Suchergebnisse

We use ideas from game theory to transform two families of authentication protocols so that even an intruder attacks a protocol, its payoff will still be lower than when it does not. This is particularly useful in resisting or discouraging a powerful and rational intruder (as present in military applications) who makes many attempts to break a protocol because (1) even the intruder fails, a denial of service attack is still mounted successfully, and (2) in a password-based protocol, the chance of a successful attack increases quite significantly as more and more attempts are launched to guess the password.

Research objective To explore the probability of substantive change in the Vietnamese accounting field, given that as approached from Bourdieu's perspective of the "habitus", most participants are likely, but not necessarily, to react conservatively to change. Research outcome From the viewpoint of the silent, dominated majority of bookkeepers in Vietnam, changes to the structure of the accounting field and to practice methods are not welcomed. However, the findings indicate that although they view real change as unlikely most of the 2,000 professional accountants are more positive. Research Questions: Do the 2 million practitioners in the Vietnamese accounting field look forward to changes that may be brought about by Anglo Saxon institutions such as, the large accounting firms, the international standards and the foreign accounting professions? Research Methods: Semi structured interviews were conducted to draw from respondents their feelings and thoughts on the possibility of change. Some 44 interviews of mostly bookkeepers, including some accountants, academics and other informed observers were conducted. Findings Of the 44 interviewees the bookkeepers were generally negative with regard to change. They preferred a compliance mode of accounting, which relied on government instructions as to suitable accounting treatments and served also the needs of tax accounting. By contrast, those representative of other groups such as professional accountants, managers and academics were more open to change and saw merit following accounting principles rather than government rules. Originality/value: The literature refers to "a paucity of studies on developing countries" with respect to the effects of exogenous changes to local accounting fields. The paper explores the Vietnamese accounting field to assess the extent and effects of such exogenous induced changes among the practitioners in the field.

The evolving electricity market has increased power demand and has brought many social benefits. Meanwhile, the transmission systems are not developed to the same extent because building new lines is difficult for environmental and political reasons. Hence, the systems are driven close to their limits resulting in congestions and critical situations endangering the system's security. Due to this, the study of enhancing the transfer capability of existing power networks to satisfy the increased power demand, maximum social welfare, and ensure its secure operation has become one of the challenges the Independent System Operator faces in the electricity market. In order to solve this problem without building more transmission lines, the installation of FACTS devices can be a better alternative. Among FACTS devices, thyristor-controlled series compensator (TCSC) is one that can redistribute power flow in the network to improve the transfer capability of the existing system effectively. However, it is very difficult to implement. This paper presents the implementation of the Cuckoo Optimization Algorithm (COA) to solve the OPF problem which is formulated as a nonlinear optimization problem with equality and inequality constraints in a power system for social welfare maximization via the optimal installation of TCSC devices. As Cuckoo Search Algorithm (CSA), the COA also starts with an initial population-based metaheuristic optimization inspired by the nature of brood parasitism of some cuckoo species. However, unlike CSA, COA uses the cuckoo's style for egg-laying to optimize the local search instead of using Lévy flights. This model is tested in IEEE 14 and IEEE 30 bus systems. Simulations results are compared with GA and GWO and show that the COA is one useful method for TCSC installation to maximize social welfare.

Background As many countries seek to slow the spread of COVID-19 without reimposing national restrictions, it has become important to track the disease at a local level to identify areas in need of targeted intervention. Methods In this prospective, observational study, we did modelling using longitudinal, self-reported data from users of the COVID Symptom Study app in England between March 24, and Sept 29, 2020. Beginning on April 28, in England, the Department of Health and Social Care allocated RT-PCR tests for COVID-19 to app users who logged themselves as healthy at least once in 9 days and then reported any symptom. We calculated incidence of COVID-19 using the invited swab (RT-PCR) tests reported in the app, and we estimated prevalence using a symptom-based method (using logistic regression) and a method based on both symptoms and swab test results. We used incidence rates to estimate the effective reproduction number, R(t), modelling the system as a Poisson process and using Markov Chain Monte-Carlo. We used three datasets to validate our models: the Office for National Statistics (ONS) Community Infection Survey, the Real-time Assessment of Community Transmission (REACT-1) study, and UK Government testing data. We used geographically granular estimates to highlight regions with rapidly increasing case numbers, or hotspots. Findings From March 24 to Sept 29, 2020, a total of 2 873 726 users living in England signed up to use the app, of whom 2 842 732 (98·9%) provided valid age information and daily assessments. These users provided a total of 120 192 306 daily reports of their symptoms, and recorded the results of 169 682 invited swab tests. On a national level, our estimates of incidence and prevalence showed a similar sensitivity to changes to those reported in the ONS and REACT-1 studies. On Sept 28, 2020, we estimated an incidence of 15 841 (95% CI 14 023–17 885) daily cases, a prevalence of 0·53% (0·45–0·60), and R(t) of 1·17 (1·15–1·19) in England. On a geographically granular level, on Sept 28, 2020, we detected 15 (75%) of the 20 regions with highest incidence according to government test data. Interpretation Our method could help to detect rapid case increases in regions where government testing provision is lower. Self-reported data from mobile applications can provide an agile resource to inform policy makers during a quickly moving pandemic, serving as a complementary resource to more traditional instruments for disease surveillance.