bluuebunny/crossref_metadata_2025 huggingface dataset:
Deformation characteristics of sedimentary rock due to continuous changes of moisture content in wetting process
Authors: Togashi Yota , Imano Takanobu , Osada Masahiko
Published: April 2021

In recent years, the number of cases where tunnels are constructed in sedimentary rock layers has increased. It is essential to investigate the deformation characteristics of sedimentary rocks for predicting tunnel deformation. The mechanical properties of sedimentary rocks are widely varied due to moisture content. The rocks are dried by tunnel excavation and wetted by groundwater gushing or backfilling. It is necessary to grasp the changes of deformation characteristics of sedimentary rocks due to moisture changes. In this study, soaking tests were conducted on Neogene period Japanese tuff sampled at Utsunomiya, Japan. In the test, the cylindrical tuff specimens are air dried by over 240 hours at first. Then the tuff specimens are taken in pure water with measuring deformations in detail. There are no effective stress increases by soaking and only uniform matric suction are acted on the specimen without any restraints. The results demonstrated that strain tensor was reached to stable state for 2 - 3 days, and the value of the normal strain perpendicular to the bedding plane is greater than the other normal components and shear strains are also observed in both cases. Although the orientation of the maximum principal strain is in the near of the bedding orientation at the initial dry state, the orientation are suddenly rotated to the normal orientation of the bedding plane. It means that the principal orientation of anisotropy are rotated due to continuous moisture changes.
Effects of the underground discharge channel/reservoir for small urban rivers in the Tokyo area
Authors: Nakamura H , Oosawa M
Published: April 2021

In the midst of global climate change, a large typhoon has hit Japan and unprecedented heavy rainfall is occurring. In large cities in Japan, underground discharge channels and underground regulating reservoirs are being developed to improve the flood control safety.

In this paper, we confirm the flood reduction effect of these underground facilities against the rainfall generated by Typhoon Hagibis in the Tokyo area in 2019.

In addition, the advantages of underground regulating reservoirs in the metropolitan area are discussed from two aspects: cost and land acquisition. It is confirmed that the underground reservoir type has remarkable advantages in both aspects.
Geothermal energy in urban planning
Authors: Akhmetzyanov Anvar , Bobylev Nikolai , Wende Wolfgang
Published: April 2021

Geothermal energy is a collective term referring to Earth heat extraction and use of the ground capacity to absorb and store thermal energy to supply heat or cold. Thermal ground exchange or shallow geothermal energy has been increasingly used in the housing sector to sustain comfortable room temperature. Increasing utilization of geothermal energy, particularly in urban areas, requires integration into urban planning processes. The question of subsurface planning, or underground space integration into land-use planning, or three-dimensional planning has been an emerging research theme in this decade. This paper will focus on specific issues that pertain to geothermal energy use in land use planning in urban areas. These issues include (1) holistic vision of underground space as a resource, (2) geothermal energy technologies in terms of using space, (3) multiple users and installations of heat pumps and their interaction, (4) possible conflicts and interference with other subsurface users and functions, (5) demand and suitability of geothermal use in housing, (6) urban densities and geothermal energy feasible use, (7) and general principles of urban geothermal land use planning. A feasibility case study of using heat pumps to provide heating for a typical historic residential multifamily building in the Petrogradsky district of the city of St. Petersburg, Russia is given.
Computer modeling analysis of METRO ticket gates impact to evacuation procedures
Authors: Rebecca Papakonstantinou , Anastasios Kallianiotis , Despina Papakonstantinou , Maria Menegaki
Published: April 2021

Subway rail system is considered the best choice for big cities to solve surface transportation problems in terms of congestion, efficiency, and speed. The increasing use of these facilities by more and more passengers has made vital the need to ensure high safety standards. The effective structure of the evacuation plan in an emergency event is essential. A critical factor for a successful evacuation is the proper functioning of the egress paths that must be clear of any obstacles.

To ensure the passengers’ proof-of-fare (POF) public transport organizations have installed ticket validation machines proportionally in the facilities. In Athens METRO system, ticket gates providing automatic fare collection have replaced these ticket validation machines. Both POF systems may be considered as egress path obstructions that need to be taken into account in the initial evacuation plan design, since these POF installations provide different available width on the evacuation paths.

The paper investigates the impact of prior ticket validator and modern automatic fare collector machines on evacuation procedures in Athens METRO stations. The impact evaluation is based on three factors: i) total evacuation time, ii) time spent in queues (overcrowding effect) and iii) egress path flow rate, evacuation obstruction, human behavior.
Parameters that affect tenability conditions during fire emergency in metro tunnels
Authors: Papakonstantinou D , Kallianiotis A , Benardos A
Published: April 2021

Underground spaces are characterized by special conditions and complexity, as well as by severe consequences in the event of an accident. Although the frequency of fire accidents in tunnels or metro stations is low, in worst cases they may lead to severe fatalities and damages. In order to have a more accurate prediction of fire impacts, most safety standards enforced worldwide suggest the development of special risk analyses. This needs to be made having in mind fire characteristics, geometrical and ventilation parameters so as to have an accurate view of the thermal and smoke propagation within the underground space. In this paper a parametric analysis is carried out, varying input values, crucial for fire risk analysis, like fire curve and heat release rate maximum (HRRmax), as well as ventilation and tunnel geometry. Key factors like visibility conditions, temperature and CO concentration are recorded through the fire dynamic simulation (FDS), in order to determine the conditions inside the metro tunnel. Furthermore, the fractional effective dose (FED) that occupants might receive in a period of time, in different positions inside the tunnel, is calculated. Based on the above, detailed data on the prevailing conditions are gathered and conclusions can be drawn regarding the influence of each parameter’s evolution on the tenability conditions inside the tunnel. Hence, the analysis can illuminate key issues to consider for performing an accurate risk analysis in an underground environment.
Visualization of 3D rock mass properties in underground tunnels using extended reality
Authors: Janiszewski M , Uotinen L , Szydlowska M , Munukka H , Dong J , Rinne M
Published: April 2021

The term extended reality (XR) refers to a family of technologies that cover Virtual Reality (VR), Augmented Reality (AR), and Mixed Reality (MR). The main benefit of XR is that it can offer a new viewpoint on the surrounding environment by augmenting it with digital data and visualizations. Recent developments of XR enable its deployment for rock engineering applications, including underground tunnels. In this paper, we demonstrate two cases of the use of XR in an underground tunnel to display spatial information on the tunnel surface. One of the tunnels in the Underground Research Laboratory of Aalto University (URLA) was digitized using Structure-from-motion (SfM) photogrammetry. As a result, a high-resolution 3D point cloud and textured model of the tunnel were created. Next, the rock joint planes were obtained semi-automatically from the digitized rock surfaces. The results are then represented in their actual positions in the tunnel geometry. In the first case, we used VR to display the rock joint planes on the textured model of the tunnel. In the second case, the data was displayed in real-time in tunnel conditions through a mobile device. The results demonstrate that XR technology can be successfully used in underground construction to digitize the workplace and provide a new perspective on the work environment, which can potentially lead to an increase in safety and productivity.
Control Strategy of RGV Operation Blockage and Deadlock in Plane Mobile Stereo Garage
Authors: Chang Lidan , Li Jianguo
Published: April 2021

Aiming at the safety requirements of multi-RGV and multi-lift planar mobile stereo garage access vehicles, a time window-based system RGV operation blocking and deadlock control strategy is proposed. Combining the improved banker algorithm with the time window principle, the banker algorithm is used to evaluate the security of the RGV running path. If an unsafe state is detected, the RGV operation blocking and deadlock control strategy based on the time window algorithm is given. The verification is detailed through specific cases. The results show that the RGV operation blocking and deadlock control strategy proposed in this paper can improve the RGV operation efficiency while increasing the system security.
Analysis of Wind-Resistant Ability and Failure Mode of Prefabricated WPC Enclosure Based on ABAQUS
Authors: Luo Tong , Chen Shangwei , Wang Qiaoyan
Published: April 2021

In this paper, a prefabricated wood-plastic enclosure finite element analysis model, and its stress distribution under wind load and the failure mode of the enclosure under the maximum wind load bearing capacity are analyzed with the ABAQUS finite element code. The results show that under the horizontally distributed load, the mid-span deflection, mid-span stress and strain of the baffle gradually increase from bottom to top. The column has greater constraints on the baffles 1-1 to 1-3, and less on the upper baffle, resulting in a gradual increase in the maximum stress of the upper baffle. When the horizontally distribution load reached the maximum load of 1.74 KPa, cracks began to appear at the support contacts of the columns, resulting in component failure.
Application of BIM Technology in Building Mechanical and Electrical Engineering Modeling and Pipeline Inspection
Authors: Hong Cheng , Ming Xia , Liu Kai , Tu Bin , Yu Jiaxing
Published: April 2021

With the development of China’s urbanization process, the development of China’s construction industry is in full swing. There are more and more large scale and special shaped buildings, and the electromechanical engineering and construction projects are more complex. The traditional architectural design and construction technology level could not meet the needs. The BIM Technology can build the whole building model completely, and carry out collision detection and analysis optimization of various specialties design stage, a series of problems can be avoided in the later stage. In this paper, Shanghai Baoshan project is taken as the research object, and the collision between the building model and the electromechanical pipeline is analyzed by using BIM software.
Research on Shear Capacity of Concrete-Filled Square Steel Tubular Column to Unequal Height Steel Beam Joint with External Diaphragm
Authors: Lin Yongan , Xu Kailong , Xu Chengxiang , Gao Jie , Fei Jianbao
Published: April 2021

In order to study the shear bearing capacity of joints with concrete-filled square steel tubular column and unequal height steel beam, 4 joints specimens were tested under low-reversed cyclic lateral loading. 17 models with different parameters were established by using OpenSees finite element software, and the nonlinear finite element analysis had been carried out. The failure models and shear strain changes of the specimens were observed. The results showed that the shear failure modes of joints can be divided into a small core panel zone mode and an entire panel zone mode. Based on the test and numerical simulation results, the simplified shear model of joints with unequal height steel beam is established, and the method for calculating the shear capacity of the joint is put forward, which is composed of the steel tube webs of the panel zone, the concrete of the panel zone, the steel tube flange of the panel zone and the external diaphragm. The calculation results are in good agreement with the experimental values and numerical simulation results. The calculation method can accurately evaluate the shear bearing capacity of this type of joints and can be used as a reference for the application of practical engineering.
A Method of the Durability Life Prediction for Chinese Historical Reinforced Concrete Structure
Authors: Jin Hui , Chun Qing
Published: April 2021

In order to evaluate the durability of historical reinforced concrete buildings with square rebars more accurately, a calculation method of durability life for this type of buildings is proposed in this paper. The method mainly includes structural component importance analysis and the calculation method of the durability life prediction for single concrete component with square rebars. Compared with the existing durability evaluation standards and methods based on round rebars, this method is closer to the actual structure status. The works of the paper can be used for the durability evaluation of square steel reinforced concrete buildings and provide a reference for its repair and protection.
Reinforcement Design of Three -Valves Towers and Effect Evaluation Based on Monitoring Data
Authors: Li Changping , Ma Xinteng , Liu Yang
Published: April 2021

Numerous three-valves towers for communication distributed around urban districts suffer from structural degradation during operation. The traditional methods using encased steel to strengthen the structure are not suitable for three-valves towers. To address this issue, a reinforcement method based on the combined section is proposed for improving the structural performance of three-valves towers. In this method, main bars are added at the side of the maximum stress axis of the original tower with multi-point hinge joints, which are also connected with the flange plate of the original tower by welding. After that, to evaluate the reinforcement effect precisely, the structural health monitoring (SHM) system for towers is established to obtain the data of horizontal displacement continuously before and after the reinforcement. Finally, the reinforcement of an actual three-valves tower is implemented using the method described above, with relatively low costs and a short period of construction. And the data acquired from the SHM system shows that the structural performance of this tower has been improved notably after the reinforcement.
Experimental Investigations on the Connection Strength of Kerf Anchorage Stone Panels
Authors: Wang Zuohu , Luo Yikang , Gao Zhanguang , Yao Yuan
Published: April 2021

Seventy-two stone panels were tested to investigate the failure mode and connection strength of the kerf anchorage stone cladding panel. The following factors were considered in this study: the distance between the kerf and the edge of the stone panel, the stone type, the kerf depth and the insertion depth of the connector. The experimental results show that the connection strength of white granite is twice as high as that of golden granite under the same conditions. Increasing the insertion depth of the connector increases the connection strength of the stone panel. The connection strength increases when the distance between the kerf and the edge of the panel is increased from 70 mm to 90 mm, and the connection strength for a 20-mm kerf depth is higher than that for a 30-mm kerf depth under the same conditions. There is still a certain error between the test results and the calculation results of current standard.
Considering Grid Division Optimization of Free-Form Surface Roof Structure
Authors: Ye Bentao , Wang Fawu , Duan Yang
Published: April 2021

The free-form surface roof structure is widely used in large-span public buildings due to its beautiful shape. Its grid division form is diverse, and the size and shape of the structural grid directly affect its bearing performance. In this paper, the grid optimization research is carried out for the free-form surface single-layer reticulated shell roof, based on the Rhino platform and the grasshopper module for parametric modeling. The karamba plug-in is used for structural analysis, and the roof structure of different grid divisions under various load conditions is analyzed, computing its response and its carrying capacity. Genetic algorithm is used to optimize free-form surface roof structure, with grid density, member bar length and section size as parameters. Comprehensive consideration of structural self-weight and maximum displacement and other design goals are considered. It provides reference for the design of free-form roof structure.
Calculation of Deformation and Ductility of Steel Fiber Reinforced High-Strength Concrete Columns
Authors: Liu Hui
Published: April 2021

Based on the simple stress-strain relationship of steel fiber concrete, the influence of strain coordination factor on the cross section is analyzed, and the calculation equation of curvature ductility coefficient is deduced. According to the law of curvature distribution of flexural members, the curvature distribution is simplified into two-segment and three-segment linear distribution, and the corresponding calculation equations of length, load and deflection of different sections are deduced, and the calculation method based on the theoretical curve of load-deflection is proposed. Compared with the test results, the ductility coefficient, the theoretical curve of load-deflection and the test results all show a high degree of coincidence.
Vibration Signal-based Structural Damage Detection through Deep Learning and Digital Image Correlation
Authors: Teng Shuai , Chen Gongfa
Published: April 2021

The methods that structural damage detection (SDD) based on vibration signal can effectively detect invisible structural damages. This paper presents a progressive SDD method using a deep learning algorithm and the digital image correlation (DIC) measurement technique. As structural damage will affect the structural mass, damping and stiffness, and then leads to changes in dynamic response, thus the vibration signal may be able to effectively reflect structural defects. A vibration signal database was established from the experimental tests of a steel frame under random excitations, a camera used to record the vibration responses of the structure. The DIC method was employed to obtain the dynamic displacements of the points of interest (POIs). The obtained POI displacement signal was employed as the training and testing data for a convolutional neural network (CNN) which was designed to classify vibration signals. The results confirm that it was feasible to employ a CNN to detect structural damage, the accuracy was nearly 100%, the computational performance and accuracy exceed back-propagation neural networks (BPNN); its uptime was only about 12% that of the BPNN. It has been demonstrated that: (1) the CNN was sensitive to the structural damage detection; (2) the computational performance of the CNN was superior to that of the BPNN.
Research on Application Practice of Rebar Mechanical Connection
Authors: Yin Yong , Zeng Hong , Deng Xinjie
Published: April 2021

The development of rebar connection technology is the key to improve the construction quality of construction projects, and the application of related technologies can also improve the construction quality and efficiency of construction projects. The connection process of mechanical connection of steel bar requires higher requirements, which is different from the welding and binding connection of steel bar. The quality of mechanical joint also needs strict inspection. At present, grade I joints are widely used in high-rise buildings. How to ensure the quality of mechanical connection has become one of the key points of high-rise building quality control. Combined with specific engineering projects, this paper mainly analyzes the practical application of rebar mechanical connection technology in construction, and elaborates on rebar processing, product protection, quality control, etc., in order to provide technical reference for the work of relevant personnel in the field of construction engineering.
Research on Rust Removal and Rust Prevention Method of Super-High-Rise Steel Structure
Authors: Yin Yong , Zeng Hong , Deng Xinjie
Published: April 2021

The super high-rise steel structure is exposed to the natural environment for a long time, due to the long construction period of super high-rise buildings and the great impact of natural and social environment. If the steel structure is not properly protected, it will cause structural quality problems. Super high-rise steel structure has large volume and high height, so its rust prevention and rust removal methods are quite different from ordinary steel structure. This paper combines the actual engineering projects and briefly describes the ultra-high-rise steel structure rust removal, rust prevention construction and quality; safety assurance measures. Through the comprehensive application of this project, the feasibility of relevant countermeasures is confirmed, with a view to the follow-up similar projects can be useful and helpful.
Experimental Study on Seismic Performance of Eccentrically Braced Steel Frame with Full Bolts Connection
Authors: Zhou Xin , Wang Xinwu , Yu Yongqiang , Li Tong , Shi Qiang
Published: April 2021

In order to study the seismic performance of fully bolted semi-rigid eccentrically braced steel frame, a pseudo-static loading test was carried out on a single-story single-span eccentrically braced steel frame. The seismic behavior of the specimen has been analyzed according to the failure mode, hysteresis curve, bearing capacity, ductility, energy dissipation performance, and stiffness degeneration etc. The experiment results show that this structural system has fairly good energy dissipation capacity, strong bearing capacity and excellent ductility. Except for the link, other members of the frame are in the elastic stage, indicating that the specimen is easy to repair after earthquake. The hysteresis curve of the specimen shows significant pinch phenomenon owing to the slip of the bolt.
Experimental Study on Joint Properties of Steel Secondary Beam Connected with Concrete Main Beam Using an Embedded Part
Authors: Sun Xiaohong , Feng Xiaoxiao , Yang Shutong , Li Shenglin , Wang Yanqiang
Published: April 2021

In this paper, a joint of I-shaped steel secondary beam connected with concrete main beam using an embedded part was simplified from a practical engineering by adopting the scale 1:3. Six specimens were tested. The effects of different concrete main beam heights (245 mm and 295 mm), concrete floor slab, rigidity of steel secondary beam and height difference between the secondary beam and main beam tops on the mechanical performance and failure mode of specimens were analyzed. Results show that flexural failure is often found in the steel secondary beam. But the failure mode is changed to joint failure in the main beam if the rigidity of steel beam is increased locally at the mid-span region. Moreover, setting floor slab and increasing rigidity of steel secondary beam can all improve the load-carrying capacity of the joint. The safety of joint can be obtained by strengthening the stirrups adjacent to the embedded part and longitudinal steel bars under the part.
Study on the Grouting Properties of Multi-Mineral Cement Paste
Authors: Liu Hengrui , Tian Zhenghong , Sun Xiao , Fan Haoyue
Published: April 2021

In this study, the effect of zeolite powder (ZP) and basalt powder (BP) on the grout properties of cement slurry was explored. The grout properties include fluidity, rheology, cohesiveness, segregation resistance and mechanical properties. In addition, the three-parameters mathematical models were established to better understanding the relationship above properties. The experimental results show that the incorporation of ZP or BP can effectively reduce the bleeding rate and improve the cohesiveness of cement paste, and this improvement become more significant with the increase of the ZP, BP content and the w/c ratio. Under the appropriate dosage, the cement paste can also have good compressive strength and rheological properties. The results of the three-parameter model indicated that rheological parameters, flow parameters, and cohesiveness-bleeding rate systems all can become the main factors affecting the 28day compressive strength. Flow parameters systems and rheological parameter systems were not the main factors that determine the cohesiveness of cement slurry. On the contrary, cohesiveness can significantly affect the rheological properties of cement paste.
Study on Compressive Strength of Self-Compacting Concrete (SCC) Based on Fly Ash
Authors: Yu Guoping , Chen Ru , Luo Changtai , Xie Banghua
Published: April 2021

Fly ash (FA) has a good effect on the fluidity and strength of self-compacting concrete (SCC). The experimental research method was adopted, equipped with C35 self-compacting concrete, w/c =0.4 and FA content a =0%∼40%. The compressive strength of SCC was studied for T=3d, 7d, 14d, 28d, 60d. It is found that FA has a great impact on the compressive strength of SCC. With the continuous addition of FA, the strength of SCC increases at first, and then decreases. When a =25%, the compressive strength of SCC is best, reaching 47.3 MPa. As with ordinary concrete, the strength of SCC varies with curing time. When T=7d-14d, SCC strength increases less.
Corrosion Cracking Performance of Corrosion Resistant Steel Bars and Carbon Reinforced Concrete Columns under Axial Compression
Authors: Zhong Xiaoping , Peng Lange , Dai Renli , Yuan Chengbin
Published: April 2021

In order to study the difference in the development of corrosion expansion cracks between corrosion-resistant steel bars and carbon reinforced concrete columns, the accelerated corrosion method of dry-wet cycle and constant current energization was used to study the distribution, shape and crack width of corrosion expansion cracks over time. The research results show that: under the coupling action of axial compression load and chloride salt, the initial corrosion cracks of 5Cr corrosion-resistant reinforced concrete columns appear later than carbon reinforced concrete columns, and the direction of corrosion cracks is along the direction of the main reinforcement. There is nearly no rust expansion crack of stirrup. In the early stage of corrosion (theoretical corrosion rate less than 5%), 5Cr corrosion-resistant reinforced concrete columns are dominated by single-sided cracking, and the total length and expansion width of cracks are less than that of carbon reinforced concrete columns; the later period of corrosion (theoretical corrosion rate between 5% and 15%) Two types of reinforced concrete columns have obvious double-sided cracking. After a long period of corrosion by chloride salt, the total length and corrosion expansion width of cracks of 5Cr corrosion-resistant reinforced concrete columns increase faster than that of carbon reinforced concrete columns. The corrosion resistance “reversed” in the later stage of corrosion.
Thin-suspended 2D materials: facile, versatile, and deterministic transfer assembly
Authors: Rebollo I G , Rodrigues-Machado F C , Wright W , Melin G J , Champagne A R
Published: April 2021

We report a deterministic 2D material (2DM) transfer method to assemble any-stacking-order heterostructures incorporating suspended ultra-thin 2DMs, such as single-layer graphene (SLG) and bilayer graphene (BLG). The transfer procedure relies on a single-step preparation nitrocellulose micro-stamp, which combines both outstanding adhesion and softness. It permits the dry pick-up of naked 2D crystals (graphene, MoS2, and hBN) directly from a SiO2 substrate, and to precisely transfer them on substrates or trenches. Optical and Raman data show that no significant defect is introduced upon transfer, even in suspended SLG and BLG. The areas transferred range up ∼1000 µm2 on substrate. High-yield transfer of suspended ultra-thin 2DMs does not require critical point drying for areas up to 15 µm2 or suspension heights down to 160 nm. To demonstrate the method’s capabilities, we assembled on-substrate and suspended optical cavities tuning BLG’s Raman scattering intensity by factors of 19 and 4, respectively. This resilient and rapid 2DM transfer procedure will accelerate the fabrication of many heterostructures and permit versatile suspension of 2DMs for research in twistronics, straintronics, and nano-opto-electro-mechanical systems.
Effects of the beam offset on microstructure and properties of electron beam welded tantalum and Inconel 718 joints
Authors: Jia Shudang , Li Dong , Tao Fu , Fan Linhao , Chen Jieshi
Published: April 2021

In this paper, electron beam welding of tantalum and Inconel 718 superalloy was performed. The formability, microstructure, defect characteristics and mechanical properties of joints were investigated by controlling the position of the electron beam. The weld zone of tantalum and Inconel 718 joints was mainly composed of columnar crystals and dendrites during the welding of non-beam offset and 0.5 mm beam offset to tantalum. The reaction layer composed of a large number of intermetallic compounds was found on the tantalum side, and it was the place where the fracture occurred. Tensile strength of the joints was 313 MPa and 138 MPa, respectively, and the joints exhibited brittle fracture mode due to the formation of voids and cracks in the reaction layer. The microhardness of the weld zone was higher than that of the base metal due to the strengthening effect of tantalum. Fortunately, when the beam deviated by 0.5 mm to the Inconel 718 side, equiaxed grains formed in the weld zone, and the morphology of the reaction layer changed, which improved the toughness of the joint. The tensile strength of the joint reached 480 MPa under the condition of 0.5 mm beam deviated to the Inconel 718 side.
A study on the static recrystallization behavior of an ultrahigh-strength stainless steel
Authors: Wang Xiao-hui , Liu Zhen-bao , Liang Jian-xiong , Yang Zhi-yong , Sun Yong-qing , Wang Chang-jun , Qi Yue
Published: April 2021

The static recrystallization (SRX) behavior of an ultrahigh-strength stainless steel (UHSSS) was investigated via double-hit isothermal compression tests. The results revealed that the kinetics of static recrystallization and the corresponding microstructural evolution were not only prominently influenced by the deformation parameters and initial microstructures but also suppressed due to the precipitation of M6C carbides below 1050 °C, which sufficiently pinned the boundaries. Numerical models for predicting the recrystallized fraction and grain sizes were proposed based on the experimental results. The kinetics model could predict the process of SRX in the deformation temperature range from 1050 °C to 1150 °C well, whereas there were some deviations between the predictions and experimental results due to the interaction of the M6C carbides and SRX when the deformation temperature was below 1050 °C.
The role of copper on the restoration of graphene oxide by chemical vapor deposition
Authors: Yang Xinliang , Zhang Zijian , He Sifan , Wu Wenjie , Shu Xiangfeng , Chen Yijun , Zhang Zhaokai , Jiang Kai , Liu Jianlong , Song Yenan
Published: April 2021

High-quality reduced graphene oxide (rGO) sheets can be accessible through Langmuir-Blodgett self-assembly (LBSA) on copper foil and dielectric substrate under high temperature ethanol vapors via chemical vapor deposition (CVD) process. Through the LBSA forming method, a uniform and smooth graphene oxide (GO) film can be obtained on the target substrate, which is more economical and efficient compared to the traditional growth strategy. Moreover, the GO-derived graphene film repaired on copper was nearly defect-free with a negligible defect density (ID/IG ratio of <0.1) and manifested a strong 2D peak, indicating high efficiency of defects restoration. The obtained rGO sheets exhibited excellent electrical properties (1.2 kΩ/sq prepared on SiO2/Si, 0.2 kΩ/sq prepared on copper and subsequently transferred to SiO2/Si) that had surpassed other GO-derived graphene ever reported. Meanwhile, we demonstrate that Cu-vapor will degrade the restoration efficiency when introduced remotely, which is quite different from previous studies on graphene growth.
Experiment on low-frequency electromagnetic waves propagating in shock-tube-generated magnetized cylindrical enveloping plasma
Authors: GUO Shaoshuai , XIE Kai , SUN Bin , XI Ruoyao , LIU Yan
Published: April 2021

We propose a method of applying a static magnetic field to reduce the attenuation of the magnetic field component (S
H) of low-frequency electromagnetic (LF EM) waves in dense plasma. The principle of this method is to apply a static magnetic field to limit electron movement, thereby increasing the equivalent resistance and thus reducing the induced current and S
H. We consider the static magnetic field acting on the plasma of the entire induced current loop rather than on the local plasma, where the induced current is excited by the magnetic field component of LF EM waves. Analytical expressions of S
H suitable for magnetized cylindrical enveloping plasma are derived by adopting an equivalent circuit approach, by which S
H is calculated with respect to various plasma parameter settings. The results show that S
H can be reduced under a static magnetic field and the maximum magnetic field strength that mitigates blackout is less than 0.1 T. Experiments in which LF EM waves propagate in a shock-tube-generated magnetized cylindrical enveloping plasma are also conducted. S
H measured under the magnetic field (the magnetic field strength B
0 acting on the magnetic field probe was about 0.06 T) reduces at f = 10 MHz and f = 30 MHz when n
e ≈ 1.9 × 1013 cm−3, which is consistent with theoretical results. The verification of the theory thus suggests that applying a static magnetic field with a weak magnetic field has the potential to improve the transmission capacity of LF EM waves in dense plasma.
A physical origin of cross-polarization and higher-order modes in two-dimensional (2D) grating couplers and the related device performance limitations
Authors: Georgieva Galina , Voigt Karsten , Seiler Pascal M , Mai Christian , Petermann Klaus , Zimmermann Lars
Published: April 2021

We explore scattering effects as the physical origin of cross-polarization and higher-order modes in silicon photonic 2D grating couplers (GCs). A simplified analytical model is used to illustrate that in-plane scattering always takes place, independent of grating geometry and design coupling angle. Experimental investigations show furthermore that grating design parameters are especially related to the modal composition of both the target- and the cross-polarization. Scattering effects and the associated cross-polarization and higher-order modes are indicated as the main reason for the higher 2D GC insertion loss compared to standard 1D GCs. In addition, they can be responsible for a variable 2D GC spectrum shape, bandwidth and polarization dependent loss.
Recent advances in acoustic diagnostics for electrochemical power systems
Authors: Majasan Jude O , Robinson James B , Owen Rhodri E , Maier Maximilian , Radhakrishnan Anand N P , Pham Martin , Tranter Thomas G , Zhang Yeshui , Shearing Paul R , Brett Dan J L
Published: April 2021

Over the last decade, acoustic methods, including acoustic emission (AE) and ultrasonic testing (UT), have been increasingly deployed for process diagnostics and health monitoring of electrochemical power devices, including batteries, fuel cells, and water electrolysers. These techniques are non-invasive, highly sensitive, and low-cost, providing a high level of spatial and temporal resolution and practicality. Their application in electrochemical devices is based on identifying changes in acoustic signals emitted from or propagated through materials as a result of physical, structural, and electrochemical changes within the material. These changes in acoustic signals are then correlated to critical processes and the health status of these devices. This review summarises progress in the use of acoustic methods for the process and health monitoring of major electrochemical energy conversion and storage devices. First, the fundamental principles of AE and UT are introduced, and then the application of these acoustic techniques to electrochemical power devices are discussed. Conclusions and perspectives on some of the key challenges and potential commercial and academic applications of the devices are highlighted. It is expected that, with further developments, acoustic techniques will form a key part of the suite of diagnostic techniques routinely used to monitor electrochemical devices across various processes, including fabrication, post-mortem examination and recycle decision support to aid the deployment of these devices in increasingly demanding applications.
A DFT study on the electronic structure of in-plane heterojunctions of graphene and hexagonal boron nitride nanoribbons
Authors: dos Santos Ramiro M , Giozza William F , de Sousa Junior Rafael T , da Silva Filho Demétrio A , Santos Renato B , Ribeiro Júnior Luiz A
Published: April 2021

The structural similarity between hexagonal boron nitride (h-BN) and graphene nanoribbons allows forming heterojunctions with small chain stress. The insulation nature of the former and the quasi-metallic property of the latter make them attractive for flat optoelectronics. Recently, shapes of graphene and h-BN domains were precisely controlled, creating sharp graphene/h-BN interfaces. Here, we investigated the electronic and structural properties of graphene (h-BN) nanoribbon domains of different sizes sandwiched between h-BN (graphene) nanoribbons forming in-plane heterojunctions. Different domain sizes for the non-passivated zigzag edge termination were studied. Results showed that the charge density is localized in the edge of the heterojunctions, regardless of the domain size. The systems with graphene domains are metallic, presenting null band gaps. The ones with the h-BN island are small-bandgap semiconductors with the highest bandgap value around 0.2 eV. The calculated bandgap has the same magnitude of the certain threshold for density functional theory. As a general trend, these materials exhibit a ferromagnetic behavior, which can be useful for magnetic applications at the nanoscale.
Microfabricated fiducial markers for digital image correlation-based micromechanical testing of LIGA Ni alloys
Authors: Liew Li-Anne , Read David T. , Martin May L. , Christenson Todd R. , Geaney John T.
Published: April 2021

Photolithographically defined thin film Au dots were used as micro fiducial markers for digital image correlation (DIC), to enable two-dimensional strain measurement of 200 μm-thick LIGA (Lithographie, Galvanformung, Abformung) nickel alloys. Due to the sensitivity of electrodeposited films’ microstructure and properties on the processing conditions, characterization of LIGA mechanical properties continues to be necessary for microsystems commercialization. DIC offers advantages over laser-based strain measurement techniques but creating suitable speckle patterns on specimens with dimensions under a millimeter is challenging. The material surface roughness itself is often used as the speckle pattern, or micro- or nanoparticles are applied to the surface. But for materials with highly polished surfaces, such as commercial LIGA alloys, the surface roughness is not always suitable, while application of particles still poses technical challenges in uniformity and reproducibility. We fabricated freestanding tensile specimens, with gauge sections 700 μm wide × 3 mm long × 200 μm thick, from electrodeposited Ni-10% Co using a commercial LIGA process, and conducted microtensile tests at strain rate 0.001 s−1. Designing and fabricating arrays of randomly oriented 1.5 μm-thick Au dots on the specimens provided a suitable way to obtain full-field surface strains over the entire gauge lengths and was reproducible from one specimen to another. Microfabricated fiducial markers therefore can be a useful surface-preparation approach for investigating micromechanical behavior, particularly plasticity and fracture, of LIGA films using DIC.
Guinea: The History of the Military as a Political Actor
Authors: Clarke Paul
Published: April 2021

The Guinean military was deeply intertwined with political power for the first 50 years after dependence in 1958. Under its founding president, Ahmed Sékou Touré, who led Guinea as a one-party state from 1958 to 1984, it was built with support from the Warsaw Pact and became a small, competent force which supported national development and regional peacekeeping. While Touré politicized the army, it was not an important political actor, and in the end it fell victim to Touré’s brutality. Colonel Lansana Conté seized power after Touré, leading a military dictatorship that fully controlled the government and succumbed to factionalism, corruption, and indiscipline. Conté died in 2008, and within a year, the successor regime had slipped into so much brutality that the military leaders accepted transition to civilian rule, making Guinea a fledging multiparty democracy since 2010, while the military returned to the barracks.
Electronic Monitoring Around the World
Authors: Nellis Mike
Published: April 2021

Since its operational beginnings in the United States in 1982—where its prototypes were first experimented with in the 1960s and 1970s—the electronic monitoring (EM) of offenders has spread to approximately 40 countries around the world, ostensibly—but not often effectively—to reduce the use of imprisonment by making bail, community supervision, and release from prison more controlling than they have hitherto been. No single authority monitors the development of EM around the world, and it is difficult to gain fully comprehensive accounts of what is happening outside the Western and Anglophone users of it. Some countries are secretive. Standpoints in writing on EM are varied and partisan. Although it still tends to be the pacesetter of technical innovation, the United States remains a relatively lower user of EM, in part because the exceptional punitiveness of its penal culture has inhibited its expansion, even when it has itself been developed in various punitive ways. Interprofessional and intergovernmental processes of “policy transfer” have contributed to EMs spreading around the world, but the commercial bodies that manufacture and market EM equipment have been of at least equal importance. In Europe, the Confederation of European Probation (CEP), a transnational probation advocacy organization, took an early interest in EM, and its regular conferences became a touchstone of international debate. As it developed globally, the United Nations reluctantly accepted that it may be of some value even in developing countries and set out standards for its use. Continuing innovations in EM technology will create new possibilities for offender supervision, both more and less punitive, but it is always culture, commerce, and politics in particular jurisdictions which shape the scale, pace, and form of its development.
Play as Curriculum
Authors: Chappell Drew
Published: April 2021

Play as an academic field comprises multiple disciplines, definitions, and objectives and acknowledges a link between play and learning. Historically and in contemporary societies, play has been used as a teaching methodology; this occurs in formal classroom pedagogy as well as outside the classroom as part of informal and improvisational curriculum. Because play generally includes a component of pleasure, as a methodology it compels entry into learning in a way other practices do not. Yet this playful learning can be problematic, depending on outcomes and structures that define the play/learning experience through narrative and power dynamics. Scholars may analyze various aspects of curricular play, including but not limited to narratives provided, students’ lived experiences within those narratives, actions allowable, objectives and advancement, and sources developing the narratives.
Music as Curriculum
Authors: Lake Robert
Published: April 2021

Throughout history, music has been a dynamic force in both formal and informal settings of education for all ages, places, and cultural identities. Music as curriculum is focused on this phenomenon in and through a wide array of cultural and historical contexts. Connections between music and curriculum may be understood through Joseph Schwab’s four commonplaces of curriculum which are milieus, teacher, learner, and subject matter. These connections are recognized and understood in greater detail by exploring the role of music in creating or affirming solidarity, empathy, cultural identity, content acquisition, educational connoisseurship, as well as learner-centered curiosity. Music as curriculum explores these aspects holistically as a way to maximize educational experiences through multiple ways of knowing that are actively present in music.
Grounding Indigenous Teacher Education Through Red Praxis
Authors: Garcia Jeremy , Shirley Valerie , Grande Sandy
Published: April 2021

Red Praxis centers Indigenous sovereignty rooted in epistemological and ontological orientations to place—to land. Applying Red Praxis requires teachers to understand, in greater detail, the ways in which settler and Indigenous ontologies represent not only different but also competing ways of being in the world. Red Praxis asks teachers to reconceptualize an intellectual space that reaffirms, reclaims, and (re)stories our relations to land as a decolonial practice and pedagogy of refusal. Red Praxis calls for Indigenous teachers and community educators to ground teaching in decolonial practices and aims to regenerate a sense of hope in rebuilding Indigenous communities. The exigencies of Red Praxis can be found within Indigenous teachers’ application of critical Indigenous theories and ongoing acknowledgement and protection of our relationship to land—the origin for our claim to exist as Indigenous peoples. In doing so, Red Praxis is about creating curriculum and enacting pedagogy that makes evident and mitigates the impact of settler colonialism on Indigenous communities’ knowledge systems and ways of being.

Red Praxis is an extension of Sandy Grande’s theory and model of Red pedagogy. Grande proposed the pedagogical framework of Red pedagogy to rethink the ways in which teaching can confront the challenges Indigenous communities face in the 21st century. Red pedagogy is about critically analyzing the material realities resulting from the settler colonial project and creating decolonial spaces of resistance, hope, self-determination, and transformative possibility in Indigenous education. In addition to addressing structural issues, it is important for Indigenous teachers to address what is taught in schools—the curriculum—as well as how it is taught—pedagogy—as key factors in revitalizing and transforming Indigenous education.