Plastic / Superplastic Forming : STRAIN RATES EFFECT ON THE THICKNESS DISTRIBUTION OF SUPERPLASTICALLY DEFORMED Ti - ALLOY PIPE INTO SPHERICAL SHAPE

Nihat Akkus,Masanori Kawahara,Hisashi Nishimura 대한금속재료학회 ( 구 대한금속학회 ) 1995 Advanced Material and Processing Vol.1 No.-

HARDY SPACE OF LOMMEL FUNCTIONS

Nihat Yagmur 대한수학회 2015 대한수학회보 Vol.52 No.3

In this work we present some geometric properties (like star- likeness and convexity of order α and also close-to-convexity of order (1 + α)/2) for normalized of Lommel functions of the first kind. In order to prove our main results, we use the technique of differential subordina- tions and some inequalities. Furthermore, we present some applications of convexity involving Lommel functions associated with the Hardy space of analytic functions, i.e., we obtain conditions for the function hμ,v(z) to belong to the Hardy space Hp.

Behavior of Injured Lamina in Lumbar Burst Fractures during Reduction Maneuvers: A Biomechanical Study

Nihat Acar 대한척추외과학회 2017 Asian Spine Journal Vol.11 No.4

Study Design: An experimental biomechanical study. Purpose: This study aims to investigate the behavior of a lamina injury in lumbar burst fractures during reduction maneuvers. Overview of Literature: Lumbar burst fractures are frequently accompanied by a lamina fracture. Many researchers concluded that any reduction maneuver will close the fractured lamina edges and possibly crush the entrapped neural elements. This conclusion did not rely on solid biomechanical trials and was based primarily on clinical experience. Methods: Eighteen fresh-frozen lamb spines were randomly divided into three groups. Using the preinjury and the dropped-mass technique, a burst fracture model was developed. A central laminectomy of 5 mm of the L3 lumbar spine was created to mimic a complete type of lamina fracture. To measure the movement of the fractured laminar edges, two holes were drilled on both sides of the upper and lower regions of the lamina to allow for optic marker placement. A single specific spine movement was applied to each group: traction, flexion, and extension. Gap changes were measured by camera extensometers. Results: After traction, the average values of the upper and lower aspects of the lamina interval showed narrowing of 1.65±0.82 mm and 1.97±1.14 mm, respectively. No statistical significance was detected between the two aspects. The upper and lower regions of the lamina gap behaved differently during extension. At 10°, 20°, and 30°, the upper part of the lamina interval was widened by an average of 0.016±0.024, 0.29±0.32, and 1.73±1.45 mm, respectively, whereas the lower part was narrowed by an average of 0.023±0.012, 0.47±0.038, and 1.94±1.46 mm, respectively. Conclusions: Neural element crushing may take place, particularly at the lower aspect of the fractured lamina gap during extension and throughout the whole lamina gap during traction. The lamina gap widens during flexion. Reduction maneuvers should be attempted after exploring the fractured lamina to prevent further neurological compromise.

A STUDY ON A RULED SURFACE WITH LIGHTLIKE RULING FOR A NULL CURVE WITH CARTAN FRAME

Nihat Ayyildiz,Tunahan Turhan 대한수학회 2012 대한수학회보 Vol.49 No.3

In this study, we investigate the curvature functions of ruled surface with lightlike ruling for a null curve with Cartan frame in Minkow\-ski 3-space. Also, we give relations between the curvature functions of this ruled surface and curvature functions of central normal surface. Finally, we use the curvature theory of the ruled surface for determine differential properties of a robot end-effector motion.

On the scalar and dual formulations of the curvature theory of line trajectories in the Lorentzian space

Nihat Ayyi ldi z,Ahmet Y 대한수학회 2006 대한수학회지 Vol.43 No.6

This paper develops in detail the dierential geometryof ruled surfaces from two perspectives, and presents the under-lying relations which unite them. Both scalar and dual curvaturefunctions which dene the shape of a ruled surface are derived.Explicit formulas are presented for the computation of these func-tions in both formulations of the dierential geometry of ruled sur-faces. Also presented is a detailed analysis of the ruled surface whichcharacterizes the shape of a general ruled surface in the same waythat osculating circle characterizes locally the shape of a non-nullLorentzian curve.

Exploring Driver Injury Severity Using Latent Class Ordered Probit Model: A Case Study of Turkey

Nihat Can Karabulut,Murat Ozen 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.3

There have been limited efforts to study the severity of traffic crashes in Turkey. This study is probably the first attempt to investigate the factors that contribute to driver injury severity patterns. Fatal injury crash data from 2015 to 2017 for the city of Mersin was used. A two-step approach was employed. First, latent class clustering was performed to capture unobserved heterogeneity inherent in the crash data. The crash database was separated into four clusters by maximizing the homogeneity within each cluster. Then, an ordered probit model was developed on each cluster to explore the factors that significantly affect the driver injury outcomes. Marginal effects were calculated to interpret the influence of significant variables across the injury levels in more detail. The presence of motorcycles, fixed objects, and run-off-road crashes were found to be the main factors associated with injury and fatality in all clusters. The results underlined the association between driving behavior and injury severity of drivers. Alcohol-impaired driving, speeding, and traffic sign/signal violations increase the likelihood of severe injury.

Influence of polled direction on the stress distribution in piezoelectric materials

Nihat İlhan,Nagihan Koç 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.5

In this paper, the influence of the polled direction of piezoelectric materials on the stress distribution is studied under time-harmonic dynamical load (time-harmonic Lamb’s problem). The system considered in this study consists of piezoelectric covering layer and piezoelectric half-plane, and the harmonic dynamical load acts on the free face of the covering layer. The investigations are carried out by utilizing the exact equations of motion and relations of the linear theory of electro-elasticity. The plane-strain state is considered. It is assumed that the perfect contact conditions between the covering layer and halfplane are satisfied. The boundary value problems under consideration are solved by employing Fourier exponential transformation techniques with respect to coordinates directed along the interface line. Numerical results on the influence of the polled direction of the piezoelectric materials such as PZT-5A, PZT-5H, PZT-4 and PZT-7A on the normal stresses, shear stresses and electric potential acting on the interface plane are presented and discussed. As a result of the analyses, it is established that the polled directions of the piezoelectric materials play an important role on the values of the studied stresses and electric potential.

Openness and the Effects of Monetary Policy on the Exchange Rates: An Empirical Analysis

( Nihat Islk ),( Mustafa Acar ),( H. Bayram Islk ) 세종대학교 경제통합연구소 (구 세종대학교 국제경제연구소) 2005 Journal of Economic Integration Vol.20 No.1

This paper examines whether the effects of monetary policy on the exchange rates depend on the degree of openness of an economy. Theoretically, it can be shown that the effect of openness on the ability of money to influence the exchange rate is ambiguous. In light of this, the purpose of this study is to investigate how the relationship between monetary policy and exchange rate is affected by openness, hence shedding some light on the theoretical ambiguity. Using annual data for a panel of 41 countries for the period 1988-2000, the paper`s empirical results indicate that the effects of monetary policy on the exchange rates are negatively affected by economy`s openness. It seems that the more open the economy, the smaller is the depreciation effects of a given increase in the money growth rate. More interestingly, contrary to conventional expectations, monetary expansions in developed countries do not seem to result in depreciation of the domestic currency.

Theoretical and Practical Changes in L2 Teacher Education: A Critical Review

( Nihat Polat ) 순천향대학교 인문과학연구소 2008 순천향 인문과학논총 Vol.22 No.-

A considerable number of recent studies have suggested that paradigmatic historical changes and challenges in different aspects of L2 teacher education have resulted in the acknowledgement of its complex constituents and thereby the inclusion of more diachronic, holistic, multifaceted, eclectic, integrative and sometimes seemingly contentious approaches and conceptualizations. This critical review addresses the most recent changes and challenges in epistemological, theoretical, metho dological and practical aspects of L2 teacher education. It shows how researchers have taken different perspectives in categorizing and interpreting these perceptible transformations and challenges in L2 teacher education. Moreover, it addresses how several recent studies on L2 teacher education have pinpointed changes and challenges and how they have been translated into domains and competencies in second/foreign teacher education program requirements. A synthesis of these selected papers also delineates certain key themes that can help educators and researchers to better understand the future direction of second/foreign language education.

Design and Development of Peltier Assisted Infrared Drying Based Soil Moisture Content Device

Nihat Dipova 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.1

The purpose of this study is to design and develop an alternative moisture content device, based on infrared heating and Peltier dehumidifying. Infrared heating is an alternative heating method which is commonly used is industrial drying. Compared to the convective drying it has some advantages such as, short drying time, less energy consumption, uniform dispersion of the temperature, ease of control and space saving. Peltier elements are thermoelectrical ceramics which are widely used in industry for cooling and heating purposes. In this study, an instrument which allows the soil sample to fast-drying, and continuous recording of the mass of soil during drying, has been developed. Evaporation of the soil moisture is provided by an infrared heater. Mass change in the sample was measured by a load cell. To isolate from the room humidity, heating and weighing were done in a cabinet. A dry air circulation module has been improved, which allow humid air to dry in the Peltier condenser and send dried air back into the cabin. An electronic card was developed for automatic control and data logging. 27 soil samples were prepared at different water contents and were dried in both an oven and in the new device. Results showed that the water content values are in good agreement. Drying in new device has been completed within 10−25 min. Energy consumption is 90−97% less than that of the conventional oven.