Blockage Rates Research Articles

Solving GMPLS Multi-Region Path Constraints

In this letter, we propose a novel binary integer program (BIP) to obtain the optimal and correct combination of switch type per link, and adaptation capabilities per node, along a multi-region traffic engineered label switched path (TE-LSP) in a generalized multiprotocol label switching (GMPLS) network. The proposed BIP considers constraints such as the nesting/un-nesting order of LSPs, the adaptation capacity per node, the bandwidth capacity per link, as well as efficiency. By efficiency constraint we refer to opting primarily for nesting/un-nesting as opposed to conversion which is a resource demanding process. Numerical results show that applying the proposed BIP in a constraint shortest path first (CSPF) algorithm achieves lower blockage rates and outperforms an existing graph transformation method which is the closest related work to our proposal.

Radiation blockage in small scale PMMA combustion

Fuel vapors, soot and products of combustion near a burning fuel surface often block much of the radiative heat feedback to the fuel surface of a burning object. The blockage phenomenon was clearly observed in experiments of small 9.5 cm diameter PMMA pool fires subjected to external radiation burning in ambient atmospheres of different oxygen concentrations. The measurements are explained by a one-dimensional model of a diffusion flame, which focuses on the radiant absorption and emission of the soot–gas mixture of the flame. An approximate Band Model was developed and inserted into Radcal to compute gas absorption and emission from MMA vapor, CO 2 and H 2O. The Radcal results are included in the one-dimensional diffusion flame model to provide a greater understanding of the radiation blockage and burning rates in various ambient atmospheres and externally imposed radiant heat fluxes. A comparison between experimental data and model prediction shows a good agreement.

Sewer Performance Reporting: Factors That Influence Blockages

Managing sewer blockages represents a significant operational challenge for water utilities. In Australia, company-level blockage rates are used to compare the effectiveness of the management strategies of different utilities. Anecdotal evidence suggests that this basis may not be a fair one for comparison because blockages are influenced by a range of factors beyond management control and vary from company to company. This issue was investigated as part of a broader research effort on sewer-blockage management undertaken in conjunction with the Water Services Association of Australia (WSAA) and its members. A Web-based survey was used to collate expert opinion on factors that influence blockage rate. The identified factors were then investigated in an exploratory analysis of blockage-related data provided by two participating utilities, supported by literature reviews. The results indicate that blockage rate is influenced by a range of factors, including asset attributes, climatic conditions, water consumption, and soil type. Because these factors vary from utility to utility, this research supports the finding that company-level blockage rate in itself is not an appropriate metric for comparing management effectiveness.

Prediction of SG Tube Support Plate Flow Area Blockage Rate Using SG Wide Range Level Measurements and Hydrodynamic Analysis

Some nuclear power plants have recently experienced hydrodynamic instability in steam generators (SGs). Instability, if present in the SG of a pressurized water reactor, results in the periodic oscillation of the water level, steam flow, feedwater flow, and the flow through the circulation loop. In this instability analysis, the major parameters are the power level and flow area of the tube support plate (TSP). The threshold power above which instability may occur is generated by variations in TSP flow area. The current method of estimating the blockage rate is the visual inspection of the SG interior. This type of visual inspection, however, requires many resources. To improve this method, we focus on measurements of the SG level. The measurements of the level change because the SG downcomer flow rate varies due to the blockage of the TSP flow area. To quantify this effect, we calculate the circulation ratio in relation to changes in TSP flow area. In addition, we evaluate the pressure drops that affect the SG water level. Sensor drift analyses of the level measurements are performed to confirm that the level variance is derived from system characteristics rather than sensor drift. Finally, the blockage rates of the TSP flow area are generated by using measurements of the SG water level.

The Use of Peripherally Inserted Central Catheters in Intensive Care: Should you Pick the PICC?

Peripherally inserted central catheters (PICCs) are useful routes for intermediate central venous access; however, there is a paucity of data regarding their use in the intensive care setting. We have been using PICCs on our ICU since 2006 and have undertaken a retrospective audit of all PICC use during one year to define complication rates. PICCs were inserted by a dedicated vascular access team (VAT). Microbiology and radiology databases were used to assess rates of line-related bacteraemias and catheter misplacements. Blockage rates were collected from VAT records. Data was available on 116 PICCs, corresponding to 1,558 line days. The median duration of placement of PICCs was 9 days (range 0–100) in situ with a misplacement rate at insertion of 12.1%. The catheter-related blood stream infection rate was zero. The blockage rate was 29.5/1,000 line days; 87% of these blockages were cleared using urokinase. We believe that PICCs can be safely used in intensive care patients.

Statistical analysis and definition of blockages-prediction formulae for the wastewater network of Oslo by evolutionary computing

Oslo Vann og Avløpsetaten (Oslo VAV)-the water/wastewater utility in the Norwegian capital city of Oslo-is assessing future strategies for selection of most reliable materials for wastewater networks, taking into account not only material technical performance but also material performance, regarding operational condition of the system.The research project undertaken by SINTEF Group, the largest research organisation in Scandinavia, NTNU (Norges Teknisk-Naturvitenskapelige Universitet) and Oslo VAV adopts several approaches to understand reasons for failures that may impact flow capacity, by analysing historical data for blockages in Oslo.The aim of the study was to understand whether there is a relationship between the performance of the pipeline and a number of specific attributes such as age, material, diameter, to name a few. This paper presents the characteristics of the data set available and discusses the results obtained by performing two different approaches: a traditional statistical analysis by segregating the pipes into classes, each of which with the same explanatory variables, and a Evolutionary Polynomial Regression model (EPR), developed by Technical University of Bari and University of Exeter, to identify possible influence of pipe's attributes on the total amount of predicted blockages in a period of time.Starting from a detailed analysis of the available data for the blockage events, the most important variables are identified and a classification scheme is adopted.From the statistical analysis, it can be stated that age, size and function do seem to have a marked influence on the proneness of a pipeline to blockages, but, for the reduced sample available, it is difficult to say which variable it is more influencing. If we look at total number of blockages the oldest class seems to be the most prone to blockages, but looking at blockage rates (number of blockages per km per year), then it is the youngest class showing the highest blockage rate. EPR allowed identifying the relation between attitude to block and pipe's attributes in order to understand what affects the possibility to have a blockage in the pipe. EPR provides formulae to compute the accumulated number of blockages for a pipe class at the end of a given period of time. Those formulae do not represent simply regression models but highlight those variables which affect the physical phenomenon in question.

Prediction of SG Tube Support Plate Flow Area Blockage Rate Using SG Wide Range Level Measurements and Hydrodynamic Analysis

Some nuclear power plants have recently experienced hydrodynamic instability in steam generators (SGs). Instability, if present in the SG of a pressurized water reactor, results in the periodic oscillation of the water level, steam flow, feedwater flow, and the flow through the circulation loop. In this instability analysis, the major parameters are the power level and flow area of the tube support plate (TSP). The threshold power above which instability may occur is generated by variations in TSP flow area. The current method of estimating the blockage rate is the visual inspection of the SG interior. This type of visual inspection, however, requires many resources. To improve this method, we focus on measurements of the SG level. The measurements of the level change because the SG downcomer flow rate varies due to the blockage of the TSP flow area. To quantify this effect, we calculate the circulation ratio in relation to changes in TSP flow area. In addition, we evaluate the pressure drops that affect the SG water level. Sensor drift analyses of the level measurements are performed to confirm that the level variance is derived from system characteristics rather than sensor drift. Finally, the blockage rates of the TSP flow area are generated by using measurements of the SG water level.

Suppression Effect of Upstream Installed Ring-Shaped Obstacle Plate on Cavitation Surge in Pump Inducers

The attachment of an inducer upstream of a main impeller is a powerful method to improve the suction performance. It is known, however, that the cavitation surge oscillation, which is focused in the present paper, occurs under the operation condition with partial flow rate and low suction pressure. The attempts to suppress the cavitation surge have been made by installing a ring-shaped obstacle plate just upstream of inducer. The ring-shaped inlet plates with various blockage rates of 14%, 27% and 39% have been tested to examine the effect of blockage rates on the suppression of cavitation surge for two kinds of inducers having two blades with the solidity of 2.0 and the different blade angles of 8° and 14° at the blade tip. In the present paper, the changes of the onset region of cavitation surge are clarified and the mechanism of cavitation surge suppression is discussed with the measured casing wall pressure distribution and inlet velocity distribution.

LAPAROSCOPIC PERITONEAL CATHETER PLACEMENT

Although cerebrospinal fluid shunting remains one of the most common neurosurgical procedures, it is fraught with high infection, blockage, and reoperation rates. It has been estimated that the economic cost of ventriculoperitoneal shunting exceeds $1 billion annually. A new laparoscopic technique that eliminates abdominal incisions overlying shunt hardware was applied to 111 patients requiring ventriculoperitoneal shunts in an effort to decrease the morbidity associated with shunting. All patients who required ventriculoperitoneal shunt insertion were eligible for this surgical technique. Patient selection was based on availability of both surgical teams (general surgery and neurological surgery) at the time of surgery. Using this technique, the distal shunt catheter is tunneled directly from the head into the peritoneal cavity under laparoscopic guidance without a skin incision directly overlying the distal catheter insertion site. Patients were followed prospectively for signs and symptoms related to shunt dysfunction, shunt infection, and incision morbidity. One hundred eleven patients underwent 113 laparoscopic ventriculoperitoneal shunt surgeries between February 2003 and December 2004. The average follow-up period was 21.7 months (range, 12-34 mo). Nearly half of the patients (49%) were discharged the next morning and the majority (81%) was discharged within 2 days of surgery. Overall, 15 patients experienced complications requiring reoperation (13.5%) with a 1-year shunt survival rate of 91%. One patient (0.9%) acquired a new shunt infection, whereas two patients (1.8%) developed recurrence from a previous shunt infection. There were no abdominal incision-related complications. This simplified laparoscopic shunt placement technique, which requires no overlying abdominal incisions, can be performed quickly with high shunt survivability and low infection rates. Furthermore, the laparoscopic method has the advantage of fast recovery time, elimination of preperitoneal or misplaced catheters, and decreased abdominal incision morbidity. The procedure can be performed by either a multidisciplinary team or entirely by neurosurgeons.

Suppression Effect of Cavitation Surge of Pump Inducer by Installing Ring-Shaped Obstacle Plate Upstream of Inducer

The attachment of an inducer upstream of the main impeller is a powerful method to improve the cavitation performance. It is known, however, that the cavitation surge oscillation, which is focused in the present paper, occurs under operation condition of partial flow rate and low suction pressure. The attempts to suppress the cavitation surge were made by installing a ring-shaped obstacle plate just upstream of inducer. The ring-shaped inlet plates with various blockage rates of 14%, 27% and 39% were tested to examine the effect of blockage rates on the suppression of cavitation surge for two kinds of inducers having two blades with the solidity of 2.0 and the different blade angle of 14° and 8°at the blade tip. In the present paper, the changes of the onset region of cavitation surge are clarified and the mechanism of cavitation surge suppression is discussed with casing wall pressure distribution and inlet velocity distribution.

Evaluation of the role of the Yersinia pestis plasminogen activator and other plasmid-encoded factors in temperature-dependent blockage of the flea.

Yersinia pestis, the plague bacillus, has a plasminogen activator (pla) gene on the 9.5-kb plasmid pPla that is hypothesized to play a role in producing the foregut blockage in the flea vector that precedes transmission. In this study, however, Y. pestis that lacked pPla, the 70-kb virulence plasmid, or both plasmids, proved able to block Xenopsylla cheopis fleas normally. Blockage rates decreased with increasing environmental temperature for fleas infected with either wild type or pPla- Y. pestis. Thus, procoagulant ability of the Y. pestis pla gene product does not mediate blockage, nor does its ability to induce fibrinolysis at>28 degreesC account for failure to block at elevated temperatures. A Y. pestis strain that lacked all or part of the third plasmid of 110 kb, however, failed to colonize the flea midgut normally, indicating that one or more genes on the large plasmid may be required for vectorborne transmission.

Some Characteristics of Water Flow through Isolated Rose Stem Segments1

Abstract Water flow through isolated 5 cm stem segments of rose (Rosa hybrida L. cv. Cara Mia) increased for 4-7 hours and then decreased linearly for several hours thereafter. Decreased rate of flow has been termed blockage rate. Flow rates varied inversely with segment length and directly with head pressure but blockage rates were unaffected by either variable. Maximum flow increased and blockage rates decreased as solution pH was decreased over a range from pH 6 to pH 3. Flow rates at 3°C were about half of flow rates at 24° and the addition of sucrose to the solution further reduced flow. Viscosity differences account for the flow rate decrease at lower temperature but did not account for the sucrose effect. Millipore filtration of water from a variety of sources resulted in substantial increase in flow rates.

Inhibition of Vascular Blockage and Extension of Vase Life in Cut Roses with an Ion Exchange Column1

Abstract Effects of a mixed bed ion exchange resin column on vascular blockage and vase life were studied in cut roses (Rosa hybrida L. cv. Red American beauty) by measuring blockage rates in excised stem sections and by determining water uptake, fresh weight retention, and longevity of cut roses held in distilled water. The ion exchange column inhibited vascular blockage in excised stem segments. Water uptake and retention of fresh weight of cut roses were enhanced significantly by the ion exchange column treatment, and early wilting, known as “bent neck” was inhibited.