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露天矿山爆破开采过程中会产生一系列的危害,严重威胁地表建筑物及人员的安全.通过现场实时监测采集了露天矿山远距离建筑物的质点振动速度及主振频率,并且根据萨道夫斯基公式对监测结果进行线性回归,推导出爆破振动波的衰减规律.试验结果表明:爆破振动质点振速与爆心距有关,随着爆心距的增大,质点振动速度逐渐减小;质点振动的三向振速中,水平径向振速最大;监测点的峰值振速均在安全允许范围之内,一般情况下对周围建筑物没有影响;爆破地震波衰减系数K=248.05,α=1.52,即爆破振动质点振速衰减规律公式为:V=248.05(3√Q/R)1.52.爆破振动监测结果和衰减规律对类似地形和地质的露天矿爆破开采具有一定的参考价值. 相似文献
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Collaboration in large-scale projects introduces challenges involving both coordination (the ability to collaborate) as well as cooperation (the willingness to do so). Existing research has shown how modular designs can improve coordination by locating interdependencies within rather than between different modules. Based on an in-depth case study of collaboration in a large-scale infrastructure project, our study highlights an effect of modularity on collaboration that previously has been overlooked. Specifically, we show that while modular designs may help overcome coordination challenges by reducing interdependencies between modules, they can in turn hamper collaboration by emphasizing specialization within modules. Therefore, though existing work typically perceives modularity and integration as opposites, we clarify how they can also act as complements. In particular, we show how firms need to complement modular designs with integrating practices that stimulate cooperation. Overall, we contribute to the literature on collaboration and modularity by explaining when and how organizations can combine modularity and integration. 相似文献
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J.S. Whyte 《Endeavour》1981,5(1):21-28
Puck, in a Shakespearean comedy set in Athens, boasted: ‘I'll put a girdle round the earth in forty minutes’. His claim was never realised, but today—thanks to submarine cable technology—the human voice can make this long journey in a tenth of a second. This article reviews the present state of submarine cable technology; its relationship to communication by satellite; and the implications of optical fibre systems. 相似文献
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Enda F. Whyte Patrick Kennelly Oliver Milton Chris Richter Siobhán O’Connor Kieran A. Moran 《Sports biomechanics / International Society of Biomechanics in Sports》2018,17(4):541-553
The effectiveness of vertical drop jumps (VDJs) to screen for non-contact ACL injuries is unclear. This may be contributed to by discrete point analysis, which does not evaluate patterns of movement. Also, limited research exists on the second landing of VDJs, potential lower limb performance asymmetries and the effect of fatigue. Statistical parametric mapping investigated the main effects of landing, limb dominance and a high intensity, intermittent exercise protocol (HIIP) on VDJ biomechanics. Twenty-two male athletes (21.9 ± 1.1 years, 180.5 ± 5.5 cm, 79.4 ± 7.8 kg) performed VDJs pre- and post-HIIP. Repeated measures ANOVA identified pattern differences during the eccentric phases of the first and second landings bilaterally. The first landing displayed greater (internal) knee flexor (η2 = 0.165), external rotator (η2 = 0.113) and valgus (η2 = 0.126) moments and greater hip (η2 = 0.062) and knee (η2 = 0.080) flexion. The dominant limb generated greater knee flexor (η2 = 0.062), external rotator (η2 = 0.110) and valgus (η2 = 0.065) moments. The HIIP only had one effect, increased thoracic flexion relative to the pelvis (η2 = 0.088). Finally, the dominant limb demonstrated greater knee extensor moments during the second landing (η2 = 0.100). ACL injury risk factors were present in both landings of VDJs with the dominant limb at potentially greater injury risk. Therefore, VDJ screenings should analyse both landings bilaterally. 相似文献
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The aim of this study was to assess the effect of time of day on physiological responses to running at the speed at the lactate threshold. After determination of the lactate threshold, using a standard incremental protocol, nine male runners (age 26.3 - 5.7 years, height 1.77 - 0.07 m, mass 73.1 - 6.5 kg, lactate threshold speed 13.6 - 1.6 km· h -1 ; mean - s ) completed a standardized 30 min run at lactate threshold speed, twice within 24 h (07:00- 09:00 h and 18:00-21:00 h). Core body temperature, heart rate, minute ventilation, oxygen uptake, carbon dioxide expired, respiratory exchange ratio and capillary blood lactate were measured at rest, after a warm-up and at 10, 20 and 30 min during the run. In addition, the rating of perceived exertion was reported every 10 min during the run. Significant diurnal variation was observed only for body temperature (36.9 - 0.9°C vs 37.3 - 0.3°C) and respiratory exchange ratio at rest (0.86 - 0.01 vs 0.89 - 0.07) ( P ? 0.05). Diurnal variation persisted for body temperature throughout the warm-up (37.1 - 0.2°C vs 37.5 - 0.3°C) and during exercise (36.2 - 0.6°C vs 38.6 - 0.4°C), but only during the warm-up for the respiratory exchange ratio (0.85 - 0.05 vs 0.87 - 0.02) ( P ? 0.05). The rating of perceived exertion was significantly elevated during the morning trial (12.7 - 0.9 vs 11.9 - 1.2) ( P ? 0.05). These findings suggest that, despite the diurnal variation in body temperature, other physiological responses to running at lactate threshold speed are largely unaffected. However, a longer warm-up may be required in morning trials because of a slower increase in body temperature, which could have an impact on ventilation responses and ratings of perceived exertion. 相似文献
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F. Chan-Dewar W. Gregson G. Whyte D. Gaze J. Waterhouse J. Wen 《Journal of sports sciences》2013,31(4):414-423
Abstract Twelve healthy participants performed two identical high-intensity 40 km cycling trials (morning and evening) under controlled laboratory conditions. Echocardiograms and venous blood samples were collected before and after each exercise bout. Cardiac electro-mechanical-delay (cEMD) was measured as QRS-complex onset to peak systolic (S’) and early diastolic (E’) tissue velocities. Myocardial strain and strain rates were assessed in longitudinal, circumferential and radial planes at the left ventricular apex and base. Cardiac troponin I (cTnI) and N-terminal Pro-Brain Natriuretic Peptide (NT-proBNP) were assessed as biomarkers of cardiomyocyte damage and wall stress. cEMD was lengthened after both morning (S’: 160 ± 30 vs. 193 ± 27; E’: 478 ± 60 vs. 620 ± 87, P < 0.05) and evening (S’: 155 ± 29 vs. 195 ± 31; E’: 488 ± 42 vs. 614 ± 61, P < 0.05) trials. A reduction in peak S’ (morning: 6.96 ± 1.12 vs. 6.66 ± 0.89; evening: 7.09 ± 0.94 vs. 7.02 ± 0.76) was correlated with cEMD (r = ?0.335, P < 0.05). Peak longitudinal strain was reduced, atrial strain rates were sporadically increased in both trials post-cycling. cTnI was elevated in only two participants (0.04 µg · L?1, 0.03 µg · L?1), whilst NT-proBNP was below the clinical cut-off point in all participants. Prolonged-cycling resulted in a lengthening of cEMD, small changes in aspects of left ventricular deformation and sporadic increases in cardiac biomarkers. None of these effects were moderated by time-of-day. 相似文献