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- 검색키워드
- 저자 : Dhaka, S. K. (검색결과 14 건)
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Dhaka, Sarita,Kumar, Rahul,Lee, Sang-hun,Kurade, Mayur B.,Jeon, Byong-Hun Elsevier 2018 Journal of Cleaner Production Vol.180 No.-
<P><B>Abstract</B></P> <P>UV-C-mediated advanced oxidation processes (AOPs) for the enhanced degradation of ethyl paraben (EP) in the presence of oxidants such as persulfate (PS), hydrogen peroxide (H<SUB>2</SUB>O<SUB>2</SUB>) and peroxymonosulfate (PMS) were systematically investigated. The AOP treatments showed 98.1%, 97.0% and 81.3% degradation of EP with rates of 0.0373, 0.0339, and 0.0202 min<SUP>−1</SUP> within 90 min for UV/PS, UV/H<SUB>2</SUB>O<SUB>2</SUB> and UV/PMS, respectively. Degradation rates of EP increased with higher initial dosages of oxidant(s), while the opposite trend was observed in the case of increasing initial EP concentration. Maximum EP removal was achieved at pH 6.5 for UV/PS and UV/PMS and at pH 3 for UV/H<SUB>2</SUB>O<SUB>2</SUB>. Humic acid significantly retarded the degradation of EP. Chloride (Cl<SUP>−</SUP>) and carbonate (CO<SUB>3</SUB> <SUP>2−</SUP>) suppressed reaction rates using UV/PS and UV/H<SUB>2</SUB>O<SUB>2</SUB> systems, whereas they elevated the degradation rates with UV/PMS treatment. Degradation of EP in each of the UV-C based AOPs followed pseudo-first-order kinetics. The use of ethanol and t-butyl alcohol as scavengers revealed that HO<SUP> </SUP> and ▪ radicals were the major reactive radicals in UV/H<SUB>2</SUB>O<SUB>2,</SUB> UV/PS, and UV/PMS treatments. The efficiency (according to electrical energy per order and total cost per cubic meter) of the systems followed the order UV/PS > UV/H<SUB>2</SUB>O<SUB>2</SUB> > UV/PMS. Thus, UV/PS process was more efficient and economical for EP degradation than the other processes examined in this study.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Aqueous phase ethyl paraben (EP) degradation using UV-C based AOPs was investigated. </LI> <LI> EP degradation was pH dependent and followed pseudo-first-order kinetics. </LI> <LI> Anions (Cl<SUP>−</SUP>, CO 3 2 − ) suppressed EP degradation in UV/PS and UV/H<SUB>2</SUB>O<SUB>2</SUB> systems. </LI> <LI> HO<SUP> </SUP> and ▪ radicals were predominant in UV/H<SUB>2</SUB>O<SUB>2</SUB> and UV/PS/PMS processes </LI> <LI> Efficiency of the processes followed the order: UV/PS > UV/H<SUB>2</SUB>O<SUB>2</SUB> >UV/PMS. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Metal–organic frameworks (MOFs) for the removal of emerging contaminants from aquatic environments
Dhaka, Sarita,Kumar, Rahul,Deep, Akash,Kurade, Mayur B.,Ji, Sang-Woo,Jeon, Byong-Hun Elsevier 2019 Coordination chemistry reviews Vol.380 No.-
<P><B>Abstract</B></P> <P>Metal–organic frameworks (MOFs) have gained attention as promising materials for aqueous-phase sorptive removal of emerging contaminants (ECs). Attributes such as large adsorption capacity, high surface area, tunable porosity, hierarchical structure, and recyclability give MOFs an edge over conventional adsorbents. The poor stability of MOFs in water is a major challenge to their real-world environmental application. The performance of MOFs and their selectivity toward targeted pollutants for removal can be regulated by judicious selection of metal ion and organic linker. A range of water-stable MOFs (e.g., MIL-53, MIL-100, MIL-101, UiO-66, and MIL-125) and their composites with other materials have been reported to remove the ECs from water. The present review critically addressed the performance of MOFs for the adsorptive removal of different categories of ECs from water and the adsorption mechanisms involved. The performance of MOFs compared with other adsorbents has also been discussed. This body of rapidly developing research signifies the emerging importance of MOFs in environmental applications and provides a future direction for the development of treatment technology to effectively remove ECs from aqueous environments.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MOFs offer great opportunities in environmental remediation of different pollutants. </LI> <LI> MOFs are potential adsorbents for water purification. </LI> <LI> Strategies to improve the aqueous phase stability of MOFs are reviewed. </LI> <LI> Performance of MOFs in aqueous phase emerging contaminants removal are highlighted. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Genetic Studies on Production Efficiency Traits in Hariana Cattle
Dhaka, S.S.,Chaudhary, S.R.,Pander, B.L.,Yadav, A.S.,Singh, S. Asian Australasian Association of Animal Productio 2002 Animal Bioscience Vol.15 No.4
The data on 512 Hariana cows, progeny of 20 sires calved during period from 1974 to 1993 maintained at Government Livestock Farm, Hisar were considered for the estimation of genetic parameters. The means for first lactation milk yield (FLY), wet average (WA), first lactation peak yield (FPY), first lactation milk yield per day of first calving interval (MCI) and first lactation milk yield per day of age at second calving (MSC) were 1,141.58 kg, 4.19 kg/day, 6.24 kg/day, 2.38 kg/day and 0.601 kg/day, respectively. The effect of period of calving was significant (p<0.05) on WA, FPY and MCI while the effect of season of calving was significant only on WA. Monsoon calvers excelled in performance for all the production efficiency traits. The effect of age at first calving (linear) was significant on all the traits except on MCI. Estimates of heritabilty for all the traits were moderate and ranged from 0.255 to 0.333 except for WA (0.161). All the genetic and phenotypic correlations among different production efficiency traits were high and positive. It may be inferred that selection on the basis of peak yield will be more effective as the trait is expressed early in life and had reasonably moderate estimate of heritability.
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Aqueous phase degradation of methyl paraben using UV-activated persulfate method
Dhaka, Sarita,Kumar, Rahul,Khan, Moonis Ali,Paeng, Ki-Jung,Kurade, Mayur B.,Kim, Sun-Joon,Jeon, Byong-Hun Elsevier 2017 Chemical Engineering Journal Vol.321 No.-
<P><B>Abstract</B></P> <P>Methyl paraben (MP), a widely used preservative, exhibits endocrine-disrupting properties with estrogenic activities. The aqueous phase degradation of MP, using UV-activated persulfate method, was investigated in the present study. The combination of UV irradiation and persulfate anion successfully degraded MP showing 98.9% removal within 90min. A quenching experiment using ethanol (EtOH) and <I>tert</I>-butyl alcohol (TBA) showed the presence of both radicals (OH<SUP> </SUP> and SO<SUB>4</SUB> <SUP> –</SUP>) in the system; near neutral pH SO<SUB>4</SUB> <SUP> –</SUP> radical was the major species. The influence of various factors such as persulfate dose, initial MP concentration, solution pH, and water matrix components on the degradation kinetics was examined in view of the practical applications of the developed process. The degradation rate of MP was considerably increased as the amount of persulfate increased. The degradation of MP in the UV/persulfate system was pH dependent and more promising near neutral pH (6.5) conditions. The presence of anions such as Cl<SUP>−</SUP>, HPO<SUB>4</SUB> <SUP>2−</SUP> and HCO<SUB>3</SUB> <SUP>−</SUP> showed inhibitory effect towards MP degradation. The presence of humic acid also suppressed the degradation efficiency of MP. The reaction rate followed pseudo-first-order kinetics for all of the degradations. The degradation of MP by UV/persulfate treatment led to the production of seven transformation byproducts, which were identified using ultra-high-performance liquid chromatography-mass spectrometry (UPLC-MS). A degradation pathway for MP degradation was also proposed. The results of the present study reveal that the UV/persulfate process could be an effective approach to remove MP from aqueous solutions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Aqueous phase MP degradation using UV/persulfate method was investigated. </LI> <LI> Degradation rate of MP followed pseudo-first-order kinetics. </LI> <LI> MP degradation was pH dependent. </LI> <LI> HCO<SUB>3</SUB> <SUP>−</SUP>, HPO<SUB>4</SUB> <SUP>2−</SUP> and humic acid exhibited inhibitory effect on MP degradation. </LI> <LI> Hydroxylation and hydrolysis were possible pathways of degradation of MP. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Factoring Central Asia into China's Afghanistan policy
Ambrish Dhaka 한양대학교 아태지역연구센터 2014 Journal of Eurasian Studies Vol.5 No.1
China's footprints in Afghanistan are vied by many, both, friends and rivals as it cautiously reveals its geostrategic goals. It would like to emulate the African and Central Asian success story in Afghanistan as well, which is not terra incognito. Afghanistan has been the fulcrum of geopolitical balance of power during the Cold war days. China's Afghanistan policy (CAP) is marked by its insecurities of terrorism, extremism and separatism in Xinjiang province. It has heavily invested in procuring Central Asian energy resources. Both, the concerns go well in formulation of CAP. However, the presence of the US and Russia make the scenario competitive, where its ‘Peaceful Rise’ may be contested. Besides, China sees South Asian Region as its new Geoeconomic Frontier. All these concerns get factored into CAP. It remains to be seen what options partake in CAP, as China prepares for durable presence in Afghanistan in the long run.
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Kumar, V.,Dhaka, S.K.,Ho, S.P.,Singh, N.,Singh, V.,Reddy, K.K.,Chun, H.Y. Elsevier Science Publishers 2017 Atmospheric research Vol.198 No.-
Association of lower tropospheric variations with the cold point tropopause (CPT) is examined on inter-seasonal basis over the tropical region (30<SUP>o</SUP>N-30<SUP>o</SUP>S) during 2007-2010 using COSMIC/FORMOST-3 Radio Occultation (RO) data. Temperature analyses for this association are shown over different regions of the globe having contrast topography namely over Western Pacific sector, Indian sector, and African sector. Correlation coefficient (r), taken as a measurement of association, show specific longitudinal differences between the lower troposphere (from 1km to 5km height) and the CPT. The northern and southern hemispheres show contrast coupling of temperature variation between lower tropospheric region and the CPT. Land and ocean effects are found to contribute in a different way to the correlation coefficient. Analyses show symmetrical structure of 'r' on both sides of the equator over the African region, as data include mostly land region on both side of equator. Data represent positive correlation (r~0.5) over 15<SUP>o</SUP>-20<SUP>o</SUP> latitudes on either side of the equator over the African region, suggesting strong hold of the inter-seasonal variation of solar diabatic heating influence over the tropic of Cancer and tropic of Capricorn. On the other hand, there is a contrast behaviour over the Indian region, 'r' is nearly negative (~-1.0) each year in the southern hemisphere (SH) and positive (~0.4) in the northern hemisphere (NH) with a maxima near tropic of Cancer. Western Pacific region is found to display a linear increase in 'r' from negative (~-1.0) in SH to positive (~0.8) in NH. In general, 'r' (positive) maximizes over the land region around 15<SUP>o</SUP>-20<SUP>o</SUP> latitudes, suggesting a control of in phase inter-seasonal solar heating on the coupling of boundary layer/lower troposphere and CPT region, whereas it turns negative over water body. Analyses suggest that variabilities in CPT over different regions of globe show significant inter-seasonal association with the lower troposphere. Thus CPT variabilities are not only governed by QBO, ENSO, gravity waves and Kelvin wave system as reported in earlier studies but also considerably affected by inter-seasonal changes taking place in the lower troposphere.
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Yadav, A.S.,Dhaka, S.S. Asian Australasian Association of Animal Productio 2001 Animal Bioscience Vol.14 No.8
Studies were carried out on forty young bulls of the Hariana breed (around 18 months of age) selected on the basis of their dam's milk yield at the animal farm of CCS HAU, Hisar during the period 1993-1999. Since animals showed variation in capacity to work over prolonged periods, they were subjected to regimes of carting without load and with 8 qtls. of load for three hours. The study revealed that maximum change took place in the pulse rate, followed by respiration rate and rectal temperature. The mean fatigue score for pulling an empty cart ranged between 1.66 to 2.20 after two hours work, and 2.36 to 2.73 after three hours work. For a cart loaded with 8 qtls., the corresponding ranges were 2.90 to 3.36 and 3.40 to 4.10, respectively. These results indicated that the animals under experiment had the capacity to pull moderate load (8 qtls.) for about two hours without showing any serious effect on the ability to recover and soon to work again.
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Effect of Working on Physiological, Biochemical and Haematological Parameters in Hariana Bullocks
Yadav, A.S.,Dhaka, S.S.,Kumar, B. Asian Australasian Association of Animal Productio 2001 Animal Bioscience Vol.14 No.8
An experiment was conducted on eight bullocks of Hariana cattle study draft efficiency using different appliances, changes in their physiological, biochemical and haematological parameters, and how the body tries to maintain these within normal physiological range. Blood collection was done at pre-exercise, three hours after exercise and two hours post exercise in summer and winter seasons of the year 1990-91. Average pulse rate and respiration rate per minute were found to be $63.09{\pm}0.78,\;25.60{\pm}0.54,\;97.21{\pm}2.51,\;63.37{\pm}2.70,\;64.05{\pm}1.90,\;25.33{\pm}1.20$, respectively, at pre-exercise, three hours exercise and two hours post exercise rest. The seasonal differences were found to significant and the values were higher in summer than in winter. After two hours post exercise rest Hariana bullocks regained their normal values for all the parameters, except that pulse rate, respiration rate and serum sodium during summer did not reach the pre - exercise levels.
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