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Piezoelectric energy harvesting systems are mainly used in low-power circuits and small sensors because of the low output power. To enhance the output power, we developed a new method that overcomes the weaknesses of piezoelectric ceramic products. In a single degree-of-freedom system, a piezoelectric cantilever composed of a piezoelectric ceramic and a substrate beam was analyzed by modeling the equivalent mechanical system. Based on this equivalent system model, a new method was designed to determine the total stiffness of module, which consists of the stiffnesses of the substrate beam and additional springs. Additional springs were connected to the free end of the substrate beam. The total stiffness of module was varied by connecting additional springs having different stiffness constants to the substrate beam. The results showed that a high total stiffness achieved using an additional spring led to a higher natural frequency of the beam. Therefore, the matching impedance was decreased, and the output power was increased. The advantage of the method is that the stiffness of the entire system can be varied using a detachable spring, without changing the piezoelectric ceramic material. Using this proposed system, the stiffness for a specific external energy can be optimized, and the efficiency of piezoelectric energy harvesting can be increased.

Due to increasing impervious surfaces resulting from urbanization and industrialization which are directly linked to urban inundation and non-point pollutants runoff, there is a need to manage them systematically. A management over urban impervious surfaces calls for pervious/impervious maps, which enable viewing the distribution of impervious surfaces. Nevertheless, relevant data are absent as now. In this respect, despite the diversity of proposed methods, pilot implementation and accuracy verification have never been conducted. Therefore, this study is aimed to produce a pilot pervious/impervious map based on previously proposed methods and to elucidate its pros and cons with a view to proposing a method for producing a GIS-based optimal pervious/impervious map. Following previously proposed methods, a pervious/impervious map of Bupyeong-gu, Incheon was produced. Then, a method of producing optimal pervious/impervious maps applicable to urban areas was proposed through the comparison of pros and cons of relevant spatial data. As a result, the map had been confirmed 99.2% of classification accuracy. Based on the present findings, future studies should establish a standardized method for producing. Also, this method should be used to produce pervious/impervious maps of other regions so that it can be applied to managing impervious surfaces in major urban areas nationwide.

In this letter, we have demonstrated low-subthreshold-slope (SS) asymmetric double-gate (DG) GaAs-on-insulator field-effect-transistors (FETs) on Si substrates via wafer bonding and epitaxial liftoff techniques. We found that DG FETs show lower SS than single-gate FETs all over the range of the drain current. A minimum value of SS was 68 mV/decade, which is very close to the theoretical limit. In addition, the achieved SS value was a record-low among the reported GaAs transistors so far.

3,4-Methylenedioxy-N-methamphetamine (MDMA, ecstasy) is an amphetamine derivative and is a popular type of drug that is abused due to its effects on the central nervous system (CNS), including alertness and euphoria. However, life-threatening (brain edema, heart failure, and coma) and fatal hyperthermia sometimes occur in some individuals taking MDMA. In a one-generation reproductive toxicity study, the potential toxicity of chronic exposure of MDMA was investigated on the reproductive capabilities of parental mice (F0), as well as the survival/development of their subsequent offspring (F1). Male and female C57BL/6 mice were administered orally MDMA at 0, 1.25, 5 or 20 mg/kg body weight (b.w.) throughout the study, beginning at the premating period, through mating, gestation, and lactation periods. MDMA did not produce any apparent clinical signs in F0 or F1 mice, and produced no significant changes in body weight, feed/water intake, or organ weights. In contrast, administration of MDMA produced external abnormalities in fetuses, stillbirth and labored delivery, and diminished viability and weaning indices in offspring, but these data were not significant. In addition, physical development of F1 mice was not markedly influenced by MDMA treatment. Nonetheless, serum biochemistry markers showed that levels of alkaline phosphatase (ALP), aspartate aminotransferase (AST), and blood urea nitrogen (BUN) were markedly elevated in a dose-dependent manner from 5 mg and higher MDMA/kg b.w., whereas levels of triglycerides (TG), potassium (K), and uric acid (UA) were reduced. Data suggest that MDMA may exert a weak reproductive and developmental toxicity, and the no-observed-adverse-effect level (NOAEL) of MDMA is estimated to be 1.25 mg/kg b.w./d.

Exposure and risk assessment was performed by evaluating levels of volatile organic compounds (VOC) benzene, toluene, ethylbenzene, and xylene (BTEX) in 207 consumer products. The products were categorized into 30 different items, consisting of products of different brands. Samples were analyzed for BTEX by headspace-gas chromatography/mass spectrometry (headspace-GC/MS) with limit of detection (LOD) of 1 ppm. BTEX were detected in 59 consumer products from 18 item types. Benzene was detected in whiteout (ranging from not detected [ND] to 3170 ppm), glue (1486 ppm), oil-based ballpoint pens (47 ppm), and permanent (marking) pens (2 ppm). Toluene was detected in a leather cleaning product (6071 ppm), glue (5078 ppm), whiteout (1130 ppm), self-adhesive wallpaper (15-1012 ppm), shoe polish (806 ppm), permanent pen (609 ppm), wig adhesive (372 ppm), tapes (2-360 ppm), oil-based ballpoint pen (201 ppm), duplex wallpaper (12-52 ppm), shoes (27 ppm), and air freshener (13 ppm). High levels of ethylbenzene were detected in permanent pen (ND-345,065 ppm), shoe polish (ND-277,928 ppm), leather cleaner (42,223 ppm), whiteout (ND-2,770 ppm), and glue (ND-792 ppm). Xylene was detected in permanent pen (ND-285,132 ppm), shoe polish (ND-87,298 ppm), leather cleaner (12,266 ppm), glue (ND-3,124 ppm), and whiteout (ND-1,400 ppm). Exposure assessment showed that the exposure to ethylbenzene from permanent pens ranged from 0 to 3.11 mg/kg/d (men) and 0 to 3.75 mg/kg/d (women), while for xylene, the exposure ranges were 0-2.57 mg/kg/d and 0-3.1 mg/kg/d in men and women, respectively. The exposure of women to benzene from whiteout ranged from 0 to 0.00059 mg/kg/d. Hazard index (HI), defined as a ratio of exposure to reference dose (RfD), for ethylbenzene was 31.1 (3.11 mg/kg/d/0.1 mg/kg/d) and for xylene (2.57 mg/kg/d/0.2 mg/kg/d) was 12.85, exceeding 1 for both compounds. Cancer risk for benzene was calculated to be 3.2 × 10(-5) based on (0.00059 mg/kg/d × 0.055 mg/kg-d(-1), cancer potency factor), assuming that 100% of detected levels in some products such as permanent pens and whiteouts were exposed in a worst-case scenario. These data suggest that exposure to VOC via some consumer products exceeded the safe limits and needs to be reduced.

Recently, TMDL has been implemented to estimate the amount of pollutant loads and to establish proper mitigation strategy to decrease the pollutant loads by the Ministry of Environment. To estimate the amount of pollutant loads with reasonable accuracy, securing landcover map with periodically updating is essential. However, in reality, due to the technical and financial difficulties, the landcover map has not been updated annually. Hence, this study mainly aims to suggest an effective GIS-based updating method in order to promote utilization of landcover map in the estimation of pollutant loads. Bupyeong-gu at the City of Incheon with the total area of was chosen for this study and spatial data including digital topographic maps, ortho aerial photo, and satellite images were collected and utilized. A total of 7,235 feature entities were newly produced through the updating process of five steps and it was revealed that the classification of landcover with the total area of was to be changed. The validity and feasibility of the suggested method were proved with the accuracy of 97.9% from the field verification. Further study needs to be made for devising more automated method to update landcover map to facilitate TMDL for individual local governments.

Flexible piezoelectric acoustic sensors have been developed to generate multiple sound signals with high sensitivity, shifting the paradigm of future voice technologies. Speech recognition based on advanced acoustic sensors and optimized machine learning software will play an innovative interface for artificial intelligence (AI) services. Collaboration and novel approaches between both smart sensors and speech algorithms should be attempted to realize a hyperconnected society, which can offer personalized services such as biometric authentication, AI secretaries, and home appliances. Here, representative developments in speech recognition are reviewed in terms of flexible piezoelectric materials, self-powered sensors, machine learning algorithms, and speaker recognition.

Hump characteristics of n-channel amorphous indium-gallium–zinc-oxide (a-InGaZnO) thin-film transistors (TFTs) after positive gate and drain bias stress (PGDBS) are investigated. With the increase of the PGDBS time, we observed not only a shift of the threshold voltage ( $V_{T}$ ) but also a generation of the hump in the transfer characteristics. The hump is caused by the localized trapping of electrons in the gate insulator over the gate-source overlap region by the high vertical field during the PGDBS ( $V_{\mathrm {GS}}=30$ , $V_{\mathbf {DS}}=30$ ; $V_{\mathrm {GD}}=V_{\mathrm {GS}}-V_{\mathrm {DS}}=0$ V). The TFT with a hump after PGDBS is modeled as a series connection of main and parasitic TFTs. The parasitic TFT for the electron trapping at the gate-source overlap region has a higher threshold voltage ( $V_{\mathrm {Tp}}$ ) and a shorter effective channel length ( $L_{\mathrm {chp}}\cong L_{\mathrm {ov}}$ ) compared with those ( $V_{\mathrm {Tm}}$ and $L_{\mathrm {ch}}$ ) of the main TFT.

The purpose of this study is to increase the durability of piezoelectric impact-based micro wind generator (PIMWG) in real application. Using new PIMWG design, numerical simulation, and experimental comparison analysis, we improved the durability of PIMWGs in real application. The experimental results show that the optimized PIMWG generated 2.4 mW (RMS value), and it did not crack within 40 h. In this study, we improved the durability of PIMWGs for real application.

In this study, we have investigated application of piezoelectricity to actual commercially operating high-speed Korean train. We recorded and analyzed the vibrations of commercial Korea Train eXpress (KTX). We experimented with different cantilever beam thicknesses (0.25 mm, 0.6 mm, and 1.0 mm) and different piezoelectric material dimensions (length × width × thickness, 10.0 mm × 10.0 mm × 0.5 mm, 20.0 mm × 10.0 mm × 0.5 mm, and 30.0 mm × 10.0 mm × 0.5 mm) on real data from recorded random frequencies and train vibration amplitudes. The addition of tip masses on the cantilever beam decreased the resonance frequency range when the vibrations were constant but not when they were random. The optimal condition was experimentally found, to involve decreasing the piezoelectric substrate beam thickness and increasing the piezoelectric substrate beam area rather than merely increasing the tip mass. The most effective method to improve the operational sensitivity was combination of decreasing the resonance frequen...

In order to investigate the relationships among strain, frequency, and output power, a novel piezoelectric energy harvesting module with controllable strain was designed. Conventional vibration module can control over strain through variation in tip mass, but it is also affected by vibration frequency. In the contrast, the designed controllable strain module allows more accurate strain control at various frequencies through adjustment of the displacement of the free end of the cantilever from 5 mm to 45 mm. Experimental results proved that both types of modules exhibit an increase in open circuit output voltage with strain. But output voltage was decreased when the piezoelectric ceramic broke at severe strain. In addition, it was confirmed that the proposed module design can keep the strain constant, which allows investigation into the relationship between frequency and output power. At constant strain, the matching impedance was found to be low at high frequency. Thus, as effect of strain to the piezoele...

This study investigated the effects of strain and crack formation on the performance of damaged piezoelectric materials as well as methods to restore damaged electrodes and reinforce the piezoelectric material. Specifically, this study investigated whether Ag paste (thickness: 0.1 mm) could restore electrical contact in damaged electrodes, and whether a coating of UV curable resin could provide reinforcement against crack formation. Experiments were conducted with a piezoelectric material on a steel cantilever substrate. The substrate was subjected to impact at various distances from the free end of the piezoelectric material to vary the applied strain. It was found that the output voltage increased with the strain (distance of impact from free end) until crack formation, which led to a large decrease in output. However, Ag paste could successfully restore electrical contact. Furthermore, before crack formation, coating with UV curable resin increased the maximum strain, and therefore, maximum electrical ...

This paper suggests the design in rectifier and array configuration for an impact-based piezoelectric energy harvesting (PEH) system, to investigate the charging efficiency. In the design of the rectifier, it is suggested that rectifying the signal from each piezoelectric module separately generates more electrical energy and charges a capacitor faster than using a single rectifier for all modules connected in series. In the structural design, the array was designed into two conditions: impacted simultaneously and impacted sequentially with a phase difference (30°, 60°, 90°, 120°, 150° and 180°). We show that when impacted sequentially with a phase difference, this allows faster charging rates of energy harvesting. Additionally, distribution of the torque required to transform the piezoelectric modules was found to be another advantage from this condition. These results could be used in the design of more-efficiently-charging impact-based PEH system.

We designed a piezoelectric energy harvesting system that can be controlled the resonance frequency to the frequency of external energy. A permanent magnet (10 mm × 10 mm × 5 mm) was affixed to the free end of cantilever, and a permanent magnet was affixed to each of the four faces of a rotor at 90° angles. The effect of the dimension of the permanent magnets (20 mm × 20 mm × 10 mm, 30 mm × 20 mm × 10 mm, and 40 mm × 20 mm × 10 mm) and the effect of the pole array (NNNN, SSSS, NSNS, and NNSS) were experimentally tested. The optimum conditions were selected by testing varied distances between the magnets at varied rpm. The experiments demonstrated that the maximum output voltage was generated for the largest magnet and the minimum distance. The most effective way to control the resonance frequency was to modify the pole arrays of magnets affixed to the rotor. Furthermore, the optimum conditions were determined at each distance by changing the pole array and rpm. Simulation software supports the experimenta...

Self-heating (SH) has emerged as an important performance, variability, and reliability concern for floating body transistors (FB-FET), namely, extremely-thin-silicon-on-insulator (ETSOI), SOI-FinFET, gate-all-round NW-FET (GAA-FETs), etc. The floating body topology offers electrostatic control, but restricts heat outflow: apparently an intrinsic trade-off. In this paper, we trace the trajectory of heat flow in a broad range of transistors to show that the trade-off is not fundamental, and self-heating can be suppressed by novel device designs that ease thermal bottlenecks. Towards this goal, we (i) characterize SH in various FB-FETs with different channel materials (Si, Ge, InGaAs) by submicron thermo-reflectance imaging; (ii) identify universal features and common thermal bottlenecks across various transistor technologies, (iii) offer novel, technology-aware device design to ease the bottlenecks and reduce self-heating, and (iv) experimentally demonstrate the effectiveness of these strategies in suppressing self-heating. We conclude that thermal aware transistor design can suppress self-heating without compromising performance and electrostatic control of the transistor.

Defect-less semiconductor-on-insulator (-OI) by a cost-effective and low temperature process is strongly needed for monolithic 3D (M3D) integration. Toward this, in this paper, we present a cost-effective fabrication of the InGaAs-OI structure featuring the direct wafer bonding (DWB) and the epitaxial lift-off (ELO) techniques as well as the re-use of the InP donor wafer. We systematically investigated the effects of the pre-patterning of the III-V layer before DWB, surface reforming (hydrophilic), and electro-chemical etching to speed up the ELO process for a fast and high-throughput process, which is essential for cost reduction. We also demonstrated the re-usability of the InP donor wafer. Finally, as a result of the high film quality of the InGaAs channel combined with DWB and ELO, fabricated InGaAs-OI MOSFETs show a record-high effective mobility of ∼2800 cm2/Vs among surface channel Ino.53Gao.47As MOSFETs reported so far.

Many researches with regard to piezoelectric energy harvesting from pressure exerted by passing cars have been conducted. In this paper, an impact-based road energy harvester as buried-type is developed with the method that the piezoelectric device is deformed directly by the pressure due to passing cars. Based on this, the developed road energy harvester is made to the size of 30 × 30 × 9 cm3. The performance of this new road energy harvester is measured with UTM (Universal Testing Machine) and MMLS3 (Third-scale Model Mobile Load Simulator) which can apply loads similar to the actual traffic loads to the harvester in lab-scale. Finally, the buried harvester is experimented with APT (Accelerated Pavement Testing).

Thin body III-V-on-insulator (III-V-OI) structure is a promising device structure for future node transistors in CMOS technology. Typically, a direct wafer bonding (DWB) is used to fabricate III-V-OI on a Si substrate [1–3]. Donor wafers were etched out [1, 2] or separated by hydrogen implantation [3]. However, the former one is extremely costly and the latter one can induce the residual defects in the channel layer. Therefore, a cost-effective and non-destructive technology to fabricate III-V-OI becomes more important. On the other hand, an epitaxial lift-off (ELO), which splits donor wafer and device active layer by selective etching of sacrificial layer located between the two, is quite promising to meet the two requirements of low cost and defect issue [5]. However, conventional ELO needs a long processing time to etch thin sacrificial layer across the whole wafer as shown in Fig. 1. In this work, we developed high-speed ELO techniques via pre-patterning and surface hydrophilization and fabricated conceptual devices of GaAs-OI transistors.

In the manufacture of plastic containers, various materials such as additives (for example, plasticizers, stabilizers, antioxidants), polymers (for example, polystyrene [PS], polycarbonate [PC], polyvinyl chloride [PVC]) are widely used. Endocrine disrupting chemicals [EDCs] can migrate as residual monomers (for example, styrene for PS or bisphenol A [BPA] for PC) presented in polymers, as additives (for example, phthalates for PVC) used in polymer manufacturing, and/or as contaminants from the polymers depending on physicochemical conditions such as temperature, UV light, pH, microwave, and mechanical stress. Some phthalates (for example, DEHP, DBP), styrene, or bisphenol have been suspected to have endocrine disrupting effects, but human toxicological effects of these compounds are very controversial. For these reasons, a comprehensive review on toxicological and risk assessment studies for these chemicals (phthalates, BPA, and styrene) was carried out to evaluate their safety in humans. On the basis of exposure estimates for the these chemicals and reference doses (RfDs), we calculated hazard index (HI = chronic daily intake/tolerable daily intake [TDI] or RfD). A HI of less than 1 suggests an exposure lower than the safety limit of the chemicals. We showed that the HI values of these chemicals were lower then 1, but there are one or several exceptions for di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), di-isodecyl phthalate (DIDP), and di-n-octyl phthalate (DnOP; for example, exposure via infant formula, packaged lunch, total exposure), where estimated their HI values are higher than 1, which suggests an exposure higher than the safety limits of the chemicals. However, the HI of BPA was 0.001–0.26 (3.57–1000 times lower than its safety limit), and the HI for styrene was 0.276 (3.62 times lower than its safety limit). In this article, we focused on recent issues concerning the endocrine-disrupting chemicals (EDCs) derived from plastic food containers or packaging. This review suggests that the use of plastic food containers might not exceed human safe limits n general with respect to endocrine disruptors aside from the exceptions of the phthalates mentioned earlier.

This study was designed to investigate the molecular mechanism underlying the chemopreventive effects of methionine on benzo[a]pyrene (B[a]P)–DNA adducts formation in HepG2 cells. Methionine significantly inhibited B[a]P–DNA adduct formation in HepG2 cells. Methionine significantly decreased the cellular uptake of [3H] B[a]P, but increased the cellular discharge of [3H] B[a]P from HepG2 cells into the media. B[a]P significantly lowered total cellular glutathione (GSH) level, but co-cultured with B[a]P and methionine, gradually attenuated intracellular GSH levels in a concentration-dependent manner, which was markedly higher at 20–500 μM methionine. The cellular proteins of treated cells were resolved by 2D-polyacrylamide gel electrophoresis. Proteomic profiles showed that phase II enzymes such as glutathione S-transferase (GST) omega-1, GSTM3, glyoxalase I (GLO1) and superoxide dismutase (SOD) were down-regulated by B[a]P treatment, whereas cathepsin B (CTSB), Rho GDP-dissociation inhibitor alpha (Rho-GDP-DIA), histamine N-methyltransferase (HNMT), spermidine synthase (SRM) and arginase-1 (ARG1) were up-regulated by B[a]P. B[a]P and methionine treatments, GST omega-1, GSTM3, GLO1 and SOD were significantly enhanced compared to B[a]P alone. Similarly, methionine was effective in diminishing the B[a]P-induced up-regulation of CTSB, Rho-GDP-DIA, HNMT, SRM and ARG1. Our data suggests that methionine might exert a chemoprotective effect on B[a]P–DNA adduct formation by attenuating intracellular GSH levels, blocking the uptake of B[a]P into cells, or by altering expression of proteins involved in DNA adduct formation.

Acute nephrotoxicities of melamine (MEL), cyanuric acid (CA), and a mixture of both melamine and cyanuric acid (MC) were comparatively investigated in male Sprague-Dawley rats at 5 doses each with 10-fold dose interval as follows: MEL at 0.0315, 0.315, 3.15, 31.5, and 315 mg/kg; CA at 0.025, 0.25, 2.5, 25, and 250 mg/kg, and MC: [1×: (0.0315 + 0.025), 10×: (0.315 + 0.25), 100×: (3.15 + 2.5), 1000×: (31.5 + 25), and (315 + 250) mg/kg]. No marked adverse effects in renal function were observed in animals treated with MEL alone or CA alone, but evidence related to nephrotoxicity was noted in rats administered MC. Renal calculi and increased kidney weights were found in rats 7 d after daily oral administration of MC. Blood urea nitrogen (BUN) and creatinine were significantly elevated in the high dose MC groups at 100× or 1000×. In addition, elevated numbers of white blood cells (WBC), neutrophils, and lymphocytes in vivo and increased levels of prostaglandin E(2) (PGE(2)) in vitro were found in the MC group. Based on these data, the NOAEL (no-observed-adverse-effect level) for nephrotoxicity for MC was estimated to be 3.15 mg/kg body weight (bw)/d (MEL) plus 2.5 mg/kg bw/d (CA). If a safety factor of 1000 or more were applied to NOAEL, tolerable daily intake (TDI) would be 0.00315 and 0.0025 mg/kg/d or less for MEL and CA, respectively, which is far below the TDI of 0.2 mg/kg/d set by World Health Organization (WHO). In addition, in vitro cytotoxicity assays showed that the ACHN human renal adenocarcinoma cell line was more sensitive to MEL, CA, and MC than the MDCK canine kidney epithelial cell line. The 24-h half maximal inhibitory concentration (IC(50)) values for MEL (4792, 2792 μg/ml) were less than those of CA (9890, 6725 μg/ml, respectively) in MDCK and ACHN cell lines, suggesting that MEL may be more cytotoxic than CA. Furthermore, the 24-h IC(50) value for MC was found to be 208 μg/ml in ACHN cells. Data suggest that NOAELs based upon acute nephrotoxic parameters for MC were low, which might require further reassessment of the current TDI.

Gastropleural fistula is a rare complication of prior lung surgery, gastric ulcer, trauma and malignancy. A 62 year old female patient who had received surgical repair of a perforated gastric wall 10 years prior, underwent open pleural decortication. At 4 days after surgery, food residuums were noticed at the chest bottles. Hence, an emergency esophagogram was done. The esophagogram revealed a gastropleural fistula. The patient received a total gastrectomy, intra-abdominal diaphragmatic repair and massive thoracic saline irrigation through a previous thoracic wound. The patient was discharged 11 days after surgery without other morbidity.