纳米钛白合成过程的分析——从钛矿到纳米钛白(英文)

钛白(TiO2)纳米粉末具有反应活性高、可见光透过性好、吸收紫外光性能强等持点,可用作高级油漆、涂料、精细陶瓷、催化剂和化妆品等的原料,具有广阔的应用前景。钛白的制备分为硫酸法和氯化法。硫酸法对钛矿的要求不高,工艺相对简单和成熟,在中国已经普遍采用,但是能耗高、污染大、产品质量差,在国际上处于淘汰的地位。相反,氯化法虽然对钛矿的要求高,但是其流程短、污染小、产品质量容易控制,是在国际上处于推广的技术,但是该技术相对不成熟需要进一步研究和完善,如:如何使用中国比较富有的矿物:钛铁矿。氯化法的工艺分为三步:矿物的前处理、矿物的氯化和四氯化钛转化制钛白。本文介绍了文献中有关矿物氯化和四氯化钛转化工艺的研究和开发进展。本文简单介绍了体系达到平衡时基于Gibbs自由能最小的热力学原理,从而确定系统的平衡组成;还介绍了可以预测气相法合成纳米颗粒直径的颗粒动力学模型。本文使用热力学原理分别分析了这三个过程,得到了这三个过程各自的最佳反应温度、最佳配比、以及杂质在矿物氯化和四氯化钛转化过程中的变化、对过程的影响,等。然后使用颗粒动力学模型,研究四氯化钛转化制钛白的反应器,以获得控制纳米颗粒尺度的策略。本文的结论是:在矿物的前处理中,应当将钛铁矿与焦碳在1 200 K的温度下,进行焙烧,钛铁矿分解为金红石矿和氧化亚铁,通过酸洗可以将氧化铁除去,同时除去钙、镁,从而得到相对较纯的金红石矿。但是在焙烧过程中,氮气的含量将控制。在氯化过程中,发现(1)将金红石矿与焦碳一起焙烧,将提高金红石矿的利用率;(2)金红石矿:氯气:焦碳的比例为1:3:3; (3)反应最好在两个流化床反应器中进行,第一流化床反应器的温度为1 200-1 500 K,第二流化床反应器的温度为1 000-1 200 K,这样金红石矿的利用率高,四氯化钛的收率高,而部分杂质将以液态形式被去除;(4)在氯气中含有一定的空气是允许的,但是其代价是将消耗更多的焦碳,产生CO;(5)金红石矿中杂质(钛铁矿、钙钛矿、镁钛矿、硅石、钒矿)的含量需要足够低, 因为这些杂质很容易转化为相应的氯化物,从而使产品的纯度降低。但是金红石矿中含有少量铝土矿是允许的。在转化制备纳米钛白的过程中,发现:(1)通过模拟计算得到的纳米颗粒的大小与实验测定值比较接近;(2)反应中总的气量增加,纳米颗粒的粒度减少;四氯化钛的进料浓度增加,纳米颗粒的粒度增加;反应温度和反应器长度的增加,纳米颗粒的粒度也将增加

内燃机中吸气和压缩过程的二维模拟(英文)

进行了发动机中空气吸气和压缩过程的二维计算机模拟．使用二维正交曲线坐标系以考虑燃烧室的复杂形状．采用 SIMPLEC算法求解流体力学模型方程．论文中分别采用4个湍流模型:标准的κ-ε模型,Realizable κ-ε模型,雷诺应力模型和亚网格尺度模型．论文中对模拟计算的预测值进行了分析．计算出的流场与实验测定值进行了对比．通过模拟计算得到了内燃机中重要的流动图象

外加磁场下磁性液丝的稳定性分析(英文)

对处于外加轴向磁场的影响下的磁性液丝进行数学模拟,研究其稳定性。考虑了磁场的作用,对液丝的长波理论模型进行必要的修正。研究了不同条件下磁性液丝的变化发展过程和受力情况,揭示了外加磁场的作用。结果表明：外加磁场减缓了磁性液丝的破裂过程,磁场力类似于非牛顿流体中的弹性行为,在一定程度上抵消了毛细管力。随着初始磁场强度和磁化率的增大,磁场力逐渐增大。当磁场力显著增大时,液丝的变化发展过程被完全阻碍

基于Oldroyd-B模型的弹性流体液滴动力学研究(英文)

本文采用Oldroyd-B模型对弹性流体中线串珠结构的动力学进行数学模拟。相对于牛顿流体而言,非牛顿流体液丝破裂过程非常缓慢。这种缓慢的破裂过程为流体提供了充足的时间显现一些有趣的现象,例如液滴的排泄和移动。通过主要作用力的总合近似分析液丝拉伸过程中的受力情况。弹性力在弹性液丝动力学中起重要作用,它显著阻碍了液丝从拉伸到排泄的变化过程

不同起始形貌气泡在磁性液体中上升的实验与数值分析(英文)

研究了气泡在磁性液体中的上升过程.用VOF方法追踪了气泡的自由界面,并预测了气泡的变形.考虑了磁场强度对不同起始形貌的气泡的影响,并且发现气泡的最终形貌受磁场强度的影响,当磁场强度较弱时,动力学压力占主导,使气泡变扁,当磁场强度强时,磁性压力占主导,使气泡变圆.当磁场较弱时,起始形貌对气泡的最终形态有影响

突扩管中磁性流体二维流动的模拟

数学模拟可以用来预测流体在突扩管中的流动并更好使用和优化产品制造。使用Herschel-Bulkley(H-B)作为本构方程。在没有磁场的条件下,通过改变参数,我们获得了不同磁性流体的流动过程并分析了回流区长度与参数之间的关系

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