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1.
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.  相似文献   
2.
Reducing airborne bioburden in total joint arthroplasty (TJA) is of critical importance. The efficacy of crystalline ultraviolet-C (C-UVC) filtration in reducing bioburden in a dynamic operating room (OR) environment has not been evaluated. We assessed whether C-UVC filtration reduced (i) total particle counts (TPC); (ii) viable particle counts (VPC); and (iii) colony-forming units (CFUs). Fifty primary TJA cases were performed in a positive-pressure OR; 25 cases with the C-UVC unit and 25 cases without. The air was sampled by a particle counter and an impact air sampler to measure particle counts and CFUs, respectively. To compare TPC, VPC, and CFU/m3 between groups, independent t tests and multivariate regression, adjusted for number of OR staff and door openings, were performed. The C-UVC group had significantly lower TPC (2.6 × 106 vs. 4.7 × 106 particles, p = 0.001) and VPC (18,605 vs. 27,516 particles, p = 0.001). There were fewer CFUs in the C-UVC group (10.9 CFU/m3 vs. 13.7 CFU/m3, p = 0.163). Multivariate analysis identified C-UVC filtration as a significant predictor of decreased TPC (β = −0.44, p = 0.002) and VPC (β = −0.47, p = 0.001) after accounting for door openings and number of OR staff. The reduction in CFUs was not significant on multivariate analysis. In this prospective pilot study, a C-UVC air disinfection and recirculation unit led to a significant reduction in both TPC and VPC and a non-significant reduction in CFU. Statement of clinical significance: Further studies are needed to investigate the effects of C-UVC filtration units on surgical-site infection rates. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:431-437, 2020  相似文献   
3.
Abstract

Small displacement detection capability becomes an important key for developing non-contact sensor for human respiration based on radar system. Frequency modulated continuous wave (FMCW) radar has been widely studied and applied for many applications. With respect to the conventional perspective, large bandwidth is needed for detecting the small displacement related to the human respiration. Meanwhile, extracting the respiration pattern from Doppler response has a drawback in identifying the small displacement location. In this paper, the modification on FMCW system was proposed for obtaining the capability in detecting the human respiration and its distance from the radar. Detecting the phase value of the low pass filter (LPF), output from conventional FMCW was investigated and applied as a modification concept. The pattern, rate and amplitude of respiration are extracted from phase detector output. Beat frequency detection is still elaborated for synthesising the reference signal for phase detection. The result shows that the modified FMCW system proposed the capability of detecting the rate and amplitude respiration and location of the target.  相似文献   
4.
Airborne wind energy (AWE) refers to a novel technology capable of harvesting energy from wind by flying crosswind patterns with tethered autonomous aircraft. Successful design of flight controllers for AWE systems relies on the availability of accurate mathematical models. Due to an expected nonconventional structure of the airborne component, the system identification procedure must be ultimately addressed via an intensive flight test campaign to gain additional insight about the aerodynamic properties. In this paper, the longitudinal dynamics of a rigid‐wing, high lift, autonomous aircraft for AWE are identified from experimental data obtained within flight tests. The aerodynamic characteristics are estimated via an efficient time‐domain multiple experiments model‐based parameter estimation algorithm.  相似文献   
5.
目的探索四川省成都市城区气传花粉的种类、数量及飘散规律。方法应用重力沉降法于2018年3月1日至2019年2月28日在四川省成都市城区进行为期1年的连续每日气传花粉曝片。结果共收集到花粉139520粒/1000 mm 2,能鉴定的花粉总计隶属36科、31属、2个种。其中构属花粉含量最高,达81754粒/1000 mm 2,占全年花粉总量的58.60%,其播粉期为3~4月,高峰期为3月下半月至4月上半月;其次是柏科花粉,达27518粒/1000 mm 2,占全年花粉总量的19.72%,其播粉期为1~3月,高峰期为1月下旬至3月上旬;大麻/葎草属占第三位,花粉含量5112粒/1000 mm 2,占全年花粉总量的3.66%,其播粉期为8~10月,高峰期为8月下旬至10月下旬。上述3种花粉为本地区优势气传花粉,合计占全年花粉总量的81.98%。含量超过1%的花粉还依次包括银杏、桦木属、松属、悬铃木属、枫杨属及蒿属花粉。全年花粉含量月分布呈现2个高峰,第一高峰为1~5月,主要气传花粉为构属、柏科、银杏、桦木属、松属、悬铃木属、枫杨属等树木花粉,占全年花粉总量的89.38%。第二高峰为8~10月,主要气传花粉为大麻/葎草属、蒿属等莠草花粉,占全年花粉总量的5.04%。结论本地区花粉季节有两个:春季为主要花粉季节,主要气传花粉为构属、柏科等树木花粉;夏秋季为次要花粉季节,主要花粉气传为大麻/葎草属、蒿属等莠草花粉。构属、柏科、大麻/葎草属花粉为本地区优势气传花粉,构属花粉为本地区绝对优势气传花粉。  相似文献   
6.
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 −10C, 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 (69). 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 −10C (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 −10C (1013). 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 −3C 8C 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 −3C and −8C), 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.  相似文献   
7.
8.
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.  相似文献   
9.
目的:收集呼和浩特气传花粉数据,分析其分布特征及气候影响因素,建立花粉浓度日播报平台,指导患者有效防护,为临床提供辅助诊疗引导。方法:花粉采集仪收集花粉,显微镜下进行阅片计数,记录同期气象因素,通过以微信公众平台为主的多种播报途径进行花粉日播报。结果:共收集花粉26825粒,鉴别种属18类,花粉播散存在春季和夏秋季两个高峰段,其分布规律与每日温差正相关,平台用户流量与花粉浓度趋势走形呈一致性变化,夏秋季用户流量峰值较春季高。结论:呼和浩特气传花粉存在两个高峰段,花粉浓度同每日温差存在正相关,花粉浓度日播报可为临床提供辅助诊疗引导。  相似文献   
10.
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.  相似文献   
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