A Traffic Model for Machine-Type Communications Using Spatial Point Processes

A source traffic model for machine-to-machine communications is presented in this paper. We consider a model in which devices operate in a regular mode until they are triggered into an alarm mode by an alarm event. The positions of devices and events are modeled by means of Poisson point processes, where the generated traffic by a given device depends on its position and event positions. We first consider the case where devices and events are static and devices generate traffic according to a Bernoulli process, where we derive the total rate from the devices at the base station. We then extend the model by defining a two-state Markov chain for each device, which allows for devices to stay in alarm mode for a geometrically distributed holding time. The temporal characteristics of this model are analyzed via the autocovariance function, where the effect of event density and mean holding time are shown.Comment: Accepted at the 2017 IEEE 28th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC) - Workshop WS-07 on "The Internet of Things (IoT), the Road Ahead: Applications, Challenges, and Solutions

Graphical workstation capability for reliability modeling

In addition to computational capabilities, software tools for estimating the reliability of fault-tolerant digital computer systems must also provide a means of interfacing with the user. Described here is the new graphical interface capability of the hybrid automated reliability predictor (HARP), a software package that implements advanced reliability modeling techniques. The graphics oriented (GO) module provides the user with a graphical language for modeling system failure modes through the selection of various fault-tree gates, including sequence-dependency gates, or by a Markov chain. By using this graphical input language, a fault tree becomes a convenient notation for describing a system. In accounting for any sequence dependencies, HARP converts the fault-tree notation to a complex stochastic process that is reduced to a Markov chain, which it can then solve for system reliability. The graphics capability is available for use on an IBM-compatible PC, a Sun, and a VAX workstation. The GO module is written in the C programming language and uses the graphical kernal system (GKS) standard for graphics implementation. The PC, VAX, and Sun versions of the HARP GO module are currently in beta-testing stages

Hybrid automated reliability predictor integrated work station (HiREL)

The Hybrid Automated Reliability Predictor (HARP) integrated reliability (HiREL) workstation tool system marks another step toward the goal of producing a totally integrated computer aided design (CAD) workstation design capability. Since a reliability engineer must generally graphically represent a reliability model before he can solve it, the use of a graphical input description language increases productivity and decreases the incidence of error. The captured image displayed on a cathode ray tube (CRT) screen serves as a documented copy of the model and provides the data for automatic input to the HARP reliability model solver. The introduction of dependency gates to a fault tree notation allows the modeling of very large fault tolerant system models using a concise and visually recognizable and familiar graphical language. In addition to aiding in the validation of the reliability model, the concise graphical representation presents company management, regulatory agencies, and company customers a means of expressing a complex model that is readily understandable. The graphical postprocessor computer program HARPO (HARP Output) makes it possible for reliability engineers to quickly analyze huge amounts of reliability/availability data to observe trends due to exploratory design changes

Work and information processing in a solvable model of Maxwell's demon

We describe a minimal model of an autonomous Maxwell demon, a device that delivers work by rectifying thermal fluctuations while simultaneously writing information to a memory register. We solve exactly for the steady-state behavior of our model, and we construct its phase diagram. We find that our device can also act as a "Landauer eraser", using externally supplied work to remove information from the memory register. By exposing an explicit, transparent mechanism of operation, our model offers a simple paradigm for investigating the thermodynamics of information processing by small systems.Comment: Main Text (6 pages, 3 figures) + Suppl. Info. (3 pages). To appear in PNA

Making Financial Markets: Contract Enforcement and the Emergence of Tradable Assets in Late Medieval Europe

The emergence of medieval markets has been seen in the literature as hampered by lack of contract enforcement and institutions like merchants’ communal responsibil-ity. Merchants traveling to a different marketplace could be held liable for debts in-curred by any merchant from their hometown. We argue that communal responsibility was effective in enforcing credit contracts and enabled merchants to use bills of ex-change in long distance trade even if reputation effects were absent. We implement this in the Lagos and Wright (2005) matching model of money demand, assuming that preference shocks follow a two-state Markov chain. We derive conditions under which cash and credit in the anonymous matching market coexist. For fixed but suffi-ciently low cost of credit, agents will pay with cash in low-quality matches, and use cash and credit in high-quality matches. The use of credit reduces the money holdup in the matching market and thus leads to Pareto improvementsCommunal responsibility, matching, money demand, credit

Communal Responsibility and the Coexistence of Money and Credit Under Anonymous Matching

Communal responsibility, a medieval institution studied by Greif (2006), supported the use of credit among European merchants in the absence of modern enforcement technologies. This paper shows how this mechanism helps to overcome enforcement problems in anonymous buyer/seller transactions. In a village economy version of the Lagos and Wright (2005) model, agents trading anonymously in decentralized markets can be identified by their citizenship and thus be held liable for each other. Enforceability within each village's centralized afternoon market ensures collateralization of credit in decentralized markets. In the resulting equilibrium, money and credit coexist in decentralized markets if the use of credit is costly. Our analysis easily extends itself to other payment systems like credit cards that provide a group identity to otherwise anonymous agents.Communal responsibility, anonymous matching, money demand, credit, bills of exchange

Communal Responsibility and the Coexistence of Money and Credit under Anonymous Matching

Communal responsibility, a medieval institution studied by Greif (2006), supported the use of credit among European merchants in the absence of modern enforcement technologies. This paper shows how this mechanism helps to overcome enforcement problems in anonymous buyer/seller transactions. In a village economy version of the Lagos and Wright (2005) model, agents trading anonymously in decentralized markets can be identified by their citizenship and thus be held liable for each other. Enforceability within each village's centralized afternoon market ensures collateralization of credit in decentralized markets. In the resulting equilibrium, money and credit coexist in decentralized markets if the use of credit is costly. Our analysis easily extends itself to other payment systems like credit cards that provide a group identity to otherwise anonymous agents.Communal responsibility, anonymous matching, money demand, credit, bills of exchange

Process-Based Design and Integration of Wireless Sensor Network Applications

Abstract Wireless Sensor and Actuator Networks (WSNs) are distributed sensor and actuator networks that monitor and control real-world phenomena, enabling the integration of the physical with the virtual world. They are used in domains like building automation, control systems, remote healthcare, etc., which are all highly process-driven. Today, tools and insights of Business Process Modeling (BPM) are not used to model WSN logic, as BPM focuses mostly on the coordination of people and IT systems and neglects the integration of embedded IT. WSN development still requires significant special-purpose, low-level, and manual coding of process logic. By exploiting similarities between WSN applications and business processes, this work aims to create a holistic system enabling the modeling and execution of executable processes that integrate, coordinate, and control WSNs. Concretely, we present a WSNspecific extension for Business Process Modeling Notation (BPMN) and a compiler that transforms the extended BPMN models into WSN-specific code to distribute process execution over both a WSN and a standard business process engine. The developed tool-chain allows modeling of an independent control loop for the WSN.

Communal Responsibility and the Coexistence of Money and Credit Under Anonymous Matching

Communal responsibility, a medieval institution studied by Greif (2006), supported the use of credit among European merchants in the absence of modern enforcement technologies. This paper shows how this mechanism helps to overcome enforcement problems in anonymous buyer/seller transactions. In a village economy version of the Lagos and Wright (2005) model, agents trading anonymously in decentralized markets can be identified by their citizenship and thus be held liable for each other. Enforceability within each village's centralized afternoon market ensures collateralization of credit in decentralized markets. In the resulting equilibrium, money and credit coexist in decentralized markets if the use of credit is costly. Our analysis easily extends itself to other payment systems like credit cards that provide a group identity to otherwise anonymous agents.Communal responsibility, anonymous matching, money demand, credit, bills of exchange

Rankine Cycle efficiency gain using thermoelectric heat pumps

The Rankine cycle remains the dominant method of thermal plant electricity generation in the world today. The cycle was described over 150 years ago and significant performance advances continue to be realised. On-going metallurgy research has enabled the operating pressure and temperature of the boiler and turbine to be increased, thereby improving the cycle efficiency. The ubiquitous use of the Rankine cycle on a massive scale in conjunction with fossil fuels as the energy source continues to motivate further efficiency improvements in the cycle.<p></p> Previous work established a theoretical basis for the use of thermoelectric heat pumps (THPs) in the condensation process of the Rankine cycle to positively impact cycle efficiency. The work presented here experimentally validates this prior work and provides performance metrics for current commercially available THPs and quantifies how their use can increase the efficiency of the Rankine cycle as implemented in a large power plant.<p></p> A commercial THP is characterised to obtain its Coefficient of Performance (COP) variation with input current and the amount of thermal energy transported. A larger-scale system comprising of a multistage thermoelectric heat pump is then considered, demonstrating that using commonly available THPs a fuel load reduction of over 1.5% is achievable for a typical generating set whilst simultaneously increasing the overall plant cycle efficiency from 44.9% to 45.05%.<p></p> The paper concludes with a cost-benefit analysis of the system, showing that over a four year period the saving in fuel used can easily re-coup the capital cost incurred by the addition of the condenser heat pump