Solving Large Location-Allocation problems by Clustering and Simulated Annealing

Globalization involves several facility location problems that need to be handled at large scale. Location Allocation (LA) is a combinatorial problem in which the distance among points in the data space matter. Precisely, taking advantage of the distance property of the domain we exploit the capability of clustering techniques to partition the data space in order to convert an initial large LA problem into several simpler LA problems. Particularly, our motivation problem involves a huge geographical area that can be partitioned under overall conditions. We present different types of clustering techniques and then we perform a cluster analysis over our dataset in order to partition it. After that, we solve the LA problem applying simulated annealing algorithm to the clustered and non-clustered data in order to work out how profitable is the clustering and which of the presented methods is the most suitable

Le réentraînement à l'effort chez l'enfant atteint de paralysie cérébrale (PC)

Le réentraînement à l'effort est présenté aujourd'hui comme un moyen efficace de lutter et réduire des déficiences chroniques chez l'adulte atteint de pathologie chronique. Il a été proposé plus récemment chez le jeune (enfant ou adolescent) atteint de pathologies neurologiques, notamment la paralysie cérébrale. De nombreuses études à ce jour présentent des résultats encourageants dans l'amélioration de certains facteurs de qualité de vie chez des jeunes patients atteints de paralysie cérébrale. Tout d'abord, un entraînement à l'effort sur la base d'exercices réalisés en endurance permet d'améliorer les capacités aérobies ainsi que le périmètre et la vitesse de marche et la motricité globale. Un entraînement à base de renforcement musculaire favoriserait aussi l'augmentation de la masse musculaire et induirait une amélioration de la motricité globale. Enfin, il semble que le type d'exercice à privilégier actuellement soit un entraînement « mixte », à base d'exercices associant les deux modes d'entraînement précédents. Pour préciser les modalités pratiques de réalisation de ces entraînements, il faudra tenir compte de différents paramètres parmi lesquels la fatigue musculaire.

Energy requirements during reproduction and reproductive effort in shrews (Soricidae)

The energy requirements of reproducing and non-reproducing females of three species of Crocidura (C. russula, C. viaria, C. olivieri), and two species of Sorex (S. coronatus, S. minutus) were measured. Members of these two genera show different rates of metabolism and reproductive strategies (extreme altriciality and larger litter size in Sorex). During pregnancy, the daily energy intake (on either an absolute or a mass-specific basis) remained close to the non-reproductive value in all species. The absolute energy intake increased strongly after parturition and was influenced by the litter size. Peak energy intake of lactating females was extremely high, typically between 100% and 200% above the non-reproductive requirements in the Crocidura and about 300% above the non-reproductive intake in the Sorex. The mass-specific daily energy intake was reduced during lactation in the three smaller species but not in C. viaria and C. olivieri. This decrease probably involves the different thermoregulatory abilities and/or basal rate of metabolism of the pups. Average reproductive effort was about 50%, in the Crocidura species and above 150% in the Sorex species. The higher effort in the latter is partly due to a larger litter size. But in addition, extreme altriciality in the Sorex leads to an earlier increase in the energy requirements and thus is an energetically more expensive reproductive mode. The present results support the hypothesis that a higher basal rate of metabolism is associated with a higher reproductive effort in shrews.

Réunion African Joint Effort (AJE)

Le 23 et 24 octobre 2003, les représentants des sièges sociaux de l'OMS et du BIT ont rencontré d'autres participants dans le cadre de l'effort conjoint OMS/BIT sur la santé

Do plants adjust their sex allocation and secondary sexual morphology in response to their neighbours?

BACKGROUND AND AIMS: Changes in the sex allocation (i.e. in pollen versus seed production) of hermaphroditic plants often occur in response to the environment. In some homosporous ferns, gametophytes choose their gender in response to chemical cues sent by neighbours, such that spores develop as male gametophytes if they perceive a female or hermaphrodite nearby. Here it is considered whether a similar process might occur in the androdioecious angiosperm species Mercurialis annua, in which males co-occur with hermaphrodites; previous work on a Spanish population of M. annua found that individuals were more likely to develop as males at high density. METHODS: Using a novel approach to treat plants with leachate from pots containing males or hermaphrodites of M. annua, the hypothesis that individuals assess their mating opportunities, and adjust their sex expression accordingly, was tested through an exchange of chemical cues through the soil. KEY RESULTS: For the population under study, from Morocco, no evidence was found for soil-signal-dependent sex expression: neither sex ratios nor sex allocation differed among experimental treatments. CONCLUSIONS: The results imply either that the Moroccan population under study behaves differently from that previously studied in Spain (pointing to potential geographical variation in plasticity for sex expression), or that our method failed to capture the signals used by M. annua for adjustment of sex expression.

Optimum power allocation for parallel Gaussian channels with arbitrary input distributions

The mutual information of independent parallel Gaussian-noise channels is maximized, under an average power constraint, by independent Gaussian inputs whose power is allocated according to the waterfilling policy. In practice, discrete signalling constellations with limited peak-to-average ratios (m-PSK, m-QAM, etc) are used in lieu of the ideal Gaussian signals. This paper gives the power allocation policy that maximizes the mutual information over parallel channels with arbitrary input distributions. Such policy admits a graphical interpretation, referred to as mercury/waterfilling, which generalizes the waterfilling solution and allows retaining some of its intuition. The relationship between mutual information of Gaussian channels and nonlinear minimum mean-square error proves key to solving the power allocation problem.

Optimum power allocation for multiuser OFDM with arbitrary signal constellations

This paper formulates power allocation policies that maximize the region of mutual informationsachievable in multiuser downlink OFDM channels. Arbitrary partitioning ofthe available tones among users and arbitrary modulation formats, possibly different forevery user, are considered. Two distinct policies are derived, respectively for slow fadingchannels tracked instantaneously by the transmitter and for fast fading channels knownonly statistically thereby. With instantaneous channel tracking, the solution adopts theform of a multiuser mercury/waterfilling procedure that generalizes the single-user mercury/waterfilling introduced in [1, 2]. With only statistical channel information, in contrast,the mercury/waterfilling interpretation is lost. For both policies, a number of limitingregimes are explored and illustrative examples are provided.

Parental investments in children: how bargaining and educational homogamy affect time allocation

This study examines parental time investment in their children, distinguishing between developmental and non-developmental care. Our analyses centre on three influential determinants: educational background, marital homogamy, and spouses' relative bargaining power. We find that the emphasis on quality care time is correlated with parents' education, and that marital homogamy reduces couple specialization, but only among the highly educated. In line with earlier research, we identify gendered parental behaviour. The presence of boys is an important condition for fathers' time dedication, but primarly among lower educated fathers. To the extent that parental stimulation is decisive for child outcomes, our findings suggest the persistence of important inequalities. This emerges through our special attention to behavioural differences across the educational distribution among households.

On Certain Greedoid Polyhedra, Partially Indexable Scheduling Problems, and Extended Restless Bandit Allocation Indices

We present a polyhedral framework for establishing general structural properties on optimal solutions of stochastic scheduling problems, where multiple job classes vie for service resources: the existence of an optimal priority policy in a given family, characterized by a greedoid (whose feasible class subsets may receive higher priority), where optimal priorities are determined by class-ranking indices, under restricted linear performance objectives (partial indexability). This framework extends that of Bertsimas and Niño-Mora (1996), which explained the optimality of priority-index policies under all linear objectives (general indexability). We show that, if performance measures satisfy partial conservation laws (with respect to the greedoid), which extend previous generalized conservation laws, then the problem admits a strong LP relaxation over a so-called extended greedoid polytope, which has strong structural and algorithmic properties. We present an adaptive-greedy algorithm (which extends Klimov's) taking as input the linear objective coefficients, which (1) determines whether the optimal LP solution is achievable by a policy in the given family; and (2) if so, computes a set of class-ranking indices that characterize optimal priority policies in the family. In the special case of project scheduling, we show that, under additional conditions, the optimal indices can be computed separately for each project (index decomposition). We further apply the framework to the important restless bandit model (two-action Markov decision chains), obtaining new index policies, that extend Whittle's (1988), and simple sufficient conditions for their validity. These results highlight the power of polyhedral methods (the so-called achievable region approach) in dynamic and stochastic optimization.

Money, Fame and the Allocation of Talent: Brain Drain, the Matthew Effect and the Institution of Science

The earning structure in science is known to be flat relative to the one in the private sector, which could cause a brain drain toward the private sector. In this paper, we assume that agents value both money and fame and study the role of the institution of science in the allocation of talent between the science sector and the private sector. Following works on the Sociology of Science, we model the institution of science as a mechanism distributing fame (i.e. peer recognition). We show that since the intrinsic performance is less noisy signal of talent in the science sector than in the private sector, a good institution of science can mitigate the brain drain. We also find that providing extra monetary incentives through the market might undermine the incentives provided by the institution and thereby worsen the brain drain. Finally, we study the optimal balance between monetary and non-monetary incentives in science.

Financial Repression in a Natural Experiment: Loan Allocation and the Change in the Usury Laws in 1714

If financial deepening aids economic growth, then financial repression should be harmful. We use a natural experiment – the change in the English usury laws in 1714 – to analyze the effects of interest rate restrictions. We use a sample of individual loan transactions to demonstrate how the reduction of the legal maximum rate of interest affected the supply and demand for credit. Average loan size and minimum loan size increased strongly, and access to credit worsened for those with little ‘social capital.’ While we have no direct evidence that loans were misallocated, the discontinuity in loan receipts makes this highly likely. We conclude that financial repression can undermine the positive effects of financial deepening.

Midwest Regional Rail Passenger Initiative Status Report December 2006

This report is submitted as required per Code of Iowa section 327J.3(5), "The director shall report annually to the general assembly concerning the development and operation of the midwest regional rail system and the state's passenger rail service." The Midwest Regional Rail Initiative (MWRRI) is a nine-state effort to develop an implementation plan for a 3,000-mile, high-speed rail system hubbed in Chicago. Studies done since 1996 have concluded that such a regional system, including a line from Chicago to Omaha through Davenport, Iowa City and Des Moines, is viable. Most of the system would be upgraded to allow 110 mile-per-hour service. Some low volume lines, including the Iowa portions, would be upgraded for 79 mile-per-hour service. The nine-state coalition released an updated 2004 executive report for the system. As reported, the updated cost estimate for the Chicago to Omaha corridor, which includes a branch to Quincy, Ill., is $638 million for infrastructure and $167 million for rolling stock. These costs are higher than first estimated in 1998 and are given in 2002 dollars, (not adjusted for the cost of inflation). Operating subsidies would be required during an extended start-up phase. The allocation of these subsidy costs among the various states has not been determined, and is still a subject for analysis and negotiation. Little progress on implementation is expected unless a federal funding package is passed for passenger rail initiatives. Continued congressional discussion on policy directions relative to Amtrak clouds the issue of passenger rail funding. However, Congress is expected to address passenger rail issues and funding in 2007. Participation of the Iowa Department of Transportation in the MWRRI is authorized under Iowa Code section 327J.3.

Sex allocation and sex-dependent selection for body size in Trypoxylon rogenhoferi Kohl (Hymenoptera, Sphecidae)

Two populations of the wasp Trypoxylon rogenhoferi Kohl, 1884 from São Carlos and Luís Antônio, State of São Paulo, Brazil, were observed and sampled from May 1999 to February 2001 using trap-nests. This mass-provisioning wasp was used to test some aspects of optimal sex allocation theory. Both populations fit all the predictions of the models of Green and Brockmann and Grafen. Maternal provisions determined the size of each offspring, and females allocated well-stocked brood cells to daughters, the sex that benefits most being large. This strategy resulted in a difference in size between the sexes. In São Carlos, female weight at emergence was 1.18 times that of males, in Luís Antônio this value was 1.13. The brood cell volume was correlated with both wing length and weight at emergence in both sexes, and the chance that a given brood cell contained a male offspring decreased with increased brood cell volume. In T. rogenhoferi female body size was related to fitness. Larger females were able to collect more mass of spiders per day, the spiders they captured were heavier, and they provisioned more brood cells per day. They also produced larger daughters. For males, no relationship between body size and fitness was found, but the data were scarce. Since the patterns of provisioning were variable among different females in both study sites, it is possible that the females not follow a unique strategy for sex allocation. The sex ratio and/or investment ratio in the São Carlos population was female-biased and in Luís Antônio, male-biased. In spite of the influence of trap-nests diameters on male production in Luís Antônio, there is some evidence that in São Carlos population the local availability of prey and/or lower rate of parasitism may be major forces in determining the observed sex ratio, but further studies are necessary to verify such hypothesis.