Improved Methods for the Prediction of Chatter in Turning, Part 1. Determination of Structural Response Parameters

1991 ◽  
Vol 13 (1) ◽  
pp. 71-72
Keyword(s):  
Structural Response ◽  
Improved Methods

Improved Methods for the Prediction of Chatter in Turning, Part 1: Determination of Structural Response Parameters

1990 ◽  
Vol 112 (1) ◽  
pp. 12-20 ◽  
Author(s):  
I. E. Minis ◽  
E. B. Magrab ◽  
I. O. Pandelidis
Keyword(s):  
Structural Response ◽  
Impact Testing ◽  
Modal Parameters ◽  
Improved Method ◽  
Input Force ◽  
Interrupted Cutting ◽  
Force Components ◽  
Cutting Point ◽  
Improved Methods

The dynamics of the structure of a lathe at the cutting point are directly identified under normal machining operation using an improved version of a method originally proposed by Opitz and Weck. The improved method is based on the interrupted cutting of a specially designed, surface-modulated workpiece that provides a strong, broadband excitation. This interrupted cutting has been theoretically shown to permit the identification of the structure’s dynamics from input-output measurements, despite the intrinsic coupling of the structure with the cutting process during machining. All three components of the cutting force and the tool’s acceleration are measured simultaneously. It was found that the input force components were correlated, so that measurements from two distinct cutting configurations had to be used to obtain the elements of the structure’s transfer matrix. The modal parameters measured during the interrupted cutting tests were compared to the results of commonly used impact tests, which can only be applied when there is no cutting. This study showed that the damping of the machine tool’s structure increases during cutting by 20 to 40 percent of that measured by impact testing.

scholarly journals Overview of the analytical methods for vancomycin and/or teicoplanin determination in biological matrices

2017 ◽  
Vol 71 (2) ◽  
pp. 87-97 ◽  
Author(s):  
Ana Stajic ◽  
Biljana Jancic-Stojanovic
Keyword(s):  
Sample Preparation ◽  
Bacterial Infections ◽  
Multidrug Resistant ◽  
Glycopeptide Antibiotics ◽  
Biological Matrices ◽  
Preparation Methods ◽  
Chromatography Tandem Mass Spectrometry ◽  
Liquid Chromatography Tandem Mass ◽  
Improved Methods

Background. Teicoplanin and vancomycin are glycopeptide antibiotics currently in use for treatment of multidrug-resistant bacterial infections. Scope and Approach. Severe undesirable effects, such as ototoxicity, nephrotoxicity and neutropenia have been reported for vancomycin and teicoplanin, which necessitates monitoring the concentration of these two drugs in different biological samples. In order to obtain precise and accurate results, sensitive, reliable and fast methods are necessary. The main aim of this mini review is to give a clear and concise overview of the recently developed, validated, novel and improved methods for glycopeptide antibiotic analyses in various biological matrices. Also, the variability of the matrices requires optimal and effective sample preparation procedures to be developed, and so these are discussed. Key Findings and Conclusions. Different liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods have been described for quantitative determination of glycopeptide antibiotics in various biological matrices. It was shown that protein precipitation was a convenient method for sample preparation despite the high number of novel sample preparation methods.

Improved methods for determination of guanylyl cyclase activity and synthesis of [α-32P]GTP

1979 ◽  
Vol 93 ◽  
pp. 124-133 ◽  
Author(s):  
Lutz Birnbaumer ◽  
Héctor N. Torres ◽  
Mirtha M. Flawiá ◽  
Robert F. Fricke
Keyword(s):  
Guanylyl Cyclase ◽  
Cyclase Activity ◽  
Improved Methods ◽  
Guanylyl Cyclase Activity

X-Ray Spectrometric Determination of Sulfate in Natural Waters

1979 ◽  
Vol 23 ◽  
pp. 133-141
Author(s):  
C. A. Seils ◽  
G. T. Tisue
Keyword(s):  
Natural Waters ◽  
Rapid Determination ◽  
Atomic Absorption Spectrophotometry ◽  
Good Choice ◽  
Small Samples ◽  
Selective Electrode ◽  
X Ray ◽  
Heavy Metal Cations ◽  
Improved Methods

A recent surge of interest in sulfur in the environment has revealed the need for improved methods of analysis for sulfate, SO4=, in rain, freshwater and sediment interstitial fluids. Ion chromatography permits the rapid determination of SO4= in the ppm range (1 ppm = 1 mgL'1 = 10 μmol L-1 sulfate) on relatively small samples with good specificity. If a suitable instrument is available, this technique is a good choice for many environmental analyses. Other approaches to sulfate analysis are based on its precipitation with organic or heavy metal cations, usually barium or lead. The amount of precipitate formed may be determined by inter alia gravimetry, turbidimetry, radiometry (using 133-Ba), atomic absorption spectrophotometry (Ba or Pb detection), potentiometry (using a Pb++ ion selective electrode) , colorimetry, or by x-ray fluorescence spectrometry (Ba, Pb or S detection)(1). Because of our experience with x-ray fluorescence analyses, we chose to develop and test a procedure using that technique.

Estimation of total arterial compliance: an improved method and evaluation of current methods

1986 ◽  
Vol 251 (3) ◽  
pp. H588-H600 ◽  
Author(s):  
Z. Liu ◽  
K. P. Brin ◽  
F. C. Yin
Keyword(s):  
Diastolic Pressure ◽  
Arterial Compliance ◽  
Aortic Pressure ◽  
Arterial System ◽  
Windkessel Model ◽  
Total Arterial Compliance ◽  
Improved Methods ◽  
Mean Aortic Pressure

Determination of arterial compliance in vivo has long interested physiologists. Most current methods for estimating this parameter assume that compliance is constant, i.e., that arterial pressure-volume (P-V) relations are linear, and they also assume that diastolic aortic pressure decay is an exponential function of time. Both of these assumptions, however, are questionable. This study proposes improved methods of estimating compliance based on a Windkessel model of the arterial system but which utilize the area under the pressure tracing rather than the waveform itself. Formulations accounting for both linear and three hypothetical nonlinear arterial P-V relations (exponential, logarithmic, and parabolic) are presented. Data from patients with congestive heart failure and hypertension are used for illustration. Compliances assuming linear P-V relations are reasonably close to those assuming nonlinear P-V relations only at mean aortic pressure. At end-diastolic pressure the linear assumption underestimates and at peak systolic it overestimates the compliances obtained assuming nonlinear P-V relations. The simpler linear assumption still allows a first approximation to compliance, but we show that existing methods for obtaining compliance under this assumption have severe theoretical as well as practical shortcomings. Our proposed method avoids these shortcomings primarily because deviations from an exact exponential form of the pressure wave have less influence on these compliance estimates than currently used methods.

Improved Methods for PCA-Based Reconstructions: Case Study Using the Steig et al. (2009) Antarctic Temperature Reconstruction

2011 ◽  
Vol 24 (8) ◽  
pp. 2099-2115 ◽  
Author(s):  
Ryan O’Donnell ◽  
Nicholas Lewis ◽  
Steve McIntyre ◽  
Jeff Condon
Keyword(s):  
Satellite Data ◽  
Expectation Maximization Algorithm ◽  
Principal Component ◽  
Temperature Reconstruction ◽  
Previous Method ◽  
West Antarctica ◽  
Temperature Trends ◽  
Temporal Relationships ◽  
Improved Methods

Abstract A detailed analysis is presented of a recently published Antarctic temperature reconstruction that combines satellite and ground information using a regularized expectation–maximization algorithm. Though the general reconstruction concept has merit, it is susceptible to spurious results for both temperature trends and patterns. The deficiencies include the following: (i) improper calibration of satellite data; (ii) improper determination of spatial structure during infilling; and (iii) suboptimal determination of regularization parameters, particularly with respect to satellite principal component retention. This study proposes two methods to resolve these issues. One utilizes temporal relationships between the satellite and ground data; the other combines ground data with only the spatial component of the satellite data. Both improved methods yield similar results that disagree with the previous method in several aspects. Rather than finding warming concentrated in West Antarctica, the authors find warming over the period of 1957–2006 to be concentrated in the peninsula (≈0.35°C decade−1). This study also shows average trends for the continent, East Antarctica, and West Antarctica that are half or less than that found using the unimproved method. Notably, though the authors find warming in West Antarctica to be smaller in magnitude and find that statistically significant warming extends at least as far as Marie Byrd Land. This study also finds differences in the seasonal patterns of temperature change, with winter and fall showing the largest differences and spring and summer showing negligible differences outside of the peninsula.

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