Hydrothermally synthesized Na₂Ti₃O₇ nanotube–V₂O₅ heterostructures with improved visible photocatalytic degradation and hydrogen evolution - Its photocorrosion suppression

Vattikuti, S.V. Prabhakar,Reddy, Police Anil Kumar,NagaJyothi, P.C.,Shim, Jaesool,Byon, Chan Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.740 No.-

<P><B>Abstract</B></P> <P>There is still a need to prepare heterostructure photocatalysts with high activity and recyclability but without using precious metals to reduce the cost of photocatalysts. Thus, a facile and simple method for the synthesis of a Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst via hydrothermal synthesis is reported herein. The chemical composition, morphology, and structural features of the photocatalyst were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), N<SUB>2</SUB> adsorption–desorption specific surface area analysis (BET), and diffuse reflectance absorption (DRS) methods. It was observed that the specific surface area of the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst increased with the incorporation of V<SUB>2</SUB>O<SUB>5</SUB>. The Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst was then used for the removal of rhodamine B (RhB) under simulated solar light irradiation. The Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst revealed excellent photocatalytic activity and photodegradation kinetics as compared to pristine Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotubes and V<SUB>2</SUB>O<SUB>5</SUB> photocatalysts. Furthermore, both the photoactivity and long-term stability of the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst were superior to those of the pristine Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotubes and V<SUB>2</SUB>O<SUB>5</SUB> photocatalysts. The excellent photocatalytic performance of the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst can be ascribed to its high specific surface area (283.71 m<SUP>2</SUP>g<SUP>−1</SUP>), mesoporous structure, highly dispersed V<SUB>2</SUB>O<SUB>5</SUB> nanoparticles, and hindrance of electron–hole pair recombination of Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> due to the V<SUB>2</SUB>O<SUB>5</SUB> incorporation, which is proven by the photoelectrochemical results, including photocurrent and electron impendence spectroscopy results. In addition, during the study of photocatalytic hydrogen evolution, the hydrogen yield of the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB>/V<SUB>2</SUB>O<SUB>5</SUB> nanocomposite was 1.83 times that of pristine Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB>, which also exhibited excellent photocatalytic activity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Heterojunction of Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs/V<SUB>2</SUB>O<SUB>5</SUB> NPs was developed via hydrothermal method. </LI> <LI> Visible photocatalytic RhB degradation studies were performed over Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs/V<SUB>2</SUB>O<SUB>5</SUB> NPs. </LI> <LI> Improved degradation efficiency was observed over Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs/V<SUB>2</SUB>O<SUB>5</SUB> NPs when compared to pristine Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs. </LI> <LI> V<SUB>2</SUB>O<SUB>5</SUB> NPs were successfully utilized as cocatalyst for pollutant degradation. </LI> <LI> Charge recombination was diminished in the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs by the addition of V<SUB>2</SUB>O<SUB>5</SUB> NPs. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Effect of Buffalo Follicular Fluid Alone and in Combination with PMSG and M199 on in vitro Buffalo Oocyte Maturation

Gupta, P.S.P.,Nandi, S.,Ravindranatha, B.M.,Sarma, P.V. 아세아태평양축산학회 2001 Animal Bioscience Vol.14 No.5

The effect of replacement of in vitro maturation medium completely with the buffalo follicular fluid (buFF) on in vitro oocyte maturation of buffalo oocytes was studied. 5 to 8 buffalo cumulus oocyte complexes were cultured in a single drop with each of the eight media studied i.e., M199+steer serum (10% v/v), M199+steer serum (10% v/v)+PMSG, M199+buFF (10% v/v), M199+buFF (10% v/v)+PMSG, M199+buFF (50% v/v), M199+buFF (50% v/v)+ PMSG, buFF (100%) and buFF+PMSG at $39^{\circ}C$ and 5% $CO_2$ in air for 24 h. Supplementation of M199 with Steer serum alone resulted in IVM rate of 35% only. When the above medium was supplemented with PMSG, the maturation rate rallied to 82%. Significant increase in the maturation rates were observed when M199 was supplemented with increasing levels of buFF. A further increase in the maturation rate was also obtained when PMSG was incorporated into the medium of M199 supplemented with buFF. The rate of maturation was to the tune of 91% when oocytes were matured in buFF alone which was increased non significantly on the addition of PMSG. Highest maturation rate (97%) obtained with M199+buFF (50%v/v)+PMSG did not differ significantly from that obtained by either M199+buFF (10%v/v)+PMSG or buFF+PMSG. It is suggested that buFF alone without any supplementation can form the effective in vitro maturation medium for buffalo oocytes.

Enhancing Performance of Dual-Gate FinFET with High-K Gate Dielectric Materials in 5 nm Technology: A Simulation Study

M. V. Ganeswara Rao,N. Ramanjaneyulu,Balamurali Pydi,Umamaheshwar Soma,K. Rajesh Babu,Satti Harichandra Prasad 한국전기전자재료학회 2023 Transactions on Electrical and Electronic Material Vol.24 No.6

The rapid advancement in nanoscale devices demands innovative gate dielectric materials to replace traditional Silicon dioxide. This paper investigates the electrical behavior and performance of a dual-gate FinFET employing different high-K gate dielectric materials (Silicon dioxide, Hafnium oxide, Titanium oxide) through ATLAS 2D simulation in 5 nm technology. We analyze how these high-K gate dielectric materials influence the device, focusing on performance enhancement. The study highlights various key performance parameters (ION, IOFF, gm, gds, RON, TF, EV, V IL, V IH, NML, NMH) and reveals a significant performance improvement with HfO2 dielectric material in the proposed Dual-Gate FinFET. Achieving impressive performance parameters ( ION : 21.59 mA, IOFF : 21 µA, Maximum net Electric field: 1221290 V/cm, g m(max) : 0.05187 S, gds(max) : 0.03462 S, RON(max) : 25.93 kΩ , TFmax: 5.02, G ainmax : 90.233, EVmax : 67.532 V, V IL : 0.21 V, V IH : 0.4 V, NML : 198 V, NMH : 600 V), this paper provides valuable insights for designing high-performance devices with HfO2 dielectric material.

Effect of crystal orientation of GaN/V₂O₅ core-shell nanowires on piezoelectric nanogenerators

Waseem, Aadil,Johar, Muhammad Ali,Hassan, Mostafa Afifi,Bagal, Indrajit V.,Ha, Jun-Seok,Lee, June Key,Ryu, Sang-Wan Elsevier 2019 Nano energy Vol.60 No.-

<P><B>Abstract</B></P> <P>GaN/V<SUB>2</SUB>O<SUB>5</SUB> core-shell nanowire (NW) piezoelectric generators of controlled crystallographic orientations were fabricated, and the device performance was characterized. Catalyst-assisted c- and m-axis GaN NWs were grown on a c-plane GaN thin film by varying the NH<SUB>3</SUB> flow rate and reactor pressure. The grown NWs were then utilized to fabricate the flexible piezoelectric nanogenerators (PNGs) to practically investigate the impact of the c- and m-axis GaN NWs on the piezoelectric response. The c-axis GaN NWs exhibited a higher piezoelectric output than m-axis GaN NWs. Furthermore, the GaN/V<SUB>2</SUB>O<SUB>5</SUB> core-shell structure was utilized in the NWs to suppress the internal carrier screening that degrades the piezoelectric output. The maximum output voltage (27 V) exhibited by core-shell c-axis NWs was thrice the voltage exhibited by pristine c-axis GaN NWs (9 V). A stability test was performed for one hour to verify the feasibility of using flexible PNGs for real applications. The high stability of PNGs was attributed to the flexibility and high crystallinity of the NWs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> C- & m-axis GaN NWs are grown by MOCVD for piezoelectric generators. </LI> <LI> The piezoelectric output for pristine c-axis NWs is twice the output of m-axis NWs. </LI> <LI> The piezoelectric output of the GaN/V<SUB>2</SUB>O<SUB>5</SUB> core-shell NWs is three times of pristine NWs. </LI> <LI> PNGs exhibited long-term stability due to excellent mechanical properties of NWs. </LI> <LI> GaN/V<SUB>2</SUB>O<SUB>5</SUB> heterojunction suppressed the junction current screening effect. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>GaN/V<SUB>2</SUB>O<SUB>5</SUB> core-shell nanowire (NW) piezoelectric generators of controlled crystallographic orientations are reported. Catalyst-assisted c- and m-axis GaN NWs grown by MOCVD are utilized to fabricate the flexible piezoelectric nanogenerators to investigate the impact of the c- and m-axis GaN NWs on the piezoelectric response. The c-axis GaN NWs exhibited the higher piezoelectric output than m-axis GaN NWs. The GaN/V<SUB>2</SUB>O<SUB>5</SUB> core-shell structure is utilized in the NWs which further enhanced the output voltage to 27 V and output current to 590 nA.</P> <P>[DISPLAY OMISSION]</P>

Effect of annealing temperature on the electrical and structural properties of V/p-GaN Schottky structures

Padma, R.,Nagaraju, G.,Rajagopal Reddy, V.,Choi, Chel-Jong Elsevier 2016 THIN SOLID FILMS - Vol.598 No.-

<P><B>Abstract</B></P> <P>The electrical and structural properties of V/p-GaN Schottky barrier diode (SBD) have been investigated as a function of annealing temperature. The Schottky barrier height (SBH) of the as-deposited contact is found to be 0.82eV (<I>I–V</I>) and 1.10eV (<I>C–V</I>). However, it is noted that the SBH increases for the contact annealed at 400°C and the values are 0.94eV (<I>I–V</I>) and 1.21eV (<I>C–V</I>). Further, with increasing annealing temperature up to 500°C, the SBH decreases to 0.92eV (<I>I–V</I>) and 1.19eV (<I>C–V</I>). Also, the rectification ratio of the V/p-GaN SBD is evaluated for as-deposited and annealed contacts. The electrical parameters of the V/p-GaN SBD are also discussed with Cheung's and Norde functions. It is noted that the interface state density decreases upon annealing at 400°C and then slightly increases after annealing at 500°C. Results reveal that the superior electrical characteristics are obtained for the contact annealed at 400°C. The electrical results are also correlated with the interfacial microstructure of the contacts. The AES and XRD results reveal that the formation of nitride phases at the interface may be the reason for the increase of SBH after annealing at 400°C. The formation of gallide phases at the interface may be reason for the decrease in the SBH.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Annealing effects on electrical and structural properties of V/p-GaN SBD are studied. </LI> <LI> Maximum barrier height is obtained on V/p-GaN SBD upon annealing at 400°C. </LI> <LI> Interface state density decreases with increasing annealing temperature up to 400°C. </LI> <LI> Electrical results are correlated with the interfacial microstructure of the contacts. </LI> <LI> Nitride interfacial phases are responsible for increase in BH after annealing at 400°C. </LI> </UL> </P>

Hydrothermal Synthesis of H2V3O8 Nanobelts from V2O5 Xerogels for Lithium Battery Applications

Sun-Il Mho,Ch.V. Reddy,Youna Kim,In-Hyeong Yeo,Su-Moon Park 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.6

Vanadium oxyhydroxide (H2V3O8) nanobelts were synthesized from V2O5 xerogels through a simple hydrothermal process in efforts to obtain nanomaterials for rechargeable Li batteries. Polymers with multidentate oxygen ligands, such as polyethylene glycol or polyethylene oxide, were shown to play a critical role in the formation of H2V3O8 nanobelts during the hydrothermal process. The specific capacity measured during the initial discharge process for the lithium battery with a cathode made of H2V3O8 nanobelts were 292 mAh/g, which stabilized at ca. 261 mAh/g corresponding to two equivalents of Li intercalation/deintercalation into H2V3O8. Lithium batteries made of a vanadium-oxyhydroxide cathode showed better cycle stability than those with a V2O5 cathode.

Fast response of sprayed vanadium pentoxide (V₂O₅) nanorods towards nitrogen dioxide (NO₂) gas detection

Mane, A.A.,Suryawanshi, M.P.,Kim, J.H.,Moholkar, A.V. Elsevier BV * North-Holland 2017 Applied Surface Science Vol.403 No.-

<P><B>Abstract</B></P> <P>The V<SUB>2</SUB>O<SUB>5</SUB> nanorods have been successfully spray deposited at optimized substrate temperature of 400°C onto the glass substrates using vanadium trichloride (VCl<SUB>3</SUB>) solution of different concentrations. The effect of solution concentration on the physicochemical and NO<SUB>2</SUB> gas sensing properties of sprayed V<SUB>2</SUB>O<SUB>5</SUB> nanorods is studied at different operating temperatures and gas concentrations. The XRD study reveals the formation of V<SUB>2</SUB>O<SUB>5</SUB> having an orthorhombic symmetry. The FE-SEM micrographs show the nanorods-like morphology of V<SUB>2</SUB>O<SUB>5</SUB>. The AFM micrographs exhibit a well covered granular surface topography. For direct allowed transition, the band gap energy values are found to be decreased from 2.45eV to 2.42eV. The nanorods deposited with 30mM solution concentration shows the maximum response of 24.2% for 100ppm NO<SUB>2</SUB> gas concentration at an operating temperature of 200°C with response and recovery times of 13s and 140s, respectively. Finally, the chemisorption mechanism of NO<SUB>2</SUB> gas on the V<SUB>2</SUB>O<SUB>5</SUB> nanorods is discussed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effect of solution concentration on physicochemical properties of sprayed V<SUB>2</SUB>O<SUB>5</SUB> nanorods is studied. </LI> <LI> Good re­sponse and short re­sponse- re­covery times of V<SUB>2</SUB>O<SUB>5</SUB> nanorods towards NO<SUB>2</SUB> gas show it is potential material for fab­ri­ca­tion of NO<SUB>2</SUB> sensor. </LI> <LI> The chemisorption mechanism of NO<SUB>2</SUB> gas on the V<SUB>2</SUB>O<SUB>5</SUB> nanorods is discussed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

정상생리주기의 불임여성에서 초기 난포기에 측정된 성선자극호르몬 및 Estradiol혈중치의 연령에 따른 차이

박재기,김완영,이종학,김종화,백원영 대한산부인과학회 1994 Obstetrics & Gynecology Science Vol.37 No.2

1992년 4월부터 1993년 3월까지 불임을 주소로 경상대학교병원 산부인과를 방문한 정상적 생리주기를 가지며 배란성 불임요인이 없는 21세에서 44세까지의 불임환자 74명, 정상적인 생리주기를 가진 미혼의 정상대조군여성 21명(Control I), 비교적 정상적 생리주기를 가지며 폐경전증후군을 호소하는 여성 10명(Control II)을 대상으로 초기난포기에 혈중 성선자극호르몬인 FSH와 LH, 주요 여성호르몬인 estradiol(E2)의 혈중치가 연령증가에 따라 어떠한 변화를 나타내는지를 알기 위하여 불임환자를 연령별로 5개의 군으로 나누어 호르몬의 혈중치의 변화를 측정하여 다음과 같은 결론을 얻었다. (Group I: 21-24 years old, Group II: 25-29 years old, Group III: 30-34 years old, Group IV: 35-39 years old, Group V: 40-44 years old) 1. 정상대조여성군(Control I)의 FSH, LH및 estradiol의 초기난포기의 평균 혈중치는 각각 10.11+-2.08mIU/ml, 6.29+-2.44mIU/ml, 39.04+-16.8pg/ml이었다. 2. 폐경기전 여성군(Control II)의 FSH, LH와 estradiol의 초기난포기의 평균 혈중치는 각각 53.43+-24.32 mIU/ml, 47.51 +-18.07mIU/ml, 24.05 +-20.79pg/ml로서 FSH 및 LH의 혈중치가 정상대조여성군 및 불임환자군에 비하여 유의하게 높았으며(p$lt;0.001), estradiol은 40세에서 44세사이의 불임환자군에서만 유의하게 낮았다(p$lt;0.005). 3. 불임환자군(Group I-V)에서 연령별 FSH의 평균혈중치는 각각 10.94+-2.83mIU/ml, 10.33+-2.66mIU/ml, 11.92+-3.91mIU/ml, 10.27+-3.78mIU/ml, 16.18+-3.25mIU/ml로서 40세에서 44세사이의 불임환자군(Group V)에서 다른 불임환자군 및 정상여성대조군(Control I)에 비하여 유의하게 높았다(p$lt;0.001). 4. 불임호나자군에서 연령별 LH의 평균혈중치는 각각 8.51+-3.27mIU/ml, 35.42+-15.12pg/ml, 44.68+-22.28pg/ml, 63.99+-63.90pg/ml로서 각 군간의 유의한 차이는 없었다(p$gt;0.05). 5. 불임환자군에서 연령별 estradiol(E2)의 평균혈중치는 각각 37.77+-20.57 pg/ml, 35.42+-15.12 pg/ml, 44.68+-22.28 pg/ml, 74.53 +-68.01pg/ml, 63.99 +-63.90pg/ml로서 각 군간의 유의한 차이는 없었다(p$gt;0.05). 6. 불임환자 각 군과 정상여성대조군 및 폐경기전 여성군의 LH/FSH ratio는 각각 0.78+-0.22, 0.83+-0.54, 0.63+-0.49, 0.74+-0.34, 0.46+-0.27, 0.66+-0.30, 0.97+-0.69로서 불임환자군인 Group V에서 Group I, II와 비교시 유의한 감소를 보였지만(p$lt;0.02) 대조군 I, II 및 다른 불임환자군간의 유의한 치이는 없었다(p$gt;0.05). 결론적으로 정상생리주기를 가진 배란성요인이 아닌 불임여성의 초기난포기에 측정된 FSH, LH 및 estradiol은 정상생리주기를 가진 가임여성과 마찬가지로 연령에 따라 유사한 변화를 한다는 것을 알 수 있었으며, FSH에 대한 독점적 억제작용을 하는 inhibin을 동시에 측정한다면 좀더 명확한 상관관계를 알 수 있을 것으로 판단되었다. Throughout a womans reproductive life there is a close relationship between the activity of the ovary and that of the hypothalamic-pituitary axis. As the menopause approaches this relationship becomes progressively disturbed. During the peri-menopause the deficiency of ovarian hormones is thought to disturb the function of the hypothalamic-pituitary axis from ovarian control, resulting in the high levels of FSH and LH found in postmenopausal women. There has been known that the change of serum levels of gonadotropin and estradiol precede the menopause and is related decreasing tendency of pregnancy rate. The aim of this study was to determine the effect of age on the serum levels of FSH, LH, estradiol in infertile women with regular menstrual cycle. Seventy-four infertile womne were evaluated according to their ages classified into 5 groups as well as control I(18-24 years old) and control II (45-55 years old)(Group I; 21-24 years old, Group Ii 25-29 years old, Group III: 30-34 years old, Group IV: 35-39 years old, Group V: 40-44 years old, respectively). 1. The mean serum levels of FSH, LH, and estradiol in control I during their early follicular phase were 10.11+-2.08 mIU/ml, 6.29+-2.44 mIU/ml, 39.04 +-16.84mIU/ml, respectively. 2. The levels of FSH and LH were significantly higher than those of control I or all infertile groups (p$lt;0.001) and the levels of estradiol were significantly lower than those of group V(p$lt;0.005). The mean serum levels of FSH, LH, and estradiol in control II during their early follicular phase were 53.43+-24.32mIU/ml, 47.51+-18.07mIU/ml,24.05+-20.79pg/ml, respectively. 3. The mean serum levels of FSH in infertile groups(group I-V) during their early follicular phase were 10.94+-2.83mIU/ml, 10.33+-2.66mIU/ml, 11.92+-3.91mIU/ml, 10.27+-3.78mIU/ml, 16.18+-3.25mIU/ml, respectively and the level of FSH in group V was significantly higher than other infertile groups and control I(p$lt;0.001). 4. The mean serum levels of LH in infertile groups during their early follicular phase were 8.51+-3.272mIU/ml, 7.90+-4.06mIU/ml, 7.41+-5.36mIU/ml, 6.38+-3.24mIU/ml. 7.56+-4.74mIU/ml, respectively and there were no significant difference among the levels of FSH in infertile groups(p$gt;0.05). 5. The mean levels of estradiol (E2) in infertile groups during their early follicular phase were 37.77+-20.57 pg/ml, 35.42 +-15.12pg/ml, 44.68 +-22.28pg/ml, 74.53 +-68.01pg/ml, 63.99 +-63.90pg/ml, respectively and there were no significant difference among the levels of estradiol in infertile groups(p$gt;0.05). 6. The LH/FSH ratio in all infertile groups and normal control groups were 0.78+-0.22, 0.83+-0.54, 0.63+-0.49, 0.74+-0.34, 0.46+-0.27, 0.66+-0.30, respectively and the LH/FSH ratio in group V was significantly lower than those of group I, II(p$gt;0.05).

Superior selectivity and enhanced response characteristics of palladium sensitized vanadium pentoxide nanorods for detection of nitrogen dioxide gas

Mane, A.A.,Suryawanshi, M.P.,Kim, J.H.,Moholkar, A.V. Academic Press 2017 Journal of Colloid and Interface Science Vol. No.

<P><B>Abstract</B></P> <P>Vanadium pentoxide (V<SUB>2</SUB>O<SUB>5</SUB>) nanorods have been deposited onto the glass substrates by spraying 75ml of 30mM vanadium trichloride (VCl<SUB>3</SUB>) solution at optimized substrate temperature of 400°C. The XRD study confirms the formation of orthorhombic crystal structure of V<SUB>2</SUB>O<SUB>5</SUB> nanorods. The FE-SEM micrograph shows the nanorods-like morphology of V<SUB>2</SUB>O<SUB>5</SUB>. The presence of palladium (Pd) in the Pd-sensitized V<SUB>2</SUB>O<SUB>5</SUB> nanorods is confirmed using EDAX study. The gas sensing measurements show that the Pd-sensitized V<SUB>2</SUB>O<SUB>5</SUB> sensing material is an outstanding candidate for nitrogen dioxide (NO<SUB>2</SUB>) gas detection. Obtained results demonstrate that the Pd-sensitized V<SUB>2</SUB>O<SUB>5</SUB> nanorods show the superior selectivity for NO<SUB>2</SUB> gas in comparison with other gases such as NH<SUB>3</SUB>, H<SUB>2</SUB>S, CO, CO<SUB>2</SUB> and SO<SUB>2</SUB> at an operating temperature of 200°C. It shows the 75% response for 100ppm NO<SUB>2</SUB> gas concentration with response and recovery times of 22s and 126s, respectively. Finally, the gas sensing mechanism based on chemisorption process is proposed to illustrate how Pd nanoparticles affect the gas sensing characteristics (response and response-recovery times).</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

V711 TAU의 채층활동

V771TAU의채층활동 한국우주과학회 1997 Journal of Astronomy and Space Sciences Vol.14 No.1

V711 Tau의 채층활동을 조사하기 위하여 자외선 영역의 Mg II 방출선의 세기와 광도 변화의 상관 관계를 유추하였다. 첫째, 가시광선 영역의 광도곡선의 형태와 자외선 영역의 광도곡선의 형태를 비교하고, 둘째, IUE 고분산 스펙트럼에서 Mg II 방출선의 세기를 위상별로 측정하고 방출선 부근의 연속선을 이용하여 자외선 광도곡선을 완성하였다. 방출선의 세기와 광도곡선을 비교한 결과 방출선이 강하게 나타나는 위상, $0.^{p}4$에서는 광도가 어둡게 나타나 최소가 되고, 방출선의 세기가 약할 때는 광도가 밝아져서 최대가 되었다. 이는 자기장이 강한 위상에서는 채층활동과 흑점의 크기가 증가하고 반대로 자기장이 약한 위상에서는 채층활동과 흑점의 크기가 작다는 것을 뜻한다. 그러므로 자기장, 채층활동, 별 표면의 흑점과의 상관 관계가 밝혀지고, V711 Tau의 변광은 표면의 채층활동과 흑점에 의한 것이다. The relationship between Mg II emission line and light variation of V711 Tau has been derived to investigate the chromospheric activity on V711 Tau. First, a shape of an optical light curve was compared with that of ultraviolet constructed from the IUE low resolution spectra. Second, the intensities of Mg II k emission lines have been reduced from IUE high resolution spectra. The intensity of Mg II k line was compared with brightness of the UV light curve at given phase. The Mg II line intensity is maximum at the phase $O.^{P}4$ where the light is minimum. The evidence of chromosperic activity is indicated by the intensity variation of the MgII emission line with orbital phase for V711 Tau.