Proceedings of the Technical University of Sofia

Manuscripts may be submitted throughout the year. Each manuscript should contain information about the authors, an abstract, keywords, an introduction, the main scientific content including the methods used and, where appropriate, experimental or numerical results, conclusions clearly indicating the scientific contribution, references, and acknowledgment where applicable.

Submitted manuscripts must present original work by the authors and must not have been published elsewhere. Previously published ideas, data, figures, or text must be appropriately cited and, where required, used with permission.

Authors must prepare the manuscript using Microsoft Word and the official template. The template contains the required margins, column widths, line spacing, PTUS styles, headings, and other formatting specifications. Authors should use the provided PTUS styles and should not manually alter the prescribed layout.

Papers that do not comply with the prescribed layout geometry and typesetting requirements will not be accepted for publication. All manuscripts are also subject to proofreading.

• Paper size: A4 (210 × 297 mm).
• Left and right margins: 18.5 mm.
• Top and bottom margins: 20 mm.
• The manuscript must be arranged in two columns with a 5 mm separation between the columns.
• The lengths of the two columns on the final page should be approximately equal.
• The full paper must be between 4 and 8 pages.
• Pages must be submitted without page numbers.

• Normal body text: Times New Roman, 10 pt.
• Paragraph first-line indentation: 3.6 mm.
• Use the corresponding PTUS style for each manuscript element.
• Do not use hard tabs.
• Avoid unnecessary hard returns; use one paragraph break at the end of each paragraph.
• Do not manually number section headings when the template provides the numbering.

The paper title and the author information appear on the first page and are centered across the full page width.

• Paper title: 24 pt, using the PTUS Paper Title style.
• Author line: 11 pt, regular, using the PTUS Authors style.
• Paper titles must use uppercase and lowercase letters and must not be written entirely in uppercase.
• Formulas, symbols, special characters, and footnotes should be avoided in the paper title.
• Full author names are preferred.
• Each author’s e-mail address must appear immediately after the author’s name in parentheses.
• When more than one affiliation is used, place a superscript numeral after each author and the same numeral before the corresponding affiliation.
• List each affiliation directly below the author line using the PTUS Affiliation style. Include the department or unit, institution, postal address, city, postal code where applicable, and country.
• Mark the corresponding author with an asterisk (*) after the affiliation number and add * Corresponding author below the affiliations.

The abstract must provide a concise but comprehensive summary of the work and the principal results.

• Abstract length: 150–200 words.
• Abstract text: 9 pt.
• The word Abstract: 9 pt italic.
• The abstract must be written as one paragraph.
• It must be self-contained and must not contain footnotes or references.
• Displayed mathematical equations and tabular material must not be included in the abstract.
• Up to five keywords or phrases should be provided in alphabetical order and separated by commas.

Main section headings must use Times New Roman, 10 pt, Small Caps, be centered, and use the PTUS Heading 1 style. Main sections are numbered using Roman numerals.

Subsection headings must use Times New Roman, 10 pt italic, be aligned left, and use the PTUS Heading 2 style. They are designated by capital letters followed by periods (A., B., etc.).

Appendix, Acknowledgment, and References use the PTUS Unnumbered Heading style.

Equations must be centered within the column. Use only Times New Roman or Symbol fonts as appropriate. All displayed equations must be numbered consecutively in the order in which they appear. Equation numbers are placed at the right margin and enclosed in parentheses.

Use the PTUS Equation style for displayed equations. Large equations should be split across multiple lines. All symbols must be defined before the equation appears or immediately after it. Mathematical symbols representing variables should be italicized.

Refer to equations as (1) in the text. At the beginning of a sentence use, for example, Equation (1) shows ....

Figures and tables should be placed as close as possible to the text where they are first referenced. Figures must be numbered in the order in which they appear.

• Figures and tables should normally occupy one column.
• Wide figures, graphs, and tables may span the full text width across both columns. Full-width elements should preferably be placed at the top or bottom of a page.
• Figure captions are placed below figures.
• Table titles are placed above tables.
• Use the PTUS Caption style for both figure captions and table titles.
• Use the PTUS Table Text style for table contents and notes below tables.
• For multipart figures, labels such as (a) and (b) must be included as part of the artwork.
• Use the abbreviation Fig., including at the beginning of a sentence.
• Do not abbreviate Table.
• Tables are numbered using Arabic numerals.

Prepare graphics using a suitable graphics-processing program. Recommended formats are PNG, TIFF, PDF, and high-quality JPEG for photographic material. Vector graphics exported as PDF are preferred when appropriate. Graphics created in Microsoft Word, PowerPoint, or Excel may be inserted directly when they retain sufficient quality and resolution.

• Recommended one-column width: approximately 85 mm.
• Recommended full text width: approximately 175 mm.
• Figures should normally not be made narrower than one column unless necessary.
• Inserted images should use Wrap Text → Inline with Text.
• Photographs, color images, and grayscale figures: minimum 300 dpi.
• Line art: minimum 600 dpi.

References must follow the IEEE reference style and must be numbered in the order in which they are first cited in the text. Use one reference number for one source.

• Cite references in square brackets, for example [1], [2], and [4]–[7].
• Sentence punctuation follows the reference citation.
• The reference list should consist primarily of published, traceable scientific and technical sources: peer-reviewed journal articles, books, book chapters, conference papers, standards, technical reports, dissertations, and patents.
• The original or primary source should be cited whenever possible.
• DOI identifiers must be included whenever available.
• General web pages and URL-only sources must not exceed 10% of the total reference list. Journal articles, books, standards, conference papers, dissertations, patents, and technical reports available online are not counted as general web sources when cited in their formal bibliographic form.
• Standards must be cited whenever standardized methods, test procedures, requirements, limits, classifications, terminology, or technical specifications are used.
• Unpublished manuscripts, preprints, personal communications, course notes, and manuscripts submitted but not accepted for publication must not be included in the reference list.
• An accepted article may be cited only when a DOI or a publicly accessible publisher record is already available.

Sources published in languages other than English: give the title in English translation only. Do not reproduce or transliterate the original-language title. Add the language at the end of the reference, for example (in Bulgarian), (in German), or (in Russian). If a journal or series has an official English title, use it; otherwise use an English translation.

Footnotes should generally be avoided unless they are necessary for the scientific content.

Define abbreviations and acronyms the first time they are used in the main text, even if they have already been defined in the abstract. Common abbreviations such as CMOS, FPGA, SI, ac, and dc do not need to be defined. Avoid abbreviations in the title unless unavoidable.

Use SI units. If mixed units are required, clearly state the units used for each quantity.

Papers for review are submitted electronically through the Proceedings web interface using the Submitting Your Paper section.

• Upload both the PDF and DOC/DOCX versions of the manuscript.
• Provide complete contact information for all authors.
• Designate one author as the corresponding author.
• Proofs will be sent to the corresponding author.

Publication is subject to the journal’s Open Access and APC policy.

The conclusion must summarize the research and clearly emphasize the scientific novelty of the paper. It may discuss the importance of the work, potential applications, and possible extensions. The conclusion should not simply reproduce the abstract.

Appendices, when required, appear before the Acknowledgment.

Acknowledgments, if any, appear as a separate unnumbered section before the list of references. Use the singular heading Acknowledgment, even when several acknowledgments are included.

All sources of financial support for the research, including funding organizations, projects, grants, and institutional support, must be stated in the Acknowledgment section.