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Yanai R.D.,SUNY ESF | Battles J.J.,University of California at Berkeley | Richardson A.D.,Harvard University | Blodgett C.A.,SUNY ESF | And 3 more authors.
Ecosystems | Year: 2010

Ecosystem nutrient budgets often report values for pools and fluxes without any indication of uncertainty, which makes it difficult to evaluate the significance of findings or make comparisons across systems. We present an example, implemented in Excel, of a Monte Carlo approach to estimating error in calculating the N content of vegetation at the Hubbard Brook Experimental Forest in New Hampshire. The total N content of trees was estimated at 847 kg ha-1 with an uncertainty of 8%, expressed as the standard deviation divided by the mean (the coefficient of variation). The individual sources of uncertainty were as follows: uncertainty in allometric equations (5%), uncertainty in tissue N concentrations (3%), uncertainty due to plot variability (6%, based on a sample of 15 plots of 0.05 ha), and uncertainty due to tree diameter measurement error (0.02%). In addition to allowing estimation of uncertainty in budget estimates, this approach can be used to assess which measurements should be improved to reduce uncertainty in the calculated values. This exercise was possible because the uncertainty in the parameters and equations that we used was made available by previous researchers. It is important to provide the error statistics with regression results if they are to be used in later calculations; archiving the data makes resampling analyses possible for future researchers. When conducted using a Monte Carlo framework, the analysis of uncertainty in complex calculations does not have to be difficult and should be standard practice when constructing ecosystem budgets. © 2010 The Author(s). Source


Weckwerth A.M.,Burns and McDonnell
4th Process Safety Management Mentoring (PSM2) Forum 2015 - Topical Conference at the 2015 AIChE Spring Meeting and 11th Global Congress on Process Safety | Year: 2015

Many professionals believe you will only understand process safety if you have seen incidents firsthand. Some professionals believe firsthand experience is more valuable than reading or hearing about the experience. I believe they are right. Does that mean if these incidents haven't happened to you that you haven't had process safety "hit home"? Does that mean you will never gain the experience unless an incident arises? I disagree. I have never been a plant engineer or an operator. I am under twenty-five years old and have worked for an engineering firm ever since I graduated from college. Even with this background, I can tell you the exact moment when process safety hit home for me (and I didn't even step foot inside a chemical facility). That moment occurred when I attended my first professional conference. At the 9th Annual GCPS, I was listening to a speaker discuss the 2012 Chevron Refinery Fire. During the presentation, I first learned about the chemical safety board and its website. I was so interested in the CSB that later that night I watched the CSB video animation for the 2005 BP Texas City incident. To say the least, I was stunned. How did I never hear about this 2005 incident in college or since graduation? Was I living under a rock? Until that day and that moment, I did not truly realize that the instrumentation and control systems that engineers design every day could impact someone's safety. Yes, my employer emphasizes safety on a daily basis. A safety moment is always shared before any meeting starts, and every Wednesday we huddle as a group and discuss a safety topic. Also, a safety email is sent out weekly and we identify opportunities to improve safety in design through LOPA and HAZOP. However, because I had never seen an incident of this magnitude until this point, this was when process safety really hit home. This video brought home the professional responsibility that I have, that we all have, as engineers to consider the broad impact of decisions we make. This was an awakening for me. Knowledge can be obtained by listening, reading, and understanding history from the "senior engineers", the experienced co-workers and peers. The younger generation doesn't need to repeat incidents to fill the senior engineers' shoes. We can learn from the senior engineers, but not in the same way they necessarily learned, through trial and error. Through collaboration and knowledge sharing, we can learn from the past. The saying "history repeats itself" does not have to exist in the world of process safety, so let's get rid of it. The future of process safety is in the hands of four essential parties: the younger generation, the senior engineers, the employers, and the technology. The younger generation has to be ready to learn without "living through" all the experiences. The senior engineers have to be ready to teach effectively. The employers have to be ready to support the resources and tools for communication between the generations. Another hindrance to learning by shared experience, I have learned, is fear of litigation. In the earlier days of small firms, knowledge was shared over the water cooler, at lunches with coworkers and other small settings. But as firms get larger and larger, with offices spread all over the country and senior engineers retiring, how do we share institutional knowledge? Some companies teach "lessons learned" or post the same on intranet sites to pass on the mistakes made, and successes achieved. But lawyers are fearful that such documented mistakes might be misused by an aggressive plaintiff's lawyer, blowing them up on a large screen for a jury to see how bad the company has been. The result is that many firms don't teach lessons learned, or do so in a limited and protected manner that does not disseminate the information to those who need it. One solution that I've recently learned about is "peer review privilege" laws passed in a few states to encourage teaching these lessons so that history does not repeat itself. Finally, technology needs to be used to keep the communication strategy effective for those individuals trying to teach and learn in the future. All parties have to work together to learn from the past and not repeat it in the future. I am so privileged that my employer chose me to attend the conference that year, where I had my "Ah-Ha" moment. Luckily, through support from my employer and from coworkers, I was able to attend the conference that year and learn about the CSB. This guided me to use technology to seek the 2005 BP Texas City animation videos which effectively communicated the situation. I did not experience that incident firsthand; however, I know that video was when process safety hit home for me. That day is when I truly realized why my employer emphasizes safety on a daily basis and how my work could impact someone's life any time they worked in a facility I designed. Source


Williams C.,Burns and McDonnell
Technical Paper - Society of Manufacturing Engineers | Year: 2014

Whether you are building a greenfield site or renovating an existing facility, planning and designing a new manufacturing operation for many people can be a once-in-a-lifetime opportunity. There are many things to take into consideration when beginning such a task including: people flow, raw material management, management and production of the finished goods, special building or environmental needs for the process, transportation of material, and removal of waste materials. What is the most efficient way to make sure all these requirements are optimized in your new facility? Lean six sigma tools that were used to assist with the design of two manufacturing facilities are described. Source


Liang X.,Memorial University of Newfoundland | Hofman J.,Burns and McDonnell
IEEE Transactions on Industry Applications | Year: 2016

Power electronic devices are widely used in power grid associated with loads and renewable energy sources. With increasing penetration levels of these devices, their response characteristics to short-circuit events can have significant impact on power system dynamics. Power electronic devices are sensitive to voltage sags; they could trip off line under severe voltage disturbances. The ride-through capability of these devices determines if they will remain online. In this paper, a generic method is proposed on how to evaluate the ride-through capability of power electronic devices through trip curves. This method is a two-step procedure. Step 1 is to create a trip curve of the device. Step 2 is to conduct a ride-through evaluation based on the created trip curve and a short-circuit study. Creating a trip curve for a particular type of power electronic devices is critical and challenging. Three case studies are demonstrated in this paper on the trip curve creation for variable-frequency drives, dc drives, and solar photovoltaic inverters based on local and international standards, power grid interconnection requirements, and manufacturer specifications. The proposed method can serve as a general guideline for the trip curve creation for power electronic devices. © 2016 IEEE. Source


Ng K.W.,University of Wyoming | Garder J.,Burns and McDonnell | Sritharan S.,Iowa State University
Engineering Structures | Year: 2015

The American Association of State Highway Transportation Officials (AASHTO) recently calls for increasing service life of bridges and optimizing structural systems. To extend its service life, this paper focuses on using an advanced Ultra High Performance Concrete (UHPC) as an alternative material for integral abutment bridge pile foundations. A parametric analysis was performed to understand the effects of key parameters in the performance of the UHPC piles. Results from this study provided the necessary technical background for selecting a test site and designing a field test for the UHPC pile as well as for future field monitoring of UHPC pile. A series of field testing was conducted to evaluate the behaviors of two 230-mm, H-shaped, UHPC test piles (i.e., P3 and P4), driven in clayey silt to silty clay, as well as a structural splice on P4 during pile installation, vertical, and lateral load tests. The field test results confirm that UHPC piles have exceeded the target axial and lateral capacities, sufficient driving resistance, and adequate performance of the splice. The analytical and experimental results provided the technical background knowledge of using UHPC and established the basis for more future research that would consider other influential factors. © 2015 Elsevier Ltd. Source

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