喷油压力和EGR策略对柴油机瞬变性能的影响

分析了喷油压力和EGR策略对柴油机恒转速增转矩的瞬变工况下累积烟度和烟度峰值的影响。研究表明:分段轨压策略中,在490N·m负荷时,增加喷油压力,累积烟度和烟度峰值的下降幅度最大;在EGR率为5%时,全程原机喷油压力策略对瞬变过程中的烟度峰值影响较小;在EGR率为5%的20%~100%恒转速增转矩瞬变工况下,提高起始负荷和采用全程原机喷油压力策略,均能有效降低烟度峰值;在20%~100%恒转速增转矩的瞬变过程开始后的1.5s关闭EGR阀,能有效降低烟度峰值,结合分段轨压策略,能进一步降低烟度峰值。

半固态ZA12合金的瞬态流变性能

采用自行研制的高温同轴双简流变仪对半固态ZA12合金的流变性能进行研究，结果表明，半固态合金的剪切应力与剪切时间的关系曲线的特征与固相分数和剪切速率有关。此外，在稳态条件和瞬态条件下。

后喷策略对柴油机瞬变过程高负荷工况性能的影响

为了改善柴油机瞬变高负荷工况下缸内燃烧恶化和烟度骤升的问题,以8.6L车用重型柴油机为对象,开展了燃油后喷策略对瞬变工况性能的影响研究。试验研究了在柴油机瞬变过程的高负荷工况段加入后喷时不同后喷参数对瞬变工况性能的影响,并利用模拟手段分析了后喷对缸内燃烧状况、缸内气体的流动和碳烟排放的影响和作用机理。为了更好地说明缸内气体混合情况,引入氧气驱动能量这一概念。研究结果表明:在主喷燃烧阶段,氧气驱动能量对混合气的形成起主导作用;随着后喷油量增多,缸内气体扰动增加,缸内稀混合气比例增加,放热率第二峰值和第三峰值均提高且相位前移;后喷油量对NO_x排放影响较小。综合考虑指示热效率和碳烟排放,对于瞬变过程90%负荷工况,主后喷间隔为4°曲轴转角且后喷量25%时排放效果整体最佳。

一种检测动力系统振动频率的新方法

为了检测动力系统的振动频率，建立了动力系统的拓扑空间 u 和非平稳正弦函数空间 M．采用拓扑 反变理论把空间 u 映射到已知的空间 M 中，通过拓扑反变算子 f∶u→M 检测未知的空间 u 振动频率．求出 这个反变算子后，通过 Poincaré映射给出该反变算子稳定的存在条件．通过此方法即能够检测出动力系统振 动特征频率的瞬变性，同时该方法具有较强的抗干扰能力．实验测试结果表明该方法是可行的．

Integrated identification method of rheological model of sandstone in Sanmenxia bauxite

Based on the uniaxial compression creep experiments conducted on bauxite sandstone obtained from Sanmenxia,typical creep experiment curves were obtained.From the characteristics of strain component of creep curves,the creep strain is composed of instantaneous elastic strain,ε（me）,instantaneous plastic strain,ε（mp）,viscoelastic strain,ε（ce）,and viscoplastic strain,ε（cp）.Based on the characteristics of instantaneous plastic strain,a new element of instantaneous plastic rheology was introduced,instantaneous plastic modulus was defined,and the modified Burgers model was established.Then identification of direct screening method in this model was completed.According to the mechanical properties of rheological elements,one- and three-dimensional creep equations in different stress levels were obtained.One-dimensional model parameters were identified by the method of least squares,and in the process of computation,Gauss-Newton iteration method was applied.Finally,by fitting the experimental curves,the correctness of direct method model was verified,then the examination of posterior exclusive method of the model was accomplished.The results showed that in the improved Burgers models,the rheological characteristics of sandstone are embodied properly,microscopic analysis of creep curves is also achieved,and the correctness of comprehensive identification method of rheological model is verified.

Transient micro-elastography:A novel non-invasive approach to measure liver stiffness in mice

AIM:To develop and validate a transient micro-elastography device to measure liver stiffness(LS) in mice.METHODS:A novel transient micro-elastography(TME) device,dedicated to LS measurements in mice with a range of measurement from 1-170 kPa,was developed using an optimized vibration frequency of 300 Hz and a 2 mm piston.The novel probe was validated in a classical fibrosis model(CCl4) and in a transgenic murine model of systemic amyloidosis.RESULTS:TME could be successfully performed in control mice below the xiphoid cartilage,with a mean LS of 4.4 ± 1.3 kPa,a mean success rate of 88%,and an excellent intra-observer agreement(0.98).Treatment with CCl4 over seven weeks drastically increased LS as compared to controls(18.2 ± 3.7 kPa vs 3.6 ± 1.2 kPa).Moreover,fibrosis stage was highly correlated with LS(Spearman coefficient = 0.88,P < 0.01).In the amyloidosis model,much higher LS values were obtained,reaching maximum values of > 150 kPa.LS significantly correlated with the amyloidosis index(0.93,P < 0.0001) and the plasma concentration of mutant hapoA-□(0.62,P < 0.005).CONCLUSION:Here,we have established the first non-invasive approach to measure LS in mice,and have successfully validated it in two murine models of high LS.

Instantaneous frequency estimation of multi-component Chirp signals in noisy environments

A classical time-varying signal, the multi-component Chirp signal has been widely used and the ability to estimate its instantaneous frequency （IF） is very useful. But in noisy environments, it is hard to estimate the 1F of a multi-component Chirp signal accurately. Wigner distribution maxima （WDM） are usually utilized for this estimation. But in practice, estimation bias increases when some points deviate from the true IF in high noise environments. This paper presents a new method of multi-component Chirp signal 1F estimation named Wigner Viterbi fit （WVF）, based on Wigner-Ville distribution （WVD） and the Viterbi algorithm. First, we transform the WVD of the Chirp signal into digital image, and apply the Viterbi algorithm to separate the components and estimate their IF. At last, we establish a linear model to fit the estimation results. Theoretical analysis and simulation results prove that this new method has high precision and better performance than WDM in high noise environments, and better suppression of interference and the edge effect. Compared with WDM, WVF can reduce the mean square error （MSE） by 50% when the signal to noise ration （SNR） is in the range of-15dB to -11dB. WVF is an effective and promising 1F estimation method.

Analysis on conducted coupling of electrical fast transient burst in mines

Under the inflammable or explosive environment, the direct measurement methods by opening up the explo- sion-proof shell of electrical installations were not adopted. So, it＇s impossible to have a quantitative analysis on the limit of conducted disturbance for electrical fast transient burst （EFT/B） in such dangerous environments. Transient conducted coupling model, which using EFT/B as its excitation source, can be built based on circuit and electromagnetic field theory. Furthermore, numerical analysis was performed. The results indicate that the capacitive coupling voltage is the same polarity as EFT/B, and is the main disturbance form of conducted coupling in mines. The inductive coupling voltage is reversed polarity with the ca- pacitive coupling voltage, and both peaks appear only in the rising time of EFT/B, which increase with the rising of load resistance. Moreover, the cable coupling voltage on the side of disturbance source is higher than the one on the other side in tunnel. To reduce the common resistance can suppress the resistive coupling disturbance.

混沌和有序——生命的复杂结构 摘要:两段对话

最近,作者以上述题目出版一本书〔《混沌和有序——生命的复杂结构》(德语)〕,用9章论述了生物的结构及其进化和瞬变性等问题。这是用简单易懂的方式处理难题的一本难得的书。在这本书中,作者为了向读者介绍这个主题,采用一种不寻常的手法:9章中每一章均以一段虚构对话开始,大多数情况下,对话的一方是18世纪格丁根著名物理学家和哲学家G.C.利希滕贝格(Lichtenberg)。这些对话是由他及特定的合作者的原话构成的。下面是作者译成英文的两段对话。

Experimental characterization of the bipolar effect on P-hit single-event transients in 65 nm twin-well and triple-well CMOS technologies

Single-event charge collection is controlled by drift, diffusion and the bipolar effect. Previous work has established that the bipolar effect is significant in the p-type metal-oxide-semiconductor field-effect transistor(PMOS) in 90 nm technology and above. However, the consequences of the bipolar effect on P-hit single-event transients have still not completely been characterized in 65 nm technology. In this paper, characterization of the consequences of the bipolar effect on P-hit single-event transients is performed by heavy ion experiments in both 65 nm twin-well and triple-well complementary metal-oxide-semiconductor(CMOS) technologies. Two inverter chains with clever layout structures are explored for the characterization. Ge(linear energy transfer(LET) = 37.4 Me V cm^2/mg) and Ti(LET = 22.2 Me V cm^2/mg) particles are also employed. The experimental results show that with Ge(Ti) exposure, the average pulse reduction is 49 ps(45 ps) in triple-well CMOS technology and 42 ps(32 ps) in twin-well CMOS technology when the bipolar effect is efficiently mitigated. This characterization will provide an important reference for radiation hardening integrated circuit design.