Perforated Region Research Articles

3D printed polymers for transseptal puncture simulation

PurposeThis study aims to examine the efficacy of 3D printing polymers to realistically mimic the fossa ovalis (FO) – a cardiac structure that is positioned in the interatrial septum – for simulating transseptal puncture (TP) procedures.Design/methodology/approachSpecimen of different materials and thicknesses were prepared and tested simulating the puncturing of the FO using a 12F ID/14F OD TP catheter. Force and tenting length results were compared with literature references. Scanning electron microscope images of the specimen were acquired to observe the perforated region as well as the structure of the specimen in the unaffected area.FindingsSignificant changes in the properties of interest were registered for the same material on specimens tested at different moments after fabrication. Suturable vessel wall polyjet material offers the best characteristics to replicate FO anatomy and mimic its behavior to puncturing.Originality/valueThe originality of the work lies in the test of different commercial materials. Similar works are already present in literature but specifically designed materials are used. Demonstrating that off-the-shelf materials could be viable for FO specimens would simplify the design of realistic TP simulators in the future.

Influence of Relative Position of the Initial Region of Double-Row Perforation of the Turbine Vane Suction Side on the Film Cooling Effectiveness in Conditions of Inlet Flow Irregularity

Influence of Relative Position of the Initial Region of Double-Row Perforation of the Turbine Vane Suction Side on the Film Cooling Effectiveness in Conditions of Inlet Flow Irregularity

Novel Approach to Color‐Neutral Transparent Solar Cells: An Organic‐Si Hybrid Achieved by Laser Microhole Drilling

AbstractTransparent solar cells (TSCs) hold promise for applications in building‐integrated photovoltaics (BIPVs) and vehicles. However, existing TSCs often have compromised color neutrality and efficiency because of the distinctive colors arising from their photoactive materials. The study proposes a novel fabrication method for TSCs based on Si wafers with the average visible transmittance (AVT) controlled by creating a microhole pattern through a combination of nanosecond laser drilling and subsequent wet etching. Through this ambient‐air process, organic–Si hybrid TSCs are successfully realized by integrating an organic PEDOT:PSS layer onto this structure with a neutral color. The power conversion efficiency (PCE) is adjusted by the fraction of the perforated region, and it attained 6.20% at 30% AVT, 5.37% at 40% AVT, and 4.67% at 50% AVT. In this hybrid TSC approach, the CIE color coordinates are closely aligned with the neutral‐color points (0, 0), resulting in color rendering index (CRI) values exceeding 99. The strategy represents a significant step toward the development of efficient color‐neutral TSCs for transparent solar applications.

Methodology for determining convective heat transfer coefficients on the tubesheet surface of shell-and-tube heat exchangers under single-phase flow

Designing shell-and-tube heat exchangers requires reliable methods to calculate the convective heat transfer coefficient (CHTC) on the tubesheet, due to its impact on thermal stress. To address this, we established numerical models for both the tube and shell sides of the tubesheet. Using computational fluid dynamics (CFD), we systematically investigated the distribution of convective heat transfer on the tubesheet surface and its variations with structural and process parameters. The results showed that when fluid flowed into the tubesheet, the average convective heat transfer coefficient on the tube side of the tubesheet surface was 26% higher than when it flowed out. Additionally, the average convective heat transfer coefficient in the perforated region of the tubesheet was 1.39 to 2.57 times greater than in its periphery. Furthermore, the local CHTC on the shell side of the tubesheet surface gradually decreased along the downstream direction from the inlet of the shell-side fluid. Through simulations conducted across various structural and process parameters, we derived empirical formulas to rapidly calculate the average CHTC on the tubesheet surface. These formulas incorporated a tubesheet porosity factor for the tube side and introduced a new method for calculating the equivalent tubesheet diameter on the shell side. Random testing verified that our proposed formula reliably predicted the numerical simulation results.

Vertically Stacked Double-Layer Substrate-Integrated Nonradiative Dielectric Waveguides for THz Applications

Nonradiative dielectric (NRD) waveguides have been studied and exploited to address the leakage issue in dielectric waveguides caused by discontinuities. With the proliferation of substrate integration technologies, planarized substrate-integrated NRD (SINRD) waveguides have emerged, which are found to be more suitable for terahertz (THz) integrated circuits and systems. However, in the making of SINRD waveguides, a process-related conflict may arise between the air-hole perforation of a hosting substrate and its essential residual metallic coating on the perforated region. In this work, a solution to this problem using a multilayer topology is formulated, where the size difference between entrance and exit of the drilled air holes is reduced. Moreover, the exposed metallic coating over both sides of the multilayer SINRD waveguide is well preserved. Therefore, a dense air-hole perforation is allowed when needed. In this letter, a vertically stacked double-layer guiding structure is presented, studied, and experimentally verified, which demonstrates the interesting features of this technique.

Microstructural Aspects of Premature Pitting Corrosion of Steel Pipe–Case Study

A premature pitting corrosion in seam-welded 3-inch L235 steel pipe was reported to occur after 8 years in service. This pipe was part of a closed ice water cooling system, where the inlet water temperature was 6 °C and the outlet water temperature was 11 °C. The present work aimed to investigate the causes of this premature pitting corrosion of the pipe through metallographic investigations. This work comprised a visual examination of the internal surfaces of the pipe and microstructural examinations of the corrosion perforation regions (pitting corrosion areas) using optical and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis. The investigations showed that the corrosion pits occurred only in areas with a huge number of specific micro-voids that can be associated with the excessive presence of trapped hydrogen dissolved in the steel, probably during steelmaking operations.

Analysis of velocity distribution in an air flow through a thin perforated plate

Modelling air flow in a curved fine perforated plate region was performed by porous zone substitution. This approach significantly simplifies the observed process, thus various limitations appeared. PIV measurements on an experimental test rig were performed and compared with the results from CFD computations.

English

BACKGROUND Infective endocarditis [IE] prophylaxis is recommended for all dental procedures that involve manipulation of gingival tissue or the periapical region of teeth or perforation of the oral mucosa. The study intended to compare the antimicrobial potency of amoxicillin, cephalexin, and clindamycin against Streptococcus mutans, the common causative organism of dental infections. The objective was to assess the potency of recommended choice of antibiotics and its efficacy among each other in infective endocarditis prophylaxis during dental procedures. METHODS Saliva samples [N = 20] were collected from patients susceptible for IE and Streptococcus mutans was cultured in Infusion Agar. The principle used in this study was based on the Kirby - Bauer disc diffusion Antimicrobial Susceptibility Test [AST] Method and minimum inhibitory concentration [MIC]. In this method, the three HiMedia antibiotic discs of amoxicillin, cephalexin and clindamycin were loaded and assessed for measurable “zone of inhibition” against mutans. RESULTS One-way ANOVA was used to compare the means of zone of inhibition of each disc. The test was statistically significant with F value of 4.093 at P value 0.038. Post hoc analysis was conducted using Tukey’s HSD test as one-way ANOVA was statistically significant. The mean difference of 13.16 mm between amoxicillin and cephalexin was found to be statistically significant at P value 0.041 with lower and upper bound at 0.527 and 25.806 respectively. The mean difference of 2.65 mm between amoxicillin and clindamycin and - 10.50 mm between cephalexin and clindamycin was not found to be statistically significant. CONCLUSIONS Amoxicillin showed to be more potent among the antibiotics chosen for this study. Clindamycin showed to be a better alternative to cephalexin and could be the first choice in case of patients allergic to penicillin group of drugs. KEY WORDS Antibiotic Prophylaxis, Infective Endocarditis, Antimicrobial Potency, Minimum Inhibitory Concentration [MIC], Antimicrobial Susceptibility Test [AST], Kirby Bauer Disk Diffusion Method

Anterior perforated substance region aneurysms: review of a series treated with microsurgical technique.

Aneurysms arising from the distal carotid, proximal A1, and proximal M1 that project posteriorly and superiorly toward the anterior perforated substance (APS) are rare. Their open surgical treatment is particularly difficult due to poorly visualized origin of the aneurysm and the abundance of surrounding perforators. We sought to analyze the anatomical and clinical characteristics of APS aneurysms and discuss surgical nuances that can optimize visualization, complete neck clip obliteration, and preservation of adjacent perforators. Thirty-two patients with 36 APS aneurysms were surgically treated between November 2000 and September 2017. Patients were prospectively enrolled in a cerebral aneurysm database and their clinical, imaging, and surgical records were retrospectively reviewed. Twenty-seven aneurysms originated from the distal ICA, 7 from the proximal A1, and 2 from the proximal M1; 15 patients presented with subarachnoid hemorrhage. Careful intraoperative dissection revealed 4 aneurysms originating at the takeoff of a perforator; another 25 had at least 1 adherent perforator. All aneurysms were clipped except for one that was trapped. Postoperatively, 3 patients had radiographic infarctions in perforator territory with only 1 developing delayed clinical hemiparesis. Good outcome (modified Rankin Scale, 0-2) was achieved in 28 patients (88%). APS aneurysms present a challenging subset of aneurysms due to their complex anatomical relationship with surrounding perforators. These should be identified on preoperative imaging based on location and projection. Successful microsurgical clipping relies on optimization of the surgical view, meticulous clip reconstruction, preservation of all perforators, and electrophysiological monitoring to minimize ischemic complication.

Deformation and failure of thin spherical shells under dynamic impact loading: Experiment and analytical model

Thin curved shells are widely used in engineering. A shallow spherical shell is an effective representation of a curved shell affected by local impact loading. Therefore, the dynamic response of spherical shells under impact loading should be investigated to provide a design reference for curved shells applicable to engineering fields. In this study, the dynamic response and perforation of an aluminum spherical shell impacted by a cylindrical projectile were investigated theoretically. An isometric transformation was adopted to describe the major bending deformation of the spherical shell around the impact point. In addition, an edge region between the major bending part and an undeformed part was observed experimentally and described using a deformation mode. Hamilton's principle was adopted to derive the governing equations of the dynamic response of the impacted spherical shell. Furthermore, a viscoplastic strengthened model was introduced to describe the membrane force and bending moment of the perforation, whereas a rigid–plastic model was used to calculate the force and moment of the other parts of the spherical shell. The governing equations combined with the strengthened model were solved using the Runge–Kutta method. A comparison between the theoretical predictions and experimental results indicated a good agreement between them. Finally, the effects of the parameters set in the governing equations of the theoretical prediction were analyzed. We observed that the theoretical model predicted dimple radius more accurately than dimple depth. The dimple depth is linearly proportional to the impact velocity. In addition, the assumed sizes of the shear region of perforation only affect the ballistic limit and deformation generated by a velocity higher than the ballistic limit. The deformation and perforation of the impacted shell are almost independent of the initial width of the edge region of deformation. Additionally, we observed that the ballistic limit of the shell is linearly proportional to the shell thickness.

Bio-Absorption of Human Dentin-Derived Biomaterial in Sheep Critical-Size Iliac Defects.

The aim of this study was to evaluate the bio-absorption and bone regeneration of human tooth-derived dentin scaffold, entitled as perforated root-demineralized dentin matrix (PR-DDM), after in vivo implantation into the critical-size iliac defects. The dentin scaffolds were prepared from human vital, non-functional teeth. Thirty artificial macro-pores (Ø 1 mm) were added after removing the enamel portion. The modified teeth were supersonically demineralized in 0.34 N HNO3 for 30 min. The microstructure was observed by scanning electron microscope (SEM). The 3D micro-CT and histological analysis were carried out to evaluate the bio-absorption of PR-DDM at 2 and 4 months. A smooth dentin collagen surface with symmetrical macro-pores and tube-type dentinal tubules (Ø 1–2 µm) with micro-cracks were observed on the perforated region. A significant number of custom-made macro-pores disappeared, and the size of the macro-pores became significantly wider at 4 months compared with the 2 months (p < 0.05) evaluated by 3D micro-CT. Histological images revealed the presence of multinucleated giant cells attached to the scalloped border of the PR-DDM. The morphological changes due to bio-absorption by the cellular phagocytes were comparable to the 3D micro-CT and histological images at 2 and 4 months. Altogether, the results demonstrated that the PR-DDM block was gradually absorbed by multinucleated giant cells and regenerated bone. Human PR-DDM might serve as a unique scaffold for extraoral bone regeneration.

Cessation of methotrexate and a small intestinal resection provide a good clinical course for a patient with a jejunum perforation induced by a methotrexate-associated lymphoproliferative disorder: a case report

BackgroundMethotrexate (MTX) is a frequently used drug in the treatment of rheumatoid arthritis (RA), but occurrences of lymphoproliferative disorders (LPD) have been reported in patients undergoing an MTX regimen. Almost half of the patients with methotrexate-associated lymphoproliferative disorders (MTX-LPD) have extranodal lesions; moreover, although extremely rare, digestive tract perforations resulting from the extranodal lesions of MTX-LPD have also been reported.Case presentationWe describe the case of an 81-year-old woman with RA who had been prescribed MTX at 6 mg per week for the past 11 years. She was admitted to our hospital with occasional abdominal pain and was first diagnosed with enteritis. Her abdominal pain did not improve, and a computed tomography scan showed abdominal effusion and free air in the abdominal cavity. She was diagnosed with a digestive tract perforation and underwent emergency surgery. The perforation site was identified in the jejunum, and she underwent small intestinal resection around the perforated region. The pathological findings showed an ulcer in the jejunum and infiltration of large atypical lymphocytes around the perforated region. An immunohistochemical examination revealed the expression of a cluster of differentiation 20 and latent membrane protein 1. Considering the patient’s history of RA treated with MTX, she was diagnosed as having Epstein–Barr virus (EBV)-related MTX-LPD with a histological diagnosis of EBVMCU. MTX was discontinued after the surgery, and her soluble interleukin-2 receptor (sIL-2R) levels had returned to normal 1 year later. She has had a good course for the 2 years since surgery and remains asymptomatic with no recurrence of MTX-LPD, as confirmed by the sIL-2R levels.ConclusionWe experienced a rare case of the jejunum perforation induced by MTX-LPD. Since only a few cases have been reported of a patient with small intestinal perforation induced by MTX-LPD, further research is necessary to evaluate the clinicopathological features of MTX-LPD. The patient had disease remission after surgery and by discontinuing MTX treatment; our case did not require chemotherapy. EBV-positive patients, especially those with a pathological presentation of EBVMCU, could have a higher likelihood of remission, which could have been a factor in the present case.

Peritonitis and Necrotizing Hepatitis in Ara ararauna Caused by a Foreign Body

Background: The ingestion of foreign bodies in parrots has already been described and associated with the curious behavior of the birds or with stressful conditions. Foreign bodies in the gastrointestinal tract are usually diagnosed through clinical signs, laboratory tests, and radiographic findings in the historical data. Foreign bodies are usually metallic and can lodge in any segment of the gastrointestinal tract, commonly found in the proventricle and gizzard. This study investigated a case of necrotizing hepatitis due to a foreign body in Ara ararauna (Linnaeus, 1758).Case: An approximately 9-month-old specimen of caninde macaw, had sudden death and was referred for autopsy. The macroscopic examination revealed a fibrous, thick, reddish membrane involving the left hepatic lobe and partially the gizzard in continuity with the peritoneum. Inside the capsule, the liver had a friable and necrotic appearance and the gizzard had a focal perforation area containing a foreign body (gavage probe). We performed the histopathological examination of the liver and gizzard and observed that the membrane surrounding the liver and partially the gizzard had a chronic inflammatory process with a marked proliferation of fibrous tissue and fibrin deposition. The hepatic parenchyma of the left lobe showed diffuse and marked necrosis, with signs of ischemic necrosis. In the region of transmural perforation of the gizzard, the mucosa showed a focal area of extensive necrosis accompanied by the presence of intralesional bacteria. The lesions observed are attributed to the perforation of the organs by the foreign body. It is not known whether the bird ingested the object accidently during food handling as a young or due to the curious behavior of the bird or even the stress it may have been exposed to. The post-mortem examination revealed localized peritonitis and encapsulating necrotizing hepatitis, focally extensive and accentuated, associated with foreign body perforation.Discussion: The curious habit of parrots, can provide the ingestion of foreign bodies, in which they lodge in the gastrointestinal tract. Generally, the clinical signs are nonspecific, however, proventricular impaction, stasis and even perforations in the mucosa of organs can be observed. In the present study, we suspect that the Caninde macaw accidentally ingested a gavage probe during feeding management as a young. This object lodged in the bird's ventricle, perforating the organ and reaching the liver, due to intimate contact with the gizzard, providing a picture of ventriculitis and necrotizing hepatitis. Necrotizing hepatitis due to foreign body has been reported in the literature due to ingestion of perforating foreign body with lesion in the left ventricle and lobe, however we have no knowledge of reports with the presence of a capsule involving the left hepatic lobe, similar to a capsule like this, we understand that our report is the first description of encapsulating necrotizing hepatitis in birds. We believe that this capsule of connective tissue was formed, due to the inflammatory process in the peritoneal cavity, in birds the deposition of fibrin can form a structure similar to a capsule, in order to trap cells and the agent responsible for inflammation, preventing septicemia. Transmural perforation in the gizzard, observed in this case, allowed bacterial translocation that may have contributed to the worsening of the chronic condition and death due to the accumulation of toxins or bacterial translocation of the gastric tract, leading to liver infection and sepsis. We concluded that the presence of the perforating foreign body was responsible for the peritonitis and encapsulating necrotizing hepatitis in Ara ararauna.

Evaluation of Stress Distributions in Mandibular Molar Teeth with Different Iatrogenic Root Perforations Repaired with Biodentine or Mineral Trioxide Aggregate: A Finite Element Analysis Study

IntroductionIn this study, finite element analysis was used to evaluate the stress distributions in simulated mandibular molar teeth with various iatrogenic root perforation types after reparation with Biodentine (Septodont, Saint-Maur-des-Fossés, France) or mineral trioxide aggregate (MTA). MethodsAn extracted human mandibular molar tooth was scanned using a micro–computed tomographic device, and a 3-dimensional solid model was created. Then, 3 different iatrogenic perforation types (furcation perforation [FP], strip perforation [SP], and post drill perforation [PDP]) and 2 different repair materials (MTA and Biodentine [BD]) were simulated on the model. In addition, a sound tooth (ST) model (control) and a model left unrepaired for each type of perforation were created; then, access cavities were restored using resin composite, except for the sound tooth model. Consequently, a total of 10 experimental models were designed. An oblique force of 300 N angled at 45° to the occlusal plane was simulated. Evaluations of von Mises stress were performed in the perforated regions. ResultsMaximum von Mises stress values were 7.76 MPa for ST/corresponding to the FP region, 8.48 MPa for ST/corresponding to the SP region, 14.20 MPa for ST/corresponding to the PDP region, 10.89 MPa for FP /MTA, 7.65 MPa for FP/BD, 14.67 MPa for FP/unrepaired, 15.92 MPa for SP/MTA, 15.82 MPa for SP/BD, 21.95 MPa for SP/unrepaired, 10.20 MPa for PDP/MTA, 9.17 MPa for PDP/BD, and 17.86 MPa for PDP/unrepaired. ConclusionsThe results of this finite element analysis indicated that BD models showed lower maximum von Mises stress values than the MTA models, and SPs exposed higher stress concentrations in root perforation regions than FPs and PDPs. The use of MTA and BD may reduce the risk of potentially harmful stress in root perforation regions.

難治性上部消化管穿孔症例に対する内視鏡的フィブリン接着剤局注療法の応用(Application of endoscopic local injection of fibrin glue to treat refractory perforation cases in the upper digestive tract)

要旨内視鏡的止血法の1つとして，フィブリン接着剤（fibrin glue: FG）局注療法が報告されている。今回我々は，難治性上部消化管穿孔例に，FG局注療法を応用し，良好な結果を得た。症例1は79歳の女性。上腹部痛を主訴に救急搬送された。壊疽性胆嚢炎，胆石性膵炎の診断にて消炎後，胆嚢摘出術を施行した。その後，膵炎に合併した仮性膵嚢胞と接する胃体後壁に穿孔を認め，内視鏡的にFG局注療法を施行した。結果，約2週間で同部の閉鎖を見た。症例2は82歳の男性。嘔気と腹痛を主訴に救急搬送された。下部食道の特発性食道破裂の診断のもと，食道破裂部単純閉鎖術を施行した。約1か月後，縫合部の再穿孔を認め，内視鏡的にFG局注療法を施行した。その後，上皮形成を認め，閉鎖した。難治性上部消化管穿孔例に対し，内視鏡的FG局注療法は有用な閉鎖術になりうると考えられた。

Spontaneous Corneal Perforation

A male patient, 59 years of age, who had undergone a pterygium operation 45 days ago in another center, applied to our clinics for itching and burning complaints. The patient was examined and thinning of the cornea at the perilimbal region and intense hyperemia, inflammation and scarred tissue in the nasal conjunctiva were observed. Additionally, the patient had chronic dacryocystitis. Firstly, an external dacryocystorhinostomy (DSR) operation was applied. Three days after the operation, corneal perforation and iris prolapse occurred. An autograft, including conjunctiva, limbus and neighbouring corneal tissue with lamellar excision from the superior region of the same eye, was taken. With the help of 10/0 monofilament nylon sutures, the autograft was implanted. In the postoperative period, the patient’s cataract, which was present before the operation, progressed. In the postoperative 6th month, a cataract operation was performed. By the postoperative 7th month, the patient’s visual acuity was 0.00 logMAR and the perforation region had recovered completely.

Metallographic Investigations of the Premature Corrosion Failure of Steel Seam-Welded Galvanized Cold Water Pipes

A premature corrosion failure in seam-welded galvanized steel cold water pipes was reported to occur after just 18–24 months in service. The aim of the present work was to investigate the causes of this premature corrosion of pipes, through metallographic investigations. This work comprised chemical analyses, visual examination of internal surfaces of pipes and microstructural examinations of the corrosion perforation regions (pitting corrosion areas) using optical and scanning electron microscopy with energy-dispersive x-ray analysis. The investigations showed that failures resulted from incorrect installation—pipes were installed with yellow brass ball valves. When mixed with yellow brass, galvanized steel triggers dezincification and results in electrolytic action when combined with nonferrous metals, such as copper and brass.

Heat Transfer Enhancement and Turbulent Flow in a Rectangular Channel Using Perforated Ribs With Inclined Holes

In internal cooling passages in a turbine blade, rib structures are widely applied to augment convective heat transfer by the coolant passing through over the ribbed surfaces. This study concentrates on perforated 90 deg ribs with inclined holes in a cooling duct with rectangular cross section, aiming at improving the perforated holes with additional secondary flows caused by inclined hole arrangements. Two sets of perforated ribs are used in the experiments with the inclined angle of the holes changing from 0 deg to 45 deg and the cross section are, respectively, circular and square. Steady-state liquid crystal thermography (LCT) is applied to measure the ribbed surface temperature and obtain corresponding convective heat transfer coefficients (HTCs). Two turbulence models, i.e., the k–ω shear stress transportation (SST) model and the detached eddy simulation (DES) model, are used in the numerical studies to simulate the flow fields. All the inclined cases have slightly larger overall averaged Nusselt number (Nu) than with straight cases. The enhancement ratio is approximately 1.85–4.94%. The averaged Nu in the half portion against the inclined direction is enlarged for the inclined hole cases. The inclined hole cases usually have smaller averaged Nu in the half portion along the inclined direction. For the straight hole case and small inclined angle case, the penetrated flows mix with the mainstream flows at the perforated regions. When the inclined angle is larger, the penetrated flows are pushed to the inclined direction and mixing with the approaching flows occurs just at the side of the inclined direction.

A computational fluid dynamics analysis of the effects of size and shape of anterior nasal septal perforations.

Nasal septal perforations (NSPs) often cause bleeding, crusting, obstruction, and/or whistling. The objective was to analyze the impact of anterior NSP size and shape on nasal physiology using computational fluid dynamics (CFD). A 3-dimensional model of the nasal cavity was constructed from a radiologically normal CT scan using imaging software. Anterior NSPs (ovoid (ONSP): 0.5, 1, 2, and 3 cm long anterior-to-posteriorly and round (RNSP, 0.5 and 1 cm)) were virtually created in the model and divided into ventral, dorsal, anterior, and posterior regions. Steady-state inspiratory airflow, heat, and water vapor transport were simulated using Fluent CFD software. Air crossover through the perforation, wall shear, heat flux, water vapor flux, resistance, and humidification were analyzed. Air crossover and wall shear increased with perforation size. Regionally, wall shear and heat and water vapor flux were highest posteriorly and lowest anteriorly, generally increasing with size in those regions. RNSPs had greater heat and water vapor flux compared to corresponding size ONSPs. Resistance decreased by 10% or more from normal only in the 3 cm ONSP. Maximum water content was achieved more posteriorly in larger NSP nasal cavities. High wall shear and heat and water vapor flux in posterior perforation regions may explain the crusting most commonly noted on posterior NSP edges. This preliminary study suggests that larger NSPs have a greater effect on nasal resistance and water content. Decrease in resistance with larger NSP size may be implicated in reported symptomatic improvement following enlargement of NSPs for treatment.

Thermal behavior and fluid flow during humping formation in high-speed full penetration gas tungsten arc welding

An unusual type of humping defect with periodic humped region and perforated region may occur in high-speed full penetration GTAW, which deteriorates the homogeneity of weld property seriously. In this paper, the thermal behavior and fluid flow during full penetration humping (FP-humping) formation is revealed by a numerical investigation to explain the defect's physical mechanism. Self-adaptive double-ellipse distributions of arc heat flux, arc pressure, arc shear stress and electromagnetic force varying with transient free surface evolution are proposed. For the first time, the actual morphology of FP-humping in GTAW can be predicted numerically. The numerical results are well verified by experimental weld geometry and high-speed melt pool images captured by a color camera. The workpiece is melted under arc heat to form the melt pool, and its free surface is gouged significantly under strong arc forces. When the depth of gouging region approaches workpiece thickness, the bottom thin liquid layer in gouging region is easily disrupted to initiate FP-humping formation. The lateral channel becomes the only transfer channel for liquid metal backward flow. The transition region between lateral channel and rear part of melt pool will be necked, and solidified instantly without the arc heat. Both scaling model of thermal conduction and numerical results imply that the premature solidification of necked lateral channel is a predominant factor to influence the FP-humping formation.