Application of Optimal Control to CPMG Refocusing Pulse Design

We apply optimal control theory (OCT) to the design of refocusing pulses suitable for the CPMG sequence that are robust over a wide range of B0 and B1 offsets. We also introduce a model, based on recent progress in the analysis of unitary dynamics in the field of quantum information processing (QIP), that describes the multiple refocusing dynamics of the CPMG sequence as a dephasing Pauli channel. This model provides a compact characterization of the consequences and severity of residual pulse errors. We illustrate the methods by considering a specific example of designing and analyzing broadband OCT refocusing pulses of length 10 t180 that are constrained by the maximum instantaneous pulse power. We show that with this refocusing pulse, the CPMG sequence can refocus over 98% of magnetization for resonance offsets up to 3.2 times the maximum RF amplitude, even in the presence of +/- 10% RF inhomogeneity.Comment: 23 pages, 10 figures; Revised and reformatted version with new title and significant changes to Introduction and Conclusions section

Refocusing properties of periodic magnetic fields

The use of depressed collectors for the efficient collection of spent beams from linear-beam microwave tubes depends on a refocusing procedure in which the space charge forces and transverse velocity components are reduced. The refocusing properties are evaluated of permanent magnet configurations whose axial fields are approximated by constant plateaus or linearly varying fields. The results provide design criteria and show that the refocusing properties can be determined from the plateau fields alone

Refocusing the Australian Army

Recent operations have distracted the Army from being best postured for regional engagement.1 As the Afghanistan commitment winds down, the Army will need to overcome this neglect by shifting its primary focus to regional priorities, where geographic determinants and great power dynamics will feature. The maturation of defence infrastructure and capability projects dating back to the 1980s, coupled with capabilities entering service soon, means that the Australian Defence Force (ADF), and the Army in particular, has a strong foundation from which to refocus on engagement with regional forces, albeit with some exceptions. For instance, recent operations have demonstrated the need for sound intelligence support and a pool of language-trained and culturally-aware personnel, but regionally-oriented skills in these areas have atrophied. Beyond maintaining broad capabilities for a wide range of contingencies, the key to ensuring the Army‟s successful reorientation will be a regionally-focused reinvestment in intelligence, language and culture skills

PRIORITAS PENGGUNAAN DANA DESA DALAM BIDANG PEMBERDAYAAN MASYARAKAT DESA TEPIAN BATANG KECAMATAN TANAH GROGOT KABUPATEN PASER TAHUN 2020

Priority use of village funds is a choice of activities that take precedence and priority over other activity options to be financed with village funds. The use of village funds is a top priority to finance the implementation of programs and activities in the field of village development and village community empowerment. The emergence of Corona Virus Disease 19 (Covid – 19) resulted in changes in the priority of using village funds. The refocusing that occurred in the community empowerment sector must be diverted to handling Covid-19 and BLT. This research uses a qualitative descriptive method through a purposive sampling method. The primary data source in this research consists of key informants, namely the Secretary, while the informants are the village community. The data collection techniques are through observation and interviews, as well as through books or documentation. The refocusing that occurs in the field of community empowerment is not part of the allocation of funds because we can see that the needs of the community are very large, therefore the government not only takes funds from the field of community empowerment, but the village government also takes funds from the village development sector in large numbers. greater possibility of increasing the budget for this Refocusing policy. The research results show that the village funds that have been compiled in the 2020 RKPDes prioritize community empowerment and village development and must be changed with the presence of Covid-19, therefore the Ministry of Rural Affairs issued PDTT Ministerial Regulation Number 6 of 2020 which causes the priority use of village funds to decline. Refocusing priorities for disaster management/Covid-19 prevention activities and providing BLT (direct cash assistance) funds to village communities using the Village Fund. The Tepian Batang village government in this research has carried out a refocusing or change in the use of village funds in the Tepian Batang village which has been running in accordance with the Minister of Village Regulation on using village funds, starting from transparency, accountability and right on target, but there are a few problems in implementing it

Construction of a polarization insensitive lens from a quasi-isotropic metamaterial slab

We propose to employ the quasiisotropic metamaterial (QIMM) slab to construct a polarization insensitive lens, in which both E- and H-polarized waves exhibit the same refocusing effect. For shallow incident angles, the QIMM slab will provide some degree of refocusing in the same manner as an isotropic negative index material. The refocusing effect allows us to introduce the ideas of paraxial beam focusing and phase compensation by the QIMM slab. On the basis of angular spectrum representation, a formalism describing paraxial beams propagating through a QIMM slab is presented. Because of the negative phase velocity in the QIMM slab, the inverse Gouy phase shift and the negative Rayleigh length of paraxial Gaussian beam are proposed. We find that the phase difference caused by the Gouy phase shift in vacuum can be compensated by that caused by the inverse Gouy phase shift in the QIMM slab. If certain matching conditions are satisfied, the intensity and phase distributions at object plane can be completely reconstructed at image plane. Our simulation results show that the superlensing effect with subwavelength image resolution could be achieved in the form of a QIMM slab.Comment: 25 pages, 8 figure

Embedded FIR filter design for real-time refocusing using a standard plenoptic video camera

Copyright 2014 Society of Photo-Optical Instrumentation Engineers and IS&T—The Society for Imaging Science and Technology. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.A novel and low-cost embedded hardware architecture for real-time refocusing based on a standard plenoptic camera is presented in this study. The proposed layout design synthesizes refocusing slices directly from micro images by omitting the process for the commonly used sub-aperture extraction. Therefore, intellectual property cores, containing switch controlled Finite Impulse Response (FIR) filters, are developed and applied to the Field Programmable Gate Array (FPGA) XC6SLX45 from Xilinx. Enabling the hardware design to work economically, the FIR filters are composed of stored product as well as upsampling and interpolation techniques in order to achieve an ideal relation between image resolution, delay time, power consumption and the demand of logic gates. The video output is transmitted via High-Definition Multimedia Interface (HDMI) with a resolution of 720p at a frame rate of 60 fps conforming to the HD ready standard. Examples of the synthesized refocusing slices are presented

Fundamental limitations in spin-ensemble quantum memories for cavity fields

Inhomogeneously broadened spin ensembles play an important role in present-day implementation of hybrid quantum processing architectures. When coupled to a resonator such an ensemble may serve as a multi-mode quantum memory for the resonator field, and by employing spin-refocusing techniques the quantum memory time can be extended to the coherence time of individual spins in the ensemble. In the present paper we investigate such a memory protocol capable of storing an unknown resonator-field state, and we examine separately the various constituents of the protocol: the storage and read-out part, the memory hold time with the spin ensemble and resonator field decoupled, and the parts employing spin refocusing techniques. Using both analytical and numerical methods we derive how the obtainable memory performance scales with various physical parameters.Comment: 15 pages, 8 figure

An 82 to 84 percent efficient, small size, 2 and 4 stage depressed collector for octave bandwidth high performance TWT's

Improvements were carried out on a TWT (traveling wave tube) for use in EMC (electronic countermeasure) systems by applying MDC (multi-stage depressed collector) and spent-beam refocusing techniques. The MDC geometric design consists of six collecting elements (electrodes) at ground and cathode potentials operating in 2 or 4 stage configuration. The refocusing system designed allows a controlled beam expansion to the point that space charge becomes negligible at the MDC entrance. Simultaneously, the standard deviation of the radial velocity (angular spread) is reduced. This system provides an analog real time readout of P(recovered). Data on all tests is obtained with an automated data acquisition system