Microbial Evaluation of Meat Contact Surfaces in Red Meat Abattoirs of Bauchi State, North-Eastern Nigeria

Microbial quality (MQ) of meat contact surfaces (MCS) of six major abattoirs was evaluated with a subsequent further isolation and identification of E. coli O157. Two hundred and forty 240 swab samples (SS) from MCS that include cutting equipment, floor, tables and transport media were collected for total aerobic plate count and isolation of E. coli O157. Results of the SS indicated a mean value 7.1 ± 0.3 log10 cfu/cm2. A minimum value of 6.4 ± 0.6 log10 cfu/cm2 was recorded oncutting instrument from Ningi abattoir, while a maximum value of 7.8 ± 0.3 log10 cfu/cm2 was obtained from tables at Darazo abattoir. Only 3 (1.2%) of the 240 SS of the MCS were positive for E. coli O157 using the latex agglutination kit (Difco, Michigan, USA).

Research on the influence of contact surface constraint on mechanical properties of rock-concrete composite specimens under compressive loads

The contact form of rock-concrete has a crucial influence on the failure characteristics of the stability of rock-concrete engineering.To study the influence of contact surface on the mechanical properties of rock-concrete composite specimens under compressive loads,the two different contact forms of rock-concrete composite specimens are designed,the mechanical properties of these two different specimens are analyzed under triaxial compressive condition,and analysis comparison on the stress-strain curves and failure forms of the two specimens is carried out.The influence of contact surface constraint on the mechanical properties of rock-concrete composite specimens is obtained.Results show that the stress and strain of rock-concrete composite specimens with contact surface constraint are obviously higher than those without.Averagely,compared with composite specimens without the contact surface,the existence of contact surface constraint can increase the axial peak stress of composite specimens by 24%and the axial peak strain by 16%.According to the characteristics of the fracture surface,the theory of microcrack development is used to explain the contact surface constraint of rock-concrete composite specimens,which explains the difference of mechanical properties between the two rock-concrete composite specimens in the experiment.Research results cannot only enrich the research content of the mechanics of rock contact,but also can serve as a valuable reference for the understanding of the corresponding mechanics mechanism of other similar composite specimens.

Research on fatigue evaluation method of high-speed train axle based on axle box acceleration

As a key safety component of the high-speed train, fatigue fracture of the axle would lead to major accidents such as derailment or overturning. The complexity of the axle dynamic stress test seriously enhances the difficulty of axle fatigue damage analysis. In this paper, the dynamic stress test of the high-speed train axle was carried out,the axle box acceleration was monitored on-track during the test, and the relationship between the axle stress spectrum and acceleration was analyzed on-track. The results show that the relationships between the axle equivalent stresses and the Root Mean Square(RMS) values of the axle box vertical acceleration and lateral acceleration exhibit a strong joint probability density distribution. The concept of the virtual surface density of wheel-rail contact is also proposed to realize the purpose of using axle box acceleration to deduce axle equivalent force. The results quantify the relationship between axle box acceleration and axle equivalent force, provide a new method for predicting the axle damage using the acceleration RMS values, and open up a new approach for structural health monitoring of high-speed train axles.

Effects of internal factors on surface wettability of corn stalk rind

Corn stalk is one of heterogeneous materials with anisotropy and variability.As the rind of corn stalk consists of rich lignin and cellulose similar to wood properties,and possessing high mechanical strength,then can be used as raw material of stalk artificial board and paper.The corn stalk rind has significant differences in fiber morphology,chemical composition and mechanical properties at different heights.Nano-SiO2 composite material contained in the epidermis of corn stalk rind is not conducive to exert adhesive into a board.To study board-making technology by intact corn stalk rind,the wettability of corn stalk rind at different sampling heights is necessary to be analyzed by keeping or removing the epidermis.To analyze the surface wettability difference,the contact angle with water,element compositions and the chemical compositions of corn stalk rind at different sampling heights were studied before and after removal of epidermis.A Fourier transform infrared(FTIR)analysis was performed.The results showed that the removal of the epidermis could significantly improve the hydrophilicity of corn stalk rind.Before removal of the epidermis,the varying contents of elements including C and Si dominate the surface wettability differences at different sampling heights of corn stalk.With an increase in the sampling height,the mass fraction of C increases while that of Si decreases,which result in increasing hydrophilicity.After removal of the epidermis,the surface wettability of corn stalk rind is mainly determined by the mass fraction of hemicellulose,and the higher the sampling height,the larger the mass fraction of hemicellulose resulting in the increase of hydrophilicity.

Rate-, state-, and pressure-dependent friction model based on the elastoplastic theory

Adhesion is one of essences with respect to rubber friction because the magnitude of the friction force is closely related to the magnitude of adhesion on a real contact area. However, the real contact area during sliding depends on the state and history of the contact surface. Therefore, the friction force occasionally exhibits rate-, state-, and pressure dependency. In this study, to rationally describe friction and simulate boundary value problems, a rate-, state-, and pressure-dependent friction model based on the elastoplastic theory was formulated. First, the evolution law for the friction coefficient was prescribed. Next, a nonlinear sliding surface (frictional criterion) was adopted, and several other evolution laws for internal state variables were prescribed. Subsequently, the typical response characteristics of the proposed friction model were demonstrated, and its validity was verified by comparing the obtained results with those of experiments conducted considering the contact surface between a rough rubber hemisphere and smooth acrylic plate.