非接触式医疗监测雷达研究进展

介绍了非接触式医疗监测雷达相比于传统的呼吸和心电监护仪的优势,从3种不同雷达体制的角度总结回顾了近10 a来医用生命监测雷达系统的研究现状,概括比较了呼吸和心跳信号的提取、分离、杂波抑制等算法,并指出了各种算法的优缺点,最后对非接触式生命监测雷达的发展趋势进行了探讨和展望.     

New insights into ice multiplication using remote-sensing observations of slightly supercooled mixed-phase clouds in the Arctic

Secondary ice production (SIP) can significantly enhance ice particle number concentrations in mixed-phase clouds, resulting in a substantial impact on ice mass flux and evolution of cold cloud systems. SIP is especially important at temperatures warmer than −10 ○C, for which primary ice nucleation lacks a significant number of efficient ice nucleating particles. However, determining the climatological significance of SIP has proved difficult using existing observational methods. Here we quantify the long-term occurrence of secondary ice events and their multiplication factors in slightly supercooled clouds using a multisensor, remote-sensing technique applied to 6 y of ground-based radar measurements in the Arctic. Further, we assess the potential contribution of the underlying mechanisms of rime splintering and freezing fragmentation. Our results show that the occurrence frequency of secondary ice events averages to <10% over the entire period. Although infrequent, the events can have a significant impact in a local region when they do occur, with up to a 1,000-fold enhancement in ice number concentration. We show that freezing fragmentation, which appears to be enhanced by updrafts, is more efficient for SIP than the better-known rime-splintering process. Our field observations are consistent with laboratory findings while shedding light on the phenomenon and its contributing factors in a natural environment. This study provides critical insights needed to advance parameterization of SIP in numerical simulations and to design future laboratory experiments.

Mixed-phase clouds, where supercooled cloud droplets and ice particles coexist, are frequently observed in the Arctic (1). These clouds play a critical role in the hydrological cycle and radiative energy balance, and they have unignorable impacts on sea ice loss and warming in the Arctic (2, 3). Recent theoretical and modeling investigations suggest that the number concentration of ice particles in mixed-phase clouds has a significant influence on the evolution of the cloud microphysical properties (4). Improper representation of ice formation compromises simulation of Arctic mixed-phase clouds in climate and regional models, which can cause considerable errors in the simulated radiative budget (5). Extensive modeling and laboratory studies have been conducted in recent years to investigate ice formation by ice nucleation, especially for heterogeneous ice nucleation for which nucleation is catalyzed by ice-nucleating particles (6–9). The fundamental underlying mechanisms of heterogeneous ice nucleation are still not fully understood, and the parameterizations that are widely used in atmospheric models are generated by fitting the results from laboratory experiments for various types of ice-nucleating particles. However, observed ice number concentrations can be several orders of magnitude greater than in simulations, especially in supercooled clouds with the temperature warmer than −10 ○C (hereafter, “slightly supercooled clouds”). In this temperature range, some biological aerosols originating from soil, plants, and the ocean are found to be efficient ice-nucleating particles that can trigger ice nucleation above −10 ○C (10–13). However, these efficient ice-nucleating particles are rare, suggesting that secondary ice production (SIP) is important (14).The best-known mechanism of SIP in slightly supercooled clouds is the rime-splintering process, also known as the Hallett–Mossop (HM) process. The HM process occurs preferentially for a temperature range of −3 ○C ∼ −8 ○C in which small ice splinters are generated during riming. The HM process has been demonstrated in the laboratory using a riming rod rotating in a small chamber filled with supercooled liquid droplets (15). SIP can also be caused by other mechanisms, such as collision fragmentation (16), freezing fragmentation (17, 18), and sublimation fragmentation (19). Details regarding the current understanding of those mechanisms can be found in recent review articles by Field et al. (20) and Korolev and Leisner (21). Among those mechanisms, the HM process is argued to be the most important mechanism for SIP in slightly supercooled clouds (20, 22). However, recent in situ measurements show that substantial numbers of needles and columns (signs of splintering) are observed in mixed-phase clouds without the presence of rimers (i.e., fast falling ice particles). Instead, the presence of large cloud droplets suggests that those observed SIP events are likely due to freezing fragmentation rather than the HM process (23). Pitter and Pruppacher (24) also found in a laboratory wind tunnel study that a noticeable fraction of freezing drizzle drops developed pronounced knobs or spikes, with the spikes breaking off in many cases. The theory of freezing fragmentation is further supported by recent laboratory experiments in which SIP was observed during freezing of a levitated droplet (17, 18). However, conditions for the occurrence of SIP are still poorly known and which SIP mechanism is dominant in mixed-phase clouds is far from clear.Although laboratory experiments can demonstrate the existence of SIP under certain controlled conditions, the idealized mechanisms used for the studies (e.g., rotating rod or a levitated droplet in a calm environment) are not directly translatable to characterizing SIP processes in atmospheric clouds. Therefore, parameterizations of SIP in models using laboratory data are of debatable accuracy (25) because we still do not understand SIP mechanisms at a fundamental level. Aircraft in situ measurements of ice particles and ice-nucleating particles can help to identify the occurrence of SIP in atmospheric clouds; however, statistical studies using such measurements are severely restricted by the small sampling volumes and limited coverage of aircraft flights (23, 26).Remote-sensing techniques provide an alternative way to observe atmospheric clouds, offering larger sampling volumes and longer periods compared with in situ measurements. These features are beneficial for observing processes that are transient and/or infrequent, as may be true for SIP. The occurrence of a SIP event in mixed-phase clouds is indicated by the presence of a large concentration of small ice particles, especially at warmer temperatures where these concentrations are unlikely to be due solely to primary ice nucleation. A common foundation of existing radar-based remote-sensing techniques for identification of SIP events includes the detection of small, nonspherical ice particles using polarimetric variables, such as differential reflectivity (ZDR) (the ratio of the power returned from horizontally versus vertically transmitted and received pulses) and linear depolarization ratio (LDR) (the ratio of cross-polarized versus copolarized power returned with respect to the polarization of transmitted pulses) (27, 28). Close to the time of SIP initiation, radar methods and in situ measurements are challenged alike, as distinguishing small spherical ice particles from cloud droplets is extremely difficult (4). As newly formed small ice particles prefer growing into needle-like ice crystals within the HM temperature zone (between −3 ○C and −8 ○C), they can then alter the value of ZDR and LDR compared with spherical hydrometers, which makes detection of SIP events possible using remote-sensing techniques. Most previous remote-sensing studies of SIP focus on specific cases, for which the thermodynamic properties of the subject mixed-phase clouds are carefully chosen such that the detection of nonspherical ice particles is a readily apparent signal of a SIP event in a small dataset (29, 30).In this study, we obtain a statistical understanding of SIP events. A remote-sensing technique is used to identify SIP events occurring within 6 y (March 2013 to May 2019) of ground-based observations of slightly supercooled liquid clouds. As detailed later, the technique determines the presence of SIP events using joint thresholds of radar LDR and spectral reflectivity and, moreover, quantifies the enhancement of needle-like particle concentrations (i.e., multiplication) based on the spectral reflectivity with respect to a base threshold. We link the occurrence of SIP to the presence of rimers and drizzle, and we estimate the enhancement in ice number concentration with respect to rimer velocity and drizzle size. We show that SIP events can significantly impact ice number concentrations locally when they occur, and we are able to assess the relative importance of two SIP mechanisms, finding that freezing fragmentation is more productive at SIP than the rime splintering normally regarded as the leading process for SIP.     

From the Cover: Volcanic history of the Imbrium basin: A close-up view from the lunar rover Yutu

We report the surface exploration by the lunar rover Yutu that landed on the young lava flow in the northeastern part of the Mare Imbrium, which is the largest basin on the nearside of the Moon and is filled with several basalt units estimated to date from 3.5 to 2.0 Ga. The onboard lunar penetrating radar conducted a 114-m-long profile, which measured a thickness of ∼5 m of the lunar regolith layer and detected three underlying basalt units at depths of 195, 215, and 345 m. The radar measurements suggest underestimation of the global lunar regolith thickness by other methods and reveal a vast volume of the last volcano eruption. The in situ spectral reflectance and elemental analysis of the lunar soil at the landing site suggest that the young basalt could be derived from an ilmenite-rich mantle reservoir and then assimilated by 10–20% of the last residual melt of the lunar magma ocean.The surface of the Moon is covered by regolith, a mixed layer of fine-grained lunar soil and ejecta deposits, which is crucial to understanding the global composition of the Moon. The lunar regolith has also recorded the complex history of the surface processes, and it is the main reservoir of ³He and other solar wind gases. The thickness of the lunar regolith was estimated to be from 2 to 8 m in the maria and up to 8–16 m in the highland areas using various methods (1), including crater morphology (2, 3), seismology with low spatial resolution (4), radar wave scattering (5), and microwave brightness temperature (6). However, no in situ measurement of spectral reflectance, elemental compositions, lunar regolith thickness, or subsurface structures has been carried out.The surface of the Moon is dominated with numerous large basins. They were formed about 3.9 Ga (7, 8), probably by the late heavy bombardment, and then filled with dark lava flows derived from partial melting of the lunar mantle, within a period mainly during 3.8–3.1 Ga (7). The Imbrium basin is the largest and was formed on Procellarum KREEP [potassium (K), rare earth elements (REE), and phosphorus (P)] Terrane (9), a unique terrain highly enriched in U, Th, and K radionuclides and other incompatible trace elements referred to as KREEP (10) and considered as the last residual melt of the Lunar Magma Ocean (11). The presence of the KREEPy materials, indicated by high concentrations of radionuclides U, Th, and K (9), around the rims of the Imbrium basin suggests that they are likely the basin-forming ejecta deposits. At least three main lava flows, dated from 3.5 Ga to 2.0–2.3 Ga (7, 12), have been recognized in Mare Imbrium with distinct FeO and TiO₂ concentrations (13, 14), which brought up interior information of this KREEP-rich terrain. The old and low-Ti basalt unit has been sampled by the Apollo 15 mission that landed at the eastern rim of the Imbrium basin. Information of other lava flows in Mare Imbrium was obtained only by remote sensing from orbit. On December 14, 2013, Chang’e-3 successfully landed on the young and high-Ti lava flow in the northeastern Mare Imbrium, about 10 km south from the old low-Ti basalt unit (Fig. 1).Open in a separate windowFig. 1.The landing site of Chang’e-3 (red cross), on the high-Ti basalt (dark gray) near the boundary in contact with the low-Ti basalt (light gray). The background image was taken by Chang’e-1.The lunar rover Yutu (named for the jade rabbit on the Moon in a Chinese fairy tale) was equipped with an active particle-induced X-ray spectrometer (APXS), a visible to near-infrared (450–945 nm) imaging spectrometer and short-wave infrared (900–2,395 nm) spectrometer (VNIS), and a lunar penetrating radar (LPR), accompanied by a stereo camera and a navigating camera. Originally, the mission planned to have the lunar rover measure chemical and mineral compositions of the lunar soil and various types of ejecta rocks and to carry out a LPR profile of the lunar regolith and subsurface structures in the first 3 mo. The mission was scheduled to extend up to 1 y and to explore the old low-Ti lava flow ∼10 km north. Unfortunately, some of Yutu’s mechanical parts failed to move just before the rover prepared for sleeping at the end of the second month due to unknown faults probably in the control system. During the first 2 mo, Yutu successfully carried out two APXS and four VNIS analyses of the lunar soil and performed a 114-m-long LPR profile along the rover track in the landing area (Fig. 2). These in situ measurements provide insights into the volcanic history of Mare Imbrium and the ground-truth data for calibration of the orbital data.Open in a separate windowFig. 2.Chang’e-3 landing site and the rover Yutu’s track. Crater A is blocky, indicating penetration through the regolith. Crater B is the largest one without blocks in the landing area. The APXS (LS1–LS2) and VNIS (CD5–CD8) analysis positions and the rover navigation points are marked. The image was composed from the series images taken by the Chang’e-3 landing camera.     

A novel method to estimate changes in stress-induced salivary α-amylase using heart rate variability and respiratory rate,as measured in a non-contact manner using a single radar attached to the back of a chair

The authors have developed a non-contact system which estimates changes in salivary α-amylase (sAA ratio) induced by stress. Before and after stressful sound exposure, a single 24?GHz compact radar which is attached to the back of a chair measures the low frequency (LF) component of heart rate variability and respiratory rate, α-amylase in the subjects’ buccal secretions was measured by using an α-amylase assay kit. Using multiple regression analysis, sAA ratio was estimated using stress-induced LF change (LF ratio) and stress-induced respiratory rate change (respiratory rate ratio). Twelve healthy subjects were tested (12 males, 22?±?2 years), who were exposed to audio stimuli with a composite tone of 2120?Hz and 2130?Hz sine waves at a sound pressure level of 95?dB after a silent period through a headphone. The result showed that sAA ratio estimated using multiple regression analysis significantly correlated with measured sAA ratio (R?=?0.76, p?相似文献   

Non-contact heart rate monitoring method for elderly people In bed with random body motions using 24 GHz dual radars located beneath the mattress In clinical settings

We have developed a non-contact heart rate monitoring system for elderly people In bed using two radars placed on the bed base. The system is designed to increase accuracy despite body motion noise and change of body position and sleeping posture In bed. In order to achieve this, we combined an automatic gaIn control (AGC) method with a real-time radar-output channel selection method which is based on a spectrum shape analysis (SSA). Field tests were carried out with elderly subjects at a nursing home. The accuracy was maintained because the system successfully avoided the null detection point (NDP) problem, respiratory harmonic interference and intermodulation problems. The heart rate accuracy (r = 0.703) was higher than that of the conventional method. The system was proved to be effective In monitoring vital signs without the need for any physical contact with the subjects.     

Non-Destructive Corrosion Inspection of Reinforced Concrete Using Ground-Penetrating Radar: A Review

Reduced maintenance costs of concrete structures can be ensured by efficient and comprehensive condition assessment. Ground-penetrating radar (GPR) has been widely used in the condition assessment of reinforced concrete structures and it provides completely non-destructive results in real-time. It is mainly used for locating reinforcement and determining concrete cover thickness. More recently, research has focused on the possibility of using GPR for reinforcement corrosion assessment. In this paper, an overview of the application of GPR in corrosion assessment of concrete is presented. A literature search and study selection methodology were used to identify the relevant studies. First, the laboratory studies are shown. After that, the studies for the application on real structures are presented. The results have shown that the laboratory studies have not fully illuminated the influence of the corrosion process on the GPR signal. Also, no clear relationship was reported between the results of the laboratory studies and the on-site inspection. Although the GPR has a long history in the condition assessment of structures, it needs more laboratory investigations to clarify the influence of the corrosion process on the GPR signal.     

Performance of two updated blood glucose monitoring systems: an evaluation following ISO 15197:2013

Objective For patients with diabetes, regular self-monitoring of blood glucose (SMBG) is essential to ensure adequate glycemic control. Therefore, accurate and reliable blood glucose measurements with SMBG systems are necessary. The international standard ISO 15197 describes requirements for SMBG systems, such as limits within which 95% of glucose results have to fall to reach acceptable system accuracy. The 2013 version of this standard sets higher demands, especially regarding system accuracy, than the currently still valid edition. ISO 15197 can be applied by manufacturers to receive a CE mark for their system.

Research design and methods This study was an accuracy evaluation following ISO 15197:2013 section 6.3 of two recently updated SMBG systems (Contour**Contour is a registered trademark of Bayer Health Care LLC, Pittsburgh, PA, USA and Contour TS; Bayer Consumer Care AG, Basel, Switzerland) with an improved algorithm to investigate whether the systems fulfill the requirements of the new standard. For this purpose, capillary blood samples of approximately 100 participants were measured with three test strip lots of both systems and deviations from glucose values obtained with a hexokinase-based comparison method (Cobas Integra??Cobas Integra is a trademark of Roche Diagnostics Operations Inc., Indianapolis, IN, USA 400 plus; Roche Instrument Center, Rotkreuz, Switzerland) were determined. Percentages of values within the acceptance criteria of ISO 15197:2013 were calculated. This study was registered at clinicaltrials.gov (NCT02358408).

Main outcome Both updated systems fulfilled the system accuracy requirements of ISO 15197:2013 as 98.5% to 100% of the results were within the stipulated limits. Furthermore, all results were within the clinically non-critical zones A and B of the consensus error grid for type 1 diabetes.

Conclusions The technical improvement of the systems ensured compliance with ISO 15197 in the hands of healthcare professionals even in its more stringent 2013 version. Alternative presentation of system accuracy results in radar plots provides additional information with certain advantages. In addition, the surveillance error grid offers a modern tool to assess a system’s clinical performance.     

A novel autonomic activation measurement method for stress monitoring: non-contact measurement of heart rate variability using a compact microwave radar

We developed a novel method for non-contact monitoring of stress-induced autonomic activation through the back of a chair, using a compact 24 GHz microwave radar (8 x 5 x 3 cm), without large-scale equipment and placing a heavy burden on the monitored individual. Following a silent period of 120 s, audio stimuli using a composite tone of 2,120 and 2,130 Hz sine-waves at 95 dB were conducted for 120 s. From dorsal, LF/HF of HRV reflecting sympatho-vagal balance was determined by microwave radar with the maximum entropy method using eight volunteers (mean age 23 +/- 1 years). Mean LF/HF measured by non-contact and contact (using electrocardiography for reference) methods during audio stimuli increased 34 and 37%, respectively, as compared with those of the silent period. Maximum cross-correlations between contact and non-contact measurements averaged 0.73 +/- 0.10. Our method appears to be promising for future monitoring of stress-induced autonomic activation of operators and may reduce stress-induced accidents.     

中成药国家基本药物保障供应综合评估模型的探索与研究

中药价格暴涨暴跌,短期上涨对投料质量的影响不容忽视,另一方面,中药的生产严格受到资源的限制,许多中成药工业生产都因资源不足或禁用而被迫停止。该研究围绕《国家基本药物目录(2012年版)》中的203种中成药,通过分析影响中药基本药物供应的因素,设计了7个中药基本药物供应保障预警指标,基于中药资源普查和动态监测服务体系数据,提出了一种基于雷达图分析法的多指标综合评估模型,为中药基本药物的供应保障情况做出全局性、整体性的评价,评估结果简明、清晰、直观。以九味羌活丸和感冒清热颗粒为实例,验证了所提出的综合评估方法简明、清晰、直观、可信,具有实际意义。     

基于自由搜索算法的干扰任务分配模型研究

如何分配干扰任务是电子对抗中的一个重点问题。本文提出了一个基于自由搜索（freesearch,FS）算法的任务分配模型。首先介绍了FS算法的基本原理,其次构造了基于FS算法的目标分配算法模型,最后进行了算法实验,对该模型进行了验证。实验结果表明,基于FS算法的目标分配模型是有效的,具有较快的收敛速度和较高的精度。