Failure of reinforced concrete and tuff stone masonry buildings as consequence of hydrogen pipeline explosions

Pipelines are the most efficient method of transporting large quantities of hydrogen, and the low volumetric energy density of gaseous hydrogen requires that the gas must be compressed to extremely high pressure to be used as a transport fuel. The failure of high pressure hydrogen gas pipelines and subsequent explosion may induce heavy damage to buildings. In this paper, such an issue is addressed for existing reinforced concrete framed buildings and tuff stone masonry buildings. Physical features such as the gas jet release process, flammable cloud size, blast generation and propagation, and explosion effects on structural components of buildings are considered and evaluated through the SLAB integral model, Multi-Energy Method and pressure‒impulse diagrams. Damage to both types of structural components was evaluated and the maximum distance of blast damage was derived in several environmental conditions, contributing to land-use planning and performance-based design/assessment of pipelines and buildings.     

Special Z-scheme CdS@WO3 hetero-junction modified with CoP for efficient hydrogen evolution

In order to explore new materials capable of producing the new energy hydrogen, co-catalyst CoP was successfully modified Z-scheme hetero-junction CdS@WO₃ to achieve efficient splitting of water under visible light. With the lactic acid solution as sacrificial agent, the H₂ production was 736.89 μmol corresponding the apparent quantum yield of 1.72%, which was 20.2 and 24.5 times than pure CdS and WO₃, respectively. The results of XRD, TEM and FESEM characterization showed that the catalyst has obvious micro-morphology and high crystallinity. The valence distribution and composition of elements in the catalyst were measured by XPS. UV-vis, PL and electrochemical detection showed that the catalyst has excellent optical and electrical properties such as rapidly photo-generated charge transfer efficiency. Not only the energy band structure of the catalyst was calculated and analyzed, simultaneously the charge transfer mechanism and HER mechanism were explored and proposed.     

Novel porous carbon felt cathode modified by cyclic voltammetric electrodeposited polypyrrole and anthraquinone 2-sulfonate for an efficient electro-Fenton process

A novelty two-step synthesized porous carbon felt (PCF) cathode modified by cyclic voltammetric (CV) electrodeposited polypyrrole (Ppy) and anthraquinone 2-sulfonate (AQS) (PCF/Ppy/AQS) for an efficient electro-Fenton process has been investigated. Brunauer Emmett Teller (BET) and scanning electron microscope (SEM) measurements verified the three-dimensional porous structure of the PCF, revealing that the specific surface area was approximately 2.5 times higher than that of the bare carbon felt (CF), which ensured more active sites available for oxygen reduction reaction (ORR). In addition, the electrodeposited Ppy decreases the charge transfer resistance (R_ct) of the PCF cathode. AQS, a type of anthraquinone that can serve as an oxygen reduction catalyzer, could accelerate the ORR process and subsequently improve the performance of the electro-Fenton system. Rotating disk electrode (RDE) analysis confirmed that the ORR catalyzed by AQS was a double-electron reduction process, which contributed to hydrogen peroxide (H₂O₂) generation. The removal efficiency of total organic carbon (TOC) from Rhodamine B (RhB) could reach 51% within 1 h in the electro-Fenton system equipped with the PCF/Ppy/AQS, resulting in an improvement of approximately 24% compared with the bare CF cathode without porous treatment. The cycle experiment showed a good stability of the PCF/Ppy/AQS cathode. Additionally, the possible mechanism of degradation process in the electro-Fenton equipped with the PCF/Ppy/AQS cathode was proposed based on the electron paramagnetic resonance (EPR) analysis and quenching experiment. The novel fabricated PCF/Ppy/AQS provides an alternative as a high-efficiency cathode, yielding energy savings in the electro-Fenton system.     

Risk appraisal of passing zones on two-lane rural highways and policy applications

Passing on two-lane rural highways is associated with risks of head-on collision resulting from unsafe completion of passing maneuvers in the opposite traffic lane. In this paper, we explore the use of time-to-collision (TTC) as a surrogate safety measure of the risk associated with passing maneuvers. Logistic regression models to predict the probability to end the passing maneuver with TTC less than 2 or 3 s-threshold were developed with the time-gap from initiation of the maneuver to arrival of the opposite vehicle (effective accepted gap), and the passing duration as explanatory variables. The data used for model estimation was collected using stationary tripod-mounted camcorders at 19 passing zones in Uganda. Results showed that passing maneuvers completed with TTC less than 3 s are unsafe and often involved sudden speed reduction, flashing headlights, and lateral shift to shoulders. Model sensitivity analysis was conducted for observed passing durations involving passenger cars or short trucks (2–3 axles), and long trucks (4–7 axles) as the passed vehicles for 3 s TTC-threshold. Three risk levels were proposed based on the probability to complete passing maneuvers with TTC less than 3 s for a range of opposite direction traffic volumes. Applications of the results for safety improvements of two-lane rural highways are also discussed.     

Control of indoor CO2 concentration based on a process model

Air-tight buildings need to have ventilation systems, although the use of these systems results in heavy energy consumption within the building sector. For this reason they have to be adequately regulated in order to achieve good indoor air quality and lower operation costs. The main challenge is to optimize regulation in office buildings, theaters, museums, and schools, where there are large fluctuations and heavy operating costs. Each further optimization leads directly to a better indoor climate and a reduction in energy consumption. In the case of ventilation systems, PI or PID regulators are usually used. In the described research an internal model control (IMC) system was designed with an internal loop, which constantly checks the momentary CO₂ concentration, and makes the necessary adjustments to the air flow. The results showed a significant improvement in the CO₂ level when using an IMC controller, in comparison with PI controller. The desired indoor air quality is achieved more than 80% of the time, with lower operating costs.     

Using mental mapping to unpack perceived cycling risk

Cycling is the most energy-efficient mode of transport and can bring extensive environmental, social and economic benefits. Research has highlighted negative perceptions of safety as a major barrier to the growth of cycling. Understanding these perceptions through the application of novel place-sensitive methodological tools such as mental mapping could inform measures to increase cyclist numbers and consequently improve cyclist safety. Key steps to achieving this include: (a) the design of infrastructure to reduce actual risks and (b) targeted work on improving safety perceptions among current and future cyclists.This study combines mental mapping, a stated-preference survey and a transport infrastructure inventory to unpack perceptions of cycling risk and to reveal both overlaps and discrepancies between perceived and actual characteristics of the physical environment. Participants translate mentally mapped cycle routes onto hard-copy base-maps, colour-coding road sections according to risk, while a transport infrastructure inventory captures the objective cycling environment. These qualitative and quantitative data are matched using Geographic Information Systems and exported to statistical analysis software to model the individual and (infra)structural determinants of perceived cycling risk.This method was applied to cycling conditions in Galway City (Ireland). Participants’ (n = 104) mental maps delivered data-rich perceived safety observations (n = 484) and initial comparison with locations of cycling collisions suggests some alignment between perception and reality, particularly relating to danger at roundabouts. Attributing individual and (infra)structural characteristics to each observation, a Generalised Linear Mixed Model statistical analysis identified segregated infrastructure, road width, the number of vehicles as well as gender and cycling experience as significant, and interactions were found between individual and infrastructural variables. The paper concludes that mental mapping is a highly useful tool for assessing perceptions of cycling risk with a strong visual aspect and significant potential for public participation. This distinguishes it from more traditional cycling safety assessment tools that focus solely on the technical assessment of cycling infrastructure. Further development of online mapping tools is recommended as part of bicycle suitability measures to engage cyclists and the general public and to inform ‘soft’ and ‘hard’ cycling policy responses.     

Modeling of degradation processes in historical mortars

The aim of presented paper is modeling of degradation processes in historical mortars exposed to moisture impact during freezing. Internal damage caused by ice crystallization in pores is one of the most important factors limiting the service life of historical structures. Coupling the transport processes with the mechanical part will allow us to address the impact of moisture on the durability, strength and stiffness of mortars. This should be accomplished with the help of a complex thermo-hygro-mechanical model representing one of the prime objectives of this work. The proposed formulation is based on the extension of the classical poroelasticity models with the damage mechanics. An example of two-dimensional moisture transport in the environment with temperature below freezing point is presented to support the theoretical derivations.     

Impact of natural weathering on medium-term self-healing performance of fiber reinforced cementitious composites with intrinsic crack-width control capability

The paper investigates the medium-term self-healing performance of fiber reinforced cementitious composites with intrinsic crack-width control capability under natural weathering. The pre-cracked specimens with different damage levels are exposed to various humidity conditions, namely, water submersion, natural weathering, and a laboratory environment with constant humidity. The medium-term self-healing performance is evaluated using a resonant frequency test, tensile test, SEM, and EDX. It is concluded that the medium-term cracked specimens can moderately recover their mechanical properties within 90 days after being submerged in water or exposed to natural weathering. In particular, they are able to resume the multiple cracking behavior and exhibit a reloading strength larger than the preloading strength. Furthermore, the identified compositions of the medium-term healing products for specimens exposed to water and natural weathering conditions are similarly characterized. The reported results imply that effective medium-term self-healing can be realized in fiber reinforced cementitious composites with intrinsic crack-width control capability under natural weathering.     

Geographies of policy knowledge: The state and corporate dimensions of contemporary policy mobilities

Situated within geographical scholarship on policy mobilities, this article aims to direct attention to the state and corporate dimensions of corporate policy mobilizations as terrains that require further conceptual development. It argues that doing so is important for two reasons. First, it shows that national states should not be seen merely as functional and institutional infrastructures across and through which policies circulate, since national state policymakers also operate as active agents of policy mobilization across space and scale, especially in contexts of strong, centralized governance. Second, it illustrates how the economic dimensions of corporate actors engaged in mobilizing policy deserve more sustained analyses for a better conception of how firms' capitalist agendas shape their participation as policy transfer agents. We suggest that a relational economic geography perspective provides a set of conceptual tools — actors, networks, and value — to unpack the corporate rationalities and knowledge-sharing processes of firms. Drawing on research conducted on the Sino-Singapore Tianjin Eco-city, we show how national state policymakers and transnational conglomerates are active agents in circulating urban sustainability expertise across space. An appreciation of these geographies of policy knowledge across the state and corporate domains of policy mobilization is a first step towards grasping these varied registers of expertise, and their implications for the form and content of policies on the move.