5 research outputs found
TOPOLOGICAL-METRIC MAPPING
No full textThis manuscript has been reproduced from the microfilm master. UMI films the text directly fmm the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, &red or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (0.g.. maps, drawings, charts) am reproduced by sectioning the original, beginning at the upper lefthand comer and continuing from left b right in equal sections with small overlaps. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6 " x 9 " black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. &I1 & H ~ l l Information and Learnin
Equilibrium and learning in queues with advance reservations.
No full textConsider a multi-class preemptive-resume M/D/1 queueing system that supports advance reservations (AR). In this system, strategic customers must decide whether to reserve a server in advance (thereby gaining higher priority) or avoid AR. Reserving a server in advance bears a cost. In this paper, we conduct a game-theoretic analysis of this system, characterizing the equilibrium strategies. Specifically, we show that the game has two types of equilibria. In one type, none of the customers makes reservation. In the other type, only customers that realize early enough that they will need service make reservations. We show that the types and number of equilibria depend on the parameters of the queue and on the reservation cost. Specifically, we prove that the equilibrium
is unique if the server utilization is below 1/2. Otherwise, there may be multiple equilibria depending on the reservation cost. Next, we assume that the reservation cost is a fee set by the provider. In that case, we show that the revenue maximizing fee leads to a unique equilibrium if the utilization is below 2/3, but multiple equilibria if the utilization exceeds 2/3.
Finally, we study a dynamic version of the game, where users learn and adapt their strategies based on observations of past actions or strategies of other users. Depending on the type of learning (i.e., action learning vs. strategy learning), we show that the game converges to an equilibrium in some cases, while it cycles in other cases.First author draf
A new methodology for assessing the impact of water-pricing scenarios: case study of small-scale irrigation schemes in South Africa
No full textWorldwide growing water scarcity has increased the call for economic instruments to stimulate rational water use in agriculture. In addition cost-recovery is now widely accepted as a cornerstone of sustainable water management. As a consequence now in developing countries, where currently agricultural water use is often still heavily subsidized, a tendency exists of introducing water-pricing as a policy to achieve more sustainable water use. The exact impact of water pricing policies on irrigation water use or on the farmers’ production system is however mostly unknown. A new two-stage methodology that allows estimating at the farm level the effects of introducing or raising a water price on the agricultural production process and water demand is introduced in this study. The first stage comprises the construction of a technical efficiency frontier and the calculation of the technical and allocative efficiency levels of each farm. This representation of the technology is used in the second stage in a profit maximization model. As an example the method is applied to the case of small-scale irrigators in South Africa. It is shown that water demand of farmers is quite responsive even to small changes in the water price. Moreover, the introduction of a water price is shown to significantly decrease farm profit. This appears to be mainly a problem for the poorer farmers.water-pricing, water savings, irrigation, data envelopment analysis, South Africa, Resource /Energy Economics and Policy,
Advance reservation games and the price of conservatism,” in
No full textABSTRACT Advance reservation (AR) services form a pillar of many branches of the economy, e.g., transportation, lodging, dining, and health care. There has also been increased interest in applying AR in cloud computing systems In most systems supporting AR, customers can choose whether making AR or not. Since the payoff of each customer is affected by decisions of other customers, it is natural to analyze the behavior of such systems as strategic games. In this work, we study a strategic non-cooperative game, referred to as an advance reservation game. In this game, players (customers) can reserve future resources in advance for a fixed reservation fee C. We consider a slotted loss system with N servers where customers are not flexible, i.e., they leave the system if they cannot be served at their desired time slots. Customers are not informed of the state of the system (i.e., the number of unreserved servers) prior to attempting a reservation. Thus, a customer opting not to make a reservation lowers its chance of finding a server available at the desired time. The number of customers in each slot is an i.i.d. Poisson random variable with parameter λ [4]. Customers have different lead times, where the lead time of a customer is defined as the time elapsing between its arrival and the slot starting time. Each customer only knows its own lead time. However, all lead times are derived from the same continuous distribution known by both the provider and the customers. In [5], we derive the equilibria structure of AR games. We show that for any C > 0, only two types of equilibria are possible. In the first type, none of the customers, regardless of their lead times, makes AR (non-make-AR equilibrium). In the second type, only customers with lead time greater than some threshold make AR (threshold equilibrium). Furthermore, we establish the existence of three different ranges of fees, such that if C falls in the first range only threshold equilibria exist, in the second range both threshold equilibria and a none-make-AR equilibrium exist, and in the third range only a none-make-AR equilibrium exists. In many cases, the fee C that maximizes the provider's profit lies in the second range. However, setting up a fee in that range carries also the risk of zero profit for the provider. Copyright is held by author/owner(s). Therefore, in order to properly set the AR fee, the provider should consider both the fee yielding the maximum possible profit and the fee yielding the maximum guaranteed profit. A guaranteed profit can be only achieved using fees falling within the first range. In this work, we introduce the concept of price of conservatism (PoC), which corresponds to the ratio of the maximum possible profit to the maximum guaranteed profit, and analyze it in different regimes. A greater PoC indicates greater potential profit loss if the provider opts to be conservative. First, we analyze a single-server regime, where we prove that for any fee the equilibrium is unique (the second range collapses in that case). Hence, P oC = 1 and the provider experiences no loss. Next, we analyze a many-server regime where λ = αN and N → ∞. We distinguish between the cases of overloaded and underloaded systems (i.e., α > 1 and α < 1 respectively). For the overloaded case, we show that P oC = α/(α−1). Hence, the price of conservatism increases in an unbounded fashion as α approaches one from above. Finally, for the underloaded case, we show that both the maximum and guaranteed profits converge to zero
Occult Serologically Confirmed Cases of SARS-CoV-2 Coronavirus among the General Population in the Era of the Fourth Vaccination
No full textBackground: Asymptomatic SARS-CoV-2 infection can significantly increase the spread of the COVID-19 pandemic. We aimed to investigate the epidemiological and clinical predictors of occult serologically confirmed SARS-CoV-2 cases among the general population during the fourth vaccination era in Israel. Methods: We conducted a cross-sectional study among individuals aged ≥18 years who had not been tested for COVID-19 in the preceding 5 months. Occult serologically confirmed cases were based on the presence of anti-N IgG antibodies. Potential risk factors were examined. Multivariable regression analysis identified independent predictors of subclinical SARS-CoV-2 infection. Results: This study included 504 participants. The prevalence of occult serologically confirmed SARS-CoV-2 was 12.5%. Chronic disease was found to be an independent predictor for the absence of occult disease (aOR) 0.4 [95% (CI): 0.18–0.87], p-value = 0.02). No significant differences were observed in age, sex, marital status, number of children, vaccination status, or exposure to COVID-19 infection between participants with and without SARS-CoV-2 sub-infection. Conclusions: We found a lower prevalence of occult serologically confirmed SARS-CoV-2 cases, compared to previous reports, and a negative correlation between chronic disease and occult SARS-CoV-2. Continued research, surveillance, and intervention strategies are needed to optimize long-term health outcomes and provide valuable insights for public health policymakers and clinicians
