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.

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.

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.

Atomic insights into regulation of graphene sheets vertically attached to the FeF3·0.33H2O (002) surface by cation doping

Yanjun Pan,Yang Li,Jinda Luo,Xianyou Wang,Zhenhua Yang 한국물리학회 2019 Current Applied Physics Vol.19 No.10

Tightly and vertically attached graphene nanosheets (GNS) on the surface of FeF3·0.33H2O is extremely desirable to substantially accelerate electron transport, promoting rate capability of FeF3·0.33H2O. Based on present experiment and calculated surface energies, firstly, it has confirmed that F-terminated FeF3·0.33H2O (002) surface (FeF3·0.33H2O (002)-F) is more stable than FeF-terminated FeF3·0.33H2O (002) surface (FeF3·0.33H2O (002)- FeF) when μF varies from −1.92 eV to −0.30 eV. Then, by analysis of the interfacial structure and adsorption energies, it was proposed that GNS is incline to stand vertically on the FeF3·0.33H2O (002) surface via C–F bond. However, structural stability of FeF3·0.33H2O/GNS heterostructure is gradually weakened with increasing the number of GNS layers. Therefore, we further reported the important role of optimal doping element (Hf) in strengthening the vertical adsorption behavior of GNS on FeF3·0.33H2O (002) surface via thorough doping element search. And it turns out interfacial structure with hexa-coordinate polyhedron consists of Hf, F and O atoms is formed by strong hybridization of atomic orbits, which induces the interaction between FeF3·0.33H2O (002) surface and GNS to be profoundly strengthened.

Multi‑objective parameter optimization of multi‑shaft ring‑plate magnetic gear

Yanjun Ge,Dongning Liu,Junyue Yang,Daming Wang 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.3

Parameter setting and optimization are key steps to improving the transmission performance of eccentric permanent magnetgear. Studying this step makes it possible to analyze the transmission relationship between the design parameters, and improve both the operation stability and the carrying capacity of eccentric permanent magnet gear. Taking multi-shaft ring-plate magnet gear (MRMG) as the research object, this paper analyzes the influence of actual structural parameters on torque performance through the comprehensive sensitivity method, and selects the parameters with the greatest influence as the main optimization parameters. Then using the BSO algorithm and the BP neural network, a prediction model of MRMG electromagnetic torque and torque density is established, the relationship between each of the parameters is analyzed, and the optimization parameter points are determined. By comparison with finite element simulations and experiments, the built model and its measured results and FEM analysis are shown to have good accuracy (error < 6%). Moreover, the model can quickly and accurately obtain optimization parameters, and greatly improve the transmission performance of the structure (the maximum torque increases by 15%, and the torque density increases by 36%).

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

Methylation of methyltrichlorosilane with methyl chloride over active metals and activated carbon

Yanjun Liu,Yiqian Jiang,Weiguang Chen,Yutang Shen,Yonghai Feng,Lingqin Shen,Aili Wang,Tingshun Jiang,Zhanao Wu 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.12

Gas phase methylation of methyltrichlorosilane with methyl chloride to high-valued dimethyldichlorosilane was carried out by using metallic aluminum as a chlorine acceptor in the co-presence of activated carbon, tin, and zinc. The addition of activated carbon in metallic aluminum significantly enhanced the methylation of methyltrichlorosilane,and dimethyldichlorosilane was dominantly produced. Activated carbon played a catalyst role in the methylation reaction. When active metals, such as tin and zinc, were added in the mixture of aluminum and activated carbon,the active metals and activated carbon synergistically catalyzed the methylation of methyltrichlorosilane with methyl chloride toward the formation of dimethyldichlorosilane.

A Lifetime-Preserving and Delay-Constrained Data Gathering Tree for Unreliable Sensor Networks

( Yanjun Li ),( Yueyun Shen ),( Kaikai Chi ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.12

A tree routing structure is often adopted for many-to-one data gathering and aggregation in sensor networks. For real-time scenarios, considering lossy wireless links, it is an important issue how to construct a maximum-lifetime data gathering tree with delay constraint. In this work, we study the problem of lifetime-preserving and delay-constrained tree construction in unreliable sensor networks. We prove that the problem is NP-complete. A greedy approximation algorithm is proposed. We use expected transmissions count (ETX) as the link quality indicator, as well as a measure of delay. Our algorithm starts from an arbitrary least ETX tree, and iteratively adjusts the hierarchy of the tree to reduce the load on bottleneck nodes by pruning and grafting its sub-tree. The complexity of the proposed algorithm is O(N⁴). Finally, extensive simulations are carried out to verify our approach. Simulation results show that our algorithm provides longer lifetime in various situations compared to existing data gathering schemes.

Impedance Coordinative Control for Cascaded Converter in Bidirectional Application

Yanjun Tian,Fujin Deng,Zhe Chen,Xiaofeng Sun,Yanting Hu 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

Two stage cascaded converters are widely used in bidirectional applications, but the negative impedance may cause system instability. Actually the impedance interaction is much different between forward power flow and reversed power flow, which will introduce more uncertainty to the system stability. This paper proposes a control method for the constant power controlled converter in cascaded system, and consequently it can change the negative impedance of constant power converter into resistive impedance, which will improve the cascaded system stability, as well as merge the impedance difference between forward and reversed power flow. This paper addresses the analysis with the topology of cascaded dualactive - bridge converter (DAB) with inverter, and the proposed control method can also be implemented in unidirectional applications and other general cascaded converter system. The effectiveness has been validated by both simulation and experimental results.