Coordinating tasks in M-form and U-form organisations

We model the coordination of specialised tasks inside an organisation as "attribute matching". Using this method, we compare the performance of organisational forms (M-form and U-form) in implementing changes such as innovation and reform. In our framework, organisational forms affect the information structure of an organisation and thus the way to coordinate changes. Compared to the U-form, the M-form organisation achieves better coordination but suffers from fewer economies of scale. The distinctive advantage of the M-form is flexibility of experimentation, which allows the organisation to introduce more innovation and reform. The theory is illustrated by the organisational differences between China and the former Soviet Union and sheds light on their different reform strategies, particularly with regard to the prevalence of the experimental approach in China

Spatiotemporal patterns and predictability of cyberattacks

A relatively unexplored issue in cybersecurity science and engineering is whether there exist intrinsic patterns of cyberattacks. Conventional wisdom favors absence of such patterns due to the overwhelming complexity of the modern cyberspace. Surprisingly, through a detailed analysis of an extensive data set that records the time-dependent frequencies of attacks over a relatively wide range of consecutive IP addresses, we successfully uncover intrinsic spatiotemporal patterns underlying cyberattacks, where the term "spatio" refers to the IP address space. In particular, we focus on analyzing {\em macroscopic} properties of the attack traffic flows and identify two main patterns with distinct spatiotemporal characteristics: deterministic and stochastic. Strikingly, there are very few sets of major attackers committing almost all the attacks, since their attack "fingerprints" and target selection scheme can be unequivocally identified according to the very limited number of unique spatiotemporal characteristics, each of which only exists on a consecutive IP region and differs significantly from the others. We utilize a number of quantitative measures, including the flux-fluctuation law, the Markov state transition probability matrix, and predictability measures, to characterize the attack patterns in a comprehensive manner. A general finding is that the attack patterns possess high degrees of predictability, potentially paving the way to anticipating and, consequently, mitigating or even preventing large-scale cyberattacks using macroscopic approaches

Large-gap quantum spin Hall insulators in tin films

The search of large-gap quantum spin Hall (QSH) insulators and effective approaches to tune QSH states is important for both fundamental and practical interests. Based on first-principles calculations we find two-dimensional tin films are QSH insulators with sizable bulk gaps of 0.3 eV, sufficiently large for practical applications at room temperature. These QSH states can be effectively tuned by chemical functionalization and by external strain. The mechanism for the QSH effect in this system is band inversion at the \Gamma point, similar to the case of HgTe quantum well. With surface doping of magnetic elements, the quantum anomalous Hall effect could also be realized

Application of Radiant Floor Heating in Large Space Buildings with Significant Cold Air Infiltration through Door Openings

Radiant Floor Heating System (RFHS) has been commonly used in railway stations in cold regions of China for its advantages in thermal comfort and energy efficiency. However, the uneven distribution and extremely cold area of the heating floor, caused by cold air infiltration through door openings, are commonly found in our filed measurements. This impact is not considered in the standardized design methods, resulting in an underestimation of the design heat flux. In this paper, CFD simulations are used to quantify the impacts of natural infiltration on surface heat transfer process. Model validation was made against field measurements. 13 simulations were performed for different speeds. As a result, the mean radiant heat flux at floor surface decreased by 36.8% as the infiltration air speed increased from 0.05 m/s to 1.2 m/s, and the noneffective area increased more than 16 times. This result highlights a significant influence of natural infiltration. Regression models were finally developed as a simple method for rough estimation of this impact on radiation, which can make up the limitations of current methods and inform designers to improve their initial design of RFHS when natural infiltration is present