Internal Cross-sectional Area Research Articles

Influences of stenosis and transplantation on behavior of blood flow in the host and grafted vessels using computational fluid dynamics

In this research, the changes of wall shear stress (WSS) of flow blood affected by stenosis and grafted vessels are studied. For the simulation of non-Newtonian fluid, blood in this paper, the Carreau fluid model is used. The severity of the stenosis is considered to reduce the internal cross-sectional area of the host vessel by 30 %. In this paper, simulations are performed on the human body in sports, which are classified into anemia (LHD), normal (NHD) and high blood pressure (HHD). Results are presented in three sections including after stenosis region, transplantation section, and after transplantation region by calculating wall shear stress (WSS). It is reported that wall shear stress is increased after stenosis location due to immediate variation in the cross-section area when blood flows. To explain, Stenosis reduces the cross-section area of the vessel which causes flow contraction. Consequently, this phenomenon increases flow velocity in the central region of blood flow whereas, after passing from stenosis, blood flow is exposed to an abrupt expansion which causes flow back from the central region to wall vicinity in lateral regions of the vessel. Maximum amounts of wall shear stress are achieved at 280 Pa, 350 Pa, and 550 Pa for anemia, normal, and hypertensive individuals in order. However, the consequence of the mentioned phenomenon in hypertensive individuals is more severe than that of anemic ones. Therefore, the geometry of veins is very important in medical surgeries to prevent vessel failure, especially in stressful points of transplantation.

Dorsal preservation rhinoplasty versus dorsal hump reduction: a randomized prospective study, functional and aesthetic outcomes.

To compare the functional and esthetic outcomes of dorsal preservation rhinoplasty (DPR) and conventional dorsal hump reduction (DHR) in primary rhinoplasty using patient-reported outcome measures (PROMs) and cone beam computed tomography (CBCT). In our randomized prospective double-blinded clinical trial, 50 patients had dorsal nasal hump surgery between October 2021 and November 2022 in our tertiary referral center. All surgeries were done by the same surgeon. Patients were randomly assigned to two groups: Group (A): 25 patients had DPR, and group (B): 25 patients underwent DHR. Pre-operative and post-operative evaluations were conducted using standardized cosmesis and health nasal outcomes survey (SCHNOS), surgeons' rhinoplasty evaluation questionnaire (SREQ), and the CBCT. Following an average of 7.22 ± 2.07 months, patients in both groups reported significantly higher levels of satisfaction, as measured by the SCHNOS score (p < 0.001) and the average of three SREQ scores (p < 0.001). These results align with the radiological analysis, which denoted an overall improvement in the average of both sides' internal nasal valve angle and cross-sectional area after surgery with (p = 0.001) and (p = 0.085), respectively, for the DPR group and with (p = 0.281) and (p = 0.014), respectively, for the DHR group. There was no statistically significant difference in outcomes between both groups (p > 0.05). Dorsal preservation is a viable alternative to conventional dorsal hump reduction in primary rhinoplasty. There was no difference in the functional and esthetic outcomes between both techniques, which were verified by radiological investigation.

Effect of local warming for arterial catheterization in adult cardiac surgery: a randomized controlled trial.

The increase in internal diameter (ID) and cross-sectional area (CSA) may facilitate better arterial catheterization. Since an increase in body temperature can cause peripheral vasodilation, we aimed to determine if local warming of the radial artery (RA) catheterization site could improve the success rate of catheterization. This randomized, controlled study enrolled 160 patients aged >18 years who were scheduled for heart surgery. They were randomized into non-warming palpation (NP), non-warming ultrasonography-guided (NU), warming palpation (WP), and warming ultrasonography-guided (WU) groups. After induction, the baseline RA ultrasonography images were collected. In the warming groups (WP, WU), local warming was applied on the catheterization site. Before catheterization, the RA ultrasonography images were collected. The primary outcome was the first-attempt success rate. The secondary outcomes included the ID and CSA of the RA and overall complications. Totally 152 adults were included in the analysis. The first-attempt success rates in each of the four groups were not significantly different (P=0.985). The rates in the non-warming (NP + NU) and warming (WP + WU) groups were also not different (P=0.827). Unlike non-warming group, the warming group had increased ID (3.34±0.78 vs. 3.02±0.73 mm; P<0.001) and CSA (6.9±2.8 vs. 5.8±2.4 mm2; P<0.001) compared with baseline. Local warming for peripheral artery catheterization does not increase the first-attempt success rate in adults undergoing cardiac surgery; however, it can increase the ID and CSA of the RA and prevent vasospasm. ClinicalTrials.gov NCT04969692.

An ultrasound imaging and computational fluid dynamics protocol to assess hemodynamics in iliac vein compression syndrome

ObjectiveElevated shear rates are known to play a role in arterial thrombosis; however, shear rates have not been thoroughly investigated in patients with iliac vein compression syndrome (IVCS) owing to imaging limitations and assumptions on the low shear nature of venous flows. This study was undertaken to develop a standardized protocol that quantifies IVCS shear rates and can aid in the diagnosis and treatment of patients with moderate yet symptomatic compression. MethodsStudy patients with and without IVCS had their iliac vein hemodynamics measured via duplex ultrasound (US) at two of the following three vessel locations: infrarenal inferior vena cava (IVC), right common iliac vein, and left common iliac vein, in addition to acquiring data at the right and left external iliac veins. US velocity spectra were multiplied by a weighted cross-sectional area calculated from US and computed tomography (CT) data to create flow waveforms. Flow waveforms were then scaled to enforce conservation of flow across the IVC and common iliac veins. A three-dimensional (3D), patient-specific model of the iliac vein anatomy was constructed from CT and US examination. Flow waveforms and the 3D model were used as a basis to run a computational fluid dynamics (CFD) simulation. Owing to collateral vessel flow and discrepancies between CT and US area measurements, flows in internal iliac veins and cross-sectional areas of the common iliac veins were calibrated iteratively against target common iliac flow. Simulation results on mean velocity were validated against US data at measurement locations. Simulation results were postprocessed to derive spatial and temporal values of quantities such as velocity and shear rate. ResultsUsing our modeling protocol, we were able to build CFD models of the iliac veins that matched common iliac flow splits within 2% and measured US velocities within 10%. Proof-of-concept analyses (1 subject, 1 control) have revealed that patients with IVCS may experience elevated shear rates in the compressed left common iliac vein, more typical of the arterial rather than the venous circulation. These results encourage us to extend this protocol to a larger group of patients with IVCS and controls. ConclusionsWe developed a protocol that obtains hemodynamic measurements of the IVC and iliac veins from US, creates patient-specific 3D reconstructions of the venous anatomy using CT and US examinations, and computes shear rates using calibrated CFD methods. Proof-of-concept results have indicated that patients with IVCS may experience elevated shear rates in the compressed left common iliac vein. Larger cohorts are needed to assess the relationship between venous compression and shear rates in patients with IVCS as compared with controls with noncompressed iliac veins. Further studies using this protocol may also give promising insights into whether or not to treat patients with moderate, yet symptomatic compression.

Factors Affecting Radial Artery Occlusion After Right Transradial Artery Catheterization for Coronary Intervention and Procedures.

To determine the factors influencing proximal radial artery occlusion (PRAO) right radial artery after coronary intervention. This is a single-center prospective observational study. A total of 460 patients were selected to undergo coronary angiography (CAG) or percutaneous coronary intervention (PCI) via the proximal transradial approach (PTRA) or distal transradial approach (DTRA). The 6F sheath tube were received by all patients. Radial artery ultrasound was performed 1 day before procedure and 1-4 days after procedure. Patients were divided into the PRAO group (42 cases) and the non-PRAO group (418 cases). General clinical data and preoperative radial artery ultrasound indexes of the two groups were compared to analyze related factors leading to PRAO. The total incidence of PRAO was 9.1%, including 3.8% for DTAR and 12.7% for PTRA. The PRAO rate of DTRA was significantly lower than that of PTRA (p < 0.05). Female, low body weight, low body mass index (BMI) and CAG patients were more likely to develop PRAO after procedure (p < 0.05). The internal diameter and cross-sectional area of the distal radial artery and proximal radial artery were smaller in the PRAO group than in the non-PRAO group, and the differences were statistically significant (p < 0.05). Multifactorial model analysis showed that the puncture approach, radial artery diameter and procedure type were predictive factors of PRAO, and the receiver operating characteristic curve showed a good predictive value. A larger radial artery diameter and DTRA may reduce the incidence of PRAO. Preoperative radial artery ultrasound can guide the clinical selection of appropriate arterial sheath and puncture approach.

A novel ex vivo tracheobronchomalacia model for airway stent testing and in vivo model refinement

ObjectivesWe sought to develop an ex vivo trachea model capable of producing mild, moderate, and severe tracheobronchomalacia for optimizing airway stent design. We also aimed to determine the amount of cartilage resection required for achieving different tracheobronchomalacia grades that can be used in animal models. MethodsWe developed an ex vivo trachea test system that enabled video-based measurement of internal cross-sectional area as intratracheal pressure was cyclically varied for peak negative pressures of 20 to 80 cm H2O. Fresh ovine tracheas were induced with tracheobronchomalacia by single mid-anterior incision (n = 4), mid-anterior circumferential cartilage resection of 25% (n = 4), and 50% per cartilage ring (n = 4) along an approximately 3-cm length. Intact tracheas (n = 4) were used as control. All experimental tracheas were mounted and experimentally evaluated. In addition, helical stents of 2 different pitches (6 mm and 12 mm) and wire diameters (0.52 mm and 0.6 mm) were tested in tracheas with 25% (n = 3) and 50% (n = 3) circumferentially resected cartilage rings. The percentage collapse in tracheal cross-sectional area was calculated from the recorded video contours for each experiment. ResultsEx vivo tracheas compromised by single incision and 25% and 50% circumferential cartilage resection produce tracheal collapse corresponding to clinical grades of mild, moderate, and severe tracheobronchomalacia, respectively. A single anterior cartilage incision produces saber-sheath type tracheobronchomalacia, whereas 25% and 50% circumferential cartilage resection produce circumferential tracheobronchomalacia. Stent testing enabled the selection of stent design parameters such that airway collapse associated with moderate and severe tracheobronchomalacia could be reduced to conform to, but not exceed, that of intact tracheas (12-mm pitch, 0.6-mm wire diameter). ConclusionsThe ex vivo trachea model is a robust platform that enables systematic study and treatment of different grades and morphologies of airway collapse and tracheobronchomalacia. It is a novel tool for optimization of stent design before advancing to in vivo animal models.

Ultrasonographic Evaluation of Internal Jugular Vein for The Prediction of Post-Spinal Hypotension in Orthopedic Surgeries

Background: Relative hypovolemia may predispose to severe or prolonged hypotension after spinal anesthesia in patients undergoing orthopedic surgeries. Empirical administration of fluid preload is time consuming, costly and might lead to volume overload, especially in elderly patients. Therefore, predicting post spinal hypotension is of great importance to reserve fluid infusion for susceptible patients. Ultrasonographic evaluation of the internal jugular vein (IJV) diameter has been used to estimate intravascular volume in the ICU. Therefore, we investigated the efficacy of sonographic measurements of the internal jugular vein parameters for predicting post spinal hypotension in patients undergoing orthopedic surgeries. Methodology: The study was conducted on 62 patients scheduled for orthopedic surgeries. Sonographic measurements of IJV diameter and cross-sectional area were recorded at supine and Trendelenburg position before spinal anaesthesia. Blood pressure was monitored for 15 minutes for all patients and hypotension was documented. Results: Twenty-eight patients (45.2%) developed hypotension. The rate of increase in the diameter and cross-sectional area of the IJV with the change in patient’s posture was significantly higher in hypotensive patients. According to ROC curves analysis, a rate of increase of 12.36% in IJV diameter, and a rate of increase of 25.55% in IJV cross sectional area showed moderate specificity and sensitivity in the prediction of spinal hypotension. Conclusion: Preoperative sonographic measurements of the internal jugular vein diameter and crosssectional area at supine and Trendelenburg position can predict the occurrence of post-spinal hypotension.

Effects of Compression of the Ulnar Artery on the Radial Artery Catheterization.

Background: The study was designed to evaluate the effects of compression of the ulnar artery on blood flow (BF) and internal cross-sectional area (CSAi) of the radial artery. We also evaluated the success rate and time of successful ultrasound-guided radial artery catheterization at the first attempt with or without compression of the ulnar artery. Methods: Patients were randomly allocated to the Compression group or Standard group to be treated with or without the application of ulnar artery compression, respectively. Hemodynamic stability was confirmed, and ultrasound-guided radial artery catheterization was performed. In the Compression group, an assistant compressed the ulnar artery at 5 cm above the wrist crease and the catheterization was performed after the loss of the distal ulnar artery BF. In the Standard group, the catheterization was performed without compression of the ulnar artery. Before and after the catheterization, BF and CSAi of the radial artery were evaluated. Success rate and time to successful catheterization at the first attempt were recorded. Results: BF and CSAi of the radial artery were similar in the two groups (37.5 [19.3–66] vs. 37.0 [20.6–53.7] mL/min, respectively, p = 0.63; 4.0 [4.0–6.0] vs. 4.0 [3.0–5.0] mm2, respectively, p = 0.095). In the Compression group, BF and CSAi were changed to 80.9 [35.9–128.5] mL/min (p < 0.001) and 5.0 [4.0–7.0] mm2 (p < 0.001), respectively, after compression of the ulnar artery. There was a trend that the success rate of ultrasound-guided radial artery catheterization at the first attempt was higher in the Compression group than in the Standard group (58/59 vs. 53/59, respectively, p = 0.05), although the difference was not statistically significant. However, the time to successful ultrasound-guided radial artery catheterization at the first attempt was significantly shorter in the Compression group than in the Standard group (34 [27–41] s vs. 46 [36–60] s, p < 0.001). Conclusion: Compression of the ulnar artery augmented BF and CSAi of the radial artery. It resulted in a significantly shorter success time for ultrasound-guided radial artery catheterization at the first attempt.

Performance characteristics of a divergent vortex tube

In this paper performance characteristics for a Ranque-Hilsch vortex tube are presented. The vortex tube was of divergent design and optimised for both size and performance, to be used to supply cold air to turbomachinery experiments with feed air in the supply pressure range 3.0–7.0 bar, and with overall feed mass flow rates in the range 0.05–0.14 kg/s. Optimum fixed parameters selected from the literature were: the ratio of cold-exit diameter to tube inlet internal diameter (0.50); the ratio of combined inlet-nozzle throat area to the tube inlet internal cross-sectional area (0.22); the vortex tube half-angle (3°); the number of inlet nozzles (6); the half-angle of the hot exhaust conical splitter (45°) and the ratio of tube length to tube inlet internal diameter (20). Free parameters that were investigated were: the overall total-to-static pressure ratio between inlet and cold-exit conditions (3.0, 5.0, and 7.0) and the cold-gas mass fraction (0.0–1.0). Comprehensive experiments were performed to characterise the vortex tube performance in terms of the following parameters: non-dimensional cold and hot-outlet temperatures; non-dimensional cold and hot-gas energy separation; isentropic efficiency referenced to cold-gas expansion; and coefficient of performance (COP). A transient heat flux correction technique was implemented to correct for unsteady heat flux terms from the working gas to the vortex chamber walls. Joule-Thomson effects were accounted for by introducing a corrected inlet total temperature. Cold-exit and hot-exit temperature separations were found to increase with pressure ratio. Non-dimensional cold-exit temperature had a minimum at cold-gas mass fraction of approximately 0.40. Non-dimensional hot-exit temperature increased approximately linearly with cold-gas mass fraction. COP decreased with increasing pressure ratio and had a peak value at cold-gas mass fraction approximately 0.60. Isentropic efficiency was relatively insensitive to pressure ratio and had a peak value at cold-gas mass fraction approximately 0.23. In the range investigated the lowest non-dimensional cold-exit temperature (normalised by inlet temperature) was 0.91, the highest coefficient of performance was 0.097, and the highest isentropic efficiency was 0.23. Full details of the design are given, allowing implementation by other researchers.

Investigation of the Process of Simple Distillation in Irrigated Pipe Elements

In modern chemical and oil refining complexes, separation processes are among the most popular and energy-intensive. Installations for their implementation should be equipped with nodes for creating vapor (evaporators) and liquid (deflegmators) irrigation. Evaporators of any type (film, thermosiphon, gas lift, cubic) belong to this class of devices. For example, in cubic evaporators, the gas flow is completely formed from flux bubbles that originate on the heat-conducting surface and float in the volume of the cubic liquid located in the apparatus. Due to the accompanying mass exchange, the bubbles are enriched with volatile components during ascent and noticeably increase in volume, and the growth of the bubble is determined, among other things, by the total flow. At the same time, in real bubbling-type equipment, the total mass transfer surface exceeds the cross-section of the device itself by more than two orders of magnitude. Thus, according to, the ratio of the internal cross-sectional area of the apparatus to the developed mass transfer surface is 0.0015–0.002. Based on the analysis of the integral equation of the diffusion boundary layer, it is shown that the presence of a resultant flow of substance through the phase interface (non-equimolarity of the process) in a two-phase gas (vapor)–liquid system leads to the transformation of the structure of the traditional mass transfer equation itself. The use of a new structure obtained for both binary and multicomponent mixtures makes it possible to significantly simplify the approach to the description and generalization of arbitrary mass transfer processes. The innovativeness of the proposed approach lies in its universality for non-equimolar processes. This simplifies the creation of models of any mass transfer devices and entire production lines. In addition, the proposed approach is a good auxiliary tool for various researchers and experimenters. It should also be noted that the separation processes of many products of organic origin during heating are characterized by the appearance of undesirable side reactions (thermal decomposition, condensation, polycondensation, formation of harmful impurities, etc.), which occur most intensively in the heating zones. At the same time, the evaporation and distillation units are subject to requirements for the minimum hydraulic resistance of the structure, the maximum separation capacity (efficiency), and the minimum residence time of the product in the apparatus (equivalent to the minimum holding capacity of the structure). It was noted that the specified requirements are most fully met by film-type devices.

Descriptive study of goat external and middle ear through computed tomography and endoscopic evaluation, compared with the human ear

ObjectiveTo describe the external and middle ear of goats, using computed tomography and endoscopic dissection, comparing them with the anatomy of the human ear, aiming to evaluate the viability of this animal model for training in otological endoscopic surgery. MethodsImages of the external and middle ear of goats were produced by computed tomography in the coronal and axial planes and analyzed. The radiological anatomy of the external and middle goat and human ear are described. Some measures of surgical interest were described, such as the length of the external auditory canal, external and internal cross-sectional area of the external auditory canal, middle ear depth, vertical angle of the external auditory canal, length of malleus and incus. After the tomographic study, we analyzed the importance of evaluations through the endoscopic dissection of the goat ear. ResultsThe bony canal is extremely tortuous and shows a bony prominence with significant elevation near the lower edge of the tympanic membrane. The middle ear has a large tympanic bulla in the hypotympanum region. The malleus is shaped similarly to that of the human, but its handle is located anterior to its head. The mastoid is not pneumatized. Compared to the human mastoid, there was a statistically significant difference in the external and internal cross-sectional area, at the depth of the middle ear, in the vertical angle of the canal and in the length of the incus. ConclusionGoat morphometric anatomy showed that this model is suitable for surgical simulation in the initial training for endoscopic otological surgery. It is an important contribution to the development of skills to accelerate the subsequent endoscopic otological surgical training in humans, despite some differences found.

Cephalopod-inspired robot capable of cyclic jet propulsion through shape change

The compliance and conformability of soft robots provide inherent advantages when working around delicate objects or in unstructured environments. However, rapid locomotion in soft robotics is challenging due to the slow propagation of motion in compliant structures, particularly underwater. Cephalopods overcome this challenge using jet propulsion and the added mass effect to achieve rapid, efficient propulsion underwater without a skeleton. Taking inspiration from cephalopods, here we present an underwater robot with a compliant body that can achieve repeatable jet propulsion by changing its internal volume and cross-sectional area to take advantage of jet propulsion as well as the added mass effect. The robot achieves a maximum average thrust of 0.19 N and maximum average and peak swimming speeds of 18.4 cm s−1 (0.54 body lengths/s) and 32.1 cm s−1 (0.94 BL/s), respectively. We also demonstrate the use of an onboard camera as a sensor for ocean discovery and environmental monitoring applications.

Design and Verification of a Single-Channel Pump Model based on a Hybrid Optimization Technique

This paper handles a hybrid multiple optimization technique to concurrently enhance hydraulic efficiency and decrease unsteady radial forces resulting from fluid-induced vibration of a single-channel pump for wastewater treatment. A single-channel impeller and volute was optimized systematically by using a hybrid particle swarm optimization and genetic algorithm coupled with surrogate modeling. Steady and unsteady Reynolds-averaged Navier–Stokes analyses were conducted to optimize the internal flow path in the single-channel pump. Design variables for controlling the internal flow cross-sectional area of the single-channel impeller and volute in the single-channel pump were chosen to concurrently optimize objective functions with hydraulic efficiency and the unsteady radial forces resulting from impeller–volute interaction. The optimization results clearly showed that the arbitrary cluster optimum design considerably enhanced hydraulic efficiency and decreased the unsteady radial forces concurrently, compared to the reference design. Finally, the hydraulic performance of the optimized prototype model was verified experimentally. Then, it was proved that the proposed technique is a practical tool for designing a single-channel pump.

Technique for Measuring the Internal Diameter and Area of Visible Vessels of the Eye

The study of the effects on the microvasculature of various vasoactive drugs requires appro-priate methods and equipment for determining the basic physiological parameters of small blood vessels: their internal diameter and cross-sectional area, specific density, and blood flow velocity. Therefore, the purpose of the article is to study the possibilities of improving the reliability of determining the internal diameter and cross-sectional area of the visible blood vessels of bulbar con-junctival of the eye.A technique for obtaining digital video recordings of the bulbar conjunctiva of the eye, based on the pulse illumination of the study area, is proposed. A prototype of the equipment with a spatial resolution of 2 µm video is described, which allows to trace all visible blood vessels, including capillaries. An algorithm for stabilizing the position of a sequence of digital images of the bulbar conjunctiva relative to the first frame is discussed. It is based on the use of subpixel interpolation when searching for a global minimum of the standard deviation of the differences in brightness of the first and selected frame.The proposed algorithms for tracing the vascular pattern and determining the internal diameter and cross-sectional area of the blood vessels are described. An original method for calculating them is proposed, which is based on determining the area and height of a cross section of a blood vessel image. The problem of verification of the obtained results is discussed.The described approach to make it possible to create diagnostic images of the visible blood vessels of the bulbar conjunctiva, including the capillaries, with an indication of their diameters. Examples of the construction of histograms of the distribution of the internal diameter and cross-sectional area of these blood vessels are presented.The proposed technique and hardware solutions have the prospect of being used in creating equipment for complex non-invasive diagnostics of the microvasculature and monitoring the effectiveness of treating various diseases of the cardiovascular system, since the conditions of the eye blood vessels correlate with the state of the blood vessels in other organs.

The effects of thoracic cage dimension and chest subcutaneous adipose tissue on outcomes of adults with in-hospital cardiac arrest: A retrospective study

BackgroundThe associations between thoracic cage dimension, chest subcutaneous adipose tissue (SAT) depth and outcomes of adults with in-hospital cardiac arrest (IHCA) remain unknown. MethodsWe retrospectively evaluated IHCA patients between January 2016 and October 2017. The thoracic cage transverse diameter, internal AP diameter, cross-sectional area, anterior and posterior SAT depths were measured in computed-tomography (CT) images. Using logistic regression models, we determined the adjusted associations between thoracic cage dimension, SAT depths and the prognosis for IHCA. The primary outcome was sustained return of spontaneous circulation (ROSC) and the secondary outcome was survival to hospital discharge. ResultsAmong 423 IHCA patients, 258 patients achieved ROSC and 70 survived to discharge. Smaller cross-sectional area and posterior SAT depth were significantly related to ROSC. Smaller posterior SAT depth was associated with ROSC. After multivariate adjustment, the smaller cross-sectional area was independently associated with ROSC (Odds ratio [OR] 0.99, 95% confidence interval [95%CI] 0.99–1.00; p = 0.008) and survival to discharge (OR 0.99, 95%CI 0.98–1.00; p = 0.024), and the smaller posterior SAT depth was independently related to ROSC (OR 0.65, 95%CI 0.44–0.96; p = 0.030), whereas no relation to survival to discharge was found. ConclusionsIn adults with IHCA, the smaller thoracic cage dimension and posterior SAT depth are associated with better survival. An adjustable compression depth based on the thoracic cage dimension might be better than the “one-size-fits-all” compression depth for resuscitating CA patients. In addition, physicians should pay extra attention to compression efficacy when resuscitating obese patients.

Three-objective optimization of a single-channel pump for wastewater treatment

The impeller and volute of a single-channel pump used for wastewater treatment were simultaneously optimized to improve the hydraulic efficiency and reduce unsteady radial force sources due to the impeller–volute interaction. Steady and unsteady Reynolds-averaged Navier–Stokes equations were solved with the shear stress transport turbulence model as the turbulence closure model using tetrahedral grids to analyze the internal flow in the single-channel pump. Five design variables related to the internal flow cross-sectional areas of the impeller and volute were selected to simultaneously optimize the hydraulic efficiency, the sweep area of the radial force during one revolution, and the distance of the mass center of the sweep area from the origin as the three objective functions. The response surface approximation model and genetic algorithm were employed to obtain three-dimensional Pareto-optimal solutions representing the trade-off between the efficiency and the radial force sources. The results of the three-objective optimization show that the representative clustered optimum designs enhanced the efficiency and reduced the radial force sources simultaneously in most cases, compared to the reference design. In addition, it was confirmed that the trade-off between the efficiency and the radial force sources clarifies with controlling the internal flow cross-sectional areas of the impeller and volute of the single-channel pump.

The dynamic response of a pressurized, hot, flexible fluid-conveying marine pipeline

ABSTRACT The transverse vibration of a pressurized, hot, flexible fluid-conveying pipe is investigated analytically via a coupled nonlinear partial differential equation where the effects of operating variables such as internal fluid temperature variation, mass ratio, pipe thickness, internal pressurization, Coriolis effect, axial acceleration of the internal fluid and cross-sectional area change, are fully captured. For this problem, a segment of a marine pipeline resting on the ocean floor is idealized as an elastic beam on an elastic foundation using the recently refined Euler-Bernoulli beam theory. Employing the hybrid Fourier-Laplace transforms, closed-form analytical expressions for the transverse natural frequencies are obtained in dimensionless form. In particular, two natural frequencies are noted to be associated with the phenomena as correctly identified in earlier results. Flow velocity was dependent on flow conditions and was found to increase with a decrease in the inlet operating temperature and thermal gradient. The operating pressure did not show any significant influence while the area deformation and pipe thickness increased. For the pipe thickness, the natural frequency was found to be similar irrespective of the thickness at the onset of the flow and decreased at a slower rate as it increased.

고효율 저유체유발진동 단일채널펌프 설계를 위한 다중목적 최적화

This paper presents the multi-objective optimization of a single-channel pump for wastewater treatment to simultaneously improve the hydraulic efficiency and reduce the unsteady radial force source caused by the impeller-volute interaction. The optimization was carried out by using a hybrid multi-objective evolutionary algorithm coupled with response surface approximation. For analyzing the internal flow in the single-channel pump, steady and unsteady Reynolds-averaged Navier-Stokes equations were solved with the shear stress transport turbulence model as a turbulence closure model. Five design variables related to the internal flow cross-sectional area of the impeller and volute were selected to optimize concurrently the two objective functions with the hydraulic efficiency and the resultant force of the unsteady radial force caused by the impeller-volute interaction. The results of the multi-objective optimization showed the representative arbitrary optimum design considerably enhanced the efficiency and reduced the resultant force of the unsteady radial force caused by the impeller-volute interaction simultaneously, compared to the reference design.

In vivo imaging of the internal nasal valve during different conditions using optical coherence tomography.

Previously, we proposed long-range optical coherence tomography (LR-OCT) to be an effective method for the quantitative evaluation of the nasal valve geometry. Here, the objective was to quantify the reduction in the internal nasal valve angle and cross-sectional area that results in subjective nasal airway obstruction and to evaluate the dynamic behavior of the valve during respiration using LR-OCT. For 16 healthy individuals, LR-OCT was performed in each naris during: 1) normal respiration, 2) peak forced inspiration, 3) lateral nasal wall depression (to the onset of obstructive symptoms), and 4) after application of a topical decongestant. The angle and the cross-sectional area of the valve were measured. A reduction of the valve angle from 18.3° to 14.1° (11° in Caucasians and 17° in Asians) and a decrease of the cross-sectional area from 0.65 cm2 to 0.55 cm2 led to subjective nasal obstruction. Forceful breathing did not significantly change the internal nasal valve area in healthy individuals. Application of nasal decongestant resulted in increased values. LR-OCT proved to be a fast and readily performed method for the evaluation of the dynamic behavior of the nasal valve. The values of the angle and the cross-sectional area of the valve were reproducible, and changes in size could be accurately delineated. 2b. Laryngoscope, 128:E105-E110, 2018.

Sonographic Evaluation of Internal Jugular Vein Diameter and Cross-sectional Area Measurements in Correlation with Left Ventricular End Diastolic Area as a Tool for Perioperative Assessment of Volume Status in Pediatric Patients Undergoing Cardiac Surgery.

Aim:The aim of this study is to compare the ultrasound estimation of the cross-sectional area (CSA) and diameter of internal jugular vein (IJV) with left ventricular end diastolic area (LVEDA) for the assessment of intravascular volume in pediatric patients during cardiac surgery.Patients and Methods:The CSA and diameter of the left IJV were defined, using ultrasound machine, and compared with LVEDA, estimated by transesophageal echo, in four times intervals (immediately after induction [T1], before the start of cardiopulmonary bypass [CPB] [T2], immediately after weaning of CPB [T3], and at the end of surgery before transfer to the Intensive Care Unit [T4]) as a tool for intravascular volume assessment in 16 pediatric patients undergoing cardiac surgery.Results:There was a poor correlation between IJV CSA and diameter with LVEDA. r values were 0.158, 0.265, 0.449, and 0.201 at the four time intervals (T1, T2, T3, and T4), respectively.Conclusion:Estimation of the CSA and diameter of the left IJV using ultrasound is not reliable and cannot be used alone to decide further management.