A Modified Real-Coded Genetic Algorithm Considering with Fitness-based Variability

A genetic algorithm (GA) is a search algorithm based on the mechanism of natural genetics. In various GAs, a real-coded GA (RCGA) employing individuals represented by real valued-genes has been proposed to solve the optimization problem in the continuous searching space. However, the conventional RCGA yields ineffective searches due to insufficient genetic diversity in the selection process. In this paper, we propose a modified RCGA with variability operator maintaining the genetic diversity of the population. In the proposed method, a variability term is newly added to the individuals selected by the ordinary selection. The degree of the variability is decided considering the fitness value of the individual. The searching performance of the proposed method is better than the conventional methods. The effectiveness and the validity of the proposed method are verified by applying it to optimization problems of continuous benchmark functions and signal sources localization

Warm Absorbers in the Radiation-driven Fountain Model of Low-mass Active Galactic Nuclei

To investigate the origins of the warm absorbers in active galactic nuclei (AGNs), we study the ionization-state structure of the radiation-driven fountain model in a low-mass AGN and calculate the predicted X-ray spectra utilizing the spectral synthesis code Cloudy. The spectra show many absorption and emission line features originating in the outflowing ionized gas. The O viii 0.654 keV lines are produced mainly in the polar region much closer to the supermassive black hole than the optical narrow-line regions. The absorption measure distribution of the ionization parameter (ξ) at a low inclination spreads over 4 orders of magnitude in ξ, indicating the multiphase ionization structure of the outflow, as actually observed in many type 1 AGNs. We compare our simulated spectra with the high energy resolution spectrum of the narrow-line Seyfert 1 galaxy NGC 4051. The model reproduces slowly outflowing (a few hundred kilometers per second) warm absorbers. However, the faster components with a few thousand kilometers per second observed in NGC 4051 are not reproduced. The simulation also underproduces the intensity and width of the O viii 0.654 keV line. These results suggest that the ionized gas launched from subparsec or smaller regions inside the torus, which is not included in the current fountain model, must be an important ingredient of the warm absorbers with a few thousand kilometers per second. The model also consistently explains the Chandra/HETG spectrum of the Seyfert 2 galaxy Circinus

The Dynamical State of the Frontier Fields Galaxy Cluster Abell 370

We study the dynamics of Abell 370 (A370), a highly massive Hubble Frontier Fields galaxy cluster, using self-consistent three-dimensional N-body/hydrodynamical simulations. Our simulations are constrained by X-ray, optical spectroscopic and gravitational lensing, and Sunyaev-Zel'dovich (SZ) effect observations. Analyzing archival Chandra observations of A370 and comparing the X-ray morphology to the latest gravitational lensing mass reconstruction, we find offsets of ∼30 and ∼100 kpc between the two X-ray surface brightness peaks and their nearest mass surface density peaks, suggesting that it is a merging system, in agreement with previous studies. Based on our dedicated binary cluster merger simulations, we find that initial conditions of the two progenitors with virial masses of $1.7\\times {10}^{15}$ and $1.6\\times {10}^{15}\\,{M}_{\\odot }$ , an infall velocity of 3500 km s-1, and an impact parameter of 100 kpc can explain the positions and the offsets between the peaks of the X-ray emission and mass surface density, the amplitude of the integrated SZ signal, and the observed relative line-of-sight velocity. Moreover, our best model reproduces the observed velocity dispersion of cluster member galaxies, which supports the large total mass of A370 derived from weak lensing. Our simulations strongly suggest that A370 is a post major merger after the second core passage in the infalling phase, just before the third core passage. In this phase, the gas has not settled down in the gravitational potential well of the cluster, which explains why A370 does not follow closely the galaxy cluster scaling relations

RESISTENZA ALLA CORROSIONE AD ALLA TENSOCORROSIONE DI ACCIAI BASSOLEGATI ED ACCIAI RESISTENTI ALLA CORROSIONE (CRAS) IN CONDIZIONI RAPPRESENTATIVE LA STIMOLAZIONE ACIDA

Nell’operazione di stimolazione acida negli impianti di estrazione di idrocarburi, sono necessari materiali altamente resistenti alla corrosione. In questo lavoro viene valutata la resistenza alla corrosione di acciai bassolegati, di acciai inossidabili martensitici e duplex, di leghe base Nichel, in alcune condizioni rappresentative la fase di ritorno degli acidi usati per la stimolazione dei pozzi, quali ad es in soluzioni di 28% HCl e 12% HCl + 3% HF in presenza di H2S e CO2 ad elevate temperature. Tutti i materiali testati per pH superiori a 4.0, hanno mostrato scarsa suscettibilità alla corrosione localizzata e alla tensocorrosione. L’acciaio superduplex e le leghe base nichel hanno mostrato un’elevata resistenza anche a pH inferiori a 3.5, mentre l’acciaio bassolegato T95e gli acciai martensitici hanno presentato tendenza alla corrosione generale e localizzata

Gas Density Perturbations in Cool Cores of CLASH Galaxy Clusters

We present a systematic study of gas density perturbations in cool cores of high-mass galaxy clusters. We select 12 relaxed clusters from the Cluster Lensing And Supernova survey with Hubble (CLASH) sample and analyze their cool core features observed with the Chandra X-ray Observatory. We focus on the X-ray residual image characteristics after subtracting their global profile of the X-ray surface brightness distribution. We find that all the galaxy clusters in our sample have, at least, both one positive and one negative excess regions in the X-ray residual image, indicating the presence of gas density perturbations. We identify and characterize the locally perturbed regions using our detection algorithm, and extract X-ray spectra of the intracluster medium (ICM). The ICM temperature in the positive excess region is lower than that in the negative excess region, whereas the ICM in both regions is in pressure equilibrium in a systematic manner. These results indicate that gas sloshing in cool cores takes place in more than 80% of relaxed clusters (95% CL). We confirm this physical picture by analyzing synthetic X-ray observations of a cool-core cluster from a hydrodynamic simulation, finding that our detection algorithm can accurately extract both the positive and negative excess regions and can reproduce the temperature difference between them. Our findings support the picture that the gas density perturbations are induced by gas sloshing, and a large fraction of cool-core clusters have undergone gas sloshing, indicating that gas sloshing may be capable of suppressing runaway cooling of the ICM.Comment: 30 pages, 8 figures, accepted for publication in Ap

Radiation-driven Fountain and Origin of Torus around Active Galactic Nuclei

We propose a plausible mechanism to explain the formation of the so-called "obscuring tori" around active galactic nuclei (AGNs) based on three-dimensional hydrodynamic simulations including radiative feedback from the central source. The X-ray heating and radiation pressure on the gas are explicitly calculated using a ray-tracing method. This radiation feedback drives a "fountain", that is, a vertical circulation of gas in the central a few to tens parsecs. Interaction between the non-steady outflows and inflows causes the formation of a geometrically thick torus with internal turbulent motion. As a result, the AGN is obscured for a wide range of solid angles. In a quasi-steady state, the opening angles for the column density toward a black hole < 10^23 cm^-2 are approximately +-30 deg and +-50 deg for AGNs with 10% and 1% Eddington luminosity, respectively. Mass inflows through the torus coexist with the outflow and internal turbulent motion, and the average mass accretion rate to the central parsec region is 2x10^-4 ~ 10^-3, M_sun/yr this is about ten times smaller than accretion rate required to maintain the AGN luminosity. This implies that relatively luminous AGN activity is intrinsically intermittent or that there are other mechanisms, such as stellar energy feedback, that enhance the mass accretion to the center.Comment: 12 pages, 9 figures, accepted publication in Ap

Research on Pupils' Progress of Mathematical Ability at Lower Secondary School Level (4) : Considering the "Number" of Test Points

Kassel-Exeter Projectによって開発された共通問題を用いて, 日本の中学生の数学的能力の発達・変容を調査し, その検討を通して, よりよい数学教育に向けての示唆を得ることが本研究の目的である。「数」調査問題をもとに1019名の公立中学校2, 3年生を対象とする調査を行ったところ, 日本の中学生の「数」得点は1年次からすでに高いレベルにあり, そのレベルを維持したままで, イギリス・ドイツなどと比して遜色のない程度の伸びを示していることがわかった。さらに, 問題ごとの正答率の変容に着目すると同時に, 被験者を3つの群に層化することによって, 正答率の変容の要因を分析した。その結果, 数学学習に対する「潜在力」の高い生徒および「潜在力」の低い生徒の「数」得点の変容に関する特徴が洗い出され, 個に応じた数学指導を考慮していく際の示唆が得られた。, The authors administered the "number" of test composed of 50 problems developed by Kassel-Exeter Project to students in Tokyo, Nara, Hiroshima, Fukuoka and Nagasaki prefectures a year earlier to identify the students' progress in mathematical ability at lower secondary school level. Analysis of the test shows that Japanese students' progress is almost comparable with the students from other countries like England and Germany, which can be attributed to the effective teaching of Mathematics.Aside from the overall analysis of the test scores, a longitudinal analysis of each problem was made. The analysis showed that Japanese pupils made remarkable progress in many problems but they showed corresponding regression on estimation of problems. Based on their points in a "potential" test, students were grouped as potentially high (PH), potentailly medium (PM) or potentially low (PL). PH students exhibited high points in comparatively difficult problem items while PL students' showed progress in comparatively easy problem items. The observed regression could be attributed to the same kind of problem items. Important implications for the improvement of the teaching of Mathematics were identified