High quality Mn-doped (Na,K)NbO3 nanofibers for flexible piezoelectric nanogenerators.

Kang, Han Byul,Chang, Jiyoung,Koh, Kisik,Lin, Liwei,Cho, Yong Soo American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.13

<P>Enhanced piezoelectric and energy-harvesting characteristics of Mn-doped (Na0.5K0.5)NbO3 (NKN) nanofibers have been investigated with actual fabrication of potential flexible nanogenerators. The electrospinning process of nanofibers has been initially optimized with the proper level of chelating agent and annealing temperature. High quality nanofibers are successfully obtained only by means of a certain level of doped-Mn, which incorporates into the NKN perovskite structure and facilitates significant grain growth. A single-particle-stacked structure along the direction of fiber length becomes more evident with increasing Mn content. An XPS analysis confirms that Mn exists in multivalent states of Mn(2+)/Mn(3+). The effective piezoelectric coefficient of the nanofibers is found to be enhanced by 5 times with Mn-doping up to 3 mol % as characterized by piezoelectric force microscopy. The resultant flexible nanogenerators on PES films have exhibited 0.3 V output voltage and 50 nA output current under a bending strain.</P>

FEM Simulation and Test Verification of PD Ultrasonic Signal Propagation in a Power Transformer Model

Zan Wang,Chaofei Gao,Liwei Zheng,Jikun Ren,Wei Wang,Yushuai Zhang,Shijie Han 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.1

Ultrasonic signals will be generated when partial discharge occurs in internal insulation faults in large oil immersed power transformers: because the ultrasonic signal has strong anti-interference ability and has no direct electromagnetic contact with the equipment, it is widely used in transformer fault detection and positioning. In this paper, the fi nite element method (FEM) is used to simulate the ultrasonic signal in a 35 kV power transformer. The infl uence of transformer case on ultrasonic signal propagation is considered, and the propagation law of the ultrasonic signal inside the transformer is obtained. Fabry–Pérot (F–P) fi bre acoustic sensors with a centre frequency of 28 kHz were fabricated. A partial discharge detection test was carried out in a 35 kV transformer winding model using the F–P sensors. The test results show that the ultrasonic waveform detected by the F–P sensors are in good agreement with the simulation results, and the propagation of the ultrasonic wave inside the transformer is verifi ed. It lays a foundation for detecting and locating PDs in power transformer by F–P acoustic sensors.

Dose dependency in the oral bioavailability of an organic cation model, tributylmethyl ammonium (TBuMA), in rats: Association with the saturation of efflux by the P-gp system on the apical membrane of the intestinal epithelium

Kim, Moon Kyoung,Han, Liwei,Choi, Min Koo,Han, Yong-Hae,Kim, Dae-Duk,Chung, Suk-Jae,Shim, Chang-Koo Wiley Subscription Services, Inc., A Wiley Company 2005 journal of pharmaceutical sciences Vol.94 No.12

<P>The oral bioavailability of tributylmethyl ammonium (TBuMA), an organic cation (OC), exhibited a dose-dependency (i.e., 17, 27, and 35% at doses of 0.4, 4, or 12 µmol/kg, respectively) in the rat. Relevant mechanisms were investigated in the present study by estimating the mucosal to serosal (m–s) and serosal to mucosal (s–m) transport of TBuMA across the rat ileum in an Ussing chamber experiment. The m–s permeability rapidly increased with TBuMA concentration in the mucosal side, and then becoming constant at high TBuMA concentrations. Various studies, including temperature- and potential-dependency and inhibition experiments, revealed that carrier-mediated transport mechanisms (most likely OCT1, OCT3, and P-gp) are involved in the s–m transport of TBuMA, and the saturation of the transport at higher concentrations is responsible for the concentration-dependency in the m–s permeability or dose-dependency of the bioavailability of TBuMA. A nonlinear regression of the m–s transport, based on the assumption of a mixed process of linear diffusion and saturable efflux, exhibited a clearance (CL<SUB>linear</SUB>) of 0.343 µL/min/cm<SUP>2</SUP> for the passive diffusion, and an apparent K<SUB>m</SUB> of 241 µM for the saturable process. The K<SUB>m</SUB> value is consistent with the concentration range in the intestine which is expected to be achieved after the oral dosing of TBuMA at a dose of 0.4 µmol/kg (i.e., 68∼185 µM). Interestingly, the m–s transport of TBuMA was increased by the presence of P-gp substrates or inhibitors in the mucosal side, but not by the mucosal presence of OCT substrates or inhibitors, suggesting that only efflux transport systems on the apical membrane (e.g., P-gp), but not those on the serosal membrane (e.g., OCT1 and OCT3), of the intestinal epithelial cells, are involved in the dose-dependency or concentration dependency. A similar relationship seems likely for drugs that are substrates of efflux transporters on the apical membrane of the intestinal epithelium. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:2644–2655, 2005</P>

Hierarchical porous ECM scaffolds incorporating GDF-5 fabricated by cryogenic 3D printing to promote articular cartilage regeneration

Wu Jiang,Fu Liwei,Yan Zineng,Yang Yu,Yin Han,Li Pinxue,Yuan Xun,Ding Zhengang,Kang Teng,Tian Zhuang,Liao Zhiyao,Tian Guangzhao,Ning Chao,Li Yuguo,Sui Xiang,Chen Mingxue,Liu Shuyun,Guo Quanyi 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00

In recent years, there has been significant research progress on in situ articular cartilage (AC) tissue engineering with endogenous stem cells, which uses biological materials or bioactive factors to improve the regeneration microenvironment and recruit more endogenous stem cells from the joint cavity to the defect area to promote cartilage regeneration.In this study, we used ECM alone as a bioink in low-temperature deposition manufacturing (LDM) 3D printing and then successfully fabricated a hierarchical porous ECM scaffold incorporating GDF-5.Comparative in vitro experiments showed that the 7% ECM scaffolds had the best biocompatibility. After the addition of GDF-5 protein, the ECM scaffolds significantly improved bone marrow mesenchymal stem cell (BMSC) migration and chondrogenic differentiation. Most importantly, the in vivo results showed that the ECM/GDF-5 scaffold significantly enhanced in situ cartilage repair.In conclusion, this study reports the construction of a new scaffold based on the concept of in situ regeneration, and we believe that our findings will provide a new treatment strategy for AC defect repair.

In Situ Magnetic Field-Assisted Low Temperature Atmospheric Growth of GaN Nanowires via the Vapor–Liquid–Solid Mechanism

Kim, Jun Sik,Mohanty, Bhaskar Chandra,Han, Chan Su,Han, Seung Jun,Ha, Gwang Heon,Lin, Liwei,Cho, Yong Soo American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.1

<P>We report the growth of GaN nanowires at a low temperature of 750 °C and at atmospheric pressure in a conventional chemical vapor deposition (CVD) setup via the vapor–liquid–solid mechanism with remarkable control of directionality and growth behavior by using an in situ magnetic field. Under typical growth conditions, without any magnetic field, the nanowires are severely twisted and kinked, and exhibit a high density of planar stacking defects. With increasing in situ magnetic field strength, the microstructural defects are found to decrease progressively, and quasi-aligned nanowires are produced. At an applied magnetic field strength of 0.80 T, near-vertical aligned straight and several micrometers long nanowires of average diameter of ∼40 nm with defect-free microstructure are routinely produced. Photoluminescence measurements show that the relative intensity of the defect-related peaks in the visible region with respect to the near-band-edge emission continuously decrease with increase in the applied in situ magnetic field strength, ascribable to the magnetic field-assisted significant structural improvement of the wires. It is found out that the degree of agglomerative Ni droplet on Si is critically influenced by the surface tension driven by the magnetic force, which in turn determines the eventual properties of the nanowires.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-1/am403085y/production/images/medium/am-2013-03085y_0007.gif'></P>

Testosterone-independent down-regulation of Oct2 in the kidney medulla from a uranyl nitrate-induced rat model of acute renal failure: Effects on distribution of a model organic cation, tetraethylammonium

Shim, Won-Sik,Park, Joo-Hyun,Ahn, Sun-Joo,Han, Liwei,Jin, Qing-Ri,Li, Hong,Choi, Min-Koo,Kim, Dae-Duk,Chung, Suk-Jae,Shim, Chang-Koo Wiley Subscription Services, Inc., A Wiley Company 2009 Journal of Pharmaceutical Sciences Vol.98 No.2

<P>Although acute renal failure (ARF) has been an area of extensive research in recent decades, our understanding of ARF is far from complete. Organic cations (OCs) are primarily excreted via vectorial transport by various renal organic cation transporters (OCTs). It is reasonable to assume that ARF may alter the expression profiles of these transporters. In a rat ARF model, induction of ARF by uranyl nitrate (UN) treatment significantly decreased the levels of Oct2 (slc22a2) mRNA and protein in the kidney medulla. mRNA expression of the other OCTs was not appreciably altered. The plasma level of testosterone, a well-known regulator of Oct2, was not changed, suggesting that the Oct2 down-regulation is testosterone-independent. The effect of reduced Oct2 expression on the distribution of a model OC, tetraethylammonium (TEA), in various rat tissues including kidney cortex and kidney medulla was investigated during steady state plasma TEA concentrations. The steady state tissue-to-plasma (T/P) TEA ratio was decreased in the kidney medulla (approximately 15-fold) during ARF. These results indicate that, in a rat model of ARF, reduced Oct2 expression in the kidney medulla results in decreased distribution of TEA to the kidney medulla, thereby reducing renal clearance of TEA in UN-ARF rats. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:739–747, 2009</P>

Decreased Secretory Transport of a Quarternary Ammonium, TBuMA, across LLC-PK1 Cells by the Anionic Kidney Extract

Won-Sik Shim,최민구,김인화,Tae-Sik Kwon,송임숙,Liwei Han,Dae-Duk Kim,정석재,심창구 대한약학회 2008 Archives of Pharmacal Research Vol.31 No.5

The effect of organic anionic (OA) fractions of various rat organ tissues on the apparent partition coefficients (APC) of quarternary ammoniums (QAs) between n-octanol and phosphate buffer (pH 7.4) and QAs transport across the LLC-PK1 cell monolayer was examined. The OA fraction was prepared by filtering the aqueous extract of each tissue through an ion-exchange cartridge (Bond Elut C18). In the presence of OA fractions of liver and kidney extracts, substantial increase in APC was observed for tributylmethylammonium (TBuMA, Mw 200) and berberine (Mw 335), but not for triethylmethylammonium (TEMA, Mw 116) and tetraethylammonium (TEA, Mw 130). Because only QAs with higher Mw than a threshold (i.e., > 200) are known to form lipophilic ion-pair complexes with certain organic anions (e.g., bile salts such as taurodeoxycholate), above results are consistent with the hypothesis that only larger Mw QAs form lipophilic ion-pair complexes with endogenous organic anionic components of the liver and kidney extracts. Considering the comparable effect between the liver and kidney extracts on the APC of TBuMA regardless of far less (1/5) content of bile salts in the kidney extract, OAs other than bile salts in the kidney appear to contribute to the formation of lipophilic ion-pair complexes. Most interestingly, the secretory (i.e., basolateral to apical direction) transport of TBuMA and berberine across the LLC-PK1 cell monolayer was decreased by the cis-presence of the kidney extract, while remained unchanged for the transport of TEMA and TEA. The kidney extract had no effect on the absorptive (i.e., apical to basolateral direction) transport and cellular (LLC-PK1) accumulation of all of these QAs. Regardless of underlying mechanisms, it is notable that OA components of liver and kidney extracts influence the APC and secretory transport of QAs with Mw >200.

EXPERIMENTAL INVESTIGATION OF IMPACTS OF INJECTION TIMING AND PRESSURE ON COMBUSTION AND PARTICULATE MATTER EMISSION IN A SPRAY-GUIDED GDI ENGINE

Miaomiao Zhang,Wei Hong,Fangxi Xie,Yan Su,Liwei Han,Bin Wu 한국자동차공학회 2018 International journal of automotive technology Vol.19 No.3

A detailed investigation of the impact of injection timing and injection pressure on combustion and particles of a spray-guided GDI engine was conducted, under different engine operating conditions. The results indicated that, more proportion of large particles were emitted when increasing engine load, and the peak of accumulation mode particles moved toward smaller size when rising engine speed. With retarding the injection timing, the in-cylinder pressure and heat release rate rose first and then dropped at 2000 rpm, but they continuously rose at lower or higher speed conditions. The total particles concentration curves at all cases showed a trend of U-shape, and the corresponding timing of the lowest particles concentration advanced as the engine speed or load increased. The minimum value of emitted particles first rose and then fell when increasing load at 2000 rpm conditions, and it continuously rose when increasing speed at 40 Nm conditions. Generally, injection pressure did no sensitively affect combustion process except that it showed a relatively strong impact at low load conditions. However, particulate matter could be effectively inhibited by elevating fuel pressure from 5.5 to 11.5 MPa at all cases. In detail, the total particles concentration continuously fell at low speed and mid speed-high load cases, but it showed a rose trend when further increase fuel injection pressure at mid speed-low load and high-speed conditions.

Decreased Secretory Transport of a Quarternary Ammonium, TBuMA, across LLC-PK1 Cells by the Anionic Kidney Extract

Shim, Won-Sik,Choi, Min-Koo,Kim, In-Wha,Kwon, Tae-Sik,Song, Im-Sook,Han, Liwei,Kim, Dae-Duk,Chung, Suk-Jae,Shim, Chang-Koo 대한약학회 2008 Archives of Pharmacal Research Vol.31 No.5

The effect of organic anionic (OA) fractions of various rat organ tissues on the apparent partition coefficients (APC) of quarternary ammoniums (QAs) between n-octanol and phosphate buffer (pH 7.4) and QAs transport across the LLC-PK1 cell monolayer was examined. The OA fraction was prepared by filtering the aqueous extract of each tissue through an ion-exchange cartridge (Bond Elut C18). In the presence of OA fractions of liver and kidney extracts, substantial increase in APC was observed for tributylmethylammonium (TBuMA, Mw 200) and berberine (Mw 335), but not for triethylmethylammonium (TEMA, Mw 116) and tetraethylammonium (TEA, Mw 130). Because only QAs with higher Mw than a threshold (i.e., > 200) are known to form lipophilic ion-pair complexes with certain organic anions (e.g., bile salts such as taurodeoxycholate), above results are consistent with the hypothesis that only larger Mw QAs form lipophilic ion-pair complexes with endogenous organic anionic components of the liver and kidney extracts. Considering the comparable effect between the liver and kidney extracts on the APC of TBuMA regardless of far less (1/5) content of bile salts in the kidney extract, OAs other than bile salts in the kidney appear to contribute to the formation of lipophilic ion-pair complexes. Most interestingly, the secretory (i.e., basolateral to apical direction) transport of TBuMA and berberine across the LLC-PK1 cell monolayer was decreased by the cis-presence of the kidney extract, while remained unchanged for the transport of TEMA and TEA. The kidney extract had no effect on the absorptive (i.e., apical to basolateral direction) transport and cellular (LLC-PK1) accumulation of all of these QAs. Regardless of underlying mechanisms,it is notable that OA components of liver and kidney extracts influence the APC and secretory transport of QAs with Mw >200.

Load Prediction Based on Optimization Ant Colony Algorithm

Li Wei,Tang Jingmin,Ma Han,Fan Min,Liu Simiao,Wang Jie 대한전기학회 2023 Vol.18 No.1

Short-term load in the power system is associated with huge computational consumption and low model utilization. Large input fl uctuation tends to increase the training error of the neural network prediction model and reduce its generalization ability. To cope with this problem, this study aimed to introduce a method of radial basis function neural network algorithm based on least squares support vector machine algorithm. Based on the electricity market in an area of Yunnan province, the short-term loads were forecasted with historical data. First, the ant colony algorithm was improved using the chaos theory. Second, the improved ant colony was used to search least squares support vector machine and output the optimal parameters of the model. Then, the optimized model was used to train the data samples, and the output regression machine was used to provide better structures and parameters for the radial basis function neural network. The fi ndings showed that compared with multiple prediction methods, the algorithm in this paper reduces the learning time and improves the fi tting degree of the algorithm on the basis of improving the prediction accuracy. It shows that the algorithm in this paper has great advantages and good application prospects.