Multi-objective Optimization of Tube Hydroforming Using Hybrid Global and Local Search

An investigation of non-linear multi-objective optimization is conducted in order to define a set of process parameters (i.e. load paths) for defect-free tube hydroforming. A generalized forming severity indicator that combines both the conventional forming limit diagram (FLD) and the forming limit stress diagram (FLSD) was adopted to detect excessive thinning, necking/splitting and wrinkling in the numerical simulation of formed parts. In order to rapidly explore and capture the Pareto frontier for multiple objectives, two optimization strategies were developed: normal boundary intersection (NBI) and multi-objective genetic algorithm (MOGA) based on the concept of dominated solutions . The NBI method produced a uniformly distributed set of solutions. For the MOGA method, a stochastic Kriging model was used as a surrogate model. Furthermore, the MOGA constraint-handling technique was improved, Kriging model updating was automated and a hybrid global-local search was implemented in order to rapidly explore the Pareto frontier. Both piece-wise linear and pulsating pressure paths were investigated for several case studies, including straight tube, pre-bent tube and industrial tube hydroforming. For straight tube hydroforming, the optimal load path was obtained using the NBI method and it showed a smaller corner radius compared to that predicted by the commercial program LS-OPT4.0. Moreover, the hybrid method coupling global search (MOGA) and local search (sequential quadratic programming: SQP) was applied for straight tube hydroforming, and the results showed a significant improvement in terms of the stress safety margin and reduced local thinning. For a commercial refrigerator door handle, the MOGA method was utilized to inversely analyze the loading path and the calculated path correlated well with the production path. For a hydroformed T-shaped tubular part, the amplitude and frequency of the pulsating pressure were optimized with MOGA. Thinning was reduced by 25% compared with experimental results. A multi-stage (prebent) tube hydroforming simulation was performed and it indicated that the reduction in formability due to bending can be largely compensated by end feeding the tube during hydroforming. The loading path optimized by MOGA showed that the expansion into the corner of the hydroforming die increased by 16.7% compared to the maximum expansion obtained during experimental trials

The State of the Art in Digital Construction of Clay Buildings: Reviews of Existing Practices and Recommendations for Future Development

Under the trend of digitization and global carbon reductions, clay construction has increasingly attracted attention due to advantages such as an excellent thermal performance, low carbon emissions, and high cost-effectiveness. In this article, an in-depth investigation is conducted into the potential, challenges, and future in the development of digital manufacturing technologies for clay architecture, especially 3D printing, robotic construction, and prefabrication systems. It is revealed through a review that digital clay construction is under rapid development and likely to provide a viable solution to achieving global carbon neutrality, which is conducive to addressing various regional issues. The key findings from this review are as follows. Firstly, as a flexible, precise, and low-carbon industrial solution, 3D printing lays a foundation for the extensive research on materials, equipment, and algorithm optimization. Secondly, the use of machine construction methods such as modern rammed earth technology and drone spraying is effective in improving efficiency and lowering costs. Lastly, the prefabricated building system shows its potential in renewing and developing the rammed earth architecture culture. These findings indicate a massive potential of digital clay construction to support sustainability efforts in the future

Additive-assisted regioselective 1,3-dipolar cycloaddition of azomethine ylides with benzylideneacetone

1,3-Dipolar cycloadditions of isatins, benzylamine and benzylideneacetones were studied to prepare a series of novel spiropyrrolidine-oxindoles – 4′-acetyl-3′,5′-diarylspiro[indoline-3,2′-pyrrolidin]-2-ones and 3′-acetyl-4′,5′-diarylspiro[indoline-3,2′-pyrrolidine]-2-ones in good yields of up to 94% and with good regioselectivities. Regioselectivities are reversible by the addition of water or 4-nitrobenzoic acid, respectively. The substituent effects on the regioselectivity were also investigated

Impact of fracturing fluid retention and flowback on development effect after large scale fracturing in shale oil wells: A case study from the shale oil of Chang 7 Member, Yanchang Formation, Ordos Basin

In order to reveal the impact of fracturing fluid retention and flowback on the development effect after large-scale fracturing in shale oil wells, and to formulate a reasonable flowback policy, this paper employs a combination of core physical simulation experiments and theoretical analysis. We have designed a specially designed device that can evaluate the development effect of quasi-natural energy in oil reservoirs. The impact of fracturing fluid retention on development is simulated by changing the amount of fracturing fluid injected into the formation in a fractured horizontal well model (referred as injection volume), and the impact on development effect is analyzed by changing the properties of fracturing fluid to adjust the difference in the degree of flowback. Based on the experimental results, the mechanism of fracturing fluid retention and flowback after large-scale fracturing in shale reservoirs is further explored. The results of the experiments show that the flowback rate of fracturing fluid exhibits a monotonic decreasing trend with increasing the volume of injected fluid, as increasing the volume of injected fluid helps to enhance its retention in the formation and reduce the flowback rate. The degree of fracturing fluid flowback is critical to the mobility of crude oil in the tight reservoir. The entering of fracturing fluid into the reservoir slows down the rate of discharge in the fracture network, effectively extending the reach of the fracturing fluid in the tight reservoir and allowing more crude oil to be used, which in turn results in higher crude oil production. However, too much injection fluid may affect the fluid production. Simulation experiments reveal that the use of fracturing fluid retention or controlling the rate of flowback by changing the viscosity of fracturing fluid can be a way to enhance the development effect of horizontal shale oil wells. The results of this paper provide a basis for understanding the mechanism of shale oil development, exploring technical ideas to improve the development effect, and making decisions on the flowback parameters

Supramolecular Polymers Formed by ABC Miktoarm Star Peptides

We report here the design and synthesis of an ABC miktoarm star peptide connecting through a lysine junction a short peptide sequence and two hydrophobic but immiscible blocks (a hydrocarbon and a fluorocarbon). The designed molecule can self-assemble into one-dimensional nanostructures with a great diversity of kinetically evolving morphologies in aqueous solution, while molecules that contain only one of the two hydrophobic blocks form structurally similar filaments. We believe the rich assembly behavior and morphological evolution are a direct reflection of the molecular frustration present within the filament core as a result of the incompatibility of the fluorocarbon and hydrocarbon segments. Our finding opens new opportunities for creating complex supramolecular polymers through the architecture design of small molecular building units

Rational Design of MMP Degradable Peptide-Based Supramolecular Filaments

One-dimensional nanostructures formed by self-assembly of small molecule peptides have been extensively explored for use as biomaterials in various biomedical contexts. However, unlike individual peptides that can be designed to be specifically degradable by enzymes/proteases of interest, their self-assembled nanostructures, particularly those rich in β-sheets, are generally resistant to enzymatic degradation because the specific cleavage sites are often embedded inside the nanostructures. We report here on the rational design of β-sheet rich supramolecular filaments that can specifically dissociate into less stable micellar assemblies and monomers upon treatment with matrix metalloproteases-2 (MMP-2). Through linkage of an oligoproline segment to an amyloid-derived peptide sequence, we first synthesized an amphiphilic peptide that can undergo a rapid morphological transition in response to pH variations. We then used MMP-2 specific peptide substrates as multivalent cross-linkers to covalently fix the amyloid-like filaments in the self-assembled state at pH 4.5. Our results show that the cross-linked filaments are stable at pH 7.5 but gradually break down into much shorter filaments upon cleavage of the peptidic cross-linkers by MMP-2. We believe that the reported work presents a new design platform for the creation of amyloid-like supramolecular filaments responsive to enzymatic degradation

Supramolecular Nanostructures Formed by Anticancer Drug Assembly

We report here a supramolecular strategy to directly assemble the small molecular hydrophobic anticancer drug camptothecin (CPT) into discrete, stable, well-defined nanostructures with a high and quantitative drug loading. Depending on the number of CPTs in the molecular design, the resulting nanostructures can be either nanofibers or nanotubes, and have a fixed CPT loading content ranging from 23% to 38%. We found that formation of nanostructures provides protection for both the CPT drug and the biodegradable linker from the external environment and thus offers a mechanism for controlled release of CPT. Under tumor-relevant conditions, these drug nanostructures can release the bioactive form of CPT and show in vitro efficacy against a number of cancer cell lines. This strategy can be extended to construct nanostructures of other types of anticancer drugs and thus presents new opportunities for the development of self-delivering drugs for cancer therapeutics