Hierarchical Transport Research Articles

Mathematical Models of the Problem of Constructing Delivery Routes of Cargo in the Internal Zones of Trunk Nodes of a Hierarchical Transport Network

Mathematical Models of the Problem of Constructing Delivery Routes of Cargo in the Internal Zones of Trunk Nodes of a Hierarchical Transport Network

Modeling the distribution of industrial enterprise products in hierarchical transport and logistics systems

Modeling the distribution of industrial enterprise products in hierarchical transport and logistics systems

A dual-height wick to improve capillary performance of vapor chambers

The wick performance is a crucial metric for ensuring the reliable and efficient operation of vapor chambers (VCs) away from dry-out. To enhance the performance of VC, a pitcher plant inspired enhanced wick characteristic dual-height microgrooves (DHMW) was fabricated on 6063 aluminum alloy by one-step picosecond laser texturing without chemical modification. This study describes the two-step capillary behavior of DHMW by high-speed camera and infrared camera. The effects of minor rib number, groove height ratio, length scale, and test liquids (water, acetone, ethanol) on the capillary performance were investigated. When using water as the working fluid, the DHMW achieved a K/Reff of 1.182 µm, which was about 71.3 % larger than that of normal microgroove wicks due to the liquid propagation effect and the flow resistance reduction effect. Furthermore, the maximum K/Reff could reach 1.819 µm of the sample with a minor rib depth of about 70 μm. However, the wetting results showed that the droplets of acetone and ethanol tend to spread laterally after contact with the surface, which is unfavorable for the formation of hierarchical transport in the DHMW. This study demonstrates that laser texturing is an effective and controllable method for the complex shaping of grooved aluminum wicks, with the potential to improve the heat transport capability of VCs.

Highly permeable PA@GO loose nanofiltration membranes enabled by hierarchical transport channels for efficient dye removal

Graphene oxide (GO) membranes exhibit ultrafast water permeation properties, which have been employed in various membrane-based separations including nanofiltration for dye removal from textile wastewater. However, it’s still a great challenge to achieve precise control over the microstructure of GO membranes and obtain ultrathin GO membranes with exceptional separation efficiency and robust membrane structure. Herein, in-situ confined interfacial polymerization (IP) is proposed for fabricating loose polyamide (PA)@GO hybrid membranes with high permeance and dye rejection as well as robust membrane stability. A new diamine of sulfadiazine (SA) with intrinsic hydrophilic and conjugated sulfonamide groups is employed as cross-linker of GO membranes and monomer of PA in IP process, simultaneously. PA is in-situ synthesized in confined GO interlayer via IP process and intercalated into GO interlayer, which enlarges the interlayer spacing of GO membranes gradiently. The combination of hydrophilic PA nanofiltration layer on GO membrane surface and the PA intercalated GO membrane with varying interlayer spacing creates hierarchical transport channels for water molecules, which contributes to the high water permeance. Moreover, the less reactive SA monomer endows PA@GO selective layer with appropriate negative charge and loose transport channels, which contributes to both of high permeance and dye rejection due to Donnon effect and size exclusion effect. The PA@GO hybrid membrane exhibits high permeance of 75.5 L/(m2·h·bar) with TB dye rejection of 99.8 %, and exhibits low NaCl rejection of 11.6 %. Moreover, PA@GO hybrid membrane shows good fouling resistance and long-term stability as well as stable separation performance under harsh conditions. Both of high permeance and dye rejection of PA@GO hybrid membrane suggests that the integration of PA nanofiltration layer and GO membrane via in-situ confined interfacial polymerization can achieve the delicate control over the interlayer channel structure and the physicochemical properties of the membrane surface of GO membranes, which offers a promising method to break through the trade-off effect between permeability and selectivity of GO membranes.

Efficient Collection of Oil Microdroplets by Hyperbranched, Space‐Filling Open Microfluidic Channels

AbstractOpen microfluidic channels, which capture and transport liquid on flat substrate surfaces through wettability contrast, offer a promising platform for the analysis, mixing, separation, etc. of small‐volume liquid samples. This study focuses on the development of open microfluidic channels featuring oleophilic/oleophobic micropatterning in a hyperbranched, space‐filling structure, thereby creating high‐density channels. These newly designed channels allow for the swift collection of microdroplets with low surface tension within less than 10 s through hierarchical transport and merging of the microdroplets within the channel. The collection efficiency reaches 66% in the channel with the optimized channel geometry. These results underscore the effectiveness of this method for the collection of low surface tension microdroplets, paving the way for the advancement in the domain of open microfluidics of oil, a field that has yet to be fully explored.

Proactive risk assessment of intrahospital transport of critically ill patients from emergency department to intensive care unit in a teaching hospital and its implications.

To explore the effects of the health failure mode and effect analysis (HFMEA) used in intrahospital transport (IHT) of critically ill patients from emergency department (ED) to the intensive care unit (ICU). Patients who were transported from ED to ICU is highly critical. IHT of these patients is potentially risky, which may associate with adverse events (AEs). The concern of safe IHT can be addressed by performing proactive risk assessments using HFMEA and implementing the findings after the ED of our hospital being reconstructed. A qualitative action research study combined with a quantitative cross-sectional method. According to the HFMEA method, the failure modes of IHT were identified and analysed, and the effect of alterations was verified. We built a project team, drawn up a IHT flow chart, defined steps of IHT, classified the failure modes, calculated risk priority number and analysed by the decision tree, then formulated an action plan and verified the effects of the alterations. Incidence of AEs of transport was compared before and after HFMEA.SQUIRE 2.0 checklist was chosen on reporting the study process. The HFMEA outlined a total of 5 major steps and 16 sub-steps in the IHT process. From this, 64 potential failure modes were identified, with 17 modes having a RPN score higher than 8. Determined by the decision tree, there were 20 priority control failure modes, of which 16 involved 8 IHT alterations. Notable work-flow alterations included use of a three-stage hierarchical transport strategy based on patients' condition assisted by the intelligent assessment system. Incidence of AEs was significantly decreased from 19.64% to 7.14% after the implementation of HFMEA (p<0.05). Application of the HFMEA in optimising IHT process can improve the safety of transportation, which is worthy of promotion. Hierarchical transport scheme can reduce the incidence of AEs in IHT of critical emergency patients, which mainly includes the integration and construction of the transport team, equipment configuration and patient information system based on the classification of patients' condition. Nurses play a crucial role in the IHT process. HFMEA can be adopted for proactive risk assessment of critically ill patients' IHT from ED to ICU which involves multiple processes. The IHT hierarchical strategy based on the results of failure mode analysis should be more widely used to further verify its clinical effects.

Hierarchical carrier transport simulator for defected nanoparticle solids

The efficiency of nanoparticle (NP) solar cells has grown impressively in recent years, exceeding 16%. However, the carrier mobility in NP solar cells, and in other optoelectronic applications remains low, thus critically limiting their performance. Therefore, carrier transport in NP solids needs to be better understood to further improve the overall efficiency of NP solar cell technology. However, it is technically challenging to simulate experimental scale samples, as physical processes from atomic to mesoscopic scales all crucially impact transport. To rise to this challenge, here we report the development of TRIDENS: the Transport in Defected Nanoparticle Solids Simulator, that adds three more hierarchical layers to our previously developed HINTS code for nanoparticle solar cells. In TRIDENS, we first introduced planar defects, such as twin planes and grain boundaries into individual NP SLs superlattices (SLs) that comprised the order of 103 NPs. Then we used HINTS to simulate the transport across tens of thousands of defected NP SLs, and constructed the distribution of the NP SL mobilities with planar defects. Second, the defected NP SLs were assembled into a resistor network with more than 104 NP SLs, thus representing about 107 individual NPs. Finally, the TRIDENS results were analyzed by finite size scaling to explore whether the percolation transition, separating the phase where the low mobility defected NP SLs percolate, from the phase where the high mobility undefected NP SLs percolate drives a low-mobility-to-highmobility transport crossover that can be extrapolated to genuinely macroscopic length scales. For the theoretical description, we adapted the Efros-Shklovskii bimodal mobility distribution percolation model. We demonstrated that the ES bimodal theory’s two-variable scaling function is an effective tool to quantitatively characterize this low-mobility-to-high-mobility transport crossover.

Nature-Inspired Chemical Engineering for Process Intensification.

A nature-inspired solution (NIS) methodology is proposed as a systematic platform for innovation and to inform transformative technology required to address Grand Challenges, including sustainable development. Scalability, efficiency, and resilience are essential to nature, as they are to engineering processes. They are achieved through underpinning fundamental mechanisms, which are grouped as recurring themes in the NIS approach: hierarchical transport networks, force balancing, dynamic self-organization, and ecosystem properties. To leverage these universal mechanisms, and incorporate them effectively into engineering design, adaptations may be needed to accommodate the different contexts of nature and engineering applications. Nature-inspired chemical engineering takes advantage of the NIS methodology for process intensification, as demonstrated here in fluidization, catalysis, fuel cell engineering, and membrane separations, where much higher performance is achieved by rigorously employing concepts optimized in nature. The same approach lends itself to other applications, from biomedical engineering to information technology and architecture.

Fluid transport through heterogeneous pore matrices: Multiscale simulation approaches

Fluids confined in nanopores exhibit several unique structural and dynamical characteristics that affect a number of applications in industry as well as natural phenomena. Understanding and predicting the complex fluid behavior under nano-confinement is therefore of key importance, and both experimental and computational approaches have been employed toward this goal. It is now feasible to employ both simulations and theoretical methods, the results of which can be validated by cutting-edge experimental quantification. Nevertheless, predicting fluid transport through heterogeneous pore networks at a scale large enough to be relevant for practical applications remains elusive because one should account for a variety of fluid–rock interactions, a wide range of confined fluid states, as well as pore-edge effects and the existence of preferential pathways, which, together with many other phenomena, affect the results. The aim of this Review is to overview the significance of molecular phenomena on fluid transport in nanoporous media, the capability and shortcomings of both molecular and continuum fluid modeling approaches, and recent progress in multiscale modeling of fluid transport. In our interpretation, a multiscale approach couples a molecular picture for fluid interactions with solid surfaces at the single nanopore level with hierarchical transport analysis through realistic heterogeneous pore networks to balance physical accuracy with computational expense. When possible, comparison against experiments is provided as a guiding roadmap for selecting the appropriate computational methods. The appropriateness of an approach is certainly related to the final application of interest, as different sectors will require different levels of precision in the predictions.

Mixed-matrix membranes with soluble porous organic molecular cage for highly efficient C3H6/C3H8 separation

Gas mixture separation of C3H6/C3H8 has great importance in industry with increasing demand for value-added polypropylene. However, realization of a cost- and energy-efficient separation procedure and its practicability is still a challenge. This work reports a group of mixed-matrix membranes (MMM) by incorporating porous organic molecular cages (POMC) within polymer. Unlike traditional solid filler, POMC filler (CC3) can be dissolved in solvent and mixed with polymer in molecular lever. The uniform distribution of CC3 particles and/or even single CC3 cage in polymer form an attractive hierarchical transport channel, which allows binary mixture permeation test (1/1, v/v) on MMM-20 wt% (0.3 MPa and 20 °C) have very fast C3H6 permeability (390 Barrer) and good C3H6/C3H8 separation factor (12.1). Gas transportation mechanism was evaluated and unveiled by positron annihilation lifetime spectroscopy and molecular dynamic simulation. More importantly, the MMM-20 wt% demonstrates stable C3H6/C3H8 separation during long term test, which is far beyond the Robeson upper bound, indicating high potential for feasible usage.

Hierarchical Transport Models In The Netherlands

The Netherlands has a few decades of experience with hierarchical transport models. They originate from limits of computation in the past and even present. Hierarchical transport models are used at different spatial scales. Their main goal is to keep consistency between the spatial scales. An example is the Dutch National Model System (NMS) and the Netherlands Regional Models (NRM). These were developed in the nineties and updated and further developed several times since then. While these models already exist for about thirty years, only since the last ten to fifteen years activities have been undertaken to make these models more consistent, both concerning their inputs such as base matrix, networks and socio-economic data as their modelling techniques. The reason for making the models more consistent stems from the fact that the models showed different results for the same parts of the road networks and matrix values as well. This situation led to unreliable results, delays in the planning process and extra costs. In order to avoid this situation, the NMS and NRM have been aligned. This improvement played and continues to play an important role between the national and regional level (the Netherlands is partitioned in four regions).Similar problems consist for the interface between the provinces (12) and the areas from which they are built up. Since about ten years a further step in hierarchic transport modelling has been made at the level of provinces. Using a province wide modelling approach, attempts were made to align the transport models of provinces with those from the different sub-regions or municipalities in the provinces. Some attempts were successful, while other attempts failed. Different causes can be mentioned, both concerning the organization as the models themselves.The Province of Noord-Brabant had a successful attempt to build a hierarchical transport model. Both concerning the model system as the organization the hierarchical transport model BBMA can be regarded as a good suite of models with one top transport model for the entire province and four regional models to serve the regions in more detail with results. The first model was realized in 2013. Currently a further improvement of this hierarchical model system is at its final stage of development, featuring even more consistent results on all levels.The paper addresses the hierarchical transport models from a historic perspective by looking at the NMS and NRM, the modelling approach used in different provinces and more specifically the Noord-Brabant hierarchical model. It deals with the problems that have been encountered in the past as well as with the current hierarchical transport model that has been built for the Province of Noord-Brabant. We will provide an overview of both Noord-Brabant models and the way they relate to each other, the problems that had to be solved (such as consistency and flexibility on data, method and results) as well as the way the Province has organized the hierarchical transport model BBMA (such as collaboration between the different stakeholders).

A nonequilibrium thermodynamics perspective on nature-inspired chemical engineering processes

Nature-inspired chemical engineering (NICE) is promising many benefits in terms of energy consumption, resilience and efficiency etc. But it struggles to emerge as a leading discipline, chiefly because of the misconception that mimicking Nature is sufficient. It is not, since goals and constrained context are different. Hence, revealing context and understanding the mechanisms of nature-inspiration should be encouraged. In this contribution we revisit the classification of three published mechanisms underlying nature-inspired engineering, namely hierarchical transport network, force balancing and dynamic self-organization, by setting them in a broader framework supported by nonequilibrium thermodynamics, the constructal law and nonlinear control concepts. While the three mechanisms mapping is not complete, the NET and CL joint framework opens also new perspectives. This novel perspective goes over classical chemical engineering where equilibrium based assumptions or linear transport phenomena and control are the ruling mechanisms in process unit design and operation. At small-scale level, NICE processes should sometimes consider advanced thermodynamic concepts to account for fluctuations and boundary effects on local properties. At the process unit level, one should exploit out-of-equilibrium situations with thermodynamic coupling under various dynamical states, be it a stationary state or a self-organized state. Then, nonlinear phenomena, possibly provoked by operating larger driving force to achieve greater dissipative flows, might occur, controllable by using nonlinear control theory. At the plant level, the virtual factory approach relying on servitization and modular equipment proposes a framework for knowledge and information management that could lead to resilient and agile chemical plants, especially biorefineries.

Rationalizing Public Transport System of Dhaka City: Proposal of Creating a Multimodal Hierarchical Transport Network to Reduce Traffic Congestion

The concept of rationalization can be defined as a structured process to increase effectiveness through a maximize use of existing resources. Rationalization in terms of road infrastructure or systems can be achieved in various ways; establishing hierarchy of routes, optimize bus-stop points with density distribution changes, proper integration of motorized and non-motorized transport and providing policy framework. In the highly densely populated city of Dhaka, rationalizing public transport is one way to minimize the mismatch between demand and supply.&#x0D; This paper is concerned with the following issues: providing a general description of the city transport system, identifying problems and demands analysis in the area of study area; studying the rationalization of public transport, particularly public transport system design (routes and their categorization) and proposing the creation of a multimodal hierarchical transport network for Dhaka. The findings suggest establishing a major component, a hierarchal-network. Beside establishing network hierarchy, rationalizing is also interdependent upon system planning, institutional framework, organization and financing, terminal locations, public-private relationships, government roles, policies, service integration, and the management of public transport. This is can be accomplished by all stakeholders sharing the relative success and failure, depending different levels of each components’ performances. The findings of this paper will help planners and decision makers to optimize the investment in the transport infrastructure.

Perfection of decision-making methods in multilevel hierarchical transport systems

The article discusses the multi-level transport linking systems of timber enterprises, which are a hierarchical structure. It consists of the regional transport system management, which distributes limited resources and several transport subsystems (types of transport) producing the same type of transport products - interchangeable transportation.

Interaction of maritime shipping and hinterland traffic using a two-level hierarchical transport network

A transport scenario based on a two-level network is developed in order to model operations in maritime transport. To enhance competitiveness and sustainability of shipping companies, the interaction between maritime shipping and hinterland traffic is considered in the novel two-level hierarchical transport network. Demand occurs on the second level, the hinterland, whereas the first level, the sea transport, acts as a pure distribution network. The two-level hierarchical transport model allows regulating the degree of interaction a liner operator has regarding the hinterland traffic. Moreover, access of vehicles to nodes or edges is given subject to feasibility constraints, relating to the size of a vehicle. In this work, the relation to existing routing models, such as the travelling salesman problem, the vehicle routing problem, or the travelling purchaser problem, is illustrated. Moreover, through the definition of a proper set of assumptions, it is possible to reduce the considered two-level hierarchical transport network to different standard routing models. These new insights allow the application of existing solution methods. Numerical experiments are conducted for a particular case and illustrate the influence of node costs on the distribution of workload to the vehicles.

The Evolution and Planning of Hierarchical Transport Networks

The continuing growth of urban regions coupled with their strong interactions with transportation systems places great emphasis on the coevolution of these systems. In this paper we introduce three developments. First, as a preliminary, the dynamic model of the evolution of retail structure is extended to show how hierarchies emerge. Secondly, these ideas are applied to a model of the evolution in transport networks. Thirdly, it is shown that such a model can be translated into a planning context and the notion of an explicitly hierarchical dynamic model is introduced. An example of the use of such a model of evolution within a network planning context is presented. This explores the planning of network evolution in a case study of Naples arising from a new harbour which is under construction. The model provides a new method for transport system planning through combining the insights from dynamic modelling, particularly with respect to the sequencing of investment, with the practicalities of budget constraints.

Hierarchical Ethernet Transport Network Architecture for backhaul cellular networks

Cellular traffic has been going through major changes in recent years. With the introduction of broadband services in 3G/4G and the continuously increasing provided data rates in high-speed packet access and Long Term Evolution (LTE), a broad range of cellular applications has emerged, changing the characteristics of cellular traffic. The traditional circuit-switched voice traffic has been taken over by packet-oriented data traffic. This shift in traffic has driven operators to prefer packet-oriented network technologies over circuit-switch technology when implementing their cellular networks. The current offered technologies, including PBB-Traffic Engineering and MPLS-TP, lack important functionality required for LTE such as automation (simple management), traffic engineering, protection, Quality of Service, and scalability. We propose a scalable Hierarchical Ethernet Transport Network Architecture (HETNA), a layer 2 transport technology that addresses these issues and brings a viable solution for cellular networks. The suggested architecture can handle streaming, real-time, multicasting, and other applications. Both connection-oriented transport services and connectionless-oriented services are supported. HETNA was simulated and prototyped, showing significant improvements over regular Ethernet in terms of buffers and control messages that enable this network to function.

Deficiencies of existing public transport system and a proposal for integrated hierarchical transport network as an improvement options: a case of Dhaka city

Public transport plays an important role in providing easy and affordable accessibility and mobility for dwellers in a city. This demand for transportation is brought about by the increased population of connecting nodes, cities, the rural-urban migration, and the scope for socio-economical facilities i.e. better opportunities for jobs, health facilities and educational scope etc. thus the economic viability of the people which leads to an increase in the usage of private vehicles. Dhaka is an over densely populated city and its transport system comprised of many different modes of travel – both motorized and non-motorized using the same road space – resulting in a high level of operational disorder, that significantly diminishes the efficiency and effectiveness of the existing transport uses. Dhaka is experiencing lots of traffic congestion and a great lack of traffic management. There has been no study dedicated to overcome the situation. Therefore, there is an urgent need to introduce a well-organized, properly scheduled rapid mass transit system minimizing the existing deficiencies. In this paper, an attempt has been made to identify the deficiencies of existing public transport system to put forward for an appropriate rapid mass transit system to recover the huge demand. An overview of the existing modes of travel and operation characteristics has been described. Finally, some proposals for integrated hierarchical transport network options are highlighted with the context of prevailing land use and transport characteristics, socio-economic context of Dhaka Metropolitan city. The findings of this research help planners and decision makers to optimize the investment in transport infrastructure.

A sustainable synthesis of nitrogen-doped carbon aerogels

The hydrothermal synthesis of nitrogen-doped monolithic carbon aerogels derived from sustainable precursors (i.e.D-glucose and ovalbumin) is presented. The protein acts as nitrogen donor and surface stabilizing agent in this saccharide hydrothermal carbonization, to generate high surface area aerogels (>240 m2g−1) composed of functional continuous large diameter mesopores with excellent hierarchical transport architecture. Post-carbonization treatment controls surface chemistry (e.g. C or N condensation), facilitating tuneable physicochemical properties on a unique continuous 3D carbonaceous pore structure. This highly flexible synthesis lays the basis for the development of a new generation of sustainable (heteroatom-doped) porous carbon aerogels suitable for a range of high value applications.

Hierarchical transport networks optimizing dynamic response of permeable energy-storage materials

Channel widths and spacing in latticelike hierarchical transport networks are optimized to achieve maximum extraction of gas or electrical charge from nanoporous energy-storage materials during charge and discharge cycles of specified duration. To address a range of physics, the effective transport diffusivity is taken to vary as a power, m , of channel width. Optimal channel widths and spacing in all levels of the hierarchy are found to increase in a power-law manner with normalized system size, facilitating the derivation of closed-form approximations for the optimal dimensions. Characteristic response times and ratios of channel width to spacing are both shown to vary by the factor 2/m between successive levels of any optimal hierarchy. This leads to fractal-like self-similar geometry, but only for m=2 . For this case of quadratic dependence of diffusivity on channel width, the introduction of transport channels permits increases in system size on the order of 10;{4} , 10;{8} , and 10;{10} , without any reduction in extraction efficiency, for hierarchies having 1, 2 and, 8 levels, respectively. However, we also find that for a given system size there is an optimum number of hierarchical levels that maximizes extraction efficiency.