Marginal Productivity Indices and Linear Programming Relaxations for Dynamic Resource Allocation in Queueing Systems

Many problems concerning resource management in modern communication systems can be simplified to queueing models under Markovian assumptions. The computation of the optimal policy is however often hindered by the curse of dimensionality especially for models that support multiple traffic or job classes. The research focus naturally turns to computationally efficient bounds and high performance heuristics. In this thesis, we apply the indexability theory to the study of admission control of a single server queue and to the buffer sharing problem for a multi-class queueing system. Our main contributions are the following: we derive the Marginal Productivity Index (MPI) and give a sufficient indexability condition for the admission control model by viewing the buffer as the resource; we construct hierarchical Linear Programming (LP) relaxations for the buffer sharing problem and propose an MPI based heuristic with its performance evaluated by discrete event simulation. In our study, the admission control model is used as the building block for the MPI heuristic deployed for the buffer sharing problem. Our condition for indexability only requires that the reward function is concavelike. We also give the explicit non-recursive expression for the MPI calculation. We compare with the previous result of the indexability condition and the MPI for the admission control model that penalizes the rejection action. The study of hierarchical LP relaxations for the buffer sharing problem is based on the exact but intractable LP formulation of the continuous-time Markov Decision Process (MDP). The number of hierarchy levels is equal to the number of job classes. The last one in the hierarchy is exact and corresponds to the exponentially sized LP formulation of the MDP. The first order relaxation is obtained by relaxing the constraint that no buffer overflow may occur in any sample path to the constraint that the average buffer utilization does not exceed the available capacity. Based on the Lagrangian decomposition of the first order relaxation, we propose a heuristic policy based on the concept of MPI. Each one of the decomposed subproblems corresponds to the admission control model we described above. The link to the decomposed sub-problems is the Lagrangian multiplier for the relaxed buffer size constraint in the first order relaxation. Our simulation study indicates the near optimal performance of the heuristic in the (randomly generated) instances investigated

Some topics in web performance analysis

This thesis consists of four papers on web performance analysis. In the first paper we investigate the performance of overload control through queue length for two different web server architectures. The simulation result suggests that the benefit of request prioritization is noticeable only when the capacities of the sub-systems match each other. In the second paper we present an M/G/1/K*PS queueing model of a web server. We obtain closed form expressions for web server performance metrics such as average response time, throughput and blocking probability. The model is validated through real measurements. The third paper studies a queueing system with a load balancer and a pool of identical FCFS queues in parallel. By taking the number of servers to infinite, we show that the average waiting time for the system is not always minimized by routing each customer to the expected shortest queue when the information used for decision is stale. In the last paper we consider the problem of admission control to an M/M/1 queue under periodic observations with average cost criterion. The problem is formulated as a discrete time Markov decision process whose states are fully observable. A proof of the existence of the average optimal policy by the vanishing discounted approach is provided. We also show that the optimal policy is nonincreasing with respect to the observed number of customers in the system

Total synthesis of (-)-paraherquamide A, The

2000 Summer.Includes bibliographical references.The first stereocontrolled total synthesis of (-)-paraherquamide A is described in 48 chemical steps. The synthesis is a convergent one, starting from ethyl glycinate, ethyl acrylate and vanillin. The longest linear route is 35 steps. Vanillin was acetylated and nitrated to provide nitrovanillins (94 and 95). These were converted to the azalactones, hydrolyzed to the α-ketocarboxylic acids, oxidatively decarboxylated to acids 99 and 108. Compound 99 was reductively cyclized to oxindoles 100, which was then demethylated to give pure oxindole 101. The oxindole was regioselectively prenylated, epoxidized, and subjected to a key seven-membered ring forming procedure to provide the unique dioxepin 104. Compound 104 was reduced to indole 105 and indoline 106 which was converted to 105 by reaction with DDQ. Indole 105 was protected and subjected to a Mannich reaction to afford the gramine derivative 60. The Michael adduct 150 from ethyl glycinate and ethyl acrylate was protected, intramolecularly condensed and reduced with Baker's yeast to give cis-β-hydroxy proline ester 129. Stereoselective α-alkylation of 129, protection, deprotection, bromoacetyl amide formation, aminolysis, cyclization and dimethoxycarbonylation provided diketopiperazine (DKP) 91. DKP 91 was alkylated with compound 60 to provide indoles 303 and 304, which were then individually decarbomethoxylated to afford four separable diastereomers anti-305 (305E/Z) and syn-306 (306E/Z). These four diastereomers were individually converted to the corresponding SN2' substrates through lactim ether formation, protection of the indole nitrogen, deprotection, allylic chloride formation and TBS ether formation. SN2' cyclization of these four SN2' substrates individually provided the same product 327. Cyclization of lactim ether 327, ring opening of the lactim ether moiety and ring closure afforded DKP 338. Selective amide group reduction of 338, N-methylation, MOM ether deprotection, oxidation, bis-deprotection by TFA provided indole-ketone 344. Oxidative spirooxidation of 344 followed by dehydration gave ketone-olefin 43. Stereoselective methyl addition to 43 afforded (-)-paraherquamide A

Impact of the Collective Forest Right System Reform on Poverty Reduction and Income Growth for Forest Farmer in Mountain Area - A Case Study of Jiangxi Province, China

Despite being a strong advocate for children’s rights in the international community, Sweden has received critique from the Committee on the Rights of the Child regarding the high number of children who have been removed from their families and that are currently living in foster homes. Previous research has not dealt with the issue of children’s rights in foster care placement processes in Sweden, nor has it included Sweden in discourse analyses on children’s rights, or sufficiently explored the relationship between discourse and implementation of the UNCRC. I use theories on discourse and translation in order to provide a comparative analysis of the articulations of children’s rights relevant for foster care placement processes in the UNCRC, and on the national and local level in Sweden. The analysis points to both similarities and differences in the discourses and identifies six aspects of the Swedish discourse that make certain activities in foster care placement processes possible, desirable and inevitable

Dual-Mass MEMS Gyroscope Structure, Design, and Electrostatic Compensation

Dual-mass MEMS gyroscope is one of the most popular inertial sensors. In this chapter, the structure design and electrostatic compensation technology for dual-mass MEMS gyroscope is introduced. Firstly, a classical dual-mass MEMS gyroscope structure is proposed, how it works as a tuning fork (drive anti-phase mode), and the structure dynamical model together with the monitoring system are presented. Secondly, the imperfect elements during the structure manufacture process are analyzed, and the quadrature error coupling stiffness model for dual-mass structure is proposed. After that, the quadrature error correction system based on coupling stiffness electrostatic compensation method is designed and evaluated. Thirdly, the dual-mass structure sensing mode modal is proposed, and the force rebalancing combs stimulation method is utilized to achieve sensing mode transform function precisely. The bandwidth of sensing open loop is calculated and experimentally proved as 0.54 times with the resonant frequency difference between sensing and drive modes. Then, proportional-integral-phase-leading controller is presented in sensing close loop to expand the bandwidth, and the experiment shows that the bandwidth is improved from 13 to 104 Hz. Finally, the results are concluded and summarized

Will cultural diversity block the process of urbanization? — Empirical Study from the perspective of dialect

Based on the data samples of 276 cities at prefecture level and above in China from 2000 to 2012, using dialect diversity as a proxy to measure cultural diversity, using random effect model, system generalized moment estimation, two-stage least square method and other methods, this paper conducted an empirical investigation on the impact of cultural diversity on China's urbanization for the first time. It is found that dialect diversity has a significant negative impact on urbanization rate; considering the possibility of missing variables, the influence of dialect diversity on urbanization rate is still significantly negative; after using the historical immigration as the instrumental variable of dialect diversity, this negative influence still exists, but the degree of influence has decreased. Therefore, the cultural variables represented by dialects are an important factor affecting the process of urbanization

The Existence of Aubry–Mather sets for the Fermi–Ulam Model

Acknowledgements This work is supported by the National Natural Science Foundations of China (11732014). The authors express their gratitude to the reviewer for fruitful comments and suggestions.Peer reviewedPostprin