The insertion loss （IL） of a T-type attenuator is theoretically analyzed. A T-type RF （ radio frequency） CMOS （ complementary metal-oxide-semiconductor ） attenuator is designed as an on-off keying（OOK） modulat...The insertion loss （IL） of a T-type attenuator is theoretically analyzed. A T-type RF （ radio frequency） CMOS （ complementary metal-oxide-semiconductor ） attenuator is designed as an on-off keying（OOK） modulator in a time-hopping ultra wide-band （TH-UWB）communication with a carrier frequency of 4 GHz. In the topology of the OOK modulator circuit, there are three parts, an oscillator with an oscillating frequency of 4 GHz, a T-type attenuator constructed by RF CMOS transistors, and an output impedance matching network with a L-type LC structure. The modulator is controlled by a time-hopping pulse position modulation（TH-PPM） signal. The envelope of the modulated signal varies with the amplitude of the controlling signal. Meanwhile, an output matching network is also designed to match a 50 Ω load. In 0. 18 μm RF CMOS technology, a modulator is designed and simulated. The implemented modulator chip has 65 mV of the output amplitude at a 50 fl load from a 1.8 V supply, and the return loss （ S11 ） at the output port is less than - 10 dB. The chip size is 0. 7 mm × 0. 8 mm, and the power consumption is 12. 3 mW.展开更多
Visible light variable optical attenuators（VOA） are essential devices in the application of channel power regulation and equalization in wavelength-division multiplexing cross-connect nodes in plastic optical fiber...Visible light variable optical attenuators（VOA） are essential devices in the application of channel power regulation and equalization in wavelength-division multiplexing cross-connect nodes in plastic optical fiber（POF） transmission systems.In this paper, a polymer/silica hybrid waveguide thermo–optic attenuator based on multimode interference（MMI） coupler is designed and fabricated to operate at 650 nm. The single-mode transmission condition, MMI coupler, and transition taper dimensions are optimized through the beam propagation method. Thermal analysis based on material properties provides the optimized heater placement angle. The fabricated VOA presents an attenuation of 26.5 dB with a 21-mW electrical input power at 650 nm. The rise time and fall time are 51.99 and 192 μs, respectively. The time–stability measurement results prove its working reliability.展开更多
Hydraulic pumps are a positive displacement pump whose working principle causes inherent output flow pulsation.Flow pulsation produces pressure pulsation when encountering liquid resistance.Pressure pulsation spreads ...Hydraulic pumps are a positive displacement pump whose working principle causes inherent output flow pulsation.Flow pulsation produces pressure pulsation when encountering liquid resistance.Pressure pulsation spreads in the pipeline and causes vibration,noise,damage,and even pipeline rupture and major safety accidents.With the development of airborne hydraulic systems with high pressure,power,and flow rate,the hazards of vibration and noise caused by pressure pulsation are also amplified,severely restricting the application and development of hydraulic systems.In this review paper,the mechanism,harm,and suppression method of pressure pulsation in hydraulic systems are analyzed.Then,the classification and characteristics of pulsation attenuators according to different working principles are described.Furthermore,the critical technology of simulation design,matching method with airborne piston pumps,and preliminary design method of pulsation attenuators are proposed.Finally,the development trend of pulsation attenuators is prospected.This paper provides a reference for the research and application of pressure pulsation attenuators.展开更多
The power consumption of a variable optical attenuator（VOA） array based on a silica planar lightwave circuit was investigated. The thermal field profile of the device was optimized using the finite-element analysis....The power consumption of a variable optical attenuator（VOA） array based on a silica planar lightwave circuit was investigated. The thermal field profile of the device was optimized using the finite-element analysis. The simulation results showed that the power consumption reduces as the depth of the heat-insulating grooves is deeper, the up-cladding is thinner,the down-cladding is thicker, and the width of the cladding ridge is narrower. The materials component and thickness of the electrodes were also optimized to guarantee the driving voltage under 5 V. The power consumption was successfully reduced to as low as 155 mW at an attenuation of 30 dB in the experiment.展开更多
A proposed inductive-phase-compensation ultra wideband CMOS digital T-type attenuator design based on an analysis of minimising phase errors is presented in this letter.In a standard CMOS technology,the proposed atten...A proposed inductive-phase-compensation ultra wideband CMOS digital T-type attenuator design based on an analysis of minimising phase errors is presented in this letter.In a standard CMOS technology,the proposed attenuator is analytically demonstrated to have low phase errors due to the inductive-phase-compensation network.A design equation is inferred and a wide-band 4dB attenuation bit digital attenuator with low phase errors is designed as a test vehicle for the proposed approach.展开更多
According to the plasma dispersion effect of silicon(Si),a silicon-on-insulator(SOI) based variable optical attenuator(VOA) with p-i-n lateral diode structure is demonstrated in this paper.A wire rib waveguide with su...According to the plasma dispersion effect of silicon(Si),a silicon-on-insulator(SOI) based variable optical attenuator(VOA) with p-i-n lateral diode structure is demonstrated in this paper.A wire rib waveguide with sub-micrometer cross section is adopted.The device is only about 2 mm long.The power consumption of the VOA is 76.3 mW(0.67 V,113.9 mA),and due to the carrier absorption,the polarization dependent loss(PDL) is 0.1dB at 20dB attenuation.The raise time of the VOA is 34.5 ns,the fall time is 37 ns,and the response time is 71.5 ns.展开更多
Numerous types of floating breakwaters have been proposed,tested and commercialized in the past decades.The majority of these breakwaters are made of solid bodies;hence,they are relatively bulky and are not readily to...Numerous types of floating breakwaters have been proposed,tested and commercialized in the past decades.The majority of these breakwaters are made of solid bodies;hence,they are relatively bulky and are not readily to be rapidly installed at the targeted sites when immediate wave protection of the coastal and offshore facilities is needed.Furthermore,the application of these hard floating structures at the recreational beaches is rather unlikely due to potential deadly marine traffic collision.To overcome these problems,a flexible air-filled wave attenuator(AFWA)has been developed in the present study.This floating breakwater is made of flexible waterproof membrane materials.The main body consists of a rectangular air-filled prism and is ballasted by sandbags located around the floating module.The objective of this study is to evaluate the wave transmission,wave reflection,energy dissipation,motion responses and mooring forces of the AFWA under the random wave actions using physical modelling.The test model located in a 20 m long wave flume was subjected to a range of wave heights and periods.The wave profiles in the vicinity of the test model were measured using wave probes for determination of wave transmission,reflection and energy loss coefficients.The motion responses in terms of heave,surge and pitch,and wave forces acting on the mooring lines were measured using a motion tracking system and load cells,respectively.The experimental results reveal that the AFWA is effective in attenuating up to 95%in the incoming wave height and has low-wave-reflection properties,which is commendable for floating breakwaters.展开更多
This paper deals with a systematical analysis and an algorithm of attenuation characteristics of a light attenuator combined by n pieces of polarizers （n-LACP） whose extinction ratios are different from each other. ...This paper deals with a systematical analysis and an algorithm of attenuation characteristics of a light attenuator combined by n pieces of polarizers （n-LACP） whose extinction ratios are different from each other. The attenuation ratio expression of a two-LACP is deduced. We find that the monotonic attenuation interval depends on the first polarizer and that the attenuation range depends on the second one. For the three-LACP, a method for obtaining a monotonic attenuation interval is proposed. Moreover, the attenuation ratio expression is demonstrated. Analysis and experiment show that when the initial status of the three-LACP is at the maximum output, if the second or third polarizer rotates alone, the minimum attenuation ratios can reach K2^-1 and K3^-1, respectively, and if the first polarizer rotates, a minimum attenuation ratio of K2^-1K3^-1 can be obtained （K1, K2 and K3 represent the extinction ratios of the three polarizers in turn）. Furthermore, the attenuation ratio expression of n-LACP and the relevant attenuation characteristics are proposed. The minimum attenuation ratio of an n-LACP is （K2K3 ... Kn）-1.展开更多
A four-stage cascaded variable optical attenuator(VOA)with a large attenuation range is presented.The VOA is based on a Mach–Zehnder interferometer(MZI)and fabricated in a silica-based planar lightwave circuit(PLC)pl...A four-stage cascaded variable optical attenuator(VOA)with a large attenuation range is presented.The VOA is based on a Mach–Zehnder interferometer(MZI)and fabricated in a silica-based planar lightwave circuit(PLC)platform.The thermo-optic effect is used to achieve intensity modulation.The measured maximum attenuation of the four-stage cascaded VOA is 88.38 d B.The chip is also tested in a quantum key distribution(QKD)system to generate signal and decoy states.The mean photon number after attenuation of the four-stage cascaded VOA is less than 0.1,which can meet the requirement of QKD.展开更多
The impact attenuator is an essential system in both race cars and urban vehicles.The structure of animpact attenuator serves as a safety barrier between the impacted surface and the driver in an accident.Attenuator m...The impact attenuator is an essential system in both race cars and urban vehicles.The structure of animpact attenuator serves as a safety barrier between the impacted surface and the driver in an accident.Attenuator materials tend to have a high price;thus,alternative materials were explored in the currentwork,i.e.,used cans from food and beverage containers.The study deployed a nonlinear finite elementalgorithm to calculate a series of impacts on the attenuator structures.The thickness of the cans andvelocity of the impact were considered as the main parameters.Analysis results concluded that the at-tenuator’s average energy was 16000 J for a can thickness of 1 mm.This value is more than two times the0.5 mm thick used cans.The attenuator’s new design was then matched with an attenuator regulation,and the results surpassed the standard value of 7350 J.展开更多
An eleetrochromic variable optical attenuator （ECVOA） was fabricated by layer-by-layer （LBL） assembly of disodium N,N-bis（p-sulfonatophenyl）naphthalenedicarboximide （Naph-SO3Na） and common cationic polymer pol...An eleetrochromic variable optical attenuator （ECVOA） was fabricated by layer-by-layer （LBL） assembly of disodium N,N-bis（p-sulfonatophenyl）naphthalenedicarboximide （Naph-SO3Na） and common cationic polymer poly（diallyldimethylammonium） chloride （PDDA）. The UV-Vis absorption spectra of the multilayer films revealed that approximately an equal amount of Naph-SO3Na was assembled in each deposition cycle. Upon one-electron reduction, multilayer films exhibited intense absorption around 452 nm and also a broad absorption band from 1200 nm to 1900 nm. Owing to the improved ionic conductivity, the optical attenuation at 1550 nm of the films showed rapid response time and reached 1.3 dB/μm within 5 s. These results indicate that layer-by-layer assembly could be an effective method for the preparation of ECVOA operating in near infrared region.展开更多
To measure the working band of a digital attenuator automatically,a program based on virtual instrument was carried out,using Agilent E8362B network analyzer as its measuring tool.In the program,the attenuation values...To measure the working band of a digital attenuator automatically,a program based on virtual instrument was carried out,using Agilent E8362B network analyzer as its measuring tool.In the program,the attenuation values can be automatically written into Excel table to form the frequency-attenuation curve.Finally,through analyzing the attenuation in different frequency,the best working band of the digital attenuator can be determined easily,and the whole process is automated.Compared with the traditional way of changing the measured parameters manually and recording the measured data one by one,the developed method in the paper can avoid the cumbersome manual operation and its possible errors to improve the measurement accuracy and efficiency.展开更多
The purpose of this paper is to determine the optimal size and number of tubes for a generic attenuator that is similar to Pelamis P2, the wave energy converter. Simulations using ANSYS Workbench, Design Modeler, and ...The purpose of this paper is to determine the optimal size and number of tubes for a generic attenuator that is similar to Pelamis P2, the wave energy converter. Simulations using ANSYS Workbench, Design Modeler, and AQWA are performed to study the energy absorption at the nodes between the tubes. The analysis is limited to linearized hydrodynamic fluid waves loading on floating bodies by employing three-dimensional radiation/diffraction theory in regular waves in the frequency domain. Three sets of tests are conducted by varying total tube number, each tube length and the order of tubes with different lengths. After a systematic study in the frequency domain, the optimal size and number of the genetic attenuator is recommended.展开更多
New techniques for controlling the amplitudes of two orthogonal linearly polarized light are presented. One is based on adjusting the DC voltage into a Mach–Zehnder modulator（MZM） to alter the amplitude of the ligh...New techniques for controlling the amplitudes of two orthogonal linearly polarized light are presented. One is based on adjusting the DC voltage into a Mach–Zehnder modulator（MZM） to alter the amplitude of the light traveling on the slow axis of a fiber into the modulator with little changes in the fast-axis light amplitude.Another is based on adjusting the input DC voltages of a dual-polarization MZM operating in the reverse direction, which enables independent control of the two input orthogonal linearly polarized light amplitudes.Experimental results demonstrate that more than 30 dB difference in slow-and fast-axis light power can be obtained by controlling an MZM input DC voltage, and over 24 dB independent power adjustment for light traveling on the slow and fast axes into a dual-polarization MZM.展开更多
In this study,polyacrylic acid(PAA)films were employed as a model system,and a series of PAA films with tunable water wettability was systematically prepared by varying molecular weight and curing temperature.Using at...In this study,polyacrylic acid(PAA)films were employed as a model system,and a series of PAA films with tunable water wettability was systematically prepared by varying molecular weight and curing temperature.Using attenuated total reflectance Fourier-transform infrared spectroscopy(ATR-FTIR),the molecular configurations of surface carboxyl groups(COOH),free carboxyl(COOH_(f))and hydrogen-bonded carboxyl(COOH_(HB),were directly correlated with the polar component of surface energy(γ^(s,p)).By decomposing theγ^(s,p)values of the PAA thin films as a sum of the contributions of COOH_(f)and COOH_(H B),the intrinsic polar component of surface energy of COOH_(H B)(γ_(H B)^(s,p*))was quantified for the first time as 8.34 mN/m,significantly lower than that of COOH_(f)(γ_(f)^(s,p*)=34 mN/m).This result highlights that hydrogen bonding markedly reduces theγ^(s,p),providing a rational explanation for the relatively large water contact angle observed on PAA thin films.Furthermore,it establishes a thermodynamic basis for estimating the fraction of surface COOH_(H B)groups(f H B)from wettability measurements.Further extension of the model to carboxyl-terminated self-assembled monolayers(COOH-SAMs)revealed that surface COOH density(ΣCOOH)critically regulates wetting behavior:whenΣCOOH ranges from 4.30 to 5.25 nm^(-2),COOH groups predominantly exist in a free state and facilitate effective hydration layers,thereby promoting superhydrophilicity.Overall,this study not only establishes a unified thermodynamic framework linking surface COOH configurations to macroscopic wettability,but also validates its universality by extending it to COOH-SAMs systems,thereby providing a unified theoretical framework for the controllable design of hydrophilicity in various COOH-functionalized surfaces.展开更多
A compact variable optical attenuator, covering C and L bands with over 50 dB attenuation range, is realized using a single liquid crystal cell with a tilted fused silica coating compensating the cell's small resi...A compact variable optical attenuator, covering C and L bands with over 50 dB attenuation range, is realized using a single liquid crystal cell with a tilted fused silica coating compensating the cell's small residual birefringence.展开更多
A wideband CMOS variable gain low noise amplifier（VGLNA） based on a single-to-differential（S2D） stage and resistive attenuator is presented for TV tuner applications.Detailed analysis of input matching,noise figur...A wideband CMOS variable gain low noise amplifier（VGLNA） based on a single-to-differential（S2D） stage and resistive attenuator is presented for TV tuner applications.Detailed analysis of input matching,noise figure（NF） and linearity for S2D is given.A highly linear passive resistive attenuator is proposed to provide 6 dB attenuation and input matching for each gain stage.The chip was fabricated by a 0.18μm 1P6M CMOS process, and the measurements show that the VGLNA covers a gain range over 36.4 dB and achieves a maximum gain of 21.3 dB,a minimum NF of 3.0 dB,an IIP3 of 0.9 dBm and an IIP2 of 26.3 dBm at high gain mode with a power consumption less than 10 mA from a 1.8 V supply.展开更多
In this Letter, we propose an optical attenuator based on the phase modulation of a spatial light modulator （SLM）. In this system, we use two polarized beam splitters （PBSs） to control the polarized light and one ...In this Letter, we propose an optical attenuator based on the phase modulation of a spatial light modulator （SLM）. In this system, we use two polarized beam splitters （PBSs） to control the polarized light and one SLM to modulate the phase of the polarized light. In the initial state, the light beam is divided into p-light and s-light when it passes through the first PBS. When the light passes through the second PBS, s-light is reflected and p-light is detected by the CCD camera. By loading different grayscales on the SLM, p-light changes its polarized state to s-light. The light power can be attenuated during the loading process. Our experiment shows that the system can obtain a wide optical attenuation from 1-27.2 dB. When loading two grayscales, the SLM has a fast switching time of 25 ms under a low actuated voltage of 5.5 V. The response time of the optical attenuator depends on the switching time of the SLM. Therefore, the system can also have a fast response time. By using the method of spatial multiplexing and adding two mirrors in the system, it can also be extended into a 1 × 2 optical switch. The results verify its feasibility. The optical attenuator has wide applications in photonic signal processing and fiber-optic communication.展开更多
Artificial intelligence(AI)is revolutionizing medical imaging,particularly in chronic liver diseases assessment.AI technologies,including machine learning and deep learning,are increasingly integrated with multiparame...Artificial intelligence(AI)is revolutionizing medical imaging,particularly in chronic liver diseases assessment.AI technologies,including machine learning and deep learning,are increasingly integrated with multiparametric ultrasound(US)techniques to provide more accurate,objective,and non-invasive evaluations of liver fibrosis and steatosis.Analyzing large datasets from US images,AI enhances diagnostic precision,enabling better quantification of liver stiffness and fat content,which are essential for diagnosing and staging liver fibrosis and steatosis.Combining advanced US modalities,such as elastography and doppler imaging with AI,has demonstrated improved sensitivity in identifying different stages of liver disease and distinguishing various degrees of steatotic liver.These advancements also contribute to greater reproducibility and reduced operator dependency,addressing some of the limitations of traditional methods.The clinical implications of AI in liver disease are vast,ranging from early detection to predicting disease progression and evaluating treatment response.Despite these promising developments,challenges such as the need for large-scale datasets,algorithm transparency,and clinical validation remain.The aim of this review is to explore the current applications and future potential of AI in liver fibrosis and steatosis assessment using multiparametric US,highlighting the technological advances and clinical relevance of this emerging field.展开更多
文摘The insertion loss （IL） of a T-type attenuator is theoretically analyzed. A T-type RF （ radio frequency） CMOS （ complementary metal-oxide-semiconductor ） attenuator is designed as an on-off keying（OOK） modulator in a time-hopping ultra wide-band （TH-UWB）communication with a carrier frequency of 4 GHz. In the topology of the OOK modulator circuit, there are three parts, an oscillator with an oscillating frequency of 4 GHz, a T-type attenuator constructed by RF CMOS transistors, and an output impedance matching network with a L-type LC structure. The modulator is controlled by a time-hopping pulse position modulation（TH-PPM） signal. The envelope of the modulated signal varies with the amplitude of the controlling signal. Meanwhile, an output matching network is also designed to match a 50 Ω load. In 0. 18 μm RF CMOS technology, a modulator is designed and simulated. The implemented modulator chip has 65 mV of the output amplitude at a 50 fl load from a 1.8 V supply, and the return loss （ S11 ） at the output port is less than - 10 dB. The chip size is 0. 7 mm × 0. 8 mm, and the power consumption is 12. 3 mW.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61205032,61475061,61405070,61177027,61275033,and 61261130586)the Science and Technology Development Plan of Jilin Province,China(Grant No.20140519006JH)
文摘Visible light variable optical attenuators（VOA） are essential devices in the application of channel power regulation and equalization in wavelength-division multiplexing cross-connect nodes in plastic optical fiber（POF） transmission systems.In this paper, a polymer/silica hybrid waveguide thermo–optic attenuator based on multimode interference（MMI） coupler is designed and fabricated to operate at 650 nm. The single-mode transmission condition, MMI coupler, and transition taper dimensions are optimized through the beam propagation method. Thermal analysis based on material properties provides the optimized heater placement angle. The fabricated VOA presents an attenuation of 26.5 dB with a 21-mW electrical input power at 650 nm. The rise time and fall time are 51.99 and 192 μs, respectively. The time–stability measurement results prove its working reliability.
基金Supprted by National Natural Science Foundation of China(Grant No.51775013)。
文摘Hydraulic pumps are a positive displacement pump whose working principle causes inherent output flow pulsation.Flow pulsation produces pressure pulsation when encountering liquid resistance.Pressure pulsation spreads in the pipeline and causes vibration,noise,damage,and even pipeline rupture and major safety accidents.With the development of airborne hydraulic systems with high pressure,power,and flow rate,the hazards of vibration and noise caused by pressure pulsation are also amplified,severely restricting the application and development of hydraulic systems.In this review paper,the mechanism,harm,and suppression method of pressure pulsation in hydraulic systems are analyzed.Then,the classification and characteristics of pulsation attenuators according to different working principles are described.Furthermore,the critical technology of simulation design,matching method with airborne piston pumps,and preliminary design method of pulsation attenuators are proposed.Finally,the development trend of pulsation attenuators is prospected.This paper provides a reference for the research and application of pressure pulsation attenuators.
基金Project supported by the National High Technology Research and Development Program of China(Grant No.2015AA016902)the National Nature Science Foundation of China(Grant Nos.61435013,61405188,and 61627820)
文摘The power consumption of a variable optical attenuator（VOA） array based on a silica planar lightwave circuit was investigated. The thermal field profile of the device was optimized using the finite-element analysis. The simulation results showed that the power consumption reduces as the depth of the heat-insulating grooves is deeper, the up-cladding is thinner,the down-cladding is thicker, and the width of the cladding ridge is narrower. The materials component and thickness of the electrodes were also optimized to guarantee the driving voltage under 5 V. The power consumption was successfully reduced to as low as 155 mW at an attenuation of 30 dB in the experiment.
文摘A proposed inductive-phase-compensation ultra wideband CMOS digital T-type attenuator design based on an analysis of minimising phase errors is presented in this letter.In a standard CMOS technology,the proposed attenuator is analytically demonstrated to have low phase errors due to the inductive-phase-compensation network.A design equation is inferred and a wide-band 4dB attenuation bit digital attenuator with low phase errors is designed as a test vehicle for the proposed approach.
基金supported by the National High Technology Research and Development Program of China(No.2013AA031402)
文摘According to the plasma dispersion effect of silicon(Si),a silicon-on-insulator(SOI) based variable optical attenuator(VOA) with p-i-n lateral diode structure is demonstrated in this paper.A wire rib waveguide with sub-micrometer cross section is adopted.The device is only about 2 mm long.The power consumption of the VOA is 76.3 mW(0.67 V,113.9 mA),and due to the carrier absorption,the polarization dependent loss(PDL) is 0.1dB at 20dB attenuation.The raise time of the VOA is 34.5 ns,the fall time is 37 ns,and the response time is 71.5 ns.
基金the Project by Yayasan Universiti Teknologi PETRONAS(No.0153AA-E95)。
文摘Numerous types of floating breakwaters have been proposed,tested and commercialized in the past decades.The majority of these breakwaters are made of solid bodies;hence,they are relatively bulky and are not readily to be rapidly installed at the targeted sites when immediate wave protection of the coastal and offshore facilities is needed.Furthermore,the application of these hard floating structures at the recreational beaches is rather unlikely due to potential deadly marine traffic collision.To overcome these problems,a flexible air-filled wave attenuator(AFWA)has been developed in the present study.This floating breakwater is made of flexible waterproof membrane materials.The main body consists of a rectangular air-filled prism and is ballasted by sandbags located around the floating module.The objective of this study is to evaluate the wave transmission,wave reflection,energy dissipation,motion responses and mooring forces of the AFWA under the random wave actions using physical modelling.The test model located in a 20 m long wave flume was subjected to a range of wave heights and periods.The wave profiles in the vicinity of the test model were measured using wave probes for determination of wave transmission,reflection and energy loss coefficients.The motion responses in terms of heave,surge and pitch,and wave forces acting on the mooring lines were measured using a motion tracking system and load cells,respectively.The experimental results reveal that the AFWA is effective in attenuating up to 95%in the incoming wave height and has low-wave-reflection properties,which is commendable for floating breakwaters.
基金Project supported by the Technological Innovation Project of Air-to-Air Missile Institute of China (Grant No.5S85000FS)
文摘This paper deals with a systematical analysis and an algorithm of attenuation characteristics of a light attenuator combined by n pieces of polarizers （n-LACP） whose extinction ratios are different from each other. The attenuation ratio expression of a two-LACP is deduced. We find that the monotonic attenuation interval depends on the first polarizer and that the attenuation range depends on the second one. For the three-LACP, a method for obtaining a monotonic attenuation interval is proposed. Moreover, the attenuation ratio expression is demonstrated. Analysis and experiment show that when the initial status of the three-LACP is at the maximum output, if the second or third polarizer rotates alone, the minimum attenuation ratios can reach K2^-1 and K3^-1, respectively, and if the first polarizer rotates, a minimum attenuation ratio of K2^-1K3^-1 can be obtained （K1, K2 and K3 represent the extinction ratios of the three polarizers in turn）. Furthermore, the attenuation ratio expression of n-LACP and the relevant attenuation characteristics are proposed. The minimum attenuation ratio of an n-LACP is （K2K3 ... Kn）-1.
基金the National Key Research and Development Program of China(Grant No.2019YFB2203504)Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB43000000)the Natural Science Foundation of Anhui Province,China(Grant No.1908085QF274)。
文摘A four-stage cascaded variable optical attenuator(VOA)with a large attenuation range is presented.The VOA is based on a Mach–Zehnder interferometer(MZI)and fabricated in a silica-based planar lightwave circuit(PLC)platform.The thermo-optic effect is used to achieve intensity modulation.The measured maximum attenuation of the four-stage cascaded VOA is 88.38 d B.The chip is also tested in a quantum key distribution(QKD)system to generate signal and decoy states.The mean photon number after attenuation of the four-stage cascaded VOA is less than 0.1,which can meet the requirement of QKD.
文摘The impact attenuator is an essential system in both race cars and urban vehicles.The structure of animpact attenuator serves as a safety barrier between the impacted surface and the driver in an accident.Attenuator materials tend to have a high price;thus,alternative materials were explored in the currentwork,i.e.,used cans from food and beverage containers.The study deployed a nonlinear finite elementalgorithm to calculate a series of impacts on the attenuator structures.The thickness of the cans andvelocity of the impact were considered as the main parameters.Analysis results concluded that the at-tenuator’s average energy was 16000 J for a can thickness of 1 mm.This value is more than two times the0.5 mm thick used cans.The attenuator’s new design was then matched with an attenuator regulation,and the results surpassed the standard value of 7350 J.
基金supported by the National Natural Science Foundation of China(Nos.20674001,20325415, 20834001)the Research Fund for Doctoral Program of Higher Education of MOE of China(No.20060001029)
文摘An eleetrochromic variable optical attenuator （ECVOA） was fabricated by layer-by-layer （LBL） assembly of disodium N,N-bis（p-sulfonatophenyl）naphthalenedicarboximide （Naph-SO3Na） and common cationic polymer poly（diallyldimethylammonium） chloride （PDDA）. The UV-Vis absorption spectra of the multilayer films revealed that approximately an equal amount of Naph-SO3Na was assembled in each deposition cycle. Upon one-electron reduction, multilayer films exhibited intense absorption around 452 nm and also a broad absorption band from 1200 nm to 1900 nm. Owing to the improved ionic conductivity, the optical attenuation at 1550 nm of the films showed rapid response time and reached 1.3 dB/μm within 5 s. These results indicate that layer-by-layer assembly could be an effective method for the preparation of ECVOA operating in near infrared region.
基金Fujian Province Key Technology Projects Fund(No.2006H0092)
文摘To measure the working band of a digital attenuator automatically,a program based on virtual instrument was carried out,using Agilent E8362B network analyzer as its measuring tool.In the program,the attenuation values can be automatically written into Excel table to form the frequency-attenuation curve.Finally,through analyzing the attenuation in different frequency,the best working band of the digital attenuator can be determined easily,and the whole process is automated.Compared with the traditional way of changing the measured parameters manually and recording the measured data one by one,the developed method in the paper can avoid the cumbersome manual operation and its possible errors to improve the measurement accuracy and efficiency.
文摘The purpose of this paper is to determine the optimal size and number of tubes for a generic attenuator that is similar to Pelamis P2, the wave energy converter. Simulations using ANSYS Workbench, Design Modeler, and AQWA are performed to study the energy absorption at the nodes between the tubes. The analysis is limited to linearized hydrodynamic fluid waves loading on floating bodies by employing three-dimensional radiation/diffraction theory in regular waves in the frequency domain. Three sets of tests are conducted by varying total tube number, each tube length and the order of tubes with different lengths. After a systematic study in the frequency domain, the optimal size and number of the genetic attenuator is recommended.
文摘New techniques for controlling the amplitudes of two orthogonal linearly polarized light are presented. One is based on adjusting the DC voltage into a Mach–Zehnder modulator（MZM） to alter the amplitude of the light traveling on the slow axis of a fiber into the modulator with little changes in the fast-axis light amplitude.Another is based on adjusting the input DC voltages of a dual-polarization MZM operating in the reverse direction, which enables independent control of the two input orthogonal linearly polarized light amplitudes.Experimental results demonstrate that more than 30 dB difference in slow-and fast-axis light power can be obtained by controlling an MZM input DC voltage, and over 24 dB independent power adjustment for light traveling on the slow and fast axes into a dual-polarization MZM.
文摘In this study,polyacrylic acid(PAA)films were employed as a model system,and a series of PAA films with tunable water wettability was systematically prepared by varying molecular weight and curing temperature.Using attenuated total reflectance Fourier-transform infrared spectroscopy(ATR-FTIR),the molecular configurations of surface carboxyl groups(COOH),free carboxyl(COOH_(f))and hydrogen-bonded carboxyl(COOH_(HB),were directly correlated with the polar component of surface energy(γ^(s,p)).By decomposing theγ^(s,p)values of the PAA thin films as a sum of the contributions of COOH_(f)and COOH_(H B),the intrinsic polar component of surface energy of COOH_(H B)(γ_(H B)^(s,p*))was quantified for the first time as 8.34 mN/m,significantly lower than that of COOH_(f)(γ_(f)^(s,p*)=34 mN/m).This result highlights that hydrogen bonding markedly reduces theγ^(s,p),providing a rational explanation for the relatively large water contact angle observed on PAA thin films.Furthermore,it establishes a thermodynamic basis for estimating the fraction of surface COOH_(H B)groups(f H B)from wettability measurements.Further extension of the model to carboxyl-terminated self-assembled monolayers(COOH-SAMs)revealed that surface COOH density(ΣCOOH)critically regulates wetting behavior:whenΣCOOH ranges from 4.30 to 5.25 nm^(-2),COOH groups predominantly exist in a free state and facilitate effective hydration layers,thereby promoting superhydrophilicity.Overall,this study not only establishes a unified thermodynamic framework linking surface COOH configurations to macroscopic wettability,but also validates its universality by extending it to COOH-SAMs systems,thereby providing a unified theoretical framework for the controllable design of hydrophilicity in various COOH-functionalized surfaces.
文摘A compact variable optical attenuator, covering C and L bands with over 50 dB attenuation range, is realized using a single liquid crystal cell with a tilted fused silica coating compensating the cell's small residual birefringence.
基金Project supported by the National Science Funding of China(No.60876019)the National S&T Major Project of China(No.2009ZX0131- 002-003-02)+2 种基金the Shanghai Rising-Star Program,China(No.09QA 1400300)the National Scientists and Engineers Service for Enterprise Program,China(No.2009GJC00046)the ASIC State-Key Laboratory Funding,China(No.09MS007)
文摘A wideband CMOS variable gain low noise amplifier（VGLNA） based on a single-to-differential（S2D） stage and resistive attenuator is presented for TV tuner applications.Detailed analysis of input matching,noise figure（NF） and linearity for S2D is given.A highly linear passive resistive attenuator is proposed to provide 6 dB attenuation and input matching for each gain stage.The chip was fabricated by a 0.18μm 1P6M CMOS process, and the measurements show that the VGLNA covers a gain range over 36.4 dB and achieves a maximum gain of 21.3 dB,a minimum NF of 3.0 dB,an IIP3 of 0.9 dBm and an IIP2 of 26.3 dBm at high gain mode with a power consumption less than 10 mA from a 1.8 V supply.
基金supported by the National Natural Science Foundation of China(Nos.61225022and 61320106015)the National"973"Program of China(No.2013CB328802)the National"863"Program of China(Nos.2015AA015902 and 2012AA011901)
文摘In this Letter, we propose an optical attenuator based on the phase modulation of a spatial light modulator （SLM）. In this system, we use two polarized beam splitters （PBSs） to control the polarized light and one SLM to modulate the phase of the polarized light. In the initial state, the light beam is divided into p-light and s-light when it passes through the first PBS. When the light passes through the second PBS, s-light is reflected and p-light is detected by the CCD camera. By loading different grayscales on the SLM, p-light changes its polarized state to s-light. The light power can be attenuated during the loading process. Our experiment shows that the system can obtain a wide optical attenuation from 1-27.2 dB. When loading two grayscales, the SLM has a fast switching time of 25 ms under a low actuated voltage of 5.5 V. The response time of the optical attenuator depends on the switching time of the SLM. Therefore, the system can also have a fast response time. By using the method of spatial multiplexing and adding two mirrors in the system, it can also be extended into a 1 × 2 optical switch. The results verify its feasibility. The optical attenuator has wide applications in photonic signal processing and fiber-optic communication.
文摘Artificial intelligence(AI)is revolutionizing medical imaging,particularly in chronic liver diseases assessment.AI technologies,including machine learning and deep learning,are increasingly integrated with multiparametric ultrasound(US)techniques to provide more accurate,objective,and non-invasive evaluations of liver fibrosis and steatosis.Analyzing large datasets from US images,AI enhances diagnostic precision,enabling better quantification of liver stiffness and fat content,which are essential for diagnosing and staging liver fibrosis and steatosis.Combining advanced US modalities,such as elastography and doppler imaging with AI,has demonstrated improved sensitivity in identifying different stages of liver disease and distinguishing various degrees of steatotic liver.These advancements also contribute to greater reproducibility and reduced operator dependency,addressing some of the limitations of traditional methods.The clinical implications of AI in liver disease are vast,ranging from early detection to predicting disease progression and evaluating treatment response.Despite these promising developments,challenges such as the need for large-scale datasets,algorithm transparency,and clinical validation remain.The aim of this review is to explore the current applications and future potential of AI in liver fibrosis and steatosis assessment using multiparametric US,highlighting the technological advances and clinical relevance of this emerging field.
