An optimization model for the container pre-marshalling problem

In most container yards around the world, containers are stacked high to utilize yard space more efficiently. In these yards, one major factor that affects their operational efficiency is the need to re-shuffle containers when accessing a container that is buried beneath other containers. One way to achieve higher loading efficiency is to pre-marshal the containers in such a way that it fits the loading sequence. In this research, we present a mathematical model for the container pre-marshalling problem. With respect to a given yard layout and a given sequence that containers are loaded onto a ship, the model yields a plan to re-position the export containers within the yard, so that no extra re-handles will be needed during the loading operation. The optimization goal is to minimize the number of container movements during pre-marshalling. The resulting model is an integer programming model composed of a multi-commodity flow problem and a set of side constraints. Several possible variations of the model as well as a solution heuristic are also discussed. Computation results are provided.     

Sonolytic degradation of dimethoate: kinetics, mechanisms and toxic intermediates controlling

The sonolytic degradation of aqueous solutions of dimethoate, O,O-dimethyl S-[2-(methylamino)-2-oxoethyl]dithiophosphate, was examined. Optimal degradation rates were obtained at 619 kHz for continuous sonolysis and 406 kHz for pulse sonolysis. The primary pathways for degradation include hydroxyl radical oxidation, hydrolysis and pyrolysis on collapsing cavitation bubble interfaces. Reaction mechanisms coupled with the corresponding kinetic models are proposed to reproduce the observed concentration versus time profiles for dimethoate, omethoate and N-(methyl) mercaptoacetamide during sonolysis. The oxidation and hydrolysis of dimethoate and omethoate occurred at the water-bubble interface was the rate-determining step for sonolytic overall degradation of dimethoate. More than 90% toxicity of dimethoate was reduced within 45 min ultrasonic irradiation. Ferrous ion at micro molar level can significantly enhance the sonolytic degradation of dimethoate and effectively reduce the yields of toxic intermediate omethoate.     

Effect of a low-molecular-weight compatibilizer on the immiscible blends of cellulose acetate propionate and poly(butylene terephthalate)

Blends of poly(butylene terephthalate) (PBT) and cellulose acetate propionate (CAP) were found to be immiscible. In order to improve the interfacial strength and miscibility of the PBT/CAP blends, a low-molecular-weight poly(ethylene glycol) (PEG) was thus pre-mixed with the CAP to form the P-CAP mixture. It was then blended with the PBT up to 15 wt% using a twin-screw extruder to prepare the PBT/P-CAP blends, and subsequently processed into the films and fibers by compression-molding and melt-spinning, respectively. The thermal and dynamic mechanical analyses suggested that the PBT and CAP became partially miscible and the interfacial strength was thus improved in the PBT/P-CAP blends, owing to the addition of PEG. The PEG was not only miscible with the CAP but also with the PBT, and it served as a plasticizer as well as a compatibilizer. From the observation of the fractured surface of the PBT/P-CAP films, the PBT component was present as dispersed particles in the P-CAP matrix with size ranging from 1.4 to 3.0 μm; yet it became nanofiber in the spun fibers. Successful fibers of the PBT/P-CAP blends with an average diameter of 20 μm could be spun, where the tensile strength and elongation at break were in the range of 0.6?0.7 g/denier and 12?16%, respectively. Finally, the ultra-fine PBT nanofibers with diameters in the range of 50?70 nm were observed after removing the P-CAP matrix with acetone from the fibers, owing to the formation of PBT nanofibers during spinning and orientation processes. This method thus could successfully produce nano-scale PBT fibers with fineness comparable with the nanofibers developed via electrospinning technology.     

黄浦江水源突发挥发酚污染应急处理研究

针对黄浦江上游水源可能发生的突发挥发酚污染事故,开展应急处理小试和中试研究,考察了混凝、PAC吸附和PAC吸附-常规工艺对原水中挥发酚的应急处理能力。结果表明,强化混凝方法无法有效应对原水突发挥发酚污染问题。PAC对原水中苯酚的Freundlich吸附等温式为q_e=0.428 6 C_e~(0.240 8),根据该式求得当原水苯酚浓度为0.008 mg/L时,PAC吸附应急处理的理论投加量为12 mg/L。PAC强化常规工艺可作为应急措施有效应对突发酚污染事故,当原水苯酚超标浓度为0.008 mg/L时,PAC最佳投加量为10 mg/L。     

Ametryn degradation in the ultraviolet (UV) irradiation/hydrogen peroxide (H2O2) treatment

Ultraviolet (UV) irradiation (253.7nm) in the presence of hydrogen peroxide (H(2)O(2)) was used to decompose aqueous ametryn. The concentrations of ametryn were measured with time under various experiment conditions. The investigated factors included H(2)O(2) dosages, initial pH, initial ametryn concentrations, and a variety of inorganic anions. Results showed that ametryn degradation in UV/H(2)O(2) process was a pseudo-first-order reaction. Removal rates of ametryn were greatly affected by H(2)O(2) dosage and initial concentrations of ametryn, but appeared to be slightly influenced by initial pH. Furthermore, we investigated the effects of four anions (SO(4)(2-), Cl(-), HCO(3)(-), and CO(3)(2-)) on ametryn degradation by UV/H(2)O(2). The impact of SO(4)(2-) seemed to be insignificant; however, Cl(-), HCO(3)(-), and CO(3)(2-) considerably slowed down the degradation rate because they could strongly scavenge hydroxyl radicals (OH) produced during the UV/H(2)O(2) process. Finally, a preliminary cost analysis revealed that UV/H(2)O(2) process was more cost-effective than the UV alone in removal of ametryn from water.     

Oxidative degradation of dimethyl phthalate (DMP) by UV/H(2)O(2) process

The photochemical degradation of dimethyl phthalate (DMP) in UV/H(2)O(2) advanced oxidation process was studied and a kinetic model based on the elementary reactions involved was developed in this paper. Relatively slow DMP degradation was observed during UV radiation, while DMP was not oxidized by H(2)O(2) alone. In contrast, the combined UV/H(2)O(2) process could effectively degraded DMP, which is attributed to the strong oxidation strength of hydroxyl radical produced. Results show that DMP degradation rate was affected by H(2)O(2) concentration, intensity of UV radiation, initial DMP concentration, and solution pH. A kinetic model without the pseudo-steady state assumption was established according to the generally accepted elementary reactions in UV/H(2)O(2) advanced oxidation process. The rate constant for the reaction between DMP and hydroxyl radical was found to be 4.0 x 10(9) M(-1)s(-1) through fitting the experimental data to this model. The kinetic model could adequately describe the influence of key factors on DMP degradation rate in UV/H(2)O(2) advanced oxidation process, and could serve as a guide in designing treatment systems for DMP removal.     

Preparation and characterization of carbon black/polybutylene terephthalate/polyethylene terephthalate antistatic fiber with sheath–core structure

In this study, antistatic sheath–core composite fibers with the core composed of polyethylene terephthalate (PET) polymer and a sheath composed of carbon black/polybutylene terephthalate (CB/PBT) polymer were fabricated using a conjugate spinning process. CB powders of various particle sizes were compounded with PBT polymers to prepare the antistatic CB/PBT pellets, and their electrical resistivities strongly depended on the intrinsic properties and dispersion of CB powders. The CB/PBT/PET fibers consisted of well-mixed CB powders within the polymer matrix showed an outstanding antistatic function, and they were employed to manufacture an antistatic glove with commercial acrylic yarns for practical applications. The antistatic glove with a reliable washing fastness is capable of being used on capacitive touch panels of smart phones, tablets, and other wearable electronic devices. This approach offers new possibilities for a variety of textile applications requiring antistatic properties.     

A study of titanium sulfate flocculation for water treatment

There are limited studies available on titanium salt flocculation. In this research, coagulation experiments of titanium sulfate were conducted using both distilled water and kaolin clay suspension. Results showed that titanium sulfate flocculation was most effective in the pH range 4-6, and negligible concentrations of titanium were found in the well-flocculated water. The floc isoelectric point (IEP) was found to be near pH 5. Measurements showed that the titanium flocs possessed greater density, diameter and settling velocity than the aluminum flocs. The titanium flocs were composed of TiO(OH)₂, which would change from the amorphous phase into anatase titanium dioxide under elevated temperatures. Floc images showed the structural similarity of titanium and aluminum flocs. Laboratory results and a pilot experiment showed that titanium sulfate could be an alternative coagulant for water and wastewater treatment.     

Measurement of dissolved organic nitrogen in a drinking water treatment plant: size fraction, fate, and relation to water quality parameters

This paper investigates the characteristics of dissolved organic nitrogen (DON) in raw water from the Huangpu River and also in water undergoing treatment in the full-scale Yangshupu drinking water treatment plant (YDWTP) in Shanghai, China. The average DON concentration of the raw water was 0.34 mg/L, which comprised a relatively small portion (~ 5%) of the mass of total dissolved nitrogen (TDN). The molecular weight (MW) distribution of dissolved organic matter (DOM) was divided into five groups: > 30, 10-30, 3-10, 1-3 and < 1 kDa using a series of ultrafiltration membranes. Dissolved organic carbon (DOC), UV absorbance at wavelength of 254 nm (UV254) and DON of each MW fraction were analyzed. DON showed a similar fraction distribution as DOC and UV254. The < 1 kDa fraction dominated the composition of DON, DOC and UV254 as well as the major N-nitrosodimethylamine formation potential (NDMAFP) in the raw water. However, this DON fraction cannot be effectively removed in the treatment line at the YDWTP including pre-ozonation, clarification and sand filtration processes. The results from linear regression analysis showed that DON is moderately correlated to DOC, UV254 and trihalomethane formation potential (FP), and strongly correlated to haloacetic acids FP and NDMAFP. Therefore, DON could serve as a surrogate parameter to evaluate the reactivity of DOM and disinfection by-products FP.     

Changes in profiles of airborne fungi in flooded homes in southern Taiwan after Typhoon Morakot

In August 2009, the historic Typhoon Morakot brought extreme rainfall and resulted in flooding which spread throughout southern Taiwan. This study compared the difference between fungal concentrations before and after the disaster in selected homes of the Tainan metropolitan area, which were hit hardest by the catastrophe. A group of 83 households available from a prior cohort established with random sampling out of a regional population in southern Taiwan was contacted successfully by telephone. Twenty-five of these reported to have suffered from floods of various degrees at this time. Around 2 weeks after the event, at which time most of the remedial process had been completed by self-efforts and public health endeavours, 14 of these 25 (56%) agreed to participate in measurements of the airborne microbial concentrations. The averages (standard deviation) of the total culturable fungal concentrations in children's bedrooms and flooded rooms were 18,181 (25,854) colony-forming units per cubic metre (CFU/m³) and 13,440 (11,033) CFU/m³, respectively. The airborne fungal spore levels in the 2 above-mentioned indoor sites were 221,536 (169,640) spores/m³ and 201,582 (137,091) spores/m³, respectively. The average indoor/outdoor ratios in the children's bedrooms were 4.2 for culturable fungi and 1.4 for fungal spores. These values were higher than the respective values measured in the same homes during the previous year: 1.1 and 0.6. In terms of the specific fungal profile, the percentages of Aspergillus spp. increased significantly in both the indoor and outdoor environments after the event. To this date, this study is among the limited research that has been conducted to quantitatively demonstrate that fungal manifestation is likely to persist in flooded homes even after seemingly robust remedial measures have been put into place. Studies to examine the potential health implications and effectiveness of better remedial technology remain much needed.