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International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163 Volume 1 Issue 8 (September 2014) ________________________________________________________________________________________________________ © 2014, IJIRAE- All Rights Reserved
    International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163   Volume 1 Issue 8 (September 2014 ) ________________________________________________________________________________________________________  © 2014, IJIRAE- All Rights Reserved Page - 244 DG SYSTEMS ARE SMALL POWER SOURCES THAT CONNECT TO DISTRIBUTION SYSTEMS Shahryar shafei 1  Shahin Shafei  2   1,2  Department of Electrical Engineering, Mahabad Branch, Islamic Azad University, Mahabad, Iran  Abstract— The operation of a distribution system in the presence of distributed generation systems has some advantages and  challenges. Optimal sizing and siting of DG systems has economic, technical, and environmental benefits in distribution  systems. Improper selection of DG systems can reduce these advantages or even result in deterioration in the normal operation  of the distribution system. DG allocation and capacity determination is a nonlinear optimization problem. The objective  function of this problem is the minimization of the total loss of the distribution system. In this paper, the ImprovedHarmony Search (IHS) algorithm has been applied to the optimization problem. This algorithm has a suitable performance for this type  of optimization problem. Active and reactive power demands of the distribution system loads are dependent on bus voltage. This  paper verifies the effect of voltage dependent loads on system power characteristics. The load model has an inevitable impact  on DG sizing and placement. The proposed algorithm implemented and tested on 69-bus distribution systems and the impact of voltage dependent load models are demonstrated. The obtained results show that the proposed algorithm has an acceptable  performance.  Keywords: Knee, MRI, low field-strength MRI I.INTRODUCTION The knee joint has a complex structure which comprises the femoral and tibial condyles, together with the patella, ligaments, menisci, interlocated bursae, and the joint capsule (Figures 1&2). Pathological conditions of the knee may arise from any one or more of these structures (Ustun, 2003; Kean et al., 1983; Beltran et al., 1990; Li et al., 1986).  Figure 1. This  s agittal T1W image of the knee joint demonstrates the components of the joint in full detail. The first step in the detection of knee joint pathologies is obtaining a detailed clinical history and performing a thorough  physical examination. The next step is imaging. Imaging is performed by different modalities, which are conventional radiography, computed tomography (CT), ultrasonography (US), arthrography, and MRI. Arthrography is an invasive imaging modality. Therefore, imaging modalities such as CT and MRI are somewhat more valuable in the imaging of the knee noninvasively. But all of these modalities possess certain limitations of their own (Ustun, 2003; Miller et al., 2002; Kean et al., 1983; Beltran et al., 1990; Li et al., 1986; Khan et al., 2014). Conventional radiography is the basic means of imaging the knee. In routine practice, orthogonal views are obtained, which demonstrate the knee region both on the anteroposterior and lateral projections. Optional views too, may be obtained, which image the knee region in varying angles and positions (Ustun, 2003; Tuncel 2002; Cherney et al., 1989). On the other hand, CT has an important place in the evaluation of the knee joint, especially its bony components. CT helps determine the degenerative and osteoporotic changes that take place in the bones of the knee joint. It is also very useful in the diagnosis of tumoral growths of the bone, together with the demonstration of tumor growth both in and out of the tumoral area. CT is also very effective in the imaging of new bone formations and calcifications. On the other hand, tumor regression following therapy can also be monitored by means of CT imaging (Ustun, 2003; Ghelman, 1985; Mosher et al., 2013). High-resolution CT imaging can also be helpful in visualizing meniscal pathologies. The drawbacks of CT imaging are that it utilizes ionizing radiation, its tissue contrast is not as good as MRI, and it cannot provide direct multiplanar imaging.    International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163   Volume 1 Issue 8 (September 2014 ) ________________________________________________________________________________________________________  © 2014, IJIRAE- All Rights Reserved Page - 245 High-resolution US is utilized for the evaluation of the soft tissue components of extremities. It is technically desirable that the transducers used for this purpose have an optimum operational frequency of 10 MHz or more. Linear transducers are utlized for this purpose, because it is more favorable that the sound beam comes perpendicular to the region of interest and the examination site is as wide as possible. US is rather insufficient in the visualization of bony pathologies and intraarticular soft tissue components. US performed with high-frequency superficial transducers is helpful in the detection of cystic and vascular  pathologies in the near vicinity of the knee joint. The extensor tendons of the knee, which are the quadriceps and patellar tendons, may be visualized by US, especially when the knee is flexed. The collateral ligaments on the other hand, usually cannot be discriminated properly due to the presence of neighboring fat tissue and articular capsule. The cruciate ligaments and menisci, on the other hand, cannot be visualized by US. In some studies, the posterior cruciate ligament (PCL) and its injuries have been investigated and visualized by means of US, and certain positive findings have been observed, such as ligament thickening and focal discontinuity (Miller et al., 2002). But MR is the modality of choice in this regard (Stoller et al., 1987; De Smet et al., 1994; Kaplan et al., 1991; Reinig et al., 1991; Mosher et al., 2013; Griffin et al., 2008). Arthrography used to be utilized with single or double contrast, in the pre-CT and pre-MR era. But it is an invasive procedure and may provide satisfactory results only when  performed with skilled hands. Arthrography is abandoned in today’s modern imaging era (Ustun, 2003; Wilson et al., 1990; Ferris et al., 1981). Arthroscopy on the other hand, is an invasive clinical modality and when performed by skilled hands, it may provide satisfactory diagnostic, as well as therapeutic, results. Today, arthroscopy is mainly a therapeutical operational procedure, and diagnostically it has limited applications such as a problem-solving function in cases whose conditions cannot be clearly evaluated  by MRI (Wilson et al., 1990; Ferris et al., 1981; Cannon et al., 1994; Rosenberg et al., 1993). Magnetic resonance (MR), as a raw technique, was first described by two researchers, Bloch and Purcell, who had been working on the same issue separately. The two researches won the Nobel prize in 1946. Lauterberg was the first scientist to use MR as an imaging modality in the 1980s. He won the Nobel prize for this great achievement in 2003. MR imaging of the knee was first described by Kean et al in 1983. MRI demonstrated a very fast development thanks to technical achievements and became the gold standard in the visualization and evaluation of the knee joint (Kean et al., 1983; Tuncel, 2002; Lee et al., 2000; Carpenter et al., 1990; Vahey et al., 1990; Khan et al., 2014; Mosher et al., 2013; Griffin et al., 2008). MRI has many advantages which make it a superior modality in diagnostic radiology. First of all, MRI is a noninvaisve imaging modality which does not utilize ionizing radiation. Secondly, it provides direct multiplanar imaging. MRI can differentiate different tissue types such as fat, water, and blood, according to the proton properties of these structures. MRI also has superb contrast resolution, and it provides excellent anatomical detail. MRI is a radiologic modality whose sensitivity is very high, while its specificity is rather low. Therefore, a thorough clinical history is mandatory for a proper MR evaluation. MRI provides reliable diagnosis in a rather short period of time (Ustun, 2003; Tuncel, 2002; Katz et al., 2001; Mosher et al., 2013; Griffin et al., 2008). The purpose of this research study was to image and evaluate the MRI findings of symptomatic knees by means of a 0.2 T low field-strength open MR scanner, and then to compare these findings with the literature data obtained from studies conducted by 1.5 T high-field MR scanners. II.MATERIALS AND METHODS 214 knees which belonged to patients who had applied to the Orthopedics Department of the Numune Teaching and Research Hospital, Adana, Turkey, with various complaints concerning the knee joint, were included in this study. The study was conducted in accordance with the Helsinki Declaration. All patients were given thorough explanations about the study prior to the  procedures. Patients gave their full-informed consents before the study took place. Conventional orthogonal X-rays of the knees were obtained prior to the MRI examinations. The initial clinical diagnoses of the patients were achieved by means of evaluating the physical findings and conventional radiograms. The clinical initial diagnoses, and their frequencies and percentages are given in Table 1. The patient group which was recruited for the study mainly comprised those with medial meniscal tears and other meniscopathies, and those who presented with the complaint of knee pain. The most frequent of these entities was medial meniscus tear, which presented a ratio of 33.2 %. MRI examinations were performed in a 0.2 T low field-strength open MRI scanner (Hitachi Airis Mate, Hitachi Corp., Japan) (Figure 3). The kness were placed properly in the special receiver coils.  Figure 2. The 0.2 T low field-strength open MRI scanner used in our study    International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163   Volume 1 Issue 8 (September 2014 ) ________________________________________________________________________________________________________  © 2014, IJIRAE- All Rights Reserved Page - 246 Initially, localizer axial GRE images were obtained. The best one of these slices was used as a baseline for sagittal and coronal studies. The sagittal cuts were obtained first, over the initial axial slices. Spin Echo T1-Weighted (SE T1W), Proton Density Weighted (PDA), and Fast SE T2-Weighted (Fast SE T2W) slices were obtained on the sagittal plane. Following the sagittal work-up, coronal imaging was performed. SE T1W, SE PDW, and FSE T2W sequences were utilized. Besides, sagittal GRE slices were obtained in addition to axial ones. The STIR sequence was not routinely performed. But this sequence was performed when needed. Table 1  (n = 214) The frequency and percentages of the clinical findings The parameters utilised in T1W imaging were as follows: TR = 400 ms, TE = 27 ms, slice thickness = 4 mm, interval = 1 mm, FOV = 16 cm, NSA = 2 (1), matrix = 280 x 260, sagittal scan time = 3 min 28 s, coronal scan time = 3 min 22 s, overall scan time = 6 min 50 s. The parameters utilized in FSE T2W imaging were as follows: TR = 4000 ms, TE = 100 ms, slice thickness = 4 mm, interval = 1 mm, NSA = 2 (1), matrix = 256 x 168, FOV = 16 cm, sagittal scan time = 5 min 4 s, coronal scan time = 5 min 36 s, overall scan time = 10 min 40 s. The parameters utilized in PDA imaging were as follows: TR = 4000 ms, TE = 20 ms, slice thickness = 4 mm, interval = 1 mm, NSA = 2 (1), matrix = 256 x168, FOV = 16 cm, sagittal scan time = 5 min 36 s, coronal scan time = 4 min 16 s, overall scan time = 9 min 52 s. The parameters utilized in GRE imaging were as follows: TR = 500 ms, TE = 17 ms, Flip Angle = 30°, slice thickness = 4 mm, interval = 1 mm, NSA = 2 (1), matrix = 224 x204, FOV = 16 cm, sagittal scan time = 5 min 4 s, axial scan time = 3 min 24 s, overall scan time = 8 min 28 s. Average MR examination time for a knee was about 30-35 minutes. No complications were experienced during the scans. In the MRI examinations, the menisci, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial and lateral collateral ligaments (MCL and LCL), joint cartilage, and peripheral soft tissues were examined and evaluated. The staging system invented by Stoller et al was used in the evaluation of meniscal degenerations and tears (Stoller et al., 1987). According to this staging model, globoid signal increase in the meniscus was defined as Grade 1, whereas linear signal increase not abutting the  joint surface was defined as Grade 2, while a signal increase in the meniscal tissue abutting one or more joint surfaces was determined as Grade 3. Grade 1 and 2 signal increases were categorized as degeneration, and Grade 3 signal increase was classified as meniscal tear. The menisci were also evaluated for any structural anomaly such as discoid meniscus. Any distortions in the anatomical unity of the ligaments, together with signal increases within the ligaments, or contour irregularities and ondulations, were investigated. Besides, periligamentous signal increases and any deviations from the normal configurations, were also studied. In the light of these findings, it was decided whether there was an injury sequela, or a partial or complete tear, in the meniscus. The presence of effusions and hematomas were evaluated by means of T2W imaging. Synovial structures were evaluated by the utilization of both the T1 and T2W sequences. Both the T1 and T2W sequences were utilized for the evaluation of the bony structures. Contusions which took place in the medullary bone following trauma were visualized as a signal decrease in T1W, and signal increase in T2W, sequences (Figure 4). Any alteration in the joint space, be it narrowing or widening, was evaluated in both the sagittal and coronal planes. The presence of patellar lateralization or medialization was assessed on the axial views. Joint cartilage was evaluated especially by the GRE sequence. Other various soft tissue planes were assessed by both T1W and T2W sequences. Clinical Finding Frequency Percentage Meniscopathy 56 26,2 Medial meniscus tear 71 33,2 Knee trauma 7 3,3 Discopathy 1 0,5 ACL tear 9 4,2 Lateral meniscus tear 10 4,7 Knee pain 46 21,5 Whole body arthralgia 4 1,9 Synovitis 3 1,4 Swelling of knee 4 1,9 Knee clicking 1 0,5 Deep vein thrombosis (DVT) 1 0,5 Knee instability 1 0,5 Sum 214 100    International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163   Volume 1 Issue 8 (September 2014 ) ________________________________________________________________________________________________________  © 2014, IJIRAE- All Rights Reserved Page - 247  Figure3 . This T2W coronal image depicts medullary edema at the intercondylar notch of the tibial plateau as a hyperintense zone. III.Results A sum of 214 knee joints were evaluated in this study. Each knee was accepted as an individual case. Of these knees, 107  belonged to male, and the other 107 belonged to female, patients. The ages of the patients varied between 13 and 75 years. The results are summoned below: Table 2  (n = 214) The frequency and percentage of discoid meniscus in the lateral and Medial menisci Discoid meniscus Frequency Percentage Lateral discoid meniscus 1 0,5 Medial discoid meniscus 0 0 Meniscus discoid configuration was encountered only in the lateral meniscus. No discoid meniscus formation was found in the medial meniscus. Table 3  (n = 214) The frequency and percentage of ACL pathologies ACL pathologies Frequency Percentage Injury sequela 23 10.7 Partial tear 8 3.7 Complete tear 9 4.2 Sum 40 18.7 The sum of overall pathological conditions of the ACL is 18.7 %, injury sequela of the ACL being the most frequent of all, with a rate of 10.7 %. The second in frequency is the complete tear of the ACL, with a frequencu of 4.2 %. Table 4  (n = 214) The frequency and percentage of PCL pathologies PCL pathologies Frequency Percentage Injury sequela 4 1,9 Partial tear 0 0 Complete tear 0 0 Sum 4 1,9  Figure 5.  PCL tear as seen on sagittal T2W sequence.


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