931 resultados para R41 - Transportation: Demand
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Objectives: To assess the difference in direct medical costs between on-demand (OD) treatment with esomeprazole (E) 20 mg and continuous (C) treatment with E 20 mg q.d. from a clinical practice view in patients with gastroesophageal reflux disease (GERD) symptoms. Methods: This open, randomized study (ONE: on-demand Nexium evaluation) compared two long-term management options with E 20 mg in endoscopically uninvestigated patients seeking primary care for GERD symptoms who demonstrated complete relief of symptoms after an initial treatment of 4 weeks with E 40 mg. Data on consumed quantities of all cost items were collected in the study, while data on prices during the time of study were collected separately. The analysis was done from a societal perspective. Results: Forty-nine percent (484 of 991) of patients randomized to the OD regimen and 46% (420 of 913) of the patients in the C group had at least one contact with the investigator that would have occurred nonprotocol-driven. The difference of the adjusted mean direct medical costs between the treatment groups was CHF 88.72 (95% confidence interval: CHF 41.34-153.95) in favor of the OD treatment strategy (Wilcoxon rank-sum test: P < 0.0001). Adjusted direct nonmedical costs and productivity loss were similar in both groups. Conclusions: The adjusted direct medical costs of a 6-month OD treatment with esomeprazole 20 mg in uninvestigated patients with symptoms of GERD were significantly lower compared with a continuous treatment with E 20 mg once a day. The OD therapy represents a cost-saving alternative to the continuous treatment strategy with E.
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Transportation planners typically use census data or small sample surveys to help estimate work trips in metropolitan areas. Census data are cheap to use but are only collected every 10 years and may not provide the answers that a planner is seeking. On the other hand, small sample survey data are fresh but can be very expensive to collect. This project involved using database and geographic information systems (GIS) technology to relate several administrative data sources that are not usually employed by transportation planners. These data sources included data collected by state agencies for unemployment insurance purposes and for drivers licensing. Together, these data sources could allow better estimates of the following information for a metropolitan area or planning region: · Locations of employers (work sites); · Locations of employees; · Travel flows between employees’ homes and their work locations. The required new employment database was created for a large, multi-county region in central Iowa. When evaluated against the estimates of a metropolitan planning organization, the new database did allow for a one to four percent improvement in estimates over the traditional approach. While this does not sound highly significant, the approach using improved employment data to synthesize home-based work (HBW) trip tables was particularly beneficial in improving estimated traffic on high-capacity routes. These are precisely the routes that transportation planners are most interested in modeling accurately. Therefore, the concept of using improved employment data for transportation planning was considered valuable and worthy of follow-up research.
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This report proposes, that for certain types of highway construction projects undertaken by the Iowa Department of Transportation, a scheduling technique commonly referred to as linear scheduling may be more effective than the Critical Path Method scheduling technique that is currently being used. The types of projects that appear to be good candidates for the technique are those projects that have a strong linear orientation. Like a bar chart, this technique shows when an activity is scheduled to occur and like a CPM schedule it shows the sequence in which activities are expected to occur. During the 1992 construction season, the authors worked with an inlay project on Interstate 29 to demonstrate the linear scheduling technique to the Construction Office. The as-planned schedule was developed from the CPM schedule that the contractor had developed for the project. Therefore, this schedule represents what a linear representation of a CPM schedule would look like, and not necessarily what a true linear schedule would look like if it had been the only scheduling technique applied to the project. There is a need to expand the current repertoire of scheduling techniques to address those projects for which the bar chart and CPM may not be appropriate either because of the lack of control information or due to overly complex process for the actual project characteristics. The scheduling approaches used today on transportation projects have many shortcomings for properly modeling the real world constraints and conditions which are encountered. Linear project's predilection for activities with variable production rates, a concept very difficult to handle with the CPM, is easily handled and visualized with the linear technique. It is recommended that work proceed with the refinement of the method of linear scheduling described above and the development of a microcomputer based system for use by the Iowa Department of Transportation and contractors for its implementation. The system will be designed to provide the information needed to adjust schedules in a rational understandable method for monitoring progress on the projects and alerting Iowa Department of Transportation personnel when the contractor is deviating from the plan.
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Weekly letting report
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The Iowa Department of Transportation Office of Research & Analytics has created this Guide to help researchers and contractors of the Iowa DOT attain compliance with Federal and Iowa DOT Public Access Policies for transportation-related research publications and datasets. This guide provides direction for filling out the data management plan template (also attached to this record) that will help satisfy Iowa DOT and U.S. DOT requirements.
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Compendium of papers presented at the Transportation Scholars Conference in 2000.
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Weekly letting report
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The goal of this research was to recommend specific changes relating to service by intercity buses and third level air carriers to propose an appropriate state role in the implementation of changes. Changes contemplated in this research were to be directed to the increased use of intercity buses and third level air carriers in such manner as to exert a benefit to user as well as the general public. Specific objectives of the project included: (1) to analyze the potential for a system of express intercity bus routes in Iowa; (2) to estimate the demand for third level air carrier services in cities having populations under 50,000; (3) to forecast the relationship between economic costs and benefits from an intercity bus system emphasizing express routes between major population centers and supporting a subsystem of local and intraregional public transportation; (4) to estimate the economic feasibility of expanded third level air carrier service with emphasis upon those routes proposed as worth of further evaluation; and (5) to provide guidance for establishing the need for state and local subsidies to institute a system of express intercity buses and to expand third level air carrier services. In addition to passenger movements, enhancing package freight shipments was also to be considered in the evaluation of proposed improvements.
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The purposes of this report (Phase II of the project) are to specify in mathematical form the individual modules of the conceptual model developed in Phase I, to identify and evaluate sources of data for the model set, and to develop the transport networks necessary to support the models.
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The purpose of this project is to develop an investment analysis model that integrates the capabilities of four types of analysis for use in evaluating interurban transportation system improvements. The project will also explore the use of new data warehousing and mining techniques to design the types of databases required for supporting such a comprehensive transportation model. The project consists of four phases. The first phase, which is documented in this report, involves development of the conceptual foundation for the model. Prior research is reviewed in Chapter 1, which is composed of three major sections providing demand modeling background information for passenger transportation, transportation of freight (manufactured products and supplies), and transportation of natural resources and agricultural commodities. Material from the literature on geographic information systems makes up Chapter 2. Database models for the national and regional economies and for the transportation and logistics network are conceptualized in Chapter 3. Demand forecasting of transportation service requirements is introduced in Chapter 4, with separate sections for passenger transportation, freight transportation, and transportation of natural resources and commodities. Characteristics and capacities of the different modes, modal choices, and route assignments are discussed in Chapter 5. Chapter 6 concludes with a general discussion of the economic impacts and feedback of multimodal transportation activities and facilities.
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Abstract
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In this thesis, I develop analytical models to price the value of supply chain investments under demand uncer¬tainty. This thesis includes three self-contained papers. In the first paper, we investigate the value of lead-time reduction under the risk of sudden and abnormal changes in demand forecasts. We first consider the risk of a complete and permanent loss of demand. We then provide a more general jump-diffusion model, where we add a compound Poisson process to a constant-volatility demand process to explore the impact of sudden changes in demand forecasts on the value of lead-time reduction. We use an Edgeworth series expansion to divide the lead-time cost into that arising from constant instantaneous volatility, and that arising from the risk of jumps. We show that the value of lead-time reduction increases substantially in the intensity and/or the magnitude of jumps. In the second paper, we analyze the value of quantity flexibility in the presence of supply-chain dis- intermediation problems. We use the multiplicative martingale model and the "contracts as reference points" theory to capture both positive and negative effects of quantity flexibility for the downstream level in a supply chain. We show that lead-time reduction reduces both supply-chain disintermediation problems and supply- demand mismatches. We furthermore analyze the impact of the supplier's cost structure on the profitability of quantity-flexibility contracts. When the supplier's initial investment cost is relatively low, supply-chain disin¬termediation risk becomes less important, and hence the contract becomes more profitable for the retailer. We also find that the supply-chain efficiency increases substantially with the supplier's ability to disintermediate the chain when the initial investment cost is relatively high. In the third paper, we investigate the value of dual sourcing for the products with heavy-tailed demand distributions. We apply extreme-value theory and analyze the effects of tail heaviness of demand distribution on the optimal dual-sourcing strategy. We find that the effects of tail heaviness depend on the characteristics of demand and profit parameters. When both the profit margin of the product and the cost differential between the suppliers are relatively high, it is optimal to buffer the mismatch risk by increasing both the inventory level and the responsive capacity as demand uncertainty increases. In that case, however, both the optimal inventory level and the optimal responsive capacity decrease as the tail of demand becomes heavier. When the profit margin of the product is relatively high, and the cost differential between the suppliers is relatively low, it is optimal to buffer the mismatch risk by increasing the responsive capacity and reducing the inventory level as the demand uncertainty increases. In that case, how¬ever, it is optimal to buffer with more inventory and less capacity as the tail of demand becomes heavier. We also show that the optimal responsive capacity is higher for the products with heavier tails when the fill rate is extremely high.
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This paper describes the state of the art of secure ad hoc routing protocols and presents SEDYMO, a mechanism to secure a dynamic multihop ad hoc routing protocol. The proposed solution defeats internal and external attacks usinga trustworthiness model based on a distributed certification authority. Digital signatures and hash chains are used to ensure the correctness of the protocol. The protocol is compared with other alternatives in terms of security strength, energy efficiency and time delay. Both computational and transmission costs are considered and it is shown that the secure protocol overhead is not a critical factor compared to the high network interface cost.
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Suolahappo kuuluu peruskemianteollisuuden tuotteisiin ja on monen eri kemianteollisuuden tuotteen raaka-aine, jota ilman tuotantoprosessi keskeytyy. Suolahapontuottajia on vain muutama Suomessa ja näiden tuottajien varassa toimii lukuisia jatkojalostusteollisuuslaitoksia. Työssä lähdettiin kehittämään suolahapontoimitusvarmuutta logistiikan keinoin. Toimitusvarmuutta haluttiin kehittää sesonkivaihteluiden ja tuotantokatkosten aikana. Työssä etsitään sopiva sesonkivarastointikapasiteetti ja varmuusvarastotaso sekä järkevä sijainti varastolle. Varastointia kehitetään kuljetukset ja tuotannon luonne huomioiden. Työn alussa esitellään yritys ja tuotantoprosessi. Tämän jälkeen analysoidaan kysyntätietoja ja kasataan ongelmat toimitusvarmuudessa. Näiden pohjalta lähdetään kehittämään teoriapohjaisia ratkaisuvaihtoehtoja, jonka jälkeen ne sovelletaan yritykselle sopivaan muotoon. Työn tuloksena saatiin esitys varastointitarpeesta sekä siitä aiheutuvista kustannuksista. Työssäesitetään myös järkevä varaston sijainti ja soveltuva kuljetuskäytäntö tähän varastoon.
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Venäjän voimakas talouskasvu on lisännyt merkittävästi myös logistiikkapalveluiden kysyntää maassa. Suuren pinta-alan, markkinapotentiaalin ja Euroopan ja Aasian välisen maantieteellisen sijainnin tarjoaman merkittävän kauttakulkupotentiaalin ansiosta Venäjä on erityisen kiinnostava investointikohde logistiikkayrityksille. Talouskasvu ei ole kuitenkaan jakautunut tasaisesti ja tämän vuoksi investoijan onkin syytä tarkoin selvittää minne Venäjän sisällä sijoittua. Tässä työssä on kartoitettu Venäjän logistiikkasektoria ja liikenneinfrastruktuuria sekä tarkasteltu kilpailutilannetta tavoitteena löytää logistiikkayrityksellekeskeisimmät sijaintikohteet Venäjällä. Moskova ja Pietari on rajattu tutkimuksen ulkopuolelle. Alan kirjallisuuteen ja aiheesta aiemmin laadittuihin tutkimuksiin perehtymällä on selvitetty yritysten sijaintipaikanvalinnalle asettamat tärkeimmät kriteerit. Logistiikkayrityksille toimivalla infrastruktuurilla on luonnollisesti oleellinen merkitys sijaintipaikkaa valittaessa, riittävän suuren markkinapotentiaalin ollessa toinen erittäin merkittävä kriteeri. Kirjallisuustarkastelun pohjalta potentiaalisiksi kohteiksi logistiikkayritykselle valikoitui 22 kaupunkia eri puolilta Venäjää. Monikriteerianalyysiin perustuvan pisteytysmenetelmän avulla toteutetussa potentiaalisten kohteiden luokittelussa kiinnostavimmiksi sijoittumiskohteiksi kohosivat Etelä-Venäjällä, Mustanmeren rannikolla sijaitsevat merkittävät satamakaupungit. Kehittyneen infrastruktuurin, merkittävän markkinapotentiaalin sekä suotuisten taloudellisten toimintaedellytysten ansiosta tarjoavat nämä erityisen merkittävän investointipotentiaalin logistiikkayrityksille.