Cost accounting | EPFL Graph Search

Cost accounting is defined by the Institute of Management Accountants as "a systematic set of procedures for recording and reporting measurements of the cost of manufacturing goods and performing services in the aggregate and in detail. It includes methods for recognizing, classifying, allocating, aggregating and reporting such costs and comparing them with standard costs". Often considered a subset of managerial accounting, its end goal is to advise the management on how to optimize business practices and processes based on cost efficiency and capability. Cost accounting provides the detailed cost information that management needs to control current operations and plan for the future. Cost accounting information is also commonly used in financial accounting, but its primary function is for use by managers to facilitate their decision-making. Origins of cost accounting All types of businesses, whether manufacturing, trading or producing services, require cost accounting to

Ab initio study of the work functions of elemental metal crystals

This thesis is concerned with the theoretical study of the physical characteristics of metallic surfaces. Ab initio quantum calculations are performed to determine the electronic properties of clean elemental metal surfaces, fully accounting for the material's atomic structure. We aim to understand the atomicscale mechanisms responsible for the dependence of the work function on the surface geometry, including the crystallographic orientation of the surface, the atomic relaxation and reconstruction, as well as the effect of surface edges. We present an accurate method to derive work functions from self-consistent thin-film calculations. By applying a technique based on a macroscopic average, we filter the atomic oscillations in the electronic density to measure precisely the electrostatic potential step at the crystal surface. Combining this quantity with the Fermi energy of a bulk crystal is shown to reduce size effects on the work functions and to yield very precise values. The microscopic origin of the work function anisotropy is studied in sodium, aluminium, copper and gold. For these metals, we find that the trends of increasing work functions for the principal surface orientations reproduce the experimental data and that the trend in aluminium is different from most other metals. The origin of the work function anisotropy is discussed in relation with the orbital character of the electronic states at the Fermi energy. Our study of metal surfaces is extended to the facets of a finite crystal. First-principles studies of the electronic structure of nanowires enable us to obtain the electrostatic potential outside a variety of infinitely-long facet edges. In particular, we determine the microscopic mechanism that allows two different work functions to coexist on either side of a facet edge.

EPFL1999

Protocol overheads in networks

Prasenjit Dey

To increase network capacity, it may not be sufficient to just increase the capacity of the networks. It may be necessary to reduce the network overhead bits, to leave more room for the data bits, to increase the network capacity. As network functions become more complicated, more elaborate protocols become necessary to manage the networks. Without a proper and fundamental understanding of the overheads resulting from protocol bits, we may have protocols with huge overheads, which diminish the network efficiency, resulting in high cost and low value networks. Most effort has been dedicated to finding higher capacity links to carry more data. Little, or no effort has been spent to define a framework and analyze the overheads in the networks with the aim of understanding their behavior and thus reducing them. In this thesis, we give some perspectives on quantifying network overheads and some policies to reduce them. In a fixed network example, we show that, one can provide a lower bound on the number of bits needed to encode each message, exchanged by a node with its neighbors, to know the connectivity information of the node to others, i.e. its network neighborhood. The lower bound also provides insights into the dynamics of protocol information and its connection to the link statistics. We then examine the overheads arising out of the network's effort to keep track of a user, equivalent to knowing the connectivity information in fixed networks, in the case of two-tier hierarchical networks in general, and cellular and peer-to-peer networks in particular. We find that there exists an optimal threshold-based announcing policy of the user, about its location, which minimizes the network overheads. Clustering of users is also found to be a good strategy, in two-tier hierarchical networks, to minimize user tracking overheads. We find the optimal clustering which minimizes the tracking overhead, and that the optimal clustering is crucial to finding the aforementioned optimal announcing policy. As a next strategy, we show that clustering of user location information can reduce the number of bits needed to represent the information. The location information updates can be sent periodically, and the necessary bits needed to un-cluster the information can be fetched on a requirement basis. Based on the location statistics of the user, one can find a clustering of the location information, such that, given the clustered information, the number of bits that need to be fetched is minimized. Bandwidth is a very important attribute of a network, which if not allocated optimally, can be an "overhead" in terms of reduced network efficiency and high service costs. We take the viewpoint that, the optimal allocation should be based on users' behavior, who are the final consumers of the bandwidth. We study the user's psychology for media and its connection to bandwidth, and show a way to optimize bandwidth allocation. The conclusions from the optimal allocation, lead us to an architecture of a low cost, high value, and fast Internet access solution.

EPFL2004

Protocol overheads in networks

Prasenjit Dey

EPFL2004