In this paper we report the composition dependent of dielectric properties in $Se_{100-x} Pb _x$ (x = 0, 2,
4, 6 and 10) glassy alloys. The temperature and frequency dependence of the dielectric ...constants and the
dielectric losses in the above glassy systems in the frequency range 1 kHz-5 MHz and temperature range
300-340 K have been measured. It has been found that dielectric constant and the dielectric loss both are
highly dependent on frequency and temperature and also found to be increased with increasing concentration
of Pb in pure amorphous Se. The results have been interpreted in terms of increase in the density of defect
states in the incorporation of Pb as a metallic additive in the aforesaid glassy system. Apart from this, the
results have been also correlated in terms of a dipolar model which considers the hopping of charge carriers
over a potential barrier between charged defect states.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
ABSTRAKVirus dengue ditularkan oleh nyamuk Aedes aegypti dan Aedes albopictus. Nyamuk-nyamuk tersebut endemik di sebagian besar daerah vektor-vektor itu muncul memiliki empat serotipe yang berbeda ...secara antigenik. Empat serotipe virus dengue: DENV-1, DENV-2, DENV-3 dan DENV-4. Penelitian ini bertujuan untuk mengetahui perbandingan pelarut yang baik terhadap virus Dengue RNA Surabaya tipe-1 (DENV-1). Pelarut yang digunakan adalah Isopropanol, dimethyl sulfoxide, 96% ethanol, methanol, acetone-Methanol (1: 1), dimethyl formamide, dan akuades. RNA diisolasi dengan metode TRIzol. TRIzol (atau TRI Reagent) adalah larutan satu fasa dari fenol dan guanidinium isothiocyanate yang secara bersamaan melarutkan bahan biologis dan mendenaturasi protein. Hasil dari penilitian ini adalah didapatkan pelarut presipitasi RNA terbaik adalah aseton-metanol (1:1), karena campuran pelarut tersebut memiliki konstanta dielektrik terendah. Studi ini menunjukkan bahwa pelarut aseton-metanol (1:1) dapat digunakan sebagai pelarut presipitasi untuk mengisolasi RNA
U ovom radu predstavljen je kompaktni postav za mjerenje dijagrama zračenja proizvoljno postavljene antene iznad površine mora. Predmet analize je vertikalni poluvalni dipol. S obzirom na ...nepraktičnost mjerenja na plovećoj platformi, postav se temelji na plitkom bazenu napunjenom stvarnom morskom vodom. Stativi za ispitivanu odašiljačku antenu i prijamnu antenu postavljeni su na čvrstom tlu na nasuprotnim stranama bazena, tako da se antene nalaze na stabilnim platformama, a putanja vala se nalazi u potpunosti iznad mora. Dodatna značajka predložene metode jest pravocrtno pomicanje prijamne antene tijekom mjerenja dijagrama zračenja. Time je izbjegnuta potreba preciznog pozicioniranja po kružnoj putanji, što je dovelo do dodatnog pojednostavnjenja metode. Obje antene izrađene su kao poluvalni dipoli u planarnoj tehnologiji. Mjerenja su provedena na ISM frekvenciji od 2.48 GHz. Odabrana frekvencija omogućuje izradu kompaktnog postava za mjerenje vertikalnog dijagrama zračenja za visine odašiljačke antene do 2_ iznad morske površine. Mjerni rezultati pokazuju dobro slaganje s analitičkim rezultatima i rezultatima simulacije za poluvalni dipol iznad mora. Provedena je i prikazana detaljna procjena mjerne nesigurnosti, kao pokazatelj kritičnih točaka u realiziranom postavu.
This book offers a timely, comprehensive guide to the essence of Casimir (and Casimir-Polder) physics that will have lasting value, serving the dual functions of an introduction and reference to the ...field. Benefits particle physicists, cosmologists and more.
In this paper, a compact setup for measuring the radiation pattern of an arbitrary positioned antenna above the sea surface is presented. The antenna of interest was a vertical half-wave dipole. Due ...to impracticalities concerning the measurements using seaborne platforms, the setup was based around a shallow pool filled with actual sea water. The transmitting antenna-under-test (AUT) and the receiving antenna stands were placed on the solid ground, at the opposite sides of the pool, thus ensuring the stable platforms as well as the wave path over sea. The need for precise positioning of the receiving antenna along the circular path was avoided and the straight measurement line was used instead, yielding further simplification of the method. Both antennas were realized as printed half-wave dipoles. The measurements were carried out in ISM frequency band at 2.48 GHz. The chosen frequency enabled the realization of a compact setup for elevation radiation pattern measurements for AUT heights up to 2λ above the sea surface. The measurement results were compared to the theoretical and simulation results for a half-wave dipole over sea, showing a good agreement. Detailed evaluation of the measurement uncertainty was undertaken, indicating the critical points in the realized setup.
Frequency and temperature dependence of dielectric constant $\varepsilon^\prime$ and dielectric loss $\varepsilon^{\prime \prime}$ are studied in glassy $Se_{1-x} Sb_x $(x = 0, 0.02, 0.04, 0.06, 0.08 ...and 0.10) in the frequency range from 1-10 kHz and in the temperature range 290 K to 360 K. The experimental results indicate that no dielectric dispersion exist in glassy Se in the operating range of frequencies. However, when Sb concentration increases in $Se_{1-x} Sb_x $ (x = 0.02, 0-04, 0.66, 0.08 and 0.10) dielectric dispersion starts in the upper frequency and temperature range. The values of $\varepsilon^\prime$ and $\varepsilon^{\prime \prime}$ ,as functions of temperature and frequency, increase with Sb concentration to x = 0.08; at which point a discontinuity is observed. Above 8%, $\varepsilon^\prime$ and $\varepsilon^{\prime \prime}$ decrease with Sb concentration. The discontinuity is explained in terms of the mechanically stabilized structure at a particular average co-ordination number. An analysis of the observed dielectric loss shows that the Guintini's theory of dielectric dispersion based on two electron hopping over a potential barrier is applicable in the present case.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Dielectric constants $\varepsilon$, viscosities $\eta$, refractive indices n and densities d have been measured over the entire mole fraction range for the water - methyl, ethyl, n-propyl alcohol ...binary systems at 298.15 K. From the experimental data excess dielectric constants $ \varepsilon^E$, excess viscosities$\eta^E$ and Kirkwood correlation factors $g_k$ have been calculated and studied. Their behaviour suggests the existence of intermolecular interactions and plotted curves show that excess dielectric constant and $g_k$ values decrease with the increasing of carbon atom number, while excess viscosity increases.
The dielectric properties of poppy seed were determined over the frequency range from 50 kHz to 10 MHz at moisture content in a range of 6.12-22.47% dry basis d.b. with bulk density changing between ...541.99 and 626.37 kg/m3 using parallel-plate capacitor sample holder. The dielectric constant, loss factor, loss tangent and the a.c. conductivity was greatly influenced by the moisture content, bulk density and frequency. The moisture content was the most significant factor affecting the dielectric properties of poppy seed. The dielectric constant and loss factor increased with an increase in moisture content and bulk density and with a decrease in frequency. The dependence of the loss factor and loss tangent on frequency was less regular than that of the dielectric constant. The a.c. conductivity was observed to increase more rapidly with increasing moisture contents than with increasing frequencies. Also, two models have been shown to estimate adequately the dielectric constant and loss factor of poppy seed within the investigated moisture content, bulk density and frequency range
$(PbO)_{0.20-x}(Bi_20_3)_{0.40}:(Ti0_2)x$, $0.0 \leq x\leq 0.02$ glasses were prepared. Dielectric properties (dielectric constant $\varepsilon^{\prime}$, loss tan $\delta$ and a.c. conductivity ...$\sigma_{ac}$, over a wide range of frequency and temperature), optical absorption, ESR and IR spectra of these glass materials have been investigated. The dielectric study has revealed that the glasses possess high insulating strength when $TiO_2$ concentration is >0.8 mol% in the glass matrix. The optical absorption spectra of these glasses exhibited bands due to $Ti^{3+}$ ions in the visible region. ESR spectral studies have also indicated that a fraction of $Ti^{4+}$ ions reduced to $Ti^{3+}$ ions. IR spectra of these glasses exhibited bands due to $TiO_4$ and $TiO_6$ structural units. Quantitative studies indicate that as concentration of $TiO_2$ is increased to 0.8 mol% in the glass matrix, a large proportion of titanium ions exist in $Ti^{3+}$ state and has influenced the physical properties of these glasses to a substantial extent.
Accuracy in complex dielectric permittivity calculations in binary dielectric mixtures in two-dimensions are reported by taking into account the shape of the inclusion phase. The dielectric ...permittivity of the mixtures were calculated using the finite element method, and the permittivities were estimated by two different procedures. The results were compared with those of analytical models based on a mean field approximation and regular arrangement of disks. We have approached the problem emphasizing the finite-size behavior in which regular polygons with n sides were assumed to mimic the disk inclusion phase. It was found that at low concentrations, < 30%, decagon-approximated circles (n = 10) cause an error of < 0.1% in the effective medium quantities compared with results obtained using analytical models.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
PDF
