758 research outputs found
SOME ASPECTS OF HYDROLOGICAL RISK MANIFESTATION IN JIJIA BASIN
Jijia river basin surface geographically fits in Moldavian Plateau, Plain of Moldavia subunit. Being lowered by 200 to 300 m compared to adjacent subunits, it appears as a depression with altitudes between 270-300 m.Through its position in the extra-Carpathian region, away from the influence of oceanic air masses, but wide open to the action of air masses of eastern, north-eastern and northern continental origin, Jijia basin receives precipitations which vary according to the average altitude differing from the northern to the southern part of the basin (564 mm in north, 529.4 mm in Iasi). A characteristic phenomenon to the climate is represented by the torrential rains in the hot season, under the form of rain showers with great intensity, fact that influences the drainage of basin rivers. Jijia hydrographic basin is characterized by frequent and sharp variations of flow volumes and levels which lead to floods and flooding throughout the basin. The high waters generally occur between March and June, when approximately 70% of the annual stock is transported. The paper analyzes the main causes and consequences of flooding in the studied area, also identifying some structural and non-structural measures of flood protection applied by authorities in Jijia hydrographic basin. As a case study, the flood recorded in Dorohoi in June 28-29, 2010 is presented
THE MEDIATING EFFECT OF SCHOOL CLIMATE ON THE RELATIONSHIP BETWEEN ACADEMIC SELF-CONCEPT AND STUDENT ENGAGEMENT
This study aimed to determine the mediating effect of school climate on the relationship between academic self-concept and student engagement in public secondary schools in Cateel I District that offer the Senior High School Program. The researcher used a quantitative, non-experimental design of research using correlational techniques to gather data from 224 senior high school student respondents, who were stratified randomly. The data was collected through a survey method using validated questionnaires. Further, the results were collated and statistically analyzed using mean, Pearson r, and regression utilizing Medgraph to determine the mediation. The study revealed that academic self-concept, student engagement, and school climate exhibited high mean scores. This study also showed a significant relationship between the level of academic self-concept and student engagement, a significant relationship between academic self-concept and school climate, and a significant relationship between student engagement and school climate. Lastly, the results of this study showed that there was a partial mediation of school climate on the relationship between academic self-concept and student engagement. It implies that the school climate conveys good academic self-concept and student engagement. Article visualizations
Decolorization of aqueous effluents using agro waste
In this study, the potential of agrowaste for a food dye sequestration from aqueous effluents was investigated. Initially, four local agrowaste waste namely pumpkin seed hull, bean null, oat straw and nut shells, were tested in natural condition. Bean hull (BH) revealed the best
uptake capacity for Food Red 14 (FR14). The agro waste was characterised before and after dye sorption process using SEM and FTIR
techniques. Those analyses were conducted in order to identify the principal connections contributing to the sorption process.
The point of zero charge of BH surface, pHpzc was assessed at 4.6, which indicated a mostly acidic surface, favorable for dye adsorption at
pH<6, when the sorbent is positively charged. The dye removal efficiency of the adsorbent has been established in relation to some factors,
such as: pH, amount of adsorbent, dye initial concentration, contact time and temperature. In order to make the sorption process
predictable, four empirical isotherms and four kinetics models were applied to the experimental data so as to enact the nature of the
sorption process. Attempts have also been made for sorbent viability by testing different solvents for FR14 desorption.
FTIR spectra reveal the main bands in FR14 sorption process: that at 1450 cm-1 corresponding to C=C bond from the aromatic ring appears
greatly diminished for FR14-BH after the sorption process and suggests a horizontal orientation of the molecules. The movement of the
band at 3442 cm-1, corresponding to -OH groups, to lower wave number suggests lower involvement of these groups in the sorption
process. The others band movement from BH spectra after the sorption process is due to physical interactions (hydrogen bond, van der
Waals force) that occur between functional groups of sorbent and dye.
The present study shows that the agro-waste bean hull is very effective as biosorbent for Food Red 14 removal from aqueous solutions,
from a large range of dye concentration in aqueous solutions (5-400 mg L-1) in batch system. Since the agricultural wastes used in this
study are friendly, abundantly and locally available, the sorbents are economically viable for aqueous effluents decolorization
Spin-dependent electron-impurity scattering in two-dimensional electron systems
We present a theoretical study of elastic spin-dependent electron scattering
caused by a charged impurity in the vicinity of a two-dimensional electron gas.
We find that the symmetry properties of the spin-dependent differential
scattering cross section are different for an impurity located in the plane of
the electron gas and for one at a finite distance from the plane. We show that
in the latter case asymmetric (`skew') scattering can arise if the polarization
of the incident electron has a finite projection on the plane spanned by the
normal vector of the two-dimensional electron gas and the initial propagation
direction. In specially preparated samples this scattering mechanism may give
rise to a Hall-like effect in the presence of an in-plane magnetic field.Comment: 4.1 pages, 2 figure
Some remarks on the visible points of a lattice
We comment on the set of visible points of a lattice and its Fourier
transform, thus continuing and generalizing previous work by Schroeder and
Mosseri. A closed formula in terms of Dirichlet series is obtained for the
Bragg part of the Fourier transform. We compare this calculation with the
outcome of an optical Fourier transform of the visible points of the 2D square
lattice.Comment: 9 pages, 3 eps-figures, 1 jpeg-figure; updated version; another
article (by M. Baake, R. V. Moody and P. A. B. Pleasants) with the complete
solution of the spectral problem will follow soon (see math.MG/9906132
Sums of products of Ramanujan sums
The Ramanujan sum is defined as the sum of -th powers of the
primitive -th roots of unity. We investigate arithmetic functions of
variables defined as certain sums of the products
, where are polynomials with
integer coefficients. A modified orthogonality relation of the Ramanujan sums
is also derived.Comment: 13 pages, revise
Asymptotically optimum estimation of a probability in inverse binomial sampling under general loss functions
The optimum quality that can be asymptotically achieved in the estimation of
a probability p using inverse binomial sampling is addressed. A general
definition of quality is used in terms of the risk associated with a loss
function that satisfies certain assumptions. It is shown that the limit
superior of the risk for p asymptotically small has a minimum over all
(possibly randomized) estimators. This minimum is achieved by certain
non-randomized estimators. The model includes commonly used quality criteria as
particular cases. Applications to the non-asymptotic regime are discussed
considering specific loss functions, for which minimax estimators are derived.Comment: Journal of Statistical Planning and Inference. Published online 201
Interpolation function of the genocchi type polynomials
The main purpose of this paper is to construct not only generating functions
of the new approach Genocchi type numbers and polynomials but also
interpolation function of these numbers and polynomials which are related to a,
b, c arbitrary positive real parameters. We prove multiplication theorem of
these polynomials. Furthermore, we give some identities and applications
associated with these numbers, polynomials and their interpolation functions.Comment: 14 page
Central limit theorem for multiplicative class functions on the symmetric group
Hambly, Keevash, O'Connell and Stark have proven a central limit theorem for
the characteristic polynomial of a permutation matrix with respect to the
uniform measure on the symmetric group. We generalize this result in several
ways. We prove here a central limit theorem for multiplicative class functions
on symmetric group with respect to the Ewens measure and compute the covariance
of the real and the imaginary part in the limit. We also estimate the rate of
convergence with the Wasserstein distance.Comment: 23 pages; the mathematics is the same as in the previous version, but
there are several improvments in the presentation, including a more intuitve
name for the considered function
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