Dynamic Interrelation of Births and Deaths: Evidence from Plant Level Data

In this paper, the dynamic panel data method is used to investigate the dynamic interrelation of plant births and plant deaths. The dynamic panel data method considers the endogenous problem and individual effects. Empirical findings support the multiplier effect. In addition, exit does not cause entry, whereas entry causes exit.

Flash-point prediction for binary partially miscible mixtures of flammable solvents

Flash point is the most important variable used to characterize fire and explosion hazard of liquids. Herein, partially miscible mixtures are presented within the context of liquid-liquid extraction processes. This paper describes development of a model for predicting the flash point of binary partially miscible mixtures of flammable solvents. To confirm the predictive efficacy of the derived flash points, the model was verified by comparing the predicted values with the experimental data for the studied mixtures: methanol + octane; methanol + decane; acetone + decane; methanol + 2,2,4-trimethylpentane; and, ethanol + tetradecane. Our results reveal that immiscibility in the two liquid phases should not be ignored in the prediction of flash point. Overall, the predictive results of this proposed model describe the experimental data well. Based on this evidence, therefore, it appears reasonable to suggest potential application for our model in assessment of fire and explosion hazards, and development of inherently safer designs for chemical processes containing binary partially miscible mixtures of flammable solvents

Bifurcations and chaos in a gear assembly with clearances for solar array drive assembly

Solar array drive assembly is an important part of the spacecraft. It is used to rotate the solar panels. The gear assembly in solar array drive assembly plays a key role in transferring power safely. Nonlinear behavior of gear assembly, like the chaotic motion, can highly affect the stability and operating life of solar array drive assembly. Clearances in gear assembly which were neglected for simplification in past years have increased the risk of failure and become a problem in accurate control. To investigate the clearances effect on nonlinear behavior, this paper establishes a new dynamic model of the gear assembly with bilateral clearances. The main difference comparing to general spur gears is its unique hysteresis stiffness may also influence the clearance effects. Transformation of the hysteresis loop is observed from theoretical equations using different parameters. Bifurcations and chaotic analysis of the system are carried out by numerical simulations in this study. The results show that the variation of clearances may induce the chaotic behavior into gear transmission even when the primary response is stable. When the system step into the chaotic region, it has a high risk of unstable vibration and fuzzy output. The influence of excitation frequency on the chaotic motion of the system is also provided. Chaos thresholds are calculated to avoid nonlinear behavior of the system in design and control. This study makes it possible to predict the unstable clearance interval in this system and avoid the system stepping into chaotic motion. Analyzing and predicting the chaotic behaviors can contribute to the further studies on design and control of the solar array drive assembly

Developing new heat pump system to improve indoor living space in senior long-term care house

The issue of an aging population is becoming increasingly acute in Taiwan; in 2018, seniors comprised over 14 % of the total population. The quality of care for senior citizens hinges on the ability of long-term care facilities to create comfortable living spaces while ensuring energy efficiency by reducing electricity consumption, thereby providing them with an environment for aging in an active and positive way. This study proposes a new heat pump system that offers a cold source in the summer and a heat source in the winter. In addition, the air-conditioning and ventilation rates required for comfort in indoor living spaces are established to ensure the high quality of the care spaces in these types of institutions. The results after installation of the heat pump system were as follows: (1) Performance of the heat pump system: the inlet temperature of the heat pump chilled water was maintained at 7-10 °C, and the outlet temperature, at 42-54 °C. (2) Energy efficiency: Based on a 95 % confidence interval, the average annual electricity consumption was 32.65 kwh/day, which was 32.65 % of the prior consumption level; the reduction of 67.35 % is comparable to those of most heat pump systems. (3) Improvement of the indoor environment: In the hottest scenario, the indoor temperature was reduced by 3 °C and the relative humidity to 55-65 %, which fall within comfortable ranges. After the heat pump system was introduced, significant improvements in ventilation, air quality and comfort were noted, as well as significant improvement in average total satisfaction scores. All improvements reached statistical significance. The overall objective of the system is to enhance the environmental quality in long-term senior care facilities and make them healthier and more energy efficient