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  • Author: Sheng Wang x
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The technology of preparing green coating by conducting micro-arc oxidation on AZ91D magnesium alloy

Abstract

Micro-arc oxidation was applied to AZ91D magnesium alloy by taking K2Cr2O7 as the colouring salt in the silicate system. It was shown that the green coating obtained through performing micro-arc oxidation on magnesium alloy consisted of Mg, Mg2SiO4, MgO, and MgCr2O4 based on analysis of X-ray diffraction (XRD), and scanning electron microscopy (SEM). Among which, MgCr2O4 was the colouring salt; there were something in the lamellar, pit, and convex forms found on the surface of the coating. The coating consisted of a porous, and a compact, layer from the outside to the inside. As demonstrated, the colour of the coating depended on the K2Cr2O7 concentration: it became gradually deeper with the addition of K2Cr2O7 and the increasing micro-arc oxidation time. The corrosion resistance and hardness of the green coating were greater than that of the matrix.

Open access
Analysing the environmental harms caused by coal mining and its protection measures in permafrost regions of Qinghai–Tibet Plateau

Abstract

The coal mining has brought a series of ecological problems and environmental problems in permafrost regions. Taking Muli coal-mining area as an example, this article attempts to analyse the environmental harms caused by coal mining and its protection measures in permafrost regions of Qinghai–Tibet Plateau. This article analyses the influence of open mining on the surrounding permafrost around the open pit by using the numerical simulation. The results show that (1) based on the interrelation between coal mining and permafrost environment, these main environmental harm include the permafrost change and the natural environment change in cold regions; (2) once the surface temperature rises due to open mining, the permafrost will disappear with the increase of exploitation life. If considering the solar radiation, the climate conditions and the geological condition around the pit edge, the maximum thaw depth will be more than 2 m; (3) the protection measures are proposed to avoid the disadvantage impact on the permafrost environment caused by coal mining. It will provide a scientific basis for the resource development and environment protection in cold regions.

Open access
A Method for Monitoring the Underground Mining Position Based on the Blasting Source Location

Abstract

Some small and medium-sized coal mines are mining beyond their mining boundary driven by profit. The illegal activities cause many mine disasters but effective supervision is very hard to achieve, especially for underground coal mining. Nowadays, artificial blasting operation is widely used in tunneling or mining in small and medium-sized coal mines. A method for monitoring the underground mining position by monitoring the blasting source position is firstly introduced in this paper. The blasting vibration waves are picked up by the detectors and dealt by the signal acquisition sub-station, and then sent to the principal computer. The blasting source is located by the principal computer and displayed in the mine’s electronic map. The blasting source position is located in 10 seconds after the first P wave reaching the detector, whose error is registered within 20 meters by field-proven method. Auto-monitoring of the underground mining position in real-time is solved better and management level is improved using this method.

Open access
Endoscopic Ultrasound-guided Gastroenterostomy: A Promising Alternative to Surgery

Abstract

Recently, with the advancement of techniques, endoscopic ultrasound-guided therapies have shown distinct advantages, especially in relieving benign and malignant gastric outlet obstruction (GOO), as well as in postoperative pancreaticobiliary diseases. Herein, we present five currently used approaches in endoscopic ultrasound-guided gastroenterostomy (EUS-GE) using lumenapposing biflanged metal stents (LAMS), along with several examples of LAMS-based EUS treatment of pancreaticobiliary diseases. Compared with traditional treatment methods, EUS-guided procedures have – to some degree – shown higher success rates, both technical and clinical. Moreover, EUS-guided therapies reduce the risk of multiple surgical adverse events, including delayed gastric emptying, prolonged hospital stay, increased costs, and delay in cancer treatment. Particularly in terms of postoperative pancreaticobiliary diseases, EUS-guided therapy has assumed an essential role as a treatment option in cases where traditional methods are difficult to perform. Nevertheless, EUS-guided gastrointestinal procedures are still relatively new, with some clinical failures, and additional prospective clinical trials are warranted.

Open access
Brief communication (Original). Pulmonary embolism in patients with chronic obstructive pulmonary disease and exacerbations of unknown origin

Abstract

Background: Despite important advances in the diagnosis and treatment of acute pulmonary embolism (APE), diagnosis of pulmonary embolism (PE) is difficult in patients with chronic obstructive pulmonary disease (COPD) and exacerbation.

Objective: We evaluated PE in patients with chronic obstructive pulmonary disease and exacerbations of unknown origin.

Methods: Two-hundred and eight patients with COPD and severe exacerbations were studied. All patients had CT pulmonary angiography (CTPA) and lower limb ultrasonography. Arterial blood gas measurements, D-dimers and endothelin-1 (ET-1) levels were recorded.

Results: The frequency of PE was 33%. The following were more common in the PE group (χ2 = 4.32-6.79, mean p < 0.05): immobilization ≥ 7 days; a ≥ 1 cm difference in edema of the lower limbs; deep venous thrombosis; syncope; S1Q3T3 syndrome; and a decrease in PaCO2 ≥ 5 mm Hg. Plasma D-dimers and ET-1 levels were significantly higher in the PE group. Risk factors identified from logistic regression analysis were immobilization ≥ 7 days, ≥ 1 cm difference in lower limb edema, and deep venous thrombosis.

Conclusions: Overall, 33% of 208 patients had a PE, and the risk was greater in those who had been immobilized, those who had a ≥ 1 cm difference in edema of the lower limbs, and those who had a deep venous thrombosis.

Open access
The relationship between human muth homolog 1 gene mutation at site 415 and sporadic colon cancers in Chinese Han population

Abstract

Background: The genetic factors of colon cancer play an important role in the tumor development and growth. The incidence of colon cancers has greatly increased in China. However, few data is available for the relationship between human muth homolog 1 (hMLH1) gene mutation at site 415 and sporadic colon cancers in Chinese population. Objective: Investigate the relationship between G→C mutation in hMLH1 gene at site 415 and sporadic colon cancers in Chinese Han population. Methods: Using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing techniques, the genotype of the hMLH1 gene was analyzed at site 415 in 97 cases of sporadic colon cancer patients and 138 controls. Reverse-transcription (RT)-PCR was used to determine the level of hMLH1 mRNA expression in normal colonic mucosa of patients with different genotype. Results: The frequency of genotype C/C at the 415 site of the hMLH1 gene was significantly higher in colon cancer patients than in controls. The expression levels of hMLH1 mRNA in normal colonic mucosa were similar in colon cancer patients with different genotypes. Conclusion: G’!C mutation in hMLH1 gene at site 415 may represent a genetic factor that is associated with sporadic colon cancer in a small group of Chinese Han population.

Open access
Dynamic response analysis of light weight pyramidal sandwich plates subjected to water impact

ABSTRACT

The fluid-solid interaction (FSI) dynamic responses for a Light Weight Pyramidal Sandwich Plate Structure (LWPSPS) under different water-entry velocities (1m/s-6m/s) are investigated numerically and theoretically. The characteristics of impact pressure and structure deformation are obtained by using LS-DYNA code based on the proposed 3D multi-physics (air-water-solid) FEM model. Numerical results show that the average water impact pressure of LWPSPS is much lower than that of the monolithic plate with same mass. Moreover, a phenomenon called “local air cushion” is observed for LWPSPS which does not exist for a monolithic plate. Theoretical hydroelasticity analysis demonstrates that the FSI effect of LWPSPS is weak when the ratio of water impact duration time to wet natural vibration period is greater than 4. In the study, an engineering estimation method to predict the maximum deformation of the LWPSPS is proposed, in which the total deformation is divided into two parts, i.e. local field deformation and global field deformation, and they are both computed using analytical model. Good agreement between the numerical results and ones obtained from the proposed engineering estimation method is achieved. Furthermore, the geometric variation sensitiveness analysis is also conducted.

Open access
Iterative methods for zero points of accretive operators in Banach spaces

Abstract

The purpose of this paper is to consider the problem of approximating zero points of accretive operators. We introduce and analysis Mann-type iterative algorithm with errors and Halpern-type iterative algorithms with errors. Weak and strong convergence theorems are established in a real Banach space. As applications, we consider the problem of approximating a minimizer of a proper lower semicontinuous convex function in a real Hilbert space

Open access
Microsatellites Reveal Clonal Growth and Genetically Distinct Groups in Cryptocarya chinensis in Fragmented Lower Subtropical Forest, China

Abstract

The lower subtropical monsoon evergreen broadleaved forest in South China (about 22° ~ 24° N) has a high conservation status, because of its uniqueness and high biodiversity. During the last few decades, most of these forests have been destroyed, and the remaining are being degraded by fragmentation. However, genetic information concerning the effects of fragmentation is currently lacking for plant species in these forests. In this study, therefore, eight microsatellites were used to study six Cryptocaya chinensis fragmented populations in Guangdong Province South China, and the results revealed a complex pattern of genetic variation within and among C. chinensis populations. Firstly, genetic variations demonstrate hitherto undetected clonal growth in C. chinensis. Secondly, current population structure of C. chinensis reflects an interaction between ancient homogeneous level of genetic variation and contemporary bottleneck via fragmentation. Small populations maintain substantial genetic variation of the initial populations through clonal growth, and do not show genetic depauperation compared to larger populations. Finally, two genetically distinct groups (West and Middle- East groups) are found in this area, connected by highly mixed contact zone.

Open access