AISI H13 steel samples were plasma nitrided to improve their surface hardness using a locally developed combined reactor.Pre-ionized RFICP plasma was employed in combination with DC glow discharge and thermal emission...AISI H13 steel samples were plasma nitrided to improve their surface hardness using a locally developed combined reactor.Pre-ionized RFICP plasma was employed in combination with DC glow discharge and thermal emission source to achieve the nitride precipitates in iron-matrix under low sample temperature.Thick nitride layers over 150 microns could be realized with low RF power of 100 W under the processing time between 1-20 h and low sample temperature of 300℃.The gas mixtures of H2 and N2 were utilized while the processing pressure and the DC bias to the sample were maintained at 0.5 torr and 300 V,respectively.Scanning electron microscope(SEM),energy dispersive X-ray spectroscopy(EDS),glancing incident angle X-ray diffractometer(GIXD)and Vickers hardness test were employed to characterize the properties of sample surfaces.Significant increases of surface hardness to over 1,000 HV were observed after treatment.展开更多
An organophosphorus-based diamine has been synthesized and used as a curing and flame retarding bifunctional agent for epoxy resins.This phosphorodiamidate functions not only as a crosslinking materials in the Epon 82...An organophosphorus-based diamine has been synthesized and used as a curing and flame retarding bifunctional agent for epoxy resins.This phosphorodiamidate functions not only as a crosslinking materials in the Epon 828 epoxy resin curing process but also as a fire retarding compound to produce thin films or composites upon curing.This phosphorus-containing reactive amine was synthesized via condensation of phenyphosphonic dichloride with ethylenediamine in the presence of sodium methoxide.The product was then purified and later characterized by NMR and FTIR spectroscopy as well as MALDI-TOF mass spectrometry.Kinetics studies of the curing reaction of the phosphorodiamidate were carried out in comparison with the non-phosphorus containing ethylenediamine reference crosslinking agent.Thermal stability of the cured epoxy ware investigated by thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC).Moreover,flame retardant properties of the obtained materials was investigated by limiting oxygen index(LOI)measurements as well as the UL-40 method.The obtained results show that epoxy resin cured with phosphorodiamidate possesses higher thermostability compared to the epoxy cured with the regular ethylenediamine counterpart.This is evident by higher amount of char formed upon burning.More importantly,the LOI value of 27 was observed in the phosphorodiamidate-cured epoxy resin compared with LOI of 20 of the epoxy resin cured with ethylenediamine where no phosphorus was present.The UL-94 highest rating of V-0 materials was obtained with only about 2-3 wt%of the phosphorus element.The chemistry,curing kinetics,and thermal properties of these new epoxy formulations are discussed.展开更多
Objective:To study the number of leptospirosis cases in relations to the seasonal pattern,and its association with climate factors.Methods:Time series analysis was used to study the time variations in the number of le...Objective:To study the number of leptospirosis cases in relations to the seasonal pattern,and its association with climate factors.Methods:Time series analysis was used to study the time variations in the number of leptospirosis cases.The Autoregressive Integrated Moving Average (ARIMA) model was used in data curve fitting and predicting the next leptospirosis cases. Results:We found that the amount of rainfall was correlated to leptospirosis cases in both regions of interest,namely the northern and northeastern region of Thailand,while the temperature played a role in the northeastern region only.The use of multivariate ARIMA(ARIMAX) model showed that factoring in rainfall(with an 8 months lag) yields the best model for the northern region while the model,which factors in rainfall(with a 10 months kg) and temperature(with an 8 months lag) was the best for the northeaslern region.Conclusions:The models are able to show the trend in leptospirosis cases and closely fit the recorded data in both regions.The models can also be used to predict the next seasonal peak quite accurately.展开更多
The work described herein represents an efficient method in the deposition of poly(3-methylthiophene),P3MeTh,thin films utilizing a microwave plasma system in combination with a simultaneous doping with iodine.It was ...The work described herein represents an efficient method in the deposition of poly(3-methylthiophene),P3MeTh,thin films utilizing a microwave plasma system in combination with a simultaneous doping with iodine.It was envisaged that,an alternative poly(3-methylthiophene),P(3MeTh),with an electron donating methyl substituent,would reduce the degree of ring opening which reportedly occur to a certain extent during the plasma polymerization process of its parent compound polythiophene.An alkyl substituent would also increase the solubility of the materials.P(3MeTh)thin film deposition has been performed utilizing microwave-induced plasma polymerization in order to directly grow films on glass substrates.Moreover,simultaneous doping of the so-formed polymer with iodine has been carried out as opposed to the post-synthesis doping method.This is aimed to prolong electrical conducting lifetime of the materials.The synthesized films were characterized by attenuated total reflection fourier transform infrared(ATR FT-IR)spectroscopy and energy dispersive X-ray spectroscopy(EDS)to confirm the incorporation of iodine dopant into the films.Scanning electron microscopy showed uniformly deposited films.It has been observed that the electrical conductivity of the doped film is 2 orders of magnitude higher than the undoped counterpart.The doped fabricated films exhibited UV-vis spectra indicative of increased π-conjugation(536 nm).Furthermore,electrical conductivity of the in situ doped P(3MeTh)is more highly sustained over a longer period of time.展开更多
Most biochemical processes in cells are usually modeled by reaction-diffusion （RD） equations. In these RD models, the diffusive process is assumed to be Gaussian. However, a growing number of studies have noted that...Most biochemical processes in cells are usually modeled by reaction-diffusion （RD） equations. In these RD models, the diffusive process is assumed to be Gaussian. However, a growing number of studies have noted that intracellular diffusion is anomalous at some or all times, which may result from a crowded environment and chemical kinetics. This work aims to computationally study the effects of chemical reactions on the diffusive dynamics of RD systems by using both stochastic and deterministic algorithms. Numerical method to estimate the mean-square displacement （MSD） from a deterministic algorithm is also investigated. Our computational results show that anomalous diffusion can be solely due to chemical reactions. The chemical reactions alone can cause anomalous sub-diffusion in the RD system at some or all times. The time-dependent anomalous diffusion exponent is found to depend on many parameters, including chemical reaction rates, reaction orders, and chemical concentrations.展开更多
文摘AISI H13 steel samples were plasma nitrided to improve their surface hardness using a locally developed combined reactor.Pre-ionized RFICP plasma was employed in combination with DC glow discharge and thermal emission source to achieve the nitride precipitates in iron-matrix under low sample temperature.Thick nitride layers over 150 microns could be realized with low RF power of 100 W under the processing time between 1-20 h and low sample temperature of 300℃.The gas mixtures of H2 and N2 were utilized while the processing pressure and the DC bias to the sample were maintained at 0.5 torr and 300 V,respectively.Scanning electron microscope(SEM),energy dispersive X-ray spectroscopy(EDS),glancing incident angle X-ray diffractometer(GIXD)and Vickers hardness test were employed to characterize the properties of sample surfaces.Significant increases of surface hardness to over 1,000 HV were observed after treatment.
文摘An organophosphorus-based diamine has been synthesized and used as a curing and flame retarding bifunctional agent for epoxy resins.This phosphorodiamidate functions not only as a crosslinking materials in the Epon 828 epoxy resin curing process but also as a fire retarding compound to produce thin films or composites upon curing.This phosphorus-containing reactive amine was synthesized via condensation of phenyphosphonic dichloride with ethylenediamine in the presence of sodium methoxide.The product was then purified and later characterized by NMR and FTIR spectroscopy as well as MALDI-TOF mass spectrometry.Kinetics studies of the curing reaction of the phosphorodiamidate were carried out in comparison with the non-phosphorus containing ethylenediamine reference crosslinking agent.Thermal stability of the cured epoxy ware investigated by thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC).Moreover,flame retardant properties of the obtained materials was investigated by limiting oxygen index(LOI)measurements as well as the UL-40 method.The obtained results show that epoxy resin cured with phosphorodiamidate possesses higher thermostability compared to the epoxy cured with the regular ethylenediamine counterpart.This is evident by higher amount of char formed upon burning.More importantly,the LOI value of 27 was observed in the phosphorodiamidate-cured epoxy resin compared with LOI of 20 of the epoxy resin cured with ethylenediamine where no phosphorus was present.The UL-94 highest rating of V-0 materials was obtained with only about 2-3 wt%of the phosphorus element.The chemistry,curing kinetics,and thermal properties of these new epoxy formulations are discussed.
基金supported by Centre of Encellecne Mathentatics CHEThailand finanieally Sudaral Chadsuthi is supported by the Commission on Higher Education Thailand for its grant support under the Strategie Scholarships for Frintier Research Network for joint Ph.D.Programssupported by the National Science and Technology Development Agency (NSTDA) and Faculty of Science,Mahidol University
文摘Objective:To study the number of leptospirosis cases in relations to the seasonal pattern,and its association with climate factors.Methods:Time series analysis was used to study the time variations in the number of leptospirosis cases.The Autoregressive Integrated Moving Average (ARIMA) model was used in data curve fitting and predicting the next leptospirosis cases. Results:We found that the amount of rainfall was correlated to leptospirosis cases in both regions of interest,namely the northern and northeastern region of Thailand,while the temperature played a role in the northeastern region only.The use of multivariate ARIMA(ARIMAX) model showed that factoring in rainfall(with an 8 months lag) yields the best model for the northern region while the model,which factors in rainfall(with a 10 months kg) and temperature(with an 8 months lag) was the best for the northeaslern region.Conclusions:The models are able to show the trend in leptospirosis cases and closely fit the recorded data in both regions.The models can also be used to predict the next seasonal peak quite accurately.
文摘The work described herein represents an efficient method in the deposition of poly(3-methylthiophene),P3MeTh,thin films utilizing a microwave plasma system in combination with a simultaneous doping with iodine.It was envisaged that,an alternative poly(3-methylthiophene),P(3MeTh),with an electron donating methyl substituent,would reduce the degree of ring opening which reportedly occur to a certain extent during the plasma polymerization process of its parent compound polythiophene.An alkyl substituent would also increase the solubility of the materials.P(3MeTh)thin film deposition has been performed utilizing microwave-induced plasma polymerization in order to directly grow films on glass substrates.Moreover,simultaneous doping of the so-formed polymer with iodine has been carried out as opposed to the post-synthesis doping method.This is aimed to prolong electrical conducting lifetime of the materials.The synthesized films were characterized by attenuated total reflection fourier transform infrared(ATR FT-IR)spectroscopy and energy dispersive X-ray spectroscopy(EDS)to confirm the incorporation of iodine dopant into the films.Scanning electron microscopy showed uniformly deposited films.It has been observed that the electrical conductivity of the doped film is 2 orders of magnitude higher than the undoped counterpart.The doped fabricated films exhibited UV-vis spectra indicative of increased π-conjugation(536 nm).Furthermore,electrical conductivity of the in situ doped P(3MeTh)is more highly sustained over a longer period of time.
基金supported by the Thailand Research Fund and Mahidol University(Grant No.TRG5880157),the Thailand Center of Excellence in Physics(ThEP),CHE,Thailand,and the Development Promotion of Science and Technology
文摘Most biochemical processes in cells are usually modeled by reaction-diffusion （RD） equations. In these RD models, the diffusive process is assumed to be Gaussian. However, a growing number of studies have noted that intracellular diffusion is anomalous at some or all times, which may result from a crowded environment and chemical kinetics. This work aims to computationally study the effects of chemical reactions on the diffusive dynamics of RD systems by using both stochastic and deterministic algorithms. Numerical method to estimate the mean-square displacement （MSD） from a deterministic algorithm is also investigated. Our computational results show that anomalous diffusion can be solely due to chemical reactions. The chemical reactions alone can cause anomalous sub-diffusion in the RD system at some or all times. The time-dependent anomalous diffusion exponent is found to depend on many parameters, including chemical reaction rates, reaction orders, and chemical concentrations.
