Structural optimization with an automatic mode identification method for tracking global vibration mode

<p>This article presents a mode identification method for structural optimization with global mode constraints to overcome the mode switching problem. In engineering design, the natural frequencies of global vibrations for a complex structure, the orders of which would not be constant in optimization loops, are usually very difficult to constrain. In this case, an incorrect constraint may lead to an unreliable design. A mode identification technique based on modal effective mass fraction is implemented to track the global modes such that the constraints will be updated subsequently and the optimizer can run correctly. A study case with comparison to traditional modal assurance criterion approaches demonstrates the advantages of this technique. An optimization framework has been developed with the new proposed mathematical model. Two numerical optimization examples, of a space truss and a simplified satellite structure, are presented to demonstrate the feasibility and applicability of this process.</p

Biomass-Based Porous N‑Self-Doped Carbon Framework/Polyaniline Composite with Outstanding Supercapacitance

Composites combining electrostatic charge accumulation and faradic reaction mechanisms are especially attractive high-performance supercapacitor electrodes for electrochemical energy storage. Up to now, it is difficult to prepare low-cost carbon composites from renewable resources. In this work, an outstanding and low-cost composite was fabricated by using sustainable N-self-doped carbon framework as a hierarchical porous carbon substrate from renewable resource. The N-self-doped carbon framework was fabricated from chitosan via a facile yet unique self-assembly and ice template method without any physical or chemical activation, and exhibited hierarchical porous structure. This texture not only allowed the efficient infiltration and uniform coating of polyaniline (PANI) in the inner network but also permitted a rapid penetration and desorption of electrolytes. Due to short diffusion pathway, uniformly coating of PANI, and high accessibility of PANI to electrolytes, the composite electrode had a very high supercapacitance of 373 F g^–1 (1.0 A g^–1) and excellent rate capability (275 F g^–1, 10 A g^–1) in a three-electrode system. The symmetric supercapacitor also showed a supercapacitance of high up to 285 F g^–1 (0.5 A g^–1), and a very high energy density of 22.2 Wh kg^–1. Furthermore, the composite also presented a good cycling stability

Boosting the Performance of Low-Platinum Fuel Cells via a Hierarchical and Interconnected Porous Carbon Support

The design of a low-platinum (Pt) proton-exchange-membrane fuel cell (PEMFC) can reduce its high cost. However, the development of a low-Pt PEMFC is severely hindered by the high oxygen transfer resistance in the catalyst layer. Herein, a carbon with interconnected and hierarchical pores is synthesized as a support for the low-Pt catalyst to lower the oxygen transfer resistance. A H2–air fuel cell assembled by Pt/hierarchical porous carbon shows 1610 mW/cm2 peak power density, 2230 mA/cm2 current density at 0.60 V, and only 18.4 S/m local oxygen transfer resistance with 0.10 mgPt/cm2 Pt loading at the cathode, which far exceeds those of various carbon black supports and commercially used Pt/C catalysts. Both the experimental and simulation results have shown the advancement of hierarchical pores toward the high efficiency of oxygen transportation

Boosting the Performance of Low-Platinum Fuel Cells via a Hierarchical and Interconnected Porous Carbon Support

The design of a low-platinum (Pt) proton-exchange-membrane fuel cell (PEMFC) can reduce its high cost. However, the development of a low-Pt PEMFC is severely hindered by the high oxygen transfer resistance in the catalyst layer. Herein, a carbon with interconnected and hierarchical pores is synthesized as a support for the low-Pt catalyst to lower the oxygen transfer resistance. A H2–air fuel cell assembled by Pt/hierarchical porous carbon shows 1610 mW/cm2 peak power density, 2230 mA/cm2 current density at 0.60 V, and only 18.4 S/m local oxygen transfer resistance with 0.10 mgPt/cm2 Pt loading at the cathode, which far exceeds those of various carbon black supports and commercially used Pt/C catalysts. Both the experimental and simulation results have shown the advancement of hierarchical pores toward the high efficiency of oxygen transportation

Boosting the Performance of Low-Platinum Fuel Cells via a Hierarchical and Interconnected Porous Carbon Support

The design of a low-platinum (Pt) proton-exchange-membrane fuel cell (PEMFC) can reduce its high cost. However, the development of a low-Pt PEMFC is severely hindered by the high oxygen transfer resistance in the catalyst layer. Herein, a carbon with interconnected and hierarchical pores is synthesized as a support for the low-Pt catalyst to lower the oxygen transfer resistance. A H2–air fuel cell assembled by Pt/hierarchical porous carbon shows 1610 mW/cm2 peak power density, 2230 mA/cm2 current density at 0.60 V, and only 18.4 S/m local oxygen transfer resistance with 0.10 mgPt/cm2 Pt loading at the cathode, which far exceeds those of various carbon black supports and commercially used Pt/C catalysts. Both the experimental and simulation results have shown the advancement of hierarchical pores toward the high efficiency of oxygen transportation

Boosting the Performance of Low-Platinum Fuel Cells via a Hierarchical and Interconnected Porous Carbon Support

The design of a low-platinum (Pt) proton-exchange-membrane fuel cell (PEMFC) can reduce its high cost. However, the development of a low-Pt PEMFC is severely hindered by the high oxygen transfer resistance in the catalyst layer. Herein, a carbon with interconnected and hierarchical pores is synthesized as a support for the low-Pt catalyst to lower the oxygen transfer resistance. A H2–air fuel cell assembled by Pt/hierarchical porous carbon shows 1610 mW/cm2 peak power density, 2230 mA/cm2 current density at 0.60 V, and only 18.4 S/m local oxygen transfer resistance with 0.10 mgPt/cm2 Pt loading at the cathode, which far exceeds those of various carbon black supports and commercially used Pt/C catalysts. Both the experimental and simulation results have shown the advancement of hierarchical pores toward the high efficiency of oxygen transportation

Synthesis of Environmentally Friendly Nanoporous Monolithic Carbon Aerogels via Ambient Pressure Drying for High-Temperature Thermal Insulators

As a promising high-temperature thermal insulation, carbon aerogel is generally prepared by the carbonization of an organic aerogel. However, the preparation processes of solvent exchange and supercritical drying are complicated and contaminated, which hinder their large-scale production and application in the field of civil high-temperature thermal insulators. Herein, the nanoporous carbon aerogels were prepared by an environmentally friendly method of ambient pressure drying without solvent exchange with the usage of water as the solvent, acetic acid as an acid catalyst, and biopolymer chitosan as a cross-linking agent and supporting template. Through the polymerization and hydrogen bonds of chitosan with precursors to strengthen the gel network, carbon aerogels exhibit good monolithic shape (130 × 130 × 18 mm) with nanoparticle size (43–107 nm) and low density (0.187–0.395 g/cm3), leading to a low thermal conductivity (0.09592 W/m·K) and high compressive strength (11.50 MPa) at the density of 0.395 g/cm3. Notably, by the copyrolysis of organic fiber-reinforced organic aerogel composite, a crack-free carbon aerogel composite (0.244 g/cm3) was prepared with enhanced mechanical properties (compressive strength of 1.63 MPa at 10% strain and bending strength of 4.27 MPa) and low thermal conductivity (0.107 W/m·K at 1100 °C). This work may provide an environmentally friendly method for the industrialized preparation of reliable nanoporous carbon aerogels for high-temperature thermal protection components

Forest plot on the expression of IL4 in decidual tissue between the experimental group and control group.

Forest plot on the expression of IL4 in decidual tissue between the experimental group and control group.</p

Subgroup analysis of MSC treatment effects on the expression of IFN-γ from decidual tissue.

Subgroup analysis of MSC treatment effects on the expression of IFN-γ from decidual tissue.</p

The forest plot of the embryo resorption rate between the experimental group and control group.

The forest plot of the embryo resorption rate between the experimental group and control group.</p