Sharif Digital Repository

Cavitation phenomenon is defined as the process of rupturing of liquid by a decrease in pressure at nearly constant temperature and it is a very complex non- linear phenomenon. Therefore the theoretical and numerical analysis of cavitation is very difficult and even impossible. A high speed cavitation tunnel is designed and manufactured for experimental understanding of cavitation. The effects of cavitation on drag force of several models such as circular cylinder, hydrofoil and wedge with after body were studied. There was a sufficient turbulence provided at upstream flow, during the tests of circular cylinder and hydrofoil within Reynolds number 105 to .Boundary layer on the cylinder is... 

Dense underflows are continuous currents that move down-slope due to their density being heavier than that of the ambient water. This difference between the dense fluid and environment fluid can be due to temperature difference, chemical materials, solved materials or suspend solid particles. In these currents, the effect of buoyancy force is produced by this difference density. In this research, many experiments performed in different flow rates, slopes and concentrations to understand the current structure and turbulence specification of the salt solution density currents and particle-laden density currents. Acoustic Doppler Velocimeter is used to measure the velocity fluctuations. The... 

Special geometrical sections, known as “duct”, which can be installed on merchant vessels stern in order to improve propulsion system and propeller performance, today have evolved considerably. The force which produces by the propeller depends on efficiency of propulsion system. In the way of improving the efficiency of propulsion systems, by using these special geometrical sections, to much research have been done from the mid-twentieth century. The Wake Equalizing Ducts (WEDs) in addition to conduct the more uniform fluid flow to the propeller disk (which causes to improve the propeller operation), affect on flow separation in ship stern zone and will decrease the separated flow zone.... 

The Study of antecedents and considering the status of Project-Based Organizations (PBOs) in our country such as MSA, Azarab, Sadad Machine, etc indicates that they are facing lots of problems in different aspects. This bad situation is in a way that amendment of part of sections guarantees the continuity of bad performance of these companies and we have to apply Business Process Reengineering and establishing a radical change in these firms. So the present research according to managers and experts opinions, several year observations of the writer and review of the literature of BPR, Project Management (PMBOK) and PBOs; and based on a library research, introduces the processes of PBOs in 3... 

The main factor ensuring safety of passing maneuvers on two lane highways is known as Passing Sight Distance (PSD). The criteria presented in Iran's code and AASHTO Green book are provided by the results of researches conducted between years 1938 & 1941 in the United States. This research intends to find out whether some changes should be applied to the PSD criteria according to current vehicles' performance and driving behavior in Iran. For this purpose, about 8 hours of video films has been recorded from 3 different sites chosen from two-lane highways in Iran, resulted in 326 passing records. In the case of passing of two passenger cars The models provided by analyzing the videos show that... 

Frontage roads are widely used to separate the main and the local traffic flows in multilane highways. Based on the studies conducted by Texas Transportation Institute, the delay imposed by ramp junction is considered for calculating the average speed in frontage roads in addition to the control delay caused by traffic lights. This delay and the capacity of frontage roads are analysed using gap acceptance theory. In this study, two different sections consisting of a basic section and merge area are selected along Tehran-Karaj special road as case studies and the required data are collected by video recording. After classifying and analysing the data, a wide range of macro traffic-analyses... 

In today's competitive market we are witnessing the continouse production of new products. This forces companies to choose their branding strategies very carefully، since a wrong decision and a failure can lead to unfortunate consequences. So، Investegiating the factors that can affect new product branding strategies have become very important. Among these strategies, brand extention strategy has been more popular since it can increase the success probability of a new product. As a result، in this research we have investigated the influencers of evaluation of two branding strategies: brand extension and new brand. More specifically، this research aims to investigate the relation between... 

Increasingly adopting of multiple channels by companies in order to achieve greater market coverage and more sale, has made managers to deal with a new challenge of avoiding conflict in multiple channels. The importance of the issue and lack of empirical research provided motivation to study approaches to minimize multiple channel conflict and explore how they reduce conflict. Therefore a qualitative study using a single case (Solico Group) was conducted. After reviewing the literature 7 approaches were identified to minimize multiple channel conflict: Superordinate goals (goals that achieving them requires efforts and resources of more than one channel), Brand (using products with different... 

Incidents are one of the main sources of delays and they have significant influences on road safety and congestions, air pollution and trip costs. In the time of an incident occurrence, minimizing the response time is essential for several reasons. The most important issue is providing aid for the injured. The faster the persons who are severely injured receive aid, the higher their chances are to be rescued. Also, if the rescue crews get to the incident scene faster the clearance procedure would be accomplished faster and this would result in fewer disturbances in traffic stream and lowering the probability of secondary incidents occurrence. Automatic Incident Detection, AID, has been... 

One of the methods that have been used in order to mitigate the air pollution problem is the IM program in order to identify the high polluting vehicle and make them to adjust their engine in accordance to the emission standards. In Iran due to the air pollution problems the government operates a rudimentary IM program based on the idle engine test utilizing an exhaust gas analyzer which should be done annually. While IM programs usually regarded as a useful tool for soothing the air pollution, one of the criticisms about the program is that it is required for the entire fleet and it reduces the cost effectiveness of the program. This research studies the relationship between the vehicular... 

In railway transportation network, there are spots that we have to intersect with highway network. These intersections break into two branches named grade crossing and unlevel crossing depend on their structure. Grade crossings from the view of protection are grouped into protected crossings and unprotected crossings. Protected crossings depend on their traffic control devices are categorized into active crossings and passive crossings.There are many factors that influence highway-railroad grade crossing design. Some of these factors can vary widely by drivers' behavior. These factors have been developed in models by AASHTO and its publications and shaped like we have them today. In order to... 

This research aims to study the trade trends of Manufactured goods, classified chiefly by Material, identified under Code 6 in the Standard International Trade Classification, SITC, and its nine divisions. The study scope covered 125 countries throughout Asia, Europe and Africa and 9 distinct years spanning a 40-year time period between 1965 and 2005. By means of this study, determinant factors for modelling and investigation of trade flow characteristics for the mentioned items can come to be better understood. The time-series data were grouped into four categories: bilateral trade value, socio-economic, geographical and transportation variables, obtained from centralized international... 

This study aimed to shed some light on travel behavior in tourist villages in Iran. Rural areas need efficacious transportation infrastructures and services to promote sustainable development and to avoid urban migration. By exploring the behavioural aspects of rural transportation, their transportation needs and demands can be effectively determined. Subsequently, accessibility and mobility of rural residents can be provided in a sustainable manner. In recent years, tourism has transformed lifestyle and behavior of some rural inhabitants. Utilizing secondary school students in Niasar, a simplified questionnaire was used to collect person and household data. Socio-economic, activity and trip... 

Although villagers and nomads are an important part of Iran's population, the growth of cities has led to neglecting them and their needs including traveling and transportation needs. The aim of this study is to recognize and to study the transportation demands in a pastoral nomadic society. For this purpose, the theory of activity-based modeling was studied. Sequential modeling was chosen which considers the daily activities of each person as a result of five sequential decisions: a) choosing daily activity pattern; b) choosing primary tour time; c) choosing primary tour mode choice; d) choosing secondary tour time; and e) choosing secondary tour mode choice. In order to conduct a survey... 

In this research, the trends of trade and transportation for the 10 subdivisions of food products and food products as a whole product based upon Standard International Trade Classification, SITC, have been appraised during the time period covering 1965 to 2005 among 125 countries in Asia, Europe and Africa. In this respect, the data of trade for the mentioned goods was gathered and other variables including gross domestic product, population, access to the international waters and area of countries and three transportation networks comprising two multimodal transportation networks and a unimodal network, during the cited period and for 125 countries was gathered. Then, regressions of trade... 

Growth of cities leads to neglecting of travel behavior of nomads, although they are an important portion of Iran’s population. The aim of this study is recognition and studying transportation demand in a nomadic society that their households are mostly farmer. Firstly, the theory of activity-based modeling was studied. Sequential modeling was chosen for modeling which consider daily activities of each person as a result of five sequential decisions: a) Choosing daily activity pattern; b) Choosing primary tour time; c) Choosing primary tour mode choice; d) Choosing secondary tour time; e) Choosing secondary tour mode choice. In order to collect pertinent information and conduct survey,... 

Compared to systematically signalized intersections, in the absence of any systematic instruction or signalization at unsignalized-prioritized intersections and due to lower levels of control, driver performance strongly steps in as a decisive factor of intersection traffic and geometric design. Therefore, the study of driver behavior at these intersections appears necessary. This thesis aims to study driver behavior at four prioritized intersections where the minor stream has to yield right of way to the main stream in the city of Mashhad, Iran. Following extraction of raw statistical data from extensive filming, the initial database was constructed consisting of 29 variables. Based on the... 

Humic compounds are considered the most portion of natural organic matter (NOM) found in many surface water sources.Humic substances have been known as precursors to disinfection by-products.because conventional treatment process can not meet disinfection by-product standards,novel method have been increasingly applied for the removal of disinfection by-products precursors.The〖UV/TiO〗_2 process is one of the advanced oxidation process using the photocatalytic technology.The most important advantages of this process are its stability and high efficiency removal.The present study aims to investigate the effect of 〖UV/TiO〗_2photo-catalytic technology on removal of humic substances.In this... 

As petroleum resources are not steadily distributed in the world and all industries and manufacturing sections are dependent on these resources, petroleum transportation is very important to the extent that availability of these resources occurs in the fastest time and costing the least possible. The objective of this study is to study the petroleum distribution through time in the world and assess its transportation efficacy during 1965-2005 in 173 countries. Collecting information about petroleum distribution between exporting countries to importing ones helped to complete the study data base. Also in this study two transportation networks, sea and land multimodal transportation network...