BibTex RIS Kaynak Göster

-

Yıl 2014, Cilt: 3 Sayı: 1, 200 - 223, 15.04.2014

Öz

Bartin University Journal of Faculty of Education (BUJFED) is a international refereed journal that is published two times a year. The responsibility lies with the authors of papers

Kaynakça

  • Atasoy, Ş., Tekbıyık, A., & Gülay, A. (2013). Beşinci sınıf öğrencilerinin ses kavramını anlamaları üzerine kavram karikatürlerinin etkisi. Türk Fen Eğitimi Dergisi, 10(1), 176-196.
  • Atasoy, Ş. (2008). Öğretmen adaylarının Newton’un hareket kanunları konusundaki kavram yanılgılarının giderilmesine yönelik geliştirilen çalışma yapraklarının etkililiğinin araştırılması. Yayınlanmamış Doktora Tezi, Karadeniz Teknik Üniversitesi, Trabzon
  • Ateş, S. (2005). The effectiveness of the learning-cycle method on teaching DC circuits to prospective female and male science teachers. Research in Science & Technological Education, 23(2), 213-227.
  • Bakaç, M., Taşoğlu, A. K., & Akbay, T. (2011). The effect of computer assisted instruction with simulation in science and physics activities on the success of student: electric current. Eurasion J. Phys. Chem. Educ. Jan, 34-42.
  • Baser, M. (2006). Effects of conceptual change and traditional confirmatory simulations on preservice teachers’ understanding of direct current circuits. Journal of Science Education and Technology, 15(5), 367-381.
  • Birisci, S., Metin, M., & Karakas, M. (2010). Pre-service elementary teachers’ views on concept cartoons: a sample from Turkey. Middle-East Journal of Scientific Research, 5(2), 91-97.
  • Bryan, J. A., & Slough, S. W. (2009). Converging lens simulation design and image predictions. Physics Education, 44(3), 264-275.
  • Bryce, T., & MacMillan, K. (2005). Encouraging conceptual change: the use of bridging analogies in the teaching of action-reaction forces and the ‘at rest’ condition in physics. International Journal of Science Education, 27, 737–763.
  • Burhan, Y. (2008). Asit ve baz kavramlarına yönelik karikatür destekli çalışma yapraklarının geliştirilmesi ve uygulanması. Yayınlanmamış Doktora Tezi, Karadeniz Teknik Üniversitesi, Trabzon.
  • Caleon, I. & Subramaniam, R. (2010). Development and application of a three-tier diagnostic test to assess secondary students’ understanding of waves. International Journal of Science Education, 32(7), 939-961.
  • Çalık, M., Okur, M., & Taylor, N. (2011). A comparison of different conceptual change pedagogies employed within the topic of “sound propagation”. J Sci Educ Technol, 20, 729-742.
  • Çelikten, O., Ertepınar, H., & Geban, Ö. (2012). The effect of the conceptual change oriented instruction through cooperative learning on 4th grade students’ understanding of earth and sky concepts. Science Education International, 23(1), 84-96.
  • Chambers, S. K., & Andre. T. (1997). Gender, prior knowledge, interest, and experience in electricity and conceptual change text manipulations in learning about direct current. Journal of Research in Science Teaching, 34(2), 107-123.
  • Chu, H.-E, Treagust, D. F., & Chandrasegaran, A. L. (2009). A stratified study of students’ understanding of basic optics concepts in different contexts using two-tier multiple-choice items. Research is Science & Technological Education, 27(3), 253-265.
  • Cohen, R., Eylon, B., & Ganiel, U. (1983). Potential difference and current in simple electric circuits: A study of student’s concepts. American Journal of Physics, 51(5), 407-412.
  • Cox, A. J., Belloni, M., & Dancy, M. (2003). Teaching thermodynamics with Physlets in introductory physics. Physics Education, 38(5), 433-440.
  • Dole, J. A., & Sinatra, G. M. (1998). Reconceptualizing change in the cognitive construction of knowledge. Educational Psychologist, 33(2/3), 109-128.
  • Dupin, J. J., & Johsua, S. (1987). Conceptions of French pupils concerning electric circuits: Structure and evolution. Journal of Research in Science Teaching, 24(9), 791-806.
  • Ekici, F., Ekici, E., & Aydın, F. (2007). Using concept cartoons in diagnosing and overcoming misconceptions related to photosynthesis. International Journal of Environmental & Science Education, 2(4), 111-124.
  • Engelhardt, P. V., & Beichner, R. J. (2004). Students’ understanding of direct current resistive electrical circuits. American Journal of Physics, 72, 98-115.
  • Eryılmaz, A. ve Sürmeli, E (2002). Üç-aşamalı sorularla öğrencilerin ısı ve sıcaklık konularındaki kavram yanılgılarının ölçülmesi. http://www.fedu.metu.edu.tr/ufbmek-5/ adresinden 20 Mart 2010 tarihinde alınmıştır.
  • Fetherstonhaugh, T., & Treagust, F. D. (1992). Students’ understanding of light and its properties: teaching to engender conceptual change. Science Education, 76, 653-672.
  • Gregoire, M. (2003). Is it a challenge or a threat? A dualprocess model of teachers’ cognition and appraisal process during conceptual change. Educational Psychology Review, 15(2), 147– 179.
  • Gürses, E., Akdeniz, A. R. & Atasoy, Ş. (2006). Durgun Elektrik Konusunda 5E Modeline Göre Geliştirilen Materyallerin Öğrenci Başarısına Etkisi. VII. Ulusal Fen Bilimleri ve Matematik Eğitimi Kongresi. Gazi Üniversitesi Eğitim Fakültesi, 6-8 Eylül 2006, Ankara.
  • Guzetti, B. J., Snyder, T. E., Glass, G. V., & Gamas, W. S. (1993). Promoting conceptual change in science: A comparative meta-analysis of instructional interventions from reading education and science education. Reading Research Quarterly, 28, 116–159.
  • Hammer, D. (1996). More than misconceptions: Multiple perspectives on student knowledge and reasoning, and an appropriate role for education research. American Journal of Physics, 64, 1316-1325.
  • Hasan, S., Bagayoko, D., & Kelley, E. L. (1999). Misconceptions and the certainty of response index (CRI). Physics Education, 34, 294-299.
  • Heller, M., & Finley, F. N. (1992). Variable uses of alternative conceptions: A case study in current electricity. J. Res. Sci. Teach, 29(3), 259-275.
  • Hynd, C., & Alvermann, D. E (1986). The role of refutation text in overcoming difficulty with science concepts. Journal of Reading, 29, 440-446.
  • Jaakkola, T., & Nurmi, S. (2008). Fostering elementary school students’ understanding of simple electricity by combining simulation and laboratory activities. Journal of Computer Assisted Learning, 24, 271-283.
  • Kabapınar, F. (2009). What makes concept cartoons more effective? Using research to inform practice. Education and Science, 34(154), 104-118.
  • Keogh, B., Naylor, S., & Wilson, C. (1998). Concept cartoons: a new perspective on physics education. Physics Education, 33(4), 219-224.
  • Keogh. B., & Naylor, S. (1999). Concept cartoons, teaching and learning in science: an evaluation. International Journal of Science Education. 21(4), 431-446.
  • Keogh. B., & Naylor, S. (2000). Teacher and learning in science using concept cartoons: why Dennis wants to stay in at playtime. Australian Primary and Junior Science Journal, 16(3).
  • Kutluay, Y. (2005). Development of a three-tier test to assess ninth grade students’ misconceptions about simple electric circuits. Unpublished Master Thesis. ODTÜ, Ankara.
  • McDermott, L.C., & Shaffer, P.S. (1992) Research as a guide for curriculum development: an example from introductory electricity. Part I: Investigation of student understanding. Am. J. Phys, 60(11), 994-1003
  • Mulhall, P., MCKittrick, B., & Gunstone, R. (2001). A perspective on the resolution of confusion in the teaching of electricity. Research in Science Education, 31, 575-587.
  • Peşman, H., & Eryılmaz, A. (2010). Development of a three-tier test to assess misconceptions about simple electric circuits. The journal of Educational Research, 103, 208-222.
  • Piquette, J. S., & Heikkinen, H. W. (2005). Strategies reported used by instructors to address student alternate conceptions in chemical equilibrium. Journal of Research in Science Teaching, 42, 1112–1134.
  • Posner, G., J., Srike, K.A., Hewson, P.W., & Gertzog, W. A. (1982). Accommodation of a scientific conception: Toward a theory of conceptual change. Science Education, 66, 211-227
  • Redish EF, Saul JM., & Steinberg RN. (1998). Student expectations in introductory physics. Am J Phys, 66(3), 212-224.
  • Ronen, M., & Eliahu, M. (2000). Simulation – a bridge between theory and reality: the case of electric circuits. Journal of Computer Assisted Learning, 16, 14-26.
  • Roth, K. J. (1985). Conceptual Change Learning and student processing of science texts. Paper presented at the annual meeting of American Research Association, Chicago, Illinois. April.
  • Sencar, S., & Eryılmaz, A. (2004). Factors mediating the effect of gender on ninth-grade Turkish students’ misconceptions concerning electric circuit. Journal of Research in Science Teaching, 41(6), 603-616.
  • Sen, A. I., & Aykutlu, I. (2008). Using concept maps as an alternative evaluation tool for students’ conceptions of electric current. Eğitim Arastırmaları-Eurasion Journal of Educational Research, 31, 75-92.
  • Shipstone, D. (1988). Pupils’ understanding of simple electrical circuits. Physics Education, 23, 92- 96.
  • Shipstone, D. M., Rhöneck, C. von, Jung, W., Kärrqvist, C., Dupin, J. J., Joshua, S., & Licht, P. (1988). A study of students’ understanding of electricity in five European countries. International Journal of Science Education, 10(3), 303-316.
  • Smit, E. L., Blakeslee, T. D., & Anderson, C. W. (1993). Teaching strategies associated with conceptual change learning in science. Journal of Research in Science Teaching, 30(2), 111- 126
  • Stephenson, P., & Warwick, P. (2002). Using concept cartoons to support progression in students’ understanding of light. Physics Education, 37(2), 135-141.
  • Taşlıdere, E. (2013a). The effect of concept cartoon worksheet on students’ conceptual understanding of geometrical optics. Education and Science, 39, 144-161.
  • Taşlıdere, E. (2103b). Effect of conceptual change oriented instruction on students’ conceptual understanding and decreasing their misconceptions in DC electric circuits. Creative Education, 4(4),273-282.
  • Taşlıdere, E., Korur, F., & Eryılmaz, A.(2012). Kavram yanılgılarının üç-aşamalı sorularla farklı bir şekilde değerlendirilmesi. X.Ulusal Fen Bilimleri Kongresi. Niğde Üniversitesi, 27-30 Haziran 2012, Niğde. s. "[CD-ROM],– Tam Metinler, 2312-29_05_2012-14" s.1-6.
  • Treagust, D.F., & Duit, R.(2008). Conceptual change: a discussion of theoretical, methodological and practical challenges for science education. Cult Stud of Sci Educ, 3, 297-328. Vosniadou, S . (2007). Conceptual Change and Education, Human Development, 50, 47-54.
  • Zacharia, Z. C. (2005). The impact of interactive computer simulations on the nature and quality of post graduate science teachers’ explanations in physics. International Journal of Science Education, 27(14), 1741-1767.

Kavramsal Değişim Yaklaşımının Doğru Akım Devreleri Konusundaki Kavram Yanılgılarının Giderilmesine Etkisi

Yıl 2014, Cilt: 3 Sayı: 1, 200 - 223, 15.04.2014

Öz

Bu çalışmada kavramsal değişim yaklaşımının doğru akım devreleri konusundaki kavram
yanılgılarının giderilmesine etkisi araştırılmıştır. Çalışma bir devlet üniversitesinde öğrenim görmekte olan
139 birinci sınıf fen bilgisi öğretmen adayı ile gerçekleştirilmiştir. Araştırmada yarı-deneysel desen
kullanılmış olup, çalışma üç hafta sürmüştür. Deney grubunda kavramsal değişim yaklaşımını temel alan
öğretim yapılırken, kontrol grubunda öğretmen merkezli geleneksel düz anlatım yöntemi kullanılmıştır.
Kavramsal değişimi sağlamak için kavram karikatürleriyle zenginleştirilmiş çalışma yaprakları geliştirilerek,
simülasyon programı ile birlikte uygulanmıştır. Üç-aşamalı kavram yanılgısı testi ölçüm aracı olarak
kullanılmış olup bu test ön-test ve son-test olarak uygulanmıştır. Ön-test ve son-test sonuçlarına göre testin
her aşamasında doğru cevap yüzdeleri ile 11 farklı kavram yanılgısı yüzdeleri frekans analizi ile
hesaplanmıştır. Sonuçlar kavram karikatürleriyle zenginleştirilmiş çalışma yaprakları ve simülasyon programı
kullanılarak gerçekleştirilen kavramsal değişim temelli öğretimin öğrencilerin doğru akım devreleri
konusundaki kavramsal anlamalarını arttırma ve kavram yanılgılarını azaltmada öğretmen merkezli düz
anlatım yöntemine göre daha etkili olduğunu göstermiştir. Fizik öğretiminde kavram yanılgılarını azaltmak
için Kavram karikatürleriyle zenginleştirilmiş çalışma yaprakları ve simülasyon programlarının kullanılması
önerilmektedir.

Kaynakça

  • Atasoy, Ş., Tekbıyık, A., & Gülay, A. (2013). Beşinci sınıf öğrencilerinin ses kavramını anlamaları üzerine kavram karikatürlerinin etkisi. Türk Fen Eğitimi Dergisi, 10(1), 176-196.
  • Atasoy, Ş. (2008). Öğretmen adaylarının Newton’un hareket kanunları konusundaki kavram yanılgılarının giderilmesine yönelik geliştirilen çalışma yapraklarının etkililiğinin araştırılması. Yayınlanmamış Doktora Tezi, Karadeniz Teknik Üniversitesi, Trabzon
  • Ateş, S. (2005). The effectiveness of the learning-cycle method on teaching DC circuits to prospective female and male science teachers. Research in Science & Technological Education, 23(2), 213-227.
  • Bakaç, M., Taşoğlu, A. K., & Akbay, T. (2011). The effect of computer assisted instruction with simulation in science and physics activities on the success of student: electric current. Eurasion J. Phys. Chem. Educ. Jan, 34-42.
  • Baser, M. (2006). Effects of conceptual change and traditional confirmatory simulations on preservice teachers’ understanding of direct current circuits. Journal of Science Education and Technology, 15(5), 367-381.
  • Birisci, S., Metin, M., & Karakas, M. (2010). Pre-service elementary teachers’ views on concept cartoons: a sample from Turkey. Middle-East Journal of Scientific Research, 5(2), 91-97.
  • Bryan, J. A., & Slough, S. W. (2009). Converging lens simulation design and image predictions. Physics Education, 44(3), 264-275.
  • Bryce, T., & MacMillan, K. (2005). Encouraging conceptual change: the use of bridging analogies in the teaching of action-reaction forces and the ‘at rest’ condition in physics. International Journal of Science Education, 27, 737–763.
  • Burhan, Y. (2008). Asit ve baz kavramlarına yönelik karikatür destekli çalışma yapraklarının geliştirilmesi ve uygulanması. Yayınlanmamış Doktora Tezi, Karadeniz Teknik Üniversitesi, Trabzon.
  • Caleon, I. & Subramaniam, R. (2010). Development and application of a three-tier diagnostic test to assess secondary students’ understanding of waves. International Journal of Science Education, 32(7), 939-961.
  • Çalık, M., Okur, M., & Taylor, N. (2011). A comparison of different conceptual change pedagogies employed within the topic of “sound propagation”. J Sci Educ Technol, 20, 729-742.
  • Çelikten, O., Ertepınar, H., & Geban, Ö. (2012). The effect of the conceptual change oriented instruction through cooperative learning on 4th grade students’ understanding of earth and sky concepts. Science Education International, 23(1), 84-96.
  • Chambers, S. K., & Andre. T. (1997). Gender, prior knowledge, interest, and experience in electricity and conceptual change text manipulations in learning about direct current. Journal of Research in Science Teaching, 34(2), 107-123.
  • Chu, H.-E, Treagust, D. F., & Chandrasegaran, A. L. (2009). A stratified study of students’ understanding of basic optics concepts in different contexts using two-tier multiple-choice items. Research is Science & Technological Education, 27(3), 253-265.
  • Cohen, R., Eylon, B., & Ganiel, U. (1983). Potential difference and current in simple electric circuits: A study of student’s concepts. American Journal of Physics, 51(5), 407-412.
  • Cox, A. J., Belloni, M., & Dancy, M. (2003). Teaching thermodynamics with Physlets in introductory physics. Physics Education, 38(5), 433-440.
  • Dole, J. A., & Sinatra, G. M. (1998). Reconceptualizing change in the cognitive construction of knowledge. Educational Psychologist, 33(2/3), 109-128.
  • Dupin, J. J., & Johsua, S. (1987). Conceptions of French pupils concerning electric circuits: Structure and evolution. Journal of Research in Science Teaching, 24(9), 791-806.
  • Ekici, F., Ekici, E., & Aydın, F. (2007). Using concept cartoons in diagnosing and overcoming misconceptions related to photosynthesis. International Journal of Environmental & Science Education, 2(4), 111-124.
  • Engelhardt, P. V., & Beichner, R. J. (2004). Students’ understanding of direct current resistive electrical circuits. American Journal of Physics, 72, 98-115.
  • Eryılmaz, A. ve Sürmeli, E (2002). Üç-aşamalı sorularla öğrencilerin ısı ve sıcaklık konularındaki kavram yanılgılarının ölçülmesi. http://www.fedu.metu.edu.tr/ufbmek-5/ adresinden 20 Mart 2010 tarihinde alınmıştır.
  • Fetherstonhaugh, T., & Treagust, F. D. (1992). Students’ understanding of light and its properties: teaching to engender conceptual change. Science Education, 76, 653-672.
  • Gregoire, M. (2003). Is it a challenge or a threat? A dualprocess model of teachers’ cognition and appraisal process during conceptual change. Educational Psychology Review, 15(2), 147– 179.
  • Gürses, E., Akdeniz, A. R. & Atasoy, Ş. (2006). Durgun Elektrik Konusunda 5E Modeline Göre Geliştirilen Materyallerin Öğrenci Başarısına Etkisi. VII. Ulusal Fen Bilimleri ve Matematik Eğitimi Kongresi. Gazi Üniversitesi Eğitim Fakültesi, 6-8 Eylül 2006, Ankara.
  • Guzetti, B. J., Snyder, T. E., Glass, G. V., & Gamas, W. S. (1993). Promoting conceptual change in science: A comparative meta-analysis of instructional interventions from reading education and science education. Reading Research Quarterly, 28, 116–159.
  • Hammer, D. (1996). More than misconceptions: Multiple perspectives on student knowledge and reasoning, and an appropriate role for education research. American Journal of Physics, 64, 1316-1325.
  • Hasan, S., Bagayoko, D., & Kelley, E. L. (1999). Misconceptions and the certainty of response index (CRI). Physics Education, 34, 294-299.
  • Heller, M., & Finley, F. N. (1992). Variable uses of alternative conceptions: A case study in current electricity. J. Res. Sci. Teach, 29(3), 259-275.
  • Hynd, C., & Alvermann, D. E (1986). The role of refutation text in overcoming difficulty with science concepts. Journal of Reading, 29, 440-446.
  • Jaakkola, T., & Nurmi, S. (2008). Fostering elementary school students’ understanding of simple electricity by combining simulation and laboratory activities. Journal of Computer Assisted Learning, 24, 271-283.
  • Kabapınar, F. (2009). What makes concept cartoons more effective? Using research to inform practice. Education and Science, 34(154), 104-118.
  • Keogh, B., Naylor, S., & Wilson, C. (1998). Concept cartoons: a new perspective on physics education. Physics Education, 33(4), 219-224.
  • Keogh. B., & Naylor, S. (1999). Concept cartoons, teaching and learning in science: an evaluation. International Journal of Science Education. 21(4), 431-446.
  • Keogh. B., & Naylor, S. (2000). Teacher and learning in science using concept cartoons: why Dennis wants to stay in at playtime. Australian Primary and Junior Science Journal, 16(3).
  • Kutluay, Y. (2005). Development of a three-tier test to assess ninth grade students’ misconceptions about simple electric circuits. Unpublished Master Thesis. ODTÜ, Ankara.
  • McDermott, L.C., & Shaffer, P.S. (1992) Research as a guide for curriculum development: an example from introductory electricity. Part I: Investigation of student understanding. Am. J. Phys, 60(11), 994-1003
  • Mulhall, P., MCKittrick, B., & Gunstone, R. (2001). A perspective on the resolution of confusion in the teaching of electricity. Research in Science Education, 31, 575-587.
  • Peşman, H., & Eryılmaz, A. (2010). Development of a three-tier test to assess misconceptions about simple electric circuits. The journal of Educational Research, 103, 208-222.
  • Piquette, J. S., & Heikkinen, H. W. (2005). Strategies reported used by instructors to address student alternate conceptions in chemical equilibrium. Journal of Research in Science Teaching, 42, 1112–1134.
  • Posner, G., J., Srike, K.A., Hewson, P.W., & Gertzog, W. A. (1982). Accommodation of a scientific conception: Toward a theory of conceptual change. Science Education, 66, 211-227
  • Redish EF, Saul JM., & Steinberg RN. (1998). Student expectations in introductory physics. Am J Phys, 66(3), 212-224.
  • Ronen, M., & Eliahu, M. (2000). Simulation – a bridge between theory and reality: the case of electric circuits. Journal of Computer Assisted Learning, 16, 14-26.
  • Roth, K. J. (1985). Conceptual Change Learning and student processing of science texts. Paper presented at the annual meeting of American Research Association, Chicago, Illinois. April.
  • Sencar, S., & Eryılmaz, A. (2004). Factors mediating the effect of gender on ninth-grade Turkish students’ misconceptions concerning electric circuit. Journal of Research in Science Teaching, 41(6), 603-616.
  • Sen, A. I., & Aykutlu, I. (2008). Using concept maps as an alternative evaluation tool for students’ conceptions of electric current. Eğitim Arastırmaları-Eurasion Journal of Educational Research, 31, 75-92.
  • Shipstone, D. (1988). Pupils’ understanding of simple electrical circuits. Physics Education, 23, 92- 96.
  • Shipstone, D. M., Rhöneck, C. von, Jung, W., Kärrqvist, C., Dupin, J. J., Joshua, S., & Licht, P. (1988). A study of students’ understanding of electricity in five European countries. International Journal of Science Education, 10(3), 303-316.
  • Smit, E. L., Blakeslee, T. D., & Anderson, C. W. (1993). Teaching strategies associated with conceptual change learning in science. Journal of Research in Science Teaching, 30(2), 111- 126
  • Stephenson, P., & Warwick, P. (2002). Using concept cartoons to support progression in students’ understanding of light. Physics Education, 37(2), 135-141.
  • Taşlıdere, E. (2013a). The effect of concept cartoon worksheet on students’ conceptual understanding of geometrical optics. Education and Science, 39, 144-161.
  • Taşlıdere, E. (2103b). Effect of conceptual change oriented instruction on students’ conceptual understanding and decreasing their misconceptions in DC electric circuits. Creative Education, 4(4),273-282.
  • Taşlıdere, E., Korur, F., & Eryılmaz, A.(2012). Kavram yanılgılarının üç-aşamalı sorularla farklı bir şekilde değerlendirilmesi. X.Ulusal Fen Bilimleri Kongresi. Niğde Üniversitesi, 27-30 Haziran 2012, Niğde. s. "[CD-ROM],– Tam Metinler, 2312-29_05_2012-14" s.1-6.
  • Treagust, D.F., & Duit, R.(2008). Conceptual change: a discussion of theoretical, methodological and practical challenges for science education. Cult Stud of Sci Educ, 3, 297-328. Vosniadou, S . (2007). Conceptual Change and Education, Human Development, 50, 47-54.
  • Zacharia, Z. C. (2005). The impact of interactive computer simulations on the nature and quality of post graduate science teachers’ explanations in physics. International Journal of Science Education, 27(14), 1741-1767.
Toplam 54 adet kaynakça vardır.

Ayrıntılar

Birincil Dil Türkçe
Bölüm Makaleler
Yazarlar

Erdal Taşlıdere

Yayımlanma Tarihi 15 Nisan 2014
Yayımlandığı Sayı Yıl 2014 Cilt: 3 Sayı: 1

Kaynak Göster

APA Taşlıdere, E. (2014). Kavramsal Değişim Yaklaşımının Doğru Akım Devreleri Konusundaki Kavram Yanılgılarının Giderilmesine Etkisi. Bartın University Journal of Faculty of Education, 3(1), 200-223.
All the articles published in the journal are open access and distributed under the conditions of CommonsAttribution-NonCommercial 4.0 International License
 88x31.png