Moderate speed impact damage to 2D-braided glass-carbon composites

Hybrid glass-carbon 2D braided composites with varying carbon contents are impacted using a gas gun by impactors of masses 12.5 and 44.5. g, at impact energies up to 50. J. The damage area detected by ultrasound C-scan is found to increase roughly linearly with impact energy, and is larger for the lighter impactor at the same impact energy. The area of whitening of the glass tows on the distal side corresponds with the measured C-scan damage area. X-ray imaging shows more intense damage, at the same impact energy, for a higher-mass impactor. Braids with more glass content have a modest increase in density, decrease in modulus, and reduction in the C-scan area and dent depth at the impact site, particularly at the higher impact energies. Impact damage is found to reduce significantly the compressive strength, giving up to a 26% reduction at the maximum impact energy. © 2012 Elsevier Ltd.

动物体节发生模型及其相关基因研究进展

脊椎动物在胚胎发育的过程中沿身体前后轴形成一定数目的暂时性结构-体节(somite),随着胚胎的继续发育每个体节分化成为生骨区、生皮区和生肌区,继而生成各种组织。近30年来,研究者们就体节的发生和分化提出了多种解释模型,这包括时钟波峰模型、反应扩散模型、时钟诱导模型、时钟痕迹模型等,这些模型从不同角度不同程度解释了动物体节发生和分化的不同现象。尽管每个模型仍然存在一些不足,但大多提出了时钟分节(segmental clock)这一概念。对鸡的c-hairy1和c-hairy2、鸡和小鼠的l-fng以及斑马

Power absorption invariance for brownian spring forcing

In [5] it was shown that, for a standard quarter-car vehicle model and a road disturbance whose velocity profile is white noise of intensity A, the mean power dissipated in the suspension is equal to kA/2 where k is the tyre vertical stiffness. It is remarkable that the power dissipation turns out to be independent of all masses and suspension parameters. The proof in [5] makes use of a spectral formulation of white noise and is specific to linear systems. This paper casts the result in a more general form and shows that it follows from a simple application of Ito calculus. © 2012 IEEE.

Shock transmission in a coupled beam system

This paper investigates the circumstances under which high peak acceleration can occur in the internal parts of a system when subjected to impulsive driving on the outside. Motivating examples include the design of packaging for transportation of fragile items. The system is modelled in an idealised form using two beams coupled with point connections. A Rayleigh-Ritz model of such coupled beams was validated against measurements on a particular beam system, then the model was used to explore the acceleration response to impulsive driving in the time, frequency and spatial domains. This study is restricted to linear vibration response and additional mechanisms for high internal acceleration due to nonlinear effects such as internal impacts are not considered. Using Monte Carlo simulation in which the indirectly driven beam was perturbed by randomly placed point masses a wide range of system behaviour was explored. This facilitates identification of vulnerable configurations that can lead to high internal acceleration. The results from the study indicate the possibility of curve veering influencing the peak acceleration amplification. The possibility of veering within an ensemble was found to be dependent on the relative coupling strength of the modes. Understanding of the mechanism may help to avoid vulnerable cases, either by design or by preparatory vibration testing. © 2013 Elsevier Ltd.

Active control of high frequency vibration in uncertain structures

The active suppression of structural vibration is normally achieved by either feedforward or feedback control. In the absence of a suitable reference signal feedforward control cannot be employed and feedback control is the only viable approach. Conventional feedback control algorithms (e.g. LQR and LQG) are designed on the basis of a mathematical model of the system and ideally the performance of the system should be robust against uncertainties in this model. The aim of this paper is to numerically investigate the robustness of LQR and LQG algorithms by designing the controller for a nominal system, and then assessing (via Monte Carlo simulation) the effects of uncertainties in the system. The ultimate concern is with the control of high frequency vibrations, where the short wavelength of the structural deformation induces a high sensitivity to imperfection. It is found that standard algorithms such as LQR and LQG are generally unfeasible for this case. This leads to a consideration of design strategies for the robust active control of high frequency vibrations. The system chosen for the numerical simulation concerns two coupled plates, which are randomized by the addition of point masses at random locations.

Hybrid-electric propulsion for aircraft

Against a background of increasing energy demand and rising fuel prices, hybrid-electric propulsion systems (HEPS) have the potential to significantly reduce fuel consumption in the aviation industry, particularly in the lighter sectors. By taking advantage of both Electric Motor (EM) and Internal Combustion Engine (ICE), HEPS provide not only a benefit in fuel saving but also a reduction in take-off noise and the emission levels. This research considers the design and sizing process of a hybrid-electric propulsion system for a single-seat demonstrator aircraft, the experimental derivation of the ICE map and the EM parameters. In addition to the experimental data, a novel modeling approach including several linked desktop PC software packages is presented to analyze and optimize hybrid-electric technology for aircraft. Further to the analysis of a parallel hybrid-electric, mid-scale aircraft, this paper also presents a scaling approach for a 20 kg UAV and a 50 tonne inter-city airliner. At the smaller scale, two different mission profiles are analyzed: an ISR mission profile, where the simulation routine optimizes the component size of the hybrid-electric propulsion system with respect to fuel saving, and a maximum duration profile; where the flight endurance is determined as a function of payload weight. At the larger scale, the performance of a 50 tonne inter-city airliner is modeled, based on a hybrid-electric gas-turbine, assuming a range of electric boost powers and battery masses.

Fast-growing transgenic common carp mounfing compensatory growth

Compensatory growth is a phase of accelerated growth apparent when favourable conditions are restored after a period of growth depression. To investigate if F-2 common 'all-fish' growth hormone gene transgenic common carp (Cyprinus carpio) could mount compensatory growth, a 9 week study at 29 degrees C was performed. The control group was fed to satiation twice a day throughout the experiment. The other two groups were deprived of feed for 1 or 2 weeks, respectively, and then fed to satiation during the re-feeding period. At the end of the experiment, the live masses of fish in the deprived groups were still significantly lower than those of the controls. During the re-feeding period, size-adjusted mean specific growth rates and mean feed intakes were significantly higher in the deprived fish than in the controls, indicating a partial compensatory growth response in these fish. No significant differences were found in food conversion efficiency between the deprived and control fish during re-feeding, suggesting that hyperphagia was the mechanism responsible for increased growth rates. The proximate composition of the deprived fish at the end of the experiment was similar to that of the control fish. This study is, to our knowledge, the first to report that fast-growing transgenic fish can achieve partial compensation of growth following starvation. (c) 2007 The Authors Journal compilation (c) 2007 The Fisheries Society of the British Isles.

Isolation and characterization of Scophthalmus maximus rhabdovirus

A rhabdovirus associated with a lethal hemorrhagic disease in cultured turbot Scophthalm us maximus Linnaeus was isolated. The virus induced typical cytopathogenic effects (CPE) in 9 of 15 fish cell lines examined and was then propagated and isolated from infected carp leucocyte cells (CLC). Electron microscopy observations revealed that the negatively stained virions had a typical bullet-shaped morphology with one rounded end and one flat base end. The bullet-shaped morphology was more obvious and clear in ultrathin sections of infected cells. Experimental infections also indicated that the S. maximus rhabdovirus (SMRV) was not only a viral pathogen for cultured turbot, but also had the ability to infect other fish species, such as freshwater grass carp. A partial nucleotide sequence of the SMRV polymerase gene was determined by RT-PCR using 2 pairs of degenerate primers designed according to the conserved sequences of rhabdovirus polymerase genes. Homology analysis, amino acid sequence alignment, and phylogenetic relationship analysis of the partial SMRV polymerase sequence indicated that SMRV was genetically distinct from other rhabdoviruses. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the purified SMRV revealed 5 major structural proteins, and their molecular masses were estimated to be about 250, 58, 47, 42, and 28 kDa. Significant serological reactivity differences were also observed between SMRV and its nearest neighbor, spring viremia of carp virus (SVCV). The data suggest that SMRV is likely a novel fish rhabdovirus, although it is closely related to rhabdoviruses in the genus Vesiculovirus.

Characterization and application of monoclonal antibodies against turbot (Scophthalmus maximus) rhabdovirus

Five monoclonal antibodies (mAbs), 1G8, 1H9, 2D2, 2D3, and 2F5, against Scophthalmus maximus rhabdovirus (SMRV) were prepared. Characterization of the mAbs included indirect enzyme-linked immunosorbent assay, isotyping, viral inhibition assay, immunofluorescence staining of virus-infected cell cultures, and Western blot analysis. Isotyping revealed that 1G8 and 1H9 were of the IgG2b subclass and that the other three were IgM. 2D2, 2D3, and 2F5 partially inhibited SMRV infection in epithelioma. papulosum cyprinid (EPC) cell culture. Western blotting showed that all five mAbs could react with two SMRV proteins with molecular masses of approximately 30 kDa (P) and 26 kDa (M). These two proteins were localized within the cytoplasm of SMRV-infected EPC cells by immunofluorescence assay. Also, progressive foci of viral replication in cell cultures were monitored from 6 to 24 h, using mAb 2D3 as the primary antibody. A flow cytometry procedure was used to detect and quantify SMRV-infected (0.01 PFU/cell) EPC cells with mAb 2D3, and 10.8% of cells could be distinguished as infected 36 h postinfection. Moreover, mAb 2D3 was successfully applied for the detection of viral antigen in cryosections from flounder tissues by immunohistochemistry tests.

Purification and characterization of hydrosoluble components from the sap of Chinese lacquer tree Rhus vernicifera

Continuous gradient elution chromatography (CGEC) was employed to purify and separate enzymes and polysaccharides from the sap of Rhus vernicifera Chinese lacquer tree. There are three different molecules with laccase enzyme activity. Two are enzymes of each other (L1, and L2), whereas the third (RL) is an entirely separate entity. Two polysaccharides (GP1 and GP2) were also found. The Rhus laccase (RL), and isoenzymes L1 and L2, have peak molecular masses of 109,100, 120,000, 103,000 respectively; each has four copper atoms per molecule, and the pI values were 8.2, 8.6, and 9.1, respectively. The structure of the laccases was studied by Fourier-transform infrared (FT-IR) and Matrix-assisted laser desorption/ionization time-of flight (MALDI-TOF) mass spectrometry. The typical amide I (1646 cm(-1)) and amide II (1545 cm(-1)) bands were observed. The results from MALDI-TOF were similar to those from CGEC, but the molecular mass from the MALDI-TOF was significantly different from that obtained from sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). (c) 2006 Elsevier B.V. All rights reserved.

Minimalistic models of an energy-efficient vertical-hopping robot

The use of free vibration in elastic structure can lead to energy-efficient robot locomotion, since it significantly reduces the energy expenditure if properly designed and controlled. However, it is not well understood how to harness the dynamics of free vibration for the robot locomotion, because of the complex dynamics originated in discrete events and energy dissipation during locomotion. From this perspective, the goals of this paper are to propose a design strategy of hopping robot based on elastic curved beams and actuated rotating masses and to identify the minimalistic model that can characterize the basic principle of robot locomotion. Since the robot mainly exhibits vertical hopping, three 1-D models are examined that contain different configurations of simple spring-damper-mass components. The real-world and simulation experiments show that one of the models best characterizes the robot hopping, through analyzing the basic kinematics and negative works in actuation. Based on this model, the self-stability of hopping motion under disturbances is investigated, and design and control parameters are analyzed for the energy-efficient hopping. In addition, further analyses show that this robot can achieve the energy-efficient hopping with the variation in payload, and the source of energy dissipation of the robot hopping is investigated. © 1982-2012 IEEE.

Mass chains with passive interconnection: Complex iterative maps and scalability

This paper introduces the problem of passive control of a chain of N identical masses in which there is an identical passive connection between neighbouring masses and a similar connection to a movable point. The problem arises in the design of multi-storey buildings which are subjected to earthquake disturbances, but applies in other situations, for example vehicle platoons. The paper will study the scalar transfer functions from the disturbance to a given intermass displacement. It will be shown that these transfer functions can be conveniently represented in the form of complex iterative maps and that these maps provide a method to establish boundedness in N of the H ∞-norm of these transfer functions for certain choices of interconnection impedance. © 2013 IEEE.

First-principles study of p-type transparent conductive oxides CuXO2 (X=Y, Sc, and Al)

Using first-principles methods we have calculated electronic structures, optical properties, and hole conductivities of CuXO2 (X=Y, Sc, and Al). We show that the direct optical band gaps of CuYO2 and CuScO2 are approximately equal to their fundamental band gaps and the conduction bands of them are localized. The direct optical band gaps of CuXO2 (X=Y, Sc, and Al) are 3.3, 3.6, and 3.2 eV, respectively, which are consistent with experimental values of 3.5, 3.7, and 3.5 eV. We find that the hole mobility along long lattice c is higher than that along other directions through calculating effective masses of the three oxides. By analyzing band offset we find that CuScO2 has the highest valence band maximum (VBM) among CuXO2 (X=Y, Sc, and Al). In addition, the approximate transitivity of band offset suggests that CuScO2 has a higher VBM than CuGaO2 and CuInO2 [Phys. Rev. Lett. 88, 066405 (2002)]. We conclude that CuScO2 has a higher p-type doping ability in terms of the doping limit rule. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2991157]

Study of valence intersubband absorption in tensile strained Si/SiGe quantum wells

The hole subband structures and effective masses of tensile strained Si/Si1-yGey quantum wells are calculated by using the 6x6 k.p method. The results show that when the tensile strain is induced in the quantum well, the light-hole state becomes the ground state, and the light hole effective masses in the growth direction are strongly reduced while the in-plane effective masses are considerable. Quantitative calculation of the valence intersubband transition between two light hole states in a 7nm tensile strained Si/Si0.55Ge0.45 quantum well grown on a relaxed Si0.5Ge0.5 (100) substrates shows a large absorption coefficient of 8400 cm(-1).

Preliminary design of a tensile-strained p-type Si/SiGe quantum well infrared photodetector

Considering tensile-strained p-type Si/Si1-yGey quantum wells grown on a relaxed Si1-xGex ( 0 0 1) virtual substrate ( y < x), the hole subband structure and the effective masses of the first bound hole state in the quantum wells are calculated by using the 6 x 6 k center dot p method. Designs for tensile-strained p-type quantum well infrared photodetectors ( QWIPs) based on the bound-to-quasi-bound transitions are discussed, which are expected to retain the ability of coupling normally incident infrared radiation without any grating couplers, have lower dark current than n-type QWIPs and also have a larger absorption coefficient and better transport characteristics than normal unstrained or compressive-strained p-type QWIPs.