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A continuous/discontinuous deformation analysis (CDDA) method based on deformable blocks for fracture

Yongchang CAI, Hehua ZHU, Xiaoying ZHUANG

《结构与土木工程前沿（英文）》 2013年第7卷第4期页码 369-378 doi: 10.1007/s11709-013-0222-x

摘要： In the framework of finite element meshes, a novel continuous/discontinuous deformation analysis (CDDA) method is proposed in this paper for modeling of crack problems. In the present CDDA, simple polynomial interpolations are defined at the deformable block elements, and a link element is employed to connect the adjacent block elements. The CDDA is particularly suitable for modeling the fracture propagation because the switch from continuous deformation analysis to discontinuous deformation analysis is natural and convenient without additional procedures. The SIFs (stress intensity factors) for various types of cracks, such as kinked cracks or curved cracks, can be easily computed in the CDDA by using the virtual crack extension technique (VCET). Both the formulation and implementation of the VCET in CDDA are simple and straightforward. Numerical examples indicate that the present CDDA can obtain high accuracy in SIF results with simple polynomial interpolations and insensitive to mesh sizes, and can automatically simulate the crack propagation without degrading accuracy.

关键词： fracture crack propagation deformable block continuous/discontinuous deformation analysis (CDDA)

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Laser ablation of block copolymers with hydrogen-bonded azobenzene derivatives

Jintang Huang, Youju Huang, Si Wu

《化学科学与工程前沿（英文）》 2018年第12卷第3期页码 450-456 doi: 10.1007/s11705-018-1735-6

摘要：

Supramolecular assemblies (PS-b-P4VP(AzoR)) are fabricated by hydrogen-bonding azobenzene derivatives (AzoR) to poly(4-vinyl pyridine) blocks of polystyrene-block-poly(4-vinyl pyridine) (PS-b-P4VP). PS-b-P4VP(AzoR) forms phase separated nanostructures with a period of ~75–105 nm. A second length scale structure with a period of 2 µm is fabricated on phase separated PS-b-P4VP(AzoR) by laser interference ablation. Both the concentration and the substituent of AzoR in PS-b-P4VP(AzoR) affect the laser ablation process. The laser ablation threshold of PS-b-P4VP(AzoR) decreases as the concentration of AzoR increases. In PS-b-P4VP(AzoR) with different substituents (R= CN, H, and CH₃), ablation thresholds follow the trend: PS-b-P4VP(AzoCN)<PS-b-P4VP(AzoCH₃)<PS-b-P4VP(AzoH). This result indicates that the electron donor group (CH₃) and the electron acceptor group (CN) can lower the ablation threshold of PS-b-P4VP(AzoR).

关键词： laser ablation block copolymers hydrogen-bond azobenzene derivatives supramolecular assembly

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Ductility improvement of GFRP-RC beams using precast confined concrete block in compression zone

《结构与土木工程前沿（英文）》 doi: 10.1007/s11709-023-0968-8

摘要： Fiber-reinforced polymers (FRPs) have received considerable research attention because of their high strength, corrosion resistance, and low weight. However, owing to the lack of ductility in this material and the quasi-brittle behavior of concrete, FRP-reinforced concrete (FRP-RC) beams, even with flexural failure, do not fail in a ductile manner. Because the limited deformation capacity of FRP-RC beams depends on the ductility of their compression zones, the present study proposes using a precast confined concrete block (PCCB) in the compression zone to improve the ductility of the beams. A control beam and four beams with different PCCBs were cast and tested under four-point bending conditions. The control beam failed due to shear, and the PCCBs exhibited different confinements and perforations. The goal was to find an appropriate PCCB for use in the compression zone of the beams, which not only improved the ductility but also changed the failure mode of the beams from shear to flexural. Among the employed blocks, a ductile PCCB with low equivalent compressive strength increased the ductility ratio of the beam to twice that of the control beam. The beam failed in pure flexure with considerable deformation capacity and without significant stiffness reduction.

关键词： ductility four-point bending test glass fiber-reinforced polymer precast confined concrete block

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Preparation of polysulfone-based block copolymer ultrafiltration membranes by selective swelling and

《化学科学与工程前沿（英文）》 2022年第16卷第5期页码 745-754 doi: 10.1007/s11705-021-2038-x

摘要： Selective swelling of block copolymers of polysulfone-b-poly(ethylene glycol) is an emerging strategy to prepare new types of polysulfone ultrafiltration membranes. Herein, we prepared nanoporous polysulfone-b-poly(ethylene glycol) ultrafiltration membranes by selective swelling and further promoted their porosity and ultrafiltration performances by using CaCO₃ nanoparticles as the sacrificial nanofillers. Different contents of CaCO₃ nanoparticles were doped into the solution of polysulfone-b-poly(ethylene glycol), and thus obtained suspensions were used to prepare both self-supported and bi-layered composite structures. Selective swelling was performed on the obtained block copolymer structures in the solvent pair of ethanol/acetone, producing nanoporous membranes with poly(ethylene glycol) lined along pore walls. The CaCO₃ nanoparticles dispersed in polysulfone-b-poly(ethylene glycol) were subsequently etched away by hydrochloric acid and the spaces initially occupied by CaCO₃ provided extra pores to the block copolymer layers. The porosity of the membranes was increased with increasing CaCO₃ content up to 41%, but further increase in the CaCO₃ content led to partial collapse of the membrane. The sacrificial CaCO₃ particles provided extra pores and enhanced the connectivity between adjacent pores. Consequently, the membranes prepared under optimized conditions exhibited up to 80% increase in water permeance with slight decrease in rejection compared to neat membranes without the use of sacrificial CaCO₃ particles.

关键词： block copolymers selective swelling ultrafiltration CaCO₃ nanoparticles sacrificial nanofillers

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Thermoresponsive block copolymer supported Pt nanocatalysts for base-free aerobic oxidation of 5-hydroxymethyl

《化学科学与工程前沿（英文）》 2021年第15卷第6期页码 1514-1523 doi: 10.1007/s11705-021-2092-4

摘要： A base-free catalytic system for the aerobic oxidation of 5-hydroxymethyl-2-furfural was exploited by using Pt nanoparticles immobilized onto a thermoresponsive poly(acrylamide-co-acrylonitrile)-b-poly(N-vinylimidazole) block copolymer, with an upper critical solution temperature of about 45 °C. The Pt nanocatalysts were well-dispersed and highly active for the base-free oxidation of 5-hydroxymethyl-2-furfural by molecular oxygen in water, affording high yields of 2,5-furandicarboxylic acid (up to>99.9%). The imidazole groups in the block copolymer were conducive to the improvement of catalytic performance. Moreover, the catalysts could be easily separated and recovered based on their thermosensitivity by cooling the reaction system below the upper critical solution temperature. Good stability and reusability were observed over these copolymer-immobilized catalysts with no obvious decrease in catalytic activity in the five consecutive cycles.

关键词： aerobic oxidation base-free 5-hydroxymethyl-2-furfural Pt nanoparticle thermoresponsive block copolymer

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Deformable image registration with geometric changes

Yu LIU,Bo ZHU

《信息与电子工程前沿（英文）》 2015年第16卷第10期页码 829-837 doi: 10.1631/FITEE.1500045

摘要： Geometric changes present a number of difficulties in deformable image registration. In this paper, we propose aglobal deformation framework to model geometric changes whilst promoting a smooth transformation between source and target images. To achieve this, we have developed an innovative model which significantly reduces the side effects of geometric changes in image registration, and thus improves the registration accuracy. Our key contribution is the introduction of a sparsity-inducing norm, which is typically L1 norm regularization targeting regions where geometric changes occur. This preserves the smoothness of global transformation by eliminating local transformation under different conditions. Numerical solutions are discussed and analyzed to guarantee the stability and fast convergence of our algorithm. To demonstrate the effectiveness and utility of this method, we evaluate it on both synthetic data and real data from traumatic brain injury (TBI). We show that the transformation estimated from our model is able to reconstruct the target image with lower instances of error than a standard elastic registration model.

关键词： Geometric changes Image registration Sparsity Traumatic brain injury (TBI)

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Molecular dynamics study of water diffusion in an amphiphilic block copolymer with large difference in

Yang Zhou, Phillip Choi

《化学科学与工程前沿（英文）》 2017年第11卷第3期页码 440-447 doi: 10.1007/s11705-017-1626-2

摘要： Isothermal-isobaric molecular dynamics simulation was used to study the diffusion mechanism of water in polyurethane- -poly( -isopropyl acrylamide) (PU- -PNIPAm) with a hydrophobic PU/hydrophilic PNIPAm mass ratio of 1.4 to 1 at 298 K and 450 K. Here, the experimental glass transition temperature ( ) of PU is 243 K while that of PNIPAm is 383 K. Different amounts of water up to 15 wt-% were added to PU- -PNIPAm. We were able to reproduce the specific volumes and glass transition temperatures (250 K and 390 K) of PU- -PNIPAm. The computed self-diffusion coefficient of water increased exponentially with increasing water concentration at both temperatures (i.e., following the free volume model of Fujita). It suggested that water diffusion in PU- -PNIPAm depends only on its fractional free volume despite the free volume inhomogeneity. It is noted that at 298 K, PU is rubbery while PNIPAm is glassy. Regardless of temperature, radial distribution functions showed that water formed clusters with sizes in the range of 0.2–0.4 nm in PU- -PNIPAm. At low water concentrations, more clusters were found in the PU domain but at high water concentrations, more in the PNIPAm domain. It is believed that water molecules diffuse as clusters rather than as individual molecules.

关键词： molecular dynamics simulation amphiphilic block copolymer free volume water diffusivity fujita model

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Perspective on gallium-based room temperature liquid metal batteries

《能源前沿（英文）》 2022年第16卷第1期页码 23-48 doi: 10.1007/s11708-022-0815-y

摘要： Recent years have witnessed a rapid development of deformable devices and epidermal electronics that are in urgent request for flexible batteries. The intrinsically soft and ductile conductive electrode materials can offer pivotal hints in extending the lifespan of devices under frequent deformation. Featuring inherent liquidity, metallicity, and biocompatibility, Ga-based room-temperature liquid metals (GBRTLMs) are potential candidates to fulfill the requirement of soft batteries. Herein, to illustrate the glamour of liquid components, high-temperature liquid metal batteries (HTLMBs) are briefly summarized from the aspects of principle, application, advantages, and drawbacks. Then, Ga-based liquid metals as main working electrodes in primary and secondary batteries are reviewed in terms of battery configurations, working mechanisms, and functions. Next, Ga-based liquid metals as auxiliary working electrodes in lithium and nonlithium batteries are also discussed, which work as functional self-healing additives to alleviate the degradation and enhance the durability and capacity of the battery system. After that, Ga-based liquid metals as interconnecting electrodes in multi-scenarios including photovoltaics solar cells, generators, and supercapacitors (SCs) are interpreted, respectively. The summary and perspective of Ga-based liquid metals as diverse battery materials are also focused on. Finally, it was suggested that tremendous endeavors are yet to be made in exploring the innovative battery chemistry, inherent reaction mechanism, and multifunctional integration of Ga-based liquid metal battery systems in the coming future.

关键词： liquid metals soft electrodes flexible batteries deformable energy supply devices epidermal electronics

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Wear mechanism of disc-brake block material for new type of drilling rig

WANG Xinhua, WANG Simin, ZHANG Siwei, WANG Deguo

《机械工程前沿（英文）》 2008年第3卷第1期页码 10-16 doi: 10.1007/s11465-008-0009-2

摘要： To improve friction and wear performance and service life of the disc-brake pair material of a drilling rig, a new type of asbestos-free frictional material with better performance for disc-brake blocks is developed, and its wear mechanism is investigated by friction and wear experiments. Topography and elementary components of the brake block’s wear surface are analyzed by employing SEM and EDAX patterns, revealing its tribological behaviour and wear mechanism. When the frictional temperature is lower, the surface film of the brake block is thinner, dense, smooth with plasticity, and divided into the mixture area, Fe-abundant area, carbon-abundant area and spalling area. The mixture area consists of various constituents of frictional pairs without ploughing and rolling trace. The Fe-abundant area mainly consists of iron and other constituents. The carbon-abundant area is the zone where graphite and organic fibre are comparatively gathered, while the spalling area is the zone where the surface film is spalled and its surface is rough and uneven, with a loose and denuded state. During the period of high frictional temperature, the frictional surface is also divided into the mixture area, Fe-abundant area and spalling area. In this case, the mixture area consists of abrasive dust from friction pairs, and the surface film is distributed with crumby hard granules, exiguous oxide, carbide granules and sheared slender fibre. The Fe-abundant area is mostly an oxide layer of iron with a flaky distribution. Fracture and spalling traces as well as an overlapping structure of multilayer surface films can be easily found on the surface film. The components of the spalling area are basically the same as that of the matrix. At the beginning of wear, the hard peaks from the friction surface of the disc-brake plough on the surface of the brake block. With increasing frictional temperature, the friction surface begins to soften and expand, and oxidized wear occurs at the same time. During the high-temperature wear period, severely influenced by friction heat, obvious softening and plastic flow can be found on the friction surface of the brake block, its anti-shearing ability is weakened, and adhesive wear is intensified. Thermal decomposition of cohesive material in the brake block is simultaneously strengthened, so that constituents shed due to loss of adhesion. Organic fibre is in a flowing state and obviously generates drawing, shearing, carbonization and oxidization. In addition, thermal cracking, thermal oxidization, carbonization and cyclization of organic substances on the surface of brake block can make the friction surface produce pores or cracks, thus fatigue wear occurs.

关键词： asbestos-free frictional Fracture cyclization friction disc-brake

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Spatial embedded reinforcement of 20-node block element for analysis PC bridges

LONG Peiheng, DU Xianting, CHEN Weizhen

《结构与土木工程前沿（英文）》 2008年第2卷第3期页码 274-280 doi: 10.1007/s11709-008-0039-1

摘要： The formula for the contribution of prestressed reinforcement on embedded reinforcement element is derived according to the mechanical behavior of PC bridges and the foundational principle of finite element method. Mechanical concept is definite and examples validate the calculation results. Reinforcement element model allows generating a finite element mesh without taking into consideration the layout of reinforcements. Furthermore, the prestressing tendon may pass through the concrete elements in an arbitrary manner. It is an effective approach that the no-node loads are diverted from the tendons to the adjacent concrete elements. A useful arithmetic analysis of the spatial curved tendon PC Bridges is provided.

关键词： arithmetic analysis calculation prestressed reinforcement mechanical arbitrary

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A block zero-padding method based on DCFT for L1 parameter estimations in weak signal and high dynamic

Chao WU,Lu-ping XU,Hua ZHANG,Wen-bo ZHAO

《信息与电子工程前沿（英文）》 2015年第16卷第9期页码 796-804 doi: 10.1631/FITEE.1500058

摘要： Weak L1 signal acquisition in a high dynamic environment primarily faces a challenge: the integration peak is negatively influenced by the possible bit sign reversal every 20 ms and the frequency error. The block accumulating semi-coherent integration of correlations (BASIC) is a state-of-the-art method, but calculating the inter-block conjugate products restricts BASIC in a low signal-to-noise ratio (SNR) acquisition. We propose a block zero-padding method based on a discrete chirp-Fourier transform (DCFT) for parameter estimations in weak signal and high dynamic environments. Compared with the conventional receiver architecture that uses closed-loop acquisition and tracking, it is more suitable for open-loop acquisition. The proposed method combines DCFT and block zero-padding. In this way, the post-correlation signal is coherently post-integrated with the bit sequence stripped off, and the high dynamic parameters are precisely estimated using the threshold set based on a false alarm probability. In addition, the detection performance of the proposed method is analyzed. Simulation results show that compared with the BASIC method, the proposed method can precisely detect the high dynamic parameters in lower SNR when the length of the received signal is fixed.

关键词： Threshold detection Discrete chirp-Fourier transform Block zero-padding High dynamic Weak L1 signal acquisition

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Repression of CDKN2C caused by PML/RARα binding promotes the proliferation and differentiation block

null

《医学前沿（英文）》 2016年第10卷第4期页码 420-429 doi: 10.1007/s11684-016-0478-3

摘要：

Inappropriate cell proliferation during oncogenesis is often accompanied by inactivation of components involved in the cell cycle machinery. Here, we report that cyclin-dependent kinase inhibitor 2C (CDKN2C) as a member of the cyclin-dependent kinase inhibitors is a target of the PML/RARα oncofusion protein in leukemogenesis of acute promyelocytic leukemia (APL). We found that CDKN2C was markedly downregulated in APL blasts compared with normal promyelocytes. Chromatin immunoprecipitation combined with quantitative polymerase chain reaction demonstrated that PML/RARα directly bound to the CDKN2C promoter in the APL patient-derived cell line NB4. Luciferase assays indicated that PML/RARα inhibited the CDKN2C promoter activity in a dose-dependent manner. Furthermore, all-trans retinoic acid treatment induced CDKN2C expression by releasing the PML/RARα binding on chromatin in NB4 cells. Functional studies showed that ectopic expression of CDKN2C induced a cell cycle arrest at the G₀/G₁ phase and a partial differentiation in NB4 cells. Finally, the transcriptional regulation of CDKN2C was validated in primary APL patient samples. Collectively, this study highlights the importance of CDKN2C inactivation in the abnormal cell cycle progression and differentiation block of APL cells and may provide new insights into the study of pathogenesis and targeted therapy of APL.

关键词： CDKN2C acute promyelocytic leukemia cell cycle arrest differentiation

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一个基于混沌的分组密码算法的分析

金晨辉

《中国工程科学》 2001年第3卷第6期页码 75-80

摘要：

“基于混沌的分组密码置换网络的设计”一文提出的一个分组密码算法在已知明文攻击和唯密文攻击下都是很容易被破译的,而且在知道加密变换的条件下,很容易利用分割攻击方法求出该分组密码的密钥。此外,基于Logistic映射的混沌序列的相邻值之间的相互制约性,以及该混沌序列的前若干值对初值的低位比特不敏感。

关键词：混沌序列分组密码移位密码唯密文攻击已知明文攻击分割攻击

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detection methods for amplify-and-forward relay-aided device-to-device systems with full-rate space-time block Article

Kang-li ZHANG, Cong ZHANG, Fang-lin GU, Jian WANG

《信息与电子工程前沿（英文）》 2017年第18卷第6期页码 788-795 doi: 10.1631/FITEE.1700018

摘要：中继辅助设备到设备通信是下一代蜂窝网络中一项极具潜力的技术。研究了适用于配置多天线的放大转发中继辅助设备到设备通信系统的不同传输方案。为了解决基于全速率空时块码传输方案的传统最大似然检测算法复杂度高的问题，文中提出两种低复杂度检测方法，分别为采用最大似然合并算法的检测方法和采用联合条件最大似然检测器的检测方法。特别是，所提的基于联合条件最大似然检测器的检测方法，能够通过牺牲一定的存储空间换取较好的并行处理能力。仿真结果表明：针对采用全速率空时块码传输方案提出的两种检测方法，能够获得与传统最大似然检测方法近乎相同的误符号率，但所提检测方法复杂度更低；同时，采用基于全速率空时块码的传输方案比复用传输方案具有更优的误码性能。仿真结果还进一步验证了对所提检测方法的分集增益分析。

关键词：设备到设备通信；中继；检测；全速率空时块码

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Stem cell research in hepatocellular carcinoma

SUN Chengyi, ZUO Shi

《医学前沿（英文）》 2008年第2卷第1期页码 1-4 doi: 10.1007/s11684-008-0001-6

摘要： The traditional view that adult human liver tumors, mainly hepatocellular carcinoma (HCC), arise from mature cell types has been challenged in recent decades. The results of several studies suggest that HCC can be derived from liver stem cells. There are four levels of cells in the liver stem cell lineage: hepatocytes, hepatic stem cells/oval cells, bone marrow stem cells and hepato-pancreas stem cells. However, whether HCC is resulted from the differentiation block of stem cells and, moreover, which liver stem cell lineage is the source cell of hepatocarcinogenesis remain controversial. In this review, we focus on the current status of liver stem cell research and their roles in carcinogenesis of HCC, in order to explore new approaches for stem cell therapy of HCC.

关键词： lineage hepato-pancreas differentiation block carcinogenesis current status