Accuracy and precision of consumer-grade GPS positioning in an urban green space environment

Ehsan Abdi,Hamid Soofi Mariv,Azade Deljouei,Hormoz Sohrabi 한국산림과학회 2014 Forest Science And Technology Vol.10 No.3

The use of global positioning systems (GPS) has increased in recent years, including for urban forestry management, as aresult of its wide range of applications, ease of use and direct use of GPS data in geographic information systems. Thisstudy was conducted in an urban green space to assess the accuracy and precision of two consumer-grade GPS receiverswith regard to ground control point (GCP) coordinates. Eleven fixed GCPs with known positions were selected and theirdata collected on four days (two seasons) and three different daytime periods (08:00, 11:00 and 14:00) each day. For eachtreatment (season and daytime) five replications were recorded. The results showed that the best mean position accuracieswere provided by the Colorado receiver in leaf-off period (4–5 m), and its corresponding position accuracies for summerranged from 9 to 12 m. The results of the Rino receiver mean position error in summer (19–36 m) and winter (10–26 m)were higher than reported in literature. Point averaging had a positive effect on accuracy in both receivers for winter. Insummer, three-point averaging was more efficient than five-point averaging. During the day, the Colorado receiver had thebest positional accuracy at 08:00 in winter, but in summer there was a large variation in the results. For the Rino receiverthere was no general trend; however, results taken at 11:00 and 14:00 were better than those at 08:00. Regarding precision,point averaging had a positive effect on the Colorado while the Rino precision indicated the contrary. The Coloradoreceiver had better precision than the Rino in both seasons, and was the best in summer. The Rino receiver had better precisionin summer compared to winter, and in both recievers daytime had no significant effect on precision. The measuredaccuracies of Colorado are acceptable for many environment and urban forestry measurement applications and satisfy mappingrequirements, but the Rino receiver showed poorer results.

Soil hydrophysical degradation associated with forest operations

Ehsan Abdi,Mostafa Moghadamirad,Elyas Hayati,Dirk Jaeger 한국산림과학회 2017 Forest Science And Technology Vol.13 No.4

Skid trails in the Hyrcanian forest of northern Iran are important for moving wood to log landings; however, they can cause soil compaction and alter water infiltration. This research therefore presents an analysis of the impact of ground-based skidding on soil hydrophysical properties in Kuhmiyan forest located in the Hyrcanian forest. Soil infiltration, bulk density, and soil resistance to penetration have been studied at three different depths of soil along the skid trails. Three sampling locations were considered: wheel ruts, center of skid trails, and undisturbed forest (control). The results showed that the total infiltration rate, and also the instantaneous infiltration rate, were significantly higher in the control treatment. The results also showed an increase of 57% and 31% for the soil bulk density at wheel ruts and centers of skid trails compared to the control. Furthermore, there was a significant difference between soil resistance in the control and the other two treatments, with wheel ruts having the highest resistance. According to the results, there was a strong negative correlation between infiltration and soil resistance (r = –0.94), and between infiltration and bulk density (r = – 0.93). Using a protective layer of slash and logging debris and residual on skid trails can be highly recommended to moderate soil compaction and mitigate the destructive impact of logging equipment.

Conus Medullaris Teratoma: Case Report and Literature Review

( Ehsan Keykhosravi ),( Amin Tavallaii ),( Hamid Rezaee ),( Kaveh Ebrahimzadeh ),( Masoud Pishjoo ),( Reza Abdi ),( Mona Maftouh ),( Behzad Aminzadeh ) 대한뇌종양학회 대한신경종양학회 2020 Brain Tumor Research and Treatment Vol.8 No.2

Teratomas are benign germ cell tumors that usually found out of their anatomical origin. Teratomas usually are found in sacrococcygeal area, gonads, mediastinum, cervicofacial region and intracranial fossa. Spinal teratomas are rare. In this study we describe a case of conus medullaris teratoma which was diagnosed based on imaging studies. The patient underwent surgery. We did bilateral laminectomy. The mass lesion had an obvious and rigid attachment to the conus medullaris. The wall of the lesion was resected as much as possible, but total resection of the lesion’s wall could not be done due to changes in neural monitoring. Previous related studies are reviewed.

The effect of occlusogingival placement of clinical bracket points on the adaptation of a straight wire to the lingual arch form

Amir Hossein Abdi,Saeed Reza Motamedian,Ehsan Balaghi,Mahtab Nouri 대한치과교정학회 2018 대한치과교정학회지 Vol.48 No.4

Objective: The aim of this study is to compare the adaptation of a straight wire between brackets positioned at the mid-lingual surface and those placed gingivally by using a three-dimensional simulation software. Methods: This cross-sectional study was performed using OrthoAid, an in-house software. The subjects were 36 adolescents with normal Class I occlusion. For each dental cast, two bracket positioning approaches, namely the middle and gingival, were examined. In the middle group, the reference points were placed on the mid-lingual surface of each tooth, while in the gingival group, the reference points were positioned lingually on the anterior teeth. A 4th degree polynomial was adopted, and the in-plane and off-plane root mean squares (RMSs) of the distances between the reference points and the fitted polynomial curve were calculated using the software. Statistical analysis was performed using the paired-samples t-test (a = 0.05). Results: The mean in-plane RMS of the polynomial curve to the bracket distance in the gingival group was significantly lower than that in the middle group (p < 0.001). The off-plane RMS was higher in the gingivally positioned brackets in the maxilla than in the middle group (p < 0.001). However, the off-plane RMS in mandible was not statistically significantly different between the two groups (p = 0.274). Conclusions: The results demonstrated that the gingival placement of lingual brackets on the anterior teeth could decrease the distance between a tooth and the straight wire.[Korean J Orthod 2018;48(4):236-244]

Effect of Polymer Stabilizer on Swelling Potential and CBR of Forest Road Material

Fatemeh Mousavi,Ehsan Abdi,Hassan Rahimi 대한토목학회 2014 KSCE Journal of Civil Engineering Vol.18 No.7

Swelling behavior of some soils, especially soils with high clay content, has a great impact on forest roads. Moisture variation in expansive soils results in their volume change. If the soil can not swell freely, it will apply pressure to surrounding structures which may eventually cause some damage or complete destruction. Therefore, it is essential to assess the swelling potential of the foundation soils and take appropriate measures to overcome such problem. In the present study, the effects of RPP as a polymer stabilizer to control swelling of expansive soils were investigated. For this purpose, different tests including Atterberg Limits, standard compaction, swelling potential, and swelling pressure, were conducted on control and treated soil samples using different Percentage of Polymer (RPP) (0.019, 0.04 and 0.06%). Also California Bearing Ratio (CBR) tests were conducted on control and treated samples based on manufacturer recommendation. To assess the effect of time on performance of polymer treated soil, samples with 0.019% RPP content were prepared and kept in sealed plastic bags for 7 and 14 days periods and then tested for Atterberg Limits, swelling potential and swelling pressure. The results showed that soil treatment with RPP, resulted in improvement of CBR and maximum dry density and reduction in Atterberg Limits, swelling potential and swelling pressure. The results also indicated that the curing 7-14 days periods had no significant effect on plasticity and swelling properties of the treated samples.

Developing a GIS database for forest road management in Arasbaran forest, Iran

Manije Talebi,Baris Majnounian,Ehsan Abdi,Fateme Berenji Tehrani 한국산림과학회 2015 Forest Science And Technology Vol.11 No.1

Forest roads are an essential infrastructure and prerequisite in the management of forested areas. Sustainable managementof roads depends on regular and timely forest road maintenance. A road inventory is the first step of forest roadmanagement, control of construction standards, and maintenance operation; and GIS can be a powerful tool foracquirement, analysis, and management of data in road management. The purpose of this study was to obtain the requiredinformation to assess existing road standards by way of a road inventory and use the results to schedule maintenanceoperations. To achieve this goal, a part of the road network from Kaleibarchay watershed in Arasbaran forest wasinventoried, and cross sectional components were measured and compared to standard ones. Culverts along the road werealso investigated. Road components, problems of surfacing, and slope stability were analyzed in ArcGIS9.3 software. Theresults showed significant differences between existing parameters and standard ones, and the exceptions were side ditchdepth and roadbed. The results of culvert assessment showed that the road segment only had one culvert. According to theresults, cross-slope has the highest consistency with standard values. Around a quarter (25.19%) of the road length had nosigns of surfacing problems. Among surfacing problems, rutting had the highest abundance and cut slope had morestability problems than fill slope. In order to have better management of drainage systems, we suggested some places forinstalling new cross drains including culverts and fords. The results of this research can be used in developing effectivemaintenance operations for the road in this study, and also as a model to study and collect required inventory data and inapplying GIS to forest roads management.