PBX炸药在摩擦作用下的点火起爆研究

为了研究PBX炸药的摩擦感度及其在摩擦作用下的点火机理,对PBX炸药进行了摩擦感度试验,并从细观结构的角度对炸药在摩擦作用下的响应过程进行了数值模拟,分析了细观结构对炸药温度场的影响,以及压力、初速度等条件对炸药摩擦点火的影响。结果表明:摩擦作用下PBX炸药的点火点位于HMX颗粒与黏结剂交界处,点火的临界温度为1 100K;向炸药施加的压力越大,其发火可靠性越高,点火时间越早;钢柱摩擦炸药的初速度增大,能够提高其发火可靠性以及点火时间。     

PBX炸药在摩擦作用下的点火起爆研究

为了研究PBX炸药的摩擦感度及其在摩擦作用下的点火机理,对PBX炸药进行了摩擦感度试验,并从细观结构的角度对炸药在摩擦作用下的响应过程进行了数值模拟,分析了细观结构对炸药温度场的影响,以及压力、初速度等条件对炸药摩擦点火的影响。结果表明:摩擦作用下PBX炸药的点火点位于HMX颗粒与黏结剂交界处,点火的临界温度为1 100K;向炸药施加的压力越大,其发火可靠性越高,点火时间越早;钢柱摩擦炸药的初速度增大,能够提高其发火可靠性以及点火时间。     

铝粉对化学敏化水胶炸药性能影响的实验研究

为研究不同形状和含量的铝粉对化学敏化水胶炸药性能的影响,在水胶炸药中分别添加质量分数为1%、2%、3%、4%片状和粒状铝粉。对比分析添加不同的质量分数及不同形状铝粉水胶炸药的爆热、爆速和猛度变化情况。结果表明:随着铝粉质量分数从0%增加到4%,炸药的爆热增加,爆速和猛度下降。当炸药中分别添加质量分数为4%的片状铝粉和粒状铝粉的水胶炸药比不含铝粉的水胶炸药,其爆热分别提高了17.99%、16.54%,爆速分别降低了15.12%、13.27%,猛度分别下降了18.18%、16.78%。     

Trend analysis of the power law process using Expectation-Maximization algorithm for data censored by inspection intervals

Trend analysis is a common statistical method used to investigate the operation and changes of a repairable system over time. This method takes historical failure data of a system or a group of similar systems and determines whether the recurrent failures exhibit an increasing or decreasing trend. Most trend analysis methods proposed in the literature assume that the failure times are known, so the failure data is statistically complete; however, in many situations, such as hidden failures, failure times are subject to censoring. In this paper we assume that the failure process of a group of similar independent repairable units follows a non-homogenous Poisson process with a power law intensity function. Moreover, the failure data are subject to left, interval and right censoring. The paper proposes using the likelihood ratio test to check for trends in the failure data. It uses the Expectation-Maximization (EM) algorithm to find the parameters, which maximize the data likelihood in the case of null and alternative hypotheses. A recursive procedure is used to solve the main technical problem of calculating the expected values in the Expectation step. The proposed method is applied to a hospital's maintenance data for trend analysis of the components of a general infusion pump.     

The assessment of the damage probability of storage tanks in domino events triggered by fire

An approach aimed to the quantitative assessment of the risk caused by escalation scenarios triggered by fire was developed. Simplified models for the estimation of the vessel time to failure (ttf) with respect to the radiation intensity on the vessel shell were obtained using a multi-level approach to the analysis of vessel wall failure under different fire conditions. Each vessel “time to failure” calculated by this approach for the specific fire scenario of concern was compared to a reference time required for effective mitigation actions and related to the escalation probability. The failure probability of each vessel was correlated to the probability of scenarios involving multiple vessel failure as a consequence of the primary fire, thus allowing a comprehensive assessment of domino scenarios triggered by fire. The application of the methodology to the analysis of several case-studies allowed the estimation of the quantitative contribution of escalation events triggered by fire to the overall individual and societal risk indexes.     

不同工艺对活性炭电吸附脱盐性能的影响

以活性炭为电极材料是利用电吸附脱盐的重点.以热解法制备了活性炭,采用酸处理及二次活化处理活性炭,并将二次活化的活性炭利用不同的工艺制成电极.研究表明:二次活化法能够使活性炭获得更高的比表面积和更大的孔容,热压和炭化结合的工艺使活性炭电极有着高的比表面积和高的孔容,适合用于苦咸水脱盐.因此,活性炭具有脱盐效果好,脱附时间短,脱盐率达到90%,是一种优良的脱盐电极材料.     

The impact of physiographic factors upon the probability of slides occurrence: a case study from the Kaoping River Basin,Taiwan

This study has investigated the influence of physiographic factors upon the probability of slide occurrence in the Kaoping River Basin. According to previous literature, statistical tests, and physical mechanisms, three physiographic factors (slope steepness, the dip slope ratio, and the time-dependent landslide ratio) were significantly related to slide occurrence. These were combined with hydrological factors (cumulative rainfall) to establish an assessment model for estimating the probability of slide occurrence using logistic regression. The model’s overall accuracy in the training and validation stages was about 81%. Overall, 20 randomly selected historical rainfall events were employed for verification, including 10 events each with and without slide occurrence. The results showed that the model accuracy was approximately 80%, if the probability threshold P_sh is set to be 0.5.

This assessment model can assist in prediction of slide occurrence and the proposed subsequent engineering measures or vegetation restoration is often able to reduce the landslide ratio and the probability of slide occurrence. After landform changes, the model’s physiographic factors can be updated to adjust the rainfall threshold for slide occurrence. Given an appropriate cumulative rainfall and an acceptable risk of slide occurrence, the model can identify priority regions for slide prevention.     

The pigment influence on the anticorrosive performance of some alkyd films

This paper presents the results regarding the pigments effect on the protective properties of alkyd films in 3% natrium chloride solution. The films were realized on carbon steel substrate from an alkyd resin using the pigments of metallic, mineral and organic type. Dry films thickness in 30–35 μm range was obtained. Electrochemical techniques (electrochemical impedance spectroscopy (EIS) and stepwise polarization) were used. The interpretation of the impedance spectra (Nyquist and Bode diagrams) with the immitance analysis Equivcrt. Programme established two electrical equivalent circuits (with two and four time constants) for the carbon steel/alkyd film systems in electrolyte solution, fitted to the experimental data. The electric capacitance and resistance of the alkyd films were monitored with the immersion time to establish the water and ions permeability of these paint films. The electrochemical parameters of alkyd coated carbon steel from the anodic potentiostatic polarisation curves were determined. The correlation of all experimental results established that the tested pigments except the green organic pigment increase the protective performances of alkyd coatings. Best protection of the carbon steel was found for the alkyd film with aluminum powder pigment.     

The influence of extrinsic and intrinsic risk factors on the probability of sustaining an injury

This study was designed to quantify the relative contributions of extrinsic and intrinsic risk factors to the probability of an injury event. A case-control design was used with data collected from injured patients at an emergency department (n=797) and a community sample matched on area of residence and time of injury (n=797). Principal components analysis was used to develop scales for the measurement of 'intrinsic' risk taking tendencies that were slightly modified versions of previously published measures. Two principal components were identified: 'health risk taking' (HRT) and 'adventurous risk taking' (ART). Logistic regression analysis identified variables that significantly predicted membership of the group of injured cases. The main hypothesis was supported by the results: that 'extrinsic' factors such as location, activity, drug and alcohol use and the type of people present at the time of the injury were related to a greater risk of injury than 'intrinsic' variables (health and adventurous risk taking tendencies). The results suggest that injury research and prevention efforts should continue to focus on the identification and modification of situational risk factors for injury rather developing programs that focus on high-risk individuals. High-risk alcohol use, use of prescribed drugs and aspects of work and recreational environments were identified as warranting particular attention.     

The effect of thin deployable construction elements of the international space station on the probability of its hull penetration by meteoroids and orbital debris

When calculating the probability of hull penetration by meteoroid and orbital debris (M/OD) for some of the International Space Station (ISS) modules (e.g. FGB, Service module, cargo vehicle “Progress”), one has to take into account their additional shielding produced by ISS deployable construction elements (such as solar panels, radiators), which decrease M/OD penetrating probabilities. The lack of developed calculation methods of accounting for this effect has arisen the necessity to investigate the law— governed nature of particle fragmentation process accompanying high velocity penetration of thin barriers, as well as to elaborate techniques for correct calculation of the probability of no penetration (PNP) of module pressure wall. The results of thorough analysis of the theoretical and experime ntal published data as well as of data obtained in joint NASA and RSA experimental program on particle fragmentation are presented in this report in the form of normalized analytical correlation between the fragment maximum size and impact parameters. On the basis of above mentioned particle fragmentation law, the method of module hull ballistic limit curves (BLC's) recalculation is determined, which include the effect of thin barriers greatly distanced from the module hull. This BLC's are used for module PNP calculations with the help of modified version of NASA BUMPER code. The special subroutines accounting for PNP changes due to the particle collisions with ISS deployable construction elements are introduced in the BUMPER algorithm. The results of the Service module PNP calculations with account for its “shadowing” by solar panels and radiators are presented.     

The influence of silicate-based nano-filler on the fracture toughness of epoxy resin

Dispersion of nano-sized, silicate-based filler in epoxy resin is expected to yield improved materials properties in several areas. Various mechanical properties, specifically improved fracture toughness, as well as improved flame-retardant effects are of interest. The final objective of the research is investigating whether a nano-modified epoxy matrix yields improved delamination resistance in a fiber-reinforced laminate compared to a laminate with neat epoxy as matrix material. As a first step towards this goal, the fracture toughness of nano-modified epoxy resin is compared with that of the neat resin. Fracture toughness improvement up to about 50% and energy release rates increased by about 20% are observed for addition of 10 wt.% of organosilicate clay.     

The influence of cellulose nanocrystal additions on the performance of cement paste

The influence of cellulose nanocrystals (CNCs) addition on the performance of cement paste was investigated. Our mechanical tests show an increase in the flexural strength of approximately 30% with only 0.2% volume of CNCs with respect to cement. Isothermal calorimetry (IC) and thermogravimetric analysis (TGA) show that the degree of hydration (DOH) of the cement paste is increased when CNCs are used. The first mechanism that may explain the increased hydration is the steric stabilization, which is the same mechanism by which many water reducing agents (WRAs) disperse the cement particles. Rheological, heat flow rate measurements, and microscopic imaging support this mechanism. A second mechanism also appears to support the increased hydration. The second mechanism that is proposed is referred to as short circuit diffusion. Short circuit diffusion appears to increase cement hydration by increasing the transport of water from outside the hydration product shell (i.e., through the high density CSH) on a cement grain to the unhydrated cement cores. The DOH and flexural strength were measured for cement paste with WRA and CNC to evaluate this hypothesis. Our results indicate that short circuit diffusion is more dominant than steric stabilization.     

底充胶及其材料模型对倒装焊热循环可靠性的影响

对倒装焊电子封装可靠性进行了热循环实验和有限元模拟,结果表明,有底充胶（underfill)时,SnPb焊点的热循环寿命可提高约16倍,并确定了Coffin-Manson半经验方程的参数,采用3种底充胶材料模型,亦即定常弹性模型,温度相关弹性模型和粘弹性材料模型,描述了底充胶U8347－3的力学性能。模拟结果表明,材料模型影响计算得到的SnPb焊点的塑性应范围,封装形变以及底充胶／芯片界面应力,采用弹性材料模型可能过高估计了SnPb焊点的热循环寿命和界面应力。     

功能材料热交联剂对UV固化油墨干燥性能的影响

在UV固化油墨中添加一定数量的热交联剂会改变UV油墨的干燥性能，研究了热交联剂对油墨干燥性能的影响。结果表明当热交联剂含量超过一定值时，即使增加紫外线照射时间，墨膜也不会彻底干燥；反之墨膜的干燥性能不会发生变化，与之对应的热交联剂的含量称为临界值。找出了热交联剂在PUA系列UV固化油墨中的临界值。该临界值的发现是研制一种新型热成型UV固化油墨的关键点。     

低温热处理条件对TFA-MOD方法制备的YBCO薄膜的影响研究

目前，三氟乙酸．金属有机沉积（简称TFA-MOD）方法是制备YBaECU307-6（简称YBCO）涂层导体最有应用前景的方法之一。系统地研究了TFA-MOD过程中低温热处理条件（升温速率和气氛）对在LaAlO3单晶基片上生长的YBCO薄膜的影响。研究结果表明，低温热处理的气氛为纯02时，200～250℃区间的分解速度不能太快，否则YBCO薄膜就不均匀和致密，薄膜中会出现较多的孔洞，薄膜的面外取向性也较差，从而影响薄膜的超导性能，然而过慢的分解速度也会使薄膜表面有较大的CuO析出物。分解速度为0．08℃／min时才可以得到结构和超导性能良好的YBCO薄膜。同时研究也发现在低温热处理过程中如果采用Ar和2．5％O2混合气氛则可以减弱三氟乙酸盐分解的剧烈程度，从而使低温热处理的分解速度提高到0．8℃／min，得到的YBCO薄膜同样具有较好的面外取向性和超导性能。     

The influence of mechanical activation by vibro-milling on the early-age hydration and strength development of cement

This paper presents results from an experimental investigation that evaluated the mechanical activation of portland cement using vibro-milling. In this investigation, the duration of the vibro-milling was systematically varied and its influence was evaluated using mortar samples. In addition, the amount of activated cement used in the mortar samples was varied and evaluated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to evaluate differences in hydration products and the structure of activated cement and mortars. The activated cements were tested to determine the influence of activation on the rate of hydration and compressive strength development. The test results suggested that the use of mechanical activation can improve early-age structure formations and compressive strength. A 32% and 25% increase in 1-day strength were observed for the systems with Type I and Class H cements, respectively. This increase in 28-day strength was 16% and 58% for Type I and Class H cement, respectively. It was observed that longer milling times did not necessarily improve performance, and 15 min appeared to be sufficient vibro-milling time to provide valuable benefits.     

The influence of pH and bath composition on the properties of Ni-Co coatings synthesized by electrodeposition

Ni-Co coatings were produced on Cu substrates by electrodeposition from electrolytes with different pH values and different Co²⁺ concentration. The current efficiency increases from 52.1% to 81.2% with the pH increasing from 2.0 to 5.4. It is clearly observed that the content of cobalt in the deposited coatings gradually increases from 9.4% to 19.6% as the pH value varies from 2.0 to 5.4. The Co content in the deposited coatings increases from 16.5% to 72.7% as the molar ratio of CoSO₄/NiSO₄ varying from 1:5 to 1:2 in electrolyte. XRD patterns reveal that the structure of the coatings strongly depends on the Co content in the binary coatings. Both granular and dendritic crystals were investigated by SEM and the different crystallization behaviors were illustrated. The saturation magnetization of the coatings goes up from 96.36 kAm⁻¹ to 136.08 kAm⁻¹ with the pH value increasing from 2.0 to 5.4. The saturation magnetization (M_s) and coercivity (H_c) move up from 144.84 kAm⁻¹ and 15.27 kAm⁻¹ to 175.13 kAm⁻¹ and 125.20 kAm⁻¹ with the increase of Co in the electrolyte, respectively.     

The influence of driver distraction on the severity of injuries sustained by teenage drivers and their passengers

Studies show that teenage drivers are at a higher risk for crashes. Opportunities to engage in technology and non-technology based distractions appear to be a particular concern among this age group. An ordered logit model was developed to predict the likelihood of a severe injury for these drivers and their passenger using a national crash database (the 2003, U.S. DOT-General Estimate System [GES]). As one would expect, speeding substantially increases the likelihood of severe injuries for teenage drivers and their passengers. The results of the analysis also reveal that teenage drivers have an increased likelihood of more severe injuries if distracted by a cell phone or by passengers than if the source of distraction was related to in-vehicle devices or if the driver was inattentive. Additionally, passengers of teenage drivers are more likely to sustain severe injuries when their driver is distracted by devices or passengers than with a non-distracted or inattentive driver. This supports the previous literature on teenage drivers and extends our understanding of injuries for this age group related to distraction-related crashes.     

结构参数对大尺寸刚性试板抗裂性试验拘束度影响的数值分析

采用有限元数值计算方法,分析了大尺寸刚性试板抗裂性试验中试验钢板厚度、加强筋厚度和拘束焊缝跨距对拘束度的影响。结果表明,随试验钢板厚度和加强筋厚度增大,拘束度呈近似正比例线性增大,其比例系数的绝对值分别为120(N/mm·mm)/mm和18(N/mm·mm)/mm;随拘束焊缝跨距增大,拘束度呈近似反比例线性减小,其比例系数的绝对值为7(N/mm·mm)/mm。     

The influence of orientation on the photoluminescence behavior of ZnO thin films obtained by chemical solution deposition

A new type of ZnO thin films synthesized from chemical solution deposition at low temperature has been presented. X-ray powder diffraction and field emission scanning electron microscopy investigation reveal that the novel structured ZnO film is uniform and its [0001] direction is parallel to the substrate. The photoluminescence spectrum of this film shows strong ultraviolet band-gap emission and weak defect-related visible emission comparing to that of [0001]-oriented film, indicating high crystal quality of the non-[0001]-oriented ZnO film.