A Common Operational Problem in DNS Servers: Failure to Communicate

2020 ◽  
Author(s):  
M. Andrews ◽  
R. Bellis
Keyword(s):  
2021 ◽  
Author(s):  
Grahame Taylor ◽  
Jonathan Wylde ◽  
Walter Samaniego ◽  
Ken Sorbie

Abstract Despite attempts to inhibit or avoid the formation of fouling deposits (polymeric amorphous dithiazine or apDTZ for short) from the use of MEA triazine, this remains a major operational problem and limits the use of this most popular and ubiquitous hydrogen sulphide (H2S) scavenger. This paper (a) reviews and summarizes previous work, (b) provides fresh insights into the reaction product and mechanism of formation, (c) proposes an effective method of removal, and (d) proposes some mechanisms of apDTZ digestion. The mechanism of apDTZ formation is discussed and reasoning is provided from a variety of perspectives as to the mechanism of MEA-triazine reaction with H2S. These include basicity and nucleophilic substitution considerations, steric properties and theoretical calculations for electron density. Novel procedures to chemically react with and destroy this solid fouling are presented with an in-depth study and experimental verification of the underlying chemistry of this digestion process. A review of agents to chemically destroy apDTZ is undertaken and a very effective solution has been found in peroxyacetic acid, which is much more powerful and effective than previously suggested peroxides. The structure of amorphous polymeric dithiazine is emphasized and the reason why this fouling cannot be 1,3,5-trithiane is stressed. This work therefore overcomes a current industry misconception by providing insight on two major paradoxes in the reaction pathway; namely i) why the thiadiazine reaction product from tris hydroxyethyl triazine (MEA triazine) is never observed and ii) why does the dithiazine in all cases never progress to the trithiane (3rd sulphur molecule substitution)? The latter issue is probably the biggest misconception in the industry and literature regarding triazine and H2S reactions. Many reasons for this are put forward and the common misconception of "overspent" triazine is refuted. A very effective chemical reaction that results in soluble by-products, counteracting the problems produced by this intractable polymer is found and their composition is proposed and experimentally verified.


Author(s):  
Basim Mekha ◽  
Alok Kumar ◽  
Mike Stark ◽  
Paul Barnett

In recent years, most fluid produced or exported has been transported using steel catenary risers (SCRs) attached to deepwater floating structures. The SCRs are terminated at the floating structures using Top Termination Units (TTUs) such as flexible joints or tapered stress joints. The flexible joints are usually designed to allow the riser to rotate with the floating structure motion and reduce the amount of moments transferred to the hull structure. The flexible joints depend on the flexibility and compressibility of the elastomer layers to allow for the rotation of the SCR. The stress joints, alternatively, provide fixed support at the hull and thus larger bending moment that has to be accounted for in the hull design. The stress joints can be made of steel or titanium material. The SCR TTU’s receptacle, which will be welded to the hull porch and contains the TTU basket, has to be designed to meet the force and reaction requirements associated with the selected TTU type. However, in some cases which could be due to failure of the TTU to meet the expected life or the operational requirements, the operators may have to replace the damaged TTU with another one or with a different TTU type. A few examples are available in the Gulf of Mexico. Recently the Flexible Joint TTU of the Independent Hub 20-inch export SCR had an operational problem. During the course of investigating the related issues and studying possible solutions, one option considered was the feasibility of replacing the Flexible Joint (FJ) with Titanium Tapered Stress Joint (TSJ). This paper highlights the issues that have to be considered in the design of the FJ existing receptacle to accommodate the force reactions of a Titanium TSJ. These issues are addressed and the results of the detailed finite element analysis performed are provided. The analysis conclusions, which are related to the feasibility of the existing receptacle to receive the loads imposed by TSJ and the modifications required to achieve this, are presented.


2019 ◽  
Vol 11 (2) ◽  
pp. 162-176
Author(s):  
Thomas Duening

Purpose This paper is based on insights from philosophy of science, centered in Gilbert Ryle’s notion of “category mistakes”. A category mistake occurs in a science when scholars have been thinking of a phenomenon as of a certain sort, when it is really nothing of the kind. This paper aims to claim that regarding sustained enterprise innovation (SEI) as a strictly operational problem commits such a category mistake. Instead, SEI is an aspirational problem and thus requires scholars to examine it from that perspective as well. Design/methodology/approach This paper begins by explicating Ryle’s notion of a category mistake. It develops the suggestion that innovation scholars have made such a mistake by thinking of innovation as a strictly operational problem. In reality, it is as much an aspirational problem. The paper then builds on the metaphor made famous by Isaiah Berlin, distinguishing between hedgehogs and foxes. A hedgehog is a leader who copes with the non-predictive nature of innovation. The paper builds on the findings from positive psychology and virtue epistemology to highlight how humans can act rationally in the face of non-predictive outcomes. Four virtues of hedgehog leadership are proposed and defined. Findings The paper concludes that hedgehog leadership is necessary for sustained enterprise innovation. It also concludes that hedgehogs can act rationally in pursuit of non-predictive outcomes by practicing a set of governing virtues. Research limitations/implications Further research needs to be conducted to validate the proposed governing virtues, to illuminate the optimal hedgehog/fox balance within the enterprise, and to validate through longitudinal work the impact of hedgehogs on sustained enterprise innovation. Practical implications Based on the continuing interest in innovation expressed by enterprise leaders around the world, hedgehogs are in increasing demand. Fortunately, hedgehogs can be made (and self-made) via deliberate practice of the governing virtues. Aspiring and current hedgehogs can be confident that practicing these virtues and becoming increasingly adept at their application will promote and effect enterprise innovation. Originality/value Very little research has been conducted on the aspirational aspect of SEI. This is an insidious gap in the literature, as it affects scholars and practitioners alike. Scholars are trapped in the “normal science” paradigm that treats the innovation problem as if it can be solved through operational techniques. This paper contends that this ubiquitous category mistake has led scholars down a blind alley. Instead, it is important for scholars and practitioners alike to view SEI as an aspirational problem that requires vastly different research frameworks and practitioner prescriptions.


1962 ◽  
Vol 15 (4) ◽  
pp. 364-369
Author(s):  
P. M. Lamb

1. Introduction. By definition a hovercraft or air-cushion vehicle is a vehicle capable of being operated so that its weight is partly or wholly supported by a self-generated cushion of air that is dependent for its effectiveness on the proximity of the surface over which the vehicle operates. Thus from the safety aspect of navigation a hovercraft must be treated as a surface vehicle or craft; for any collision risks involved are proportional to the amount of conventional surface vehicles or craft and static obstructions, in the area of operation. The clearance of minor obstacles less than the hoverheight is practicable; but on present experimental craft with an undersurface clearance of three feet, these clearances are limited to small buoys, waterlogged obstructions and rock outcrops of limited height.


1979 ◽  
Author(s):  
S. M. Kowleski ◽  
C. D. Harrington

This paper describes the planning, developmental, equipment selection and operational problem phases of the high-speed ferry system presently being operated on San Francisco Bay by the Golden Gate Bridge, Highway and Transportation District. The reasons for the selection of the vessel propulsion package consisting of gas turbine engines and waterjet pumps are discussed in some detail. Most importantly, the paper covers the problems experienced to date with this equipment in continuous marine operation.


1985 ◽  
Vol 1 (S1) ◽  
pp. 144-145
Author(s):  
Rodney Dreifuss ◽  
Emil Pascarelli

Perhaps the greatest operational problem faced by the New York City Emergency Medical Service (EMS) today is the sheer volume of calls entering the system, and the fact that many of those requests for medical aid are not life-threatening emergencies requiring ambulance transport. This creates two situations that New York City is all too familiar with: (l) ambulances are not available for true emergencies; and (2) response times for ambulances to arrive at the scene of an emergency are extended.A four-month pilot “on-scene triage” program was initiated by EMS as a possible solution to these problems. The program ran from May to August of 1980. A marked EMS car was designated as the “Triage Car” and was in operation during those hours when ambulance requests were at their peak (usually two to ten PM).


2011 ◽  
Vol 58-60 ◽  
pp. 1767-1772
Author(s):  
Kee Rong Wu ◽  
Chung Wei Yeh

We proposed a two-layer scheme of Deoxyribonucleic acid (DNA) based computation, DNA-01MKP, to solve the typical NP-hard combinatorial optimization problem, 0-1 multidimensional knapsack problem (0-1 MKP). DNA-01MKP consists of two layers of procedures: (1) translation of the problem equations to strands and (2) solution of problems. For layer 1, we designed flexible well-formatted strands to represent the problem equations; for layer 2, we constructed the DNA algorithms to solve the 0-1 MKP. Our results revealed that this molecular computation scheme is able to solve the complicated operational problem with a reasonable time complexity of O(n×k), though it needs further experimental verification in the future. By adjusting the DNA-based procedures, the scheme may be used to resolve different NP-hard problems.


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