The clearance gaps in twin-screw compressors are critical for their performance and reliable operation, as the leakage flows through these clearances influence the volumetric and adiabatic efficiencies. The amount of leakage flows depends on the clearance size and shape as well as various geometric and operating parameters. Usually, the isentropic nozzle equations along with appropriate flow coefficients are used for more accurate estimation of the leakage flow rates through the clearance gaps. Hence, a proper understanding of the flow coefficients and their relationship with the dimensionless parameters (such as pressure ratio, Reynolds number, and aspect ratios) is critical for an accurate prediction of the leakage flows. In the present study, considering the interlobe clearance gap in screw compressor in terms of rectangular openings, the interlobe leakage flow rates are estimated for various opening sizes and pressure conditions using isentropic nozzle equations and an iterative method. The flow coefficients are determined by comparing the experimental values obtained using a specialized test rig and the flow rates obtained from the analytical methods. The dimensionless parameters are varied to see their individual effect on the leakage mass flow rates and on the flow coefficients. The mean deviation from the experimental results when using an analytical iterative procedure (-8. 5%) is substantially lower in comparison to the mean deviation (+26. 8%) using the isentropic nozzle equations. The study validates that the iterative method can be preferred (for an interlobe leakage flow rate prediction) over the isentropic nozzle equation method.

Introduction: In recent years, significant developments have been taking place in caries removal and cavity preparation using laser in dentistry. As laser use is considered for cavity preparation, it is necessary to determine the quality of restoration margins. Glass ionomer cements have great applications for conservative restoration in the pediatric field. The purpose of this in vitro study was to compare resin-modified glass ionomer restorations micro-leakage in cavities prepared by Er: YAG (Erbium-Doped Yttrium Aluminum Garnet) laser irradiation and conventional method in primary teeth.Methods: This was an in vitro experimental study. Forty primary canine teeth were divided into 2 groups: group 1 represented cavities prepared by the no.008 diamond bur, group 2 represented cavities prepared by Er: YAG laser. After cavity preparation, samples were restored by resinmodified glass ionomer. The teeth were thermocycled for 700 cycles, placed in 2% methylene blue for 24h and sectioned in the buccolingual direction. The degree of dye penetration was scored by 3 examiners. Data was analyzed using Mann-Whitney Test.Results: There was no statistical difference in micro-leakage between the two modes of cavity preparation (P=0.862) Conclusion: Since preparing conservative cavities is very important in pediatric dentistry, it is possible to use Er: YAG laser because of its novel and portable technology. However, further investigations of other restorative materials and other laser powers are required.

Introduction: Endodontic surgery is a valuable option for maintaining patient's natural dentition when previous orthograde endodontic treatments fail to succeed. Proper rootend preparation and placement of a retro-filling material are recommended for successful endodontic surgery. The objective of this experimental study was to compare sealing ability of Resilon/Epiphany system, as a potential root-end filling material, with ProRoot MTA using both dye and bacterial leakage models.Materials and Methods: Ninety two single-rooted extracted human teeth were decoronated and prepared endodontically. Specimens were randomly divided into four experimental groups (n=20) and four control groups (n=3). After removal of apical 3 mm and root-end cavity preparation, MTA, or Resilon were used to fill root end cavities. For bacterial leakage, specimens (20 for each experimental group, 3 negative, and 3 positive controls) were subjected to E. faecalis over a 70-day period. Methylene blue was used for dye leakage (the same in number as before). Using stereomicroscope (40× mag.) complete dye leakage was assessed after 72 h. Kaplan-Meier survival analysis was performed for bacterial leakage. The data was analyzed using t-test and Chi-square analysis (a=0.05).Results: All of the positive controls and none of negative controls revealed leakage.Result of log rank test showed no significant difference between MTA and Resilon in time of bacterial leakage at the end of the 70 days (P>0.05) There was also no statistical difference in complete dye leakage for both groups (P>0.05).Conclusion: Leakage occurred in both MTA and Resilon as root-end filling material but the difference was not statistically significant. Resilon might be noticed as a potential root-end filling material if good isolation is attainable.

To reduce the amount of water wastage caused by leakage, the utilities have to monitor and detect leakage of water distribution networks periodically. In order to identify leaking pipelines efficiently when limited resources are available, a cluster identification method (CIM) is proposed to establish a priority for leakage detection and to assess whether spatial clusters of high failure-prone areas exist. The proposed CIM evaluates the difference between the observed data and simulated trials to determine the statistical significance of each cluster; a method previously applied only in epidemiology studies to assess the occurrence probabilities of rare diseases for spatial clusters. The CIM suggested in this study is the overlapping local case proportions (OLCP) that uses grids to scope the entire area and then to simulate the number of failures in the neighborhood of each grid. The simulated failure ratios are then compared with the existing records to determine the statistical significance. The statistical significance represents the potential of the grid requiring further leakage detection. Three failure probability estimation methods, including local average, global average, and empirical equation, are utilized to analyze the suitability of the OLCP for use with various probability inputs. A case study in the central region of Taiwan was implemented to demonstrate the applicability of the proposed method. The results indicate that the rate of failure in the following year found within the spatial clusters determined by the OLCP was twice the average amount and thus provided valuable information used to prioritize the pipelines for further inspection.