In order for additive-manufactured parts to become widely utilized and trusted in application, their mechanical properties must be characterized. This study investigates the fatigue behavior and failure mechanisms of Ti-6Al-4V specimens fabricated using Laser Engineered Net Shaping (LENS), an additive manufacturing (AM) process. Fully-reversed strain-controlled fatigue tests were conducted on Ti-6Al-4V specimens manufactured via LENS in their as-built and heat-treated conditions. Scanning Electron Microscopy (SEM) is used to examine the fracture surfaces to qualify the failure mechanism, crack initiation sites, and defects. Due to the relatively high localized heating and cooling rates experienced during deposition, fabricated parts possess anisotropic microstructures and different mechanical properties than those of their traditionally-manufactured wrought counterparts. Porosity promotes unpredictable fatigue behavior, as evidenced by data scatter. Pore shape, size, location, and number were found to impact the fatigue behavior of additive-manufactured parts.

Laser Engineered Net Shaping (LENS™) is a rapid-manufacturing procedure that involves complex thermal, mechanical, and metallurgical interactions. The finite element method (FEM) may be used to accurately model this process, allowing for optimized selection of input parameters, and, hence, the fabrication of components with improved thermo-mechanical properties. In this study the commercial FEM code SYSWELD® is used to predict the thermal histories and residual stresses generated in LENS™-produced thin plates of AISI 410 stainless steel built by varying the process parameters laser power and stage translation speed. The computational results are compared with experimental measurements for validation, and a parametric study is performed to determine how the thermo-mechanical properties vary with these parameters. Thermal calculations are also performed with the code ABAQUS® to evaluate its potential use as a modeling tool for the LENS™ process.

No description available.

No description available.

No description available.

No description available.

The new and forthcoming generation of mobile networks intend to operate at considerably higher frequencies than the previous systems. This lift in frequency of operation alleviates today’s communication systems’ crowded bandwidth and allows for faster data rates than previously possible. However, the suggested increase in frequency of operation introduces new challenges and new antenna solutions are required. One possible candidate for the future communication systems is the Luneburg lens antenna that offers high gain, a simple feeding network and wide-angle scanning. Scanning of lens antennas occurs by placing several feeds along its focal line, but where the width size of the feed place a major constraint on the achievable crossover level between beams. In this thesis, we aim to increase the crossover level between beams in a geodesic Luneburg lens antenna. The importance of a high crossover level is to ensure a more equal performance in terms of data rate transfer to all end users. Here, we investigate two different methods on achieving a higher crossover level. The first method is to utilize a near-field lens while the other method concerns the usage of a generalized Luneburg lens that allows to displace the focal point outside the lens’ contour. A comparison study of these two alternatives are made where it is shown that a generalized Luneburg lens is the preferable choice. A generalized geodesic Luneburg lens is thereafter designed that attains a crossover level of -3:87 dB at the central frequency 62 GHz for the center port. The lens performs well with a bandwidth of 15% and a scanning range between ±52°. The reflection coefficient is below -13 dB in the frequency range of interest and the cross-talk is below -17:9 dB. The realized gain is simulated to 19:01 dBi at 57 GHz, 20:85 dBi at 62 GHz and 21:34 dBi at 67 GHz for the central port. / Den nya och de kommande generationerna av mobilnät avser att fungera på betydande högre frekvenser än tidigare system. Det här lyftet i frekvens minskar den trånga bandbredden i dagens kommunikationssytem och tillåter för snabbare datahastigheter än tidigare möjligt. Däremot, den förslagna ökningen av frekvens introducerar nya utmaningar och därmed behövs nya antennlösningar. En möjlig kandidat för det framtida kommunikationssystemet är Luneburg linsantennen som erbjuder en hög antennförstärkning, ett enkelt matningsnätverk och en bred vinkelskanning. Vinkelskanning av linsantenner sker genom att placera flera matningar längs dess fokallinje, men där bredden på matningarna utgör en stor begränsning för den nåbara korsningsnivån mellan strålningsfält. Det här examensarbetets syfte är att öka korsningsnivåerna mellan strålningsfälten i en geodetisk Luneburg linsantenn. Betydelsen att ha höga korsningsnivåer mellan strålningsfält är att säkerhetsställa en mer jämn prestanda av datahastigheter för alla slutanvändare. Vi undersöker två olika metoder för att uppnå högre korsningsnivåer. Den första metoden använder en närfältslins medan den andra metoden använder sig av en generaliserad Luneburg lins som tillåter att förflytta fokalpunkten utanför linsens kontur. En jämförelsestudie mellan dessa två metoder är genomförd där det visas att den generaliserade Luneburg linsen är det fördelsaktiga valet. En generaliserad Luneburg lins är därefter designad som uppnår korsningsnivåer på -3:87 dB på den centrala frekvensen 62 GHz för center porten. Linsen fungerar väl med en bandbredd på 15% och vinkelskanning mellan ±52°. Reflektionskoefficienten är under -13 dB i frekvensområdet av intresse och kopplingen mellan olika portar är under -17:9 dB. Den realiserade antennförstärkningen är simulerad till 19:01 dBi vid 57 GHz, 20:85 dBi vid 62 GHz och 21:34 dBi vid 67 GHz.

Maintenance of reduced protein sulfhydryl groups is an important function of lens metabolism. In an attempt to inter-relate how lens sulfhydryl metabolism, low molecular weight peptides and trace molecular weight Zn-containing protein population was studied. The concentration of rate lens Zn-containing protein population was studied. The concentration of rat lens Zn decreased 30% from day 10 to day 35 postpartum. After 6 weeks on a low-Zn diet, rats had 25% less lens Zn than control groups. Selenite-induced cataract did not affect lens Zn concentration. Of the total lens Zn, 25% was recovered in the ultrafiltration fraction of less than 20,000 molecular weight which contained 1% of the total soluble protein. Lens tissue has low molecular weight TCA-soluble components that can bind Hg. Isoelectric points of low molecular weight protein fractions were between pI 5.2-5.5. Polypeptide molecular weight was determined to be less than 5,000 daltons by gel filtration chromatography. Aggregation on SDS-polyacrylamide gel electrophoresis yielded apparent higher molecular weights of these proteins. Although the proteins isolated had metallothionein-like character in that they were of low molecular weight, contained Zn and had acidic pI values, the paucity of cysteine residues indicates that metallothionein is not a component of low molecular weight Zn-containing lens proteins. / Master of Science

Yes / Background: The aim was to profile transient accommodative axial length changes from early adulthood to advanced presbyopia and to determine whether any differences exist between the responses of myopic and emmetropic individuals. Methods: Ocular biometry was measured by the LenStar biometer (Haag-Streit, Switzerland) in response to zero, 3.00 and 4.50 D accommodative stimuli in 35 emmetropes and 37 myopes, aged 18 to 60 years. All results were corrected to reduce errors arising from the increase in crystalline lens thickness with accommodation. Accommodative responses were measured sequentially by the WAM 5500 Auto Ref/Keratometer (Grand Seiko, Hiroshima, Japan). Results: Axial length increased significantly with accommodation (p < 0.001), with a mean corrected increase in axial length of 2 18 μm and 8 16 μm observed at 3.00 and 4.50 D, respectively. The magnitude of accommodative change in axial length was not dependent on refractive error classification (p = 0.959); however, a significant reduction in the magnitude and variance of axial length change was evident after 43 to 44 years of age (p < 0.002). Conclusion: The negative association between transient increase in axial length and age, in combination with reduced variance of data after age 43 to 44 years, is consistent with a significant increase in posterior ocular rigidity, which may be influential in the development of presbyopia. / DL received funds from the College of Optometrists, UK

“We provide a solution that allows saving 15 to 20 euros per invoice...It is very important in a strategy of service and cost reductions for our customers and for us.” “For us, it is very important as we generally reduce our inventories by 30%, thus we recover cash flow. It is not negligible.” These quotes out of my case studies show that the primary goal of the implementation of Web-based applications is the achievement of transaction cost efficiencies: cost cutting, time saving, and information integration. But do they achieve such results? Sometimes they do sometime they don’t. In order to understand why, I consider it is necessary to take a different perspective from the one taken until now. Indeed, existing studies on interorganizational information systems focus on economical and strategic issues and consider organizations as opaque entities. First, issues at hand may not be economic or strategic but social or legal. Next, they neglect that inter-organizational relationships imply a number of long-standing social interactions between individuals of each organization. Moreover, these individuals interpret the mediation project and act taking decision, implementing, or using the mediating technology – that these individuals make sense of the IT mediation project. In the present research, I propose to open the black box of organizations and explore how people sensemaking conditions the achievement of transaction cost benefits and is conditioned by the interorganizational context. My overarching research question is: How do people make sense of the Internet mediation of long-standing interorganizational relationships?