超声振动对5A06铝合金自冲铆接头静力学性能影响

自冲铆接工艺作为一种性能优异、绿色、高效的连接新技术,可实现同种、异种和多层轻合金薄板材料的连接,广泛应用于新能源汽车等领域,成为实现车身轻量化的关键技术之一。但由于自冲铆接头是典型的紧密连接构件,在交变应力或振动作用下,易发生微动损伤,致使接头提前疲劳失效。本文选用5A06铝合金薄板材料,分别进行自冲铆接和不同超声焊接工具头下的超声自冲铆复合连接试验,基于拉伸-剪切和电子显微镜测试,研究超声振动对5A06铝合金自冲铆接头静力学性能的影响。研究表明:超声振动可有效提高自冲铆接头的静力学性能;超声金属焊接与自冲铆接复合连接时会在板材之间形成固相焊接,这是提高复合接头力学性能的根本原因;超声金属焊接头的焊接面积影响自冲铆接头的力学性能,焊接面积较大时超声固相焊的程度较高;超声焊接会使铆钉温度升高,一定程度影响接头稳定性。

Impact of the COVID-19 Pandemic on the Management Course of Paediatric Rheumatic Diseases in a Tertiary Care Hospital of Bangladesh

Background: The COVID-19 pandemic had a significant impact on every aspect of life. Like other chronic diseases, pediatric rheumatic diseases (PRDs) also faced unique challenges during the pandemic, including limited access to care, concerns regarding infection risk, drug shortages and social isolation. Objective: The objective of the study was to identify the impact of the COVID-19 pandemic on the management course of children with rheumatic diseases. Methods: This cross-sectional study was conducted in the department of paediatrics, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka from April 2021 to March 2022. Two hundred and twenty patients were enrolled. A predesigned questionnaire was completed which included socio-demographic, clinical and laboratory parameters. Disease activity was assessed clinically and from laboratory profile. Data were calculated manually and by using SPSS version 22. Z-proportion test and chi square test were done when applicable. Results: Among the enrolled PRD cases 87.7% were Juvenile Idiopathic Arthritis (JIA), 7.7% were Systemic Lupus Erythematosus (SLE) and 4.6% were other cases. Irregular follow-ups were found in 69.9% JIA cases, 82.4% SLE cases and 60% other PRD cases. Poor drug compliance was present in 18.2% of cases. A significant number of patients had higher disease activity or flare during the COVID-19 pandemic. Conclusion: During COVID-19 pandemic most (70.5%) of the PRD patients were irregular in their follow-ups. Poor drug compliance was also more than in the pre-COVID period. Disease activity status significantly worsened during this period.

Disseminated Intravascular Coagulation at Diagnosis in Acute Myeloblastic Leukaemia

Background: Disseminated Intravascular Coagulation (DIC) is a life threatening complication frequently observed in acute leukemia. Among the morphological varieties of Acute Myeloid Leukaemia (AML), Acute Promyelocytic Leukaemia (APL) is well established to cause DIC. But there have been reports noted that abnormal DIC parameters also commonly observed in the patients with non-APL AML. This study evaluated the DIC parameters & DIC score according to International Society of Thrombosis and Haemostasis (ISTH) in newly diagnosed non-APL AML patients. Materials and Methods: This cross-sectional observational study was conducted in the Department of Haematology, BSMMU, Dhaka, Bangladesh. 48 newly diagnosed non-APL AML patients were enrolled. Platelets count was measured by auto analyzer (Sysmax XT 2000i/Pentra ABX-120DX) as well as checked manually. Prothrombin time, fibrinogen, D-Dimer were measured using STAGO Coagulation analyzer. The ISTH-DIC scoring system was used to calculate DIC score. The statistical analysis was carried out using the Statistical Package for Social Sciences version 24.0 for Windows. Chi-Square test & Fisher exact test was used for categorical variables. Unpaired t-test was used to compare mean between groups. For all statistical tests, p-value less than 0.05 was considered as statistically significant. Results: By analyzing 48 newly diagnosed patients with non-APL AML, found that DIC developed in 14.6% patients at presentation. Among the DIC parameters, PT and D-dimer were significantly higher in patients presented with DIC. Patients with DIC exhibit lower expression of CD117, CD34, HLA-DR and statistically significant association with negative expression of HLA-DR (p-value 0.034). No significant association was found between presence of DIC and age, gender, bleeding at presentation, morphological type, WBC count or peripheral blast percentage. Conclusion: Abnormalities of DIC parameters in common in patients with AML. A significant portion of patients with DIC have no apparent symptom or bleeding. So, routine screening of DIC parameter at presentation is recommended for early diagnosis & effective management of DIC.

Efficacy of Some Botanical Extracts on the Control of Late Blight Disease in Experimental Potato Field

Late blight caused by Phytophthora infestans (Mont.) De Bary is the most devastating disease of potato. This study was carried out to evaluate the efficacy of ten botanical extracts against the late blight disease incidence and severity in experimental potato field at University of Rajshahi, Bangladesh during 2019-2020. Crude aqueous extract of leaves of Syzygium cumini, Psidium guajava, Eucalyptus globusus, Carica papaya and Lawsonia inermis;fruits of Terminalia bellirica, T. chebula and Piper nigrum;flower buds of Syzygium aromaticum and cloves of Allium sativum were used at 5% (w/v) concentration for evaluation. Out of ten botanicals, Syzygium cumini leaves extract was found most effective in controlling the late blight disease incidence and severity up to 66 DAS (days after sowing) and increased the potato yield by 71.29% compare to untreated control. The efficacy of Lawsonia inermis extract against late blight disease was found promising and increased the potato yield by 48.51%. Other four botanical extracts (Terminalia chebula, Piper nigrum, Syzygium aromaticum and Carica papaya) showed moderate efficacy against the incidence and severity of late blight disease, and increased 30% more potato yield compare to control. These results suggest that botanical extract of Syzygium cumini has a great potential as an alternative of chemical fungicides to control the late blight disease of potato in eco-friendly way.

Photocatalytic Degradation of p-Nitrophenol (PNP) in Aqueous Suspension of TiO₂

The effects of initial concentrations of PNP, doses of TiO2, cations and anions have been investigated to find out the conditions for the maximum degradation of PNP in presence of 254 nm UV light. The rate of photocatalytic degradation of PNP was increased with increasing TiO2 dose until the dose concentration reached at a value 0.4 g/100 mL. Further increase of TiO2 decreased the degradation. The maximum degradation of PNP was found with the catalyst dose 0.4 g/100 mL at pH 3. The degradation of PNP was decreased with increasing of PNP concentration. About 90% degradation of PNP was observed when 1.0 × 10﹣4 M PNP was irradiated for 2 hours in 0.4 g/100 mL of TiO2 suspension. The effect of Cu(II) and Fe(II) ions on the degradation was also investigated. Addition of Cu(II) ions enhances the percent degradation but excess of Cu(II) ions decreases the degradation. Under the same experimental conditions, the presence of and is found to be detrimental to the photodegradation of PNP. Hydrogen ion concentration of reaction mixture was found to increase continuously during photodegradation suggesting mineralization of PNP.

Control Schemes for Passive Teleoperation Systems over Wide Area Communication Networks with Time Varying Delay

In this paper,the problem of time varying telecommunication delays in passive teleoperation systems is addressed.The design comprises delayed position,velocity and position-velocity signals with the local position and velocity signals of the master and slave manipulators.Nonlinear adaptive control terms are employed locally to cope with uncertain parameters associated with the gravity loading vector of the master and slave manipulators.Lyapunov-Krasovskii function is employed for three methods to establish asymptotic tracking property of the closed loop teleoperation systems.The stability analysis is derived for both symmetrical and unsymmetrical time varying delays in the forward and backward communication channel that connects the local and remote sites.Finally,evaluation results are presented to illustrate the efectiveness of the proposed design for real-time applications.