1,721,019 research outputs found
磺化功能改性聚乙烯研究进展
No full textAs one of the most important functionalization methods, sulfonation was effective in improving chemical polarity, stiffness and thermal stability of polyethylene (PE). In this paper, research advances are reviewed on the structural evolution and performance modification of sulfonated PE as well as the sulfonation mechanisms, based on which the prospective research and application of sulfonated PE are discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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High-Speed Sub-THz/THz Interconnects with Advanced Spatial Multiplexing
Full text linkEver-increasing data generation and transmission demands have been driving great advancements in wireline communications from both electrical and optical approaches for short- and long-distance scenarios, respectively. In the meter range scenario, both electrical and optical approaches face great challenges. That is, the lossy and bandwidth limited channels are the bottlenecks of electrical interconnect. For optical interconnect, the features, such as the required complex fabrication and the high environment sensitivity, increase the power and cost budgets significantly, making it uneconomical for short-distance communications. To mitigate these issues, low-loss dielectric channel-based interconnects have been investigated and demonstrated. However, all the design reported are all for point-to-point configurations, not suitable for multi-drop distributed architectures.Besides CMOS transmitters and receivers, advanced spatial multiplexing schemes are fully investigated and architectures of wireline communication system at sub-THz/THz are selected according to the application scenarios. This dissertation also investigates the most used passive and active, on-chip and off-chip components, circuit modeling, layout optimization, and design strategies, such as neutralization and power maximization methods.Two sub-THz interconnect systems, FDM based dual-band sub-THz interconnect and MDM multi-drop sub-THz interconnect, are proposed and demonstrated.A low-loss and wideband Si DWG coupled with a pair of diplexers is employed to support two highly isolated and low loss sub-channels simultaneously. The proposed sub-THz interconnect achieves the energy efficiency of 1.58 pJ/b with the aggregate data rate of 22.6 Gb/s and BER better than 1e-12. It demonstrates the record bandwidth density of 150.7 Gb/s/mm2. Channelization provides a venue to boost the interconnect key metric of bandwidth density by taking full advantages of the abundant THz spectrum resource.The theory of DWG mode coupler is derived and explained, and it can guide the multi-mode multi-drop waveguide design and provide optimization strategies effectively. Then a multi-drop sub-THz interconnect system is demonstrated, enabling three simultaneous logical channels for E11^y, E21^y and E31^y mode and supporting data rates of 24 Gb/s, 22 Gb/s and 19 Gb/s, respectively, with the BER better than 1e-12. The demonstrated aggregate data rate of the three channels is 65 Gb/s with the energy efficiency of 1.6 pJ/b. To the authors’ knowledge, This is the first time to demonstrate multi-mode multi-drop DWG based interconnect. One note to make is that although the demonstration channel length is 5.2 cm, this is due to the size constraint of the wafer used to fabricate the channel. This interconnect system can be readily extended to the meter range due to the channel ultra-low loss feature. Furthermore, it can also scale to more modes to support more logic channels per physical link and can be extended to multi-dimension, two-/three- dimension, interconnect systems. Besides, with more advanced semiconductor technologies for active circuits, the data rate per channel will be further increased. Therefore, we believe that demonstrated multi-mode multi-drop sub-THz interconnect systems open a new path with high potentials to complement the existing electrical and optical interconnect to address the challenging meter range wireline communication scenarios
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Coupling Effect in Doppler Radar System Used for Remote Sensing
Full text linkRemote vital sign detection has gained popular interests from researchers to conduct through-clothing and non-contact measurements of the chest wall motion induced by the heart beat and the respiration of the human subjects. Although many architectures have achieved the vital sign detection with decent sensitivity, the Doppler radar system is widely adopted by researchers due to its simple architecture, perfect phase coherence and its cost effectiveness. On the other hand, improvements on the Doppler radar system are imperatively needed on the topics of radar system sensitivity for increased detection robustness, spatial resolution for multi-subject detection and linear displacement demodulation. This dissertation is devoted to improve the Doppler radar system through comprehensive study on the coupling effect during the Doppler radar system.In this dissertation, we first discussed the development on the system integration of a dual-PLL low-IF Doppler radar system using PLL with a shared input reference. Followed by this, a compact module design has been achieved for constructing the first 6x6 Doppler MIMO radar system. This Doppler MIMO radar has been measured with a detection angle accuracy within 1.5 degrees, which helps to accurately allocate the motion-sensitive area of the subject to increase the detection sensitivity. The 18-degree spatial resolution enables the device to distinguish between vital sign signals from two different subjects measured at the same distance of 1.9 m away.Next, we analyzed the coupling effect contributing to the residual phase noise in the dual-PLL low-IF system architecture and validated it through controlled experiments. Followed by this analysis, an integrated automatic RF cancellation module has been developed using microcontrollers along with the designed cancellation algorithm. This module has been tested under both in-air and through-wall vital sign detection scenarios, resulting in an effective SNR increase of more than 15 dB with a less-than 2 seconds of implementation time.Lastly, the coupling effect has been studied on the modulation scheme associated with the remote target motion. Instead of the phase modulation due to the Doppler effect, the coupling effect also results in amplitude modulation at the received waveform. Our work investigated such effect through both theoretical derivations and interpretations in an IQ plot. Based on this finding, a new system architecture has been proposed for remote displacement sensing. The developed new architecture demonstrated a superior performance without using the mixer component, which greatly improves the power utilization efficiency for remote displacement sensing
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High Resolution Permittivity Sensing in THz CMOS Technology
Full text linkPermittivity sensing has wide applications in a variety of industries such as petroleum, agriculture,food production, etc.. The complex permittivity serves as an effective indicator of the
valuable information of the sample material such as their constitute, moisture or quality, which
are critical in the process of product development, production, and treatment. The nondestructive
nature of the permittivity sensing makes it highly cost-effective and enables it for real time material
characterization. This calls for the adoption of CMOS technologies to achieve a high level
of integration of signal processing capabilities for cost-effective and ubiquitous applications without
sacrificing precision and accuracy. Therefore, numerous works featuring CMOS permittivity
sensor have been developed. Among all aspects of CMOS permittivity sensing systems, high resolution
sensing is of particular importance, which enables CMOS sensing in applications such as
high precision biosensing, precision medicine, etc. High resolution sensing enables high throughput
measurement, capturing fast process in real time, etc. To achieve high resolution, the prior art
focuses on two key aspects: permittivity sensor’s sensitivity boost and system noise reduction.
In the optical community, ultra-high sensitivity is achieved by utilizing resonator based sensors,
whose resonant frequency is shifted by the permittivity of different MUT’s. Sharp curvature and
steep slope of the transmission coefficient of the high Q resonator sensors result in high sensitivity.
Whispering gallery mode (WGM) resonators show particularly high sensitivity due to its high Q
and the strong field interaction with the MUT’s. However, the expensive and bulky tunable optical
sources and the limited signal processing and readout capabilities severely constrain the applications
of the high sensitivity optical sensors.
To advance the state of the arts of the high resolution permittivity sensors, this dissertation dedicates
to the theory, design and implementation of sub-THz WGM resonator based CMOS permittivity
sensor. Thanks to its short wavelength, the WGM resonator sensor at sub-THz possesses
a compact form-factor, achieving a high level of integration with the CMOS transceivers (TRX).
Like its optical counterparts, the compactness of the sub-THz sensor also enables high sensitivity
detection while requiring a smaller amount of MUT samples than sensors working at GHz frequency
range. The CMOS TRX generates the sub-THz signal to excite the WGM sensor and readout the
signal to obtain the permittivity information.
The dissertation analyzes the EM mechanisms of the WGM resonator sensor, including the loss
analysis and coupling condition analysis, lays theoretical foundations for the sensitivity optimization
for high resolution sensing. A novel mechanism to detect complex permittivity using the
WGM resonator sensor is proposed for the first time in the permittivity sensing and resonator
sensor community. A low power permittivity sensing system at 160 GHz is prototyped to verify
the permittivity sensing capability of the WGM resonator sensor integrated with the CMOS TRX
IC, which demonstrates a permittivity sensing resolution of 0.098 for a integration time of 10 us
with a power consumption of only 9 mW. A high resolution complex permittivity sensing system
at 160 GHz is implemented that adopts a band-stop WGM disk resonator based sensor structure
and multi-fold noise suppression techniques, which demonstrates a record of 0.05% complex sensing
resolution within 14-us integration time and consumes 54 mW of DC power.
In the process of designing the high resolution permittivity sensing system, mathematical derivations
are developed to predict the noise suppression effect of the three noise reduction techniques:
the phase noise suppression by the coherent phase noise cancellation, the flicker noise suppression
by the chopping scheme and the thermal noise suppression by the integrator. Since these three noise
reduction techniques are commonly used in sensing / imaging systems, the developed derivation in
this dissertation can be readily applied to predict the noise suppression effect numerically and to
guide the design of the noise reduction circuitry
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