Classical Location Research Articles

Optimal sensor placement in timber structures by means of a multi-scale approach with material uncertainty

SUMMARY This paper investigates the optimal location of sensors in a timber structure when parametric uncertainty is considered in the microstructure of the material. In order to describe the proposed methodology, a timber beam is chosen for our numerical simulations. A classical sensor location methodology based on the Fisher information matrix is employed. Within a finite element framework, a homogenization-based multi-scale approach is adopted to model the constitutive response of timber, along with stochastic properties in the definition of the material. Nevertheless, by considering uncertainty in the micromechanical properties of wood, a significant computational cost is added to the solution of a large set of realizations represented by expensive multi-scale analyses. In order to tackle this high cost, we build a statistical approximation to the output of the computer model, known as a Bayesian emulator. Following this strategy, three micromechanical parameters are chosen to study their influence on the selection of different configurations of sensor placement. The optimal location of sensors is assessed with three different criteria: the Fisher matrix determinant, the modal assurance criterion error and the condition number. Furthermore, the robustness of this configuration is investigated in the presence of noise. Copyright © 2014 John Wiley & Sons, Ltd.

Upper Palaeolithic occupation in the Wachtberg area of Krems: The evidence of surveys, sections and core samples

The classic Upper Palaeolithic location of the Wachtberg in Krems (eastern Austria) features a multitude of exposures in a limited area of about 50,000 m2. In addition to Gravettian sites which have been investigated in detail in the course of recent years using modern methods, there are the records of old excavations, several documented sections, as well as a considerable number of core samples displaying heterogeneous documentation standards. This paper provides an overview of these different sources of information and aims at synthesizing the data for a comprehensive understanding of the local loess sedimentation and Palaeolithic occupation.

Clinicopathologic Features of Oral Squamous Cell Carcinoma: Do They Vary in Different Age Groups?

To analyze clinicopathologic parameters of oral squamous cell carcinoma (OSCC) in different age groups. We hypothesized that clinical and pathologic parameters of OSCCs will vary in different age groups. A retrospective cohort study was performed. All patients who were treated for a primary manifestation of OSCC at a single institution from 2001 to 2012 were reviewed and allocated to predefined age groups (predictor variable) as follows: young (≤40 years), middle-aged (40-80 years), and very elderly (≥80 years). The following outcome variables were recorded: demographic parameters, classic risk factors, tumor location and size, neck node involvement, histopathologic and therapeutic details, and association with human papillomavirus (HPV). The descriptive statistics were computed. Parametric and nonparametric tests were used for additional analysis. The significance level was set at P < .05. We reviewed 739 patients and identified 11 (1.4%) young (mean age 34.2 ± 2.8 years) and 17 (2.3%) very elderly patients (mean age 83.1 ± 1.2 years). The predilection site for OSCC was the oral tongue (63%) in young patients, the floor of the mouth (52%) in middle-aged patients, and the alveolar process (60%) in very elderly patients. One patient in the young group (9%) and 8 patients in the very elderly group (47%) had been exposed to risk factors; however, all of the examined middle-aged patients had had such exposure. The association of OSCC with HPV was distributed equally among the age groups. No age-related differences in the histopathologic parameters of OSCC were found. The features of OSCC that vary at different ages are the anatomic predilection site and the association with classic risk factors. HPV was not an age-related independent risk factor for OSCC development in the present study.

Ulcerative Colitis – What Can We Learn from the Asia-Pacific Region?

A recent epidemiological study clearly demonstrated that inflammatory bowel disease (IBD), especially ulcerative colitis, is a rapidly emerging disease in the Asia Pacific region (1). A systematic review of the global incidence and prevalence of IBD before publication of the Asia Pacific data (2) confirmed the worldwide nature of IBD. In time-trend analyses, it showed that 75% of Crohn disease studies and 60% of ulcerative colitis studies reported statistically significant increases in incidence (2). The emergence of IBD in the Asia Pacific region suggests strong environmental influence on the pathogenesis of IBD including socioeconomic, lifestyle and dietary changes. The age-standardized incidence of ulcerative colitis in the Asia Pacific region ranged from 0.24 to 7.47 per 100,000 population, with the lowest incidence in Bangkok and the highest in Australia. Even highly westernized Asian countries, such as Hong Kong, have an ulcerative colitis incidence of 1.30 per 100,000 population (1). The incidence of Crohn disease in Australia was nearly double that of ulcerative colitis; however, in the Asian countries, ulcerative colitis was generally more prevalent than Crohn disease. In a recent Asia Pacific epidemiology study of IBD incidence (1), the distribution of ulcerative colitis location in Australia and in Asia were similar, with approximately one-third each being proctitis, left-sided colitis, and extensive or total colitis (1). The Asia Pacific epidemiology study did not include South Korea, Japan or India, which tend to have a higher incidence of IBD than other Asian countries. However, in the current issue of the Journal, Park et al (3) (pages 125 to 130) reported a retrospective analysis of disease location at diagnosis in 240 ulcerative colitis patients diagnosed at Asan Medical Centre, Seoul, South Korea. Approximately 19% of patients had an atypical distribution of disease, including patchy or skip lesions or, less commonly, rectal sparing. Such atypical distribution was more common in patients reported to demonstrate appendiceal orifice inflammation. Skip lesions were more common in the proximal colon. While such atypical distribution inevitably raises the question of Crohn’s colitis, 67% of ulcerative colitis patients showing atypical distribution at diagnosis had reverted to the typical distribution of lesions at follow-up colonoscopy. The ulcerative colitis disease course and outcome of individuals with atypical disease location was similar to those with more classical disease location. While such atypical distribution of ulcerative colitis has been sporadically reported in the West (4,5), including 27% of ulcerative colitis patients showing discontinuous inflammation of the appendiceal orifice in a prospective study, rectal sparing is considered to be unusual in the West after meticulous pathological examination of colectomy specimens (6). This is not surprising given that in the study by Park et al (3), follow-up colonoscopy showed that the distribution of ulcerative colitis had reverted to the classical in the majority of patients. However, several reports from Asia, especially Japan, Korea and India, with higher incidence of ulcerative colitis in Asia, have reported atypical distribution of ulcerative colitis (7–9) despite the contrary data in the recent Asia Pacific epidemiology study. Although single-centre and retrospective, the study by Park et al (3) substantiates these previous findings. It is important to recognize that the Asia Pacific region is a vast, inhomogeneous area with multiple cultures, lifestyles, environment, diet and genetics. For example, three regions of mainland China had ulcerative colitis incidences of 2.05, 0.42 and 0.41 per 100,000 population (1), suggesting unique environmental influences in specific regions. The study by Park et al (3) and previous studies encourage us to obtain additional epidemiological and environmental data collected prospectively from geographical regions with emerging IBD. It will be important to understand whether disease presentation varies in different geographical areas based on colonic microbiome, dietary habits and genetics. This may shed light on its pathogenesis and provide more evidence to answer the question whether ulcerative colitis is ‘one disease or many’. This discussion may be even more relevant in the case of Crohn disease. It especially points to the challenges of epidemiological studies that attempt to distinguish between ulcerative colitis and Crohn’s colitis.

Reliable Facility Systems Design Subject to Edge Failures: Based on the Uncapacitated Fixed-Charge Location Problem

The reliability of facility location problem has aroused wide concern recently. Many researchers focus on reliable and robust facility systems design under component failures and have obtained promising performance. However, the target and reliability of a facility system are to a large degree adversely affected by the edge failures in the network, which remains a deep study. In this paper, we focus on facility systems’ reliability subject to edge failures. For a facility location system, we formulate two models based on classical uncapacitated fixed-charge location problem under deterministic and stochastic cases. For a specific example, location decisions and the comparison of reliability under different location models are given. Extensive experiments verify that significant improvements in reliability can be attained simply by increasing the amount of operating cost.

Solving the Bilevel Facility Location Problem under Preferences by a Stackelberg-Evolutionary Algorithm

This research highlights the use of game theory to solve the classical problem of the uncapacitated facility location optimization model with customer order preferences through a bilevel approach. The bilevel model provided herein consists of the classical facility location problem and an optimization of the customer preferences, which are the upper and lower level problems, respectively. Also, two reformulations of the bilevel model are presented, reducing it into a mixed-integer single-level problem. An evolutionary algorithm based on the equilibrium in a Stackelberg’s game is proposed to solve the bilevel model. Numerical experimentation is performed in this study and the results are compared to benchmarks from the existing literature on the subject in order to emphasize the benefits of the proposed approach in terms of solution quality and estimation time.

Optimizing the Electric Charge Station Network of EŞARJ

In this study, we adopt the classic capacitated p-median location model for the solution of a network design problem,in the domain of electric charge station network design, for a leading company in Turkey. Our model encompasses the location preferences of the company managers as preference scores incorporated into the objective function. Our model also incorporates the capacity concerns of the managers through constraints on maximum number of districts and maximum population that can be served from a location. The model optimally selects the new station locations and the visualization of model results provides additional insights.

Automated seismic event location by waveform coherence analysis

SUMMARY Automated location of seismic events is a very important task in microseismic monitoring operations as well for local and regional seismic monitoring. Since microseismic records are generally characterized bylowsignal-to-noiseratio,automated locationmethods arerequested to be noise robust and sufficiently accurate. Most of the standard automated location routines arebasedontheautomatedpicking,identificationandassociationofthefirstarrivalsofPandS waves and on the minimization of the residuals between theoretical and observed arrival times of the considered seismic phases. Although current methods can accurately pick P onsets, the automatic picking of the S onset is still problematic, especially when the P coda overlaps the S wave onset. In this paper, we propose a picking free earthquake location method based on the use of the short-term-average/long-term-average (STA/LTA) traces at different stations as observed data. For the P phases, we use the STA/LTA traces of the vertical energy function, whereas for the S phases, we use the STA/LTA traces of a second characteristic function, which is obtained using the principal component analysis technique. In order to locate the seismic event, we scan the space of possible hypocentral locations and origin times, and stack the STA/LTA traces along the theoretical arrival time surface for both P and S phases. Iterating this procedure on a 3-D grid, we retrieve a multidimensional matrix whose absolute maximum corresponds to the spatial coordinates of the seismic event. A pilot application was performed in the Campania-Lucania region (southern Italy) using a seismic network (Irpinia Seismic Network) with an aperture of about 150km. We located 196 crustal earthquakes (depth < 20km) with magnitude range 1.1 < ML < 2.7. A subset of these locations were compared with accurate manual locations refined by using a double-difference technique. Our results indicate a good agreement with manual locations. Moreover, our method is noise robust and performs better than classical location methods based on the automatic picking of the P and S waves first arrivals.

Proximal Alpha Angle Persists Abnormal in Patients with a Residual Bony Prominence after Surgery for Femoroacetabular Impingement

Proximal Alpha Angle Persists Abnormal in Patients with a Residual Bony Prominence after Surgery for Femoroacetabular Impingement

Uncapacitated facility location problem with self-serving demands

In classical uncapacitated facility location problems (UFLP) the goal is to satisfy requirements of some demand points by setting up some servers, among potential facility locations, such that the total cost including service costs and fixed costs are minimized. In this paper a generalization of UFLP is considered in which some demand points, called self-serving, could be served exclusively by a new server at that point. Numerical experiments show that near optimal solutions are achieved by the proposed method.

Improving seismotectonics and seismic hazard assessment along the San Ramón Fault at the eastern border of Santiago city, Chile

The San Ramón Fault is an active west-vergent thrust fault system located along the eastern border of the city of Santiago, at the foot of the main Andes Cordillera. This is a kilometric crustal-scale structure recently recognized that represents a potential source for geological hazards. In this work, we provide new seismological evidences and strong ground-motion modeling from hypothetic kinematic rupture scenarios, to improve seismic hazard assessment in the Metropolitan area of Central Chile. Firstly, we focused on the study of crustal seismicity that we relate to brittle deformation associated with different seismogenic fringes in the main Andes in front of Santiago. We used a classical hypocentral location technique with an improved 1D crustal velocity model, to relocate crustal seismicity recorded between 2000 and 2011 by the National Seismological Service, University of Chile. This analysis includes waveform modeling of seismic events from local broadband stations deployed in the main Andean range, such as San José de Maipo, El Yeso, Las Melosas and Farellones. We selected events located near the stations, whose hypocenters were localized under the recording sites, with angles of incidence at the receiver <5° and S–P travel times <2 s. Our results evidence that seismic activity clustered around 10 km depth under San José de Maipo and Farellones stations. Because of their identical waveforms, such events are interpreted like repeating earthquakes or multiplets and therefore providing first evidence for seismic tectonic activity consistent with the crustal-scale structural model proposed for the San Ramón Fault system in the area (Armijo et al. in Tectonics 29(2):TC2007, 2010). We also analyzed the ground-motion variability generated by an M w 6.9 earthquake rupture scenario by using a kinematic fractal k −2 composite source model. The main goal was to model broadband strong ground motion in the near-fault region and to analyze the variability of ground-motion parameters computed at various receivers. Several kinematic rupture scenarios were computed by changing physical source parameters. The study focused on statistical analysis of horizontal peak ground acceleration (PGAH) and ground velocity (PGVH). We compared the numerically predicted ground-motion parameters with empirical ground-motion predictive relationships from Kanno et al. (Bull Seismol Soc Am 96:879–897, 2006). In general, the synthetic PGAH and PGVH are in good agreement with the ones empirically predicted at various source distances. However, the mean PGAH at intermediate and large distances attenuates faster than the empirical mean curve. The largest mean values for both, PGAH and PGVH, were observed near the SW corner within the area of the fault plane projected to the surface, which coincides rather well with published hanging-wall effects suggesting that ground motions are amplified there.

Effective location models for sorting recyclables in public management

The recycling of urban solid wastes is a critical point for the “closing supply chains” of many products, mainly when their value cannot be completely recovered after use. In addition to environmental aspects, the process of recycling involves technical, economic, social and political challenges for public management. For most of the urban solid waste, the management of the end-of-life depends on selective collection to start the recycling process. For this reason, an efficient selective collection has become a mainstream tool in the Brazilian National Solid Waste Policy. In this paper, we study effective models that might support the location planning of sorting centers in a medium-sized Brazilian city that has been discussing waste management policies over the past few years. The main goal of this work is to provide an optimal location planning design for recycling urban solid wastes that fall within the financial budget agreed between the municipal government and the National Bank for Economic and Social Development. Moreover, facility planning involves deciding on the best sites for locating sorting centers along the four-year period as well as finding ways to meet the demand for collecting recyclable materials, given that economic factors, consumer behavior and environmental awareness are inherently uncertain future outcomes. To deal with these issues, we propose a deterministic version of the classical capacity facility location problem, and both a two-stage recourse formulation and risk-averse models to reduce the variability of the second-stage costs. Numerical results suggest that it is possible to improve the current selective collection, as well as hedge against data uncertainty by using stochastic and risk-averse optimization models.

GRASP for the uncapacitated r-allocation p-hub median problem

In this paper we propose a heuristic for the Uncapacitated r-Allocation p-Hub Median Problem. In the classical p-hub location problem, given a set of nodes with pairwise traffic demands, we must select p of them as hub locations and route all traffics through them at a minimum cost. We target here an extension, called the r-allocation p-hub median problem, recently proposed by Yaman [19], in which every node is assigned to r of the p selected hubs (r≤p) and we are restricted to route the traffic of the nodes through their associated r hubs.As it is usual in this type of problems, our method has three phases: location, assignment and routing. Specifically, we propose a heuristic based on the GRASP methodology in which we consider three local search procedures. The combinatorial nature of this problem makes them time-consuming. We therefore propose a filtering mechanism to discard low-quality constructions and skip its improvement, saving its associated running time. We perform several experiments to first determine the values of the key-search parameters of our method and then to compare with previous algorithms. Computational results on 465 instances show that while only small instances can be optimally solved with exact methods, the heuristic is able to find high-quality solutions on larger instances in short computing times. Moreover, when targeting the classical p-hub versions (with r=1 or r=p), our heuristic is competitive with the state of the art methods.

Residential location choice of knowledge-workers: The role of amenities, workplace and lifestyle

This study investigates the residential location choice of knowledge-workers at the intra-metropolitan level by applying discrete choice models. The models represent housing choices of 833 knowledge-workers in high-technology and financial services and analyze the relative importance of lifestyle and cultural amenities in addition to classic location factors. Hence, the model bridges the gap between the recent lifestyle-oriented and the classical utility-oriented conceptualizations of the residential choice of knowledge-workers. The most important factors are municipal socioeconomic level, housing affordability and commuting time, while substantial secondary factors are cultural and educational land-use and culture-oriented lifestyle.

Approximation Algorithms for Integrated Distribution Network Design Problems

In this paper, we study approximation algorithms for two supply chain network design problems, namely, the warehouse-retailer network design problem (WRND) and the stochastic transportation-inventory network design problem (STIND). These two problems generalize the classical uncapacitated facility location problem by incorporating, respectively, the warehouse-retailer echelon inventory cost and the warehouse cycle inventory together with the safety stock costs. The WRND and the STIND were initially studied, respectively, by Teo and Shu (Teo CP, Shu J (2004) Warehouse-retailer network design problem. Oper. Res. 52(3):396–408) and Shu et al. (Shu J, Teo CP, Shen ZJM (2005) Stochastic transportation-inventory network design problem. Oper. Res. 53(1):48–60), where they are formulated as set-covering problems, and column-generation algorithms were used to solve their linear programming relaxations. Both problems can be regarded as special cases of the so-called facility location with submodular facility costs proposed by Svitkina and Tardos (Svitkina Z, Tardos É (2010) Facility location with hierarchical facility costs. ACM Trans. Algorithms 6(2), Article No. 37), for which only a logarithmic-factor approximation algorithm is known. Our main contribution is to obtain efficient constant-factor approximation algorithms for the WRND and the STIND, which are capable of solving large-scale instances of these problems efficiently.

Robustness of optimal sensor placement under parametric uncertainty

This paper examines the influence of parametric uncertainties on the optimal sensor placement methodologies for the modal analysis of a truss bridge. Four classical sensor location methodologies are employed: two based on the Fisher information matrix and the other two based on energy matrix rank optimization. Young's modulus, mass density and cross sectional dimensions are considered as uncertain parameters. The independent and cumulative effects of these uncertain variables on the sensor placement are studied. The optimal locations of sensors under parametric uncertainty are assessed with three different criteria: the Fisher matrix determinant, the modal assurance criterion error and the condition number. Furthermore, the robustness of this configuration is investigated for the case of random and bias errors. The numerical results show the parametric uncertainties have significant influence on the optimal sensor configuration of a truss bridge.

Multi-product Capacitated Single-Allocation Hub Location Problems: Formulations and Inequalities

In this paper we extend the classical capacitated single-allocation hub location problem by considering that multiple products are to be shipped through the network. We propose a unified modeling framework for the situation in which no more than one hub can be located in each node. In particular, we consider the case in which all hubs are dedicated to handling a single-product as well as the case in which all hubs can handle all products. The objective is to minimize the total cost, which includes setup costs for the hubs, setup costs for each product in each hub and flow routing costs. Hubs are assumed to be capacitated. For this problem several models are proposed which are based on existing formulations for the (single-product) capacitated single-allocation hub location problem. Additionally, several classes of inequalities are proposed in order to strengthen the models in terms of the lower bound provided by the linear relaxation. We report results of a set of computational experiments conducted to test the proposed models and their enhancements.

Developing Network Location Model in Uncertainty Mode (Robust Mode)

In this research, facility location problem-network design under uncertainty robust mode has been discussed. In this regard a model will be developed, so that the uncertainty in parameters such as demand and problem’s various costs considered. Facility location-network design, unlike classical facility location models, which are assumed that network structure is pre-defined and pre-specified, will also decide on the structure of the network.

A specialized branch & bound & cut for Single-Allocation Ordered Median Hub Location problems

The Single-Allocation Ordered Median Hub Location problem is a recent hub model introduced by Puerto et al. (2011) [32] that provides a unifying analysis of the class of hub location models. Indeed, considering ordered objective functions in hub location models is a powerful tool in modeling classic and alternative location paradigms, that can be applied with success to a large variety of problems providing new distribution patterns induced by the different users’ roles within the supply chain network. In this paper, we present a new formulation for the Single-Allocation Ordered Median Hub Location problem and a branch-and-bound-and-cut (B&B&Cut) based algorithm to solve optimally this model. A simple illustrative example is discussed to demonstrate the technique, and then a battery of test problems with data taken from the AP library are solved. The paper concludes that the proposed B&B&Cut approach performs well for small to medium sized problems.

Reliability Analysis and Design of Facility Systems Based on Edge Failures: A Review

Reliability of facility systems is to a large degree affected by the edge (facility) failures. In this paper, we review the models and methods of the analysis and the design of reliable facility systems based on the classical location problems subject to edge failures. It shows that the reliability of facility systems will increase when considering the edge failures in locating decision.