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Studies on the shortwave spectrum, namely short-gravity, gravity-capillary, and parasitic-capillary waves, reveal that spectrum representation may modify the estimate of momentum transport at the air-sea interface. However, in numerical simulations, the shortwave spectra are usually approximated by simplified formulations. The effect of three shortwave spectrum formulations on the momentum balance at the air-sea interface was quantitatively evaluated for light to high wind speeds and fully developed seas. In the simulations, the spectra considered were: (i) obtained by an extrapolated function, (ii) dependent on the wave age derived from the observations, and (iii) from the solution of the energy balance equation. Considering computational time, the second was the fastest. while the first and third the computational time increased, respectively, by approximately 2–7% and 15–30%, depending on the wind speed. Concerning the observations, the mean square slope, the coupling parameter, and the drag coefficient, the second and third formulations showed better agreement, while the first one showed a large discrepancy. The results highlighted the importance of shortwave formulations in the analysis of the interaction between wind and wave. [ABSTRACT FROM AUTHOR]

Modern mining enterprises widely use rotary drilling rigs equipped with ball drill heads, which are used to drill holes ∅250 - ∅320 mm in hard rocks for blasting operations. Drilling of such wells is associated with the use of significant axial forces and torques, which cause longitudinal deformation (compression) and torsional deformation of the rods and the drillstock as a whole. Therefore, the intensification of rotary drilling processes to increase the diameter of the drilled well is associated with significant technical difficulties and economic costs. In a number of practical cases, it is possible to drill large diameter wells in two stages. The first stage involves drilling a small-diameter (∅250 - ∅320 mm) advance well from the outer horizons of a mining enterprise (e.g., a mine) to a lower horizon or a network of horizontal workings connected to a pit. After drilling the advance borehole (∅250 - ∅320 mm), a drill bit is lowered to the horizon below, which is put on a drill bit instead of a small diameter crown. After replacing the working tool with a diameter of ∅250 - ∅320 mm with a drill bit with a diameter of ∅1500 - ∅3000 mm, drilling is carried out vertically upwards (sometimes at an angle). When drilling, the drill stand is subjected to torque and tensile axial force. In this mode of operation, the loads on the drillstring increase significantly, but the longitudinal axis of the drillstring remains straight, as the influence of longitudinal bending is eliminated, and the influence of drillstring unbalance due to initial misalignment and centrifugal forces is reduced. However, the moment of friction forces during drilling increases significantly, the influence of the drillstring stiffness increases, and there is a possibility of longer stops during the driller's operation in the bottom hole, while the value of the elastic forces of the drillstring decreases with an increase in its length, and therefore the twist angle increases. In the case of an increase in the angle of rotation of the drill string, the dynamic torque and tangential stresses increase due to significant differences in the angular speed of rotation of the string (from to 0). In this case, there are significant changes in the kinetic energy of the pile with a decrease in the angular velocity of its rotation. In fact, a decrease in the rigidity of the mill leads to an increase in the increase in the kinetic energy of the system on the drill. That is, the dynamic angle of shaft torsion increases and leads to the manifestation of a torsional impact with a large coefficient of dynamism (). As follows from the industrial tests of the 2KV 3000 machine, the possibility of a torsional impact in the driller-drillstock-rotator system under the influence of a variable torque of friction forces between the rock and the tool was not taken into account. Therefore, at the maximum length of the drillstring, the increase in the kinetic energy of the impact causes the largest dynamic angle of twisting of the drillstring, which is perceived by the first rods from the driller, and they experience the ultimate induced normal stresses that lead to rod breakage. For these reasons, for the efficient operation of drilling rigs in the drilling mode, it is necessary to create and apply an engineering methodology for calculating the dynamic parameters of the drill string and the rig as a whole under the influence of the frictional interaction between the tool and the rock. [ABSTRACT FROM AUTHOR]

Photovoltaic solar thermal integration is a new idea for buildings to fully utilize clean energy for energy saving and emission reduction. The digital modeling of photovoltaic solar thermal integration in buildings is finished by creating the energy balance equation of the energy supply system and the physical model of the main equipment. The objective function is established and the constraints are set to achieve optimization of the operation model through planning and solving problems. The TRNSYS simulation platform carries the integrated operation model and optimization scheme, and the optimization effect is simulated and validated. The results of computer simulation effect analysis show that the RMS of the parameters is 2.74%, 11.71%, 8.55%, and 2.47%, respectively, and the simulated and experimental values are consistent. The average system thermal efficiency and average water tank thermal efficiency of the optimized scheme are better than those of the PV/T-FPC system, and the cumulative cost savings in the whole life cycle after replacing the proposed scheme in Beijing and other five cities are 8432 yuan, 5937 yuan, 3513 yuan, 31744 yuan, 34893 yuan, and 31877 yuan, respectively, and the optimization effect is significant.

The purpose of this paper is to investigate the performance improvement mechanism of a high power vertical centrifugal pump by using numerical calculations. Therefore, a comparative study of energy losses and internal flow characteristics in the original and optimized models was carried out with special attention to the hydraulic component matching. The optimized model (model B) was obtained by optimizing the vaned diffuser and volute based on the original model (model A), mainly the diffuser inlet diameter, diffuser inlet vane angle, volute channel inlet width and volute throat area were changed. Firstly, the comparative results on performance and energy losses of two models showed that the efficiency and head of model B was significantly increased under design and part-load conditions. It is mainly due to the dramatic reduction of energy loss PL in the diffuser and volute. Then, the comparisons of PL and flow patterns in the vaned diffuser showed that the matching optimization between the model B impeller outlet flow angle and diffuser inlet vane angle resulted in a better flow pattern in both the circumferential and axial directions of the diffuser, which leads to the PL3 reduction. The meridian velocity Vm of model B was significantly increased at diffuser inlet regions and resulted in improvements of flow patterns at diffuser middle and outlet regions as well as pressure expansion capacity. Finally, the comparisons of PL and flow characteristics in the volute showed that the turbulence loss reduction in the model B volute was due to the flow pattern improvement at diffuser outlet regions which provided better flow conditions at volute inlet regions. The matching optimization between the diffuser and volute significantly reduced the turbulence loss in volute sections 1–4 and enhanced the pressure expansion capacity in sections 8–10. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Crop water stress indices (CWSIs) quantify plant water status based on measurement of plant temperature. The goal of CWSI formulation is to normalize measured leaf temperatures based on reference temperatures to remove sensitivity to ambient environmental conditions (e.g., air temperature, humidity, radiation), while retaining sensitivity to plant water status as reflected by stomatal conductance. This study sought to better understand the sensitivity of these temperatures to ambient environmental conditions, and ultimately how they influence various CWSIs. The surface energy balance was modeled to simulate the impacts of input parameter variation on leaf temperature and reference surface temperatures used to calculate four different CWSIs. The performance of the CWSIs were assessed based on their ability to maximize sensitivity to stomatal conductance while minimizing the relative sensitivity to ambient environmental conditions. The sensitivity analyses indicated that all four CWSIs performed poorly in shaded conditions, as they had relatively low sensitivity to stomatal conductance and were sensitive to all environmental parameters. Two CWSIs had high sensitivity to stomatal conductance, and low sensitivity to all environmental parameters except wind speed. None of CWSIs could remove sensitivity to all environmental parameters while retaining sensitivity to stomatal conductance.

Crop water stress indices (CWSIs) quantify plant water status based on measurement of plant temperature. The goal of CWSI formulation is to normalize measured leaf temperatures based on reference temperatures to remove sensitivity to ambient environmental conditions (e.g., air temperature, humidity, radiation), while retaining sensitivity to plant water status as reflected by stomatal conductance. This study sought to better understand the sensitivity of these temperatures to ambient environmental conditions, and ultimately how they influence various CWSIs. The surface energy balance was modeled to simulate the impacts of input parameter variation on leaf temperature and reference surface temperatures used to calculate four different CWSIs. The performance of the CWSIs were assessed based on their ability to maximize sensitivity to stomatal conductance while minimizing the relative sensitivity to ambient environmental conditions. The sensitivity analyses indicated that all four CWSIs performed poorly in shaded conditions, as they had relatively low sensitivity to stomatal conductance and were sensitive to all environmental parameters. Two CWSIs had high sensitivity to stomatal conductance, and low sensitivity to all environmental parameters except wind speed. None of CWSIs could remove sensitivity to all environmental parameters while retaining sensitivity to stomatal conductance.

In order to contribute knowledge on the method used to calculate the actual crop evapotranspiration, soil, crop, atmosphere, and water spatial structure were integrated into a complete system. Based on the energy balance equation and aerodynamic equation, the meteorological data was reduced and the crop physiological parameter was increased, then the crop evapotranspiration calculation model under natural conditions was derived. The crop evapotranspiration calculation model was verified by the water balance formula using data generated from corn, potato, and flue‐cured tobacco grown under field conditions for three consecutive years from 2017 to 2019. The results showed that: from 2017 to 2019, the average root mean square error for measured and calculated evapotranspiration of corn, potato, and flue‐cured tobacco at different growth times were 0.5948, 0.4753, and 0.3326, respectively, the mean deviation, mean absolute error, and mean relative error were small, and the coefficient of determination and consistency index were both greater than 0.9100. The measured and calculated crop evapotranspiration of the selected crops increased at first and then decreased gradually as the crops matured, and finally decreased to harvest evapotranspiration, showing a parabolic trend. The crop evapotranspiration calculation model not only reflects the actual evapotranspiration of crops at different growth time but also reflects the change law of actual crop evapotranspiration. The model does not need the correction of soil moisture content, irrigation method, and crop coefficient and can directly calculate the actual crop evapotranspiration. It has the characteristics of consistency between the calculated value and the measured value, strong applicability, simple calculation process, and high accuracy and has the best effect on monitoring soil moisture and crop water shortage sensitivity. The model is significance in that it guides for monitoring soil moisture, determining actual crop evapotranspiration, crop water shortage index, and high yield and efficiency under water‐saving conditions. [ABSTRACT FROM AUTHOR]

In bladed energy conversion machines, the tip leakage vortex (TLV) is a prevalent phenomenon, which can lead to both flow losses and cavitation. Numerous scholars in recent years have proposed effective methods for TLV suppression, utilizing either active or passive control strategies. This work focuses on the implementation of the hole-pit (HP) structure located at the leading edge 2%–25% chord position of the hydrofoil to induce passive jets and separate flows for suppressing TLV structures. The rotating curvature correction (CC) shear stress transport (SST) k - ω turbulence model and Zwart-Gerber-Belamri (ZGB) cavitation model are employed to clarify the control effect and mechanism of HP structure through numerical analysis and experimental verification. The results reveal that the passive jet and pit-separated flow from the HP structures effectively divide the TLV into distinct segments, giving rise to new vortical structures. These vortical structures are categorized hole separation vortex (HSV), pit separation vortex (PSV), newborn tip separation vortex (NTSV), and weakened tip leakage vortex (WTLV). The control ability of HP structures in different schemes is strongly correlated with their number and arrangement. Optimal control effects are achieved when the HP is positioned near the separation vortex over the top of the foil. Specifically, when the number of drainage holes is 3 or 4, the theoretical TLV cavitation length is suppressed by at least 63.93%. The passive jet induced by the HP structure alters the distribution of different kinds of energy losses in tip clearance and TLV core through the effect gap leakage flow, leading to a sharp rise in the value of total energy loss. This results in a weakening of gap leakage flow energy and TLV intensity, accompanied by a raised vortex core pressure. Thus, the research successfully realizes the purpose of suppressing both TLV and TLV cavitation. • A novel flow control method suppressing tip leakage vortex (TLV) is proposed. • The suppression effect of HP structures on TLV is evaluated in different aspects. • The HP structure can suppress TLV by changing the energy distribution of the leakage flow and TLV. [ABSTRACT FROM AUTHOR]

This paper discusses closed-form demonstrations of the damping effect for a basic mass, spring, and damper (MSD) and a single degree of freedom (SDOF) system that are exposed to harmonic loading. Initially, the energy balance equations of the systems were solved in closed form by considering the damping ratio and loading frequency. Verification of the solutions obtained for SDOF systems is achieved by shake table tests. Based on the analytical and experimental results, it was found that the damping effect is highly related to the ratio of loading frequency to the natural vibrational frequency of the system. For the lower and higher values of the ratio, damping is found to be almost ineffective. However, the effect becomes substantial when the ratio reaches unity i.e. at the resonant frequency. Damping has a reverse relation with seismic energy at the dominant frequency. In contrast, the relation is proportional in the vicinity of resonance frequencies. Hence, considering the damping as a parameter for the energy-based design of structures is suggested. [ABSTRACT FROM AUTHOR]

In a grid-tied type-4 wind turbine generator (WTG) system, the frequency of sub/super-synchronous oscillation varies in a wide range, making it difficult to suppress the oscillation. In view of this problem, an active damping control strategy based on energy feedback is proposed. First, the energy balance equation of stored energy, dissipation energy, and interaction energy in a grid-tied type-4 WTG system is established. And the mathematical relationship between the increasing/decreasing trend of stored energy and the divergence/convergence of oscillation, no matter how the oscillation frequency varies, is derived. Then, by calculating the contribution degrees of different energy feedback branches to the variation rate of stored energy, the key energy feedback branches that cause the stored energy to increase are selected. And then, with the variation rate of stored energy being made negative as the control objective, this article derives a reactive current compensation function and constructs an additional energy feedback branch to eliminate the effect of key energy feedback branches, thus realizing active damping suppression of oscillations in a broad frequency band. Finally, the real-time digital simulator based hardware-in-loop test platform with a practical controller of a real 2.5-MW type-4 WTG and experimental platform are both built on which the proposed strategy is verified. Simulation results show that the proposed method can realize effective damping control of oscillations in a broad frequency range. In addition, this article is accompanied by a video demonstrating hardware-in-loop test results. [ABSTRACT FROM AUTHOR]

We successfully extend a multiscale simulation (MSS) method to nonisothermal well-entangled polymer melt flows between two coaxial cylinders. In the multiscale simulation, the macroscopic flow system is connected to a number of microscopic systems through the velocity gradient tensor, stress tensor and temperature. At the macroscopic level, in addition to the momentum balance equation, we consider the energy balance equation, where heat generation plays an important role not only in the temperature distribution but also in the flow profile. At the microscopic level, a dual slip-link model is employed for well-entangled polymers. To incorporate the temperature effect into the microscopic systems, we used the time-temperature superposition rule for the slip-link model, in which the temperature dependence of the parameters is not known; on the other hand, the way to take into account the temperature effect in the macroscopic equations has been well established. We find that the extended multiscale simulation method is quite effective in revealing the relation between nonisothermal polymeric flows for both steady and transient cases and the microscopic states of polymer chains expressed by primitive paths and slip-links. It is also found that the temperature-dependent reptation-time-based Weissenberg number is a suitable measure for understanding the extent of the polymer chain deformation in the range of the shear rate used in this study.

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper shows that the zero flow treatment algorithm and the convergence criteria of EPANET 2.2, the latest version of the EPANET 2 open-source software package, may be responsible for convergence to distinctly inaccurate results in the case of networks with low-resistance pipes. As an alternative, the paper suggests a zero flow treatment method proposed earlier, which is based on the smallness of the flow rather than the flow derivative of the head loss as in EPANET 2.2. To avoid spurious convergence, the EPANET 2.2 convergence criteria may be complemented with a criterion based on the flow residuals of the energy balance equations. The monotony of the head loss vs. flow relationship allows these residuals to be checked for a specified tolerance without solving the energy balance equations for the flow. [ABSTRACT FROM AUTHOR]

The energy consumption of particle breakage is added to the Cambridge energy balance equation so that the energy balance equation for coarse-grained soil is obtained. To reasonably measure the energy consumption of particle breakage, a function of friction coefficient relating to the axial strain is proposed to replace the friction coefficient as a constant in the energy balance equation based on the evolution rule of particle breakage. Then, according to the energy balance equation of coarse-grained soil, the energy consumption of particle breakage is calculated, and the particle breakage energy increases with axial strain increasing, which satisfies the thermodynamic law. Based on this energy balance equation, a simple stress dilatancy relationship is developed. In this stress dilatancy relationship, the relationship between d E b / p d ε s and M / M f can be described by a simple function with acceptable accuracy. This stress dilatancy relationship is validated with the satisfactory capability to predict the dilatancy behavior of coarse-grained soils, which can be the effective choice to build the constitutive model. [ABSTRACT FROM AUTHOR]

According to the new hollow glass window with double suspended films, from the perspective of heat transfer, a theoretical support was provided for the research and development of the structure. Based on the ISO 10077-2 algorithm, the energy balance equation of hollow glass unit with double suspended films was established, followed by the thermal calculation of hollow glass unit with double suspended films using the software WINDOW. Finally, using the software THERM to calculate the U-val¬ue and dew point temperature of hollow glass window with double suspended films. The results show that the hollow glass window with double suspended films has excellent thermal insulation performance and anti-condensation performance under the premise that the cavity is not filed with rare gas. The method is applicable to the thermal calculation of hollow glass window with double suspended films, and is the theoretical basis for its thermal performance. [ABSTRACT FROM AUTHOR]

Crop production is accompanied by a set of tasks, each of which for different soil and climatic conditions has its own characteristics and standards. Irrigation is one of the types of water reclamation in areas with insufficient and unstable natural moisture, aimed at preventing soil and partially atmospheric droughts. Determination of crops moisture supply and irrigation norms is the most important task when growing crops in arid regions. The objective of our work is to develop an automated information technology for decision-making during irrigation. The main indicators of moisture supply of the irrigated field is the reference, potential and actual evapotranspirations, crop water stress index. Indicators of moisture supply are determined according to the monitoring of agro/meteorological, physiological parameters of crops. For monitoring tasks in the Agro/physical Institute (St. Petersburg), an automated mobile field agro/meteorological complex (AMFAC) was created. The software of the complex allows real-time saving of synchronously measured data time series, which are used for automated calculation of reference, potential and actual evapotranspirations, crop water stress index and irrigation norms. As a result of the field experiments, methods for assessing the evapotranspiration and crop water stress index were tested. Automated information technology, including monitoring, the creation of a database, and computational algorithms for models of energy exchange in the «soil – plant – atmospheric surface layer» system can serve as the basis for an expert decision-making system for irrigation.

In the United States, recent studies have demonstrated weight gain over Thanksgiving contributing to a significant portion of annual national weight gain. Understanding the social context of how Thanksgiving celebrations were perceived is critical for preventing and reducing excess weight during this time. Energy intake from present-day data was back-calculated from body weight data collected in participants before and after Thanksgiving. Similar calculations were performed in studies that also included Christmas. A Latent Dirichlet Allocation analysis of topics scraped from Twitter under the hashtag #thanksgiving was performed. The top topics and search queries from Google Trends on Thanksgiving 2020 were also identified. Since 1621, the social context of Thanksgiving has evolved from a focus on prayer and celebrated gratitude to a focus on food, football, and retail. What is served on Thanksgiving and its energy content has not substantially changed since the late 18th century. On the other hand, body weights and mean energy intake have steadily increased over time with the most rapid increases occurring since 1941. The shift in the social context of Thanksgiving and other factors of an existing obesogenic environment have likely combined to generate increased energy intake and weight gain during Thanksgiving. [ABSTRACT FROM AUTHOR]

In this work, studies of mode transition, as well as negative ion production in case of hydrogen discharge in Helicon Plasma Source (HeliPS), are performed in detail. Mode transition is studied in the plasma production or source chamber and the formation of negative ions is studied in the downstream expansion chamber. Hydrogen being the smallest diatomic molecule, it requires very high energy for ionization in comparison with oxygen. Also, due to the higher mobility of hydrogen ions, charged particle loss is much higher as compared to other gases in such a discharge. Therefore, unlike other gases such as oxygen, very high radio frequency (RF) power is required to attain the critical density for mode transition in case of hydrogen discharge. Also, the production of negative hydrogen ion (H–) is investigated in the expansion chamber and it is found that the negative ion fraction α (n– /ne) varies between ~0.07 to ~0.5 and increases with the increase in RF power and working pressure. The observed trends of the variation of the density of negative ions, electrons and positive ion are explained using the reactions responsible for the production and destruction of negative hydrogen ions and the mode transition is explained by using the energy balance equation. [ABSTRACT FROM AUTHOR]

The article concerns a theoretical investigation on the ground thermal energy storage (GTES) applied to a low-temperature district heating (LTDH) distribution network. A general formula describing the time-dependent GTES temperature variation was introduced. The highest values of the GTES operating parameters were obtained for the second model. The ground temperature of a varying liquid fraction content (0, 0.1, 0.2) reached a value of 33.42 °C, 33.29 °C and 33.07 °C, respectively. After the GTES was applied, the heat flux transferred to the end-users increased by 14.5 kW. Deactivation of the GTES caused that the heat flux transferred to the consumers had a constant value of 149.5 kW. The LTDH heat supplier was able to provide the heat flux which decreased in time by 8.26% when the GTES was activated. The impact of the GTES insulation on the ground temperature was studied. The results have shown that reducing the insulation by 1/3 results in the GTES temperature decrease by about 3%. It was also found out that inappropriate GTES operation mode may cause larger thermal depletion of the GTES. • A general formula allowing the GTES mean temperature calculation is introduced. • The GTES in the LTDH increases the heat flux transferred to the consumers. • The GTES in the LTDH increases water's outlet temperature of the supply pipe. • Random charging/discharging duration time of the GTES causes its thermal depletion. • 1/3 insulation reduction translates to 2.93% decrease in the GTES temperature. [ABSTRACT FROM AUTHOR]

Seismic input energy per unit mass (EI/m) imparted into a structure is a function of earthquake (duration, frequency content, amplitude etc.), soil (shear velocity, dominant period etc.) and the structural (vibrational periods etc.) characteristics. Generally, the damping properties of the structure is assumed negligible for seismic input energy. Most of the existing spectral equations derived for SDOF systems generally use a constant damping ratio of 5%. In this study, the damping effect on EI/m is investigated experimentally and numerically on SDOF systems with distinct damping ratios. Experimental investigation and numerical computations proved that seismic input energy is very sensitive to variation of damping within the vicinity of fundamental frequencies. Specifically, up to 50% increment was observed in the plateau region of the input energy spectrum, where maximum EI/m values occur, by variation of damping from 2% to 10%. Hence, a novel damping modification factor (DMF), which could be utilized for existing energy spectra, is proposed in this paper. Validation studies of the proposed DMF are achieved through the various energy spectra found in the literature. [ABSTRACT FROM AUTHOR]

We are concerned with the numerical solution of a linear transport problem with nonzero divergence velocity field that originates from the spectral energy balance equation describing the evolution of wind waves and swells in coastal seas. The discretization error of the commonly used first‐order upwind finite difference and first‐order vertex‐centered upwind finite volume schemes in one space dimension is analyzed. Smoothness of nondivergent velocity field plays a crucial role in this. No such analysis has been attempted to date for such problems. The two schemes studied differ in the manner in which they treat the scalar flux numerically. The finite difference variant is shock captured, whereas the vertex‐centered finite volume approximation employs an arithmetic mean of the velocity and appears not to be flux conservative. The methods are subsequently extended to two dimensions on triangular meshes. Numerical experiments are provided to verify the convergence analysis. The main finding is that the finite difference scheme displays optimal rates of convergence and offers higher accuracy over the finite volume scheme, regardless the regularity of the velocity field. The latter scheme notably yields convergence rates of 0.5 and 0 in L2‐norm and L∞‐norm, respectively, when the velocity field is not smooth. A test case illustrating wave shoaling and refraction over submerged shoals is also presented and demonstrates the practical importance of flux conservation. [ABSTRACT FROM AUTHOR]

Heat pumps (HPs) combined with groundwater have been used for heating greenhouses. Visualizing the coefficient of performance (COP) of an HP system through a display panel in the greenhouse or a remote display on a device such as a mobile phone could help farmers avoid wasting power and overpumping groundwater and enable them to use HPs in an energy-efficient manner. Simple COP estimation is important for reducing the number of temperature sensors attached to HPs; doing so could make HPs systems including visualization affordable for farmers. In this study, the COP was measured using an HP converted from an affordable air conditioner into a liquid-to-liquid heat exchanger unit. The COP equation was used with the temperatures of condensers and evaporators, which can be measured easily. The water temperature was simulated to verify this COP equation based on the energy balance equation incorporated with variables such as tank water temperature, water injection rate, and temperature of tank water inflow and outflow. The results obtained using equations with two and three coefficients showed good agreement with the measured values, particularly when the tank water temperature was 5–40 °C. [ABSTRACT FROM AUTHOR]

Copyright of Dokuz Eylul University Muhendislik Faculty of Engineering Journal of Science & Engineering / Dokuz Eylül Üniversitesi Mühendislik Fakültesi Fen ve Mühendislik Dergisi is the property of Dokuz Eylul Universitesi Muhendislik Fakultesi Fen ve Muhendislik Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recent studies show disordered materials such as amorphous silicon (a-Si), in spite of their low mobility, can efficiently amplify photocurrent via carrier multiplication process. Detectors with a thin (~40nm) a-Si multiplication layer has demonstrated single photon sensitivity at high speed under room temperature. It is believed that the abundance of bandtail states that cause low mobility of the amorphous materials actually contribute to the detector’s superior performance because carrier impact ionization involving these states, which can be modeled by donor-acceptor pairs (DAPs), relax the k-selection rule of the many-body carrier multiplication process. Our paper presents a theoretical framework to calculate the carrier multiplication process in a-Si or other disordered materials involving DAPs. Our analysis also establishes the relations between detector characteristics and key parameters such as the density of band tail states, layer thickness, and applied electric field. DAP assisted carrier multiplication rate is computed first. Carrier multiplication coefficients for electrons and holes under given applied field are then calculated using a trial distribution function that satisfies both the continuity equation and the energy balance equation. Our analysis shows that thinner a-Si gives rise to higher multiplication efficiency than thicker a-Si because of its higher carrier kinetic energy when the layer thickness is shorter than the length of energy relaxation by phonon scattering. Using the calculated carrier multiplication coefficients, voltage dependent gain of the device is computed and the results agree well with the measured results of a-Si cycling excitation process (CEP) detectors. [ABSTRACT FROM AUTHOR]

With the development of IC manufacturing process, the device dimensions have been on the nanoscale, while the device performance, such as the electron velocity, mobility and thermal noise, is significantly affected by the hot carrier effect. This paper proposes an electron temperature model to accurately predict the hot carrier effect. The channel transverse electric field is firstly derived by using the channel electric potential equation, taking into account the boundary conditions of the electric field. Based on the electric field equation, the energy balance equation is solved involving the impact of the temperature gradient and then the electron temperature model is established. The impact of the electron temperature on the channel mobility and of temperature gradient on the electron velocity has also been investigated. The results show that when the device enters the nanoscale, the electron mobility is more susceptible to the influence of the electric field and the electron temperature, and the impact of the temperature gradient on the velocity becomes obviously greater. The electron temperature model proposed in this paper can be applied to the performance analysis and modeling of nanosized MOSFETs. [ABSTRACT FROM AUTHOR]

Summary: An energy‐conserving and decaying time integration method is derived from the discretized energy balance equation in this paper. Based on the Gauss‐Legendre quadrature rule, the new method evaluates the mean internal force by collecting the internal forces of several quadrature points in the time interval. Compared with previous conserving methods, the new method avoids the reconstruction of finite element models as used in the energy‐momentum method, and the computation of energy functions as used in the constraint energy method, so it is simple and straightforward, and has no difficulty in implementation for dynamics with general nonlinear resilience including nonlinear damping force and internal force. By employing enough quadrature nodes, this method can preserve system energy accurately for conservative system, and then the unconditional stability is achieved automatically. In addition, the energy‐decaying method is developed by introducing the energy dissipation term to the energy balance equation, and two free parameters controlling the numerical dissipation are determined based on linear spectral analysis. Finally, the performance of the proposed method is checked on several examples and the results are compared with that of the trapezoidal rule. [ABSTRACT FROM AUTHOR]

The operating temperature of photovoltaic (PV) modules affects the photovoltaic conversion process. The operating temperature depends on various environmental conditions and on material-dependent properties of the PV modules. Many expressions for the operating temperature have been proposed in the literatures, some are simplified working Equation as NOCT (Nominal Operating Cell Temperature), and others are more complex, being based on a combination of the energy balance Equation and NOCT. The present study offers a new approach (model) for determining the PV module temperature based on the energy balance Equation and on the solar spectrum irradiance. While using the new model, the operating temperature has been determined for four module technologies: c-Si, a-Si/ μ c-Si, CdTe, and CIGS and it shows that the operating temperatures for the different cell types are close to the manufacturers' NOCT data-sheet temperatures. For c-Si technology, for example, the simulation resulted in 43.2° and 46° for the spectrum and NOCT models, respectively. The proposed new model offers a new approach for determining the operating temperature of PV modules. [ABSTRACT FROM AUTHOR]

This paper outlines a Hamiltonian energy‐balance function for computing stable and unstable regions of power systems. Once the generator model is defined, a certain number of variables (holonomic constraints) specifies its state properties (prefault, fault‐on, and postfault) entirely. The change between the postfault (final) and prefault (initial) states is expressed by an energy balance equation (crucial for solving many dynamical problems). State equations (instead of swing equation) with the properties (or functions) of the system are built using the prefault and postfault energies (kinetic and potential) of the generators. When a large disturbance occurs, the 'migration' from one state to another is computed using concepts of least action principle, conservation, and dissipation of energy, perturbation theory and calculus of variations. The method is tested with two electric power systems, where the classical model represents the synchronous generators. Prefault, fault‐on, and postfault regions are clearly characterised on 3D energy surfaces indicating whether the generators remain (or not) stable after a fault in the power system. The trajectories of the Hamiltonian energies of the generators are projected on 2D planar projection maps. The results provided important insights into transient stability problems not seen so far. [ABSTRACT FROM AUTHOR]

Background: Substance abuse can cause a range of harmful secondary health consequences, including body weight changes. These remain poorly understood but can lead to metabolic disorders including obesity and diabetes. Energy balance is a function of the equation: energy balance = energy intake - energy expenditure; an imbalance to this equation results in body weight changes. Currently, in the clinical setting, changes to food intake (energy intake) are considered as the primary mediator of body weight changes related to substance abuse, reflected in the current treatment focus on nutritional intervention. The influence of substance abuse on energy expenditure receives less attention. The aim of this think-piece is to consider potential causes of body weight changes during active substance abuse and abstinence, by focussing on the components of the energy balance equation. Methods: We discuss both human and animal studies on the effects of substance abuse on energy balance, with particular focus on animal models utilising pair-feeding, which enable investigation of energy balance whilst controlling for the effects of altered food intake. Results: We demonstrate that whilst some drugs of abuse affect food intake, this effect is inconsistent. Furthermore, body weight changes do not match food intake changes. Conclusion: We provide evidence that drugs of abuse can affect both energy intake and energy expenditure; contributing to the observed body weight changes. This think-piece highlights that treatment strategies for body weight changes related to substance abuse cannot focus solely on nutritional interventions, but should consider the impact of broader disruptions to energy balance. [ABSTRACT FROM AUTHOR]

Aerodynamic and canopy resistances have long been considered to be of key interest in model equation parameterization, particularly for the accurate estimation of crop evapotranspiration. However, model parameters applied in greenhouses showed variation affected by the micrometeorological environment. Three experiments were carried out in a plastic greenhouse to evaluate microclimate effects on resistances of a soilless cucumber crop. The regression analysis of canopy-to-air temperature (Tc − Ta) difference on air vapor pressure deficit (VPD) was substituted into the energy balance equation for the estimation of aerodynamic and canopy resistance values. As expected, a fan and pad evaporative cooling system proved to be the more efficient method of decreasing crop temperature (Tc) compared to the forced air ventilation system. The estimated transpiration by the Penman–Monteith model based on calculated aerodynamic and canopy resistance values successfully validated values measured with lysimeters in different growing periods. In this article, we report for the first time the calculation of aerodynamic and canopy resistance values inside a greenhouse based on equations for an open field that were found in the literature. Results may be helpful in Mediterranean greenhouses for direct determinations of plant water evaporative demand and smart climate control systems.