Analysis of natural and man-made accidents happened in subway stations and trains: based on statistics of accident cases

Sometimes subway stations and trains can be very crowded for large passenger flows. However, some stations and trains may be vulnerable when natural or man-made disasters happen, thus the safety of passengers and stuff is threatened. Therefore, it is meaningful to make a deep analysis to these disasters that may happen in subway stations and trains. By collecting cases of accidents include fire disaster, terrorist attack, flood, earthquake and stampede that happened in subway stations or on trains around the world, the causes, consequence and their own characters were analysed. Besides, some recommendations and beneficial measures aim to prevent these disasters mentioned above were also presented and discussed

Engineering Donor-Acceptor Conjugated Polymers for High-Performance and Fast-Response Organic Electrochemical Transistors

To date, high-performance organic electrochemical transistors (OECTs) have mostly been based on polythiophene systems. Donor–acceptor (D–A) conjugated polymers are expected to be promising materials for OECTs owing to their high mobility and comparatively low crystallinity (good for ion diffusion). However, the OECT performance of D–A polymers lags far behind that of the polythiophenes. Here we synergistically engineered the backbone and side chain of a series of diketopyrrolopyrrole (DPP)-based D–A polymers and found that redox potential, molecular weight, solution processability, and film microstructures all have a severe impact on their performance. After systematic engineering, P(bgDPP-MeOT2) exhibited the best figure-of-merit (μC*) of 225 F cm−1 V−1 s−1, amongst the highest performance of the reported D–A polymers. Besides, the DPP polymers exhibited high hole mobility of over 1.6 cm2 V−1 s−1, leading to fast response OECTs with a record low turn-off response time of 30 μs. The polymer also exhibited good operation stability with a current retention of 98.8% over 700 electrochemical switching cycles. This work reveals the complexity and systematicness in the development of D–A polymer based high-performance OECTs

Improvement of Flame Retardancy of Polyurethane Foam Using DOPO-Immobilized Silica Aerogel

In this work, silica aerogel was modified by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-1-oxide (DOPO). Then DOPO-immobilized silica aerogel nanoparticles were used as a flame retardant to prepare flame-retardant polyurethane foams. Microscale combustion calorimeter and cone calorimeter tests were employed to evaluate the flame retardancy of polyurethane foams. It was found that both the heat release rate and the total heat release of the composites were reduced with the incorporation of DOPO immobilized silica aerogel. It is speculated that the DOPO-immobilized silica aerogel nanoparticles can inhibit the degradation of polyurethane and catalyze the formation of carbonaceous carbon on the surface

Analysis of natural and man-made accidents happened in subway stations and trains: based on statistics of accident cases

Sometimes subway stations and trains can be very crowded for large passenger flows. However, some stations and trains may be vulnerable when natural or man-made disasters happen, thus the safety of passengers and stuff is threatened. Therefore, it is meaningful to make a deep analysis to these disasters that may happen in subway stations and trains. By collecting cases of accidents include fire disaster, terrorist attack, flood, earthquake and stampede that happened in subway stations or on trains around the world, the causes, consequence and their own characters were analysed. Besides, some recommendations and beneficial measures aim to prevent these disasters mentioned above were also presented and discussed

Understanding Impacts of Security Check on Passenger Flow in a Metro Station and Improving Measures: A Case Study in Guangzhou, China

In order to ensure the safety of passengers using metro stations and staff working at them, some cities choose to set security checks at the entrances of metro stations. There is no doubt that security check can help keep dangerous objects out of a metro station. However, the security check can also slow down the entering speed of passenger flow and lead to congestions that may affect passengers’ travel plans. How security check will impact the passenger flow and how to reduce the impact are questions that need to be addressed. In this study, metro station models were constructed using the building structure and passenger flow data of a realistic metro station in Guangzhou, China. By using the AnyLogic simulation software, the traffic characteristics of passenger flow under the scenarios with and without a security check were compared and discussed. The congested areas in the station hall and possible causes were analyzed. In addition, possible improving measures such as adding security check machines and ticket vending machines were also modeled to test their effectiveness on reducing the congestion in the station. Results show that when security checks are set at each entrance of the station being studied, the flow rate of passengers entering the gate machine could be decreased by 49.4%~83.3%, which can cause serious congestion at the entrance during rush hours. By adding security check machines and ticket vending machines at the entrances with high passenger traffic demands, the congestion near these entrances could be greatly reduced

Quantum Hamiltonian Algorithms for Maximum Independent Sets

Two quantum Hamiltonian algorithms have been proposed to solve the maximum independent set problem: the PK algorithm, introduced in [Phys. Rev. A 101 (2020) 012318; Chin. Phys. Lett. 38, (2021) 030304], and the the HV algorithm, presented in [Science 376 (2022) 1209]. Here we demonstrate that the two algorithms are mathematically equivalent. Specifically, the Hamiltonian in the PK algorithm can be viewed as the HV Hamiltonian in the interaction picture. We remark on potential practical advantages of the PK algorithm.Comment: 3page

Influence of

In order to evaluate the influence of Daphnia magna and Ceratophyllum demersum on the control of algae under different phosphorus concentrations, Cyclotella sp., Microcystis aeruginosa, and Chlorella vulgaris were selected to establish an aquatic microcosmic model. When the phosphorus concentration ranged from 0.05 to 2 mg L−1, D. magna significantly inhibited the three species of algae from different phylum, particularly M. aeruginosa, and the total growth rates of the three species of algae decreased with the increase of phosphorus concentration. When the phosphorus concentration ranged from 0.05 to 2 mg L−1, C. demersum imparted a significant inhibition of the three species of algae, particularly M. aeruginosa. The total growth rates of the three species of algae were reduced with higher phosphorus concentrations; however, the effect was lower than that of D. magna, with C. vulgaris as the dominant species. When the phosphorus concentration ranged from 0.05 to 2 mg L−1, D. magna combined with C. demersum inhibited the growth of the three species of algae to a considerable degree, which was an improvement over that of other experimental groups using only D. magna or C. demersum by themselves. The total growth rates of algae were reduced with higher phosphorus concentrations. When the phosphorus concentration ranged from 0.05 to 0.1 mg L−1, the removal rates of phosphorus exceeded 90%, and the phosphorus concentration became the limiting factor in the culture system. We observed that under higher initial phosphorus concentrations, the nitrogen removal rate increased, whereas the phosphorus removal rate decreased.Three species of water blooms algae from different phylum (Cyclotella sp., Microcystis aeruginosa, Chlorella vulgaris), zooplankton (Daphnia magna), and aquatic macrophyte (Ceratophyllum demersum) were selected to establish an aquatic microcosmic model, which was to facilitate quantitative study of the relationships between the concentrations of nitrogen or phosphorus and the three types of organism. The results of the study will provide an important reference for the control of water blooms

Engineering Donor-Acceptor Conjugated Polymers for High-Performance and Fast-Response Organic Electrochemical Transistors

To date, high-performance organic electrochemical transistors (OECTs) are all based on polythiophene systems. Donor-acceptor (D-A) conjugated polymers are expected to be promising materials for OECTs owing to their high mobility and comparatively low crystallinity (good for ion diffusion). However, the OECT performance of D-A polymers lags far behind that of the polythiophenes. Here we synergistically engineered the backbone, side chain of a series of diketopyrrolopyrrole (DPP)-based D-A polymers and found that redox potential, molecular weight, solution processability, and film microstructures are essential to their performance. Among the polymers, P(bgDPP-MeOT2) exhibited a figure-of-merit (μC*) of 225 F cm–1 V–1 s–1, over one order of magnitude higher than previously reported D-A polymers. Besides, the DPP polymers exhibited high hole mobility over 2 cm2 V−1 s−1, significantly higher than all D-A polymers employed in OECTs, leading to fast response OECTs with a record low turn-off response time of 30 μs. The polymer also exhibited better stability than polythiophene systems with current retention of 98.8% over 700 electrochemical switching cycles. This work provides a systematic solution to unleash the high-performance and fast-response nature of D-A polymers in OECTs

Revealing the Role of Polaron Distribution on the Performance of n-Type Organic Electrochemical Transistors

Organic electrochemical transistors (OECTs) have shown great potential in bioelectronics and neuromorphic computing. However, the low performance of n-type OECTs impedes the construction of complementary-type circuits for low-power-consumption logic circuits and high-performance sensing. Compared with their p-type counterparts, the low electron mobility of n-type OECT materials is the primary challenge, leading to low μC* and slow response speed. Nevertheless, no successful method has been reported to address the issue. Here, we find that the charge carrier mobility of n-type OECTs can be significantly enhanced by redistributing the polarons on the polymer backbone. As a result, 1 order of magnitude higher electron mobility is achieved in a new polymer, P(gPzDPP-CT2), with a simultaneously enhanced μC* value and faster response speed. This work reveals the important role of polaron distribution in enhancing the performance of n-type OECTs

Recent Advances in Decellularized Extracellular Matrix-Based Bioinks for 3D Bioprinting in Tissue Engineering

In recent years, three-dimensional (3D) bioprinting has been widely utilized as a novel manufacturing technique by more and more researchers to construct various tissue substitutes with complex architectures and geometries. Different biomaterials, including natural and synthetic materials, have been manufactured into bioinks for tissue regeneration using 3D bioprinting. Among the natural biomaterials derived from various natural tissues or organs, the decellularized extracellular matrix (dECM) has a complex internal structure and a variety of bioactive factors that provide mechanistic, biophysical, and biochemical signals for tissue regeneration and remodeling. In recent years, more and more researchers have been developing the dECM as a novel bioink for the construction of tissue substitutes. Compared with other bioinks, the various ECM components in dECM-based bioink can regulate cellular functions, modulate the tissue regeneration process, and adjust tissue remodeling. Therefore, we conducted this review to discuss the current status of and perspectives on dECM-based bioinks for bioprinting in tissue engineering. In addition, the various bioprinting techniques and decellularization methods were also discussed in this study