A numerical method for functional Hammerstein integro-differential equations

In this paper, a numerical method is presented to solve functional Hammerstein integro-differential equations. The presented method combines the successive approximations method with trapezoidal quadrature rule and natural cubic spline interpolation to solve the mentioned equations. The existence and uniqueness of the problem is also investigated. The convergence and numerical stability of the problem are proved, and finally, the accuracy of the method is verified by presenting some numerical computations

A Comparison of IRT and Rasch Procedures in a Mixed-Item Format Test

This study investigated the effects of test length (10, 20 and 30 items), scoring schema (proportion of dichotomous ad polytomous scoring) and item analysis model (IRT and Rasch) on the ability estimates, test information levels and optimization criteria of mixed item format tests. Polytomous item responses to 30 items for 1000 examinees were simulated using the generalized partial-credit model and SAS software. Portions of the data were re-coded dichotomously over 11 structured proportions to create 33 sets of test responses including mixed item format tests. MULTILOG software was used to calculate the examinee ability estimates, standard errors, item and test information, reliability and fit indices. A comparison of IRT and Rasch item analysis procedures was made using SPSS software across ability estimates and standard errors of ability estimates using a 3 x 11 x 2 fixed factorial ANOVA. Effect sizes and power were reported for each procedure. Scheffe post hoc procedures were conducted on significant factos. Test information was analyzed and compared across the range of ability levels for all 66-design combinations. The results indicated that both test length and the proportion of items scored polytomously had a significant impact on the amount of test information produced by mixed item format tests. Generally, tests with 100% of the items scored polytomously produced the highest overall information. This seemed to be especially true for examinees with lower ability estimates. Optimality comparisons were made between IRT and Rasch procedures based on standard error rates for the ability estimates, marginal reliabilities and fit indices (-2LL). The only significant differences reported involved the standard error rates for both the IRT and Rasch procedures. This result must be viewed in light of the fact that the effect size reported was negligible. Optimality was found to be highest when longer tests and higher proportions of polytomous scoring were applied. Some indications were given that IRT procedures may produce slightly improved results in gathering available test information. Overall, significant differences were not found between the IRT and Rasch procedures when analyzing the mixed item format tests. Further research should be conducted in the areas of test difficulty, examinee test scores, and automated partial-credit scoring along with a comparison to other traditional psychometric measures and how they address challenges related to the mixed item format tests

Superconducting properties of the In-substituted topological crystalline insulator, SnTe

We report detailed investigations of the properties of a superconductor obtained by substituting In at the Sn site in the topological crystalline insulator (TCI), SnTe. Transport, magnetization and heat capacity measurements have been performed on crystals of Sn$_{0.6}$In$_{0.4}$Te, which is shown to be a bulk superconductor with $T_c^{\rm{onset}}$ at $\sim4.70(5)$~K and $T_c^{\rm{zero}}$ at $\sim3.50(5)$~K. The upper and lower critical fields are estimated to be $\mu_0H_{c2}(0)=1.42(3)$~T and $\mu_0H_{c1}(0)=0.90(3)$~mT respectively, while $\kappa=56.4(8)$ indicates this material is a strongly type II superconductor

A Comparative Study of Different Teaching Strategies Based on Text Types on Students' Speaking Competency

This study aimed at comparing the effect of different teaching strategies based on text types on students' speaking competency. Post-test Only Comparison Group Design was applied as the research design. After the treatment sessions, post-test was administered to discover the impact of the treatments. The data obtained from the post-test were analyzed by using descriptive and inferential statistical analyses. Through descriptive analysis, it was found that the mean scores of the two samples for descriptive text were 71.63 and 73.96 and for procedure text were 74.93 and 76.80. The difference between students' speaking competency who were taught using different teaching strategies was analyzed through two-way Anova. Based on the result of the hypothesis testing, it was found that; there was a significant difference between two teaching strategies on students' speaking competency and there was no interactional effect between two teaching strategies and the text types on students' speaking competency. These findings provide empirical evidence of the importance to determine teaching strategies that suit the text types taught in speaking class. Key terms : speaking competency, speaking random club, panauricon and text type

Understanding complex magnetic order in disordered cobalt hydroxides through analysis of the local structure

In many ostensibly crystalline materials, unit-cell-based descriptions do not always capture the complete physics of the system due to disruption in long-range order. In the series of cobalt hydroxides studied here, Co(OH)$_{2-x}$(Cl)$_x$(H$_2$O)$_{n}$, magnetic Bragg diffraction reveals a fully compensated N\'eel state, yet the materials show significant and open magnetization loops. A detailed analysis of the local structure defines the aperiodic arrangement of cobalt coordination polyhedra. Representation of the structure as a combination of distinct polyhedral motifs explains the existence of locally uncompensated moments and provides a quantitative agreement with bulk magnetic measurements and magnetic Bragg diffraction

Influence of the Secondary Arc on the Operation of Single Phase Autoreclosure of the 400 kV interconnection between Hungary and Croatia

Faults on EHV lines are generally single-phase-to-ground ones and not permanent in the majority of cases. Thus single phase auto reclosure (SPAR), at which the faulty phases are tripped for a short time, eliminates the predominant part of the faults [1,2]. The secondary arc, which follows the high power arc after tripping the faulty phases at both side of the line may endanger the successfulness of reclosing if the duration of the switched off interval (dead time) is not long enough to ensure the extinction of the arc. The secondary arcing times recorded on different EHV lines or measured in laboratory tests show significant spread, consequently, to select a dead time according to the longest experimental secondary arc extinction time is not feasible. During commissioning of the double circuit 420 kV interconnection between Hungary and Croatia several staged faults were initiated to analyze the arc extinction performance. Initially the line was in operation by connecting the two circuits in parallel along the 1/3rd of the full length. In this configuration the longest secondary arc extinction time was 4 seconds and the secondary arc has not extinguished in 27s in one of the tests, so the line had to be tripped out to clear the staged fault. Later on, the length of the Croatian section of the line has been significantly shortened after putting a new substation into service. The increased performance of SPAR of the new arrangement has been proved with field tests. A realistic representation of the secondary arcs is essential in determining the auto-reclosure performance of EHV transmission lines. As shown in the paper, the random variation of the arc parameters influences significantly the arc extinction time. The results of the field tests confirmed the importance of the distributed nature of the transmission line and the nonlinear characteristic of the arc resistance in the intermittent region of arcing, where temporary extinctions and sudden re-ignitions in the arc channel produce transient wave processes along the line

Electronic structure and magnetic properties of the spin-1/2 Heisenberg system CuSe2O5

A microscopic magnetic model for the spin-1/2 Heisenberg chain compound CuSe2O5 is developed based on the results of a joint experimental and theoretical study. Magnetic susceptibility and specific heat data give evidence for quasi-1D magnetism with leading antiferromagnetic (AFM) couplings and an AFM ordering temperature of 17 K. For microscopic insight, full-potential DFT calculations within the local density approximation (LDA) were performed. Using the resulting band structure, a consistent set of transfer integrals for an effective one-band tight-binding model was obtained. Electronic correlations were treated on a mean-field level starting from LDA (LSDA+U method) and on a model level (Hubbard model). In excellent agreement of experiment and theory, we find that only two couplings in CuSe2O5 are relevant: the nearest-neighbour intra-chain interaction of 165 K and a non-frustrated inter-chain coupling of 20 K. From a comparison with structurally related systems (Sr2Cu(PO4)2, Bi2CuO4), general implications for a magnetic ordering in presence of inter-chain frustration are made.Comment: 20 pages, 8 figures, 3 table

Effect of an educational program in primary care: the case of lipid control in cardio-cerebrovascular prevention.

Lowering blood cholesterol levels reduces the risk of coronary heart disease. However, the effect of interventions depends on the patients' adherence to treatment. Primary care plays an important role in the detection, treatment and monitoring of disease, therefore different educational programs (EP) have been implemented to improve disease management in general practice. The present study is aimed to assess whether a general practitioner auditing and feedback EP may improve dyslipidaemia management in a primary care setting and to evaluate patients' adherence to prescribed lipid-lowering treatment. The quality of cardiovascular and cerebrovascular disease prevention before and after the implementation of an EP offered to 25 general practitioners (GPs), was evaluated. Clinical and prescription data on patients receiving at least one lipid-lowering treatment was collected. To evaluate the quality of the healthcare service provided, clinical and biochemical outcomes, and drug-utilization, process indicators were set up. Adherence was evaluated before and after the EP as the "Medication Possession Ratio" (MPR). A correlation analysis was carried out to estimate the effect of the MPR in achieving pre-defined clinical end-points. Prescription data for lipid-lowering drugs was collected in a sample of 839 patients. While no differences in the achievement of blood lipid targets were observed, a slight but significant improvement of the MPR was registered after the EP (MPR >0.8=64.2% vs 60.6%, p=0.0426). Moreover, high levels of statin adherence were associated with the achievement of total blood cholesterol target (OR=3.3 for MPR >0.8 vs MPR 0.8 vs MPR <0.5,95% CI: 1.5–7.2). The EP partially improved the defined clinical targets; probably, a more patient-based approach could be more appropriate to achieve the defined target. Further studies are needed to identify how healthcare services can be improved