高空核爆电磁脉冲效应的数值分析

高空核爆炸瞬发的γ光子与大气层发生相互作用,产生突然增大的康普顿电子流,从而激发出很强的电磁脉冲。该电磁脉冲从源区的边缘以不同的角度向地面辐射,覆盖范围非常广,频带分布也较宽,可以很容易的耦合到架空导线、天线塔以及无线电设备中,对电力系统和其他设备产生干扰。目前,对于高空爆炸激励的电磁脉冲研究,多数是将其作平面波处理,并用双指数函数波来近似。虽然这种近似方法所得到的结果与实验结果在时域上吻合较好,但是不能反映出空间变化规律。因为爆炸当量不同,不同空间位置上的电磁脉冲波形不同、其幅值和上升时间也是不同。对于以上问题,本文对不同爆炸当量下高空核爆炸产生的γ光子,以及γ光子激励出的电磁脉冲覆盖范围、..

The electromagnetic properties of plasma produced by hypervelocity impact

The change of electron density in moving plasma in this paper is empirically determined according to multiple ground-based experimental results and the assumption of the Maxwell distribution. Moreover, the equation of the magnetic field intensity, dominated by the current due to the collective electron movement during the expansion, is presented on the basis of the Biot-Savart law, and its relationship with time and space is subsequently depicted. In addition, hypervelocity impact experiments on a 2AL12 target have been carried out using a two-stage light gas gun to accelerate a 2AL12 projectile of 6.4mm to 6.2 km/s. Spiral coils are designed to measure the intensity of the electromagnetic field induced by this impact. The experimental results show that the magnetic field strength is an alternate pulse maintaining nearly 1ms and its maximum is close to 15 mu T, which is strong enough to interfere with the communication circuit and chip in spacecrafts. Lastly, numerical simulation of the magnetic field intensity using this experimental parameter reveals that the intensity in our estimation from our theory tends to be well consistent with the experimental data in the first peak of the pulse signal. Published by AIP Publishing

A decoupling operation model of flux losses and ohmic losses in magnetic flux compression generator

研究螺旋型爆磁压缩发生器的损耗机理,建立了一种磁通损耗项和电阻损耗项解耦表示的爆磁压缩发生器运行模型,并给出了物理意义明确的损耗项解析式;经实验验证,对于损耗机理更为复杂的紧凑型级联爆磁压缩发生器,本模型仿真结果与实验结果仍符合良好,仿真波形与实验波形总体趋势一致,螺距变化的节点处过度清晰,定子均绕段的波形相似度较高

材料电子束蒸发速率的稳定性实验研究

高速电子束能够得到很高的能量密度并且可以进行有效的电气控制,所以电子束蒸发法已成为高速沉积高纯物质薄膜的一种主要的加热方法。该沉积过程中残余气体压力、蒸发材料的性质、电子束的特性等诸多因素都会影响被蒸发材料的蒸发速率。为了得到更稳定的蒸发速率,本文详细分析了蒸发速率不稳定的因素,并且对Cu,Y,BaF_2三种材料进行了多组蒸发实验,得到了材料性质、蒸发速率、蒸发时间不同时,电子枪阳极高压、材料状态对蒸发速率的影响。实验结果表明:阳极高压稳定性对Cu块蒸发速率的影响不明显,而对熔融态的Y和BaF_2蒸发速率的影响比较明显。当阳极高压稳定在8 kV、蒸发时间为20分钟时,Cu块的蒸发速率比较稳定,..

物理气相沉积界面吸附系数与薄膜组分的相互依赖关系

以YBa_2Cu_3O_(7-δ)高温超导薄膜制备中的组分控制问题为背景,通过电子束三源共蒸发实验定性分析了Y_t,BaF_2和Cu_3种组元的吸附系数对温度、界面组分的依赖关系。结果表明:Y_t和BaF_2的吸附系数与温度、沉积界面组分的相关度非常小;Cu的吸附系数在室温沉积时也与界面组分不相关,而在300℃和600℃下高温沉积时Cu的吸附系数随着BaF_2组分的增大而显著降低。最后,借助分子动力学模拟诠释了上述规律的物理机制。此研

沉积温度对电子束物理气相沉积制备YBCO薄膜性能与结构的影响

采用力学研究所自主研制的多元电子束物理气相沉积系统两步法生长YBCO薄膜。所用衬底为{001}LaAlO_3(简称LAO)单晶,尺寸为15mm×15mm,厚度为0.5mm。蒸发源选用Y,BaF_2和Cu,其纯度均高于99%。电子束蒸镀时衬底温度分别为室温、300℃和600℃。研究了不同沉积温度对YBCO薄膜结构、表面形貌及超导性能的影响。X射线衍射(XRD)和扫描电

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

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel

JUNO sensitivity on proton decay p → ν K + searches*

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this study, the potential of searching for proton decay in the $p\to \bar{\nu} K^+$ mode with JUNO is investigated. The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar{\nu} K^+$ is 36.9% ± 4.9% with a background level of $0.2\pm 0.05({\rm syst})\pm$$0.2({\rm stat})$ events after 10 years of data collection. The estimated sensitivity based on 200 kton-years of exposure is $9.6 \times 10^{33}$ years, which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies