Applied Mechanics and Materials Vol. 302

Abstract: A new model was built to predict hydrogen element in coal-fired based on partial least squares regression algorithm, in which there were 4 input vectors, which were the moisture, ash content, volatile matter and low calorific value, and one output vectors, which was the hydrogen element. By comparison of the predicted and experimental results of test samples, the maximal relative error of the model was less than 10.0%, so, the partial least-squares regression algorithm model is reasonable and feasible. It provides an effective method for the operation personnel to anticipate the hydrogen element under conditions of known coal industrial analysis component.

Abstract: In this paper, the theophylline(TP)-nicotinamide(NCT) cocrystal was chosenas an example for studying the preparation analysis-identification and thermodynamic analysis of cocrystal systems. TP-NCT cocrystal was prepared by the methods of grinding, gringding, slurry and evaporation crystallization respectively. The dependence of the cocrystal solubility on the concentration of cocrystal components in solution were measured and correlatedby cocrystal solubility product. The results indicatethatTP and NCT do not ionize or form complexes in ethanol, and with the temperature increasing, both the solubility of theTP-NCTcocrystal and the solubility product increase.Finally, the ternary phasediagrams for the system of TP-NCT-ethanol at (298.15 and 308.15) K, which can provide the theoretical basis forcrystallization processes, are presented.

Abstract: The grain boundary segregation of carbon atoms is influenced by grain size and annealing condition. Increasing grain size and improving the final cooling ( ＜400 oC) rate can improve the bake hardening property, due to the decreasing of carbon segregation at grain boundaries. Cooling rates have a great effect on bake hardening property of ULC steel with smaller grains

Abstract: When fabricating a small diameter arterial prosthesis, the performance requirements include controlling dimensions, maintaining a uniform structure, ensuring superior mechanical properties as well as excellent biocompatibility. Material selection and fabricating methods can influence these factors. In this study, three 100% polyester prostheses, three bicomponent polyester/silk prostheses and three 100% silk prostheses were woven into seamless tubular prototype prostheses with three different basic weaves. After degumming/scouring they met the target inner diameter of 3.83 ± 0.30 mm which demonstrates that weaving is a precise and accurate way to manufacture small caliber arterial prostheses. In conclusion, the woven samples had a uniform wall structure along their strength and a range of low water permeability values and probe bursting strengths depending on their cover factor.

Abstract: In order to improve the magnetic properties, copper was added to cold-rolled non-oriented electrical steel with low carbon and low silicon. The grain sizes and precipitates in hot-rolled bands of the investigated steel were quantitatively studied. The results show that the recrystallization of deformed grains has been completed in the coiled bands and the recrystallized grains are fine due to low coiling temperature and pinning effect of precipitates. But grains grew up obviously after normalizing annealing at 850°C for 1h because the mobility of grain boundary is so good at elevated temperature that pinning effect of precipitates can’t prevent the migration of grain boundary. Thus, normalizing annealing is necessary to obtain large grains in hot-rolled band. In addition, the typical morphologies of precipitates in hot-rolled bands are square, rectangular, hexagonal and triangular and they are identified as AlN phase based on EDS and SEAD analysis, which can form by epitaxial growth mode. For the hot-rolled bands coiled at 550°C, the increase of average size and volume fraction of AlN particles with coiling time is mainly related to the growth of AlN particles, whereas for the hot-rolled bands coiled at 650°C, the decrease of average size and the increase of volume fraction of AlN particles with coiling time are chiefly attributed to the precipitation of many small AlN particles. The volume fraction of AlN particles increases with coiling temperature because they precipitate more quickly at 650°C than at 550°C.

Abstract: As a novel Cu-IUD material, it is necessary for copper/low-density polyethylene (Cu/LDPE) porous composite to have some suitable mechanical properties if it is used to prepare a clinical Cu-IUD with frame. However, it is not clear how the porosity of the porous structure affects the mechanical properties of Cu/LDPE porous composites. Therefore, the influence of the porosity of porous structure on the mechanical properties of Cu/LDPE porous composites is investigated in the present paper. The results show that the porosity has significant effects on the mechanical properties of Cu/LDPE porous composites. The mechanical properties of the Cu/LDPE porous composites decrease with the increasing of porosity, for the effective load area decreases, the chance for occurrence of cracks increases and the crystallinity degree of LDPE matrix increases with the increasing of porosity. These results are very important and they can be applied to guide the design of Cu/LDPE porous composite IUD for use in the future clinical application.

Abstract: In order to investigate the susceptibility of HSLA steels to hydrogen embrittlement (HE) when cathodic protection system was applied, a new electrochemical hydrogen permeation test method was performed to measure the hydrogen permeation current behavior through X65 steel and X80 steel in artificial seawater with different polarized potentials. Besides, slow strain rate test (SSRT) was introduced to study the effect of penetrated hydrogen atoms on the HE susceptibility of the steels. Results showed that with the decrease of the polarized potential, the sub-surface hydrogen concentration in the steels became higher and higher, and the corresponding HE susceptibility increased as well. What’s more, the X80 steel was more vulnerable to HE, and that owns to the minor grain size and M-A microstructure, which may trap more hydrogen atoms, and thus led to the HE susceptibility difference between the two steels. All these findings would be used as guidance when cathodic protection were carried out for offshore HSLA steel structures.

Abstract: In this study, we have compared the efficiency of the short time Fourier transform (STFT) and autoregressive modelling (AR) and autoregressive moving average (ARMA) of the femoral Doppler artery ultrasonic signals, in order to determine the spectral broadening index (SBI). Our aim is to detect the impact of the two modelling approaches on sonograms and of power spectral density- frequency diagrams obtained from femoral arterial Doppler Signals. The sonograms have been then used to compare the methods in terms of their frequency resolution and effects in determining the stenosis of femoral artery. In this paper we have used generated frequency envelopes from the Doppler spectrum to determine an index showing the degree of severity of stenosis cases. This index called broadening spectral index is calculated for various real cases.

Abstract: Since there has been a rapid progress to understand the dynamics of an offshore floating body under an ocean environment, we undertake to generate the ocean waves in a lab-scale wind-wave flume. The study is aiming to observe and optimize the similar ocean environmental condition as input wave and to reduce the wall reflective wave. Several absorption methods are suggested to optimize the propagate wave by measuring the maximum and minimum of the standing wave envelope. There has been no optimized absorption method, as they highly depend on the wave period and the wave length. One of the methods - two fixed wave gauges measuring two wave heights and one wave phase - is applied in this study. In the present paper various approaches were used to analyze the results using the flume, by position of probes, with absorber and without absorber, different position, condition and angle of the wave absorber, This paper also focuses on the analysis of fundamental equations which describe the separating method of the incident and reflective wave, and finally we confirm that the wave absorber is highly efficient considering all the permutation and combination.From the study it is clear that there is a change in the wave amplitude at the receiving end then the generated end; wave absorber is a strong source to control the energy of the coming wave. With the changing the period of the wave, the reflectance is increasing when the period becomes larger.

Abstract: In practice, most mechanical and electrical products life obeys Weibull distribution.This paper based on the relationship between Weibull distribution and exponential distribution, improved the point estimate of characteristic life during the normal stress and enhanced the precision of analysis. The point estimate of the shape parameter under normal stress level was presented, when the assumption that the shape parameter under different stress levels keeps invariable was got rid of. Meanwhile, a means was put forward to give interval estimation of the Weibull distribution parameter and the lower confidence limit of the reliability. Finally, an example of the mechanical and electrical product’s constant-stress accelerated life test was given and proved that the proposed approach is accuracy. It should be valuable for implement of engineering.