Pipeline Problem Research Articles

Pipelined fission for stream programs with dynamic selectivity and partitioned state

There is an ever increasing rate of digital information available in the form of online data streams. In many application domains, high throughput processing of such data is a critical requirement for keeping up with the soaring input rates. Data stream processing is a computational paradigm that aims at addressing this challenge by processing data streams in an on-the-fly manner, in contrast to the more traditional and less efficient store-and-then process approach. In this paper, we study the problem of automatically parallelizing data stream processing applications in order to improve throughput. The parallelization is automatic in the sense that stream programs are written sequentially by the application developers and are parallelized by the system. We adopt the asynchronous data flow model for our work, which is typical in Data Stream Processing Systems (DSPS), where operators often have dynamic selectivity and are stateful. We solve the problem of pipelined fission, in which the original sequential program is parallelized by taking advantage of both pipeline parallelism and data parallelism at the same time. Our pipelined fission solution supports partitioned stateful data parallelism with dynamic selectivity and is designed for shared-memory multi-core machines. We first develop a cost-based formulation that enables us to express pipelined fission as an optimization problem. The bruteforce solution of this problem takes a long time for moderately sized stream programs. Accordingly, we develop a heuristic algorithm that can quickly, but approximately, solve the pipelined fission problem. We provide an extensive evaluation studying the performance of our pipelined fission solution, including simulations as well as experiments with an industrial-strength DSPS. Our results show good scalability for applications that contain sufficient parallelism, as well as close to optimal performance for the heuristic pipelined fission algorithm.

“Eight days a week”: A national snapshot of academic mothers’ realities in Canadian psychology departments.

Researchers (e.g., Faludi, 1991; Schwartz, 1989) in the late 1980s and early 1990s explored and critiqued the phenomenon of the track (i.e., prioritising mothering) by noting that professional mothers are relegated to lower-status and lowerpaying jobs because of perceived expectations associated with their parental roles (Cummins, 2012). In academic settings, the discrimination associated with perceived mommy tracking has been put forth to explain, in part, the (van Anders, 2004) and (Mason, 2011). The leaky pipeline and pyramid problem are used to describe the tendency for university faculty who are women to occupy the lowest levels of the academic hierarchy. That is, at each successive level within academic institutions, the representation of women decreases (van Anders, 2004). Of the teaching positions at universities within Canada, 40% are occupied by women, almost half of them are mothers (CAUT, 2013), and so parental status may indeed be involved in the disproportionate representation of women at the highest academic ranks.Research has suggested that women faculty perceive the current climate in academic institutions to be less than welcoming to mothers (Castaneda & Isgro, 2013). Armenti (2004) interviewed 19 Canadian women professors who had engaged or anticipated having to engage in strategies to minimise the negative repercussions associated with their motherhood status (e.g., not being hired, negative effect on promotion and tenure reviews), and alleviate disapproval from colleagues. Results from the qualitative analysis revealed that participants with grown children reported having timed their pregnancies to coincide with the end of the academic year, and younger professors who might have started to have children opted to delay pregnancies until they had secured tenure. Overall, the perceived lack of support for academic mothers may cause some women to leave academia, delay tenure or promotions, or accept positions at teaching-focused, as opposed to research-focused, universities to prioritise their families (Damiano-Teixeira, 2006).In an effort to understand the barriers faced by academic women, Comer and Stites-Doe (2006) developed a theoretical model of three factors that complicate (or facilitate) one's ability to balance academic and parental roles. First, the phase of a woman's career (i.e., pre- or posttenure) and the stage of her family can affect a woman's role-balancing capacity. Women professors who have preschool-aged children, and women who are working toward tenure, have been theorized to experience greater difficulty. Second, the extent to which a woman's partner contributes to household and childcare tasks affects a woman's role balancing; specifically, the greater the contributions from one's partner, the better a woman's ability to balance roles. Indeed, compared with live-in support from other relatives, only spousal/partner support has been found to actually decrease the hours mothers work inside the home (Abroms & Goldscheider, 2002). Third, institutional factors (e.g., placement in a research- or teaching-focused university, work-family culture, and presence/absence of campus childcare) can affect women's role balancing.Despite the plethora of variables that could theoretically result in barriers for women, much of the empirical work examining differences between academic women and men has relied extensively on one key metric, namely, their respective publication records. Researchers consistently find that faculty men produce greater research output, and identify the ranks of assistant and full professor where this gap is most noticeable (e.g., Carleton, Parkerson, & Horswill, 2012; Nakhaie, 2002; Stack, 2004). Although number of publications is undoubtedly an important metric to consider, Ward and Wolf-Wendel (2004) caution that discrepancies in academic women's productivity (compared with academic men) may be due to breaks women take to have children. …

A Novel Method to Enhance Pipeline Trajectory Determination Using Pipeline Junctions.

Pipeline inspection gauges (pigs) have been used for many years to perform various maintenance operations in oil and gas pipelines. Different pipeline parameters can be inspected during the pig journey. Although pigs use many sensors to detect the required pipeline parameters, matching these data with the corresponding pipeline location is considered a very important parameter. High-end, tactical-grade inertial measurement units (IMUs) are used in pigging applications to locate the detected problems of pipeline using other sensors, and to reconstruct the trajectories of the pig. These IMUs are accurate; however, their high cost and large sizes limit their use in small diameter pipelines (8″ or less). This paper describes a new methodology for the use of MEMS-based IMUs using an extended Kalman filter (EKF) and the pipeline junctions to increase the position parameters’ accuracy and to reduce the total RMS errors even during the unavailability of above ground markers (AGMs). The results of this new proposed method using a micro-electro-mechanical systems (MEMS)-based IMU revealed that the position RMS errors were reduced by approximately 85% compared to the standard EKF solution. Therefore, this approach will enable the mapping of small diameter pipelines, which was not possible before.

Method of Corrosion Prevention in Steel Pressure Pipelines in Sewerage Systems

Problems of sewer pipelines arising due to corrosion and biofouling are analyzed. Currently used methods of corrosion control of steel pressure pipes are designed to eliminate the consequences rather than the causes of surface oxidation. The task of preventing or achieving the lowest possible corrosion damage intensity is to ensure maximum efficiency of the pipeline protection which will increase as a result of economic indicators of the systems under consideration. Contemporary sewage pipelines represent a complicated complex of interrelated structures where various physical, chemical and biological processes take place. The implementation of such processes is not controlled and is accompanied by considerable costs connected in particular with pipeline replacement, repair of the sewage wells, reimbursement of harm done to water handling facilities. Recommendations about the prevention and the protection against the corrosion of existing and sewer pipelines that are being designed are provided.

Solving the problem of pipeline freezing with respect to external heat exchange

The paper proposes a solution to the problem of freezing of heating pipelines in engineering systems in buildings in emergency situations. A mathematical process model is proposed, wherein heat emissions induced by viscous friction and phase transition are taken into account. Formulas for estimating the rate of freezing have been obtained. Calculation results obtained by using numerical methods are presented. Recommendations on the proper choice of pipe-line diameters to reduce the probability of liquid freezing therein are provided as well. DOI: https://dx.doi.org/10.5755/j01.mech.21.5.11411

The influence of the heating temperature on the yield stress and pour point of waxy crude oils

Abstract The yield stress and pour point are two important parameters related to flow assurance problems in waxy crude oil pipelines. The yield stresses at temperatures below the pour points of five waxy crude oils after heating to different temperatures have been investigated in the present paper. Both the experimental results in this work and data from the literature show that the yield stress values increase exponentially with the decreasing measurement temperature. The experimental results show that the heating temperature has an obvious influence on the yield stress and the pour point. However, it was noted that the yield stress values at the gel point temperature, defined as the highest temperature at which the movement of the sample cannot be observed during the quiescent pour point testing process, are approximately the same for a waxy crude oil after heating to different temperatures. An exponential relationship exists between the yield stress and the difference between the measurement temperature and gel point that is independent of the heating temperature. To explore this phenomenon, the relative magnitudes of the gravitational stress and the structural strength of the wax crystal network during the gel point test has been analyzed, and it was found that the yield stress value at the gel point has a favorable linear relationship with the oil density.

Hypoxic incident in the operating theatre due to a central oxygen pipeline problem

The Sri Lankan Journal of Anaesthesiology is the official journal of the College of Anaesthesiologists of Sri Lanka. It publishes clinical investigations, research articles, audits, case reports, review articles and CME articles relating to anaesthesiology, critical care and pain. It is published bi annually in January and June. Sri Lankan Journal of Anaesthesiology is included on DOAJ and Scopus.

Capacity of, and Demand for, Neonatal Nurse Practitioner Educational Programs: A Missing Piece of the Workforce Puzzle.

Studies have demonstrated a dramatic increase in the number of new nurse practitioners (NPs) overall completing NP education each year. However, NPs who provide specialized care to children have not experienced increases in their pipeline at all. This has resulted in shortages of neonatal nurse practitioners (NNPs). The aim of this study was to gain a greater understanding of the NNP pipeline and potential for increasing the number of new NNPs graduating each year. Telephone survey of all NNP educational programs. Approximately one fourth of all NNP education programs had closed over the past several years. This is despite a strong job market, planned increases in hiring NNPs, and a seemingly growing shortage of NNPs. Problems with the NNP pipeline are not due to a lack of capacity of existing programs, but rather to difficulties in increasing the enrollment demand.

From description to explanation: An empirical exploration of the African-American pipeline problem in STEM

We conducted a mixed-methods study of matriculation issues for African-Americans in the STEM pipeline. The project compares the experiences of students currently majoring in science (N = 304) with the experiences of those who have succeeded in earning science degrees (N = 307). Participants were surveyed about their pipeline experiences based on theories that are commonly used to explain matriculation issues. The results of the study revealed that although both groups recognized the major role of race in their experiences, the primary factor distinguishing between students and professionals was their sense of Alignment with their respective community and their different experiences with subtle forms of racism (Microaggressions). African-American scientists were far more likely to report a weak sense of belonging to their community and were far more likely to report subtle encounters with racism. By contrast, African-American science students were more likely to feel comfortable with the science community and less likely to report subtle racist encounters. The findings of this study are indicative of the pervasive impact of racial bias and conflict as a gatekeeper in providing access to science careers. © 2015 Wiley Periodicals, Inc. J Res Sci Teach

Упругопластическая модель механического конусно-раструбного соединения труб

Background One of the problems of the industrial pipelines is the protection against internal corrosion. This article discusses the mechanical cone-spigot steel pipe joint with an internal protective coating and the conditions for achieving equal strength at different combinations of mechanical properties of metals and sizes of the pipe. There were investigated the basic laws of cone-spigot connections strength, the requirements of a maximum pressure rating at different combinations of input data; there was offered an algorithm for the calculation of process parameters. Aims and Objectives To investigate the strength of the cone-spigot connections under the different factors that determine the dissimilarity of the connected pipes on the mechanical properties and dimensions within standard tolerances. To improve the calculation method to ensure the uniform strength. To evaluate the effect of operating pressure on strength. Methods The Genki-Ilyushin provisions of deformation theory of plasticity were used in the mathematical apparatus. The calculations were carried out by the finite element method in conjunction with the methods and iterations of successive approximations. Results There were investigated the influence of the following properties of the pipe: the ratio of diameters and wall thicknesses, the mechanical properties of metals within the elastic and plastic deformations, as well as the operating pressure on the mechanical strength of the cone-spigot connections. There were made the recommendations, allowing to provide uniform strength of cone-spigot connection with various combinations of initial parameters.

Design of Underground Pipelines under Arbitrary Seismic Loading

On the basis of Hamilton-Ostrogradskiy variation principle a system of equations of linear pipeline vibrations interacting with surrounding soil is derived with appropriate boundary and initial conditions under arbitrary direction of seismic effect. Dynamic problem of underground pipeline is solved by finite difference method of the second order of accuracy with different combinations of boundary conditions under the effect of seismic load on a given law with arbitrary direction. Numerical implementation of the problem is realized.

European regulatory experience with drugs for central nervous system disorders.

Butlen-Ducuing and colleagues analyse ~20 years of data on regulatory applications assesssed by the European Medicines Agency in psychiatry and neurology, with the aim of illuminating challenges that underlie the 'pipeline problem' for drugs for central nervous system disorders.

Study on Dissolution of Low Density Polyethylene (LDPE)

The world is currently facing the problem brought by plastic waste, as well as energy crisis. It is known that catalytic cracking of low density polyethylene (LDPE) waste can produce liquid fuels with similar properties to fossil fuels, hence serve as a solution to the problems mentioned. However, the problem of pipelines clogging by molten plastic feed during the cracking process has to be solved before the process can be up-scaled to continuous process. It was proposed that LDPE waste can be dissolved in suitable solvent before being catalytically cracked under suitable conditions. This study was done to investigate the behavior of virgin LDPE (in powder form) dissolved in several chosen solvents, namely benzene, toluene, chlorobenzene, isooctane, xylene and trichloroethylene, and compare the result with previous work. From the study, it was observed that LDPE samples could dissolve in benzene and toluene to a high extent. On the other hand, isooctane acted as a weak solvent towards LDPE powder. The difference of LDPE solubility in solvents was attributed to the surface area per unit mass of LDPE samples. Despite the superior property of benzene as solvent for LDPE, the safety factor study showed that toluene, xylene and trichloroethylene were more suitable to be used in LDPE dissolution. However, care should be taken to minimize possible effects of the solvents towards the body while using the solvents mentioned.

Start-up flows of Dullaert–Mewis viscoplastic–thixoelastic fluids: A two-dimensional analysis

The restart problem of pipelines filled with gelled waxy crude oils is investigated numerically using the finite volume method (FVM). Based on the rheological data obtained using the MCR-301 rheometer for a typical Iranian waxy crude oil, the Dullaert–Mewis (DM) rheological model was adopted to represent the viscoplastic/thixoelastic nature of such oils. A full two-dimensional analysis was used with the only assumption being that the flow is axisymmetric. Based on the numerical results obtained in the present work, it is concluded that the gel’s elasticity has a negative effect on the restart operation. That is to say that, for highly-elastic gels the restart operation is predicted to fail completely. For weakly-elastic gels, the restart operation is predicted to be successful but the gel’s elasticity still lowers the flow throughput. A complete parametric study was undertaken in order to investigate the effect of different parameters in the DM fluid model on the start-up flow.

Determination of the Content of C80 Tetraacids in Petroleum

In order to formulate mitigation strategies before the onset of oil pipeline and topside deposition problems caused by so-called calcium naphthenates or chelates of “ARN” acids, it is necessary to develop an analytical technique suitable for the quantification of the constituent C80 tetraacids in small samples (∼1 g) of crude oils at low parts per million (ppm) concentrations. Here we report a method for the (semi)quantitative determination of tetraacids in crude oils using a relevant C80 8-ring acid as an internal standard. After addition of the internal standard, an “acid” fraction is isolated from the oil using sequential ion exchange solid-phase extraction (SPE) and the acids converted to their per-methylated esters before further SPE refinement to obtain a “tetraacid” fraction. Tetraacids are analyzed as the ammoniated adducts of their per-methyl esters using liquid chromatography coupled with electrospray ionization-mass spectrometry. This method has a limit of quantitation (LOQ) of approximately 0.1 ppm for individual tetraacids in crude oils. As an example, the use of this method for the determination of the individual and total tetraacid contents of five crude oils is shown.

Full Scale Fatigue Experiment on Submarine Pipelines

This paper focus on fatigue problem of submarine pipelines, four points bending full scale fatigue experiment were conducted on X65 pipelines butt joints specimens, utilizing pipeline full scale fatigue test machine developed by CNPC. Meanwhile contrast test was also carried out on small specimens. The results show that the fatigue strength of full scale welded joints is lower than the small scale joints. Owing to having no regard for the influence of residual stress and size effect, the small test would provide dangerous results. The fatigue property of full scale welded joints only meets the requirement of DNV C203 W3 curve, and meets the needs of DNV C203 F3 curve basically while not meet BS 7608 F2 curve’s requirements which relatively demand higher. Weld toe and geometric discontinuous near weld root is the weak point for the whole welded joints.

Decimated Signal Diagonalization Method for Improved Spectral Leak Detection in Pipelines

Leak detection is an important issue in piping that deals with the management of water resources; nowadays large amounts of water in the network are dispersed as reported in current scientific literature. Among the methods for leak detection in water pipes, spectral analysis is very interesting. A classical spectral method is fast Fourier transform, but in this paper, we present an alternative method of spectral analysis, which has higher performance in terms of resolution and fast processing, namely decimated signal diagonalization (DSD). It is a nonlinear, parametric method for fitting time domain signals represented in terms of exponentially damped time signals. The aim is to reconstruct the unknown components as the harmonic variables, estimating the fundamental complex frequencies, and amplitudes. The DSD method partly uses the principles of the filter diagonalization method (FDM), which constructs matrices of a generalized eigenvalue problem directly from measured time signals of arbitrary length. However, the DSD because of its windowing technique produces a considerable reduction of size of the original data matrix, and consequently acquisition time can be shorter. We have tested the DSD method for leak detection problem in an experimental zigzag pipeline. We show as the DSD method produces good results in terms of resolution than FDM one.

Cultural brokers: How immigrant youth in multicultural societies navigate and negotiate their pathways to college identities

Abstract A crucial indicator of immigrant youth's incorporation in their receiving countries is their educational success, which can open pathways to economic mobility and civic participation. So we are especially concerned about the academic pipeline problem , when disproportionate numbers of immigrant, ethnic minority, and low-income youth leave school prematurely. Scholars trace the roots and remedies of these inequalities with theories of capital , alienation , and challenge . Social capital theories point to cultural reproduction, seen when youth with college-educated parents are the most likely to develop college identities. Alienation theories propose that immigrant parents dream of their children's school success, but poverty and discrimination dim these hopes, while their children develop marginalized identities. Finally, such challenges can motivate youth to succeed on behalf of their families and build college identities by navigating among their cultural worlds. This paper reports two longitudinal studies with U.S.-Mexican immigrant youth and traces parallels and contrasts across nations as well as research–practice–policy linkages, with special attention to how cultural brokers can be resources for opening academic pipelines.

The effect of a variable plastic viscosity on the restart problem of pipelines filled with gelled waxy crude oils

The effect of a variable plastic viscosity is numerically investigated on the success of the restart operation for a pipeline filled with fully-gelled waxy crude oil. To investigate the separate effects of structure- and shear-dependent viscosity, waxy crude oil is assumed to obey the Houska rheological model. In order to precisely capture the shape and position of the yielding surface, a variational approach is used to formulate the restart problem for this particular fluid model. The numerical results show that a variable plastic viscosity has a significant effect on the restart operation. For certain set of parameters the restart operation is shown to fail if the plastic viscosity is constant but is successful if the plastic viscosity is (moderately) structure-dependent. However, the time needed by the liquefied gel to discharge from the pipe outlet section is increased if the plastic viscosity is structure-dependent. Surprisingly, the shear-thinning behavior of waxy crude oil is predicted to lower the (steady) flow rate even when the restart is successful.

Updated CO2/H2S internal corrosion model of natural gas pipelines based on flow field calculations

The ‘A line’ of the Sichuan Natural Gas East Transportation in China was used as the subject of the study, and an existing CO2/H2S corrosion model was utilised to predict the uniform corrosion rate. Then, the flow parameters were simulated by computational fluid dynamics based on turbulence theory, and the influence on the corrosion rate of the pipeline was analysed in a detail to more accurately describe the corrosion problems of natural gas pipelines that contain CO2/H2S. After that, an updated CO2/H2S corrosion model under the influence of flow filed was proposed by modifying the existing CO2/H2S corrosion model. The actual condition was calculated by the updated CO2/H2S corrosion model. Results show that flow parameters, namely, velocity, turbulent kinetic energy and phase distribution, affect pipeline corrosion. The flow parameters did not change significantly at the small scale changes in the pipeline (5 and 15°) of a broad and smooth flow channel of the large diameter gas transport pipeline. The shape of corrosion often appears in the form of an elliptical sheet. The corrosion location and the corrosion rate calculated by the updated model are consistent with the wall thickness detection data in the site conditions, which verified that the updated CO2/H2S corrosion model is valid. The updated CO2/H2S corrosion model influenced by the flow field can predict the corrosion distribution and the corrosion rate of the three-dimensional key positions in natural gas pipelines.