Crest Length Research Articles

Analysis of spatial and temporal evolution of disturbance waves and ripples in annular gas–liquid flow

Wavy structure of liquid film in downward annular gas–liquid flow is studied with high-speed laser-induced fluorescence technique. Film thickness measurements are resolved in both longitudinal distance and time with high spatial and temporal resolution. A method is developed to identify the characteristic lines of individual disturbance waves. Change of frequency of disturbance waves with downstream distance is modelled based on the obtained distributions of the disturbance waves by velocity and separation time. Using obtained characteristic lines further investigation of ripples’ properties is performed in reference system moving with the disturbance wave. As a result, velocities, amplitudes and frequencies of ripples are measured with relation to the distance from disturbance waves. Fast ripples travelling over crests of disturbance waves and slow ripples travelling over back slopes of disturbance waves and over the base film are studied separately. Besides, the average length of crest and back slope of disturbance waves were measured.

Effects of dietary fracture toughness and dental wear on chewing efficiency in geladas (Theropithecus gelada).

Chewing efficiency has been associated with fitness in mammals, yet little is known about the behavioral, ecological, and morphological factors that influence chewing efficiency in wild animals. Although research has established that dental wear and food material properties independently affect chewing efficiency, few studies have addressed the interaction among these factors. We examined chewing efficiency, measured as mean fecal particle size, as a function of seasonal shifts in diet (and corresponding changes in food fracture toughness) in a single breeding population of a grazing primate, the gelada monkey, at Guassa, Ethiopia. We also measured dental topographic traits (slope, angularity, and relief index) and relative two- and three-dimensional shearing crest lengths in a cross-sectional wear series of gelada molars. Chewing efficiency decreased during the dry season, a pattern corresponding to the consumption of foods with higher fracture toughness. Older individuals experienced the most pronounced decreases in chewing efficiency between seasons, implicating dental wear as a causal factor. This pattern is consistent with our finding that dental topographic metrics and three-dimensional relative shearing crest lengths were lowest at the last stage of wear. Integrating these lines of behavioral, ecological, and morphological evidence provides some of the first empirical support for the hypothesis that food fracture toughness and dental wear together contribute to chewing efficiency. Geladas have the highest chewing efficiencies measured thus far in primates, and may be analogous to equids in their emphasis on dental design as a means of particle size reduction in the absence of highly specialized digestive physiology.

Plumage ornaments in male Northern Lapwings Vanellus vanellus may not be a reliable indicator of their mating success

Conspicuous morphological traits that signal aspects of physical state of the owner may be used as cues in mate choice, leading to sexual selection of ornamental traits. In birds, colour patterns as well as structural attributes may constitute ornaments affecting mate choice. In the breeding season, Northern Lapwing Vanellus vanellus males possess long crests, contrast-rich black and white facial markings, a black breast, and a shining greenish dorsal side. In non-breeding and juvenile plumages, and in females, crests are shorter, facial patterns have less clear contrasts, and breast and dorsal side possess varying amounts of light fringes. Depending onmoult energetics in latewinter/early spring, when males acquire their breeding plumage, the state of these characters could potentially signal male condition to females prospecting for mates. We examined if these traits correlated with male mating success in this polygynous species, predicting males with the most expressed ornamental characters (a) tomate earlier and (b) to gain more mates.Trait states were ranked for 31 males of which breeding phenology and number of mates were known. No correlationwas found between trait expression and date of first egg laid on the territory and number of mates did not correlate with trait expression. Thus, the study did not confirm that females use crest length, breast blackness and face contrasts or lack of dorsal fringes as cues in their mate choice. This could be because the elaborate traits do not have an ornamental function important for femalemate choice, but experimental studies would be needed to rigorously test this hypothesis.

A Note on the Phillips Spectral Framework for Ocean Whitecaps*

Abstract There has been a recent upsurge in interest in quantifying kinematic, dynamic, and energetic properties of wave breaking in the open ocean, especially in severe sea states. The underpinning observational and modeling framework is provided by the seminal paper of O. M. Phillips. In this note, a fundamental issue contributing to the scatter in results between investigators is highlighted. This issue relates to the choice of the independent variable used in the expression for the spectral density of the mean breaking crest length per unit area. This note investigates the consequences of the different choices of independent variable presently used by various investigators for validating Phillips model predictions for the spectral density of the breaking crest length per unit area and the associated spectral breaking strength coefficient. These spectral measures have a central role in inferring the associated turbulent kinetic energy dissipation rate and the momentum flux to the upper ocean from breaking wave observations.

Sonographic anatomy of the pubic symphysis in healthy nulliparous women.

Pregnancy-related symphyseal pain is a condition commonly encountered by clinicians but its pathogenesis is poorly understood. The pubic symphysis is readily visualized with ultrasound, yet the normal sonographic anatomy of the joint has not been accurately documented. This study aimed to describe the anatomy of the pubic symphysis in healthy, nulliparous women using ultrasound. An experienced and inexperienced sonographer scanned the joint in 30 female volunteers (mean age 26 years). Interobserver and intraobserver reliability of ultrasound measurements were examined and the accuracy of these measurements was validated by ultrasound and dissection of six female cadaver pelves (mean age 75 years). In healthy young women, pubic symphysis morphology varied, and six categories of anterosuperior joint shape were defined. Mean values of several anatomic parameters were obtained in supine and standing positions: joint width (widest 10.1 mm, narrowest 2.6 mm); superior pubic ligament (SPL) length and depth (41.4 and 3.4 mm, respectively); and pubic crest length (left 24.4 mm, right 24.4 mm). Statistically significant relationships between SPL width and depth and anthropometric variables (body mass index, pelvic width, and body fat percentage) were established. Larger ultrasonographic measurements, such as wide joint width and SPL length, could be measured more reliably than smaller measurements, such as narrow joint width and SPL depth, in both healthy volunteers and cadavers. Findings from this study provide normative reference data for examination of the pubic symphysis in pregnant women and may therefore be relevant to understand pregnancy-related symphyseal pain.

Generation sites of internal solitary waves in the southern Taiwan Strait revealed by MODIS true-colour image observations

Based on 12 years (2000–2011) of Moderate Resolution Imaging Spectroradiometer (MODIS) true-colour images, statistical characteristics of internal solitary waves (ISWs) in the southern Taiwan Strait were studied. Two types of ISWs with a distinct scale of wave crest length and geographic distributions were identified: Type-I waves have larger wave crest lengths and span a large area from the southern Taiwan Strait to the northern South China Sea, while Type-II waves have smaller wave crest lengths and appear only at the southeastern corner of the Taiwan Strait. Further analyses based on an empirical model of ISW propagation and on the calculations of the depth-integrated internal tide-generating body force suggested that Type-I waves mainly originate from the Luzon Strait, while Type-II waves are locally generated at the shelf break in the southeastern corner of the Taiwan Strait.

Investigation of Dynamic Characteristics of Concrete Dam by Underwater Blasts in the Head Race of the Reservoir under Field Conditions

Results are presented for full-scale dynamic investigations of a concrete dam with a height of 120 m and crest length of 1040 m by excitation of its free vibrations with pulsed loads created by underwater blasts in the reservoir in advance of the thrust face of the dam. Use of this method made it possible to determine the natural frequencies, vibration forms, vibration decrements, and the dynamic elastic modulus of the concrete in the dam.

원형으로 배열된 다수 부이에 의한 파랑에너지 추출

The wave power, extracted from a circular array of small power buoys, is investigated under the potential theory. It is assumed that the buoy's radius, the draft, and the separation distance are much smaller than the water depth, the wave length, and the radius of a circular deployment area. The boundary value problem involving the macro-scale boundary condition on the mean surface covered by buoys is solved using the eigenfunction expansion method. The capture width, which is defined as the ratio of the extracted power to the wave power per unit length of the incident wave crest, is assessed for various combinations of packing ratio, radius of a circular array, and PTO damping coefficient. It is found that the circular array deployment is more effective in the viewpoint of efficiency than the single large buoy of the same total displaced volume. 핵심용어: wave energy converter, circular array, extracted power, eigenfunction expansion method, capture width, íŒŒë ¥ë°œì „ìž¥ì¹˜, 원형 배열, 추출 파워, ê³ ìœ í•¨ìˆ˜ì „ê°œë²•, 취득 폭

Characterization of the Supinator Tubercle for Lateral Ulnar Collateral Ligament Reconstruction.

Background:Lateral ulnar collateral ligament (LUCL) reconstruction requires proper understanding and identification of anatomic structures about the lateral elbow. The insertion site of the LUCL is based on the supinator tubercle.Purpose:To characterize the supinator tubercle relative to other surrounding anatomic landmarks.Study Design:Descriptive laboratory study.Methods:Computed tomography (CT) scans of 10 adult elbows were retrospectively reviewed. These CT scans were converted into patient-specific 3-dimensional computer models. Using a user-defined coordinate system, an ulnar Cartesian coordinate system was defined with anatomic landmarks as reference points to standardize the position of each model. The length of the supinator crest was measured. Following this, the crest was examined for a distinct raised bony tuberosity that would be consistent with the supinator tubercle. If no distinctly raised tubercle was noted, the most prominent appearing location of the crest distal to the radial notch was considered the tubercle. The distance from the proximal radial head junction to the supinator tubercle was recorded. Finally, the distance from the supinator crest at the radial head junction to the posterior cortex in the sagittal plane was measured.Results:The supinator tubercle was found to be prominent in 5 of 10 ulnar models. The supinator crest was 43.59 ± 13.28 mm long, and the supinator tubercle lateral extrusion was 5.60 ± 0.90 mm. The distance between the radial head junction and the supinator tubercle was found to be 15 ± 2.37 mm, and the distance from the supinator crest at the radial head junction to the posterior cortex was 10.25 ± 2.07 mm.Conclusion:The supinator tubercle is frequently not prominent or easily recognizable. Its relationship to other structures is of value. The proximal border of the radial head, residing 15 mm proximal to the most predictable location of the supinator tubercle, is a useful landmark when drilling tunnels during LUCL reconstructions.Clinical Relevance:Results of this study may aid proper anatomic LUCL reconstruction.

SAR observing large-scale nonlinear internal waves in the White Sea

The compiled archive of synthetic aperture radar (SAR) images acquired by the Advanced SAR (ASAR) onboard the Envisat satellite over the White Sea during the extended summer periods (May–September) between 2007 and 2011, provides the first detailed analysis of 2-D patterns of internal waves (IWs) in the White Sea. Unambiguously, the primary region of IW activity is the southwestern (SW) Gorlo Strait (GS). IW packets emerging from this area are regularly observed to reach crest lengths up to 200km, and also to propagate a few hundred kilometers from their origin. Model results confirm that large-scale IWs can be generated every tidal cycle and are able to cross the entire sea. As suggested, the source of these packets is governed by the intense dynamics of the frontal zone in the tidal cycle over local complex bottom. As further revealed, these large-scale IWs cascade into intense large-amplitude short IW packets on the shoaling White Sea shelf, significantly impacting vertical turbulent exchange and the overall hydrology.

A STUDY ON PERFORMANCE OF AIR-TO-AIR HEXAGONAL PLASTIC PLATE HEAT EXCHANGER

In this research, 3D analysis model of air-to-air hexagonal plastic plate heat exchanger (HX) is developed numerically and compared with the available experiment. The heat transfer performances with polypropylene (PP) and aluminum (Al) indicate that PP HX can transfer heat as good as Al under this HX application. On the basis of this model, the crest length, the crest pitch and the inlet and outlet chamfer size are designed as three key parameters to improve the heat transfer performances of HX.

Discharge Characteristics of a Trapezoidal Labyrinth Side Weir with One and Two Cycles in Subcritical Flow

AbstractA labyrinth weir provides an effective way to increase weir crest length without an associated increase in structure width. Labyrinth side weirs have important advantages compared to conventional side weirs in term of discharge capacity, length of the channel opening, and nappe height over the weir. A different equation is needed for each number of cycles to determine the discharge coefficient of labyrinth side weir. Unlike labyrinth spillways, one or two cycles are mostly sufficient for the labyrinth side weirs to accommodate the required discharge. This study examines the hydraulic characteristics of trapezoidal labyrinth side weirs with two cycles in a subcritical situation and the effect on discharge capacity of using single or multiple cycles in side weirs with the same length openings and crest lengths. The results show that a side weir with one cycle has slightly greater discharge coefficient. In addition, the variation of the discharge capacity was investigated for both one-cycle and two-c...

Submerged Flows over Rectangular Weirs of Finite Crest Length

AbstractThis work presents a critical analysis of submerged flow over rectangular weirs of finite crest length. For finite crest length weirs, because the existing data sets are not extensive, new experiments for these weirs with sharp-edged and rounded crest were conducted. Based on these data, a diagram is developed to show the variation of the normalized tailwater depth with ho/L where ho is the free flow head and L is the length of the crest, to predict the onset of submergence or the modular limit. Water surface profiles of flow over weirs of finite crest length with square-edge and rounded crests were plotted to study the formation of waves in modular and submerged conditions. Characteristics length scales such as wave length and amplitude at the modularity limit and the location of the first trough downstream of the weir were measured to generalize surface profiles at different flow discharges. An empirical equation for the discharge reduction factor was also formulated. This equation has two expon...

北太平洋柔鱼两个群体角质颚形态差异及生长特性研究

PDF HTML阅读 XML下载 导出引用 引用提醒 北太平洋两个柔鱼群体角质颚形态及生长特征 DOI: 10.5846/stxb201301110083 作者: 作者单位: 上海海洋大学海洋科学学院;上海海洋大学海洋科学学院,上海海洋大学大洋渔业资源可持续开发省部共建教育部重点实验室;上海海洋大学大洋渔业资源可持续开发省部共建教育部重点实验室;上海海洋大学海洋科学学院;上海海洋大学海洋科学学院;上海海洋大学海洋科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（NSFC41276156）；国家863计划（2012AA092303）；上海市科技创新行动计划（12231203900） Morphology and growth of beaks in two cohorts for neon flying squid (Ommastrephes bartramii) in the North Pacific Ocean Author: Affiliation: College of Marine Sciences,Shanghai Ocean University;College of Marine Sciences,Shanghai Ocean University,The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources,Ministry of Education;College of Marine Sciences,Shanghai Ocean University;College of Marine Sciences,Shanghai Ocean University;College of Marine Sciences,Shanghai Ocean University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:根据2011年5-11月我国鱿钓船在北太平洋海域（150°E-176°W）采集的渔获物样本，对柔鱼两个群体各项角质颚外部形态和生长进行分析。结果表明，角质颚参数值雌性均大于雄性，冬春生群体雌雄参数值间差异要大于秋生群体；角质颚各项参数值中，上头盖长（Upper Hood length， UHL）、上脊突长（Upper Crest length， UCL）、下脊突长（Lower crest length， LCL）、下翼长（Lower Wing length， LWL）与胴长、体重分别呈线性和指数关系（P < 0.01）。主成分分析认为，秋生群体雌、雄个体角质颚第一主成分因子均为UCL/ML，第二主成分因子均为UWL/ML，冬春生群体雌、雄个体角质颚第一主成分因子分别ULWL/ML和LLWL/ML，第二主成分分别与URW/ML和LRL/ML，这些这成分因子代表了角质颚水平和垂直方向上的生长特征。两个群体的雌性个体角质颚形态上存在显著差异，但雄性个体间差异不显著。方差分析（ANOVA）表明，2个群体不同胴长组间的角质颚形态均存在着显著差异（P < 0.01）；LSD法分析认为，除了秋生群体雌性个体上头盖长、上喙长、下头盖长、下喙宽在胴长组<250 mm和250-300 mm间不存在差异外，其他组之间均有着显著差异（P < 0.01）。同一群体不同性腺成熟度等级间的柔鱼角质颚形态存在显著差异（P < 0.01），但性成熟度为Ⅰ期和Ⅱ期时2个群体角质颚各项形态指标均存在显著差异（P < 0.01），而性成熟度Ⅲ期时则不存在差异（P > 0.05）。研究认为，不同群体的柔鱼角质颚形态及生长特征均存在着一定差异。 Abstract:Neon flying squid Ommastrephes bartramii an economically and ecologically important cephalopod, is one of main targeted species in the Chinese jigging squid fishery. In this paper, based on the samples collected by the Chinese squid jigging vessels during May to November in 2011 in the high seas of North Pacific Ocean (150°E-176°W), we compared differences in morphology and growth characteristics of beaks for two cohorts of O. bartramii. The results showed that females dominated in both the fall cohort and the winter-spring cohort. The morphological values in females' beak were larger than those of males, and the difference in these parameters between males and females in the winter-spring cohort was greater than that for the fall cohort. The upper hood length (UHL), upper crest length (UCL), lower crest length (LCL), lower wing length (LWL) had significant linear correlations with mantle length (ML) and significant exponential relationships with body weight (BW)(P < 0.01). The principal component analysis showed that the first principal component for the beak morphology of the fall cohort was related to UCL/ML of both males and females, and the second was UWL/ML. While for the winter-spring cohort, the first principal components of beak morphology were ULWL/ML and LLWL/ML, and the seconds were URW/ML and LRL/ML respectively, both represented the growth characteristics in horizontal and vertical directions. The morphology of beak for the two cohorts of female squid had significant differences, but no differences were found for male squid. The ANOVA indicated that the morphology of beak had significant differences among different ML groups(P < 0.01). However, the Least Significant Difference (LSD) analysis showed that the significant difference existed between the groups(P < 0.01)for all the morphological measurements except for UHL, URL, LHL and Lower Rostral width within the ranges of 250mm ML and 250-300mm ML for females of fall cohort. For the same corhot, the morphology of beak also had significant differences among different sex maturity stages(P < 0.01). The maturity stages I and II showed significant difference between the two cohorts, but no difference was found for stage III. In conclusion, the morphology and growth of beak for the two cohorts of O. bartramii differed with cohort, mantle length and sexual maturity. 参考文献 相似文献 引证文献

New Stage-Discharge Relationship for Weirs of Finite Crest Length

AbstractThe flow process of weirs of finite crest length is analyzed on the basis of the dimensional analysis and incomplete self-similarity theory. The crest length is incorporated in the functional stage-discharge relationship for weirs of finite crest length. The theoretically deduced stage-discharge formula was then calibrated using the experimental data compiled in this research. According to the current experimental data it is also concluded that the performance of the proposed stage-discharge formula is better than the previous dimensional stage-discharge formulae. Also, the proposed stage-discharge formula is applicable for all types of the weirs, i.e., long-crested, broad-crested, short-crested, and sharp-crested ones.

Discussion of “Discharge Characteristics of Weirs of Finite Crest Length with Upstream and Downstream Ramps” by Amir Hossein Azimi, Nallamuthu Rajaratnam, and David Z. Zhu

C. Di Stefano; V. Ferro; and M. Bijankhan, Aff.M.ASCE Researcher, Dipartimento di Scienze Agrarie e Forestali, Universita degli Studi di Palermo, Viale delle Scienze, Palermo 90128, Italy. E-mail: costanza.distefano@unipa.it Full Professor, Dipartimento di Scienze Agrarie e Forestali, Universita degli Studi di Palermo, Viale delle Scienze, Palermo 90128, Italy (corresponding author). E-mail: vito.ferro@unipa.it Ph.D. Candidate, Irrigation and Reclamation Engineering Dept., Univ. of Teheran Karaj, P.O. Box 31587-4111, Karaj 31587-77871, Iran. E-mail: bijankhan@ut.ac.ir

Vortex generation by deep-water breaking waves

AbstractThe connection between wave dissipation by breaking deep-water surface gravity waves and the resulting turbulence and mixing is crucial for an improved understanding of air–sea interaction processes. Starting with the ensemble-averaged Euler equations, governing the evolution of the mean flow, we model the forcing, associated with the breaking-induced Reynolds shear stresses, as a body force describing the bulk scale effects of a breaking deep-water surface gravity wave on the water column. From this, we derive an equation describing the generation of circulation, $\Gamma $, of the ensemble-average velocity field, due to the body force. By examining the relationship between a breaking wave and an impulsively forced fluid, we propose a functional form for the body force, allowing us to build upon the classical work on vortex ring phenomena to both quantify the circulation generated by a breaking wave and describe the vortex structure of the induced motion. Using scaling arguments, we show that $\Gamma = \alpha {(hk)}^{3/ 2} {c}^{3} / g$, where ($c, h, k$) represent a characteristic speed, height and wavenumber of the breaking wave, respectively, $g$ is the acceleration due to gravity and $\alpha $ is a constant. This then allows us to find a direct relationship between the circulation and the wave energy dissipation rate per unit crest length due to breaking, ${\epsilon }_{l} $. Finally, we compare our model and the available experimental data.

Wave breaking in developing and mature seas

In response to the growing need for robust validation data for Phillips (1985) breaking wave spectral framework, we contribute new field results observed from R/P FLIP for the breaking crest length distributions, Λ, during two different wind‐wave conditions, and breaking strength during one wind‐wave condition. The first experiment in Santa Barbara Channel had developing seas and the second experiment in the central Pacific Ocean south of Hawaii had mature seas. These are among the first experiments to use dissipation rate measurements probing up into the breaking crest together with simultaneous measurements of breaking crest length distributions. We directly measured the effective breaking strength parameter to be in mature seas with wave age, , of 40–47. We also found that the velocity scale of the breaking dissipation rate peak decreases with increasing wave age. Further, the breaking crest length spectrum falls off slower than the behavior predicted by Phillips (1985). The integrated dissipation rate was consistently higher for mature seas compared to developing seas due to higher energy and momentum fluxes from the wind.

Variations in landform definition: a quantitative assessment of differences between five maps of glacial cirques in the Ţarcu Mountains (Southern Carpathians, Romania)

Geomorphological mapping is an important tool in geomorphology and related disciplines, yet it depends on the expertise and experience of the practitioner. The reliability of the technique and its products has not been subject to sufficient quantitative evaluation. In this study, we evaluated the magnitudes of differences in mapping glacial cirques between five maps in a mountainous area in the Southern Carpathians in Romania and attempted to identify the causes of the differences observed and possible solutions for obtaining more objective geomorphological mapping. We found notable differences between maps (in paired sample comparisons in all cases for the total values in each dataset) in the number of cirques, the total area and in headwall crest lengths. Statistically significant differences were found between datasets based on different semantic models of glacial cirques. Differences in mapping arise mainly from differences in conceptualising glacial cirques. When mapping relied on an explicit semantic model (a geomorphometric approach), differences were significantly smaller. Therefore, explicit semantic models of landforms based on land surface variables can result in more similar maps and further facilitate the transition from manual delineation to automated recognition of landforms from Digital Elevation Models (DEMs).

Analysis of beak morphology of Loligo beka in the East China Sea

Using data collected from the bottom trawl surveys conducted in the East China Sea during September 2010 and May 2011,this paper presents beak morphology of Loligo beka found in this region,and analyzes the relative stability of indices related to beak length,mantle length,and relative growth.Length measurements ob-tained for the upper beak,including the rostrum length(RL),hood length(HL),crest length(CL),wing length(WL),and wing width(WW) showed a higher variability than those corresponding to the lower beak.Hood growth in relation to that of the rostrum was isometric,while growth rates relative to the crest and the wing were allomet-ric.Beak length indices were clearly affected by individual growth patterns.Beak length indices increased linearly with the mantle length.However,the ratios of RL/HL,RL/CL,HL/CL remained very stable,and did not alter ob-servably with changes in mantle length or body weight.These ratios could be used as stable beak indices of the morphological characteristics of Loligo beka.