Gama absorpsiyon tekniği ile kıymetli metallerin analizi ve değerlendirilmesi

Silver, platinum and gold are described as precious metals; they are most popular jewelry and preferable metals in modern society. In this study, a nuclear technique as namely "Gamma Absorption Technique" is used for the analysis of the three main precious metals. Samples have been supplied for four different silver alloys, four different platinum alloys and five different gold alloys. Am-241 has been used for Ag analysis and Ba-133 gamma radioisotopes has been used for Pt and Au analysis as gamma sources. Experiment device consist of a gamma source, collimator, NaI (Tl) detector, multi-channel analyzer with shielding materials. Experiments repeated at least five times and average net counting rate is calculated.  Calibration curves could be drawn as a result of the experiments. These curves were examined by unknown samples and it was shown the reliability of the curves. The mass attenuation coefficients of alloys were measured. Theoretical mass attenuation coefficient values were obtained using the WinXCom program. The comparison of the experimental results with the theoretical values was in a good and acceptable agreement. Precious metals analysis can be observed and mass attenuation coefficients were determined at near energy of elements K absorption edge. So, it can be offered that the gamma absorption technique can be used for the determination of the mass attenuation coefficients.Keywords: Gamma absorption technique, silver, platinum, gold, mass attenuation coefficient.Bu çalışmada, nükleer bir teknik olan gama absorpsiyon tekniği, kıymetli metallerden gümüş, platin ve altının analizine ilişkin olarak kullanılmıştır. Numuneler; gümüş için dört, platin için dört ve altın için beş farklı ayarda temin edilmiştir. Gama radyoizotop kaynağı olarak gümüş için Am-241, platin ve altın için  Ba-133 radyoizotopları kullanılmıştır. Deneylerden elde edilen sonuçlarla kalibrasyon eğrileri çizilebilmiştir. Bu çalışmanın özgünlüğü çerçevesinde çalışılan numunelerin kütle zayıflatma katsayıları deneysel olarak tayin edilmiştir. Deneysel sonuçlar WinXCom programından elde edilen sayısal sonuçlarla mukayese edilmiş ve birbirleri ile ileri derecede uyum sağladığı gösterilmiştir. Bu şekilde, gama absorpsiyon tekniğinin kütle zayıflatma katsayılarının deneysel olarak tayininde kullanılabileceği önerilmektedir.   Anahtar Kelimeler: Gama absorpsiyon tekniği, gümüş, altın, platin,kütle zayıflatma katsayısı.&nbsp

Investigation and discharge state analysis for narrow water ways with radiation tracing technique

Bu güne kadar ulaşılmış olan yayınların incelenmesi sonucunda literatürde deniz kazaları ve deniz çevre kirliliğinin önemle üzerinde durulduğu ve bu konuda farklı yöntemlerle çalışmalar yapılmış olmasına karşın, nükleer bir teknik olan infrared ölçümleme ile takip şeklinde laboratuvar çalışması biçiminde çalışıldığına ilişkin bir yayına rastlanmamış olup, bu çalışma ile radyasyonla izleme tekniği bağlamında dar deniz yolları için mazotun denize bırakımının, bırakım miktarının farklı olması durumlarında, deneysel olarak incelenmesi amaçlanmıştır. Öte yandan, deniz kazası senaryosu olarak, farklı ve kapsamlı bir uygulama yapılması da hedeflenmiştir. Dolayısı ile, deneysel açıdan inceleme şartları belirli, fakat yine de uygulamada sıkça karşılaşılan çeşitli farklılıkları içeren denize bırakım halleri incelenmiştir. Anahtar Kelimeler: Radyasyon izleme, kızıl ötesi ölçümleme, mazot, dar su yolları, deniz kazası, petrol dökülmesi, gemi kaynaklı kirlilik.In this study, it is primarily aimed, at carrying out experimental research with radiation tracing technique relating on marine casualties. The literature survey is carried out extensively and in this respect it is investigated that wide range of scientific research studies are available in the application field of marine environmental protection. The significance of this study is to analyse the discharge quantities of diesel oil with radiation tracing technique which is not carried out in the previous research studies. The experimental research is designed for the determination of various discharge quantities of diesel oil for narrow water ways utilising radiation tracing technique. Besides the marine accident scenario, different and detailed application is aimed. Hence the experimental investigation conditions are fixed, the various discharge quantities are taken into account that are frequently encountered in real life examples. Experiments are held for ten various discharge quantities of the diesel oil. The results of the experiments are found to be realistic and consistent. Consequently the experimental and mathematical investigations? implementation perspective enables this study to be applied real life applications and offers adequate convergence.Keywords: Radiation tracing, Infrared measurement, diesel oil, narrow water ways, marine casualty, petroleum discharge, ship sourced pollution

Surface salinity determination for the Bosphorous with nuclear technique, a new analytical model and evaluation

İstanbul Boğazı, Türk Boğazlar Sistemini oluşturan Marmara Denizi ve Çanakkale Boğazı’ndan daha özel bir önem taşımaktadır. Karadeniz’den gelen nispeten az tuzlu su üst akış olarak ve Marmara Denizi’nden gelen daha tuzlu su alt akış olarak İstanbul Boğazı boyunca iki katmanlı akışı oluşturmaktadır. Yoğunluk farkından dolayı iki katmanlı akış halinde boğaz boyunca akan tuzlu suda farklı akış rejimlerinden dolayı karışımlar meydana gelmektedir. Önemli bir dar su yolu olan İstanbul Boğazı’nın yüzey tuzluluk değerleri farklı lokasyon ve mevsimlerde nötron aktivasyon analiziyle tayin edilmiştir. Günümüzde çok çeşitli tuzluluk tayin yöntemleri kullanılmakla beraber literatürde, nötron aktivasyon analiziyle tuzluluk tayinine ilişkin bir yayına rastlanmamıştır. Nötron aktivasyon analizi element analizinde sıkça kullanılan bir nükleer teknik durumundadır. Tuzluluk tayini için kullanılan nötron akivasyon analizi yönteminde sodyum konsantrasyonu elde edilerek  tuzluluk değerlerine gidilmiştir. Nötron aktivasyon analizi tuzluluk sonuçlarını kıyaslamak için konvansiyonel bir tuzluluk tayin tekniği olan uçurma yöntemi seçilmiştir. Nötron aktivasyon analizi tuzluluk sonuçlarının uçurma sonuçlarına yakınsadığı gösterilmiştir. Nötron aktivasyon analizi tuzluluk değerleri kullanılarak yere ve zamana bağlı matematik bir model geliştirilmiştir. Bu yeni model İstanbul Boğazı’na özgü parametreleri barındırmaktadır. Deneysel ve matematik model sonuçları FEMLAB 3.1 programında tek boyutlu difüzyon denkleminin çözülmesiyle oluşan simülasyon sonuçlarıyla kıyaslanmıştır. Deneysel ve teorik sonuçların iyi bir uyum içinde olduğu ortaya çıkmıştır. Böylelikle nötron aktivasyon analizi ile deniz suyu tuzluluk tayininin yapılabileceği ve önerilen analitik modelin güvenilirlikle kullanılabileceği gösterilmiştir.Anahtar Kelimeler: İstanbul Boğazı, tuzluluk, Na-24, uçurma yöntem, nötron aktivasyon analizi. Turkish Strait System consists of the Bosphorous, Marmara Sea and Dardanelles. The Bosphorous is the most interesting one because of its strategic role. The Bosphorous is a very important channel in which there are two flows with different salinities. The seawater of Black Sea passes by as the top layer flow and the seawater of Marmara Sea as the bottom layer because of the density difference. For years, the oceanographers work on the Bosphorous two- layer flow. This two-layer flow mixes along the Bosphorous causing salinity dispersion. To have an idea about the surface salinity dispersion, the salinity levels should be determined along the channel. The main aim of the experimental work is to measure the surface salinity level with neutron activation analysis. There are many studies to determine the salinity with different methods which are primarily based on physical and chemical principles. Physical salinity determination methods depend on refractive index, density and electrical conductivity measurements. On the other hand chemical methods are based on chlorinity determination. Beyond the physical and chemical methods there are alternative salinity measuring systems as well. These can be called as  "alternative methods". In this study for the salinity determination, neutron activation analysis has been chosen as the experimental method but in the literature there is no study that deals with salinity determination by neutron activation analysis. Neutron activation analysis is a nuclear technique that has widely been used for the element analysis. In neutron activation analysis the sample is irradiated and the isotopes of the mother elemental is formed. The activated samples are usually gamma-active and detecting the gamma rays, the concentration and the element identification can be performed Neutron activation analysis can be named as the "new alternative method for salinity measurement". Initially, surface salinity of the Bosphorous was determined by the neutron activation analysis. On the other hand. evaporation technique which is a routine salinity determination method has been chosen. From the specified sample locations along the Bosphorous, the seawater samples have been collected and stored in polymer bottles. In order to determine the salinity of the samples, small amounts of samples were prepared. First of all, the water of the small samples about 100 cc. were evaporated and from the salt remaining after the water evaporation, again small samples have been prepared for the irradiation. The Bosphorous samples were irradiated with a reference salt sample. The salinity of the Bosphorous samples were determined with an equation which allows a  comparison of the reference results with those of the irradiated samples. The results of neutron activation analysis have been compared with those of evaporation and literature. Neutron activation analysis results were in good accuracy with those of evaporation and the literature. With the neutron activation analysis results, a model which depends on position and time has been offered. The offered model was a product of two independent functions. The function depending on the position is an exponential and the time dependent one is a sinusoid. The parameters of the independent functions have been determined by neutron activation salinity results. They have been compared with those of evaporation. The model results were in good agreement with the evaporation ones. A theoretical comparison has also been chosen to be done with the results of neutron activation analysis which have been compared in many ways. For this comparison, a widely used computer programme. FEMLAB 3.1 (Finite Element Method Laboratory). has been selected. This programme has widely been used in many different studies where finite element method is valid. The suitable geometry for the Bosphorous has been formed and one dimensional diffusion equation has also been solved with the parameters of the Bosphorous. The values obtained from one dimensional diffusion equation that has been solved for the Bosphorous have been used in comparison with those of neutron activation analysis, evaporation and the  mathematical model  and it has been concluded that neutron activation results have been  in good accuracy with those of the programme. It is also concluded that neutron activation analysis can be used to determine the salinity and mathematical model as well in relevance. A different study has been done in terms of the experimental work and the analytical model. Keywords: Bosphorous, salinity, Na-24, evaporation method, neutron activation analysis

Dosimetric evaluation of gamma doses using irradiated lead-alkali-silicate glass

Kurşun-alakali-silika cam örnekleri 1-36 kGy arasında ışınlanarak, gama radyasyonuna maruz bırakılmıştır. Bu çalışmada, gama ışın kaynağı olarak, Co-60 radyoizotop kaynak kullanılmıştır. Gama ışınlarına maruz kalmış kurşun-alkali-silika camların, soğurduğu doz seviyesine bağlı olarak, renklerinin giderek koyulaştığı belirlenmiştir. Kurşun-alkali-silika cam yapının radyasyonla uyartılması sonucu, bu camların, görünür bölgedeki, geçirgenlik, yansıtıcılık ve soğurma değerlerinin değiştiği tespit edilmiştir. Optik özelliklerdeki değişimlerin incelenmesi, elektromanyetik spektrumun, 380-1500 nm dalgaboyu aralığına düşen bölgesinde yapılmıştır. Işınlanmış camlar ile ışınlanmamış camların optik parametrelerinde meydana gelen değişimler karşılaştırılarak, farklı doz seviyelerinde ışınlanan, kurşun-alkali-silika camlarının, dozimetre olarak kullanılabilirliği incelenmiştir. Anahtar kelimeler: Cam dozimetreler, dozimetri, kurşun-alkali-silika cam, soğurulan doz.Dosimetric evaluation is important especially at the high dose levels. Glass dosimeters are used in dosimetry in several high-level exposure applications, employing mainly spectrophotometric or densitometric analysis of colour-center formation. The chemical composition of lead-alkali-silicate glass was determined using a wavelength dispersive X-ray fluorescence spectrometer. The balance between the ionic forms of the glass impurity atoms, which are transition metals, determines the glass colour to the transition elements ferric iron, titanium and nickel, and post transition elements like antimony. The radiation-induced absorption in the visible spectral region in Pb-containing glasses undergoes rapid thermal and optical bleaching, provided the glass does not contain alkali ions. The addition of just a few percent alkali ions stabilises the absorption. Lead-alkali-silicate glass samples were irradiated with 1-36 kGy dose levels using a Co-60 radioisotope source. The colour of the lead-alkali-silicate glass turned to brownish orange with absorbed dose. Radiation-induced changes in the properties of visible light transmittance and absorbance were examined between wavelengths of 380 and 1500 nm using a spectrophotometer. Changes in the optical density were determined and compared with those of unexposed glasses. The optical density was investigated for different dose levels in this study. The optical density curves indicated the strong radiation induced absorption in a band around 700 nm wavelength. Keywords: Absorbed dose, dosimetry, glass dosimeter, lead-alkali-silicate glass

Ramulator 2.0: A Modern, Modular, and Extensible DRAM Simulator

We present Ramulator 2.0, a highly modular and extensible DRAM simulator that enables rapid and agile implementation and evaluation of design changes in the memory controller and DRAM to meet the increasing research effort in improving the performance, security, and reliability of memory systems. Ramulator 2.0 abstracts and models key components in a DRAM-based memory system and their interactions into shared interfaces and independent implementations. Doing so enables easy modification and extension of the modeled functions of the memory controller and DRAM in Ramulator 2.0. The DRAM specification syntax of Ramulator 2.0 is concise and human-readable, facilitating easy modifications and extensions. Ramulator 2.0 implements a library of reusable templated lambda functions to model the functionalities of DRAM commands to simplify the implementation of new DRAM standards, including DDR5, LPDDR5, HBM3, and GDDR6. We showcase Ramulator 2.0's modularity and extensibility by implementing and evaluating a wide variety of RowHammer mitigation techniques that require different memory controller design changes. These techniques are added modularly as separate implementations without changing any code in the baseline memory controller implementation. Ramulator 2.0 is rigorously validated and maintains a fast simulation speed compared to existing cycle-accurate DRAM simulators. Ramulator 2.0 is open-sourced under the permissive MIT license at https://github.com/CMU-SAFARI/ramulator

Stress distribution in masonry infills connected with stiff and flexible interface

Masonry infills are largely used in RC structures for various purposes, and in seismic zones, they are also preferred for providing earthquake resistant systems. However, due to the rigid connection between infills and RC frames, these systems are vulnerable when large deformations are demanded. Cyclic loads that are occurring during seismic excitations cause stress concentration level to increase, particularly in frame-infill contact zones. As a result of stress increment, infill panels get weaker in terms of both in-plane and out-of-plane resistance. These drawbacks cause loss of lives and properties, thus affecting governments and societies adversely. In order to overcome this obstacle, an innovative solution is proposed which uses flexible polymers (Polyurethane PM) as joint elements for protecting the structural elements. The research is focused on numerical analyses of three types of frames with masonry infills, which are excited through both in-plane and out-of-plane directions by different earthquake records. Infill walls are connected to the frames in three manners: stiffly (classical approach), with flexible joints at 3-boundaries and with flexible joints at 4-boundaries. Differences in calculated stress distribution as well as some other linear and non-linear results are presented and discussed. The primary results give promising outcomes that this new method might be used in seismic zones for protecting structures

The Evaporative Stress Index as an indicator of agricultural drought in Brazil: An assessment based on crop yield impacts

To effectively meet growing food demands, the global agronomic community will require a better understanding of factors that are currently limiting crop yields and where production can be viably expanded with minimal environmental consequences. Remote sensing can inform these analyses, providing valuable spatiotemporal information about yield-limiting moisture conditions and crop response under current climate conditions. In this paper we study correlations for the period 2003-2013 between yield estimates for major crops grown in Brazil and the Evaporative Stress Index (ESI) - an indicator of agricultural drought that describes anomalies in the actual/reference evapotranspiration (ET) ratio, retrieved using remotely sensed inputs of land surface temperature (LST) and leaf area index (LAI). The strength and timing of peak ESI-yield correlations are compared with results using remotely sensed anomalies in water supply (rainfall from the Tropical Rainfall Mapping Mission; TRMM) and biomass accumulation (LAI from the Moderate Resolution Imaging Spectroradiometer; MODIS). Correlation patterns were generally similar between all indices, both spatially and temporally, with the strongest correlations found in the south and northeast where severe flash droughts have occurred over the past decade, and where yield variability was the highest. Peak correlations tended to occur during sensitive crop growth stages. At the state scale, the ESI provided higher yield correlations for most crops and regions in comparison with TRMM and LAI anomalies. Using finer scale yield estimates reported at the municipality level, ESI correlations with soybean yields peaked higher and earlier by 10 to 25 days in comparison to TRMM and LAI, respectively. In most states, TRMM peak correlations were marginally higher on average with municipality-level annual corn yield estimates, although these estimates do not distinguish between primary and late season harvests. A notable exception occurred in the northeastern state of Bahia, where the ESI better captured effects of rapid cycling of moisture conditions on corn yields during a series of flash drought events. The results demonstrate that for monitoring agricultural drought in Brazil, value is added by combining LAI with LST indicators within a physically based model of crop water use. Published by Elsevier Inc.Embrapa Visiting Scientist Program ; Labex US, an international scientific cooperation program - Brazilian Agricultural Research Corporation - Embrapa, ; United States Department of Agriculture (USDA

DRAM Bender: An Extensible and Versatile FPGA-based Infrastructure to Easily Test State-of-the-art DRAM Chips

To understand and improve DRAM performance, reliability, security and energy efficiency, prior works study characteristics of commodity DRAM chips. Unfortunately, state-of-the-art open source infrastructures capable of conducting such studies are obsolete, poorly supported, or difficult to use, or their inflexibility limit the types of studies they can conduct. We propose DRAM Bender, a new FPGA-based infrastructure that enables experimental studies on state-of-the-art DRAM chips. DRAM Bender offers three key features at the same time. First, DRAM Bender enables directly interfacing with a DRAM chip through its low-level interface. This allows users to issue DRAM commands in arbitrary order and with finer-grained time intervals compared to other open source infrastructures. Second, DRAM Bender exposes easy-to-use C++ and Python programming interfaces, allowing users to quickly and easily develop different types of DRAM experiments. Third, DRAM Bender is easily extensible. The modular design of DRAM Bender allows extending it to (i) support existing and emerging DRAM interfaces, and (ii) run on new commercial or custom FPGA boards with little effort. To demonstrate that DRAM Bender is a versatile infrastructure, we conduct three case studies, two of which lead to new observations about the DRAM RowHammer vulnerability. In particular, we show that data patterns supported by DRAM Bender uncovers a larger set of bit-flips on a victim row compared to the data patterns commonly used by prior work. We demonstrate the extensibility of DRAM Bender by implementing it on five different FPGAs with DDR4 and DDR3 support. DRAM Bender is freely and openly available at https://github.com/CMU-SAFARI/DRAM-Bender.Comment: To appear in TCAD 202

RowPress: Amplifying Read Disturbance in Modern DRAM Chips

Memory isolation is critical for system reliability, security, and safety. Unfortunately, read disturbance can break memory isolation in modern DRAM chips. For example, RowHammer is a well-studied read-disturb phenomenon where repeatedly opening and closing (i.e., hammering) a DRAM row many times causes bitflips in physically nearby rows. This paper experimentally demonstrates and analyzes another widespread read-disturb phenomenon, RowPress, in real DDR4 DRAM chips. RowPress breaks memory isolation by keeping a DRAM row open for a long period of time, which disturbs physically nearby rows enough to cause bitflips. We show that RowPress amplifies DRAM's vulnerability to read-disturb attacks by significantly reducing the number of row activations needed to induce a bitflip by one to two orders of magnitude under realistic conditions. In extreme cases, RowPress induces bitflips in a DRAM row when an adjacent row is activated only once. Our detailed characterization of 164 real DDR4 DRAM chips shows that RowPress 1) affects chips from all three major DRAM manufacturers, 2) gets worse as DRAM technology scales down to smaller node sizes, and 3) affects a different set of DRAM cells from RowHammer and behaves differently from RowHammer as temperature and access pattern changes. We demonstrate in a real DDR4-based system with RowHammer protection that 1) a user-level program induces bitflips by leveraging RowPress while conventional RowHammer cannot do so, and 2) a memory controller that adaptively keeps the DRAM row open for a longer period of time based on access pattern can facilitate RowPress-based attacks. To prevent bitflips due to RowPress, we describe and evaluate a new methodology that adapts existing RowHammer mitigation techniques to also mitigate RowPress with low additional performance overhead. We open source all our code and data to facilitate future research on RowPress.Comment: Extended version of the paper "RowPress: Amplifying Read Disturbance in Modern DRAM Chips" at the 50th Annual International Symposium on Computer Architecture (ISCA), 202

TuRaN: True Random Number Generation Using Supply Voltage Underscaling in SRAMs

Prior works propose SRAM-based TRNGs that extract entropy from SRAM arrays. SRAM arrays are widely used in a majority of specialized or general-purpose chips that perform the computation to store data inside the chip. Thus, SRAM-based TRNGs present a low-cost alternative to dedicated hardware TRNGs. However, existing SRAM-based TRNGs suffer from 1) low TRNG throughput, 2) high energy consumption, 3) high TRNG latency, and 4) the inability to generate true random numbers continuously, which limits the application space of SRAM-based TRNGs. Our goal in this paper is to design an SRAM-based TRNG that overcomes these four key limitations and thus, extends the application space of SRAM-based TRNGs. To this end, we propose TuRaN, a new high-throughput, energy-efficient, and low-latency SRAM-based TRNG that can sustain continuous operation. TuRaN leverages the key observation that accessing SRAM cells results in random access failures when the supply voltage is reduced below the manufacturer-recommended supply voltage. TuRaN generates random numbers at high throughput by repeatedly accessing SRAM cells with reduced supply voltage and post-processing the resulting random faults using the SHA-256 hash function. To demonstrate the feasibility of TuRaN, we conduct SPICE simulations on different process nodes and analyze the potential of access failure for use as an entropy source. We verify and support our simulation results by conducting real-world experiments on two commercial off-the-shelf FPGA boards. We evaluate the quality of the random numbers generated by TuRaN using the widely-adopted NIST standard randomness tests and observe that TuRaN passes all tests. TuRaN generates true random numbers with (i) an average (maximum) throughput of 1.6Gbps (1.812Gbps), (ii) 0.11nJ/bit energy consumption, and (iii) 278.46us latency