Micro-electroforming metallic bipolar electrodes for mini-DMFC stacks

This paper describes the development of metallic bipolar plate fabrication using micro-electroforming process for mini-DMFC (direct methanol fuel cell) stacks. Ultraviolet (UV) lithography was used to define micro-fluidic channels using a photomask and exposure process. Micro-fluidic channels mold with 300 micrometers thick and 500 micrometers wide were firstly fabricated in a negative photoresist onto a stainless steel plate. Copper micro-electroforming was used to replicate the micro-fluidic channels mold. Following by sputtering silver (Ag) with 1.2 micrometers thick, the metallic bipolar plates were completed. The silver layer is used for corrosive resistance. The completed mini-DMFC stack is a 2x2 cm2 fuel cell stack including a 1.5x1.5 cm2 MEA (membrane electrode assembly). Several MEAs were assembly into mini-DMFC stacks using the completed metallic bipolar plates. All test results showed the metallic bipolar plates suitable for mini-DMFC stacks. The maximum output power density is 9.3mW/cm2 and current density is 100 mA/cm2 when using 8 vol. % methanol as fuel and operated at temperature 30 degrees C. The output power result is similar to other reports by using conventional graphite bipolar plates. However, conventional graphite bipolar plates have certain difficulty to be machined to such micro-fluidic channels. The proposed micro-electroforming metallic bipolar plates are feasible to miniaturize DMFC stacks for further portable 3C applications.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/16838

Transformasi Pekan Parit Raja: kajian terhadap kesejahteraan hidup masyarakat

Isu utama yang dibangkitkan dalam kajian ini adalah mengenai isu kesejahteraan hidup masyarakat ekoran transformasi yang berlaku di Pekan Parit Raja dan kesannya. Transformasi pembangunan yang berlaku di pekan kecil pada asasnya menunjukkan pencapaian positif dalam pelbagai sudut mencakupi perkembangan ekonomi, perindustrian, prasarana dan perumahan. Namun turut memberi kesan kepada persekitaran fizikal. Kesan daripada keadaan itu turut membawa ke arah kemerosotan serta memberi tekanan yang kuat terhadap kesejahteraan hidup masyarakat setempat. Objektif kajian ini ialah (i) meninjau perkembangan pembangunan di Pekan Parit Raja, (ii) mengenalpasti perubahan sosio ekonomi penduduk setempat, (iii) mengenalpasti keperluan penduduk setempat mengikut perkembangan semasa dan (iv) membentuk indeks penunjuk kesejahteraan hidup bagi masyarakat Pekan Parit Raja. Skop kajian tertumpu di Pekan Parit Raja dengan tumpuan terhadap transformasi pembangunan yang dialami dari segi perkembangan fizikal, sosial dan ekonomi. Responden yang terpilih terdiri daripada wakil Pihak Berkuasa Tempatan, wakil komuniti dan masyarakat setempat. Kajian dijalankan berdasarkan kepada pengumpulan data primer dan sekunder. Sejumlah 367 responden telah dipilih secara persampelan rawak bersrata. Data yang dikumpul telah dianalisis menggunakan program SPSS. Analisis kajian mendapati perubahan ruang ekonomi yang berlaku di Pekan Parit Raja adalah sangat ketara. Hasil kajian menunjukkan keluasan had pembangunan di Pekan Parit Raja telah meningkat sebanyak 2.51% antara tahun 1998 sehingga tahun 2003 dan tertinggi berbanding lima (5) bandar utama lain. Faktor pembangunan sosio ekonomi yang positif menyebabkan unjuran penduduk dijangka mencapai sehingga 9.9% sehingga tahun 2020. Sebanyak 53.8% responden telah berjaya meningkatkan pendapatan sehingga hampir sekali ganda dalam tempoh 20 tahun. Sebahagian besar responden pula berkemampuan dari segi pemilikan perumahan dan kereta masing-masing dengan peningkatan sehingga 86.6% dan 98.0% pada sekitar tahun 2010. Ianya sangat berbeza dengan 20 tahun lepas. Walau bagaimanapun, 72.5% responden menyatakan beberapa keperluan perlu ditambah atau diperbaiki dengan jalan raya merupakan keperluan utama. Pada masa yang sama, 75.7% responden menyatakan jenis keperluan yang paling penting perlu disediakan adalah perpustakaan awam. Dapatan keseluruhan kajian akhirnya telah membentuk indeks penunjuk kesejahteraan hidup dari aspek ekonomi, kualiti perumahan, keharmonian sosial dan alam sekitar kesan transformasi pembangunan ke atas kesejahteraan hidup masyarakat setempat. Beberapa cadangan telah dikemukakan agar pembangunan yang membawa perubahan kepada sosio ekonomi dan persekitaran seharusnya mengambil kira kesejahteraan hidup masyarakat dan kelestarian alam sekitar untuk mencapai kualiti hidup yang lebih baik di masa akan datang

Neural computations underlying action-based decision making in the human brain

Action-based decision making involves choices between different physical actions to obtain rewards. To make such decisions the brain needs to assign a value to each action and then compare them to make a choice. Using fMRI in human subjects, we found evidence for action-value signals in supplementary motor cortex. Separate brain regions, most prominently ventromedial prefrontal cortex, were involved in encoding the expected value of the action that was ultimately taken. These findings differentiate two main forms of value signals in the human brain: those relating to the value of each available action, likely reflecting signals that are a precursor of choice, and those corresponding to the expected value of the action that is subsequently chosen, and therefore reflecting the consequence of the decision process. Furthermore, we also found signals in the dorsomedial frontal cortex that resemble the output of a decision comparator, which implicates this region in the computation of the decision itself

Fabrication of Electrically Conductive, Fluid Impermeable Direct Methanol Fuel Cell (DMFC) Graphite Bipolar Plates by Indirect Selective Laser Sintering (SLS)

Graphite bipolar plates are highly desirable due to their properties of high electrical conductivity and low weight but are associated with prohibitive machining costs arising from poor mechanical properties. Bipolar plates made by indirect Selective Laser Sintering (SLS) offer the advantages of complex part production in shorter times at lower cost. Due to the nature of the SLS process, the as-produced (green part) plates are porous and possess low electrical conductivity which can be improved by carbonizing the phenolic resin binder at high temperatures (brown part). It has been found that the electrical conductivity increases significantly (> 200 S/cm) with a corresponding increase in pyrolyzing temperature which correlates well with literature on the carbonization of phenol formaldehyde resins. The brown parts are subsequently infiltrated with low viscosity (~5 - 10 cps) cyanoacrylate to seal up the open pores, rendering the plates fluid impermeable.Mechanical Engineerin

Experimental measurement technique for the assessment of the fuel crossover diffusion coefficient in the membrane electrode assembly of a direct methanol fuel cell

Since the cross-over still seems to be the main issue of the direct methanol fuel cells, an experimental evaluation of the diffusive cross-over is performed. Even if the relationship of the rate through the membrane is the sum of the three terms of diffusive, osmotic and drag, the diffusive component is also present at open circuit lowering the Open Circuit Voltage of the single cell up to 50 % with respect to the Nernst potential. The goal of the research is to develop a direct measurement technique of the crossover that can provide the effective values of the parameters that characterize the membrane electrode assembly. The experimental set up consists in the pressure, flow and temperature control and acquisition using Labview. A sensitive analysis for three values of temperatures at 60°C, 65°C and 70°C is performed for first. Then, a small overpressure was generated in the cathode side by a valve located at the cathode outlet. A set of pressure were analysed for 0, 30 and 90 mbar of overpressure at the cathode. The tested fuel cell has a commercial Nafion 117 membrane and carbon paper gas diffusion layers 700 cm2 large. Preliminary results show that the differential concentration term seems to be significantly larger than the osmotic term. The diffusion coefficients are useful for fuel cell modelling and for the calibration of the operating conditions in the sensor less DMFC systems

Probabilistic Models of Yield, Price, and Revenue Risks for Fed Cattle Production

Livestock Production/Industries,

Catalytic fuel cell used as an analytical tool for methanol and ethanol determination. Application to ethanol determination in alcoholic beverages

A small direct catalytic methanol 'fuel cell' was used for analytical purposes. Three different formats were investigated for methanol and ethanol determination: two different Open Circuit Voltage (OCV) formats and a potentiostatic (i.e. amperometric) format; the latter was used if the current supplied by the cell was recorded. The measurement times using one or other of these three formats were much different. The time required by the potentiostatic format was more short for a suitable analytical measurement. The cell was used to check ethanol content in several commercial wine and beer samples and the possibility of using the fuel cell for the analytical measures in real samples, discussed. Lastly the results were compared with those obtained using two conventional amperometric enzyme sensors and statistical tests carried out. (C) 2016 Elsevier Ltd. All rights reserved

Possibilities of upgrading solid underutilized lingo-cellulosic feedstock (carob pods) to liquid bio-fuel: Bio-ethanol production and electricity generation in fuel cells - A critical appraisal of the required processes

The exploitation of rich in sugars lingo-cellulosic residue of carob pods for bio-ethanol and bio-electricity generation has been investigated. The process could take place in two (2) or three (3) stages including: a) bio-ethanol production originated from carob pods, b) direct exploitation of bio-ethanol to fuel cells for electricity generation, and/or c) steam reforming of ethanol for hydrogen production and exploitation of the produced hydrogen in fuel cells for electricity generation. Surveying the scientific literature it has been found that the production of bio-ethanol from carob pods and electricity fed to the ethanol fuel cells for hydrogen production do not present any technological difficulties. The economic viability of bio-ethanol production from carob pods has not yet been proved and thus commercial plants do not yet exist. The use, however, of direct fed ethanol fuel cells and steam reforming of ethanol for hydrogen production are promising processes which require, however, further research and development (R&D) before reaching demonstration and possibly a commercial scale. Therefore the realization of power generation from carob pods requires initially the investigation and indication of the appropriate solution of various technological problems. This should be done in a way that the whole integrated process would be cost effective. In addition since the carob tree grows in marginal and partly desertified areas mainly around the Mediterranean region, the use of carob’s fruit for power generation via upgrading of its waste by biochemical and electrochemical processes will partly replace fossil fuels generated electricity and will promote sustainability

Quality Risk and Profitability in Cattle Production: A Multivariate Approach

This study evaluates quality, production, and price risk within the context of overall profit variability in fed cattle production. The approach used offers a flexible way to estimate a large system of equations with more than three jointly related censored outcomes. Trade-offs between quality and yield grade levels and production measures, such as average daily gain and feeding efficiency, are evaluated. Simulation procedures are used to assess the impact of quality risk on overall profit variability. Results make an important contribution to existing research by explaining why price signals through grid quality grade premiums may not generate intended producer responses.censoring, copula, fed cattle, grid pricing, multivariate, quality risk, Livestock Production/Industries,