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Faculty of Informatics - Papers (Archive)

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Articles 1651 - 1680 of 2013

Full-Text Articles in Physical Sciences and Mathematics

Harmonic Allocation Constant For Implementation Of As/Nzs 61000.3.6, D A. Robinson, Victor J. Gosbell, Sarath Perera Jan 2001

Harmonic Allocation Constant For Implementation Of As/Nzs 61000.3.6, D A. Robinson, Victor J. Gosbell, Sarath Perera

Faculty of Informatics - Papers (Archive)

Allocation of equal harmonic emission rights to MV customers having the same maximum demand is a key concept in the new Australian harmonic standard AS/NZS 61000.3.6 [1]. Some difficulty can arise with the application of the standard when customers are spread out along a feeder with significantly different fault levels. One proposed method of overcoming this problem is to reduce the allocation as the square root of the fault level [2]. This method requires the calculation of an allocation constant that is applied to all customers connected to the same zone substation. This paper gives a methodology for calculating the …

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Harmonic Survey Of An Mv Distribution System, Victor J. Gosbell, Damian Mannix, D A. Robinson, Sarath Perera Jan 2001

Harmonic Survey Of An Mv Distribution System, Victor J. Gosbell, Damian Mannix, D A. Robinson, Sarath Perera

Faculty of Informatics - Papers (Archive)

The harmonic survey of a medium voltage distribution system involves three major aspects: (i) the choice of harmonic monitor, (ii) the choice of monitoring site, (iii) processing and presentation of results. As well as a discussion of the methodology for these aspects, the paper will discuss the harmonic levels measured, the minimum survey requirements for finding useful data and the harmonic parameters of residential, commercial and industrial loads.

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Characterisation Of High Temperature Superconducting Coils, Christopher David Cook, Sarath Perera, Thomas Hardjono Jan 2001

Characterisation Of High Temperature Superconducting Coils, Christopher David Cook, Sarath Perera, Thomas Hardjono

Faculty of Informatics - Papers (Archive)

Some power engineering systems, such as efficient energy storage for power quality improvement, can be potentially made more efficient if implemented with large coils made of high temperature superconductors (HTS). However, the losses of HTS coils carrying AC current limit their usage in practical applications. It has been shown previously that a thin pancake coil with relatively large diameter can be modelled as straight tapes arranged in a face-to-face stack. This paper reviews those results. In addition, measurements on a more realistic larger HTS coil were carried out. It is shown that the model assumptions provide less accurate results for …

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Signal Analysis Using A Multiresolution Form Of The Singular Value Decomposition, Ramakrishna Kakarala, Philip Ogunbona Jan 2001

Signal Analysis Using A Multiresolution Form Of The Singular Value Decomposition, Ramakrishna Kakarala, Philip Ogunbona

Faculty of Informatics - Papers (Archive)

This paper proposes a multiresolution form of the singular value decomposition (SVD) and shows how it may be used for signal analysis and approximation. It is well-known that the SVD has optimal decorrelation and subrank approximation properties. The multiresolution form of SVD proposed here retains those properties, and moreover, has linear computational complexity. By using the multiresolution SVD, the following important characteristics of a signal may be measured, at each of several levels of resolution: isotropy, sphericity of principal components, self-similarity under scaling, and resolution of mean-squared error into meaningful components. Theoretical calculations are provided for simple statistical models to …

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2d To Pseudo-3d Conversion Of "Head And Shoulder" Images Using Feature Based Parametric Disparity Maps, Chaminda Weerasinghe, Philip Ogunbona, Wanqing Li Jan 2001

2d To Pseudo-3d Conversion Of "Head And Shoulder" Images Using Feature Based Parametric Disparity Maps, Chaminda Weerasinghe, Philip Ogunbona, Wanqing Li

Faculty of Informatics - Papers (Archive)

This paper presents a method of converting a 2D still photo containing the head & shoulders of a human (e.g. a passport photo) to pseudo-3D, so that the depth can be perceived via stereopsis. This technology has the potential to be included in self-serve photo booths and, also as an added accessory (i.e. software package) for digital still cameras and scanners. The basis of the algorithm is to exploit the ability of the human visual system in combining monoscopic and stereoscopic cues for depth perception. Common facial features are extracted from the 2D photograph, in order to create a parametric …

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Short Amicable Sets And Kharaghani Type Orthogonal Designs, C. Koukouvinos, Jennifer Seberry Jan 2001

Short Amicable Sets And Kharaghani Type Orthogonal Designs, C. Koukouvinos, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

Short amicable sets were introduced recently and have many applications. The construction of short amicable sets had lead to the construction of many orthogonal designs, weighing matrices and Hadamard matrices. In this paper we give some constructions for short amicable sets as well as some multiplication theorems. We also present a table of the short amicable sets known to exist and we construct some infinite families of short amicable sets and orthogonal designs.

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An Algorithm To Find Formulae And Values Of Minors For Hadamard Matrices, C. Koukouvinos, M. Mitrouli, Jennifer Seberry Jan 2001

An Algorithm To Find Formulae And Values Of Minors For Hadamard Matrices, C. Koukouvinos, M. Mitrouli, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

We give an algorithm to obtain formulae and values for minors of Hadamard matrices. One step in our algorithm allows the (n – j) x (n – j) minors of an Hadamard matrix to be given in terms of the minors of a 2j-1 x 2j-1 matrix. In particular we illustrate our algorithm by finding explicitly all the (n – 4) x (n – 4) minors of an Hadamard matrix.

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Values Of Minors Of An Infinite Family Of D-Optimal Designs And Their Application To The Growth Problem, C. Koukouvinos, M. Mitrouli, Jennifer Seberry Jan 2001

Values Of Minors Of An Infinite Family Of D-Optimal Designs And Their Application To The Growth Problem, C. Koukouvinos, M. Mitrouli, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

We obtain explicit formulae for the values of the 2v — j minors, j = 0, 1, 2 of D-optimal designs of order 2v = x2 + y2, v odd, where the design is constructed using two circulant or type 1 incidence matrices of either two SBIBD(2s2 + 2s + 1, s2, s2-s/2) or 2 — {2s2 + 2s + 1; s2, s2; s(s–1)} sds. This allows us to obtain information on the growth problem for families of matrices with moderate growth. Some of our theoretical formulae imply growth greater than 2(2s2 + 2s + 1) but experimentation has not …

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A New Algorithm For Computer Searches For Orthogonal Designs, S. Georgiou, C. Koukouvinos, M. Mitrouli, Jennifer Seberry Jan 2001

A New Algorithm For Computer Searches For Orthogonal Designs, S. Georgiou, C. Koukouvinos, M. Mitrouli, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

We present a new algorithm for computer searches for orthogonal designs. Then we use this algorithm to find new sets of sequences with entries from {0, ±a, ±b, ±c, ±d} on the commuting variables a, b, c, d with zero autocorrelation function.

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E-Business: Revolution, Evolution, Or Hype?, T. Coltman, T. M. Devinney, A. Latukefu, D. F. Midgley Jan 2001

E-Business: Revolution, Evolution, Or Hype?, T. Coltman, T. M. Devinney, A. Latukefu, D. F. Midgley

Faculty of Informatics - Papers (Archive)

As the Internet continues to grow in size and capability, many firms are implementing Web-based applications and Internet-derived economic change continues to occur. If this change is revolutionary, now or in the near future, then many managers will be required to rethink their firm strategies and managerial responses in a profound way. On the other hand, if the change is simply evolutionary, it will apply more to some firms than to others, and pre-Internet strategies and managerial responses will still be appropriate in many circumstances. While it is premature to categorize e-business as revolutionary, e-business is not a silver bullet, …

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On The Complete Pivoting Conjecture For Hadamard Matrices Of Small Orders, C. Koukouvinos, M. Mitrouli, Jennifer Seberry Jan 2001

On The Complete Pivoting Conjecture For Hadamard Matrices Of Small Orders, C. Koukouvinos, M. Mitrouli, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

In this paper we study explicitly the pivot structure of Hadamard matrices of small orders 16, 20 and 32. An algorithm computing the (n — j) x (n — j) minors of Hadamard matrices is presented and its implementation for n = 12 is described. Analytical tables summarizing the pivot patterns attained are given.

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Infinite Families Of Orthogonal Designs : I, Christos Koukouvinos, Jennifer Seberry Jan 2001

Infinite Families Of Orthogonal Designs : I, Christos Koukouvinos, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

We generalise a method inspired by Kharaghani and Holzmann to obtain infinite families of 6-variables orthogonal designs, OD(8t;k,k,k,k,k,k), and OD(8t;,k,k,k,k,2k,2k), for the first time for odd t.

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Values Of Minors Of (1,-1) Incidence Matrices Of Sbibds And Their Application To The Growth Problem, C Koukouvinos, M Mitrouli, Jennifer Seberry Jan 2001

Values Of Minors Of (1,-1) Incidence Matrices Of Sbibds And Their Application To The Growth Problem, C Koukouvinos, M Mitrouli, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

We obtain explicit formulae for the values of the v j minors, j = 0, 1,2 of (1, -1) incidence matrices of SBIBD(v, k, λ). This allows us to obtain explicit information on the growth problem for families of matrices with moderate growth. An open problem remains to establish whether the (1, -1) CP incidence matrices of SBIBD(v, k, λ), can have growth greater than v for families other than Hadamard families.

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The Application Of Iec 61000-3-6 To Mv Systems In Australia, Victor J. Gosbell, D A. Robinson, Sarath Perera, Alex Baitch Jan 2001

The Application Of Iec 61000-3-6 To Mv Systems In Australia, Victor J. Gosbell, D A. Robinson, Sarath Perera, Alex Baitch

Faculty of Informatics - Papers (Archive)

IEC 61000-3-6 [1] comprises a number of stages and tests to determine harmonic emission allowances for customers connected to MV or HV networks. Of particular importance is the section concerning loads distributed along a feeder, each having a different fault level. Although a common situation, the treatment given in the IEC standard is poorly described, being largely illustrated by one atypical example. This allows simplifying assumptions to be made which are invalid in practical cases. This paper outlines a more general approach that is relatively easy to apply.

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Design Of A High Temperature Superconductor Magnetic Energy Storage Systems, R L Causley, Christopher David Cook, Steve Gower Jan 2001

Design Of A High Temperature Superconductor Magnetic Energy Storage Systems, R L Causley, Christopher David Cook, Steve Gower

Faculty of Informatics - Papers (Archive)

The University of Wollongong (UoW) has received funding for the research and development of a 20 kJ high temperature superconducting magnetic energy storage device (HTS SMES). This SMES will be operated at 25 K in contrast to most existing HTS designs, which operate at 77K. This paper includes a literature review of the current technology for the configuration of the SMES coil and a summary of the work done at UoW to date. Solenoidal and toroidal coils designs are compared to determine which will provide the required level of energy stored for a minimum superconductor and device volume. The design …

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Sag Testing Of Dairy Farm Milking Equipment, V. J. Gosbell, V. Smith, D. A. Robinson, B. S. Perera Dec 2000

Sag Testing Of Dairy Farm Milking Equipment, V. J. Gosbell, V. Smith, D. A. Robinson, B. S. Perera

Faculty of Informatics - Papers (Archive)

Sags are widely reported as being one of the worst power quality problems and are particularly common in rural areas. Automated milking equipment on dairy farms are thus very susceptible to malfunction by sags. In assessing the relative cost/benefits of sag mitigation in the dairy or the supply network it is important to know the dairy equipment immunity level. It is shown how a harmonic generator can be used to determine this information. Testing revealed that the motor contactor was a critical component as it was unable to ride through a 40% sag longer than about 0.5 seconds. The milking …

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On Amicable Sequences And Orthogonal Designs, S. Georgiou, C. Koukouvinos, Jennifer Seberry Dec 2000

On Amicable Sequences And Orthogonal Designs, S. Georgiou, C. Koukouvinos, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

In this paper we give a general theorem which can be used to multiply the length of amicable sequences keeping the amicability property and the type of the sequences. As a consequence we have that if there exist two, four or eight amicable sequences of length m and type (al, a2), (al, a2, a3, a4) or (al, a2, ... , a8) then there exist amicable sequences of length ℓ ≡ 0 (mod m) and of the same type. We also present a theorem that produces a set of 2v amicable sequences from a set of v (not necessary amicable) sequences …

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Codes Identifying Bad Signatures In Batches, J. Pastuszak, J. Pieprzyk, Jennifer Seberry Dec 2000

Codes Identifying Bad Signatures In Batches, J. Pastuszak, J. Pieprzyk, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

The work is concerned with identification of bad signatures in a sequence which is validated using batching. Identification codes (id-codes) are defined and their general properties are investigated. A taxonomy of id-codes is given. The generic construction for a wide range of id-codes is given and its instantiation using mutually orthogonal Latin squares is described. Hierarchical identification is studied for two cases when the identification procedure uses a family of id-codes and when there is a single underlying id-code. Remarks about future research conclude the work.

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Label Switching Using The Ipv6 Address Hierarchy, P. Boustead, Joe F. Chicharo Nov 2000

Label Switching Using The Ipv6 Address Hierarchy, P. Boustead, Joe F. Chicharo

Faculty of Informatics - Papers (Archive)

Current label switching protocols can use routing, address, and address hierarchy information to group flows for cut-throughs that bypass IP forwarding. This paper examines a label switching solution that uses the IP version 6 (IPv6) address structure to classify and cut-through flows based on address hierarchy. The performance of this approach is examined using actual backbone traffic traces with associated hierarchical address information obtained from Internet address registries, routing arbiter databases and route servers. This hierarchical address information is used to map a hierarchical address structure over the packet level trace. We investigate the relationship between aggregation bit-mask size versus …

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Formal Tools For Managing Inconsistency And Change In Re, Aditya K. Ghose Nov 2000

Formal Tools For Managing Inconsistency And Change In Re, Aditya K. Ghose

Faculty of Informatics - Papers (Archive)

Dealing with inconsistencies and change in requirements engineering (RE) is known to be a difficult problem. We propose a formal, integrated approach to inconsistency handling and requirements evolution with a focus on providing automated support. We define a novel representation scheme that is expressive and able to maintain several key semantic distinctions. Based on this scheme, we define a toolkit of inconsistency handling technique. We define a principled process for evolving such specifications, with minimal computational cost and user intervention. Finally, we describe the REFORM system which implements some of these techniques.

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Using Labview To Prototype An Industrial-Quality Real-Time Solution For The Titan Outdoor 4wd Mobile Robot Controller, D. Ratner, Phillip J. Mckerrow Oct 2000

Using Labview To Prototype An Industrial-Quality Real-Time Solution For The Titan Outdoor 4wd Mobile Robot Controller, D. Ratner, Phillip J. Mckerrow

Faculty of Informatics - Papers (Archive)

In the Titan project we applied a new approach to prototyping mobile robots by choosing tools which are commonly used by leading aerospace manufacturers and many other industries. We have gained substantial experience when using the LabVIEW real-time programming environment coupled with the industrial quality data acquisition cards, both are made by National Instruments. The methodology of virtual instruments software tools combined with the graphical programming environment was found to be very efficient for interactive cycles of design and testing, which are at the core of robotics prototyping.

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Establishment Of Typical Harmonic Voltage Levels In Radial Distribution Systems, D. A. Robinson, V. J. Gosbell, B. S. Perera, D. J. Mannix Oct 2000

Establishment Of Typical Harmonic Voltage Levels In Radial Distribution Systems, D. A. Robinson, V. J. Gosbell, B. S. Perera, D. J. Mannix

Faculty of Informatics - Papers (Archive)

This paper reports on a simple method to identify problem areas with relation to harmonic distortion within radial distribution systems at the planning stage. The purpose of the work is to produce a simple method of establishing harmonic distortion levels throughout a study distribution system when only limited system data and load information is available. The preliminary work presented in this paper is aimed at establishing useful planning guidelines for utilities to help with the analysis of harmonics in medium voltage (MV) distribution systems during the design phase. Harmonic analysis during the design of a distribution system is seen as …

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Improved Signal Analysis And Time-Synchronous Reconstruction In Waveform Interpolation Coding, N. R. Chong-White, I. Burnett Sep 2000

Improved Signal Analysis And Time-Synchronous Reconstruction In Waveform Interpolation Coding, N. R. Chong-White, I. Burnett

Faculty of Informatics - Papers (Archive)

This paper presents a waveform-matched waveform interpolation (WMWI) technique which enables improved speech analysis over existing WI coders. In WMWI, an accurate representation of speech evolution is produced by extracting critically-sampled pitch periods of a time-warped, constant pitch residual. The technique also offers waveform-matching capabilities by using an inverse warping process to near-perfectly reconstruct the residual. Here, a pitch track optimisation technique is described which ensures the speech residual can be effectively decomposed and quantised. Also, the pitch parameters required to efficiently quantise and recreate the pitch track, on a period-by-period basis, are identified. This allows time-synchrony between the original …

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Exploiting Simultaneously Masked Linear Prediction In A Wi Speech Coder, Jason Lukasiak, I. Burnett Sep 2000

Exploiting Simultaneously Masked Linear Prediction In A Wi Speech Coder, Jason Lukasiak, I. Burnett

Faculty of Informatics - Papers (Archive)

This paper uses a method of incorporating simultaneous masking into the calculation of a linear predictive filter (SMLPC) as the front end to a 2 kbps waveform interpolation (WI) speech coder. A modification to the masking threshold calculation used in SMLPC is proposed. This modification improves the performance of SMLPC in noise like sections by placing greater emphasis on strongly voiced speech. MOS test results reveal that the modified SMLPC improved the perceptual quality of the WI coder. The improvement is significant for female speakers whilst the quality for male speech is virtually unchanged. This result conflicts with previous results …

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Exploring The Characteristics Of Analytic Decomposition Of Speech Signals, J Lukasiak, I. Burnett Sep 2000

Exploring The Characteristics Of Analytic Decomposition Of Speech Signals, J Lukasiak, I. Burnett

Faculty of Informatics - Papers (Archive)

This paper investigates the properties of analytic transformation of speech into envelope and phase functions. The envelope is shown to evolve slowly with the pitch of the input speech, whilst the phase consists of two components; one evolving slowly with pitch and another that exhibits a more rapid evolution. We investigate decomposing the phase component further using two distinct methods: (a) filtering of the phase in the pitch evolutionary direction and (b) performing a second analytic decomposition of the phase into secondary envelope and phase components. To examine the characteristics of the pitch cycle evolution, the analytic transform is employed …

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Very Low Rate Speech Coding Using Temporal Decomposition And Waveform Interpolation, C. H. Ritz, I. Burnett, J Lukasiak Sep 2000

Very Low Rate Speech Coding Using Temporal Decomposition And Waveform Interpolation, C. H. Ritz, I. Burnett, J Lukasiak

Faculty of Informatics - Papers (Archive)

In very low rate coding the aim is to accurately represent speech characteristics as efficiently as possible. High coding gains for the spectral features can be achieved through the use of temporal decomposition. Waveform interpolation coders accurately represent the excitation using characteristic waveforms (CWs) extracted at a constant rate. In this paper, the two approaches are combined into a very low rate coder operating at around 1 kbps. It is shown that the evolution of the excitation is related to the evolution of the speech spectrum. To minimise bit rates, the transmission of CWs is adapted to the spectral parameter …

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Query Scrambling In Distributed Multidatabase Systems, J. R. Getta Sep 2000

Query Scrambling In Distributed Multidatabase Systems, J. R. Getta

Faculty of Informatics - Papers (Archive)

This work addresses the problem of efficient query processing in multidatabase systems distributed over wide-area networks. The solution unifies the query scrambling and reduction approaches to dynamic optimization of query processing plans at the data integration stage. The paper presents a new data integration algorithm based on query scrambling and the extended reduction technique. The algorithm both reschedules data integration operations and reductions of arguments and permits the concurrent computations of operations and reductions.

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Construction Of Cubic Homogeneous Boolean Bent Functions, Jennifer Seberry, Tianbing Xia, J. Pieprzyk Sep 2000

Construction Of Cubic Homogeneous Boolean Bent Functions, Jennifer Seberry, Tianbing Xia, J. Pieprzyk

Faculty of Informatics - Papers (Archive)

We prove that cubic homogeneous bent functions f : V2n → GF(2) exist for all n ≥ 3 except for n = 4.

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On The Spectrum Of An F-Square, L. Fitina, Jennifer Seberry Sep 2000

On The Spectrum Of An F-Square, L. Fitina, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

Given an F-square of some type F(n; αo, αl, ..., αv-1) what critical set sizes can we obtain for this type? Such a question was considered by Donovan and Howse (1999), in the case of Latin squares. In this note we solve this question for the type F(n;1,n – 1), and also obtain partial results for type F(n; 2,n – 2).

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Normal Numbers Without Measure Theory, R. Nillsen Aug 2000

Normal Numbers Without Measure Theory, R. Nillsen

Faculty of Informatics - Papers (Archive)

Any number can be expanded to the base 10, leading to a sequence of digits between 0 and 9 corresponding to the number. Also, any number can be expanded to the base 2, leading to a sequence of digits, each one being either 0 or 1, corresponding to the number. It is result due to Émile Borel in 1904 that “almost all” numbers have the property that, when expanded to the base 2, each of the digits 0 and 1 appears with an asymptotic frequency of 1/2. That is, if we regard the sequence of digits in the expansion to …

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