3D topology optimization for cost and time minimization in additive manufacturing

Structural and Multidisciplinary Optimization - As the frontier of modern-day engineering challenges pushes forward, the integration of multiple strategies to reduce manufacturing cost and increase...     

Implementing Evaluation of the Measurement Process in an Automotive Manufacturer: a Case Study

Reducing process variability is presently an area of much interest in manufacturing organizations. Programmes such as Six Sigma robustly link the financial performance of the organization to the degree of variability present in the processes and products of the organization. Data, and hence measurement processes, play an important part in driving such programmes and in making key manufacturing decisions. In many organizations, however, little thought is given to the quality of the data generated by such measurement processes. By using potentially flawed data in making fundamental manufacturing decisions, the quality of the decision‐making process is undermined and, potentially, significant costs are incurred. Research in this area is sparse and has concentrated on the technicalities of the methodologies available to assess measurement process capability. Little work has been done on how to operationalize such activities to give maximum benefit. From the perspective of one automotive company, this paper briefly reviews the approaches presently available to assess the quality of data and develops a practical approach, which is based on an existing technical methodology and incorporates simple continuous improvement tools within a framework which facilitates appropriate improvement actions for each process assessed. A case study demonstrates the framework and shows it to be sound, generalizable and highly supportive of continuous improvement goals. Copyright © 2003 John Wiley & Sons, Ltd.     

The effect of the threshold stress on the determination of the Weibull parameters in probabilistic failure analysis

In the analysis of brittle materials and components the probability of failure is commonly modelled using a two-parameter Weibull distribution. Occasionally, a three-parameter model is used when the material shows significant threshold behaviour. In this paper two methods for determining the three-parameter constants are discussed. Two theoretical two- and three-parameter distributions are then analysed to examine the number of samples needed to determine the parameters accurately. The two-parameter models are the best fits of the three-parameter models and their failure distributions are very similar to the three-parameter distributions. It is concluded that far more specimens need to be tested than is usually the case to be confident that the correct distribution has been found.     

Some formulation factors influencing the rate of drug release from bioadhesiw matrices

The development of monolithic matrices with controlled release and mucosa-adhesive properties was investigated. After an initial screening procedure for formulations that showed stability and minimal swelling, the rate of release of a model water soluble drug from various polyacrylic acid containing matrices was evaluated. All the formulations gave a prolonged drug release relative to a lactose containing control formulation. A formulation containing Carbopol 934P and CaCl₂, was found to give the slowest rate of drug release (t_50% of 7.77h), with release kinetics nearest to the ideal zero order. When tested in a modified tensiometer it was found that the inclusion of a relatively high loading of a model drug did not adversely affect the adhesive properties of these formulations.     

The incidence, morbidity, and mortality of surgical procedures after orthotopic heart transplantation

OBJECTIVE: The authors present their experience with patients having undergone orthotopic heart transplantation (OHT) in whom surgical conditions subsequently developed that required operative intervention. The incidence, morbidity, and mortality of these procedures are reported. SUMMARY BACKGROUND DATA: Several studies have evaluated the management options of biliary tract disease after OHT. Multiple reports of patients having undergone OHT who subsequently underwent peripheral vascular reconstructions, plastic reconstructive, and thoracic procedures also have been published. METHODS: A chart review of 349 patients who underwent OHT between 1985 and 1996 was conducted to identify surgical procedures that were required in the post-transplant period. Their outcomes are reported. RESULTS: Of 349 patients who underwent OHT, conditions requiring 94 surgical procedures developed in 54 patients (15%). Biliary tract disease developed in 17 patients (5%) who required cholecystectomy, 2 of the 5 patients with acute cholecystitis died. Eight patients (2%) underwent orthopedic procedures with no operative mortality. Flap advancements for sternal wound infections were performed in five patients and four deaths occurred. Seventeen thoracic procedures were performed in 11 patients with an overall mortality of 45%. Twenty-one vascular procedures were performed on 17 patients with 1 delayed death due to a malignancy. Seven patients underwent procedures of the colon and rectum with no mortality. Seven patients underwent repair of inguinal or incisional hernias with no mortality. Various infections occurred with one resultant death after operative intervention. Six procedures were performed for diseases of the small intestine with no resultant mortalities. CONCLUSIONS: Patients having undergone OHT and chronic immunosuppression are at increased risk of having complications develop from infection. Acute cholecystitis and sternal wound infection caused an inordinate risk of complications and death. Malignancies developed in four patients who required surgical intervention. A heightened awareness of coexisting peripheral vascular disease in patients transplanted for ischemic cardiomyopathy should exist. Close screening before surgery and surveillance after surgery to identify risk factors for infection and vascular disease and to screen for malignancies are essential.     

Flow due to a sink near a vertical wall, in infinitely deep fluid

Flow caused by a point sink in an otherwise stagnant fluid is studied using numerical methods based on integral-equation techniques and an asymptotic solution for small Froude number. There is a vertical wall present on a plane close to the sink, so that the flow is fully three dimensional. The fluid is of infinite depth, but a free-surface bounds it above. Steady solutions are presented for various Froude numbers and distances of the source from the wall. It is shown that the numerical results and asymptotic formula are in good agreement for small Froude numbers, but the results suggest that the non-linear solution ultimately forms some limiting structure at sufficiently large Froude number.     

HLA-DR4 (DRB1*0401) transgenic mice expressing an altered CD4-binding site: specificity and magnitude of DR4-restricted T cell response

Optimum function of HLA-DR molecules in transgenic mice requires efficient interaction between the class II molecules on APCs and CD4 on T cells. Residues 110 and 139 of the second domain of class II molecules are considered to be critical for recognition of CD4. We generated an HLA-DR4beta(NT) transgene construct in which positions 110 and 139 were altered to resemble endogenous mouse H2 Abeta molecules. This construct was introduced into (B10 x SWR) embryos, and DR4beta(NT) transgenic mice were produced. The transgene was transferred into B10.RFB3 (Ebeta0 EalphaP) mice. The transgene-encoded DR4beta molecules paired with endogenous Ealpha chains to form stable DR4beta/Ealpha dimers expressed on the cell surface. The hybrid dimers showed similar Ag-binding specificity to HLA-DR4 molecules and positively selected CD4+ T cells in vivo. Immunization of HLA-DR4beta(NT) transgenic mice with DR4-restricted peptides induced T cell proliferation in vitro. While the purified T cells from DR4beta(NT) transgenic mice responded strongly to the HA(307-319) presented by M12C3 transfectants expressing altered DR4beta/Ealpha heterodimers, the response to the same peptides presented by transfectants expressing wild-type DR4beta/Ealpha molecules was substantially reduced. Taken together, these data confirmed in vitro studies on the importance of these residues in CD4-MHC class II interaction. The altered HLA-DR4beta transgenic mice were able to overcome the species barrier and generate efficient HLA-DR4-restricted CD4-specific immune responses. Thus, residues 110 and 139 were critical for the interaction of class II with CD4 T cells during thymic selection as well as peripheral immune responses.     

Enterogastric bile reflux during technetium-99m-sestamibi cardiac imaging

Twenty-six patients with squamous cell cancer of the cervix were treated with i.v. paclitaxel, 250 mg/m2 over 3 h every 21 days. They received steroid, H1 and H2 blocker premedications, and granulocyte-colony-stimulating factor (G-CSF) support (5 microgram/kg/day). No prior chemotherapy, except as a radiation sensitizer, was allowed. The median age was 50 (range, 36-81) years, and performance status Zubrod was 1 (range, 0-2). Eight (33%) patients had prior surgery, and 22 (92%) had prior radiation therapy. Twenty-four patients were evaluable for response; 2 were later found to be ineligible. Five patients had partial responses (21%; 95% confidence interval, 6-40%), and 14 (58%; 95% confidence interval, 35-78%) had stable disease. The median duration of response was 10 (range, 3-27+) weeks. The responses were within the radiation port (four responses) and outside of it (one response). The median interval from the start of irradiation to the start of paclitaxel in responding patients was 94 weeks, whereas in patients with stable disease it was 68 weeks, and in patients whose disease progressed it was 46 weeks. Eighty-eight percent of the 105 cycles of paclitaxel were administered at a dose of 250 mg/m2 or higher. Granulocytopenia was brief and noncumulative, with grades 3 and 4 experienced by 5 and 3 patients, respectively. G-CSF was used for a median of 7 (range, 2-14) days/cycle. Anemia was mild, with G3 noted in 3 patients, and thrombocytopenia was not significant. Infections and musculoskeletal pain were mild and infrequent. Sensory (14 patients G1 or G2 and 2 patients G3) and motor (4 patients G1 or G2 and 1 patient G3) neurotoxicity was noted. There was no significant cardiovascular toxicity. Paclitaxel is active in patients with squamous cell cancer of the cervix and is well tolerated at this dose schedule with G-CSF support.