Context: The major challenges of cotton cultivation in Côte d’Ivoire are the improvement of field yields and fiber quality. One of the methods proposed to ensure the quality of cotton fiber is split cotton harve...Context: The major challenges of cotton cultivation in Côte d’Ivoire are the improvement of field yields and fiber quality. One of the methods proposed to ensure the quality of cotton fiber is split cotton harvesting. In order to study the influence of this practice on the technological characteristics of cotton fiber, a study was undertaken in three production zones in Côte d’Ivoire. In the present study, seed cotton was harvested at 50%, 75% and 100% boll opening. After ginning, the fibers were analyzed on an HVI chain and their main technological characteristics were evaluated. Results: The results obtained show that regardless of the area, the crop splitting influences the parameters studied, such as the length, short fiber rate, tenacity, brightness and yellowness index of the fiber. Thus, harvesting at 50% capsule opening improves the fiber length by 1.5 mm, tenacity by 1.04 g/tex and brightness by 1.23, while reducing the short fiber rate by 0.84% and the yellowness index by 0.47. As for harvesting at 75% capsule opening, it increases the length by 0.72 mm, tenacity by 0.79 g/tex and brightness by 1.13, while decreasing the short fiber rate by 0.69% and the yellowness index by 0.45. Conclusion: Splitting the cotton harvest improves the quality of the fiber. It is therefore a practice to be recommended to producers in order to preserve the quality of the fiber, especially that carried out at 50% opening of the cotton bolls.展开更多
Ultra-high performance fiber reinforced concretes （UHPFRC） were prepared by replacing 60% of cement with ultra-fine industrial waste powder. The dynamic mechanical behaviour of UHPFRC with different fiber volume fra...Ultra-high performance fiber reinforced concretes （UHPFRC） were prepared by replacing 60% of cement with ultra-fine industrial waste powder. The dynamic mechanical behaviour of UHPFRC with different fiber volume fraction was researched on repeated compressive impact in four kinds of impact modes through split Hopkinson pressure bar （SHPB）. The experimental results show that the peak stress and elastic modulus decrease and the strain rate and peak strain increase gradually with the increasing of impact times. The initial material damage increases and the peak stress of the specimen decreases from the second impact with the increasing of the initial incident wave. Standard strength on repeated impact is defined to compare the ability of resistance against repeated impact among different materials. The rate of reduction of standard strength is decreased by fiber reinforcement under repeated impact. The material damage is reduced and the ability of repeated impact resistance of UHPFRC is improved with the increasing of fiber volume fraction.展开更多
The optimization of the fiber-coupled terahertz time-domain spectroscopy（THz-TDS） system is performed by changing the polarization of the optical excitation pulse centered at 1550 nm. In Ga As/In Al As multilayer st...The optimization of the fiber-coupled terahertz time-domain spectroscopy（THz-TDS） system is performed by changing the polarization of the optical excitation pulse centered at 1550 nm. In Ga As/In Al As multilayer structures based photoconductive antennas are used in TDS setup as both the emitter and receiver. The experimental results demonstrate that not only the THz signal power but also the temporal waveform vary with the rotation of the exciting pulse polarization. Maximum output power of the emitter is obtained when the polarization of the pump pulse is perpendicular to the edge of the metal electrodes. At this moment the THz waveform is close to a single-cycled pulse. However, double THz pulses could be recorded when the pump laser polarization is parallel to the electrodes. Laser pulse splitting induced by the birefringence of the optical fiber may attribute to the polarizationdependent performance of the fiber-coupled THz-TDS system.展开更多
Experiments were carried out to design polyvinyl alcohol （PVA） fiber reinforced cementitous composites （PVA-FRCCs） holding high ductility and energy consumption ability. Besides, the properties of each ingredients...Experiments were carried out to design polyvinyl alcohol （PVA） fiber reinforced cementitous composites （PVA-FRCCs） holding high ductility and energy consumption ability. Besides, the properties of each ingredients in composites, mixing method and technology for fresh mixture were described in detail. Then, the pseudo-strain-hardening （PSH） behavior was investigated in uniaxial tension test. As a result, the maximum ultimate tensile strain can reach 0.7 percent. On the other hand, the single edge notch （SEN） thin sheet specimens were employed to gain the normal tensile load via crack mouth opening displacement （CMOD） curves, which can show obvious PSH behavior. In addition, the curves can be divided into four zones whose fracture toughness calculation methods were discussed. The wedge splitting （WS） test method can be applied to discuss the fracture toughness. Moreover, fracture energy of SEN and WS specimens were both approximately evaluated.展开更多
文摘Context: The major challenges of cotton cultivation in Côte d’Ivoire are the improvement of field yields and fiber quality. One of the methods proposed to ensure the quality of cotton fiber is split cotton harvesting. In order to study the influence of this practice on the technological characteristics of cotton fiber, a study was undertaken in three production zones in Côte d’Ivoire. In the present study, seed cotton was harvested at 50%, 75% and 100% boll opening. After ginning, the fibers were analyzed on an HVI chain and their main technological characteristics were evaluated. Results: The results obtained show that regardless of the area, the crop splitting influences the parameters studied, such as the length, short fiber rate, tenacity, brightness and yellowness index of the fiber. Thus, harvesting at 50% capsule opening improves the fiber length by 1.5 mm, tenacity by 1.04 g/tex and brightness by 1.23, while reducing the short fiber rate by 0.84% and the yellowness index by 0.47. As for harvesting at 75% capsule opening, it increases the length by 0.72 mm, tenacity by 0.79 g/tex and brightness by 1.13, while decreasing the short fiber rate by 0.69% and the yellowness index by 0.45. Conclusion: Splitting the cotton harvest improves the quality of the fiber. It is therefore a practice to be recommended to producers in order to preserve the quality of the fiber, especially that carried out at 50% opening of the cotton bolls.
基金Funded by the National Natural Science Foundation of China (No. 50808101)Jiangsu Provincial Program for Basic Research (Natural Science Foundation) (No.BK2008417)China Postdoctoral Science Foundation (No. 20080431100)
文摘Ultra-high performance fiber reinforced concretes （UHPFRC） were prepared by replacing 60% of cement with ultra-fine industrial waste powder. The dynamic mechanical behaviour of UHPFRC with different fiber volume fraction was researched on repeated compressive impact in four kinds of impact modes through split Hopkinson pressure bar （SHPB）. The experimental results show that the peak stress and elastic modulus decrease and the strain rate and peak strain increase gradually with the increasing of impact times. The initial material damage increases and the peak stress of the specimen decreases from the second impact with the increasing of the initial incident wave. Standard strength on repeated impact is defined to compare the ability of resistance against repeated impact among different materials. The rate of reduction of standard strength is decreased by fiber reinforcement under repeated impact. The material damage is reduced and the ability of repeated impact resistance of UHPFRC is improved with the increasing of fiber volume fraction.
基金supported by National Basic Research Program of China under Grant No.2014CB339802,No.2011CB808100National Natural Science Foundation of China under Grant No.11174156
文摘The optimization of the fiber-coupled terahertz time-domain spectroscopy（THz-TDS） system is performed by changing the polarization of the optical excitation pulse centered at 1550 nm. In Ga As/In Al As multilayer structures based photoconductive antennas are used in TDS setup as both the emitter and receiver. The experimental results demonstrate that not only the THz signal power but also the temporal waveform vary with the rotation of the exciting pulse polarization. Maximum output power of the emitter is obtained when the polarization of the pump pulse is perpendicular to the edge of the metal electrodes. At this moment the THz waveform is close to a single-cycled pulse. However, double THz pulses could be recorded when the pump laser polarization is parallel to the electrodes. Laser pulse splitting induced by the birefringence of the optical fiber may attribute to the polarizationdependent performance of the fiber-coupled THz-TDS system.
基金Committee on Science and Technology Foundation of China(No.50438010)The Research of Formation Progress and Control Technology of Concrete Structure Cracks
文摘Experiments were carried out to design polyvinyl alcohol （PVA） fiber reinforced cementitous composites （PVA-FRCCs） holding high ductility and energy consumption ability. Besides, the properties of each ingredients in composites, mixing method and technology for fresh mixture were described in detail. Then, the pseudo-strain-hardening （PSH） behavior was investigated in uniaxial tension test. As a result, the maximum ultimate tensile strain can reach 0.7 percent. On the other hand, the single edge notch （SEN） thin sheet specimens were employed to gain the normal tensile load via crack mouth opening displacement （CMOD） curves, which can show obvious PSH behavior. In addition, the curves can be divided into four zones whose fracture toughness calculation methods were discussed. The wedge splitting （WS） test method can be applied to discuss the fracture toughness. Moreover, fracture energy of SEN and WS specimens were both approximately evaluated.
