Bishay's Research Team
Fall 2022-Spring 2023 Graduate Students
Graduate Students from left to right: Utsav Swami, Annamaria Viazzo, Erik Serrano, Nelson Richardson, and Antonio Buendia.
Fall 2022-Spring 2023 NSF-M3X Research Team
Students from left to right: Alfredo Gonzalez-Martinez, Matthew Gosparini, Annamaria Viazzo, Jack Wilgus, and Calvin Tan.
Fall 2019-Spring 2020 Graduate Students
(Each graduate student in this picture published at least one journal paper with Dr. Bishay)
Graduate students from left to rgiht: Andrew Theodore, James Martinez, Julian Rodriguez, Arshak Amirbekyan, and Christian Aguilar.
Graduate Students
Ian Sherrill
Thesis topic: Multiscale design optimization of 3D-printed structures via generative design and experimentally-optimized print settings (Jun. 2024 - Dec. 2025)
Education
- M.Sc. Mechanical Engineering,
California State University, Northridge, 2025.
- B.Sc. Mechanical Engineering,
California State University, Northridge, 2024.
Achievements with Dr. Bishay
- CSU-LSAMP Summer Research Award, 2024 ($1,000).
- Oral presentation at CSUN's 2024 Senior Design Project Showcase.
- First place (Award certificates and $300) at the 10-min oral presentation competition (Undergradute, Completed Stage) of CSUN's 28th annual research and creative works symposium (CSUNposium). Presentation title: "Multiscale design optimization of 3D-printed structures via generative design and experimentally-optimized print settings" [As an undergraduate student].
- Employed as an MMCL lab assistant, Spring 2024.
- SoCalGas STEM-NET Student Research Fellowship award ($ 2,500), Spring 2024 [As an undergraduate student].
- Project sub-team lead: Smart Prosthetics Senior Design Project (2023-24).
- Undergraduate research assistant, NSF-M3X grant "Improving motor learning and rehabilitation via experimental bidirectional dynamic human-virtual reality interaction systems".
--------------------------------------------------------------------------------------------------------------
Gerbert Funes Alfaro
Thesis topic: Development of foot controller for a full arm prosthetic device (Jun. 2024 - Dec. 2025)
Education
- M.Sc. Mechanical Engineering,
California State University, Northridge, 2025.
- B.Sc. Mechanical Engineering,
California State University, Northridge, 2024.
Achievements with Dr. Bishay
- CSU-LSAMP Summer Research Award, 2024 ($1,000).
- Paper:
Bishay, P. L.; McKinney, T.; Kline, G.; Manzo, M.; Parian, A.; Bakhshi, D.; Langwald, A.; Ortega, A.; Gagnon, M., Alfaro, G.F. (2024): SCAMORSA-1: a camber-morphing wind turbine blade with sliding composite skin. Journal of Engineering Research. [As an undergraduate student].
- Paper:
Bishay, P. L.; Wilgus, J.; Chen, R.; Valenzuela, D.; Medina, V.; Tan, C.; Ittner, T.; Caldera, M.; Rubalcava, C.; Safarian, S.; Alfaro, G.F.; Gonzalez-Martinez, A.; Gosparini, M.; Fuentes-Perez, J.; Lima, A.; Villalobos, J.; Solis A. (2023): Controlling a Below-the-Elbow Prosthetic Arm Using the Infinity Foot ControllerProsthesis, Vol. 5(4), 1206-1231, DOI: 10.3390/prosthesis5040084. [As an undergraduate student].
- First place (award certificate and $500) at the annual CSU statewide research competition, CSU San Luis Obispo (Apr. 27, 2024). Presentation title: "
Infinity Foot Controller: A new means of below-the-elbow prosthesis control" [As an undergraduate student].
- Oral presentation at
CSUN's 2024 Senior Design Project Showcase.
- 10-min oral presentation at
CSUN's 28th annual research and creative works symposium (CSUNposium). Presentation title: "
Controlling prosthetic arms with reciprocity between the physical and virtual worlds" [As an undergraduate student].
- Crowd Favorite Poster Award at the 36th Annual CSU Biotechnology Conference (Santa Clara, CA, Jan. 11-13, 2024). Presentation title: "
Foot Controller and Haptic Feedback Systems for Below-the-Elbow Prosthetic Arms"(Only 4 posters received this award out of 242 posters presented from Biology, Chemistry, Physics, and Engineering). [As an undergraduate student].
- CSUN-M3X Fellowship award ($8,000), Spring 2024. [As an undergraduate student].
- Project lead: Smart Prosthetics Senior Design Project (2023-24).
- Undergraduate research assistant, NSF-M3X grant "Improving motor learning and rehabilitation via experimental bidirectional dynamic human-virtual reality interaction systems". [As an undergraduate student].
--------------------------------------------------------------------------------------------------------------
Estefany Ortega
Thesis topic: Experimental and Computational Analyses of a Bio-Inspired Composite Bird-like Morphing Wing (Aug. 2023 - Dec. 2024)
Education
- M.Sc. Mechanical Engineering,
California State University, Northridge, 2024.
- B.Sc. Mechanical Engineering,
California State University, Northridge, 2023.
Achievements with Dr. Bishay
- Supported by CSUN's "Thesis/Project/Dissertation Support Program", 2024 ($700).
- Employed as an MMCL lab assistant, Spring 2024.
--------------------------------------------------------------------------------------------------------------
Utsav Swami
Thesis topic: Experimental and Computational Analysis of Periodic Laminated Sandwich Beams. (July 2022 - Aug. 2024)
Education
- M.Sc. Mechanical Engineering,
California State University, Northridge, 2023.
- B.Sc. Mechanical Engineering,
California State University, Northridge, 2018.
Work Experience
- Coming soon
Achievements with Dr. Bishay
- First place (Award certificates and $300) at the 10-min oral presentation competition (Gradute, Completed Stage) at the CSUN's 27th annual research and creative works symposium (CSUNposium). Presentation title: "Experimental and Computational Analyses of Metallic and Composite Periodic Beams".
- First place (Award certificates and $300) at the 10-min oral presentation competition (Gradute, Completed Stage) at the CSUN's 28th annual research and creative works symposium (CSUNposium). Presentation title: "Experimental and Computational Frequency Analyses of Metallic and Composite Periodic Beams".
- Supported by CSUN's "Thesis/Project/Dissertation Support Program", 2022 ($1,000).
- Supported by RSCA grant. (Fall 2022 - Spring 2023).
--------------------------------------------------------------------------------------------------------------
Graduate Alumni
Erik Serrano
Thesis topic: Experimental Characterization of the Dynamic Strength of Vibrating Metalic Beams (Sept. 2022 - May 2024)
Supported by NASA-MSFC grant.
Education
- M.Sc. Mechanical Engineering,
California State University, Northridge, 2023.
- B.Sc. Mechanical Engineering,
California State University, Northridge, 2021.
Achievements with Dr. Bishay
- Podium Presentation at CSUN's 27th annual research and creative works symposium (CSUNposium), April 2023.
- Supported by CSUN's "Thesis/Project/Dissertation Support Program", 2023 ($800).
- Supported by NASA-MSFC grant. (Fall 2022 - Spring 2023).
- Paper: chaal, N.; Bishay, P.L.; Serrano, E.; Knight, B. (2024): Method development for experimental characterization of dynamic strength of aluminum structures. SEM International Modal Analysis Conference (IMAC XLII 2024), Orlando, FL, Jan. 29 – Feb. 1, 2024.
--------------------------------------------------------------------------------------------------------------
Nelson Richardson
Thesis topic: Static and Dynamic Analyses of Laminated Composite Beams with Delamination (Aug. 2021 - Aug. 2023)
Education
- M.Sc. Mechanical Engineering (Systems Design),
California State University, Northridge, 2022.
- B.Sc. Mechanical Engineering,
California State University, Northridge, 2021.
Work Experience
Laboratory student assistant, CSUN's Keck Composites lab,
California State University, Northridge, Sept. 2021 - May 2022.
Achievements with Dr. Bishay
- Received Skurka research grant, $5,000 (Spring 2023).
- Supported by CSUN's "Thesis/Project/Dissertation Support Program", 2022 ($1,000).
- Podium Presentation at CSUN's 26th annual research and creative works symposium (CSUNposium), April 2022.
- Podium Presentation at CSUN's 27th annual research and creative works symposium (CSUNposium), April 2023.
--------------------------------------------------------------------------------------------------------------
Andrew Theodore
Thesis topic: Experimental and Computational Analysis of Morphing Composite Laminates with Embedded Shape Memory Alloy Actuators (Aug. 2019 - Aug. 2021)
Education
- M.Sc. Mechanical Engineering (Systems Design),
California State University, Northridge, 2021.
- B.Sc. Civil Engineering,
California State University, Northridge, 2018.
Work Experience
- Mechanical Engineer, Crane Aerospace and Electronics, 2016-present
Professional Associations
- Tau Beta Pi Engineering Honor Society
Achievements with Dr. Bishay
- Paper:
Theodore, A. J.; Bishay, P. L. (2022): Experimental analysis of fiber-reinforced laminated composite plates with embedded SMA wire actuators. Composite Structures, Vol. 292, Art. 115678, DOI: 10.1016/j.compstruct.2022.115678.
- Supported by CSUN's "Thesis/Project/Dissertation Support Program", 2020 ($1,000).
--------------------------------------------------------------------------------------------------------------
James Martinez
Thesis topic: Reliability Analysis of Smart Composite Structures Using Artificial Neural Networks (Aug. 2019 - May 2021)
Education
- M.Sc. Mechanical Engineering (Systems Design),
California State University, Northridge, 2021.
- edX Micromasters, Statistics and Data Science,
Massachusetts Institute of Technology, 2020.
- B.Sc. Civil Engineering, Cum Laude,
California State University, Northridge, 2017.
Work Experience
- Electronics Engineer, Edwards Air Force Base, CA (Jan. 2021 - Present)
- Math and Science Tutor - College of the Canyons, Santa Clarita, CA (Feb. 2014 - Dec. 2020)
- Associate Quality Engineer - Medtronic, Northridge, CA (Dec. 2017 - Jun. 2018)
- Mechanical Engineering Associate - Medtronic, Boulder, CO (Summer 2017)
Achievements with Dr. Bishay
- Thesis received CSUN’s Distinguished Thesis/Project Competition Award (May 2021) and CECS Distinguished Thesis Award.
- Paper:
Martinez, J. R.; Bishay, P. L.; Tawfik, M. E.; Sadek, E. A. (2022): Reliability analysis of smart laminated composite plates under static loads using artificial neural networks . Heliyon, vol. 8(12), article: e11889, DOI: 10.1016/j.heliyon.2022.e11889.
- Paper:
Martinez, J. R.; Bishay, P. L. (2020): On the stochastic first-ply failure analysis of laminated composite plates under in-plane tensile loading. Composites Part C: Open Access, vol. 4, article: 100102 (15 pages) DOI: 10.1016/j.jcomc.2020.100102.
- Podium Presentation at CSUN's 24th annual research and creative works symposium (CSUNposium), March 2020.
--------------------------------------------------------------------------------------------------------------
Christian Aguilar
Thesis topic: Development of a Seamless Composite Skin for a Twist-Morphing Wing (Aug. 2019 - May 2021)
Education
- M.Sc. Mechanical Engineering (Systems Design),
California State University, Northridge, 2021.
- B.Sc. Mechanical Engineering,
California State University, Northridge, 2019.
Achievements with Dr. Bishay
- Paper:
Bishay, P. L.; Aguilar, C. (2021): Parametric Study of a Composite Skin for a Twist-Morphing Wing. Aerospace, vol. 8(9), article 259. DOI: 10.3390/aerospace8090259.
- Supported by CSUN's "Thesis/Project/Dissertation Support Program", 2020 ($800)
- Podium Presentation at CSUN's 24th annual research and creative works symposium (CSUNposium), March 2020.
- (During seniopr design project): Paper:
Bishay, P. L.; Aguilar, C.; Amirbekyan, A.; Vartanian, K.; Arjon-Ramirez, M.; Pucio, D. B. (2021):
Design of a lightweight shape memory alloy stroke-amplification and locking system in a transradial prosthetic arm. ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS), September 14-15, 2021.
--------------------------------------------------------------------------------------------------------------
Arshak Amirbekyan
Thesis topic: Analysis and Design of Periodic Composite Beams with Piezoelectric Elements (Aug. 2019 - May 2021)
Education
- M.Sc. Mechanical Engineering (Systems Design),
California State University, Northridge, 2021.
- B.Sc. Mechanical Engineering,
California State University, Northridge, 2019.
Work Experience
- Meggitt Aerospace; Simi Valley, California
Mechanical Engineering Intern (5/19 to Present)
- Replacement Parts Industries, Inc. ; Simi Valley, California
2D/3D Drafter (8/17 to 5/19)
Achievements with Dr. Bishay
- Paper:
Bishay, P. L.; Amirbekyan, A. (2021): Design of periodic laminated composite beams in free vibration. Structures, vol. 34, pp. 2030-2040, DOI: 10.1016/j.istruc.2021.08.071.
- Supported by CSUN's "Thesis/Project/Dissertation Support Program", 2020 ($700)
- Placed 1st for the 10-minute presentation competition at the 24th Annual Student Research and Creative Works Symposium (CSUNposium, 2020) in the CECS graduate students session.
- Placed 1st for the 15-minute oral presentation competition at the 2019 CSUN Senior Design Project Showcase (SDPS), CSUN
- Placed 1st for the 10-minute presentation competition at the 23rd Annual Student Research and Creative Works Symposium (CSUNposium, 2019), CSUN
- Placed 1st for Poster Presentation at 2018 California Renewable Energy and Storage Technology (CREST) conference, CSUN
- (During seniopr design project): Paper:
Bishay, P. L.; Aguilar, C.; Amirbekyan, A.; Vartanian, K.; Arjon-Ramirez, M.; Pucio, D. B. (2021):
Design of a lightweight shape memory alloy stroke-amplification and locking system in a transradial prosthetic arm. ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS), September 14-15, 2021.
--------------------------------------------------------------------------------------------------------------
Julian Rodriguez
Thesis topic: Computational and Experimental Analysis and Design of Periodic Composite Beams (Aug. 2018 - May 2020)
Education
- M.Sc. Mechanical Engineering (Systems Design),
California State University, Northridge, 2020.
- B.Sc. Mechanical Engineering,
California State University, Northridge, 2018.
Achievements with Dr. Bishay
- Paper: Bishay, P. L.; Rodriguez, J. (2021):
Analysis of Periodic Laminated Fiber-Reinforced Composite Beams in Free Vibration.
Journal of Vibration and Control, DOI: 10.1177/10775463211028683.
- Podium Presentation at CSUN's 24th annual research and creative works symposium (CSUNposium), March 2020.
- Podium Presentation at CSUN's 23rd annual research and creative works symposium (CSUNposium), April 2019.
- (During seniopr design project): Paper:
Bishay, P. L.; Fontana, J.; Raquipiso, B.; Rodriguez, J.; Borreta, M.J.; Enos, B.; Gay T.; Mauricio, K. (2020): Development of a biomimetic transradial prosthetic arm with shape memory alloy muscle wires.
Engineering Research Express, vol. 2, no. 3, article: 035041 (15 pages) DOI: 10.1088/2631-8695/abb710.
--------------------------------------------------------------------------------------------------------------
Nicholas Fabry
Thesis topic: Computational Simulation of Chemo-Elastic Solids (Oct. 2016 - Dec. 2017)
Education
- M.Sc. Mechanical Engineering (Systems Design),
California State University, Northridge, 2017 (GPA: 3.50)
- B.Sc. Mechanical Engineering, Cum Laude
California State University Northridge/ University of Bradford, 2014 (GPA: 3.64)
Work Experience
- Aerojet Rocketdyne; Canoga Park, California
Engineering Designer II (2/16 to Present)
- State University Northridge; Northridge, California
Graduate Instructor (8/15 to 12/16)
- Haskel International; Burbank, California
Mechanical Design Engineer (2/13 to 2/16)
Professional Training and Certification
- ASME Y14.5 GD&T Training – 88 Hours
- PMI Project Management Training – 56 Hours
- Lean Six Sigma Greenbelt Training (IASSC Certified Greenbelt 1-0581) – 64 Hours
- Adept Engineering Document Management Program Administrator Training – 40 Hours
Achievements with Dr. Bishay
- Poster Presentation at 2017 California Renewable Energy and Storage Technology (CREST) conference, California State University, Northridge (CSUN)
- Paper:
Bishay, P. L.; Sladek, J.; Fabry, N.; Sladek V.; Zhang, C. (2019): Perturbation finite element solution for chemo-elastic boundary value problems under chemical equilibrium.
Acta Mechanica Sinica, vol.35, pp. 981–991.
--------------------------------------------------------------------------------------------------------------
Muzaffaruddin Syed
Thesis topic: Computational Analysis and Design of Smart Periodic Beams (Mar. 2016 - Dec. 2017)
Education
- M.Sc. Mechanical Engineering,
California State University, Northridge, 2017
- B.E. Mechanical Engineering,
Osmania University, India, 2014
Work Experience
- Designer – Mechanical Division
SS Comfort Systems Pvt Ltd(Carrier), India (May 2013 – July 2014)
Professional Membership
- American Society of Mechanical Engineers (ASME), Student Member.
Achievements with Dr. Bishay
- Thesis received CSUN’s Distinguished Thesis/Project Competition Award (May 2018).
- Paper:
Syed, M.; Bishay, P. L. (2018): Analysis and Design of Periodic Beams for Vibration Attenuation.
Journal of Vibration and Control, vol. 25, no. 1, pp. 228-240.
- Podium Presentation at CSUN's 21st annual research and creative works symposium (CSUNposium), April 2017.
- Poster Presentation at 2016 California Renewable Energy and Storage Technology (CREST) conference, California State University, Northridge (CSUN)
--------------------------------------------------------------------------------------------------------------
Bhavin N. Sampat
Thesis topic: Study of Thermo-Electro-Mechanical Effects in Quantum Dots with Functionally Graded Lattice Mismatch Strain (Sept. 2015 - Aug. 2017)
Education
- M.Sc. Mechanical Engineering,
California State University, Northridge, 2017 (GPA: 3.46)
- B.E. Mechanical Engineering,
University of Pune, India, 2014
Work Experience
- Mechanical Design Engineer
Noribachi Corporation, Harbor City, CA (March 2015 – Present)
-Design Intern
Reliance Engineering Co. Ltd. Nashik, India (Aug 2013 - June 2014)
Professional Membership
- American Institute for Aeronautics and Astronautics, Student Member.
Achievements with Dr. Bishay
- Paper:
Bishay, P. L.; Sampat, B.; Sladek J.; Pan, E.; Sladek, V. (2017): Effect of Lattice Mismatch Strain Grading on the Electromechanical Behavior of Functionally Graded Quantum Dots. Key Engineering Materials, vol. 759, pp. 71-75. (International Conference on Advanced Functional Materials (ICAFM), Los Angeles, CA, USA, Aug. 4-6, 2017)
--------------------------------------------------------------------------------------------------------------
Ardalan R. Sofi
Thesis topic: Geometrically Nonlinear Analysis of Laminated Composite Space Frame Structures Using the Finite Element Method with a Newly Derived Explicit Tangent Stiffness Matrix (Oct. 2015 - May 2017)
Education
- M.Sc. Mechanical Engineering (Solid design),
California State University, Northridge, 2017 (GPA: 3.84)
- B.Sc. Mechanical Engineering,
Azad University, Tehran, Iran, 2013 (GPA: 3.7)
Honors and Awards
- Mechanical Engineering Outstanding Academic Achievement Award, California State University (May 2017)
- Sally Casanova Pre-Doctoral Scholarship Award, California State University, 2016-2017
Work Experience
- Building Mechanical System Engineering analyst
DDAB Enterprises Inc. (May 2016-present)
- Process engineer analyst
Kahanroba Machine CO (June 2013-January 2014)
Achievements with Dr. Bishay
- Paper:
Bishay, P. L.; Sofi, A. (2018): Sensitivity analysis of a smart soft composite robotic finger design using geometrically nonlinear laminated composite finite beam elements. Materials Today Communications,
vol. 16, pp. 111-118.
- Paper:
Sofi, A.; Bishay, P. L.; Atluri, S. N. (2017): Explicit tangent stiffness matrix for the geometrically nonlinear analysis of laminated composite frame structures. Composite Structures, vol. 187, pp. 566-578.
- Mechanical Engineering Outstanding Academic Achievement Award (May 2017).
- Podium Presentation at CSUN's 21st annual research and creative works symposium (CSUNposium), April 2017.
- Sally Casanova Pre-Doctoral Scholarship Award (June 2016).
--------------------------------------------------------------------------------------------------------------
Undergraduate Alumni
Jack Wilgus, Calvin Tan, Matthew Gosparini, and Alfredo Gonzalez-Martinez
Project topic: Development of a foot control system for different physical and virtual prosthetic arms (July 2022 - May 2023)
Achievements with Dr. Bishay
- NSF-Mind, Machine and Motor Nexus (M3X) grant: "RUI: Improving motor learning and rehabilitation via experimental bidirectional dynamic human-virtual reality interaction systems" (2022-2023).
- Jack Wilgus: Provisional Patent application: "Foot Controller for Prosthetic Arms, Their Methods of Production and Use" (April 29, 2023)
--------------------------------------------------------------------------------------------------------------
Other Graduate Researchers
Annamaria Viazzo
Thesis topic: Development of a Foot Control System for Different Physical and Virtual Prosthetic Arms (Sept. 2022 - May 2024)
Supported by NSF-M3X grant.
Education
- M.Sc. Mechanical Engineering,
California State University, Northridge, 2024.
- B.Sc. Biology,
State University of New York, Stony Brook, 2014.
Achievements with Dr. Bishay
- Podium Presentation at CSUN's 27th annual research and creative works symposium (CSUNposium), April 2023.
- Supported by CSUN's "Thesis/Project/Dissertation Support Program", 2022 ($1,200).
- Supported by NSF-M3X grant (Fall 2022 - Spring 2023).
--------------------------------------------------------------------------------------------------------------
Antonio Buendia
Research topic: Design of a Morphing Composite Wind Turbine Blade with Embedded Shape Memory Alloy (SMA) Actuators (Aug. 2021 - May 2022)
Education
- M.Sc. Mechanical Engineering (Systems Design),
California State University, Northridge, 2022.
- B.Sc. Mechanical Engineering,
California State University, Northridge, 2021.
Professional Associations
- AIAA : American Institute of Aeronautics and Astronautics
Achievements with Dr. Bishay
- Supported by CSUN's "Thesis/Project/Dissertation Support Program", 2022 ($1,200).
- (During seniopr design project): Paper:
Bishay, P.L., Kok, J.S., Ferrusquilla, L.J., Espinoza, B.M., Heness, A., Buendia, A., Zadoorian, S., Lacson, P., Ortiz, J.D., Basilio B. and Olvera D. (2022): Design and Analysis of MataMorph-3: A Fully Morphing UAV with Camber-Morphing Wings and Tail Stabilizers .
Aerospace, Vol. 9(7), 382, DOI: 10.3390/aerospace9070382.
- (During seniopr design project): Second place at the AIAA regional student conference and competition
[Team category: Smart Morphing Wing SDP] (2021).
--------------------------------------------------------------------------------------------------------------
Andrew Heness
Research topic: Development of a Multi-Morphing Composite Wing Skin (Jun. 2021 - May 2022)
Education
- M.Sc. Mechanical Engineering (Systems Design),
California State University, Northridge, 2022.
- B.Sc. Mechanical Engineering,
California State University, Northridge, 2021.
Work Experience
- Mechanical engineer Intern,
NASA Jet Propulsion Laboratory, November 2019 – November 2020.
Professional Associations
- AIAA : American Institute of Aeronautics and Astronautics
- SHPE : Society of Hispanic Professional Engineers
- NSLS : Nation Society of Leadership and Success
Achievements with Dr. Bishay
- Supported by CSUN's "Thesis/Project/Dissertation Support Program", 2022 ($1,200).
- CSU-LSAMP Summer Research Award, 2021 ($1,000).
- (During seniopr design project): Paper:
Bishay, P.L., Kok, J.S., Ferrusquilla, L.J., Espinoza, B.M., Heness, A., Buendia, A., Zadoorian, S., Lacson, P., Ortiz, J.D., Basilio B. and Olvera D. (2022): Design and Analysis of MataMorph-3: A Fully Morphing UAV with Camber-Morphing Wings and Tail Stabilizers .
Aerospace, Vol. 9(7), 382, DOI: 10.3390/aerospace9070382.
- (During seniopr design project): Second place at the AIAA regional student conference and competition
[Team category: Smart Morphing Wing SDP] (2021).
--------------------------------------------------------------------------------------------------------------