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光盘用光学头物镜性能的综合评估 总被引:1,自引:0,他引:1
论述了采用波象差均方根、点扩展函数、光学传递函数对高次旋转对称非球面光学头物镜性能进行综合评估的方法。作者在正则坐标理论基础〔1〕上编制了光学头物镜性能综合评估软件。给出了评估实例。 相似文献
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火力发电厂中各类泵与风机的能量消耗在厂用电中所占的比重很大,应该采用更加节能的调节方式来降低泵和风机的能耗,减少厂用电.变频调速技术可以实现无级、大幅度的调节,是一种高效的调节方式.主要介绍了变频调速技术的基本原理和节能原理,分析了某电厂4#锅炉机组送引风机系统变频改造后的节能效果. 相似文献
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Hua Zhou Yang Su Rong Wang Yong Zhu Huiping Shen Tao Pu Chuanxin Wu Jiyong Zhao Baofu Zhang Zhiyong Xu 《Quantum Information Processing》2017,16(10):247
Online reconstruction of a time-variant quantum state from the encoding/decoding results of quantum communication is addressed by developing a method of evolution reconstruction from a single measurement record with random time intervals. A time-variant two-dimensional state is reconstructed on the basis of recovering its expectation value functions of three nonorthogonal projectors from a random single measurement record, which is composed from the discarded qubits of the six-state protocol. The simulated results prove that our method is robust to typical metro quantum channels. Our work extends the Fourier-based method of evolution reconstruction from the version for a regular single measurement record with equal time intervals to a unified one, which can be applied to arbitrary single measurement records. The proposed protocol of evolution reconstruction runs concurrently with the one of quantum communication, which can facilitate the online quantum tomography. 相似文献
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In developing network-enabled embedded systems, developers are often forced to spend a great deal of time and effort analyzing and solving network performance problems. In this paper, we address one such problem: TCP performance interference on an asymmetric link. The upload or download throughput abruptly degrades if there is simultaneously upload and download TCP traffic on the link. While the problem has been addressed by many researchers, their solutions are incomplete as they only improve throughput in one direction, require TCP protocol modifications in end-user devices or are effective for a limited range of network configurations.In order to overcome such limitations, we propose ACKs-first variable-size queuing (AFVQ) for a gateway. In doing so, we have derived an analytic model of the steady-state TCP performance with bidirectional traffic to clearly identify the two sources of the problem: the excessive queuing delay of ACK packets and the excessive number of ACK packets in the queue. Our AFVQ mechanism is designed to directly eliminate the two causes. Specifically, we have based AFVQ on two policies. First, ACKs-first scheduling is used to shorten the queuing delay of ACK packets. Second, the queue size for ACK packets is dynamically adjusted depending on the number of data packets queued in the gateway so that the number of ACK packets is reduced when packets are congested in the gateway. By applying the two policies simultaneously at the uplink and downlink output queue in the gateway, AFVQ achieves balanced TCP throughput improvements in both directions. In this way, it breaks circular dependencies between upload and download traffic.We have implemented AFVQ in our ADSL-based residential gateway using the traffic control module of the Linux kernel. Our gateway yields 95.2% and 93.8% of the maximum download and upload bandwidth, respectively. We have also evaluated the proposed mechanism using the ns-2 simulator over a wide range of network configurations and have shown that AFVQ achieves better upload and download throughput than other representative gateway-based mechanisms such as ACQ, ACKs-first scheduling and ACK Filtering. 相似文献