A Comparison between Different Materials Based on Transition Metal Oxides as Additivesfor Laser Bonding on Stainless Steel

In this work, a new modification of the laser bonding is considered. Only one specific transition metal oxide is used to create an additive coating on a stainless surface. The following materials have been selected for comparative analysis: MoO3, WO3 and a commercial laser bond ink produced by TherMark. Temperatures over 2,000 K at the focal spot, with a very steep temperature increasing front of 107 K/s and spatial gradients of 107 K/m, have been evaluated. The mechanical properties of the coating have been studied by ramp scratch and Vickers hardness tests. The structural state and adhesive properties have been studied by X-ray diffraction (XRD) and Raman spectroscopy. A spectrophotometer has been used to estimate the contrast. The experimental results show a hard coating with excellent adhesion to the substrate with a thickness of several m. The presence of intermediated oxides has been detected, which is an indication of oxidation processes. The good adhesion is explained by a chemical bond between the oxide and the substrate

TRANSITION METAL OXIDES AS MATERIALS FOR ADDITIVE LASER MARKING ON STAINLESS STEEL

The product information plays an important role in the improvement of the manufacturing, allowing the tracking of the part through the full life cycle. Laser marking is one of the most versatile techniques for this purpose. In this paper, a modification of the powder bed selective laser melting for additive laser marking of stainless steel parts is presented. This modification is based on the use of only one transition metal oxide chemically bonded to the stainless steel substrate, without using any additional materials and cleaning substances. The resulting additive coatings, produced from initial MoO3 and WO3 powders, show strong adhesion, high hardness, long durability and a high optical contrast. For estimation of the chemical and structural properties, the Raman and X-Ray Diffraction (XRD) spectroscopy have been implemented. A computer model of the process of the laser melting and re-solidification has been developed as well. A comparative analysis of the properties of both (MoO3 and WO3) additive coatings has been performed. An attempt for a qualitative explanation of the thermo-chemical phenomena during the marking process has been undertaken

Finite Element Analysis of Cardiovascular Stents

The cardiovascular diseases have become contemporary and continuously growing healthcare problems. The main reasons for such problems are the intra-vessel depositions of plaque, cholesterol, etc., that give rise to thrombus formation, arterial blockage and stenosis. A traditional cure for said problems is to implant a stent. According to the “Guidance for Industry and FDA Staff - Non-Clinical Engineering Tests and Recommended Labeling for Intravascular Stents and Associated Delivery Systems”, an intravascular stent is a tubular structure intended for permanent implant in native or graft vasculature. The stent is designed to provide mechanical radial support after deployment. This support is meant to enhance vessel patency over the life of the device. Once the stent reaches the intended location, it is expanded by a balloon or self-expanding mechanisms described below. There are two types of stents: the so-called balloon-expandable stents and self-expanding stents. The balloon-expandable stents are expanded by a catheter. They retain the required diameter after deflation of the catheter. The self-expandable stents are expanded from the pre-deployed to the post-deployed diameter size in absence of a catheter. This can be a result of the properties of the material or/and geometry. This work presents the finite element analysis (FEA) of mechanical behavior of balloon-expandable stents, produced from stainless steel 316L and Cobalt-Chromium alloy L-605

Simulation and Control of One-room Heating, Ventilation and Air-conditioning System

In the present study, a practical model of one-room thermodynamic behavior is proposed handling different dynamic modes of operation of air-conditioner and the corresponding adapted controllers. The developed model is based on the algorithm of Van Schijndel coupling the CFD modelling with SimuLink environment. A S-function block has been programmed which provides 5 input entities and 8 output entities to the Sfunction block thus simulating conditions close to the practice including unavoidable perturbation and constituting a MIMO system. The optimal position of the sensor has been achieved and the corresponding characteristics and optimal performance of standard PID/PI controller have been tuned in attempt to reach maximum comfort and cost effective conditions

ADDITIVE LASER BARCODE PRINTING ON HIGH REFLECTIVE STAINLESS STEEL

In this paper, the process of an additive laser marking on stainless steel parts for barcode printing is presented. It is based on the use of one transition metal oxide chemically-well bonded to the stainless steel substrate, without a usage of any additional materials and cleaning substances. The resulting additive coatings, produced from initial MoO3 powder by irradiation with a laser beam, reveal strong adhesion, high hardness, long durability and high optical contrast, which make the process suitable for barcode printing on materials such as high reflective stainless steel, which was always a challenge for the classical laser marking technologies. The obtained bar patterns are in a compliance with the requirements of the existing standards

Transition metal oxides as materials for additive laser marking on stainless steel

The product information plays an important role in the improvement of the manufacturing, allowing the tracking of the part through the full life cycle. Laser marking is one of the most versatile techniques for this purpose. In this paper, a modification of the powder bed selective laser melting for additive laser marking of stainless steel parts is presented. This modification is based on the use of only one transition metal oxide chemically bonded to the stainless steel substrate, without using any additional materials and cleaning substances. The resulting additive coatings, produced from initial MoO₃ and WO₃ powders, show strong adhesion, high hardness, long durability and a high optical contrast. For estimation of the chemical and structural properties, the Raman and X-Ray Diffraction (XRD) spectroscopy have been implemented. A computer model of the process of the laser melting and re-solidification has been developed as well. A comparative analysis of the properties of both (MoO₃ and WO₃) additive coatings has been performed. An attempt for a qualitative explanation of the thermo-chemical phenomena during the marking process has been undertaken

Distal transradial access. Initial experience. Results

Въведение: Конвенционалният достъп през радиалната артерия (cTRA) е стандартен подход при коронарни интервенции. За съжаление той крие риск от дългосрочни компликации като оклузия на радиалната артерия (RAO)и локални усложнения –хематоми. Цел: Споделяне на начален опит в прилагането на дистален трансрадиален достъп (dTRA) при 134 пациенти от един оператор в един център и приложимостта му при STEMI. Необходимият брой процедури за усвояване на достъпа, оценено по степента на редукция на неуспешните процедури. Материали и методи: От 08.03.21 г. до 18.11.21 г. 134 пациенти с dTRA (110 успешни, 24 неуспешни) са включени в студията. За dTRA се приема достъпа в анатомичния snuffbox. За успех на достъпа се приема завършването на цялата процедура, а не само успешна пункция или поставяне на интродюсер. Резултати: Установи се, че успеваемостта на метода е 82% при заложените критерии. От успешните процедури 48% са били интервенции. От тях с ОКС са били 71%, като 43,6% са били със STEMI. При 3-ма пациенти е използван достъпът за СТО. При двама пациенти е извършена ротаблация с използване на интодюсер 7в 6 Fr. 98% от пациентите са били с 6 Fr интродююсер. При 93% от пациентите е използван десен dTRA. От извършените 134 процедури бива установено, че 92% от неуспешните случаи са до 80-та процедура. След 80-та процедура честотата на неуспешните случай значително намаля. Усложнения ‒ 3 малки хематома и 2 изтръпвания на палеца, които не са изисквали допълнителни интервенции. Заключение: При висок процент от пациентите се постига успешно завършване на процедурата с dTRA включително и при рисковите пациенти с ОКС и STEMI. След 80-та процедура на dTRA е достигнато ниво на тренираност с ниска честота на неуспешни процедури. Това дава убеждението, че dTRA може да бъде алтернатива на стандартния радиален достъп с цел превенция на оклузията на радиалната артерия, което е потвърдено от предходни проучвания, по-добър комфорт на пациента и по-нисък риск от усложнения. Резултатите се постигат без да има нужда от редукция на диаметъра на интродюсерите или използване на специални устройства за хемостаза. Introduction: Conventional access through the radial artery (cTRA) is a standard approach in coronary interventions. Unfortunately, it carries a risk of long-term complications such as radial artery occlusion (RAO) and local complications, usually hematomas. Aim: Sharing initial experience in the application of distal transradial access (dTRA) on 134 patients, from single operator in one center and its applicability on patients with STEMI. Number of procedures required to get experience with this access, assessed by the degree of reduction of failed procedures. Materials and methods: From 08.03.21 to 18.11.21, 134 patients with dTRA (110 successful, 24 unsuccessful) were included in the study. dTRA is comsidered to be an access to the anatomical snuffbox. Completion of the entire procedure, not just a successful puncture or insertion of an introducer, was considered the access successful. Results: It was found that the success of the method was 82% of the criteria preset. Among the successful procedures, 48% were interventions. Of these, 71% had ACS and 43.6% had STEMI. The access was used on 3 patients who had CTO. Two patients underwent rotablation using a 7 in 6 Fr introduser. On 98% of the patients a 6 Fr introducer was used. Right dTRA was used on 93% of patients. From the 134 procedures performed, it was found that 92% of failures were up to the 80th procedures. After the 80’th procedures the frequency of failures decreased significantly. Complications ‒ 3 small hematomas and 2 numbness in the thumb, which did not require additional interventions. Conclusion: The procedure with dTRA was successfully completed by high percentage of patients, including the high-risk patients with ACS and STEMI. After the 80th dTRA procedure was reached level of skills with a low frequency of failed procedures. This suggests that dTRA can be an alternative to standard radial access to prevent radial artery occlusion, which has been confirmed by previous studies, better patient comfort, and lower risk of complications. The results were achieved without the need of reduction of the introducer’s diameter or use of special devices for hemostasis