Subjects: Environmental Sciences, Resource Sciences >> Other Disciplines of Environmental Sciences, Resource Sciences submitted time 2021-03-02 Cooperative journals: 《干旱区研究》
Abstract：运用再分析资料（NCEP/NCAR）分析了新疆区域高空年均气温变化特征，同时运用逐步回归法对新疆高空冷月（1月）、暖月（7月）实测气温数据进行缺测插补，并通过交叉验证法对插补数据进行精度检验，在此基础上分析了新疆区域冷月、暖月高空气温变化特征，运用插补重建后的高空实测数据对1月、7月再分析资料（NCEP/NCAR）进行精度验证。结果表明：（1）新疆区域高空缺测插补后的数据精度较高效果较好，能够反映新疆高空气温变化的客观事实。（2）通过对新疆区域对流层（低、中、上）、平流层下层的冷、暖月和年平均变化趋势分析来看，随着高度的上升气温变化趋势由升温转为降温，并且随着高度的上升升温率在减小，减温率在增大；气温越高的月份，随着高度的升高，气温变化趋势发生改变的高度就越高；2000年后，对流层各层多为偏暖年，平流层下层多为偏冷年。（3）850 hPa和700 hPa年均温转折点均发生在1996年，由冷转暖；100 hPa发生在1995—1997年，由暖转冷；500hPa和300 hPa均未出现明显的突变年份。（4）1月、7月再分析资料（NCEP/NCAR）与实测数据相关系数大多在0.9以上，总体误差相对较小。
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology submitted time 2020-11-19 Cooperative journals: 《干旱区地理》
Abstract： 在干旱少雨的山区开展小流域的暴雨山洪预报预警关键技术研究，对防灾减灾意义重大。2018年7月31日新疆哈密北部山区出现特大暴雨，发生罕见的山洪灾害，致使射月沟流域水库漫坝溃口，下游受灾严重。射月沟流域气象观测站点少且缺乏水文监测资料，为客观定量分析射月沟流域大暴雨面雨量、形成的洪水汇水量以及致灾水库过程。通过采用空间插值法和多源融合逐时降水资料（CMPAS）计算了射月沟水库上游面雨量并进行检验分析。根据不同面雨量驱动Floodarea模型得出射月沟水库上游累计汇水量，结果表明：多源融合降水产品估算所得最大洪峰流量和累计汇水量与水利部门事后调查数据较吻合，最大洪峰量为1 756 m3·s-1，精确性达到调查值的95%，射月沟水库上游暴雨山洪总量为2.64×107 m3，远超该水库的防洪库容和溢洪道承载能力。
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2019-05-10 Cooperative journals: 《计算机应用研究》
Abstract： The flow rate based direct sequence spread spectrum (DSSS) flow watermarking technique used the same pseudo-random (PN) code to modulate the multi-bit watermark signal, as a result, the DSSS watermarked flow had self-similarity, and the mean-square autocorrelation (MSAC) attack could detect the existence of the DSSS flow watermark by using single DSSS watermarked flow, which seriously destroyed the stealthiness of the DSSS flow watermark. Although the PN code orthogonalization method could eliminate the autocorrelation of the DSSS watermarked flow and thus resisted the MSAC attack, however, the orthogonal PN codes were difficult to generate, which limit its application range. Therefore, this paper proposed the PN code randomization based MSAC attack resistance (PNCR-MAR) method, when the watermark signal was embedded into the target flow, the PN codes of different lengths, randomly selected from a PN code set, were used to spread each watermark bit, so that the mean-square autocorrelation of the flow rate of the watermarked flow no longer exhibited periodic peaks, as a result, this PNCR-MAR method could defend against the MSAC attack. Theoretical analysis and experimental results show that this proposed PNCR-MAR method can effectively resist the MSAC attack, and the adopted PN codes are easy to generate, which is suitable for deployment and application.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-04-17 Cooperative journals: 《计算机应用研究》
Abstract： The existing technologies for protecting IPv6 nodes by address hopping rely on time synchronization or event synchronization, utilizing the good mobility feature of IPv6 and multiple care-of address registration mechanisms, this paper proposed a proactive defense scheme of IPv6 based on virtual mobile. By assigning a dynamically changing care-of address to an IPv6 node, the IPv6 node presented the continuously moving feature in the network, reduced the attack probability of an attacker, and ensured the continuity of communications. Theoretical analysis and experimental tests show that the scheme has good anti-attack ability and less system overhead.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-04-17 Cooperative journals: 《计算机应用研究》
Abstract： In order to test the defensive capability of IPv6 firewall to against potential IPv6 network threats, this paper studied IPv6 firewall defensive capability testing technology. Through the research of IPv6 protocol, this paper constructed five kinds of test packets with security risks, such as ICMPv6, single extended header, multi-extension header, fragmentation and address scopes, proposed a firewall testing framework with C/S architecture, built independent test modules for every kind of testing based the framework and test packets, set up test environments that can be used to test stateful firewalls, and provided appropriate test methods. Using the method, this paper tested a Cisco ASA5505 firewall and found its advantages and disadvantages.
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