<!DOCTYPE article
PUBLIC "-//NLM//DTD JATS (Z39.96) Journal Publishing DTD v1.4 20190208//EN"
       "JATS-journalpublishing1.dtd">
<article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" article-type="research-article" dtd-version="1.4" xml:lang="en">
 <front>
  <journal-meta>
   <journal-id journal-id-type="publisher-id">Bulletin of scientific research results</journal-id>
   <journal-title-group>
    <journal-title xml:lang="en">Bulletin of scientific research results</journal-title>
    <trans-title-group xml:lang="ru">
     <trans-title>Бюллетень результатов научных исследований</trans-title>
    </trans-title-group>
   </journal-title-group>
   <issn publication-format="online">2223-9987</issn>
  </journal-meta>
  <article-meta>
   <article-id pub-id-type="publisher-id">110184</article-id>
   <article-id pub-id-type="doi">10.20295/2223-9987-2025-4-167-177</article-id>
   <article-categories>
    <subj-group subj-group-type="toc-heading" xml:lang="ru">
     <subject>Общетехнические задачи и пути их решения</subject>
    </subj-group>
    <subj-group subj-group-type="toc-heading" xml:lang="en">
     <subject>GENERAL TECHNICAL PROBLEMS AND SOLUTION APPROACH</subject>
    </subj-group>
    <subj-group>
     <subject>Общетехнические задачи и пути их решения</subject>
    </subj-group>
   </article-categories>
   <title-group>
    <article-title xml:lang="en">The Influence of Laser Hardening on the Metallographic and Tribotechnical Properties of Class 55 Steel Used in Diesel Locomotive Camshafts</article-title>
    <trans-title-group xml:lang="ru">
     <trans-title>Влияние лазерной закалки на металлографические и триботехнические характеристики стали 55 распределительного вала дизеля тепловоза</trans-title>
    </trans-title-group>
   </title-group>
   <contrib-group content-type="authors">
    <contrib contrib-type="author">
     <contrib-id contrib-id-type="orcid">https://orcid.org/0000-0001-9278-6925</contrib-id>
     <name-alternatives>
      <name xml:lang="ru">
       <surname>Бирюков</surname>
       <given-names>Владимир Павлович</given-names>
      </name>
      <name xml:lang="en">
       <surname>Biryukov</surname>
       <given-names>Vladimir Pavlovich</given-names>
      </name>
     </name-alternatives>
     <email>nfo@imash.ru</email>
     <bio xml:lang="ru">
      <p>кандидат технических наук;</p>
     </bio>
     <bio xml:lang="en">
      <p>candidate of technical sciences;</p>
     </bio>
     <xref ref-type="aff" rid="aff-1"/>
    </contrib>
    <contrib contrib-type="author">
     <name-alternatives>
      <name xml:lang="ru">
       <surname>Миряха</surname>
       <given-names>Андрей Николаевич</given-names>
      </name>
      <name xml:lang="en">
       <surname>Miryaha</surname>
       <given-names>Andrey Nikolaevich</given-names>
      </name>
     </name-alternatives>
     <email>miryahaan@yandex.ru</email>
     <xref ref-type="aff" rid="aff-2"/>
    </contrib>
    <contrib contrib-type="author">
     <contrib-id contrib-id-type="orcid">https://orcid.org/0000-0001-9721-2525</contrib-id>
     <name-alternatives>
      <name xml:lang="ru">
       <surname>Якубовский</surname>
       <given-names>Антон Алексеевич</given-names>
      </name>
      <name xml:lang="en">
       <surname>Yakubovsky</surname>
       <given-names>Anton Alekseevich</given-names>
      </name>
     </name-alternatives>
     <email>anton.at444@gmail.com</email>
     <xref ref-type="aff" rid="aff-3"/>
    </contrib>
    <contrib contrib-type="author">
     <contrib-id contrib-id-type="orcid">https://orcid.org/0000-0003-1716-2180</contrib-id>
     <name-alternatives>
      <name xml:lang="ru">
       <surname>Кулаков</surname>
       <given-names>Олег Игоревич</given-names>
      </name>
      <name xml:lang="en">
       <surname>Kulakov</surname>
       <given-names>Oleg Igorevich</given-names>
      </name>
     </name-alternatives>
     <email>kulakov@imash.ru</email>
     <xref ref-type="aff" rid="aff-4"/>
    </contrib>
    <contrib contrib-type="author">
     <name-alternatives>
      <name xml:lang="ru">
       <surname>Горюнов</surname>
       <given-names>Ярослав Алексеевич</given-names>
      </name>
      <name xml:lang="en">
       <surname>Goryunov</surname>
       <given-names>Yaroslav Alekseevich</given-names>
      </name>
     </name-alternatives>
     <email>yarosgorun22112000@gmail.com</email>
     <xref ref-type="aff" rid="aff-5"/>
    </contrib>
   </contrib-group>
   <aff-alternatives id="aff-1">
    <aff>
     <institution xml:lang="ru">Институт машиноведения им. А.А. Благонравова Российской академии наук (ИМАШ РАН)</institution>
     <city>Москва</city>
     <country>Россия</country>
    </aff>
    <aff>
     <institution xml:lang="en">Mechanical Engineering Research Institute of the Russian Academy of Sciences</institution>
     <city>Moscow</city>
     <country>Russian Federation</country>
    </aff>
   </aff-alternatives>
   <aff-alternatives id="aff-2">
    <aff>
     <institution xml:lang="ru">ООО НПП «ИНЖЕКТ»</institution>
     <country>Россия</country>
    </aff>
    <aff>
     <institution xml:lang="en">INJECT RME LLC</institution>
     <country>Russian Federation</country>
    </aff>
   </aff-alternatives>
   <aff-alternatives id="aff-3">
    <aff>
     <institution xml:lang="ru">Институт машиноведения им. А.А. Благонравова Российской академии наук (ИМАШ РАН)</institution>
     <city>Москва</city>
     <country>Россия</country>
    </aff>
    <aff>
     <institution xml:lang="en">Mechanical Engineering Research Institute of the Russian Academy of Sciences</institution>
     <city>Moscow</city>
     <country>Russian Federation</country>
    </aff>
   </aff-alternatives>
   <aff-alternatives id="aff-4">
    <aff>
     <institution xml:lang="ru">Институт машиноведения им. А.А. Благонравова Российской академии наук (ИМАШ РАН)</institution>
     <city>Москва</city>
     <country>Россия</country>
    </aff>
    <aff>
     <institution xml:lang="en">Mechanical Engineering Research Institute of the Russian Academy of Sciences</institution>
     <city>Moscow</city>
     <country>Russian Federation</country>
    </aff>
   </aff-alternatives>
   <aff-alternatives id="aff-5">
    <aff>
     <institution xml:lang="ru">Институт машиноведения им. А.А. Благонравова Российской академии наук (ИМАШ РАН)</institution>
     <country>Россия</country>
    </aff>
    <aff>
     <institution xml:lang="en">Mechanical Engineering Research Institute of the Russian Academy of Sciences</institution>
     <country>Russian Federation</country>
    </aff>
   </aff-alternatives>
   <pub-date publication-format="print" date-type="pub" iso-8601-date="2025-12-15T14:51:17+03:00">
    <day>15</day>
    <month>12</month>
    <year>2025</year>
   </pub-date>
   <pub-date publication-format="electronic" date-type="pub" iso-8601-date="2025-12-15T14:51:17+03:00">
    <day>15</day>
    <month>12</month>
    <year>2025</year>
   </pub-date>
   <volume>2025</volume>
   <issue>4</issue>
   <fpage>167</fpage>
   <lpage>177</lpage>
   <history>
    <date date-type="received" iso-8601-date="2025-06-15T00:00:00+03:00">
     <day>15</day>
     <month>06</month>
     <year>2025</year>
    </date>
    <date date-type="accepted" iso-8601-date="2025-07-28T00:00:00+03:00">
     <day>28</day>
     <month>07</month>
     <year>2025</year>
    </date>
   </history>
   <self-uri xlink:href="https://itt-pgups.ru/en/nauka/article/110184/view">https://itt-pgups.ru/en/nauka/article/110184/view</self-uri>
   <abstract xml:lang="ru">
    <p>Цель: Определение влияния режимов обработки прямоугольным пятном полупроводникового лазера на изменения глубины зон закалки стали 55, микротвердости, микроструктуры, триботехнических свойств при трении по закаленной стали 45 при подаче масла капельным способом. Методы: Лазерное термоупрочнение поверхности трения образцов стали 55 было выполнено прямоугольным пятном полупроводникового лазера. Определение металлографических свойств зон лазерного упрочнения было выполнено с использованием оптической системы МС-1000, цифрового микроскопа АМ-419, микротвердомера ПМТ-3 с цифровой камерой МС-8,3С при нагрузке 0,98 Н. В качестве эталона был выбран образец стали 18ХГ после цементации с твердостью 56−59 HRC. Триботехнические испытания по схеме: «плоский прямоугольный образец стали 55 — кольцевая поверхность оправки контробразца из стали 45», установленной в патрон шпинделя машины трения. Измерение моментов трения и усилия нагружения образцов было выполнено с применением тензодатчиков в непрерывном режиме с отображением данных на дисплее персонального компьютера. Также на машине трения установлен бесконтактный индуктивный датчик частоты вращения шпинделя с выводом на тахометр, закрепленный на верхней крышке машины. Результаты: Исследования показали, что при лазерном упрочнении микроструктура зон закалки содержит мелкодисперсные иглы мартенсита. Твердость этих зон составляет 7470−10 980 МПа. Давление заедания при различных скоростях скольжения контробразца из стали 45 в 1,5−1,6 раза, а износостойкость — в 2 раза выше, чем у образцов стали 18ХГТ после цементации. При этом коэффициенты трения значительно ниже. Практическая значимость: Технологический процесс изготовления распределительного вала дизеля из стали 18ХГТ с последующей цементацией может быть заменен на лазерную закалку распределительного вала из стали 55 прямоугольным лучом полупроводникового лазера. При этом значительно снижается энергоемкость и повышается экологическая чистота производственного процесса.</p>
   </abstract>
   <trans-abstract xml:lang="en">
    <p>Purpose: This research investigates the effect of semiconductor laser processing parameters, specifically with a rectangular spot, on the hardening depth, microhardness, microstructure, and tribotechnical properties of Class 55 steel. These properties were evaluated under conditions of friction against hardened Class 45 steel, utilizing a drip oil lubrication system. Methods: Laser thermal hardening of the friction surface of Class 55 steel samples was performed using a semiconductor laser with a rectangular spot. Metallographic analysis of the laser-hardened zones was conducted using an MS1000 optical system, an AM419 digital microscope, and a PMT-3 microhardness tester. The microhardness measurements were performed with a load of 0.98 N and recorded using an MS-8.3 S digital camera. The reference sample selected for this study was Class 18XG steel after undergoing carburizing treatment, which demonstrated a hardness level of 56-59 HRC. Tribotechnical tests were carried out according to the scheme that included a flat rectangular block of Class 55 steel and a ring-shaped counter-plate composed of steel 45, both of which were in the spindle chuck of a friction-testing machine. Continuous measurements of the friction moments and the applied load on the samples were obtained using strain gauges, with the data being displayed on a computer screen in real time. Furthermore, a non-contact inductive sensor was installed on the friction machine to measure the spindle rotational frequency, with the output directed to a tachometer affixed to the top cover of the machine. Results: The study have shown that following laser hardening, the microstructure of the hardened zones contains finedisperse martensite needles. The hardness within these zones varies from 7470 to 10,980 MPa. The adhesive wear pressure at different sliding speeds of the 45 steel counter-plate is 1.5-1.6 times greater, and the wear resistance is twice as high compared to the samples of 18XGT after carburizing. Concurrently, the friction coefficients are significantly lower. Practical significance: The technological process for manufacturing a diesel camshaft made of 18XGT  steel with subsequent carburizing can be replaced by laser hardening of the camshaft made from Class 55 steel using a semiconductor laser with a rectangular beam. This alternative approach significantly reduces energy consumption and enhances the ecological sustainability of the production process.</p>
   </trans-abstract>
   <kwd-group xml:lang="ru">
    <kwd>Лазерное упрочнение</kwd>
    <kwd>микротвердость</kwd>
    <kwd>микроструктура</kwd>
    <kwd>коэффициент трения</kwd>
    <kwd>интенсивность изнашивания</kwd>
    <kwd>износостойкость</kwd>
   </kwd-group>
   <kwd-group xml:lang="en">
    <kwd>Laser hardening</kwd>
    <kwd>microhardness</kwd>
    <kwd>microstructure</kwd>
    <kwd>coefficient of friction</kwd>
    <kwd>wear rate</kwd>
    <kwd>wear resistance</kwd>
   </kwd-group>
  </article-meta>
 </front>
 <body>
  <p></p>
 </body>
 <back>
  <ref-list>
   <ref id="B1">
    <label>1.</label>
    <citation-alternatives>
     <mixed-citation xml:lang="ru">Guarino S. High Power Diode Laser (HPDL) surface hardening of low carbon steel: Fatigue life improvement analysis / S. Guarino, M. Barletta, A. Afilal // Journal of Manufacturing Processes. — 2017, — Vol. 28. — Pp. 266–271.</mixed-citation>
     <mixed-citation xml:lang="en">Guarino S. High Power Diode Laser (HPDL) surface hardening of low carbon steel: Fatigue life improvement analysis / S. Guarino, M. Barletta, A. Afilal // Journal of Manufacturing Processes. — 2017, — Vol. 28. — Pp. 266–271.</mixed-citation>
    </citation-alternatives>
   </ref>
   <ref id="B2">
    <label>2.</label>
    <citation-alternatives>
     <mixed-citation xml:lang="ru">Nemova G. Brief Review of Recent Developments in Fiber Lasers // Applied Sciences. — 2024. — Vol. 14. — P. 2323.</mixed-citation>
     <mixed-citation xml:lang="en">Nemova G. Brief Review of Recent Developments in Fiber Lasers // Applied Sciences. — 2024. — Vol. 14. — P. 2323.</mixed-citation>
    </citation-alternatives>
   </ref>
   <ref id="B3">
    <label>3.</label>
    <citation-alternatives>
     <mixed-citation xml:lang="ru">Kennedy E. A review of the use of high-power diode lasers in surface hardening / E. Kennedy, G. Byrne, D.N. Collins // Journal of Materials Processing Technology. — 2004. — Vol. 155–156. — Pp. 1855–1860.</mixed-citation>
     <mixed-citation xml:lang="en">Kennedy E. A review of the use of high-power diode lasers in surface hardening / E. Kennedy, G. Byrne, D.N. Collins // Journal of Materials Processing Technology. — 2004. — Vol. 155–156. — Pp. 1855–1860.</mixed-citation>
    </citation-alternatives>
   </ref>
   <ref id="B4">
    <label>4.</label>
    <citation-alternatives>
     <mixed-citation xml:lang="ru">Tan C. Y. Influence of laser parameters on microstructures and surface properties in laser surface modification of biomedical magnesium alloys / C. Y. Tan, C. Wen, H. Q. Ang // Journal of Magnesium and Alloys. — 2024. — Vol. 12. — Pp. 72–97.</mixed-citation>
     <mixed-citation xml:lang="en">Tan C. Y. Influence of laser parameters on microstructures and surface properties in laser surface modification of biomedical magnesium alloys / C. Y. Tan, C. Wen, H. Q. Ang // Journal of Magnesium and Alloys. — 2024. — Vol. 12. — Pp. 72–97.</mixed-citation>
    </citation-alternatives>
   </ref>
   <ref id="B5">
    <label>5.</label>
    <citation-alternatives>
     <mixed-citation xml:lang="ru">Tan S. Progress and prospects in laser additive manufacturing of key materials for aircraft engines / S. Tan, F. Weng, S. Sui, Y. Chew et al. // International Journal of Machine Tools and Manufacture. — 2021. — Vol. 170. — P. 103804.</mixed-citation>
     <mixed-citation xml:lang="en">Tan S. Progress and prospects in laser additive manufacturing of key materials for aircraft engines / S. Tan, F. Weng, S. Sui, Y. Chew et al. // International Journal of Machine Tools and Manufacture. — 2021. — Vol. 170. — P. 103804.</mixed-citation>
    </citation-alternatives>
   </ref>
   <ref id="B6">
    <label>6.</label>
    <citation-alternatives>
     <mixed-citation xml:lang="ru">Homberg D. PID control of laser surface hardening of steel / D. Homberg, W. Weiss // IEEE Transactions on Control Systems Technology. — 2006. — Vol. 14. — Pp. 896–904.</mixed-citation>
     <mixed-citation xml:lang="en">Homberg D. PID control of laser surface hardening of steel / D. Homberg, W. Weiss // IEEE Transactions on Control Systems Technology. — 2006. — Vol. 14. — Pp. 896–904.</mixed-citation>
    </citation-alternatives>
   </ref>
   <ref id="B7">
    <label>7.</label>
    <citation-alternatives>
     <mixed-citation xml:lang="ru">Lasota I. Laser surface hardening of engine camshaft cams / I. Lasota, V. Protsenko,  A. Matyushkin, M. Kuznetsov et al. // Materials Today: Proceedings. — 2020. — Vol. 30. — Pp. 478–482.</mixed-citation>
     <mixed-citation xml:lang="en">Lasota I. Laser surface hardening of engine camshaft cams / I. Lasota, V. Protsenko,  A. Matyushkin, M. Kuznetsov et al. // Materials Today: Proceedings. — 2020. — Vol. 30. — Pp. 478–482.</mixed-citation>
    </citation-alternatives>
   </ref>
   <ref id="B8">
    <label>8.</label>
    <citation-alternatives>
     <mixed-citation xml:lang="ru">Patwa R. Predictive modeling of laser hardening of AISI5150H steels / Patwa R., Shin Y. C. // International Journal of Machine Tools and Manufacture. — 2007, — Vol. 47. — Pp. 307–320.</mixed-citation>
     <mixed-citation xml:lang="en">Patwa R. Predictive modeling of laser hardening of AISI5150H steels / Patwa R., Shin Y. C. // International Journal of Machine Tools and Manufacture. — 2007, — Vol. 47. — Pp. 307–320.</mixed-citation>
    </citation-alternatives>
   </ref>
   <ref id="B9">
    <label>9.</label>
    <citation-alternatives>
     <mixed-citation xml:lang="ru">Maharjan N. Comparative study of laser surface hardening of 50CrMo4 steel using continuouswave laser and pulsed lasers with ms, ns, ps and fs pulse duration / N. Maharjan, W. Zhou, Y. Zhou, Y. Guan et al. // Surface and Coatings Technology. — 2019 — Vol. 366. — Pp. 311–320.</mixed-citation>
     <mixed-citation xml:lang="en">Maharjan N. Comparative study of laser surface hardening of 50CrMo4 steel using continuouswave laser and pulsed lasers with ms, ns, ps and fs pulse duration / N. Maharjan, W. Zhou, Y. Zhou, Y. Guan et al. // Surface and Coatings Technology. — 2019 — Vol. 366. — Pp. 311–320.</mixed-citation>
    </citation-alternatives>
   </ref>
   <ref id="B10">
    <label>10.</label>
    <citation-alternatives>
     <mixed-citation xml:lang="ru">Maharjan N. Direct laser hardening of AISI 1020 steel under controlled gas atmosphere / N. Maharjan, W. Zhou, N. Wu // Surface and Coatings Technology. — 2020. — Vol. 385. — P. 125399. 11. Frerichs F. Process signature for laser hardening / F. Frerichs, Y. Lu, T. Lübben, T. Radel // Metals. — 2021. — Vol.</mixed-citation>
     <mixed-citation xml:lang="en">Maharjan N. Direct laser hardening of AISI 1020 steel under controlled gas atmosphere / N. Maharjan, W. Zhou, N. Wu // Surface and Coatings Technology. — 2020. — Vol. 385. — P. 125399. 11. Frerichs F. Process signature for laser hardening / F. Frerichs, Y. Lu, T. Lübben, T. Radel // Metals. — 2021. — Vol.</mixed-citation>
    </citation-alternatives>
   </ref>
   <ref id="B11">
    <label>11.</label>
    <citation-alternatives>
     <mixed-citation xml:lang="ru">— P. 465.</mixed-citation>
     <mixed-citation xml:lang="en">— P. 465.</mixed-citation>
    </citation-alternatives>
   </ref>
   <ref id="B12">
    <label>12.</label>
    <citation-alternatives>
     <mixed-citation xml:lang="ru">Naprimerova E. D. Impact of laser hardening on surface properties of billets from structural materials / E. D. Naprimerova, K. Yu. Pashkeev, E. V. Yurasova, K. S. Litvinyuk et al. // Metallurgist. — 2024. — Iss. 11. — Pp. 89–93.</mixed-citation>
     <mixed-citation xml:lang="en">Naprimerova E. D. Impact of laser hardening on surface properties of billets from structural materials / E. D. Naprimerova, K. Yu. Pashkeev, E. V. Yurasova, K. S. Litvinyuk et al. // Metallurgist. — 2024. — Iss. 11. — Pp. 89–93.</mixed-citation>
    </citation-alternatives>
   </ref>
   <ref id="B13">
    <label>13.</label>
    <citation-alternatives>
     <mixed-citation xml:lang="ru">Patwa R. Predictive modeling of laser hardening of AISI5150H steels / R. Patwa, Y. C. Shin // International Journal of Machine Tools and Manufacture. — 2007. — Vol. 47. — Pp. 307–320.</mixed-citation>
     <mixed-citation xml:lang="en">Patwa R. Predictive modeling of laser hardening of AISI5150H steels / R. Patwa, Y. C. Shin // International Journal of Machine Tools and Manufacture. — 2007. — Vol. 47. — Pp. 307–320.</mixed-citation>
    </citation-alternatives>
   </ref>
   <ref id="B14">
    <label>14.</label>
    <citation-alternatives>
     <mixed-citation xml:lang="ru">Zhang B. Applications of laser surface treatment in gears: a review / B. Zhang, L. Sun, N. Zhao, J. Li // Journal of Materials Engineering and Performance. — 2024. — Vol. 34. — Pp. 1–35. 2025/4 Bulletin оf Scientific Research ResultsОбщетехнические﻿задачи﻿и﻿пути﻿их﻿решения﻿ 175</mixed-citation>
     <mixed-citation xml:lang="en">Zhang B. Applications of laser surface treatment in gears: a review / B. Zhang, L. Sun, N. Zhao, J. Li // Journal of Materials Engineering and Performance. — 2024. — Vol. 34. — Pp. 1–35. 2025/4 Bulletin of Scientific Research ResultsObschetehnicheskie﻿zadachi﻿i﻿puti﻿ih﻿resheniya﻿ 175</mixed-citation>
    </citation-alternatives>
   </ref>
   <ref id="B15">
    <label>15.</label>
    <citation-alternatives>
     <mixed-citation xml:lang="ru">Komanduri R. Thermal analysis of the laser surface transformation hardening process /  R. Komanduri, Z. Hou // International Journal of Heat and Mass Transfer. — 2001. — Vol. 44. —  Pp. 2845–2862.</mixed-citation>
     <mixed-citation xml:lang="en">Komanduri R. Thermal analysis of the laser surface transformation hardening process /  R. Komanduri, Z. Hou // International Journal of Heat and Mass Transfer. — 2001. — Vol. 44. —  Pp. 2845–2862.</mixed-citation>
    </citation-alternatives>
   </ref>
   <ref id="B16">
    <label>16.</label>
    <citation-alternatives>
     <mixed-citation xml:lang="ru">Куксенова Л. И. Методы испытаний на трение и износ: монография / Л. И. Куксенова, В. Г. Лаптева, А. Г. Колмаков, Л. М. Рыбакова — М.: Интермет Инжиниринг, 2001. — 152 с. 17. Патент №  2683600 Российская Федерация, МПК G01N 3/56. Способ измерения износа металлических материалов и покрытий / В. П. Бирюков, Э. Г. Гудушаури, А. А. Фишков. — Заявл. 23.05.2018; опубл. 29.03.2019. — Бюл. №  10.</mixed-citation>
     <mixed-citation xml:lang="en">Kuksenova L. I. Metody ispytaniy na trenie i iznos: monografiya / L. I. Kuksenova, V. G. Lapteva, A. G. Kolmakov, L. M. Rybakova — M.: Intermet Inzhiniring, 2001. — 152 s. 17. Patent №  2683600 Rossiyskaya Federaciya, MPK G01N 3/56. Sposob izmereniya iznosa metallicheskih materialov i pokrytiy / V. P. Biryukov, E. G. Gudushauri, A. A. Fishkov. — Zayavl. 23.05.2018; opubl. 29.03.2019. — Byul. №  10.</mixed-citation>
    </citation-alternatives>
   </ref>
  </ref-list>
 </back>
</article>
