Analysis of blasting vibration duration considering frequency and energy and its application.

Blasting vibration's effect on ground vibration is essentially an energy transfer and transformation process (Hongtao et al., 2010) [1]. In engineering, the blasting vibration duration is often used as an objective index to evaluate the blasting vibration hazard. Thus, this study on the factors influencing blasting vibration duration is essential. In this study, the blasting vibration duration prediction formula uses frequency and energy as independent parameters, which are analysed using a statistical t probability distribution. With the blasting vibration duration prediction formula, the delay time taken for the structure to reach the resonance frequency is obtained by calculating the dominant frequency of the structure. The results indicate that the frequency and energy of the blasting vibration signal are highly correlated with the duration of blasting vibration, and their introduction as independent parameters in the prediction formula can better improve the prediction accuracy. The dominant frequency should not be neglected in blasting vibration safety evaluations, and the use of blasting vibration duration prediction to calculate the dominant frequency can better avoid the resonance phenomenon in the structure.

Physical activity during pregnancy and the risk of gestational diabetes mellitus: a systematic review and meta-analysis of randomised controlled trials.

OBJECTIVES: We performed a systematic review and meta-analysis to assess the effects of physical activity in preventing gestational diabetes mellitus (GDM). SEARCH STRATEGY: We searched the literature in six electronic databases and bibliographies of relevant articles. SELECTION CRITERIA: We included randomised controlled trials on pregnant women who did not have GDM and other complications previously and had increased physical activity as the only intervention. The risk of developing GDM was documented separately for the intervention and control groups. DATA COLLECTION AND ANALYSIS: Two reviewers extracted data and assessed quality independently. Data from the included trials were combined using a fixed-effects model. The effect size was expressed as relative risk (RR) and 95% CI. MAIN RESULTS: Of the 1110 studies identified, six randomised controlled trials met the inclusion criteria. In three trials, the incidence of GDM was lower in the intervention group than in the control group, whereas two trials showed a higher incidence of GDM in the intervention group and the remaining trial found no GDM in either the intervention or control group. The meta-analysis resulted in a relative risk (RR) of GDM of 0.91 (95% CI 0.57 to 1.44), suggesting no significant difference in the risk of developing GDM between the intervention and the control groups. No indication of publication bias was found. CONCLUSIONS: Evidence was insufficient to suggest that physical activity during pregnancy might be effective to lower the risk of developing GDM.

[Evidence-based medical approach to clinical medicine and health policy-making in the 21st century].

In the late part of the 20th century, due to the change of disease spectra, rapid increase of health expenditure and imbalanced distribution of health resources, the health management sectors and doctors increasingly demand the scientific decision-making. With the development of clinical evidences and research, evidence-based medicine (EBM) became emerged in the early 1990's. EBM, the medical science in compliance with the best available clinical evidence, integrates clinical epidemiology (CE), systematic reviews (SRs) and health technology assessment (HTA) as the major technology, to emphasize that the clinical practice should be based on the combination of the best available clinical evidence, medical experiences and patient desire to cope with the demand of medical decision-making. Some governments and international organizations like WHO, and Australia have now adopted the high-quality evidence of EBM for decision-making. As the largest developing country, China is challenged by variety of health problems. The introduction, adaptation and implementation of EBM will improve the decision-making and health care services, which should enhance the competitive capacity of medical and pharmaceutical manufactures, as well as promote the popularization of EBM, and protect the doctors and patients rights.