Untuk Kegunaan UKM sahaja

For UKM use only

Curriculum Vitae


MAKLUMAT ASAS

PROF. MADYA DR. KHAIRIL AZNAN BIN MOHAMED KHAN

PENSYARAH PERGIGIAN
JABATAN KESIHATAN PERGIGIAN KELUARGA
aznankhan@ukm.edu.my
No.rasmi UKM : 03 8921 5555
BIOGRAFI /BIOGRAPHY

Seorang pembimbing klinikal berpengalaman, mesra berinteraksi serta mempunyai skil pengurusan yang baik. Seorang pakar klinikal yang diiktiraf di dalam bidangnya, mesra bersama pesakit dan dikenali oleh rakan kesepakaran. Seorang penyelidik yang berkolaborasi bersama bidang Sains Pertuturan dan Klef Mulut serta mempunyai minat kajian terhadap hubungan di antara pertuturan dan ortodontik.
An enthusiast clinical educator with good experience, good interpersonal skill and good in management. An excellent clinician with high credential, warm with patients and well known by peers. A researcher with Speech Science and Cleft Lip collaboration and special interest in the relationship between speech & orthodontics.

KELAYAKAN AKADEMIK / ACADEMIC QUALIFICATION
(Bidang Pengajian),(Peringkat),(Institusi),(Tahun)
, Sarjana Kepakaran , UNIVERSITY OF SHEFFIELD , 2004
, Doktor (Pergigian) , UNIVERSITY OF WESTERN AUSTRALIA , 1997
KEPAKARAN / EXPERTISE
CLINICAL AND HEALTH SCIENCES - DENTAL (Orthodontics)
PENERBITAN TERKINI / LATEST PUBLICATION

Penerbitan WOS

S. Nagarajan M. P. Sockalingam, Khairil Aznan Mohamed Khan, And Elavarasi Kuppusamy.  (2018).  Interceptive Correction Of Anterior Crossbite Using Short-span Wire-fixed Orthodontic Appliance: A Report Of Three Cases.  - Case Report In Dentistry. 

Penerbitan SCOPUS/ERA

Khan Kam, Law, Badrulzaman.  (2021).  Speech Effect Of Fixed Labial Orthodontic Appliance In Patient With Class Iii Incisor Relationship.  - International Journal Of Dentistry And Oral Science (ijdos).  2277-2282. 
S. Nagarajan M.p. Sockalingam, Ahmad Shuhud Irfani Zakaria, Khairil Aznan Mohamed Khan, Fayyadhah Mohd Azmi, Nurhidayah Muhd Noor.  (2020).  Simple Orthodontic Correction Of Rotated Malpositioned Teeth Using Sectional Wire And 2 X 4 Orthodontic Appliances In Mixed-dentition: A Report Of Two Cases.  - Case Reports In Dentistry.  1-5. 
S. Nagarajan M. P. Sockalingam, Khairil Aznan Mohamed Khan, And Elavarasi Kuppusamy.  (2018).  Interceptive Correction Of Anterior Crossbite Using Short-span Wire-fixed Orthodontic Appliance: A Report Of Three Cases.  - Case Report In Dentistry. 
K.aznan, M. Khan And Philip E. Benson.  (2007).  Gingival Temperature Measurements With Fluoride And Nonfluoride Elastomeric Ligatures.  - American Journal Of Orthodontics And Dentofacial Orthopedics.  131(3):378-83. 

Buku Penyelidikan

Tuti Ningseh Mohd Dom, Murshida Marizan Nor, Hasherah Mohd Ibrahim, Haslina Rani, Suziyani Mohamed, Azianura Hani Shaari, Khairil Aznan Mohamed Khan, Syed Nabil Syed Omar, Zainal Azhar Ahmad, Zuraini Ghazali.  (2022).  Kebolehkerjaan Belia Berkeperluan Khas.  - 16. 

Bab Dalam Buku

Tuti Ningseh Mohd Dom, Murshida Marizan Nor, Hasherah Mohd Ibrahim, Haslina Rani, Suziyani Mohamed, Azianura Hani Shaari, Khairil Aznan Mohamed Khan, Syed Nabil Syed Omar, Zainal Azhar Ahmad, Zuraini Ghazali.  (2022).  Kebolehkerjaan Belia Berkeperluan Khas.  - 16. 

Penerbitan Lain-lain

Eugene Yeoh Zhen Herr, Khairil Aznan Mohamed Khan, Murshida Marizan Nor, Badiah Baharin , Haslina Rani.  (2023).  In Vitro Evaluation Of The Stain Removal Efficacy Of Dentaklin White Whitening Dentifrice During Orthodontic Treatment.  - 29th Malaysia Association Of Orthodontists International Scientific Conference And Trade Exhibition.  32. 
Khairil Aznan Mohamed Khan, Eugene Yeoh Zhen Herr, Murshida Marizan Nor, Haslina Rani, Badiah Baharin.  (2023).  The Stain Removal Efficacy Of A Newly Developed Whitening Dentifrice: An In-vitro Study.  - Ddcu (faculty Dentistry Chulalongkorn University) International Symposium Of 2023.  71. 
Eugene Zhen Herr Yeoh, Khairil Aznan Mohamed Khan.  (2022).  Tooth-bleaching During Conventional Orthodontic Treatment: A Review.  - The 13th Asian Pacific Orthodontic Congress, Seoul, South Korea & The 55th Annual Scientific Congress Korean Association Of Orthodontists 2022.  181. 
Murshida Marizan Nor, Jonathan Yuen Jun Xian, Khairil Aznan Mohamed Khan.  (2022).  A Cross Sectional Study Of Live Versus Recorded Video Demonstrations For Undergraduate Orthodontic Examination And Diagnosis Teaching And Learning.  - 33rd South East Asian Association For Dental Education (seaade) 2022.  115. 
Tuti Ningseh Mohd Dom, Haslina Rani, Murshida Marizan Nor, Khairil Aznan Mohamed Khan, Syed Nabil Syed Omar, Hasherah Ibrahim, Suziyani Mohamed, Azianura Hani Shaari, Zainal Ahmad, Zuraini Ghazali.  (2021).  Enhancing Employability Values & Skills Among B40 Youths With Cleft Lip And Palate (clp).  - 1-44. 
Thum Chen, Pow Kah Jun, Murshida Marizan Nor, Tuti Ningseh Mohd Dom, Khairil Aznan Mohd Khan.  (2021).  Speech Problems, Self-esteem And Employment Challenges Among Youths With Cleft Lip And Palate.  - 1-92. 
Khairil Aznan Mohamed Khan.  (2016).  Health+.  - Braces Boost Self-confidence, Social Interactions.  32. 
Wan Nor Aziani Mohd Azmi, S. Nagarajan M.p.sockalingam , Khairil Aznan Mohamed Khan.  (2012).  Unerupted Maxillary Incisor: A Case Report.  - 8th Biennial Conference Pediatric Dentistry Association Of Asia "diverse Clinical Experiences Contribute To Novel Quality Of Pediatric Dentist Community". 
Ooi Hui Tieng, Tan Bee Ting, Tang Sook Hui, Dr Khairil Aznan M Khan, Dr. S. Nagarajan M.p Sockalingam.  (2012).  Prevalence Of Unerupted Permanent Maxillary Central Incisors Among Children Aged 8-12 In Universiti Kebangsaan Malaysia (ukm) Dental Clinic.  - Proceeding And Abstract Book : 10th Dental Students` Colloquium "synergizing Quality Research Towards Best Clinical Practices". 
Nur Raihanah M, Mohd Nazimi Aj, Khairil Aznan Mk, Alida M, Safura Anita B, Jasmina Qz, Rifqah N, Ruszymah Bhi, Marina Mb, Roszalina R..  (2011).  The Regeneration Of Dental Hard Tissues From Cultured Rat Tooth Bud Cells.  - Abstracts: Tissue Engineerieng Research Group: Progress Update. 
Ss Hamzah, K Othman, Kam Khan, Safura B.  (2011).  A Radiographic Study Of Maxillary Canine Roots Resorption Using 2 Types Of Orthodontic Brackets System; Self-ligating Vs Conventional.  - Kolokium Mahasiswa Pergigian Ukm Ke-9: Energizing Research Culture In Meeting Global Challenges. 
M Nur Raihanah, B Safura, A Mahyuddin, Aj Mohd Nazimi, Mk Khairil Aznan, Qz Jasmina, N Rofqah, Bhi Ruszymah, Mb Marina, R Ramli.  (2011).  Serial Miro Ct Analysis Confirms The Progression Of Tooth Tissue Formation In Nude Mice.  - 20th Scientific Conference Of The Electron Microscopy Society Of Malaysia. 
Nur Raihanah M, Mohd Nazimi Aj, Khairil Aznan Mk, Alida M, Safura Anita B, Jasmina Qz, Rifqah N, Ruszymah Bhi, Marina Mb, Roszalina R.  (2011).  The Regeneration Of Dental Hard Tissues From Cultured Rat Tooth Bud Cells.  - Medicine & Health. 
Elavarasi Kuppusamy, Malini Arumugam, Khairil Aznan Mohamed Khan.  (2010).  Hawley Retainer And Distortion Of Speech Articulation.  - Proceeding And Abstract Book, 8th Ukm Dental Students` Colloquium `learning Through Research`. 
Tiong Ing Teck, Tan Yann Ling, Khairil Aznan Mohamed Khan.  (2009).  Interceptive Orthodontics In Ukm.  - Proceeding And Abstract Book : 7th Dental Students` Colloquium "dental Research And Education - A Life-long Quest". 
Mardziah Mohamad, Noorlela Mastam, Khairil Aznan Mohamed Khan.  (2007).  Audit: Twin Block In Ukm.  - Seminar Pembentangan Projek Elektif Ke-4 Sesi 2005/2006 : Program & Abstrak. 
PROJEK PENYELIDIKAN / RESEARCH PROJECT
(Tajuk),(Peranan),(Tempoh),(Tahap)

Aktif

Evaluation of the Quality of Pre-treatment Records in Orthodontic Postgraduate Clinic Compared to Standards , Ketua Projek , 17-04-2024 sehingga 16-10-2025 , Universiti
A Comparison of Surface Characterization of Teeth and Orthodontic Fixed Appliance Using Different Orthodontic Toothbrushes , Ketua Projek , 11-12-2023 sehingga 10-05-2026 , Universiti
Clinical Performance and Patient Perception of Orthodontic Miniscrews Insertion in the Infrazygomatic Crest: A Randomized Clinical Trial , Penyelidik Bersama , 15-01-2024 sehingga 14-07-2026 , Universiti
Analysis of Undiagnosed Pathological Increase in Nasal Resistance Among Individuals Requiring Orthodontic Treatment – A Pilot Study , Penyelidik Bersama , 12-10-2023 sehingga 11-07-2025 , Universiti
THE STAIN REMOVAL EFFICACY OF A NEWLY DEVELOPED WHITENING DENTIFRICE: AN IN-VITRO STUDY , Penyelidik Bersama , 01-03-2022 sehingga 31-03-2025 , Universiti

Tamat

Effects Of Fixed Labial Orthodontic Appliance On Speech In Class II Division 1 Patients , Ketua Projek , 14-09-2017 sehingga 13-07-2019 , Universiti
Factors And Awareness Of Getting Orthodontic Treatment From Non-Dentist Among Generation Y: A Pilot Study , Ketua Projek , 12-01-2017 sehingga 11-09-2017 , Universiti
RETROSPECTIVE STUDY OFIMPACTED PERMANENT MANDIBULAR SECOND MOLAR , Ketua Projek , 01-07-2015 sehingga 30-06-2016 , Universiti
Prevalence of Unerupted Permanent Maxillary Central Incisors among Children Aged 8-12 in UKM Dental Clinic , Ketua Projek , 01-01-2011 sehingga 31-12-2011 , Universiti
Perceptual Analysis of Fricative Sounds in Typically Developing Individuals with Dental Malocclusion , Penyelidik Bersama , 28-03-2019 sehingga 27-02-2020 , Universiti
Perceptual Analysis of Speech in Cleft Lip and/or Palate School Age Children , Penyelidik Bersama , 28-03-2019 sehingga 27-01-2020 , Universiti
Enhancing Employability Values & Skills among B40 Youths with Cleft Lip and Palate (CLP) , Penyelidik Bersama , 01-12-2018 sehingga 31-05-2021 , Universiti
Fake Braces as a Trend or Treatment of Malocclusion , Penyelidik Bersama , 22-06-2015 sehingga 30-04-2016 , Universiti
The regeneration of Dental hard Tissues from cultured rat tooth bud cells , Penyelidik Bersama , 01-12-2007 sehingga 28-02-2010 , Kebangsaan
ANUGERAH DAN PENGURUSAN / AWARD AND STEWARDSHIP
(Nama Anugerah/Pentadbiran),(Institusi Penganugerahan),(Tahun)

Anugerah UKM

Anugerah Perkhidmatan Cemerlang / Anugerah Perkhidmatan Cemerlang , 2010
PENYELIAAN PELAJAR / SUPERVISION

Pelajar Sarjana

DR. NOORUNISA BINTI SHAWAL HAMID, Sarjana
Perbandingan Klinikal Peretrakan Kanin Maksila diantara Braket Konvensional dan Braket, DR. SHARINA BINTI SHARUDIN, Sarjana
Perselisihan Saiz Gig Bolton Di Kalangan Pesakit - Pesakit Ortodontik, DR. ASMAK BINTI SHAARI, Sarjana
KAJIAN IN-VITRO KEBERKESANAN UBAT GIGI PEMUTIH BAHARU (DENTALKIN WHITE OLEH DR. IRMA) DALAM MENGHILANGKAN KOTORAN EKSTRINSIK SEMASA RAWATAN ORTODONTIK, DR. EUGENE YEOH ZHEN HERR, Sarjana
Kesan Pengunyahan Terhadap Kadar Pergerakan Gigi Ortodontik, DR. MALATHI A/P DEVA TATA, Sarjana
KESAN PERTUTURAN APLIANS TETAP ORTODONTIK LABIAL DALAM PESAKIT YANG MEMPUNYAI HUBUNGAN INSISIF KELAS III, DR. LAW SIAW WEE, Sarjana
POTENSI LARUT LESAP ION LOGAM BERBAHAYA DARIPADA PERALATAN, DR. NORA RIZKA BINTI MOHAMAD, Sarjana
Penilaian Secara Prospektif Pengherotan Penyebutan di Kalangan Pesakit Memakai, SITI NORHAIZA BINTI IBRAHIM, Sarjana
KESAN APLIANS TETAP ORTODONTIK LABIAL TERHADAP PERTUTURAN, DR. FARAH LIYANA BINTI JAAFAR, Sarjana

Pelajar Doktor Falsafah

CLINICAL PERFORMANCE AND PATIENT PERCEPTION OF ORTHODONTIC, ARRON LIM YAN RAN, Doktor Falsafah
A COMPARISON OF SURFACE CHARACTERIZATION OF TEETH AND ORTHODONTIC, LIM SHEA LEE, Doktor Falsafah
Analysis of Dysfunctional Breathing in Patients Requiring Fixed Orthodontic, LEE SHEAN-WOEI, Doktor Falsafah
KHIDMAT SOSIAL / SOCIAL @ PUBLIC ENGAGEMENT
(Sumbangan),(Tempoh),(Peringkat)

Khidmat Luar

PANEL PEPERIKSAAN KELAYAKAN PROFESIONAL , 15-09-2015 sehingga 01-01-1970 , Kebangsaan
ORTHODONTIC GOVERNANCE IN MALAYSIA - CHALLENGES AHEAD , 21-04-2015 sehingga 21-10-2015 , Kebangsaan
CPG MANAGEMENT OF ANTERIOR CROSSBITE IN MIXED DENTITION , 01-04-2013 sehingga 31-10-2013 , Kebangsaan
KELAB KEBAJIKAN & REKREASI PEGAWAI BERSEKUTU JPAM SELANGOR , 01-07-2014 sehingga 30-06-2016 , Negeri
Advances of Surgical Management of Craniofacial Deformities , 11-05-2019 sehingga 13-05-2019 , Antarabangsa
PANEL PENYEDIAAN SOALAN KELAYAKAN PROFESIONAL MDC , 15-09-2015 sehingga 14-09-2022 , Kebangsaan
HIPODONTIA BUKAN SINDROMIK DAN KAITANNYA DENGAN MALOKLUSI DAN MORFOLOGI RANGKA , 04-08-2021 sehingga 01-01-1970 , Kebangsaan
ORANG YANG BERTANGGUNGJAWAB , 01-07-2021 sehingga 30-06-2023 , Kebangsaan
LEMBAGA PENGAJIAN PROGRAM SISWAZAH (1+3) TAHUN FAKULTI PERGIGIAN UKM , 15-07-2020 sehingga 14-07-2021 , Kebangsaan
PAKAR PERGIGIAN KLINIK PERGIGIAN PAKAR MERS UKM KESIHATAN , 01-01-2021 sehingga 01-01-4948 , Kebangsaan
PENILAI HOSPITAL MESRA KANAK-KANAK HPKK , 23-04-2021 sehingga 12-04-2022 , Kebangsaan
KETUA KLINIK PERGIGIAN PAKAR MERS , 01-07-2021 sehingga 30-06-0023 , Kebangsaan
Integrative Airway Summit 2022 , 25-02-2022 sehingga 27-02-0019 , Antarabangsa
EXPERTS PERSPECTIVE: ADVANCEMENT TOWARDS EDUCATION & RESEARCH , 29-09-2022 sehingga 29-09-2022 , Kebangsaan
UITM , 01-07-2022 sehingga 30-06-2023 , Kebangsaan
UNIVERSITI MAHSA , 01-09-2022 sehingga 31-10-2022 , Kebangsaan
MAJLIS PROFESOR NEGARA , 01-09-2022 sehingga 10-01-0019 , Kebangsaan
EFFECT OF LOW-LEVEL LASER THERAPY ON STABILITY DURING RETENTION PHASE AFTER ORHODONTIC TREATMENT: A RANDOMIZED CONTROLLED TRIAL , 03-01-2024 sehingga 01-01-1970 , Kebangsaan
JAWATANKUASA PENGAJIAN FAKULTI PERGIGIAN, UNIVERSITI MALAYA , 13-05-2024 sehingga 12-05-2027 , Kebangsaan
JAWATANKUASA TEKNIKAL TEKNOPOLIS KESIHATAN FAKULTI PERGIGIAN, UKM , 02-09-2024 sehingga 01-09-2025 , Kebangsaan

Khidmat Dalam

13th UKM DENTAL STUDENTS , 12-03-2015 sehingga 13-03-2015 , Fakulti / Institut / Pusat Perkhidmatan
BENGKEL PEMBANGUNAN KURIKULUM PROGRAM PENGAJIAN SISWAZAH(1+3) FAKULTI PERGIGIAN , 28-08-2019 sehingga 29-08-2019 , Fakulti / Institut / Pusat Perkhidmatan
CONJOINT MOCK EXAMINATION UKM-UITM, DCLINDENT (ORTHODONTICS) 2021 , 27-10-2021 sehingga 29-10-2021 , Pusat Pengajian / Jabatan / Pusat Penyelidikan / Unit
JAWATANKUASA PEMILIHAN CALON PROGRAM IJAZAH DOKTOR PERGIGIAN (DDS), FAKULTI PERGIGIAN UKM SESI AKADEMIK 2024/2025 , 16-06-2024 sehingga 17-06-2024 , Fakulti / Institut / Pusat Perkhidmatan
JAWATANKUASA PEMILIHAN CALON PROGRAM IJAZAH DOKTOR PERGIGIAN PENGAMBILAN SESI AKADEMIK 2023/2024 , 20-06-2023 sehingga 20-06-2023 , Fakulti / Institut / Pusat Perkhidmatan
JAWATANKUASA TASK FORCE PROJEK TEKNOPOLIS KESIHATAN FAKULTI PERGIGIAN UKM , 27-05-2022 sehingga 26-05-2025 , Fakulti / Institut / Pusat Perkhidmatan
Jawatankuasa dan ahli-ahli di bawah Timbalan Dekan (Jaringan Dan Alumni) , 01-08-2020 sehingga 31-07-2022 , Fakulti / Institut / Pusat Perkhidmatan
KEMASUKAN & TEMUDUGA CALON SISWAZAH, DOKTOR PERGIGIAN KLINIKAL (ENDODONTOLOGI, PERGIGIAN PEDIATRIK, PERGIGIAN RESTORATIF, ORTODONTIK, BEDAH MULUT DAN MAKSILOFASIAL) , 01-12-2019 sehingga 31-03-2021 , Universiti
KOLOKIUM ANTARABANGSA PENYELIDIKAN, INOVASI DAN KEUSAHAWANAN FAKULTI PERGIGIAN UKM 5.0 2023 BERSAMA DENGAN KOLOKIUM PRASISWAZAH (KE-21), SIMPOSIUM SISWAZAH (KE-4) PERGIGIAN UKM DAN HARI INOVASI KE-6; HARI KEUSAHAWANAN KE-3 , 09-05-2023 sehingga 10-05-2023 , Fakulti / Institut / Pusat Perkhidmatan
KOLOKIUM MAHASISWA PERGIGIAN KE-16 2018 , 13-03-2018 sehingga 14-03-2018 , Fakulti / Institut / Pusat Perkhidmatan
MESYUARAT PENJANAAN SOALAN PEPERIKSAAN KELAYAKAN PROFESIONAL MAJLIS PERGIGIAN MALAYSIA , 30-03-2016 sehingga 01-04-2016 , Universiti
PELANTIKAN SEBAGAI PENILAI PROJEK PENYELIDIKAN PRASISWAZAH , 10-03-2023 sehingga 10-03-2023 , Fakulti / Institut / Pusat Perkhidmatan
PEMBANGUNAN KURIKULUM PENGAJIAN SISWAZAH (1+3) TAHUN 2020-2023, FGG UKM , 01-01-2020 sehingga 31-12-2023 , Universiti
PEMBENTANGAN CADANGAN PENYELIDIKAN BAGI PROGRAM SARJANA SAINS GUNAAN PERGIGIAN SESI 2023/2024 , 23-02-2024 sehingga 20-03-2024 , Fakulti / Institut / Pusat Perkhidmatan
PEMILIHAN CALON PROGRAM PENGAJIAN SISWAZAH SESI 2017/2018 , 05-06-2017 sehingga 13-06-2017 , Fakulti / Institut / Pusat Perkhidmatan
PEMURNIAN PROFORMA KURSUS TERAS BAGI PROGRAM SISWAZAH BAHARU SARJANA FAKULTI PERGIGIAN , 18-09-2019 sehingga 18-09-2019 , Fakulti / Institut / Pusat Perkhidmatan
PENUBUHAN KLINIK PERGIGIAN PAKAR MERS FAKULTI PERGIGIAN , 01-01-2017 sehingga 31-12-2019 , Fakulti / Institut / Pusat Perkhidmatan
PERLANTIKAN AHLI JAWATANKUASA PEMILIHAN CALON PROGRAM PENGAJIAN SISWAZAH SESI 2018/2019 IJAZAH SARJANA SAINS PERGIGIAN , 28-08-2018 sehingga 28-08-2018 , Fakulti / Institut / Pusat Perkhidmatan
PROGRAM MOBILITI (INBOUND) SISWAZAH FAKULTAS KEDOKTERAN GIGI, UNIVERSITAS SUMATERA UTARA (USU) KE FAKULTI PERGIGIAN UKM , 13-05-2024 sehingga 17-05-2024 , Fakulti / Institut / Pusat Perkhidmatan
Pemilihan Pelajar Program Sarjana Sains Gunaan Pergigian (Selektif Ortodontik) Fakulti Pergigian, UKM Sesi 2022-2023 , 12-07-2022 sehingga 14-07-2022 , Fakulti / Institut / Pusat Perkhidmatan
SESI TEMUDUGA CALON PROGRAM IJAZAH DOKTOR PERGIGIAN SESI 2015/2016 , 27-05-2015 sehingga 29-05-2015 , Fakulti / Institut / Pusat Perkhidmatan
Skill Up with damon System: Clinical Pearl & Perils , 29-07-2022 sehingga 29-07-2022 , Fakulti / Institut / Pusat Perkhidmatan
URUSETIA SESI TEMUDUGA PROGRAM IJAZAH DOKTOR PERGIGIAN SESI 2018/2019 , 06-06-2018 sehingga 10-06-2018 , Fakulti / Institut / Pusat Perkhidmatan
WEBINAR PENGURUSAN RAWATAN PERGIGIAN UNTUK PESAKIT KLEF, FGG UKM 2021 , 27-10-2021 sehingga 27-10-2021 , Pusat Pengajian / Jabatan / Pusat Penyelidikan / Unit
“ORMCO PRODUCTS INTRODUCTION : EFFICIENCY IN ORTHODONTIC PRACTICE” , 01-07-2022 sehingga 01-07-2022 , Fakulti / Institut / Pusat Perkhidmatan