Poplar alkaline peroxide mechanical pulp(APMP)was refined in a PFI mill at varied revolution and the properties of the refined fibers and the resulting hand sheets were tested.The raw poplar APMP fibers are stiff and ...Poplar alkaline peroxide mechanical pulp(APMP)was refined in a PFI mill at varied revolution and the properties of the refined fibers and the resulting hand sheets were tested.The raw poplar APMP fibers are stiff and have been detached from the lamella during APMP pulping process.During the refining process,the APMP fibers did not swell and fibrillate;they were easily broken and formed into fragments.The breaking length of formed hand sheets increased as the heating degree increased because lots of hydrogen bonds were formed between fibers and fine pieces.The tear strength of hand sheets first increased and then decreased as the beating degree changed from 17 to 70~SR.The maximum tear strength was achieved at 61~SR of the beating degree.These results indicated that the hydrogen bond between the fibers was the main factor influencing the tear index followed by the fiber length.Along with the increase of the beating degree,the sheet density increased while the opacity decreased.展开更多
Background Virtual Reality(VR)technologies have advanced fast and have been applied to a wide spectrum of sectors in the past few years.VR can provide an immersive experience to users by generating virtual images and ...Background Virtual Reality(VR)technologies have advanced fast and have been applied to a wide spectrum of sectors in the past few years.VR can provide an immersive experience to users by generating virtual images and displaying the virtual images to the user with a head-mounted display(HMD)which is a primary component of VR.Normally,an HMD contains a list of hardware components,e.g.,housing pack,micro LCD display,microcontroller,optical lens,etc.Settings of VR HMD to accommodate the user's inter-pupil distance(IPD)and the user's eye focus power are important for the user's experience with VR.Methods Although various methods have been developed towards IPD and focus adjustments for VR HMD,the increased cost and complexity impede the possibility for users who wish to assemble their own VR HMD for various purposes,e.g.,DIY teaching,etc.In our paper,we present a novel design towards building a customizable and adjustable HMD for VR in a cost-effective manner.Modular design methodology is adopted,and the VR HMD can be easily printed with 3D printers.The design also features adjustable IPD and variable distance between the optical lens and the display.It can help to mitigate the vergence and accommodation conflict issue.Results A prototype of the customizable and adjustable VR HMD has been successfully built up with off-the-shelf components.A VR software program running on Raspberry Pi board has been developed and can be utilized to show the VR effects.A user study with 20 participants is conducted with positive feedback on our novel design.Conclusions Modular design can be successfully applied for building up VR HMD with 3D printing.It helps to promote the wide application of VR at affordable costs while featuring flexibility and adjustability.展开更多
Holographic near-eye augmented reality(AR)displays featuring tilted inbound/outbound angles on compact optical combiners hold significant potential yet often struggle to deliver satisfying image quality.This is primar...Holographic near-eye augmented reality(AR)displays featuring tilted inbound/outbound angles on compact optical combiners hold significant potential yet often struggle to deliver satisfying image quality.This is primarily attributed to two reasons:the lack of a robust off-axis-supported phase hologram generation algorithm;and the suboptimal performance of ill-tuned hardware parts such as imperfect holographic optical elements(HOEs).To address these issues,we incorporate a gradient descent-based phase retrieval algorithm with spectrum remapping,allowing for precise hologram generation with wave propagation between nonparallel planes.Further,we apply a camera-calibrated propagation scheme to iteratively optimize holograms,mitigating imperfections arising from the defects in the HOE fabrication process and other hardware parts,thereby significantly lifting the holographic image quality.We build an off-axis holographic near-eye display prototype using off-the-shelf light engine parts and a customized full-color HOE,demonstrating state-of-the-art virtual reality and AR display results.展开更多
文摘Poplar alkaline peroxide mechanical pulp(APMP)was refined in a PFI mill at varied revolution and the properties of the refined fibers and the resulting hand sheets were tested.The raw poplar APMP fibers are stiff and have been detached from the lamella during APMP pulping process.During the refining process,the APMP fibers did not swell and fibrillate;they were easily broken and formed into fragments.The breaking length of formed hand sheets increased as the heating degree increased because lots of hydrogen bonds were formed between fibers and fine pieces.The tear strength of hand sheets first increased and then decreased as the beating degree changed from 17 to 70~SR.The maximum tear strength was achieved at 61~SR of the beating degree.These results indicated that the hydrogen bond between the fibers was the main factor influencing the tear index followed by the fiber length.Along with the increase of the beating degree,the sheet density increased while the opacity decreased.
基金Supported by the Computing Science Program jointly offered by Singapore Institute of Technology and University of Glasgow.
文摘Background Virtual Reality(VR)technologies have advanced fast and have been applied to a wide spectrum of sectors in the past few years.VR can provide an immersive experience to users by generating virtual images and displaying the virtual images to the user with a head-mounted display(HMD)which is a primary component of VR.Normally,an HMD contains a list of hardware components,e.g.,housing pack,micro LCD display,microcontroller,optical lens,etc.Settings of VR HMD to accommodate the user's inter-pupil distance(IPD)and the user's eye focus power are important for the user's experience with VR.Methods Although various methods have been developed towards IPD and focus adjustments for VR HMD,the increased cost and complexity impede the possibility for users who wish to assemble their own VR HMD for various purposes,e.g.,DIY teaching,etc.In our paper,we present a novel design towards building a customizable and adjustable HMD for VR in a cost-effective manner.Modular design methodology is adopted,and the VR HMD can be easily printed with 3D printers.The design also features adjustable IPD and variable distance between the optical lens and the display.It can help to mitigate the vergence and accommodation conflict issue.Results A prototype of the customizable and adjustable VR HMD has been successfully built up with off-the-shelf components.A VR software program running on Raspberry Pi board has been developed and can be utilized to show the VR effects.A user study with 20 participants is conducted with positive feedback on our novel design.Conclusions Modular design can be successfully applied for building up VR HMD with 3D printing.It helps to promote the wide application of VR at affordable costs while featuring flexibility and adjustability.
基金National Key Research and Development Program of China(2021YFB2802200)National Natural Science Foundation of China(62322217,62005154)+1 种基金Natural Science Foundation of Shanghai Municipality(20ZR1420500)University Grants Committee(ECS27212822,GRF 17208023)。
文摘Holographic near-eye augmented reality(AR)displays featuring tilted inbound/outbound angles on compact optical combiners hold significant potential yet often struggle to deliver satisfying image quality.This is primarily attributed to two reasons:the lack of a robust off-axis-supported phase hologram generation algorithm;and the suboptimal performance of ill-tuned hardware parts such as imperfect holographic optical elements(HOEs).To address these issues,we incorporate a gradient descent-based phase retrieval algorithm with spectrum remapping,allowing for precise hologram generation with wave propagation between nonparallel planes.Further,we apply a camera-calibrated propagation scheme to iteratively optimize holograms,mitigating imperfections arising from the defects in the HOE fabrication process and other hardware parts,thereby significantly lifting the holographic image quality.We build an off-axis holographic near-eye display prototype using off-the-shelf light engine parts and a customized full-color HOE,demonstrating state-of-the-art virtual reality and AR display results.
