A control theoretic approach to achieve proportional fairness in 802.11e EDCA WLANs

This paper considers proportional fairness amongst ACs in an EDCA WLAN for provision of distinct QoS requirements and priority parameters. A detailed theoretical analysis is provided to derive the optimal station attempt probability which leads to a proportional fair allocation of station throughputs. The desirable fairness can be achieved using a centralised adaptive control approach. This approach is based on multivariable statespace control theory and uses the Linear Quadratic Integral (LQI) controller to periodically update CWmin till the optimal fair point of operation. Performance evaluation demonstrates that the control approach has high accuracy performance and fast convergence speed for general network scenarios. To our knowledge this might be the first time that a closed-loop control system is designed for EDCA WLANs to achieve proportional fairness

Mechanisms Regulating the Self-Renewal and Differentiation of Nephron Progenitors

Nephrons, the basic functional units of the kidney, are built from an embryonic progenitor population called the cap mesenchyme (CM). Although stem-like in many aspects, these progenitors exhaust before or shortly after birth when nephron numbers reach a species appropriate limit termed nephron endowment . The actual number of nephrons varies greatly between individuals, and low nephron numbers have been linked to hypertension and other renal diseases. However, the mechanisms that lead to the depletion of CM cells remain elusive. We hypothesized that cell intrinsic changes of the CM actively regulate the lifespan of CM cells. To test this hypothesis, we established a new assay system where the ability of CM to remain as nephron progenitors could be evaluated upon transplantation into an endogenous CM niche. By co-transplanting nephron progenitors isolated from different embryonic stages, we discovered that young and old progenitors display differential proliferation rate, adhesion properties and their ability to remain in the niche is inversely correlated with age. Importantly, an unbiased transcriptome profiling of nephron progenitors at the single cell level revealed distinct transcriptional signature of different age groups, further supporting an intrinsic difference. Interestingly, although most old progenitors exit the niche sooner than young progenitors, a few of them could remain in the niche beyond their endogenous lifespan when completely surrounded by young neighbors, indicating that age-related changes are possibly reversible. Together, these data is consistent with a gradual intrinsic change in the CM preceding the cessation of nephrogenesis. Manipulating age-related changes may open the door to increasing nephron endowment in at-risk individuals

Numerical modelling of multiple borehole heat exchanger array for sustainable utilisation of shallow geothermal energy

A PhD dissertation which presented a numerical modelling study on the long-term behavior in the multiple borehole heat exchanger array system for sustainable utilisation of shallow geothermal energy

The positive effect of women’s education on fertility in low-fertility China

Despite pervasive evidence of more educated women having lower fertility, it remains unclear whether education reduces women’s fertility. This study presents new evidence of the causal effect of women’s education on fertility from China, where fertility has remained below the replacement level since the early 1990s. To account for endogeneity, the study exploits the timing and varying intensity of China’s higher education expansion as exogenous sources of increase in women’s education. Using data from China General Social Survey (2010–2012), findings show that each year of women’s education induced by the higher education expansion increases the number of children ever born by 10%. According to the average marginal effects, each additional year of women’s education increases the number of children ever born by 0.14, decreases the probability of having no children by 3 percentage points, and increases the probability of having two or more children by 4 percentage points. Two mechanisms drive the positive effect of education: first, education does not cause an increase in the mean age at first marriage; second, among ever-married women, education increases their demand for children. Findings from this study have important implications for China and other low-fertility developing countries