Tube Junction Research Articles

Numerical Simulation Study of an Artificial Percolation Riverbed and Its Hydraulic Characteristics under Different Reynolds Numbers

The direct extraction of clear water from a sandy river is a difficult task and can only be achieved through specific engineering measures. This paper proposes an artificial percolation riverbed structure for extracting clean water from sandy rivers, using a numerical simulation to study the flow field distribution characteristics of the structure under clean water conditions. The main conclusions are as follows: When the percolation vortex tube opening rate is 1.4%, the vortex tube with or without opening the percolation hole has little influence on the distribution characteristics of the flow field in the artificial riverbed, and the purpose of water extraction can be achieved while constructing a helical flow field. The axial flow velocity and circumferential flow velocity of the vortex tube cross-section under different Reynolds numbers show the distribution of a low-flow velocity close to the center of the vortex tube, and a high-flow velocity close to the vortex tube side-wall area. The average axial flow velocity and average circumferential flow velocity of the vortex tube show a trend of increasing and then decreasing distribution along the axial axis of the vortex tube in the direction of the sediment transport flume. The mean axial flow velocity of the vortex tube along the axis of the vortex tube toward the sediment transport flume and the mean circumferential flow velocity both show a distribution trend of increasing and then decreasing. At the junction of the vortex tube and the sediment transport flume, there are obvious pressure changes, and the pressure changes drastically under the same horizontal line. Along the direction of the bottom line of the vortex tube, the pressure at the vortex tube is obviously greater than that at the sediment transport flume. The vortex of the artificial percolation riverbed is mainly concentrated in the vicinity of the vortex tube, and the maximum value of the vortex intensity generally occurs at the junction of the vortex tube and the sediment transport flume. With the increase in the Reynolds number, the vortex intensity has an overall increasing trend, and the distribution of the vortex is more complex. This study helps to elucidate the distribution characteristics of the flow field in the artificial percolation riverbed, and it provides a reference basis for the future study of the flow field of artificial percolation riverbeds of sandy rivers.

(Invited) Synthesis and Application of 1D vdW Heterostructures Based on Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes (SWCNTs) with diverse optical and electronic properties (metallic or semiconducting) depending on chiral indices (n, m) have been the key nanomaterials in advanced applications [1,2]. Even though a mixture of metallic and semiconducting SWCNT can be used for bulk and film-form applications such as batteries and solar cells [3], the controlled growth of (n, m) or the sorting of (n, m) is essential for electronics applications such as field effect transistors (FET) [4]. On the other hand, the controlled modulation of properties can also be possible either by employing the inner space of the SWCNTs to encapsulate various materials or by externally wrapping the SWCNT template with additional atomic layers [5]. Here, I mainly discuss the latter case as a one-dimensional (1D) van der Waals (vdW) heterostructure based on SWCNT [6]. We have demonstrated the atomically precise one-dimensional (1D) van der Waals (vdW) heterostructure -- SWCNTs, boron nitride nanotubes (BNNTs), and molybdenum disulfide (MoS2) sequentially wrapped in radial direction -- by chemical vapor deposition in 2020 [6]. One of the obvious extensions of this work is the use of BNNT-SWCNT [7], which have superior semiconductor properties such as field effect transistors [8,9]. We have developed various characterization techniques for BNNT-SWCNT for the growth optimization and quality control of BNNT in various kinds of SWCNT [10-12]. Yet another extension is the various kinds of transition metal dichalcogenides (TMD) nanotubes. We have optimized CVD conditions for various metal dichalcogenides such as tungsten disulfide (WS2), niobium disulfide (NbS2), and molybdenum diselenide (MoSe2) so far in addition to the original MoS2. Here, we further broaden the concept of 1D vdW heterostructure by combining 2 transition metal species. By setting WS2 growth right after the MoS2 growth, we can observe the axial junction of the outermost tube, MoS2 - WS2. The junction is atomically smooth within a few nanometers. On the other hand, by setting the 2 transition metal species at the same CVD time, we can observe {WxMo(1-x)}S2 alloy nanotube. Both axial junction and alloy nanotubes are preferentially monolayers.Part of this work was supported by JSPS KAKENHI Grant Numbers JP23H00174, JP23H05443 and by JST, CREST Grant Number JPMJCR20B5, Japan.

하이퍼루프 초전도 전자석과 진공튜브 연결부 사이에 발생하는 자기 저항력 특성 연구

하이퍼루프 초전도 전자석과 진공튜브 연결부 사이에 발생하는 자기 저항력 특성 연구

Study on the law and mechanism of anisotropic conductivity of carbon nanotubes film prepared by floating catalytic chemical vapor deposition method

Carbon nanotubes (CNTs) film has attracted extensive attention in the field of electronics, sensors, and other potential applications due to their excellent electrical conductivity. The conductivity of CNTs film is one of the most important aspects of engineering applications. This study investigates the conductivity of CNTs film with varying areal density, prepared using the floating catalyst chemical vapor deposition (FCCVD) method and densified by rolling. The square resistance of pre- and post-rolling films was measured to characterize the electrical properties. Experimental results indicate that square resistance decreases with increasing areal density and stabilizes eventually. A mathematical formula was derived to explain the relationship between areal density and square resistance, incorporating volume and areal density formulas. Experimental data curves of pre- and post-rolling films were fitted, yielding mathematical relations consistent with the derived formulas. The electrical conductivity of post-rolling CNTs film was superior to pre-rolling in experiment and calculation. The charge carrier transport mechanism in CNTs film was studied by analyzing its internal structure and electrical properties. Surface conductivity was over 1000 times higher than volume conductivity, attributed to the distribution of CNTs bundles in collection and thickness directions. Charge carrier transport capacity decreased with increasing layers in thickness direction due to contact resistance and large resistance at tube–tube junctions. Layers of CNTs near the current application surface significantly contribute to charge carrier transport at high areal density levels.

Evaluation of Convective Heat Transfer and Natural Circulation in an Evacuated Tube Solar Collector

The evacuated tube solar collector ETC is studied intensively and extensively by experimental andtheoretical works, in order to investigate its performance and enhancement of heat transfer, for Baghdad climatefrom April 2011 till the end of March 2012. Experimental work is carried out on a well instrumented collectorconsists of 16 evacuated tubes of aspect ratio 38.6 and thermally insulated tank of volume 112L. The relationbetween convective heat transfer and natural circulation inside the tube is estimated, collector efficiency, effect oftube tilt angles, incidence angle modifier, The solar heating system is investigated under different loads pattern (i.eclosed and open flow) to evaluate the heat loss coefficient from tank and tubes, test the collector with variousaspect ratios (32.9 and 27.2). The enhancement in collector performance is studied by using two reflectors (FlatPlate and Curved Plate) and nanofluid (Water-AL2O3).Theoretical work is run by software (Fluent 6.3), to computethe velocity and temperature profiles within the tube, for different tube diameters, effect of tube junction angle andstagnant region in the bottom of the evacuated tube. The experimental results shows that the heat loss coefficientfor tube is W/m2.K and for tank is W/m2.K, the maximum collector temperature is 79°C in winter and99°C in summer, while that belong to nanofluid collector is 99°C in winter. The best tilted angle (optimum) ofevacuated tube is 41° annually. The collector efficiency increased when using nanofluid of (1, 0.6, 0.3)% volumefraction as(28.4, 6.8, 0.6)% respectively. The efficiency decreases as (33, 62)% when decreasing tube aspect ratiofrom 38.6% to 32.9% and 27.2% respectively. An increase of (16.9 and 7.08)% in collector efficiency is obtainedwhen using curved and flat plate reflectors respectively. From simulation the best junction angle of the tank is22.5°. The stagnant region is influenced with changing heat flux, tilted angle and aspect ratio.

Investigations on nonlinear processes of a Gifford-McMahon type orifice pulse tube refrigerator

The target of this investigation is to illustrate the nonlinear fluid flow, heat transfer, and vortex formation phenomena in an orifice pulse tube refrigerator by numerical simulation. Numerical results confirm that jet streaming is generated at the low-temperature end of the pulse tube in between the junction of U-shaped tube and pulse tube. The primary vortex, which is generated due to the minor loss, continuously grows because of velocity change and eventually leads to the formation of secondary eddy. Consequently, flow straighteners have been adopted at the hot side of the regenerator, hot heat exchanger, and both sides of U-shaped tube. It is noticed that, jet streaming has been suppressed at the cold end of the pulse tube. Nevertheless, the streaming effect generated due to the oscillating flow of the gas parcels within the pulse tube, and third type of streaming have not been suppressed with the flow-straightener. Additionally, the numerical simulation shows different gas flow behaviors within the pulse tube that occurs due to the oscillating pressure pulse. An experimental investigation is conducted to compare experimental results with the numerical results and a valid agreement is observed between them.

SurgAI3.8K: A Labeled Dataset of Gynecologic Organs in Laparoscopy with Application to Automatic Augmented Reality Surgical Guidance

We focus on explaining the concepts underlying Artificial Intelligence (AI), using Uteraug, a laparoscopic surgery guidance application based on Augmented Reality (AR), to provide concrete examples. AI can be used to automatically interpret the surgical images. We are specifically interested in the tasks of uterus segmentation and uterus contouring in laparoscopic images. A major difficulty with AI methods is their requirement for a massive amount of annotated data. We propose SurgAI3.8K, the first gynaecological dataset with annotated anatomy. We study the impact of AI on automating key steps of Uteraug. We constructed the SurgAI3.8K dataset with 3800 images extracted from 79 laparoscopy videos. We created the following annotations: the uterus segmentation, the uterus contours and the regions of the left and right fallopian tube junctions. We divided our dataset into a training and a test dataset. Our engineers trained a neural network from the training dataset. We then investigated the performance of the neural network compared to the experts on the test dataset. In particular, we established the relationship between the size of the training dataset and the performance, by creating size-performance graphs. University PATIENTS: NA INTERVENTION: NA MEASUREMENTS AND MAIN RESULTS: The size-performance graphs show a performance plateau at 700 images for uterus segmentation and 2000 images for uterus contouring. The final segmentation scores on the training and test dataset were 94.6% and 84.9% (the higher, the better) and the final contour error were 19.5% and 47.3% (the lower, the better). These results allowed us to bootstrap Uteraug, achieving AR performance equivalent to its current manual setup. We describe a concrete AI system in laparoscopic surgery with all steps from data collection, data annotation, neural network training, performance evaluation, to final application.

Measuring the Diameter of Single-Wall Carbon Nanotubes Using AFM.

In this work, we identify two issues that can significantly affect the accuracy of AFM measurements of the diameter of single-wall carbon nanotubes (SWCNTs) and propose a protocol that reduces errors associated with these issues. Measurements of the nanotube height under different applied forces demonstrate that even moderate forces significantly compress several different types of SWCNTs, leading to errors in measured diameters that must be minimized and/or corrected. Substrate and nanotube roughness also make major contributions to the uncertainty associated with the extraction of diameters from measured images. An analysis method has been developed that reduces the uncertainties associated with this extraction to <0.1 nm. This method is then applied to measure the diameter distribution of individual highly semiconducting enriched nanotubes in networks prepared from polyfluorene/SWCNT dispersions. Good agreement is obtained between diameter distributions for the same sample measured with two different commercial AFM instruments, indicating the reproducibility of the method. The reduced uncertainty in diameter measurements based on this method facilitates: (1) determination of the thickness of the polymer layer wrapping the nanotubes and (2) measurement of nanotube compression at tube-tube junctions within the network.

Diameter-Dependent Semiconducting Carbon Nanotube Network Transistor Performance

Single-walled carbon nanotube (SWCNT) network based devices show application potentials due to their extraordinary electric and optical properties, and the device performance is largely determined by the network morphology and tube–tube junction interactions. In this work, five SWCNT samples with narrow bandgap distributions covering a wide diameter range of 0.7–1.6 nm were purified by the conjugated polymer extraction (CPE) process. Both chirality distribution and semiconducting purity of these samples were systematically characterized by optical methods. Uniform high density network based thin film transistors (TFTs) were fabricated, and their performance can be related to tube bandgap/diameter and defects density or tube length. The diameter-dependent tube–tube junction resistance, the most important parameter for nanowire network devices, was extracted using a network predictive model. It was found that junction resistance inversely scales with tube diameter and is about 2 orders of magnitude higher than tube intrinsic resistance. The impacts of network morphology, tube diameter, and length on their network TFT performance were further discussed. We hope these results can provide some guideline to address various application challenges for SWCNT network based devices.

Recombinant Human Arresten and Canstatin Inhibit Angiogenic Behaviors of HUVECs via Inhibiting the PI3K/Akt Signaling Pathway.

Angiogenetic inhibitors are crucial in tumor therapy, and endogenous angiogenesis inhibitors have attracted considerable attention due to their effectiveness, safety, and multi-targeting ability. Arresten and canstatin, which have anti-angiogenesis effects, are the c-terminal fragments of the α1 and α2 chains of type IV collagen, respectively. In this study, human arresten and canstatin were recombinantly expressed in Escherichia coli (E. coli), and their effects on the proliferation, migration and tube formation of human umbilical vein endothelial cells (HUVECs) were evaluated. Regarding the cell cycle distribution test and 5-ethynyl-2′-deoxyuridine (EdU) assays, arresten and canstatin could repress the proliferation of HUVECs at a range of concentrations. Transwell assay indicated that the migration of HUVECs was significantly decreased in the presence of arresten and canstatin, while tube formation assays suggested that the total tube length and junction number of HUVECs were significantly inhibited by these two proteins; moreover, they could also reduce the expression of vascular endothelial growth factor (VEGF) and the phosphorylation levels of PI3K and Akt, which indicated that the activation of the 3-kinase/serine/threonine-kinase (PI3K/Akt) signaling pathway was inhibited. These findings may have important implications for the soluble recombinant expression of human arresten and canstatin, and for the related therapy of cancer.

Comparison of Methods for Cleaning Enteral Feeding Tube Junctions of the New International Standard (ISO 80369-3)

Introduction: International standards for enteral feeding involving the use of feeding tubes with junctions have been introduced. If these junctions are not properly cleaned, they can become contaminated, leading to microbial infections. We aimed to compare the ease and effectiveness of cleaning of four methods using the number of bacteria. Methods: We compared enteral nutrition tube junctions cleaned using four methods such as water, toothbrush, cotton swab, and EnClean® brush with an uncleaned control. Once daily for 7 days, the tubes were injected with nutrients, cleaned, and incubated at 37°C. Samples for bacterial culture were collected before injections on days 7, 14, 21, and 28. The culture samples were incubated at 37°C for 48 h, and the number of colonies was counted. Results: The number of residual bacteria on day 28 did not differ between the four cleaning methods and the control group. Moreover, no significant difference was observed in bacterial counts among the four wash methods. The number of washes did not differ among cleaning methods. Conclusion: The bacterial count in the ISO-standardized tube junction increased, and none of the cleaning methods decreased the counts.

Perianesthesia emergency repair of a cut endotracheal tube’s inflatable tube: A case report

BACKGROUNDDuring the perianesthesia period, emergency situations threatening the life and safety of patients can occur at any time. When dealing with some emergencies, occasional confusion is inevitable.CASE SUMMARYThis case report describes the rare situation wherein a surgeon inadvertently detached the inflatable tube of an endotracheal tube during a tonsillectomy, and positive pressure ventilation could not be provided. While reintubation may increase the risk of respiratory tract infection and aspiration, patients with a difficult airway might die due to apnea. The best treatment method is to optimize the damaged tracheal tube junction to avoid secondary intubation and ensure patient safety. An intravenous needle and cannula were used to repair the damaged gap in the current case. Following the repair, the anesthesia machine showed no indication of low tidal volume, and there was no deflation of the endotracheal tube cuff. Subsequently, the patient was transferred to the post-anesthesia recovery room, and the tracheal tube was removed with satisfactory results.CONCLUSIONUsing an intravenous needle to repair a break in the inflatable tube surrounding an endotracheal tube is safe and reliable.

A new patch technique for valve-sparing aortic root repair in acute type A aortic dissection.

Valve-sparing aortic root replacement is an attractive option for younger patients with acute type A aortic dissection. This study aimed to design a new patch technique for reconstructing the aortic root and preserving the aortic valve following aortic dissection. Between July 2017 and December 2018, 35 patients underwent valve-sparing aortic root repair using this new patch technique. All participants were in the supine position, transesophageal echocardiography and median sternotomy were routinely performed. After thrombi at the aortic root were removed in acute type A dissection, the luminal aortic intimal dissection was removed until the aortic condition was normalized. In each aortic sinus involved in the dissection, a Dacron-graft patch with the shape corresponding to the defect was sutured to the normal remnant vascular wall or aortic annulus in the aortic sinus using 5-0 Prolene suture to reconstruct the aortic root. A total of 2 patients died, and 1 cerebral infarction, and 3 cases of transient brain dysfunction were recorded. The sinus tube junction and sinus diameter were within the normal ranges when they were reexamined 3 months after surgery. This new patch technique circumvents the redesign of the spatial 3D structure of the aortic valve, is simple to operate, and easy to master. It completely removes the diseased dissection tissue, avoids the use of glue, and is an alternative surgical technique, especially for beginners.

IS UMBILICAL TUBE TECHNIQUE THE BEST METHOD TO GAIN INTRAPERITONEAL ACCESS? A PROSPECTIVE ANALYSIS OF 1532 CASES

Background: Intraperitoneal access in laparoscopic surgery is the first and most important step to start a procedure. Many methods have been described in literature for the same. We share our experience of umbilical tube technique using a vertical infra umbilical or supra umbilical incision for the better cosmetic result.&#x0D; Methods: This study is a retrospective study of laparoscopy performed for various indications. Umbilical tube technique was performed. In 1532 cases performed from July2016to January 2019. A vertical incision was used instead of a commonly performed curve incision to access the umbilical tube. A vertical incision is again taken after exposing the junction of rectus sheath and umbilical tube. Vertical incision is again taken over the tube to gain access to peritoneal cavity. The closure is done in a similar way with skin closed in subcuticular fashion. No Institutional Review Board (IRB) approval was required for this paper.&#x0D; Result: The technique is found to be safe, can be performed with technical ease as anatomy is well defined, good cosmesis is achieved. The longest follow up is for a period of one year. No incidence of port site hernia or infection was seen.&#x0D; Conclusion: The umbilical tube technique using a vertical incision is found to be safe and effective, can be reproduced with technical ease. In our opinion this method can be considered as a standard approach to intraperitoneal access.&#x0D; Keywords: umbilical tube, intraperitoneal access, port site infection, port site hernia. Laparoscopy.

Net flow generation in closed-loop valveless pumping

Net flow generation in valveless pumping, met in many physiological applications and recently in micropumping devices, constitutes an open fluid dynamics issue due to the complex interaction between the fluid medium and the flexible walls of the pump. In the context of the present experimental work, the conditions of the net flow generation are examined in a closed-loop horizontal valveless pump, which consists of a rigid and an elastic tube of equal diameters and lengths, and a pincher that forces the liquid within the tube to oscillate at Reynolds and Womersley numbers up to 7800 and 48, respectively. Pinching off as well as at the mid-length of the pump flexible tube, net flow is generated at certain pinching frequencies for which details are presented based on simultaneous recording of the pressure at the two tube junctions, the flow rate and the displacement of the pincher. Pinching off the mid-length of the pump at low pinching frequencies, net flow rate is practically null due to the almost identical pressure waveforms at the tube junctions, which vary in phase with the pincher motion. However, close to the first natural frequency of the hydraulic loop, the reflection of the pressure waves at the tube junctions combined with their increased phase difference cause high axial pressure gradients, which when they increase simultaneously with the squeezing of the tube, net flow rate maximization occurs. Pinching at the flexible tube mid-length area, nonzero net flow rates can also be generated, the sign of which changes when the pincher mid-point crosses the tube mid-length without being nullified.

Mepilex Border Dressings for the Prevention of Pressure Ulcers Caused by Nephrostomy Tube Securement

Objective: To investigate the clinical effectiveness of Mepilex Border dressings for the prevention of medical device-related pressure ulcers (MDR PUs) caused by the nephrostomy tube securement with the drainage tube. Methods: Equally randomized 60 obstructive hydronephrosis patients in our hospital who were treated by ultrasound-guided percutaneous nephrolithotomy (from March 2018 to March 2019) into observation group and control group. The observation group was applied dressings beneath the junctions of nephrostomy tubes and drainage tubes before secured with 5*5cm I-shaped 3M elastic adhesive tape to avoid direct contact to patients’ skin; the control group was only secured with 5*5cm I-shaped 3M elastic adhesive tape to the bare skin. The incidences of skin indentations, local pain and pressure ulcers under the junctions were compared between two groups. Results: There were statistical significance (P<0.05) among two groups: all patients in control group (n=30) were presented with skin indentations in different degrees, 21 with local pain, 6 with first-stage pressure ulcers, while no evidence of the above situations was found in the observation group. Conclusions: Application of Mepilex Border dressings can prevent the occurrence of MDR PUs to improve patient comfort.

MicroRNA‑21 contributes to renal cell carcinoma cell invasiveness and angiogenesis via the PDCD4/c‑Jun (AP‑1) signalling pathway.

Accumulating evidence has demonstrated that microRNAs are associated with malignant biological behaviour, including tumorigenesis, cancer progression and metastasis via the regulation of target gene expression. Our previous study demonstrated that programmed cell death protein 4 (PDCD4), which is a tumour suppressor gene, is a target of microRNA‑21 (miR‑21), which affects the proliferation and transformation capabilities of renal cell carcinoma (RCC) cells. However, the role of miR‑21 in the molecular mechanism underlying the migration, invasion and angiogenesis of RCC remains poorly understood. The effects of miR‑21 on the invasion, migration and angiogenesis of RCC cells was determined through meta‑analysis and regulation of miR‑21 expression invitro. After searching several databases, 6 articles including a total of 473patients met the eligibility criteria for this analysis. The combined results of the meta‑analysis revealed that increased miR‑21 expression was significantly associated with adverse prognosis in patients with RCC, with a pooled hazard ratio estimate of 1.740. In invitro experiments, we demonstrated that a miR‑21 inhibitor decreased the number of migrating and invading A498 and 786‑O RCC cells, along with a decrease in PDCD4, c‑Jun, matrix metalloproteinase (MMP)2 and MMP9 expression. Additionally, inhibition of miR‑21 was revealed to reduce tube formation and tube junctions in the endothelial cell line HMEC‑1 by affecting the expression of angiotensin‑1 and vascular endothelial growth factor A, whereas PDCD4 small interfering RNA exerted opposite effects on the same cells. Overall, these findings, along with evidence‑based molecular biology, demonstrated that miR‑21 expression promoted the migration, invasion and angiogenic abilities of RCC cells by directly targeting the PDCD4/c‑Jun signalling pathway. The results may help elucidate the molecular mechanism underlying the development and progression of RCC and provide a promising target for microRNA‑based therapy.

Optimal Y-shaped constructs heat sinks under different size constraints

Losses due to irreversible processes accompanying the heat and fluid flows. This paper addresses the fundamental question of what the shape of parent and offspring branches should be, to minimize the total irreversibility. I explore how the delivery of fluid and heat influences both the optimal size of Y-assemblies of tubes and Y-shaped junctions of tubes filled with a packing material, that are used as an elemental unit to construct tree-shaped flow networks. The geometric features of these constructs are obtained from the global minimization of expenditure of power associated to fluid flow and heat transfer. The optimal step factors for tube diameters and for tube lengths, and the optimal angle between the branches are obtained under different size-limiting constraints (surface area and volume). Among other results, I show that the geometrical features of the construct may be influenced by the heat flux. Besides, it is crucial to include the size-limiting requirements in agreement with goal of the system.For similar geometries, the heat and mass transfer correlations are analogous. Then, optimal size ratios and optimal angles of branching obtained here are also valid for mass flux by replacing the heat transfer dimensionless numbers by the equivalent mass transfer numbers. The analytical expressions obtained here provide fundamental information for designers assemble the inserts that formed a tree-shaped flow network.

Transient Self-Heating at Nanowire Junctions in Silver Nanowire Network Conductors

Nanostructured transparent conducting electrodes (TCEs) may be suitable replacements for transparent conductive oxides due to their optical, electrical, and mechanical properties. Because nanowire (NW) nanowire or tube–tube junctions are the transport bottlenecks in network-based conductors, understanding the properties of these junctions and their connectivity within the network is crucial to understanding and controlling electrical conduction through these networks. Quantifying local self-heating within the network can provide information on the coupled electrothermal response, local conduction pathways, and potential reliability. In this study, self-heating thermal transients within a silver NW network are characterized using high-resolution transient thermoreflectance imaging that provides high temporal (∼200 ns) and spatial (∼200 nm) resolution. The self-heating induced by an applied voltage pulse results in distinct temperature changes at microscopic hotspots formed at individual NW–NW junctions. For both heating and cooling cycles, thermal time constants less than $\text{1 }\mu {\text{s}}$ are observed at various hotspots. For a representative hotspot, line scans along two crossing NWs, taken at different time instants ranging from 0 to 2 μ s, show the temporal and spatial evolution of the temperature profile. We estimate the van der Waals force (∼−4.0244 N), contact width (∼5 nm), and interface thermal resistance (∼1.6 × 105 K/W) between NWs and the underlying substrate. A heat transfer model that considers local power generated at a hotspot, local coupling between the NWs and substrate, heat conduction along the NWs and heat transfer into the substrate, is developed and used to interpret the experimental data. The heat transfer model and experimental temperature profile help to quantify the local power generated at the hotspot and the fraction of this power propagating along each wire. The ability to resolve the local self-heating with such temporal and spatial resolution uniquely enables understanding of electrothermal response and current pathways in the distributed conductors.

Dual estimation based vocal tract shape computation

This paper presents a new method for direct estimation of vocal tract shape from the speech signal. The method computes cross-sectional areas of uniform-length cylindrical tubes comprising the vocal tract. Cross-sectional areas are calculated from reflection coefficients at tube junctions whose values depend on the areas of adjoining tubes. A new state space representation of the speech production system has been formulated in which reflection coefficients are parameters. The state space model has been constructed using state equations of the glottal flow signal and vocal tract formulated from Liljencrants–Fant model and concatenated tube model respectively. Dual extended Kalman filtering algorithm has been used for estimation of unknown parameters of the system. The estimated reflection coefficients are then used to compute cross-sectional areas of the vocal tract. The performance of proposed technique has been compared to an existing shape estimation method proposed by Wakita. For both synthesized and natural speech signals, the performance of proposed method has been found to be comparable to the existing one. Nevertheless, the Kalman filter algorithm used in proposed method has provisions to tune measurement noise covariance which can be adjusted based on the noise level in speech. Therefore, the performance of proposed method has been seen to be comparatively more robust to noise than the existing technique.