A simple approach for monitoring business service time variation.

Control charts are effective tools for signal detection in both manufacturing processes and service processes. Much of the data in service industries comes from processes having nonnormal or unknown distributions. The commonly used Shewhart variable control charts, which depend heavily on the normality assumption, are not appropriately used here. In this paper, we propose a new asymmetric EWMA variance chart (EWMA-AV chart) and an asymmetric EWMA mean chart (EWMA-AM chart) based on two simple statistics to monitor process variance and mean shifts simultaneously. Further, we explore the sampling properties of the new monitoring statistics and calculate the average run lengths when using both the EWMA-AV chart and the EWMA-AM chart. The performance of the EWMA-AV and EWMA-AM charts and that of some existing variance and mean charts are compared. A numerical example involving nonnormal service times from the service system of a bank branch in Taiwan is used to illustrate the applications of the EWMA-AV and EWMA-AM charts and to compare them with the existing variance (or standard deviation) and mean charts. The proposed EWMA-AV chart and EWMA-AM charts show superior detection performance compared to the existing variance and mean charts. The EWMA-AV chart and EWMA-AM chart are thus recommended

Performance comparison of transverse and longitudinal fractured horizontal wells over varied reservoir permeability

Since the first application in the mid-1980\u27s, multiple fractured horizontal wells have proven to be an effective means of extracting hydrocarbons. These wells require careful consideration of wellbore orientation relative to the horizontal principle stress. Wellbore orientation can lead to transverse fractures which are perpendicular to the wellbore, or longitudinal fractures parallel the wellbore. Questions arise regarding whether one fracture orientation is consistently preferred over the other, or if certain conditions affect the choice. Historical work has examined the impact of horizontal wellbore azimuth in the Barnett and Marcellus Shale where public data was reviewed and statistical well analysis was conducted respectively. Comparison between transverse and longitudinal fracturing in moderate gas reservoirs has been performed with experimental study. This work includes both simulations and actual field cases studies. It compares transverse multiple fractured horizontal wells with longitudinal ones in terms of both well performance and economics. The study covers both gas and oil reservoirs and extends prior work to unconventional resources by extending the reservoir permeability to 0.00005 md. A range of reservoir permeability is identified for the preferable fracture configuration through simulations. Field production history of the Bakken, Barnett, Eagle Ford and Delaware formations are investigated and compared to the simulation results. In addition, this work analyzes the impact of fracture conductivity, lateral length, fracture half-length, completion method and hydrocarbon prices. The conclusions can be used as a reference in decision making on horizontal drilling and hydraulic fracturing for both unconventional and conventional resources --Abstract, page iii

Liquidity and speculative trading: evidence from stock price adjustments to quarterly earnings announcements

This dissertation studies whether stock price reactions to quarterly earnings announcements depend on stock liquidity. Baker and Stein (2004) and Scheinkman and Xiong (2003) develop models showing that liquidity can be affected by investor sentiment or speculative trading. With short-sale constraints, liquid stocks have more trading from optimistic, overconfident investors and tend to be overvalued. In this study, we hypothesize that if a liquid stock is overpriced due to intensive speculative trading, the overpricing should be corrected partially or fully after quarterly earnings announcements which convey the information about the fundamental value of stocks and synchronize investors\u27 adjustment to mispricing. Our results show that liquid stocks earn significant lower abnormal returns at the announcements than illiquid stocks. Furthermore, prior to the announcements, liquid stocks also have significant speculative trading. After controlling for other determinants of abnormal returns, we find the return difference between liquid and illiquid stocks during the 12-day earnings announcement period is 4.11%, which is about one-third of the annual liquidity premium. Our findings suggest that the effect of investors\u27 speculative behavior on stock prices is not negligible and that earnings announcements serve as an important mechanism for regulating overpricing caused by speculative trading