Orbit Control of an Earth Orbiting Solar Sail Satellite

Halis Can Polat,Ozan Tekinalp 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.1

A concept for the utilization of solar sail satellite’s propellant-free thrust capability at Low earth orbit (LEO) is proposed and its orbit control strategy is analyzed. Thrust vector control of the sail’s normal direction is used to harvest the solar radiation pressure for generating the necessary acceleration to change the orbital elements. The required control vector direction is determined with two approaches. The first approach is realized by approximating the Gaussian Variational Equations at the employed orbit properties and deriving the optimal force direction in the orbital frame as a function of true anomaly. The second approach is accomplished by implementing a Lyapunov-based nonlinear feedback controller that continuously gives solar thrust in the orbital frame. The simulation results for the orbit control methods are given and discussed to show the solar sail satellite’s capability for altering the orbital elements at LEO are stated. It is demonstrated that both approaches give satisfactory results.

Effect of Treadmill Backward Walking Training on Motor Capacity in Cerebral Palsy: A Randomized Controlled Study

Halis Doğan,Fatma Mutluay 대한재활의학회 2023 Annals of Rehabilitation Medicine Vol.47 No.2

Objective To evaluate treadmill backward walking training (BWT) effects on walking speed, balance, mobility, and walking endurance in children with cerebral palsy (CP). Methods The study evaluated 41 children with CP (age, 6–18; Gross Motor Function Classification System levels I and II). They were randomly allocated into control and BWT groups. BWT was applied (two sessions/week, 15 min/session for 8-week) to BWT group after the neurodevelopmental-based physiotherapy program routinely followed by all participants while the control group did not receive BWT. 10-Meter Walk Test (10MWT), Pediatric Balance Scale (PBS), Timed Up and Go Test (TUG), and Two-Minute Walk Test (2MWT) were selected as outcome measures for assessing walking speed, balance, mobility and endurance respectively. Results In BWG, 2MWT distance (3.5%), PBS (3.5%) increased significantly, and TUG decreased by 5.1% (all p<0.001) after training, 10MWT was shorter by 6.1% for BWG, corresponding to 7.4% faster walking speed (p<0.01). Control group assessment variations were stationary and not statistically significant. Conclusion Backward treadmill walking training induces small but statistically significant motor capacity improvements in children with CP.

Differential Effects of Pentoxifylline on Learning and Memory Impairment Induced by Hypoxic-ischemic Brain Injury in Rats

Hülya Halis,Soner Bitiktaş,Osman Baştuğ,Burak Tan,Şehrazat Kavraal,Tamer Güneş,Cem Süer 대한정신약물학회 2019 CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE Vol.17 No.3

Objective: Hypoxic-ischemic (HI) brain injury in the human perinatal period often leads to significant long-term neurobehavioral dysfunction in the cognitive and sensory-motor domains. Using a neonatal HI injury model (unilateral carotid ligation followed by hypoxia) in postnatal day seven rats, the present study investigated the long-term effects of HI and potential behavioral protective effect of pentoxifylline. Methods: Seven-day-old rats underwent right carotid ligation, followed by hypoxia (FiO2 = 0.08). Rats received pentoxifylline immediately after and again 2 hours after hypoxia (two doses, 60‒100 mg/kg/dose), or serum physiologic. Another set of seven-day-old rats was included to sham group exposed to surgical stress but not ligated. These rats were tested for spatial learning and memory on the simple place task in the Morris water maze from postnatal days 77 to 85. Results: HI rats displayed significant tissue loss in the right hippocampus, as well as severe spatial memory deficits. Low-dose treatment with pentoxifylline resulted in significant protection against both HI-induced hippocampus tissue losses and spatial memory impairments. Beneficial effects are, however, negated if pentoxifylline is administered at high dose. Conclusion: These findings indicate that unilateral HI brain injury in a neonatal rodent model is associated with cognitive deficits, and that low dose pentoxifylline treatment is protective against spatial memory impairment

Network Analysis Algorithm for the Solution of Discrete Time-Cost Trade-off Problem

Önder Halis Bettemir,M. Talat Birgönül 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.4

Optimum solution of time-cost trade-off problem has significant importance since it provides the highest profit opportunity. For this reason, exact, heuristic, and meta-heuristic algorithms are adapted to obtain the optimum or near-optimum solution. However, heuristic algorithms may not always converge into the global optimum, while meta-heuristic algorithms require significant computation to converge into global optimum and exact methods are complex for construction planners to implement. Therefore, minimum cost-slope based fast converging network analysis algorithm, which provides optimum or near-optimum solutions, is proposed for discrete time-cost trade-off problem. The algorithm searches the global optimum through the feasible crashing options. Number of feasible crashing options increase tremendously in large projects. Therefore, an elimination algorithm is embedded to reduce the number of crashing options. The crashing option with the lowest unit crashing cost is executed and global optimum is searched by stepwise crashing. Tests on 18 and 63-Activity projects revealed that the network analysis algorithm converges to optimum or near-optimum solution by only one percent of the computational demand of meta-heuristic algorithms. Consequently, the proposed heuristic algorithm is a convenient optimization method for the solution of time-cost trade-off problem.

Effects of Calcium Channel Blockers On Hyaluronidaseinduced Capillary Vascular Permeability

Zekai Halici,Halis Suleyman,Elif Cadirci 대한약학회 2008 Archives of Pharmacal Research Vol.31 No.7

Inflammation and increased capillary permeability is a significant aspect of the pathogenesis of many diseases including atherosclerosis. L-type calcium channel blockers (CCB) are commonly used as cardiovascular drugs. Amlodipine, lacidipine, and nicardipine were evaluated for anti-inflammatory activity on the paw oedema produced by carrageenan. The effect of these drugs was compared with the activity of indomethacin. Their effects on vascular permeability were also tested by hyaluronidase-induced capillary permeability. In our animal experiments, amlodipine decreased the carrageenan-induced paw oedema at doses of 1, 3, and 6 mg kg-1 by 27.3%, 43.7%, and 67.3% four hour after carrageenan administration; the same doses of lacidipine and nicardipine decreased paw oedema by 37.1%, 55.6%, 76.4%, 11.2%, 31.0%, 91%; and indomethacin decreased oedema by 38.2% at a dose of 6 mg kg-1. Lacidipine significantly inhibited the hyaluronidase-induced increase in capillary permeability at doses of 1, 3, and 6 mg kg-1 compared with the control group. However, amlodipine and nicardipine significantly inhibited the hyaluronidase-induced increase in capillary permeability at 3 and 6 mg kg-1 doses. A 6 mg kg-1 dose of indomethacin significantly decreased the capillary permeability which was increased by hyaluronidase. These results suggest that CCBs can be efficient anti-inflammatories, and can also significantly decrease capillary permeability.

Unilateral postoperative visual loss in a patient undergoing hip arthroscopy in the supine position

Sivashanmugam Raju,Halis Atil Atilla 대한마취통증의학회 2016 Korean Journal of Anesthesiology Vol.69 No.6

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Effects of Calcium Channel Blockers On Hyaluronidaseinduced Capillary Vascular Permeability

Halici, Zekai,Suleyman, Halis,Cadirci, Elif 대한약학회 2008 Archives of Pharmacal Research Vol.31 No.7

Inflammation and increased capillary permeability is a significant aspect of the pathogenesis of many diseases including atherosclerosis. L-type calcium channel blockers (CCB) are commonly used as cardiovascular drugs. Amlodipine, lacidipine, and nicardipine were evaluated for anti-inflammatory activity on the paw oedema produced by carrageenan. The effect of these drugs was compared with the activity of indomethacin. Their effects on vascular permeability were also tested by hyaluronidase-induced capillary permeability. In our animal experiments, amlodipine decreased the carrageenan-induced paw oedema at doses of 1, 3, and $6\;mg\;kg^{-1}$ by 27.3%, 43.7%, and 67.3% four hour after carrageenan administration; the same doses of lacidipine and nicardipine decreased paw oedema by 37.1%, 55.6%, 76.4%, 11.2%, 31.0%, 91%; and indomethacin decreased oedema by 38.2% at a dose of $6\;mg\;kg^{-1}$. Lacidipine significantly inhibited the hyaluronidase-induced increase in capillary permeability at doses of 1, 3, and $6\;mg\;kg^{-1}$ compared with the control group. However, amlodipine and nicardipine significantly inhibited the hyaluronidase-induced increase in capillary permeability at 3 and $6\;mg\;kg^{-1}$ doses. A $6\;mg\;kg^{-1}$ dose of indomethacin significantly decreased the capillary permeability which was increased by hyaluronidase. These results suggest that CCBs can be efficient anti-inflammatories, and can also significantly decrease capillary permeability.

International Productivity Differences and the Roles of Domestic Investment, FDI and Trade

Gouranga G. Das,Hiranya K Nath,Halis Murat Yildiz 한국국제경제학회 2009 International Economic Journal Vol.23 No.1

This paper calculates Theil's entropy index to measure the extent of productivity differences across 92 countries for the period from 1970 to 2003. While there is evidence of increasing differences in productivity across these countries, we observe different patterns when we group the countries by income levels. These differences seem to be decreasing among middle income developing and developed countries, whereas they seem to be widening among low and high income developing countries. The results of our multivariate time series analysis also suggest that FDI increases productivity differences among low and high income developing countries, whereas GDI reduces these differences among low income countries in the long-run. Granger causality test results indicate that while an increase in GDI leads to a decline in growth of trade, a higher growth of trade appears to be important for attracting FDI to middle income countries. Furthermore, a reduction in productivity differences and a higher FDI growth lead to higher growth of trade in developed countries.

A comparative investigation of biochemical and histopathological effects of thiamine and thiamine pyrophosphate on ischemia– reperfusion induced oxidative damage in rat ovarian tissue

Ismail Demiryilmaz,Ebru Sener,Nihal Cetin,Durdu Altuner,Fatih Akcay,Halis Suleyman 대한약학회 2013 Archives of Pharmacal Research Vol.36 No.9

In this study, the biochemical and histopathologicaleffects of thiamine and thiamine pyrophosphate onischemia–reperfusion induced oxidative damage in ratovarian tissue were investigated. Animals were divided intofour groups of six rat each, ovarian ischemia–reperfusion(IR), 25 mg/kg thiamine ? ovarian ischemia–reperfusion(TIR), 25 mg/kg thiamine pyrophosphate ? ovarian ischemia–reperfusion (TPIR) and Sham group (SG). The resultsof the biochemical experiments have shown that the ratovarian tissue with thiamine treatment, the level of MDA,GSH and the 8-hydroxyguanine are almost the same as theIR group; while in the group with thiamine pyrophosphatetreatment, the level of MDA, GSH and the 8-hydroxyguanineare almost the same as the SG. Ovarian tissue of rats inthe IR group were congested and dilated vessels, edema,hemorrhage, necrotic and apoptotic cells. In this group, themigration and the adhesion of the polymorphonuclear leucocytesto the endothelium were observed. Both ovaries inTPIR group, there was no difference according to the SG. Histopathology of ovarian tissues in the TIR group wasalmost the same with the IR group. Our results indicate thatthiamine pyrophosphate significantly prevents the ischemia–reperfusion induced oxidative damage in ovarian tissue,whereas thiamine has no effect. In conclusion, we havefound that thiamine pyrophosphate prevents oxidativedamage due to ischemia–reperfusion injury, whereasthiamine does not have this effect. Furthermore, we haveconfirmed that the results of our biochemical analyses are inconcordance with the histopathological findings.

Growth regime and environmental remediation of microalgae

Ademola Monsur Hammed,Sanjeev Kumar Prajapati,Senay Simsek,Halis Simsek 한국조류학회I 2016 ALGAE Vol.31 No.3

Microalgal bioremediation of CO2, nutrients, endocrine disruptors, hydrocarbons, pesticides, and cyanide compounds have evaluated comprehensively. Microalgal mitigation of nutrients originated from municipal wastewaters, surface waters, and livestock wastewaters has shown great applicability. Algal utilization on secondary and tertiary treatment processes might provide unique and elegant solution on the removing of substances originated from various sources. Microalgae have displayed 3 growth regimes (autotrophic, heterotrophic, and mixotrophic) through which different organic and inorganic substances are being utilized for growth and production of different metabolites. There are still some technology challenges requiring innovative solutions. Strain selection investigation should be directed towards identification of algal that are extremophiles. Understanding and manipulation of metabolic pathways of algae will possible unfold solution to utilization of algae for mitigation of dissolve organic nitrogen in wastewaters.