The changes on the vegetables oil trading environment might change the foundation of palm oil pricing and induce a structural change to the price model. Failing to take it account the structural change in a data series might lead to misspecification of the actual model. This study, however, showed that structural change was not present in the monthly, January 1983 to July 1995, palm oil price, but it was present on the unconditional variance. The underlying model of this series was ARIMA (3, 1, 0) with ARCH (1). The critical change of the unconditional variance took place in April 1989.
Perubahan dalam suasana perdagangan minyak sayuran boleh mengubah asas harga minyak kelapa sawit. Seterusnya ia merangsang perubahan dalam struktur model harga minyak tersebut. Kegagalan untuk mengambil kira perubahan struktur dalam siri data menjadikan model itu tidak menepati spesifikasi daripada model sebenar. Kajian ini mendapati bahawa perubahan struktur tidak berlaku bagi data harga minyak sawit dari Januari 1983 hingga Julai 1995. Tetapi perubahan berlaku pada varians tidak bersyaratnya. Model asas bagi siri ini adalah ARIMA (3,1,0) dengan ARCH(1). Didapati juga bahawa perubahan yang kritikal bagi varians tidak bersyarat berlaku pada bulan April 1989.
Dengue is one of the main factors of mortality of inhabitants in the region of South East Asia. Malaysia is one of the countries which is facing a high incidence of dengue, particularly in the 70's and early 80's. The Ministry of Health has taken various measures in order to reduce the dengue epidemic. These include educating people about dengue and conducting research such as investigation of factors that influence the epidemic of dengue. In this study, a sequential Bayesian approach is applied to data of the proportion of death due to dengue over the period from 1982 to 1992. In the sequential Bayesian approach, the data for the year 1982 becomes the prior information for the 1983 data and so on. The data for the different periods are combined in a chronological manner until the final posterior distribution of the proportion of death due to dengue is obtained. It is found that the overall proportion is 0.59% and its standard deviation is 0.00002%.
Denggi adalah satu daripada faktor utama kematian bagi penduduk di rantau Asia Tenggara. Malaysia pula merupakan satu daripada negara yang sedang mengalami kadar insiden denggi yang tinggi, khususnya dalam tahun 70-an dan pada awal 80-an. Kementerian Kesihatan telah mengambil pelbagai langkah untuk mengurangkan wabak denggi. Ini termasuk memberikan pendidikan tentang denggi dan membuat kajian tentang faktor-faktor yang mempengaruhinya. Dalam kajian ini kaedah Bayesan jujukan digunakan terhadap data perkadaran yang mati akibat denggi dalam tempoh 1982 hingga 1992. Dalam kaedah ini, data tahun 1982 digunakan sebagai maklumat prior untuk data tahun 1983 dan seterusnya. Data dari tahun yang berlainan digabungkan secara kronologi sehingga diperoleh taburan posterior yang terakhir bagi perkadaran yang mati akibat denggi. Didapati bahawa perkadaran keseluruhan ialah 0.59% dan sisihan piawainya 0.00002%.
A total of 13 samples of sausages were analyzed for proximate composition and mineral (sodium, calcium, potassium, phosphorus and iron) content. The sausages were of UKM formulation, local brand and imported brand. Results from proximate analyses indicated water content ranged between 58.18Â-71.30g/100g, protein 11.4-16.52g/100g, fat 8.19-22.87g/100g, carbohydrate 2.00-10.2g/100g, ash 1.52-2.99g/100g and fiber 0.69-2. 199/100g. In comparing the three groups of sausages no significant differences were found for water, fat and carbohydrate contents, while the ash and protein contents of the local brand were lower (p<0.05) compared to the other two formulaÂtions. UKM formulated sausages contain the least fibre. Overall the average values for sodium and phosphorus of local brand sausages were found to be lowest while calcium, potassium and iron were lowest for UKM formulated sausages.
Tiga belas jenis sosej ayam telah dianalisis untuk komposisi proksimat dan kandungan mineral (natrium, kalsium, kalium, fosforus, ferum). Sosej ini ialah sosej formulasi UKM, sosej tempatan dan sosej import. Dari keputusan analisis proksimat, didapati kandungan air berjulat di antara 58.18-71.30g/ 100g, protein 11.4 -16.52 g/100g, lemak 8.19-22.87g/100g, karbohidrat 2.00Â-10.2g/100g, abu 1.52-2.99g/100g dan gentian 0.67-2.19g/100g. Apabila dibandingkan di antara tiga kumpulan sosej didapati tiada perbezaan bererti (p<0.05) bagi air, lemak dan karbohidrat sementara kandungan abu dan protein sosej tempatan adalah terendah berbanding sosej formulasi UKM dan import. Manakala bagi kandungan gentian pula, sosej formulasi UKM adalah paling rendah. Secara keseluruhan, purata kandungan mineral natrium dan fosforus didapati paling rendah bagi sosej tempatan manakala kandungan kalsium, kalium dan ferum pula adalah terendah bagi sosej formulasi UKM.
A study of the heavy metal bio-accumulation by fresh water fish, Tilapia nilotica around Lohan Dam was carried out in aquarium system. The study showed that the fish tissues cultured in contaminated water samples, (location S3 and 54) contain higher heavy metals concentration compared with the fish cultured in uncontaminated water samples (S1 and S2). The concentrations of Fe, Zn, Mn, Cu, Ni and Cr in fish tissues are higher compared with those of Co, Cd and Pb. The bio-accumulation rates of Zn, Mn, Cu, Ni and Co are 25 times higher than those of the base levels and 10 times higher than those of the controls. The heavy metal bio-accumulation order in T. nilotica is as follows: Mn> Cu> Cr> Ni> Co> Zn> Pb> Cd> Fe. The heavy metal intakes by fish during the experimental period did not exceed the level concentration levels.
Kajian bioakumulasi logam berat oleh ikan air tawar, Tilapia nilotica di perairan sekitar Empangan Lohan dilakukan dengan kaedah ternakan akuarium. Hasil kajian menunjukkan tisu ikan yang diternak dalam sampel air tercemar (lokasi S3 dan S4) mengandungi logam berat yang lebih tinggi dari tisu ikan yang diternak dalam sampel air tidak tercemar (lokasi S1 dan S2). Kepekatan logam berat seperti Fe, Zn, Mn, Cu, Ni dan Cr didapati tinggi dalam tisu ikan berbanding dengan kepekatan Co, Cd dan Pb. Kadar bioakumulasi logam berat daIam ikan didapati tinggi bagi Zn, Mn, Cu, Ni dan Co yang masing-masing melebihi 25 kali ganda dari paras asal dan lebih 10 kali ganda dari paras kawalan. Siri bioakumulasi logam berat yang dikaji dalam ikan T. nilotica menurut urutan; Mn> Cu> Cr> Ni> Co> Zn> Pb> Cd> Fe. Kepekatan logam berat yang dapat diambil oleh ikan dalam masa kajian tidak mencapai nilai yang dapat menyebabkan kematian kepada ikan.
In the theory of the confluent hypergeometric differential equation, Laguerre polynomials Lnm(x), satisfy the equation xy" + (m+l-x)y' + (n-m)y=0, for non-negative integers of n ≥ m, including zero. When n are non-integers, the solutions to the equation are not polynomials, but infinite series that is difficult to evaluate in closed from. A new method is introduced whereby it is possible to generate a table of Laguerre polynomials (for integer n) and Laguerre functions (for non-integer n) through evaluation of one common integral equation. The method uses the Bateman and the Yaacob-Bateman equations as new tools of solution to the radial Schroedinger equation for the hydrogen atom.
Mengikut teori persamaan perbezaan hipergeometrik konfluen, polinomial Laguerre Lnm(x), memenuhi persamaan xy" + (m+l-x)y' + (n-m)y=0, untuk kesemua nombor genap positif n ≥ m, termasuk sifar. Di dalam keadaan n bukan nombor genap, penyelesaian kepada persamaan Laguerre bukan berbentuk polinomial, tetapi suatu siri tak terhingga yang sukar untuk disimpulkan di dalam bentuk fungsi tertutup. Suatu kaedah baru dikenali di mana jadual polinomial Laguerre (n nombor genap) dan fungsi Laguerre (n bukan nombor genap) dapat diterbitkan melalui penyelesaian kepada persamaan kamiran. Kaedah ini menggunakan teknik novel melalui penyelesaian kepada persamaan Bateman dan persamaan Yaacob-Bateman untuk mendapat penyelesaian kepada persamaan jejari Schroedinger untuk atom hidrogen.
A study was conducted to examine the usage of application software and its development practices in Malaysia. The study has shown that the use of application software is greatly emphasized by organizations in their respective businesses. And for most organizations, the application software is supplied by a vendor or through in house development. For the software development practices, the deployment of a current technique and technology is still inadequate. Therefore, most of the existing information technology practitioners should be given additional training on the latest techniques of software development. Other aspect of improvement on software development practices is also discussed.
Satu kajian terhadap status pemakaian dan kegiatan pembangunan perisian gunaan di Malaysia telah dijalankan. Kajian ini menunjukkan yang aspek pemakaian sangat diberi penekanan oleh organisasi. Manakala proses perolehan perisian gunaan pula terbahagi secara setara di antara buat sendiri dengan menggunakan pihak ketiga. Namun begitu yang ketara ialah kadar penggunaan teknologi dan teknik terkini dalam kegiatan pembangunan perisian masih berkurangan. Oleh itu disarankan supaya aspek latihan teknik kakitangan teknologi maklumat organisasi perlu dipertingkatkan secara berterusan. Di samping itu kajian ini memaparkan beberapa aspek amalan pembangunan perisian yang boleh diperbaiki lagi.
NEUCOMP2 is a parallel Neural Network Compiler for a shared-memory parallel machine. It compiles a program written as a list of mathematical specifications of Neural Network (NN) models and then translates it into a chosen target program which contains parallel codes. In this paper we present the performance results for intertwined spiral problem on popular NN models. The models are the Backpropagation, Kohonen, and Counter propagation models. NEUCOMP2 was developed on the Sequent 8000 computer system at PARC.
NEUCOMP2 adalah Pengkompilasi Rangkaian Neuron selari untuk mesin selari berkongsi-ingatan. Ia mengkompilasi atur cara yang ditulis dalam bentuk senarai spesifikasi matematik bagi model Rangkaian Neuron (RN) dan kemudian menterjemahkannya kepada atur cara sasaran yang dipilih mengandungi kod-kod selari. Dalam makalah ini dibentangkan keputusan prestasi penyelesaian masalah lingkaran berkembar menggunakan modelÂ-model RN tertentu. Model-model ini adalah model rangkaian Perambatan Balik, Kohonen, dan Lawan Perambatan. EUCOMP2 dibangunkan pada sistem komputer Sequent 8000 di PARC.
The evolution of microemulsion microstructure formed from didodecyl dimethyl ammonium bromide, water and cyclohexane which started from being structureless (fiat scattering profile) to a mean-field Ginsburg-Landau behaviour is shown. The evolution gave the characteristic Lorentzian scattering profile as the system approaches phase separation.
Evolusi mikrostruktur mikroemulsi yang terbentuk daripada didodesil dimetil ammonium bromida, air dan sildoheksana tiada berstruktur (profil serakan yang malar) kepada medan-min Ginsburg-Landau. Evolusi tersebut memberikan serakan Lorentz apabila komposisinya menghampiri sempadan pemisahan fasa.
This study provides new information on the coastal current along the northern region of the east coast of Peninsular Malaysia. A self-recording S4 current meter, 3 m deep, from July to September 1996, about one nautical mile from the coastline of Kuala Terengganu, was used to determine the speed and direction of the coastal current. The results confirm the presÂence of coastal current along the northern region of the east coast of Peninsular Malaysia, during the southwest (SW) monsoon season. The coastal current has a maximum speed of over 30 cm/s. Its direction off low is affected by tide. It flows northward (southward) during ebb (flood) tide. However, its net direction of flow is southeastward.
Kajian ini memberikan maklumat baru arus pantai di sepanjang bahagian utara Pantai Timur Semenanjung Malaysia. Meter arus rekod sendiri S4, telah dipasangkan di kedalaman 3 m, dari Julai hingga September 1996, lebih kurang satu batu nautika dari pantai Kuala Terengganu, untuk menentukan halaju dan arah arus pantai. Hasil kajian ini mengesahkan kehadiran arus pantai di sepanjang bahagian utara pantai timur Semenanjung Malaysia, dalam monsun barat daya. Arus pantai mempunyai halaju maksimum melebihi 30 cm/s. Arahnya dipengaruhi oleh air pasang surut. Ia mengalir ke utara (selatan) ketika air surut (pasang). Walau bagaimanapun, pengaliran bersihnya adalah ke arah tenggara.
Cynopterus brachyotis, a fruit, leaf and nectar eating bat is a common frugivorous bat in Southeast Asia. In the present study, changes in the reproductive hormones of these bats were measured. Bats were captured and blood samples were taken monthly for seven months (January to July 1997) in the surrounding areas of Universiti Kebangsaan Malaysia (UKM) campus in Bangi. The concentration of the reproductive hormones in the blood, such as testosterone (male) and progesterone (female) were measured using ELISA. The results showed that body weight and concentration of reproductive hormones was correlated with the monthly rainfall. Abundance of food during the rainy season was believed to be the important factor in influencing body weight gain and increase in reproductive hormone synthesis.
Cynopterus brachyotis merupakan kelawar frugivor pemakan buah-buahan, daun dan nektar yang lazim di Asia Tenggara. Matlamat penyelidikan ini ialah untuk menentukan aras hormon yang dirembeskan oleh gonad kelawar frugivor ini, Kelawar-kelawar ini telah ditangkap dan diambil sampel darah pada setiap bulan selama tujuh bulan (Januari hingga Julai 1997) di sekitar kampus Universiti Kebangsaan Malaysia (UKM) di Bangi. Aras hormon pembiakan, iaitu testosteron pada kelawar jantan dan progesteron pada betina ditentukan dengan menggunakan kaedah ELISA. Hasil kajian menunjukkan bahawa berat badan dan aras hormon pembiakan berkait rapat dengan jumlah taburan hujan bulanan. Kelimpahan sumber makanan pada masa taburan hujan yang tinggi dipercayai merangsang pertambahan berat badan dan sintesis hormon pembiakan pada kelawar ini.
Conglomerates of continental origin are widely distributed in the Eastern Belt of the Malay Peninsular. Murau Conglomerate is the best example. Similar deposits outcrop at Pulau Redang, Pulau Kapas and Bukit Keluang. With an exception of Pulau Redang Conglomerate, similarities in lithologic, sedimentologic and stratigraphic characters of these conglomerates suggested that they can be combined into one group. Their stratigraphic position that is overlying the Upper Paleozoic unconformities reveals that these rock units are representing the basal part of the continental sediments that are found in the Eastern Belt. The sediments have been deposited as early as in the Late Permain and the deposition continued until Triassic. This interpretation is based on the occurrence of the Upper Paleozoic unconformities in the Eastern Belt and also on the age of sediments beneath the unconformities at Pulau Redang. The uplift that gives rise to this unconformity may be attributed to the granite emplacement in the Eastern Belt in the Late Permian-Early Triassic time. This was followed by depositions of the basal conglomerate mentioned above. The basal conglomerates were then overlain by fined grained sediments which are represented by Panti Sandstone, Lotong Sandstone and other equivalent deposits of Jurassic Cretaceous age.
Konglomerat endapan benua banyak tertabur di lalur Timur Semenanjung Malaysia. Konglomerat Murau adalah satu contoh yang terbaik. Konglomerat yang mempunyai, ciri-ciri yang sama terdapat di beberapa lokaliti di Pulau Redang, Pulau Kapas dan Bukit Keluang. Ciri-ciri litologi sedimentologi dan stratigrafi kesemua konglomerat ini mencadangkan bahawa mereka boleh dikumpulkan di dalam satu kumpulan yang. sama kecuali Konglomerat Pulau Redang. Kedudukannya langsung di atas satah ketakselarasan Paleozoik Atas mencadang unit-unit konglomerat ini merupakan bahagian dasar kepada sedimen kebenuaan yang terdapat di Jalur Timur dan mungkin juga di jalur Tengah. Sedimen ini mula terendap semenjak Perm Akhir hingga Trias berdasarkan ketakselarasan yang terdapat di Jalur Timur dan juga usia sedimen di bawah satah ketakselarasan yang terdapat di Pulau Redang. Pengangkatan yang berkaitan mungkin terhasil daripada perejahan granit di Jalur Timur semasa Perm Akhir-Trias Awal. Pengangkatan ini diikuti oleh pemendapan konglomerat dasar yang disebut di atas. Pengenapan seterusnya diikuti oleh sedimen berbutir lebih halus yang menindihnya yang diwakili oleh Batu Pasir Panti, Batu Pasir Lotong dan yang lain-lain yang setara dengannya yang mungkin berusia Jura-Kapur.
A survey to characterize seismic and ultrasonic properties of a granite weathering profile have been carried out at a roadcut slope exposure along Kuala Lumpur-Karak highway at kilometres 39.9. The terraced cut slope shows a complete weathering profile beginning from fresh grade I rock to grade VI residual soil. Together with in situ seismic measurement, rock samples have been collected for ultrasonic tests in laboratory. The range of velocities representing grades and indices of weathered rocks and soils are determined from the in situ seismic surveys. The range of ultrasonic velocities and elastic moduli are obtained from the laboratory measurements.
Satu survei untuk mencirikan sifat seismos dan ultrasonik profil luluhawa granit telah dilakukan di singkapan potongan jalan, cerun utara lebuhraya Kuala Lumpur-Karak pada lokaliti 39.9 km. Potongan berteres ini mempamirkan satu profil luluhawa lengkap iaitu mulai batuan gred 1 yang segar hingga ke tanah baki bergred VI. Di samping pengukuran seismos secara in situ, sampel batuan juga diambil untuk dibuat pengukuran halaju ultrasonik di makmal. Julat halaju yang mewakili gred dan indeks luluhawa bagi tanah dan batuan diperolehi daripada survei seismos in situ. Julat halaju trasonik dan modulus kenyal diperolehi hasil pengukuran di makmal.
A detailed and comprehensive study that covers the aspects of facies and palinology has been carried out on the Nenering bed to determine its depositional history and age. Field evidence based on sedimentary logs of outcrop shows that the sediments have been deposited in a limited intermontane basin. Its sedimentary facies reveal that the sediments were derived from the adjacent older sedimentary rocks. The sediments were transported and deposited in the basin by ephemeral streams. Coarse-Âgrained facies are more dominant in the basin margin area whereby finer-grained facies are more concentrated along the basin axis. Vertical facies changes reveal that in the earlier stage of deposition the basin axis was dominated by finer-grained facies which was then succeeded by the coarserÂgrained sediments brought-in by ephemeral streams. Palynological avidence reveals that the deposition in the basin took place during the Late Cretaceous (? Aptian-Albian).
Lapisan Nenering yang dilaporkan sebelum ini telah dikaji dari aspek sedimentologi don polinologi secara menyelurnh. Bukti-bukti lapangan berdasarkan log turus sedimen pada keseluruhan singkapan mendapati unit batuan sedimen ini telah dimendapkan di dalam lembangan yang kecil yang wujud di antara pergunungan. Fasies sedimennya menunjukkan punca sedimen telah diterbitkan daripada batuan tua di sekitarya. Sedimen dimendapkan di dalam lembangan secara bermusim oleh sungai-sungai efemeral. Fasies berbutir kasar tertumpu ke bahagian tepian lembangan sementara bahagian tengah didominasi oleh sedimen butiran halus. Perubahan fasies secara menegak pula menunjukkan, pada awal pemendapan bahagian tengah lembangan dinominasi oleh sedimen berbutir halus dan kemudian berlaku kemasukan sedimen butiran kasar yang dibawa oleh sungai-sungai berkala. Bukti-bukti palinologi menunjukkan pemendapan sedimen di dalam Lembangan Nenering berlaku paling mungkin semasa Kapur Akhir (? Aptian-Albian).
From the weighted least-squares fit, two methods of calculation of χ2 test were derived and investigated. The first method which uses a mean weight yields the well known standard method. ie. χ2cal1 = (x)-1 Σ(x-xi)2 and the second method which uses the statistical weight yields χ2cal2 = Σ(x)-1 (x-xi)2. It is theoretically shown that each method has its own type of . ie. arithmetic mean for χ2cal1 and harmonic mean for χ2cal2. Application to the experimentally determined nuclear data, however showed that the two methods gave almost the same χ2cal values, I irrespective of x used. An approach to verify that the mean weight equals to (x)-1 in the standard method is also discussed.
Dari penyesuaian kedua-dua terkecil berpemberat, dua kaedah pengiraan ujian χ2 diterbitkan dan dikaji. Kaedah pertama yang menggunakan pemberat purata memberikan kaedah standard yang terkenal, iaitu χ2cal1 = (x)-1 Σ(x-xi)2 dan kaedah kedua yang menggunnakan pemberat statistik memberikan χ2cal2 = Σ(x)-1 (x-xi)2 . Ditunjukkan secara teori setiap kaedah mempunyai tersendiri, iaitu purata aritmatik untuk χ2cal1 dan purata harmonik untuk χ2cal2. Penggunaan teori ini kepada data nuklear ujikaji, walau bagaimanapun, menunjukkan yang kedua-dua kaedah memberikan nilai χ2cal yang hampir sama, bebas dari jenis x yang digunakan. Pendekatan untuk menentusahkan pemberat malar bersamaan dengan (x)-1 dalam kaedah piawai juga dibincangkan.
There is great interest in gas sensing especially for toxic gases such as carbon monoxide. This paper reports the use of Langmuir-Blodgett films of hematin mixed with arachidic acid to detect carbon monoxide gas in nitrogen at room temperature. The detection was studied based on changes in the optical absorption and reflection of the film using a spectrophotometer and an optical fiber system, respectively. The absorption spectra of a 20 layers LB film decreased when exposed to 10, 100, 1000 ppm CO gas, and had fast recovery time when the gas flow was stopped. An optical fiber system consists of a laser diode as light source, a fiber reflectance probe, thin film sample on a reflecting mirror and a light detector was setup. Using this system it was found that the intensity of the reflected light increased when the film was exposed to the gas. The sensing sensitivity of the films increased after the films were annealed for one hour at 100°C. The result is explained using the atomic force microscope (AFM) images of the LB films taken before and after annealing.
Terdapat minat yang besar terhadap penderiaan gas terutama bagi gas toksik seperti karbon monoksida. Kertas ini melaporkan penggunaan filem Langmuir-Blodgett (LB) hematin bercampur asid arakidik untuk mengesan gas karbon monoksida dalam gas nitrogen pada suhu bilik. Pengesanan dikaji berasaskan perubahan serapan optik dan pantulan filem yang masing-masing menggunakan spektrofotometer dan satu sistem serat optik. Spektrum serapan bagi 20 lapisan filem LB berkurang apabila filem itu didedahkan kepada 10, 100, 1000 ppm gas CO, dan mempunyai masa pulihan yang pantas apabila aliran gas dihentikan. Satu sistem serat optik yang terdiri daripada satu sumber cahaya diod laser, penduga pantulan, sampel filem nipis di atas satu cermin pemantul dan pengesan cahaya telah dibina. Menggunakan sistem ini didapati keamatan cahaya yang terpantul meningkat selepas filem disempuhlindap selama satu jam pada 100°C. Keputusan ini dijelaskan menggunakan imej mikroskop daya atom (AFM) filem LB yang diambil sebelum dan selepas sempuhlindap.
Chemical structure of treated and untreated Aciplex membrane has been studied by X-ray Photoelectron Spectroscopy (XPS). Survey spectra showed that both membrane surfaces consist of Fluorine, Carbon, Oxygen, Sulphur and trace of Titanium. Binding energies for the elements are (C1s at 290.6 eV, F1s at 687.5 eV, O1s at 531.3 eV, S2P at 168.1 eV and Ti2P at 454.4 eV). Analysis of narrow scan XPS-spectra of each element demonstrate the presence of (-CF, -CF2, CF3, C-O-C and SO-3) groups, which are in agreement with the structural formula as disclosed by the manufacturer. There is no significant change in chemical states of untreated and treated membrane, which reflect its stability to treatment conditions.
Struktur kimia Aciplex membran yang sudah dibersihkan dan yang belum dibersihkan telah dikaji menggunakan Spektroskopi Fotoelektron Sinaran-X (XPS). Spektra yang telah ditinjau menunjukkan bahawa kedua-dua permukaan membran mengandungi Florin, Karbon, Oksigen, Sulfur dan sedikit Titanium. Tenaga ikatan bagi unsur-unsur tersebut adalah (C1s pada 290.6 eV, F1s pada 687.5 eV. O1s pada 531.3 eV, S2P pada 168.2 eV dan Ti2P pada 454.4 eV). Analisis imbasan kecil spektra-xps bagi setiap unsur menunjukkan kehadiran kilmpulan (-CF, - CF2, CF3, C-O-C dan SO-3) yang bertepatan dengan formula struktur dari pihak pembekal. Tiada terdapat perubahan nyata berhubung dengan keadaan kimia membran yang sudah dibersihkan dan yang belum dibersihkan yang menggambarkan kestabilannya terhadap keadaan pembersihan.
Measurement of the natural 40K body gamma-ray radioactivity via the whole-body counter (WBC) technique may yield the total body potassium (TBK) status, from which for example, the body cell mass can be derived (Moore et al. 1963). The accuracy of the derived TBK is of course critically dependent on the assumed value of the ratio 40K:TBK. Potassium chloride (KCI) has been widely used as the 40K calibration standard. In reviewing the literature (Burkinshaw 1967; Ross & Morris 1968; Havlik 1970, Young et al 1975; Manocha & Mohindra 1976; Holtzman 1977; Graham 1983; HMSO 1985-1986, Lykken et al 1987; Lan & Weng 1989; Fenwick et al. 1991), it is apparent that inconsistencies occur in the use of 40K activity per gram of natural potassium. It varies between 27.33 to 31.31 Bq per gram of potassium. The objectives of this study were to independently measure and calculate the 40K activity per gram of natural potassium in an attempt to reduce the uncertainty in the accepted figure. Experimentally the activity of 40K from a known amount of K was determined by measuring the 40K photon emission of an analar grade KCI sample solution and the absolute efficiency of the detection system at energy 1460 KeV. Both the photopeak count-rate and the absolute efficiency were measured using the gamma-ray spectroscopy technique. The 40K activity is also calculated from its half-life (IAEA 1989) and the number of atoms present in the sample. The measured and calculated values obtained were 30.18 ± 0.72 Bq g-1 and 31.00 ± 0.33 Bq g-1 respectively. The difference is of the order of 2.6%. The measured value is consistent with the literature values being close to the mean of the values, namely 29.77. In conclusion, it is believed that the experimental values reported in this work is one of the few experimentally determined results and it is reassuring to note that the experimental and theoretical values are in reasonable agreement.
The activity of two liquid mixed radionuclide sources in NPL'S standard glass ampoules were determined by gamma-ray spectrometry measurement using a standard point source placed at 38.5 cm axially above the detector. A radio nuclide 137Cs was chosen, Results obtained were within 3% agreement with the calculated value. The same degree of deviation was obtained when the NPL standard source of equal geometry, chemical composition and density was used.
Keaktifan dua sumber radionuklid campuran cecair yang terkandung dalam bekas kaca piawai NPL ditentukan dengan kaedah pengukuran spektrometri sinar-gama menggunakan satu sumber titik piawai diletakkan pada 38.5 em di atas pengesan, Satu sumber radionuklid 137Cs dipilih. Keputusan yang diperoleh bersetuju dalam lingkungan 3% dengan nilai yang dikira. Darjah simpangan yang sama diperoleh apabila sumber piawai NPL yang sama dari segi geometri, komposisi kimia dan ketumpatan digunakan,
The a.c. electrical response of a polycrystalline Li0.25Ni0.2Zn0.3Fe2.25O4 ferrite is studied by means of impedance spectroscopy. The impedance measurement was performed at different input voltage amplitudes in ten decades of frequency (1 mHz - 10 MHz). Two overlapping semicircles with negative capacitance phenomenon below 1 Hz are observed at all amplitudes. The two semicircles are mainly attributed to the grain and grain boundary processes at high and low frequencies respectively. The grain boundary impedance shows a non-linear dependence on the input voltage, where the corresponding impedance semicircle is smaller for larger amplitude. However, a linear response is observed for the grain component. The dependence of the a.c. electrical properties of the grain and grain boundary components on the amplitude of the input voltage is discussed.
Ransangan elektrik a.u. daripada ferit Li0.25Ni0.2Zn0.3Fe2.25O4 berpolihablur dikaji dengan menggunakan spektroskopi impedans. Pengukuran impedans dilakukan pada beberapa amplitud voltan masukan dalam julat sepuluh dekad frekuensi (1 mHz - 10 MHz). Dua lengkung separuh bulatan yang bertindih dengan fenomena kapasitans negatif di bawah frekuensi 1 Hz dapat diperhatikan pada setiap nilai amplitud. Kedua-dua lengkung separuh bulatan tersebut berpunca daripada proses-proses butiran dan sempadan butiran masing-masing pada frekuensi tinggi dan rendah. Impedans sempadan butiran menunjukkan persandaran tak-linear ke atas voltan masukan, dengan separuh bulatan impedans yang berpadanan yang mengecil dengan peningkatan amplitud. Akan tetapi, suatu ransangan linear dapat diperhatikan bagi komponen butiran. Kebergantungan sifat elektrik a.u. bagi komponen-Âkomponen butiran dan sempadan butiran kepada amplitud voltan masukan dibincangkan.
Blends of fibre-reinforced rubber based on natural rubber-thermoplastic (NR/LLDPE) reinforced by aramid fibre have been done using melt blending process. Two different processing methods were used; internal mixer and extrusion compounding in twin screw extruder. Twaron loading in the system was varied from 0 to 30%. It was found that increasing the amount of aramid fibre led to an increase in the tensile strength, tensile modulus and hardness of the composites while the strain decreased rapidly. The results showed that the optimum composition of filler loading in NR/LLDPE blend is 20%. The ,echanical behaviour was caused by the strong Twaron-matrices interaction in the composites and effective stress concentrating function of Twaron. Composites prepared using the twin-screw extruder have a higher tensile strength and tensile using the twin-screw extruder have a higher tensile stength and tensile modulus but lower impact strength compared to those prepared using internal mixer. Study of the fracture surface by scanning electron microscopy showed that the composite prepared using the internal mixer produced random fiber orientation while the twin-screw extruder produced the fibers aligned to the longitudinal direction. The results indicate that the mechanical properties of the composite were significantly influenced by the processing technique.
Penyediaan komposit getah asli termoplastik daripada NR/LLDPE yang diperkuat gentian Twaron telah dijalankan melalui proses adunan leburan. Dua kaedah penyediaan yang berbeza digunakan iaitu menggunakan mesin pencampur dalaman manakala kaedah kedua menggunakan pengekstrud skru kembar. Kandungan Twaron di dalam komposit telah diubah daripada 0 hingga 30%. Keputusan menunjukkan bahawa penambahan Twaron telah meningkatkan nilai tegasan maksima, modulus Young dan kekuatan hentaman komposit tetapi menurunkan nilai terikan maksima. Kandungan Twaron yang optimum adalah 20%. Kehadiran Twaron telah membentuk satu jaringan saling tindak gentian-matriks menyebabkan kekuatan regangan komposit meningkat. Twaron juga berfungsi sebagai penyerap hentaman yang berkesan. Penyediaan komposit menggunakan pengekstrud skru berkembar telah menghasilkan nilai kekuatan regangan yang lebih tinggi berbanding penggunaan pencampur dalaman sebaliknya kekuatan hentaman yang lebih rendah. Kajian morfologi menggunakan mikroskop imbasan elektron mendapati komposit yang disediakan menggunakan pencampur dalaman menghasilkan gentian dengan orientasi rawak manakala pengekstrud skru kembar menghasilkan orientasi gentian yang selari. Keputusan ini menunjukkan bahawa sifat mekanik komposit NR/LLDPE yang diperkuat Twaron sangat dipengaruhi oleh teknik pemprosesan.