17,606 research outputs found
Integrated Optical Fiber Sensor for Simultaneous Monitoring of Temperature, Vibration, and Strain in High Temperature Environment
Important high-temperature parts of an aero-engine, especially the power-related fuel system and rotor system, are directly related to the reliability and service life of the engine. The working environment of these parts is extremely harsh, usually overloaded with high temperature, vibration and strain which are the main factors leading to their failure. Therefore, the simultaneous measurement of high temperature, vibration, and strain is essential to monitor and ensure the safe operation of an aero-engine.
In my thesis work, I have focused on the research and development of two new sensors for fuel and rotor systems of an aero-engine that need to withstand the same high temperature condition, typically at 900 °C or above, but with different requirements for vibration and strain measurement.
Firstly, to meet the demand for high temperature operation, high vibration sensitivity, and high strain resolution in fuel systems, an integrated sensor based on two fiber Bragg gratings in series (Bi-FBG sensor) to simultaneously measure temperature, strain, and vibration is proposed and demonstrated. In this sensor, an L-shaped cantilever is introduced to improve the vibration sensitivity. By converting its free end displacement into a stress effect on the FBG, the sensitivity of the L-shaped cantilever is improved by about 400% compared with that of straight cantilevers. To compensate for the strain sensitivity of FBGs, a spring-beam strain sensitization structure is designed and the sensitivity is increased to 5.44 pm/με by concentrating strain deformation. A novel decoupling method ‘Steps Decoupling and Temperature Compensation (SDTC)’ is proposed to address the interference between temperature, vibration, and strain. A model of sensing characteristics and interference of different parameters is established to achieve accurate signal decoupling. Experimental tests have been performed and demonstrated the good performance of the sensor.
Secondly, a sensor based on cascaded three fiber Fabry-Pérot interferometers in series (Tri-FFPI sensor) for multiparameter measurement is designed and demonstrated for engine rotor systems that require higher vibration frequencies and greater strain measurement requirements. In this sensor, the cascaded-FFPI structure is introduced to ensure high temperature and large strain simultaneous measurement. An FFPI with a cantilever for high vibration frequency measurement is designed with a miniaturized size and its geometric parameters optimization model is established to investigate the influencing factors of sensing characteristics. A cascaded-FFPI preparation method with chemical etching and offset fusion is proposed to maintain the flatness and high reflectivity of FFPIs’ surface, which contributes to the improvement of measurement accuracy. A new high-precision cavity length demodulation method is developed based on vector matching and clustering-competition particle swarm optimization (CCPSO) to improve the demodulation accuracy of cascaded-FFPI cavity lengths. By investigating the correlation relationship between the cascaded-FFPI spectral and multidimensional space, the cavity length demodulation is transformed into a search for the highest correlation value in space, solving the problem that the cavity length demodulation accuracy is limited by the resolution of spectral wavelengths. Different clustering and competition characteristics are designed in CCPSO to reduce the demodulation error by 87.2% compared with the commonly used particle swarm optimization method. Good performance and multiparameter decoupling have been successfully demonstrated in experimental tests
Beam scanning by liquid-crystal biasing in a modified SIW structure
A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium
A Simple and Efficient RSS-AOA Based Localization with Heterogeneous Anchor Nodes
Accurate and reliable localization is crucial for various wireless
communication applications. Numerous studies have proposed accurate
localization methods using hybrid received signal strength (RSS) and angle of
arrival (AOA) measurements. However, these studies typically assume identical
measurement noise distributions for different anchor nodes, which may not
accurately reflect real-world scenarios with varying noise distributions. In
this paper, we propose a simple and efficient localization method based on
hybrid RSS-AOA measurements that accounts for the varying measurement noises of
different nodes. We derive a closed-form estimator for the target location
based on the linear weighted least squares (LWLS) algorithm, with each LWLS
equation weight being the inverse of its residual variance. Due to the unknown
variances of LWLS equation residuals, we employ a two-stage LWLS method for
estimation. The proposed method is computationally efficient, adaptable to
different types of wireless communication systems and environments, and
provides more accurate and reliable localization results compared to existing
RSS-AOA localization techniques. Additionally, we derive the Cramer-Rao Lower
Bound (CRLB) for the RSS-AOA signal sequences used in the proposed method.
Simulation results demonstrate the superiority of the proposed method
Підвищення продуктивності низькоенергетичних безпроводових каналів зв’язку сенсорних телекомунікаційних систем
Шмігель Б. О. Підвищення продуктивності низькоенергетичних
безпроводових каналів зв’язку сенсорних телекомунікаційних систем. –
Кваліфікаційна наукова праця на правах рукопису.
Дисертація на здобуття наукового ступеня доктора філософії за
спеціальністю 172 – Телекомунікації та радіотехніка. – Національний технічний
університет України «Київський політехнічний інститут імені Ігоря
Сікорського», Київ, 2022.
В сучасному світі, життя людини нерозривно пов’язане з обміном
інформацією. Надзвичайно швидкими темпами зростають і вимоги користувачів
до якості, швидкості і безпеки прийому та передачі даних, зберігаючи при цьому
можливість вільного пересування. Задовольняти ці потреби – власне і є ціллю
безпроводових мереж.
Сенсорні мережі займають ключову роль у разі необхідності оперативного
розгортання, мобільності, гнучкості організації мережі і широті можливих
додатків, у багатьох випадках будучи єдиним економічно виправданим
рішенням. Однією із ключових задач забезпечення функціонування сенсорної
мережі є забезпечення надійного та продуктивного передавання інформації в
умовах обмежених ресурсів, зокрема, енергетичних.
Враховуючи розмір сенсора, основною вимогою до сенсорних мереж – є
забезпечення низького енергоспоживання та достовірного прийому.
Автономність роботи залежить від енергії, що споживається вузлами системи.
Для досягнення достовірного зв’язку, мають місце наступні компоненти:
- достатня енергетика (обмежена для сенсорних мереж)
- мала швидкість передачі (обмежена вимогами до сенсорних мереж)
- інструменти для підтримання достовірності (завадостійке
кодування)
Під низькою енергетикою будемо вважати відношення сигнал-шум
h
2 <10. Параметр h
2
є результатом взаємодії трьох незалежних параметрів:
- потужністю сигналу в точці прийому
- спектральної щільності шуму
- швидкості передачі символів
Продуктивність – це фактична швидкість передачі інформації джерела.
Ключ до вирішення задачі отримання максимальної продуктивності лежить у
площині теорії інформації, засновником якої є К. Шеннон.
Інструментом досягнення максимальної продуктивності, як міри
наближення швидкості передачі повідомлень джерела до границі Шеннона є
вибір оптимальних сигнально-кодових конструкцій, які дозволяють передавати
повідомлення з максимально можливою швидкістю і заданою якістю.
Міра наближення продуктивності каналу зв’язку до його пропускної
здатності характеризує інформаційну ефективність системи передачі інформації.
Метою роботи є синтез сигналів, що максимально наближають
продуктивність каналу зв’язку до пропускної здатності при обмежених ресурсах
каналу.
У роботі досліджена актуальна задача підвищення продуктивності
низькоенергетичних безпроводових каналів зв’язку. На відміну від традиційних
систем безпроводового зв’язку, сенсорна мережа включає велику кількість
пристроїв, які повинні передавати інформацію до базової станції. Сенсорні вузли
можуть встановлюватися стаціонарно або мати можливість довільно
пересуватися в певному просторі, тому вони повинні бути автономними,
самоорганізованими та не потребують установки. Область покриття такої мережі
вкрай обмежена і може досягати десятки та сотні метрів. Тому однією з головних
умов до такої мережі – це забезпечення мінімального енергоспоживання та
достовірного прийому в умовах низької енергетики. Основною задачею при
побудови сенсорної мережі є достовірна оцінка енергетичних характеристик
безпроводового каналу зв’язку.
Виходячи із вищесказаного, для розгортання сенсорних мереж актуальним
питанням є ефективне проектування сенсорної мережі: необхідна кількість
пристроїв, їх характеристики, розміщення, енергетичні характеристики каналів,
траси розповсюдження, тощо.
Для вирішення обмежень ресурсу каналу зв’язку, перспективним являється
пошук нових методів передачі інформації, вибору ефективного виду модуляції
та завадостійкого кодування.
Основним інструментом для передачі інформації є сигнали
багатопозиційної маніпуляції. Вибір поєднання типу модуляції і швидкості
завадостійкого коду, забезпечує максимально можливу ефективність,
забезпечуючи відповідну надійність каналу зв’язку. В якості розглянутих
сигналів обрано сигнали багатопозиційної маніпуляції BPSK, QPSK, QAM16.
Високошвидкісні види модуляції не розглядаються, так як сенсорна мережа не
передбачує передачу великих масивів інформації, а також має обмежену енергію
сигналу.
Широкосмугові сигнали є одним з відомих методів для підвищення
завадостійкості каналу, але властивості таких сигналів в умовах обмеженого
ресурсу та енергії сигналу не досліджені. Для визначення найбільш
оптимального способу передачі сигналів в умовах низької енергетики, проведено
дослідження властивостей ШСС на основі моделей оцінки якості каналів зв’язку,
а також порівняння характеристики завадостійкості з ВСС та еквівалентною
енергією сигналу.
Для визначення максимальної продуктивності передачі в безпроводових
низькоенергетичних каналах зв’язку, необхідно дослідити показники
продуктивності використання сигналів заданого виду модуляції та порівняти їх
з широкосмуговими сигналами з різними значеннями бази сигналу B. Виявилося,
що широкосмугові сигнали не забезпечують кращої достовірності в порівнянні з
вузькосмуговими при однаковій потужності випромінювання та способі
обробки.
Класичні формули для оцінки завадостійкості багатопозиційних сигналів
достовірні для високої енергетики, однак для h
2 - 0 не є точними. Тому для
точного визначення точної достовірності прийому для таких умов, пропонується
використання векторно-фазового методу. Векторно-фазовий метод дозволяє
отримати точні розрахунки при будь-якій енергетиці, на відміну від формул
Прокіса, що можуть використовуватись тільки для високої енергетики.
Загальним підсумком дослідження є оцінка продуктивності СКК, яка
дозволяє в каналі з заданими частотно-енергетичними параметрами визначити
ефективність використання визначеного виду модуляції та кодування за
критерієм наближення до границі Шеннона, або максимуму інформаційної
ефективності при заданій достовірності сигналу в точці прийому. Методика
дозволяє оцінити ефективність використання ресурсів каналів зв’язку з
багатопозиційною маніпуляцією та завадостійким кодуванням, а також
кількісно оцінити витрати на реалізацію заходів щодо підвищення достовірності
або продуктивності у вимірі запропонованих показників.
Дослідження питань підвищення продуктивності низькоенергетичних
безпроводових каналів зв’язку забезпечить побудову сенсорних
телекомунікаційних систем для успішного виконання поставлених завдань.
Новими в дисертації є наступні результати:
1. Вдосконалено використання векторно-фазового методу для
визначення завадостійкості багатопозиційних сигналів в умовах
низької енергетики. Класичні формули Прокіса не є точними для
низької енергетики.
2. Вдосконалено методику синтезу сигналу, яка дозволяє знайти
екстремум продуктивності каналу зв’язку та наблизити до його
пропускної здатності – границі Шеннона.
3. Вдосконалено методику оцінки ефективності використання ресурсів
каналу зв’язку.Shmihel B. Increasing the performance of low-power wireless communication
channels of sensor telecommunication systems – Scientific qualification work on the
rights of the manuscript.
Dissertation for the Doctor of Philosophy degree in technical sciences, specialty
172 - Telecommunications and radio engineering. – National Technical University of
Ukraine "Igor Sikorsky Kyiv Polytechnic Institute", Kyiv, 2022.
In the modern world, human life is inextricably connected with the exchange of
information. User requirements for the quality, speed, and security of receiving and
transmitting data are also growing extremely fast while maintaining the possibility of
mobility. Satisfying these needs is the purpose of wireless networks.
Sensor networks play a key role in the need for rapid deployment, mobility,
networking flexibility and a variety of possible applications, in many cases being the
only cost-effective solution. One of the key tasks of functioning in the sensor network
is to ensure reliable and efficient data transmission in conditions of limited resources.
Given the size of the sensor, the main requirement for sensor networks is to
provide low power consumption and reliable reception. Their autonomy depends on
the energy consumed by the nodes of the system.
To achieve the necessary reliability, the following components take place:
- sufficient energy (limited for sensor networks)
- low transmission rate (limited by requirements for sensor networks)
- tools for maintaining reliability (noise-correcting coding)
By low energy, we will consider the signal-to-noise ratio h
2 <10. Parameter h
2
is
the result of the interaction of three independent parameters:
- signal strength at the receiving point
- noise spectral density
- symbol rate
Performance is the actual speed of information transfer of the source. The key to
solving the problem of obtaining maximum performance lies in the plane of the theory
of information, founded by K. Shannon.
The tool for achieving maximum performance, as the approach of the channel
performance to its bandwidth, is the choice of optimal signal-code constructions that
allow messages to be transmitted at the highest possible speed and with a given quality.
The approach of the channel performance to its bandwidth characterizes the
information efficiency of the information transmission system.
The research aims to synthesize signals that bring the channel performance as
close as possible to the throughput with limited channel resources.
The research contains the actual problem of increasing productivity in lowenergy wireless communication channels. Unlike traditional wireless communication
systems, a sensor network includes many devices that should transmit information to a
base station. Sensor nodes can be placed permanently or be able to move in a certain
space, so they must be autonomous, self-organized and do not require installation. The
coverage area of such a network is extremely limited and can reach tens and hundreds
of meters. The main task in building a sensor network is a reliable assessment of the
energy characteristics of a wireless communication channel.
Based on the foregoing, for the deployment of sensor networks, an important
issue is the effective design of a sensor network: the required number of devices, their
characteristics, placement, energy characteristics of channels, propagation paths, etc.
To solve the limitations of the communication channel, it is promising to search
for new methods for transmitting information, choosing an effective type of modulation
and error-correcting coding.
The basic tool for transmitting information is the signals of multi-position
modulation. The choice of a combination of modulation type and error code rate
provides the highest possible efficiency while providing adequate reliability to the
communication channel. The multi-position modulation signals BPSK, QPSK and
QAM16 were chosen as the considered signals. High-speed modulation types are not
considered, since the sensor network does not involve the transmission of large
amounts of information and has limited signal energy.
Broadband signals are one of the well-known methods for improving the noise
immunity of a channel, but the properties of such signals under conditions of limited
resources and signal energy have not been studied. To determine the most optimal
method of signal transmission in low energy conditions, research on the properties of
the narrowband signals was carried out based on models for assessing the quality of
communication channels and comparing the noise immunity characteristic of wideband
signals with equivalent signal energy.
To determine the maximum transmission performance in wireless low-energy
communication channels, it is necessary to investigate the performance indicators of a
given type of modulation signals and compare them with wideband signals with
different values of the signal base B. It turned out that wideband signals do not provide
better reliability compared to narrowband signals with the same transmission power
and processing method.
The classical formulas for estimating the noise immunity of multi-position
signals are accurate for high energy, but for h2 - 0 they are not accurate. Therefore, to
determine the exact reliability for such conditions, it is proposed to use the vectorphase method. The vector-phase method helps to obtain accurate calculations for any
energy, in contrast to the Prokis formulas, which can only be used for high energy.
The overall result of the research is performance evaluation of signal-code
construction, that allows determining the efficiency of using a certain type of
modulation and coding in a channel with given frequency and energy parameters
according to the criterion of maximum approach to the Shannon bound, or the
maximum of information efficiency for given signal reliability. Using this technique,
it possible to evaluate the efficiency of using the resources of communication channels
with multi-position modulation and error-correcting coding and calculate the costs of
implementing measures to improve the reliability or performance of the proposed
indicators.
Research on improving the performance of low-energy wireless communication
channels will help to build sensor telecommunication systems for the successful
completion of tasks.
Research contains the following new results:
1. The use of the vector-phase method for determining the noise immunity
of multi-position signals under low energy conditions has been improved.
The classic Prokis formulas are not accurate for low energy.
2. The method of signal synthesis has been improved, which makes it is
possible to find the extremum of the communication channel performance
and bring it closer to its capacity – the Shannon bounds.
3. The methodology for evaluating the effectiveness of the communication
channel resources has been improved
Recommended from our members
Distributed Fusion Filtering for Nonlinear Time-Varying Systems Over Amplify-and-Forward Relay Networks: An H∞ Quantized Framework
National Natural Science Foundation of China (Grant Number: 61973102, 61933007 and U22A2044);
China Postdoctoral Science Foundation (Grant Number: 2022M710683);
Jiangsu Funding Program for Excellent Postdoctoral Talent of China (Grant Number: 2022ZB128);
Royal Society of the U.K., the Alexander von Humboldt Foundation of Germany
Sensing User's Activity, Channel, and Location with Near-Field Extra-Large-Scale MIMO
This paper proposes a grant-free massive access scheme based on the
millimeter wave (mmWave) extra-large-scale multiple-input multiple-output
(XL-MIMO) to support massive Internet-of-Things (IoT) devices with low latency,
high data rate, and high localization accuracy in the upcoming sixth-generation
(6G) networks. The XL-MIMO consists of multiple antenna subarrays that are
widely spaced over the service area to ensure line-of-sight (LoS)
transmissions. First, we establish the XL-MIMO-based massive access model
considering the near-field spatial non-stationary (SNS) property. Then, by
exploiting the block sparsity of subarrays and the SNS property, we propose a
structured block orthogonal matching pursuit algorithm for efficient active
user detection (AUD) and channel estimation (CE). Furthermore, different
sensing matrices are applied in different pilot subcarriers for exploiting the
diversity gains. Additionally, a multi-subarray collaborative localization
algorithm is designed for localization. In particular, the angle of arrival
(AoA) and time difference of arrival (TDoA) of the LoS links between active
users and related subarrays are extracted from the estimated XL-MIMO channels,
and then the coordinates of active users are acquired by jointly utilizing the
AoAs and TDoAs. Simulation results show that the proposed algorithms outperform
existing algorithms in terms of AUD and CE performance and can achieve
centimeter-level localization accuracy.Comment: Submitted to IEEE Transactions on Communications, Major revision.
Codes will be open to all on https://gaozhen16.github.io/ soo
Stretch sensors for measuring knee kinematics in sports
The popularity of wearable technology in sport has increased, due to its ability to provide unobtrusive
monitoring of athletes. This technology has been used to objectively measure kinetic and kinematic
variables, with the aim of preventing injury, maximising athletic performance and classifying the skill
level of athletes, all of which can influence training and coaching practices. Wearable technologies
overcome the limitations of motion capture systems which are limited in their capture volume, enabling
the collection of data in-field, during training and competition. Inertial sensors are a common form of
technology used in these environments however, their high-cost and complex calibration due to multiple
sensor integration can make them prohibitive for widespread use.
This thesis focuses on the development of a strain sensor that can be used to measure knee range
of motion in sports, specifically rowing and cycling, as a potential low-cost, lightweight alternative to
inertial sensors which can also be integrated into clothing, making them more discreet. A systematic
review highlighted the lack of alternate technologies to inertial sensors such as strain sensors, as well
as the limited use of wearable technologies in both rowing and cycling.
Strain sensors were fabricated from a carbon nanotube-natural rubber composite using solvent exchange techniques and employed a piezoresistive sensing mechanism. These were then characterised
using mechanical testing, to determine their electrical properties under cyclical strain. The strain sensors displayed hysteretic behaviour, but were durable, withstanding over 4500 strain cycles. Statistical
analysis indicated that over 60% of the tests conducted had good intra-test variability with regards to
the resistance response range in each strain cycle and sensor response deviating by less than 10% at
strain rates below 100 mm/min and less than 20% at a strain rate of 350 mm/min.
These sensors were integrated into a wearable sensor system and tested on rowing and cycling
cohorts consisting of ten athletes each, to assess the translational use of the strain sensor. This
preliminary testing indicated that strain sensors were able to track the motion of the knee during the
rowing stroke and cycling pedalling motion, when compared to the output of a motion capture system.
Perspectives of participants on the wearable system were collected, which indicated their desire for a
system that they could use in their sport, and they considered the translation of this system for real-life
use with further development to improve comfort of the system and consistency of the sensor response.
The strain sensors developed in this project, when integrated into a wearable sensor system, have the
potential to provide an unobtrusive method of measuring knee kinematics, helping athletes, coaches
and other support staff make technical changes that can reduce injury risk and improve performance.Open Acces
Reinforcement Learning Empowered Unmanned Aerial Vehicle Assisted Internet of Things Networks
This thesis aims towards performance enhancement for unmanned aerial vehicles (UAVs) assisted internet of things network (IoT). In this realm, novel reinforcement learning (RL) frameworks have been proposed for solving intricate joint optimisation scenarios. These scenarios include, uplink, downlink and combined. The multi-access technique utilised is non-orthogonal multiple access (NOMA), as key enabler in this regime. The outcomes of this research entail, enhancement in key performance metrics, such as sum-rate, energy efficiency and consequent reduction in outage. For the scenarios involving uplink transmissions by IoT devices, adaptive and tandem rein forcement learning frameworks have been developed. The aim is to maximise capacity over fixed UAV trajectory. The adaptive framework is utilised in a scenario wherein channel suitability is ascertained for uplink transmissions utilising a fixed clustering regime in NOMA. Tandem framework is utilised in a scenario wherein multiple-channel resource suitability is ascertained along with, power allocation, dynamic clustering and IoT node associations to NOMA clusters and channels. In scenarios involving downlink transmission to IoT devices, an ensemble RL (ERL) frame work is proposed for sum-rate enhancement over fixed UAV trajectory. For dynamic UAV trajec tory, hybrid decision framework (HDF) is proposed for energy efficiency optimisation. Downlink transmission power and bandwidth is managed for NOMA transmissions over fixed and dynamic UAV trajectories, facilitating IoT networks. In UAV enabled relaying scenario, for control system plants and their respective remotely deployed sensors, a head start reinforcement learning framework based on deep learning is de veloped and implemented. NOMA is invoked, in both uplink and downlink transmissions for IoT network. Dynamic NOMA clustering, power management and nodes association along with UAV height control is jointly managed. The primary aim is the, enhancement of net sum-rate and its subsequent manifestation in facilitating the IoT assisted use case. The simulation results relating to aforesaid scenarios indicate, enhanced sum-rate, energy efficiency and reduced outage for UAV-assisted IoT networks. The proposed RL frameworks surpass in performance in comparison to existing frameworks as benchmarks for the same sce narios. The simulation platforms utilised are MATLAB and Python, for network modeling, RL framework design and validation
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Effects of Particle Swarm Optimisation on a Hybrid Load Balancing Approach for Resource Optimisation in Internet of Things
This article belongs to the Special Issue Emerging Machine Learning Techniques in Industrial Internet of ThingsCopyright © 2023 by the authors. The internet of things, a collection of diversified distributed nodes, implies a varying choice of activities ranging from sleep monitoring and tracking of activities, to more complex activities such as data analytics and management. With an increase in scale comes even greater complexities, leading to significant challenges such as excess energy dissipation, which can lead to a decrease in IoT devices’ lifespan. Internet of things’ (IoT) multiple variable activities and ample data management greatly influence devices’ lifespan, making resource optimisation a necessity. Existing methods with respect to aspects of resource management and optimisation are limited in their concern of devices energy dissipation. This paper therefore proposes a decentralised approach, which contains an amalgamation of efficient clustering techniques, edge computing paradigms, and a hybrid algorithm, targeted at curbing resource optimisation problems and life span issues associated with IoT devices. The decentralised topology aimed at the resource optimisation of IoT places equal importance on resource allocation and resource scheduling, as opposed to existing methods, by incorporating aspects of the static (round robin), dynamic (resource-based), and clustering (particle swarm optimisation) algorithms, to provide a solid foundation for an optimised and secure IoT. The simulation constructs five test-case scenarios and uses performance indicators to evaluate the effects the proposed model has on resource optimisation in IoT. The simulation results indicate the superiority of the PSOR2B to the ant colony, the current centralised optimisation approach, LEACH, and C-LBCA.This research received no external funding
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