A conceptual view of exergy destruction in mergers and acquisitions

Company mergers are complex where several firm-specific and contextual factors interact with each other impacting the outcome of the process. Although many firms merge with or acquire others to increase the value of their firms, have more market power and gain more ability to negotiate with suppliers or customers, most of mergers and acquisitions result in failures. Despite the poor performances, firms continue to merge and acquire. The existing literature on the other hand lacks in providing a robust theory to the issue of poor post-merger performance. This study thus responds to exploring the issue of high failure rates in mergers and acquisitions in an entirely different way. As the first output of a research programme on the conceptual, theoretical and empirical issues in merger and acquisitions research, we conceptualize the loss of performance or exergy in mergers and acquisitions using thermodynamic analysis of the mixing process in physical systems. Three propositions are developed that conceptualize the ideal conditions for mergers in terms of firm size, relatedness between the merging firms and the ambient states. The exergy loss due to merging increases with the increasing levels of strategic or cultural incompatibility between the two firms. When the sizes of two firms differ, it is preferable for the larger firm to have higher knowledge base than the smaller firm. Lastly, the knowledge intensity of the country that the merging takes place as well as the relative knowledge base of the merging firms do interact and change the post-merger performance significantly

Drag force and jet propulsion investigation of a swimming squid

Gökçen, Gökhan (Dogus Author)In this study, CAD model of a squid was obtained by taking computer tomography images of a real squid. The model later placed into a computational domain to calculate drag force and performance of jet propulsion. The drag study was performed on the CAD model so that drag force subjected to real squid was revealed at squid's different swimming speeds and comparison has been made with other underwater creatures (e.g., a dolphin, sea lion and penguin). The drag coefficient (referenced to total wetted surface area) of squid is 0.0042 at Reynolds number 1.6x106 that is a %4.5 difference from Gentoo penguin. Besides, jet flow of squid was simulated to observe the flow region generated in the 2D domain utilizing dynamic mesh method to mimic the movement of squid's mantle cavity

Evaluating the effectiveness of 2 different flow diverter stents based on the stagnation region formation in an aneurysm sac using lagrangian coherent structure

BACKGROUND: Flow diverter stents are often used in the treatment of giant aneurysms at carotid arteries. Although these stents promise to decrease blood flow into the aneurysm sac, little is known about hemodynamics inside the aneurysm once the stent is planted into the aneurysm neck. To further explore this, computational fluid dynamics and Lagrangian coherent structure (LCS) techniques were used to evaluate the time evolution mechanism of stagnation regions inside an aneurysm. The purpose of this work is to provide a quantitative effectiveness comparison of 2 different flow diverter stents placed into the aneurysm neck based on their stagnation zone formations in the sac.METHODS: In numerical modeling, Womersley function, and fluidsolid interaction were defined as the 3 cardiac cycles for blood velocity and the aneurysm wall, respectively. Moreover, blood was accepted as a non-Newtonian fluid, and mean arterial blood pressure of the patient was entered into the computational domain to accurately mimic the hemodynamics inside the aneurysm sac accurately.RESULTS: The numerical analyses revealed that the use of a Fred-type stent in the aneurysm neck causes fluid flow zone formations yielding to sequenced stagnated regions. Time evolution of stagnation regions in an aneurysm sac was shown just after a flow diverter stent was employed at a patient's aneurysm neck. Furthermore, the stagnation field in the Fred stent-fitted aneurysm was nearly 4.8 times the stagnation area of the Surpass brand stent-attached aneurysm.CONCLUSIONS: Finite time Lyapunov exponent fields obtained from the LCS techniques demonstrated a good agreement with the patient's digital subtraction angiography images obtained just after treatment

Numerical investigation of coalescing plate system to understand the separation of water and oil in water treatment plant of petroleum industry

The most widely utilized process of produced water treatment is considered to be use of coalescing or corrugated plate systems in the oil industry because these systems have promising results in the acceleration of the separation process. Even use of corrugated plate systems seem to be effective in separation processes, the geometrical parameters of the plate system could greatly influence the performance of separation process. In this study, a two-dimensional computational fluid dynamics model for coalescing plates was developed to investigate Reynolds number and plate hole shape on separation efficiency. Spacing between plates was set to 12 mm while fluid mixture’s Reynolds number varied between 5 and 45 for the computational model. Hole profile and dimensions were determined to be cylindrical, rectangular and ellipse shapes as 10, 15 and 20 mm based on hydraulic diameter definition, respectively. Furthermore, when hole profiles of coalescing plates were chosen to be ellipse and rectangular shapes, separation efficiency nearly stayed constant regardless of hole dimension. The study also reported that change of oil fraction from 5% to 15% caused approximately 30% increase in the separation efficiency. The investigation also revealed Reynolds number of the mixture was inversely proportional to the separation efficiency. It was also found that the highest separation efficiency was obtained for a cylindrical shape with a hole diameter of 15 mm when distance between plates was 12 mm and Reynolds number was 18

Petrol projelerinde kullanılan su arıtma tesislerinde su ve petrolün ayrıştırılması için tasarlanan birleştirilmiş plakaların CFD simülasyonu

Petrol üretimi, çevreye zararlı etkileri olabilecek bol miktarda yağ ile kirlenmiş su ortaya çıkarmaktadır. Aynı zamanda üretilen su petrol endüstrisinin ürettiği en büyük atık akımdır. Geçmiş yıllarda dikkat, üretilen su işlemleri üzerineyken suyu yağdan ayırma yöntemleri zamanla önemli şekilde iyileştirildi. Bu çalışma kapsamında birleşik plakalarda, plakalar arasındaki mesafenin, orifis çapının ve karışım giriş hızının ayırma verimine olan etkilerini incelemek için iki-boyutlu hesaplamalı akışkanlar dinamiği (HAD) modeli kullanıldı. Ayrılma verimini etkiyen parametreleri belirleyebilmek için 8, 12, 16, 20, 24 mm plakalar arası mesafesi, 10, 15, 20 mm farklı enine kesit (örneğin, silindirik, dikdörtgen, elips ve üçgen) orifis çap değerleri ile 0.02, 0.03, 0.04, 0.05 m/s olan dört farklı karışım giriş hızları kullanıldı. Bu inceleme plakalar arası mesafedeki artışın, karışım giriş hızındaki artışın veya kütle akış debisinin ayrılma verimi ile ters orantılı olduğunu ortaya çıkardı. Diğer taraftan en yüksek ayrılma verimi 15 mm delik çaplı silindir şeklindeki orifiste elde edildi. Üstelik ayrılma veriminin, plakalar arasındaki mesafeye ve karışım giriş hızlarına bağlı olarak %25’ten %99.25’e kadar değiştiği gözlemlenmiştir

Computational investigation of heat transfer and pressure drop in a typical louver fin-and-tube heat exchanger for various louver angles and fin pitches

In this study 3-D numerical simulations on heat transfer and pressure drop characteristics for a typical louver fin-and- double-row tube heat exchanger were carried out. The heat transfer improvement and the corresponding pressure drop amounts were investigated depending on louver angles, fin pitch and Reynolds number, and reported in terms of Colburn j-factor and Fanning friction factor f. The heat transfer improvement and the corresponding pressure drop amounts were investigated depending on louver angles between 20° ≤Ө≤ 30°, louver pitch of Lp=3.8 mm and frontal velocities of U between 1.22 m/s - 3 m/s. In addition, flow visualization of detailed flow features results, such as velocity vectors, streamlines and temperature counters have been shown to understand heat transfer enhancement mechanism. The present results indicated that louver angle and fin pitch noticeably affected the thermal and hydraulic performance of heat exchanger. It has been seen that increasing louver angle, increases thermal performance while decreasing hydraulic performance associated to pressure drop for fin pitches of 3.2 mm and 2.5 mm. Fin pitch determines the flow behaviour that for fin pitch of 2 mm, increasing louver angle decreased heat transfer and pressure drop. Velocity vectors and streamlines give considerable information about the flow whether it is duct directed or louver directed. For all conditions the flow is louver directed

Beyin Anevrizmalarında Hemodinamik Kuvvetlerin Kanın Newtoniyen ve Newtoniyen Olmayan Durumlarında Hesaplamalı Akışkanlar Dinamiği ile İncelenmesi

Günümüz teknolojisi sayesinde farklı teknikler ile elde edilen damar yapılarını, bilgisayar ortamına aktarmak mümkün hale gelmiştir. Bilgisayar ortamına aktarılan bu görüntüler sayesinde damarlara hesaplamalı akışkanlar dinamiği (HAD) yöntemi uygulanabilmekte ve kişilere özel çeşitli tedaviler geliştirilebilmektedir. Bu çalışmada da benzer şekilde gerçek bir hastadan alınan damar modelleri kılcal yapılardan arındırılarak kullanılmıştır. Hazırlanan HAD modeli için kanın viskozitesi; Newtoniyen ve Newtoniyen olmayan Power Law modeli ve yine Newtoniyen olmayan Carreu modeli olmak üzere üç farklı şekilde tanımlanmıştır. Böylece HAD modelleriyle anevrizma bölgesindeki hemodinamik akışı belirleyen parametreler olan hız değerleri, basınç düşüşü ve kayma gerilmeleri hesaplanmıştır. Elde edilen veriler görsel olarak sunularak gereken değerlendirmeler yapılmış, kanı Newtoniyen ya da Newtoniyen olmayan şekilde modellemenin sonuçlara etkisi belirlenmiştir. Kanın Newtoniyen olarak modellenmesi durumunda anevrizma içinde daha yüksek hız değerleri elde edilirken hem basınç hem de duvar kayma gerilimleri değişimlerinde ise Newtoniyen modellemede daha düşük değerler elde edilmiştir. Yapılan çalışmada, HAD yönteminin hastaların tedavisinde hastaya özgü bir yöntem olarak kullanılabileceği görülmüştür

Drag force and jet propulsion investigation of a swimming squid

In this study, CAD model of a squid was obtained by taking computer tomography images of a real squid. The model later placed into a computational domain to calculate drag force and performance of jet propulsion. The drag study was performed on the CAD model so that drag force subjected to real squid was revealed at squid’s different swimming speeds and comparison has been made with other underwater creatures (e.g., a dolphin, sea lion and penguin). The drag coefficient (referenced to total wetted surface area) of squid is 0.0042 at Reynolds number 1.6x106 that is a %4.5 difference from Gentoo penguin. Besides, jet flow of squid was simulated to observe the flow region generated in the 2D domain utilizing dynamic mesh method to mimic the movement of squid’s mantle cavity

Investigation of the effect of anticoagulant usage in the flow diverter stent treatment of the patient-specific cerebral aneurysm using the Lagrangian coherent structures

Anticoagulants are prescribed to the flow diverter treated patients to diminish the risk of embolism in the arteries. In the present study, digital subtraction angiography images of a 49-year-old female patient with a left paraophthalmic aneurysm were used to build a numerical model to investigate the effect of an anticoagulant on hemodynamics at the aneurysm site. The Carreau-Yasuda viscosity model was utilized to define blood viscosity, and the coefficients of the viscosity model were updated based on the usage of warfarin. The five-cardiac cycle-long numerical simulations were performed, and Lagrangian coherent structures, hyperbolic time, and fluid particle analyses were also employed in the numerical models. These analyses allowed us to evaluate the formation of stagnated regions, recirculation zones, and the number of jailed particles inside the aneurysm sac following a flow diverter placement. It is realized that anticoagulant use caused blood to be less viscous, yielding a substantial amount of incoming blood flow to enter the aneurysm sac. Only 12% of the nearly 25,000 fluid particles seeded from the artery inlet have stayed inside the sac. Furthermore, the deviation between warfarin added blood and normal blood flow becomes more extensive, with every heartbeat undermining the effectiveness of patient-specific CFD models when the use of anticoagulants is overlooked in the viscosity models.This work has been supported by TUBITAK (The Scientific and Technological Research Council of Turkey) under 1001 Program, Project #: 117M491