ABSTRACT. There are several types of amplifier classes, and this includes the class E amplifier. The class E can achieve its efficiency up to 100%. This paper thus aims on getting the best model in estimating the power added efficiency of Class E power amplifier circuit using Silicon Carbide MESFET. Twelve models are obtained from three independent variables; DC current (Idc), drain voltage (Vdc), and power out (Pout). The original data set of 7 is generated to become 105 data samples (21 sets x 5 observations where each set with two missing observations) using the Jackknife sampling technique at the first stage (7C2). The power added efficiency model employs the Multiple Regression (MR) technique up to the second order of interactions. The best model is based on the eight selection criteria (8SC). The best model is found to be model M12.5.0, chosen from the six selected model).Efficiency factors affect the power added efficiency estimation are found to be X3(IDC) and X12(interaction between Pout and VDS).

KEYWORDS. Multiple Regression; Jackknife; interactions; Power Added Efficiency; Efficiency Factors.

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Aminatul Hawa Yahaya, Noraini Abdullah, & Zainodin H. J. 2012. Multiple Regression Models up to First-order Interaction on Hydrochemistry Properties. Asian Journal of
Mathematics and Statistics, 5 (4): 121-131.

Bameri, H, Hakimi, A., & Movahhdi, M. 2011. A Linear-high Range Output Power Control Technique for Cascade Power Amplifier. Microelectronics Journal, 42: 1025-1031.

Franco, M., & Katz, A. J. 2005. Class E Silicon Carbide VHF Power Amplifier. IEEE MTT-S International Microwave Symposium Digest, The College of New Jersey, Ewing, NJ,  08628, USA.

Lucyszyn, S. 1997. Power-added Efficiency Errors with RF Power Amplifiers. International Journal of Electronics 82 (3): 303-312.

Lee, Y. S., & Jeong Y. H. 2007. A High-Efficiency Class-E Amplifier Using Sic MESFET. Microwave and Optical Technology Letters, 49 (6): 1447-1449.

Milosevic, D., Van Der Tang, J., & Van Roermun, A. 2002. Investigation on Technological Aspects of Class E RF Power Amplifier for UMTS Applications, in CiteSeerX.

Noraini Abdullah, Zainodin Haji Jubok, & Nigel Jonney J. B. 2008. Multiple Regression Models of the Volumetric Stem Biomass. WSEAS Transactions on Mathematics, 7 (7): 492-502.

Noraini Abdullah, Zainodin Haji Jubok, & Amran Ahmed. 2012. Sustainable Urban Forest Using Multiple Regression Models. Research Journal of Forestry, 6 (1):1-15.

Lind, D. A, Marchal, W. G., & Mason, R. D. 2005. Statistical Technique in Business and Economics, 11th Edn., McGraw-Hill Inc, New York, USA.

Quenouille, M. H. 1949. Problems in Plane Sampling. Annal of Mathematical Statistics, 20 (3): 355- 375. Power Added Efficiency Model for Mesfet Class E Power Amplifier using Jackknife Resampling 51

Stepan Lucyszyn, 1997. “Power-added Efficiency Errors with RF Power Amplifiers” . International Journal of Electronics, 82 (3): 303-312.

Soumya Shatakshi Panda & P.Manikandan. 2012. An Efficient And Power Optimized Cascode Stage RF Tuned Class-E Power Amplifier. International Journal of Engineering Research & Technology (IJERT), 10 (1): 1-6.

Tichelaar, B. W., & Ruff, L. J. 1989. How Good Are Our Best Models? Jackknifing, Bootstrapping, and Earthquake Depth. Eos, 70 (20): 593-606.

Zainodin, H. J, Noraini, A., & Yap, S. J. 2011. An Alternative Multicollinearity Approach in Solving Multiple Regression Problem. Trends in Applied Sciences Research, 6 (11): 1241-1255


ABSTRACT. A vertical electrical sounding (VES) survey was conducted in Dent Peninsular, Lahad Datu Sabah. The main objectives of the study are to determine the geo-electrical characteristic curves of the sediments and to relate them to various rock formations and layer of aquifer potential. In this study, the schlumberger electrode configuration was adopted for the acquisition of VES data in the field. A total of 31 VES stations were occupied within Sebahat, Ganduman and Togopi Formation of the study area. Resistivity curve types identified ranges from simple H until HQ, QH, KA, AA and QQ curve types, reflecting facies or lithological variations in the area. Four typical geo-electrical resistivity curves obtained can be associated with different rock formations in the study area. Four pattern of resistivity curves were obtained for Sebahat Formation with no typical characteristic type of curves which include HQ, QQ, QH and H types. Two typical resistivity curves were observed for the Lower Ganduman Formation (HQ and QQ) and three typical curves characterized the Upper Ganduman Formation (H, HQ and KA). Similarly, three typical resistivity curves (HQ, AA and H) were obtained for Togopi Formation. Interpreted 2D geo-electrical resistivity section obtained for all the sedimentary rock formations were used to evaluate the potential aquifer in the study area. The results show that the thick sandstone layers found in the Lower Ganduman and Togopi Formation have potential to become good groundwater aquifers. In addition, there is also a possibility of variable thickness of sandstone layer in the Upper Ganduman Formation to become a possible unconfined aquifer.

Vertical Electrical Sounding, groundwater, geo-electrical characterization, Schlumberger.

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Abd. Manaf Ishak, Gamble, D. H. F., & Krishna Kumar. 1990. Dent Peninsular Water  Supply: Supply to Village D and The Industrial Complex. Groundwater & the Environment: Proceedings of The 2nd International Groundwater Conference, Kota Bharu. Hlm. B26-B36.

Hadi Tahmasbi Nejad. 2009. Geoelectrict Investigation of the Aquifer Characteristic and Groundwater Potential in Behbahan Azad University Farm, Khuzestan Province, Iran.Journal of Applied Science, 9 (20): 3691-3698.

Haile, N. S., & Wong, N. R. Y. 1965. The Geology and Mineral Resources of Dent Peninsula, Sabah. Geological Survey, Borneo Region, Malaysia. Memoir 16. Kuching, Sarawak: Vincent Kiew Fah San, Goverment Printer.

Hutchison, C. S. 2005. Geology of North-West Borneo: Sarawak, Brunei and Sabah. Kuala Lumpur: Universiti Malaya.

Ismail Che Mat Zin. 1994. Dent Group and its Equivalent in the Offshore Kinabatangan Area, East Sabah. Bulletin Geology Society of Malaysia, 36: 127-143.

Koeffoed, O. 1979. Geosounding Principle: 1, Resistivity Sounding Measurements. Amsterdam: Elsevier.

Loke, M. H. 2012. Tutorial 2D and 3D Electrical Imaging Surveys. Revision date 2012.

Geotomo Software, Malaysia. Retrieved from www.geotomosoft.com.

Mooney, H. M. 1980. Handbook of Engineering Geophysics,Volume 2: Electrical Resistivity. United State of America: Bison Instrument INC.

Oseji, J. O., Atakpo, E. A., & Okolie, E. C. 2005. Geoelectric Investigation of the Aquifer Characteristics and Groundwater Potential in Kwale, Delta State, Nigeria. Journal of
Applied Science Environmental, 9 (1): 157 – 160.

Oseji, J.O., & Ujuanbi, O. 2009. Hydrogeophysical Investigation of Groundwater Potential in Emu kingdom, Ndokwa Land of Delta State, Nigeria. International Journal of Physical Sciences, 4 (5): 275-284.

Parasnis, D. S. 1962. Principles of Applied Geophysics. London: Chapman & Hall.

Sanudin Tahir, & Baba Musta. 2007. Pengenalan Kepada Stratigrafi. Kota Kinabalu, Sabah: Penerbit UMS.

Sanudin Tahir., Shariff A. K. Omang, & Majeed M. F. 1995. Middle Miocene Volcanic Sequence in Eastern Sabah. Borneo Science, 1 (1): 9-27.

Telford, W. M., Geldart, L. P., Sheriff, R. E., & Keys, D. A. 1990. Applied Geophysics. 2nd ed. Cambridge: Cambridge University Press.


ABSTRACT. Banteng cattle have been domesticated in several places in the Southeast Asia. A domesticated form of Banteng, called ‘Bali cattle’ considered to be the same species and occurs widely in Indonesia and has been introduced to other areas of the world. Banteng cattle were classified as endangered species by IUCN Red List. In the past few years an effort has been made by Department of Veterinary Services and Animal Industry (DVSAI) Sabah, Malaysia in Banteng research for conservation and breeding program purposes. Electroejaculation technique was applied on fifteen Banteng cattle for semen collection. Collected fresh semen then analyzed for semen volume, pH, sperm concentration and motility. The objective of this study was to determine the fresh semen quality of domesticated Banteng cattle reared in Sabah, Malaysia. Results in this study show the semen volume was between 2.2 to 11.5 ml (mean; 6.28±2.3 ml), pH 6.63 to 7.48 (mean;7.01±0.24), sperm concentration between 30 to 470 x 106 sperm/ml (mean; 266 x 106 sperm/ml) and sperm motility between 10 to 70% (mean; 56.08±16.72 %). We conclude that data generated in this study were useful and important hedge against the complete loss of threatened populations of Banteng cattle, in making the decision for conservation and breeding program where the sources were very limited.

KEYWORDS. Banteng, Bali cattle, semen quality

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Al-Hakim, M. K., Ali, S. B. A., & Singh, B. P. 1984. Study on Semen Characteristics of Karadi (Kurdi) Bulls. Indian Journal of Animal Health, 23: 163-169.

Aghangari, Y. T. 1992. Cryopreservation of ram semen for AI. Thesis PhD, University of Wales.

Amann, R. P. 1989. Can the Fertility Potential of a Seminal Sample be Predicted Accurately? Journalof Andrology, 10: 89-98.

Andrews, L. G. 1972. The Major Non-infectious Causes of Reproductive Wastage in Beef Cattle in the Northern Territory. Australian Veterinary Journal, 48: 41-46.

Arifiantini, R. I., Wiresdiyati, T., & Retnani, E. F. 2006. Sperm Morphology Assessment of Bali Bull Cattle using “William” Stain. Journal of the Indonesian Tropical Animal Agriculture, 31: 105-110.

Ballester, J., Johannisson, A., Saravia, F., Haard, M., Gustafsson, H., Bajramovic, D., & Rodriguez-Martinez, H. 2007. Post-thaw Viability of Bull AI-doses with Low-sperm Numbers. Theriogenology, 68: 934-943.

Barth, A. D. 2000. Bull Breeding Soundness Evaluation Manual. 2nd edition. The Western Canadian Association of Bovine Practitioners. Lacombe, Alberta, Canada.

Bearden, H. J., & Fuquay, J. W. 1997. Applied Animal Reproduction. 4th edition. New Jersey:

Prentice-Hall Inc., Upper Saddle River, USA.

Brito, L. F. C., Silva, A. D. E. F., Rodrigues, L. H., Vieira, F. V., Deragon, A. G., & Kastelic,

J. P. 2002. Effect of Environmental Factors, Age and Genotype on Sperm Production and Semen Quality of B. indicus and B. taurus AI bulls in Brazil. Theriogenology, 70: 181-190.

Copland, R. S. 1974. Observations on Banteng Cattle in Sabah. Tropical Animal Health and Production, 6: 89-94.

Dahmani, Y. 2012. Semen Evaluation Methods in Cattle. Magapor R&D Department. Retrieved 25 November 2012, from http://www.magapor.com/images/Veterinarios/iDoc_18.pdf

Darmadja, D. 1980. Half Century of Traditional Bali Cattle Farming in Baliness Agricultural Ecosystem. Thesis PhD. Padjadjaran University, Bandung, Indonesia.

Devendra, C. T., Choo, L. K., & Pathmasingan, M. 1973. The productivity of Bali cattle in Malaysia. Malaysian Agriculture Journal, 49: 183-197.

Falk, A. J., Waldner, C. L., Cotter, B. S., Gudmundson, J., & Barth, A. D. 2001. Effects of Epidural Lidocaine Anesthesia on Bulls during Electroejaculation. Canadian Veterinary Journal, 42: 116-120.

Fiaz, M., Usmani, R. H., Abdullah, M., & Ahmad, T. 2010. Evaluation of Semen Quality of Holstein Friesian and Jersey Bulls Maintained under Subtropical Environment. Pakistan Veterinary Journal, 30: 75-78.

Gil, M. A., Roca, J., Cremades, T., Hernandez, M., Vazquez, J. M., Rodriguez-Martinez, H., & Martinez, E. A. 2005. Does Multivariate Analysis of Post-thaw Sperm Characteristics Accurately Estimate in Vitro Fertility of Boar Individual Ejaculates? Theriogenology, 64: 305-316.

Hafez, E. S. E. 1974. Reproduction in Farm Animals. 3rd edition. Philadelphia: Lea and Fibiger, USA.

Hedges, S. 1996. Proposal for Inclusion of Banteng (Bos javanicus) in CITES Appendix I. IUCN/SSC Asian Wild Cattle Specialist Group, IUCN/SSC Wildlife Trade Programme, Thai Government, Bangkok.

Huat, K. S. 1973. Semen Characteristics of Crossbred Goats. (Kambing Kajong Jamnapari). Kajian Veterinar (Malaysia Singapore), 7: 63-66.

Ismail, M. I., Jaffar, F. F., Zainalabidin, F. A., Mail, M. H., Hajarian, H., Ismail, Z., Karim, A. A. A., Jaffar, F. H. F., Nang, C. F., Hassan, N., Mohamad, S. F. S., Ibrahim, S. F., Osman, K., & Othman, A. M. 2010. Semen Analysis of Bali Cattle (Bos Javanicus) Bulls Ranched in Oil Palm Plantation in Malaysia. Reproductive Biotechnology, 7: 46.

Iswadi, M. I., Ann, Z. F., Hafiz, M. M., Hafiz, M. D., Fahrul, F. J., Hajarian, H., Wahid, H., Zawawi, I., Khairiah, M. S., & Mazni, O. A. 2012. Collection, Analysis and Cryopreservation of Semen from Malayan Gaur (Bos gaurus Hubbacki): A Preliminary Study. Open Veterinary Journal, 2: 109-114.

International Union for Conservation of Nature. 2012. IUCN Red List of threatened species. World Conservation Union, Gland, Switzerland. Retrieved 25 November 2012, from http:// www.iucnredlist.org.

Januskauskas, A., Johannisson, A., & Rodriguez-Martinez, H. 2003. Subtle Membrane Changes in Cryopreserved Bull Semen in Relation with Sperm Viability, Chromatin Structure, and Field Fertility. Theriogenology, 60: 743-758.

Johari, J. A., & Jasmi, Y. 2009. Breeds and Breeding Program for Beef Production in Malaysia. Proceeding of the 8th Malaysia Congress on Genetics, 4-6 August 2009, Genting Highlands, Malaysia: 22-28.

Johnson, L. A., Weitze, K. F., Fiser, P., & Maxwell, W. M. 2000. Storage of Boar Semen. Animal Reproduction Science, 62: 143-172.

Kirby, G. W. M. 1972. Bantengs, a New Source of Genes. Turn Off, 4: 6-8.

Mamabolo, M. J. 1999. Dietary, Seasonally and Environmental Influences on Semen Quality and Fertility Status Indigenous Goats in Mpumalanga Province, South Africa. M. Inst. Agrar. Thesis, University of Pretoria, South Africa.

Martojo, H. 2002. A Simple Selection Program for Smallholder Bali Cattle Farmers. Proceeding of an ACIAR Workshop on Strategies to Improve Bali Cattle in Eastern Indonesia, Denpasar, Bali, Indonesia: 43-47.

Mathevon, M., Bhyr, R. M., & Dekkers, J. C. 1998. Environmental, Management and Genetic Factors Affecting Semen Production in Holstein Bulls. Journal of Dairy Science, 81: 3321-3330.

McGowan, M. 2004. Approach to Conducting Bull Breeding Soundness Examinations. In Practice, 26: 485-491.

Parkinson, T. J. 2004. Evaluation of Fertility in Natural Service Bulls. Veterinary Journal, 168: 215-229.

Patel, B. R., & Siddiquee, G. M. 2013. Physical and Morphological Characteristics of Kankrej Bull Semen. Veterinary World, 6: 405-408.

Payne, W. J. A. 1970. Cattle Production in the Tropics, 1 vol.: Breeds and Breeding.

Tropical Agriculture Series, Longman Group Ltd., London: 336.

Purwantara, B., Noor, R. R., Andersson, G., & Rodriguez-Martinez, H. 2012. Banteng and Bali Cattle in Indonesia: Status and Forecasts. Reproduction in Domestic Animals, 47: 2-6. Roberts, S. J. 1986. Veterinary Obstetrics and Genital Diseases (Theriogenology), 3 rd Edition. Woodstock VT, USA: 622.

Sarder, M. J. U. 2007. Environment Related Variations in the Semen Characteristics of Bulls used for Artificial Insemination (AI) Programme In Bangladesh. University Journal of Zoology, Rajshahi University, 26: 81-88.

Shaha, S. P., Alam, M. G. S., Khatun, M., & Ahmed, J. U. 2008. Breeding Soundness of Stud Bulls. The Bangladesh Veterinary Journal, 25: 51-61.

Sharma, M., Singh, M., Kapoor, S., & Jasial, S. 2012. Inter Relationship Between Some Routine Semen Evaluation Parameters in Jersey X Local Hill Cattle Crossbred Bulls. Open Veterinary Journal, 2: 26-31.

Mohd Iswadi Ismail, Fazly Ann Zainalabidin, Mohd Hafiz Mail, Siti Romaino Mohd Nor, Loo Shu San, Fahrul Firdaus Jaffar, Punimin Abdullah, Daud Yusof, Abd Wahid Haron, & Abas Mazni Othman 32

Talib, C., Entwistle, K., Sirega, A., Budiarti-Turner, S., & Lindsay, D. 2002. Survey of Population and Production Dynamics of Bali Cattle and Existing Breeding Programs in Indonesia. Proceeding of an ACIAR Workshop on Strategies to Improve Bali Cattle in Eastern Indonesia, Denpasar, Bali, Indonesia: 3-9.

Toelihere, M. R. 2002. Increasing the Success Rate and Adoption of Artificial Insemination for Genetic Improvement of Bali Cattle. Proceeding of an ACIAR Workshop on Strategies to Improve Bali Cattle in Eastern Indonesia, Denpasar, Bali, Indonesia: 48-53.

Van Denmark, N. L., & Free, M. J. 1970. Temperature Effect. In Johnson AD, Ggomes WR and Van Denmark NL. The Testis, volume 3. Academic Press, New York, USA: 233- 312.

Wells, M. E., Smith, S., Breuer, D. J., & Stotts, B. A. 1976. Ejaculate Characteristics of Angus and Hereford Bulls Finishing Test Gain. Research Report, Agricultural Experiment Station, Oklahoma State University: 134-136.


ABSTRACT. One of the famous heritages in Sabah is the traditional musical instrument called sompoton. This instrument has several parts with the vibrator being the most important of all. In this paper, the vibrator is modeled as a cantilever beam with uniformly distributed mass. Using this model, the fundamental frequency is analyzed using Rayleigh’s energy theory. The vibrator made from aluminum is fabricated at different dimensions and is excited using constant air jet to obtain its fundamental resonance frequency. The measured fundamental frequency is then compared with the theoretical values calculated based on cantilever beam model and Rayleigh’s energy theories. It was found that the experimental and theoretical results exhibit the same trend but differ in magnitude. To overcome this, a correction factor is added to the theoretical formulation to account for fabrication error.

KEYWORDS. Vibrator, cantilever beam, Rayleigh’s energy theory, resonance frequency, single degree of freedom system.

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Bansal, R. K. 2010. A Text Book of Strength of Materials (4th ed). Daryaganj, New Delhi: Laxmi Publications (P) Ltd.

Erkut, C., Karjalainen, M., Huang, P., & Välimäki, V. 2002. Acoustical Analysis and Model Based Sound Synthesis of the Kantele. Journal of the Acoustical Society of America, 112(4): 1681-1691.

Gere, J. M., & Goodno, B. J. 2008. Mechanics of Materials (7th ed). Toronto, Kanada: Cengage Learning.

Hopkin, B. 1996. Musical Instrument Design: Practical Information for Instrument Design. Tucson, Arizona: See Sharp Press.

Ismail, A., Samad, S. A., Hussain, A., Azhari, C. H., & Zainal, M. R. M. 2006. Analysis of the Sound of the Kompang for Computer Music Synthesis. IEEE 4th Student Conference on Research and Development (SCOReD 2006). 27-28 June 2006, Shah Alam, Selangor, Malaysia.

Marasan, R. 2003. Alat Muzik Sompoton Negeri Sabah. Pejabat Kebudayaan dan Kesenian Negeri Sabah, Sabah, Malaysia.

Merriman, M. 1924. Mechanics of Materials. John Wiley & Sons.

Ong, C. W., & Dayou, J. 2009. Frequency Characteristic of Sound from Sompoton Musical Instrument. Borneo Science, 25: 71-79.

Rujinirum, C., Phinyocheep, P., Prachyabrued, W., & Laemsak, N. 2005. Chemical Treatment of Wood for Musical Instruments. Part I: Acoustically Important Properties of Wood for the Ranad (Thai Traditional Xylophone). Wood Science and Technology, 39(1): 77-85.

Serway, R. A., & Jewett, J. W. 2006. Principles of Physics: A Calculus-Based Text, 4th Edition (Available 2010 Titles Enhanced Web Assign)., USA: Brooks/Cole-Thomson Learning.

Someya, S., & Okamoto, K. 2007. Measurement of the Flow and Its Vibration in Japanese Traditional Bamboo Flute Using the Dynamic PIV. Journal of Visualization, 10(4): 397-404.


ABSTRACT. The study demonstrated the effect of different flow channel length on the spinneret with respect to the ceramic hollow fiber membrane morphology. A smartly designed spinneret is utilized for the spinning process where the nozzle used can be change to different length via the use of adapters. Thus, allowing the effect of having different flow channel length to be investigated. Three spinneret adapters with different nozzle length were fabricated at 29 mm, 34 mm, and 39 mm. Ceramic hollow fiber membrane is produced using these configurations in the spinning process. Then, the micrographic cross sections of hollow fiber membranes is investigated using Scanning Electron Microscope (SEM) where it shows finger like, dense layer and damage structure morphology. Out of the samples investigated, hollow fiber membrane spun using 39 mm nozzle length produce the best concentricity. CFD simulation is initiated to study the flow behavior inside the flow channel to correlate with that of the experimental result attained.

KEYWORDS. Hollow fiber, Spinneret, Flow Channel, CFD

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Bird, R. B., Armstrong, R. C., & Hassager, O. 1987. Dynamics of Polymeric Liquids, Fluid Mechanics (Volume 1). Vol. 1, 2nd ed., John Wiley and Sons.

Bonyadi, S., & Chung, T. S. 2007. Investigation of Corrugation Phenomenon in the Inner Contour of Hollow Fibers during the Non-solvent Induced Phase-separation Process, Journal of Membrane Science, 299: 200.

Chung, T. S., Teoh, S. K., Lau, W. W. Y., & Srinivasan, M. P. 1998. Effect of Shear Stress within the Spinneret on Hollow Fiber Membrane Morphology and Separation Performance. Industrial & Engineering Chemistry Research, 37: 3930.

Chung, T. S., Qin, J. J., & Gu, J. 2001. Effect of Shear Rate within the Spinneret on Morphology, Separation Performance and Mechanical Properties of Ultrafiltration Polyethersulfone Hollow Fiber Membranes. Chemical Engineering Science, 56: 5869.

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Larson, R. G. 1992. Instabilities in Viscoelastic Flows. Rheologica Acta, 31: 213

Li, K. 2007. Ceramic Membranes for Separation and Reaction. West Sussex, England: John Willey and Sons Ltd.

Moynihan, R. H., Baird, D. G., & Ramanathan. 1990. Additional Observations on the Surface Melt Fracture Behavior of Linear Low-density Polyethylene. Journal of Non Newtonian Fluid Mechanics, 34: 255.

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Nijdam, W., de Jong, J., van Rijn, C. J. M., Visser, L. Versteeg, Kapantaidakis, G., Koops, H., & Wessling, M. 2005. High Performance Micro-engineered Hollow Fiber Membranes by Smart Spinneret Design. Journal of Membrane Science, 256: 209.

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Piau, J. M., Kissi, N. E., & Tremblay, B. 1990. Influence of Upstream Instabilities and Wall Slip on Melt Fracture and Sharkskin Phenomena during Silicones Extrusion through Orifice Dies. Journal of Non-Newtonian Fluid Mechanics, 34.

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Qin, J. J., Gu, J., & Chung, T. S. 2001. Effect of Wet and Wet-jet Spinning on the Shearinduced Orientation during the Formation of Ultrafiltration Hollow Fiber Membranes. Journal of Membrane Science.

Santoso, Y. E., Chung, T. S., Wang, K. Y., & Weber, M. 2006. The Investigation of Irregularinner-Skin Morphology of Hollow Fiber Membranes at High Speed Spinning and the Solutions to Overcome It. Journal of Membrane Science, 182: 57.

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Wang, K. Y., Matsuura, T., Chung, T. S., & Guo, W. F. 2004. The Effects of Flow Angle and Shear Rate within the Spinneret on the Separation Performance of Poly (Ethersulfone) (PES) Ultrafiltration Hollow Fiber Membranes. Journal of Membrane Science, 240: 67.

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Widjojo, N., Chung, T. S., Arifin, D. Y., Weber, M., & Warzelhan, V. 2010. Elimination of Die Swell and Instability in Hollow Fiber Spinning Process of Hyperbranched Polyethersulfone (HPES) via Novel Spinneret Designs and Precise Spinning Conditions. Chemical Engineering Journal, 163: 143-153.

Yang, Q., Chung, T. S., Chen, S. B., & Weber, M. 2008. Pioneering Explorations of Rooting causes for Morphology and Performance Differences in Hollow Fiber Kidney dialysis Membranes Spun from Linear and Hyperbranched Polyethersulfone. Journal of Membrane Science, 313: 190.

Yang, Q., Chung, T. S., Weber, M., & Wollny, K. 2009. Rheological Investigations of Linear and Hyperbranched Polyethersulfone Towards Their As-spun Phase Inversion Membranes’ Differences. Polymer, 50: 524.