如何让数学课堂充满活力——以《有余数的除法》教学为例

何为有活力的课堂?学生思维活跃、活动多、学生有探索意识和自主能力的课堂便可称得上是有活力的课堂。众所周知,数学教学是数学活动的教学,更是数学思维的教学。一位教育家曾说:"教学的艺术不在于传授知识,而在于激励和鼓舞,在于通过学生的提问,训练学生的思维。"如果教师在课堂上能做到这些,那么将是一节成功有效且充满活力的课堂。本文谈谈构建活力课堂的几点做法。

Thermal Decomposition and Kinetics of Mixtures of Polylactic Acid and Biomass during Copyrolysis

Thermal decomposition of polylactic acid （PLA） was studied in the presence of pine wood sawdust （PS）, walnut shell （WS）, corncob （CC） in order to understand the pyrolytic behavior of these components occurring in waste. A thermogravimetric analyzer （TGA） was applied for monitoring the mass loss profiles under heating rate of 10℃·min^-1. Results obtained from this comprehensive investigation indicated that PLA was decomposed in the temperature range 300 -372℃, whereas the thermal degradation temperature of biomass is 183-462℃. The difference of mass loss （AW） between experimental and theoretical ones, calculated as algebraic sums of those from each separated component, is about 17%-46% at 300-400℃. These experimental results indicated a significant synergistic effect during PLA and biomass copyrolysis. Moreover, a kinetic analysis was performed to fit thermogravimetric data, the global processes being considered as one to two consecutive reactions. A reasonable fit to the experimental data was obtained for all materials and their blends.

Pharmacokinetics of radioimmunotherapeutic agent of direct labeling mAb ^(188)Re-HAb18

AIM:To labed Anti-hepatoma monoclonal antibody(mAb) fragment HAb18 F(ab')_2 was labeled with 188 Re for the pharmacokinetic model of ^(188)Re-HAb18 F(ab')_2 and to evaluate its pharmacokinetic parameters in hepatoma- bearing nude mice. METHODS:HAb18 F(ab')_2 was directly labeled with ^(188)Re using 2-mercaptoethanol(2-ME)as reducing agents. Labeling efficiency and immunoreactivity of ^(188)Re-HAb18 F (ab')_2 were evaluated by Whatman 3MM paper chromatography and live cell assay,respectively. Biodistribution analysis was also conducted in nude mice bearing human hepatoma in which animals were sacrificed at different time points(1,4,18,24 and 24h)after ^(188)Re-HAb18 F(ab')_2 was injected through tail-vein into hepatoma-bearing nude mice.The blood and radioactivity of organs and mass were measured.The concentrations of ^(188)Re-HAb18 F(ab')_2 were evaluated with a pharrnacokinetic 3P97 software. RESULTS:The optimum labeling efficiency and immunoreactive fraction were 91.7% and 0.78%, respectively.The parameters of ^(188)Re-HAb18 F(ab')_2 were: T_(1/2),2.29h;Vd,1.49×10^(-9)L·Bq^(-1);AUC,20.49×10~9Bq·h· L^(-1);CL,0.45×10^(-3)L·h^(-1).^(188)Re-HAb18 F(ab')_2 could locate specially in hepatoma with high selective reactivity of HAb18 F(ab')_2.^(188)Re-HAbl8 F(ab')_2 was mainly eliminated by kidney.The maximal tumor to blood ratio was at 48h,and maximal tumor to liver ratio was at 18h. CONCLUTION:The pharmacokinetics of ^(188)Re-HAb18 F(ab')_2 fit a I-compartment model.^(188)Re-HAb18 F(ab')_2 can be uptaken selectively at the hepatoma site.

Prospect on Present-Day Crustal Kinematics and Dynamics Research in Sichuan-Yunnan Area with Geodetic Data

Combining the dense GPS and gravity observation data in Sichuan-Yunnan area, where there are the relatively complete active tectonic zones and seismic data, this paper applies the geodesy and geophysical inversion technique and the advanced numerical simulation to the synthesis study of geodesy inversion to find the dynamic process of tectonic movement and deformation in the area and finally to investigate the kinematics characteristic of the geological structure of different layer and different scale. This paper discusses the kinematics, dynamics model about the crustal movement of active blocks in Sichuan-Yunnan area and its adjacent areas.

Numerical Research on Wave-making Resistance of Trimaran

A 3D rankine panel method was developed for calculating the linear wave-making resistance of a tri-maran with Wigley hulls. In order to calculate the normal vector and derivative of the body surface accurately, non-uniform rational B-spline (NURBS) was adopted to represent body surface and rankine source density. The radiation condition is satisfied using the numerical technology of staggered grids. Numerical results show that the linear wave-making resistance of the trimaran can be calculated effectively using this method.

Kinetics of Ortho-nitrochlorobenzene Hydrogenation on Platinum/Carbon Catalyst

The kinetics of catalytic hydrogenation of ortho-nitrochlorobenzene to 2,2′-dichloroazoxybenzene on platinum/carbon catalyst is investigated in a slurry reactor with the temperature range of 313-343 K, and orthochloroaniline is formed as a byproduct. Models based on Rideal-Eley and Langmuir-Hinshelwood mechanism have been proposed based on the rate data and the kinetic regime. The former model can be used to fit the experimental data better. Reaction controlling steps are physical adsorption of hydrogen and adsorbed ortho-nitrochlorobenzene reacted on the surface of catalyst.

Kinetic Study of Hydrothermal Stripping from Iron-Loaded Organic Phase

The iron-loaded organic phase of naphthenic acid-isooctyl alcohol-kerosene was prepared, and the process kinetics of hydrothermal stripping of iron from the phase was studied. Several factors affecting hydrothermal stripping, such as the polymer of naphthenic acid, initial concentrations of iron and naphthenic acid, temperature and agitation time, were investigated, and based on experimental results and theoretical analysis, two kinetic models were established.The stripping rate equation suggests that the hydrothermal stripping process activation energy is 96.4 kJ·mol-1 and the stripping is controlled by hydrolysis of naphthenic complex of iron. The values calculated by the stripping fraction equation comparatively accord with the experimental data.

Dynamics and Control of Grinding Machine with Micropositioning Workpiece Table

To improve the machining precision of a surface grinding machine, a micropositioning workpiece table with high performance was used as auxiliary infeed mechanism to implement nanometer level positioning and dynamic compensation. To better understand the characteristics of the grinding machine modulated with micropositioning workpiece table, the dynamic model of the grinding system was established with modal synthesis and Lagrange＇s equation methods. The grinding system was divided into five subsystems. For each subsystem, the generalized kinematic and potential energies were obtained. Accordingly the dynamic model of the grinding system was given in the modal domain. The waviness of the grinding process was achieved based on the wheel and workpiece vibration. A nonlinear proportional integral derivative （PID） controller with differential trackers was developed to realize dynamic control. The simulation results show that the machining accuracy of the workpiece can be effectively improved by utilizing the micropositioning workpiece table to implement dynamic compensation. An experimental test was carried out to verify the proposed method, and the waviness of the workpiece can be reduced from 0.46 μm to 0.10 μm.

Dynamics of Meandering Spiral Waves Driven by Two-Point Feedback

We numerically study the dynamics of meandering spiral waves in the excitable system subjected to a feedback signal coming from two measuring points located on a straight line together with the initial spiral core. The core location and size radius of the final attractors are computed, and they change with the position of the moving measuring point in a unique way. By the Fourier Spectral analysis, we find the frequency-locked behaviors different from the driving scheme of the external periodic force. It when the moving measuring point approaches closely is also found that the meandering spiral wave can be eliminated the boundary and its feedback gain is large enough. This offers an effective and convenient method for eliminating meandering spiral waves.

Dynamic simulation and experimental study of inspection robot for high-voltage transmission-line

A mobile robot developed by Wuhan University for full-path hotline inspection on 220 kV transmission lines was presented. With 4 rotating joints and 2 translational ones, such robot is capable of traveling along non- obstaclestraight-line segment and surmounting straight-line segment obstacles as well as transferring between two spans automatically. Lagrange’s equations were utilized to derive dynamic equations of all the links, including items of inertia, coupling inertia, Coriolis acceleration, centripetal acceleration and gravity. And a dynamic response experiment on elemental motions of robot prototype’s travelling along non-obstacle straight-line segment and surmounting obstacles was performed on 220 kV 1∶1 simulative overhanging transmission-line in laboratory. In addition, dynamic numerical simulation was conducted in the corresponding condition. Comparison and analysis on results of experiment and numerical simulation have validated theoretical model and simulation resolution. Therefore, the dynamic model formed hereunder can be used for the study of robot control.

Orientation and Motion of Water Molecules at Air/Water Interface

Here we report a quantitative study of the orientational structure and motion of water molecule at the air/water interface. Analysis of Sum Frequency Generation （SFG） vibrational peak of the free O-H stretching band at 3700 cm^-1 in four experimental configurations showed that orientational motion of water molecule at air/water interface is libratory within a limited angular range. The free OH bond of the interracial water molecule is tilted around 33°from the interface normal and the orientational distribution or motion width is less than 15°. This picture is significantly different from the previous conclusion that the interracial water molecule orientation varies over a broad range within the ultrafast vibrational relaxation time, the only direct experimental study concluded for ultrafast and broad orient, ational motion of a liquid interface by Wei et al. （Phys. Rev. Lett. 86, 4799, （2001）） using single SFG experimental configuration.

Visualization of Bubble Dynamics for Pool Boiling of Binary Refrigerant Mixture R11-R113

A digital photographic study of pool boiling with binary mixture Rll（CC13）-Rll3（CCl3CF3） was performed on a horizontal transparent heater at pressure of 0.1MPa. A high speed digital camera was applied to record the bubble behaviors in boiling process. Strong effects of composition on bubble departure diameter, deparatre time, nucleation density were observed, which was attributed to the nature of the activation of the boiling surface and mass diffusion effects. The bubble departure diameter, departure period and nucleation density as functions of composition for binary mixtures R 11-R 113 were presented respectively. From the video images, it can be concluded that evaporation of microlayer is very important to the growth of bubble. It is also observed that there is not any liquid recruited into the microlayer below the bubble.

Determination of Clarithromycin in Human Plasma by Liquid Chromatography-Tandem Mass Spectrometry： Validation and Application in Clinical Pharmacokinetic Study

Aim To develop a liquid chromatographic-tandem mass spectrometric (LC-MS-MS)method to determine clarithromycin in human plasma. Methods The analyte and internal standardroxithromycin were extracted from plasma samples by n-nexane-dichloromethane-isopropanol(300:150:15, V/V/V) and chromalographed on a C_(18) column. The mobile phase consisted ofmethanol-water-formic acid (80 = 20:1, V/V/V) . Detection was performed on a triple quadrupoletandem mass spectrometer via electrospray ionization source (ESI) in the positive mode. Results Themethod had a lower limit of quantification of 10.0 ng·mL^(-1) when 0.2 mL plasma was used. Thelinear calibration curves were obtained in the concentration range of 10.0 - 5000 ng·mL^(-1) . Theintra- and inter-run precisions were lower than 3.3% in terms of relative standard deviation (RSD),and the accuracy ranged +- 0.7% in terms of relative error (RE). T_(max), C_(max), T_(1/2) andAUC_(0-24h), values were found to be (3.1 +- 2.7)h, (8 750+-4734) ng·mL^(-1), (5.3+-2.2) h, and(5932+-2449)ng·mL^(-1), respectively, after a single oral dose of 250 mg clarithromycin tablet to18 volunteers. Conclusion This validated method was successful in the evaluation of phaimacokineticprofiles of clarithromycin tablets administered to 18 healthy male volunteers.

The Kinetic Study on the Anionic Polymerization of Isoprene

The kinetic study of the anionic polymerization of isoprene is carried out in tetrahy-drofuran(THF), using n-BuLi as initiator. Kinetic parameters are obtained, which comprise chain propagation rate constant, kp, and partial rate constants, k3 and k4 + k5, propagation orders with respect to monomer and active species concentrations, α and β, real activation energy, E, as well as partial activation energies, E3 and E4+5 and so on. The relationship between the microstruc-ture of polyisoprene and the ratio of [THF]/[n-BuLi] has been investigated. On the basis of the studies mentioned above, a reasonable mechanism of the anionic polymerization of isoprene in THF is proposed.

Study on Kinetics of Dissolving Biomass Using Sodium Hypochlorite in the Recovery of Poly-β-hydroxybutyrate

The effects of sodium hypochlorite concentration in the recovery of poly-β-hydroxybutyrate (PHB) are investigated. A simple reaction equation and a mathematical model describe the reaction kinetics. Results showed that the stoichiometric coefficient increases with increasing CAO/CBO, where CAO is the concentration of the active chlorine at t = 0 and CBO is the initial concentration of the non-PHB materials.

Numerical Study on Flow-induced Noise for a Steam Stop-valve Using Large Eddy Simulation

The noise induced by the fluctuant saturated steam flow under 250 °C in a stop-valve was numerically studied.The simulation was carried out using computational fluid dynamics（CFD） and ACTRAN.The acoustic field was investigated with Lighthill＇s acoustic analogy based on the properties of the flow field obtained using a large-eddy simulation that employs the LES-WALE dynamic model as the sub-grid-scale model.Firstly,the validation of mesh was well conducted,illustrating that two million elements were sufficient in this situation.Secondly,the treatment of the steam was deliberated,and conclusions indicate that when predicting the flow-induced noise of the stop-valve,the steam can be treated as incompressible gas at a low inlet velocity.Thirdly,the flow-induced noises under different inlet velocities were compared.The findings reveal it has remarkable influence on the flow-induced noises.Lastly,whether or not the heat preservation of the wall has influence on the noise was taken into account.The results show that heat preservation of the wall had little influence.

Dynamics of Communal Land Degradation and Its Implications in the Arid Mountains of Pakistan:A Study of District Karak, Khyber Pakhtunkuwa

Similar to other areas of Pakistan, land resources in Khyber Pakhtunkhwa(KP) is kept under various ownership regimes for socio-economic and ecological benefits. For the last three to four decades, communal lands and resources are subjected to high rate of degradation and deterioration, which is leading to multifarious socio-economical and ecological implications. This paper intends to look into factors that are responsible for the degradation of communal land and the adaptability of the management mechanisms developed by the local inhabitants to conserve these resources. Moreover, this study also explores the sustainability of these adopted strategies in present circumstances. Data regarding socio-economic parameters of the inhabitants and their interactions with communal lands were collected through questionnaire cum interview method. As long-term climatic data for the area do not exist therefore focus group discussions were conducted to document the changing trend in rainfall regimes and temperature variations for the last about four decades. Results indicate that communal lands are highly vulnerable to degradation due to biophysical and anthropogenic factors. Local inhabitants have developed suitable measures to control the situation, however, accelerated socioeconomic transformations in the area have weakened the role of local institutions and that led to further degradation of these resources. Nevertheless, a number of locally formulated rules have been revived and implemented and it is hoped that these threatened resources would be conserved.

Predicting climate anomalies:A real challenge

In recent decades,the damage and economic losses caused by climate change and extreme climate events have been increasing rapidly.Although scientists all over the world have made great efforts to understand and predict climatic variations,there are still several major problems for improving climate prediction.In 2020,the Center for Climate System Prediction Research(CCSP) was established with support from the National Natural Science Foundation of China.CCSP aims to tackle three scientific problems related to climate prediction—namely,El Ni?o-Southern Oscillation(ENSO) prediction,extended-range weather forecasting,and interannual-to-decadal climate prediction—and hence provide a solid scientific basis for more reliable climate predictions and disaster prevention.In this paper,the major objectives and scientific challenges of CCSP are reported,along with related achievements of its research groups in monsoon dynamics,land-atmosphere interaction and model development,ENSO variability,intraseasonal oscillation,and climate prediction.CCSP will endeavor to tackle key scientific problems in these areas.

Dynamic Interaction of Parallel Moving Ships in Close Proximity

Nowadays,there are many studies conducted in the field of marine hydrodynamics which focus on two vessels traveling and floating in sufficiently close proximity to experience significant interactions.The hydrodynamic behavior of parallel moving ships in waves is an interesting and important topic of late.A numerical investigation has been carried out for the prediction of wave exciting forces and motion responses of parallel moving ships in regular waves.The numerical solution was based on 3D distribution technique and using the linear wave theory to determine the exciting forces and ship＇s motion.The speed effects have been considered in the Green function for more realistic results.The numerical computations of wave exciting forces and motion responses were carried out for a Mariner and Series 60 for the purpose of discovering different Froude numbers and different separation distances in head sea conditions.Based on the numerical computations,it was revealed that the sway,roll and yaw have a significant effect due to hydrodynamic interaction.

EFFECT OF ACU-MOXIBUSTION ON BLOOD RHEOLOGY IN PATIENTS WITH AORTO-ARTERITIS

In the present paper, the authors compared the therapeutic effects of acu moxibustion and medication in the treatment of 80 cases of aorto arteritis and observed their effects on blood rheology of the limbs. Results showed that in acu moxibustion group (n=40) and medication group (n=40), the cure rates were 15% and 0, the markedly effective rates 62.5% and 12.5%, and the total effective rates 95% and 75% respectively. The therapeutic effect of acu moxibustion group was significantly superior to that of medication group (P<0.01). Following acu moxibustion treatment, the blood pressure and blood flow velocity of the brachial artery, the amplitude of the air volume wave of the wrist and the amplitude of the digital volume pulse wave increased remarkably compared with pre treatment (P<0.01), and after treatment with medication, only the blood velocity of brachial artery increased evidently in comparison with pre treatment (P<0.05). Comparison between two groups showed that values of the 4 indexes of acu moxibustion group were all significantly higher than those of medication group (P<0.01), displaying that the therapeutic effect of acu moxibustion is superior to that of medication. It provides experimental evidence for clinical effective treatment of aorto arteritis (branchiocephalic artery type) with acupuncture and moxibustion.