Pola Pemanfaatan Lahan dan Faktor-faktor Perkembangan Wilayah Perkotaan di Kabupaten Sleman dan Kabupaten Bantul

Penelitian ini bertujuan untuk menganalisis pertumbuhan wilayah perkotaan, terutama dinamika wilayah periurban yang menjadi target perluasan aktivitas perkotaan, terutama permukiman. Fenomena urbanisasi kontemporer ini terjadi akibat migrasi kelompok ekonomi menengah ke pinggiran kota seiring dengan meningkatnya kepadatan pusat kota yang berdampak pada penurunan kualitas lingkungan hidup. Keinginan untuk mencari lingkungan permukiman yang lebih baik merupakan faktor pendorong utama, di samping keterbatasan lahan permukiman di pusat kota. Hasil yang didapat menunjukkan bahwa perambahan lahan di wilayah periurban telah merubah struktur ruang dan pola pemanfaatan lahan. Pada dimensi ekonomi, perkembangan aktivitas perkotaan di wilayah periurban telah memicu pergeseran struktur ekonomi primer yang berbasis potensi agraris menuju sektor jasa dan perdagangan akibat perubahan struktur sosial

Fundamental aspects of appropriate technology: Proceedings of the international workshop on appropriate technology, Delft University of Technology, Center for Appropriate Technology, September 4-7, 1979

Delft University of Technolog

Will ortho-enriched water increase the durability of concrete?

Water molecules exist as two spin isomers, differing by the relative orientation of the nuclear spins of the two hydrogen atoms: either antiparallel (para-water, S=0) or parallel (ortho-water, S=1) [1]. The transition between these nuclear spin states can be achieved through magnetic symmetry breaking via a field gradient across the spins applied by a suitably placed magnetic moment for a sufficiently long time [2]. The contradictory mechanisms of interaction between water or an aqueous solution and magnetic field were reviewed, especially the one expanded on Dynamically Ordered Liquid Like Oxyanion Polymers (DOLLOP) [3]. Then the state of art agreements that have been proved by reproductive experiments or theories were discussed. A new hypothesis for the magnetic effects on the interconversion of nuclear spin isomers of water at the interface of water-O2 was proposed, as well as its applicability in the structure modification of C-S-H.Materials and Environmen

A review: Reaction mechanism and strength of slag and fly ash-based alkali-activated materials

Alkali-activated materials (AAM) are known to be environmentally friendly alternatives to cement-based materials because they can potentially reduce greenhouse gas emissions and reutilize industrial by-products/wastes. To study the factors influencing the strength of slag based alkali-activated materials (BFS-AAM), fly ash based alkali-activated materials (FA-AAM), slag, and fly ash-based alkali-activated materials (BFS/FA-AAM), and clarifying their reaction mechanisms, this paper reviews current knowledge about the mechanical properties and the reaction mechanisms of BFS-AAM, FA-AAM, and BFS/FA-AAM. The precursor requirements and the strength control factors are summarized. The control factors for the strength of BFS/FA-AAM are the BFS/binder ratio, the Na2O/binder ratio, the SiO2/Na2O ratio, and the w/binder ratio. Ion concentrations, determined by these control factors, play a decisive role in the development of strength. Generally, the strength is proportional to the BFS/FA ratio. The optimal values of the Na2O/binder ratio of BFS-AAM and FA-AAM are between 5.5% and 8% and between 7 and 10%, respectively. The optimal values of the SiO2/Na2O ratio of BFS-AAM and FA-AAM are between 0.85 and 1.4 and between 0.6 and 1, respectively. Increasing the w/binder ratio will only benefit workability but will affect the strength negatively. A w/binder ratio of around 0.4 may strike a balance between strength and workability.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Materials and Environmen

Integrating dynamic signaling commands under fixed-block signaling systems into train dispatching optimization problems

In railway operations, when a disruption occurs, train dispatchers aim to adjust the affected schedule and to minimize negative consequences during and after the disruption. As one of the most important components of the railway system, railway signals are used to guarantee the safety of train services. We study the train dispatching problem with consideration of railway signaling commands under the fixed-block signaling system. In such a system, signaling commands dynamically depend on the movement of the preceding trains in the network. We clarify the impact of the signaling commands on train schedules, which has so far been neglected in the literature on railway train dispatching, and we propose an innovative set of signaling constraints to describe the impact. The determination of the signal indicators is presented using “if-then” constraints, which are further transformed into linear inequalities by applying two transformation properties. Activation of the train speed limits that result from the signaling commands is the core purpose of the signaling constraints, and this is implemented by using the signal indicators. Moreover, we formulate the Greenwave (GW) policy, which requires that trains always proceed under green signals, and we further investigate the impact of the GW policy on delays. In numerical experiments, the proposed signaling constraints are employed within a time-instant optimization problem, which is a mixed-integer linear programming (MILP) problem. The experimental results demonstrate the effectiveness of the proposed signaling constraints and show the impact of the signaling commands and GW policy on the train dispatching solution.Transport Engineering and LogisticsTeam DeSchutte

Insights in the chemical fundamentals of ASR and the role of calcium in the early stage based on a 3D reactive transport model

Prediction of alkali silica reaction is still difficult due to the lack of a comprehensive understanding of its chemical fundamentals. In-site experimentally revealing the fundamentals is not realistic as ASR shows over several years or even decades and is affected by many factors. In this paper, by utilizing a 3D reactive-transport simulation model at microscale, we have numerically explored the fundamentals of ASR in the early stage under the influence of reactive silica fraction, alkali concentration, silica disorder degree and aggregate porosity. Based on the simulation results, the chemical sequences of ASR, the initial location of ASR products, the mechanism behind and the role of calcium under the influence of the above factors are elaborated. Furthermore, a comprehensive mechanism to explain the pessimum reactive aggregate content is derived. The results of this paper give some insights about ASR in the early stage such as the initial expansion locations.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Materials and Environmen

Multi-Area Predictive Control for Combined Electricity and Natural Gas Systems

The optimal operation of an integrated electricity and natural gas system is investigated. The couplings between these two systems are modeled by energy hubs, which serve as interface between the loads and the transmission infrastructures. Previously, we have applied a distributed control scheme to a static three-hub benchmark system. In this paper, we propose an extension of this distributed control scheme for application to energy hubs with dynamics. The dynamics that we consider here are due to storage devices present in the multi-carrier system. We propose a distributed model predictive control approach for improving the operation of the system by taking into account predicted behavior and operational constraints. Simulations in which the proposed scheme is applied to the three-hub benchmark system illustrate the potential of the approach.Delft Center for Systems and ControlMechanical, Maritime and Materials Engineerin

Effect of Activator Solutions on the Thixotropic Behavior of Alkali-Activated Slag Concrete

Alkali-activated material (AAM) is developed as a green alternative binder to replace Portland cement (PC) in the construction field. However, the large-scale application with AAM concrete is limited so far, with the insufficient knowledge of rheological behavior being a major obstruct. Thixotropy of concrete is of great interest, which can be helpful to predict various early-age performances. The current study dedicates to evaluating the thixotropy of alkali-activated slag (AAS) concrete mixtures with different silicate and water content in activator solutions. In specific, the silicate modulus (Ms) and water to binder (w/b) ratio have been varied. The thixotropic index calculated by the initial and equilibrium shear stress from the stress growth test, as well as the breakdown area obtained by applying different shear speeds were used to evaluate the thixotropy of AAM concrete. Results indicate a good correlation between different approaches. It was found that an increase in Ms led to more pronounced thixotropic behaviors in AAS concrete due to the rapid nucleation and accumulation of early hydration products, resulting in significant increases in peak torque values and slight reductions of torque at equilibrium. Besides, the concrete thixotropy gradually declined by applying a higher w/b ratio.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Materials and Environmen

Model-based predictive control applied to multi-carrier energy systems

The optimal operation of an integrated electricity and natural gas infrastructure is investigated. The couplings between the electricity system and the gas system are modeled by so-called energy hubs, which represent the interface between the loads on the one hand and the transmission infrastructures on the other. To increase reliability and efficiency, storage devices are present in the multi-carrier energy system. In order to optimally incorporate these storage devices in the operation of the infrastructure, the capacity constraints and dynamics of these have to be taken into account explicitly. Therefore, we propose a model predictive control approach for controlling the system. This controller takes into account the present constraints and dynamics, and in addition adapts to expected changes of loads and/or energy prices. Simulations in which the proposed scheme is applied to a three-hub benchmark system are presented.Delft Center for Systems and ControlMechanical, Maritime and Materials Engineerin

A mix design methodology of slag and fly ash-based alkali-activated paste

In this paper, a series of experiments were conducted to systematically and quantitively explore the effects of control factors on the early age properties, i.e., workability and strength of slag and fly ash-based alkali-activated paste (BFS/FA-AAP). The control factors on the workability (flowability and setting time) of BFS/FA-AAP include the Na2O/b ratio, the SiO2/Na2O ratio, the w/b ratio, and the BFS/b ratio. The control factors on strength (compressive strength and flexural strength) of BFS/FA-AAP further also include the curing condition and the curing age. The results show that a higher BFS/b ratio and Na2O/b ratio could increase the strength while decreasing the workability. A higher w/b ratio could increase the workability while slightly decreasing the strength. Higher SiO2/Na2O ratio increases both strength and workability. Despite that, higher Na2O/b ratio and SiO2/Na2O ratio could hinder the strength development. Sealed curing condition is proved to be a simple but efficient way to assure the steady strength development of BFS/FA-AAP. Although the strength of BFS/FA-AAP could generally stabilize after 90 days, the strength development rate varies with different mix proportions. In addition, a general methodology have been proposed to predict the compressive strength of BFS/FA-AAP and verified with experiments. Finally, a mix design table is proposed for the preliminary design of BFS/FA-AAP according to the principle of satisfying early age requirements.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Materials and Environmen