EXPLORING THE ROLE OF SWITCHING COSTS IN EXPLAINING MICRO-GROUP ADHERENCE FROM THE SOCIO-TECHNICAL PERSPECTIVE

Micro-group is a commonly used function provided by most of China micro-blog platforms though which friends or people with common interests can share conversations like an online community. In this study, we draw from established socio-technical theory in Information Systems to develop an integrated model of customers’ adherence to micro-groups from the view of switching cost. The results of the empirical analysis confirmed that switching cost increases when the user perceived that the system was secure, full-functional or when there is a high level of network size, information value and network status. In the same way, greater switching cost was also found to have a positive influence on user adherence to micro-groups. Based on the findings, strategies to help micro-group site develop an enhanced “lock-in” effect are proposed

A robust and efficient statistical method for genetic association study using case and control samples from multiple cohorts

BACKGROUND: The theoretical basis of genome-wide association studies (GWAS) is statistical inference of linkage disequilibrium (LD) between any polymorphic marker and a putative disease locus. Most methods widely implemented for such analyses are vulnerable to several key demographic factors and deliver a poor statistical power for detecting genuine associations and also a high false positive rate. Here, we present a likelihood-based statistical approach that accounts properly for non-random nature of case–control samples in regard of genotypic distribution at the loci in populations under study and confers flexibility to test for genetic association in presence of different confounding factors such as population structure, non-randomness of samples etc. RESULTS: We implemented this novel method together with several popular methods in the literature of GWAS, to re-analyze recently published Parkinson’s disease (PD) case–control samples. The real data analysis and computer simulation show that the new method confers not only significantly improved statistical power for detecting the associations but also robustness to the difficulties stemmed from non-randomly sampling and genetic structures when compared to its rivals. In particular, the new method detected 44 significant SNPs within 25 chromosomal regions of size < 1 Mb but only 6 SNPs in two of these regions were previously detected by the trend test based methods. It discovered two SNPs located 1.18 Mb and 0.18 Mb from the PD candidates, FGF20 and PARK8, without invoking false positive risk. CONCLUSIONS: We developed a novel likelihood-based method which provides adequate estimation of LD and other population model parameters by using case and control samples, the ease in integration of these samples from multiple genetically divergent populations and thus confers statistically robust and powerful analyses of GWAS. On basis of simulation studies and analysis of real datasets, we demonstrated significant improvement of the new method over the non-parametric trend test, which is the most popularly implemented in the literature of GWAS

Gaussian Distribution-Based Inertial Control of Wind Turbine Generators for Fast Frequency Response in Low Inertia Systems

Decline of rotating inertia due to the high share of renewable sources cause challenges in controlling grid frequency. With recent grid codes, large-scale wind turbines (WTs) are required to provide frequency support. Existing stepwise inertial control methods suggest immediate incremental power injection by WTs, followed by the abrupt over-production termination to avoid over-deceleration of the rotor speed. Unfortunately, these methods are not practically desirable as they impose severe secondary-frequency-drops (SFD) or considering unrealistic constant wind speed for tens of seconds. This paper proposes a novel inertial control scheme that can improve frequency nadir without rotor speed over-deceleration. Upon detecting a power imbalance, WT increases the output power with an incremental power and declines it following a Gaussian distribution trajectory controlled by a standard deviation parameter, to ensure convergence to an equilibrium point. The proposed scheme can be practically implemented for fast frequency response. This scheme is tested on the wind-integrated IEEE 9-bus system and IEEE 39-bus system and compared with other methods reported in literature. Furthermore, experimental tests are conducted to verify the performance of the proposed scheme in practice. Blade fatigue is studied using FAST Code. Results show reliable operation during abrupt wind speed changes or cascade events