Transmission shielding technology for bistatic sonar

基线附近区域为双基地声呐的探测盲区,当目标位于基线区域时,目标回波与强直达波干扰同时同向到达,基于空域滤波等的传统直达波抑制方法失效。为实现双基地声呐对盲区内目标的探测,提出了一种适用于多发射阵元系统的发射声屏蔽技术。发射声屏蔽技术利用目标回波与直达波相异的多途信道结构特性,自动屏蔽在接收站位置处的直达波而不影响目标回波,且不需接收站进行任何后续处理。在已知回波信道信息时,发射声屏蔽技术可进一步实现对回波信号的聚焦,提高信干比。仿真结果表明,在不同信道条件下发射声屏蔽均能有效抑制直达波干扰。利用发射声屏蔽技术,双基地声呐能够实现对基线区内目标的检测。The area near the baseline is a dead zone for bistatic sonar.The echo and the strong direct wave will arrive in the same place simultaneously when the target is in the baseline area and the direct wave suppression method based on a spatial filter will fail.To detect targets in the dead zone,a transmission shielding method for a multi-element transmit system is proposed.The transmission shielding automatically suppresses the direct wave at the receiving station utilizing structural differences in multiple channels between the echo and the direct wave.The transmission shielding further focuses on the echo,so as to improve the Signal-Noise Ratio,using known echo channel information.The simulation results show the transmission shielding method can suppress direct wave interference for different multipath channels.Bistatic sonar can detect targets in the baseline area utilizing the transmission shielding method.国家自然科学基金资助项目(51179034); 海洋工程国家重点实验室(上海交通大学)资助项目(1211

CH_4-CO_2混合气体水合物在NaCl溶液中生成过程

To study the influence of salinity on hydrate growth rates and gas distributions in hydrate phase,gas hydrates were crystallized in pure water,3.4%,5.0%sodium chloride solution respectively using CH_4-CO_2 gas mixtures.Results showed that the gases neede

ch4co2混合气体水合物在nacl溶液中生成过程

To study the influence of salinity on hydrate growth rates and gas distributions in hydrate phase,gas hydrates were crystallized in pure water,3.4%,5.0%sodium chloride solution respectively using CH_4-CO_2 gas mixtures.Results showed that the gases neede

Crystallization of the CH_4-CO_2 Mixed Gas Hydrates in NaCl Solutions

To study the influence of salinity on hydrate growth rates and gas distributions in hydrate phase,gas hydrates were crystallized in pure water,3.4%,5.0%sodium chloride solution respectively using CH_4-CO_2 gas mixtures.Results showed that the gases neede

天山山区草地变化与气候要素的时滞效应分析/Temporal responses of NDVI to climate factors in Tianshan Mountainous Area[J]

通过选取新疆天山山区作为研究区,分析该地区气候参数(降水、温度、光照)对草地季节变化影响的滞后性特征.利用研究区内各气象站点的气温、降水和日照时数的逐句数据、SPOTVGT时序数据和土地利用覆盖数据,运用时滞相关分析和GIS空间分析方法.根据13个滞后期(0～12旬)和13个时间尺度(1～13旬)分析了植被NDVI与同期及前期气温、降水、日照时数之间的相关关系.结果表明:天山山区草地长势与同期气温和降水的相关性较强,而与同期日照时数的相关关系较弱(0.099).在1旬的时间尺度下,草地NDVI对气温、降水、日照时数响应的滞后时间分别为2旬、1旬和7旬.同时,考虑到草地的长势可能受到前期数旬气象条件的影响,进一步在多旬时间尺度下进行滞后分析.结果发现,就气温而言,草地与当旬气温和前2旬气温的累积量相关性最好;降水的滞后时间尺度略长于气温,当旬降水和之前一个月(0-3旬)降水累积量对于草地长势的影响最大;日照时数对于草地影响的最佳滞后时间尺度为10旬,草地NDVI与当旬和前9旬的日照时数累积量的相关性最好

Aripiprazole versus other atypical antipsychotics for schizophrenia

BACKGROUND: In most western industrialised countries, second generation (atypical) antipsychotics are recommended as first line drug treatments for people with schizophrenia. In this review we specifically examine how the efficacy and tolerability of one such agent - aripiprazole - differs from that of other comparable second generation antipsychotics. OBJECTIVES: To evaluate the effects of aripiprazole compared with other atypical antipsychotics for people with schizophrenia and schizophrenia-like psychoses. SEARCH METHODS: We searched the Cochrane Schizophrenia Group Trials Register (November 2011), inspected references of all identified studies for further trials, and contacted relevant pharmaceutical companies, drug approval agencies and authors of trials for additional information. SELECTION CRITERIA: We included all randomised clinical trials (RCTs) comparing aripiprazole (oral) with oral and parenteral forms of amisulpride, clozapine, olanzapine, quetiapine, risperidone, sertindole, ziprasidone or zotepine for people with schizophrenia or schizophrenia-like psychoses. DATA COLLECTION AND ANALYSIS: We extracted data independently. For dichotomous data we calculated risk ratios (RR) and their 95% confidence intervals (CI) on an intention-to-treat basis based on a random-effects model. Where possible, we calculated illustrative comparative risks for primary outcomes. For continuous data, we calculated mean differences (MD), again based on a random-effects model. We assessed risk of bias for each included study. MAIN RESULTS: We included 12 trials involving 6389 patients. Aripiprazole was compared to olanzapine, risperidone and ziprasidone. All trials were sponsored by an interested drug manufacturer. The overall number of participants leaving studies early was 30% to 40%, limiting validity (no differences between groups).When compared with olanzapine no differences were apparent for global state (no clinically important change: n = 703, 1 RCT, RR short-term 1.00 95% CI 0.81 to 1.22; n = 317, 1 RCT, RR medium-term 1.08 95% CI 0.95 to 1.22) but mental state tended to favour olanzapine (n = 1360, 3 RCTs, MD total Positive and Negative Syndrome Scale (PANSS) 4.68 95% CI 2.21 to 7.16). There was no significant difference in extrapyramidal symptoms (n = 529, 2 RCTs, RR 0.99 95% CI 0.62 to 1.59) but fewer in the aripiprazole group had increased cholesterol levels (n = 223, 1 RCT, RR 0.32 95% CI 0.19 to 0.54) or weight gain of 7% or more of total body weight (n = 1095, 3 RCTs, RR 0.39 95% CI 0.28 to 0.54).When compared with risperidone, aripiprazole showed no advantage in terms of global state (n = 384, 2 RCTs, RR no important improvement 1.14 95% CI 0.81 to 1.60) or mental state (n = 372, 2 RCTs, MD total PANSS 1.50 95% CI -2.96 to 5.96).One study compared aripiprazole with ziprasidone (n = 247) and both the groups reported similar change in the global state (n = 247, 1 RCT, MD average change in Clinical Global Impression-Severity (CGI-S) score -0.03 95% CI -0.28 to 0.22) and mental state (n = 247, 1 RCT, MD change PANSS -3.00 95% CI -7.29 to 1.29).When compared with any one of several new generation antipsychotic drugs the aripiprazole group showed improvement in global state in energy (n = 523, 1 RCT, RR 0.69 95% CI 0.56 to 0.84), mood (n = 523, 1 RCT, RR 0.77 95% CI 0.65 to 0.92), negative symptoms (n = 523, 1 RCT, RR 0.82 95% CI 0.68 to 0.99), somnolence (n = 523, 1 RCT, RR 0.80 95% CI 0.69 to 0.93) and weight gain (n = 523, 1 RCT, RR 0.84 95% CI 0.76 to 0.94). Significantly more people given aripiprazole reported symptoms of nausea (n = 2881, 3 RCTs, RR 3.13 95% CI 2.12 to 4.61) but weight gain (7% or more of total body weight) was less common in people allocated aripiprazole (n = 330, 1 RCT, RR 0.35 95% CI 0.19 to 0.64). Aripiprazole may have value in aggression but data are limited. This will be the focus of another review. AUTHORS' CONCLUSIONS: Information on all comparisons are of limited quality, are incomplete and problematic to apply clinically. Aripiprazole is an antipsychotic drug with a variant but not absent adverse effect profile. Long-term data are sparse and there is considerable scope for another update of this review as new data emerges from the many Chinese studies as well as from ongoing larger, independent pragmatic trials