Parallel Stages Research Articles

Effect of high-efficiency emitter on noise characteristics of electron amplifiers

Electron-optical devices with microchannel amplification have many advantages, except poor noise characteristics. In order to increase gain and reduce a noise factor a layer with increased secondary emission is deposited on the top of a contact conducting layer at the entrance of channels. Effects, arising in the channel amplifier with the high-efficiency emitter, are investigated in this work using the computational method, developed by the author. A computational method for simulation of stochastic processes of an electron multiplication is based on 3D Monte Carlo simulations and the theorems of serial and parallel amplification stages proposed by the author. The method provides a high calculation accuracy with minimal cost of computations. The computational model is used to investigate the effect on the noise factor of the incidence angle of the input electron beam, nonuniformity of the emitter surface, the depth and secondary emission yield of the high-efficiency emitter.

A 3 W High‐Voltage Single‐Chip Green Light‐Emitting Diode with Multiple‐Cells Network

A parallel and series network structure was introduced into the design of the high‐voltage single‐chip (HV‐SC) light‐emitting diode to inhibit the effect of current crowding and to improve the yield. Using such a design, a 6.6 × 5 mm2 large area LED chip of 24 parallel stages was demonstrated with 3 W light output power (LOP) at the current of 500 mA. The forward voltage was measured to be 83 V with the same current injection, corresponding to 3.5 V for a single stage. The LED chip’s average thermal resistance was identified to be 0.28 K/W by using infrared thermography analysis.

A parallelogram-based compliant remote-center-of-motion stage for active parallel alignment.

Parallel alignment stage with remote-center-of-motion (RCM) is of key importance in precision out-of-plane aligning since it can eliminate the harmful lateral displacement generated at the output platform. This paper presents the development of a parallelogram-based compliant RCM stage for active parallel alignment. Different from conventional parallelogram-based RCM mechanism, the proposed stage is designed with compliant mechanisms, which endows the stage with many attractive merits when used in precision micro-/nanomanipulations. A symmetric double-parallelogram mechanism (SDPM) based on flexure hinges is developed as the rotary guiding component to realize desired RCM function. Due to the geometrical constraint of the SDPM, the operating space of the stage can be easily adjusted by bending the input links without loss of rotational precision. The stage is driven by a piezoelectric actuator and its output motion is measured by non-contact displacement sensors. Based on pseudo-rigid-body simplification method, the analytical models predicting kinematics, statics, and dynamics of the RCM stage have been established. Besides, the dimensional optimization is conducted in order to maximize the first resonance frequency of the stage. After that, finite element analysis is conducted to validate the established models and the prototype of the stage is fabricated for performance tests. The experimental results show that the developed RCM stage has a rotational range of 1.45 mrad while the maximum center shift of the RCM point is as low as 1 μm, which validate the effectiveness of the proposed scheme.

Application of similarity theory to load capacity of gearboxes

This study suggests the theoretical methodology to construct a small-sized similarity model having the same load capacity as a large gearbox. The prototype gearbox was a 2-MW wind turbine gearbox consisting of two planetary gear stages and one parallel shaft gear stage, and the specifications of its 1/4 scale similarity model were determined by applying similarity theory. The constructed similarity model was validated by comparing load capacity parameters with those of the prototype gearbox using analysis tool. The validation results showed that the nominal tooth root and contact stresses of the similarity model and prototype gearbox were identical, whereas the tooth root and contact stresses satisfied the similarity condition within 2% difference. Furthermore, most factors that influenced the tooth root and pitting stress limits were identical. Thus, information related to load capacity, one of the major design evaluation criteria for gears, of large-size gearbox can be replicated by its similarity model. Although this is a theoretical methodology and still has many difficulties to apply to practical situations, these results have opened up the possibility of applying similarity theory to load capacity of gearboxes. Because the load capacity is the primary cause of commercial gearbox failure, this result also shows the possibility of life similarity in the gearbox application, although some further study is needed.

Research on the Optimal Design and Gear Modification of Gearbox of a Wind Turbine Based on the Virtual Prototype

This article describes a new mixed transmission system about the wind power gearbox. It is composed of one NGW planetary gear stage and two parallel gear stages. The modeling and optimization analysis of gearbox have been performed using Romax designer software. The load case of gear, gear modification, transmission error and Fast Fourier Transform Harmonics of wind gearbox have been carried out to investigate various performances of gearbox system. Results of the investigation show the maximum load per unit length of gear reduces about 7.2%, Transmission Error of gear reduces 74.3% and Fast Fourier Transform Harmonics decreases 77.4% after gear modification. This kind of design method has a remarkable effect on smooth running. And it provides a new research method for gear box of wind turbine.

Research on dynamical characteristics of wind turbine gearboxes with flexible pins

Wind energy is believed as one of the most efficient clean renewable energies and is explored more often currently. The dynamic behaviors of wind turbine gearboxes are concerned by engineers since they affect the whole working performances and the service lives of wind turbines. In this work, a coupled dynamic model is developed for a wind turbine gearbox with flexible pins. For the planetary gear stage, the sun gear is floated and the planetary gears are flexibly supported by flexible pins. The sub-transmission system of the gearbox, which consists of a planetary gear stage and a parallel gear stage, and the body sub-system are coupled through the bearings which are simulated as springs. The dynamic behaviors of the system are studied using a lumped parameter model, in which the stiffnesses of the gearbox body is predicted using the finite element method, the results is also verified by experiments conducted on a test rig.

Acquired prosopagnosia structural basis and processing impairments

Cognitive models propose a hierarchy of parallel processing stages in face perception, and functional neuroimaging shows a network of regions involved in face processing. Reflecting this, acquired prosopagnosia is not a single entity but a family of disorders with different anatomic lesions and different functional deficits. One classic distinction is between an apperceptive variant, in which there is impaired perception of facial structure, and an associative/amnestic variant, in which perception is relatively intact, with subsequent problems matching perception to facial memories, because of either disconnection or loss of those memories. These disorders also have to be distinguished from people-specific amnesia, a multimodal impairment, and prosop-anomia, in which familiarity with faces is preserved but access to names is disrupted. These different disorders can be conceived as specific deficits at different processing stages in cognitive models, and suggests that these functional stages may have distinct neuroanatomic substrates. It remains to be seen whether a similar anatomic and functional variability is present in developmental prosopagnosia.

Step Kinematic Calibration of a XY-Theta Parallel Stage Using Vision-based Metrology

Step Kinematic Calibration of a XY-Theta Parallel Stage Using Vision-based Metrology

A 12.1 mW 50–67‐GHz CMOS up‐conversion mixer with 6‐dB conversion gain and 30.7‐dB LO‐RF isolation

ABSTRACTA 50–67‐GHz double‐balanced mixer for direct up‐conversion using standard 90‐nm CMOS technology is reported. The up‐conversion mixer comprises an enhanced double‐balanced Gilbert cell with current injection for power consumption reduction, and negative resistance compensation for conversion gain (CG) enhancement, a parallel and differential intermediate frequency (IF) transconductance stage for bandwidth and linearity enhancement, a Marchand balun for converting the single local oscillator (LO) input signal to differential signal, and another Marchand balun for converting the differential radio‐frequency (RF) output signal to single signal. The mixer consumes 12.1 mW and achieves IF‐port input return loss of −12.8 dB at 0.1 GHz, LO‐port input return loss of −9.5 to −11.4 dB and RF‐port input return loss of −10.7 to −12.5 dB for frequencies 57–64 GHz. At IF of 0.1 GHz, the mixer achieves CG of 3.1–6 dB and LO‐RF isolation of 26.4–30.7 dB for RF of 50–67 GHz. The corresponding 3‐dB bandwidth of RF is larger than 17 GHz (the measurement range of 50–67 GHz). To the authors' knowledge, the CG and power consumption are the best results ever reported for a 60‐GHz CMOS/BiCMOS up‐conversion mixer. In addition, the measured IIP3 is −6.4 dBm at RF of 60 GHz. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:475–483, 2014

A three-stage Data Envelopment Analysis model with application to banking industry

The changing economic conditions have challenged many financial institutions to search for more efficient and effective ways to assess their operations. Data Envelopment Analysis (DEA) is a widely used mathematical programming approach for comparing the inputs and outputs of a set of homogenous Decision Making Units (DMUs) by evaluating their relative efficiency. The traditional DEA treats DMUs as black boxes and calculates their efficiencies by considering their initial inputs and their final outputs. As a result, some intermediate measures are lost in the process of changing the inputs to outputs. In this study we propose a three-stage DEA model with two independent parallel stages linking to a third final stage. We calculate the efficiency of this model by considering a series of intermediate measures and constraints. We present a case study in the banking industry to exhibit the efficacy of the procedures and demonstrate the applicability of the proposed model.

A force-decoupled compound parallel alignment stage for nanoimprint lithography

This paper presents the development of a force-decoupled compound parallel alignment stage for nanoimprint lithography. Parallel alignment stage is a critical component of nanoimprint machine to implement the uniform surface contact between the template with predefined micro/nano patterns and the substrate that accepts the patterns. A combination of a high-stiffness spherical air bearing and a multi degree-of-freedom flexure-based mechanism is adopted in the parallel alignment stage. Apart from the parallel alignment function, the proposed stage can also endure a large imprinting force (more than 1000 N) but does not cause any damage to the delicate flexure-based mechanism. The stage performance is evaluated to satisfy the alignment requirement through the theoretical modeling and finite element analysis. Experiments are conducted on the parallel alignment stage to verify its performance on the transferred grating patterns with linewidth of 2.5 μm. This result demonstrates that the proposed approach can enhance the load capacity of the parallel alignment stage without degrading its alignment accuracy for nanoimprint lithography.

English

The treatment performance of two parallel continuous single stage activated sludge bioreactor: an aerobic bioreactor (ABR) operated at dissolved oxygen (DO) levels of 3-4 mg/L, and an innovative micro-aerobic bioreactor (MABR) operated at DO levels of 0.4-0.8 mg/L and the microbial diversity of MABR was investigated and compared. Under the similar conditions, at a hydraulic time (HRT) of 25 h, an organic loading rate (OLR) of 3.4±0.1 kg COD /m3·d, the influent total phosphate (TP) was 44±2 mg/L. The COD removal efficiencies of the MABR and the ABR were 93±3 and 90±3%, respectively, and no significant difference in performance was noted between the two systems (P=0.087>0.05). It was, however, noted that TP removal efficiency of the MABR (62±4%) was significantly higher than that of ABR (43±2%) (P=0.00). Phylogenetic analysis indicated that bacteria in the MABR was highly diverse. It is likely that facultative anaerobes, microaerophile and aerobes were able to coexist in the MABR. These findings might be helpful in developing an economic treatment system, which can be a better alternative for treatment of many pollutants requiring aerobic/anaerobic sequential treatment.   Key words: Biodiversity, micro-aerobic bioreactor, phosphorous removal, phylogenetic analysis.

Comparative transcriptome analysis between somatic embryos (SEs) and zygotic embryos in cotton: evidence for stress response functions in SE development

As a product of asexual reproduction in plants, the somatic embryo (SE) differentiates into a new plantlet via a zygotic embryogenesis-like process. Here, we present the phenotypic and cellular differences between SEs and zygotic embryos (ZEs) revealed by histological section scanning using three parallel development stages of the two types of embryos of cotton (Gossypium hirsutum cv. YZ1), including globular, torpedo and cotyledonary-stages. To identify the molecular characteristics of SE development in cotton, the digital gene expression system was used to profile the genes active during SE and ZE development. A total of 4242 differentially expressed genes (DEGs) were identified in at least one developmental stage. Expression pattern and functional classification analysis based on these DEGs reveals that SE development exhibits a transcriptional activation of stress responses. RT-PCR analysis further confirmed enhanced expression levels of stress-related genes in SEs than in ZEs. Experimental stress treatment, induced by NaCl and ABA, accelerated SE development and increased the transcription of genes related to stress response, in parallel with decelerated proliferation of embryogenic calluses under stress treatment. Our data reveal that SE development involves the activation of stress responses, which we suggest may regulate the balance between cell proliferation and differentiation. These results provide new insight into the molecular mechanisms of SE development and suggest strategies that can be used for regulating the developmental processes of somatic embryogenesis.

Computational models for investigation of channel amplifier’s optimal parameters

Microchannel electron multipliers, which amplify the input current of electrons through complicated stochastic processes, have found wide applications in different areas of science and engineering due to a number of remarkable properties. However, the loss of information caused by the statistical fluctuations in the gain of the channels, increases a noise factor which is a measure of the loss of available information. Investigations dealing with reducing of the noise factor are of considerable practical interest. The method, based on 3D Monte Carlo simulations and theorems about serial and parallel amplification stages, is used to show the dependence of the average gain and noise factor on the energy and the incidence angle of the input electron beam, and to find their optimal combination. The spread in incidence coordinates of the electrons of the input beam on the interior surface of a channel is taken into account in the model. The results are compared with a model where the incidence coordinate is same for all input electrons. The numerical experiments show that the spread in the collision coordinates of primary electrons significantly affects the average gain and the noise factor, and must be taken into account in theoretical models. The optimal combinations of the energy and the angle of the input electron beam, which provide the minimal noise factor and maximum gain, are obtained. Such investigations are effectively conducted using the method of serial and parallel amplification stages, and would be practically impossible using only direct simulations by the Monte Carlo methods.

An Asymptotic Approach to Parallel Equalization of Filter Bank Based Multicarrier Signals

A novel equalization structure for filter bank based multicarrier (FBMC) based modulations is proposed in this paper. The equalizer architecture is derived by assuming that the number of carriers is asymptotically large, and it consists of multiple parallel stages that are linearly combined on a per-subcarrier basis. The traditional single-tap per-subcarrier equalizer is obtained as a special case of the proposed architecture when the number of stages is fixed to one. An analytical characterization of the output signal to noise plus distortion ratio is provided, which can be used in practice to fix the number of parallel stages of the equalizer in order to obtain a certain performance level at the minimum complexity. Both simulations and analytical predictions indicate that high performance gains can be obtained with respect to more conventional FBMC equalization approaches. Furthermore, the proposed architecture is also shown to present important advantages in terms of computational complexity when compared with classical FBMC equalization architectures.

General Cognitive Ability and the Psychological Refractory Period

Identifying the precise locus of general cognitive ability (g) in the flow of information between perception and action is an important goal of differential psychology. To localize the negative correlation between g and reaction time to a specific processing stage, we administered a speeded number-comparison task to two groups differing in average g. The participants had to respond to two stimuli in each trial, which produced the well-known slowing of the second reaction time known as the psychological refractory period. The difference in the second reaction time favoring the high-g group doubled as the stimulus onsets became very close together. This finding affirms that the faster reaction times of higher-g individuals reflect an advantage exclusively in the serial bottleneck of central processing and not in the parallel peripheral stages.

8-channel acquisition system for time-correlated single-photon counting

Nowadays, an increasing number of applications require high-performance analytical instruments capable to detect the temporal trend of weak and fast light signals with picosecond time resolution. The Time-Correlated Single-Photon Counting (TCSPC) technique is currently one of the preferable solutions when such critical optical signals have to be analyzed and it is fully exploited in biomedical and chemical research fields, as well as in security and space applications. Recent progress in the field of single-photon detector arrays is pushing research towards the development of high performance multichannel TCSPC systems, opening the way to modern time-resolved multi-dimensional optical analysis. In this paper we describe a new 8-channel high-performance TCSPC acquisition system, designed to be compact and versatile, to be used in modern TCSPC measurement setups. We designed a novel integrated circuit including a multichannel Time-to-Amplitude Converter with variable full-scale range, a D∕A converter, and a parallel adder stage. The latter is used to adapt each converter output to the input dynamic range of a commercial 8-channel Analog-to-Digital Converter, while the integrated DAC implements the dithering technique with as small as possible area occupation. The use of this monolithic circuit made the design of a scalable system of very small dimensions (95 × 40 mm) and low power consumption (6 W) possible. Data acquired from the TCSPC measurement are digitally processed and stored inside an FPGA (Field-Programmable Gate Array), while a USB transceiver allows real-time transmission of up to eight TCSPC histograms to a remote PC. Eventually, the experimental results demonstrate that the acquisition system performs TCSPC measurements with high conversion rate (up to 5 MHz/channel), extremely low differential nonlinearity (<0.04 peak-to-peak of the time bin width), high time resolution (down to 20 ps Full-Width Half-Maximum), and very low crosstalk between channels.

Practical speculative parallelization of variable-length decompression algorithms

Variable-length coding is widely used for efficient data compression. Typically, the compressor splits the original data into blocks and compresses each block with variable-length codes, hence producing variable-length compressed blocks. Although the compressor can easily exploit ample block-level parallelism, it is much more difficult to extract such coarse-grain parallelism from the decompressor because a block boundary cannot be located until decompression of the previous block is completed. This paper presents novel algorithms to efficiently predict block boundaries and a runtime system that enables efficient block-level parallel decompression, called SDM . The SDM execution model features speculative pipelining with three stages: Scanner, Decompressor, and Merger. The scanner stage employs a high-confidence prediction algorithm that finds compressed block boundaries without fully decompressing individual blocks. This information is communicated to the parallel decompressor stage in which multiple blocks are decompressed in parallel. The decompressed blocks are merged in order by the merger stage to produce the final output. The SDM runtime is specialized to execute this pipeline correctly and efficiently on resource-constrained embedded platforms. With SDM we effectively parallelize three production-grade variable-length decompression algorithms?zlib, bzip2, and H.264?with maximum speedups of 2.50× and 8.53× (and geometric mean speedups of 1.96× and 4.04×) on 4-core and 36-core embedded platforms, respectively.

A mixed-gas miniature Joule–Thomson cooling system

A mixed-gas Joule–Thomson (JT) cooling system is investigated in which a micromachined JT cold stage of 60×10×0.7mm3 is combined with a linear compressor. The cooling system is operated between 1.3bar and 9.4bar with a ternary gas mixture of 39mol% methane, 20mol% ethane and 41mol% isobutane. It cools down to below 130K, and at a cold-tip temperature of 150K, a cooling power of 46mW is obtained at a mass-flow rate of 1.35mgs−1. The background losses are experimentally determined to be 20mW and are in good agreement with the calculated value of 21mW. The linear compressor can be used to drive 19 of these miniature JT cold stages in parallel, e.g. for cooling optical detectors in future space missions. In this mode, the compressor pressure ratio is slightly less, resulting in a net cooling power of 23mW per miniature JT cold stage.

Thermal Conductivity Detector for Gas Chromatography: Very Wide Gain Range Acquisition System and Experimental Measurements

The aim of this paper is to present an acquisition system featuring a very wide gain range and experimental measurements of a new micromachined thermal conductivity detector ( $\mu$ TCD), applied downstream of a gas-chromatography (GC) system. We describe a simple and innovative electronics for $\mu$ TCD control and data acquisition, outlining its resistance control, native imbalance compensation, and automatic gain control (AGC) algorithm. The acquisition electronics features two parallel amplification stages with programmable gain: a high-gain stage (gain: 70–1280) and a low-gain or attenuating stage (gain: 0.6–30). The resulting detection range turns out to be very wide, with full scales ranging between 3.9 mV and 6.5 V while voltage is acquired with a 10-b-resolution analog-to-digital converter. Measurements and sensitivity tests have been carried out by connecting our $\mu$ TCD and acquisition system downstream of the microfluidic section and GC column of a commercial GC system. Sensitivity measurements on several toluene masses gave very good results, having observed a system sensitivity of $15.2 \pm 0.6 \mu\hbox{Vs/ng}$ . This high sensitivity will enable the $\mu$ TCD to be used in many portable applications like in-line quality control, and industrial security and safety. We also show the good operation of the AGC algorithm.