Analisis spektrum gelombang permukaan (SASW) adalah kaedah seismos yang menggunakan ciri serakan gelombang Rayleigh yang merambat pada lapisan bahan bagi memperolehi profil halaju gelombang ricih. Kaedah SASW merupakan satu kaedah insitu tanpa musnah untuk pencirian tapak geoteknik yang lebih kos efektif berbanding kaedah konvensyenal secara penggerudian. Dalam kajian ini sebanyak 20 stesen yang terdiri daripada 13 tapak kajian telah dipilih. Perisian (WINSASW 2.0) telah digunakan dalam proses penyongsangan untuk menghasilkan profil halaju gelombang ricih melawan kedalaman. Profil-profil ini kemudian dianalisis secara berasingan bagi memperolehi beberapa parameter geologi kejuruteraan jasad batuan seperti kekukuhan, nilai Penanda Mutu Batuan (RQD), anisotropi dan sifat kebolehkorekan. Analisis data SASW dijalankan dengan menganggap bahawa jasad batuan adalah homogen dan isotrop serta mengandungi pelbagai intensiti ketakselanjaran yang mempengaruhi perambatan halaju gelombang permukaan. Pengukuran sifat kedinamikan tanah dijalankan dengan menggunakan halaju gelombang ricih dan nilai ketukan N daripada Ujian Penusukan Piawai (NSPT) dalam lubang gerudi. Satu persamaan linear baharu, Vs = 4.44 NSPT + 213.84 yang mengaitkan halaju gelombang ricih dan NSPT telah diperolehi. Satu persamaan empirik telah dikemukakan bagi mengukur nilai Penanda Mutu Batuan (RQD) berasaskan halaju gelombang ricih yang diperolehi daripada kaedah SASW dan halaju daripada ujian ultrasonik. Persamaan ini memberikan hasil yang perbezaannya kurang daripada 10% berbanding data RQD daripada lubang gerudi. Analisis keanisotropan jasad batuan dijalankan menggunakan halaju gelombang ricih yang diperolehi berdasarkan kaedah SASW yang diukur dalam empat arah. Plot nisbah halaju gelombang ricih - halaju ultrasonik melawan halaju ultrasonik telah digunakan untuk menentukan sifat kebolehkorekan jasad batuan. Sebanyak lima kelas lengkungan kebolehkorekan jasad batuan telah dapat dikemukakan iaitu lengkungan Mudah korek, Mudah koyak, Susah koyak, Pemecah hidraulik dan Peletupan.
This paper presents a printed wide-slot antenna design and prototyping on available low-cost polymer resin composite material fed by a microstrip line with a rotated square slot for bandwidth enhancement and defected ground structure for gain enhancement. An I-shaped microstrip line is used to excite the square slot. The rotated square slot is embedded in the middle of the ground plane, and its diagonal points are implanted in the middle of the strip line and ground plane. To increase the gain, four L-shaped slots are etched in the ground plane. The measured results show that the proposed structure retains a wide impedance bandwidth of 88.07%, which is 20% better than the reference antenna. The average gain is also increased, which is about 4.17 dBi with a stable radiation pattern in the entire operating band. Moreover, radiation efficiency, input impedance, current distribution, axial ratio, and parametric studies of S11 for different design parameters are also investigated using the finite element method-based simulation software HFSS.
The water decoction of Labisia pumila var. alata is used traditionally in childbirth, as well as for the treatment of flatulence, dysentery, dysmenorrhoea and join pains. This study was carried out to determine the best method and optimum parameters of aqueous axtraction of the leaves and roots of this species. The laboratory methos esed were maceration, ddecoction, reflux and Saxhlet, whereas the parameters studied were temperature, duration and pH of axtraction. The yields and thin layer chromatographic profiles of the freeze-dried extracts were analysed. The study showed that in general the percentage yields of the water soluble extracts were higher for the roots than the leaves, as well as the extracts obtained from heating than those obtained at room temperature. The most effective extraction parameters for L. pumila var. alata were as follows:maceration (25 C, at least 6 hr), decoction (60 C, not exceeding 10 min) and reflux (100 C, not exceeding 4 hr). Saxhlet method was found to be the least effective. The pH analysis had shown the possibility of degradation of some of the phytochemicals at extreme pH values of 1,2 and 14.
Satisfactory composite restoration depends upon its smooth finish, quality of polishing agents, type of composite material used, and its composition. The present study evaluated the effect of different polishing systems on the surface roughness of composite resin.
Teknik reka bentuk untuk meningkatkan gandaan bagi menambah baik prestasi antena tompok mikrojalur konvensional dibincangkan. Kaedah suapan prob tersongsang jalur lebar bagi antena tompok mikrojalur berbilang lubang alur bertindan dicadangkan. Reka bentuk tersebut menggabungkan beberapa teknik kontemporari iaitu kaedah suapan prob, struktur tompok tersongsang dan tompok berbilang lubang alur bertindan. Kesan komposit daripada penyatuan pelbagai teknik ini dan dengan memperkenalkan bentuk elemen tompok yang baru, memberikan profil yang rendah, jalur lebar yang lebih luas, gandaan tinggi dan elemen antena yang padat. Keputusan menunjukkan peningkatan gandaan di mana gandaan maksimum adalah 11.42 dBi. Reka bentuk ini sesuai untuk aplikasi tata susunan terutama untuk stesen tapak.
Kajian ini dijalankan untuk mencirikan kepelbagaian kelakuan cuaca dalam lapisan bawah dan atas atmosfera, terutama kebergantungannya kepada keadaan di dalam troposfera dan ionosfera pada enam stesen yang berbeza di UKM Bangi, Selangor. Pengukuran adalah berasaskan pemonitoran jangka pendek wap air bolehmendak (PWV) dalam troposfera dan jumlah kandungan elektron (TEC) dalam ionosfera menggunakan penerima GPS Bumi. Data PWV, TEC dan pengukuran meteorologi permukaan adalah dicerap bermula 12 November sehingga 7 Disember 2007. Hasil pemonitoran menunjukkan bahawa kedua-dua profil kebolehubahan PWV dan TEC memperlihatkan kitaran harian. Purata harian PWV dan TEC adalah tinggi, masing-masing dengan nilai ~42 mm dan ~35 TECU. Perubahan kedua-duanya didapati dipengaruhi aktiviti Matahari.
This study compared the surface roughness of selected tooth coloured restorative materials that were polished according to manufacturers’ instructions and Sof-Lex. It also assessed the surface roughness of polished materials after thermocycling.Filtek Z350XT, Beautifil-Bulk Restorative and Cention N, were used in this study. A stainless steel mould (10mm diameter x 2mm height) was used to fabricate 75 cylindrical specimens: 15 Filtek Z350XT (FZ), 30 Beautifil-Bulk Restorative (BB) and 30 Cention N (CN). All 15 FZ specimens were polished with Sof-Lex. Fifteen BB and CN specimens were polished according to manufacturers’ instructions. The remaining fifteen BB and CN specimens were polished using Sof-Lex. All the specimens were subjected to thermocycling (1000 cycles). Surface roughness was assessed quantitatively with profilometry after specimen preparation (Mylar stage), polishingand thermocycling. Data were analysed using SPSS version 25.0 at α=0.05. When polished according to manufacturers’ instructions, BB had the lowest mean surface roughness (Ra) values (0.13±0.01μm) followed sequentially by CN (0.14±0.03μm) and FZ (0.15±0.02μm). The differences were not statistically significant. When polished with Sof-Lex, BB exhibited the smoothest surface (0.116±0.03μm) followed sequentially by and FZ (0.150±0.02μm) and CN (0.157±0.02μm). Thermocycling caused an increase in the Ra. The differences were statistically significant. All materials tested had Ra values below the threshold value of 0.2 μm at Mylar stage and after polishing with their recommended polishing system and Sof-Lex. Thermocycling produced rougher surfaces that did not exceed the threshold Ra value. Polishability was material dependent.
Dalam makalah ini, masalah aliran genangan dalam bendalir mikrokutub terhadap permukaan mencancang yang telap dengan fluks haba boleh ubah dipertimbangkan. Dengan menggunakan penjelmaan keserupaan, persamaan asas yang menakluk aliran bendalir dan pemindahan haba dijelmakan kepada satu set persamaan perbezaan biasa. Persamaan yang dijelmakan tertakluk kepada syarat-syarat sempadan yang berkaitan kemudiannya diselesaikan secara berangka menggunakan kaedah tembakan. Kesan parameter sedutan/semburan fw ke atas profil halaju dan suhu serta pekali geseran kulit dan nombor Nusselt setempat diperoleh dan dibincangkan. Keputusan berangka menunjukkan bahawa penyelesaian dual wujud dalam kedua-dua aliran membantu dan aliran menentang.
Penyelesaian berangka bagi masalah aliran lapisan sempadan olakan bebas mantap terhadap silinder bulat mengufuk yang dijanakan oleh pemanasan Newtonan, iaitu pemindahan haba dari permukaan berkadar langsung dengan suhu permukaan setempat, dipertimbangkan. Persamaan lapisan sempadan terjelma diselesaikan secara berangka dengan suatu skim berangka beza terhingga tersirat yang dikenali sebagai kaedah kotak Keller. Penyelesaian berangka diperoleh bagi pekali geseran kulit, pekali pemindahan haba setempat, suhu dinding serta profil halaju dan suhu. Ciri-ciri aliran dan pemindahan haba bagi suatu julat nilai nombor Prandtl yang besar dianalisis dan dibincangkan.
Dental composite resins are widely used in dental practice and are continually being developed in order to obtain better products. To gain full benefit from these materials, it is important for the clinician to understand their properties. The following is a review of the more common characteristics of composites in current use.
The aim of this study was to evaluate colour stability upon exposure to spices of a nano-filled and a micro-hybrid resin composite finished either with Sof-Lex™ discs (SLD) or against plastic strips (PS).
Silane is a dominant coupler that is widely used in dentistry to promote adhesion among the components of dental composites. Silica-based fillers can be easily silanized because of their similarly ordered structure. However, silane is hydrolytically degraded in the aqueous oral environment and inefficiently bonds to non-silica fillers. Thus, the development of hydrolytically stable dental composites is an important objective in the research on dental materials. Titanate coupling agents (TCAs) exhibit satisfactory interfacial bonding, enhanced homogeneous filler dispersion, and improved mechanical properties of the composites. Titanates also provide superior hydrolytic stability in wet environments, which should be considered in fabricating dental composites. The addition of a small amount of titanates can improve the resistance of the composites to moisture. This paper reviews the effects of the instability of silanes in moisture on the performance of dental composites and presents TCAs as alternative couplers to silanes for fabricating dental composites.
Damage assessment is a key element in structural health monitoring of various industrial applications to understand well and predict the response of the material. The big uncertainty in carbon fiber composite materials response is because of variability in the initiation and propagation of damage. Developing advanced tools to design with composite materials, methods for characterizing several damage modes during operation are required. While there is a significant amount of work on the analysis of acoustic emission (AE) from different composite materials and many loading cases, this research focuses on applying an unsupervised clustering method for separating AE data into several groups with distinct evolution. In this paper, we develop an adaptive sampling and unsupervised bivariate data clustering techniques to characterize the several damage initiations of a composite structure in different lay-ups. An adaptive sampling technique pre-processes the AE features and eliminates redundant AE data samples. The reduction of unnecessary AE data depends on the requirements of the proposed bivariate data clustering technique. The bivariate data clustering technique groups the AE data (dependent variable) with respect to the mechanical data (independent variable) to assess the damage of the composite structure. Tensile experiments on carbon fiber reinforced composite laminates (CFRP) in different orientations are carried out to collect mechanical and AE data and demonstrate the damage modes. Based on the mechanical stress-strain data, the results show the dominant damage regions in different lay-ups of specimens and the definition of the different states of damage. In addition, the states of the damage are observed using Scanning Electron Microscope (SEM) analysis. Based on the AE data, the results show that the strong linear correlation between AE and mechanical energy, and the classification of various modes of damage in all lay-ups of specimens forming clusters of AE energy with respect to the mechanical energy. Furthermore, the validation of the cluster-based characterization and improvement of the sensitivity of the damage modes classification are observed by the combined knowledge of AE and mechanical energy and time-frequency spectrum analysis.
This study aimed to investigate the effect of various framework designs on the failure of posterior fiber reinforced composite (FRC) bridges and assess the post crack performances of the repaired prostheses. Thirty samples were prepared into three different groups of framework designs: cuspal support (CS), anatomic features (AF) and circular reinforcement (CR). All specimens were subjected to static loading test and acoustic emission analysis. Significant differences were found in the load and time of initial failures among the three groups (p<0.001). CS was identified as the optimum framework design. Samples with composite delamination at the pontic site were selected and repaired with a clinically simplified protocol. Significant differences were also observed between the repaired and original FRC bridges (p=0.01). The performance of these prostheses was highly dependent on the framework design and the perspective of repairing FRC bridges may warrant future investigations.
Objectives: To evaluate the marginal microleakage of Class II cavities restored with various types of composite resins.
Materials and Methods: Standard Class II slot cavities were prepared at the proximal surfaces of 40 intact premolars which were divided into 4 groups. Four types of composite resins (Esthet-X-Denstply, USA, FiltekTMZ350- 3M ESPE, USA, Beautifil- Shofu, Japan and Solare P-GC, Japan) were used to restore the slot cavities. All the specimens were thermocycled and immersed in 0.5% basic fuschin dye for 24 hours. The specimens were then sectioned in mesio-distal direction. The marginal microleakage at the occlusal and cervical margin was scored using the ISO microleakage scoring system. Data was entered using SPSS Version 12.0 and analyzed using STATA software programme.
Results and discussion: All composite resins exhibited worse microleakage at the cervical margin compared to occlusal margin. Esthet-X showed significantly better microleakage score at the occlusal margin compared to Beautifil and Solare P. FiltekTMZ350 and Beautifil showed mainly microleakage into enamel only at the occlusal margin. Solare P demostrated better resistance against microleakage at the cervical margin compared to other composite resin tested. Esthet-X, Filtek Z350 and Beautiful is not significantly different from each other in terms of microleakage at the cervical margin.
Conclusion: This study showed that none of the materials used in this study is able to eliminate microleakage. Composite resin restorations exhibited worse micorleakage at cervical margin in comparison to occlusal margin.
The aim of the study was to evaluate post-polymerization of resin composite by measuring NanoHardness (H), Young’s Modulus (E) and Degree of Conversion (DC) using nanoindentation and Micro-Raman spectroscopy. For this purpose a computer-controlled NanoIndenter™ and a Renishaw 1000 Raman Spectrometer fitted with an Olympus microscope attachment, operated at 638 nm, were used. A light-activated resin composite was used in this study, (Z250, 3MESPE). Sub-groups (n=3) of specimens were irradiated for 20, 30, 40 s. All samples for nanoindentation were polished metallographically and typically 50 nanoindentations were performed per specimen. After curing and polishing, half of the samples were tested immediately (Group 1); the others after being stored dry at 37 °C for 7 days (Group 2) to allow scope for postpolymerization. H values ranged from 1.08 to 1.40 GPa for Group 1, and from 1.64 to1.71 GPa for Group 2. E values in Group 1 ranged from 19.60 to 19.94 GPa and for Group 2, from 21.42 to 22.05 GPa. DC values ranged from 55 to 66.39%, and 60.90 to 66.47% for Group 1 and Group 2 respectively. All values obtained shown significant different between Groups 1 and 2 (p
Choosing the right light-curing unit can be a very difficult task for some orthodontists. Currently, there are various types of light curing units available in the market with various trade names and specifications. Most of the time information regarding light curing units is obtained from advertisements, websites or manufacturers’ catalogues. Sometimes such information can be misleading. This article attempts to provide several tips for orthodontists in selecting light curing units.
The purpose of this study was to investigate the light intensity of selected light curing units with varying distance and angulation of the light curing tip and lightmeter. Materials and method: Four types of light units; Spectrum 800 (Dentsply), Coltulux 3 (Coltene), Elipar FreeLight 2 (3M Espe) and Starlight Pro (Mectron) were evaluated for light intensity at various distances between the light curing tip and the radiometer Cure Rite Denstply (0,1,3,5,10 and 15 mm). The light curing units were tested at right angles to the aperture of the light meter and at the angles of 45°, 60° to it at a standardized 5 mm distance. Results: The highest light intensity was obtained when the tip of light curing unit was in contact with the lightmeter aperture. The light intensity decreased significantly when the light tip was placed 5mm, 10mm and 15mm away from the lightmeter aperture. However, no significant differences (p> .05) were detected between Omm, Imm and 3mm. There was a decrease in light intensity when light~·tip was angulated at 45° and 60° except for Coltolux 3. Conclusions: The intensity of the curing light was affected by the distance between the light curing tip and the lightmeter. However, the decrease in light intensity of the light curing unit was found not to obey the inverse square law for the distances 0 to 15 mm. The study found that there was no significant difference between 45° and 60° angulation between the light curing tip and the lightmeter. However, the decrease in light intensity was significant when compared to the light tip placed perpendicular (90°) to the aperture of the light meter.