Ultra Compact Research Articles

An Ultra-Compact X-ray Regenerative Amplifier Free-Electron Laser

There is a growing interest in designing and building compact X-ray Free Electron Lasers (FELs) for scientific and industry applications. In this paper, we report an X-ray Regenerative Amplifier FEL (XRAFEL) design based on a proposed Ultra Compact X-ray FEL configuration. Our results show that an XRAFEL can dramatically enhance the temporal coherence and increase the spectral brightness of the radiation in the hard X-ray regime without increasing the footprint of the FEL configuration. The proposed compact, fully coherent, and high-flux hard X-ray source holds promise as a valuable candidate for a wide range of high-impact applications in both academia and industry.

The isolated elliptical galaxy NGC 5812–MOND or dark matter?

AbstractThere exist isolated elliptical galaxies, whose dynamics can be modeled without resorting to dark matter or MOND, for example, NGC 7507. Such objects lack understanding within the current framework of galaxy formation. The isolated elliptical NGC 5812 is another object to investigate a possible role of isolation. We use globular clusters (GCs) and the galaxy light itself as dynamical tracers to constrain its mass profile. We employ Gemini/GMOS mask spectroscopy, apply the GMOS reduction procedures provided within IRAF, measure GC velocities by cross correlation methods and extract the line‐of‐sight kinematics of galaxy spectra using the tool pPXF. We identify 28 GCs with an outermost galactocentric distance of 20 kpc, for which velocities could be obtained. Furthermore, 16 spectra of the integrated galaxy light out to 6 kpc have been used to model the central kinematics. These spectra provide evidence for a disturbed velocity field, which is plausible given the disturbed morphology of the galaxy. We construct spherical Jeans models for the galaxy light and apply tracer mass estimators for the globular clusters. With the assumptions inherent to the mass estimators, MOND is compatible with the mass out to 20 kpc. However, a dark matter free galaxy is not excluded, given the uncertainties related to a possible nonsphericity and a possible nonequilibrium state. We find one globular cluster with an estimated mass of , the first Ultra Compact Dwarf in an isolated elliptical. We put NGC 5812 into the general context of dark matter or alternative ideas in elliptical galaxies. The case for a MONDian phenomenology also among early‐type galaxies has become so strong that deviating cases appear astrophysically more interesting than agreements. The baryonic Tully Fisher relation (BTFR) as predicted by MOND is observed in some samples of early‐type galaxies, in others not. However, in cases of galaxies that deviate from the MONDian prediction, data quality and data completeness are often problematic.

The Detection of Higher-order Millimeter Hydrogen Recombination Lines in the Large Magellanic Cloud

We report the first extragalactic detection of the higher-order millimeter hydrogen recombination lines (Δn > 2). The γ-, ϵ-, and η-transitions have been detected toward the millimeter continuum source N 105–1 A in the star-forming region N 105 in the Large Magellanic Cloud with the Atacama Large Millimeter/submillimeter Array. We use the H40α line, the brightest of the detected recombination lines (H40α, H36β, H50β, H41γ, H57γ, H49ϵ, H53η, and H54η), to determine the electron temperature and study ionized gas kinematics in the region, and the 3 mm free–free continuum emission to determine the physical parameters: the size, emission measure, and electron density. We compare the physical properties of N 105–1 A to a large sample of Galactic compact and ultracompact (UC) H ii regions and conclude that N 105–1 A is similar to the most luminous (L > 105 L ⊙) UC H ii regions in the Galaxy. N 105–1 A is ionized by an O5.5 V star; it is deeply embedded in its natal molecular clump, and likely associated with a (proto)cluster. We incorporate high-resolution molecular line data including CS, SO, SO2, and CH3OH (∼0.12 pc), and HCO+ and CO (∼0.087 pc) to explore the molecular environment of N 105–1 A. Based on the CO data, we find evidence for a cloud–cloud collision that likely triggered star formation in the region. We find no clear outflow signatures, but the presence of filaments and streamers indicates ongoing accretion onto the clump hosting the UC H ii region. Sulfur chemistry in N 105–1 A is consistent with the accretion shock model predictions.

On the Maximum Energy Release from Formation of Static Compact Objects

Type II Supernova 1987A (SN 1987A), observed in 1987, released an energy of Q≈3×1053 erg. This huge energy is essentially the magnitude of gravitational potential or self-gravitational energy (PE) of a new born cold neutron star having a gravitational compactness or redshift zb≈0.15. One may wonder what could be the upper limit on the amount of energy that might be released with the formation of a cold Ultra Compact Object (UCO) with an arbitrary high zb. Accordingly, here, for the first time, we obtain an analytical expression for the PE of a homogeneous general relativistic UCO assuming it to be cold and static. It is found that the PE of a homogeneous UCO of mass M may exceed Mc2 and be as large as 1.34 Mc2. This result, though surprising, follows from an exact and correct analytical calculation based on the standard General Theory of Relativity (GTR). Further, UCOs supported by tangential stresses may be inhomogeneous and much more massive than neutron stars with PE ∼ 2.1 Mc2 Thus, in principle, formation of an UCO of a few solar masses (M⊙) might release an energy Q∼1055 erg.

An Ultra Compact Microstrip Branch Line Coupler with Wide Stopband Using LCL Filter and Meandered Stubs for Microwave Applications

A branch line coupler (BLC) with ultra-compact size and harmonic suppression ability using an LCL filter and meandered stubs is proposed in this paper. There are some important factors in microstrip coupler design, including size reduction, harmonic suppression, and low insertion loss. Thus, improving each of these factors will contribute to a more efficient design. In the proposed circuit, for the first time, LCL filters, including four T-shaped circuits and four meandered line open-ended stubs, were used together to reduce the circuit size and suppress unwanted harmonics. The proposed LCL filters, incorporated in the BLC branches, resulted in superior size reduction and harmonic suppression for the presented BLC. The proposed BLC correctly worked at 900 MHz with 300 MHz operating bandwidth, which showed 33% fractional bandwidth (FBW). Additionally, a wide suppression band from 1.4 GHz to 8.8 GHz, with more than 20 dB attenuation level was obtained, which suppressed the second to ninth unwanted harmonics. The overall size of the proposed 900 MHz coupler was only 11 mm × 10.4 mm (0.044 λ × 0.042 λ) while the size of the conventional 900 MHz coupler was 61.5 mm × 62.5 mm (0.25 λ × 25 λ). The proposed BLC had a very small size and only occupied 3% of the size of the conventional coupler, which corresponded to a 97% size reduction. To the best of the authors’ knowledge, to date, the best size reduction has been obtained among the published couplers. Furthermore, the experimental results verified the simulated and analyzed results of the proposed technique and demonstrate its potential for improving the performance and miniaturizing the size of other similar BLCs.

A Possible Chemical Clock in High-mass Star-forming Regions: N(HC3N)/N(N2H+)?

We conducted observations of multiple HC3N (J = 10−9, 12−11, and 16−15) lines and the N2H+ (J = 1−0) line toward a large sample of 61 ultracompact (UC) H ii regions, through the Institut de Radioastronomie Millmétrique 30 m and the Arizona Radio Observatory 12 m telescopes. The N2H+ J = 1−0 line is detected in 60 sources and HC3N is detected in 59 sources, including 40 sources with three lines, 9 sources with two lines, and 10 sources with one line. Using the rotational diagram, the rotational temperature and column density of HC3N were estimated toward sources with at least two HC3N lines. For 10 sources with only one HC3N line, their parameters were estimated, taking one average value of T rot. For N2H+, we estimated the optical depth of the N2H+ J = 1−0 line, based on the line intensity ratio of its hyperfine structure lines. Then the excitation temperature and column density were calculated. When combining our results in UC H ii regions and previous observation results on high-mass starless cores, the N(HC3N)/N(N2H+) ratio clearly increases from the region stage. This means that the abundance ratio changes with the evolution of high-mass star-forming regions (HMSFRs). Moreover, positive correlations between the ratio and other evolutionary indicators (dust temperature, bolometric luminosity, and luminosity-to-mass ratio) are found. Thus we propose the ratio of N(HC3N)/N(N2H+) as a reliable chemical clock of HMSFRs.

Global kinematics study of OH masers in W49N

Context. Star formation is underway in the W49N molecular cloud (MC) at a high level of efficiency, with almost twenty ultra-compact (UC) HII regions observed thus far, indicating a recent formation of massive stars. Previous works have suggested that this cloud is undergoing a global contraction. Aims. We analyse the data on OH masers in the molecular cloud W49N, observed with the VLBA at the 1612, 1665, and 1667 MHz transitions in left circular polarization (LCP) and right circular polarization (RCP) with an aim to study the global kinematics of the masers. Methods. We carried out our study based on the locations and observed velocities of the maser spots, Vobs. We found the location (α, δ)m of the maximum correlation between V = Vobs−Vsys (with Vsys the systemic velocity) and distance to it. The velocities were fitted to the straight line of Vobs−Vsys versus d(α,δ)m, resulting in Vftd. The difference between the fitted values and those obtained from observations is ∆ V = (Vobs−Vsys)-Vftd. The Vobs−Vsys velocity shows a gradient as a function of the distance to (α, δ)m, where the closer spots have the largest velocities. Spots with similar velocities are located in different sectors, with respect to (α, δ)m. Then, we assumed that the spots are moving towards a contraction centre (CCOH), which is at the apex of a CONUS. We also assumed that the distance of each spot to CCOH is dcc = √2 d(α,δ)m and that they fall with a velocity Vcc = √2Vftd, with the total velocity being VTot = Vcc + √2 Δ V. Using this velocity, we estimated the free-fall velocity. Results. The coordinates of (α, δ)m are effectively (α2000 = 19:10:13.1253, δ2000 = 9:6:13.570). The observed dispersion with respect to the global trend against dcc, shows a maximum at 0.12 pc, with a decay from 0.12 to 0.19 pc, which is faster than that taking place between 0.19 and 0.42 pc. Based on VTot, an inner mass of Minn = 2500 M⊙ was estimated. In addition, the estimated accretion rate is Ṁ = 1.4×10−3 M⊙yr−1, which requires a time of tinn = 1.8×106 yr to accumulate Minn. The free-fall time, assuming n = 1×10−4 cm−3, is tff = 3.4×105 yr. Performing the same procedure with published data that are of lower spatial resolution (than the VLBA data) produces similar results. For example, based on the available data, we find that (α, δ)m = (19:10:13.1392, 9:6:13.4387) J2000, which is at ≲ 0.3 asec from what has been calculated with the VLBA data, with an estimated inner mass of 2700 M⊙. A sub-collapse appears to be taking place in the region traced by the OH maser spots. Based on methanol maser cloudlets data, which lie in a smaller region, another possible centre of contraction is identified, which could be due to a sub-collapse towards a 75 M⊙ inner mass. Conclusions. The velocities of the OH spots at W49N, along with their positions with respect to (α, δ)m, make it possible to trace a global kinematics that is apparently due to a sub-collapse in the W49N MC.

The ultracompact regions G40.54+2.59 and G34.13+0.47: A new detection of compact radio sources

Abstract We report the detection of three compact (<0.001 pc) radio sources (CRSs) at the Ka-band (0.9 cm) in the ultra-compact (UC) H ii regions G040.54+2.59 (two CRSs) and G034.13+0.47 (one CRS). These CRSs have weak flux densities and are located at the center of their respective UC H ii regions. We found no clear association between massive ionizing stars and CRSs but some radiative influence on the latter, as suggested by their large emission measures (>107 cm−6 pc), typical of photo-evaporating neutral objects close to or associated with massive stars. Our modelling of G40.54+2.59 shows that its CRSs supply enough ionized material to shape its morphology while significantly extending its observable lifetime. On the other hand, despite the possible relation of the CRS with the large-scale outflow signatures observed in G034.13+0.47, the influence of this CRS on the evolution of the UC H ii region is unlikely. Our results show that the presence of CRSs can alleviate the so-called lifetime problem of UC H ii regions. Still, to address the dynamical evolution of these regions adequately, the scenario must include additional mechanisms like ambient confinement, or the role of the kinematics of their associated stellar objects.

U/Pb geochronology of fossil fish dentine from Romualdo Formation, Araripe Basin, northeast of Brazil

Absolute dating of sedimentary rocks and fossils from the Mesozoic are still rare, mainly due to the difficulties arising from diagenetic changes. Diagenesis promotes changes in the primary structure and chemical composition of biomineralization, which should remain unchanged from the time of deposition and fossilization. Three bioapatite teeth extracted from a jaw fragment of Cladocyclus gardneri from the Romualdo Formation, Araripe Basin, Northeastern Brazil were dated by the U/Pb method in order to obtain an absolute age. The rocks that contain this fossil are dated to Aptian by biostratigraphy of palynomorphs (Sergipea variverrucata biozone, Petrobras P-270), ostracods (Damonella grandiensis biozone, Petrobras) and from the international biozoning of planktonic foraminifera Microhedbergella miniglobularis. The teeth were mounted in 25 mm epoxy resin rounds, imaged by optical microscope and SEM and dated with a Nu Instruments AttoM single-collector ICP-MS coupled to an NWR193nm UC (Ultra Compact) ArF excimer laser system. A Discordia U–Pb date obtained from three separate Cladocyclus gardneri dentine is 110.5 ± 7.4 Ma (2s, MSWD = 2.6), consistent with the biostratigraphic age. This date was based on 155 integrations of line scan analyses (spot size of 30 μm, scan moved at 2 μm per second/100 μm in total length). 238U/206Pb ratios that differed from the mean value by more than 2SD for each tooth were excluded based on the likelihood they reflect U-redistribution during fossilization/post-fossilization fluid alteration. Remaining variations in 238U/206Pb and 207Pb/206Pb ratios along the Discordia reflect variable contributions from common Pb, both within and between the three teeth. They reflect primary U/Pb compositions given that they date the expected age of fossilization.

Evolutions of CH3CN abundance in molecular clumps

To investigate the effects of massive star evolution on surrounding molecules, we select nine massive clumps previously observed with the Atacama Pathfinder Experiment (APEX) telescope and the Submillimeter Array (SMA) telescope. Based on the observations of APEX, we obtain luminosity to mass ratios L clump/M clump that range from 10 to 154 L ⊙/M ⊙, where some of them embedded ultra compact (UC) HII region. Using the SMA, CH3CN (12K–11K) transitions were observed toward nine massive star-forming regions. We derive the CH3CN rotational temperature and column density using the XCLASS program, and calculate its fractional abundance. We find that CH3CN temperature seems to increase with the increase of L clump/M clump when the ratio is between 10 to 40 L ⊙/M ⊙, then decrease when L clump/M clump ≥ 40 L ⊙/M ⊙. Assuming that the CH3CN gas is heated by radiation from the central star, the effective distance of CH3CN relative to the central star is estimated. The distance ranges from ∼ 0.003 to ∼ 0.083 pc, which accounts for ∼ 1/100 to ∼ 1/1000 of clump size. The effective distance increases slightly as L clump/M clump increases (R eff ∼ (L clump/M clump)0.5±0.2). Overall, the CH3CN abundance is found to decrease as the clumps evolve, e.g., X CH3CN ∼ (L clump/M clump)−1.0 ± 0.7. The steady decline of CH3CN abundance as the clumps evolution can be interpreted as a result of photodissociation.

Design and Fabrication of a Novel Ultra Compact Microstrip Diplexer Using Interdigital and Spiral Cells

A dual-band bandpass-bandpass microstrip diplexer with very small size and good performance is designed in this work. The proposed diplexer has a novel structure which is introduced for the first time in this paper. In comparison with the previously reported diplexers, it occupies the most compact size of 0.002 λg2 (226.7 mm2), fabricated on 0.787 mm dielectric substrate height. The resonance frequencies of the presented diplexer are located at 0.76 GHz and 1.79 GHz making it suitable for the global system for mobile communications (GSM) applications. It has a wide flat channels with two fractional bandwidths (FBWs) of 41.1% and 50%. Another feature of the proposed diplexer is its ability to suppress the harmonics. It can attenuate the 1st to 7th harmonics. Moreover, it has low insertion losses and low group delays at both channels while the isolation and return losses are acceptable. Finally, the proposed diplexer is fabricated and measured to verify the simulation results, where a good agreement between the simulation and measurement results is obtained.

Radio Stars of the SKA

Radio emission from stars can be used, for example, to study ionized winds or stellar flares. The radio emission is faint and studies have been limited to few objects. The Square Kilometer Array (SKA) brings a survey ability to the topic of radio stars. In this paper we investigate what the SKA can detect, and what sensitivity will be required for deep surveys of the stellar Milky Way. We focus on the radio emission from OB stars, Be stars, flares from M dwarfs, and Ultra Compact HII regions. The stellar distribution in the Milky Way is simulated using the Besançon model, and various relations are used to predict their radio flux. We find that the full SKA will easily detect all UltraCompact HII regions. At the limit of 10 nJy at 5 GHz, the SKA can detect 1500 Be stars and 50 OB stars per square degree, out to several kpc. It can also detect flares from 4500 M dwarfs per square degree. At 100 nJy, the numbers become about 8 times smaller. SKA surveys of the Galactic plane should be designed for high sensitivity. Deep imaging should consider the significant number of faint flares in the field, even outside the plane of the Milky Way.

EXPLORING THE NATURE OF COMPACT RADIO SOURCES ASSOCIATED TO UCHII REGIONS

We present Very Large Array 7 mm continuum observations of four ultracompact (UC) HII regions, observed previously at 1.3 cm, in order to investigate the nature of the compact radio sources associated with these regions. We detect a total of seven compact radio sources, four of them with thermal emission, and two compact radio sources with clear non- thermal emission. The thermal emission is consistent with the presence of an ionized envelope, either static (i.e., trapped in the gravitational radius of an associated massive star) or flowing away (i.e., a photo-evaporative flow). The nature of the non-thermal sources remains unclear and several possibilities are proposed. The possibility that most of these compact radio sources are photo-evaporating objects, and the remaining ones more evolved objects, is consistent with previous studies on UCHII regions.

Ultra Compact, High Contrast Ratio Based all Optical OR Gate Using Two Dimensional Photonic Crystals

In this paper, Two Dimensional Photonic Crystals (2DPC) based all-optical two/three input OR gate is proposed and designed. A logic gate is an elementary building block of a digital circuit. The proposed all-optical OR gate is designed by creating Y shaped defect with ring resonator in a hexagonal lattice structure. The performance of the proposed all-optical OR gate is investigated using the Plane Wave Expansion (PWE) and Finite Difference Time Domain (FDTD) method. The functional parameters namely normalized efficiency, contrast ratio, response time and bit rate, are calculated. The proposed all-optical OR gate operates at a wavelength of 1550 nm. The size of the proposed structure is compact in nature. It offers high contrast ratio and minimum delay time. Hence it is suitable for optical processors, high speed optical integrated circuits and switching devices.

Recombination Lines and Molecular Gas from Hypercompact H ii regions in W51 A

Abstract We present a detailed characterization of the population of compact radio-continuum sources in W51 A using subarcsecond Very Large Array and Atacama Large Millimeter/submillimeter Array observations. We analyze their 2 cm continuum, the recombination lines (RLs) H77α and H30α, and the lines of , , and . We derive diameters for 10/20 sources in the range D ∼ 10−3 to ∼10−2 pc, thus placing them in the regime of hypercompact H ii regions (HC H ii’s). Their continuum-derived electron densities are in the range n e ∼ 104 –105 cm−3, lower than typically considered for HC H ii’s. We combined the RL measurements and independently derived n e, finding the same range of values but significant offsets for individual measurements between the two methods. We find that most of the sources in our sample are ionized by early B-type stars, and a comparison of n e versus D shows that they follow the inverse relation previously derived for ultracompact (UC) and compact H ii’s. When determined, the ionized-gas kinematics is always (7/7) indicative of outflow. Similarly, 5 and 3 out of the 8 HC H ii’s still embedded in a compact core show evidence for expansion and infall motions in the molecular gas, respectively. We hypothesize that there could be two different types of hypercompact (D < 0.05 pc) H ii regions: those that essentially are smaller, expanding UC H ii’s; and those that are also hyperdense (n e > 106 cm−3), probably associated with O-type stars in a specific stage of their formation or early life.

Ultracompact H ii regions with extended emission: the case of G43.89–0.78 and its molecular environment

ABSTRACT The Karl Jansky Very Large Array (VLA), Owens Valley Radio Observatory (OVRO), Atacama Large Millimetric Array (ALMA), and the infrared Spitzer observatories are powerful facilities to study massive star formation regions and related objects such as ultra-compact (UC) H ii regions, molecular clumps, and cores. We used these telescopes to study the UC H ii region G43.89–0.78. The morphological study at arcminute scales using NVSS and Spitzer data shows that this region is similar to those observed in the bubble-like structures revealed by Spitzer observations. With this result, and including a physical characterization based on 3.6 cm data, we suggest G43.89–0.78 be classified as an UC H ii region with Extended Emission because it meets the operational definition given in this paper comparing radio continuum data at 3.6 and 20 cm. For the ultra-compact component, we use VLA data to obtain physical parameters at 3.6 cm confirming this region as an UC H ii region. Using ALMA observations, we detect the presence of a dense (2.6 × 107 cm−3) and small (∼ 2.0 arcsec; 0.08 pc) molecular clump with a mass of 220 M⊙ and average kinetic temperature of 21 K, located near to the UC H ii region. In this clump, catalogued as G43.890–0.784, water masers also exist, possibly tracing a bipolar outflow. We discover in this vicinity two additional clumps which we label as G43.899–0.786 (Td = 50 K; M = 11 M⊙) and G43.888–0.787 (Td = 50 K; M = 15 M⊙).

From clump to disc scales in W3 IRS4

Context. High-mass star formation typically takes place in a crowded environment, with a higher likelihood of young forming stars affecting and being affected by their surroundings and neighbours, as well as links between different physical scales affecting the outcome. However, observational studies are often focused on either clump or disc scales exclusively. Aims. We explore the physical and chemical links between clump and disc scales in the high-mass star formation region W3 IRS4, a region that contains a number of different evolutionary phases in the high-mass star formation process, as a case-study for what can be achieved as part of the IRAM NOrthern Extended Millimeter Array (NOEMA) large programme named CORE: “Fragmentation and disc formation in high-mass star formation”. Methods. We present 1.4 mm continuum and molecular line observations with the IRAM NOEMA interferometer and 30 m telescope, which together probe spatial scales from ~0.3−20′′ (600−40 000 AU or 0.003−0.2 pc at 2 kpc, the distance to W3). As part of our analysis, we used XCLASS to constrain the temperature, column density, velocity, and line-width of the molecular emission lines. Results. The W3 IRS4 region includes a cold filament and cold cores, a massive young stellar object (MYSO) embedded in a hot core, and a more evolved ultra-compact (UC)H II region, with some degree of interaction between all components of the region that affects their evolution. A large velocity gradient is seen in the filament, suggesting infall of material towards the hot core at a rate of 10−3−10−4 M⊙ yr−1, while the swept up gas ring in the photodissociation region around the UCH II region may be squeezing the hot core from the other side. There are no clear indications of a disc around the MYSO down to the resolution of the observations (600 AU). A total of 21 molecules are detected, with the abundances and abundance ratios indicating that many molecules were formed in the ice mantles of dust grains at cooler temperatures, below the freeze-out temperature of CO (≲35 K). This contrasts with the current bulk temperature of ~50 K, which was obtained from H2CO. Conclusions. CORE observations allow us to comprehensively link the different structures in the W3 IRS4 region for the first time. Our results argue that the dynamics and environment around the MYSO W3 IRS4 have a significant impact on its evolution. This context would be missing if only high resolution or continuum observations were available.

Design and Analysis of Interdigital Coupled Ultra Wideband Bandpass Filter using Multimode Resonator

In this paper, an interdigital coupled microstrip bandpass filter incorporated with shorted stub multi-mode resonator at ultra-wideband spectrum is presented. Proposed filter is characterized by its ultra compactness achieved through multi-mode resonator. The proposed filter is incorporated with interdigitated transmission line based on Lange Coupler topology. This structure enhances capacitive coupling between feed line and MMR which improves lower frequency selectivity of BPF. The parameters viz. fractional bandwidth of 105%, return loss above 20 dB and insertion loss below 1 dB at centre frequency of 4.875 GHz are recorded. The bandwidth of the filter is measured to be 5.15 GHz (2.3 to 7.45 GHz). The filter shows good linearity with its group delay recorded 0.2 ns with small variations of 0.1 ns at maximum in its passband. The compactness of proposed filter makes it suitable for various modern wireless applications.

A Research on Microstrip Ultrawide Band Filters using Defected Ground Structure Techniques

In this paper, microstrip ultra-wideband (UWB) filters using various defected ground structures are studied. Miniature microstrip filters employed in transceiver of modern wireless communication systems play vital role in controlling and regulating frequency response. DGS techniques are etched in ground plane to design compact microstrip based low pass, high pass, bandpass and band reject filters used in modern wireless systems. Various modified and hybrid defected ground structure techniques are employed to achieve high return loss, low insertion loss, ultra compactness, good selectivity and linearity in filters. Study reveals that the proper selection and incorporation of DGS techniques while designing microstrip ultra wideband filter optimizes the various vital parameters which enhances its performance and practicability for various modern wireless communication applications.

Analysis of an Additively Manufactured Cooled Ultra Compact Combustor Vane

The ultra compact combustor (UCC) aims to increase the thrust-to-weight ratio of an aircraft gas turbine engine by decreasing the size, and thus weight, of the engine’s combustor. The configuration of the UCC as a primary combustor enables a unique cooling scheme to be employed for the hybrid guide vane (HGV). A previous effort conducted a computational fluid dynamics (CFD) analysis that evaluated whether it would be possible to cool this vane by drawing in freestream flow at the stagnation region of the airfoil. Based on this study, a cooling scheme was designed and modified with internal supports to make additive manufacturing of the vanes possible. This vane was computationally evaluated comparing the results with those of a solid vane and hollow vane without cooling holes as a demonstration of the improvements offered by this design. Furthermore, the effects of the internal support structure were deemed beneficial to surface cooling when evaluated through comparisons of internal pressure distribution and overall effectiveness. Following the computational study, the vane was manufactured and experimentally evaluated with the results compared to those of an uncooled solid vane. The experimental results validated the computational analysis and demonstrated through pressure and temperature measurements that the cooled vane had a reduced surface temperature compared to the uncooled vane and that pressure distributions supported coolant flow through film-cooling holes.