Cost benefits from standardization of the packaging glass bottles

This study deals with a recycling system with two competing brewers. It is assumed that they coordinate their manufacturing operations through standardization of their glass bottles for easy implementation of extended producer responsibility (EPR). Immediate benefits from the standardization are three folds. Firstly, the sorting and exchange processes of the bottles collected for reuse by each brewer become no longer necessary. Secondly, cost reduction is achieved through streamlining of collection and reuse processes. Finally, under the stochastic demand of glass bottles their inventory holding costs and lost sales cost are reduced via inventory pooling. Through the development of the mathematical models we determine an optimal operation policy of the two brewers that maximizes the sum of benefits obtained from standardization. Numerical examples are solved to show the validity of the model. Sensitivity tests are also performed to examine the effects of system parameters on the objective function value and decision variables.     

Analysis of the false-positive error rate of tagged fragment marking scheme

IP traceback is an effective measure to deter internet attacks. A number of techniques have been suggested to realize IP traceback. The Fragment Marking Scheme (FMS) is one of the most promising techniques. However, it suffers a combinatorial explosion when computing the attacker?s location in the presence of multiple attack paths. The Tagged Fragment Marking Scheme (TFMS) has been suggested to suppress the combinatorial explosion by attaching a tag to each IP fragment. Tagging is effective because it allows the victim to differentiate IP fragments belonging to different routers, thereby greatly reducing the search space and finding the correct IP fragments. TFMS, however, increases the number of false positives when the number of routers on the attack path grows beyond some threshold. In this paper, we rigorously analyze the performance of TFMS to determine the correlation between the number of routers and the false positive error rate. Using a probabilistic argument, we determine the formulas for combination counts and error probabilities in terms of the number of routers. Under TFMS, our results show that we can reduce the required time to find an attacker?s location at the cost of a low error rate for a moderate number of routers.     

The effect of grain size and retained austenite on the ductile-brittle transition of a titanium-gettered iron alloy

The effect of microstructural changes on the ductile-brittle transition temperature (DBTT) was studied in a titanium-getter ed Fe-8Ni-2 Mn-0.15 Ti alloy. A fairly strong grain size dependence of the transition temperature, 8°C/mm^?1/2, was found. Grain size refinement from 38 μm (ASTM #6.5) to 1.5 μm (ASTM #15.5) through a four-step thermal treatment lowered the transition temperature by 162°C. A small amount of retained austenite was introduced into this grain-refined microstructure, and the transition temperature was reduced by an additional 120 ~ 150°C. The reduction of the DBTT due to retained austenite was smaller when the austenite was in a large-grained structure (64°C). The distribution and stability of retained austenite were also studied.     

A novel way to improve the dispersion-limited transmission distance of electroabsorption modulated lasers

We propose and demonstrate a way to improve the dispersion-limited reach of electroabsorption modulated lasers (EMLs). We generate continuous-phase frequency-shift keying/amplitude-shift keying (ASK) signals with the EML by applying a small current modulation to the laser diode (LD) on top of electroabsorption-modulated ASK signals. The amount of frequency deviation induced by the current modulation is adjusted to have the EML output signals experience /spl pi/ phase shift at every space. The experimental demonstration shows that with the proposed scheme we can increase the dispersion-limited transmission distance of the EML-based transmitter by 25%-75%, and it can be further improved by employing an LD with flat frequency-modulation response.     

Parallel optical transmitter module using angled fibers and a V-grooved silicon optical bench for VCSEL array

We propose an advanced structure of optical subassembly (OSA) for packaging of the vertical-cavity surface-emitting laser (VCSEL) array, using (111) facet mirror of the V-groove ends formed in a silicon optical bench (SiOB) and angled fiber apertures. The feature of our OSA can provide a low optical crosstalk between neighboring channels, a low feedback reflection, and a large misalignment tolerance along the V-groove. We describe the optimized design of fiber angle, VCSEL position, and fiber position. The fabricated OSA structure consists of 12 channels of angled fiber array, 54.7/spl deg/ V-grooves, Au-coated mirrors on (111) end facet of the V-grooves, and flip-chip-bonded VCSEL array on a SiOB. In this structure, the beam emitted from the VCSEL is deflected at the 54.7/spl deg/ mirror of (111) end facet and propagated into the angled fiber. The angled fiber array was polished by 57/spl deg/. Fabricated OSAs showed a coupling efficiency of 30%-50% that is 25 times larger than that obtained from an OSA with a vertically flat fiber array. Our OSA showed large misalignment tolerance of about 90 /spl mu/m along the longitudinal direction in the V-groove. We fabricated a parallel optical transmitter module using the OSA and demonstrated 12 channels /spl times/2.5 Gb/s data transmission with a clear eye diagram.     

Performance Analysis on Coexistence of EDCA and Legacy DCF Stations in IEEE 802.11 Wireless LANs

The distributed coordination function (DCF) scheme of IEEE 802.11 MAC protocol does not support any concepts of quality of service (QoS) but the enhanced distributed channel access (EDCA) scheme in IEEE 802.11e standard provides QoS according to access categories using different access parameters. However, the legacy DCF stations may be used together with EDCA stations. In this letter, we investigate and analyze the performance discrimination when EDCA and DCF stations operate simultaneously     

Dynamic deformation behavior of ultrafine-grained low-carbon steels fabricated by equal-channel angular pressing

The dynamic deformation behavior of ultrafine-grained low-carbon steels fabricated by equal-channel angular pressing (ECAP) was investigated in this study. Dynamic torsional tests, using a torsional Kolsky bar, were conducted on four steel specimens, two of which were annealed at 480 °C after ECAP, and then the test data were compared in terms of microstructures, tensile properties, and adiabatic shear-band formation. The equal-channel angular pressed specimen consisted of very fine, equiaxed grains of 0.2 to 0.3 μm in size, which were slightly coarsened after annealing. The dynamic torsional test results indicated that maximum shear stress decreased with increasing annealing time, whereas fracture shear strain increased. Some adiabatic shear bands were observed at the gage center of the dynamically deformed torsional specimen. Their width was smaller in the equal-channel angular pressed specimen than in the 1-hour-annealed specimen, but they were not found in the 24-hour-annealed specimen. Ultrafine, equiaxed grains of 0.05 to 0.2 μm in size were formed inside the adiabatic shear band, and their boundaries had characteristics of high-angle grain boundaries. These phenomena were explained by dynamic recrystallization due to a highly localized plastic strain and temperature rise during dynamic deformation.     

Factors Affecting Hydrogen Production from Food Wastes by Clostridium-Rich Composts

This study used the technique of response surface approach to analyze the combined effects of heat-shocking temperature and time on anaerobic grass composts. Results indicate that the grass composts under heat-shocking temperature and time of 80°C and 3?h, respectively, could yield high populations of hydrogen-producing microorganisms. Metabolic results demonstrate that the composts are reliable, having considerable hydrogen-producing Clostridia. The multivariate analysis with response surface by considering specific hydrogen-producing potential and rate simultaneously indicate that the cultural media with Fe2+ = 132?mg/L; NH4+ = 537?mg/L; and PO43? = 1,331?mg/L were optimal for the hydrogen-producing Clostridia-rich composts using high-solids food wastes. The specific hydrogen production potential and rate were 77±3?mL?H2/gTVS and 520±20?mL?H2/g?TVS/day, respectively. The former was 38% of theoretical hydrogen-producing potential of Clostridium sp. using glucose. Of these factors, ammonium and phosphate are nutrients for the hydrogen-producing Clostridia growth while iron exerts a synergistic influence on them in the conversion of the food wastes into hydrogen.