Optimized Construction Process Research Articles

Three-dimensional-printed calcium alginate/graphene oxide porous adsorbent with super-high lead ion adsorption ability in aqueous solution

Using three-dimensional (3D) printing technology, a 3D calcium alginate/graphene oxide (3D CA/GO) adsorbent, with a hierarchical macroporous structure, was successfully constructed. Owing to the optimized construction process, the 3D CA/GO showed an enhanced adsorption capacity (490.2 mg/g at pH = 3.0) for lead (Pb(II)) in aqueous solution, which was two times higher than reported in the literature). Meanwhile, the selective adsorption ratio of 3D CA/GO for Pb(II) reached 99.8% when positive ions occurred. In addition, after eight adsorption–desorption cycles, the adsorption capacity did not experience a significant decrease and the structure remained stable. Meanwhile, the adsorbed Pb(II) could be eluted by hydrochloric acid. Moreover, through characterization analysis and Ca(II) releasing experiment, we confirmed that the adsorption mechanism of 3D CA/GO consisted of electrostatic interactions, ion exchange and chelation. According to the actual application experimental, the waste water of medical environment was chosen, and the 3D CA/GO was verified as capable of removing and recycling Pb(II). The immersion experiment using simulation wastewater solution containing heavy metal ions also indicated that 3D CA/GO could maintain structural stability and sustain its adsorption capacity. The excellent structural stability, strong adsorption capacity, and outstanding selective adsorption capacity for 3D CA/GO were attributed to the controllable construction and optimized structure of hierarchical macroporous materials by 3D printing technology.

A Novel Flexible Electrochemical Molecular Imprinted Sensor for the Determination of GABA in Serum of Depressed Mice

The content of γ-aminobutyric acid (GABA) in human serum has been proved to be closely related to depression, so the rapid, sensitive, highly selective and accurate determination of GABA is of great significance for the objective diagnosis of depression. In this study, a molecularly imprinted electrochemical sensor based on high-performance magnetically functionalized reduced graphene oxide (MRGO) was constructed for the sensitive detection of GABA in the serum of depressed mice. Using MRGO modified the flexible electrode (ITO-PET), 2,4-dinitrofluorobenzene derivative of GABA as the template and pyrrole with self-polymerization effect as the functional monomer and cross-linking agent, the molecularly imprinted sensor MIP/MRGO/ITO-PET was successfully constructed by simple electropolymerization and stirring elution. Under the optimal construction process, the sensor realized the accurate detection of GABA in the range of 250 pM ∼ 100 μM, and the detection limit was as low as 1.25 × 10−10 M (S/N = 3). The simultaneous possession of high sensitivity and selectivity, good stability, repeatability and reproducibility enables this sensor to be successfully applicable for the determination of GABA in mice serum. The results showed that the sensor is expected to provide a basis for objective diagnosis of depression in clinic.

Surrounding Rock Stability in Unsupported Roof Area and Rapid Heading Technique for Deep Arch Coal Roadways under Goaf

In order to achieve rapid heading of deep arch coal roadways under goaf, the maximum unsupported roof distance (URD), surrounding rock stability of unsupported roof area and influencing factors, and rapid heading equipment and processes for these roadways are investigated in the context of the working face geology and mining conditions of Coal #9 of a certain coal mine, through theoretical analysis, numerical simulation, equipment modification, and construction process optimization. The following work is carried out: (1) Based on the thin shell theory, a mechanical model of a top cover cylindrical shell for roadways with an arch section is built. The formula for calculating the maximum URD of arch roadways is developed. The influences of roadway width, tensile strength, buried depth, and arch height on the maximum URD are analyzed. The theoretical maximum URD is worked out to be 2.4 m. (2) Numerical simulation reveals that when the URD is around 2 m, the arch roadway is free of tensile failure and the surrounding rock is well stable; when the URD is greater than 4 m, tensile failure occurs on the roadway sides, and the surrounding rock becomes less stable. Therefore, the maximum URD for numerical computation is set to 2–3 m. No additional failure occurs on the arch roof with the increase in URD, suggesting that an arch roof has the best stability. Properly increasing URD can help U-steel to gain support strength more quickly. In the shallow part of a roadway surrounding rock under goaf, failures are primarily determined by vertical stresses, whereas in the deep part, failures are determined by horizontal stresses. (3) A combined onboard standing platform + onboard beam lift device and a new onboard temporary support device for long excavation are developed as a solution to the low shed and temporary support efficiency and safety of roadways with a URD of 2.4 m and used on-site in conjunction with the optimized construction process. The result shows an average footage of over 550 m per month with a peak footage of 846.4 m and 16 supports totaling 14.1 m per shift. Additionally, the forming quality of a shed roadway is good enough to accommodate normal mining of the working face, consequently the rapid heading of the roadway.

The USGT Method for Suspender Tensioning of Self‐Anchored Suspension Bridges

Unlike earth‐anchored suspension bridges, self‐anchored suspension bridges (SASBs) involve a special construction stage, namely, suspender tensioning, in which the tensioning force and sequence are crucial and complicated. Against this background, an example bridge A, a SASB with a steel‐concrete composite beam, is introduced in detail. Using MIDAS finite element software, a suspender tensioning scheme is formulated based on a combination method of the unstrained state method and graded tension method (the USGT method), in which a suspender is tensioned according to its unstrained length. By analyzing the bending moment change of the beam and deflection of the main cable throughout the entire construction process, a “high‐to‐low” suspender tensioning sequence is proposed that also involves symmetrical tensioning from the main towers to the midspan or the anchor positions. In the optimized construction process, the deviation and stress of the main towers are controlled well, thereby ensuring the safety of the main beam and main towers in the construction process.

Simulating quality assurance and efficiency analysis between construction management and engineering geodesy

Abstract High-rise building construction is highly complex and involves many different disciplines. Such projects can only be accomplished efficiently and with appropriate quality by means of an overall optimized construction process. However, the understanding of the term “quality” among involved participants is not always equivalent. E.g. providing required tolerances of elevator shaft walls constantly throughout the concrete works is often a challenging task during the execution of in-situ concrete works. This paper is based on the scientific research project “Efficiency optimization and quality control of engineering geodesy processes in civil engineering” (Effizienzoptimierung und Qualitatssicherung ingenieurgeodatischer Prozesse im Bauwesen - EQuiP), which aimed at developing a method for instant quality assurance in construction based on geodetic surveying techniques, and at the same time optimizing the efficiency of the process, e.g. with respect to time. This paper shows how hierarchical and modular modeling of construction and geodetic processes using high-level Petri nets delivers a base for a real time quality evaluation and re-planning on construction site. As an example, this modeling approach is simulated for the construction of concrete stairs and elevators core of a characteristic high-rise structure. The concrete works were considered to be carried out using climbing formwork. Three different scenarios are shown in this paper. The first scenario is simulated with deterministic durations and validates the developed Petri net. The second scenario uses stochastic process durations to show the robustness of the construction process. Finally, disturbances and delays are integrated and an automated rescheduling based on prioritized alternative paths is used.

Workflow dependency approach for modular building construction manufacturing process using Dependency Structure Matrix (DSM)

The modular construction method is efficient for line production processes in factories. However, many modular unit production factories are having difficulty that how to prevent bottleneck effect, rework, and work congestion through the appropriate level of work packages composition by each work stations to achieve the smooth production. To solve these problems and improve production flow, the authors of this paper propose an optimized construction process at the factory production stage using a Dependency Structure Matrix (DSM) that considers the process approach based on flow of construction information in work activities. To test its effectiveness, the proposed process was applied to a modular factory and was found to reduce the number of main activities from 65 to 43 in comparison with as-is processes. Using this method, a manufacturing manager can thus improve production flow by analyzing the characteristics of work activities that form the plan for the manufacturing sequence decision phase. Moreover, while modular activities are independent of main assembly, there exist strong internal dependencies among these activities such that the manager can check the quality of each module. Furthermore, the research here might help save time in the manufacturing phase in factories.

Delay Minimization for Progressive Construction of Satellite Constellation Network

During the construction of satellite constellation, communication relay service could be provided by a partially constructed constellation through buffering data and forwarding it at a later time. However, this will introduce extra end-to-end delay during the construction period. We propose a scheme to determine an optimal construction process, which is used to insert satellites into appropriate positions in each stage of construction. Simulation results show that our scheme can reduce the average end-to-end delay by 70.1% compared to the traditional scheme.

地域施設整備過程の最適経路の性質

In the planning process of regional facilities, there are many interest groups who have the different opinions respectively. In common sense, it seems that the optimal construction process is determined by their opinions. In this paper, a basic model of construction process of regional facility is formulated. Using the theory of Maximum Principle by Pontryagin, we show that the optimal construction process is independent on the opinions of interest groups. Furthermore, we show the condition on the possibility of construction process.