Instability during cohesive zone growth

Tensile microcracking of quasi-brittle materials is studied by means of micromechanics, based on (i) an elasto-damaging cohesive zone model accounting for cohesive softening and (ii) a dilute distribution of non-interacting microcracks of uniform orientation and size. Considering virgin microcracks (initially without cohesive zones), macroscopic tensile load increase results in growth of cohesive zones ahead of stationary (non-propagating) cracks and, subsequently, in crack propagation which, notably, will be encountered before the cohesive zones are fully developed i.e. onset of instable cohesive zone growth will be encountered at a load level (i) at which tractions are still transmitted across the inner edges of the cohesive zones and (ii) at which the separation at the inner edges of the cohesive zones is smaller than its critical value. Focusing on onset of instable cohesive zone growth, the chosen approach allows for accessing quantities characterizing the stability limit (e.g., the intensity of the macroscopic loading and the opening at the inner edges of the cohesive zones), without raising the need for non-linear Finite Element analyses. It is shown that the tensile macrostrength of materials containing virgin microcracks is larger than the one related to cracks with already initially fully developed cohesive zones, and related strength differences are quantified for a wide class of cohesive softening behavior. The proposed model is validated by comparing model predictions with an exact solution (available for the special case of constant cohesive tractions) and with results from reliable Finite Element analyses. The paper will be of interest for engineers involved in testing and/or in modeling of quasi-brittle media including cementitious materials and rock.     

EVS助力北京奥运会赛事转播——EVS设备在BOB及CCTV的成功应用

一奥运相关背景与数据 2008年北京夏季奥运会设有28项比赛和302枚金牌，分别在37个比赛场馆举行。参加本次奥运会的运动员共有10708名。奥运会设有国际广播中心（IBC），总面积为9万平方米。参与本届奥运会转播工作的工作人员共有16000人，其中BOB的工作人员有4000人。在奥运期间．BOB一共制作了4000小时的电视节目。     

Efficient computer analysis of ideal switched-capacitor circuits using matrix compaction techniques

In this paper we describe how three simple observations can be used in order to obtain an efficient algorithm for the computer analysis of ideal switched-capacitor circuits. the resulting algorithm is linear in the number of phases. the first observation uses the structure of the r-domain MNA-matrix to come up with a new LU-decomposition scheme which is gradual per timeslot. the second observation allows a great reduction in size of the z-domain MNA-matrix by a matrix compaction algorithm which also operates gradually per timeslot and which can be interleaved with the first gradual LU-decomposition process. This leads to a small matrix which can then be used for a time- and direct frequency-domain analysis. Third, the computations of transfer functions, aliasing functions and sensitivities can be optimized by applying appropriate excitations and making appropriate combinations of the terms in the expressions. These algorithms have been implemented in the SC-analysis program DIANA.SC. the usefulness and efficiency of the program is then illustrated with some examples.     

Changes in proteasome activity during postmortem aging of bovine muscle

The effects of adding commercial-grade and eggshell calcium lactate on the microbiological and physicochemical properties of Nhams (Thai-style fermented pork sausage) were studied. The Nham calcium levels were 150, 300 and 450 mg/100 g. Compared to controls (no added calcium), calcium fortification did not affect the number of lactic acid bacteria or the colour value. The shear force of Nhams fortified with eggshell calcium lactate decreased (P<0.05) from 32.2 N in the controls to 19.5-22.8 N in Nhams fortified with eggshell calcium lactate. However, Nhams fortified with commercial calcium lactate had the same shear force as the controls. Sensory scores of sour taste, flavour and overall acceptance were not different between the control and calcium-fortified Nhams at a calcium level of 150 mg/100 g.     

Multigrid preconditioned conjugate-gradient method for large-scale wave-front reconstruction

We introduce a multigrid preconditioned conjugate-gradient (MGCG) iterative scheme for computing open-loop wave-front reconstructors for extreme adaptive optics systems. We present numerical simulations for a 17-m class telescope with n = 48756 sensor measurement grid points within the aperture, which indicate that our MGCG method has a rapid convergence rate for a wide range of subaperture average slope measurement signal-to-noise ratios. The total computational cost is of order n log n. Hence our scheme provides for fast wave-front simulation and control in large-scale adaptive optics systems.     

Multiple-scattering lidar retrieval method: tests on Monte Carlo simulations and comparisons with in situ measurements

A multiple-field-of-view (MFOV) lidar measurement and solution technique has been developed to exploit the retrievable particle extinction and size information contained in the multiple-scattering contributions to aerosol lidar returns. We describe the proposed solution algorithm. The primary retrieved parameters are the extinction coefficient at the lidar wavelength and the effective particle diameter from which secondary products such as the extinction at other wavelengths and the liquid-water content (LWC) of liquid-phase clouds can be derived. The solutions are compared with true values in a series of Monte Carlo simulations and with in-cloud measurements. Good agreement is obtained for the simulations. For the field experiment, the retrieved effective droplet diameter and LWC for the available seven cases studied are on average 15% and 35% (worst case) smaller than the measured data, respectively. In the latter case, the analysis shows that the differences cannot be attributed solely to lidar inversion errors. Despite the limited penetration depth (150-300 m) of the lidar pulses, the results of the studied cases indicate that the retrieved lidar solutions remain statistically representative of measurements performed over the full cloud extent. Long-term MFOV lidar monitoring could thus become a practical and economical option for cloud statistical studies but more experimentation on more varied cloud conditions, especially for LWC, is still needed.     

A Linear Image Reconstruction Framework Based on Sobolev Type Inner Products

Exploration of information content of features that are present in images has led to the development of several reconstruction algorithms. These algorithms aim for a reconstruction from the features that is visually close to the image from which the features are extracted. Degrees of freedom that are not fixed by the constraints are disambiguated with the help of a so-called prior (i.e. a user defined model). We propose a linear reconstruction framework that generalizes a previously proposed scheme. The algorithm greatly reduces the complexity of the reconstruction process compared to non-linear methods. As an example we propose a specific prior and apply it to the reconstruction from singular points. The reconstruction is visually more attractive and has a smaller 핃₂-error than the reconstructions obtained by previously proposed linear methods. Bart Jansen, Frans Kanters and Remco Duits are joint main authors of this article.     

On‐the‐job Innovation: The Impact of Job Design and Human Resource Management through Production Ownership

A growing number of practitioners and academics endorse that the ability of organizations to foster, develop and use the innovative potential of their employees contributes to organizational success. Yet empirical investigation of individual innovation processes is lacking. In this research we address the question of whether both more flexibility in an employees’ job design and commitment‐oriented HRM activities promote individual innovative work behaviour. Findings suggest that a multifunctional job design and the perceived HRM system promote employee involvement in innovative activities through increased feelings of ownership for work‐related issues and problems.