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Experimental study on the fluidelastic instability (FEI) of a curved tube bundle in single phase downward cross flow is investigated for the design qualification and analysis input preparation of helical coiled steam generator tubing. A 6x9 normal square curved tube array with equal and different vertical/horizontal pitch-to-diameter ratio was under-tested up to 6 m/s in term of gap flow velocity to measure the critical velocity for FEI. The critical velocity for FEI was measured at the turning point from the vibration amplitude plot along the gap flow velocity. Our test results were compared with straight tube results and published data in the design guideline. The applicability of the current design guidelines to a curved tube bundle is also assessed. We found that introducing frequency difference in a curved tube array increases the critical velocity for fluidelastic instability.

Background Based on a description of acupuncture to treat a bone disease resembling osteoporosis in the ancient text of Huangdi Neijing, we aimed to assess the effects of electroacupuncture (EA) at GB points in ovariectomised (OVX) rats.Methods 40 female Wistar rats were randomly divided into four groups (n=10 each): ovariectomised model group (OVX); ovariectomised group treated with EA at GB points (OVX+GB); ovariectomised group treated with EA at non-GB points (OVX+N) in the hindlimb; and a sham surgery group (Sham). Three months after ovariectomy, rats in the OVX+GB and OVX+N groups received EA treatment for 3 months. Urine, blood and femur samples were collected from each animal for analysis.Results Bodyweight (BW) in the OVX+GB group decreased after EA treatment, reaching a minimum of ~12% below the OVX and OVX+N groups at 1 month. Concentrations of urine deoxypyridinoline, a bone resorption marker, were significantly elevated in the OVX and OVX+N groups but not the OVX+GB group. Concentrations of serum bone specific alkaline phosphatase, a bone formation marker, were significantly higher in the OVX+GB group versus the Sham and OVX groups. Bone mineral density (BMD) did not differ between the OVX, OVX+GB and OVX+N groups, but was ~10% lower than the Sham group. However, BMD/BW in the OVX+GB group was significantly higher than in the OVX and OVX+N groups and similar to the Sham group. Histological assessment of the femur showed that EA at GB points improved the bone architecture.Conclusions EA treatment at GB points had anti-osteoporotic effects in a rat model of osteoporosis.

This paper considers the problem of finite dimensional output feedback $H_{\infty} $ control for a class of nonlinear spatially distributed processes described by highly dissipative partial differential equations (PDEs), whose state is observed by a sensor network (SN) with a given topology. This class of systems typically involves a spatial differential operator whose eigenspectrum can be partitioned into a finite-dimensional slow one and an infinite-dimensional stable fast complement. Motivated by this fact, the modal decomposition and singular perturbation techniques are initially applied to the PDE system to derive a finite-dimensional ordinary differential equation model, which accurately captures the dominant dynamics of the PDE system. Subsequently, based on the slow system and the SN topology, a set of finite-dimensional distributed consensus observers is constructed to estimate the state of the slow system. Then, a centralized control scheme, which only uses the available estimates from a specified group of SN nodes, is proposed for the PDE system. An $H_{\infty} $ control design is developed in terms of a bilinear matrix inequality (BMI) , such that the closed-loop PDE system is exponentially stable and a prescribed level of disturbance attenuation is satisfied for the slow system. Furthermore, a suboptimal $H_{\infty} $ controller is also provided to make the attenuation level as small as possible, which can be obtained via a local optimization algorithm that treats the BMI as a double linear matrix inequality. Finally, the proposed method is applied to the control of the 1-D Kuramoto–Sivashinsky equation system.

The gear transmission system was parametric modeled in the software Pro/E to establish the prototype, and imported into ADAMS. The meshing force curves of time domain and frequency domain were reached through dynamic simulation. Then the gear system was optimized with several constraint conditions, such as the number of surface modes, helix angle, cutting conditions, minimum tooth width, the contact fatigue strength, and tooth root bending fatigue strength. The optimization was calculated with these constraint conditions, and got the best design of gear system. After optimization, the gear transmission system was simulated again to reach the dynamic analysis and made a contract with the former simulation results. The simulation of the optimized gear system shows that the optimized gear has good mechanical properties.

Heavy-duty gas turbine is used widely in power generation industry for many advantages. Gas turbine exhaust system is an important component of the gas turbine. The work to study the exhaust system was less in the past. In fact, structure design of the exhaust system has important influence on performance and life of the gas turbine. In this paper, the three-dimensional structural model of gas turbine exhaust system is built, the thermal field and stress field for the exhaust system are analyzed by using finite element method (FEM). The maximum stress and distribution characteristics of stress field, the highest temperature and distribution characteristics of thermal field in the exhaust system are computed. These provide a reliable basis for reasonable design and safety evaluation of the exhaust system in gas turbine.

Background Scalp acupuncture (SA) therapy on strokes has been empirically established and widely used in clinics in China. The evidence from clinical studies suggests that SA produces significant benefits for some patients with stroke.Methods The effect of scalp acupuncture was studied using MRI for two different stroke models: spontaneously hypertensive stroke-prone (SHR-SP) rats and rats with transiently induced focal cerebral ischaemia by middle cerebral artery occlusion for 2 h (MCAO rats).Results Stroke onset in SHR-SP rats was characterised by a development of vasogenic oedema without any appearance of cytotoxic oedema. Scalp acupuncture reduced rapidly neurological dysfunction in SHR-SP rats and reduced the volume of the vasogenic oedema during the same period. In contrast, in MCAO rats, focal cerebral ischaemia caused an immediate development of cytotoxic oedema without any appearance of vasogenic oedema. Vasogenic oedema developed after reperfusion. Scalp acupuncture had no significant effects on the cytotoxic oedema, vasogenic oedema or neurological dysfunction of the MCAO rats within the time span examined.Conclusion Scalp acupuncture had a rapid and strong effect on neurological dysfunction only in the hypertensive stroke-model by reducing the vasogenic oedema. Our results suggest that, if there are similar underlying mechanisms in human strokes, scalp acupuncture may be more beneficial for patients with strokes of hypertension-caused vasogenic origin than ischaemic origin.

LetJbe the zero set of the gradientfxof a functionf∶Rn→R. Under fairly general conditions the stochastic approximation algorithm ensuresd(f(xk), f(J))→0, ask→∞. First of all, the paper considers this problem: Under what conditions the convergenceimplies. It is shown that such implication takes place iffxis continuous andf(J)is nowhere dense. Secondly, an intensified version of Sard's theorem has been proved, which itself is interesting. As a particular case, it provides two independent sufficient conditions as answers to the previous question: Iffis aC1function and either i)Jis a compact set or ii) for any bounded setB, f−1(B) is bounded, thef(J)is nowhere dense. Finally, some tools in algebraic geometry are used to prove thatf(J)is a finite set iffis a polynomial. Hencef(J)is nowhere dense in the polynomial case.

The design of a diffractive phase element (DPE) that simultaneously implements wavelength demultiplexing and focusing is carried out on the basis of the general theory of amplitude-phase retrieval. The designed DPE is fabricated with optical contact lithography. Three masks are needed to produce the surface-relief structure of the DPE with eight quantized levels in depths. Experiments demonstrate that the designed DPE can successfully implement both the functions of demultiplexing three different-wavelength beams and focusing each component at a predesignated position simultaneously. Experimental measurements are in good agreement with the results of numerical simulations.

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We proposed a new method of Lloyd's mirror interference in a medium for determining the photoelastic index variation. The experimental results for the masked thermal oxidised GaAs samples agree with the theoretical calculations within an order of magnitude.

We present for the first time the semiquantitative analysis and computer simulation for LPE growth on profiled substrates. Our theoretical results are in agreement with the experimental data and can be used for improving the design and fabrication of heterojunction lasers and integrated optic devices.

Transcriptional repression is a key mechanism for the spatial specification of gene expression and cell fate determination. During kidney development, proliferating cell nuclear antigen (PCNA) is expressed in the nephrogenic zone and is downregulated rapidly as renal epithelial cells enter terminal differentiation and acquire functional characteristics. Our laboratory reported that the transcription factor p53 stimulates the terminal differentiation of renal epithelial cells by means of transcriptional activation of renal function genes (Saifudeen Z, Dipp S, and El-Dahr SS. J Clin Invest 109: 1021-1030, 2002). Because p53-induced growth arrest correlates with downregulation of PCNA gene expression, we examined the impact of p53 inactivation on PCNA expression in mice and evaluated the effect of p53 on PCNA transcription. Immunohistochemistry revealed that the transition from nephrogenesis to terminal epithelial cell differentiation correlates with accumulation of the transcription factor p53. Importantly, the spatially restricted pattern of PCNA expression is disrupted in kidneys of p53-deficient pups, in which there was a redistribution of PCNA expression into the differentiation zone (without a change in total kidney PCNA content) and distortion of the tubular architecture. Electrophoretic mobility shift assays revealed that the binding of kidney nuclear extracts to the p53 response elements in human and rat PCNA promoters is developmentally regulated. Transient transfection assays performed in p53-deficient HeLa cells revealed that exogenous p53 strongly represses transcription from human PCNA promoter-reporter constructs. Interestingly, deletion of the p53-binding site confers enhanced responsiveness to p53-mediated repression, suggesting that transcriptional repression of PCNA by p53 is achieved by a mechanism other than direct DNA binding. On the basis of these results, we propose the hypothesis that p53-mediated transcriptional repression plays a role in the spatial restriction of PCNA gene expression during normal renal development.