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Biomass is a solid fuel that can be used instead of coal to address the issue of greenhouse gases. Currently, biomass is used directly in combustion or via co-combustion in coal-fired power plants. However, its use is limited due to calorific value and ash problems. In this study, wet torrefaction (WT) was carried out at various temperatures (160 °C, 180 °C, and 200 °C) and the properties of the product were evaluated. In comparison to dry torrefaction, the ash contained in biomass was extracted by an acidic solution (i.e., acetic acid) from the overreaction of the biomass. From examining the ash content of the treated WT, it was confirmed that K2O of basic ash was mainly extracted. In particular, in the case of K2O, since the main cause of combustion problems are issues such as fouling and slagging, the removed WT can be stably combusted in the boiler. Finally, the combustion and emission behaviors were evaluated by TGA-DTG and TGA-FTIR. As the fuel-N was decreased in the WT proess, the NOx in the emission gas after combustion was lower than that of raw miscanthus, and SO2 showed a similar value. As a result, it was confirmed that the WT sample is an advanced fuel in terms of fuel upgrading, alkali minerals, and NOx emission compared to raw miscanthus.

Developing effective, economical, and environmentally sound approaches for sewage sludge management remains an important global issue. In this paper, we propose a bioethanol-lignin (nonfood biomass)-based sewage sludge upgrading process for enhancing the heating value and reducing air pollutants of hybrid sewage sludge fuel (HSF) for the effective management of sewage sludge. Sewage sludge paste with the lignin-CaO solution implies drying at 105 °C accompanied by torrefaction at 250 °C. During torrefaction, moisture and partly volatile matter begin to evaporate, and are almost vaporized out to the surface. In this study, the proposed process enhances the net caloric value (NCV) to 37%. The lignin-embedded HSF shows a two-in-one combustion peak regardless of the mixing ratio, resulting in a 70% reduction of unburned carbon (UBC) emissions, which is one of the particular matter (PM) sources of combustion flue gas. Other air pollutants, such as CO, hydrocarbon, NOx, and SOx, were also reduced by the proposed process. In particular, SOx emission remained at ~1 ppm (average value) regardless of the sulfur content of the fuel.

Obstructive sleep apnea (OSA) is the most prevalent type of sleep apnea, and oral appliance may be one of the options for treatment of OSA. But, the problems with the oral appliance are high cost, possible low compliance, and complications such as temporomandibular disorder. In this article, we described a severe OSA case that was successfully improved by using temporary mandible advancement device, which was designed for therapeutic effect of mandible advancement with low cost and simplified fabrication procedure.

This paper presents a generalized expression of the modified load networks (MLNs) for Doherty power amplifiers (DPAs) with an extended output power back-off (OBO) range. Based on the analysis using this new expression, a new circuit structure generally applicable to any combination of the multiple MLNs is proposed. The load network has a simple structure including impedance matching circuits and offset lines for the carrier and peaking amplifiers. A design procedure for the proposed load network is presented. A DPA using any optimized combination of the multiple MLNs can be easily designed using the proposed load network. For verification, a GaN-HEMT symmetrical DPA based on a combination of the virtual open-stub (VOS) and out-phased current combining (OCC) methods was designed and implemented for the frequency band of 3.4 - 3.7 GHz. The reversed uneven power splitting method is adopted in the design for higher power gain. Using the 5G New Radio (NR) signal with a peak-to average power ratio (PAPR) of 7.9 dB and a signal bandwidth of 100 MHz, the proposed DPA exhibited DE of 55.3 - 60.9% with a power gain of 11.9 - 12.7 dB at an average output power of 33.7 dBm. An adjacent channel leakage power ratio (ACLR) of −42.6 - −44.8 dBc was achieved at the average power level by using a digital predistortion (DPD) technique across the band.

The microwave power transfer (MPT) system requires a massive Tx array for building a focused radio wave to efficiently transfer power to the Rx. Beamforming IC is one of the core elements for the massive Tx array. This paper presents a 5.8 GHz 4-channel beamforming Tx IC based on a CMOS process. The beamforming Tx IC includes a resistive 4-way power splitter, 5-bit differential phase shifters, drive amplifiers, and power amplifiers. Each channel is designed to transmit a power of no less than 100 mW. To verify the Tx IC, a 16-channel beamforming Tx module based on 16 patch antennas and four 4-channel Tx ICs was designed. The module also includes a PLL, a frequency doubler, and a 4-way Wilkinson power divider. MPT experiments to verify the beamforming IC and module were carried out using the implemented 16-channel Tx module at 5.8 GHz. Received power levels of 13 dBm and 2.1 dBm were achieved at distances of 0.4 and 1.4 m, respectively. The results are almost similar to the values acquired from the calculation using the Friis equation.

This article presents a hybrid envelope tracking (ET) supply modulator (SM) integrated circuit (IC) based on a Class-AB linear amplifier (LA) with supply voltage and temperature insensitive quiescent current. For ET mode, to further improve efficiency of the ET-SM, the supply voltage of the LA can be modulated using an additional dc-dc converter according to the average output power. An adaptive quiescent current controller for the LA of the ET-SM is proposed to maintain its quiescent current for large variations in voltage and temperature. Due to the insensitive quiescent current over the voltage of the LA, the supply voltage to the LA can be controlled in a wider range for the average output power, which allows the power amplifier (PA) in the ET mode to have a greater improvement in efficiency. The size of the output stage of the LA is also discretely reconfigured using 3-bit digital control to reduce the power consumption of the LA according to the output power level. For the low average output power levels, the operation mode is changed to APT mode, which supplies a reduced dc voltage according to the reduced average output power to the PA. The proposed SM, dc/dc converter and PA ICs were designed and implemented using CMOS processes for 0.9 GHz LTE application. Using an LTE uplink signal with a signal bandwidth of 5 MHz and a PAPR of 7.5 dB, a PAE of 38.4% at an average output power of 24.0 dBm was obtained under an ACLR of −30.0 dBc for the overall ET-PA. At a 6 dB back-off for the average output power, a PAE of 24.6% was achieved using the ET mode. A maximum PAE improvement of 8.0% point using the proposed SM IC was achieved compared to the stand-alone PA.

Due to its greater physical–chemical stability, ceramic nanofiltration (NF) membranes were used in a number of industrial applications. In this study, a novel NF membrane was prepared by co-depositing a titanium dioxide (TiO2) and graphene oxide (GO) composite layer directly onto a porous α-Al2O3 hollow fiber (HF) support. An 8 µm-thick TiO2/GO layer was deposited to the surface of α-Al2O3 HF support by vacuum deposition method to produce advanced TiO2/GO-Al2O3 HF NF membrane. Scanning electron microscope (SEM) micrographs, energy dispersive spectrometer (EDS), X-ray powder diffraction (XRD), thermogravimetric analyzer (TGA), porosity, 3-point bending strength, zeta potential analysis, and hydrophilic properties by water contact angle are used for TiO2/GO-Al2O3 HF NF membrane characterization. The results show that the developed membrane’s MWCO ranged from 600 to 800 Da. The water flux, rejection of lignin, and sodium ions were 5.6 L/m2 h·bar, ~92.1%, and ~5.5%, respectively. In a five-day NF process, the TiO2/GO-Al2O3 HF NF membrane exhibits good lignin permeation stability of about 14.5 L/m2 h.

In this paper we report on the improvement of performance by minimizing scallop size through deep reactive-ion etching (DRIE) of rotors in micro-wind turbines based on micro-electro-mechanical systems (MEMS) technology. The surface profile of an MEMS rotor can be controlled by modifying the scallop size of the DRIE surface through changing the process recipe. The fabrication of a planar disk-type MEMS rotor through the MEMS fabrication process was carried out, and for the comparison of the improvements in the performance of each rotor, RPM testing and open circuit output voltage experiments of stators and permanent magnets were performed. We found that the smooth etching profile with a minimized scallop size formed using DRIE results in improved rotation properties in MEMS-based wind turbine rotors.

In the above article [1], the received power in dc referred from the reference [2], which is the reference [35] in the original article [1], was incorrectly introduced. It was written as 0.2 W (dc) in the introduction of [1], but the correct received power in the specified condition is 2 W (dc).

Background: Botulinum toxin (BoNT) is widely used to treat masseter muscle hypertrophy. Changes in the muscle thickness have been found in many studies, but there has been no report on changes in the thickness from the skin surface to the masseter muscle.Objectives: We aimed to use ultrasonography to measure not only changes in the muscle thickness but also changes in subcutaneous thickness.Methods: This study enrolled 20 volunteer patients: 10 were assigned to an experimental group (injected with each side 25 U of botulinum toxin into both masseter muscles) and 10 to a control group (injected with normal saline). The thicknesses were measured before the injection and at 4, 8, and 12 weeks after the injection both at rest and during maximum muscle contraction.Results: The subcutaneous thickness did not differ significantly over time either at rest (P = 0.063) or during maximal contraction (P = 0.392), or between the experimental and control groups at rest (P = 0.392) or during maximum contraction (P = 0.259). The muscle thickness in the experimental group differed significantly over time.Conclusions: Botulinum toxin injection only changes the muscle thickness and does not affect the subcutaneous thickness from the skin surface to the masseter muscle. [ABSTRACT FROM AUTHOR]

Gelatin is extensively used as a biomaterial for diverse pharmaceutical and medical applications due to its excellent biocompatibility and biodegradability. Here we present bio-inspired tissue-adhesive gelatin hydrogels prepared by the enzyme-mediated synthesis of L-3,4-dihydroxyphenylalanine (L-DOPA) and Fe3+ ion crosslinking. Gelatin of human origin was obtained through two major steps, extracellular matrix (ECM) extraction from human adipose tissue and gelatin isolation from the ECM. The tyrosine residues in human gelatin were converted into DOPA by enzymatic reaction with tyrosinase. Upon the addition of Fe3+ ions, the DOPA-modified gelatin formed a sticky hydrogel within seconds through complexation between the DOPA molecules and Fe3+ ions. The final DOPA-modified, Fe3+ ion-crosslinked gelatin hydrogels retained their hydrogel stability well at body temperature in an aqueous environment and exhibited appropriate mechanical properties. The hemostatic ability of the DOPA-Fe3+ gelatin hydrogels was explored using a hemorrhaging liver rat model. Shortly after the injection of the DOPA-Fe3+ gelatin hydrogel, the bleeding was arrested in the hemorrhaging site of the liver. Overall results suggest that the DOPA-Fe3+ gelatin hydrogel, with its good elastic and hemostatic properties, is a promising tissue adhesive for use in a wide variety of surgical operations. [ABSTRACT FROM AUTHOR]

This paper presents a Class-E/F3 switching power amplifier (SPA) with reduced second harmonic leakage using parallel resonant circuit in series for the second harmonics. The proposed Class-E/F3 SPA has a structure utilizing a series resonant circuit in shunt for the third harmonic, designed to function as a shunt capacitor for the fundamental, and an additional parallel resonant circuit for the second harmonic, designed to operate as a series inductor for the fundamental. Using the proposed scheme, a Class-E/F3 SPA was designed and implemented for 6.78 MHz, and was evaluated with various supply voltages. It exhibited output power levels ranging from 10.26 to 59.98 W (40.11 to 47.78 dBm) with supply voltages ranging from 10 to 24 V. The efficiency was maintained at over 89.25%. Additionally, it demonstrated very low second and third harmonic distortion levels, each not exceeding −49.98 dBc, while the total harmonic distortion (THD) ranged from 1.54% to 2.15%.

The load networks of advanced Doherty power amplifiers (DPAs) have traditionally been designed according to the ABCD parameters. In this paper, design conditions as an impedance transformation condition and an effective electrical length were used to design the output matching networks (OMNs) for the carrier and peaking amplifiers of the virtual-stub DPAs (VS-DPAs). An optimization method for the effective electrical length was proposed that was specifically constructed for the load impedances of the carrier amplifier at the low power level to have broadband characteristics through the load-pull simulation. Using the optimized design conditions for broadband design, compact OMNs for the carrier and peaking amplifiers were designed using quasi-lumped components. Moreover, an asymmetric structure with an increased power capacity of the peaking amplifier for the VS-DPA was proposed to compensate for a relatively low peak fundamental current of the peaking amplifier due to its deep class-C operation as well as the extended output back-off (OBO) range of the VS-DPA. To verify the proposed load network, a broadband asymmetric VS-DPA for the 3.3 - 4.2 GHz band was designed and implemented using GaN HEMTs with power capacities of 6 and 10 W. Using a 5G new radio (5G NR) signal with a signal bandwidth of 100 MHz and a peak-to-average power ratio (PAPR) of 7.8 dB, power gain of 8.2 - 9.1 dB, DE of 46.0 - 57.0%, ACLR of better than −45 dBc after DPD linearization at an average power of 35.0 dBm were achieved at the broad frequency range of 3.3 - 4.2 GHz.

This paper presents a new compact load network for Doherty power amplifiers (DPAs) with only two matching networks, such as an output matching network of the carrier amplifier, and the post-matching network (PMN), even in the presence of parasitic circuits of the packaged transistor. The load network of the carrier amplifier can be configured using a simple L-section matching structure for the complex load impedance. No matching network is required between the peaking amplifier and the current combining junction. As a result, the proposed load network can have a very compact structure with only a short transmission line, and a shunt element for the carrier amplifier, in addition to the PMN. To verify the proposed circuit, a DPA based on two packaged GaN-HEMTs was designed and implemented to have a peak output power of more than 43 dBm for the 3.5-4.0 GHz band. By the measurement results using a 5G NR signal with a peak-to-average power ratio (PAPR) of 7.9 dB and a signal bandwidth of 100 MHz, a power gain of more than 10.5 dB, and a drain efficiency (DE) of 49.5-55.4% at an average power of 36.5 dBm in the frequency band was exhibited. After applying digital pre-distortion (DPD), an adjacent channel leakage power ratio (ACLR) of -51.0 dBc was achieved.

A new load modulation combiner (LMC) having the capability of back-off control is proposed for a Doherty power amplifier (DPA). The proposed LMC consists of two transmission lines tied at the combining node, and a shunt element across the other ends of the transmission lines. The shunt element of the LMC becomes virtually open-circuited at the peak power level and allows the carrier amplifier to have an arbitrary load impedance at the low power level. The operating principle and circuit structure of the DPA based on the proposed LMC are presented in detail. The proposed DPA was implemented using GaN-HEMT for the 3.5 - 4.0 GHz band. Using a 5G NR signal with a peak-to-average power ratio (PAPR) of 7.9 dB and signal bandwidth of 100 MHz, the implemented DPA showed drain efficiency (DE) of 49.6 - 54.4% and power gain of 11.1 - 13.0 dB at an average output power of 34.5 dBm. An adjacent channel leakage power ratio (ACLR) was obtained as −50.4 - −45.0 dBc at the average power level with a digital pre-distortion (DPD) technique.

In this paper, a simple and novel method of expanding the operating range of inclinations and of increasing the sensitivity of convection-based tilt sensors is shown. Even though the previously reported convective tilt sensors fabricated in our laboratory have their own merits in performing dual-axes inclination measurement with excellent linearity and symmetric sensitivity, they showed limited operating range from −90 to 90° because of their structural limitations. However, this proposed tilt sensor has overcome the structural limitations and it detects inclinations wider than the ±90° range on two axes with symmetric sensitivity. The improved performance could be achieved by removing the membrane at the bottom of the microheater and temperature sensors for unlimited gas movement in the cavity when it tilted over the ±90° range. The operating range of the newly proposed tilt sensor expands to ±180° compared with that of the previously reported convective tilt sensor. Moreover, various designs of cavities and cap substrates were adopted to improve the sensitivity of the proposed convective tilt sensor. The mass production of the proposed convection-based tilt sensor is still feasible because it can be fabricated at a low cost because of its simple fabrication step. Its sensitivity is high and it has a very wide-angle detection range. [ABSTRACT FROM AUTHOR]

The load network of the carrier amplifier for the conventional Doherty power amplifier (DPA) consists of an impedance matching circuit, an offset line, and a $\lambda $ /4 transmission line (TL), so that the overall electrical length of the network can easily exceed the minimum value of 90°. Then for appropriate impedance modulation, it should be 270° with an additional 180°. This excessive electrical length of the load matching network limits the bandwidth at either the low-power or peak-power level. In this paper, a compact quasi-lumped $\lambda $ /4 impedance transformer (ITF) having simultaneous multiple functions of impedance matching and load impedance modulation with a controlled electrical length of 90° is presented. The proposed load network includes the internal components of the transistor, the simplest high-pass network using a shunt inductor, and a low-pass L-C network. Using the optimized value of the shunt inductor, the electrical length of the load network can be adjusted to 90°, while other components are accordingly changed to match the optimum load impedance. To verify the proposed load network, a DPA was designed and implemented using 10 W GaN-HEMTs for both carrier and peaking amplifiers. Using a 5G New Radio (NR) signal with signal bandwidth of 100 MHz and peak-to-average power ratio (PAPR) of 7.8 dB, a drain efficiency (DE) of 47 - 54.2%, and adjacent channel leakage power ratio (ACLR) of −27.9 - −23 dBc were achieved at an average output power level of 35.8 - 36.3 dBm for the frequency band of 3.4 - 3.8 GHz.