Duct Shape Research Articles

Management of Pediatric Patients Presenting with Acute Abdomen Accompanying Dilatation of the Common Bile Duct.

PurposeThe aim of this study was to describe our treatment experiences with patients who had acute abdomen (AA) with common bile duct (CBD) dilatation.MethodsThe treatment outcomes in children with AA and CBD dilatation were retrospectively reviewed. According to the shape of the intrahepatic bile ducts on ultrasonography (US), the origin of the pain was estimated as choledochal cyst (CC) complication or choledocholithiasis in normal CBD. Patients with complicated CC underwent surgery, and patients with choledocholithiasis in a normal appearing CBD underwent symptomatic treatment initially.ResultsOf the 34 patients, 30 (88.2%) were female. The mean age of the patients was 6.4±4.9 (range, 0.8–17) years. Seventeen (50.0%) patients had CBD stones and 17 (50.0%) did not. Surgical treatment was performed in 20 (58.8%) patients, 2 of whom underwent preoperative stone removal with endoscopic retrograde cholangiopancreatography and an operation. Conservative treatment was applied in 12 (35.3%) patients (8 with and 4 without stones), 1 of whom developed symptom relapse and underwent an operation. Among the 8 patients with CBD stones, 4 (4/17, 23.5%) had complete resolution of the stones and recovery of the CBD diameter after conservative treatment. US findings of patients with stone showed a fusiform or cylindrical shape of the CBD in 14 (82.4%) patients.ConclusionThe presence of stones in the distal CBD and the US features of CBD dilatation may be helpful to diagnose and treat the causes of biliary dilatation. Conservative treatment can be considered as initial therapy in patients with uncomplicated CBD dilatation with stone.

On the question of solid-propellant rocket engine design preventing unstable operation in the combustion chamber

The paper presents results of a numerical investigation concerning the effect that the flow duct shape and combustion rate equation have on the gas dynamic vortex flow pattern and self-excited pressure oscillations in the combustion chamber of a solid-propellant rocket engine. We provide guidelines on upgrading solid-propellant rocket engines in order to decrease the magnitude of pressure pulses in the case of pulsating combustion.

Penetration mechanics of a beetle intromittent organ with bending stiffness gradient and a soft tip.

Hyper-elongated structures and their penetration are widespread among insects, for example, intromittent organs, ovipositors, and piercing-sucking mouthparts. The penetration of thin structures with high aspect ratio without buckling and rupturing is mechanically very challenging. However, this problem is economically solved in nature, and the solutions might be helpful for, for example, in the development of harmless catheters. We focus on the penetration process of a hyper-elongated structure of a cassidine beetle intromittent organ, termed a flagellum. We applied a three-point bending test for the flagellum to measure its bending stiffness along the entire flagellum. We demonstrated the bending stiffness gradient, in which the basal half is relatively stiff and the apical half is softer, whose good performance during copulation had been previously numerically demonstrated. The stiffness gradient is the result of the flagellum shape, which is cylindrical and tapered toward the tip. Moreover, the curved tip comprises a harder outer curve and a softer inner curve. Considering the findings of preceding studies, the flagellum works in the following way: (i) the bending stiffness gradient supports the flagellum, easily fitting to a shape of a highly coiled spermathecal duct, (ii) the stiffness property of the very tip may make the tip tougher, and (iii) the curled tip and homogeneously cylindrical shape of the organ help the very tip to fit the shape of the spermathecal duct of the female. Our study shows that the apparently simple flagellum penetration is achieved with numerous elaborate mechanical adaptations.

Variations in cochlear duct shape revealed on clinical CT images with an automatic tracing method

Cochlear size and morphology vary greatly and may influence the course of a cochlear implant electrode array during insertion and its final intra-cochlear position. Detailed insight into these variations is valuable for characterizing each cochlea and offers the opportunity to study possible correlations with surgical or speech perception outcomes. This study presents an automatic tracing method to assess individual cochlear duct shapes from clinical CT images. On pre-operative CT scans of 479 inner ears the cochlear walls were discriminated by interpolating voxel intensities along radial and perpendicular lines within multiplanar reconstructions at 1 degree intervals from the round window. In all 479 cochleas, the outer wall could be traced automatically up to 720 degrees. The inner wall and floor of the scala tympani in 192 cochleas. The shape of the cochlear walls were modelled using a logarithmic spiral function including an offset value. The vertical trajectories of the scala tympani exhibited a non-monotonous spiral slope with specific regions at risk for CI-related insertion trauma, and three slope categories could be distinguished. This presented automatic tracing method allows the detailed description of cochlear morphology and can be used for both individual and large cohort evaluation of cochlear implant patients.

Physiology in Medicine: Understanding dynamic alveolar physiology to minimize ventilator-induced lung injury.

Acute respiratory distress syndrome (ARDS) remains a serious clinical problem with the main treatment being supportive in the form of mechanical ventilation. However, mechanical ventilation can be a double-edged sword: if set improperly, it can exacerbate the tissue damage caused by ARDS; this is known as ventilator-induced lung injury (VILI). To minimize VILI, we must understand the pathophysiologic mechanisms of tissue damage at the alveolar level. In this Physiology in Medicine paper, the dynamic physiology of alveolar inflation and deflation during mechanical ventilation will be reviewed. In addition, the pathophysiologic mechanisms of VILI will be reviewed, and this knowledge will be used to suggest an optimal mechanical breath profile (MBP: all airway pressures, volumes, flows, rates, and the duration that they are applied at both inspiration and expiration) necessary to minimize VILI. Our review suggests that the current protective ventilation strategy, known as the “open lung strategy,” would be the optimal lung-protective approach. However, the viscoelastic behavior of dynamic alveolar inflation and deflation has not yet been incorporated into protective mechanical ventilation strategies. Using our knowledge of dynamic alveolar mechanics (i.e., the dynamic change in alveolar and alveolar duct size and shape during tidal ventilation) to modify the MBP so as to minimize VILI will reduce the morbidity and mortality associated with ARDS.

A study on heatsink fin wave optimization for climate control seat

This research optimizes a heatsink fin wave that improves the cooling and heating efficiency in a Climate control seat (CCS). The design of existing CCS considers the occupant’s pressure, duct shape, blower blade shape, blower cogging torque, and mesh nozzles. However, the heatsink fin wave shape is overlooked in spite of its outstanding thermal efficiency. To address such problems, this research optimized the shape of the heatsink by defining the wave pitch, height pitch, and fin pitch. Parametric analysis (PA) was used such that the effective decision of the variables could be selected within each range of the variances. As a result, the cooling and the heating system operated more efficiently and the time required to reach the target temperature was reduced when compared to the existing system. The performance of the CCS was demonstrated by simulations and experiments.

Air flow optimization for energy efficient blower of biosafety cabinet class II A2

An energy efficient Biosafety Cabinet (BSC) has become a big challenge for manufacturers to develop BSC with the highest level of protection. The objective of research is to increase air flow velocity discharge from centrifugal blower. An aerodynamic duct shape inspired by the shape of Peregrine Falcon’s wing during diving flight is added to the end of the centrifugal blower. Investigation of air movement is determined by computational fluid dynamics (CFD) simulation. The results showed that air velocity can be increased by double compared to typical manufactured BSC and no air recirculation. As conclusion, a novel design of aerodynamic duct shape successfully developed and proved that air velocity can be increase naturally with same impeller speed. It can contribute in increasing energy efficiency of the centrifugal blower. It is vital to BSC manufacturer and can be apply to Heating, Air Ventilation and Air Conditioning (HVAC) industries.

Conceptual duct shape design for horizontal-axis hydrokinetic turbines

In the present paper, conceptual duct shape design for kinetic energy extraction with hydrokinetic turbines is discussed. The goal is to nd a single-passage axisymmetric geometry that holds stable flow with maximum kinetic energy ux at duct throat. For nding the optimum duct shape, the fluid flow was numerically simulated in a wedge shaped space with Flow-Simulation Software. In a multi-stage conceptual design, tabulated con gurations were employed to study each geometrical characteristic separately. These include curvature of pro le camber, trailing edge shape, pro le tip shape, and duct exit cross sectional area. The revolved pro le of each duct consists of a well constrained composite curve with few degrees of freedom. The Sketcher environment of SolidWorks Software provides a feasible method of rebuilding constrained curves. Duct shape optimization was performed based on successive flow simulation and approximation of optimum geometric dimension at optimum flow condition. The drag coecients were compared with available experiments. Based on the numerical simulations with needle shaped leading edge, the duct throat velocity can be increased. Inversely, the flow blockage can reduce the kinetic energy flux at duct throat. The optimum duct shape has shown the greatest frictional drag coecient and the minimum flow separation.

Cone beam computed tomography and histological evaluations of a straight electrode array positioning in temporal bones

Conclusion: CBCT allows a precise evaluation of the dimensions and of the shape of the cochlear duct that is of primary importance for the choice of the length and the design of the electrode array. This radio-histological study confirms that CBCT is a reliable tool to be used in clinical studies to evaluate the position of straight electrode arrays within the cochlear scala.Objective: To validate the reliability of cone beam computed tomography (CBCT) in the evaluation of cochlear anatomy and positioning of a straight electrode array, by comparing radiological images to histological analysis of cochlear implanted temporal bones.Methods: Eight temporal bones for four subjects were analysed before and after cochlear implantation with a straight electrode array. The size of the cochlea, the dimensions, and shape of the cochlear duct at 180° and 360° were evaluated on CBCT performed before implantation. Temporal bones then underwent histological analysis to determine the position of the electrode array. Scalar localization of the electrode array was assessed on CBCT performed after implantation, and compared with histological study.Results: CBCT is a reliable radiological technique to differentiate variability not only of cochlear dimensions, but also of size and shape of the cochlea. Histological analysis confirmed the scalar position of the electrode array assessed by the CBCT in 7/8 temporal bones, but soft tissue trauma such as dissection of the spiral ligament was not identified by the CBCT.

Aerodynamic design of gas turbine engine intake duct

Purpose The purpose of this paper is to provide a design solution of an engine intake duct suitable for delivering air to the compressor of a gas turbine engine of a general aviation turboprop aircraft, where the initial duct shape suffers a problem of flow distortion due to flow separation at the compressor inlet. Design/methodology/approach Aerodynamic design uses a three-dimensional inverse-by-optimization approach where the deviation from a desirable target pressure distribution is minimized by means of the adjoint method. Findings By virtue of a minimization algorithm, the specified target pressure distribution does not necessarily have to be fully realizable to drive the initial pressure distribution towards one with a favourable pressure gradient. The resulting optimized engine intake duct features a deceleration region, in a diverging channel, followed by an acceleration region, in a contracting channel, inhibiting flow separation on the compressor inlet plane. Practical implications The flow separation at the compressor inlet has been eliminated allowing proper installation of the engine and flight testing of the aircraft. Originality/value Placement and shaping of the intake duct of a turboshaft and turboprop gas turbine engine is a common industrial problem which can be challenging when the available space is limited. The inverse-by-optimization approach based on a reduced flow model, i.e. inviscid flow based on the Euler equations, and a specification of a simple target pressure distribution constitutes an efficient method to overcome the challenge.

Laminar forced convection in power-law and Bingham plastic fluids in ducts of semi-circular and other cross-sections

In this work, the effects of the power-law and Bingham plastic viscosity on the flow and heat transfer characteristics of laminar forced convection through non-circular ducts of a range of cross-sections have been investigated numerically over the wide ranges of Peclet number, 10⩽(Pe=Re·Pr)⩽104, power-law index, 0.2⩽n⩽2 and Bingham number, 0⩽Bn⩽15. Two different thermal boundary conditions (constant wall temperature and constant wall heat flux) on the duct wall have been implemented. Extensive results for the flow and temperature fields in terms of the dimensionless velocity and temperature profiles, pressure drop and local and average Nusselt number are presented and discussed both in the developing and fully developed regions. For the sake of conciseness, the results for three duct shapes, namely, semi-circular, four cusped and rectangular, are presented and discussed in detail whereas that for the other shapes are summarised in a tabular form. The dependence of the Poiseuille number (f·Re) and asymptotic Nusselt number (Nu) on the power-law index (n) and Bingham number (Bn) is studied under fully developed (hydrodynamically and thermally) conditions. It is shown that the fanning friction factor has a positive dependence on the increasing values of power-law index while an opposite dependence is observed for the Nusselt number. Finally, simple predictive correlations for hydrodynamic entrance length and Nusselt number are developed as functions of the generalised Reynolds number (Reg), Graetz number (Gz), power-law index or the Bingham number. The paper is concluded by comparing the predictions of the power-law model with that of the extended modified power-law (EMPL) model for a semi-circular duct in order to ascertain the influence of the deficiencies of the power-law equation in capturing the zero- and infinite-shear viscosities on the present results.

Assessing Anidolic Daylighting System for efficient daylight in open plan office in the tropics

The current study seeks to determine the Anidolic Daylighting System (ADS) variables that are applicable under tropical climate, according to modified duct shapes, duct width, duct length and distributor configuration. Our study involves experimental scale model and Integrated Environmental Solutions 〈Virtual Environment〉 (IES〈VE〉) computer simulation. We use physical scale model (1:10) to validate the simulation tool and to determine the appropriate orientation. Subsequently, the ADS simulation involves different variables of duct shapes, duct width, duct length and distributor configuration in an open plan office. The analysis of results for daylight quantity is based on absolute Work Plan Illuminance (WPI), daylight factor and daylight ratio. The results suggest that the ADS performed well for all orientations, but its performance in the South orientation is better than other orientations. This means that the developed ADS by rectangular duct shape and three meter duct width can transfer daylight as deep as 12.5m and 20m from window wall in overcast and intermediate sky conditions respectively. The study findings can give architects, engineers and built environment scientists some insights into exploring opportunities of using ADS to improve of occupants visual comfort as well as energy saving designs.

Optimisation of Ducted Propellers for Hybrid Air Vehicles Using High-Fidelity CFD

ABSTRACTThis paper presents performance analysis and design of ducted propellers for lighter-than-air vehicles. High-fidelity computational fluid dynamics simulations were first performed on a detailed model of the propulsor, and the results were in very good agreement with available experimental data. Additional simulations were performed using a simplified geometry, to quantify the effect of the duct and of the blade twist on the propeller performance. It was shown that the duct is particularly effective at low flight speed and that the blades with relatively high twist have better performance over the flight envelope. Design of the optimal twist distribution and of the duct shape was also attempted by coupling the flow solver with a quasi-Newton optimisation method. Flow gradients were computed by solving the discrete adjoint of the Reynolds-averaged Navier-Stokes equations using a fixed-point iteration scheme or a nested Krylov method with deflated restarting. The results show that the ducted propeller propulsive efficiency can be increased by 2%.

Reply.

TO THE EDITOR: We are pleased that the authors read our article with great interest. We strongly disagree with the authors' comment that corner‐sparing and mucosal eversion is essentially the same as the Hilar plate and Glissonian sheath (HPGS) method. The approach previously described by the authors is essentially the method of donor duct division.1 In other words, they have ascribed the improvement of biliary complications essentially to the way they divide the donor duct. There are many ways a donor duct can be divided, and it varies from center to center. The basic principle of duct division is to preserve the hilar plate along with its vascular plexus in periductal tissue. As described in our article, we believe in a precise and sharp division of the donor duct without disturbing the hilar plate. The end result of this method is the same as the HPGS approach. Unlike HPGS, which is one of the methods of donor duct division, our article focuses on anastomosis rather than on donor duct division.2 The high hilar division described in our article is essentially for the recipient duct, with the aim being to get the second‐ or third‐order biliary orifices. These orifices can be tailored and joined together to yield a funnel‐shaped recipient bile duct, which can be easily everted. The authors have further raised anatomic and practical reservations with our concepts. The first issue raised is regarding the eversion of the donor duct. If read carefully, the authors will notice that we have not mentioned donor duct eversion in our article because we are aware that it cannot be everted due to the short stump.2 Mucosal eversion is for the recipient duct. Eversion of the recipient duct is a very important component of our technique in many ways. First, it allows us to anastomose with healthy and well‐vascularized mucosa because the end of the cut stump may be of doubtful vascularity. Second, adventitial tissue does not pop in‐between the sutures, giving us a near perfect mucosal apposition. Third, the overhanging part of the duct forms a supporting cuff around the anastomosis. The second issue raised is about the corner‐sparing component of our technique. Corner‐sparing sutures in our article are mainly for the donor duct rather than for the recipient duct as perceived by the authors. Corner‐sparing sutures in the recipient duct are placed just to match and correspond to the corner‐sparing sutures in the donor duct. Corner‐sparing of the donor duct (avoiding sutures at 3 and 9 o'clock) is a very crucial and important part of our technique for 2 reasons. First, corners are the weakest part of the donor duct because the hilar plate splits at the corners. We have learned from our experience (re‐explorations and endoscopic retrograde cholangiography) that most posttransplant bile leaks are from the corners. Sparing of the corners avoids any cut‐through or necrosis of the donor duct at the corners during or after tying knots. Second, the natural shape of the donor duct is like a slit with 2 ends as corners (to be avoided in sutures). Corner‐sparing anterior and posterior sutures in the donor duct actually convert the slit into a square or rectangle (which further simplifies anterior suturing). On the contrary, if corners are included in the sutures, it further accentuates the slit and makes suturing difficult. This concept of squaring is beautifully shown in the photograph presented in our original article. As mentioned in the original article, we refute the component of a learning curve because we had had significant experience before modifying our technique. At our center, we do not reject or select the donor based on biliary anatomy. We have stopped doing preoperative magnetic resonance cholangiopancreatography in our protocol for selecting a donor for the last 350 patients. The corner‐sparing and mucosal eversion technique is very promising and significantly reduces the overall biliary complications to <4%. We have further used this technique for more than 200 patients since our original publication with a similar low incidence of biliary complications.

Heat and Mass Transfer in Planar Anode-Supported Solid Oxide Fuel Cells: Effects of Interconnect Fuel/Oxidant Channel Flow Cross Section

Heat and mass transfer in a planar anode-supported solid oxide fuel cell (SOFC) module, with bipolar-plate interconnect flow channels of different shapes are computationally simulated. The electrochemistry is modeled by uniform supply of volatile species (moist hydrogen) and oxidant (air) to the electrolyte surface with constant reaction rate via interconnect channels of rectangular, trapezoidal, and triangular cross sections. The governing three-dimensional equations for fluid mass, momentum, energy, and species transport, along with those for electrochemical kinetics, where the homogeneous porous-layer flow is in thermal equilibrium with the solid matrix, are coupled with the electrochemical reaction rate to properly account for the heat and mass transfer across flow-ducts and electrode-interfaces. The results highlight effects of interconnect duct shapes on lateral temperature and species distributions as well as the attendant frictional losses and heat transfer coefficients. It is seen that a relatively shallow rectangular duct offers better heat and mass transfer performance to affect improved thermal management of a planar SOFC.

Theoretic Assessment of Possibility of Leg Ventilation Duct in Thermal Insulation System of a Renovated Apartment Building

The aim of this paper is to present a thermal technical assessment of the new innovative way of placing ventilation ducts in a thermal insulation system of a renovated apartment building. Suitability of various shapes of ducts and various thicknesses of thermal insulation system is assessed. The assessment is based on determination of heat gains and losses of the ventilation system in summer season, including effect of solar radiation. Thermomechanical numerical simulation of 2D heat conduction is carried out in software CalA using theory of heat transfer with the criteria of similarity. The obtained results demonstrate the optimal shape of ducts and their optimal position in the thermal insulation system.

Non-Newtonian Shear-Thinning Fluid Passing Through a Duct with an Obstacle, Using a Power Law Model

Non-Newtonian fluids have not been frequently considered in different research although they are common fluid type in the industry and environment in comparison to Newtonian fluids. In this paper, a non-Newtonian fluid with a shear-thinning property is considered in a specific geometric condition. The flow is considered to be laminar, and the geometric subject of the research is a rectangular duct with an obstacle, which is assumed to be in the middle of the duct with a height of half the duct width. This research provides a numerical solution using a written MATLAB code with a SIMPLEC algorithm and a power law model. This code is validated by comparing code results with analytical results for a specific condition. The results of this research show variations of velocity and viscosity in the duct, which can be extremely useful in future research and applications, not only because of frequent usage of shear-thinning fluids in industrial applications but also because of the common duct shape facilities in different processes in several industries.

Male penile propulsion into spiraled spermathecal ducts of female chrysomelid beetles: A numerical simulation approach

Genital diversification in animals is an interesting evolutionary phenomenon. Sexual selection is the main driving force behind the diversification. However, evolutionary mechanisms that have established and maintained variations in genitalia shape parameters observed in related species are not well understood. Here, for the first time, we used numerical simulations to test the hypothesis that variations in female spermathecal duct shapes among related beetle species mechanically interfere with penile propulsion in varying ways. Our numerical simulations showed that high curvature of the spiraled spermathecal ducts of the female have effects with a threshold-based interaction on male penile insertion. The relative size of spirals observed in the beetle, Cassida rubiginosa, studied here is not small enough to interfere with penile propulsion. But the model revealed that propulsion is impeded by the presence of reverse turns in spermathecal ducts. This type of morphology leads to an increase in the velocity of the propulsion but also to an increase in the propulsion energy cost for males. Our results showed that quantitative differences in spermathecal duct shape can mediate qualitative differences in penile motion. This explains, in part, the mechanism behind origin and maintenance of genital divergence among closely related species in general.

Comparative leaf anatomy of some species of Abies and Picea (Pinaceae)

A number of conifer species are still lacking anatomical data, which is significant because morphological and anatomical data are essential for systematic study. Leaf anatomy was studied in selected species of Abiesand Piceausing light and scanning electron microscopy. Both genera were found to have typical coniferous and highly xerophytic leaves with sunken stomata and an epidermis covered by a thick cuticle. In the genus Abies, species can be differentiated by the nature of the lignified hypodermis and the number and position of resin ducts. Abies firma and A. holophylla have a continuous hypodermis whereas in A. koreana and A. nephrolepis the hypodermis is discontinuous and represented by isolated cells or groups of four or five cells. On the other hand, in Picea leaf shape, stomata arrangement, and number, position, and nature of resin ducts are the key features for species differentiation. Picea jezoensis has a flattened leaf with stomata distributed on the adaxial surface whereas P. abies and P. koraiensis have a rectangular leaf with stomata found on surfaces.

Use of MDCT to Differentiate Autoimmune Pancreatitis From Ductal Adenocarcinoma and Interstitial Pancreatitis.

The purposes of this study were to identify the most common imaging features of autoimmune pancreatitis and to evaluate the utility of MDCT for differentiating autoimmune pancreatitis from two more frequently encountered differential diagnoses--pancreatic ductal adenocarcinoma and acute interstitial pancreatitis. Dual-phase contrast-enhanced MDCT images of 91 patients (39 with autoimmune pancreatitis, 25 with pancreatic ductal adenocarcinoma, 27 with acute interstitial pancreatitis) were evaluated by two radiologists in consensus for distribution of pancreatic abnormality, sausage shape, low-attenuation halo, pancreatic duct dilatation, peripancreatic stranding, lymphadenopathy, biliary abnormality, vascular involvement, and renal lesions. Chi-square tests, multiple logistic regression analysis, and ROC analysis were performed. The most common imaging features of autoimmune pancreatitis were sausage shape (25/39 [64%]) and low-attenuation halo (23/39 [59%]). Pancreatic duct dilatation (20/25 [80%]) and biliary dilatation (11/25 [44%]) were most frequent in pancreatic ductal adenocarcinoma. Peripancreatic stranding (22/27 [81%]) was most frequent in acute interstitial pancreatitis. Sausage shape, low-attenuation halo, and absence of a pancreatic duct or biliary dilatation differentiated autoimmune pancreatitis from pancreatic ductal adenocarcinoma with an accuracy of 0.88. Sausage shape and absence of peripancreatic stranding differentiated autoimmune pancreatitis from acute interstitial pancreatitis with an accuracy of 0.82. There was no significant difference in the frequency of vascular involvement or of lymphadenopathy among these diagnoses. Typical cases of autoimmune pancreatitis can be accurately differentiated from pancreatic ductal adenocarcinoma and acute interstitial pancreatitis on the basis of characteristic MDCT features. However, autoimmune pancreatitis should be considered in the presence of atypical features.