Guard Plates Research Articles

Structure and operation mode of centrifugal side-throwing organic fertilizer spreader for greenhouses

A centrifugal side-throwing organic fertilizer spreader is designed to improve the versatility of organic fertilizer spreaders. A discrete-element method is used to investigate the driving layer limit height of the conveyor and the diversion of the guide vane, observe the jet and the disk distribution of organic fertilizer at different fertilizer drop positions, and determine that the gap between the fan blade and guard plate significantly affects the distribution of the organic fertilizer. A mathematical model of openings and flow rate is established using bench tests. Static tests reveal that the coefficient of variation (CV) can be optimized to 15–35%. The operation mode is investigated in dynamic tests by selecting two groups of representative static test results. Group 2 had a coefficient of variation of 15.73% at 0 mm overlap. Group 3 had a coefficient of variation of 18.52% at 1200 mm overlap. The study provides a feasible solution for the design of organic fertilizer spreaders for greenhouses.

An open dataset for intelligent recognition and classification of abnormal condition in longwall mining

The underground coal mine production of the fully mechanized mining face exists many problems, such as poor operating environment, high accident rate and so on. Recently, the intelligent autonomous coal mining is gradually replacing the traditional mining process. The artificial intelligence technology is an active research area and is expect to identify and warn the underground abnormal conditions for intelligent longwall mining. It is inseparable from the construction of datasets, but the downhole dataset is still blank at present. This work develops an image dataset of underground longwall mining face (DsLMF+), which consists of 138004 images with annotation 6 categories of mine personnel, hydraulic support guard plate, large coal, towline, miners’ behaviour and mine safety helmet. All the labels of dataset are publicly available in YOLO format and COCO format. The availability and accuracy of the datasets were reviewed by experts in coal mine field. The dataset is open access and aims to support further research and advancement of the intelligent identification and classification of abnormal conditions for underground mining.

An Investigation on the Ground Impact of Electric Vehicle

Ground impact caused by road debris can result in very severe fire accidents of Electric Vehicles (EVs). To improve the mechanical safety of EVs, the test and verification conditions of Bottom scraping and Bottom supporting for ground impact safety of EVs are formulated through market safety accident investigation. Moreover, the assessment method and verification equipment are developed to satisfy the consumer’s demands. The investigations of ground impact show that whether the battery pack is at the lowest point has a great impact on the safety under the Bottom scraping condition, while the material of the Bottom guard plate has a great impact on the safety under the Bottom supporting test condition. Finally, 11 EVs are tested to evaluate the safety performance against ground impact by the scoring rule of multiple indicators. The results provide important guidance for the safety design of the ground impact of EVs.

Development and Performance Evaluation of Locally Fabricated Thermal Conductivity Apparatus

This paper presents the design and construction of a Guarded Hot Plate (GHP) apparatus for the accurate assessment of thermal conductivities of some Nigerian local building materials. The GHP apparatus is a steady-state measurement device. This apparatus is designed to measure the thermal conductivities of masonry building materials of different compositions. The design features included hot and cold plates fabricated with aluminum plates of 6 mm thickness and varying dimensions; the guard plates also made of aluminum, but of 6.35 mm thickness, forms a rigid enclosure for the specimen all encased in a mild steel housing. The operating measuring temperature range is from -20 for varying specimen thickness up to 60mm. Results are presented for concrete, laterite, and a mixture of cement with laterite, clay, and sand respectively, and it covers a range of thermal conductivities of 0.77W/mK to 1.80 W/mK. Moisture effect on concrete was recorded for the lightweight concrete as the thermal conductivity value reduced from 1.80W/m.K to 1.32W/m.K for the oven-dried concrete sample over a 1.5% (by weight) reduction in water content. The performance evaluation of the locally fabricated GHP apparatus showed a 3.03% percentage difference over ASHRAE’s published data on oven-baked concrete thermal conductivities

Analysis of piping and support weld defects of VVP system in nuclear power plant and study on treatment measures

The main steam system(VVP) support of nuclear power plant protects the main pipe by welding the guard plate on the main pipe. This paper takes defect treatment of the VVP main steam system(VVP) pipe and support weld in a nuclear power plant as an example. From the analysis of the effective mechanism of the weld generation to the proposal, discussion and implementation of the final scheme, the technical points are comprehensive described, defect types were determined by penetrant testing and metallographic observation, and further root reason analysis was carried out. Accordingly, the defects are eliminated by technical means to avoid the expansion of defects and ensure the safe and stable operation of the unit. The analysis and treatment scheme of the defects in this project provides a technical scheme for inspection and maintenance in the nuclear power field, and provides an important reference for the future treatment of defects.

Verification and validation of an advanced guardedhot plate for determination of thermal conductivity

The guarded hot plate (GHP) method is a widely used technique to measure thermal conductivity of thermal insulation specimens in steady-state conditions. In this paper, an advance of GHP has been developed in the Laboratory for Thermal Technique and Fire Protection in Institute IMS. The innovative GHP has been applied for measuring thermal conductivity using additional heat flux meters. The design of this GHP is similar to the design of the plate for GHP apparatus, however, it has different design: smaller width of thermal barrier, which is filled with insulation glue. Heaters inside hot and guard plates are built from wire for thermocouples, which is a unique type of heater. Geometry of heater has been optimized inside plates to achieve uniform temperature distribution along the specimen surface. Temperature uniformity of GHP and energy balance were experimentally determined. The verification and validation results of improved GHP have been shown. The test method was validated comparing test results of thermal conductivity with results of the round-robin test. Four national companies participated in the round-robin comparison on thermal conductivity measurement by GHP method. The measurement was performed on the same specimen of thermal insulation material (expanded polystyrene) according to SRPS EN 12667 at temperatures ranging between 10-40?C. The measured thermal conductivity of all participants in the round-robin test was input data for statistical processing according to SRPS ISO 5725-2 and ISO 13528. To evaluate the performance of the participants, the ?z? score has been used. Measurements were conducted successively for all participants. Since 2020, the Accreditation Body of Serbia also approved this test method.

Monitoring method of recovery state of hydraulic support guard plate based on image recognitio

Monitoring method of recovery state of hydraulic support guard plate based on image recognitio

Construction and preliminary testing of a guarded hot plate apparatus for thermal conductivity measurements at high temperatures

We constructed a guarded hot plate (GHP) apparatus that can be used for thermal conductivity measurements from 100 °C to 1000 °C. The apparatus measures the effective thermal conductivity of square-shaped thermal insulation materials of 300 mm per side in a controlled gas environment. As a preliminary test for the high temperature GHP apparatus, we first measured the amount of electrical power required for heaters at various locations to maintain the temperature at up to 900 °C. After this, two specimens of thermal insulation material whose thermal conductivities are ≈0.044 W·m–1 K–1 and ≈0.025 W m–1 K–1 at room temperature were tested at a thermally steady state with unilateral heat flow at temperatures between 100 °C and 800 °C. We applied an offset to the guard plate to actively compensate for the lateral heat flow across the air gap. The measurements showed that the linearity between the temperature difference on the two sides of the specimen and the power dissipated across the specimen was extremely good (with a standard deviation of 0.1%). After some modifications suggested from the preliminary test, we expect that the high temperature GHP will work within the technical specification CEN/TS 15548-1:2014 in the range up to 800 °C, but rigorous uncertainty assessment is yet to be performed after such modifications.

Free-air ionization chamber, FAC-IR-300, designed for medium energy X-ray dosimetry

The primary standard for X-ray photons is based on parallel-plate free-air ionization chamber (FAC). Therefore, the Atomic Energy Organization of Iran (AEOI) is tried to design and build the free-air ionization chamber, FAC-IR-300, for low and medium energy X-ray dosimetry. The main aim of the present work is to investigate specification of the FAC-IR-300 ionization chamber and design it. FAC-IR-300 dosimeter is composed of two parallel plates, a high voltage (HV) plate and a collector plate, along with a guard electrode that surrounds the collector plate. The guard plate and the collector were separated by an air gap. For obtaining uniformity in the electric field distribution, a group of guard strips was used around the ionization chamber. These characterizations involve determining the exact dimensions of the ionization chamber by using Monte Carlo simulation and introducing correction factors.

Investigation of electric field distribution on FAC-IR-300 ionization chamber

One of the important parameters for establishing charge particle equilibrium (CPE) conditions of free-air ionization chamber is an electric field distribution. In this paper, electric field distribution inside the ionization chamber was investigated by finite element method. For this purpose, the effects of adding guard plate and guard strips on the electric field distribution in the ionization chamber were studied. it is necessary to apply a lead box around the ionization chamber body to avoid of scattered radiation effects on the ionization chamber operation, but the lead box changes the electric field distribution. In the following, the effect of lead box on the electric field distribution was studied. Finally, electric field distribution factor (kfield) was calculated by the simulation. The results of the simulation showed that presence of the guard plate and guard strips, and applying a suitable potential to lead box, a convergence of kfield to 1 was achieved.

Sensitivity Analysis for a Guarded-Hot-Plate Apparatus: A Methodology Based on Orthogonal Experiment Designs

Abstract Results and analyses of a sensitivity study of six controlled variables on the response of the National Institute of Standards and Technology (NIST) 500 mm guarded-hot-plate apparatus are presented. The effects of four factors held constant as well as three uncontrolled environmental variables were also examined. The goal of the study is to derive a sensitivity analysis ranking of the relative importance of factors and interactions affecting the apparatus. Sixty-six thermal conductivity measurements were conducted across three experiments at a mean temperature of 310 K for a pair of fibrous-glass specimens (120 kg·m−3) having nominal dimensions 500 mm in diameter and 26 mm in thickness. The apparatus response was studied using an orthogonal fractional factorial design, a one-factor-at-a-time design, and a full factorial design for a subset of factors from the fractionated design. The results indicate that most important factor affecting the thermal conductivity measurement was the temperature difference across the air space separating the central meter plate and the surrounding guard plate, described here as the gap temperature difference (ΔTg). The study also revealed an interaction between the gap temperature difference and the temperature difference across the specimen (ΔTavg). An empirical model for the results of the sensitivity study is presented. Results of the gap temperature difference (ΔTg) are similar to published results from another guarded-hot-plate apparatus. Improvements for equipment operation, as well as insights to the sources of experimental uncertainty, are presented.

Study on thermal resistance of multilayered fabrics under different compressional loads

In this work, the thermal resistance of multilayered fabric ensembles meant for cold weather conditions were studied under different compressional loads. An instrument has been developed to study the thermal resistance of fabrics under different compressional loads. The instrument consists of a test plate, guard plates and a bottom plate. The test plate and guard plates were assembled together as a single entity, which can be moved up and down with a screw shaft. A load cell was connected to the plate assembly to apply the required compressional load on the fabric specimen. Thermal resistance of multilayered fabrics was studied in the developed instrument under different loading conditions. Single-jersey knitted fabric, needle punched fabric and polytetraflouroethylene (PTFE) coated fabrics were used in the inner, middle and outer layer, respectively. Twenty different multilayered fabric ensembles with the same inner and outer layers were studied. The middle layers, i.e. needle punched nonwoven fabrics, were produced from polyester hollow fibres, with varying linear density of fibre, mass per unit area and punch density. The thermal resistance of multilayered fabrics obtained from the developed instrument was compared with the thermal resistance of instruments, namely sweating guarded hot plate (SGHP) and Alambeta. Regression equations were developed and the contour plots were drawn to analyse the effect of the fibre, fabric and process parameters. ANOVAs were conducted to find the significance of the compressional load, linear density of fibre, mass per unit area and punch density on the thermal resistance of fabrics. It was found that the thermal resistance obtained from the instrument follows the same trend as that of thermal resistance obtained from SGHP and Alambeta. Mass per unit area was found to have significant effect on the thermal resistance of multilayered fabrics under different compressional loads. The effect of punch density decreases with the increase in compressional load on the thermal resistance of multilayered fabrics. The thermal conductivity of multilayered fabrics was observed to increase with the increase in the compressional load.

One-step method for measuring the effect of humidity on powder resistivity

Abstract We present a method for measuring powder resistivity as a function of moisture using a one-step process. The developed new resistivity cell consists of narrow horizontal electrode surrounded by a grounded guard electrode and simultaneous measurement of humidity within the powder bed. The system was modeled using computer simulations. As an example, resistivities of three different lactoses, wheat flour and quartz are presented. Resistivity was found to decrease several orders of magnitude between 10 RH% and 90 RH%. Simulated results showed that if no guard plate is used, measurement errors caused by humidity gradient are of order of magnitude.

Effects of a guard plate on the characteristics of an electrospray in the cone-jet mode

The effects of an additional electric field established near the capillary nozzle on the performance of the electrospray were evaluated through experiments and simulations. Applying the additional electric field, a circular guard plate was connected to a capillary nozzle. The stable cone-jet voltage, droplet size, spray plume angle, and spray current were measured for three types of nozzles. An electrospray nozzle with a nonconducting guard plate (nozzle I), and electrospray nozzles having a conducting guard plate (nozzles II, III) were employed. For the electrospray with the conducting guard plate, the stable cone-jet mode is initiated at a higher voltage and maintained in a wider range of applied voltage than that of the electrospray with the nonconducting guard plate, because the conducting guard plate reduces the electric field near the cone-tip and prevents some electric disturbances. In addition, as the capillary tip to the conducting guard plate distance became smaller, the effect of the guard plate on the spray characteristics appeared more clearly. For the motion of spray droplets, the spray angle became smaller for the case employing the conducting guard plate. The spray plume angles of nozzles II and III were about 17° and 24°, respectively, while the spray plume angle of nozzle I was about 68°. On the other hand, if only the cone-jet mode is initiated, there is not a big difference between all three types of nozzles for the droplet size and the spray current. Therefore, a conducting guard plate could be appropriate for some applications which need a narrow spray plume angle, high velocity droplets, and a wide operating voltage range while maintaining the original advantages of the cone-jet mode.

DEVELOPMENT OF HOT/COLD PLATE APPARATUS FOR DETERMINING HEAT TRANSPORT MECHANISMS IN MULCH MATERIALS

To study the effects of mulches and crop residues on soil temperature, researchers have frequently used simulationmodels. In such models, quantification of heat transport within the mulch material is often weak and heat transportmechanisms are poorly understood. In this paper we describe an apparatus to quantify heat transport through dry mulchmaterials. In addition, heat transport mechanisms (conduction, thermal radiation, free and forced convection) can beidentified and quantified using this apparatus. The apparatus consists of precisely controlled and monitored 0.9 m by 0.9 mhot and cold plates. The hot plate actually consists of three component plates: a test, a guard, and a bottom plate that areindividually controlled (temperature) and monitored (temperature and power). The guard plate surrounds the test plate,minimizing undesired lateral heat flow. The bottom plate is positioned in parallel with the test and guard plates to insure thatall wattage into the test plate moves off the top of the plate through the mulch. The correct functioning of the hot plate wasverified using three reference materials with a known thermal resistance.<br><br>The cold plate is based on techniques using thermoelectric devices (Peltier coolers). In addition, heat sinks and fans areused to transport heat away from the cold plate. A twodimensional numerical simulation showed that errors caused by lateralheat flow in a sample contained between the hot and the cold plate can be neglected. The thermal conductivity of air wasmeasured using the apparatus, yielding a value of 0.026 W m 1
C 1 , exactly matching the theoretical value, thus confirmingthe correct functioning of the hot/cold plate combination.

Currents related to the sodium-calcium exchange in squid giant axon

We report the measurement of a Ca i-activated membrane current in dialyzed squid axon under membrane potential control with a low-noise voltage clamp. Two additional voltage clamp systems were used to clamp the external guard plates to a value that prevented the establishment of potential differences between the central and lateral compartments of the experimental chamber. This reduced to a minimum the contribution of membrane currents generated at the axon ends to the current measured in the central pool. This latter current was reduced by using internal and external solutions designed to diminish at a maximum membrane currents, while maintaining the conditions for optimal operation of the Na +-Ca 2+ exchange. Thus TTX was used to block Na + channels and prolonged exposure to K +-free media was used to eliminate K + conductance. The maximum concentration of external sodium was 200 mM. The addition of fixed amounts of free ionic calcium to the internal solution, activated a current whose direction and magnitude depended on the thermodynamic driving forces for calcium and sodium. When the experimental conditions determined an inwardly directed current, this depended on the presence of external sodium, and lithium could not substitute for it. The Ca i-activated current, was blocked by external lanthanum and showed a high temperature dependence. In experiments in which the reversal potential was measured fof the Ca i-activated current, it was found to be strikingly similar to the value calculated according to E r = 3 E Na, suggesting that the current is the electrical manifestation of the Na +-Ca 2+ exchange operating with an stoichiometry of 3Na +:1Ca 2+.

Railgun current guard plates: active current management and augmentation

A system of auxiliary conductors designed to reduce current density peaks in railgun rails is described, and the effects on rail current density and projectile force are discussed. Performance comparisons with simple railguns and typical augmented railguns are made. It is shown that the wrap-around design of the guard plates can produce four to eight times the force produced by the usual augmented railgun design, without increasing local peak current densities. The range of performance contained in the factors between four and eight is primarily a function of the complexity of design. The more complex designs involve allowing the guard plates to overhang the rail slightly (intruding into the bore space, similar to rifling in a conventional gun barrel), and the use of separate power supplies for the rail and guard-plate conductors. These added complexities represent unacceptable complications for many applications, but may be justifiable for others.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Fabrication of catheter-tip and sidewall miniature pressure sensors

Silicon-diaphragm miniature pressure sensors, which use the piezoresistive effect, were developed for biomedical applications. We fabricated two types of sensors; that is, a catheter-tip (1.2-mm outside diameter, 0.17 mm thick) and a sidewall (1.4 × 3.45 × 0.22 mm) sensor, both having a thin circular diaphragm. Their diaphragms, 10 µm in thickness and 0.55 mm in diameter, were formed by an electrochemical etching method. Since the stability of pressure sensors is the most important requirement for precise pressure measurements, attractive approaches have been investigated to improve stability. The major instabilities of the present miniature pressure sensors are electrical drifts caused by leakage currents and thermal disturbances related to packaging stress. A shield and a guard plate can prevent the device from leakage currents. A thick supporting rim structure of the sensor and mounting on a stainless steel support with elastic material contribute to eliminate the packaging stress. For the purpose of easy lead attachment to the catheter-tip sensor, we use a unique structure having deep contact holes in deposited thick polysilicon layer (0.05 mm thick). Experimental results are as follows: Initial drift after power up was improved to about one tenth. Thermal disturbances, as temperature zero shift, thermal transient response, and temperature cycle hysteresis were greatly reduced. Low-temperature zero shift of 0.2 mmHg/°C was obtained using a simple temperature compensation method. Long-term drift was 0.6 mmHg/day. The catheter of 1.8-mm outer diameter having two sidewall sensors has been satisfactorily used for the study of urodynamics.

44—SIMULATION OF THE ELECTRIC FIELD IN EVENNESS-TESTING CAPACITORS

A method for simulating the capacitive field of a yarn-evenness tester by a resistive technique is presented and is used to study the effect of guard plates, and of the presence of a yarn on the field. More precise detection of the yarn is achieved with guard plates, and the potential applied to them is shown not to be too critical.

23—THE TRANSMISSION OF HEAT THROUGH TEXTILE FABRICS. PART III. A NEW THERMAL-TRANSMISSION APPARATUS

Details are given of a new thermal-transmission apparatus which is automatic in operation, which does not depend on the measurement of a heat flux, and which requires no guard plates to eliminate edge heat losses. The apparatus works on the principle that for conductors in series with respect to direction of heat flow, the ratio of the temperature drop across them equals the ratio of their thermal resistances, and the only measurements involved are those of temperature in the equilibrium state. The apparatus is suitable for testing the thermal-transmission properties of textile materials up to at least 1 in. thick. Data are presented for the thermal-transmission properties of timber and of plate glass determined with the new apparatus.