Effect of moisture content and grain direction on the dielectric properties of rubber wood at low frequencies

Dielectric constant and dielectric loss factor of rubber wood have been studied at different moisture content, grain direction and frequency. Different dielectric dispersion mechanisms are also observed at different ranges of moisture content. The moisture content above the fiber saturation point does not contribute much to the dielectric properties following a single dielectric mechanism. But the moisture content below the fiber saturation point shows considerable effect on the variations of dielectric properties having different dispersion processes at different moisture content ranges. Based on the shape of the curves, five different moisture content ranges have been identified such as 1) 25% and above, 2) 18-25%, 3) 11-17%, 4) 5-10% and 5) below 5%. It may be possible to explain all these dispersion processes by means of dielectric mechanism for dipole, quasi-dc and diffusive processes. Longitudinal direction shows a higher dielectric constant when compared to radial and tangential directions in ovendry condition. This dielectric anisotropy may be attributed to the microscopic, macroscopic and molecular structures of wood

Dielectric properties of rubber wood at microwave frequencies measured with an open-ended coaxial line

Dielectric properties of rubber wood were studied at different microwave frequencies, structural directions, and moisture contents using an open-ended coaxial probe. Frequencies used for this study were 1.00, 2.45, 6.0, 8.0, 10.0, 14.0, and 17.0 GHz; and the measurements were carried out at a room temperature of 22-24°C. The dielectric constant and dielectric loss factor were found to increase continuously as the moisture content increased. A sharp rise in the dielectric constant and dielectric loss factor was obtained at high moisture content, and the trends became concave upward. As the frequency increased, the dielectric constant decreased, whereas the dielectric loss factor increased. The dielectric loss factor remained almost constant above the frequency of 6 GHz for all structural directions. Fourth-order polynomial equations were found suitable for the best fit curve. Dielectric constant and dielectric loss factor of oven-dry wood were higher in the longitudinal direction than in the radial and tangential directions. With respect to frequency, the dielectric loss factor exhibited a peak value around 10 GHz. The dielectric anisotropy of wood may be attributed to the microscopic and macroscopic molecular structures as well as to chemical constituents of wood

Culture of microalgae using interstitial water extracted from shrimp pond bottom sediments

Interstitial water, extracted from the bottom sediment of a shrimp culture pond, was rich in nutrients containing total phosphorus with concentration of 25.98 mg/l and total nitrogen of 65.45 mg/l. A diatom, Chaetoceros calcitrans, a green alga, Nannochloropsis oculata, and a cyanobacterium, Oscillatoria sp., were cultured in pure interstitial water (PIW), diluted interstitial water (DIW) and in Conway medium (CM). C. calcitrans showed a significantly higher (P 0.05) in the growth rate of Oscillatoria sp. cultured in interstitial water and that with added silica or a combination of nitrogen, phosphorus and silica. This study indicates that interstitial water extracted from aquaculture ponds, in sterilized diluted form, has the potential to be used as an effective medium for the culture of microalgae. © 2001 Elsevier Science B.V. All rights reserved

A Review of Explicit Vocabulary Instructions for ESL Learners during COVID-19 Pandemic

During COVID-19 pandemic, alternative learning arrangements have been applied and used, so that it is possible to perform distance learning. Teachers have typically changed their teaching practises from conventional classroom meetings to distance learning by using electronic equipment, either online or offline. Internet networks have been the cornerstone during this time, with the use of social media apps such as Whatsapp and Telegram, social networking sites such as Facebook Live and Instagram Live, and platforms for video conferencing such as Google Meet and Zoom. In order to deal with the COVID-19 period for the better, English language teaching has also improved. The learning of English vocabulary also tailored to accommodate for distance learning as the use of vocabulary for good communication in one's life is crucial, regardless of whether or not one is in the midst of COVID-19 pandemic. This paper systematically reviews previous research undertaken on explicit instructions for vocabulary and suggests a structure for discussing English vocabulary teaching strategies. In learning, teaching, and undertaking vocabulary studies, this analysis may have some theoretical consequences for learners, educators, and researchers

Effect of moisture content and grain angle on the ultrasonic properties of rubber wood

The ultrasonic velocity and elastic stiffness constant of rubber wood were studied using ultrasonic technique in three main symmetry axes and an angle rotating from the symmetry axes. The effects of moisture content were also determined in each case. A strong correlation was found between the velocity and the moisture content. As the moisture content increased, the velocity and the stiffness constant were found to decrease. The longitudinal direction showed the highest velocity and hence the elastic stiffness constant. Linear regression equations were obtained between velocity and grain angle with R2 from 0.86 to 0.99

Dielectric and ultrasonic properties of rubber wood. Effect of moisture content, grain direction and frequency

Dielectric properties of rubber wood have been studied at low and microwave frequencies with different moisture content and grain direction. The ultrasonic properties were studied with pulsed longitudinal waves of frequency 45 kHz, Two anisotropic directions have been considered for this study — parallel and perpendicular to grain. The low frequencies were of 0.01, 0.1, L0, 10 and 100 Hz and microwave frequencies were of 1, 2.45, 6, 8, 10, 14 and 17 GHz. The moisture content affected the dielectric constant and dielectric loss factor both at low and microwave frequencies? The moisture content above 30% showed little influence on dielectric properties whereas it increases linearly from 0 to 30% in both the grain directions at low frequencies. A continuous increase of dielectric properties was obtained with the increase of moisture content at microwave frequencies and the trend becomes concave upward. Dielectric properties increase as the frequencies increase except dielectric loss factor at microwave frequencies where reverse trends were observed. Little change of dielectric loss factor was obtained at frequencies above 6 GHz. The parallel to grain direction showed higher dielectric constant and dielectric loss factor compared to perpendicular to grain direction. This dielectric anisotropy of wood may be attributed due to the microscopic, macroscopic molecular as well as chemical constituents of wood. Ultrasonic properties were also affected considerably by the moisture content and grain direction. The dried wood showed higher ultrasonic velocity and elastic stiffness constant compared to green wood. The parallel to grain direction exhibits higher ultrasonic velocity and elastic stiffness constant than perpendicular to grain

Konsep pembangunan semula Kampus Taman Siswa, Universiti Utara Malaysia

Kertas Kerja ini membincangkan cadangan konsep pembangunan semula kampus UUM di Taman Siswa, Jitra dan pelan strategik perlaksanaan projek yang telah dicadangkan.Kawasan kampus Taman Siswa UUM berkenaan telah menjangkau usia 32 tahun dan kini hanya beroperasi sebagai kawasan perumahan dan penginapan yang disewa kepada orang awam, pekerja industri, staf dan pelajar antarabangsa UUM. Faktor usia bangunan yang telah lama dan keadaan bangunan yang semakin uzur menyebabkan pihak pengurusan UUM terpaksa memperuntukan perbelanjaan kewangan yang tinggi bagi tujuan kos penyelenggaraan bangunan dan infrastruktur di persekitaran kawasan kampus tersebut yang berkeluasan 19 ekar.Beban kos penyelenggaraan yang semakin tinggi dan lokasi kawasan kampus yang sangat strategik di pusat tumpuan pembangunan baharu di Bandar Darul Aman menjadikan potensi pembangunan semula kampus berkenaan amat rasional dan berdaya maju.Hasil penemuan kajian mendapati potensi pembangunan semula kawasan kampus Taman Siswa amat tinggi dengan konsep tumpuan pembangunan berbentuk Pembangunan Bercampur iaitu melibatkan aktiviti perniagaan berkapasiti tinggi, perumahan bertingkat esklusif, pusat perubatan pakar, pusat pendidikan antarabangsa dan pembinaan utama iaitu Menara UUM yang menempatkan pusat pengajian siswazah UUM. Pembangunan baharu yang dicadangkan berupaya menjadi mercu tanda baharu pembangunan moden di Jitra dan menaikkan imej prestij UUM sebagai sebuah universiti pengurusan terkemuka

Konsep pembangunan semula Kampus Taman Siswa, Universiti Utara Malaysia

Kertas Kerja ini membincangkan cadangan konsep pembangunan semula kampus UUM di Taman Siswa, Jitra dan pelan strategik perlaksanaan projek yang telah dicadangkan.Kawasan kampus Taman Siswa UUM berkenaan telah menjangkau usia 32 tahun dan kini hanya beroperasi sebagai kawasan perumahan dan penginapan yang disewa kepada orang awam, pekerja industri, staf dan pelajar antarabangsa UUM. Faktor usia bangunan yang telah lama dan keadaan bangunan yang semakin uzur menyebabkan pihak pengurusan UUM terpaksa memperuntukan perbelanjaan kewangan yang tinggi bagi tujuan kos penyelenggaraan bangunan dan infrastruktur di persekitaran kawasan kampus tersebut yang berkeluasan 19 ekar.Beban kos penyelenggaraan yang semakin tinggi dan lokasi kawasan kampus yang sangat strategik di pusat tumpuan pembangunan baharu di Bandar Darul Aman menjadikan potensi pembangunan semula kampus berkenaan amat rasional dan berdaya maju.Hasil penemuan kajian mendapati potensi pembangunan semula kawasan kampus Taman Siswa amat tinggi dengan konsep tumpuan pembangunan berbentuk Pembangunan Bercampur iaitu melibatkan aktiviti perniagaan berkapasiti tinggi, perumahan bertingkat esklusif, pusat perubatan pakar, pusat pendidikan antarabangsa dan pembinaan utama iaitu Menara UUM yang menempatkan pusat pengajian siswazah UUM. Pembangunan baharu yang dicadangkan berupaya menjadi mercu tanda baharu pembangunan moden di Jitra dan menaikkan imej prestij UUM sebagai sebuah universiti pengurusan terkemuka