Assessment of zonal isolation risk to changes in design parameters

The Well Containment Screening Tool (WCST) focuses on well integrity evaluation after well control incident. The WCST favors a greater wall thickness and, hence, a narrower cementing annulus, potentially increasing the risk of cement loss. We develop a structured and systematic physical model to simulate and track formation damage. A simulation process is conducted to assess the sensitivity of zonal isolation risk as design parameters are changed. In this paper, a physical model involving wellbore, casing and cement fluid is developed to understand the interaction between cement fluid and the formation. Two failure metrics are defined that provide a comprehensive understanding of the zonal isolation risk. Quantitative risk assessment is implemented with Monte Carlo simulation to assess the risk of zonal isolation problems when design parameters are changed. Models of production casing and intermediate casing are studied to verify the generality of this analysis. Taking both failure metrics into consideration, sensitivity analysis for models of production casing and intermediate casing present common observations regarding changes of design parameters. Our analysis suggests that minor increases (within 0.05”) in casing thickness, due to increased outer diameter, has little influence on the risk of cement loss, as does slight decreases in mean open hole diameter (within 0.05”). To verify the generality of this approach, in addition to casing and wellbore parameters, the sensitivity to cement fluid flow rate is analyzed. We find that risk is not significantly affected by small increase of flowrate (e.g. from 40 to 100 gpm). This paper applies a novel quantitative risk analysis to assess the influence of different design parameters on zonal isolation problems. This approach, if well implemented, can help to assess the impact of changes in design parameters (e.g., casing length and depth, mud density and cement fluid density, etc.) on drilling safety. It can also help to inform drilling decisions by providing forecasts of zonal isolation risk for particular geological condition.Mechanical Engineerin

Regulating stepping during fixed-speed and self-paced treadmill walking

textBackground: Treadmill walking should closely simulate overground walking for research validation and optimal skill transfer. Traditional fixed-speed treadmill (FS) walking may not simulate natural walking because of the fixed belt speed and lack of visual cues. Self-paced (SP) treadmill walking, especially feedback controlled SP treadmill walking, enables close-to-real-time belt speed changes with users' speed changes. Different sensitivity levels of SP treadmill feedback determine how fast the treadmill respond to user's speed change. Few studies have examined the differences between FS and SP treadmill walking, or the difference between sensitivity levels of SP treadmills, and their methods were questionable because of averaging kinematics and kinetics parameters, and failing to examine directly treadmill and subjects' speed data. This study compared FS with two SP modes with variation of treadmill speed and user's speed as dependent variables. Method: Thirteen young healthy subjects participated. Subjects walked on a motorized split-belt treadmill under FS, high sensitivity SP (SP-H) and low sensitivity SP (SP-L) conditions at normal walking speed. Root mean square error (RMSE) for subject's pelvis global speed (Vpg), pelvis speed with respect to treadmill speed (Vpt), and treadmill speed (Vtg) data were collected for all trials. Results: Significant condition effects were found between FS and the two SP modes in all RMSE values (p < 0.001). The two sensitivity levels of SP had similar speed patterns. Large subject × condition interaction effects were found for all variables (p < 0.001). Only small subject effects were found. Conclusions: The results of the study reveal different walking patterns between FS and SP. However, the two sensitivity levels failed to differ much. More habituation time may be needed for subjects to learn to optimally respond to the SP algorithm. Future work should include training subjects for more natural responses, applying a feed-forward algorithm, and testing the effect of optic flow on FS and SP speed variation.Kinesiology and Health Educatio

Haigui's predicament in the job market : is there opportunity at the end of the tunnel?

textDriven by the desire for a bright future and a successful career, many young people in China are embarking on overseas odysseys to pursue higher education degrees in order to get decent jobs when they return to China. Those people who are educated abroad and come back with higher education diplomas are called "Haigui" in Chinese. Although they excel in their fields and are capable of the occupations that they dream of, most of them fail to get the jobs they so crave because of reasons beyond their control, such as the slump of the job market, unfair parental privilege, and the high density of Haigui in large cities. This story depicts the job-hunting experiences of four characters -- Ye, Zhang, Erin and Wu. (They requested not to use their real names for privacy concerns.) Their accounts showcase different facets of why Haigui employment in China is so dire. Until the job market in China improves and stops favoring nepotism, the number of Haigui will continue to rise as more and more Chinese students leave the country in search of better futures.Journalis

Design of a 3 GHz fine resolution LC DCO

In this thesis, the design of a fine resolution LC digitally controlled oscillator (DCO) is introduced. Two NMOS varactor banks are used to achieve 12 bits medium and fine frequency tuning. Both delta-sigma modulator and capacitive divider circuit are implemented to achieve a finer resolution and a larger dynamic range. The LC-oscillator has a coarse tuning range from 3.05 GHz to 3.85 GHz and a fine tuning range of 50MHz. It features a phase noise level of -115dBc/Hz at 1MHz frequency offset and consumes 5.4mW. Efficient simulation methodology is explored. Finally, this DCO is simulated in an All-Digital Phase Locked Loop (ADPLL) with other ideal behavior blocks implemented using Verilog-A, and the performance of the DCO is evaluated.Electrical and Computer Engineerin

An experimental evaluation and possible extensions of SyPet

Program synthesis is an automated programming technique that automatically constructs a program which satisfies given specifications. SyPet is a recently published novel component-based synthesis tool that assembles a straight-line Java method body that invokes a sequence of methods from a given set of libraries to implement desired functionality that is defined by a given test suite. In this report, we experimentally evaluate the correctness and performance of the publicly available SyPet implementation, at the black-box level, focusing on the size of test suites. We then demonstrate how SyPet can be extended to support some other applications, such as synthesizing non-straight-line methods and program repair. Finally, we conjecture an alternative technique that is conceptually simpler for synthesizing straight-line methods and present a few initial experimental results.Electrical and Computer Engineerin

SiOx-based resistive switching memory integrated in nanopillar structure fabricated by nanosphere lithography

textA highly compact, one diode-one resistor (1D-1R) SiOx-based resistive switching memory device with nano-pillar architecture has been achieved for the first time using nano-sphere lithography. The average nano-pillar height and diameter are 1.3 μm and 130 nm, respectively. Low-voltage electroforming using DC bias and AC pulse response in the 50ns regime demonstrate good potential for high-speed, low-energy nonvolatile memory. Nano-sphere deposition, oxygen-plasma isolation, and nano-pillar formation by deep-Si-etching are studied and optimized for the 1D-1R configurations. Excellent electrical performance, data retention and the potential for wafer-scale integration are promising for future non-volatile memory applications.Materials Science and Engineerin

Atmospheric neutrino data : Active-Active ×\times Active-Sterile oscillations

I summarize here the results of a global fit to the full data set corresponding to 33.0 kt-yr of data of the Super-Kamiokande experiment as well as to all other experiments in order to compare the active-active and active-sterile neutrinos oscillation channels to the atmospheric neutrino anomaly.Comment: 3 pages, uses espcrc2.sty (Nuclear Physics style) and epsfig.sty, 2 PS files. To appear in the Proceedings of the XTH Int. Symposium on Very High Energy Cosmic Ray Interactions, Laboratory Nazionali del Gran Sasso, Assergi, Italy, July 12-17 199

Active paper for active learning

Recent research into distance learning and the virtual campus has focused on the use of electronic documents and computer‐based demonstrations to replace or reinforce traditional learning material. We show how a computer‐augmented desk, the DigitalDesk, can provide the benefits of both paper and electronic documents using a natural interface based on real paper documents. Many electronic documents, particularly those created using the guidelines produced by the Text Encoding Initiative (TEI), include detailed semantic and linguistic information that can be used to good effect in learning material. We discuss potential uses of TEI texts, and describe one simple application that allows a student's book to become an active part of a grammar lesson when placed on the DigitalDesk. The book is integrated into an interactive point‐and‐click interface, and feedback is related to the currently visible pages of the boo

The tumor-promoting functions of Ataxia-telangiectasia mutated (ATM) in cancer cells

textAtaxia-telangiectasia mutated (ATM) protein kinase regulates the DNA damage response (DDR) and is associated with cancer suppression by protecting cells from DNA double-strand breaks (DSBs). However, how ATM functions outside of DSB signaling is less clearly understood. Here, we report a new cancer-promoting role for ATM in stimulating cell migration and invasion independently of DSB signaling or induction. We used two highly metastatic human breast cancer cell lines to corroborate that ATM is required for cell migration and invasion. Microarray analysis of cells depleted for ATM identified interleukin-8 (IL-8) as a target since the exogenous addition of IL-8 rescued migration and invasion defects in ATM-deficient cells. Finally, ATM depletion in human cancer cells reduced lung metastasis in a mouse xenograft model. These findings shed light on tumor-promoting functions of ATM. Therefore, in addition to its canonical roles in tumor suppression, ATM promotes tumor progression as well.Cellular and Molecular Biolog