System Level Solutions for Memory Reliability

DoctorReliability of a memory subsystem is one of the most important feature to computer system stability, since memory errors can make whole system failures. Past few years, as VLSI technology node scales down, various factors which are degrading the reliability of memory operation have been appeared. This dissertation addresses memory errors in SRAM and DRAM, which are commonly used to on-chip cache memory and main memory, respectively. In the SRAM-based cache memory, SRAMs limit the lowest supply voltage in processor since they suffer from process variation-induced bit errors at a low supply voltage. Therefore, on-chip SRAM-based caches are the practical bottleneck to reducing supply voltage which is one of the key parameters for lowering energy consumption. In order to address this problem, a novel cache architecture is proposed to resolve the performance degradation at a low supply voltage which is caused by cache misses in accesses to faulty resources. The proposed solution utilizes cache access locality and error-free resources in a cost-effective manner. First, cache lines are classified into fully and partially accessed groups and apply appropriate methods to each group. For the partially accessed group, memory access behavior and error locations are matched with intra-cache line word-level remapping. In order to reduce the area overhead used to store the cache access information history, an access pattern-learning line-fill buffer is adopted. For the fully accessed group, the proposed solution utilizes error-free assist functions such as a line-fill buffer and victim cache with no process variation-induced error at the target minimum supply voltage. The solution also present an error-aware prefetch method that allows it to utilize the error-free victim cache to achieve a further reduction in cache misses due to faulty resources. In the DRAM-based main memory, bit errors are expected to increase at a rapid pace as DRAM approaches its scaling limit. At high bit error rates, the conventional strong error correction mechanisms are not sufficient for reliable computing. Therefore, a novel architectural solution for DRAM-based main memory is proposed to provide better reliability, at low cost, than conventional solutions under scaling-induced DRAM cell faults. By utilizing modification of the existing two-dimensional error correction scheme and error correcting table scheme, multi-bit errors can be tolerate in this solution. The solution has two implementations, i.e. in-DRAM and SRAM parity methods, depending on whether DRAM capacity can be sacrificed or not for parity storage. In both cases, in order to avoid the performance overhead incurred by additional data read operations (called pre-data reads) for parity calculations, partial parity and a last-level cache (LLC) architecture that manages partial parity are utilized. When parity bits can be stored in main memory (referred to as in-DRAM parity method), in order to hide the latency of additional parity accesses to DRAM, it is possible to exploit the slack between an eviction from the LLC and the associated initial write to the LLC, thereby hiding the additional latency of accessing parity in DRAM. Since the proposed solutions are applied to different scopes in memory subsystem, they can be jointly utilized by same memory subsystem. Therefore, jointly applying both of the solutions, reliability of the system can be improved for various operating condition such as low supply voltage condition and defective DRAM-based main memory

Development of an Ergonomic Design Framework for Determination of Smartphone Hard Key Locations

DoctorThe location of smartphone hard key need to be ergonomically designed to improve grip stability and operational efficiency for better usability. Smartphone hard key includes power key to screen on/off for efficient energy management and volume key to volume up/down for intuitive volume control. Hard key could cause various usability problems such as grip loss, discomfort, and unintended operation if the location is improperly designed. In addition, the locations of commercial smartphones are different from manufacturer to manufacturer and from device to device even designed by the same manufacturer, which implies ergonomic design guide for hard key location is not available. While many studies for ergonomic user interface design have been conducted on the graphical user interface (GUI) design on a touchscreen and design dimensions of a device, research on the ergonomic design location of the hard key is a few. Hard keys need to be carefully located as they are impossible to be relocated once manufactured unlike GUIs on a touchscreen, also, changing the location during design is difficult as well because the locations of the other parts are all related to each other. Therefore, development of an ergonomic design method for determining the location of hard keys on smartphones with various sizes is necessary. The objectives of the present study are (1) development of a design methodology for hard key location which determines recommended design location based on the analysis of preferred control range in preferred grip postures by users with various hand sizes, (2) application of the methodology on the design of hard key locations for various smartphone sizes, and (3) validation of the methodology by evaluation of operational satisfaction for the hard key locations. The developed design methodology first analyzes the characteristics of target device, user, task, and use context, then preferred grip postures by users are analyzed. Next, preferred hard key control range in the preferred grip postures are investigated to derive preference distribution for control area. Finally recommended design location is determined by considering the size of hard key and preference for the control area. Preferred grip postures of 45 participants were analyzed for operating power key and volume key on 9 smartphones with 3.0” to 7.0” screens. Out of 9 identified grip postures, 3 fingers at the left side-1 finger at the right side-1 finger at the back (L3-R1-K1), 4 fingers at the left side-1 finger at the right side (L4-R1), and 3 fingers at the left side-1 finger at the right side-1 finger at the top (L3-R1-T1) were the major grip postures with more than 95% of preference in total. Effect of device size on the preference for each preferred grip posture was significant that the preference of L3-R1-K1 increased from 32.2% to 84.4% when screen size increased from 3.0” to 7.0” (p < 0.01). Recommended design locations for power key and volume key of 9 smartphones with 3.0” to 7.0” screens were investigated from preferred control ranges of 52 participants. The recommended design locations for power key and volume key were derived by accumulating the preference for each control location by participants with various hand sizes. The recommended hard key design locations moved from 69 mm to 116 mm above the bottom for power key and moved from 61 mm to 104 mm above the bottom for volume key. Effectiveness of the design methodology of smartphone hard key location was validated by the evaluation of operational satisfactions from 70 participants for the three hard key locations (recommended location, 10 mm above/below) on 4 smartphones with 5.0” to 6.5” screens. Mean operational satisfactions for the recommended locations on the 4 smartphones were 1.2 point higher than the others with averages of 4.2 to 4.9 points (p < 0.01). The developed design methodology for smartphone hard key location would be usefully applied to the design for user interface of various portable products in addition to smartphones

Preparation of the Sulfonated Carbon Mateials and Their Application for the Proton Exchange Membranes

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Sitting Strategy Analysis based on Driving Posture and Seating Pressure Distribution

MasterIn the design of comfortable automobile seats, driving posture and seating pressure have been considered importantly. Automobile seats can be examined by driving posture analysis of whether drivers can control the steering wheel or the pedals with their preferred posture, and by the seating pressure distribution analysis of whether the seat supports a driver's body appropriately so that the driver doesn't feel fatigue easily. However, considering all the postures and seating pressure distributions of drivers negatively affect the efficiency of the design process. In order to overcome this situation, several studies which classified representative sitting strategies were conducted, but it is known that the classification of the sitting strategy had been done by visual observation, and it should be classified by a quantitative method to be used in the automobile seat design process.There are 3 objectives of the present research. First, sitting strategies were quantitatively classified by driving posture. Second, sitting strategies were quantitatively classified by seating pressure. Lastly, the relationship between the two types of sitting strategies was analyzed. Twenty female and twenty male participants were recruited and a seating buck which is reconfigurable into a coupe, sedan, or SUV type had been used to consider the effect of the occupant package layout (OPL) type of the seat. The driving postures were captured by a motion capture system, and the seating pressures were measured by two pressure mats attached on each seatback and seatpan of the seat.First, the sitting strategies by driving posture were classified, and the characteristics were found. The sitting strategies by driving posture were quantitatively classified by cluster analysis on 6 joint angles (head, neck, trunk, hip, knee, and ankle). As a result, 3 strategies (Reclined, Erect, and Slouched) for upper-body and 3 strategies (Knee bent, Knee extended, and Upper-leg lifted) for lower-body were extracted, and it is shown that there are gender effect on the upper-body strategy and the OPL type effect on the lower-body strategy.Second, the sitting strategies by seating pressure were classified, and the characteristics were found. The sitting strategies by seating pressure were quantitatively classified by cluster analysis on the body pressure ratio (BPR) data which is the pressure ratio on 17 body parts in comparison with the total pressure on the whole body. As a result, it is shown that the seating pressure based sitting strategies of the upper-body and lower-body were dependent to each other. Therefore, the combined sitting strategies for the upper-body and lower-body were classified into 5 types (Mid-back & Scapular, HipMid-back & Scapular, Hip & Mid-thighMid-back & Lumbar, HipMid-back & Lumbar, Hip & Mid-thighand Lumbar, Hip & Mid-thigh). The OPL type effect was significant on the combined sitting strategy by seating pressure. Lastly, the relationship between the two types of sitting strategies by driving posture and seating pressure was analyzed. In order to analyze the relationship, a Chi-square test on 2 sets (driving posture and seating pressure) of 9 sitting strategies (combination of upper and lower body sitting strategy) was conducted. However, the result was not significant. It is assumed to be the effect of seat configuration, so a follow-up study is required.In summary, the sitting strategies by driving posture were classified into 3 types each for upper-body and lower-body, and the strategies by seating pressure were classified into 5 types for the whole body. Furthermore, the relationship between the two sitting strategy types is not significant

Sulfonated Carbon for Proton Exchange Membranes

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Scrub Period Evaluations of Multi-Level Cell PRAM

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Preparation of Sulfonated Carbon Membranes and Their Application for Proton Exchange Membranes Fuel Cell under Low Humidified Condition

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Development and Usability Testing of a User-Centered 3D Virtual Liver Surgery Planning System

Objective: The present study developed a user-centered 3D virtual liver surgery planning (VLSP) system called Dr. Liver to provide preoperative information for safe and rational surgery. Background: Preoperative 3D VLSP is needed for patients&apos; safety in liver surgery. Existing systems either do not provide functions specialized for liver surgery planning or do not provide functions for cross-check of the accuracy of analysis results. Method: Use scenarios of Dr. Liver were developed through literature review, benchmarking, and interviews with surgeons. User interfaces of Dr. Liver with various user-friendly features (e.g., context-sensitive hotkey menu and 3D view navigation box) was designed. Novel image processing algorithms (e.g., hybrid semi-automatic algorithm for liver extraction and customized region growing algorithm for vessel extraction) were developed for accurate and efficient liver surgery planning. Usability problems of a preliminary version of Dr. Liver were identified by surgeons and system developers and then design changes were made to resolve the identified usability problems. Results: A usability testing showed that the revised version of Dr. Liver achieved a high level of satisfaction (6.1 ± 0.8 out of 7) and an acceptable time efficiency (26.7 ± 0.9 min) in liver surgery planning. Conclusion: Involvement of usability testing in system development process from the beginning is useful to identify potential usability problems to improve for shortening system development period and cost. Application: The development and evaluation process of Dr. Liver in this study can be referred in designing a user-centered system.22kc