The Empirical Assessment of Vibration in HVAC Systems

Background and purpose: Vibration caused by ventilation systems in buildings is one of the harmful physical factors that can cause harm to residents. Therefore, measuring and controlling vibration is important. Materials and Methods: In the first step of the study, the vibration accelerometer was placed on the base of a fan where the vibrations were sent toward the duct wall. A vibration assessment of the building was conducted in the other steps to compare with guidelines. In the next step, isolation method was used to control vibration. By placing the isolator on the duct wall, the accelerometer was located on the body of the duct wall and the value of vibration was measured in a millimeter per second. All stages of the experiment were performed in the Faculty of Health of Isfahan University of Medical Sciences in 2018. Results: The maximum vibration velocity reduction in the building was related to the frequency of 68 Hz, which reached 33 mm/s after isolation. In addition, the fan vibration at 485 Hz was equal to 2.1 m /s, which decreased to 2 mm /s after isolation. Conclusion: Comparison of vibration after fan isolation with standard showed that this method has been effective in reducing the fan vibration resulting in the vibration to reach below the standard.

Mediastinal thoracic duct cyst: A rare entity

Thoracic Duct Cysts (TDCs) are exceedingly rare benign masses of the posterior mediastinum. They are thought to arise from congenital or degenerative weakening in the thoracic duct wall. We bring to light an incidentally detected posterior mediastinal cystic lesion that caused dysphagia in our patient and was found to be a thoracic duct cyst.

Spontaneous common bile duct perforation due to choledocolithiasis accompanied with pancreaticobiliary maljunction in an adult: a case report

Background Spontaneous common bile duct (CBD) perforation is an extremely rare disease in adults. We report an adult case of CBD perforation due to choledocolithiasis accompanied with pancreaticobiliary maljunction, which is, to our knowledge, the first such case report based on a search using PubMed. Case presentation A 71-year-old woman with consciousness disorder was transported to the emergency department of another hospital. She was diagnosed as having severe peritonitis with septic shock and transferred to our hospital for emergency surgery. Enhanced computed tomography (CT) revealed supraduodenal CBD dilation similar to a diverticulum and a defect of bile duct wall continuity. Furthermore, CT showed a long common channel of the pancreaticobiliary duct, so she was diagnosed as having spontaneous CBD perforation with pancreaticobiliary maljunction. Emergency surgery was performed that revealed a necrotic diverticulum-like change on the supraduodenal part, and a 2.5 × 1 cm perforation was found on the anterolateral wall of the CBD. Peritoneal lavage was performed, and CBD perforation was resolved with a T-tube. The patient suffered refractory intra-abdominal and retroperitoneal abscess formation and bleeding from the abdominal wall, which required a long period of postoperative management. The T-tube was removed on day 136, and the patient was transferred on day 153. Conclusion The cause of CBD perforation is commonly considered to be increased intraductal pressure or weakness of the bile duct wall. In this case, pancreaticobiliary maljunction may have significantly influenced onset and the postoperative course. This case suggests that early surgical intervention and appropriate drainage are important to ensure survival.

Screening for Hilar Biliary Invasion in Ampullary Cancer Patients

Background: The treatment for ampullary cancer is pancreatoduodenectomy or local ampullectomy. However, effective methods for the preoperative investigation of hilar biliary invasion in ampullary cancer patients have not yet been identified. In this study, we aimed to determine an appropriate method for investigating hilar biliary invasion of ampullary cancer.Methods: Among 43 ampullary cancer patients, 34 underwent endoscopic treatment (n = 9) or surgery (n = 25). Imaging findings (thickening and enhancement of the bile duct wall on contrast-enhanced CT (CECT), irregularity on endoscopic retrograde cholangiography (ERC), thickening of the entire bile duct wall on intraductal ultrasonography (IDUS), and partial thickening of the bile duct wall on IDUS) and biliary biopsy results were compared with respect to their ability to diagnose hilar biliary invasion of ampullary cancer.Results: Hilar invasion was not observed in every patient. Among the patients who did not undergo biliary stent insertion, the combination of partial thickening of the bile duct wall on IDUS and biliary biopsy showed the highest accuracy (100%) for diagnosing biliary invasion. However, each imaging finding and biliary biopsy yielded some false positive results.Conclusions: Although some false positive results were obtained with each method, the combination of partial thickening of the bile duct wall on IDUS and biliary biopsy was useful for diagnosing hilar biliary invasion of ampullary cancer. However, hilar invasion of ampullary cancer is rare; therefore, the investigation of hilar biliary invasion of ampullary cancer might be unnecessary.Trial registration: not applicable

A 3D Numerical Simulation on Heat Transfer Behavior in Eagle ID1 In-Pile Test Using Finite Volume Particle Method

The EAGLE in-pile ID1 test was performed by Japan Atomic Energy Agency to demonstrate the effectiveness of fuel discharge from a fuel subassembly with an inner duct structure during a core disruptive accident in a sodium-cooled fast reactor. The experimental results suggested that early duct wall failure observed in the test was initiated by high heat flux from the molten pool of fuel and steel mixture, and the post-test numerical calculation and analyses showed that the high thermal load may be enhanced effectively by molten steel with a rather high thermal conductivity. In this study, to overcome weakness in conventional fluid-dynamic calculations, we adopted a fully 3D Lagrangian approach based on the finite volume particle method to analyze the mechanisms of heat transfer from the molten pool to the duct wall in the ID1 test. A series of behaviors representing pin disruption, molten pool formation, as well as the mixing and separation of molten steel and fuel in the pool was simulated to investigate their effects on molten pool-to-duct wall heat transfer. The present 3D particle-based simulation, which moderated some inherent defects in our previous 2D calculations, clarified that direct contact of the solid fuel with nuclear heat and liquid steel near the duct wall can expose the duct wall to a large thermal load, which led to the duct wall failure in the experiment.

Synthesis of Aluminum Foam and Its Application in reducing Noise Pollution in a Gas Power Plant Under Construction

: The noise pollution is among the major challenges of installing the equipment and development of industries. Controlling produced noise in small power plants is a necessity for its development. The present study was conducted to predict the reduction of exhaust noise pollution in a 25 MW gas power plant using the synthesized aluminum foam in a gas power plant under the construction. The noise pollution was measured in a similar gas power plant to predict noise sources in the Tarasht gas power plant. One centimeter thick aluminum foam was synthesized with an average size of about 300 - 500 µm and a porosity of 90%. The impedance tube was used to determine the sound absorption coefficient of aluminum foam. Then, the sound pressure level was predicted by ANSYS software before and after applying aluminum foam in a simulated environment on the exhaust duct wall. Results showed that with the 10 cm of thick insulation layer includes punctuating stainless steel plates, refractory fabric, and closed-cell aluminum foam at high frequency, at least an 8 dB reduction in the noise pollution was obtained the exhaust duct wall compared to the duct wall without the aluminum foam. Aluminum foam can be used as a suitable sound insulator in the power plant industry. Furthermore, it has various advantages over other insulators, such as the resistance to moisture, heat, and vibration attenuation due to noise, proper high rigidity at a low weight, and most importantly, less environmental pollution.

Studies on Flows Development in a Suddenly Expanded Circular Duct at Supersonic Mach Numbers

This article focuses on the flow development and the static wall pressure distribution along the circular duct from the convergent-divergent (CD) nozzle. The study aims to examine the quality of the stream in the conduit when the control is employed. The microjets are activated at the base at (PCD) of 13 mm, and the diameter of the microjets is 1 mm. Mach numbers of the investigation are 1.3, 1.9, and 2.4. The length of the duct considered was from L = 10D to 1D. The diameter of the enlarged tube was 16 mm. The experiments were conducted for NPRs from 3 to 11. The results revealed that the lowest duct length mandatory for the flow continued to attach with the circular duct wall are L/D = 1, 2, and 3 for Mach numbers 1.3, 1.9, and 2.4, respectively. The investigation outcome indicates that there are mild oscillations in the flow-field for correctly expanded flows. The oscillatory trend has a pronounced impact on the duct's flow when the jets are operated at higher NPRs. The control does not adversely affect the flow field, and the magnitude of wall pressure is nearly similar.