The main purpose of electromagnetic interference (EMI) shielding coatings is the insulation of sensitive devices and protect people from electromagnetic field exposure due to its effects on the human body. This paper investigates the dielectric properties, and electromagnetic shielding performances of graphite and carbon black (CB) filled epoxy matrix composites produced by the mechanical mixing method. The sample compositions were created at rates ranging from 1 to 7 wt%. Samples were analyzed by Vector Network Analyzer (VNA) using the coaxial method in the range of 1–14 GHz, including L band, S band, C band, X band and partially Ku band. After determining the scattering parameters with VNA, AC conductivity, absorption, reflection and total shielding efficiency values were calculated. At high frequencies, almost all the samples showed higher AC conductivity. CB-filled samples show higher AC conductivity than graphite-filled samples. The total shielding efficiency (SET) of the graphite-added samples (19–21 dB) is slightly higher than the carbon black-added samples (8–17 dB). Distinct filling ratios in graphite-added samples result in closer shielding behavior in contrast to carbon black-added samples. However, higher shielding efficiency is observed as the CB filler ratio increases. The shielding efficiencies of the samples with both types of filling materials vary little depending on the frequency. Reflection is the main mechanism of the shielding efficiency, which constitutes the majority of total efficiency for all types of samples.
ÖzetAmaç: Pterjium oluşmasında mesleğin etkilerini araştırmak. Ge reç ve Yön tem: Kahramanmaraş Pazarcık Devlet Hastanesi Göz Hastalıkları Polikliniğinde Ağustos 2012-Ekim 2012 tarihleri arasında muayene olup pterjium tanısı alan 182 hastanın dosyası geriye dönük olarak incelendi. Hastaların meslekleri analiz edildi ve mesleklerin pterjium oluşumundaki etkileri araştırıldı. Sonuçlar: Çalışmamıza muayene edilen 2328 hastadan, pterjium tanısı alan 182 (%7,8) hasta dâhil edilmiştir. Olguların ortalama yaşı 52,2±1,6 yıl (16 yaş-87 yaş) idi. Hastalarımızın 82 (%45,1)'si tarım işçisi veya çiftçi, 12 (%6,6)'si devlet memuru, 48 (%26,4)'i ev hanımı, 39 (%21,4)'u serbest meslek sahibi, biri (%0,5) öğrenci idi. Pterjium dokusu, hastalarımızın 62 (%34,1)'sinde sağ gözde, 57 (%31,3)'sinde sol gözde, 63 (%34,6)'ünde her iki gözde idi. Olguların 51 (%28)'i 40 yaş ve altında, 131 (%72)'i 40 yaş üzerindeydi. Pterjium dokusu uzunluğu hastaların 69 (%37,9)'unda 1,5 mm altında, 88 (%48,4)'inde 1,5-3 mm arasında, 25 (%13,7)'inde 3 mm üzerindeydi. Hastaların 86 (%47)'sı erkek, 96 (%53)'sı kadındı. Tarım işçisi veya çiftçileri içeren meslek grubunda, yaş arttıkça pterjium görülme oranının arttığı saptandı (p=0,015). Serbest meslek grubunda yaş arttıkça pterjium görülme oranının arttığı saptandı (p=0,014). Tarım işçisi veya çiftçileri içeren meslek grubuyla pterjium dokusu uzunluğunun arasındaki ilişkinin anlamlı olduğu ve bu grupta dokunun daha uzun olduğu saptandı (p=0,043). Tar t›fl ma: Çalışmamızda, pterjium en sık tarım işçileri ve çiftçilerde görüldü. Yaş ilerledikçe tarım işçileri ve çiftçilerde ve serbest meslek grubunda pterjium sıklığının arttığı ve tarım işçileri ve çiftçilerde pterjiumun daha uzun olduğu saptandı. Özellikle kırsal kesimde ve dış ortamda çalışan meslek gruplarında pterjiumun daha fazla görülmesi, güneşin etkilerinden korunmak için güneş gözlüğü ile beraber yeterli büyüklükte şapka kullanılmasının yararlı olacağını düşündürmektedir. (Turk J Ophthalmol 2013; 43: 245-9) Anah tar Ke li me ler: Pterjium, mesleki gruplar, risk faktörleri Sum maryPur po se: To investigate the effects of job on the development of pterygium. Ma te ri al and Met hod:We retrospectively evaluated the files of 182 patients who were diagnosed as having pterygium between August 2012 and October 2012 in the Ophthalmology Clinic at Kahramanmaraş Pazarcık State Hospital. Patients' jobs were analyzed and the effects of job on the formation of pterygium were investigated. Re sults: In our study, we did ophthalmic examination on 2328 patients and included 182 (7.8%) patients who had pterygium. The average age was 52.2± 1.6 years (range: 16 -87 years). 82 (45.1%) patients were agricultural workers or farmers,12 (6.6%) were officers, 48 (26.4%) were housewives, 39 (21.4%) were independent workers, and one was student. The tissue of pterygium in 62 patients (34.1%) was on the right eye, in 57 (31.3%) -on the left eye, in 63 (34.6%) -on both eyes. 51 (28%) patients were 40 years old or younger, and 131 (72%) were older than 40 years. The length of ...
S teels with martensitic microstructure (low carbon) and high creep resistance can be used at high temperatures for a long period of time. One of the potential applications of these materials is thermal and nuclear power plants. Over the years, the demand on the service temperature level in these plants have increased. As a result, studies on the development of new steel-based materials with enhanced creep and corrosion resistance have soared. The graph shown in Fig. 1 shows the need for service temperatures and pressures depending on years. Steels with 9-12% Cr content have been started to be used in these applications since 1950s. These steels
In this study, the fracture toughness of Fe2B boride layer on boronized AISI 304 stainless steel was investigated. Samples were boronized in an indirect heated fluidized bed furnace with Ekabor 1™ boronizing agent at 1123 K, 1223 K, and 1323 K for 1 h, 2 h, and 4 h, respectively. The boride phases were investigated by X-ray diffraction (XRD) analysis. Hardness and fracture toughness of borides were measured via Vickers indentation. With increasing boriding temperature and time the fracture toughness values were reduced. The boride layer thickness formed on the boronized samples ranged between 12 μm and 176 μm. The hardness of the borides ranged between 1709 HV0.1 and 2119 HV0.1 and fracture toughness was in the range of 2.19–4.47 MPa × m1/2 depending on the layer thickness and hardness.
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