Two-tier Distribution Research Articles

Assessing the Rural–Urban Transition of China during 1980–2020 from a Coordination Perspective

Under the context of global rapid urbanization, exploring the dynamics of rural–urban transition in China can provide valuable experience for the Global South. In this study, we evaluate the rural–urban transition in China, from 1980 to 2020, based on socioeconomic data and a rural–urban transition coordination model by constructing a rural–urban development and integration index system. We identify the state and transition types, and we present optimization paths. The results show that, since the reform and opening-up, the rural–urban development index (URDI) in China has gradually expanded among regions while the rural–urban integrated index (URII) has experienced a trend of decline followed by an increase. Over the past 40 years, the spatial distribution characteristics of the ΔURDI have been “south high–north low”, while the ΔURII has had a balanced spatial distribution. Over the first two decades of the past 40 years, the rural–urban transition in eastern coastal China was more coordinated, while regions with less coordination showed a two-tiered distribution pattern; over the last two decades, the coordination degree has increased. Over the past 40 years, the spatial distribution of high coordination presents “T-shaped” coastal and riverside characteristics. The transition types and coupling relationships of state regions are identified. Finally, optimization pathways are proposed for each type to further promote rural–urban integration.

Optimizing the location selection of urban consolidation centers with sustainability considerations in the city of Bordeaux

The delivery of parcels in city centers is nowadays a topical issue and a major challenge for the local authorities. In this paper, we tackle the parcels distribution network in the city of Bordeaux. This city is at the very beginning of the process of moving from direct deliveries towards city center, to a more rational organization based on joint deliveries. We focus on the potential contributions of a two-tier distribution system made up of warehouses, proximity logistics spaces and intermediate depots so-called urban consolidation centers (UCCs). We seek to optimize the costs of the distribution network (i.e. transport and UCCs) and the selection of UCCs, while assessing the impact in terms of sustainable development by measuring CO2 emissions. We analyze and compare different scenarios using different deliveries' variants (with or without UCCs), different total UCCs capacities and different truck speeds. The findings demonstrate the benefits of using UCCs for city center distribution. The reductions in total cost and CO2 are most significant when the size of the UCCs is balanced with the total deliveries demands.

Group Buying of Competing Retailers with Strategic Inventory

Group buying involves cooperation and competition among multiple retailers, and strategic inventory can affect this relationship. To investigate the interaction between them, we consider a two-tier distribution channel consisting of one supplier and two competing retailers who can hold strategic inventory, and explore the effect of strategic inventory on the operational decisions and profits of all members of the supply chain. In this research, we make a major contribution by integrating strategic inventory into group buying. Furthermore, we make another major contribution by examining the impact of strategic inventory on the operational decisions of the supplier and the retailers in a competing environment. We construct a Stackelberg game, where the supplier is the leader and the retailers are followers. We find that the retailers will hold strategic inventory under group buying only when the holding cost is low or the basic wholesale price is high. Moreover, a higher holding cost is detrimental to the retailers while beneficial to the supplier, and intensified competition is detrimental to both the retailers and the supplier. Interestingly, contrary to the common view that inventory should be reduced or not held, the retailers have incentives to hold strategic inventory. The supplier also prefers that because strategic inventory benefits her. Therefore, strategic inventory achieves a win–win outcome for the supplier and the retailers. In addition, strategic inventory can improve supply chain performance and consumer surplus.

Research on Differences and Effects of Lateral Distribution Characteristics of Multi-lane Traffic Flow on Freeway

In order to obtain the probability distribution characteristics and change rules of the vehicle flow in different lanes of the expressway, based on the WIM data, the probability statistics analysis of the distribution characteristics of the vehicle type, the distance between the heads, the vehicle weight, and the speed on the different lanes of the expressway was carried out, and based on the extreme value theory. The extreme vehicle weights of different lanes were extrapolated, and the load effect was further analyzed. The results show that the probability distribution of vehicle types in each lane is different. Vehicles on one-way two-lane expressways have obvious two-tier distribution probabilities. For slow lanes, the selection probability of vehicles with 3 axles and above exceeds 0.85;The selection probability of cars with 3 axles and above on the slow lane of a one-way 3-lane expressway is higher than 0.4, while the selection probability of cars with 2 axles is about 0.15; The lateral distribution of vehicle weight meets the law of increasing from the inner lane to the outer side. The average vehicle weight of the same model on the slow lane is about 1.3-2.0 times that of the fast lane, and the average total weight of the middle lane of the three lane high-speed is the largest; The probability density distribution of vehicle weight in slow lane shows the characteristics of thick tail and long tail, while that in fast lane shows single peak distribution, and the vehicle weight is mainly concentrated in 3000kg; Each vehicle has a specific speed range, and the vehicle mixing ratio has a certain impact on the vehicle speed. The average speed of 2-axle vehicles in the same lane is 20km · h-1 higher than that of 3-axle and above vehicles. The extrapolation results of the extreme value of the load effect show that the bending moment effect of the slow lane is about 1.3-1.4 times that of the fast lane and 1.1-1.2 times that of the middle lane. The middle-span bending moment effect value increases from the inner lane to the outer lane. The transverse reduction coefficients of vehicle load on multi-lane expressways are all higher than the normative values.

Optimisation of the Two-Tier Distribution System in Omni-Channel Environment

This paper deals with the problem of the design and configuration of a distribution system that supports the delivery of goods to customers using various commercial channels. In this sense, a modelled distribution system, called an omni-channel distribution system, should ensure the delivery of the same products in different ways while guaranteeing its highest efficiency. The authors propose a single-criterion mixed-integer programming model for the configuration of a complex distribution system of goods in an omni-channel environment. A minimized cost function, composed of key logistics elements including transport, warehouse location, and manipulation processes, is the objective function. The model was experimentally verified, and as a result, potential savings of around 5–8% of the omni-channel design distribution system costs versus the multi-channel distribution system costs were identified. In the paper, an extended sensitivity analysis is also performed to show how specific parameters of the model can change the final recommendation.

The Impact of the Handling Unit on Logistics Costs: The Case of a Portuguese Food Retail Supply Chain

In the food retail industry, the agility and responsiveness of the supply chain are crucial because demand is volatile and short lead times are mandatory. The logistics performance is of critical importance to provide a high level of efficiency in operations and a high degree of customer satisfaction. The Handling Unit, or the minimum quantity to send to retail stores (the ship-pack), is a factor of considerable influence on logistics efficiency and costs. In this work, it was developed a simple analytical cost model for a Portuguese food retail two-tier distribution system (distribution centre and store) to support the evaluation of the conversion of the handling unit to half-pallet. The results of the model, considering a pilot study with three scenarios, suggest an economic gain of approximately 75% (comparatively to the current situation) in logistics costs. These quantitative results were decisive to guide decision-makers.

A Multi-commodity Network Flow Model for Sustainable Performance Evaluation in City Logistics: Application to the Distribution of Multi-tenant Buildings in Tokyo

The distribution of goods in crowded city centers is a major challenge. In this paper, we propose a methodology for evaluating the performance of a parcel distribution network in city logistics. This methodology encompasses the main entities of a two-tier distribution system made up of carriers, huge shopping centers (multi-tenant buildings) and intermediate depots (urban consolidation centers), as well as the parcel flows between them. This methodology aims to optimize the transport flows (distance traveled) of a given distribution network while also quantifying the impact in terms of sustainable development by measuring gas emissions. Two different states of the network with different connectivity degrees are evaluated and compared: the current state of the network as well as its future state. The transport network modeling is based on a network flow, which is expressed in linear programming and implemented with an optimization solver. The validation of this methodology is based on the parcel distribution of the Multi-tenant Buildings of the city of Tokyo. The findings are that the network with greater connectivity between the entities brings significant traveled distance reduction as well as a reduction of emissions of CO2. Another finding is that the grouping of the parcels (i.e., pooling) brings a reduction of the distance traveled compared to the transport organization without grouping and contributes to a reduction in the number of trucks.

Scenario-based optimisation of a two-tier distribution network with a simplified route construction

The paper deals with an optimisation of a distribution network design (DND) problem combined with a location routing problem (LRP). A combinatorial model of a two-tier distribution network (DN) is proposed, where the objective function cumulates costs of transport, handling and facilities. A generic mathematical model (GMM) of the problem is constructed, where a function of simplified route construction (FSRC) is suggested to linearize a problem formulation. Additionally, a set of business-oriented constraints is proposed, including facility relocations, regularity changes, time limits of deliveries, and vehicle’s capacity changes. It helps to define several scenario-based extensions of GMM and each scenario is a combination of these constraints. The problem is iteratively solved with exact algorithms. This methodology has been experimentally applied to optimise the DN of drugstore chain, where five alternative scenarios of DN configuration have been tested. Each of them has been optimised and the results have ranged from 7% increase to 30% reduction of objective function, referred to a current state. A recommended scenario assuming 12% cost reduction has been implemented in practice and the expected result has been proved.

A classification of two-tier distribution systems based on mobile depots

Urban freight transport is an important enabling factor for economic growth and social activities in cities but despite its benefits, it also generates important negative externalities including traffic congestion, pollution, noise and overall less safety. Moreover, increased limitations on urban freight transport, including access constraints, limited kerbside and private parking spaces for loading/unloading, and the often prohibitive costs of installing logistics infrastructures in city centres, have further constrained urban freight transport. To address these issues, several city logistics solutions have been proposed, such as two-tier distribution systems and distribution systems based on mobile depots.In this paper, we focus on two-tier urban freight distribution systems based on mobile depots, where little or no physical infrastructure is considered and where storage is not permitted at transfer locations. In these types of systems, coordination and synchronisation between vehicles are essential, and the main objective is to have vehicles at the transfer locations in a need-to-be basis as a way of minimising the negative externalities.We review and analyse 13 cases found in the scientific literature, trial reports and online resources, and propose a classification of these systems based on the level of mobility and accessibility of transportation modes operating at the first-tier. Furthermore, we characterise the main components and operational features of the different systems, including the existence of multi-trips, the types of transport modes used at both tiers, transported loads and the organisation of the transfer sites (satellites). This work aims to contribute for a clearer characterisation of two-tier urban distribution systems based on mobile depots, to later support the development of the most adequate mathematical models and solution methods to be applied to each variant of this type of systems.

DR3 på flow og streaming – en todelt kanalanalyse

Denne artikel foretager en todelt analyse af DR3’s udvikling i de seneste fem år og finder store forskelle på, hvilke DR3-programmer og genrer der dominerer seertallene på henholdsvis flow-tv og streaming: Sport, store musikevents og et spinoffprogram er blandt de mest sete på flowkanalen, mens fiktion (primært SKAM) dominerer streamingtallene. Dette understreger vanskelighederne i, hvad artiklen kalder den todelte distributionsstrategi og i at skulle producere til to forskellige platforme og seerskarer, som kan have meget forskellige genrepræferencer, og at det næsten er som at skulle administrere to forskellige tv-kanaler på én gang. Artiklens kvalitative bidrag viser to strømninger i kanalens mange faktaprogrammer – henholdsvis de journalistiske eksperimenter og de intime dokumentariske portrætter – der skal understøtte DR3-brandets kerneværdier om hudløs ærlighed, eksperimenter på egen krop og absurditeter i samfundet. Sammenholdt med kanalens nyere fiktionsstrategi peger konklusionen på en kanal, der kan have potentialet til at være en sandkassekanal for DR ved at afprøve nye programkoncepter og tidsformater. Artiklen bidrager ligeledes med en diskussion af problemerne i Seerundersøgelsens metode, som tegner et billede af to inkompatible måleparadigmer, og den diskuterer uforeneligheden mellem flow og streaming i både målemetoder og kanalbranding.

End-to-End Predictive Analytics and Optimization in Ingram Micro’s Two-Tier Distribution Business

Ingram Micro, the world’s largest distributor of technology products, operates in a high-volume low-margin environment. The company started its Business Intelligence and Analytics practice in North America in 2009. This group has since built and deployed a scalable, innovative price-optimization engine, a set of analytics applications to identify sales opportunities for Ingram Micro’s sales force and an integrated digital marketing platform to run data-driven marketing campaigns for its customers and end-user businesses. Since 2011, these products and analytics programs have generated $1.3 billion of incremental product revenue and $42 million of incremental gross profit. Our next steps are to continue to implement these best practices in regions outside of North America and continue our activities that enable our sales force to generate revenue.

Optimal Supply Chain Structure for Distributing Essential Drugs in Low Income Countries: Results from a Randomized Experiment

Despite increased investments in health commodity procurement, the availability of essential medicines at health facilities remains very low in many low and middle income countries. The lack of a well-functioning supply chain for essential medicines is often the cause of this poor availability. Using a randomized experiment conducted in over 400 health facilities and 24 districts in Zambia, this study helps understand the optimal supply chain structure for essential medicines distribution in the public sector in low income countries. It focuses on the availability of 15 essential medicines at the health facility level and compares between a cross-dock based two-tier distribution network and a three-tier network. The study shows that a two-tier “cross-dock” like system out-performs a traditional three-tier drug distribution system due to better information flow and better management accountability even though stock is positioned closer to the health facilities in the three-tier system. Results from the study advance existing knowledge in the area of public sector distribution system design in general and drug distribution systems in developing countries in particular.

Service network design models for two-tier city logistics

This paper focuses on two-tier city logistics systems for advanced management of urban freight activities and, in particular, on the first layer of such systems where freight is moved from distribution centers on the outskirts of the city to satellite platforms by urban vehicles, from where it will be distributed to customers by a different fleet of dedicated vehicles. We address the issue of planning the services of this first tier system, that is, select services, their routes and schedules, and determine the itineraries of the customer-demand flows through these facilities and services. We propose a general scheduled service network design modelling framework that captures the fundamental concepts related to the definition of urban-vehicle tactical plans within a two-tier distribution network. We examine several operational assumptions regarding the management of the urban-vehicle fleet and the flexibility associated with the delivery of goods, and show how the proposed modelling framework can evolve to represent an increasing level of detail. A discussion of algorithmic perspectives completes the paper.

Locating disaster response facilities in Istanbul

We study the problem of locating disaster response and relief facilities in the city of Istanbul, where a massively destructive earthquake is expected to occur in the near future. The Metropolitan Municipality of Istanbul decided to establish facilities to preposition relief aid and execute post-disaster response operations. We propose a two-tier distribution system that utilizes existing public facilities locally in addition to the new facilities that will act as regional supply points. We develop mathematical models to decide on the locations of the new facilities with the objectives of minimizing the average-weighted distance between casualty locations and closest facilities, and opening a small number of facilities, subject to distance limits and backup requirements under regional vulnerability considerations. We analyze the trade-offs between these two objectives under various disaster scenarios and investigate the solutions for several modelling extensions. The results demonstrate that a small number of facilities will be sufficient and their locations are robust to various parameter and modelling changes.

P02-227 - Imprinting in the schizophrenia candidate gene GABRB2

Imprinting, characterized by unequal expression of the offspring's genes in a parent-of-origin dependent manner, has been functionally implicated in brain development and in psychiatric disorders. In this study, unambiguous distortion in paternal but not maternal transmission of the disease-associated single-nucleotide polymorphism (SNP) rs6556547 (T/G) clearly indicated the presence of parent-of-origin effect (POE) in the GABAA receptor β2 subunit gene (GABRB2). ‘Flipping’ of allelic mRNA expression in heterozygotes of SNP rs2229944 (C/T) and the observed two-tiered distribution of mRNA expression levels in heterozygotes of the disease-associated SNP rs1816071 (G/A) furnished important support for the occurrence of imprinting at GABRB2. Imprinting in effect introduced heterozygotes from different parents-of-origin endowed with dissimilar mRNA expression capabilities. The deficit of upper-tiered expressions accounted for the lowered mRNA expression levels in the schizophrenic heterozygotes. This pointed to the necessity of differentiating between two kinds of heterozygotes of different parental origins in disease association studies on GABRB2. Bisulfite sequencing revealed hypermethylation in the neighborhood of SNP rs1816071, and methylation differences between controls and schizophrenia patients. Notably, allele-specific methylation was observed at the disease-associated SNPs rs6556547 and rs1816071. These findings raised the possibility that CpG methylation status of these sites could have an impact on the expression of GABRB2 and the risk of schizophrenia. Furthermore, the occurrence of imprinting and allele-specific methylation in the schizophrenia candidate gene GABRB2 was compatible with the epigenetic hypothesis for schizophrenia pathophysiology, thereby calling for the need to explore the role of epigenetic factors in mediating susceptibility to schizophrenia.

Imprinting in the schizophrenia candidate gene GABRB2 encoding GABAA receptor β2 subunit

Schizophrenia is a complex genetic disorder, the inheritance pattern of which is likely complicated by epigenetic factors yet to be elucidated. In this study, transmission disequilibrium tests with family trios yielded significant differences between paternal and maternal transmissions of the disease-associated single-nucleotide polymorphism (SNP) rs6556547 and its haplotypes. The minor allele (T) of rs6556547 was paternally undertransmitted to male schizophrenic offsprings, and this parent-of-origin effect strongly suggested that GABRB2 is imprinted. 'Flipping' of allelic expression in heterozygotes of SNP rs2229944 (C/T) in GABRB2 or rs2290732 (G/A) in the neighboring GABRA1 was compatible with imprinting effects on gene expression. Clustering analysis of GABRB2 mRNA expressions suggested that imprinting brought about the observed two-tiered distribution of expression levels in controls with heterozygous genotype at the disease-associated SNP rs1816071 (A/G). The deficit of upper-tiered expressions accounted for the lowered expression levels in the schizophrenic heterozygotes. The occurrence of a two-tiered distribution furnished support for imprinting, and also pointed to the necessity of differentiating between two kinds of heterozygotes of different parental origins in disease association studies on GABRB2. Bisulfite sequencing revealed hypermethylation in the neighborhood of SNP rs1816071, and methylation differences between controls and schizophrenia patients. Notably, the two schizophrenia-associated SNPs rs6556547 and rs1816071 overlapped with a CpG dinucleotide, thereby opening the possibility that CpG methylation status of these sites could have an impact on the risk of schizophrenia. Thus multiple lines of evidence pointed to the occurrence of imprinting in the GABRB2 gene and its possible role in the development of schizophrenia.

Models for Evaluating and Planning City Logistics Systems

City logistics aims to reduce the nuisances associated to freight transportation in urban areas while supporting their economic and social development. The fundamental idea is to view individual stakeholders and decisions as components of an integrated logistics system. This implies the coordination of shippers, carriers, and movements as well as the consolidation of loads of several customers and carriers into the same environment-friendly vehicles. City logistics explicitly aims to optimize such advanced urban transportation systems. We focus on a challenging city logistics planning issue, the integrated short-term scheduling of operations and management of resources, for the general case involving a two-tiered distribution structure. We investigate the main issues related to the problem, introduce a new problem class, propose both a general model and formulations for the main system components, and identify promising solution avenues.

Trace element diagenesis in pyrite-rich sediments of the Achterwasser lagoon, SW Baltic Sea

The early diagenesis of trace elements (V, Cr, Co, Cu, Zn, As, Cd, Ba, U) in anoxic sediments of the Achterwasser, a shallow lagoon in the non-tidal Oder estuary in the Baltic Sea, was investigated in the context of pyrite formation. The dissolved major redox parameters show a two-tier distribution with transient signals in the occasionally re-suspended fluid mud layer (FM) and a permanently established diagenetic sequence in the sediment below. Intense microbial respiration leads to rapid depletion of O 2 within the uppermost mm of the FM. The reduction zones of Mn, Fe and sulfate overlap in the FM and in the permanently anoxic sediment section which appears to be a typical feature of estuarine sediments, under low-sulfate conditions. Degrees of pyritization (DOP) range from 50% in the FM to remarkably high values > 90% at 50 cm depth. Pyrite formation at the sediment surface is attributed to the reaction of Fe-monosulfides with intermediate sulfur species via the polysulfide pathway. By contrast, intense pyritization in the permanently anoxic sediment below is attributed to mineral growth via adsorption of aqueous Fe-sulfide complexes onto pyrite crystals which had originally formed in the surface layer. The studied trace elements show differential behavior patterns which are closely coupled to the diagenetic processes described above: (i) Zn, Cu and Cd are liberated from organic matter in the thin oxic layer of the sediment and diffuse both upwards across the sediment/water boundary and downwards to be trapped as monosulfides, (ii) V, Cr, Co and As are released during reductive dissolution of Mn- and Fe-oxyhydroxides, (iii) U removal from pore water occurs concomitantly to Fe reduction in the FM and is attributed to reduction of U(VI) to U(IV), (iv) the Ba distribution is controlled by reductive dissolution of authigenic barite in the sulfate reduction zone coupled with upward diffusion and re-precipitation. The incorporation of trace elements into pyrite is most intense for Co, Mn and As, intermediate for Cu and Cr and little to negligible for U, Zn, Cd, V and Ba. The observed trend is largely in agreement with previous studies and may be explained with differing rates for ligand exchange. Slow and fast ligand exchange and thus precipitation kinetics are also displayed by downcore increasing (Mn, Cr, Co and As) or constantly low (Zn, Cu, Cd) pore water concentrations. The downward increasing degrees of trace metal pyritization (DTMP) for Co, Cu, Zn and As are, in analogy to pyrite growth, assigned to adsorption of sulfide complexes or As oxyanions onto preexisting pyrite minerals.