Microstructural Evolution of TP347H upon Long-Term Service in Power Plants

Fang, Chao,He, Yin Sheng,Yoo, Keun Bong,Jung, Jine Sung,Shin, Kee Sam Trans Tech Publications, Ltd. 2017 Key Engineering Materials Vol.727 No.-

<P>Effects of welding and long-term service on the microstructural evolution of superheater tubes of TP347H stainless steel used in power plants were investigated by optical microscope (OM), scanning electron microscope (SEM), electron back-scattered diffraction (EBSD), and transmission electron microscope (TEM). Analyses after welding or long-term service, showed fine NbCs in grains, which will precipitaion strengthen the matrix. When TP347 was long-term serviced in power plants, M23C6 formed preferentially on the grain boundaries and on twin boundaries, which was attributed to the embrittlement and the intergranular corrosion and fracture. The steam side had less recrystallization rate and more oxide compared to the fire side, which is part of the reason for the cracking from steam side to the fire side. And HAZ is more brittle than the matrix, because of α-Fe phase and coarse grains, due to which, cracks tend to initiate in the steam side of HAZ and propagate to the fire side.</P>

Optimal Harvest-Use-Store Design for Delay-Constrained Energy Harvesting Wireless Communications

Fangchao Yuan,Shi Jin,Kai-Kit Wong,Q. T. Zhang,Hongbo Zhu 한국통신학회 2016 Journal of communications and networks Vol.18 No.6

Recent advances in energy harvesting (EH) technologyhave motivated the adoption of rechargeable mobile devicesfor communications. In this paper, we consider a point-to-point(P2P) wireless communication system in which an EH transmitterwith a non-ideal rechargeable battery is required to send agiven fixed number of bits to the receiver before they expire accordingto a preset delay constraint. Due to the possible energy lossin the storage process, the harvest-use-and-store (HUS) architectureis adopted. We characterize the properties of the optimal solutions,for additive white Gaussian channels (AWGNs) and thenblock-fading channels, that maximize the energy efficiency (i.e.,battery residual) subject to a given rate requirement. Interestingly,it is shown that the optimal solution has a water-filling interpretationwith double thresholds and that both thresholds are monotonic. Based on this, we investigate the optimal double-thresholdbased allocation policy and devise an algorithm to achieve thesolution. Numerical results are provided to validate the theoreticalanalysis and to compare the optimal solutions with existing schemes.

Optimal Harvest-Use-Store Design for Delay-Constrained Energy Harvesting Wireless Communications

Yuan, Fangchao,Jin, Shi,Wong, Kai-Kit,Zhang, Q.T.,Zhu, Hongbo The Korea Institute of Information and Commucation 2016 Journal of communications and networks Vol.18 No.6

Recent advances in energy harvesting (EH) technology have motivated the adoption of rechargeable mobile devices for communications. In this paper, we consider a point-to-point (P2P) wireless communication system in which an EH transmitter with a non-ideal rechargeable battery is required to send a given fixed number of bits to the receiver before they expire according to a preset delay constraint. Due to the possible energy loss in the storage process, the harvest-use-and-store (HUS) architecture is adopted. We characterize the properties of the optimal solutions, for additive white Gaussian channels (AWGNs) and then block-fading channels, that maximize the energy efficiency (i.e., battery residual) subject to a given rate requirement. Interestingly, it is shown that the optimal solution has a water-filling interpretation with double thresholds and that both thresholds are monotonic. Based on this, we investigate the optimal double-threshold based allocation policy and devise an algorithm to achieve the solution. Numerical results are provided to validate the theoretical analysis and to compare the optimal solutions with existing schemes.

Extraction of Cellulose Nanofibrils with Ultraviolet Blocking from Agro-industrial Wastes: A Comparative Study

Xin Zhao,Fangchao Cheng,Yingcheng Hu 한국섬유공학회 2021 Fibers and polymers Vol.22 No.1

Cellulose nanofibrils (CNFs) were successfully isolated from agro-industrial waste (cornstalk, corn flesh, andcorncob) by subjecting the raw materials to organosolv and peroxide treatment, followed by ultrasonication. A detailedcomparative study was performed. Characterization results showed that the CNFs from cornstalk (CS) exhibited higher yieldand lignin content (20.81 %), compared with CNFs from corn flesh (CF) and corncob (CC). The CNFs from CF and CCexhibited similar morphology, particle size, crystallinity, and thermal stability but showed improved ultraviolet blockingability and optical transparency relative to those of CS. The CNFs from CF showed higher dispersion stability andmechanical properties than those from CS and CC. Peroxide treatment negatively influenced crystallinity and thermalstability, but exerted no apparent effect on optical transparency and mechanical strength. Thus, this study demonstrates thatagro-industrial wastes are sustainable resources for CNF production, which can potentially have a wide range of value-addedapplications. Ionic liquid-aided solvothermal treatment followed by ultrasonication is a facile and ideal method to produceCNFs with ultraviolet blocking ability.

Effects of vertical ribs protruding from facades on the wind loads of super high-rise buildings

Yong Quan,Fangchao Hou,Ming Gu 한국풍공학회 2017 Wind and Structures, An International Journal (WAS Vol.24 No.2

The auxiliary structures of a high-rise building, such as balconies, ribs, and grids, are usually much smaller than the whole building; therefore, it is difficult to simulate them on a scaled model during wind tunnel tests, and they are often ignored. However, they may have notable effects on the local or overall wind loads of the building. In the present study, a series of wind pressure wind tunnel tests and high-frequency force balance (HFFB) wind tunnel tests were conducted on rigid models of an actual super high-rise building with vertical ribs protruding from its facades. The effects of the depth and spacing of vertical ribs on the mean values, fluctuating values and the most unfavorable values of the local wind pressure coefficients were investigated by analyzing the distribution of wind pressure coefficients on the facades and the variations of the wind pressure coefficients at the cross section at 2/3 of the building height versus wind direction angle. In addition, the effects of the depth and spacing of vertical ribs on the mean values, fluctuating values and power spectra of the overall aerodynamic force coefficients were studied by analyzing the aerodynamic base moment coefficients. The results show that vertical ribs significantly decrease the most unfavorable suction coefficients in the corner recession regions and edge regions of facades and increase the mean and fluctuating along-wind overall aerodynamic forces.

Effects of vertical ribs protruding from facades on the wind loads of super high-rise buildings

Quan, Yong,Hou, Fangchao,Gu, Ming Techno-Press 2017 Wind and Structures, An International Journal (WAS Vol.24 No.2

The auxiliary structures of a high-rise building, such as balconies, ribs, and grids, are usually much smaller than the whole building; therefore, it is difficult to simulate them on a scaled model during wind tunnel tests, and they are often ignored. However, they may have notable effects on the local or overall wind loads of the building. In the present study, a series of wind pressure wind tunnel tests and high-frequency force balance (HFFB) wind tunnel tests were conducted on rigid models of an actual super high-rise building with vertical ribs protruding from its facades. The effects of the depth and spacing of vertical ribs on the mean values, fluctuating values and the most unfavorable values of the local wind pressure coefficients were investigated by analyzing the distribution of wind pressure coefficients on the facades and the variations of the wind pressure coefficients at the cross section at 2/3 of the building height versus wind direction angle. In addition, the effects of the depth and spacing of vertical ribs on the mean values, fluctuating values and power spectra of the overall aerodynamic force coefficients were studied by analyzing the aerodynamic base moment coefficients. The results show that vertical ribs significantly decrease the most unfavorable suction coefficients in the corner recession regions and edge regions of facades and increase the mean and fluctuating along-wind overall aerodynamic forces.