Life Cycle Component Research Articles

Two-Stage Based Life Cycle and Principal Component Analysis for Decision Support of Potential Municipal Solid Wastes Management Scenarios, Case study Dar es Salaam, Tanzania

In most of the urban areas of Tanzania, poor and inadequate solid waste management is a growing environmental and public health concern. Despite an array of solid waste management options, choosing an appropriate one remains a challenge. This study applied a novel two-stage-based approach to assess the environmental impacts and sustainability performance of the 27 scenarios for municipal solid wastes (MSW) management of Dar es Salaam City, Tanzania. In the first stage, the study utilized a life cycle analysis (LCA) to quantify the environmental impacts of MSW scenarios. In the second stage, the study used the principal component analysis (PCA) to assess the sustainability performance of the same. The LCA results indicated that no scenario performed better in all environmental impacts. The current SWM option, which involves landfilling most of the wastes at the Pugu landfill, leads to adverse environmental impacts and therefore poses an environmental and public health risks potential. The PCA results indicated that the scenario that involves the composting of organic wastes, recycling of the recyclable materials and landfilling the rest of the waste is the more sustainable option with a score of -1.7105. Based on the sensitivity analysis, the transportation process is responsible for the higher environmental burdens in most scenarios. Thus, promoting resource recovery at the premises of the waste generation would be crucial for minimizing the environmental impacts. This study demonstrated that the decision-makers could potentially use a combined LCA-PCA methodology to select the optimal MSW scenario.

Finite-State Markov-Chain Approximations: A Hidden Markov Approach

This paper proposes a novel finite-state Markov chain approximation method for Markov processes with continuous support, providing both an optimal grid and transition probability matrix. The method can be used for multivariate processes, as well as non-stationary processes such as those with a life-cycle component. The method is based on minimizing the information loss between a Hidden Markov Model and the true data-generating process. We provide sufficient conditions under which this information loss can be made arbitrarily small if enough grid points are used. We compare our method to existing methods through the lens of an asset-pricing model, and a life-cycle consumption-savings model. We find our method leads to more parsimonious discretizations and more accurate solutions, and the discretization matters for the welfare costs of risk, the marginal propensities to consume, and the amount of wealth inequality a life-cycle model can generate.

Intra-Life Cycle Information Transfers

We investigate the presence of a shared life cycle component in earnings and test whether the earnings of one firm are relevant for valuing other firms in the same life cycle stage. We find that firm-pairs in the same life cycle stage have greater accounting comparability and greater co-movement in their returns, operating performance, and investments than firm-pairs consisting of firms in different life cycle stages. We further document economically significant transfers of information from announcing firms to non-announcing life cycle peers around an announcing firm’s earnings announcement. The magnitudes are comparable to that of intra-industry information transfers and do not depend on whether the life cycle peers are also active in the same industry. In contrast, we find that intra-industry information transfers are smaller for industry peers in different life cycle stages. Information transfers are stronger for life cycle peers that have greater (transient) institutional cross-holdings, suggesting that institutional trading is an important mechanism by which life cycle information spills over. Overall, this study provides insight into the factors that shape a firm’s earnings generation process and investors’ use of such factors. Furthermore, this study complements prior literature on firm life cycle by providing additional evidence on the importance of life cycle in the valuation process.

Unpacking Summary Measures of Ethnic Residential Segregation Using an Age Group and Age Cohort Perspective

The residential segregation literature has underplayed the significance of age in shaping the ethnic compositions of neighbourhoods. This paper develops an age group and age cohort perspective as a way to unpack summary measures of residential segregation. Harmonised small area data for England and Wales (2001–2011) are used as a case study to explore the potential of this methodology for understanding better the role of age in the evolution of ethnic residential geographies. Our findings demonstrate the age-specificity of residential segregation, for both cross-sectional patterns and change over time. Levels of segregation vary among age groups and age cohorts and between ethnic groups, with a changing pattern of segregation as people age. Exploring change over a 10-year period, we observe that residential segregation decreases during young adulthood for all age cohorts, then increases during the late 20s and early 30s, and continues to increase until retirement. These trends are, for the most, consistent between ethnic groups. Our findings emphasise how residential segregation is a dynamic process with a significant life cycle component, with commonalities in residential decision-making between ethnic groups through the life course.

Environmental and spatial assessment for the ecodesign of a cladding system with embedded Phase Change Materials

New building materials and techniques are increasingly developed to respond to the challenges posed by the need of reducing energy demand of buildings while keeping adequate answer to housing needs. The potential of Cement Based Composites (CBCs) panels in which a large amount Phase Change Materials (PCMs) is embedded have been explored in this study. The technological development of the CBCs panel, and the optimization thereof, have been supported by a tailored methodology, combining environmental, spatial and climate-based assessment. Concerning the environmental assessment, Life Cycle Assessment (LCA), at material and component level, has been applied through all the steps of the panel design process to ensure that the use of the innovative product leads to an absolute reduction of the environmental impacts. The assessment of product environmental profile along life cycle stages have been performed covering 15 different impact categories. Based on LCA results, glycerine and fatty acids – if they are secondary material (e.g. from the purification of waste cooking oil) – showed a great potential to be environmentally preferable compared to paraffin. Moreover, the spatial and climate-based assessment has been carried out, considering the climatic conditions of the first 50 most populated cities in the European Union. It allowed identifying the EU cities with the highest potential for PCMs application and the optimal configuration of the CBC panel (single or dual layer). Lastly, when compared to sandwich panels available in the market, environmental benefits are expected from the use of PCMs when the insulating layer can be reduced by 25% without affecting the thermal performance.

Household production and consumption over the life cycle: National Time Transfer Accounts in 14 European countries

While the importance of unpaid household labour in total economic output is recognized, little is known about the demographics of its production and consumption. Our goal is to give a comprehensive estimation on the value of production and consumption of unpaid labour by age and gender and analyse non-market economic transfers in 14 European countries, which represent about 80 per cent of the population of the European Union. Our calculations are based on publicly available harmonised data. We introduce a novel imputation method of harmonised European time use data (HETUS) to the EU income survey (EU-SILC) in order to assign time spent on home production to consumers in households. Monetary values are attributed to unpaid labour activities using harmonised data on earnings (SES). Apart from pointing out key country specific results, we make two important observations on the age patterns of non-market economic activity. First, the economic lifecycle of men and women differ. The gender gap in household production is not evenly distributed over the lifecycle and cohorts of working age women contribute the most in net terms. Secondly, the main beneficiaries of unpaid household labour are children, not adult men, nor the elderly. In contrast with the national economy, in which intergenerational flows are important in sustaining both childhood and old age, working age people almost exclusively support only children in the household economies of Europe. Older cohorts consume household goods and services mostly produced by them. With our analysis we add a new focus to the research on home production. While keeping the gender aspect, we demonstrate the importance of the lifecycle component of unpaid household labour.

Concurrent Design & Life Cycle Engineering in Automotive Lightweight Component Development

Lightweight design is a major trend in automotive component development. This is induced by regulatory requirements targeting the use phase of vehicles. The predominant approach is the introduction of new materials, either in single- or multi-material designs. Taking an environmental life cycle perspective, new materials typically cause increased burdens from raw materials provision that need to be compensated by energy savings from the vehicles use phase. Interfaces between life cycle engineering, component design and manufacturing of automotive lightweight components are elaborated. A redesign process for a roof structure serves as an exemplary case. Based on these activities, research demands in data acquisition, methods and tools in design and life cycle evaluation are presented. A special focus is set on the conceptual design stage, as emerging materials and manufacturing processes routes lead to a broadening of the concept variety.

The product life cycle and sample representativity bias in price indexes

ABSTRACTOfficial price indexes are usually calculated using matched samples of products. If products exhibit systematic price trends at different points in their life cycle then matched sample methods may introduce bias if the life cycle movement in the sample does not adequately reflect that in the population. This article explores the extent of these life cycle pricing effects and then examines the bias it can introduce in measured inflation. A large US supermarket scanner data set for six cities and six products over 12 years is used. Using hedonic methods we find that the life cycle component of price change is important across a range of products and cities. To explore the bias introduced by these movements, we use simulations that construct indexes with different sample update frequency. For indexes that are never completely resampled, we find an annual absolute bias of 0.88 and 0.59 percentage points depending upon whether we use the actual prices or prices imputed from our hedonic model. This compares with absolute biases of 0.34 and 0.10 percentage points for the corresponding cases for samples, which are re-selected annually. Thus our results provide strong support for more frequently updating index samples.

The Product Life Cycle and Sample Representativity Bias in Price Indexes

Official price indexes are usually calculated using matched samples of products. If products exhibit systematic price trends at different points in their life cycle then matched sample methods may introduce bias if the life cycle movement in the sample does not adequately reflect that in the population. This article explores the extent of these life cycle pricing effects and then examines the bias it can introduce in measured inflation. A large US supermarket scanner data set for 6 cities and 6 products over 12 years is used. Using hedonic methods we find that the life cycle component of price change is important across a range of products and cities. To explore the bias introduced by these movements we use simulations which construct indexes with different sample update frequency. For indexes which are never completely re-sampled we find an annual bias of 0.88 and 0.59 percentage points depending upon whether we use the actual prices or prices imputed from our hedonic model. This compares with absolute biases of 0.24 and 0.08 percentage points for the corresponding cases for samples which are re-selected annually. Thus our results provide strong support for more frequently updating index samples.

Signaling with Convertible Debt in High-Risk Industries

This paper analyzes how convertible debt is used in a high-risk, emerging industry setting. We argue that there is a lifecycle component to the design and market impact of convertible debt securities. Contrary to prior cross-industry research findings, we show that convertible debt in the renewable energy industry tends to have a debt-like structure, and its issue is associated with strongly nega¬tive announce¬ment returns. We further show that convertible issuers face high adverse selection costs, which they attempt to mitigate by sending signals about firm quality. However, these signals tend to fail because the market anticipates this behavior, and perceives convertible issuers as being priced out of the equity markets. Firm and industry characteristics support this view, because financial distress indicators suggest the use of more equity-like financing instruments.

VERIFICATION OF CONJUNCTIVE ARTIFACT-CENTRIC SERVICES

An artifact-centric service is a stateful service that holistically represents both the data and the process in terms of a (dynamic) artifact. An artifact is constituted by a data component, holding all the data of interest for the service, and a lifecycle, which specifies the process that the service enacts. In this paper, we study artifact-centric services whose data component is a full-fledged relational database, queried through (first-order) conjunctive queries, and the lifecycle component is specified as sets of condition-action rules, where actions are tasks invocations, again based on conjunctive queries. Notably, the database can evolve in an unbounded way due to new values (unknown at verification time) inserted by tasks. The main result of the paper is that verification in this setting is decidable under a reasonable restriction on the form of tasks, called weak acyclicity, which we borrow from the recent literature on data exchange. In particular, we develop a sound, complete and terminating verification procedure for sophisticated temporal properties expressed in a first-order variant of μ-calculus.

The evolution of plant pathogens in response to host resistance: Factors affecting the gain from deployment of qualitative and quantitative resistance

Disease resistance genes are valuable natural resources which should be deployed in a way which maximises the gain to crop productivity before they lose efficacy. Here we present a general epidemiological model for plant diseases, formulated to study the evolution of phenotypic traits of plant pathogens in response to host resistance. The model was used to analyse how the characteristics of the disease resistance, and the method of deployment, affect the size and duration of the gain. The gain obtained from growing a resistant cultivar, compared to a susceptible cultivar, was quantified as the increase in green canopy area resulting from control of foliar disease, integrated over many years—termed ‘Healthy Area Duration (HAD) Gain’. Previous work has suggested that the effect of crop ratio (the proportion of land area occupied by the resistant crop) on the gain from qualitative (gene-for-gene) resistance is negligible. Increasing the crop ratio increases the area of uninfected host, but the resistance is more rapidly broken; these two effects counteract each other. We tested the hypothesis that similar counteracting effects would occur for quantitative, multi-genic resistance, but found that the HAD Gain increased at higher crop ratios. Then we tested the hypothesis that the gain from quantitative host resistance could differ depending on the life-cycle component (sporulation rate or infection efficiency) constrained by the resistance. For the patho-system considered, a quantitative resistant cultivar that reduced the infection efficiency gave a greater HAD Gain than a cultivar that reduced sporulation rate, despite having equivalent transmission rates.

The Image of the Institution

Problem, research strategy, and findings: How do we make coherent urban plans in an incoherent institutional setting? How are institutions born, how do they evolve? Can they be meaningfully reformed? Or are they destined to bloat and muddle through? Using in situ interviews, document analysis, and participant observation, I investigate the role of urban plans in institutional design to address sociologist Talcott Parson's call for a theory of the dynamics of institutional change. Planners used images that they invented to build new and better planning institutions. Politicians used city and metropolitan planning as a political strategy to build the institutions of metropolitan and regional governance. Plan images were tools that coordinated spatial planning and urban policy. The institutional structure of urban planning and its governance is rooted in images of urban form that extend back several generations. These empirical findings formed the basis for a cognitive, lifecycle theory of institutional change. The cognitive component of the theory adds content to institutional theory, which had been based on structure and agency. The lifecycle component spans the gaps among existing theories of institutional evolution—incremental structuration, radical revolt, and institutional design—while incorporating lifecycle end points of creation and demise. Takeaway for practice: The plan matters because the images of place that are contained in plans not only guide the planning process and the development of territory; they also shape the entire institution of governance in which planning is situated. The role of the planners—to create the image of place—points to an important leadership quality, and to a key role for planning: institutional design. Research support: The J. William Fulbright Foreign Scholarship Board, the Program for Cultural Cooperation Between Spain's Ministry of Culture and United States Universities, the Catalonian Studies Program and the Center for German and European Studies at the University of California at Berkeley, the University of California Regents, and Texas A&M University.

The effects of inbreeding and heat stress on male sterility inDrosophila melanogaster

Understanding the consequences of inbreeding in combination with stress is important for the persistence of small endangered populations in a changing environment. Inbreeding and stress can influence the population at all stages of the life cycle, and in the last two decades a number of studies have demonstrated inbreeding depression for most life-cycle components, both in laboratory populations and in the wild. Although male fertility is known to be sensitive to temperature extremes, few studies have focused on this life-cycle component. We studied the effects of inbreeding on male sterility in benign and stressful environments using Drosophila melanogaster as a model organism. Male sterility was compared in 21 inbred lines and five non-inbred control lines at 25.0 and 29.0 degrees C. The effect of inbreeding on sterility was significant only at 29.0 C. This stress-induced increase in sterility indicates an interaction between the effects of inbreeding and high-temperature stress on male sterility. In addition, the stress-induced temporary and permanent sterility showed significant positive correlation, as did stress-induced sterility and the decrease in egg-to-adult viability. This suggests that the observed stress-induced decline in fitness could result from conditionally expressed, recessive deleterious alleles affecting both sterility and viability simultaneously. (C) 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104, 432-442.

Consumer Bankruptcy: A Fresh Start

There has been considerable public debate on the relative merits of alternative consumer bankruptcy rules. The option to discharge one’s debt provides partial insurance against bad luck, but by driving up interest rates makes lifecycle smoothing more difficult. We construct a quantitative model of consumer bankruptcy to address this trade-off. We argue that such a model should have three key feature: a life-cycle component, idiosyncratic earnings uncertainty and expense uncertainty (exogenous negative shocks to household balance sheets). We further show that transitory and persistent earnings shocks have very different implications for evaluating bankruptcy rules – while persistent shocks make bankruptcy option desirable, transitory shocks have the opposite implication. Our findings suggest that the current US bankruptcy system may be desirable for reasonable parameter values.

Consumer Bankruptcy: A Fresh Start

Consumer bankruptcy provides partial insurance against bad luck, but, by driving up interest rates, makes life-cycle smoothing more difficult. We argue that to assess this trade-off one needs a quantitative model of consumer bankruptcy with three key features: life-cycle component, idiosyncratic earnings uncertainty, and expense uncertainty (exogenous negative shocks to household balance sheets). We find that transitory and persistent earnings shocks have very different implications for evaluating bankruptcy rules. More persistent shocks make the bankruptcy option more desirable. Larger transitory shocks have the opposite effect. Our findings suggest the current US bankruptcy system may be desirable for reasonable parameter values. (JEL D14, D91, K35)

The Sensitivity of the Epidemic Growth Rate to Weather Variables, with an Application to Yellow Rust on Wheat

ABSTRACT We first show how to estimate the exponential epidemic growth rate, r, for different combinations of three weather variables. Then we derive a method to quantify the sensitivity of r to a weather variable as a function of the pathogen life cycle variables of latent period, basic reproductive number, and the mean and standard deviation of the sporulation curve. The method can be used to identify the most important weather variable and pathogen life cycle component in terms of epidemic progress. The method is applied to yellow rust, caused by Puccinia striiformis, on winter wheat. We conclude that the most important weather variable for the progress of yellow rust is temperature, followed by dew period and light quantity. By far, the most important pathogen life cycle component is the basic reproductive number, especially at low and high temperatures. This disagrees with the general view that latent period is the most important variable at low temperatures. We discuss explanations of this.

An overlapping generations model with non-ordered preferences and numeraire-incomplete markets*

This paper shows that, even with a life-cycle component, the standard model of competitive consumption and asset trading can be extended to encompass general preference relations, which do not necessarily hinge upon special assumptions such as time or state separability, or even completeness or transitivity. More precisely, this paper addresses the equilibrium existence for an overlapping generations pure-exchange economy with non-ordered preferences and incomplete financial markets of numeraire assets. Mathematics Subject Classification (2000): 91B50, 91B62 Journal of Economic Literature Classification: D52, D91

ENVIRONMENTAL FACTORS IN PARAMETRIC DESIGN OF COMPUTER CHASSIS

Environmental issues in industry have transformed from those of compliance to those of competitive advantage through increasingly stringent environmental regulations, the emergence of product take-back and recycling initiatives, and growing consumer preference for green products. While there has been much research devoted to systems-level disassembly and recycling of computer products, a significant life-cycle component of the wastes associated with the product occurs at the primary manufacturing stages. This paper examines the linkages between manufacturing process waste generation and decisions made at the component design stage. An application of this linkage is in the area of sheet metal components for computer chassis. Critical processes include blanking, punch, metal deformation, finishing and welding. The availability of data at several levels of aggregation is supplemented by the development of analytical models of process physics to derive a process-level inventory of energy utilization, primary scrap and secondary catalysts (tool, fluid and vapor waste streams). The mass flows of waste streams can be weighted by the impact on factors such as toxicity, carcinogenesis, reactivity, flammability and irritation using material safety data and survey of site-specific factors. The trade-offs between environmental, manufacturing and product performance factors are discussed, as well as the environmental impact of material selection and definition of geometric features. The methodology for estimating energy utilization and process wastes is demonstrated through calculations for the manufacture of a workstation chassis. Several case studies of chassis components are also presented to illustrate the influence of incremental component design decisions on environmental impact. The role of product specifications such as aesthetics, thermal requirements, shielding and structural requirements are examined.

Life Cycle Productivity in Academic Research: Evidence from Cumulative Publication Histories of Academic Economists

Casual observation suggests that the temporal pattern of productivity varies dramatically across individuals, particularly in risky endeavors such as a research career in academia. Some individuals remain productive researchers throughout their career. Others who show early promise become deadwood before their time. Some authors produce papers like a well oiled machine, while others publish at a highly erratic rate. Opposing this is a widely held view that there is a common life-cycle component underlying individual productivity. The aging process itself is thought to lead to the initial rise and eventual decline of creative productivity. In addition, human capital models typically imply that investment in skills will decline with age [7]. Both of these ideas suggest that output will be hump-shaped over the life cycle. Econometric studies of life cycle productivity have addressed this with regressions which are quadratic functions of age or experience [1; 5]. The quadratic conveniently delivers the sought after hump-shaped pattern in productivity. There are conceptual problems with the quadratic however. It implies a symmetric output path centered on its peak, which is inappropriate if productivity peaks early in the career but remains significant thereafter. In addition, data on publishing productivity is heavily affected by the zeros problem: the most common number of publications for an active professor in any given year is zero. This requires an estimation procedure designed to accommodate a high probability mass at zero. Levin and Stephan [5] address this problem with the tobit regression. The tobit is a truncated regression model, where in this context publications are distributed as a truncated normal random variable if a vector combination of attributes and coefficients exceeds a threshold level, and are zero other-