In this paper, we propose a novel image recompression frame- work and image quality assessment （IQA） method to efficiently recompress Internet images. With this framework image size is significantly reduced without ...In this paper, we propose a novel image recompression frame- work and image quality assessment （IQA） method to efficiently recompress Internet images. With this framework image size is significantly reduced without affecting spatial resolution or perceptible quality of the image. With the help of IQA, the relationship between image quality and image evaluation scores can be quickly established, and the optimal quality factor can be obtained quickly and accurately within a pre - determined perceptual quality range. This process ensures the image＇s perceptual quality, which is applied to each input image. The test results show that, using the proposed method, the file size of images can be reduced by about 45%-60% without affecting their visual quality. Moreover, our new image -reeompression framework can be used in to many different application scenarios.展开更多
Monolayers of porphyrin and phthalocyanine at the air-water interface were studied bymeans of film balance and Brewster angle microscopy (BAM). ResultS showed that the final point ofcompression isotherm and that of re...Monolayers of porphyrin and phthalocyanine at the air-water interface were studied bymeans of film balance and Brewster angle microscopy (BAM). ResultS showed that the final point ofcompression isotherm and that of recompression isotherm were coincident or not coincidentdepending on the target pressures. Results were discussed in terms of the morphology of monolayersobserved by BAM.展开更多
The vapor recompression heat pump(VRHP) distillation technology offers significant improvements in energy efficiency for distillation systems with small temperature differences between the top and bottom of the column...The vapor recompression heat pump(VRHP) distillation technology offers significant improvements in energy efficiency for distillation systems with small temperature differences between the top and bottom of the column. However, the separation of wide-boiling binary mixtures leads to substantial temperature differences between the top and bottom of the column. This limits the applicability of conventional VRHP due to high capital costs and strict performance requirements of the compressor. To overcome these challenges and to accommodate compressor operating conditions, a novel synthesis and design method is introduced to integrate VRHPs with wide-boiling binary mixture distillation columns(WBMDCs). This method enables quick determination of an initial configuration for the integrated WBMDC-VRHP system and helps identify the optimum configuration with the minimum total annual cost. Two examples, namely the separation of benzene/toluene and isopropanol/chlorobenzene, are employed to derive optimum configurations of the WBMDC-VRHP and compare them with the WBMDC. A systematic comparison between the WBMDC-VRHP and WBMDC demonstrates the superior steady-state performance and economic efficiency of the WBMDC-VRHP.展开更多
JPEG-Compatibility steganalysis detects the presence of secret message embedded in the JPEG decompressed images and estimates the embedding rate. We propose a JPEG-Compatibility steganalysis algorithm that estimates t...JPEG-Compatibility steganalysis detects the presence of secret message embedded in the JPEG decompressed images and estimates the embedding rate. We propose a JPEG-Compatibility steganalysis algorithm that estimates the embedding rate based on the difference between the stego image and its recompression based predicted co-vet image. In particular, compression artifacts and embedding changes are distinguished based on the amplitude of pixel value changes. This is done independent of the embedding positions, thus is effective for both content non-adaptive and content adaptive steganography. In addition, we also improve the recompression prediction scheme to more accurately estimate the JPEG quantization table. Experimental results show that the proposed algorithm is significantly more effective in detecting spatial ±1 steganography across a wide range of quality factors and embedding rates, when compared to the previous works.展开更多
Solvent extraction of crude oil from oilseeds is widely applied for its high production capacity and low cost. In this process, solvent recovery and tail gas treatment are usually performed by adsorption, paraffin scr...Solvent extraction of crude oil from oilseeds is widely applied for its high production capacity and low cost. In this process, solvent recovery and tail gas treatment are usually performed by adsorption, paraffin scrubbing, or even cryogenics （at low tail gas flow rates）. Membrane separation, which has a lower energy consumption than these techniques, spans a broad range of admissible concentrations and flow rates, and is moreover easily combined with other techniques. Vapor recompression has potentials to reduce the heat loss in association with distillation and evaporation. In this study, we proved the possibility of combining membrane separation and vapor recompression to improve the conventional vegetable oil production, by both experiments and process simulation. Nearly 73% of energy can be saved in the process of vegetable oil extraction by the novel processing approach. By further environmental assessment, several impact categories show that the optimized process is environmentally sustainable.展开更多
Following the popularity of digital video application,video copying and dissemination have become very easy;however,this makes video hacking and piracy a potential threat in video communication.Video watermarking tech...Following the popularity of digital video application,video copying and dissemination have become very easy;however,this makes video hacking and piracy a potential threat in video communication.Video watermarking technology can solve the problem of copyright protection,and thus,it has been extensively researched.The robustness of the video watermarking algorithm in the bitstream domain is poor,especially the anti-recompression ability,since the watermarked video may be compressed again before transmitting.Considering this,this paper proposes a video watermarking algorithm in the bitstream domain based on moving object detection.To increase the robustness of the watermarking scheme,the moving macroblocks that belong to the moving object in each P frame can be identified via the moving object detection algorithm.Then,watermark embedding in the moving macroblocks is performed using codeword substitution to ensure the consistency of the bitstream.Moving object detection and watermark embedding are independent and are both carried out in the bitstream domain by partially decoding the bitstream;this avoids the complete decoding and reconstruction of the video,making the method to be highly efficient.The simulation results confirm that the proposed method is robust against recompression and has little impact on the video visual quality and no influence on the bit rate.展开更多
A novel power and cooling cogeneration system which combines a supercritical CO_(2) recompression cycle(SCRC), an ammonia-water absorption refrigeration cycle(AARC) and a Kalina cycle(KC) is proposed and investigated ...A novel power and cooling cogeneration system which combines a supercritical CO_(2) recompression cycle(SCRC), an ammonia-water absorption refrigeration cycle(AARC) and a Kalina cycle(KC) is proposed and investigated for the recovery of medium-temperature waste heat. The system is based on energy cascade utilization, and the waste heat can be fully converted through the simultaneous operation of the three sub-cycles. A steady-state mathematical model is built for further performance study of the proposed system. When the exhaust temperature is 505℃, it is shown that under designed conditions the thermal efficiency and exergy efficiency reach 30.74% and 61.55%, respectively. The exergy analysis results show that the main exergy destruction is concentrated in the heat recovery vapor generator(HRVG). Parametric study shows that the compressor inlet pressure, the SCRC pressure ratio, the main compressor and the turbine I inlet temperature, and the AARC generator pressure have significant effects on thermodynamic and economic performance of the combined system. The findings in this study could provide guidance for system design to achieve an efficient utilization of medium-temperature waste heat(e.g., exhaust heat from gas turbine, high-temperature fuel cells and internal combustion engine).展开更多
Interplay between dispersion and nonlinearity in optical fibers is a fundamental research topic of nonlinear fiber optics.Here we numerically and experimentally investigate an incoherent continuous-wave(CW)optical fie...Interplay between dispersion and nonlinearity in optical fibers is a fundamental research topic of nonlinear fiber optics.Here we numerically and experimentally investigate an incoherent continuous-wave(CW)optical field propagating in the fiber with normal dispersion,and introduce a distinctive spectral evolution that differs from the previous reports with coherent mode-locked fiber lasers and partially coherent Raman fiber lasers[Nat.Photonics 9,608(2015).].We further reveal that the underlying physical mechanism is attributed to a novel interplay between groupvelocity dispersion(GVD),self-phase modulation(SPM)and inverse four-wave mixing(IFWM),in which SPM and GVD are responsible for the first spectral broadening,while the following spectral recompression is due to the GVD-assisted IFWM,and the eventual stationary spectrum is owing to the dominant contribution of GVD effect.We believe this work can not only expand the light propagation in the fiber to a more general case and help advance the physical understanding of light propagation with different statistical properties,but also benefit the applications in sensing,telecommunications and fiber lasers.展开更多
Nowadays,the recompression supercritical carbon dioxide(R-SCO_(2))cycle has emerged as a promising option for power conversion systems because of its boundless potential to tackle energy and environmental issues.In th...Nowadays,the recompression supercritical carbon dioxide(R-SCO_(2))cycle has emerged as a promising option for power conversion systems because of its boundless potential to tackle energy and environmental issues.In this study,we examined the performance of the solar parabolic trough collector(SPTC)integrated combined cogeneration system for the purpose of power generation as well as recovery of waste exhaust heat from the R-SCO_(2) cycle with the help of the organic Rankine cycle(ORC).An exergy and energy analysis was performed for a combined recompression cycle(R-SCO_(2)-ORC)by varying the input variables such as intensity of solar irradiation(Gb),pressure at the inlet of SCO_(2) turbine(P_(5)),mass flow rate of SCO_(2)()&mSCO_(2) inlet temperature of SCO_(2) turbine(T5),inlet temperature of main compressor(T_(9))and effectiveness of the high-and low-temperature recuperator( HTR and LTR).Eight organic working fluids were considered for the ORC:R123,R290,isobutane,R1234yf,R1234ze,toluene,isopentane and cyclohexane.The study revealed that R123-based R-SCO_(2)-ORC demonstrates the highest thermal and exergy efficiency:~73.4 and 40.89%at G_(b)=0.5 kW/m^(2);78.8 and 43.9%at P_(5)=14 MPa;63.86 and 35.57%at T5=650 K;74.84 and 41.69%at&mSCO 7kg s;2=/85.83 and 47.82%at T_(9)=300 K;84.57 and 47.11%at HTR 65;=0.85.06 and 47.38%at LTR 65,=0.respectively.Alternatively,R290 showed the minimum value of exergy and thermal efficiency.As can be seen,the maximum amount of exergy destruction or exergy loss occurs in a solar collector field,~58.25%of the total exergy destruction rate(i.e.6703 kW)and 18.99%of the solar inlet exergy(i.e.20562 kJ).Moreover,R123 has the highest net work output,~4594 kJ at T5=650 K and 6176 kJ at T_(9)=300 K.展开更多
Current study deals with performance evaluation of the solar power tower driven recompression with main com-pressor intercooling(RMCIC)supercritical CO_(2)cycle incorporating the parallel double evaporator organic Ran...Current study deals with performance evaluation of the solar power tower driven recompression with main com-pressor intercooling(RMCIC)supercritical CO_(2)cycle incorporating the parallel double evaporator organic Rank-ine cycle(PDORC)as bottoming cycle using low global warming potential fluids to reduce the global warming and ozone depletion.Using the PDORC instead of the basic organic Rankine cycle,waste heat from the intercooler and cycle exhaust were recovered simultaneously to enhance performance of the standalone RMCIC cycle.Exergy,thermal efficiency,efficiency improvement and waste recovery ratio were considered as performance parameters.A computer program was made in engineering equation solver to simulate the model.It was concluded that by the incorporation of the PDORC thermal efficiency was improved by 7-8%at reference conditions.Maximum combined cycle’s thermal and exergy efficiency were found 54.42%and 80.39%respectively of 0.95 kW/m^(2)of solar irradiation based on R1243zf working fluid.Among the results it was also found that maximum waste heat was recovered by the R1243zf about 54.22%at 0.95 effectiveness of low temperature recuperator.展开更多
In this study,vapor recompression and heat integration assisted distillation arrangements with either the low or high pressure in the reflux drum are proposed to reduce and/or eliminate the application of the costly r...In this study,vapor recompression and heat integration assisted distillation arrangements with either the low or high pressure in the reflux drum are proposed to reduce and/or eliminate the application of the costly refrigerant for the separation of n-heptane and isobutanol mixture.The high-pressure arrangement with vapor recompression and heat integration is the most attractive among these four intensified configurations since it can reduce total annual cost by 18.10%,CO_(2) emissions by 75.01%based on natural gas(78.78%based on heavy oil fuel),and second-law efficiency by 61.20%compared to a conventional refrigerated distillation system.Furthermore,exergy destruction in each component is calculated for the heat integration configurations and is shown in pie diagrams.The results demonstrate that the high-pressure configuration presents unique advantages in terms of thermodynamic efficiency compared to the low-pressure case.In addition,dynamic control investigation is performed for the economically efficient arrangement and good product compositions are well controlled through a dual-point temperature control strategy with almost negligible product offsets and quick process responses when addressing 20%step changes in production rate and feed composition.Note that there are no composition measurement loops in our developed control schemes.展开更多
For dividing-wall distillation columns(DWDCs) separating a heavy-component dominated and wide boiling-point ternary(HCDWBT) mixture, a significant amount of excessive heat exists inevitably in stripping the heavy-comp...For dividing-wall distillation columns(DWDCs) separating a heavy-component dominated and wide boiling-point ternary(HCDWBT) mixture, a significant amount of excessive heat exists inevitably in stripping the heavy-component from the intermediate-component and it can be employed to initiate the development of vapor recompression heat pump(VRHP) assisted DWDC(VRHP-DWDC). Despite dividing wall may locate in the top, middle, and bottom, the optimum VRHP-DWDC is found to involve uniformlytwo VRHP circles. While the first one serves to compress and transform the excessive heat resulted from the separation of the heavy-component from the intermediate-component, the second one to compress and transform the overhead vapor stream of the light-component pre-heated sequentially with the condensate from the first one and the bottom product stream of the heavy-component, both releasing the temperature-elevated latent heat to the pre-fractionator's or common stripping section. The processing of two HCDWBT mixtures of benzene/toluene/o-xylene and n-pentane/n-hexane/n-heptane are selected to assess the derived optimum topological configurations of the VRHP-DWDC and their optimality is confirmed through detailed comparisons with the DWDC and two VRHP-DWDCs involving only one VRHP circle. The proposed strategy helps to tap the full potential of the VRHP-DWDC with considerably alleviated complication in process development.展开更多
In this paper, through two case studies, evaporation systems are considered in the context of overall process, and then are optimized to obtain energy-saving effect. The possible evaporation schemes are given when int...In this paper, through two case studies, evaporation systems are considered in the context of overall process, and then are optimized to obtain energy-saving effect. The possible evaporation schemes are given when integrated with the background process and how to optimize the evaporator is shown. From the case studies, it can be seen that sometimes incomplete integration and heat pump evaporation are better than complete integration so should be considered as candidate retrofit schemes.展开更多
Considering the problem of mode ranks revealing of d-dimensional array (tensor) given in canonical form,we propose fast algorithm based on cross approximation of Gram matrices of unfoldings.
Compared with the multi-effect distilled water machine,the mechanical vapor recompression(MVR)distilled water machine has many advantages,and has been a trend to replace the traditional distilled water machine.Based o...Compared with the multi-effect distilled water machine,the mechanical vapor recompression(MVR)distilled water machine has many advantages,and has been a trend to replace the traditional distilled water machine.Based on the conservation equations of mass and energy,this paper designs an MVR distilled water production process and establishes the corresponding thermodynamic model.Effects of the produced water temperature,heat exchange temperature difference,compressor adiabatic efficiency,and pipeline loss to the produced water energy consumption,energy saving rate and coefficient of performance(COP)were studied.Research shows that the MVR distilled water machine is more suitable for occasions with low water production temperature.Appropriate heat exchangers and compressors should be selected to improve comprehensive performance through heat exchange temperature differences and improving adiabatic efficiency.展开更多
Brayton power cycles for fusion reactors have been investigated, using Helium in classical configurations and CO2 in a recompression layout. Thermal sources from the reactor have strongly constrained the cycle configu...Brayton power cycles for fusion reactors have been investigated, using Helium in classical configurations and CO2 in a recompression layout. Thermal sources from the reactor have strongly constrained the cycle configurations, hindering use of a recuperator in Helium cycles and conditioning the outlet turbine temperature in CO2 ones. In both cycles, it is possible to take advantage of the exhaust thermal energy by coupling the Brayton to a Rankine cycle, with an organic fluid in the helium case （iso-butane has been investigated） and steam in the CO2 case. The highest efficiency achieved with Helium cycle is 38.5% using Organic Rankine Cycle and 32.6% with Helium alone. The efficiency changes from 46.7% using Rankine cycle to 41% with CO2 alone. The Helium cycle is highly sensitive to turbine efficiency and in a moderate way to compressor efficiency and pressure drops, being nearly insensitive to thermal effectiveness in heat exchangers. On the other hand, CO2 is nearly insensitive to all the parameters.展开更多
Due to the topological structure of double columns and multiple separating sections in dividing-wall distillation columns(DWDCs),the development of vapor recompressed dividing-wall distillation columns(DWDC-VRHPs)repr...Due to the topological structure of double columns and multiple separating sections in dividing-wall distillation columns(DWDCs),the development of vapor recompressed dividing-wall distillation columns(DWDC-VRHPs)represents a challenging issue with great complexities and tediousness.For the separations of light-component dominated and wide boiling-point ternary mixtures,because the purification of the light-component from the intermediate-and heavy-components incurs the primary energy dissipation,the application of vapor recompressed heat pumps(VRHP)should be aimed to reduce the irreversibility and this leads to the generation of the optimum topological structures of the DWDC-VRHPs,i.e.,a DWDC plus a two-stage VRHP.The first-stage VRHP is to preheat feed,not only taking the advantages of the small temperature elevation available but also favoring the mass transfer between the vapor and liquid phases through feed splitting.The second-stage VRHP is to reduce further separation irreversibility.The philosophy can be applied to any DWDCs no matter where the dividing wall locates.Two case studies on the separations of ternary mixtures of benzene,toluene,and o-xylene and n-pentane,n-hexane,and n-heptane demonstrate the economic optimality of the proposed DWDC-VRHPs and reveal the inherent interplay between internal and external process integration.展开更多
Recently, device storage capacity and transmission bandwidth requirements are facing a heavy burden on account of massive internet images. Generally, to improve user experience and save costs as much as possible, a lo...Recently, device storage capacity and transmission bandwidth requirements are facing a heavy burden on account of massive internet images. Generally, to improve user experience and save costs as much as possible, a lot of internet applications always focus on how to achieve appropriate image reeompression. In this paper, we propose a novel framework to efficiently customize image recompression according to a variety of applications. First of all, we evaluate the input image＇s compression level and predict an initial compression level which is very close to the final output of our system using a prior learnt from massive images. Then, we iteratively recompress the input image to different levels and measure the perceptual similarity between the input image and the new result by a block-based coding quality method. According to the output of the quality assessment method, we can update the target compression level, or switch to the subjective evaluation, or return the final recompression result in our system pipeline control. We organize subjective evaluations based on different applications and obtain corresponding assessment report. At last, based on the assessment report, we set up a series of appropriate parameters for customizing image recompression. Moreover, our new framework has been successfully applied to many commercial applications, such as web portals, e-commerce, online game, and so on.展开更多
基金supported in part by China"973"Program under Grant No.2014CB340303
文摘In this paper, we propose a novel image recompression frame- work and image quality assessment （IQA） method to efficiently recompress Internet images. With this framework image size is significantly reduced without affecting spatial resolution or perceptible quality of the image. With the help of IQA, the relationship between image quality and image evaluation scores can be quickly established, and the optimal quality factor can be obtained quickly and accurately within a pre - determined perceptual quality range. This process ensures the image＇s perceptual quality, which is applied to each input image. The test results show that, using the proposed method, the file size of images can be reduced by about 45%-60% without affecting their visual quality. Moreover, our new image -reeompression framework can be used in to many different application scenarios.
文摘Monolayers of porphyrin and phthalocyanine at the air-water interface were studied bymeans of film balance and Brewster angle microscopy (BAM). ResultS showed that the final point ofcompression isotherm and that of recompression isotherm were coincident or not coincidentdepending on the target pressures. Results were discussed in terms of the morphology of monolayersobserved by BAM.
文摘The vapor recompression heat pump(VRHP) distillation technology offers significant improvements in energy efficiency for distillation systems with small temperature differences between the top and bottom of the column. However, the separation of wide-boiling binary mixtures leads to substantial temperature differences between the top and bottom of the column. This limits the applicability of conventional VRHP due to high capital costs and strict performance requirements of the compressor. To overcome these challenges and to accommodate compressor operating conditions, a novel synthesis and design method is introduced to integrate VRHPs with wide-boiling binary mixture distillation columns(WBMDCs). This method enables quick determination of an initial configuration for the integrated WBMDC-VRHP system and helps identify the optimum configuration with the minimum total annual cost. Two examples, namely the separation of benzene/toluene and isopropanol/chlorobenzene, are employed to derive optimum configurations of the WBMDC-VRHP and compare them with the WBMDC. A systematic comparison between the WBMDC-VRHP and WBMDC demonstrates the superior steady-state performance and economic efficiency of the WBMDC-VRHP.
基金This work was supported in part by National Natural Science Foundation of China，National 973 Basic Research Program of China，the Fundamental Research Funds for the Central Universities,HUST
文摘JPEG-Compatibility steganalysis detects the presence of secret message embedded in the JPEG decompressed images and estimates the embedding rate. We propose a JPEG-Compatibility steganalysis algorithm that estimates the embedding rate based on the difference between the stego image and its recompression based predicted co-vet image. In particular, compression artifacts and embedding changes are distinguished based on the amplitude of pixel value changes. This is done independent of the embedding positions, thus is effective for both content non-adaptive and content adaptive steganography. In addition, we also improve the recompression prediction scheme to more accurately estimate the JPEG quantization table. Experimental results show that the proposed algorithm is significantly more effective in detecting spatial ±1 steganography across a wide range of quality factors and embedding rates, when compared to the previous works.
基金This work was supported by the National Basic Research Program of China （973 program, Grant Nos. 2013CB733600 and 2012CB72520）, the National Natural Science Foundation of China （Grant Nos. 21390202 and 21436002）.
文摘Solvent extraction of crude oil from oilseeds is widely applied for its high production capacity and low cost. In this process, solvent recovery and tail gas treatment are usually performed by adsorption, paraffin scrubbing, or even cryogenics （at low tail gas flow rates）. Membrane separation, which has a lower energy consumption than these techniques, spans a broad range of admissible concentrations and flow rates, and is moreover easily combined with other techniques. Vapor recompression has potentials to reduce the heat loss in association with distillation and evaporation. In this study, we proved the possibility of combining membrane separation and vapor recompression to improve the conventional vegetable oil production, by both experiments and process simulation. Nearly 73% of energy can be saved in the process of vegetable oil extraction by the novel processing approach. By further environmental assessment, several impact categories show that the optimized process is environmentally sustainable.
基金supported by the National Natural Science Foundation of China(No.61702563)。
文摘Following the popularity of digital video application,video copying and dissemination have become very easy;however,this makes video hacking and piracy a potential threat in video communication.Video watermarking technology can solve the problem of copyright protection,and thus,it has been extensively researched.The robustness of the video watermarking algorithm in the bitstream domain is poor,especially the anti-recompression ability,since the watermarked video may be compressed again before transmitting.Considering this,this paper proposes a video watermarking algorithm in the bitstream domain based on moving object detection.To increase the robustness of the watermarking scheme,the moving macroblocks that belong to the moving object in each P frame can be identified via the moving object detection algorithm.Then,watermark embedding in the moving macroblocks is performed using codeword substitution to ensure the consistency of the bitstream.Moving object detection and watermark embedding are independent and are both carried out in the bitstream domain by partially decoding the bitstream;this avoids the complete decoding and reconstruction of the video,making the method to be highly efficient.The simulation results confirm that the proposed method is robust against recompression and has little impact on the video visual quality and no influence on the bit rate.
基金supported by the Shandong Provincial Natural Science Foundation of China(No.ZR2019MEE045)the National Natural Science Foundation of China(No.51776203)the Key Project of National Natural Science Foundation of China(No.61733010)。
文摘A novel power and cooling cogeneration system which combines a supercritical CO_(2) recompression cycle(SCRC), an ammonia-water absorption refrigeration cycle(AARC) and a Kalina cycle(KC) is proposed and investigated for the recovery of medium-temperature waste heat. The system is based on energy cascade utilization, and the waste heat can be fully converted through the simultaneous operation of the three sub-cycles. A steady-state mathematical model is built for further performance study of the proposed system. When the exhaust temperature is 505℃, it is shown that under designed conditions the thermal efficiency and exergy efficiency reach 30.74% and 61.55%, respectively. The exergy analysis results show that the main exergy destruction is concentrated in the heat recovery vapor generator(HRVG). Parametric study shows that the compressor inlet pressure, the SCRC pressure ratio, the main compressor and the turbine I inlet temperature, and the AARC generator pressure have significant effects on thermodynamic and economic performance of the combined system. The findings in this study could provide guidance for system design to achieve an efficient utilization of medium-temperature waste heat(e.g., exhaust heat from gas turbine, high-temperature fuel cells and internal combustion engine).
基金National Natural Science Foundation of China(NSFC)(61905284,62035015,62061136013).
文摘Interplay between dispersion and nonlinearity in optical fibers is a fundamental research topic of nonlinear fiber optics.Here we numerically and experimentally investigate an incoherent continuous-wave(CW)optical field propagating in the fiber with normal dispersion,and introduce a distinctive spectral evolution that differs from the previous reports with coherent mode-locked fiber lasers and partially coherent Raman fiber lasers[Nat.Photonics 9,608(2015).].We further reveal that the underlying physical mechanism is attributed to a novel interplay between groupvelocity dispersion(GVD),self-phase modulation(SPM)and inverse four-wave mixing(IFWM),in which SPM and GVD are responsible for the first spectral broadening,while the following spectral recompression is due to the GVD-assisted IFWM,and the eventual stationary spectrum is owing to the dominant contribution of GVD effect.We believe this work can not only expand the light propagation in the fiber to a more general case and help advance the physical understanding of light propagation with different statistical properties,but also benefit the applications in sensing,telecommunications and fiber lasers.
文摘Nowadays,the recompression supercritical carbon dioxide(R-SCO_(2))cycle has emerged as a promising option for power conversion systems because of its boundless potential to tackle energy and environmental issues.In this study,we examined the performance of the solar parabolic trough collector(SPTC)integrated combined cogeneration system for the purpose of power generation as well as recovery of waste exhaust heat from the R-SCO_(2) cycle with the help of the organic Rankine cycle(ORC).An exergy and energy analysis was performed for a combined recompression cycle(R-SCO_(2)-ORC)by varying the input variables such as intensity of solar irradiation(Gb),pressure at the inlet of SCO_(2) turbine(P_(5)),mass flow rate of SCO_(2)()&mSCO_(2) inlet temperature of SCO_(2) turbine(T5),inlet temperature of main compressor(T_(9))and effectiveness of the high-and low-temperature recuperator( HTR and LTR).Eight organic working fluids were considered for the ORC:R123,R290,isobutane,R1234yf,R1234ze,toluene,isopentane and cyclohexane.The study revealed that R123-based R-SCO_(2)-ORC demonstrates the highest thermal and exergy efficiency:~73.4 and 40.89%at G_(b)=0.5 kW/m^(2);78.8 and 43.9%at P_(5)=14 MPa;63.86 and 35.57%at T5=650 K;74.84 and 41.69%at&mSCO 7kg s;2=/85.83 and 47.82%at T_(9)=300 K;84.57 and 47.11%at HTR 65;=0.85.06 and 47.38%at LTR 65,=0.respectively.Alternatively,R290 showed the minimum value of exergy and thermal efficiency.As can be seen,the maximum amount of exergy destruction or exergy loss occurs in a solar collector field,~58.25%of the total exergy destruction rate(i.e.6703 kW)and 18.99%of the solar inlet exergy(i.e.20562 kJ).Moreover,R123 has the highest net work output,~4594 kJ at T5=650 K and 6176 kJ at T_(9)=300 K.
文摘Current study deals with performance evaluation of the solar power tower driven recompression with main com-pressor intercooling(RMCIC)supercritical CO_(2)cycle incorporating the parallel double evaporator organic Rank-ine cycle(PDORC)as bottoming cycle using low global warming potential fluids to reduce the global warming and ozone depletion.Using the PDORC instead of the basic organic Rankine cycle,waste heat from the intercooler and cycle exhaust were recovered simultaneously to enhance performance of the standalone RMCIC cycle.Exergy,thermal efficiency,efficiency improvement and waste recovery ratio were considered as performance parameters.A computer program was made in engineering equation solver to simulate the model.It was concluded that by the incorporation of the PDORC thermal efficiency was improved by 7-8%at reference conditions.Maximum combined cycle’s thermal and exergy efficiency were found 54.42%and 80.39%respectively of 0.95 kW/m^(2)of solar irradiation based on R1243zf working fluid.Among the results it was also found that maximum waste heat was recovered by the R1243zf about 54.22%at 0.95 effectiveness of low temperature recuperator.
文摘In this study,vapor recompression and heat integration assisted distillation arrangements with either the low or high pressure in the reflux drum are proposed to reduce and/or eliminate the application of the costly refrigerant for the separation of n-heptane and isobutanol mixture.The high-pressure arrangement with vapor recompression and heat integration is the most attractive among these four intensified configurations since it can reduce total annual cost by 18.10%,CO_(2) emissions by 75.01%based on natural gas(78.78%based on heavy oil fuel),and second-law efficiency by 61.20%compared to a conventional refrigerated distillation system.Furthermore,exergy destruction in each component is calculated for the heat integration configurations and is shown in pie diagrams.The results demonstrate that the high-pressure configuration presents unique advantages in terms of thermodynamic efficiency compared to the low-pressure case.In addition,dynamic control investigation is performed for the economically efficient arrangement and good product compositions are well controlled through a dual-point temperature control strategy with almost negligible product offsets and quick process responses when addressing 20%step changes in production rate and feed composition.Note that there are no composition measurement loops in our developed control schemes.
基金The financial support from National Natural Science Foundation of China (21878011)。
文摘For dividing-wall distillation columns(DWDCs) separating a heavy-component dominated and wide boiling-point ternary(HCDWBT) mixture, a significant amount of excessive heat exists inevitably in stripping the heavy-component from the intermediate-component and it can be employed to initiate the development of vapor recompression heat pump(VRHP) assisted DWDC(VRHP-DWDC). Despite dividing wall may locate in the top, middle, and bottom, the optimum VRHP-DWDC is found to involve uniformlytwo VRHP circles. While the first one serves to compress and transform the excessive heat resulted from the separation of the heavy-component from the intermediate-component, the second one to compress and transform the overhead vapor stream of the light-component pre-heated sequentially with the condensate from the first one and the bottom product stream of the heavy-component, both releasing the temperature-elevated latent heat to the pre-fractionator's or common stripping section. The processing of two HCDWBT mixtures of benzene/toluene/o-xylene and n-pentane/n-hexane/n-heptane are selected to assess the derived optimum topological configurations of the VRHP-DWDC and their optimality is confirmed through detailed comparisons with the DWDC and two VRHP-DWDCs involving only one VRHP circle. The proposed strategy helps to tap the full potential of the VRHP-DWDC with considerably alleviated complication in process development.
文摘In this paper, through two case studies, evaporation systems are considered in the context of overall process, and then are optimized to obtain energy-saving effect. The possible evaporation schemes are given when integrated with the background process and how to optimize the evaporator is shown. From the case studies, it can be seen that sometimes incomplete integration and heat pump evaporation are better than complete integration so should be considered as candidate retrofit schemes.
基金supported by RFBR grants 08-01-00115supported by RFBR grants 09- 01-12058+1 种基金RFBR/DFG grant 09-01-91332Priority Research Program of Dep.Math. RAS No.3 and 5
文摘Considering the problem of mode ranks revealing of d-dimensional array (tensor) given in canonical form,we propose fast algorithm based on cross approximation of Gram matrices of unfoldings.
基金the research project of Shaanxi Provincial Department of Education(Grant No.19JK0374)Xi’an Polytechnic University doctoral research fund(Grant No.BS201807)Xi’an key laboratory of modern intelligent textile equipment(Grant No.2019220614SYS021CG043).
文摘Compared with the multi-effect distilled water machine,the mechanical vapor recompression(MVR)distilled water machine has many advantages,and has been a trend to replace the traditional distilled water machine.Based on the conservation equations of mass and energy,this paper designs an MVR distilled water production process and establishes the corresponding thermodynamic model.Effects of the produced water temperature,heat exchange temperature difference,compressor adiabatic efficiency,and pipeline loss to the produced water energy consumption,energy saving rate and coefficient of performance(COP)were studied.Research shows that the MVR distilled water machine is more suitable for occasions with low water production temperature.Appropriate heat exchangers and compressors should be selected to improve comprehensive performance through heat exchange temperature differences and improving adiabatic efficiency.
文摘Brayton power cycles for fusion reactors have been investigated, using Helium in classical configurations and CO2 in a recompression layout. Thermal sources from the reactor have strongly constrained the cycle configurations, hindering use of a recuperator in Helium cycles and conditioning the outlet turbine temperature in CO2 ones. In both cycles, it is possible to take advantage of the exhaust thermal energy by coupling the Brayton to a Rankine cycle, with an organic fluid in the helium case （iso-butane has been investigated） and steam in the CO2 case. The highest efficiency achieved with Helium cycle is 38.5% using Organic Rankine Cycle and 32.6% with Helium alone. The efficiency changes from 46.7% using Rankine cycle to 41% with CO2 alone. The Helium cycle is highly sensitive to turbine efficiency and in a moderate way to compressor efficiency and pressure drops, being nearly insensitive to thermal effectiveness in heat exchangers. On the other hand, CO2 is nearly insensitive to all the parameters.
基金financial financial support from National Natural Science Foundation of China(218780112167601121808007)。
文摘Due to the topological structure of double columns and multiple separating sections in dividing-wall distillation columns(DWDCs),the development of vapor recompressed dividing-wall distillation columns(DWDC-VRHPs)represents a challenging issue with great complexities and tediousness.For the separations of light-component dominated and wide boiling-point ternary mixtures,because the purification of the light-component from the intermediate-and heavy-components incurs the primary energy dissipation,the application of vapor recompressed heat pumps(VRHP)should be aimed to reduce the irreversibility and this leads to the generation of the optimum topological structures of the DWDC-VRHPs,i.e.,a DWDC plus a two-stage VRHP.The first-stage VRHP is to preheat feed,not only taking the advantages of the small temperature elevation available but also favoring the mass transfer between the vapor and liquid phases through feed splitting.The second-stage VRHP is to reduce further separation irreversibility.The philosophy can be applied to any DWDCs no matter where the dividing wall locates.Two case studies on the separations of ternary mixtures of benzene,toluene,and o-xylene and n-pentane,n-hexane,and n-heptane demonstrate the economic optimality of the proposed DWDC-VRHPs and reveal the inherent interplay between internal and external process integration.
基金supported by a joint project of Tencent Research and Shanghai Jiao Tong Universitysupported by the National Basic Research 973 Program of China under Grant No.2011CB302203+2 种基金the National Natural Science Foundation of China under Grant Nos.61073089,61133009the Open Projects Program of National Laboratory of Pattern Recognition of Chinathe Open Project Program of the State Key Lab of CAD&CG of Zhejiang University of China under Grant No.A1206
文摘Recently, device storage capacity and transmission bandwidth requirements are facing a heavy burden on account of massive internet images. Generally, to improve user experience and save costs as much as possible, a lot of internet applications always focus on how to achieve appropriate image reeompression. In this paper, we propose a novel framework to efficiently customize image recompression according to a variety of applications. First of all, we evaluate the input image＇s compression level and predict an initial compression level which is very close to the final output of our system using a prior learnt from massive images. Then, we iteratively recompress the input image to different levels and measure the perceptual similarity between the input image and the new result by a block-based coding quality method. According to the output of the quality assessment method, we can update the target compression level, or switch to the subjective evaluation, or return the final recompression result in our system pipeline control. We organize subjective evaluations based on different applications and obtain corresponding assessment report. At last, based on the assessment report, we set up a series of appropriate parameters for customizing image recompression. Moreover, our new framework has been successfully applied to many commercial applications, such as web portals, e-commerce, online game, and so on.
