Wichita State University

About: Wichita State University is a education organization based out in Wichita, Kansas, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 4988 authors who have published 9563 publications receiving 253824 citations. The organization is also known as: WSU & Fairmount College.

Global change effects on plant communities are magnified by time and the number of global change factors imposed

Abstract: Global change drivers (GCDs) are expected to alter community structure and consequently, the services that ecosystems provide. Yet, few experimental investigations have examined effects of GCDs on plant community structure across multiple ecosystem types, and those that do exist present conflicting patterns. In an unprecedented global synthesis of over 100 experiments that manipulated factors linked to GCDs, we show that herbaceous plant community responses depend on experimental manipulation length and number of factors manipulated. We found that plant communities are fairly resistant to experimentally manipulated GCDs in the short term (<10 y). In contrast, long-term (≥10 y) experiments show increasing community divergence of treatments from control conditions. Surprisingly, these community responses occurred with similar frequency across the GCD types manipulated in our database. However, community responses were more common when 3 or more GCDs were simultaneously manipulated, suggesting the emergence of additive or synergistic effects of multiple drivers, particularly over long time periods. In half of the cases, GCD manipulations caused a difference in community composition without a corresponding species richness difference, indicating that species reordering or replacement is an important mechanism of community responses to GCDs and should be given greater consideration when examining consequences of GCDs for the biodiversity–ecosystem function relationship. Human activities are currently driving unparalleled global changes worldwide. Our analyses provide the most comprehensive evidence to date that these human activities may have widespread impacts on plant community composition globally, which will increase in frequency over time and be greater in areas where communities face multiple GCDs simultaneously.

Extension of Oxley’s Analysis of Machining to Use Different Material Models

Abstract: The aim of the present work is to extend the applicability of Oxley's analysis of machining to a broader class of materials beyond the carbon steels used by Oxley and co-workers. The Johnson-Cook material model, history dependent power law material model and the Mechanical Threshold Stress (MTS) model are used to represent the mechanical properties of the material being machined as a function of strain, strain rate and temperature. A few changes are introduced into Oxley's analysis to improve the consistency between the various assumptions. A new approach has been introduced to calculate the pressure variation along the alpha slip lines in the primary shear zone including the effects of both the strain gradient and the thermal gradient along the beta lines. This approach also has the added advantage of ensuring force equilibrium of the primary shear zone in a macroscopic sense. The temperature at the middle of the primary shear zone is calculated by integrating the plastic work thereby eliminating the unknown constant η. Rather than calculating the shear force from the material properties corresponding to the strain, strain rate and temperature of the material at the middle of the shear zone, the shear force is calculated in a consistent manner using the energy dissipated in the primary shear zone. The thickness of the primary and secondary shear zones, the heat partition at the primary shear zone, the temperature distribution along the tool-chip interface and the shear plane angle are all calculated using Oxley's original approach. The only constant used to fine tune the model is the ratio of the average temperature to the maximum temperature at the tool-chip interface (ψ). The performance of the model has been studied by comparing its predictions with experimental data for 1020 and 1045 steels, for aluminum alloys 2024-T3, 6061-T6 and 6082-T6, and for copper. It is found that the model accurately reproduces the dependence of the cutting forces and chip thickness as a function of undeformed chip thickness and cutting speed and accurately estimates the temperature in the primary and secondary shear zones.

Total system JIT outcomes: inventory, organization and financial effects

Abstract: Despite anecdotal evidence of the performance implications of just‐in‐time (JIT) implementation, little empirical research has been conducted. Examines total system JIT’s empirical relationships with a variety of performance outcomes. Total system JIT encompasses JIT purchasing, JIT production, and JIT selling. In a mail survey of 200 logistics executives, total system JIT was found to be: inversely related to weeks of inventory (inclusive of inbound, in‐process, and outbound); inversely related to the number of layers in various functional areas (e.g. marketing); and positively related to three different indicators of financial performance (ROI, profits, and ROS). Results, managerial implications, and further research are discussed.

Bias and variance of validation methods for function approximation neural networks under conditions of sparse data

Abstract: Neural networks must be constructed and validated with strong empirical dependence, which is difficult under conditions of sparse data. The paper examines the most common methods of neural network validation along with several general validation methods from the statistical resampling literature, as applied to function approximation networks with small sample sizes. It is shown that an increase in computation, necessary for the statistical resampling methods, produces networks that perform better than those constructed in the traditional manner. The statistical resampling methods also result in lower variance of validation, however some of the methods are biased in estimating network error.