Impact of Jet-Grouting Pressure on the Strength and Deformation Characteristics of Sandy and Clayey Soils in the Compression Zone

Mutluhan Akin,İsmail Akkaya,Müge K. Akin,Ali Özvan,Yusuf Ak 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.8

Jet-grouting as a soil improvement method is extensively preferred in today’s civil engineering practice. High-modulus grout columns constructed by extremely high jetting pressures displace the surrounding soil causing a densification in soil particles. Accordingly, the strength as well as the deformation characteristics of subsurface soils are relatively improved across the compression zone which is under the influence of high jetting pressure. In this study, the modification of soil properties in compression zone after jetgrouting in sandy and clayey soils is investigated by standard penetration tests (SPT) and multi-channel analysis of surface waves (MASW) performed at a couple of construction sites along established jet-grout column rows. The in-situ test results point out significant improvement of the measured parameters compared to initial values. The rate of enhancement in the compression zone is higher in sandy strata than that of clayey deposits. The strengthening of soil due to jetting pressure is validated by finite element analyses as well. Furthermore, very low shear strain values are obtained in clayey soils with respect to the improved characteristics of compression zone representing extremely low shear deformation under foundation.

Investigation of bonding properties of denture bases to silicone-based soft denture liner immersed in isobutyl methacrylate and 2-hydroxyethyl methacrylate

Akin, Hakan,Tugut, Faik,Mutaf, Burcu,Guney, Umit The Korean Academy of Prosthodonitics 2014 The Journal of Advanced Prosthodontics Vol.6 No.2

PURPOSE. The purpose of this study was to investigate the bonding properties of denture bases to silicone-based soft denture liners immersed in isobutyl methacrylate (iBMA) and 2-hydroxyethyl methacrylate (HEMA) for various lengths of time. MATERIALS AND METHODS. Polymethyl methacrylate (PMMA) test specimens were fabricated (75 mm in length, 12 mm in diameter at the thickest section, and 7 mm at the thinnest section) and then randomly assigned to five groups (n=15); untreated (Group 1), resilient liner immersed in iBMA for 1 minute (Group 2), resilient liner immersed in iBMA for 3 minutes (Group 3), resilient liner immersed in HEMA for 1 minute (Group 4), and resilient liner immersed in HEMA for 3 minutes (Group 5). The resilient liner specimens were processed between 2 PMMA blocks. Bonding strength of the liners to PMMA was compared by tensile test with a universal testing machine at a crosshead speed of 5 mm/min. Data were evaluated by 1-way ANOVA and post hoc Tukey-Kramer multiple comparisons tests (${\alpha}$=0.05). RESULTS. The highest mean value of force was observed in Group 3 specimens. The differences between groups were statistically significant (P<.05), except between Group 1 and Group 4 (P=.063). CONCLUSION. Immersion of silicone-based soft denture liners in iBMA for 3 minutes doubled the tensile bond strength between the silicone soft liner and PMMA denture base materials compared to the control group.

비즈니스 리더가 다가오는 변화에 맞서 계획을 수립하는 방법

AKIN AKINPELU 중앙일보에스 2024 Forbes Korea = 포브스 코리아 Vol.2024 No.2

On the structure of discrete spectrum of the non-selfadjoint system of differential equations in the first order

Akin, Omer,Bairamov, Elgiz Korean Mathematical Society 1995 대한수학회지 Vol.32 No.3

This paper is concerned with the problem given below $$ (1.1) i\frac{dx}{du_1(x,\lambda)} + q1(x)u_2(x,\lambda) = \lambdau_1(x,\lambda) 0 \leq x < \infty - i\frac{dx}{du_2(x,\lambda)} + q2(x)u_1(x,\lambda) = \lambdau_2(x,\lambda), $$ $$ (2) u_2(0,\lambda) - hu_1(0,\lambda) = 0 $$ where $\lambda$ is a complex parameter and h is a non-zero complex number.

Analysis of aerodynamic characteristics of 2 MW horizontal axis large wind turbine

Akin Ilhan,Mehmet Bilgili,Besir Sahin 한국풍공학회 2018 Wind and Structures, An International Journal (WAS Vol.27 No.3

In this study, aerodynamic characteristics of a horizontal axis wind turbine (HAWT) were evaluated and discussed in terms of measured data in existing onshore wind farm. Five wind turbines (T1, T2, T3, T4 and T5) were selected, and hub-height wind speed, UD, wind turbine power output, P and turbine rotational speed, Ω data measured from these turbines were used for evaluation. In order to obtain characteristics of axial flow induction factor, a, power coefficient, Cp, thrust force coefficient, CT, thrust force, T and tangential flow induction factor, a', Blade Element Momentum (BEM) theory was used. According to the results obtained, during a year, probability density of turbines at a rotational speed of 16.1 rpm was determined as approximately 45%. Optimum tip speed ratio was calculated to be 7.12 for most efficient wind turbine. Maximum Cp was found to be 30% corresponding to this tip speed ratio.

Analysis of aerodynamic characteristics of 2 MW horizontal axis large wind turbine

Ilhan, Akin,Bilgili, Mehmet,Sahin, Besir Techno-Press 2018 Wind and Structures, An International Journal (WAS Vol.27 No.3

In this study, aerodynamic characteristics of a horizontal axis wind turbine (HAWT) were evaluated and discussed in terms of measured data in existing onshore wind farm. Five wind turbines (T1, T2, T3, T4 and T5) were selected, and hub-height wind speed, $U_D$, wind turbine power output, P and turbine rotational speed, ${\Omega}$ data measured from these turbines were used for evaluation. In order to obtain characteristics of axial flow induction factor, a, power coefficient, $C_p$, thrust force coefficient, $C_T$, thrust force, T and tangential flow induction factor, a', Blade Element Momentum (BEM) theory was used. According to the results obtained, during a year, probability density of turbines at a rotational speed of 16.1 rpm was determined as approximately 45%. Optimum tip speed ratio was calculated to be 7.12 for most efficient wind turbine. Maximum $C_p$ was found to be 30% corresponding to this tip speed ratio.

Effects of Surface Shapes and Geotechnical Conditions on the Ground Motion

Oguz Akin Düzgün,Ahmet Budak 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.5

The influences of surface geometry and local soil properties on ground motion are parametrically studied. The system response is numerically evaluated. In the modelling, finite and infinite elements are applied. Three types of topography (single-faced slopes, canyons and ridges) are taken into account. According to the results, topographic conditions, depth of the rigid bedrock and geotechnical properties have significance in the alteration of ground motion at the irregular soil surface and its surroundings. For all selected surface shapes, the most critical cases occur at top corners especially when the slope gets steeper. These cases are independent on the natural period of structures. The results correspond with those earthquakes where topographical effects are observed and could be seemed to be worthwhile from the perspective of earthquake engineering and seismology.

Relapsed Wilms' tumor with multiple brain metastasis

Akakin, Akin,Yilmaz, Baran,Eksi, Murat Sakir,Yapicier, Ozlem,Kilic, Turker The Korean Pediatric Society 2016 Clinical and Experimental Pediatrics (CEP) Vol.59 No.no.sup1

Wilms' tumor is the most common malignant renal tumor in childhood. The brain metastasis of a Wilms' tumor with anaplastic histopathology is rare. We present the case of an 8-year-old girl with Wilms' tumor, who presented with multiple brain metastases 5 years after her primary diagnosis. The brain masses were diagnosed after a generalized tonic-clonic seizure attack. The big solid mass in the cerebellum was resected, and whole-brain radiotherapy was performed, after which, she succumbed to her disease. In the case of clinical suspicion, cranial surveillance should be included in the routine clinical work-up for Wilms' tumor. Combined aggressive therapy (surgery+radiotherapy+chemotherapy) should be applied whenever possible, for both better survival and palliative aspects.

A Study on Strengthening of Reinforced Concrete Frames using Precast Concrete Panels

Arife Akin,Rifat Sezer 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.6

This study describes the effectiveness of the behavior resulting from strengthening infill walls in existing reinforced concrete frame systems with low resistance against earthquake effects using precast concrete panels. In this study, a strengthening method that can be applied without building occupants having to leave the building was investigated. For this purpose, six 1/2 scale, two-story and single span test specimens with brick infill walls and low earthquake resistance, which have common errors seen in existing reinforced concrete buildings, were generated. The first of test frames with equivalent properties was tested as the reference specimen under reversible repeatable lateral loads. Others were tested after high-strength concrete panels produced in different geometric shapes were strengthened by bonding them onto existing frame infill walls. Brick infill walls strengthened using concrete panels were modeled as shell elements by SAP2000 software package and the accuracy of experimental studies were compared with analytical results. Experimental and analytical studies demonstrated that the reinforcement method significantly improved properties, such as resistance to lateral loads, energy dissipation capacity, of brick infill reinforced concrete frames.

The "Da Ming Hunyi Tu": Repurposing a Ming Map in Sino-African Diplomacy

Alexander Akin 고려대학교 민족문화연구원 2016 Cross-Currents Vol.- No.21

In 2002, an exhibition at South Africa’s parliament included a reproduction of the Da Ming Hunyi Tu (Amalgamated map of the Great Ming), citing it as the earliest world map to depict the entire African continent. As part of its broader efforts to shape a narrative of long-standing and peaceful international relations with Africa, the People’s Republic of China formally presented a replica of this map as a gift to the South African government in conjunction with the exhibition. In official statements and popular media coverage alike, the map was described as evidence of a distinctly Chinese approach to global relations, based on benevolence and mutual respect. In particular, the map was ahistorically intertwined with the legacy of Zheng He’s diplomatic expeditions, which reached the East African coast in the early 1400s. To the cartographic historian, however, the depiction of Africa in the Da Ming Hunyi Tu is clearly derived from non-Chinese sources that predate Zheng He’s expeditions. This article examines the ways in which the map has been divorced from its original context to suit modern needs, exemplifying the deployment of cartography to deflect anxieties about the nature of Chinese economic influence in South Africa.