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1.
Optimal R&D investments of the firm 总被引:6,自引:0,他引:6
Peter M. Kort 《OR Spectrum》1998,20(3):155-164
This paper examines irreversible decisions on innovative activities where it takes time to complete an R&D project. The total
amount of R&D investments that the firm needs to undertake in order to obtain the breakthrough in the innovation process is
uncertain. R&D investments are limited by the restriction that they must be self-financed. It is shown that R&D investments
are more valuable when the level of uncertainty is large. Especially, it is very attractive to undertake R&D investments if
a project faces many uncertainties during its early phases. Furthermore we study how R&D behavior is influenced by different
levels of the discount rate and the financing limit. Moreover, the effects of R&D subsidies, spillover benefits and a payoff
that decreases over time are analyzed.
Received: 9 October 1997 / Accepted: 19 March 1998 相似文献
2.
The resource renting problem subject to temporal constraints 总被引:1,自引:0,他引:1
Hartwig Nübel 《OR Spectrum》2001,23(3):359-381
We introduce a project scheduling problem subject to temporal constraints where the resource availability costs have to be
minimized. As an extension of known project scheduling problems which consider only time-independent costs, this problem includes
both time-independent procurement costs and time-dependent renting costs for the resources. Consequently, in addition to projects
where all resources are bought, we can deal with projects where resources are rented. Based on the enumeration of a finite
set of schedules which is proved to contain an optimal schedule, we develop a depth-first branch-and-bound procedure. Computational
experience with a randomly generated test set containing 10800 problem instances is reported.
Received: December 1, 1999 / Accepted: November 8, 2000 相似文献
Received: December 1, 1999 / Accepted: November 8, 2000 相似文献
3.
This paper provides a survey of the research in and an annotated bibliography of multiple objective combinatorial optimization,
MOCO. We present a general formulation of MOCO problems, describe the main characteristics of MOCO problems, and review the
main properties and theoretical results for these problems. The main parts of the paper are a section on the review of the
available solution methodology, both exact and heuristic, and a section on the annotation of the existing literature in the
field organized problem by problem. We conclude the paper by stating open questions and areas of future research.
Received: February 7, 2000 / Accepted: April 14, 2000 相似文献
4.
Strategic technology investment under uncertainty 总被引:7,自引:0,他引:7
In this paper the technology investment decision of a firm is analyzed, while competition on the output market is explicitly
taken into account. Technology choice is irreversible and the firms face a stochastic innovation process with uncertainty
about the speed of arrival of new technologies. The innovation process is exogenous to the firms. For reasons of market saturation
and the fact that more modern technologies are invented as time passes, the demand for a given technology decreases over time.
This implies that also the sunk cost investment of each technology decreases over time.
The investment decision problem is transformed into a timing game, in which the waiting curve is introduced as a new concopt.
An algorithm is designed for solving this (more) general timing game. The algorithm is applied to an information technology
investment problem. The most likely outcome exhibits diffusion with equfal payoffs for the firms.
Received: December 16, 1999 / Accepted: February 7, 2001 相似文献
5.
Niklas Wagner 《OR Spectrum》2003,25(3):317-328
Potentially increasing volatility and downside risk is essential to financial risk management which is concerned with the
tails, or particularly, the lower tail, of the distribution of speculative asset returns. Applying extreme value theory, the
present paper outlines a simple model capturing time-varying tail behavior and studies conditional daily return quantiles
for the German DAX. Our results indicate an overall increased risk of large one-day holding-period losses related to a structural
break given by the 1987 crash, systematic out-of-sample underestimation of the magnitude of extreme quantiles as well as clustering
in estimated quantile exceedances which cannot be fully explained by the forecasting model.
RID="*"
ID="*" Part of the paper was written while the author was visiting the Center for Mathematical Sciences at Munich University
of Technology. He is grateful for the members' hospitality and thanks Claudia Klüppelberg for helpful discussions as well
as two anonymous referees for comments improving the paper. 相似文献
6.
Planning and scheduling in the process industry 总被引:15,自引:0,他引:15
Josef Kallrath 《OR Spectrum》2002,24(3):219-250
Since there has been tremendous progress in planning and scheduling in the process industry during the last 20 years, it
might be worthwhile to give an overview of the current state-of-the-art of planning and scheduling problems in the chemical
process industry. This is the purpose of the current review which has the following structure: we start with some conceptional
thoughts and some comments on special features of planning and scheduling problems in the process industry. In Section 2 the
focus is on planning problems while in Section 3 different types of scheduling problems are discussed. Section 4 presents
some solution approaches especially those applied to a benchmark problem which has received considerable interest during the
last years. Section 5 allows a short view into the future of planning and scheduling. In the appendix we describe the Westenberger-Kallrath
problem which has already been used extensively as a benchmark problem for planning and scheduling in the process industr
y. 相似文献
7.
Matthew I. Campbell Jonathan Cagan Kenneth Kotovsky 《Research in Engineering Design》1999,11(3):172-192
This paper provides an introduction to a new design methodology known as A-Design, which combines aspects of multi-objective
optimization, multi-agent systems, and automated design synthesis. The A-Design theory is founded on the notion that engineering
design occurs in interaction with an ever-changing environment, and therefore computer tools developed to aid in the design
process should be adaptive to these changes. In this paper, A-Design is introduced along with some simple test problems to
demonstrate the capabilities of different aspects of the theory. The theory of A-Design is then shown as the basis for a design
tool that adaptively creates electro-mechanical configuration designs for changing user preferences. 相似文献
8.
Abstract. In this paper we investigate how to determine optimal locations of the microwave antennas being circularly ordered in a hyperthermia
device. The heated area containing the tumor should have minimal volume. Based on a simple geometric model for the two and
three dimensional case we develop algorithms for the computation of these volumes and present numerical results for the optimal
locations.
Correspondence to: J. Jahn 相似文献
9.
Critical design decisions are commonly made throughout the product development process assuming known material and process
behavior. However, stochastic variation during manufacture can inadvertently result in inferior or unacceptable product performance
and reduced production yields. Stochastic simulations have been developed to estimate the end-use performance distribution
prior to the commitment of hard tooling. This article proposes a definition for integrated product and process robustness,
and extends existing stochastic methods to model the important role of the manufacturing flexibility in elimination of defects
and product optimization. The goal is to enable the designer to understand and account for not only the negative effects of
manufacturing variation, but also the positive impact of manufacturing flexibility wherein instantaneous corrections in the
manufacturing process can frequently improve the product quality and eliminate flaws in the product design. Then, a methodology
is introduced and contrasted with conventional development methods in the evaluation of best practices for development of
a molded plastic component. 相似文献
10.
Thomas Balzer 《OR Spectrum》2003,25(1):61-84
The performance of a portfolio manager is in practice usually measured by the result of his trading strategy compared to
a benchmark. Therefore the information whether there exists a strategy that allows to outperform the benchmark is of high
value for an active investor. The article shows how this information can be generated in the binomial model. In this context
the connection between trading strategies and the investor's expectations concerning future asset prices is analyzed. Based
on these findings several conditions are derived that allow the portfolio manager to judge whether the benchmark can be outperformed
by an active trading strategy.
RID="*"
ID="*" Thomas Balzer now works in the Risk Measurement & Management Department of Credit Suisse First Boston in London. The
views expressed in this article are those of the author, and do not necessarily represent those of Credit Suisse Group or
Credit Suisse First Boston. The author thanks Dr. Michael Olbrich for careful reading and several useful comments. 相似文献
11.
Karl-Heinz Küfer Alexander Scherrer Michael Monz Fernando Alonso Hans Trinkaus Thomas Bortfeld Christian Thieke 《OR Spectrum》2003,25(2):223-249
Abstract. Radiation therapy planning is often a tight rope walk between dangerous insufficient dose in the target volume and life threatening
overdosing of organs at risk. Finding ideal balances between these inherently contradictory goals challenges dosimetrists
and physicians in their daily practice. Todays inverse planning systems calculate treatment plans based on a single evaluation
function that measures the quality of a radiation treatment plan. Unfortunately, such a one dimensional approach cannot satisfactorily
map the different backgrounds of physicians and the patient dependent necessities. So, too often a time consuming iterative
optimization process between evaluation of the dose distribution and redefinition of the evaluation function is needed. In
this paper we propose a generic multi-criteria approach based on Pareto's solution concept. For each entity of interest –
target volume or organ at risk – a structure dependent evaluation function is defined measuring deviations from ideal doses
that are calculated from statistical functions. A reasonable bunch of clinically meaningful Pareto optimal solutions are stored
in a data base, which can be interactively searched by physicians. The system guarantees dynamic planning as well as the discussion
of tradeoffs between different entities. Mathematically, we model the inverse problem as a multi-criteria linear programming
problem. Because of the large scale nature of the problem it is not possible to solve the problem in a 3D-setting without
adaptive reduction by appropriate approximation schemes. Our approach is twofold: First, the discretization of the continuous
problem results from an adaptive hierarchical clustering process which is used for a local refinement of constraints during
the optimization procedure. Second, the set of Pareto optimal solutions is approximated by an adaptive grid of representatives
that are found by a hybrid process of calculating extreme compromises and interpolation methods.
Correspondence to: K.-H. Küfer 相似文献
12.
Graham Coates Robert Ian Whitfield Alex H. B. Duffy Bill Hills 《Research in Engineering Design》2000,12(2):73-89
This is the second of two papers surveying research in coordination approaches and systems. This paper is concerned with operational
coordination, which is aimed at coordinating activities such that the design process can be performed in a near optimal manner
with respect to time, and the allocation and utilisation of resources. Aspects of coordination categorised as operational
include resource management, scheduling and planning. The first of these two papers presents a review of coordination from
a strategic perspective, which is concerned with the decision management aspects of coordination. Greater emphasis is now
being placed on the significance of organising the design process as this affects time to market, product quality, cost, and
consequently product success. The aim of this paper is to present a fundamental review of operational coordination approaches
and systems. The 1990s has seen much progress being made towards a greater understanding and appreciation of coordination
in various disciplines through the development of a wide range of approaches and systems. However, there remains a requirement
to formally identify the key issues involved in coordination such that a widely accepted representation can be agreed upon.
Consequently, research should continue to be supported in the exploration for a unified approach to coordination which will
permit a broader and greater understanding of those aspects involved. 相似文献
13.
Inspired by a case study from industry, the production of special chemical products is considered. In this industrial environment,
multi-purpose equipment is operated in batch mode to carry out the diverse processing tasks. Often, extensive set-up and cleaning
of the equipment are required when production switches between different types of products. Hence, processes are scheduled
in campaign mode, i.e. a number of batches of the same type are processed in sequence. The production of chem ical products
usually involves various stages with significant cumulative lead times. Typically, these production stages are assigned to
different plants. A hierarchical modelling approach is presented which co-ordinates the various plant operations within the
entire supply network. In the first stage, the length of the campaigns, their timing, the corresponding material flows, and
equipment requirements have to be determined. At this stage, an aggregation scheme based on feasibility constraints is employed
in order to reflect the limited availability of the various types of production equipment. The second stage consists of an
assignment model, which allocates the available equipment units between the production campaigns determined in the first stage
of the solution procedure. In the third stage, resource conflicts are resolved, which may occur if clean-out operations and
minimal campaign lengths have to be considered. The proposed hierarchical approach allows a more compact model formulation
compared to ot her approaches known from the literature. As a result, a very efficient and flexible solution approach is obtained.
In particular, commercially available standard solvers can be used to solve a wide range of campaign planning problems arising
in the chemical industry. 相似文献
14.
A scheduling method for Berth and Quay cranes 总被引:12,自引:2,他引:10
This paper discusses a method for scheduling Berth and Quay cranes, which are critical resources in port container terminals.
An integer programming model is formulated by considering various practical constraints. A two-phase solution procedure is
suggested for solving the mathematical model. The first phase determines the Berthing position and time of each vessel as
well as the number of cranes assigned to each vessel at each time segment. The subgradient optimization technique is applied
to obtain a near-optimal solution of the first phase. In the second phase, a detailed schedule for each Quay crane is constructed
based on the solution found from the first phase. The dynamic programming technique is applied to solve the problem of the
second phase. A numerical experiment was conducted to test the performance of the suggested algorithms.
RID="*"
ID="*" This research has been supported in part by Brain Korea 21 Program (1999–2002).
Correspondence to: Y.-M. Park 相似文献
15.
Strategic technology planning in hospital management 总被引:1,自引:0,他引:1
Abstract. Hospital managers regularly are confronted with their patients' demand for increased service performance on the one hand
and tight budgets on the other. As medical technologies influence both the costs and the service spectrum, strategic technology
planning is among the critical tasks in hospital management. This paper addresses the corresponding problem of selecting the
“best” portfolio of medical devices and proposes an appropriate decision support system. It starts with a multiobjective mathematical
programming model that determines the solution space of all efficient portfolios of medical technology investments. The members
of the planning committee with their diverging interests then are supported by their interactive exploration of that space
until they jointly reach a satisfying portfolio and are not willing to make any further compromises between its objective
levels. As one of its salient features the system does not require a priori preference information.
RID="*"
ID="*" A previous version of this paper has been presented at the Wiesbaden 2000 Meeting of the GOR-Working Group “Operations
Research in Health Care”. The authors thank Andrea Lührs and Thomas Rollins, both from Siemens AG, for their valuable support.
Moreover, thanks are due to the anonymous referees for their comments on a previous version of this paper.
Correspondence to: C. Stummer 相似文献
16.
On scalarizing functions in multiobjective optimization 总被引:1,自引:1,他引:0
Scalarizing functions play an essential role in solving multiobjective optimization problems. Many different scalarizing
functions have been suggested in the literature based on different approaches. Here we concentrate on classification and reference
point-based functions. We present a collection of functions that have been used in interactive methods as well as some modifications.
We compare their theoretical properties and numerical behaviour. In particular, we are interested in the relation between
the information provided and the results obtained. Our aim is to select some of them to be used in our WWW-NIMBUS optimization
system.
Received: June 11, 2001 / Accepted: October 31, 2001 相似文献
17.
A Theory of Complexity, Periodicity and the Design Axioms 总被引:1,自引:1,他引:1
Nam P. Suh 《Research in Engineering Design》1999,11(2):116-132
One of the topics that has received the attention of mathematicians, scientists and engineers is the notion of complexity.
The subject is still being debated, as it lacks a common definition of complexity, concrete theories that can predict complex
phenomena, and the mathematical tools that can deal with problems involving complexity. In axiomatic design, complexity is
defined only when specific functional requirements or the exact nature of the query are defined. Complexity is defined as
a measure of uncertainty in achieving a set of specific functions or functional requirements. Complexity is related to information,
which is defined in terms of the probability of success of achieving the Functional Requirements (FRs). There are two classes
of complexity: time-dependent complexity and time-independent complexity. There are two orthogonal components of time-independent
complexity, i.e., real complexity and imaginary complexity. The vector sum is called absolute complexity. Real complexity of coupled design is larger than that of uncoupled or decoupled designs. Imaginary complexity can be reduced
when the design matrix is known. As an example of time-independent imaginary complexity, the design of a printing machine
based on xerography is discussed. There are two kinds of time-dependent real complexity: time-dependent combinatorial complexity and time-dependent periodic complexity. Using a robot-scheduling problem as an example, it is shown that a coupled design with a combinatorial complexity can be
reduced to a decoupled design with periodic complexity. The introduction of periodicity simplifies the design by making it
deterministic, which requires much less information. Whenever a combinatorial complexity is converted to a periodic complexity,
complexity and uncertainty is reduced and design simplified. 相似文献
18.
Evaluation Metrics for the Rating and Optimization of Snap-fits 总被引:1,自引:0,他引:1
Current snap-fit design guides recommend sizing snap-fit features on the basis of insertion force and allowable strain during
assembly. Retention force information in such guides is often inaccurate, although this is considered to be the primary attribute
of the snap-fit after assembly. The authors contend that these (insertion force, allowable strain, retention force) are not
the only critical performance criteria for snap-fit features. Designers have to contend with several other constraints and
design requirements. Additional performance metrics for snap-fit features are proposed by drawing upon considerable experience
with plastic part design issues. Locking ratio, dimensional and volumetric retention force, consideration of the characteristic
dimension of the joint and snap-fit, feature stiffness, required over-insertion and consideration of snap-fit strength relative
to part strength are proposed to supplement currently used metrics for evaluating and rating snap-fit designs. The applicability
of these metrics is illustrated with real-life examples, and their merits and demerits discussed. A chart of achievable locking
ratios for different snap-fit topologies is presented for use as a design tool for the initial selection of snap-fit topologies.
Its use as a rational basis for selection and optimization of snap-fits is suggested. Adoption of proposed metrics will allow
designers to better quantify, and thereby optimize the performance of, snap-fit features. These ideas will be built upon in
the future, and used as a basis for a comprehensive snap-fit selection and detailed design tool. 相似文献
19.
Serdar Tumkor 《Research in Engineering Design》2000,12(3):163-171
The Internet and World Wide Web (WWW) are evolving as an important communication technology. This paper examines the development
of an Internet-based online catalogue on the WWW. An interactive website is prepared that helps a remote designer to design
shafts and bearings based on various input parameters provided. The web site also provides solid models of the shaft to perform
CAD and FEM analysis. This permits the user to make further investigations, and helps to modify the design satisfactory. 相似文献
20.
In this paper, related product functions are determined for a group of approximately 70 consumer products. Using customer
need data, a new matrix approach is introduced to identify these relationships. Techniques are then created for determining
product similarity. These techniques are clarified and validated through three case studies, including beverage brewers and
material-removal products. The results of these case studies are argued to have significant impact on design-by-analogy procedures,
benchmarking methods, mass customization strategies and modular design. The paper concludes with a discussion of applications
and related procedures for product development. 相似文献