Nonadiabatic geometric phase in a doubly driven two-level system

We study theoretically the nonadiabatic geometric phase of a doubly driven two-level system with an additional relative phase between the two driving modes introduced in. It is shown that the time evolution of the system strongly depends on this relative phase. The condition for the system returning to its initial state after a single period is given by the means of the Landau–Zener–Stückelberg–Majorana destructive interference. The nonadiabatic geometric phase accompanying a cyclic evolution is shown to be related to the Stokes phase as well as this relative phase. By controlling the relative phase, the geometric phase can characterize two distinct phases in the adiabatic limit.

WIST:基于三维查找表的SM4算法新型白盒设计

随着密码攻击方式更加多样、隐蔽且破坏性更强,密码分析者可能拥有越来越多的攻击权限与攻击能力,甚至能够获取算法的内部结构.为了更有效保护密钥,本文提出一种基于三维查找表的白盒SM4密码算法实现方案WIST.首先将SM4分组密码算法的线性变换用矩阵表示,设计了能对密钥信息进行隐藏保护的三维查找表,利用输入编码和输出编码对查找表混淆处理,同时采用仿射函数作为外部编码,完成了SM4算法的白盒化实现,并验证了此算法的正确性.效率分析表明WIST占用内存空间适中,具有较高安全性;安全性分析表明WIST能抵抗BGE攻击、MGH攻击、侧信道攻击、线性攻击与差分攻击等常见攻击类型.WIST可以在白盒攻击环境下更好地保护密钥信息.

基于新型BIST的LUT测试方法研究

针对FPGA内部的LUT资源覆盖测试,提出一种新型BIST的测试方法。通过改进的LFSR实现了全地址的伪随机向量输入,利用构造的黄金模块电路与被测模块进行输出比较,实现对被测模块功能的快速测试,并在Vivado 2018.3中完成了仿真测试。通过ATE测试平台,加载设计的BIST测试向量,验证结果与仿真完全一致,仅2次配置即可实现LUT的100%覆盖率测试。此外,还构建了LUT故障注入模拟电路,人为控制被测模块的输入故障,通过新型BIST的测试方法有效诊断出被测模块功能异常,实现了准确识别。以上结果表明,该方法不仅降低了测试配置次数,而且能够准确识别LUT功能故障,适用于大规模量产测试。

Chiral bound states in a staggered array of coupled resonators

We study the chiral bound states in a coupled-resonator array with staggered hopping strengths,which interacts with a two-level small atom through a single coupling point or two adjacent ones.In addition to the two typical bound states found above and below the energy bands,this system presents an extraordinary chiral bound state located within the energy gap.We use the chirality to quantify the breaking of the mirror symmetry.We find that the chirality value undergoes continuous changes by tuning the coupling strengths.The preferred direction of the chirality is controlled not only by the competition between the intracell and the intercell hoppings in the coupled-resonator array,but also by the coherence between the two coupling points.In the case with one coupling point,the chirality values varies monotonously with difference between the intracell hopping and the intercell hoppings.While in the case with two coupling points,due to the coherence between the two coupling points the perfect chiral states can be obtained.

基于FPGA的永磁同步电机SVPWM的数字电路设计

针对永磁同步电机矢量控制算法中的空间矢量脉冲宽度调制(Space Vector Pulse Width Modulation,SVPWM)在现场可编程门阵列(Field-Programmable Gate Array,FPGA)中不能直接实现正余弦计算、无理数乘法的问题进行优化设计。设计了基于查表法和一次线性补偿的正余弦数值计算、有符号数的√3乘法计算模块,并使用Cyclone IV FPGA的硬件乘法器资源,对反Park变换、扇区判断和三相作用时间的计算进行了时序约束,对输入电机编码器数值、旋转坐标系的V_d和V_q参数经过进行计算,输出带死区功能的三相七段式PWM控制信号。在FPGA中实现SVPWM算法精度为3.0×10^(-5),计算时间为1.6μs,对比高性能STM32F429微处理器有一定优势,满足了永磁同步电机的矢量控制要求。

Linux虚拟文件系统层的路径检索加速

为解决Linux内核传统路径检索日益凸显的开销问题,提出Staged Lookup以加速路径检索,通过动态缓存热目录来减少文件访问的时延。Staged Lookup的核心在于缓存频繁使用的目录项,从而避免从根节点重复遍历路径。不同于从根结点开始的检索操作,Staged Lookup扩展了搜索策略,允许从最近缓存的目录项向后或向前进行路径检索。在Linux内核版本3.14和5.4上部署Staged Lookup的原型,并开展实际系统测试。实验数据显示,相比于传统的路径检索方式,Staged Lookup能实现高达46.9%的性能提升。

基于遥感云计算平台的卫星影像大气校正应用系统的设计

针对传统大气校正处理模式在数据共享以及业务流程等方面的不足,依托PIE-Engine遥感云计算平台,采用FastAPI Web框架的前后端分离技术,设计了支持PSG等高性能大气辐射传输模型的卫星影像大气校正在线应用系统。在此基础上,开发了一种可指定传感器、目标点位和观测时间等输入条件,运用自适应查找表快速处理业务的大气校正原型系统。该系统的设计和研究,有效拓展了遥感云计算平台的应用领域,也为日后实现功能完备的遥感影像处理分析在线应用系统提供了技术支持。

基于FDC氢燃料电池堆在线智能监测系统

在氢燃料电池汽车中,Fuel Cell DC-DC变换器(FDC)在氢燃料电池堆(氢堆)和逆变器之间起着关键的接口作用,其输出直流母线电压的稳定是保证电机等负载正常工作的关键环节。为此本文提出一种新型滑模预测控制,首先改进FDC拓扑结构并建立基于滑模面的预测模型,然后设计基于滑模面价值函数提高FDC跟踪精度;在此基础上为实现氢堆在线智能监测,进一步采用变步长线性插值查表法对氢堆阻抗进行在线精确估算,首先通过数字控制使FDC自生成变频的微小正弦谐波,并根据FDC输入侧电压电流采样,估算氢堆多频段阻抗值;然后采用变步长分段线性插值查表法,对比阻抗估算值与设计标准值,评判氢堆当前状态,实现氢堆在线智能监测。最后进行仿真及实验验证,验证数据显示:①当实验参考电流设定为100 A,传统PI控制时系统电流超调及响应时间分别为20 A、15 ms,应用滑模预测控制时系统电流超调及响应时间分别为1.5 A、2.5 ms;②额定工况下,FDC对自生成谐波的跟踪精度能控制在2%以内;③采用变步长线性插值查表法能实现氢堆阻抗的精确估算,验证算法的有效性。

基于FPGA的访问控制列表并行查找设计与实现

在高安全要求的网络环境中,多种类型的网络设备均需要部署基于规则的访问控制功能。访问控制列表通过五元组进行规则匹配,实现对网络报文的筛选、过滤、处理、控制等操作。如何利用有限的资源实现更高查表性能、更多规则数量的访问控制列表,是相关设备的关键技术之一。通过分析网络通信设备中访问控制列表的一般工作流程,文章提出了一种改进的基于现场可编程逻辑门阵列(Field Programmable Gate Array,FPGA)实现的访问控制列表并行查找设计方法,并详细阐述了具体模块的实现方案。实验结果表明,该方案可以充分利用FPGA的存储与逻辑资源,实现较大规模的支持范围匹配的规则表项,并可以支持10 Gpbs速率等级网络通信的查表需求。

电动助力转向机滑移力影响因子分析方法研究

为解决生产现场滑移力不合格问题,提出一种滑移力影响因子分析方法,依据电动助力转向机工作原理,运用多阶段元件查找方法和滑移力拆解分析方法,对比BOB件和WOW件各零部件滑移力贡献值,锁定影响滑移力的关键因子是配置螺母。所提方法可有效分析并解决生产现场滑移力不合格问题,为新项目设计开发提供优化方向。

浅谈LOOKUP等函数的实际应用

Microsoft Excel是最优秀的电子表格软件之一,但其不仅仅是电子表格,其具有强大的数据处理和数据分析能力。在销售、工资核算等工作中经常用到多表联合查询与计算等操作,使用Excel内置的LOOKUP和VLOOKUP等函数可以产生类似操作数据库的效果,轻松地完成工作。

A DISCRETE TIME TWO-LEVEL MIXED SERVICE PARALLEL POLLING MODEL

We present a discrete time single-server two-level mixed service polling systems with two queue types, one center queue and N normal queues. Two-level means the center queue will be successive served after each normal queue. In the first level, server visits between the center queue and the normal queue. In the second level, normal queues are polled by a cyclic order. Mixed service means the service discipline are exhaustive for center queue, and parallel 1-limited for normal queues. We propose an imbedded Markov chain framework to drive the closed-form expressions for the mean cycle time, mean queue length, and mean waiting time. Numerical examples demonstrate that theoretical and simulation results are identical the new system efficiently differentiates priorities.

FAST UPDATE ALGORITHM FOR TCAM-BASED ROUTING LOOKUPS

Routing technology has been forced to evolve towards higher capacity and per port packet processing speed. The ability to achieve high forwarding speed is due to either software or hardware technology. TCAM (Ternary Content Addressable Memory) provides a performance advantage over other software or hardware search algorithms, often resulting in an order of magnitude reduction of search time. But slow updates may affect the performance of TCAM based routing lookup. So the key is to design a table management algorithm, which supports high speed updates in TCAMs. This paper presented three table management algorithms, and then compared their performance. Finally, the optimal one after comparing was given.

Robust Watermarking with Kernels-Alternated Error Diffusion and Weighted Lookup Table in Halftone Images

A halftone watermarking method of high quality, robustness, and capacity flexibility is presented in this paper. An objective halftone image quality evaluation method based on the human visual system obtained by a least-mean-square algorithm is also introduced. In the encoder, the kernels-alternated error diffusion （KAEDF） is applied. It is able to maintain the computational complexity at the same level as ordinary error diffusion. Compared with Hel-Or using ordered dithering, the proposed KAEDF yields a better image quality through using error diffusion. We also propose a weighted lookup table （WLUT） in the decoder instead of lookup table （LUT）, as proposed by Pei and Guo, so as to achieve a higher decoded rate. As the experimental results demonstrate, this technique is able to guard against degradation due to tampering, cropping, rotation, and print-and-scan processes in error-diffused halftone images.

刍议Lookup函数在体育成绩评分上的应用

本文通过对Lookup函数进行体育成绩评定方法的论述,使体育教师对学生体育成绩的统计从以往手工操作转向函数换算。不但解决了体育教师在体育成绩评定上效率不高、容易出错的问题,并且对当前体育教师的办公现代化有积极地促进作用。

TWO-LEVEL MULTISCALE FINITE ELEMENT METHODS FOR THE STEADY NAVIER-STOKES PROBLEM

In this article, on the basis of two-level discretizations and multiscale finite element method, two kinds of finite element algorithms for steady Navier-Stokes problem are presented and discussed. The main technique is first to use a standard finite element discretization on a coarse mesh to approximate low frequencies, then to apply the simple and Newton scheme to linearize discretizations on a fine grid. At this process, multiscale finite element method as a stabilized method deals with the lowest equal-order finite element pairs not satisfying the inf-sup condition. Under the uniqueness condition, error analyses for both algorithms are given. Numerical results are reported to demonstrate the effectiveness of the simple and Newton scheme.

Two-level percutaneous endoscopic lumbar discectomy for highly migrated upper lumbar disc herniation: A case report

BACKGROUND The technique of percutaneous endoscopic lumbar discectomy(PELD)as a transforaminal approach has been used to treat highly migrated lower lumbar disc herniations.However,due to the different anatomic characteristics of the upper lumbar spine,conventional transforaminal PELD may fail to remove the highly migrated upper lumbar disc nucleus pulposus.Therefore,the purpose of this study was to describe a novel surgical technique,two-level PELD,for the treatment of highly migrated upper lumbar disc herniations and to report its related clinical outcomes.CASE SUMMARY A 60-year-old male presented with a complaint of pain at his lower back and right lower limb.The patient received 3 mo of conservative treatments but the symptoms were not alleviated.Physical examination revealed a positive femoral nerve stretch test and a negative straight leg raise test for the right leg,and preoperative visual analog scale(VAS)score for the lower back was 6 points and for the right leg was 8 points.Magnetic resonance imaging(MRI)demonstrated L2-L3 disc herniation on the right side and the herniated nucleus pulposus migrated to the upper margin of L2 vertebral body.According to physical examination and imaging findings,surgery was the primary consideration.Therefore,the patient underwent surgical treatment with two-level PELD.The pain symptom was relieved and the VAS score for back and thigh pain was one point postoperatively.The patient was asymptomatic and follow-up MRI scan 1 year after operation revealed no residual nucleus pulposus.CONCLUSION Two-level PELD as a transforaminal approach can be a safe and effective procedure for highly migrated upper lumbar disc herniation.

Single photon transport properties in coupled cavity arrays nonlocally coupled to a two-level atom in the presence of dissipation

We discuss the effects of dissipation on the behavior of single photon transport in a system of coupled cavity arrays, with the two nearest cavities nonlocally coupled to a two-level atom. The single photon transmission amplitude is solved exactly by employing the quasi-boson picture. We investigate two different situations of local and nonlocal couplings, respectively. Comparing the dissipative case with the nondissipative one reveals that the dissipation of the system increases the middle dip and lowers the peak of the single photon transmission amplitudes, broadening the line width of the transport spectrum. It should be noted that the influence of the cavity dissipation to the single photon transport spectrum is asymmet- ric. By comparing the nonlocal coupling with the local one, one can find that the enhancement of the middle dip of single photon transmission amplitudes is mostly caused by the atom dissipation and that the reduced peak is mainly caused by the cavity dissipation, no matter whether it is a nonlocal or local coupling case. Whereas in the nonlocal coupling case, when the coupling strength gets stronger, the cavity dissipation has a greater effect on the single photon transport spectrum and the atom dissipation affection becomes weak, so it can be ignored.

Bio-Inspired Binary Bees Algorithm for a Two-Level Distribution Optimisation Problem

Two uncoupleable distributions, assigning missions to robots and allocating robots to home stations, accompany the use ofmobile service robots in hospitals.In the given problem, two workload-related objectives and five groups of constraints areproposed.A bio-mimicked Binary Bees Algorithm (BBA) is introduced to solve this multiobjective multiconstraint combinatorialoptimisation problem, in which constraint handling technique (Multiobjective Transformation, MOT), multiobjectiveevaluation method (nondominance selection), global search strategy (stochastic search in the variable space), local searchstrategy (Hamming neighbourhood exploitation), and post-processing means (feasibility selection) are the main issues.TheBBA is then demonstrated with a case study, presenting the execution process of the algorithm, and also explaining the change ofelite number in evolutionary process.Its optimisation result provides a group of feasible nondominated two-level distributionschemes.

Vacuum induced transparency and slow light phenomena in a two-level atomic ensemble controlled by a cavity

We study the optical properties of a two-level atomic ensemble controlled by a high-finesse cavity. Even though the cavity is initially in the vacuum state in the absence of external driving, the probe response of the atomic ensemble can be dramatically modified. When the collectively enhanced atom–cavity coupling is strong enough and the cavity decay rate is much smaller than the atomic damping rate, an electromagnetically induced transparency-like coherent phenomenon emerges with a dip absorption for the response of the two-level atoms in the cavity without driving, and thus is called vacuum induced transparency. We also show the slow light with very low group velocity in such an atomic ensemble.