Circular Dependency Research Articles

STUDY OF MACRO-BENDING OF POLYMER FIBER IN MULTIMODE POF COUPLERS DEVELOPMENT BY LAPPING TECHNIQUE

An experimental study of coupling efficiency of a circular multimode fiber coupler dependency of radiation from macro-bending is investigated. The study is done by experimental set-up using various radii of circular blocks customized with matching refractive index material. The aim is to provide a considerable explanation on the differences in splitting ratio, excess loss and insertion loss when different bending radii due to radii of circular blocks is applied to the couplers. Other factors that contribute to the characterization of the coupler include fiber diameters and forces exerted upon the two fibers that lapped together forming the coupler developed. The technique used is proven to develop a low-cost coupler using mechanical lapping technique.

Planning Wafer Starts Using Nonlinear Clearing Functions: A Large-Scale Experiment

The nonlinear, circular dependency between workload and cycle times for production resources governed by queueing behavior has been a longstanding difficulty in the production planning domain. The issue is particularly important for semiconductor wafer fabrication facilities, which must operate at relatively high utilization to be profitable. Nonlinear clearing functions that relate the expected output of a resource in a planning period to the amount of work available to it have been proposed as an alternative approach. While computational tests on small systems have been promising, the question of whether the results remain valid for large-scale systems has remained open. In this paper we evaluate the performance of a clearing function based production planning model using a simulation of a large-scale wafer fab with two products and several hundred operations. Results indicate that, consistent with the results of previous experiments, the clearing function model yields substantial improvements in profit over conventional linear programming models.

Prevention slot flow‐control mechanism for low latency torus network‐on‐chip

The challenge for on-chip networks is to provide low latency communication in a very low power budget. To reduce the latency and maintain the simplicity of a mesh topology, torus topology is proposed. As torus topology has an inherent circular dependency, additional effort is needed to prevent deadlock, even if deadlock free routing algorithms are used. The authors propose a novel flow-control mechanism to address cost/performance constraints in torus networks and ensure deadlock freedom. They achieve flow-control by using a prevention mechanism and ensure deadlock freedom while requiring only a single packet buffer per input port. They simplify the router design by having a simple switch allocator that prioritises in-flight packets, and a single packet buffer per input port that eliminates the need for virtual channels. They also propose a mechanism to avoid starvation that can arise because of the prioritised arbitration. Experimental validation reveals that the authors design achieves significant improvement in throughput, as compared with the traditional design, while using significantly fewer buffers.

Efficient Spread Spectrum Communication without Preshared Secrets

Spread spectrum (SS) communication relies on the assumption that some secret is shared beforehand among communicating nodes to establish the spreading sequence for long-term wireless communication. Strasser et al. identified this as the circular dependency problem (CDP). This problem is exacerbated in large networks, where nodes join and leave the network frequently, and preconfiguration of secrets through physical contact is infeasible. In this work, we introduce an efficient and adversary-resilient secret sharing mechanism based on two novel paradigms (intractable forward decoding, efficient backward decoding) called Time Reversed Message Extraction and Key Scheduling (TREKS) that enables SS communication without preshared secrets. TREKS is four orders of magnitude faster than previous solutions to the CDP. Furthermore, our approach can be used to operate long-term SS communication without establishing any keys. The energy cost under TREKS is provably optimal with minimal storage overhead, and computation cost at most twice that of traditional SS. We evaluate TREKS through simulation and empirically using an experimental testbed consisting of USRP, GNU Radio, and GPU-equipped nodes. Using TREKS under a modest hardware setup, we can sustain a 1--Mbps long-term SS communication spread by a factor of 100 (i.e., 100 Megachips per second) over a 200-MHz bandwidth in real time.

An explicit physics-based model of ionic polymer-metal composite actuators

The Poisson-Nernst-Planck system of equations is used to simulate the charge dynamics due to ionic current and resulting time-dependent displacement of ionic polymer-metal composite (IPMC) materials. Measured data show that currents through the polymer of IPMC cause potential gradients on the electrodes. Existing physics based models of IPMC do not explicitly consider how this affects the charge formation near the electrodes and resulting actuation of IPMC. We have developed an explicit physics based model that couples the currents in the polymer to the electric current in the continuous electrodes of IPMC. The coupling is based on the Ramo-Shockley theorem. The circular dependency concept is used to explain how the dependency between the ionic current and the potential drop in the electrodes is calculated and how they affect each other. Simulations were carried out using the finite element method. Calculated potential gradients, electric currents, and tip displacement of IPMC were validated against experimental data. We also show how the model is general in respect to the different types of currents in the polymer and how it can be used in more complicated cases such as 3D simulations.

Context-aware trust negotiation in peer-to-peer service collaborations

Service-oriented architecture (SOA) and Software as a Service (SaaS) are the latest hot topics to software manufacturing and delivering, and attempt to provide a dynamic cross-organisational business integration solution. In a dynamic cross-organisational collaboration environment, services involved in a business process are generally provided by different organisations, and lack supports of common security mechanisms and centralized management middleware. On such occasions, services may have to achieve middleware functionalities and achieve business objectives in a pure peer-to-peer fashion. As the participating services involved in a business process may be selected and combined at run time, a participating service may have to collaborate with multiple participating services which it has no pre-existing knowledge in prior. This introduces some new challenges to traditional trust management mechanisms. Automated Trust Negotiation (ATN) is a practical approach which helps to generate mutual trust relationship for collaborating principals which may have no pre-existing knowledge about each other without in a peer-to-peer way. Because credentials often contain sensitive attributes, ATN defines an iterative and bilateral negotiation process for credentials exchange and specifies security policies that regulate the disclosure of sensitive credentials. Credentials disclosure in the iterative process may follow different orders and combinations, each of which forms a credential chain. It is practically desirable to identify the optimal credential chain that satisfies certain objectives such as minimum release of sensitive information and minimum performance penalty. In this paper we present a heuristic and context-aware algorithm for identifying the optimal chain that uses context-related knowledge to minimize 1) the release of sensitive information including both credentials and policies and 2) the cost of credentials retrieving. Moreover, our solution offers a hierarchical method for protecting sensitive policies and provides a risk-based strategy for handling credential circular dependency. We have implemented the ATN mechanisms based on our algorithm and incorporated them into the CROWN Grid middleware. Experimental results demonstrate their performance-related advantages over other existing solutions.

Bootstrapping for extracting relations from large corpora

A new approach of relation extraction is described in this paper. It adopts a bootstrapping model with a novel iteration strategy, which generates more precise examples of specific relation. Compared with previous methods, the proposed method has three main advantages: first, it needs less manual intervention; second, more abundant and reasonable information are introduced to represent a relation pattern; third, it reduces the risk of circular dependency occurrence in bootstrapping. Scalable evaluation methodology and metrics are developed for our task with comparable techniques over TianWang 100G corpus. The experimental results show that it can get 90% precision and have excellent expansibility.

Robust Adaptive Metrics for Deadline Assignment in Distributed Hard Real-Time Systems

Distributed real-time applications usually consist of several component tasks and must be completed by its end-to-end (E-T-E) deadline. As long as the E-T-E deadline of an application is met, the strategy used for dividing it up for component tasks does not affect the application itself. One would therefore like to “slice” each application E-T-E deadline and assign the slices to component tasks so as to maximize the schedulability of the component tasks, and hence the application. Distribution of the E-T-E deadline over component tasks is a difficult and important problem since there exists a circular dependency between deadline distribution and task assignment. We propose a new deadline-distribution scheme which has two major improvements over the best scheme known to date. It can distribute task deadlines prior to task assignment and relies on new adaptive metrics that yield significantly better performance in the presence of high resource contention. The deadline-distribution problem is formulated for distributed hard real-time systems with relaxed locality constraints, where schedulability analysis must be performed at pre-run-time, and only a subset of the tasks are constrained by pre-assignment to specific processors. Although it is applicable to any scheduling policy, the proposed deadline-distribution scheme is evaluated for a non-preemptive, time-driven scheduling policy. Using extensive simulations, we show that the proposed adaptive metrics deliver much better performance (in terms of success ratio and maximum task lateness) than their non-adaptive counterparts. In particular, the simulation results indicate that, for small systems, the adaptive metrics can improve the success ratio by as much as an order of magnitude. Moreover, the new adaptive metrics are found to exhibit very robust performance over a large variety of application and architecture scenarios.

Cache investment

Emerging distributed query-processing systems support flexible execution strategies in which each query can be run using a combination of data shipping and query shipping. As in any distributed environment, these systems can obtain tremendous performance and availability benefits by employing dynamic data caching. When flexible execution and dynamic caching are combined, however, a circular dependency arises: Caching occurs as a by-product of query operator placement, but query operator placement decisions are based on (cached) data location. The practical impact of this dependency is that query optimization decisions that appear valid on a per-query basis can actually cause suboptimal performance for all queries in the long run. To address this problem, we developed Cache Investment - a novel approach for integrating query optimization and data placement that looks beyond the performance of a single query. Cache Investment sometimes intentionally generates a “suboptimal” plan for a particular query in the interest of effecting a better data placement for subsequent queries. Cache Investment can be integrated into a distributed database system without changing the internals of the query optimizer. In this paper, we propose Cache Investment mechanisms and policies and analyze their performance. The analysis uses results from both an implementation on the SHORE storage manager and a detailed simulation model. Our results show that Cache Investment can significantly improve the overall performance of a system and demonstrate the trade-offs among various alternative policies.

Thoughts on saving the world's rain forests

The proposed work aims at visual subspace clustering and addresses two challenges: an efficient visual subspace clustering workflow and an intuitive visual description of subspace structure. Handling the first challenge is to escape the circular dependency between detecting meaningful subspaces and discovering clusters. We propose a dimension relevance measure to indicate the cluster significance in the corresponding subspace. The dynamic dimension relevance guides the subspace exploring in our visual analysis system. To address the second challenge, we propose hyper-graph and the visualization of it to describe the structure of subspaces. Dimension overlapping between subspaces and data overlapping between clusters are clearly shown with our visual design. Experimental results demonstrate that our approach is intuitive, efficient, and robust in visual subspace clustering.

Natürliche 13C-Isotopenmarkierung in Bäumen

Summary Isotopic ratios of carbon in wood samples from annual rings were measured in order to obtain information about the long-term 13 C/ 12 C-trend in atmospheric CO 2 . The results cannot be interpreted in terms of variations in the 13 C/ 12 C-ratio in the atmosphere alone, but must also allow for the influence of biological factors. The small but accurately measurable fluctuations in the order of 2 ‰ (relative) are considered to be of importance, as regarded in their role as a natural isotopic labelling useful in plant physiological research. The δ 13 C-dependence on stem height of only 0.01 ‰ · m -1 was small in comparison with oscillations in the horizontal direction in wood slices (circular dependency). The absence of any remarkable isotopic fractionation in the vertical direction allows the correlative analysis of stem sections supplied by the same phloem current. The δ 13 C-value for lignin in Quercus was found to be significantly negative with respect to that for cellulose, thus reflecting isotopic effects in the various steps via which the former substance is synthesized.