桥式起重机吊装过程动力学分析及最大动力响应解算

吊钩桥式起重机吊装过程中的最大动力响应发生在货载起吊离地和全速下降制动2个瞬间。本文对这2个瞬间动力过程进行详细研究,包括影响因素分析及力学、数学模型的建立等,并用MATLAB软件对一桥式起重机吊装过程的最大动力响应进行解算,解算结果可以作为吊具选用及强度设计的依据。

劳务经济:农民市民化的最大动力源

改革开放以来,亿万农民从农村走向城市,从务农走向务工经商,创造了劳务经济,不仅开辟了增加收入新渠道,而且成为我国经济发展新的增长极、新的亮点 准确把握当前劳务经济的内在特征、积极解决制约农村劳动力转移的难点问题,加快农民市民化进程,对于不断增加农民收入,从根本上解决好“三农”问题意义十分重大。

地震作用下结构的AMTMD主动控制策略

提出了一种新的控制策略——主动多重调谐质量阻尼器(AMTMD),AMTMD控制系统频率呈线性分布。AMTMD保持相同的刚度和阻尼但质量变化。AMTMD的主动控制力采用Roorda(1975)提出的生成模式。基于结构的广义振型模型,导出了设置AMTMD时结构的动力放大系数(DMF)。于是AMTMD优化准则选择为结构最大动力放大系数的最小值的最小化。分别使用位移、速度和加速度传感器,通过最优搜寻,研究了反映AMTMD有效性和鲁棒性的参数。这些参数包括:频率间隔、平均阻尼比、调谐频率比、Min.Min.Max.DMF、标准化反馈增益系数和环增益系数。为比较,同时考虑了多重调谐质量阻尼器和主动调谐质量阻尼器。而且,数值结果表明:AMTMD比MTMD具有更高的有效性和鲁棒性且比ATMD也有更高的有效性。

绿色的回亿

从儿时起,我便喜欢两种颜色:雪的洁白,军营的草绿。 由于出身在军人家庭,从记事起,在我眼前飘动的就都是绿军装的影子。看到父亲母亲身穿军装的那种威武劲儿,我真是羡慕极了,就经常用他们的衣服把自己“全副武装”起来,别看那军装肥大得裹住了我的全身,可我还是感到挺神气的。母亲见了,说:“快点长大吧,长大了送你去参军。” 后来,我真的参军了,那时我还是那么小,小得让母亲担心。

浅谈“课堂论坛”在英语教学中的作用

“课堂论坛”是每节课前以学生为主角的一个固定环节，学生在这个平台上大胆参与，展示自己的知识和能力，得到大家的认可和赞赏，从而获得学习的最大动力，体验成功和快乐。

Features of pipe transportation of paste-like backfilling in deep mine

Based on the pipe transportation of paste-like backfilling system of a certain deep coal mine,its dynamics process was simulated and analyzed.A two-dimensional dynamic model of extraordinary deep and lone pipe was built by GAMBIT,on the basis of which the simulation was done by implicit solver of FLUENT 2ddp.The results show that hydraulic loss of pipe transportation is less than the pressure produced by gravity,which means the backfilling material can flow by itself.When the inlet velocity is 3.2 m/s,the maximum velocity of 4.10 m/s is at the elbow and the maximum velocity in the horizontal pipe is 3.91 m/s,which can both meet the stability requirement.The results of the simulation are proved to be reliable by the residual monitor plotting of related parameter,so it can be concluded that the system of pipe transportation is safe.

Adsorption of Chlortetracycline from Water by Rectories

The removal of antibiotics from water by clay minerals has become the focus of research due to their strong adsorptive ability. In this study, adsorption of chlortetracycline (CTC) onto rectories was conducted and the effects of time, concentration, temperature and pH were investigated. Experimental results showed that adsorption equilibrium was reached in 8 h. Based on the Langmuir model, the maximum adsorption capacity of CTC on rectories was 177.7 mg·g 1 at room temperature. By the study on adsorption dynamics, it is found that the kinetic date fit the pseudo-second-order model well. The adsorption of CTC by rectories is endothermic and the free energy is in the range of 10 to 30 kJ·mol 1 . The pH value of solution has significant effects on adsorption and the optimal pH is at acidity (pH 2-6). At concentration of 2500 mg·L 1 , the intercalated CTC produces an interlayer space with a height of 1.38 nm, which is 1.12 nm in raw rectories, suggesting that the adsorption occurs between layers of rectories.

Submaximal oxygen uptake kinetics, functional mobility, and physical activity in older adults with heart failure and reduced ejection fraction

Background Submaximal oxygen uptake measures are more feasible and may better predict clinical cardiac outcomes than maximal tests in older adults with heart failure （HF）. We examined relationships between maximal oxygen uptake, submaximal oxygen kinetics, fianctional mobility, and physical activity in older adults with HF and reduced ejection fraction. Methods Older adults with HF and reduced ejection fraction （n = 25, age 75 ：i： 7 years） were compared to 25 healthy ageand gender-matched controls. Assessments included a maximal treadmill test for peak oxygen uptake （VO2p^ak）, oxygen uptake kinetics at onset of and on recovery from a submaximal treadmill test, functional mobility testing [Get Up and Go （GUG）, Comfortable Gait Speed （CGS）, Unipedal Stance （US）], and self-reported physical activity （PA）. Results Compared to controls, HF had worse performance on GUG, CGS, and US, greater delays in submaximal oxygen uptake kinetics, and lower PA. In controls, VO2peak was more strongly associated with functional mobility and PA than submaximal oxygen uptake kinetics. In HF patients, submaximal oxygen uptake kinetics were similarly associated with GUG and CGS as VO2peak, but weakly associated with PA. Conclusions Based on their mobility performance, older HF patients with reduced ejection fraction are at risk for adverse functional outcomes. In this population, submaximal oxygen uptake measures may be equivalent to VO2 peak in predicting functional mobility, and in addition to being more feasible, may provide better insight into how aerobic function relates to mobility in older adults with HF.

Maximally Generalized Yang-Mills Model and Dynamical Breaking of Gauge Symmetry

A maximally generalized Yang-Mills model, which contains, besides the vector part Vμ, also an axial-vector part Aμ, a scalar part S, a pseudoscalar part P, and a tensor part Tμv, is constructed and the dynamical breaking of gauge symmetry in the model is also discussed. It is shown, in terms of the Nambu Jona-Lasinio mechanism, that the gauge symmetry breaking can be realized dynamically in the maximally generalized Yang-Mills model. The combination of the maximally generalized Yang-Mills model and the NJL mechanism provides a way to overcome the difficulties related to the Higgs field and the Higgs mechanism in the usual spontaneous symmetry breaking theory.

Generation of Entangled Multi-atom Dicke States in Cavity Quantum Electrodynamics

We propose a scheme to generate two-atom maximally entangled state in cavity quantum electrodynamies （QED）. The scheme can 5e extended to generation of entangled multi-atom Dicke states if we control the interaction time of atoms with cavity modes. We use adiabatically state evolution under large atom-cavity detuning, so the scheme is insensitive to atomic spontaneous decay. The influence of cavity decay on fidelity and success probability is discussed.

Analysis and Improvement of Standing-Up Action for Elderly People from a Chair Using a Cushion-Type Support Tool

This paper reports the problems that elderly people have when they stand up from a chair, and proposes an adequate standing-up procedure that solves these problems. The important points for an adequate standing-up procedure are ＂leaning the upper body forward＂ and ＂pulling the legs to the side＂. Furthermore, this paper proposes a standing-up support tool. The characteristics of the support tool are a cushion-type shape with an adjustable flange and an air-pressure-driven mechanism. When the proposed standing-up procedure and support tool are applied to elderly people, the measured values related to standing-up, such as maximum acceleration, arm force, standing-up time, heel position and forward-bending angle, are improved. Furthermore, elderly people felt that it made the standing-up action easy. We could confirm the effectiveness of the proposed standing-up procedure and support tool.

Vibration compaction characteristics of rock filling embankment

The dynamic model experiment of the rock filling embankment was carried out to investigate the vibration compaction mechanism. The rock filling materials were compacted by the plate-vibrated compactor, and the characteristics of the rock filling materials, such as settlement, pressure change and response waveform, were measured by the dynamic earth pressure gauge and aceelerometer. Moreover, a new method for detecting the compactness of the rock filling embankment was proposed based on the maximum dry density and modulus of deformation. The results show that the process of vibration compaction includes compact, elastic deformation and loose stages, and the vibratory pressure transfers to the surroundings from the vibration center in non-linear rule. Furthermore, the test results obtained by the present method are basically in agreement with those obtained by the traditional method, and the maximum relative error between them is about 0.5%.

Diffusion-Controlled Adsorption Kinetics of Triton X-100 at Air/Solution Interface

In this paper, the equilibrium surface tension and the dynamic surface tension of aqueous Triton X-100 solution at temperature 25 ℃ were measured by means of Wilhelmy plate method and maximal bubble pressure method respectively. The determined critical micellar concentration（cmc） of Triton X-100 at 25 ℃ is (2.2×10-4) mol/dm3. The adsorption mechanics of Triton X-100 at air/solution was determined. For the submicellar concentrations it is diffusion-controlled. The diffusion coefficient was calculated from the experimental data in the range of short limit. In the range of long time adsorption, the subsurface concentration is fitted from the measured dynamic surface tensions.

Distribution of acceleration and empirical formula for calculating maximum acceleration of rockfill dams

To find the distribution patterns of dynamic amplification coefficients for dams subjected to earthquake, 3D seismic responses of concrete-faced rockfill dams with different heights and different shapes of river valley were analyzed by using the equivalent-linear model. Statistical analysis was also made to the seismic coefficient, and an empirical formula for calculating the maximum acceleration was provided. The results indicate that under the condition of the same dam height and the same base acceleration excitations, with the increase of the river valley width, the position of the maximum acceleration on the axis of the top of the dam moves from the center to the riversides symmetrically. For the narrow valleys, the maximum acceleration occurs in the middle of the axis at the top of the dam; for wide valleys the maximum acceleration appears near the riversides. The result negates the application of 2D dynamical computation for wide valleys, and shows that for the seismic response of high concrete-faced rockfill dams, the seismic coefficient along the axis should be given, except for that along the dam height. Seismic stability analysis of rockfill dams using pseudo-static method can be modified according to the formula.

Software Package Evaluation for Lyapunov Exponent and Others Features of Signals Evaluating Condition Monitoring Performance of Nonlinear Dynamic Systems

Efficient use of industrial equipment, increase its availability, safety and economic issues spur strong research on maintenance programs based on their operating conditions. Machines normally operate in a linear range, but when malfunctions occur, nonlinear behavior might set in. By studying and comparing five nonlinear features, which listed in decreasing order by their damage detection capability are： LLE （largest Lyapunov exponent）, embedded dimension, Kappa determinism, time delay and cross error values; i.e., LLE performs best. Using somewhat similar ideas from Chaos control, i.e., vary the ＂mass imbalance＂ forcing parameters, we aim to stabilize the Lorenz equation. Quite interestingly, for certain imbalance excitation values, the system is stabilized. The previous even when paradigmatically chaotic parameters for Lorenz system are used （plus our forcing terms）. This quasi-control approach is validated studying signals obtained from the previously mentioned lab test. Finally, it is concluded that analyzing and comparing nonlinear features extracted from baseline vs. malfunction condition （test acquired）, one might increase the efficiency and the performance of machine condition monitoring.

3 m Twin-Segment Solid Rocket Engine Tested Successfully

On August 2,a twin-segment solid rocket motor of the largest diameter,grain mass and thrust in China completed its ground test firing with success.The3 m solid motor was independently developed by the Academy of Aerospace Solid Propulsion Technology（AASPT）under CASC.

Unmanned air vehicle flow separation control using dielectric barrier discharge plasma at high wind speed

The present paper described an experimental investigation of separation control of an Unmanned Aerial Vehicle(UAV)at high wind speeds.The plasma actuator was based on Dielectric Barrier Discharge(DBD)and operated in a steady manner.The flow over a wing of UAV was performed with smoke flow visualization in theΦ0.75 m low speed wind tunnel to reveal the flow structure over the wing so that the locations of plasma actuators could be optimized.A full model of the UAV was experimentally investigated in theΦ3.2 m low speed wind tunnel using a six-component internal strain gauge balance.The effects of the key parameters,including the locations of the plasma actuators,the applied voltage amplitude and the operating frequency,were obtained.The whole test model was made of aluminium and acted as a cathode of the actuator.The results showed that the plasma acting on the surface of UAV could obviously suppress the boundary layer separation and reduce the model vibration at the high wind speeds.It was found that the maximum lift coefficient of the UAV was increased by 2.5%and the lift/drag ratio was increased by about 80%at the wind speed of 100 m/s.The control mechanism of the plasma actuator at the test configuration was also analyzed.

Dynamics of a Function Related to the Primes

Let n = p1p2 ··· pk, where pi(1 ≤ i ≤ k) are primes in the descending order and are not all equal. Let Ωk(n) = P(p1 + p2)P(p2 + p3) ··· P(pk-1+ pk)P(pk+ p1), where P(n) is the largest prime factor of n. Define w0(n) = n and wi(n) = w(wi-1(n)) for all integers i ≥ 1. The smallest integer s for which there exists a positive integer t such thatΩs k(n) = Ωs+t k(n) is called the index of periodicity of n. The authors investigate the index of periodicity of n.

Dynamical cavitation and oscillation of an anisotropic incompressible hyper-elastic sphere

Dynamical cavitation and oscillation of an anisotropic two-family fiber-reinforced incompressible hyper-elastic sphere subjected to a suddenly applied constant boundary dead load are examined within the framework of finite elasto-dynamics.An exact differential equation between the radius of the cavity and the applied load is obtained.The curves for the variation of the maximum radius of the cavity with the load and the phase diagrams are obtained by vibration theories and numerical computation.It is shown that there exists a critical value for the applied load.When the applied load is larger than the critical value,a spherical cavity will suddenly form at the center of the sphere.It is proved that the evolution of the cavity radius with time follows that of nonlinear periodic oscillation,and oscillation of the anisotropic sphere is not the same as that of the isotropic sphere.