Single Photon Detection Technology in Underwater Wireless Optical Communication:Modulation Modes and Error Correction Coding Analysis

This study explores the application of single photon detection(SPD)technology in underwater wireless optical communication(UWOC)and analyzes the influence of different modulation modes and error correction coding types on communication performance.The study investigates the impact of on-off keying(OOK)and 2-pulse-position modulation(2-PPM)on the bit error rate(BER)in single-channel intensity and polarization multiplexing.Furthermore,it compares the error correction performance of low-density parity check(LDPC)and Reed-Solomon(RS)codes across different error correction coding types.The effects of unscattered photon ratio and depolarization ratio on BER are also verified.Finally,a UWOC system based on SPD is constructed,achieving 14.58 Mbps with polarization OOK multiplexing modulation and 4.37 Mbps with polarization 2-PPM multiplexing modulation using LDPC code error correction.

Fault tolerant control of electric pitch control system based on single current detection

In view of the current sensors failure in electric pitch system,a variable universe fuzzy fault tolerant control method of electric pitch control system based on single current detection is proposed.When there is single or two-current sensor fault occurs,based on the proposed method the missing current information can be reconstructed by using direct current（DC）bus current sensor and the three-phase current can be updated in time within any two adjacent sampling periods,so as to ensure stability of the closed-loop system.And then the switchover and fault tolerant control of fault current sensor would be accomplished by fault diagnosis method based on adaptive threshold judgment.For the reconstructed signal error caused by the modulation method and the main control target of electric pitch system,a variable universe fuzzy control method is used in the speed loop,which can improve the anti-disturbance ability to load variation,and the robustness of fault tolerance system.The results show that the fault tolerant control method makes the variable pitch control system still has ideal control characteristics in case of sensor failure although part of the system performance is lost,thus the correctness of the proposed method is verified.

Single-cell omics analyses with single molecular detection:challenges and perspectives

The ultimate goal of single-cell analyses is to obtain the biomolecular content for each cell in unicellular and multicellular organisms at different points of their life cycle under variable environmental conditions.These require an assessment of:a)the total number of cells,b)the total number of cell types,and c)the complete and quantitative single molecular detection and identification for all classes of biopolymers,and organic and inorganic compounds,in each individual cell.For proteins,glycans,lipids,and metabolites,whose sequences cannot be amplified by copying as in the case of nucleic acids,the detection limit by mass spectrometry is about 105 molecules.Therefore,proteomic,glycomic,lipidomic,and metabolomic analyses do not yet permit the assembly of the complete single-cell omes.The construction of novel nanoelectrophoretic arrays and nano in microarrays on a single 1-cm-diameter chip has shown proof of concept for a high throughput platform for parallel processing of thousands of individual cells.Combined with dynamic secondary ion mass spectrometry,with 3D scanning capability and lateral resolution of 50 nm,the sensitivity of single molecular quantification and identification for all classes of biomolecules could be reached.Further development and routine application of such technological and instrumentation solution would allow assembly of complete omes with a quantitative assessment of structural and functional cellular diversity at the molecular level.

A glass nanopore electrode for single molecule detection

We have developed a simple method for fabricating robust and low noise glass nanopore electrodes with pore size 10±5 nm to detect single molecules.β-Cyclodextrin was used as model compound for characterization.In 1.0 mol/L NaCl solution,the molecules generated current pulses of 2-5 pA with noise level less than 0.8 pA.A slide mode and a plug mode were suggested for the way ofβ-cyclodextrin single molecule moving into the glass nanopores.

Internal cancellation of spikes using two avalanche photodiodes in series for single photon detection

We propose a method of improving the performance of InGaAs/InP avalanche photodiodes by using two avalanche photodiodes in series as single photon detectors for 1550-nm wavelength. In this method, the raw single photon avalanche signals are not attenuated, thus a high signal-to-noise ratio can be obtained compared with the existing results. The performance of the scheme is investigated and the ratio of the dark count rate to the detection efficiency is obtained to be 1.3×10^-4 at 213 K.

Combination of Micro-fluidic Chip with Fluorescence Correlation Spectroscopy for Single Molecule Detection

A single molecule detection technique was developed by the combination of a single channel poly （dimethylsiloxane）/glass micro-fluidic chip and fluorescence correlation spectroscopy （FCS）. This method was successfully used to determine the proportion of two model components in the mixture containing fluorescein and the rhodamine-green succinimidyl ester.

Detection and Diagnosis of Gear Fault By the Single Gear Tooth Analysis Technique

This paper presents a procedure of sing le gear tooth analysis for early detection and diagnosis of gear faults. The objec tive of this procedure is to develop a method for more sensitive detection of th e incipient faults and locating the faults in the gear. The main idea of the sin gle gear tooth analysis is that the vibration signals collected with a high samp ling rate are divided into a number of segments with the same time interval. The number of signal segments is equal to that of the gear teeth. The analysis of i ndividual segments reveals more sensitively the changes of the vibration signals in both time and frequency domain caused by gear faults. In addition, the locat ion of a failed tooth can be indicated in terms of the position of the segment t hat deviates from the normal segments. An experimental investigation verified th e advantages of the single gear tooth analysis.

Afterpulsing characteristics of InGaAs/InP single photon avalanche diodes

In Ga As/In P single photon avalanche diodes（SPADs） are more and more available in many research fields. They are affected by afterpulsing which leads to a poor single photon detection probability. We present an In Ga As/In P avalanche photodiode with an active quenching circuit on an application specific integrated circuit（ASIC）. It can quench the avalanche rapidly and then reduce the afterpulse rate. Also this quenching circuit can operate in both free-running and gated modes.Furthermore, a new technique is introduced to characterize the influence of the higher order of afterpulses, which uses a program running on a field programmable gate array（FPGA） integrated circuit.

A new measuring technique in detecting of high voltage three phase induction motor for single phasing

Open phase in three phase induction motors is a common fault that can occur as a result of a fuse blowing or a pro- tective device failing on one phase of the motor. This paper introduces a new method,which is based on the transient mea- surement and can distinguish the fault of one phase connecting ground. The method has been proved to be in correspondence with the simulation results by Matlab and LabVIEW in practice, The method has merits of simplicity, accuracy and ease of USe.

Development and evaluation of an online monitoring single-particle optical particle counter with polarization detection

We developed a single-particle optical particle counter with polarization detection(SOPC)for the real-time measurement of the optical size and depolarization ratio(defined as the ratio of the vertical component to the parallel component of backward scattering)of atmospheric particles,the polarization ratio(DR)value can reflect the irregularity of the particles.The SOPC can detect aerosol particles with size larger than 500 nm and the maximum particle count rate reaches~1.8×10^(5)particles per liter.The SOPC uses a modulated polarization laser to measure the optical size of particles according to forward scattering signal and the DR value of the particles by backward S and P signal components.The sampling rate of the SOPC was 106#/(sec·channel),and all the raw data were processed online.The calibration curve was obtained by polystyrene latex spheres with sizes of 0.5-10μm,and the average relative deviation of measurement was 3.96% for sub 3μm particles.T-matrix method calculations showed that the DR value of backscatter light at 120°could describe the variations in the aspect ratio of particles in the above size range.We performed insitu observations for the evaluation of the SOPC,the mass concentration constructed by the SOPC showed good agreement with the PM_(2.5)measurements in a nearby state-controlled monitoring site.This instrument could provide useful data for source appointment and regulations against air pollution.

Identification of thermal front dynamics in the northern Malacca Strait using ROMS 3D-model

The thermal front in the oceanic system is believed to have a significant effect on biological activity.During an era of climate change,changes in heat regulation between the atmosphere and oceanic interior can alter the characteristics of this important feature.Using the simulation results of the 3D Regional Ocean Modelling System(ROMS),we identified the location of thermal fronts and determined their dynamic variability in the area between the southern Andaman Sea and northern Malacca Strait.The Single Image Edge Detection(SIED)algorithm was used to detect the thermal front from model-derived temperature.Results show that a thermal front occurred every year from 2002 to 2012 with the temperature gradient at the location of the front was 0.3°C/km.Compared to the years affected by El Ni?o and negative Indian Ocean Dipole(IOD),the normal years(e.g.,May 2003)show the presence of the thermal front at every selected depth(10,25,50,and 75 m),whereas El Ni?o and negative IOD during 2010 show the presence of the thermal front only at depth of 75 m due to greater warming,leading to the thermocline deepening and enhanced stratification.During May 2003,the thermal front was separated by cooler SST in the southern Andaman Sea and warmer SST in the northern Malacca Strait.The higher SST in the northern Malacca Strait was believed due to the besieged Malacca Strait,which trapped the heat and make it difficult to release while higher chlorophyll a in Malacca Strait is due to the freshwater conduit from nearby rivers(Klang,Langat,Perak,and Selangor).Furthermore,compared to the southern Andaman Sea,the chlorophyll a in the northern Malacca Strait is easier to reach the surface area due to the shallower thermocline,which allows nutrients in the area to reach the surface faster.

A Study on the Monitoring System for the FMS

Introduces a new monitoring method in FMS explicated in some detail by means of the MSF(Monitoring System of FMS)under development by the au- thors.In order to push FMS technology forword,enhance machining flexibility and the flexibility of human operaters and equipment in a FMS,the authors have made some breakthroughs in traditional ways of single item,unit monitoring and self-han- dling,and suggested the idea of integrated inspection and put the MSF into more practicability.The working status of FMS can be monitored on the CRT of a micro- computer of the MSF,system troubles will be shown with icons,by the flash of the system characteristic symbol or by alarming,and so on.This explores a new way for FMS inspection in a wholly integrated manner.

Progress in the development of techniques based on light scattering for single nanoparticle detection

Nanoparticles have recendy attracted extensive attention in view of their great potential in biomedicine and bioanalytical applications. Single particle detection via light scattering offers a simple and efficient approach for the size, size distribution, and concentration analysis of nanoparticles. In particular, intrinsic heterogeneity or rare events masked by ensemble averaging can be revealed. However, the sixth power dependence of Rayleigh scattering on particle size makes it very challenging to detect individual nanoparficles of small sizes. This article is intended to provide an overview of recent progress in the development of techniques based on light scattering for the detection of single nanoparticles.

Passively and actively enhanced surface plasmon resonance sensing strategies towards single molecular detection

Surface plasmonic resonance(SPR)has been a corner stone for approaching single molecular detection due to its highsensitivity capability and simple detection mechanism,and has brought major advancements in biomedicine and life science technology.Over decades,the successful integration of SPR with versatile techniques has been demonstrated.However,several crucial limitations have hindered this technique for practical applications,such as long detection time and low overall sensitivity.This review aims to provide a comprehensive summary of existing approaches in enhancing the performance of SPR sensors based on“passive”and“active”methods.Firstly,passive enhancement is discussed from a material aspect,including signal amplification tags and modifications of conventional substrates.Then,the focus is on the most popular active enhancement methods including electrokinetic,optical,magnetic,and acoustic manipulations that are summarized with highlights on their advantageous features and ability to concentrate target molecules at the detection sites.Lastly,prospects and future development directions for developing SPR sensing towards a more practical,single molecular detection technique in the next generation are discussed.This review hopes to inspire researchers’interests in developing SPR-related technology with more innovative and influential ideas.

Photon counts modulation in optical time domain reflectometry

The quantum fluctuation of photon counting limits the field application of optical time domain reflection. A method of photon counts modulation optics time domain reflection with single photon detection at 1.55 μm is presented. The influence of quantum fluctuation can be effectively controlled by demodulation technology since quantum fluctuation shows a uniform distribution in the frequency domain. Combined with the changing of the integration time of the lock-in amplifier, the signal to noise ratio is significantly enhanced. Accordingly the signal to noise improvement ratio reaches 31.7 dB compared with the direct photon counting measurement.

Direct measurement of the surface dynamics of supercooled liquid-glycerol by optical scanning a film

The surface dynamics of supercooled liquid-glycerol is studied by scanning the thickness of the glycerol film with single photon detection. Measurements are performed at room temperature well above the glyeerol＇s glass transition temperature. It is shown that the surface dynamics of the glycerol film is very sensitive to the temperature. The linear relationship between the thickness of the film and the viscosity predicted by the Vogel Pulcher-Tammann Hesse （VFTH） law is also presented experimentally.

Single-atom metal-nitrogen-carbon catalysts energize single molecule detection for biosensing

Biosensors featuring single molecule detection present huge opportunities as well as challenges in food safety inspection,disease diagnosis,and environmental monitoring.Single-molecule detection is largely lacking of high enough activity,precision molecule selectivity,and understanding in the exact operating mechanism.Single-atom catalysts(SACs),especially those metals-nitrogen-carbon that mimic the natural metalloenzyme structure,and with well-defined metal atom bond configurations,high level of molecular selectivity,and easy fabrication,endow single molecule detections with practical-use feasibilities.The recent advances in single-atom catalysts also present new pathways in the key mechanism understandings.In this short review,we will first visit the brief history and advantages of SACs that have been explored only recently for molecule-scale biosensors,where they are analogous and also differentiated from those nanozymes and natural metalloenzymes.Their applications in electrochemical,photochemical,and photoelectrochemical sensors are then discussed comprehensively by focusing on the different molecule-scale sensing modes in achieving local coordination-modulated signal amplifications.Finally,we identify new opportunities and challenges faced by these SACs-based single molecule detections in the further development of biosensors.

Specific detection and effective inhibition of a single bacterial species in situ using peptide mineralized Au cluster probes

Increasingly serious microbial infections call for the development of new simpler methods for the precise diagnosis and specific inhibition of such pathogens. In this work, a peptide mineralized Au cluster probe was applied as a new simplified strategy to both recognize and inhibit a single bacteria species of Staphylococcus aureus(S. aureus) simultaneously. The probes are composed of peptides and Au clusters. Moreover, the peptides specifically target S. aureus cells and the Au clusters provide fluorescent imaging and have an antibacterial effect. These new probes enable the simultaneous specific detection and effective destruction S. aureus cells in situ.

An advanced SEU tolerant latch based on error detection

This paper proposes a latch that can mitigate SEUs via an error detection circuit.The error detection circuit is hardened by a C-element and a stacked PMOS.In the hold state,a particle strikes the latch or the error detection circuit may cause a fault logic state of the circuit.The error detection circuit can detect the upset node in the latch and the fault output will be corrected.The upset node in the error detection circuit can be corrected by the C-element.The power dissipation and propagation delay of the proposed latch are analyzed by HSPICE simulations.The proposed latch consumes about 77.5%less energy and 33.1%less propagation delay than the triple modular redundancy（TMR）latch.Simulation results demonstrate that the proposed latch can mitigate SEU effectively.

A sensitive charge scanning probe based on silicon single electron transistor

Single electron transistors（SETs） are known to be extremely sensitive electrometers owing to their high charge sensitivity. In this work, we report the design, fabrication, and characterization of a silicon-on-insulatorbased SET scanning probe. The fabricated SET is located about 10 m away from the probe tip. The SET with a quantum dot of about 70 nm in diameter exhibits an obvious Coulomb blockade effect measured at 4.1 K. The Coulomb blockade energy is about 18 me V, and the charge sensitivity is in the order of 10^-（5）–10（^-3）e/Hz^（1/2）. This SET scanning probe can be used to map charge distribution and sense dynamic charge fluctuation in nanodevices or circuits under test, realizing high sensitivity and high spatial resolution charge detection.