Proxy Implementation Research Articles

Information Stratification: An Understanding of Rural Governance in the New Media Era

Current research on media governance emphasizes the technological aspect of information as a tool but lacks sufficient attention to the digital transformation of information subjects. This paper aims to focus on the internal information characteristics of rural governance in the digital age, thus understanding the changes of rural governance subjects in the information society under new media contexts. Based on more than a decade of fieldwork in rural areas of Beijing conducted by the research team, this study employs in-depth interviews and participant observation in a multi-case study, exploring the structural representation of rural governance from an information perspective. The research reveals that in the new media era, rural society, under multiple governance bodies, generates differentiated information stratification, specifically manifesting as instrumental rational information in the formal governance layer, proxy implementation information in the semi-formal governance layer, and livelihood-adaptive information in the informal governance layer. Among these, the authority-driven governance information in the formal layer is the core part of the rural governance system. The subjects and structures of information under multiple governance bodies are interconnected and coexist within the internal field of rural governance, subsequently driving the centralization of formal governance information, the collaboration of semi-formal governance information, and the alienation of informal governance information. This leads to the emergence of orderly information stratification within the multi-layered governance structure. Information stratification deepens the explanatory pathway of multi-layered governance in rural social studies and proposes new perspectives for understanding rural governance issues in the new media era.

Selecting the best solar EUV proxy for long-term timescale applications

Solar EUV proxies are a solution to the difficulties in obtaining solar EUV time series covering extended periods or during times without measurements available. Despite being very similar at interannual and decadal timescales, proxies are not identical. The upper atmosphere, highly sensitive to this spectral range, can serve as a “witness” of solar EUV variations to help selecting the best proxy. Its choice can be critical depending on the problem we are trying to solve through the proxy implementation and on the nature of the proxies’ non-identical part variation. We analyze the best proxy selection process whose outcome depends on the method and on the physics knowledge we have of the system. This study aims to contribute and highlight certain critical aspects of selection methodologies. A case where this issue becomes critical is upper atmosphere long-term trends’ estimation in order to detect the increasing greenhouse gas effect along the last decades.

A proxy implementation of thermal pressurization for earthquake cycle modelling on rate-and-state faults

SUMMARY The reduction of effective normal stress during earthquake slip due to thermal pressurization of fault zone pore fluids is a significant fault weakening mechanism. Explicit incorporation of this process into frictional fault models involves solving the diffusion equations for fluid pressure and temperature outside the fault at each time step, which significantly increases the computational complexity. Here, we propose a proxy for thermal pressurization implemented through a modification of the rate-and-state friction law. This approach is designed to emulate the fault weakening and the relationship between breakdown energy and slip resulting from thermal pressurization and is appropriate for fully dynamic simulations of multiple earthquake cycles. It preserves the computational efficiency of conventional rate-and-state friction models, which in turn can enable systematic studies to advance our understanding of the effects of fault weakening on earthquake mechanics. In 2.5-D simulations of pulse-like ruptures on faults with finite seismogenic width, based on our thermal pressurization proxy, we find that the spatial distribution of slip velocity near the rupture front is consistent with the conventional square-root singularity, despite continued slip-weakening within the pulse, once the rupture has propagated a distance larger than the rupture width. An unconventional singularity appears only at shorter rupture distances. We further derive and verify numerically a theoretical estimate of the breakdown energy dissipated by our implementation of thermal pressurization. These results support the use of fracture mechanics theory to understand the propagation and arrest of very large earthquakes.

Design of a Standard and Programmatically Accessible Interface for Smart Meters to Allow Monitoring Automation of the Energy Consumed by the Execution of Computer Software

Software has become more computationally demanding nowadays, turning out high-performance software in many cases, implying higher energy and economic expenditure. Indeed, many studies have arisen within the IT community to mitigate the environmental impact of software. Collecting and measuring software’s power consumption has become an essential task. This paper proposes the design of a standard interface for any currently available smart meter, which is programmatically accessible from any software application and can collect consumption data transparently while a program is executed. This interface is structured into two layers. The former is a driver that provides an OS-level standard interface to the meter, while the latter is a proxy offering higher-level API for a concrete programming language. This design provides many benefits. It makes it possible to substitute the meter for a different device without affecting the proxy layer. It also allows the presence of multiple proxy implementations to offer a programmatic interface to the meter for several languages. A prototype of the proposed interface design has been implemented for a concrete smart meter and OS to demonstrate its feasibility. It has been tested with two experiments. Firstly, its correct functioning has been validated. Later, the prototype has been applied to monitor the execution of a high-performance program, a machine learning application to select the most relevant features of electroencephalogram data.

Capture of real-time data from electronic health records: scenarios and solutions.

The integration of real-time data (RTD) in the electronic health records (EHRs) is transforming the healthcare of tomorrow. In this work, the common scenarios of capturing RTD in the healthcare from EHRs are studied and the approaches and tools to implement real-time solutions are investigated. Delivering RTD by representational state transfer (REST) application programming interfaces (APIs) is usually accomplished through a Publish-Subscribe approach. Common technologies and protocols used for implementing subscriptions are REST hooks and WebSockets. Polling is a straightforward mechanism for obtaining updates; nevertheless, it may not be the most efficient or scalable solution. In such cases, other approaches are often preferred. Database triggers and reverse proxies can be useful in RTD scenarios; however, they should be designed carefully to avoid performance bottlenecks and potential issues. The implementation of subscriptions through REST hooks and WebSocket notifications using a Fast Healthcare Interoperability Resources (FHIR) REST API, as well as the design of a reverse proxy and database triggers is described. Reference implementations of the solutions are provided in a GitHub repository. For the reverse proxy implementation, the Go language (Golang) was used, which is specialized for the development of server-side networking applications. For FHIR servers a python script is provided to create a sample Subscription resource to send RTD when a new Observation resource for specific patient id is created. The sample WebSocket client is written using the "websocket-client" python library. The sample RTD endpoint is created using the "Flask" framework. For database triggers a sample structured query language (SQL) query for Postgres to create a trigger when an INSERT or UPDATE operation is executed on the FHIR resource table is available. Furthermore, a use case clinical example, where the main actors are the healthcare providers (hospitals, physician private practices, general practitioners and medical laboratories), health information networks and the patient are drawn. The RTD flow and exchange is shown in detail and how it could improve healthcare. Capturing RTD is undoubtedly vital for health professionals and successful digital healthcare. The topic remains unexplored especially in the context of EHRs. In our work for the first time the common scenarios and problems are investigated. Furthermore, solutions and reference implementations are provided which could support and contribute to the development of real-time applications.

A Disequilibrium Reactive Transport Model for Mantle Magmatism

AbstractBesides standard thermo-mechanical conservation laws, a general description of mantle magmatism requires the simultaneous consideration of phase changes (e.g. from solid to liquid), chemical reactions (i.e. exchange of chemical components) and multiple dynamic phases (e.g. liquid percolating through a deforming matrix). Typically, these processes evolve at different rates, over multiple spatial scales and exhibit complex feedback loops and disequilibrium features. Partially as a result of these complexities, integrated descriptions of the thermal, mechanical and chemical evolution of mantle magmatism have been challenging for numerical models. Here we present a conceptual and numerical model that provides a versatile platform to study the dynamics and nonlinear feedbacks inherent in mantle magmatism and to make quantitative comparisons between petrological and geochemical datasets. Our model is based on the combination of three main modules: (1) a Two-Phase, Multi-Component, Reactive Transport module that describes how liquids and solids evolve in space and time; (2) a melting formalism, called Dynamic Disequilibirum Melting, based on thermodynamic grounds and capable of describing the chemical exchange of major elements between phases in disequilibrium; (3) a grain-scale model for diffusion-controlled trace-element mass transfer. We illustrate some of the benefits of the model by analyzing both major and trace elements during mantle magmatism in a mid-ocean ridge-like context. We systematically explore the effects of mantle potential temperature, upwelling velocity, degree of equilibrium and hetererogeneous sources on the compositional variability of melts and residual peridotites. Our model not only reproduces the main thermo-chemical features of decompression melting but also predicts counter-intuitive differentiation trends as a consequence of phase changes and transport occurring in disequilibrium. These include a negative correlation between Na2O and FeO in melts generated at the same Tp and the continued increase of the melt’s CaO/Al2O3 after Cpx exhaustion. Our model results also emphasize the role of disequilibrium arising from diffusion for the interpretation of trace-element signatures. The latter is shown to be able to reconcile the major- and trace-element compositions of abyssal peridotites with field evidence indicating extensive reaction between peridotites and melts. The combination of chemical disequilibrium of major elements and sluggish diffusion of trace elements may also result in weakened middle rare earth to heavy rare earth depletion comparable with the effect of residual garnet in mid-ocean ridge basalt, despite its absence in the modelled melts source. We also find that the crystallization of basalts ascending in disequilibrium through the asthenospheric mantle could be responsible for the formation of olivine gabbros and wehrlites that are observed in the deep sections of ophiolites. The presented framework is general and readily extendable to accommodate additional processes of geological relevance (e.g. melting in the presence of volatiles and/or of complex heterogeneous sources, refertilization of the lithospheric mantle, magma channelization and shallow processes) and the implementation of other geochemical and isotopic proxies. Here we illustrate the effect of heterogeneous sources on the thermo-mechanical-chemical evolution of melts and residues using a mixed peridotite–pyroxenite source.

A novel caching algorithm for VoD proxy implementation and its evaluation including a new set of metrics for efficiency analysis

Video on demand (VoD) is a fast-growing digital service that requires a substantial amount of hardware resources for its implementation. To reduce the costs of running this service, an alternative is to use proxies that cache the most important portions of the video collection in order to meet the demand for this content in place of the primary server of the VoD system. To improve the efficiency of the proxies, we proposed a novel caching algorithm that explores the positioning of the active clients to determine the density of clients inside a time window existing in front of each video chunk. The algorithm attributes a higher caching priority to the video chunks with greater aggregate density in the memory. To evaluate our approach, we compared it with others of similar nature using both traditional metrics like hit ratio, as well as physical metrics such as the use of processing resources. This complementary set of metrics is produced by our simulator that, as far as we know, is the first one of its kind to enable the evaluation of hardware consumption used to implement the VoD proxy. Results show that the novel algorithm can achieve a higher hit ratio while requiring a little more effort from the hardware. Additionally, it was identified that the processor constitutes the major bottleneck to this application when demand increases. Among the recent emergence of caching strategies which consider the positioning of clients as criterion for caching, the strategy of prioritizing the chunks with greater density of previous clients showed to be a more efficient solution.

CCNxTomcat: An extended web server for Content-Centric Networking

TCP/IP networks are the backbone of the Internet today, and browser/server is the mainstream web architecture on it. Recently, Content-Centric Networking (CCN) has emerged as a clean-slate future network architecture, with totally different protocols than a host-based TCP/IP network. However, current web servers are mainly designed for HTTP over a TCP/IP network and can not directly support CCN-based web applications. Therefore, how to effectively support the dominant browser-based web applications is a key to the success of CCN. Instead of providing a transitional HTTP/CCN transforming gateway or proxy, we design and develop the first practical CCN-enabled web server (called CCNxTomcat) based on open source Apache Tomcat and the CCNx library to natively support CCN-based web applications. The CCN functions are integrated into the web server for content distribution by seamlessly coordinating with the underlying CCN network. To support legacy applications and a smooth evolution from an IP network to CCN, CCNxTomcat also supports the HTTP protocol besides the CCN. Experimental results show that CCNxTomcat outperforms the existing HTTP/CCN proxy implementations by 58% in a single request, and by a factor of three in 1000 concurrent requests, in terms of throughput. Furthermore, we design and implement a novel cache (called ccncache) for the Servlet response, performing name lookups for Content Packets with a high efficiency. The results indicate that ccncache is 2.5 times faster than the existing CCNx Content Store, with only 30% additional memory consumption. In addition, a real CCN-based web application is deployed on a CCN experimental network, which validates the applicability of CCNxTomcat.

Ghost: A uniform and general-purpose proxy implementation

A proxy object is a surrogate or placeholder that controls access to another target object. Proxy objects are a widely used solution for different scenarios such as remote method invocation, future objects, behavioral reflection, object databases, inter-language communications and bindings, access control, lazy or parallel evaluation, security, among others.Most proxy implementations support proxies for regular objects but are unable to create proxies for objects with an important role in the runtime infrastructure such as classes or methods. Proxies can be complex to install, they can have a significant overhead, they can be limited to certain kind of classes, etc. Moreover, proxy implementations are often not stratified and there is no clear separation between proxies (the objects intercepting messages) and handlers (the objects handling interceptions).In this paper, we present Ghost: a uniform and general-purpose proxy implementation for the Pharo programming language. Ghost provides low memory consuming proxies for regular objects as well as for classes and methods.When a proxy takes the place of a class, it intercepts both the messages received by the class and the lookup of methods for messages received by its instances. Similarly, if a proxy takes the place of a method, then the method execution is intercepted too.

Network proxy research and implementation for Internet of things applications based on constrained application protocol

To solve the problem of high technology bottleneck caused by the three-layer research and development independence of Internet of Things( IoT), a solution based on Constrained Application Protocol( CoAP) was proposed. This solution developed CoAP-HTTP network proxy based on CoAP implementation, which enabled users to access the IoT node resources through the browser directly, to discover resources, to query data and to subscribe resources, etc. The test results show that the proxy mode does not affect the response rate of the system and it is stable enough to support multiple users accessing the network node data at the same time. The CoAP Agent model can help application developers circumvent the complexity of low-level software development and data exchange development; hence they are able to generate a new application independently. The CoAP Agent model provides a new way for the application development of IoT.

Safe uniform proxies for Java

The proxy abstraction has a long-lasting tradition in object-oriented programming. From design patterns to inherent programming language support, and from remote method invocations to simple forms of behavioral reflection, incarnations as well as applications of proxies are innumerable.Since version 1.3, Java has supported the concept of a dynamic proxy. Such an object conforms to a set of types specified by the program and can be used wherever an expression of any of these types is expected, yet it reifies invocations performed on it. This ability has allowed dynamic proxies to be used to implement paradigms such as behavioral reflection, structural conformance, or multi-methods. Alas, these proxies are only available “for interfaces”. The case of creating dynamic proxies for a set of types including a class has not been addressed, meaning that it is currently not possible to create a dynamic proxy that conforms to an application-defined class type. This weakness strongly limits any application of dynamic proxies beyond the inherent limitations of proxies, which have motivated deeper programming language support for features such as behavioral reflection.In this paper, we unfold the current support for dynamic proxies in Java, assessing it in the light of a set of generic criteria for proxy implementations. We present an approach to supporting dynamic proxies “for classes”, consisting in transformations performed on classes at load-time, including a generic scheme for enforcing encapsulation upon field accesses. These transformations seamlessly extend the scope of the current support for dynamic proxies from the programmer’s perspective. We argue for the safety of our transformations, and discuss the precise benefits and costs of our extension in terms of the criteria introduced through an implementation of future method invocations balancing safety and transparency.

Improving quality of experience in wireless VoIP through novel call scheduling

In the last few years we have experienced a dramatic increase in the use of IP networks for voice applications (VoIP) over wireless networks due to increased bandwidth availability and enhanced device capabilities. Since demand often exceeds available capacity, Call Admission Control mechanisms are in place to prevent the uncontrolled usage of bandwidth. Through the use of an intermediary gateway, VoIP calls are in many cases terminated to a normal landline or cellphone; the capacity of such a gateway is also a finite resource since the number of users can vary significantly as many are mobile. In this article we propose an enhanced scheme that aims to manage access to the lines available so that they are used in a fair manner and utilized to the highest degree possible. This management is facilitated by enhancing a proxy implementation with a number of call scheduling policies. The ability to satisfy pending call requests as soon as lines become available, results in increased user service satisfaction. Moreover, it increases line utilization which is crucial from an economic viewpoint. The ultimate goal is to improve Quality of Experience which is deemed as highly important especially considering that wireless network users experience opportunistic and intermittent connectivity.

Expanding mobile ad hoc grids with wired grid resources

PurposeAlthough wireless grids have been originally thought of as isolated processing clusters, the possibility of their approaching – and connecting to – a fixed network allows for a huge expansion of their processing power, due to the resources available in wired grids potentially accessible through such a network. The interoperation of mobile ad hoc grids and resources available in wired grids is, however, a problem still to be tackled in the literature. The purpose of this paper is to tackle this problem.Design/methodology/approachA prototype is developed to demonstrate the feasibility of the interoperation between wireless and wired grids, thus providing a basis for the development of novel applications that can build on this interoperation.FindingsThe outcome of the paper comprises the analysis of the necessary requirements for the interoperation between wireless and wired grids, the proposal of two different interoperation approaches, and the provision of a qualitative assessment of the implications of these approaches.Research limitations/implicationsThere are many points that the authors intend to address as future work. First, they are aware of the need for performing some quantitative analyses of their proxy implementations. Second, they intend to investigate the possibility of mobile ad hoc grids to process tasks coming from wired grids. Third, they are interested in allowing the submission of tasks that present interdependencies (workflows) from mobile devices in the mobile ad hoc grid.Practical implicationsThe paper investigates the interoperation of wireless and wired grids. Such an interoperation may open new perspectives of practical use of wireless devices in scenarios such as emergency response networks and field research systems, to name a few.Originality/valueThe paper provides a first step into the interoperation of wireless and wired grids, thus yielding a basis for the development of novel applications that can build upon this interoperation. This is believed to be of interest to both the grid and mobile computing communities.

Uniform proxies for Java

The proxy abstraction has a longlasting tradition in object settings. From design pattern to inherent language support, from remote method invocations to simple forms of behavioral reflection - incarnations as well as applications of proxies are innumerable.Since version 1.3, Java supports the concept of dynamic proxy. Such an object conforms to a set of types specified by the program and can be used wherever an expression of any of these types is expected, yet reifies invocations performed on it. Dynamic proxies have been applied to implement paradigms as diverse as behavioral reflection, structural conformance, or multi-methods. Alas, these proxies are only available "for interfaces". The case of creating dynamic proxies for a set of types including a class type has not been considered, meaning that it is currently not possible to create a dynamic proxy mimicking an instance of a given class. This weakness strongly limits any application of dynamic proxies.In this paper we unfold the current support for dynamic proxies in Java, assessing it in the light of a set of generic criteria for proxy implementations. We present an approach to supporting dynamic proxies "for classes" in Java, consisting in transformations performed on classes at load-time, including a generic scheme for enforcing encapsulation upon field accesses. These transformations seemlessly extend the scope of the current support for dynamic proxies. We discuss the precise benefits and costs of our extension in terms of the criteria introduced, and illustrate the usefulness of uniformly available proxies by implementing future method invocations both safely and transparently.

Measuring proxy performance with the Wisconsin Proxy Benchmark

As Web proxies become increasingly widespread, there is a critical need to establish a benchmark that can compare the performance of different proxy servers and predict their performance in practice. In this paper, we describe the Wisconsin Proxy Benchmark (WPB) and the performance comparison of four proxy software using the benchmark. Using the benchmark, we also study the effect of more disk arms on proxy performance, and the effect of low-bandwidth modem client connections. We find that proxy implementations differ in their performance characteristics significantly. In addition, though disk arms appear to be the bottleneck limiting proxy throughput, adding extra disks does not result in performance improvement for every proxy implementation. Finally, we find that the latency advantage of caching proxies vanishes in the presence of modem connections.