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How territoriality affects the density of an egg predator： Habitat renovation and reintroduction as a method of conserving two endangered desert spring fish

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Current Zoology 2014年第4期60卷 527-533页

作者： Timothy PACIOREK Layla AL-SHAER Murray ITZKOWITZ Department of Biological Sciences Lehigh University Bethlehem PA 18015 USA

Conservation of endangered sympatric species must be carefully executed to ensure that the protection of one species does not negatively impact the survival of another. Critically endangered Pecos gambusia Gambusia nobilis and Leon Springs pupfish Cyprinodon bovinus, which are endemic to a threatened desert spring habitat, exemplify one such scenario. Recently, this habitat has been expanded, and captively bred C. bovinus were released to repopulate an area historically known to contain this species. A previous study suggested that G. nobilis are detrimental to C. bovinus populations, due to their tendency to congregate near spawning pairs and feed on their eggs. Whether G. nobilis are attracted to territorial C. bovinus, regardless of spawning behavior, remains unclear. To determine this, the number of G. nobilis in occupied and unoccupied breeding territories of both wild and captively bred C. bovinus was measured. Gambusia nobilis densities were similar between unoccupied and occupied territorial sites, suggesting that they do not show a preference for C. bovinus territories. Regardless of habitat location or prior captivity, territorial C. bovinus significantly excluded G. nobilis within their direct vicinity （5 cm）, but not from their entire territory. Decreased G. nobilis density within the habitat may allow C. bovinus to defend their breeding territories more readily during the summer spawning season. This study provides empirical evidence of captively raised individuals behaving similarly to wild indi- viduals upon reintroduction to their natural habitat and support for conservation methods that focus on common limiting factors between endangered species [Current Zoology 60 （4）： 527-533, 2014].

关键词： Pupfish Gambusia Habitat Conservation Territory Density

Population differentiation at a regional scale in spadefoot toads： contributions of distance and divergent selective environments

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Current Zoology 2016年第2期62卷 193-206页

作者： Amber M. RICE Michael A. MCQUILLAN Heidi A. SEEARS Joanna A. WARREN Department of Biological Sciences Lehigh University BethLehem PA 18015 USA

The causes of population differentiation can provide insight into the origins of early barriers to gene flow. Two key drivers of population differentiation are geographic distance and local adaptation to divergent selective environments. When reproductive isolation arises because some populations of a species are under selection to avoid hybridization while others are not, population differentiation and even speciation can result. Spadefoot toad populations Spea multiplicata that are sympatric with a congener have undergone reinforcement. This reinforcement has resulted not only in increased reproductive isolation from the congener, but also in the evolution of reproductive isolation from nearby and distant conspecific allopatric populations. We used multiple approaches to evaluate the contributions of geographic distance and divergent selective environments to population structure across this regional scale in S. multiplicata, based on genotypes from six nuclear microsatellite markers. We compared groups of populations varying in both geographic location and in the presence of a congener. Hierarchical F-statistics and results from cluster analyses and discriminant analyses of principal components all indicate that geographic distance is the stronger contributor to genetic differentiation among S. multiplicata populations at a regional scale. However, we found evidence that adaptation to divergent selective environments also contributes to population structure. Our findings highlight how variation in the balance of evolutionary forces acting across a species＇ range can lead to variation in the relative contributions of geographic distance and local adaptation to population differentiation across different spatial scales.

关键词： cascade reinforcement character displacement reproductive isolation spatial scale Spea multipficata speciation

DPCM-based vibration sensor data compression and its effect on structural system identification

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Earthquake Engineering and Engineering Vibration 2005年第1期4卷 153-163页

作者：张云峰李健 Department of Civil & Environmental Engineering Lehigh University Bethlehem PA 18015 USAAssistantProfessor Department of Civil & Environmental Engineering Lehigh University Bethlehem PA 18015 USA Graduate Researcher

Due to the large scale and complexity of civil infrastructures, structural health monitoring typically requires a substantial number of sensors, which consequently generate huge volumes of sensor data. Innovative sensor data compression techniques are highly desired to facilitate efficient data storage and remote retrieval of sensor data. This paper presents a vibration sensor data compression algorithm based on the Differential Pulse Code Modulation (DPCM) method and the consideration of effects of signal distortion due to lossy data compression on structural system identification. The DPCM system concerned consists of two primary components: linear predictor and quantizer. For the DPCM system considered in this study, the Least Square method is used to derive the linear predictor coefficients and Jayant quantizer is used for scalar quantization. A 5-DOF model structure is used as the prototype structure in numerical study. Numerical simulation was carried out to study the performance of the proposed DPCM-based data compression algorithm as well as its effect on the accuracy of structural identification including modal parameters and second order structural parameters such as stiffness and damping coefficients. It is found that the DPCM-based sensor data compression method is capable of reducing the raw sensor data size to a significant extent while having a minor effect on the modal parameters as well as second order structural parameters identified from reconstructed sensor data.

关键词： data compression instrumentation linear predictor modal parameters sensor system identification vibration

Web C: toward a portable framework for deploying legacy code in web browsers

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Science China(Information Sciences) 2015年第7期58卷 113-127页

作者： YIN Jie TAN Gang BAI XiaoLong HU ShiMin Department of Computer Science and Technology Tsinghua University Department of Computer Science and Engineering Lehigh University

For security, most web applications are developed in some type-safe language, such as Java Script or Java. However, there is a huge amount of legacy codes developed in unsafe languages, which provide rich functionality and are more efficient than their type-safe counterparts. To allow browsers to incorporate type-safe components in a secure way, previous approaches use the software-based fault isolation(SFI) to isolate untrusted legacy code. The SFI approach performs machine-code transformation for security, but the downside is the loss of architecture independence. We propose Web C, a system that allows legacy code transmitted over the web via the Low Level Virtual Machine(LLVM) bitcode format. The untrusted bitcode is transformed by Web C into code in the Web C security language, which enforces both memory isolation and control-flow integrity. Compared with previous approaches, Web C is more portable, provides stronger security, and allows more flexible memory management. Experimental results show that the average runtime overhead of Web C is modest.

关键词： Web C software fault isolation symbol link shadow memory area portable

Resonant Raman scattering in GaN single crystals and GaN-based heterostructures: feasibility for laser cooling

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Chinese Optics Letters 2013年第1期11卷 63-71页

作者： Yujie J. Ding Jacob B. Khurgin Department of Electrical and Computer Engineering Lehigh University Department of Electrical and Computer Engineering The Johns Hopkins University

The recent progress on Raman scattering in GaN single crystals and GaN/A1N heterostructures is re- viewed. Anti-Stokes Raman scattering is used to determine electron-phonon scattering time and decay time constant for longitudinal-opticat phonons. In a typical high electron mobility transistor based on GaN/A1N heterostructures, strong resonances are reached for the first-order and second-order Raman scattering processes. Therefore, both Stokes and anti-Stokes Raman intensities are dramatically enhanced. The feasibility for laser cooling of a nitride structure is studied. A further optimization will enable us to reach the threshold for laser cooling. Raman scattering have potential applications in up-conversion lasers and laser cooling of nitride ultrafast electronic and optoelectronic devices.

关键词： GaN Ra Resonant Raman scattering in GaN single crystals and GaN-based heterostructures feasibility for laser cooling

Ductility demands on buckling-restrained braced frames under earthquake loading

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Earthquake Engineering and Engineering Vibration 2003年第2期2卷 255-268页

作者： Larry A.Fahnestock Richard Sause James M.Ricles Le-Wu Lu Department of Civil and Environmental Engineering ATLSS CenterLehigh UniversityBethlehemPennsylvaniaUSA Graduate Research Assistant Department of Civil and Environmental Engineering ATLSS CenterLehigh UniversityBethlehemPennsylvaniaUSA Professor

Accurate estimates of ductility demands on buckling-restrained braced frames(BRBFs)are crucial to performance-based design of *** analytical study on the seismic behavior of BRBFs has been conducted at the ATLSS Center,lehigh university to prepare for an upcoming experimental *** analysis program DRAIN-2DX was used to model a one-bay,four-story prototype BRBF including material and geometric *** buckling- restrained brace(BRB)model incorporates both isotropic and kinematic *** static pushover and time- history analyses were performed on the prototype *** objectives for the BRBs were defined and used to evaluate the time-history analysis *** emphasis was placed on global ductility demands and ductility demands on the *** demands were compared with anticipated ductility *** analysis results,along with results from similar previous studies,are used to evaluate the BRBF design provisions that have been recommended for codification in the United *** results show that BRB maximum ductility demands can be as high as 20 to *** demands significantly exceed those anticipated by the BRBF recommended *** from the static pushover and time- history analyses are used to demonstrate why the ductility demands exceed those anticipated by the recommended provisions. The BRB qualification testing protocol contained in the BRBF recommended provisions is shown to be inadequate because it requires only a maximum ductility demand of at most *** to the testing protocol are recommended.

关键词： buildings buckling-restrained braced frames buckling-restrained braces structural response seismic response ductility demand seismic codes and standards

On the Methods of Beam Direction and MisorientationAngle/Axis Determination by Systematic Tilt

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Journal of Materials Science & Technology 1999年第5期15卷 410-414页

作者： Rong, YH He, G Chen, SP Hu, GX Gao, M Wei, RP Shanghai Jiao Tong univ Sch Mat Sci & Engn Shanghai 200030 Peoples R China lehigh univ Dept Mech Engn & Mech Bethlehem PA 18015 USA

The methods for determining electron beam direction and misorientation angle/axis of grain boundaries are described in this paper. The present methods are based on a series of diffraction spot patterns obtained by systematic tilt of the crystal, combined with simple mathematical calculations. Instead of the use of Kikuchi patterns, the limitations resulting from the visibility or sharpness of Kikuchi lines and the number of Kikuchi pole(s) existed are avoided and a sufficient accuracy of determination has been achieved.

关键词： Transmission electron microscopy

Photoluminescence properties and energy transfer in Y_2O_3:Eu^(3+) nanophosphors

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Chinese Physics B 2014年第5期23卷 568-573页

作者：崔航朱培芬祝洪洋李红东崔啟良 State Key Laboratory of Superhard Materials Jilin University Department of Electrical and Computer Engineering Lehigh University

The photoluminescence （PL） properties of Y203 ：Eu^3＋ nanophosphors were systematically investigated with the goal of improving the color quality and quantum efficiency of Y2O3 ：Eu^3＋ nanophosphors for potential applications in nano-scale devices. The emission spectra, excitation spectra and fluorescence decay curves were employed to trace the energy transfer process from Eu^3＋ at C3i site to Eu^3＋ at C2 site. The experimental results show that the energy transfer process becomes more and more efficient with the increase in the Eu^3＋ concentration. The emission of Eu^3＋ at C2 site is favorable because it has high radiative efficiency and better color quality. The successful suppress of the emission Eu^3＋ at C3i is especially important for its applications in general illumination or display technology. The quantum efficiency and color quality of Y203 ：Eu^3＋ can be improved by controlling the energy transfer between the Eu^3＋ at S6 site and Eu^3＋ at C2 site.

关键词： Y2O3 :Eu^3+ photoluminescence energy transfer fluorescence lifetime

Solutions to Some Open Problems in Fluid Dynamics

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Chinese Annals of Mathematics,Series B 2008年第2期29卷 179-198页

作者： Linghai ZHANG Department of Mathematics Lehigh University 14 East Packer Avenue Bethlehem Pennsylvania 18015

Let u=u（x,t,uo）represent the global solution of the initial value problem for the one-dimensional fluid dynamics equation ut-εuxxt＋δux＋γHuxx＋βuxxx＋f（u）x=αuxx,u（x,0）=uo（x）, whereα〉0,β〉0,γ〉0,δ〉0 andε〉0 are *** equation may be viewed as a one-dimensional reduction of n-dimensional incompressible Navier-Stokes equations. The nonlinear function satisfies the conditions f（0）=0,｜f（u）｜→∞as ｜u｜→∞,and f∈C^1（R）,and there exist the following limits Lo=lim sup/u→o f（u）/u^3 and L∞=lim sup/u→∞ f（u）/u^5 Suppose that the initial function u0∈L^I（R）∩H^2（R）.By using energy estimates,Fourier transform,Plancherel＇s identity,upper limit estimate,lower limit estimate and the results of the linear problem vt-εv（xxt）＋δvx＋γHv（xx）＋βv（xxx）=αv（xx）,v（x,0）=vo（x）, the author justifies the following limits（with sharp rates of decay） lim t→∞[（1＋t）^（m＋1/2）∫｜uxm（x,t）｜^2dx]=1/2π（π/2α）^（1/2）m!!/（4α）^m[∫R uo（x）dx]^2, if∫R uo（x）dx≠0, where 0!!=1,1!!=1 and m!!=1·3…（2m-3）…（2m-1）.Moreover lim t→∞[（1＋t）^（m＋3/2）∫R｜uxm（x,t）｜^2dx]=1/2π（x/2α）^（1/2）（m＋1）!!/（4α）^（m＋1）[∫Rρo（x）dx]^2, if the initial function uo（x）=ρo′（x）,for some functionρo∈C^1（R）∩L^1（R）and∫Rρo（x）dx≠0.

关键词： Exact limits Sharp rates of decay Fluid dynamics equation Global smooth solutions