Search

In order to elucidate the effect of cooling rate on the carbide formation during the solidification process of high manganese steel Mn13, the solidification process is artificially divided into two stages, namely the liquid-solid phase transition stage and solid-state cooling stage. The final Mn13 samples with different cooling rates are used to the analysis of solidification structure and carbides by high-temperature confocal microscopy (HTCLSM), optical microscopy (OM), electron backscatter diffraction (EBSD), and scanning electron microscopy (SEM). The result shows that the change of cooling rate at the liquid-solid phase transition stage has a great influence on the solidification structure and carbide precipitation. At this stage, with the increase of cooling rate from 0.2 °C/s to 5.0 °C/s, the dendrite structure is obviously refined, and the secondary dendrite arm spacing and cooling rate are satisfied with the relationship: λΠ=54.14×v−0.33. Also, the average grain size in the Mn13 sample decreases from 549 μm to 346 μm, and the aspect ratio of gains in the Mn13 sample increases from 1.7 to 2.0. Moreover, the distribution of carbide in the interdendritic regions and grain boundaries increases, and the morphology of carbide at the grain boundary change from block to dendrite. But it seems that the change of cooling rate from 1 °C/s to 5.0 °C/s at the solid-state cooling stage has a slight effect on the secondary dendrite arm spacing, the average size and aspect ratio of the grain structure and the amount and morphology of carbide precipitation at the grain boundary. more...

The damage evolution process of non-penetrating cracks often causes some unexpected engineering disasters. Gypsum specimens containing non-penetrating crack(s) are used to study the damage evolution and characteristics under cyclic loading. The results show that under cyclic loading, the relationship between the number of non-penetrating crack(s) and the characteristic parameters (cyclic number, peak stress, peak strain, failure stress, and failure strain) of the pre-cracked specimens can be represented by a decreasing linear function. The damage evolution equation is fitted by calibrating the accumulative plastic strain for each cycle, and the damage constitutive equation is proposed by the concept of effective stress. Additionally, non-penetrating cracks are more likely to cause uneven stress distribution, damage accumulation, and local failure of specimen. The local failure can change the stress distribution and relieve the inhibition of non-penetrating crack extension and eventually cause a dramatic destruction of the specimen. Therefore, the evolution process caused by non-penetrating cracks can be regarded as one of the important reasons for inducing rockburst. These results are expected to improve the understanding of the process of spalling formation and rockburst and can be used to analyze the stability of rocks or rock structures. more...

The bulge formed joint is a novel free-form surface thin-wall joint structure used in truss structure systems, and its shape characteristics strongly influence the bearing capacity of the structure. The isogeometric analysis method provides a new way to analyze and optimize these free-form surface structures. To enhance the aesthetic appearance, such as the smoothness of the form, and increase the bearing capacity of the structures, an optimal design method for the bulge formed joint based on isogeometric analysis is proposed in this paper. This paper proposes a joint shape evaluation index based on NURBS surface characteristics. It establishes an optimization model for shell surface shape within the isogeometric analysis framework, derives an analytical expression for the sensitivity of design variables, and employs h-refinement to propagate sensitivity across multiple mesh models. The optimization design of joint configuration is realized by combining the moving asymptote method. The optimization results of the T-type and K-type bulge formed joints show that the mechanical properties and morphological smoothness of the free-form surface joint are improved. more...

During the continuous casting process of low carbon steel, the solidified hook formed in the mold has great effects on the surface quality of the cast slab. Some factory experiments have been conducted to investigate the microscopic characteristics and reveal the influence of process parameters on solidified hooks. The depth of the hooks showed a positive correlation with the deflection angle, length, and oscillation mark (OM) depth, which indicates that the OM depth can serve as an approximate indicator for evaluating the depth of the solidified hooks. On the wide and narrow faces of the cast slab, the depth of the solidified hooks and the temperature distribution in the mold show opposite trends, with lower depths of solidified hooks at positions with higher temperatures. In addition, the influence of process parameters on solidified hooks was analyzed. With the increase in superheat, not only the depth of solidified hooks gradually decreases, but also the ratio of depression-typed marks increases. Increasing casting speed and decreasing immersion depth of the submerged entry nozzle will both lead to a decrease in the depth of the solidified hook. more...

The study aimed to investigate the short‐term outcomes of hospitalized patients with chronic liver disease (CLDs) and assess the prognostic impact of predisposition and precipitants, which currently remains unclear. The study included 3970 hospitalized patients with CLDs from two prospective longitudinal multicenter studies (NCT02457637 and NCT03641872) conducted in highly endemic hepatitis B virus (HBV) areas. Competing risk analysis was used to evaluate the effect of predispositions, including the etiology and severity of CLDs and precipitants; on sequential 28, 90, and 365‐day liver transplantation (LT)‐free mortality. Among all enrolled patients, 76.8% of adverse outcomes (including death and LT) within one year occurred within 90 days. Compared with alcoholic etiology, the association of HBV etiology with poorer outcomes was remarkably on the 28thday (hazard ratio [HR], 1.81; 95% confidence interval [CI], 1.07–3.06; p= 0.026); however, and diminished or became insignificant at 90 days and 365 days. Cirrhosis increased the adjusted risk for 365‐day (HR, 1.50; CI, 1.13–1.99; p= 0.004) LT‐free mortality when compared with noncirrhosis. In patients with cirrhosis, prior decompensation (PD) independently increased the adjusted risk of 365‐day LT‐free mortality by 1.25‐fold (p= 0.021); however, it did not increase the risk for 90‐day mortality. Neither the category nor the number of precipitants influenced the adjusted risk of 28 or 90‐day LT‐free mortality. The 90‐day outcome should be considered a significant endpoint for evaluating the short‐term prognosis of hospitalized patients with CLD. Predisposing factors, other than etiology, mainly affected the delayed (365‐day) outcome. Timely effective therapy for CLD etiology, especially antiviral treatments for HBV, and post‐discharge long‐term surveillance monitoring in cirrhotic patients undergoing PD are suggested to enhance disease management and reduce mortality. This study revealed the predisposition and precipitant factors that affect short‐term outcomes in hospitalized patients with chronic liver diseases (CLDs). Numerous 1‐year adverse outcomes (death and liver transplantation) occurred within 90 days in CLDs. The 90‐day outcome should be considered a major endpoint for evaluating the short‐term prognosis of hospitalized patients with CLDs. Predisposing factors, other than etiology, mainly impacted the delayed short‐term outcome. Compared to alcoholic etiology, hepatitis B virus (HBV) had a significantly poorer 28‐day outcome. Timely antiviral therapy for HBV and post‐discharge long‐term surveillance monitoring in patients with cirrhosis with prior decompensation are suggested to enhance disease management. Significant findings of the studyNumerous 1‐year adverse outcomes (death and liver transplantation) occurred within 90 days in chronic liver diseases (CLDs). Predisposing factors, other than etiology, mainly impacted the delayed short‐term outcome. Compared to alcoholic etiology, hepatitis B virus (HBV) had a significantly poorer 28‐day outcome.What this study addsThe 90‐day outcome should be considered a major endpoint for evaluating the short‐term prognosis of hospitalized patients with CLDs. Timely antiviral therapy for HBV and postdischarge long‐term surveillance monitoring in patients with cirrhosis with prior decompensation are suggested to enhance disease management. Significant findings of the study Numerous 1‐year adverse outcomes (death and liver transplantation) occurred within 90 days in chronic liver diseases (CLDs). Predisposing factors, other than etiology, mainly impacted the delayed short‐term outcome. Compared to alcoholic etiology, hepatitis B virus (HBV) had a significantly poorer 28‐day outcome. What this study adds The 90‐day outcome should be considered a major endpoint for evaluating the short‐term prognosis of hospitalized patients with CLDs. Timely antiviral therapy for HBV and postdischarge long‐term surveillance monitoring in patients with cirrhosis with prior decompensation are suggested to enhance disease management. more...

Transcriptome analysis based on high-throughput sequencing of a cDNA library has been widely applied to functional genomic studies. However, the cDNA dependence of most RNA sequencing techniques constrains their ability to detect base modifications on RNA, which is an important element for the post-transcriptional regulation of gene expression. To comprehensively profile the N6-methyladenosine(m6A) and N5-methylcytosine(m5C) modifications on RNA, direct RNA sequencing(DRS) using the latest Oxford Nanopore Technology was applied to analyze the transcriptome of six tissues in rice. Approximately 94 million reads were generated, with an average length ranging from 619 nt to 1013 nt, and a total of 45,707 transcripts across 34,763 genes were detected. Expression profiles of transcripts at the isoform level were quantified among tissues. Transcriptome-wide mapping of m6A and m5C demonstrated that both modifications exhibited tissue-specific characteristics. The transcripts with m6A modifications tended to be modified by m5C, and the transcripts with modifications presented higher expression levels along with shorter poly(A) tails than transcripts without modifications, suggesting the complexity of gene expression regulation. Gene Ontology analysis demonstrated that m6A- and m5C-modified transcripts were involved in central metabolic pathways related to the life cycle, with modifications on the target genes selected in a tissue-specific manner. Furthermore, most modified sites were located within quantitative trait loci that control important agronomic traits, highlighting the value of cloning functional loci. The results provide new insights into the expression regulation complexity and data resource of the transcriptome and epitranscriptome, improving our understanding of the rice genome. more...

A 3D numerical model was built to investigate the transport phenomena in slab continuous casting process to investigate the influence of strand electromagnetic stirring (S-EMS) combined with mechanical reduction (MR) on macrosegregation in continuously cast slab. The model was validated by measured strand surface temperature and magnetic induction intensity. The results show that the S-EMS with two pairs of electromagnetic stirring rollers in the opposite direction significantly affects the crater end profile and centerline carbon segregation in slab. The maximum solidification end position difference along the crater end profile of slab ΔLreduced from 0.82 m to 0.52 m, and the centerline carbon segregation is improved by the weak S-EMS, when the current intensity increases from 0 to 250 A. But, the maximum solidification end position difference along the crater end profile of slab ΔLincreases from 0.52 m to 1.05 m, the carbon segregation at the 1/4 centerline length position near the right narrow side of slab deteriorates when the current intensity increases from 250 to 350 A. With the combined application of MR near the crater end of continuously cast slab, the solidification delay phenomenon caused by the S-EMS can be significantly improved. But, the solidification delayed cannot be suppressed with current intensity higher than 250A. Therefore, the harmonious application of weak stirring of S-EMS with current intensity of 250A and MR with reduction amount of 4 mm just before the crater end of slab is most benefit for the centerline carbon segregation improvement in continuously cast slab. more...

This paper focused on the relationship between the precipitation of TiN and the continuous casting process of 20CrMnTi billet. A reliable cross scale simulation combining the heat transfer, solute micro-segregation, and TiN precipitation was carried out. Results show that for a specific site, the cooling rate in the mushy state increases with the solidification proceeding, especially in the later stage of solidification. The closer to the center of billet, the lower the initial cooling rate is. However, the cooling rate in the later stage of solidification near the center of billet is higher than that of the intermediate site. The solidification path of 20CrMnTi at 20, 40, and 60 mm below the inner arc surface is L → L + δ → L + δ + γ → L + γ → γ, and the peritectic reaction occurs at the solid fraction of 0.81. The solute segregates more severe as the site moves to the inner billet, especially among the coarse equiaxed dendrites at 60 mm. The precipitation of TiN just slows down the enriching rate of Ti in the liquid phase, but causes the concentration of N declining. The predicted maximum sizes of TiN are 6.128, 7.836, and 7.593 μm at 20, 40, and 60 mm, and its tendency is consistent with the measurements in the billet. With the decrease of N's initial content, the formation of TiN is postponed to higher solid fraction, and TiN becomes smaller. Moreover, the decisive factor for TiN's size at 40 and 60 mm changes from the concentration difference to the growth time. In addition, increasing the secondary cooling intensity can also refine TiN. more...

ABSTRACTContinuous casting is a dominant process for steel production with high productivity, low cost and high automation, but it always suffers from corner defects in the strand. Thus, an in-situ and highly efficient detection of the strand corner crack is very urgent for high-quality steel production. In the present study, several models, namely, YOLOv5x, YOLOv5-S (YOLOv5 + ShuffleNet v2), YOLOv5-SF (YOLOv5 + ShuffleNet v2 + Focus) and YOLOv5-SFA (YOLOv5 + ShuffleNet v2 + Focus + Adam optimizer), are proposed. The experimental results show that among the four models, the mAP for YOLOv5-SFA increases fastest and the number of epochs for mAP reaches the maximum is least. The loss value is less than 0.01 and the training time is 0.369 h, which is reduced by 58.86% with the comparison of YOLOv5x. When only 100 images are used as training data, the detection accuracy is 99.64%, which increases 11.19% with comparison of YOLOv5x, and the detection time is only 0.021 s. more...

Continuous casting is a dominant process for steel production with high productivity, low cost and high automation, but it always suffers from corner defects in the strand. Thus, an in-situ and highly efficient detection of the strand corner crack is very urgent for high-quality steel production. In the present study, several models, namely, YOLOv5x, YOLOv5-S (YOLOv5?+?ShuffleNet v2), YOLOv5-SF (YOLOv5?+?ShuffleNet v2?+?Focus) and YOLOv5-SFA (YOLOv5?+?ShuffleNet v2?+?Focus?+?Adam optimizer), are proposed. The experimental results show that among the four models, the mAP for YOLOv5-SFA increases fastest and the number of epochs for mAP reaches the maximum is least. The loss value is less than 0.01 and the training time is 0.369 h, which is reduced by 58.86% with the comparison of YOLOv5x. When only 100 images are used as training data, the detection accuracy is 99.64%, which increases 11.19% with comparison of YOLOv5x, and the detection time is only 0.021 s. more...

Due to the high similarity of fine-grained image subclasses, small inter-class changes and large intra-class changes are caused, which leads to the difficulty of fine-grained image classification task. However, existing convolutional neural networks have been unable to effectively solve this problem. Aiming at the above-mentioned fine-grained image classification problem, this paper proposes a multi-scale and multi-level ViT model. First, through data augmentation techniques, the accuracy of fine-grained image classification can be effectively improved. Secondly, the small-scale input and large-scale input of the model make the input image have more feature ex-pressions. The subsequent multi-layeredness effectively utilizes the results of the previous layer of ViT, so that the data of the previous layer can be more effectively used in the next layer of ViT. Finally, cross-attention allows the results of two scale inputs to be fused in a reasonable way. The proposed model is competitive with current mainstream state-of-the-art methods on multiple datasets. more...

In the present study, a GPU-accelerated 3D PF-LBM model, which is a combination of the phase field method (PF) and the lattice Boltzmann method (LBM), is established to predict the multi-dendritic growth of Fe–C binary alloy. In order to solve the problems of insufficient memory and low data transfer efficiency faced by the GPU-based parallel computation for 3D dendritic growth, the memory segment loading method is implemented with the cudaMemcpy function in parallel computing architecture CUDA, and the optimum thread block size of 128 is determined. The computation performance analysis of the present GPU-accelerated 3D PF-LBM model shows that the present model gets rid of the limitation of GPU memory and the speedup ratio of present model reaches 1700 times for the cell number of 5123. Then, the present model is used to investigate the stationary single/multiple dendritic growth in an undercooled melt of Fe-2mol pct C binary alloy with or without a forced fluid flow of 0.05 m/s, and the results show that the rejected solute at the solid/liquid interface is washed away by the forced flow and the solute is enriched at the downstream. But the solute enrichment at the interdendritic space is hardly washed away by the forced flow, when the dendrites are fully developed. Thus, the solute enrichment becomes more significant in the downstream region, especially at the interdendritic space. Therefore, the equiaxed dendrite morphology shows a significant asymmetrical morphology for the multiple-dendritic growth with forced fluid flow. more...

ABSTRACTEarly risk assessments and interventions for metabolic syndrome (MetS) are limited because of a lack of effective biomarkers. In the present study, several candidate genes were selected as a blood-based transcriptomic signature for MetS. We collected so far the largest MetS-associated peripheral blood high-throughput transcriptomics data and put forward a novel feature selection strategy by combining weighted gene co-expression network analysis, protein-protein interaction network analysis, LASSO regression and random forest approaches. Two gene modules and 51 hub genes as well as a 9-hub-gene signature associated with metabolic syndrome were identified. Then, based on this 9-hub-gene signature, we performed logistic analysis and subsequently established a web nomogram calculator for metabolic syndrome risk (https://xjtulgz.shinyapps.io/DynNomapp/). This 9-hub-gene signature showed excellent classification and calibration performance (AUC = 0.968 in training set, AUC = 0.883 in internal validation set, AUC = 0.861 in external validation set) as well as ideal potential clinical benefit. more...

ABSTRACTThe lack of efficient biomarkers is the main reason for the inaccurate early diagnosis and poor treatment outcomes of patients with metabolic syndrome (MetS). The current study aimed to identify several novel microRNA (miRNA) biomarkers for metabolic syndrome via high-throughput sequencing and comprehensive bioinformatics analysis. Through high-throughput sequencing and differentially expressed miRNA (DEM) analysis, we first identified two upregulated and 36 downregulated DEMs in the plasma samples of patients with MetS compared to the healthy volunteers. Additionally, we also predicted 379 potential target genes and subsequently carried out enrichment analysis and protein–protein interaction network analysis to investigate the signaling pathways and functions of the identified DEMs as well as the interactions between their target genes. Furthermore, we selected two upregulated and top 10 downregulated DEMs with the highest |log2FC| values as the key microRNAs, which may serve as potential biomarkers for MetS. RT-qPCR was performed to validated these result. Finally, hsa-miR-526b-5p, hsa-miR-6516-5p was identified as the novel biomarkers for MetS. more...

ABSTRACTThe deflection of columnar grains grown under melt flow is characteristic of the alloy solidification structure and strongly influences the performance of products. Here, a model of grain growth in melt flow was established with the cellular automaton (CA) method. After validation by comparison to an analytical model, the model was used to investigate the deflection of columnar grains in high-carbon steel. The deflection angle of columnar grains increases with the flow velocity and decreases with the melt undercooling. At the flow velocity of 0.10 m s–1and the melt undercooling of 2°C, a maximum deflection angle of 18.2° is achieved. The deflection angles predicted by the model agree well with the empirical values. The melt flow was found to promote the grains with a preferred growth orientation towards the upstream direction over others. This flow-influenced selection mechanism is a key reason for the deflection of columnar grains. more...

The deflection of columnar grains grown under melt flow is characteristic of the alloy solidification structure and strongly influences the performance of products. Here, a model of grain growth in melt flow was established with the cellular automaton (CA) method. After validation by comparison to an analytical model, the model was used to investigate the deflection of columnar grains in high-carbon steel. The deflection angle of columnar grains increases with the flow velocity and decreases with the melt undercooling. At the flow velocity of 0.10 m s–1and the melt undercooling of 2°C, a maximum deflection angle of 18.2° is achieved. The deflection angles predicted by the model agree well with the empirical values. The melt flow was found to promote the grains with a preferred growth orientation towards the upstream direction over others. This flow-influenced selection mechanism is a key reason for the deflection of columnar grains. more...

Based on our previously proposed three-phase solidification model, a comprehensive analysis on the impact of the only electromagnetic stirring (EMS) and combined EMS on the microscopic structure evolution and solute segregation behavior in a 500 mm diameter 42CrMo steel of continuously cast round bloom. The results indicate that M-EMS has a notable impact on expediting the dissipation of superheat, enhancing the initiation of grain formation, and enlarging the equiaxed region. The percentage of equiaxed grains increased from 59.26 to 63.37% with the increment in current intensities of M-EMS from 250 to 350 A. However, higher M-EMS current intensities were found to enhance local positive segregation in the transition zone between columnar and equiaxed grains. The impact of M-EMS on improving center positive segregation was minimal, as the ratio of center positive segregation remained consistently around 1.17. Furthermore, the implementation of F-EMS demonstrated its effectiveness in reducing center positive segregation. The ratio of center positive segregation decreased from 1.14 to 1.10, when the current intensity increases from 150 to 250 A. However, it should be noted that F-EMS alone did not contribute to the expansion of the equiaxed zone. On the other hand, when M-EMS was combined with F-EMS (referred to as combined EMS), it showed potential in mitigating center segregation during continuous casting round blooms. The benefits observed with M-EMS in terms of promoting grain nucleation and expanding the equiaxed grain zone were also evident in this combined EMS process. Furthermore, a notable enhancement in the equiaxed grain ratio up to 60.13% was observed combined EMS models were simultaneously employed during continuous casting of round blooms. And, there was a reduction in center segregation ratio for round blooms to as low as 1.09. more...

The relationship between anemia and the outcome of patients with cirrhosis is not completely clear. Therefore, we performed this large-scale epidemiological study to investigate the prevalence and severity of anemia in patients with cirrhosis and acute decompensation or liver injury and how anemia impacts short-term and long-term outcomes. more...

Transcriptome analysis based on high-throughput sequencing of a cDNA library has been widely applied for functional genomic studies. However, the cDNA dependence of most RNA sequencing techniques constrains their ability to detect base modifications on RNA, which is an important element for the post-transcriptional regulation of gene expression. To comprehensively profile the N6-methyladenosine(m6A) and N5-methylcytosine(m5C) modifications on RNA, direct RNA sequencing (DRS) using the latest Oxford Nanopore Technology was applied to analyze the transcriptome of six tissues in rice. Approximately 94 million reads were generated, with an average length ranging from 619 to 1013 nt, and a total of 45,707 transcripts across 34,763 genes were detected. Expression profiles of transcripts at the isoform level were quantified among tissues. Transcriptome-wide mapping of m6A and m5C demonstrated that both modifications exhibited tissue-specific characteristics. The transcripts with m6A modification tended to be modified by m5C, and the transcripts with modifications presented higher expression levels along with shorter poly(A) tail than transcripts without modification, suggesting the complexity of gene expression regulation. Gene ontology analysis demonstrated that m6A- and m5C-modified transcripts are involved in central metabolic pathways related to the life cycle, with modifications on the target genes selected in a tissue-specific manner. Furthermore, most modified sites were located within quantitative trait loci that control important agronomic traits, highlighting the value of cloning functional loci. The results provide new insights into the expression regulation complexity and data resource of the transcriptome and epitranscriptome, improving our understanding of the rice genome. more...

A numerical model of heat transfer was developed to investigate the heat transfer of continuously cast billet with the aid of surface temperature tests by ThermaCAM™ researcher and nail shooting experiments. The effects of secondary cooling practice and casting speed on the solidification process and central segregation of carbon were investigated as well with the actual central segregation tests. The results show that the surface center and billet center temperatures exhibit a different pattern during solidification, and the solidified shell thickness is presented as an “S” type. With the increase of secondary cooling intensity and the decrease of casting speed, the end points of the solidus line and the liquidus line move forward, and the central segregation level of carbon decreases. The optimal casting condition is suggested for continuously cast high carbon billet with F-EMS (final electromagnetic stirring). more...

A numerical model of heat transfer was developed to investigate the heat transfer of continuously cast billet with the aid of surface temperature tests by ThermaCAM™ researcher and nail shooting experiments. The effects of secondary cooling practice and casting speed on the solidification process and central segregation of carbon were investigated as well with the actual central segregation tests. The results show that the surface center and billet center temperatures exhibit a different pattern during solidification, and the solidified shell thickness is presented as an “S” type. With the increase of secondary cooling intensity and the decrease of casting speed, the end points of the solidus line and the liquidus line move forward, and the central segregation level of carbon decreases. The optimal casting condition is suggested for continuously cast high carbon billet with F-EMS (final electromagnetic stirring). more...

A final electromagnetic stirring model was developed for billet continuous casting of high carbon steel using the commercial software ANSYS and CFX, and the numerical model was validated by the magnetic flux density measured under a Teslameter CT-3. The magnetic flux density and fluid flow in the liquid pool at the location of final electromagnetic stirring (F-EMS) were calculated by the present numerical model. Meanwhile, the plant trials were carried out to determine the optimum current intensity and frequency of F-EMS for the continuously cast billet of high carbon steel. The numerical results show that, through increasing the current intensity by 100 A, the corresponding increases of magnetic induction intensity, tangential electromagnetic force and flow velocity at the solid/liquid interface in the strand are 0.025 T, 1933 N/m3and 6.9 cm/s, respectively. Moreover, the industrial trial results showed that for the continuously cast billet of 60 steel, the optimum current intensity and frequency of F-EMS, which is 8.2 m from the meniscus, are respectively 380 A and 6 Hz. With the optimum F-EMS parameters, the significant improvement of center segregation of billet is achieved, and the center carbon segregation index in billet reaches 1.04. more...

With rapid development of cloud computing services, traffic in data centers (DCs) increases dramatically. Top‐of‐rack Ethernet switches dominate network cost and energy consumptions in DCs. Optical switching technologies have been introduced into DC networks to increase switching capacity and to reduce energy consumption. However, how to design high‐performance optical intrarack networks is still a great challenge. This paper presents a software‐defined passive optical intrarack network (SD‐POIRN) based on optical coupler fabrics. The data plane of SD‐POIRN is a broadcast‐and‐select optical network combining wavelength division multiplexing and time division multiplexing technologies. The control plane of SD‐POIRN has a centralized rack controller for scheduling intrarack data transmissions. This paper proposes a software‐defined media access control (SD‐MAC) protocol for SD‐POIRN. The SD‐MAC utilizes dynamic transmission and receiving server grouping methods and max‐min fair share bandwidth allocation algorithms to dynamically allocate bandwidth among servers in an efficient and fair manner. Network performance evaluation results show that, when the offered load is high, the proposed SD‐MAC protocol effectively increases network throughput and reduces average packet delay compared with previous works. This paper presented a software‐defined passive optical intrarack network SD‐POIRN based on optical coupler fabrics. This paper proposed a software‐defined media access control SD‐MAC protocol in the control plane for scheduling intrarack data transmissions. The SD‐MAC uitlizes dynamic server grouping methods and max‐min fair share bandwidth allocation algorithms to improve network throughput and to reduce average packet delay. more...

AbstractIn this study, the effects of pH on the growth, relative expressions of bontAand botRgenes, and neurotoxin formation of foodborne pathogens Clostridium botulinumtype A were systematically studied throughout its growth stage. As in the previous reports, no C. botulinumgrowth was observed at extremely acidic pH. However, the effect of alkaline pH on the growth and neurotoxin production of C. botulinumwas first revealed in this study. The maximum growth rate at pH 9.0 was similar to that at other pH values, although the lag phase at pH 9.0 was 16 h longer than that at pH 8.0. The peak of bontAmRNA expression at pH 9.0 was only 15.5% compared with that at pH 7.0. However, the neurotoxin concentration quantified in the cultures did not differ significantly. BotRis a known regulatory protein of bontA. The quantitative relationship between bontAand botRat different growth stages was first determined in this study. The mRNA levels of bontAwere found to be positively correlated with those of botR, and the ratio of the mRNA transcript varied with pH. All these findings provide important physiological information on C. botulinumand thereby contribute to the improvement of food safety. more...

Abstract: The efficiency of QoS-aware service composition is important since most service composition problems are known to be NP-hard. With the growing number of web services, service composition is like a decision problem on selecting services or/and execution plans to satisfy the users'' end-to-end QoS requirements (e.g. response time, throughput). Composite services with the same functionality may have different execution plans, which may cause different end-to-end QoS. This paper presents a model combining semantic data-links and QoS, which leads to an efficient approach to automatic construction of a composite service with optimal end-to-end QoS. The approach is based on a greedy algorithm to select both services and execution plans for composite services. Empirical and theoretical analyses of the approach show that its time complexity is O(mn 2) for a repository with n services and an ontology with m concepts. Moreover, the approach increases linearly in time when using an index to search services in the repository. Tests with a repository with 20 000 services and an ontology with 300 000 concepts show that the algorithm significantly outperforms current existing algorithms in terms of composition efficiency while achieving optimal end-to-end QoS. [Copyright &y& Elsevier] more...