No description available.

No description available.

Sherman M. Chan, Michael Athans. / Bibliography: leaf 9. / Caption title. "August 15, 1981." / Supported by the U.S. Department of Energy, Division of Electric Energy Systems, under Contract DE-AC01-78RA03395

We discuss the pole placement problem for single-input or multi-input control models of the form _x=Ax+Bu. This is the problem of determining a linear state feedback of the formu=F xsuch that in the closed-loop system _x= (A+BF)x, the matrixA+BFhas a prescribed set of eigenvalues. We analyze the conditioning of this problem and show that it is an intrinsically ill-conditioned problem, and especially so when the system dimension is large. Thus even the best numerical methods for this problem may yield very bad results. On the other hand, we also discuss the question of whether one really needs to solve the pole placement problem. In most circum- stances what is really required is stabilization or that the poles are in a specified region of the complex plane. This related problem may have much better conditioning. We demonstrate this via the example of stabilization.

We discuss the pole placement problem for single-input or multi-input control models of the form _x=Ax+Bu. This is the problem of determining a linear state feedback of the formu=F xsuch that in the closed-loop system _x= (A+BF)x, the matrixA+BFhas a prescribed set of eigenvalues. We analyze the conditioning of this problem and show that it is an intrinsically ill-conditioned problem, and especially so when the system dimension is large. Thus even the best numerical methods for this problem may yield very bad results. On the other hand, we also discuss the question of whether one really needs to solve the pole placement problem. In most circum- stances what is really required is stabilization or that the poles are in a specified region of the complex plane. This related problem may have much better conditioning. We demonstrate this via the example of stabilization.

Idag styr och planerar de flesta organisationer i någon form, det gäller både den privata sektorn som den offentliga sektorn. Det finns olika sätt och modeller man kan använda för att styra en verksamhet t.ex. genom balanserad styrkort. Styrning startas oftast från centrala direktiv som t ex en affärs/verksamhetsplan, budget, prognos, resultatmål, avkastnings mål etc. Styrningen kan baseras på mer eller mindre komplexa styrmodeller och hanteras rent praktiskt via någon form av systemstöd men ibland endast med hjälp av Word- och Exceldokument. Gemensamt för alla styrmodeller är att de kräver en uppföljning och rapportering för att kunna göra någon nytta. Detta projekt uppstod genom en förfrågan om projektets ämne passade ihop med företagets behov av aktuell information kring hur företag och organisationer styr och planerar sin verksamhet och vilka systemstöd som används för detta ändamål. Projektet var ett uppdrag hos företaget Konsultnet Scandinavian AB. Mitt uppdrag var att hjälpa företaget med att arbeta fram en analys av de trender som finns inom verksamhetsstyrning både inom näringslivet samt offentlig sektor. I uppdraget ingick att analysera hur verksamhetsstyrning sker rent praktiskt och vilka systemstöd som används för detta ändamål. Detta projekt innefattar både ett verksamhetsperspektiv och ett systemperspektiv. Resultatet av uppdraget skall vara till hjälp för företaget i arbetet med att utveckla ett nytt systemstöd för budget, prognos och verksamhetsplanering. Metoden som använts för inhämtning utav information, är i form av både enkäter och intervjuer. Tanken med enkäterna var att i första hand få en grundläggande information om organisationernas verksamhetsstyrning och vilka systemstöd de använde sig av inom den finansiella och operativa planeringen. Efter att ha fått en grundläggande syn på de organisationer som besvarat enkäten analyserades svaren, vilket resulterade i from utav följdfrågor. Eftersom projektet var tidsbegränsat fanns inte möjligheten till att gå vidare med alla organisationer. Istället valdes ett antal organisationer bestående av både offentliga och privata för att gå vidare med följdfrågor, det vill säga intervju. Detta arbete har framtagits genom användning av en lättrörlig metod, det vill säga en metod som ger stöd till att vara anpassbar och även flexibel efter de varierande arbetsförhållandena som uppstår under projektets gång. Denna lättrörliga metod bestämdes redan vid början av arbetet. Metoden kallas för EBREM (Event-Based Requirement Elicitation Method) som inriktar sig för att identifiera eventuella risker som kan framkomma kring arbetsprocessen. Slutsatsen som jag kommit fram till inom detta arbete är att det finns en varierande syn på vad verksamhetsstyrning egentligen innebär och hur styrningen ska ske rent praktiskt. Det som har varit väldigt gemensamt hos enkätföretagen är deras uppföljning utav finansiella planer. / Today, most organizations control and plan in some way, this yields both for the private sector as well as the public sector. There are different ways and models which can be used to control an organization, for example through balanced scorecard. Control is usually launched from central directives, such as business/operational plan, budget, forecast, performance, yield goals etc. Control can be based on more or less complex control models and is handled usefully via some form of system, but sometimes just with help of Word – and Excel – documents. Common to all control models is that they require a follow up and reporting in order to do any good. This project arose by that the request about the topic of the project matched the company´s need for timely information about how companies and organizations control and plan their activities and the support systems that are used for this purpose. The project was a mission from the company, Konsultnet Scandinavian AB. My mission was to help the company to develop an analysis of the trends that are in performance management both in business and the public sector. The assignment was to analyze how performance management is practical and which support systems are used for this purpose. This project was screened both a business perspective and a system perspective. The mission will be a help to the company in the process of developing a new system for budgeting, forecasting and business management. The methodology used for collecting and analyzing information, is in the form of both surveys and interviews. The idea of the survey was to get basic overview information about other organizations performance management and the system support they use within their financial and operational planning. After getting a basic knowledge from the organizations who had answered the survey, an analysis took place which resulted in supplementary questions. Since the project work had a deadline, it was not possible to proceed with all of the organizations. Instead, a number of organizations were chosen, including both private and public organizations. This project has been developed using an agile method, which gives support to be adaptable and flexible to the varying working conditions which takes place during the project. This agile method was decided in the beginning of this work. The method is named EBREM and stands for (Event-Based Requirement Elicitation Method) which focuses to identify any risks that may emerge around this work. The conclusion which I have reached in this work is that there are a variety of views on what performance management really means and how management should be done in practice. What has been very common in survey companies is their follow-up of total financial plans.

Cloud computing is becoming increasingly popular among all types of companies due to its inherent benefits. However, because of its infrastructure, it might be difficult to manage access rights between users and resources. To address these difficulties, Amazon Web Services (AWS) provides Identity and Access Management (IAM) and features that support the use of different access control models, for example, Role-based Access Control (RBAC) and Attribute-based Access Control (ABAC). Access control models are used for authorisation within systems to decide who gets access to what. Therefore, to determine what constitutes an efficient (the average time it takes to perform a task in AWS IAM) and secure access control model, a thorough study of background material and related work was conducted. Through this study, it was found that RBAC lacked scalability whilst ABAC lacked administrative capabilities. It was also found that flexibility and scalability were two important factors when designing access control models. Furthermore, by conducting a survey and designing an access control model for AWS through various iterations, a new access control model called Entity-centric Attribute- & Role-based Access Control (EARBAC) was developed. In an experiment comparing it with the RBAC model, the EARBAC model was found to be both efficient and secure, in addition to its flexibility and scalability. Furthermore, EARBAC was also found to be 27% faster than RBAC in AWS IAM. These results suggest that the model is useful when developing cloud infrastructures in AWS.

Bakgrund och problemdiskussion: Lagerstyrning är olika aktiviteter som rör hur ett lager hanteras och styrs. Styrningen av ett lager har en stor påverkan på ett företags lönsamhet då det hanterar de aktiviteter som berör lager och därmed också det bundna kapitalet. Lagerstyrning är dock inget som görs i en handvändning, utan det är många delar som ska stämma överens. Lagerstyrningen blir än mer komplex när företag handlar med volatila råvaror. När det kommer till lagerstyrning av produkter med volatila inköpspriser är det viktigt att ta hänsyn till dessa förändringar, för att på så sätt kunna hitta den mest optimala lagerstyrningen. Syfte: Syftet med denna studie är att undersöka vilka konsekvenser som uppstår av att Alutrade inte tar hänsyn till volatila inköpspriser i sin nuvarande lagerstyrning, samt att identifiera vilka lagerstyrningsmetoder, och därmed lagerstyrningspolicy som är lämplig att tillämpa när inköpspriser är volatila för att optimera och uppnå en kostnadseffektiv lageromsättningshastighet. Metod: Uppsatsen behandlas utifrån ett positivistiskt synsätt och ett deduktivt angreppssätt. Uppsatsen har en kvalitativ forskningsmetod men innehåller både kvalitativ och kvantitativ data. Datan har samlats in genom ostrukturerade och semistrukturerade intervjuer, samt mailintervjuer. Resultat: Eftersom Alutrade i dagsläget inte tar så stor hänsyn till de prisförändringar som råder på aluminium marknaden uppstår en del konsekvenser, vilket gör att företagets lagerstyrning påverkas negativt. För att undvika dessa konsekvenser har en lagerstyrningspolicy, som tar hänsyn till volatila inköpspriser, tagits fram. Denna policy utgår från en ABC-klassificering och innehåller lagerstyrningsmetoder såsom modifierad EOQ, beställningspunktsystem vid volatila inköpspriser, säkerhetslager som ett uppskattat antal dagars medelefterfrågan och säkerhetslager beräknat från önskad servicenivå. Med hjälp av den framtagna lagerstyrningspolicyn kan Alutrade undvika konsekvenserna och uppnå de kostnadsbesparingarna som påvisas. / Background: Inventory control is different activities related to how a warehouse is managed. The management of inventory has a big impact on a company's profitability as it manages the activities that concern the inventory and thus has an affect on the tied up capital. However, inventory control is nothing that can be rushed through, since many activities must match. The inventory control becomes even more complex when companies deals with volatile raw materials. When it comes to inventory control of these types of products, it is important to take these changes into account, in order to find the most optimal inventory control. Purpose: The purpose of this thesis is to investigate which consequences that occurs when Alutrade does not take volatile purchase prices into account, furthermore to identify which inventory control methods, and thus inventory control policy, that is suitable to apply when purchase prices are volatile to optimize and achieve a cost-effective inventory turnover. Method: The thesis is based on a positivistic and deductive approach. The study has a qualitative research method but contains both qualitative and quantitative data. The data has been collected through unstructured and semi-structured interviews, as well as mail interviews. Results: As Alutrade currently does not take the price volatility on the aluminum market into much account a number of consequences arise, which means that the company's inventory control is negatively affected. In order to avoid these consequences a inventory control policy, which takes the price volatility into account, has been developed. This policy is based on an ABC classification and contains inventory control methods such as modified EOQ, reorder point system for volatile purchase prices, safety stock as an estimated number of demand days and safety stock calculated from a desired service level. Using the developed inventory control policy, Alutrade can avoid the consequences and achieve the cost savings that are shown.

No description available.

Information flow properties are away of specifying security properties of systems ,dating back to the work of Goguen and Meseguer in the eighties. In this framework ,a system is modeled as having high-level (or confidential)events as well as low-level (or public) events, and a typical property requires that the high-level events should not “influence ”the occurrence of low-level events. In other words, the sequence of low-level events observed from a system execution should not reveal “too much” information about the high-level events that may have taken place. For example, the trace-based “non-inference” property states that for every trace produced by the system, its projection to low-level events must also be a possible trace of the system. For a system satisfying non-inference, a low-level adversary (who knows the language generated by the system) viewing only the low-level events in any execution cannot infer any in-formation about the occurrence of high-level events in that execution. Other well-known properties include separability, generalized non-interference, non-deducibility of outputs etc. These properties are trace-based. Similarly there is another class of properties based on the structure of the transition system called bisimulation-based information flow properties, defined by Focardiand Gorrieriin1995. In our thesis we study the problem of model-checking the well-known trace-based and bisimulation-based properties for some popular classes of infinite-state system models. We first consider trace-based properties. We define some language-theoretic operations that help to characterize language-inclusion in terms of satisfaction of these properties. This gives us a reduction of the language inclusion problem for a class of system models, say F, to the model-checking problem for F, whenever F, is effectively closed under these language-theoretic operations. We apply this result to show that the model-checking problem for Petri nets, push down systems and for some properties on deterministic push down systems is undecidable. We also consider the class of visibly pushdown systems and show that their model-checking problem is undecidable in general(for some properties).Then we show that for the restricted class of visibly pushdown systems in which all the high (confidential) event are internal, the model-checking problem becomes decidable. Similarly we show that the problem of model-checking bisimulation-based properties is undecidable for Petrinets, pushdown systems and process algebras. Next we consider the problem of detecting information leakage in programs. Here the programs are modeled to have low and high inputs and low outputs. The well known definition of“ non-interference” on programs says that in no execution should the low outputs depend on the high inputs. However this definition was shown to be too strong to be used in practice, with a simple(and considered to be safe)“password-checking” program failing it.“Abstract non-interference(ANI)”and its variants were proposed in the literature to generalize or weaken non-interference. We call these definitions qualitative refinements of non-interference. We study the problem of model-checking many classes of finite-data programs(variables taking values from a bounded domain)for these refinements. We give algorithms and show that this problem is in PSPACE for while, EXPTIME for recursive and EXPSPACE for asynchronous finite-data programs. We finally study different quantitative refinements of non-interference pro-posed in the literature. We first characterize these measures in terms of pre images. These characterizations potentially help designing analysis computing over and under approximations for these measures. Then we investigate the applicability of these measures on standard cryptographic functions.