Coxeter transformation and inverses of Cartan matrices for coalgebras

Let C be a coalgebra and consider the Grothendieck groups of the categories of the socle-finite injective right and left C-comodules. One of the main aims of the paper is to study Coxeter transformation, and its dual, of a pointed sharp Euler coalgebra C, and to relate the action of these transformations on a class of indecomposable finitely cogenerated C-comodules N with almost split sequences starting or ending with N. We also show that if C is a pointed K-coalgebra such that the every vertex of the left Gabriel quiver of C has only finitely many neighbours, then for any indecomposable non-projective left C-comodule N of finite K-dimension, there exists a unique almost split sequence of finitely cogenerated left C-comodules ending at N. We show that the dimension vector of the Auslander-Reiten translate given by the Coxeter transformation, if C is hereditary, or more generally, if inj.dim DN=1 and Hom(C,DN)=0

Rail Track Maintenance Planning: An Assessment Model

In Australia, railway track maintenance costs comprise between 25-35 percent of total freight train operating costs. Track maintenance planning models have been shown to reduce maintenance costs by 5 to 10 percent though improved planning. This paper describes a model which has been developed to deal with the track maintenance planning function at the medium to long-term levels. This model simulates the impacts of degrading railway track conditions and related maintenance work, in contrast to tradition models that mainly use expert systems. The model simulates the degrading track condition using an existing track degradation model. Track condition data from that model is used to determine if safety related speed restrictions are needed and what immediate maintenance work may be required for safe train operations. The model outputs the net present value of the benefits of undertaking a given maintenance strategy, when compared with a base-case scenario. The model approach has advantages over current models in investigating what if scenarios. The track engineer can assess the possible benefits in reduced operating costs from upgrading track infrastructure or from the use of improved maintenance equipment. After describing the model inputs and the assumptions used, the paper deals with the simulation of track maintenance and of train operating costs over time. The results of applying the model to a test track section using a number of different maintenance strategies are also given

Submodule Categories of Wild Representation Type

Let $\Lambda$ be a commutative local uniserial ring of length at least seven with radical factor ring $k$. We consider the category $S(\Lambda)$ of all possible embeddings of submodules of finitely generated $\Lambda$-modules and show that $S(\Lambda)$ is controlled $k$-wild with a single control object $I\in S(\Lambda)$. In particular, it follows that each finite dimensional $k$-algebra can be realized as a quotient \End(X)/\End(X)_I of the endomorphism ring of some object $X\in S(\Lambda)$ modulo the ideal \End(X)_I of all maps which factor through a finite direct sum of copies of $I$.Comment: 13 page

Understanding Database Reconstruction Attacks on Public Data

In 2020 the U.S. Census Bureau will conduct the Constitutionally mandated decennial Census of Population and Housing. Because a census involves collecting large amounts of private data under the promise of confidentiality, traditionally statistics are published only at high levels of aggregation. Published statistical tables are vulnerable to DRAs (database reconstruction attacks), in which the underlying microdata is recovered merely by finding a set of microdata that is consistent with the published statistical tabulations. A DRA can be performed by using the tables to create a set of mathematical constraints and then solving the resulting set of simultaneous equations. This article shows how such an attack can be addressed by adding noise to the published tabulations, so that the reconstruction no longer results in the original data

Rancang Bangun Roller Conveyor Adjustable dengan Metode Banchmarking

Abstract Technology that is increasingly rapidly developing encourages all parties to compete to create or develop better technology, and has great benefits and efficiency. In these moving activities, an efficient, practical and economical means of transport is needed to facilitate the transfer process. The objectives of this research are: 1. Applying Benchmarking method in the design of adjustable roller conveyor. 2. Analyze the function and material components, and record the advantages and disadvantages. This research was conducted using the Benchmarking method, the results of this study were in the form of product designs and products for adjustable roller conveyors as material transferers. The conclusions of this study are: 1. Design of an adjustable roller conveyor based on benchmaking with two Roller conveyor tools, this tool is very well suited and very easy in the transfer process, especially for materials that are very far away. 2. The manufacture of adjustable roller conveyors has gone through an analysis process in terms of function, and the component materials used are in accordance with the aspects that have been designed with the advantages and disadvantages made

Book Review of iPhone and iOS Forensic: Investigation, Analysis and Mobile Security for Apple iPhone, iPad and iOS Devices

Hoog, A., and Strzempka, K. (2011).  iPhone and iOS Forensic: Investigation, Analysis and Mobile Security for Apple iPhone, iPad and iOS Devices. Syngress, Elsevier, xv + 310 pages; ISBN-10: 1597496596; ISBN-13: 978-1597496599, $69.95Reviewed by Simson Garfinkel, Naval Postgraduate SchoolIn April 2011 news outlets around the world revealed shocking news about Apple’s iPhone: for reasons that were not apparently clear, every iPhone contained a small SQLite database that logged where and when the user had been whenever the phone was turned on, and those records went back for pretty much as long as the user had owned their phone. Apple eventually declared that the data cache was the result of a bug and issued a software update to prune the database (it had previously grown without limit). Privacy activists rejoiced that their beloved iPhones were once again trustworthy. But forensics examiners just shook their heads: many had known about the iPhone’s tracking capabilities for more than a year and had kept quiet. They had made good use of that data. Apple’s pro-privacy patch was actually a setback for law enforcement.(see PDF for full review)</p

Book review – The rise of Africa’s middle class: Myths, realities and critical engagements, by Henning Melber(ed.)

The Rise of Africa’s Middle Class: Myths, Realities and Critical Engagements seeks to wrestle back the African middle class debate from the Afro-optimists with mixed success, according to LSE’s Rebecca Simson

Rank Dependent Utility, Tax Evasion and Labor Supply

In the simple Allingham-Sandmo portfolio model of tax evasion an expected utility maximizer will cheat more than what is estimated in empirical studies. Two main types of explanation have been suggested as solutions to this puzzle: (1) Tax payers act according to some non-expected utility theory, and (2) Individual ethical norms and social stigma induce people not to cheat. In the present study we test two hypotheses within these broad explanations: (1) Tax payers are weighting subjective probabilities of being penalised according to the rank dependent utility theory, and (2) Tax payers’ beliefs about social norms have an effect on their decision to evade taxes. Our model is characterized by a simultaneous determination of tax evasion and labour supply, including the effect on tax payers of a social norm of not cheating. Using Norwegian survey data our hypotheses are corroborated. Our estimates imply that if the objective probability of being penalized is, say 3 %, the weighted probability is about 23 %. Our study provides an independent confirmation of the rank dependent expected utility theory. The model explains data 53% better than pure random choices and predicts hours worked in the regular economy, among tax evaders as well non tax evaders, rather precisely. The model is an example of a two sector choice model and the results indicate that an overall wage increase may shift labor supply away from the irregular part of the economy towards the regular.labor supply, tax evasion, rank dependent utility