COST EFFECTIVENESS OF RECYCLING: A SYSTEMS MODEL

Financial analytical models of waste management systems have often found that recycling costs exceed direct benefits, and in order to economically justify recycling activities, externalities such as household expenses or environmental impacts must be invoked. Certain more empirically based studies have also found that recycling is more expensive than disposal. Other work, both through models and surveys, have found differently. Here we present an empirical systems model, largely drawn from a suburban Long Island municipality. The model accounts for changes in distribution of effort as recycling tonnages displace disposal tonnages, and the seven different cases examined all show that curbside collection programs that manage up to between 31% and 37% of the waste stream should result in overall system savings. These savings accrue partially because of assumed cost differences in tip fees for recyclables and disposed wastes, and also because recycling can result in a more efficient, cost-effective collection program. These results imply that increases in recycling are justifiable due to cost-savings alone, not on more difficult to measure factors that may not impact program budgets

Sparsely Faceted Arrays: A Mechanism Supporting Parallel Allocation, Communication, and Garbage Collection

Conventional parallel computer architectures do not provide support for non-uniformly distributed objects. In this thesis, I introduce sparsely faceted arrays (SFAs), a new low-level mechanism for naming regions of memory, or facets, on different processors in a distributed, shared memory parallel processing system. Sparsely faceted arrays address the disconnect between the global distributed arrays provided by conventional architectures (e.g. the Cray T3 series), and the requirements of high-level parallel programming methods that wish to use objects that are distributed over only a subset of processing elements. A sparsely faceted array names a virtual globally-distributed array, but actual facets are lazily allocated. By providing simple semantics and making efficient use of memory, SFAs enable efficient implementation of a variety of non-uniformly distributed data structures and related algorithms. I present example applications which use SFAs, and describe and evaluate simple hardware mechanisms for implementing SFAs. Keeping track of which nodes have allocated facets for a particular SFA is an important task that suggests the need for automatic memory management, including garbage collection. To address this need, I first argue that conventional tracing techniques such as mark/sweep and copying GC are inherently unscalable in parallel systems. I then present a parallel memory-management strategy, based on reference-counting, that is capable of garbage collecting sparsely faceted arrays. I also discuss opportunities for hardware support of this garbage collection strategy. I have implemented a high-level hardware/OS simulator featuring hardware support for sparsely faceted arrays and automatic garbage collection. I describe the simulator and outline a few of the numerous details associated with a "real" implementation of SFAs and SFA-aware garbage collection. Simulation results are used throughout this thesis in the evaluation of hardware support mechanisms

Run-time Support for Distributed Object Sharing in Safe Programming Languages

We present a new run-time system that supports object sharing in a distributed system. The key insight in this system is that a handle-based implementation of such a system enables effcient and transparent sharing of data with both fine-grained and coarse-grained access patterns. In addition, it supports effcient execution of garbage-collected programs. In contrast, conventional distributed shared memory (DSM) systems are limited to providing only one granularity with good performance, and have experienced diffculty in effciently supporting garbage collection. A safe language, in which no pointer arithmetic is allowed, can transparently be compiled into a handle-based system and constitutes its preferred mode of use. A programmer can also directly use a handle-based programming model that avoids pointer arithmetic on the handles, and achieve the same performance but without the programming benefits of a safe programming language. This new run-time system, DOSA (Distributed Object Sharing Architecture), provides a shared object space abstraction rather than a shared address space abstraction. The key to its effciency is the observation that a handle-based distributed implementation permits VM-based access and modification detection without suffering false sharing for fine-grained access patterns. We compare DOSA to TreadMarks, a conventional DSM system that is effcient at handling coarse-grained sharing. The performance of fine-grained applications and garbage-collected applications is considerably better than in TreadMarks. The performance of coarse-grained applications is nearly as good as in TreadMarks. Since the performance of such applications is already good in TreadMarks, we consider this an acceptable performance penalty

Compiler and Runtime Optimizations for Fine-Grained Distributed Shared Memory Systems

Bal, H.E. [Promotor

Differences in Waste Generation, Waste Composition, and Source Separation across Three Waste Districts in a New York Suburb

Six tonnes of discards and recyclables from three waste districts in a New York suburb were sorted in 2012. The districts were chosen because one had a higher recycling percentage, one had median performance, and one was a low performing district. ASTM standards were followed for the waste composition sorting. The results showed, as expected, that the waste district with the highest recycling rate appeared to have the highest separation efficiencies, leading to greater amounts of recyclable materials being source separated. The waste districts also had different overall waste generation, both in terms of the amounts of wastes generated, and their composition. The better recycling district generated less waste, but had a higher percentage of recyclables in the waste stream. Therefore, in some sense, its waste stream was enriched in recyclables. Thus, although the residents of that district recovered materials at a higher rate, they also left large amounts of recyclables in their discards – as did the residents of the other districts. In fact, the districts only recycled between one quarter and less than half of all available recyclables, so that their discards were comprised of up to one third recyclable materials. This level of performance does not appear to be unique to this Town; therefore, we believe that additional recovery efforts through post-collection sorting for recyclables may be warranted

Disaggregated Memory at the Edge

This paper describes how to augment techniques such as Distributed Shared Memory with recent trends on disaggregated Non Volatile Memory in the data centre so that the combination can be used in an edge environment with potentially volatile and mobile resources. This article identifies the main advantages and challenges, and offers an architectural evolution to incorporate recent research trends into production-ready disaggregated edges. We also present two prototypes showing the feasibility of this proposal

Software DSM protocols that adapt between single writer and multiple writer

We present two software DSM protocols that dynamically adapt between a single writer (SW) and a multiple writer (MW) protocol based on the application's sharing patterns. The first protocol (WFS) adapts based on write-write false sharing; the second (WFS+WG) based on a combination of write-write false sharing and write granularity. The adaptation is automatic. No user or compiler information is needed. The choice between SW and MW is made on a per-page basis. We measured the performance of our adaptive protocols on an 8-node SPARC cluster connected by a 155 Mbps ATM network. We used eight applications, covering a broad spectrum in terms of write-write false sharing and write granularity. We compare our adaptive protocols against the MW-only and the SW-only approach. Adaptation to write-write false sharing proves to be the critical performance factor, while adaptation to write granularity plays only a secondary role in our environment and for the applications considered. Each of the two adaptive protocols matches or exceeds the performance of the best of MW and SW in seven out of the eight application

Examination of the scoring structure of the psychopathology instrument for mentally retarded adults

"The purpose of this study was to assess the validity of an instrument designed to assist in the diagnosis of mental illness in individuals diagnosed with mental retardation titled "The Psychopathology Inventory for Mentally Retarded Adults (PIMRA)." Procedures included conducting an exploratory factor analysis (EFA) to identify a more parsimonious model and a series of confirmatory factor analyses (CFA) to test the hypotheses of factorial invariance, first, with two random samples, and then with three groups based on level of mental retardation. A series of logistic regression analyses were conducted to assess the ability of each scoring model to predict the "true" mental health diagnosis. Results of CFA of the PIMRA found the model to be ill fitting. Examination of the factor correlations, item correlations and item R2 values found significant problems such that the scoring model of the PIMRA was found to be unsupported. Results of the EFA identified an interpretable six factor solution. A confirmatory factor analysis of the six factor solution revealed a model that approached adequacy after deleting ten items. The hypothesis of factorial invariance was not supported in two random samples and three groups based on level of mental retardation. Results of the logistic regressions revealed that both models were better predictors of schizophrenia, affective disorder and psychosexual disorder than other mental health disorders. Both models are better predictors of lack of diagnosis rather than diagnosis. The six factor model was only slightly better than the PIMRA. These results suggest that neither the PIMRA nor the six-factor scoring model provide any diagnostic in determining the mental health status of an individual with mental retardation."--Abstract from author supplied metadata

Classification and Its Risks: How Psychiatric Status Contributes to Homelessness Policy

This article examines the extent to which psychiatric classification in public policy research contributes to the equation of homelessness and mental illness. Surveys that measure psychiatric status of homeless persons are reviewed to understand whether they contribute to biased rates of mental illness among homeless persons. The relationship between psychiatric classification and the concept of need is examined and alternatives to current classification are proposed. Classification is discussed particularly in relation to policies of segmentation for single homeless adults