Relocation Scheme Research Articles

Mining-based File Caching in a Hybrid Storage System

In this work, we propose a new mining-based file caching scheme for a hybrid storage disk system. In particular, we focus our efforts on reducing the latency of launching applications. The proposed scheme identifies correlated file accesses in a file access sequence via sequential pattern mining algorithm. Our scheme caches correlated files together to maximize the caching efficiency. The correlated files are extracted from the access patterns through the proposed mining scheme, which consists of three steps: frequent pattern based file extraction, cluster moving gap based file sort, and frequency and size based file prioritization. The extracted correlated files are relocated to an SSD during idle time. DiskSim and NANDSim are used to evaluate the proposed scheme, called Informed Mining. The proposed scheme is compared with a disk only scheme and five other mining based file relocation schemes: Mining based file relocation scheme (Miner), minimum distance based file relocation scheme (Min_Dist), frequency-based relocation scheme (Fre), size-based relocation scheme (Size), and one that relocates files with highest value of (file size * file access number) first to the SSD (Fr*Sz). From the simulation based experiment, launch time is reduced by about 50% using only 10% of sum of all file sizes accessed during a launch of an application.

An RDL UBM Structural Design for Solving Ultralow-K Delamination Problem of Cu Pillar Bump Flip Chip BGA Packaging

Copper (Cu) pillar bumps tend to induce high thermal–mechanical stress during environmental tests and fabrication processes due to the high hardness of Cu, especially when applied with an ultralow-K (ULK) chip. A previous experiment showed that interfacial delamination was often observed in the ULK layers of conventional Cu pillar bump-type flip chip ball grid array (FCBGA) packages under thermal cycling, where under bump metallurgy (UBM) layers directly sit on the metal pads of silicon chips (herein termed ‘‘direct UBM structure’’). In this study, a UBM pad relocation scheme through redistribution layer (RDL) technology (herein termed ‘‘RDL UBM structure’’) is proposed to relieve the stress or ULK delamination issue. The proposed technique is tested on Cu pillar bump-type FCBGA packages subjected to thermal loading, the effectiveness of which is demonstrated through finite element stress simulation and experimental reliability tests. Simulation results reveal that the RDL UBM structure can greatly reduce the maximum stress in the ULK layers by as much as about 10% to 44%. Besides, it turns out that the Cu pillar bump-type FCBGA packages with the RDL UBM structure show good interconnect reliability performance in terms of thermal cycling, highly accelerated stress, and high-temperature storage.

Sensor Relocation Technique Based Lightweight Integrated Protocol for WSN

While deploying sensor nodes for sensitive services, we need to focus on both the coverage and connectivity. The sensor relocation scheme had been proposed earlier, where the sensors themselves move towards the required position to make proper coverage and connection. From our experimental results, we noted that this work achieves good coverage. However, this approach fails to focus on connectivity issue due to node migration and secured communication too, which may compromise our collecting data. To address these serious issues, we proposed an efficient sensor relocation technique based lightweight integrated protocol (LIP). We have implemented and studied thoroughly our proposed work. From our experimental results, our proposed work LIP outperforms the existing sensor relocation scheme in terms of network connectivity, coverage, throughput, packet delivery fairness, energy consumption, energy loss, network resiliency, and secured communication. It is also noted that our proposed model maximizes the lifetime of wireless sensor networks.

Multiple description discrete cosine transform-based image coding using DC coefficient relocation and AC coefficient interpolation

The development of an effective and dependable multiple description coding scheme over a lossy communication system is described. A general framework of an effective multiple description robust communication system with two-channel and four-channel cases is presented with a proposed block-based DC coefficient relo- cation and AC coefficient interpolation approach. A benefit of such system is that, if all the channels work properly, a very good quality, probably lossless, reconstruction can be obtained from the received descriptions. On the other hand, if some of the channels do not work properly, a lower but still quite satisfactory quality of reconstruction can be obtained. The performance of the proposed scheme is mea- sured with mean squared error, peak signal-to-noise ratio, entropy, and bit rate to analyze the reconstruction quality, and the computed results are matched with that of the other schemes. The system complexity is also computed and compared. Comparing the simula- tion results, it is observed that the proposed scheme, which uses a DC coefficient relocation and AC coefficient interpolation scheme, gives comprehensive enhancements over the other recently devel- oped schemes. © 2013 SPIE and IS&T (DOI: 10.1117/1.JEI.22.2 .023030)

Feedback-Aided Pilot Placement and Subcarrier Pairing for AF OFDM Relay Channels

This paper examines the use of channel feedback to adaptively determine pilot placement among subcarriers in amplify-and-forward (AF) orthogonal frequency-division multiplexing (OFDM) relay systems. With feedback of the previous channel estimate, pilot subcarriers at the source and relay can be reassigned to reduce channel estimation error and ensure that good subcarriers are made available for data transmission. The minimum effective signal-to-noise ratio (SNR) among data subcarriers is utilized as the performance metric for the optimization of the pilot locations. The effective SNR is defined as the receive SNR at the destination, taking into consideration the source-to-relay (SR) and relay-to-destination (RD) channels, as well as their respective channel estimation errors. The feedback gain, which is defined as the ratio between the minimum effective SNR achieved with the optimal feedback-aided pilot placement and that achieved with the equal-spaced pilot placement, is used to measure the gains achieved through feedback. In this paper, we first derive an analytic lower bound on the optimal feedback gain and show its rate of increase with respect to the number of subcarriers. These studies are performed for systems both without and with subcarrier pairing (SP) at the relay. Specifically, in systems without SP, the relay forwards each datum on the same subcarrier on which it is received. In systems with SP, the relay is allowed to reassign the subcarriers used to forward the data received from the source. With the goal of maximizing the minimum effective SNR, the optimal SP scheme is shown to be an inverse mapping between the SR and RD subcarriers with respect to their channel gains. Due to the complexity of finding the optimal placement, a suboptimal but efficient algorithm called the iterative pilot relocation (IterPR) scheme is then proposed. The effectiveness of the proposed IterPR schemes is demonstrated through numerical simulations.

Socio-Environmental Considerations at the Usuma Reservoir in Abuja, Nigeria

Reservoirs are Man's attempt towards water re-distribution fro m regions/seasons of abundance/surplus to regions/seasons of scarcity. This study focuses on socio-environmental impacts of the Lower Usuma dam in Abuja, on its four surrounding communities. Strat ified random samp ling technique was emp loyed in the administration of a questionnaire to 200 respondents. Using descriptive statistics and the student t-test for the analysis, the study discovered that: (i) there has been no significant imp rovement in infrastructure provision by Government; (ii) cases of water-borne diseases are high; (iii) the communities have lost land for cultivation; and, (iv) the communit ies believe that the resettlement scheme is not commensurate with their losses. It is recommended, thus: (i) the relocation scheme imp lemented for the four commun ities be reviewed with a view to imp roving the living conditions of the affected commun ities in terms of providing infrastructure (water and roads, educational and health facilities), and (ii) Strategic Environ mental Assessment is encouraged for such projects.

Tracking and Verification of East Atlantic Tropical Cyclone Genesis in the NCEP Global Ensemble: Case Studies during the NASA African Monsoon Multidisciplinary Analyses

Abstract This study evaluates the performance of the NCEP global ensemble forecast system in predicting the genesis and evolution of five named tropical cyclones and two unnamed nondeveloping tropical systems during the NASA African Monsoon Multidisciplinary Analyses (NAMMA) between August and September 2006. The overall probabilities of the ensemble forecasts of tropical cyclone genesis are verified relative to a genesis time defined to be the first designation of the tropical depression from the National Hurricane Center (NHC). Additional comparisons are also made with high-resolution deterministic forecasts from the NCEP Global Forecast System (GFS). It is found that the ensemble forecasts have high probabilities of genesis for the three strong storms that formed from African easterly waves, but failed to accurately predict the pregenesis phase of two weaker storms that formed farther west in the Atlantic Ocean. The overall accuracy for the genesis forecasts is above 50% for the ensemble forecasts initialized in the pregenesis phase. The forecast uncertainty decreases with the reduction of the forecast lead time. The probability of tropical cyclone genesis reaches nearly 90% and 100% for the ensemble forecasts initialized near and in the postgenesis phase, respectively. Significant improvements in the track forecasts are found in the ensemble forecasts initialized in the postgenesis phase, possibly because of the implementation of the NCEP storm relocation scheme, which provides an accurate initial storm position for all ensemble members. Even with coarser resolution (T126L28 for the ensemble versus T384L64 for the GFS), the overall performance of the ensemble in predicting tropical cyclone genesis is compatible with the high-resolution deterministic GFS. In addition, false alarm rates for nondeveloping waves were low in both the GFS and ensemble forecasts.

A Vortex Relocation Scheme for Tropical Cyclone Initialization in Advanced Research WRF

Abstract This paper introduces a relocation scheme for tropical cyclone (TC) initialization in the Advanced Research Weather Research and Forecasting (ARW-WRF) model and demonstrates its application to 70 forecasts of Typhoons Sinlaku (2008), Jangmi (2008), and Linfa (2009) for which Taiwan’s Central Weather Bureau (CWB) issued typhoon warnings. An efficient and dynamically consistent TC vortex relocation scheme for the WRF terrain-following mass coordinate has been developed to improve the first guess of the TC analysis, and hence improves the tropical cyclone initialization. The vortex relocation scheme separates the first-guess atmospheric flow into a TC circulation and environmental flow, relocates the TC circulation to its observed location, and adds the relocated TC circulation back to the environmental flow to obtain the updated first guess with a correct TC position. Analysis of these typhoon cases indicates that the relocation procedure moves the typhoon circulation to the observed typhoon position without generating discontinuities or sharp gradients in the first guess. Numerical experiments with and without the vortex relocation procedure for Typhoons Sinlaku, Jangmi, and Linfa forecasts show that about 67% of the first-guess fields need a vortex relocation to correct typhoon position errors while eliminates the topographical effect. As the vortex relocation effectively removes the typhoon position errors in the analysis, the simulated typhoon tracks are considerably improved for all forecast times, especially in the early periods as large adjustments appeared without the vortex relocation. Comparison of the horizontal and vertical vortex structures shows that large errors in the first-guess fields due to an incorrect typhoon position are eliminated by the vortex relocation scheme and that the analyzed typhoon circulation is stronger and more symmetric without distortions, and better agrees with observations. The result suggests that the main difficulty of objective analysis methods [e.g., three-dimensional variational data assimilation (3DVAR)], in TC analysis comes from poor first-guess fields with incorrect TC positions rather than not enough model resolution or observations. In addition, by computing the eccentricity and correlation of the axes of the initial typhoon circulation, the distorted typhoon circulation caused by the position error without the vortex relocation scheme is demonstrated to be responsible for larger track errors. Therefore, by eliminating the typhoon position error in the first guess that avoids a distorted initial typhoon circulation, the vortex relocation scheme is able to improve the ARW-WRF typhoon initialization and forecasts particularly when using data assimilation update cycling.

Dynamic resource location with tropical algebra

The traditional dynamic resource location problem attempts to minimize the cost of servicing a number of sequential requests, given foreknowledge of a limited number of requests. This paper presents an algebraic framework for addressing this question in general, and relates he algebraic properties of a generating set to questions in long-term optimizability, addressing the two questions: for a given graph, is there a finite quantity of future knowledge with which a server’s relocation scheme can be completely optimized, and if not, then how does the performance of a non-omniscient optimization scheme improve as the quantity of future knowledge increases?

The optimization of sensor relocation in wireless mobile sensor networks

Wireless Sensor Networks (WSNs) have been an active research area these years due to their broad range of potential applications. Several research issues, which include energy-aware routing, sensor deployment problems, data aggregation, etc., have been broadly discussed in this network environment. Among these researches, the most important issue is to conserve the usage of the limited battery energy of the sensor in the WSN to prolong its network lifetime for as long as possible. This paper considers a movement-assisted sensor deployment problem in a cluster-based WSN, in which the sensor devices are capable of moving. Based on this mobility assumption for sensors, the redundant sensors can relocate their positions to the low battery energy clusters to increase the overall network lifetime of the WSN. A network optimization problem called the Optimization of Movement-Assisted Deployment Problem (OMADP) is formulated. The OMADP aims to determine the optimum sensor relocation scheme such that the network lifetime value of the resulting network will be maximized. The NP-hardness result of the OMADP was also conducted. We propose a heuristic algorithm to give an approximate solution to the OMADP. The simulation results show that the proposed method performed better in prolonging the network lifetime of a WSN in practice, compared to other movement-assisted deployment algorithms.

A hierarchical extension to RSVP-TE for fast lightpath setup in dynamic optical networks

This paper studies the problem of designing survivable optical wavelength division multiplexed (WDM) networks. A wavelength-routed wide area backbone network supporting circuit-switched traffic is considered. This paper also considers the use of optical wavelength conversion technology which has been shown to help improve network performance. However, wavelength conversion is still an expensive technology and using optical conversion could potentially result in signal quality degradation. In survivable networks, protection against failures is provided using backup paths that are determined when a session is established. In this paper, we present three primary and backup route computation mechanisms that attempt to improve overall network performance compared to existing solutions. One of the key design goals is to reduce the number of required converters per node. First, we present a routing algorithm, termed conversion free primary routing (CFPR) that computes primary paths without wavelength conversion, as far as possible. Next, we present a converter multiplexing technique that is used to share wavelength converters among multiple backup paths. This significantly reduces the number of connections blocked due to wavelength converter unavailability and reduces the number of wavelength converters required at each node, thus reducing system cost. Finally, we propose a backup path relocation scheme that migrates existing backup paths, whenever needed, to accommodate more primary paths and also to obtain primary routes with fewer hops. This is done to improve network utilization and reduce blocking probability. The proposed techniques are analyzed in detail using a discrete-event simulation model. The results show that significant reduction in blocking probability is possible with the proposed mechanisms. The number of converters required at each node to achieve a given blocking probability is also seen to be four times lower, compared to existing architectures based on static shortest path routing.

An EDF schedulability test for periodic tasks on reconfigurable hardware devices

In this paper, we consider the scheduling of periodic real-time tasks on reconfigurable hardware devices. Such devices can execute several tasks in parallel. All executing tasks share the hardware resource, which makes the scheduling problem differ from single- and multiprocessor scheduling. We adapt the global EDF multiprocessor scheduling approach to the reconfigurable hardware execution model and define two preemptive scheduling algorithms, EDF-First-k-Fit and EDF-Next-Fit . For these algorithms, we present a novel linear-time schedulability test and give a proof based on a resource augmentation technique. Then, we propose a task placement and relocation scheme utilizing partial device reconfiguration. This scheme allows us to extend the schedulability test to include reconfiguration time overheads. Experiments with synthetic workloads compare the scheduling test with the actual scheduling performance of EDF-First-k-Fit and EDF-Next-Fit . The main evaluation result is that the reconfiguration overhead is acceptable if the task computation times are one order of magnitude higher than the device reconfiguration time.

Scalable Clustering Algorithms with Balancing Constraints

Clustering methods for data-mining problems must be extremely scalable. In addition, several data mining applications demand that the clusters obtained be balanced, i.e., of approximately the same size or importance. In this paper, we propose a general framework for scalable, balanced clustering. The data clustering process is broken down into three steps: sampling of a small representative subset of the points, clustering of the sampled data, and populating the initial clusters with the remaining data followed by refinements. First, we show that a simple uniform sampling from the original data is sufficient to get a representative subset with high probability. While the proposed framework allows a large class of algorithms to be used for clustering the sampled set, we focus on some popular parametric algorithms for ease of exposition. We then present algorithms to populate and refine the clusters. The algorithm for populating the clusters is based on a generalization of the stable marriage problem, whereas the refinement algorithm is a constrained iterative relocation scheme. The complexity of the overall method is O(kN log N) for obtaining k balanced clusters from N data points, which compares favorably with other existing techniques for balanced clustering. In addition to providing balancing guarantees, the clustering performance obtained using the proposed framework is comparable to and often better than the corresponding unconstrained solution. Experimental results on several datasets, including high-dimensional (>20,000) ones, are provided to demonstrate the efficacy of the proposed framework.

Supporting User Mobility through Cache Relocation

Traffic and access delay can be reduced in a mobile network by caching data objects at network nodes near the clients. Traditional caching techniques, however, are unsuitable in this environment because they do not account for the changing location of the users. To deal with this problem, cache relocation techniques can be applied to dynamically relocate data objects so they remain close to the moving clients. Existing relocation techniques rely heavily on path prediction. Unfortunately, the inaccuracy of path prediction can lead to high relocation overhead and poor response time. This paper presents an analytical study of the effects of client mobility on network cache performance. Two new cache relocation techniques are proposed to deal with the issue of poor path prediction and reduce the overhead of existing cache relocation schemes. The first technique, 2PR, compensates for poor path prediction by temporarily moving data objects to a common parent node prior to a handover. Objects are moved to the correct destination once the client′s new location has been confirmed. The second technique, ROLP, reduces the traffic overhead associated with cache relocation by ensuring duplicate objects are not relocated and relocation of objects are performed only from the nearest node to the destination. Test results show that 2PR reduces the query delay experienced by mobile clients by 60 to 83% after handovers, while ROLP reduces the overhead of cache relocation by between 33 to 65% compared to existing schemes.

A Quasigeostrophic Analysis of a Meander in the Palamós Canyon: Vertical Velocity, Geopotential Tendency, and a Relocation Technique

The quasigeostrophic geopotential tendency and omega equations are integrated to examine the dynamics of an upper-ocean coastal meander sampled during an intensive survey in the Palamos Canyon (northwestern Mediterranean Sea). Results for dynamic height tendency reveal that the meander is not growing or decaying but is propagating downstream at a velocity of about 4 km day21. This propagation speed implies a problem of synopticity in the field observations, which is solved through a data relocation scheme. The station relocation has important consequences on the magnitude of crucial dynamical variables such as the vertical velocity: maximum values of 20 m day21 before the relocation reduce to 10 m day21 after the relocation. The impact of bottom boundary conditions in the solution of the omega equation is also analyzed. Results indicate that for the stratification encountered during the survey, effects of topographic forcing are negligible above approximately 300 m.

Factors contributing to the development performance of slum relocation projects in Bangkok, Thailand

Slum relocation has become a study issue of increasing importance in Thailand, and especially in Bangkok, in light of the many slum and squatter settlement evictions during the past three decades. In response, two major approaches have been applied to help resolve the issue of displacement of people, namely, 'land-sharing' and 'slum relocation'. In the majority of relocation schemes, the landowners (both private and government) have negotiated with the residents and paid them compensation to relocate, thereby reacquiring their land for redevelopment purposes while allowing those being relocated sufficient resources to minimise negative impacts of the resettlement. These projects have proven the viability of the relocation approach in low-income housing development. This article seeks to investigate factors contributing to the development performance of such relocation projects. The conclusions indicate that there are a number of prerequisites for achieving success, including factors both external and inte...

Building an urban poor people’s movement in Phnom Penh, Cambodia

This photo-essay shows how the urban poor and their organizations are working with government agencies, NGOs and international donors in Phnom Penh, Cambodia’s capital, to develop homes and neighbourhoods and income generation and, where needed, to manage relocation schemes. It also describes how the city’s urban poor developed their own Solidarity and Urban Poor Federation, drawing on the advice of similar federations from other countries. The process was much helped by the interchanges between urban poor groups within the city and by the visits by urban poor representatives and city officials to projects managed by urban poor federations in other countries. The Federation’s work centres on linking and supporting community savings groups that develop their own schemes. The Federation also supports community-mapping and surveys to document conditions in the city’s many low-income settlements. The essay emphasizes the strengths and resources that the urban poor can bring to developing housing and jobs if external agencies allow them to do so and support their organizations.

A spatial decision support system prototype for housing mobility program planning

This paper presents a GIS-based decision support system prototype intended for use by public housing authority (PHA) administrators and planners designing policy for housing mobility programs. Housing mobility programs enable low-income families, many of whom live in government-operated public housing, to move to more desirable private-market rentals via rent subsidies. Unfortunately, housing authority planners have limited ability to visualize alternative relocation schemes of cohorts of low-income families or the impacts associated with these relocation policies. Thus, they are often not able to give highest-quality advice to clients regarding places to search for private-market rental housing. Housing Location Planner assists PHA planners in three ways: it analyzes spatial, demographic and housing market characteristics of the study area, selects certain portions of the study area for input to an optimization model which generates alternative family allocations, and displays optimization model results in a way that links decision variable values and objective function values. Housing Location Planner is seen as a first step in the development of even more sophisticated multi-stakeholder spatial decision support systems for subsidized housing planning in which one or more alternative allocations of families across a study area is chosen as a basis for policy initiatives.

Learning from informal markets: Innovative approaches to land and housing provision

Substandard and insecure housing conditions are recognised as a crucial aspect of urban poverty. In most large cities in the developing world, the formal market serves only a minority of the population. It is estimated that between 30 and 70 per cent live in 'irregular' settlements, and that up to 85 per cent of the new housing stock is produced in an extra-legal manner, with severe social and environmental consequences. John Turner's groundbreaking work and the first Habitat conference in 1976 marked a paradigm shift towards an enabling and participatory approach to housing provision. However, little progress has been made in translating the new paradigm into practical and sustainable policies. Relocation schemes, social housing, slum upgrading, and sites and services are beset by two related problems: first, they are far too small scale to serve the growing demand and, second, products are far too expensive to be affordable for low-income groups. The paper states that the informal sector's strategy of incremental development and improvement of housing and infrastructure can be incorporated into public policies, and introduces cases from the Philippines and Pakistan as best practices in this direction.

Decision Support for a Housing Mobility Program Using a Multiobjective Optimization Model

As result of public housing reform and welfare reform, the operating environment of public housing authorities has changed significantly. Given these policy initiatives, housing mobility programs represent viable strategies for providing public housing residents with access to economically healthy, integrated neighborhoods. In this paper we present a decision support methodology to assist the design of housing mobility programs. This methodology incorporates economic models for estimating dollar-valued impacts associated with tenant relocation, and a multiobjective optimization model for generating alternative relocation schemes associated with various objective function weights. Using data for Lake County, Illinois and Chicago, we demonstrate that nondominated allocations represent significant trade-offs between dollar-valued and non-dollar-valued policy objectives; existing distributions of subsidized housing represent suboptimal solutions to the housing relocation problem; and increases in available rental housing can result in housing dispersion schemes that have positive net economic benefits relative to the status quo.