's correlation, Schrock and Grossman's correlation, and Dengler and Addoms's correlation may be derived from a generalized form of the newly developed correlation.
A Study on Subjectivities of Type 1 and 2 in Parameters of Differential Equations

This study presents the Verhulst's model for the analysis of population growth with the rate of reproductivity depending on the fertility rate and the country economic development. These linguistic variables are defined through Fuzzy Rule-Based Systems (FRBS). The analysis is made for FRBS types 1 and 2 where in the first case, the inference method used is Mamdani's and the defuzzification is the center of gravity. For type-2 FRBS is used as input variables interval type-2 fuzzy sets, and as output intervals. The output is defuzzificated by the Type Reducer method that use the algorithm of Karnik-Mendel (KM). The aim of this study is to compare the solutions of the Verhulst's model where the parameter, rate of reproductivity, is determined through the type-1 and type-2 FRBS. The comparison is made computing the region built from the solutions corresponding to the minimum and maximum rate. It has been noticed that the region corresponding to type-2 FRBS is contained in the region built similarly from type-1 FRBS, showing a higher accuracy in the response (1), (2) and (4).
No “Maunder Minimum” Candidates in M67: Mitigating Interstellar Contamination of Chromospheric Emission Lines

The solar analogs of M67 let us glimpse the probable behavior of the Sun on timescales surpassing the duration of human civilization. M67 can serve as a solar proxy because its stars share a similar age and composition with the Sun. Previous surveys of M67 observed that 15% of its Sun-like stars exhibited chromospheric activity levels below solar minimum, which suggest that these stars might be in activity-minimum states analogous to the Maunder Minimum. The activity diagnostic used, the HK index (relative intensities of the Ca ii H & K lines integrated over 1 Å bandpasses), was measured from low-resolution spectra (R ≈ 5000), as is traditional and suitable for nearby, bright stars. However, for stars beyond the Local Bubble, the interstellar medium (ISM) imprints absorption lines in spectra at Ca ii H & K, which negatively bias activity measurements when these lines fall within the HK index bandpass. I model the ISM clouds in the M67 foreground with high-resolution spectra of blue stragglers and solar analogs. I demonstrate that ISM absorption varies across the cluster and must be accounted for on a star-by-star basis. I then apply the ISM model to a solar spectrum and broaden it to the lower spectral resolution employed by prior surveys. Comparing HK indices measured from ISM-free and ISM-contaminated spectra, I find that all stars observed below solar minimum can be explained by this ISM bias. I conclude that there is no compelling evidence for Maunder Minimum candidates in M67 at this time.
Experimental evidence for topological surface states wrapping around a bulk SnTe crystal

We demonstrate that the metallic topological surface states wrap on all sides the three-dimensional topological crystalline insulator SnTe. This is achieved by studying oscillatory quantum magnetotransport and magnetization at tilted magnetic fields, which enables us to observe simultaneous contributions from neighboring sample sides. Taking into account pinning of the Fermi energy by the SnTe reservoir, we successfully describe theoretically the de Haas--van Alphen oscillations of magnetization. The determined $\ensuremath{\pi}$--Berry phase of surface states confirms their Dirac fermion character. We independently observe oscillatory contributions of magnetotransport and magnetization originating from the bulk SnTe reservoir of high hole density. It is concluded that the bulk and surface Landau states exist in parallel. Our main result that the bulk reservoir is surrounded on all sides by the topological surface states has a universal character.
Primordial black hole and wormhole formation by domain walls

In theories with a broken discrete symmetry, Hubble sized spherical domain walls may spontaneously nucleate during inflation. These objects are subsequently stretched by the inflationary expansion, resulting in a broad distribution of sizes. The fate of the walls after inflation depends on their radius. Walls smaller than a critical radius fall within the cosmological horizon early on and collapse due to their own tension, forming ordinary black holes. But if a wall is large enough, its repulsive gravitational field becomes dominant much before the wall can fall within the cosmological horizon. In this ``supercritical'' case, a wormhole throat develops, connecting the ambient exterior FRW universe with an interior baby universe, where the exponential growth of the wall radius takes place. The wormhole pinches off in a time-scale comparable to its light-crossing time, and black holes are formed at its two mouths. As discussed in previous work, the resulting black hole population has a wide distribution of masses and can have significant astrophysical effects. The mechanism of black hole formation has been previously studied for a dust-dominated universe. Here we investigate the case of a radiation-dominated universe, which is more relevant cosmologically, by using numerical simulations in order to find the initial mass of a black hole as a function of the wall size at the end of inflation. For large supercritical domain walls, this mass nearly saturates the upper bound according to which the black hole cannot be larger than the cosmological horizon. We also find that the subsequent accretion of radiation satisfies a scaling relation, resulting in a mass increase by about a factor of 2.
The potential of tracing the star formation history with H I 21-cm in intervening absorption systems

Unlike the neutral gas density, which remains largely constant over redshifts of 0 ≲ z ≲ 5, the star formation density, ψ ∗ , exhibits a strong redshift dependence, increasing from the present day before peaking at a redshift of z ≈ 2.5. Thus, there is a stark contrast between the star formation rate and the abundance of raw material available to fuel it. However, using the ratio of the strength of the H i 21-cm absorption to the total neutral gas column density to quantify the spin temperature, T spin , of the gas, it has recently been shown that 1 / T spin may trace ψ ∗ . This would be expected on the grounds that the cloud of gas must be sufficiently cool to collapse under its own gravity. This, however, relies on very limited data and so here we explore the potential of applying the above method to absorbers for which individual column densities are not available (primarily Mg ii absorption systems). By using the mean value as a proxy to the column density of the gas at a given redshift, we do, again, find that 1 / T spin (degenerate with the absorber-emitter size ratio) traces ψ ∗ . If confirmed by higher redshift data, this could offer a powerful tool for future surveys for cool gas throughout the Universe with the Square Kilometre Array.
Understanding the Offline Criminal Behavior of Individuals Who Live Stream Child Sexual Abuse

Live streaming of child sexual abuse (CSA) involves the procurement and viewing of sexual abuse of children across the internet in real time, in exchange for money. These offenses leave little tangible evidence of the offense beyond a financial transaction, and metadata relating to the live-streaming session. This research analyzed the demographic, criminal history, and financial transaction characteristics of 209 individuals who live streamed child sexual abuse. A machine learning clustering technique was implemented to consider whether there were sub-groups present among these offenders, and in particular the prevalence of contact sexual offending among any detected sub-groups. Findings revealed that offenders tend to engage in live streaming around the same age, before making regular transactions with facilitators at brief intervals, with the majority of offenders featuring limited criminal history. This analysis identified a notable sub-group of live-streaming offenders that also engaged in contact sexual offending. This is the first study to empirically demonstrate an intersection between live streaming of CSA, and contact sexual offenses against children and adults. This research highlighted the importance of financial transactions data in detecting, and disrupting this crime type. Further, the identification of an intersection between live-streaming CSA offenders, and contact sexual offenders suggests that these individuals may pose a risk to both local and international communities.
Dynamical TAP approach to mean field glassy systems

The Thouless, Anderson and Palmer (TAP) approach to thermodynamics of mean field spin glasses is generalized to dynamics. A method to compute the dynamical TAP equations is developed and applied to the p-spin spherical model. In this context we show to what extent the dynamics can be represented as an evolution in the free energy landscape. In particular the relationship between the long-time dynamics and the local properties of the free energy landscape shows up explicitly within this approach. Conversely, by an instantaneous normal modes analysis we show that the local properties of the energy landscape seen by the system during its dynamical evolution do not change qualitatively at the dynamical transition.
First-principles thermodynamic theory of Seebeck coefficients

Thermoelectric effects, measured by the Seebeck coefficients, refer to the phenomena in which a temperature difference or gradient imposed across a thermoelectric material induces an electrical potential difference or gradient, and vice versa, enabling the direct conversion of thermal and electric energies. All existing understanding and first-principles calculations of Seebeck coefficients have been based on the Boltzmann kinetic transport theory. Here we demonstrate that the Seebeck coefficient is a well-defined thermodynamic quantity that can be determined from the change in the chemical potential of electrons induced by the temperature change and thus can be efficiently computed solely based on the electronic density of states through first-principles calculations at different temperatures. The proposed approach is demonstrated using the prototype PbTe and SnSe thermoelectric materials. The proposed thermodynamic approach dramatically simplifies the calculations of Seebeck coefficients, making it possible to search for high performance thermoelectric materials using high-throughput first-principles calculations.
Social Determinants of Health that Influence the Uptake of the PMTCT Program

Addressing the social determinants of health is crucial to achieve health equity. The authors explore the social determinants that influence and challenge the uptake of the PMTCT program in Rwanda. Critical ethnography was the research design used for this study. The intersectionality framework guided this project. The research population included HIV+ women; healthcare providers working in the PMTCT program; policy makers; and PMTCT leaders. Purposive sampling was used to recruit 55 participants. Observation and field-notes; individual and focus group interviews, and documents reviews were used to collect the data. Data analysis included reflexivity, thematic analysis, and use of ATLAS.ti software. This study contributed to understanding the complex associations between poverty, health literature
A dynamic allocation index for the discounted multiarmed bandit problem

SUMMARY Earlier work by the present authors has established the existence of and a characterization of a priority index giving the Bayes rule for the discounted multiarmed bandit problem. The calculation of this index is described and illustrated, and the results obtained briefly discussed. The two-armed bandit problem is so-called because it models the situation faced by a gambler using a fruit machine with two arms, instead of just one. When an arm is pulled the result is that the gambler either wins a prize or not. All the prizes are of the same value, and for each arm there is a certain constant, and in general unknown, probability of success every time it is pulled, which is different for the two arms. The gambler's problem is to choose a sequence of pulls on the two arms, which depends in a sequential manner on the record of successes and failures, in such a fashion as to maximize his expected total gains. In one version of the problem the gambler is allowed a fixed number of pulls in total. Alternatively we may consider a discounted version of the problem for which the value of a prize received at the tth pull, irrespective of the arms pulled on the previous (t - 1) pulls, is multiplied by at-1, for some a < 1. Multiarmed bandit problems are similar, but with more than two arms. Their chief practical motivation comes from clinical trials, though they are also of interest as probably the simplest worthwhile set of problems in the sequential design of experiments. Recent numerical investigation of Bayesian rules for the two-armed bandit problem with independent arms by P. W. Jones (1975) and Wahrenberger, Antle & Klimko (1977) have shown significant improvements when compared with other rules which have been proposed. However, the calculation of these rules is costly in terms of computer storage and time, and the reported results are all for a total number of trials which does not exceed 50. The present authors (1974) showed that for the discounted case with an infinite number of trials, first considered by Bellman (1956), the Bayes rule is given by a function which, for each arm, depends on the posterior distribution for the unknown success probability. The Bayes rule is always to pull the arm for which the current value of the function is larger, for which reason the function was termed a dynamic allocation index. Moreover, this result holds for the multiarmed bandit problem. Gittins (1979) obtained a characterization of the dynamic allocation index which actually holds for a range of problems of which the multiarmed bandit is just one example. The present paper reports on a numerical investigation of the dynamic allocation index using this characterization, which shows that some further
The Effects of Sub-chronic Administration of the Ethanolic Extract of Chromolaena odorata Leaves on the Immune System and Spleen of Male Wistar Rats

Chromolaena odorata, a neglected weed with wide spectrum is a multipurpose plant that contains high concentration of anti-inflammatory, anti-diarrheal, anti-hypertensive agents that protects against tissue damage. This study was designed to evaluate the effect of ethanolic leaf extract of Chromolaena odorata on the immune system and spleen of Albino Wistar Rats. 41 adult male rats weighing between 110g -140g were used for this study. LD50 was carried out using 13 rats while 28 rats were used for the experiment proper. The rats used for the experiment proper were divided into four groups of 7 animals each. Group A served as control group and received animal feed and distilled water only, Group B received 1000mg/kg of the leaf extract and water, Group C received 3000mg/kg of the leaf extract and water, and Group D received 6000mg/kg of the leaf extract and water. The ethanolic leaf extract of Chromolaena odorata was administered 4-times per week for 13 weeks. The animals were killed using diethyl ether suffocation, blood samples were collected by ocular puncture for haematological analysis of RBC, WBC and differentials, Platelets, CD4 and CD8 cells count, the spleen and peyer’s patches harvested, weighed and the spleen immediately fixed in 10% formol saline for histological analysis. Data was considered significant at p<0.05. Result showed a significant increase (p<0.05) in body weight in the groups when compared to the control group A. Peyer’s patches had a significant decrease (p<0.05) in group B and C, while group D had a significant increase (p>0.05). Hemoglobin concentration, and PCV revealed a significant (p<0.05) decrease when compared to the control group. RBC result showed a significant (p<0.05) decrease when compared to group A. Platelet count revealed a significant (p<0.05) increase in the groups. CD4 and CD8 count also revealed a significant increase. Histopathological study showed reactive lymphoid follicles in group B, circumferential zone of necrosis around a disc shaped eosinophilic, foreign material was seen in group C, and group D had necrosis when compared to control group. In conclusion, the ethanolic leaf extract of Chromolaena odorata have toxic effect on hematological indices of RBC, PCV with no effect on immune cell functions of Cd4 and CD8 cell counts and white blood cells.