Thermal Behavior in the Lens Process

Direct laser metal deposition processing is a promising manufacturing technology which could significantly impact the length oftime between initial concept and finished part. For adoption ofthis technology in the manufacturing environment, further understanding is required to ensure robust components with appropriate properties are routinelyfabricated. This requires a complete understanding ofthe thermal history.during part fabrication and control ofthis behavior. This paper will describe our research to understand the thermal behavior for the Laser Engineered Net Shaping (LENS) process!, where a component is fabricated by focusing a laser beam onto a substrate to create a molten pool in which powder particles are simultaneously injected to build each layer. The substrate is moved beneath the l~ser beam to deposit a thin cross section, thereby creating the desired geometry for each layer. After deposition of each layer, the powder delivery nozzle and focusing lens assembly is incremented in the positive Z-direction, thereby building a three dimensional component layer additively. It is important to control the thermal behavior to reproducibly fabricate parts. The ultimate intent is to monitor the thermal signatures and to incorporate sensors and feedback algorithms to control part fabrication. With appropriate control, the geometric properties (accuracy, surface finish, low warpage) as well as the materials' properties (e.g. strength, ductility) of a component can be dialed into the part through the fabrication parameters. Thermal monitoring techniques will be described, and their particular benefits highlighted. Preliminary details in correlating thermal behavior with processing results will be discussed.Mechanical Engineerin

Geochemical fractionation and ecological risks assessment of benthic sediment-bound heavy metals from coastal ecosystems off the Equatorial Atlantic Ocean

This studydeterminesthepollution,fractionation,andecologicalrisksofsediment-boundheavymetals from coastalecosystemsofftheEquatorialAtlanticOcean.ContaminationFactor(CF),pollutionload index(PLI),andgeoaccumulationindex(Igeo) wereusedtoassesstheextentoftheheavymetalpol- lution, whilethepotentialecologicalriskwasevaluatedusingtherisksassessmentcode(RAC)and Håkanson potentialecologicalrisk.Theanalysisrevealedconcentrations(mg/g,dw)ofthecadmium(Cd), chromium (Cr),copper(Cu),nickel(Ni),andlead(Pb)insedimentsforwetanddryseasonsvaryfrom 4.40–5.08, 14.80–21.09,35.03–44.8,2.14–2.28, and172.24–196.39,respectively.Theresultsalsoshowed that themetalfractionationpercentagesintheresidual,oxidizable,andreduciblefractionsarethemost significant, whiletheexchangeableandcarbonateboundtracemetalsarerelativelylow.TheRACvalues indicate noriskforCdandNiandlowriskforothermetalsatallthestudiedsitesduringbothseasons. PotentialecologicalriskanalysisoftheheavymetalconcentrationsindicatesthatCdhadhighindividual potentialecologicalrisk,whiletheothermetalshavelowriskatallinvestigatedsites.Themulti-ele- mental potentialecologicalriskindices(R1) indicatehighecologicalriskinalltheecosystem

The Hidden Dimension of Social Norms in Ibibio: Tri-Tangential Trajectory of Ibibio Indigenous Knowledge on Morality

This study examined the hidden ethical elements of norms in Ibibio culture and its dayto- day manifestations within the periscope of ethical prerequisite. This study presents a socio-cultural description of Ibibio norms which are an integral part of the culture, social custom, rituals and beliefs governing social coexistence. It argues that though norm is a cultural production with emphasis on prohibitions, Ibibio norms dictates behavioral and/ or conversational re-orientation

A Qualitative Study of Perceived Risk for HIV Transmission among Police Officers in Dar es Salaam, Tanzania.

Understanding people's views about HIV transmission by investigating a specific population may help to design effective HIV prevention strategies. In addition, knowing the inherent sexual practices of such a population, as well as the risky circumstances that may facilitate HIV transmission, is crucial for the said strategies to become effective. In this article, we report how police officers in Dar es Salaam, Tanzania, perceived the problem of HIV and AIDS in their local context, particularly in relation to unsafe sexual practices. The study was done with the view to recommending ways by which HIV transmission could be minimised within the police force. The study was conducted among members of the police force in Dar es Salaam, Tanzania. Eight focus group discussions (FGDs) were conducted, with a total of 66 participants who were mixed in terms of age, gender, and marital status. Some of these were caregivers to patients with AIDS. Data were analysed using the interpretive description approach. The participants believed that both individual sexual behaviour and work-related circumstances were sources of HIV infection. They also admitted that they were being tempted to engage in risky sexual practices because of the institutional rules that prohibit officers from getting married during their training and for three years after. Nevertheless, as members of the Police Force, they stressed the fact that the risky sexual behaviour that exposes them to HIV is not limited to the force; it is rather a common problem that is faced by the general population. However, they complained, the nature of their job exposes them to road accident victims, subjecting them further to possible infection, especially when they have to handle these road accident casualties without proper protective gear. Individual sexual behaviour and job-related circumstances are worth investigating if proper advice is to be given to the police regarding HIV prevention strategies. In order to improve the lives of these police officers, there is a need to review the existing institutional rules and practices to accommodate individual sexual needs. In addition, improving their working environment may minimize the risk of HIV transmission from handling casualties in emergency situations

Effects of Livelihood Sustenance Activities on Off-Farm Income of Poultry Farmers in IMO State, Nigeria

The study analysed the off farm income and its effect on livelihood sustenance of poultry farmers in Imo state.Multistage sampling technique was used to select 120 respondents. Data for the study were obtained with the aid of structured questionnaire and analysed using descriptive statistics and ordinary least square bivariate regression model. Results showed that: the mean off-farm income of poultry farmers was N410223 per annum. Livelihood sustenance activities of poultry farmers positively and significantly affected their off-farm income. It is recommend that government should come up policies that will center on establishment of more livelihood sustenance activities for poultry farmers that will generate increased off-farm income and promote agricultural development simultaneously

Effect of canine hyperimmune plasma on TNFα and inflammatory cell levels in a lipopolysaccharide-mediated rat air pouch model of inflammation

The purpose of this study was to test the effect of canine hyperimmune frozen plasma (HFP), which is known to contain elevated levels of soluble TNFα receptor 1 (sTNFR1), on TNFα and inflammatory cell levels in a LPS-mediated rat air pouch model of inflammation. There appears to be a correlation between elevated levels of sTNFR1 and depression of TNFα and neutrophil levels in the pouch fluid of HFP dosed rats (r = -0.73, P < 0.0001). The data suggest that canine HFP, which has been demonstrated to contain elevated levels of sTNFR1 compared with FFP, has a direct effect on depressing TNFα levels and neutrophil sequestration in the rat air pouch model of inflammation. These data suggest that HFP may be worthy of further investigation to determine whether such preparations have a therapeutic potential for treatment of acute inflammatory diseases in which TNFα is implicated

Entrance Surface Air Kerma for Chest X-ray Examination in some Diagnostic Radiologic Facilities in Akwa Ibom State, Nigeria

This study evaluated patient doses in diagnostic radiology facilities in Akwa Ibom State. Patient doses were evaluated using equations and software. One thousand five hundred and forty one (1541) patients took part in the study. Eight hundred and six (52.3 %) were female while six hundred and thirty five were male patients. Sixty  percent (60 %) patients were of mean  age group below 50 years, and 40 % of the patients were of mean aged above 50 years, their mean body thickness  range between 6.5-8.0 Kg/m, their height range between 1.5-1.7 cm and mean body mass range between 43.2-82.0 Kg. The ESAK value obtained from the software ranged between (0.38-1.69) mGy for male and  female ESAK ranged (0.37-1.69) mGy while  0.015 – 0.091mGy for male nd 0.015- 0.095 mGy for female were obtained from equation. This study shows that, 6 facilities representing 66.6 % of the facilities recorded mean ESAK values that are within the UK range while only 3 facilities representing 33.3 % recorded ESAK higher than the UK range but within the Montenegro and Serbian range.  Mean ED (mSv) values obtained for the examinations in the different facilities show ED ranges of (0.03-0.12) mSv. The differences in mass and height of patients affect the ESAK value from equation because body thickness of the patient depends on body mass and height. Other reasons for this dose variation are chiefly human factor

Government Agricultural Credit Policy and Macroeconomic Fundamentals: a case study of Agricultural Credit Guarantee Scheme Fund (ACGSF) in Nigeria

The study established the relationship between amount of loan guaranteed by the Agricultural Credit Guarantee Scheme Fund (ACGSF) and some key macroeconomic variables in Nigeria. Augmented Dickey-Fuller unit root test and improved ADF-GLS unit root test conducted on the specified time series showed that all series were integrated of order one. The short-run and long-run elasticities of amount of loan guaranteed by ACGSF with respect to some key macro-economic fundamentals were determined using the techniques of co-integration and error correction models. The empirical results revealed that in the long run, the coefficients of interest rate charged by commercial banks and value of oil revenue has a significant negative and positive relationship respectively with the amount of loan guaranteed by the ACGSF in the country. Whereas in the short run, the coefficients of the previous amount of loan guaranteed and value of oil revenue as well as the real GDP has a positive association with the current amount of loan guaranteed by ACGSF while the external debt has a negative association. The results were further substantiated by the variance decomposition and impulse response analysis of the dependent variable with respect to changes in the explanatory variables. The findings call for appropriate short and long term economic policy packages that should focused on the stabilization of the identified significant macroeconomic shifters of amount of loan guaranteed by ACGSF in the country. Special attention should be given to the interest charged on agricultural loan by participating banks. Also, diversification of the country’s economy and drastic reduction in external debt would boost the operation of ACGSF in the country and enhances credit availability to Nigerian farmers. Keywords: Credit, policy, macroeconomic, external debt, interest rate, ACGSF, Nigeri

Need for Prior Geotechnical Engineering Studies for Foundation Design: Cases of Collapsed Buildings in Port Harcourt and Environs, Nigeria

Cases of collapsed buildings have been on the increase in the city of Port Harcourt and environs in Rivers State, in particular and other major cities in Nigeria in recent times. A critical evaluation of the modes of failures indicates that absence of and / or inadequate subsurface geotechnical investigations have been responsible for these building foundation failures. Case histories of four major building foundation failures within the municipality of Port Harcourt and environs in the southern Niger Delta sub-region of Nigeria in recent times are presented and discussed in this paper. The first case history involves a five-storey building that collapsed because it was constructed across a river channel that had sand and gravels as major subsurface materials beneath the building site. As a result of excessive increase in groundwater table during the rainy season and the attendant excessive pore water pressures build-up that led to a rapid loss of the bearing strength of the subsurface materials, it collapsed in the form of a “punching failure”. The second case was a bearing capacity failure due to rapid construction that did not leave enough time for the dissipation of pore water pressures to allow the foundation soils gain shear strength. It collapsed soon after construction was completed. The third case failed as a result of lack of sufficient time to allow for curing of the block materials used for the building. This was a case of structural failure. The fourth case failed as a result of a complete lack of soil investigations that prevented a detailed foundation design for the residential buildings near the banks of a creek at Opobo town, a suburban settlement along a tidal creek. The paper presents and discusses in details the geology, hydrogeology and modes of failures of these four structures and draws attention to the need to carry out detailed subsurface investigations and abide within the building codes (if any)

Optical method of penetration sensing for pulsed Nd:YAG laser welding

The ability to monitor and control the depth of a laser weld in real-time is critical in many laser welding applications. Consequently, the authors have investigated the use of an optical method to sense weld depth. Welds were generated on kovar samples, using a pulsed Nd:YAG laser. The sensing method uses digital high-speed photography to measure the velocity of the plume of vaporized metal atoms ejected from the metal surface. An energy balance equation is then used to relate the plume velocity to the size of the weld. Numerical solution of the energy balance equation yielded values for weld depth that were within 8% of the actual measured values