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Impurity profile of macitentan in tablet dosage form using a stability-indicating high performance liquid chromatography method and forced degradation study 预览
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作者 Narasimha S LAKKA Chandrasekar KUPPAN Parthasarathy RANGASAMY 《色谱》 CAS CSCD 北大核心 2019年第1期100-110,共11页
Macitentan(MAC)is a pulmonary arterial hypertension(PAH)drug marketed as a tablet and often has stability issues in the final dosage form.Quantitative determination of MAC and its associated impurities in tablet dosag... Macitentan(MAC)is a pulmonary arterial hypertension(PAH)drug marketed as a tablet and often has stability issues in the final dosage form.Quantitative determination of MAC and its associated impurities in tablet dosage form has not been previously reported.This study quantified impurities present in Macitentan tablets using a binary solvent-based gradient elution method using reversed phase-high performance liquid chromatography.The developed method was validated per International Conference on Harmonization(ICH)guidelines and the drug product was subjected to forced degradation studies to evaluate stability.The developed method efficiently separated the drug and impurities(48 min)without interference from solvents,excipients,or other impurities.The developed method met all guidelines in all characteristics with recoveries ranging from 85%-115%,linearity with r^2≥0.996 6,and substantial robustness.The stability-indicating nature of the method was evaluated using stressed conditions(hydrolysis:1 N HCl at 80℃/15min;1 N NaOH at 25℃/45min;humidity stress(90%relative humidity)at 25℃for 24h,oxidation:at 6%(v/v)H2O2,80℃/15min,thermolysis:at 105℃/16h and photolysis:UV light at 200Wh/m^2;Fluorescent light at 1.2 million luxh).Forced degradation experiments showed that the developed method was effective for impurity profiling.All stressed samples were assayed and mass balance was>96%.Forced degradation results indicated that MAC tablets were sensitive to hydrolysis(acid and alkali)and thermal conditions.The developed method is suitable for both assay and impurity determination,which is applicable to the pharmaceutical industry. 展开更多
关键词 reverse phase-high performance liquid chromatography(RP-HPLC) STABILITY-INDICATING METHOD forced degradation STUDY binary solvent gradient ENDOTHELIN receptor antagonist(ERA) pulmonary arterial hypertension(PAH) macitentan(MAC) IMPURITY profiling
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Effects of hurricane forward speed and approach angle on storm surges:an idealized numerical experiment 预览
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作者 Chenguang Zhang Chunyan Li 《海洋学报:英文版》 SCIE CAS CSCD 2019年第7期48-56,共9页
The effects of hurricane forward speed(V)and approach angle(θ)on storm surge are important and a systematic investigation covering possible and continuous ranges of these parameters has not been done before.Here we p... The effects of hurricane forward speed(V)and approach angle(θ)on storm surge are important and a systematic investigation covering possible and continuous ranges of these parameters has not been done before.Here we present such a study with a numerical experiment using the Finite Volume Community Ocean Model(FVCOM).The hurricane track is simplified as a straight line,such that V andθfully define the motion of the hurricane.The maximum surge is contributed by both free waves and a forced storm surge wave moving with the hurricane.Among the free waves,Kelvin-type waves can only propagate in the down-coast direction.Simulations show that those waves can only have a significant positive storm surge when the hurricane velocity has a down-coast component.The optimal values of V andθthat maximize the storm surge in an idealized semi-circular ocean basin are functions of the bathymetry.For a constant bathymetry,the maximum surge occurs when the hurricane approaches the coast from the normal direction when the free wave generation is minimal;for a stepped bathymetry,the maximum surge occurs at a certain acute approach angle which maximizes the duration of persistent wind forcing;a step-like bathymetry with a sloped shelf is similar to the stepped bathymetry,with the added possibility of landfall resonance when the free and forced waves are moving at about the same velocity.For other cases,the storm surge is smaller,given other parameters(hurricane size,maximum wind speed,etc.)unchanged. 展开更多
关键词 storm SURGE experiments FVCOM HURRICANE forward speed APPROACH ANGLE KELVIN waves forced and free SURGE interactions
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Advancing USP compendial methods for fixed dose combinations: A case study of metoprolol tartrate and hydrochlorothiazide tablets 预览
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作者 Qun Xu 《药物分析学报:英文版》 CAS CSCD 2019年第2期77-82,共6页
The current United States Pharmacopeia–National Formulary (USP–NF) includes more than 250 monographs of fixed dose combinations (FDCs),and some of them need to be updated due to incompleteness of impurity profiles a... The current United States Pharmacopeia–National Formulary (USP–NF) includes more than 250 monographs of fixed dose combinations (FDCs),and some of them need to be updated due to incompleteness of impurity profiles and obsolescence of analytical methodologies.A case study of metoprolol tartrate and hydrochlorothiazide tablets is presented to summarize challenges encountered during the USP monograph modernization initiative of FDCs and to highlight an “adoption and adaptation” approach employed for method development.To this end,a single stability-indicating HPLC method was developed to separate the two drug substances and eight related compounds with resolution 2.0 or higher between all critical pairs.Chromatographic separations were achieved on a Symmetry column (C18,100mm × 4.6 mm,3.5 μm) using sodium phosphate buffer (pH 3.0;34 mM) and acetonitrile as mobile phase in a gradient elution mode.The stability-indicating capability of this method has been demonstrated by analyzing stressed samples of the two drug substances.The developed HPLC method was validated for simultaneous determination of metoprolol tartrate and hydrochlorothiazide and relevant impurities in the tablets.Moreover,the developed method was successfully applied to the analysis of commercial tablet dosage forms and proved to be suitable for routine quality control use.The case study could be used to streamline USP's monograph modernization process of FDCs and strengthen compendial procedures. 展开更多
关键词 METOPROLOL TARTRATE HYDROCHLOROTHIAZIDE METOPROLOL TARTRATE and HYDROCHLOROTHIAZIDE tablets Forced degradation USP MONOGRAPH MODERNIZATION
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Evolution of the microstructure and solute distribution of Sn-10wt% Bi alloys during electromagnetic field-assisted directional solidification
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作者 Zhe Shen Minghu Peng +6 位作者 Dongsheng Zhu Tianxiang Zheng Yunbo Zhong Weili Ren Chuanjun Li Weidong Xuan Zhongming Ren 《材料科学技术学报:英文版》 SCIE EI CAS CSCD 2019年第4期568-577,共10页
The effects of forced flows at different velocities on microstructure and solute distribution during the directional solidification of Sn-10 wt% Bi alloys under a simultaneous imposition of a transverse static magneti... The effects of forced flows at different velocities on microstructure and solute distribution during the directional solidification of Sn-10 wt% Bi alloys under a simultaneous imposition of a transverse static magnetic field(TSMF) and an external direct current(DC) have been investigated experimentally and numerically. The experimental results show that the solid-liquid interface will gradually become sloping with the increase of the forced flow velocity when the thermoelectric magnetic convection(TEMC)dominates the forced flow at solidification front. However, the interface will gradually become planar as the flow velocity further increases when the electromagnetic convection(EMC) dominates the forced flow. Moreover, when the flow velocity gradually increases, the primary dendrite spacing decreases from384 to 105 μm accordingly. The simulation results show that the solute distribution at the two sides of the sample can be significantly changed by the forced flow at solidification front. The rejected solute will be unidirectionally transported to one side of the sample along the TEMC(a low-velocity forced flow),thereby causing the formation of a sloping interface. However, the rejected solute will be returned back along the EMC(a higher-velocity force flow), which results in a planar interface. Furthermore, the solute content at the two sides of the sample under the forced flows at different velocities was measured. The results are in good agreement with the simulation results, which shows that the solute content difference between the two sides of the sample reaches the maximum when a 0.5 T TSMF is applied, while the solute content difference decreases to zero with a simultaneous application of a 0.5 T TSMF and a 1.6 × 10~5 A/m~2 external DC. 展开更多
关键词 Directional SOLIDIFICATION SN-BI alloy FORCED flow SOLUTE distribution Numerical simulation ELECTROMAGNETIC field
Automatic de-noising and recognition algorithm for drilling fluid pulse signal 预览
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作者 HU Yongjian HUANG Yanfu LI Xianyi 《石油勘探与开发:英文版》 2019年第2期393-400,共8页
Wavelet forced de-noising algorithm is suitable for denoising of unsteady drilling fluid pulse signal, including baseline drift rectification and two-stage de-noising processing of frame synchronization signal and ins... Wavelet forced de-noising algorithm is suitable for denoising of unsteady drilling fluid pulse signal, including baseline drift rectification and two-stage de-noising processing of frame synchronization signal and instruction signal. Two-stage de-noising processing can reduce the impact of baseline drift and determine automatic peak detection threshold range for signal recognition by distinguishing different features of frame synchronization pulse and instruction pulse. Rising and falling edge relative protruding threshold is defined for peak detection in signal recognition, which can make full use of the degree of the signal peak change and detect peaks flexibly with rising and falling edge relative protruding threshold combination. A synchronous decoding method was designed to reduce position uncertainty of the frame synchronization pulse and eliminate the accumulative error of time base drift, which determines the first instruction pulse position according to position of the frame synchronization pulse and decodes subsequent instruction pulse by taking current instruction pulse as new bit synchronization pulse. Special tool software was developed to tune algorithm parameters, which has a decoding success rate of about 95% for the universal coded signals. For the special coded signals with check byte, decoding success rate using the automatic threshold adjustment algorithm is as high as 99%. 展开更多
关键词 drilling fluid pulse SIGNAL SIGNAL processing DECODING success rate AUTOMATIC DE-NOISING and recognition wavelet FORCED DE-NOISING peak detection SYNCHRONOUS DECODING
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含有强迫项的高阶非线性中立型微分方程的振动性 预览
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作者 李静 蔡海 王培光 《河北大学学报:自然科学版》 CAS 北大核心 2019年第2期118-123,共6页
考虑了一类含有强迫项的高阶非线性中立型微分方程,通过运用Krasnoselskii′s不动点定理和分析技巧,得到了该方程每一个有界解振动或趋于零的充要条件.所得结果改进了一些已知结论,并给出了实例验证.
关键词 中立型方程 强迫 有界解
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Applying resolved-scale linearly forced isotropic turbulence in rational subgrid-scale modeling 预览
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作者 Chuhan Wang Mingwei Ge 《力学学报:英文版》 SCIE EI CAS CSCD 2019年第3期486-494,共9页
In previous attempts of rational subgrid-scale (SGS) modeling by employing the Kolmogorov equation of filtered (KEF) quantities, it was necessary to assume that the resolved-scale second-order structure function is st... In previous attempts of rational subgrid-scale (SGS) modeling by employing the Kolmogorov equation of filtered (KEF) quantities, it was necessary to assume that the resolved-scale second-order structure function is stationary. Forced isotropic turbulence is often used as a framework for establishing and validating such SGS models based on stationary restrictions, for it generates statistical stationary samples. However, traditional forcing method at low wavenumbers cannot provide an analytic form of forcing term for a complete KEF in physical space, which has been illustrated to be essential in the modeling of such SGS models. Thus, an alternative forcing method giving an analytic forcing term in physical space is needed for rational SGS modeling. Giving an analytic linear driving term in physical space, linearly forced isotropic turbulence should be considered an ideal theoretical framework for rational SGS modeling. In this paper, we demonstrate the feasibility of establishing a rational SGS model with stationary restriction based on linearly forced isotropic turbulence. The performance of this rational SGS model is validated. We, therefore, propose the use of linearly forced isotropic turbulence as a complement to free-decaying isotropic turbulence and low-wavenumber forced isotropic turbulence for SGS model validations. 展开更多
关键词 Homogeneous isotropic TURBULENCE Large-eddy simulation SUBGRID-SCALE model FORCED TURBULENCE
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Study of thermo-fluidic characteristics for geometric-anisotropy Kagome truss-cored lattice
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作者 Chi HOU Guangmeng YANG +1 位作者 Xiaopeng WAN Jie CHEN 《中国航空学报:英文版》 SCIE EI CAS CSCD 2019年第7期1635-1645,共11页
The aim of this paper is to provide a comprehensive comparison of the thermal insulation and heat transfer performance for Kagome truss-cored lattice along two perpendicular orientations OA and OB. Three test conditio... The aim of this paper is to provide a comprehensive comparison of the thermal insulation and heat transfer performance for Kagome truss-cored lattice along two perpendicular orientations OA and OB. Three test conditions are conducted under forced air convection for the titanium sandwich panel fabricated by 3 D printing technology. The thermo-fluidic characteristics are further explored by numerical simulation to reveal the underlying mechanisms of heat transfer enhancement.The results indicate that the orientation OB exhibits better thermal insulation than orientation OA under the identical temperature loading, while the latter outperforms the former by up to 20% higher overall heat transfer performance. In particular, the endwalls and lattice core in orientation OA achieve 9.7% and 22.5% higher area-averaged Nusselt number respectively than that in orientation OB for a given Reynolds number. The heat transfer superiority of orientation OA comes from the unique topology which induces the large scale spiral primary flows, facilitating the heat exchange between the cooling air and the surfaces of sandwich panel. However, the complex flow mixing leads to a maximum of 20% higher friction factor in orientation OA than that in orientation OB. 展开更多
关键词 FORCED CONVECTION Heat transfer KAGOME Pressure DROP Topology direction
Mitigation of power system forced oscillations based on unified power flow controller 预览
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作者 Ping JIANG Zikai FAN +3 位作者 Shuang FENG Xi WU Hui CAI Zhenjian XIE 《现代电力系统与清洁能源学报(英文)》 CSCD 2019年第1期99-112,共14页
Forced oscillations(FOs), or low-frequency oscillations(LFOs) caused by periodic, continuous, small power disturbances, threaten the security and stability of power systems.Flexible AC transmission system(FACTS)device... Forced oscillations(FOs), or low-frequency oscillations(LFOs) caused by periodic, continuous, small power disturbances, threaten the security and stability of power systems.Flexible AC transmission system(FACTS)devices can effectively mitigate LFOs via stability control.We propose a novel method that mitigates FOs by shifting the resonant frequency.Based on the features of the linearized swing equation of a generator, a resonant frequency shift can be achieved by controlling the synchronous torque coefficient using a unified power flow controller(UPFC).Because of the resonance mechanism, the steady-state response of an FO can be effectively mitigated when the resonant frequency changes from the original one, which was close to the disturbance frequency.The principle is that a change in resonant frequency affects the resonance condition.Simulations are conducted in a single-machine infinite-bus(SMIB) system, and the simulation results verify that the method is straightforward to implement and can significantly mitigate FOs.The controller robustness when the resonant frequency is not accurately estimated is also analyzed in the simulations. 展开更多
关键词 FORCED OSCILLATIONS Flexible AC transmission systems UNIFIED power flow CONTROLLER Stability control
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一类具有强迫项的有限时滞Lienard方程周期解的存在唯一性
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作者 黄燕革 黄勇 《数学的实践与认识》 北大核心 2019年第3期280-288,共9页
利用重合度的Mawhin延拓定理,构造新算子,使用新技巧,证明一类具有强迫项的有限时滞Lienard方程x″(t)+f1(x)x′(t)+f2(x)(x′(t))^2+g(x(t-τ))=e(t)存在唯一周期解的条件,得到了周期解存在唯一的新的结果.
关键词 强迫项 时滞 LIENARD方程 周期解 Mawhin延拓定理 存在唯一性
Antidepressant activity and HPTLC fingerprinting of stearic acid in different days of wheat seedlings 预览
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作者 Palanisamy Ravikumar Muthusamy Jeyam 《粮油科技:英文版》 2019年第1期6-10,共5页
Depression is a chronic,recurring and potentially life threatening illness and affects up to 20%of the world population and in the year 2020,depression will become the second most common disease in the world.To find t... Depression is a chronic,recurring and potentially life threatening illness and affects up to 20%of the world population and in the year 2020,depression will become the second most common disease in the world.To find the remedy from nutraceuticals,the present study was designed to evaluate the antidepressant activity of stearic acid(SA)and to quantify its maximum content in different dayold wheat seedlings and wheat grains.Forced swimming test(FST)and tail suspension test(TST)were done to evaluate the antidepressant activity of SA.HPTLC fingerprinting of SA was done in different days(3,5 and 7 d)of wheat seedlings and wheat grains to quantify its maximum content.In the antidepressant study,when compared with the control(326.67±3.02 s),SA showed potential antidepressant activity in TST(131.67±2.60 s)and SA also showed very good antidepressant activity in FST(124.83±5.37 s)when compared with the control(215.83±6.64 s).In HPTLC fingerprinting,the maximum content of SA was identified in 3-d-old wheat seedlings(89.43μg)when compared to wheat grains(84.69μg),5-d-old(86.43μg)and 7-d-old(85.32μg)wheat seedlings.Hence,the present study concludes that SA has a potential antidepressant activity and 3-d-old wheat seedlings are the essential sources of SA among the different dayold wheat seedlings. 展开更多
关键词 Depression Forced SWIMMING TEST TAIL suspension TEST Stearic acid HPTLC fingerprinting 3-d-old wheat SEEDLINGS
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A Review of Computational Aeroelasticity of Civil Fan Blades 预览
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作者 M.Vahdati K.B Lee S.Stapelfeldt 《风机技术》 2018年第5期42-52,共11页
The aim of this paper is to present the state-of-the art in computational aeroelasticity methods that are available for analyzing fan blades on modern civil aircraft.Fan blades in modern high-bypass aero-engines typic... The aim of this paper is to present the state-of-the art in computational aeroelasticity methods that are available for analyzing fan blades on modern civil aircraft.Fan blades in modern high-bypass aero-engines typically produce around 80%of the thrust.In order to improve specific fuel consumption and reduce the level of noise emitted from the engine,civil turbofan engine designs are moving toward even larger fan diameters with lower tip speeds and hence the importance of this component of aero-engine becomes even more prominent.To reduce weight,future fan blades will be made of composite materials and shorter intakes are used.The new designs are highly loaded and will be more susceptible to aerodynamic and aeroelastic instabilities,and hence computationally efficient aeroelastic modelling tools for such blades are paramount. 展开更多
关键词 UnsteadyAerodynamics Aeroelasticity FLUTTER BIRD STRIKE INLET DISTORTION FORCED Response
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A Semi-Analytical Method for the PDFs of A Ship Rolling in Random Oblique Waves 预览
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作者 LIU Li-qin LIU Ya-liu +2 位作者 XU Wan-hai LI Yan TANG You-gang 《中国海洋工程:英文版》 SCIE EI CSCD 2018年第1期74-84,共11页
The PDFs (probability density functions) and probability of a ship rolling under the random parametric and forced excitations were studied by a semi-analytical method. The rolling motion equation of the ship in random... The PDFs (probability density functions) and probability of a ship rolling under the random parametric and forced excitations were studied by a semi-analytical method. The rolling motion equation of the ship in random oblique waves was established. The righting arm obtained by the numerical simulation was approximately fitted by an analytical function. The irregular waves were decomposed into two Gauss stationary random processes, and the CARMA (2, 1) model was used to fit the spectral density function of parametric and forced excitations. The stochastic energy envelope averaging method was used to solve the PDFs and the probability. The validity of the semi-analytical method was verified by the Monte Carlo method. The C11 ship was taken as an example, and the influences of the system parameters on the PDFs and probability were analyzed. The results show that the probability of ship rolling is affected by the characteristic wave height, wave length, and the heading angle. In order to provide proper advice for the ship's manoeuvring, the parametric excitations should be considered appropriately when the ship navigates in the oblique seas. 展开更多
关键词 ship RANDOM rolling PARAMETRIC and FORCED excitations stochastic energy ENVELOPE AVERAGING method probability density function parameter influence analysis
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Hydrodynamics of the Semi-Immersed Cylinder by Forced Oscillation Model Testing 预览
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作者 SONG Chun-hui FU Shi-xiao +3 位作者 TANG Xiao-ying HU Ke MA Lei-xin REN Tong-xin 《中国海洋工程:英文版》 SCIE EI CSCD 2018年第1期110-116,共7页
In this paper, the hydrodynamic coefficients of a horizontal semi-immersed cylinder in steady current and oscillatory flow combining with constant current are obtained via forced oscillation experiments in a towing ta... In this paper, the hydrodynamic coefficients of a horizontal semi-immersed cylinder in steady current and oscillatory flow combining with constant current are obtained via forced oscillation experiments in a towing tank. Three nondimensional parameters (Re, KC and Fr) are introduced to investigate their effects on the hydrodynamic coefficients.The experimental results show that overtopping is evident and dominates when the Reynolds number exceeds 5×105 in the experiment. Under steady current condition, overtopping increases the drag coefficient significantly at high Reynolds numbers. Under oscillatory flow with constant current condition, the added mass coefficient can even reach a maximum value about 3.5 due to overtopping while the influence of overtopping on the drag coefficient is minor. 展开更多
关键词 semi-immersed cylinder HYDRODYNAMIC coefficient FORCED oscillation experiment OVERTOPPING
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Forced Learning:Manifestations,Hazards,and Coping Strategies 预览
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作者 CUI Shuang-yi 《美中教育评论:B》 2018年第9期404-411,共8页
“Forced learning”refers to the fact in China that some students are forced to learn by parents and teachers,regardless of their own wishes.Sometimes,some parents and teachers even force students to learn through dis... “Forced learning”refers to the fact in China that some students are forced to learn by parents and teachers,regardless of their own wishes.Sometimes,some parents and teachers even force students to learn through disciplinary actions.Specifically,students are imposed in the following four aspects by parents and teachers:learning time,learning contents,learning frequency,and learning difficulty,so it caused bad consequences that some students’study took too much time,covered excess contents,is repeated too much and is too difficult.“Forcing learning”destroyed the nature of students,overdrew students’potential,and harmed students’physical and mental health.In order to change this existing situation of“forced learning”,parents and teachers should clarify the nature of knowledge and broaden the way students acquire knowledge,activate students’inner study motive,and guide them to learn consciously and actively,create a harmonious educational environment,and make full use of students’“children”nature;parents and teachers strengthen cooperation to give students scientific guidance on psychology,emotion,and learning. 展开更多
关键词 FORCED LEARNING MANIFESTATIONS hazards STRATEGIES
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Novel degradation products of argatroban:Isolation,synthesis and extensive characterization using NMR and LC-PDA-MS/Q-TOF 预览
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作者 Vinodh Guvvala Venkatesan Chidambaram Subramanian +1 位作者 Jaya Shree Anireddy Mahesh Konda 《药物分析学报:英文版》 CAS CSCD 2018年第2期86-95,共10页
Forced degradation study of argatroban under conditions of hydrolysis(neutral,acidic and alkaline),oxidation,photolysis and thermal stress,as suggested in the ICH Q1A(R2),was accomplished.The drug showed significant d... Forced degradation study of argatroban under conditions of hydrolysis(neutral,acidic and alkaline),oxidation,photolysis and thermal stress,as suggested in the ICH Q1A(R2),was accomplished.The drug showed significant degradation under hydrolysis(acidic,alkaline)and oxidation(peroxide stress)conditions.The drug remained stable under thermal and photolytic stress conditions.In total,seven novel degradation products(DP-1 to DP-7)were found under diverse conditions,which were not reported earlier.The chemical structures of these degradation products were characterized by 1H NMR,13C NMR,2D NMR,Q-TOF-MSn and IR spectral analysis and the proposed degradation products structures were further confirmed by the individual synthesis. 展开更多
关键词 ARGATROBAN FORCED degradation NMR LC-PDA LC-MS/Q-TOF-MSn
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Structural confirmation of sulconazole sulfoxide as the primary degradation product of sulconazole nitrate 预览
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作者 Qun Xu Ashraf Khan +4 位作者 Di Gao Kristie M.Adams Fatkhulla Tadjimukhamedov Shane Tan John T.Simpson 《药物分析学报:英文版》 CAS CSCD 2018年第2期96-102,共7页
Sulconazole has been reported to degrade into sulconazole sulfoxide via sulfur oxidation;however,structural characterization data was lacking and the potential formation of an N-oxide or sulfone could not be excluded.... Sulconazole has been reported to degrade into sulconazole sulfoxide via sulfur oxidation;however,structural characterization data was lacking and the potential formation of an N-oxide or sulfone could not be excluded.To clarify the degradation pathways and incorporate the impurity profile of sulconazole into the United States Pharmacopeia–National Formulary(USP–NF)monographs,a multifaceted approach was utilized to confirm the identity of the degradant.The approach combines stress testing of sulconazole nitrate,chemical synthesis of the degradant via a hydrogen peroxide-mediated oxidation reaction,semi-preparative HPLC purification,and structural elucidation by LC–MS/MS and NMR spectroscopy.Structural determination was primarily based on the comparison of spectroscopic data of sulconazole and the oxidative degradant.The mass spectrometric data have revealed a McLafferty-type rearrangement as the characteristic fragmentation pathway for alkyl sulfoxides with aβ-hydrogen atom,and was used to distinguish the sulfoxide from N-oxide or sulfone derivatives.Moreover,the generated sulconazole sulfoxide was utilized as reference material for compendial procedure development and validation,which provides support for USP monograph modernization. 展开更多
关键词 Sulconazole NITRATE Sulconazole SULFOXIDE FORCED DEGRADATION STRUCTURAL characterization LC–MS/MS
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Countermeasure Against Regenerative and Forced Chatter of Flexible Workpieces in Milling Processs Using Bi-directional Excitation 预览
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作者 Nakano Yutaka De Silva Amal Dilanka +1 位作者 Takahara Hiroki Akiyama Yu 《南京航空航天大学学报:英文版》 EI CSCD 2018年第1期10-19,共10页
A novel extended methodology for chatter suppression in milling process by applying external forced vibrations to the workpiece in two orthogonal directions which are the feed and cross-feed directions.Both the regene... A novel extended methodology for chatter suppression in milling process by applying external forced vibrations to the workpiece in two orthogonal directions which are the feed and cross-feed directions.Both the regenerative and forced chatter suppression during the milling process of flexible workpieces are investigated.Here,the workpiece is subject to a sinusoidal periodic force in the feed direction to disrupt the regenerative effect.Additionally,to minimize the forced chatter,the workpiece is subject to the periodic excitation force in cross-feed direction.This force is proportional to the magnitude of the estimated cutting force in cross-feed direction and has a phase opposite to the cutting force to minimize the vibration amplitudes.The effectiveness of the proposed method is evaluated numerically and experimentally,for the spindle speed located in both the local minima and local maxima of the stability lobe diagram.The numerical simulations indicate significant suppression effect in terms of vibration amplitudes,resulting in suppression of both the regenerative chatter and the forced chatter.Experiments were conducted by using a workpiece-mounted active stage composed of flexure hinges and driven by piezoelectric actuators.The experimental results agree qualitatively with the numerical simulations.The proposed method indicates a remarkable vibration reduction effect for both regenerative and forced chatters. 展开更多
关键词 self-excited VIBRATION VIBRATION control REGENERATIVE chatter FORCED chatter MILLING
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Frequency-amplitude behavior in the incipient movement of grains under vibration
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作者 Karina A.Valenzuela Aracena Jesica G.Benito +3 位作者 Luc Oger Irene Ippolito Rodolfo O.Ufiac Ana M.Vidales 《中国颗粒学报:英文版》 SCIE EI CAS CSCD 2018年第5期1-9,共9页
The onset of the movement of particles placed on a horizontal rough surface subject to a vertical sinusoidal vibration is investigated through tracking experiments,theoretical analysis,and numerical simulations. The f... The onset of the movement of particles placed on a horizontal rough surface subject to a vertical sinusoidal vibration is investigated through tracking experiments,theoretical analysis,and numerical simulations. The frequency of vibration needed to move particles decays exponentially with the amplitude of the oscillatory input.This behavior is explained through a simple mechanism in which a forced damped harmonic oscillator with a spring constant represents all the interactions between the particle and the surface.The numerical results compare well with experimental data,demonstrating that the forces included in the numerical calculations suitably account for the main particle response,even though the complexity of the surface is not fully taken into account.Describing the way in which frequency varies with amplitude could be relevant to technological applications such as cleaning of material surfaces. 展开更多
关键词 VIBRATION Incipient MOVEMENT FORCED OSCILLATOR 3D DEM simulation
Effect of fluid flow on solidified equiaxed dendrite morphology evolution based on phase field-lattice Boltzmann method
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作者 Wei-zhao Sun Rui Yan +2 位作者 Xiong Wan Hong-biao Dong Tao Jing 《中国铸造:英文版》 SCIE 2018年第6期422-427,共6页
Fluid flow can significantly change the evolution of microstructural morphology. However, relatively little is known how the fluid flow, concentration and microstructure affect each other quantitatively, which is esse... Fluid flow can significantly change the evolution of microstructural morphology. However, relatively little is known how the fluid flow, concentration and microstructure affect each other quantitatively, which is essential to optimize processing parameters. A quantitative simulation study of Al-Cu solidified equiaxed dendrite evolution under forced flow based on phase field-lattice Boltzmann method(PF-LBM) is carried out. Results obtained are validated by Gibbs-Thomson relation at the dendrite tip. Compared with the equiaxed dendrite evolution without flow, the upstream dendrite arm is enhanced while the downstream arm is inhibited. Besides, as the inlet flow rate increases, the secondary arms attached onto the upstream primary arm and the upstream side of the primary arm normal to the inflow velocity has been well developed. Results show that sidewise instabilities of the primary dendrite arm and onset of secondary arm is caused by the local concentration perturbation and will be enhanced or inhabited by the flow. It is believed that the coupled PF-LBM method is able to handle dendrite evolution under forced flow quantitatively, which helps in investigating the solidified dendrite morphology evolution. 展开更多
关键词 phase field lattice BOLTZMANN method FORCED flow instability
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