Solving Ratio-Dependent Predator-Prey System with Constant Effort Harvesting using Variational Iteration Method

Due to wide range of interest in use of bio-economic models to gain insight into the scientific management of renewable resources like fisheries and forestry,variational iteration method (VIM) is employed to approximate the solution of the ratio-dependent predator-prey system with constant effort prey harvesting.The results are compared with the results obtained by Adomian decomposition method and reveal that VIM is very effective and convenient for solving nonlinear differential equations

A semi-analytical approach for the response of nonlinear conservative systems

This work applies Parameter expanding method (PEM) as a powerful analytical technique in order to obtain the exact solution of nonlinear problems in the classical dynamics. Lagrange method is employed to derive the governing equations. The nonlinear governing equations are solved analytically by means of He’s Parameter expanding method. It is demonstrated that one term in series expansion is sufficient to generate a highly accurate solution, which is valid for the whole domain of the solution and system response. Comparison of the obtained solutions with the numerical ones indicates that this method is an effective and convenient tool for solving these types of problems

Higher-order approximation of cubic–quintic duffing model

We apply an Artificial Parameter Lindstedt-Poincaré Method (APL-PM) to find improved approximate solutions for strongly nonlinear Duffing oscillators with cubic–quintic nonlinear restoring force. This approach yields simple linear algebraic equations instead of nonlinear algebraic equations without analytical solution which makes it a unique solution. It is demonstrated that this method works very well for the whole range of parameters in the case of the cubic-quintic oscillator, and excellent agreement of the approximate frequencies with the exact one has been observed and discussed. Moreover, it is not limited to the small parameter such as in the classical perturbation method. Interestingly, This study revealed that the relative error percentage in the second-order approximate analytical period is less than 0.042% for the whole parameter values. In addition, we compared this analytical solution with the Newton– Harmonic Balancing Approach. Results indicate that this technique is very effective and convenient for solving conservative truly nonlinear oscillatory systems. Utter simplicity of the solution procedure confirms that this method can be easily extended to other kinds of nonlinear evolution equations

Re-assessing co-movements among G7 equity markets: evidence from iShares

iShares funds are products designed to mimic the movements of MSCI stock market indices. Being devoid of problems associated with trading restrictions, exchange-rate fluctuations and non-synchronous trading, iShares data are better suited for measuring, firstly, equity-market co-movements and, secondly, diversification potential than national indices data; the latter data are used by most of the studies in the area. Applying recent time-varying methodology for the analysis of short- and long-term co-movements, a detailed analysis of the dynamics of the equity market linkages over the period 1996-2005 is provided. Evidence is found of increasing conditional correlations and significant time-varying long-run relationships between the US and the majority of other G7 markets since 2001, as measured by iShares. However, the extent of both short-term and long-term linkages between the G7 equity markets is lower for national indices data. Our findings suggest that (i) the results of earlier studies that are based on stock market indices should be interpreted with caution, since using these may overestimate the extent of available diversification benefits; and (ii) iShares funds do not represent perfect diversification products. These results appear to be robust to alternative model specifications, data frequency and conditioning bias

Analytical solutions to nonlinear mechanical oscillation problems

In this paper the Max-Min Method is utilized for solving the nonlinear oscillation problems. The proposed approach is applied to three systems with complex nonlinear terms in their motion equations. By means of this method the dynamic behavior of oscillation systems can be easily approximated using He Chengtian’s interpolation. The comparison of the obtained results from Max-Min method with time marching solution and the results achieved from literature verifies its convenience and effectiveness. It is predictable that He's Max-Min Method will find wide application in various engineering problems as indicated in the following cases

Achievement high level goals in E-learning with comprehensive feedback; (Standards and Criteria)

Background and Objective:The separation of learner and teacher from each other in e-learning, has made feedback as the most important challenge in this type of learning. Despite, there is no comprehensive framework based on the science of education, so that how to create educational feedback based on learning objectives. The purpose of this study was to compilation the educational standards and their indicators based on the Bloom- Methods: Anderson’s taxonomy for design effective and on time feedback for any educational goal. Qualitative research approach is used and based this approach, the phenomenological design strategy has been used. The population included 12 persons of subject matter and faculty member in academic e-learning centers which were selected through purposeful sampling. Those individuals included in the sample who had three characteristics: a) academic education in e-learning, b) teaching in higher education in the faculties of educational sciences, and c) working in e-learning centers of universities and educational institutions. To gather data semi-structured interviews were used. Qualitative data generated from interviews were coded and analysis by Corbin and Strauss method and Maxquda software. Findings: The results of the study led to the development of 4 educational standards and 25 indicators based on the Bloom-Anderson’s taxonomy to design a comprehensive feedback in the field of e-learning. According to the results of this study, educational technologists can evaluate or design more effective e-learning environments. Conclusion: Overall, feedback plays a key role in e-learning process that can pave the way for identifying problems in the teaching-learning process and proposing improvements to these challenges. However, timing of the feedback is critical. Lack of time shows that the potential benefits of feedback are often not achieved, and instructors are often unable to provide feedback tailored to educational conditions and goals. The results of this study can provide appropriate design and presenting of the feedback with the aim of learning and effective use of educational technologies at the right time. In this regard it can help designers of e-learning environments in a way that the right time to provide feedback is not wasted and always provide feedback at the right time and in the right way. Based on the results of the research, evaluators and administrators of e-learning environments can use the e-learning evaluation form of the paper prepared based on the standards and criteria in a Likert scale to evaluate the feedback method of e-learning instructors.   ===================================================================================== COPYRIGHTS  ©2020 The author(s). This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, as long as the original authors and source are cited. No permission is required from the authors or the publishers.  ====================================================================================

Compatibility of the entomopathogenic fungus Beauveria bassiana with the insecticides fipronil, pyriproxyfen and hexaflumuron

The compatibility of Beauveria bassiana isolate DEBI 002 (Atashgah) with fipronil, pyriproxyfenand hexaflumuron insecticides was assayed. To determine the impact of the insecticides on thegermination of the fungal spore, different concentrations of the compounds were added to the culturemedium (malt agar). In order to calculate the mycelial growth in different treatments, each colonydiameter was measured and the spores were counted in the surface area to assess its sporulation. Theresults showed that pyriproxyfen at 1500 ppm and hexaflumuron at 80 ppm completely inhibited mycelialgrowth, while the inhibitory effect of fipronil at 1600 ppm remained at 76.6%. The inhibitory effect oflower concentrations of all three insecticides was between 10 and 20%. All tested insecticides inhibitedthe spore production between 80 to 100% at the highest concentrations without any significantdifferences. Pyriproxyfen at 400 ppm and hexaflumuron at all concentrations completely inhibited sporegermination, with significant difference, comparing with the rest of treatments. The results indicate thathexaflumuron has the highest inhibitory effect on the spore germination and is not recommended to beused simultaneously with B. bassiana against the insect pests

First record of 3 species of Parasitoid wasps on Coccoidea from Iran

During faun survey on parasitoids wasps of Coccoidea in Mazandaran province (north of Iran) collected two species of the family Encyrtidae and one species of Aphelinidae family (2010-2013). One species collected from Chionaspis salicis on Salix acmophylla from Amool in April 2012. This parasitoid was later identified as Adelencyrtus brachycaudae Xu& Shi, 1999. The other species was collected from Planococcus citri on Citrus aurantum from Jouybar in April 2013. This parasitoid identified as Clausenia purpurea Ishii, 1933.Theses parasitoid wasps belonging to Encyrtidae. Also Coccophagus yoshidae Nakayama, 1921 collected from Coccus hesperidum on Euonymus fortune from Sari in September 2013. This parasitoid wasp belonging to Aphelinidae. All of these parasitoid wasps identified by Dr. Zhi Hong Xu from China. These parasitoid wasps are new for Iranian fauna

The Effect of Chrysin Nanoparticles in Preventing the Growth of Mcf-7 Cancer Cells

BACKGROUND AND OBJECTIVE: Chrysin is a natural and biologically active compound extracted from plants, honey and propolis. Since chrysin has pharmacological activities such as antioxidant, anti-inflammatory and anti-cancer properties, this study was conducted to compare the effect of chrysin and its nanoparticle on breast cancer cells (Michigan Cancer Foundation-7). METHODS: In this study, chrysin nanoparticles were prepared using chitosan, and then the prepared nanoparticles were dissolved in water, and the cytotoxic effects of 20, 40 and 80 μM chrysin and chrysin dissolved in dimethyl sulfoxide (at the same concentrations) on MCF7 cells were investigated. Cell viability was measured using MTT assay after 24, 48 and 72 hours, and was compared with viability of the control samples. FINDINGS: The results of this study showed that chrysin and chrysin nanoparticles prevented the growth and proliferation of MCF7 cell line. These effects depend on the concentration of chrysin and its nanoparticles, and it has been shown that the effect of chrysin nanoparticle on cells at a concentration of 40 μM in 72 hours is significant with p<0.001 while it is significant with p<0.01 at the same concentration in 24 and 48 hours. The IC50 value of chrysin nanoparticle was approximately 40 μM. CONCLUSION: The results of the study showed that the chrysin nanoparticle exhibits anti-proliferative activity in breast cancer cells in the laboratory and its effect is greater than that of chrysin