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Understanding of effects of water on crack propagation and crack failure modes of coal is important to determine the required width of the coal pillars in underground reservoirs and calculate the area of fractured zones containing flowing water. In this paper, we apply acoustic emission (AE) techniques, X-ray diffraction (XRD), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP), alongside uniaxial compressive tests to develop new insights into the mechanics of crack developments and failure modes of partially saturated coal samples with a range of moisture contents (0%, 6.00%, 9.75%, and 10.96%). We present new relationships between tensile/shear cracks and failure modes incorporating the effects of water intrusion on the micro-tensile/shear cracks and macro tensile/shear failure modes. The results show that the presence of hydrophilic illite (clay mineral) has strong influence on water absorption capacity of coal. The uniaxial compressive tests carried out in this study, show that the AE activity is mainly appeared after the crack damage threshold (point D) and it is independent to water content. The AE activity decreases with increasing moisture content as the water reduces the internal connections between the coal particles and increases the possibility of sliding failure. Studying the RA (rise time divided by peak amplitude) and AF values (counts divided by duration) demonstrated that the cracks generated in the coal samples consist of a large number of micro tensile and shear cracks, whilst tensile- or shear-only cracks were not found to be evident. For the samples studied, the higher moisture content is associated with the lower AF and higher RA values. Under the scope of the experimental investigations, we conclude that the higher moisture content corresponds to a lower number of total cracks and tensile cracks in coal. However, a greater proportion of shear cracks can be created by the increasing water content. Increasing the water level can reduce the number of tensile failure planes and the percentage of tensile failure planes against total failure planes. Therefore, the higher water content can increase shear failure planes and promote the possibility of shear failure in coal.

Failure envelope method is comprehensively used in failure mode prediction of multi-bolt composite joints. The method is based on the assumption that bolt load distribution proportion is constant till failure. However, bearing damage and net-section damage must have some influence on the load distribution and then change structure failure mode. In this paper, tensile experiments of two-bolt and three-bolt joints were conducted to obtain the failure modes and other properties. Three dimensional (3D) finite element models involving damage were constructed, and the results were consistent with experimental data. Then, the models were used to study the effect of damage on failure mode of multi-bolt composite joints. The results show that failure mode prediction with failure envelope method should involve the effect of composite damage. Compared with net-section damage, bearing damage has greater influence on failure mode. Based on conventional failure envelope method, a new evaluation procedure involving damage was proposed.

In this paper, tensile behavior of box-joint structure fabricated by resin transfer moulding (RTM) was investigated. A finite element model (FEM) of the box joint based on cohesive zone model was established to study the joint tensile behavior. Hashin failure criterion and degradation rules were applied to simulate damage modes and to predict failure strength. The FEM results show a good agreement with experimental results. Based on the model, the influences of bolt location and lap length on the joint tensile performances were analyzed. The results show that the delamination between the L-shape part and box-shape parts is the main failure mode. Bolt location affects the damage modes, ultimate load and structure stiffness of the joint, and longer lap length has a tendency to promote ultimate load and structure stiffness.

In this paper, tensile experiments were conducted into single-lap bolted joint between composite laminate and steel with countersunk fastener, and two three-dimensional explicit finite element models were developed using Abaqus/Explicit. Continuum shell elements (SC8R) were used to model in-plane ply failure with built-in damage model while cohesive elements were selected to predict interlaminar damage in model I. 8-node reduced integration solid elements (C3D8R) were chosen to model all the parts with 3D Hashin-type initiation criteria and Camanho degradation law implemented in a VUSDFLD subroutine in model II. The results simulated by both models accurately predicted the elastic loading response and captured overall damage profile compared with the experimental results. The numerical analysis using explicit solver provided acceptable accuracy which highlighted the robust nature and high computational efficiency without convergence issues compared with implicit solver. In addition, the effect of cohesive elements on computational efficiency was investigated to simplify the countersunk joints analysis.

Reversals of magnetization and exchange bias field were observed around 19 K in polycrystalline perovskite chromite YbCrO3. Both the reversals can be elucidated based on the antiferromagnetic interaction between the ferromagnetic component of Cr3+ moments and the Yb3+ moments. The low field magnetization exhibits a perfect linear correlation with the magnetization shift resulted from the exchange bias effect. Distinguished from other exchange bias systems, the dependence of HE at 10 K on the cooling field shows an almost undamped feature up to 85 kOe, indicating the stable exchange bias states in respective temperature region.

In order to maximize inventory benefits or minimize costs, reliability and cost of inventory control models need to be identified and analyzed. These importance measures are one important approach to recognize and evaluate system weaknesses. However, importance measures have fewer applications in inventory systems&rsquo, reliability. Considering the cost, this paper mainly discusses the reliability change of performance parameters with the importance measures in inventory systems. The calculation methods of differential importance and Birnbaum importance are studied in the inventory control model with shortages. By comparing the importance values of various parameters in the model, the optimization analysis of the inventory model can be used to identify the key parameters, so as to effectively reduce the total inventory cost. The importance order and the identification of key parameters are helpful to increase the operational efficiency of the inventory control and provide effective methods for improving the inventory management. Lastly, a case study with a shortage and limited inventory capacity is used to demonstrate the proposed model.

Background Arbutin is a plant-derived glycoside with potential antioxidant, antibacterial and anti-inflammatory activities. Currently, it is mainly produced by plant extraction or enzymatic processes, which suffers from expensive processing cost and low product yield. Metabolic engineering of microbes is an increasingly powerful method for the high-level production of valuable biologicals. Since Pseudomonas chlororaphis has been widely engineered as a phenazine-producing platform organism due to its well-characterized genetics and physiology, and faster growth rate using glycerol as a renewable carbon source, it can also be engineered as the cell factory using strong shikimate pathway on the basis of synthetic biology. Results In this work, a plasmid-free biosynthetic pathway was constructed in P. chlororaphis P3 for elevated biosynthesis of arbutin from sustainable carbon sources. The arbutin biosynthetic pathway was expressed under the native promoter Pphz using chromosomal integration. Instead of being plasmid and inducer dependent, the metabolic engineering approach used to fine-tune the biosynthetic pathway significantly enhanced the arbutin production with a 22.4-fold increase. On the basis of medium factor optimization and mixed fed-batch fermentation of glucose and 4-hydroxybenzoic acid, the engineered P. chlororaphis P3-Ar5 strain led to the highest arbutin production of 6.79 g/L with the productivity of 0.094 g/L/h, with a 54-fold improvement over the initial strain. Conclusions The results suggested that the construction of plasmid-free synthetic pathway displays a high potential for improved biosynthesis of arbutin and other shikimate pathway derived biologicals in P. chlororaphis. Electronic supplementary material The online version of this article (10.1186/s12934-018-1022-8) contains supplementary material, which is available to authorized users.

Shikimic acid is an important intermediate for the manufacture of the antiviral drug oseltamivir (Tamiflu®) and many other pharmaceutical compounds. Much of its existing supply is obtained from the seeds of Chinese star anise (Illicium verum). Nevertheless, plants cannot supply a stable source of affordable shikimate along with laborious and cost-expensive extraction and purification process. Microbial biosynthesis of shikimate through metabolic engineering and synthetic biology approaches represents a sustainable, cost-efficient, and environmentally friendly route than plant-based methods. Metabolic engineering allows elevated shikimate production titer by inactivating the competing pathways, increasing intracellular level of key precursors, and overexpressing rate-limiting enzymes. The development of synthetic and systems biology-based novel technologies have revealed a new roadmap for the construction of high shikimate-producing strains. This review elaborates the enhanced biosynthesis of shikimate by utilizing an array of traditional metabolic engineering along with novel advanced technologies. The first part of the review is focused on the mechanistic pathway for shikimate production, use of recombinant and engineered strains, improving metabolic flux through the shikimate pathway, chemically inducible chromosomal evolution, and bioprocess engineering strategies. The second part discusses a variety of industrially pertinent compounds derived from shikimate with special reference to aromatic amino acids and phenazine compound, and main engineering strategies for their production in diverse bacterial strains. Towards the end, the work is wrapped up with concluding remarks and future considerations.

Single lap bolted joints subjected to tensile load are essential joining methods in engineering design. Lateral displacement of the grip in single lap bolted joint experiment was examined and analyzed. This was different from early investigations that considered the joint fully gripped with no lateral degree of freedom. The lateral stiffness of the grip was tested to obtain the test machine properties. Tensile experiments on single lap composite-to-aluminum bolted joints were conducted, and the lateral displacement of the grip measured. Other measurements included tensile displacement, out-of-plane displacement, and surface strains. By allowing for lateral displacement, the novel finite element model predicted good results. The influence of lateral displacement of the grip was analyzed using the novel and traditional models. The novel model predicted 13 % smaller joint stiffness than traditional model. The parameters related to secondary bending were found different and the failure load of the joint was delayed because of lateral displacement of the grip.

This present work investigated the failure mechanism of a novel composite bolted π-joint subjected to bending load by experimental and finite element simulation. A test sample manufactured by resin transfer moulding process (RTM) was tested. A 3D progressive damage model developed in ABAQUS/Standard was used to simulate the failure of the π-joint. Based on good correlation of failure load and damage distribution between experimental results and FE prediction, further investigation was extended to the effect of two primary assembly clearances on mechanical behavior of the π-joint. The study results reveal that delamination of the fillet region in L-preform is the π-joint's failure mode. Moreover, the assembly clearances have little effect on the failure load of the joint.

Additional file 1. Additional Figure S1â S4 and Tables S1â S2. Table S1. Main primers designed and used in this study. Table S2. The corresponding accession numbers of nucleotide sequence data. Figure S1. Identification of arbutin by LC-MC analyses. Figure S2. The change of pH value of P3-Ar5 cultures in KBG medium. Figure S3. The arbutin titer of the plasmid-free strain P3-Ar5 after culturing for 1â 30 generations in KBG medium.

4-Hydroxybenzoic acid (4-HBA) has recently emerged as a promising intermediate for several value-added bioproducts with potential biotechnological applications in food, cosmetics, pharmacy, fungicides, etc. Over the past years, a variety of biosynthetic techniques have been developed for producing the 4-HBA and 4-HBA-based products. At this juncture, synthetic biology and metabolic engineering approaches enabled the biosynthesis of 4-HBA to address the increasing demand for high-value bioproducts. This review summarizes the biosynthesis of a variety of industrially pertinent compounds such as resveratrol, muconic acid, gastrodin, xiamenmycin, and vanillyl alcohol using 4-HBA as the starting feedstock. Moreover, potential research activities with a close-up look at the future perspectives to produce new compounds using 4-HBA have also been discussed.

Mn3O4 nanoparticles of different sizes were synthesized at low-temperature by a facile and simple auto-combustion method. Homogeneous potato-shaped grains with an average diameter of about 30, 60 and 90 nm were obtained. The ignition temperature has a significant influence on the particle size of the product. Magnetization of the Mn3O4 nanoparticles shows a ferrimagnetic behavior at low temperature. The coercivity is approximately four times larger than that of bulk Mn3O4 due likely to the particle size effect, which may also be responsible for the observed complex hysteresis that exhibits at least two different magnetic behaviors. This work offers an environmental friendly and industrially robust route towards tailored, uniform and high-quality Mn3O4 nanoparticles.

Glassy magnetic behavior and exchange bias phenomena are observed in single phase Mn3O4 nanoparticles. Dynamics scaling analysis of the ac susceptibility and the Henkel plot indicate that the observed glassy behavior at low temperature can be understood by taking into account the intrinsic behavior of the individual particles consisting of a ferrimagnetic (FIM) core and a spin-glass surface layer. Field-cooled magnetization hysteresis loops display both horizontal and vertical shifts. Dependence of the exchange bias field (H E) on the cooling field shows an almost undamped feature up to 70 kOe, indicating the stable exchange bias state in Mn3O4. H E increases as the particle size decreases due to the higher surface/volume ratio. The occurrence of the exchange bias can be attributed to the pinning effect of the frozen spin-glass surface layer upon the FIM core.

Promoter of alcohol oxidase I (PAOX1) is the most efficient promoter involved in the regulation of recombinant protein expression in Pichia pastoris (P. pastoris). PAOX1 is tightly repressed by the presence of glycerol in the culture medium; thus, glycerol must be exhausted before methanol can be taken up by P. pastoris and the expression of the heterologous protein can be induced. In this study, a candidate glycerol transporter (GT1, GeneID: 8197545) was identified, and its role was confirmed by further studies (e.g. bioinformatics analysis, heterologous complementation in Schizosaccharomyces pombe (S. pombe)). When GT1 is co-expressed with enhanced green fluorescent protein (EGFP), it localizes to the membrane and S. pombe carrying gt1 but not the wild-type strain can grow on medium containing glycerol as the sole carbon source. The present study is the first to report that AOX1 in the X-33gt1 mutant can achieve constitutive expression in medium containing glycerol; thus, knocking down gt1 can eliminate the glycerol repression of PAOX1 in P. pastoris. These results suggest that the glycerol transporter may participate in the process of PAOX1 inhibition in glycerol medium.

With an increasing emphasis on the emerging automatic handicap personal identification applications, living fingerprint-based identification and Smart cards are receiving a lot of attention. So as to achieve secure and reliable identity verification and the tracking of documentary files and stationary, the paper presents an identity verification unit and management system based on living fingerprint identification techniques and Internet of things (IOT). Additionally, for the goal of non-paper office, the unit resolves issues, e.g., the insecurity and simplex function in traditional identification unit, by providing professional function such as electronic seal.

In various physical science and social economic phenomena, the long memory processes are widely found and studied in scientific work on phenomena ranging from the microscopic to the cosmic. Utilizing the decorrelation property of wavelet to long memory processes, we improve on the traditional maximum likelihood estimation and present the multi-scale maximum likelihood estimation (MSMLE) which based on discrete wavelet transform and discrete wavelet packet transform respectively. Simulation results show that under certain precision demand, this improved approximate algorithm decreases the burden of computations greatly and can be used as an alternative of parameter estimation