Investigation of distinct welding parameters on mechanical and corrosion properties of dissimilar welded joints between stainless steel and low carbon steel.

The tensile strength and corrosion behavior of dissimilar welded joints are currently a subject of concern. In this work, gas metal arc welding (GMAW) and distinct welding parameters (welding current, arc voltage, and welding speed) were used to join 304 stainless steel (SUS304) and SS400 low carbon steel, and the ultimate tensile strength (UTS) of the dissimilar welded joints was investigated. A corrosion test was conducted by immersion in 3.5 wt.% sodium chloride (NaCl) solution for 7, 14, and 21 days. Based on tensile strength and Tafel testing, the welding parameters "Item 4" (welding current: 170 A, arc voltage: 20 V, welding speed: 40 cm/min) yielded good mechanical strength and low corrosion characteristics. The microstructure characterization showed that the area around the welded joints and SUS304 had more granular corrosion and corrosion tubercles with increasing immersion time. The chromium content gradually decreased. When exposed to the chloride environment, these welded joints easily underwent corrosion due to the loss of passivity. However, high-velocity oxygen-fuel (HVOF) spray used on the welded joints reduced the corrosion current density. Compared with the non-thermal spray sample (corrosion current density:7.49e - 05 A/cm2) while the corrosion current density (7.89e - 10 A/cm2) is five orders of magnitude lower. This spray effectively slowed down the corrosion rate of the welded joints and gave the structural objects good protection in the sodium chloride solution.

Theoretical system dynamics modeling for Taiwan pediatric workforce in an era of national health insurance and low birth rates.

BACKGROUND: In an era of declining birth rates and a single-payer health care system, the pediatric workforce might overreact to its demands. System dynamics (SD) were therefore applied to establish models to predict the future need and demand for the pediatric workforce. MATERIALS AND METHODS: Data of population and workforce were extracted from national databases and models developed using Vensim software. RESULTS: In the past decade, the child-to-pediatrician ratio correlated with infant mortality in Taiwan (p < 0.001, r(2) = 0.88, child-to-pediatrician ratio = 146 + 354 × infant mortality/1000 live births). Currently, the child-to-pediatrician ratio is 1742:1. Using the Millennium Development Goals (2.437/1000 live births) for infant mortality, the child-to-pediatrician ratio was estimated as 1009:1. The pediatric population model incorporated the birth and mortality rates in each age category, accurately predicted population changes between 1974 and 2010, and projected a decreasing trend until 2017. The pediatric workforce model, which considered rates of enrollment, completion, certification, and retention, predicted a decrease in the supply of pediatricians in the mid-2010s that could be delayed by policy incentives. When targeting the base scenario, the model indicated that discrepancies between demands and supply of pediatricians would occur in the late 2010s toward 2020. When targeting the Millennium Development Goals scenario, however, the discrepancies would be consistent. CONCLUSION: Effective SD models were developed for the population and health care workforce. The strengths of the SD models are derived from simulation, which is subject to influence from new policies. Policies can, therefore, be examined and intervened in a timely manner.