二氧化碳加氢一步法合成二甲醚的研究进展   总被引：1，自引：0，他引：1  

胡生隆  李治霖  查飞  陈浩斌 《兰州石化职业技术学院学报》2008,8(4):9-13

对二氧化碳加氢直接合成二甲醚的热力学、动力学行为、反应机理及催化剂的研究进展作了综述。  相似文献   

Changes in joint kinetics during learning the longswing on high bar     

Genevieve K.R. Williams  Gareth Irwin  David G. Kerwin  Karl M. Newell 《Journal of sports sciences》2015,33(1):29-38

Biomechanics helps us understand the association between technique changes and performance improvement during learning. The aim of this research was to investigate joint kinetic characteristics of technique during learning of the longswing on the high bar. Twelve male, novice participants took part in the learning study. During swing attempts in 8 weekly testing sessions, kinematic data were collected. Inverse dynamics analysis was performed from known zero forces at the toes to quantify joint moments and power at the hips and shoulders. Key biomechanical constraints that limited performance outcome were identified based on changes in joint kinetics during learning. These constraints were the ability to perform a large shoulder power and to overcome passive kinetics acting during the downswing. Constraints to action at the level of joint kinetics differentially challenge learners and therefore could underpin more individual, specific learning interventions. Functional phases, defined by maximum hyperextension to flexion of the hips and maximum flexion to extension of the shoulders, did not describe the key joint kinetics of the hip and shoulder for novices. The functional phases may serve however to identify novices that were unable to overcome the passive kinetic constraint.  相似文献   

贮藏期间菠菜微生物生长动力学模型的研究     

房晓  齐沙沙  范维江  侯宗良  王树庆  郭风军 《山东商业职业技术学院学报》2014,14(5):118-120

目的 研究贮藏期内不同温度下菠菜上的微生物生长趋势.方法 将用保鲜膜封装好的菠菜分别置于3℃、15℃、25℃、35℃四个温度下贮藏,定期对菌落总数进行测定.首先,使用修正的Compertz方程建立不同温度下微生物生长的初级模型,其次,结合Belehradek方程讨论微生物的μmax（最大比生长速率）和λ（延滞时间）与温度的关系,并建立微生物生长的二级模型和货架期模型.结果 研究认为,修正的Compertz方程能够较好地拟合不同温度下菠菜微生物生长的一级模型,R2均大于0.90;微生物的Nmax随着温度的变化波动不大,平均值为（9.4704±1.1472）lg（CFU/g）;μmax随着温度的上升而变大,λ随温度的增加而减小,二级模型为√μmax=0.0215×[T-（-26.5286）]、√1/λ=0.0226 × [T-（-34.0620）],R2分别为0.9967、0.9461.结论 建立了具有较高的拟合度的微生物生长的初级模型、二级模型,也确立了菠菜的微生物货架期模型.  相似文献   

Biomechanics of increased spin velocity of flying discs during forehand throws by skilled and unskilled throwers     

Kei Sasakawa  Koji Umegaki  Shinji Sakurai 《Journal of sports sciences》2018,36(8):843-851

We aimed to assess the relationship between throwing distance and kinematic release parameters of the flying disc in unskilled throwers, and to assess the relationship between kinetic variables acting on flying discs and the change in spin velocity during long forehand throws by skilled and unskilled throwers. Ten skilled and eleven unskilled throwers performed throws at maximum effort. Reflective marker positions on the disc and body were recorded with a 3D motion capture system during the throws to derive kinematic variables of a disc and kinetic variables acting on the disc. The analysis interval was from maximum external shoulder rotation to disc release. Significant correlations were observed between the throwing distance and spin velocity in skilled (r = 0.722, P < 0.05) and unskilled throwers (r = 0.794, P < 0.01), between the change in spin velocity and the angular impulse of moments of force, in unskilled throwers (r = 0.703, P < 0.05), and between the change in spin velocity and the angular impulse of torque among skilled throwers (r = 0.680, P < 0.01). Therefore, a strategy for increasing spin velocity in unskilled throwers could be used to generate a larger torque, similar to that observed in skilled throwers.  相似文献   

Long-term Tai Chi exercise increases body stability of the elderly during stair ascent under high and low illumination*     

Qipeng Song  Shen Wang  Del P. Wong  Jingyi Zhou  Wei Sun  Cui Zhang 《Sports biomechanics / International Society of Biomechanics in Sports》2018,17(3):402-413

The effects of long-term Tai Chi exercise on body stability of the elderly during stair ascent under high and low illumination were investigated. Forty-five healthy elderly women were divided into three groups, namely, Tai Chi exercise group, brisk walking group and no-exercise control group. All the participants ascended a staircase, during which force platforms and a motion capture system collected the data. Under the high illumination, Tai Chi exercise participants exhibited higher loading rate and anteroposterior centre of pressure (COP_ap) displacement as well as a lower braking impulse than no-exercise group. Under the low illumination, Tai Chi exercise participants demonstrated higher COP_ap and mediolateral centre of pressure (COP_ml) displacements as well as lower braking and lateral impulses compared with no-exercise participants. The centre of mass (COM)_ml sway in Tai Chi and no exercise participants were higher, the loading rates in Tai Chi and walking participants were higher, and the lateral impulse in no exercise participants was higher under low illumination than under high illumination. Thus, low illumination increases the risk of falling. Tai Chi participants increased their foot clearance, head inclination angle and COP_ap displacement under low illumination to increase their stability during stair ascent.  相似文献   

Test–retest reliability of the Tekscan® F-Scan® 7 in-shoe plantar pressure system during treadmill walking in healthy recreationally active individuals     

Kyle Patrick 《Sports biomechanics / International Society of Biomechanics in Sports》2018,17(1):83-97

In-shoe plantar pressure systems are commonly used in clinical and research settings to assess foot function during functional tasks. Recently, Tekscan® has updated their F-Scan® in-shoe plantar pressure system; however, this system’s test–retest reliability has not been established. Therefore, the purpose of this study was to determine the test–retest reliability of the F-Scan® 7 system in recreationally active individuals during treadmill walking. Seventeen healthy adults completed 2 sessions of treadmill walking. For each session, participants were fitted for shoes and pressure insoles and walked on a treadmill at a self-selected pace for 30 s. Following the sessions, the test–retest reliability peak pressure, pressure time integral, average pressure and pressure contact area over 4 regions of the foot (heel, mid-foot, forefoot and toes) was assessed by calculating intraclass coefficients (ICC 2,k) and coefficient of variation percentage (CoV%). Pressure contact area consistently had the highest ICCs and lowest CoV% (ICCs: 0.91–0.98; CoV%: 2.7–7.8%). Whereas, the forefoot and toe regions had the highest ICCs for all 4 measures (ICCs: 0.83–0.98; CoV%: 3.1–13.4%). During treadmill walking in healthy recreationally active individuals, the reliability of the new Tekscan F-Scan® ranged from poor to high and was dependent on the measure and region of the foot.  相似文献   

Textured insoles reduce vertical loading rate and increase subjective plantar sensation in overground running     

Michael Wilkinson  Alistair Ewen  Nicholas Caplan  David O’leary  Neil Smith  Richard Stoneham 《European Journal of Sport Science》2018,18(4):497-503

The effect of textured insoles on kinetics and kinematics of overground running was assessed. 16 male injury-free-recreational runners attended a single visit (age 23?±?5 yrs; stature 1.78?±?0.06 m; mass 72.6?±?9.2?kg). Overground 15-m runs were completed in flat, canvas plimsolls both with and without textured insoles at self-selected velocity on an indoor track in an order that was balanced among participants. Average vertical loading rate and peak vertical force (F_peak) were captured by force platforms. Video footage was digitised for sagittal plane hip, knee and ankle angles at foot strike and mid stance. Velocity, stride rate and length and contact and flight time were determined. Subjectively rated plantar sensation was recorded by visual scale. 95% confidence intervals estimated mean differences. Smallest worthwhile change in loading rate was defined as standardised reduction of 0.54 from a previous comparison of injured versus non-injured runners. Loading rate decreased (?25 to ?9.3?BW?s^?1; 60% likely beneficial reduction) and plantar sensation was increased (46–58?mm) with the insole. F_peak (?0.1 to 0.14?BW) and velocity (?0.02 to 0.06?m?s^?1) were similar. Stride length, flight and contact time were lower (?0.13 to ?0.01 m; ?0.02 to?0.01?s; ?0.016 to ?0.006?s) and stride rate was higher (0.01–0.07 steps?s^?1) with insoles. Textured insoles elicited an acute, meaningful decrease in vertical loading rate in short distance, overground running and were associated with subjectively increased plantar sensation. Reduced vertical loading rate could be explained by altered stride characteristics.  相似文献   

水溶性苯胺蓝的热氧降解过程与动力学     

魏月英  林木良  李晓燕 《中山大学学报论丛》1998,(4)

用差热分析方法（ＤＴＡ）、热重分析法（ＴＧ）和微分热重分析法（ＤＴＧ）研究水溶性苯胺蓝在空气中流中的热氧降解过程和动力学,发现水溶性苯胺蓝热氧降解过程由３个紧连步骤组成．用ＣｏａｔｓＲｅｄｆｅｒｎ方程进行动力学处理,确定水溶性苯胺蓝热氧降解的表观反应级数分别为１７,２０,０９和活化能为２５４６,３３１５,５９７７ｋＪ／ｍｏｌ．  相似文献   

净化空气功能性内墙涂料的甲醛分解     

王晓强  张剑平  朱惟德  施利毅 《上海大学学报(英文版)》2007,11(5):527-530

A novel nano-TiO2-xNx composite was used as photocatalyst and added to the interior wall paint. The average diameter of nano-TiO2-xNx was about 20 nm. The majority crystal component of the sample was anatase and its optical absorption edge was shifted from 387 nm to 520 nm significantly. Nano-composite paint containing different dosage of nano- TiO2-xNx was investigated to study the properties of formaldehyde decomposition in the air. Testing results show that the formaldehyde decomposition ratio of that nano-paint can almost reach above 80%, especially for that of the paint containing 3% （w/w） nano-TiO2-xNx which exceeded 90%. The primary investigation on the reaction kinetics of photocatalytic formaldehyde decomposition indicated that the experiment data well fit the model of first-order reaction kinetics.  相似文献   

影响高校高水平男子三级跳远各阶段速度因素的运动参数分析     

霍俊哲 《体育科技》2010,31(2):41-44

通过高速摄影和录像解析等方法对湖北省2008高校高水平男子三级跳远运动员三跳各阶段水平速度变化情况进行相关比较与研究,结果显示,高校高水平男子三级跳远运动员各时相水平速度在助跑、踏板、起跳、单足跳、跨步跳、跳跃等由于诸多因素造成水平速度降低,特别是跨步跳造成的损失成为影响总成绩的关键。  相似文献