The role of Time, Income and Expenditure Patterns in Pedestrian decision-making in the Kumasi Metropolis (Ghana)

This research was undertaken in May 2012 using a sample size of 174 respondents in four proxy communities in the Kumasi Metropolis of Ghana. Using cross-tabulation quantitative methods, the research shows that walking speed is directly related to age. Also, when presented with the choice to walk or not in different scenarios, respondents with higher incomes prefer to trade money for time whiles lower income earners would trade time to save money. In addition, motorised transport costs represent 15% of the average monthly income of respondents and 18% off their expenditure; of which lower income earners cannot afford on a regular basis and therefore walk to 'survive'. Keywords: Pedestrian, Travel time, Kumasi, Income, Expenditure, Pedestrian behaviour, Ghan

The contradiction of Demotorisation: a Literature Argument

This paper is aimed at outlining the flexibility of capitalist consumption (Harvey, 1990) through a review of literature that has condemned the modernist era of the automobile for its consumerist tendencies but has failed to recognise that this flexibility of capitalism has been re-invented through demotorisation as a new tool for consumer culture. Demotorisation here is used to refer to the removal or partial removal of cars from roads and replacing it with cycling and walking. The research employs a review of theoretical as well as secondary empirical analysis. It must be emphasised that this paper is not aimed at discrediting demotorisation of streets but rather to point its postmodern nuances. Key Words: Demotorisation, Pedestrianisation, Consumerism, Automobile, Cycling, gentrification

Incommensurable languages of value and petro-geographies: Land-use, decision-making and conflict in South-Western Ghana

Petroleum in Ghana has created new dilemmas for land control and spatial planning. This paper explores petro-geographies using the concept of “incommensurable values” to situate the multiple, conflicting, and intersecting values and framings attached to land. We identify languages of value used by non-state actors that reflect the need for social-market investments, gainful employment, food security, and protection from expropriation and pollution. We find that these languages are incommensurate with those of state actors, who emphasize efficiency, competitiveness, and voluntariness in pursuit of the “highest and best use of land and petroleum resources”. The spatial outcomes reflect a singularization of local incommensurable land values into commensurable spatial forms, creating an enabling environment for private and centralized extractive capital. Rural displacement and urban gentrification have become the costs of speculative “oil city projects” and “petro-industrial hubs”. The central government, state agencies, oil companies, and other stakeholders, have engaged in “value-legitimation” processes reflecting different values, backgrounds, and power positions. These processes delegitimize local conceptions of value in land, creating new contradictions and avenues for conflict. As a result, local knowledge and values are replaced with logics of market deregulation and “efficiency” in a “locking-in” of a new approach to planning and spatial development that will have significant impacts on economies, livelihoods and food security

The effect of mechanical activation on synthesis and properties of MgAl2O4 ceramics

Magnesium aluminate, MgAl2O4 and other alumina-based spinels are ceramics with high hardness, high melting point and mechanical strenght. Spinels can also be used as dielectrics in microwave applications. The goal of this study was to examine the effects of mechanical activation and sintering temperatures on physico-chemical properties of spinel. MgAl2O4 was produced by solid state reaction between MgO and α-Al2O3. The starting powders were mixed by ball milling to homogenize without significant particle size reduction. Mechanical activation of mixed powders was performed in a high-energy planetary ball mill in air for 1 h. Powders were compacted at 300 MPa. Heat treatments were performed in air, at temperatures ranging from 1200 to 1600 °C with 2 h dwell time, to determine the amount of spinel formation as a function of temperature. Phase composition and microstructure of initial powders and heated samples were determined by means of X-ray diffraction, particle size analysis, and scanning electron microscopy. The influences of milling and consolidation parameters were studied by electrical measurements and mechanical characterization. The main conclusion of this study was that mechanical activation for 60 min initiated a mechano-chemical reaction, resulted in spinel formation at much lower temperatures than within non-activated powders, and indicated that final sintering stage started at much lower temperatures for activated powders. Changes in microstructure parameters, as a consequence of mechanical treatment and subsequent heating of investigated powder mixtures, strongly affect electrical and mechanical properties of the final ceramics.This is the peer-reviewed version of the article: Obradović, Nina, W. G. Fahrenholtz, Suzana Filipović, Darko Kosanović, A. Dapčević, Antonije Đorđević, Igor Balać, and Vladimir B. Pavlović. 2019. “The Effect of Mechanical Activation on Synthesis and Properties of MgAl2O4 Ceramics.” Ceramics International, [https://doi.org/10.1016/j.ceramint.2019.03.095

Development of microsurgery and reconstructive surgery at the Clinical Hospital Centre in Rijeka

Klinička mikrovaskulama kirurgija afirmirala se prvo u replantacijama amputiranih prstiju i udova. Iz literatureje teško odrediti gdje je učinjena prva mikrovaskulama replantacija. Temeljni radovi o replantaciji obavljeni su 1975. - dr. Chen, NR Kina, 6. narodna bolnica Shanghai. U KBC Rijeka prva uspješna replantacija podlaktice učinjena je 1983. godine. Od tada su u KBC-u učinjene brojne replantacije prstiju i dijelova gornjih ekstremiteta. Kod uspješnih replantacija rezultati su funkcionalno i estetski zadovoljavajući. Koristili smo sljedeći red operacijsko-rekonstmkcijskih zahvata: osteosintezu, anastomozu, rekonstmkciju vaskulamih elemenata, rekonstrukciju živaca, rekonstmkciju tetiva ili mišića, rekonstmkciju mekog pokrova (direktne suture, slobodni kožni transplantati i prijenos kože i potkožja u smislu slobodnih režnjeva ili vezanih ingvinalnih režnjeva). Kako bismo izbjegli kolamu nekrozu kod replantacije, posebice na nadlakticama i podlakticama, pri rekonstrukciji koštanih elemenata činili smo skraćenje otprilike do 8 i 10 cm bez znatnih funkcionalnih i estetskih oštećenja. Iste metode koristimo kod rekonstrukcije živčanih elemenata kada postoji oštećenje istih jer usporedni rezultati direktnih epineuralnih sutura živaca i interfascikulame transplantacije su u korist direktnih epineuralnih šavova. Pravu sliku vrijednosti mikrokirurgije (replantacije) dobivamo u usporedbi invalidima bez udova iz vremena kada nisu činjene replantacije ili s neuspješnim rekonstrukcijama.Clinical microvascular surgery was first affirmed with replantations of amputated digits and limbs. From the literature it is very difficult to determine exactly when the first microvascular replantation took place. The basic replantation activities began in 1975 by Dr Chen of the 6th National Hospital in Shanghai, China. The first successful forearm replantation at the Clinical Hospital Centre in Rijeka was performed in 1983. Since then many of digit and upper limb parts\u27 replantations have been done. In a successful replantation the results are satisfactory both functionaly and esthetically. During replantation, operative reconstructive grips are performed in the following order: osteosynthesis, anastomosis and reconstruction of vascular elements, reconstruction of nerves, reconstruction of tendons or muscles, reconstruction of soft covering (direct sutures, free skin transplants and skin and subcutaneous tissue transfers in form of free flaps or island groin flaps). In order to avoid collar necrosis in replantation, especially in the upper arm and the forearm, during reconstruction of osseous elements a shortening of up to 8-10 cm was performed, without considerable functional and aesthetic defects. The same methods were used in the reconstruction of defective nervous elements, because the compared results of direct epineural sutures of nerves and interfascicular transplantation are in favour of direct epineural sutures. The real value of microsurgery (replantation) is understood when comparing successfully treated patients with the disabled people with amputated extremities from the time when replantations were not performed or as a result of an unsuccessful reconstructions

Elevated Temperature Thermal Properties of ZrB2 with Tungsten Additions

The thermal properties of zirconium diboride (ZrB2) ceramics with tungsten additions of up to 5 wt% were characterized up to 2000°C. Densification was promoted by the addition of 0.5 wt% carbon. ZrB2 ceramics were prepared from commercially available powder by hot pressing. The crystalline phases present were determined by x-ray diffraction. The microstructure and density change as a result of the addition of tungsten, but this does not affect much the thermal behavior of ZrB2 at room and elevated temperatures. Thermal diffusivity at 200°C decreased from 0.158 cm2/s for nominally pure ZrB2 to 0.149 cm2/s for ZrB2 with 5 wt% Tungsten carbide (WC). The thermal diffusivity decreased with increasing temperature, reaching a value of 0.145 cm2/s at 2000°C for ZrB2 with 5 wt% Tungsten carbide (WC). Heat capacity, unlike thermal diffusivity, did not change during thermal cycling. Thermal conductivity, which was calculated from thermal diffusivity, heat capacity, and density, was as high as 77.9 W/(m·K) at 2000°C for ZrB2 with 5 wt% Tungsten carbide (WC). Any level of Tungsten carbide (WC) contamination reduces thermal conductivity. Properties, including hardness, oxygen content, elastic modulus, strength were measured and will be discussed

High-fidelity 3D microstructural characterization of ZrB2 during hot-pressing (Invited)

Standard ultra-high temperature ceramic (UHTC) manufacturing results in components with large differences in properties due to variability in microstructural “critical flaw” distributions. Critical flaws can be any irregularity in a component, such as a secondary phase, cracks, pores, etc. This is problematic when designing reproducible UHTC components. The goal of this project is to understand how these critical flaws evolve during hot pressing of ZrB2 (a UHTC) by examining them in 3D. This study incorporates 3D imaging such as (i) preliminary in-situ high-temperature pressureless sintering X-ray µ-CT, (ii) ex-situ X-ray µ-CT, and (iii) 3D electron imaging and backscattered diffraction data collected at different stages of densification. 3D microstructure statistics along with unique observations of individual pore and secondary phase evolution will be presented. This data is brought together to give a holistic view of the densification of ZrB2 during hot pressing at multiple length scales. This data will be incorporated into a process-structure-property (PSP) database for statistical modeling to reduce uncertainty during ZrB2 processing

Mechanical properties of zirconium diboride ceramics

Zirconium diboride(ZrB2) belongs to the group of ultrahigh temperature ceramics (UHTCs) because of its high melting point (3250°C). Due to its excellent properties, such as the melting temperature, high strength and hardness, high thermal and electrical conductivities relative to other ceramics and good corrosion resistance to molten metals, it has attracted great interest from materials scientists. Fully dense ZrB2 ceramics were successfully obtained by hot pressing at 2150oC for 10 minutes. Prior to hot pressing, commercially available ZrB2 powder was ball milled for 24hr with ZrB2 media. Carbon was added as a densification aid in the amount of 0.5 wt.% using phenolic resin. For mechanical testing, three different methods were compared. Three point bending was performed in air at room temperature and the obtained strength was 546±55 MPa. Four-point bend strengths were measured under same conditions resulting in strengths of 476±112 MPa. Finally, the fracture toughness of pure ZrB2 ceramics was determined by the chevron notched beam method to be 4.1 ± 0.5 MPa•m1/2. The obtained results of mechanical testing make this ceramic material applicable as cutting tools, and parts for hypersonic aerospace vehicles