Chemical incompatibility between polymerizing HEMA and rubber balloons used for selective endovascular treatment of intracranial aneurysms

Permanent selective occlusion by detachable balloons with parent vessel preservation is considered to be the endovascular treatment of choice of intracranial aneurysms. It has been proposed that replacement of contrast material within the balloon with a polymerizing substance will eliminate balloon deflation. Despite this solution, our clinical experience with polyisoprene rubber balloons shows that deflation can still occur when the balloons are filled with poly(2-hydroxyethyl methacrylate). Experimental data are presented that demonstrate the chemical incompatibility between hydroxyethyl methacrylate (HEMA) and polyisoprene rubber. The resulting degradation of the polyisoprene rubber accounts well for balloon failure. Thein vitro behaviour of silicone balloons and of a new HEMA sponge formulation to fill the balloons are compared.     

Properties of nylon 12 balloons after thermal and liquid carbon dioxide treatments

Critical design attributes of angioplasty balloons include the following: tear resistance, high burst pressures, controlled compliance, and high fatigue. Balloons must have tear resistance and high burst pressures because a calcified stenosis can be hard and nominal pressures of up to 16 atm can be used to expand the balloon. The inflated balloon diameter must be a function of the inflation pressure, thus compliance is predictable and controlled. Reliable compliance is necessary to prevent damage to vessel walls, which may be caused by over-inflation. Balloons are often inflated multiple times in a clinical setting and they must be highly resistant to fatigue. These design attributes are dependent on the mechanical properties and polymer morphology of the balloon. The effects of residual stresses on shrinkage, crystallite orientation, balloon compliance, and mechanical properties were studied for angioplasty nylon 12 balloons. Residual stresses of these balloons were relieved by oven heat treatment and liquid CO₂ exposure. Residual stresses were measured by quantifying shrinkage at 80 °C of excised balloon samples using a dynamic mechanical analyzer. Shrinkage was lower after oven heat treatment and liquid CO₂ exposure compared to the as-received balloons, in the axial and radial directions. As-received, oven heat treated, and liquid CO₂-exposed balloon samples exhibited similar thermal properties (T_g, T_m, X_t). Crystallite orientation was not observed in the balloon cylindrical body using X-ray scattering and polarized light microscopy, which may be due to balloon fabrication conditions. Significant differences were not observed between the stress–strain curves, balloon compliance, and average burst pressures of the as-received, oven heat treated, and liquid CO₂-exposed balloons.     

Lifting options for stratospheric aerosol geoengineering: advantages of tethered balloon systems

The Royal Society report 'Geoengineering the Climate' identified solar radiation management using albedo-enhancing aerosols injected into the stratosphere as the most affordable and effective option for geoengineering, but did not consider in any detail the options for delivery. This paper provides outline engineering analyses of the options, both for batch-delivery processes, following up on previous work for artillery shells, missiles, aircraft and free-flying balloons, as well as a more lengthy analysis of continuous-delivery systems that require a pipe connected to the ground and supported at a height of 20 km, either by a tower or by a tethered balloon. Towers are shown not to be practical, but a tethered balloon delivery system, with high-pressure pumping, appears to have much lower operating and capital costs than all other delivery options. Instead of transporting sulphuric acid mist precursors, such a system could also be used to transport slurries of high refractive index particles such as coated titanium dioxide. The use of such particles would allow useful experiments on opacity, coagulation and atmospheric chemistry at modest rates so as not to perturb regional or global climatic conditions, thus reducing scale-up risks. Criteria for particle choice are discussed, including the need to minimize or prevent ozone destruction. The paper estimates the time scales and relatively modest costs required if a tethered balloon system were to be introduced in a measured way with testing and development work proceeding over three decades, rather than in an emergency. The manufacture of a tether capable of sustaining the high tensions and internal pressures needed, as well as strong winds, is a significant challenge, as is the development of the necessary pumping and dispersion technologies. The greatest challenge may be the manufacture and launch of very large balloons, but means have been identified to significantly reduce the size of such balloons or aerostats.     

Inverse Design Strategies for 3D Surfaces Formed by Mechanically Guided Assembly

Deterministic transformations of 2D patterns of materials into well-controlled 3D mesostructures serve as the basis for manufacturing methods that can bypass limitations of conventional 3D micro/nanofabrication. Here, guided mechanical buckling processes provide access to a rich range of complex 3D mesostructures in high-performance materials, from inorganic and organic semiconductors, metals and dielectrics, to ceramics and even 2D materials (e.g., graphene, MoS₂). Previous studies demonstrate that iterative computational procedures can define design parameters for certain targeted 3D configurations, but without the ability to address complex shapes. A technical need is in efficient, generalized inverse design algorithms that directly yield sets of optimized parameters. Here, such schemes are introduced, where the distributions of thicknesses across arrays of separated or interconnected ribbons provide scalable routes to 3D surfaces with a broad range of targeted shapes. Specifically, discretizing desired shapes into 2D ribbon components allows for analytic solutions to the inverse design of centrally symmetric and even general surfaces, in an approximate manner. Combined theoretical, numerical, and experimental studies of ≈20 different 3D structures with characteristic sizes (e.g., ribbon width) ranging from ≈200 µm to ≈2 cm and with geometries that resemble hemispheres, fire balloons, flowers, concave lenses, saddle surfaces, waterdrops, and rodents, illustrate the essential ideas.     

Cutting balloon angioplasty for resistant venous stenoses in hemodialysis patients

Purpose:  To report our initial experience of using cutting balloons angioplasty in the treatment of resistant venous stenoses of Brescia‐Cimino fistulas. Materials and Methods:  Forty‐eight patients with Brescia‐Cimino fistulas underwent percutaneous transluminal angioplasty (PTA) of 62 venous stenoses. Of these 48 patients, we encountered 8 venous stenoses (8/62, 12.9%) in 7 patients that were not successfully dilated with 6–8 mm high‐pressure balloons inflated up to 24 atm. In each of 8 stenoses, peripheral cutting balloons with diameters of 5–8 mm were employed to dilate resistant stenoses. Results:  The locations of stenoses were 3 at the surgical vein mobilization site ("swing point"), 4 at the cephalic vein downstream from the anastomosis, and 1 at the cephalic arch. The grade of stenosis after high‐pressure balloon angioplasty ranged from 57% to 87%(mean, 76%). Cutting balloons expanded completely in all stenoses and the residual stenosis after cutting balloon PTA ranged from 0% to 24%(mean, 7%). Residual stenosis was virtually nonexisistent at the 3 stenoses of "swing point." A focal rupture with a large hematoma occurred at the cephalic arch stenosis, which was treated by a stent placement. One minimal rupture that did not require any treatment occurred at the stenosis of downstream cephalic vein. No repeat angioplasty has been needed during follow‐up period (range, 74–249 days). Conclusion:  Our early experience demonstrated that when high‐pressure balloons fail to dilate stenoses of Brescia‐Cimino fistulas, peripheral cutting balloons with diameters of 5–8 mm can be effectively used to overcome the resistance of stenoses.     

Miniaturized ultraviolet ozonesonde for atmospheric measurements

The design and test results of a simple single-beam ultraviolet photometer for ozone measurements are presented. The instrument has several features that distinguish it from former UV absorption instruments, all of which contribute to a smaller size and much lower power consumption while retaining the advantages of the UV measurement technique. A novel airflow system and advanced electronics are among the most important changes from earlier reported systems. The instrument fits into a package 10 cm in diameter by 60 cm long and weighs under 1.5 kg. Hence, it is well-suited for lightweight airborne applications using kites and balloons, as well as other portable measurement needs. Independent measurements of ozone are made every 4 s, with a sensitivity of 0.3 ppbv ozone (limit of detection for S/N = 3) and a precision of ±2%.     

A non-monotonous damage function to characterize stress-softening effects with permanent set during inflation and deflation of rubber balloons

A non-monotonous stress-softening phenomenological model is applied to study the Mullins effect with residual strains to characterize the inflation and deflation of rubber balloons. It is shown that analytical predictions based on our proposed non-monotonous softening function and the modified stress-softening non-Gaussian average-stretch full-network constitutive equation that accounts for residual strains are consistent with experimental data. Also, we use the constitutive equation for equibiaxial extension to predict stress-softening behavior in a kinematically equivalent simple compression deformation state.     

Lightweight diode laser spectrometer CHILD (Compact High-altitude iN-situ Laser Diode) for balloonborne measurements of water vapor and methane

A new lightweight near-infrared tunable diode laser spectrometer CHILD (Compact High-altitude In-situ Laser Diode spectrometer) was developed for flights to the stratosphere as an additional in situ sensor on existing balloonborne payloads. Free-air absorption measurements in the near infrared are made with an open-path Herriott cell with new design features. It offers two individual absorption path lengths optimized for CH4 with 74 m (136 pass) and H2O with 36 m (66 pass). New electronic features include a real-time gain control loop that provides an autocalibration function. In flight-ready configuration the instrument mass is approximately 20 kg, including batteries. It successfully measured stratospheric CH4 and H2O profiles on high-altitude balloons on four balloon campaigns (Environmental Satellite validation) between October 2001 and June 2003. On these first flights, in situ spectra were recorded from ground level to 32,000-m altitude with a sensitivity of 0.1 ppm [(parts per million), ground] to 0.4 ppm (32,000 m) for methane and 0.15-0.5 ppm for water.     

Drug‐Coated Angioplasty Balloon Catheters: Coating Compositions and Methods

Flow‐limiting stenosis or total occlusion of coronary, cerebral, or peripheral arteries is very common. Minimally invasive treatment with balloon catheters optionally combined with stent implantation immediately relieves symptoms. However, renarrowing of dilated vessel segments due to excessive scar formation frequently reverses the initial success observed soon after treatment. Coating of balloons with antiproliferative drugs is a promising approach to overcome this problem. The coating of angioplasty balloon membranes is a challenging task. It must ensure homogeneous distribution of the antiproliferative agent and adherence to the balloon membrane during handling and on the way to the treatment site in a distant artery, where the agent should be immediately released and transferred to the vessel wall when the balloon is inflated. In vitro and in vivo testing methods are described. The impact of different kinds of balloons, drugs, additives, and coating methods has been investigated, and the results of representative examples including clinically tested products are presented and discussed.     

The sensitivity of an eulerian hydrocode impact analysis to user-selected impact parameters

In this analysis, the impact of a tungsten projectile on an aeroshield or spacecraft debris shield was calculated using the PINON hydrocode. The phenomena that took place during the impact and led to the formation of thin-shelled balloons of debris is described. The effect of variations in several user-selected input parameters was examined and a set of parameters was selected. The most significant finding from these parameter variation studies is that a very fine noding os required to accurately resolve the axial distribution of the tungsten debris.     

Achieving robust design through statistical effect screening

This work proposes a method for statistical effect screening to identify design parameters of a numerical simulation that are influential to performance while simultaneously being robust to epistemic uncertainty introduced by calibration variables. Design parameters are controlled by the analyst, but the optimal design is often uncertain, while calibration variables are introduced by modeling choices. We argue that uncertainty introduced by design parameters and calibration variables should be treated differently, despite potential interactions between the two sets. Herein, a robustness criterion is embedded in our effect screening to guarantee the influence of design parameters, irrespective of values used for calibration variables. The Morris screening method is utilized to explore the design space, while robustness to uncertainty is quantified in the context of info‐gap decision theory. The proposed method is applied to the National Aeronautics and Space Administration Multidisciplinary Uncertainty Quantification Challenge Problem, which is a black‐box code for aeronautic flight guidance that requires 35 input parameters. The application demonstrates that a large number of variables can be handled without formulating simplifying assumptions about the potential coupling between calibration variables and design parameters. Because of the computational efficiency of the Morris screening method, we conclude that the analysis can be applied to even larger‐dimensional problems. (Approved for unlimited, public release on October 9, 2013, LA‐UR‐13‐27839, Unclassified.) Copyright © 2015 John Wiley & Sons, Ltd.     

基于嵌入操作系统的总线式断路器智能控制器的研制

针对智能断路器控制器的技术要求,提出了基于DSP和us／OS-Ⅱ嵌入式操作系统的总线式低压断路器智能控制器的设计思路和实现方案,介绍了嵌入式系统的硬件和软件,阐述了Profibus—DP总线接口模块的设计及us／OS-Ⅱ在TMS320LF2407A芯片上的移植．现场试验表明,该控制器可靠性高,试验结果达到预期的设计要求．     

An algorithm for engineering design optimization

In this paper a new concept for development of algorithms for optimal design of engineering systems is presented. The basic idea is to use upper and lower bounds on optimum cost to develop iterative search strategies. The main feature of the concept is that it does not rely on one-dimensional search to compute a step size at any design iteration. Implication of the feature is that the algorithms based on this concept require evaluation of constraint functions only once at any design iteration. This is highly desirable for optimal design of engineering systems because evaluation of functions for such systems is very expensive due to their implicit dependence on design variables. An algorithm based on the new concept is derived in the paper. Several new step sizes are introduced and their relation to proper reduced optimal design problems are presented. A new step size based on the constant cost requirement at some design iterations is introduced. Numerical aspects for the algorithm are also presented. Based on the new algorithm, a general-purpose computer code GRP2 is developed. The code is used to solve several problems to gain experience and insight for the algorithm. Numerical experience with examples is discussed. It is concluded that algorithms based on bounding optimum cost have substantial potential for applications in optimal design of engineering systems.     

N-way planar high-power combiner design for RF power amplifiers

The complete design using a novel technique for an N-way planar high-power combiner is introduced for radio-frequency (RF) power amplifiers (PAs) at high-frequency (HF) range for the first time. On the basis of this design technique, a three-way planar combiner is simulated, designed and built on a ceramic-based material that allowed a surface-mount application. Design charts for a thermally reliable operation under high-power conditions are given. The simulated and measured results are compared and found to be very close. The design technique for planar combiners introduced here can be used for RF PAs to obtain power level in the several-kilowatt range in HF communication for industrial and military applications.     

Tensile instability of initially spherical balloons

Using a new elastic constitutive relation for rubber-like materials previously proposed by the author, a large deformation analysis of the inflation of rotationally symmetric balloons is developed and specialized to the inflation of an initially spherical balloon. An investigation of the pressure versus radius characteristic reveals the existence of a local maximum indicating the occurrence of a tensile instability. Observing the form of the total potential energy function at various equilibrium positions yields much insight into the tensile instability phenomenon. An analogy to snap-through buckling is recognized and discussed in detail.     

采用VBA在AutoCAD中实现设计知识管理

提出了采用VBA技术在AutoCAD中实现设计知识管理的开发方法.从需求出发,设计了功能模块并构建了系统结构.根据设计知识的特点,提出了采用"类"抽象非结构化的知识表达方法及其界面定制的原理;介绍了结构化和非结构化知识管理的具体实现,用户可以在产品设计过程中查询和存储设计知识和经验.     

分形设计：复杂产品设计的新途径

运用非线性科学研究面向ＣＩＭＳ的智能设计，即以创新设计为核心的人机智能化设计系统，提出了分形设计作为面向复杂产品的设计方法学。从设计对象，设计思维和设计实施等方面介绍了分形设计的核心内容概要，其结果表明：设计对象的分形结构是其复杂性之源，设计思维的混沌机制是其创造性之源；设计实施的嵌套模式是其有效性之源。分形设计为复杂产品设计提供了新的途径。     

On Pseudo-Elastic Models for Stress Softening in Elastomeric Balloons

The phenomenon of stress softening observed in the cyclic inflation of spherical balloons or membranes is quantitatively and qualitatively examined. A new measure of the stress softening extent is proposed which correctly captures the main feature of this phenomenon. This measure of the stress softening is related to the relevant response functions in the constitutive models proposed in the literature to describe this effect. Using these relationships, the predictive capability of the theoretical models is examined. It is shown that only those theoretical models which admit a non-monotone character of the stress softening can properly describe this phenomenon.     

分布式协同环境中的虚拟产品设计研究

提出了协同环境下虚拟产品设计系统的体系结构.对该系统的体系结构和设计流程进行了详细分析,对系统的主要支撑技术作了介绍,为产品虚拟设计的系统实现和安全维护提供有效途径.