Showing papers in "Transactions of Tianjin University in 2013"
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TL;DR: In this paper, the first offshore wind turbine with integrated installation was established in Qidong sea area of Jiangsu Province, China, which led to the implementation phase of one-step-installation technique based on the design and construction of large-scale bucket-top-bearing (LSBTB) bucket foundation.
Abstract: In 2010, the first offshore wind turbine with integrated installation was established in Qidong sea area of Jiangsu Province, China, which led to the implementation phase of one-step-installation technique based on the design and construction of large-scale bucket-top-bearing (LSBTB) bucket foundation. The critical technique of LSBTB bucket foundation included self-floating towing, penetration with adjustment of horizontal levelness, removability and one-step-installation. The process of one-step-installation included the prefabrication of LSBTB bucket foundation in onshore construction base, installation and debugging of wind power, overall water transportation of foundation and wind power system, and installation of foundation and offshore wind turbine on the appointed sea area. The cost of one-step-installation technique was about 5 000 Yuan/kW, which was 30%-50% lower than that of the existing technique. The prefabrication of LSBTB bucket foundation took about two months. During the one-step-installation process, the installation and debugging of wind power and overall water transportation need about one to two days in sea area within 35 m depth. After the proposed technique is industrialized, the cost will be further reduced, and the installation capacity is expected to be up to 500 wind turbines per year.
60 citations
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TL;DR: In this paper, heparin was grafted onto polycarbonate urethane (PCU) surface via a three-step procedure utilizing αω-diamino-poly(ethylene glycol) (APEG, M n = 2 000) as a spacer.
Abstract: Heparin was grafted onto polycarbonate urethane (PCU) surface via a three-step procedure utilizing, αω-diamino-poly(ethylene glycol) (APEG, M
n=2 000) as a spacer. In the first step, isocyanate functional groups were introduced onto PCU surface by the treatment of hexamethylene diisocyanate (HDI) in the presence of di-n-butyltin dilaurate (DBTDL) as a catalyst. In the second step, APEG was linked to the PCU surface to obtain the APEG conjugated PCU surface (PCU-APEG). In the third step, heparin was covalently coupled with PCU-APEG in the presence of N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylamidopropyl) carbodiimide (EDAC). The amount of heparin (1.639 μg/cm2) covalently immobilized on the PCU-APEG surface was determined by the toluidine blue method. The modified surface was characterized by water contact angle, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The hemocompatibility was preliminarily studied by platelet adhesion test. The results indicated that heparin was successfully grafted onto the PCU surface, and meanwhile the hydrophilicity and hemocompatibility of the modified PCU surface were improved significantly compared with the blank PCU surface.
23 citations
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TL;DR: A fault diagnosis model is proposed based on fuzzy support vector machine (FSVM) combined with fuzzy clustering (FC) that achieves high performances both in identifying fault types and fault degrees.
Abstract: A fault diagnosis model is proposed based on fuzzy support vector machine (FSVM) combined with fuzzy clustering (FC). Considering the relationship between the sample point and non-self class, FC algorithm is applied to generate fuzzy memberships. In the algorithm, sample weights based on a distribution density function of data point and genetic algorithm (GA) are introduced to enhance the performance of FC. Then a multi-class FSVM with radial basis function kernel is established according to directed acyclic graph algorithm, the penalty factor and kernel parameter of which are optimized by GA. Finally, the model is executed for multi-class fault diagnosis of rolling element bearings. The results show that the presented model achieves high performances both in identifying fault types and fault degrees. The performance comparisons of the presented model with SVM and distance-based FSVM for noisy case demonstrate the capacity of dealing with noise and generalization.
12 citations
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TL;DR: In this article, the degradation process of organosol coated tinplate in beverage was investigated by electrochemical noise (EN) technique combined with morphology characterization using phase space reconstruction theory.
Abstract: The degradation process of organosol coated tinplate in beverage was investigated by electrochemical noise (EN) technique combined with morphology characterization. EN data were analyzed using phase space reconstruction theory. With the correlation dimensions obtained from the phase space reconstruction, the chaotic behavior of EN was quantitatively evaluated. The results show that both electrochemical potential noise (EPN) and electrochemical current noise (ECN) have chaotic properties. The correlation dimensions of EPN increase with corrosion extent, while those of ECN seem nearly unchanged. The increased correlation dimensions of EPN during the degradation process are associated with the increased susceptibility to local corrosion.
12 citations
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TL;DR: The results confirmed the conjugation of PCL onto gelatin chains and the PCL modified gelatin can be used as biomaterials owing to their biocompatibility and biodegradation.
Abstract: Hydrophilic degraded gelatin was modified with hydrophobic poly(ɛ-caprolactone) (PCL) via a chemical grafting route. Firstly, PCL with one hydroxyl end group was prepared by the ring-opening polymerization of ɛ-caprolactone (ɛ-CL) with tin (II) 2-ethylhexanoate as catalyst and n-butyl alcohol as initiator. Secondly, the PCL reacted with isophorone diisocyanate (IPDI) to prepare PCL with isocyanate functional group (PCL-NCO). Hydroxylamine was used to degrade gelatin by the cleavage between asparagine and glycine residues of gelatin. PCL-NCO reacted with the hydroxyl/amino groups of degraded gelatin in a homogeneous system and yielded the PCL modified gelatin copolymers. The gelatin grafted PCL copolymers were measured by means of XRD, FTIR, DSC and 1H NMR. The results confirmed the conjugation of PCL onto gelatin chains. The PCL modified gelatin can be used as biomaterials owing to their biocompatibility and biodegradation.
11 citations
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TL;DR: In this paper, the authors established a decomposition model by using the structural decomposition analysis (SDA) method at a regional level, and employed this model to empirically analyze the changes of Beijing's energy intensity.
Abstract: As China’s energy intensity fluctuated in recent years, it is necessary to examine whether this fluctuation happened at a regional level. This paper establishes a decomposition model by using the structural decomposition analysis (SDA) method at a regional level. Then this model is employed to empirically analyze the changes of Beijing’s energy intensity. The conclusions are as follows: during 2002–2010, except petroleum, the energy intensity decreased and the changes were mostly attributed to the technology changes, while the final use variation actually increased the energy intensity; comparing different periods of 2002–2010, the decline rates of energy intensity for coal and hydropower were decreasing, resulting from the production technology being more energy-intensive than before; the energy intensity changes of petroleum firstly increased substantially and then decreased moderately.
10 citations
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TL;DR: In this article, the microstructure characteristics and hardness behavior of 21% Cr ferritic stainless steel welded by pulsed gas tungsten arc welding at different pulse frequencies were investigated.
Abstract: Thin plates of 21% Cr ferritic stainless steel welded by pulsed gas tungsten arc welding at different pulse frequencies were investigated for the microstructure characteristics and hardness behavior. The welds contained columnar grains in the outer part and fine equiaxed grains in the central region due to the pulsed process.
10 citations
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TL;DR: In this paper, negative pressure and electroosmosis were combined to ensure the cover-bearing mode of offshore wind turbines, and the results showed that soil reinforcement by negative pressure was quicker and more obvious during the early phase, and electro-osmotic method can affect more range of soil by rational arrangement of electrodes.
Abstract: Cover-bearing-type bucket foundation for offshore wind turbines has been paid more and more attention due to its low cost and great bearing capacity. In order to ensure the cover-bearing mode, the muddy soil inside the bucket foundation should be reinforced by some soil consolidation methods, such as negative pressure and electroosmosis. Firstly, tests were conducted to obtain the reasonable current density. Meanwhile, to improve the electroosmotic speed and effectiveness, other factors such as intermittent power and layout of electrode, were also studied in the tests. Then, the soil reinforcing tests by negative pressure combined with electro-osmosis were performed for the muddy soil consolidation inside the bucket foundation. The results showed that soil reinforcement by negative pressure was quicker and more obvious during the early phase, and electro-osmotic method can affect more range of soil by rational arrangement of electrodes. Compared with negative pressure, the electro-osmotic method was a continuous and relatively slow process of reinforcement, which was complementary to the negative pressure method. The voltage value of electro-osmosis had little effect on the muddy soil reinforcement inside the bucket foundation, and 1.5 A was chosen as the most reasonable current value for scale model testing in the electro-osmotic method.
9 citations
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TL;DR: In this article, two new sorbitol derivative gelators were designed and synthesized in contrast to MDBS in order to study the gel properties of gelators with different structures.
Abstract: 1, 3:2, 4-di-p-methylbenzylidene-D-sorbitol (MDBS) is known to be an efficient sorbitol derivative gelator. Two new sorbitol derivative gelators were designed and synthesized in contrast to MDBS in order to study the gel properties of gelators with different structures. Their gelation behavior to 30 solvents was investigated. It was found that the gelation behavior was related to the molecular structure of gelators. Compared with MDBS, the gelator with more hydroxyl in the molecular structure could gel water and that with more aromatic ring could gel aromatic solvent. The fibrous and three-dimensional network of the gels was obtained by scanning electron microscopy (SEM). Ultravioletvisible (UV-Vis) spectroscopy revealed that π-π interaction was one of the main driving forces for the formation of gels. The π-π stacking of gelation increases with the number of aromatic rings in the molecular structure of gelator. Fourier transform infrared (FT-IR) spectroscopy revealed that the hydrogen bonding was also the main driving force for the formation of gels. The layered structure of the gels was studied by X-ray diffraction (XRD).
9 citations
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TL;DR: In this paper, a series of magnetic ZSM-5 zeolites were prepared by hydrothermal synthesis with the addition of magnetic Fe3O4 particles during the crystalline process.
Abstract: In order to separate ZSM-5 zeolite powders from solution easily, a series of magnetic ZSM-5 zeolites were prepared by hydrothermal synthesis with the addition of magnetic Fe3O4 particles during the crystalline process. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared (IR) spectrum, energy dispersive X-ray (EDX), specific surface area, magnetic susceptibility and adsorption capability. It was found that the magnetic ZSM-5 zeolites had good magnetism and the magnetic susceptibility increased with the increasing amount of Fe3O4 particles. Compared with the pure ZSM-5 zeolite, the adsorption capability of magnetic ZSM-5 zeolites was acceptable. When the magnetic zeolites were used to adsorb Pb2+ from solution, the magnetic zeolite powder could be conveniently separated with magnetic separation technology.
9 citations
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TL;DR: In this paper, the corrosion process of tinplate in deaerated functional beverage was investigated by using electrochemical impedance spectroscopy (EIS) combined with scanning electron microscopy (SEM) and energy dispersive spectroscopic (EDS) techniques.
Abstract: The corrosion process of tinplate in deaerated functional beverage was investigated by using electrochemical impedance spectroscopy (EIS) combined with scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques. The results reveal that the uncoated tinplate shows a poor corrosion resistance and the corrosion type is detinning. During the initial stage of immersion, EIS spectrum consisted of two capacitance arcs with obvious time-constant dispersion effect, which was attributed to the two-dimensional and three-dimensional inhomogeneous distribution of the electrode surface. With the increase of immersion time, the capacitance arc of high frequency shrunk and degenerated, due to the corrosion of tin coating. The pore resistance of tin coating and the charger transfer resistance of substrate, which are determined from the electrochemical equivalent circuit, can be used as the indicators of tinplate corrosion process. The decrease of the pore resistance of tin coating indicates that the corrosion degree of tin layer becomes more severe, whereas the decrease of the charger transfer resistance of substrate implies that the corrosion degree of steel substrate also becomes more severe as the immersion time prolongs.
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TL;DR: Simulations showed that the proposed method outperformed the other four demosaicking methods for average color peak signal to noise ratios and maintained a relatively low complexity owing to constant color-difference interpolation step and a reasonable terminating condition of iteration.
Abstract: An efficient adaptive approximation demosaicking algorithm based on the sampled edge pattern was presented for mosaic images from Bayer color filter array. The proposed algorithm determined edge patterns by four nearest green values surrounding the green interpolation location. Then according to the edge patterns, different adaptive interpolation steps were applied. Simulations on 12 Kodak photos and 15 IMAX high-quality images showed that the proposed method outperformed the other four demosaicking methods (bilinear, effective color interpolation, Lu’s method and Chen’s method) for average color peak signal to noise ratios and maintained a relatively low complexity owing to constant color-difference interpolation step and a reasonable terminating condition of iteration.
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TL;DR: In this article, the authors presented the heating performance and energy distribution of a system with the combination of ground-source heat pump and solar collector or a solar-assisted ground source heat pump system (SAGSHPS) by calculation and experiment.
Abstract: This paper presents the heating performance and energy distribution of a system with the combination of ground-source heat pump and solar collector or a solar-assisted ground-source heat pump system (SAGSHPS) by calculation and experiment. The results show that the average absolute error is less than 0.6 °C and the relative error is less than 5% under the pulse load when the analytical solution to the 2-D solid cylindrical source model is used for the SAGSHPS. The coefficient of performance (COP) of the SAGSHPS is 2.95–4.70. The average fluid temperature in the borehole heat exchanger can increase by 3 °C with the assistance of solar collector, which will improve the COP of the heat pump by approximately 10% from the experimental data. The energy contributions to the total heating load of soil, electricity and solar are 56.30%, 36.87% and 6.83%, respectively.
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TL;DR: Growth kinetics of calcite were studied in seeded stirred batch experiments in MEG-water solutions at 40 °C and 70 °C, conditions relevant for the processing of natural gas as mentioned in this paper.
Abstract: Growth kinetics of the most stable polymorph of calcium carbonate, calcite, has been studied in seeded stirred batch experiments in MEG-water solutions at 40 °C and 70 °C, conditions relevant for the processing of natural gas. It was found that MEG changes the growth order from two in pure water to one in solvent mixtures of MEG and water. Assuming parabolic growth (growth order is equal to two), it could be shown that MEG decreases the growth rate constant for calcite from 0.52 nm/s to 0.11 nm/s (70 °C) when the MEG-content is increased from 0 wt% MEG to 65 wt% MEG. Decreasing the temperature from 70 °C to 40 °C has a similar effect on the growth rate constant as raising the level of MEG to 65 wt%.
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TL;DR: Lipoic acid (LA) was employed as a linker for the attachment of antibody to the gold surface of surface plasmon resonance (SPR) chip as discussed by the authors.
Abstract: Lipoic acid (LA) has received great attention in the area of gold surface functionalization. In this study, LA was employed as a linker for the attachment of antibody to the gold surface of surface plasmon resonance (SPR) chip. By using this chip in a homemade SPR immunosensor, low molecular weight compound 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) can be detected at a low level of 0.01 ng/mL. There is a good linear relationship (R
2=0.943 1) between the results of SPR biosensor and enzyme-linked immunosorbent assay(ELISA).
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TL;DR: In this article, the effects of repairing strategies on the failure probability of the pipe systems in process industries based on the time-average fault tree approach, especially the in-operation repairing strategies including pressured inoperation repairing activities.
Abstract: In petrochemical plant, the in-operation repairing is usually a repairing strategy with pressured inoperation repairing for avoiding huge economic losses caused by unplanned shutdown when some slight local leakage happens in pipes. This paper studies the effects of repairing strategies on the failure probability of the pipe systems in process industries based on the time-average fault tree approach, especially the in-operation repairing strategies including pressured in-operation repairing activities. The fault tree model can predict the effect of different repairing plans on the pipe failure probability, which is significant to the optimization of the repairing plans. At first pipes are distinguished into four states in this model, i.e., successive state, flaw state, leakage state and failure state. Then the fault tree approach, which is usually applied in the studies of dynamic equipment, is adopted to model the pipe failure. Moreover, the effect of pressured in-operation repairing is also considered in the model. In addition, this paper proposes a series of time-average parameters of the fault tree model, all of which are used to calculate node parameters of the fault tree model. At last, a practical case is calculated based on the fault tree model in a repairing activity of pipe thinning.
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TL;DR: The ability of RS-racemate to form one of the above three polymorphic modifications (M1, M2, and Tc) or their mixtures containing various proportions and combinations of the components (M 1+M2, M 1+Tc, or M 2 +Tc) was found to depend on the type of crystallization medium (a melt, aqueous medium, ethanol or acetone solution), crystallization rate (from 2-3 minutes to 4 months), and crystallization temperature as mentioned in this paper.
Abstract: Enantiomers (R(+) and S(−)), RS-racemate (double compound) and (R+S)-conglomerate (mechanical mixture of enantiomers) of malic acid C4H6O5 have been investigated by means of X-ray diffractometry and high temperature X-ray diffraction method. The RS-racemate was found to be able to form three polymorphic modifications, which we denominated as M1 (monoclinic, space group P21/c), M2 (monoclinic, space group Cc), and Tc (triclinic, space group P-1), the latter modification having been unknown before. Modification Tc was also described, and its Xray diffraction characteristics, including interplanar spacings d, hkl indices, unit cell parameters, were defined. In addition, X-ray diffraction characteristics for both reported earlier M1 and M2 monoclinic polymorphic modifications were measured with higher accuracy. The ability of RS-racemate to form one of the above three modifications (M1, M2, and Tc) or their mixtures containing various proportions and combinations of the components (M1+M2, M1+Tc, or M2 +Tc) was found to depend on the type of crystallization medium (a melt, aqueous medium, ethanol or acetone solution), crystallization rate (from 2–3 minutes to 4 months), and crystallization temperature. Heating S-enantiomer and M1 RS-racemate up to their respective melting points (100 °C and 124 °C, correspondingly) only made them undergo thermal deformations, while heating (R+S)-conglomerate in the temperature range of 96–110 °C resulted in its homogenization to form M2 RS-racemate, which, near the melting point (118 °C), namely, in the range of 112–116 °C, was transformed into M1 RS-racemate.
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TL;DR: In this article, the seismic behavior of autoclaved aerated concrete loadbearing masonry wall (AACLMW) with different constructional measures in terms of failure mode, hysteretic curve, deformation capacity and displacement ductility was investigated.
Abstract: To investigate the seismic behavior of autoclaved aerated concrete load-bearing masonry wall (AACLMW), a piece of control block wall without constructional measures and five pieces of block walls with different constructional measures were tested under low reversed cyclic loading which imitated low to moderate earthquake force. The seismic behavior of AACLMW with different constructional measures in terms of failure mode, hysteretic curve, deformation capacity and displacement ductility was studied and compared with that without constructional measures. The experimental results indicate that the constructional measures comprising constructional columns and horizontal concrete strips are effective for improving the seismic behavior of AACLMW. The study in this paper can provide a reliable experimental basis for further analysis and engineering application of AACLMW in the future.
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TL;DR: In this paper, a dynamic velocity feed-forward compensation control (DVFCC) approach with RBF neural network (RBF-NN) dynamic model identification was presented for the adaptive trajectory tracking of industrial robots.
Abstract: A dynamic velocity feed-forward compensation control (DVFCC) approach with RBF neural network (RBF-NN) dynamic model identification was presented for the adaptive trajectory tracking of industrial robots. The proposed control approach combined the advantages of traditional feedback closed-loop position control and computed torque control based on inverse dynamic model. The feed-forward compensator used a nominal robot dynamics as accurate dynamic model and on-line identification with RBF-NN as uncertain part to improve dynamic modeling accuracy. The proposed compensation was applied as velocity feed-forward by an inverse velocity controller that can convert torque signal into velocity in the standard industrial controller. Then, the need for a torque control interface was avoided in the real-time dynamic control of industrial robot. The simulations and experiments were carried out on a gas cutting manipulator. The results show that the proposed control approach can reduce steady-state error, suppress overshoot and enhance tracking accuracy and efficiency in joint space and Cartesian space, especially under highspeed condition.
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TL;DR: In this article, the influence of small organics on the adsorption characteristics of activated carbon produced from industrial pyrolytic tire char (APTC) for malachite green (MG) was investigated by a batch method.
Abstract: The influence of small organics on the adsorption characteristics of activated carbon produced from industrial pyrolytic tire char (APTC)for malachite green (MG) was investigated by a batch method. Phenol was chosen as the representative of small organics. The effects of phenol on adsorption equilibrium, kinetics and thermodynamics were studied systematically. The results indicate that APTC is a potential adsorbent for MG. The presence of phenol decreases the adsorption capacity of APTC for MG, but improves the rate of adsorption, while the adsorption characteristics, such as equilibrium, kinetics and thermodynamics are not affected by phenol. The adsorption equilibrium data follow Langmuir isotherm and the kinetic data are well described by the pseudo-second-order kinetic model. The adsorption process follows intra-particle diffusion model and the adsorption rate is determined by more than one process. Thermodynamic study shows that the adsorption is an endothermic and spontaneous physisorption process.
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TL;DR: In this article, the bursting process in a U-shaped open-channel flume with the intention of investigating the bursting phenomena in the meander channel was investigated using the three-dimensional quadrant analysis.
Abstract: Experiments were conducted in a U-shaped open-channel flume with the intention of investigating the bursting phenomena in the meander channel. The experimental results of the secondary flow fields and the Reynolds shear stress distributions show that the velocity and velocity fluctuation in the transverse direction are not negligible. Moreover, the bursting process is investigated using the three-dimensional quadrant analysis, which is more accurate than using the traditional two-dimensional quadrant analysis for the meandering channel. It is obtained from the experimental results that the internal group of events occurs more frequently than the external group, particularly the internal ejection and internal sweep events. In addition, the transition probabilities of the movements, which are defined as the changes of events from the current situation to the next situation in a time series, show that the stable organizations of events are the most possible movements, whereas the cross organizations of events have the least possible movements.
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TL;DR: The results indicate that the HPLC-DAD method is simple, accurate and reproducible so that it can be used for the simultaneous determination of the five saponins in Chinese patent medicines containing the three kinds of herbs.
Abstract: To establish a method for determining five saponins (notoginsenoside R1, ginsenoside Rg1, ginsenoside Re, ginsenoside Rb1 and ammonium glycyrrhizinate) in Glycyrrhizae, Notoginseng and Ginseng, the high performance liquid chromatography with diode array detector (HPLC-DAD) method was applied to an Inertsil ODS-SP column (4.6 mm×250 mm, 5 μm) with a mobile phase consisting of acetonitrile-0.05% phosphoric acid in a gradient elution manner. The flow rate was 1.0 mL/min. The column temperature was 30 °C and the detection wavelengths were 203 nm and 237 nm, respectively. The linear ranges were 0.700 0–7.000 0 μg for R1 (r=1.000 0), 0.751 1–7.511 4 μg for Rg1 (r=1.000 0), 0.677 2–6.771 6 μg for Re (r=1.000 0), 0.733 9–7.339 1 μg for Rb1(r= 1.000 0), and 0.540 0–5.399 8 μg for ammonium glycyrrhizinate (r=0.999 9), respectively. In addition, their average recoveries were 100.28%, 105.83%, 104.09%, 99.36% and 98.54%, respectively. The relative standard deviations (RSDs) of precision, reproducibility and recovery were all less than 1.5%. The results indicate that the method is simple, accurate and reproducible so that it can be used for the simultaneous determination of the five saponins in Chinese patent medicines containing the three kinds of herbs.
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TL;DR: In this article, a digital image processing method was used to calculate the local deformations and local stresses for any region on the surface of triaxial soil specimens, and the results showed that the deformations were more uniform in the middle region compared with the entire specimen.
Abstract: A data processing method was proposed for eliminating the end restraint in triaxial tests of soil. A digital image processing method was used to calculate the local deformations and local stresses for any region on the surface of triaxial soil specimens. The principle and implementation of this digital image processing method were introduced as well as the calculation method for local mechanical properties of soil specimens. Comparisons were made between the test results calculated by the data from both the entire specimen and local regions, and it was found that the deformations were more uniform in the middle region compared with the entire specimen. In order to quantify the nonuniform characteristic of deformation, the non-uniformity coefficients of strain were defined and calculated. Traditional and end-lubricated triaxial tests were conducted under the same condition to investigate the effects of using local region data for deformation calculation on eliminating the end restraint of specimens. After the statistical analysis of all test results, it was concluded that for the tested soil specimen with the size of 39.1 mm × 80 mm, the utilization of the middle 35 mm region of traditional specimens in data processing had a better effect on eliminating end restraint compared with end lubrication. Furthermore, the local data analysis in this paper was validated through the comparisons with the test results from other researchers.
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TL;DR: In this paper, an equivalent visco-elastic model of saturated soft clay was studied under unconsolidated undrained (UU) condition, which can be used to evaluate the stability of ocean foundation.
Abstract: An equivalent visco-elastic model of saturated soft clay was studied under unconsolidated undrained (UU) condition, which can be used to evaluate the stability of ocean foundation. Cyclic triaxial compression and extension tests were conducted to study the parameters of the model. Results showed that the relationships of the damping ratio and the octahedral shear modulus with the octahedral cyclic shear strain were nearly unique, when the initial octahedral shear stress ratios of specimens were equal to 0.3, 0.5 and 0.7. The relationships of the damping ratio and the octahedral shear modulus with the octahedral cyclic shear strain determined from the cyclic triaxial compression tests were basically the same as those determined from the cyclic triaxial extension tests. Furthermore, the relationships were not related to the initial stress condition, the test stress state and the octahedral cyclic shear stress ratio. The relationships determined from the cyclic triaxial tests under no deviatoric stress were basically the same as those determined from the cyclic triaxial tests under deviatoric stress. The change of the octahedral cyclic accumulative strain with the number of cycles was unique under different tests stress states. An equivalent visco-elastic constitutive model of saturated soft clay under UU condition was initially established.
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TL;DR: In this paper, the safety and the fatigue comfort were compared between a domestic and a Japanese postal bicycle, and the results showed that the riding fatigue comfort of the Japanese bicycle is better than the domestic bicycle.
Abstract: The safety and the fatigue comfort were compared between a domestic and a Japanese postal bicycle. Firstly, the fatigue comfort of these two kinds of bicycles was evaluated by surface electromyographic signal (sEMG) experiment, in which human lower limb muscle groups were research objects, and the average EMG (AEMG) index and median frequency (MF) were chosen as the evaluation indexes. Secondly, the safety of these two kinds of bicycle frames was analyzed and compared by using the finite element analysis. The results show that the riding fatigue comfort of the Japanese postal bicycle is better, and the Japanese postal bicycle frame is more safe and reasonable although both the postal bicycles meet the requirement for strength. Finally, based on the above analysis, the frame structure and related parameters of the domestic postal bicycle were improved with reference to the Japanese postal bicycle and biomechanics theory.
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TL;DR: In this paper, a hybrid adaptive compensation control scheme is proposed to compensate the friction occurrence and other nonlinear disturbance factors that exist in the high-precision servo system, and the system can be treated as a simple linear model after being compensated, then the proportional derivative control law is applied to enhance the control performance.
Abstract: In this paper, a hybrid adaptive compensation control scheme is proposed to compensate the friction occurrence and other nonlinear disturbance factors that exist in the high-precision servo system. An adaptive compensation controller with a dual-observer structure is designed, while the LuGre dynamic friction model with non-uniform parametric uncertainties characterizes the friction torque. Considering the influence of the periodic disturbance torque and parametric uncertainties, fuzzy systems and a robust term are employed. In this way, the whole system can be treated as a simple linear model after being compensated, then the proportional-derivative (PD) control law is applied to enhancing the control performance. On the basis of Lyapunov stability theory, the global stability and the asymptotic convergence of the tracking error are proved. Numerical simulations demonstrate that the proposed scheme has potentials to restrain the impact of disturbance and improving the tracking performance.
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TL;DR: In this article, a two-shared pixel structure adopting two-stage charge transfer is introduced, together with the rolling shutter with an undersampling readout timing, which can reduce the addition operations by half in the pixel array.
Abstract: An addition scheme applicable to time-delay integration (TDI) CMOS image sensor is proposed, which adds signals in the charge domain in the pixel array. A two-shared pixel structure adopting two-stage charge transfer is introduced, together with the rolling shutter with an undersampling readout timing. Compared with the conventional TDI addition methods, the proposed scheme can reduce the addition operations by half in the pixel array, which decreases the power consumption of addition circuits outside the pixel array. The timing arrangement and pixel structure are analyzed in detail. The simulation results show that the proposed pixel structure can achieve the charge addition with negligible nonlinearity, therefore the power consumption of the periphery addition circuits can be reduced by half theoretically.
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TL;DR: A global image reconstruction scheme in ground texture surface using Fourier transform (FT) for damage detection for the ground texture surfaces of engineering ceramics has shown that the proposed method is effective.
Abstract: Ground textures seriously interfere with the exact identification of grinding damage. The common nondestructive testing techniques for engineering ceramics are limited by their difficulty and cost. Therefore, this paper proposes a global image reconstruction scheme in ground texture surface using Fourier transform (FT). The lines associated with high-energy frequency components in the spectrum that represent ground texture information can be detected by Hough transform (HT), and the corresponding high-energy frequency components are set to zero. Then the spectrum image is back-transformed into the spatial domain image with inverse Fourier transform (IFT). In the reconstructed image, the main ground texture information has been removed, whereas the surface defects information is preserved. Finally, Canny edge detection is used to extract damage image in the reconstructed image. The experimental results of damage detection for the ground texture surfaces of engineering ceramics have shown that the proposed method is effective.
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TL;DR: In this article, a scaled boundary finite element (SBFEM) is extended to predict the dynamic crack propagation in brittle materials, where the structure is firstly divided into a number of superelements, only the boundaries of which need to be discretized with line elements.
Abstract: The prediction of dynamic crack propagation in brittle materials is still an important issue in many engineering fields. The remeshing technique based on scaled boundary finite element method (SBFEM) is extended to predict the dynamic crack propagation in brittle materials. The structure is firstly divided into a number of superelements, only the boundaries of which need to be discretized with line elements. In the SBFEM formulation, the stiffness and mass matrices of the super-elements can be coupled seamlessly with standard finite elements, thus the advantages of versatility and flexibility of the FEM are well maintained. The transient response of the structure can be calculated directly in the time domain using a standard time-integration scheme. Then the dynamic stress intensity factor (DSIF) during crack propagation can be solved analytically due to the semi-analytical nature of SBFEM. Only the fine mesh discretization for the crack-tip super-element is needed to ensure the required accuracy for the determination of stress intensity factor (SIF). According to the predicted crack-tip position, a simple remeshing algorithm with the minimum mesh changes is suggested to simulate the dynamic crack propagation. Numerical examples indicate that the proposed method can be effectively used to deal with the dynamic crack propagation in a finite sized rectangular plate including a central crack. Comparison is made with the results available in the literature, which shows good agreement between each other.
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TL;DR: The proposed method is feasible and it obtains better effects than the fuzzy comprehensive evaluation method and fuzzy matter-element method, and the problem of less evaluation indexes and inapparent linear relationship is solved.
Abstract: A comprehensive evaluation model based on improved set pair analysis is established. Considering the complexity in decision-making process, the model combines the certainties and uncertainties in the schemes, i.e., identical degree, different degree and opposite degree. The relations among different schemes are studied, and the traditional way of solving uncertainty problem is improved. By using the gray correlation to determine the difference degree, the problem of less evaluation indexes and inapparent linear relationship is solved. The difference between the evaluation parameters is smaller in both the fuzzy comprehensive evaluation model and fuzzy matter-element method, and the dipartite degree of the evaluation result is unobvious. However, the difference between each integrated connection degree is distinct in the improved set pair analysis. Results show that the proposed method is feasible and it obtains better effects than the fuzzy comprehensive evaluation method and fuzzy matter-element method.