检索结果-南通市图书馆

Computational Study on a Squid-Like Underwater Robot with Two Undulating Side Fins

在线全文

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2011年第1期8卷 25-32页

作者： md. Mahbubar rahman Yasuyuki Toda Hiroshi Miki Department of Naval Architecture and Ocean Engineering Graduate School of Engineering Osaka University 2-1 Yamadaoka Suita City Osaka 565-0871 Japan

The undulating fin propulsion system is an instance of the bio-inspired propulsion systems. In the current study, the swimming motion of a squid-like robot with two undulating side fins, mimicking those of a Stingray or a Cuttlefish, was investigated through flow computation around the body. We used the finite analytic method for space discretization and Euler implicit scheme for time discretization along with the PISO algorithm for velocity pressure coupling. A body-fitted moving grid was generated using the Poisson equation at each time step. Based on the computed results, we discussed the features of the flow field and hydrodynamic forces acting on the body and fin. A simple relationship among the fin＇s principal dimensions was established. Numerical computation was done for various aspect ratios, fin angles and frequencies in order to validate the proposed relationship among principal dimensions. Subsequently, the relationship was examined base on the distribution of pressure difference between upper and lower surfaces and the distribution of the thrust force. In efficiency calculations, the undulating fins showed promising results. Finally, for the fin, the open characteristics from computed data showed satisfactory conformity with the experimental results.

关键词： biomimetics squid robot undulating fin propulsion efficiency hydrodynamics CFD

Synthesis and photoswitching properties of azobenzene liquid crystals with a pentafluorobenzene terminal

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2014年第12期25卷 1611-1614页

作者： md.lutfor rahman Gurumuthy Hegde Shaheen M.Sarkar Mashitah Mohd Yusoff Faculty of Industrial Sciences  Technology Universiti Malaysia PahangKuantan 26300Malaysia

The fluorine-substituted benzoate ester rod-shaped liquid crystals containing an azobenzene side chain linked with terminal double bonds were synthesized and *** mesophase and photoswitching properties were determined by polarizing optical microscopy（POM）,differential scanning calorimetry（DSC） and UV-visible *** rod-shaped compound 4a having an odd number of carbon atoms in the alkyl chains exhibits nematic phase and SmA type phase whereas compound 4b having an even number of carbon atoms showed only nematic *** fluorinecontaining compounds 4c and 4d showed only SmA type *** photoswitching properties of these compounds showed a rate of trans to cis isomerization ranging 19-20 s,whereas reverse process took around 230 min in *** materials may be ideal in the field of optically rewritable applications where both on and off rates should be crucial.

关键词： Liquid crystals Azobenzene Photoswitching Fluorine compounds

Cyclic liquefaction screening of sand with non-plastic fines:Critical state approach

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2020年第2期11卷 429-438页

作者： md.Mizanur rahman TGSitharam Natural and Built Environments Research Centre(NBERC) School of Natural and Built EnvironmentsUniversity of South AustraliaMawson LakesSA 5095Australia Department of Civil Engineering Indian Institute of Science(IISc)BangaloreIndia

There have been significant advances in the application of critical state,CS,in liquefaction potential *** was done by comparing state parameter,j with estimated characteristic cyclic stress ratio,CSR due to an earthquake.A cyclic resistance ratio,CRR curve,which can be determined from cyclic liquefaction tests,separates historical liquefied and non-liquefied data points(j,CSR).On the other hand,the concepts of equivalent granular state parameter,j*,which was developed for sands with fines,can be used in lieu j to provide a unifying framework for characterizing the undrained response of sands with non/low plasticity fines,irrespective of fines content(fc).The present work combines these two propositions,and by merely substituting j*for j into the aforementioned CS approach to capture the influence of fc.A series of static and cyclic triaxial tests were conducted,separately and independently of the concept of j*,for sand with up to fc of 30%.The clean sand was collected from Sabarmati river belt at Ahmedabad city in India which was severely affected during the Bhuj earthquake,*** experimental data gave a single relation for CRR and j*which was then used to assess liquefaction potential for a SPT based case study,where fc varies along the *** prediction matched with the field observation.

关键词： Critical state State parameter Liquefaction Sands Fines Constitutive model

Influence of prey availability on the movement pattern of breeding saker falcons(Falco cherrug)in Mongolia

在线全文

学校读者我要写书评

暂无评论

Current Zoology 2024年第6期70卷 810-820页

作者： Batbayar Bold md.lutfor rahman Gankhuyag Purev-Ochir Amarsaikhan Saruul Xiangjiang Zhan Andrew Dixon Key Laboratory of Animal Ecology and Conservation Biology Institute of ZoologyChinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Wildlife Science and Conservation Center of Mongolia Ulaanbaatar 14230Mongolia Cardiff University-Institute of Zoology Joint Laboratory for Biocomplexity Research Chinese Academy of SciencesBeijing 100101China Mongolian Bird Conservation Center Ulaanbaatar 14200Mongolia International Wildlife Consultants Ltd. PO Box 19CarmarthenWalesUK Mohamed Bin Zayed Raptor Conservation Fund Abu DhabiUnited Arab Emirates

As an apex predator in arid steppe,saker falcon plays a crucial role in maintaining ecosystem *** their movement patterns concerning conspecific competition and prey availability is important for their *** aim to understand how movement pattern of breeding saker falcons relates to prey *** adult sakers were tracked during the breeding seasons,using satellite *** the breeding season,sakers exhibited territorial behavior,with minimal overlap in range use among neighboring *** occupied larger areas(mean=2,397 ha,median=1,221 ha),compared to females(mean=1,241 ha,median=554 ha),and it remained consistent throughout breeding *** home range size increased notably during a late nestling stage and post-fledging dependence periods,indicating release from brooding ***,we found a negative relationship between male home range size and prey *** high rodent density areas,males occupied smaller areas(mean=1,135 ha,median=1,034 ha),contrasting with low rodent density areas(mean=6,815 ha,median=6,516 ha).However,no significant relationship was observed between female home range size and prey *** also noted instances of nest abandonment and early dispersal behavior in some females,potentially influenced by a handicapping effect of *** findings offer valuable insight into how prey availability shapes saker falcon space use and defines their spatial requirements for successful *** knowledge is crucial for the conservation and management of globally endangered saker falcons,informing targeted habitat protection and resource management strategies.

关键词： birds of prey distance from the nest home range prey availability territory tagging effect

Infant and Under-five Mortality in Bangladesh: Discriminant Analysis

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Population,Resources and Environment 2010年第4期8卷 79-84页

作者： rahman md. Mahfuzar IsIam md. Rafiqul Population Science and Human Resource Development University of Rajshahi

Bangladesh is on target for achieving the Millennium Development Goal 4 relating to infant and under-five mortality because of very rapid reduction in mortality in recent years. But this rate of reduction may be difficult to sustain and may hamper the achievement of Millennium Development Goal 4. Therefore, the main objective of this paper is to discuss and compare the dif- ferent covariates of infant and under-five mortality in the context of overall country, urban and rural levels of Bangladesh using discriminant analysis. For this, the data are taken from Bangladesh Demographic and Health Survey, 2004. In discriminant analysis, the stepwise procedure has been picked up and only the significant variables are ranked according to the rank of Wilk's Lambda val- ues. The canonical discriminant function coefficients (unstandard- ized and standardized) for the predictor variables have also been calculated. Both the results show that breastfeeding is the most important variable in discriminating the two groups of mothers, i.e., mothers experiencing to infant mortality or not and mothers experiencing to under-five mortality or not. The related results of discriminant function also indicate that the discriminant func- tion is statistically significant and discriminates well. Therefore, improvements in the health system are essential for promoting the breastfeeding practices (both inclusive and exclusive), which may be the effective strategies to reach families and communities with targeted messages and information.

关键词： infant and under-five mortality breastfeeding prac- tices discriminant analysis

Kenaf cellulose-based poly(amidoxime) ligand for adsorption of rare earth ions

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2019年第3期38卷 259-269页

作者： md.lutfor rahman Mohd Sani Sarjadi Sazmal Effendi Arshad Mashitah M. Yusoff Shaheen M. Sarkar Baba Musta Faculty of Science and Natural Resources Universiti Malaysia Sabah Faculty of Industrial Sciences and Technology University Malaysia Pahang

A well-known adsorbent, poly(amidoxime)ligand, was prepared from polyacrylonitrile(PAN) grafted kenaf cellulose, and subsequent characterization was performed by Fourier transform infrared spectroscopy(FTIR),field emission scanning electron microscope(FESEM) and inductively coupled plasma mass spectrometry(ICP-MS).The adsorption capacities of the prepared ligand for rare earth metals are found to be excellent, with adsorptions of La^(3+), Ce^(3+), Pr^(3+), Gd^(3+) and Nd^(3+) experimentally determined to be 262, 255, 244, 241 and 233 mg·g^(-1), respectively, at pH 6. The experimental values of the adsorption of rare earth metals are well matched with the pseudosecond-order rate equation. The reusability of the adsorbent is examined for seven cycles of sorption/desorption,demonstrating that the proposed adsorbent could be reused for over seven cycles without any significant loss in the original removal capability of the ligand.

关键词： Adsorption Poly(amidoxime) Rare earths Separation Kenaf cellulose

Nutrient dynamics associated with leaf litter decomposition of three agroforestry tree species (Azadirachta indica, Dalbergia sissoo, and Melia azedarach) of Bangladesh

在线全文

学校读者我要写书评

暂无评论

Journal of Forestry Research 2011年第4期22卷 577-582页

作者： Mahmood Hossain Mohammad Raqibul Hasan Siddique md. Saidur rahman md. Zaber Hossain md. Mahedi Hasan Forestry and Wood Technology Discipline Khulna University Khulna - 9208 Bangladesh Soil Science Discipline Khulna University Khulna-9208 Forestry and Wood Technology Discipline Khulna University Khulna- 9208

Azadirachta indica A. Juss, Dalbergia, sissoo Roxb., and Melia azedarach L. are little studied species in nutrient return capabilities from leaf litter decomposition to maintenance of the soil fertility despite their importance in agroforestry practices of Bangladesh. A leaf litter decomposition experiment was conducted using a litterbag teeh7 nique to assess the nutrient reaun efficiency of these species. The de- composition rate of leaf litter was highest for M. azedarach and lowest for D. sissoo. Rainfall and temperature of study sites showed a significant （p〈0.05） positive relationship with the rate of leaf litter decomposition. The highest decay constant was observed for M. azedarach （6.67）. Nitrogen and Phosphorus concentration in leaf litter showed a decreased trend sharply at the end of the first month, whereas rapid decrease of Potassium concentration was reported within 10 days. Conversely, higher concentration of nutrient was observed at the later stages of decomposition. All three species showed a similar pattern of nutrient release （K 〉 N 〉 P） during the decomposition process of leaf litter. Among the studied species, D. sissoo was best in terms of N and P return and A. indica was best in terms of K return.

关键词： agroforestry decay constant decomposition leaf litter andnutrient dynamics

Can picnic influence floral diversity and vitality of trees in Bhawal National Park of Bangladesh?

在线全文

学校读者我要写书评

暂无评论

Forestry Studies in China 2009年第3期11卷 148-157页

作者： md. Mizanur rahman Harald VACIK Institute of Silviculture Department of Forest and Soil Sciences University of Natural Resources and Applied Life Sciences Vienna A-1190 Austria

We examined the impact of picnic activities on forest diversity, structure, regeneration and vitality of tree species in the Bhawal National Park of Bangladesh. The study area was classified as a non-used, occasionally used and frequently used area on the basis of the intensity of the picnic activities. A total of 43 plant species were enumerated in the whole study area. The highest plant species richness （41 species） was observed in the non-used area whereas the lowest species richness （11 species） in the frequently used area. The diversity index decreased with the increase of picnic intensity whereas the concentration of dominance increased. Density of all plant groups except mature trees, and the basal area of the mature trees showed a declining trend from the non-used to frequently used area. The frequently used area exhibited very poor regeneration. Tree vitality decreased with the increase of picnic intensity. The relevance of our study as a basis for further research to determine the impact of tourism on biodiversity in Bangladesh is discussed.

关键词： species richness diversity index concentration of dominance regeneration intensity

Braking Performance of a Biomimetic Squid-Like Underwater Robot

在线全文

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2013年第3期10卷 265-273页

作者： md. Mahbubar rahman Sinpei Sugimori Hiroshi Miki Risa Yamamoto Yugo Sanada Yasuyuki Toda Laboratory of Hull Form Design Department of Naval Architecture and Ocean Engineering Graduate School of Engineering Osaka University Osaka 565-0871 Japan

In this study, the braking performance of the undulating fin propulsion system ofa biomimetic squid-like underwater robot was investigated through free run experiment and simulation of the quasi-steady mathematical model. The quasi-steady equa- tions of motion were solved using the measured and calculated hydrodynamic forces and compared with free-run test results. Various braking strategies were tested and discussed in terms of stopping ability and the forces acting on the stopping stage. The stopping performance of the undulating fin propulsion system turned out to be excellent considering the short stopping time and short stopping distance. This is because of the large negative thrust produced by progressive wave in opposite direction. It was confirmed that the undulating fin propulsion system can effectively perform braking even in complex underwater explorations.

关键词： biomimetics squid-like underwater robot undulating fin propulsion system braking performance motion simulation