SEABASS: Symmetric-keychain Encryption and Authentication for Building Automation Systems

There is an increasing security risk in Building Automation Systems (BAS) in that its communication is unprotected, resulting in the adversary having the capability to inject spurious commands to the actuators to alter the behaviour of BAS. The communication between the Human-Machine-Interface (HMI) and the controller (PLC) is vulnerable as there is no secret key being used to protect the authenticity, confidentiality and integrity of the sensor data and commands. We propose SEABASS, a lightweight key management scheme to distribute and manage session keys between HMI and PLCs, providing a secure communication channel between any two communicating devices in BAS through a symmetric-key based hash-chain encryption and authentication of message exchange. Our scheme facilitates automatic renewal of session keys periodically based on the use of a reversed hash-chain. A prototype was implemented using the BACnet/IP communication protocol and the preliminary results show that the symmetric keychain approach is lightweight and incurs low latency

The hierarchical structure of a firm: a geometric approach

This paper develops a novel, geometric approach to modelling a firm's hierarchical structure. We model the firm''s hierarchy as the sector of a circle, in which the radius represents the height of the hierarchy and the angle of the sector represents the width of the hierarchy. The firm then chooses the height and angle in order to maximise profit. We analyse the impacts of changes in economies of scale, input substitutability and labour productivity on the firm''s hierarchical structure. We find that the firm will unambiguously become more hierarchical as specialisation of its workers increases or as its output price increases. The effect of changes in scale economies is contingent on the level of task specialisation and output price.

When is Sirt1 activity bad for dying neurons?

10.3389/fncel.2013.00186Frontiers in Cellular NeuroscienceOCT

Reposts Influencing the Effectiveness of Social Reporting System: An Empirical Study from Sina Weibo

Social media platforms are transforming individuals from passive receivers as in traditional one-way communication channels to active senders who react to and disseminate information easily. However, such feature breeds a wide spreading of unverified information online, i.e., rumor. Previous research pointed out the duality of social media that it can serve as a potential tool for social reporting by leveraging users\u27 collective intelligence, but it could also become a collective rumor mill. We propose that repost amount will positively influence the survival time of rumor, which we use to indicate the effectiveness of social reporting system. The preliminary results support our hypothesis and social contagion theory are adopted to explain the mechanism. We elaborate on the potential contribution and future research plan as well

The probabilities of absolute ruin in the renewal risk model with constant force of interest

In this paper we consider the probabilities of finite- And infinite-time absolute ruins in the renewal risk model with constant premium rate and constant force of interest. In the particular case of the compound Poisson model, explicit asymptotic expressions for the finite- and infinite-time absolute ruin probabilities are given. For the general renewal risk model, we present an asymptotic expression for the infinite-time absolute ruin probability. Conditional distributions of Poisson processes and probabilistic techniques regarding randomly weighted sums are employed in the course of this study. © Applied Probability Trust 2010.postprin

Capital Budgeting Evaluation Practices of Building Contractors in Hong Kong

This paper reports the results of an investigation into capital budgeting evaluation practicesin the construction industry of Hong Kong. The aim of this study was to identify thepopularity and extent of usage of various techniques for capital budget evaluation, investmentappraisal, risk analysis, and management science. The current study was comparedwith a similar survey conducted in 1994 to establish the changes in the capital budgetingevaluation practices of contracting firms over time. The results indicate that there was ageneral increase in the popularity and extent of usage in certain capital budget evaluationtechniques such as “best/worst estimate” and “formal financial evaluation”. In addition,the evaluation techniques examined were fitted into a discriminant function analysis (DFA),and a model has been developed which allows contracting firms to be classified accordingto their predominant characteristics in capital budget evaluation

Electrospray synthesis of PLGA TIPS microspheres

We successfully demonstrate the synthesis of polymer microspheres using a single electrospray source, and show their physical characterisation. Electrospray has proven to be a versatile method to manufacture particles, giving tight control over size with quasi-monodisperse size distributions. It is a liquid atomisation technique that generates a monodisperse population of highly charged liquid droplets over a broad size range (nanometres to tens of microns). The droplets contain liquid precursors for the in-flight synthesis of particles, and control over the trajectory of these droplets can be precisely manipulated with the use of electric fields to drive them to a grounded substrate. This study reports a method to synthesize poly(lactic-co-glycolic) acid (PLGA) microspheres using the electrospray and thermally induced phase separation (TIPS) techniques, followed by subsequent freeze-drying, for particle production. These microspheres are of interest as vehicles for controlled drug release systems