Attitude Stabilization Using Modified Rodrigues Parameters without Angular Velocity Measurements

The optimal stabilization of a rigid body motion without angular velocity measurements is considered with the help of three internal rotors that effected by internal frictions. In this paper, the orientation of the body will be described in terms of the Modified Rodrigues parameters (MRPs). The optimal control law which stabilizes asymptotically this motion and minimizes the require like-energy cost is obtained in terms of the MRPs. Numerical study and simulation are introduced.

Clinical Efficacy of Modified Erchen Decoction on Cervical Spondylotic Vertebral Arteriopathy with Stagnation and Blockade of Phlegm-dampness Syndrome and Effects on Cerebral Blood Flow Parameters

OBJECTIVE: To observe the effect of Modified Erchen Decoction on cervical spondylotic vertebral arteriopathy with stagnation and blockade of phlegm-dampness syndrome and effects on cerebral blood flow parameters. METHODS: A total of 80 cervical spondylotic vertebral arteriopathy(CSA) patients with stagnation and blockade of phlegmdampness syndrome admitted to our hospital from October 2016 to April 2017 were selected and randomly divided into observation group and control group, with 40 cases in each group. The observation group was treated with Modified Erchen Decoction and the control group was given conventional treatment with Western medicine. After 4 weeks of treatment, the main clinical symptoms and signs(vertigo, neck and shoulder pain, headache, psychological and social adjustment, daily life and work) and cerebral blood flow parameters [the peak values of intracranial vertebral-basal artery diastolic blood flow velocity(Vd) and systolic blood flow velocity(Vp)] were compared between the 2 groups. The total clinical effective rate and adverse reactions during treatment were also compared. RESULTS: After treatment, the total effective rate of the observation group was 90.0%, which was significantly higher than that of the control group(77.5%). The difference between the two groups was statistically significant(P < 0.05). After treatment, The scores of vertigo, neck and shoulder pain, headache, psychology and society adaptation, daily life and work were significantly increased(P < 0.05), and the above scores of the observation group were increased more obviously. The difference between the groups was statistically significant(P < 0.05). After treatment, the levels of Vd and Vp were significantly increased(P < 0.05), and the increase of the above indexes was more obvious in the observation group. The difference between the 2 groups was statistically significant(P < 0.05). There were no significant abnormalities in blood routine, urine routine, liver function and renal function. There was no significant difference in the incidence of adverse reactions between the 2 groups.(P > 0.05). CONCLUSION: The treatment of vertebral artery type cervical spondylopathy with stagnation and blockade of phlegm-dampness syndrome by Modified Erchen Decoction can effectively relieve the main clinical symptoms and signs, improve cerebral blood flow parameters, and improve the peak values of vertebral-basal artery diastolic blood flow velocity(Vd) and systolic blood flow velocity(Vp), which is safe and effective, and helps to promote the recovery of cervical function.

Modified Projective Synchronization of a New Hyperchaotic System with Known or Unknown Parameters

This work presents two different methods-nonlinear control method and adaptive control approach to achieve the modified projective synchronization of a new hyperchaotic system with known or unknown parameters.Based on Lyapunov stability theory,nonlinear control method is adopted when the parameters of driving and response systems are known beforehand;when the parameters are fully unknown,adaptive controllers and parameters update laws are proposed to synchronize two different hyperchaotic system and identify the unknown parameters.Moreover,the rate of synchronization can be regulated by adjusting the control gains designed in the controllers.The corresponding simulations are exploited to demonstrate the effectiveness of the proposed two methods.

MODIFIABLE QUARTIC AND QUINTIC CURVES WITH SHAPE-PARAMETERS

This paper presents a method for creating modificable quartic and quintic curves with shape parameters. The curves can achieve C 2 even C 3 continuity and unify both interpolation and approximation to the control points without solving a system of equations or inserting additional control points. They have the local properties like the cubic B spline. Besides, the quintic curve would be able globally to tend the control polygon.

Numerical Study on Hydraulic Characteristics and Discharge Capacity of Modified Piano Key Weir with Various Inlet/Outlet Width Ratio

A modified piano key weir with a rounded nose and a parapet wall (MPKW) can improve the discharge capacity significantly compared to a standard piano key weir. However, the optimum of the inlet/outlet width ratio (Wi/Wo) on the discharge efficiency of MPKW is still not investigated numerically. The present work utilized the numerical modeling to investigate and analyze the effects of the inlet/outlet key width ratios on the hydraulic characteristics and discharge capacity of the MPKW. To validate the numerical model with the experimental data, the results indicate that the average relative error is 2.96%, which confirms that the numerical model is fairly well to predictthe specifications of flow over on the MPKW. Numerical simulation results indicated that the discharge capacity of the MPKW can be improved up to 8.5% by optimizing the Wi/Wo ratio ranging from 1.53 to 1.67 even if the other parameters of the MPKW keep unchanged. A big Wi/Wo ratio generally leads to an increase in discharge capacity at low heads and a little effect on the discharge efficiency at high heads. The discharge efficiency of the inlet and outlet crests increases up to 9.6% for high heads, while discharge efficiency of the lateral crest decreases up to 23.5% compared with the reference model. The findings of the study revealed that the intrinsic influencing mechanism of the Wi/Wo ratio on the discharge performance of MPKWs.

Modified OMP method for multi-target parameter estimation in frequency-agile distributed MIMO radar

Introducing frequency agility into a distributed multipleinput multiple-output(MIMO)radar can significantly enhance its anti-jamming ability.However,it would cause the sidelobe pedestal problem in multi-target parameter estimation.Sparse recovery is an effective way to address this problem,but it cannot be directly utilized for multi-target parameter estimation in frequency-agile distributed MIMO radars due to spatial diversity.In this paper,we propose an algorithm for multi-target parameter estimation according to the signal model of frequency-agile distributed MIMO radars,by modifying the orthogonal matching pursuit(OMP)algorithm.The effectiveness of the proposed method is then verified by simulation results.

MULTI-PARAMETER ACCELERATED MODIFIED NEWTON-RAPHSON METHODS FOR RIGIDPLASTIC FE ANALYSIS

Applications of certain multi-parameter acceleration techniques used with themodified New-ton-Raphson (mN-R) methods to solve the nonlinear equations arising from rigid-plasticfinite element analysis are investigated. New modified multi-parameter techniques, developed fromCrisfield's multi-parameter methods, are utilized to solve these nonlinear equations. The numericalperformance of these techniques is compared with the standard Newton-Raphson method (sN-R),Crisfield's single parameter method (C1), Crisfield's two parameter method (C2) and Crisfield'sthree parameter method (C3). The new techniques do not involve additional residual force calculationand require little extra computational effort. In addition, they are more robust and efficient thanother existing acceleration techniques.

Electromagnetism and Absorptivity of the Modified Micro-coiled Chiral Carbon Fibers

Micro-coiled chiral carbon fibers are modified by nano-Ni. X-ray diffraction （XRD） and scanning electron microscopy （SEM） are used to compare the composition and morphology of the unmodified and the modified fibers. The results show that electromagnetism parameters of the modified are different from those of the unmodified. After modification by nano-Ni, the micro-coiled chiral carbon fibers have decreased permittivity and electrical loss. The permeability and magnetic loss of the modified carbon fibers become larger than those of the unmodified ones. Moreover, the modification of unmodified chiral carbon fibers into the modified is much like changing hollow electric windings into those with magnetic cores inside. The modifier intensifies the cross polarization of the chiral carbon fibers and makes the permittivity and the permeability get closer to each other which improves the matching performance and enhances absorbability of coatings. In the range of 6-18 GHz, the reflectivity of the coating is 6-8dB and the bandwidth is 12 GHz. The area density of the coating is below 3 kg/m^2.

Three-stage Method for Identifying the Dynamic Model Parameters of Stranded Wire Helical Springs

The dynamic behavior of the stranded wire helical spring is described by a modified Bouc-Wen model while the model parameters must be identified using an identification method and experimental data. Existing identification methods usually relies either solely nonlinear iterative algorithms or manually trial and error. Therefore, the identification process can be rather time consuming and effort taking. As a result, these methods are not ideal for engineering applications. To come up with a more practical method, a three-stage identification method is proposed. Periodic loading and identification simulations are carried out to verify the effectiveness of the proposed method. Noises are added to the simulated data to test the performance of the proposed method when dealing with noise contaminated data. The simulation results indicate that the proposed method is able to give satisfying results when the noise levels are set to be 0.01, 0.03, 0.05 and 0.07. In addition, the proposed method is also applied to experimental data and compared with an existing method. The experimental data is acquired through a periodic loading test. The experiment results suggest that the proposed method features better accuracy compared with the existing method. An effective approach is proposed for identifying the model parameters of the stranded wire helical spring.

Statistical Analysis of Thunderstorms on the Eastern Tibetan Plateau Based on Modified Thunderstorm Indices

The Tibetan Plateau, with an average altitude above 4000 m, is the highest and largest plateau in the world. The frequency of thunderstorms in this region is extremely high. Many indices are used in operational forecasting to assess the stability of the atmosphere and predict the probability of severe thunderstorm development. One of the disadvantages of many of these indices is that they are mainly based on observations from plains. However, considering the Plateau＇s high elevation, most convective parameters cannot be applied directly, or their application is ineffective. The pre-convective environment on thunderstorm days in this region is investigated based on sounding data obtained throughout a five-year period（2006–10）.Thunderstorms occur over the Tibetan Plateau under conditions that differ strikingly from those in plains. On this basis,stability indices, such as the Showalter index（including SI and SICCL）, and the K index are improved to better assess the thunderstorm environments on the Plateau. Verification parameters, such as the true-skill statistic（TSS） and Heidke skill score（HSS）, are adopted to evaluate the optimal thresholds and relative forecast skill for each modified index. Lastly, the modified indices are verified with a two-year independent dataset（2011–12）, showing satisfactory results for the modified indices. For determining whether or not a thunderstorm day is likely to occur, we recommend the modified SICCLindex.

Reverse Engineering of Machine-tool Settings with Modified Roll for Spiral Bevel Pinions

Although a great deal of research has been dedicated to the synthesis of spiral bevel gears, little related to reverse engineering can be found. An approach is proposed to reverse the machine-tool settings of the pinion of a spiral bevel gear drive on the basis of the blank and tooth surface data obtained by a coordinate measuring machine(CMM). Real tooth contact analysis(RTCA) is performed to preliminary ascertain the contact pattern, the motion curve, as well as the position of the mean contact point. And then the tangent to the contact path and the motion curve are interpolated in the sense of the least square method to extract the initial values of the bias angle and the higher order coefficients(HOC) in modified roll motion. A trial tooth surface is generated by machine-tool settings derived from the local synthesis relating to the initial meshing performances and modified roll motion. An optimization objective is formed which equals the tooth surface deviation between the real tooth surface and the trial tooth surface. The design variables are the parameters describing the meshing performances at the mean contact point in addition to the HOC. When the objective is optimized within an arbitrarily given convergence tolerance, the machine-tool settings together with the HOC are obtained. The proposed approach is verified by a spiral bevel pinion used in the accessory gear box of an aviation engine. The trial tooth surfaces approach to the real tooth surface on the whole in the example. The results show that the convergent tooth surface deviation for the concave side on the average is less than 0.5 μm, and is less than 1.3 μm for the convex side. The biggest tooth surface deviation is 6.7 μm which is located at the corner of the grid on the convex side. Those nodes with relative bigger tooth surface deviations are all located at the boundary of the grid. An approach is proposed to figure out the machine-tool settings of a spiral bevel pinion by way of reverse engineering without having known the theoretical tooth surfaces and the corresponding machine-tool settings.

Size dependent free vibration analysis of functionally graded piezoelectric micro/nano shell based on modified couple stress theory with considering thickness stretching effect

Higher-order shear and normal deformation theory is used in this paper to account thickness stretching effect for free vibration analysis of the cylindrical micro/nano shell subjected to an applied voltage and uniform temperature rising.Size dependency is included in governing equations based on the modified couple stress theory.Hamilton’s principle is used to derive governing equations of the cylindrical micro/nano shell.Solution procedure is developed using Navier technique for simply-supported boundary conditions.The numerical results are presented to investigate the effect of significant parameters such as some dimensionless geometric parameters,material properties,applied voltages and temperature rising on the free vibration responses.

Creep Characteristics of Crumb Rubber Modified Asphalt Binder

Crumb rubber modified asphalt containing 20 percent crumb rubber particles of 30 mesh has been examined by Scanning Electron Microscope （SEM） to observe the microcosmic appearance and the characteristic distribution of crumb rubber particles in asphalt. The SEM pictures reveal that the crumb rubber particles distribute evenly in the asphalt and they are compatible well with asphalt. The shear creep test of crumb rubber modified asphalt was carried out at -10 ℃ and 40 ℃ by Dynamic Shear Rheology （DSR）. The shearing deformation at different temperature and creep stiffness modulus curve at loading stage of crumb rubber modified asphalt have been measured. The stiffness modulus of crumb rubber modified asphalt is much temperature sensitive and it decays much quick at the early stage of loading than normal asphalt. The rate of decay of stiffness modulus is slow at the subsequent stage and stiffness modulus approaches to a stable value at the final stage at a higher temperature. In addition, Burgers model is suitable to describe and simulate experimental results of viscoelastic properties of the crumb rubber modified asphalt.

PREDICTION OF SURFACE ROUGHNESS FOR END MILLING TITANIUM ALLOY USING MODIFIED PARTICLE SWARM OPTIMIZATION LS-SVM

It is difficult to construct the prediction model for titanium alloy through analyzing the formation mechanism of surface roughness due to the complicated relation between influential factors and surface roughness.A novel algorithm based on the modified particle swarm optimization ( PSO ) least square support vector machine ( LSSVM ) is proposed to predict the roughness of the end milling titanium alloys.According to Taguchi method and features in milling titanium alloys , the influences of cutting speed , feed rate and axial depth of cut on surface roughness are investigated with the analysis of variance ( ANOVA ) of the experimental data.The research results show that the construction speed of the modified PSO LS-SVM model is two orders of magnitude faster than that of back propagation ( BP ) model.Moreover , the prediction accuracy is about one order of magnitude higher than that of BP model.The modified PSO LS-SVM prediction model can explain the influences of cutting speed , feed rate and axial depth of cut on the surface roughness of titanium alloys.Either a higher cutting speed , a lower feed rate or a smaller axial depth of cut can lead to the decrease of surface roughness.

Removal of astrazon golden yellow 7GL from colored wastewater using chemically modified clay

Chemically modified clay(CMC) was used as an adsorbent for the removal of Astrazon Golden Yellow 7GL(AGY-7GL), which is a basic dye from wastewater. For this purpose, the chemically modified clay was first characterized by determining zero point of charge(p Hzpc), and using BET, SEM and FTIR. Then effects of operational parameters on adsorption of AGY-7GL were studied in a batch system. The effect of various parameters such as contact time(0-180 min), pH(2-8), temperature(293-323 K), CMC concentration(0.075-0.5 mg/L) and initial AGY-7GL concentration(75-250 mg/L) were investigated on the adsorption efficiency and capacity adsorption of CMC for the removal of AGY-7GL. Thermodynamic and kinetic parameters were calculated from the results of the adsorption experiment. The evaluation of kinetic models shows that this data best fits the pseudo-second-order model. It is determined that the adsorption equilibrium data works very well with the nonlinear Freundlich isotherm model. Thermodynamic parameters such as ?H^0(19.0 k J/mol), ?G^0(-28.8 k J/mol) and ?S^0(0.148 k J/mol) were also determined. According to the experimental results, it is concluded that CMC could be used as an alternative low cost potential adsorbent for the removal of AGY-7GL from wastewater.

生物质挤压成型数值模拟及模孔参数优化

为研究生物质挤压成型过程中物料的变化规律,针对生物质材料在压实过程中逐渐变化的特性,以弹塑性理论为基础,通过一种修正的Drucker-Prager Cap材料本构模型,借助有限元分析软件ABAQUS及其二次开发子程序VUSDFLD模拟物料单向压制过程,并验证该模型的准确性。对环模单模孔的制粒过程进行模拟研究,设计正交试验获得模孔参数对成型密度以及比能耗的影响规律,进而对模孔参数进行优化分析。结果表明:修正的Drucker-Prager Cap本构模型能够准确的模拟生物质材料的挤压成型过程;增大锥孔深度以及锥孔锥度均可提高物料的成型密度和比能耗,以成型密度和比能耗为评价指标,最优参数组合为锥孔深度7mm,锥度60°。

表面修饰石墨烯制备工艺及其在金属材料中的应用研究

为解决石墨烯在金属基复合材料应用中易团聚、难分散、与金属基体之间的润湿性差、高温下易与Al、Ti、Fe等金属发生界面反应的问题,对石墨烯进行表面修饰制得镀铜石墨烯,研究了镀覆过程中镀覆温度、镀覆时间、镀液pH对镀铜石墨烯镀层连续性、完整性的影响,优化镀覆工艺参数,获得了质量优良的表面修饰石墨烯;并将其分别添加到铁基摩擦材料和W-Mo-Cu复合材料中,对其作用效果进行了研究。结果表明:石墨烯在50℃、pH为12.5的化学镀液中镀覆30 min可以获得连续性、完整性较好的镀层,从而制得缺陷密度较小、质量较好的表面修饰石墨烯;在铁基摩擦材料中添加0.8%(质量分数)表面修饰石墨烯可以使材料晶粒细化并获得片层间距较小的珠光体组织,材料硬度提高30%,磨损率降低约70%,摩擦系数下降约12%;添加了0.2%(质量分数)表面修饰石墨烯的W-Mo-Cu材料,其组织均匀性和致密度均获得了提高,电导率提升约21%,硬度提高8%。证实了表面修饰石墨烯的添加能够促进金属基复合材料综合性能的提高。

磷石膏改性沥青高低温性能研究

为评价固废磷石膏作为沥青改性剂的可能性,对磷石膏改性沥青的高低温性能进行评价。分别将不同掺量的磷石膏加入到70#基质沥青中,以制备磷石膏改性沥青。通过动态剪切流变仪的温度扫描、频率扫描、多重应力蠕变模式测试磷石膏改性沥青高温流变特性,并基于Sigmoidal方程建立流变主曲线,通过弯曲梁流变仪评价磷石膏改性沥青低温抗裂性。研究结果表明,随着磷石膏的加入,磷石膏改性沥青的复数剪切模量(G^(*))提高并高于70#基质沥青,相位角(δ)差距不大,Shenoy车辙参数[G^(*)/(1-1/sinδtanδ)]明显提高;磷石膏的掺入能提高沥青在0.1,3.2 kPa的蠕变恢复率,并且降低在0.1,3.2 kPa的不可恢复柔量。添加磷石膏会增强基质沥青的高温性能,同时会略微降低沥青的低温抗裂性能,但是不会影响PG低温分级中的设计温度。

基于改进Weibull模型的高强缝合锚钉缝线强度预测

为消除缝合锚钉缝线在使用过程中存在断裂的风险,以8.3 tex超高分子量聚乙烯纤维为原材料,采用编织工艺制备了单层编织缝线和轴向衬纱双层编织缝线。为了研究其力学性能,选择8、16、24、32、40、48 mm隔距对单纤维的断裂强力进行测试,选择50、200 mm隔距对8.3 tex复丝的断裂强力进行测试,选择200 mm隔距对单层编织缝线和轴向衬纱双层编织缝线的断裂强力进行测试。对纤维的直径和缝线中纤维与轴向夹角的角度进行测量。采用两参数Weibull模型和改进Weibull模型对单纤维、8.3 tex复丝和单层编织缝线的断裂强度进行预测。结果表明:单层编织缝线的断裂强力为299.8 N,轴向衬纱双层编织缝线的断裂强力高达393.0 N。对8.3 tex复丝和单层编织缝线的断裂强度进行预测,改进Weibull模型的预测值准确度高。高强骨锚钉缝线的强力比同类型医用缝线更高,改进Weibull模型可对高强缝合锚钉缝线的强力进行精准预测,实现了从单纤维到复丝再到纱线的断裂强度预测,可为医用缝线结构设计和力学性能分析提供理论依据。