Unification in a Parallel Environment

This paper presents a method which allows standard data structure sharing techniques to be applied in a parallel environment. The techniques used are explained in the context of many parallel processors executing the same unification algorithm on different data concurrently. This operation can create complex structures to be transmitted between processors and naive algorithms could take an exponential amount of time to achieve the communication. The approach is compared to that advocated for the FFP machine. To demonstrate the techniques, we describe how a linear unification algorithm may be executed locally at each parallel processor and a single chosen resolvent communicated through an interconnection network to other processors. The structures are transmitted without applying substitutions and can be recreated at the receiver. The algorithms were developed as part of basic research related to the parallel Logic Programming System (LPS) under design at Columbia University. They have been implemented on a working prototype parallel machine, DADO1

Effective Scheduling of Grid Resources Using Failure Prediction

In large-scale grid environments, accurate failure prediction is critical to achieve effective resource allocation while assuring specified QoS levels, such as reliability. Traditional methods, such as statistical estimation techniques, can be considered to predict the reliability of resources. However, naive statistical methods often ignore critical characteristic behavior of the resources. In particular, periodic behaviors of grid resources are not captured well by statistical methods. In this paper, we present an alternative mechanism for failure prediction. In our approach, the periodic pattern of resource failures are determined and actively exploited for resource allocation with better QoS guarantees. The proposed scheme is evaluated under a realistic simulation environment of computational grids. The availability of computing resources are simulated according to real trace that was collected from our large-scale monitoring experiment on campus computers. Our evaluation results show that the proposed approach enables significantly higher resource scheduling effectiveness under a variety of workloads compared to baseline approaches

March Test Generation Revealed

Memory testing commonly faces two issues: the characterization of detailed and realistic fault models and the definition of time-efficient test algorithms. Among the different types of algorithms proposed for testing static random access memories, march tests have proven to be faster, simpler, and regularly structured. The majority of the published march tests have been manually generated. Unfortunately, the continuous evolution of the memory technology introduces new classes of faults such as dynamic and linked faults and makes the task of handwriting test algorithms harder and not always leading to optimal results. Although some researchers published handmade march tests able to deal with new fault models, the problem of a comprehensive methodology to automatically generate march tests addressing both classic and new fault models is still an open issue. This paper proposes a new polynomial algorithm to automatically generate march tests. The formal model adopted to represent memory faults allows the definition of a general methodology to deal with static, dynamic, and linked faults. Experimental results show that the new automatically generated march tests reduce the test complexity and, therefore, the test time, compared to the well-known state of the art in memory testin

Harmonising Coexistence of Machine Type Communications with Wi-Fi Data Traffic under Frame-Based LBT

© 1972-2012 IEEE. The existence of relatively long LTE data blocks within the licensed-assisted access (LAA) framework results in bursty machine-type communications (MTC) packet arrivals, which cause system performance degradation and present new challenges in Markov modeling. We develop an embedded Markov chain to characterize the dynamic behavior of the contention arising from bursty MTC and Wi-Fi data traffic in the LAA framework. Our theoretical model reveals a high-contention phenomenon caused by the bursty MTC traffic, and quantifies the resulting performance degradation for both MTC and Wi-Fi data traffic. The Markov model is further developed to evaluate three potential solutions aiming to alleviate the contention. Our analysis shows that simply expanding the contention window, although successful in reducing congestion, may cause unacceptable MTC data loss. A TDMA scheme instead achieves better MTC packet delivery and overall throughput, but requires centralized coordination. We propose a distributed scheme that randomly spreads the MTC access processes through the available time period. Our model results, validated by simulations, demonstrate that the random spreading solution achieves a near TDMA performance, while preserving the distributed nature of the Wi-Fi protocol. It alleviates the MTC traffic contention and improves the overall throughput by up to 10%

PUBA: Privacy-Preserving User-Data Bookkeeping and Analytics

In this paper we propose Privacy-preserving User-data Bookkeeping & Analytics (PUBA), a building block destined to enable the implementation of business models (e.g., targeted advertising) and regulations (e.g., fraud detection) requiring user-data analysis in a privacy-preserving way. In PUBA, users keep an unlinkable but authenticated cryptographic logbook containing their historic data on their device. This logbook can only be updated by the operator while its content is not revealed. Users can take part in a privacy-preserving analytics computation, where it is ensured that their logbook is up-to-date and authentic while the potentially secret analytics function is verified to be privacy-friendly. Taking constrained devices into account, users may also outsource analytic computations (to a potentially malicious proxy not colluding with the operator).We model our novel building block in the Universal Composability framework and provide a practical protocol instantiation. To demonstrate the flexibility of PUBA, we sketch instantiations of privacy-preserving fraud detection and targeted advertising, although it could be used in many more scenarios, e.g. data analytics for multi-modal transportation systems. We implemented our bookkeeping protocols and an exemplary outsourced analytics computation based on logistic regression using the MP-SPDZ MPC framework. Performance evaluations using a smartphone as user device and more powerful hardware for operator and proxy suggest that PUBA for smaller logbooks can indeed be practical

Impacts of transitioning from firm fixed price to fixed price incentive firm target contracts in PEO Missiles and Space

The objective of this project is to analyze the impacts to major weapon systems programs in Program Executive Office (PEO) Missiles and Space as a result of transitioning from firm fixed price (FFP) contracts to fixed price incentive firm target (FPIF) contracts. This project presents an in-depth examination of FFP and FPIF contract types, including definitions, profit mechanisms, and advantages and disadvantages associated with each type. This project reviews three iterations of Better Buying Power, with a specific focus on profitability and the use of FPIF contracts. The project presents and analyzes data collected through interviews with PEO Missiles and Space program management and contracting personnel who support programs that have transitioned from FFP to FPIF. The project also examines defense industry profitability and considers the perspective of defense contractors regarding Department of Defense profit policy. The analysis results indicate that the PEO is appropriately applying guidance for choosing FPIF contracts in follow-on production, and that there are both benefits and challenges associated with FPIF contracts. Recommendations include continuing to assess FPIF use for production programs, obtaining actual cost data, and improving incentive contracting workforce training. Further research on the longer-term effects of transitioning to FPIF is recommended.http://archive.org/details/impactsoftransit1094550587Civilian, Department of ArmyCivilian, Department of ArmyCivilian, Department of ArmyApproved for public release; distribution is unlimited

The ideal site of cement application in cement augmented sacroiliac screw fixation: the biomechanical perspective.

PURPOSE To compare construct stability of cement augmented sacroiliac screws using two different cementation sites in a biomechanical fragility fracture model of the pelvis. METHODS A fracture model with an incomplete fracture of the sacral ala and complete fracture of the anterior pelvic ring mimicking a FFP IIB fragility fracture of the pelvis was established in five fresh frozen human cadaveric pelvises. Sacral fracture stabilization was achieved with bilateral 7.3 mm fully threaded sacroiliac screws. Cement augmentation was performed at the tip of the screw (body of S1; Group A) on one side, and at the midshaft of the screw (sacral ala; Group B) on the contralateral side. Biomechanical testing was conducted separately on both sides comprising cyclic loading of axial forces transferred through the tested hemipelvis from L5 to the ipsilateral acetabulum. Combined angular displacement in flexion and internal rotation ("gap angle"), angular displacement of the ilium in relation to the screw ("screw tilt ilium"), and screw tip cutout were evaluated. RESULTS Relative interfragmentary movements were associated with significantly higher values in group A versus group B for "gap angle" (2.4° vs. 1.4°; p < 0.001), and for "screw tilt ilium" (3.3° vs. 1.4°; p < 0.001), respectively. No significant difference was indicated for screw tip cutout between the two groups (0.6 mm [Group A] vs. 0.8 mm [Group B]; p = 0.376). CONCLUSION The present study demonstrated less fragment and screw displacements in a FFP IIB fracture model under physiologic cyclic loading by cement augmentation of sacroiliac screws at the level of the lateral mass compared to the center of vertebral body of S1

Fit-for-Purpose Land Administration - Providing Secure Land Rights at Scale

This Special Issue provides an insight, collated from 26 articles, focusing on various aspects of the Fit-for-Purpose Land Administration (FFPLA) concept and its application [...