The higher strength 7xxx aluminum alloys exhibited low resistance to stress corrosion cracking (SCC) when aged to the peak hardness (T6 temper). The overaged alloys (T7 temper) developed to enhance the SCC with loss in the strength of the alloy. Recently, retrogression and re-aging (RRA) heat treatments are used for improving the SCC behavior for alloys in T6 tempers such as 7075, 7475 and 8090. In this study, an application of retrogression and re-aging heat treatment processes are carried out to enhance toughness properties of the 7079-T651 aluminum alloy, while maintaining the higher strength of T651-temper. The results of charpy impact energy and electrical conductivity tests show a significantly increases in absorbed energy and electrical conductivity values, when the alloys are exposed to various retrogression temperatures (190, 200, 210°C) and times (20, 40, 60 minutes), and then re-aged at 160°C for 18 hours.

ABSTRACT

Increasing the private vehicles namely own car, taxi, microbuses and coaches as

a mode of transport is due to its inherent advantages associated with its usage. In

Tripoli due to rapid increase in private vehicles usage associated with no public

transport system namely public buses and train has resulted in increase of traffic

congestion problem, accidents and inadequate of parking spaces. The objective of

this study which identify the factors encourage users of own car and private

vehicles to shifting to public transport system. Re-establish of public transport

system and decreasing own car users simultaneously has become necessary for

solving traffic congestion problems and reduces road accidents and travel time

for all trips. A questionnaire survey was carried out on users of private vehicles

transport in the Tripoli such as car owners, passengers, taxis and microbuses

drivers (n = 900). The probability of car drivers shifting to public transport was

examined based on scenario several options such as reduction and improve in

public transport travel time. Improve travel time by70% will be encourage

switching about 82.3% to switch from use own car to use public transport system

services. Logistic regression technique has been used to analyses the factor that

impact users to switch their trips to public transportation system alternatives.

Statistical Package for Social Science (SPSS) version 19 and Excel 2007

software were used to analysis the questionnaire in this study.

.

Keyword: Improve travel time, reduction traffic congestion, public transport,

road safety

Abstract: Currently, Tripoli the capital city of Libya experiences a steady increase in traffic

volumes on its road network especially in the city centre. The increase has caused traffic

problems. Tripoli has registered an increase private cars ownership approaching 743,796

vehicles of the total registered vehicles in the city, which reach more than one million at the

end of 2009. A study has been carried out in Tripoli city authority areas among own car users

who live in the areas with lack of private transport and no public transport (PT) services. A

questionnaire survey in Tripoli area was carried out to study the potential reduction of private

cars on road through optimal use of suitable public transportation system in order to reduce

traffic problems and travel time. Logistic regression model has been used to analyse the factor

that impacts users to switch their trips to public transportation alternatives.

Key Words: own car, private transport, travel time, logistic regression

Abstract: Increasing dominance of private car as a mode of transport is due to its inherent advantages

associated with its usage. In Tripoli, Libya due to rapid increase in car usage associated with poor

public transport system, has resulted in increase of traffic congestion, road accidents and street parking

spaces. This study aims to identify the factors encourage users of own car to switching to public

transport. Introducing the public transport (PT) system and reduce own car users simultaneously has

become necessary for solving congestion problems and reduces road accidents and improve travel time

for all trips. A questionnaire survey was carried out on users of transport in the city such as car

owners, passengers, taxis and micro buses drivers (n = 600). The probability of car drivers switching

to public transport was examined based on scenario several options such as reduce and improve in

public transport travel time. Logistic regression technique has been used to analyses the factor that

impact users to switch their trips to public transportation alternatives. Statistical Package for Social

Science (SPSS) and Excel 2007 software were used to analysis the questionnaire in this study.

Key words: Travel time, traffic congestion, public transport, road safety, logistic regression technique

Abstract— Transport modes are very important to Libyan’s Tripoli residents for their daily trips. However, the total number of own car and private transport namely taxi and micro buses on the road increases and causes many problems such as traffic congestion, accidents, air and noise pollution. These problems then causes other related phenomena to the travel activities such as delay in trips, stress and frustration to motorists which may affect their productivity and efficiency to both workers and students. Delay may also increase travel cost as well inefficiency in trips making if compare to other public transport users in some Arabs cities. Switching to public transport (PT) modes alternatives such as buses, light rail transit and underground train could improve travel time and travel costs. A transport study has been carried out at Tripoli City Authority areas among own car users who live in areas with inadequate of private transport and poor public transportation services. Analyses about relation between factors such as travel time, travel cost, trip purpose and parking cost have been made to answer research questions. Logistic regression technique has been used to analyse these factors that influence users to switch their trips mode to public transport alternatives.

Keywords --- Own car, private transport, public transport, parking cost, logistic regression. 

Abstract— Transport modes are very important to Libyan’s Tripoli residents for their daily trips. However, the total number of own

car and private transport namely taxi and micro buses on the road increases and causes many problems such as traffic congestion,

accidents, air and noise pollution. These problems then causes other related phenomena to the travel activities such as delay in trips,

stress and frustration to motorists which may affect their productivity and efficiency to both workers and students. Delay may also

increase travel cost as well inefficiency in trips making if compare to other public transport users in some Arabs cities. Switching to

public transport (PT) modes alternatives such as buses, light rail transit and underground train could improve travel time and travel

costs. A transport study has been carried out at Tripoli City Authority areas among own car users who live in areas with inadequate

of private transport and poor public transportation services. Analyses about relation between factors such as travel time, travel cost,

trip purpose and parking cost have been made to answer research questions. Logistic regression technique has been used to analyse

these factors that influence users to switch their trips mode to public transport alternatives.

Keywords --- Own car, private transport, public transport, parking cost, logistic regression.

ABSTRACT:

The own car is the first most common mode of transportation using in Tripoli. About 66 % Tripoli’s

resident prefer and used own car for all trips propose and 34 % who’s prefer to use the private

transport such as private taxi and private buses namely (micro bus with capacity from 8 to 16 person)

in Tripoli city. The rapid increase in the use of own car model transport with the poor public transport

system in Tripoli as caused acute traffic jam, accidents, environmental impacts such as (air pollution

and noise) and land use damage for building more new car parks. In this paper, policy aimed at

discouraging the use own car and private transport in the Tripoli city. Also this paper research to

identify factors that prevent own car and private transport users from used public transport so that

logical policies could be formulated to support greater use of public transport. A survey was carried

out on users of own cars and private transport namely (private taxi and private buses) (n= 900).

Descriptive and analytical transportation issue is the main research methodology in this paper. The

most important variables found likely to support the use of public transport were reduced travel time;

reduce the distance from home to public transport stop and suitable fares. In conclusion for the

traveller to change from private vehicles to public transport, proper incentives need to be provided for

better performance.

Keywords: Own car, Private transport, poor public transport, Descriptive and analytical

ABSTRACT

Most of the Arabic capitals cities are suffering from severe traffic congestion as a result of

continuing increase in both road users and private vehicle ownerships. Tripoli capital city of Libya

is one of these cities where majority of the travellers prefer to using private transportation mode

namely own cars which is 88% of the traffic volume for work, study and shop trips. Government

statistical data on the city for October 2009 revealed that out of the total 945,203 vehicles

comprised of 743,796 own cars and 47,031 units of taxis and micro buses. This paper evaluates

traffic characteristics on the three main entrances into the city; the southern entrance covers the AlGabis, Airport Road and Al-Hadaba (Salah Al-Din) entrances; the west entrance includes Al-Giran

entrance; and the east covers Tajora (Al-Bive) entrance. The entrance routes lead to several

downtown roads and main streets in the city, such as two way Omar Al-Mukhtar Street, Mizran

Street, First of September Street at the city centre and Al-Fatah Street along the Tripoli city port.

There are also other old and modern streets traverses in the city centre. As the number of private

cars usage increased, the traffic congestion got more acute. Tripoli streets need to expedite and

support the use of public transportation system namely bus, train and light rail transit into the city.

A questionnaire survey was carried out in Tripoli area to explore the potential reduction of private

cars usage on road through optimal use of suitable public transportation system.

Key words: Traffic volume, traffic congestion, public transport, entrances

Due to the inherent complexity of decision making in supply chain management (SCM), there is a growing need for modelling supply chain systems with different methodologies. A large number of manufacturing organisations in particular the cement industry in Libya is seeking techniques that can help, identify and implement strategies for developing and improving their supply chain network. Developing a supply chain management system requires the analysis of the manufacturing processes from the initial sourcing to the end customers. The paper reports that the Libyan cement industry has problems related to its productivity. In order to face these problems, cement factories need to increase their production. To accomplish this, they require a clear strategy towards an efficient supply chain.

In this paper, the performance of limited feedback precoded spatial multiplexing multiple-input multiple-output orthogonal frequency division multiplexing (MIMO - OFDM) systems is investigated in time varying fading channels. Most studies into limited feedback precoded (MIMO - OFDM) systems are based on the notion of time invariant channels throughout transmission. Therefore, the precoding matrix for each subcarrier can be designed at the receiver in terms of the current channel state, fed back to the transmitter, and used for the subsequent block of data symbols. However, in time varying channels, the feedback information becomes outdated, which results in significant system performance degradation. To mitigate this system performance degradation caused by outdated information due to a delay in the feedback channel, this paper considers a more practical system, where the channel varies from one block