md bellal hossain, mohammad rashed iqbal faruque, sabirin abdullah, mohammad tariqul islam.  (2024).  optimization-driven design of a 2-bit coding based metasurface absorber for enhanced emi shielding and rcs reduction.  - ain shams engineering journal.  1-14. 

m b hossain, m r i faruque, s abdullah.  (2023).  modified combination of triple split ring resonator based triple band single negative metamaterial for satellite applications.  - the 2022 international conference on science & technology applications in climate change (staclim 2022).  1-9. 

md salah uddin afsar, mohammad rashed iqbal faruque, sabirin abdullah, k s al-mugren.  (2023).  compact and polarization insensitive satellite band perfect metamaterial absorber for effective electromagnetic communication system.  - materials.  1-15. 

md. salah uddin afsar, mohammad rashed iqbal faruque, sabirin abdullah, mohammad tariqul islam.  (2023).  royal crown shaped polarization insensitive perfect metamaterial absorber for c-, x-, and ku-band applications.  - computers, materials & continua.  455-469. 

mohamad zulfahmi bin mohamad izham, mardina binti abdullah, siti aminah binti bahari, gan kok beng & sabirin bin abdullah.  (2023).  development of graphical interface software for solar flare monitoring system.  - jurnal kejuruteraan.  257-264. 

md salah uddin afsar, mohammad rashed iqbal faruque, sabirin abdullah, mohammad tariqul islam, mayeen uddin khandaker, k s al mugren.  (2023).  an innovative compact split-ring-resonator-based power tiller wheel-shaped metamaterial for quad-band wireless communication.  - materials.  1-16. 

mardina bt. abdullah;lilia bt. halim;badariah binti bais;mohd azlan shah bin jaafar;noridawaty binti mat daud;roslinda binti rosli;siti aminah binti bahari;gan kok beng;nurul shazana binti abdul hamid;nurul hajijah binti hair;sabirin bin abdullah;norsuzli.  (2023).  pengembangan profesionalisma guru dalam sains angkasa melalui aktiviti pengalamian sistem ukm-sidπ™.  - .  . 

mst ishrat jahan, mohammad rashed iqbal faruque, md bellal hossain, sabirin abdullah.  (2023).  an ultra-thin, triple-band, incident angle-insensitive perfect metamaterial absorber.  - materials.  1-13. 

mardina abdullah, roslinda rosli, siti aminah bahari, noridawaty mat daud, nor syaidah bahri, sabirin abdullah, badariah bais, gan kok beng, lilia halim, nurul shazana abdul hamid.  (2022).  teknologi pengajaran dan pembelajaran ketika covid-19: inklusif, imersif dan integratif.  - .  167. 

air mohammad siddiky, mohammad rashed iqbal faruque, sabirin abdullah, mohammad tariqul islam, jamel nebhen.  (2022).  the circularly bent split ring resonator with a high effective medium ratio for multi frequency satellite band applications.  - journal of magnetism and magnetic materials.  1-17. 

air mohammad siddiky, mohammad rashed iqbal faruque, sabirin abdullah,mohammad tariqul islam, mayeen uddin khandaker, k s al mugren.  (2022).  dual square split ring enclosed spiral shaped hybrid metamaterial resonator with size miniaturisation for microwave wireless applications.  - scientific reports.  1-19. 

mohammad rashed iqbal faruque;norbahiah binti misran;mohd fais bin mansor;sabirin bin abdullah.  (2022).  a new split-triangular metamaterial for electromagnetic radiation reduction in human body .  - .  . 

mohammad mominur rahman, mohammad rezaul islam, mohammad touhidul islam, mohammad harun-or-rashid, mahfuzul islam, sabirin abdullah, mohammad borhan uddin, sumit das, mohammad saidur rahaman, muniruddin ahmed, fahad a. alhumaydhi, talha bin emran, etc.  (2022).  stem cell transplantation therapy and neurological disorders: current status and future perspectives.  - biology-basel.  1-42. 

ismatul n idrus, mohammad r i faruque, sabirin abdullah, mohammad t islam, mayeen u khandaker, jamel nebhen.  (2022).  an octagonal split ring resonator-based double negative metamaterial for s-, x- and ku-band applications.  - proceedings of the institution of mechanical engineers, part l: journal of materials: design and applications.  2269-2280. 

mohammad rashed iqbal faruque;mohammad tariqul islam;sabirin bin abdullah.  (2022).  functional graded nickel based nanocomposite coatings for oil and gas industry.  - .  . 

ismatul nisak idrus,mohammad rashed iqbal faruque, sabirin abdullah, mayeen uddin khandaker, nissren tamam, abdelmoneim sulieman.  (2022).  an oval square shaped split ring resonator based left handed metamaterial for satellite communications and radar applications.  - micromachines.  1-20. 

air mohammad siddiky, mohammad rashed iqbal faruque, mohammad tariqul islam, sabirin abdullah, mayeen uddin khandaker, k s almugren.  (2022).  dual-square-split-ring-enclosed microstrip-based sensor for noninvasive label-free detection.  - materials.  1-18. 

air mohammad siddiky, mohammad rashed iqbal faruque, mohammad tariqul islam, sabirin abdullah, mayeen uddin khandaker, nissren tamam, abdelmoneim sulieman.  (2022).  body-centered double-square split-ring enclosed nested meander-line-shaped metamaterial-loaded microstrip-based resonator for sensing applications.  - materials.  1-21. 

air mohammad siddiky, mohammad rashed iqbal faruque, sabirin abdullah,mohammad tariqul islam, jamel nebhen.  (2022).  double negative circular shaped inductively coupled metamaterial power splitter for the c-, x band applications.  - optik.  1-16. 

sabirin abdullah, johari talib.  (2021).  high-frequency trend during intense solar activity september 2017: equatorial studies.  - indian journal of physics.  1967-1976. 

mardina bt. abdullah;lilia bt. halim;badariah binti bais;rosadah binti abd majid;mohd azlan shah bin jaafar;noridawaty binti mat daud;roslinda binti rosli;gan kok beng;nurul shazana binti abdul hamid;nurul hajijah binti hair;sabirin bin abdullah.  (2021).  program pemantauan suar matahari menggunakan ukm-sidπ.  - .  . 

teh wai leong;mardina bt. abdullah;sabirin bin abdullah.  (2021).  magnetic classification and structure of sunspots in the active regions associated with solar flares.  - .  . 

rafidah abd malik, mardina abdullah, sabirin abdullah.  (2021).  komunikasi hf: hubungan ionosfera dan matahari.  - .  193. 

sabirin bin abdullah;mardina bt. abdullah;mohammad rashed iqbal faruque;teh wai leong.  (2021).  metamaterial based invisibility cloak for electromagnetic radiation control in space applications.  - .  . 

mohammad rashed iqbal faruque;mardina bt. abdullah;norbahiah binti misran;mohammad tariqul islam;sabirin bin abdullah.  (2021).  development of open mesh meta-atom mirror for solar radiation absorption.  - .  . 

mohammad rashed iqbal faruque, air mohammad siddiky, eistiak ahamed, mohammad tariqul islam, sabirin abdullah.  (2021).  parallel lc shaped metamaterial resonator for c and x band satellite applications with wider bandwidth.  - scientific reports.  1-15. 

roslinda rosli, mardina abdullah, nur choiro siregar, siti aminah bahari, nurul shazana abdul hamid, sabirin abdullah, gan kok beng, lilia halim, noridawaty mat daud, badariah bais.  (2021).  raising students' awareness and achievement in space science with solar flare monitoring project- based approach.  - 7th international conference on space science and communication (iconspace).  290-293. 

roslinda rosli, mardina abdullah, nur choiro siregar, siti aminah bahari, nurul shazana abdul hamid, sabirin abdullah, gan kok beng, lilia halim, noridawaty mat daud, badariah bais.  (2021).  raising students' awareness and achievement in space science with solar flare monitoring project-based approach.  - 2021 7th international conference on space science and communication.  1-4. 

air mohammad siddiky, mohammad rashed iqbal faruque, mohammad tariqul islam, sabirin abdullah, mayeen uddin khandaker.  (2021).  parabolic split ring resonator (psrr) based mnz metamaterial with angular rotation for wifi/wimax/wireless/ism band applications.  - chinese journal of physics.  753-769. 

tayaallen ramachandran,mohammad rashed iqbal faruque,sabirin abdullah,mohammad tariqul islam,muhammad roszaini roslan.  (2021).  left-handed compact multi-band circular metamaterial for s-, c- and ku-band applications.  - materials today: proceedings (second international conference on advances in intelligent systems, soft computing and optimization techniques 2020 (icaisco 2020).  1374-1381. 

air mohammad siddiky,mohammad rashed iqbal faruque,mohammad tariqul islam,sabirin abdullah.  (2021).  a multi-split based square split ring resonator for multiband satellite applications with high effective medium ratio.  - results in physics.  1-13. 

siti aminah bahari, nurul shazana abdul hamid, mardina abdullah, sabirin abdullah.  (2021).  examination of solar flare monitoring using a low cost vlf receiver.  - 7th international conference on space science and communication (iconspace).  5-10. 

sabirin bin abdullah;tamby subahan bin mohd. meerah;mohd. alauddin bin mohd. ali;alina marie binti hasbi;mohd azlan shah bin jaafar;siti aminah binti bahari;gan kok beng;kalaivani a/p chellappan;saadiah binti ramli;siti raihanah abdani.  (2020).  space science virtual task training knowledge portal development.  - .  . 

mohd. nizam bin mohd. said;mardina bt. abdullah;khairul nizam abdul maulud;mohd azlan shah bin jaafar;noridawaty binti mat daud;farhanah binti md isa;rawshan ara begum;siti aminah binti bahari;muhamad roszaini bin roslan;nurul hajijah binti hair;sabirin b.  (2020).  low cost earth-space monitoring system.  - .  . 

kalaivani a/p chellappan;iskandar bin yahya;seri mastura binti mustaza;sabirin bin abdullah;dahlila putri binti dahnil sikumbang.  (2020).  iot activated quay crane storm protection system.  - .  . 

roslinda rosli, mardina abdullah, nur choiro siregar, nurul shazana abdul hamid, sabirin abdullah, gan kok beng, lilia halim, noridawaty mat daud, siti aminah bahari, rosadah abd majid, badariah bais.  (2020).  student awareness of space science: rasch model analysis for validity and reliability.  - world journal of education.  170-177. 

sabirin abdullah, roslinda rosli,gan kok beng, mardina abdullah, lilia halim, norisza dalila ismail.  (2020).  stem outreach program of smart control helicopter competition in malaysia: a descriptive analysis.  - jurnal kejuruteraan.  29-34. 

mohammad tariqul islam;mardina bt. abdullah;sabirin bin abdullah;mohammad rashed iqbal faruque.  (2020).  development of a new double-negative metamaterial inspired multi-band antenna for satellite communication.  - .  . 

air mohammad siddiky, mohammad rashed iqbal faruque, mohammad tariqul islam, sabirin abdullah, mayeen uddin khandaker.  (2020).  inverse double-c shaped square split ring resonator based metamaterial with multi-resonant frequencies for satellite band applications.  - results in physics.  1-12. 

roslinda rosli,mardina abdullah, nur choiro siregar, nurul shazana abdul hamid, sabirin abdullah, gan kok beng, lilia halim,noridawaty mat daud, siti aminah bahari, rosadah abd majid, badariah bais.  (2019).  exploring space science through the ukm-sid pi outreach program.  - proceeding of the 2019 6th international conference on space science and communication (iconspace).  253-256. 

sabirin bin abdullah;mardina bt. abdullah;mohammad tariqul islam.  (2019).  modeling of maximum useable frequency (muf) for hf communication in malaysia.  - .  1-5. 

tayaallen ramachandran,mohammad rashed iqbal faruque, eistiak ahmed, sabirin abdullah.  (2019).  specific absorption rate reduction of multi split square ring metamaterial for l and s band application.  - results in physics.  1-10. 

mardina bt. abdullah;mohd azlan shah bin jaafar;siti aminah binti bahari;nurul shazana binti abdul hamid;sabirin bin abdullah;teh wai leong.  (2019).  investigation of ionospheric plasma bubbles occurrence due to wavelike structure modulation.  - .  1-5. 

j. talib, s. abdullah, k. wang.  (2019).  atmospheric radio noise effect towards hf communication in equatorial region at peninsular malaysia.  - 5th international conference on communication and computer engineering 2018.  1-6. 

ahmed mahfuz tamim, mohammad rashed iqbal faruque, mohammad tariqul islam, sabirin abdullah.  (2019).  split ring resonator loaded ef-structured left-handed metamaterial for modern electronic communications.  - european physical journal applied physics.  1-10. 

syahril amir mohd, kok beng gan, sabirin abdullah, mardina abdullah.  (2019).  the use of raspberry pi and high resolution sound card for very low frequency signal detection.  - proceeding of the 2019 6th international conference on space science and communication (iconspace).  261-266. 

nurul shazana binti abdul hamid;mardina bt. abdullah;sabirin bin abdullah;teh wai leong.  (2019).  investigation of the ionospheric bottom-side profile parameters along the equatorial sector.  - .  1-6. 

m j hossain, m r i faruque, m r ahmed, s abdullah, m t islam.  (2019).  design and analysis of compact perfect metamaterial absorber for xband applications.  - iop conf. series: earth and environmental science.  1-9. 

rafidah abd malik, mardina abdullah, sabirin abdullah, yokoyama tatsuhiro & clara y. yatini.  (2019).  development of hf modelling in peninsular malaysia during the rise of solar cycle 24.  - defence s & t technical bulletin.  51-60. 

lilia h., kalaivani c., ruhizan m.yasin, kamisah o., zanaton h.iksan, azmin sham r., w.juliana w.ahmad, effandi z., hafizah h., mardina a, rizafizah o., m.izwan mahmud,roslinda r.,abu yazid a.bakar, t.mastura t.soh, m.sattar rasul,sabirin a, s.mistima.  (2018).  futuristic multidiscipline stem mentoring program.  - rampai penyelidik siri 6.  . 

sabirin bin abdullah;mardina bt. abdullah;mohammad tariqul islam;mohammad rashed iqbal faruque.  (2018).  development of a small satellite with novel compact microstrip patch antenna for high speed communication.  - .  . 

rafidah abd malik, mardina abdullah, sabirin abdullah & mariyam jamilah homam.  (2018).  comparison of measured and predicted hf operating frequencies during low solar activity.  - international conference on space science and communication (iconspace2017).  . 

md. jubaer alam, mohammad rashed iqbal faruque, taya allen, sabirin abdullah, mohammad tariqul islam, khairul nizam abdul maulud,eistiak ahamed.  (2018).  depiction and analysis of a modied theta shaped double negative metamaterial for satellite application.  - open physics.  . 

liliahalim,kalaivanichellappan,ruhizanyasin,kamisahosman,zanatoniksan,azminshamrambely,wjulianawahmad,effandizakaria,hafizahhusain,mardinaabdullah,rizafizahothaman,mdizwanmahmud,roslindarosli,ayazidabakar,tmastura tsoh,m.sattar rasul,sabirinab&sitimistima.  (2018).  futuristic multidiscipline stem mentoring program.  - the 17th international expo on inventions and innovations.  . 

sabirin abdullah & ahmad faizal mohd zain.  (2018).  space science and communication for sustainability.  - .  12. 

dr. sabirin abdullah, nurul hajijah hair & prof. ir. dr. mardina abdullah.  (2018).  mengawal helikopter dengan alat kawalan mikro.  - impak sekolah @ ukm.  . 

rafidah abd malik, mardina abdullah, sabirin abdullah & mariyam jamilah homam.  (2018).  comparison of measured and predicted hf pperating frequencies during low solar activity.  - international conference on space science and communication (iconspace2017).  . 

rawshan ara begum, fatimah pk ahamad, mohammad rashed iqbal faruque, sabirin abdullah & khairul nizam abd maulud.  (2018).  proceedings of ipi research colloquium 2017.  - proceedings of ipi research colloquium 2017.  . 

rawshan ara begum, fatimah pk ahamad, mohammad rashed iqbal faruque, sabirin abdullah, khairul nizam abd maulud.  (2018).  proceedings of ipi research colloqium 2017.  - proceedings of ipi research colloqium 2017.  . 

md. jubaer alam, mohammad rashed iqbal faruque,mohammad jakir hossain, mohammad tariqul islam & sabirin abdullah.  (2018).  depiction of a combined split p-shaped compact metamaterial for dual-band microwave application.  - proceedings of the second international conference on the future of asean icofa.  . 

eistiak ahamed, md. mehedi hasan, mohammad rashed iqbal faruque, mohd fais bin mansor, sabirin abdullah, mohammad tariqul islam.  (2018).  left-handed metamaterial inspired by joint td geometry on flexible nial2o4 substrate.  - plos one.  . 

m. m. hasan,e. ahamed,m. r. i. faruque,m. t. islam,s. abdullah.  (2018).  reconfigurable metamaterial for 5g application.  - journal of optoelectronics and advanced materials.  . 

md. jubaer alam, mohammad rashed iqbal faruque, sabirin abdullah, mohammad tariqul islam.  (2018).  double-split labyrinth resonator with defective ground system for wide-band band-stop filter application.  - aip advances.  . 

md. jubaer alam, mohammad rashed iqbal faruque, md. iqbal hossain, mohammad tariqul islam & sabirin abdullah.  (2017).  a combined double h-shaped microstrip patch antenna for x-band operation.  - international conference on electrical, computer and communication engineering (ecce).  . 

mohammad jakir hossain, mohammad rashed iqbal faruque, md. iqbal hossain, mohammad tariqul islam & sabirin abdullah.  (2017).  effective medium ratio obeying multiple octagonal split-ring resonators based metamaterial for tri-band applications.  - international conference on electrical, computer and communication engineering (ecce).  . 

suparta w, ismail m, abdullah m, faruque m r i, khairul nizam abdul maulud, mohd shahrul mohd nadzir, mandeep singh jit singh, zamri zainal abidin,sabirin abdullah,teh wai leong, md firoz khan, islam m t, bahari s a, daud n m.  (2017).  2017 international conference on space science and communication.  - 2017 international conference on space science and communication.  1-337. 

malik, r. a, abdullah, m, abdullah, s, homam, m. j, yokoyama, t, yatini, c. y.  (2017).  prediction and measurement of high frequency radio frequencies in peninsular malaysia and comparisons with the international reference ionosphere model.  - advanced science letters.  1294-1298. 

md amanath ullah, touhidul alam, sabirin abdullah, mohd fais mansor, norbahiah binti misran & mohammad tariqul islam.  (2017).  a 3d unidirectional antenna for microwave application.  - 2017 progress in electromagnetics research symposium - spring (piers).  . 

sabirin bin abdullah.  (2017).  galaxy forum southeast asia - malaysia 2016.  - earth to space ipi buletin.  12-13. 

r.a. malik,m. abdullah, s. abdullah, m.j. homam.  (2016).  comparison of maximum usable frequency (muf) variability over peninsular malaysia with iri model during the rise of solar cycle 24.  - journal of atmospheric and solar-terrestrial physics.  87-92. 

rosadah abd majid, mardina abdullah, badariah bais, gan kok beng, sabirin abdullah, nor syaidah bahri.  (2016).  pengayaan pembelajaran sains angkasa menggunakan raspberry pi.  - kongres knovasi pnp ukm 2016.  . 

khairul nizam abdul maulud, mardina abdullah, wayan suparta, sabirin abdullah, mohammad rashed iqbal furuque, teh wai leong, farhanah md isa, nurul hajijah hair, muhamad roszaini roslan, mohd sayuti c.  (2016).  laporan konsolidasi program pengajian siswazah sarjana sains secara penyelidikan, institut perubahan iklim.  - .  . 

mardina abdullah, badariah bais, rosadah abd majid, gan kok beng, sabirin abdullah, noridawaty mat daud, siti aminah bahari, nor syaidah bahri.  (2016).  raspberry pi: green technology for space weather monitoring.  - impact.  . 

mardina abdullah, kok beng gan, sabirin abdullah, badariah bais, rosadah abd majid.  (2016).  ionospheric flare detection using raspberry pi.  - iswi newsletter.  . 

malik, r. a., abdullah, m., abdullah, s., homam, m. j., yokoyama, t., yatini, c.y..  (2016).  correlation of the ionospheric f2-layer parameters with muf during the rise of solar cycle 24.  - .  . 

khairul nizam abdul maulud, mardina abdullah, wayan suparta, sabirin abdullah, mohammad rashed iqbal furuque, teh wai leong, farhanah md isa, nurul hajijah hair, muhamad roszaini roslan, mohd sayuti c.  (2016).  laporan konsolidasi program pengajian siswazah doktor falsafah secara penyelidikan, institut perubahan iklim.  - .  . 

sr. dr. khairul nizam abdul maulud, prof. ir. dr. mardina abdullah, prof. madya dr. wayan suparta, dr. sabirin abdullah, dr. mohammad rashed iqbal furuque, dr. teh wai leong, farhanah md isa.  (2015).  laporan semakan program pengajian siswazah sarjana sains (sains angkasa) secara penyelidikan, institut perubahan iklim.  - .  . 

malik r.a., abdullah m., abdullah s., homam m.j..  (2015).  the influence of sunspot number on high frequency radio propagation.  - 2014 ieee asia-pacific conference on applied electromagnetics, apace 2014 - proceeding.  107-110. 

malik r. a., abdullah m., abdullah s., homam m. j., yokoyama t., michi, n..  (2015).  ionospheric empirical model: initial approach to muf modeling in the malaysian region.  - proceeding of the 2015 international conference on space science and communication (iconspace), 10-12 august 2015, langkawi, malaysia.  252-255. 

sr. dr. khairul nizam abdul maulud, prof. ir. dr. mardina abdullah, prof. madya dr. wayan suparta, dr. sabirin abdullah, dr. mohammad rashed iqbal furuque, dr. teh wai leong, farhanah md isa.  (2015).  laporan semakan program pengajian siswazah doktor falsafah (sains angkasa) secara penyelidikan, institut perubahan iklim.  - .  . 

sr. dr. khairul nizam abdul maulud, prof. ir. dr. mardina abdullah, prof. madya dr. wayan suparta, dr. sabirin abdullah, dr. mohammad rashed iqbal furuque, dr. teh wai leong, farhanah md isa.  (2015).  laporan semakan program pengajian siswazah doktor falsafah (astronautik) secara penyelidikan, institut perubahan iklim.  - .  . 

sr. dr. khairul nizam abdul maulud, prof. ir. dr. mardina abdullah, prof. madya dr. wayan suparta, dr. sabirin abdullah, dr. mohammad rashed iqbal furuque, dr. teh wai leong, farhanah md isa.  (2015).  laporan semakan program pengajian siswazah sarjana sains (astronautik) secara penyelidikan, institut perubahan iklim.  - .  . 

sr. dr. khairul nizam abdul maulud, prof. ir. dr. mardina abdullah, prof. madya dr. wayan suparta, dr. sabirin abdullah, dr. mohammad rashed iqbal furuque, dr. teh wai leong, farhanah md isa.  (2015).  laporan semakan program pengajian siswazah sarjana sains (pengurusan angkasa dan polisi) secara penyelidikan, institut perubahan iklim.  - .  . 

sr. dr. khairul nizam abdul maulud, prof. ir. dr. mardina abdullah, prof. madya dr. wayan suparta, dr. sabirin abdullah, dr. mohammad rashed iqbal furuque, dr. teh wai leong, farhanah md isa.  (2015).  laporan semakan program pengajian siswazah doktor falsafah (pengurusan angkasa dan polisi) secara penyelidikan, institut perubahan iklim.  - .  . 

malik, r. a., abdullah, m., abdullah, s., homam, m. j..  (2014).  the influence of sunpsot number on high frequency radio propagation.  - 2014 ieee asia-pacific conference on applied electromagnetics (apace).  . 

sabirin bin abdullah, muhamad roszaini bin roslan, mohd azlan shah bin jaafar.  (2014).  permodenan frekuensi kritikal dari kajian gelombang radio menggunakan penderung ionosfera.  - .  . 

ho y.h., abdullah s., mokhtar m.h..  (2014).  global positioning system (gps) positioning errors during ionospheric scintillation event.  - jurnal teknologi (sciences and engineering).  33 - 38. 

kalaivani chellappan, sabirin abdullah.  (2013).  angkasa research knowledge organization system : a needs analysis study.  - proceeding of the 2013 ieee international conference on space science and communication (iconspace).  . 

ahmad faizal mohd. zain , sabirin bin abdullah and zeti akma rhazali.  (2013).  dermination of gyro frequency from critical frequency measurements over parit raja, malaysia.  - proceeding of the 2013 ieee international conference on space science and communication (iconspace).  . 

y.h. ho., s. abdullah, m. h. mokhtar.  (2013).  global positioning system (gps) positioning errors modeling using global ionospheric scintillation model (gism).  - proceeding of the 2013 ieee international conference on space science and communication (iconspace).  . 

sabirin abdullah, ahmad faizal mohd. zain.  (2012).  diurnal and seasonal variation of critical frequency in malaysia from 2005 to 2007.  - applied mechanics and materials.  .