Computational investigation of structure, dynamics and nucleation kinetics of a family of modified Stillinger-Weber model fluids in bulk and free-standing thin films

In recent decades, computer simulations have found increasingly widespread use as powerful tools of studying phase transitions in wide variety of systems. In the particular and very important case of aqueous systems, the commonly used force-fields tend to offer quite different predictions with respect to a wide range of thermodynamic and kinetic properties, including the ease of ice nucleation, the propensity to freeze at a vapor-liquid interface, and the existence of a liquid-liquid phase transition. It is thus of fundamental and practical interest to understand how different features of a given water model affect its thermodynamic and kinetic properties. In this work, we use the forward-flux sampling technique to study the crystallization kinetics of a family of modified Stillinger-Weber (SW) potentials with energy ($\epsilon$) and length ($\sigma$) scales taken from the monoatomic water (mW) model, but with different tetrahedrality parameters ($\lambda$). By increasing $\lambda$ from 21 to 24, we observe the nucleation rate increases by 48 orders of magnitude at a supercooling of ${\zeta}=T/T_m=0.845$. Using classical nucleation theory, we are able to demonstrate that this change can largely be accounted for by the increase in $|\Delta\mu|$, the thermodynamic driving force. We also perform rate calculations in freestanding thin films of the supercooled liquid, and observe a crossover from a surface-enhanced crystallization at $\lambda = 21$ to a bulk-dominated crystallization for $\lambda\ge22$.Comment: 10 pages, 9 figures, five table

Percolation in Networks with Voids and Bottlenecks

A general method is proposed for predicting the asymptotic percolation threshold of networks with bottlenecks, in the limit that the sub-net mesh size goes to zero. The validity of this method is tested for bond percolation on filled checkerboard and "stack-of-triangle" lattices. Thresholds for the checkerboard lattices of different mesh sizes are estimated using the gradient percolation method, while for the triangular system they are found exactly using the triangle-triangle transformation. The values of the thresholds approach the asymptotic values of 0.64222 and 0.53993 respectively as the mesh is made finer, consistent with a direct determination based upon the predicted critical corner-connection probability.Comment: to appear, Physical Review E. Small changes from first versio

Universal condition for critical percolation thresholds of kagome-like lattices

Lattices that can be represented in a kagome-like form are shown to satisfy a universal percolation criticality condition, expressed as a relation between P_3, the probability that all three vertices in the triangle connect, and P_0, the probability that none connect. A linear approximation for P_3(P_0) is derived and appears to provide a rigorous upper bound for critical thresholds. A numerically determined relation for P_3(P_0) gives thresholds for the kagome, site-bond honeycomb, (3-12^2), and "stack-of-triangle" lattices that compare favorably with numerical results.Comment: Several new figures and small change

Towards a historical ecology of intertidal foraging in the Mafia Archipelago: archaeomalacology and implications for marine resource management

Understanding the timing and nature of human influence on coastal and island ecosystems is becoming a central concern in archaeological research, particularly when investigated within a historical ecology framework. Unfortunately, the coast and islands of eastern Africa have not figured significantly within this growing body of literature, but are important given their historically contingent environmental, social, and political contexts, as well as the considerable threats now posed to marine ecosystems. Here, we begin developing a longer-term understanding of past marine resource use in the Mafia Archipelago (eastern Africa), an area of high ecological importance containing the Mafia Island Marine Park. Focusing on the comparatively less researched marine invertebrates provides a means for initiating discussion on potential past marine ecosystem structure, human foraging and environmental shifts, and the implications for contemporary marine resource management. The available evidence suggests that human-environment interactions over the last 2000 years were complex and dynamic; however, these data raise more questions than answers regarding the specific drivers of changes observed in the archaeomalacological record. This is encouraging as a baseline investigation and emphasizes the need for further engagement with historical ecology by a range of cognate disciplines to enhance our understanding of these complex issues

Characterization and analysis of N2 plasma DC glow discharge at different voltage

In this work, the plasma glow discharge characteristics of nitrogen gas will be studied and analyzed at different pressures, and we will study the effect of these pressures on the I-V curve, the Panchen curve, the I-P curve, the current-voltage curve, and their effect on the electrical conductivity of the generated plasma. The distance between the glow electrodes was (15.5) cm. The pressures that were used in this work were (0.025, 0.05, 1.5, 5) T. The results indicated that the discharge was operating in the atypical glow region. On the other hand, the discharge current decreased as the gas pressure increased. On the other hand. Also, the conductivity decreased in its values with the increase in applied pressure as well as the voltage of the plasma focus

Developing Students' Ability of Mathematical Connection Through Using Outdoor Mathematics Learning

The Purpose of this study is to determine the achievement and improvement of students' mathematical connectionability through using outdoor mathematics learning. 64 students from the fifth grade of Primary School at SDN 65 and SDN 67 Bengkulu City were taken as the sample of this study. While the method of the research used in this research is experiment with quasi-experimental designs non-equivalent control group. The results of the study are as follows: (1) There is an increasing ability found in mathematical connection of students whom taught by using outdoors mathematics learning is 0,53; (2) Based on statical computation that achievement of students' ability of mathematical connection is taught by using outdoor mathematics learning score is 71,25. It is higher than the students score 66,25 which were taught by using the conventional learning. So as to improve students' mathematical connection, teachers are suggested to use the outdoors mathematics learnin

Enhancing Physical Layer Security in AF Relay Assisted Multi-Carrier Wireless Transmission

In this paper, we study the physical layer security (PLS) problem in the dual hop orthogonal frequency division multiplexing (OFDM) based wireless communication system. First, we consider a single user single relay system and study a joint power optimization problem at the source and relay subject to individual power constraint at the two nodes. The aim is to maximize the end to end secrecy rate with optimal power allocation over different sub-carriers. Later, we consider a more general multi-user multi-relay scenario. Under high SNR approximation for end to end secrecy rate, an optimization problem is formulated to jointly optimize power allocation at the BS, the relay selection, sub-carrier assignment to users and the power loading at each of the relaying node. The target is to maximize the overall security of the system subject to independent power budget limits at each transmitting node and the OFDMA based exclusive sub-carrier allocation constraints. A joint optimization solution is obtained through duality theory. Dual decomposition allows to exploit convex optimization techniques to find the power loading at the source and relay nodes. Further, an optimization for power loading at relaying nodes along with relay selection and sub carrier assignment for the fixed power allocation at the BS is also studied. Lastly, a sub-optimal scheme that explores joint power allocation at all transmitting nodes for the fixed subcarrier allocation and relay assignment is investigated. Finally, simulation results are presented to validate the performance of the proposed schemes.Comment: 10 pages, 7 figures, accepted in Transactions on Emerging Telecommunications Technologies (ETT), formerly known as European Transactions on Telecommunications (ETT

A Novel Approach to Mutation Operator Design for MDE Languages

Due to the increasing reliance on the software of systems, such as enterprise systems, a wide array of approaches has been found to facilitate the development of software for such systems. The growth of system complexity, however, has provoked concerns about the quality of the software. One approach that copes with complexity is model driven engineering that uses models containing only essential domain concepts, in order to represent complex systems. With some level of automation, models are then maintained by programs that are prone to error, as they are man-made. In order to find errors in programs, software engineers use mutation testing to build strong test inputs by introducing faults into the tested software using mutation operators. They then study if the introduced faults are detected by the test inputs. There have been few attempts to design mutation operators for model driven languages, which have common metamodeling language models, compared with traditional programming languages. This thesis presents an effective language-agnostic approach for mutation operator design for the rapidly emerging model driven engineering languages by considering metamodeling languages. The approach produces generic operators that can be instantiated to generate concrete ones for a given language model, which can be used to mutate program models that conform to the language model. The approach and generic operators are evaluated using empirical mutation analysis experiments over programs written in the ATL and EOL languages. The results show that the generic operators generated from the approach are instantiatable over ATL and EOL metamodels and have produced low proportions of invalid and equivalent mutants that can impact negatively on any mutation testing process. Also, the generic operators have produced useful mutants such as live and not trivially detected kinds of mutants