85 research outputs found
A study on the optimal PPP model for transport: the case of road and rail in South Korea
No full textIn recent decades the Public Private Partnership (PPP) has been widely regarded as an innovative way to construct transport infrastructures and to improve the quality of service. As the number of PPP cases has increased, many countries have tried to standardise PPP models to minimise the costs of trial and error. South Korea, where 426 PPP projects have been undertaken since 1994, usually preferred the BTO (Build-Transfer-Operate) model for transport. In the BTO model, the private sector recoups its investment by charging end users directly and hence should bear the traffic demand risk. However, the Korean Government shared the demand risk through a minimum revenue guarantee to induce private sector involvement, and this led to many criticisms of the BTO model. Tariffs in the BTO case were much higher than those of public operators, but the Government still had to pay large amounts of guaranteed revenue. Thus, BTL (Build-Transfer-Lease), where the demand risk is on the public sector, has become an alternative model. The BTL is the “service sold to the public sector” model which is similar to the DBFO (Design-Build-Finance-Operate) in the UK. This thesis examines which of the BTO and the BTL PPP models is optimal to save governmental expenditure for transport infrastructures such as road and rail. Appropriate traffic demand risk sharing, which a particularly controversial issue in South Korea, is explored. These research objectives are examined through five case studies: the Incheon Airport Expressway and the Oksan-Ochang Expressway cases for road PPP; the Incheon Airport Railway, the Daegok-Sosa Railway and the Seoul Metro 9 cases for rail PPP. Through a detailed literature review and five case studies, the thesis shows that the optimal PPP model, which is measured by the VFM (Value for Money) assessment, needs to satisfy the interests of public sector, private sector, and end users. Based on these assessments and including these three viewpoints, it is concluded that the optimal PPP model for road can be the BTL where the public sector can save expenditure or reduce the level of tariff. Traffic demand risk for roads is relatively low, so the public sector does not have to transfer it to the private sector with high profit rate. In the case of rail, the limited revenue and high cost make a project difficult to be financially free standing by the BTO model. However, the BTO can be a better option in urban rail if traffic demand risk is shared appropriately
Simulating CONWIP and CONWIP- BtO production strategies
No full textThesis: M. Eng. in Advanced Manufacturing and Design, Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 106-108).When ramping up production volumes, hardware startups are required to identify and tackle obstacles in multiple areas of business including finance, sales, engineering, manufacturing, and servicing. NVBOTS, a Boston based 3D printer manufacturing startup, is going through a similar phase of production ramp-up of its printers. This thesis documents the process that the MIT M.Eng. team went through to identify such obstacles at NVBOTS. This process provides insights into what other startups in similar positions may explore. The topic of manufacturing systems was identified as a potential area of improvement as NVBOTS ramps up its production. Discrete event manufacturing simulation models are developed to evaluate two base production strategies -- CONWIP and CONWIP-BtO hybrid. This thesis details the modeling mechanisms used to develop the simulation models. Performance trade-offs that exist for these two production strategies with respect to lead time and production floor inventory levels are analyzed. Effects of various policy levers such as CONWIP and BtO batch sizes are studied, and recommendations for these levers are made. The CONWIP policy is recommended for when lead time requirements for NVBOTS become strict. The CONWIP-Build to Order policy is not recommended given the low lead time benefit it offers compared to a pure Build to Order policy. Following feedback from NVBOTS on these two policies, an advanced Late Stage Differentiation CONWIP-BtO model is developed. This is done to evaluate the potential of late stage differentiation for when NVBOTS expands its product lines. Performance of this policy with respect to lead time and inventory levels is studied for different values of CONWIP and BtO batch sizes, number of workers and worker utilization. Potential plans of action for NVBOTS to tackle higher demands in the future are analyzed. The work described in this thesis covers roughly half of the project on manufacturing systems at NVBOTS. The other half is covered in Alexander Willem Anton van Grootel's thesis [1]. Van Grootel's thesis focuses on capacity estimation of NVBOTS' current facility and variants of the BtO policy. In contrast, this thesis analyzes CONWIP and CONWIP-BtO policies.by Yugal Raj Jain.M. Eng. in Advanced Manufacturing and Desig
Vernieuwd onderzoeksprogramma drinkwatersector: één jaar op weg
No full textDe Nederlandse drinkwaterbedrijven investeren al meer dan veertig jaar in een collectief onderzoeksprogramma (BTO) en een gezamelijk kennisinstituut (KWR). Deze bundeling van krachten resulteert in internationaal toonaangevend drinkwateronderzoek; het kennisnetwerk, ontmoetingsplatform en cofinancieringsbrug. Eens per jaar vindt een uitgebreide evlauatie van het BTO plaats. De resultaten over het eerste jaar van het nieuwe BTO zijn onlamgs bekend gemaakt. Wat is de stand van zaken en wat zijn de lessen die we kunnen leren?Water ManagementCivil Engineering and Geoscience
Bayesian hierarchical modelling of continuous non-negative longitudinal data with a spike at zero : an application to a study of birds visiting gardens in winter
No full textThe development of methods for dealing with continuous data with a spike at zero has lagged behind those for overdispersed or zero‐inflated count data. We consider longitudinal ecological data corresponding to an annual average of 26 weekly maximum counts of birds, and are hence effectively continuous, bounded below by zero but also with a discrete mass at zero. We develop a Bayesian hierarchical Tweedie regression model that can directly accommodate the excess number of zeros common to this type of data, whilst accounting for both spatial and temporal correlation. Implementation of the model is conducted in a Markov chain Monte Carlo (MCMC) framework, using reversible jump MCMC to explore uncertainty across both parameter and model spaces. This regression modelling framework is very flexible and removes the need to make strong assumptions about mean‐variance relationships a priori. It can also directly account for the spike at zero, whilst being easily applicable to other types of data and other model formulations. Whilst a correlative study such as this cannot prove causation, our results suggest that an increase in an avian predator may have led to an overall decrease in the number of one of its prey species visiting garden feeding stations in the United Kingdom. This may reflect a change in behaviour of house sparrows to avoid feeding stations frequented by sparrowhawks, or a reduction in house sparrow population size as a result of sparrowhawk increase.Peer reviewe
Optimizing shipping pricing on Dell.com on BTO notebooks to United States consumers across customer experience, profitability and working capital
No full textThesis: M.B.A., Massachusetts Institute of Technology, Sloan School of Management, in conjunction with the Leaders for Global Operations Program at MIT, 2017.Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, in conjunction with the Leaders for Global Operations Program at MIT, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (page 53).Current shipping pricing for BTO notebooks on Dell.com is uniform across products and provides customers with three levels of service Express, Expedited, and Standard. In October 2016, Dell launched a program to give customers more information and better choices when they select their shipping method with the goal of improving the customer order experience. The goal of this research was to develop an optimization model that will recommend shipping prices to maximize the value that Dell realizes across three levers: customer experience, profitability, and working capital. The value of customer experience is measured by the cost of customer dissatisfaction associated with different shipping levels including the cost of returns, exchanges, customer contacts, and order disruptions. Key components of logistics profitability are logistics costs and shipping price. Dell does not have current shipping price elasticity data to forecast attach rates to upgraded shipping at different price points. To collect this data, an experiment has been designed to measure the results of three price treatments across three BTO product brands. This experiment is scheduled to launch in summer 2017. The optimization model would have to be updated following the results of this experiment and rerun before implementation of changes to delivery pricing. The third lever of the model, working capital, becomes increasingly important as customers move to the new fastest shipping option, Express, which was first launched in October 2016. This lane provides the fastest delivery times on BTO products in the industry. It also reduces the number of days the product is in Dell inventory leading to an inverse relationship between express shipping attach rate and working capital required. Finally, it allows Dell to bill the customer faster improving their cash conversion cycle. The optimization model indicated that there is the opportunity to increase delivery value by 28% through reduced delivery pricing leading to increased attach rates. This value based approach to delivery pricing can be applied across industries to online retailers looking to create value through their delivery pricing.by Carrie Beyer.M.B.A.S.M
ANALISIS KINERJA PELAYANAN RAWAT INAP PADA RUMAH SAKIT KASIH IBU DITINJAU DARI RASIO BOR, LOS, TOI, BTO, NDR, DAN GDR PERIODE 2012 - 2014
No full textQuality of service becomes very important for the hospital in Indonesia.
Services are provided to patients by health workers as well and full of empathy in
accordance with the needs of patients, knowledge, skills and standards. The
purpose of this study was to analyze the performance of services in Kasih Ibu’s
Hospital based on ratio of BOR, LOS, TOI, BTO, NDR and GDR.
Based on the results of this study, Kasih Ibu’s Hospital has a good service
performance seen from the ratio of Bed Occupancy Rate, Length Of Stay, Turn
Over Interval and Net Death Rate. It happens because the ratio shows result are in
accordance with the national standards for quality of service indicators for years
2012-2014. Meanwhile, if the result viewed from the Bed Turn Over Ratio and
Gross Death Rate, the calculation results declined in every year, but the results of
this calculation still above national standards for quality of service indicators, so
that it can be concluded that the ratio of BTO and GDR shows the results of poor
performance.
Results of this analysis, the author gives some advice to Kasih Ibu’s
Hospital, that is a need for additional beds in each ward, so the Bed Turn Over
ratio can be decreased annually and in accordance with national standards for
quality of service indicators. In addition, Kasih Ibu’s Hospital also need to
provide training to medical personnel especially trained in dealing with patients
who are going through a critical period that the general mortality rate or Gross
Death Rate can be decreased in each year.
Keywords: service performance, service performance ratio analysi
Characterization of Perovskite Oxide/Semiconductor Heterostructures
No full textabstract: Integrated oxide/semiconductor heterostructures have attracted intense interest for device applications which require sharp interfaces and controlled defects. The research of this dissertation has focused on the characterization of perovskite oxide/oxide and oxide/semiconductor heterostructures, and the analysis of interfaces and defect structures, using scanning transmission electrom microscopy (STEM) and related techniques.
The SrTiO3/Si system was initially studied to develop a basic understanding of the integration of perovskite oxides with semiconductors, and successful integration with abrupt interfaces was demonstrated. Defect analysis showed no misfit dislocations but only anti-phase boundaries (APBs) in the SrTiO3 (STO) films. Similar defects were later observed in other perovskite oxide heterostructures.
Ferroelectric BaTiO3 (BTO) thin films deposited directly onto STO substrates, or STO buffer layers with Ge substrates, were grown by molecular beam epitaxy (MBE) in order to control the polarization orientation for field-effect transistors (FETs). STEM imaging and elemental mapping by electron energy-loss spectroscopy (EELS) showed structurally and chemically abrupt interfaces, and the BTO films retained the c-axis-oriented tetragonal structure for both BTO/STO and BTO/STO/Ge heterostructures. The polarization displacement in the BTO films of TiN/BTO/STO heterostructures was investigated. The Ti4+ atomic column displacements and lattice parameters were measured directly using HAADF images. A polarization gradient, which switched from upwards to downwards, was observed in the BTO thin film, and evidence was found for positively-charged oxygen vacancies.
Heterostructures grown on Ge substrates by atomic layer deposition (ALD) were characterized and compared with MBE-grown samples. A two-step process was needed to overcome interlayer reaction at the beginning of ALD growth. A-site-rich oxide films with thicknesses of at least 2-nm had to be deposited and then crystallized before initiating deposition of the following perovskite oxide layer in order to suppress the formation of amorphous oxide layers on the Ge surface. BTO/STO/Ge, BTO/Ge, SrHfTiO3/Ge and SrZrO3/Ge thin films with excellent crystallinity were grown using this process.
Metal-insulator-metal (MIM) heterostructures were fabricated as ferroelectric capacitors and then electrically stressed to the point of breakdown to correlate structural changes with electrical and physical properties. BaTiO3 on Nb:STO was patterned with different top metal electrodes by focused-ion-beam milling, Au/Ni liftoff, and an isolation-defined approach.Dissertation/ThesisDoctoral Dissertation Materials Science and Engineering 201
Ultrathin Piezoelectric Resonators Based on Graphene and Free-Standing Single-Crystal BaTiO<sub>3</sub>
No full textSuspended piezoelectric thin films are key elements enabling high-frequency filtering in telecommunication devices. To meet the requirements of next-generation electronics, it is essential to reduce device thickness for reaching higher resonance frequencies. Here, the high-quality mechanical and electrical properties of graphene electrodes are combined with the strong piezoelectric performance of the free-standing complex oxide, BaTiO3 (BTO), to create ultrathin piezoelectric resonators. It is demonstrated that the device can be brought into mechanical resonance by piezoelectric actuation. By sweeping the DC bias voltage on the top graphene electrode, the BTO membrane is switched between the two poled ferroelectric states. Remarkably, ferroelectric hysteresis is also observed in the resonance frequency, magnitude and Q-factor of the first membrane mode. In the bulk acoustic mode, the device vibrates at 233 GHz. This work demonstrates the potential of combining van der Waals materials with complex oxides for next-generation electronics, which not only opens up opportunities for increasing filter frequencies, but also enables reconfiguration by poling, via ferroelectric memory effect.QN/Steeneken LabImPhys/Practicum supportQN/van der Zant LabQN/Steele LabQN/Groeblacher LabQN/Caviglia LabDynamics of Micro and Nano SystemsQRD/Wimmer Grou
Resistive switching in MoSe2/BaTiO3 hybrid structures
No full textHere we study the resistive switching (RS) effect that emerges when ferroelectric BaTiO3 (BTO) and few-layer MoSe2 are combined in a single structure. The C–V loops reveal the ferroelectric nature of both Al/Si/SiOx/BTO/Au and Al/Si/SiOx/MoSe2/BTO/Au structures and the high quality of the SiOx/MoSe2 interface in the Al/Si/SiOx/MoSe2/Au structure. Al/Si/SiOx/MoSe2/BTO/Au hybrid structures show electroforming free resistive switching that is explained on the basis of the modulation of the potential distribution at the MoSe2/BTO interface via ferroelectric polarization flipping. This structure shows promising resistive switching characteristics with a switching ratio of ≈102 and a stable memory window, which are highly required for memory applications.This work was supported by: (i) Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding Contracts UID/FIS/04650/2013 and UID/CTM/04540/2013; (ii) Project Norte-070124-FEDER-000070 Nanomateriais Multifuncionais. The author J.P.B.S. is grateful for financial support through the FCT Grant SFRH/BPD/92896/2013. C.A.M. acknowledges a scholarship funded by the UID/CTM/04540 contract. The authors would also like to thank Dr Ana S. Viana from CQB-FCUL for the AFM analyses and Engineer Jose Santos for technical support at Thin Films Laboratory.info:eu-repo/semantics/publishedVersio
Existence of multi crystallographic phase in BNT-BTO solid solution near morphotropic phase boundary (MPB)
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