Thermogravimetric Analysis Apparatus Research Articles

Thermal Decomposition and Kinetic Parameters of Three Biomass Feedstocks for the Performance of the Gasification Process Using a Thermogravimetric Analyzer

Thermogravimetric analysis (TGA) is a powerful technique and useful method for characterizing biomass as a non-conventional fuel. A TGA apparatus has been utilized to experimentally investigate the impact of biomass feedstock diversity on the performance of the gasification of hardwood (HW), softwood (SW) pellets, and refuse-derived fuel (RDF) materials. The solid conversion rate and the volatile species formation rate have been estimated to quantify the rates of devolatilization for each material. In addition, the combustion kinetic characteristics of the three biomass feedstocks were investigated using TGA at different heating rates, and a thermal kinetic analysis was conducted to describe the gasification process. Therefore, the kinetic parameters have been evaluated for different thermal reactions and non-isothermal kinetic models that depend on the relationships between heating rates and temperature profiles. The results show that the amount of tar content from the RDF was higher than that of pure hardwood and softwood feedstocks. Hence, tar removal must be part of any process using syngas produced from RDF feedstocks in a gas engine to produce electricity.

Designing porous C/C composites for oxidation resistance with an analytical model based on the kinetic and architectural features of fibers and matrix

Carbon/Carbon composites used in rocket propulsion contain many process-related pores and have a porosity-dependent oxidation recession rate. A 1D analytical model has been developed to describe this behavior and assess the structure-reactivity relationship for the oxidation of such composites. The model has been compared to experiments for validation. Oxidation experiments have been carried out using samples featuring individually different matrix fractions in a thermogravimetric analysis apparatus under dry air. Post-test morphologies were characterized with X-ray micro-computerized tomography and a 3D-image correlation technique. Finally, guidelines are given for the design and optimization of porous C/C composites with respect to oxidation resistance.

Thermal Adsorption and Mechanical Behaviour of Polypropylene Hybrid Composite Synthesized by Glass/Hemp Fibre via an Injection Moulding Process

Thermoplastic-based polymers are gathering importance in several engineering fields like electrical, electronic, automotive, aerospace, and structural. The additions of secondary phase reinforcements such as natural and synthetic fibre improve thermoplastic-based polymer’s properties. The thermoplastic and natural fibre combinations are found to have low mechanical strength and incompatibility and need special treatment for synthesizing the natural fibre. The present experimental investigation deals with the enhancement of polypropylene hybrid composite by using the combinations of glass (synthetic)/hemp (natural) fibre for the ratio of 0 : 35, 5 : 30, 10 : 25, and 15 : 20 reinforced with 5 wt% compatibilizer through injection moulding. The revealed test results of polypropylene hybrid composite showed improved mechanical impact and flexural and tensile strength of 37.5%, 14.2%, and 21.1%, respectively. The thermal adsorption characteristics were evaluated by thermogravimetric analysis apparatus. It showed the decomposition of composite limited by hemp fibre at 27°C to 700°C.

Oxidation kinetics of SPS-densified U3Si2 fuels—Microstructure impact

U3Si2 is a potential candidate for accident tolerant fuels because of its high uranium density and excellent thermal conductivity in comparison to UO2. However, U3Si2 suffers from oxidation, steam corrosion, and subsequent disintegration/pulverization. The detailed investigation of kinetics that incorporates fundamental treatment of oxidation of U3Si2 is scarcely reported, and the oxidation mechanisms have not been fully elucidated. In this paper, the oxidation behavior of microcrystalline (mc-) and nanocrystalline (nc-) U3Si2 have been systematically investigated using a thermogravimetric analysis (TGA) apparatus through a series of isothermal and non-isothermal kinetic studies. The isothermal kinetic study with a model-fitting approach indicates oxidation activation energy of 85 kJ/mol for dense mc-U3Si2 and 96.4 kJ/mol for nc-U3Si2 pellets, while the isoconversional approach leads to an activation energy in the range of 70–85 kJ/mol for mc-U3Si2 and 75–86 kJ/mol for nc-U3Si2 with three most common model-free methods, including Kissinger–Akahira–Sunose, Flynn–Wall–Ozawa, and Friedman methods. The derivation of oxidation activation energies using both isothermal and isoconversional methods highlights the approach to evaluate the oxidation resistance of nuclear materials using TGA quantitatively and makes it possible to compare among various nuclear fuels.

DETERMINATION OF THE SUITABILITY OF OIL PALM FIBRE COMPOSITE FOR BUILDING APPLICATIONS BY CONE CALORIMETER AND THERMAL ANALYSIS

The high yielding of oil pam fibre reinforced composite (OPFC) to fire has necessitated research to improve and develop fire retardants (FR) to mitigate the spread of fire. Researchers relied on Flame Retardants (FR) classified as either halogenated or non-halogenated based FR to improve the performance of composites with emphasis on flammability properties (FP). The main object of this paper is to evaluate the effect of six non-halogenated FR species in OPFC to meet required fire safety standards for building purposes. The six FR species comprising aluminum tri-hydroxide (ATH), ammonium polyphosphate (APP), Gum Arabic powder (GAP) and carbon black (CB) were processed with OPFC at 0, 15 and 18% loading ratio using hand lay-up compression moulding technique. Specimens cut from the OPFC panels were tested for flammability and thermal properties using thermogravimetric analysis (TGA/DSC Metlar Toledo) and cone calorimeter apparatus respectively. The result obtained for thermal analysis shows that the panel was thermally stable at 391.6OC before degradation began compared to those without FR while peak flammability properties obtained for heat released rates, mass loss rates and smoke production rates showed the OPFC panels rapid fire response were significantly reduced respectively by 67.4%, 50.9% and 37.5% compared to those without FR. It can be concluded that the hybrid FR comprising APP-GAP showed a stable char structure during fire and thus prevented the escape of combustible volatiles which reduced the peak FP values of the OPFC panels. These flammability properties could be said to meet required fire safety standards for building applications.

Structural integrity of calcium hydroxide granule bulks for thermochemical energy storage

Thermochemical energy storage using the gas-solid reaction of calcium oxide with water vapour is a promising approach especially for high-capacity applications such as CSP. Current research is mainly concerned with lowering reactor cost and therefore concentrating on dynamic systems with granules instead of powder as solid storage material. As stresses affecting the structural integrity of the granules increase with increasing bulk size, small samples as used for thermogravimetric analysis (TGA) might underestimate their impact on granule stability. This work complements existing literature on granule stability by experiments at bulk scale: two shaped granule samples and two ceramic encapsulated granule samples as well as a reference powder were cycled in a lab-scale reactor as well as within a TGA apparatus. Even though preservation of the granule structure was observed after cycling within the TGA apparatus, crushing strength measurements already indicated a decrease of mechanical stability of 81–88% for the shaped granules and 6–11% for the encapsulated granules. As a consequence, structural integrity of the granule bulk was only preserved in case of partial hydration. Given high reactivity, the granule structure – shaped and encapsulated – was destroyed after the first hydration causing a bulk volume expansion of up to a factor of 2.5. Reaction behaviour of the reference powder was consistent despite formation of cm-sized agglomerates. This work confirms that reaction conditions within a bulk are more challenging regarding structural integrity of storage material granules due to greater stresses acting on the single granule. These stresses can be significantly reduced by partial hydration.

Alkali Treatment Effect: Mechanical, Thermal, Morphological, and Spectroscopy Studies on Abutilon Indicum Fiber-Reinforced Composites

ABSTRACT Applicability of natural fiber-reinforced composites in automobile, aerospace like sectors has been increasing as more number of research works is concentrating on natural fibers owing to their eco-friendly nature. Biodegradability of natural fibers is main advantage of them over artificial fibers. Natural fiber-reinforced composite possesses good thermal and mechanical properties besides other requirements. For this reason, investigation of one such natural fiber-reinforced composites has been the focus of the present study. In the present work, composites made up of abutilon indicum fiber reinforced with epoxy have been prepared. Mechanical, morphological, thermal, and spectroscopic studies on the test specimens prepared using the above composites were carried out to evaluate their respective strengths. Also, the effect of alkali treatment (NaOH) for the fibers was studied and evaluated. Scanning electron microscope results indicated that the composite made up of alkali-treated fibers possessed better mechanical properties. Using differential thermal analysis–thermogravimetric analysis apparatus thermal behavior of the composites and using Fourier transform infrared spectroscopic studies, the presence of function groups like C–O, C–H was determined. Thus, characterization of abutilon indicum fiber-reinforced epoxy composites has been carried and properties are evaluated for their applicability to automotive, aerospace similar industries.

Development of novel method for quantitative determination of carbon chemical reactivity

AbstractThe coke reactivity index (CRI) measurement determined with the ASTM standard is affected by both the chemical and physical properties of the coke. The contribution made by each of these factors to the measurement result cannot be easily distinguished and quantified. A new thermogravimetric analysis (TGA) technique was developed to provide further information about the chemical behaviour of the coke to facilitate an improved interpretation of the CRI measurement. The development of the technique takes into consideration the potential change in reaction rate controlling mechanism in TGA equipment. It makes use of the shrinking core model to identify the reaction rate control regime and to extract reaction rate parameters from experimental measurement. A rigorous data processing procedure was developed to ensure consistent interpretation of the measurement data while repeatability was established through measurement repetition. The sensitivity of common variable factors between different TGA apparatus on measurement results was also examined. It was demonstrated that the measurement results of this new technique are highly repeatable and reproducible.

Molten salt chemistry in nitrate salt storage systems: Linking experiments and modeling

Sensible heat storage in molten nitrate salts is a key technology when it comes to thermal energy storage in combination with concentrating solar power (CSP) plants. Currently, a mixture of sodium and potassium nitrate called Solar Salt is used at temperatures between 280 and 560 °C. Our research approaches comprise an improvement of Solar Salt stability at temperatures above 560 °C, which comes along with a broadening of the operating temperature range. In this way, a higher storage capacity and efficiency, as well as economic advances can be achieved. Numerous publications about the chemistry of molten nitrate salt mixtures reveal the formation of chemical species such as nitrite ions, nitrous gases and oxide ions and carbonate ions. Among these, the reversible reaction of nitrate to nitrite with release of oxygen is the predominant reaction at temperatures below 560 °C. So far, there is a lack of literature that pays particular attention on the contributions of reaction kinetics and mass transport effects on the reaction velocity of the nitrate/nitrite-reaction. However, understanding of these physico-chemical phenomena is essential, because further decomposition reactions build on the nitrate/nitrite-reaction. In this study, experiments at different scales (50 mg to 100 g) are compared with regard to the reduction reaction velocity at 500 °C. A data treatment procedure for thermogravimetric analysis experiments successfully eliminates effects of salt evaporation on the measured mass changes. The chemical equilibrium of the salt samples turned out to be reasonable, when compared to literature values. It was found, that the surface-to-volume ratio of the salt melt samples significantly affects the evaporation rates and the reaction velocity. The time period that is needed until chemical equilibrium is reached at 500 °C clearly increases when the surface-to-volume ratio decreases. The thermogravimetric analysis apparatus enables experiments, which measure reaction kinetics without mass transport limitations. It is demonstrated that a simulation model adapted from literature displays a reaction velocity that incorporates both reaction kinetics and mass transport without differentiation of the two phenomena.

Thermal performance and reduction kinetic analysis of cold-bonded pellets with CO and H2 mixtures

Cold-bonded pellets, to which a new type of inorganic binder was applied, were reduced by H2–CO mixtures with different H2/CO molar ratios (1:0, 5:2, 1:1, 2:5, and 0:1) under various temperatures (1023, 1123, 1223, 1323, and 1423 K) in a thermogravimetric analysis apparatus. The effects of gas composition, temperature, and binder ratio on the reduction process were studied, and the microstructure of reduced pellets was observed by scanning electron microscopy–energy-dispersive spectrometry (SEM-EDS). The SEM-EDS images show that binder particles exist in pellets in two forms, and the form that binder particles completely surround ore particles has a more significant hinder effect on the reduction. The reduction equilibrium constant, effective diffusion coefficient, and the reaction rate constant were calculated on the basis of the unreacted core model, and the promotion effect of temperature on reduction was further analyzed. The results show that no sintering phenomenon occurred at low temperatures and that the increasing reaction rate constant and high gas diffusion coefficient could maintain the promotion effect of temperature; however, when the sintering phenomenon occurs at high temperatures, gas diffusion is hindered and the promotion effect is diminished. The contribution of the overall equilibrium constant to the promotion effect depends on the gas composition.

Upgrading pyrolytic residue from waste tires to commercial carbon black

The managing and recycling of waste tires has become a worldwide environmental challenge. Among the different disposal methods for waste tires, pyrolysis is regarded as a promising route. How to effectively enhance the added value of pyrolytic residue (PR) from waste tires is a matter of great concern. In this study, the PRs were treated with hydrochloric and hydrofluoric acids in turn under ultrasonic waves. The removal efficiency for the ash and sulfur was investigated. The pyrolytic carbon black (PCB) obtained after treating PR with acids was analyzed by X-ray fluorescence spectrophotometry, Fourier transform infrared spectrometry, X-ray diffractometry, laser Raman spectrometry, scanning electron microscopy, thermogravimetric (TG) analysis, and physisorption apparatus. The properties of PCB were compared with those of commercial carbon black (CCB) N326 and N339. Results showed PRs from waste tires were mainly composed of carbon, sulfur, and ash. The carbon in PCB was mainly from the CCB added during tire manufacture rather than from the pyrolysis of pure rubbers. The removal percentages for the ash and sulfur of PR are 98.33% (from 13.98 wt % down to 0.24 wt %) and 70.16% (from 1.81 wt % down to 0.54 wt %), respectively, in the entire process. The ash was mainly composed of metal oxides, sulfides, and silica. The surface properties, porosity, and morphology of the PCB were all close to those of N326. Therefore, PCB will be a potential alternative of N326 and reused in tire manufacture. This route successfully upgrades PR from waste tires to the high value-added CCB and greatly increases the overall efficiency of the waste tire pyrolysis industry.

Experimental Studies and Modeling of the Drying Kinetics of Multicomponent Polymer Films

The process of drying thin polymer films is an important operation that influences the film structure and solid state, and the stability of the product. The purpose of this work was to study and model the drying kinetics of multicomponent films based on two polymers: hydroxypropyl methylcellulose (HPMC, amorphous) and polyvinyl alcohol (PVA, semicrystalline). The isothermal drying kinetics of the films at different temperatures (40, 60, and 80°C) were studied using thermo-gravimetric analysis (TGA) and convection oven methods. Solid-state characterization tools used in the study included polarization and hot-stage microscopy, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The drying kinetics of HPMC and PVA films in the TGA apparatus and convection oven were comparable. The three-parameter (Wmax, τ, n) Hill equation successfully modeled the experimental drying kinetics. The time factor τ in the Hill equation nicely explained two drying phases in the films. Solid-state phase changes occurring in the films during dehydration had a bearing on the drying kinetics and mechanisms. TGA can be used as a simple tool to determine the end points in drying processes using ovens or tunnels. The three-parameter Hill equation explained the drying kinetics and diffusion mechanisms of the solvent through the polymer films for the first time. This study advances our understanding of film drying, in particular for pharmaceutically relevant thin films.

Experimental and Theoretical Study of the Interactions between Fe2O3/Al2O3 and CO

The behavior of Fe2O3/Al2O3 particles as oxygen carriers (OCs) for CO chemical looping combustion (CLC) under different reaction temperatures (700 °C, 800 °C, 900 °C, and 1000 °C) were tested in a lab-scale fluidized bed and a thermogravimetric analysis (TGA) unit. The results show that the oxygen carrier presents the highest reactivity at 800 °C, even after 30 cycles of redox reaction in a fluidized bed, while more obvious carbon deposition occurred for the case at 700 °C, and agglomeration for the case at 1000 °C. Moreover, the detailed behavior of the prepared Fe2O3/Al2O3 particle was detected in the TGA apparatus at different reaction temperatures. Furthermore, temperature-programming TGA experiments were performed to investigate the influence of different CO concentrations and CO/CO2 concentrations on the reaction between CO and OC during the chemical looping combustion processes. Based on these experimental behaviors of the prepared Fe2O3/Al2O3 during the CLC of CO, the detailed models and electronic properties of the pure and reduced Fe2O3/Al2O3 supported the slabs, CO adsorption, and oxidation, and the decomposition reactions on these surfaces were revealed using density functional theory (DFT) calculations which went deep into the nature of the synergetic effect of the support of Al2O3 on the activity of Fe2O3 for the CLC of CO.

Hydrothermal synthesis and mechanism of triangular prism-like monocrystalline CeO2 nanotubes via a facile template-free hydrothermal route

Monocrystalline CeO2 tablet-like nanostructures and triangular prism-like nanotubes were synthesized by thermal conversion of cerium carbonate hydroxide (CeOHCO3) precursors prepared by a simple template-free hydrothermal method using Ce(NO3)3·6H2O as cerium source, CO(NH2)2 as both precipitator and carbon source and polyvinylpyrrolidone (PVP) as surfactant. X-ray diffractometer (XRD) images inferred that the as-synthesized Ce(CO3)(OH) has a hexagonal structure, and the CeO2 obtained by calcining the Ce(CO3)(OH) at 500°C for 5h has a cubic fluorite structure. Scanning electron microscope (SEM) was employed to reveal the transformation from tablet-like to triangular prism-like structures, and then to triangular prism-like nanotubes with the increase of temperature from 120 up to 200°C. Monocrystalline structure was revealed by high resolution transmission electron microscope (HRTEM) and select area electron diffraction (SAED) patterns. The thermal decomposition process of the as-synthesized Ce(CO3)(OH) was investigated by thermo-gravimetric differential thermal analysis (TG–DTA) apparatus, and the possible formation mechanism of CeO2 has been discussed. The spectral properties were characterized by Fourier transform infrared spectrum (FT-IR), Raman scattering, Photoluminescence (PL) spectra and UV–vis spectroscopy. There is a red-shifting in the band gap of the material compared to bulk one, which is mainly attributed to the influences of the Ce3+ ions, oxygen vacancies and the change of morphology.

High temperature oxidation behaviour of nanostructured cermet coatings in a mixed CO2 – O2 environment

Nanostructured ceramic-metallic (cermet) coatings composed of nanosized ceramic particles (α-Al2O3 and TiO2) dispersed in a nickel matrix were co-electrodeposited and then oxidized at 500°C, 600°C and 700°C in a mixed gas using a Thermo-gravimetric Analysis (TGA) apparatus. The mixed gas was composed of 15% CO2, 10% O2 and 75% N2. This research investigates the effects of CO2 and O2 partial pressures on time-depended oxidation rates for coatings and compared them to the results from atmospheric oxidation under similar temperatures. The increase in partial pressure of oxygen due to the presence of CO2 at each tested temperature was calculated and correlated to the oxidation rate of the coatings. The results showed that the presence of CO2 in the system increased the oxidation rate of cermet coatings when compared to atmospheric oxidation at the same temperature. It was also shown that the increase in the oxidation rate is not the result of CO2 acting as the primary oxidant but as a secondary oxidant which results in an increase of the total partial pressure of oxygen and consequently higher oxidation rates. The WDS and XRD analyses results showed that the presence of nanosized TiO2 particles in a nickel matrix can improve oxidation behaviour of the coatings by formation of Ni-Ti compounds on oxidizing surface of the coating which was found beneficiary in reducing the oxidation rates for cermet coatings.

Human collagen-based multilayer scaffolds for tendon-to-bone interface tissue engineering

The natural tendon-to-bone region has a gradient in structure and composition, which is translated into a spatial variation of chemical, physical, and biological properties. This unique transitional tissue between bone and tendon is not normally recreated during natural bone-to-tendon healing. In this study, we have developed a human collagen-based multilayer scaffold mimicking the tendon-to-bone region. The scaffold consists of four different layers with the following composition gradient: (a) a tendon layer composed of collagen; (b) an uncalcified fibrocartilage layer composed of collagen and chondroitin sulfate; (c) a calcified fibrocartilage layer composed of collagen and less apatite; (d) a bone layer composed of collagen and apatite. The chemical, physical, and mechanical properties of the scaffold were characterized by a scanning electron microscope, porosimeter, universal tensile machine, Fourier transform infrared spectrometer, energy dispersive X-ray analysis apparatus, and thermogravimetric analysis apparatus. The multilayer scaffold provided a gradual transition of the physical, chemical, and mechanical environment and supported the adhesion and proliferation of human fibroblasts, chondrocytes, and osteoblasts toward each corresponding matrix. Overall, our results suggest the feasibility of a human collagen-based multilayer scaffold for regeneration of hard-to-soft interface tissues.

Reduction and Oxidation Kinetics of a CaMn0.9Mg0.1O3−δOxygen Carrier for Chemical-Looping Combustion

The objective of this study was to establish the reaction kinetics involved in redox cycles of the CaMn0.9Mg0.1O3−δ material to be used as an oxygen carrier in the chemical-looping-combustion process. The oxygen-transport capacity and reactivity of this material during consecutive reduction and oxidation steps with gaseous compounds (CH4, H2, CO, and O2) were studied in a thermogravimetric analysis apparatus. The oxygen uncoupling properties of this material were also analyzed. It was found that material reactivity increased with the number of redox cycles, whereas the oxygen-transport capacity decreased with the cycle number until it was stabilized or “activated”. Conversion versus time curves at different temperatures (973–1273 K) and reacting gas concentrations (5–60 vol %) were used for kinetic determination. The grain model with control by chemical reaction and diffusion through the product layer was used to obtain the kinetic parameters for fresh and “activated” particles.

마그네슘 분진의 열분해 및 발화온도 특성

본 연구에서는 Mg분진의 분진입경과 승온속도에 따른 열분해 및 발화온도 특성을 실험적으로 조사하였다. 이를 위해 시료는 평균 입경이 서로 다른 38, 142, <TEX>$567{\mu}m$</TEX>의 Mg분진을 사용하였다. 실험에서는 열중량분석장치(TGA)와 IEC 61241-2-1규격에 따라 제작한 자연발화온도(MIT) 실험장치를 사용하여 실시하였다. 실험 결과 퇴적 Mg에 있어서 공기중 승온속도가 증가하면 중량개시온도는 증가하였으며, 동일한 승온속도 조건에서 입경의 증가는 발화온도의 증가로 나타났다. 또한 부유 Mg분진의 최저발화온도(MIT)는 평균 입경이 증가할수록 증가하는 경향을 보였다. The study was conducted experimentally on characteristic of thermal decomposition and minimum ignition temperature of magnesium dusts. For this purpose, three different Mg dusts of mean diameter (38, 142, <TEX>$567{\mu}m$</TEX>) were used. Experimental investigations were conducted by using TGA(Thermo gravimetric analysis) and MIT(Minimum Ignition Temperature) apparatus made in accordance with IEC 61241-2-1 standard. As the results, temperature of weight gain in Mg dust layers increased with increasing of heating rates in air and, under the same heating rate condition, minimum ignition temperature increased with particle size. Also the MIT of suspended Mg dust clouds tended to increase with increasing of mean diameter.

Facile synthesis and performances of PEG/SiO2 composite form-stable phase change materials

A facile route based on ultrasound-assisted sol–gel method has been developed and applied to rapid synthesis of polyethylene glycol (PEG)/silicon dioxide (SiO2) composite form-stable phase change materials (PCMs) without co-solvent and surfactant. This method was carried out under ultrasonic power of 300W using HCl and Na2CO3 as the acidic and alkaline catalyst, respectively. The temperature is below 50°C. The PCMs were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC) and thermogravimetric analysis apparatus (TGA) measurements. The PCMs display low density, high volume energy density, excellent form-stable effect, good phase-change and temperature control performance, which are very important for the actual application of PCMs in energy-saving construction materials.

Steam-Enhanced Calcium Looping Cycles with Calcium Aluminate Pellets Doped with Bromides

This study explores the effect of calcium bromide (CaBr2) doping of lime-based sorbents in the presence of steam during calcination/carbonation cycles. Two sorbents were tested: natural limestone (Cadomin, Canada) and a synthetic sorbent (pellets) prepared from Cadomin limestone with addition of calcium aluminate cement. The mixture of calcined limestone and cement was pelletized in a mechanical granulator that uses spray water as the part of the pelletization process. Both the original limestone and the prepared pellets were impregnated with a dilute CaBr2 solution to achieve a Ca/Br mole ratio of 500:1. The CO2 carrying activities of the sorbents were tested during calcination/carbonation cycles in a thermogravimetric analysis (TGA) apparatus. Realistic calcination conditions during the reaction cycles were employed: 900 °C with a CO2 sweep gas. Multicycle tests were carried out with steam 15% and without steam present in the carbonation gas stream (20% CO2, 15% steam or 0% steam, N2 balance in both cas...