Comparison of the peak heights of the AVK to the pressure altitude they are calculated for, henceforth called the nomi- nal height, indicates that the AVK at the upper and the lower limit of the pressure range displayed do not peak at the nom- inal level, implying perturbations in the true profile are at- tributed to an incorrect altitude. To check for correct attribu- tion between the altitudes of the retrieved profile compared to the true profile a numerical criterion is established. This work defines that the difference between the nominal height of the AVK and its peak height must not exceed 25 % of the AVK’s width. This altitude difference is displayed in Fig. 6 together with its upper limit and the FWHM of the AVK giv- ing a measure for the spatial resolution of the radiometers is displayed in Fig. 7. cWASPAM3 meets the above defined criterion at altitudes between 0.7 and 0.006 hPa, for MIRA 5 it is fulfilled at altitudes between 10 and 0.01 hPa and for MIAWARA-C the range is 6 to 0.1 hPa.
But in particular for the tropospheric retrieval, this con- cept lacks because the measurement response exceeds 100 % at middle tropospheric altitudes (as in the example in Fig. 6). In terms of mathematics, the measurement response is not limited to 100 %. A possible interpretation of this effect is an oversensitivity of the retrieval against perturbations in the specific altitude range. Herein, the less stringent term sen- sitivity will be used instead and enhanced sensitivity is as- sumed for values above 0.8/80 %. For the tropospheric re- trieval, this is true between about 3 and 7 km a.s.l.
The spectrum which is obtained from astronomical sources has been pivotal in advancing our understanding of the chemical, dynamical and thermal structure of these objects. This is because the particles within the sources emit or absorb radiation at particular energy levels, manifesting at specific locations in their observed spectrum, thus allowing them to be identified and compared with known elements on Earth. In maser emission, molecules are pumped to an energetically excited state through stimulation and return to a ground (or more stable) state by releasing photons at specific wavelengths. Such an emitted photon might be reabsorbed by a neighbouring ground state molecule, which is then energized to an excited state until it too undergoes spontaneous emission. This process of absorption and emission is repeated, resulting in a chain reaction in the molecular environment. If the conditions in the medium are favourable (e.g Cragg et al. 2002, 1992; Elitzur 1976; Cook 1968) the emission of photons can be amplified via a collimation process into coherent beams known as masers. Astrophysical masers are prominent, point–like radio sources, which are associated with interstellar and stellar sources, as well as with galactic nuclei, comets and planets. A detailed survey of all masing sources and their associated molecules and transitions is therefore be- yond the scope of a single review, and the focus of this thesis will be on interstellar masers associated with HMSF. Masing activity in HMSF occurs within relatively dense conditions, with a highly luminous source to provide the pumping energy. The maser molecules them- selves are in the immediate region surrounding the protostellar source, and are hence referred to as interstellar masers (Reid & Moran 1981). Research into maser emission associated with HMSFRs has been focused on the class II methanol masers characterised by the 6.7 and 12.2 GHz transitions, class I methanol masers in the 44 GHz transition, water masers at 22GHz and OH masers at 1.6 GHz. Where there has been an overlap of these, comparative studies of HMSF masing regions (Forster & Caswell 1999, 1989; Caswell 1997; Caswell et al. 1995a) suggests that the maser spots (except class I methanol and water masers) are usually contained within a region of 30 mpc (∼6200 AU), corresponding to an angular diameter of about 1 00 at typical distances of 6 kpc to HMSFRs in our Galaxy (Breen et al. 2010a; Caswell 1997; Forster & Caswell 1989). The study of masers has shed light on the HMSF process by characterising circumstellar disks, bipolar outflows, magnetic fields and internal motions; and are beginning to provide a rudimentary timeline for classifying the evolutionary stage of young high–mass stars.
Use Committee of the National Institute on Alcohol Abuse and Alcoholism, NIH. Briefly, pregnant, day 3 of gestation, Long-Evans rats were purchased (Charles River, Portage, MI, USA) and fed a 22:6n-3 free, but n-3 fatty acid adequate diet (3.1% of total fatty acids as α -linolenic acid, 18:3n-3). Animals were maintained in our animal facility with ad libitum water and at a controlled temperature (23 ± 1°C) and a 12-hr light/dark cycle. At postnatal day 2, male pups were collected from each litter and randomized to one of five experimental groups. The groups included a dam-reared group and groups artificially reared on one of four experimental milks. The composition of the experi- mental milks was based on an artificial milk with fat con- tent from hydrogenated coconut oil (Dyets, Bethlehem, PA, USA), medium chain triglycerides (Mead Johnson Nutritionals, Evansville, IN, USA) and oleic and linoleic ethyl esters with purified docosapentaenoic n-6 and/or docosahexaenoic ethyl esters added (Nu-Chek Prep, Ely- sian, MN, USA). Thus, the five treatments included a dam- reared diet (DAM) where the dams received an n-3 fatty acid adequate (3.1% of total fatty acids as α -linolenic acid) but 22:6n-3 free diet, and four artificially reared (AR) groups. The four AR groups received the following diets: a 15% of total fatty acid 18:2n-6 based diet (AR-LA), the 18:2n-6 based diet with 1% of total fatty acids 22:5n- 6 (AR-DPAn-6), the LA based diet with 1% of total fatty acids 22:6n-3 (AR-DHA) and a 18:2n-6 based diet with 1% of total fatty acids 22:6n-3 and 0.4% of total fatty acids 22:5n-6 diet (AR-DHA+DPAn-6). Details on the composition of the diets have been presented previously . A summary of the fatty acid compositions as deter- mined by gas chromatography are presented in Table 6. Pups were hand reared until they could feed ad libitum
Ultra-wideband (UWB) technology is one of the most recent communication technologies which enable data transmission over a wide spectrum of frequency bands from 3.1 to 10.6 GHz with very low power and high data rates . This technology has attracted many researchers to exploit this higher data rate and wider bandwidth wireless applications in comparison to other technologies such as Bluetooth and WiMAX. Many UWB techniques have been presented in the literatures such as IR-UWB, MBOFDM- UWB which are suitable for high data rate applications and FM-UWB that is commonly applied for low data rate applications. UWB technology can be applied in sensor networks, imaging systems, wireless personnel area network (WPAN) and so on. The IEEE 802.15.3 High Rate Task Group 3a is chartered to draft a new standard for high-rate wireless personal area network (WPAN) [2,3,4]. The most current proposal for such a standard has target data transmission rates from 22 Mbps to 1320 Mbps with 2 individual bands of 3.1 - 4.85 GHz and 6.2 - 9.7 GHz. To support the high end of the data rates, the radio frond end must be able to provide a simple and cost effective solution to cover a bandwidth close to that allocated by the FCC. Uniform performance specifications must be satisfied across a large bandwidth.
are consistent with the sub-sample we consider here. The fact that the water masers show the largest velocity range is expected, partic- ularly because of their tendency to trace high-velocity outflow, but the median velocity of the HOPS sources is significantly lower than either of the Breen et al. (2010b) or Titmarsh et al. (2014, 2016) targeted water maser observations which have medians of 15 and 17 kms −1 , respectively. A part of this difference can be accounted for by the fact that the Walsh et al. (2014) quoted peak velocities of spots and therefore results in an underestimation of the velocity ranges of sites, but some of the difference is due to the unbiased nature of HOPS. The fact that the velocity range of the excited-state OH masers exceed the 12.2-GHz methanol masers is perhaps sur- prising given that 12.2-GHz methanol masers generally have much higher peak flux densities, and suggests that the excited-OH emis- sion is arising from a larger volume of gas than the 12.2-GHz maser emission.
The primary advantage of a two-port system is that it allows for higher input power and hence higher power absorption by the sample, which can greatly improve the sensitivity of the technique. This improvement is demonstrated in the automated sweeping of the athermally-detected SFMR spectra. Here the first module port provides 1 kHz chopped excitation signal to the sample via a 1-22GHz signal generator and the second port feeds the transmitted sig- nal into a 30 GHz bandwidth scalar spectrum analyser, such that the power dissipation can be monitored. The resonant response is mon- itored by the lock-in demodulated and processed SQUID voltage. A pulsed signal from a TTi arbitrary waveform generator provides synchronised triggering to both the signal generator (to initialise a linear frequency sweep) and to an oscilloscope connected to the
Figure 4-10: Dependency of tensile shear strength with the IMC layer thickness. It is interesting to compare the mechanical strength of the samples prepared in this experimental work with the strength obtained by other researchers. The maximum mechanical strength measured in this work is similar to the other authors who had their samples failing on the parent material and thus, having successful joints. However, those results are for thin sheets (about 1 mm thick) whereas in the present work the aluminium and steel plates are 6 and 2 mm thick, respectively. The interfacial failure of the specimens is possibly related with the lap joint configuration and the material thickness. During the mechanical tensile shear test the lap joint experiences a complex state of stresses, with both shear and bending stresses acting on the joint, because the specimen is not symmetric to the loading. This is observed in the specimens with higher mechanical strength which were bent after the tensile shear test, showing the rotation experienced during the mechanical test (Figure 4-11).
AF 1 = e j(kx+ky)d/2 + e j(−kx−ky)d/2 (4) AF 2 = e j(kx−ky)d/2 + e j(−kx+ky)d/2 (5) Next, a PDM-RAM is proposed, which utilizes a 4 × 4 PDMAMC to fill in the AMC area. As the complete chessboard structure is too computationally intensive to be fully modeled, a unit cell configuration based on a 2 × 2 array as depicted in Fig. 4(b) is analyzed. Element dimensions are fixed to 60 × 60 mm. Then, we compare the RCS results to those of a PEC plate with comparable dimensions and show monostatic RCS reduction of the frequency dependence of chessboard configuration for normal incidence. The results are done for x and y polarizations [see Fig. 5]. Except for some frequency shift, the two operational frequencies (5.16 GHz, 9.98 GHz) and three operational frequencies (3.98 GHz, 5.02 GHz, 7.66 GHz), of which the RCS have been reduced, agree well with the operational frequencies, around which the effective zero-phase condition is satisfied. The discrepancies are probably because ideal infinite periodic structures are used in the simulations of reflection phase. Since this PDM-RAM presents polarization-dependence and multiband characteristics, the energy impinging upon it is simply redirected for y- and x-polarizations at 7.66 GHz and 9.98 GHz, which show the backscattering characteristics at ϕ = 0 cut plane, as may be seen from Figs. 6 and 7, respectively. We can see that the RCS has a reduction of about 27.4 dB and 18.5 dB, respectively. The RCS of RAM is larger than the ones of PEC plate out of the design frequencies because there are no loss components in the composite RAM surface.
etching slots with different shapes. The slot can be placed either horizontally or vertically and is determined by the shape and size of the patch or the ground plane. Due to limited size of ground plane, two λ/4 S-shaped slots are positioned symmetrically on either side of the feed line on the ground plane to reject 5–6GHz band. A circular ring slot is etched on the radiator to reject WiMax band. A narrow rectangular slot is etched on the ground plane beneath the microstrip feed line to eliminate the frequency outside 3.1–10.6 GHz. The optimal dimension of the antenna and the photograph of the fabricated antenna are shown in Figure 1.
and − 134 . 47 ◦ , respectively. Fig. 6(b) presents that over the whole locking range, the phases deviate from − 90 ◦ , − 45 ◦ , 90 ◦ and 135 ◦ , and are less than 4.5 ◦ , 2.9 ◦ , 4.7 ◦ and 3.3 ◦ , respectively. The phase error is primarily caused by connectors, cables and mismatch of the on-chip devices, and the output waveforms are asymmetric. However, the main reason is that the buﬀer circuits suﬀer from the process variation and device mismatch.
Information technology – Real-time locating systems (RTLS) – Part 22: Direct Sequence Spread Spectrum (DSSS) 2,4 GHz air interface protocol: Transmitters operating with multiple spread codes and employing a QPSK data encoding and Walsh offset QPSK (WOQPSK) spreading scheme
The design and performance of a tetra-frequency microstrip antenna for the application in four frequencies for 5 GHz band (5.215 GHz, 5.5 GHz, and 5.69 GHz) and 6.16 GHz are described here. The frequencies are selected by studying the existing work for quadruple frequency antenna [19, 20, 21], so that the antenna contains a new set of frequencies. One of the uses of this multi-frequency antenna can be in automobiles where:
The design is started with a QSC antenna having rectangular boundary and fed by a tapered microstrip line, which helps in achieving a wide impedance band. A stepped impedance matching structure and ﬁshhook-like slit are created on the ground plane to obtain a better impedance matching over the UWB. The ﬂower boundary shown in Fig. 2 is beneﬁcial for achieving antenna compactness as it increases the current path length of the proposed antenna. The ﬂower-shaped boundary is obtained through making a composition of ﬁve circles and two triangles as shown in Fig. 1(c). The radius of the four smaller circles is calculated by equation R1 = (w2 − w3)/(4(1 + sin(f i))), and the radius of the bigger circle is calculated by equation R2 = (w2 − 4 × R1)/2. By adjusting parameter “fi ” (f i = 38 ◦ ), the angle of the triangular shape described in Fig. 1, a lower cut-in frequency is obtained. Fig. 2 shows the impedance matching evolution of the QSCA without notch band. As shown in Fig. 2, a lower cut-in frequency decreased from 3.85 GHz to 3.25 GHz is obtained with a compact size of 9 × 17.5 × 1 mm 3 .
slot and the T-shaped patch, while the shorter one is from the feed point to the end of the inner circular slot. It can be seen that the length of the longer path is much greater than the length of the rectangular patch, which makes the fundamental resonant frequency of the proposed antenna greatly lowered. In the proposed design shown in Figure 6, this length is about 54 mm, which is slightly less than half- wavelength of the operating frequency at 2.45 GHz. This difference is largely due to the effect of the supporting FR4 substrate, which reduces the resonant length of the radiating element.
For the analysis of the radiation of the antenna and the resonant frequencies, it is important to analyze the current distribution, which will be discussed in this section. The excitation of the particular GSM/UMTS/ LTE bands, surface current distributions on the Gamma-shaped driven monopole internal printed loop matching circuit at resonant frequencies are shown in Figure-3 (a)0.7895 GHz, (b)0.9881 GHz, (c)2.088 GHz, and (d)2.376 GHz.