Optimization of the time the chromatograph thermostats exit to a given temperature

2020 ◽  
pp. 40-45
Author(s):  
Nadezhda O. Vzduleva ◽  
Valery B. Gitlin
Keyword(s):  
Heating Rate ◽  
Entire Range ◽  
Gas Chromatograph ◽  
Heating And Cooling ◽  
Operating Temperatures ◽  
The Stability

The problems of ensuring the stability of the temperature of the chromatographic experiment carried out using a serial gas chromatograph LGH-3000 are considered. Limiting the permissible heating rate of the chromatograph thermostats does not allow a quick transition to the new conditions of the chromatographic experiment in accordance with the requirements of the technical conditions. The processes of heating and cooling the thermostat are analyzed. It is shown that the ratio of the duration of the interval equal to the sum of the durations of the heating and cooling intervals to the duration of the heating interval is inversely proportional to the temperature of the chromatographic experiment. Based on this situation, an empirical algorithm is proposed for heating the thermostat to a given temperature, which made it possible to reduce the time it takes to reach a given temperature in the entire range of operating temperatures.

scholarly journals Prediction of Second Melting Temperatures Already Observed in Pure Elements by Molecular Dynamics Simulations

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6509
Author(s):  
Robert F. Tournier ◽  
Michael I. Ojovan
Keyword(s):  
Glass Transition ◽  
Heating Rate ◽  
Homogeneous Nucleation ◽  
Glassy State ◽  
Singular Values ◽  
Md Simulations ◽  
Melting Temperatures ◽  
Heating And Cooling ◽  
Dynamics Simulations ◽  
Universal Law

A second melting temperature occurs at a temperature Tn+ higher than Tm in glass-forming melts after heating them from their glassy state. The melting entropy is reduced or increased depending on the thermal history and on the presence of antibonds or bonds up to Tn+. Recent MD simulations show full melting at Tn+ = 1.119Tm for Zr, 1.126Tm for Ag, 1.219Tm for Fe and 1.354Tm for Cu. The non-classical homogeneous nucleation model applied to liquid elements is based on the increase of the Lindemann coefficient with the heating rate. The glass transition at Tg and the nucleation temperatures TnG of glacial phases are successfully predicted below and above Tm. The glass transition temperature Tg increases with the heating rate up to Tn+. Melting and crystallization of glacial phases occur with entropy and enthalpy reductions. A universal law relating Tn+ and TnG around Tm shows that TnG cannot be higher than 1.293Tm for Tn+= 1.47Tm. The enthalpies and entropies of glacial phases have singular values, corresponding to the increase of percolation thresholds with Tg and TnG above the Scher and Zallen invariant at various heating and cooling rates. The G-phases are metastable up to Tn+ because the antibonds are broken by homogeneous nucleation of bonds.

scholarly journals Effect of Pyrolysis Conditions on the Performance of Co–Doped MOF–Derived Carbon Catalysts for Oxygen Reduction Reaction

Catalysts ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1163
Author(s):  
Ning Cui ◽  
Kexiao Bi ◽  
Wei Sun ◽  
Qianqian Wu ◽  
Yinan Li ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Heating Rate ◽  
Reduction Reaction ◽  
Half Wave ◽  
Step Heating ◽  
The Stability ◽  
Carbon Catalysts ◽  
Co Doped

MOF–derived porous carbon is a type of promising catalyst to replace expensive Pt–based catalysts for oxygen reduction reaction (ORR). The catalytic activity for ORR depends closely on pyrolysis conditions. In this work, a Co–doped ZIF–8 material was chosen as a research object. The effect of pyrolysis conditions (temperature, heating rate, two–step heating) on the ORR performance of ZIF–derived carbon catalysts was systematically studied. The Co–ZIF–8 catalyst carbonized at 900 °C exhibits better ORR catalytic activity than that carbonized at 800 °C and 1000 °C. Moreover, a low heating rate can enhance catalytic activity. Two–step pyrolysis is proven to be an effective way to improve the performance of catalysts. Reducing the heating rate in the low–temperature stage is more beneficial to the ORR performance, compared to the heating rate in the high–temperature stage. The results show that the Co–ZIF–8 catalyst exhibits the best performance when the precursor was heated to 350 °C at 2 °C/min, and then heated to 900 °C at 5 °C/min. The optimum Co–ZIF–8 catalyst shows a half–wave potential of 0.82 V and a current density of 5.2 mA·cm−2 in 0.1 M KOH solution. It also exhibits high content of defects and good graphitization. TEM mapping shows that Co and N atoms are highly dispersed in the polyhedral carbon skeleton. However, two–step pyrolysis has no significant effect on the stability of the catalyst.

The Influence of Heating and Cooling on the Stability of a Liquid Layer

1980 ◽  
Vol 23 (176) ◽  
pp. 224-230 ◽  
Author(s):  
Yasuo IWASAKI ◽  
Eiji HASEGAWA
Keyword(s):  
Liquid Layer ◽  
Heating And Cooling ◽  
The Stability

Modification of Banding in Dual-Phase Steels via Thermal Processing

2014 ◽  
Vol 783-786 ◽  
pp. 1067-1072 ◽  
Author(s):  
K. Mukherjee ◽  
L.S. Thomas ◽  
C. Bos ◽  
David K. Matlock ◽  
John G. Speer
Keyword(s):  
Heating Rate ◽  
Thermal Processing ◽  
Thermomechanical Processing ◽  
Rolled Sheet ◽  
Dual Phase ◽  
Heating And Cooling ◽  
Heat Treated ◽  
Cold Rolled ◽  
Dp780 Steel ◽  
Microscopic Techniques

The potential to utilize controlled thermal processing to minimize banding in a DP780 steel with 2 wt pct Mn was evaluated on samples processed on a Gleeble® 3500 thermomechanical processing simulator. All processing histories were selected to result in final dual-phase steel microstructures simulating microstructures achievable during annealing of initially cold rolled sheet. Strip samples were processed to evaluate the effects of heating rate, annealing time, annealing temperature, and cooling rate. The degree of banding in the final microstructures was evaluated with standard light optical microscopic techniques. Results are presented to illustrate that the extent of banding depended on control of both heating and cooling rates, and a specific processing history based on a two-stage heating rate can be used to minimize visible banding in selected final heat treated products.

scholarly journals Temperature Control of Gas Chromatograph Based on Switched Delayed System Techniques

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Xiao-Liang Wang ◽  
Ming-Xu Zhang ◽  
Kun-Zhi Liu ◽  
Xi-Ming Sun
Keyword(s):  
Temperature Control ◽  
Lyapunov Functional ◽  
Reference Signal ◽  
Pi Controller ◽  
Temperature Control System ◽  
Linear Matrix ◽  
Matrix Inequalities ◽  
Gas Chromatograph ◽  
Delayed System ◽  
The Stability

We address the temperature control problem of the gas chromatograph. We model the temperature control system of the gas chromatograph into a switched delayed system and analyze the stability by common Lyapunov functional technique. The PI controller parameters can be given based on the proposed linear matrix inequalities (LMIs) condition and the designed controller can make the temperature of gas chromatograph track the reference signal asymptotically. An experiment is given to illustrate the effectiveness of the stability criterion.

scholarly journals Effect of the Heating Rate on the Stability of the Three-phase Interstellar Medium

2018 ◽  
Vol 862 (1) ◽  
pp. 55 ◽  
Author(s):  
Alex S. Hill ◽  
Mordecai-Mark Mac Low ◽  
Andrea Gatto ◽  
Juan C. Ibáñez-Mejía
Keyword(s):  
Interstellar Medium ◽  
Heating Rate ◽  
Three Phase ◽  
The Stability

scholarly journals Density, Microstructure, Strength and Fractography of Spark Plasma and Conventionally Sintered Mn Steels

2017 ◽  
Vol 17 (2) ◽  
pp. 93-103
Author(s):  
M. Tenerowicz-Zaba ◽  
M. Kupkova ◽  
M. Kabatova ◽  
E. Dudrova ◽  
M. Dzupon ◽  
...  
Keyword(s):  
Heating Rate ◽  
Spark Plasma Sintering ◽  
Failure Mechanisms ◽  
Uniaxial Pressure ◽  
Preliminary Results ◽  
Heating And Cooling ◽  
Plasma Sintering ◽  
Conventional Sintering ◽  
Spark Plasma ◽  
Sintered Materials

Abstract The aim of the study was to investigate Spark Plasma Sintering (SPS) of 1-3%Mn steels and compare the resultant microstructures, strengths and failure mechanisms with those of conventionally sintered materials. SPS was performed in a vacuum of 5 Pa at 1000°C for 15min under a uniaxial pressure of 20 MPa. The heating rate of 100°C/min was applied. For conventional processing, mixtures of powders were prepared in a Turbula mixer for 30 minutes. Samples were single pressed at 660 MPa, according to PN-EN ISO 2740 standard. Sintering of compacts was carried out in a laboratory tube furnace at 1120°C and 1250°C for 60 minutes in a mixture of 95%N2-5%H2. Heating and cooling rates were 75C°/min and 60°C/min, respectively. The density of SPS samples was higher (up to 7.37 g/cm3) than those after conventional sintering (up to 6.7 g/cm3). Yield strengths of SPS samples were in the range 920-1220 MPa, compared to the maximum of 602 MPa for conventionally sintered Fe-3%Mn-0.8%C. Transverse rupture strengths were the same for this alloy, 1234 MPa, but reached 1473 MPa for SPS 2Mn variant. Interfaces in SPS samples were significantly less contaminated with oxides, which is the result of a more favorable microclimate and pressure acting during SPS. These preliminary results indicate that further research on the SPS of Mn steels is warranted.

The Stability of the Self-Lubricated Journal Slider Bearing

2014 ◽  
Author(s):  
Valentin Stingelin
Keyword(s):  
Entire Range ◽  
The Self ◽  
Stable Operation ◽  
Slider Bearing ◽  
Operational Parameters ◽  
Dimensionless Numbers ◽  
Operational Conditions ◽  
Reaction Forces ◽  
The Stability

Un-equivocal criteria could be established assuring a perfectly stable operation of the shaft in a restricted, but nevertheless technically interesting range of operational conditions. It enables bearing designers to choose all physical and operational parameters in order to avoid the so called “half speed whirl”. This study hopes to bring enough new elements to attenuate the ill merited reputation of such bearings. Therefore the relevant dimensionless numbers were identified and quantified. What was done for an L/D=1, can be applied to any other bearing configuration, provided the quasi-steady reaction forces, acting on the shaft, are known for the entire range of eccentricities 0<ε<0.9.

Snapping of Low Pinned Arches on an Elastic Foundation

1973 ◽  
Vol 40 (3) ◽  
pp. 741-744 ◽  
Author(s):  
G. J. Simitses
Keyword(s):  
Critical Load ◽  
Elastic Foundation ◽  
Critical Loads ◽  
Entire Range ◽  
Buckling Load ◽  
Stability Studies ◽  
Deflection Curve ◽  
The Stability ◽  
Load Deflection Curve ◽  
Range Of Values

The problem of a low half-sine pinned arch under a quasi-statically applied half-sine load is considered. The low arch is resting on an elastic foundation. Critical loads are obtained by investigating the stability of the equilibrium positions by considering all possible modes of deformation. It is assumed that the behavior of the arch is linearly elastic up to the critical load. The entire range of values for the modulus of the foundation is considered. The results are presented graphically as either critical load (snap-through) or classical buckling load (stable bifurcation) versus the rise parameters for a large number of values of the modulus of foundations. This investigation presents an interesting model for stability studies, because, depending on the value of the rise parameter and the modulus of the foundation, the load-deflection curve exhibits the possibilities of the top-of-the-knee buckling, snap-through buckling through unstable bifurcation, and classical buckling (stable bifurcation).

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