4,183 research outputs found
A Subgradient Method for Free Material Design
A small improvement in the structure of the material could save the
manufactory a lot of money. The free material design can be formulated as an
optimization problem. However, due to its large scale, second-order methods
cannot solve the free material design problem in reasonable size. We formulate
the free material optimization (FMO) problem into a saddle-point form in which
the inverse of the stiffness matrix A(E) in the constraint is eliminated. The
size of A(E) is generally large, denoted as N by N. This is the first
formulation of FMO without A(E). We apply the primal-dual subgradient method
[17] to solve the restricted saddle-point formula. This is the first
gradient-type method for FMO. Each iteration of our algorithm takes a total of
foating-point operations and an auxiliary vector storage of size O(N),
compared with formulations having the inverse of A(E) which requires
arithmetic operations and an auxiliary vector storage of size . To
solve the problem, we developed a closed-form solution to a semidefinite least
squares problem and an efficient parameter update scheme for the gradient
method, which are included in the appendix. We also approximate a solution to
the bounded Lagrangian dual problem. The problem is decomposed into small
problems each only having an unknown of k by k (k = 3 or 6) matrix, and can be
solved in parallel. The iteration bound of our algorithm is optimal for general
subgradient scheme. Finally we present promising numerical results.Comment: SIAM Journal on Optimization (accepted
ACE: A Consent-Embedded privacy-preserving search on genomic database
In this paper, we introduce ACE, a consent-embedded searchable encryption
scheme. ACE enables dynamic consent management by supporting the physical
deletion of associated data at the time of consent revocation. This ensures
instant real deletion of data, aligning with privacy regulations and preserving
individuals' rights. We evaluate ACE in the context of genomic databases,
demonstrating its ability to perform the addition and deletion of genomic
records and related information based on ID, which especially complies with the
requirements of deleting information of a particular data owner. To formally
prove that ACE is secure under non-adaptive attacks, we present two new
definitions of forward and backward privacy. We also define a new hard problem,
which we call D-ACE, that facilitates the proof of our theorem (we formally
prove its hardness by a security reduction from DDH to D-ACE). We finally
present implementation results to evaluate the performance of ACE
An Efficient Way to Allocate and Read Directory Entries in the Ext4 File System
CÂlem t©to prce je zvit vkon sekvenĂnÂho prochzen adres v souborov©m syst©mu ext4. Datov struktura HTree, jen je v souĂasn© dobĂ pouita k implementaci adresu v ext4 zvld velmi dobe nhodn© pÂstupy do adrese, avak nen optimalizovna pro sekvenĂn prochzenÂ. Tato prce pin analzu tohoto probl©mu. Nejprve studuje implementaci souborov©ho syst©mu ext4 a dalÂch subsyst©mu Linuxov©ho jdra, kter© s nÂm souvisÂ. Pro vyhodnocen vkonu souĂasn© implementace adresov©ho indexu byla vytvoena sada test. Na zkladĂ vsledk tĂchto test bylo navreno eenÂ, kter© bylo nslednĂ implementovno do Linuxov©ho jdra. V zvĂru t©to prce naleznete vyhodnocen pÂnosu a porovnn vkonu nov© implementace s dalÂmi souborovmi syst©my v Linuxu.The aim of this thesis is to improve the performance of sequential directory traversal in the ext4 file system. The HTree data structure that is used to store directories in ext4 at the moment works very well for random accesses, however, it is not optimal when it comes to traversing a directory sequentially. This thesis investigates the issue; it explores the implementation of ext4 and the associated Linux kernel subsystems. To assess the performance of the directory index, a set of test cases and benchmarks was implemented. Based on the analysis, an optimization was designed and implemented to the ext4 driver within the Linux kernel. The implementation was tested, evaluated, and compared to other native Linux file systems in the last chapter of this document.
Characteristics of the Menstrual Cycle After Discontinuation of Oral Contraceptives
Background: Menstrual cycle function may continue to be altered after discontinuation of oral contraceptives (OC). Few studies have been published on the effects of recent OC use on menstrual cycle parameters; none have examined characteristics of the menstrual flow or the quality of cervical mucus. The purpose of this retrospective matched cohort study is to assess biomarkers of the menstrual cycle after discontinuation of OCs.
Methods: Among a sample of women who daily recorded observations of menstrual cycle biomarkers, 70 women who had recently discontinued OCs were randomly matched by age and parity with 70 women who had not used OCs for at least 1 year. Outcomes investigated included overall cycle length, length of the luteal phase, estimated day of ovulation, duration of menstrual flow, menstrual intensity, and mucus score. Differences between recent OC users and controls were assessed using random effects modeling.
Results: Recent OC users had statistically significantly lower scores for mucus quality for cycles 1 and 2. Additionally, OC users had a later estimated day of ovulation that was statistically significant in cycle 2 and a decreased intensity of menstrual flow that was significant in the first four cycles (difference = â0.48 days). In random effects modeling, all these parameters were significantly different for the first six cycles combined.
Conclusions: Menstrual cycle biomarkers are altered for at least two cycles after discontinuation of OCs, and this may help explain the temporary decrease in fecundity associated with recent OC use
A modular methodology for converting large, complex books into usable, accessible and standards-compliant ebooks
This report describes the methodology used for ebook creation for the Glasgow Digital Library (GDL), and provides detailed instructions on how the same methodology could be used elsewhere. The document includes a description and explanation of the processes for ebook creation followed by a tutorial
A Business Continuity Solution for Telecommunications Billing Systems
The billing system is a critical component in a Telecommunications service provider\u27s suite of business support systems - without the billing system the provider cannot invoice their customers for services provided and therefore cannot generate revenue. Typically billing systems are hosted on a single large Unix/Oracle system located in the company\u27s data centre. Modern Unix servers with their redundant components and hot swap parts are highly resilient and can provide levels of availability when correctly installed in properly managed data centre with uninterruptible power supplies, cooling etc. High Availability clustering through the use of HP MC/ServiceGuard, Sun Cluster, IBM HACMP (High Availability Cluster Multi-Processing) or Oracle Clusterware/RAC (Real Application clusters) can bring this level of availability even higher. This approach however can only protect against the failure of a single server or component of the system, it cannot protect against the loss of an entire data centre in the event of a disaster such as a fire, flood or earthquake. In order to protect against such disasters it is necessary to provide some form of backup system on a site sufficiently remote from the primary site so that it would not be affected by any disaster, which might befall the primary site. This paper proposes a cost effective business continuity solution to protect a Telecommunications Billing system from the effects of unplanned downtime due to server or site outages. It is aimed at the smaller scale tier 2 and tier 3 providers such as Mobile Virtual Network Operators (MVNOs) and startup Competitive Local Exchange Carriers (CLECs) who are unlikely to have large established IT systems with business continuity features and for whom cost effectiveness is a key concern when implementing IT systems
Formalizing Data Deletion in the Context of the Right to be Forgotten
The right of an individual to request the deletion of their personal data by
an entity that might be storing it -- referred to as the right to be forgotten
-- has been explicitly recognized, legislated, and exercised in several
jurisdictions across the world, including the European Union, Argentina, and
California. However, much of the discussion surrounding this right offers only
an intuitive notion of what it means for it to be fulfilled -- of what it means
for such personal data to be deleted.
In this work, we provide a formal definitional framework for the right to be
forgotten using tools and paradigms from cryptography. In particular, we
provide a precise definition of what could be (or should be) expected from an
entity that collects individuals' data when a request is made of it to delete
some of this data. Our framework captures several, though not all, relevant
aspects of typical systems involved in data processing. While it cannot be
viewed as expressing the statements of current laws (especially since these are
rather vague in this respect), our work offers technically precise definitions
that represent possibilities for what the law could reasonably expect, and
alternatives for what future versions of the law could explicitly require.
Finally, with the goal of demonstrating the applicability of our framework
and definitions, we consider various natural and simple scenarios where the
right to be forgotten comes up. For each of these scenarios, we highlight the
pitfalls that arise even in genuine attempts at implementing systems offering
deletion guarantees, and also describe technological solutions that provably
satisfy our definitions. These solutions bring together techniques built by
various communities
- âŠ