We report a case of a 63-year-old male who experienced an iatrogenic sigmoid perforation repaired combining three endoscopic techniques.The lesion was large and irregular with three discrete perforations,therefore,we ...We report a case of a 63-year-old male who experienced an iatrogenic sigmoid perforation repaired combining three endoscopic techniques.The lesion was large and irregular with three discrete perforations,therefore,we decided to close it by placing one clip per perforation,and then connecting all the clips with two endoloops.Finally we chose to use a fibrin glue injection to obtain a complete sealing.Four days after the colonoscopy the patient underwent a laparoscopic right hemicolectomy due to evidence of a large polyp of the caecum with high grade dysplasia and focal carcinoma in situ.Inspection of the sigma showed complete repair of the perforation.This report underlines how a conservative approach,together with a combination of various endoscopic techniques,can resolve complicated iatrogenic perforations of the colon.展开更多
Objective:Although endoscopic treatment has been used by many pediatric urologists for the treatment of vesicoureteral reflux(VUR),it has no considerable success in high-grade VUR.We aimed to describe the primary outc...Objective:Although endoscopic treatment has been used by many pediatric urologists for the treatment of vesicoureteral reflux(VUR),it has no considerable success in high-grade VUR.We aimed to describe the primary outcomes of unilateral periureteral injection technique(PIT),as well as bilateral PIT in high-grade VUR.Methods:In this prospective study,we examined 92 ureters in 45 boys and 40 girls from February 2010 to May 2018.Bilateral PIT and unilateral PIT were applied in 67 and 25 refluxing units,respectively.In the unilateral PIT,the subureteral injection site was only at the 5-or 7-o’clock position.However,in the bilateral PIT,the subureteral injection sites were at 5-and 7-o’clock position.Pre-and post-operative reflux grades were evaluated by voiding cystourethrography 6 months after surgery.Results:Seven patients had bilateral reflux.Overall,75(81.5%)ureters showed Grade IV VUR,while 17(18.5%)had primary Grade V VUR.The mean age of the subjects was 39.2 months.In unilateral PIT ureters,VUR was resolved in 23(92.0%)refluxing units.It was downgraded to Grade III in one ureter(4.0%)and to Grade II in another ureter(4.0%).In addition,in bilateral PIT cases,VUR was resolved in 60(89.6%)ureters;it downgraded to Grades II and III in 3(4.5%)and 4(6.0%)refluxing units,respectively.Conclusion:Unilateral PIT can be highly effective in the treatment of selected ureters of high-grade VUR.However,further studies are needed to confirm our results.展开更多
Delivered by intramuscular (IM) injections, Long Acting Injections (LAI), offering comparatively long term medicinal effects from several weeks to several months, are gaining much attention. The aim of this article wa...Delivered by intramuscular (IM) injections, Long Acting Injections (LAI), offering comparatively long term medicinal effects from several weeks to several months, are gaining much attention. The aim of this article was to indicate a safe and effective IM injection technique based on evidenced data derived from ultrasonographic data. Accurate anatomical knowledge is necessary in order to administer IM injections. It is possible to gain an adequate understanding of injection site anatomical structures by using ultrasound diagnostic devices. In particular, ultrasonography offers real-time diagnostic data allowing for observation of injection site, subcutaneous tissues, fat layers, muscle membrane, muscles and bones. To deliver the drug accurately into the muscle is essential, to achieve maximum drug efficacy and prevent injection site reactions. Therefore, when administering IM injections to the buttocks area, a suitable injection needle between 23G 25 mm to 21G or 22G 38 mm must be chosen depending on physique and drug characteristics. Needles determined as safe and effective through ultrasonographic evidence are needed such as in the case of a deltoid injection site, in which a 23G 25 mm injection needle is used in the absence of notable obesity. Not only the needle type is essential, but also the IM procedure itself. It is important to stretch the skin, inserting the needle at 90 degree angle to ensure depth of needle insertion to the muscle. Until new con-firmed evidence becomes available, it is necessary to increase the understanding of injection site selection methods, needle insertion depth, needle angle, and established IM injection techniques. The application of ultrasound devices in the development of next-generation techniques for IM injection is promising. Importantly, these techniques provide critical information from a risk management perspective.展开更多
Objective:To review the current literature on the practice of intramuscular injections(IMIs),focusing on immunizations.Methods:The present study comprises 2 reviews,characterized by high-quality evidence,per taining t...Objective:To review the current literature on the practice of intramuscular injections(IMIs),focusing on immunizations.Methods:The present study comprises 2 reviews,characterized by high-quality evidence,per taining to the deployment of the slow injection technique without aspiration(referred to in this paper as the without-aspiration slow injection technique[WASi T])and combined with the Zeta-track technique(ZTT).The literature review is oriented toward the analysis of 2 features associated with IMIs techniques:safety and pain,integrating new evidence on vaccinee positioning for each muscle site and general relaxation techniques in the multi-parametric analysis.Results:The rigorous and in-depth reviews in the current study reveal the usefulness of including,among the international guidelines for via intramuscular immunizations,the adoption of WASi T only for compliant vaccinees,and in combination with all validated techniques for IMIs,and the use of ZTT limitedly if specific well-developed muscles are indicated.All the technique's limitations are exposed.Conclusions:Future research directions are presented by including the author's study designs to provide indirect evidence for the validity of the rationale of the slow injection technique using scientific methods,and for the conduction of future randomized controlled trials(RCTs)focused on revisiting the adoption of ZTT in a dynamic and integrated immunizations protocol in anterolateral thigh(ALT),ventrogluteal(VG),and also in the deltoid muscle,in the specific cases analyzed.展开更多
The increase in the number of databases accessed only by some applications has made code injection attacks an important threat to almost any current system. If one of these applications accepts inputs from a client an...The increase in the number of databases accessed only by some applications has made code injection attacks an important threat to almost any current system. If one of these applications accepts inputs from a client and executes these inputs without first validating them, the attackers are free to execute their own queries and therefore, to extract, modify or delete the content of the database associated to the application. In this paper a deep analysis of the LDAP injection techniques is presented. Furthermore, a clear distinction between classic and blind injection techniques is made.展开更多
BACKGROUND ： Experimental animal models of intracerebral hemorrhag （ICH） are greatly needed, so the process of establishment should be ideal in hematoma formation and easy to operate. OBJECTIVE ： To construct mode...BACKGROUND ： Experimental animal models of intracerebral hemorrhag （ICH） are greatly needed, so the process of establishment should be ideal in hematoma formation and easy to operate. OBJECTIVE ： To construct model of ICH in rats with double injection of autologous blood taken from the cut tail cut and double withdrawal of the needle （shortened as two-step injection model）, and compare with those induced by single and double injections. DESIGN ： A randomized controlled tria SETTING： Department of Neurology, General Hospital of Military Area Command of Chinese PLA. MATERIALS： Thirty male Wistar rats of 10 to 12 months, weighing （400±25） g, provided by the Experimental Center of Medical Animals, General Hospital of Shenyang Military Area Command of Chinese PLA, were divided randomly into 3 groups with 10 rats in each group： two-step injection group, single injection group, double injection group. METHODS ： The experiment was carried out in the Department of Neurology, General Hospital of Military Area Command of Chinese PLA from March to June in 2004. Autologous blood ICH model in rats were established as follows： In the two-step injection group, 50 μL unclotted autologous blood was taken from the rat tail cut, then injected with microsyringe into the caudate nucleus, 10 μL injected at first, paused for 2 minutes, and then the rest 40 μL injected slowly and continuously within 2 minutes. After the injection, the needle was kept immovable for about 4 minutes, withdrawn 2.0 mm, again kept immovable for about 4 minute, and then removed wholly at a slow speed. In the single injection group, 50 μL unclotted tail blood was injected slowly and continuously all within 2 minutes and the needle was slowly removed;（4） In the double injection group, 10 mL blood was injected at first, paused for 2 minutes, the rest 40 μL injected evenly within 2 minutes, and then the needle was withdrawn slowly and uninterruptedly. Neurologic findings were scored in accordance with Longa＇s five-point scale （0-4 scores, the higher the score, the severer the neurological dysfunction）. The rats were killed to remove and sections were prepared, the morphological features of hematomas were grossly observed, the maximal diameter and size of hematomas in each slice were measured with the imaging analytical system, and the volume was calculated. Meanwhile, the conveniences of the techniques were compared. MAIN OUTCOME MEASURES： The morphological features and volume of hematomas, neurologic deficit score （NDS）, and the convenience of the techniques were compared. RESULTS： All the 30 rats were involved in the analysis of results without deletion. （1） Results of the morphological observation of volume of hematoma： In the two-step injection group, hematomas located in the right caudate nucleus area regularly in circular or analogously circular shape in each slice. The formation rate of hematomas in the single injection group and double injection group were lower than those in the two-step injection group [60% （6/10）, 80% （8/10）, 100% （10/10）, P〈 0.01, 0.05]. The volume of hematomas in the single injection group and double injection group were smaller than those in the two-step injection group [（28.5±14.8）, （33.4±7.4）, （41.6±3.9） mm3, P〈 0.01, 0.05]. （2） NDS results： The NDS scores in the single injection group and double injection group were smaller than that in the two-step injection group （0.90±0.83, 1.30±0.78, 1.90±0.57, P〈 0.05）. （3）Comparison of the convenience of the techniques： The double injection method allowed generating reproducible hematomas in rats with shortcomings that it needed autologous arterial blood from femoral artery, and precision instruments such as microinfusion pump. The two-step injection injected fresh unclotting blood taken directly from the tail cut with microsyringe into the rat brain, and it has the advantages of easy operation, no influence on the activity of thrombase, shorter duration for model establishment, and higher rate of hematoma formation, which could generate ideal and economical models of ICH. The two-step injection induced hemotoma regularly in circular or analogously circular shape in each slice, but those induced by single and double injections were mostly in strip or fusiform shapes and extending along the needle tracks or into the ventricle or subarachnoid space. CONCLUSION ： The autologous blood ICH model induced by the two-step injection method is a reproducible and reliable one in regular shape, which is better than those induced by double and single injections.展开更多
HIV and AIDS has continued to be a major public health concern, and hence one of the epidemics that the world resolved to end by 2030 as highlighted in sustainable development goals (SDGs). A colossal amount of effort...HIV and AIDS has continued to be a major public health concern, and hence one of the epidemics that the world resolved to end by 2030 as highlighted in sustainable development goals (SDGs). A colossal amount of effort has been taken to reduce new HIV infections, but there are still a significant number of new infections reported. HIV prevalence is more skewed towards the key population who include female sex workers (FSW), men who have sex with men (MSM), and people who inject drugs (PWID). The study design was retrospective and focused on key population enrolled in a comprehensive HIV and AIDS programme by the Kenya Red Cross Society from July 2019 to June 2021. Individuals who were either lost to follow up, defaulted (dropped out, transferred out, or relocated) or died were classified as attrition;while those who were active and alive by the end of the study were classified as retention. The study used density analysis to determine the spatial differences of key population attrition in the 19 targeted counties, and used Kilifi county as an example to map attrition cases in smaller administrative areas (sub-county level). The study used synthetic minority oversampling technique-nominal continuous (SMOTE-NC) to balance the datasets since the cases of attrition were much less than retention. The random survival forests model was then fitted to the balanced dataset. The model correctly identified attrition cases using the predicted ensemble mortality and their survival time using the estimated Kaplan-Meier survival function. The predictive performance of the model was strong and way better than random chance with concordance indices greater than 0.75.展开更多
Plugging agent treatment and acid stimulation have completely different mechanisms for improving injection profiles. In this paper, a hybrid procedure is introduced to reduce the damage of the plugging agent to low a...Plugging agent treatment and acid stimulation have completely different mechanisms for improving injection profiles. In this paper, a hybrid procedure is introduced to reduce the damage of the plugging agent to low and medium permeability zones and the penetration radius of acid into high permeability zones. The procedure is: First inject plugging agent to block high permeability zones, and then inject acid to remove plugging agent damage from the low and medium permeability zones and stimulate them. To perform this procedure successfully, three kinds of plugging agents, namely strong strength plugging agent for the wells with fractures or high permeability streaks, weak gel for those with thick layer in which serious heterogeneity exists, temporary plugging agent for those in which the absorption ability of high permeability zones needs maintaining, were screened out for use in different reservoirs. Several acid systems were evaluated to be compatible with the three kinds of plugging agents. The objectives of this paper are:(1)To show the screen results about the compatible plugging agent and acid; 2 To show how to optimize the operation process;(3)To tell some experience gained ( ) from the oilfield applications of this technique. From Jan. 2001 to Dec. 2002, 46 operations using this procedure were carried out in Weicheng and Mazhai Oilfields of SINOPEC. Results show that the average benefit/cost ratio is over 3.5. Experience acquired from these applications was summarized in the paper.展开更多
A new method for the determination of trace non-rare earth elements in high purity rare earth oxides by ICP-AES with preconcentration on an active carbon-silica gel microcolumn in a flow injection system is described ...A new method for the determination of trace non-rare earth elements in high purity rare earth oxides by ICP-AES with preconcentration on an active carbon-silica gel microcolumn in a flow injection system is described in this paper. Experimental parameters such as pH, flow rate,reagent concentration,length of reaction coil,eluent acidity,etc. were optimized. In the buffer solution of NH3. H2O/NH4Cl at pH 4. 6,Al,Cr,Cu,Fe, Pb, V and Zn can be preconcentrated and then eluted with 4. 5 mol/L nitric acid utilizing stop-flow technique. The enrichment factors were in range of 8. 1￣12. 6 with detection limits of μg/m level ,and the RSD with metals at μg/g level were 2. 3￣5. 0% (n= 7). The method proposed can reduce the matrix interference effectively , and has been applied to the determination of non-rare earth metals atμg/g level in high purity Eu2O3 with satisfactory results.展开更多
In this research study,the mechanical properties of several Polymer matrix composites are investigated.These composites are multi-phase materials in which reinforcing materials are properly mixed with a polymer matrix...In this research study,the mechanical properties of several Polymer matrix composites are investigated.These composites are multi-phase materials in which reinforcing materials are properly mixed with a polymer matrix.More precisely,Nylon 6 reinforced with 5,15 and 25 wt.%of silicon carbide(SiC)and Nylon 6 reinforced with 5,15 and 25 wt.%of boron carbide(B_(4)C),prepared by means of an injection moulding process at three different injection pressures are considered.Specific attention is paid to the tensile and impact strength of these composites.The Taguchi technique is used to optimize the process parameters such as reinforcement material,its percentage and the injection pressure.It is observed that the specimens 5%SiC with 80 MPa injection pressure display a better tensile strength and similarly the specimen 5%B_(4)C with 90 MPa injection pressure have a superior impact strength.展开更多
A low power low phase noise frequency synthesizer with subharmonic injection locking is proposed for ZigBee applications. The PLL is based on a ring VCO to decrease area and production cost. In order to improve phase ...A low power low phase noise frequency synthesizer with subharmonic injection locking is proposed for ZigBee applications. The PLL is based on a ring VCO to decrease area and production cost. In order to improve phase noise performance, a high frequency injection signal of which frequency varies with channel number is used. The circuit is designed in TSMC 0.18 μm CMOS technology and simulated in ADS (Advanced Design System). The phase noise at 3.5 and 10 MHz offsets is -116 and -118 dBc/Hz, respectively, and total circuit consumes 2.2 mA current.展开更多
文摘We report a case of a 63-year-old male who experienced an iatrogenic sigmoid perforation repaired combining three endoscopic techniques.The lesion was large and irregular with three discrete perforations,therefore,we decided to close it by placing one clip per perforation,and then connecting all the clips with two endoloops.Finally we chose to use a fibrin glue injection to obtain a complete sealing.Four days after the colonoscopy the patient underwent a laparoscopic right hemicolectomy due to evidence of a large polyp of the caecum with high grade dysplasia and focal carcinoma in situ.Inspection of the sigma showed complete repair of the perforation.This report underlines how a conservative approach,together with a combination of various endoscopic techniques,can resolve complicated iatrogenic perforations of the colon.
文摘Objective:Although endoscopic treatment has been used by many pediatric urologists for the treatment of vesicoureteral reflux(VUR),it has no considerable success in high-grade VUR.We aimed to describe the primary outcomes of unilateral periureteral injection technique(PIT),as well as bilateral PIT in high-grade VUR.Methods:In this prospective study,we examined 92 ureters in 45 boys and 40 girls from February 2010 to May 2018.Bilateral PIT and unilateral PIT were applied in 67 and 25 refluxing units,respectively.In the unilateral PIT,the subureteral injection site was only at the 5-or 7-o’clock position.However,in the bilateral PIT,the subureteral injection sites were at 5-and 7-o’clock position.Pre-and post-operative reflux grades were evaluated by voiding cystourethrography 6 months after surgery.Results:Seven patients had bilateral reflux.Overall,75(81.5%)ureters showed Grade IV VUR,while 17(18.5%)had primary Grade V VUR.The mean age of the subjects was 39.2 months.In unilateral PIT ureters,VUR was resolved in 23(92.0%)refluxing units.It was downgraded to Grade III in one ureter(4.0%)and to Grade II in another ureter(4.0%).In addition,in bilateral PIT cases,VUR was resolved in 60(89.6%)ureters;it downgraded to Grades II and III in 3(4.5%)and 4(6.0%)refluxing units,respectively.Conclusion:Unilateral PIT can be highly effective in the treatment of selected ureters of high-grade VUR.However,further studies are needed to confirm our results.
文摘Delivered by intramuscular (IM) injections, Long Acting Injections (LAI), offering comparatively long term medicinal effects from several weeks to several months, are gaining much attention. The aim of this article was to indicate a safe and effective IM injection technique based on evidenced data derived from ultrasonographic data. Accurate anatomical knowledge is necessary in order to administer IM injections. It is possible to gain an adequate understanding of injection site anatomical structures by using ultrasound diagnostic devices. In particular, ultrasonography offers real-time diagnostic data allowing for observation of injection site, subcutaneous tissues, fat layers, muscle membrane, muscles and bones. To deliver the drug accurately into the muscle is essential, to achieve maximum drug efficacy and prevent injection site reactions. Therefore, when administering IM injections to the buttocks area, a suitable injection needle between 23G 25 mm to 21G or 22G 38 mm must be chosen depending on physique and drug characteristics. Needles determined as safe and effective through ultrasonographic evidence are needed such as in the case of a deltoid injection site, in which a 23G 25 mm injection needle is used in the absence of notable obesity. Not only the needle type is essential, but also the IM procedure itself. It is important to stretch the skin, inserting the needle at 90 degree angle to ensure depth of needle insertion to the muscle. Until new con-firmed evidence becomes available, it is necessary to increase the understanding of injection site selection methods, needle insertion depth, needle angle, and established IM injection techniques. The application of ultrasound devices in the development of next-generation techniques for IM injection is promising. Importantly, these techniques provide critical information from a risk management perspective.
文摘Objective:To review the current literature on the practice of intramuscular injections(IMIs),focusing on immunizations.Methods:The present study comprises 2 reviews,characterized by high-quality evidence,per taining to the deployment of the slow injection technique without aspiration(referred to in this paper as the without-aspiration slow injection technique[WASi T])and combined with the Zeta-track technique(ZTT).The literature review is oriented toward the analysis of 2 features associated with IMIs techniques:safety and pain,integrating new evidence on vaccinee positioning for each muscle site and general relaxation techniques in the multi-parametric analysis.Results:The rigorous and in-depth reviews in the current study reveal the usefulness of including,among the international guidelines for via intramuscular immunizations,the adoption of WASi T only for compliant vaccinees,and in combination with all validated techniques for IMIs,and the use of ZTT limitedly if specific well-developed muscles are indicated.All the technique's limitations are exposed.Conclusions:Future research directions are presented by including the author's study designs to provide indirect evidence for the validity of the rationale of the slow injection technique using scientific methods,and for the conduction of future randomized controlled trials(RCTs)focused on revisiting the adoption of ZTT in a dynamic and integrated immunizations protocol in anterolateral thigh(ALT),ventrogluteal(VG),and also in the deltoid muscle,in the specific cases analyzed.
文摘The increase in the number of databases accessed only by some applications has made code injection attacks an important threat to almost any current system. If one of these applications accepts inputs from a client and executes these inputs without first validating them, the attackers are free to execute their own queries and therefore, to extract, modify or delete the content of the database associated to the application. In this paper a deep analysis of the LDAP injection techniques is presented. Furthermore, a clear distinction between classic and blind injection techniques is made.
文摘BACKGROUND ： Experimental animal models of intracerebral hemorrhag （ICH） are greatly needed, so the process of establishment should be ideal in hematoma formation and easy to operate. OBJECTIVE ： To construct model of ICH in rats with double injection of autologous blood taken from the cut tail cut and double withdrawal of the needle （shortened as two-step injection model）, and compare with those induced by single and double injections. DESIGN ： A randomized controlled tria SETTING： Department of Neurology, General Hospital of Military Area Command of Chinese PLA. MATERIALS： Thirty male Wistar rats of 10 to 12 months, weighing （400±25） g, provided by the Experimental Center of Medical Animals, General Hospital of Shenyang Military Area Command of Chinese PLA, were divided randomly into 3 groups with 10 rats in each group： two-step injection group, single injection group, double injection group. METHODS ： The experiment was carried out in the Department of Neurology, General Hospital of Military Area Command of Chinese PLA from March to June in 2004. Autologous blood ICH model in rats were established as follows： In the two-step injection group, 50 μL unclotted autologous blood was taken from the rat tail cut, then injected with microsyringe into the caudate nucleus, 10 μL injected at first, paused for 2 minutes, and then the rest 40 μL injected slowly and continuously within 2 minutes. After the injection, the needle was kept immovable for about 4 minutes, withdrawn 2.0 mm, again kept immovable for about 4 minute, and then removed wholly at a slow speed. In the single injection group, 50 μL unclotted tail blood was injected slowly and continuously all within 2 minutes and the needle was slowly removed;（4） In the double injection group, 10 mL blood was injected at first, paused for 2 minutes, the rest 40 μL injected evenly within 2 minutes, and then the needle was withdrawn slowly and uninterruptedly. Neurologic findings were scored in accordance with Longa＇s five-point scale （0-4 scores, the higher the score, the severer the neurological dysfunction）. The rats were killed to remove and sections were prepared, the morphological features of hematomas were grossly observed, the maximal diameter and size of hematomas in each slice were measured with the imaging analytical system, and the volume was calculated. Meanwhile, the conveniences of the techniques were compared. MAIN OUTCOME MEASURES： The morphological features and volume of hematomas, neurologic deficit score （NDS）, and the convenience of the techniques were compared. RESULTS： All the 30 rats were involved in the analysis of results without deletion. （1） Results of the morphological observation of volume of hematoma： In the two-step injection group, hematomas located in the right caudate nucleus area regularly in circular or analogously circular shape in each slice. The formation rate of hematomas in the single injection group and double injection group were lower than those in the two-step injection group [60% （6/10）, 80% （8/10）, 100% （10/10）, P〈 0.01, 0.05]. The volume of hematomas in the single injection group and double injection group were smaller than those in the two-step injection group [（28.5±14.8）, （33.4±7.4）, （41.6±3.9） mm3, P〈 0.01, 0.05]. （2） NDS results： The NDS scores in the single injection group and double injection group were smaller than that in the two-step injection group （0.90±0.83, 1.30±0.78, 1.90±0.57, P〈 0.05）. （3）Comparison of the convenience of the techniques： The double injection method allowed generating reproducible hematomas in rats with shortcomings that it needed autologous arterial blood from femoral artery, and precision instruments such as microinfusion pump. The two-step injection injected fresh unclotting blood taken directly from the tail cut with microsyringe into the rat brain, and it has the advantages of easy operation, no influence on the activity of thrombase, shorter duration for model establishment, and higher rate of hematoma formation, which could generate ideal and economical models of ICH. The two-step injection induced hemotoma regularly in circular or analogously circular shape in each slice, but those induced by single and double injections were mostly in strip or fusiform shapes and extending along the needle tracks or into the ventricle or subarachnoid space. CONCLUSION ： The autologous blood ICH model induced by the two-step injection method is a reproducible and reliable one in regular shape, which is better than those induced by double and single injections.
文摘HIV and AIDS has continued to be a major public health concern, and hence one of the epidemics that the world resolved to end by 2030 as highlighted in sustainable development goals (SDGs). A colossal amount of effort has been taken to reduce new HIV infections, but there are still a significant number of new infections reported. HIV prevalence is more skewed towards the key population who include female sex workers (FSW), men who have sex with men (MSM), and people who inject drugs (PWID). The study design was retrospective and focused on key population enrolled in a comprehensive HIV and AIDS programme by the Kenya Red Cross Society from July 2019 to June 2021. Individuals who were either lost to follow up, defaulted (dropped out, transferred out, or relocated) or died were classified as attrition;while those who were active and alive by the end of the study were classified as retention. The study used density analysis to determine the spatial differences of key population attrition in the 19 targeted counties, and used Kilifi county as an example to map attrition cases in smaller administrative areas (sub-county level). The study used synthetic minority oversampling technique-nominal continuous (SMOTE-NC) to balance the datasets since the cases of attrition were much less than retention. The random survival forests model was then fitted to the balanced dataset. The model correctly identified attrition cases using the predicted ensemble mortality and their survival time using the estimated Kaplan-Meier survival function. The predictive performance of the model was strong and way better than random chance with concordance indices greater than 0.75.
文摘Plugging agent treatment and acid stimulation have completely different mechanisms for improving injection profiles. In this paper, a hybrid procedure is introduced to reduce the damage of the plugging agent to low and medium permeability zones and the penetration radius of acid into high permeability zones. The procedure is: First inject plugging agent to block high permeability zones, and then inject acid to remove plugging agent damage from the low and medium permeability zones and stimulate them. To perform this procedure successfully, three kinds of plugging agents, namely strong strength plugging agent for the wells with fractures or high permeability streaks, weak gel for those with thick layer in which serious heterogeneity exists, temporary plugging agent for those in which the absorption ability of high permeability zones needs maintaining, were screened out for use in different reservoirs. Several acid systems were evaluated to be compatible with the three kinds of plugging agents. The objectives of this paper are:(1)To show the screen results about the compatible plugging agent and acid; 2 To show how to optimize the operation process;(3)To tell some experience gained ( ) from the oilfield applications of this technique. From Jan. 2001 to Dec. 2002, 46 operations using this procedure were carried out in Weicheng and Mazhai Oilfields of SINOPEC. Results show that the average benefit/cost ratio is over 3.5. Experience acquired from these applications was summarized in the paper.
文摘A new method for the determination of trace non-rare earth elements in high purity rare earth oxides by ICP-AES with preconcentration on an active carbon-silica gel microcolumn in a flow injection system is described in this paper. Experimental parameters such as pH, flow rate,reagent concentration,length of reaction coil,eluent acidity,etc. were optimized. In the buffer solution of NH3. H2O/NH4Cl at pH 4. 6,Al,Cr,Cu,Fe, Pb, V and Zn can be preconcentrated and then eluted with 4. 5 mol/L nitric acid utilizing stop-flow technique. The enrichment factors were in range of 8. 1￣12. 6 with detection limits of μg/m level ,and the RSD with metals at μg/g level were 2. 3￣5. 0% (n= 7). The method proposed can reduce the matrix interference effectively , and has been applied to the determination of non-rare earth metals atμg/g level in high purity Eu2O3 with satisfactory results.
文摘In this research study,the mechanical properties of several Polymer matrix composites are investigated.These composites are multi-phase materials in which reinforcing materials are properly mixed with a polymer matrix.More precisely,Nylon 6 reinforced with 5,15 and 25 wt.%of silicon carbide(SiC)and Nylon 6 reinforced with 5,15 and 25 wt.%of boron carbide(B_(4)C),prepared by means of an injection moulding process at three different injection pressures are considered.Specific attention is paid to the tensile and impact strength of these composites.The Taguchi technique is used to optimize the process parameters such as reinforcement material,its percentage and the injection pressure.It is observed that the specimens 5%SiC with 80 MPa injection pressure display a better tensile strength and similarly the specimen 5%B_(4)C with 90 MPa injection pressure have a superior impact strength.
文摘A low power low phase noise frequency synthesizer with subharmonic injection locking is proposed for ZigBee applications. The PLL is based on a ring VCO to decrease area and production cost. In order to improve phase noise performance, a high frequency injection signal of which frequency varies with channel number is used. The circuit is designed in TSMC 0.18 μm CMOS technology and simulated in ADS (Advanced Design System). The phase noise at 3.5 and 10 MHz offsets is -116 and -118 dBc/Hz, respectively, and total circuit consumes 2.2 mA current.
