A brief history of the concept of waste in production

Purpose: The concept of waste has been used in relation to production since the beginning of the 20th century. As it is well-known, it is a foundational notion for the Toyota Production System and its derivatives, like lean production. However, waste is not a prevalent concept in the mainstream literature on economics, operations management, construction management or management. The reasons for this apparent aversion to the concept of waste are not well-understood. In view of this, we present an overview on the historical development and diffusion of the concept of waste. It is anticipated that such a long-term view would contribute to the current discussion of the place of this concept in the theory and practice of production. Method: The historical method is followed. Findings: The history of the concept of waste can naturally be divided into a number of periods: nascence up to the end of the 18th century, emergence of the classical notion in the 19th century, flourishing during scientific management, decline starting in the second quarter of the 20th century, and re-emergence in last quarter of that century. From these, especially the emergence of the classical notion of waste as well as its decline have been poorly understood. It is also an important insight that across the different periods, waste has been understood in two dimensions: instrumentally and intrinsically (morally). Implications: Through an historical account, the relevance and texture of the concept of waste can be better appreciated. The focus can be directed to critically assessing the justification of the arguments that led to the decline of waste. All in all, the need for the revival of waste as a basic concept in managerial discourse is illuminate

Theoretical Investigation of Submerged Inlets at Low Speeds

The general characteristics of the flow field in a submerged air inlet are investigated by theoretical, wind-tunnel, and visual-flow studies. Equations are developed for calculating the laminar and turbulent boundary-layer growth along the ramp floor for parallel, divergent, and convergent ramp walls, and a general equation is derived relating the boundary-layer pressure losses to the boundary-layer thickness. It is demonstrated that the growth of the boundary layer on the floor of the divergent-ramp inlet is retarded and that a vortex pair is generated in such an inlet. Functional relationships are established between the pressure losses in the vortices and the geometry of the inlet. A general discussion of the boundary layer and vortex formations is included, in which variations of the various losses and of the incremental external drag with mass-flow ratio are considered. Effects of compressibility are also discussed

Analysis framework for the interaction between lean construction and building information modelling

Building with Building Information Modelling (BIM) changes design and production processes. But can BIM be used to support process changes designed according to lean production and lean construction principles? To begin to answer this question we provide a conceptual analysis of the interaction of lean construction and BIM for improving construction. This was investigated by compiling a detailed listing of lean construction principles and BIM functionalities which are relevant from this perspective. These were drawn from a detailed literature survey. A research framework for analysis of the interaction between lean and BIM was then compiled. The goal of the framework is to both guide and stimulate research; as such, the approach adopted up to this point is constructive. Ongoing research has identified 55 such interactions, the majority of which show positive synergy between the two

A theoretical investigation of the aerodynamics of slender wing-body combinations exhibiting leading-edge separation

Theoretical investigation of aerodynamics of slender wing-body combinations exhibiting leading edge separatio

Agent-based simulation of construction workflows using a relational data model

To what extent is uncertainty concerning process status a cause of waste in construction workflows? Work studies and action research are expensive methods for investigation of such questions concerning construction workflow control policies and their results have limited applicability. Agent-based simulation (ABS) is particularly suitable for modelling peoples' behavior and interaction in complex settings, like in construction, and therefore represents an alternative. We present a parametric ABS system (EPIC 2.0) developed using a relational data model for modelling construction workflow; the model enables users to specify the construction subjects (subcontractor trade crews), their work methods, the amount of work, the workspaces (locations), dependencies between the works, etc. The simulation encapsulates both variability and uncertainty in the construction workflow. Variability arising from design changes, quality checks and working conditions may lead to random change in workload and performance. Uncertainty arises from the fact that agents do not have full or perfect information. The major advantages of this ABS system are its ability to run differently configured virtual projects in terms of work crews, locations and production system control policies and to test the relative impacts of various approaches to communication of process status information. Simulation results conclude information asymmetry causes erroneous task maturity judgments and inappropriate work assignments, and of course affects the construction workflow

Constraints on the Quasiparticle Density of States in High-TcT_c Superconductors

In this Letter we present new tunneling data on YBa$_2$Cu$_3$O$_7$ thin films by low temperature scanning tunneling spectroscopy. Unusual peak-dip-hump features, previously reported in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, are also found in YBa$_2$Cu$_3$O$_7$. To analyse these common signatures we propose a new heuristic model in which, in addition to the d-wave symmetry, the gap function is energy dependent. A simple expression for the quasiparticle density of states is derived, giving an excellent agreement with the experiment. The dynamics of the quasiparticle states and the energy scales involved in the superconducting transition are discussed.Comment: 4 page Letter with 3 figure

Modified NASA-Lewis chemical equilibrium code for MHD applications

A substantially modified version of the NASA-Lewis Chemical Equilibrium Code was recently developed. The modifications were designed to extend the power and convenience of the Code as a tool for performing combustor analysis for MHD systems studies. The effect of the programming details is described from a user point of view

Local tunneling spectroscopy of the electron-doped cuprate Sm1.85Ce0.15CuO4

We present local tunneling spectroscopy in the optimally electron-doped cuprate Sm2-xCexCuO4 x=0.15. A clear signature of the superconducting gap is observed with an amplitude ranging from place to place and from sample to sample (Delta~3.5-6meV). Another spectroscopic feature is simultaneously observed at high energy above \pm 50meV. Its energy scale and temperature evolution is found to be compatible with previous photoemission and optical experiments. If interpreted as the signature of antiferromagnetic order in the samples, these results could suggest the coexistence on the local scale of antiferromagnetism and superconductivity on the electron-doped side of cuprate superconductors

Information modeling of earthquake-damaged reinforced concrete structures

Accurate and reliable information about buildings can greatly improve post-earthquake responses, such as search and rescue, repair and recovery. Building Information Modeling (BIM), rapid scanning and other assessment technologies offer the opportunity not only to retrieve as-built information but also to compile as-damaged models. This research proposes an information model to facilitate the data flow for post-earthquake assessment of reinforced concrete structures. The schema development was based on typical damage modes and the existing Industry Foundation Class (IFC) schema. Two examples of damaged structures from recent earthquake events, compiled using an experimental damage modeling software, illustrate the use of the data model. The model introduces two new classes, one to represent segments of building elements and the other to model the relationships between segments and cracks. A unique feature is the ability to model the process of damage with a binary tree structure. Methods for exporting as-damaged instance models using IFC are also discussed