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Copyright of Technikgeschichte is the property of Nomos Verlagsgesellschaft mbH & Co. KG and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Historia Contemporanea is the property of Historia Contemporania and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The work proposes a method for evaluating the functioning of IP - based networks by using monitoring tools and mathematical distributions. The traffic flows in an IP-based corporate network have been studied. The protocols and packets that are exchanged in the network are monitored. A breakdown of their size and type has been made. The time delay of the packets is also monitored. Based on the data about the time delay of packets and their size, mathematical distributions are made. The distributions give additional information about the functioning of the network. The types of audio codecs used by the IP telephone exchanges are also observed. [ABSTRACT FROM AUTHOR]

State-based telephone surveys are often designed to make estimates at substate levels, such as county or county group. Under a traditional random-digit-dial design, the telephone exchange of a landline number could be used to accurately identify the county for which the associated household resides. However, initially, no good analogous data methods existed for the cellphone frame. This required survey methodologists to draw random samples of cellphone numbers from the entire state, making it difficult to target areas within a state. To overcome this shortcoming, sample vendors have used a cellphone number's rate center (where the number was activated) as a proxy estimate for the county where the cellphone owner resides. Our paper shows that county assignations that are based on rate center data may have classification error rates as high as 30%. These high classification error rates make it difficult to accurately devise a cellphone frame sample allocation using the rate center data. This paper proposes a new method—the Rate Center Plus method—which uses rate centers and an estimate of the classification probabilities to stratify and allocate the desired respondent sample to counties. The new method uses Bayes' rule to distribute a desired county-level sample allocation across rate center counties. We demonstrate how the Rate Center Plus method was applied to the 2015 Ohio Medicaid Assessment Survey and the resulting efficacy of the method. Finally, we evaluate whether the new approach is more efficient than the traditional statewide sample method. In addition, we look at four approaches to estimating the necessary classification probabilities. We found that the Rate Center Plus method can be more cost efficient than the statewide sample method when the classification probabilities are reasonably estimated, reducing data collection costs as much as 12.8%. [ABSTRACT FROM AUTHOR]

This paper describes an application of line balancing and mixed-model sequencing theory to the assembly of 'frames' used in the production of telephone exchanges. The approach used is based on the Dar-/El/Cother mixed-model sequencing algorithm, extended to include in additional station lower bound. Preliminary investigations suggest the possibility of reducing the company's present workforce of 160 to 117 operators. A step-by-step description is presented, enabling others to attempt similar applications for the design of mixed-model assembly lines. [ABSTRACT FROM AUTHOR]

Reducing the energy consumption of the wireless networks is significantly important for the economic and ecological sustainability of the ICT industry, as high energy consumption may limit the performance of wireless networks, and is one of the main network costs. To solve the energy consumption problem, especially on the terminal side, a scheme known as distributed mobile cloud (DMC) is considered to be a potential solution. Multiple mobile terminals (MTs) can cooperatively take advantage of good quality links among the MTs to save energy when receiving from the Base Station. In this paper, we aim to find the optimal transmit power to further reduce the energy consumption of DMC. From simulation studies, it is shown that up to 80% energy savings can be accomplished when using optimal transmit power, compared to using the standard DMC without exploring the optimal transmit power. [ABSTRACT FROM AUTHOR]

This article proposes an approximation for the blocking probability in a many-server loss model with a non-Poisson time-varying arrival process and flexible staffing (number of servers) and shows that it can be used to set staffing levels to stabilize the time-varying blocking probability at a target level. Because the blocking probabilities necessarily change dramatically after each staffing change, we randomize the time of each staffing change about the planned time. We apply simulation to show that (i) the blocking probabilities cannot be stabilized without some form of randomization, (ii) the new staffing algorithm with randomiation can stabilize blocking probabilities at target levels and (iii) the required staffing can be quite different when the Poisson assumption is dropped. © 2017 Wiley Periodicals, Inc. Naval Research Logistics 64: 177-202, 2017 [ABSTRACT FROM AUTHOR]

In this paper, we address the problem of planning the universal mobile telecommunication system base stations location for uplink direction. The objective is to maximize the total traffic covered and minimize the total installation cost based on data involving fuzziness. To define the cost, researchers used the current period market prices as constants. However prices may change over time. Our aim here is to deal with the imprecise and uncertain information of prices. For this we introduce a model of problem where each cost is a fuzzy variable, and then we present a decision-making model based on possibility theory. To solve the problem we propose a search algorithm based on the hybridization of genetic algorithm and local search method. To validate the proposed method some numerical examples are given. [ABSTRACT FROM AUTHOR]

Current research on the risks associated with mobile phone suggests that many European citizens, at least in the developed countries, have negative perceptions of mobile phone base stations technologies and perceive different health risks associated with the proximity of mobile phone base stations. Less research has been conducted in the East European countries regarding risk perceptions on electromagnetic fields. In the current research study we conducted a content analysis of news regarding mobile phone technology in Romania - mobile phone masts and mobile phone radiations, using two of the most important news portals (www.hotnews.ro and www.ziare.com). A systematic search was conducted based on a closed list of keywords (see Elvers et al., 2009) and time frame was January 2009 to December 2013. The results show little concern of media with the topic of electromagnetic radiations and mobile phone base sitting. Most articles are found in the popular media and have rather emotional discourse, using the words "cancer" and "radiations" and we found few articles that debated over the contradictory effects of the current studies on the mobile phone technology and health risks. [ABSTRACT FROM AUTHOR]

We consider a finite buffer capacity GI/GI/c/K-type retrial queueing system with constant retrial rate. The system consists of a primary queue and an orbit queue. The primary queue has $$c$$ identical servers and can accommodate up to $$K$$ jobs (including $$c$$ jobs under service). If a newly arriving job finds the primary queue to be full, it joins the orbit queue. The original primary jobs arrive to the system according to a renewal process. The jobs have i.i.d. service times. The head of line job in the orbit queue retries to enter the primary queue after an exponentially distributed time independent of the length of the orbit queue. Telephone exchange systems, medium access protocols, optical networks with near-zero buffering and TCP short-file transfers are some telecommunication applications of the proposed queueing system. The model is also applicable in logistics. We establish sufficient stability conditions for this system. In addition to the known cases, the proposed model covers a number of new particular cases with the closed-form stability conditions. The stability conditions that we obtained have clear probabilistic interpretation. [ABSTRACT FROM AUTHOR]

A comparative study, based on three different measurements (direction of ray arrival, time difference of arrival and received signal strength), to compute the unknown position of mobile stations in indoor environments is presented in this paper. The comparison is carried out considering the results of analyses in a real building in Madrid. To overcome the problems that arise in indoor areas due to the presence of non line of sight conditions, the fingerprinting technique is applied in each of the cases. Data for computations are provided by a simulation tool based on the uniform theory of diffraction and ray-tracing techniques. This information is stored in the fingerprinting database and contains information related to every mobile station, every reference node and every access point located inside the environment under analysis. Experimental results compare the mean error when localizing several mobile stations by using the three different approaches. The goal is to obtain high precision in the localization by means of alternative methods to the received signal strength classical measurement. These techniques will be useful in critical environments where high operational security requirement are demanded. [ABSTRACT FROM AUTHOR]

The combination of OFDM with joint pre-processing in adaptive multi-antenna systems offers both an ease of equalization in frequency-selective channels and keeping the signal processing at the mobile stations simple. In addition, the spatial dimension can be efficiently exploited to ensure high system throughput. With the utilization of higher-order modulation the performance of the system is highly sensitive to multiple access interference and nonorthogonal subchannels due to hardware impairments or insufficient adaptation to the current channel conditions. A further source of error in TDD systems are the non-reciprocal transceivers inhibiting the baseband-to-baseband channel reciprocity required for accurate channel state acquisition based on the uplink channel estimate. In this paper, measurement results of a low-cost hardware-based calibration are presented and the drawbacks are discussed leading to the utilization of a recently introduced relative calibration. The latter is applied to an OFDM system and achieves or at least approximates the baseband-to-baseband reciprocity. Thus, it enables the link adaptation using the uplink channel state information. Furthermore, preliminary hardware implementations of the relative calibration running on a real-time system show accurate results. [ABSTRACT FROM AUTHOR]

One of the major problems in the telecommunication industry is the intermittent behaviors of the telephone switch. The application of IT technologies that make use of telephone network is dramatically increasing. There is a growing demand to rapidly detect and repair fault telecommunication lines, thus calls for proper monitoring. This paper discussed a means of detecting fault on a telephone line by the use of Artificial Neural Networks, current anticipation and localization procedures and suggest means of identifying potential faults within the network. It also discusses at the results that were obtained when using an Artificial Neural network to create voice sensitive music software. As a result of the data intensity of a TSS, an ANN architecture called feed forward back propagation is adopted and trained using MATLAB neural network toolbox. The results btained provides a better way of detecting fault in a telephone network. [ABSTRACT FROM AUTHOR]

Within three years of the invention of the telephone in 1876 attempts were being made for the partial machine switching of calls. A step-by-step system was developed by A.B. Strowger of the USA in the years 1889 to 1892 and from the beginning of the twentieth century was the first automatic exchange system to come into widespread use there. Conditions in Britain at the time were not conducive to the adoption of machine switching while telephone service was divided between the Post Office and the National Telephone Company (NTC) but the Post Office undertook a review of USA practice. The Post Office completed the purchase of NTC in January 1912 and instituted a series of trials of available automatic systems. The first of these, the public exchange at Epsom, Surrey, opened in May 1912 using the Strowger system. The paper describes the installation and operation of the equipment at Epsom and how it was received by its users and the wider public. In 1922 the Post Office decided to standardize on a development of Strowger step-by-step for British requirements. Ironically, when Epsom exchange required enlargement in the early 1930s it was instead replaced by a new manual exchange. A few examples of equipment from the pioneer British automatic exchange systems survive in preservation. [ABSTRACT FROM AUTHOR]

Motivated by call center cosourcing problems, we consider a service network operated under an overflow mechanism. Calls are first routed to an in-house (or dedicated) service station that has a finite waiting room. If the waiting room is full, the call is overflowed to an outside provider (an overflow station) that might also be serving overflows from other stations. We establish approximations for overflow networks with many servers under a resource-pooling assumption that stipulates, in our context, that the fraction of overflowed calls is nonnegligible. Our two main results are (i) an approximation for the overflow processes via limit theorems and (ii) asymptotic independence between each of the in-house stations and the overflow station. In particular, we show that, as the system becomes large, the dependency between each in-house station and the overflow station becomes negligible. Independence between stations in overflow networks is assumed in the literature on call centers, and we provide a rigorous support for those useful heuristics. [ABSTRACT FROM AUTHOR]

We obtain a heavy traffic limit for the GI/M/n+GI queue, which includes the entire patience time distribution. Our main approach is to scale the hazard rate function of the patience time distribution in such a way that our resulting diffusion approximation contains the entire hazard rate function. We then show through numerical studies that for various performance measures, our approximations tend to outperform those commonly used in practice. The robustness of our results is also demonstrated by applying them to solving constraint satisfaction problems arising in the context of telephone call centers. [ABSTRACT FROM AUTHOR]

Objectives: The aim of our study was to assess the health conditions and subjective symptoms of the inhabitants living in the base stations vicinity and to analyse the relationship between the complaints and level of exposure to electromagnetic fields (EMF). Materials and Methods: Our study was performed in housing estates located in five regions of Łódź. The electric field measurements were performed in the buildings located closest to the azimuth of the antennas. Respondents were selected by trained interviewers using an uniform procedure. The number of the households to be examined was set at a minimum of 420. The questionnaire contained: demographic data, occupational and environmental exposure to EMF, health condition, subjective complaints. Results were adjusted for confounders (age, gender, EMF at the workplace and EMF emitted by household equipment) using multiple regression model. Results: 181 men and 319 women from 500 households were examined. Electric field above 0.8 V/m was recorded in 12% of flats. There was no significant correlation between electric field strength and the distance of examined flats from the base stations. To make possible comparison with relevant literature, we analysed also the frequency of the reported symptoms vs. the distance. Headache was declared by 57% people, most frequently (36.4%) living 100-150 m away from the base station compared to people living at longer distances (p = 0.013). 24.4% subjects, mostly living at a distance above 150 m, declared impaired memory. Difference was statistically significant in comparison with people living at other distances (p = 0.004). Conclusions: The explanation why we did not find any correlation between the electric field strength and frequency of subjective symptoms but found a correlation between subjective symptoms and distance from base station needs further studies. Maybe new metrics of exposure assessment should be adopted for this purpose. [ABSTRACT FROM AUTHOR]

Copyright of Espacio, Tiempo y Forma. Serie VII, Historia del Arte is the property of Editorial UNED and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: This article mainly studies the reliability evaluation of an overall-terminal multistate flow network whose arcs are all bi-directed in terms of MPs (minimal paths). The telephone-communication system (in which each node denoting a telephone station can either call or receive a phone) and computer-communication system are typical ones of such networks. Given the system demand where is the required demand between the node pair (i, j)∈ B with a specified set of node pairs B and d the total demand requirement among all nodes, an algorithm is proposed first to find out all lower boundary points of (namely -MPs here) in terms of MPs. The system reliability can then be calculated in terms of the family of all -MPs. One example is illustrated to show how all its -MPs are generated and how the reliability nay be calculated. [Copyright &y& Elsevier]

Mobile communication has become a ubiquitous part of today's life. The ongoing growth of this technology, however, involves the construction of new mobile phone base stations in order to assure network coverage. The selection of a new base station site often results in conflicts between providers and public authorities, on the one hand, and residents on the other. The aim of the present study was to examine public preferences regarding base station sites. A random sample of 503 persons from the German speaking part of Switzerland was interviewed face-to-face in their homes. Conjoint analysis was used to evaluate participants' preferences for various attributes of base stations (appearance, location, building, decision process). The results show that location plays the most important role in participants' acceptance of base stations. The findings also indicate that most people would prefer a covered or camouflaged base station to a freely visible one. By means of a cluster analysis, several segments were distinguished, showing that base station siting preferences were not homogeneous. Implications for risk communication are discussed. [ABSTRACT FROM AUTHOR]

The paper analyzes the mathematical models of call centers that take into account repeated calls and the specific features and key aspects of modeling call centers as retrial queues. Queuing systems M/ M/ c/0/ L/ H j, M/ M/ c/0/// E2, and M/ M/ c/0/ L// E2 are considered as models of call centers. Numerical results for the performance indices of these systems are given. [ABSTRACT FROM AUTHOR]

Algorithms for approximate evaluation of the characteristics of microcellular wireless networks with queues of new and handover calls are developed. It is assumed that unlike calls may leave the queue if their waiting time is greater than some threshold value. Results of numerical experiments are presented. [ABSTRACT FROM AUTHOR]

In this pair of papers (Part I and Part!! in this issue), we investigate the issue of power control and subcarrier assignment in a sectorized two-cell downlink OFDMA system impaired by multicell interference. As recommended for WiMAX, we assume that the first part of the available bandwidth is likely to be reused by different base stations (and is thus subject to multicell interference) and that the second part of the bandwidth is shared in an orthogonal way between the different base stations (and is thus protected from multicell interference). Although the problem of multicell resource allocation is nonconvex in this scenario, we provide in Part I the general form of the global solution. In particular, the optimal resource allocation turns out to be "binary" in the sense that, except for at most one pivot-user in each cell, any user receives data either in the reused bandwidth or in the protected bandwidth, but not in both. The determination of the optimal resource allocation essentially reduces to the determination of the latter pivot-position. [ABSTRACT FROM AUTHOR]

Random digit dial (RDD) sampling methodology was developed over two decades ago when local telephone exchanges used 100-series telephone banks as physical building blocks for telephone number assignment. During the intervening decades the telecommunication industry has undergone a number of fundamental changes that have had drastic effects on the efficiency and coverage of RDD samples. Based on a new study of landline telephone numbers, which was conducted during the second quarter of 2008, this paper reexamines the assumptions that are relied upon for construction of list-assisted RDD samples; quantifies the extent of undercoverage in the corresponding sampling frames; investigates alternative methods of frame construction for RDD samples; and evaluates other sample design options that can offer greater coverage with varying degrees of efficiency. [ABSTRACT FROM PUBLISHER]

Background and Aims: Coeval with the expansion of mobile phone technology and the associated obvious presence of mobile phone base stations, some people living close to these masts reported symptoms they attributed to electromagnetic fields (EMF). Public and scientific discussions arose with regard to whether these symptoms were due to EMF or were nocebo effects. The aim of this study was to find out if people who believe that they live close to base stations show psychological or psychobiological differences that would indicate more strain or stress. Furthermore, we wanted to detect the relevant connections linking self-estimated distance between home and the next mobile phone base station (DBS), daily use of mobile phone (MPU), EMFhealth concerns, electromagnetic hypersensitivity, and psychological strain parameters. Design, Materials and Methods: Fifty-seven participants completed standardized and non-standardized questionnaires that focused on the relevant parameters. In addition, saliva samples were used as an indication to determine the psychobiological strain by concentration of alpha-amylase, cortisol, immunoglobulin A (IgA), and substance P. Results: Self-declared base station neighbors (DBS ⩽ 100 meters) had significantly higher concentrations of alpha-amylase in their saliva, higher rates in symptom checklist subscales (SCL) somatization, obsessive-compulsive, anxiety, phobic anxiety, and global strain index PST (Positive Symptom Total). There were no differences in EMF-related health concern scales. Conclusions: We conclude that selfdeclared base station neighbors are more strained than others. EMF-related health concerns cannot explain these findings. Further research should identify if actual EMF exposure or other factors are responsible for these results. [ABSTRACT FROM AUTHOR]

The term “mass service theory” introduced by A.Ya. Khinchin implies that the probability theory is applied to the studies of diverse problems of servicing which often are related to formation of queues. The problems of design and calculation of the communication networks and their elements are pivotal here. In the shop language of the communication community this domain of knowledge is called the teletraffic theory. The first publication of A.K. Erlang whose centenary is celebrated this year was devoted namely to this theory. It is not occasional that this jubilee is observed. Today the mankind has the worldwide communication network offering fabulous possibilities in information transmission, storage, and processing. Creation of such a network would not be possible without wide use of the teletraffic theory. [ABSTRACT FROM AUTHOR]

Abstract: Studying effects of mobile phone base station signals on health have been discouraged by authoritative bodies like WHO International EMF Project and COST 281. WHO recommended studies around base stations in 2003 but again stated in 2006 that studies on cancer in relation to base station exposure are of low priority. As a result only few investigations of effects of base station exposure on health and wellbeing exist. Cross-sectional investigations of subjective health as a function of distance or measured field strength, despite differences in methods and robustness of study design, found indications for an effect of exposure that is likely independent of concerns and attributions. Experimental studies applying short-term exposure to base station signals gave various results, but there is weak evidence that UMTS and to a lesser degree GSM signals reduce wellbeing in persons that report to be sensitive to such exposures. Two ecological studies of cancer in the vicinity of base stations report both a strong increase of incidence within a radius of 350 and 400m respectively. Due to the limitations inherent in this design no firm conclusions can be drawn, but the results underline the urgent need for a comprehensive investigation of this issue. Animal and in vitro studies are inconclusive to date. An increased incidence of DMBA induced mammary tumors in rats at a SAR of 1.4W/kg in one experiment could not be replicated in a second trial. Indications of oxidative stress after low-level in vivo exposure of rats could not be supported by in vitro studies of human fibroblasts and glioblastoma cells. From available evidence it is impossible to delineate a threshold below which no effect occurs, however, given the fact that studies reporting low exposure were invariably negative it is suggested that power densities around 0.5–1mW/m2 must be exceeded in order to observe an effect. The meager data base must be extended in the coming years. The difficulties of investigating long-term effects of base station exposure have been exaggerated, considering that base station and handset exposure have almost nothing in common both needs to be studied independently. It cannot be accepted that studying base stations is postponed until there is firm evidence for mobile phones. [Copyright &y& Elsevier]

Currents induced in human feet near a cellular phone base station were calculated by the finite-difference time-domain method and measured by a parallel plate meter at 1,869 MHz. From simulation results and measurement data, it is found that the theory of finite-difference time-domain method agrees well with the experiment. It is also found that the maximum foot currents of 20.73 and 18.51 mA were obtained by measurements and calculations when a human stands barefoot at a distance of 10 m from the cellular phone base station, respectively. From measurements and calculations, the foot currents are reduced by a factor of about 0.72-0.91 and 0.8 when the condition is changed from standing barefoot to wearing shoes, respectively. Layer currents distributed in the human body are also obtained by the finite-difference time-domain method. It is found that the highest layer currents distributed in the human body occur in the area of the chest. From the layer current profiles, it is also found that the maximum induced body current density is below the excitation threshold level of 1 mA/cm2. The impact of clothes on the induced currents is also presented. It is found that there is only a little difference in the magnitude of current distributions between the human model with and without clothes. [ABSTRACT FROM AUTHOR]

This article draws on fieldwork conducted with nurses in two sites of NHS Direct, the English tele-nursing service. Theoretically it has two objectives. Firstly to examine a group of professional workers in order to show how the discourse of work transformation associated with the call centre paradigm interacts in a non-mass, non-commercial public sector setting where workers remain attached to their occupational identity and institutional community which mediate call centre values and rationalities. In relation to this objective, the article shows how call centre values inform NHS Direct but do not produce the same outcomes as in commercial settings. Secondly, the article establishes that nurses, as knowledgeable actors, can control, manipulate and create knowledge, without having their autonomy subordinated to the clinical software they are required to use. The article contributes to the labour process approach of call centre working and debates on knowledge management in the workplace. [ABSTRACT FROM AUTHOR]

The nature of call centre 'logics' and their predominance in routine commercial areas of the economy underscored much of the early research into call centre operations. Recent regulatory, structural and technological developments in advanced economies underscored subsequent migrations of call centres from the private to the public sector (Glucksman, 2004; Taylor and Bain, 2007). Further call centre migrations have also occurred into more skilled occupations in the public sector. Drawing on published and unpublished research on in-bound call centres operating in social work and nursing in the UK and Australia, this discussion analyses the dual migration of call centres from routine commercial operations to professional public sector services. The following discussion recognizes the viability of cost efficient and customer service dualities, however, given shifts into more complex areas of service delivery, pre-existing norms of professional practice became another important driver of call centre labour processes. [ABSTRACT FROM AUTHOR]

Construction of rural telecenters has been recently promoted by Chinese government officials as an innovative way to solve the problem of underdevelopment in rural areas. To address questions on the project's effectiveness and manageability, this article attempts to do a case study on the United Nations Development Programme--Ministry of Science and Technology (UNDP--MoST) telecenter project by analyzing the deliberative nature of its institutional framework. Such an analysis seems to indicate the coexistence of a collaborative network-building effort and a continuity of traditional institutional hierarchy, division, and lack of public deliberation. Although policy innovations should be celebrated, further efforts should be taken to promote the complexity of the framework and enable further participatory deliberation in the project policy-making process. [ABSTRACT FROM AUTHOR]

Abstract: Given that a significant amount of research and development efforts go into the creation of software tools, it is important that the most effective verification and validation methods be applied. Traditional methods for evaluating the accuracy and benefits of collaborative business process platforms created by East and Kirby, to date, do not constitute a sufficient proof that these tools are actually operating as designed or provide maximum possible value to all users. Verification through user interviews and surveys demonstrates that the software is performing as expected under test conditions, but is insufficient to identify off-purpose uses. Validation efforts performed at discrete points in time, such as economic analysis, describe specific cases and require assumptions of generality. Subjective continuous evaluations, such as user-submitted Call Center tickets, provide a continuous but incomplete measure of users'' experience. This paper provides a new taxonomy that can help researchers and developers to frame future verification and validation efforts. The four dimensions of this taxonomy are Objectivity, Sample Size, Frequency, and Purpose. Software users can also apply the taxonomy to evaluate the extent to which products have been evaluated beyond the standard case studies typically found in software vendor literature. [Copyright &y& Elsevier]

Abstract: In this paper, we present the use of different mathematical models to forecast service requests in support centers (SCs). A successful prediction of service request can help in the efficient management of both human and technological resources that are used to solve these eventualities. A nonlinear analysis of the time series indicates the convenience of nonlinear modeling. Neural models based on the time delay neural network (TDNN) are benchmarked with classical models, such as auto-regressive moving average (ARMA) models. Models achieved high values for the correlation coefficient between the desired signal and that predicted by the models (values between 0.88 and 0.97 were obtained in the out-of-sample set). Results show the suitability of these approaches for the management of SCs. [Copyright &y& Elsevier]