潜油电泵零部件螺纹旋和率的研究

本文通过对螺纹孔的标准分析以及对螺纹加工的方法的跟踪。对采用不同的加工工艺检验方法获得的不同精度等 级的螺纹进行试验论证,获得对于潜油电泵的螺纹的旋和率的合理推荐值。

Ocean mesoscale structure–induced air–sea interaction in a high-resolution coupled model

Using the Community Earth System Model framework, the authors build a very-high-resolution quasi-global coupled model by coupling an eddy-resolving quasi-global ocean model with a high-resolution atmospheric model. The model is successfully run for six years under present climate conditions, and the simulations are evaluated against observational and reanalysis data.The model is capable of simulating large-scale oceanic and atmospheric circulation patterns, sea surface temperature(SST) fronts, oceanic eddy kinetic energy, and fine-scale structures of surface winds. The ocean mesoscale structure–induced air–sea interaction characteristics are explored in detail. The model can effectively reproduce positive correlations between SST and surface wind stress induced by mesoscale structures through comparison with observations. The positive correlation is particularly significant over regions with strong oceanic fronts and eddies.However, the responses of wind stress to eddy-induced SST are weaker in the simulation than in the observations, although different magnitudes exist in different areas. Associated with weak wind responses, surface sensible heat flux responses to eddy-induced SST are underestimated slightly, while surface latent heat flux responses are overestimated because of the drier atmospheric boundary layers in the model. Both momentum mixing and pressure adjustment mechanisms play important roles in surface wind changes over oceanic fronts and eddies in the high-resolution model.

Significant decrease in prevalence ofHelicobacter pylori in the Czech Republic

AIM:To study possible decrease in prevalence of Helicobacter pylori(H.pylori) infection in the Czech Republic within a 10-year period.METHODS:A total of 22 centres entered the study.The catchment areas of these centres covered cities and towns with more than 20 000 inhabitants,smaller towns(≤ 20 000 inhabitants) with surrounding villages and rural areas,and were spread over the whole country,corresponding well to the geographical distribution of the Czech population.A total of 1 837 subjects(aged 5-98 years) took part in the study,randomly selected out of 38 147 people from the general population.H.pylori infection was investigated by means of a 13 C-urea breath test.Breath samples in duplicates were analysed using isotope ratio mass spectrometry.The cut-off point was 3.5.Social and demographic characteristics were based on data from self-completed questionnaires.RESULTS:The overall prevalence of H.pylori infection was 23.5%(430/1826),and 4.8%(20/420) in children aged 15 or less.There was no statistically significant difference in prevalence between males(24.3%;208/857) and females(22.9%,222/969,P = 0.494).H.pylori infection was strongly associated with higher age,among subjects aged 55+ years,prevalence of H.pylori infection was 39.8%(252/633,P < 0.001).The highest prevalence of H.pylori infection was found among persons aged 55-64 years(43.9%,97/221) and 75+ years(37.9%,58/153).Among study subjects aged 15+ years,prevalence of H.pylori infection was significantly increased in those with lowest education(odds risk 3.19,95% CI 1.87-5.47).Compared to never married(14.1%),the prevalence of H.pylori infection was statistically significantly higher among married(35.4%,246/694,P < 0.001),divorced(36.8%,49/133,P < 0.001) and widowed study subjects(40.2%,45/112,P < 0.001),both in minimally and fully adjusted analysis.There was no significant difference in the prevalence of H.pylori infection between married and widowed subjects(35.4%,246/694 vs 40.2%,45/112,P = 0.389).There was little variation in smoking prevalence across categories of smoking and there was no evidence of an increased risk ofH.pylori infection among current or past smokers in our data(odds risk 1.04 with 95% CI 0.78-1.40 for current smokers;odds ratio 0.83 with 95% CI 0.60-1.16 for former smokers).The current prevalence of H.pylori in 2011 was significantly lower compared to the prevalence reported from identical geographical areas in 2001(23.5%vs 41.7%,P < 0.001).CONCLUSION:The overall prevalence of H.pylori infection in the general population has fallen substantially in the Czech Republic over the past 10 years.