scholarly journals EFFECT OF BROKEN DOLOSSE ON BREAKWATER' STABILITY

1976 ◽  
Vol 1 (15) ◽  
pp. 145 ◽  
Author(s):  
D. Donald Davidson ◽  
Dennis G. Markle
Keyword(s):  
Structural Integrity ◽  
Accurate Determination ◽  
Wave Forces ◽  
Design Data ◽  
Hydraulic Design ◽  
Overall Stability ◽  
Physical Limitations ◽  
The Stability ◽  
Water Bottom

Although the use of rubble-mound structures for protection of coastal areas is common throughout the world and considerable hydraulic design data have been developed to aid the designer, very little data are provided on the structural integrity of individual armor units and the effect of broken units on the stability of such structures. The forces to which such structures are subjected are complicated and vary with type and geometry of the structure, depth of water, bottom configuration seaward of the structure, water level relative to the crown of the structure, and wave dimensions. Since all of these parameters are involved, accurate determination of wave forces cannot be calculated; and although it is not impossible to model the structural strength of armor units or measure forces on individual armor units, there are physical limitations which make the tasks extremely difficult. There is one way, however, that a breakwater stability model, as it exists today, can provide useful information on this subject and that is to purposely break given numbers of armor units and observe the effect on the overall stability of the structure. Such tests have been conducted at the U. S. Army Engineer Waterways Experiment Station for the Atlantic Generating Station (AGS) Breakwater in which specific answers were desired; thus, the data are limited to the dolos armor unit. The data do provide, however, significant indications regarding the type and extent of breakage (cluster or random) that is most detrimental to the overall stability of the structure; whether costly reinforcing steel is warranted to assure reduced armor breakage; and where necessary, data from this type study can be used as a basis for setting maintenance criteria that will prevent deterioration of the breakwater due to armor unit breakage.

New Methodology for the Determination of the Vertical Center of Gravity of In-Service Semisubmersibles: Proposal and Numerical Assessment

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Ivan N. Porciuncula ◽  
Claudio A. Rodríguez ◽  
Paulo T. T. Esperança
Keyword(s):  
Accurate Determination ◽  
Center Of Gravity ◽  
Practical Implementation ◽  
Numerical Assessment ◽  
Neutral Equilibrium ◽  
Inclination Angles ◽  
Numerical Tools ◽  
The Stability ◽  
Metacentric Height

Along its lifetime, an offshore unit is subjected to several equipment interventions. These modifications may include large conversions in loco that usually are not adequately documented. Hence, the accurate determination of the platform's center of gravity (KG) is not possible. For vessels with low metacentric height (GM), such as semisubmersibles, Classification Societies penalize the platform's KG, inhibiting the installation of new equipment until an accurate measurement of KG is provided, i.e., until an updated inclining test is performed. For an operating semisubmersible, the execution of this type of test is not an alternative because it implies in removing the vessel from its in-service location to sheltered waters. Relatively recently, some methods have been proposed for the estimation of KG for in-service vessels. However, as all of the methods depend on accurate measurements of inclination angles and, eventually, on numerical tools for the simulation of vessel dynamics onboard, they are not straightforward for practical implementation. The objective of the paper is to present a practical methodology for the experimental determination of KG, without the need of accurate measurements of inclinations and/or complex numerical simulations, but based on actual operations that can be performed onboard. Indeed, the proposed methodology relies on the search, identification, and execution of a neutral equilibrium condition where, for instance, KG = KM. The method is exemplified using actual data of a typical semisubmersible. The paper also numerically explores and discusses the stability of the platform under various conditions with unstable initial GM, as well as the effect of mooring and risers.

Factors affecting constancy of acetate concentration and correct determination of methanogenic activity in pH-stat experiments

2003 ◽  
Vol 48 (6) ◽  
pp. 111-118
Author(s):  
M. Mösche ◽  
U. Meyer
Keyword(s):  
Accurate Determination ◽  
Original Method ◽  
Experimental Conditions ◽  
Methanogenic Activity ◽  
Factors Affecting ◽  
Acetate Concentration ◽  
Correct Determination ◽  
Ph Stat ◽  
The Stability

The determination of methanogenic activity with a pH-stat titration bioassay is evaluated utilising a mathematical model of this system. For given kinetic parameters and experimental conditions the model calculates the development of titrant flow and acetate concentration during experiments. Simulations of experiments under various conditions are compared. They show that the original method inherently causes a strong drift of acetate concentration during the experiments and a misestimation of methanogenic activity. As a solution to these disadvantages the addition of sodium hydroxide to the titrant and a careful control of pH during flushing the reactor with gas prior to the experiment are recommended. In this way a better constancy of acetate concentration and a more accurate determination of methanogenic activity should be achievable. The accuracy of this method is limited by the stability of pH-electrode calibration parameters.

scholarly journals Thermodynamic and Spectroscopic Studies of the Complexes Formed in Tartaric Acid and Lanthanide(III) Ions Binary Systems

Molecules ◽  
2020 ◽  
Vol 25 (5) ◽  
pp. 1121 ◽  
Author(s):  
Michal Zabiszak ◽  
Martyna Nowak ◽  
Zbigniew Hnatejko ◽  
Jakub Grajewski ◽  
Kazuma Ogawa ◽  
...  
Keyword(s):  
Tartaric Acid ◽  
Stability Constants ◽  
Binary Systems ◽  
Equilibrium Constants ◽  
Spectroscopic Studies ◽  
Luminescence Spectroscopy ◽  
Binary Complexes ◽  
Overall Stability ◽  
The Stability

Binary complexes of tartaric acid with lanthanide(III) ions were investigated. The studies have been performed in aqueous solution using the potentiometric method with computer analysis of the data for detection of the complexes set, determination of the stability constants of these compounds. The mode of the coordination of complexes found was determined using spectroscopy, which shows: Infrared, circular dichroism, ultraviolet, visible as well as luminescence spectroscopy. The overall stability constants of the complexes as well as the equilibrium constants of the reaction were determined. Analysis of the equilibrium constants of the reactions and spectroscopic data allowed the effectiveness of the carboxyl groups in the process of complex formation.

Factors affecting the stability and estimation of carotene in artificially dried grass and hays

1940 ◽  
Vol 30 (4) ◽  
pp. 622-638 ◽  
Author(s):  
S. K. Kon ◽  
S. Y. Thompson
Keyword(s):  
Chromatographic Analysis ◽  
Accurate Determination ◽  
Total Loss ◽  
Carotene Content ◽  
Factors Affecting ◽  
Ordinary Temperature ◽  
Initial Drop ◽  
The Difference ◽  
The Stability

1. The influence of storage in the light and in the dark at ordinary temperature and in a heated room at 70–80° F. on the carotene content of finely ground artificially dried grass stored in paper sacks and jute sacks was studied. There was an initial drop in carotene content from 61·1 to 46·5 mg./100 g., i.e. 23·9%, in the first month, and a total loss of 31·4% during 6 months' storage (August to February). No difference could be detected either between treatments or types of containers.2. There was a marked loss of carotene during 13 months' storage of baled artificially dried grass and of hays, amounting to 30–40% of the original value.3. Two methods of estimating carotene were compared. The method of Ferguson & Bishop (1936) gave higher results than the method of Peterson, Hughes & Freéman (1937). The difference is probably due to incomplete extraction in the latter method.4. Chromatographic analyses of “carotene” fractions from the above grasses showed the presence of coloured impurities amounting to 20·5–33·8% of the total recovered pigments.5. As these impurities are biologically inactive, chromatographic analysis or the use of special solvents are probably necessary for the accurate determination of carotene in forage.

scholarly journals Continuous low-maintenance CO<sub>2</sub>/CH<sub>4</sub>/H<sub>2</sub>O measurements at the Zotino Tall Tower Observatory (ZOTTO) in Central Siberia

2010 ◽  
Vol 3 (4) ◽  
pp. 1113-1128 ◽  
Author(s):  
J. Winderlich ◽  
H. Chen ◽  
C. Gerbig ◽  
T. Seifert ◽  
O. Kolle ◽  
...  
Keyword(s):  
Water Vapor ◽  
Accurate Determination ◽  
Field Tests ◽  
Central Siberia ◽  
Mixing Ratios ◽  
Air Sample ◽  
The Stability ◽  
Carbon Dioxide Co2 ◽  
Tall Tower

Abstract. To monitor the continental carbon cycle, a fully automated low maintenance measurement system is installed at the Zotino Tall Tower Observatory in Central Siberia (ZOTTO, 60°48' N, 89°21' E) since April 2009. A cavity ring-down spectroscopy (CRDS) analyzer continuously measures carbon dioxide (CO2) and methane (CH4) from six heights up to 301 m a.g.l. Buffer volumes in each air line remove short term CO2 and CH4 mixing ratio fluctuations associated with turbulence, and allow continuous, near-concurrent measurements from all tower levels. Instead of drying the air sample, the simultaneously measured water vapor is used to correct the dilution and pressure-broadening effects for the accurate determination of dry air CO2 and CH4 mixing ratios. The stability of the water vapor correction was demonstrated by repeated laboratory and field tests. The effect of molecular adsorption in the wet air lines was shown to be negligible. The low consumption of four calibration tanks that need recalibration only on decadal timescale further reduces maintenance. The measurement precision (accuracy) of 0.04 ppm (0.09 ppm) for CO2 and 0.3 ppb (1.5 ppb) for CH4 is compliant with the WMO recommendations. The data collected so far (until April 2010) reveals a seasonal cycle amplitude for CO2 of 30.4 ppm at the 301 m level.

scholarly journals Evaluation of Synthetic Cannabinoid Metabolites in Human Blood in the Absence of Parent Compounds: A Stability Assessment

2020 ◽  
Author(s):  
Alex J Krotulski ◽  
Sandra C Bishop-Freeman ◽  
Amanda L A Mohr ◽  
Barry K Logan
Keyword(s):  
Accurate Determination ◽  
Synthetic Cannabinoids ◽  
The United States ◽  
Storage Conditions ◽  
Synthetic Cannabinoid ◽  
Blood Samples ◽  
Flight Mass Spectrometry ◽  
Acid Metabolites ◽  
The Stability

Abstract Synthetic cannabinoids represent a chemically diverse class of novel psychoactive substances (NPS) responsible for large analytical and interpretative challenges for forensic toxicologists. Between 2016 and 2019, the three most prevalent synthetic cannabinoids in the United States were MMB-FUBINACA (FUB-AMB), 5F-MDMB-PINACA (5F-ADB) and 5F-MDMB-PICA, based on results from seized drug and toxicology testing. In 2018, accurate determination of synthetic cannabinoid positivity was brought into question as it was determined that the metabolites of these drug species were present in the absence of parent compounds in forensically relevant blood samples. During this study, the stability of MMB-FUBINACA, 5F-MDMB-PINACA and 5F-MDMB-PICA was evaluated, as well as the characterization of breakdown products. A liquid–liquid extraction method was assessed for recovery of basic parent compounds and acidic metabolites and deemed fit for use in this study. Analysis was performed by liquid chromatography–quadrupole time-of-flight mass spectrometry (LC–QTOF-MS) using a SCIEX TripleTOF® 5600+. All three synthetic cannabinoids were found to be unstable when stored in blood at either room temperature or refrigerated; all analytes were considerably more stable when stored in the freezer. All three synthetic cannabinoids degraded to their respective butanoic acid metabolites: MMB-FUBINACA 3-methylbutanoic acid, 5F-MDMB-PINACA 3,3-dimethylbutanoic acid and 5F-MDMB-PICA 3,3-dimethylbutanoic acid. All three of these metabolites were studied and determined to be stable in blood at all storage conditions. Considering these results, our laboratory continued testing for synthetic cannabinoid metabolites in blood samples and found 83 positives (21%) for only a synthetic cannabinoid metabolite. A case report is presented herein where 5F-MDMB-PINACA 3,3-dimethylbutanoic acid was identified in the absence of 5F-MDMB-PINACA. Forensic toxicologists should be aware of the results of this study as they directly impact analytical consideration for test development and implementation, as well as interpretation of findings.

103Rh-NMR-Untersuchungen an Chloro-Bromo-Rhodaten(III) und Bestimmung der Stabilitätskonstanten im System [RhClnBr6-n]3-, n = 0-6 / 103Rh NMR Studies of Chloro-Bromo-Rhodates(III) and Determination of the Stability Constants in the System [RhCl„Br6-n]3-, n = 0-6

1989 ◽  
Vol 44 (11) ◽  
pp. 1402-1406 ◽  
Author(s):  
W. Kuhr ◽  
G. Peters ◽  
W. Preetz
Keyword(s):  
Nmr Spectroscopy ◽  
High Resolution ◽  
Stability Constant ◽  
Stability Constants ◽  
Trans Isomers ◽  
Nmr Studies ◽  
Downfield Shift ◽  
Overall Stability ◽  
The Stability

By 103Rh NMR spectroscopy the ten compounds of the system [RhCl„Br6_„]3-, n = 0-6 are identified by separate signals. A downfield shift of approximately 160 ppm is observed per substitution of Cl by Br, and the stereoisomers for n = 2, 3, 4 are separated by at least 4 ppm. From the relative intensities of the 103Rh signals in equilibrated solutions, whose total contents of Rh. Cl and Br are known, six individual stability constants are calculated. Their product gives the overall stability constant, indicating [RhBr6]3- to be 36,300 times more stable than [RhCl6]3-. On treatment of [RhBr6]3- with HCl cis/fac isomers are formed stereospecifically, whereas the reaction of [RhCl6]3- with HBr gives trans isomers, n = 2 and 4, containing 20—30% of the cis compounds; only mer-[RhCl3Br3] 3- is obtained pure. The high resolution spectra of [RhCl6]3- and [RhBr6]3- are exhibit five signals each, reflecting the intensity patterns of the most abundant isotopomers within [Rh35Cln37Cl6-n]3-, n = 2-6, and [Rh79Br„81Br6_„]3-, n = 1-5, respectively.

An Experimental Study of the Stability of an Externally Pressurized, Gas-Lubricated Thrust Bearing

1966 ◽  
Vol 33 (1) ◽  
pp. 25-30 ◽  
Author(s):  
L. Licht ◽  
H. G. Elrod
Keyword(s):  
Experimental Study ◽  
Experimental Investigation ◽  
Thrust Bearing ◽  
Accurate Determination ◽  
Experimental Program ◽  
The Subject ◽  
The Stability ◽  
Stability Limits ◽  
Prior Analysis

The subject of this experimental investigation is the phenomenon of self-excited vibrations occurring in externally pressurized, gas-lubricated bearings. The experimental program pursued here is guided by predictions based on prior analysis. An apparatus is designed and instrumented to provide for the variation of governing parameters and for the accurate determination of their critical values. Stability bounds are obtained for a circular thrust bearing and the experimental results are compared and contrasted with previously reported, theoretical stability limits.

scholarly journals A structural ensemble of a tau-microtubule complex reveals regulatory tau phosphorylation and acetylation mechanisms

2021 ◽  
Author(s):  
Z. Faidon Brotzakis ◽  
Philip Lindstedt ◽  
Ross Taylor ◽  
Gonçalo Bernardes ◽  
Michele Vendruscolo
Keyword(s):  
Excited States ◽  
Structural Biology ◽  
Chemical Mutagenesis ◽  
Macromolecular Complexes ◽  
Structure And Dynamics ◽  
Cryo Electron Microscopy ◽  
Overall Stability ◽  
The Stability ◽  
Structural Ensemble

Abstract Tau is a microtubule-associated protein that regulates the stability of microtubules. We use metainference cryo-electron microscopy, an integrative structural biology approach, to determine an ensemble of structures representing the structure and dynamics of a tau-microtubule complex comprising the entire microtubule-binding region of tau. We thus identify the ground state of the complex and a series of excited states of lower populations. A comparison of the interactions in these different states reveals positions along the tau sequence that are important to determine the overall stability of the tau-microtubule complex. This analysis leads to the identification of positions where phosphorylation and acetylation events have destabilising effects, which we validate by using site-specific post-translationally modified tau variants obtained by chemical mutagenesis. Taken together, these results illustrate how the simultaneous determination of ground and excited states of macromolecular complexes reveals functional and regulatory mechanisms.

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