探讨移动互联时代公民理性“发声”机制

移动互联时代,倡导公民的理性"发声"能减少不良信息的危害,营造良好的舆论环境。要形成公民理性发声的机制,必须遵循法制规制与宽容接纳相结合,技术限制与技术监控相结合,公民自律与媒介素养再教育相结合的原则,从而促进移动互联技术善用并有助于为国家培养现代公民。

Physical and mechanical properties of Beishan granite after different high temperature treatments

In China,Beishan granite is chosen as a potential host surrounding rock of a high-level radioactive waste(HLW)repository.For this research,Beishan granite specimens were heated up to 300℃,400℃ and 500℃,respectively.And conventional triaxial compression tests were conducted after cooling down the samples.The results show that after 300℃,400℃ and 500℃ heating treatment,the diameter of samples increases by 0.066%,0.143%and 0.409%,respectively,which is a little larger than the axial length changes.Mechanical tests show that peak strength increases slightly with increasing temperature.However,the dilatancy threshold is lower than that observed for samples which have not experienced heating treatment.Peak strain and dilatancy threshold strain show a strong temperature dependence.The higher the temperature,the greater the strain.Furthermore,increasing temperature has negative influence on threshold elastic modulus E_(c) and tangent elastic modulus E_(t).Poisson ratio decreases when temperature increases from 300℃ to 500℃,but it is still larger than that observed for samples which have not experienced heating treatment.In addition,AE monitoring shows a quiet period in the initial loading stage,which proves that the micro cracks are closed during heating and contribute to the increase of peak strength.

Macro and meso characteristics evolution on shear behavior of rock joints

Direct shear tests were conducted on the rock joints under constant normal load(CNL), while the acoustic emission(AE) signals generated during shear tests were monitored with PAC Micro-II system. Before and after shearing, the surfaces of rock joints were measured by the Talysurf CLI 2000. By correlating the AE events with the shear stress-shear displacement curve, one can observe four periods of the whole course of shearing of rock joints. By the contrast of AE location and actual damage zone, it is elucidated that the AE event is related to the morphology of the joint. With the increase of shearing times, the shear behavior of rock joints gradually presents from the response of brittle behavior to that of ductile behavior. By combining the results of topography measurement, four morphological parameters of joint surface, S p(the maximum height of joint surface), N(number of islands), A(projection area) and V(volume of joint) were introduced, which decrease with shearing. Both the joint roughness coefficient(JRC) and joint matching coefficient(JMC) drop with shearing, and the shear strength of rock joints can be predicted by the JRC-JMC model. It establishes the relationship between micro-topography and macroscopic strength, which have the same change rule with shearing.

The Numerical Simulation of Collapse Pressure and Boundary of the Cavity Cloud in Venturi

The idea that the collapse proceeds from the outer boundary of the cavity cloud towards its center for the ultrasonic cavitation proposed by Hasson and Morch in 1980s is further developed for calculating the collapse pressure and boundaries of cavity cloud at the collapse stage of bubbles for hydraulic cavitation flow in Venturi in present research. The numerical simulation is carried out based on Gilmore＇s eouations of bubble dynamics, which take account of the compressibility of fluid besides the viscosity and interfacial tension. The collapse of the cavity cloud is considered to proceed layer by layer from the outer cloud towards its inner part. The simulation results indicate that thepredicted boundaries of the cavity cloudat the collapse stage agree.well with the exPerimental ones.It is also found that the maximum collapse pressure of the cavity cloud is several times as high as the collapse pressure of outside boundary, and it is located at a point in the axis, where the cavity cloud disappears completely. This means that a cavity cloud has higher collapse pressure or strength than that of a single bubble due to the interactions of the bubbles. The effects of operation and structural parameters on the collapse pressure are also analyzed in detail.

Study on correlation between pathology and the contrast-enhanced ultrasound characteristics of primary liver cancer

Objective:The aim of this study was to evaluate the value of contrast-enhanced ultrasound(CEUS) for blood perfusion of primary liver cancer(PHC) and investigate the correlation between microvascular architecture of PHC and pathological differentiation.Methods:Two hundred and seventy-eight patients with 329 PHC lesions were examined by CEUS and analysised the contrast enhancement pattern and correlation with pathology.Results:1.CEUS patterns of PHC:71.7%(236/329) showed "swift enhancement in the arterial phase and swift expurgation in the portal phase",13.4%(44/329) for as "swift enhancement and slow expurgation",7.3%(24/329) as "swift enhancement and simultaneity expurgation",4.3%(14/329) for the "slow enhancement and swift expurgation",2.1%(7/329) as "slow enhancement and expurgation",1.2%(4/329) as "not fast forward".2.90.3%(297/329) of PHC lesions were hypervascular liver cancer and 9.7%(32/329) were hypovascular.Hepatocellular carcinoma(HCC) were hypervascular lesions and intrahepatic cholangiocarcinoma(ICC) were hypovascular lesions.3.PHC size had a significant difference on the contrast media purfusion pattern(P < 0.05),but not on the contrast media expurgation pattern.4.The accuracy of PHC by CEUS were 97.3% and compared to pathology,9 lesions of PHC were misdiagnosed.Conclusion:CEUS can show the different blood perfusion characteristics of PHC with closely related to pathological differentiation,which be valuable to diagnose liver cancer.

Nonlinear oscillation of pathological vocal folds during vocalization

The extended two-mass model is adopted to analyze the nonlinear oscillation of pathological vocal folds during vocalization. Redundant tissue or area in laryngeal patients is modeled as a massless rigid connected to the upper mass of the vocal folds, and a parameter Q is introduced to represent the change of glottal configurations and tension imbalance between the left and right sides of vocal folds. Numerical simulations demonstrate that the pathological vocal-fold decreases the threshold of Q to generate nonlinear vocal oscillation, indicating the improvement of the sensitivity of vocal folds to asymmetries and enhancing the coupling between two sides. Furthermore, the pathological vocal-fold can lower the fundamental frequency and eliminate high-order harmonics, For example, the fundamental frequency decreases from 119.94 Hz to 84.95 Hz when Q=0.58 and the sub-glottal pressure 1450 Pa. However, there are no prominent effects on the amplitudes of sub-harmonic and low-order harmonics.