Optimization of lead- and cadmium-free front contact silver paste formulation to achieve high fill factors for industrial screen-printed Si solar cells

Screen-printed n⁺–p–p⁺ solar cells were fabricated on Cz single crystalline Si material, with a 45 Ω/sq emitter and PECVD SiNx antireflective coating with a thickness of 700 Å, using different Ag pastes and commercial leaded reference paste (CN33-462, Ferro Corp.). Ag and Al contacts were co-fired using a mass-production line equipped with mesh belt conveyer furnace systems (Centrotherm thermal solution GmbH & Co. KG). The average results for single crystalline Si solar cells (156 cm²) are: I_sc=5.043 A, V_oc=0.621 V, R_s=0.0087 Ω, R_sh=15.3 Ω, FF=0.773, and E_ff=16.45%. R_sh and fill factor values of fabricated cells were slightly higher when compared with the commercial leaded Ag paste, although cells were fabricated by metallizing the lead-free silver pastes. For the lead-free Ag paste used in this study, the line pattern continuity is retained with improved edge definition in sharp contrast to that of reference Ag paste. Average value of R_s was also equivalent approximately to that of the leaded Ag paste.     

Study of impact energy propagation phenomenon and modal characteristics of an armored vehicle undergoing high velocity impact

A new manufacturing technology is being employed to build a new type of armored vehicle. While thick panels are welded together in the old manufacturing technology, relatively thin panels are welded to a frame structure in the new manufacturing technology. The structural integrity of the new type of armor vehicles can be maintained mainly by the frame structures while the panel thickness is reduced significantly to reduce the total vehicle weight. Since the dynamic characteristics of a frame-panel hybrid structure are different from those of the old type of structure which consists of only thick panels, they should be identified to achieve a good performance of the vehicle. For this purpose, a proper FE model of the hybrid type of structure needs to be developed. In the present study, FE models are proposed to represent the frame-panel hybrid type structure efficiently. The impact energy propagation, the transient response and the modal characteristics are investigated with the FE models. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Hong-Hee Yoo received a B.S. and M.S. degree in Mechanical Engineering from Seoul National University in 1980 and 1982. He then went on to receive his Ph.D. degree from Michigan State University in 1989. Dr. Yoo is currently a Professor at the School of Mechanical Engineering at Hanyang University in Seoul, Korea. His research interests are in the area of Flexible body dynamics, vibration.     

Promising zeolite-type hydrocarbon trap catalyst by a knowledge-based combinatorial approach

Libraries consisting of more than 100 zeolite samples were prepared and examined for developing a promising HC trap catalyst. Parallel adsorptions of toluene onto the catalyst samples were conducted over a 10 × 10 array reactor under dry and wet conditions with or without a heating process three knowledge-based conditions for developing an automotive catalyst during the cold-start period. FAU and BEA type zeolites revealed a high performance of toluene adsorption under the dry condition. However, FAU type zeolite significantly decreased the amount of toluene adsorbed in the presence of water in the feed gas stream, mainly due to the hydrophobicity of the catalyst surface. Over Beta type zeolites, the toluene adsorbed was found to be considerably preserved, even after forced desorption temperature-ramping to the warm-up condition of an automotive engine. Li, K, or Ag ion-exchanged Beta zeolites seem to be particularly promising as an HC trap catalyst.     

A study on driver’s workload of telematics using a driving simulator: A comparison among information modalities

Recently, diffusion of telematics services and an explosive increase of in-vehicle display devices, such as Car Navigation Systems (CNSs), are becoming the new causes of traffic accidents. This is due to ‘inattention’ caused by an increase in the driver’s mental workload while he/she is driving. This situation has lead many countries to consider controlling the use of in-vehicle devices while driving through legislation. This research studies the effect of voice or display information systems on drivers through the Driver Eye Movement Analysis and the measurement of response ability. The experiment is carried out in a driving simulator and the results are presented through the comparative analysis of the driver’s visual field via the gaze tracking device and the average of correct answer rates for arithmetic problems.     

Effects of milk proteins and gums on quality of bread made from frozen dough

BACKGROUND: Mixtures of milk proteins and gums incorporated into bread formulations may enhance the quality of bread and retard the deterioration of frozen dough. Our objective was to investigate the effects of mixtures of milk proteins (casein (C) and whey protein (W)) and gums (sodium alginate (A) and κ‐carrageenan (K) on the quality of bread made from frozen dough. We hypothesized that bread containing milk proteins and gums would be of improved quality. Milk proteins improve texture, moisture retention and specific volume, and reduce the size of ice crystals, while gums incorporated into the bread improve moisture retention, control water mobility and prevent the growth of ice crystals, so we hypothesized milk proteins and gums would suppress the quality deterioration of bread during frozen storage. RESULTS: We found that mixtures of milk proteins and gums proved effective with regard to the maintenance of the baking quality of frozen dough. Breads containing CA had a higher specific loaf volume than the control bread. The addition of WK enhanced crumb firmness during extended frozen storage. In sensory evaluation, the addition of WA and CA contributed to the improvement of baking quality, taste, texture and acceptability. CONCLUSION: These findings are consistent with the hypothesis that mixtures of milk proteins and gums improved baking quality by reducing the deterioration of frozen dough. These results indicate that the addition of CA and WA improved the bread quality and WK could effectively be used as an anti‐staling agent in bread. Copyright © 2009 Society of Chemical Industry     

A raw material storage yard allocation problem for a large-scale steelworks

This paper addresses a raw material storage yard allocation problem at a large-scale steelworks. At the steelworks, raw materials such as coal and iron ore are imported by ships from overseas, discharged from the ships by unloading equipment, and transported into and stored in the yards. The stored materials then are transported and used in the production equipment such as steel mills. The yard allocation decision, i.e., where to store the materials, determines the travel distance of the materials as well as the storage efficiency of the yards. Here, the yard allocation problem is solved using a mixed integer programming model. The solution compares favorably with the current practice of the steelworks.     

Evaluation of the physical and mechanical properties of high drug load formulations: Wet granulation vs. novel foam granulation

The purpose of this study was to evaluate the influences of intrinsic drug mechanical properties and different granulation binder delivery processes on the physical and mechanical properties of high drug load granulations after wet granulation. Formulations (80% w/w) of acetaminophen (APAP), metformin and aspirin, which are brittle, viscoelastic, and ductile, respectively; were granulated by high-shear wet granulation. Two modes of binder delivery for wet granulation, either conventional or binder foam, were investigated. Particle size, surface area and pore size of the granulations were characterized. Compacts were prepared at a solid fraction of 0.9 under tri-axial decompression and Hiestand indices (worst-case bonding index (BI_w) and brittle fracture index (BFI)) of the compacts were determined. APAP formulations exhibited the smallest geometric mean particle sizes (d_g) and showed only slight differences in d_g values between the two granulation processes. Binder delivery mode affected mechanical properties of the granulated model drugs differently. Foam granulation appeared to enhance the granule plasticity for APAP while aspirin showed a mixed deformation mechanism based on both its high BI_w and high BFI values. The higher BI_w value for aspirin after foam granulation may be attributed to improved binder distribution among particles during granulation. On the other hand, conventional wet granulation improved the plasticity of metformin as measured by the higher BI_w and lower BFI values. Therefore, conventional wet granulation process conferred advantages in manufacturability and product quality for metformin; as compared to foam granulation which did not enhance plasticity for metformin. Based on this study, a wet granulation process can be selected based on knowledge of the intrinsic drug mechanical properties.     

Continuous hydrothermal synthesis of HT-LiCoO2 in supercritical water

A detailed investigation was made into the production of high temperature lithium cobalt oxide (HT-LiCoO₂) particles by continuous hydrothermal synthesis via the reaction of cobalt nitrate, lithium hydroxide, and hydrogen peroxide. The experiments were carried out in both subcritical and supercritical water, at temperatures ranging from 300 to 411 °C, with residence times less than 1 min in all instances. Although Co₃O₄ particles were synthesized in subcritical water at similar reaction conditions designed for comparison, well-ordered particles of HT-LiCoO₂ were obtained in supercritical water. In supercritical conditions, the variations in temperature and residence time did not have significant impacts on the average particle size, particle size distribution, or morphology of obtained HT-LiCoO₂. However, it was important to supply excessive lithium hydroxide and hydrogen peroxide in order to synthesize single-phased HT-LiCoO₂ particles without undesired by-products. The hydrothermal synthetic route for LiCoO₂, CoO, and Co₃O₄ in both subcritical and supercritical conditions was postulated.