An Interference Matrix Based Approach to Bounding Worst-Case Inter-Thread Cache Interferences and WCET for Multi-Core Processors

Yan, Jun,Zhang, Wei Korean Institute of Information Scientists and Eng 2011 Journal of Computing Science and Engineering Vol.5 No.2

Different cores typically share the last-level cache in a multi-core processor. Threads running on different cores may interfere with each other. Therefore, the multi-core worst-case execution time (WCET) analyzer must be able to safely and accurately estimate the worst-case inter-thread cache interference. This is not supported by current WCET analysis techniques that manly focus on single thread analysis. This paper presents a novel approach to analyze the worst-case cache interference and bounding the WCET for threads running on multi-core processors with shared L2 instruction caches. We propose to use an interference matrix to model inter-thread interference, on which basis we can calculate the worst-case inter-thread cache interference. Our experiments indicate that the proposed approach can give a worst-case bound less than 1%, as in benchmark fib-call, and an average 16.4% overestimate for threads running on a dual-core processor with shared-L2 cache. Our approach dramatically improves the accuracy of WCET overestimatation by on average 20.0% compared to work.

Bounding Worst-Case Performance for Multi-Core Processors with Shared L2 Instruction Caches

Yan, Jun,Zhang, Wei Korean Institute of Information Scientists and Eng 2011 Journal of Computing Science and Engineering Vol.5 No.1

As the first step toward real-time multi-core computing, this paper presents a novel approach to bounding the worst-case performance for threads running on multi-core processors with shared L2 instruction caches. The idea of our approach is to compute the worst-case instruction access interferences between different threads based on the program control flow information of each thread, which can be statically analyzed. Our experiments indicate that the proposed approach can reasonably estimate the worst-case shared L2 instruction cache misses by considering the inter-thread instruction conflicts. Also, the worst-case execution time (WCET) of applications running on multi-core processors estimated by our approach is much better than the estimation by simply assuming all L2 instruction accesses are misses.

Evaluation of Pp/Clay Composites as Soundproofing Material

Yan, Jun,Kim, Myung-Sub,Kang, Kyung-Min,Joo, Kyung-Hoon,Kang, Yeon-June,Ahn, Sung-Hoon RAPRA 2014 POLYMERS AND POLYMER COMPOSITES Vol.22 No.1

Noise should be disappeared or reduced by using soundproofing materials in our daily life. Polypropylene (PP)/Clay composites are interesting because of their physical and mechanical properties dramatically increased by small quantity of clay filled in PP matrix. In this paper, different types of specimens were made at 0.9, 2.9, 4.8, 6.5, 8.2 and 9.9 wt.% of organically modified clay reinforced PP (100 gram) by solvent based techniques. A heating press and laser cutting process were used to create specimens with thickness 3 mm, diameter 29 mm and 100 mm for high and low sound frequency test, respectively. The soundproofing property was measured by sound transmission loss (TL) through impedance tube method. The measured results showed that about 7 similar to 14.8 dB sound TL was increased for 29 mm diameter PP/Clay (6.5 wt.%) composite specimens compared with pure PP at 3200 similar to 6400Hz. And about 3.3 similar to 5.3 dB sound TL was increased for 100 mm diameter PP/Clay (6.5 wt.%) composite specimens compared with pure PP at 520 similar to 640Hz. In addition, mechanical properties of this composite were measured, and TEM images were taken in order to observe the micro-structure for research on relationship between soundproofing property and micromechanism.

Computing and Reducing Transient Error Propagation in Registers

Yan, Jun,Zhang, Wei Korean Institute of Information Scientists and Eng 2011 Journal of Computing Science and Engineering Vol.5 No.2

Recent research indicates that transient errors will increasingly become a critical concern in microprocessor design. As embedded processors are widely used in reliability-critical or noisy environments, it is necessary to develop cost-effective fault-tolerant techniques to protect processors against transient errors. The register file is one of the critical components that can significantly affect microprocessor system reliability, since registers are typically accessed very frequently, and transient errors in registers can be easily propagated to functional units or the memory system, leading to silent data error (SDC) or system crash. This paper focuses on investigating the impact of register file soft errors on system reliability and developing cost-effective techniques to improve the register file immunity to soft errors. This paper proposes the register vulnerability factor (RVF) concept to characterize the probability that register transient errors can escape the register file and thus potentially affect system reliability. We propose an approach to compute the RVF based on register access patterns. In this paper, we also propose two compiler-directed techniques and a hybrid approach to improve register file reliability cost-effectively by lowering the RVF value. Our experiments indicate that on average, RVF can be reduced to 9.1% and 9.5% by the hyperblock-based instruction re-scheduling and the reliability-oriented register assignment respectively, which can potentially lower the reliability cost significantly, without sacrificing the register value integrity.

A Level Set Method to Image Segmentation Based on Local Direction Gradient

( Yanjun Peng ),( Yingran Ma ) 한국인터넷정보학회 2018 KSII Transactions on Internet and Information Syst Vol.12 No.4

For image segmentation with intensity inhomogeneity, many region-based level set methods have been proposed. Some of them however can’t get the relatively ideal segmentation results under the severe intensity inhomogeneity and weak edges, and without use of the image gradient information. To improve that, we propose a new level set method combined with local direction gradient in this paper. Firstly, based on two assumptions on intensity inhomogeneity to images, the relationships between segmentation objects and image gradients to local minimum and maximum around a pixel are presented, from which a new pixel classification method based on weight of Euclidian distance is introduced. Secondly, to implement the model, variational level set method combined with image spatial neighborhood information is used, which enhances the anti-noise capacity of the proposed gradient information based model. Thirdly, a new diffusion process with an edge indicator function is incorporated into the level set function to classify the pixels in homogeneous regions of the same segmentation object, and also to make the proposed method more insensitive to initial contours and stable numerical implementation. To verify our proposed method, different testing images including synthetic images, magnetic resonance imaging (MRI) and real-world images are introduced. The image segmentation results demonstrate that our method can deal with the relatively severe intensity inhomogeneity and obtain the comparatively ideal segmentation results efficiently.

Optimized Resource Allocation for Utility-Based Routing in Ad Hoc and Sensor Networks

( Yanjun Li ),( Jianji Shao ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.5

Utility-based routing is a special type of routing approach using a composite utility metric when making routing decisions in ad hoc and sensor networks. Previous studies on the utility-based routing all use fixed retry limit and a very simple distance related energy model, which makes the utility maximization less efficient and the implementation separated from practice. In this paper, we refine the basic utility model by capturing the correlation of the transmit power, the retry limit, the link reliability and the energy cost. A routing algorithm based on the refined utility model with adaptive transmit power and retry limit allocation is proposed. With this algorithm, packets with different priorities will automatically receive utility-optimal delivery. The design of this algorithm is based on the observation that for a given benefit, there exists a utility-maximum route with optimal transmit power and retry limit allocated to intermediate forwarding nodes. Delivery along the utility-optimal route makes a good balance between the energy cost and the reliability according to the value of the packets. Both centralized algorithm and distributed implementations are discussed. Simulations prove the satisfying performance of the proposed algorithm.

A Utility-Based and QoS-Aware Power Control Scheme for Wireless Body Area Networks

( Yanjun Li ),( Jian Pan ),( Xianzhong Tian ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.9

Power control is widely used to reduce co-channel interference in wireless networks and guarantee the signal-to-interference plus noise ratio (SINR) of ongoing connections. This technique is also effective for wireless body area networks (WBANs). Although achieving satisfactory SINR is important for WBAN users, they may not be willing to achieve it at arbitrarily high power levels since power is a scarce resource in WBANs. Besides, for WBANs with different purposes, the QoS requirements and concern about the power consumption may be different. This motivates us to formulate the power control problem using the concepts from microeconomics and game theory. In this paper, the QoS objective is viewed as a utility function, which represents the degree of user satisfaction, while the power consumption is viewed as a cost function. The power control problem consequently becomes a non-cooperative multiplayer game, in which each player tries to maximize its net utility, i.e., the utility minus the cost. Within this framework, we investigate the Nash equilibrium existence and uniqueness in the game and derive the best response solution to reach the Nash equilibrium. To obtain the optimal transmission power in a distributed way, we further propose a utility-based and QoS-aware power control algorithm (UQoS-PCA). Tunable cost coefficient in UQoS-PCA enables this scheme to be flexible to satisfy diverse service requirements. Simulation results show the convergence and effectiveness of the proposed scheme as well as improvements over existing algorithm.

Engineering geological zonation using interaction matrix of geological factors: An example from one section of Sichuan-Tibet Highway

Yanjun Shang,Hyeong-Dong Park,Zhifa Yang 한국지질과학협의회 2005 Geosciences Journal Vol.9 No.4

Brittle fracture and plastic creep of the completely decomposed granite presented in CT

Yanjun Shang,Zhongqi Yue,박형동,현창욱 한국자원공학회 2015 Geosystem engineering Vol.18 No.6

Completely decomposed granite (CDG) with different structures shows different patterns in deformation and failure as brittle fracture or as plastic creep in triaxial test. It is necessary to monitor and to compare the fabric changes due to stress in real time during test. By means of the computerized tomography (CT) technique for monitoring deformation and failure of soils in real time without suspending the mechanical test and disturbing samples, a newly designed triaxial test machine was used to test CDG from Hong Kong in a procedure of saturation, consolidation and undrained condition. It was found that CT data (images and values) depicts the failure patterns as brittle fracture or as plastic creep at 3-D in real time. The results were concordant with stress–strain curves and observation of the appearance of samples before and after tests.

Design of an Ultrasonic Concentrator for Vibro-tactile Sensors Using Electro-mechanical Analogy

Yanjun Qian,한상욱,권혁주 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.10

Vibro-tactile sensors have been utilized to measure the mechanical properties of soft materials based on the shift of resonant frequency. However, their low signal to noise ratio (SNR) has impeded them from critical applications where accurate measurements are required. One of the ways to improve the SNR is to add an ultrasonic concentrator as a mechanical filter to the vibro-tactile sensor. In order to maximize the SNR, the concentrator should be optimally designed; however, systematic design approach of the concentrator has rarely been considered so far. In this paper, a hybrid design approach employing both analytical analysis and numerical simulation is presented. For analytical analysis, impedance analogy was used to facilitate the designing process, and the numerical simulation using FEA was conducted to carry out the parametric refinement of the design. The performance of the final design was verified by mechanical and electrical characteristics tests. Tests results indicate that the longitudinal resonance mode of the sensor was significantly enhanced and the increase in its mechanical quality factor was achieved by the ultrasonic concentrator. The tactile sensing experiments on the silicone rubber samples showed the high potential of the vibro-tactile sensor in estimating the elastic moduli of soft materials in the range of 5–100 kPa, which is not readily available with conventional testing methods.