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energetics and conserved quantity of an axially moving string undergoing three-dimensional nonlinear vibration

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Acta Mechanica Sinica 2008年第2期24卷 215-221页

作者： Liqun Chen C. W. Lim Hu Ding Department of Mechanics Shanghai University Shanghai 200444 China Department of Construction and Building City University of Hong Kong Hong Kong China Shanghai Institute of Applied Mathematics and Mechanics Shanghai 200072 China

Nonlinear three-dimensional vibration of axially moving strings is investigated in the view of energetics. The governing equation is derived from the Eulerian equation of motion of a continuum for axially accelerating strings. The time-rate of the total mechanical energy associated with the vibration is calculated for the string with its ends moving in a prescribed way. For a string moving in a constant axial speed and constrained by two fixed ends, a conserved quantity is proved to remain unchanged during three-dimensional vibration, while the string energy is not conserved. An approximate conserved quantity is derived from the conserved quantity in the neighborhood of the straight equilibrium configuration. The approximate conserved quantity is applied to verify the Lyapunov stability of the straight equilibrium configuration. Numerical simulations are performed for a rubber string and a steel string. The results demonstrate the variation of the total mechanical energy and the invariance of the conserved quantity.

关键词： Nonlinear free vibration Axial movingstring energetics Conserved quantity Stability

GLOBAL VIEW OF MICROSTRUCTURAL EVOLUTION:energetics,KINETICS AND DYNAMICAL SYSTEMS

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Acta Mechanica Sinica 1996年第2期12卷 144-157页

作者：杨卫锁志钢 Dept.Eng.Mech. Tsinghua Univ.Beijing 100084China Mech.Environ.Eng.Dept. Univ.CaliforniaSanta BarbaraCA 93106USA

An evolving material structure is in a non-equilibrium state, with free energy expressed by the generalized coordinates. A global approach leads to robust computations for the generalized thermodynamic forces. Those forces drive various kinetic processes, causing dissipation at spots, along curves, surfaces and interfaces, and within volumetric regions. The actual evolution path, and therefore the final equilibrium state, is determined by the energetics and kinetics. A virtual work principle Links the free energy landscape and the kinetic processes, and assigns a viscous environment to every point on the landscape. The approach leads to a dynamical system that governs the evolution of generalized coordinates. The microstructural evolution is globally characterized by a basin map in the coordinate space; and by a diversity map and a variety map in the parameter space. The control of basin boundaries raises the issue of energetic and kinetic bifurcations. The variation of basin boundaries under different sets of controlling parameters provides an analytical way to plot the diversity maps of structural evolution.

关键词： microstructural evolution energetics kinetics dynamic system

Structures,energetics,and Infrared Spectra of the Cationic Monomethylamine-Water Clusters

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Chinese Journal of Chemical Physics 2020年第1期33卷 31-36页

作者： Shu-kang Jiang Dong Yang Xiang-tao Kong Chong Wang Xiang-yu Zang Hui-jun Zheng Gang Li Hua Xie Wei-qing Zhang Xue-ming Yang Ling Jiang Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201210China State Key Laboratory of Molecular Reaction Dynamics Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023China School of Physical Science and Technology ShanghaiTech UniversityShanghai 201210China University of Chinese Academy of Sciences Beijing 100049China

The structures,energetics,and infrared(IR)spectra of the cationic monomethylamine-water clusters,[(CH3NH2)(H2O)n]^+(n=1-5),have been studied using quantum chemical calculations at the MP2/6-311+G(2d,p)level.The results reveal that the formation of protontransferred CH2NH3+ ion core structure is preferred via the intramolecular proton transfer from the methyl group to the nitrogen atom and the water molecules act as the acceptor for the O…HN hydrogen bonds with the positively charged NH3^+ moiety of CH2NH3^+,whose motif is retained in the larger clusters.The CH3NH2^+ ion core structure is predicted to be less energetically favorable.Vibrational frequencies of CH stretches,hydrogen-bonded and free NH stretches,and hydrogen-bonded OH stretches in the calculated IR spectra of the CH2NH3^+ and CH3NH2^+ type structures are di erent from each other,which would a ord the sensitive probes for fundamental understanding of hydrogen bonding networks generated from the radiation-induced chemical processes in the[(CH3NH2)(H2O)n]+complexes.

关键词： Monomethylamine Water Structure energetics Infrared spectroscopy

SIUDIES ON THE BIOCHEMICAL COMPOSITION,energetics AND ESSENTIAL AMINO ACIDS OF THREE MUDSKIPPERS IN XIAMEN HARBOUR

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Chinese Journal of Oceanology and Limnology 1995年第4期13卷 374-379页

作者：王军苏永全 Institute of Subtropical Oceanography Xiamen University Xiamen

Measurements were made on the contents of protein,lipid,glycogen(PLG)and water,and on caloric values and amino acids,in muscle of three mudskippers periophthalmus cantonensis,Scarteiaosviridis and Boleophthalmus pectinirostris collected from Haicang,Xiamen.The essential amino acids(EAA)for these fishes were also studied with radioisotopic trace method.The results showed:(1)Thecontent of each component in tested fish muscles differed slightly,and protein was the most importantcomponent making up from 6.685% to 9.891% of the wet weight (about 44.21%-50.45% of dryweight);(2)Energy calculated from the sum of protein, lipid and glycogen in wet muscle was low (<4.3kJ/g) in these Fishes, especially in B. pectinirostris(<3.1 kJ/g), the ratios of energy to protein content (E/P) also were low(<39.873-45.535kJ/g), (3)Seventeen amino acids were determined in thesethree fishes.The content of the same amino acid(among the seventeen) tested in different species andsexes varied slightly.The amounts of methionine,

关键词： biochemical composition energetics amino acids mudskippers

Maximizing recovery time between knock-out races improves sprint cross-country skiing performance

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Journal of Sport and Health Science 2022年第1期11卷 21-29页

作者： Kerry McGawley Coline Van Waerbeke Karl-Johan Westberg Erik P.Andersson Swedish Winter Sports Research Centre Department of Health SciencesMid Sweden UniversityOstersund 83125Sweden

Background:In a sprint cross-country(XC)ski competition,the difference in recovery times separating the first and the second semi-final(SF)heats from the final(F)may affect performance.The aim of the current study was to compare the effects of longer vs.shorter recovery periods prescribed between the 3 knock-out races of a simulated sprint XC ski competition involving a prologue(P),quarter-final(QF),SF,and F.Methods:Eleven well-trained XC ski athletes completed 2 simulated sprint XC ski competitions on a treadmill involving 4×883-m roller-ski bouts at a 4°incline using the gear 3 ski-skating sub-technique.The first 3 bouts were completed at a fixed speed(PFIX,QFFIX,and SFFIX)corresponding to~96%of each individual’s previously determined maximal effort.The final bout was performed as a self-paced sprint time trial(FSTT).Test conditions differed by the time durations prescribed between the QFFIX,SFFIX,and FSTT,which simulated real-world XC ski competition conditions using maximum(MAX-REC)or minimum(MIN-REC)recovery periods.Results:The FSTT was completed 5.4±5.5 s faster(p=0.009)during MAX-REC(179.2±18.1 s)compared to MIN-REC(184.6±20.0 s),and this was linked to a significantly higher power output(p=0.010)and total metabolic rate(p=0.009).The pre FSTT blood lactate(BLa)concentration was significantly lower during MAX-REC compared to MIN-REC(2.5±0.8 mmol/L vs.3.6±1.6 mmol/L,respectively;p=0.027),and the pre-to-post FSTT increase in BLa was greater(8.8±2.1 mmol/L vs.7.1±2.3 mmol/L,respectively;p=0.024).No other differences for MAX-REC vs.MIN-REC reached significance(p>0.05).Conclusion:Performance in a group of well-trained XC skiers is negatively affected when recovery times between sprint heats are minimized which,in competition conditions,would occur when selecting the last QF heat.This result is combined with a higher pre-race BLa concentration and a reduced rise in BLa concentration under shorter recovery conditions.These findings may help inform decision making when XC skiers are faced with selecting a QF heat wi

关键词： energetics Repeated sprints Roller skiing Simulated competition Tactics

Metabolic cost of level,uphill,and downhill running in highly cushioned shoes with carbon-fiber plates

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Journal of Sport and Health Science 2022年第3期11卷 303-308页

作者： Clarissa S.Whiting Wouter Hoogkamer Rodger Kram Locomotion Laboratory Department of Integrative PhysiologyUniversity of ColoradoBoulderCO 80309USA Integrative Locomotion Lab Department of KinesiologyUniversity of MassachusettsAmherstMA 01003USA

Background:Compared to conventional racing shoes,Nike Vaporfly 4% running shoes reduce the metabolic cost of level treadmill running by4%.The reduction is attributed to their lightweight,highly compliant,and resilient midsole foam and a midsole-embedded curved carbon-fiber plate.We investigated whether these shoes also could reduce the metabolic cost of moderate uphill(+3°) and downhill(-3°) grades.We tested the null hypothesis that,compared to conventional racing shoes,highly cushioned shoes with carbon-fiber plates would impart the same ~4%metabolic power(W/kg) savings during uphill and downhill running as they do during level running.Methods:After familiarization,16 competitive male runners performed six 5-min trials(2 shoes × 3 grades) in 2 Nike marathon racing-shoe models(Streak 6 and Vaporfly 4%) on a level,uphill(+3°),and downhill(-3°) treadmill at 13 km/h(3.61 m/s).We measured submaximal oxygen uptake and carbon dioxide production during Minutes 4-5 and calculated metabolic power(W/kg) for each shoe model and grade combination.Results:Compared to the conventional shoes(Streak 6),the metabolic power in the Vaporfly 4% shoes was 3.83%(level),2.82%(uphill),and2.70%(downhill)less(all p <0.001).The percent of change in metabolic power for uphill running was less compared to level running(p=0.04;effect size(ES)=0.561) but was not statistically different between downhill and level running(p=0.17;ES=0.356).Conclusion:On a running course with uphill and downhill sections,the metabolic savings and hence performance enhancement provided by Vaporfly 4% shoes would likely be slightly less overall,compared to the savings on a perfectly level race course.

关键词： energetics Incline Locomotion Oxygen consumption Running economy

An Analysis of the Spectral energetics for a Planet Experiencing Rapid Greenhouse Gas Emissions

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Atmospheric and Climate Sciences 2017年第1期7卷 117-126页

作者： André Ferreira Aranha José Augusto P. Veiga UNINORTE Laureate International Universities Manaus Brazil Department of Meteorology Institute of Technology Amazonas State University Manaus Brazil

So far, energetics studies related to climate change have focused on the disturbed and undisturbed kinetic and potential energies, as well as their transformations, without dealing with the energetics involved in the phenomena of different spatial scales. Thus, the present work reports the first analysis of the spectral energetics for a condition of climate change, followed by the high-range emission scenario, RCP8.5, which originated from the new Max Planck Institute Earth System Model (MPI-ESM). The results showed that both types of generation (Go and Gn), baroclinic processes (Co and Cn), kinetic energies (Ko and Kn) and the barotropic process, Mn, significantly increase in the condition of a warming climate. Moreover, the results still reveal that in the most components of the energetics, is the planetary scale waves that are the most impacted under a climate change scenario. These results highlight that global warming can have different impacts on particular types of motions.

关键词： energetics Global energetics Spectral energetics Climate Change MPI-ESM Model

Surface energetics Study and Determination of the Combined Negative Hamaker Coefficient for Hepatitis C Virus Infected Human Blood Cells

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Journal of Biomedical Science and Engineering 2018年第11期11卷 307-319页

作者： C. H. Achebe S. Iweriolor J. L. Chukwuneke Department of Mechanical Engineering Nnamdi Azikiwe University Awka Nigeria Department of Mechanical Engineering Delta State Polytechnic Ogwashi-Uku Nigeria

This study investigated the interactive effects of Hepatitis C virus on human cells using the contact angle approach. The methodology involves the use of sessile drop approach to determine the contact angle formed on the infected and uninfected blood cells in the presences of glycerin as the probe liquid. It was observed that the presence of the virus in the human blood cells depleted the immune system of infected cells giving rise to a decreased CD4 count on the average of 514.5 ± 243.10 when compared with the uninfected cells CD4 count of 1267.2 ± 368.27. The measurement of contact angle also unveils that among the blood components separated in the course of the experiment, the white blood cell is the principal target of the virus with the highest average contact angle of 63.4 ± 3.20 while the uninfected white blood cells have a lower contact angle of 48.5 ± 2.75. The result of the measured contact angle was used for MATLAB computation to determine the surface energy, force of adhesion and the Hamaker coefficient. Response surface methodology was also employed in this study to visualize the viral impact on the blood cells as well as generating model equations for prediction of the interaction between the virus and the blood cells. Infected surfaces on the average have higher values of Hamaker coefficient than uninfected surfaces. It was discovered that an increase in the contact angles causes a significant increase in Hamaker coefficient with a corresponding decrease in the CD4 counts on the infected surfaces. This increase is attributed to the presence of the HCV virus in the infected samples and the highest value was observed in the white blood cell component. Computation of the combined negative Hamaker coefficient revealed that there exists a possibility of separating the virus from the human lymphocyte, hence a negative value of the A132 of the infected sample was seen to be −0.150 × 10−18 mJ/m2 (−0.150 × 10−25 J). This is in agreement with the value reported in literature when an a

关键词： Absolute Hamaker Coefficient Blood Components Contact Angle Hepatitis C Lymphocytes Surface energetics

Climatology of energetics of Cyclones over Indian Seas

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Journal of Atmospheric Science Research 2019年第1期2卷 1-9页

作者： Somenath Dutta Geena Sandhu Sanjay G Narkhedkar Sunitha Devi Meteorological training Institute India Meteorological DepartmentPune-411008India Met office INS HansaDabolimVasco Da GamaSouth GoaGoa-403801India Indian Institute of Tropical Meteorology Dr.Homi Bhaba RoadPune-411008India National Weather Forecasting Centre India Meteorological DepartmentMausam BhavanLodi RoadNew Delhi- 110003India

An attempt has been made to bring out a climatology of the energetics associated with the tropical cyclones formed over North Indian Seas, viz., the Arabian Sea (AS) and the Bay of Bengal (BOB). Study period is from 1991 to 2013. During this period a total 88 cyclones that developed over the Indian Seas have been considered. These intense systems are categorized on the basis of their formation region and season of formation. It is seen that during the study period, the frequency of formation of cyclones over BOB is twice that over AS which is consistent with the climatology of the regions. Further, it is noticed that over both the regions, they are more frequently formed in the post monsoon period compared to pre monsoon. The trend analysis of the frequency of cyclones forming over both basins, season wise shows that the overall trend for both basins is of just decreasing type. However, for Arabian Sea;the decreasing trend is more apparent in the post monsoon season, whereas in the case of the Bay of Bengal the decreasing trend is more evident in the pre-monsoon season. Various energy terms, their generation and conversion terms have been computed using NCEP/NCAR reanalysis data. Day to day quantitative analysis of these parameters is studied critically during various stages of the cyclones. The composites of these categorized systems are formed and studied. The formative, intensification and dissipation stages showed variations in their energy terms.

关键词： Cyclone Climatology energetics