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This work was aimed to study the water vapor transport inside microwave ovens (MWO), both experimentally and through mathematical modeling and simulation. The evaporated water from foods must be purged from the oven to prevent its accumulation. When vapor reaches the oven cold walls, it may condense and produces drops, which continue to grow until they eventually fall. This can cause damage to the containers due to the rapid heating of the water on them. In this work, the airflow circulating inside an MWO was experimentally determined. Afterwards, a 3D model of the MWO geometry was built and the air inlet and outlet sections were approximated with rectangles. Given the low measured airflow a laminar model was sufficient to simulate the airflow inside the oven. Various airflow simulations were performed inside the oven. After that, heating experiments with water in a glass were carried out (power: 10, 20 and 30%); the humidity and temperature of the outlet air and the water temperature on the glass during the process were measured. Subsequently, the geometry of the glass with water and the magnetron and waveguide were incorporated into the model, in such a way that includes the energy and mass balance. The electromagnetic field in the oven and the fluid dynamics in air were solved in steady state, and then the velocity field was used to solve the energy and mass balance in transient state in the air. The accuracy of humidity and temperature predictions were acceptable compared to the experimental values. Fil: Arballo, Javier Ramiro. Universidad Nacional de La Plata. Facultad de Ingenierí­a. Departamento de Ingeniería Química; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentina Fil: Goñi, Sandro Mauricio. Universidad Nacional de La Plata. Facultad de Ingenierí­a. Departamento de Ingeniería Química; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentina Fil: Mascheroni, Rodolfo Horacio. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentina. Universidad Nacional de La Plata. Facultad de Ingenierí­a. Departamento de Ingeniería Química; Argentina

This research aimed to evaluate the profile of temperature and moisture content in Pinus oocarpa wood being dried with heating oven and microwave oven. The size of samples were (25x70x120) mm3. The temperature profiles in heating oven and microwave oven drying were taken every 10 minutes and 0.5 minutes, respectively. The moisture profiles in heating oven and microwave oven drying were made in every 24 hours and 10 minutes, respectively. The heating oven was set at 60 °C, while microwave oven was set for 2 minutes intermittently with 5 minutes break. In microwave drying, the temperature inside the boards increased faster and higher compared to that in the heating oven, which resulted in a faster moisture movement to the board’s surface. The drying rate of pine increased 48-72 times in microwave compared to that in heating oven. The moisture content in the centre of boards being dried in heating oven was much higher than that of in the outer parts. On the other hand, the moisture profile in the woods being dried in microwave oven distributed more evenly.

This study compares the values of the electromagnetic fields generated by three types of microwave ovens with the values available in scientific literature, guides and protocols, considering their impact on human health. Variations in electromagnetic radiation have been determined during and outside the operating time of the microwave ovens at different distances from the oven and in different positions, thereof. The obtained data show higher values of the radiation leakage during operation than those provided by the regulations in force, for all types of studied ovens. The results of the study suggest the need to reduce the time spent near these devices and to optimize the equipment in order to reduce these radiation leakages.

This paper discusses a combined methodology for the design of solid-state-fed microwave ovens. The presented approach joins the design methodologies of both, active and passive component of the microwave oven to deliver to the heating system designers and manufacturers a full advantage of the opportunities brought by the solid-state technology. For the passive component design, new electromagnetic simulation regime is developed to accurately mimic the solid-state source operation and decrease computer effort required for the analysis, making the process more efficient. The combined active and passive methodology is experimentally validated in the industrial laboratory environment for dual-aperture microwave oven prototype and the results are discussed.

Metallic stirrers are commonly used in mode-stirred reverberation chambers but are less common in microwave ovens, because the use of a metallic axis creates a coaxial port in the cavity wall where the axis is introduced, which may result in significant microwave leakage levels. However, due to electromagnetic, mechanical, temperature, or chemical requirements, metallic axes must be used in some cases. In this paper, we present a high power coaxial filter that enables the use of metallic stirrers in microwave applications. The filter employs two-port coaxial cavities that are analyzed to determine their design parameters. These cavities are coupled via coaxial lines to achieve proper attenuation levels. The cavities were designed using commercial electromagnetic (EM) software, and a filter prototype was validated using vector network analyzer (VNA) measurements. The simulated and measured results show that a three-stage configuration can achieve attenuations greater than 70 dB at the 2.45 GHz ISM band, allowing the use and external handling of the metallic axis inserted into microwave ovens with negligible microwave radiation leakage.

This paper proposes a probe to monitor the electromagnetic field inside the microwave oven. Although magnetrons are now small and efficient, and solid-state ovens can control the power delivered to the food, neither can “see” the electromagnetic field inside the microwave oven. Therefore, the proposed field detector probe, which is a rectenna (antenna and rectifier), converts the RF (2.45 GHz) signal, inside the cavity, to a dc voltage. The antenna is a simple planar monopole, which is not matched due to the high power levels inside the oven. Two types of rectifiers are proposed, the first one is based on diodes (SMP1302 or SMP1304) and the second one is based on an LDMOS power transistor—BLC2425M8LS300P, provided by Ampleon. By comparing the output dc voltage of the probe when connected to a signal generator (in the laboratory) with the voltage generated by the field detector probe (inside the microwave oven), the electromagnetic field can be mapped. Doing this allows microwave oven manufacturers to optimize and adjust the cooking appliance based on the electromagnetic field, which induces food heating.

Heating uniformity inside materials, as a concerned issue of microwave processing, influences essentially the energy utilization of microwave equipment and desired quality of the final product. For the microwave drying of granular materials like germinated brown rice (GBR) on a turntable in microwave ovens, the mode and route of microwave transmission considering sample rotation and the existence of pores inside GBR stacked bulk were investigated, and further to analyze the heating uniformity. The developed physics-based model and simulation strategy can describe microwave drying of GBR stacked bulk. The edge diffraction and uneven surface reflection for the stacked bulk of GBR dominates the transmission of microwaves. Under the fixed magnetron arrangement, same microwave input power, and geometry shape of the sample, the absorption of microwave energy inside GBR stacked bulk mainly relies on the changes in dielectric properties of materials other than those of the electric field. The absorption of microwave energy in GBR stacked bulk greatly dominates the uniformity of temperature distribution. Rotation improves the uniformity of temperature distribution along with equatorial other than radial direction for GBR stacked bulk on a turntable under microwave drying. Sensitivity analysis indicated that increasing rotating speed of the sample has little effect on the heating uniformity as beyond a certain value of 5 circles per minute, and a low bed porosity for GBR stacked bulk relatively improve the heating uniformity, but temperature uniformity is relatively not sensitive to the capillary diffusivity. Research results may enhance understanding of the interaction between microwaves and the stacked bulk of granular materials like GBR with porosity.

Organisms acquire more calories from eating hot food than eating the identical food cold; thus, the widespread use of microwave ovens might have played a small role in the current obesity epidemic, just as the widespread use of refrigerators might have retarded the historic increase in obesity a century ago. Analysis of the British Cohort Study showed that, net of dietary habit, physical activities, genetic predisposition, and other demographic factors, the ownership of a microwave was associated with an increase of .781 in body mass index (BMI) and 2.1 kg in weight (when the ownership of other kitchen appliances was not associated with increased BMI or weight), and it more than doubled the odds of being overweight. In the United States from 1960 to 2015, the adult overweight, obesity, and extreme obesity rates were very highly correlated ( r = .94–.98) with the proportion of households with microwaves, and it was not because both were consequences of increasing wealth. Net of median household income, the proportion of households with microwaves was very strongly ( ds > 1.0) associated with adult overweight, obesity, and extreme obesity rates, while median household income was not at all associated with them. Individual data from the United Kingdom and historical data from the United States highlighted the possible role of the widespread use of microwave ovens in the obesity epidemic.

This chapter is concerned with modeling of excitation in real-life microwave ovens. This is in extension to Chapter 18 , where the computational model is truncated within the waveguide connecting the oven to the source, and the actual source is represented by the fundamental waveguide mode, assumed to have a well-defined frequency (or frequency range) and amplitude. In the first major part of this chapter, we summarize the uncertainties associated with the frequency spectrum of signals generated by magnetrons in domestic ovens. We further show how those uncertainties can be taken into account in deterministic modeling of the oven scenarios. Specifically, we propose an efficient time-domain approach, which allows one to generate load heating patterns and to calculate the overall oven efficiency in a single simulation performed in response to a Gaussian pulse whose spectrum mimics that of the magnetron. In the final part, we refer to new oven design perspectives associated with solid-state sources and discuss several modeling regimes that make such design work easier and faster.

Inverter microwave ovens (inv. MWOs) are day-to-day appliances that can severely interfere with 2.4 GHz wireless LAN (WLAN) devices. However, interference is avoidable by using a signal detection method that recognizes MWO signals. In our previous work, we have proposed a specialized detection method that recognizes characteristic power levels of leakage signals from inv. MWOs, which drastically vary depending on the switching of the inverter. Using experimental MWO data obtained in a shielded room, we also demonstrated that the proposed method correctly detects inv. MWO signals with robustness against different products, different receiving environments, and the presence of other signals. In this paper, we begin with a discussion of the influence of MWO interference, and then review process and evaluation of the proposed method, along with new additional analysis. By simplifying the process, we also provide a test chip implementation for method realization and real-time signal detection to enhance the reliability of WLAN systems. Finally, we use the test chip to show that it is also possible to detect jammer signals.

We show how a common microwave oven, a coat-hanger and a coffee cup can be used to decontaminate N-95 respirators in 30 seconds. Tulane virus in the artificial saliva was reduced by >3 log and Geobacillus stearothermophilus spores were reduced by >6 log. Respirators maintained filtration and fit even after 10 cycles. Filtration and fit tests performed by the CDC confirmed there was no damage to the respirators. Spectroscopy of the plasma reveals that OH and C-containing radicals as the most prevalent active species.

Introduction Scald burn injuries are the leading cause of burn-related emergency room visits and hospitalizations for young children. An increasing portion of these injuries occur when children are removing items from microwave ovens. Many of these occur on the face/chest and can have lifelong physical, functional, aesthetic and psychological consequences. Over the past 15 years we have published a series of studies supporting our advocacy for a change in microwave oven design to protect children from severe scalds. Requiring microwave oven doors to be more difficult for a child to open would help to protect young children from these types of burn injuries. Our analysis of the National Electronic Injury Surveillance System found an estimated 7000 young children were treated in US emergency departments over the last decade for burns suffered when the child opened a microwave oven door and spilled the heated contents. This report describes our continued research and advocacy to finally get a regulatory agency to pass a “child-safety” mechanism for opening microwave doors. Methods In the United States, microwave ovens must meet the published microwave standard administered by Underwriters Laboratories (UL 923). In 2013, we formally proposed a change in the standard which underwent a voting process by the Standards Technical Panel. Microwave makers are well represented on the panel. This attempt did not pass. We continued to publish focused research, presented at national meetings, enlisted engineering students to design “child-resistant” microwave doors to demonstrate feasibility, and created a video to put a face to the statistics. In 2017, we became active members of a National Task Group convened by UL, and two authors became voting members on the 17 member microwave Standards Technical Panel. A new proposal was introduced by the Association of Home Appliances Manufacturers requiring “two distinct actions” to make it more difficult for a young child to open a microwave oven door. Multiple concerns were addressed including those related to the impact on seniors. We lobbied members who appeared undecided. Results On September 17, 2018, the UL 923 STP voted by a narrow margin to pass the measure. In the future, new microwave ovens sold in the United States will be required to be made with “child-resistant doors”. Conclusions Research and advocacy work together to protect children. Child scald risk will be reduced as microwaves with child-resistant doors replace current models. Applicability of Research to Practice Our research demonstrated that very young children are able to open microwave ovens putting them at risk for burn injuries. We worked diligently through various advocacy channels to actively improve the safety of microwave ovens. With the approved changes for future microwave design requirements, research and advocacy have now resulted in practice changes.

The facile growth of carbon nanotubes (CNTs) using microwave radiation reveals a new way for the cost-effective synthesis of CNTs for a wide range of applications. In this regard, domestic microwave ovens can be used as convenient plasma reactors to grow CNTs in a very fast, simple, energy-saving and solvent-free manner. The special heating mechanism of microwaves can not only accomplish the fast growth of high-density CNT brushes within tens of seconds, but also eliminate the need for a flammable gaseous carbon source and an expensive furnace. By carefully selecting the substrate and catalyst, low-temperature growth of CNTs can also be achieved on low-melting point organic polymers at atmospheric pressure. Highly localized heating near the catalyst nanoparticles was observed under microwave irradiation, and this phenomenon can be utilized to grow CNTs at desired locations on the substrate to fabricate CNT-based nanoelectronics in situ. Finally, the microwave growth of CNTs is highly adaptive to different carbon sources, substrates and catalysts, showing enormous potential to generate functionalized CNT-based composites for emerging advanced applications.

Conventional microwave ovens rely on users for their cooking time. In other words, the user must set the oven’s cooking time manually. This paper aims to design a fuzzy logic-based controller to resolve the above-mentioned issue by determining the cooking time of the microwave oven automatically. The time determined depends on the quantity and type of food. During the fuzzy logic process, we used the Mamdani fuzzy model. This model involves determining the crisp input, fuzzification, rule evaluation, and defuzzification, to obtain the crisp output result. Input real variables used were the type of food and quantity of food, whereas the output variable used was cooking time. A fuzzy logic toolbox on MATLAB software was used to design and simulate the whole system. Considering the IF-THEN rules and functions, we used the value of food as 50, and the type of food as 50 and we obtained the cooking time as 25 minutes. The result showed that Fuzzy models are good at determining cooking time in Microwave ovens and that their cooking time depends on the inputs. Using fuzzy logic in microwave ovens helps to maintain food quality, saves users’ time, and controls the energy used by the oven.

[ESP] La energía de microondas se emplea habitualmente en muchas aplicaciones industriales, científicas y médicas, las cuales requieren frecuentemente la participación de personas en contacto directo con los equipos de microondas. Específicamente, los hornos industriales de microondas suelen emplear puertos abiertos en guía de onda para permitir un flujo continuo del material a procesar. Por esta razón, las cuestiones de seguridad son un aspecto primordial en estos sistemas, con el fin de evitar posibles efectos peligrosos en tejidos humanos debidos a fugas de energía de microondas. Varias alternativas para lidiar con este problema se han propuesto en la literatura técnica. Una de las elecciones más efectivas está basada en filtros corrugados reactivos, los cuales reflejan hacia atrás la energía que intenta escapar del aplicador. Pero en esta tesis se han encontrado algunas limitaciones de estas estructuras, particularmente en lo que se refiere a las propiedades dieléctricas del material procesado. La presente tesis aborda el objetivo de mejorar estos filtros reactivos cuando el horno requiere un flujo continuo de material. Para ello, se proponen nuevas estructuras que solucionan los inconvenientes que presentan los filtros tradicionales, así como algoritmos de optimización que reducen el tiempo de diseño. Adicionalmente, se proponen nuevas técnicas de calibración y caracterización aplicadas a dispositivos en guía de onda. [ENG] Microwave energy is extensively used in many industrial, scientific and medical applications, which frequently require the participation of human beings in direct contact with microwave equipment. Specifically, industrial microwave ovens often employ open-ended waveguide ports in order to allow a continuous flow of the material to be processed. For this reason, safety issues become a main concern in such systems to prevent possible dangerous effects on human tissues due to microwave energy leakage. Some alternatives to deal with this leakage problem have been proposed in technical literature. One of the most effective choices is based on corrugated reactive filters which reflect back the energy escaping from the applicator. But some limitations have been found in this work for those traditional structures, particularly regarding the dielectric properties of the processed material. The present thesis addresses the goal of improving these reactive filters when the oven requires a continuous-flow of the material to be processed. In order to do that, new structures are proposed which solve the inconveniences that traditional filters show, along with the use of optimization algorithms that reduce the design time. Additionally, some innovative calibration and characterization techniques are proposed and applied to waveguide devices., Universidad Politécnica de Cartagena

In this reported work it is shown that one of the most employed filtering systems for use in continuous-flow industrial microwave ovens, namely doubly corrugated filters, does not work properly for many values of the electric permittivity of the processed material when it is partially filled. Thus, a novel bandstop filter which solves these inconveniences, based on a combination of metallic irises and double corrugations, is designed by means of CST Microwave Studio® and experimentally validated. This work was supported in part by the Fundación Séneca under the fellowship 16381/FPI/10 and the project 11689/PI/09.

Developing a simple and industrially scalable method to produce graphene with high quality and low cost will determine graphene's future. The two conventional approaches, chemical vapor deposition and liquid-phase exfoliation, require either costly substrates with limited production rate or complicated post treatment with limited quality, astricting their development. Herein, an extremely simple process is presented for synthesizing high quality graphene at low-cost in the gas phase, similar to "snowing," which is catalyst-free, substrate-free, and scalable. This is achieved by utilizing corona discharge of SiO2 /Si in an ordinary household microwave oven at ambient pressure. High quality graphene flakes can "snow" on any substrate, with thin-flakes even down to the monolayer. In particular, a high yield of ≈6.28% or a rate of up to ≈0.11 g h-1 can be achieved in a conventional microwave oven. It is demonstrated that the snowing process produces foam-like, fluffy, 3D macroscopic architectures, which are further used in strain sensors for achieving high sensitivity (average gauge factor ≈ 171.06) and large workable strain range (0%-110%) simultaneously. It is foreseen that this facile and scalable strategy can be extended for "snowing" other functional 2D materials, benefiting their low-cost production and wide applications.

Aluminum and zirconia oxides are ceramic materials widely used in the manufacturing of dental products, however, the thermal treatment stages demand high temperatures. Aiming at the reduction of the energy consumption and of the time necessary for the thermal treatments, this work intends to evaluate the influence of the microwave energy over the thermal processes of alumina substrate and of the alumina/zirconia system. The samples were made by slip-casting and then submitted to different thermal treatments. For the microwave oven, we used powers of 1.44 and 1.66 kW and heating times of 10, 15 and 20 minutes. The samples were submitted to the determination of physico-mechanical properties: flexural strength at three points, porosity and Vickers microhardness. Based on the analysis, we conclude that the microwaves energy is promising for the processing of dental ceramic, causing a significant reduction in the firing time.

To understand the interactions of microwaves with dielectric materials and their conversion to thermal energy in aqueous systems, the effect of ionic concentration has been studied. Aqueous solutions of inorganic ions were exposed to microwaves (2.45 GHz) in a modified oven under identical conditions. Difference in solution temperatures with reference to pure (deionized) water was monitored in each case. A significant decrease in the temperature was observed with an increase in the quantity of ions. Experiments were repeated with several inorganic ions varying in size and charge. The information can be helpful in understanding the role of ions during dielectric heating.

Inverter microwave ovens (MWOs) are day-to-day appliances that can act as fatal interferers for 2.4 GHz wireless LAN (WLAN) systems. However, the interference is avoidable, if it is possible to detect the MWO signal. In this paper, we propose an inverter MWO signal detection method in the time and frequency domains for reliable wireless communication. The operating inverter MWOs inherently generate RF signal whose leakage power level drastically varies depending on the switching of the inverter. The proposed method recognizes the changing signal power level due to the switching. In addition, we confirm the effectiveness of the proposed method in the presence or absence of WLAN systems by using the experimental MWO data obtained in a shielded room. It is revealed that the proposed method is able to detect the inverter MWO signal correctly and is robust against different products, different receiving environment, and presence of other signals.

This chapter discusses the many factors relating to the design and operation of a domestic microwave oven, and the product being heated, that affect the temperatures reached in the product, their uniformity, and their repeatability when heated in a domestic microwave oven. Knowledge of these factors is vital when designing foods to be cooked or reheated in a microwave oven to ensure that the food is heated to safe temperatures without impacting on quality. Current standard methods of assessing microwave power provide limited information for the food manufacturers developing heating instructions for chilled and frozen foods. Alternative methods have been developed for specific types of food product (e.g., chilled convenience meals) and are discussed, as well as food simulant materials.

Percy Lebaron Spencer was yet another American farm boy. He was born in 1894 in Howland in Maine and had a very hard upbringing as his father died when he was still an infant. His mother could not cope and he was taken in by a poor uncle and aunt and as a result had little formal schooling. However, he became interested in electricity and educated himself in the subject. Joining the Navy before the First World War he went to Radio School and learned about the upcoming field of electronics. When discharged at the end of the war he was thoroughly conversant with the subject.1

In this study, snapshots of operating frequency profiles of domestic microwave ovens were collected to reveal the extent of microwave frequency variations under different operation conditions. A computer simulation model was developed based on the finite difference time domain method to analyze the influence of the shifting frequency on heating patterns of foods in a microwave oven. The results showed that the operating frequencies of empty and loaded domestic microwave ovens varied widely even among ovens of the same model purchased on the same date. Each microwave oven had its unique characteristic operating frequencies, which were also affected by the location and shape of the load. The simulated heating patterns of a gellan gel model food when heated on a rotary plate agreed well with the experimental results, which supported the reliability of the developed simulation model. Simulation indicated that the heating patterns of a stationary model food load changed with the varying operating frequency. However, the heating pattern of a rotary model food load was not sensitive to microwave frequencies due to the severe edge heating overshadowing the effects of the frequency variations.

Microwave assisted chemical reaction is increasingly studied in recent years by using the modified domestic microwave oven to heating on chemical reaction in the laboratory scale study. But the problems of temperature distribution non-uniformity and low power efficiency in the heating process are becoming a new obstacle in the application of microwave chemistry. An optimized microwave oven with two sources is proposed in this paper from the view of feeding system to overcome these disadvantages. As water is usually concerned as important solvent and reactant, a beaker of water is used as heating load in this study. By modeling the process of heating water for 180 s, the standard deviation and the average temperature are compared between the domestic microwave oven and the optimized microwave oven with two sources. As a result, the power is utilized more efficiently as a 20.14% increase can be seen by using the optimized microwave oven under the same microwave power and more uniformity is obtained ...

Due to the inherent nature of standing wave patterns of microwaves inside a domestic microwave oven cavity and varying dielectric properties of different food components, microwave heating produces non-uniform distribution of energy inside the food. Non-uniform heating is a major food safety concern in not-ready-to-eat (NRTE) microwaveable foods. In this study, we present a method for assessing heating rate and non-uniform heating in domestic microwave ovens. In this study a custom designed container was used to assess heating rate and non-uniform heating of a range of microwave ovens using a hedgehog of 30 T-type thermocouples. The mean and standard deviation of heating rate along the radial distance and sector of the container were measured and analyzed. The effect of the location of rings and sectors was analyzed using ANOVA to identify the best location for placing food on the turntable. The study suggested that the best location to place food in a microwave oven is not at the center but near the edge of the turntable assuming uniform heating is desired. The effect of rated power and cavity size on heating rate and non-uniform heating was also studied for a range of microwave ovens. As the rated power and cavity size increases, heating rate increases while non-uniform heating decreases. Sectors in the container also influenced heating rate (p < 0.0001), even though it did not have clear trend on heating rate. In general, sectors close to the magnetron tend to heat slightly faster than sectors away from the magnetron. However, the variation in heating rate among sectors was only 2 degrees C/min and considered not practically important. Overall heating performance such as mean heating rate and non-uniform heating did not significantly vary between the two replications that were performed 4 h apart. However, microwave ovens were inconsistent in producing the same heating patterns between the two replications that were performed 4 h apart.

There have been a few methods described in this journal and elsewhere for measuring the wavelength of the standing electromagnetic waves in a microwave oven. Typically, these involve melting chocolate, cheese, or some other substance on a plate that is prevented from rotating. In this article I describe a more dynamic and colorful technique that utilizes a temperature-sensitive liquid crystal sheet. With this method one can not only measure the wavelength of the microwaves, but also calculate the speed of these waves, which intriguingly turns out to be the speed of light. It also has the advantage of looking more like a wave than the other methods.

Physics is essential for students who want to succeed in science and engineering. Excitement and interest in the content matter contribute to enhancing this success. We have developed a laboratory experiment that takes advantage of microwave ovens to demonstrate important physical concepts and increase interest in physics. This experiment investigates leaked electromagnetic radiation from microwave ovens. We compare the data that are obtained to national standards in order to relate the fields of physics, health and engineering. The experiment is designed to provide for added enquiry and stimulation of thought-provoking questions.

The domestic microwave oven is now commonplace in the home and is often used to reheat chilled ready meals. Previous studies by the authors have demonstrated that the power output of such ovens can drop significantly within the first few minutes of use. This study has demonstrated that this power output reduction can have a significant affect on the expected final food temperatures after heating. A reproducible procedure was used to carry out heating tests of simulated chilled ready meals in 16 different models of domestic microwave ovens. All of the test loads had lower minimum measured temperatures (mean of three replicates) after heating in the hot ovens (ovens that had been in use for 15 min prior to the heating test) compared to when they were heated for the same time in the cold ovens (ovens that had not been used for ⩾6 h). Minimum measured temperatures fell from a mean of 70.3 °C in the cold ovens to mean of 61.3 °C (range 50.3–67.6 °C) in the hot ovens. In 12 out of the 16 ovens (75%) these reductions in minimum temperature were statistically significant ( P ⩽ 0.05). There is an increased risk in terms of the potential for survival of bacteria such as Listeria monocytogenes when reheating food products to these lower temperatures. It was evident that at the minimum temperatures attained in the food simulant test loads heated in all the hot microwave ovens, the heat treatment would be insufficient to produce a 10 6 reduction of L. monocytogenes even allowing for an acceptable standing time.

The purpose of this study was to identify the extent of adoption of microwave ovens by older adults in Blacksburg, Virginia. Level of adoption was defined and determined as a function of 1) frequency of use of the microwave oven in comparison to the range, and 2) complexity of food preparation. Mere ownership was not considered as an indicator of adoption. Focusing on the final stage of Rogers theory of adoption (1962), three levels of adoption were determined: High, medium, and low. A random sample of 75 adults 65 years and older was selected from the listing of retired personnel in the 1997-98 Virginia Polytechnic Institute and State University faculty and staff directory. Telephone interviews were conducted to collect information regarding current microwave oven usage patterns and decisions for future use and purchase. Relationships between level of adoption, and user characteristics and microwave oven characteristics were statistically tested. Results from the study indicate that 56% of these older adults who own a microwave oven are high adopters; i.e. they used the microwave more than the range and performed high complexity tasks. About 52% reported using the microwave oven more frequently than the range. Nearly all respondents were satisfied with the microwave oven in terms of speed and convenience, while 60% were satisfied with quality of foods cooked in the microwave oven. There was no significant difference in level of adoption with age, gender, health condition, and knowledge of microwave oven use. However, level of adoption was significantly higher among older adults who were "never" married or "previously" married compared to those that were "currently" married. Also, level of adoption was significantly lower among those older adults who had touch controls on their microwave oven compared to those with rotary dials. Other significant results of this study dealt with future use and purchase decisions. About 93% of the respondents indicated a desire to continue using a microwave oven in the future and about 76% indicated that they would purchase one in the future if their current microwave oven "dies." Results from this study have implications for appliance manufacturers who can increase sales by targeting this group, researchers in household equipment who can study adoption of other innovative appliances, and developers of retirement communities who might consider providing a microwave oven for use by residents or provide a space where one can be placed. Master of Science

Recent house electrical appliances generate a number of auditory signals, when a user operates an appliance or an appliance draws attention to a user. In this paper, we focus on multi-functional microwave ovens, which commonly have several auditory signals for user's operation, error occurrence, completion of cooking, and so on. A wide variety of auditory signals for current microwave ovens have two problems: it is difficult for users to image what the auditory signals inform, and the auditory signals including high frequency components are not friendly for elderly users. In this paper, popular auditory signals for microwave ovens were subjectively evaluated with/without an elderly-simulated band-pass filter, which simulated an averaged audiogram of elder people, on the five grade scales of easiness of perception, unpleasantness, and emergency. Experimental results suggest that young and elderly people might imagine different function for a single auditory signal. Finally, suitable auditory signals both for young and elderly users are proposed in the viewpoints of frequency and temporal patterns.

The fabrication of zirconium dioxide (ZrO2) dental prosthetic substructures requires an extended sintering process (8 to 10 hours) in a conventional oven. Microwave sintering is a shorter process (2 hours) than conventional sintering.The purpose of this study was to compare the fracture toughness of 3 mol % Y2O3-stabilized ZrO2 sintered in a conventional or microwave oven.Partially sintered ZrO2 specimens from 3 manufacturers, KaVo, Lava 3M, and Crystal HS were milled (KaVo Everest engine) and randomly divided into 2 groups: conventional sintering and microwave sintering (n=16 per group). The specimens were sintered according to the manufacturers' recommendations and stored in artificial saliva for 10 days. Fracture toughness was determined by using a 4-point bend test, and load to fracture was recorded. Mean fracture toughness for each material was calculated. A 2-way ANOVA followed by the Tukey HDS post hoc test was used to assess the significance of sintering and material effects on fracture toughness, including an interaction between the 2 factors (α=.05).The 2-way ANOVA suggested a significant main effect for ZrO2 manufacturer (P.001). The post hoc Tukey HSD test indicated that mean fracture toughness for the KaVo ZrO2 (5.85 MPa·m(1/2) ±1.29) was significantly higher than for Lava 3M (5.19 MPa·m(1/2) ±0.47) and Crystal HS (4.94 MPa·m(1/2) ±0.66) (P.05) and no significant difference was observed between Lava 3M and Crystal HS (P.05). The main effect of the sintering process (Conventional [5.30 MPa·m(1/2) ±1.00] or Microwave [5.36 MPa·m(1/2) ±0.92]) was not significant (P=.76), and there was no interaction between sintering and ZrO2 manufacturer (P=.91).Based on the results of this study, no statistically significant difference was observed in the fracture toughness of ZrO2 sintered in microwave or conventional ovens.

Summary The power output of five recent domestic microwave ovens (on the market 2003/2004) was measured using a standard 1000 g water load during 30 min of continuous use. The power output of the ovens declined significantly (P ≤ 0.05) in the first 5 min of use, ranging from a minimum of 7.0% to a maximum of 19.7%. Further but not always significant declines (P ≤ 0.05) were measured after 20 min of continuous use. No significant reductions were measured between 20 and 30 min. Overall, the mean reduction in power output after 30 min of continuous use was 17.3% for these five ovens compared with 13.5% for five ovens in a previous study. Based on trials carried out approximately a decade apart, there has not been any improvement in the performance of domestic microwave ovens in terms of the decline in power output after continuous or prolonged use. The authors believe that many users, including consumers, caterers and those using domestic microwave ovens for research purposes, would benefit from a greater awareness and understanding of how the rapid reduction in power output in the first 5–20 min of use is likely to affect the expected heating performance.

To date, there is research carried out on the effects of electromagnetic radiation on living organisms, studies are conducted on substratums that were subjected to microwave radiation. This radiation comes from a common household appliance; however, the effect of this type of radiation on the vitality of organisms is poorly researched. The purpose of the current analysis is to identify the morphological changes in vegetative organs of the test objects using microwave-irradiated water as a substrate. The object of the study – the onion plant (Allium сера L.), which is perfect for objectifying environmental risks. The results showed that using the water warmed up in a microwave increased the level of oppression in the morphometric parameters. In particular, there was a clear trend of reduction of growth parameters of vegetative organs and decrease in their mass (in the test group compared to the the main one the length of the root and shoot of a plant are less than 20.5% and 27.5%, and the weight is 32.3% and 63.8% less, respectively). The correlation analysis showed that the root length is the most reliable morphometric indicator that reacts sensitively to changes in water quality caused by microwave irradiation (r = –0.9995). DOI: https://doi.org/10.3846/aainz.2016.15

Sample preparation is an important step in the analytical process because it can introduce different error sources. Its efficiency is checked based on the quality and reliability of the data obtained, and the time spent on this task. This work evaluates medicinal plant decomposition parameters using polypropylene mini-vials heated by microwave radiation, applying the single vessel concept. As an example, sample mass amount (5 mg), mixture of oxidant agents (200 µL conc. HNO3+150 µL 30% v/v H2O2), microwave time and power were evaluated by heating 24 mini-vials in both closed-vessel (CV) and focused (F) microwave ovens. In order to achieve the best-optimised condition for sample preparation, cadmium and residual carbon determinations were carried out for all experiments. The residual carbon (between 0.30 and 0.45%) was determined by CHN elemental analysis and the cadmium concentration (up to 0.80 µg g−1) by thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) in three different medicinal plants. The accuracy of the proposed methods was assessed using certified reference materials (rye grass, BCR 281 and bovine liver, NIST 1577b) as well as conventional microwave assisted decomposition. The new method used a minimum sample amount (5 mg) and reagent volume (ca. 400 µL) and only 4 and 10 min of microwave sample decomposition for CV and F ovens, respectively. In addition, the capacity of both microwave ovens was increased up to 4 times while contamination risks were inherently reduced with the single vessel concept.

Theoretical and experimental investigations are carried out on the degradation in the performance of DS-SS wireless LAN systems (WLANs) (IEEE802.11b) systems caused by electromagnetic noise radiating from microwave ovens in the 2.4-GHz frequency band. Based on the time-domain oven-noise model, theoretical expressions for short-duration bit-error rates (BERs) and packet-error rate (PERs) are derived. Measurements were done using commercially available microwave ovens and a noise simulator that consisted of a function generator and an RF synthesizer. The PERs measured with actual oven noise were found to correlate well with those derived by simulated noise, and they were in reasonable agreement with the theoretical estimates given by the derived approximate formulae. It is concluded that the noise simulator and the derived approximate expressions were very useful in evaluating the BER and PER of WLAN systems that have incurred interference from microwave ovens.

The study was about to produce red ginsengs easily, using a household microwave oven to promote the consumption of fresh ginsengs in the home. Producing red ginsengs with a household microwave oven 'defrost function' takes 13 minutes (A), 'cook function' 6 minutes (B), and finally, 'defrost function' 44 minutes (C). For characteristics of microwave-produced red ginsengs, total saponin loss, color of powder, polyphenol content and saponin composition were compared with common red ginsengs. The color test for red ginseng powder showed that the color of household microwave-produced 6-minute cooked red ginseng (B) or 44-minute defrosted red ginseng (C) was closer to that of the common red ginsengs (E). The total saponin content in water eluted during red ginseng production showed that the saponin loss in microwave red ginseng was negligible compared to the common red ginsengs. Microwave red ginsengs showed no difference in phenol content that of the and higher total ginsenoside content than common red ginsengs. The ginsenoside Rg 1, Re, Rf, Rg2+Rh1, Rb1, Rc, Rb2, Rb3, Rd and Rg3 contents of microwave red ginsengs (A, B) were higher compared to that of the common red ginsengs; the ginsenoside Re, Rc, Rb2, Rb3, Rd and Rg3 contents of 44-minute defrosted red ginseng (C) were higher compared to the common red ginsengs. It is considered that red ginseng production, using microwave oven at home, can be a fast and convenient way to produce highly functional red ginsengs with high ginsenoside content.

How to guide designers to create product for meeting consumers’ sensational expectations effectively is one of the important aims of Kansei Engineering. The difficult is to reveal the relationship between the emotional imagery and product design elements. The SD and JK methods are selected to build the test sample, emotional vocabulary and deconstructing design elements, then the BP neural network is applied to form the quantitative relationship model between the emotional imagery and design elements. That the front panel of computer-based microwave is taken as research object, the validity of the model has been verified.

Reducing the sensitivity of microwave oven heating and cooking performance to load volume, load placement and load properties has been a long-standing challenge for microwave and microwave-convection oven designers. Conventional design problem and solution methods are reviewed to provide greater insight into the challenge and optimum operation of a microwave oven after which a new strategy is introduced. In this methodology, a special load isolating and energy modulating device called a transducer-exciter is used containing an iris, a launch box, a phase, amplitude and frequency modulator and a coupling plate designed to provide spatially distributed coupling to the oven. This system, when applied to a combined microwave-convection oven, gives astounding performance improvements to all kinds of baked and roasted foods including sensitive items such as cakes and pastries, with the only compromise being a reasonable reduction in the maximum available microwave power. Large and small metal utensils can be used in the oven with minimal or no performance penalty on energy uniformity and cooking results. Cooking times are greatly reduced from those in conventional ovens while maintaining excellent cooking performance.

Summary A test procedure has been developed and used to characterise the performance of domestic microwave ovens in relation to the heating of chilled ready meals. The procedure uses reproducible test loads, which simulate the heating and weight loss characteristics of a chilled ready meal under consumer use. The temperature distribution after heating from 5 °C to a defined minimum temperature of 70 °C is measured in the food simulant using a purpose designed multipoint thermocouple ‘hedgehog’ probe. The temperature, weight loss and heating time data from the test are entered into a spreadsheet analysis program, which provides a simple oven performance ‘score’ and/or comprehensive heating performance data.

多機能オーブンレンジのオーブン（Ov），グリル（Gr），スチーム（Sm），マイクロ波（Mw）加熱機能および過熱水蒸気のオーブン加熱機能（SSO），過熱水蒸気のグリル加熱機能（SSG），スチームとマイクロ波の併用加熱機能（Sm＋Mw）の違いを，食パンのテクスチャー，水分，焦げ色を指標として比べた．（1） 過熱水蒸気を使用したSSG, SSOでは加熱初期に急速に軟化し，軟らかさとパリ感を兼ね備えた破断特性が得られた．オーブンとスチームを併用したSm 180℃では軟化効果のみが認められた．（2） 過熱水蒸気のグリル機能（SSG）では焦げ速度がGrの約2.5倍，過熱水蒸気のオーブン機能（SSO）では焦げ速度がOvの約2倍速く，Sm 180℃では焦げ速度がOvの約1.2倍速かった．（3） 一定の焦げ色に到達した時間はSSG＜SSO＜Gr＜Sm 180℃＜Ovの順となり，短時間で焦げた試料ほど残存水分量が多くなった．（4） モデル系を使って水分布を調べた結果，SSG, SSOに特有の破断特性は，試料表面の乾燥の速さ，焦げ速度の速さ，内部水分量の多さによって説明することができた．（5） マイクロ波加熱したパンは急速に硬化し，Ovの約2倍大きい破断特性を示した．スチームを併用することによって硬化時間は遅くなったが，長く加熱するとMwと同じ硬さになった．

BACKGROUND: Scald burn injuries are the leading cause of burn-related emergency room visits and hospitalizations for young children. A portion of these injuries occur when children are removing items from microwave ovens. This study assessed the ability of typically developing children aged 15 months to 5 years to operate, open, and remove the contents from a microwave oven. METHODS: The Denver Developmental Screening Test II was administered to confirm typical development of the 40 subjects recruited. All children recruited and enrolled in this study showed no developmental delays in any domain in the Denver Developmental Screening Test II. Children were observed for the ability to open both a push and pull microwave oven door, to start the microwave oven, and to remove a cup from the microwave oven. RESULTS: All children aged 4 years were able to open the microwaves, turn on the microwave, and remove the contents. Of the children aged 3 years, 87.5% were able to perform all study tasks. For children aged 2 years, 90% were able to open both microwaves, turn on the microwave, and remove the contents. In this study, children as young as 17 months could start a microwave oven, open the door, and remove the contents putting them at significant risk for scald burn injury. CONCLUSIONS: Prevention efforts to improve supervision and caregiver education have not lead to a significant reduction in scald injuries in young children. A redesign of microwave ovens might prevent young children from being able to open them thereby reducing risk of scald injury by this mechanism. Language: en

The present work focuses on the development of direct integral approach for the electromagnetic field computation on high frequency domain with immediate application to the problem of microwave ovens cavities. The dyadic Green’s function of the Helmholz vectorial operator is presented and then integral representations as well as boundary integral operators are deduced. The formulation permits thus the computation of the electric field from the obtained values of the tangential components of these vectors on the boundaries of interest. We then elaborate on solution of the problem either by means of a collocation method or by obtaining a weak form of the formulation with a Galerkin type approach.

The introduction of several Not-Ready-to-Eat (NRTE) products, beginning in 2007, has resulted in several recalls and has caused serious concerns about their safe-cooking in microwave ovens. These products are not fully-thermally processed prior to sale but depend upon the consumer to finish cooking them to the safe minimum temperatures, defined by the USDA, in order to destroy any sources of foodborne illnesses. While microwave ovens are a primary means of this finish-cooking step, they are known to cook foods unevenly in terms of temperature distribution, especially from a frozen state, and this may cause parts of the food to be below the required safe-temperature. Hence there are concerns regarding how reliably microwave ovens can provide the minimum required safe temperatures in order to avoid the possibility of foodborne illnesses. To determine this, temperature profiling tests were preformed upon three frozen NRTE entrees, heating them in eight new brand-name 1100-watt and 1200-watt microwave ovens in order to evaluate how well the minimum temperatures were reached throughout the products. By comparison, these same tests were repeated using three "smart" microwave ovens in which internal computer-control makes them user-independent. In addition, a comparison was also made of the microwave output power claimed by the manufacturers of these ovens to that determined using the IEC procedures.