Dynamics of a Predator-Prey Model with Fear Effect and Time Delay

In this paper, we propose a time-delayed predator-prey model with Holling-type II functional response, which incorporates the gestation period and the cost of fear into prey reproduction. The dynamical behavior of this system is both analytically and numerically investigated from the viewpoint of stability, permanence, and bifurcation. We found that there are stability switches, and Hopf bifurcations occur when the delay τ passes through a sequence of critical values. The explicit formulae which determine the direction, stability, and other properties of the bifurcating periodic solutions are given by using the normal form theory and center manifold theorem. We perform extensive numerical simulations to explore the impact of some important parameters on the dynamics of the system. Numerical simulations show that high levels of fear have a stabilizing effect while relatively low levels of fear have a destabilizing effect on the predator-prey interactions which lead to limit-cycle oscillations. We also found that the model with or without a delay-dependent factor can have a significantly different dynamics. Thus, ignoring the delay or not including the delay-dependent factor might result in inaccurate modelling predictions.

Perception of Complexity in Engineering Design

This paper evaluates perception of complexity in a novel explanatory model that relates product performance and engineering effort. Complexity is an intermediate factor with two facets: it enables desired product performance but also requires effort to achieve. Three causal mechanisms explain how exponential growth bias, excess complexity, and differential perception lead to effort overruns. Secondary data from a human subject experiment validates the existence of perception of complexity as a context-dependent factor that influences required design effort. A two-level mixed effects regression model quantifies differences in perception among 40 design groups. Results summarize how perception of complexity may contribute to effort overruns and outline future work to further validate the explanatory model and causal mechanisms.

Impact of Work from Home Policy Implementation on Work Effectiveness and Productivity in Tangerang City

This research was conducted based on the desire of the researchers to find out how much influence the Work from Home policy has on the effectiveness and productivity of work, especially for workers in the Tangerang area The dependent factor studied was the Work from Home policy as the independent variable (Y), while the independent factors were effectiveness (X1) and work productivity (X2). The resulting t value for the work effectiveness variable is 0.647 with sig 0.519. The results of this significance analysis are greater than 0.05, so it means that individually the work effectiveness variable does not have an impact due to the WFH policy. The resulting t value for work productivity variable is 6.103 with sig 0.000. The results of this significant analysis are smaller than 0.05, meaning that individually the work productivity variable has a significant impact on the implementation of WFH policies. The results obtained in this study are based on the SPSS calculation, the F count is 19.504 with F sig. 0,000 where F sig. 0.000 is smaller than 0.05, so Ho is rejected. It can be interpreted that simultaneously work effectiveness (X1) and work productivity (X2) have a significant impact on the implementation of WFH policy (Y). This calculation also forms the equation Y = 9,112 + 0.108 X1 + 0.681 X2 + e. The R square value obtained from the SPSS calculation of 0.236 (23.6%) can be interpreted that work effectiveness (X1) and work productivity (X2) explain the impact of variations in the variable implementation of WFH policy (Y) by 23.6% and the rest is influenced other independent variables amounted to 76.4%.

AIC Algorithm for Online Purchasing Intention

In recent years, the internet market in Vietnam has developed strongly, leading to many forms of electronic business being born and with rapid growth. Online shopping is seen as the solution to cost-effective, fast, and convenient shopping. This chapter was based on concepts and theoretical grounds related to behavior intention to accept and apply new technology to form the proposed research model. It consists of three independent factors—(1) utility perception, (2) trust, (3) social influence—and one dependent factor, online purchasing intention. This study reveals the optimal choice by the AIC algorithm.

Modeling of trihalomethane compounds formation in Baghdad water supply network

This study was conducted to measure the concentrations of four trihalomethane compounds (THMs) in raw, treated, and drinking water of seven water purification plants and the residential neighborhoods nearby in Baghdad. About 350 samples gathered between January and October 2017 and analyzed by the gas chromatography method. Results showed that THM annual levels in tap water ranged between 12 and 97.3 μg·l–1 in winter and summer consecutively, with a mean concentration of 60 μg·l–1, these concentrations did not exceed the level recommended by the WHO and the Iraqi standards. Statistical modeling by SPSS software for the formation of THM (the dependent factor) in the water supply network was undertaken using the measured water quality parameters (as independent factors) and utilizing multiple regression analysis. The model obtained has a high correlation (r = 0.842) and approved that the most affecting parameters on THM formation are total organic carbon, temperature, turbidity, total solids, and chlorine dose. The model that was derived may be used for the purposes of choosing appropriate THM-reduction procedures and the use of chlorine for improving the method of disinfection.

Factors Identification for Human Development Index

Human development index matters a lot for the economic condition of a country. It can be calculated with the help of the education index, health index, and GDP. So, by looking only at the value of the human development index (HDI), the economy of the country can be judged. The contribution of this research project is the identification of factors related to human development. The factors include the availability of the basic necessities, facilities related to education, health, and income. For this purpose, different important factors have been observed for the Multan district by taking MICS (2007-2008) survey data. Logistic regression is applied for the purpose of analysis. Significant factors are noted in each regression analysis based on the dependent factor.