Space Savings Research Articles

Applications of Parameterized st-Orientations

An st-orientation of a biconnected undirected graph denes a directed graph with no cycles, a single source s and a single sink t. Given an undirected graph G as input, linear-time algorithms have been proposed for computing an st-orientation of G. Such an orientation is useful especially in graph drawing algorithms which use it at their rst stage [23]. Namely, before they process the original undirected graph they receive as input, they transform it into an st-DAG, by computing an st-orientation of it. In this paper we observe that using st-orientations of dierent longest path lengths in various applications can result in dierent solutions, each one having its own merit. Guided by this intuition, we present results concerning applications of proposed algorithms for longest path parameterized st-orientations. Specically, we show how to achieve considerable space savings (e.g., O(n)) for visibility representations of planar graphs by using st-orientations computed by algorithms that can control the length of the longest path. Also, we apply our results to the graph coloring problem, where we use an st-orientation as an intermediate step to compute a good coloring of a graph, and to other problems, such as computing space-ecient orthogonal drawings and longest paths.

Report Preparation on Result Turnaround Time and Savings in Cost, Time, and Space

To evaluate whether introduction of a densitometry workflow, data-storage, and reporting software system would result in streamlined workflow with fewer expenses and quicker result turnaround time. BoneStation was implemented March 30, 2009, in a large, urban, tertiary referral center performing more than 6000 bone mineral density studies annually at 3 different geographic sites. The times of scan acquisition, report preparation, and final signature in the online medical record were recorded, and the delays from scan to report and from scan to final signature in the online medical record were calculated for each patient during 2 representative weeks before (n = 274) and 2 weeks after (n = 235) implementation of BoneStation. Use of BoneStation reduced time from scan to report from 2.11 +/- 0.16 days to 0.46 +/- 0.05 days (P<.001). BoneStation saved our practice $8.94 per scan, while costing only $3 per scan, resulting in net savings. Considering that the total reimbursement from Medicare in 2010 for dual-energy x-ray absorptiometry is projected to be $55.44, this constitutes cost savings of 10.7% of the total reimbursement. The introduction of a specialized electronic medical system for data storage and reporting reduced costs and improved result turnaround time in a densitometry practice.

Performance comparison between the key representation database and the original database

Statistical database (SDB) provides statistics (such as sum, average, etc.) on subsets of records, and individuals' data should not be disclosed. Key representation auditing scheme (KRAS) is proposed to guarantee the security of online and dynamic SDBs. The core idea is to convert the original database into key representation database (KRDB), and convert each new query from string representation into key representation query (KRQ) and store it in the audit query table (AQ table). Three audit stages are proposed to protect SDBs from being disclosed. Also, cost estimation for this scheme is performed, and we illustrate the savings in CPU time and storage space using KRDB. In this paper, we provide statistical analysis to compare between the means/variances of the original database and the KRDB populations. Comparisons are provided in terms of record size and number of blocks. The results of the tests showed that the differences are statistically significant.

Transmission of Shielding Materials for Particle Therapy Facilities

A typical particle therapy facility consists of an injector, a cyclotron or a synchrotron, a high-energy transport beam line, several treatment rooms including fixed-beam and gantry rooms, and even a research area. During the operation of these facilities, radiation is produced with neutrons being the dominant component outside the shielding. These facilities have large amounts of shielding with concrete thicknesses ranging up to ~5 m or more. Space required for shielding can be minimized by using composite shielding or high-density material such as Ledite® (manufactured by Atomic International, Frederick, Pennsylvania). Transmission data for radiation from protons and carbon ions incident on tissue targets with energies in the therapeutic energy range of interest were derived using the Monte Carlo code FLUKA for three different compositions of Ledite. Use of Ledite® or composite shielding results in space savings when compared to concrete.

Assessing the Potential for a National Print Repository: Results of an Australian Overlap Study

This paper reports on research assessing the potential space savings that can be made if Australian academic libraries implement a national repository for the storage of legacy print collections. The paper includes data derived from a collection overlap study based on members of the CARM (CAVAL Archival and Research Materials) Centre to estimate the impact of a fully implemented national repository. It includes a calculation of the shelf and floor space that libraries might potentially retrieve for other purposes.

Assessing the Potential for a National Print Repository: Results of an Australian Overlap Study

This paper reports on research assessing the potential space savings that can be made if Australian academic libraries implement a national repository for the storage of legacy print collections. The paper includes data derived from a collection overlap study based on members of the CARM (CAVAL Archival and Research Materials) Centre to estimate the impact of a fully implemented national repository. It includes a calculation of the shelf and floor space that libraries might potentially retrieve for other purposes.

Computing Robust Plans in Continuous Domains

We define the robustness of a sequential plan as the probability that it will execute successfully despite uncertainty in the execution environment. We consider a rich notion of uncertainty over continuous domains that includes stochastic action effects, and changes to state variables due to unpredictable exogenous events. Given a characterization of this uncertainty in terms of probability distributions (e.g., Gaussian) our contributions are two-fold: First, we describe a novel approach to computing the robustness of a plan in the situation calculus, which (a) separates the projection problem from the problem of reasoning about probability, and (b) explicitly reveals the relevance and statistical independence of random variables and events (i.e., conditions that contain random variables). Then, building on this approach, we describe a forward search based planner that generates maximally robust plans, exploiting the revealed structure for speed-up. Preliminary empirical results demonstrate that our approach can realize exponential savings in both time and space compared to the classical sampling approach.

Graph Compression by BFS

The Web Graph is a large-scale graph that does not fit in main memory, so that lossless compression methods have been proposed for it. This paper introduces a compression scheme that combines efficient storage with fast retrieval for the information in a node. The scheme exploits the properties of the Web Graph without assuming an ordering of the URLs, so that it may be applied to more general graphs. Tests on some datasets of use achieve space savings of about 10% over existing methods.

Large diameter RO elements: A summary of recent operating experiences

In recent years, the use of large diameter reverse osmosis (RO) elements has gained some considerable momentum as a potential means of lowering the overall cost of desalination by membrane treatment. By the beginning of 2008, a number of systems have been installed so operating experience exists. Along with some design issues, this paper will review some of the currently operating installations and discuss why large diameter elements were selected for specific projects. The commercial availability of large diameter elements also offers opportunities for alternative system and building layouts. These considerations have implications for cost and space savings. This paper will also review the design approach for large volume systems using the large diameter elements, looking at factors such as the array and rack designs, plant layout and pump sizing.

A probabilistic approach to determine mobile station location with application in cellular networks

A probabilistic approach to the mobile station location problem is analyzed, and an algorithm that implements such an approach is presented. Information about the mobile station location is collected in the form of two-dimensional probability density functions provided from various sources. Combining the probability density functions into a joined probability density function is addressed. To provide computational efficiency, a method to limit the space of a possible location of the mobile station to a rectangular region of the minimal size is presented. Discretization of space is performed next, reducing the probability density functions to matrices of probabilities. The algorithm for combining the probability density functions is adjusted for an application with the matrices of probabilities. To reduce the computational burden further, probability density functions of the exclusion type, taking only two values, zero and nonzero, are introduced, providing savings in storage space and computational time. Information about the timing advance parameter value and the received signal level are interpreted by probability density functions of the exclusion type. Application of the algorithm is illustrated by two sets of measurements performed in an urban and a suburban region.

Integration method delivers yield improvements, space savings in sensor arrays

Integration method delivers yield improvements, space savings in sensor arrays

Distributed Markovian Bisimulation Reduction aimed at CSL Model Checking

The verification of quantitative aspects like performance and dependability by means of model checking has become an important and vivid area of research over the past decade.An important result of that research is the logic CSL (continuous stochastic logic) and its corresponding model checking algorithms. The evaluation of properties expressed in CSL makes it necessary to solve large systems of linear (differential) equations, usually by means of numerical analysis. Both the inherent time and space complexity of the numerical algorithms make it practically infeasible to model check systems with more than 100 million states, whereas realistic system models may have billions of states.To overcome this severe restriction, it is important to be able to replace the original state space with a probabilistically equivalent, but smaller one. The most prominent equivalence relation is bisimulation, for which also a stochastic variant exists (Markovian bisimulation). In many cases, this bisimulation allows for a substantial reduction of the state space size. But, these savings in space come at the cost of an increased time complexity. Therefore in this paper a new distributed signature-based algorithm for the computation of the bisimulation quotient of a given state space is introduced.To demonstrate the feasibility of our approach in both a sequential, and more important, in a distributed setting, we have performed a number of case studies.

Capacitively coupled electrical substitution for resistive bolometer enhancement

A new electrical substitution method for resistive bolometers is proposed to operate them in a closed-loop configuration. This method was implemented and evaluated with a resistive bolometer based on metallic layers over a 120 µm thick glass membrane. Based on an electrical substitution (ES) directly at the place of the resistive sensing element, the new method allows for space savings and a simplification of the technological manufacturing while maintaining the time response improvement linked to a closed-loop operation. Compared to a previously available ES solution, this new method is applicable to all resistive bolometers. Time response and signal-to-noise ratio (SNR) were evaluated through measurements and compared for three operation configurations of the resistive bolometer: open loop, classical ES closed loop and with the proposed capacitively coupled electrical substitution (CCES) closed loop.

Just-in-Time Connectivity for Large Spiking Networks

The scale of large neuronal network simulations is memory limited due to the need to store connectivity information: connectivity storage grows as the square of neuron number up to anatomically relevant limits. Using the NEURON simulator as a discrete-event simulator (no integration), we explored the consequences of avoiding the space costs of connectivity through regenerating connectivity parameters when needed: just in time after a presynaptic cell fires. We explored various strategies for automated generation of one or more of the basic static connectivity parameters: delays, postsynaptic cell identities, and weights, as well as run-time connectivity state: the event queue. Comparison of the JitCon implementation to NEURON's standard NetCon connectivity method showed substantial space savings, with associated run-time penalty. Although JitCon saved space by eliminating connectivity parameters, larger simulations were still memory limited due to growth of the synaptic event queue. We therefore designed a JitEvent algorithm that added items to the queue only when required: instead of alerting multiple postsynaptic cells, a spiking presynaptic cell posted a callback event at the shortest synaptic delay time. At the time of the callback, this same presynaptic cell directly notified the first postsynaptic cell and generated another self-callback for the next delay time. The JitEvent implementation yielded substantial additional time and space savings. We conclude that just-in-time strategies are necessary for very large network simulations but that a variety of alternative strategies should be considered whose optimality will depend on the characteristics of the simulation to be run.

Reinterpreting the Hospital Corridor: “Wasted Space” or Essential for Quality Multidisciplinary Clinical Care?

The planning of New South Wales (NSW) and other Australian health facilities is guided by the Australasian Health Facility Guidelines (AHFG), which prescribe allowances for circulation (corridors and similar areas for movement between spaces) of between 10% and 40% of functional floor areas. A further allowance of up to 28% for Travel and Engineering is then assumed (University of NSW & Health Capital Asset Managers' Consortium, 2005). Therefore the "circulation" and "travel" space manifested as the corridors and similar movement spaces within health facilities is both extensive and expensive. Consequently, such space often becomes regarded as a necessary evil and, in the name of efficiency, is often minimized wherever possible. This paper revisits the view that corridor space allocations (circulation) must always be minimized to achieve design or functional efficiencies. Minimizing circulation or travel inevitably assumes that the realized space savings will then be reallocated to "more important" areas of the facility. Yet the corridors and other movement spaces also are very important to the functioning of multidisciplinary clinical teams and the quality of care delivery. Ultimately, inflexibly reducing the space allocated to such spaces may be regarded as a false economy.

Access pattern-based code compression for memory-constrained systems

As compared to a large spectrum of performance optimizations, relatively less effort has been dedicated to optimize other aspects of embedded applications such as memory space requirements, power, real-time predictability, and reliability. In particular, many modern embedded systems operate under tight memory space constraints. One way of addressing this constraint is to compress executable code and data as much as possible. While researchers on code compression have studied efficient hardware and software based code compression strategies, many of these techniques do not take application behavior into account; that is, the same compression/decompression strategy is used irrespective of the application being optimized. This article presents an application-sensitive code compression strategy based on control flow graph (CFG) representation of the embedded program. The idea is to start with a memory image wherein all basic blocks of the application are compressed, and decompress only the blocks that are predicted to be needed in the near future. When the current access to a basic block is over, our approach also decides the point at which the block could be compressed. We propose and evaluate several compression and decompression strategies that try to reduce memory requirements without excessively increasing the original instruction cycle counts. Some of our strategies make use of profile data, whereas others are fully automatic. Our experimental evaluation using seven applications from the MediaBench suite and three large embedded applications reveals that the proposed code compression strategy is very successful in practice. Our results also indicate that working at a basic block granularity, as opposed to a procedure granularity, is important for maximizing memory space savings.

Editorial SMI 64

Henning Muller, Eusebio Passaretti This special issue of Swiss Medical Informatics (SMI No 64) brings together the best articles submitted to the 21st Congress of the Swiss Society for Medical Informatics (SGMI-SSIM). The congress took place in Sierre (Valais) at the University of Applied Sciences Western Switzerland (HES SO) from 5–6 June 2008, and featured 4 invited presentations, 19 oral scientific presentations and 6 scientific posters. In total, 27 papers were submitted and reviewed by the scientific programme committee on the basis of novelty of approach and technical quality of presentation. From this evaluation process the best eight papers were selected for the present special issue covering a wide range of subjects from the field of medical informatics. Two other papers were added for their practical interest to SGMI-SSIM members, bringing the total up to ten papers. Two articles deal with financial analysis of hospital data [1, 2] and two with image management and storage [3, 4], partly in the context of diagnostic aid. The patient record is traditionally well represented at these conferences, from access models for research [5] to patient identification [6]. Finally, two articles on specific diseases or disease categories are presented [7, 8]. The articles additionally selected describe practical approaches, one to the choice of an integrated electronic patient record at the Inselspital Berne [9], and the other on context-navigated search inside a clinical patient record [10]. In the first article [1] Rodolphe Meyer describes an extensive analysis of data on hospitals to define models measuring the impact of particular information and communication technologies on hospital productivity. This paper also received the award for the best scientific contribution to the conference. Alexandre Gnaegi [2] then describes a project on data mining within attributes of a hospital’s data warehouse in order to estimate income for released but not fully coded patients. The goal is to estimate the income for cases that have left the hospital within a reporting period but have not been fully coded. Off-the-shelf data mining tools have markedly increased the precision of such estimations for the Valais hospital network. Mechthild Uesback [3] describes the introduction of a PACS in Zurich University Hospital from 2004–2007. The results were major space savings and financial gains, with optimisation of workflows engendering a more productive work environment. Adrien Depeursinge then presents a diagnostic aid tool for emergency radiology [4] in the diagnosis of interstitial lung diseases. The tool analyses the texture of the lung tissue in CT images to classify it into healthy and several abnormal tissues. Clinical data are also taken into account since age or environmental factors can significantly change the lung texture properties. Jimison Iavindrasana’s article [5] reports on a framework for data access to a life clinical record with all its security constraints. The context is the EU project AneurIST whose aim is to improve the treatment and understanding of cerebral aneurysms. Tobias Mettler [6] then presents an approach to patient identification and tracking in a processoriented manner. A global view of the identification process across organisations focused on the patient can significantly improve identification. Marc Oertle [7] describes another diagnostic aid tool which targets patients with chronic heart failure and implements evidence-based medicine using information and communication technologies. The goal is standardisation of the care process to reduce variability in treatment. Christina Lovis [8] then outlines another European Union-funded project also targeting a particular group of diseases: nosocomial infections. The goal of this project is to develop new ways of fighting antibiotic resistances of bacteria by analysing large amounts of routine clinical data. The outcome of this project is expected to be IT-biotics, IT technology to fight bacteria. Oliver Handgratiger [9] describes, in the setting of the Inselspital Bern, the process of selecting a new electronic patient record covering all medical specialties and partners in the hospital, and outlines the criteria for selecting a particular solution. The effort to obtain each criterion with its discriminative power is then described. This practical and detailed approach should be useful for other hospitals as well. In the last article of this issue, Ela Bielecki [10] presents Solothurn hospital’s project for Prof. Dr. Henning Muller University of Applied Sciences Sierre & University and Hospitals of Geneva Business Information Systems Institute HES-SO Valais, TechnoArk 3 3960 Sierre, Switzerland henning.mueller@hevs.ch

Scoring Unusual Words with Varying Mismatch Errors

Patterns consisting of strings with a bounded number of mismatches are central to coding theory and find multiple applications in text processing and computational biology. In this latter field, the presence of over-represented patterns of this kind has been linked, for instance, to modeling regulatory regions in biosequences. The study and computation of expected number of occurrences and related scores for these patterns is made difficult by the sheer explosion of the roster of candidates that need to be evaluated. In recent work, properties of pattern saturation and score monotonicity have proved capable to mitigate this problem. In such a context, expectation and score monotonicity has been established within the i.i.d. model for all cases of interest except that of a fixed word length with a varying number of mismatches. The present paper completes this investigation by showing that the expected number of occurrences in a textstring for such a word is bi-tonic, that is, behaves as a unimodal function of the number of errors. This extends to this case the time and space savings brought about by discovery algorithms based on pattern saturation.

Replication degree customization for high availability

Object replication is a common approach to enhance the availability of distributed data-intensive services and storage systems. Many such systems are known to have highly skewed object request probability distributions. In this paper, we propose an object replication degree customization scheme that maximizes the expected service availability under given object request probabilities, object sizes, and space constraints (e.g., memory/storage capacities). In particular, we discover that the optimal replication degree of an object should be linear in the logarithm of its popularity-to-size ratio. We also study the feasibility and effectiveness of our proposed scheme using applications driven by real-life system object request traces and machine failure traces. When the data object popularity distribution is known a priori, our proposed customization can achieve 1.32-2.92 "nines" increase in system availability (or 21-74% space savings at the same availability level) compared to uniform replication. Results also suggest that our scheme requires a moderate amount of replica creation/removal overhead (weekly changes involve no more than 0.24% objects and no more than 0.11% of total data size) under realistic object request popularity changes.

Hygienische und ökonomische Bedeutung von Schleusen im Krankenhaus: Die bauliche Umsetzung der Richtlinie des Bundesgesundheitsamtes*

The hygienic importance of barrier zoning in hospitals has been evaluated on the basis of the relevant international literature between 1970 and 1989. There have been only a very few pertinent publications and in none has there been any pointer which would support the hypothesis of barriers having an infection-preventing effect. Using four University Hospitals in Baden-Würtemberg as paradigms, a model was prepared for calculating what space and cost savings were possible, if a simpler system could be installed, instead of the one demanded under federal regulations and already planned for the four hospitals. It was found that it would save a realizable area of 319,5 m2 at a potential cost saving of DM 1,138,335. By dispensing with hygienically not justifiable building work at the planning stage of new hospitals considerable greater costs could be avoided.