Cross-sectional Area Distribution Research Articles

Regional patterns and local variations of sediment distribution in the Hudson River Estuary

The Hudson River Benthic Mapping Project, funded by the New York State Department of Environmental Conservation, resulted in a comprehensive data set consisting of high-resolution multibeam bathymetry, sidescan sonar, and sub-bottom data, as well as over 400 sediment cores and 600 grab samples. This detailed data set made it possible to study the regional pattern and the local variations of the sediment distribution in the Hudson River Estuary. Based on these data we describe the distribution of sediment texture and process-related sedimentary environments for the whole 240-km long estuary together with along-river variations of depth, cross-sectional area, and grain size distribution. We compare these parameters with changes in surrounding geology and tributary input and, as a result, divide the Hudson River Estuary in eight sections with distinct combinations of channel morphology, bedrock type, sediment texture, and sediment dynamics. The regional sediment distribution consists of marine sand-dominated sediments near the ocean end of the estuary, a large, mud-dominated central section, and fluvial sand-dominated sediments in the freshwater section of the Hudson River Estuary. This regional trend is highly modified by small-scale variations in the sediment distribution. These local variations are controlled by changes in morphology, bedrock, and tributary input, as well as by anthropogenic modifications of the estuary. In some areas these local variations are larger than the overall trend in sediment distribution and control the actual sediment type, as well as the condition of erosion and deposition in the estuary.

볼류트 형상이 원심 펌프의 성능에 미치는 영향에 대한 수치 해석적 연구

In this study, the effects of volute area distribution on the performance of a centrifugal pump were numerically studied using a commercial CFD code. To reduce the shutoff head, maintaining head and efficiency at a design flow rate, the flat head-capacity characteristic curves in which the head varies only slightly with capacity from shutoff to design capacity are frequently required. In order to control the shutoff head of a pump, several volute cross-sectional area distributions were proposed as a main parameter with the same impeller geometry. The calculation results show that the slope of the performance characteristic curve of the centrifugal pump can be controlled by modifying the area distribution from volute tongue to volute outlet with fixed volute outlet area and also varied volute outlet area.

Age and sex affect human muscle fibre adaptations to heavy‐resistance strength training

This study assessed age and sex effects on muscle fibre adaptations to heavy-resistance strength training (ST). Twenty-two young men and women (20-30 years old) and 18 older men and women (65-75 years old) completed 9 weeks of heavy-resistance knee extension exercises with the dominant leg 3 days week(-1); the non-dominant leg served as a within-subject, untrained control. Bilateral vastus lateralis muscle biopsies were obtained before and after ST for analysis of type I, IIa and IIx muscle fibre cross-sectional area (CSA) and fibre type distribution. One-repetition maximum (1-RM) strength was also assessed before and after ST. ST resulted in increased CSA of type I, IIa and IIx muscle fibres in the trained leg of young men, type I and IIa fibres in young women, type IIa fibres in older men, and type IIx fibres in older women (all P<0.05). Analysis of fibre type distribution revealed a significant increase in the percentage of type I fibres (P<0.05) along with a decrease in type IIx fibres (P=0.054) after ST only in young women. There were no significant changes in muscle fibre CSA or fibre type distribution in the untrained leg for any group. All groups displayed significant increases in 1-RM (27-39%; all P<0.01). In summary, ST led to significant increases in 1-RM and type II fibre CSA in all groups; however, age and sex influence specific muscle fibre subtype responses to ST.

Alterations in Vessel Size in Twigs Of Quercus Robur and Q. Petraea Upon Defoliation and Consequences For Water Transport Under Drought

In the complex of natural factors responsible for damage to the Central European oak species Quercus robur and Q. petraea, repeated defoliation and drought are considered the most important ones. To investigate the impact of these factors on xylem anatomy and hydraulic conductance, saplings of both species were manually defoliated in the spring of two consecutive years, and equal fractions of defoliated and control saplings were subjected to drought stress in the third year of the study. Defoliation did not significantly reduce the annual ring width of the twigs, but in the twigs of Q. robur it resulted in a significant reduction of the cross-sectional area of early- and latewood vessels, and in a shift in the distribution of the earlywood vessel cross-sectional areas towards smaller size classes in the year after the first defoliation. In the earlywood of Q. petraea twigs, repeated defoliation led to a significant increase in the cross-sectional vessel areas and to a shift in their distribution towards larger size classes. No significant differences in the percentage loss of hydraulic conductance (PLC) occurred between trees that had been defoliated in two successive years prior to the drought experiment and control trees. However, PLC was significantly increased by drought. The different responses of the oak species are attributed to their different capability to recover from the applied stress factors.

Influence of the stereometric and morphometric structure of composite coatings on the hydrogen evolution process

Nickel-based composite coatings, in the matrix of which there is an electrodeposited powder of metals (W, Ti, Mo, Al, etc.) that cannot be easily deposited from aqueous solutions, are of great significance in practical applications. The effectiveness of, e.g., the hydrogen evolution reaction on such coatings is a function of the parameters of their electrolytic production and thermal treatment. Both processes determine the phase composition and structure of the coatings as well as their surface morphology. The surface stereometric structure (SSS) is vital, inter alia, for the effectiveness of hydrogen electroevolution. In this paper, the possibility is shown of characterizing SSS by means of parameters and a functional 3D description of such properties of the coatings as: the distribution of the cross-sectional area of the pores, the area of their development and volume, and their number as a function of depth. Synergism of the stereometric structural parameters' and intermetallic phases' effects on modeling the electrochemical activity of the coatings is shown.

Effect of salbutamol on innervated and denervated rat soleus muscle

The objective of the present investigation was to perform a 14-day time-course study of treatment with salbutamol, a beta2 adrenoceptor agonist, on rat soleus muscle in order to assess fiber type selectivity in the hypertrophic response and fiber type composition. Male Wistar rats were divided into four groups: control (N = 10), treated with salbutamol (N = 30), denervated (N = 30), and treated with salbutamol after denervation (N = 30). Salbutamol was injected intraperitoneally in the rats of the 2nd and 4th groups at a concentration of 0.3 mg/kg twice a day for 2 weeks. The muscles were denervated using the crush method with pean. The animals were sacrificed 3, 6, 9, 12, and 14 days after treatment. Frozen cross-sections of soleus muscle were stained for myosin ATPase, pH 9.4. Cross-sectional area and percent of muscle fibers were analyzed morphometrically by computerized image analysis. Treatment with salbutamol induced hypertrophy of all fiber types and a higher percentage of type II fibers (21%) in the healthy rat soleus muscle. Denervation caused marked atrophy of all fibers and conversion from type I to type II muscle fibers. Denervated muscles treated with salbutamol showed a significantly larger cross-sectional area of type I muscle fibers, 28.2% compared to the denervated untreated muscle. Moreover, the number of type I fibers was increased. These results indicate that administration of salbutamol is able to induce changes in cross-sectional area and fiber type distribution in the early phase of treatment. Since denervation-induced atrophy and conversion from type I to type II fibers were improved by salbutamol treatment we propose that salbutamol, like other beta2 adrenoceptor agonists, may have a therapeutic potential in improving the condition of skeletal muscle after denervation.

On the characteristics of optimum beams with optimum length surrounded by a Winkler’s medium

In this paper an analytical approach is used to optimize a beam surrounded by a Winkler’s medium and laterally loaded by a force at the top. The optimization regards both the distribution of the mass along the beam and the beam length in order to minimize the top displacement. Therefore, after having defined a transversality condition, we implement an algorithm to optimize the length of optimum beams. After having achieved the dimensionless extremals of optimum beams with optimum length, we show that the found solutions describe a central field of moment extremals defined along the beam and with the origin at the top. Having achieved the Jacobi’s condition and the strengthened Legendre’s condition for an extremal of optimum beam length, a sufficient condition for a weak minimum along the beam is also achieved. Besides, a given set of cross-sections whose moment of inertia divided by a dimensioned constant is obtained by raising their area to the same exponent. The optimized distribution of the dimensionless cross-sectional area as well as the dimensionless rigidity of the Winkler’s medium are intrinsic properties of all optimum beams with optimum length whose cross-sections belong to the same set.

Simple Numerical Method to Calculate Pressure Fluctuation Due to Train Passage

This paper proposes a quick method to calculate pressure fluctuation when a train passes. The method is applicable to design of train nose configuration. It takes into consideration only the distribution of cross-sectional area of the train nose as the effect of a train, which is represented as a line monopole souroe concentrated on its axis. The governing equation is expressed in an integral form by using the Green's function. The results obtained by this method were compared with those by a three-dimensional boundary element method (BEM) to confirm the accuracy of the proposed method. The calculation point to be compared is at 12.5 m distant from the train axis. The results by this method were in excellent agreement with those by BEM with 2 to 3% errors. Moreover, we expanded the method to include the effect of a pressure barrier. Comparison with those by BEM showed moderately good agreement with 5 to 30% errors.

On the stability of Kelvin cell foams under compressive loads

It has been previously shown that the nonlinearity exhibited in the compressive response of open cell foams is governed by cell ligament buckling. Significant insight into this behavior can be gained by idealizing such foams as periodic, space-filling Kelvin cells assigned several of the geometric characteristics of actual foams. The cells are elongated in the rise direction; the ligaments are assumed to be straight, to have Plateau border cross sections, and nonuniform cross sectional area distribution. The mechanical response of such foams can be established using models of a characteristic cell assigned appropriate periodicity conditions. The ligaments are modeled as shear deformable beams. The periodicity of this microstructure allows the use of Bloch wave theory to conduct the search for the critical state efficiently. The method tailored to the present microstructure is outlined. It is subsequently used to establish the critical states for uniaxial and a set of triaxial loadings. A rich variety of buckling modes are identified which are affected by the anisotropy and the mutliaxiality of the applied loads. Under some loadings the critical modes have long wavelengths which are shown to lead to unstable postbuckling behavior involving localization. Under other loading conditions the modes are either local to the characteristic cell or involve an assemblage of a few such cells. For the cases analyzed local modes were found to have a stable postbuckling response.

A fractal analysis of the radial distribution of bronchial capillaries around large airways

We analyzed published measurements of the bronchial circulation and airway wall (Anderson JC, Bernard SL, Luchtel DL, Babb AL, and Hlastala MP. Respir Physiol Neurobiol 132: 329-339, 2002) and determined that the radial distribution of bronchial capillary cross-sectional area was fractal. We limited our analysis to bronchial capillaries, diameter < or =10 mum, that resided between the epithelial basement membrane and adventitia-alveolar boundary, the airway wall tissue. Thirteen different radial distributions of capillary-to-tissue area were constructed simply by changing the number of annuli (i.e., the annular size) used to form each distribution. For the 13 distributions created, these annuli ranged in size from to of the size of the airway wall area. Radial distributions were excluded from the fractal analysis if the sectioning procedure resulted in an annulus with a radial thickness less than the diameter of a capillary. To determine the fractal dimension for a given airway, the coefficient of variation (CV) for each distribution was calculated, and ln(CV) was plotted against the logarithm of the relative piece area. For airways with diameter >2.4 mm, this relationship was linear, which indicated the radial distribution of bronchial capillary cross-sectional area was fractal with an average fractal dimension of 1.27. The radial distribution of bronchial capillary cross-sectional area was not fractal around airways with diameter <1.5 mm. We speculated on how the fractal nature of this circulation impacts the distribution of bronchial blood flow and the efficiency of mass transport during health and disease. A fractal analysis can be used as a tool to quantify and summarize investigations of the bronchial circulation.

Compressive response of open-cell foams. Part I: Morphology and elastic properties

This study is concerned with the understanding and modeling of the compressive response of open cell foams. The response starts with a nearly linear elastic regime which terminates into a limit load followed by an extensive load plateau. The plateau, which is responsible for the excellent energy absorption capacity of foams, is followed by a second stiff branch. Results from polyester urethane open cell foams with relative densities of about 0.025 are used to illustrate this behavior using experiments coupled with several levels of modeling. The experiments include characterization of the microstructure and the properties of the base material and measurement of the compressive response of the foams of various cell sizes. A sequence of models for predicting the complete response of such foam is developed. The foam is idealized to be periodic using the space-filling Kelvin cell assigned the major geometric characteristics found in the foams tested. The cells are elongated in the rise direction, the ligaments are assumed to be straight, to have Plateau border cross-sections and nonuniform cross-sectional area distribution. The ligaments are modeled as shear-deformable extensional beams and the base material is assumed to be linearly elastic. Prediction of the initial elastic moduli are addressed in Part I. Closed form expressions for the material constants are presented as well as results using a FE model of the characteristic cell. Comparison between measurements and predictions is very favorable. The paper finishes with results from a limited parametric study of the elastic moduli. The results demonstrate that inclusion of the geometric complexities mentioned above is essential for successful prediction of the moduli of such foams. The nonlinear parts of the response including the foam crushing behavior are addressed in Part II.

Changes in root morphology after precommercial thinning in balsam fir stands

Precommercial thinning is often used to control stand density in naturally regenerated balsam fir (Abies balsamea (L.) Mill.) stands. Early stand density control could have beneficial effects on longer term stand stability through a modification of stem shape and root development. To assess the effect of precommercial thinning, two thinned and two unthinned stands were selected. Root sections were collected at 25 cm from the centre of the stem for all major roots (diameter greater than 2 cm). A disk was also cut at breast height level. From these disks, response in radial growth was determined. Detailed root measurements were taken on the sample disks to assess treatment effect on the following variables: asymmetry in root cross-sectional area (CSA) distribution, individual root shape, as well as changes in root shape over time. A quick and pronounced response in root growth occurred. This response was greater than that observed in the trunk. No asymmetry in root CSA distribution was observed at the stand level. Trees allocated more to radial growth above the biological centre of the root both in treated and control stands, but this trend was increased by thinning. Roots also tended to develop T-beam shapes over time, both in control and thinned stands. Most roots initially did not possess an I-beam shape and did not develop one during the course of the study. According to our results, trees respond quickly to the new growing conditions created by thinning by increasing biomass allocation to parts of the roots where mechanical stresses are greater.

Nerve fibre composition of the palmar cutaneous branch of the median nerve and clinical implications

Fifteen fresh human cadaver hands were dissected, using ×2.8 loupe magnification, to study the subcutaneous innervation at the site of the incision (in the line with the radial border of the ring finger) for standard open carpal tunnel decompression. Subcutaneous nerve branches were detected and traced proximally to determine their origin. Morphometric analysis of nerve cross sections from the site of the incision and from the main nerve trunk proximal to cutaneous arborisation was performed using light and transmission electron microscopy and a computer-based image analysis system. At the site of the incision, the ulnar sub-branch (US) of the palmar cutaneous branch of the median nerve (PCBMN), which innervates the skin over the hypothenar eminence, was found in 10 of 15 cases. Branches from the ulnar side were not detected. The main trunk of PCBMN consisted on average of 1000 (SD 229) myelinated axons arranged in 1–4 fascicles. In the US of the PCBMN there were on average 620 (SD 220) myelinated axons, 80% of them smaller than 40 μm 2 i.e. thin myelinated axons, and on average 2037 (SD 1106) unmyelinated axons, arranged in 1–3 fascicles. The ratio of the number of myelinated axons in the US and the main trunk of the PCBMN was on average 63% (SD 19%). Frequency distribution of cross-sectional areas of myelinated axons shows no significant difference between the US and the main nerve trunk of the PCBMN. The importance of incision trauma to subcutaneous innervation of palmar triangle is emphasised and possible mechanisms of scar discomfort are discussed.

Alterations in skeletal muscle structure are minimized with steroid withdrawal after renal transplantation.

Limitations in exercise capacity in kidney transplant recipients are thought to result in part from changes in muscle structure and function associated with immunosuppression therapy. We compared the percent distribution of skeletal muscle fiber types, cross-sectional areas, and ultrastructural morphologies in kidney transplant recipients treated with standard prednisone maintenance therapy (n=21) to those undergoing rapid withdrawal of prednisone using Simulect (interleukin 2 receptor inhibitor) (n=13). Skeletal muscle biopsy specimens from the vastus lateralis were analyzed at 3 and 12 months after transplantation and compared with sedentary controls (n=15). Compared with the control group, the group receiving prednisone maintenance therapy had a significantly lower percentage of type I fibers and a higher percentage of type IIB/x fibers, evident at 3 and 12 months. Fiber type distribution in patients withdrawn from prednisone did not differ from controls. In patients withdrawn from prednisone, the cross-sectional areas of type I and IIA fibers were lower and the area of type IIB/x fibers was higher compared with controls. Likewise, ultrastructural studies revealed reduced volume densities of myofibrils and higher densities of interfibrillar and subsarcolemmal mitochondria. At 12 months there were no ultrastructural differences between the patients withdrawn from prednisone and controls. We conclude that prednisone maintenance therapy contributes to the lower exercise capacity by altering the ratio of type I to type IIB/x fibers and by reducing myofilament density. The increase in mitochondria in patients receiving prednisone may reflect a switch from carbohydrate to lipid metabolism resulting from the glucocorticoid therapy.

Effects of Immediate and Delayed Facial–Facial Nerve Suture on Rat Facial Muscle

Objective—To investigate regeneration of the mimic musculature after delayed facial nerve repair.Materials and Method—In 30 rats the facial nerve on the right side was resected and immediately repaired with an end-to-end anastomosis. The entire levator labii muscle was removed on the right side and histochemically and morphometrically analyzed at 7, 14, 21, 28, 90 and 180 days after immediate nerve repair. In a further 20 rats, reinnervation was performed after 4 weeks in a further operation and the muscle was assessed at 14, 28, 90 and 180 days. Seven muscles of four normal rats were used as controls.Results—Three muscle fiber types could be identified by comparative histochemical analysis of two enzymes of succinate dehydrogenase (SDH) and m-ATPase: oxidative glycolytic (FOG) fibers, fast glycolytic (FG) fibers and intermediate muscle fibers that were designated SDH-INT. The number of fibers and the frequency distribution of single-fiber cross-sectional areas were determined for each type of fiber. No significant difference in the cross-sectional area of all fiber types was noted after 180 days when comparing immediate and delayed end-to-end sutures. In contrast, comparison of the fiber-type composition showed a significant increase in the number of FG fibers in the delayed suture, at the expense of FOG fibers. After immediate reinnervation the muscle approximately attained its natural fiber-type composition, whereas after delayed reinnervation the muscle showed an overall loss of oxidative capacity and differentiation towards phasic activity.Conclusion—Changes in fiber-type composition following delayed nerve suture are irreversible and have specific effects on the precise function of the muscle. Immediate nerve repair improves axonal reinnervation.

Effect of End Platens on Microstructure Evolution in Dilatant Specimens

End platen conditions are known to affect the global response of triaxial specimens during laboratory testing of soils. For example, these effects lead to barrel-shaped specimens in axial compression tests with associated difficulties in determining cross-sectional area and stress distributions. This paper presents the results of a study that used optical analysis of images captured from resin impregnated specimens at various global axial strain levels to study how internal microstructure varied as a function of the end platen conditions. Tests were performed on dilatant specimens with different slenderness ratios and different end platen configurations. The global response was quantified in terms of axial and radial strain behavior. The microstructure was quantified in terms of spatial void ratio distribution and local void ratio distribution. Analysis relating observed global response to internal microstructure evolution is presented. The results of this experimental study show that the end platen constraint is critical for microstructure evolution in dilatant specimens.

Method to Simulate Generation of Compression Wave Inside a Tunnel at Train Entry with a Simple Geometry Model (Influence of the Offset of Train Axis and the Ground Plane)

A method to simulate the generation of tunnel compression wave at train entry is investigated by using a simple geometry model. The tunnel is represented by a circular and the train by an axisymmetric body which has a cross-sectional area distribution equivalent to that of an actual train. In order to simulate the entry into a double tracked tunnel, the train center axis is positioned offset from the tunnel axis and the effect of the ground plane is treated by the mirror image method. Analysis and model experiments are performed to confirm the validity of the present method to use a simple geometry model. The difference of the peak pressure gradient of the compression wave has turned out to be within a few percent between field measurements and model experiments.

Integrated Vehicle Comparison of Turbo-Ramjet Engine and Pulsed Detonation Engine

The pulsed detonation engine (PDE) is a unique propulsion system that uses the pressure rise associated with detonations to efficiently provide thrust. A study was conducted under the direction of the NASA Langley Research Center to identify the flight applications that provide the greatest potential benefits when incorporating a PDE propulsion system. The study was conducted in three phases. The first two phases progressively screened a large matrix of possible applications down to three applications for a more in-depth, advanced design analysis. The three applications best suited to the PDE were (1) a supersonic tactical aircraft, (2) a supersonic strike missile, and (3) a hypersonic single-stage-to-orbit (SSTO) vehicle. The supersonic tactical aircraft is the focus of this paper. The supersonic, tactical aircraft is envisioned as a Mach 3.5 high-altitude reconnaissance aircraft with possible strike capability. The high speed was selected based on the perceived high-speed fuel efficiency benefits of the PDE. Relative to a turbo-ramjet powered vehicle, the study identified an 11% to 21% takeoff gross weight (TOGW) benefit to the PDE on the baseline 700 n.mi. radius mission depending on the assumptions used for PDE performance and mission requirements. The TOGW benefits predicted were a result of the PDE lower cruise specific fuel consumption (SFC) and lower vehicle supersonic drag. The lower vehicle drag resulted from better aft vehicle shaping, which was a result of better distribution of the PDE cross-sectional area. The reduction in TOGW and fuel usage produced an estimated 4% reduction in life cycle cost for the PDE vehicle. The study also showed that the simplicity of the PDE enables concurrent engineering development of the vehicle and engine.

Predicting the permeability of sandstone from image analysis of pore structure

A model is developed that allows accurate prediction of the permeability of a core sample of sedimentary rock, based on two-dimensional image analysis of its pore structure. The pore structure is idealized as consisting of a cubic network of pore tubes, with the tubes having an arbitrary distribution of cross-sectional areas and shapes. The areas and perimeters of the individual pores are estimated from image analysis of scanning electron micrographs of thin sections, with appropriate stereological corrections introduced to account for the angle between axis of the pore tube and plane of the thin section. The individual conductances of each tube are estimated from the measured areas and perimeters, using the hydraulic radius approximation. Variations in the pore diameter along the length of the tube are accounted for with a “constriction factor” whose derivation is based on laminar flow through an irregular tube. Effective-medium theory is used to find the effective single-tube conductance, based on the measured distribution of individual conductances. This procedure is applied to several consolidated North Sea reservoir sandstones, and some outcrop sandstones, with permeabilities ranging from 20 to 1400 mD. The predicted permeabilities are typically within a factor of 2 of the measured values, with an average error in logk of only 0.168.

電気インピーダンス法による導電率分布の可視化

Electrical impedance tomography (EIT) is one of the cheapest ways in order to get a tomography. Principal purpose of the EIT is to obtain a conductivity distribution of a two-dimensional cross-sectional target area by injecting the current. EIT utilizes a functional relationship between the injection current and surface potential distribution depending on the conductivity difference. This functional relationship of EIT reveals that EIT has versatile possibilities but it is essentially reduced into solving for an ill-posed inverse problem. In order to develop the EIT, we try to apply the generalized vector sampled pattern matching (GVSPM) method to the inverse problem accompanying with EIT. As an initial test experiment of EIT development, we try to evaluate a resistance distribution in a planer circuit by measuring entire nodal voltages while changing the electrodes for current injection. As a result, it is revealed that a fairly good result could be obtained as an initial test example.