Electromagnetic transmission of an oblique waveguide array

Transverse magnetic (TM) and transverse electric (TE) wave transmissions of an oblique parallel-plate waveguide array is studied. The scattered wave is represented in terms of continuous and discrete modes based on the Fourier transform and series, respectively. The tangential field continuities at the boundary are enforced to obtain simultaneous equations for the discrete modal coefficients. Residue calculus is utilized to transform the radiation field and reflection coefficient into numerically efficient forms. Numerical computations are performed to illustrate the behavior of wave radiation and reception by an oblique waveguide array.     

A pilot study on accelerated sludge degradation by a high-concentration membrane bioreactor coupled with sludge pretreatment.

A new sludge treatment process combining a high MLSS membrane bioreactor with sludge pretreatment techniques was studied in pilot-scale experiments. The membrane bioreactor (MBR) was adopted for high efficiency aerobic digestion. The combination of alkaline-ozone treatment of the mixed liquor in the MBR reactor accelerated the biodegradation process by enhancing biodegradability of the sludge. The hydraulic retention time (HRT) of the reactor was set as 3.1 days and the DO level was 1 mg/L on average. After 5 months of operation, the accumulative total solids reduction was more than 70%. Removal efficiency of volatile solids and non-volatile solids were 76% and 54%, respectively. It was found that a considerable portion of the non-volatile solids was dissolved into ions and then flushed out with the effluent. Also, about 41% and 28% of T-N and T-P in the raw sludge were removed although no biological nutrient removal process was adopted. The experiment was run smoothly without significant membrane fouling, even at the relatively high levels of MLSS concentration (11,000-25,000 mg/L). It is concluded that the newly proposed process can significantly increase the sludge reduction efficiency with much shorter retention times.     

Fracture behavior in medium-carbon martensitic Si- and Ni-steels

A study of fracture behavior in medium-carbon martensitic Ni- and Si-steels has been made. Charpy impact testing was conducted in order to investigate fracture mode as a function of test temperature. Whereas the transgranular cleavage fracture becomes the primary brittle fracture mode with decreasing test temperature in the Si-steel, intergranular fracture is the only brittle fracture mode observed at low temperatures in the Ni-steel. The different fracture behavior between these steels appears to be due to variation in intrinsic matrix toughness. Since Si may impair the intrinsic matrix toughness, the occurrence of transgranular cleavage fracture becomes relatively easy with decreasing test temperature. On the other hand, since Ni may improve considerably the intrinsic matrix toughness, the transgranular cleavage fracture is not able to occur although the test temperature decreases. Thus, the intrinsic matrix toughness can play a significant role in controlling the fracture behavior.     

High-power performance limitation of an ESQW SEED in an AFP etalonstructure

We report the effects of a high power light beam on the performance of a self electro-optic effect device, which employs an extremely shallow quantum well in an asymmetric Fabry-Perot etalon structure. For a continuously incident laser beam having 4 mW power and 7 μm diameter, for example, we observed the change of reflectivity difference from 25% to 13% and the change of contrast ratio from 16 to 5, both of which we attribute to the rise of local temperature induced by laser heating. Experimental measurements and a simplified thermal analysis show that the device degradation by ohmic heating at reverse bias of -5 V is more pronounced than that by the exciton absorption saturation at forward bias     

Near room-temperature continuous-wave operation of all-monolithic InAlGaAs/InP 1.3 /spl mu/m VCSELs

InAlGaAs/InP-based all-monolithic 1.3 /spl mu/m VCSELs operating continuous wave up to 18/spl deg/C are demonstrated. The whole structure is grown by a single step of MOCVD. Selective wet etching of an InP layer is used to form an air-gap aperture for the current confinement. The threshold current of an 8 /spl mu/m device at 15/spl deg/C is /spl sim/2.8 mA.     

Replication of microlens arrays by injection molding

Injection molding could be used as a mass production technology for microlens arrays. It is of importance, and thus of our concern in the present study, to understand the injection molding processing condition effects on the replicability of microlens array profile. Extensive experiments were performed by varying processing conditions such as flow rate, packing pressure and packing time for three different polymeric materials (PS, PMMA and PC). The nickel mold insert of microlens arrays was made by electroplating a microstructure master fabricated by a modified LIGA process. Effects of processing conditions on the replicability were investigated with the help of the surface profile measurements. Experimental results showed that a packing pressure and a flow rate significantly affects a final surface profile of the injection molded product. Atomic force microscope measurement indicated that the averaged surface roughness value of injection molded microlens arrays is smaller than that of mold insert and is comparable with that of fine optical components in practical use.This paper was presented at the Fifth International Workshop on High Aspect Ratio Microstructure Technology HARMST 2003 in June 2003.The authors would like to thank Korean Ministry of Science and Technology for the financial supports via the National Research Laboratory Program (2000-N-NL-01-C-148) and RAYGEN Co., Ltd. for the technical help in using the 3D profile measuring system.     

Electrochemical behaviors of li electrode in organic electrolytes

Characterizations of the morphology of lithium deposited in organic electrolytes were carried out using Ni substrates pretreated with H₂ and CO₂ gases prior to electrodeposition. The electrolytes used were 1 M LiC1O₄/EC-2MeTHF and 1 M LiPF₆/EC-2MeTHF. Based on electrochemical measurements, XPS and SEM analyses, it seems that the morphology of lithium during electrodeposition is related to the physical properties of the electrolyte itself rather than the chemical composition of a passive layer formed on the lithium surface.     

Presurgical columellar elongation and primary retrograde nasal reconstruction in one-stage bilateral cleft lip and nose repair

We present a new combined approach to primary bilateral cleft lip, nose, and alveolus repair using presurgical nasoalveolar molding combined with a one-stage lip, nose, and alveolus repair. Presurgical alveolar molding is used to bring the protruding premaxilla back into proper alignment with the lateral segments in the maxillary arch. Presurgical nasal molding produces tissue expansion of the short columella and nasal lining. A coordinated surgical approach involves a one-stage repair of the lip, nose, and alveolus. The nasal repair uses a retrograde approach in which the prolabial flap and columella are reflected over the nasal dorsum by continuing the dissection behind the prolabium up the membranous septum and over the septal angle. Tissues are dissected out from between the tip cartilages, and the domes are sutured together in the midline. This method joins a new class of bilateral cleft repairs that place the primary emphasis on correction of the deformity of the nasal tip cartilages.     

Definition of optimal substrate recognition motifs of Ca2+-calmodulin-dependent protein kinases IV and II reveals shared and distinctive features

The substrate recognition determinants of Ca2+-calmodulin-dependent protein kinase (CaMK) IV and CaMKIIalpha were investigated using peptide substrates modeled on the amino acid sequence encompassing Ser-9 of synapsin I. For both kinases, hydrophobic residues (Leu or Phe) at the -5 position, are well tolerated, whereas non-hydrophobic residues (Arg, Ala, or Asp) decrease Vmax/Km by 55- to >4000-fold. At the -3 position, substitution of Ala for Arg leads to decreases of 99- and 343- fold in Vmax/Km for CaMKIV and CaMKIIalpha, respectively. For both kinases, the nature of the residues occupying the -4, -1, and + 4 positions exerts relatively little influence on phosphorylation kinetics. CaMKIV and CaMKIIalpha respond differently to substitutions at the -2 and +1 positions. Substitution of Arg at the -2 position with non-basic residues (Gln or Ala) leads to 6-fold decreases in Vmax/Km for CaMKIV, but 17-28-fold increases for CaMKIIalpha. Additionally, peptides containing Leu, Asp, or Ala at the +1 position are phosphorylated with similar efficiencies by CaMKIV, whereas the Leu-substituted peptide is preferred by CaMKIIalpha (by a factor of 5.8-9.7-fold). Thus, CaMKIV and CaMKIIalpha preferentially phosphorylate substrates with the motifs: Hyd-X-Arg-X-X-Ser*/Thr*, and Hyd-X-Arg-NB-X-Ser*/Thr*-Hyd, respectively, where Hyd represents a hydrophobic, X any, and NB a non-basic amino acid residue. The different specificities of the two kinases may contribute to their targeting to distinct physiological substrates during Ca2+-dependent cellular events.