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在制作加工箱形钢结构井架过程中，采用原制作加工工艺和原设计接头形式时，由于加工制作工艺不合理和原设计接头形式很难控制，容易造成箱形钢结构梁的断面对角线几何尺寸和宽度几何尺寸超出国家标准等质量问题，通过对箱形钢结构梁的特性、设计要点、施工工艺的分析，结合机械制造企业本身的特点，采用改进后的加工制作工艺和接头形式，使箱形钢结构梁的质量一次合格率达到了100％，同时大幅度提高组装速度，而且还节约了组对材料，提高了企业的经济效益。 相似文献
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Ayako Higashihara Yasuharu Nagano Kazumasa Takahashi Toru Fukubayashi 《Journal of sports sciences》2015,33(13):1366-1375
This study aimed to investigate the effects of forward trunk lean on hamstring muscle kinematics during sprinting. Eight male sprinters performed maximal-effort sprints in two trunk positions: forward lean and upright. A three-dimensional musculoskeletal model was used to compute the musculotendon lengths and velocity of the biceps femoris long head, semitendinosus, and semimembranosus muscles during the sprinting gait cycle. The musculotendon lengths of all the three hamstring muscles at foot strike and toe-off were significantly greater during the forward trunk lean sprint than during the upright trunk sprint. In addition, a positive peak musculotendon lengthening velocity was observed in the biceps femoris long head and semimembranosus muscles during the late stance phase, and musculotendon lengths at that instant were significantly greater during the forward trunk lean sprint than during the upright trunk sprint. The present study provides significant evidence that a potential for hamstring muscle strain injury involving forward trunk lean sprinting would exist during the stance phase. The results also indicate that the biceps femoris long head and semimembranosus muscles are stretched during forward trunk lean sprinting while contracting eccentrically in the late stance phase; thus, the elongation load on these muscles could be increased. 相似文献
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时下,低碳已成为政府和学者共同关心的热点,低碳交通亦成为一种必然趋势.其中,设计低碳排放的城市主干道横断面显得尤为必要.本文通过交通排碳量及道路绿化固碳量计算,综合比较两者之间的关系,并结合各绿化树种的固碳能力,通过定量分析,试图探寻一种低碳排放的城市主干道横断面的设计方式,以期推动低碳城市与低碳经济的发展,为发展城市低碳交通提供有益的尝试和借鉴. 相似文献
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介绍缙云县有线电视网络的历史和现状,论述缙云县有线电视环网的方案设计,分析有线电视环网建设中的各项技术指标。 相似文献
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MSTP作为一种基于SDH的高效数据业务接入方式,在当前通信运营商中得到了大量的应用。本文介绍了处理MSTP低速率故障的经验,并对其故障原因进行了分析。 相似文献
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Guillaume Mornieux Dominic Gehring Patrick Fürst Albert Gollhofer 《Journal of sports sciences》2014,32(13):1255-1262
AbstractAnticipatory postural adjustments (APAs), i.e. preparatory positioning of the head, the trunk and the foot, are essential to initiate cutting manoeuvres during football games. The aim of the present study was to determine how APA strategies during cutting manoeuvres are influenced by a reduction of the time available to prepare the movement.Thirteen football players performed different cutting tasks, with directions of cutting either known prior to the task or indicated by a light signal occurring 850, 600 or 500 ms before ground contact.With less time available to prepare the cutting manoeuvre, the head was less orientated towards the cutting direction (P = 0.033) and the trunk was even more rotated in the opposite direction (P = 0.002), while the foot placement was not significantly influenced. Moreover, the induced higher lateral trunk flexion correlated with the increased knee abduction moment (r = 0.41; P = 0.009).Increasing lateral trunk flexion is the main strategy used to successfully perform a cutting manoeuvre when less time is available to prepare the movement. However, higher lateral trunk flexion was associated with an increased knee abduction moment and therefore an increased knee injury risk. Reducing lateral trunk flexion during cutting manoeuvres should be part of training programs seeking the optimisation of APAs. 相似文献
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健身瑜伽对中老年女性慢性腰痛的防治研究 总被引：6，自引：0，他引：6
陈丽霞 《北京体育大学学报》2006,29(1):85-86,109
为研究健身瑜伽对中老年女性慢性腰痛的防治效应,将70名中老年慢性腰痛病人分成A、B两组,C组由正常组35名无腰痛病史的中老年女性组成.对A、C进行9个月健身瑜伽训练.运用Neuromatic 2000 M/C神经肌电仪测试各组训练前后骶棘肌肌电指标,PPX-L型双能X线骨度仪测量各组训练前后骨密度值,分别进行组间比较.结果:慢性腰痛组(A、B)训练前腰背肌波幅低于正常组(P<0.01)时程大于正常组(P<0.01),训练之后腰痛组(A)和正常组(C)波幅都得到提高(P<0.01和P<0.05)时程都降低(P<0.01和P<0.05).疗效评定得出慢性腰痛治愈显效率达82.86%.结论:健身瑜伽对中老年女性慢性腰痛具有较好的防治作用. 相似文献
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Machar Reid Bruce Elliott 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(1):47-68
The study investigated differences in the one‐ (SH) and two‐handed (DH) backhands when hit flat, across‐court (AC) and down‐the‐line (DL), and with heavy topspin DL (TDL). The ability to disguise each of these backhands when hitting the above strokes was also assessed. Eighteen college‐level male tennis players, identified as having a high performance topspin SH (n = 6) or DH (n = 12) backhand drive, participated in the study. Players were required to hit three AC, DL and TDL backhands from the baseline with their preferred technique, while being filmed with two high‐speed video cameras operating at 200 Hz. The highest horizontal velocity backhand for each stroke was analysed. Results indicated that the sequential coordination of five body segments (hips, shoulder, upper arm, forearm, and hand/racquet rotations) was required for the execution of the SH stroke. The same number of segments were generally coordinated in the DH stroke (hips, shoulders, and varying degrees of upper arm and forearm rotations followed by hand/racquet movement). Mature players produced comparable racquet horizontal velocities 0.005 s prior to impact using either the SH or DH backhand technique. The SH backhand was characterised by a more rotated shoulder alignment than the DH stroke (SH: 119.1°; DH: 83.4°) at the completion of the backswing. At impact the ball was impacted further in front (SH: 0.59 m; DH: 0.40 m) and a similar distance to the side of the body (SH: 0.75 m; DH: 0.70 m). Players using the DH backhand technique delayed the horizontal acceleration of the racquet towards the ball (SH: 0.13 s; DH: 0.08 s prior to impact) and thus were capable of displaying a similar hitting motion closer to impact than players with a SH technique. 相似文献