世界最新科技包装

可透气的啤酒瓶盖 美国研究人员开发了可透气的啤酒瓶盖，可解决瓶爆炸和啤酒变质的问题。     

新型防渗透气砂防渗透气性能的研究

防渗透气砂作为一种新型功能材料具有变废为宝的现实意义。本试验用自制防渗透气测试装置测试了防渗透气砂的渗透压、透气速率,在自制防渗透气砂性能量化的同时,通过测试结果分析防渗透气砂的性能影响因素。为防渗透气砂的应用提供参考依据。     

一种具有透气功能的粮食用集装袋

本文介绍了一种具有透气功能的粮食用集装袋,涉及集装运输领域。该具有透气功能的粮食用集装袋,包括集装袋本体,所述集装袋本体的底部缝纫连接有底座,所述集装袋本体的外表面缝纫连接有承重带,所述承重带的顶端缝纫连接有起重挂耳,所述集装袋本体的内壁底部固定连接有十字形透气管。该具有透气功能的粮食用集装袋,通过集装袋本体内壁连接的通气网布层,透气网布层为防丝棉材质,可提高集装袋内部的粮食进行空气流通,减少粮食的发热,且通过集装带本体内部设置的透气管,透气管的外表面开设有透气孔二,且透气管的形状呈S形可将集装带内部的粮食进行透气操作,进一步提高了粮食的透气性,减少粮食因为空气不流通导致的发热。     

盒式气调包装下温度对薄膜透气性能的影响

以高阻隔膜、双层膜、聚丙烯(PP)膜及双向拉伸聚丙烯(BOPP)膜为材料,采用小袋法,分析了盒式气调包装下,各薄膜在4,10,25,30℃温度下的薄膜透气系数和透气系数比的变化规律。结果表明:随着温度的升高,4种薄膜的透气系数都呈上升趋势;同时,高阻隔膜和双层膜的透气系数比显著降低,而BOPP膜和PP膜的透气系数比则逐渐升高。同一温度条件下,PP膜的透气性能最好,BOPP膜次之,双层膜和高阻隔膜的透气性能较低。试验中,透气系数的自然对数与绝对温度的倒数满足阿累尼乌斯方程,以此可求得不同薄膜材料在其他温度下的透气系数。     

科学看待压力差与材料透气性的关系

本文详细分析了认为在压差法中气体压力差的存在会影响透气性测试结果这种观点的错误之处，并通过大量实测数据证明了在压差法透气性测试中施加在试样两侧的压力差不会对材料的透气性（透气量和透气系数）带来影响。     

美开发防御生化武器的纳米布料

美国劳伦斯·利弗莫尔国家实验室（LLNL）、麻省理工学院等多家机构研究人员正在为军方开发一种新型制服，这种制服的布料用一种新型碳纳米管纤维制成，可防御化学和生物武器。这种布料能从透气状态迅速转变到防护状态，它的膜上有许多微孔，由仅几纳米宽的垂直对称的碳纳米管（CNT）构成，高度透气，并用一种化学制剂反应功能层进行了改良。     

PI/TiO2纳米复合膜的气体分离性能

通过溶胶-凝胶法制备出系列聚酰亚胺PI(HQDPA—DMMDA)／TiO2纳米复合气体分离膜．采用TEM、WAXD和DSC等手段测试了复合膜的某些物理特性；研究了复合膜对H2、N2、O2、CO2和CH4等五种气体的透气性能及其与温度的关系，并对复合膜的结构与透气性能的关系作了推测．结果表明，TiO2的引入并未明显改变PI的分子链间距．随着PI中TiO2含量的增加，复合膜的透气系数开始逐渐增加，当TiO2含量为22．3％时，则显著增加，且仍保持很高的分离系数．提出用无机纳米网络促进传输作用来解释复合膜的透气机理．     

食品包装薄膜的透气性测试研究

通过对薄膜透气机理的研究,确立了一种方便可行的透气测试方法,为薄膜应用于食品包装提供较快、较实用的选择数据。并分别测试了江西塑料制品试验厂生产的高压聚乙烯膜在常温、常压下CO_2和O_2的透气系数     

双醚二酐型聚醚酰亚胺的分子结构与透气性能

合成了一系列单环芳二胺型聚醚酰亚胺，研究了它们对Ｈ２、Ｏ２和Ｎ２３种气体的透过性能。这类双醚二酐（ＨＱＤＥＡ）型聚醚酰亚胺的分子结构对其透气性和透气选择性有很大的影响，随着二胺单体分子中甲基的增多，聚醚酰亚胺的透气性增大，透气选择性减小；由３，５－二氨基苯甲酸合成的ＨＱＥＤＡ－ＤＡＢ具有较高的透Ｈ２系数和很高的Ｈ２／Ｎ２分离系数。     

开槽切角机加工纸箱透气小孔装置

介绍一种槽切角机加工纸箱透气小孔的装置,使透气小孔的加工直接在开槽机上与切角同时进行,大大的提高了工作效率。     

Thermoelastic contact of a retaining ring with a cylinder under the conditions of frictional heat generation

We give the mathematical statement and construct the solution of the static thermoelastic problem of contact interaction of an elastic retaining ring with a circular hollow cylinder inserted in it. The bodies are compressed by a load varying along the axis of the system under the conditions of load-free contact on the surface of the ring or along an arc of the circle. In the case where radial displacements of the contact surface of the retaining ring are approximated by displacements of the surface of a long circular hollow cylinder and the process of stationary frictional heat generation is taken into account, we reduce the posed problem to systems of integral equations whose structure is determined by the type of conditions of thermal contact. We propose a numerical algorithm for the solution of these systems and study the influence of the input parameters of the problem on the distributions of contact pressure and temperature. On the basis of these results, we make a conclusion that the influence of the character of variation of the compressive load along the axis on the distribution of contact pressure is significant in the case where the kinematic conditions of interaction of the bodies are described by the Hertz theory. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 36. No. 3. pp. 42–52, May-June, 2000.     

Plane problem for a piecewise-homogeneous anisotropic body with elastic inclusion in the form of a strip

A plane problem of the theory of elasticity for a piecewise-homogeneous anisotropic plane with elastic inclusions in the form of strips is solved by the method of jump functions. Inclusions are simulated by the jumps of the vector of stresses and the derivative of the vector of displacements on the median surfaces. By using complex potentials, we obtain the dependences of the components of the stress tensor and the vector of displacements on the load and unknown jump functions. In view of the conditions of interaction of a thin inclusion with an anisotropic medium, the problem is reduced to a system of singular integral equations for the jump functions. In the general case, this system is solved by the collocation method. For the cases of a slot and a perfectly rigid inclusion, we deduce the dependences of the generalized stress intensity factors on the concentrated forces and edge dislocations. Franko L'viv University, L'viv; Pidstryhach Institute of Applied Problems of Mechanics and Mathematics. Ukranian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 35, No. 6, pp. 7–16. November–December, 1999.     

Graphite-fibre/carbide-matrix composites—II: Structure and electrical properties

The measurement of electrical properties of ceramic-matrix composites supplies data which can be used directly with information about the structure of the composites. The structures of graphite-fibre/carbide-matrix composites may be varied within large intervals of appropriate parameters, as shown in a previous publication. A corresponding variety of behaviour patterns of such materials in the electrical field had been expected and was actually observed. The matrices of the composites were boron, niobium, and tantalum carbides, and the fibres were Kulon and VMN-4. The electrical conductivity of graphite-fibre/carbide-matrix composites has been determined, including that at cryogenic temperatures. A preliminary series of experiments gives the characteristics of piezo-resistance of the C/NbC composites. The experimental data yield a set of characteristics of the fibre, matrix, and composite structure. The conductivity characteristics of the graphite fibres and carbide matrices obtained in this way correspond to the expected ones. That also includes a type of conductivity behaviour revealed by the temperature dependence of the conductivity. Graphite fibre behaviour is of the metallic type, while boron carbide is a semiconductor-type material. The conductivity of pure matrices differs essentially from that of the matrices obtained as an extrapolation of the conductivity versus fibre volume fraction dependence to zero fibre content. Active diffusion of carbon from the fibre/matrix interface makes the stoichiometry of a carbide better and its conductivity higher. But a distinctive dependence of the piezo-resistance of the C/NbC composites on the fibre volume fraction may lead to an assumption about the possibility of the existence of another mode of influence of the carbon fibres on the conductive properties of carbides. Calculation of the ineffective length of a fibre (from the viewpoint of conductivity) yields an estimate of the conductivity of the interface. It is clearly connected to the structure of the interface.     

Relaxation methods for the investigation of the influence of surfactants on the rate of corrosion

We develop a theory of the application of low-level relaxation methods (basic and pulse potentiostatic methods, basic and pulse galvanostatic methods, and the method of electrode impedance) to the investigation of the influence of surfactants on the rate of corrosion. To evaluate the possibilities of this theory. we consider an example of a corrosion model characterized by the adsorption of surfactants which affects the rates of both cathodic and anodic processes. The cathodic process includes the adsorption of hydrogen atoms and the anodic process includes the adsorption of subions of the metal. We deduce equations for the calculation of the electrode parameters of the model on the basis of the experimental data and show that the complexity of the proposed model is maximum for all relaxation methods, except the method of electrode impedance. Dneprodzerzhinsk State Technical University, Dneprodzerzhinsk. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 32, No. 4, pp. 75–80, July–August, 1996.     

Probabilistic models and statistical methods for the analysis of vibrational signals in the problems of diagnostics of machines and structures

We consider probabilistic models of vibrations of machines in the form of periodically correlated random processes and almost periodically correlated random processes. The problem of selection of diagnostic symptoms from the entire set of the experimental data is formulated on the basis of the developed methods for the analysis of the probabilistic characteristics of periodically correlated random processes and almost periodically correlatted random processes. Within the framework of the spectral correlation theory of the indicated classes of nonstationary random processes, we check the validity of the general approaches to the investigation of stochastically amplitude- and phase-modulated signals. We propose new methods for the assessment of the probabilistic characteristics of periodically correlated random processes and their generalizations. The problem of finding hidden periodicities in vibrational signals is solved in a new statement. On the basis of the developed methods, we designed a computerized information-measuring system for the vibrodiagnostics of machines and structures. The possibility of inspection of the technical state of a bearing unit of an electric motor is illustrated on the basis of the analysis of its vibrations. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 33, No. 5, pp. 61–74, September-October, 1997.     

Special Features in the Realization of Film Boiling on Wire Heaters. Distilled Water

The existence of a region of self-oscillatory instability of heat transfer is revealed under conditions of film boiling of water subcooled to the saturation temperature. In the case of short heaters, whose length is commensurable with the Taylor instability wavelength, the process is regular. For heaters of the same length, the form of oscillations and their characteristics are fully reproducible. An increase in the heater length results in the emergence of spatially distributed oscillations. It is found that an increase in subcooling on the interface between the modes of boiling is accompanied by the formation of a structure consisting of a system of single domains of continuously decreasing size. The formation of this structure causes a significant change in the temperature distribution in the zone adjoining that of nucleate boiling, which considerably reduces the film stability. A single domain of the film mode of boiling was stable at any temperature of the liquid. The singularities of realization of minimal-size domains of the film mode of boiling under conditions of stabilization of the integral mean temperature of the heater are investigated. It is found that the minimal zone of the film mode of boiling is a system of three elementary domains.     

The initial section of a plane nonisothermal jet developing under asymmetric conditions with and without combustion

A solution of the problem obtained with the method of integral relations is given here. It is obtained in the form of simple algebraic formulas for the boundaries of the mixing zones on both sides of the jet, the position of the flame front, and the axis of the jet at the end of the initial section. It is found that asymmetry of the boundary conditions has a substantial effect on the characteristics of the jet: the position of the axis of the jet at the end of the initial section can change its sign, depending on the temperature ratio at the boundaries of the jet and for given ratios of the velocity at the boundaries of the jet to the velocity of the jet outflow, the length of the initial section can change several fold.Moscow State Aviation Institute, Moscow, Russia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 3, pp. 372–379, May–June, 1995.     

OPTIMAL DESIGN FOR NON-STEADY-STATE METAL FORMING PROCESSES—II. APPLICATION OF SHAPE OPTIMIZATION IN FORGING

This paper is the second part of a two-part article about shape optimization of metal forming processes. This part is focused on numerical applications of the optimization method which has been described in the first paper. The main feature of this work is the analytical calculations of the derivatives of the objective function for a non-linear, non-steady-state problem with large deformations. The calculations are based on the differentiation of the discrete objective function and on the differentiation of the discrete equations of the forging problem. Our aim here is to show the feasibility and the efficiency of such a method with numerical examples. We recall the formulation and the resolution of the direct problem of hot axisymmetrical forging. Then, a first type of shape optimization problem is considered: the optimization of the shape of the initial part for a one-step forging operation. Two academic problems allow for checking the accuracy of the analytical derivatives, and for studying the convergence rate of the optimization procedure. Both constrained and unconstrained problems are considered. Afterwards, a second type of inverse problem of design is considered: the shape optimization of the preforming tool, for a two-step forging process. A satisfactory shape is obtained after few iterations of the optimization procedure.     

On the effective constitutive properties of a thin adhesive layer loaded in peel

An experimental method to determine the complete stress-elongation relation for a structural adhesive loaded in peel is presented. Experiments are performed on the double cantilever beam specimen, which facilitates a more stable experimental set-up as compared with conventional methods like the butt-joint test. The method is based on the concept of equilibrium of the energetic forces acting on the specimen. Two sources of energetic forces are identified: the start of the adhesive layer and the positions of the two acting loads. By use of the concept of equilibrium of energetic forces, it is possible to measure the energy release rate of the adhesive layer instantaneously during an experiment. The complete stress-elongation relation is found to be the derivative of the energy release rate with respect to the elongation of the adhesive layer at its start. By this procedure, an effective property of the adhesive layer is measured. That is, the fields are assumed to be constant through the thickness of the layer and only vary along the layer. To investigate the validity of this approach, experiments are performed on five different groups of specimens with different dimensions. This leads to large variations in the length of the damage zone at the start of the adhesive layer. Four of the experimental groups are used to determine the stress-elongation relation. This is found to be independent of the geometry. For the remaining experimental group, the adherends deform plastically and simulations are performed with the stress-elongation relation determined from the four elastic groups. It is found that the relation cannot be used to accurately predict the behaviour of the experiments where the adherends deform plastically. This indicates that the stress-elongation relation has limited applicability.