Error issues

An analytical result is never perfect. It is always affected by a certain number of errors categorized as systematic (bias) and random errors. For example, an autosampler commits systematic errors when it injects I.I pL of a sample at a speed of 12 pL.s when the specification is to inject a volume of 1.0 pL at 10 pL.s 

The autosampler errors pervade the whole series of samples. If an operator injects a sample by hand, he commits subjective random errors, for example, by varying the volume injected or the injection speed. 

Accuracy— Accuracy expresses the narrowness of the span between the average value obtained from a series of trial results and a value accepted as conventionally true, or as an admitted reference value. Accuracy problems indicate systematic errors. 

---

It eliminates blend sampling error issues related to thief sampling. 

Stanton, N.A. and Stevenage, S.V. (1998). Learning to predict human error issues of acceptability, reliability and validity. Ergonomics, 41(11), 1737-1756. 

Associated with each of these demands that may cause the hazardous event were various protective systems. These were either hardware (e.g., ventilation system, flammable gas detectors) or procedural (e.g., instructions on allowable maintenance activities). For any particular demand to lead to the hazardous event, all the protective systems designed to protect against that demand must have failed to perform. Again, this failure may be a hardware failure (e.g., the gas detector has drifted out of calibration) or a human error issue (e.g., the flammable gas detector alarm warned of a flammable leak but Ihe operator failed to take appropriate action). 

A kinetics text with a strong theoreticai bent that overviews transient kinetic methods and discusses data anaiysis issues such as error propagation and sensitivity anaiysis. 

Computational issues that are pertinent in MD simulations are time complexity of the force calculations and the accuracy of the particle trajectories including other necessary quantitative measures. These two issues overwhelm computational scientists in several ways. MD simulations are done for long time periods and since numerical integration techniques involve discretization errors and stability restrictions which when not put in check, may corrupt the numerical solutions in such a way that they do not have any meaning and therefore, no useful inferences can be drawn from them. Different strategies such as globally stable numerical integrators and multiple time steps implementations have been used in this respect (see [27, 31]). 

There are a number of other technical details associated with HF and other ah initio methods that are discussed in other chapters. Basis sets and basis set superposition error are discussed in more detail in Chapters 10 and 28. For open-shell systems, additional issues exist spin polarization, symmetry breaking, and spin contamination. These are discussed in Chapter 27. Size-consistency and size-extensivity are discussed in Chapter 26. 

Until now we have been discussing the kinetics of catalyzed reactions. Losses due to volatility and side reactions also raise questions as to the validity of assuming a constant concentration of catalyst. Of course, one way of avoiding this issue is to omit an outside catalyst reactions involving carboxylic acids can be catalyzed by these compounds themselves. Experiments conducted under these conditions are informative in their own right and not merely as means of eliminating errors in the catalyzed case. As noted in connection with the discussion of reaction (5.G), the intermediate is stabilized by coordination with a proton from the catalyst. In the case of autoprotolysis by the carboxylic acid reactant, the rate-determining step is probably the slow reaction of intermediate [1] ... 

An extremely important safety issue with respect to ah. wood product manufacturing processes is personal worker safety. Ah of the processes use much moving machinery, usuahy including many saws or knives. Workers must continuahy remember the inherent dangers these machines involve as weh as other possible dangerous situations which could result from malfunctions or other errors. In addition, most processes are more or less dusty and noisy. Most employers require use of safety glasses and many require hearing protection, safety shoes, and hardhats as weh as other kinds of protection needed for Specific jobs. 

If, upon review of the patent, the patentee discovers that the claims contain a formal error, are too narrow, or are too broad in view of the prior art, the patentee may ask the U.S. PTO to correct this error. There are four administrative vehicles for correcting errors in issued patents. The appHcation of each of these mechanisms is dependent on the nature and severity of the error, as weU as the source of its creation. 

The Notice of Errors. The first mechanism for correction of errors is called a "Notice of Errors." This document may be filed by the patentee after issuance of the patent with the U.S. PTO and references the patent number, issue date, and the errors contained in the patent. The purpose of a Notice of Errors is to clarify the examination history of the patent and such notice dispositively corrects any misspellings, or typographical errors or omissions. One example of a problem which may be clarified by a Notice of Errors is an omitted chemical bond in a compound used in an exemplary embodiment of the invention. In short, the error is obvious and easily corrected. 

The Notice of Errors should resolve those problems which are evident on the face of the patent but which also may be, by their nature, obvious and correctable problems to someone reading only the patent. The Notice of Errors does not result in a further pubHcation by the U.S. PTO, but rather it is instead placed into the examination history of the issued patent and thus is available to anyone who may wish to read this examination history. The Notice of Errors is appropriate for correcting simple matters which do not affect the claim scope or the vaHdity of the patent. 

The Certificate of Correction. Another mechanism for correcting the patent is the "Certificate of Correction," which is essentially a petition filed by the patentee to correct minor errors in the patent produced either by the U.S. PTO or inadvertentiy by the appHcant. Unlike the Notice of Errors, a Certificate of Correction does result in an additional pubHcation from the U.S. PTO, and anyone requesting a copy of a patent in which a Certificate of Correction has been filed will also obtain the Certificate of Correction. A Certificate of Correction reflects amendments made during the examination of the patent which were entered by the examiner but not found within the issued patent. The omission of such amendments can be in the body of the patent or in the patent claims. The Certificate of Correction may also be used to correct errors in the issued patent which were not present in the patent appHcation when it was filed. If the error was caused by the patent appHcant prior to or during examination, the patent appHcant bears the cost of filing and... 

Understanding the behavior of all the chemicals involved in the process—raw materials, intermediates, products and by-products, is a key aspect to identifying and understanding the process safety issues relevant to a given process. The nature of the batch processes makes it more likely for the system to enter a state (pressure, temperature, and composition) where undesired reactions can take place. The opportunities for undesired chemical reactions also are far greater in batch reaction systems due to greater potential for contamination or errors in sequence of addition. This chapter presents issues, concerns, and provides potential solutions related to chemistry in batch reaction systems. 

Safety issues in batch reaction systems relating to human errors and procedures are presented in Table 6. The table is meant to be illusttative but not comprehensive. 

Listed below are operator related safety issues that are more prevelant in batch operations. Keep in mind, however, that human error consists of more facets than operator error alone. 

You should consider obtaining internal and external quality assurance reviews of the study (to ferret out errors in modeling, data, etc.). Independent peer reviews of the QRA results can be helpful by presenting alternate viewpoints, and you should include outside experts (either consultants or personnel from another plant) on the QRA review panel. You should also set up a mechanism wherein disputes between QRA team members (e.g., technical arguments about safety issues) can be voiced and reconciled. All of these factors play an essential role in producing a defendable, high-quality QRA. Once the QRA is complete, you must formally document your response to the project team s final report and any recommendations it contains. 

This allows for the equivalence between crossed cylinders and the particle on a plane problem. Likewise, the mechanics of two spheres can be described by an equivalently radiused particle-on-a-plane problem. The combination of moduli and the use of an effective radius greatly simplifies the computational representation and allows all the cases to be represented by the same formula. On the other hand, it opens the possibility of factors of two errors if the formula are used without realizing that such combinations have been made. Readers are cautioned to be aware of these issues in the formulae that follow. 

There is increasing interest in human factors issues in the CPI. Kletz (1991), Lorenzo (1990) and Mill (1992) address human error in the CPI, Kletz (1994) addresses human factors through case studies. 

Instructions concerning safety and environmental issues should be integrated into the control and operating procedures such that the instructions are given at the stage in the process when they apply. In this way staff do not have to consult several documents and the chance of error is reduced. 

Another barrier to a systematic consideration of human error is the belief that increasing computerization and automation of process plants will make the human unnecessary. The fallacy of this belief can be shown from the numerous accidents that have arisen in computer controlled plants. In addition, considerable human involvement will continue to be necessary in the critical areas of maintenance and plant modification, even in the most automated process (see Chapter 2 for a further discussion of this issue). 

Despite the lack of interest in human factors issues in the CPI in the past, the situation is now changing. In 1985, Trevor Kletz published his landmark book on human error in the CPI An Engineer s View of Human Error (revised in 1991). Several other books by the same author e.g., Kletz (1994b) have also addressed the issue of human factors in case studies. Two other publications have also been concerned specifically with human factors in the process industry Lorenzo (1990) was commissioned by the Chemical Manufacturers Association in the USA, and Mill (1992), published by the U.K. Institution of Chemical Engineers. In 1992, CCPS and other organizations sponsored a conference on Human Factors and Human Reliability in Process Safety (CCPS, 1992c). This was further evidence of the growing interest in the topic within the CPI. 

---