Thermal Management of On-Chip Caches Through Power Density Minimization

Various architectural power reduction techniques have been proposed for on-chip caches in the last decade. In this paper, we first show that these power reduction techniques can be suboptimal when thermal effects are considered. Then, we propose a thermal-aware cache power-down technique that minimizes the power density of the active parts by turning off alternating rows of memory cells instead of entire banks. The decrease in the power density lowers the temperature, which then exponentially reduces the leakage. Thus, leakage power of the active parts is reduced in addition to the power eliminated from the parts that are turned off. Simulations based on SPEC2000, NetBench, and MediaBench applications in a 70-nm technology show that the proposed thermal-aware architecture can reduce the total energy consumption by 53% compared to a conventional cache, and 14% compared to a cache architecture with thermal-unaware power reduction scheme. Second, we show a block permutation scheme that can be used during the design of the caches to maximize the distance between blocks with consecutive addresses. Because of spatial locality, blocks with consecutive addresses are likely to be accessed within a short time interval. By maximizing the distance between such blocks, we minimize the power density of the hot spots in the cache, and hence reduce the peak temperature. This, in return, results in an average leakage power reduction of 8.7% compared to a conventional cache without affecting the dynamic power and the latency. Overall, both of our architectures add no extra run-time penalty compared to the thermal-unaware power reduction schemes, yet they result in a significant reduction in the total energy consumption of a cache     

Structure and durability evaluation of YSZ + Al2O3 composite TBCs with APS and HVOF bond coats under thermal cycling conditions

Plasma sprayed thermal barrier coatings (TBCs) are applied to gas turbine components for providing thermal insulation and oxidation resistance. The TBC systems currently in use on superalloy substates typically consists of a metallic MCrAlY based bond coat and an insulating Y₂O₃ partially stabilized ZrO₂ as a ceramic top coat (ZrO₂ 7–8 wt.% Y₂O₃). The oxidation of bond coat underlying yttria stabilized zirconia (YSZ) is a significant factor in controlling the failure of TBCs. The oxidation of bond coat induces to the formation of a thermally grown oxide (TGO) layer at the bond coat/YSZ interface. The thickening of the TGO layer increases the stresses and leads to the spallation of TBCs. If the TGO were composed of a continuous scale of Al₂O₃, it would act as a diffusion barrier to suppress the formation of other detrimental mixed oxides during the extended thermal exposure in service, thus helping to protect the substrate from further oxidation and improving the durability. The TBC layers are usually coated onto the superalloy substrate using the APS (Atmospheric plasma spray) process because of economic and practical considerations. As well as, HVOF (High velocity oxygen fuel) bond coat provides a good microstructure and better adhesion compared with the APS process. Therefore, there is a need to understand the cycling oxidation characteristic and failure mode in TBC systems having bond coat prepared using different processes. In the present investigation, the growth of TGO layers was studied to evaluate the cyclic oxidation behavior of YSZ/Al₂O₃ composite TBC systems with APS-NiCrAlY and HVOF-NiCrAlY bond coats. Interface morphology is significantly effective factor in occurrence of the oxide layer. Oxide layer thickening rate is slower in APS bond coated TBCs than HVOF bond coated systems under thermal cycle conditions at 1200 °C. The YSZ/Al₂O₃ particle composite systems with APS bond coat have a higher thermal cycle life time than with the HVOF bond coating.     

A new conducting polymer of 2,5-bis(2-thienyl)-1H-(pyrrole) (SNS) containing carbazole subunit: Electrochemical, optical and electrochromic properties

We report here the synthesis of a new electroactive monomer 3,6-di-tert-butyl-[4-(2,5-di-2-thienyl-1H-pyrrol-1-yl)phenyl]-9H-carbazole in five steps and polymerization of this monomer by two different procceses: Kumada Coupling and electro-oxidative. The product obtained by chemical polymerization exhibits a high thermal stability and narrow molecular weight distribution. While, in the UV–vis absorption spectrum of monomer the absorption peaks appear at 338 nm, the chemically synthesized polymer absorbs at 428 nm with 90 nm red shift. Cyclic voltammogram of monomer shows two separate oxidation processes which reflect the first oxidation at +0.84 V and a second one at +1.43 V. When the polymeric film prepared by electrochemical process was subjected to a repeated cyclic scan between −0.2 V and +1.0 V, it switches among three different colors (orange, green and blue). The oxidation and reduction response times were calculated as 2.0 s for this polymer film and exhibits high redox stability. The results anticipate that this kind of polymers can be used for designing electrochromics based on the use of one molecule for the generation of three basic colors (RGB).     

A reactive power control relay design with a new approach

In this study, the design and implementation of a mixed-signal microcontroller based reactive power control relay that is superior to existing reactive power control relays is presented. This device measures the fundamental reactive power of the system and determines the switching pattern of the capacitor banks which brings the measured fundamental reactive power to the desired value. During measurement, it yields minimal computational load for the fundamental reactive power measurement by employing the Goertzel algorithm instead of the fast Fourier transform (FFT). Consequently, measurement accuracy can be increased without increasing the time required for the FFT-based power measurement by a running average using the last five measured values of the fundamental reactive power. Possible mechanical and electrical failures in capacitor banks are detected by using a simple feedback loop and the user is warned. It has all the other classical features such as P, Q, I, V, and power factor measurement, harmonic analysis, and failure warning signals that a relay should possess.     

Prevalence of juvenile chronic arthritis and familial Mediterranean fever in Turkey: a field study

OBJECTIVE: To investigate the prevalence of juvenile chronic arthritis (JCA), familial Mediterranean fever (FMF), and Beh?et's disease in Turkish children through a field survey. METHODS: The field survey was based on cluster centering with 2 level strata. A total of 46,813 children were screened. For the diagnosis of chronic arthritis and Beh?et's previously suggested criteria were used. We have developed criteria for the diagnosis of probable FMF. Children previously diagnosed to have these diseases were also defined and included. RESULTS: JCA was found in 6.4/10,000. 2.8/10,000 children were previously diagnosed as FMF (minimum phenotype frequency). Together with the probable diagnosis of FMF, the prevalence increased to 9.3/10,000. The findings were also compared with those of our center. None of the 46,813 children had Beh?et's disease. CONCLUSION: The prevalence of chronic arthritis is similar to the other childhood populations reported. However, FMF has a very high prevalence.     

A new application for the valorisation of pomegranate seed oil: nanoencapsulation of pomegranate seed oil into electrospun nanomats for food preservation

Pomegranate seed oil (PSO) contains many bioactive materials including antimicrobials, antioxidants, tocopherol and unsaturated fatty acids such as punicic acids. Utilising PSO with nanotechnological ways is a novel approach. Therefore, in this study, PSO-loaded nanomats having an average diameter of 327 nm with 97.6% encapsulation efficiency were produced. Then, the protection potential of nanomats was determined in terms of the microbial and oxidative deterioration of food samples. On the 1st day of storage, the TMAB load of the control kashar cheese was 4.35 log CFU g⁻¹, while it was 3.05 log CFU g⁻¹ in the coated cheese (change: 1.3 logs). On the 20th day of storage, the TMAB load of the CK sample and PSc sample was 5.52 and 4.22 log CFU g⁻¹, respectively (change: 1.3 logs). For fish fillets, nanoencapsulated PSO enabled a bacterial reduction of 1.22 log cycles after 9 days of storage. The total mould and yeast number of cheese samples increased during storage, but the increase was lower in the coated group. Nanomats also increased the oxidative stability of food samples. Thiobarbituric acid values of coated samples were lower than uncoated samples.     

Development of a one-dimensional and semi-empirical model for a high temperature proton exchange membrane fuel cell

High temperature proton exchange membrane fuel cells (HT-PEMFC), which operate between 160 °C and 200 °C, can be generally used in portable and stationary power generation applications. In this study, a one-dimensional, semi-empirical, and steady-state model of a HT-PEMFC fed with a gas mixture consisting of hydrogen and carbon monoxide is developed. Some modeling parameters are adjusted using empirical data, which are obtained conducting experiments on a HT-PEMFC for different values of Pt loading and cell temperature. For adjusting these parameters, the total summation of the square of the difference between the cell voltages found using the experimental and theoretical methods is minimized using genetic algorithm. After finding the values of the adjusted parameters, the effects of different cell temperature, Pt loading, phosphoric acid (PA) percentage, and different binders (PBI and PVDF) on the performance of the fuel cell are examined. It was found that, the performance of the fuel cell using PVDF binder exhibited better performance as compared to that using PBI binder.     

Persistent left superior vena cava: Two case reports and a review from nephrologists’ perspective

Thoracic venous anomalies without congenital heart anomalies are present in minority of the population, but they are frequent enough to be encountered while placing hemodialysis catheters through the jugular or subclavian veins. Persistent left superior vena cava is the most commonly seen anomaly and it is rarely noticed before the observation of an unusual course of hemodialysis catheter or guidewire on chest X‐ray. We present two patients with previously unspotted persistent left superior vena cava and uncomplicated hemodialysis catheter insertions through the internal jugular veins with good catheter functions. Review of the relevant literature from a nephrologists’ perspective with technical aspects is provided.     

Comparison of Oxidation and Thermal Shock Performance of Thermal Barrier Coatings

Operating temperatures in gas turbine engines have reached to 1200°C with the latest developments in coating technology. Thermal shock and furnace oxidation tests are widely used to determine thermal barrier coating (TBC) performance and its durability in aircraft applications. This paper presents the results of thermal shock and furnace oxidation tests, carried out with regard to the microstructure and TGO (thermally grown oxide) growth behavior of TBC systems. Isothermal oxidation behavior of TBCs was evaluated through examination of microstructure, formation, and growth behavior of TGO layers at 1200°C for different time periods in furnace oxidation tests. On the other hand, thermal shock behavior of TBC was evaluated through examination of its durability at 1200°C with thermal shock test, which was carried out until the coating failure became visible. The relationship between the TGO growth and oxidation behavior was discussed using furnace oxidation test results.