Environment has significant effects on the water absorption of concrete materials. This paper presents an experimental study of the influence of water absorption on the durability of concrete ...materials. A detailed analysis is also presented in order to establish useful relationship between them. Concrete specimens of different water absorption were prepared through different curing conditions, and results indicated that curing condition can significantly affect the surface water absorption. SEM photos also showed that different curing conditions caused different microstructure. After 28-days curing, compressive strength, permeability, sulfate attack, and chloride ion diffusion of concrete samples were investigated. As a result, both of surface sorptivity and internal sorptivity have no clear relationship with compressive strength. Results obtained also showed that only surface water absorption related to the performance of concrete including permeability, sulfate attack, and chloride ion diffusion. In addition, both impermeability and resistance to sulfate attack were linearly associated with surface sorptivity, and both correlation coefficients were not less than 0.9. Furthermore, chloride ion diffusion coefficient has exponent relation to surface water absorption with higher correlation coefficient. However, no apparent relationship was found between internal water absorption and durability like impermeability, resistance to sulfate attack, and chloride ion diffusion.
A tunable stiffness and damping vibration isolator based on magnetorheological elastomers (MREs) is developed. In this isolator, four MRE elements are used as the tunable springs, whose stiffness can ...be controlled by varying the magnetic field. A voice coil motor, which is controlled by the relative velocity feedback of the payload, is used as the tunable damper of the isolator. Under the combined ON–OFF control, the proposed vibration isolator shows satisfying isolation effect. The experimental results indicate that the responses of the payload are suppressed significantly in comparison to the passive system. The transmissibility of the payload around the resonant frequency is decreased by 61.5%. The root mean square (RMS) value and the maximum value of the displacement responses of the payload are decreased by 36.0% and 50.0%, respectively. In addition, the RMS values and maximum values of the velocity responses are decreased by 45.4% and 52.5%, respectively.
Abstract Background Gastric cancer is one of most common malignancies in the world. Currently the prognostic prediction is entirely based on the TNM staging system. In this study, we evaluated ...whether metastatic lymph node ratio (rN) at the time of surgery would improve the prognostic prediction in conjunction with the TNM staging system. Methods This retrospective study includes 745 patients, who had been referred for surgery due to gastric cancer between 1995 and 2007 and had at least 15 lymph nodes examined at the time of surgery without preoperative treatment. Clinicopathologic features and overall survival were analyzed using univariate and multivariate modes to identify the risk factors for overall survival. Results Median overall survival of all patients analyzed is 57.8 months and 5-year overall survival is 49.5%. Tumor site, macroscopic type, pTNM stage, and rN stage are identified as independent prognostic factors. Increased positive lymph node ratio correlates with shorter survival in all patients and in each T and N stage. In stage III gastric cancer patients, rN stage shows additional prognostic value on overall survival ( p < 0.001). Conclusions rN stage is a simple and promising prognostic factor of gastric cancer after surgery in addition to the TNM stage system especially in stage III patients. But the independent prognostic value of rN stage in stage I, II and IV gastric cancer is yet to be determined.
•The flow boiling experiment are conducted in porous-wall (PW) microchannels.•The effect of mass flux, heat flux and vapor quality on microchannels are studied.•PW microchannels reduce the wall ...superheat for ONB and improve the CHF.•PW microchannels exhibit obvious heat transfer enhancement with pressure drop reduction.•The uniformity and stability of wall temperature are analyzed in PW microchannels.
In this work, we proposed a porous-wall (PW) microchannel heat sink, in which micro pin fin arrays were fabricated on sidewalls of rectangular microchannels by MEMS (Microelectrical Mechanical System) technique. High speed flow visualizations were performed simultaneously with heat transfer and pressure drop measurements to investigate the flow boiling characteristics of PW microchannel heat sink. Conventional rectangular (Rec) microchannel heat sink was also explored together as a comparison. Experiments were carried out with pure acetone liquid at inlet temperature of 30 °C, mass flux from 255 kg/(m2·s) to 843 kg/(m2·s), heat flux from 4 W/cm2 to 110 W/cm2 and the maximum vapor quality at the outlet of the channel was 0.88. Experimental results demonstrated that the PW microchannels reduce wall superheat of onset of nucleate boiling (ONB) and improve critical heat flux (CHF) compared to the Rec microchannels. Moreover, the PW microchannels show significant heat transfer enhancement, pressure drop reduction and mitigation of two-phase flow instability. The porous walls provide numerous nucleation sites and the intensive pin fins arrangements introduce significant wicking effect to maintain the liquid rewetting, which contribute to the above notable flow boiling enhancement.
The as-extruded AZ91D magnesium alloy processed by conventional extrusion exhibits a yield strength of 320 MPa, an ultimate tensile strength of 382 MPa and a fracture elongation of 13.8%, superior ...than most AZ91D alloys reported so far, which is mainly attributed to ultra-fine grains, sub-micron precipitates, and strong texture.
•A novel porous-wall microchannels was designed and fabricated, in which the solid walls were replaced by the micro pin fin arrangements.•With the porous-wall inter-connect effect, the mass and ...pressure can be propagated between adjacent channels.•For semi-stable/moderate/severe unstable two-phase flow, the variation of wall temperatures was not in accordance with ΔP.
In this work, a porous-wall microchannel heat sink was designed and fabricated, and the wall regions were etched with the micro pin fin arrangement instead of solid walls. The porous-wall can be divided into three regions: the densely/intermediate densely/sparely pin fin region with the fin gap of 5 μm/7.5 μm/10 μm, respectively. Flow boiling tests in porous-wall microchannels were carried out at mass fluxes of 250–510 kg/(m2·s) and heat fluxes of 120–720 kW/m2. The effects of the porous-wall on suppressing the flow instabilities and manipulating the boiling flow were studied, and different boiling flow behaviors of pressure drops and temperatures as well as corresponding flow patterns were measured and observed. The experimental results showed that: (1) With the porous-wall inter-connect effect, the premature ONB (Onset of Nucleate Boiling) can be occurred, the nucleate boiling flow in whole channel can be triggered in less than 2 ms, the boiling flow instability can be suppressed, and the duration of two-phase flow can be prolonged; (2) The boiling instabilities in porous-wall microchannels were classified into four flow modes, and the temporal behaviors of temperatures and pressure drops corresponding to each flow instability mode were observed and analyzed. (3) By PSD (Power Spectral Density) combined with WT (Wavelet Transform) analysis method, the coupled wall temperature oscillations in each instability type were decoupled into different instability sub-types at different amplitudes and timescales. Moreover, the analysis of ms-timescale flow instability induced by the flow pattern transition helps to better understanding the dominant influence of the porous-wall on the resulting temperature oscillations.
Highlights • Cx26 deletion after birth can lead to late-onset, progressive hearing loss. • The deletion leads to hearing loss by the reduction of active cochlear amplification. • The deletion shifts ...outer hair cell NLC to reduce active amplification. • This study provides a new deafness mechanism due to Cx26 deficiency.
This paper focuses on the bending behavior of flange-plate connections under pure-bending and aims for putting forward a practical design model. Four basic types of bolted flange-plate connections ...are tested and related finite element analysis is implemented. The finite element model is verified by experimental results and proved to be precise and reliable. Based on the finite element analysis, the distribution of von-Mises strain and contact pressure at end plates of the connections is revealed. The valuable information can be directly used in the theoretical model to present a relatively clear yield line mechanism and definite pressure center. The bending capacity determined by flange-plates is derived with the virtual work principle. It is proved that the theoretical model can give a good prediction for the yield bending capacity of the connections. Meanwhile, traditional T-stub analogy is introduced to obtain the bending capacity determined by bolts. Combining with the two different design models and assuming that the end plates should fail before high strength bolts, a practical design procedure is put forward. The connections designed according to this procedure will meet the demand of safety and economy. Furthermore, the design model herein can provide useful reference for practical design of other kinds of bolted flange-plate connections.
► The safety margin of the stiffened connections is better for both CHS and SHS. ► FEA can give a precise prediction of bending behavior. ► The pressure center and a relatively clear yield line mechanism of plates are found. ► A simplified model based on T-stub analogy is proposed to calculate prying forces. ► A practical design procedure combining two models is put forward.
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