Supply chain network design with unreliable suppliers: a Lagrangian relaxation-based approach

This paper deals with the integrated facility location and supplier selection decisions for the design of supply chain network with reliable and unreliable suppliers. Two problems are addressed: (1) facility location/supplier selection; and (2) facility location/supplier reliability. We first consider the facility location and supplier selections problem where all the suppliers are reliable. The decisions concern the selection of suppliers, the location of distribution centres (DCs), the allocation of suppliers to DCs and the allocation of retailers to DCs. The objective is to minimise fixed DCs location costs, inventory and safety stock costs at the DCs and ordering costs and transportation costs across the network. The introduction of inventory costs and safety stock costs leads to a non-linear NP-hard optimisation problem. To solve this problem, a Lagrangian relaxation-based approach is developed. For the second problem, a two-period decision model is proposed in which selected suppliers are reliable in the first period and can fail in the second period. The corresponding facility location/supplier reliability problem is formulated as a non-linear stochastic programming problem. A Monte Carlo optimisation approach combining the sample average approximation scheme and the Lagrangian relaxation-based approach is proposed. Computational results are presented to evaluate the efficiency of the proposed approaches.     

厌氧—混凝—高级氧化工艺处理转运站污水的中试研究

开发了转运站污水厌氧生化调节池和基于混凝沉淀及高级氧化技术的快速处理设备,在转运站现场建立中试系统,优化系统运行的工艺参数,研究中试规模下组合工艺对转运站污水的处理效果,并进行了技术经济分析。该组合工艺可将CODCr从进水的15 000 mg/L降至1 230 mg/L,油脂从进水的10 000 mg/L以上降至50 mg/L,色度去除率在90%以上,出水澄清透明且无恶臭。     

Elasto-plastic buckling of curved webs

This paper presents an investigation on elastic buckling strength of curved girder webs subjected to uniform shears or bending stresses at the edges.An elastic 20 degrees of freedom finite element model was used to formulate the eigenvalue problem and a Gauss-Seidel iterative procedure was employed to yield the lowest critical edge loads.In case of pure bending, the investigation is extended into the plastic range. The deformation theory of plasticity in conjunction with a new formulation of the secant modulus is used to derive the elasto-plastic buckling equations. The same Gauss-Seidel iterative procedure was used to find the critical load for each assumed stress level. Further iterations with incremental stress were done to match the elasto-plastic buckling stresses. The material is assumed to be elastic-perfectly plastic and incompressible.In order to aid design professions, the dimensions of the web panel studied are within the practical ranges of curved plate girders. Four boundary conditions that represent various constrain conditions from flanges to stiffeners of plate girder designs, were considered.The results are presented in graphical forms. Interaction curves relating to various dimensionless parameters are constructed. Comparisons and convergence studies were made with existing available data. It is found that boundary conditions and aspect ratio influence the buckling stresses greatly. However, curvature effect is relatively insignificant over the range of practical application.     

Improving sanitation in informal settlements of East African cities: hybrid of market and state-led approaches

This paper analyzes how sanitation can be improved in the informal settlements of East African cities through a hybrid model. Qualitative research was carried out in eight settlements in three cities. Findings show that all cities apply a hybrid model (with some variation) when providing improved sanitation to their residents. Sanitation services were available in all cities, but there was no evidence of the state actively organizing a functioning sanitation market in Kampala or Kisumu. This implies that a hybrid model with a strong and committed developmental state is the right choice in the context of the informal settlements of East African cities.     

Theranostic nanomedicine

Nanomedicine formulations aim to improve the biodistribution and the target site accumulation of systemically administered (chemo)therapeutic agents. Many different types of nanomedicines have been evaluated over the years, including for instance liposomes, polymers, micelles and antibodies, and a significant amount of evidence has been obtained showing that these submicrometer-sized carrier materials are able to improve the balance between the efficacy and the toxicity of therapeutic interventions. Besides for therapeutic purposes, nanomedicine formulations have in recent years also been increasingly employed for imaging applications. Moreover, paralleled by advances in chemistry, biology, pharmacy, nanotechnology, medicine and imaging, several different systems have been developed in the last decade in which disease diagnosis and therapy are combined. These so-called (nano) theranostics contain both a drug and an imaging agent within a single formulation, and they can be used for various different purposes. In this Account, we summarize several exemplary efforts in this regard, and we show that theranostic nanomedicines are highly suitable systems for monitoring drug delivery, drug release and drug efficacy. The (pre)clinically most relevant applications of theranostic nanomedicines relate to their use for validating and optimizing the properties of drug delivery systems, and to their ability to be used for pre-screening patients and enabling personalized medicine. Regarding the former, the combination of diagnostic and therapeutic agents within a single formulation provides real-time feedback on the pharmacokinetics, the target site localization and the (off-target) healthy organ accumulation of nanomedicines. Various examples of this will be highlighted in this Account, illustrating that by non-invasively visualizing how well carrier materials are able to deliver pharmacologically active agents to the pathological site, and how well they are able to prevent them from accumulating in potentially endangered healthy tissues, important information can be obtained for optimizing the basic properties of drug delivery systems, as well as for improving the balance between the efficacy and the toxicity of targeted therapeutic interventions. Regarding personalized medicine, it can be reasoned that only in patients which show high levels of target site accumulation, and which respond well to the first couple of treatment cycles, targeted therapy should be continued, and that in those in which this is not the case, other therapeutic options should be considered. Based on these insights, we expect that ever more efforts will be invested in developing theranostic nanomedicines, and that these systems and strategies will contribute substantially to realizing the potential of personalized medicine.     

Exploring the effects of montmorillonite and halloysite nanotubes on mechanical,optical and barrier properties of poly (butylene adipate-co-terephthalate) blown films: Implications for sustainable packaging and food storage

Biodegradable packaging plastics combining good mechanical properties and low gas permeability is required to avoid environmental and food safety concerns. This study explores the impact of montmorillonite (MMT) and halloysite nanotubes (HNT), on the mechanical, optical, and oxygen permeability of blown film poly (butylene adipate-co-terephthalate) (PBAT) composites. The morphology of the films was evaluated by x-ray diffraction (XRD), differential scanning calorimetry and scanning electron microscopy. Good distribution/dispersion of clays is found in the PBAT-MMT films. Besides, there is an increase in the crystallinity of PBAT due to the nucleating effect of HNT. Improvement in the tensile strength and elongation at break in the machine direction is obtained up to a clay content of 1.5 vol%. The incorporation of 1.5 vol% of MMT and 1 vol% of HNT leads to a reduction in the oxygen permeability of the PBAT film by 29% and 38% respectively. Furthermore, the films remain transparent regardless of clay content. Finally, the feasibility of the films for food storage is tested in grapes, obtaining extended shelf life. The favorable mechanical, barrier and optical properties of the biodegradable films, along with the scalable production process, make them attractive for application in the storage and preservation of food products.     

Internal currents in response to a load change during fuel cell start-up

The transient response of proton exchange membrane fuel cells during start-up is an important issue for backup power systems. These require a very short start-up time which limits the use of batteries during a blackout. In this study the fuel cell was initially inerted with nitrogen at the cathode and thus the start-up procedures occurred in two stages: gas supply in open-circuit and load connection. The influence of the current time-profile, the cell voltage at the connection and the gas flow rates on the voltage variation were investigated using a segmented fuel cell permitting the measurements of the internal local currents. We found that the voltage during the filling of the cathode is not sufficient to determine which fraction of the cathode was filled with oxygen. In the case of a step change in current, the start-up time decreases as the voltage at the moment the cell is connected increases. In response to a ramp, the asymptotic power value is reached quickly.     

泡沫金属作为毛细层的风冷型平板环路热管传热性能研究

该文研究了以水为工质及最终热沉采用风冷的平板型环路热管,其蒸发腔采用凹槽微结构并叠加压缩铜泡沫。实验研究加热功率、热管倾斜角度及充液比对环路热管热性能的影响,获得了环路热管各部件的温度分布及不同运行条件下的热性能数据。结果表明:当充液比为50%及倾斜角度为270时,环路热管的热性能最佳。当加热功率为110 W时,环路热管蒸发受热面最高温度可控制在85℃以下,能满足大功率发光二极管(light emitting diode,LED)等电子设备冷却的需要。