In this paper the reflection coefficient of electromagnetic wave incidence on the walls of the buildings and obstacles that occurs in mobile communication Path was modified by solving the Riccati nonlinear equations. For this purpose, the building walls are assumed inhomogeneous layers where their permittivity changes as function of the wall thickness. Using this reflection coefficient, a new propagation model based on urn and GID (uniform geometrical theory of diffraction and geometrical theory of diffraction) for multiple diffraction Paths is proposed. Using this model, the diffraction Loss as well as the Path Loss for a row of buildings with two in homogeneous faces is calculated and compared with measured data. Comparison of theoretical and measured results reveals that the modified reflection coefficient can adequately predict the reflective properties of the building walls. Moreover, results obtained with the proposed UID model are in good agreement with the measurement data. Therefore, the modified reflection coefficients well as the new UID model can be used for estimation of multiPath signals strength, diffraction Loss and also Path delay in ray tracing algorithms used in mobile communication, radar and radio links.

Purpose: To report visual and anatomical outcome of flap Loss after LASIK surgery for correction of high myopia. Materials & Methods: Retrospective evaluation of flap Loss in two eyes of two patients, a rare complication of LASIK Surgery. Case No. 1: 27 y/o woman with Ref. OD -9.75; 2.75*177 VA. CC: 20/60 KR OD: 41.86*77 39.86 * 168 & partial amblyopia due to anisometropia. Case No. 2: 38 y/o woman with Ref OD. -9.50 1.0*177 VA CC: 20/30 KR OD: 42.06*77 40.99 * 167. Results: In both patients during LASIK surgery free cap complication occurred and after Laser therapy free cap positioned over the stromal bed, but the next day after operation flaps were lost. For case NO.1only medical management performed and after 4.5 years F/U cornea has 2° central haziness. For case NO.2 another corneal flap from donor globe cut and sutured with Nylon 10/0 and after 18 months F/U cornea is clear. Conclusion: In patients with flat keratometry less than 41.0 Diopter rate of free cap are high and after laser therapy for high myopia the keratometry became more flat. If surgeon doesn't suture flap the rate of flap Loss increase so for prevent of corneal haziness and corneal ectazia this evaluation suppose to perform donor corneal flap graft.      

The study of Path Loss propagation is of high importance in telecommunication, for optimizing the efficiency of wireless communication networks. In this paper, four Path Loss propagation models, free space Path Loss (FSPL) model, Okumura model, Okumura-Hata model, and COST 231-Hata model were compared. The models were compared using measurement data from Choba, Port Harcourt, Nigeria. The data is gotten from a 4G walk test using two mobile applications. The first mobile application Network, Signal Info (version 5. 68. 07), was used to acquire the received signal strength in and the distance between the BTS antenna and the mobile antenna. While the second mobile application, G-NetTrack Lite (version 14. 8), was used to map out the track Path followed during the test. Choba, the study area, is a coastal suburban area with map coordinates 4. 8941° N, 6. 9263° E. The measured distance range was from 0. 09 km to 0. 45 km, and a Path Loss range of 69dB to 81dB. While the BTS and mobile antenna heights were 32 m and 1m respectively, with a carrier frequency of 800MHz. BTS transmission power of 23 dBm was assumed, based on 3GPP eNodeB recommendations. A graph comparison of the studied models showed that Okumura-Hata model and COST 231-Hata model had the closest predictions to the measured Path Loss. The need for better Path Loss models for 4G and 5G propagations was observed

The quality of signal at a particular location is essential to determine the performance of mobile system. The problem of poor network in Lagos, Nigeria needs to be addressed especially now that the attention is toward online learning and meetings. Existing empirical Path Loss (PL) models designed elsewhere are not appropriate for predicting the 4G Long-Term Evolution (LTE) signal in Nigeria. This research developed a modified Okumura-Hata model in 4G network. The Okumura-Hata model being the closest to the measured values was modified using the PL exponent. The modified model was enhanced by Gravitational Search Algorithm (GSA). The measured data, modified and existing models were simulated using MATLAB R2018a software. Root Mean Square (RMSE) was used to evaluate the performance modified and existing and models. The result showed that Enhanced GSA model outperformed the existing models. The study successfully developed a modified PL model for LTE in Lagos, Nigeria. Therefore, modified model will be a good model in network planning for voice and fast online data connection in 4G LTE network.

Path Loss models estimate the average Path Loss a signal experiences at a particular distance from a transmitter. However, each type of existing Path Loss propagation model is designed to predict Path Loss in a particular environment that may be inaccurate in other different; hence selecting the best Path Loss model and optimizing it will minimize that inaccuracy. This work presents a comparative analysis of five empirical Path Loss models, COST- 231, ECC-33, Hata, SUI, and Ericsson model, with respect to the measured data from the 14 selected sites in Hawassa city, Ethiopia at 1800 MHz frequency bands. A drive test methodology was adopted for data collection and Nemo Handy and Nemo Outdoor were used as measuring tools for the test. Error measuring tools such as root mean square error, mean absolute error, standard deviation, and mean absolute percentage error were used to select the terrain type of each site and the Path Loss model that best fits that site. The results show that not only Hawassa city consists of urban and sub-urban terrains but also ECC-33 and Hata are better estimators for Hawassa urban and sub-urban areas with RMSE of 4.18 and 7.86 respectively. The model tuning using the least square method reduced the RMSE of ECC-33 and Hata to 2.46 and 5.18 respectively. The reduction in RMSE shows that the tuned versions are close to the environment. Hence, using the tuned versions of the selected models will result in good cellular network design and enhance the service quality.

The linkage between sustainable agriculture, poverty and agricultural extension efforts and their impacts on rural centers in Behbahan Shahrestan has been discussed in this paper. Data were collected from 200 farmers in 40 villages of this Shahrestan. A multi-stage stratified random sampling technique was used for selecting villages and farmers. The findings of Path analysis in three different causal models provide the complexity of relationships between variables and environmental degradation so that there is a causal relationship between poverty and unsustainability. Lack of direct causal effect of use of technology and extension efforts on sustainability in three models indicated the structural and institutional limitations of extension in diffusion of appropriate technologies. Finally, recommendations regarding regional planning with respect to socio-economic characteristics and changing from TOT approach to other alternatives and revising the education programs of extension agents are provided.

Purpose: Report a case of iatrogenic medial rectus Loss in exotropia surgery and its management with review literature.Case Report: A 14-year-old female with a history of cerebral palsy and left exotropia underwent strabismus surgery in another center when she was 7 years old. As her surgeon reported, after 8 mm medial rectus resection, it was lost and he could not retrieve it; so, to balance the forces of adduction and abduction, the surgeon disinserted left lateral rectus, but 2 months later, because of large angle exotropia and severe limitation in adduction, she was referred to this center. We explored the area and could not find the lost medial rectus; so, half tendon transposition of superior rectus and inferior rectus to the previous insertion site of medial rectus was performed and left lateral rectus was fixated to the lateral orbital periosteum. Two months after the operation, she was orthotropic and ocular movements were significantly balanced.Conclusion: Half tendon transposition of vertical recti to the site of lost medial rectus associated with periosteal fixation of lateral rectus can improve the strabismus of lost medial rectus muscle.