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Thermoanalytical and Fourier transform infrared spectral curve-fitting techniques used to investigate the amorphous indomethacin formation and its physical stability in Indomethacin-Soluplus® solid dispersions

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INTERNATIONAL JOURNAL OF PHARMACEUTICS 2015年第2期496卷 457-465页

作者： Lin, Shan-Yang Lin, Hong-Liang Chi, Ying-Ting Huang, Yu-Ting Kao, Chi-Yu Hsieh, Wei-Hsien Yuanpei Univ Med Technol Dept Biotechnol & Pharmaceut Technol Hsinchu 30015 Taiwan

The amorphous form of a drug has higher water solubility and faster dissolution rate than its crystalline form. However, the amorphous form is less thermodynamically stable and may recrystallize during manufacturing and storage. Maintaining the amorphous state of drug in a solid dosage form is extremely important to ensure product quality. The purpose of this study was to quantitatively determine the amount of amorphous indomethacin (INDO) formed in the Soluplus (R) solid dispersions using thermoanalytical and Fourier transform infrared (FTIR) spectral curve-fitting techniques. The INDO/Soluplus (R) solid dispersions with various weight ratios of both components were prepared by air-drying and heat-drying processes. A predominate IR peak at 1683 cm(-1) for amorphous INDO was selected as a marker for monitoring the solid state of INDO in the INDO/Soluplus (R) solid dispersions. The physical stability of amorphous INDO in the INDO/Soluplus (R) solid dispersions prepared by both drying processes was also studied under accelerated conditions. A typical endothermic peak at 161 degrees C for gamma-form of INDO (gamma-INDO) disappeared from all the differential scanning calorimetry (DSC) curves of INDO/Soluplus (R) solid dispersions, suggesting the amorphization of INDO caused by Soluplus (R) after drying. In addition, two unique IR peaks at 1682 (1681) and 1593 (1591) cm(-1) corresponded to the amorphous form of INDO were observed in the FTIR spectra of all the INDO/Soluplus (R) solid dispersions. The quantitative amounts of amorphous INDO formed in all the INDO/Soluplus (R) solid dispersions were increased with the increase of gamma-INDO loaded into the INDO/Soluplus (R) solid dispersions by applying curve-fitting technique. However, the intermolecular hydrogen bonding interaction between Soluplus (R) and INDO were only observed in the samples prepared by heat-drying process, due to a marked spectral shift from 1636 to 1628 cm(-1) in the INDO/Soluplus (R) solid dispersio

关键词： Indomethacin (INDO) Soluplus (R) Amorphous Solid dispersion DSC FTIR curve-fitting technique Physical stability

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Experimental identification of high damping ratios in single-degree-of-freedom systems

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ARCHIVE OF APPLIED MECHANICS 2023年第7期93卷 2667-2680页

作者： Yokoyama, Takashi Okayama Univ Sci Dept Mech Engn Okayama 7000005 Japan

A curve-fitting technique using a minimum error criterion was presented for identifying higher damping ratios near the critical damping ratio in single-degree-of-freedom systems. Free vibration decay tests were performed on a linear spring-mass-damper system with constant initial conditions using a modified commercial vibration apparatus. A vibration mass was supported with an extremely low-friction air-bearing guide. Mass displacement was measured using a laser displacement sensor. The magnitude of the viscous damping forces was varied and controlled using an electromagnetic damper installed in the apparatus. Higher damping ratios (? > 0.8) were accurately identified using the curve-fitting technique, while lower and medium damping ratios (0 < ? < 0.7) were estimated using the conventional logarithmic decrement method from the measured free vibration decay curves.

关键词： Free decaying vibration curve-fitting technique Logarithmic decrement Electromagnetic damper Viscous damping force

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DESIGN-BASED COMPUTATIONAL-PROCEDURE FOR PERFORMANCE PREDICTION AND ANALYSIS OF SELF-EXCITED INDUCTION GENERATORS USING MOTOR DESIGN PACKAGES

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IEE PROCEEDINGS-B ELECTRIC POWER APPLICATIONS 1988年第1期135卷 8-16页

作者： MURTHY, SS NAGARAJ, HS KURIYAN, A KIRLOSKAR ELECT CO LTD BANGALORE 560055INDIA

A computer algorithm is explained in order to determine the performance of capacitor self-excited induction generators (SEIG) taking the machine design details as the input data. The magnetisation characteristic which forms the basis of analysis is obtained using theB/Hcurve of the core material and by employing a curve-fitting technique. The predicted parameter and performance characteristics of a normal induction motor operating as SEIG are compared with corresponding experimental results. Effects of variation of realistic design parameters are studied to obtain guidelines on optimum design. Typical results on a range of normal induction machines are presented to assess their suitability as SEIG.

关键词： performance analysis asynchronous generators Power engineering computing design parameters induction motors performance prediction electric machine analysis computing curve-fitting technique magnetisation characteristic B/H curve capacitor selfexcited induction generators design-based computation input data core material machine design details computer algorithm motor design packages optimum design Asynchronous machines

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FTIR study on structural changes of different-rank coals caused by single/multiple extraction with cyclohexanone and NMP/CS₂ mixed solvent

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FUEL PROCESSING TECHNOLOGY 2016年 154卷 210-218页

作者： Tian, Bin Qiao, Ying-yun Tian, Yuan-yu Xie, Ke-chang Liu, Qing Zhou, Hai-feng China Univ Petr East China State Key Lab Heavy Oil Proc Qingdao 266580 Peoples R China Taiyuan Univ Technol State Key Lab Breeding Base Coal Sci & Technol Co Taiyuan 030024 Peoples R China Taiyuan Univ Technol Minist Sci & Technol Taiyuan 030024 Peoples R China Shandong Univ Sci & Technol Shandong Prov Key Lab Univ Qingdao 266590 Shandong Peoples R China Shandong Univ Sci & Technol Coll Low Carbon Energy Qingdao 266590 Shandong Peoples R China Shandong Univ Sci & Technol Coll Chem Technol Qingdao 266590 Shandong Peoples R China

A novel multiple extraction (ME) process integrated heat reflux extraction (HRE) with cyclohexanone (CYC) followed by ultrasonic assisted extraction (UAE) with N-methyl-2-pyrrolidone/CS2 (NMP/CS2) mixed solvent was developed for extraction of four different rank demineralized coals. Raw coals and their demineralized coals were evaluated by X-ray diffraction, X-ray fluorescence, and Fourier transform infrared (FTIR) spectroscopy analytical techniques to determine HCl/HF leaching on the properties and FTIR spectra of coals first. And then the demineralized coals as well as their extraction residues were studied using FTIR spectrometry and curve-fitting technique to clarify the performance of ME process and investigate the structural changes in coals during extraction. The results showed that acids treatment could remove most of the mineral matters in coals and did not seem to produce significant changes in IR spectra of the coals except for disappearance of those peaks caused by mineral matters. The removal of solvents soluble portions led to decrease in the amount of organic species containing C=C vibration mode and carbon content in all coal samples. The alkyl side chains on aromatics of all coal samples except for NM lignite became longer and less branched after extraction according to the curve-fitting study in the region 3000-2700 cm(-1). In addition, it was found that the contents of carbon and organic portions containing C=C vibration mode, C-O bonds, and aliphatic hydrogen for SD, HLJ, and NX coals all decreased following the order of raw coal > extraction residue with CYC > extraction residue with NMP/CS2 > extraction residue from ME process during extraction processes. This result inferred that the NMP/CS2 mixed solvent could only show good solubility to coals after they were initially extracted using CYC. Furthermore, the detectable concentration of hydroxy groups in coals increased after extraction, especially for the HRE process of NM coal with CYC. (C) 2

关键词： HCl/HF leaching Multiple extraction Structural change FTIR curve-fitting technique Interaction mechanism

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INFLUENCE OF BIAS CURRENT AND SIGNAL POWER ON BEHAVIOR OF AN ANTIREFLECTION-COATED LASER-AMPLIFIER

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ELECTRONICS LETTERS 1986年第5期22卷 255-256页

作者： WEBB, RP DEVLIN, WJ British Telecom Research Laboratories Martlesham Heath Ipswich Suffolk IP5 7RE UK

The variation of gain with wavelength of a 1.5 ??m semiconductor-laser amplifier with antireflection-coated facets has been measured over several modes. The internal gain and resonant wavelength were found using a cur... 详细信息

关键词： curve-fitting technique Fabry-Perot cavity internal gain laser cavity resonators antireflection coatings signal power laser amplifier planar buried heterostructure semiconductor-laser Optoelectronics resonant wavelength bias current antireflection-coated facets laser transitions laser modes semiconductor junction lasers antireflection laser variables measurement Laser amplifiers 1.5 microns wavelength amplifiers

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CLOSED FORM EXPRESSIONS FOR THE COMPUTER-AIDED-DESIGN OF SUSPENDED MICROSTRIP CIRCUITS FOR MILLIMETER-WAVE APPLICATIONS

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IEE PROCEEDINGS-H MICROWAVES ANTENNAS AND PROPAGATION 1987年第4期134卷 386-388页

作者： BEDAIR, SS Electrical Engineering Dept. University of Duisburg Duisburg West Germany

In the paper, a combination of a dividing-the-capacitance approach and a curvefitting technique is used to derive closed form expressions for the characteristics of suspended microstrip line with zero strip thickness. These expressions are mainly used for the computeraided design of suspended microstrip circuits for millimetre-wave applications. Calculated results using the derived expressions are found to be in very good agreement with available numerical results. The range of validity of the derived expressions is also included.

关键词： Electronic engineering computing zero strip thickness Waveguides and microwave transmission lines MM wave application strip lines suspended microstrip circuits Computer-aided circuit analysis and design circuit CAD millimeter wave applications curve-fitting technique computer-aided design CAD closed form expressions dividing-the-capacitance approach suspended microstrip line

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Constant head-transient method using pressure and flow data for determining permeability and specific storage of tight rocks

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METHODSX 2024年 13卷 102899页

作者： Song, Insun Korea Inst Geosci & Mineral Resources Climate Change Response Res Div Daejeon 34132 South Korea

This paper describes a 'constant head-transient method' for estimating permeability and specific storage of tight rock samples, such as shale and crystalline rocks. Experimental tests are conducted using a cylindrical rock sample subjected to confining pressure, through which pressure diffusion occurs from a constant upstream pressure (or constant head) to a finite downstream storage. Unlike the pulse-transient method, the upstream fluid flow into the sample can be measured using a syringe pump because of no change in upstream pressure. By minimizing the downstream storage, the test time can be significantly reduced, but only the downstream pressure transient data do not yield accurate results on permeability and specific storage estimations. By combining the flow data with the pressure data, the proposed method aims at saving the test time and improving the accuracy of their estimations in extremely low permeability rock samples. center dot A constant head-transient method for measuring the hydraulic properties of tight rocks was developed with a boundary condition of constant upstream pressure and finite downstream storage. center dot The test time can be saved by minimizing the downstream storage, and the upstream flow can be measured to improve the accuracy in measuring the hydraulic properties. center dot Combining the flow and pressure objective functions yields the best curve fitting for both pressure and flow curves.

关键词： Hydraulic property measurement Pressure transient Pressure and flow analysis Objective function curve-fitting technique

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A method to determine the transition point of fatigue crack growth rate from near-ΔK_th to Paris regions

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JOURNAL OF TESTING AND EVALUATION 1999年第4期27卷 304-305页

作者： Zheng, JH Powell, BE Univ Reading Dept Engn Reading RG6 6AY Berks England Univ Portsmouth Dept Mech & Mfg Engn Portsmouth PO1 3DJ Hants England

The transition point of fatigue crack growth (FCG) between the near-Delta K-th and the Paris regions is an important value to study fatigue behavior. This study introduces a curve-fitting technique to identify this point for nickel-based superalloy U720 with stress ratio of R = 0.1 at room temperature. The value of Delta K-th under these conditions is also determined.

关键词： fatigue crack growth transition point threshold value curve-fitting technique nickel-based superalloy U720

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