摘要 :
NAND flash memory has decreasing storage reliability, as the density or program/erase (P/E) cycle increases. To ensure data integrity, error correction codes (ECCs) are widely employed and typically stored in the out-of-band area ...
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NAND flash memory has decreasing storage reliability, as the density or program/erase (P/E) cycle increases. To ensure data integrity, error correction codes (ECCs) are widely employed and typically stored in the out-of-band area (OOB) of flash pages. However, the worst-case oriented ECC is largely under-utilized in the early stage (small P/E cycles), and the required ECC redundancy may be too large to fit in OOB in the late stage (high P/E cycles). In this paper, we propose LAE-FTL, which employs a lifetime-adaptive ECC scheme, to improve the performance and lifetime of NAND flash memory. LAE-FTL uses weak ECCs in the early stage and strong ECCs in the late stage to guarantee the storage reliability. Since OOB is large enough to store weak ECCs in the early stage, small and size-incremental codewords are adaptively used to improve data transfer and decoding parallelism. In the late stage, strong ECCs have to be employed and the ECC redundancies become too large to be stored in OOB. Thus, LAE-FTL stores the exceeding ECC redundancies in the data space of flash pages and stores user data in a cross-page fashion. Finally, our trace-driven simulation results show that LAE-FTL improves the read performance by up to 63.42%, compared to the worst-case oriented ECC scheme in the early stage, and significantly improve the storage reliability at low cost in the late stage.
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摘要 :
NAND flash memory has decreasing storage reliability, as the density or program/erase (P/E) cycle increases. To ensure data integrity, error correction codes (ECCs) are widely employed and typically stored in the out-of-band area ...
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NAND flash memory has decreasing storage reliability, as the density or program/erase (P/E) cycle increases. To ensure data integrity, error correction codes (ECCs) are widely employed and typically stored in the out-of-band area (OOB) of flash pages. However, the worst-case oriented ECC is largely under-utilized in the early stage (small P/E cycles), and the required ECC redundancy may be too large to fit in OOB in the late stage (high P/E cycles). In this paper, we propose LAE-FTL, which employs a lifetime-adaptive ECC scheme, to improve the performance and lifetime of NAND flash memory. LAE-FTL uses weak ECCs in the early stage and strong ECCs in the late stage to guarantee the storage reliability. Since OOB is large enough to store weak ECCs in the early stage, small and size-incremental codewords are adaptively used to improve data transfer and decoding parallelism. In the late stage, strong ECCs have to be employed and the ECC redundancies become too large to be stored in OOB. Thus, LAE-FTL stores the exceeding ECC redundancies in the data space of flash pages and stores user data in a cross-page fashion. Finally, our trace-driven simulation results show that LAE-FTL improves the read performance by up to 63.42%, compared to the worst-case oriented ECC scheme in the early stage, and significantly improve the storage reliability at low cost in the late stage.
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摘要 :
Every year the use of polymers and composites in the DoD increases, Improved performance, Corrosion Resistance, Ease of Maintenance, Reduced Cost, Example: F14 contains ～2 wt% composite materials, F-22 contains ～24 wt% composite...
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Every year the use of polymers and composites in the DoD increases, Improved performance, Corrosion Resistance, Ease of Maintenance, Reduced Cost, Example: F14 contains ～2 wt% composite materials, F-22 contains ～24 wt% composites, JSF (F-35) contains >30 wt% composites.
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摘要 :
Every year the use of polymers and composites in the DoD increases, Improved performance, Corrosion Resistance, Ease of Maintenance, Reduced Cost, Example: F14 contains ～2 wt% composite materials, F-22 contains ～24 wt% composite...
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Every year the use of polymers and composites in the DoD increases, Improved performance, Corrosion Resistance, Ease of Maintenance, Reduced Cost, Example: F14 contains ～2 wt% composite materials, F-22 contains ～24 wt% composites, JSF (F-35) contains >30 wt% composites.
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摘要 :
An in-pipe robot with a novel differential mechanism is developed for solving the movement interference problem of wheel-type in-pipe robots, when driving through the pipelines with irregular internal wall or complex conditions. B...
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An in-pipe robot with a novel differential mechanism is developed for solving the movement interference problem of wheel-type in-pipe robots, when driving through the pipelines with irregular internal wall or complex conditions. Based on the four-axial differential mechanism, the differential locomotion of the in-pipe robot is only forced by the contact conditions of driving wheels without additional control signals. The mechanical model of the pipe diameter adaptive mechanism applying a typical ball screw pair is established, which is validated by the following simulation experiment and shows high reliability. The active steering mechanism with two rotational degrees of freedom is designed and meanwhile, the brake mechanism for preventing driving wheels from slipping and the elastic support mechanism for front-end support are introduced. Subsequently, the planned steering trajectory of the robot turning in a branch pipe is given and discussed. Finally, the validation of the in-pipe robot is demonstrated by the simulation experiments.
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The impact of simulation methods for social research in the Information Systems (IS) research field remains low. A concern is our field is inadequately leveraging the unique strengths of simulation methods. Although this low impac...
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The impact of simulation methods for social research in the Information Systems (IS) research field remains low. A concern is our field is inadequately leveraging the unique strengths of simulation methods. Although this low impact is frequently attributed to methodological complexity, we offer an alternative explanation - the poor construction of research value. We argue a more intuitive value construction, better connected to the knowledge base, will facilitate increased value and broader appreciation. Meta-analysis of studies published in IS journals over the last decade evidences the low impact. To facilitate value construction, we synthesize four common types of simulation research contribution: Analyzer, Tester, Descriptor, and Theorizer. To illustrate, we employ the proposed typology to describe how each type of value is structured in simulation research and connect each type to instances from IS literature, thereby making these value types and their construction visible and readily accessible to the general IS community.
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摘要 :
The impact of simulation methods for social research in the Information Systems (IS) research field remains low. A concern is our field is inadequately leveraging the unique strengths of simulation methods. Although this low impac...
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The impact of simulation methods for social research in the Information Systems (IS) research field remains low. A concern is our field is inadequately leveraging the unique strengths of simulation methods. Although this low impact is frequently attributed to methodological complexity, we offer an alternative explanation - the poor construction of research value. We argue a more intuitive value construction, better connected to the knowledge base, will facilitate increased value and broader appreciation. Meta-analysis of studies published in IS journals over the last decade evidences the low impact. To facilitate value construction, we synthesize four common types of simulation research contribution: Analyzer, Tester, Descriptor, and Theorizer. To illustrate, we employ the proposed typology to describe how each type of value is structured in simulation research and connect each type to instances from IS literature, thereby making these value types and their construction visible and readily accessible to the general IS community.
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While an important problem in the vision community is to design algorithms that can automatically caption images, few publicly-available datasets for algorithm development directly address the interests of real users. Observing th...
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While an important problem in the vision community is to design algorithms that can automatically caption images, few publicly-available datasets for algorithm development directly address the interests of real users. Observing that people who are blind have relied on (human-based) image captioning services to learn about images they take for nearly a decade, we introduce the first image captioning dataset to represent this real use case. This new dataset, which we call VizWiz-Captions, consists of over 39,000 images originating from people who are blind that are each paired with five captions. We analyze this dataset to (1) characterize the typical captions, (2) characterize the diversity of content found in the images, and (3) compare its content to that found in eight popular vision datasets. We also analyze modern image captioning algorithms to identify what makes this new dataset challenging for the vision community. We publicly-share the dataset with captioning challenge instructions at https://vizwiz.org.
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摘要 :
While an important problem in the vision community is to design algorithms that can automatically caption images, few publicly-available datasets for algorithm development directly address the interests of real users. Observing th...
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While an important problem in the vision community is to design algorithms that can automatically caption images, few publicly-available datasets for algorithm development directly address the interests of real users. Observing that people who are blind have relied on (human-based) image captioning services to learn about images they take for nearly a decade, we introduce the first image captioning dataset to represent this real use case. This new dataset, which we call VizWiz-Captions, consists of over 39,000 images originating from people who are blind that are each paired with five captions. We analyze this dataset to (1) characterize the typical captions, (2) characterize the diversity of content found in the images, and (3) compare its content to that found in eight popular vision datasets. We also analyze modern image captioning algorithms to identify what makes this new dataset challenging for the vision community.
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We propose a secure yet efficient data query system for cloud-based key-value store. Our system supports encryption and compression to ensure confidentiality and query efficiency simultaneously. To reconcile encryption and compres...
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We propose a secure yet efficient data query system for cloud-based key-value store. Our system supports encryption and compression to ensure confidentiality and query efficiency simultaneously. To reconcile encryption and compression without compromising performance, we propose a new encrypted key-value storage structure based on the concept of horizontal-vertical division. Our storage structure enables fine-grained access to compressed yet encrypted key-value data. We further combine several cryptographic primitives to build secure search indexes on the storage structure. As a result, our system supports rich types of queries including key-value query and range query. We implement a prototype of our system on top of Cassandra. Our evaluation shows that our system increases the throughput by up to 7 times and compression ratio by up to 1.3 times with respect to previous works.
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