Elastic Valley Spin Controlled Chiral Coupling in Topological Valley Phononic Crystals

Distinct from the phononic valley pseudo-spin, the real physical spin of elastic waves adds a novel tool-kit capable of envisaging the valley-spin physics of topological valley phononic crystals from a local viewpoint. Here, we report the observation of local elastic valley spin as well as the hidden elastic spin-valley locking mechanism overlooked before. We demonstrate that the selective one-way routing of valley phonon states along the topological interface can be reversed by imposing the elastic spin meta-source at different interface locations with opposite valley-spin correspondence. We unveil the physical mechanism of selective directionality as the elastic spin controlled chiral coupling of valley phonon states, through both analytical theory and experimental measurement of the opposite local elastic spin density at different interface locations for different transport directions. The elastic spin of valley topological edge phonons can be extended to other topological states and offers new tool to explore topological metamaterials.Comment: 5 pages, 3 figures, of main text + supplementary 10 figures. To be published in Phys. Rev. Let

DDC-PIM: Efficient Algorithm/Architecture Co-design for Doubling Data Capacity of SRAM-based Processing-In-Memory

Processing-in-memory (PIM), as a novel computing paradigm, provides significant performance benefits from the aspect of effective data movement reduction. SRAM-based PIM has been demonstrated as one of the most promising candidates due to its endurance and compatibility. However, the integration density of SRAM-based PIM is much lower than other non-volatile memory-based ones, due to its inherent 6T structure for storing a single bit. Within comparable area constraints, SRAM-based PIM exhibits notably lower capacity. Thus, aiming to unleash its capacity potential, we propose DDC-PIM, an efficient algorithm/architecture co-design methodology that effectively doubles the equivalent data capacity. At the algorithmic level, we propose a filter-wise complementary correlation (FCC) algorithm to obtain a bitwise complementary pair. At the architecture level, we exploit the intrinsic cross-coupled structure of 6T SRAM to store the bitwise complementary pair in their complementary states ($Q/\overline{Q}$), thereby maximizing the data capacity of each SRAM cell. The dual-broadcast input structure and reconfigurable unit support both depthwise and pointwise convolution, adhering to the requirements of various neural networks. Evaluation results show that DDC-PIM yields about $2.84\times$ speedup on MobileNetV2 and $2.69\times$ on EfficientNet-B0 with negligible accuracy loss compared with PIM baseline implementation. Compared with state-of-the-art SRAM-based PIM macros, DDC-PIM achieves up to $8.41\times$ and $2.75\times$ improvement in weight density and area efficiency, respectively.Comment: 14 pages, to be published in IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems (TCAD

Based on Japan’s Indo-Pacific strategy, explore the development path of China-Japan relations

Japan was the first country to propose the concept of “Indo-Pacific strategy” and was also a staunch supporter and active promoter of it. The formation of Japan’s Indo-Pacific strategy has gone through four stages of evolution: initial appearance, initial formation, extension, and all-round development, and has continuously promoted the development of the Indo-Pacific strategy in a more institutionalized and mature direction from many fields, It has formed a strategic layout in many fields such as comprehensive value sharing, economic and trade competition, maritime security, and multilateral mechanisms. Under the influence of the increasingly fierce competition between China and the US and the policy of putting the United States first, Japan has changed from a proposer of the Indo-Pacific strategy to a promoter, and the Japanese government actively seeks Japan and the United States to jointly dominate the Indo-Pacific economic security order. The accession of the United States has made international relations in the Indo-Pacific region more complex and changeable, and it will have a significant impact on China’s national interests and strategic orientation in the Indo-Pacific area. Sorting out the Japanese Indo-Pacific strategy will help explain the mechanism, rationale, and implementation effect of Japan’s policy choices under the China-US competition, and can also provide a reference for China’s decision-making

Numerical Simulation of Mutual Influence in 470 Sailing Hull and Rudder at Different Hull Speeds

A 470 sailing race requires effective cooperation between athletes to optimize the hull position and the correct heading. To understand the effect of the hull on the maneuverability of the rudder and the influence of the rudder on the stability and rapidity of the hull at different ship speeds, requires numerical 3D simulation and research on the viscous flow field of 470 sailing based on Reynolds-averaged Navier-Stokes equations. The results show that the rudder can reduce the wave making characteristics of the hull, reducing energy loss and thus improving the hull’s rapidity when the speed is greater than 6 m/s, as the effective area of rudder decrease and increases the stall angle, which reduces the manipulatable performance of the rudder to some extent. This study could quantify the performance of the hull and rudder at different speeds. Moreover, this study might provide strategies for the athletes to effectively control the rudder and hull at different speeds

Accurate time-frequency estimation in sαs noise via memory-dependent derivative

This letter presents a time-frequency estimation approach based on memory-dependent derivative to obtain accurate spectrograph interpolation information. The memory correlation derivative is the convolution of a time-varying signal with a dynamic weighting function over a past time period with respect to a common derivative. Considering the described method, discrete data from previous times can be derived to estimate the signal values at the current time and to reduce the effect of noise. Fourier transforms with different scales and delay transforms are used as kernel functions to obtain energy-concentrated time-frequency curves with higher resolution and without frequency leakage. Besides, the memory-dependent derivative with adjustable scale factor is used to overcome time-frequency grid mismatches. Furthermore, differing from the phase accumulation manner of conventional time-frequency estimation, ℓ 1 -norm suppresses the heavy-tailed effect from outliers, thus the robustness of estimator can be enhanced greatly. By suitably choices of scale factor, the estimator can be tuned to exhibit high resolution in targeted regions of the time-frequency spectrum