Pulse Train Method Research Articles

Efficient operation of atomic frequency comb optical memory using an optical frequency comb in 167Er3+:Y2SiO5

We demonstrated a highly efficient optical memory operation using an atomic frequency comb (AFC) created from a spectrally flattened optical frequency comb with an isotopically pure 167Er3+:Y2SiO5 crystal under zero magnetic field. Compared with standard AFC creation methods such as pulse train method, our method, called comb transfer method, can create a broadband and high-efficiency AFC at lower power and with less effort. This technique can make a significant improvement in the quality of AFCs in crystals doped with low concentrations of rare-earth ions.

Micro Drilling EDM with Non-contact Controlled Pulse Train Method

Micro Drilling EDM with Non-contact Controlled Pulse Train Method

Increasing discharge energy of micro-EDM with electrostatic induction feeding method through resonance in circuit

This paper describes the method to increase discharge energy in micro-EDM using electrostatic induction feeding as the pulse generator. In a previous study, controlled pulse train method was introduced to increase discharge energy and enlarge unit removal per discharge by allowing multiple discharges to occur at the same spot. During observation, it was found that the oscillation of discharge current is excited at higher amplitude even if the same capacitance is used. In this paper, the influence of frequency on discharge energy was investigated. It was found that higher discharge energy can be obtained when machining was done at the resonant frequency of the circuit. Influence of capacitance and inductance on resonant frequency was studied. Probability of discharge continuity at different frequencies was examined. The results confirmed that higher discharge continuity within the pre-determined pulse train duration can be achieved when machining is conducted at resonant frequency, leading to higher material removal rate (MRR).

Micro-EDM with Controlled Pulse Train Method Using Small Feeding Capacitance

This paper describes the implementation of controlled pulse train method (CPTM) and CPTM considering resonance in the circuit. This work was performed using the setup of non-contact electrical feeding micro EDM with high speed tool electrode rotation. In this setup, a cylindrical feeding electrode is fixed coaxially to the tool electrode holder. Capacitance C1 is formed between the two surfaces, realizing the non-contact electrical feeding and permits the tool to be rotated at high speed without vibration. Using this setup however, since C1 is very small, machining with large discharge energy is difficult. Hence, CPTM was developed to allow several discharges to occur within the pulse train duration. Thus, larger diameter of crater was achieved. Furthermore, CPTM considering resonance in the circuit resulted in higher average discharge energy per pulse. As a result, largest diameter of discharge was achieved under the same C1. An observation of discharge location through a transparent electrode from the direction normal to the machining surface was conducted using a high-speed video camera. The results show that discharges within a pulse train duration are concentrated at the same location even if there is an interval between the discharges.

Comparison between Electrostatic Induction Feeding with Controlled Pulse Train Method and Relaxation Pulse Generator for Micro EDM

Comparison between Electrostatic Induction Feeding with Controlled Pulse Train Method and Relaxation Pulse Generator for Micro EDM

Improving Discharge Energy in Micro-EDM with Electrostatic Induction Feeding by Controlled Pulse Train Method

Improving Discharge Energy in Micro-EDM with Electrostatic Induction Feeding by Controlled Pulse Train Method

Development of a Prototype Detector Using APD-Arrays Coupled With Pixelized Ce:GAGG Scintillator for High Resolution Radiation Imaging

A novel digital PET scanner based on Time over Threshold method is developed. The positron emission tomography (PET) is composed of 144channel Ce:Gd3Al2Ga3O12 (GAGG)-Avaranche photodiode (APD) detector arrays individually coupled with custom designed Time over Threshold (ToT) application-specific integrated circuit (ASIC) to realize the high count rate and good spatial resolution. Such an imaging system provides a simple front-end circuit and flexible digital signal processing like multiplexing such as a pulse train method. The measured energy resolution of the detector system was 6.7% for the 511 keV peak, and 4.25 ns time resolution was measured with a single detector module. The measured spatial resolution for a point source was 1.37 mm FWHM for our initial data with a columnar 22Na source.

Simplified Transfer Function of Write Compensation for Phase-Change Optical Disks

A simplified transfer function for write compensation is given by the inverse function of the cooling transfer function of a phase-change optical disk. The areas at a phase-change recording layer irradiated with an optical beam melt and change to marks. The marks are formed when the area is rapidly cooled; however, the marks disappear in a slowly cooled situation. Thus, the cooling process was considered essential for the mark formation on a phase-change optical disk. Therefore, the transfer function of the mark formation combined a heating component before mark formation with that after mark formation using a lag element. It was also found that the transfer function for write compensation could be achieved using a two-stage pulse train method. Experimental results showed that long marks were recorded by the pulse train method with the same frequency characteristic as our theoretical analysis.

Novel Front-End Pulse Processing Scheme for PET System Based on Pulse Width Modulation and Pulse Train Method

The architecture of a multi-channel front-end system is important for realizing a high-resolution PET system. We propose a novel front-end pulse processing scheme with pulse width modulation (PWM) and pulse train method for PET systems. Each channel of the proposed system consists of a preamplifier, a shaping amplifier, a comparator, and a digital circuit that generates a pulse train for each event. The preamplifier-shaper-discriminator module first generates a trigger pulse with time-over-threshold (ToT), which contains the energy information. The trigger pulse is then processed through a digital circuit that adds subsequent pulses to form a pulse train. These additional pulses encode channel information, timing information, etc. The digital signal output of each channel can be connected by simple wired-OR logic, and the output is read in one transmission line. This multi-channel, low power consumption front-end scheme can acquire enough pulse height (energy) and position information to realize a PET system with a significantly smaller number of output pins in the front-end ASIC. The pulse width encoding also simplifies the digital processing system. We designed a new ASIC based on this concept. The proposed architecture can be applied to high-resolution PET systems with multi-channel ASICs.

Electrodeposition of Co/Cu Multilayered Thin films and Microposts

Multilayer Co/Cu thin films were galvanostatically deposited onto n-type (100) silicon wafers with a 20 nm Cu seed layer. Both a regular square-wave pulse and a pulse train method were examined. The current-in-plane (CIP) giant magnetoresistance (GMR) that resulted when the cobalt layers were pulsed in a pulse train fashion together with a single copper layer pulse, showed a maximum in the GMR value with duty cycle. X-ray lithography and electrodeposition were combined to deposit an array of CoCu/Cu multilayer microposts into deep recesses for novel GMR architectures. The GMR was measured with the current perpendicular to the plane of the multilayers (CPP) in a single micropost with a height of 500 μm and a cross section of 183×183 μm.

Transesophageal low-energy synchronous cardioversion of atrial flutter/fibrillation in the dog

The purpose of this study was to determine the feasibility and efficacy of terminating atrial flutter/fibrillation using low-energy synchronous shocks delivered through a transesophageal catheter in dogs with talc-induced pericarditis. Atrial flutter/fibrillation was induced by employing the pulse train method. The minimum effective cardioversion energy level was compared for three different methods—method A, delivery between a distal esophageal electrode and a proximal esophageal electrode; method B, delivery of shocks through a distal ecophageal electrode and a plate placed on the chest; method C, transthoracic cardioversion. The minimum effective cardioversion energy level did not differ significantly between methods A and B (1.30 ± 0.46 joules versus 1.29 ± 0.35 joules). Transesophageal cardioversion decreased the defibrillation threshold three- to fourfold from that of conventional transthoracic cardioversion. There were no complications of heart block, ventricular fibrillation, or any pathologic evidence of esophageal injury. Thus transesophageal low-energy synchronous cardioversion is considered a feasible and effective method for the treatment of atrial flutter/fibrillation.

Composite events: computationally efficient method for generating 1/f noise

The task of generating 1/f noise via the random pulse train method is inherently numerically intensive. The computational efficiency has been increased by ten orders of magnitude by combining many elementary events into a single composite event. This approach is used to efficiently generate 1/f noise over a finite bandwidth. Further investigation and generalisation of the method may be of use to advancing the theory of 1/fnoise.

The Pulse-Train Method and its Application to The Measurement of Phonograph Cartridges

Conventionally, a sweep oscillator and a coordinating pen-recoder are often used to measure a transfer function of audio devices. However, an impulse signal has been found to be convenient to measure such a characteristic where the transfer function is invariable with respect to driving signals in the linear system.

Measurements of Chemical-Shift Tensors in KH2PO4 by First-Moment Method

A method is described which allows chemical shifts in solids to be detected to a good accuracy by sharply determining the first moment. The analysis is made by using spin-temperature concepts and it is shown that the chemical-shift tensor can be determined if a single tensor contributes to the spectrum, and the average if more than one tensor contributes. Measurements are made in a single crystal of KH 2 PO 4 . The average tensors obtained are axially symmetric about the c axis with σ // =-25.6 ppm and σ ⊥ =-8.3 ppm relative to C 6 H 12 for 1 H(300 K), and with σ // =-1.1 ppm and σ ⊥ =-16.5 ppm relative to 85% H 3 PO 4 for 31 P(77 K). These values are discussed qualitatively. The 19 F chemical shift in CaF 2 is also obtained, and the result is in good agreement with that of pulse train method.