Investigation of Adhesive’s Material in Hermetic MEMS Package for Interfacial Crack between the Silver Epoxy and the Metal Lid during the Precondition Test

A hermetic Micro-Electro-Mechanical Systems (MEMS) package with a metal lid is investigated to prevent lid-off failure and improve its reliability during the precondition test. While the MEMS package benefits from miniaturization and low cost, a hermetic version is highly sensitive to internal pressure caused by moisture penetration and the reflow process, thus affecting its reliability. In this research, the finite element method is applied to analyze the contact stress between the metal lid and the silver epoxy by applying the cohesive zone model (CZM). Moreover, the red dye penetration test is applied, revealing a microcrack at the metal lid/silver epoxy interface. Further analyses indicate that the crack is caused by internal pressure. According to the experimental testing and simulation results, the silver epoxy material, the curing process, the metal lid geometry, and the bonding layer contact area can enhance the bonding strength between the metal lid and the substrate.     

Pantograph Sliding Strips Failure—Reliability Assessment and Damage Reduction Method Based on Decision Tree Model

Damage to the pantograph or sliding strip may cause the blocking of the railway line. This is the main reason for which the prediction of pantographs’ failure is important for railway carriers and researchers. This article presents a sliding strips failure prediction method as a main means of preventing disruptions to the transport chain. To develop the best predictive model based on the decision tree, the complex tree, medium tree and simple tree machine learning methods were tested. Using a decision tree, the categorization of the given technical conditions can be properly realized. The obtained results showed that the presented model can reduce sliding strip failure by up to 50%. Special attention was paid to the current collector (AKP-4E, 5ZL type), measured during periodic reviews of locomotives EU07 and EU09. To assess the reliability of the selected pantograph strips, a non-destructive degradation analysis was carried out. On the basis of the wear measurements of the strips and the critical value of wear, a failure distribution model was developed. Operational data, collected during periodic technical reviews, were provided by one of the biggest railway carriers in Poland. The results of the performed analyses may be used to build a preventive maintenance strategy to protect pantographs. The applied reliability models of wear propagation can be extended by the parameters of the cost and repair time becoming the basis for estimating the costs of operation and maintenance.     

Outcomes of venous ulcer care: results of a longitudinal study

A longitudinal study involving 81 patients with venous ulcers was conducted to explore the outcomes and cost of wound care in a home healthcare (HHC) setting and an outpatient care setting. Ulcers were managed with a saline gauze or hydrocolloid dressing and compression hosiery, or covered with an Unna's boot. Outcomes did not vary between physician's office and home care. Patients preferred home care, but costs and charges were much higher for HHC than for patients managed in the physician's office. Recurrence rates and costs varied greatly. Eighty-eight percent of ulcers in the saline dressing group did not heal or recurred compared to 21% of ulcers in the Unna's boot and 13% of ulcers in the hydrocolloid dressing group. The data also suggest hydrocolloid dressings are more cost-effective than Unna's boot or saline-gauze dressings. Controlled clinical studies to ascertain the cost-effectiveness of venous ulcer care in different patient care settings and the use of different treatment modalities, as well as care system oriented toward outcome for the patient rather than service, design, and distribution, are needed.     

A New Approach for Fatigue Reliability Analysis of Thin-Walled Structures with DC-ILSSVR

Fatigue analysis is of great significance for thin-walled structures in the spacecraft industry to ensure their service reliability during operation. Due to the complex loadings of thin-walled structures under thermal–structural–acoustic coupling conditions, the calculation cost of finite element (FE) simulations is relatively expensive. To improve the computational efficiency of dynamic reliability analysis on thin-walled structures to within acceptable accuracy, a novel probabilistic approach named DC-ILSSVR was developed, in which the rotation matrix optimization (RMO) method was used to initially search for the model parameters of least squares support vector regression (LS-SVR). The distributed collaborative (DC) strategy was then introduced to enhance the efficiency of a component suffering from multiple failure modes. Moreover, a numerical example with respect to thin-walled structures was used to validate the proposed method. The results showed that RMO performed on LS-SVR model parameters provided competitive prediction accuracy, and hence the reliability analysis efficiency of thin-walled pipe was significantly improved.     

Sliding State Analysis of Fractal Rough Interface Based on the Finite Element Method

Local high temperature, stress concentration, and abnormal friction coefficients will appear at the friction pair in a wet clutch as a result of surface topography real-time changing. In order to improve the reliability of clutch friction components and reduce the failure phenomenon, the three-dimensional fractal surface topography data of the actual rough surface asperities are scanned, extracted, and processed successively, and then the finite element model of the rotary sliding friction pair is established considering the micro surface topography. Based on the finite element model, the variation of surface stress and strain is analyzed, and the friction coefficient measured experimentally is taken as the model input. It is concluded that when the rough surface and smooth surface make contact with each other, the maximum stress and plastic strain appear at the inner radius edge. Therefore, this research has a guiding significance for the structural design and processing technology of the friction components in a vehicle clutch.     

The Effect of the Crucible on the Temperature Distribution for the Growth of a Large Size AlN Single Crystal

The appropriate distribution of temperature in the growth system is critical for obtaining a large size high quality aluminum nitride (AlN) single crystal by the physical vapor transport (PVT) method. As the crystal size increases, the influence of the crucible on the temperature distribution inside the growth chamber becomes greater. In order to optimize the field of temperature and study the specific effects of various parts of the crucible on the large size AlN single crystal growth system, this study carried out a series of numerical simulations of the temperature field of two crucibles of different materials and put forward the concept of a composite crucible, which combines different materials in the crucible parts. Four composite crucible models were established with different proportions and positions of tantalum carbide (TaC) parts and graphite parts in the crucible. Calculations reveal that different parts of the crucible have different effects on the internal temperature distribution. The axial temperature gradient at the crystal was mainly governed by the crucible wall, whereas the temperature gradient was determined by the integrated effect of the crucible lid and the crucible wall in the radial direction. One type of composite crucible was chosen to minimize the thermal stress in grown AlN crystal, which is applicable to the growth of large sized AlN crystals in the future; it can also be used to grow AlN single crystals at present as well.     

Enhancing the Accuracy of Linear Finite Element Models of Vehicle Structures Considering Spot-Welded Flanges

Structural engineering simulations have required increasingly complex computational models to replace physical tests accurately. This work focuses on the numerical analysis of vehicle body structures, whose size and complexity make the use of very accurate nonlinear models unfeasible due to the prohibitive computational costs involved. The purpose of this study is to find a new approach to model spot-welded joints in linear finite element models of thin-wall vehicle body structures, improving the accuracy of the model without increasing its complexity. Using a set of simplified nonlinear models, we fitted the stiffness and damping properties of these welded joints and used those adjusted values into a linear model of the entire vehicle body structure. The results were compared with experimental tests, showing a clear improvement in the accuracy of the modal and frequency responses provided by the linear finite element model, but keeping its initial complexity level. The adjusted model was then used in an optimization analysis to reduce the structure’s weight, leading to interesting cost savings and important reductions in the use of natural resources and carbon emissions.     

A study of the distribution of some risk factors in patients with myocardial infarct. Different cardiovascular prevention methods in relation to age

In order to evaluate whether a different method of preventive approach to ischemic cardiopathy is appropriate in relation to age, the distribution of some classic cardiovascular risk factors (cigarette smoke, cholesterol) and a stress-related risk factor (type of work) was studied in two groups of patients, aged respectively over and under 60, admitted to hospital for acute myocardial infarction. The most significant data were: blood cholesterol values less than 220 mg/ml, found mainly in older patients; a larger number of heavy smokers in the group of patients aged under 60; the majority of patients were employees. In the light of these results, the paper discussed the need for different forms of preventive intervention, both clinical and epidemiological, for Ischemic cardiopathy in relation to age.     

Sudden death prevention in heart failure.

Heart failure is one of the main clinical entities in modern society, with a prevalence of 0.4 to 2% in Europe. It has an adverse prognosis, with 5 to 20% annual mortality, even when properly medicated. Mortality in heart failure is frequently due to sudden death, which means preventive strategies should be adopted. Risk stratification is essential in order to identify which patients will benefit most. The main risk factor for sudden death is low ejection fraction. However, ECG data, Holter monitoring and electrophysiological studies are also useful. In primary prevention, all reversible conditions and precipitating factors should be identified and heart failure treatment optimized. The best preventive strategy, after appropriate patient selection, is ICD implantation. Recently, devices with both cardioversion-defibrillation and cardiac resynchronization have proved beneficial in terms of morbidity, quality of life and survival.     

Effect of the Position of the Boundary Rivets on the Quality of Riveted Single Strap Butt Joints

Riveting is widely used in aircraft manufacturing. The strap butt joint is often used in the aircraft’s main bearing area such as the aircraft docking area. The connection quality affects the reliability and safety of the aircraft directly. To study the effect of the rivet position on the connection quality of the strap butt joints, this paper analyzed the distribution of stress around the rivet hole at different positions by the finite element method, and then further analyzed the influence of the different rivet layouts on the connection quality of the strap butt joints by experiments. The static load tensile failure test of the joints was carried out, and the obtained tensile strength and failure mode of the strap butt joints showed that the main static tensile failure form of the single strap butt joint is that the whole rivets is sheared and the connecting sheets are separated. By changing the layout of different rivets, the connection strength can be maximized by reducing the outer row spacing (ORSD) of rivets. The results can be used for reference in the design of the riveting structure of aircraft panels.     

A Two-Dimensional Model for Pin-Load Distribution and Failure Analysis of Composite Bolted Joints

Multibolt composite joints are widely used in aircraft structures. The determination of the pin-load distribution among the bolts is a critical step in the failure prediction of bolted joints. In this paper, a two-dimensional model of the multibolt composite structure is established for the pin-load distribution analysis. Its accuracy is validated by experimental results and the results from a 3D finite element model. Based on the determined pin-load distribution, FE models for a laminated plate with three-row fastener joints are built for failure prediction. Hashin stress criteria and the degradation guidelines of the material stiffness with respect to the different failure modes proposed by Tserpes are applied for the failure evaluation and the material degradation, respectively. The failure location and ultimate load are well predicted, which further validates the effectiveness and applicability of the proposed model for the pin-load distribution analysis.     

Failure Evaluation of Bridge Deck Based on Parallel Connection Bayesian Network: Analytical Model

Failure is a major element that causes deterioration, which in turn affects the serviceability of long span bridges. Currently, the Bayesian network, which relates to probability statistics, is widely used for evaluating fatigue failure reliability. In particular, Bayesian network can not only calculate the fatigue failure at the system level, but also deduce the fatigue failure at the weld level. In this study, a system-level fatigue reliability evaluation model of a bridge deck (BD), which is seen as a parallel system, is proposed based on the Bayesian network. A fatigue probability reliability model of the BD was derived using the master S-N curve. In addition, the Monte Carlo (MC) method was applied to solve the multi-dimensional and complex analytical expressions in the Bayesian network. The applicability of the proposed model was demonstrated by three numerical case studies.     

Treatment of resistant venous stasis ulcers and dermatitis with the end-diastolic pneumatic compression boot

The end-diastolic pneumatic compression boot was used to treat 17 patients with difficult or refractory stasis dermatitis and ulcers. Decreases in induration, pigmentation, and palpable thrombi were observed and all patients were improved or healed. The boot treatment allowed effective local administration of antibiotics on gauze wrappings. Removal of the latter after treatments provided a means of nonsurgical debridement. Healing was maintained by periodic outpatient boot treatments in patients with close followup. Ulcers recurred in patients lost to followup but responded again to boot treatment. One diabetic man with knee contractures and both severe venous and arterial disease relapsed repetitively and lost both legs in spite of bilateral femoral-popliteal bypasses and his boot treatments.     

Studies on Wear of a Milling Chuck for a Production Line of Specialized Elements Used in Lockstitch Machines

The study aims to determine the wear intensity of selected milling chuck assembly surfaces covered with a protective DLC (Diamond Like Carbon) coating, used on the production line for elements of selected lockstitch machines, and to analyze the stress distributions in the object fixed with such a chuck for the characteristic load systems of this object during its processing. A model of the workpiece was developed using the finite element method. The boundary conditions, including the load and the method of clamping the workpiece, resulted from the parameters of the milling process and the geometric configuration of the milling chuck. Stress distributions in the workpiece for specific milling parameters and for various configurations of the milling chuck holding the workpiece are included in the article. The model experimental studies of wear were conducted in the contact zone between two surfaces covered with DLC: one on the element of the milling chuck pressing the workpiece and the other on the eccentric cams of this holder. The obtained wear values and shapes for the worn surfaces are also shown. The wear intensities for the steel plunger fins modelling swivel arm of the holder were by an order higher than those of corresponding steel shaft shoulders modelling eccentric cam of the holder. The linear wear intensities for these mating components may be expressed in terms of a function of average contact pressure and sliding speed in a corresponding contact zone. The indentation of eccentric cam into mating surface of the swivel arm of the holder increased nonlinearly with the enhancement of number of cycles of the eccentric cam.     

Is heart failure with preserved systolic function an overlooked enigma?

Heart failure with preserved systolic function, or diastolic heart failure, represents the neglected other half of the pandemic of heart failure. Unlike previously held beliefs, diastolic heart failure carries with it the same connotation of morbidity and mortality as systolic heart failure, particularly in the elderly. Due to lack of standards in application of the diagnosis of diastolic heart failure, studies are difficult to interpret due to heterogeneity in the clinical criteria applied to the patient enrollment. It is imperative that preventive efforts be implemented in high-risk groups, and screening measures with newer biomarkers be considered for identifying underlying structural heart disease in order to employ preventive therapy early in the course of illness. No evidence-based therapeutic strategy to reduce morbidity and mortality has been established, even after the diagnosis of diastolic heart failure is manifest. Current therapy targets lusitropic abnormalities in the realm of impaired relaxation, abnormal diastolic compliance, avoidance of tachycardia, and restoration of atrial booster pump function. Outcomes-based placebocontrolled clinical trials are currently underway to define appropriate therapeutic strategies in diastolic heart failure.     

Experimental study and simulation on the chip sticking–welding of the carbide cutter’s rake face

For the study of the tool-chip sticking–welding principle and welding layer formation conditions of the carbide cutter’s rake face, the actual conditions of sticking–welding occurrence during the cutting process were analyzed and the cutting test system which is equivalent to sticking–welding phenomenon was set up. Combined with the finite element simulation technology, sticking–welding phenomenon was analyzed. The effect of stress and temperature field with different cutting parameters on the occurrence of tool-chip sticking–welding and adhesion failure was revealed and adhesion failure location resulting from tool-chip sticking–welding was also obtained. Then aimed at the cutting temperature in the damaged area of the rake face, the mapping model was established using design-expert based on the response surface methodology. The trend of cutting temperature and the state of sticking–welding under the interaction between different parameters were obtained, which provided a theoretical basis for the selection of cutting parameters to avoid sticking–welding.     

Treatment of corticotroph deficiency

Corticotroph deficiency is a crucial element of anterior pituitary failure requiring careful management. Clinicians should always look for corticotroph deficiency in patients with pituitary disease and also consider the diagnosis in patients with unexplained fatigue, especially when associated with weight loss and/or hypotension. The diagnosis is based on the morning (8 a.m.) serum cortisol level, generally completed with a stimulation test, keeping in mind its poor sensitivity. Metopirone or insulin tolerance tests may be needed. Treatment is based on administration of hydrocortisone at the daily dose of about 20mg, fractionated into two or three doses if possible. There are no reliable biological parameters for monitoring therapeutic efficacy. Treatment is adapted as a function of clinical criteria: fatigue, blood pressure, body weight, and skin trophicity. Therapeutic education is a key element for the prevention of acute adrenal failure, which can occur if the treatment is not correctly adapted during episodes of gastrointestinal disease or stress.     

Familial resemblance of body fat distribution: the Minneapolis Children's Blood Pressure Study.

Although many reports have shown that obesity (as defined by weight for height indices) tends to run in families, considerably fewer data are available concerning the familial resemblance of body fat distribution as defined by the waist to hip ratio (WHR), which is a risk factor for coronary heart disease. This question was examined among 712 participants of the Minneapolis Children's Blood Pressure Study. For each family member separately (son, daughter, father and mother) the distribution of the WHR was divided into quintiles. Quintiles of WHR were cross-classified between child and parent to examine the proportion of subjects clustering in each quintile. A significantly higher than expected proportion of parent-child WHRs clustered in the top quintile. For example, 42.5% of sones were placed in the top quintile of their father's WHR (P less than 0.001) and 36.7% of daughters were placed in the top quintile of their mother's WHR (P less than 0.001). Multiple linear regression analyses revealed that these findings were independent of parent and child body mass indices and other covariates. These results indicate significant familial aggregation of body fat distribution and may aid in suggesting specific primary preventive strategies targetted at appropriate families to reduce the risk of cardiovascular disease.     

Influence of social class on time trends in BMI distribution in 5-year-old French children from 1989 to 1999

AIMS: To assess the prevalence of obesity and changes in body mass index (BMI) distribution between 1989 and 1999 in 5-y-old children, and to study the influence of parental socioeconomic status on these parameters. METHODS: Two cohorts of children in the final year of nursery school (in the city of Lille, France) were enrolled in 1989 (705 children: mean age=5.6+/-0.4 y) and 1999 (1258 children: mean age=5.6+/-0.5 y). Weight and height were measured, and data about parental occupation were collected during a school medical examination. International Obesity Task Force cutoff points were used to define overweight and obesity. Parental occupation was classified into four categories. RESULTS: The prevalence of obesity increased from 1.8 to 4.9%, and the prevalence of overweight rose from 9.6 to 16.9%. Mean-difference plots allowed qualitative comparisons of the BMI distribution between the surveys: for children from the highest social classes, there was no change in BMI; for children from intermediate classes, there was a up-shift only in the upper part of the distribution with the heaviest children becoming heavier still; finally, for children from the lowest class, there was an increase in BMI across the entire population. CONCLUSIONS: This study of the changes in BMI distribution gives greater insight into the 'obesity epidemic'. Our results show the influence of an interaction between genetic and environmental factors. The increase in BMI in the upper part of the distribution suggests that this is a population with a high degree of susceptibility, whereas the increase in BMI across the whole population in the lowest social class suggests a strong influence of the environment on this group and thus the necessity of appropriate, preventive measures.     

Assessment of chronic heart failure using gas exchange: which variable and when to correct for body mass.

We investigated whether correction for body mass is appropriate when using variables derived from gas exchange measurements in the assessment of chronic heart failure. Patients with heart failure were studied either on a bicycle ergometer (22 subjects) or on a treadmill (28 subjects). For bicycle exercise testing either peak V(O2) or peak V(CO2) uncorrected for body mass reflected exercise capacity. However, for treadmill exercise, body mass correction was necessary to relate exercise capacity to peak V(O2) or peak V(CO2). Mass correction is therefore appropriate for treadmill but not for bicycle exercise.