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Erosion is a main failure of tubings and downhole tools in Changqing gas field. It is necessary to evaluate the erosion rate for the safety of tubing and strings. In this paper, the erosion of P110 steel, in the 0.2%wt guar gum fracturing fluid which contains sands, is investigated by weight loss method in the self-made jet experiment device. It is indicated that the erosion rate increases with the increment of slurry velocity exponentially. When the slurry velocity is in low velocity area, the electrochemical corrosion of dissolved oxygen dominates in erosion mechanism; when slurry velocity increases into middle velocity area, the weight loss is controlled by the synergism of corrosion-erosion; and when the slurry velocity increases into high velocity area, the weight loss rate is dominantly depended on erosion of particles. The results can provide guidelines for large-scale fracturing work of Changqing gas fields.

To carry out a preliminary study on the emotional problems and parenting locus of control among children with anxiety disorders.A total of 110 children with simple anxiety disorders (AD group) and 113 normal children (control group) from September to December 2005 were enrolled. Children were asked to complete the Depression Self-Rating Scale for Children (DSRSC), the Screen for Child Anxiety Related Emotional Disorders (SCARED), and the Parenting Locus of Control Scale (PLOC).A total of 197 valid scales were returned.The scores of somatic, generalized anxiety, separation anxiety, social phobia anxiety, school phobia anxiety, total anxiety, and total depression were all higher in the AD group than in the control group (P0.01). The score of "education effects" for parents was significantly higher in the AD group than that in the control group (P0.01).Children with anxiety disorders tend to have more emotional problems and poorer parental education effects.

To investigate the prevalence of psychiatric disorders in a representative sample of primary and middle school students in Hunan Province.A total of 9 495 children aged 5-17 years from Hunan urban and rural schools were enrolled by a cluster sampling and a two-phase design. The students' psychiatric status was assessed using the Investigation Screening Inventory for Child Mental Disorder and a semi-structured interview designed based on the DSM-IV criteria.The overall prevalence of psychiatric disorders was 16.22%. Attention-deficit and disruptive behavior disorders were the commonest in the diagnostic categories of psychiatric disorders (10.69%). Regarding specific disorders, the most prevalent was attention-deficit/hyperactivity disorder (5.95%). Psychiatric disorders were more prevalent in boys than in girls (20.49% vs 11.16%; p0.01). The prevalence of attention-deficit and disruptive behavior disorders in boys was higher than in girls (14.76% vs 5.87%; p0.01). The prevalence of psychiatric disorders in middle school students (12-17 years) was significantly higher than in primary students (5-11 years) (18.38% vs 14.64%; p0.01). There were no significant differences in the prevalence of psychiatric disorders between urban and rural students.Psychiatric disorders are common among primary and middle school students in Hunan Province. The prevalence of this disorder in boys is higher than in girls. The middle school students have higher prevalence than primary students.

To study the family rearing pattern of attention deficit hyperactivity disorder (ADHD) with or without anxiety disorder and to explore its risk factors.9495 children and their parents were sampled at random in Hunan province, using two-stage investigation. Those who were diagnosed ADHD and the normal control filled out Egna Minnen av Barndoms Uppfostran and family adaptability and cohesion scale by themselves.The comparison of factors as: actual family cohesion, parents' punishments, rejection, mother's excessive protection, intervention and father's excessive protection were significantly different between ADHD with or without anxiety disorder and normal children (P0.05). The comparison of parents' punishments, rejection, excessive protection and intervention were obviously different between ADHD with anxiety disorder and simple ADHD (P0.05). Mother's rejection was the influencing factor of simple ADHD, with OR as 1.122. Ideal family cohesion, mother's rejection and father's punishments were the influencing factors of ADHD with anxiety disorder, with OR as 0.966, 1.215 and 1.089 respectively.There were some problems in the parental rearing pattern of ADHD with or without anxiety disorder. Mother's rejection, father's punishments and ideal family cohesion were suggested to be correlated with ADHD and anxiety disorder.