A randomized concave programming method for choice network revenue management

Models incorporating more realistic models of customer behavior, as customers choosing froman offer set, have recently become popular in assortment optimization and revenue management.The dynamic program for these models is intractable and approximated by a deterministiclinear program called the CDLP which has an exponential number of columns. However, whenthe segment consideration sets overlap, the CDLP is difficult to solve. Column generationhas been proposed but finding an entering column has been shown to be NP-hard. In thispaper we propose a new approach called SDCP to solving CDLP based on segments and theirconsideration sets. SDCP is a relaxation of CDLP and hence forms a looser upper bound onthe dynamic program but coincides with CDLP for the case of non-overlapping segments. Ifthe number of elements in a consideration set for a segment is not very large (SDCP) can beapplied to any discrete-choice model of consumer behavior. We tighten the SDCP bound by(i) simulations, called the randomized concave programming (RCP) method, and (ii) by addingcuts to a recent compact formulation of the problem for a latent multinomial-choice model ofdemand (SBLP+). This latter approach turns out to be very effective, essentially obtainingCDLP value, and excellent revenue performance in simulations, even for overlapping segments.By formulating the problem as a separation problem, we give insight into why CDLP is easyfor the MNL with non-overlapping considerations sets and why generalizations of MNL posedifficulties. We perform numerical simulations to determine the revenue performance of all themethods on reference data sets in the literature.

A new compact linear programming formulation for choice network revenue management

The choice network revenue management model incorporates customer purchase behavioras a function of the offered products, and is the appropriate model for airline and hotel networkrevenue management, dynamic sales of bundles, and dynamic assortment optimization.The optimization problem is a stochastic dynamic program and is intractable. A certainty-equivalencerelaxation of the dynamic program, called the choice deterministic linear program(CDLP) is usually used to generate dyamic controls. Recently, a compact linear programmingformulation of this linear program was given for the multi-segment multinomial-logit (MNL)model of customer choice with non-overlapping consideration sets. Our objective is to obtaina tighter bound than this formulation while retaining the appealing properties of a compactlinear programming representation. To this end, it is natural to consider the affine relaxationof the dynamic program. We first show that the affine relaxation is NP-complete even for asingle-segment MNL model. Nevertheless, by analyzing the affine relaxation we derive a newcompact linear program that approximates the dynamic programming value function betterthan CDLP, provably between the CDLP value and the affine relaxation, and often comingclose to the latter in our numerical experiments. When the segment consideration sets overlap,we show that some strong equalities called product cuts developed for the CDLP remain validfor our new formulation. Finally we perform extensive numerical comparisons on the variousbounds to evaluate their performance.

Parallel scheduling of multiclass M/M/m queues: Approximate and heavy-traffic optimization of achievable performance

We address the problem of scheduling a multiclass $M/M/m$ queue with Bernoulli feedback on $m$ parallel servers to minimize time-average linear holding costs. We analyze the performance of a heuristic priority-index rule, which extends Klimov's optimal solution to the single-server case: servers select preemptively customers with larger Klimov indices. We present closed-form suboptimality bounds (approximate optimality) for Klimov's rule, which imply that its suboptimality gap is uniformly bounded above with respect to (i) external arrival rates, as long as they stay within system capacity;and (ii) the number of servers. It follows that its relativesuboptimality gap vanishes in a heavy-traffic limit, as external arrival rates approach system capacity (heavy-traffic optimality). We obtain simpler expressions for the special no-feedback case, where the heuristic reduces to the classical $c \mu$ rule. Our analysis is based on comparing the expected cost of Klimov's ruleto the value of a strong linear programming (LP) relaxation of the system's region of achievable performance of mean queue lengths. In order to obtain this relaxation, we derive and exploit a new set ofwork decomposition laws for the parallel-server system. We further report on the results of a computational study on the quality of the $c \mu$ rule for parallel scheduling.

Department of Commerce - Iowa Utilities Board, Performance Report, Performance Results Achieved for Fiscal Year 2007, December 2007

The report highlights the services the IUB provided to Iowans, along with results achieved to ensure reliability, and to improve and expand utility service infrastructure in Iowa. This information is provided in accordance with the State of Iowa Accountable Government Act, Iowa Code chapter 8E. The two basic business functions of the IUB are utility regulation and compliance, and resource management. This report covers performance information for both of these areas.

Logistics-production, logistics-marketing and external integration: Their impact on performance

Highly competitive environments are leading companies to implement SupplyChain Management (SCM) to improve performance and gain a competitiveadvantage. SCM involves integration, co-ordination and collaborationacross organisations and throughout the supply chain. It means that SCMrequires internal (intraorganisational) and external (interorganisational)integration. This paper examines the Logistics-Production and Logistics-Marketing interfaces and their relation with the external integrationprocess. The study also investigates the causal impact of these internaland external relationships on the company s logistical service performance.To analyse this, an empirical study was conducted in the Spanish Fast MovingConsumer Goods (FMCG) sector.

Management of patient dose and image noise in routine pediatric CT abdominal examinations.

The aim was to propose a strategy for finding reasonable compromises between image noise and dose as a function of patient weight. Weighted CT dose index (CTDI(w)) was measured on a multidetector-row CT unit using CTDI test objects of 16, 24 and 32 cm in diameter at 80, 100, 120 and 140 kV. These test objects were then scanned in helical mode using a wide range of tube currents and voltages with a reconstructed slice thickness of 5 mm. For each set of acquisition parameter image noise was measured and the Rose model observer was used to test two strategies for proposing a reasonable compromise between dose and low-contrast detection performance: (1) the use of a unique noise level for all test object diameters, and (2) the use of a unique dose efficacy level defined as the noise reduction per unit dose. Published data were used to define four weight classes and an acquisition protocol was proposed for each class. The protocols have been applied in clinical routine for more than one year. CTDI(vol) values of 6.7, 9.4, 15.9 and 24.5 mGy were proposed for the following weight classes: 2.5-5, 5-15, 15-30 and 30-50 kg with image noise levels in the range of 10-15 HU. The proposed method allows patient dose and image noise to be controlled in such a way that dose reduction does not impair the detection of low-contrast lesions. The proposed values correspond to high- quality images and can be reduced if only high-contrast organs are assessed.

The effects of uncertainty avoidance on brand performance: Marketing creativity, product innovation and the brand duration

This paper investigates the link between brand performance and cultural primes in high-risk,innovation-based sectors. In theory section, we propose that the level of cultural uncertaintyavoidance embedded in a firm determine its marketing creativity by increasing the complexityand the broadness of a brand. It determines also the rate of firm product innovations.Marketing creativity and product innovation influence finally the firm marketingperformance. Empirically, we study trademarked promotion in the Software Security Industry(SSI). Our sample consists of 87 firms that are active in SSI from 11 countries in the period1993-2000. We use the data coming from SSI-related trademarks registered by these firms,ending up with 2,911 SSI-related trademarks and a panel of 18,213 observations. We estimatea two stage model in which first we predict the complexity and the broadness of a trademarkas a measure of marketing creativity and the rate of product innovations. Among severalcontrol variables, our variable of theoretical interest is the Hofstede s uncertainty avoidancecultural index. Then, we estimate the trademark duration with a hazard model using thepredicted complexity and broadness as well as the rate of product innovations, along with thesame control variables. Our evidence confirms that the cultural avoidance affects the durationof the trademarks through the firm marketing creativity and product innovation.

Cumulative dominance and heuristic performance in binary multi-attribute choice

Several studies have reported high performance of simple decision heuristics multi-attribute decision making. In this paper, we focus on situations where attributes are binary and analyze the performance of Deterministic-Elimination-By-Aspects (DEBA) and similar decision heuristics. We consider non-increasing weights and two probabilistic models for the attribute values: one where attribute values are independent Bernoulli randomvariables; the other one where they are binary random variables with inter-attribute positive correlations. Using these models, we show that good performance of DEBA is explained by the presence of cumulative as opposed to simple dominance. We therefore introduce the concepts of cumulative dominance compliance and fully cumulative dominance compliance and show that DEBA satisfies those properties. We derive a lower bound with which cumulative dominance compliant heuristics will choose a best alternative and show that, even with many attributes, this is not small. We also derive an upper bound for the expected loss of fully cumulative compliance heuristics and show that this is moderateeven when the number of attributes is large. Both bounds are independent of the values ofthe weights.

Supply chain management as a competitive advantage in the Spanish grocery sector

Adversarial relationships have long dominated business relationships,but Supply Chain Management (SCM) entails a new perspective. SCM requiresa movement away from arms-length relationships toward partnership stylerelations. SCM involves integration, co-ordination and collaborationacross organisations and throughout the supply chain. It means that SCMrequires internal (intraorganisational) and external (interorganisational)integration. This paper analyses the relationship between internal andexternal integration processes, their effect on firms performance andtheir contribution to the achievement of a competitive advantage.Performance improvements are analysed through costs, stock out and leadtime reductions. And, the achievement of a better competitive positionis measured by comparing the firm s performance with its competitors performance. To analyse this, an empirical study has been conducted inthe Spanish grocery sector.

An enhanced concave program relaxation for choice network revenue management

The network choice revenue management problem models customers as choosing from an offer-set, andthe firm decides the best subset to offer at any given moment to maximize expected revenue. The resultingdynamic program for the firm is intractable and approximated by a deterministic linear programcalled the CDLP which has an exponential number of columns. However, under the choice-set paradigmwhen the segment consideration sets overlap, the CDLP is difficult to solve. Column generation has beenproposed but finding an entering column has been shown to be NP-hard. In this paper, starting with aconcave program formulation based on segment-level consideration sets called SDCP, we add a class ofconstraints called product constraints, that project onto subsets of intersections. In addition we proposea natural direct tightening of the SDCP called ?SDCP, and compare the performance of both methodson the benchmark data sets in the literature. Both the product constraints and the ?SDCP method arevery simple and easy to implement and are applicable to the case of overlapping segment considerationsets. In our computational testing on the benchmark data sets in the literature, SDCP with productconstraints achieves the CDLP value at a fraction of the CPU time taken by column generation and webelieve is a very promising approach for quickly approximating CDLP when segment consideration setsoverlap and the consideration sets themselves are relatively small.

Behavioral assumptions and management ability

The paper explores the consequences that relying on different behavioral assumptions intraining managers may have on their future performance. We argue that training with anemphasis on the standard assumptions used in economics (rationality and self-interest) is goodfor technical posts but may also lead future managers to rely excessively on rational and explicitsafeguarding, crowding out instinctive relational heuristics and signaling a bad human type topotential partners. In contrast, human assumptions used in management theories, because oftheir diverse, implicit and even contradictory nature, do not conflict with the innate set ofcooperative tools and may provide a good training ground for such tools. We present tentativeconfirmatory evidence by examining how the weight given to behavioral assumptions in the corecourses of the top 100 business schools influences the average salaries of their MBA graduates.Controlling for the self-selected average quality of their students and some other schools characteristics, average salaries are seen to be significantly greater for schools whose core MBAcourses contain a higher proportion of management courses as opposed to courses based oneconomics or technical disciplines.

Performance Report for Fiscal Year, 2005

I am pleased to present the performance report for the Iowa Department for the Blind for fiscal year 2005. This report is provided in compliance with sections 8E.210 and 216B.7 of the Code of Iowa. It contains valuable information about the services the Department and its partners provided for Iowans during the past fiscal year in the areas of vocational rehabilitation, library services, and resource management. Major accomplishments of the year included new food service opportunities in the Randolph-Sheppard program, extensive remodeling of the Adult Orientation and Adjustment Center, and continued national prominence in vocational rehabilitation as measured by the U.S. Rehabilitation Services Administration, which on June 13, 2005 released data on federal standards and indicators for the year ended September 30, 2004. Earnings ratios and the percentage of employment for vocational rehabilitation clients of the Department remain among the best in the nation. This is corroborated by a report released in September, 2005 by the U.S. Government Accountability Office, which tested and summarized datasets compiled by the U.S. Department of Education for the nation’s 80 vocational rehabilitation agencies. Overall, we met or exceeded 26 of 32 results targets included in this report. Key strategic challenges, developments, and trends are also discussed in the "Department Overview" that follows. Sincerely, Allen C. Harris Director, Iowa Department for the Blind

Performance Report for Fiscal Year, 2006

I am pleased to present the performance report for the Iowa Department for the Blind for fiscal year 2006. This report is provided in compliance with sections 8E.210 and 216B.7 of the Code of Iowa. It contains valuable information about the services the Department and its partners provided for Iowans during the past fiscal year in the areas of vocational rehabilitation, library services, and resource management. Major accomplishments of the year included successful administration of a federally-funded mentoring program (Pathfinders) that matches young adults ages 16-26 who are blind or visually impaired with mentors who also have vision loss, installed a state-of-the art digital recording studio in the library, and continued national prominence in vocational rehabilitation. Earnings ratios and the percentage of employment for vocational rehabilitation clients of the Department remain among the best in the nation, as measured by the U.S. Rehabilitation Services Administration, which on July 3, 2006 released data on federal standards and indicators for the year ended September 30, 2005. Overall, we met or exceeded 15 of 20 results targets included in this report. Key strategic challenges, developments, and trends are also discussed in the "Department Overview" that follows. Sincerely, Allen C. Harris Director, Iowa Department for the Blind

Performance Report for Fiscal Year, 2007

I am pleased to present the performance report for the Iowa Department for the Blind for fiscal year 2007. This report is provided in compliance with sections 8E.210 and 216B.7 of the Code of Iowa. It contains valuable information about the services the Department and its partners provided for Iowans during the past fiscal year in the areas of Vocational Rehabilitation, Independent Living, Library Services, and Resource Management. The Department determines its competitive success in a number of ways. We look at the federal standards and indicators to learn our ranking in relation to the performance of other public rehabilitation agencies. We compare our library's production and circulation figures with those from previous years to determine trends. We set our own standards for success by looking at such factors as the number of successful case closures, average hourly wage at case closure, skills training provided, and compliance with regulations. Results show that the Department is working positively toward achieving its strategic goals of increasing the independence and productivity of blind Iowans and improving access to information for blind Iowans. Major accomplishments of the year included the selection of our Library as the only agency authorized to distribute educational materials using the National Instructional Materials Accessibility Standard (NIMAS) to students in Iowa. Our Independent Living program received the Shining Star award at the Governor's Conference on Aging for its work with and outreach to older blind Iowans. The Department, the Iowa Braille School, and the Department of Education implemented new cooperative efforts to improve the coordination and delivery of services to blind and visually impaired students in Iowa. Finally, earnings ratios and the percentage of employment for vocational rehabilitation clients of the Department remain among the best in the nation, as measured by the U.S. Rehabilitation Services Administration, which on June 27, 2007 released data on federal standards and indicators for the year ended September 30, 2006. Overall, we met or exceeded 11 of 16 results targets included in this report. A discussion of the Department's services, customers, organizational structure, and budget appears in the "Department Overview" that follows. The success of the Department's programs is evident in the success achieved by blind Iowans. It is reflected in the many blind persons who can be seen traveling about independently, going to their jobs and to the community and family activities in which they participate. Sincerely, Allen C. Harris Director, Iowa Department for the Blind

Performance Report for Fiscal Year, 2008

I am pleased to present the performance report for the Iowa Department for the Blind for fiscal year 2008. This report is provided in compliance with sections 8E.210 and 216B.7 of the Code of Iowa. It contains valuable information about results achieved because of the services that we and our partners provided to blind and visually impaired Iowans during the past fiscal year in the areas of Vocational Rehabilitation, Independent Living, Library Services, and Resource Management. We determine our competitive success in a number of ways. We look at the federal standards and indicators to learn our ranking in relation to the performance of other public rehabilitation agencies. We compare our library's production and circulation figures with those from previous years to determine trends. We set our own standards for success by looking at such factors as the number of successful case closures, average hourly wage at case closure, skills training provided, and compliance with regulations. Results show that the Department is working positively toward achieving its strategic goals of increasing the independence and productivity of blind Iowans and improving access to information for blind Iowans. Major accomplishments of the year included:  The selection of our Library as one of eight libraries to receive the new digital talking book machines and books in digital media from the National Library Service for the Blind and Physically Handicapped. Priority for distribution of the machines is given to Library patrons who are veterans.  The Department, the Iowa Braille School, and the Department of Education have been promoting the new expanded core curriculum as part of their continued efforts to improve the coordination and delivery of services to blind and visually impaired students in Iowa.  The Department's five-year grant funded Pathfinders mentoring program ended this year. A total of 49 blind youths aged 16-26 were paired with successful blind adult mentors. Assessments of the program clearly showed that participation in the program had a measurable positive effect on the youth involved.  Finally, earnings ratios and the percentage of employment for vocational rehabilitation clients of the Department are among the best in the nation, as measured by the U.S. Rehabilitation Services Administration's standards and indicators for the year ended September 30, 2007. Overall, we met or exceeded 13 of 18 targets included in this report. A discussion of the Department's services, customers, and organizational structure, and budget appears in the "Department Overview" that follows. Information pertaining to performance results appears in the final section of this document. The success of the Department's programs is evident in the success achieved by blind Iowans. It is reflected in the many blind persons who can be seen traveling about independently, going to their jobs and to the community and family activities in which they participate. Sincerely, Karen A. Keninger, Director Iowa Department for the Blind