INTEGRATION OF CELL FORMATION AND LAYOUT DESIGN IN THE UNIDIRECTIONAL LOOP MATERIAL HANDLING ENVIRONMENT

A two-phase approach is proposed to deal with the integration problem in theloop layout. Tabu search is applied to cell construction in phase 1 to minimize the inter-cell flow,and the heuristic for layout design is used as phase 2 to optimize the sum of intra-cell andinter-cell transportation cost. The final computational results demonstrate the validation of thetwo-phase approach.

Integrated Manufacturing Cell Formation Technology Orienting Multi-product Type and Variant Volume Production

What is pursued by multi-product type and variant volume（MPTVV） production is rapid response and quick switching,so that structure of transferring line in manufacturing system is no longer unalterable.Cell formation（CF） algorithm is the key technology of cellular manufacturing system（CMS）.Currently,CF methods are mainly extended on the idea of group technology（GT） that covers a lot on analysis of resource capability matching and its algorithm.Various constraints are considered,but seldom utilized comprehensively.Aimed to the problem of manufacturing cell（MC） formation under MPTVV production mode,integrated formation technologies for typical MC as group type of cell（GC）,flow type of cell（FC） and inherited cell（IC） are presented based on technical analysis of CF.Oriented to practical production constraints like delivery time,product batch,equipment ability,key machine,key part and machine sharing,etc,an integrated formation model is constructed and internal interrelations of these constraints are analyzed synthetically.Ulteriorly,formation goals of types of MCs and their formation procedures under joint effect of formation constraints and rules are spread.In case study,three highly balanced GC are formed first;then FC formation are implemented based on the same data which indicate good balancing effect of cell load and flow-style production for key tasks;When task is adjusted,a new scheme is constructed on the result of FC configuration by using IC formation method,and more optimal performance of flow-style production is manifested.The proposed comparative study of different type of cells strongly explains the validation of integrated MC formation in support of rapid manufacturing resource transformation under MPTVV production mode.

Improved PSO for integrating dynamic cell formation and layout problems

To decrease the impact of shorter product life cycles,dynamic cell formation problems(CFPs)and cell layout problems(CLPs)were simultaneously optimized.First,CFPs and CLPs were formally described.Due to the changes of product demands and the lim it of machine capacity,the existing layout needed to be rearranged to a high degree.Secondly,a mathematical model was established for the objective function of minimizing the total costs.Thirdly,a novel dynamic multi-swarm particle swarm optimization(DMS-PSO)algorithm based on the communication learning strategy(CLS)was developed.Toavoid falling into local optimum and slow convergence,each swarm shared their optimal locations before regrouping.Finally,simulation experiments were conducted under different conditions.Numerical results indicate that the proposed algorithm has better stability and it converges faster than other existing algorithms.

Integrated optimal method for cell formation and layout problems based on hybrid SA algorithm with fuzzy simulation

To adapt to the complex and changeable market environment,the cell formation problems(CFPs) and the cell layout problems(CLPs) with fuzzy demands were optimized simultaneously. Firstly,CFPs and CLPs were described formally. To deal with the uncertainty fuzzy parameters brought,a chance constraint was introduced. A mathematical model was established with an objective function of minimizing intra-cell and inter-cell material handling cost. As the chance constraint of this problem could not be converted into its crisp equivalent,a hybrid simulated annealing(HSA) based on fuzzy simulation was put forward. Finally,simulation experiments were conducted under different confidence levels. Results indicated that the proposed hybrid algorithm was feasible and effective.

EVOLUTIONARY ALGORITHMS WITH PREFERENCE FOR MANUFACTURING CELLS FORMATION

Due to the combinatorial nature of cell formation problem and the characteristics of multi-objective and multi-constrain, a novel method of evolutionary algorithm with preference is proposed. The analytic hierarchy process （AHP） is adopted to determine scientifically the weights of the sub-objective functions. The satisfaction of constraints is considered as a new objective, the ratio of the population which doesn＇t satisfy all constraints is assigned as the weight of new objective. In addition, the self-adaptation of weights is applied in order to converge more easily towards the feasible domain. Therefore, both features multi-criteria and constrains are dealt with simultaneously. Finally, an example is selected from the literature to evaluate the performance of the proposed approach. The results validate the effectiveness of the proposed method in designing the manufacturing cells.

RANKL signaling in bone marrow mesenchymal stem cells negatively regulates osteoblastic bone formation

RANKL signaling is essential for osteoclastogenesis. Its role in osteoblastic differentiation and bone formation is unknown. Here we demonstrate that RANK is expressed at an early stage of bone marrow mesenchymal stem cells(BMSCs) during osteogenic differentiation in both mice and human and decreased rapidly. RANKL signaling inhibits osteogenesis by promoting β-catenin degradation and inhibiting its synthesis. In contrast, RANKL signaling has no significant effects on adipogenesis of BMSCs.Interestingly, conditional knockout of rank in BMSCs with Prx1-Cre mice leads to a higher bone mass and increased trabecular bone formation independent of osteoclasts. In addition, rank: Prx1-Cre mice show resistance to ovariectomy-(OVX) induced bone loss. Thus, our results reveal that RANKL signaling regulates both osteoclasts and osteoblasts by inhibition of osteogenic differentiation of BMSCs and promotion of osteoclastogenesis.

LRP6 in mesenchymal stem cells is required for bone formation during bone growth and bone remodeling

Lipoprotein receptor-related protein 6 （LRP6） plays a critical role in skeletal development and homeostasis in adults. However, the role of LRP6 in mesenchymal stem cells （MSCs）, skeletal stem cells that give rise to osteoblastic lineage, is unknown. In this study, we generated mice lacking LRP6 expression specifically in nestin＋ MSCs by crossing nestin-Cre mice with LRP6 flox mice and investigated the functional changes of bone marrow MSCs and skeletal alterations. Mice with LRP6 deletion in nestin＋ cells demonstrated reductions in body weight and body length at I and 3 months of age. Bone architecture measured by microCT （uCT） showed a significant reduction in bone mass in both trabecular and cortical bone of homozygous and heterozygous LRP6 mutant mice. A dramatic reduction in the numbers of osteoblasts but much less significant reduction in the numbers of osteoclasts was observed in the mutant mice. Osterix＋ osteoprogenitors and osteocalcin＋ osteoblasts significantly reduced at the secondary spongiosa area, but only moderately decreased at the primary spongiosa area in mutant mice. Bone marrow MSCs from the mutant mice showed decreased colony forming, cell viability and cell proliferation. Thus, LRP6 in bone marrow MSCs is essential for their survival and proliferation, and therefore, is a key positive regulator for bone formation during skeletal growth and remodeling.

ERK phosphorylation functions in invadopodia formation in tongue cancer cells in a novel silicate fibre-based 3D cell culture system

To screen for additional treatment targets against tongue cancer, we evaluated the contributions of extracellular signal-related kinase(ERK), AKT and ezrin in cancer development. Immunohistochemical staining showed that ERK and ezrin expressions were significantly higher in invasive squamous cell carcinoma than in carcinoma in situ. To investigate the roles of ERK and ezrin in cancer development, we used the non-woven silica fibre sheet Cellbedwith a structure resembling the loose connective tissue morphology in a novel 3 D culture system. We confirmed that the 3 D system using CellbedTMaccurately mimicked cancer cell morphology in vivo. Furthermore, cell projections were much more apparent in 3 D-cultured tongue cancer cell lines than in 2 D cultures. Typically, under conventional 2 D culture conditions, F-actin and cortactin are colocalized in the form of puncta within cells.However, in the 3 D-cultured cells, colocalization was mainly observed at the cell margins, including the projections. Projections containing F-actin and cortactin colocalization were predicted to be invadopodia. Although suppressing ezrin expression with small interfering RNA transfection caused no marked changes in morphology, cell projection formation was decreased, and the tumour thickness in vertical sections after 3 D culture was markedly decreased after suppressing ERK activity because both the invasion ability and proliferation were inhibited. An association between cortactin activation as well as ERK activity and invadopodia formation was detected. Our novel 3 D culture systems using Cellbed? are simple and useful for in vitro studies before conducting animal experiments. ERK contributes to tongue cancer development by increasing both cancer cell proliferation and migration via cortactin activation.

Layout Planning Technology of Cellular Manufacturing System Based on Process Interconnection Analysis

With sustaining change of production mode,layout planning is no longer a thing built once for all.Cellular layout(CL) is becoming a hotspot in the research field of manufacturing system layout.Traditional researches on layout planning are mainly concentrating on aspects of layout arithmetic,style and evaluation,etc.Relatively seldom efforts are paid to CL and its specific problems as cell formation(CF),equipment sharing and CL analysis.Through problem analyzing of layout in cellular manufacturing system(CMS),research approach of cell formation,interactive layout and layout analysis threaded with process interconnection relationship(PIR) is proposed.Typical key technologies in CL like CF technology based on similarity analysis of part processes,interactive visual layout technology,layout evaluation technology founded on PIR analysis and algorithm of cell equipment sharing are put forward.Against the background of one enterprise which encounters problems of low utility of key equipments and disperse material logistic,an example of four-cell layout is given.The CL adjustment and analysis results show that equipment with high level of sharing degree should be disposed around the boundary of its main cell,and be near to other sharing cells as possible; process route should be centralized by all means,so equipment adjustment is to be implemented along direction that route intersection can be decreased; giving consideration to the existence of discrete cell,logistic route and its density should be centralized to cells formed.The proposed research can help improve equipment utility and material logistic efficiency of CL,and can be popularized to other application availably.

Woody plant cell walls:Fundamentals and utilization

Cell walls in plants,particularly forest trees,are the major carbon sink of the terrestrial ecosystem.Chemical and biosynthetic features of plant cell walls were revealed early on,focusing mostly on herbaceous model species.Recent developments in genomics,transcriptomics,epigenomics,transgenesis,and associated analytical techniques are enabling novel insights into formation of woody cell walls.Here,we review multilevel regulation of cell wall biosynthesis in forest tree species.We highlight current approaches to engineering cell walls as potential feedstock for materials and energy and survey reported field tests of such engineered transgenic trees.We outline opportunities and challenges in future research to better understand cell type biogenesis for more efficient wood cell wall modification and utilization for biomaterials or for enhanced carbon capture and storage.

OsMAPK6 Affects Male Fertility by Reducing Microspore Number and Delaying Tapetum Degradation in Oryza sativa L.

The mitogen-activated protein kinase(MAPK)cascade is important in stress signal transduction and plant development.In the present study,we identified a rice(Oryza sativa L.)mutant with reduced fertility,Oryza sativa mitogen-activated protein kinase 6(osmapk6),which harbored a mutated MAPK gene.Scanning and transmission electron microscopy,quantitative RT-PCR analysis,TUNEL assays,RNA in situ hybridization,longitudinal and transverse histological sectioning,and map-based cloning were performed to characterize the osmapk6 mutant.The gene OsMAPK6 was expressed throughout the plant but predominantly in the microspore mother cells,tapetal cells,and microspores in the anther sac.Compared with the wild type,the total number of microspores was reduced in the osmapk6 mutant.The formation of microspore mother cells was reduced in the osmapk6 anther sac at an early stage of anther development,which was the primary reason for the decrease in the total number of microspores.Programmed cell death of some tapetal cells was delayed in osmapk6 anthers and affected exine formation in neighboring microspores.These results suggest that OsMAPK6 plays pivotal roles in microspore mother cell formation and tapetal cell degradation.

On the role of Zn and Fe doping in nitrogen-carbon electrocatalysts for oxygen reduction

Zn is a frequently used and sometimes even an inevitably involved element (when zeolitic imidazolate framework-8 (ZIF-8) is adopted as the precursor) for preparing high-performance Fe-N-C oxygen reduction reaction (ORR) catalysts. However, how the Zn element affects the physicochemical architecture of the catalysts, how it enhances the catalytic activity and whether Zn atoms serve as the active centers remain unclear. Herein, we proposed a novel route that adopted pyrrole as the precursor and flexibly controlled the addition of exogenous Zn and Fe dopants before pyrrole polymerization. In this way, a series of nitrogen-carbon catalysts with or without Zn or Fe doping were synthesized. The detailed characterization revealed the role of Zn and Fe doping in the catalyst morphology, pore structure, active site configurations, ORR catalytic activity and fuel cell performance. Importantly, the findings revealed that Zn doping has little effect on the ORR mechanism and pathway. It enhances ORR activity primarily by increasing the number of active sites via introducing more micro- and meso-pores, rather than by creating new active sites. While Fe doping participated in forming both pores and active site centers. Moreover, the catalyst that co-doped with Zn and Fe atoms (Zn-FeNC), synthesized via this simple and template-free route we proposed, presented a unique hollow and hierarchical pore structure with highly boosted ORR activity. It exhibited a 40 mV higher E 1/2 value than Pt/C in alkaline media, along with a rapid current response in air-cathode of the direct formate fuel cell. These results are valuable in guiding the synthesis of high-performance Fe-N-C catalysts.

Three-dimensional porous electrodes for direct formate fuel cells

The dual-layer electrode for fuel cells is typically prepared by binding discrete catalyst nanoparticles onto a diffusion layer.Such a random packing forms a dense catalyst layer and thus creates a barrier for mass/ion transport,particularly for direct liquid fuel cells.Three-dimensional porous electrodes,a thin nano-porous catalyst layer uniformly distributed on the matrix surface of a foam-like structure,are typically employed to improve the mass/ion transport.Such a three-dimensional porous structure brings two critical advantages:(i)reduced mass/ion transport resistance for the delivery of the reactants via shortening the transport distance and(ii)enlarged electrochemical surface area,via reducing the dead pores,isolated particles and severe aggregations,for interfacial reactions.Moreover,the three-dimensional design is capable of fabricating binder-free electrodes,thereby eliminating the use of ionomers/binders and simplifying the fabrication process.In this work,three types of three-dimensional porous electrode are fabricated,via different preparation methods,for direct formate fuel cells:(i)Pd/C nanoparticles coating on the nickel foam matrix surface(Pd-C/NF)via a dip-coating method,(ii)Pd nanoparticles depositing on the nickel foam matrix surface(Pd/NF)via reduction reaction deposition,and(iii)Pd nanoparticles embedding in the nickel foam matrix(Pd/(in)NF)via replacement reaction deposition.The latter two are binder-free three-dimensional porous electrodes.As a comparison,a conventional dual-layer design,Pd/C nanoparticles painting on the nickel foam layer(Pd-C//NF),is also prepared via direct painting method.It is shown that the use of the three-dimensional Pd-C/NF electrode as the anode in a direct formate fuel cell results in a peak power density of 45.0 mW cm^(-2)at 60℃,which is two times of that achieved by using a conventional dual-layer design(19.5 mW cm^(-2)).This performance improvement is mainly attributed to the unique three-dimensional structure design,which effectively enhances the mass/ion transport through the porous electrode and enlarges the electrochemical surface area(accessible active area)for interfacial reactions.In addition,the delivery of the fuel solution is still sufficient even when the flow rate is as low as 2.0 mL min^(-1).It is also demonstrated that direct formate fuel cells using two binder-free electrodes yield the peak power densities of 13.5 mW cm^(-2)(Pd/(in)NF)and 14.0 mW cm^(-2)(Pd/NF)at 60℃,respectively,both of which are much lower than the power density achieved by using the Pd-C/NF electrode.This is because the electrochemical surface areas of two binderfree electrodes are much smaller than the Pd/C-based electrodes,since the specific area of Pd/C nanoparticles is much larger.