Gas turbines play core roles in clean energy supply and the construction of comprehensive energy systems.The control performance of primary frequency modulation of gas turbines has a great impact on the frequency cont...Gas turbines play core roles in clean energy supply and the construction of comprehensive energy systems.The control performance of primary frequency modulation of gas turbines has a great impact on the frequency control of the power grid.However,there are some control difficulties in the primary frequency modulation control of gas turbines,such as the coupling effect of the fuel control loop and speed control loop,slow tracking speed,and so on.To relieve the abovementioned difficulties,a control strategy based on the desired dynamic equation proportional integral(DDE-PI)is proposed in this paper.Based on the parameter stability region,a parameter tuning procedure is summarized.Simulation is carried out to address the ease of use and simplicity of the proposed tuning method.Finally,DDE-PI is applied to the primary frequency modulation system of an MS6001B heavy-duty gas turbine.The simulation results indicate that the gas turbine with the proposed strategy can obtain the best control performance with a strong ability to deal with system uncertainties.The proposed method shows good engineering application potential.展开更多
Laozi’s concept of desire has rich ideological connotations,not only referring to reducing personal desires.Laozi’s concept of desire is based on“desire”as human nature,acknowledging the legitimacy and necessity o...Laozi’s concept of desire has rich ideological connotations,not only referring to reducing personal desires.Laozi’s concept of desire is based on“desire”as human nature,acknowledging the legitimacy and necessity of desire and demand.The rational criticism of“having desire”formed by“no desire”is the value pursuit of Laozi’s concept of desire.From both personal physical and mental aspects and social order,“no desire”plays an important guiding role.Nature is the essence of Laozi’s concept of desire,and being in harmony with nature is the best state of desire.Laozi’s concept of desire reveals a deep spirit of love,and the“ethics of love”highlights Laozi’s strong sense of care for the“other”and ethical attitude towards responsibility.Laozi’s contemplation of desire contains a strong humanistic spirit,with the aim of promoting the healthy and sustainable development of life and society.展开更多
We propose a general approach based on the gradient descent method to study the inverse problem,making it possible to reversely engineer the microscopic configurations of materials that exhibit desired macroscopic pro...We propose a general approach based on the gradient descent method to study the inverse problem,making it possible to reversely engineer the microscopic configurations of materials that exhibit desired macroscopic properties.Particularly,we demonstrate its application by identifying the microscopic configurations within any given frequency range to achieve transparent phonon transport through one-dimensional harmonic lattices.Furthermore,we obtain the phonon transmission in terms of normal modes and find that the key to achieving phonon transparency or phonon blocking state lies in the ratio of the mode amplitudes at ends.展开更多
A new method of confirming the desired safety headway distance and desired deceleration is put forward according to the detected static or moving target and its simulation results in Matlab are also presented. The val...A new method of confirming the desired safety headway distance and desired deceleration is put forward according to the detected static or moving target and its simulation results in Matlab are also presented. The validity of the algorithm to calculate the reference speeds of both the ACC vehicle and the targeted car according to the vector quadrangle composed of the relative distance, the relative azimuth angle, the relative speeds of the vehicles has also been demonstrated through numerical example in Matlab. New laws to obtain the desired deceleration by estimating the braking force according to the vehicle analyses force equation are established too.展开更多
As one of the most well- known plays of Henrik Ibsen, A Doll's House's publishment and premiere in 1879 aroused great controversy on the ideas and beliefs reflected in this play. The female protagonist, Nora, ...As one of the most well- known plays of Henrik Ibsen, A Doll's House's publishment and premiere in 1879 aroused great controversy on the ideas and beliefs reflected in this play. The female protagonist, Nora, is especially the center of dispute.In Act II, a scene of Nora's dancing Tarantella is worth discussing. It can not only be understood as a way of relieving, but the two men who gives Nora much pressure as well. Tarantella is also a dance of desire which leads to her breakaway from the loveless marriage and her departure from the family.展开更多
Desire Under the Elms was a drama written by Eugene O'Neill in 1924,which is called the first greatest drama in American history.Through analyzing the naturalistic features in this drama and the combination of nat...Desire Under the Elms was a drama written by Eugene O'Neill in 1924,which is called the first greatest drama in American history.Through analyzing the naturalistic features in this drama and the combination of naturalism and realism reflected in Desire Under the Elms,this article aims to help readers understand the lines and the relevant connotations better.展开更多
Desire under the Elms reveals a tragedy of spiritual and survival desire of human being. O'Neill creates many Bible archetypes in Desire under the Elms. The thesis analyzes and appreciates Desire under the Elms fr...Desire under the Elms reveals a tragedy of spiritual and survival desire of human being. O'Neill creates many Bible archetypes in Desire under the Elms. The thesis analyzes and appreciates Desire under the Elms from aspect of Bible archetype to highlight the destructive power of improper desires in Desire under the Elms.展开更多
Changes in natural environment are usually the reflection of human inner world.The Storm was a short story written by Kate Chopin,an America female writer.In the story storm not only creates the setting for her immora...Changes in natural environment are usually the reflection of human inner world.The Storm was a short story written by Kate Chopin,an America female writer.In the story storm not only creates the setting for her immoral behavior,but also symbolizes the female protagonist,Calixta's desire for love.展开更多
The prevalence of,and related factors to,stress urinary incontinence (SUI) among perimenopausal Chinese women and its impact on daily life among those women with sexual desire problem in Hubei province were investigat...The prevalence of,and related factors to,stress urinary incontinence (SUI) among perimenopausal Chinese women and its impact on daily life among those women with sexual desire problem in Hubei province were investigated.In this study,1519 perimenopausal women aged 40 to 65 years were selected from three urban communities in the Wuhan area,and two impoverished,mountainous communities in Hubei province,and followed from April to October 2014.Detailed information about demographic characteristics,menstruation,pregnancy,sexual life and chronic diseases was collected.A cross-sectional survey was carried out following information collection by Chi-square test and multiple logistic regression analysis.Univariate and multivariate logistic regression analysis demonstrated that the potential factors associated with developing SUI were old age (OR=3.4,95% CI:1.92-6.04),vaginal delivery (OR=0.623,95% CI:0.45-0.87),low income (OR=0.063,95% CI:0.40-0.92),atrophic vaginitis (OR=1.4,95% CI:1.03-1.80),pelvic organ prolapse (OR=2.81,95% CI:1.36-5.80),chronic pelvic pain (OR=2.17,95% CI:1.90-4.03),constipation (OR=1.44,95% CI:1.07-1.93) and incontinence of feces (OR=3.32,95% CI:2.03-5.43).Moreover,the ratio of SUI (33.2%) was higher than the ratio of urgency urinary incontinence (24.1 %) or the ratio of mixed urinary incontinence (17.4%),and SUI had a greater impact on daily life among women with decreased sexual desire.In conclusion,SUI is a common disorder affecting over one third of the women surveyed,and has a severe impact on the daily life of perimenopausal women with declined sexual desire.Age,mode of delivery,and monthly income are major risk factors involved in the development of SUI.展开更多
The satisfaction rate of desired velocity in the case of a mixture of fast and slow vehicles is studied by using a cellular automaton method. It is found that at low density the satisfaction rate depends on the maxima...The satisfaction rate of desired velocity in the case of a mixture of fast and slow vehicles is studied by using a cellular automaton method. It is found that at low density the satisfaction rate depends on the maximal velocity. However, the behavior of the satisfaction rate as a function of the coefficient of variance is independent of the maximal velocity. This is in good agreement with empirical results obtained by Lipshtat [Phys. Rev. E 79 066110 (2009)]. Furthermore, our numerical result demonstrates that at low density the satisfaction rate takes higher values, whereas the coefficient of variance is close to zero. The coefficient of variance increases with increasing density, while the satisfaction rate decreases to zero. Moreover, we have also shown that, at low density the coefficient variance depends strongly on the probability of overtaking.展开更多
Based on the pioneering work of Konishi et al., in consideration of the influence of drivers' steady desired speed ef/ect on the traffic flow, we develop a new coupled map car-following model in the real world. By us...Based on the pioneering work of Konishi et al., in consideration of the influence of drivers' steady desired speed ef/ect on the traffic flow, we develop a new coupled map car-following model in the real world. By use of the control theory, the stability condition of our model is derived. The validity of the present theoretical scheme is verified via numerical simulation, confirming the correctness of our theoretical analysis.展开更多
In this study,2~5 (five factors at two-level factorial design) design of experiment was applied to investigate a set of optimal machining parameters to achieve a minimum surface roughness value for Abies nordmannian...In this study,2~5 (five factors at two-level factorial design) design of experiment was applied to investigate a set of optimal machining parameters to achieve a minimum surface roughness value for Abies nordmanniana.Wood specimens were prepared using different values of spindle speed,feed rate,depth of cut,tool radius,and cutting directions.Average surface roughness (R_z) values were applied using a stylus.The objectives were to:(1)obtain the effective variables of wood surface roughness;(2) analyze which of these factors had an impact on variability in the CNC machining process;(3) evaluate the optimal cutting values within the range of different cutting levels of machining parameters.The results indicate that the design of experiment(DOE) based on the desirability function approach determined the optimal machining parameters successfully,leading to minimum R_a compared to the observed value.Minimum surface roughness values of tangential and radial cutting directions were 3.58 and 3.21 μm,respectively.展开更多
Due to the nonlinearity and uncertainty, the precise control of underwater vehicles in some intelligent operations hasn’t been solved very well yet. A novel method of control based on desired state programming was pr...Due to the nonlinearity and uncertainty, the precise control of underwater vehicles in some intelligent operations hasn’t been solved very well yet. A novel method of control based on desired state programming was presented, which used the technique of fuzzy neural network. The structure of fuzzy neural network was constructed according to the moving characters and the back propagation algorithm was deduced. Simulation experiments were conducted on general detection remotely operated vehicle. The results show that there is a great improvement in response and precision over traditional control, and good robustness to the model’s uncertainty and external disturbance, which has theoretical and practical value.展开更多
To reduce the fuel consumption and emissions and also enhance the molten aluminum quality, a mathematical model with user-developed melting model and burning capacity model, were established according to the features ...To reduce the fuel consumption and emissions and also enhance the molten aluminum quality, a mathematical model with user-developed melting model and burning capacity model, were established according to the features of melting process of regenerative aluminum melting furnaces. Based on validating results by heat balance test for an aluminum melting furnace, CFD (computational fluid dynamics) technique, in association with statistical experimental design were used to optimize the melting process of the aluminum melting furnace. Four important factors influencing the melting time, such as horizontal angle between burners, height-to-radius ratio, natural gas mass flow and air preheated temperature, were identified by PLACKETT-BURMAN design. A steepest descent method was undertaken to determine the optimal regions of these factors. Response surface methodology with BOX-BEHNKEN design was adopted to further investigate the mutual interactions between these variables on RSD (relative standard deviation) of aluminum temperature, RSD of furnace temperature and melting time. Multiple-response optimization by desirability function approach was used to determine the optimum melting process parameters. The results indicate that the interaction between the height-to-radius ratio and horizontal angle between burners affects the response variables significantly. The predicted results show that the minimum RSD of aluminum temperature (12.13%), RSD of furnace temperature (18.50%) and melting time (3.9 h) could be obtained under the optimum conditions of horizontal angle between burners as 64°, height-to-radius ratio as 0.3, natural gas mass flow as 599 m3/h, and air preheated temperature as 639 ℃. These predicted values were further verified by validation experiments. The excellent correlation between the predicted and experimental values confirms the validity and practicability of this statistical optimum strategy.展开更多
Lipopeptides are currently re-emerging as an interesting subgroup in the peptide research field, having historical applications as antibacterial and antifungal agents and new potential applications as antiviral, antit...Lipopeptides are currently re-emerging as an interesting subgroup in the peptide research field, having historical applications as antibacterial and antifungal agents and new potential applications as antiviral, antitumor, immune-modulating and cell-penetrating compounds. However, due to their specific structure, chromatographic analysis often requires special buffer systems or the use of trifluoroacetic acid, limiting mass spectrometry detection. Therefore, we used a traditional aqueous/acetonitrile based gradient system, containing 0.1% (m/v) formic acid, to separate four pharmaceutically relevant lipopeptides (polymyxin B1, caspofungin, daptomycin and gramicidin A1), which were selected based upon hierarchical cluster analysis (HCA) and principal component analysis (PCA).In total, the performance of four different C18 columns, including one UPLC column, were evaluated using two parallel approaches. First, a Derringer desirability function was used, whereby six single and multiple chromatographic response values were rescaled into one overall D-value per column. Using this approach, the YMC Pack Pro C18 column was ranked as the best column for general MS-compatible lipopeptide separation. Secondly, the kinetic plot approach was used to compare the different columns at different flow rate ranges. As the optimal kinetic column performance is obtained at its maximal pressure, the length elongation factor λ(Pmax/Pexp) was used to transform the obtained experimental data (retention times and peak capacities) and construct kinetic performance limit (KPL) curves, allowing a direct visual and unbiased comparison of the selected columns, whereby the YMC Triart C18 UPLC and ACE C18 columns performed as best. Finally, differences in column performance and the (dis)advantages of both approaches are discussed.展开更多
A Streetcar Named Desire is regarded as one of the most successful masterpieces of Tennessee Williams. An outstanding feature of the play is the wide use of symbolism. Symbols can be seen everywhere and even all the s...A Streetcar Named Desire is regarded as one of the most successful masterpieces of Tennessee Williams. An outstanding feature of the play is the wide use of symbolism. Symbols can be seen everywhere and even all the symbols in the play are con nected with the protagonist Blanche DuBois. Williams applies symbolism throughout the play to make Blanche's tragic fate more vivid to the readers. Her tragic fate lies in her clinging to illusion, thus she is bound to be abandoned by the harsh reality. There fore, the thesis attempts to give a comprehensive analysis of some specific symbols: symbols of illusion represented by the Chinese paper lantern and a paper moon, and symbol of reality represented by the light to further illustrate Blanche's tragically symbolic fate.展开更多
Tennessee Williams' successful drama,A Streetcar Named Desire is a world-classic.Its unique plot,well-established structure,and carefully arranged symbols and hints are so attracting that the drama and the charact...Tennessee Williams' successful drama,A Streetcar Named Desire is a world-classic.Its unique plot,well-established structure,and carefully arranged symbols and hints are so attracting that the drama and the characters has been studied and admired by readers around the world.To provide a detailed analysis of the character,this essay will discuss about and compare various aspect of the main character Blanche DuBois.展开更多
基金supported by Science and Technology Project of Jiangsu Frontier Electric Technology Co.,Ltd. (Grant Number KJ202004),Gao A.M. (author who received the grant).
文摘Gas turbines play core roles in clean energy supply and the construction of comprehensive energy systems.The control performance of primary frequency modulation of gas turbines has a great impact on the frequency control of the power grid.However,there are some control difficulties in the primary frequency modulation control of gas turbines,such as the coupling effect of the fuel control loop and speed control loop,slow tracking speed,and so on.To relieve the abovementioned difficulties,a control strategy based on the desired dynamic equation proportional integral(DDE-PI)is proposed in this paper.Based on the parameter stability region,a parameter tuning procedure is summarized.Simulation is carried out to address the ease of use and simplicity of the proposed tuning method.Finally,DDE-PI is applied to the primary frequency modulation system of an MS6001B heavy-duty gas turbine.The simulation results indicate that the gas turbine with the proposed strategy can obtain the best control performance with a strong ability to deal with system uncertainties.The proposed method shows good engineering application potential.
文摘Laozi’s concept of desire has rich ideological connotations,not only referring to reducing personal desires.Laozi’s concept of desire is based on“desire”as human nature,acknowledging the legitimacy and necessity of desire and demand.The rational criticism of“having desire”formed by“no desire”is the value pursuit of Laozi’s concept of desire.From both personal physical and mental aspects and social order,“no desire”plays an important guiding role.Nature is the essence of Laozi’s concept of desire,and being in harmony with nature is the best state of desire.Laozi’s concept of desire reveals a deep spirit of love,and the“ethics of love”highlights Laozi’s strong sense of care for the“other”and ethical attitude towards responsibility.Laozi’s contemplation of desire contains a strong humanistic spirit,with the aim of promoting the healthy and sustainable development of life and society.
基金supported by the National Natural Science Foundation of China(Grant No.12075199)the Natural Science Foundation of Fujian Province(Grant No.2021J01006)Jiangxi Province(Grant No.20212BAB201024)。
文摘We propose a general approach based on the gradient descent method to study the inverse problem,making it possible to reversely engineer the microscopic configurations of materials that exhibit desired macroscopic properties.Particularly,we demonstrate its application by identifying the microscopic configurations within any given frequency range to achieve transparent phonon transport through one-dimensional harmonic lattices.Furthermore,we obtain the phonon transmission in terms of normal modes and find that the key to achieving phonon transparency or phonon blocking state lies in the ratio of the mode amplitudes at ends.
文摘A new method of confirming the desired safety headway distance and desired deceleration is put forward according to the detected static or moving target and its simulation results in Matlab are also presented. The validity of the algorithm to calculate the reference speeds of both the ACC vehicle and the targeted car according to the vector quadrangle composed of the relative distance, the relative azimuth angle, the relative speeds of the vehicles has also been demonstrated through numerical example in Matlab. New laws to obtain the desired deceleration by estimating the braking force according to the vehicle analyses force equation are established too.
文摘As one of the most well- known plays of Henrik Ibsen, A Doll's House's publishment and premiere in 1879 aroused great controversy on the ideas and beliefs reflected in this play. The female protagonist, Nora, is especially the center of dispute.In Act II, a scene of Nora's dancing Tarantella is worth discussing. It can not only be understood as a way of relieving, but the two men who gives Nora much pressure as well. Tarantella is also a dance of desire which leads to her breakaway from the loveless marriage and her departure from the family.
文摘Desire Under the Elms was a drama written by Eugene O'Neill in 1924,which is called the first greatest drama in American history.Through analyzing the naturalistic features in this drama and the combination of naturalism and realism reflected in Desire Under the Elms,this article aims to help readers understand the lines and the relevant connotations better.
文摘Desire under the Elms reveals a tragedy of spiritual and survival desire of human being. O'Neill creates many Bible archetypes in Desire under the Elms. The thesis analyzes and appreciates Desire under the Elms from aspect of Bible archetype to highlight the destructive power of improper desires in Desire under the Elms.
文摘Changes in natural environment are usually the reflection of human inner world.The Storm was a short story written by Kate Chopin,an America female writer.In the story storm not only creates the setting for her immoral behavior,but also symbolizes the female protagonist,Calixta's desire for love.
文摘The prevalence of,and related factors to,stress urinary incontinence (SUI) among perimenopausal Chinese women and its impact on daily life among those women with sexual desire problem in Hubei province were investigated.In this study,1519 perimenopausal women aged 40 to 65 years were selected from three urban communities in the Wuhan area,and two impoverished,mountainous communities in Hubei province,and followed from April to October 2014.Detailed information about demographic characteristics,menstruation,pregnancy,sexual life and chronic diseases was collected.A cross-sectional survey was carried out following information collection by Chi-square test and multiple logistic regression analysis.Univariate and multivariate logistic regression analysis demonstrated that the potential factors associated with developing SUI were old age (OR=3.4,95% CI:1.92-6.04),vaginal delivery (OR=0.623,95% CI:0.45-0.87),low income (OR=0.063,95% CI:0.40-0.92),atrophic vaginitis (OR=1.4,95% CI:1.03-1.80),pelvic organ prolapse (OR=2.81,95% CI:1.36-5.80),chronic pelvic pain (OR=2.17,95% CI:1.90-4.03),constipation (OR=1.44,95% CI:1.07-1.93) and incontinence of feces (OR=3.32,95% CI:2.03-5.43).Moreover,the ratio of SUI (33.2%) was higher than the ratio of urgency urinary incontinence (24.1 %) or the ratio of mixed urinary incontinence (17.4%),and SUI had a greater impact on daily life among women with decreased sexual desire.In conclusion,SUI is a common disorder affecting over one third of the women surveyed,and has a severe impact on the daily life of perimenopausal women with declined sexual desire.Age,mode of delivery,and monthly income are major risk factors involved in the development of SUI.
文摘The satisfaction rate of desired velocity in the case of a mixture of fast and slow vehicles is studied by using a cellular automaton method. It is found that at low density the satisfaction rate depends on the maximal velocity. However, the behavior of the satisfaction rate as a function of the coefficient of variance is independent of the maximal velocity. This is in good agreement with empirical results obtained by Lipshtat [Phys. Rev. E 79 066110 (2009)]. Furthermore, our numerical result demonstrates that at low density the satisfaction rate takes higher values, whereas the coefficient of variance is close to zero. The coefficient of variance increases with increasing density, while the satisfaction rate decreases to zero. Moreover, we have also shown that, at low density the coefficient variance depends strongly on the probability of overtaking.
基金Project supported by the Major Consulting Project of Chinese Academy of Engineering(Grant No.2012-ZX-22)the National Natural Science Foundation of China(Grant No.71201178)+3 种基金the Natural Science Foundation of Chongqing City,China(Grant No.cstc2012jjB40002)the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20120191110047)the Engineering Center Research Program of Chongqing City,China(Grant No.cstc2011pt-gc30005)the Key Technology R&D Project of Chongqing City,China(Grant Nos.cstc2011AB2052 and cstc2012gg-yyjsB30001)
文摘Based on the pioneering work of Konishi et al., in consideration of the influence of drivers' steady desired speed ef/ect on the traffic flow, we develop a new coupled map car-following model in the real world. By use of the control theory, the stability condition of our model is derived. The validity of the present theoretical scheme is verified via numerical simulation, confirming the correctness of our theoretical analysis.
基金performed in the laboratuary of Istanbul University,Faculty of Forestry where the authors are employed at present
文摘In this study,2~5 (five factors at two-level factorial design) design of experiment was applied to investigate a set of optimal machining parameters to achieve a minimum surface roughness value for Abies nordmanniana.Wood specimens were prepared using different values of spindle speed,feed rate,depth of cut,tool radius,and cutting directions.Average surface roughness (R_z) values were applied using a stylus.The objectives were to:(1)obtain the effective variables of wood surface roughness;(2) analyze which of these factors had an impact on variability in the CNC machining process;(3) evaluate the optimal cutting values within the range of different cutting levels of machining parameters.The results indicate that the design of experiment(DOE) based on the desirability function approach determined the optimal machining parameters successfully,leading to minimum R_a compared to the observed value.Minimum surface roughness values of tangential and radial cutting directions were 3.58 and 3.21 μm,respectively.
基金Supported by the National High Technology and Development Program Foundation of China under Grant No. 2002AA420090.
文摘Due to the nonlinearity and uncertainty, the precise control of underwater vehicles in some intelligent operations hasn’t been solved very well yet. A novel method of control based on desired state programming was presented, which used the technique of fuzzy neural network. The structure of fuzzy neural network was constructed according to the moving characters and the back propagation algorithm was deduced. Simulation experiments were conducted on general detection remotely operated vehicle. The results show that there is a great improvement in response and precision over traditional control, and good robustness to the model’s uncertainty and external disturbance, which has theoretical and practical value.
基金Project(2009BSXT022) supported by the Dissertation Innovation Foundation of Central South University, ChinaProject(07JJ4016) supported by Natural Science Foundation of Hunan Province, ChinaProject(U0937604) supported by National Natural Science Foundation of China
文摘To reduce the fuel consumption and emissions and also enhance the molten aluminum quality, a mathematical model with user-developed melting model and burning capacity model, were established according to the features of melting process of regenerative aluminum melting furnaces. Based on validating results by heat balance test for an aluminum melting furnace, CFD (computational fluid dynamics) technique, in association with statistical experimental design were used to optimize the melting process of the aluminum melting furnace. Four important factors influencing the melting time, such as horizontal angle between burners, height-to-radius ratio, natural gas mass flow and air preheated temperature, were identified by PLACKETT-BURMAN design. A steepest descent method was undertaken to determine the optimal regions of these factors. Response surface methodology with BOX-BEHNKEN design was adopted to further investigate the mutual interactions between these variables on RSD (relative standard deviation) of aluminum temperature, RSD of furnace temperature and melting time. Multiple-response optimization by desirability function approach was used to determine the optimum melting process parameters. The results indicate that the interaction between the height-to-radius ratio and horizontal angle between burners affects the response variables significantly. The predicted results show that the minimum RSD of aluminum temperature (12.13%), RSD of furnace temperature (18.50%) and melting time (3.9 h) could be obtained under the optimum conditions of horizontal angle between burners as 64°, height-to-radius ratio as 0.3, natural gas mass flow as 599 m3/h, and air preheated temperature as 639 ℃. These predicted values were further verified by validation experiments. The excellent correlation between the predicted and experimental values confirms the validity and practicability of this statistical optimum strategy.
基金funded by PhD grants of ‘Institute for the Promotion of Innovation through Science and Technology in Flanders (IWT-Vlaanderen)’ (Nos. 101529 (MD) and 121512 (BG))The Special Research Fund (BOF) of Ghent University (01J22510 (EW) and 01D38811 (SS))
文摘Lipopeptides are currently re-emerging as an interesting subgroup in the peptide research field, having historical applications as antibacterial and antifungal agents and new potential applications as antiviral, antitumor, immune-modulating and cell-penetrating compounds. However, due to their specific structure, chromatographic analysis often requires special buffer systems or the use of trifluoroacetic acid, limiting mass spectrometry detection. Therefore, we used a traditional aqueous/acetonitrile based gradient system, containing 0.1% (m/v) formic acid, to separate four pharmaceutically relevant lipopeptides (polymyxin B1, caspofungin, daptomycin and gramicidin A1), which were selected based upon hierarchical cluster analysis (HCA) and principal component analysis (PCA).In total, the performance of four different C18 columns, including one UPLC column, were evaluated using two parallel approaches. First, a Derringer desirability function was used, whereby six single and multiple chromatographic response values were rescaled into one overall D-value per column. Using this approach, the YMC Pack Pro C18 column was ranked as the best column for general MS-compatible lipopeptide separation. Secondly, the kinetic plot approach was used to compare the different columns at different flow rate ranges. As the optimal kinetic column performance is obtained at its maximal pressure, the length elongation factor λ(Pmax/Pexp) was used to transform the obtained experimental data (retention times and peak capacities) and construct kinetic performance limit (KPL) curves, allowing a direct visual and unbiased comparison of the selected columns, whereby the YMC Triart C18 UPLC and ACE C18 columns performed as best. Finally, differences in column performance and the (dis)advantages of both approaches are discussed.
文摘A Streetcar Named Desire is regarded as one of the most successful masterpieces of Tennessee Williams. An outstanding feature of the play is the wide use of symbolism. Symbols can be seen everywhere and even all the symbols in the play are con nected with the protagonist Blanche DuBois. Williams applies symbolism throughout the play to make Blanche's tragic fate more vivid to the readers. Her tragic fate lies in her clinging to illusion, thus she is bound to be abandoned by the harsh reality. There fore, the thesis attempts to give a comprehensive analysis of some specific symbols: symbols of illusion represented by the Chinese paper lantern and a paper moon, and symbol of reality represented by the light to further illustrate Blanche's tragically symbolic fate.
文摘Tennessee Williams' successful drama,A Streetcar Named Desire is a world-classic.Its unique plot,well-established structure,and carefully arranged symbols and hints are so attracting that the drama and the characters has been studied and admired by readers around the world.To provide a detailed analysis of the character,this essay will discuss about and compare various aspect of the main character Blanche DuBois.