Viscoelastic Material Characterization: A Realistic Approach to Stress Analysis

This paper presents an advanced method in materials characterization for the mold compound material in semiconductor packages to build models that can technically explain the actual warpage or stress observations under different thermal conditions and time history. In the study, the mold compound material characterization was conducted using Dynamic Mechanical Analyzer (DMA) followed by curve fitting to obtain parameters for the computer modeling input requirement. Thermo-mechanical modeling using viscoelastic material properties was conducted on a bi-material test sample model. Results showed that the new characterized viscoelastic material properties exhibited dependence on time and temperature. Slow cool down from post mold cure (PMC) to room temperature resulted in lower warpage or stress. This observed rate dependent response was explained using viscoelastic material properties in contrast to the usual linear elastic material simplification. Thus, a realistic result from stress or warpage analysis could be achieved using viscoelastic material characterization.

Monte Carlo simulation of aerosol evolution in a planar mixing layer

Purpose – The purpose of this paper is to investigate aerosol evolution in a planar mixing layer from a Lagrangian point of view. After using Monte Carlo (MC) method to simulate the evolution of aerosol dynamics along particles trajectories, the particles size distributions are obtained, which are unavailable in mostly used methods of moments. Design/methodology/approach – Nucleation and growth of dibutyl phthalate (DBP) particles are simulated using the quadrature method of moments in a planar mixing layer, where a fast hot stream with DBP vapor is mixing with a slow cool stream without vapor. Trajectories of aerosol particles are recorded. MC method is used to simulate the aerosol evolution along trajectories. Findings – Investigation on aerosol evolution along the trajectories prompts to classify these trajectories into three groups: first, trajectories away from the active nucleation zone; second, trajectories starting from the active nucleation zone; and third, trajectories crossing over the active nucleation zone. Particle size distributions (psds) along selected representative trajectories are investigated. The psd evolution exhibits interesting behavior due to the synthetic effects of nucleation and condensation. Condensation growth tends to narrow down the psd, and form a sharp front on the side of big particle size. Nucleation is able to broaden the psd through generating the smallest particles. The duration and strength of nucleation have significant effect on the shape of psd. Originality/value – As far as the authors knowledge, it is the first simulation of aerosol evolution that takes a Lagrangian point of view, and uses MC simulation along particles trajectories to provide the particles size distribution.

Application of Thermal Hydraulic and Severe Accident Code SOCRAT/V3 for Calculation of Air Ingress Experiment QUENCH-16

The thermal hydraulic and SFD (Severe Fuel Damage) best estimate computer modelling code SOCRAT/V3 has been used for the calculation of QUENCH-16 experiment which was performed in the frame of the EC supported LACOMECO programme. The QUENCH-16 test conditions simulated a representative scenario of LOCA (Loss of Coolant Accident) nuclear power plant accident sequence in which the overheated up to 1800K core would be reflooded from the bottom by ECCS (Emergency Core Cooling System). The QUENCH-16 experiment included the following phases: first heat-up phase, pre-oxidation phase, slow cool-down phase (preparatory to air ingress), air ingress phase and bottom water flooding phase. The test QUENCH-16 was successfully conducted at the Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany, on July 27, 2011. The primary objective of this test was to investigate the oxidation of Zircaloy in the air following a limited pre-oxidation in the steam and to achieve a long period of oxygen starvation to promote the interaction with the nitrogen. Unexpectedly high cladding oxidation rate was detected during flooding phase which resulted in huge hydrogen production in QUENCH-16. It was due to zirconium nitride (ZrN) formation in a cladding which induced a diffusion transparency of zirconium dioxide layer. QUENCH facility is designed for studies of the PWR fuel assemblies behaviour under conditions simulating design basis, beyond design basis and severe accidents. SOCRAT/V3 computer modelling code was used for estimation of basic thermal hydraulic, oxidation and air ingress parameters in QUENCH-16. The calculated results are in a reasonable agreement with experimental data which justifies the adequacy of modeling capabilities of SOCRAT code for application to such a complicated test as QUENCH-16.

INDUCED NANOCRYSTALLIZATION OF DEXTROSE MONOHYDRATE

Modern ultrasound induction is very much useful in crystallization process. It uses piezoelectric transducers or quartz crystals to convert mechanical waves to electrical signals and vice versa. Growth of a crystal is environment dependent. The characteristics of grown crystals depend on impurities, temperature, preparation of the solution and mechanical agitation. The properties and size of a crystal can be tailored by controlling any one or all the above factors. The most interesting fact is that the ultrasound influences the properties and size of a crystal. It is found that the characteristics are improved and tailored for a specific need of the industry when a crystal is grown by radiating ultrasonic wave. In some cases, it produces nanocrystals. We used a device which generates the Ultrasonic wave of 15 MHz, which is applied to the crystal right from the time before nucleation till the crystal formation. The Dextrose monohydrate crystals are grown by conventional slow cool batch method. In the same slow cool batch method, Ultrasonic waves of 15 MHz are allowed to pass, influence the nucleation, crystal formation and growing process. The crystal formation process under the exposure of Ultrasound is allowed to continue for a sufficiently long time to yield the desired nanocrystals. The FTIR, UV, microhardness and SEM analysis are taken for the crystals with and without ultrasound.

Quench Sensitivity and Quench-Induced Precipitation in High Strength 7xxx Series Aluminum Alloys

This paper investigates the quench sensitivity of some selected 7xxx series Al alloys based on a Jominy End Quench method. The precipitate microstructures as a function of cooling rate during quenching are also characterized by using transmission electron microscopy (TEM). The results indicated that quench sensitivity and therefore the mechanical properties inhomogeneity in large plates or forgings can be predicted more accurately by the simultaneous combination of hardness and electrical conductivity measurements based on Jominy end quench. The hardness drop and conductivity increase in the novel alloy following a low cooling rate are much reduced compared to AA7050 and 7B04 because of a lower sensitivity to quench-induced precipitation on dispersoids. The novel alloy exhibited the least quench sensitivity, and the 7B04 Al alloy was the most quench sensitive. If the 90% of the maximum hardness is defined as the depth of quenching, the depth of 7B04 Al alloy, AA7050 through Jominy end quenching is about 20 and 55 mm respectively. Meanwhile, the depth of greater than 150 mm is achievable in the novel alloy, and hence it can be recommended to fabricate large section plates or forgings without compromising properties in the center of the part after a slow cool.

108 THE EFFECTS OF FORSKOLIN ON BRAHMAN IN VIVO-PRODUCED EMBRYOS AND SUBSEQUENT PREGNANCY RATES POST-THAW

It has been hypothesised that lower survival rates post-thaw of Brahman (BR) embryos is due in part to higher intracellular lipids. The objective of this study was to determine whether pregnancy rates of in vivo–produced BR embryos could be enhanced by exposing them to 10 μM of forskolin (FSK; lipolytic agent) before slow cool freezing, thawing and direct transfer. A previous report (Phase II) indicated that the addition of FSK to culture 24 h before freezing 7 days in vitro–produced, BR-sired embryos can increase survival and blastocyst hatching rates (Pryor et al. 2010 Reprod. Fertil. Dev. 22, 214). For this study (Phase III), 11 BR cows were injected with 25 mg of Lutalyse® (Pfizer Animal Health, New York, NY, USA) to synchronize oestrus. On Day 0 (7 days after synchronized oestrus), all donors were inserted with a CIDR (Controlled Intravaginal Releasing Device; Pharmacia Co., Kalamazoo, MI, USA) and injected with 50 mg of progesterone plus 2.5 mg of oestradiol 17 β (Medshop, Longview, TX, USA). On Day 4, decreasing doses of Folltropin (Bioniche, Pullman, WA, USA) ranging from 160 to 264 mg were given twice daily for 3 days along with 0.625 mg of cloprostenol (Estrumate; Merck/Schering-Plough Animal Health, Whitehouse Station, NJ, USA) given twice on Day 6 (AM and PM) and CIDR removal on Day 7 AM. Donors were artificially inseminated 12 and 24 h post-oestrus (oestrus = Day 8) with frozen/thawed BR semen. On Day 14 (embryo age 6 days), donors were nonsurgically collected, producing a total of 75 grade-one morulae, which were randomly allocated and cultured for 24 h in Evolve (Zenith Biotechnology, Canada) supplemented with 4 mg mL–1 of Probumin BSA (Millipore, Norcross, GA, USA; control) or with FSK (Sigma, St. Louis, MO, USA) at 38.5°C under a 5% CO2, 5% O2 and 90% N2 humidified atmosphere. Immediately following treatment, 7 days compact morula/blastocysts were washed in Vigro Holding Plus medium (Bioniche, Belleville, Ontario, Canada) and submitted to Vigro Ethylene Glycol Freeze Plus medium (Bioniche) for 5 to 7 min before being frozen at 0.5°C min–1 from –6°C to –32°C and plunged in liquid nitrogen. Frozen embryos (n = 35 FSK; n = 35 control) were air thawed for 7 s and then immersed in 30°C H2O for 10 s before being nonsurgically transferred into synchronized recipients. Pregnancy rates were assessed by ultrasonography via rectal palpation 30 to 60 days post-transfer. Contingency analysis was performed using forskolin treatment, technician and embryo stage and location as independent variables (JMP 8.0, SAS Institute Inc., Cary, NC, USA). There were no statistical differences or interactions for any of the analysed variables. Pregnancy rates between control and FSK treatments did not vary (34.3 and 31.4%, respectively; chi-square P = 0.80). In conclusion, treating in vivo–produced BR embryos with 10 μM of forskolin for 24 h did not alter pregnancy rates. The authors acknowledge support from the American Brahman Breeders Association.

70 REFREEZING POST-THAWED GOAT SEMEN

The ability to successfully refreeze caprine sperm could provide a means of salvaging semen that was mistakenly thawed. The objective of this study was to compare treatment post-thaw semen parameters of twice-frozen caprine semen. Frozen semen from six mature Boer bucks (range in age from 2 to 6 years) was utilised for this experiment. Semen from each buck was extended in an egg yolk-based extender and packaged in 0.5-mL plastic straws before freezing and stored in liquid nitrogen. Three units of frozen semen from each buck was randomly allotted to each of four treatments as follows: (A) thaw and evaluate (control), (B) thaw, then plunge into liquid nitrogen, thaw, and evaluate, (C) thaw, incubate for 3 min at 37°C, slow cool and freeze, thaw, and evaluate, and (D) thaw, incubate for 5 min at 37°C, slow cool and freeze, thaw, and evaluate. Post-thaw parameters included total motility (TM), progressive motility (PM), membrane integrity (MI), and sperm abnormalities (AB). To obtain MI and AB, samples were stained with an eosin-nigrosin stain. A computerized programmable freezer was used to refreeze semen samples in treatment (Trt) C and Trt D. During the slow cooling portion of the protocol, samples were allowed to equilibrate at 38°C, then cooled to 4°C at a rate of 0.30°C min–1, and then held for 5 min. Samples were then cooled to –8°C at a rate of 15°C min–1, seeded, and cooled to –10°C at 15°C min–1, samples were then ramped to –80°C at 30°C min–1 before plunging into liquid nitrogen. Results indicate that post-thaw TM was significantly greater for Trt A (60%) when compared with Trt B, C, and D (0.05, 35, and 39%, respectively). Mean TM were not different between Trt C (35%) and Trt D (39%) but were greater than that for Trt B (0.05%). The PM for post-thaw semen in Trt A was also significantly greater (P < 0.05) when compared with that for Trt B and C (0.05 and 25%); however, no difference was found for mean PM for Trt A (47%) and Trt D (30%), nor were differences found between Trt C (25%) or Trt D (30%). Membrane integrity was higher in Trt A (27%) when compared to Trt B (2.2%). No differences in membrane integrity where found between Trt A, C, and D (27, 13, and 14%, respectively). Additionally, no differences were found between Trt B, C, and D for membrane integrity. Sperm morphology were not different were found with across all treatment groups. These results (i.e. Trt C and D) indicate that semen from mature Boer bucks can undergo a second freeze thaw cycle and still retain motility without dramatically affecting sperm morphology and membrane integrity. These findings indicate that directly plunging recently thawed semen back into liquid nitrogen should not be used for artificial insemination.

110 THE USE OF FORSKOLIN AND ITS EFFECT ON IN VITRO-PRODUCED BRAHMAN-SIRED EMBRYOS SUBMITTED TO SLOW COOL FREEZING OR VITRIFICATION

The objective of this study was to further test the lipolytic effect of 10 μM forskolin on developmental differences between bovine in vitro produced (IVP) embryos submitted to slow cool (SC) freezing or vitrification (VT). Previously reported (phase I) IVP embryo hatching rates for control embryos (62%) were no different than 10 μM forskolin (67%; Pryoretal et al. 2009 Reprod. Fertil. Dev. 21, 163). For phase II: on Day 6 post-fertilization (IVF = Day 0), 207 Brahman-sired viable embryos were evenly divided and cultured for 24 h in G2.5 medium (Vitrolife, Englewood, CO, USA) with or devoid of 10 μL forskolin (Sigma, St. Louis, MO, USA). On Day 7, compact morula (CM, n = 31), blastocyst (BL, n = 76), and expanded BL (XBL, n = 100) were washed in Vigro Holding Plus medium (Bioniche, Pullman, WA, USA) and randomly allocated to 4 treatment groups; control SC (CSC; no treatment, n = 52), 10 μM forskolin SC (FSC; n = 55), control VT (CVT; n = 49), and 10 μM forskolin VT (FVT; n = 51). All embryos were packaged in sterile 0.25-mL plastic straws. The SC embryos were submitted to Vigro Ethylene Glycol Freeze Plus medium (Bioniche) for 5 min before freezing at 0.5°C/min from -6°C to -32°C and plunging in LN2. Embryos were vitrified using a bovine VT kit (Bioniche): VS1, 3 min; VS2, 45 s in 15 μL; diluent, in straw with VS2 separated by air columns, vitrified in LN2 vapor 1 cm from liquid for 1 to 15 min before plunging. The SC embryos were air thawed 5 s and placed in 30°C H2O bath for 10 s. The VT straws were air warmed 10 s and then in 35°C H2O for 20 s prior to shaking them down to mix columns. All embryos were cultured in G2.5 for 24-h survival and 48-h hatching rates. All percentage data were transformed using arcsin square root function prior to analysis, and means were compared for statistical significance using Student’s t. For mean survival rates, FSC was different than CSC but showed no difference between FVT and CVT (81.7 ± 0.09, 42.6 ± 0.09, 59.4 ± 0.09, 49.0 ± 0.10, respectively (P < 0.01). There were no statistical differences for hatching rates for combined embryo stages (58.2 ± 0.10, 37.8 ± 0.10, 34.4 ± 0.10, 28.1 ± 0.11 for FSC, FVT, CSC, and CVT, respectively; P > 0.07). However, when comparing hatching rates of only the blastocyst stage embryos (n = 176), FSC was superior to CSC and CVT but not different than FVT (74.8 ± 0.11, 29.5 ± 0.11, 29.1 ± 0.11, 48.5 ± 0.11, respectively; P < 0.01). In conclusion, FSC yielded significantly higher survival and blastocyst hatching rates than CSC, but there were no differences between CVT and FVT for survival and FVT for blastocyst hatching rates. These results indicate that the addition of 10 μM forskolin to culture 24 h prior to freezing 7 d IVP Brahman-sired embryos can increase survival and blastocyst hatching rates. The authors acknowledge support from the American Brahman Breeders Association.