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Purpose The purpose of this study is to propose the use of a pre-deposition heating system for fused filament fabrication (FFF) as a means to enhance interlayer bonding by elevating the substrate temperature. The effects of the heating on thermal profile at the bonding interface and the mechanical properties of three-dimensional printed parts are investigated. Design/methodology/approach A 12-W laser head is integrated to a commercial printer as the pre-deposition heating system. The laser beam heats up substate before the deposition of a fresh filament. Effects of laser powers are investigated and the thermal profile is measured with thermocouple, infrared camera and finite element model. The correlation between the temperature at the bonding interface and the bonding quality is investigated by conducting tensile testing and neck width measurement with microscope. Findings The pre-deposition heating system is proven to be effective in enhancing the inter-layer strength in FFF parts. Tensile testing of specimens along build direction (Z) shows an increase of around 50% in ultimate strength. A linear relationship is observed between the pre-deposition temperature at bond interface and bonding strength. It is evident that elevating the pre-deposition temperature promotes interlayer polymer diffusion as shown by the increased neck width between layers. Originality/value Thermocouples that are sandwiched between layers are used to achieve accurate measurement of the interfacial temperature. The temperature profiles under pre-deposition heating are analyzed and correlated to the interlayer bonding strengths.

Vessel sealing using bipolar electrosurgery is becoming a common practice in modern operating rooms. Despite all the advantages such as faster operation, less bleeding, and shorter postsurgery recovery time, side effects including sticking, charring, and rebleeding still occur, leading to increased surgery time and sometimes fatal complications. Tissue impedance during the electrosurgical process has been used to determine the electrical power of the process. However, little has been done to understand the dynamic tissue impedance and its effectiveness in monitoring the vessel sealing process. Moreover, the samples used in previous studies all had small diameters of 2–5 mm. In this study, an experimental setup was developed to perform vessel sealing tests using large-diameter blood vessel samples with mimicking blood flow. The tissue impedance during the heating process was obtained. Burst pressures after sealing were measured. A finite element simulation model was developed to understand the dynamic impedance behavior. It is seen that the tissue impedance increases rapidly in the beginning of the heating process and remains at a level that is several orders of magnitude higher than the initial value. This rapid impedance increase indicates protein denaturing, thus can be used to monitor the electrosurgical vessel sealing process. An impedance-based monitoring algorithm was developed, with which a burst pressure at least twice the normal human systolic blood pressure was achieved.

Objective: Electrosurgical vessel sealing is a process commonly used to control bleeding during surgical procedures. Finite element (FE) modeling is often performed to obtain a better understanding of thermal spread during this process. The accuracy of the FE model depends on the implemented material properties. Thermal conductivity is one of the most important properties that affect temperature distribution. The goal of this study is to determine the tissue thermal conductivity as a function of thermal dose. Methods: We developed an iterative approach to correlating tissue thermal conductivity to more accurately calculated thermal dose, which cannot be experimentally measured. The resulting regression model was then implemented into an electrosurgical vessel sealing FE model to examine the accuracy of this FE model. Results: The results show that with the regression model, more reasonable temperature and thermal dose prediction can be achieved at the center of the sealed vessel tissue. The resulting electrical current and impedance from the FE model match with the experimental results. Conclusion: The developed approach can be used to determine the correlation between thermal dose and thermal conductivity. Describing the thermal conductivity as a function of thermal dose allows modeling of irreversible changes in tissue properties. Significance: By having a more accurate temperature estimation at the center of the sealed vessel, more insight is provided into how the tissue reacts during the vessel sealing process.

Electrosurgical vessel joining is commonly performed in surgical procedures to maintain hemostasis. This process requires elevated temperature to denature the tissue and while compression is applied, the tissue can be joined together. The elevated temperature can cause thermal damages to the surrounding tissues. In order to minimize these damages, it is critical to understand how the tissue properties change and how that affects the thermal spread. The purpose of this study is to investigate the changes of tissue thermal conductivity and how the changes correlate to thermal dose during the joining process. We propose a hybrid method combining experimental measurement with inverse heat transfer analysis to determine thermal conductivity of thin tissue sample. Porcine aorta arterial tissues were used to investigate tissue thermal conductivity with variable thermal dose. Different joining times were used to create different amounts of thermal dose. A 36% decrease in tissue thermal conductivity was found when the thermal dose reaches the threshold for second-degree burn. When thermal dose is beyond the threshold of third-degree burn, the tissue thermal conductivity does not decrease significantly. A regression model was also developed and can be used to predict tissue thermal conductivity based on the thermal dose.

Vessel sealing with a bipolar electrosurgical device has become a common practice in modern operation rooms. Despite all the advantages, such as easier operation, less bleeding, and shorter post-surgery recovery time, side effects including sticking, charring, and rebleeding, often occur, leading to increased operation time and sometimes complications that are potentially fatal. Tissue impedance during the electrosurgical procedure has been used to improve the surgical outcome However, this method has only been effective for small-diameter vessels of 3–5 mm. Overall, little is found in literature on dynamic impedance monitoring of blood vessel sealing using bipolar electrosurgical devices. In this study, an experimental setup was designed and built to perform vessel sealing tests on large-diameter blood vessels with mimicking blood flow. Ex vivo porcine carotid artery samples with a diameter about 7 mm were used. Burst pressures after sealing were measured. It was found that the tissue impedance started with an initial decrease, followed by a rapid increase, and ended with a plateau that was orders of magnitude higher than the initial impedance. The rapid increase of impedance provides indication of protein denaturing, thus the seal completion. This feature was used to monitor the electrosurgical vessel sealing process. It is shown that a burst pressure at least twice the normal human systolic blood pressure can be achieved with heating until the maximum tissue impedance is reached. A FEA model was developed in COMSOL to understand the dynamic impedance behavior in the vessel sealing process.

Minimally invasive surgery is a popular surgical method which allows surgeons to be able to employ small incisions to perform surgical procedures. Electrosurgical tissue joining is one method used in minimally invasive surgery to achieve hemostasis. The two major issues need to be concerned are the quality of the tissue joint and the potential thermal damage to the surrounding tissues. In this study, a new sequential compression concept was introduced. This concept uses a pair of smaller electrodes to sequentially compress and join multiple locations across the tissue to form a joint. Due to the smaller area of the electrode surface, a higher compression level can be achieved with a smaller compressive force. In this study, different joining times including 1.5, 1.6, 1.7, 1.9, 2.1 seconds with a 98% compression ratio were used to join porcine arterial tissue. In each test, three locations were sequentially compressed and joined. The resulting tensile strength, specific strength, energy consumption, and thermal dose from the sequential compression method were compared with those resulting from the nonsequential single compression method. For the 1.9-second joining time, the specific strength is 2.5 times higher than the highest specific strength achieved by the single joining method, meaning that only 40% of energy is needed to achieve an equivalent joint strength. A finite element model was built to estimate the temperature and thermal dose during the sequential joining process and also confirmed that the resulting thermal dose is much lower than the single joining method. The results validated that the sequential compression concept has the potential to minimize the thermal damage during the tissue joining process.

Electrosurgical tissue joining is an effective way to create hemostasis, especially in surgical procedures performed in the minimally invasive manner. The quality of tissue joints and potential thermal damages to the surroundings are the two main concerns when using electrosurgical tissue joining tools. A more robust method for quality control is still needed. The goal of this study is to characterize the joining process using dynamic impedance and energy efficiency. Three joining times (4, 6, and 8 s) and three compression levels (80%, 90%, and 95%) were used to join porcine arterial tissues while the process parameters including voltage, current, and impedance were monitored. Tensile tests were performed to evaluate the quality of tissue joints. A new index, the strength-energy coefficient (mmHg/J), which is defined as the tensile strength divided by the consumed energy, is introduced to evaluate the energy efficiency of the joining process. Strength-energy coefficient offers a new way to estimate the required joining time to achieve sufficient joining strength while minimizing the energy consumption to reduce thermal damages. The 95% compression level has the highest strength-energy coefficient for 4- and 6-s joining times. This indicates that the 95% compression level has higher energy efficiency and can form a good tissue joint with less energy and time in comparison with those required by a lower compression level. The progression of the tissue joining process was characterized by the real-time impedance measurement, which can be used as a tool for quality control.

Electrosurgical tissue joining is an effective way to create hemostasis, especially in surgical procedures performed in the minimally-invasive manner. The quality of tissue joints and potential thermal damage to the surroundings are the two main concerns when using electrosurgical tissue joining tools. A more robust method for quality control is still needed. In this study, we developed an experimental setup to join tissues and performed tensile tests to evaluate the quality of the tissue joint, while also monitoring the process parameters including voltage, current, impedance, temperature and thermal dose. Three joining times (4, 6, and 8 seconds) and three compression levels (80%, 90%, and 95%) were used to join porcine arterial tissues. It was found that 95% compression can form a strong joint with a shorter joining time and less energy, but the joint strength decreases when the joining time is extended to 8 seconds. A lower compression level can still form a quality joint but requires longer joining time and energy which could lead to more thermal damages. A new index, specific strength (mmHg/J), which is defined as the ratio between tensile strength and the consumed energy, is proposed. Specific strength offers a new way to estimate the required joining time to achieve sufficient joining strength while minimizing the energy consumption to reduce thermal damages.

The current study shows computational and experimental analysis of multiphase flows (gas-liquid two-phase flow) in channels with sudden area change. Four test sections used for sudden contraction and expansion of area in experiments and computational analysis. These are 0.5–0.375, 0.5–0.315, 0.5–0.19, 0.5–0.14, inversely true for expansion channels. Liquid Flow rates ranging from 0.005 kg/s to 0.03 kg/s employed, while gas flow rates ranging from 0.00049 kg/s to 0.029 kg/s implemented. First, single-phase flow consists of only water, and second two-phase Nitrogen-Water mixture flow analyzed experimentally and computationally. For Single-phase flow, two mathematical models used for comparison: the two transport equations k-epsilon turbulence model (K-Epsilon), and the five transport equations Reynolds stress turbulence interaction model (RSM). A Eulerian-Eulerian multiphase approach and the RSM mathematical model developed for two-phase gas-liquid flows based on current experimental data. As area changes, the pressure drop observed, which is directly proportional to the Reynolds number. The computational analysis can show precise prediction and a good agreement with experimental data when area ratio and pressure differences are smaller for laminar and turbulent flows in circular geometries. During two-phase flows, the pressure drop generated shows reasonable dependence on void fraction parameter, regardless of numerical analysis and experimental analysis.

Electrosurgical vessel joining is commonly performed in surgical procedures to maintain hemostasis. This process requires elevated temperature to denature the tissue and while compression is applied, the tissue can be joined together. The elevated temperature can cause thermal damages to the surrounding tissues. In order to minimize these damages, it is critical to understand how the tissue properties change and how that affects the thermal spread. This study used porcine aorta arterial tissue to investigate tissue thermal conductivity with variable thermal dose. Seven joining times (0, 0.5, 1, 1.5, 2, 4, and 6 seconds) were used to create different amounts of thermal dose. A hybrid method that uses both experimental measurement and inverse heat transfer analysis was conducted to determine the thermal conductivity of thin tissue samples. In general, the tissue thermal conductivity decreases when thermal dose increases. Accordingly, 36% decrease in tissue thermal conductivity was found when the thermal dose reaches the threshold for second-degree burn (with 2-second joining time). When thermal dose is beyond the threshold of third-degree burn, the tissue thermal conductivity does not decrease significantly. A regression model was also developed and can be used to predict tissue thermal conductivity based on the thermal dose.

Electrosurgical vessel sealing, a tissue joining process, has been widely used in surgical procedures, such as prostatectomies for bleeding control. The heat generated during the process may cause thermal damages to the surrounding tissues which can lead to detrimental postoperative problems. Having better understanding about the thermal spread helps to minimize these undesired thermal damages. The purpose of this study is to investigate the changes of tissue thermal conductivity during the joining process. We propose a hybrid method combining experimental measurement with inverse heat transfer analysis to determine thermal conductivity of thin tissue sample. Instead of self-heating the tissue by the thermistor, we apply an external cold boundary on the other side of the tissue sample to stimulate a higher temperature gradient without denaturing the tissue in comparison to the heated method. The inverse heat transfer technique was then applied to determine the tissue thermal conductivity. Tissue thermal conductivity at different levels (0%, 25%, 50%, 75%, and 100%) of the joining process was measured. The results show a decreasing trend in tissue thermal conductivity with increasing joining level. When the tissue is fully joined, an average of 60% reduction in tissue thermal conductivity was found.Copyright © 2016 by ASME

Haplotypes, rather than genotypes are required in some disease susceptibilities and drug response tests. However, it is both time-consuming and expensive to obtain haplotypes experimentally. Therefore usually genotype data are collected in the laboratory at first, then, haplotype data are inferred from them resorting to some computational approaches. Different from Clark's well-known haplotype inference method, Gusfield and Wang et al. proposed a new model according to the maximum parsimony principle. It tries to find a minimum set of haplotypes that can explain the genotype samples. This parsimony model overcomes some weaknesses of Clark's method. For the parsimony this paper presents model a polynomial time greedy algorithm and a compound algorithm that combines the greedy policy with the branch-and-bound strategy in a uniform framework. Compared with the original complete algorithm proposed by Wang et al., the greedy approximation algorithm runs much faster, and in the meanwhile, produces relatively higher accurate results. The compound algorithm is also a complete algorithm. Simulation results show that it is much more efficient and can be applied to instances of much larger scales than the