Sulfated polysaccharides exerted potent biological property which was relative to degree of sulfation, molecular weight, substitution position and chain conformation. In present study, the ...polysaccharide with low molecular weight (LEP) from Enteromorpha linza was sulfated with chlorosulfuric acid in formamide. The obtained polysaccharide sulfate was selected to evaluate their antioxidant activities and the anticoagulant activity in the coagulation assays, activated partial thromboplastin time (APTT), thrombin time (TT) and prothrombin time (PT). The data obtained in vitro models indicated that high DS and moderate Mw showed the best anticoagulant and antioxidant activities.
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Enabling pervasive WiFi devices with non-contact sensing capability is an important topic in the field of integrated sensing and communication. Doppler effect has been widely exploited to estimate ...targets' velocity from wireless signals. However, the separation of signal sources and receivers complicates the relationship between Doppler frequency shift (DFS) and target velocity in WiFi-based non-contact sensing systems. In contrast to existing works that rely on either approximated relations or coarse-grained information such as whether a target is moving toward or away from WiFi transceivers, this paper investigates rigorously the dependency of velocity estimation accuracy on target locations and headings in WiFi sensing systems. The theoretical insights allow us to derive a closed-form solution and understand the fundamental limitation of velocity estimation. To optimize velocity estimation performance, we devise a receiving device selection scheme that dynamically chooses the optimal set of receivers among multiple available WiFi devices. A prototype real-time target tracking system has been implemented using commodity WiFi devices. Extensive experimental results show that the proposed system outperforms state-of-the-art approaches in velocity estimation and tracking, and is able to achieve <inline-formula> <tex-math notation="LaTeX">9.38cm/s </tex-math></inline-formula>, 13.42°, <inline-formula> <tex-math notation="LaTeX">31.08cm </tex-math></inline-formula> median errors in speed, heading and location estimation amongst experiments conducted in three indoor environments with three device placements and eight human subjects over 15 trajectories.
Placement Matters Wang, Xuanzhi; Niu, Kai; Xiong, Jie ...
Proceedings of ACM on interactive, mobile, wearable and ubiquitous technologies,
03/2022, Volume:
6, Issue:
1
Journal Article
Peer reviewed
WiFi-based contactless sensing has found numerous applications in the fields of smart home and health care owning to its low-cost, non-intrusive and privacy-preserving characteristics. While ...promising in many aspects, the limited sensing range and interference issues still exist, hindering the adoption of WiFi sensing in real world. In this paper, inspired by the SNR (signal-to-noise ratio) metric in communication theory, we propose a new metric named SSNR (sensing-signal-to-noise-ratio) to quantify the sensing capability of WiFi systems. We theoretically model the effect of transmitter-receiver distance on sensing coverage. We show that in LoS scenario, the sensing coverage area increases first from a small oval to a maximal one and then decreases. When the transmitter-receiver distance further increases, the coverage area is separated into two ovals located around the two transceivers respectively. We demonstrate that, instead of applying complex signal processing scheme or advanced hardware, by just properly placing the transmitter and receiver, the two well-known issues in WiFi sensing (i.e., small range and severe interference) can be greatly mitigated. Specifically, by properly placing the transmitter and receiver, the coverage of human walking sensing can be expanded by around 200%. By increasing the transmitter-receiver distance, a target's fine-grained respiration can still be accurately sensed with one interferer sitting just 0.5 m away.
Enabling WiFi Sensing on New-generation WiFi Cards Yi, Enze; Zhang, Fusang; Xiong, Jie ...
Proceedings of ACM on interactive, mobile, wearable and ubiquitous technologies,
01/2024, Volume:
7, Issue:
4
Journal Article
Peer reviewed
Open access
The last few years have witnessed the rapid development of WiFi sensing with a large spectrum of applications enabled. However, existing works mainly leverage the obsolete 802.11n WiFi cards (i.e., ...Intel 5300 and Atheros AR9k series cards) for sensing. On the other hand, the mainstream WiFi protocols currently in use are 802.11ac/ax and commodity WiFi products on the market are equipped with new-generation WiFi chips such as Broadcom BCM43794 and Qualcomm QCN5054. After conducting some benchmark experiments, we find that WiFi sensing has problems working on these new cards. The new communication features (e.g., MU-MIMO) designed to facilitate data transmissions negatively impact WiFi sensing. Conventional CSI base signals such as CSI amplitude and/or CSI phase difference between antennas which worked well on Intel 5300 802.11n WiFi card may fail on new cards. In this paper, we propose delicate signal processing schemes to make wireless sensing work well on these new WiFi cards. We employ two typical sensing applications, i.e., human respiration monitoring and human trajectory tracking to demonstrate the effectiveness of the proposed schemes. We believe it is critical to ensure WiFi sensing compatible with the latest WiFi protocols and this work moves one important step towards real-life adoption of WiFi sensing.
WiMeasure Wang, Xuanzhi; Niu, Kai; Yu, Anlan ...
Proceedings of ACM on interactive, mobile, wearable and ubiquitous technologies,
06/2023, Volume:
7, Issue:
2
Journal Article
Peer reviewed
In the past few years, a large range of wireless signals such as WiFi, RFID, UWB and Millimeter Wave were utilized for sensing purposes. Among these wireless sensing modalities, WiFi sensing attracts ...a lot of attention owing to the pervasiveness of WiFi infrastructure in our surrounding environments. While WiFi sensing has achieved a great success in capturing the target's motion information ranging from coarse-grained activities and gestures to fine-grained vital signs, it still has difficulties in precisely obtaining the target size owing to the low frequency and small bandwidth of WiFi signals. Even Millimeter Wave radar can only achieve a very coarse-grained size measurement. High precision object size sensing requires using RF signals in the extremely high-frequency band (e.g., Terahertz band). In this paper, we utilize low-frequency WiFi signals to achieve accurate object size measurement without requiring any learning or training. The key insight is that when an object moves between a pair of WiFi transceivers, the WiFi CSI variations contain singular points (i.e., singularities) and we observe an exciting opportunity of employing the number of singularities to measure the object size. In this work, we model the relationship between the object size and the number of singularities when an object moves near the LoS path, which lays the theoretical foundation for the proposed system to work. By addressing multiple challenges, for the first time, we make WiFi-based object size measurement work on commodity WiFi cards and achieve a surprisingly low median error of 2.6 mm. We believe this work is an important missing piece of WiFi sensing and opens the door to size measurement using low-cost low-frequency RF signals.
Despite intensive research efforts in radio frequency noncontact sensing, capturing fine-grained geometric properties of objects, such as shape and size, remains an open problem using commodity WiFi ...devices. Prior attempts are incapable of characterizing object shape or size because they predominantly rely on weak signals reflected off objects in a very small number of directions. In this paper, motivated by the observation that the diffracted signals around an object between two WiFi devices carry the contour information of the object, we formulate the problem of reconstructing the 2D target profile and develop WiProfile, the first WiFi-based system that unlocks the diffraction effects for target profiling. We introduce a CSI-Profile model to characterize the relationship between the CSI measured at different target positions and the target profile in the diffraction zone. With suitable approximations, the inverse problem of deriving the target profile from CSI can be solved by the inverse Fresnel transform. To mitigate CSI measurement errors on commodity WiFi devices, we propose a novel antenna placement strategy. Comprehensive experiments demonstrate that WiProfile can accurately reconstruct profiles with median absolute errors of less than 1 cm under various conditions, and effectively estimate the profiles of everyday objects of diverse shapes, sizes, and materials. We believe this work opens up new directions for fine-grained target imaging using commodity WiFi devices.
WiFi sensing has emerged as a promising technology for smart services, including gesture recognition and trajectory tracking. One of the key challenges in these applications is accurately extracting ...velocity from WiFi signals. In this paper, we report our latest development to investigate the impact of location and orientation on velocity extraction in WiFi sensing systems. The proposed theory demonstrates that the velocity extraction significantly depends on the target’s location and orientation. Thus careful consideration of the target’s location and orientation is necessary for WiFi sensing system design. Specifically, two real-world applications (gesture recognition and trajectory tracking) are presented to illustrate how to eliminate the impact of location and orientation independent in velocity extraction.
To produce selectable marker-free （SMF） transgenic rice resistant to chewing insects, the Bacillus thuringiensis crylA （c） gene （Bt） was introduced into two elite japonica rice varieties by using two ...Agrobacterium-mediated co-transformation systems. One system is with a single mini-twin T-DNA binary vector in one Agrobacterium strain, which consists of two separate T-DNA regions, one carrying the Bt while the other contains the selectable marker gene, hygromycin resistant gene （HPT）. The other system uses two separate binary vectors in two separate Agrobacterium cultures, containing the Bt or HPT gene on individual plasmids. A lot of independent transgenic rice lines harboring both Bt and selectable marker genes were obtained. The results showed that the co-transformation frequency of the Bt gene and HPT gene was much higher by using the mini-twin T-DNA vector system （29.87%） than that by the two separate binary vector systems （4.52%）. However, the frequency of the SMF transgenic rice plants obtained from the offspring of co-transgenic plants （21.74%） was lower for the mini-twin T-DNA vector system than that for the latter （50-60%）. The data of ELISA implied that the expressed Bt proteins were quantitated as 0.025-0. 103% of total leaf soluble proteins in the transgenic plant. Therefore, several elite transgenic rice lines, free of the selectable marker gene, were chosen. The results from both in vitro and in vivo insect bioassays indicated that the SMF transgenic rice was shown to be highly resistant to the striped stem borer and rice leaf folder. Moreover, in a natural field condition without any insecticide applied, all the transgenic rice plants were found to be not injured by the rice leaf folder, whereas the wild types were impaired seriously.
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Although WiFi-based contactless sensing has made significant progress in the past decade, most prior work still focus on the reflection zone far from WiFi transceivers, while few studies explore the ...diffraction zone near transceivers. Additionally, previous diffraction models only consider the CSI amplitude signal and ignore the impact of multipath. In this work, we develop an accurate diffraction model to characterize the relationship between both CSI amplitude and phase and target's movement in the diffraction zone. We further put forward the deformation forms of the model under static multipath conditions and find that the CSI patterns vary significantly with multipath. Consequently, the common assumption of a one-to-one mapping between CSI patterns and activities in existing work fails due to multipaths, degrading sensing performance when multipath changes. To address this challenge, we propose to extract a relative change pattern from CSI signals to recover the one-to-one mapping relations and eliminate the impact of static multipath. Extensive experiments under various multipath conditions demonstrate an accuracy higher than 96% for the coarse-grained intrusion detection and an average error rate of 0.6 bpm for the fine-grained respiration monitoring.
Direct and efficient photocatalytic water splitting is critical for sustainable conversion and storage of renewable solar energy. Here, we propose a conceptual design of two-dimensional C3N4-based ...in-plane heterostructure to achieve fast spatial transfer of photoexcited electrons for realizing highly efficient and spontaneous overall water splitting. This unique plane heterostructural carbon ring (Cring)–C3N4 nanosheet can synchronously expedite electron–hole pair separation and promote photoelectron transport through the local in-plane π-conjugated electric field, synergistically elongating the photocarrier diffusion length and lifetime by 10 times relative to those achieved with pristine g-C3N4. As a result, the in-plane (Cring)–C3N4 heterostructure could efficiently split pure water under light irradiation with prominent H2 production rate up to 371 μmol g–1 h–1 and a notable quantum yield of 5% at 420 nm.
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