Nonlinear Ultrasonic C-Scan Imaging for Contact-Type Defects in Diffusion-Bonded Joints-A Case Study.

Diffusion bonding technology is widely used in the connection of precision components, yet accurately and reliably detecting contact-type defects on the bond interface still remains a significant problem. Nonlinear ultrasonic methods have been proven to be sensitive to contact-type defects; however, the use of continuous wave or tone burst wave excitation limits its wider application. In this paper, dual-probe nonlinear ultrasonic testing with pulse wave excitation is proposed to detect contact-type defects in diffusion-bonded joints. A titanium alloy diffusion-bonded specimen with artificial defects was fabricated, and the corresponding detection device was designed based on the existing ultrasonic C-scan testing system. A C-scan imaging program based on nonlinear parameters was developed by extracting the fundamental and second harmonic waves of the reflection echo on the bond interface. The results demonstrated that the proposed detection scheme can obtain the nonlinear parameters of diffusion-bonded interfaces, and the nonlinear ultrasonic C-scan image of the bond interface is also obtained. The nonlinear parameter in the contact-type defects areas calculated from the bond interface echo is about 10 times (20 dB) higher than that in macro defects areas, whose gap is about 10 µm. The results indicate that the nonlinear ultrasonic methods seem to be more sensitive to contact-type defects and have a great potential to complement the insufficient detection capability of linear ultrasound for diffusion-bonded joints.

[Capacity of Caragana microphylla shrub on counteracting snow movement and its influence on snow morphology in the Xilinhot Steppe, China.] / é”¡æž—æµ©ç‰¹è‰åŽŸå°å¶é”¦é¸¡å„¿çŒä¸›çš„é˜»é›ªèƒ½åŠ›åŠå ¶å¯¹ç§¯é›ªå½¢æ€çš„å½±å“.

The aim of this study was to examine the impacts of characteristics of the shrub (shrub height, shrub width on the windward side, shrub length on the downwind side) on the snow morphology (snow height, snow width, and snow tail length) in the typical steppe of Xilinhot, China. The relationship between shrub height and parameters of snow morphology showed significant quadratic polynomial regression. The relationship between shrub width on the windward side, length on the downwind side and parameters of snow morphology showed significant power function (exponent was less than 1). The morphology and development characteristics of shrub snow were affected by the shrub characteristic parameters. Shrub height had the greatest influence on snow height. Shrub width at the windward side had the greatest influence on snow width and snow tail length. The snow morphology developed faster when the shrub was small, and then tended to be stable. The two-dimensional snow retention range model of shrub directly reflected the disturbance range of shrub to wind and the potential range of snow, indirectly reflected the capacity of shrub to retard snow movement. The three-dimensional snow blocking volume model of shrub snow directly reflected the snow resistance capacity of shrub under certain snow sources and wind conditions. Both models established here would provide a theoretical basis for estimating snow resources and preventing snow disaster in the wind blown snow area of typical steppe.

[Endemic situation of schistosomiasis in a surveillance site of river and lake regions in Haining City, 2012-2014].

OBJECTIVE: To understand the endemic dynamics and situation of schistosomiasis in a provincial surveillance site in Haining City, Zhejiang Province. METHODS: The Oncomelania hupensis snail status, schistosome infection situations of permanent residents and floating population in Qinmin Village, Haining City were monitored from 2012 to 2014 according to The Surveillance Programs of Schistosomiasis in Surveillance Sites of Zhejiang Province. RESULTS: Totally 600 permanent residents were examined from 2012 to 2014. The total positive rate of the serum antibody against Schistosoma japonicum was 3.17% (19/600). The rates in each year were 2.50% (5/200), 0 (0/200), and 7.00% (14/200), respectively, and the rate in 2014 were significantly higher than that in 2013 (χ2 = 14.508, P < 0.01), but no positives were found in the fecal examination. Totally 1 591 floating population were involved in the surveillance, the positive rate of serum antibody were 0.94% (15/1 591). The rates in active surveillance and passive surveillance were 0.92% (14/1 521) and 1.43% (1/70), respectively, and there were no statistically significant difference between them (χ2 = 1.659, P > 0.05). The positive rates of serum antibody among each year were 1.50% (8/534), 0.56% (3/531), and 0.76% (4/526), respectively, and the difference was not statistically significant (χ2 = 2.752, P >0.05), but no positives were found in the fecal examination. The snail surveillance showed that there were no environments with infected snails and imported snails. CONCLUSIONS: There exist the infection sources of schistosomiasis in Haining City. Therefore, we should be on high alert for the potential of local endemic of the disease. Meanwhile, we still should strengthen the snail surveillance as well as the infection surveillance among the floating population.

[Investigation of the characteristics of HCV genotypes of Han and Korean in Yanbian area of Jilin province].

OBJECTIVE: To investigate the characteristics of HCV genotypes of Han and Korean in Yanbian area of Jilin Province. METHODS: The HCV RNA load and genotypes of the 119 chronic hepatitis C patients in Yanbian area of Jilin Province were determined by real-time PCR and LiPA. The differences of the HCV genotypes in Han and Korean cases, in severity of the diseases, in HCV-RNA load, and in the relation with type 2 diabetes mellitus were analyzed. RESULTS: There was no significant difference in the distribution of each HCV genotype between Han and Korean patients (P > 0.05) with chronic hepatitis C. The difference between HCV genotype and HCV-RNA load was not significant (P > 0.05). With and without type 2 diabetes mellitus in these patients. The distribution of HCV genotype was also not significantly different (P > 0.05). The type 1b of HCV genotype in the moderate to severe chronic hepatitis C patients accounted for 58.06%. It was different compared with mild chronic hepatitis C patients (P < 0.05). CONCLUSION: 1) The type 1b is the most popular HCV genotype in Yanbian area of Jilin Province, type 2a is the second and there are still a few other genotypes. 2) There is no significant difference in the distribution of HCV genotypes between Han and Korean cases. 3) The HCV genotypes has nothing to do with the load of HCV-RNA. 4) The distribution of HCV genotypes in chronic hepatitis C patients with and without diabetes mellitus is not significantly different. 5) Type 1b of HCV infection is relatively severe.

Investigation of the characteristics of HCV genotypes of Han and Korean in Yanbian area of Jilin province / 中华实验和临床病毒学杂志

<p><b>OBJECTIVE</b>To investigate the characteristics of HCV genotypes of Han and Korean in Yanbian area of Jilin Province.</p><p><b>METHODS</b>The HCV RNA load and genotypes of the 119 chronic hepatitis C patients in Yanbian area of Jilin Province were determined by real-time PCR and LiPA. The differences of the HCV genotypes in Han and Korean cases, in severity of the diseases, in HCV-RNA load, and in the relation with type 2 diabetes mellitus were analyzed.</p><p><b>RESULTS</b>There was no significant difference in the distribution of each HCV genotype between Han and Korean patients (P > 0.05) with chronic hepatitis C. The difference between HCV genotype and HCV-RNA load was not significant (P > 0.05). With and without type 2 diabetes mellitus in these patients. The distribution of HCV genotype was also not significantly different (P > 0.05). The type 1b of HCV genotype in the moderate to severe chronic hepatitis C patients accounted for 58.06%. It was different compared with mild chronic hepatitis C patients (P < 0.05).</p><p><b>CONCLUSION</b>1) The type 1b is the most popular HCV genotype in Yanbian area of Jilin Province, type 2a is the second and there are still a few other genotypes. 2) There is no significant difference in the distribution of HCV genotypes between Han and Korean cases. 3) The HCV genotypes has nothing to do with the load of HCV-RNA. 4) The distribution of HCV genotypes in chronic hepatitis C patients with and without diabetes mellitus is not significantly different. 5) Type 1b of HCV infection is relatively severe.</p>

[Spatial structure of Quercus mongolica forest in Beijing Songshan Mountain Nature Reserve].

Based on the survey data of a 0.6 hm2 plot in Songshan Mountain Nature Reserve, and by using the uniform angle index, neighborhood comparison and mingling degree, this paper analyzed the spatial structural characteristics of Quercus mongolica forest in the Reserve. There were 10 populations in the tree layer of the forest, among which, Q. mongolica had the obvious advantage in population density and basal area, being the dominant and constructive species of the tree layer. The average mingling degree of the forest was 0.299, suggesting the low mingling degree of stands. The dominant species was mainly none- or less-mixed, while the accompanying species were generally well-mixed. In the spatial structural units, Q. mongolica and Pinus tabulaeformis populations were mainly of dominant, sub-dominant, and intermediate trees, accounting for 68% and 58% of the total plants of the populations, respectively, while the advantages of other populations were not obvious, being mostly of suppressed trees. The spatial pattern of the stands was of aggregative distribution, but the aggregation degree was not high and the aggregation scale was not large.

Nonparaxial multi-Gaussian beam models and measurement models for phased array transducers.

A nonparaxial multi-Gaussian beam model is proposed in order to overcome the limitation that paraxial Gaussian beam models lose accuracy in simulating the beam steering behavior of phased array transducers. Using this nonparaxial multi-Gaussian beam model, the focusing and steering sound fields generated by an ultrasonic linear phased array transducer are calculated and compared with the corresponding results obtained by paraxial multi-Gaussian beam model and more exact Rayleigh-Sommerfeld integral model. In addition, with help of this novel nonparaxial method, an ultrasonic measurement model is provided to investigate the sensitivity of linear phased array transducers versus steering angles. Also the comparisons of model predictions with experimental results are presented to certify the accuracy of this provided measurement model.