共查询到20条相似文献,搜索用时 93 毫秒
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为了消除或减少低频噪声,该文 提出了一种低频通风超材料吸声体,该吸声体由对称的折叠通道结构组成,具有深度亚波长、高通风空间占比和低频高效吸声的特性.通过传递矩阵方法、有限元模拟和四麦克风实验法,揭示了对称折叠通道结构通风吸声的物理机制.首先在理论上分析单个吸声体的通风吸声性能并进行了仿真模拟,在共振频率423 Hz附近,吸声系数大于0.9,通风空间占比高达40%.吸声单体的共振频率可通过改变折叠通道的长度来灵活调控,组合多个不同共振频率的吸声单体可以拓宽吸声体的有效吸声带宽.由四个吸声单体组合的通风吸声体可实现314-366 Hz频率范围内的高效声吸收(吸声系数大于0.8),且通风空间占比达到35%,而结构厚度仅为314 Hz时波长的1/10.该低频通风吸声体具有结构简单、结构强度高和容易制造等特点,在低频通风降噪领域有着潜在的应用前景. 相似文献
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由上海市环保局下达、上海大学承担、同济大学协作完成的新型宽频高效吸声体于1996年10月3O日通过了科学技术鉴定。新型宽频高效吸声体,是在分析研究国内外现有吸声体的基础上,采用经济实用的玻璃棉管和硬质矿渣棉板吸声材料,通过不同布置方法的科学组合,充分发挥并提高了吸声材料的降噪作用,取得了低频吸声系数高(。125为0.5-0.8、。25。为0.8一卫.O)、单位吸声量的重量轻(wt20kg/m2)、单位吸声量的价格低(10元/m2)的成果,解决了常用吸声材料和吸声结构低频吸声系数低的问题,填补了国内空白,具有国内领先水平。该型吸声体广泛应用于建筑声学和噪声控制工程,例如各类体育馆、礼堂、剧院、百 相似文献
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圆筒式电动可调吸声体的设计与试验 总被引:1,自引:0,他引:1
可调混响技术在大型剧院式多功能演播厅中设计应用在国内尚属先例。本文介绍的圆筒式电动可调吸声体的技术设计综合了声学、建筑、装修、机械及电气等多方面的要求,文中着重阐述了可调吸声体的声学设计、结构设计及传动设计技术,并对可调吸声体的混响室试验结果作了简要的分析。 相似文献
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通过对3个吸声构件进行了多测点的混响室吸声测量的实验结果进行分析,发现旋转扩散体静止在不同角度状态对测量结果有显著影响,进而提出同一测点在多个旋转扩散体的角度状态下进行测量的测量方法。并使用这一测量方法,比较了混响室顶角测点位置和与按照ISO标准和国标要求选择的空间测点位置所得的测量结果,分析得出顶角测点和空间测点的平均结果是一致的,且顶角位置处的测量结果拥有更小的离散度。因此可以在矩形混响室角落设置少量测点,通过改变旋转扩散体角度状态进行混响室吸声测量。 相似文献
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试车台的噪声比一般民用噪声源的噪声大得多。在试车台室内中高频噪声大,在室外环境低频噪声大。根据上述特点,在室内采用了墙壁吸声层、吸声尖劈、顶棚悬挂空间吸声体、进气活动消声装置等;在排气系统中采用了隔声室、扩张消声室、吸声导流板、迷宫消声空、吸声顶棚、墙面吸声砖、排气塔等技术。综合治理后,达到了《工业企业噪声卫生标准》和《城市区域环境噪声标准》的规定。 相似文献
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介绍了我国在新型吸声体微穿孔板和微缝板的特点、首创、理论分析、加工制作、多方面的应用情况,以及其在国外的影响。也讨论了这些吸声体的部分发展方向。 相似文献
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We study the entanglement cost under quantum operations preserving the positivity of the partial transpose (PPT operations). We demonstrate that this cost is directly related to the logarithmic negativity, thereby providing the operational interpretation for this entanglement measure. As examples we discuss general Werner states and arbitrary bipartite Gaussian states. Then we prove that for the antisymmetric Werner state PPT cost and PPT entanglement of distillation coincide. This is the first example of a truly mixed state for which entanglement manipulation is asymptotically reversible, which points towards a unique entanglement measure under PPT operations. 相似文献
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R. L. Gallawa 《Fiber and Integrated Optics》1981,3(4):299-322
This report is based on published cost figures of the TAT-6 submarine coaxial cable system which went into service on July 27, 1976. Assuming readiness of long wavelength (1300 nm) devices by the late 1980s, we project the expected cost of a fiber cable system based on the TAT-6 experience. The study shows an expected normalized cost savings (dollar per channel kilometer) of 37 to 52 percent, in constant dollars. 相似文献
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直接解调成像的快速算法 总被引:1,自引:0,他引:1
直接解调方法(Direct Demodulate Method, DD)中运用的最多的迭代方法是Richardson-Lucy (RL)迭代. RL迭代的公式可以改写成矩阵形式, 其中包含了主要计算量的两次矩阵乘法在点扩展函数满足平移不变性的情况下可以写成卷积的形式, 而卷积可以使用快速傅里叶变换(Fast Fourier Transform, FFT)做快速计算. 详细介绍了上述过程, 并将该方法应用到了硬X射线调制望远镜(Hard X-ray Modulate Telescope,HXMT)的DD成像中, 通过理论的和模拟的计算对比了优化前后DD方法对计算资源的开销. 相似文献
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The International Linear Collider (ILC), which is based on super-conducting RF acceleration technology, requires the damping rings to provide beams with extremely small equilibrium emittance, and large acceptance to ensure good injection efficiency for high-emittance, and high-energy spread beam from the positron source. In order to reduce the cost for ILC damping rings, an alternative lattice which is different from the baseline configuration design has been designed with modified FODO arc cells, and the total quadrupole number has been reduced by half. At the same time, to decrease the total cost involved in constructing access shafts needed to supply power, cryogenics etc. for the wigglers and other systems, the number of wiggler sections is decreased from 8 to 4, and further to 2. This new lattice has been optimized to have a good dynamic aperture. This alternative ILC damping ring lattice design will reduce the cost largely as compared with the baseline design. 相似文献
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Kyohei Shibano Reo Kontani Hiroshi Hirai Mikio Hasegawa Kazuyuki Aihara Hisao Taoka David McQuilkin Rikiya Abe 《The European physical journal. Special topics》2014,223(12):2611-2620
In recent years, practical research related to distributed power generation and networked distribution grids has been increasing. This research uses a relatively abstract model for the cost reduction in the Digital Grid Power Network. In the Digital Grid, the traditional wide-area synchronous grid is divided into smaller segmented grids which are connected asynchronously. In this paper, we demonstrate how to formulate the minimized cost of power generation by using linear programming methods, while considering the cost of electric transmission and distribution and using asynchronous power interchange among separate grids. 相似文献
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This paper proposes an adaptive buffer replacement algorithm for NAND flash memory-based databases, which is called HDC. HDC introduces an efficient replacing index for selecting pages to be evicted. This replacing index considers two factors: the hot degree of each page and the cost of writing the victim page back to NAND flash memory. It can adaptively change the weight of each factor according to the cost ratio of NAND flash memory. HDC also introduces an efficient partial update scheme, which only writes the dirty data within the dirty victim page back to NAND flash memory for further reducing the number of write operations and writes the dirty data to the free block with the lowest erase count for improving the wear-leveling degree of NAND flash memory. We conduct trace-driven simulations on two kinds of NAND flash memories the cost ratios of which are 118:1 and 2:1. The experimental results show that HDC outperforms the state-of-the-art algorithms on both these kinds of NAND flash memories. 相似文献
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基于节能的绿色光网络路由算法的研究 总被引:1,自引:0,他引:1
在传统的网络路由算法中,一般采用最短路径算法进行路由选路,最短路径算法以节点间的距离为权重,计算一条由源节点至目的节点的权重最小的路径以完成路由。最短路径算法虽然最小化了距离长度代价,却没有考虑能耗问题,所以使用最短路径算法所得出路径的能耗并不一定是最小的。针对这一问题,提出一种新型的综合性绿色路由算法,设定能耗作为节点间的权重,融合光旁路及业务量疏导,同时考虑路由和波长分配(RWA)问题,将完成每个业务所需要的能耗最小化,实现节能。仿真结果表明,与最短路径算法相比,绿色路由算法在较大规模网络中能够节省约40%的能耗,节能效果相当显著。 相似文献
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在换热网络优化问题中,采用内部公用工程代替换热温度交叉的不可行匹配能使优化得以继续,同时扩大求解空间,但可能因增加额外的固定投资费用而使其作为差解在进化过程中被接受下来,导致优化效率下降.鉴于此,首先分析内部公用工程对优化进程可能造成的负面影响,提出一种内部公用工程的进化策略,对于具有一对内部公用工程的结构,首先通过扩大其年综合费用以进行惩罚,从而降低其接受的概率,继之,针对仍被接受的内部公用工程结构,在每次迭代时均强制内部公用工程进行随机游走,合理调整其大小,从而改善结构性能.采用两个算例验证策略提升了算法优化效率. 相似文献
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This article examines a multi-user mobile edge computing (MEC) system for the Internet of Vehicle (IoV), where one edge point (EP) nearby the vehicles can help assist in processing the compute-intensive tasks. For the MEC networks, the majority of existing works concentrate on the minimization of system cost of task offloading under the perfect channel estimation, which however fails to consider the practical limitation of imperfect channel estimation (CSI) because of vehicles’ high-mobility. Therefore, the goal of our study is to reduce the delay as well as energy consumption (EC) of computation and communication with imperfect CSI, which are the two significant performance metrics of MEC network. With this aim, we first express the system cost as a form of the linear combination of the delay and EC, and then formulate the optimization problem for the system cost. Moreover, a novel deep approach is proposed, which is integrated by deep reinforcement learning (DRL) with the Lagrange multiplier to jointly minimize the system cost. In particular, the DRL algorithm is employed to obtain the capable offloading strategy, while the Lagrange multiplier is used to obtain the bandwidth allocation. The simulated results are finally presented to show that the devised approach outperforms the traditional ones. 相似文献