Search

This work proposes a microwave resonator built from gallium arsenide using integrated passive device (IPD) technology. It consists of a three-layered interlaced spiral structure with airbridges and inner interdigital structures. For integrated systems, IPD technology demonstrated outstanding performance, robustness, and a tiny size at a low cost. The airbridges were made more compact, with overall dimensions of 1590 × 800 µm2 (0.038 × 0.019 λg2). The designed microwave resonator operated at 1.99 GHz with a return loss of 39 dB, an insertion loss of 0.07 dB, and a quality factor of 1.15. Additionally, an experiment was conducted on the properties of the airbridge and how they affected resistance, inductance, and S-parameters in the construction of the resonator. To investigate the impact of airbridges on the structure, E- and H-field distributions of the resonator were simulated. Furthermore, its use in sensing applications was explored. Various concentrations of glucose solutions were used in the experiment. The proposed device featured a minimum detectable concentration of 0.2 mg/mL; high sensitivity, namely, 14.58 MHz/mg·mL−1, with a linear response; and a short response time. Thus, this work proposes a structure that exhibits potential in integrated systems and real-time sensing systems with high sensitivity.

A dual-band branch-line coupler with ultra-wideband harmonic suppression is proposed in this paper. The conventional quarter-wavelength transmission lines are replaced with π-shaped lines to achieve a dual band. In addition, ultra-wideband harmonic suppression is obtained by the frequency-selecting coupling structure (FSCS) providing three transmission zeros. The two operating frequencies are 0.9 GHz and 2.0 GHz, and the corresponding −10 dB bandwidth at 0.9 GHz and 2.0 GHz is 18.9% and 10.5%, respectively. A wide harmonic suppression band is generated from 3.7 GHz to 8.3 GHz. The simulation and measurement results are in good agreement.

Endophytic fungi were isolated from needle leaves of two conifer species in Korea. The fungal isolates were identified based on their morphological characteristics and phylogenetic analyses of their internal transcribed spacer and large-subunit rDNA regions. Three species of endophytic fungi, namely Celosporium laricicola, Neocatenulostroma germanicum, and Phaeophleospora eucalypticola were the first records in Korea. In this study, we reported the morphological and phylogenetic characteristics of these fungi.

The complete mitochondrial genome of Tremoctopus violaceus was sequenced to analyze its organization and phylogenetic status within the order Octopoda. The mitochondrial genome of T. violaceus had a structure and organization similar to that of other Octopoda. The content of the nucleotides A, C, G, and T was 31.68 %, 7.71 %, 20.02 %, and 40.58 %, respectively. All protein-coding genes (PCG) began with the ATG codon, excluding ND4 and ATP6, which began with ATC and ATT, respectively, and terminated with TAG, TAA, TA, or T. Codons for isoleucine were the most used codons, whereas those for arginine were used the least. Two extra tRNAs, trnN and trnL, were found in the control region. These tRNAs have a D-armless structure. The control region had excess A + T content (83.16 %) and a stem-loop structure with two elements, which is reported for the first time in Octopoda by our study. Bayesian inference using 13 PCG revealed that Octopus and Octopodidae were polyphyletic, and that Tremoctopodidae diverged relatively earlier within Octopoda. The mitochondrial genome of T. violaceus and its characteristics may help to understand the evolutionary history of Octopoda and establish a marine biodiversity conservation strategy.

The truffle and ectomycorrhizal roots formed by Tuber sp. were collected from the rhizosphere of Quercus aliena in Korea. The morphological characteristics of the ascoma, and molecular phylogenetic analysis using sequences from the internal transcribed spacer (ITS) and large subunit (LSU) of ribosomal DNA, translation elongation factor 1-alpha (TEF), and RNA polymerase second largest subunit (RPB2) regions confirmed the distinct morphology of the truffle. This truffle belongs to a monophyletic clade among the other Tuber species in the phylogeny. This study describes the truffle, Tuber koreanum, as a new species reported from Korea.

In this study, endophytic fungi were isolated from the leaves of evergreen woody plants in Hansando Island in South Korea. The fungal isolates were identified based on morphological characteristics and phylogenetic analysis of the DNA sequences of the internal transcribed spacer and the large subunit regions of rDNA. It was confirmed that two endophytic fungal species, Muyocopron lithocarpi and Didymocyrtis cladoniicola, isolated in this study have not previously been reported in South Korea.

We collected the ascomata of Tuber species from the rhizosphere of Quercus dentata in Danyang, Korea. We observed the morphological characteristics of ectomycorrhizal roots and ascomata, and identified the species based on the results of the phylogenetic analysis conducted using the DNA sequences of an internal transcribed spacer, a large-subunit rDNA, translation elongation factor 1-α DNA (TEF1), and MAT. Finally, we identified the fungal species as Tuber himalayense B.C. Zhang & Minter, which has not been recorded previously in Korea. We evaluated the morphological characteristics and conducted phylogenetic analysis of the ascoma and mycorrhiza (associated with Q. dentata) of T. himalayense.

In this study, we analyzed the diversity of ectomycorrhizal (ECM) fungal communities of Quercus spp. roots in the limestone area. We identified 45 generd of ECM using next generation sequencing (NGS) analysis. Soil chemical composition analysis confirmed soil pH, substitution calcium concentration, total nitrogen content, organic phosphate, and organic matter content. Shannon’s Index was calculated according to the changes in soil chemical composition. The results of cluster analysis showed that Sebacina, Tomentella, Tuber, Densospora, Inocybe, Suillus, and Piloderma were the main genera of symbiotic ECM fungi that thrived in soil with high pH and calcium content.

We isolated endophytic fungi from Smilax china and Cryptomeria japonica. These fungal strains were identified based on their morphological characteristics and phylogenetic analyses of their internal transcribed spacer, large subunit rDNA, and translation elongation factor 1-α DNA. Among them, we discovered two fungi belonging to the genus Phyllosticta, which have not been previously recorded in Korea. We have described these two fungal strains, Phyllosticta ericarum 19E458 and Phyllosticta philoprina 19E012 in this study.

Substrate-integrated waveguides (SIWs) are widely used in microwave systems owing to their low cost and ease of integration. In this study, an SIW-based resonator that reacts to the complex permittivity variation of solutions with dimensions of 79.2 mm × 59.8 mm is introduced. This octagon-shaped sensor can be installed on a preliminary monitoring system to test water quality by observing the parameter variations caused by external factors. The resonant structure was used to test different concentrations of ethanol–water and acetone–water mixtures for verification. The resonant frequency and quality factor (Q-factor) were found to vary with the relative complex permittivity of the liquid in the S-band, and the electric field distribution varied when liquid droplets were placed in the center of the substrate. The designed sensor operates at 2.45 GHz in the air, and the observed minimum resonant frequency shift with liquid was 15 MHz. The measurement error was approximately 3.1%, and the results reveal a relationship between the resonant frequency and temperature as well. Considering the observed sources of error, the measured relative permittivity is consistent with the actual values. The proposed sensor is economically convenient and suitable for various test environments.

Permittivity sensing is commonly utilized in multiple fields for various applications. In this study, an enhanced RFID (Radio Frequency Identification) permittivity sensor system is designed. Additionally, we investigated the signal processing procedures in a stepwise manner to obtain the resultant graphs. For validation, a simplified system including a reader and a tag is tested. The reader in the system comprises a pulse generator and a pair of antennas connected to an oscilloscope, whereas the tag comprises an antenna and a delay line sensor. The pulse generator produces short pulses of less than 1 ns periodically, whereas the short-ended delay line on the tag acts as a sensor, wherein the delay time of the traversing wave is primarily associated with the relative permittivity of the material under test (MUT). We tested the system to derive an equation for the value of relative permittivity of the MUT using the measured signal. The system was calibrated by performing both unloaded and air tests to obtain measurement equations. Moreover, an additional test validated the water permittivity sensing, and the relative permittivity measured was 78.1. Considering the errors affecting the measurements, the measured relative permittivity of water concurs with the actual value.

We isolated endophytic fungi from the leaves of woody plants inhabiting the Ulleungdo Island and Yeosu in South Korea. The fungal strains were identified based on their morphological characteristics in conjunction with phylogenetic analysis, which was performed using sequences of the internal transcribed spacer, large subunit rDNA, and β-tubulin DNA. We confirmed the presence of Neofusicoccum mangiferae and Thyronectria cucurbitula, two endophytic fungal species that had not been previously recorded in Korea. In this report, we describe the morphological characteristics of these fungal strains and results of the DNA-based phylogenetic analysis.

The fruiting bodies and roots of a Tuber species were collected from the rhizosphere of Quercus dentata in Pohang, Korea. The morphological characteristics of the ascoma and ectomycorrhizal roots were studied, and phylogenetic analyses were performed using the sequences of the internal transcribed spacer, large subunit rDNA, and β-tubulin DNA. Based on the features of the fruiting bodies, the species was identified to be Tuber huidongense, which has not been reported earlier in Korea. The morphological characteristics and phylogenetic analysis of T. huidongense are described in the present study.

Endophytic fungi were isolated from the leaves of plants inhabiting the Hansando Island in Korea. We identified the fungal strains based on their morphological characteristics and on the phylogenetic analysis using DNA sequences of the internal transcribed spacer, small subunit rDNA, large subunit rDNA, and translation elongation factor 1- α regions. In this study, we isolated five endophytic fungi that have not been recorded in Korea, Arthrinium camelliae-sinensis, Beltraniella humicola, B. portoricensis, Microxiphium theae, and Piceomphale pinicola. Their morphological characteristics as well as the results of molecular phylogenetic analysis are reported here.

In this paper, a tri-band Gysel power divider (PD) based on zero-degree composite right-/left-handed (CRLH) transmission lines (TLs) is presented. Compared to the generalized design methods in which multiple passbands are realized by replacing conventional impedance transformers with quarter-wavelength CRLH-TLs, the employed zero-degree CRLH-TLs include high design flexibility for the characteristic impedance and phase responses of the composed left-handed and right-handed TLs, which can be used to separately control the bandwidths of the three passbands. In addition, the microstrip-to-slotline transition is utilized to replace the conventional 180° TL, which can expand the realizable range of the three center frequencies and reduce the circuit size, as well. The proposed theory is validated using two designs: One involves a broadband PD with a center frequency of 2.5 GHz, while the other is a tri-band PD centered at 3.5 GHz, 2.5 GHz, and 1.5 GHz. Good agreement between the simulated and measured results are obtained; for the first PD, a fractional 3-dB bandwidth of up to 116% is achieved, whereas, for the tri-band PD, a size reduction of 80% is achieved with good impedance matching and isolation performance.

Abstract The complete mitochondrial (mt) genome of Stereolepis doederleini was sequenced from a specimen collected in a commercial aquarium in Jeju Island. The sequence was 16,513 base pairs in length and, similar to other vertebrate mt genomes, included 37 mt genes and a noncoding control region; the gene order was identical to that of typical vertebrate mt genome. Mitochondrial genome sequences of 17 species from 12 families were used to reconstruct phylogenetic relationships within the order Pempheriformes. The phylogenetic trees were constructed with three methods (neighbor joining [NJ], maximum likelihood [ML], and Bayesian method) using 12 protein coding genes, but not ND6. In all phylogenetic trees, Pempheriformes were clustered into three strongly supported clades. Two Acropomatidae species (Synagrops japonicus in clade-Ⅰ and Doederleinia berycoides in clade-Ⅲ) were polyphyletic; S. japonicus was close to Lateolabracidae and was the sister of Glaucosomatidae + (Pempheridae/(Percophidae+Creediidae)), and D. berycoides was sister to Howellidae + Epigonidae. All phylogenetic trees supported a sister relationship between Creediidae and Percophidae in clade-Ⅰ. Glaucosomatidae formed a sister clade with Pempheridae. The relationships within clade-Ⅱ, which was composed of four families (Pentacerotidae, Polyprionidae, Banjosidae, and Bathyclupeidae), slightly differed between NJ/ML and BI tree topologies. In clade-Ⅲ, the relationships among Howellidae, Epigonidae, and Acropomatidae were strongly supported.

In this paper, a size-reduced tri-band Gysel power divider (PD) with ultra-wideband harmonics suppression performance, simple structure, high-power handling capability, and independently controllable bandwidth is first presented. The three passbands are introduced by two tri-band biasing networks whose impedances can also be utilized to control the bandwidths of the three passbands independently. With the introduction of slow-wave transmission lines and coupled lines with series open-circuited stubs, a reduced size and ultra-wide stopband can be obtained, respectively. Detailed closed-form design equations are derived and validated with a design of PD operating at 2.0, 2.5, and 3.0 GHz. Also, two additional circuits are designed, simulated, and fabricated. One is utilized to obtain the optional range of the three passbands, and the other is to make a comparison with the proposed PD. All the measured results agree well with the corresponding simulated ones. Proper impedance matching, isolation, and a wider 3-dB fractional bandwidth can be obtained, which is 18.5%, 20.7%, and 13.0%, respectively, at each passband. In addition, more bands can be easily extended to the proposed PD by introducing more open-circuited stubs in the tri-band biasing networks.

A new equivalent circuit model of an electrical size-reduced coupled line radio frequency Marchand balun is proposed and investigated in this paper. It consists of two parts of coupled lines with significantly reduced electrical length. Compared with the conventional Marchand balun, a short-circuit ending is applied instead of the open-circuit ending, and a capacitive feeding is introduced. The electrical length of the proposed balun is reduced to around 1/3 compared with that of the conventional Marchand balun. Detailed mathematical analysis for this design is included in this paper. Groups of circuit simulation results are shown to verify the conclusions. A sample balun is fabricated in microstrip line type on the Teflon substrate, with low dielectric constant of 2.54. It has a dimension of 0.189λg × 0.066λg with amplitude imbalance of 0.1 dB and phase imbalance of 179.09° ± 0.14°. The simulation and experiment results are in good agreement.

This paper presents a compact planar rectenna with high conversion efficiency in the ISM band. The proposed rectenna is developed by the decomposing of a planar rectenna topology into two functional parts and then recombining the two parts into a new topology to make the rectenna size reduction. The operation mechanism of the antenna and rectifying circuit in the proposed novel topology is explained and the design methodology is presented in detail. The proposed topology not only reduces the rectenna design cycle time but also leads to easy realization at the required frequency ranges with a very low cost. For validation, a 2.45 GHz rectenna system is designed and measured to show their microwave performances.

Free burning arcs, where the work piece acts as an anode, are frequently used for a number of applications. Our investigation is exclusively concerned with a simplified unified model of arcs and their electrodes under steady state conditions at atmospheric pressure. The model is used to make predictions of arc and electrode temperatures and arc voltage for a 200 A arc in argon. The computed temperatures along the axis between the cathode tip and the anode surface compare well the measured data.