Search

The microstructures and shape memory behaviors of Ti-18Nb-6Zr (at.%) alloy subjected to different heat treatments were investigated through optical microscopy (OM), X-ray diffraction (XRD), Transmission electron microscopy (TEM) and tensile tests. Recrystallization occurs in cold-rolled Ti-18Nb-6Zr alloy after solution treatment at 600~800 °C. The cooling rate after solution treatment at 800°C shows a dramatic effect on the microstructure of the alloy. The microstructures for the water quenching (WQ) and oil quenching (OQ) specimens are composed of single α'' martensite phase, while for the air cooling (AC) specimen, the microstructure consists of predominant β phase and a small amount of fine athermal ω phase. During tensile deformation, two-stage yielding is observed in the alloy subjected to 800°C/0.5h/WQ heat treatment. The stress for martensite variants reorientation and the yield stress for plastic deformation are 310MPa and 455MPa, respectievely, and the maximum shape memory strain of 3.1% is obtained with pre-strain of 6%.

The Ti-6.5Al-2Sn-4Zr-1.5Mo-2Nb-0.25Fe-0.2Si (wt%) alloy is a novel two-phase high temperature alloy for short-term application. The effects of different heat treatments on the microstructure and mechanical properties were investigated through electron probe microanalysis (EPMA), optical microcopy (OM), scanning electron microscope (SEM), electron backscattered diffraction (EBSD) and tensile tests at room temperature and 650°C. Subjected to the annealing treatment at α+β region (1010 °C/2 h, FC to 990 °C+990 °C/2 h, AC), the microstructure was composed of bimodal structure, which consists of equiaxed primary α (αp) phase and lamellar transformed β (βt) structure. As a strong β stabilizer, the content of Fe in α phase is much less than that in β phase. Annealing at β region (1040 °C/2 h, AC) resulted in the formation of widmannstatten structure, consisting of coarse raw β grain and secondary α phase precipitated on the β grain. With respect to the tensile property, different heat-treated alloys obtained similar strength. However, widmannstatten structure was characterized by lower plasticity, with the elongation only half that of bimodal structure. The fracture characteristics at room temperature for the alloy with bimodal structure and widmannstatten structure are dominated by ductile fracture and cleavage fracture, respectively.

This paper aimed to study the dynamic compression properties of Ti-6Al-4V titanium alloy sections. The Ti-6Al-4V sections were extruded above the β-transus temperature with extruding ratio of 85, and then heat treated by conventional annealing at 750°C, or annealing at 1200°C by two routes. Dynamic compression properties were investigated by Split Hopkinson Pressure Bar system at strain rate of 3000±200 s-1. The results show that the dynamic compression properties of as-extruded specimens are comparable to the specimens after conventional annealing at 750°C. Compared to Widmannstatten microstructure with original beta grains in size of 200 μm ~ 300 μm obtained by conventional annealing, the microstructure obtained by annealing at 1200°C with coarse grains consisted of fine α-lamellae exhibits comparable dynamic strength but the capability of plastic deformation reduced about 20%. For the microstructure obtained by annealing at 1200°C with coarse grains consisted of coarse α-lamellae, the dynamic strength slightly decreased, while the capability of plastic deformation reduced about 60%.

The effects of single annealing on microstructure and mechanical properties of an (α+β) high-temperature titanium alloy (Ti-6.5Al-2Sn-4Zr-2Mo-2Nb-1W-0.2Si) were studied by optical microscopy (OM), scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and tensile testing. The results showed that with annealing temperature increasing the volume fraction of primary α phase decreased gradually, while the volume fractions of transformed β structure and secondary α phase increased, and the sizes of these phases became coarse. Elevating the annealing temperature, the room temperature strength didn't change at first and then decreased, the high temperature strength increased gradually, and the ultimate tensile strength and yield strength at 650°C can reach more than 700 MPa and 500 MPa, respectively. Meanwhile, both room temperature and high temperature ductility decreased with the annealing temperature increasing. In order to acquire good strength at high temperature and plasticity at room temperature, the best single annealing temperature is 980°C.

The effects of ultrasonic impact treatment (UIT) on the distribution of residual stress and on the microstructure of TA15 (Ti-6.5Al-2Zr-1Mo-1V) alloy joints by electron beam welding (EBW) were investigated. The results demonstrated that a marked microstructure change occurred after welding and the microstructure of welded joint presented a transitional change, i.e. martensite appeared in the fusion zone while equiaxed α in base mental. The residual stress in fusion zone was mainly tensile stress, and the maximum longitudinal stress value was 817MPa, which located in the centerline of welded joint. The results indicated that different impact methods have different influence on residual stress distribution. After employing UIT on welding toe, the residual stress near the welded joint exhibited a uniform distribution and the maximum tensile stress dropped to-153MPa. While after applying UIT on full coverage, the curve of the residual stress was steep and the maximum stress was still tensile stress. After UIT, no significant change occurred in microstructure and the tensile strength has a little change.

In this paper, three different double annealing treatments were applied on the 3mm-thick Ti-6Al-2Sn-4Zr-1Mo-2Nb-0.2Si (Ti62421S) alloy plate. Optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and tensile tests were used to investigate the microstructure and mechanical properties under different temperatures of Ti62421S alloy. The results show that the content of primary α phase (αp) decreases while transformed β structure (βt) increases with the increasing first-stage annealing temperature. After double annealing treatment, ordered α2 phase particles precipitate within αp and the size increases with first annealing temperature. This leads to that with increasing first annealing temperature, ultimate tensile strength (UTS) at 600~650°C increases while elongation decreases. After 1000°C/1h/AC+ 750°C/2h/AC annealing, Ti62421S alloy plate exhibits superior combination of mechanical properties at room and elevated temperatures.

Ti-6Al-3Sn-3Zr-3Mo-3Nb-1W-0.2Si (BTi-6431S) alloy is a novel two-phase high temperature titanium alloy for short-term using in aerospace industry up to 700°C. The effects of heat treatment on the microstructure evolution of BTi-6431S alloy bar were investigated through optical microscopy (OM), X-ray diffraction (XRD), electron probe microanalysis (EPMA) and transmission electron microscopy (TEM). The results show that solution treatment in β region at 1010°C followed by water quenching results in the formation of orthorhombic martensite α′′ phase, while air cooling leads to the formation of hexagonal martensite α′ phase. When solution-treated in α+β phase field at temperatures from 900°C to 980°C following by water quenching, the content of primary α phase decreases with the increase of heat treatment temperature. For the alloy subjected to identical heat treatment, the content of Al in α phase is much higher than that in β phase, while the contents of Nb, Mo and W elements in α phase are much less than those in β phase.

This paper aimed to study the quasi-static and dynamic properties of a titanium alloy plate with nominal composition Ti-3.5Al-2.5V-1.5Fe-0.25O (ATI 425TM titanium alloy with lower limit of Al element) in thickness of 8 mm. The quasi-static tensile properties were investigated by MTSTM testing system at strain rate of 10-3 s-1, while dynamic compression properties by Split Hopkinson Pressure Bar system at strain rate of 3000±200 s-1. The results show that the quasi-static prperties of the Ti-3.5Al-2.5V-1.5Fe-0.25O plate are comparable to the commercial Ti-6Al-4V plate in 8mm-thick. The Ti-3.5Al-2.5V-1.5Fe-0.25O plate exhibats good dynamic strength. The average dynamic flow stress is 100MPa higher than that of Ti-6Al-4V plate. However, the maximum strain during homogeneous plastic deformation of Ti-3.5Al-2.5V-1.5Fe-0.25O plate is only 50~60% of that of Ti-6Al-4V plate.

The effects of stress-relief annealing on the distribution of residual stress and on the microstructure of TA15 (Ti-6.5Al-2Zr-1Mo-1V) alloy joints by electron beam welding (EBW) were investigated. The results indicated that the microstructure of welded joint presented a transitional change, i.e. basket-weave structure appeared in the fusion zone while equiaxed α structure in base metal. No significant change occurred in microstructure after annealing at 650°C for 2 h. The residual stress in fusion zone was mainly tensile stress and the maximum longitudinal stress value was 473MPa. After annealing, the residual stress near the welded joint exhibited a uniform distribution and the maximum stress droped to 150 MPa. The yield stress and tensile stress of the TA15 welding zone were 1016 MPa and 1100 MPa respectively.

The degradation of polycarbonate (PC) food contact materials was studied based on analysis with GC-MS, FTIR, UV-Vis and TG techniques. It was evident that the processing temperature of the materials significantly enhanced the release of bisphenol A, an endocrine disruptor. Investigation of the redshift of UV band also revealed that high temperatures accelerated the aging degradation of PC.

A method for the determination of seven hazardous elements in Non-stick Pan Materials in five food simulants by inductively coupled plasma mass spectrometry (ICP-MS) was established. Using this method, the experiments were carried out on the samples of imitated migratory elements (Cr、Mn、Ni、Cu、As、Pb、Cd) in food simulants of water, 4%(W/V) acetic acid solution, 10%(V/V) ethanol solution, 2g/L sodium chloride solution and olive oil. The sample preparation method of five food simulants was confirmed through experiment. Experiments by resolution, stability, sensitivity and other parameters were adjusted tuning instrument to determine the instrument to achieve the best working condition. The linear range of this methods was 0.1~50ng/ml. For all elements, the correlation coefficient of the calibration curves was above 0.9990 and the detection limits were within the range of 0.008~0.12ng/ml. Most of the recoveries at 1ng/ml concentration level was from 85.34%~112.3%, while the RSD was from 0.37%~4.1%.

This paper study the migration characteristics and degradation kinetics of bisphenol A using TGA - gas chromatography - mass spectrometry and found that bisphenol A polycarbonate in the thermal oxidative aging conditions of 130 °C de-gradated to bisphenol A. At the range of 0 h to 120 h, the bisphenol A content of environmental hormones increased with time. When it reached 120 h, bisphenol A environmental hormone content decreased slightly with aging time. The content of bisphenol A reached 495mg/kg when the thermal oxidative aging time was 168 h, which was decreased compared to the content of 442mg/kg at 120 h. Polycarbonate thermal decomposition kinetics study showed that the thermal decomposition of polycarbonate can be divided into three phases. The first thermal decomposition occurred at the range of 415° C to 425 ° C, the polycarbonate end groups fracture of the second stage at 493.6°C , the main fracture of the main chain rearrangement and crosslinking, and the third stage at 598.7°C, the degradation of the chain continues to decompose and the decomposition of the crosslinked carbon precursor; thermal oxidation aging of polycarbonate decreased the heat stability and promote the thermal decomposition of polycarbonate. Comparing the oxidation induction period, thermal weight loss rate and activation energy of polycarbonate before and after thermal oxidative aging, it c found that the thermal stability of the hot oxygen aging of polycarbonate is reduced.

Polyethylene terephthalate (PET) is usually used as food packaging materials. And the heavy metal introduced during the process of manufacture usually exists in the spaces between macromolecules as monomer form. When PET contacts with real food, some heavy metals will migrate into the food since the motion of these molecules overcomes the binding power. As a result, it does great harm to our health. In this article PET was disposed in different thermal ageing conditions in order to accelerate its aging process. Then the original and aged PET samples were tested by Different Scanning Calorimeter (DSC) to characterize its crystallinity. And migration experiments was conducted on them using 4% acetic acid (V/V) as food simulate, the heavy metal content in food simulates was detected by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), so that we can get the migration characteristics of heavy metal. The results show that different aging conditions can do harm to the structure of PET in varying degrees by changing its crystallinity and molecules arrangement. But the difference of crystallinity has no obvious effect on Sb migration characteristic of PET samples. While, the migration quantity of Sb increases significantly with the increase of migrate temperature. It will provide an important reference to the evaluation of use security and service life of PET in real usage to study the relation between heavy metal migration features and aging degree.

Titanium and its alloys have been widely used as implants replacing hard human tissues in biomedical fields. To improve the stability of implants in the surrounding bone tissues, the materials with porous structures were fabricated. In this paper powder metallurgy technique was employed to fabricate porous Ti-39Zr-6Nb (wt.%) alloys. The porous structures and mechanical properties of the porous alloys were examined by scanning electron microscopy (SEM) and compressive tests. The results showed that with increasing the sintering temperature the porosity of the alloys decreased and the compressive strength and the elastic modulus increased. The porosity of the alloys was in the range from 20.8% to 23.2%, and the pore sizes mostly centered in 10~30μm. The compressive strength and the elastic modulus were in the range from 110.4 to 292.4MPa and 4.7 to 12.4GPa respectively, which was close to human bone.

In this study, four poly (ester-block-ether) copolymers were synthesized via the macromolecular transesterification method from different hydrophobic polyester segments prepared from precursors, dimethyl terephthalate (DMT), ethylene glycol (EG), dimethyl-5-hydroxyisophthalate (DHIP) and neopentyl glycol (NPG), and hydrophilic polyether, polyethylene glycol (PEG) or polyetheramine (PEA). The hydrolysis-resistance performance at alkaline condition and hydrophilicity of these four synthetic poly (ester-block-ether) copolymers were characterized by hydrolysis degree and water solubility with Nuclear Magnetic Resonance (NMR) and UV-Absorption Spectroscopy. The results showed that the hydrolysis degree and water solubility of poly (ester-block-ether) copolymers were mainly dominated by the molecular components, the molecular weights of polyester and polyether chains, and the connecting bonds between polyester and hydrophilic chains. The hydrolysis degree was listed from high to low: P(DHIP-NPG)-b-PEA, P(DMT-NPG)-b-PEA, P(DMT-EG)-b-PEA, then P(DMT-EG)-b-PEG. The P(DHIP-NPG)-b-PEA copolymer possesses the best hydrolysis-resistance performance, the hydrolysis degree of which reached only 4.1% after hydrolysis for 14 days, meanwhile, it showed excellent adsorption property on polyester fabrics and the surfaces of the treated fabrics exhibited well hydrophilicity. This study provides a light to explore novel poly (ester-block-ether) copolymers with well hydrolysis-resistance performance and high hydrophilicity through precisely constructing their molecular components, and further extend their potential applications in special auxiliaries and intermediates.

A novel class of cationic gemini fluorosurfactants with different spacer and same hydrophobic chain were synthesized. They were structurally characterized by NMR (1H and 19F), FT-IR, ESI-MS and elemental analysis. The equilibrium surface tensions were studied. The results showed that the gemini fluorosurfactants with the shorter spacer displayed higher surface activity, lower surface tension (21.48 mN/m) can be reached. Besides, the synergistic properties of these synthesized gemini fluorosurfactants with sodium dodecyl benzene sulfonate (SDBS) were investigated.

In micro-scale flow condition, the flow rate and fluid extrusion expansibility are always affected by the wall slip between the fluid and tube wall. In this research, a wall slip model based on a micro-tube flow was developed, and then the wall slip effect on the viscous fluid micro-extrusion process was explored by computational fluid dynamics (CFD) with different extruding pressures. The results showed that wall slip make the fluid resistance and expansibility decrease, and the fluid mass flow rate increase.

Neutral un-effectual grounded system (NUGS) is widely used in Chinese medium voltage power distribution network. However, existing earthed fault location methods in NUGS are not satisfactory in practical application due to weak fault current and unstable arc. Based on analysis of spectrum characteristics of current signals in single-phase earthed fault feeder, this paper proposed an earthed fault location method based on support vector machine (SVM). Firstly, the zero sequence current signal was sampled, and its spectrum was gotten by discrete Fourier transform. Secondly, the three dimensional feature vector that constituted by fundament, harmonic, inter harmonic component, had been extracted as the input of SVM. Furthermore, the SVM was trained with the samples obtained by simulation under different fault distance, different fault resistance and different fault close angle. Finally, the earthed fault feeder is selected using the trained SVM. The simulation results indicate that the fault location by the presented method is more precise.

Due to the earthquake of Yushu in April 14, 2010, Airport Road landslide No.3 deformed cracking, resulting in lower stability of slope, triggering landslides and other diseases. Selecting the section 2-2 (mileage K823 + 809) of Airport Road landslide No.3 as the calculation section, we use the ABAQUS finite element program to establish landslide numerical mode. The slip mass of landslide was simulated by the elastic-plastic damage constitutive model, and the bedrock was analyzed as Mohr - Coulomb constitutive model. Landslide No3 is analyzed for example, and showed that earthquake triggering mechanism elastplastic damage constitutive model can describe the landslide very well.

Power quality disturbance detection and identification is the prerequisite and basis for the power quality management and control. This paper presents a new power quality disturbance detection and classification method. Firstly, the time-time transform is applied to power quality disturbance signal analysis. According to spectrum analysis results of the diagonal elements of time-time transform matrix, a preliminary judge about whether the disturbance signal contains harmonics and inter harmonic was given. For disturbances with non-harmonics, based on time-time transform modulus matrix diagonal sequence, the beginning and ending time of the disturbance is located, and the disturbance amplitude is calculated. For the disturbances which contain harmonics, time-time transform is perform twice to get the row mean value curve and the column mean value curve, which are required by disturbance time location and amplitude measurement. Finally, disturbance classification had realized by using rule tree. Simulation results reveal that this method is very robust and adaptable, which can identify transient power quality disturbance with minor magnitude under noisy environment, and the recognition rate is satisfactory.

On the condition of protecting the critical load, it is necessary to restore the service of outage area without fault as soon as possible after the occurrence of fault in smart distribution system. A fast service restoration method is proposed for medium-voltage distribution system with distributed generations, which combines intentional islanding of DGs for network reconfiguration. Under the condition of safety limits, the out of service areas are achieved maximization of restoration, making full use of DGs. The whole process of restoration is regarded as a multi-stages decision problem, and divided into four stages. Compared to the existing algorithms, this method can effectively avoid the time-consuming and search results problems, and the simulation results are better. The effectiveness and practicality of the propose approach is demonstrated by simulations on a PG&E 69-nodes system with DGs.

With the rapid expansion of the grid, how to solve the security and stability of power system has become a hot problem. As a power system after a serious accident the necessary security measures, black-start programs are expected to play an extremely important role in reducing the loss of equipment and user outage and decreasing the outage time. The present paper proposes a series of advantages about distributed generator (DG) and raises evaluation indexes of DG in black-start. The fuzzy hierarchical model is built based on the general steps of fuzzy decision theory. According to the concept of triangular fuzzy number, considering the indexes of which the weight value is judged by means of trapezoidal fuzzy number complementary judgment matrix. Finally, by actually case anglicizing, the paper demonstrates the scientific nature, effective and easy to operate of the method. And a new decision-making method for the optimal DG start-up sequences based on fuzzy AHP is proposed.

La0.3Ca0.7Fe0.7Ni0.3O3 perovskite-type composite was prepared by glycine-nitrate combustion method , Zinc Oxide was prepared by liquid crystal precipitation, then we synthesized ZnO/La0.3Ca0.7Fe0.7Ni0.3O3/Ppy nanocomposites with different content of Ppy in situ method. XRD,SEM,UV-vis were used to characterized the crystal structure and morphology of the nanocomposites and their photocatalytic activity. Cyclic voltammetry of the composites were conducted in 1mol/L KCl solutions to discuss their electrochemical properties.According to the electrochemical properties, we found that with the increase of the zinc oxide content,the redox peak current of the composites becomes larger, also their reversible redox properties was improved.

This paper describes a wearable technology sub-health monitoring system based on the description of the system and physiological signals by Zigbee module sub-health data collection, acquisition and transfer process, as well as PC using BP neural network for sub-health algorithm model state assessments; simulation tests to verify the rationality and practicality of the system. In short, the system has a simple and accurate calculation of benefits for sub-health can quickly assess and provide comprehensive, objective and scientific decision-making reference, extensive prospects.

A 32 m simply supported concrete box bridge is taken as the research object. The box bridge structure noise induced by the static loads and how the ground reflection affects it are studied by the modal acoustic transfer vector (MATV) method. The results show that it is commendable to analyze the box bridge structure noise using the MATV method; the regularities of the sound field distribution are changed obviously by the ground reflection, and the directivity is very obvious in the far-field region and there has the stratification of the vertical sound field under the box bridge; the ground reflection enhances the overall sound level of the sound field except the region above the box bridge, and the vertical sound field in the far field is affected very obviously. The buildings, especially the high-rise buildings, are mostly in the far field area, so the influences of the ground reflection on the box bridge structure noise must be paid attention to.

Soil nutrient in greenhouse soil was studied in Haicheng Municipality, Liaoning province. Results showed that the soil nutrient including organic matter, total nitrogen, total phosphorus, alkaline hydrolysis nitrogen, available phosphorus and available potassium presented parabolic curve change with increasing cultivating years. The highest contents all appeared in 8 years, which are 3.2 and 2.8 times higher than those in open field at 0-20 cm and 20-40 cm depth, respectively. The vertex of nitrate and soluble salt were also appeared in 8 years. Correlation analysis suggested the relationships among nutrients were very significant. It is also suggested the salinization of soil was the inevitable result of the excessive organic fertilizer and chemical fertilizer.

The power saving and energy-saving control plays a crucial role in green building design. An intelligent electricity and heat saving control method is proposed based on PID control optimization control, this algorithm is applied in the design of green building, the collection of data is taken with feedback processing, the design method of energy saving and heat savingcontrol unit is presented in intelligent building, it provides the accurate basis for energy-saving and heat saving cycle control optimization design. The application of energy circulation control in design of green buildings is realized. The four layers real building is taken as the subjects in the experiment, the experimental results show that, the controller is applied in energy saving control of green building, it can effectively improve the control accuracy.

A rapid ultrasonic wave-assisted dansylation procedure was developed for the derivatization of cadaverine prior to HPLC determination. Cadaverine was quantitatively dansylated in 10 min using a ultrasonic power of 200 W and a operating frequency of 40 KHz .In this case, the excellent derivatising condition are determined as follows: pH of buffer, 9.5; concentration of dansyl chloride, 5 mg/mL; time of reaction, 10 min. This method is fast, reproducible and practical for the analysis of cadaverine.

With the development of computer technology, computer-aided translation software is widely applied to translation. It is able to improve translation efficiency and quality. Meanwhile, it is in accordance with the requirement of market-oriented translation workshop. The paper compares the strengths and weaknesses of the major computer-aided translation software, which provides the software consumers with practical suggestion. The design principle is also discussed in the paper to facilitate the design of satisfactory computer-aided translation software to the users.

In clothing customization manufacture, cutting schemes are worked out mostly based on manual experience. This not only wastes extra time and workforce, but also induces mistakes, especially for various orders in business wear customization industry. The cutting plan optimization system designed by our paper realizes the function of the automatic and interactive production of cutting plan. The system’s application reduces the cost and the sub-bed error, improves the efficiency and optimizes the management.

This paper is based on literature research on mobile learning theory and language learning theory to design and develop learning clients for College English listening on an Android platform and build up a comprehensive listening learning system by adding performance tests and advancing listening practice and feedback to help English learners improve listening capability step by step and create a better service for College English listening learning.

In this paper, based on the Android operating system, an electronic dictionary system on mobile devices is designed. Local word searching is achieved by SQLite database storing and managing data, local word library being built on the res\raw directory in the Android project, and then the Input Stream data being written to corresponding files in other directories; By using the interface of Unabridged Dictionary, calling utf8 encoding scheme to implement the web-based word search.

Based on a 125 - days natural environment temperature changing observation of one cable-stayed bridge in zhejiang province and the reasonable simplification of the thermal field and stress distribution of concrete bridge tower, the bridge tower thermal stress finite element analysis is done through the first kind boundary condition and the third kind boundary condition. It is confirmed that the deviation of thermal stress between the first kind boundary condition and the third kind boundary condition is below 6% because the outside temperature change range is limited in the practical engineering case. Using the first kind boundary condition can meet the accuracy requirement of the project at the same time greatly simplify the calculation process.

In order to study the influence of bend tube on firing accuracy due to gravity, a finite element model of sniper rifle, only considering the interaction between bullet and tube, was established based on nonlinear finite element method. The initial disturbance of bullet was taken as a measuring standard of firing accuracy. The model was used to simulate the launch process of sniper rifle under the condition of gravity static equilibrium in the method of the mixing calculation which had advantages of both dynamic explicit algorithm and static implicit algorithm. The simulation results show that vertical stiffness increases due to gravity and then the instantaneous velocity and attitude of bullet are largely influenced. Bending tube has a great influence on bullet motion.

This paper is devoted to an English Pronunciation training system on the Android platform with functions like English transcription, word pronunciation demonstration, listening and repeating, pronunciation comparison, grading, pronunciation feedback and correction. The training system is designed and developed in line with the characteristics of Android operation system, giving full play to the advantages of Android platform by calling the relevant functions of function interface and components to improve the development efficiency of the system. The system is of high real-time and reliability with a series of multimedia techniques like the pronunciation mouth video-based animation, internal mouth structure figure, pronunciation guidance of mouth and tongue positions, and can effectively guide the learners to learn and practice English pronunciation.

The teaching platform system is so designed that the main function of it is activated by "hot link menus" and the hot issues of users’ concern are set on with "hot tags". An automatic 2-tiered structure comes into shape that the more frequent a user clicks on, the higher the tag ranks. The script combination techniques of Ajax and CSS are employed in the design of hot tags and menus, connection to the backstage database being there for state storage. Based on the techniques of hot tags and menus, teachers themselves can always determine what hot issues to teach and modify the order of knowledge teaching, thus the priority is always given to the teaching matters of importance in teaching management.

Ti-6Al-4V plates in thickness of 8 mm were directly hot rolled and then heat treated in various routes by a single electron beam cold hearth melted (EBCHM) ingot, in which the weight percentage of recycled titanium scraps was at least about 50 wt%. The dynamic stress-strain behaviors of the plates with typical microstructures were investigated by Split Hopkinson Pressure Bar system at the strain rates of 2000 s-1~ 3000 s-1. The results show that the dynamic compression properties of EBCHM-ingot Ti-6Al-4V plates are relative to that of commercial VAR-ingot plates. The dynamic properties in normal direction of the plates are not sensitive to variations in the fraction of primary alpha phase.

Digital PID control is one of the most widely used control methods in the manufacturing process. Based on the analysis of PID control algorithm, the system has designed and simulated the incremental PID controller using the LPM macro module built-in FPGA,and also designed the PWM module. The combination of two modules can be used for a variety of applications. The results show that the design is feasible and correct.

The bridge tower crack extension probability is very large because of the stress concentration at the crack tip, combined with the fatigue stress. Based on the long-term observations of temperature fatigue load spectrums of a bridge tower and the experiment of concrete fatigue performance parameters, the problem of crack propagation is analyzed by infinite life safety reliability model and safe and reliable crack extension randomness model. It is concluded that the concrete structure crack extension probability is close to 98.6% and reasonable repair cycle should be about 3 years.

It is important to explore the data type of test content and the comparative data by the realization of automation in data migration process based on the basic idea of ETL technology. It is in order to work efficiently than complete data, improve work efficiency and the coverage of test data which free the human from a single repetitive labor in the business intelligence project. Quality data is an important prerequisite for the success of on-line system, and also a powerful guarantee stable operation of the system in the future. The design of the comparative data in automated implementation is provide an important guarantee for the normal operation of the system.

A tension-compression cycle fatigue test was performed in order to study the fatigue property of C50 concrete with pre-cracks in cyclic loading. The stress ratio was-1 and the amplitude was 0.2 MPa ~1.30 MPa. The results show that the modified coefficient of fatigue strength is 0.198~0.265 and the infinite life fatigue strength is below 0.45MPa. While the log value of fatigue life is approximately linear with the amplitude of fatigue load stress, the discreteness of fatigue life, the particularity of concrete, has little to do with the amplitude. The S-N, P-N fatigue life curves and the constant fatigue life diagram of pre-crack concrete are obtained.

As an important part of pipeline safety, pipeline leak detection is usually done by extracting feature vectors of leakage signal. Many researchers used wavelet packet algorithm to extract feature vector, but because of mixing effects of wavelet packet, the acquired feature vector may be not accurate. To solve this problem, the authors propose an improved wavelet packet algorithm to extract the feature vector. The improved algorithm is different from the traditional algorithm in decomposition and reconstruction and the feature vector is constituted by three time-frequency domain parameters. A lot of experiments have been performed to extract feature vector based on the proposed algorithm, with the results showing that the proposed algorithm can overcome the mixing effects and accurately extract the feature vector.

Traditional watermark embedding introduces inevitably some perceptible quality degradation of the host image. Another problem is the inherent conflict between imperceptibility and robustness. However, the zero-watermarking technique can extract some essential characteristics from the host image and use them for watermark registration and detection. The original image was decomposed into series of multiscale and directional subimages after lifting wavelet transformation (LWT). The high order bit-plane of low-frequency subimage and watermark image are inputs of the cellular neural network (CNN), and the zero-watermarking registration image is the output. To investigate and improve the security and robustness, the original watermark and registration image are scrambled or encrypted. The watermark image can be extracted from the secret image. This algorithm is simple and robust. The proposed method is also simple for hardware realization.

To solve the problem of image information transmission delay in the network multimedia teaching system, the compression and multicast solutions are put forward on the basis of usual screen blocking skill of data. According to the characteristics of the multimedia teaching system, the screen changes typically little at smaller intervals. It means that only a few screen blocks, which are changing, are needed to be transferred by screen blocking skill. At the same time, the network video data transmission volume is further curtailed through compression and multicast so that the multimedia information network transmission delay is decreased. The minimal buffer size for allocation is determined to ensure the smooth transmission of video data in the multimedia teaching system.

The adsorption capability of Cd2+with δ-MnO2was studied in water. The results indicated: the adsorption strongly relied on pH values. At 303K, the pH values were above 6.05, adsorption percentages of Cd2+were nearly 100%. When pH values were below 2.3, adsorption rates of Cd2+was below 20%. The adsorption processes was completely controlled by reaction rate and diffusion factor. The reaction rate of adsorption increased with pH values and temperatures. The adsorption activated energy of Cd2+was 54.66 KJ•mol-1at pH value 3.28, and it was 31.98 KJ•mol-1at pH value 6.05. δ-MnO2may be effectively desorpted after adsorption Cd2+at the pH values below 2.05. The desorption rates were about 75%.

In this paper, we propose a special Multi-class SVMs (MSVM) data fusion strategy which is applied to classify vehicle based on multiple pavement structural strain time histories. The centralized and distributed fusion strategies are applied to combine information from several data sources. In the centralized strategy, all information from several data sources is centralized and combined to construct an input space. Then a MSVM classifier is trained. In distributed schemes, the individual data sources are processed separately and modeled by using the MSVM. Then new data fusion strategies are used to combine the information from the individual MSVM to acquire the final classification outputs. Two popular Multi-class SVMs algorithms (One-against-all OAA, One-against-one OAO) are used to construct classifier based on aforementioned two fusion strategies, respectively. The results are compared between SVM-based fusion approach and single data source SVM using two MSVM algorithms, respectively. The result shows this SVM-based fusion approach significantly improves the results of classification accuracy and robustness. The proposed Multisensor data fusion methods can also be applied in other fields.

Applying TRNSYS, this paper introduced a numerical simulation of annual dynamic air conditioning load for the standard floor, the refuge floor and the top floor of a high-rise building in Tianjin. Results suggest that even though the refuge floor and the top floor share similar load characteristics of heating & cooling air-conditioning, they have different load sizes, and the load characteristic of the standard floor is different from them.

In this paper, aiming at the poor performance of the existing symbol rate estimation methods when SNR is low, we proposed a method based on the timing square which can be simply calculated and applied to MASK/MPSK/MQAM modulated signal, improved the performance of signal symbol rate estimation compared with the existing method. Based on the principle of the timing square, the signal modules were squared to calculate the fourier coefficient modulus corresponding to different sampling ratios. Then the characteristic line was searched in the transform spectrum which contains symbol rate information and obtained an estimation of the symbol rate. The impact of the roll-off factor and the carrier wave was analyzed and solution was proposed in this paper. Simulation results show that the performance of symbol rate estimation of the improved method is better than the original method, the wavelet transform method and the cyclostationary method in low SNR and low roll-off factor environment.