Objective: to improve the effectiveness of surgical treatment of hiatal hernia (HH) by timely prevention of complications associated with Nissen fundoplication. Material and methods : the study included 140 patients with НН who were divided into two groups. The control group consisted of 67 patients who underwent traditional laparoscopic Nissen fundoplication combined with cruroplasty (hiatal crural repair). The study group consisted of 73 patients, who underwent a modified technique of laparoscopic Nissen fundoplication with cruroplasty, and the use of a composite mesh implant. The study group also underwent proprietary procedures for preventing early postoperative complications were implemented, that allowed for a more complete assessment of their impact on treatment outcomes. Results : in the study group, early postoperative complications of varying severity occurred in 12 (16.4%) patients: dysphagia - in 4, reflux esophagitis grade A - in 7 cases, postoperative pneumonia - in 1 case. In the control group, after standard laparoscopic Nissen fundoplication with cruroplasty, early postoperative complications were noted in 29 (43.3%) cases: early dysphagia in 13 (19.4%) cases, failure of the fundoplication cuff in 2 (3.0%) cases, reflux esophagitis grades A and B in 12 (17.9%) cases, postoperative pneumonia in 2 (3.0%) cases. Conclusion : the study results confirm that implementation of the proposed preventive measures reduces the risk of mechanical dysphagia after surgery. Therefore, the proposed approach can be considered an effective strategy for preventing these postoperative complications.
Cemented carbides of fine-grained WC-Co combined with VC has high hardness and strength for cutting tool. VC is known as a grain growth inhibitor; however, its effect on the microscopic mechanical properties, especially the WC-WC bonding strength, remains unclear. In this study, we investigated the WC-WC interfacial structure and the strength of WC-Co, WC-Ni and WC-VC-Co. Microcantilevers, including the WC-WC interface, were fabricated using mechanical polishing and focused ion beam (FIB) methods. Bending tests were performed using the nanoindentation technique to determine the WC-WC interfacial bonding strength. The results showed that the WC-VC-Co have lower strength than WC-Co. Transmission electron microscopy (TEM) observations indicated the segregation of V on the WC surface. The V-based thin layer reduces the strength between the WC grains, resulting in poor mechanical properties that induce WC-particle dropout. Hence, appropriately controlling the amount and size of VC is crucial for achieving good mechanical properties.
Stainless steel is used in a wide range of applications due to excellent mechanical properties and corrosion resistance. However, there is a difficulty in forming unmachinable small diameter and deep holes since stainless steel is a difficult-to-cut material. Additionally, the application of sintered stainless steel is limited to items that do not require airtightness due to the presence of pores inside the material. Although a method of increasing the density using liquid phase sintering was considered to reduce internal pores of sintered stainless steel, it significantly affects dimensional accuracy and post-processing after sintering because of the generation of large amount of shrinkage. In order to solve the above issues, we developed a high-density green machining method that combines a technique to increase density during powder compaction and a green machining process. We have succeeded in producing a stainless steel sintered material with a density of 95 vol% that does not leak even when evaluated for tightness under high-pressure hydrogen conditions of 70 MPa.
Parking support parts are used for the parking lock system, which keeps a vehicle when it is parked. These parts have a wide variety of shapes depending on the layout of the transmission unit. In applying the PM technology to parking support parts, we advanced techniques such as powder removal compacting, undercut compacting, and irregular-shaped two-piece compacting by proposing product shapes suitable for net shape manufacturing. Furthermore, partial laser hardening was applied where wear resistance is required, ensuring accuracy. This method contributed to a 94.5 % reduction in CO2 emissions compared with conventional carburizing and quenching and enabled the development of environmentally friendly parking support parts.
ISO Standard 23519:2010 defines the surface roughness of sintered metal parts: Rk and Rpk, and it intends to provide relevant surface roughness data regardless of porosity,- however the data reliability tends to be insufficient in practice. The following parameters might influence the surface roughness data in accordance with the standard such as; measuring probe, instruments, filters, and others. The effect of such parameters was investigated and compared with an optical method using white light interferometry. 3 different measuring instruments were used. The measured surfaces of specimens having density of 6.4, 6.8 and 7.2 are punch facing side. In this study, details of the results are presented.
