Formation of gas barrier films by Cat-CVD method using organic silicon compounds

Silicon nitride (SiN_x) and silicon oxynitride (SiO_xN_y) films have been formed by catalytic chemical vapor deposition (Cat-CVD) method using hexamethyldisilazane (HMDS). Addition of NH₃ gas and increase in gas pressure can prevent carbonization of tungsten (W) catalyzer. These SiO_xN_y films have high gas barrier ability compare to the case of SiO_xN_y films using SiH₄ and thus are expected for novel sealing films.     

A rapid method to determine the barrier requirements for dehydrated oatmeal product using flexible packaging films

Product was packaged in two types of flexible packaging films, poor moisture-high oxygen barrier and high moisture-poor oxygen barrier, and stored under standard tropical conditions. Physical, chemical and biological changes were investigated regularly to find the shelf-life determining factors. Control samples were packaged in glass bottles and stored at 0°C. OTR and WVTR of packaging films were measured. Packaging film permeability and analytical data, obtained from storage tests, were used to determine the barrier requirements for dehydrated oatmeal product, intended for distribution and storage in a tropical climate for 9 months shelf-life. © 1997 John Wiley & Sons, Ltd.     

Efficient decomposition of NO by ammonia radical-injection method using an intermittent dielectric barrier discharge

Although many NO decomposition systems have been developed using plasmas such as dielectric barrier discharges (DBDs), corona discharges, surface discharges, glow discharges, and microwave discharges, the present system is unique on the viewpoint of the use of an intermittent one-cycle sinusoidal power source to generate DBD plasma. There are several features of the system: (1) easy control of the electric power consumed in the DBD plasma, and (2) DBD-plasma generation used only for the production of ammonia radicals. The system employs a radical injection system, where the radicals are produced in a separate discharge chamber, called radical injector, from NO flow field. This enables an efficient production of ammonia radicals being appropriate for DeNOx. It is shown from the temperature dependence of NO removal (DeNOx) characteristics that the present system is a low-temperature DeNOx system compared to a conventional thermal DeNOx system, and NO decomposition is performed over a wide range of gas temperature containing NO. Surveying parametric characteristics of DeNOx, the energy efficiency is improved by a factor of 30% compared to the previously obtained result.     

一种基于元操作的宏模块功耗建模方法

为了有效支持系统芯片(SOC)的功耗分析和第三方IP的功耗评估,并有效保护知识产权,提出了元操作的概念,给出了一种基于元操作的宏模块功耗建模方法,建立了元操作功耗模型.该模型是一种周期精确的功耗模型,它描述了宏模块每个时钟周期的动态功耗变化情况.文中论述了这一模型的开发方法和使用方法,并指出,建立元操作功耗模型的关键是模块的功能定义、模块的功能到元操作的映射以及门级功耗样本的产生和收集.通过与门级功耗分析的实验数据对比,此元操作功耗模型的功耗分析误差在4%以内,功耗分析效率可以提高百倍以上.     

A crash-prediction model for road tunnels

Considerable research has been carried out into open roads to establish relationships between crashes and traffic flow, geometry of infrastructure and environmental factors, whereas crash-prediction models for road tunnels, have rarely been investigated. In addition different results have been sometimes obtained regarding the effects of traffic and geometry on crashes in road tunnels. However, most research has focused on tunnels where traffic and geometric conditions, as well as driving behaviour, differ from those in Italy. Thus, in this paper crash prediction-models that had not yet been proposed for Italian road tunnels have been developed. For the purpose, a 4-year monitoring period extending from 2006 to 2009 was considered. The tunnels investigated are single-tube ones with unidirectional traffic. The Bivariate Negative Binomial regression model, jointly applied to non-severe crashes (accidents involving material-damage only) and severe crashes (fatal and injury accidents only), was used to model the frequency of accident occurrence. The year effect on severe crashes was also analyzed by the Random Effects Binomial regression model and the Negative Multinomial regression model. Regression parameters were estimated by the Maximum Likelihood Method. The Cumulative Residual Method was used to test the adequacy of the regression model through the range of annual average daily traffic per lane. The candidate set of variables was: tunnel length (L), annual average daily traffic per lane (AADT_L), percentage of trucks (%Tr), number of lanes (N_L), and the presence of a sidewalk. Both for non-severe crashes and severe crashes, prediction-models showed that significant variables are: L, AADT_L, %Tr, and N_L. A significant year effect consisting in a systematic reduction of severe crashes over time was also detected. The analysis developed in this paper appears to be useful for many applications such as the estimation of accident reductions due to improvement in existing tunnels and/or to modifications of traffic control systems, as well as for the prediction of accidents when different tunnel design options are compared.     

非连续弹性圆柱实心桩屏障对弹性波的隔离

采用波函数展开法和Graf加法定理,根据桩土界面处位移和应力连续的边界条件,得到了非连续弹性圆柱实心桩屏障对入射平面P波和SH波散射系数的理论解,通过引入无量纲位移,即屏障后某处土体内由入射波和散射波引起的总的纵向位移和水平位移与未设屏障时由入射平面P波和SH波在该处土体内单独引起的位移幅值的比值,根据求得的散射系数的理论解,绘制了平面P波和SH波单独入射情况下,弹性圆柱实心桩屏障后不同位置的无量纲位移、不同剪切模量的弹性圆柱实心桩屏障后的无量纲位移等值线和透射系数随桩间距的变化曲线,通过研究这些图件进而分析了屏障后不同位置、剪切模量、桩间距和入射频率对非连续弹性圆柱实心桩屏障的隔离效果的影响,为非连续弹性屏障的隔振设计提供了理论依据.     

Simulation of the effect of material properties and interface roughness on the stress distribution in thermal barrier coatings using finite element method

A Finite Element Model (FEM) was developed to evaluate the stresses induced by the thermal cycling in a typical plasma-sprayed thermal barrier coating system (TBCs). The thermo-mechanical model of this multi-layer system takes into account the effects of thermal and mechanical properties, morphology of the top-coat/bond-coat interface and oxidation on the local stresses that are responsible for the micro-crack nucleation during cooling, especially near the metal/ceramic interface.Two top-coat/bond-coat geometries corresponding to different interfacial asperity morphologies (semicircle or sinusoidal) are modeled considering a two dimensional and periodic geometry. The effect of the geometry and the amplitude of asperities on stress distribution are examined to study the cause of the subsequent delamination of the TBCs system. Moreover, the effect of the creep in all layers and plastic deformation in the bond-coat as well as the oxidation in the perpendicular direction of the top-coat/bond-coat interface are examined toward the stress development and critical sites with respect to possible crack paths. In addition, crack initiation and propagation at the system was predicted.     

Sensitivity analysis of an accident prediction model by the fractional factorial method

Sensitivity analysis of a model can help us determine relative effects of model parameters on model results. In this study, the sensitivity of the accident prediction model proposed by Zegeer et al. [Zegeer, C.V., Reinfurt, D., Hummer, J., Herf, L., Hunter, W., 1987. Safety Effect of Cross-section Design for Two-lane Roads, vols. 1-2. Report FHWA-RD-87/008 and 009 Federal Highway Administration, Department of Transportation, USA] to its parameters was investigated by the fractional factorial analysis method. The reason for selecting this particular model is that it incorporates both traffic and road geometry parameters besides terrain characteristics. The evaluation of sensitivity analysis indicated that average daily traffic (ADT), lane width (W), width of paved shoulder (PA), median (H) and their interactions (i.e., ADT-W, ADT-PA and ADT-H) have significant effects on number of accidents. Based on the absolute value of parameter effects at the three- and two-standard deviation thresholds ADT was found to be of primary importance, while the remaining identified parameters seemed to be of secondary importance. This agrees with the fact that ADT is among the most effective parameters to determine road geometry and therefore, it is directly related to number of accidents. Overall, the fractional factorial method was found to be an efficient tool to examine the relative importance of the selected accident prediction model parameters.     

舰船总体性能可靠性建模方法研究

分析了舰船总体性能可靠性问题的产生原因，将其分为2类．对于舰载设备本身存在可靠性问题而造成的，以航速可靠性为例，在舰船总体可靠性的背号下，借助相关数学工具进行了建模方法分析；对于外界随机因素影响而造成的，如横稳性的可靠性问题，则从分析外界随机因素与船体设计参数之间关系入手．初步建立了一套研究舰船总体性能可靠性问题的建模方法．实例计算表明，将所建模型用于分析舰船总体性能比常规方法具有明显的优越性．     

Process design for heat fusion of thermoplastic composites using molecular dynamics and a response surface method

This study investigates efficient optimization of heat fusion conditions between thermoplastics using molecular dynamics (MD) and a response surface method. The heat fusion process between polypropylene and polyethylene and the uniaxial elongation for evaluation of the interfacial bonding strength were modeled using coarse-grained MD simulation. To determine the optimal conditions of heat fusion, experimental points were selected on the basis of a central composite design, and a second-order polynomial response surface was created by setting temperature, pressure, and polymerization degree as explanatory variables and the strength of fused interface as the response. The obtained optimal solution under constrained conditions yielded the highest strength when compared with other experimental points and random points.     

无霜冰箱蒸发器化霜系统的改进设计

依据无霜冰箱蒸发器化霜原理,针对现有化霜系统存在的问题,提出了改进的设计方案,把铝管加热化霜改为石英管辐射化霜,取消了化霜恒温器固定盒;通过对改进前后的比较与分析,证实了改进的可行性;分析表明,通过改进设计提高了冰箱工作的可靠性和经济性.     

Time estimation method for manual assembly using MODAPTS technique in the product design stage

This paper aims to propose an accurate and quick assembly time estimation method using the modular arrangement of predetermined time standards in the product design stage. It describes a classification of 2382 assembly operations that are incurred in manually assembling consumer electronics such as air conditioners, washing machines and refrigerators, and a method of choosing representative motions comprising work elements by examining the frequency distribution of the assembly operation’s motions. It then presents criteria for assigning time values associated with the movement of the representative motions using the design factors employed in design for assembly and the layout factors of an assembly line. A case study then presents the practicality of the method, the statistical results of which indicate that the proposed method would be accurate enough for practical purposes.     

A method for the preliminary design of gears using a reduced number of American Gear Manufacturers Association (AGMA) correction factors

Typically, the preliminary design of mechanical components such as gears is carried out using standardized design processes such as those developed by the American Gear Manufacturers Association (AGMA). These design standards include a large number of ‘correction factors’ to account for various uncertainties. As the knowledge about these uncertainties increases, it becomes possible to include them systematically in the design procedure, thereby reducing the number of empirical correction factors. Robust design provides a way to design in the presence of various uncertainties. In this article, a design method is proposed to eliminate empirical correction factors and is demonstrated by eliminating two correction factors from the AGMA design standards for a spur gear, namely, the factor of safety in contact and the reliability factor by the formal introduction of uncertainty in the magnitude of load and material properties. The proposed method is illustrated with the design of an automotive gear with desired reliability, cost and robustness.     

工业建筑预埋件三维快速装配设计方法

当前工业建筑结构预埋件设计主要采用二维CAD软件,效率较低且容易出错。为此提出基于广义参数化模板的三维预埋件快速装配设计方法。该方法建立包含三维参数化形状结构、安装定位方式和二维投影简图等各种信息的预埋件广义参数化模板;通过构建预埋件参数化模板库,采用基于历史的装配设计技术,实现预埋件的快速安装设计。该文方法已经集成到商品化工业建筑结构三维CAD软件InteRDS中,并在实际工程设计中得到应用。     

Characteristics of SiOxNy films deposited by inductively coupled plasma enhanced chemical vapor deposition using HMDS/NH3/O2/Ar for water vapor diffusion barrier

SiO_xN_y thin films were deposited by inductively coupled plasma enhanced chemical vapor deposition (ICP-PECVD) using hexamethyldisilazane (HMDS, 99.9%)/NH₃/O₂/Ar at a low temperature, and examined for use as a water vapor diffusion barrier. The film characteristics were investigated as a function of the O₂:NH₃ ratio. An increase in the O₂:NH₃ ratio decreased the level of impurities such as -CH_x, N-H in the film through a reaction with oxygen. Thereby, a more transparent and harder film was obtained. In addition, an increase in the O₂:NH₃ ratio decreased the nitrogen content in the film resulting in a more SiO₂-like SiO_xN_y film. Using SiO_xN_y fabricated with an O₂:NH₃ ratio of 1:1, a multilayer thin film consisting of multiple layers of SiO_xN_y/parylene layers was formed on a polyethersulfone (PES, 200 μm) substrate, and its water vapor transmittance rate (WVTR) was investigated. A WVTR < 0.005 g/(m² day) applicable to organic thin film transistors or organic light emitting diodes was obtained using a multilayer composed of SiO_xN_y (260 nm)/parylene (< 1.2 μm) on the PES.     

Robust optimization based on the Propagation of Variance method for analytic design models

The robust optimisation is performed in the preliminary design phase dealing with analytic models. The analytic models come either from the finite element models or from the physical laws approximation. The variability on the design parameters is defined using random variables identified by their first two Moments, the Mean and the Standard deviation. A robust design approach is proposed that determines whether a robust design solution exists or not to the given design problem. This approach combines a reformulation of the analytic model with the new design specifications. It integrates the parameter uncertainties (Mean and Standard deviation) and a deterministic optimisation algorithm (SQP algorithm). The Means and the Standard deviation are computed using the Propagation of Variance method. The engineering application of an electrical actuator design is introduced and used to show the implementation and the effectiveness of the proposed robust approach.     

An Improved multivariate generalised likelihood ratio control chart for the monitoring of point clouds from 3D laser scanners

Statistical quality control techniques are crucial for manufacturing companies with tight tolerances but high-volume data generated from laser scanners has pushed the limits of traditional control charts. In a previous work, multivariate generalised likelihood ratio control (MGLR) chart was used to identify process shifts and locate defects on artefacts by converting 3D point cloud data to a 2D image. This paper presents a 3D MGLR control chart that retains the 3D nature of the point cloud data and uses a Fourier transform of the point errors. The average run length (ARL1) of the proposed 3D MGLR was tested using a designed experiment with ten replications and varying the number of past scans and number of Regions of Interest (ROIs). The designed experiment was repeated using three defects: incorrect surface curvature, surface scratch, and surface dent. The proposed methodology identified the dent while the prior methodology never identified it. In addition, the proposed methodology had a significantly shorter ARL1 than the prior methodology for the scratch and no significant difference in the ARL1 for the incorrect surface curvature. The proposed 3D MGLR control chart enabled the usage of 3D data without needing to convert it to a 2D image.     

A method for the hierarchical planning of the structure,dimension and material requirements of manufacturing systems

Growing competition creates pressure among companies to run their production in a cost-optimal way and yet adapt immediately to changes in their environmental conditions. Decisions must always consider the integration of the companies in globalised markets on both the demand and supply side. This paper deals with the optimal planning of decisions concerning the structure and dimension of production facilities. The methods used for material requirements planning are selected and configured according to these decisions. These decision problems are represented in the form of four hierarchically layered partial models, each of them realised and iteratively solved by a mathematical optimisation model. The hierarchical planning method is evaluated using a practical case example based on a valve production system of a manufacturing company.     

Deposition of WNxCy thin films for diffusion barrier application using the dimethylhydrazido (2) tungsten complex (CH3CN)Cl4W(NNMe2)

Tungsten nitride carbide (WN_xC_y) thin films were deposited by chemical vapor deposition using the dimethylhydrazido (2⁻) tungsten complex (CH₃CN)Cl₄W(NNMe₂) (1) in benzonitrile with H₂ as a co-reactant in the temperature range 300 to 700 °C. Films were characterized using X-ray diffraction (XRD), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy and four-point probe to determine film crystallinity, composition, atomic bonding, and electrical resistivity, respectively. The lowest temperature at which growth was observed from 1 was 300 °C. For deposition between 300 and 650 °C, AES measurements indicated the presence of W, C, N, and O in the deposited film. The films deposited below 550 °C were amorphous, while those deposited at and above 550 °C were nano-crystalline (average grain size < 70 Å). The films exhibited their lowest resistivity of 840 µΩ-cm for deposition at 300 °C. WN_xC_y films were tested for diffusion barrier quality by sputter coating the film with Cu, annealing the Cu/WN_xC_y/Si stack in vacuum, and performing AES depth profile and XRD measurement to detect evidence of copper diffusion. Films deposited at 350 and 400 °C (50 and 60 nm thickness, respectively) were able to prevent bulk Cu transport after vacuum annealing at 500 °C for 30 min.     

An efficient simulation method for reliability analysis of linear dynamical systems using simple additive rules of probability

This paper presents a simulation technique for reliability analysis of linear dynamical systems. It is based on simple additive rules of probability (in contrast to other probabilistic approaches such as importance sampling). It is shown that the proposed appoach is identical to a newly developed approach, Importance Sampling using Elementary Events (ISEE) [Au SK, Beck JL. First excursion probabilities for linear sytems by very efficient importance sampling. Probabl Eng Mech 2001;16(3):193–208]. A simple formula for the coefficient of variation of the estimator of the failure probability using the samples is also given. A 10-story building model with nonstationary excitation is utilized to demonstrate the accuracy and efficiency of the proposed method.